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 contact between a rotary shaft and the slide bearing is avoided.SOLUTION: A coolant circulation system 100 to circulate a coolant in which CO2 contains oil includes a motor 1 including a slide bearing 14 that lubricates using a coolant compressed with a compressor 3 and supports a rotary shaft 13, a coolant passage 22 to supply the coolant to the slide bearing, a decompression device 10 configured to decompress the pressure of the coolant supplied from the coolant passage to the slide bearing, and an acceleration sensor 47, an external information acquisition device 49, and a control device 80 configured to determine the possibility of the contact of the rotary shaft with the slide bearing in the motor. When it is determined that the rotary axis is possibly in contact with the slide bearing, the control device is configured to control to operate the decompression device.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Conventionally, refrigerant circulation systems have been used in refrigeration cycles used in air conditioners and the like, in which a refrigerant is circulated through a compressor, a heat exchanger, and the like. In this type of refrigerant circulation system, a refrigerant containing oil (refrigerating machine oil) is generally used to lubricate and seal the compressor, and this oil also circulates within the system. For example, Patent Document 1 discloses a technology in which, at the start of the system, the oil-containing refrigerant discharged from the compressor is separated and the oil is extracted, and only the oil is supplied to the suction side of the compressor, thereby sufficiently lubricating the compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-170457 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 liquefies when compressed by a compressor.At the same time, the present inventors considered using a refrigerant that contains oil, as described above, to ensure the lubrication of the motor's sliding bearing.

[0006] Here, when the vehicle collides (which generates a large impact load) or when the vehicle experiences large acceleration in the longitudinal, lateral, yaw, roll, or pitch directions, the rotating shaft of the motor may tilt, causing the rotating shaft to come into contact with the sliding bearing.In such cases, it would be ideal to avoid contact between the rotating shaft and sliding bearing by using oil in the refrigerant to quickly improve the load capacity of the sliding bearing.

[0007] The present invention has been made to solve the problems of the conventional technology described above, and has an object to prevent contact between the rotating shaft of a motor and the sliding bearing in a refrigerant circulation system that circulates an oil-containing refrigerant and uses this refrigerant to lubricate the sliding bearing of a motor. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention is a refrigerant circulation system that circulates a refrigerant made of CO2 containing oil, and is characterized by having: a motor including a compressor that compresses the refrigerant, a rotor and a stator, a rotating shaft connected to the rotor, and a plain bearing that is lubricated using liquid refrigerant compressed by the compressor and supports the rotating shaft; a refrigerant passage for supplying refrigerant to the plain bearing of the motor; a pressure reducing device configured to reduce the pressure of the refrigerant supplied from the refrigerant passage to the plain bearing; a contact determination device configured to determine the possibility of the rotating shaft of the motor coming into contact with the plain bearing; and a control device configured to control the operation of the pressure reducing device when the contact determination device determines that there is a possibility of the rotating shaft coming into contact with the plain bearing.

[0009] In the present invention configured as described above, when there is a possibility that the rotating shaft of the motor may come into contact with the sliding bearing, the control device activates the pressure reducing device, reducing the pressure (ambient pressure) inside the motor and reducing the refrigerant pressure between the rotating shaft and the sliding bearing below liquefaction pressure. This causes the liquid CO2 in the refrigerant to evaporate, causing the highly viscous oil in the refrigerant to precipitate. This precipitated oil adheres to the outer circumferential surface of the rotating shaft and the inner circumferential surface of the sliding bearing. As a result, an oil film (a refrigerant with 100% oil content, i.e., oil itself) forms on the outer circumferential surface of the rotating shaft and the inner circumferential surface of the sliding bearing, rapidly improving the load capacity of the sliding bearing. Therefore, this invention accurately avoids physical contact between the rotating shaft and the sliding bearing.

[0010] 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 refrigerant flowing out from the motor to the compressor, and the pressure reducing device has a pressure reducing tank that stores negative pressure, a pressure reducing passage connected to the second refrigerant passage and in which the pressure reducing tank is provided, and a pressure reducing valve provided on the pressure reducing passage, and the control device is configured to open the pressure reducing valve of the pressure reducing device when the contact determination device determines that there is a possibility that the rotating shaft will come into contact with the sliding bearing. According to the present invention configured as described above, the pressure inside the motor can be quickly reduced by using the negative pressure stored in the pressure reducing tank of the pressure reducing device.

[0011] In the present invention, the pressure reducing device is preferably configured to store the negative pressure created by the operation of the compressor in a pressure reducing tank. According to the present invention configured in this manner, negative pressure can be efficiently stored in the decompression tank.

