Patent Publication Number: US-11384760-B2

Title: Rotary compressor for enhancing efficiency and suppressing vibration

Description:
CROSS REFERENCE TO PRIOR APPLICATION 
     This application is a National Stage Patent Application of PCT International Patent Application No. PCT/JP2018/027969 (filed on Jul. 25, 2018) under 35 U.S.C. § 371, which claims priority to Japanese Patent Application No. 2017-161565 (filed on Aug. 24, 2017), which are all hereby incorporated by reference in their entirety. 
     FIELD 
     The present invention relates to a rotary compressor. 
     BACKGROUND 
     In an air conditioner and a refrigeration apparatus, for example, a two-cylinder rotary compressor is used for compressing a refrigerant. In the two-cylinder rotary compressor, in order to reduce fluctuation in torque per one rotation of a rotating shaft as much as possible, in general, two upper and lower cylinders are configured such that the processes of suction, compression, and discharge are performed in phases different by 180°. Except for peculiar operation conditions such as at the time of start-up, in the operation of the air conditioner at normal outdoor temperature and indoor temperature, the discharge process of one cylinder occupies approximately ⅓ in one rotation. Thus, ⅓ in one rotation is the discharge process (the process in which a discharge valve is opened) of one cylinder, another ⅓ is the discharge process of the other cylinder, and the remaining ⅓ is the process in which both discharge valves are closed. 
     When both of the two discharge valves of the upper cylinder and the lower cylinder are closed and there is no flow of refrigerant discharged from compression chambers, both an upper muffler chamber (hereinafter also referred to as an upper end-plate cover chamber) and a lower muffler chamber (hereinafter also referred to as a lower end-plate cover chamber) have the same pressure as that in a compressor housing that is the outside of the upper muffler chamber. In the discharge process of one of the cylinders, the pressure of the compression chamber that is the uppermost stream of the refrigerant flow is the highest in the compressed high-pressure area, and then the muffler chamber and the inside of the compressor housing, where is the outside of the upper muffler chamber, are high in this order. Accordingly, immediately after the discharge valve of the upper cylinder is opened, the pressure of the upper muffler chamber is higher than the pressure in the compressor housing outside of the upper muffler chamber and the pressure in the lower muffler chamber. Thus, at the next moment, the flow of refrigerant from the upper muffler chamber into the inside of compressor housing, where is the outside of the upper muffler chamber, and the flow of refrigerant from the upper muffler chamber to the lower muffle chamber by a backward flow through a refrigerant passage hole, arise. As just described, what is called a refrigerant backward flow phenomenon, in which a part of the refrigerant that is compressed to high pressure in the upper cylinder and is discharged to the upper muffler chamber flows backward through the refrigerant passage hole and flows into the lower muffler chamber, arises. 
     The flow from the upper muffler chamber into the inside of the compressor housing, where is the outside of the upper muffler chamber, is the original flow, but the refrigerant that has flowed from the upper muffler chamber to the lower muffler chamber flows into the inside of the compressor housing, where is the outside of the upper muffler chamber, through the refrigerant passage hole and the upper muffler chamber again, after finishing the discharge process of the upper cylinder. The flow into the compressor housing is a flow not needed originally, and that results in an energy loss and deteriorates the efficiency of the rotary compressor. Then, if the lower muffler chamber, which is formed to a lower end plate and a lower end-plate cover, is made too large, as space for which the refrigerant flows backward from the upper muffler chamber flows into the lower muffler chamber, becomes large, the deterioration in the efficiency of the rotary compressor tends to become large. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Laid-open Patent Publication No. 2016-118142 
     SUMMARY 
     Technical Problem 
     Hence, in order to reduce the deterioration in the efficiency of the rotary compressor, techniques to make the lower muffler chamber small and reduce the deterioration in the efficiency of the rotary compressor, by forming the lower end plate cover in a flat-plate shape, or by forming a bulging portion only on a part of the lower end plate cover, have been known. 
     However, when the volume of the bulging portion of the lower end plate cover is made too small, as the lower muffler chamber becomes too small, the refrigerant compressed in the lower compression chamber of the lower cylinder flows early from the lower muffler chamber to the upper muffler chamber through the refrigerant passage hole. Thus, there is a problem in that the pressure pulsation in the lower muffler chamber becomes large, a proper silencing effect by the lower muffler chamber is not obtainable, and the amplitude of vibration generated in the lower end-plate cover increases. 
     Meanwhile, when the volume of the bulging portion of the lower end plate cover is increased, the pressure pulsation in the lower muffler chamber is reduced, and the increase in the amplitude of vibration generated in the rotary compressor along with the pressure pulsation, is suppressed. However, in this case, as the space into which the refrigerant that has flowed backward from the upper muffler chamber through the refrigerant passage hole to the lower muffler chamber flows, is increased, it leads to the deterioration of the efficiency of the rotary compressor. 
     Based on the above, when an area where the bulging portion occupies in a cross section orthogonal to the shaft direction of the rotating shaft, is increased so that a proper volume is ensured in the volume of the bulging portion of the lower end plate cover for satisfying both the enhancement of the efficiency of the rotary compressor and the suppression of vibration of the rotary compressor, there has been a case where the refrigerant discharged into the lower muffler chamber may be not smoothly discharged from the refrigerant passage hole only by the refrigerant passage hole arranged in the vicinity of the lower discharge hole. 
     The disclosed technology has been made in view of the foregoing, and an object thereof is to provide a rotary compressor capable of enhancing the efficiency and suppressing the vibration. 
