Electric compressor

Abstract

[Problem] To prevent accumulation of a refrigerant liquid at a two-stage compression mechanism and thereby ensure the reliability of an electric compressor. [Solution] An electric compressor (50) includes a two-stage compression mechanism (110), a compressor housing (70) that defines an intermediate pressure chamber (71) that accommodates the two-stage compression mechanism (110) and a discharge chamber (144) into which refrigerant is discharged from the two-stage compression mechanism (110), an intermediate pressure communication passage (145) that allows the intermediate pressure chamber (71) and the discharge chamber (144) to communicate, and an intermediate pressure relief valve (147) that allows the refrigerant to flow only from the intermediate pressure communication passage (145) to the discharge chamber (144).

Description

Electric compressor

[0001] The present invention relates to an improved technique for an electric compressor including a compression mechanism that compresses a refrigerant in two stages and a motor that drives the compression mechanism.

[0002] Among electric compressors, there is a rolling piston type rotary compressor that performs two-stage compression. As such electric compressors, the technologies disclosed in Patent Document 1 and Patent Document 2 are known, for example.

[0003] According to the technology disclosed in Patent Document 1, the electric compressor has a two-stage compression mechanism, i.e., a lower-stage compression mechanism disposed below a motor and a higher-stage compression mechanism disposed below the lower-stage compression mechanism, within a housing. The interior of the housing is divided by a partition member into a first sealed chamber housing the motor and a second sealed chamber housing the compression mechanism. The suction passage of the lower-stage compression mechanism is connected to the first sealed chamber. The discharge passage of the lower-stage compression mechanism is open to the second sealed chamber. The suction passage of the higher-stage compression mechanism is connected to the second sealed chamber. The discharge passage of the higher-stage compression mechanism is connected to a discharge chamber for high-pressure refrigerant. An injection pipe is connected to the second sealed chamber. Gas injection of intermediate-pressure refrigerant from an air conditioning system circuit into the second sealed chamber via the injection pipe creates an intermediate-pressure atmosphere in the second sealed chamber.

[0004] According to the technology disclosed in Patent Document 2, in a two-stage compressor, the volume of the suction cylinder (compression chamber) of the high-pressure compression element mechanism is set to correspond to the volume of refrigerant gas discharged from the low-pressure compression element mechanism, and is smaller than the volume of the suction cylinder (compression chamber) of the low-pressure compression element mechanism.

[0005] JP-A-2000-054975 JP-A-5-133368

[0006] However, as in the technology disclosed in Patent Document 1, when a compressor in a vehicle air conditioner is idle for a long period of time, the pressure in the refrigeration cycle reaches equilibrium, and the refrigerant gas in the refrigeration cycle liquefies at the coldest point in the refrigeration cycle. The compressor has the largest heat capacity of all the components in the refrigeration cycle and is therefore slow to warm up in response to changes in outside air temperature. As a result, the refrigerant gas in the refrigeration cycle liquefies inside the compressor. When the refrigerant liquefies inside the compressor, refrigerant liquid accumulates in the first and second sealed chambers.

[0007] When the electric compressor starts operating with this refrigerant liquid accumulated, the low-stage compression mechanism draws in the refrigerant liquid accumulated in the first sealed chamber and discharges it into the second sealed chamber. The high-stage compression mechanism draws in the refrigerant liquid accumulated in the second sealed chamber and discharges it into the discharge chamber. However, because the volume of refrigerant liquid does not change when compressed, refrigerant liquid accumulates in the second sealed chamber by the difference in volume between the compression chambers of the low-stage compression mechanism and the high-stage compression mechanism. If operation continues, the refrigerant liquid accumulated in the second sealed chamber will further increase, and refrigerant liquid may flow back into the injection pipe connected to the second sealed chamber. As a result, normal refrigeration cycle operation will not be possible.

[0008] In the technology disclosed in Patent Document 2, a check valve is provided to prevent refrigerant liquid from flowing back into the injection pipe. However, simply providing a check valve results in refrigerant liquid continuing to accumulate in the second sealed chamber. When refrigerant liquid accumulates to the entire volume of the second sealed chamber, the pressure in the second sealed chamber increases due to the discharge of refrigerant liquid from the low-stage compression mechanism. The generation of excessive pressure is undesirable in terms of ensuring the reliability of the electric compressor, from the viewpoints of the durability of the low-stage compression mechanism and preventing refrigerant leakage from the second sealed chamber.

[0009] 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 ensure the reliability of an electric compressor by preventing refrigerant liquid from accumulating in a two-stage compression mechanism.

[0010] 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.

[0011] According to the present disclosure, firstly, there is provided an electric compressor (50) comprising: a two-stage compression mechanism (110) having a high-stage side compressor (130) and a low-stage side compressor (120) having a larger suction volume than the high-stage side compressor (130); a motor (100) that drives the two-stage compression mechanism (110); a compressor housing (70) that defines an intermediate pressure chamber (71) that houses the two-stage compression mechanism (110) and a discharge chamber (144) from which a refrigerant is discharged from the two-stage compression mechanism (110); an intermediate pressure communicating passage (145) that communicates the intermediate pressure chamber (71) with the discharge chamber (144); and an intermediate pressure relief valve (147) that allows a refrigerant to flow only from the intermediate pressure communicating passage (145) to the discharge chamber (144).

[0012] Secondly, preferably, in the electric compressor described in the first aspect, the intermediate pressure relief valve (147) is a reed valve constituted by a first valve seat (147a) that opens and closes the intermediate pressure communicating passage (145), a first stopper (147b) that regulates the opening amount of the first valve seat (147a), and a first fixing member (147c) that fixes the first valve seat (147a) and the first stopper (147b).

[0013] Third, preferably, the electric compressor according to the second aspect further comprises: a discharge communication passage (146) that communicates a discharge passage (136) of the high-stage compressor (130) with the discharge chamber (144); and a discharge valve (148) that allows refrigerant to flow only from the discharge communication passage (146) to the discharge chamber (144), wherein the discharge valve (148) is a reed valve that includes a second valve seat (148a) that opens and closes the discharge communication passage (146), a second stopper (148b) that regulates the opening amount of the second valve seat (148a), and a second fixing member (148c) that fixes the second valve seat (148a) and the second stopper (148b), and wherein the first valve seat (147a) and the second valve seat (148a) are a single component that is integrally formed, The first stopper (147b) and the second stopper (148b) are a single component integrally formed, and the first fixing member (147c) also serves as the second fixing member (148c).

