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 content ratio of the oil in the coolant is changed suitably.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, an oil tank 6 to store oil, a coolant passage 21 where the coolant from the compressor flows, an oil passage 25 where the oil from the oil tank flows, a coolant passage 24 that supplies a coolant in which the oil from the oil passage is mixed with the coolant from the coolant passage to the slide bearing, and a first flow rate regulation valve 30 and an oil flow rate regulation valve 33 provided at the coolant passage and the oil passage, respectively. A control device 80 controls these flow rate regulation valves so that the oil content ratio in the coolant changes in accordance with the number of rotations of the motor.SELECTED DRAWING: Figure 3

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, while typical refrigerant circulation systems use refrigerants containing oil (refrigerating machine oil) to lubricate and seal the compressor, it can be said that even in systems that use the above-mentioned refrigerant to lubricate the sliding bearings of motors, it is desirable to use refrigerants containing oil to ensure the lubrication of the sliding bearings. In this case, it is thought that the need for oil in the refrigerant to lubricate the sliding bearings varies depending on the motor's operating conditions. Specifically, when the motor rotation speed is relatively low, the load capacity of the sliding bearings tends to be low, so the need for oil in the refrigerant increases to ensure the bearing's load capacity. In contrast, when the motor rotation speed is relatively high, while the load capacity of the sliding bearings is ensured by the wedge effect and throttling effect, losses due to oil resistance tend to increase, so the need for oil in the refrigerant decreases. Therefore, the present inventors conceived of controlling the oil content in the refrigerant (which corresponds to the refrigerant's viscosity) according to the motor rotation speed.

[0007] The present invention has been made to solve the problems of the conventional technology described above, and has an object to provide a refrigerant circulation system that circulates an oil-containing refrigerant and uses this refrigerant to lubricate the sliding bearings of a motor, where the oil content in the refrigerant can be accurately changed in accordance with the motor rotation speed. [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 equipped with 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; an oil tank that stores the oil; a first passage through which refrigerant supplied from the compressor flows, a second passage through which oil supplied from the oil tank flows, and a third passage that connects the first passage with the second passage and supplies the refrigerant obtained by mixing the refrigerant from the first passage with oil from the second passage to the sliding bearing of the motor; flow control valves provided in the first passage and / or the second passage; a motor rotation speed sensor that detects the rotation speed of the motor; and a control device configured to control at least the flow control valve, wherein the control device is configured to control the flow control valve so as to change the oil content of the refrigerant supplied from the third passage to the sliding bearing, in accordance with the rotation speed detected by the motor rotation speed sensor (motor rotation speed).

[0009] In the present invention configured in this manner, the control device controls the flow adjustment valves provided in the first passage through which refrigerant from the compressor flows and / or the second passage through which oil from the oil tank flows, thereby making it possible to appropriately vary the oil content (which corresponds to the viscosity of the refrigerant) in the refrigerant used to lubricate the sliding bearing in accordance with the operating conditions of the motor. For example, the control device can increase the oil content when the motor rotation speed is relatively low, and decrease the oil content when the motor rotation speed is relatively high. In this way, the present invention makes it possible to both ensure the load capacity of the sliding bearing and reduce friction in the sliding bearing (reduce lubrication resistance) in accordance with the operating conditions of the motor.

[0010] In the present invention, the control device is preferably configured to control the flow rate adjustment valve so that the oil content increases as the rotation speed decreases. According to the present invention configured in this way, when the motor rotation speed is relatively low, a refrigerant containing a sufficient amount of oil can be supplied to the sliding bearing, ensuring the load capacity of the sliding bearing. On the other hand, when the motor rotation speed is relatively high, a refrigerant with a reduced oil content can be supplied to the sliding bearing, reducing oil-induced friction in the sliding bearing.

