Patent Publication Number: US-7585163-B2

Title: Compression system, multicylinder rotary compressor, and refrigeration apparatus using the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a Divisional of prior application Ser. No. 11/174,476 filed on Jul. 6, 2005, now U.S. Pat. No. 7,524, 174 the entire contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a compression system, a multicylinder rotary compressor constituting the system, and a refrigeration apparatus using the compressor. 
   This type of compression system has heretofore comprised a multicylinder rotary compressor, a control device which controls an operation of the multicylinder rotary compressor and the like. Examples of this multicylinder rotary compressor includes a two-cylinder rotary compressor comprising first and second rotary compression elements. The compressor includes a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, and these elements are housed in a sealed container. The first and second rotary compression elements comprise: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders, respectively; and first and second vanes which abut on the first and second cylinders to partition the insides of the respective cylinders into low-pressure and high-pressure chamber sides. The first and second vanes are constantly urged toward the first and second rollers by the spring members. 
   Moreover, when the driving element is driven by the control device, a low-pressure refrigerant gas is sucked from a suction passage on the low-pressure chamber sides of the respective cylinders of the first and second rotary compression elements. The gas is compressed by operations of each roller and vane to constitute a high-temperature/pressure refrigerant gas, and discharged from the high-pressure chamber side of each cylinder to a discharge muffling chamber via a discharge port. Thereafter, the gas is discharged into the sealed container, and discharged to the outside (see, e.g., Japanese Patent Application Laid-Open No. 5-99172). 
   In the compression system comprising this multicylinder rotary compressor, in a case where a compression operation is performed by both the first and second cylinders in a small capacity region at a light load time or a low-speed rotation time, the refrigerant gas has to be sucked and compressed for displacement volumes of both the cylinders. Therefore, a rotation number of the driving element is lowered by a corresponding number by the control device to operate the element. However, when the rotation number drops excessively, a problem occurs that efficiency of the driving element drops and leak loss increases to lower the operation efficiency remarkably. 
   Therefore, in view of this problem, a compression system has been developed in which a one-cylinder operation and a two-cylinder operation are switchable in accordance with the capacity. That is, either spring member is eliminated from the spring members which urge the first and second vanes of the multicylinder rotary compressor toward the first and second rollers. For example, the spring member is eliminated which urges the second vane toward the second roller. A refrigerant pressure is applied as a back pressure of the second vane on discharge sides of both the rotary compression elements by the control device at the two-cylinder operation. Accordingly, the second vane is urged on a second-roller side to perform a compression work. 
   On the other hand, when the two-cylinder operation is switched to the one-cylinder operation, a refrigerant pressure is applied as the back pressure of the second vane on suction sides of both the rotary compression elements by the control device. Since this suction pressure is a low pressure, the second vane cannot be urged on the second-roller side. Therefore, the compression work is not substantially performed by the second rotary compression element, and the compression work of the refrigerant is performed only by the first rotary compression element. 
   When the one-cylinder operation is performed in a small capacity region in this manner, an amount of the refrigerant gas to be compressed can be reduced, and the rotation number can be raised by the amount. Consequently, the operation efficiency of the driving element is improved, and the leak loss can be reduced. 
   Here, in the second rotary compression element in which any spring member is not disposed during the two-cylinder operation as described above, as to the discharge-side pressures of both the rotary compression elements which urge the second roller, pressure fluctuations are large, a follow-up property of the vane is deteriorated by the pressure fluctuation, and a collision sound is generated between the second roller and the second vane. Therefore, the applicant has tried the application of an intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements as the back pressure of the second roller. 
   However, when the above-described intermediate pressure is applied as the back pressure of the second vane, and the one-cylinder operation is switched to the two-cylinder operation, much time is required for allowing the second vane to follow up the second roller, the second vane collides with the second roller during the follow-up, and a disadvantage has occurred that a collision sound is generated. 
   On the other hand, since equal suction-side pressures are applied to the pressure in a second cylinder and the back pressure of the second vane at the time of the one-cylinder operation, the second vane does not easily retreat from the second cylinder during the switching from the two-cylinder operation to the one-cylinder operation. There has a problem that the second vane collides with the second roller and the collision sound is generated even during the switching. 
   On the other hand, pressure pulsation is caused on the back-pressure side of the vane (side opposite to the roller) by the urging operation of the vane with respect to the roller at the time of the operation of the multicylinder rotary compressor. However, in the second vane in which any spring member is not disposed, the pressure pulsation causes a problem that the follow-up property of the second vane is deteriorated, the vane collides with the second roller, and the collision sound is generated. 
   Furthermore, as to the discharge-side pressures of both the rotary compression elements, which are applied as the back pressure of the second vane, the pressure fluctuation is large, accordingly the follow-up property is deteriorated in the second vane in which any spring member is not disposed, and the collision sound is generated between the second roller and the second vane. 
   Moreover, the second roller is brought into an idling state in the second rotary compression element during the one-cylinder operation. At this time, the equal suction-side pressures are applied to the pressure in the second cylinder and the back pressure of the second vane. Therefore, the second vane protrudes into the second cylinder by the function of the balance between both spaces. Even in this case, there has been a problem that the second vane collides with the second roller, and the collision sound is generated. 
   SUMMARY OF THE INVENTION 
   The present invention has been developed to solve the problems of the conventional technique, and an object thereof is to avoid generation of a collision sound of a second vane at the time of switching of an operation mode in a compression system comprising a multicylinder rotary compressor in which an only first vane is urged toward a first roller by a spring member. The compressor is usable by switching of a first operation mode in which both rotary compression elements perform a compression work and a second operation mode in which an only first rotary compression element substantially performs a compression work. 
   According to the present invention, there is provided a compression system comprising: a multicylinder rotary compressor in which a sealed container stores a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, the first and second rotary compression elements comprising: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders; and first and second vanes which abut on the first and second rollers to partition the inside of each cylinder into low and high-pressure chamber sides, the only first vane being urged toward the first roller by a spring member, the compressor being configured to be used by switching of a first operation mode in which both the rotary compression elements perform a compression work and a second operation mode in which the only first rotary compression element substantially performs the compression work, wherein discharge-side pressures of both the rotary compression elements are applied as a back pressure of the second vane, and thereafter an intermediate pressure is applied which is between suction-side pressures and the discharge-side pressures of both the rotary compression elements, when the second operation mode is switched to the first operation mode. 
   Moreover, according to the present invention, there is provided a compression system comprising: a multicylinder rotary compressor in which a sealed container stores a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, the first and second rotary compression elements comprising: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders; and first and second vanes which abut on the first and second rollers to partition the inside of each cylinder into low and high-pressure chamber sides, the only first vane being urged toward the first roller by a spring member, the compressor being configured to be used by switching of a first operation mode in which both the rotary compression elements perform a compression work and a second operation mode in which the only first rotary compression element substantially performs the compression work, the system further comprising: a valve device for controlling circulation of a refrigerant into the second cylinder, wherein the valve device interrupts flowing of the refrigerant into the second cylinder, and thereafter suction-side pressures of both the rotary compression elements are applied as a back pressure of the second vane, when the first operation mode is switched to the second operation mode. 
   Furthermore, according to the present invention, there is provided a compression system comprising: a multicylinder rotary compressor in which a sealed container stores a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, the first and second rotary compression elements comprising: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders; and first and second vanes which abut on the first and second rollers to partition the inside of each cylinder into low and high-pressure chamber sides, the only first vane being urged toward the first roller by a spring member, the compressor being configured to be used by switching of a first operation mode in which both the rotary compression elements perform a compression work and a second operation mode in which the only first rotary compression element substantially performs the compression work, the system further comprising: a valve device for controlling circulation of a refrigerant into the second cylinder, wherein the valve device allows the refrigerant to flow into the second cylinder, and an intermediate pressure is applied as a back pressure of the second vane in the first operation mode, the intermediate pressure being between suction-side and discharge-side pressures of both the rotary compression elements, the valve device stops the flowing of the refrigerant into the second cylinder, and the suction-side pressures of both the rotary compression elements are applied as the back pressure of the second vane in the second operation mode, the discharge-side pressures of both the rotary compression elements are applied as the back pressure of the second vane, and thereafter the intermediate pressure is applied which is between the suction-side and discharge-side pressures of both the rotary compression elements to switch the second operation mode to the first operation mode, and the valve device interrupts the flowing of the refrigerant into the second cylinder, and the suction-side pressures of both the rotary compression elements are applied as the back pressure of the second vane to switch the first operation mode to the second operation mode. 
   Additionally, in the compression system of the present invention, in the above-described respective inventions, the driving element of the multicylinder rotary compressor is rotated at a low speed, and a compression ratio of the first rotary compression element or both the rotary compression elements is set to 3.0 or less at the mode switching time. 
   According to the present invention, when the second operation mode is switched to the first operation mode, the discharge-side pressures of both the rotary compression elements are applied as the back pressure of the second vane, and thereafter the intermediate pressure is applied which is between the suction-side and discharge-side pressures of both the rotary compression elements. Therefore, the second vane is configured to move toward the second roller in an early stage by the discharge-side pressures of both the rotary compression elements. Consequently, a follow-up property of the second vane is improved, operation efficiency is improved, and generation of a collision sound of the second vane can be avoided at the switching time from the second operation mode to the first operation mode. 
   Moreover, after applying to the second vane the discharge-side pressures of both the rotary compression elements, and allowing the second vane to follow up the second roller, the intermediate pressure is applied which is between the suction-side and discharge-side pressures of both the rotary compression elements. Accordingly, a pressure fluctuation is remarkably reduced as compared with a case where the discharge-side pressures of both the rotary compression elements are applied to the back pressure of the second vane. Therefore, after the switching of the operation mode, the follow-up property of the second vane is improved, and the compression efficiency of the second rotary compression element is improved in the multicylinder rotary compressor. Moreover, it is possible to avoid generation of a collision sound between the second roller and the second vane in the first operation mode. 
   Furthermore, when the first operation mode is switched to the second operation mode, the valve device interrupts the flowing of the refrigerant into the second cylinder, and thereafter the suction-side pressures of both the rotary compression elements are applied as the back pressure of the second vane. Therefore, the pressure in the second cylinder can be set to be higher than the back pressure of the second vane. Accordingly, the second vane of the multicylinder rotary compressor is pushed on a side opposite to the second roller by the pressure in the second cylinder. Since the second vane does not come into the second cylinder, it is possible to avoid beforehand a disadvantage that the second vane collides with the second roller to generate the collision sound. 
   Moreover, as described above, the compressor is usable by the switching of the first operation mode in which the first and second rotary compression elements perform the compression work and the second operation mode in which the only first rotary compression element substantially performs the compression work. In this case, performance and reliability of the multicylinder rotary compressor are enhanced, and the performance of the compression system can be remarkably enhanced. 
   Especially when the mode is switched, the driving element of the multicylinder rotary compressor is rotated at a low speed, the compression ratio of the first rotary compression element or both the rotary compression elements is set to 3.0 or less, and then the pressure fluctuation can be suppressed at the operation mode switching time. 
   Moreover, according to the present invention, there is provided a refrigeration apparatus comprising: a refrigerant circuit using the compression system according to the above-described inventions. 
   According to the present invention, since the refrigerant circuit of the refrigeration apparatus is constituted using the compression system of each of the above-described inventions, the operation efficiency of the whole refrigeration apparatus can be improved. 
   Furthermore, an object of the present invention is to avoid generation of a collision sound of a second vane at a starting time in a compression system comprising a multicylinder rotary compressor which urges an only first vane toward a first roller by a spring member. 
   That is, according to the present invention, there is provided a compression system comprising: a multicylinder rotary compressor in which a sealed container stores a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, the first and second rotary compression elements comprising: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders; and first and second vanes which abut on the first and second rollers to partition the inside of each cylinder into low and high-pressure chamber sides, the only first vane being urged toward the first roller by a spring member, wherein the multicylinder rotary compressor is started in a state in which suction-side pressures of both the rotary compression elements are applied as a back pressure of the second vane, when the compressor is started, discharge-side pressures of both the rotary compression elements are applied as the back pressure of the second vane after the starting, and thereafter the back pressure of the second vane is set to be an intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements. 
   Moreover, in the compression system of the present invention, in the above-described invention, the multicylinder rotary compressor is configured to be used by switching of a first operation mode in which both the rotary compression elements perform a compression work and a second operation mode in which the only first rotary compression element substantially performs a compression work. 
   According to the present invention, when the multicylinder rotary compressor is started, the compressor is started in a state in which the suction-side pressures of both the rotary compression elements are applied as the back pressure of the second vane, and accordingly the compression work is not substantially performed by the second rotary compression element. 
   Moreover, after the compressor is started, the discharge-side pressures of both the rotary compression elements are applied as the back pressure of the second vane. Accordingly, the second vane is urged toward the second roller, and the compression work is started in the second rotary compression element. 
   Furthermore, after applying the discharge-side pressures of both the rotary compression elements as the back pressure of the second vane, the back pressure of the second vane is set to the intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements. Consequently, the pressure fluctuation is reduced as compared with a case where the discharge-side pressures of both the rotary compression elements are applied to the back pressure of the second vane. Therefore, in the multicylinder rotary compressor at a usual operation time after the starting, the follow-up property of the second vane is improved, the compression efficiency of the second rotary compression element is improved, and it is possible to avoid beforehand the generation of the collision sound between the second roller and the second vane. 
   Especially, the multicylinder rotary compressor is usable by the switching of the first operation mode in which the first and second rotary compression elements perform the compression work and the second operation mode in which the only first rotary compression element substantially performs the compression work. The performance and reliability of the compressor are enhanced, and the performance of the compression system can be remarkably enhanced. 
   Moreover, according to the present invention, there is provided a refrigeration apparatus comprising a refrigerant circuit using the compression system according to the above-described inventions. 
   According to the present invention, since the refrigerant circuit of the refrigeration apparatus is constituted using the compression system of each of the above-described inventions, the operation efficiency of the whole refrigeration apparatus can be improved. 
   Furthermore, an object of the present invention is to improve a follow-up property of a second vane and avoid generation of a collision sound of the second vane in a multicylinder rotary compressor which urges an only first vane toward a first roller by a spring member and a compression system comprising the multicylinder rotary compressor. 
   That is, according to the present invention, there is provided a multicylinder rotary compressor in which a sealed container stores a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, the first and second rotary compression elements comprising: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders; and first and second vanes which abut on the first and second rollers to partition the inside of each cylinder into low and high-pressure chamber sides, the only first vane being urged toward the first roller by a spring member, the compressor further comprising: a back-pressure chamber for applying a back pressure to the second vane to urge the second vane toward the second roller, the back-pressure chamber being constituted as a muffler chamber having a predetermined space volume. 
   In the present invention, since the back-pressure chamber constitutes the muffler chamber having a predetermined space volume, pressure pulsation generated by the urging operation of the second vane is reduced by the space volume, and it is possible to reduce pressure fluctuations of the discharge-side pressures of both the rotary compression elements, which are applied as the back pressure of the second vane. 
   Consequently, the follow-up property of the second vane is improved, the compression efficiency of the second rotary compression element is improved, and it is possible to avoid the generation of the collision sound between the second roller and the second vane as much as possible. 
   Furthermore, as described above, the multicylinder rotary compressor is usable by the switching of the first operation mode in which the first and second rotary compression elements perform the compression work and the second operation mode in which the only first rotary compression element substantially performs the compression work. The performance and reliability of the compressor can be enhanced. 
   Moreover, according to the present invention, there is provided a multicylinder rotary compressor in which a sealed container stores a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, the first and second rotary compression elements comprising: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders; and first and second vanes which abut on the first and second rollers to partition the inside of each cylinder into low and high-pressure chamber sides, the only first vane being urged toward the first roller by a spring member, the compressor further comprising: a back-pressure passage for applying a back pressure to the second vane, wherein a sectional area of the back-pressure passage is set to be not less than an average value of a surface area of the second vane exposed into the second cylinder. 
   In this invention, when the sectional area of the passage for the back pressure is set to be not less than the average value of the surface area of the second vane exposed into the second cylinder, a sufficient passage for the back pressure can be sufficiently secured. Pressure pulsation is reduced which is generated by an urging operation of the second vane, and pressure fluctuation of a refrigerant can be reduced. The refrigerant is applied as the back pressure of the second vane. 
   Consequently, a follow-up property of the second vane is improved, a compression efficiency of the second rotary compression element is improved, and it is possible to avoid generation of a collision sound between the second roller and the second vane as much as possible. 
   As described above, performance and reliability of the multicylinder rotary compressor can be enhanced. In the compressor, the only first vane is urged toward the first roller by the spring member. 
   Moreover, according to the present invention, there is provided a multicylinder rotary compressor in which a sealed container stores a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, the first and second rotary compression elements comprising: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders; and first and second vanes which abut on the first and second rollers to partition the inside of each cylinder into low and high-pressure chamber sides, the first vane being urged toward the first roller by a spring member, the compressor being configured to be used by switching of a first operation mode in which both the rotary compression elements perform the compression work and a second operation mode in which the only first rotary compression element substantially performs the compression work, the compressor further comprising: urging means for urging the second vane toward the second roller, wherein an urging force of the urging means is set to be not more than that in a case where a suction-side pressure of both the rotary compression elements or the first rotary compression element is applied as a back pressure of the second vane. 
   Furthermore, in the multicylinder rotary compressor of the present invention, in the above-described invention, the compressor further comprising: a valve device for controlling circulation of a refrigerant into the second cylinder, wherein the valve device allows the refrigerant to flow into the second cylinder, and an intermediate pressure is applied as a back pressure of the second vane, the intermediate pressure being between suction-side and discharge-side pressures of both the rotary compression elements, or the discharge-side pressures of both the rotary compression elements are applied in the first operation mode, and the valve device interrupts the flowing of the refrigerant into the second cylinder, and the suction-side pressures of both the rotary compression elements are applied as the back pressure of the second vane in the second operation mode. 
   Moreover, according to the present invention, there is provided a compression system comprising: a multicylinder rotary compressor in which a sealed container stores a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, the first and second rotary compression elements comprising: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders; and first and second vanes which abut on the first and second rollers to partition the inside of each cylinder into low and high-pressure chamber sides, the first vane being urged toward the first roller by a spring member, the compressor being configured to be used by switching of a first operation mode in which both the rotary compression elements perform a compression work and a second operation mode in which the only first rotary compression element substantially performs the compression work, the system further comprising: a valve device for controlling circulation of a refrigerant into the second cylinder; and urging means for urging the second vane toward the second roller, wherein an urging force of the urging means is set to be not more than that in a case where a suction-side pressure of both the rotary compression elements or the first rotary compression element is applied as a back pressure of the second vane, the valve device allows the refrigerant to flow into the second cylinder, and an intermediate pressure is applied as the back pressure of the second vane, the intermediate pressure being between suction-side and discharge-side pressures of both the rotary compression elements, or the discharge-side pressures of both the rotary compression elements are applied in the first operation mode, and the valve device interrupts the flowing of the refrigerant into the second cylinder, and the suction-side pressures of both the rotary compression elements are applied as the back pressure of the second vane in the second operation mode. 