     Solution to Problem 
     To solve the above problem and attain the object, a rotary compressor disclosed in this application, according to an aspect, includes: a sealed and vertical cylindrical compressor housing provided with a refrigerant discharge portion at an upper portion and a refrigerant suction portion at a lower portion; a compression unit arranged at a lower portion of the compressor housing and configured to compress refrigerant that is sucked from the suction portion and to discharge the refrigerant from the discharge portion; and a motor arranged at an upper portion of the compressor housing and configured to drive the compression unit, wherein the compression unit includes: an annular upper cylinder and an annular lower cylinder, an upper end plate closing an upper side of the upper cylinder and a lower end plate closing a lower side of the lower cylinder, an intermediate partition plate arranged between the upper cylinder and the lower cylinder and closing a lower side of the upper cylinder and an upper side of the lower cylinder, a rotating shaft supported by a main bearing portion provided on the upper end plate and by a sub-bearing portion provided on the lower end plate, and rotated by the motor, an upper eccentric portion and a lower eccentric portion provided on the rotating shaft with a phase difference of 180° from each other, an upper piston fitted in the upper eccentric portion and configured to revolve along an inner peripheral surface of the upper cylinder and form an upper cylinder chamber in the upper cylinder, a lower piston fitted in the lower eccentric portion and configured to revolve along an inner peripheral surface of the lower cylinder and form a lower cylinder chamber in the lower cylinder, an upper vane projecting into the upper cylinder chamber from an upper vane groove provided on the upper cylinder and brought into contact with the upper piston so as to section the upper cylinder chamber into an upper suction chamber and an upper compression chamber, a lower vane projecting into the lower cylinder chamber from a lower vane groove provided on the lower cylinder and brought into contact with the lower piston so as to section the lower cylinder chamber into a lower suction chamber and a lower compression chamber, an upper end plate cover covering the upper end plate, forming an upper end-plate cover chamber between the upper end plate and the upper end plate cover, and having an upper end-plate cover discharge hole communicating with the upper end-plate cover chamber and an inside of the compressor housing, a lower end plate cover covering the lower end plate and forming a lower end-plate cover chamber between the lower end plate and the lower end plate cover, an upper discharge hole provided on the upper end plate and communicating with the upper compression chamber and the upper end-plate cover chamber, a lower discharge hole provided on the lower end plate and communicating with the lower compression chamber and the lower end-plate cover chamber, and a plurality of refrigerant passage holes running through the lower end plate, the lower cylinder, the intermediate partition plate, the upper end plate, and the upper cylinder and communicating with the lower end-plate cover chamber and the upper end-plate cover chamber, the lower end plate includes: a plurality of bolt holes that is provided along a circumferential direction of the lower end plate and through which bolts that couple the compression unit penetrate, a lower discharge valve of a reed valve type that is configured to open and close the lower discharge hole, a lower discharge-valve accommodating recessed portion that extends in a groove shape up to a portion between the bolt holes adjacent in the circumferential direction from the lower discharge hole and into which the lower discharge valve is accommodated, and a lower discharge-chamber recessed portion formed so as to overlap with the lower discharge hole side of the lower discharge-valve accommodating recessed portion, the lower end plate cover is formed in a flat-plate shape and is provided with a bulging portion having a portion facing the lower discharge hole, the lower end-plate cover chamber is formed by the lower discharge-valve accommodating recessed portion, the lower discharge-chamber recessed portion, and the bulging portion, the refrigerant passage holes include a main refrigerant passage hole provided on the lower discharge-chamber recessed portion, and a sub-refrigerant passage hole provided between the bolt hole and the lower discharge-valve accommodating recessed portion away from the lower discharge-valve accommodating recessed portion, and the bulging portion is, in a cross section orthogonal to the rotating shaft, formed so as to overlap with at least a part of each of the main refrigerant passage hole and the sub-refrigerant passage hole. 
     Advantageous Effects of Invention 
     According to one aspect of the rotary compressor disclosed in the present application, it is possible to enhance the efficiency of the rotary compressor and to suppress the vibration. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a longitudinal sectional view illustrating a rotary compressor of an embodiment. 
         FIG. 2  is an exploded perspective view illustrating a compression unit of the rotary compressor of the embodiment. 
         FIG. 3  is a plan view of a lower end plate of the rotary compressor of the embodiment as viewed from below. 
         FIG. 4  is a plan view of a lower end plate cover of the rotary compressor of the embodiment as viewed from below. 
         FIG. 5  is a cross-sectional view illustrating the lower end plate cover of the rotary compressor of the embodiment viewed along the B-B line in  FIG. 4 . 
         FIG. 6  is a cross-sectional view illustrating a principal portion of the rotary compressor of the embodiment viewed along the A-A line in  FIG. 3 . 
         FIG. 7  is a perspective plan view of the lower end plate cover attached to the lower end plate in the rotary compressor of the embodiment as viewed from below. 
         FIG. 8  is a longitudinal sectional view illustrating a principal portion of the rotary compressor of the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     The following describes in detail an exemplary embodiment of a rotary compressor disclosed in the present application with reference to the accompanying drawings. The rotary compressor disclosed in the present application is not limited by the following exemplary embodiment. 
     Embodiment 
     Configuration of Rotary Compressor 
       FIG. 1  is a longitudinal sectional view illustrating a rotary compressor of an embodiment.  FIG. 2  is an exploded perspective view illustrating a compression unit of the rotary compressor of the embodiment.  FIG. 3  is a plan view of a lower end plate of the rotary compressor of the embodiment as viewed from below. 
     As illustrated in  FIG. 1 , a rotary compressor  1  includes a compression unit  12  arranged at a lower portion in a sealed and vertical cylindrical compressor housing  10 , a motor  11  arranged at an upper portion in the compressor housing  10  and configured to drive the compression unit  12  via a rotating shaft  15 , and a sealed and vertical cylindrical accumulator  25  fixed to an outer peripheral surface of the compressor housing  10 . 
