Refrigerant circuit

Abstract

To provide a refrigerant circuit which can inhibit damage of a bearing supporting a rotary shaft of a compressor.SOLUTION: A refrigerant circuit includes: a compressor which has a gas dynamic pressure bearing rotatably supporting a rotary shaft and compresses a refrigerant; a condenser which condenses the refrigerant compressed by the compressor; an expansion valve which decompresses the refrigerant condensed by the condenser; an evaporator which evaporates the refrigerant decompressed by the expansion valve; a suction pipe in which the refrigerant suctioned into the compressor flows; and a liquid refrigerant flow adjustment part 76 which adjusts a flow rate of a liquid refrigerant so as to increase the flow rate of the liquid refrigerant supplied to the suction pipe as a temperature of the refrigerant decreases.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a refrigerant circuit. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2004-44954 (Patent Document 1) discloses a refrigerator that includes a compressor in which a compressor shaft to which an impeller is directly connected and which is driven by a drive source is supported by a gas bearing, and in which a portion of the gas refrigerant pressurized by the compressor is guided to the gas bearing of the compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-44954 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a compressor equipped with gas bearings in which the bearings are lubricated with a gas refrigerant, if the temperature of the suction refrigerant is low, the load capacity of the gas bearings decreases due to the low density and viscosity of the refrigerant, and the shaft cannot be lifted, which may result in damage to the bearings.

[0005] The present disclosure proposes a refrigerant circuit that can suppress damage to a bearing that supports a rotating shaft of a compressor. [Means for solving the problem]

[0006] According to the present disclosure, there is proposed a refrigerant circuit comprising: a compressor having a rotating shaft and a gas dynamic bearing rotatably supporting the rotating shaft, which compresses a refrigerant; a condenser which condenses the refrigerant compressed by the compressor; an expansion valve which reduces the pressure of the refrigerant condensed by the condenser; an evaporator which evaporates the refrigerant reduced in pressure by the expansion valve; a suction piping through which the refrigerant sucked into the compressor flows; and a liquid refrigerant flow rate adjustment unit which adjusts the flow rate of the liquid refrigerant so as to increase the flow rate of the liquid refrigerant supplied to the suction piping as the temperature of the refrigerant decreases.

[0007] In this refrigerant circuit, the flow rate of liquid refrigerant supplied to the suction pipe is increased as the refrigerant temperature drops, decreasing the dryness of the refrigerant drawn into the compressor. The refrigerant drawn into the compressor becomes wet, increasing its density and viscosity, which increases the load capacity of the bearings supporting the compressor's rotating shaft. This makes it easier for the rotating shaft to float, thereby preventing damage to the bearings.

[0008] The refrigerant circuit may further include a gas-liquid separator that separates a liquid refrigerant from a gas refrigerant, and the liquid refrigerant flow rate adjustment unit may adjust the amount of liquid refrigerant flowing out from the gas-liquid separator. The gas-liquid separator may be provided in a refrigerant path between the evaporator and the compressor.

[0009] In the above refrigerant circuit, the liquid refrigerant flow rate adjuster may include a displacement member that autonomously changes its position in accordance with a change in temperature of the liquid refrigerant.

[0010] The refrigerant circuit may further include a sensor for detecting a temperature of the refrigerant flowing through the suction pipe. The liquid refrigerant flow rate regulator may include a valve. The refrigerant circuit may further include a controller for controlling an opening degree of the valve in accordance with a detection result of the sensor. Effect of the Invention

[0011] According to the refrigerant circuit according to the present disclosure, damage to the bearings that support the rotating shaft of the compressor can be suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a side cross-sectional view of a compressor that constitutes a refrigerant circuit. [Diagram 2] FIG. 2 is a schematic diagram showing a schematic configuration of a refrigerant circuit. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing an internal configuration of an accumulator. [Figure 4] FIG. 2 is a diagram showing a schematic configuration of an example of a liquid refrigerant flow rate adjusting unit. [Diagram 5] FIG. 13 is a diagram showing the state in which the height of the expansion / contraction section is lowered. [Figure 6] 8 is a diagram showing a schematic configuration of a liquid refrigerant flow rate adjusting section of a second embodiment. FIG. [Figure 7] 11A and 11B are diagrams illustrating a state in which the warping direction of the bimetal has changed. [Figure 8] FIG. 11 is a schematic diagram showing a schematic configuration of a refrigerant circuit according to a third embodiment. [Figure 9] 4 is a flowchart showing a process for controlling the opening degree of a valve. [Figure 10] FIG. 13 is a diagram showing a schematic configuration of a valve according to a fourth embodiment. [Figure 11] FIG. 13 is a diagram showing a schematic configuration of a valve according to a fifth embodiment. [Figure 12] FIG. 13 is a diagram showing a state in which the valve of the fifth embodiment increases the opening area of ​​the liquid return hole. [Figure 13] FIG. 13 is a diagram showing a schematic configuration of a valve according to a sixth embodiment. [Figure 14] FIG. 13 is a diagram showing a state in which the valve of the sixth embodiment increases the opening area of ​​the liquid return hole. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. It is also intended from the beginning that any configuration may be extracted from the embodiments and that they may be combined in any desired manner.

[0014] [First embodiment] Fig. 1 is a side cross-sectional view of a compressor 1 that constitutes a refrigerant circuit. The fluid to be compressed by the compressor 1 shown in Fig. 1 is a refrigerant that circulates through the refrigerant circuit.

[0015] As shown in Fig. 1, the compressor 1 includes a cylindrical housing 10. The housing 10 is made of a metal material, for example, aluminum. The housing 10 includes a rear housing 11, a motor housing 12, a first compressor housing 13, a second compressor housing 14, a partition wall 15, a first intermediate housing 16, and a second intermediate housing 17.

