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 1 which has a gas dynamic pressure bearing rotatably supporting a rotary shaft and compresses a refrigerant; a condenser 2 which condenses the refrigerant compressed by the compressor 1; an expansion valve 3 which decompresses the refrigerant condensed by the condenser 2; an evaporator 4 which evaporates the refrigerant decompressed by the expansion valve 3; a suction pipe 5 in which the refrigerant suctioned into the compressor 1 flows; and a valve 83 which adjusts a flow rate of a liquid refrigerant to be supplied to the suction pipe 5 based on a rotation number of the compressor 1.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] JP 2009-511803 A (Patent Document 1) discloses a fluid compressor having an aerostatic bearing. The aerostatic bearing includes a floating pressurized region. A compressed fluid accumulator is fluidly connectable to the floating pressurized region. When the compressor starts, compressed fluid stored inside the compressed fluid accumulator is moved to the floating pressurized region of the aerostatic bearing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2009-511803 Summary of the Invention [Problem to be solved by the invention]

[0004] One type of gas bearing that uses a gas refrigerant to lubricate the bearing is a hydrodynamic bearing, which generates hydrodynamic pressure in the lubricant film by the relative sliding motion between the rotating shaft and the bearing, thereby levitating the rotating shaft. In a compressor equipped with a hydrodynamic bearing, when the rotation speed of the compressor is reduced, the sliding speed between the rotating shaft and the bearing decreases, causing the gas film to become thinner, and the shaft cannot be levitated, which may damage the bearing.

[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 pipe through which the refrigerant sucked into the compressor flows; and a liquid refrigerant flow rate adjustment unit which adjusts the flow rate of liquid refrigerant supplied to the suction pipe based on the rotation speed of the compressor.

[0007] In this refrigerant circuit, the flow rate of liquid refrigerant supplied to the suction pipe is increased based on the compressor rotation speed to reduce 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 suppressing damage to the bearings.

[0008] In the above refrigerant circuit, the liquid refrigerant flow rate adjusting unit may increase the flow rate of the liquid refrigerant when the rotation speed of the compressor decreases. The liquid refrigerant flow rate adjusting unit may increase the flow rate of the liquid refrigerant when the rotation speed of the compressor is lower than a threshold value.

[0009] 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.

[0010] The refrigerant circuit may further include a sensor that detects a rotation speed of the compressor. The liquid refrigerant flow rate regulator may include a valve. The refrigerant circuit may further include a controller that controls an opening degree of the valve in accordance with a detection result of the sensor.

[0011] In the above refrigerant circuit, the liquid refrigerant flow rate regulator may include a valve, and the controller may output a control command value that commands the rotation speed of the compressor, and control the opening degree of the valve in accordance with the control command value. Effect of the Invention

[0012] 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]

[0013] [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] 4 is a flowchart showing a process for controlling the opening degree of a valve. [Diagram 5] 4 is a graph for explaining a decrease in the rotation speed of a compressor. [Figure 6] FIG. 11 is a schematic cross-sectional view showing an internal configuration of an accumulator according to a second embodiment. [Figure 7] FIG. 6 is a schematic diagram showing a schematic configuration of a refrigerant circuit according to a second embodiment. [Figure 8] FIG. 13 is a diagram showing a schematic configuration of a valve according to a third embodiment. [Figure 9] FIG. 13 is a diagram showing a schematic configuration of a valve according to a fourth embodiment. [Figure 10] FIG. 13 is a diagram showing a state in which the valve of the fourth embodiment increases the opening area of ​​the liquid return hole. [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 schematic diagram showing a schematic configuration of a refrigerant circuit of a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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.

[0015] [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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] Outlet pipe 73 has a U-shaped pipe shape inside case 71. The bent portion of the U-shape forms the lowermost portion of outflow pipe 73, and is disposed in the liquid refrigerant LR at the lower portion of case 71.

[0050] Returning to FIG. 2, the refrigerant circuit further includes a controller 80, a liquid return pipe 81, a rotation speed sensor 82, and a valve 83.

[0051] The controller 80 includes a CPU (Central Processing Unit) and executes a computer program that controls the refrigerant circuit.