     The compressor housing  10  includes an upper suction pipe  105  and a lower suction pipe  104  that suck in a refrigerant, and the upper suction pipe  105  and the lower suction pipe  104  are provided at a lower lateral portion of the compressor housing  10 . The accumulator  25  is connected to an upper cylinder chamber  130 T (see  FIG. 2 ) of an upper cylinder  121 T via the upper suction pipe  105  and an accumulator-upper curved pipe  31 T as a suction portion, and is connected to a lower cylinder chamber  130 S (see  FIG. 2 ) of a lower cylinder  121 S via the lower suction pipe  104  and an accumulator-lower curved pipe  31 S as a suction portion. In the present embodiment, in the circumferential direction of the compressor housing  10 , the positions of the upper suction pipe  105  and the lower suction pipe  104  overlap and are located at the same position. 
     The motor  11  includes a stator  111  arranged on the outside, and a rotor  112  arranged on the inside. The stator  111  is fixed to the inner peripheral surface of the compressor housing  10  by shrink fitting or welding. The rotor  112  is fixed to the rotating shaft  15  by shrink fitting. 
     In the rotating shaft  15 , a sub-shaft portion  151  below a lower eccentric portion  152 S is rotatively supported by a sub-bearing portion  161 S provided on a lower end plate  160 S, and a main shaft portion  153  above an upper eccentric portion  152 T is rotatively supported by a main bearing portion  161 T provided on an upper end plate  160 T. On the rotating shaft  15 , the upper eccentric portion  152 T and the lower eccentric portion  152 S are provided with a phase difference of 180 degrees from each other, and an upper piston  125 T is supported by the upper eccentric portion  152 T and a lower piston  125 S is supported by the lower eccentric portion  152 S. As a result, the rotating shaft  15  is rotatively supported with respect to the entire compression unit  12  and also, by the rotation, makes an outer peripheral surface  139 T of the upper piston  125 T revolve along an inner peripheral surface  137 T of the upper cylinder  121 T, and makes an outer peripheral surface  139 S of the lower piston  125 S revolve along an inner peripheral surface  137 S of the lower cylinder  121 S. 
     In the inside of the compressor housing  10 , lubricating oil  18  is sealed by an amount that substantially immerses the compression unit  12 , in order to ensure lubricity of sliding portions such as the upper cylinder  121 T and the upper piston  125 T, the lower cylinder  121 S and the lower piston  125 S, and the like sliding in the compression unit  12  and to seal an upper compression chamber  133 T (see  FIG. 2 ) and a lower compression chamber  133 S (see  FIG. 2 ). On the lower side of the compressor housing  10 , fixed is a mounting leg  310  (see  FIG. 1 ) that latches to a plurality of elastic supporting members (not illustrated) that support the entire rotary compressor  1 . 
     As illustrated in  FIG. 1 , the compression unit  12  compresses the refrigerant sucked in from the upper suction pipe  105  and the lower suction pipe  104  and discharges the refrigerant from a discharge pipe  107  which will be described later. As illustrated in  FIG. 2 , the compression unit  12  is made up of, from above, stacking an upper end plate cover  170 T having a bulging portion  181  in which a hollow space is formed inside, the upper end plate  160 T, the annular upper cylinder  121 T, an intermediate partition plate  140 , the annular lower cylinder  121 S, the lower end plate  160 S, and a flat plate-shaped lower end plate cover  170 S. The entire compression unit  12  is fixed from above and below by a plurality of through bolts  174  and  175  and auxiliary bolts  176  arranged substantially concentrically. 
     On the upper cylinder  121 T, the cylindrical inner peripheral surface  137 T is formed. On the inner side of the inner peripheral surface  137 T of the upper cylinder  121 T, the upper piston  125 T, which has an outer diameter smaller than the inner diameter of the inner peripheral surface  137 T of the upper cylinder  121 T, is arranged, and between the inner peripheral surface  137 T of the upper cylinder  121 T and the outer peripheral surface  139 T of the upper piston  125 T, the upper compression chamber  133 T, which sucks, compresses, and discharges the refrigerant, is formed. On the lower cylinder  121 S, the cylindrical inner peripheral surface  137 S is formed. On the inner side of the inner peripheral surface  137 S of the lower cylinder  121 S, the lower piston  125 S, which has an outer diameter smaller than the inner diameter of the inner peripheral surface  137 S of the lower cylinder  121 S, is arranged, and between the inner peripheral surface  137 S of the lower cylinder  121 S and the outer peripheral surface  139 S of the lower piston  125 S, the lower compression chamber  133 S, which sucks, compresses, and discharges the refrigerant, is formed. 
     As illustrated in  FIG. 2 , the upper cylinder  121 T includes an upper lateral projecting portion  122 T projecting from the outer peripheral portion toward the outer peripheral side in the radial direction of the cylindrical inner peripheral surface  137 T. On the upper lateral projecting portion  122 T, an upper vane groove  128 T, which extends radially outward from the upper cylinder chamber  130 T, is provided. In the upper vane groove  128 T, an upper vane  127 T is arranged to be slidable. The lower cylinder  121 S includes a lower lateral projecting portion  122 S projecting from the outer peripheral portion toward the outer peripheral side in the radial direction of the cylindrical inner peripheral surface  137 S. On the lower lateral projecting portion  122 S, a lower vane groove  128 S, which extends radially outward from the lower cylinder chamber  130 S, is provided. In the lower vane groove  128 S, a lower vane  127 S is arranged to be slidable. 
     The upper lateral projecting portion  122 T is formed extending over a predetermined projecting range, along the circumferential direction of the inner peripheral surface  137 T of the upper cylinder  121 T. The lower lateral projecting portion  122 S is formed extending over a predetermined projecting range, along the circumferential direction of the inner peripheral surface  137 S of the lower cylinder  121 S. The upper lateral projecting portion  122 T and the lower lateral projecting portion  122 S are used as chuck holding portions for fixing to a machining jig when machining the upper cylinder  121 T and the lower cylinder  121 S. As the upper lateral projecting portion  122 T and the lower lateral projecting portion  122 S are fixed to the machining jig, the upper cylinder  121 T and the lower cylinder  121 S are positioned at predetermined positions. 