[0016] The motor housing 12 is a cylindrical member with a bottom, and includes a plate-like end wall portion 12a and a peripheral wall portion 12b extending cylindrically from the outer periphery of the end wall portion 12a. The second intermediate housing 17 is connected to the motor housing 12 so as to cover the opening of the motor housing 12. A motor chamber 18 is defined by the end wall portion 12a, the peripheral wall portion 12b, and the second intermediate housing 17 of the motor housing 12. A suction hole (not shown) is formed in the motor housing 12 to draw in the refrigerant. The suction hole is connected to the motor chamber 18. Therefore, the refrigerant is drawn into the motor chamber 18 through the suction hole.

[0017] A circular shaft insertion hole 17a is formed in the center of the second intermediate housing 17. The second intermediate housing 17 has a cylindrical first bearing retaining portion 19 on its inner circumferential surface. The inside of the first bearing retaining portion 19 communicates with the shaft insertion hole 17a. A first radial bearing 20 is retained in the first bearing retaining portion 19.

[0018] The end wall portion 12a of the motor housing 12 has a cylindrical second bearing retaining portion 21. The second bearing retaining portion 21 is formed in the center of the end wall portion 12a. A second radial bearing 22 is retained in the second bearing retaining portion 21.

[0019] A first chamber forming recess 17b is formed on the outer surface of the second intermediate housing 17 opposite the motor chamber 18. The first chamber forming recess 17b communicates with the shaft insertion hole 17a. The second intermediate housing 17 has a plurality of communication holes 23. Each communication hole 23 is located near the outer periphery of the second intermediate housing 17.

[0020] The first intermediate housing 16 is connected to the second intermediate housing 17 so as to cover the opening of the first chamber forming recess 17b. A thrust bearing accommodating chamber 25 is defined by the first intermediate housing 16 and the first chamber forming recess 17b of the second intermediate housing 17. Each communication hole 23 communicates between the motor chamber 18 and the thrust bearing accommodating chamber 25. A circular shaft insertion hole 16a is formed in the center of the first intermediate housing 16.

[0021] The first intermediate housing 16 has a plurality of communication holes 16b. Each communication hole 16b is located toward the outer periphery of the first intermediate housing 16. A second chamber forming recess 16c is formed on the outer surface of the first intermediate housing 16 opposite the thrust bearing accommodating chamber 25. The second chamber forming recess 16c communicates with the shaft insertion hole 16a. Each communication hole 16b communicates between the thrust bearing accommodating chamber 25 and the internal space of the second chamber forming recess 16c.

[0022] The first compressor housing 13 is cylindrical and has a circular hole-shaped first suction port 24 in the center. The first compressor housing 13 is connected to the first intermediate housing 16 so as to cover the opening of the second chamber forming recess 16c. The first suction port 24 communicates with the second chamber forming recess 16c.

[0023] The partition wall 15 is connected to an end face of the first compressor housing 13 opposite to the first intermediate housing 16. The partition wall 15 is plate-shaped. A through hole penetrating the partition wall 15 in the thickness direction is formed in the center of the partition wall 15. The central axis of the through hole coincides with the central axis of the first suction port 24.

[0024] Between the partition wall 15 and the first compressor housing 13, there are formed a first impeller chamber that communicates with the first suction port 24 and accommodates a first impeller 51, a first discharge chamber 29 that extends circumferentially radially outside the first impeller chamber, and a first diffuser passage 30 that communicates between the first impeller chamber and the first discharge chamber 29.

[0025] The second compressor housing 14 is connected to an end face of the partition wall 15 opposite to the first compressor housing 13. An intermediate pressure chamber 31 is formed across the first compressor housing 13, the partition wall 15, and the second compressor housing 14. The intermediate pressure chamber 31 communicates with the first discharge chamber 29 via a passage (not shown). The second compressor housing 14 is formed with a circular hole-shaped second suction port 32 communicating with the intermediate pressure chamber 31. The first discharge chamber 29 and the second suction port 32 communicate with each other via the intermediate pressure chamber 31.

[0026] Between the partition wall 15 and the second compressor housing 14, there are formed a second impeller chamber that communicates with the second intake port 32 and accommodates the second impeller 52, a second discharge chamber 34 that extends circumferentially radially outside the second impeller chamber, and a second diffuser passage 35 that communicates between the second impeller chamber and the second discharge chamber 34.

[0027] The rear housing 11 is connected to the second compressor housing 14. The rear housing 11 defines an intermediate pressure chamber 31. The rear housing 11 is plate-shaped.

[0028] The compressor 1 includes a rotating shaft 40. The rotating shaft 40 is accommodated in the housing 10. The rotating shaft 40 extends in the axial direction of the housing 10, passing through the motor chamber 18, the inside of the first bearing retaining portion 19, the shaft insertion hole 17a, the thrust bearing accommodating chamber 25, the shaft insertion hole 16a, the first suction port 24, the first impeller chamber, the second impeller chamber, and the second suction port 32 in this order from the inside of the second bearing retaining portion 21. A first end 40a, which is one end of the rotating shaft 40, is disposed in the second compressor housing 14. A second end 40b, which is the other end of the rotating shaft 40, is disposed in the end wall portion 12a of the motor housing 12.

[0029] The axis L of the rotating shaft 40 coincides with the central axis of each of the first bearing holder 19, the second bearing holder 21, the shaft insertion hole 17a, the shaft insertion hole 16a, the first suction port 24, and the second suction port 32. In the following description, the direction in which the axis L of the rotating shaft 40 extends is referred to as the thrust direction, and the radial direction of the rotating shaft 40 is referred to as the radial direction.

[0030] The first radial bearing 20 and the second radial bearing 22 support the rotating shaft 40 rotatably in the radial direction. The radial bearings 20, 22 are gas dynamic pressure bearings that support the rotating shaft 40 by the dynamic pressure of a gas (gas refrigerant) generated as the rotating shaft 40 rotates. The radial bearings 20, 22 support the radial load of the rotating shaft 40 in a non-contact manner.

