Electric compressor

Abstract

[Problem] To stabilize lubrication by eliminating the difference in the amount of oil supplied to two compression mechanisms in an electric compressor provided with a two-stage compression mechanism. [Solution] An electric compressor (10) includes: a two-stage compression mechanism (70) driven by a drive shaft (61); an oil separator (120) for separating oil in a refrigerant discharged from the two-stage compression mechanism (70); and an oil storage unit (123) for storing the oil. The drive shaft (61) has an in-shaft oil passage (150) that communicates with the oil storage unit (123). The in-shaft oil passage (150) includes: an axial hole (151) extending in the axial direction of the drive shaft (61); a first radial passage (161) for supplying the oil in the axial hole (151) to a low-stage side compression mechanism (80); and a second radial passage (162) for supplying the oil to a high-stage side compression mechanism (90). A minimum passage area (A1) of the first radial passage (161) is smaller than a minimum passage area (A2) of the second radial passage (162).

Description

Electric compressor

[0001] The present invention relates to an improved technique for an electric compressor used in a refrigeration cycle, which includes a compression mechanism for compressing a refrigerant and a motor for driving the compression mechanism.

[0002] Among electric compressors, there is a rolling piston type rotary compressor equipped with multiple compression mechanisms. Such compressors include a parallel compressor in which the flow paths of the multiple compression mechanisms are arranged in parallel to suck in and compress refrigerant in parallel, and a multi-stage compressor in which the compression flow paths of the multiple compression mechanisms are arranged in series to compress refrigerant in a lower-stage compression mechanism and further compress it in a higher-stage compression mechanism. For example, the technology disclosed in Patent Document 1 is known as an electric compressor equipped with parallel compression mechanisms.

[0003] According to the electric compressor equipped with a horizontal parallel compression mechanism (single-stage compression mechanism) known from Patent Document 1, refrigerant is sucked into the compressor housing and compressed in parallel by two compression mechanisms, and the discharged refrigerant is merged in a discharge muffler chamber and discharged.

[0004] Patent Document 1 discloses a lubrication structure for a parallel compression mechanism. According to this lubrication structure, the sliding parts of each compressor are lubricated by drawing oil stored in an oil reservoir into an oil passage in a drive shaft due to the pressure difference between discharge pressure and suction pressure, and then supplying the oil from this oil passage to each compressor through each guide hole. Because this electric compressor is a single-stage compression mechanism, the sliding parts of each compressor are under the same pressure.

[0005] Japanese Patent Application Laid-Open No. 2021-042687

[0006] In a multi-stage compression mechanism, for example, a two-stage compressor having two compression mechanisms connected in series, the pressure of the refrigerant drawn into each compression mechanism varies, resulting in different pressures of the refrigerant gas inside and leaking from the cylinders of each compression mechanism. Therefore, if the lubrication structure of the parallel compression mechanism known from Patent Document 1 is applied directly to a two-stage compression mechanism, the oil supply to bearings and sliding parts will not be uniform, which may result in insufficient or excessive lubrication.

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a technology that can eliminate the difference in the amount of oil supplied to the two compression mechanisms and stabilize lubrication in an electric compressor equipped with a two-stage compression mechanism in which two compressors are arranged in series to compress.

[0008] In the following description, reference numerals in the accompanying drawings are placed in parentheses to facilitate understanding of the present invention, but the present invention is not limited to the illustrated forms.

[0009] According to the present disclosure, firstly, there is provided an electric compressor (10) for use in a refrigeration cycle, the electric compressor (10) comprising: a housing (11, 20, 30); a two-stage compression mechanism (70) having a low-stage compression mechanism (80) that compresses and discharges a refrigerant drawn from the refrigeration cycle; and a high-stage compression mechanism (90) that draws in, compresses, and discharges the refrigerant compressed and discharged by the low-stage compression mechanism (80) into a discharge chamber (32); a drive shaft (61) that drives the two-stage compression mechanism (70); an oil separator (120) that can separate oil contained in the refrigerant introduced from the discharge chamber (32); an oil reservoir (123) that accumulates the oil separated by the oil separator (120); and an oil supply passage (130) that can supply the oil accumulated in the oil reservoir (123) to the two-stage compression mechanism (70), the oil supply passage (130) includes an in-shaft oil passage (150) formed inside the drive shaft (61), the in-shaft oil passage (150) including: an axial hole (151) extending in the axial direction of the drive shaft (61) and opening at a tip end surface (61 b) of one end of the drive shaft (61), a first radial passage (161) communicating from the axial hole (151) to an outer circumferential surface of the drive shaft (61) and capable of supplying the oil to the low-stage side compression mechanism (80), and a second radial passage (162) communicating from the axial hole (151) to the outer circumferential surface of the drive shaft (61) and capable of supplying the oil to the high-stage side compression mechanism (90), and a minimum passage area (A1) of the first radial passage (161) is smaller than a minimum passage area (A2) of the second radial passage (162).

[0010] Secondly, preferably, in the electric compressor described in the first aspect, the housing (11) includes a motor housing (20) that houses a motor (60) that drives the drive shaft (61), a compression mechanism housing (30) that houses the two-stage compression mechanism (70) and defines the discharge chamber (32), and a partition block (40) that is sandwiched between the motor housing (20) and the compression mechanism housing (30), the partition block (40) is provided with a shaft insertion hole (41) through which the drive shaft (61) can be inserted and a bearing (64) that rotatably supports the drive shaft (61), and the intra-shaft oil passage (150) has a third radial passage (163) that communicates from the axial hole (151) to the outer circumferential surface of the drive shaft (61) and can supply the oil to the bearing (64).

[0011] Thirdly, preferably, in the electric compressor described in the second aspect, the partition block (40) is provided with a shaft seal (43) that seals between the shaft insertion hole (41) and the outer peripheral surface of the drive shaft (61), the bearing (64) is located on the motor chamber (21) side inside the motor housing (20) with respect to the shaft seal (43), and the third radial passage (163) communicates with the outer peripheral surface of the drive shaft (61) between the bearing (64) and the shaft seal (43).

