Coolant circulation system

Abstract

To provide a coolant circulation system to lubricant a slide bearing of a motor with a coolant containing oil, in which the load capacity of the slide bearing is secured at the start of the motor.SOLUTION: A coolant circulation system 100 to circulate a coolant in which CO2 contains oil includes a motor 1 including a slide bearing 14 that lubricates using a coolant compressed with a compressor 3 and supports a rotary shaft 13, a coolant passage 22 to supply the coolant to the slide bearing 14 of the motor 1, a first flow rate regulation valve (oil content ratio regulation valve) 30 configured to regulate the oil content ratio in the coolant supplied from the coolant passage 22 to the slide bearing 14, and a control device 80 configured to control the first flow rate regulation valve 30 so that the oil content ratio becomes larger when the stationary motor 1 starts to operate than when the motor 1 is in operation.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a refrigerant circulation system that circulates an oil-containing refrigerant. [Background technology]

[0002] Conventionally, refrigerant circulation systems have been used in refrigeration cycles used in air conditioners, in which a refrigerant is circulated through a compressor, a heat exchanger, etc. In recent years, such refrigerant circulation systems have also been used to cool components inside vehicles, for example, the batteries of electric vehicles and hybrid vehicles. As one example, Patent Document 1 discloses a vehicle that shares a single compressor and supplies the refrigerant flowing out from the compressor to the air conditioner and battery, thereby achieving a smaller and less expensive system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-037294 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, rolling bearings and sliding bearings have traditionally been used as bearings to support the rotating shaft of, for example, a vehicle's power source (engine or motor). However, when rolling bearings are used in motors such as electric vehicles, the motor's rotating shaft rotates at high speeds of, for example, over 30,000 rpm, which can lead to problems with rolling fatigue and reduced lifespan. On the other hand, when a typical sliding bearing that uses oil as a lubricant is used in a motor, loss due to oil agitation resistance caused by the motor's rotating shaft becomes significant.

[0005] Therefore, the present inventors considered applying a motor to a refrigerant circulation system such as the one described above, and applying a sliding bearing to the motor's rotating shaft that uses, as a lubricant, the refrigerant circulated in this system - in particular a CO2 refrigerant that is liquefied when compressed by a compressor.At the same time, the present inventors also considered having this motor perform part of the function of the refrigeration cycle of the refrigerant circulation system, specifically functioning as an expansion valve or evaporator in the refrigeration cycle.

[0006] Here, in typical refrigerant circulation systems, a refrigerant containing oil (refrigeration oil) is used to lubricate and seal the compressor, but even in systems that use the above-mentioned refrigerant to lubricate the sliding bearing of a motor, it can be said that it is desirable to use a refrigerant containing oil to ensure the lubrication of the sliding bearing.In this case, when a stopped motor is started, contact between the rotating shaft and the sliding bearing is likely to occur, and therefore it is thought desirable to use oil to accurately ensure the load capacity of the sliding bearing.

[0007] The present invention has been made to solve the problems with the conventional technology described above, and has an object to accurately ensure the load capacity of the sliding bearing when the motor is started, in a refrigerant circulation system that circulates an oil-containing refrigerant and uses this refrigerant to lubricate the sliding bearing of the motor. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a refrigerant circulation system that circulates a refrigerant made of CO2 containing oil, comprising: a motor including a compressor that compresses the refrigerant; a rotor and a stator; a rotating shaft connected to the rotor; and a sliding bearing that supports the rotating shaft and is lubricated using liquid refrigerant compressed by the compressor; a refrigerant passage that supplies refrigerant to the sliding bearing of the motor; an oil content adjustment valve configured to adjust the oil content of the refrigerant supplied from the refrigerant passage to the sliding bearing; and a control device configured to control the oil content adjustment valve when a stopped motor is started so that the oil content is higher than when the motor is operating.

[0009] In the present invention configured in this manner, the control device controls the oil content adjustment valve to increase the oil content in the refrigerant supplied to the sliding bearing when the motor is started; in other words, a refrigerant with a relatively high viscosity can be supplied to the sliding bearing. This makes it possible to accurately ensure the load capacity of the sliding bearing when the motor is started. Meanwhile, according to the present invention, the oil content in the refrigerant supplied to the sliding bearing can be reduced while the motor is operating; in other words, a refrigerant with a relatively low viscosity can be supplied to the sliding bearing. This makes it possible to reduce the lubrication resistance (friction) caused by the oil in the sliding bearing while the motor is operating.

[0010] In the present invention, the control device is preferably configured to control the oil content adjustment valve so that the oil content becomes approximately 100% when the stopped motor is started. According to the present invention configured in this manner, the load capacity of the sliding bearing can be effectively ensured when the motor is started.

[0011] In the present invention, preferably, a plurality of refrigerant passages are provided in the plain bearing so as to supply refrigerant to a plurality of positions in the circumferential direction, a plurality of oil content adjustment valves are provided so as to adjust the oil content of the refrigerant supplied from the plurality of refrigerant passages, respectively, and the control device is configured to control one or more oil content adjustment valves among the plurality of oil content adjustment valves provided in one or more refrigerant passages so as to increase the oil content from one or more refrigerant passages among the plurality of refrigerant passages that are provided to supply refrigerant to the lower part of the plain bearing when a stopped motor is started, compared to when the motor is operating. With the present invention configured in this way, when the motor is started, the refrigerant is sprayed from one or more refrigerant passages located below, in other words, static pressure is applied from below the rotating shaft, causing the rotating shaft to float against its own weight from the sliding bearing, thereby making it possible to effectively ensure the load capacity of the sliding bearing when the motor is started. Note that the "lower part" of a sliding bearing refers to the lower half when the sliding bearing is divided vertically. Also, the "upper part" of a sliding bearing refers to the upper half when the sliding bearing is divided vertically.