[0014] Fourth, preferably, in the electric compressor according to any one of the first to third aspects, the intermediate pressure chamber (71) and the discharge chamber (144) are arranged along a center line (CL1) of a rotation shaft (101) of the two-stage compression mechanism (110), the space between the intermediate pressure chamber (71) and the discharge chamber (144) is closed by a flat closing plate (143), a radially outer peripheral surface (143c) of the closing plate (143) faces the intermediate pressure chamber (71), a first end surface (143a) of the closing plate (143) perpendicular to the center line (CL1) covers an end surface (134b) of the two-stage compression mechanism (110), and a second end surface (143b) of the closing plate (143) opposite to the first end surface (143a) faces the discharge chamber (144), The intermediate pressure communication passage (145) communicates from the outer peripheral surface (143c) of the closure plate (143) to the second end surface (143b).

[0015] Fifth, preferably, in the electric compressor according to any one of the first to fourth aspects, the electric compressor (50) is a horizontally-mounted electric compressor in which a rotating shaft (101) of the two-stage compression mechanism (110) can be arranged horizontally, the intermediate-pressure communicating passage (145) is located below the horizontally-oriented rotating shaft (101), and the suction passages (125, 135) and the discharge passages (126, 136) of the two-stage compression mechanism (110) are located above the horizontally-oriented rotating shaft (101).

[0016] In the present invention, the reliability of the electric compressor can be ensured by preventing the accumulation of refrigerant liquid in the two-stage compression mechanism.

[0017] Fig. 1A is a conceptual diagram showing one example of an injection type refrigeration cycle according to an embodiment, and Fig. 1B is a conceptual diagram showing another example of an injection type refrigeration cycle according to an embodiment. A cross-sectional view of the electric compressor shown in Fig. 1. An enlarged view of the area around the two-stage compression mechanism shown in Fig. 2. A cross-sectional view of the low-stage side compressor shown in Fig. 3, seen from the axial direction of the motor shaft. A cross-sectional view of the high-stage side compressor shown in Fig. 3, seen from the axial direction of the motor shaft. A cross-sectional view of the area around the two-stage compression mechanism, intermediate pressure chamber, discharge chamber, intermediate pressure communicating passage, and intermediate pressure relief valve shown in Fig. 3. A cross-sectional view taken along line 7-7 in Fig. 3. An exploded perspective view of the discharge valve and intermediate pressure relief valve shown in Fig. 7.

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. Note that the embodiments shown in the accompanying drawings are merely examples of the present invention, and the present invention is not limited to these embodiments.

[0019] 1 to 8, an electric compressor 50 according to an embodiment and injection-type refrigeration cycles 10 and 30 including the electric compressor 50 will be described.

[0020] 1A shows an example of an injection-type refrigeration cycle 10 (hereinafter, abbreviated as "refrigeration cycle 10"). This refrigeration cycle 10 is used, for example, in an automotive air conditioning system, and performs cooling and heating using an interior air conditioning unit (not shown). Note that the use of this refrigeration cycle 10 is not limited. Furthermore, this refrigeration cycle 10 is suitable for use with R744 refrigerant, but other refrigerants (e.g., R134a refrigerant and R1234yf refrigerant) can also be used.

[0021] Here, the injection type refers to a system in which the refrigeration cycle 10 expands a high-pressure refrigerant in two stages and returns the intermediate-pressure refrigerant gas (gas-phase refrigerant) separated into gas and liquid to the electric compressor 50. This intermediate-pressure refrigerant gas returned to the electric compressor 50 is called injection refrigerant gas.

[0022] More specifically, the refrigeration cycle 10 includes an evaporator 11 , a gas cooler 12 , a first expansion valve 13 , a second expansion valve 14 , a gas-liquid separator 15 , and an electric compressor 50 .

[0023] The electric compressor 50 includes a two-stage compression mechanism 110. The two-stage compression mechanism 110 includes a low-stage compressor 120 and a high-stage compressor 130. The electric compressor 50 also includes an intake port 68 through which refrigerant can be drawn from the outside (evaporator 11), an outlet port 75 through which refrigerant can be discharged to the outside (gas cooler 12), and an injection inlet 151 through which injection refrigerant gas can be introduced.

[0024] A refrigerant outlet of the gas cooler 12 is connected to a refrigerant inlet of the gas-liquid separator 15 via a first flow path 21 and a first expansion valve 13. A refrigerant outlet of the gas-liquid separator 15 is connected to an injection pipe 22 through which injected refrigerant gas flows and a second flow path 23 through which refrigerant liquid flows. The injection pipe 22 is connected to an injection inlet 151 of the electric compressor 50.

[0025] The second flow path 23 is connected to the refrigerant inlet of the evaporator 11 via the second expansion valve 14. The refrigerant outlet of the evaporator 11 is connected to the suction port 68 of the electric compressor 50 via the third flow path 24. The discharge port 75 of the electric compressor 50 is connected to the refrigerant inlet of the gas cooler 12 via the fourth flow path 25.

[0026] 1A. That is, the refrigerant that has exchanged heat with outside air by the gas cooler 12 flows to the suction port 68 of the electric compressor 50 via the first flow path 21, the first expansion valve 13, the gas-liquid separator 15, the second expansion valve 14, and the evaporator 11, and is compressed to a high pressure. The refrigerant compressed to a high pressure by the electric compressor 50 flows to the gas cooler 12 via the fourth flow path 25.

[0027] In this way, the refrigerant that has exchanged heat with the outside air by the gas cooler 12 is rapidly adiabatically expanded by the first expansion valve 13 and the second expansion valve 14, and then returns to the evaporator 11. In other words, the refrigerant that has left the gas cooler 12 is expanded in two stages by the first expansion valve 13 and the second expansion valve 14.