[0031] The compressor 1 includes a disk-shaped support plate 65 that protrudes radially outward from the outer circumferential surface of the rotating shaft 40. The support plate 65 rotates integrally with the rotating shaft 40. The support plate 65 is disposed in the thrust bearing accommodating chamber 25.

[0032] A thrust bearing 66 is disposed between the first intermediate housing 16 and the support plate 65, and between the second intermediate housing 17 and the support plate 65. Both thrust bearings 66 support the rotating shaft 40 rotatably in the thrust direction. Both thrust bearings 66 are gas dynamic pressure bearings that support the rotating shaft 40 by the dynamic pressure of a gas (gas refrigerant) generated as the rotating shaft 40 rotates. Both thrust bearings 66 support the thrust load of the rotating shaft 40 in a non-contact manner.

[0033] The compressor 1 includes an electric motor 41. The electric motor 41 is accommodated in the motor chamber 18. The electric motor 41 is an example of a drive source that drives the rotary shaft 40 to rotate. The electric motor 41 includes a stator 42 and a rotor 43.

[0034] The stator 42 has a cylindrical stator core 44 and a coil 45 wound around the stator core 44. The stator core 44 is fixed to the inner circumferential surface of the peripheral wall portion 12b of the motor housing 12.

[0035] The rotor 43 is disposed radially inside the stator core 44. The rotor 43 has a rotor core 43a fixed to the rotating shaft 40 and a plurality of permanent magnets (not shown) provided on the rotor core 43a. The rotor 43 of the electric motor 41 rotates when electric power controlled by an inverter device (not shown) is supplied to the coil 45. The rotating shaft 40 rotates integrally with the rotor 43.

[0036] The first impeller 51 and the second impeller 52 are connected to the rotating shaft 40 and rotate integrally with the rotating shaft 40. The electric motor 41, the first impeller 51, and the second impeller 52 are arranged in this order in the axial direction of the rotating shaft 40 from the second end 40b to the first end 40a. The first impeller 51 is made of aluminum, for example. The second impeller 52 is made of resin, for example.

[0037] The first impeller 51 has a generally truncated cone shape with an outer circumferential surface that expands in diameter from the tip surface located on the first suction port 24 side toward the back surface. The back surface of the first impeller 51 faces the partition wall 15 in the axial direction of the rotary shaft 40. The first impeller 51 has a plurality of blades on the outer circumferential surface. The second impeller 52 has a generally truncated cone shape with an outer circumferential surface that expands in diameter from the tip surface located on the second suction port 32 side toward the back surface. The back surface of the second impeller 52 faces the partition wall 15 in the axial direction of the rotary shaft 40. The second impeller 52 has a plurality of blades on the outer circumferential surface.

[0038] The electric motor 41 drives and rotates a rotor including the rotary shaft 40, the first impeller 51, and the second impeller 52, and rotates the rotors integrally about the axis line L. The first impeller 51 compresses the refrigerant by rotating. The second impeller 52 compresses the refrigerant compressed by the first impeller 51 by rotating. The first impeller 51 is disposed on the upstream side in the flow direction of the refrigerant, and the second impeller 52 is disposed on the downstream side.

[0039] The first impeller 51 and the second impeller 52 are provided on the rotating shaft 40 such that the back surface of the first impeller 51 and the back surface of the second impeller 52 face each other via the partition wall 15. A hollow cylindrical spacer 54 is disposed between the first impeller 51 and the second impeller 52. The spacer 54 has a first end facing the back surface of the first impeller 51 and a second end facing the back surface of the second impeller 52.

[0040] A hollow cylindrical fitting member 55 is attached to the outer circumferential surface of the rotating shaft 40 at the first end 40a of the rotating shaft 40. The fitting member 55 is attached to the rotating shaft 40 by, for example, a screw action. The fitting member 55 abuts against the tip surface of the second impeller 52. The fitting member 55 supports the second impeller 52 in the axial direction of the rotating shaft 40.

[0041] FIG. 2 is a schematic diagram showing a schematic configuration of a refrigerant circuit. The refrigerant circuit of the present disclosure is used, for example, to adjust the temperature of a battery. The refrigerant circuit is filled with refrigerant. The refrigerant circulates within the refrigerant circuit. The refrigerant circuit includes the compressor 1, condenser 2, expansion valve 3, evaporator 4, and accumulator 7 described with reference to FIG. 1, and refrigerant piping connecting these devices. The suction piping 5 is a piping through which the refrigerant suctioned into the compressor 1 flows, and constitutes a part of the refrigerant piping.

[0042] The compressor 1 compresses a low-temperature, low-pressure gas refrigerant and discharges a high-temperature, high-pressure gas refrigerant. The condenser 2 condenses the gas refrigerant compressed by the compressor 1. The expansion valve 3 reduces the pressure of the high-temperature, high-pressure liquid refrigerant condensed and liquefied in the condenser 2 to produce a low-temperature, low-pressure two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant flows in the evaporator 4. Therefore, the depressurized liquid refrigerant flows in the evaporator 4. The evaporator 4 evaporates the liquid refrigerant depressurized by the expansion valve 3.

[0043] The accumulator 7 is provided in the refrigerant path between the evaporator 4 and the compressor 1. The accumulator 7 is provided on the outlet side (downstream side in the refrigerant flow direction) of the evaporator 4, and on the suction side (upstream side in the refrigerant flow direction) of the compressor 1. The accumulator 7 separates the refrigerant supplied to the accumulator 7 into liquid refrigerant that did not evaporate in the evaporator 4 and gas refrigerant. The accumulator 7 functions as a "gas-liquid separator." The accumulator 7 stores the liquid refrigerant inside. The accumulator 7 has the role of preventing the inflow of liquid refrigerant into the compressor 1, preventing liquid compression, and protecting the compressor 1.

[0044] 3 is a cross-sectional schematic diagram showing the internal configuration of the accumulator 7. The accumulator 7 has a case 71 that constitutes a main body. A liquid refrigerant LR is stored in the lower part of the internal space of the case 71. A gas refrigerant GR is accommodated in the upper part of the internal space of the case 71.