     On the upper lateral projecting portion  122 T, from the outer lateral surface at the position overlapping the upper vane groove  128 T, an upper spring hole  124 T is provided at a depth not running through the upper cylinder chamber  130 T. At the upper spring hole  124 T, an upper spring  126 T is arranged. On the lower lateral projecting portion  122 S, from the outer lateral surface at the position overlapping the lower vane groove  128 S, a lower spring hole  124 S is provided at a depth not running through the lower cylinder chamber  130 S. At the lower spring hole  124 S, a lower spring  126 S is arranged. 
     Furthermore, on the upper cylinder  121 T, formed is an upper pressure guiding path  129 T that guides the compressed refrigerant in the compressor housing  10  by making the outside in the radial direction of the upper vane groove  128 T communicate with the inside of the compressor housing  10  via an opening, and that applies a back pressure to the upper vane  127 T by the pressure of the refrigerant. On the lower cylinder  121 S, formed is a lower pressure guiding path  129 S that guides the compressed refrigerant in the compressor housing  10  by making the outside in the radial direction of the lower vane groove  128 S communicate with the inside of the compressor housing  10 , and that applies a back pressure to the lower vane  127 S by the pressure of the refrigerant. 
     On the upper lateral projecting portion  122 T of the upper cylinder  121 T, an upper suction hole  135 T, to which the upper suction pipe  105  is fitted in, is provided. On the lower lateral projecting portion  122 S of the lower cylinder  121 S, a lower suction hole  135 S, to which the lower suction pipe  104  is fitted in, is provided. 
     As illustrated in  FIG. 2 , the upper cylinder chamber  130 T is closed by the upper end plate  160 T on the upper side, and is closed by the intermediate partition plate  140  on the lower side. The lower cylinder chamber  130 S is closed by the intermediate partition plate  140  on the upper side, and is closed by the lower end plate  160 S on the lower side. 
     The upper cylinder chamber  130 T is, as the upper vane  127 T is pressed by the upper spring  126 T and is brought into contact with the outer peripheral surface  139 T of the upper piston  125 T, sectioned into an upper suction chamber  131 T that communicates with the upper suction hole  135 T, and into the upper compression chamber  133 T that communicates with an upper discharge hole  190 T provided on the upper end plate  160 T. The lower cylinder chamber  130 S is, as the lower vane  127 S is pressed by the lower spring  126 S and is brought into contact with the outer peripheral surface  139 S of the lower piston  125 S, sectioned into a lower suction chamber  131 S that communicates with the lower suction hole  135 S, and into the lower compression chamber  133 S that communicates with a lower discharge hole  190 S provided on the lower end plate  160 S. 
     Furthermore, the upper discharge hole  190 T is provided in the vicinity of the upper vane groove  128 T, and the lower discharge hole  190 S is provided in the vicinity of the lower vane groove  128 S. The refrigerant compressed in the upper compression chamber  133 T is discharged passing through the upper discharge hole  190 T from the inside of the upper compression chamber  133 T. The refrigerant compressed in the lower compression chamber  133 S is discharged passing through the lower discharge hole  190 S from the inside of the lower compression chamber  133 S. 
     As illustrated in  FIG. 2 , on the upper end plate  160 T, the upper discharge hole  190 T, which passes through the upper end plate  160 T and communicates with the upper compression chamber  133 T of the upper cylinder  121 T, is provided. On the outlet side of the upper discharge hole  190 T, an upper valve seat  191 T is formed around the upper discharge hole  190 T. On the upper side (upper end plate cover  170 T side) of the upper end plate  160 T, an upper discharge-valve accommodating recessed portion  164 T, which extends in a groove shape toward the outer periphery of the upper end plate  160 T from the position of the upper discharge hole  190 T, is formed. 
     In the inside of the upper discharge-valve accommodating recessed portion  164 T, an entire upper discharge valve  200 T of a reed valve type and an entire upper discharge valve presser  201 T, which regulates an opening degree of the upper discharge valve  200 T, are accommodated. In the upper discharge valve  200 T, a base end portion is fixed in the upper discharge-valve accommodating recessed portion  164 T with an upper rivet  202 T, and a distal end portion opens and closes the upper discharge hole  190 T. In the upper discharge valve presser  201 T, a base end portion is overlapped with the upper discharge valve  200 T and fixed in the upper discharge-valve accommodating recessed portion  164 T with the upper rivet  202 T, and a distal end portion is curved (warped) toward the direction in which the upper discharge valve  200 T is opened, and regulates the opening degree of the upper discharge valve  200 T. Furthermore, the upper discharge-valve accommodating recessed portion  164 T is formed having a width slightly larger than the widths of the upper discharge valve  200 T and the upper discharge valve presser  201 T, and accommodates the upper discharge valve  200 T and the upper discharge valve presser  201 T, and also performs positioning of the upper discharge valve  200 T and the upper discharge valve presser  201 T. 
     As illustrated in  FIG. 3 , on the lower end plate  160 S, the lower discharge hole  190 S, which passes through the lower end plate  160 S and communicates with the lower compression chamber  133 S of the lower cylinder  121 S, is provided. On the outlet side of the lower discharge hole  190 S, an annular lower valve seat  191 S is formed around the lower discharge hole  190 S. The lower valve seat  191 S is formed so as to be raised with respect to the bottom surface of a lower discharge-chamber recessed portion  163 S which will be described later. On the lower side (lower end plate cover  170 S side) of the lower end plate  160 S, a lower discharge-valve accommodating recessed portion  164 S, which extends in a groove shape toward the outer periphery of the lower end plate  160 S from the position of the lower discharge hole  190 S, is formed. 
