Patent Publication Number: US-7223082-B2

Title: Rotary compressor

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a rotary compressor equipped with first and second rotary compressing elements driven by a rotary shaft of a driving element, which are accommodated in a hermetically sealed vessel. 
   In this type of conventional rotary compressor, especially an internal intermediate pressure multistage compression type rotary compressor, a refrigerant gas is introduced through a suction port of the first rotary compression element into a low-pressure chamber of a cylinder wherein the refrigerant gas is compressed to have an intermediate pressure by a roller and a vane, and then discharged from a high-pressure chamber of the cylinder into the hermetically sealed vessel through the intermediary of a discharge port and a discharge muffling chamber. The refrigerant gas having the intermediate pressure in the hermetically sealed vessel is then drawn into the low-pressure chamber of the cylinder through a suction port of the second rotary compressing element and subjected to second-stage compression by the roller and the vane. This causes the refrigerant gas to turn into a hot, high-pressure refrigerant gas, which flows from the high-pressure chamber into an external radiator or the like through the intermediary of the discharge port and the discharge muffling chamber (refer to, for example, Japanese Patent No. 2507047). 
   The rotary shaft has an oil bore vertically formed around an axial center thereof and a horizontal lubrication bore in communication with the oil bore. Oil is drawn up from an oil reservoir located at bottom inside the hermetically sealed vessel  12  by an oil pump, serving as a lubricating device, installed at the bottom end of the rotary shaft. The oil moves up through the oil bore to be supplied to the rotary shaft and sliding portions in the rotary compressing elements through the lubrication bore, thereby to accomplish lubrication and sealing. 
   If a refrigerant exhibiting a considerable high/low pressure difference, such as carbon dioxide (CO 2 ), which is a natural refrigerant, is used in the abovementioned rotary compressor, then the refrigerant pressure reaches 12 MPaG in the second rotary compressing element, which is the high pressure side, while it reaches 8 MPaG (intermediate pressure) in the first rotary compressing element, which is the low pressure side. 
   In such a rotary compressor, an upper open surface of the cylinder of the second rotary compressing element is closed by a supporting member, and the lower open surface thereof is closed with an intermediate partitioner. A roller is provided in a cylinder of the second rotary compressing element. The roller is fitted to an eccentric member of the rotary shaft. For a design reason or for preventing wear on the roller, a small gap is formed between the roller and the supporting member disposed above the roller, and between the roller and the intermediate partitioner disposed under the roller. These gaps inconveniently allow a high-pressure refrigerant gas, which has been compressed by the cylinder of the second rotary compressing element, to enter into the roller (a space around the eccentric member inside the roller). Thus, the high-pressure refrigerant gas accumulates inside the roller. 
   The high-pressure refrigerant gas built up inside the roller causes the pressure inside the roller to become higher than the pressure (intermediate pressure) of the hermetically sealed vessel, which has its bottom portion serving as the oil reservoir. This makes it extremely difficult to supply oil to the inside of the roller from the lubrication bore through the oil bore in the rotary shaft by utilizing a pressure difference, resulting in shortage of a lubricant to the area around the eccentric member inside the roller. 
   As a conventional solution to the abovementioned problem, a passage  200  that provides communication between the inside of the roller (adjacent to the eccentric member) of the second rotary compressing element and the interior of the hermetically sealed vessel has been formed in the upper supporting member  201  disposed above the cylinder of the second rotary compressing element, as shown in  FIG. 16 . The passage  200  releases the high-pressure refrigerant gas accumulated inside the roller into the hermetically sealed vessel so as to prevent the pressure inside the roller from rising to a high level. 
   However, to form the passage  200  for the communication between the inside of the roller and the hermetically sealed vessel, two passages have to be formed by machining, namely, a passage  200 A formed in an inner edge portion of the upper supporting member  201  in an axial direction that opens adjacently to the inside of the roller, and a horizontal passage  200 B for providing communication between the passage  200 A and the hermetically sealed vessel. This has been posing a problem of increased machining cost for forming the passages with resultant higher production cost. 
   Furthermore, the pressure (high pressure) in the cylinder of the second rotary compressing element becomes higher than the pressure (intermediate pressure) in the hermetically sealed vessel having its bottom portion serving as the oil reservoir. This makes it extremely difficult to supply oil through the oil bore and the lubrication bore in the rotary shaft into the cylinder of the second rotary compressing element by utilizing a pressure difference. As a result, lubrication is performed only by the oil in a refrigerant drawn in, thus posing a problem of insufficient lubrication. 
   Furthermore, in the internal intermediate pressure multistage compression type rotary compressor, the pressure in the cylinder (high pressure) of the second rotary compressing element rises higher than the pressure in the hermetically sealed vessel (intermediate pressure) having its bottom portion serving as the oil reservoir. This makes it extremely difficult to supply oil through the oil bore in the rotary shaft into the cylinder by utilizing a pressure difference. As a result, lubrication is performed only by the oil in a refrigerant drawn in, thus posing a problem of insufficient lubrication. 
   Thus, the intermediate partitioner and the cylinder of the second rotary compressing element have to be provided with small bores to provide communication between the oil bore of the rotary shaft and the inlet port of the cylinder so as to supply oil to the second rotary compressing element. This, however, has been posing a problem of increased production cost because of the need for forming the small bores in the intermediate partitioner and the cylinder. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention has been made with a view toward solving the problems with the prior art described above, and it is an object thereof to provide a so-called internal intermediate pressure multistage compression type rotary compressor capable of restraining a pressure inside a roller from inconveniently increasing and also of permitting smooth and reliable lubrication of a cylinder of a second rotary compressing element by a relatively simple construction. 
   It is another object of the present invention to provide an internal intermediate pressure multistage compression type rotary compressor that allows a lubricant to be supplied smoothly and reliably into a cylinder of a second rotary compressing element, whose pressure therein reaches a high level, at low cost. 
   According to one aspect of the present invention, there is provided a so-called internal intermediate pressure multistage compression type rotary compressor having: a first cylinder for constituting a first rotary compressing element and a second cylinder for constituting a second rotary compressing element; a roller that is provided in each of the cylinders and fitted onto an eccentric member of the rotary shaft to eccentrically rotate; an intermediate partitioner provided between the cylinders and the rollers to partition the rotary compressing elements; supporting members that close open surfaces of the cylinders and have bearings for the rotary shaft; and an oil bore formed in the rotary shaft, wherein a surface of the intermediate partitioner that is adjacent to the second cylinder has a groove for communication between the oil bore and a low-pressure chamber in the second cylinder, and the intermediate partitioner has a through bore for communication between an interior of a hermetically sealed vessel and the inside of the rollers. The through bore formed in the intermediate partitioner allows a high-pressure refrigerant gas accumulating inside the rollers to be released into the hermetically sealed vessel. 
   Moreover, even if the pressure in the second cylinder of the second rotary compressing element becomes higher than that in the hermetically sealed vessel having an intermediate pressure, a suction pressure loss in the course of suction in the second rotary compressing element can be utilized to reliably supply oil into a low-pressure chamber of the second cylinder of the second rotary compressing element through the oil bore of the rotary shaft through the intermediary of the groove formed in the intermediate partitioner. 
   According to another aspect of the present invention, there is provided a so-called internal intermediate pressure multistage compression type rotary compressor having: a first cylinder for constituting a first rotary compressing element and a second cylinder for constituting a second rotary compressing element; a roller that is provided in each of the cylinders and fitted onto an eccentric member of the rotary shaft to eccentrically rotate; an intermediate partitioner provided between the cylinders and the rollers to partition the rotary compressing elements; supporting members that close open surfaces of the cylinders and have bearings for the rotary shaft; and an oil bore formed in the rotary shaft, wherein a surface of the intermediate partitioner that is adjacent to the second cylinder has a groove extended from an inner periphery to an outer periphery of the intermediate partitioner to provide communication among the oil bore and the insides of the rollers, a low-pressure chamber in the second cylinder, and the hermetically sealed vessel. The groove formed so as to extend from the inner periphery to the outer periphery of the intermediate partitioner allows a high-pressure refrigerant gas accumulating inside the rollers to be released into the hermetically sealed vessel. 
   Moreover, even if the pressure in the second cylinder of the second rotary compressing element becomes higher than that in the hermetically sealed vessel having an intermediate pressure, a suction pressure loss generated in the course of suction in the second rotary compressing element can be utilized to reliably supply oil into a low-pressure chamber of the second cylinder of the second rotary compressing element through the oil bore of the rotary shaft through the intermediary of the groove formed in the intermediate partitioner. 
   Preferably, the driving element is an rpm-controlled motor started up at low speed upon actuation. 