[0045] The refrigerant flows into case 71 of accumulator 7 through inflow pipe 72. Inflow pipe 72 penetrates a ceiling surface of case 71 and is connected to case 71. An open end of inflow pipe 72 in case 71 is disposed at an upper portion of case 71, at a position where gas refrigerant GR is present.

[0046] The outflow pipe 73 penetrates the ceiling surface of the case 71 and is connected to the case 71. An open end of the outflow pipe 73 in the case 71 is arranged at an upper portion of the case 71, at a position where the gas refrigerant GR is present. The open end of the outflow pipe 73 may be arranged lower than the open end of the inflow pipe 72 as shown in FIG. 3, or may be arranged at the same height as or higher than the open end of the inflow pipe 72. The outflow pipe 73 communicates with the suction piping 5 shown in FIG. 2. The gas refrigerant GR flows out of the case 71 of the accumulator 7 via the outflow pipe 73. The gas refrigerant GR flowing out of the case 71 is sucked into the compressor 1 via the suction piping 5.

[0047] A baffle member 74 is disposed at an upper portion of the case 71 at a position where the gas refrigerant GR is present. The baffle member 74 may be interposed between an open end of the inlet pipe 72 and an open end of the outlet pipe 73. The baffle member 74 promotes separation of the refrigerant flowing from the inlet pipe 72 into the case 71 into a liquid refrigerant LR and a gas refrigerant GR. The baffle member 74 prevents the liquid refrigerant from flowing into the outlet pipe 73 from the open end of the outlet pipe 73. The baffle member 74 may be attached to the case 71, in which case the baffle member 74 may have a function of supporting the outlet pipe 73.

[0048] The outflow pipe 73 has a U-shaped pipe shape in the case 71. The bent portion of the U-shape forms the lowest portion of the outflow pipe 73 and is disposed in the liquid refrigerant LR at the lower portion of the case 71. A liquid return hole 75 is formed in the bent portion of the outflow pipe 73. The liquid return hole 75 is disposed at a position where it is always immersed in the liquid refrigerant LR. The liquid return hole 75 may be formed on the side surface of the bent portion of the outflow pipe 73. The liquid return hole 75 extends from the outer surface of the outflow pipe 73 until it communicates with the pipe in the outflow pipe 73. The liquid refrigerant LR in the accumulator 7 enters the outflow pipe 73 through the liquid return hole 75 and flows toward the compressor 1 together with the gas refrigerant GR flowing into the outflow pipe 73 from the open end of the outflow pipe 73.

[0049] The refrigerant circuit includes a liquid refrigerant flow rate adjustment unit 76. Fig. 4 is a diagram showing a schematic configuration of one example of the liquid refrigerant flow rate adjustment unit 76. The liquid refrigerant flow rate adjustment unit 76 is disposed inside the accumulator 7. The liquid refrigerant flow rate adjustment unit 76 can adjust the flow rate of the liquid refrigerant LR stored in the lower part of the case 71 of the accumulator 7 flowing out from the accumulator 7. The liquid refrigerant flow rate adjustment unit 76 can adjust the flow rate of the liquid refrigerant LR flowing into the outflow pipe 73. The liquid refrigerant flow rate adjustment unit 76 can adjust the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 via the outflow pipe 73.

[0050] The liquid refrigerant flow rate adjusting unit 76 of this embodiment has an expandable portion 77 and a valve body 78. The expandable portion 77 is disposed in the liquid refrigerant LR. The expandable portion 77 is disposed in a position where it is always immersed in the liquid refrigerant LR. The expandable portion 77 is attached to the inner surface of the case 71. The expandable portion 77 may be attached to the side wall surface or floor surface of the case 71, for example. The height H1 shown in FIG. 4 is the height at which the expandable portion 77 protrudes from the case 71. The expandable portion 77 has a base end attached to the case 71 and a tip end which is the end opposite to the base end. The height H1 is the length from the inner surface of the case 71 to the tip of the expandable portion 77. The expandable portion 77 may be attached to the inner surface of the case 71 via another member, or may be attached to a member other than the case 71.

[0051] The valve body 78 has a conical shape. The valve body 78 is attached to the tip of the expandable portion 77. The valve body 78 shown in Fig. 4 has a bottom surface attached to the tip of the expandable portion 77, and the tip portion is inserted into the liquid return hole 75. In the state shown in Fig. 4, the valve body 78 reduces the opening area of ​​the liquid return hole 75. Therefore, the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return hole 75 is reduced.

[0052] The expandable portion 77 expands and contracts in accordance with the change in temperature of the liquid refrigerant LR, changing its length in the vertical direction in Figs. 4 and 5. The expandable portion 77 may be, for example, a solid body made of a material with a high thermal expansion coefficient, and in this case, the expandable portion 77 may have a heat transfer portion on its outer circumferential surface that promotes heat transfer between the liquid refrigerant LR and the expandable portion 77, such as a fin that increases the surface area. The expandable portion 77 may be a thermoelement that converts the temperature of the liquid refrigerant LR into the amount of movement of the piston. The thermoelement may change its height by the thermal expansion of the wax contained therein. The expandable portion 77 may be an internal vacuum bellows that has a thin-walled hollow cylindrical shape with a bellows structure and has a vacuum inside.

[0053] FIG. 5 is a diagram showing a state in which the height of the expandable portion 77 has been reduced. In FIG. 5, the temperature of the liquid refrigerant LR is lower than in FIG. 4. The expandable portion 77 contracts as the temperature of the liquid refrigerant LR decreases. The expandable portion 77 shown in FIG. 5 has a height H2. The height H2 of the expandable portion 77 is smaller than the height H1 shown in FIG. 4. As the height of the expandable portion 77 is reduced, the position of the valve body 78 attached to the tip of the expandable portion 77 changes. The valve body 78 corresponds to an example of a "displacement member" that autonomously changes its position in accordance with the change in temperature of the liquid refrigerant LR.