[0012] In the present invention, preferably, when the refrigerant passage is a first refrigerant passage, the refrigerant circulation system further includes a third refrigerant passage that communicates with the first refrigerant passage and allows refrigerant from the compressor to flow into the first refrigerant passage, an oil passage that communicates with the first refrigerant passage and allows oil to flow into the first refrigerant passage, a refrigerant flow control valve provided on the third refrigerant passage, and an oil flow control valve provided on the oil passage, and the control device is configured to, when the contact determination device determines that there is a possibility that the rotating shaft will come into contact with the sliding bearing, control the pressure reducing device to operate, and also control the refrigerant flow control valve to fully close and the oil flow control valve to fully open. According to the present invention configured in this way, when the pressure inside the motor (ambient pressure) is reduced by operating the pressure reducing device, the pressure of the refrigerant supplied from the first refrigerant passage to the plain bearing can be further reduced. This makes it possible to quickly reduce the pressure of the refrigerant between the rotating shaft and the plain bearing, enabling the oil in the refrigerant to precipitate more quickly.

[0013] In the present invention, preferably, the refrigerant circulation system further includes an oil tank connected to the oil passage and configured to store oil, and the oil tank is configured to separate the oil contained in the refrigerant and store the oil. According to the present invention configured as described above, the oil can be appropriately recovered from the refrigerant and stored in the oil tank.

[0014] In a preferred example of the present invention, the refrigerant circulation system is mounted on a vehicle, and the contact determination device includes one or more sensors that detect acceleration occurring in the vehicle in at least one of the longitudinal, lateral, yaw, pitch, and roll directions, and is configured to determine the possibility of the rotating shaft coming into contact with the sliding bearing based on the output of the one or more sensors. According to the present invention configured in this manner, it is possible to accurately determine the possibility of the rotating shaft coming into contact with the sliding bearing, based on various accelerations that occur in the vehicle.

[0015] Furthermore, in a preferred example of the present invention, the refrigerant circulation system is mounted on a vehicle, and the contact determination device is equipped with an external information acquisition device that acquires external information about the vehicle, and is configured to determine the possibility of the rotating shaft coming into contact with the sliding bearing based on the external information acquired by the external information acquisition device. According to the present invention configured in this manner, it is possible to accurately determine the possibility of the rotating shaft coming into contact with the sliding bearing based on various pieces of information outside the vehicle. [Effects of the Invention]

[0016] According to the present invention, in a refrigerant circulation system in which an oil-containing refrigerant is circulated and the sliding bearing of a motor is lubricated by this refrigerant, contact between the rotating shaft of the motor and the sliding bearing can be avoided. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of a vehicle to which a refrigerant circulation system according to an embodiment of the present invention is applied; [Figure 2] 1 is a schematic configuration diagram of a motor according to an embodiment of the present invention. [Figure 3] 1 is a schematic configuration diagram of a refrigerant circulation system according to an embodiment of the present invention. [Figure 4] 1 is a block diagram showing an electrical configuration of a refrigerant circulation system according to an embodiment of the present invention. [Figure 5] 4 is a time chart showing a basic control according to an embodiment of the present invention. [Figure 6] FIG. 4 is an explanatory diagram of contact avoidance control according to an embodiment of the present invention. [Figure 7] 4 is a time chart showing contact avoidance control according to an embodiment of the present invention. [Figure 8] 4 is a flowchart illustrating a basic control according to an embodiment of the present invention. [Figure 9] 4 is a flowchart showing contact avoidance control according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

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

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

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

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

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

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

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

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

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

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

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

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

[0031] As shown in FIG. 3, in addition to the motor 1, compressor 3, and heat exchanger 5 described above (FIG. 1), the refrigerant circulation system 100 includes an oil tank 6 that stores oil used as a refrigerant, a pressure reduction device 10 including a pressure reduction tank 7 that stores negative pressure for reducing the pressure in the space 15a of the motor 1 (hereinafter referred to as "ambient pressure"), and an air conditioner evaporator 8 that is used in the air conditioner of a 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 in the pressure reduction device 10 using the pressure reduction tank 7. The refrigerant passage 22, the refrigerant passage 24, and the refrigerant passage 21 correspond to the "first refrigerant passage," the "second refrigerant passage," and the "third refrigerant passage," respectively, in the present invention.

