Abstract:
An object is to solve a problem that the smaller the number of rotations of a rotary compressor is, the more an efficiency decrease of the compressor is generated owing to an increase of a rotary vibration and an efficiency decrease of a motor. In the rotary compressor including, in a sealed vessel, a electromotive element and a rotary compression element driven by this electromotive element, on one of an upper end face of a rotor constituting the electromotive element (on a side opposite to a compression mechanism) and a lower end face of the rotor (on a compression mechanism side), a rotation inertia article capable of obtaining a rotation inertia moment is disposed. In consequence, it is possible to obtain the compressor having a high efficiency in which an increase of the rotary vibration of the compressor is suppressed even during an operation having the small number of the rotations of the compressor.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a rotary compressor including, in a sealed vessel, a electromotive element, a rotary compression element driven by a rotary shaft of this electromotive element and a cantilever bearing which rotatably supports the rotary shaft of this rotary compression element.  
         [0002]     Heretofore, a rotary compressor such as a multistage compression type rotary compressor including first and second rotary compression elements includes, in a sealed vessel, a electromotive element and the first and second rotary compression elements driven by a rotary shaft of this electromotive element.  
         [0003]     An electromotive element is constituted of an annular stator fixed along an inner peripheral surface which defines an upper space of the sealed vessel by welding; and a rotor inserted in the element so that a slight interval is disposed between the rotor and an inner periphery of this stator. This rotor is fixed to the rotary shaft passed through the center of the element in a vertical direction.  
         [0004]     Moreover, the first and second rotary compression elements include an intermediate partition plate; upper and lower cylinders disposed on and under this intermediate partition plate; rollers which are fitted into eccentric portions disposed on the rotary shaft with a phase difference of 180 degrees to eccentrically rotate in these cylinders; vanes which abut on the rollers to define the insides of the cylinders into low pressure chamber sides and high pressure chamber sides, respectively; an upper support member and a lower support member which block an upper opening surface of the upper cylinder and a lower opening surface of the lower cylinder and which have bearings of the rotary shaft, respectively; and upper and lower discharge muffling chambers, respectively. Each discharge muffling chamber is connected to the high pressure chamber side in each cylinder by a discharge port. In each discharge muffling chamber, a discharge valve is disposed which openably blocks the discharge port (see, e.g., Japanese Patent Application Laid-Open No. 2004-19599).  
         [0005]     In the rotor of the conventional rotary compressor, a rotation angular speed inversely proportional to a rotation inertia moment is generated in proportion to a difference between a compression torque and a torque of a motor, and a fluctuation (reaction of the rotation angular speed) of the rotation angular speed, which is inversely proportional to the rotation inertia moment, is a cause for a rotary vibration of the rotary compressor. The rotation angular speed of the rotor is an integral of the rotation angular speed inversely proportional to the rotation inertia moment with respect to a time. After one rotation, the rotation angular speed returns to an original rotation angular speed. Therefore, the smaller the number of the rotations of the compressor is, the longer a time required for one rotation becomes. Moreover, a fluctuation width of the rotation angular speed during one rotation increases. Therefore, there is a problem that the vibration of the compressor increases.  
         [0006]     Furthermore, when there is a large fluctuation width of the rotation angular speed during one rotation, a ratio increases at which the compressor is operated in a rotation angular speed range having a small efficiency, and an efficiency of the motor decreases. Therefore, the smaller the number of the rotations of the motor is, the more the efficiency of the compressor decreases. When the compressor or the motor is miniaturized, the rotation inertia moment decreases, and the increase of the compressor vibration and the decrease of the efficiency easily appear.  
       SUMMARY OF THE INVENTION  
       [0007]     A rotary compressor of a first invention has, in a sealed vessel, a electromotive element, a compression mechanism driven by this electromotive element and a cantilever bearing which rotatably supports a rotary shaft of the electromotive element, and the rotary compressor has, on the bottom of a rotor (on a compression mechanism side), a mass article which extends to a lower part of a stator and which obtains a rotation inertia moment.  
         [0008]     Moreover, a rotary compressor of a second invention has, in a sealed vessel, a electromotive element, a compression mechanism driven by this electromotive element and a cantilever bearing which rotatably supports a rotary shaft of the electromotive element, and the rotary compressor has, on the top of a rotor (on a side opposite to the compression mechanism), a mass article which extends to a lower part of a stator and which obtains a rotation inertia moment.  