     In the inside of the lower discharge-valve accommodating recessed portion  164 S, an entire lower discharge valve  200 S of a reed valve type and an entire lower discharge valve presser  201 S, which regulates an opening degree of the lower discharge valve  200 S, are accommodated. In the lower discharge valve  200 S, a base end portion is fixed in the lower discharge-valve accommodating recessed portion  164 S with a lower rivet  202 S, and a distal end portion opens and closes the lower discharge hole  190 S. In the lower discharge valve presser  201 S, a base end portion is overlapped with the lower discharge valve  200 S and fixed in the lower discharge-valve accommodating recessed portion  164 S with the lower rivet  202 S, and a distal end portion is curved (warped) toward the direction in which the lower discharge valve  200 S is opened, and regulates the opening degree of the lower discharge valve  200 S. Furthermore, the lower discharge-valve accommodating recessed portion  164 S is formed having a width slightly larger than the widths of the lower discharge valve  200 S and the lower discharge valve presser  201 S, and accommodates the lower discharge valve  200 S and the lower discharge valve presser  201 S, and also performs positioning of the lower discharge valve  200 S and the lower discharge valve presser  201 S. 
     In addition, between the upper end plate  160 T and the upper end plate cover  170 T, which has the bulging portion  181 , that are closely fixed to each other, an upper end-plate cover chamber  180 T is formed. Between the lower end plate  160 S and the flat plate-shaped lower end plate cover  170 S that are closely fixed to each other, a lower end-plate cover chamber  180 S (see  FIG. 3 ) is formed. A plurality of refrigerant passage holes  136  (shaded portions in  FIG. 3 ), which run through the lower end plate  160 S, the lower cylinder  121 S, the intermediate partition plate  140 , the upper end plate  160 T, and the upper cylinder  121 T, and which communicates with the lower end-plate cover chamber  180 S and the upper end-plate cover chamber  180 T, is provided. The refrigerant passage holes  136  will be described later. 
     As illustrated in  FIG. 3 , the lower discharge-chamber recessed portion  163 S communicates with the lower discharge-valve accommodating recessed portion  164 S. The lower discharge-chamber recessed portion  163 S is formed to the same depth as the depth of the lower discharge-valve accommodating recessed portion  164 S so as to overlap with the lower discharge hole  190 S side of the lower discharge-valve accommodating recessed portion  164 S. The lower discharge hole  190 S side of the lower discharge-valve accommodating recessed portion  164 S is accommodated in the lower discharge-chamber recessed portion  163 S. The refrigerant passage holes  138 A and  136 B overlap with at least a part of the lower discharge-chamber recessed portion  163 S, and are arranged at positions communicating with the lower discharge-chamber recessed portion  163 S. 
     On the lower surface of the lower end plate  160 S (contact surface with the lower end plate cover  170 S), in an area other than the area where the lower discharge-chamber recessed portion  163 S and the lower discharge-valve accommodating recessed portion  164 S are formed, a plurality of bolt holes  138  ( FIG. 3 ), through which the through bolts  175  and the like that couple the compression unit  12  penetrate, is provided. The bolt holes  138  are provided at intervals along the circumferential direction of the lower end plate  160 S. 
     As for an upper discharge-chamber recessed portion  163 T and the upper discharge-valve accommodating recessed portion  164 T formed on the upper end plate  160 T, although detailed depiction is omitted, they are formed in the same shapes as those of the lower discharge-chamber recessed portion  163 S and the lower discharge-valve accommodating recessed portion  164 S that are formed on the lower end plate  160 S. The upper end-plate cover chamber  180 T is formed by the dome-shaped bulging portion  181  of the upper end plate cover  170 T, the upper discharge-chamber recessed portion  163 T, and the upper discharge-valve accommodating recessed portion  164 T. 
     The following describes the flow of refrigerant by the rotation of the rotating shaft  15 . In the upper cylinder chamber  130 T, by the rotation of the rotating shaft  15 , as the upper piston  125 T fitted to the upper eccentric portion  152 T of the rotating shaft  15  revolves along the inner peripheral surface  137 T of the upper cylinder  121 T, the upper suction chamber  131 T sucks the refrigerant from the upper suction pipe  105  while expanding the volume, the upper compression chamber  133 T compresses the refrigerant while reducing the volume, and when the pressure of the compressed refrigerant becomes higher than the pressure of the upper end-plate cover chamber  180 T outside of the upper discharge valve  200 T, the upper discharge valve  200 T is opened and the refrigerant is discharged from the upper compression chamber  133 T to the upper end-plate cover chamber  180 T. The refrigerant, which is discharged to the upper end-plate cover chamber  180 T, is discharged into the compressor housing  10  from an upper end-plate cover discharge hole  172 T (see  FIG. 1 ), which is provided on the upper end plate cover  170 T. 
     Furthermore, in the lower cylinder chamber  130 S, by the rotation of the rotating shaft  15 , as the lower piston  125 S, which is fitted to the lower eccentric portion  152 S of the rotating shaft  15 , revolves along the inner peripheral surface  137 S of the lower cylinder  121 S, the lower suction chamber  131 S sucks the refrigerant from the lower suction pipe  104  while expanding the volume, the lower compression chamber  133 S compresses the refrigerant while reducing the volume, and when the pressure of the compressed refrigerant becomes higher than the pressure of the lower end-plate cover chamber  180 S outside of the lower discharge valve  200 S, the lower discharge valve  200 S is opened and the refrigerant is discharged from the lower compression chamber  133 S to the lower end-plate cover chamber  180 S. The refrigerant, which is discharged to the lower end-plate cover chamber  180 S, passes through the refrigerant passage holes  136  and the upper end-plate cover chamber  180 T, and is discharged into the compressor housing  10  from the upper end-plate cover discharge hole  172 T, which is provided on the upper end plate cover  170 T. 