   Furthermore, according to the present invention, there is provided a multicylinder rotary compressor in which a sealed container stores a driving element and first and second rotary compression elements driven by a rotation shaft of the driving element, the first and second rotary compression elements comprising: first and second cylinders; first and second rollers which are fitted into eccentric portions formed in the rotation shaft and which eccentrically rotate in the respective cylinders; and first and second vanes which abut on the first and second rollers to partition the inside of each cylinder into low and high-pressure chamber sides, the first vane being urged toward the first roller by a spring member, the compressor being configured to be used by switching of a first operation mode in which both the rotary compression elements perform a compression work and a second operation mode in which the only first rotary compression element substantially performs the compression work, the compressor further comprising: a weak spring for a tensile load on a side of the second vane opposite to a second roller side, wherein a tensile force of this weak spring is set to be not more than an urging force in a case where a suction-side pressure of both the rotary compression elements or the first rotary compression element is applied as a back pressure of the second vane. 
   According to this invention, for example, the urging means comprising the weak spring or the like can improve a follow-up property of the second vane in the first operation mode. Especially, in the first operation mode, the valve device allows the refrigerant to flow into the second cylinder, and the intermediate pressure is applied as the back pressure of the second vane, the intermediate pressure being between the suction-side and discharge-side pressures of both the rotary compression elements, or the discharge-side pressures of both the rotary compression elements are applied. In this case, the follow-up property of the second vane deteriorates by pressure pulsation of the intermediate pressure or the discharge-side pressure. This disadvantage can be avoided by the urging means beforehand. 
   Moreover, the urging force of the urging means is set to be not more than that in a case where the suction-side pressure of both the rotary compression elements or the first rotary compression element is applied as the back pressure of the second vane. In the second operation mode, the valve device interrupts the flowing of the refrigerant into the second cylinder, and the suction-side pressures of both the rotary compression elements are applied as the back pressure of the second vane. Consequently, by the pressure in the second cylinder, the urging force for urging the second vane on a back-pressure side can be set to be larger than the suction-side pressure for urging the second vane toward the second roller, and the urging force of the urging means. 
   Consequently, even when the urging means is disposed for urging the second vane toward the second roller, or an urging member is disposed in the second operation mode, the second vane of the multicylinder rotary compressor does not come into the second cylinder by the pressure in the second cylinder. Therefore, it is possible to avoid beforehand a disadvantage that the second vane collides with the second roller to generate a collision sound. 
   Furthermore, as described above, the multicylinder rotary compressor is configured to be used by the switching of the first operation mode in which the first and second rotary compression elements perform the compression work and the second operation mode in which the only first rotary compression element substantially performs the compression work. Performance and reliability of the compressor are enhanced, and performance of the compression system can be remarkably enhanced. 
   Additionally, the second vane does not come into the second cylinder by the tensile force of the weak spring in the second operation mode by the weak spring for the tensile load. Therefore, it is possible to avoid beforehand the disadvantage that the second vane collides with the second roller to generate the collision sound. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a vertically sectional side view of a multicylinder rotary compressor of a compression system according to an embodiment of the present invention; 
       FIG. 2  is another vertically sectional side view of the multicylinder rotary compressor of  FIG. 1 ; 
       FIG. 3  is a refrigerant circuit diagram of an air conditioner using the compression system of the embodiment of the present invention; 
       FIG. 4  is a diagram showing a switching operation from a second operation mode to a first operation mode of the multicylinder rotary compressor of  FIG. 1 ; 
       FIG. 5  is a vertically sectional side view of a multicylinder rotary compressor of a compression system according to Embodiment 2 of the present invention; 
       FIG. 6  is a diagram showing a switching operation from the first operation mode to the second operation mode of the multicylinder rotary compressor of  FIG. 5 ; 
       FIG. 7  is a diagram showing a switching operation from the second operation mode to the first operation mode of the multicylinder rotary compressor of  FIG. 5 ; 
       FIG. 8  is a vertically sectional side view of a multicylinder rotary compressor of a compression system according to Embodiment 3 of the present invention; 
       FIG. 9  is a diagram showing an operation of each electromagnetic valve in the second operation mode of a multicylinder rotary compressor of a compression system according to Embodiment 5 of the present invention; 
       FIG. 10  is a vertically sectional side view of a multicylinder rotary compressor according to Embodiment 7 of the present invention; 
       FIG. 11  is a flat sectional view of a second cylinder according to Embodiment 8 of the multicylinder rotary compressor; 
       FIG. 12  is a flat sectional view of the second cylinder in a case where the second roller of the second rotary compression element is positioned in a top dead center according to Embodiment 11 of the multicylinder rotary compressor of the present invention; 
       FIG. 13  is a flat sectional view of the second cylinder in a case where the second roller of the second rotary compression element is positioned in a bottom dead center according to Embodiment 11 of the multicylinder rotary compressor of the present invention; 
       FIG. 14  is a vertically sectional side view of a multicylinder rotary compressor according to Embodiment 14 of the present invention; 
       FIG. 15  is another vertically sectional side view of the multicylinder rotary compressor of  FIG. 14 ; 
       FIG. 16  is a flat sectional view of the second cylinder of a second rotary compression element of the multicylinder rotary compressor of  FIG. 14 ; 
       FIG. 17  is a refrigerant circuit diagram of an air conditioner using a compression system of Embodiment 14; 
       FIG. 18  is a diagram showing a flow of a refrigerant in a first operation mode of the multicylinder rotary compressor of Embodiment 14; 
       FIG. 19  is a diagram showing a flow of a refrigerant in a second operation mode of the multicylinder rotary compressor of Embodiment 14; 
       FIG. 20  is a diagram showing a flow of a refrigerant in the first operation mode of a multicylinder rotary compressor of another embodiment; 
       FIG. 21  is a vertically sectional side view of a multicylinder rotary compressor according to Embodiment 15 of the present invention; 
       FIG. 22  is another vertically sectional side view of the multicylinder rotary compressor of  FIG. 21 ; 
       FIG. 23  is an enlarged view of a weak spring of a second rotary compression element in the multicylinder rotary compressor of  FIG. 21 ; 
       FIG. 24  is an enlarged view of a weak spring of a second rotary compression element according to another embodiment of the multicylinder rotary compressor of  FIG. 23 ; and 
       FIG. 25  is an enlarged view of a weak spring of a second rotary compression element according to another embodiment of the multicylinder rotary compressor of  FIG. 23 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Embodiments of the present invention will be described hereinafter in detail. 
   Embodiment 1 
     FIG. 1  is a vertically sectional side view of an inner high pressure type rotary compressor  10  comprising first and second rotary compression elements according to an embodiment of a multicylinder rotary compressor of a compression system CS of the present invention, and  FIG. 2  is a vertically sectional side view (showing a section different from that of  FIG. 1 ) of the rotary compressor  10  of  FIG. 1 . It is to be noted that the compression system CS of the present embodiment constitutes a part of a refrigerant circuit of an air conditioner which is a refrigeration apparatus for conditioning air in a room. 
   In each figure, the rotary compressor  10  of the embodiment is an inner high pressure type rotary compressor. In a vertically cylindrical sealed container  12  formed of a steel plate, elements are stored: an electromotive element  14  which is a driving element disposed in an upper part of an inner space of this sealed container  12 ; and a rotary compression mechanism section  18  which is disposed under the electromotive element  14  and which is constituted of first and second rotary compression elements  32 ,  34  driven by a rotation shaft  16  of the electromotive element  14 . 
   A bottom part of the sealed container  12  is an oil reservoir, and the container comprises a container main body  12 A which houses the electromotive element  14  and the rotary compression mechanism section  18 ; and a substantially bowl-shaped end cap (lid body)  12 B which closes an upper opening of the container main body  12 A. A circular attaching hole  12 D is formed in the upper surface of the end cap  12 B, and a terminal (wiring is omitted)  20  for supplying a power to the electromotive element  14  is attached to this attaching hole  12 D. 
   Moreover, a refrigerant discharge tube  96  described later is attached to the end cap  12 B, and one end of the refrigerant introducing tube  96  communicates with the inside of the sealed container  12 . Moreover, an attaching base  11  is disposed in a bottom part of the sealed container  12 . 
   The electromotive element  14  comprises: a stator  22  annularly welded/fixed along an inner peripheral surface of an upper space of the sealed container  12 ; and a rotor  24  inserted/disposed with a slight interval inside the stator  22 . This rotor  24  is fixed to the rotation shaft  16  which passes through a center and extends in a vertical direction. 
   The stator  22  has: a laminated member  26  in which donut-shaped electromagnetic steel plates are stacked; and a stator coil  28  which is wound around a tooth portion of the laminated member  26  by a direct winding (concentrated winding) system. The rotor  24  is also formed by a laminate member  30  of electromagnetic steel plates in the same manner as in the stator  22 . 
   An intermediate partition plate  36  is held between the first and second rotary compression elements  32 ,  34 . That is, the first and second rotary compression elements  32 ,  34  comprise: the intermediate partition plate  36 ; first and second cylinders  38 ,  40  disposed on/under the intermediate partition plate  36 ; first and second rollers  46 ,  48  which are fitted into upper and lower eccentric portions  42 ,  44  disposed in the rotation shaft  16  with a phase difference of 180 degrees in the first and second cylinders  38 ,  40  and which eccentrically rotate in the respective cylinders  38 ,  40 , respectively; first and second vanes  50 ,  52  which abut on the first and second rollers  46 ,  48  to partition the insides of the respective cylinders  38 ,  40  into low-pressure and high-pressure chamber sides; and upper and lower support members  54 ,  56  which close an upper opening face of the first cylinder  38  and a lower opening face of the second cylinder  40  and which also function as bearings of the rotation shaft  16 . 
   The first and second cylinders  38 ,  40  are provided with suction passages  58 ,  60  which communicate with the insides of the first and second cylinders  38 ,  40 , and the suction passages  58 ,  60  are connected to refrigerant introducing tubes  92 ,  94  described later. 
   Moreover, a discharge muffling chamber  62  is disposed on the upper support member  54 , and a refrigerant gas compressed by the first rotary compression element  32  is discharged to the discharge muffling chamber  62 . This discharge muffling chamber  62  is formed in a substantially bowl-shaped cup member  63  having in its center a hole for passing through the rotation shaft  16  and the upper support member  54  which also functions as the bearing of the rotation shaft  16 . The member covers an electromotive element  14  side (upper side) of the upper support member  54 . Moreover, the electromotive element  14  is disposed above the cup member  63  with a predetermined interval from the cup member  63 . 
   A discharge muffling chamber  64  is disposed in the lower support member  56 . The chamber is formed by closing of a depressed portion formed in a lower part of the lower support member  56  by a cover which is a wall. That is, the discharge muffling chamber  64  is closed by a lower cover  68  which defines the discharge muffling chamber  64 . 
   A guide groove  70  is formed in the first cylinder  38 , and the above-described first vane  50  is stored in the groove. A housing section  70 A is formed outside the guide groove  70 , that is, in a back surface of the first vane  50 , and the section houses a spring  74  which is a spring member. The spring  74  abuts on a back-surface end portion of the first vane  50  to urge the first vane  50  constantly on the side of the first roller  46 . A discharge-side pressure (high-pressure) described later is also introduced, for example, from the sealed container  12  into the housing section  70 A, and is applied as the back pressure of the first vane  50 . Moreover, the housing section  70 A opens on the sides of the guide groove  70  and sealed container  12  (container main body  12 A), a plug  137  formed of a metal is disposed on the sealed container  12  side of the spring  74  housed in the housing section  70 A, and the plug prevents the spring  74  from coming off. 
   Moreover, a guide groove  72  is formed in the second cylinder  40  to house the second vane  52 , and a back-pressure chamber  72 A is formed outside the guide groove  72 , that is, on a back-surface side of the second vane  52 . The back-pressure chamber  72 A opens on the sides of the guide groove  72  and the sealed container  12 , an opening on the sealed container  12  side communicates with a pipe  75  described later, and the opening is sealed together with the inside of the sealed container  12 . 
   On the side surface of the container main body  12 A of the sealed container  12 , sleeves  141  and  142  are welded/fixed to positions corresponding to the suction passages  58 ,  60  of the first and second cylinders  38 ,  40 . These sleeves  141  and  142  are vertically adjacent to each other. 
   Moreover, one end of the refrigerant introducing tube  92  for introducing a refrigerant gas into the first cylinder  38  is inserted/connected into the sleeve  141 , and one end of the refrigerant introducing tube  92  communicates with the suction passage  58  of the upper cylinder  38 . The other end of the refrigerant introducing tube  92  opens in an accumulator  146 . 
   One end of the refrigerant introducing tube  94  for introducing the refrigerant gas into the second cylinder  40  is Inserted/connected into the sleeve  142 , and one end of the refrigerant introducing tube  94  communicates with the suction passage  60  of the second cylinder  40 . The other end of the refrigerant introducing tube  94  opens in the accumulator  146  in the same manner as in the refrigerant introducing tube  92 . 
   The accumulator  146  is a tank which separates a gas/liquid of a sucked refrigerant, and is attached to the upper side surface of the container main body  12 A of the sealed container  12  via a bracket  147 . Moreover, the refrigerant introducing tubes  92 ,  94  are inserted into the accumulator  146  from its bottom portion, and other end openings are positioned in an upper part of the accumulator  146 . One end of a refrigerant pipe  100  is inserted into the upper part of the accumulator  146 . 
   It is to be noted that the discharge muffling chamber  64  communicates with the discharge muffling chamber  62  via the upper and lower support members  54 ,  56 , the first and second cylinders  38 ,  40 , or a communication path  120  extending through the intermediate partition plate  36  in an axial center direction (vertical direction). Moreover, the refrigerant gas is compressed by the second rotary compression element  34 , and discharged to the discharge muffling chamber  64 , and this gas having high-temperature/pressure is then discharged to the discharge muffling chamber  62  via the communication path  120 . The gas flows with respect to a high-temperature/pressure refrigerant gas compressed by the first rotary compression element  32 . 
   Moreover, the discharge muffling chamber  62  communicates with the inside of the sealed container  12  via a hole (not shown) which extends through the cup member  63 . Through this hole, the high-pressure refrigerant gas is discharged into the sealed container  12 . The gas has been compressed by the first and second rotary compression elements  32  and  34 , and discharged to the discharge muffling chamber  62 . 
   Here, a refrigerant pipe  101  is connected to a middle portion of the refrigerant pipe  100 , and the pipe is connected to the pipe  75  via an electromagnetic valve  105 . A refrigerant pipe  102  also communicates with/is connected to a middle portion of the refrigerant discharge tube  96 , and the pipe is connected to the pipe  75  via an electromagnetic valve  106  in the same manner as in the refrigerant pipe  101 . These electromagnetic valves  105 ,  106  are controlled in such a manner as to open/close by a controller  210  described later. That is, when the controller  210  opens the valve device  105 , and closes the valve device  106 , the refrigerant pipe  101  communicates with the pipe  75 . Accordingly, after flowing through the refrigerant pipe  100  into the accumulator  146 , a part of the refrigerant on a suction side of both the rotary compression elements  32 ,  34  enters the refrigerant pipe  101 , and flows into the back-pressure chamber  72 A from the pipe  75 . Accordingly, suction-side pressures of both the rotary compression elements  32 ,  34  are applied as a back pressure of the second vane  52 . 
   Moreover, when the controller  210  closes the valve device  105 , and opens the valve device  106 , the refrigerant discharge tube  96  communicates with the pipe  75 . Accordingly, after being discharged from the sealed container  12  and passed through the refrigerant discharge tube  96 , a part of the refrigerant on a discharge side of both the rotary compression elements  32 ,  34  flows into the back-pressure chamber  72 A from the pipe  75  via the refrigerant pipe  102 . Accordingly, discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . 
   Here, the controller  210  constitutes a part of the compression system CS of the present invention, and controls a rotation number of the electromotive element  14  of the rotary compressor  10 . As described above, the controller also controls the opening/closing of the electromagnetic valve  105  of the refrigerant pipe  101 , and the electromagnetic valve  106  of the refrigerant pipe  102 . 
   Next,  FIG. 3  shows a refrigerant circuit diagram of the air conditioner constituted using the compression system CS. That is, the compression system CS of the embodiment constitutes a part of the refrigerant circuit of the air conditioner shown in  FIG. 3 , and comprises the rotary compressor  10 , the controller  210  and the like. The refrigerant discharge tube  96  of the rotary compressor  10  is connected to an inlet of an outdoor heat exchanger  152 . The controller  210 , rotary compressor  10 , and outdoor heat exchanger  152  are disposed in an outdoor unit (not shown) of the air conditioner. A pipe connected to an outlet of the outdoor heat exchanger  152  is connected to an expansion valve  154  which is pressure reducing means, and a pipe extending out of the expansion valve  154  is connected to an indoor heat exchanger  156 . These expansion valve  154  and indoor heat exchanger  156  are disposed in an indoor unit (not shown) of the air conditioner. The refrigerant pipe  100  of the rotary compressor  10  is connected to an outlet of the indoor heat exchanger  156 . 
   It is to be noted that an HFC or HC-based refrigerant is used as the refrigerant. As oils which are lubricants, existing oils are used such as a mineral oil, an alkyl benzene oil, an ether oil, and an ester oil. 
   Next, an operation of the rotary compressor  10  constituted as described above will be described. 
   (1) First Operation Mode (Operation at Usual or High Load Time) 
   First, a first operation mode will be described in which both the rotary compression elements  32 ,  34  perform a compression work. The controller  210  controls a rotation number of the electromotive element  14  of the rotary compressor  10  based on an operation instruction input of an indoor-unit-side controller (not shown) disposed in the indoor unit. In a usual or high load indoor state, the controller  210  executes the first operation mode. In this first operation mode, the controller  210  closes the electromagnetic valve  105  of the refrigerant pipe  101  and the electromagnetic valve  106  of the refrigerant pipe  102 . 
   Moreover, when the stator coil  28  of the electromotive element  14  is energized via a terminal  20  and wiring (not shown), the electromotive element  14  starts, and the rotor  24  rotates. By this rotation, the first and second rollers  46 ,  48  are fitted into the upper and lower eccentric portions  42 ,  44  integrally disposed in the rotation shaft  16 , and eccentrically rotate in the first and second cylinders  38 ,  40 . 
   Accordingly, the low-pressure refrigerant flows into the accumulator  146  from the refrigerant pipe  100  of the rotary compressor  10 . Since the electromagnetic valve  105  of the refrigerant pipe  100  is closed as described above, all the refrigerant passed through the refrigerant pipe  100  flows into the accumulator  146  without flowing into the pipe  75 . 
   Moreover, the low-pressure refrigerant which has flown into the accumulator  146  is separated into gas/liquid, and thereafter the only refrigerant gas enters the respective refrigerant discharge tubes  92 ,  94  which open in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  is passed through the suction passage  58 , and sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and the first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas is passed through a discharge port (not shown) from the high-pressure chamber side of the first cylinder  38 , and is discharged to the discharge muffling chamber  62 . 
   On the other hand, the low-pressure refrigerant gas which has flown into the refrigerant introducing tube  94  is passed through the suction passage  60 , and sucked on the low-pressure chamber side of the second cylinder  40  of the second rotary compression element  34 . The refrigerant gas sucked on the low-pressure chamber side of the second cylinder  40  is compressed by the operations of the second roller  48  and the second vane  52 . 