         [0009]     Furthermore, in a rotary compressor of a third invention, the above inventions are characterized in that the mass article disposed on the rotor is formed into a shape having an outer diameter which is equal to or smaller than an outer diameter of the rotor until a necessary insulation distance is reached from a stator coil, and after the insulation distance, the outer diameter of the shape is enlarged toward an inner wall of the sealed vessel into such as size as to cover the stator coil.  
         [0010]     In addition, in a rotary compressor of a fourth invention, the above inventions are characterized in that a discharge port to discharge a compressed gas from the rotary compression element into the sealed vessel is disposed in a position corresponding to ½ or less of the maximum outer diameter of the mass article disposed on the rotor.  
         [0011]     According to the first or second invention, the rotary compressor comprises, in the sealed vessel, the electromotive element, the rotary compression element driven by this electromotive element and the cantilever bearing which rotatably supports the rotary shaft of the electromotive element. The mass article capable of obtaining the rotation inertia moment is attached to one of an upper end face of the rotor (on the side opposite to the compression mechanism) and a lower end face of the rotor (on the compression mechanism side). In consequence, it is possible to provide the compressor having a high efficiency in which a vibration increase of the compressor is suppressed even during an operation having the small number of rotations of the compressor. Furthermore, the mass article to be attached extends toward the stator. Therefore, when a dimension of the mass article in a width direction is enlarged, a dimension of the article in a thickness direction can be decreased, and the whole compressor can be miniaturized in a height direction.  
         [0012]     Moreover, in addition to the above inventions, according to the third invention, the mass article disposed on the rotor is formed into the shape having the outer diameter which is equal to or smaller than the outer diameter of the rotor until the necessary insulation distance from the stator coil is reached. After the insulation distance, the outer diameter of the shape is enlarged toward the inner wall of the sealed vessel into such a size as to cover the stator coil. In consequence, a necessary rotation inertia moment can be obtained.  
         [0013]     Furthermore, in addition to the above inventions, according to the fourth invention, the discharge port to discharge the compressed gas from the rotary compression element into the sealed vessel is disposed in the position corresponding to ½ or less of the maximum outer diameter of the mass article disposed on the rotor. In consequence, an oil in the discharged gas is separated by the mass article, and an amount of the oil to be discharged from the compressor can be decreased. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a vertically sectional view of a rotary compressor in Embodiment 1 of the present invention (an example in which a rotation inertia article is attached to a compression mechanism side);  
         [0015]      FIG. 2  is a vertically sectional view of the rotary compressor in Embodiment 1 of the present invention (an example in which a rotation inertia article is attached to a side opposite to a compression mechanism);  
         [0016]      FIG. 3  is a vertically sectional view of a rotary compressor in Embodiment 2 of the present invention; and  
         [0017]      FIG. 4  is an enlarged view showing positions of the rotation inertia article and a discharge port in Embodiment 2 of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]     The present invention is characterized in that a rotary compressor having a high efficiency in which a vibration increase of the compressor is suppressed even in a region having the small number of rotations is realized by attaching a rotation inertia article to a rotor. It is also possible to cope with a vibration increase and an efficiency decrease due to miniaturization of the compressor. A mass article disposed on the rotor is formed into a shape having an outer diameter which is equal to or smaller than an outer diameter of the rotor until a necessary insulation distance is reached from a stator coil, and after the insulation distance, the outer diameter of the shape is enlarged toward an inner wall of a sealed vessel into such a size as to cover the stator coil. In consequence, a necessary rotation inertia moment is obtained. Moreover, a discharge port to discharge a compressed gas from a rotary compression element into a sealed vessel is disposed in a position corresponding to ½ or less of the maximum outer diameter of the mass article disposed on the rotor. In consequence, an oil contained in the discharged gas is separated by the mass article, and an amount of the oil to be discharged from the compressor is decreased.  
       Embodiment 1  
       [0019]     Next, an embodiment of the present invention will be described in detail with reference to the drawings.  FIG. 1  shows a vertically sectional view of a high inner pressure type rotary compressor  10  as an embodiment of a rotary compressor of the present invention. The rotary compressor includes first and second rotary compression elements  32 ,  34 , and a mass article, that is, a rotation inertia article  82  attached to a rotor  24  with a rivet  73  on a compression mechanism side.  FIG. 2  shows a vertically sectional view of the rotary compressor  10  in a second invention.  