     The refrigerant, which is discharged into the compressor housing  10 , is guided to the upper side of the motor  11  through a cutout (not illustrated), which is provided on the outer periphery of the stator  111  and communicates with the upper and lower portions, a gap (not illustrated) in a winding portion of the stator  111 , or a gap  115  (see  FIG. 1 ) between the stator  111  and the rotor  112 , and is discharged from the discharge pipe  107  as a discharge portion arranged on the upper portion of the compressor housing  10 . 
     Characteristic Configuration of Rotary Compressor 
     Next, a characteristic configuration of the rotary compressor  1  of the embodiment will be described. In the present embodiment, the refrigerant passage holes  136  of the lower end plate  160 S and a bulging portion  171 S of the lower end plate cover  170 S are features.  FIG. 4  is a plan view of the lower end plate cover  170 S of the rotary compressor  1  of the embodiment as viewed from below.  FIG. 5  is a cross-sectional view illustrating the lower end plate cover  170 S of the rotary compressor  1  of the embodiment viewed along the B-B line in  FIG. 4 .  FIG. 6  is a cross-sectional view illustrating a principal portion of the rotary compressor  1  of the embodiment viewed along the A-A line in  FIG. 3 .  FIG. 7  is a perspective plan view of the lower end plate cover  170 S attached to the lower end plate  160 S in the rotary compressor of the embodiment as viewed from below.  FIG. 8  is a longitudinal sectional view illustrating a principal portion of the rotary compressor  1  of the embodiment. 
     Configuration of Refrigerant Passage Holes 
     As illustrated in  FIG. 3  and  FIG. 7 , the lower end plate  160 S includes, as the refrigerant passage holes  136  (shaded portions in  FIG. 3 ), a first main refrigerant passage hole  136 A and a second main refrigerant passage hole  136 B, which are provided on the lower discharge-chamber recessed portion  163 S, and includes a first sub-refrigerant passage hole  136 C and a second sub-refrigerant passage hole  136 D, which are provided between the bolt hole  138  and the lower discharge-valve accommodating recessed portion  164 S away from the lower discharge-valve accommodating recessed portion  164 S. The first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D are the refrigerant passage holes  136  supplementally added to the first main refrigerant passage hole  136 A and the second main refrigerant passage hole  136 B. 
     The first main refrigerant passage hole  136 A and the second main refrigerant passage hole  136 B are formed in a circular shape and are arranged adjacent to each other along the outer peripheral surface of the lower end plate  160 S. The first main refrigerant passage hole  136 A is, in the lower discharge-chamber recessed portion  163 S, arranged on the outer peripheral side of the lower end plate  160 S with respect to the lower discharge hole  190 S and is in contact with the inner peripheral surface of the lower discharge-chamber recessed portion  163 S. The second main refrigerant passage hole  136 B is arranged so as to overlap partially with the inner peripheral surface of the lower discharge-chamber recessed portion  163 S. The second main refrigerant passage hole  136 B is formed having a diameter larger than that of the first main refrigerant passage hole  136 A, and is arranged on the base end portion side (lower rivet  202 S side) of the lower discharge valve  200 S relative to the first main refrigerant passage hole  136 A. Although the present embodiment includes two of the first main refrigerant passage hole  136 A and the second main refrigerant passage hole  136 B, the embodiment may be configured with only either one of the first main refrigerant passage hole  136 A and the second main refrigerant passage hole  136 B. 
     The first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D are formed in a circular shape, and are provided between each bolt hole  138  adjacent in the circumferential direction of the lower end plate  160 S and the lower discharge-valve accommodating recessed portion  164 S away from the lower discharge-valve accommodating recessed portion  164 S. In other words, the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D are each provided on both sides of the lower discharge-valve accommodating recessed portion  164 S in the circumferential direction of the lower end plate  160 S. As the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D are thus arranged, they are arranged at positions where, without too much deteriorating the mechanical strength of the compression unit  12  along with opening of the sub-refrigerant passage holes  136  on the lower end plate  160 S, an appropriate mechanical strength is ensured and where the operation of the compression unit  12  is not affected. 
     Furthermore, in the present embodiment, the first main refrigerant passage hole  136 A, the second main refrigerant passage hole  136 B, and the second sub-refrigerant passage hole  136 D have an equal hole diameter. Thus, the refrigerant passage holes  136  can be worked by using a common cutting tool, and the productivity of the rotary compressor  1  can be increased. The refrigerant passage holes  136  for which the hole diameter is made equal, are not limited, and by making the hole diameter of at least two out of the first main refrigerant passage hole  136 A, the second main refrigerant passage hole  136 B, the first sub-refrigerant passage hole  136 C, and the second sub-refrigerant passage hole  136 D equal, the productivity of the rotary compressor  1  can be increased. 
     In the present embodiment, the four refrigerant passage holes  136  (the first main refrigerant passage hole  136 A, the second main refrigerant passage hole  136 B, the first sub-refrigerant passage hole  136 C, and the second sub-refrigerant passage hole  136 D) are provided, but the number of the refrigerant passage holes  136  is not limited. For example, depending on the air volume and the like of the rotary compressor  1 , it may be configured to have only either one of the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D, for example. Furthermore, in addition to the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D, a third refrigerant passage hole and the like (not illustrated) may further be provided. The refrigerant passage holes  136  are not limited to a circular shape and may be formed in other cross-sectional shapes such as an elliptical shape, for example. 
     Configuration of Bulging Portion 
     As illustrated in  FIG. 4  and  FIG. 5 , the lower end plate cover  170 S is formed in a flat-plate shape, and includes the bulging portion  171 S that bulges downward of the rotary compressor  1 . The bulging portion  171 S forms the lower end-plate cover chamber  180 S. Thus, as illustrated in  FIG. 6 , the lower end-plate cover chamber  180 S is formed by the lower discharge-chamber recessed portion  163 S and the lower discharge-valve accommodating recessed portion  164 S, which are provided on the lower end plate  160 S, and by the bulging portion  171 S of the lower end plate cover  170 S. 
