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, a coolant passage 22 that supplies the coolant to the slide bearing, an oil tank 6 to store oil, an oil passage 25 to supply the oil to the slide bearing, a flow rate regulation valve 30 provided on the coolant passage, an oil pump 32 provided on the oil passage, and a control device 80 controlling the flow rate regulation valve and the oil pump so that the oil content in the coolant supplied to the slide bearing increases as the number of rotations of the motor detected by a motor rotation number sensor 44 decreases.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 operating conditions of the motor. 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 load capacity of the bearings. 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 (friction losses) tend to increase, so the need for oil in the refrigerant decreases. Therefore, the present inventors conceived of controlling the oil content of the refrigerant (in other words, the mixture ratio (mixing proportion), which corresponds to the viscosity of the refrigerant) 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 in which oil is contained in CO2, 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 for supplying the refrigerant to the sliding bearing of the motor, an oil tank that stores oil, an oil passage for supplying the oil stored in the oil tank to the sliding bearing of the motor, an oil content adjustment mechanism configured to adjust the oil content in the refrigerant supplied to the sliding bearing, including the refrigerant from the refrigerant passage and the oil from the oil passage; a motor rotation speed sensor that detects the rotation speed of the motor; and a control device configured to control the oil content adjustment mechanism in accordance with the rotation speed detected by the motor rotation speed sensor, and the control device is configured to control the oil content adjustment mechanism so that the oil content increases as the rotation speed decreases.

[0009] In the present invention configured as described above, the control device controls the oil content adjustment mechanism to appropriately change the oil content (corresponding to the viscosity of the refrigerant) in the refrigerant used to lubricate the sliding bearing, depending on the motor rotation speed detected by the motor rotation speed sensor. Specifically, the control device controls the oil content adjustment mechanism so that the oil content increases as the motor rotation speed decreases. This allows a refrigerant containing a sufficient amount of oil to be supplied to the sliding bearing when the motor rotation speed is relatively low, ensuring the load capacity of the sliding bearing. On the other hand, the control device controls the oil content adjustment mechanism so that the oil content decreases as the motor rotation speed increases. This allows a refrigerant with a reduced oil content to be supplied to the sliding bearing when the motor rotation speed is relatively high, reducing oil-induced friction (lubrication resistance) in the sliding bearing. As described above, the present invention makes it possible to both ensure the load capacity of the sliding bearing and reduce friction (lubrication resistance) in the sliding bearing, depending on the operating conditions of the motor.

[0010] In the present invention, the control device is preferably configured to control the oil content adjustment mechanism 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.

[0011] In the present invention, the control device is preferably configured to control the oil content adjustment mechanism so that when the rotation speed is in the low rotation speed range, the absolute value of the rate of change of the content relative to the rotation speed is larger than when the rotation speed is in the medium rotation speed range, which is higher than the low rotation speed range, and so that when the rotation speed is in the medium rotation speed range, the absolute value of the rate of change of the content relative to the rotation speed is larger than when the rotation speed is in the high rotation speed range, which is higher than the medium rotation speed range. With the present invention configured in this manner, it is also possible to effectively ensure the load capacity of the sliding bearing and reduce friction in the sliding bearing.

[0012] In the present invention, the oil content adjustment mechanism preferably includes a flow rate adjustment valve provided in the refrigerant passage for adjusting the flow rate of refrigerant flowing through the refrigerant passage, and an oil pump provided in the oil passage for pressurizing oil stored in the oil tank to the sliding bearing, and the control device is configured to control the opening of the flow rate adjustment valve and the discharge rate of the oil pump in order to adjust the content. According to the present invention configured as described above, the oil content is adjusted by the flow rate adjustment valve and the oil pump, so that control responsiveness can be ensured.