[0012] In the present invention, preferably, the control device is configured to control one or more oil content adjustment valves provided in the one or more refrigerant passages so that the oil content from the one or more refrigerant passages becomes approximately 100% when the stopped motor is started. According to the present invention configured in this manner, the load capacity of the sliding bearing can be more effectively ensured when the motor is started.

[0013] In the present invention, preferably, the control device is further configured to control the oil content adjustment valve so that when the operating motor is stopped, the oil content is greater than when the motor is operating. According to the present invention configured in this manner, the load capacity of the sliding bearing can be ensured when the motor is stopped, and the rotating shaft, which is in a rotating state, can be prevented from contacting the sliding bearing.

[0014] In the present invention, preferably, the refrigerant circulation system further includes an oil passage that supplies oil to the refrigerant passage, and an oil tank connected to the oil passage that stores the oil, and the oil tank is configured to separate the oil contained in the refrigerant and store the oil. According to the present invention configured as described above, the oil can be appropriately recovered from the refrigerant and stored in the oil tank.

[0015] In a preferred example of the present invention, if the refrigerant passage is referred to as a first refrigerant passage, the refrigerant circulation system further has a second refrigerant passage that communicates with the first refrigerant passage and allows refrigerant from the compressor to flow into the first refrigerant passage, and the oil content adjustment valve communicates with the first refrigerant passage, the second refrigerant passage, and the oil passage; thereby, by controlling the oil content adjustment valve, it is possible to change the mixing ratio of refrigerant from the second refrigerant passage and oil from the oil passage and adjust the oil content in the refrigerant supplied from the first refrigerant passage to the sliding bearing. According to the present invention configured in this manner, the oil content in the refrigerant supplied to the sliding bearing can be accurately adjusted by the oil content adjustment valve. [Effects of the Invention]

[0016] According to the present invention, in a refrigerant circulation system in which an oil-containing refrigerant is circulated and this refrigerant is used to lubricate the sliding bearings of a motor, it is possible to accurately ensure the load capacity of the sliding bearings when the motor is started. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of a vehicle to which a refrigerant circulation system according to an embodiment of the present invention is applied; [Figure 2] 1 is a schematic configuration diagram of a motor according to an embodiment of the present invention. [Figure 3] 1 is a schematic configuration diagram of a refrigerant circulation system according to an embodiment of the present invention. [Figure 4] 3 is a schematic configuration diagram for specifically explaining a first flow rate adjustment valve and a refrigerant passage according to the embodiment of the present invention. FIG. [Figure 5] 1 is a block diagram showing an electrical configuration of a refrigerant circulation system according to an embodiment of the present invention. [Figure 6] FIG. 1 is an explanatory diagram illustrating a basic concept of control according to an embodiment of the present invention. [Figure 7] 4 is a time chart showing control according to an embodiment of the present invention. [Figure 8] 4 is a flowchart illustrating a control according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a refrigerant circulation system according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0019] [Overall configuration] First, the overall configuration of a refrigerant circulation system according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of a vehicle to which the refrigerant circulation system according to this embodiment is applied.

[0020] 1, vehicle 200 is, for example, an electric vehicle, and has a refrigerant circulation system 100 that circulates a refrigerant in a refrigeration cycle. This refrigerant circulation system 100 has a motor (electric motor) 1 that generates power to drive vehicle 200, a compressor (compressor) 3 that compresses the refrigerant to be supplied to motor 1, and a heat exchanger (condenser) 5 that includes a condenser, a fan, etc., and that cools the refrigerant compressed by compressor 3.

[0021] The refrigerant circulation system 100 circulates a CO2 refrigerant as a natural refrigerant. To this end, the compressor 3 is configured to compress the refrigerant to extremely high pressures. The motor 1 is configured to function as an expansion valve and an evaporator in a refrigeration cycle by using the liquid (typically supercritical) refrigerant compressed by the compressor 3 to lubricate the sliding bearings that support the rotating shaft and to cool the rotor and stator (details will be described later). For example, in the refrigerant circulation system 100, a high-temperature, high-pressure refrigerant is supplied from the compressor 3 to the heat exchanger 5, a room-temperature, high-pressure supercritical refrigerant is supplied from the heat exchanger 5 to the motor 1, and a room-temperature, low-pressure gaseous refrigerant is supplied from the motor 1 to the compressor 3. In this case, the motor 1 is cooled by the latent heat of vaporization of the refrigerant. The refrigerant circulated by the refrigerant circulation system 100 may also be used for an air conditioner that conditions the interior of the vehicle 200.

[0022] In particular, the refrigerant circulation system 100 circulates a refrigerant in which CO2 is mixed with oil (refrigerating machine oil such as PAG, including additives). Such oil is easily soluble in the refrigerant in the liquid phase, and the solubility (content) increases particularly as the refrigerant pressure increases. However, in the gas phase, the oil is almost insoluble in the refrigerant.

[0023] [Motor configuration] Next, the configuration of the motor 1 according to this embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic diagram of the motor 1 according to this embodiment. Specifically, Fig. 2 is a cross-sectional view of the motor 1 as seen along the axial direction.

[0024] As shown in Figure 2, the motor 1 is a system that mainly includes a rotor 11, a stator 12, a rotating shaft 13 that is connected to the rotor 11 and has one end connected to a transaxle (not shown) of the vehicle 200, a pair of plain bearings 14 that support the rotating shaft 13, and a housing 15 that houses the rotor 11, stator 12, rotating shaft 13, plain bearings 14, etc.