[0012] Fourth, preferably, in the electric compressor according to the second or third aspect, a minimum passage area (A3) of the third radial passage (163) is smaller than the minimum passage area (A1) of the first radial passage (161).

[0013] Fifth, preferably, in the electric compressor according to any one of the first to fourth aspects, the oil supply passage (130) is provided with a pressure reducing means (181) for reducing the pressure in the axial hole (151) relative to the pressure in the oil reservoir (123).

[0014] The present disclosure provides a technology that can eliminate the difference in the amount of oil supplied to the two compression mechanisms and stabilize lubrication in an electric compressor equipped with a two-stage compression mechanism that compresses by arranging two compressors in series.

[0015] Fig. 3A is a cross-sectional view of an electric compressor according to an embodiment; Fig. 3B is an enlarged view of the area around the two-stage compression mechanism shown in Fig. 1; Fig. 3A is a cross-sectional view of the low-stage compression mechanism shown in Fig. 2 as seen from the axial direction of the drive shaft, and Fig. 3B is an enlarged view of 3B of Fig. 3A; Fig. 4A is a cross-sectional view of the high-stage compression mechanism shown in Fig. 2 as seen from the axial direction of the drive shaft, and Fig. 4B is an enlarged view of 4B of Fig. 4A; Fig. 5A is an enlarged view of the area around the oil separator and oil supply passage shown in Fig. 2, and Fig. 5B is an enlarged view of 5B of Fig. 5A; and Fig. 5B is an enlarged view of the area around the drive shaft and oil passage shown in Fig. 5.

[0016] An embodiment of the present invention will be described below with reference to the accompanying drawings. Note that the embodiment shown in the accompanying drawings is an example of the present invention, and the present invention is not limited to this embodiment. In the drawings, "Up" indicates the top, and "Dn" indicates the bottom.

[0017] <Example> Figure 1 shows the overall configuration of an electric compressor 10 used in a refrigeration cycle using R744 as a refrigerant. In addition to PAG, POE, etc., can be used as the oil for the refrigeration cycle. This electric compressor 10 is configured as a so-called horizontally mounted electric compressor, in which a two-stage compression mechanism 70 is disposed next to a motor 60, for example. This electric compressor 10 includes a housing 11, a motor 60, and a two-stage compression mechanism 70 driven by the motor 60.

[0018] The housing 11 is configured to be installable horizontally and includes a motor housing 20, a compression mechanism housing 30 arranged beside the motor housing 20, and a partition block 40 sandwiched between the motor housing 20 and the compression mechanism housing 30. The motor housing 20, the compression mechanism housing 30, and the partition block 40 are made by casting or forging metal materials such as aluminum (including aluminum alloys).

[0019] The motor housing 20 is a cylindrical member with a bottom and a motor chamber 21 that houses the motor 60. One axial end of the motor housing 20 is closed by a bottom wall 22. The other axial end of the motor housing 20 is completely open. The motor housing 20 also has a suction port 23 that draws refrigerant into the motor chamber 21 from an external refrigeration cycle (not shown).

[0020] The compression mechanism housing 30 defines an intermediate pressure chamber 31 that houses the two-stage compression mechanism 70, a discharge chamber 32 from which the refrigerant compressed by the two-stage compression mechanism 70 is discharged, and an oil separation chamber 33 that constitutes an oil separator 120 that can separate the oil contained in the refrigerant introduced from the discharge chamber 32.

[0021] More specifically, the compression mechanism housing 30 is a cylindrical member with a bottom. One axial end of the compression mechanism housing 30 is closed by a bottom wall 34. This bottom wall 34 is, for example, formed integrally with the compression mechanism housing 30. The other axial end of the compression mechanism housing 30 is completely open. In this manner, the open end face of the compression mechanism housing 30 is closed by a partition block 40, and the closed interior is partitioned by a partition plate 110 (described later), thereby dividing the compression mechanism housing 30 into an intermediate pressure chamber 31 on the partition block 40 side and a discharge chamber 32 on the bottom wall 34 side.

[0022] The partition block 40 is a disk-shaped member that separates the motor chamber 21 and the intermediate pressure chamber 31, and is sandwiched between the open end face of the motor housing 20 and the open end face of the compression mechanism housing 30.

[0023] The gap between the end face of the motor housing 20 and the partition block 40, and the gap between the end face of the compression mechanism housing 30 and the partition block 40 are sealed by sealing members (not shown), such as gaskets or O-rings. The partition block 40 is restricted in both relative rotation and axial movement with respect to the motor housing 20 and the compression mechanism housing 30. For example, the partition block 40 is fixed integrally with the motor housing 20 and the compression mechanism housing 30 by fastening members 51, such as bolts.

[0024] Next, a description will be given of the motor 60. As shown in Fig. 1, the motor 60 includes an output shaft 61, a rotor 62 fixed to the output shaft 61, and a cylindrical stator 63 surrounding the rotor 62.

[0025] The output shaft 61 has its rotation center on the axial center line CL1 of the motor housing 20, extends from the motor chamber 21 toward the intermediate pressure chamber 31, and penetrates the partition block 40. The two-stage compression mechanism 70 is drivably coupled to the output shaft 61. In other words, the output shaft 61 of the motor 60 can be disposed laterally (e.g., horizontally) and also serves as the drive shaft 61 that drives the two-stage compression mechanism 70. Hereinafter, the output shaft 61 of the motor 60 may be referred to as the "drive shaft 61." This output shaft 61 is rotatably supported by a first bearing 64 provided in the partition block 40 and a second bearing 65 provided in the bottom wall 22 of the motor housing 20. The first bearing 64 and the second bearing 65 are formed of rolling bearings such as ball bearings.