[0013] In the present invention, preferably, the refrigerant circulation system further includes, when the refrigerant passage is a first refrigerant passage, a second refrigerant passage for supplying the refrigerant flowing out from the motor to the compressor via an oil tank, a bypass passage for supplying the refrigerant flowing out from the motor to the compressor without passing through the oil tank, and a third refrigerant passage for supplying the refrigerant compressed by the compressor to the oil tank, and the oil content adjustment mechanism includes a first switching valve provided at a connection point between the second refrigerant passage and the bypass passage on the upstream side of the oil tank, and for switching the passage through which the refrigerant flows between the second refrigerant passage and the bypass passage; The oil tank further includes a second switching valve provided at a connection point between the second refrigerant passage and the bypass passage downstream of the oil tank, for switching the passage through which the refrigerant flows between the second refrigerant passage and the bypass passage; an oil discharge valve provided on the oil passage for discharging oil stored in the oil tank to the sliding bearing; and an oil pressurization valve provided on the third refrigerant passage for pressurizing the inside of the oil tank by the pressure of the refrigerant. The control device is configured to control the switching of the passage through which the refrigerant flows by the first and second switching valves, and the opening and closing of the oil discharge valve and oil pressurization valve, in order to adjust the content. According to the present invention configured as described above, the oil content is adjusted by the first and second switching valves, etc., which simplifies control and reduces the cost of the system.

[0014] 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 control each of the first switching valve, the second switching valve, the oil discharge valve, and the oil pressurization valve to adjust the content based on the oil level detected by the oil level sensor. According to the present invention configured as described above, the oil content in the refrigerant can be accurately determined, and the oil content can be efficiently adjusted.

[0015] In the present invention, preferably, when the refrigerant passage is a first refrigerant passage, the refrigerant circulation system further has a second refrigerant passage for supplying the refrigerant flowing out from the motor to the compressor, and the oil tank is provided on the second refrigerant 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.

[0016] 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 when the oil level detected by the oil level sensor is below a predetermined value. According to the present invention configured in this manner, it is possible to prevent problems that may occur due to a lack of oil when there is not enough 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 a first embodiment of the present invention. [Figure 4] 1 is a block diagram showing the electrical configuration of a refrigerant circulation system according to a first embodiment of the present invention. [Figure 5] FIG. 1 is an explanatory diagram of the basic concept of control according to a first embodiment of the present invention. [Figure 6] 4 is a time chart showing control according to the first embodiment of the present invention. [Figure 7] 3 is a flowchart showing a control according to the first embodiment of the present invention. [Figure 8] FIG. 4 is a schematic configuration diagram of a refrigerant circulation system according to a second embodiment of the present invention. [Figure 9] FIG. 5 is a block diagram showing the electrical configuration of a refrigerant circulation system according to a second embodiment of the present invention. [Figure 10] FIG. 6 is an explanatory diagram of control when increasing the oil content in the second embodiment of the present invention. [Figure 11] FIG. 6 is an explanatory diagram of control when reducing the oil content in the second embodiment of the present invention. [Figure 12] 6 is a flowchart showing a control according to a second 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 is provided with oil passage 25 for mixing oil with the refrigerant supplied from refrigerant passage 22 to sliding bearing 14 as described above. Specifically, oil passage 25, like refrigerant passage 22, supplies oil to the gap between rotating shaft 13 and sliding bearing 14. In this embodiment, sliding bearing 14 is configured to be lubricated using a refrigerant that is a mixture of refrigerant (which also contains oil) from refrigerant passage 22 and oil from oil passage 25, in order to ensure its lubrication.

[0031] 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.

[0032] [First embodiment] Next, a first embodiment of the present invention will be described. First, a refrigerant circulation system 100 according to the first embodiment will be specifically described with reference to Fig. 3. Fig. 3 is a schematic configuration diagram of the refrigerant circulation system 100 according to the first embodiment.

[0033] 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, and an air conditioner evaporator 8 that is used in an air conditioner in a vehicle 200. In addition to refrigerant passages 22, 23, and 24 and an oil passage 25 connected to the motor 1 (Fig. 2), the refrigerant circulation system 100 also includes refrigerant passages 21 and 27 through which a refrigerant flows. Note that the refrigerant passage 22 and the refrigerant passage 24 correspond to the "first refrigerant passage" and the "second refrigerant passage," respectively, in the present invention.