   At this time, since the electromagnetic valves  105 ,  106  are closed as described above, a closed space is formed in the pipe  75  connected to the back-pressure chamber  72 A of the second vane  52 . Furthermore, since not a little refrigerant in the second cylinder  40  flows into the back-pressure chamber  72 A between the second vane  52  and the housing section  70 A, a pressure in the back-pressure chamber  72 A of the second vane  52  is an intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 , and the intermediate pressure is applied as the back pressure of the second vane  52 . By this intermediate pressure, the second vane  52  can be sufficiently urged toward the second roller  48  without using any spring member. 
   Moreover, a high pressure which is the discharge-side pressure of both the rotary compression elements  32 ,  34  has heretofore been applied as the back pressure of the second vane  52 . However, in this case, since the discharge-side pressure has large pulsation, and any spring member is not disposed, a follow-up property of the second vane  52  is deteriorated by the pulsation, a compression efficiency drops, and a problem has occurred that a collision sound is generated between the second vane  52  and the second roller  48 . 
   However, by the application of the intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34  as the back pressure of the second vane  52 , the pressure pulsation is remarkably reduced as compared with a case where the discharge-side pressure is applied as described above. Especially in the present embodiment, the electromagnetic valves  105 ,  106  are closed to interrupt the flowing of the suction-side and discharge-side refrigerants of both the rotary compression elements  32 ,  34  from the pipe  75 . Therefore, pulsation of the back pressure of the second vane  52  can be further suppressed. Accordingly, the follow-up property of the second vane  52  is improved in the first operation mode, and the compression efficiency of the second rotary compression element  34  is enhanced. 
   It is to be noted that the refrigerant gas is compressed by the operations of the second roller  48  and second vane  52  to obtain a high-temperature/pressure. The gas is passed through a discharge port (not shown) from the high-pressure chamber side of the second cylinder  40 , and is discharged to the discharge muffling chamber  64 . The refrigerant gas discharged to the discharge muffling chamber  64  is discharged to the discharge muffling chamber  62  via the communication path  120 , and flows together with the refrigerant gas compressed by the first rotary compression element  32 . Moreover, the joined refrigerant gas is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . In the exchanger, the refrigerant gas emits heat, pressure of the gas is reduced by the expansion valve  154 , and thereafter the gas flows into the indoor heat exchanger  156 . In the exchanger, the refrigerant evaporates, heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   (2) Second Operation Mode (Operation at Light Load Time) 
   Next, a second operation mode will be described. In a case where the inside of the room has a state in which a load is light, the controller  210  shifts to the second operation mode. In this second operation mode, the only first rotary compression element  32  substantially performs a compression work. The operation mode is performed in a case where the inside of the room has a light load and the electromotive element  14  rotates at a low speed in the first operation mode. When the only first rotary compression element  32  substantially performs the compression work in a small capacity region of the compression system CS, an amount of the refrigerant gas to be compressed can be reduced as compared with a case where the first and second cylinders  38 ,  40  perform the compression work. Therefore, the rotation number of the electromotive element  14  is raised also at the light load time by the corresponding amount, the operation efficiency of the electromotive element  14  is improved, and a leak loss of the refrigerant can be reduced. 
   In this case, the controller  210  opens the electromagnetic valve  105  of the refrigerant pipe  101 , and closes the electromagnetic valve  106  of the refrigerant pipe  102 . Accordingly, the refrigerant pipe  101  communicates with the pipe  75 , a suction-side refrigerant of the first rotary compression element  32  flows into the back-pressure chamber  72 A, and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   On the other hand, the controller  210  energizes the stator coil  28  of the electromotive element  14  via the terminal  20  and the wiring (not shown), and rotates the rotor  24  of the electromotive element  14  as described above. By this rotation, the first and second rollers  46 ,  48  are fitted into the upper and lower eccentric portions  42 ,  44  disposed integrally with the rotation shaft  16 , and eccentrically rotate in the first and second cylinders  38 ,  40 . 
   Accordingly, the low-pressure refrigerant flows into the accumulator  146  from the refrigerant pipe  100  of the rotary compressor  10 . Since the electromagnetic valve  105  of the refrigerant pipe  101  opens at this time as described above, a part of the refrigerant on the suction side of the first rotary compression element  32  passes through the refrigerant pipe  100 , and flows into the back-pressure chamber  72 A from the refrigerant pipe  101  via the pipe  75 . Accordingly, the back-pressure chamber  72 A has a suction-side pressure of the first rotary compression element  32 , and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   Here, the suction-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second rotary compression element  34 , and this pressure is a low pressure. Therefore, the second vane  52  cannot be urged toward the second roller  48 . Therefore, the compression work is not substantially performed in the second rotary compression element  34 , and the compression work of the refrigerant is performed only by the first rotary compression element  32  provided with the spring  74 . 
   On the other hand, the low-pressure refrigerant which has flown into the accumulator  146  is separated into gas/liquid, and thereafter the refrigerant gas only enters the refrigerant discharge tube  92  which opens in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  flows through the suction passage  58 , and is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and the first vane  50  to constitute a high-temperature/pressure refrigerant gas, and the gas is discharged to the discharge muffling chamber  62  from the high-pressure chamber side of the first cylinder  38  through a discharge port (not shown). At this time, since the discharge muffling chamber  62  functions as an expanded type muffling chamber, and the discharge muffling chamber  64  functions as a resonant type muffling chamber in the second operation mode, it is further possible to reduce pressure pulsation of the refrigerant compressed by the first rotary compression element  32 . Consequently, a muffling effect can be substantially further enhanced in the second operation mode in which the only first rotary compression element  32  performs the compression work. 
   The refrigerant gas discharged to the discharge muffling chamber  62  is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . There, the refrigerant gas emits heat. After the pressure of the gas is reduced by the expansion valve  154 , the gas flows into the indoor heat exchanger  156 . The refrigerant evaporates in the indoor heat exchanger  156 , the heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   (3) Switching from Second Operation Mode to First Operation Mode 
   On the other hand, when the above-described light load state turns to a usual load or high load state in the room, the controller  210  shifts from the second operation mode to the first operation mode. Here, an operation will be described in switching the second operation mode to the first operation mode with reference to  FIG. 4 . In this case, the controller  210  rotates the electromotive element  14  at a low speed (rotation number of 50 Hz or less), and controls a compression ratio of both the rotary compression elements  32 ,  34  into 3.0 or less. The controller  210  closes the electromagnetic valve  105  of the refrigerant pipe  101 , and opens the electromagnetic valve  106  of the refrigerant pipe  102  ( FIG. 4  (2)). 
   Accordingly, the refrigerant pipe  102  communicates with the pipe  75 , discharge-side refrigerants of both the rotary compression elements  32 ,  34  flow into the back-pressure chamber  72 A, and the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . 
   When the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 , the back-pressure chamber  72 A of the second vane  52  has a pressure which is remarkably higher than that inside the second cylinder  40 . Therefore, the second vane  52  is pushed toward the second roller  48  to follow up the roller by the high pressure of the back-pressure chamber  72 A. 
   Here, when the discharge-side pressures of both the rotary compression elements are applied as the back pressure of the second vane  52  at a switching time, the second vane  52  can be sufficiently pushed out on the side of the second roller  48 . That is, when the second operation mode shifts to the first operation mode, the intermediate pressure is applied as the back pressure of the second vane  52  as in the above-described usual operation time in the first operation mode. The intermediate pressure is between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 . At this intermediate pressure, a pressure difference is small between the inside of the second cylinder  40  and the back-pressure chamber  72 A. Therefore, much time is required for the second vane  52  to follow up the second roller  48 . During this time, a disadvantage has occurred that the second vane  52  collides with the second roller  48 , and the collision sound is generated. 
   However, in the present invention, the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52  at the switching time from the second operation mode to the first operation mode. Accordingly, the second vane  52  is sufficiently urged toward the second roller  48  by the discharge-side pressure, and the second roller  48  can follow up in an early stage. 
   Consequently, at the switching time from the second operation mode to the first operation mode, the follow-up property of the second vane  52  is improved,-the operation efficiency is improved, and it is possible to avoid the generation of the collision sound of the second vane  52 . 
   Moreover, at the switching time, the controller  210  rotates the electromotive element  14  at a low speed (rotation number of 50 Hz or less), and controls the compression ratio of both the rotary compression elements  32 ,  34  into 3.0 or less. Accordingly, since a pressure fluctuation can be suppressed, an influence is not easily exerted by the pressure fluctuation even in a case where the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second rotary compression element  34 . 
   It is to be noted that the controller  210  applies the discharge-side pressures of both the rotary compression elements  32 ,  34  to the second vane  52 . After the second vane  52  follows up the second roller  48 , the controller applies the intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34  ( FIG. 4  (3)). Accordingly, the pressure fluctuation is remarkably reduced as compared with the application of the discharge-side pressures of both the rotary compression elements  32 ,  34  to the back pressure of the second vane  52  as described above. Therefore, in the rotary compressor  10  after the switching of the operation mode, the follow-up property of the second vane  52  is improved, the compression efficiency of the second rotary compression element  34  is improved, and it is possible to avoid beforehand the generation of the collision sound between the second vane  52  and the second roller  48  in the first operation mode. 
   As described above in detail, according to the present invention, the performance and reliability of the compression system CS can be enhanced. The system comprises the rotary compressor  10  which is usable by the switching of the first operation mode in which the first and second rotary compression elements  32 ,  34  perform the compression work and the second operation mode in which the only first rotary compression element  32  substantially performs the compression work. 
   Consequently, when the refrigerant circuit of the air conditioner is constituted using the compression system CS, the operation efficiency and performance of the air conditioner are enhanced, and power consumption can be reduced. 
   Embodiment 2 
   Next, another embodiment of a compression system CS of the present invention will be described.  FIG. 5  shows a vertically sectional side view of an inner high pressure type rotary compressor  110  comprising first and second rotary compression elements, which is a multicylinder rotary compressor of the compression system CS in this embodiment. It is to be noted that, in  FIG. 5 , when components are denoted with the same reference numerals as those of  FIGS. 1 to 4 , the components produce the same or similar effects. 
   In  FIG. 5 , reference numeral  200  denotes a valve device, and the device is disposed in a middle portion of a refrigerant introducing tube  94  on an inlet side of the sealed container  12  on an outlet side of an accumulator  146 . This electromagnetic valve  200  is a valve device for controlling flowing of a refrigerant into a second cylinder  40 , and is controlled by the above-described controller  210  which is a control device. 
   It is to be noted that in the present embodiment, an HFC or HC-based refrigerant is used as a refrigerant in the same manner as in the above-described embodiment. As oils which are lubricants, existing oils are used such as a mineral oil, an alkyl benzene oil, an ether oil, and an ester oil. 
   Next, an operation of the rotary compressor  110  constituted as described above will be described. 
   (1) First Operation Mode (Operation at Usual or High Load Time) 
   First, a first operation mode will be described in which both rotary compression elements  32 ,  34  perform a compression work. The controller  210  controls a rotation number of an electromotive element  14  of the rotary compressor  110  based on an operation instruction input of an indoor-unit-side controller (not shown) disposed in the above-described indoor unit. Moreover, in a usual or high load indoor state, the controller  210  executes the first operation mode. In this first operation mode, the controller  210  opens the electromagnetic valve  200  of the refrigerant introducing pipe  94 , and closes an electromagnetic valve  105  of a refrigerant pipe  101 , and an electromagnetic valve  106  of a refrigerant pipe  102 . 
   Moreover, when a stator coil  28  of the electromotive element  14  is energized via a terminal  20  and wiring (not shown), the electromotive element  14  starts, and a rotor  24  rotates. By this rotation, first and second rollers  46 ,  48  are fitted into upper and lower eccentric portions  42 ,  44  integrally disposed in a rotation shaft  16 , and eccentrically rotate in first and second cylinders  38 ,  40 . 
   Accordingly, a low-pressure refrigerant flows into the accumulator  146  from a refrigerant pipe  100  of the rotary compressor  110 . Since the electromagnetic valve  105  of the refrigerant pipe  100  is closed as described above, all the refrigerant passed through the refrigerant pipe  100  flows into the accumulator  146  without flowing into a pipe  75 . 
   Moreover, the low-pressure refrigerant which has flown into the accumulator  146  is separated into gas/liquid, and thereafter the only refrigerant gas enters refrigerant discharge tubes  92 ,  94  which open in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  is passed through a suction passage  58 , and sucked on a low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of a first roller  46  and a first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas flows through a discharge port (not shown) from the high-pressure chamber side of the first cylinder  38 , and is discharged to a discharge muffling chamber  62 . 
   On the other hand, the low-pressure refrigerant gas which has flown into the refrigerant introducing tube  94  is passed through a suction passage  60 , and sucked on the low-pressure chamber side of the second cylinder  40  of the second rotary compression element  34 . The refrigerant gas sucked on the low-pressure chamber side of the second cylinder  40  is compressed by the operations of the second roller  48  and a second vane  52 . 
   At this time, since the electromagnetic valves  105 ,  106  are closed as described above, a closed space is formed in the pipe  75  connected to a back-pressure chamber  72 A of the second vane  52 . Furthermore, since not a little refrigerant in the second cylinder  40  flows into the back-pressure chamber  72 A between the second vane  52  and a housing section  70 A, a pressure in the back-pressure chamber  72 A of the second vane  52  is an intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 , and the intermediate pressure is applied as the back pressure of the second vane  52 . By this intermediate pressure, the second vane  52  can be sufficiently urged toward the second roller  48  without using any spring member. 
   Consequently, the follow-up property of the second vane  52  is improved in the first operation mode, and the compression efficiency of the second rotary compression element  34  can be enhanced in the same manner as in the above-described embodiment. 
   It is to be noted that the refrigerant gas is compressed by the operations of the second roller  48  and second vane  52  to obtain a high-temperature/pressure. The gas is passed through a discharge port (not shown) from the high-pressure chamber side of the second cylinder  40 , and is discharged to the discharge muffling chamber  64 . The refrigerant gas discharged to the discharge muffling chamber  64  is discharged to the discharge muffling chamber  62  via the communication path  120 , and flows together with the refrigerant gas compressed by the first rotary compression element  32 . Moreover, the joined refrigerant gas is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . In the exchanger, the refrigerant gas emits heat, pressure of the gas is reduced by an expansion valve  154 , and thereafter the gas flows into an indoor heat exchanger  156 . In the indoor heat exchanger  156 , the refrigerant evaporates, the heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  110 . The refrigerant repeats this cycle. 
   (2) Switching from First Operation Mode to Second Operation Mode 
   Next, when the above-described usual or high load state turns to a light load state in the room, the controller  210  shifts to a second operation mode from the first operation mode. 
   Here, a switching operation will be described from the first operation mode to the second operation mode with reference to  FIG. 6 . It is to be noted that at a mode switching time, the controller  210  rotates the electromotive element  14  at a low speed, a rotation number is set, for example, to 50 Hz or less, and a compression ratio of the rotary compression element  32  is controlled into 3.0 or less. 
   First, the controller  210  closes the above-described electromagnetic valve  200 , and interrupts the flowing of the refrigerant into the second cylinder  40  ( FIG. 6  (2)). Accordingly, any compression work is not performed in the second rotary compression element  34 . When the refrigerant is inhibited from being passed into the second cylinder  40 , a pressure in the second cylinder  40  is slightly higher than a suction-side pressure of both the rotary compression elements  32 ,  34  (the second roller  48  rotates, a high pressure in the sealed container  12  slightly flows from a gap of the second cylinder  40  or the like, and therefore the pressure in the second cylinder  40  becomes slightly higher than the suction-side pressure). 
   It is to be noted that in the first operation mode, the pressure in the back-pressure chamber  72 A is an intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34  as described above. Therefore, the pressure in the second cylinder  40  is substantially equal to that in the back-pressure chamber  72 A of the second vane  52 . 
   Moreover, the controller  210  opens the electromagnetic valve  105  of the refrigerant pipe  101 . It is to be noted that the electromagnetic valve  106  of the refrigerant pipe  102  remains to be closed ( FIG. 6  (3)). Accordingly, the refrigerant pipe  101  communicates with the pipe  75 , the suction-side refrigerant of the first rotary compression element  32  flows into the back-pressure chamber  72 A, and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   Accordingly, the refrigerant passes through the refrigerant pipe  100  on the suction side of the first rotary compression element  32 , and a part of the refrigerant flows into the back-pressure chamber  72 A from the refrigerant pipe  101  via the pipe  75 . Accordingly, the back-pressure chamber  72 A has a suction-side pressure of the first rotary compression element  32 , and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   As described above, the pressure of the second cylinder  40  is higher than the suction-side pressure of the first rotary compression element  32 . Therefore, when the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 , the pressure in the back-pressure chamber  72 A of the second vane  52  is higher than that of the second cylinder  40 . Therefore, the second vane  52  is pushed toward the back-pressure chamber  72 A on a side opposite to the second roller  48  by the pressure in the second cylinder  40 , and housed in the guide groove  72 . Consequently, at the switching time to the second operation mode, the second vane  52  can be retracted from the inside of the second cylinder  40 , and housed in the guide groove  72  in an early stage. Therefore, it is possible to avoid beforehand a disadvantage that the second vane  52  collides with the second roller  48 , and the collision sound is generated. 
   (3) Second Operation Mode 
   Next, an operation of the rotary compressor  110  will be described in a second operation mode. The low-pressure refrigerant flows into the accumulator  146  from the refrigerant pipe  100  of the rotary compressor  110 . After the refrigerant is separated into the gas/liquid in the accumulator, the only refrigerant gas enters the refrigerant discharge tube  92  which opens in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  flows through the suction passage  58 , and is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and the first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas is discharged to the discharge muffling chamber  62  from the high-pressure chamber side of the first cylinder  38  through a discharge port (not shown). The refrigerant gas discharged to the discharge muffling chamber  62  is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . In the exchanger, the refrigerant gas emits heat. After the pressure of the gas is reduced by the expansion valve  154 , the gas flows into the indoor heat exchanger  156 . In the exchanger, the refrigerant evaporates. At this time, the heat is absorbed from air circulated in the room to exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked into the rotary compressor  110 , and this cycle is repeated. 
   It is to be noted that in the second operation mode, the controller  210  closes the above-described electromagnetic valve  200 . The operation is performed while stopping the flowing of the refrigerant into the second cylinder  40 . Accordingly, in the second operation mode, the pressure in the second cylinder  40  is kept to be higher than the back pressure of the second vane  52 . Therefore, the second vane  52  is pushed toward the back-pressure chamber  72 A opposite to the second roller  48  by the pressure in the second cylinder  40 , and the vane does not come into the second cylinder  40 . Consequently, it is possible to avoid beforehand a disadvantage that the second vane  52  comes into the second cylinder  40  during the operation in the second operation mode, the vane collides with the second roller  48 , and the collision sound is generated. 
   (4) Switching from Second Operation Mode to First Operation Mode 
   On the other hand, when the above-described light load state turns to a usual or high load state in the room, the controller  210  shifts from the second operation mode to the first operation mode. Here, an operation will be described in switching the second operation mode to the first operation mode with reference to  FIG. 7 . In this case, the controller  210  opens the electromagnetic valve  200  and allows the refrigerant to flow into the second cylinder  40 . Moreover, the controller closes the electromagnetic valve  105  of the refrigerant pipe  101 , and opens the electromagnetic valve  106  of the refrigerant pipe  102  ( FIG. 7  (2)). 