[0052] 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.

[0053] The rotation speed sensor 82 detects the rotation speed of the compressor 1. The rotation speed sensor 82 detects the rotation speed of the rotor 43 of the electric motor 41. The rotation speed sensor 82 detects the rotation speed of the rotating shaft 40. The rotation speed sensor 82 may be disposed close to the rotating shaft 40 to directly measure the rotation speed of the rotating shaft 40. The rotation speed sensor 82 may calculate the rotation speed of the rotating shaft 40 from the value of power supplied to the coil 45. The rotation speed sensor 82 outputs a detection signal SN1 indicative of the detection result of the rotation speed of the compressor 1. The detection signal SN1 is input to the controller 80.

[0054] The valve 83 is provided in the liquid return pipe 81. The controller 80 transmits a control signal SN2 to the valve 83. The controller 80 controls the opening of the valve 83 according to the detection result of the rotation speed sensor 82. The flow rate of the liquid refrigerant LR flowing through the liquid return pipe 81 is adjusted by adjusting the opening of the valve 83. The valve 83 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 flow rate of the liquid refrigerant LR supplied to the suction pipe 5 via the liquid return pipe 81 can be adjusted by adjusting the opening of the valve 83. The valve 83 functions as a "liquid refrigerant flow rate adjustment unit." The valve 83 can adjust the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 by external control.

[0055] The valve 83 is a control valve capable of continuously changing the valve opening. As shown in Fig. 3, the valve 83 has an actuator 85, such as an electric, pneumatic, or hydraulic actuator, and a valve body 84 driven by the actuator 85. The valve body 84 has a needle-like shape. The actuator 85 generates a driving force for driving the valve body 84. The valve body 84 increases or decreases the flow path area of ​​the liquid refrigerant LR in the liquid return pipe 81, thereby adjusting the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 via the liquid return pipe 81.

[0056] 4 is a flowchart showing the flow of a process for controlling the opening degree of valve 83. When battery temperature adjustment is not required, the refrigerant circuit may be operated by reducing the rotation speed of compressor 1 in order to suppress power consumption. As shown in FIG. 4, in step S11, rotation speed sensor 82 detects the rotation speed of compressor 1. A detection signal SN1 indicating the detection result of the rotation speed of compressor 1 is input from rotation speed sensor 82 to controller 80.

[0057] In step S12, the controller 80 determines whether the rotation speed of the compressor 1 has decreased. The controller 80 periodically acquires the rotation speed of the compressor 1. The controller 80 repeatedly acquires the rotation speed of the compressor 1 at regular time intervals. The controller 80 compares the most recently acquired rotation speed with the previously acquired rotation speed. If the most recently acquired rotation speed is smaller than the previously acquired rotation speed, the controller 80 determines that the rotation speed of the compressor 1 has decreased.

[0058] FIG. 5 is a graph for explaining the decrease in the rotation speed of the compressor 1. The horizontal axis of FIG. 5 indicates time, and the vertical axis indicates the rotation speed of the compressor 1. The controller 80 acquires the rotation speed of the compressor 1 at time T0, and recognizes that the rotation speed of the compressor 1 is rotation speed R0 at time T0. The controller 80 acquires the rotation speed of the compressor 1 at time T1, and recognizes that the rotation speed of the compressor 1 is rotation speed R0 at time T1. The controller 80 determines that the rotation speed of the compressor 1 has not decreased, since the rotation speed R0 acquired at time T0 is equal to the rotation speed R0 acquired at time T1 (NO in the determination of step S12).

[0059] If the rotation speed of the compressor 1 is not reduced, the relative sliding velocity between the rotating shaft 40 and the dynamic pressure bearing does not decrease, and the gas film does not become thinner. Therefore, in this case, the controller 80 maintains the opening of the valve 83 and ends the process as it is ("End" in FIG. 4).

[0060] The controller 80 acquires the rotation speed of the compressor 1 at time T2 and recognizes that the rotation speed of the compressor 1 at time T2 is rotation speed R2 which is lower than rotation speed R0. The controller 80 determines that the rotation speed of the compressor 1 has decreased because the rotation speed R2 acquired at time T2 is relatively lower than the rotation speed R0 acquired at time T1.