[0026] The center line CL1 in the axial direction of the motor housing 20 may be referred to as the "center line CL1 of the output shaft 61 (drive shaft 61)." The output shaft 61 of the motor 60 may be configured as a separate member from the drive shaft of the two-stage compression mechanism 70. In that case, the output shaft 61 of the motor 60 is connected to the drive shaft of the two-stage compression mechanism 70 by a connecting member such as a coupling.

[0027] The rotor 62 is rotatable about a center line CL1 of the output shaft 61. The stator 63 is disposed radially outward of the rotor 62 and is fixed to an inner peripheral surface 20a of the motor housing 20.

[0028] 2, the partition block 40 has a shaft insertion hole 41 through which the drive shaft 61 can be inserted, and a shaft support portion 42 for mounting and supporting the first bearing 64. The shaft insertion hole 41 and the shaft support portion 42, which are integrally formed with the partition block 40, are coaxial with the center line CL1 of the drive shaft 61. The shaft support portion 42 protrudes from the partition block 40 toward the motor chamber 21. As a result, the first bearing 64 is located in the motor chamber 21.

[0029] The partition block 40 further includes a shaft seal 43. The shaft seal 43 is a member that seals between the shaft insertion hole 41 and the outer peripheral surface of the drive shaft 61, and is configured, for example, as a lip seal. The shaft seal 43 prevents refrigerant present in the intermediate pressure chamber 31 from leaking through the shaft insertion hole 41 into the motor chamber 21. The shaft seal 43 is located on the intermediate pressure chamber 31 side of the partition block 40. Therefore, an empty space 44 (space portion 44) exists in the shaft insertion hole 41 in the axial direction of the drive shaft 61 between the first bearing 64 and the shaft seal 43.

[0030] Next, the two-stage compression mechanism 70 will be described. As shown in FIG. 2 , the low-stage compression mechanism 80 and the high-stage compression mechanism 90 constituting the two-stage compression mechanism 70 each have the configuration of a so-called rolling piston rotary compressor, compressing air using rotating bodies 82, 92 (pistons 82, 92) and cylinders 84, 94. The low-stage compression mechanism 80 and the high-stage compression mechanism 90 have substantially the same configuration and are arranged on the center line CL1 of the drive shaft 61. The low-stage compression mechanism 80, which has a larger suction volume than the high-stage compression mechanism 90, is located on the partition block 40 side of the intermediate pressure chamber 31. The high-stage compression mechanism 90 is located on the bottom wall 34 side of the compression mechanism housing 30 of the intermediate pressure chamber 31.

[0031] Here, the suction volume refers to the stroke volume of the pistons 82, 92 when the drive shaft 61 rotates once. In other words, since the electric compressor 10 of the present invention employs the two-stage compression mechanism 70, it is preferable to set the discharge volume (volume of compressed refrigerant) of the low-stage compression mechanism 80 and the suction volume of the high-stage compression mechanism 90 to be the same so that refrigerant gas does not stagnate or is insufficient in the intermediate pressure chamber 31 between the compression mechanisms 80, 90. As a result, the suction volume of the low-stage compression mechanism 80 is larger than the suction volume of the high-stage compression mechanism 90. The suction volume is determined based on compressible refrigerant gas.

[0032] The two-stage compression mechanism 70 will be described in more detail. As shown in FIGS. 2 and 3A , the low-stage compression mechanism 80 includes a first eccentric shaft 81 integrally or integrally provided with the drive shaft 61, an annular first piston 82 (first rotor 82) fitted onto the first eccentric shaft 81, and a flat first cylinder 84 having a first cylinder chamber 83 that allows rotational movement of the first piston 82. A first annular bushing 85 is preferably interposed between the first eccentric shaft 81 and the first piston 82. A center line CL2 of the first eccentric shaft 81 is offset from a center line CL1 of the drive shaft 61. Relative rotation of the first cylinder 84 with respect to the compression mechanism housing 30 is restricted.

[0033] The first cylinder chamber 83 is a circular hole concentric with the center line CL1 of the drive shaft 61 and penetrates the first cylinder 84 in the axial direction. The first cylinder 84 further has a first suction passage 86 and a first discharge passage 87 that communicate with the first cylinder chamber 83. The first suction passage 86 and the first discharge passage 87 open to the surface of the first cylinder 84 that faces the partition block 40. As shown in FIG. 3A , the first suction passage 86 and the first discharge passage 87 are located above the drive shaft 61, which faces horizontally.

[0034] The outer diameter of the first piston 82 is smaller than the inner diameter of the first cylinder chamber 83. A vertical plate-shaped first vane 88 is in contact with the outer peripheral surface of the first piston 82 and is movable back and forth. The tip of the first vane 88 is pressed against the outer peripheral surface of the first piston 82 by a first spring 89. The first vane 88 divides the first cylinder chamber 83 into a first suction chamber 83a and a first compression chamber 83b. The first suction chamber 83a communicates with a first suction passage 86. The first compression chamber 83b communicates with a first discharge passage 87. The first piston 82 revolves within the first cylinder chamber 83. Refrigerant introduced from the first suction passage 86 to the first suction chamber 83a is compressed by the orbital motion of the first piston 82 and is discharged from the first compression chamber 83b through the first discharge passage 87.

[0035] 2 and 4A , similar to the low-stage compression mechanism 80, the high-stage compression mechanism 90 includes a second eccentric shaft 91 provided integrally or integrally with the drive shaft 61, an annular second piston 92 (second rotor 92) fitted onto the second eccentric shaft 91, and a flat-plate-shaped second cylinder 94 having a second cylinder chamber 93 that allows rotational movement of the second piston 92. A second annular bushing 95 is preferably interposed between the second eccentric shaft 91 and the second piston 92. A center line CL3 of the second eccentric shaft 91 is offset from a center line CL1 of the drive shaft 61. Relative rotation of the second cylinder 94 with respect to the compression mechanism housing 30 is restricted.