   Accordingly, the refrigerant pipe  102  communicates with the pipe  75 , discharge-side refrigerants of both the rotary compression elements  32 ,  34  flow into the back-pressure chamber  72 A, and the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . 
   When the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 , the back-pressure chamber of the second vane  52  has a pressure which is remarkably higher than that inside the second cylinder  40 . Therefore, the second vane  52  is pushed toward the second roller  48  to follow up the roller by the high pressure of the back-pressure chamber  72 A. 
   Here, when the discharge-side pressures of both the rotary compression elements are applied as the back pressure of the second vane  52  at a switching time, the second vane  52  can be sufficiently pushed out on the side of the second roller. That is, when the second operation mode shifts to the first operation mode, the intermediate pressure is applied as the back pressure of the second vane  52  as in the above-described usual operation time in the first operation mode. The intermediate pressure is between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 . At this intermediate pressure, a pressure difference is small between the inside of the second cylinder  40  and the back-pressure chamber  72 A. Therefore, much time is required for the second vane  52  to follow up the second roller  48 . During this time, a disadvantage has occurred that the second vane  52  collides with the second roller  48 , and the collision sound is generated. 
   However, in the present invention, the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52  at the switching time from the second operation mode to the first operation mode. Accordingly, the second vane  52  is sufficiently urged toward the second roller  48  by the discharge-side pressure, and the second roller  48  can follow up in an early stage. 
   Consequently, at the switching time from the second operation mode to the first operation mode, the follow-up property of the second vane  52  is improved, the operation efficiency is improved, and it is possible to avoid the generation of the collision sound of the second vane  52 . 
   Moreover, at the switching time, the controller  210  rotates the electromotive element  14  at a low speed (rotation number of 50 Hz or less), and controls the compression ratio of both the rotary compression elements  32 ,  34  into 3.0 or less. Accordingly, since a pressure fluctuation can be suppressed, an influence is not easily exerted by the pressure fluctuation even in a case where the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second rotary compression element  34 . 
   It is to be noted that the controller  210  applies the discharge-side pressures of both the rotary compression elements  32 ,  34  to the second vane  52 . After the second vane  52  follows up the second roller  48 , the controller closes the electromagnetic valve  106  ( FIG. 7  (3)), and applies the intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 . Accordingly, the pressure fluctuation is remarkably reduced as compared with the application of the discharge-side pressures of both the rotary compression elements  32 ,  34  to the back pressure of the second vane  52  as described above. Therefore, in the rotary compressor  110  after the switching of the operation mode, the follow-up property of the second vane  52  Is improved, the compression efficiency of the second rotary compression element  34  is improved, and it is possible to avoid beforehand the generation of the collision sound between the second vane  52  and the second roller  48  in the first operation mode. 
   As described above in detail, also in the present embodiment, the performance and reliability of the compression system CS can be enhanced. The system comprises the rotary compressor  110  which is usable by the switching of the first operation mode in which the first and second rotary compression elements  32 ,  34  perform the compression work and the second operation mode in which the only first rotary compression element  32  substantially performs the compression work. 
   Consequently, when the refrigerant circuit of the air conditioner is constituted using the compression system CS, the operation efficiency and performance of the air conditioner are enhanced, and power consumption can be reduced. 
   Embodiment 3 
   It has been described in the above-described embodiments that an HFC or HC-based refrigerant is used as a refrigerant, but a refrigerant having a large high/low pressure difference may be used such as carbon dioxide. For example, a combination of carbon dioxide and polyalkyl glycol (PAG) may be used as the refrigerant. In this case, since the refrigerant compressed by rotary compression elements  32  and  34  has a very high pressure, there is a possibility that a cup member  63  is broken by the high pressure in a case where a discharge muffling chamber  62  is formed into a shape to cover an upper support member  54  with the cup member  63  as in the respective embodiments. 
   Therefore, when the discharge muffling chamber is formed into a shape shown in  FIG. 8 , resistance to pressure can be secured. The chamber is above the upper support member  54  in which refrigerants compressed by both the rotary compression elements  32 ,  34  flow together. That is, in a discharge muffling chamber  162  of  FIG. 8 , a depressed portion is formed in an upper part of the upper support member  54 , and the depressed portion is closed by an upper cover  66  which is a cover to constitute the chamber. Consequently, the present invention is applicable even to a case where a refrigerant having a large high/low pressure difference is contained like carbon dioxide. 
   Embodiment 4 
   Next, an operation will be described at the time of starting of a compression system CS in the present invention. It is to be noted that the present embodiment uses the same compression system CS, multicylinder rotary compressor, and refrigerant circuit as those used in Embodiment 1 of  FIGS. 1 to 3 . Therefore, description of these constitutions is omitted. It is to be noted that an HFC or HC-based refrigerant is used as a refrigerant for use in the same manner as in the above-described embodiments. As oils which are lubricants, existing oils are used such as a mineral oil, an alkyl benzene oil, an ether oil, and an ester oil. 
   Here, an operation will be described in starting a rotary compressor  10  of the present embodiment with reference to  FIG. 9 . A controller  210  energizes an electromotive element  14  of a rotary compressor  10  based on an operation instruction input of an indoor-unit-side controller (not shown) disposed in the above-described indoor unit. At this time, simultaneously with the energization of the electromotive element  14 , the controller  210  opens an electromagnetic valve  105  of a refrigerant pipe  101 , and closes an electromagnetic valve  106  of a refrigerant pipe  102  ( FIG. 9  (1)). Accordingly, the refrigerant pipe  101  communicates with a pipe  75 . The controller  210  controls a rotation number of the electromotive element  14  of the rotary compressor  10  to start the compressor in a state in which suction-side pressures of both rotary compression elements  32 ,  34  are applied as a back pressure of a second vane  52 . 
   Moreover, when a stator coil  28  of the electromotive element  14  is energized via a terminal  20  and wiring (not shown), the electromotive element  14  starts, and a rotor  24  rotates. By this rotation, first and second rollers  46 ,  48  are fitted into upper and lower eccentric portions  42 ,  44  integrally disposed in a rotation shaft  16 , and eccentrically rotate in first and second cylinders  38 ,  40 . 
   Accordingly, the refrigerant flows into an accumulator  146  from a refrigerant pipe  100  of the rotary compressor  10 . Since the electromagnetic valve  105  of the refrigerant pipe  101  is opened as described above, a part of the refrigerant passed through the refrigerant pipe  100  on suction sides of both rotary compression elements  32 ,  34  flows into a back-pressure chamber  72 A via the refrigerant pipe  101  and the pipe  75 . 
   On the other hand, the refrigerant which has flown into the accumulator  146  is separated into gas/liquid in the accumulator. Thereafter, an only refrigerant gas enters a refrigerant introducing tube  92  which opens in the accumulator  146 . The refrigerant gas which has entered the refrigerant introducing tube  92  is sucked on a low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32  via a suction passage  58 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by operations of the first roller  46  and a first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas passes through a discharge port (not shown) from a high-pressure chamber side of the first cylinder  38 , and is discharged to a discharge muffling chamber  62 . The refrigerant gas discharged to the discharge muffling chamber  62  is discharged into a sealed container  12  from a hole (not shown) extending through a cup member  63 . 
   Here, there is an equilibrium pressure in a refrigerant circuit at a starting time of the rotary compressor  10 . That is, after stopping the previous operation of the rotary compressor  10 , the pressure is gradually equalized. After elapse of a predetermined time, the inside of the refrigerant circuit has the equilibrium pressure. Therefore, when the rotary compressor  10  is started in a state in which the inside of the refrigerant circuit is brought into the equilibrium pressure, immediately after starting the rotary compressor  10 , the equilibrium pressure is substantially indicated by pressures of suction-side refrigerants of both the rotary compression elements  32 ,  34 . The pressures are applied as a back pressure of the second vane  52 . Similarly, the pressure inside the second cylinder  40  also indicates a substantially equilibrium pressure. Therefore, since the second vane  52  cannot be urged toward the second roller  48 , the compression work is not substantially performed in the second rotary compression element  34 , and the compression work of the refrigerant is performed only by the first rotary compression element  32  provided with a spring  74 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from a refrigerant discharge tube  96  formed in an end cap  12 B of the sealed container  12 , and flows into an outdoor heat exchanger  152 . In the exchanger, the refrigerant gas emits heat, pressure of the gas is reduced by an expansion valve  154 , and thereafter the gas flows into an indoor heat exchanger  156 . The refrigerant which has flown into the indoor heat exchanger  156  evaporates in the exchanger, heat is absorbed from air circulated in a room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   On the other hand, when the rotary compressor  10  starts, and a predetermined time elapses, a high/low pressure difference is constituted in the refrigerant circuit, and a state in the refrigerant circuit is stabilized. It is to be noted that, at this time, the pressures of the suction-side refrigerants of both the rotary compression elements  32 ,  34  are low which are applied as the back pressure of the second vane  52 , but the second vane  52  cannot be urged toward the second roller  48  at this low pressure, and therefore the compression work is substantially performed only by the first rotary compression element  32 . 
   Here, when the rotary compressor  10  starts, and a predetermined time elapses, as shown in  FIG. 9  (2), the controller  210  closes the electromagnetic valve  105  of the refrigerant pipe  101 , and opens the electromagnetic valve  106  of the refrigerant pipe  102 . Accordingly, the refrigerant pipe  102  communicates with the pipe  75 , and all the refrigerant flowing through the refrigerant pipe  100  of the rotary compressor  10  flows into the accumulator  146 . 
   Moreover, a part of the refrigerant discharged to the refrigerant discharge tube  96  from the sealed container  12  flows into the back-pressure chamber  72 A from the refrigerant pipe  102  through the pipe  75 . Accordingly, the back-pressure chamber  72 A has discharge-side pressures of both the rotary compression elements  32 ,  34 , and the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . 
   When the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 , the back-pressure chamber of the second vane  52  has a pressure which is remarkably higher than that in the second cylinder  40 . Therefore, the second vane  52  is urged toward the second roller  48  to follow up the roller by the high pressure of the back-pressure chamber  72 A, and the compression work is started in the second rotary compression element  34 . 
   That is, the only refrigerant gas separated into the gas/liquid in the accumulator  146  enters the respective refrigerant discharge tubes  92 ,  94  which open In the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  flows through the suction passage  58 , and is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32  as described above. 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and the first vane  50  to constitute a high-temperature/pressure refrigerant gas, and the gas is discharged to the discharge muffling chamber  62  from the high-pressure chamber side of the first cylinder  38  through a discharge port (not shown). 
   On the other hand, the low-pressure refrigerant gas which has entered the refrigerant introducing tube  94  flows through the suction passage  60 , and is sucked on the low-pressure pressure chamber side of the second cylinder  40  of the second rotary compression element  34 . The refrigerant gas sucked on the low-pressure chamber side of the second cylinder  40  is compressed by the operations of the second roller  48  and the second vane  52 . 
   Here, the controller  210  closes the electromagnetic valve  105 , opens the electromagnetic valve  106 , and starts the rotary compressor  10  in a state in which the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . In this case, the pressure in the refrigerant circuit immediately after the starting is a substantially equilibrium pressure as described above. Therefore, even when the electromagnetic valve  106  is opened, the pressure applied as the back pressure of the second vane  52  is the equilibrium pressure, and much time is required until the discharge-side pressures of both the rotary compression elements  32 ,  34  reach high pressures. Therefore, the second vane  52  cannot follow up the second roller  48  until the discharge-side pressures of both the rotary compression elements  32 ,  34  rise to a certain degree. 
   Moreover, immediately after the starting, the state in the refrigerant circuit is unstable. Therefore, pulsations of the discharge-side pressures of both the rotary compression elements  32 ,  34  also remarkably increase. Therefore, when the compressor is started in a state in which the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied, disadvantages have occurred that a follow-up property of the second vane  52  is deteriorated by the pulsations of the discharge-side pressures of both the rotary compression elements  32 ,  34 , the second vane  52  collides with the second roller  48 , and a collision sound is generated. 
   However, as in the present invention, the electromagnetic valve  105  is opened, the compressor is started in a state in which the suction-side pressures of both the rotary compression elements  32 ,  34  are applied, the second vane  52  is not allowed to follow up the second roller  48 , and the compression work in the second rotary compression element  34  is substantially invalidated. Moreover, when the compressor is started, and the inside of the refrigerant circuit is stabilized, the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied, and the second vane  52  is urged toward the second roller  48  to follow up the first cylinder  38  by the discharge-side pressures. Consequently, the above-described disadvantages can be avoided, and the follow-up property of the second vane  52  can be improved at the starting time. 
   Consequently, the operation efficiency of the rotary compressor  10  is improved, and it is possible to avoid the generation of the collision sound of the second vane  52 . 
   It is to be noted that the refrigerant gas is compressed by the operations of the second roller  48  and the second vane  52  to have a high-temperature/pressure, the gas passes through the discharge port (not shown) from the high-pressure chamber side of the second cylinder  40 , and is discharged to the discharge muffling chamber  64 . The refrigerant gas discharged to the discharge muffling chamber  64  is discharged to the discharge muffling chamber  62  via the communication path  120 , and the gas joins the refrigerant gas compressed by the first rotary compression element  32 . Moreover, the joint refrigerant gas is discharged into the sealed container  12  via a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . The discharge-side refrigerants of both the rotary compression elements  32 ,  34  pass through the refrigerant discharge tube  96 . Since the electromagnetic valve  106  is opened as described above, a part of the refrigerant flows into the back-pressure chamber  72 A from the refrigerant pipe  102  via the pipe  75 . Accordingly, the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . 
   On the other hand, the refrigerant gas which has flown into the outdoor heat exchanger  152  emits heat in the exchanger, the pressure of the gas is reduced by the expansion valve  154 , and thereafter the gas flows into the indoor heat exchanger  156 . The refrigerant evaporates in the indoor heat exchanger  156 , the heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   On the other hand, when the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied, and the second vane  52  follows up the second roller  48 , the controller  210  thereafter closes the electromagnetic valve  106  ( FIG. 9  (3)). Accordingly, a closed space is formed in the pipe  75  connected to the back-pressure chamber  72 A of the second vane  52 . Here, since not a little refrigerant in the second cylinder  40  flows into the back-pressure chamber  72 A between the second vane  52  and the housing section  70 A, the pressure in the back-pressure chamber  72 A of the second vane  52  is an intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 , and the intermediate pressure is applied as the back pressure of the second vane  52 . By this intermediate pressure, the second vane  52  can be sufficiently urged toward the second roller  48  without using any spring member. 
   Here, when a high pressure continues to be applied as the back pressure of the second vane  52 , the discharge-side pressure has large pulsation. The high pressure corresponds to the discharge-side pressures of both the rotary compression elements  32 ,  34 . Additionally, since any spring member is not disposed in the second rotary compression element  34 , this pulsation causes a problem that the follow-up property of the second vane  52  is deteriorated, the compression efficiency drops, and the collision sound is generated between the second vane  52  and the second roller  48 . 
   Moreover, the rotary compressor  10  is started, and the intermediate pressure is applied as the second vane  52  without applying the high pressure corresponding to the discharge-side pressure of both the rotary compression elements  32 ,  34 . The intermediate pressure is between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 . With this intermediate pressure, a pressure difference is small between the inside of the second cylinder  40  and the back-pressure chamber  72 A. Therefore, much time is required for the second vane  52  to follow up the second roller  48 . During this time, a disadvantage occurs that the second vane  52  collides with the second roller  48 , and the collision sound is generated. 
   Therefore, the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . The second vane  52  is urged toward the second roller  48  to follow up the second roller  48  by the discharge-side pressure. Thereafter, the back-pressure chamber  72 A is brought into the intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 . Consequently, the follow-up property of the second vane  52  is improved, the compression efficiency of the second rotary compression element  34  is improved, and it is possible to avoid beforehand the generation of the collision sound between the second vane  52  and the second roller  48  at the starting time. 
   It is to be noted that in the present embodiment, simultaneously with the energization of the electromotive element  14 , the controller  210  exerts a control in such a manner as to open the electromagnetic valve  105  and close the electromagnetic valve  106 . The electromagnetic valves  105 ,  106  may be opened/closed before starting the rotary compressor  10 . For example, the controller  210  may open the electromagnetic valve  105 , and close the electromagnetic valve  106  before the energization of the electromotive element  14 . 
   Moreover, since operations similar to those of Embodiment 1 are performed in the first operation mode performed at the usual or high load time and the second operation mode performed at the light load time, description thereof is omitted. 
   Embodiment 5 
   Furthermore, in a compression system CS of the present invention, an electromagnetic valve  200  is disposed in a middle portion of a refrigerant introducing tube  94  on an inlet side of a sealed container  12  on an outlet side of an accumulator  146  as shown in  FIG. 5  of Embodiment 2, and the electromagnetic valve  200  may be controlled by a controller  210 . 
   When the electromagnetic valve  200  is disposed in the refrigerant introducing tube  94  in this manner, the electromagnetic valve is closed at a starting time, flowing of a refrigerant into a second rotary compression element  34  is completely interrupted, an electromagnetic valve  106  of a refrigerant pipe  102  is opened, and the electromagnetic valve  200  is opened. Even in this case, the present invention is effective. 
   Moreover, the system is operated in a state in which the controller  210  closes the electromagnetic valve  200  to stop the flowing of the refrigerant into a second cylinder  40  in a second operation mode. Accordingly, a pressure inside the second cylinder  40  can be set to be higher than a suction-side pressure of a first rotary compression element  32 . 
   It is to be noted that in the present embodiment, an HFC or HC-based refrigerant is used as a refrigerant in the same manner as in the above-described embodiments. As oils which are lubricants, existing oils are used such as a mineral oil, an alkyl benzene oil, an ether oil, and an ester oil. 
   An operation in this case will be described. The controller  210  closes the above-described electromagnetic valve  200  to stop the flowing of the refrigerant into the second cylinder  40 . Accordingly, any compression work is not performed in the second rotary compression element  34 . When the flowing of the refrigerant into the second cylinder  40  is stopped, the pressure in the second cylinder  40  is slightly higher than the suction-side pressures of both the rotary compression elements  32 ,  34  (since a second roller  48  rotates, and a high pressure in the sealed container  12  slightly flows via a gap of the second cylinder  40 , the pressure in the second cylinder  40  becomes slightly higher than the suction-side pressure). 
   Moreover, the controller  210  opens an electromagnetic valve  105  of a refrigerant pipe  101 , and closes an electromagnetic valve  106  of a refrigerant pipe  102 . Accordingly, the refrigerant pipe  101  communicates with a pipe  75 , the suction-side refrigerant of the first rotary compression element  32  flows into a back-pressure chamber  72 A, and the suction-side pressure of the first rotary compression element  32  is applied as a back pressure of a second vane  52 . 
   Furthermore, the refrigerant passes through a refrigerant pipe  100  of a rotary compressor  110  on a suction side of the first rotary compression element  32 , and a part of the refrigerant flows into a back-pressure chamber  72 A from the refrigerant pipe  101  via a pipe  75 . Accordingly, the back-pressure chamber  72 A has the suction-side-pressure of the first rotary compression element  32 , and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   Here, the electromagnetic valve  200  is closed to stop the flowing of the refrigerant into the second cylinder  40 , and the pressure in the second cylinder  40  is set to be higher than the suction-side pressure of the first rotary compression element  32 . In this case, when the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 , the pressure in the second cylinder  40  becomes higher than the back pressure of the second vane  52 . Therefore, the second vane  52  is pushed toward the back-pressure chamber  72 A opposite to the second roller  48  by the pressure in the second cylinder  40 , and the vane does not come into the second cylinder  40 . Consequently, it is possible to avoid beforehand a disadvantage that the second vane  52  comes into the second cylinder  40  to collide with the second roller  48 , and a collision sound is generated. 