     As illustrated in  FIG. 4  and  FIG. 6 , the bulging portion  171 S of the lower end plate cover  170 S is provided extending over the base end portion side (lower rivet  202 S side) of the lower discharge valve presser  201 S from a position facing the distal end portion of the lower discharge valve presser  201 S (position facing the lower discharge hole  190 S). As illustrated in  FIG. 4  and  FIG. 5 , the bulging portion  171 S has a sidewall portion  171   b  bulged from a peripheral edge portion  171   a , and a portion (bottom portion) facing the lower discharge hole  190 S, and overlaps with the lower discharge hole  190 S in a cross section orthogonal to the shaft direction of the rotating shaft  15 . 
     As illustrated in  FIG. 7 , at least a part of the bulging portion  171 S is formed overlapping with each of the lower discharge-chamber recessed portion  163 S and the lower discharge-valve accommodating recessed portion  164 S, in a cross section orthogonal to the shaft direction of the rotating shaft  15  (see  FIG. 3 ). Thus, the bulging portion  171 S can be formed such that, by expanding the area occupying in the cross section orthogonal to the shaft direction of the rotating shaft  15 , the proper volume is ensured and such that the depth in the thickness direction of the lower end plate cover  170 S is made shallow. Furthermore, because the bulging portion  171 S is formed in a shape including a portion, for which the volume in the cross section orthogonal to the shaft direction of the rotating shaft  15  is changed, that is, what is called a throttle portion, the flow of the refrigerant in the lower end-plate cover chamber  180 S can be disturbed, and the flow of the refrigerant can be adjusted as appropriate. 
     Then, in a cross section orthogonal to the rotating shaft  15 , as illustrated in  FIG. 7 , the bulging portion  171 S is formed so as to overlap with at least a part of each of the first main refrigerant passage hole  136 A, the second main refrigerant passage hole  136 B, the first sub-refrigerant passage hole  136 C, and the second sub-refrigerant passage hole  136 D. Thus, the first main refrigerant passage hole  136 A, the second main refrigerant passage hole  136 B, the first sub-refrigerant passage hole  136 C, and the second sub-refrigerant passage hole  136 D are made to communicate with the lower end-plate cover chamber  180 S via the bulging portion  171 S. 
     As just described, by having the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D in addition to the first main refrigerant passage hole  136 A and the second main refrigerant passage hole  136 B, even if the bulging portion  171 S is expanded so as to cover the lower discharge-chamber recessed portion  163 S and the lower discharge-valve accommodating recessed portion  164 S, the refrigerant discharged into the lower end-plate cover chamber  180 S can be smoothly discharged via the four refrigerant passage holes  136  (the first main refrigerant passage hole  136 A, the second main refrigerant passage hole  136 B, the first sub-refrigerant passage hole  136 C, and the second sub-refrigerant passage hole  136 D) arranged in the periphery of the bulging portion  171 S. 
     Furthermore, as illustrated in  FIG. 8 , the bulging portion  171 S of the lower end plate cover  170 S is brought into contact with the lower surface of the lower end plate  160 S over the entire peripheral edge portion  171   a  of the bulging portion  171 S. As a result, because the bulging portion  171 S has no portion extending over the sub-bearing portion  161 S, the refrigerant is prevented from leaking from the lower end-plate cover chamber  180 S due to variations in the shape of the bulging portion  171 S and the shape of the sub-bearing portion  161 S, and the airtightness in the bulging portion  171 S is enhanced. Note that, in the bulging portion  171 S, in the thickness direction of the lower end plate  160 S, a portion of the distal end portion of the lower discharge valve presser  201 S projecting toward the lower end plate cover  170 S side from the lower discharge-chamber recessed portion  163 S, may be accommodated. 
     Furthermore, as illustrated in  FIG. 4  and  FIG. 5 , in the middle of the lower end plate cover  170 S, a circular through-hole  145 , into which the sub-shaft portion  151  is inserted, is formed. Furthermore, on the lower end plate cover  170 S, in an area that is other than the bulging portion  171 S and is other than the area facing the lower discharge-chamber recessed portion  163 S and the lower discharge-valve accommodating recessed portion  164 S of the lower end plate  160 S, the bolt holes  138  ( FIG. 4 ) through which the through bolts  175  and the like penetrate is provided. 
     As in the foregoing, the refrigerant passage holes  136  of the lower end plate  160 S in the rotary compressor  1  of the embodiment include the main refrigerant passage holes  136  (the first main refrigerant passage hole  136 A and the second main refrigerant passage hole  136 B) provided on the lower discharge-chamber recessed portion  163 S, and include the sub-refrigerant passage holes  136  (the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D) provided between the bolt hole  138  and the lower discharge-valve accommodating recessed portion  164 S away from the lower discharge-valve accommodating recessed portion  164 S. In a cross section orthogonal to the rotating shaft  15 , the bulging portion  171 S is formed so as to overlap with at least a part of each of the main refrigerant passage holes  136  (the first main refrigerant passage hole  136 A and the second main refrigerant passage hole  136 B) and the sub-refrigerant passage holes  136  (the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D). Thus, the proper volume of the bulging portion  171 S can be ensured and also the refrigerant discharged into the lower end-plate cover chamber  180 S can be smoothly discharged via the refrigerant passage holes  136 . As a result, according to the embodiment, as the pressure pulsation is suppressed, the efficiency of the rotary compressor  1  can be enhanced and also the vibration of the rotary compressor  1  can be suppressed. Furthermore, as the sub-refrigerant passage holes  136  (the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D) are arranged between the bolt hole  138  and the lower discharge-valve accommodating recessed portion  164 S away from the lower discharge-valve accommodating recessed portion  164 S, without decreasing the mechanical strength of the compression unit  12  along with opening of the sub-refrigerant passage holes  136  on the lower end plate  160 S, an appropriate mechanical strength can be ensured. 