         [0020]     In  FIG. 1 , the rotary compressor  10  of the present embodiment is the high inner pressure type rotary compressor  10  including, in a vertically cylindrical sealed vessel  12  constituted of a steel plate, an electromotive element  14  as a driving element disposed in an upper space of this sealed vessel  12 ; and a rotary compression mechanism portion  18  constituted of the first and second rotary compression elements  32 ,  34  disposed under this electromotive element  14  and driven by a rotary shaft  16  of the electromotive element  14 . It is to be noted that in the rotary compressor  10  of the present embodiment, carbon dioxide is used as a refrigerant.  
         [0021]     The sealed vessel  12  is constituted of a vessel main body  12 A having a bottom part as an oil reservoir and containing the electromotive element  14  and the rotary compression mechanism portion; and a substantially bowl shaped end cap (lid body)  12 B which blocks an upper opening of this vessel main body  12 A. Moreover, a circular attachment hole  12 D is formed in the top of this end cap  12 B, and a terminal (a wiring line is omitted)  20  for supplying a power to the electromotive element  14  is attached to this attachment hole  12 D.  
         [0022]     The electromotive element  14  is constituted of an annular stator  22  fixed along an inner peripheral surface of an upper part of the sealed vessel  12  by welding; the rotor  24  inserted in the element so that a slight interval is disposed between the rotor and an inner periphery of the stator  22 ; and the rotation inertia article  82  attached to the rotor  24  with the rivet  73 . The rotor  24  and the rotation inertia article  82  are fixed to the rotary shaft  16  extending through the center of the element in a vertical direction.  
         [0023]     Here, the rotation inertia article  82  is formed into a shape having an outer diameter which is equal to or smaller than an outer diameter of the rotor until the minimum necessary insulation distance (changes with a voltage to be applied) is reached from a stator coil  28 , and after the insulation distance is reached, the outer diameter of the shape is enlarged toward an inner wall of the sealed vessel  12  into such a size as to cover the stator coil  28 . Since the outer diameter of the shape of the article is enlarged, it is possible to obtain a large rotation inertia moment with a small amount of a material.  
         [0024]     Moreover, in this case, as the material of the rotation inertia article  82 , copper or a copper alloy is used. The article is formed as a cast article, a forged article or a laminated article formed by laminating plates of copper or the copper alloy.  
         [0025]     The stator  22  has a laminated article  26  constituted by laminating donut-shaped electromagnetic steel plates; and the stator coil  28  wound around teeth portions of this laminated article  26  by a direct winding (concentrated winding) system. Moreover, the rotor  24  is formed of a laminated article  30  constituted of electromagnetic steel plates in the same manner as in the stator  22 .  
         [0026]     An intermediate partition plate  36  is sandwiched as an intermediate partition member between the first rotary compression element  32  and the second rotary compression element  34 , the second rotary compression element  34  as a second stage is disposed on the side of the electromotive element  14  in the sealed vessel  12 , and the first rotary compression element  32  as a first stage is disposed on a side opposite to the electromotive element  14 . That is, the first rotary compression element  32  and the second rotary compression element  34  include a lower cylinder  40  as a first cylinder and an upper cylinder  38  as a second cylinder which constitute the first and second rotary compression elements  32 ,  34 ; and the intermediate partition plate  36  interposed between the cylinders  38  and  40  to block an (upper) opening of the lower cylinder  40  on the side of the electromotive element  14  and a (lower) opening of the upper cylinder  38  on a side opposite to the electromotive element  14 . The elements also include a first roller  48  and a second roller  46  which are fitted into first and second eccentric portions  42 ,  44  disposed on the rotary shaft  16  with a phase difference of 180 degrees in the upper and lower cylinders  38 ,  40  to eccentrically rotate in the cylinders  38 ,  40 , respectively; and vanes (not shown) which abut on the rollers  46 ,  48  to define the insides of the cylinders  38 ,  40  into low-pressure chamber sides and high-pressure chamber sides, respectively. The elements further include a lower support member  56  as a first support member which blocks a (lower) opening of the lower cylinder  40  on the side opposite to the electromotive element  14  and which has a bearing  56 A of the rotary shaft  16 ; and an upper support member  54  as a second support member which blocks an (upper) opening of the upper cylinder  38  on the side of the electromotive element  14  and which has a bearing  54 A of the rotary shaft  16 , respectively. On outer sides of the bearings  54 A,  56 A of the upper and lower support members  54 ,  56 , there are arranged a cover  63  attached to the upper support member  54  to define a discharge muffling chamber  62 ; and a blocking plate  68  to define an intermediate pressure discharge muffling chamber  64  in the lower support member  56 , respectively.  