[0025] Furthermore, in the motor 1, the refrigerant compressed by the compressor 3 is supplied to the sliding bearing 14 and the stator 12 via refrigerant passages 22 and 23. Specifically, the refrigerant is supplied through refrigerant passage 22 to the gap between the rotating shaft 13 and the sliding bearing 14. The sliding bearing 14 is configured to be lubricated using the refrigerant (CO2 refrigerant) supplied in this way from refrigerant passage 22 as a lubricant. In this case, the sliding bearing 14 is lubricated using a liquid refrigerant (specifically, a refrigerant containing CO2 in a supercritical state).

[0026] If a rolling bearing is applied to the motor 1, for example in an electric vehicle, the rotating shaft 13 of the motor 1 rotates at a high rotation speed of, for example, over 30,000 rpm, causing a problem of shortened lifespan due to rolling fatigue. On the other hand, if a general sliding bearing that uses oil is applied to the motor 1, the loss of oil agitation resistance caused by the rotating shaft 13 becomes large. Therefore, in this embodiment, a sliding bearing 14 that uses a refrigerant that has been compressed into a liquid state (supercritical state) by the compressor 3 is applied to the motor 1. This makes it possible to solve problems such as rolling fatigue and oil agitation resistance.

[0027] The refrigerant supplied from refrigerant passage 23 is used to cool stator 12, more specifically, to cool the coil (not shown) of stator 12. The refrigerant used to cool stator 12 in this way, and the refrigerant used to lubricate plain bearing 14 as described above, flows out of refrigerant passage 24 and is returned to compressor 3 ( FIG. 1 ). Note that the refrigerant after being used to lubricate plain bearing 14 is also supplied to stator 12 and used to cool stator 12.

[0028] In such a motor 1, the refrigerant is supplied from the gap between the rotating shaft 13 and the sliding bearing 14 to the space 15a in the housing 15 in which the rotor 11 and the stator 12 are provided, reducing the pressure, so that the motor 1 functions as an expansion valve in the refrigeration cycle, and also functions as an evaporator in the refrigeration cycle because the refrigerant exchanges heat with the relatively high temperature stator 12 (at which time the refrigerant evaporates in the coil of the stator 12).

[0029] Furthermore, motor 1 further includes a seal member 18 for sealing the side of rotating shaft 13 that is connected to a transaxle or the like. This seal member 18 is provided to prevent refrigerant from leaking to the outside from a gap between rotating shaft 13 and housing 15. On the other hand, the end of rotating shaft 13 opposite the side connected to the transaxle or the like is not provided with such a seal member 18, and is instead covered and sealed by housing 15.

[0030] [Specific configuration of the refrigerant circulation system] Next, the refrigerant circulation system 100 according to this embodiment will be specifically described with reference to Fig. 3. Fig. 3 is a schematic diagram of the refrigerant circulation system 100 according to this embodiment.

[0031] As shown in Fig. 3, in addition to the motor 1, compressor 3, and heat exchanger 5 described above (Fig. 1), the refrigerant circulation system 100 also includes an oil tank 6 that stores oil used as a refrigerant, a pressure reduction tank 7 that stores negative pressure for reducing the pressure inside the space 15a of the motor 1, and an air conditioner evaporator 8 that is used in the air conditioner of the vehicle 200. In addition to refrigerant passages 22, 23, and 24 connected to the motor 1 (Fig. 2), the refrigerant circulation system 100 also includes refrigerant passages 21, 28, and 29 through which the refrigerant flows, oil passages 25 and 26 through which the oil flows, and a pressure reduction passage 27 for reducing the pressure using the pressure reduction tank 7. The refrigerant passage 22 and the refrigerant passage 21 correspond to the "first refrigerant passage" and the "second refrigerant passage," respectively, in the present invention.

[0032] Specifically, refrigerant passage 21 is a passage for supplying refrigerant from compressor 3 to motor 1 via heat exchanger 5, and is connected to both refrigerant passages 22 and 23. As described above, refrigerant passage 22 is a passage for supplying refrigerant to the sliding bearing 14 of motor 1, and refrigerant passage 23 is a passage for supplying refrigerant to the stator 12 of motor 1 (FIG. 2). Refrigerant passage 22 is connected to refrigerant passage 21 and oil passage 25 via first flow control valve 30, a three-way valve with an adjustable opening. This allows refrigerant obtained by mixing refrigerant from refrigerant passage 21 with oil from oil passage 25 to flow through refrigerant passage 22 and be supplied to the sliding bearing 14 of motor 1. In this case, by controlling the opening of first flow control valve 30, the mixing ratio of refrigerant from refrigerant passage 21 and oil from oil passage 25 can be changed, making it possible to adjust the oil content of the refrigerant supplied from refrigerant passage 22 to the sliding bearing 14. In addition, refrigerant passage 22 is provided with a pressure sensor 40 that detects the pressure of the refrigerant. On the other hand, the refrigerant passage 23 is connected to the refrigerant passage 21 upstream of the first flow rate control valve 30, and is provided with a second flow rate control valve 31 that adjusts the flow rate of the refrigerant. The first flow rate control valve 30 corresponds to the "oil content adjustment valve" in this invention.

[0033] Refrigerant passage 24 is a passage for supplying (recirculating) the refrigerant flowing out from motor 1 to compressor 3, and is provided with a pressure sensor 41 that detects pressure, an oil tank 6 that stores oil, and a check valve 36. The pressure sensor 41 detects the pressure of the refrigerant upstream of oil tank 6 (corresponding to the pressure in space 15a of motor 1 and the pressure in oil tank 6). Oil tank 6 is configured to separate the oil from the refrigerant flowing through refrigerant passage 24 (gas-liquid separation) and store the separated oil while allowing the remaining refrigerant (which may also contain a small amount of oil) to flow downstream to compressor 3. In addition, oil tank 6 is provided with an oil level sensor 43 that detects the level of the stored oil.