[0034] Specifically, refrigerant passage 21 is a passage for supplying refrigerant from compressor 3 via heat exchanger 5 to motor 1, and is connected to both refrigerant passages 22 and 23. Refrigerant passage 21 is also provided with a pressure sensor 41 that detects the pressure of the refrigerant. As described above, refrigerant passage 22 is a passage for supplying refrigerant to sliding 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 23 is provided with a flow rate adjustment valve 30 that adjusts the flow rate of the refrigerant, and refrigerant passage 22 is provided with a check valve 31.

[0035] Refrigerant passage 24 is a passage for supplying (recirculating) the refrigerant flowing out from motor 1 to compressor 3, and is provided with an oil tank 6 for storing oil. Oil tank 6 is configured to separate the oil in 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 for detecting the level of the stored oil.

[0036] Furthermore, the oil passage 25 described above 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 sliding bearing 14 of the motor 1 (FIG. 2). The oil passage 25 supplies the oil stored in the oil tank 6 to the sliding bearing 14, thereby mixing the oil with the refrigerant supplied to the sliding bearing 14 from the refrigerant passage 22. Specifically, an oil pump 32 that pumps the oil, a hydraulic pressure sensor 42 that detects the oil pressure (hydraulic pressure), and a check valve 33 are provided on the oil passage 25.

[0037] One end of the refrigerant passage 27 is connected to the downstream side of the heat exchanger 5 in the refrigerant passage 21 and upstream side of the connection point of the refrigerant passages 22 and 23, and the other end is connected to the downstream side of the oil tank 6 in the refrigerant passage 24, and is provided with an air conditioner evaporator 8 and an expansion valve 34 that decompresses the refrigerant.

[0038] Next, the electrical configuration of the refrigerant circulation system 100 according to the first 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 the first 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 sensor 41, oil pressure sensor 42, and oil level sensor 43 described above, the refrigerant circulation system 100 also has a motor rotation speed sensor 44 that detects the motor rotation speed of the motor 1 (the rotation speed of the rotor 11, rotating shaft 13, which is synonymous with rotational speed), a vehicle speed sensor 45 that detects the speed (vehicle speed) of the vehicle 200, and an accelerator opening sensor 46 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 41 to 46, the control device 80 supplies control signals to the motor 1, the compressor 3, the flow rate adjustment valve 30, the oil pump 32, and the oil level warning light 36. The oil level warning light 36 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 opening of the flow rate adjustment valve 30 and the discharge rate of the oil pump 32 so as to change the oil content in the refrigerant supplied to the sliding bearing 14 of the motor 1 (in other words, so as to change the viscosity of the refrigerant) in accordance with the motor rotation speed detected by the motor rotation speed sensor 44. In this case, the control device 80 controls the flow rate adjustment valve 30 and the oil pump 32 so as to increase the oil content as the motor rotation speed decreases, and decrease the oil content as the motor rotation speed increases. The flow rate adjustment valve 30 and the oil pump 32 constitute the "oil content adjustment mechanism" of the present invention.