[0036] The second cylinder chamber 93 is a circular hole concentric with the center line CL1 of the drive shaft 61 and penetrates the second cylinder 94 in the axial direction. The second cylinder 94 also has a second suction passage 96 and a second discharge passage 97 that communicate with the second cylinder chamber 93. The second suction passage 96 opens to the outer peripheral surface of the second cylinder 94, thereby communicating the second cylinder chamber 93 with the intermediate pressure chamber 31. The second discharge passage 97 opens to the surface of the second cylinder 94 that faces the discharge chamber 32. As shown in FIG. 4A , the second suction passage 96 and the second discharge passage 97 are located above the drive shaft 61, which is oriented horizontally.

[0037] The outer diameter of the second piston 92 is smaller than the inner diameter of the second cylinder chamber 93. A vertical plate-shaped second vane 98 is movably attached to the outer peripheral surface of the second piston 92. The tip of the second vane 98 is pressed against the outer peripheral surface of the second piston 92 by a second spring 99. The second vane 98 divides the second cylinder chamber 93 into a second suction chamber 93a and a second compression chamber 93b. The second suction chamber 93a communicates with a second suction passage 96. The second compression chamber 93b communicates with a second discharge passage 97. The second piston 92 revolves within the second cylinder chamber 93. Refrigerant introduced from the second suction passage 96 into the second suction chamber 93a (second cylinder chamber 93) is compressed by the orbital motion of the second piston 92 and discharged from the second compression chamber 93b through the second discharge passage 97.

[0038] The center line CL2 of the first eccentric shaft 81 and the center line CL3 of the second eccentric shaft 91 are provided at positions symmetrical with respect to the center line CL1 of the drive shaft 61.

[0039] 2, the first cylinder chamber 83 is closed on the partition block 40 side by a flat first closing plate 101. This first closing plate 101 is sandwiched between the partition block 40 and the first cylinder 84. Furthermore, the first closing plate 101 has a first through hole 101a communicating with the first suction passage 86 and a second through hole 101b communicating with the first discharge passage 87. The first through hole 101a and the second through hole 101b penetrate the first closing plate 101 in the plate thickness direction.

[0040] The first suction passage 86 passes through a first through-hole 101a of the first closing plate 101 and communicates with the suction passage 45 of the partition block 40. This suction passage 45 penetrates the partition block 40 in the axial direction of the motor housing 20. Therefore, the first cylinder chamber 83 communicates with the suction port 23 (see FIG. 1) of the motor housing 20 via the first suction passage 86, the first through-hole 101a of the first closing plate 101, the suction passage 45 of the partition block 40, and the motor chamber 21.

[0041] The partition block 40 has a communication groove 46 (discharge recess 46) that communicates the second through-hole 101b of the first closure plate 101 with the intermediate pressure chamber 31. This communication groove 46 is formed on the surface of the partition block 40 facing the first closure plate 101. A discharge valve 47 that opens and closes the opening of the second through-hole 101b is provided in the communication groove 46. This discharge valve 47 is a check valve, such as a reed valve, that allows refrigerant to flow only from the first discharge passage 87 to the communication groove 46. The first cylinder chamber 83 communicates with the second suction chamber 93a of the second cylinder chamber 93 (see FIG. 4A ) via the first discharge passage 87, the second through-hole 101b, the communication groove 46, the intermediate pressure chamber 31, and the second suction passage 96.

[0042] The space between the first cylinder chamber 83 and the second cylinder chamber 93 is closed by a flat second closing plate 102. The second closing plate 102 is sandwiched between the first cylinder 84 and the second cylinder 94.

[0043] The second cylinder chamber 93 is closed on the side facing the bottom wall 34 of the compression mechanism housing 30 by a flat partition plate 110. More specifically, the partition plate 110 covers the axial end face of the second cylinder 94. The surface of the partition plate 110 opposite the second cylinder 94 faces the bottom wall 34 of the compression mechanism housing 30. The gap between the outer peripheral surface of the partition plate 110 and the inner peripheral surface of the compression mechanism housing 30 is sealed by a sealing member such as an O-ring.

[0044] A discharge chamber 32 is defined inside the compression mechanism housing 30 and is surrounded by a bottom wall 34 and a partition plate 110. The intermediate pressure chamber 31 and the discharge chamber 32 are arranged along a center line CL1 of the drive shaft 61 of the two-stage compression mechanism 70.

[0045] Furthermore, the partition plate 110 has an extension portion 111 that extends toward the bottom wall 34 of the compression mechanism housing 30. This extension portion 111 is a disk-shaped portion that has a smaller diameter than the partition plate 110 and is offset with respect to the center line CL1 of the drive shaft 61, and is formed integrally with the partition plate 110. A tip surface 111a of the extension portion 111 (the surface 111a on the bottom wall 34 side) is close to the inner wall surface 34a of the bottom wall 34 of the compression mechanism housing 30.

[0046] The first cylinder 84, the second cylinder 94, the first closing plate 101, the second closing plate 102 and the partition plate 110 (including the extension portion 111) are fixed to the partition block 40 by fastening members such as bolts (not shown).

[0047] The partition plate 110 (including the extension 111) has a shaft support portion 113 for mounting a third bearing 112. This shaft support portion 113 is configured as a recess that is open to the intermediate pressure chamber 31 side, and is located on the center line CL1 of the drive shaft 61. A tip end portion 61a (see FIG. 5A) of the drive shaft 61 that faces the bottom wall 34 of the compression mechanism housing 30 is rotatably supported by the third bearing 112. This third bearing 112 is configured as a sliding bearing.

[0048] Furthermore, the partition plate 110 has a discharge communication hole 114 that connects the second discharge passage 97 of the second cylinder 94 with the discharge chamber 32. A discharge valve 115 is provided in the discharge chamber 32 to allow refrigerant to flow only from the discharge communication hole 114 to the discharge chamber 32. The discharge valve 115 is configured as, for example, a reed valve.