[0028] The intermediate-pressure refrigerant that has passed through only the first expansion valve 13 of the two expansion valves 13, 14, passes through the gas-liquid separator 15 and flows through the injection pipe 22 to the injection inlet 151 of the electric compressor 50. By appropriately adjusting the openings of the first expansion valve 13 and the second expansion valve 14 in accordance with operating requirements, the amount branched to the injection inlet 151 of the compressor 50 can be adjusted.

[0029] 1B shows another example of an injection-type refrigeration cycle 30 (hereinafter, abbreviated as "refrigeration cycle 30"). The refrigeration cycle 30 of this example includes an internal heat exchanger 31 instead of the gas-liquid separator 15 of the refrigeration cycle 10. A refrigerant outlet of the gas cooler 12 is connected to a refrigerant inlet of the internal heat exchanger 31 via a first flow path 21. A portion 21a of the first flow path 21 between the gas cooler 12 and the internal heat exchanger 31, i.e., a branch point 21a, is branched by a branch path 41 and connected to the inlet of the internal heat exchanger 31 via a first expansion valve 13. An outlet of the internal heat exchanger 31 is connected to an injection inlet 151 of the electric compressor 50 via an injection pipe 22.

[0030] In another example of the refrigeration cycle 30, the refrigerant branched from the branch point 21a between the gas cooler 12 and the internal heat exchanger 31 is adiabatically expanded by the first expansion valve 13, and then heated by the internal heat exchanger 31, and the heated refrigerant gas is passed through the injection pipe 22 to the injection inlet 151 of the electric compressor 50.

[0031] Next, the overall configuration of the electric compressor 50 will be described. As shown in Fig. 2, the electric compressor 50 has a so-called horizontally mounted electric compressor configuration in which a two-stage compression mechanism 110 is disposed next to a motor 100. The electric compressor 50 includes a housing 51, the motor 100, and the two-stage compression mechanism 110 driven by the motor 100.

[0032] The housing 51 is configured to be installable horizontally. The housing 51 includes a motor housing 60 having a motor chamber 61 that houses the motor 100, a rear head 70 having an intermediate pressure chamber 71 that houses the two-stage compression mechanism 110, and a partition block 80 sandwiched between the motor housing 60 and the rear head 70. The motor housing 60, the rear head 70, and the partition block 80 are formed by castings of a metal material such as aluminum (including an aluminum alloy).

[0033] The motor housing 60 is a cylindrical member with a bottom. One axial end of the motor housing 60 is closed by a bottom wall 62. This bottom wall 62 is, for example, formed integrally with the motor housing 60. The other axial end of the motor housing 60 is completely open. The open end face 63 of the motor housing 60 is sometimes referred to as the first end face 63. This first end face 63 is a flat surface perpendicular to the axial center line CL1 of the motor housing 60. A motor chamber 61 is formed inside the motor housing 60. An inverter housing 65 is attached to the outer wall surface 62a of the bottom wall 62 of the motor housing 60. The inverter housing 65 houses an inverter device 66 for supplying drive power to the motor 100.

[0034] The motor housing 60 further has a suction port 68 through which refrigerant is drawn from the outside into the motor chamber 61. The suction port 68 is connected to the third flow path 24 (refrigerant supply pipe 24) shown in FIG.

[0035] The rear head 70 (compressor housing 70) is a cylindrical member with a bottom. One axial end of the rear head 70 is closed by a bottom wall 72. This bottom wall 72 is formed integrally with the rear head 70, for example. The other axial end of the rear head 70 is completely open. The open end face 73 of the rear head 70 is sometimes referred to as the second end face 73. This second end face 73 is a flat surface perpendicular to the axial center line CL1 of the motor housing 60 and faces the first end face 63 of the motor housing 60.

[0036] Furthermore, rear head 70 has an oil separation chamber 74 that separates oil from the refrigerant compressed by two-stage compression mechanism 110, and a discharge port 75 that discharges to the outside the gaseous refrigerant (refrigerant gas) from which the oil has been separated by this oil separation chamber 74. This discharge port 75 is connected to fourth flow path 25 (refrigerant discharge pipe 25) shown in FIG.

[0037] The partition block 80 is a disk-shaped member that separates the motor chamber 61 and the intermediate pressure chamber 71, and is sandwiched between the first end face 63 of the motor housing 60 and the second end face 73 of the rear head 70. More specifically, as shown in Fig. 3, the partition block 80 has a first mating surface 81 that faces the first end face 63 of the motor housing 60 and the motor chamber 61, and a second mating surface 82 that faces the second end face 73 of the rear head 70 and the intermediate pressure chamber 71. The first mating surface 81 and the second mating surface 82 are flat surfaces that are perpendicular to the axial center line CL1 of the motor housing 60. The first mating surface 81 and the second mating surface 82 may be referred to as the "first flat surface 81 and the second flat surface 82" as appropriate.

[0038] The gap between the first end face 63 of the motor housing 60 and the first mating surface 81 of the partition block 80, and the gap between the second end face 73 of the rear head 70 and the second mating surface 82 of the partition block 80 are sealed by sealing members (not shown), such as gaskets or O-rings. The partition block 80 is restricted in both relative rotation and axial movement with respect to the motor housing 60 and the rear head 70. For example, the partition block 80 is fixed integrally with the motor housing 60 and the rear head 70 by fastening members 91, such as bolts.

[0039] Next, a description will be given of the motor 100. As shown in Fig. 2, the motor 100 includes an output shaft 101 (motor shaft 101), a rotor 102 fixed to the output shaft 101, and a cylindrical stator 103 surrounding the rotor 102.

[0040] The output shaft 101 has a rotation center on the axial center line CL1 of the motor housing 60, extends from the motor chamber 61 toward the intermediate pressure chamber 71, penetrates the partition block 80, and is drivingly connected to the two-stage compression mechanism 110. In other words, the output shaft 101 of the motor 100 can be disposed laterally (for example, horizontally) and also serves as the rotating shaft 101 of the two-stage compression mechanism 110. Hereinafter, the output shaft 101 of the motor 100 may be appropriately referred to as the "rotating shaft 101 of the two-stage compression mechanism 110." This output shaft 101 (rotating shaft 101) is rotatably supported by a first bearing 104 provided in the partition block 80 and a second bearing 105 provided in the bottom wall 62 of the motor housing 60.