         [0027]     The upper support member  54  and the lower support member  56  include suction passages  58 ,  60  which communicate with the upper and lower cylinders  38 ,  40  via suction ports  160 ,  161 ; and the discharge muffling chamber  62  and the intermediate pressure discharge muffling chamber  64 , respectively. The discharge muffling chamber  62  is formed by depressing the surface of the upper support member  54  on a side opposite to the upper cylinder  38 , and blocking this depressed portion with the cover  63  as described above. The intermediate pressure discharge muffling chamber  64  is formed by depressing the surface of the lower support member  56  on a side opposite to the lower cylinder  40 , and blocking this depressed portion with the blocking plate  68  so that the chamber is defined by the blocking plate  68 . That is, the discharge muffling chamber  62  is blocked with the cover  63 , and the intermediate pressure discharge muffling chamber  64  is blocked with the blocking plate  68 .  
         [0028]     In this case, the bearing  54 A is erected in the center of the upper support member  54 . Around the outer periphery of the bearing  54 A, the discharge muffling chamber  62  is defined by the cover  63 . A gas discharged from a discharge port (not shown) passes through the discharge muffling chamber  62 , and is discharged into the sealed vessel  12  from a communication passage  65  as a donut-shaped gap between an upper portion of the upper bearing  54 A and the cover  63 .  
         [0029]     Moreover, the bearing  56 A is passed through the center of the lower support member  56 . The bearing  56 A substantially has a donut shape centering on the rotary shaft  16  and having a central hole through which the rotary shaft  16  passes. In the outer periphery of the bearing  56 A, the intermediate pressure discharge muffling chamber  64  is disposed. On the other hand, the blocking plate  68  is formed of a donut-shaped circular steel plate, and fixed to the lower support member  56  from below with bolts  80  attached to four portions of a peripheral part of the plate, and the plate blocks an opening in the bottom of the intermediate pressure discharge muffling chamber  64  which communicates with the lower cylinder  40  of the first rotary compression element  32  by a discharge port (not shown). The bolts  80  are bolts for assembling the first and second rotary compression elements  32 ,  34 , and distant ends of the bolts engage with the upper cylinder  38 . That is, the upper cylinder is provided with screw grooves to be engaged with screw heads formed on distant end portions of the bolts  80 .  
         [0030]     Here, there will be described a procedure to assemble the rotary compression mechanism portion  18  constituted of the first and second rotary compression elements  32 ,  34 . First, the cover  63 , the upper support member  54  and the upper cylinder  38  are positioned, and two upper bolts  78 ,  78  to be engaged with the upper cylinder  38  are inserted from a cover  63  side (from above) in an axial center direction (downwards) to integrate the cover, the upper support member and the upper cylinder. In consequence, the second rotary compression element  34  is assembled.  
         [0031]     Next, the second rotary compression element  34  integrated with the upper bolts  78  is inserted along the rotary shaft  16  from an upper end. Next, the intermediate partition plate  36  is assembled with the lower cylinder  40 , inserted along the rotary shaft  16  from a lower end, and aligned with the upper cylinder  38  already attached. Two upper bolts (not shown) to be engaged with the lower cylinder  40  are inserted from the cover  63  side (from above) in the axial center direction (downwards) to fix the intermediate partition plate, the lower cylinder and the upper cylinder.  
         [0032]     Moreover, after the lower support member  56  is inserted along the rotary shaft  16  from below, the blocking plate  68  is similarly inserted along the rotary shaft  16  from the lower end to close the depressed portion of the lower support member  56 . The four lower bolts  80  are inserted from a blocking plate  68  side (from below) in the axial center direction (upwards), and the distant end portions of the bolts are engaged with the screw grooves formed in the upper cylinder  38 , respectively, to assemble the first and second rotary compression elements  32 ,  34 . It is to be noted that since the rotary shaft  16  is provided with the first and second eccentric portions  42 ,  44 , the components cannot be attached to the rotary shaft  16  in an order other than the above order. Therefore, the blocking plate  68  is finally attached to the rotary shaft  16 .  