[0011] In the present invention, the control device is preferably configured to control the flow rate adjustment valve to adjust the content so that the load capacity of the sliding bearing remains substantially constant regardless of the rotation speed. According to the present invention configured in this manner, it is possible to effectively ensure both the load capacity of the sliding bearing and reduce friction in the sliding bearing.

[0012] In the present invention, preferably, the flow rate control valve comprises a refrigerant flow rate control valve provided on the first passage and an oil flow rate control valve provided on the second passage, and the control device is configured to reduce the opening of the refrigerant flow rate control valve while increasing the opening of the oil flow rate control valve so that the content increases as the rotation speed decreases. According to the present invention configured in this way, by controlling the aperture of the refrigerant flow rate adjustment valve and the oil flow rate adjustment valve, it is possible to reliably supply refrigerant containing a sufficient amount of oil to the sliding bearing when the motor rotation speed is low, and to effectively ensure the load capacity of the sliding bearing.

[0013] In the present invention, the control device is preferably configured to fully close the refrigerant flow rate adjustment valve and fully open the oil flow rate adjustment valve when the motor is started. With the present invention configured in this way, it is possible to supply a refrigerant with a very high oil content at the time of motor start-up, at which time the load capacity of the sliding bearing becomes extremely low, and it is possible to effectively ensure the load capacity of the sliding bearing.

[0014] In the present invention, preferably, the refrigerant circulation system further has a fourth passage for supplying the refrigerant flowing out from the motor to the compressor, and the oil tank is provided on the fourth passage and configured to separate 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 after use in the motor and stored in the oil tank.

[0015] In the present invention, preferably, the refrigerant circulation system further includes an oil level sensor that detects the oil level of the oil stored in the oil tank, and the control device is configured to notify the user that the oil level detected by the oil level sensor is below a predetermined value and to stop the motor. According to the present invention configured in this manner, problems that may occur due to a lack of oil when there is not enough oil stored in the oil tank can be reliably prevented in advance.

[0016] In a preferred example of the present invention, the coolant circulation system may further include an oil pump that is provided on the second passage and that pumps out oil stored in the oil tank. [Effects of the Invention]

[0017] 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, the oil content of the refrigerant can be accurately changed in accordance with the motor rotation speed. [Brief explanation of the drawings]

[0018] [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] 1 is a block diagram showing an electrical configuration of a refrigerant circulation system according to an embodiment of the present invention. [Figure 5] FIG. 1 is an explanatory diagram of a basic concept of control according to an embodiment of the present invention. [Figure 6] 4 is a time chart showing control according to an embodiment of the present invention. [Figure 7] 4 is a flowchart illustrating a control according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a refrigerant circulation system according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0020] [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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] [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.

[0025] 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.

[0026] 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).

[0027] 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.

[0028] 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.

[0029] 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).

[0030] 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.

[0031] [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.

[0032] 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 further 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 21, the oil passage 25, the refrigerant passage 22, and the refrigerant passage 24 correspond to the "first passage," the "second passage," the "third passage," and the "fourth passage," respectively, in the present invention.

[0033] 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 slide bearing 14 of motor 1, and refrigerant passage 23 is a passage for supplying refrigerant to stator 12 of motor 1 (FIG. 2). Refrigerant passage 21 and refrigerant passage 23 are provided with a first flow control valve 30 and a second flow control valve 31, respectively, to adjust the flow rate of refrigerant flowing through these passages. More specifically, first flow control valve 30 is provided in refrigerant passage 21 between the connection point of refrigerant passage 22 and the connection point of refrigerant passage 23. Refrigerant passage 22 is also provided with a pressure sensor 40 that detects the pressure of the refrigerant. The first flow control valve 30 corresponds to the "refrigerant flow control valve" in this invention.

[0034] 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.