[0034] Furthermore, the oil tank 6 is connected to the oil passage 25. One end of this oil passage 25 is connected to the oil tank 6, and the other end is connected to the refrigerant passage 21 and the refrigerant passage 22 via the first flow control valve 30. The oil passage 25 supplies oil stored in the oil tank 6 to the refrigerant passage 22 via the first flow control valve 30, so that the refrigerant mixed with the oil from the refrigerant passage 21 can be supplied to the sliding bearing 14 of the motor 1. Specifically, an oil pump 32 that pumps oil and an oil pressure sensor 42 that detects the oil pressure (oil pressure) are provided on the oil passage 25. Furthermore, an oil passage 26 for returning oil is further connected to the oil tank 6. Typically, the oil passage 26 functions to return oil that did not flow through the oil passage 25 to the oil tank 6 via a check valve (relief valve) 37 when the oil passage 26 side of the first flow control valve 30 is closed.

[0035] One end of the pressure reduction passage 27 is connected to the oil tank 6, specifically to the refrigerant passage 24 via the oil tank 6, and the other end is connected to the refrigerant passage 24 downstream of the oil tank 6. The pressure reduction passage 27 is provided with a pressure reduction tank 7, a pressure reduction valve 34, and a check valve 38. Negative pressure created by the operation of the compressor 3 is supplied to the pressure reduction tank 7 via the pressure reduction passage 27 and refrigerant passage 24 on the downstream side (compressor 3 side) of the pressure reduction tank 7, and this negative pressure is stored. When the pressure reduction valve 34 is opened, the negative pressure stored in the pressure reduction tank 7 acts to reduce the pressure inside the space 15a of the motor 1 via the pressure reduction passage 27 and refrigerant passage 24 on the upstream side (oil tank 6 side) of the pressure reduction tank 7. Note that this space 15a is the space inside the motor 1 (inside the housing 15) to which refrigerant is supplied.

[0036] One end of refrigerant passage 28 is connected to refrigerant passage 21 upstream of first and second flow control valves 30, 31, and the other end is connected to refrigerant passage 24 downstream of oil tank 6 or the like, and is provided with a pressure sensor 44 that detects the pressure of the refrigerant and a check valve 39. When first and second flow control valves 30, 31 are closed, refrigerant passage 28 functions to allow refrigerant that did not flow through refrigerant passages 22, 23 to flow into refrigerant passage 24 via check valve (relief valve) 39. One end of refrigerant passage 29 is connected upstream of the connection point of refrigerant passage 21 to refrigerant passage 28, and the other end is connected downstream of the connection point of refrigerant passage 24 to refrigerant passage 28, and is provided with air-conditioner evaporator 8 and expansion valve 35 that decompresses the refrigerant.

[0037] Next, the specific configuration of the refrigerant passage 22 and the first flow rate adjustment valve 30 according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a schematic diagram for specifically explaining the refrigerant passage 22 and the first flow rate adjustment valve 30 according to this embodiment. Fig. 4 is a schematic diagram in which a plurality of refrigerant passages 22 and a plurality of first flow rate adjustment valves 30 are applied to a cross section of the rotating shaft 13 and the sliding bearing 14 in the motor 1.

[0038] As shown in FIG. 4, refrigerant passage 22 has four refrigerant passages 22a to 22d that penetrate sliding bearing 14 to supply refrigerant to different circumferential positions in the gap between the outer circumferential surface of rotating shaft 13 and the inner circumferential surface of sliding bearing 14. Refrigerant passages 22a to 22d are arranged at the same axial position and evenly spaced apart at 90-degree intervals along the circumferential direction. In FIG. 4, refrigerant passage 22a is located at the lower right, refrigerant passage 22b is located at the lower left, refrigerant passage 22c is located at the upper left, and refrigerant passage 22d is located at the upper right. In this case, refrigerant passages 22a and 22b are located below refrigerant passages 22c and 22d. In other words, refrigerant passages 22a and 22b are located at the bottom of sliding bearing 14, and refrigerant passages 22c and 22d are located at the top of sliding bearing 14. In addition, in the rotation direction A1 of the rotating shaft 13, the refrigerant passage 22a is provided upstream of the refrigerant passage 22b, the refrigerant passage 22b is provided upstream of the refrigerant passage 22c, and the refrigerant passage 22c is provided upstream of the refrigerant passage 22d.

[0039] The first flow rate adjustment valve 30 has four first flow rate adjustment valves 30a to 30d so as to adjust the oil content of the refrigerant supplied from these four refrigerant passages 22a to 22d to the sliding bearing 14. These four first flow rate adjustment valves 30a to 30d are provided so as to connect the refrigerant passages 22a to 22d to the refrigerant passage 21 and the oil passage 25, respectively.

[0040] By using four refrigerant passages 22a-22d and four first flow control valves 30a-30d in this way, it is possible to supply refrigerant from different circumferential positions (four positions) to the gap between the rotating shaft 13 and the sliding bearing 14, and the oil content of the refrigerant supplied from these different positions can be changed respectively, that is, the oil content can be set in various ways depending on the circumferential position. Note that below, when there is no need to distinguish between the refrigerant passages 22a-22d, they will be simply referred to as the "refrigerant passage 22," and when there is no need to distinguish between the first flow control valves 30a-30d, they will be simply referred to as the "first flow control valve 30."