         [0033]     Thus, the second rotary compression element  34 , the intermediate partition plate  36 , the lower cylinder  40 , the lower support member  56  and the blocking plate  68  are successively attached to the rotary shaft  16 , and the four bolts  80  are inserted from below the blocking plate  68  finally attached to engage with the upper cylinder  38 . In consequence, the first and second rotary compression elements  32 ,  34  can be fixed to the rotary shaft  16 .  
         [0034]     Moreover, in this case, as the refrigerant, carbon dioxide (CO 2 ) described above which is a natural refrigerant eco-friendly to global environments is used in consideration of combustibility, toxicity and the like, and as a lubricant, an existing oil is used such as a mineral oil, an alkyl benzene oil, an ether oil, an ester oil or a polyalkyl glycol (PAG) oil.  
         [0035]     Furthermore, on the side surface of the vessel main body  12 A of the sealed vessel  12 , sleeves  140 ,  141  and  142 , a refrigerant discharge tube  96  and a service tube  97  are fixed by welding to positions corresponding to those of the suction passages  58 ,  60  of the upper support member  54  and the lower support member  56 , the discharge muffling chamber  64  and the upper part of the electromotive element  14 , respectively. The sleeve  140  is disposed vertically adjacent to the sleeve  141 , and the sleeve  142  is substantially disposed along a diagonal line of the sleeve  141 .  
         [0036]     One end of a refrigerant introducing tube  92  for introducing a refrigerant gas into the upper cylinder  38  is inserted into the sleeve  140 , and the one end of the refrigerant introducing tube  92  is connected to the suction passage  58  of the upper cylinder  38 . This refrigerant introducing tube  92  passes above the sealed vessel  12  to reach the sleeve  142 , and the other end of the tube is inserted into the sleeve  142  and connected to the intermediate pressure discharge muffling chamber  64 .  
         [0037]     Moreover, one end of a refrigerant introducing tube  94  for introducing the refrigerant gas into the lower cylinder  40  is inserted into the sleeve  141 , and the one end of this refrigerant introducing tube is connected to the suction passage  60  of the lower cylinder  40 . The refrigerant discharge tube  96  is fixed to the vessel main body  12 A by welding, and one end of this refrigerant discharge tube  96  is inserted into the sealed vessel  12 .  
         [0038]     Next, there will be described an operation of the rotary compressor  10  constituted as described above. When a power is supplied to the stator coil  28  of the electromotive element  14  via the terminal  20  and a wiring line (not shown), the electromotive element  14  is started to rotate the rotor  24 . When this rotor rotates, the first and second rollers  46 ,  48  fitted into the first and second eccentric portions  42 ,  44  integrated with the rotary shaft  16  eccentrically rotate in the upper and lower cylinders  38 ,  40 .  
         [0039]     In consequence, a refrigerant gas having a low pressure (a first stage suction pressure is about 4 MPaG) is passed through the refrigerant introducing tube  94  and the suction passage  60  formed in the lower support member  56 , sucked from the suction port  161  into the lower cylinder  40  on a low pressure chamber side, and compressed by operations of the first roller  48  and a vane (not shown) to obtain an intermediate pressure. The refrigerant gas having the intermediate pressure is discharged from a high pressure chamber side of the lower cylinder  40  into the intermediate pressure discharge muffling chamber  64  formed in the lower support member  56  via the discharge port (not shown).  
         [0040]     Moreover, the intermediate pressure refrigerant gas discharged into the intermediate pressure discharge muffling chamber  64  passes through the refrigerant introducing tube  92  inserted into the intermediate pressure discharge muffling chamber  64 , and is sucked from the suction port  160  into the upper cylinder  38  on a low pressure chamber side via the suction passage  58  formed in the upper support member  54 .  
         [0041]     The sucked refrigerant gas having the intermediate pressure is compressed in a second stage by operations of the roller  46  and a vane (not shown) to constitute a refrigerant gas having a high temperature and a high pressure (about 12 MPaG). Moreover, the refrigerant gas having the high temperature and the high pressure is discharged from the high pressure chamber side of the upper cylinder  38  into the discharge muffling chamber  62  formed in the upper support member  54  via a discharge port (not shown).  