[0035] Furthermore, an oil passage 25 is connected to the oil tank 6. 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. More specifically, it is connected to the refrigerant passage 21 downstream of the first flow rate control valve 30. The oil passage 25 supplies oil stored in the oil tank 6 to the refrigerant passage 21, and the refrigerant mixed with the refrigerant in the refrigerant passage 21 is supplied from the refrigerant passage 22 to the sliding bearing 14 of the motor 1. Specifically, an oil pump 32 that pressurizes the oil, an oil flow rate control valve 33 that adjusts the oil flow rate, and an oil pressure sensor 42 that detects the oil pressure (oil pressure) are provided on the oil passage 25. An oil passage 26 for returning the oil is also 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 flow rate control valve 33 is closed.

[0036] 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.

[0037] 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.

[0038] Next, the electrical configuration of the refrigerant circulation system 100 according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a block diagram showing the electrical configuration of the refrigerant circulation system 100 according to this embodiment.

[0039] 4, 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.

[0040] 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.

[0041] Based on the detection signals from these sensors 40 to 48, the control device 80 supplies control signals to the motor 1, compressor 3, first and second flow rate adjustment valves 30, 31, oil pump 32, oil flow rate adjustment valve 33, pressure reducing valve 34, and 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.

[0042] In this embodiment, the control device 80 controls the first and second flow rate adjustment valves 30, 31 and the oil flow rate adjustment valve 33 to change the oil content in the refrigerant supplied to the sliding bearing 14 of the motor 1 (in other words, to change the viscosity of the refrigerant) in accordance with the motor rotation speed detected by the motor rotation speed sensor 45. In this case, the control device 80 reduces the aperture of the first and second flow rate adjustment valves 30, 31 while increasing the aperture of the oil flow rate adjustment valve 33 so that the oil content increases as the motor rotation speed decreases, and conversely, increases the aperture of the first and second flow rate adjustment valves 30, 31 while decreasing the aperture of the oil flow rate adjustment valve 33 so that the oil content decreases as the motor rotation speed increases.

[0043] [Control content] Next, the control performed by the control device 80 of the refrigerant circulation system 100 in this embodiment will be described in detail. First, the basic concept of the control performed by the control device 80 in this embodiment will be described with reference to Fig. 5. In Fig. 5, the horizontal axis represents the motor rotation speed, and the vertical axis represents the load capacity and oil content of the sliding bearing 14. The load capacity shown on the vertical axis is expressed on a logarithmic scale.

[0044] Graph G1 in Figure 5 shows the load capacity of the sliding bearing 14 that should be achieved in this embodiment according to the motor rotation speed. This graph G1 means that the load capacity of the sliding bearing 14 is kept approximately constant, regardless of the motor rotation speed. In this embodiment, in order to achieve the load capacity of the sliding bearing 14 as shown in graph G1, the control device 80 controls the first and second flow rate adjustment valves 30, 31 and the oil flow rate adjustment valve 33 described above so as to change the oil content (i.e. the viscosity of the refrigerant) in accordance with the motor rotation speed, as shown in graph G2.

[0045] Graph G2 is a map that defines the oil content to be applied according to the motor rotation speed. This map is defined so that the lower the motor rotation speed, the higher the oil content, and vice versa. This is because, at low motor rotation speeds, the load capacity of the sliding bearing 14 is low, so a large amount of oil needs to be applied to the refrigerant to ensure the desired load capacity. Conversely, at high motor rotation speeds, the load capacity of the sliding bearing 14 is ensured by the wedge effect and throttle effect, so there is no need to apply as much oil to the refrigerant. In particular, the map of graph G2 is defined so that the absolute value of the rate of change of the oil content relative to the motor rotation speed is generally larger in the low rotation speed range (e.g., below 3000 rpm) than in the medium rotation speed range (e.g., from 3000 rpm to less than 10000 rpm), and so that the absolute value of the rate of change of the oil content relative to the motor rotation speed is generally larger in the medium rotation speed range than in the high rotation speed range (e.g., above 10000 rpm). That is, this map is defined so that the absolute value of the rate of change of the oil content relative to the motor rotation speed becomes larger as the motor rotation speed decreases, and becomes smaller as the motor rotation speed increases.