[0054] In Fig. 5, the valve body 78 has moved closer to the inner surface of the case 71. The valve body 78 is entirely disposed outside the liquid return hole 75. Compared to Fig. 4, the opening area of ​​the liquid return hole 75 has increased. The flow of the liquid refrigerant LR is no longer impeded by the valve body 78, and the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return hole 75 has increased. The flow rate of the liquid refrigerant LR flowing out of the accumulator 7 has increased.

[0055] As a result of a larger amount of the liquid refrigerant LR flowing into the outflow pipe 73, the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 increases. As a result, the dryness fraction of the refrigerant sucked into the compressor 1 decreases. The refrigerant sucked into the compressor 1 becomes wet, and the density and viscosity of the refrigerant increase.

[0056] The radial bearings 20, 22 and thrust bearing 66 of the compressor 1 described with reference to Fig. 1 are gas dynamic pressure bearings that support the rotating shaft 40 by the dynamic pressure of the refrigerant drawn into the housing 10. Increasing the density and viscosity of the refrigerant increases the load capacity of the radial bearings 20, 22 and thrust bearing 66. This makes it easier for the rotating shaft 40 to float, thereby making it possible to suppress damage to the radial bearings 20, 22 and thrust bearing 66.

[0057] Since the liquid refrigerant flow rate adjustment unit 76 is configured to adjust the flow rate of the liquid refrigerant LR in a temperature autonomous manner without including any electrical components, the flow rate adjustment function of the liquid refrigerant LR is not impaired due to failure of the electrical components, and reliability can be improved.

[0058] [Second embodiment] 6 is a diagram showing a schematic configuration of a liquid refrigerant flow rate adjusting section 76 of the second embodiment. The liquid refrigerant flow rate adjusting section 76 of the second embodiment has a bimetal 79 instead of the expansion and contraction section 77 described in the first embodiment. The bimetal 79 is a metal bonded plate in which two types of metal plates with different thermal expansion coefficients are bonded together, and warps and deforms in response to temperature changes. The valve body 78 has a conical shape and is attached to the bimetal 79. The bimetal 79 is disposed in the liquid refrigerant LR.

[0059] 6 is warped upwardly. At this time, the tip of the valve body 78 is inserted into the liquid return hole 75, and the valve body 78 reduces the opening area of ​​the liquid return hole 75, so that the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return hole 75 is reduced.

[0060] Fig. 7 is a diagram showing a state in which the warping direction of the bimetal 79 has changed. In Fig. 7, the temperature of the liquid refrigerant LR is lower than in Fig. 6. The bimetal 79 changes the amount of warping as the temperature of the liquid refrigerant LR decreases. The bimetal 79 shown in Fig. 7 has changed its warping direction and is warped downward convexly.

[0061] The position of the valve element 78 changes due to the deformation of the bimetal 79. The valve element 78 autonomously changes its position in response to changes in the temperature of the liquid refrigerant LR. The valve element 78 is entirely disposed outside the liquid return hole 75. Compared to FIG. 6, the opening area of ​​the liquid return hole 75 is increased. This increases the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return hole 75.

[0062] Since a larger amount of liquid refrigerant LR flows into the outflow pipe 73 and the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 increases, the dryness fraction of the refrigerant drawn into the compressor 1 decreases. The refrigerant drawn into the compressor 1 becomes wet, and the density and viscosity of the refrigerant increase. The increased density and viscosity of the refrigerant increase the load capacity of the radial bearings 20, 22 and the thrust bearing 66 of the compressor 1. This makes it easier for the rotating shaft 40 of the compressor 1 to float, thereby suppressing damage to the radial bearings 20, 22 and the thrust bearing 66.

[0063] [Third embodiment] 8 is a schematic diagram showing a schematic configuration of a refrigerant circuit of the third embodiment. The refrigerant circuit of the third embodiment further includes a controller 80, a liquid return pipe 81, a temperature sensor 82, and a valve 83.

[0064] The controller 80 includes a CPU (Central Processing Unit) and executes a computer program that controls the refrigerant circuit.

[0065] The liquid return pipe 81 has one end connected to the accumulator 7 and the other end connected to the suction pipe 5. One end of the liquid return pipe 81 is connected, for example, to the bottom surface of the accumulator 7. The liquid refrigerant LR stored in the lower part of the case 71 of the accumulator 7 is supplied to the suction pipe 5 via the liquid return pipe 81.

[0066] The temperature sensor 82 is provided in the suction piping 5 and detects the temperature of the refrigerant flowing through the suction piping 5. The temperature sensor 82 is disposed downstream in the refrigerant flow direction from the junction where the suction piping 5 and the liquid return piping 81 join. The temperature sensor 82 is disposed at a position closer to the compressor 1 than the junction of the suction piping 5 and the liquid return piping 81. The temperature sensor 82 detects the temperature of the refrigerant after the refrigerant flowing into the outflow pipe 73 and flowing out of the accumulator 7 and the liquid refrigerant LR flowing through the liquid return piping 81 join together. The temperature sensor 82 detects the temperature of the refrigerant sucked into the compressor 1.

[0067] The temperature sensor 82 outputs a detection signal SN1 indicative of the detection result of the refrigerant temperature. The detection signal SN1 is input to the controller 80.

[0068] The valve 83 is provided in the liquid return piping 81. The controller 80 sends a control signal SN2 to the valve 83. The controller 80 controls the opening of the valve 83 in accordance with the detection result of the temperature sensor 82. By adjusting the opening of the valve 83, the flow rate of liquid refrigerant LR flowing through the liquid return piping 81 is adjusted. The valve 83 is capable of adjusting the flow rate of liquid refrigerant LR supplied to the suction piping 5 via the liquid return piping 81. The valve 83 has a function as the liquid refrigerant flow rate adjustment unit 76. The liquid refrigerant flow rate adjustment unit 76 of the third embodiment is capable of adjusting the flow rate of liquid refrigerant LR supplied to the suction piping 5 by external control.