[0061] If it is determined that the rotation speed of the compressor 1 has decreased (YES in step S12), in step S13, the controller 80 reads out the threshold value of the rotation speed stored in the storage device. The controller 80 compares the rotation speed of the compressor 1 detected in step S11 with the threshold value. The controller 80 determines whether the most recent rotation speed of the compressor 1 is smaller than the threshold value.

[0062] A straight line drawn in the left-right direction in FIG. 5 indicates the threshold value RT of the rotation speed. As shown in FIG. 5, the rotation speed R2 is greater than the threshold value RT. The controller 80 determines that the rotation speed R2 of the compressor 1 is not less than the threshold value RT (NO in step S13). If the rotation speed of the compressor 1 is higher than the threshold value RT and a sufficient relative slip velocity is obtained to lift the rotating shaft 40, the phenomenon of the gas film becoming thin does not occur. Therefore, in this case, the controller 80 maintains the opening of the valve 83 and ends the process as it is ("End" in FIG. 4).

[0063] The controller 80 acquires the rotation speed of the compressor 1 at time T3, and recognizes that the rotation speed of the compressor 1 at time T3 is R3, which is lower than the rotation speed R2. The controller 80 determines that the rotation speed of the compressor 1 has decreased because the rotation speed R3 acquired at time T3 is lower than the rotation speed R2 acquired at time T2. The controller 80 determines that the rotation speed R3 is lower than the threshold value RT (YES in step S13), proceeds to step S14, and increases the opening of the valve 83.

[0064] The controller 80 transmits a control signal SN2 to the valve 83 to command it to increase the opening of the valve 83. Upon receiving the control signal SN2, the valve 83 increases its opening, thereby increasing the flow rate of the liquid refrigerant LR in the accumulator 7 flowing out of the accumulator 7. The amount of liquid refrigerant LR flowing into the liquid return piping 81 increases. The flow rate of the liquid refrigerant LR supplied to the suction piping 5 via the liquid return piping 81 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.

[0065] 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 sucked 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 of the compressor 1. This makes it easier for the rotating shaft 40 of the compressor 1 to float, thereby making it possible to suppress damage to the radial bearings 20, 22 and thrust bearing 66.

[0066] 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.

[0067] 4, the control for increasing the flow rate of the liquid refrigerant LR when the rotation speed of the compressor 1 decreases and is smaller than the threshold value RT has been described. The determination in step S13 for comparing the rotation speed of the compressor 1 with the threshold value RT may be omitted. Control may be performed in such a way that the process in step S14 for increasing the opening degree of the valve 83 to increase the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 is performed only under the condition that it is determined in step S12 that the rotation speed of the compressor 1 has decreased.

[0068] [Second embodiment] 6 is a cross-sectional schematic diagram showing the internal configuration of the accumulator 7 of the second embodiment. 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 in 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.

[0069] 7 is a schematic diagram showing a schematic configuration of a refrigerant circuit according to the second embodiment. The valve 83 according to the second embodiment is an ON / OFF valve capable of switching the valve opening degree between two stages, full open and full closed. The valve 83 may be, for example, a solenoid valve.

[0070] A liquid return hole 75 is formed in the outflow pipe 73 of the accumulator 7 at a position where it is always immersed in the liquid refrigerant LR, and a constant amount of liquid refrigerant LR flows into the outflow pipe 73 from the liquid return hole 75. In this case, by fully closing the valve 83, only the flow of liquid refrigerant LR is generated via the liquid return hole 75. By fully opening the valve 83, two flows of liquid refrigerant LR are generated: 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 liquid refrigerant LR supplied to the suction pipe 5 can be adjusted in two stages.

[0071] As in the process described with reference to FIGS. 4 and 5, the controller 80 increases the opening of the valve 83 if the rotation speed of the compressor 1 detected by the rotation speed sensor 82 is decreasing and is smaller than a threshold value. The controller 80 switches the valve 83 from a closed state to an open state. By increasing the opening of the valve 83, the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 increases. Therefore, the dryness 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 increase in the density and viscosity of the refrigerant increases 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.