[0041] Next, the electrical configuration of the refrigerant circulation system 100 according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a block diagram showing the electrical configuration of the refrigerant circulation system 100 according to this embodiment.

[0042] 5, the refrigerant circulation system 100 has a control device 80 configured to perform various controls in the system. The control device 80 is configured by a computer including one or more processors 80a (typically a CPU) and memory 80b such as ROM and RAM that stores various programs interpreted and executed by the processor 80a (including basic control programs such as an OS and application programs that are started on the OS and realize specific functions) and various data.

[0043] In addition to the pressure sensors 40, 41, 44, oil pressure sensor 42, and oil level sensor 43 described above, the refrigerant circulation system 100 also has a motor rotation speed sensor 45 that detects the motor rotation speed of the motor 1 (the rotation speed of the rotor 11 and rotating shaft 13, which is synonymous with rotational speed), a vehicle speed sensor 46 that detects the speed (vehicle speed) of the vehicle 200, an acceleration sensor 47 that detects the acceleration of the vehicle 200, and an accelerator opening sensor 48 that detects the accelerator opening corresponding to the amount of depression of the accelerator pedal in the vehicle 200.

[0044] Based on the detection signals from these sensors 40 to 48, the control device 80 supplies control signals to the motor 1, the compressor 3, the first flow rate control valves 30a to 30d, the second flow rate control valve 31, the oil pump 32, the pressure reducing valve 34, and the oil level warning light 50. The oil level warning light 50 is a lamp that warns that the level of oil stored in the oil tank 6 (detected by the oil level sensor 43) is below a predetermined value.

[0045] In this embodiment, when a stopped motor 1 is started, the control device 80 controls the first flow rate adjustment valve 30 so that the oil content of the refrigerant supplied from the refrigerant passage 22 to the sliding bearing 14 is higher than when the motor 1 is operating. In this case, the control device 80 controls the first flow rate adjustment valves 30a, 30b provided in the refrigerant passages 22a, 22b so as to increase the oil content particularly from the refrigerant passages 22a, 22b that are provided among the refrigerant passages 22a to 22d so as to supply refrigerant to the lower part of the sliding bearing 14, typically so that the oil content in the refrigerant passages 22a, 22b is approximately 100%.

[0046] Furthermore, when an operating motor 1 is stopped, the control device 80 controls the first flow rate adjustment valve 30 so as to increase the oil content in the refrigerant supplied from the refrigerant passage 22 to the sliding bearing 14, just as it does when the motor 1 is started. In particular, the control device 80 controls the first flow rate adjustment valves 30a, 30b so as to increase the oil content in the refrigerant supplied from refrigerant passages 22a, 22b that are provided to supply refrigerant to the lower part of the sliding bearing 14, typically so that the oil content in the refrigerant passages 22a, 22b is approximately 100%.

[0047] Furthermore, in this embodiment, when motor 1 is operating, control device 80 controls each of first flow rate adjustment valves 30a-30d so that the oil content from refrigerant passage 22a, which is arranged to supply refrigerant to the lower part of sliding bearing 14 among refrigerant passages 22a-22d and is located upstream in rotation direction A1, is greater than the oil content from the other refrigerant passages 22b-22d. Typically, control device 80 controls each of first flow rate adjustment valves 30a-30d so that the oil content from refrigerant passage 22a is close to 100% and the oil content from refrigerant passages 22b-22d is close to 0%.

[0048] [Control content] Next, the control performed by the control device 80 of the refrigerant circulation system 100 in this embodiment will be specifically described. First, the basic concept of control according to this embodiment will be described with reference to Fig. 6. Fig. 6 is a schematic diagram of a cross section of the rotating shaft 13 and the sliding bearing 14 (including the refrigerant passages 22a to 22d) in the motor 1.

[0049] As shown in the left diagram of Fig. 6, when the motor 1 is stopped, the supply of refrigerant from the refrigerant passages 22a-22d into the sliding bearing 14 is stopped, and the outer peripheral surface of the lower part of the rotating shaft 13 is in contact with the inner peripheral surface of the lower part of the sliding bearing 14 due to its own weight. When the stopped motor 1 is started, specifically just before the motor 1 starts (that is, before the motor rotation speed begins to increase after a motor start request is issued), in this embodiment, as shown in the center diagram of Fig. 6, the control device 80 controls the first flow control valves 30a, 30b provided in the refrigerant passages 22a, 22b that supply refrigerant to the lower part of the sliding bearing 14 so as to increase the oil content of the refrigerant supplied from these refrigerant passages. In particular, the control device 80 controls the first flow control valves 30a, 30b so as to make the oil content in the refrigerant passages 22a, 22b 100%. As a result, when motor 1 starts, the refrigerant (refrigerant with a 100% oil content, i.e., oil itself) sprayed from refrigerant passages 22a, 22b, in other words, static pressure caused by the refrigerant, acts from below on rotating shaft 13, causing rotating shaft 13 to float against its own weight from the inner circumferential surface of the lower part of sliding bearing 14 (arrow A2). Therefore, the load capacity of sliding bearing 14 can be adequately ensured when motor 1 starts.