[0069] The valve 83 may be an ON / OFF valve that can switch the valve opening between two stages, full open and full closed. The valve 83 may be, for example, a solenoid valve. In this case, as shown in FIG. 3, the outflow pipe 73 of the accumulator 7 may be formed with a liquid return hole 75 at a position where the outflow pipe 73 is always immersed in the liquid refrigerant LR, and a certain amount of liquid refrigerant LR flows into the outflow pipe 73 from the liquid return hole 75. By fully closing the valve 83, only the flow of liquid refrigerant LR via the liquid return hole 75 is formed. By fully opening the valve 83, two flows of liquid refrigerant LR are formed, namely, the flow of liquid refrigerant LR via the liquid return hole 75 and the flow of liquid refrigerant LR via the liquid return pipe 81. By opening and closing the valve 83, the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 can be adjusted in two stages.

[0070] The valve 83 may be a control valve capable of continuously changing the valve opening. The valve 83 may have an actuator, such as an electric, pneumatic, or hydraulic actuator, and a valve body driven by the actuator. By adjusting the opening of the valve 83, it is possible to adjust the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 via the liquid return pipe 81. In this case, the outflow pipe 73 of the accumulator 7 may or may not have a liquid return hole 75 formed therein.

[0071] Fig. 9 is a flowchart showing a process flow for controlling the opening degree of the valve 83. As shown in Fig. 9, in step S1, the temperature sensor 82 detects the temperature of the refrigerant flowing through the suction piping 5. A detection signal SN1 indicating the detection result of the refrigerant temperature is input from the temperature sensor 82 to the controller 80.

[0072] In step S2, the controller 80 determines whether the temperature of the refrigerant is low. The controller 80 reads out a temperature threshold value stored in the storage device. The controller 80 compares the temperature of the refrigerant detected in step S1 with the threshold value. The controller 80 determines whether the detected temperature of the refrigerant is lower than the threshold value.

[0073] If it is determined that the refrigerant temperature is low (YES in step S2), then in step S3, the controller 80 transmits a control signal SN2 to the valve 83 to command the valve 83 to set the opening degree of the valve 83 to a low-temperature opening degree. Upon receiving the control signal SN2, the valve 83 increases the opening degree as the temperature of the liquid refrigerant LR decreases, thereby increasing the amount of liquid refrigerant LR in the accumulator 7 flowing into the liquid return pipe 81. The flow rate of the liquid refrigerant LR supplied to the suction pipe 5 via the liquid return pipe 81 increases. As a result, the dryness fraction of the refrigerant sucked into the compressor 1 decreases.

[0074] The refrigerant sucked into the compressor 1 becomes wet, and the density and viscosity of the refrigerant increase. The increased density and viscosity of the refrigerant increase the load capacity of the radial bearings 20, 22 and the thrust bearing 66 of the compressor 1. This makes it easier for the rotating shaft 40 of the compressor 1 to float, and therefore damage to the radial bearings 20, 22 and the thrust bearing 66 can be suppressed.

[0075] The liquid return pipe 81 is connected to the suction pipe 5 instead of the compressor 1, and the liquid refrigerant LR flowing via the liquid return pipe 81 is returned to the suction pipe 5 instead of the compressor 1. This allows the structure of the compressor 1 to be simplified, and the compressor 1 to be made smaller in size.

[0076] If it is determined that the temperature of the refrigerant flowing through the suction piping 5 is not low (NO in the determination in step S2), the process proceeds to step S4, where the controller 80 determines whether the temperature of the refrigerant is high. The controller 80 reads out a temperature threshold value stored in the storage device. The controller 80 compares the temperature of the refrigerant detected in step S1 with the threshold value. The controller 80 determines whether the detected temperature of the refrigerant is higher than the threshold value. The temperature threshold value used in the determination in step S4 may be a higher temperature than the temperature threshold value used in the determination in step S2.

[0077] If it is determined that the refrigerant temperature is high (YES in step S4), then in step S5, the controller 80 sends a control signal SN2 to the valve 83 to instruct it to set the opening of the valve 83 to a high temperature opening. Upon receiving the control signal SN2, the valve 83 decreases the opening as the temperature of the liquid refrigerant LR increases, thereby reducing the amount of liquid refrigerant LR in the accumulator 7 flowing into the liquid return pipe 81. The flow rate of liquid refrigerant LR supplied to the suction pipe 5 via the liquid return pipe 81 decreases.

[0078] When the temperature of the refrigerant is high, the radial bearings 20, 22 and the thrust bearing 66 of the compressor 1 have sufficient load capacity, so that it is not necessary to perform a process to increase the density and viscosity of the refrigerant. At this time, the efficiency of the refrigerant circuit can be improved by reducing the liquid refrigerant LR supplied to the suction pipe 5.

[0079] If the judgment in step S4 is NO and the refrigerant temperature is between the threshold value in the judgment in step S2 and the threshold value in the judgment in step S4, the process of changing the opening degree of valve 83 is not performed and the process ends as it is ("End" in Figure 9).

[0080] [Fourth embodiment] 10 is a diagram showing a schematic configuration of a valve 83 of the fourth embodiment. In the third embodiment, an example has been described in which the flow rate of the liquid refrigerant LR flowing through the liquid return piping 81 is increased or decreased. In order to adjust the flow rate of the liquid refrigerant LR supplied to the suction piping 5 by external control, the liquid return piping 81 does not necessarily have to be provided.

[0081] The outflow pipe 73 shown in Fig. 10 is formed with a liquid return hole 75. The valve 83 has a valve body 84 and an actuator 85. The valve body 84 is disposed within the case 71 of the accumulator 7. The valve body 84 is disposed in the liquid refrigerant LR at the bottom of the case 71. The valve body 84 is disposed in a position where it is constantly immersed in the liquid refrigerant LR. As shown in Fig. 10, the valve body 84 may have a needle-like shape.