[0041] 3, a shaft support portion 83 for mounting the first bearing 104 is formed integrally with the partition block 80. In other words, the partition block 80 is integrally provided with the shaft support portion 83 that supports the rotating shaft 101 of the two-stage compression mechanism 110. This shaft support portion 83 protrudes from the first mating surface 81 of the partition block 80 toward the motor chamber 61. Note that the shaft support portion 83 includes a configuration that directly supports the rotating shaft 101 without using the first bearing 104.

[0042] The center line CL1 in the axial direction of the motor housing 60 may be referred to as the "center line CL1 of the output shaft 101 (rotating shaft 101)." The output shaft 101 of the motor 100 may be configured as a separate member from the output shaft of the two-stage compression mechanism 110. In that case, the output shaft 101 of the motor 100 is connected to the output shaft of the two-stage compression mechanism 110 by a connecting member such as a coupling.

[0043] The rotor 102 is rotatable about a center line CL1 of the output shaft 101 (rotating shaft 101). The stator 103 is disposed radially outward of the rotor 102 and is fixed to an inner peripheral surface 60b of the motor housing 60.

[0044] Next, the two-stage compression mechanism 110 will be described. As shown in FIG. 3 , the low-stage compressor 120 and the high-stage compressor 130 constituting the two-stage compression mechanism 110 each have a so-called rolling piston type rotary compressor configuration, compressing air using rotating bodies 122, 132 (pistons 122, 132) and cylinders 124, 134 that rotate. The low-stage compressor 120 and the high-stage compressor 130 have substantially the same configuration and are arranged on the center line CL1 of the rotary shaft 101 (output shaft 101). The low-stage compressor 120, which has a larger suction volume than the high-stage compressor 130, is located on the partition block 80 side of the intermediate pressure chamber 71. The high-stage compressor 130 is located on the bottom wall 72 side of the rear head 70 of the intermediate pressure chamber 71.

[0045] Here, the suction volume refers to the stroke volume of the pistons 122, 132 when the rotary shaft 101 makes one rotation. In other words, since the electric compressor 50 of the present invention employs the two-stage compression mechanism 110, it is preferable to set the discharge volume (volume of compressed refrigerant) of the low-stage compression mechanism 120 and the suction volume of the high-stage compression mechanism 130 to be the same so that refrigerant gas does not stagnate or is insufficient between the compressors 120, 130. As a result, the suction volume of the low-stage compression mechanism 120 is larger than the suction volume of the high-stage compression mechanism 130. The assumption for determining this volume is that a compressible refrigerant gas is used.

[0046] The two-stage compression mechanism 110 will be described in more detail. As shown in Figures 3 and 4, the low-stage compressor 120 includes a first eccentric shaft 121 that is integrally provided with the rotary shaft 101, an annular first piston 122 (first rotor 122) that is fitted onto the first eccentric shaft 121, and a flat first cylinder 124 that has a first cylinder chamber 123 that allows rotational movement of the first piston 122. A center line CL2 of the first eccentric shaft 121 is offset from a center line CL1 of the rotary shaft 101.

[0047] The first cylinder 124 is restricted from rotating relative to the rear head 70. The first cylinder 124 has a first surface 124a facing the second mating surface 82 of the partition block 80 and a second surface 124b facing the second cylinder 134 of the high-stage compressor 130. The first surface 124a and the second surface 124b of the first cylinder 124 are flat surfaces that are perpendicular to the axial center line CL1 of the motor housing 60.

[0048] The first cylinder chamber 123 is a circular hole concentric with the center line CL1 of the rotary shaft 101 and passes through the first cylinder 124. The first cylinder 124 further has a first suction passage 125 and a first discharge passage 126 which communicate with the first cylinder chamber 123. The first suction passage 125 and the first discharge passage 126 open to a first surface 124a of the first cylinder 124.

[0049] The outer diameter of the first piston 122 is smaller than the inner diameter of the first cylinder chamber 123. A vertical plate-shaped first vane 127 is in contact with the outer peripheral surface of the first piston 122 and is movable back and forth. The tip of this first vane 127 is pressed against the outer peripheral surface of the first piston 122 by a first spring 128. The first vane 127 divides the first cylinder chamber 123 into a first suction chamber 123a and a first compression chamber 123b. The first suction chamber 123a is in communication with a first suction passage 125. The first compression chamber 123b is in communication with a first discharge passage 126. The first piston 122 revolves within the first cylinder chamber 123. The refrigerant introduced into the first suction chamber 123a (first cylinder chamber 123) from the first suction passage 125 is compressed by the revolution of the first piston 122 and is discharged from the first compression chamber 123b through the first discharge passage 126.

[0050] 3 and 5 , similar to the low-stage compressor 120, the high-stage compressor 130 includes a second eccentric shaft 131 provided integrally with the rotating shaft 101, an annular second piston 132 (second rotating body 132) fitted onto the second eccentric shaft 131, and a flat second cylinder 134 having a second cylinder chamber 133 that allows rotational movement of the second piston 132. A center line CL3 of the second eccentric shaft 131 is offset from a center line CL1 of the rotating shaft 101.

[0051] The second cylinder 134 is restricted from rotating relative to the rear head 70. The second cylinder 134 further has a first surface 134a facing the second surface 124b of the first cylinder 124 and a second surface 134b facing the bottom wall 72 of the rear head 70. The first surface 134a and the second surface 134b of the second cylinder 134 are flat surfaces that are perpendicular to the axial center line CL1 of the motor housing 60.

[0052] The second cylinder chamber 133 is a circular hole concentric with the center line CL1 of the rotary shaft 101 and passes through the second cylinder 134. The second cylinder 134 further has a second suction passage 135 and a second discharge passage 136 that communicate with the second cylinder chamber 133. The second suction passage 135 opens to the outer peripheral surface of the second cylinder 134, thereby communicating the second cylinder chamber 133 with the intermediate pressure chamber 71. The second discharge passage 136 opens to a second surface 134b of the second cylinder 134.