   According to yet another aspect of the present invention, there is provided a rotary compressor having: a first cylinder for constituting a first rotary compressing element and a second cylinder for constituting a second rotary compressing element; an intermediate partitioner provided between the cylinders to partition the rotary compressing elements; supporting members that close open surfaces of the cylinders and have bearings for the rotary shaft of the driving element; and an oil bore formed in the rotary shaft, wherein a lubrication bore for communication between the oil bore and a low-pressure chamber in the second cylinder is formed in the intermediate partitioner. With this arrangement, even if the pressure in the cylinder of the second rotary compressing element becomes higher than that in the hermetically sealed vessel having an intermediate pressure, a suction pressure loss generated in the course of suction in the second rotary compressing element can be utilized to reliably supply oil into the cylinder through the lubrication bore formed in the intermediate partitioner. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal sectional view of an internal intermediate pressure multistage compression type rotary compressor according to an embodiment of the present invention; 
       FIG. 2  is a top plan view of an intermediate partitioner of the rotary compressor shown in  FIG. 1 ; 
       FIG. 3  is a longitudinal sectional view of the intermediate partitioner of the rotary compressor shown in  FIG. 1 ; 
       FIG. 4  is a top plan view of an upper cylinder of a second rotary compressing element of the rotary compressor shown in  FIG. 1 ; 
       FIG. 5  is a diagram showing changes in pressure at an inlet end of the upper cylinder of the rotary compressor shown in  FIG. 1 ; 
       FIG. 6  is a diagram illustrating a stroke of suction-compression of a refrigerant performed by the upper cylinder of the rotary compressor shown in  FIG. 1 ; 
       FIG. 7  is a longitudinal sectional view of an internal intermediate pressure multistage compression type rotary compressor according to another embodiment of the present invention; 
       FIG. 8  is a top plan view of an intermediate partitioner of the rotary compressor shown in  FIG. 7 ; 
       FIG. 9  is a longitudinal sectional view of the intermediate partitioner of the rotary compressor shown in  FIG. 7 ; 
       FIG. 10  is a top plan view of a cylinder of a second rotary compressing element of the rotary compressor shown in  FIG. 7 ; 
       FIG. 11  is a diagram showing changes in pressure at an inlet end of an upper cylinder of the rotary compressor shown in  FIG. 7 ; 
       FIG. 12  is a longitudinal sectional view of a rotary compressor according to another embodiment of the present invention; 
       FIG. 13  is a sectional view of an intermediate partitioner of the rotary compressor shown in  FIG. 12 ; 
       FIG. 14  is a top plan view of an upper cylinder  38  of the rotary compressor shown in  FIG. 12 ; 
       FIG. 15  is a diagram illustrating a stroke of suction-compression of a refrigerant performed by the upper cylinder of the rotary compressor shown in  FIG. 12 ; and 
       FIG. 16  is a longitudinal sectional view of an upper supporting member of a conventional rotary compressor. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments according to the present invention will be described in detail in conjunction with the attached drawings.  FIG. 1  is a longitudinal sectional view of an internal intermediate pressure multistage (2-stage) compression type rotary compressor  10 , which is an embodiment of a rotary compressor in accordance with the present invention. The rotary compressor  10  has a first rotary compressing element  32  and a second rotary compressing element  34 . 
   Referring to  FIG. 1 , the internal intermediate pressure multistage compression type rotary compressor  10  that uses carbon dioxide (CO 2 ) as a refrigerant is constructed of a cylindrical hermetically sealed vessel  12  formed of a steel plate, a driving element  14  disposed at an upper side of the internal space of the hermetically sealed vessel  12 , and a rotary compressing mechanism unit  18  that includes a first rotary compressing element  32  (first stage) and a second rotary compressing element  34  (second stage) that are disposed under the driving element  14  and driven by a rotary shaft  16  of the driving element  14 . 
   The hermetically sealed vessel  12  having its bottom portion working as an oil reservoir is constructed of a vessel main body  12 A accommodating the driving element  14  and the rotary compressing mechanism unit  18 , and a substantially bowl-shaped end cap or cover  12 B that closes an upper opening of the vessel main body  12 A. A circular mounting hole  12 D is formed at the center of an upper surface of the end cap  12 B. A terminal (wires not shown)  20  for supplying electric power to the driving element  14  is installed in the mounting hole  12 D. 
   The driving element  14  is a series-wound DC motor constructed of a stator  22  annularly installed along an upper inner peripheral surface of the hermetically sealed vessel  12  and a rotor  24  inserted in the stator  22  with a slight gap on the inner side. The rotor  24  is fixed to the rotary shaft  16  that extends in a vertical direction, passing through a center. 
   The stator  22  has a laminate  26  formed of stacked toroidal electromagnetic steel plates, and a stator coil  28  wound around teeth of the laminate  26  by a series winding (concentrated winding) method. The rotor  24  is also formed of a laminate  30  made of electromagnetic steel plates, as in the stator  22 . A permanent magnet MG is inserted in the laminate  30 . 
   An oil pump  102 , serving as a lubricating device, is provided at the bottom end of the rotary shaft  16 . The oil pump  102  draws up lubricating oil from the oil reservoir formed at the bottom of the hermetically sealed vessel  12 . The lubricating oil passes through an oil bore  80  formed in a vertical direction along the axial center of the rotary shaft  16  and through horizontal lubrication bores  82  and  84  (formed also in upper and lower eccentric members  42  and  44 ) in communication with the oil bore  80  to reach sliding portions and the like of the upper and lower eccentric members  42  and  44 , and the first and second rotary compressing elements  32  and  34 . This restrains wear on the first and second rotary compressing elements  32  and  34 , and also provides sealing. 
   The rotary compressing mechanism unit  18  includes a lower cylinder (first cylinder)  40  constituting the first rotary compressing element  32  and an upper cylinder (second cylinder)  38  constituting the second rotary compressing element  34 , upper and lower rollers  46  and  48 , which eccentrically rotate, being fitted onto the upper and lower eccentric members  42  and  44 , respectively, which are provided on the rotary shaft  16  with a 180-degree phase difference in the upper and lower cylinders  38  and  40 , respectively, an intermediate partitioner  36  provided between the upper and lower cylinders  38  and  40  and the rollers  46  and  48  to separate the first and second rotary compressing elements  32  and  34 , a vane  50  (the lower vane being not shown) abutting against the rollers  46  and  48  to separate interiors of the upper and lower cylinders  38  and  40  into low-pressure chambers and high-pressure chambers, and an upper supporting member  54  and a lower supporting member  56  that cover the upper opening surface of the upper cylinder  38  and the lower opening surface of the lower cylinder  40 , respectively, and also serve as bearings of the rotary shaft  16 . 
   The upper supporting member  54  and the lower supporting member  56  are provided with suction passages  58  and  60  in communication with the interiors of the upper and lower cylinders  38  and  40 , respectively, through suction ports  161  and  162 , respectively, and discharge muffling chambers  62  and  64  partly formed by recessions that are closed by an upper cover  66  and a lower cover  68 , respectively. A bearing  54 A is protuberantly formed at the center of the upper supporting member  54  and a bearing  56 A is protuberantly formed at the center of the lower supporting member  56  to support the rotary shaft  16 . 
   The lower cover  68  formed of a toroidal steel plate is fixed to the lower supporting member  56  from below by main bolts  129  at four peripheral locations. Distal ends of the main bolts  129  are screwed into the upper supporting member  54 . 
   The discharge muffling chamber  64  of the first rotary compressing element  32  and the interior of the hermetically sealed vessel  12  are in communication through a communication passage. The communication passage is formed of a bore (not shown) that penetrates the lower supporting member  56 , the upper supporting member  54 , the upper cover  66 , the upper and lower cylinders  38  and  40 , and the intermediate partitioner  36 . In this case, an intermediate discharge pipe  121  is vertically provided at the upper end of the communication passage, and an intermediate-pressure refrigerant is discharged through the intermediate discharge pipe  121  into the hermetically sealed vessel  12 . 
   The upper cover  66  closes the upper surface opening of the discharge muffling chamber  62  in communication with the interior of the upper cylinder  38  of the second rotary compressing element  34  through a discharge port  39 . The driving element  14  is provided above the upper cover  66  with a predetermined gap therebetween in the hermetically sealed vessel  12 . A peripheral portion of the upper cover  66  is fixed to the upper supporting member  54  from above by four main bolts  78 . The distal ends of the main bolts  78  are screwed in the lower supporting members  56 . 
   The intermediate partitioner  36  has a through bore  131  providing communication between the interior of the hermetically sealed vessel  12  and inside the roller  46  by small-diameter boring, as shown in  FIGS. 2 and 4 .  FIG. 2  is a top plan view of the intermediate partitioner  36 , and  FIG. 4  is a top plan view of the upper cylinder  38  of the second rotary compressing element  34 . An accommodating chamber  70  is formed in the upper cylinder  38 . The vane  50  is housed in the accommodating chamber  70  and abutted against the roller  46 . One side (right side in  FIG. 4 ) of the vane  50  has the discharge port  39 , while the other side (left) with the vane  50  therebetween has the suction port  161 . The vane  50  separates compression chambers formed between the upper cylinder  38  and the roller  46  into low-pressure chambers LR and high-pressure chambers HR. The suction port  161  is associated with the low-pressure chambers LR, while the discharge port  39  is associated with the high-pressure chambers HR. 