[0032] Specifically, refrigerant passage 21 is a passage for supplying refrigerant from compressor 3 to motor 1 via heat exchanger 5, and is connected to both refrigerant passages 22 and 23. As described above, refrigerant passage 22 is a passage for supplying refrigerant to 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.

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

[0034] Furthermore, 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.

[0035] One end of the pressure reduction passage 27 in the pressure reduction device 10 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 atmospheric pressure in 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 a space within the motor 1 (inside the housing 15) to which refrigerant is supplied.

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

[0037] Next, the 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.

[0038] 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.

[0039] 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 includes 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 occurring in the vehicle 200, an accelerator opening sensor 48 that detects the accelerator opening corresponding to the amount of depression of the accelerator pedal in the vehicle 200, and an external information acquisition device 49 that acquires external information about the vehicle 200.

[0040] Specifically, the acceleration sensor 47 includes a plurality of sensors that detect accelerations occurring in the longitudinal, lateral, yaw, pitch, and roll directions of the vehicle 200. The external information acquisition device 49 also includes a camera that captures images of the surroundings of the vehicle 200, a radar (millimeter-wave radar, laser radar) that measures the positions and speeds of various objects around the vehicle 200, an ultrasonic sensor, a navigation system, etc. The navigation system includes a positioning system (GPS system or gyro system) that detects the current position of the vehicle 200, map information, etc., and is capable of identifying roads (traveling paths), intersections, traffic signals, buildings, etc. that exist around the vehicle 200 from these.

[0041] Based on signals from the sensors 40 to 48 and the external information acquisition device 49, the control device 80 supplies control signals to the motor 1, the compressor 3, the first and second flow rate adjustment valves 30, 31, the oil pump 32, the oil flow rate adjustment valve 33, the pressure reducing valve 34, and the oil level warning light 50. The oil level warning light 50 is a lamp that warns that the level of oil stored in the oil tank 6 (detected by the oil level sensor 43) is below a predetermined value.

[0042] In this embodiment, the control device 80 performs basic control (hereinafter referred to as "basic control") on the first and second flow control valves 30, 31 and the oil flow control valve 33 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 45. In this case, the control device 80 reduces the aperture of the first and second flow control valves 30, 31 while increasing the aperture of the oil flow control 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 control valves 30, 31 while decreasing the aperture of the oil flow control valve 33 so that the oil content decreases as the motor rotation speed increases.

[0043] Furthermore, in this embodiment, when there is a possibility that the rotating shaft 13 of the motor 1 will come into contact with the sliding bearing 14, the control device 80 performs control to avoid contact between the rotating shaft 13 and the sliding bearing 14 (hereinafter referred to as "contact avoidance control"). Specifically, as contact avoidance control, the control device 80 performs control to open the pressure reducing valve 34 of the pressure reducing device 10, thereby reducing the atmospheric pressure of the motor 1 using the negative pressure stored in the pressure reducing tank 7. In this way, oil in the refrigerant between the rotating shaft 13 and the sliding bearing 14 is precipitated, and the load capacity of the sliding bearing 14 is quickly improved, thereby avoiding contact between the rotating shaft 13 and the sliding bearing 14.

[0044] More specifically, the control device 80 determines the possibility that the rotating shaft 13 of the motor 1 will come into contact with the plain bearing 14, based on the acceleration in the longitudinal, lateral, yaw, pitch, and roll directions detected by the acceleration sensor 47, and / or external information about the vehicle 200 acquired by the external information acquisition device 49. Essentially, the control device 80 determines a state in which there is a high possibility that the rotating shaft 13 will come into contact with the plain bearing 14 (i.e., a state in which the rotating shaft 13 is about to come into contact with the plain bearing 14), rather than determining a state in which the rotating shaft 13 has actually come into contact with the plain bearing 14. The control device 80, together with the acceleration sensor 47 and the external information acquisition device 49, constitutes the "contact determination device" of the present invention.

[0045] [Control content] Next, the control performed by the control device 80 of the refrigerant circulation system 100 in this embodiment will be specifically described.

[0046] First, the flow of basic control performed by the control device 80 in this embodiment will be described with reference to Fig. 5. Fig. 5 is a time chart showing basic control according to this embodiment. From top to bottom, Fig. 5 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] 5, 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, the contact avoidance control performed by the control device 80 in this embodiment will be described with reference to Figures 6 and 7. First, the basic concept of the contact avoidance control according to this embodiment will be described with reference to Figure 6. Figure 6 is a schematic diagram of a cross section of the rotating shaft 13 and the sliding bearing 14 (including the refrigerant passage 22) in the motor 1.