[0053] The outer diameter of the second piston 132 is smaller than the inner diameter of the second cylinder chamber 133. A vertical plate-shaped second vane 137 is in contact with the outer peripheral surface of the second piston 132 and is movable back and forth. The tip of this second vane 137 is pressed against the outer peripheral surface of the second piston 132 by a second spring 138. The second vane 137 divides the second cylinder chamber 133 into a second suction chamber 133a and a second compression chamber 133b. The second suction chamber 133a is in communication with a second suction passage 135. The second compression chamber 133b is in communication with a second discharge passage 136. The second piston 132 revolves within the second cylinder chamber 133. The refrigerant introduced from the second suction passage 135 into the second suction chamber 133a (second cylinder chamber 133) is compressed by the revolution of the second piston 132 and is discharged from the second compression chamber 133b through the second discharge passage 136.

[0054] The center line CL2 of the first eccentric shaft 121 and the center line CL3 of the second eccentric shaft 131 are provided at positions symmetrical with respect to the center line CL1 of the rotation shaft 101.

[0055] 3, the first cylinder chamber 123 is closed on the partition block 80 side by a flat first closing plate 141. This first closing plate 141 is sandwiched between the second mating surface 82 of the partition block 80 and the first surface 124a of the first cylinder 124.

[0056] Furthermore, the first closing plate 141 has a first through hole 141a communicating with the suction port 125a of the first suction passage 125 and a second through hole 141b communicating with the first discharge passage 126. The first through hole 141a and the second through hole 141b penetrate the first closing plate 141 in the plate thickness direction.

[0057] The suction port 125a of the first suction passage 125 communicates with the suction passage 84 of the partition block 80 through the first through-hole 141a of the first closing plate 141. This suction passage 84 penetrates the partition block 80 in the axial direction of the motor housing 60. In other words, the suction passage 84 is located inside the partition block 80. Therefore, the first cylinder chamber 123 communicates with the suction port 68 of the motor housing 60 (see FIG. 2) via the first suction passage 125, the first through-hole 141a of the first closing plate 141, the suction passage 84 of the partition block 80, and the motor chamber 61.

[0058] The partition block 80 has a communication groove 85 (discharge recess 85) that connects the second through-hole 141b of the first closing plate 141 with the intermediate pressure chamber 71. This communication groove 85 is formed in the second mating surface 82 of the partition block 80. A discharge valve 86 that opens and closes the opening of the second through-hole 141b is provided in the communication groove 85. This discharge valve 86 is a check valve, such as a reed valve, that allows refrigerant to flow only from the first discharge passage 126 to the communication groove 85. The first cylinder chamber 123 is in communication with the second suction chamber 133a of the second cylinder chamber 133 via the first discharge passage 126, the second through-hole 141b, the communication groove 85, the intermediate pressure chamber 71, and the second suction passage 135.

[0059] The space between the first cylinder chamber 123 and the second cylinder chamber 133 is closed by a flat second closing plate 142. This second closing plate 142 is sandwiched between the second surface 124b of the first cylinder 124 and the first surface 134a of the second cylinder 134.

[0060] The second cylinder chamber 133 is closed on the side facing the bottom wall 72 of the rear head 70 by a flat third closing plate 143. This third closing plate 143 entirely covers the second surface 134b of the second cylinder 134. Furthermore, the step surface 76 inside the rear head 70 restricts the third closing plate 143 from moving toward the bottom wall 72 of the rear head 70.

[0061] The first cylinder 124 , the second cylinder 134 , the first closing plate 141 , the second closing plate 142 and the third closing plate 143 are sandwiched in the axial direction of the rear head 70 by the step surface 76 of the rear head 70 and the partition block 80 .

[0062] A discharge chamber 144 is formed inside the rear head 70 and is partitioned by the bottom wall 72 and a third closure plate 143. In other words, the space between the intermediate pressure chamber 71 and the discharge chamber 144 is closed by the flat third closure plate 143. The intermediate pressure chamber 71 and the discharge chamber 144 are arranged along the center line CL1 of the rotary shaft 101 of the two-stage compression mechanism 110.

[0063] 6, a first end surface 143a of the third closure plate 143, which is perpendicular to the center line CL1 of the rotary shaft 101, covers a second surface 134b of the second cylinder 134 (two-stage compression mechanism 110). A second end surface 143b of the third closure plate 143 opposite to the first end surface 143a faces the discharge chamber 144, that is, the bottom wall 72 of the rear head 70 shown in FIG. 3. A radial outer peripheral surface 143c of the third closure plate 143 faces the intermediate pressure chamber 71, that is, the inner peripheral surface 70a of the cylindrical rear head 70 with a bottom.

[0064] As shown in Figure 3, the third closure plate 143 has an intermediate pressure communication passage 145 that connects the intermediate pressure chamber 71 and the discharge chamber 144, and a discharge communication hole 146 that connects the second discharge passage 136 of the second cylinder 134 and the discharge chamber 144.

[0065] 6 , the intermediate pressure communicating passage 145 is formed in an L-shape, with an inlet 145a on the radial outer peripheral surface 143c of the third closure plate 143 and an outlet 145b on the second end surface 143b of the third closure plate 143. In the electric compressor 50 in which the rotating shaft 101 is oriented horizontally, the inlet 145a of the intermediate pressure communicating passage 145 faces downward and opens to the intermediate pressure chamber 71. In the electric compressor 50 in which the rotating shaft 101 is oriented horizontally, the outlet 145b of the intermediate pressure communicating passage 145 is preferably close to the lowest end of the discharge chamber 144.

[0066] 3, an intermediate pressure relief valve 147 that allows refrigerant to flow only from the intermediate pressure communicating passage 145 to the discharge chamber 144, and a discharge valve 148 that allows refrigerant to flow only from the discharge communicating passage 146 to the discharge chamber 144 are provided in the discharge chamber 144. These valves 147, 148 are attached to the second end surface 143b of the third closing plate 143.