   A small gap is formed between the intermediate partitioner  36  and the rotary shaft  16 , an upper side of the gap being in communication with the inside of the roller  46  (the space around the eccentric member  42  inside the roller  46 ). Furthermore, a lower side of the gap between the intermediate partitioner  36  and the rotary shaft  16  is in communication with the inside of the roller  48  (the space around the eccentric member  44  inside the roller  48 ). The through bore  131  serves as a passage for releasing, into the hermetically sealed vessel  12 , a high-pressure refrigerant gas that leaks into the roller  46  (the space around the eccentric member  42  inside the roller  46 ) through a gap formed between the roller  46  in the cylinder  38  and the upper supporting member  54  closing the upper open surface of the cylinder  38  or the intermediate partitioner  36  closing the lower open surface, and then flows into the gap between the intermediate partitioner  36  and the rotary shaft  16  and inside the roller  48 . 
   The high-pressure refrigerant gas leaking inside the roller  46  passes through the gap between the intermediate partitioner  36  and the rotary shaft  16  and enters the through bore  131 , thus flowing out into the hermetically sealed vessel  12 . 
   Thus, the high-pressure refrigerant gas leaking inside the roller  46  can be released through the through bore  131  into the hermetically sealed vessel  12 . This makes it possible to avoid the inconvenience of the high-pressure refrigerant gas accumulating inside the roller  46 , in the gap between the intermediate partitioner  36  and the rotary shaft  16 , and inside the roller  48 . With this arrangement, oil can be supplied inside the roller  4 ! 6  and the roller  48  through the lubrication bores  82  and  84  of the rotary shaft  16  by making use of a pressure difference. 
   An increase in machining cost can be minimized particularly because a high-pressure refrigerant gas leaked into the roller  46  can be released into the hermetically sealed vessel  12  simply by forming the through bore  131  horizontally penetrating the intermediate partitioner  36 . 
   The surface of the intermediate partitioner  36  that is adjacent to the cylinder  38  has a lubrication groove  133  extending from the inner peripheral surface over a predetermined distance in a radial direction, as shown in  FIG. 2  to  FIG. 4 . The lubrication groove  133  is formed under an area α extending from a position where the vane  50  of the cylinder  38  shown in  FIG. 4  abuts against the roller  46  to an edge on the opposite side from the vane  50  of the suction port  161 . An outer portion of the lubrication groove  133  is in communication with the low-pressure chamber LR of the cylinder  38 . 
   An opening on the inner peripheral surface side of the lubrication groove  133  of the intermediate partitioner  36  is in communication with the oil bore  80  through the intermediary of the lubrication bores  82  and  84 . Thus, the lubrication groove  133  provides communication between the oil bore  80  and the low-pressure chamber LR in the upper cylinder  38 . 
   As will be discussed later, the hermetically sealed vessel  12  will have an intermediate pressure therein, so that supply of oil into the upper cylinder  38 , which is the second stage and will have a high pressure therein, is difficult. However, the lubrication groove  133  formed in the intermediate partitioner  36  allows oil drawn up by the oil pump  102  from the oil reservoir at the inner bottom of the hermetically sealed vessel  12  to move up in the oil bore  80  into the lubrication bores  82  and  84 , and then enter the lubrication groove  133  of the intermediate partitioner  36 , thus being supplied to the low-pressure chamber LR of the upper cylinder  38 . 
     FIG. 5  shows changes in pressure in the upper cylinder  38 , P 1  in the diagram denoting a pressure on the inner peripheral side of the intermediate partitioner  36 . The internal pressure (suction pressure) of the low-pressure chamber LR of the upper cylinder  38  denoted by LP in the diagram drops lower than the pressure P 1  on the inner peripheral surface side of the intermediate partitioner  36  due to a suction pressure loss in a suction stroke. During that particular period, oil is injected through the oil bore  80  of the rotary shaft  16  into the low-pressure chamber LR in the upper cylinder  38  through the lubrication groove  133  of the intermediate partitioner  36 , thus accomplishing lubrication. 
     FIG. 6A  through  FIG. 6L  illustrate a refrigerant suction-compression stroke of the upper cylinder  38  of the second rotary compressing element  34 . If it is assumed that the eccentric member  42  of the rotary shaft  16  rotates counterclockwise in the figures, then the suction port  161  is closed by the roller  46  in  FIGS. 6A and 6B . In  FIG. 6C , the suction port  161  opens and suction of a refrigerant is begun, while a refrigerant is being discharged at the opposite side. The suction of the refrigerant continues during the steps of  FIGS. 6C to 6E . During this period, the lubrication groove  133  is covered by the roller  46 . 
   In  FIG. 6F , the roller  46  exposes the lubrication groove  133 , so that the oil is drawn into the low-pressure chamber LR surrounded by the vane  50  and the roller  46  in the upper cylinder  38 , beginning the lubrication (the beginning of the supply period shown in  FIG. 5 ). From steps shown in  FIGS. 6G to 6I , the suction of the oil is performed. The lubrication continues until the upper side of the lubrication groove  133  is covered by the roller  46  in  FIG. 6J , thus stopping the lubrication (the end of the supply period shown in  FIG. 5 ). From steps shown in  FIGS. 6K through 6L  to  FIGS. 6A and 6B , suction of a refrigerant is carried out. Thereafter, the refrigerant will be compressed and discharged through the discharge port  39 . 
   Thus, even if the pressure in the upper cylinder  38  of the second rotary compressing element  34  becomes higher than the intermediate pressure in the hermetically sealed vessel  12 , the lubrication groove  133  allows oil to be securely supplied into the upper cylinder  38  by making use of a suction pressure loss during a suction stroke in the second rotary compressing element  34 . 
   With this arrangement, the second rotary compressing element  34  can be securely lubricated, permitting performance to be secured and reliability to be improved. In particular, oil can be supplied into the upper cylinder  38  of the second rotary compressing element  34  simply by forming the groove in the surface of the intermediate partitioner  36  that is adjacent to the cylinder  38 . This obviates the need for forming thin bores in the intermediate partitioner  36  and the upper cylinder  38 , as in the prior art. With this arrangement, the construction can be simplified, so that an increase in production cost can be restrained. 
   Moreover, a bore for releasing high pressures (the through bore  131 ) formed inside the roller  46 , and the groove for supplying oil (the lubrication groove  133 ) are separately formed, so that the configuration of the lubrication groove  133  for supplying oil can be changed as desired. This means that, if a groove or bore is to be used to release high pressures inside the roller  46  and also to supply oil, then the groove or the bore has to have a certain size or diameter to release the high pressures inside the roller  46 . An excessively small diameter of the groove or bore would fail to adequately release a high-pressure gas accumulating inside the roller  46 . On the other hand, an excessively large diameter thereof would cause excessive oil to be supplied and discharged from the compressor  10 , and may adversely affecting a refrigerant cycle or cause shortage of oil in the compressor  10 . 
   The high pressure releasing bore (the through bore  131 ) inside the roller  46  and the oil supplying groove (the lubrication groove  133 ) are separately formed, so that the groove diameter of the through bore  131  and the size of the lubrication groove  133  can be freely adjusted. Furthermore, the amount of oil supplied to the low-pressure chamber LR of the upper cylinder  38  can be adjusted by adjusting the size of the lubrication groove  133 . 
   Thus, high pressure inside the roller  46  can be released and oil can be supplied to the upper cylinder  38  of the second rotary compressing element  34  at low cost. In addition, secured performance and higher reliability of the rotary compressor  10  can be achieved. 
   In this case, carbon dioxide (CO 2 ), which is a natural refrigerant gentle to the global environment, is used, considering flammability, toxicity, etc. Oil sealed in the hermetically sealed vessel  12  as a lubricant may be an existing oil, such as a mineral oil, alkyl benzene oil, ether oil, ester oil, and polyalkylene glycol (PAG). 
   A side surface of the vessel main body  12 A of the hermetically sealed vessel  12  has sleeves  141 ,  142 ,  143 , and  144  welded and fixed at positions matching the positions of the suction passages  58  and  60  of the upper supporting member  54  and the lower supporting member  56 , the discharge muffling chamber  62 , and above the upper cover  66  (a position substantially matching the bottom end of the driving element  14 ), respectively. The sleeves  141  and  142  are vertically adjacent, while the sleeve  143  is positioned substantially on a diagonal line with respect to the sleeve  141 . Positionally, the sleeve  144  and the sleeve  141  are shifted by about 90 degrees. 
   One end of a refrigerant introduction pipe  92  for introducing a refrigerant gas into the upper cylinder  38  is inserted in and connected to the sleeve  141 , and the end of the refrigerant introduction pipe  92  is in communication with the suction passage  58  of the upper cylinder  38 . The refrigerant introduction pipe  92  is routed above the hermetically sealed vessel  12  to the sleeve  144 , the other end thereof being inserted in and connected to the sleeve  144  to be in communication with the interior of the hermetically sealed vessel  12 . 