     Thus, according to the embodiment, the enhancement in energy consumption efficiency (coefficient of performance (COP)) in the refrigeration cycle using the rotary compressor  1  and the suppression of vibration of the rotary compressor  1  can be both satisfied appropriately. 
     Furthermore, at least a part of the bulging portion  171 S of the lower end plate cover  170 S in the rotary compressor  1  of the embodiment is formed overlapping with each of the lower discharge-valve accommodating recessed portion  164 S and the lower discharge-chamber recessed portion  163 S, in a cross section orthogonal to the shaft direction of the rotating shaft  15 . By expanding the area occupying in the cross section orthogonal to the shaft direction of the rotating shaft  15  in this manner, the bulging portion  171 S can be formed such that the proper volume is ensured and such that the depth in the thickness direction of the lower end plate cover  170 S is made shallow. 
     Furthermore, the rotary compressor  1  of the embodiment includes, as the sub-refrigerant passage holes  136 , the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D provided between each bolt hole  138  adjacent in the circumferential direction of the lower end plate  160 S and the lower discharge-valve accommodating recessed portion  164 S. As the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D are thus arranged, without decreasing the mechanical strength of the compression unit  12  along with opening of the first sub-refrigerant passage hole  136 C and the second sub-refrigerant passage hole  136 D on the lower end plate  160 S, an appropriate mechanical strength can be ensured. 
     Furthermore, the rotary compressor  1  of the embodiment includes, in a cross section orthogonal to the rotating shaft  15 , the first main refrigerant passage hole  136 A that is arranged in the lower discharge-chamber recessed portion  163 S, and the second main refrigerant passage hole  136 B that is arranged overlapping partially with the lower discharge-chamber recessed portion  163 S, as the main refrigerant passage holes  136 . As a result, the refrigerant, which is discharged from the lower discharge hole  190 S, can be discharged smoothly via the first main refrigerant passage hole  136 A and the second main refrigerant passage hole  136 B. 
     Furthermore, at least two out of the first main refrigerant passage hole  136 A, the second main refrigerant passage hole  136 B, the first sub-refrigerant passage hole  136 C, and the second sub-refrigerant passage hole  136 D in the rotary compressor  1  of the embodiment have the same hole diameter. Thus, the refrigerant passage holes  136  can be worked by using a common cutting tool, and the productivity of the rotary compressor  1  can be increased. 
     Furthermore, the bulging portion  171 S of the lower end plate cover  170 S in the rotary compressor  1  of the embodiment is in contact with the lower surface of the lower end plate  160 S over the entire peripheral edge portion  171   a  of the bulging portion  171 S. As a result, because the bulging portion  171 S has no portion extending over the sub-bearing portion  161 S, the refrigerant can be prevented from leaking from the lower end-plate cover chamber  180 S due to variations in the shape of the bulging portion  171 S and the shape of the sub-bearing portion  161 S, and the airtightness in the bulging portion  171 S can be increased. 
     As in the foregoing, the embodiment has been described, but the embodiment is not limited by the above-described content. Furthermore, the above-described constituent elements include elements easily achieved by a person skilled in the art, elements being substantially the same as the constituent elements, and elements within the scope of equivalents of the constituent elements. Moreover, the above-described constituent elements may be combined as appropriate. Furthermore, at least one of various omissions, substitutions, and modifications of the constituent elements can be made without departing from the scope of the embodiment. 
     REFERENCE SIGNS LIST 
     
         
           1  ROTARY COMPRESSOR 
           10  COMPRESSOR HOUSING 
           11  MOTOR 
           12  COMPRESSION UNIT 
           15  ROTATING SHAFT 
           104  LOWER SUCTION PIPE (SUCTION PORTION) 
           105  UPPER SUCTION PIPE (SUCTION PORTION) 
           107  DISCHARGE PIPE (DISCHARGE PORTION) 
           121 T UPPER CYLINDER 
           121 S LOWER CYLINDER 
           125 T UPPER PISTON 
           125 S LOWER PISTON 
           127 T UPPER VANE 
           127 S LOWER VANE 
           128 T UPPER VANE GROOVE 
           128 S LOWER VANE GROOVE 
           130 T UPPER CYLINDER CHAMBER 
           130 S LOWER CYLINDER CHAMBER 
           131 T UPPER SUCTION CHAMBER 
           131 S LOWER SUCTION CHAMBER 
           133 T UPPER COMPRESSION CHAMBER 
           133 S LOWER COMPRESSION CHAMBER 
           136  REFRIGERANT PASSAGE HOLE 
           136 A FIRST MAIN REFRIGERANT PASSAGE HOLE 
           136 B SECOND MAIN REFRIGERANT PASSAGE HOLE 
           136 C FIRST SUB-REFRIGERANT PASSAGE HOLE 
           136 D SECOND SUB-REFRIGERANT PASSAGE HOLE 
           138  BOLT HOLE 
           140  INTERMEDIATE PARTITION PLATE 
           160 T UPPER END PLATE 
           160 S LOWER END PLATE 
           163 T UPPER DISCHARGE-CHAMBER RECESSED PORTION 
           163 S LOWER DISCHARGE-CHAMBER RECESSED PORTION 
           164 T UPPER DISCHARGE-VALVE ACCOMMODATING RECESSED PORTION 
           164 S LOWER DISCHARGE-VALVE ACCOMMODATING RECESSED PORTION 
           170 S LOWER END PLATE COVER 
           171 S BULGING PORTION 
           174 ,  175  THROUGH BOLT 
           176  AUXILIARY BOLT 
           180 T UPPER END-PLATE COVER CHAMBER 
           180 S LOWER END-PLATE COVER CHAMBER 
           190 T UPPER DISCHARGE HOLE 
           190 S LOWER DISCHARGE HOLE 
           200 T UPPER DISCHARGE VALVE 
           200 S LOWER DISCHARGE VALVE