[0046] Next, the flow of control performed by the control device 80 in this embodiment will be described with reference to Fig. 6. Fig. 6 is a time chart showing control according to this embodiment. From top to bottom, Fig. 6 shows changes over time in the motor rotation speed, motor start request, opening degree of the oil flow control valve 33, opening degree of the first flow control valve 30, and opening degree of the second flow control valve 31. The motor start request is issued in response to operation of a start switch or accelerator pedal for starting the vehicle 200, for example.

[0047] 6, at time t11, a motor start request is issued, causing the control device 80 to fully open the oil flow rate control valve 33 while keeping the first and second flow rate control valves 30, 31 fully closed. The control device 80 maintains the oil flow rate control valve 33 fully open and the first and second flow rate control valves 30, 31 fully closed until the motor 1 actually starts (until time t12). As a result, when the motor 1 starts, or more specifically, from the time the motor start request is issued until the motor rotation speed begins to increase (times t11 to t12), a refrigerant with a 100% oil content (high viscosity refrigerant) is supplied to the sliding bearing 14 of the motor 1.

[0048] Then, at time t12, the control device 80 starts the motor 1 and increases the motor rotation speed. From time t12, the control device 80 reduces the aperture of the oil flow control valve 33 while increasing the aperture of the first flow control valve 30 in response to the increase in motor rotation speed. As a result, a refrigerant with a decreasing oil content (refrigerant with decreasing viscosity) is supplied to the sliding bearing 14 of the motor 1 in response to the increase in motor rotation speed. Meanwhile, at time t12, the control device 80 once rapidly increases the aperture of the second flow control valve 31 and then immediately rapidly decreases the aperture of the second flow control valve 31. Furthermore, at time t13, which follows time t12, the control device 80 keeps the motor rotation speed constant while maintaining the apertures of the oil flow control valve 33 and the first and second flow control valves 30 and 31 constant.

[0049] Next, a flowchart showing specific control according to this embodiment will be described with reference to Fig. 7. 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.

[0050] 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. 4). 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.

[0051] 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.

[0052] 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.

[0053] In step S17, the control device 80 starts the oil pump 32 and the compressor 3. The control device 80 then proceeds to step S18 and determines the apertures of the oil flow control valve 33 and the first and second flow control valves 30, 31. For example, the control device 80 determines the required viscosity of the refrigerant supplied to the sliding bearing 14 of the motor 1 (i.e., the required oil content) based on the target rotation speed of the motor 1, and determines the aperture of each valve according to this required viscosity. In a typical example, the control device 80 sets the required oil viscosity to a viscosity corresponding to an oil content of 100%, and determines to fully open the oil flow control valve 33 and fully close the first and second flow control valves 30, 31.

[0054] Next, the control device 80 proceeds to step S19, where it controls the oil flow rate adjustment valve 33 and the first and second flow rate adjustment valves 30, 31 so that they are set to the opening degrees determined in step S18. Then, the control device 80 proceeds to step S20, where it starts the motor 1, and then ends the control related to this flow.

[0055] 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 S21. In step S21, 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 S21 that there is a request to change the motor rotation speed (step S21: Yes), the control device 80 proceeds to step S22, and if it does not determine that there is a request to change the motor rotation speed (step S21: No), the control related to this flow ends.

[0056] In step S22, the control device 80 determines the aperture of each of the oil flow rate adjustment valve 33 and the first and second flow rate adjustment valves 30 and 31. For example, the control device 80 calculates the required viscosity of the refrigerant (i.e., the required oil content) to be supplied to the sliding bearing 14 of the motor 1 based on the motor rotation speed to be changed (target rotation speed) and determines the aperture of each valve according to this required viscosity. Basically, the control device 80 sets a smaller required viscosity as the motor rotation speed increases. When a smaller required viscosity is set according to the motor rotation speed in this way, the control device 80 determines at least a relatively small value as the aperture of the oil flow rate adjustment valve 33 and a relatively large value as the aperture of the first flow rate adjustment valve 30.