   One end of the refrigerant introduction pipe  94  for introducing a refrigerant gas into the lower cylinder  40  is inserted in and connected to the sleeve  142 , the one end of the refrigerant introduction pipe  94  being in communication with the suction passage  60  of the lower cylinder  40 . A refrigerant discharge pipe  96  is inserted in and connected to the sleeve  143 , one end of the refrigerant discharge pipe  96  being in communication with the discharge muffling chamber  62 . 
   An operation of the rotary compressor  10  having the aforementioned construction will now be described. Energizing the stator coil  28  of the driving element  14  via the terminal  20  and the wires (not shown) actuates the driving element  14  to rotate the rotor  24 . This causes the upper and lower rollers  46  and  48  to eccentrically rotate in the upper and lower cylinders  38  and  40 , respectively, the rollers  46  and  48  being fitted to the upper and lower eccentric members  42  and  44 , respectively, that are integrally formed with the rotary shaft  16 . 
   A refrigerant gas of a low pressure (4 MPaG) drawn into the low-pressure chamber of the lower cylinder  40  through the suction port  162  via the refrigerant introduction pipe  94  and the suction passage  60  formed in the lower supporting member  56  is compressed to have an intermediate pressure (8 MPaG) by the roller  48  and a vane (not shown), passes through the discharge port  41  from the high-pressure chamber of the lower cylinder  40  into the discharge muffling chamber  64  formed in the lower supporting member  56 , and then it is discharged into the hermetically sealed vessel  12  through the intermediate discharge pipe  121  via a communication passage (not shown). 
   Then, the intermediate-pressure refrigerant gas in the hermetically sealed vessel  12  leaves the sleeve  144 , passes through the refrigerant introduction pipe  92  and the suction passage  58  formed in the upper supporting member  54 , and reaches the low-pressure chamber LR of the upper cylinder  38  through the suction port  161 . The intermediate-pressure refrigerant gas that has been drawn in is subjected to the second-stage compression explained with reference to  FIG. 6  by the roller  46  and the vane  50  so as to turn into a hot, high-pressure refrigerant gas (the pressure being about 12 MPaG). The hot, high-pressure refrigerant gas flows from the high-pressure chamber HR, passes through the discharge port  39 , the discharge muffling chamber  62  formed in the upper supporting member  54 , and the refrigerant discharge pipe  96 , and then it is discharged to an external radiator or the like of the compressor  10 . 
   Thus, the lubrication groove  133  formed in the surface of the intermediate partitioner  36  that is adjacent to the cylinder  38  provides communication between the oil bore  80  and the low-pressure chamber LR of the cylinder  38  through the lubrication bores  82  and  84 , so that even if the pressure in the cylinder  38  of the second rotary compressing element  34  becomes higher than the intermediate pressure in the hermetically sealed vessel  12 , the lubrication groove  133  allows oil to be securely supplied into the low-pressure chamber of the cylinder  38  by making use of a suction pressure loss during a suction stroke in the second rotary compressing element  34 . 
   The through bore  131  drilled in the intermediate partitioner  36  provides communication between the interior of the hermetically sealed vessel  12  and the inside of the roller  46 , so that a high-pressure refrigerant gas leaked into the inside of the roller  46  can be released into the hermetically sealed vessel  12  through the through bore  131 . 
   With this arrangement, oil is smoothly supplied to the inside of the roller  46  and the roller  48  through the lubrication bores  82  and  84  of the rotary shaft  16  by making use of a pressure difference. This makes it possible to avoid shortage of oil around the eccentric member  42  inside the roller  46  and around the eccentric member  44  inside the roller  48 . 
   Thus, the inconvenience of the pressure inside the roller  46  becoming high can be avoided, and smooth and reliable lubrication of the second rotary compressing element  34  can be achieved by the relatively simple construction. This feature allows the rotary compressor  10  to achieve secured performance and higher reliability. 
   In the present embodiment, the upper side of the gap formed between the intermediate partitioner  36  and the rotary shaft  16  is in communication with the inside of the roller  46 , while the lower side thereof is in communication with the inside of the roller  48 . Alternatively, however, only the upper side of the gap formed between the intermediate partitioner  36  and the rotary shaft  16  may be in communication with the inside of the roller  46 , that is, the lower side thereof may not be in communication with the inside of the roller  48 . Further alternatively, the inside of the roller  46  and the inside of the roller  48  may be separated by the intermediate partitioner  36 . In this case also, a high pressure inside the roller  46  can be released into the hermetically sealed vessel  12  by forming a bore in an axial direction that is in communication with the inside of the roller  46  in a middle of the through bore  131  of the intermediate partitioner. Moreover, oil can be supplied to the suction end of the second rotary compressing element  32  through the lubrication bore  82 . 
   As explained in detail above, according to the present invention, a so-called internal intermediate pressure multistage compression type rotary compressor is equipped with: a first cylinder for constituting a first rotary compressing element and a second cylinder for constituting a second rotary compressing element; a roller that is provided in each of the cylinders and fitted onto an eccentric member of the rotary shaft to eccentrically rotate; an intermediate partitioner provided between the cylinders and the rollers to partition the rotary compressing elements; supporting members that close open surfaces of the cylinders and have bearings for the rotary shaft; and an oil bore formed in the rotary shaft, wherein a surface of the intermediate partitioner that is adjacent to the second cylinder has a groove for communication between the oil bore and a low-pressure chamber in the second cylinder, and the intermediate partitioner has a through bore for communication between an interior of a hermetically sealed vessel and inside the rollers. The through bore formed in the intermediate partitioner allows a high-pressure refrigerant gas accumulating inside the rollers to be released into the hermetically sealed vessel. 
   With this arrangement, oil is smoothly supplied into the rollers through the oil bore of the rotary shaft by making use of a pressure difference, so that shortage of oil around the eccentric members inside the rollers can be avoided. 
   In addition, even if the pressure in the second cylinder of the second rotary compressing element becomes higher than that in the hermetically sealed vessel having an intermediate pressure, a suction pressure loss generated in the course of suction in the second rotary compressing element can be utilized to reliably supply oil into the low-pressure chamber of the second cylinder of the second rotary compressing element through the oil bore of the rotary shaft via the groove formed in the intermediate partitioner. 
   Thus, the inconvenience of the pressure inside a roller becoming high can be avoided, and reliable lubrication of a second rotary compressing element can be achieved by the relatively simple construction. This feature allows the rotary compressor to achieve secured performance and higher reliability. 
     FIG. 7  is a longitudinal sectional view of another internal intermediate pressure multistage (2-stage) compression type rotary compressor  10 , which is an embodiment of a rotary compressor in accordance with the present invention. The rotary compressor  10  has a first rotary compressing element  32  and a second rotary compressing element  34 . 
   Referring to  FIG. 7 , the internal intermediate pressure multistage compression type rotary compressor  10  that uses carbon dioxide (CO 2 ) as a refrigerant is constructed of a cylindrical hermetically sealed vessel  12  formed of a steel plate, a driving element  14  disposed at an upper side of the internal space of the hermetically sealed vessel  12 , and a rotary compressing mechanism unit  18  that includes a first rotary compressing element  32  (first stage) and a second rotary compressing element  34  (second stage) that are disposed under the driving element  14  and driven by a rotary shaft  16  of the driving element  14 . 
   The hermetically sealed vessel  12  having its bottom portion working as an oil reservoir is constructed of a vessel main body  12 A accommodating the driving element  14  and the rotary compressing mechanism unit  18 , and a substantially bowl-shaped end cap or cover  12 B that closes an upper opening of the vessel main body  12 A. A circular mounting hole  12 D is formed at the center of an upper surface of the end cap  12 B. A terminal (wires not shown)  20  for supplying electric power to the driving element  14  is installed in the mounting hole  12 D. 
   The driving element  14  is a series-wound DC motor constructed of a stator  22  annularly installed along an upper inner peripheral surface of the hermetically sealed vessel  12  and a rotor  24  inserted in the stator  22  with a slight gap on the inner side. The rotational speed and torque of the driving element  14  is controlled by an inverter. The rotational speed of the driving element  14  is controlled by the inverter so that the driving element  14  is actuated at low speed when starting up the rotary compressor  10 , and then increased to a desired speed. The rotor  24  is fixed to the rotary shaft  16  that extends in a vertical direction, passing through a center. 
   The stator  22  has a laminate  26  formed of stacked toroidal electromagnetic steel plates, and a stator coil  28  wound around teeth of the laminate  26  by a series winding (concentrated winding) method. The rotor  24  is also formed of a laminate  30  made of electromagnetic steel plates, as in the stator  22 . A permanent magnet MG is inserted in the laminate  30 . 
   An oil pump  102 , serving as a lubricating device, is provided at the bottom end of the rotary shaft  16 . The oil pump  102  sucks up lubricating oil from the oil reservoir formed at the bottom of the hermetically sealed vessel  12 . The lubricating oil passes through an oil bore  80  formed in a vertical direction along the axial center of the rotary shaft  16  and through horizontal lubrication bores  82  and  84  (formed also in upper and lower eccentric members  42  and  44 ) in communication with the oil bore  80  to reach sliding portions and the like of the upper and lower eccentric members  42  and  44 , and the first and second rotary compressing elements  32  and  34 . This restrains wear on the first and second rotary compressing elements  32  and  34 , and provides sealing. 