[0050] Next, in this embodiment, when the motor 1 is operating (i.e., while the vehicle 200 is traveling), as shown in the right diagram of FIG. 6 , the control device 80 supplies refrigerant to the lower part of the sliding bearing 14 and controls each of the first flow control valves 30a-30d so that the oil content of the refrigerant passage 22a, which is located upstream in the rotational direction A1, is greater than the oil content of the other refrigerant passages 22b-22d. In particular, the control device 80 controls each of the first flow control valves 30a-30d so that the oil content of the refrigerant passage 22a is close to 100% and the oil content of the refrigerant passages 22b-22d is close to 0%. This allows the viscosity of the refrigerant to be locally increased, that is, the load capacity to be locally increased. Specifically, by flowing a high-viscosity refrigerant below the rotating shaft 13 in the rotational direction A1, the load capacity below the rotating shaft 13 can be improved. As a result, it is possible to reliably prevent the lower part of the rotating shaft 13 from contacting the sliding bearing 14 due to its own weight (arrow A3). On the other hand, the viscosity of the refrigerant is low in areas other than below the rotating shaft 13 (i.e., areas where load capacity is not required), which reduces the lubrication resistance (friction) caused by the oil in the sliding bearing 14. Note that if the average viscosity of the refrigerant supplied to the sliding bearing 14 is made the same, the torque difference will disappear.

[0051] Next, when the operating motor 1 is stopped, specifically immediately before the motor 1 is stopped (i.e., before the motor rotation speed drops to 0), in this embodiment, as shown in the center diagram of FIG. 6, the control device 80 controls the first flow control valves 30a, 30b to supply 100% oil to the refrigerant passages 22a, 22b that supply refrigerant to the lower part of the sliding bearing 14, as in the case of starting the motor 1 described above. This allows a high-viscosity refrigerant to be supplied below the rotating shaft 13 when the motor 1 is stopped, thereby maintaining the floating state of the rotating shaft 13 (arrow A2). Therefore, the floating state of the rotating shaft 13 can be maintained until the rotation of the rotating shaft 13 completely stops, making it possible to accurately prevent the rotating shaft 13 from contacting the sliding bearing 14.

[0052] Next, the overall flow of control according to this embodiment will be described with reference to Fig. 7. Fig. 7 is a time chart showing control according to this embodiment. From top to bottom, Fig. 7 shows the motor rotation speed, a motor start request, the oil content of the refrigerant supplied from refrigerant passage 22a, the oil content of the refrigerant supplied from refrigerant passage 22b, the oil content of the refrigerant supplied from refrigerant passage 22c, and the oil content of the refrigerant supplied from refrigerant passage 22d over time. The motor start request is issued in response to operation of a start switch or accelerator pedal to start vehicle 200.

[0053] As shown in FIG. 7, at time t1, a motor start request is issued, and the control device 80 controls the first flow control valves 30a and 30b provided in the refrigerant passages 22a and 22b, which supply refrigerant to the lower part of the sliding bearing 14, so that the oil content from these refrigerant passages 22a and 22b is 100% (center diagram in FIG. 6). Meanwhile, at time t1, the control device 80 controls the first flow control valves 30c and 30d provided in the refrigerant passages 22c and 22d, which supply refrigerant to the upper part of the sliding bearing 14, so as to maintain the suspension of refrigerant supply from these refrigerant passages 22c and 22d. Immediately after time t1, the control device 80 controls the first flow control valves 30c and 30d so that the oil content of the refrigerant supplied from the refrigerant passages 22c and 22d is also 100%. Note that the oil content is not limited to being strictly 100% as described above, and the oil content may be a value close to 100% (for example, 70 to 80% or more).

[0054] After that, at time t2, the control device 80 starts the motor 1, thereby starting to increase the motor rotation speed. Then, at time t3, while the motor 1 is operating, the control device 80 supplies refrigerant to the lower part of the sliding bearing 14 and controls each of the first flow control valves 30a-30d so that the oil content from the refrigerant passage 22a, which is upstream in the rotation direction A1, is close to 100%, and the oil content from the other refrigerant passages 22b-22d is close to 0% (right diagram in FIG. 6).

[0055] Next, a flowchart showing specific control according to this embodiment will be described with reference to Fig. 8. This flow is repeatedly executed at a predetermined cycle by the control device 80. In detail, the processor 80a in the control device 80 reads a program stored in the memory 80b and executes the program, thereby realizing the control related to this flow.

[0056] First, in step S10, the control device 80 acquires various information such as the detection values ​​detected by the above-mentioned sensors 40 to 48 (FIG. 5). Then, the control device 80 proceeds to step S11 and determines whether the oil level detected by the oil level sensor 43 is equal to or greater than a predetermined value. As a result, if the control device 80 does not determine that the oil level is equal to or greater than the predetermined value (step S11: No), that is, if the oil level is less than the predetermined value, the control device 80 proceeds to step S12 and turns on the oil level warning light 50.

[0057] The control device 80 then proceeds to step S13, where it determines whether the motor 1 is not stopped based on the motor rotation speed detected by the motor rotation speed sensor 45, etc. As a result, if the control device 80 determines that the motor 1 is not stopped (step S13: Yes), that is, if the motor 1 is operating, it proceeds to step S14, where it stops the motor 1. Thereafter, the control device 80 ends the control related to this flow. On the other hand, if the control device 80 does not determine that the motor 1 is not stopped (step S13: No), that is, if the motor 1 is already stopped, it ends the control related to this flow.

[0058] On the other hand, if the control device 80 determines in step S11 that the oil level is equal to or higher than the predetermined value (step S11: Yes), the process proceeds to step S15. In step S15, the control device 80 determines whether the motor 1 is stopped based on the motor rotation speed detected by the motor rotation speed sensor 45, etc. If the control device 80 determines that the motor 1 is stopped (step S15: Yes), the process proceeds to step S16, where it determines whether a motor start request has been made based on the start switch of the vehicle 200 and the accelerator opening detected by the accelerator opening sensor 48, etc. If the control device 80 determines that a motor start request has been made (step S16: Yes), the process proceeds to step S17. In this case, the control device 80 sets a target rotation speed according to the accelerator opening, etc. On the other hand, if the control device 80 does not determine that a motor start request has been made (step S16: No), the process terminates the control of this flow.