[0049] The discharge chamber 32 is connected to an oil separation chamber 33 that constitutes a part of the oil separator 120. The refrigerant in the high-stage compression mechanism 90 can flow into the oil separation chamber 33 through the second discharge passage 97, the discharge communication hole 114, and the discharge chamber 32.

[0050] 5A, the oil separator 120 separates oil contained in the refrigerant introduced from the discharge chamber 32, and is configured as, for example, a centrifugal separator that separates oil by centrifugal force. The oil separator 120 includes an oil separation chamber 33, a refrigerant introduction hole 121 that introduces refrigerant from the discharge chamber 32 into the oil separation chamber 33, and a separation pipe 122 housed in the oil separation chamber 33. The oil separation chamber 33 is a space that is vertically elongated and has a circular cross section, and is defined on the outer surface of the bottom wall 34 (the surface opposite to the inner wall surface 34a of the bottom wall 34) inside the compression mechanism housing 30 (see FIG. 2).

[0051] The refrigerant inlet hole 121 is located tangentially to the upper end of the circular oil separation chamber 33. Therefore, the refrigerant introduced into the oil separation chamber 33 from the refrigerant inlet hole 121 forms a swirling flow and swirls around the separation pipe 122. The separation pipe 122 extends in the longitudinal direction of the oil separation chamber 33. The separation pipe 122 may be disposed concentrically with the oil separation chamber 33, or may be disposed offset radially from the oil separation chamber 33 so as not to obstruct the swirling flow of the introduced refrigerant.

[0052] The refrigerant that flows from the discharge chamber 32 into the oil separation chamber 33 swirls around the separation pipe 122, and the oil contained in the refrigerant is separated by centrifugal force. The gaseous refrigerant (refrigerant gas) from which the oil has been separated passes through the separation pipe 122 and is discharged to the outside from the discharge port 35 of the compression mechanism housing 30. Meanwhile, the oil separated from the refrigerant falls downward in the oil separation chamber 33 due to its own weight and accumulates in the oil reservoir 123.

[0053] The oil reservoir 123 may be formed integrally with the bottom of the oil separation chamber 33, or may be a separate member from the oil reservoir 123. The oil stored in the oil reservoir 123 is supplied to each lubrication part through the oil supply passage 130 due to the pressure difference between the oil reservoir 123 and each lubrication part.

[0054] The oil supply passage 130 includes a relay passage 140 that communicates with the oil reservoir 123 and an in-shaft oil passage 150 that communicates with the relay passage 140 .

[0055] The relay passage 140 relays the flow of oil from the oil reservoir 123 to the intra-shaft oil passage 150 of the drive shaft 61. The relay passage 140 includes, for example, a first relay passage 141 that passes from the oil reservoir 123 to the inner wall surface 34a of the bottom wall 34, a second relay passage 142 that opens to the tip surface 111a of the extension portion 111 so as to be able to communicate with the first relay passage 141, a third relay passage 143 that passes from the second relay passage 142 in the radial direction of the extension portion 111, and a fourth relay passage 144 that passes from the third relay passage 143 in the axial direction of the drive shaft 61.

[0056] The first relay path 141 penetrates the bottom wall 34 along the axial direction of the drive shaft 61. The second relay path 142 is configured as a recess that opens to the tip surface 111a of the extending portion 111 and has a larger diameter than the first relay path 141. The third relay path 143 is formed inside the extending portion 111 and has a smaller diameter than the second relay path 142. The third relay path 143 penetrates the outer peripheral surface of the extending portion 111, and this penetrated portion is closed by a plug 145. The fourth relay path 144 is formed inside the extending portion 111, coincides with the center line CL1 of the drive shaft 61, and extends to the tip surface 61b of the drive shaft 61.

[0057] The gap between the inner wall surface 34a of the bottom wall 34 and the tip surface 111a of the extension portion 111 is sealed around the second relay path 142 by a sealing member 146 such as a gasket or an O-ring. As a result, the boundary between the first relay path 141 and the second relay path 142 is sealed.

[0058] 5A and 6 , in-shaft oil passage 150 is formed inside drive shaft 61 and can communicate with oil reservoir 123 via relay passage 140. Note that in-shaft oil passage 150 only needs to be able to communicate with oil reservoir 123 directly or indirectly via relay passage 140. In-shaft oil passage 150 includes an axial hole 151 extending in the axial direction of drive shaft 61 and four radial passages 161 to 164 that communicate from axial hole 151 to the outer circumferential surface of drive shaft 61.

[0059] To distinguish one from another, the four radial passages 161 to 164 may be referred to as a first radial passage 161, a second radial passage 162, a third radial passage 163, and a fourth radial passage 164. At least one of the four radial passages 161 to 164 is in communication with one another via pressure reduction means 171, 173. These pressure reduction means 171, 173 are members that reduce the pressure in the radial passages 161 to 164 relative to the pressure in the axial hole 151, and are formed, for example, by orifices. For example, the first radial passage 161 and the third radial passage 163 are provided with pressure reduction means 171, 173. The pressure reduction means 171 provided in the first radial passage 161 may be referred to as the "first pressure reduction means 171," and the pressure reduction means 173 provided in the third radial passage 163 may be referred to as the "third pressure reduction means 173."

[0060] The axial hole 151 extends in the axial direction of the drive shaft 61 from the tip end surface 61b of the drive shaft 61 to the location of the first bearing 64, and coincides with the center line CL1 of the drive shaft 61. In the tip end surface 61b of the drive shaft 61, the axial hole 151 communicates with the fourth relay passage 144.

[0061] 5A and 5B , the oil supply passage 130 is provided with a pressure reducing means 181. More specifically, the axial hole 151 and the oil reservoir 123 are in communication with each other via the pressure reducing means 181. The pressure in the oil reservoir 123 is greater than the pressure in the axial hole 151. The pressure reducing means 181 is a member that reduces the pressure in the axial hole 151 relative to the pressure in the oil reservoir 123, and is formed, for example, by an orifice. By providing the pressure reducing means 181, the pressure in the axial hole 151 can be reduced to a pressure suitable for supplying oil from the axial hole 151 to the high-stage compression mechanism 90. The pressure reducing means 181 may be provided in the relay path 140, for example, in the first relay path 141.