[0082] The actuator 85 generates a driving force for driving the valve body 84. The actuator 85 may be disposed inside the case 71 of the accumulator 7, or may be disposed outside the case 71. A power transmission member for transmitting the driving force generated by the actuator 85 to the valve body 84 may be disposed penetrating the case 71.

[0083] The controller 80 controls the opening of the valve 83 according to the temperature of the refrigerant flowing through the suction pipe 5 detected by the temperature sensor 82. The actuator 85 drives the valve element 84 according to a control signal SN2 that controls the opening of the valve 83 and is sent from the controller 80. As the valve element 84 moves upward in Fig. 10, the opening area of ​​the liquid return hole 75 decreases, and the flow rate of the liquid refrigerant LR passing through the liquid return hole 75 and entering the outflow pipe 73 decreases. As the valve element 84 moves downward in Fig. 10, the opening area of ​​the liquid return hole 75 increases, and the flow rate of the liquid refrigerant LR passing through the liquid return hole 75 and entering the outflow pipe 73 increases.

[0084] 9, the controller 80 increases the opening of the valve 83 as the temperature of the refrigerant flowing through the suction pipe 5 detected by the temperature sensor 82 decreases. Specifically, the controller 80 drives the actuator 85 to move the valve element 84 so that the valve element 84 faces the outside of the liquid return hole 75. By increasing the opening of the valve 83, the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return hole 75 increases.

[0085] As more liquid refrigerant LR flows into the outflow pipe 73, the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 increases. As a result, the dryness fraction of the refrigerant sucked into the compressor 1 decreases. The refrigerant sucked into the compressor 1 becomes wet, and the density and viscosity of the refrigerant increase. The increased density and viscosity of the refrigerant increase the load capacity of the radial bearings 20, 22 and thrust bearing 66 of the compressor 1. This makes it easier for the rotating shaft 40 of the compressor 1 to float, thereby suppressing damage to the radial bearings 20, 22 and thrust bearing 66.

[0086] [Fifth embodiment] Fig. 11 is a diagram showing a schematic configuration of a valve 83 of the fifth embodiment. As in the fourth embodiment, the valve 83 has a valve body 84 and an actuator 85. The shape of the valve body 84 is not limited to the needle shape described in the fourth embodiment. As shown in Fig. 11, the valve body 84 may have a flat plate shape and open and close the liquid return hole 75 in a shutter-like manner.

[0087] Fig. 12 is a diagram showing a state in which the valve 83 of the fifth embodiment increases the opening area of ​​the liquid return hole 75. The actuator 85 moves the valve body 84 in the left-right direction in Figs. 11 and 12. In Fig. 11, a part of the valve body 84 covers a part of the liquid return hole 75 from below. The valve body 84 reduces the opening area of ​​the liquid return hole 75. As a result, the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return hole 75 is reduced.

[0088] In Fig. 12, the valve body 84 has moved to the left in the figure. The valve body 84 is positioned so as not to cover the liquid return hole 75. Compared to Fig. 11, the opening area of ​​the liquid return hole 75 has increased. This increases the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return hole 75. The flow rate of the liquid refrigerant LR flowing out of the accumulator 7 has increased.

[0089] 9, the controller 80 increases the opening of the valve 83 as the temperature of the refrigerant flowing through the suction pipe 5 detected by the temperature sensor 82 decreases. Specifically, the controller 80 drives the actuator 85 to move the valve element 84 to the position shown in Fig. 12 where the valve element 84 does not cover the liquid return hole 75. By increasing the opening of the valve 83, the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return hole 75 increases.

[0090] As more liquid refrigerant LR flows into the outflow pipe 73, the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 increases. As a result, the dryness fraction of the refrigerant sucked into the compressor 1 decreases. The refrigerant sucked into the compressor 1 becomes wet, and the density and viscosity of the refrigerant increase. The increased density and viscosity of the refrigerant increase the load capacity of the radial bearings 20, 22 and thrust bearing 66 of the compressor 1. This makes it easier for the rotating shaft 40 of the compressor 1 to float, thereby suppressing damage to the radial bearings 20, 22 and thrust bearing 66.

[0091] [Sixth embodiment] Fig. 13 is a diagram showing a schematic configuration of a valve 83 of a sixth embodiment. The liquid return hole 75 formed in the outflow pipe 73 is not limited to one, and may be multiple. The valve 83 may have pairs of valve bodies 84 and actuators 85 in the same number as the number of liquid return holes 75. Fig. 13 shows an example in which three liquid return holes 75 are formed in the outflow pipe 73, and three pairs of valve bodies 84 and actuators 85 are provided. The valve 83 shown in Fig. 13 and Fig. 14 described later is configured to open and close the liquid return hole 75 like a lid by rotating the valve body 84 about a rotation axis.

[0092] In Fig. 13, the liquid return hole 75 on the right side of the figure is in an open state, and the two liquid return holes 75 on the left side of the figure are in a closed state. The liquid refrigerant LR in the case 71 of the accumulator 7 passes through the liquid return hole 75 on the right side of the figure and enters the outflow pipe 73. The liquid refrigerant LR does not flow into the outflow pipe 73 from the two liquid return holes 75 on the left side of the figure.

[0093] Fig. 14 is a diagram showing a state in which the valve 83 of the sixth embodiment increases the opening area of ​​the liquid return hole 75. In Fig. 14, all three liquid return holes 75 shown are open, and the liquid refrigerant LR in the case 71 of the accumulator 7 passes through the three liquid return holes 75 and enters the outflow pipe 73. Because the opening area of ​​the liquid return holes 75 is increased, the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return holes 75 is increasing. The flow rate of the liquid refrigerant LR flowing out of the accumulator 7 is increasing.

[0094] 9, the controller 80 increases the opening of the valve 83 as the temperature of the refrigerant flowing through the suction pipe 5 detected by the temperature sensor 82 decreases. Specifically, the controller 80 drives the actuator 85 to move the valve element 84 to the position shown in Fig. 14 where the valve element 84 does not cover the liquid return hole 75. By increasing the opening of the valve 83, the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return hole 75 increases.