[0057] Next, the control device 80 proceeds to step S23, where it controls the oil flow rate adjustment valve 33 and the first and second flow rate adjustment valves 30, 31 so as to set the opening degrees determined in step S22. Then, the control device 80 proceeds to step S24, where it controls the motor 1 to change the motor rotation speed, and then ends the control related to this flow.

[0058] [Action and effect] Next, the operation and effects of the refrigerant circulation system 100 according to this embodiment will be described.

[0059] In this embodiment, a refrigerant circulation system 100 that circulates a refrigerant (CO refrigerant) in which CO contains oil includes a compressor 3 that compresses the refrigerant, a rotor 11, a stator 12, a rotating shaft 13 connected to the rotor 11, a motor 1 that is lubricated with a liquid refrigerant compressed by the compressor 3 and includes a sliding bearing 14 that supports the rotating shaft 13, an oil tank 6 that stores oil, a refrigerant passage 21 through which the refrigerant supplied from the compressor 3 flows, an oil passage 25 through which oil supplied from the oil tank 6 flows, and a lubricant passage 21 that communicates with the oil passage 25 and that is resistant to the refrigerant from the refrigerant passage 21. the oil passage 25 is connected to the sliding bearing 14; a first flow control valve 30 and an oil flow control valve 33 are provided in the refrigerant passage 21 and the oil passage 25, respectively; a motor rotation speed sensor 45 that detects the motor rotation speed; and a control device 80 configured to control the first flow control valve 30 and the oil flow control valve 33, and the control device 80 controls the first flow control valve 30 and the oil flow control valve 33 so as to change the oil content of the refrigerant supplied to the sliding bearing 14 via the refrigerant passage 22 according to the motor rotation speed.

[0060] According to this embodiment, the control device 80 controls the first flow rate adjustment valve 30 and the oil flow rate adjustment valve 33, thereby appropriately changing the oil content (corresponding to the viscosity of the refrigerant) in the refrigerant used to lubricate the sliding bearing 14 of the motor 1 in accordance with the operating conditions of the motor 1. Typically, the control device 80 increases the oil content when the motor rotation speed is relatively low, and decreases the oil content when the motor rotation speed is relatively high. As a result, when the motor rotation speed is relatively low, a refrigerant containing a sufficient amount of oil is supplied to the sliding bearing 14, ensuring the load capacity of the sliding bearing 14, while when the motor rotation speed is relatively high, a refrigerant with a reduced oil content is supplied to the sliding bearing 14, reducing friction (lubrication resistance) caused by the oil in the sliding bearing 14.

[0061] Furthermore, according to this embodiment, the lower the motor rotation speed, the greater the oil content, so that the control device 80 reduces the opening of the first flow rate adjustment valve 30, while increasing the opening of the oil flow rate adjustment valve 33. This makes it possible to reliably supply refrigerant containing a sufficient amount of oil to the sliding bearing 14 when the motor rotation speed is low, and effectively ensure the load capacity of the sliding bearing 14.

[0062] Furthermore, according to this embodiment, the control device 80 adjusts the oil content so that the load capacity of the sliding bearing 14 remains approximately constant regardless of the rotation speed, making it possible to effectively both ensure the load capacity of the sliding bearing 14 and reduce friction on the sliding bearing 14.

[0063] Furthermore, according to this embodiment, when starting the motor 1, the control device 80 fully closes the first flow rate adjustment valve 30 and fully opens the oil flow rate adjustment valve 33. This makes it possible to supply a refrigerant with a very high oil content when starting the motor 1, when the load capacity of the sliding bearing 14 becomes very small, and effectively ensure the load capacity of the sliding bearing 14.