[0043] Next, the control performed by the control device 80 of the refrigerant circulation system 100 in the first embodiment will be described in detail. First, the basic concept of the control performed by the control device 80 in the first 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 flow rate adjustment valve 30 and oil pump 32 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 the first embodiment will be described with reference to Fig. 6. Fig. 6 is a time chart showing control according to the first embodiment. From top to bottom, Fig. 6 shows changes over time in the motor rotation speed, motor start request, discharge rate of the oil pump 32 (corresponding to the rotation speed of the oil pump 32), and opening of the flow rate adjustment valve 30. 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, when a motor start request is issued at time t11, the control device 80 sets the discharge rate of the oil pump 32 to a relatively large amount (for example, near the maximum) with the flow rate adjustment valve 30 fully closed. The control device 80 maintains the fully closed state of the flow rate adjustment valve 30 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 an oil content of approximately 100% (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 this time t12, the control device 80 reduces the discharge rate of the oil pump 32 while increasing the aperture of the flow rate control valve 30 in response to the increase in motor rotation speed. Specifically, at time t12, the control device 80 once suddenly increases the aperture of the flow rate control valve 30 and then immediately thereafter suddenly decreases the aperture of the flow rate control valve 30. As a result, immediately after time t12, refrigerant from refrigerant passage 21 is supplied to the stator 12 via refrigerant passage 23, but thereafter, refrigerant from refrigerant passage 21 is supplied to the sliding bearing 14 via refrigerant passage 22; that is, the amount of refrigerant supplied to the sliding bearing 14 increases. As a result, the oil content of the refrigerant supplied to the sliding bearing 14 decreases (the viscosity decreases) in response to the increase in motor rotation speed. Then, at time t13 after time t12, the control device 80 keeps the motor rotation speed constant, and also keeps the discharge amount of the oil pump 32 and the opening degree of the flow rate adjustment valve 30 constant.

[0049] Next, a flowchart showing specific control according to the first 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 according 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 41 to 46 (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 36.

[0051] 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 control device 80 proceeds to step S13. In step S13, the control device 80 determines whether the motor 1 is stopped based on the motor rotation speed detected by the motor rotation speed sensor 44, etc. If the control device 80 determines that the motor 1 is stopped (step S13: Yes), the control device 80 proceeds to step S14, 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 S14: Yes), the control device 80 proceeds to step S15, where it starts the motor 1. On the other hand, if the control device 80 does not determine that the motor 1 is stopped in step S13 (step S13: No), the control device 80 proceeds to step S16, and if the control device 80 does not determine that a motor start request has been made in step S14 (step S14: No), the control device 80 ends the control of this flow.

[0052] Next, after step S15 described above, the control device 80 proceeds to step S16, where it determines the oil content to be applied according to the current motor rotation speed detected by the motor rotation speed sensor 44 (from the map of graph G2 in FIG. 5), and determines the required rotation speed of the oil pump 32 to be set to achieve this oil content. For example, the required rotation speed of the oil pump 32 to be applied according to the oil content is also specified in advance in a map or the like. Then, the control device 80 proceeds to step S17, where it controls the oil pump 32 so that the required rotation speed is set to the required rotation speed determined in step S16.

[0053] Next, the control device 80 proceeds to step S18, where it determines the required opening of the flow rate control valve 30 that should be set to achieve the oil content determined in step S16 above. For example, the required opening of the flow rate control valve 30 that should be applied depending on the oil content is also specified in advance in a map or the like. Then, the control device 80 proceeds to step S19, where it controls the flow rate control valve 30 so that it is set to the required opening determined in step S18. After this, the control device 80 ends the control related to this flow.

[0054] Next, the operation and effects of the refrigerant circulation system 100 according to the first embodiment will be described. In the first embodiment, the control device 80 controls the flow rate adjustment valve 30 and the oil pump 32 so that the oil content of the refrigerant supplied to the sliding bearing 14 of the motor 1 increases as the motor rotation speed detected by the motor rotation speed sensor 44 decreases. This allows a refrigerant containing a sufficient amount of oil to be supplied to the sliding bearing 14 when the motor rotation speed is relatively low, ensuring the load capacity of the sliding bearing 14. On the other hand, the control device 80 controls the flow rate adjustment valve 30 and the oil pump 32 so that the oil content decreases as the motor rotation speed increases. This allows a refrigerant with a reduced oil content to be supplied to the sliding bearing 14 when the motor rotation speed is relatively high, reducing oil-induced friction (lubrication resistance) in the sliding bearing 14. As described above, according to the first embodiment, it is possible to both ensure the load capacity of the sliding bearing 14 and reduce friction (lubrication resistance) of the sliding bearing 14, depending on the operating conditions of the motor 1.