   On the other hand, the low-pressure refrigerant which has flown into the accumulator  146  is separated into gas/liquid in the accumulator. Thereafter, an only refrigerant gas enters a refrigerant introducing tube  92  which opens in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  is sucked on a low-pressure chamber side of a first cylinder  38  of the first rotary compression element  32  via a suction passage  58 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by operations of the first roller  46  and a first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas passes through a discharge port (not shown) from a high-pressure chamber side of the first cylinder  38 , and is discharged to a discharge muffling chamber  62 . The refrigerant gas discharged to the discharge muffling chamber  62  is discharged into the sealed container  12  from a hole (not shown) extending through a cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from a refrigerant discharge tube  96  formed in an end cap  12 B of the sealed container  12 , and flows into an outdoor heat exchanger  152 . The refrigerant gas emits heat in the exchanger, the pressure of the gas is reduced by an expansion valve  154 , and thereafter the gas flows into an indoor heat exchanger  156 . The refrigerant evaporates in the indoor heat exchanger  156 , the heat is absorbed from air circulated in a room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  110 . The refrigerant repeats this cycle. 
   As described above, the electromagnetic valve  200  is disposed in the middle portion of the refrigerant introducing tube  94 , and the compressor is operated in a state in which the controller  210  closes the electromagnetic valve  200  to stop the flowing of the refrigerant into the second cylinder  40  in the second operation mode. Accordingly, in the second operation mode, the pressure in the second cylinder  40  is kept to be higher than the back pressure of the second vane  52 . Therefore, the second vane  52  is pushed toward the back-pressure chamber  72 A opposite to the second roller  48  by the pressure in the second cylinder  40 , and the vane does not come into the second cylinder  40 . Consequently, it is possible to avoid beforehand the disadvantage that the second vane  52  comes into the second cylinder  40  to collide with the second roller  48 , and the collision sound is generated during the operation in the second operation mode. 
   As described above in detail, according to the present invention, the performance and reliability of a compression system CS can be enhanced. The system comprises the rotary compressor  110  which is usable by the switching of the first operation mode in which the first and second rotary compression elements  32 ,  34  perform the compression work and the second operation mode in which the only first rotary compression element  32  substantially performs the compression work. 
   Consequently, when the refrigerant circuit of the air conditioner is constituted using the compression system CS, the operation efficiency and performance of the air conditioner are enhanced, and power consumption can be reduced. 
   Embodiment 6 
   Moreover, it has been described in Embodiments 4 and 5 described above that an HFC or HC-based refrigerant is used as a refrigerant, but a refrigerant having a large high/low pressure difference may be used such as carbon dioxide. For example, a combination of carbon dioxide and polyalkyl glycol (PAG) may be used as the refrigerant. In this case, since the refrigerant compressed by rotary compression elements  32  and  34  has a very high pressure, there is a possibility that a cup member  63  is broken by the high pressure in a case where a discharge muffling chamber  62  is formed into a shape to cover an upper support member  54  with the cup member  63  as in the respective embodiments. 
   Therefore, when the discharge muffling chamber is formed into a shape shown in  FIG. 8 , resistance to pressure can be secured. The chamber is above the upper support member  54  in which the refrigerant compressed by both the rotary compression elements  32 ,  34  flows together. That is, in a discharge muffling chamber  162  of  FIG. 8 , a depressed portion is formed in an upper part of the upper support member  54 , and the depressed portion is closed by an upper cover  66  which is a cover to constitute the chamber. Consequently, the present invention is applicable even to a case where a refrigerant having a large high/low pressure difference is contained like carbon dioxide. 
   Embodiment 7 
   Next, still another embodiment of a multicylinder rotary compressor will be described according to the present invention.  FIG. 10  is a vertically sectional side view of the multicylinder rotary compressor according to the present invention in this case. Another vertically sectional side view of the multicylinder rotary compressor of the present embodiment is the same as  FIG. 1  of Embodiment 1, and a refrigerant circuit diagram is also the same as  FIG. 3 . Therefore, an only constitution different from that of Embodiment 1 will be described in the present embodiment. It is to be noted that in the present embodiment, components denoted with the same reference numerals as those of  FIGS. 1 to 3  produce the same or similar effects. 
   In the present embodiment, a back-pressure chamber  172 A opens on the sides of a guide groove  72  and a sealed container  12 , a pipe  75  described later communicates with/is connected to an opening on the sealed container  12  side, and the pipe is sealed together with the inside of the sealed container  12 . 
   Moreover, the back-pressure chamber  172 A of the present invention is constituted as a muffler chamber having a predetermined space volume. As shown in  FIG. 10 , the back-pressure chamber  172 A of the embodiment has a shape in which a concavely depressed chamber having the predetermined space volume is disposed in a position constituting a connection portion of the pipe  75  to the guide groove  72  on a lower support member  56 . That is, the back-pressure chamber  172 A of the present embodiment is formed by a concavely depressed portion formed in a position corresponding to the pipe  75  and the guide groove  72  on the upper surface of the lower support member  56  which closes an opening face under a second cylinder  40 . In the depressed portion, an opening in the lower surface of the second cylinder  40  is closed by the lower support member  56 . 
   When the back-pressure chamber  172 A is formed in such a manner as to have the predetermined space volume ad described above, the back-pressure chamber  172 A can reduce pressure pulsation caused by an urging operation of a second vane  52 , and pulsation of a pressure applied as a back pressure of the second vane  52 . 
   It is to be noted that an HFC or HC-based refrigerant is used as a refrigerant. As oils which are lubricants, existing oils are used such as a mineral oil, an alkyl benzene oil, an ether oil, and an ester oil. 
   An operation of a rotary compressor  10  including the above-described constitution will be described. 
   (1) First Operation Mode (Usual or High Load Time) 
   First, a first operation mode will be described in which both rotary compression elements  32 ,  34  perform a compression work. A controller  210  controls a rotation number of an electromotive element  14  of the rotary compressor  10  based on an operation instruction input of an indoor-unit-side controller (not shown) disposed in the above-described indoor unit. Moreover, in a usual or high load indoor state, the controller  210  executes the first operation mode. In this first operation mode, the controller  210  closes an electromagnetic valve  105  of a refrigerant pipe  101  and opens an electromagnetic valve  106  of a refrigerant pipe  102 . Accordingly, the refrigerant pipe  102  communicates with the pipe  75 , suction-side refrigerants of both the rotary compression elements  32 ,  34  flow into the back-pressure chamber  172 A, and suction-side pressures of both the rotary compression elements  32 ,  34  are applied as a back pressure of the second vane  52 . 
   Moreover, when a stator coil  28  of the electromotive element  14  is energized via a terminal  20  and wiring (not shown), the electromotive element  14  starts, and a rotor  24  rotates. By this rotation, first and second rollers  46 ,  48  are fitted into upper and lower eccentric portions  42 ,  44  integrally disposed in a rotation shaft  16 , and eccentrically rotate in first and second cylinders  38 ,  40 . 
   Accordingly, a low-pressure refrigerant flows into an accumulator  146  from a refrigerant pipe  100  of the rotary compressor  10 . Since the electromagnetic valve  105  of the refrigerant pipe  100  is closed as described above, all the refrigerant passed through the refrigerant pipe  100  flows into the accumulator  146  without flowing into the pipe  75 . 
   Moreover, the low-pressure refrigerant which has flown into the accumulator  146  is separated into gas/liquid, and thereafter the only refrigerant gas enters refrigerant discharge tubes  92 ,  94  which open in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  is sucked on a low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32  via a suction passage  58 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and a first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas is passed through a discharge port (not shown) from the high-pressure chamber side of the first cylinder  38 , and is discharged to a discharge muffling chamber  62 . 
   On the other hand, the low-pressure refrigerant gas which has flown into the refrigerant introducing tube  94  is passed through a suction passage  60 , and sucked on the low-pressure chamber side of the second cylinder  40  of the second rotary compression element  34 . The refrigerant gas sucked on the low-pressure chamber side of the second cylinder  40  is compressed by the operations of the second roller  48  and the second vane  52 . 
   At this time, pressure pulsation is caused on the side of the back-pressure chamber  172 A opposite to the second roller  48  of the second vane  52  by an urging operation of the second vane  52  toward the second roller  48  as described above. In this case, in the second rotary compression element  34  in which any spring member has not heretofore been disposed, a problem has occurred that a follow-up property of the second vane  52  is deteriorated with respect to the second roller by the pressure pulsation. 
   Furthermore, the discharge-side pressures of both the rotary compression elements  32 ,  34 , applied as a back pressure of the second vane  52 , have large pulsations. Additionally, any spring member is not disposed, and therefore the follow-up property of the second vane  52  Is deteriorated by the pulsation. Consequently, a problem has occurred that the compression efficiency is deteriorated, and a collision sound is generated between the second vane  52  and the second roller  48 . 
   However, when the back-pressure chamber  172 A is formed into the muffler chamber having the predetermined space volume as in the present invention, it is possible to reduce the pressure pulsation generated by the urging operation of the second vane  52 . As to the discharge-side refrigerants of both the rotary compression elements  32 ,  34  from the pipe  75 , the pressure pulsation is remarkably reduced in a process in which the refrigerants pass through the back-pressure chamber  172 A. Accordingly, the second vane  52  can be sufficiently urged toward the second roller  48  without using any spring member. 
   Consequently, the follow-up property of the second vane  52  is improved in the first operation mode, and the compression efficiency of the second rotary compression element  34  is enhanced. Furthermore, since the follow-up property of the second vane  52  is improved, it is possible to avoid the collision with the second roller  48 . Therefore, it is possible to avoid as much as possible the disadvantage that the collision sound is generated between the second vane and the second roller  48 . 
   It is to be noted that the refrigerant gas is compressed by the operations of the second roller  48  and second vane  52  to obtain a high-temperature/pressure. The gas is passed through a discharge port (not shown) from the high-pressure chamber side of the second cylinder  40 , and is discharged to a discharge muffling chamber  64 . The refrigerant gas discharged to the discharge muffling chamber  64  is discharged to the discharge muffling chamber  62  via a communication path  120 , and flows together with the refrigerant gas compressed by the first rotary compression element  32 . Moreover, the joined refrigerant gas is discharged into a sealed container  12  from a hole (not shown) extending through a cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from a refrigerant discharge tube  96  formed in an end cap  12 B of the sealed container  12 , and flows into an outdoor heat exchanger  152 . On the other hand, since the electromagnetic valve  106  is opened by the controller  210  as described above, a part of the discharge-side refrigerant flows into the back-pressure chamber  172 A from the refrigerant pipe  102  via the pipe  75 . The discharge-side refrigerants of both the rotary compression elements  32 ,  34  flow through the refrigerant discharge tube  96 . Accordingly, the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . 
   On the other hand, the refrigerant gas which has flown into the outdoor heat exchanger  152  emits heat in the exchanger, the pressure of the gas is reduced by an expansion valve  154 , and thereafter the gas flows into an indoor heat exchanger  156 . The refrigerant evaporates in the indoor heat exchanger  156 , the heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   It is to be noted that in the above-described first operation mode, the controller  210  closes the electromagnetic valve  105  of the refrigerant pipe  101 , and opens the electromagnetic valve  106  of the refrigerant pipe  102  in such a manner that the refrigerant pipe  102  communicates with the pipe  75 . The discharge-side pressures of both the rotary compression elements  32 ,  34  are high pressures, and are applied as the back pressure of the second vane  52 . However, an intermediate pressure may be applied as the back pressure of the second vane  52  in the first operation mode, and the intermediate pressure is between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 . In this case, for example, the controller  210  closes the electromagnetic valve  105  of the refrigerant pipe  101  and the electromagnetic valve  106  of the refrigerant pipe  102  to form a closed space inside the pipe  75  connected to the back-pressure chamber  172 A of the second vane  52 . Then, not a little refrigerant in the second cylinder  40  flows into the back-pressure chamber  172 A between the second vane  52  and the housing section  70 A. Therefore, the pressure in the back-pressure chamber  172 A of the second vane  52  constitutes the intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 , and this intermediate pressure is applied as the back pressure of the second vane  52 . 
   Even when the intermediate pressure is applied as the back pressure of the second vane  52  in this manner, the second vane  52  can be sufficiently urged toward the second roller  48  by the intermediate pressure without using any spring member. Furthermore, the pressure pulsation is remarkably reduced as compared with the application of the discharge-side pressures of both the rotary compression elements  32 ,  34 . Therefore, in addition to a pulsation reducing effect by the back-pressure chamber  172 A, the pulsation can further be reduced. Especially, when the electromagnetic valves  105 ,  106  are closed as described above to interrupt the flowing of the suction-side and discharge-side refrigerants of both the rotary compression elements  32 ,  34  from the pipe  75 , the pulsation of the back pressure of the second vane  52  can be further suppressed. 
   (2) Second Operation Mode (Operation at light Load Time) 
   Next, a second operation mode will be described. In a case where the inside of the room has a state in which a load is light, the controller  210  shifts to the second operation mode. In this second operation mode, the only first rotary compression element  32  substantially performs a compression work. The operation mode is performed in a case where the inside of the room has a light load and the electromotive element  14  rotates at a low speed in the first operation mode. When the only first rotary compression element  32  substantially performs the compression work in a small capacity region, an amount of the refrigerant gas to be compressed can be reduced as compared with a case where the first and second cylinders  38 ,  40  perform the compression work. Therefore, the rotation number of the electromotive element  14  is raised also at the light load time by the corresponding amount, the operation efficiency of the electromotive element  14  is improved, and a leak loss of the refrigerant can be reduced. 
   In this case, the controller  210  opens the electromagnetic valve  105  of the refrigerant pipe  101 , and closes the electromagnetic valve  106  of the refrigerant pipe  102 . Accordingly, the refrigerant pipe  101  communicates with the pipe  75 , a suction-side refrigerant of the first rotary compression element  32  flows into the back-pressure chamber  172 A, and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   On the other hand, the controller  210  energizes the stator coil  28  of the electromotive element  14  via the terminal  20  and the wiring (not shown), and rotates the rotor  24  of the electromotive element  14  as described above. By this rotation, the first and second rollers  46 ,  48  are fitted into the upper and lower eccentric portions  42 ,  44  disposed integrally with the rotation shaft  16 , and eccentrically rotate in the first and second cylinders  38 ,  40 . 
   Accordingly, the low-pressure refrigerant flows into the accumulator  146  from the refrigerant pipe  100  of the rotary compressor  10 . Since the electromagnetic valve  105  of the refrigerant pipe  101  opens at this time as described above, a part of the refrigerant on the suction side of the first rotary compression element  32  passes through the refrigerant pipe  100 , and flows into the back-pressure chamber  172 A from the refrigerant pipe  101  via the pipe  75 . Accordingly, the back-pressure chamber  172 A has a suction-side pressure of the first rotary compression element  32 , and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   Here, the suction-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second rotary compression element  34 , and this pressure is a low pressure. Therefore, the second vane  52  cannot be urged toward the second roller  48 . Therefore, the compression work is not substantially performed in the second rotary compression element  34 , and the compression work of the refrigerant is performed only by the first rotary compression element  32  provided with the spring  74 . 
   In this case, since equal suction-side pressures are applied to the pressure inside the second cylinder  40  and the back pressure of the second vane, there has heretofore been a problem that the second vane comes into the second cylinder by a fluctuation of balance between both spaces, the vane collides with the second roller, and the collision sound is generated. However, since the fluctuation can be reduced by the back-pressure chamber  172 A having the predetermined space volume in the present invention, it is possible to avoid as much as possible the disadvantage that the second vane  52  comes into the second cylinder  40 , collides with the second roller  48 , and generates a collision sound. 
   On the other hand, the low-pressure refrigerant which has flown into the accumulator  146  is separated into gas/liquid, and thereafter the refrigerant gas only enters the refrigerant discharge tube  92  which opens in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  flows through the suction passage  58 , and is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and the first vane  50  to constitute a high-temperature/pressure refrigerant gas, and the gas is discharged to the discharge muffling chamber  62  from the high-pressure chamber side of the first cylinder  38  through a discharge port (not shown). The refrigerant gas discharged to the discharge muffling chamber  62  is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . There, the refrigerant gas emits heat. After the pressure of the gas is reduced by the expansion valve  154 , the gas flows into the indoor heat exchanger  156 . The refrigerant evaporates in the indoor heat exchanger  156 , the heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   As described above in detail, according to the present invention, the performance and reliability of the rotary compressor  10  can be enhanced. The compressor is usable by the switching of the first operation mode in which the first and second rotary compression elements  32 ,  34  perform the compression work and the second operation mode in which the only first rotary compression element  32  substantially performs the compression work. 
   Consequently, when the refrigerant circuit of the air conditioner is constituted using the rotary compressor  10 , the operation efficiency and performance of the air conditioner are enhanced, and power consumption can be reduced. 
   Embodiment 8 
   It is to be noted that in Embodiment 7 a back-pressure chamber  172 A is formed into a shape having a concavely depressed chamber having a predetermined space volume, but the present invention is not limited to this embodiment, and the back-pressure chamber of the present invention is not limited as long as the chamber has a predetermined space volume. The present invention is also effective, for example, in a case where the back-pressure chamber has a shape shown in  FIG. 11 . It is to be noted that  FIG. 11  is a flat sectional view of a second cylinder in this case. In  FIG. 11 , components denoted with the same reference numerals as those of  FIGS. 1 to 10  produce the same or similar effects. 
   In  FIG. 11 , reference numeral  49  denotes a discharge port of the second rotary compression element  34 . A back-pressure chamber  272 A of the present embodiment has an expanded portion having a predetermined space volume in a transverse direction of a second cylinder  40 , and entirely has a substantially cylindrical shape. Even when the back-pressure chamber  272 A is formed into the shape of the present embodiment in this manner, the back-pressure chamber  272 A can reduce pressure pulsation, improve a follow-up property of a second vane  52 , and avoid collision with a second roller  48 . 
   Embodiment 9 
   It is to be noted that even in Embodiments 7 and 8 described above, as shown in  FIG. 5 , an electromagnetic valve  200  is disposed in a middle portion of a refrigerant introducing tube  94  on an inlet side of a sealed container  12  on an outlet side of an accumulator  146  of a rotary compressor  10  in such a manner as to control flowing of a refrigerant into a second rotary compression element  34 . In a second operation mode, the electromagnetic valve  200  may be closed to interrupt the flowing of the refrigerant into a second cylinder  40 . 
   In this case, when the refrigerant is inhibited from being passed into the second cylinder  40 , a pressure in the second cylinder  40  is slightly higher than a suction-side pressure of both the rotary compression elements  32 ,  34  (the second roller  48  rotates, a high pressure in the sealed container  12  slightly flows from a gap of the second cylinder  40  or the like, and therefore the pressure in the second cylinder  40  becomes slightly higher than the suction-side pressure). 