[0062] 3A , 3B , and 5A , the first radial passage 161 can supply oil in the axial hole 151 to the low-stage compression mechanism 80. The first eccentric shaft 81 of the low-stage compression mechanism 80 has a first communication hole 81a that penetrates radially from inside to outside and communicates with the first radial passage 161. The oil in the axial hole 151 passes through the first radial passage 161 (including the first pressure reduction means 171) and the first communication hole 81a, and flows between the outer circumferential surface of the first eccentric shaft 81 and the inner circumferential surface of the first piston 82, thereby lubricating the sliding portions between them (including the first bushing 85). Note that it is preferable that the outer circumferential surface of the drive shaft 61 has a first oil flow portion 161a that communicates with the first radial passage 161 to smooth the flow of oil from the first radial passage 161 to the first communication hole 81a. The first oil flow portion 161 a is a space (recess) formed by chipping off a portion of the outer circumferential surface of the drive shaft 61 .

[0063] 4A , 4B , and 5A , the second radial passage 162 can supply oil in the axial hole 151 to the high-stage compression mechanism 90. The second eccentric shaft 91 of the high-stage compression mechanism 90 has a second communication hole 91a that penetrates radially from inside to outside and communicates with the second radial passage 162. The oil in the axial hole 151 passes through the second radial passage 162 and the second communication hole 91a and flows between the outer circumferential surface of the second eccentric shaft 91 and the inner circumferential surface of the second piston 92, thereby lubricating the sliding portions between them (including the second bushing 95). Note that it is preferable that the outer circumferential surface of the drive shaft 61 has a second oil flow portion 162a that communicates with the second radial passage 162 to smooth the flow of oil from the second radial passage 162 to the second communication hole 91a. The second oil flow portion 162 a is a space (recess) formed by chipping off a portion of the outer circumferential surface of the drive shaft 61 .

[0064] 5A and 6 , the third radial passage 163 can supply oil from the axial hole 151 to the first bearing 64. This third radial passage 163 is preferably located in the empty space 44 between the first bearing 64 and the shaft seal 43 in the shaft insertion hole 41 of the partition block 40. The oil from the axial hole 151 can flow through the third radial passage 163 (including the third pressure reduction means 173) and the empty space 44 to lubricate the first bearing 64. Note that the outer peripheral surface of the drive shaft 61 preferably has a third oil flow portion 163a that communicates with the third radial passage 163 to facilitate the flow of oil from the third radial passage 163 to the empty space 44. The third oil flow portion 163a is a space (recess) formed by chipping off a portion of the outer peripheral surface of the drive shaft 61.

[0065] 5A and 6 , the fourth radial passage 164 can supply oil in the axial hole 151 to the third bearing 112. The oil in the axial hole 151 can pass through the fourth radial passage 164 and flow to the third bearing 112 to lubricate it. Note that it is preferable that the outer peripheral surface of the drive shaft 61 has a fourth oil flow portion 164a that communicates with the fourth radial passage 164 to facilitate the flow of oil from the fourth radial passage 164 to the third bearing 112. The fourth oil flow portion 164a is a space (recess) formed by chipping off a portion of the outer peripheral surface of the drive shaft 61.

[0066] Here, the relationship between pressures P1 to P4 (not shown) at each lubrication location will be described. The pressure P1 in the first compression chamber 83b (see FIG. 3A) of the low-stage compression mechanism 80 will be referred to as the first pressure P1. The pressure P2 in the second compression chamber 93b (see FIG. 4A) of the high-stage compression mechanism 90 will be referred to as the second pressure P2. The pressure P3 in the motor chamber 21 in which the first bearing 64 is located will be referred to as the third pressure P3. The pressure P4 in the shaft support portion 113 of the partition plate 110 in which the third bearing 112 is located will be referred to as the fourth pressure P4.

[0067] The first pressure P1 in the first compression chamber 83b is higher than the third pressure P3 in the motor chamber 21. The second pressure P2 in the second compression chamber 93b is higher than the first pressure P1 in the first compression chamber 83b. The fourth pressure P4 in the shaft support portion 113 is approximately the same as the second pressure P2 in the second compression chamber 93b. In other words, the pressure relationship is "P3 < P1 < P2 ≒ P4".

[0068] In contrast, in this embodiment, since there are differences among the pressures P1 to P4, in order to stabilize the lubrication of each lubrication portion, the minimum passage areas A1 to A5 of the axial hole 151 and the four radial passages 161 to 164 are set as follows, as shown in FIG. 6 : The minimum passage area A1 of the first radial passage 161 is referred to as the first minimum passage area A1, which corresponds to the minimum area of ​​the first pressure reduction means 171. The minimum passage area A2 of the second radial passage 162 is referred to as the second minimum passage area A2. The minimum passage area A3 of the third radial passage 163 is referred to as the third minimum passage area A3, which corresponds to the minimum area of ​​the third pressure reduction means 173. The minimum passage area A4 of the fourth radial passage 164 is referred to as the fourth minimum passage area A4. The minimum passage area A5 of the axial hole 151 is referred to as the minimum passage area A5.

[0069] The third minimum passage area A3 of the third radial passage 163 (third pressure reduction means 173) is smaller than the first minimum passage area A1 of the first radial passage 161. The first minimum passage area A1 of the first radial passage 161 (first pressure reduction means 171) is smaller than the second minimum passage area A2 of the second radial passage 162. The second minimum passage area A2 of the second radial passage 162 is the same as (or includes approximately the same area as) the fourth minimum passage area A4 of the fourth radial passage 164. In other words, the relationship is "A3 < A1 < A2 ≒ A4". Furthermore, the minimum passage areas A1 to A4 of all of the radial passages 161 to 164 are smaller than the minimum passage area A5 of the axial hole 151.