[0055] Furthermore, in the first embodiment, the control device 80 controls the flow rate adjustment valve 30 and the oil pump 32 to adjust the oil content so that the load capacity of the sliding bearing 14 remains approximately constant regardless of the motor rotation speed. By adjusting the oil content in this way to keep the load capacity approximately constant, it is possible to effectively both ensure the load capacity of the sliding bearing 14 and reduce friction on the sliding bearing 14.

[0056] Furthermore, in the first embodiment, the control device 80 controls the flow rate adjustment valve 30 and the oil pump 32 so that the absolute value of the rate of change of the oil content relative to the motor speed is greater in the low rotation speed range than in the medium rotation speed range, and so that the absolute value of the rate of change of the oil content relative to the motor speed is greater in the medium rotation speed range than in the high rotation speed range. By adjusting the oil content in this way, it is possible to effectively both ensure the load capacity of the sliding bearing 14 and reduce friction on the sliding bearing 14.

[0057] In the first embodiment, 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 collected from the refrigerant after use in the motor 1 and stored in the oil tank 6.

[0058] Furthermore, according to this embodiment, when the oil level detected by the oil level sensor 43 is below a predetermined value, the control device 80 issues a notification to that effect using the oil level warning light 36. This makes it possible to prevent problems that may occur due to a lack of oil. Note that notification is not limited to using the oil level warning light 36, and notification that the oil level is below the predetermined value may also be issued using a displayed image, sound, or the like.

[0059] [Second embodiment] Next, a second embodiment of the present invention will be described. Note that, in the following, descriptions of the same configurations as those in the first embodiment will be omitted as appropriate. In other words, configurations that are not particularly described here are assumed to be the same as those in the first embodiment.

[0060] First, a refrigerant circulation system 100a according to the second embodiment will be described in detail with reference to FIG. 8. FIG. 8 is a schematic diagram of the refrigerant circulation system 100a according to the second embodiment. Like the refrigerant circulation system 100 according to the first embodiment, the refrigerant circulation system 100a according to the second embodiment is applied to the vehicle 200 shown in FIG. 1 and includes a motor 1, a compressor 3, a heat exchanger 5, an oil tank 6, and an air-conditioning evaporator 8, as well as refrigerant passages 21, 22, and 24 and an oil passage 25. However, unlike the refrigerant circulation system 100 according to the first embodiment, the refrigerant circulation system 100a according to the second embodiment does not include the refrigerant passage 23, but instead includes a bypass passage 50 and a refrigerant passage 51. The refrigerant passage 51 corresponds to the "third refrigerant passage" in the present invention.

[0061] Furthermore, in the refrigerant circulation system 100a according to the second embodiment, unlike the refrigerant circulation system 100 according to the first embodiment, an oil pump 32 is not provided on the oil passage 25, and instead an oil discharge valve 53 is provided for discharging oil stored in the oil tank 6 to the sliding bearing 14.

[0062] In the refrigerant circulation system 100a according to the second embodiment, the bypass passage 50 is connected at both ends to the refrigerant passage 24, and is a passage for supplying the refrigerant flowing from the motor 1 to the compressor 3 without passing through the oil tank 6. A first switching valve 54 is provided at the connection between the upstream end of the bypass passage 50 and the refrigerant passage 24, upstream of the oil tank 6, for switching the passage through which the refrigerant flows between the refrigerant passage 24 and the bypass passage 50. A second switching valve 55 is provided at the connection between the downstream end of the bypass passage 50 and the refrigerant passage 24, downstream of the oil tank 6, for switching the passage through which the refrigerant flows between the refrigerant passage 24 and the bypass passage 50. These first and second switching valves 54, 55 are three-way valves that switch the passages.

[0063] One end of the refrigerant passage 51 is connected to the refrigerant passage 21 downstream of the heat exchanger 5, and the other end is connected to the oil tank 6. An oil pressurization valve 56 is provided on the refrigerant passage 51, and by opening this oil pressurization valve 56, the refrigerant compressed by the compressor 3 is supplied to the oil tank 6, and the inside of the oil tank 6 can be pressurized by the pressure of the refrigerant.