[0067] 3, the intermediate pressure relief valve 147 is preferably set to open when refrigerant liquid accumulates in the intermediate pressure chamber 71, causing the pressure in the intermediate pressure chamber 71 to rise even slightly above the pressure in the discharge chamber 144. This allows refrigerant liquid accumulated in the intermediate pressure chamber 71 to be quickly discharged to the discharge chamber 144, preventing an excessive rise in pressure in the intermediate pressure chamber 71. The intermediate pressure relief valve 147 is a reed valve composed of a first valve seat 147a that opens and closes the intermediate pressure communicating passage 145, a first stopper 147b that regulates the opening amount of the first valve seat 147a, and a first fixing member 147c such as a bolt that fixes the first valve seat 147a and the first stopper 147b.

[0068] The discharge valve 148 opens due to the pressure difference between the refrigerant gas pressure in the second compression chamber 133b and the internal pressure of the discharge chamber 144. The discharge valve 148 is a reed valve that includes a second valve seat 148a that opens and closes the discharge communication passage 146, a second stopper 148b that regulates the opening amount of the second valve seat 148a, and a second fixing member 148c that fixes the second valve seat 148a and the second stopper 148b.

[0069] See also Figures 7 and 8. The first valve seat 147a and the second valve seat 148a are formed as a single, integral part. The first stopper 147b and the second stopper 148b are formed as a single, integral part. The first fixing member 147c also serves as the second fixing member 148c.

[0070] 3, the operational relationship between the intermediate pressure relief valve 147 and the discharge valve 148 will be described. During normal operation of the electric compressor 50, the discharge pressure of the second compression chamber 133b of the high-stage compressor 130 is higher than the pressure of the discharge chamber 144. The pressure of this discharge chamber 144 is higher than the pressure of the intermediate pressure chamber 71. At this time, the discharge valve 148 is open, and the intermediate pressure relief valve 147 is closed.

[0071] However, in the electric compressor 50, refrigerant gas in the refrigeration cycle may liquefy, resulting in refrigerant liquid accumulating in internal spaces such as the motor chamber 61, the intermediate pressure chamber 71, and the discharge chamber 144. For example, if the electric compressor 50 is stopped for an extended period of time, the refrigerant gas in the refrigeration cycle may liquefy due to temperature differences between day and night. Because the electric compressor 50 has a relatively large heat capacity among the components of the refrigeration cycle, it is difficult to warm up and remains cold, making it prone to refrigerant liquid accumulation. Furthermore, the electric compressor 50 may be mounted in a low position to facilitate the return of lubricating oil in the refrigerant gas from the refrigeration cycle to the electric compressor 50, making it prone to refrigerant liquid accumulation. As a result, refrigerant liquid accumulates in the internal spaces of the electric compressor 50. When the electric compressor 50 is started with refrigerant liquid accumulated, the refrigerant liquid accumulated in the motor chamber 61 is sucked into the low-stage compressor 120 and sent to the intermediate pressure chamber 71. The refrigerant liquid accumulated in the intermediate pressure chamber 71 is sucked into the high-stage compressor 130 and sent to the discharge chamber 144. Furthermore, the suction volume of the low-stage compressor 120 is larger than the suction volume of the high-stage compressor 130. Therefore, the amount of refrigerant liquid in the intermediate pressure chamber 71 discharged from the low-stage compressor 120 is greater than the amount of refrigerant liquid sucked into the high-stage compressor 130. The refrigerant liquid rapidly accumulates in the intermediate pressure chamber 71. As a result, it is expected that the pressure in the intermediate pressure chamber 71 will rise rapidly before the discharge pressure of the high-stage compressor 130 rises.

[0072] In contrast, the intermediate pressure relief valve 147 of the present invention is a differential pressure valve that opens when the pressure in the intermediate pressure chamber 71 rises even slightly above the pressure in the discharge chamber 144. When the pressure in the intermediate pressure chamber 71 rises even slightly above the pressure in the discharge chamber 114, the intermediate pressure relief valve 147 quickly opens, preventing the generation of abnormally high pressure in the intermediate pressure chamber 71. As a result, refrigerant leakage into or out of the intermediate pressure chamber 71 can be prevented. This is the primary reason why the electric compressor 50 is provided with the intermediate pressure relief valve 147.

[0073] 7 shows that the electric compressor 50 is a horizontally-mounted electric compressor in which the rotating shaft 101 can be disposed horizontally. The arrow Up points upward relative to the rotating shaft 101, and the arrow Dn points downward. The motor housing 60 (see FIG. 3) is equipped with installation brackets 69, 69 for disposing the electric compressor 50 horizontally. The intermediate-pressure communicating passage 145 is located below the horizontally-oriented rotating shaft 101. The suction passages 125, 135 and the discharge passages 126, 136 of the two-stage compression mechanism 110 are located above the horizontally-oriented rotating shaft 101.

[0074] 3 , the discharge chamber 144 is in communication with the oil separation chamber 74. The refrigerant in the high-stage compressor 130 can flow into the oil separation chamber 74 through the second discharge passage 136, the communication hole 146, and the discharge chamber 144. It is preferable that the tip end of the rotating shaft 101 be rotatably supported by a third bearing 149 provided on the third closure plate 143.

[0075] 6, the partition block 80 has an injection inlet 151, an injection outlet 152, and an injection passage 153. The injection passage 153 communicates between the injection inlet 151 and the injection outlet 152. At least the injection outlet 152 and the injection passage 153 are disposed within the partition block 80.

[0076] The injection inlet 151 is formed integrally with, for example, the partition block 80. More specifically, a boss portion 154 that protrudes radially outward is provided on the outer peripheral surface 87 of the partition block 80. The injection inlet 151 opens at this boss portion 154. The injection inlet 151 can introduce injection refrigerant gas by connecting the injection pipe 22 (see FIG. 1 ).

[0077] The injection outlet 152 is connected to the intermediate pressure chamber 71 by opening to a second mating surface 82 (second flat surface 82) of the partition block 80 that faces the intermediate pressure chamber 71. Therefore, the injection outlet 152 can guide the injected refrigerant gas into the intermediate pressure chamber 71.

[0078] A check valve 160 is provided at the injection outlet 152. This check valve 160 allows the injection refrigerant gas to flow only from the injection passage 153 to the intermediate pressure chamber 71. In other words, when the pressure in the injection passage 153 increases to exceed the pressure in the intermediate pressure chamber 71, the check valve 160 opens due to the pressure difference.