   Therefore, the second vane  52  is pushed toward a back-pressure chamber  172 A (or the back-pressure chamber  272 A) opposite to the second roller  48 , and does not come into the second cylinder  40  by the pressure in the second cylinder  40 . Therefore, in addition to the above-described effect of the back-pressure chamber  172 A (or the back-pressure chamber  272 A), it is possible to avoid more effectively a disadvantage that the second vane  52  collides with the second roller  48 . 
   Embodiment 10 
   It has been described in Embodiments 7, 8, and 9 that an HFC or HC-based refrigerant is used as a refrigerant, but a refrigerant having a large high/low pressure difference may be used such as carbon dioxide. For example, a combination of carbon dioxide and polyalkyl glycol (PAG) may be used as the refrigerant. In this case, since the refrigerant compressed by rotary compression elements  32  and  34  has a very high pressure, there is a possibility that a cup member  63  is broken by the high pressure in a case where a discharge muffling chamber  62  is formed into a shape to cover an upper support member  54  with the cup member  63  as in the respective embodiments. 
   Therefore, when the discharge muffling chamber is formed into a shape shown in  FIG. 8 , resistance to pressure can be secured. The chamber is above the upper support member  54  in which the refrigerants compressed by both the rotary compression elements  32 ,  34  flow together. That is, in a discharge muffling chamber  162  of  FIG. 8 , a concavely depressed portion is formed in an upper part of the upper support member  54 , and the concavely depressed portion is closed by an upper cover  66  which is a cover to constitute the chamber. Consequently, the present invention is applicable even to a case where a refrigerant having a large high/low pressure difference is contained like carbon dioxide. 
   Embodiment 11 
   Next, still another embodiment of a multicylinder rotary compressor of the present invention will be described with reference to  FIGS. 12 and 13 .  FIG. 12  is a flat sectional view of a second cylinder in a case where a second roller of a second rotary compression element is positioned in a top dead center in the multicylinder rotary compressor of the present invention, and  FIG. 13  is a flat sectional view of the second cylinder in a case where the second roller of the second rotary compression element is positioned in a bottom dead center. 
   It is to be noted that a vertically sectional side view of the multicylinder rotary compressor of the embodiment is the same as  FIGS. 1 and 2  of Embodiment 1, and a refrigerant circuit diagram is the same as  FIG. 3  of Embodiment 1. Therefore, the figures are omitted. Therefore, in the present embodiment. an only part different from that of a constitution of Embodiment 1 will be described. It is to be noted that in the present embodiment, components denoted with the same reference numerals as those of  FIGS. 1 to 3  produce the same or similar effects. 
   Here, a back-pressure chamber  72 A is formed on a back-surface side of a second vane  52 . The back-pressure chamber  72 A opens on the sides of a guide groove  72  and a sealed container  12 . An opening on a sealed container  12  side communicates with/is connected to a pipe  375  which is a passage for a back pressure ( FIGS. 12 and 13 ), and is sealed together with the inside of the sealed container  12 . 
   The pipe  375  is a back-pressure passage for applying a back pressure to the second vane  52  of a second rotary compression element  34 . The pipe communicates with a refrigerant pipe  100  on a suction side of rotary compression elements  32  and  34  via a refrigerant pipe  101  described later, and a refrigerant discharge tube  96  on a discharge side of both the rotary compression elements  32 ,  34  via a refrigerant pipe  102 . Moreover, discharge-side refrigerants of both the rotary compression elements  32 ,  34  flow into the back-pressure chamber  72 A from a pipe  75 , or suction-side refrigerants of both the rotary compression elements  32 ,  34  flow into the chamber. As the back pressure of the second vane  52 , the discharge-side or suction-side pressures of both the rotary compression elements  32 ,  34  are added. 
   Moreover, in the present invention, a sectional area of the pipe  375  is set to be not less than an average value of a surface area of the second vane  52  exposed into a second cylinder  40 . That is, the average value of the sectional area of the second vane  52  is calculated which is exposed into the second cylinder  40  from when the second vane  52  moves from the top dead center in which the vane is not most exposed into the second cylinder  40  as shown in  FIG. 12  to the bottom dead center in which the second vane  52  is most exposed into the second cylinder  40  as shown in  FIG. 13  (a broken line of the second vane  52  of  FIG. 13  shows a portion exposed into the second cylinder  40 ). The second vane follows up a second roller  48  which eccentrically rotates in the second cylinder  40 . The sectional area of the pipe  375  is set to be not less than the average value of the surface area. 
   When the sectional area of the pipe  375  is set to be not less than the average value of the surface area of the second vane  52  exposed into the second cylinder  40  in this manner, a sufficient area can be sufficiently secured on a back-pressure chamber  72 A side opposite to the second roller  48  of the second vane  52 . 
   It is to be noted that an HFC or HC-based refrigerant is used as the refrigerant. As oils which are lubricants, existing oils are used such as a mineral oil, an alkyl benzene oil, an ether oil, and an ester oil. 
   Next, an operation of the rotary compressor  10  constituted as described above will be described. 
   (1) First Operation Mode (Usual or High Load Time) 
   First, a first operation mode will be described in which both the rotary compression elements  32 ,  34  perform a compression work. A controller  210  controls a rotation number of an electromotive element  14  of a rotary compressor  10  based on an operation instruction input of an indoor-unit-side controller (not shown) disposed in the above-described indoor unit. Moreover, in a usual or high load indoor state, the controller  210  executes the first operation mode. In this first operation mode, the controller  210  closes an electromagnetic valve  105  of the refrigerant pipe  101  and opens an electromagnetic valve  106  of the refrigerant pipe  102 . Accordingly, the refrigerant pipe  102  communicates with the pipe  375 , discharge-side refrigerants of both the rotary compression elements  32 ,  34  flow into the back-pressure chamber  72 A, and the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as a back pressure of the second vane  52 . 
   Moreover, when a stator coil  28  of the electromotive element  14  is energized via a terminal  20  and wiring (not shown), the electromotive element  14  starts, and a rotor  24  rotates. By this rotation, first and second rollers  46 ,  48  are fitted into upper and lower eccentric portions  42 ,  44  integrally disposed in a rotation shaft  16 , and eccentrically rotate in the first and second cylinders  38 ,  40 . 
   Accordingly, a low-pressure refrigerant flows into an accumulator  146  from the refrigerant pipe  100  of the rotary compressor  10 . Since the electromagnetic valve  105  of the refrigerant pipe  100  is closed as described above, all the refrigerant passed through the refrigerant pipe  100  flows into the accumulator  146  without flowing into the pipe  375 . 
   Moreover, the low-pressure refrigerant which has flown into the accumulator  146  is separated into gas/liquid, and thereafter the only refrigerant gas enters refrigerant discharge tubes  92 ,  94  which open in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32  via a suction passage  58 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and a first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas is passed through a discharge port (not shown) from the high-pressure chamber side of the first cylinder  38 , and is discharged to a discharge muffling chamber  62 . 
   On the other hand, the low-pressure refrigerant gas which has flown into the refrigerant introducing tube  94  is sucked on the low-pressure chamber side of the second cylinder  40  of the second rotary compression element  34  via a suction passage  60 . The refrigerant gas sucked on the low-pressure chamber side of the second cylinder  40  is compressed by the operations of the second roller  48  and the second vane  52 . 
   At this time, pressure pulsation is caused on the side of the back-pressure chamber  72 A opposite to the second roller  48  of the second vane  52  by an urging operation of the second vane  52  toward the second roller  48  as described above. In this case, in the second rotary compression element  34  in which any spring member has not heretofore been disposed, a problem has occurred that a follow-up property of the second vane  52  is deteriorated with respect to the second roller by the pressure pulsation. 
   Furthermore, the discharge-side pressures of both the rotary compression elements  32 ,  34 , applied as a back pressure of the second vane  52 , have large pulsations. Additionally, any spring member is not disposed in the second rotary compression element  34 , and therefore the follow-up property of the second vane  52  is deteriorated by the pulsation. Consequently, a problem has occurred that the compression efficiency is deteriorated, and a collision sound is generated between the second vane  52  and the second roller  48 . 
   However, when the sectional area of the pipe  375  is set to be not less than the average value of the surface area of the second vane  52  exposed into the second cylinder  40 , it is possible to secure a sufficient area on a back-pressure chamber  72 A side opposite to the second roller  48  of the second vane  52 , and it is also possible to reduce the pressure pulsation generated by the urging operation of the second vane  52 . As to the discharge-side refrigerants of both the rotary compression elements  32 ,  34  from the pipe  375 , the pressure pulsation is remarkably reduced in a process in which the refrigerants pass through the pipe  375 . Accordingly, the second vane  52  can be sufficiently urged toward the second roller  48  without using any spring member. 
   Consequently, the follow-up property of the second vane  52  is improved in the first operation mode, and the compression efficiency of the second rotary compression element  34  is enhanced. Furthermore, since the follow-up property of the second vane  52  is improved, it is possible to avoid the collision with the second roller  48 . Therefore, it is possible to avoid as much as possible the disadvantage that the collision sound is generated between the second vane and the second roller  48 . 
   It is to be noted that the refrigerant gas is compressed by the operations of the second roller  48  and second vane  52  to obtain a high-temperature/pressure. The gas is passed through a discharge port  49  from the high-pressure chamber side of the second cylinder  40 , and is discharged to the discharge muffling chamber  64 . The refrigerant gas discharged to the discharge muffling chamber  64  is discharged to the discharge muffling chamber  62  via the communication path  120 , and flows together with the refrigerant gas compressed by the first rotary compression element  32 . Moreover, the joined refrigerant gas is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in an end cap  12 B of the sealed container  12 , and flows into an outdoor heat exchanger  152 . Here, since the electromagnetic valve  106  of the refrigerant pipe  102  is opened as described above, a part of the discharge-side refrigerant of both the rotary compression elements  32 ,  34  passed through the refrigerant discharge tube  96  enters the pipe  375  from the refrigerant pipe  102  as described above, and is applied as the back pressure of the second vane  52 . 
   On the other hand, the refrigerant gas which has flown into the outdoor heat exchanger  152  emits heat in the exchanger, pressure of the gas is reduced by an expansion valve  154 , and thereafter the gas flows into an indoor heat exchanger  156 . In the indoor heat exchanger  156 , the refrigerant evaporates, the heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   It is to be noted that in the above-described first operation mode, the controller  210  closes the electromagnetic valve  105  of the refrigerant pipe  101 , and opens the electromagnetic valve  106  of the refrigerant pipe  102  in such a manner that the refrigerant pipe  102  communicates with the pipe  375 . The discharge-side pressures of both the rotary compression elements  32 ,  34  are high pressures, and are applied as the back pressure of the second vane  52 . However, an intermediate pressure may be applied as the back pressure of the second vane  52 , and the intermediate pressure is between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 . In this case, for example, the controller  210  closes the electromagnetic valve  105  of the refrigerant pipe  101  and the electromagnetic valve  106  of the refrigerant pipe  102  to form a closed space inside the pipe  375  connected to the back-pressure chamber  72 A of the second vane  52 . Then, not a little refrigerant in the second cylinder  40  flows into the back-pressure chamber  72 A between the second vane  52  and the housing section  70 A. Therefore, the pressure in the back-pressure chamber  72 A of the second vane  52  constitutes the intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 , and this intermediate pressure is applied as the back pressure of the second vane  52 . 
   Even when the intermediate pressure is applied as the back pressure of the second vane  52  in this manner, the second vane  52  can be sufficiently urged toward the second roller  48  by the intermediate pressure without using any spring member. Furthermore, the pressure pulsation is remarkably reduced as compared with the application of the discharge-side pressures of both the rotary compression elements  32 ,  34 . Therefore, in addition to the effect by the pipe  375 , the pulsation can further be reduced. Especially, when the electromagnetic valves  105 ,  106  are closed as described above to interrupt the flowing of the suction-side and discharge-side refrigerants of both the rotary compression elements  32 ,  34  from the pipe  75 , the pulsation of the back pressure of the second vane  52  can be further suppressed. 
   (2) Second Operation Mode (Operation at Light Load Time) 
   Next, a second operation mode will be described. In a case where the inside of the room has a state in which a load is light, the controller  210  shifts to the second operation mode. In this second operation mode, the only first rotary compression element  32  substantially performs a compression work. The operation mode is performed in a case where the inside of the room has a light load and the electromotive element  14  rotates at a low speed in the first operation mode. When the only first rotary compression element  32  substantially performs the compression work in a small capacity region, an amount of the refrigerant gas to be compressed can be reduced as compared with a case where the first and second cylinders  38 ,  40  perform the compression work. Therefore, the rotation number of the electromotive element  14  is raised also at the light load time by the corresponding amount, the operation efficiency of the electromotive element  14  is improved, and a leak loss of the refrigerant can be reduced. 
   In this case, the controller  210  opens the electromagnetic valve  105  of the refrigerant pipe  101 , and closes the electromagnetic valve  106  of the refrigerant pipe  102 . Accordingly, the refrigerant pipe  101  communicates with the pipe  75 , a suction-side refrigerant of the first rotary compression element  32  flows into the back-pressure chamber  72 A, and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   On the other hand, the controller  210  energizes the stator coil  28  of the electromotive element  14  via the terminal  20  and the wiring (not shown), and rotates the rotor  24  of the electromotive element  14  as described above. By this rotation, the first and second rollers  46 ,  48  are fitted into the upper and lower eccentric portions  42 ,  44  disposed integrally with the rotation shaft  16 , and eccentrically rotate in the first and second cylinders  38 ,  40 . 
   Accordingly, the low-pressure refrigerant flows into the accumulator  146  from the refrigerant pipe  100  of the rotary compressor  10 . Since the electromagnetic valve  105  of the refrigerant pipe  101  opens at this time as described above, a part of the refrigerant on the suction side of the first rotary compression element  32  passes through the refrigerant pipe  100 , and flows into the back-pressure chamber  72 A from the refrigerant pipe  101  via the pipe  375 . Accordingly, the back-pressure chamber  72 A has a suction-side pressure of the first rotary compression element  32 , and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   Here, the suction-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second rotary compression element  34 , and this pressure is a low pressure. Therefore, the second vane  52  cannot be urged toward the second roller  48 . Therefore, the compression work is not substantially performed in the second rotary compression element  34 , and the compression work of the refrigerant is performed only by the first rotary compression element  32  provided with the spring  74 . 
   In this case, since equal suction-side pressures are applied to the pressure inside the second cylinder  40  and the back pressure of the second vane, there has heretofore been a problem that the second vane  52  comes into the second cylinder  40  by a fluctuation of balance between both spaces, the vane collides with the second roller  48 , and the collision sound is generated. However, when the sectional area of the pipe  375  communicating with/connected to the back-pressure chamber  72 A of the second vane  52  is set to be not less than the average value of the surface area of the second vane  52  exposed in the second cylinder  40 , fluctuation can be reduced by the pipe  375 . Therefore, it is possible to avoid as much as possible the disadvantage that the second vane  52  comes into the second cylinder  40 , collides with the second roller  48 , and generates a collision sound. 
   On the other hand, the low-pressure refrigerant which has flown into the accumulator  146  is separated into gas/liquid, and thereafter the refrigerant gas only enters the refrigerant discharge tube  92  which opens in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  flows through the suction passage  58 , and is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and the first vane  50  to constitute a high-temperature/pressure refrigerant gas, and the gas is discharged to the discharge muffling chamber  62  from the high-pressure chamber side of the first cylinder  38  through a discharge port (not shown). The refrigerant gas discharged to the discharge muffling chamber  62  is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . There, the refrigerant gas emits heat. After the pressure of the gas is reduced by the expansion valve  154 , the gas flows into the indoor heat exchanger  156 . The refrigerant which has flown into the indoor heat exchanger  156  evaporates in the exchanger, the heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   As described above in detail, according to the present invention, the performance and reliability of the rotary compressor  10  can be enhanced. The compressor is usable by the switching of the first operation mode in which the first and second rotary compression elements  32 ,  34  perform the compression work and the second operation mode in which the only first rotary compression element  32  substantially performs the compression work. 
   Consequently, when the refrigerant circuit of the air conditioner is constituted using the rotary compressor  10 , the operation efficiency and performance of the air conditioner are enhanced, and power consumption can be reduced. 
   Embodiment 12 
   It is to be noted that, as shown in  FIG. 5 , an electromagnetic valve  200  is disposed in a middle portion of a refrigerant introducing tube  94  on an inlet side of a sealed container  12  on an outlet side of an accumulator  146  of a rotary compressor  10  in such a manner as to control flowing of a refrigerant into a second cylinder  40  of a second rotary compression element  34 . In a second operation mode, the electromagnetic valve  200  may be closed to interrupt the flowing of the refrigerant into the second cylinder  40 . It is to be noted that in  FIG. 5 , components denoted with the same reference numerals as those of  FIGS. 1 to 13  produce similar effects. 
   In this case, when the refrigerant is inhibited from being passed into the second cylinder  40 , a pressure in the second cylinder  40  is slightly higher than a suction-side pressure of both the rotary compression elements  32 ,  34  (the second roller  48  rotates, a high pressure in the sealed container  12  slightly flows from a gap of the second cylinder  40  or the like, and therefore the pressure in the second cylinder  40  becomes slightly higher than the suction-side pressure). 
   Therefore, the second vane  52  is pushed toward a back-pressure chamber  72 A opposite to the second roller  48 , and does not come into the second cylinder  40  by the pressure in the second cylinder  40 . Therefore, in addition to the above-described effect of the pipe  375 , it is possible to avoid more effectively a disadvantage that the second vane  52  collides with the second roller  48 . 
   Embodiment 13 
   It has been described in Embodiments 11 and 12 that an HFC or HC-based refrigerant is used as a refrigerant, but a refrigerant having a large high/low pressure difference may be used such as carbon dioxide. For example, a combination of carbon dioxide and polyalkyl glycol (PAG) may be used as the refrigerant. In this case, since the refrigerant compressed by rotary compression elements  32  and  34  has a very high pressure, there is a possibility that a cup member  63  is broken by the high pressure in a case where a discharge muffling chamber  62  is formed into a shape to cover an upper support member  54  with the cup member  63  as in the respective embodiments. 
   Therefore, when the discharge muffling chamber is formed into a shape shown in  FIG. 8 , resistance to pressure can be secured. The chamber is above the upper support member  54  in which the refrigerants compressed by both the rotary compression elements  32 ,  34  flow together. That is, in a discharge muffling chamber  162  of  FIG. 8 , a concavely depressed portion is formed in an upper part of the upper support member  54 , and the concavely depressed portion is closed by an upper cover  66  which is a cover to constitute the chamber. Consequently, the present invention is applicable even to a case where a refrigerant having a large high/low pressure difference is contained like carbon dioxide. 
   Embodiment 14 
   Next, another embodiment of a compression system CS of the present invention will be described.  FIG. 14  shows a vertically sectional side view of an inner high pressure type rotary compressor  10  comprising first and second rotary compression elements according to an embodiment of a multicylinder rotary compressor of the compression system CS of the present invention, and  FIG. 15  shows a vertically sectional side view (showing a section different from that of  FIG. 1 ) of the rotary compressor  10  of  FIG. 1 . It is to be noted that the compression system CS of the present embodiment constitutes a part of a refrigerant circuit of an air conditioner which is a refrigerating device for conditioning air in a room. It is to be noted that in  FIGS. 14 and 15 , components denoted with the same reference numerals as those of  FIGS. 1 to 13  of the above-described embodiments produce the same or similar effects, and description thereof is omitted. 