[0064] Next, the electrical configuration of the refrigerant circulation system 100a according to the second embodiment will be described with reference to Fig. 9. Fig. 9 is a block diagram showing the electrical configuration of the refrigerant circulation system 100a according to the second embodiment.

[0065] As shown in FIG. 9 , in the second embodiment, a control device 80 supplies control signals to an oil discharge valve 53, a first selector valve 54, a second selector valve 55, and an oil pressurization valve 56 based on detection signals from the various sensors 41 to 46. Specifically, the control device 80 controls the switching of the refrigerant passages by the first selector valve 54 and the second selector valve 55 and the opening and closing of the oil discharge valve 53 and the oil pressurization valve 56 so as 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 44. In this case, the control device 80 controls the oil discharge valve 53, the first selector valve 54, the second selector valve 55, and the oil pressurization valve 56 so as to increase the oil content as the motor rotation speed decreases and decrease the oil content as the motor rotation speed increases. The oil discharge valve 53, the first selector valve 54, the second selector valve 55, and the oil pressurization valve 56 constitute an “oil content adjustment mechanism” in the present invention.

[0066] Next, control of the oil discharge valve 53, the first switching valve 54, the second switching valve 55, and the oil pressurizing valve 56 according to the second embodiment will be specifically described with reference to Figures 10 and 11. Figure 10 is an explanatory diagram of control when the oil content rate is increased, and Figure 11 is an explanatory diagram of control when the oil content rate is decreased.

[0067] As shown in FIG. 10 , when increasing the oil content, the control device 80 controls the first and second switching valves 54, 55 to switch the passage through which the refrigerant flows to the bypass passage 50, and also controls the oil discharge valve 53 and oil pressurization valve 56 to open. In this case, the refrigerant that flows out of the motor 1 flows through the bypass passage 50 without flowing to the oil tank 6 via the refrigerant passage 24. Furthermore, the refrigerant compressed by the compressor 3 flows to the oil tank 6 via the refrigerant passage 51 and the oil pressurization valve 56. As a result, the inside of the oil tank 6 is pressurized by the compressed refrigerant, and the oil stored in the oil tank 6 is supplied to the sliding bearing 14 via the oil passage 25 and the oil discharge valve 53. As a result, the oil content of the refrigerant supplied to the sliding bearing 14 increases.

[0068] 11 , when the oil content is to be reduced, the control device 80 controls the first and second switching valves 54, 55 to switch the passage through which the refrigerant flows to the oil tank 6, and also controls the oil discharge valve 53 and oil pressurization valve 56 to close. In this case, the refrigerant that flows out of the motor 1 flows to the oil tank 6 without flowing through the bypass passage 50. On the other hand, the refrigerant compressed by the compressor 3 does not flow to the oil tank 6 via the refrigerant passage 51 because the oil pressurization valve 56 is closed, and the oil in the oil tank 6 is not supplied to the sliding bearing 14 via the oil passage 25 because the oil discharge valve 53 is closed. As a result, the oil content of the refrigerant supplied to the sliding bearing 14 decreases.

[0069] Next, a flowchart showing specific control according to the second embodiment will be described with reference to Fig. 12. This flow is also repeatedly executed at a predetermined cycle by the control device 80. More specifically, the processor 80a in the control device 80 reads a program stored in the memory 80b and executes the program, thereby realizing the control according to this flow.

[0070] 7, the description of steps S20 to S25 will be omitted and only step S26 and thereafter will be described. First, in step S26, the control device 80 performs control to adjust the rotation speed of the compressor 3 in accordance with the operating conditions of the vehicle 200 and the motor 1.