[0059] In step S17, the control device 80 starts the oil pump 32 and the compressor 3. Then, the control device 80 proceeds to step S18, where it controls the first flow control valves 30a and 30b provided in the refrigerant passages 22a and 22b so that the oil content of the refrigerant supplied from these refrigerant passages 22a and 22b becomes 100%. Thereafter, in step S19, the control device 80 controls the first flow control valves 30c and 30d so that the oil content of the refrigerant supplied from the refrigerant passages 22c and 22d becomes 100%. Then, the control device 80 proceeds to step S20, where it starts the motor 1.

[0060] Next, the control device 80 proceeds to step S21 and determines the aperture of each of the first flow control valves 30a-30d. For example, the control device 80 determines the required viscosity (i.e., the required oil content) of the refrigerant supplied to the sliding bearing 14 of the motor 1 based on the target rotation speed of the motor 1, and determines the aperture of each of the valves 30a-30d according to this required viscosity. Basically, the control device 80 sets a smaller required viscosity as the target motor rotation speed increases. The control device 80 also determines the aperture of each of the valves 30a-30d so that the oil content of the refrigerant supplied from the refrigerant passage 22a, which is lower among the refrigerant passages 22a-22d and upstream in the rotation direction A1 of the rotating shaft 13, is greater than the oil content of the refrigerant supplied from the other refrigerant passages 22b-22d. The control device 80 then proceeds to step S22 and controls each of the first flow control valves 30a-30d to the aperture determined in step S21, and then ends the control of this flow.

[0061] On the other hand, if the control device 80 does not determine in step S15 that the motor 1 is stopped (step S15: No), that is, if the motor 1 is operating, the control device 80 proceeds to step S23. In step S23, the control device 80 determines whether there is a request to change the motor rotation speed based on the accelerator opening detected by the accelerator opening sensor 48, etc. Note that a request to change the motor rotation speed also includes a request to stop the motor 1. If the control device 80 determines in step S23 that there is a request to change the motor rotation speed (step S23: Yes), the control device 80 proceeds to step S24, and if it does not determine that there is a request to change the motor rotation speed (step S23: No), the control related to this flow ends.

[0062] In step S24, the control device 80 determines the aperture of each of the first flow control valves 30a-30d. For example, the control device 80 determines the required viscosity (i.e., the required oil content) of the refrigerant supplied to the sliding bearing 14 of the motor 1 based on the motor rotation speed (target rotation speed) to be changed, and determines the aperture of each of the valves 30a-30d according to this required viscosity. Basically, the control device 80 sets a lower required viscosity as the motor rotation speed increases. The control device 80 also determines the aperture of each of the valves 30a-30d so that the oil content of the refrigerant supplied from refrigerant passage 22a, which is lower among refrigerant passages 22a-22d and upstream in the rotation direction A1 of the rotating shaft 13, is higher than the oil content of the refrigerant supplied from the other refrigerant passages 22b-22d. The control device 80 then proceeds to step S25 and controls each of the first flow control valves 30a-30d to the aperture determined in step S24. Then, the control device 80 proceeds to step S26, controls the motor 1 to change the motor rotation speed, and then ends the control according to this flow.

[0063] [Action and effect] Next, the operation and effects of the refrigerant circulation system 100 according to this embodiment will be described.

[0064] In this embodiment, the refrigerant circulation system 100, which circulates a refrigerant (CO2 refrigerant) containing oil in CO2, includes a compressor 3 that compresses the refrigerant, a motor 1 having a rotor 11 and a stator 12, a rotating shaft 13 connected to the rotor 11, a sliding bearing 14 that is lubricated using the liquid refrigerant compressed by the compressor 3 and supports the rotating shaft 13, a refrigerant passage 22 that supplies the refrigerant to the sliding bearing 14 of the motor 1, a first flow control valve 30 configured to adjust the oil content in the refrigerant supplied from the refrigerant passage 22 to the sliding bearing 14, and a control device 80 configured to control the first flow control valve 30 when the stopped motor 1 is started so that the oil content is higher than when the motor 1 is operating.

[0065] According to this embodiment, by controlling the first flow rate adjustment valve 30, the control device 80 can increase the oil content in the refrigerant supplied to the sliding bearing 14 when the motor 1 is started; in other words, a refrigerant with a relatively high viscosity can be supplied to the sliding bearing 14. This makes it possible to accurately ensure the load capacity of the sliding bearing 14 when the motor 1 is started. On the other hand, according to this embodiment, while the motor 1 is operating, the oil content in the refrigerant supplied to the sliding bearing 14 can be reduced; in other words, a refrigerant with a relatively low viscosity can be supplied to the sliding bearing 14. This makes it possible to reduce the lubrication resistance (friction) caused by the oil in the sliding bearing 14 while the motor 1 is operating.

[0066] Furthermore, in this embodiment, when the motor 1 is started after being stopped, the control device 80 controls the first flow control valve 30 so that the oil content becomes approximately 100%. This makes it possible to effectively ensure the load capacity of the sliding bearing 14 when the motor 1 is started.

[0067] Furthermore, in this embodiment, the refrigerant passage 22 has a plurality of refrigerant passages 22a to 22d provided in the plain bearing 14 so as to supply refrigerant to a plurality of positions circumferentially on the rotating shaft 13, and the first flow control valve 30 has a plurality of first flow control valves 30a to 30d provided so as to adjust the oil content of the refrigerant supplied from these refrigerant passages 22a to 22d, respectively, and the control device 80 controls the first flow control valves 30a, 30b provided in these refrigerant passages 22a, 22b so as to increase the oil content from the refrigerant passages 22a, 22b provided so as to supply refrigerant to the lower part of the plain bearing 14 within the refrigerant passages 22a to 22d when the motor 1 is started after having been stopped, compared to when the motor 1 is operating.