   The rotary compressing mechanism unit  18  includes a lower cylinder (first cylinder)  40  constituting the first rotary compressing element  32  and an upper cylinder (second cylinder)  38  constituting the second rotary compressing element  34 , upper and lower rollers  46  and  48 , which eccentrically rotate, being fitted onto the upper and lower eccentric members  42  and  44 , respectively, which are provided on the rotary shaft  16  with a 180-degree phase difference in the upper and lower cylinders  38  and  40 , respectively, an intermediate partitioner  36  provided between the cylinders  38  and  40  and the rollers  46  and  48  to separate the first and second rotary compressing elements  32  and  34 , a vane  50  (the lower vane being not shown) abutting against the rollers  46  and  48  to separate interiors of the upper and lower cylinders  38  and  40  to low-pressure chambers and high-pressure chambers, and an upper supporting member  54  and a lower supporting member  56  that cover the upper opening surface of the upper cylinder  38  and the lower opening surface of the lower cylinder  40 , respectively, and also serve as bearings of the rotary shaft  16 . 
   The upper supporting member  54  and the lower supporting member  56  are provided with suction passages  58  and  60  in communication with the interiors of the upper and lower cylinders  38  and  40 , respectively, through suction ports  161  and  162 , respectively, and discharge muffling chambers  62  and  64  partly formed by recessions that are closed by an upper cover  66  and a lower cover  68 , respectively. A bearing  54 A is protuberantly formed at the center of the upper supporting member  54  and a bearing  56 A is protuberantly formed at the center of the lower supporting member  56  to support the rotary shaft  16 . 
   The lower cover  68  is formed of a toroidal steel plate and fixed to the lower supporting member  56  from below by main bolts  129  at four peripheral locations. Distal ends of the main bolts  129  are screwed into the upper supporting member  54 . 
   The discharge muffling chamber  64  of the first rotary compressing element  32  and the interior of the hermetically sealed vessel  12  are in communication through a communication passage. The communication passage is formed of a bore (not shown) that penetrates the lower supporting member  56 , the upper supporting member  54 , the upper cover  66 , the upper and lower cylinders  38  and  40 , and the intermediate partitioner  36 . In this case, an intermediate discharge pipe  121  is vertically provided at the upper end of the communication passage, and an intermediate-pressure refrigerant is discharged through the intermediate discharge pipe  121  into the hermetically sealed vessel  12 . 
   The upper cover  66  closes the upper surface opening of the discharge muffling chamber  62  in communication with the interior of the upper cylinder  38  of the second rotary compressing element  34  through a discharge port  39 . The driving element  14  is provided above the upper cover  66  with a predetermined gap therebetween in the hermetically sealed vessel  12 . A peripheral portion of the upper cover  66  is fixed to the upper supporting member  54  from above by four main bolts  78 . The distal ends of the main bolts  78  are screwed in the lower supporting members  56 . 
   The surface of the intermediate partitioner  36  that is adjacent to the cylinder  38  has a through groove  170  that extends from the inner periphery to the outer periphery of the intermediate partitioner  36 , as shown in  FIG. 8  and  FIG. 10 . The through groove  170  provides communication between lubrication bores  82 ,  84  in communication with an oil bore  80 , and the inside of the roller  46  and the low-pressure chamber of the cylinder  38 .  FIG. 8  is a top plan view of the intermediate partitioner  36 ,  FIG. 9  is a longitudinal sectional view of the intermediate partitioner  36 , and  FIG. 10  is a top plan view of the upper cylinder  38 . 
   A small gap is formed between the intermediate partitioner  36  and the rotary shaft  16 , an upper side of the gap being in communication with the inside of the roller  46  (the space around the eccentric member  42  inside the roller  46 ). Furthermore, the gap between the intermediate partitioner  36  and the rotary shaft  16  has its lower side in communication with the inside of the roller  48  (the space around the eccentric member  44  inside the roller  48 ). The low-pressure chamber of the cylinder  38  and the inner periphery of the intermediate partitioner  36  are in communication through the through groove  170 , as shown in  FIG. 9 . The through groove  170  is formed beneath an area a extending from a position where the vane  50  of the upper cylinder  38  shown in  FIG. 10  abuts against the roller  46  to an edge on the opposite side from the vane  50  of the suction port  161 . 
   A high-pressure refrigerant gas that leaks inside the roller  46  (the space around the eccentric member  42  inside the roller  46 ) through the gap formed between the roller  46  in the cylinder  38  and the upper supporting member  54  that closes the upper opening surface of the cylinder  38  or the intermediate partitioner  36  that closes the lower opening surface thereof, and flows into the gap between the intermediate partitioner  36  and the rotary shaft  16  and inside the roller  48  can be released into the hermetically sealed vessel  12  through the through groove  170 . 
   In other words, the high-pressure refrigerant gas leaking inside the roller  46  passes through the gap formed between the intermediate partitioner  36  and the rotary shaft  16 , enters the through groove  170 , and flows into the hermetically sealed vessel  12  via the through groove  170 . 
   Thus, the high-pressure refrigerant gas leaking inside the roller  46  can be released through the through groove  170  into the hermetically sealed vessel  12 . This makes it possible to avoid the inconvenience of the high-pressure refrigerant gas accumulating inside the roller  46 , in the gap between the intermediate partitioner  36  and the rotary shaft  16 , and inside the roller  48 . With this arrangement, oil can be supplied inside the roller  46  and the roller  48  through the lubrication bores  82  and  84  of the rotary shaft  16  by making use of a pressure difference. 
   An increase in machining cost can be minimized particularly because a high-pressure refrigerant gas leaked inside the roller  46  can be released into the hermetically sealed vessel  12  simply by forming the through groove  170  horizontally penetrating the intermediate partitioner  36 . 
   The rotary shaft  16  includes the oil bore  80  formed in the vertical direction along an axial center and horizontal lubrication bores  82  and  84  (formed also in the upper and lower eccentric members  42  and  44 ) that are in communication with the oil bore  80 . The inner periphery of the through groove  170  of the intermediate partitioner  36  is in communication with the oil bore  80  via the lubrication bores  82  and  84 . Thus, the through groove  170  provides communication between the oil bore  80  and the low-pressure chamber in the cylinder  38  via the lubrication bores  82  and  84 . 
   In this case, as will be discussed hereinafter, the inside of the hermetically sealed vessel  12  has an intermediate pressure, so that it is difficult to supply oil into the upper cylinder  38  that has a high pressure in the second stage. However, the through groove  170  formed in the intermediate partitioner  36  causes the oil to be drawn up from the oil reservoir at the bottom in the hermetically sealed vessel  12  and moved up through the oil bore  80 . The oil coming out of the lubrication bores  82  and  84  enters the through groove  170  of the intermediate partitioner  36  so as to be supplied to the low-pressure chamber (suction side) of the upper cylinder  38 . 
     FIG. 11  shows changes in pressure in the upper cylinder  38 , P 1  in the diagram denoting a pressure on the inner peripheral side of the intermediate partitioner  36 . The internal pressure (suction pressure) of the low-pressure chamber of the upper cylinder  38  in the diagram drops below the pressure P 1  on the inner peripheral side of the intermediate partitioner  36  due to a suction pressure loss in a suction stroke. During that particular period, oil is injected through the oil bore  80  of the rotary shaft  16  into the low-pressure chamber in the upper cylinder  38  through the through groove  170  of the intermediate partitioner  36 , thus accomplishing lubrication. 
   As described above, the through groove  170  allows the high-pressure refrigerant gas leaking inside the roller  46  to be released into the hermetically sealed vessel  12 . In addition, even if the pressure in the cylinder  38  of the second rotary compressing element  34  becomes higher than that in the hermetically sealed vessel  12  whose pressure reaches an intermediate pressure, a suction pressure loss in the course of suction in the second rotary compressing element  34  can be utilized to reliably supply oil into the cylinder  38 . 
   Moreover, simply forming the through groove  170  extending from the inner periphery to the outer periphery of the intermediate partitioner  36  makes it possible to release high pressures inside the roller  46  and also to reliably supply oil to the second rotary compressing element  34 . This obviates the conventional need for separately providing a bore for releasing high pressures in the roller  46  and a bore for supplying oil to the second rotary compressing element  34 , or for forming the bores for supplying oil in the two members, namely, the intermediate partitioner  36  and the cylinder  38 . Thus, improved performance and higher reliability of a compressor can be achieved with a simple structure and at low cost. 
   In summary, the problem in that the pressure inside the roller  46  of the second rotary compressing element becomes high can be solved, and the lubrication of the second rotary compressing element  34  can be reliably accomplished, thus permitting the rotary compressor  10  to provide secured performance and improved reliability. 
   Furthermore, as mentioned above, the rotational speed of the driving element  14  is controlled by an inverter so as to be started up at low speed when actuating the compressor. Therefore, at the startup of the rotary compressor  10 , it is possible to restrain adverse effect caused by compressing a liquid when oil is drawn in from the oil reservoir at the inner bottom of the hermetically sealed vessel  12  through the through groove  170 , permitting deterioration of reliability to be avoided. 