[0079] The check valve 160 is provided on the flat second mating surface 82 of the partition block 80, which faces the intermediate pressure chamber 71. The check valve 160 is formed, for example, by a reed valve 161. The reed valve 161 has one end of a thin, elastic plate fixed and opens in only one direction, that is, only in the direction that allows injection refrigerant gas to flow from the injection passage 153 to the intermediate pressure chamber 71. As shown in FIG. 7 , the injection outlet 152 is located above the horizontally oriented rotation shaft 101.

[0080] Next, the flow of refrigerant within the electric compressor 50 will be described. As shown in Figure 2, the refrigerant (refrigerant gas) drawn into the suction port 68 of the motor housing 60 passes through gaps in the motor 100 disposed in the motor chamber 61, cooling the motor 100, and then flows into the suction passage 84 of the partition block 80. The refrigerant that has passed through the suction passage 84 passes through the first through-hole 141a of the first closure plate 141 and the first suction passage 125 of the low-stage compressor 120, and enters the first suction chamber 123a of the first cylinder chamber 123.

[0081] 3, refrigerant compressed by the low-stage compressor 120 flows from the first compression chamber 123b of the first cylinder chamber 123 through the first discharge passage 126, the second through-hole 141b of the first closing plate 141, the communicating groove 85 of the partition block 80, the intermediate pressure chamber 71, and the second suction passage 135 to the second suction chamber 133a of the second cylinder chamber 133. Refrigerant further compressed by the high-stage compressor 130 flows from the second compression chamber 133b of the second cylinder chamber 133 through the second discharge passage 136, the discharge communicating passage 146 of the third closing plate 143, the discharge chamber 144, and the oil separation chamber 74 to the discharge port 75 of the rear head 70.

[0082] When refrigerant liquid accumulates in the intermediate pressure chamber 71, the intermediate pressure relief valve 147 opens. The refrigerant liquid accumulated in the intermediate pressure chamber 71 is discharged to the discharge chamber 144 through the intermediate pressure communication passage 145.

[0083] The above explanation can be summarized as follows.

[0084] As shown in FIG. 2 , the electric compressor 50 includes a two-stage compression mechanism 110 having a high-stage compressor 130 and a low-stage compressor 120 having a larger suction volume than the high-stage compressor 130, a motor 100 that drives the two-stage compression mechanism 110, a compressor housing 70 (rear head 70) that defines an intermediate pressure chamber 71 that houses the two-stage compression mechanism 110 and a discharge chamber 144 from which refrigerant is discharged from the two-stage compression mechanism 110, an intermediate pressure communicating passage 145 that communicates between the intermediate pressure chamber 71 and the discharge chamber 144, and an intermediate pressure relief valve 147 that allows refrigerant to flow only from the intermediate pressure communicating passage 145 to the discharge chamber 144.

[0085] Therefore, when liquefaction of refrigerant gas occurs in the refrigeration cycle inside the two-stage compression mechanism 110, causing refrigerant liquid to accumulate in the intermediate pressure chamber 71 and causing even a slight increase in pressure in the intermediate pressure chamber 71, the intermediate pressure relief valve 147 opens to quickly discharge the refrigerant liquid accumulated in the intermediate pressure chamber 71 to the discharge chamber 144. This prevents refrigerant liquid from accumulating in the intermediate pressure chamber 71, and as a result, prevents excessive pressure from being generated in the intermediate pressure chamber 71. This ensures the durability of the two-stage compression mechanism 110, prevents refrigerant leakage from the intermediate pressure chamber 71, and ensures the reliability of the electric compressor 50.

[0086] As shown in FIG. 3, the intermediate pressure relief valve 147 is a reed valve composed of a first valve seat 147a that opens and closes the intermediate pressure communicating passage 145, a first stopper 147b that regulates the opening amount of the first valve seat 147a, and a first fixing member 147c that fixes the first valve seat 147a and the first stopper 147b.

[0087] The intermediate pressure relief valve 147 is configured as a reed valve. Therefore, the intermediate pressure relief valve 147 can have a simple configuration with a small number of parts, and the valve opening amount of the intermediate pressure relief valve 147 can be easily set.

[0088] As shown in FIGS. 3 and 7 , the electric compressor 50 further includes a discharge communication passage 146 that connects the discharge passage 136 of the high-stage compressor 130 with the discharge chamber 144, and a discharge valve 148 that allows refrigerant to flow only from the discharge communication passage 146 to the discharge chamber 144. The discharge valve 148 is a reed valve that includes a second valve seat 148a that opens and closes the discharge communication passage 146, a second stopper 148b that regulates the opening amount of the second valve seat 148a, and a second fixing member 148c that fixes the second valve seat 148a and the second stopper 148b. The first valve seat 147a and the second valve seat 148a are integrally formed as a single component. The first stopper 147b and the second stopper 148b are also integrally formed as a single component. The first fixing member 147c also serves as the second fixing member 148c.

[0089] In this way, the discharge valve 148 is configured as a reed valve. Therefore, the discharge valve 148 can be configured with a small number of parts and with a simple structure, and it is easy to set the valve opening amount of the discharge valve 148. Furthermore, by sharing parts between the intermediate pressure relief valve 147 and the discharge valve 148, it is possible to reduce the number of parts of the intermediate pressure relief valve 147 and the discharge valve 148, and it is easy to assemble the valves 147, 148.

[0090] As shown in FIG. 6 , the intermediate pressure chamber 71 and the discharge chamber 144 are arranged along the center line CL1 of the rotary shaft 101 of the two-stage compression mechanism 110. The space between the intermediate pressure chamber 71 and the discharge chamber 144 is closed by a flat closure plate 143 (third closure plate 143). A radial outer peripheral surface 143c of the closure plate 143 faces the intermediate pressure chamber 71. A first end surface 143a of the closure plate 143, which is perpendicular to the center line CL1 of the rotary shaft 101, covers an end surface 134b of the two-stage compression mechanism 110 (the second surface 134b of the second cylinder 134). A second end surface 143b of the closure plate 143, which is opposite to the first end surface 143a, faces the discharge chamber 144. An intermediate pressure communicating passage 145 communicates from the outer peripheral surface 143c of the closure plate 143 to the second end surface 143b.