[0072] [Third embodiment] 8 is a diagram showing a schematic configuration of a valve 83 of the third embodiment. In the first and second embodiments, 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.

[0073] 8 is formed with a liquid return hole 75. The valve 83 is capable of adjusting the opening area of ​​the liquid return hole 75. The valve 83 is capable of adjusting the flow rate of the liquid refrigerant LR stored in the lower part of the case 71 of the accumulator 7 flowing out of the accumulator 7. The valve 83 is capable of adjusting the flow rate of the liquid refrigerant LR flowing into the outflow pipe 73 via the liquid return hole 75. The valve 83 is capable of adjusting the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 via the outflow pipe 73.

[0074] The valve 83 has a valve element 84 and an actuator 85. The valve element 84 is disposed within the case 71 of the accumulator 7. The valve element 84 is disposed in the liquid refrigerant LR at the bottom of the case 71. The valve element 84 is disposed in a position where it is constantly immersed in the liquid refrigerant LR. As shown in Fig. 8, the valve element 84 may have a needle-like shape.

[0075] 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.

[0076] The controller 80 controls the opening of the valve 83 according to the rotation speed of the compressor 1 detected by the rotation speed 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. 8, the opening area of ​​the liquid return hole 75 decreases, and the flow rate of the liquid refrigerant LR that passes through the liquid return hole 75 and enters 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 that passes through the liquid return hole 75 and enters the outflow pipe 73 increases.

[0077] 4 and 5, if the rotation speed of the compressor 1 detected by the rotation speed sensor 82 is decreasing and is smaller than a threshold value, the controller 80 increases the opening of the valve 83. Specifically, the controller 80 drives the actuator 85 to move the valve body 84 so that the valve body 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.

[0078] 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.

[0079] [Fourth embodiment] Fig. 9 is a diagram showing a schematic configuration of a valve 83 of the fourth embodiment. As in the third 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 third embodiment. As shown in Fig. 9, the valve body 84 may have a flat plate shape and open and close the liquid return hole 75 in a shutter-like manner.

[0080] Fig. 10 is a diagram showing a state in which the valve 83 of the fourth 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. 9 and 10. In Fig. 9, 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.

[0081] In Fig. 10, 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. 9, 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.

[0082] 4 and 5, the controller 80 increases the opening of the valve 83 if the rotation speed of the compressor 1 detected by the rotation speed sensor 82 is decreasing and is smaller than a threshold value. Specifically, the controller 80 drives the actuator 85 to move the valve body 84 to a position shown in Fig. 10 where the valve body 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.

[0083] 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.

[0084] [Fifth embodiment] Fig. 11 is a diagram showing a schematic configuration of a valve 83 of a fifth 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. 11 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. 11 and Fig. 12 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.

[0085] In Fig. 11, 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.

[0086] Fig. 12 is a diagram showing a state in which the valve 83 of the fifth embodiment has increased the opening area of ​​the liquid return hole 75. In Fig. 12, 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 has increased, the flow rate of the liquid refrigerant LR entering the outflow pipe 73 from the liquid return holes 75 has increased. The flow rate of the liquid refrigerant LR flowing out of the accumulator 7 has increased.

[0087] 4 and 5, the controller 80 increases the opening of the valve 83 if the rotation speed of the compressor 1 detected by the rotation speed sensor 82 is decreasing and is smaller than a threshold value. Specifically, the controller 80 drives the actuator 85 to move the valve body 84 to a position shown in Fig. 12 where the valve body 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.

[0088] 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.

[0089] 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 third embodiment or the valve body 84 that opens and closes like a shutter described in the fourth 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.

[0090] [Sixth embodiment] 13 is a schematic diagram showing a schematic configuration of a refrigerant circuit of a sixth embodiment. In the above embodiments, an example has been described in which the refrigerant circuit includes a rotation speed sensor 82, and the controller 80 adjusts the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 based on the rotation speed of the compressor 1 detected by the rotation speed sensor 82. The refrigerant circuit does not necessarily have to include the rotation speed sensor 82 that detects the rotation speed of the compressor 1.