[0071] Next, the control device 80 proceeds to step S27, where it determines whether the oil level detected by the oil level sensor 43 (corresponding to the oil (deposited oil) stored in the oil tank 6, hereinafter referred to as the "deposited oil level" as appropriate) is equal to or greater than a predetermined value. The deposited oil level indicates the oil content in the refrigerant (current oil content). This is because the amount of oil used throughout the refrigerant circulation system 100a is known, and the current oil content is determined by subtracting the amount of oil corresponding to the deposited oil level in the oil tank 6 (the amount of oil stored in the oil tank 6) from this amount. Meanwhile, the predetermined value used in the determination in step S27 corresponds to the oil content that should be applied according to the current motor rotation speed. The control device 80 sets this predetermined value based on the oil content that corresponds to the current motor rotation speed detected by the motor rotation speed sensor 44, with reference to the map of graph G2 in FIG. 5. For this reason, in step S27, the control device 80 determines whether the current oil content is the oil content that should be applied according to the motor rotation speed.

[0072] If, as a result of the determination in step S27, the control device 80 determines that the deposited oil level is equal to or greater than the predetermined value (step S27: Yes), it proceeds to step S28. In this case, the deposited oil level is high and the current oil content is less than the oil content that should be applied in accordance with the motor rotation speed, so it can be said that the oil content of the refrigerant supplied to the sliding bearing 14 should be increased. Therefore, in step S28, the control device 80 controls the first and second switching valves 54, 55 to switch the passage through which the refrigerant flows to the bypass passage 50. The control device 80 then proceeds to step S29, where it controls the oil discharge valve 53 and the oil pressurization valve 56 to open so as to pressurize the oil stored in the oil tank 6 via the refrigerant passage 51 and supply the oil from the oil passage 25 to the sliding bearing 14. After this, the control device 80 ends the control related to this flow.

[0073] On the other hand, if the determination in step S27 indicates that the deposited oil level is not equal to or greater than the predetermined value (step S27: No), i.e., if the deposited oil level is less than the predetermined value, the control device 80 proceeds to step S30. In this case, the deposited oil level is low and the current oil content is equal to or greater than the oil content that should be applied according to the motor rotation speed, so it can be said that the oil content of the refrigerant supplied to the sliding bearing 14 should be reduced. Therefore, in step S30, the control device 80 controls the oil discharge valve 53 and the oil pressurization valve 56 to close in order to stop pressurizing the oil tank 6 via the refrigerant passage 51 and the supply of oil from the oil passage 25. The control device 80 then proceeds to step S31 and controls the first and second switching valves 54 and 55 to switch the refrigerant flow passage to the oil tank 6 side. After this, the control device 80 terminates control of this flow. Note that the reason the first and second switching valves 54 and 55 are controlled after the oil discharge valve 53 and the oil pressurization valve 56 are closed is to prevent backflow of the refrigerant and oil.

[0074] Next, the operation and effects of the refrigerant circulation system 100a according to the second embodiment will be described. In the second embodiment, the control device 80 controls the switching of the refrigerant passages by the first changeover valve 54 and the second changeover valve 55, and the opening and closing of the oil discharge valve 53 and the oil pressurization valve 56, so that the oil content increases as the motor rotation speed decreases, and decreases as the motor rotation speed increases. This also makes it possible to both ensure the load capacity of the sliding bearing 14 and reduce friction (reduce lubrication resistance) of the sliding bearing 14, depending on the operating conditions of the motor 1.

[0075] In particular, unlike the first embodiment, the second embodiment adjusts the oil content by mainly controlling the first and second switching valves 54, 55, without using the flow rate adjustment valve 30 and the oil pump 32, thereby simplifying control and reducing the cost of the system. Note that the first embodiment is more expensive than the second embodiment, but has higher responsiveness in controlling the oil content.