         [0042]     Furthermore, after the refrigerant discharged into the discharge muffling chamber  62  is discharged from the communication passage  65  disposed in the cover  63  into the sealed vessel  12 , the refrigerant passes through a gap formed in the electromotive element  14  to move to the upper part of the sealed vessel  12 , and is discharged from the rotary compressor  10  through the refrigerant discharge tube  96  connected to the upper part of the sealed vessel  12 .  
         [0043]     Since the rotation inertia article  82  is attached to the rotor  24  in this manner, a necessary rotation inertia moment can be obtained. In consequence, it is possible to obtain the having a high efficiency in which a rotary vibration can be suppressed even in a region where the compressor has the small number of rotations. Since the rotation inertia article  82  is made of copper, the copper alloy or the like, it is possible to obtain the rotation inertia moment necessary for the decrease of the vibration with the inexpensive material without enlarging the shape of the rotor  24  constituted of an expensive material.  
       Embodiment 2  
       [0044]     Next,  FIGS. 3, 4  show another embodiment of the present invention, and  FIG. 3  shows a vertically sectional view of a rotary compressor in the present invention.  FIG. 4  is an enlarged view showing a positional relation between a rotation inertia article and discharge ports  65  which discharge a gas to be discharged in the present invention. It is to be noted that the same components as those of the above embodiment are denoted with the same reference numerals, and description thereof is omitted. As described above in the first embodiment, in a rotary compressor  10 , a rotation inertia article  84  is formed into such an enlarged shape as to cover the whole stator coil  28 .  
         [0045]     Moreover, as shown in  FIG. 4 , the discharge ports  65  which discharge the gas from a rotary compression mechanism portion  18  into a sealed vessel  12  are disposed in positions corresponding to ½ or less of the maximum outer diameter of the rotation inertia article  84 .  
         [0046]     Furthermore, an oil-containing refrigerant gas discharged from the discharge ports  65  abuts on the rotation inertia article  84 , and is separated into an oil and a refrigerant by a rotary force of the rotation inertia article. The separated oil returns to an oil reservoir of the compressor, and the separated gas passes through a gap made between an outer periphery of an electromotive element  14  and an inner periphery of the sealed vessel  12  to move into the upper part of the sealed vessel  12 . The gas is discharged from the rotary compressor  10  through a refrigerant discharge tube  96  connected to the upper part of the sealed vessel  12 .  
         [0047]     Since the discharge ports  65  are disposed in the positions corresponding to ½ or less of the maximum outer diameter of the rotation inertia article  84 , an oil separating capability obtained by the rotation of the rotation inertia article can effectively be used, an amount of the oil to be discharged can be decreased, and the oil can stably be supplied.  
         [0048]     It is to be noted that in the present embodiments, as the rotary compressor, the high inner pressure type rotary compressor  10  has been described which includes the first and second rotary compression elements  32 ,  34 , but the present invention is not limited to this rotary compressor, and may be applied to a rotary compressor including a single cylinder or a rotary compressor including three or more stage rotary compression elements. The present invention is not limited to the high inner pressure type rotary compressor  10 , and may be applied to an intermediate inner pressure type rotary compressor in which a refrigerant compressed by a first rotary compression element is discharged into a sealed vessel and then compressed by a second rotary compression element.  
         [0049]     Moreover, it is assumed in the embodiments that the second rotary compression element  34  disposed on the side of the electromotive element  14  is a second stage, the first rotary compression element  32  disposed on the side opposite to the electromotive element  14  is a first stage, and the refrigerant compressed by the first rotary compression element  32  is compressed by the second rotary compression element  34 . However, the present invention is not limited to the embodiments, and the refrigerant compressed by the second rotary compression element may be compressed by the first rotary compression element.  
         [0050]     Furthermore, when a displacement volume of the first compression mechanism is different from that of the second compression mechanism in the multistage compressor, a weight balance of the rotation inertia article  84  may be changed in accordance with the displacement volume of each compression mechanism to achieve the whole balance.  
         [0051]     In addition, in the present embodiments, it has been described that the rotary shaft is of a vertically disposed type, but needless to say, the present invention may be applied to a rotary compressor having a rotary shaft of a horizontally disposed type. It has been described carbon dioxide is used as the refrigerant of the rotary compressor, but another refrigerant may be used.