[0070] Setting the minimum passage areas A1 to A5 in this manner makes it possible to equalize the flow rate of oil passing through the axial hole 151 and the four radial passages 161 to 164. The oil pressure in the axial hole 151 becomes constant, and the amount of oil supplied (oil flow rate) is determined by each of the radial passages 161 to 164. As a result, differences in the amount of oil supplied from the four radial passages 161 to 164 are eliminated, and lubrication of each lubrication part can be stabilized.

[0071] To set the minimum passage areas A1 to A5, for example, the minimum diameter d5 of the axial hole 151 and the minimum diameters d1 to d4 of the four radial passages 161 to 164 are set as follows: The minimum diameter d3 of the third radial passage 163 (the minimum diameter d3 of the third pressure reduction means 173) is smaller than the minimum diameter d1 of the first radial passage 161 (the minimum diameter d1 of the first pressure reduction means 171). The minimum diameter d1 of the first radial passage 161 (the minimum diameter d1 of the first pressure reduction means 171) is smaller than the minimum diameter d2 of the second radial passage 162. The minimum diameter d2 of the second radial passage 162 is the same as (or approximately the same as) the minimum diameter d4 of the fourth radial passage 164. In other words, the relationship is "d3 < d1 < d2 ≒ d4." Furthermore, the minimum diameters d1 to d4 of the four radial passages 161 to 164 are smaller than the minimum diameter d5 of the axial hole 151.

[0072] The above explanation can be summarized as follows.

[0073] As shown in FIG. 1 , an electric compressor 10 used in a refrigeration cycle includes housings 11, 20, and 30; a two-stage compression mechanism 70 having a low-stage compression mechanism 80 that compresses and discharges refrigerant drawn from the refrigeration cycle and a high-stage compression mechanism 90 that draws in, compresses, and discharges the refrigerant compressed and discharged by the low-stage compression mechanism 80 into a discharge chamber 32; a drive shaft 61 that drives the two-stage compression mechanism 70; an oil separator 120 that can separate oil contained in the refrigerant introduced from the discharge chamber 32; an oil reservoir 123 that collects the oil separated by the oil separator 120; and an oil supply passage 130 that can supply the oil collected in the oil reservoir 123 to the two-stage compression mechanism 70.

[0074] 5A, the oil supply passage 130 includes an in-shaft oil passage 150 formed inside the drive shaft 61. The in-shaft oil passage 150 includes an axial hole 151 extending in the axial direction of the drive shaft 61 and opening at a tip end surface 61b of one end of the drive shaft 61, a first radial passage 161 communicating with the axial hole 151 to the outer circumferential surface of the drive shaft 61 and capable of supplying oil to the low-stage side compression mechanism 80, and a second radial passage 162 communicating with the axial hole 151 to the outer circumferential surface of the drive shaft 61 and capable of supplying oil to the high-stage side compression mechanism 90. As shown in FIG. 6, the minimum passage area A1 (first minimum passage area A1) of the first radial passage 161 is smaller than the minimum passage area A2 (second minimum passage area A2) of the second radial passage 162.

[0075] Because the pressure of the low-stage side compression mechanism 80 is lower than the pressure of the high-stage side compression mechanism 90, the minimum passage area A1 of the first radial passage 161 is made small so that the amount of oil supplied to the low-stage side compression mechanism 80 does not become excessive. Therefore, the amount of oil supplied from the axial hole 151 to the low-stage side compression mechanism 80 can be made equal to the amount of oil supplied from the axial hole 151 to the high-stage side compression mechanism 90. As a result, the difference in the amount of oil supplied to the low-stage side compression mechanism 80 and the high-stage side compression mechanism 90 is eliminated, and lubrication can be stabilized.

[0076] 5A , the housing 11 includes a motor housing 20 that houses a motor 60 that drives a drive shaft 61, a compression mechanism housing 30 that houses a two-stage compression mechanism 70 and defines a discharge chamber 32, and a partition block 40 that is sandwiched between the motor housing 20 and the compression mechanism housing 30. The partition block 40 is provided with a shaft insertion hole 41 through which the drive shaft 61 can be inserted, and a bearing 64 (first bearing 64) that rotatably supports the drive shaft 61. The in-shaft oil passage 150 has a third radial passage 163 that communicates from the axial hole 151 to the outer circumferential surface of the drive shaft 61 and can supply oil to the bearing 64.

[0077] The partition block 40 separates the motor chamber 21 inside the motor housing 20 from the intermediate pressure chamber 31 inside the compression mechanism housing 30. The intermediate pressure chamber 31 houses the two-stage compression mechanism 70. The partition block 40 is provided with a bearing 64 that supports the drive shaft 61. This bearing 64 supports the drive shaft 61 near a portion that receives a large load from the two-stage compression mechanism 70, and plays an important role as a main bearing. This bearing 64 can also be lubricated by a sufficient supply of oil through the in-shaft oil passage 150.

[0078] 2 and 5A, the partition block 40 is provided with a shaft seal 43 that seals the gap between the shaft insertion hole 41 and the outer peripheral surface of the drive shaft 61. The bearing 64 (first bearing 64) is located on the motor chamber 21 side of the motor housing 20 with respect to the shaft seal 43. The third radial passage 163 communicates with the outer peripheral surface of the drive shaft 61 between the bearing 64 and the shaft seal 43 (space 44).

[0079] The shaft seal 43 seals the gap between the low-pressure motor chamber 21 and the medium-pressure intermediate pressure chamber 31. Therefore, the shaft seal 43 prevents refrigerant present in the intermediate pressure chamber 31 from leaking into the motor chamber 21 through the shaft insertion hole 41. Furthermore, the bearing 64 is located on the motor chamber 21 side of the shaft seal 43. Therefore, the shaft seal 43 prevents the bearing 64 from being exposed to refrigerant present in the intermediate pressure chamber 31. In addition, the shaft seal 43 prevents oil supplied from the third radial passage 163 from leaking into the intermediate pressure chamber 31. The oil supplied from the third radial passage 163 to the space 44 (between the bearing 64 and the shaft seal 43) can sufficiently lubricate the bearing 64.