[0095] As more liquid refrigerant LR flows into the outflow pipe 73, the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 increases. As a result, the dryness fraction of the refrigerant sucked into the compressor 1 decreases. The refrigerant sucked into the compressor 1 becomes wet, and the density and viscosity of the refrigerant increase. The increased density and viscosity of the refrigerant increase the load capacity of the radial bearings 20, 22 and thrust bearing 66 of the compressor 1. This makes it easier for the rotating shaft 40 of the compressor 1 to float, thereby suppressing damage to the radial bearings 20, 22 and thrust bearing 66.

[0096] When multiple liquid return holes 75 are formed in the outflow pipe 73, in order to adjust the opening area of ​​the liquid return holes 75, the needle-shaped valve body 84 described in the fourth embodiment or the valve body 84 that opens and closes like a shutter described in the fifth embodiment may be used, and it goes without saying that the needle-shaped valve body 84, the valve body 84 that opens and closes like a shutter, and the valve body 84 that opens and closes like a lid may be appropriately combined.

[0097] In the above-described embodiments, an example has been described in which the liquid refrigerant LR stored in the case 71 of the accumulator 7 is supplied to the suction piping 5. The source from which the liquid refrigerant LR is taken out is not limited to the accumulator 7. For example, the liquid refrigerant LR may be extracted from a liquid reservoir in the evaporator 4 and supplied to the suction piping 5. A supercooled liquid of the refrigerant after condensation in the condenser 2 may be supplied to the suction piping 5. The wet vapor of the refrigerant after expansion in the expansion valve 3 may be separated into gas and liquid, and the liquid refrigerant LR may be supplied to the suction piping 5.

[0098] [Note] The above description includes the following additional features.

[0099] (Appendix 1) a compressor having a rotating shaft and a gas dynamic pressure bearing that rotatably supports the rotating shaft, and compresses a refrigerant; a condenser that condenses the refrigerant compressed by the compressor; an expansion valve for reducing the pressure of the refrigerant condensed in the condenser; an evaporator that evaporates the refrigerant decompressed by the expansion valve; a suction pipe through which a refrigerant to be sucked into the compressor flows; a liquid refrigerant flow rate adjusting unit that adjusts a flow rate of the liquid refrigerant supplied to the suction pipe so as to increase a flow rate of the liquid refrigerant supplied to the suction pipe as a temperature of the refrigerant decreases.

[0100] (Appendix 2) The refrigerant cool ... 2. The refrigerant circuit according to claim 1, wherein the liquid refrigerant flow rate adjustment unit adjusts the amount of the liquid refrigerant flowing out from the gas-liquid separator.

[0101] (Appendix 3) 3. The refrigerant circuit according to claim 2, wherein the gas-liquid separator is provided in a refrigerant path between the evaporator and the compressor.

[0102] (Appendix 4) The refrigerant circuit according to any one of claims 1 to 3, wherein the liquid refrigerant flow rate adjustment unit includes a displacement member that autonomously changes a position in accordance with a change in temperature of the liquid refrigerant.

[0103] (Appendix 5) 5. The refrigerant circuit according to claim 1, further comprising a sensor for detecting a temperature of the refrigerant flowing through the suction pipe.

[0104] (Appendix 6) The liquid refrigerant flow rate adjustment unit includes a valve, 6. The refrigerant circuit according to claim 5, further comprising a controller that controls an opening degree of the valve in accordance with a detection result of the sensor.

[0105] Although the embodiment has been described above, the disclosed embodiment should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include the meaning equivalent to the claims, and all modifications within the scope of the claims. [Explanation of symbols]

[0106] 1 compressor, 2 condenser, 3 expansion valve, 4 evaporator, 5 suction piping, 7 accumulator, 20 first radial bearing, 22 second radial bearing, 40 rotating shaft, 41 electric motor, 51, 52 impeller, 65 support plate, 66 thrust bearing, 71 case, 72 inlet pipe, 73 outlet pipe, 75 liquid return hole, 76 liquid refrigerant flow rate adjustment section, 77 expansion section, 78, 84 valve body, 79 bimetal, 80 controller, 81 liquid return piping, 82 temperature sensor, 83 valve, 85 actuator, GR gas refrigerant, H1, H2 height, LR liquid refrigerant, SN1 detection signal, SN2 control signal.

Claims

1. a compressor having a rotating shaft and a gas dynamic pressure bearing that rotatably supports the rotating shaft, and compresses a refrigerant; a condenser that condenses the refrigerant compressed by the compressor; an expansion valve for reducing the pressure of the refrigerant condensed in the condenser; an evaporator that evaporates the refrigerant decompressed by the expansion valve; a suction pipe through which a refrigerant to be sucked into the compressor flows; a liquid refrigerant flow rate adjusting unit that adjusts a flow rate of the liquid refrigerant supplied to the suction pipe so as to increase a flow rate of the liquid refrigerant supplied to the suction pipe as a temperature of the refrigerant decreases.

2. The refrigerant cool ... The refrigerant circuit according to claim 1 , wherein the liquid refrigerant flow rate adjusting unit adjusts the amount of the liquid refrigerant flowing out from the gas-liquid separator.

3. The refrigerant circuit according to claim 2 , wherein the gas-liquid separator is provided in a refrigerant path between the evaporator and the compressor.

4. The refrigerant circuit according to claim 1 , wherein the liquid refrigerant flow rate adjusting section includes a displacement member that autonomously changes its position in accordance with a change in temperature of the liquid refrigerant.

5. The refrigerant circuit according to claim 1 , further comprising a sensor for detecting a temperature of the refrigerant flowing through the suction pipe.

6. The liquid refrigerant flow rate adjustment unit includes a valve, The refrigerant circuit according to claim 5 , further comprising a controller that controls an opening degree of the valve in accordance with a detection result of the sensor.

Images