[0076] In addition, in the second embodiment, the control device 80 adjusts the oil content based on the oil level detected by the oil level sensor 43, so that the oil content in the refrigerant can be accurately grasped and the oil content can be adjusted efficiently. [Explanation of symbols]

[0077] 1 motor 3 Compressor 5 Heat exchanger 6. Oil Tank 11 rotor 12 Stator 13 Rotation axis 14 Plain bearings 21, 22, 23, 24, 51 Refrigerant passage 25 Oil passage 30 Flow control valve 32 Oil pump 43 Oil level sensor 44 Motor rotation speed sensor 50 Bypass Passage 53 Oil discharge valve 54 First switching valve 55 Second switching valve 56 Oil pressure valve 80 Control device 100, 100a 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 for supplying the refrigerant to the sliding bearing of the motor; an oil tank that stores the oil; an oil passage for supplying the oil stored in the oil tank to the sliding bearing of the motor; an oil content adjustment mechanism configured to adjust the content of oil in the refrigerant supplied to the sliding bearing, the refrigerant including the refrigerant from the refrigerant passage and the oil from the oil passage; a motor rotation speed sensor for detecting the rotation speed of the motor; a control device configured to control the oil content adjustment mechanism in accordance with the rotation speed detected by the motor rotation speed sensor; and The control device is configured to control the oil content adjustment mechanism so that the content increases as the rotation speed decreases.

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

3. 3. The refrigerant circulation system according to claim 1, wherein the control device is configured to control the oil content adjustment mechanism so that, when the rotation speed is in a low rotation speed range, the absolute value of the rate of change of the content with respect to the rotation speed is larger than when the rotation speed is in a medium rotation speed range higher than the low rotation speed range, and so that, when the rotation speed is in the medium rotation speed range, the absolute value of the rate of change of the content with respect to the rotation speed is larger than when the rotation speed is in a high rotation speed range higher than the medium rotation speed range.

4. the oil content adjustment mechanism includes: a flow rate adjustment valve that is provided in the refrigerant passage and that adjusts the flow rate of the refrigerant flowing through the refrigerant passage; and an oil pump that is provided in the oil passage and that pressure-feeds the oil stored in the oil tank to the sliding bearing, The control device is configured to control the opening degree of the flow rate adjustment valve and the discharge amount of the oil pump in order to adjust the content rate. The refrigerant circulation system according to claim 1 or 2.

5. In the refrigerant circulation system, when the refrigerant passage is a first refrigerant passage, a second refrigerant passage for supplying the refrigerant flowing out from the motor to the compressor via the oil tank; a bypass passage for supplying the refrigerant flowing out of the motor to the compressor without passing through the oil tank; a third refrigerant passage for supplying the refrigerant compressed by the compressor to the oil tank, The oil content adjusting mechanism is a first switching valve provided at a connection point between the second refrigerant passage and the bypass passage on the upstream side of the oil tank, for switching a passage through which the refrigerant flows between the second refrigerant passage and the bypass passage; a second switching valve provided at a connection point between the second refrigerant passage and the bypass passage downstream of the oil tank, for switching a passage through which the refrigerant flows between the second refrigerant passage and the bypass passage; an oil discharge valve provided on the oil passage for discharging the oil stored in the oil tank to the sliding bearing; an oil pressurizing valve provided on the third refrigerant passage for pressurizing the inside of the oil tank by the pressure of the refrigerant, The control device is configured to control switching of the passage through which the refrigerant flows by the first switching valve and the second switching valve, and opening and closing of the oil discharge valve and the oil pressurizing valve in order to adjust the content. The refrigerant circulation system according to claim 1 or 2.

6. The refrigerant circulation system 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 control each of the first switching valve, the second switching valve, the oil discharge valve, and the oil pressurizing valve to adjust the content based on the oil level detected by the oil level sensor. The refrigerant circulation system according to claim 5 .

7. When the refrigerant passage is defined as a first refrigerant passage, the refrigerant circulation system further includes a second refrigerant passage for supplying the refrigerant flowing out of the motor to the compressor, the oil tank is provided on the second refrigerant passage and is configured to separate the oil contained in the refrigerant and store the oil. The refrigerant circulation system according to claim 1 or 2.

8. The refrigerant circulation system 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 when the oil level detected by the oil level sensor is lower than a predetermined value. The refrigerant circulation system according to claim 1 or 2.

Images