   In this embodiment also, carbon dioxide (CO 2 ), which is a natural refrigerant gentle to the global environment, is used, considering flammability, toxicity, etc. Oil sealed in the hermetically sealed vessel  12  as a lubricant may be an existing oil, such as a mineral oil, alkyl benzene oil, ether oil, ester oil, and polyalkylene glycol (PAG). 
   A side surface of the vessel main body  12 A of the hermetically sealed vessel  12  has sleeves  141 ,  142 ,  143 , and  144  welded and fixed at positions matching the positions of the suction passages  58  and  60  of the upper supporting member  54  and the lower supporting member  56 , the discharge muffling chamber  62 , and above the upper cover  66  (a position substantially matching the bottom end of the driving element  14 ), respectively. The sleeves  141  and  142  are vertically adjacent, while the sleeve  143  is positioned substantially on a diagonal line with respect to the sleeve  141 . Positionally, the sleeve  144  and the sleeve  141  are shifted by about 90 degrees. 
   One end of a refrigerant introduction pipe  92  for introducing a refrigerant gas into the upper cylinder  38  is inserted in and connected to the sleeve  141 , and the end of the refrigerant introduction pipe  92  is in communication with the suction passage  58  of the upper cylinder  38 . The refrigerant introduction pipe  92  is routed above the hermetically sealed vessel  12  to the sleeve  144 , the other end thereof being inserted in and connected to the sleeve  144  to be in communication with the interior of the hermetically sealed vessel  12 . 
   One end of the refrigerant introduction pipe  94  for introducing a refrigerant gas into the lower cylinder  40  is inserted in and connected to the sleeve  142 , the one end of the refrigerant introduction pipe  94  being in communication with the suction passage  60  of the lower cylinder  40 . A refrigerant discharge pipe  96  is inserted in and connected to the sleeve  143 , one end of the refrigerant discharge pipe  96  being in communication with the discharge muffling chamber  62 . 
   An operation of the rotary compressor  10  having the aforementioned construction will now be described. Before the rotary compressor  10  is started up, the oil level (oil surface) in the hermetically sealed vessel  12  is normally above an opening of the through groove  170  formed in the intermediate partitioner  36 , the opening being adjacent to the hermetically sealed vessel  12 . This causes the oil in the hermetically sealed vessel  12  to flow into the through groove  170  from the opening of the through groove  170  that is adjacent to the hermetically sealed vessel  12 . 
   Energizing the stator coil  28  of the driving element  14  by the inverter via the terminal  20  and the wires (not shown) actuates the driving element  14  to rotate the rotor  24 . As mentioned above, the speed is low at the startup, and then increased. This causes the upper and lower rollers  46  and  48  to eccentrically rotate in the upper and lower cylinders  38  and  40 , respectively, the rollers  46  and  48  being fitted to the upper and lower eccentric members  42  and  44 , respectively, that are integrally formed with the rotary shaft  16 . 
   A refrigerant gas of a low pressure (4 MPaG) drawn into the low-pressure chamber of the lower cylinder  40  through the suction port  162  via the refrigerant introduction pipe  94  and the suction passage  60  formed in the lower supporting member  56  is compressed to have an intermediate pressure (8 MPaG) by the roller  48  and a vane (not shown), passes through the discharge port  41  from the high-pressure chamber of the lower cylinder  40  into the discharge muffling chamber  64  formed in the lower supporting member  56 , and then it is discharged into the hermetically sealed vessel  12  through the intermediate discharge pipe  121  via a communication passage (not shown). 
   Then, the intermediate-pressure refrigerant gas in the hermetically sealed vessel  12  leaves the sleeve  144 , passes through the refrigerant introduction pipe  92  and the suction passage  58  formed in the upper supporting member  54 , and reaches the low-pressure chamber of the upper cylinder  38  through the suction port  161 . 
   When the rotary compressor  10  is activated, the oil that has entered from the opening of the through groove  170  adjacent to the hermetically sealed vessel  12  is drawn into the low-pressure chamber of the cylinder  38  of the second rotary compressing element  34 . The intermediate-pressure refrigerant gas and oil drawn into the low-pressure chamber of the cylinder  38  are subjected to the second-stage compression by the roller  46  and the vane  50  so as to turn into a hot, high-pressure refrigerant gas (12 MPaG). 
   In this case, the oil that has entered together with the intermediate-pressure refrigerant gas from the opening of the through groove  170  adjacent to the hermetically sealed vessel  12  is also compressed. However, the rotational speed of the rotary compressor  10  is controlled by the inverter such that the rotary compressor  10  is operated at low speed at a startup, so that the torque is small. Therefore, the compressed oil hardly affects the rotary compressor  10 , allowing normal operation to be performed. 
   The rotational speed is increased according to a predetermined control pattern, and the driving element  14  is eventually operated at a desired rotational speed. Although the oil level lowers below the through groove  170  during the operation, oil is supplied through the through groove  170  to the low-pressure chamber of the upper cylinder  38 , making it possible to avoid shortage of oil supplied to the sliding portions of the second rotary compressing element  34 . 
   Thus, the through groove  170  extending from the inner periphery to the outer periphery of the intermediate partitioner  36  is formed in the surface of the intermediate partitioner  36  adjacent to the cylinder  38  so as to provide communication among the oil bore  80 , the inside of the roller  46 , the low-pressure chamber of the cylinder  38 , and the hermetically sealed vessel  12 . With this arrangement, a high-pressure refrigerant gas leaked inside the roller  46  can be released through the through groove  170  into the hermetically sealed vessel  12 . 
   Thus, oil is smoothly supplied inside the roller  46  and the roller  48  through the lubrication bores  82  and  84  of the rotary shaft  16  by making use of a pressure difference. This makes it possible to avoid shortage of oil around the eccentric member  42  inside the roller  46  and around the eccentric member  44  inside the roller  48 . 
   Furthermore, even if the pressure in the cylinder  38  of the second rotary compressing element  34  becomes higher than the intermediate pressure in the hermetically sealed vessel  12 , the through groove  170  allows oil to be securely supplied into the low-pressure chamber of the cylinder  38  by making use of a suction pressure loss during a suction stroke in the second rotary compressing element  34 . 
   In summary, the problem in that the pressure inside the roller  46  becomes high can be solved, and the lubrication of the second rotary compressing element  34  can be reliably accomplished, thus permitting the rotary compressor  10  to provide secured performance and improved reliability. 
   Furthermore, the driving element  14  is an rpm-controlled motor activated at low speed at a startup. Therefore, at the startup of the rotary compressor  10 , it is possible to restrain adverse effect caused by compressing a liquid when oil is drawn in from the oil reservoir at the inner bottom of the hermetically sealed vessel  12  through the through groove  170 , permitting deterioration of reliability to be avoided. 
   In the present embodiment, the upper side of the gap formed between the intermediate partitioner  36  and the rotary shaft  16  is in communication with the inside of the roller  46 , while the lower side thereof is in communication with the inside of the roller  48 . Alternatively, however, only the upper side of the gap formed between the intermediate partitioner  36  and the rotary shaft  16  may be in communication with the inside of the roller  46 , that is, the lower side thereof may not be in communication with the inside of the roller  48 . Further alternatively, the inside of the roller  46  and the inside of the roller  48  may be separated by the intermediate partitioner  36 . In this case also, a high pressure inside the roller  46  can be released into the hermetically sealed vessel  12  by forming a bore in an axial direction that is in communication with the inside of the roller  46  in a middle of the through groove  170  of the intermediate partitioner. Moreover, oil can be supplied to the low-pressure chamber of the cylinder  38  through the lubrication bore  82 . 
   As explained in detail above, in the rotary compressor in accordance with the present invention, the groove extending from the inner periphery to the outer periphery of the intermediate partitioner allows a high-pressure refrigerant gas accumulating in the roller to be released into the hermetically sealed vessel. 
   Thus, oil is smoothly supplied inside the rollers through the lubrication bores of the rotary shaft by making use of a pressure difference. This makes it possible to avoid shortage of oil around the eccentric members inside the rollers. 
   Furthermore, even if the pressure in the second cylinder of the second rotary compressing element becomes higher than the intermediate pressure in the hermetically sealed vessel, the groove formed in the intermediate partitioner allows oil to be securely supplied into the low-pressure chamber of the second cylinder of the second rotary compressing element through the oil bores in the rotary shaft by making use of a suction pressure loss during a suction stroke in the second rotary compressing element. 
   The aforementioned construction therefore enables the rotary compressor to provide secured performance and improved reliability. In particular, a high pressure in a roller can be released and oil can be supplied to the second rotary compressing element simply by forming the groove that provides communication between the hermetically sealed vessel and the inside of the roller. This permits a simplified construction and reduced cost to be achieved. 