[0068] According to this embodiment, when the motor 1 starts, the refrigerant injected from the refrigerant passages 22a, 22b, in other words the static pressure of the refrigerant, acts from below on the rotating shaft 13, causing the rotating shaft 13 to float against its own weight from the inner circumferential surface of the lower part of the sliding bearing 14. This makes it possible to effectively ensure the load capacity of the sliding bearing 14 when the motor 1 starts.

[0069] Furthermore, in this embodiment, when the motor 1 is started after being stopped, the control device 80 controls the first flow rate adjustment valves 30a, 30b so that the oil content from the refrigerant passages 22a, 22b becomes approximately 100%. This makes it possible to more effectively ensure the load capacity of the sliding bearing 14 when the motor 1 is started.

[0070] Furthermore, in this embodiment, when the operating motor 1 is stopped, the control device 80 also controls the first flow control valve 30 so that the oil content is higher than when the motor 1 is operating. This ensures the load capacity of the plain bearing 14 when the motor 1 is stopped, and makes it possible to prevent the rotating shaft 13, which is in a rotating state, from coming into contact with the plain bearing 14.

[0071] In this embodiment, the refrigerant circulation system 100 further includes an oil passage 25 that supplies oil to the refrigerant passage 22, and an oil tank 6 that is connected to the oil passage 25 and stores the oil, and the oil tank 6 is configured to separate the oil contained in the refrigerant and store the oil. This allows the oil to be appropriately recovered from the refrigerant and stored in the oil tank 6.

[0072] [Variations] In the above-described embodiment, the refrigerant circulation system 100 uses two refrigerant passages 22a, 22b as the refrigerant passage 22 that supplies refrigerant to the lower part of the plain bearing 14, but in modified examples, only one refrigerant passage 22 may be used as the refrigerant passage 22 that supplies refrigerant to the lower part of the plain bearing 14, or three or more refrigerant passages 22 may be used. [Explanation of symbols]

[0073] 1 motor 3 Compressor 5 Heat exchanger 6. Oil Tank 7. Decompression Tank 11 rotor 12 Stator 13 Rotation axis 14 Plain bearings 21, 23, 24 Refrigerant passages 22(22a~22d) Refrigerant passage 25 Oil passage 27 Decompression Passage 30 (30a-30d) First flow control valve (oil content control valve) 31 Second flow control valve 32 Oil pump 34 Pressure reducing valve 43 Oil level sensor 80 Control device 100 Refrigerant Circulation System 200 vehicles

Claims

1. CO 2 A refrigerant circulation system that circulates a refrigerant containing oil, a compressor that compresses the refrigerant; a motor including a rotor, a stator, a rotating shaft connected to the rotor, and a sliding bearing that supports the rotating shaft and is lubricated using the liquid refrigerant compressed by the compressor; a refrigerant passage that supplies the refrigerant to the sliding bearing of the motor; an oil content adjustment valve configured to adjust the oil content of the refrigerant supplied from the refrigerant passage to the sliding bearing; a control device configured to control the oil content adjustment valve when the motor is started from a stopped state so that the oil content is higher than when the motor is running; A refrigerant circulation system comprising:

2. 2. The refrigerant circulation system according to claim 1, wherein the control device is configured to control the oil content adjustment valve so that the oil content becomes approximately 100% when the motor that has been stopped is started.

3. a plurality of the refrigerant passages are provided in the sliding bearing so as to supply the refrigerant to a plurality of positions in a circumferential direction, and a plurality of the oil content adjustment valves are provided so as to adjust the oil content in the refrigerant supplied from the plurality of refrigerant passages, respectively; the control device is configured to control one or more oil content adjustment valves among the plurality of oil content adjustment valves provided in one or more refrigerant passages so as to increase the oil content from one or more refrigerant passages among the plurality of refrigerant passages that are provided to supply the refrigerant to a lower part of the sliding bearing when the stopped motor is started, compared to when the motor is operating. The refrigerant circulation system according to claim 1 or 2.

4. 4. The refrigerant circulation system according to claim 3, wherein the control device is configured to control the one or more oil content adjustment valves provided in the one or more refrigerant passages so that the oil content from the one or more refrigerant passages becomes approximately 100% when the motor that has been stopped is started.

5. 3. The refrigerant circulation system according to claim 1, wherein the control device is further configured to control the oil content adjustment valve so that, when the operating motor is stopped, the oil content is greater than when the motor is operating.

6. 3. The refrigerant circulation system according to claim 1, further comprising: an oil passage that supplies the oil to the refrigerant passage; and an oil tank connected to the oil passage that stores the oil, wherein the oil tank is configured to separate the oil contained in the refrigerant and store the oil.

7. When the refrigerant passage is defined as a first refrigerant passage, the refrigerant circulation system further includes a second refrigerant passage that communicates with the first refrigerant passage and allows the refrigerant from the compressor to flow into the first refrigerant passage, The oil content adjustment valve is in communication with the first refrigerant passage, the second refrigerant passage, and the oil passage, and thereby, by controlling the oil content adjustment valve, it is possible to change the mixing ratio of the refrigerant from the second refrigerant passage and the oil from the oil passage, and adjust the oil content in the refrigerant supplied from the first refrigerant passage to the sliding bearing. The refrigerant circulation system according to claim 6.

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