   Moreover, a guide groove  72  is formed in a second cylinder  40 , and a housing section  472 A is formed outside the guide groove  72 , that is, on a back-surface side of the second vane  52 . The guide groove houses the second vane  52 , and the housing section houses a weak spring  76  which is urging means as shown in  FIG. 16 . The housing section  472 A opens on the sides of the guide groove  72  and a sealed container  12 , an opening on a sealed container  12  side communicates with/is connected to a pipe  75  described later, and the opening is sealed together with the inside the sealed container  12 . 
   The above-described weak spring  76  urges the second vane  52  toward a second roller  48 , one end of the spring abuts on a back surface side end portion of the second vane  52 , and the other end of the spring is attached to/fixed to a tip of the pipe  75  communicating with/connected to a sealed container  12  side of the housing section  472 A. An urging force of the weak spring  76  is set to be not more than an urging force in a case where a suction-side pressure of both rotary compression elements  32 ,  34  or the first rotary compression element  32  is applied as a back pressure of the second vane  52 . 
   Moreover, an electromagnetic valve  200  is disposed in a middle portion of a refrigerant introducing tube  94  on an inlet side of the sealed container  12  on an outlet side of an accumulator  146 . This electromagnetic valve  200  is a valve device for controlling flowing of a refrigerant into the second cylinder  40 , and is controlled by a controller  210  described later which is a control device. 
   Here, the above-described controller  210  constitutes a part of the compression system CS of the present invention, and controls a rotation number of an electromotive element  14  of the rotary compressor  10 . As described above, the controller controls opening/closing of the electromagnetic valve  200  of the refrigerant introducing tube  94 , an electromagnetic valve  105  of a refrigerant pipe  101 , and an electromagnetic valve  106  of a refrigerant pipe  102 . 
   Next,  FIG. 17  shows a refrigerant circuit diagram of the air conditioner constituted using the compression system CS. That is, the compression system CS of the embodiment constitutes a part of a refrigerant circuit of the air conditioner shown in  FIG. 17 , and comprises the rotary compressor  10 , the controller  210  and the like. A refrigerant discharge tube  96  of the rotary compressor  10  is connected to an inlet of an outdoor heat exchanger  152 . The controller  210 , rotary compressor  10 , and outdoor heat exchanger  152  are disposed in an outdoor unit (not shown) of the air conditioner. A pipe connected to an outlet of the outdoor heat exchanger  152  is connected to an expansion valve  154  which is pressure reducing means, and a pipe extending out of the expansion valve  154  is connected to an indoor heat exchanger  156 . These expansion valve  154  and indoor heat exchanger  156  are disposed in an indoor unit (not shown) of the air conditioner. A refrigerant pipe  100  of the rotary compressor  10  is connected to an outlet side of the indoor heat exchanger  156 . 
   It is to be noted that an HFC or HC-based refrigerant is used as the refrigerant. As oils which are lubricants, existing oils are used such as a mineral oil, an alkyl benzene oil, an ether oil, and an ester oil. 
   Next, an operation of the rotary compressor  10  constituted as described above will be described. 
   (1) First Operation Mode (Operation at Usual or High Load Time) 
   First, a first operation mode will be described in which both the rotary compression elements  32 ,  34  perform a compression work with reference to  FIG. 18 . It is to be noted that  FIG. 18  is a diagram showing a flow of a refrigerant in the first operation mode of the rotary compressor  10  (a bold line in the figure shows the flow of the refrigerant). 
   The controller  210  energizes the electromotive element  14  of the rotary compressor  10  based on an operation instruction input of an indoor-unit-side controller (not shown) disposed in the indoor unit. At this time, simultaneously with the energization of the electromotive element  14 , the controller  210  opens the electromagnetic valve  200  of the refrigerant introducing tube  94  and the electromagnetic valve  106  of the refrigerant pipe  102 , and closes the electromagnetic valve  105  of the refrigerant pipe  101  ( FIG. 18 ). Accordingly, the refrigerant pipe  102  communicates with the pipe  75 , and the controller  210  controls a rotation number of the electromotive element  14  of the rotary compressor  10  to start the compressor in a state in which the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . It is to be noted that simultaneously with the energization of the electromotive element  14 , the controller  210  executes a control in such a manner as to open the electromagnetic valves  200  and  106 , and close the electromagnetic valve  105 . The electromagnetic valves  200 ,  105 ,  106  may be opened/closed before starting the rotary compressor  10 . For example, the controller  210  may open the electromagnetic valves  200  and  106  and close the electromagnetic valve  105  before energizing the electromotive element  14 . 
   Moreover, when the stator coil  28  of the electromotive element  14  is energized via a terminal  20  and wiring (not shown), the electromotive element  14  starts, and a rotor  24  rotates. By this rotation, first and second rollers  46 ,  48  are fitted into upper and lower eccentric portions  42 ,  44  integrally disposed in a rotation shaft  16 , and eccentrically rotate in first and second cylinders  38 ,  40 . 
   Accordingly, a refrigerant flows into the accumulator  146  from the refrigerant pipe  100  of the rotary compressor  10 . Since the electromagnetic valve  105  of the refrigerant pipe  101  is closed as described above, the refrigerant on suction sides of both the rotary compression elements  32 ,  34  passes through the refrigerant pipe  100 , and all flows into the accumulator  146  without flowing into the pipe  75 . 
   The refrigerant which has flown into the accumulator  146  is separated into gas/liquid in the accumulator, and thereafter the only refrigerant gas enters the respective refrigerant discharge tubes  92 ,  94  which open in the accumulator  146 . The refrigerant gas which has entered the refrigerant introducing tube  92  is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32  via a suction passage  58 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and the first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas is passed through a discharge port (not shown) from the high-pressure chamber side of the first cylinder  38 , and is discharged to a discharge muffling chamber  62 . 
   On the other hand, the low-pressure refrigerant gas which has entered the refrigerant introducing tube  94  is passed through a suction passage  60 , and sucked on the low-pressure chamber side of the second cylinder  40  of the second rotary compression element  34 . The refrigerant gas sucked on the low-pressure chamber side of the second cylinder  40  is compressed by the operations of the second roller  48  and the second vane  52 . 
   Here, there is an equilibrium pressure in the refrigerant circuit at the time of the starting of the rotary compressor  10 . That is, after stopping the previous operation of the rotary compressor  10 , the pressure is gradually equalized. After elapse of a predetermined time, the inside of the refrigerant circuit entirely has the equilibrium pressure. Therefore, when the rotary compressor  10  is started in a state in which the inside of the refrigerant circuit is entirely brought into the equilibrium pressure, immediately after starting the rotary compressor  10 , the equilibrium pressure is substantially indicated by pressures of suction-side refrigerants of both the rotary compression elements  32 ,  34 . The pressures are applied as a back pressure of the second vane  52 . Similarly, the pressure inside the second cylinder  40  also indicates a substantially equilibrium pressure. 
   Therefore, in a constitution in which the second vane  52  is urged toward the second roller only by the back pressure, the second vane  52  cannot follow up the second roller  48  until the discharge-side pressures of both the rotary compression elements  32 ,  34  rise to certain degrees. Therefore, the compression work is not substantially performed in the second rotary compression element  34 , and the compression work of the refrigerant is performed only by the first rotary compression element  32  provided with a spring  74 . 
   Moreover, immediately after the starting, the state in the refrigerant circuit is unstable. Therefore, pulsations of the discharge-side pressures of both the rotary compression elements  32 ,  34  also remarkably increase. Therefore, when the compressor is started in a state in which the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied without disposing any urging means in the second vane  52 , disadvantages have occurred that a follow-up property of the second vane  52  is deteriorated by the pulsations of the discharge-side pressures of both the rotary compression elements  32 ,  34 , the second vane  52  collides with the second roller  48 , and a collision sound is generated. 
   However, since the weak spring  76  is disposed to urge the second vane  52  toward the second roller  48 , the second vane  52  can follow up the second roller  48  by the urging force of the weak spring  76  even at a starting time when the inside of the second cylinder  40  has a pressure (equilibrium pressure) substantially equal to that of the housing section  472 A. Consequently, the follow-up property of the second vane  52  can be improved at the starting time. Since the compression work can be performed even in the second rotary compression element  34  at the starting time, the performance of the air conditioner comprising the rotary compressor  10  can be enhanced. 
   It is to be noted that the refrigerant gas is compressed by the operations of the second roller  48  and second vane  52  to obtain a high-temperature/pressure. The gas is passed through the discharge port  49  from the high-pressure chamber side of the second cylinder  40 , and is discharged to the discharge muffling chamber  64 . The refrigerant gas discharged to the discharge muffling chamber  64  is discharged to the discharge muffling chamber  62  via the communication path  120 , and flows together with the refrigerant gas compressed by the first rotary compression element  32 . Moreover, the joined refrigerant gas is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . On the other hand, since the electromagnetic valve  106  is opened by the controller  210  as described above, a part of the refrigerant passed through the refrigerant discharge tube  96  flows into the housing section  472 A from the refrigerant pipe  102  via the pipe  75 . 
   On the other hand, the refrigerant gas which has flown into the outdoor heat exchanger  152  emits heat, pressure of the gas is reduced by the expansion valve  154 , and thereafter the gas flows into the indoor heat exchanger  156 . In the indoor heat exchanger  156 , the refrigerant evaporates, the heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   (2) Switching from First Operation Mode to Second Operation Mode (Operation at Light Load Time) 
   Next, when the above-described usual or high load state turns to a light load state in the room, the controller  210  shifts to a second operation mode from the first operation mode. This second operation mode is a mode in which the only first rotary compression element  32  substantially performs a compression work. The operation mode is performed in a case where the inside of the room has a light load, and the electromotive element  14  rotates at a low speed in the first operation mode. When the only first rotary compression element  32  substantially performs the compression work in a small capacity region of the compression system CS, an amount of the refrigerant gas to be compressed can be reduced as compared with a case where both the first and second cylinders  38 ,  40  perform the compression work. Therefore, the rotation number of the electromotive element  14  can be raised also at a light load time by the corresponding amount, the operation efficiency of the electromotive element  14  is improved, and leak loss of the refrigerant can be reduced. 
   Here, at a mode switching time from the first operation mode to the second operation mode, the controller  210  rotates the electromotive element  14  at the low speed, a rotation number is set, for example, to 50 Hz or less, and a compression ratio of the rotary compression element  32  is controlled into 3.0 or less. 
   Furthermore, the controller  210  closes the above-described electromagnetic valve  200 , and interrupts the flowing of the refrigerant into the second cylinder  40  as shown in  FIG. 19 . Accordingly, any compression work is not performed in the second rotary compression element  34 . When the refrigerant is inhibited from being passed into the second cylinder  40 , a pressure in the second cylinder  40  is slightly higher than a suction-side pressure of both the rotary compression elements  32 ,  34  (the second roller  48  rotates, a high pressure in the sealed container  12  slightly flows from a gap of the second cylinder  40  or the like, and therefore the pressure in the second cylinder  40  becomes slightly higher than the suction-side pressure). 
   Moreover, the controller  210  opens the electromagnetic valve  105  of the refrigerant pipe  101 , and closes the electromagnetic valve  106  of the refrigerant pipe  102 . Accordingly, the refrigerant pipe  101  communicates with the pipe  75 , the suction-side refrigerant of the first rotary compression element  32  passes through the refrigerant pipe  100 , and a part of the refrigerant flows into the back-pressure chamber  72 A from the refrigerant pipe  101  via the pipe  75 . Accordingly, the housing section  472 A has a suction-side pressure of the first rotary compression element  32 , and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   Here, since the urging force of the weak spring  76  onto the second roller  48  is set to be not more than the suction-side pressure of the first rotary compression element  32 , the pressure in the second cylinder  40  is set to be higher than the suction-side pressure of the first rotary compression element  32  as described above, and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . Accordingly, the pressure in the second cylinder  40  becomes higher than the pressure of the housing section  472 A for urging the second vane  52  toward the second roller  48 , and the urging force of the weak spring  76 . 
   That is, the urging force for urging the second vane  52  on a back-pressure side (housing section  472 A side) by the pressure in the second cylinder  40  is larger than the pressure of the housing section  472 A for urging the second vane  52  toward the second roller  48  and the urging force of the weak spring  76 . Therefore, the second vane  52  is pushed on the housing section  472 A side opposite to the second roller  48 , and housed in the guide groove  72 . Accordingly, at the time of the switching to the second operation mode, the second vane  52  can be retracted from the second cylinder  40  in an early stage, and housed in the guide groove  72 . 
   At this time, when the urging means is not disposed on the back-pressure side of the second vane  52 , and when the second vane  52  is pushed by the pressure in the second cylinder  40 , and retracted from the second cylinder  40  at the switching time, a problem occurs that the second vane  52  collides with a wall portion of the housing section  472 A or a tip of the pipe  75  to generate a collision sound. However, when the weak spring  76  is disposed, and when the second vane  52  retreats from the second cylinder  40 , impact can be absorbed by the weak spring  76 . Therefore, it is possible to avoid beforehand a disadvantage that the second vane  52  collides with the second roller  48  to generate the collision sound, and the mode can shift to the second operation mode in which the only first rotary compression element  32  substantially performs the compression work. 
   (3) Second Operation Mode 
   Next, an operation of the rotary compressor  10  will be described in a second operation mode. It is to be noted that in the same manner as in the switching time from the first operation mode to the second operation mode, the electromagnetic valve  200  of the refrigerant introducing tube  94  is closed, the electromagnetic valve  105  of the refrigerant pipe  101  is opened, and the electromagnetic valve  106  of the refrigerant pipe  102  remains to be closed ( FIG. 19 ). The low-pressure refrigerant flows into the accumulator  146  from the refrigerant pipe  100  of the rotary compressor  110 . After the refrigerant is separated into the gas/liquid in the accumulator, the only refrigerant gas enters the refrigerant discharge tube  92  which opens in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  flows through the suction passage  58 , and is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32 . 
   Since the electromagnetic valve  105  of the refrigerant pipe  101  is opened by the controller  210 , a part of the refrigerant passed through the refrigerant pipe  100  flows into the housing section  472 A from the refrigerant pipe  101  via the pipe  75 . Accordingly, the housing section  472 A obtains the suction-side pressure of the first rotary compression element  32 , and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   On the other hand, the refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and the first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas is discharged to the discharge muffling chamber  62  from the high-pressure chamber side of the first cylinder  38  through a discharge port (not shown). The refrigerant gas discharged to the discharge muffling chamber  62  is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . It is to be noted that since the electromagnetic valve  106  is closed as described above, the refrigerant flows through the refrigerant discharge tube  96  on the discharge side of the first rotary compression element  32 , and all flows into the outdoor heat exchanger  152  without flowing through the pipe  75 . Moreover, the refrigerant gas which has flown into the outdoor heat exchanger  152  emits heat. After the pressure of the gas is reduced by the expansion valve  154 , the gas flows into the indoor heat exchanger  156 . In the exchanger, the refrigerant evaporates. At this time, the heat is absorbed from air circulated in the room to exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked into the rotary compressor  110 , and this cycle is repeated. 
   It is to be noted that in the second operation mode, the controller  210  closes the above-described electromagnetic valve  200 . The operation is performed while stopping the flowing of the refrigerant into the second cylinder  40 . Accordingly, in the second operation mode, the pressure in the second cylinder  40  is kept to be higher than the back pressure of the second vane  52 . Therefore, the second vane  52  is pushed toward the housing section  472 A (weak spring  76  side) opposite to the second roller  48  by the pressure in the second cylinder  40 , and the vane does not come into the second cylinder  40 . Consequently, it is possible to avoid beforehand a disadvantage that the second vane  52  comes into the second cylinder  40  during the operation in the second operation mode, collides with the second roller  48 , and generates the collision sound. 
   (4) Switching from Second Operation Mode to First Operation Mode 
   On the other hand, when the above-described light load state turns to a usual or high load state in the room, the controller  210  shifts from the second operation mode to the first operation mode. Here, an operation will be described in switching the second operation mode to the first operation mode. In this case, the controller  210  rotates the electromotive element  14  at the low speed (rotation number of 50 Hz or less), and the compression ratio of both the rotary compression elements  32 ,  34  is controlled into 3.0 or less. The controller  210  opens the electromagnetic valve  200  and allows the refrigerant to flow into the second cylinder  40 . Moreover, the controller closes the electromagnetic valve  105  of the refrigerant pipe  101 , and opens the electromagnetic valve  106  of the refrigerant pipe  102 . 
   Accordingly, the refrigerant pipe  102  communicates with the pipe  75 , discharge-side refrigerants of both the rotary compression elements  32 ,  34  flow into the housing section  472 A, and the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . 
   When the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 , the housing section  472 A of the second vane  52  has a pressure which is higher than that inside the second cylinder  40 . Therefore, the second vane  52  is pushed toward the second roller  48  to follow up the roller by the high pressure of the housing section  472 A and the weak spring  76 . Accordingly, the second rotary compression element  34  restarts the compression work. 
   Since the weak spring  76  is disposed in this manner, the second vane  52  is sufficiently urged on the second roller  48  side, and can follow up the second roller  48  in an early stage at the switching time from the second operation mode to the first operation mode. 
   Consequently, at the switching time from the second operation mode to the first operation mode, the follow-up property of the second vane  52  is improved, the operation efficiency is improved, and it is possible to avoid the generation of the collision sound of the second vane  52 . 
   As described above in detail, according to the present invention, the performance and reliability of the compression system CS can be enhanced. The system comprises the rotary compressor  10  which is usable by the switching of the first operation mode in which the first and second rotary compression elements  32 ,  34  perform the compression work and the second operation mode in which the only first rotary compression element  32  substantially performs the compression work. 
   Consequently, when the refrigerant circuit of the air conditioner is constituted using the compression system CS, the operation efficiency and performance of the air conditioner are enhanced, and power consumption can be reduced. 
   It is to be noted that in the present embodiment, in the first operation mode, and at the starting time, and the switching operation time from the second operation mode to the first operation mode, the controller  210  opens the electromagnetic valve  106  of the refrigerant pipe  102 , and the refrigerant pipe  102  communicates with the pipe  75 . The discharge-side refrigerants flow into the housing section  472 A from both the rotary compression elements  32 ,  34 , and the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . However, the present invention is not limited to this embodiment, and an intermediate pressure may be applied as the back pressure of the second vane  52 . The intermediate pressure is between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 . 
   In this case, for example, as shown in  FIG. 20 , the controller  210  closes the electromagnetic valves  105  and  106  to form a closed space in the pipe  75  connected to the housing section  472 A of the second vane  52 . Then, not a little refrigerant in the second cylinder  40  flows into the housing section  472 A between the second vane  52  and the housing section  70 A. Therefore, the pressure in the housing section  472 A of the second vane  52  is an intermediate pressure between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 , and the intermediate pressure is applied as the back pressure of the second vane  52 . 
   Even when the intermediate pressure is applied as the back pressure of the second vane  52  in this manner, the second vane  52  can be sufficiently urged toward the second roller  48  to follow up the roller in an early stage because the urging force of the weak spring  76  is applied in the same manner as in the above-described embodiments. 