   Furthermore, the driving element is constructed of an rpm-controlled motor activated at low speed at a startup. Therefore, it is possible to restrain adverse effect caused by compressing a liquid when the second rotary compressing element draws oil in at a startup from the hermetically sealed vessel through the through groove in the intermediate partitioner in communication with the hermetically sealed vessel. This restrains the reliability of the rotary compressor from deteriorating. 
     FIG. 12  is a longitudinal sectional view of still another internal intermediate pressure multistage (2-stage) compression type rotary compressor  10 , which is an embodiment of a rotary compressor in accordance with the present invention. The rotary compressor  10  has a first rotary compressing element  32  and a second rotary compressing element  34 . 
   Referring to  FIG. 12 , the internal intermediate pressure multistage (2-stage) compression type rotary compressor  10  that uses carbon dioxide (CO 2 ) as a refrigerant is constructed of a cylindrical hermetically sealed vessel  12  formed of a steel plate, a driving element  14  disposed at an upper side of the internal space of the hermetically sealed vessel  12 , and a rotary compressing mechanism unit  18  that includes a first rotary compressing element  32  (first stage) and a second rotary compressing element  34  (second stage) that are disposed under the driving element  14  and driven by a rotary shaft  16  of the driving element  14 . 
   The hermetically sealed vessel  12  having its bottom portion working as an oil reservoir is constructed of a vessel main body  12 A accommodating the driving element  14  and the rotary compressing mechanism unit  18 , and a substantially bowl-shaped end cap or cover  12 B that closes an upper opening of the vessel main body  12 A. A terminal (wires not shown)  20  for supplying electric power to the driving element  14  is installed on the top surface of the end cap  12 B. 
   The driving element  14  is constructed of a stator  22  annularly installed along an upper inner peripheral surface of the hermetically sealed vessel  12  and a rotor  24  inserted in the stator  22  with a slight gap on the inner side. The rotor  24  is fixed to the rotary shaft  16  that extends in a vertical direction, passing through a center. 
   The stator  22  has a laminate  26  formed of stacked toroidal electromagnetic steel plates, and a stator coil  28  wound around teeth of the laminate  26  by a series winding (concentrated winding) method. The rotor  24  is also formed of a laminate  30  made of electromagnetic steel plates, as in the stator  22 . A permanent magnet MG is inserted in the laminate  30 . 
   The rotary compressing mechanism unit  18  includes a lower cylinder (first cylinder)  40  constituting the first rotary compressing element  32  and an upper cylinder (second cylinder)  38  constituting the second rotary compressing element  34 , upper and lower rollers  46  and  48 , which eccentrically rotate, being fitted onto the upper and lower eccentric members  42  and  44 , respectively, which are provided on the rotary shaft  16  with a 180-degree phase difference in the upper and lower cylinders  38  and  40 , respectively, an intermediate partitioner  36  provided between the cylinders  38  and  40  and the rollers  46  and  48  to separate the first and second rotary compressing elements  32  and  34 , a vane  50  (the lower vane being not shown) abutting against the rollers  46  and  48  to separate interiors of the upper and lower cylinders  38  and  40  to a low-pressure chamber LR ( FIG. 15F ) and a high-pressure chamber ( FIG. 15F ), and an upper supporting member  54  and a lower supporting member  56  that cover the upper opening surface of the upper cylinder  38  and the lower opening surface of the lower cylinder  40 , respectively, and also serve as bearings of the rotary shaft  16 . 
   The upper supporting member  54  and the lower supporting member  56  are provided with suction passages  58  and  60  in communication with the interiors of the upper and lower cylinders  38  and  40 , respectively, through suction ports  161  and  162 , respectively, and discharge muffling chambers  62  and  64  partly formed by recessions that are closed by an upper cover  66  and a lower cover  68 , respectively. A bearing  54 A is protuberantly formed at the center of the upper supporting member  54  and a bearing  56 A is protuberantly formed at the center of the lower supporting member  56  to fixedly support the rotary shaft  16 . 
   In this case, the lower cover  68  formed of a toroidal steel plate and fixed to the lower supporting member  56  from below by main bolts  129  at four peripheral locations closes a lower opening of the discharge muffling chamber  64  in communication with the interior of the lower cylinder  40  of the first rotary compressing element  32  at a discharge port (not shown). Distal ends of the main bolts  129  are screwed into the upper supporting member  54 . 
   The discharge muffling chamber  64  and the side of the upper cover  66  that is closer to the driving element  1 – 4  in the hermetically sealed vessel  12  are in communication through a communication passage (not shown) that penetrates the upper and lower cylinders  38  and  40  and the intermediate partitioner  36 . In this case, an intermediate discharge pipe  121  is vertically provided at the upper end of the communication passage, and the intermediate discharge pipe  121  is directed toward the gap between adjoining stator coils  28  and  28  wound around the stator  22  of the above driving element  14 . 
   The upper cover  66  closes the upper surface opening of the discharge muffling chamber  62  in communication with the interior of the upper cylinder  38  of the second rotary compressing element  34  through a discharge port  39 . The driving element  14  is provided above the upper cover  66  with a predetermined gap therebetween in the hermetically sealed vessel  12 . A peripheral portion of the upper cover  66  is fixed to the upper supporting member  54  from above by four main bolts  78 . The distal ends of the main bolts  78  are screwed in the lower supporting members  56 . 
     FIG. 14  is a top plan view of the upper cylinder  38  of the second rotary compressing element  34 . An accommodating chamber  70  is formed in the upper cylinder  38 . The vane  50  is housed in the accommodating chamber  70  and abutted against the roller  46 . One side (right side in  FIG. 14 ) of the vane  50  has the discharge port  39 , while the other side (left) with the vane  50  therebetween has the suction port  161 . The vane  50  separates compression chambers formed between the upper cylinder  38  and the roller  46  into low-pressure chambers LR and high-pressure chambers HR. The suction port  161  is associated with the low-pressure chambers LR, while the discharge port  39  is associated with the high-pressure chambers HR. 
   The intermediate partitioner  36 , which is substantially toroidal, closes the lower opening surface of the upper cylinder  38  and the upper opening surface of the lower cylinder  40 . The intermediate partitioner  36  has a lubrication bore  180  that provides communication between the oil bore  80 , which will be discussed later, and the low-pressure chamber LR of the upper cylinder  38 . More specifically, the lubrication bore  180  provides communication between the low-pressure chamber LR of the upper cylinder  38  on the upper surface of the intermediate partitioner  36  (the surface adjacent to the upper cylinder  38 ) and the inner peripheral surface of the intermediate partitioner  36 , the upper end thereof being open in the low-pressure chamber LR of the upper cylinder  38 . The lubrication bore  180  is formed under an area a extending from a position where the vane  50  of the upper cylinder  38  shown in  FIG. 14  abuts against the roller  46  to an edge on the opposite side from the vane  50  of the suction port  161 . The upper end of the lubrication bore  180  is in communication with the low-pressure chamber LR (suction side) in the upper cylinder  38 . 
   The rotary shaft  16  includes the oil bore  80  formed in the vertical direction along an axial center thereof and horizontal lubrication bores  82  and  84  (formed also in the upper and lower eccentric members  42  and  44 ) that are in communication with the oil bore  80 . The opening of the lubrication bore  180  in the intermediate partitioner. 36 , which opening is on the inner periphery end, is in communication with the oil bore  80  via the lubrication bores  82  and  84 . Thus, the lubrication bore  180  provides communication between the oil bore  80  and the low-pressure chamber LR in the upper cylinder  38 . 
   As will be discussed hereinafter, the pressure inside the hermetically sealed vessel  12  reaches an intermediate level, so that it is difficult to supply oil into the upper cylinder  38  whose interior pressure reaches a high level in the second stage. However, the lubrication bore  180  formed in the intermediate partitioner  36  lets the oil be drawn up from the oil reservoir at the bottom in the hermetically sealed vessel  12  and move up through the oil bore  80 . The oil coming out of the lubrication bores  82  and  84  enters the lubrication bore  180  of the intermediate partitioner  36  so as to be supplied to the low-pressure chamber LR (suction side) of the upper cylinder  38 . 
   The changes in pressure in the upper cylinder  38  in this case are similar to those shown in  FIG. 5  discussed above. More specifically, P 1  in the diagram denotes a pressure on the inner peripheral side of the intermediate partitioner  36 . As indicated by a curve LP in  FIG. 5 , the internal pressure (suction pressure) of the low-pressure chamber LR of the upper cylinder  38  drops below the pressure P 1  on the inner peripheral side of the intermediate partitioner  36  due to a suction pressure loss in a suction stroke. During that particular period, oil is injected through the oil bore  80  of the rotary shaft  16  into the low-pressure chamber LR in the upper cylinder  38  through the lubrication bore  180  of the intermediate partitioner  36 , thus accomplishing lubrication. 
     FIG. 15A  through  FIG. 15L  illustrate a refrigerant suction-compression stroke of the upper cylinder  38  of the second rotary compressing element  34 . If it is assumed that the eccentric member  42  of the rotary shaft  16  rotates counterclockwise in the figures, then the suction port  161  is closed by the roller  46  in  FIGS. 15A and 15B . In  FIG. 15C , the suction port  161  opens and suction of a refrigerant is begun, while a refrigerant is being discharged at the opposite side. The suction of the refrigerant continues during the steps of  FIGS. 15C to 15E . During this period, the lubrication bore  180  is covered by the roller  46 . 