[0064] Furthermore, according to this embodiment, the refrigerant circulation system 100 further includes a refrigerant passage 24 for supplying the refrigerant flowing out from the motor 1 to the compressor 3, and the oil tank 6 is provided on the refrigerant passage 24 and 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 after use by the motor 1 and stored in the oil tank 6.

[0065] Furthermore, according to this embodiment, the refrigerant circulation system 100 further includes an oil level sensor 43 that detects the oil level of the oil stored in the oil tank 6. When the oil level detected by the oil level sensor 43 is below a predetermined value, the control device 80 issues a warning to that effect using the oil level warning light 50 and stops the motor 1. This makes it possible to reliably prevent problems that may occur due to a lack of oil in a situation where there is not enough oil stored in the oil tank 6. Note that the warning is not limited to being issued by the oil level warning light 50, and the fact that the oil level is below the predetermined value may also be notified by a displayed image, sound, or the like.

[0066] [Variations] In the above-described embodiment, the refrigerant circulation system 100 has the first flow control valve 30 and the oil flow control valve 33, and the oil content is changed by controlling the aperture of both of these valves. However, in another example, the refrigerant circulation system 100 may have only one of the first flow control valve 30 and the oil flow control valve 33, and the oil content may be changed by controlling the aperture of this one valve. [Explanation of symbols]

[0067] 1 motor 3 Compressor 5 Heat exchanger 6. Oil Tank 7. Decompression Tank 11 rotor 12 Stator 13 Rotation axis 14 Plain bearings 21, 22, 23, 24 Refrigerant passages 25 Oil passage 27 Decompression Passage 30 First flow control valve 31 Second flow control valve 32 Oil pump 33 Oil flow control valve 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; an oil tank that stores the oil; a first passage through which the refrigerant supplied from the compressor flows, a second passage through which the oil supplied from the oil tank flows, and a third passage that communicates the first passage with the second passage and supplies the refrigerant, which is a mixture of the refrigerant from the first passage and the oil from the second passage, to the sliding bearing of the motor; a flow rate adjusting valve provided in the first passage and / or the second passage; a motor rotation speed sensor for detecting the rotation speed of the motor; a controller configured to control at least the flow regulating valve; and the control device is configured to control the flow rate adjustment valve so as to change the oil content in the refrigerant supplied to the sliding bearing from the third passage, in accordance with the rotation speed detected by the motor rotation speed sensor. A refrigerant circulation system.

2. The refrigerant circulation system according to claim 1 , wherein the control device is configured to control the flow rate adjustment valve so that the content increases as the rotation speed decreases.

3. 3. The refrigerant circulation system according to claim 1, wherein the control device is configured to control the flow rate adjustment valve to adjust the content so that the load capacity of the sliding bearing is approximately constant regardless of the rotation speed.

4. the flow rate adjustment valve includes a refrigerant flow rate adjustment valve provided on the first passage and an oil flow rate adjustment valve provided on the second passage, The control device is configured to decrease the opening degree of the refrigerant flow rate control valve while increasing the opening degree of the oil flow rate control valve so that the content increases as the rotation speed decreases. The refrigerant circulation system according to claim 2 or 3.

5. The refrigerant circulation system according to claim 4 , wherein the control device is configured to fully close the refrigerant flow rate adjustment valve and fully open the oil flow rate adjustment valve when the motor is started.

6. a fourth passage for supplying the refrigerant flowing out of the motor to the compressor; the oil tank is provided on the fourth passage and configured to separate the oil contained in the refrigerant and store the oil. The refrigerant circulation system according to claim 1 or 2.

7. The oil tank further includes an oil level sensor that detects the oil level of the oil stored in the oil tank, The control device is configured to notify a user that the oil level detected by the oil level sensor is lower than a predetermined value and to stop the motor. The refrigerant circulation system according to claim 1 or 2.

8. 3. The refrigerant circulation system according to claim 1, further comprising an oil pump provided on the second passage for pumping the oil stored in the oil tank.

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