[0091] In this way, the closure plate 143 has its outer surface 143c facing the intermediate pressure chamber 71 and its second end surface 143b facing the discharge chamber 144, so that an intermediate pressure communication passage 145 connecting the intermediate pressure chamber 71 and the discharge chamber 144 can be easily formed.

[0092] 3 and 7, the electric compressor 50 is a horizontally-mounted electric compressor in which the rotating shaft 101 of the two-stage compression mechanism 110 can be arranged horizontally. The intermediate-pressure communicating passage 145 is located below the horizontally-oriented rotating shaft 101. The suction passages 125, 135 and the discharge passages 126, 136 of the two-stage compression mechanism 110 are located above the horizontally-oriented rotating shaft 101.

[0093] The density of refrigerant liquid is greater than the density of refrigerant gas. Therefore, refrigerant liquid accumulates below the intermediate pressure chamber 71 and the discharge chamber 144. Meanwhile, refrigerant gas accumulates above 144. By locating the intermediate pressure communicating passage 145 below the intermediate pressure chamber 71 and the discharge chamber 144, refrigerant liquid can be actively discharged from the intermediate pressure chamber 71 to the discharge chamber 144.

[0094] 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 compressor housing 70 (rear head 70) may have a configuration that separates the intermediate pressure chamber 71 and the discharge chamber 144, and is not limited to a configuration in which the second end surface 73 is open. The compressor housing 70 may also have a configuration in which the second end surface 73 is closed by a closing member such as a partition block 80. The intermediate pressure communicating passage 145 may be formed as a diagonal linear hole in the third closing plate 143 or may be formed in the rear head 70, as long as it can connect the intermediate pressure chamber 71 and the discharge chamber 144. The motor 100 may also be formed as a motor that is separate from the compressor housing 70, as long as it is capable of driving the two-stage compression mechanism 110.

[0095] The electric compressor 50 of the present invention is suitable for use in the refrigeration cycles 10 and 30 .

[0096] DESCRIPTION OF SYMBOLS 50 Electric compressor 70 Compressor housing (rear head) 71 Intermediate pressure chamber 80 Partition block 100 Motor 101 Rotating shaft (rotating shaft of two-stage compression mechanism) 110 Compression mechanism (two-stage compression mechanism) 120 Low-stage compressor 125 Intake passage of two-stage compression mechanism (first suction passage of low-stage compressor) 126 Discharge passage of two-stage compression mechanism (first discharge passage of low-stage compressor) 130 High-stage compressor 134b End face of two-stage compression mechanism (second surface of second cylinder) 135 Intake passage of two-stage compression mechanism (second suction passage of high-stage compressor) 136 Discharge passage of two-stage compression mechanism (second discharge passage of high-stage compressor) 143 Closing plate (third closing plate) 143a First end face 143b Second end face 143c Radial outer circumferential surface 144 Discharge chamber 145 Intermediate pressure communication passage 146 Discharge communication passage 147 Intermediate pressure relief valve 147a First valve seat 147b First stopper 147c First fixing member 148 Discharge valve 148a Second valve seat 148b Second stopper 148c Second fixing member CL1 Center line

Claims

1. A two-stage compression mechanism (110) having a high-stage compressor (130) and a low-stage compressor (120) with a larger suction volume than the high-stage compressor (130); a motor (100) for driving the two-stage compression mechanism (110); an intermediate pressure chamber (71) for housing the two-stage compression mechanism (110); a compressor housing (70) defining a discharge chamber (144) from which refrigerant is discharged from the two-stage compression mechanism (110); an intermediate pressure communication passage (145) communicating the intermediate pressure chamber (71) and the discharge chamber (144); and an intermediate pressure relief valve (147) that allows only the flow of refrigerant from the intermediate pressure communication passage (145) to the discharge chamber (144), characterized in that it is an electric compressor (50).

2. The electric compressor according to claim 1, wherein the intermediate pressure relief valve (147) is a reed valve constituted by a first valve seat (147a) that opens and closes the intermediate pressure communication passage (145), a first stopper (147b) that regulates the opening amount of the first valve seat (147a), and a first fixing member (147c) that fixes the first valve seat (147a) and the first stopper (147b).

3. Further provided with a discharge communication passage (146) that communicates the discharge passage (136) of the high-stage compressor (130) and the discharge chamber (144), and a discharge valve (148) that allows only the flow of refrigerant from the discharge communication passage (146) to the discharge chamber (144), wherein the discharge valve (148) is a reed valve constituted by a second valve seat (148a) that opens and closes the discharge communication passage (146), a second stopper (148b) that regulates the opening amount of the second valve seat (148a), and a second fixing member (148c) that fixes the second valve seat (148a) and the second stopper (148b), the first valve seat (147a) and the second valve seat (148a) are a single integrated part, the first stopper (147b) and the second stopper (148b) are a single integrated part, and the first fixing member (147c) also serves as the second fixing member (148c), the electric compressor according to claim 2.

4. The intermediate pressure chamber (71) and the discharge chamber (144) are arranged along the center line (CL1) of the rotating shaft (101) of the two-stage compression mechanism (110). Between the intermediate pressure chamber (71) and the discharge chamber (144), it is closed by a flat closing plate (143). The radially outer peripheral surface (143c) of the closing plate (143) faces the intermediate pressure chamber (71). Among the closing plate (143), the first end surface (143a) perpendicular to the center line (CL1) covers the end surface (134b) of the two-stage compression mechanism (110). Among the closing plate (143), the second end surface (143b) on the side opposite to the first end surface (143a) faces the discharge chamber (144). The intermediate pressure communication passage (145) communicates from the outer peripheral surface (143c) of the closing plate (143) to the second end surface (143b). The electric compressor according to claim 1.

5. The electric compressor (50) according to claim 1 is a horizontally placed electric compressor capable of arranging the rotating shaft (101) of the two-stage compression mechanism (110) horizontally. The intermediate pressure communication passage (145) is located below the horizontally placed rotating shaft (101). The suction passages (125, 135) and the discharge passages (126, 136) of the two-stage compression mechanism (110) are located above the horizontally placed rotating shaft (101). The electric compressor according to claim 1.

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