[0080] As shown in FIGS. 5A and 6 , the minimum passage area A3 of the third radial passage 163 is smaller than the minimum passage area A1 of the first radial passage 161 .

[0081] The pressure in the motor chamber 21 in which the bearing 64 is disposed is lower than the pressure in the intermediate pressure chamber 31. In contrast, in the present invention, the minimum passage area A3 of the third radial passage 163 is reduced so as to prevent an excessive amount of oil from being supplied to the bearing 64. As a result, the amount of oil supplied from the axial hole 151 to the low-stage side compression mechanism 80 and the high-stage side compression mechanism 90 can be stabilized.

[0082] As shown in FIGS. 5A and 5B, the oil supply passage 130 is provided with a pressure reducing means 181 that reduces the pressure in the axial hole 151 relative to the pressure in the oil reservoir 123 .

[0083] The pressure in the oil reservoir 123 is greater than the pressure in the axial hole 151. In contrast, in the present invention, the pressure in the axial hole 151 can be reduced by the pressure reducing means 181 to a pressure suitable for supplying oil from the axial hole 151 to the high-stage side compression mechanism 90. As a result, the amount of oil supplied from the in-shaft oil passage 150 to the low-stage side compression mechanism 80 and the high-stage side compression mechanism 90 can be stabilized.

[0084] As long as the functions and effects of the present invention are achieved, the present invention is not limited to the embodiments. For example, the compression mechanism 70 may be configured as a multi-stage compression mechanism in which multiple compressors are arranged in series to compress the refrigerant. Furthermore, the bearings 64, 65 are not limited to rolling bearings and may be configured as, for example, plain bearings. Furthermore, the refrigerant is not limited to R744 and may be, for example, R134a, R1234yf, R290, or the like.

[0085] The electric compressor 10 of the present invention is suitable for use in a refrigeration cycle.

[0086] DESCRIPTION OF SYMBOLS 10 Electric compressor 11 Housing 20 Motor housing 21 Motor chamber 22 Bottom wall 30 Compression mechanism housing 31 Intermediate pressure chamber 32 Discharge chamber 33 Oil separation chamber 40 Partition block 43 Shaft seal 60 Motor 61 Drive shaft 64 Bearing (first bearing) 70 Two-stage compression mechanism 80 Low-stage compression mechanism 90 High-stage compression mechanism 110 Partition plate 112 Bearing (third bearing) 120 Oil separator 123 Oil reservoir 130 Oil supply passage 140 Relay passage 150 In-shaft oil passage 151 Axial hole 161 First radial passage 162 Second radial passage 163 Third radial passage 181 Pressure reduction means A1 Minimum passage area of ​​first radial passage A2 Minimum passage area of ​​second radial passage A3 Minimum passage area of ​​the third radial passage CL1 Center line of the drive shaft

Claims

1. An electric compressor (10) for use in a refrigeration cycle, comprising: a housing (11, 20, 30); a two-stage compression mechanism (70) having a low-stage compression mechanism (80) that compresses and discharges a refrigerant drawn from the refrigeration cycle; and a high-stage compression mechanism (90) that draws in, compresses, and discharges the refrigerant compressed and discharged by the low-stage compression mechanism (80) into a discharge chamber (32); a drive shaft (61) that drives the two-stage compression mechanism (70); an oil separator (120) that can separate oil contained in the refrigerant introduced from the discharge chamber (32); an oil reservoir (123) that collects the oil separated by the oil separator (120); and an oil supply passage (130) that can supply the oil collected in the oil reservoir (123) to the two-stage compression mechanism (70); the oil supply passage (130) includes an in-shaft oil passage (150) formed inside the drive shaft (61), the in-shaft oil passage (150) including: an axial hole (151) extending in the axial direction of the drive shaft (61) and opening at a tip end surface (61 b) of one end of the drive shaft (61), a first radial passage (161) communicating from the axial hole (151) to an outer circumferential surface of the drive shaft (61) and capable of supplying the oil to the low-stage-side compression mechanism (80), and a second radial passage (162) communicating from the axial hole (151) to the outer circumferential surface of the drive shaft (61) and capable of supplying the oil to the high-stage-side compression mechanism (90), and a minimum passage area (A1) of the first radial passage (161) is smaller than a minimum passage area (A2) of the second radial passage (162).

2. The electric compressor according to claim 1, wherein the housing (11) includes a motor housing (20) that houses a motor (60) that drives the drive shaft (61), a compression mechanism housing (30) that houses the two-stage compression mechanism (70) and defines the discharge chamber (32), and a partition block (40) that is sandwiched between the motor housing (20) and the compression mechanism housing (30), wherein the partition block (40) is provided with a shaft insertion hole (41) through which the drive shaft (61) can be inserted and a bearing (64) that rotatably supports the drive shaft (61), and wherein the intra-shaft oil passage (150) has a third radial passage (163) that communicates from the axial hole (151) to the outer circumferential surface of the drive shaft (61) and can supply the oil to the bearing (64).

3. An electric compressor as described in claim 2, wherein the partition block (40) is provided with a shaft seal (43) that seals between the shaft insertion hole (41) and the outer peripheral surface of the drive shaft (61), the bearing (64) is located on the motor chamber (21) side inside the motor housing (20) with respect to the shaft seal (43), and the third radial passage (163) communicates with the outer peripheral surface of the drive shaft (61) between the bearing (64) and the shaft seal (43).

4. The electric compressor according to claim 2 or 3, wherein the minimum passage area (A3) of the third radial passage (163) is smaller than the minimum passage area (A1) of the first radial passage (161).

5. An electric compressor according to claim 1, wherein the oil supply passage (130) is provided with a pressure reducing means (181) for reducing the pressure in the axial hole (151) relative to the pressure in the oil reservoir (123).

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