[0091] 13 outputs a control signal SN3, which is a control command value that commands the rotation speed of the compressor 1, to the compressor 1. Upon receiving the input of the control signal SN3, the compressor 1 supplies, to the coil 45, electric power such that the electric motor 41 of the compressor 1 rotates at a rotation speed according to the control command value.

[0092] The controller 80 controls the opening of the valve 83 in accordance with the command rotation speed to the compressor 1. As in the processes described with reference to Figures 4 and 5, the controller 80 commands the compressor 1 to reduce the rotation speed, and increases the opening of the valve 83 if the command rotation speed to the compressor 1 is smaller than a threshold value. By increasing the opening of the valve 83, the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 increases.

[0093] Therefore, 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.

[0094] 13 shows an example in which a valve 83 is provided in the liquid return pipe 81, and the controller 80 controls the flow rate of the liquid refrigerant LR flowing through the liquid return pipe 81. Of course, the controller 80 may control the flow rate of the liquid refrigerant LR supplied to the suction pipe 5 by increasing or decreasing the opening area of ​​the liquid return hole 75 in accordance with a control command value that commands the rotation speed of the compressor 1.

[0095] 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.

[0096] [Note] The above description includes the following additional features.

[0097] (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 based on a rotation speed of the compressor.

[0098] (Appendix 2) 2. The refrigerant circuit according to claim 1, wherein the liquid refrigerant flow rate adjustment unit increases the flow rate of the liquid refrigerant when a rotation speed of the compressor decreases.

[0099] (Appendix 3) 3. The refrigerant circuit according to claim 2, wherein the liquid refrigerant flow rate adjustment unit increases the flow rate of the liquid refrigerant when a rotation speed of the compressor is lower than a threshold value.

[0100] (Appendix 4) The refrigerant cool ... 4. The refrigerant circuit according to claim 1, wherein the liquid refrigerant flow rate adjustment unit adjusts an amount of the liquid refrigerant flowing out from the gas-liquid separator.

[0101] (Appendix 5) 5. The refrigerant circuit according to claim 4, wherein the gas-liquid separator is provided in a refrigerant path between the evaporator and the compressor.

[0102] (Appendix 6) 6. The refrigerant circuit according to claim 1, further comprising a sensor for detecting a rotation speed of the compressor.

[0103] (Appendix 7) The liquid refrigerant flow rate adjustment unit includes a valve, 7. The refrigerant circuit according to claim 6, further comprising a controller that controls an opening degree of the valve in accordance with a detection result of the sensor.

[0104] (Appendix 8) The liquid refrigerant flow rate adjustment unit includes a valve, 7. The refrigerant circuit according to any one of Supplementary Note 1 to Supplementary Note 6, further comprising a controller that outputs a control command value that commands a rotation speed of the compressor and controls an opening degree of the valve in accordance with the control command value.

[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, 80 controller, 81 liquid return piping, 82 rotation speed sensor, 83 valve, 84 valve body, 85 actuator, GR gas refrigerant, LR liquid refrigerant, R0, R2, R3 rotation speed, RT threshold, SN1 detection signal, SN2, SN3 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 based on a rotation speed of the compressor.

2. The refrigerant circuit according to claim 1 , wherein the liquid refrigerant flow rate adjusting unit increases the flow rate of the liquid refrigerant when a rotation speed of the compressor decreases.

3. The refrigerant circuit according to claim 2 , wherein the liquid refrigerant flow rate adjusting unit increases the flow rate of the liquid refrigerant when a rotation speed of the compressor is lower than a threshold value.

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

5. The refrigerant circuit according to claim 4 , wherein the gas-liquid separator is provided in a refrigerant path between the evaporator and the compressor.

6. The refrigerant circuit according to claim 1 , further comprising a sensor for detecting a rotation speed of the compressor.

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

8. The liquid refrigerant flow rate adjustment unit includes a valve, 4. The refrigerant circuit according to claim 1, further comprising a controller that outputs a control command value that commands a rotation speed of the compressor and controls an opening degree of the valve in accordance with the control command value.

Images