   Embodiment 15 
   Next, a multicylinder rotary compressor of a compression system will be described according to another embodiment of the present invention.  FIGS. 21 and 22  are vertically sectional side views of a rotary compressor  310  according to the present embodiment, respectively. It is to be noted that in  FIGS. 21 and 22 , components denoted with the same reference numerals as those of  FIGS. 1 to 20  produce the same or similar effects. 
   In  FIG. 22 , reference numeral  176  denotes a weak spring for a tensile load, and the spring is disposed outside a guide groove  72  which houses a second vane  52  of a second rotary compression element  34 , that is, in a housing section  472 A on a back-surface side of the second vane  52 . This weak spring  176  pulls the second vane  52  on a side opposite to the second roller  48 . One end of the spring is attached to a tip of the second vane  52 , and the other end is attached to a pipe  75 . The tensile force of the weak spring  176  is set to be not more than the urging force in a case where a suction-side pressure of both rotary compression elements  32 ,  34  or the first rotary compression element  32  is applied as a back pressure of the second vane  52 . 
   Here, a method of attaching the weak spring  176  will be described with reference to  FIG. 23 . As to this weak spring  176 , diameters of opposite ends are formed to be larger than other portions. Moreover, a groove  52 A which matches one end of the weak spring  176  is formed in a center of an end portion on a side of the second vane  52  which does not abut on the second roller  48 , and one end of the weak spring  176  is fitted into the groove  52 A. Similarly, a groove  75 A which matches the other end of the weak spring  176  is formed in an inner wall of the pipe  75  connected to the housing section  472 A, and the other end of the weak spring  176  is fitted in the groove  75 A. Accordingly, the weak spring  176  can be attached to the back surface of the second vane  52 , and the second vane  52  can be pulled on a side opposite to the second roller  48 . It is to be noted that not only in a case where the weak spring  176  is used having the large-diameter opposite ends and the other small portions but also in a case where a spring is used entirely having an equal diameter, for example, as shown in  FIG. 24 , the spring can be attached. In the latter case, when pitches of the opposite end portions of the spring are enlarged, the weak spring can be attached without abutting on the second vane  52 . Moreover, as shown in  FIG. 25 , a hook  177  is disposed in one end of the weak spring, the hook  177  is attached to the second vane  52  (a hole  178  for attaching the hook  177  is formed in the second vane  52 ), and the second vane  52  may be pulled. 
   An operation of the rotary compressor  310  constituted as described above will be described. 
   (1) First Operation Mode (Operation at Usual or High Load Time) 
   First, a first operation mode will be described in which both the rotary compression elements  32 ,  34  perform a compression work. A controller  210  energizes an electromotive element  14  of a rotary compressor  310  based on an operation instruction input of an indoor-unit-side controller (not shown) disposed in the above-described indoor unit. At this time, simultaneously with the energization of the electromotive element  14 , the controller  210  opens an electromagnetic valve  106  of a refrigerant pipe  102 , and closes an electromagnetic valve  105  of a refrigerant pipe  101 . Accordingly, the refrigerant pipe  102  communicates with the pipe  75 . The controller  210  controls a rotation number of the electromotive element  14  of the rotary compressor  310  to start the compressor in a state in which discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as a back pressure of the second vane  52 . It is to be noted that simultaneously with the energization of the electromotive element  14 , the controller  210  exerts a control in such a manner as to open the electromagnetic valve  105  and close the electromagnetic valve  106 . The electromagnetic valves  105 ,  106  may be opened/closed before starting the rotary compressor  310 . For example, the controller  210  may open the electromagnetic valve  106 , and close the electromagnetic valve  105  before the energization of the electromotive element  14 . 
   Moreover, when a stator coil  28  of the electromotive element  14  is energized via a terminal  20  and wiring (not shown), the electromotive element  14  starts, and a rotor  24  rotates. By this rotation, first and second rollers  46 ,  48  are fitted into upper and lower eccentric portions  42 ,  44  integrally disposed in a rotation shaft  16 , and eccentrically rotate in first and second cylinders  38 ,  40 . 
   Accordingly, a refrigerant flows into an accumulator  146  from a refrigerant pipe  100  of the rotary compressor  310 . The electromagnetic valve  105  of the refrigerant pipe  101  is closed as described above. Therefore, when the refrigerant flows through the refrigerant pipe  100  on suction sides of both the rotary compression elements  32 ,  34 , all the refrigerant flows into the accumulator  146  without flowing into the pipe  75 . 
   The refrigerant which has flown into the accumulator  146  is separated into gas/liquid in the accumulator, and thereafter the only refrigerant gas enters refrigerant discharge tubes  92 ,  94  which open in the accumulator  146 . The refrigerant gas which has entered the refrigerant introducing tube  92  is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32  via a suction passage  58 . 
   The refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and a first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas is passed through a discharge port (not shown) from the high-pressure chamber side of the first cylinder  38 , and is discharged to a discharge muffling chamber  62 . 
   Here, there is an equilibrium pressure in a refrigerant circuit at a starting time of the rotary compressor  310 . That is, after stopping the previous operation of the rotary compressor  310 , the pressure is gradually equalized. After elapse of a predetermined time, the inside of the refrigerant circuit has the equilibrium pressure. Therefore, when the rotary compressor  310  is started in a situation in which the inside of the refrigerant circuit is entirely brought into the equilibrium pressure, immediately after starting the rotary compressor  310 , the equilibrium pressure is substantially indicated by pressures of suction-side refrigerants of both the rotary compression elements  32 ,  34 . The pressures are applied as a back pressure of the second vane  52 . Similarly, the pressure inside the second cylinder  40  also indicates a substantially equilibrium pressure. 
   Therefore, the second vane  52  cannot follow up the second roller  48  until the discharge-side pressures of both the rotary compression elements  32 ,  34  rise to certain degrees. Therefore, the compression work is not substantially performed in the second rotary compression element  34 , and the compression work of the refrigerant is performed only by the first rotary compression element  32  provided with a spring  74 . 
   In this case, immediately after the starting, the state in the refrigerant circuit is unstable. Therefore, pulsations of the discharge-side pressures of both the rotary compression elements  32 ,  34  also remarkably increase. Therefore, when the compressor is started in a state in which the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied, disadvantages occur that a follow-up property of the second vane  52  is deteriorated by the pulsations of the discharge-side pressures of both the rotary compression elements  32 ,  34 , and the second vane  52  collides with the second roller  48  to generate a collision sound. 
   However, in the present embodiment, the weak spring  176  for the tensile load is disposed. The spring pulls the second vane  52  on a side opposite to the second roller  48 . Accordingly, the second vane  52  does not come into the second cylinder  40  by the tensile force of the weak spring  76 . Therefore, it is possible to avoid beforehand the disadvantage that the second vane  52  collides with the second roller  48  to generate the collision sound. 
   On the other hand, the refrigerant gas is compressed by the first rotary compression element  32 , discharged to the discharge muffling chamber  62 , and then discharged into the sealed container  12  via a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from a refrigerant discharge tube  96  formed in an end cap  12 B of the sealed container  12 , and flows into an outdoor heat exchanger  152 . On the other hand, since the electromagnetic valve  106  is opened by the controller  210  as described above, a part of the refrigerant passed through the refrigerant discharge tube  96  flows into the housing section  472 A from the refrigerant pipe  102  via the pipe  75 . 
   On the other hand, the refrigerant gas which has flown into the outdoor heat exchanger  152  emits heat, pressure of the gas is reduced by an expansion valve  154 , and thereafter the gas flows into an indoor heat exchanger  156 . The refrigerant evaporates in the indoor heat exchanger  156 , the heat is absorbed from air circulated in a room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  310 . The refrigerant repeats this cycle. 
   On the other hand, when the rotary compressor  310  starts, and a predetermined time elapses, a high/low pressure difference is generated in the refrigerant circuit  10 . That is, the suction-side pressure of the first rotary compression element  32  is a low pressure, and the discharge-side pressure is a high pressure. Accordingly, the second vane  52  follows up the second roller  48  by the discharge-side pressure, and the compression work is performed even in the second rotary compression element  34 . Here, the tensile force of the weak spring  176  is set to be not more than an urging force in a case where the suction-side pressure of the first rotary compression element  32  (or both the rotary compression elements  32 ,  34 ) is applied as the back pressure of the second vane  52  as described above. Therefore, the second vane  52  can follow up the second roller  48  by the high pressure which is the discharge-side pressure without any trouble. 
   It is to be noted that the refrigerant gas is compressed by the operations of the second roller  48  and second vane  52  to obtain a high-temperature/pressure. The gas is passed through the discharge port  49  from the high-pressure chamber side of the second cylinder  40 , and Is discharged to the discharge muffling chamber  64 . The refrigerant gas is discharged to the discharge muffling chamber  64 , discharged to the discharge muffling chamber  62  via the communication path  120 , and flows together with the refrigerant gas compressed by the first rotary compression element  32 . Moreover, the joined refrigerant gas is discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . On the other hand, since the electromagnetic valve  106  is opened by the controller  210  as described above, a part of the refrigerant passed through the refrigerant discharge tube  96  flows into the housing section  472 A from the refrigerant pipe  102  via the pipe  75 . 
   On the other hand, the refrigerant gas which has flown into the outdoor heat exchanger  152  emits heat, pressure of the gas is reduced by the expansion valve  154 , and thereafter the gas flows into the indoor heat exchanger  156 . In the indoor heat exchanger  156 , the refrigerant evaporates, the heat is absorbed from air circulated in the room to thereby exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked by the rotary compressor  10 . The refrigerant repeats this cycle. 
   (2) Switching from First Operation Mode to Second Operation Mode (Operation at Light Load Time) 
   Next, when the above-described usual or high load state turns to a light load state in the room, the controller  210  shifts to a second operation mode from the first operation mode. This second operation mode is a mode in which the only first rotary compression element  32  substantially performs a compression work. The operation mode is performed in a case where the inside of the room has a light load, and the electromotive element  14  rotates at a low speed in the first operation mode. When the only first rotary compression element  32  substantially performs the compression work in a small capacity region of the compression system CS, an amount of the refrigerant gas to be compressed can be reduced as compared with a case where both the first and second cylinders  38 ,  40  perform the compression work. Therefore, the rotation number of the electromotive element  14  can be raised also at a light load time by the corresponding amount, the operation efficiency of the electromotive element  14  is improved, and leak loss of the refrigerant can be reduced. 
   Here, at a mode switching time from the first operation mode to the second operation mode, the controller  210  rotates the electromotive element  14  at the low speed, a rotation number is set, for example, to 50 Hz or less, and a compression ratio of the rotary compression element  32  is controlled into 3.0 or less. 
   Furthermore, the controller  210  opens the electromagnetic valve  105  of the refrigerant pipe  101 , and closes the electromagnetic valve  106  of the refrigerant pipe  102 . Accordingly, the refrigerant pipe  101  communicates with the pipe  75 , the refrigerant passes through the refrigerant pipe  100  on the suction sides of both the rotary compression elements  32 ,  34 , and a part of the refrigerant flows into the housing section  472 A from the refrigerant pipe  101  via the pipe  75 . Consequently, the housing section  472 A has the suction-side pressures of both the rotary compression elements  32 ,  34 , and the suction-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . 
   Here, the back pressures inside the second cylinder  40  and the second vane  52  correspond to equal suction-side pressures of both the rotary compression elements  32 ,  34 . At this time, when the weak spring  176  is not disposed on the back-pressure side of the second vane  52 , the pressure in the second cylinder  40  is equal to that of the second vane  52  as described above. Therefore, a problem has occurred that much time is required for the second vane  52  to retreat from the second cylinder  40 , and during this time, the second vane  52  collides with the second roller  48  to generate the collision sound. 
   However, since the weak spring  176  for the tensile load is disposed, the second vane  52  is pulled on a housing section  472 A side opposite to the second roller  48  by the tensile force of the weak spring  176 , and the second vane  52  is housed in the guide groove  72 . Consequently, at the switching time to the second operation mode, the second vane  52  is retracted from the second cylinder  40  in an early stage, and can be housed in the guide groove  72 . 
   Consequently, it is possible to avoid beforehand the disadvantage that the second vane  52  collides with the second roller  48  to generate the collision sound. The mode can shift to the second operation mode in which the only first rotary compression element  32  substantially performs the compression work. 
   (3) Second Operation Mode 
   Next, an operation of the rotary compressor  310  will be described in a second operation mode. It is to be noted that in the same manner as in the switching time from the first operation mode to the second operation mode, the electromagnetic valve  105  of the refrigerant pipe  101  is opened, and the electromagnetic valve  106  of the refrigerant pipe  102  remains to be closed. The low-pressure refrigerant flows into the accumulator  146  from the refrigerant pipe  100  of the rotary compressor  310 . After the refrigerant is separated into the gas/liquid in the accumulator, the only refrigerant gas enters the refrigerant discharge tube  92  which opens in the accumulator  146 . The low-pressure refrigerant gas which has entered the refrigerant introducing tube  92  flows through the suction passage  58 , and is sucked on the low-pressure chamber side of the first cylinder  38  of the first rotary compression element  32 . 
   Since the electromagnetic valve  105  of the refrigerant pipe  101  is opened by the controller  210 , a part of the refrigerant passed through the refrigerant pipe  100  flows into the housing section  472 A from the refrigerant pipe  101  via the pipe  75 . Accordingly, the housing section  472 A obtains the suction-side pressure of the first rotary compression element  32 , and the suction-side pressure of the first rotary compression element  32  is applied as the back pressure of the second vane  52 . 
   On the other hand, the refrigerant gas sucked on the low-pressure chamber side of the first cylinder  38  is compressed by the operations of the first roller  46  and the first vane  50  to constitute a high-temperature/pressure refrigerant gas. The gas is discharged to the discharge muffling chamber  62  from the high-pressure chamber side of the first cylinder  38  through a discharge port (not shown). The refrigerant gas is discharged to the discharge muffling chamber  62 , and discharged into the sealed container  12  from a hole (not shown) extending through the cup member  63 . 
   Thereafter, the refrigerant in the sealed container  12  is discharged to the outside from the refrigerant discharge tube  96  formed in the end cap  12 B of the sealed container  12 , and flows into the outdoor heat exchanger  152 . It is to be noted that since the electromagnetic valve  106  is closed as described above, the refrigerant flows through the refrigerant discharge tube  96  on the discharge side of the first rotary compression element  32 , and all flows into the outdoor heat exchanger  152  without flowing through the pipe  75 . Moreover, the refrigerant gas which has flown into the outdoor heat exchanger  152  emits heat. After the pressure of the gas is reduced by the expansion valve  154 , the gas flows into the indoor heat exchanger  156 . In the exchanger, the refrigerant evaporates. At this time, the heat is absorbed from air circulated in the room to exert a cooling function, and the inside of the room is cooled. Moreover, the refrigerant emanates from the indoor heat exchanger  156  and is sucked into the rotary compressor  310 , and this cycle is repeated. 
   It is to be noted that in the second operation mode, the second vane  52  is pulled on the housing section  472 A side (weak spring  176  side) opposite to the second roller  48  by the weak spring  176 , and the second vane does not come into the second cylinder  40 . Consequently, it is possible to avoid beforehand the disadvantage that the second vane  52  comes into the second cylinder  40  and collides with the second roller  48  to generate the collision sound during the operation in the second operation mode. 
   (4) Switching from Second Operation Mode to First Operation Mode 
   On the other hand, when the above-described light load state turns to a usual or high load state in the room, the controller  210  shifts from the second operation mode to the first operation mode. Here, an operation will be described in switching the second operation mode to the first operation mode. In this case, the controller  210  rotates the electromotive element  14  at the low speed (rotation number of  50  Hz or less), and the compression ratio of both the rotary compression elements  32 ,  34  is controlled into 3.0 or less. The controller  210  closes the electromagnetic valve  105  of the refrigerant pipe  101 , and opens the electromagnetic valve  106  of the refrigerant pipe  102 . 
   Accordingly, the refrigerant pipe  102  communicates with the pipe  75 , discharge-side refrigerants of both the rotary compression elements  32 ,  34  flow into the housing section  472 A, and the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . 
   When the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 , the urging force for urging the second vane  52  toward the second roller  48  becomes larger than the tensile force of the weak spring  176 . Therefore, the second vane  52  is pushed toward the second roller  48  to follow up the roller by the high pressure of the housing section  472 A. Accordingly, the second rotary compression element  34  restarts the compression work. 
   As described above in detail, according to the present invention, the performance and reliability of the compression system CS can be enhanced. The system comprises the rotary compressor  310  which is usable by the switching of the first operation mode in which the first and second rotary compression elements  32 ,  34  perform the compression work and the second operation mode in which the only first rotary compression element  32  substantially performs the compression work. 
   Consequently, when the refrigerant circuit of the air conditioner is constituted using the compression system CS, the operation efficiency and performance of the air conditioner are enhanced, and power consumption can be reduced. 
   It is to be noted that in the present embodiment, in the first operation mode, and at the starting time, and the switching operation time from the second operation mode to the first operation mode, the controller  210  opens the electromagnetic valve  106  of the refrigerant pipe  102 , and the refrigerant pipe  102  communicates with the pipe  75 . The discharge-side refrigerants flow into the housing section  472 A from both the rotary compression elements  32 ,  34 , and the discharge-side pressures of both the rotary compression elements  32 ,  34  are applied as the back pressure of the second vane  52 . However, the present invention is not limited to this embodiment, and an intermediate pressure may be applied as the back pressure of the second vane  52 . The intermediate pressure is between the suction-side and discharge-side pressures of both the rotary compression elements  32 ,  34 . Even in this case, the tensile force of the weak spring  176  is set to be not more than the urging force in the application of the suction-side pressure of both the rotary compression elements  32 ,  34  or the first rotary compression element  32  as the back pressure of the second vane  52 . Therefore, the second vane  52  can follow up the second roller  48  without any trouble. 
   It is to be noted that in the above-described embodiments an HFC or HC-based refrigerant is used as a refrigerant, but a refrigerant having a large high/low pressure difference may be used such as carbon dioxide. For example, a combination of carbon dioxide and polyalkyl glycol (PAG) may be used as the refrigerant. In this case, since the refrigerant compressed by rotary compression elements  32  and  34  has a very high pressure, there is a possibility that the cup member  63  is broken by the high pressure in a case where the discharge muffling chamber  62  is formed into a shape to cover the upper support member  54  with the cup member  63  as in the respective embodiments. 
   Therefore, when the discharge muffling chamber is formed into a shape shown in  FIG. 8 , resistance to pressure can be secured. The chamber is above the upper support member  54  in which the refrigerants compressed by both the rotary compression elements  32 ,  34  flow together. That is, in a discharge muffling chamber  162  of  FIG. 8 , a concavely depressed portion is formed in an upper part of the upper support member  54 , and the concavely depressed portion is closed by an upper cover  66  which is a cover having a predetermined thickness to constitute the chamber. Consequently, the present invention is applicable even to a case where a refrigerant having a large high/low pressure difference is contained like carbon dioxide. 
   It is to be noted that the above-described embodiments have been described using the rotary compressor in which the rotation shaft  16  is vertically laid, but needless to say, this invention is applicable to the use of the rotary compressor in which the rotation shaft is horizontally laid. 
   Furthermore, in the above-described embodiments, the two-air-cylinder rotary compressor has been used, but the present invention may be adapted to a compression system comprising a multicylinder rotary compressor comprising three air cylinders or more rotary compression elements.