   In  FIG. 15F , the roller  46  exposes the lubrication bore  180 , so that the oil is drawn into the low-pressure chamber LR surrounded by the vane  50  and the roller  46  in the upper cylinder  38 , beginning the lubrication (the beginning of the supply period shown in  FIG. 5 ). From steps shown in  FIGS. 15G to 15I , the suction of the oil is performed. The lubrication continues until the upper side of the lubrication bore  180  is covered by the roller  46  in  FIG. 15J , thus stopping the lubrication (the end of the supply period shown in  FIG. 5 ). From steps shown in  FIGS. 15K through 15L  to  FIGS. 15A and 15B , suction of a refrigerant is carried out. Thereafter, the refrigerant will be compressed and discharged through the discharge port  39 . 
   In this embodiment, carbon dioxide (CO 2 ), which is a natural refrigerant gentle to the global environment, is used as a refrigerant, considering flammability, toxicity, etc. Oil as a lubricant may be an existing oil, such as a mineral oil, alkyl benzene oil, ether oil, ester oil, and polyalkylene glycol (PAG). 
   A side surface of a vessel main body  12 A of the hermetically sealed vessel  12  has sleeves  141 ,  142 ,  143 , and  144  welded and fixed at positions matching the positions of the suction passages  58  and  60  of the upper supporting member  54  and the lower supporting member  56 , the discharge muffling chamber  62 , and above the upper cover  66  (a position substantially matching the bottom end of the driving element  14 ), respectively. The sleeves  141  and  142  are vertically adjacent, while the sleeve  143  is positioned substantially on a diagonal line with respect to the sleeve  141 . Positionally, the sleeve  144  and the sleeve  141  are shifted by about 90 degrees. 
   One end of a refrigerant introduction pipe  92  for introducing a refrigerant gas into the upper cylinder  38  is inserted in and connected to the sleeve  141 , and the end of the refrigerant introduction pipe  92  is in communication with the suction passage  58  of the upper cylinder  38 . The refrigerant introduction pipe  92  is routed above the hermetically sealed vessel  12  to the sleeve  144 , the other end thereof being inserted in and connected to the sleeve  144  to be in communication with the interior of the hermetically sealed vessel  12 . 
   One end of the refrigerant introduction pipe  94  for introducing a refrigerant gas into the lower cylinder  40  is inserted in and connected to the sleeve  142 , the one end of the refrigerant introduction pipe  94  being in communication with the suction passage  60  of the lower cylinder  40 . A refrigerant discharge pipe  96  is inserted in and connected to the sleeve  143 , one end of the refrigerant discharge pipe  96  being in communication with the discharge muffling chamber  62 . 
   An operation of the rotary compressor  10  having the aforementioned construction will now be described. Energizing the stator coil  28  of the driving element  14  via the terminal  20  and the wires (not shown) actuates the driving element  14  to rotate the rotor  24 . This causes the upper and lower rollers  46  and  48  to eccentrically rotate in the upper and lower cylinders  38  and  40 , respectively, as mentioned above, the rollers  46  and  48  being fitted to the upper and lower eccentric members  42  and  44 , respectively, that are integrally formed with the rotary shaft  16 . 
   A refrigerant gas of a low pressure (about 4 MPaG) drawn into the low-pressure chamber of the lower cylinder  40  through the suction port  162  via the refrigerant introduction pipe  94  and the suction passage  60  formed in the lower supporting member  56  is compressed to have an intermediate pressure (about 8 MPaG) by the roller  48  and a vane (not shown), passes through a discharge port (not shown) from the high-pressure chamber of the lower cylinder  40  into the discharge muffling chamber  64  formed in the lower supporting member  56 , and then it is discharged into the hermetically sealed vessel  12  through the intermediate discharge pipe  121  via a communication passage (not shown). 
   At this time, the intermediate discharge pipe  121  is directed toward the gap between adjoining stator coils  28  and  28  wound around the stator  22  of the above driving element  14 . Hence, it is possible to positively supply the refrigerant gas of a relatively low temperature toward the driving element  14 , so that temperature rise in the driving element  14  is restrained. This causes the pressure inside the hermetically sealed vessel  12  to reach an intermediate level. 
   Then, the intermediate-pressure refrigerant gas in the hermetically sealed vessel  12  leaves the sleeve  144 , passes through the refrigerant introduction pipe  92  and the suction passage  58  formed in the upper supporting member  54 , and reaches the low-pressure chamber LR of the upper cylinder  38  through the suction port  161 . The intermediate-pressure refrigerant gas that has been drawn in is subjected to the second-stage compression explained with reference to  FIG. 15  by the roller  46  and the vane  50  so as to turn into a hot, high-pressure refrigerant gas (the pressure being about 12 MPaG). The hot, high-pressure refrigerant gas flows from the high-pressure chamber HR, passes through the discharge port  39 , the discharge muffling chamber  62  formed in the upper supporting member  54 , and the refrigerant discharge pipe  96 , and then it is discharged to an external radiator or the like of the compressor  10 . 
   Thus, oil is securely supplied through the lubrication bore  180  into the upper cylinder  38  of the second rotary compressing element  34  of the compressor  10 , as mentioned above. This makes it possible to avoid the inconvenient shortage of oil supplied to the second rotary compressing element  34 . 
   This arrangement ensures reliable lubrication of the second rotary compressing element  34 , permitting secured performance and higher reliability. The lubrication bore  180 , in particular, can be made simply by providing the intermediate partitioner  36  with the horizontal bore in communication with the oil bore  80  and a vertical bore in communication with the low-pressure chamber LR of the upper cylinder  38 . Hence, the construction can be simplified and an increase of production cost can be controlled, as compared with the conventional construction in which the bores are formed in the intermediate partitioner and the cylinder of the second rotary compressing element. 
   If the construction for lubricating the second rotary compressing element  34  is such that a groove is formed in the upper surface of the intermediate partitioner  36  (the surface adjacent to the upper cylinder  38 ) from the inner peripheral surface in the radial direction of the upper cylinder  38 , and the outer diameter portion of the groove is in communication with the low-pressure chamber LR of the upper cylinder  38 , then the area in which the groove and the low-pressure chamber LR of the upper cylinder  38  are in communication varies, depending on the position of the roller  46 . This makes it extremely difficult to adjust the amount of oil supplied into the cylinder  38 . 
   According to the present invention, however, the communication with the low-pressure chamber LR of the upper cylinder  38  through the lubrication bore  180  makes it possible to adjust the diameter of the bore and the position of the communication with the low-pressure chamber LR of the upper cylinder  38 , thus permitting arbitrary adjustment of the amount of oil supplied into the upper cylinder  38 . In adjustment of the position of the communication with the low-pressure chamber LR of the upper cylinder  38 , if the position of the communication is set closer toward the rotary shaft  16  (central portion), then the time during which the lubrication bore  180  remains in communication with the low-pressure chamber LR of the upper cylinder  38  by the rotation of the roller  46  is shorter and a smaller amount of oil will be supplied. Setting the aforesaid position of communication farther from the rotary shaft  16  prolongs the time during which the lubrication bore  180  remains in communication with the low-pressure chamber LR of the upper cylinder  38  by the rotation of the roller  46 , so that the amount of oil supplied can be increased. 
   With these features, oil can be smoothly and more securely supplied to the second rotary compressing element  34  at low cost, permitting the rotary compressor  10  to achieve further improved reliability. 
   As discussed above in detail, the rotary compressor in accordance with the present invention is equipped with a first cylinder for constituting a first rotary compressing element and a second cylinder for constituting a second rotary compressing element, an intermediate partitioner provided between the cylinders to partition the rotary compressing elements, supporting members that close open surfaces of the cylinders and have bearings for the rotary shaft of the driving element, and an oil bore formed in the rotary shaft, wherein a lubrication bore for communication between the oil bore and a low-pressure chamber in the second cylinder is formed in the intermediate partitioner. With this arrangement, even if the pressure in the cylinder of the second rotary compressing element becomes higher than that in the hermetically sealed vessel whose internal pressure reaches an intermediate pressure, a suction pressure loss generated in the course of suction in the second rotary compressing element can be utilized to reliably supply oil into the cylinder through the lubrication bore formed in the intermediate partitioner. 
   With this arrangement, the lubrication of the second rotary compressing element can be reliably accomplished, so that secured performance and higher reliability can be accomplished. In particular, the lubrication bore can be made simply by forming a bore in the intermediate partitioner, making it possible to simplify the structure and restrain an increase of production cost. 
   In the embodiments described above, the 2-stage compression type rotary compressors provided with the first and second rotary compression elements have been used; however, the present invention is not limited thereto. For example, the present invention may be applied also to a multistage compression type rotary compressor equipped with rotary compression elements of three stages, four stages, or more stages.