[0050] As shown in the left diagram of Figure 6, under normal circumstances when there is no possibility that the rotating shaft 13 will come into contact with the sliding bearing 14, a relatively low-viscosity refrigerant (a refrigerant with a relatively low oil content) lubricates the space between the rotating shaft 13 and the sliding bearing 14 (symbol A1). Under such normal circumstances, the refrigerant at least between the rotating shaft 13 and the sliding bearing 14 is in a supercritical state, that is, it has a pressure equal to or greater than the supercritical pressure.

[0051] 6, when vehicle 200 collides (causing a large impact load) or when large acceleration occurs in vehicle 200 in the longitudinal, lateral, yaw, roll, or pitch directions, rotating shaft 13 tilts and moves radially (arrow A2). At this time, in this embodiment, control device 80 determines that there is a possibility that rotating shaft 13 will come into contact with sliding bearing 14 based on the acceleration detected by acceleration sensor 47 and external information acquired by external information acquisition device 49, and performs control to open pressure reduction valve 34 of pressure reduction device 10 to prevent this contact. As a result, the atmospheric pressure inside motor 1 is reduced, and the pressure of the refrigerant between rotating shaft 13 and sliding bearing 14 becomes less than the liquefaction pressure (less than the supercritical pressure). As a result, the liquid CO2 in the refrigerant evaporates and the oil turns into mist (symbol A31), and the highly viscous oil in the refrigerant quickly precipitates, causing the precipitated oil to adhere to the outer surface of the rotating shaft 13 and the inner surface of the sliding bearing 14 (symbols A32, A33).

[0052] As a result, as shown in the right diagram of Figure 6, an oil film (a refrigerant with a 100% oil content, i.e., oil itself) is formed on the outer peripheral surface of the rotating shaft 13 and the inner peripheral surface of the sliding bearing 14 (reference signs A41 and A42), improving the load capacity of the sliding bearing 14. This prevents physical contact between the rotating shaft 13 and the sliding bearing 14 (reference sign A43).

[0053] Here, during contact avoidance control, when the control device 80 performs control to open the pressure reducing valve 34 described above (hereinafter referred to as "first control"), it also performs control to quickly fully open the oil flow rate adjustment valve 33 and quickly fully close the first and second flow rate adjustment valves 30, 31 (hereinafter referred to as "second control") in order to supply high-viscosity refrigerant from the refrigerant passage 22 to the sliding bearing 14 (reference symbol A44 in the right diagram in FIG. 6). This second control has lower responsiveness than the first control, and therefore the second control alone is not enough to prevent contact between the rotating shaft 13 and the sliding bearing 14 due to the large acceleration generated in the vehicle 200 as described above.

[0054] For this reason, in this embodiment, the control device 80 performs the second control in contact avoidance control in addition to the first control, which has high responsiveness. In particular, the control device 80 performs the second control on the oil flow rate adjustment valve 33 and the first and second flow rate adjustment valves 30, 31 so that the pressure of the refrigerant supplied to the sliding bearing 14 is less than the liquefaction pressure. This achieves both a reduction in ambient pressure through the first control and a reduction in the refrigerant supply pressure through the second control, thereby allowing the oil in the refrigerant to precipitate more quickly.

[0055] Next, the overall flow of contact avoidance control according to this embodiment will be described with reference to Fig. 7. Fig. 7 is a time chart showing contact avoidance control according to this embodiment. Fig. 7 shows, from top to bottom, the changes over time in acceleration, the opening degree of the pressure reducing valve 34, the opening degree of the oil flow rate control valve 33, the opening degree of the first flow rate control valve 30, and the opening degree of the second flow rate control valve 31.

[0056] 7, at time t21, the acceleration of vehicle 200 detected by acceleration sensor 47 exceeds a threshold value, and so control device 80 determines that there is a possibility that rotating shaft 13 will come into contact with sliding bearing 14 and starts contact avoidance control. Specifically, in order to quickly improve the load capacity of sliding bearing 14 by reducing the pressure of the refrigerant between rotating shaft 13 and sliding bearing 14 and causing the oil in the refrigerant to precipitate, control device 80 performs control to open pressure reduction valve 34 of pressure reduction device 10 (first control), and also performs control to quickly fully open oil flow adjustment valve 33 and quickly fully close first and second flow adjustment valves 30, 31 (second control).

[0057] After that, at time t22, the acceleration of vehicle 200 detected by acceleration sensor 47 becomes less than the threshold value. Therefore, control device 80 ends contact avoidance control. Specifically, control device 80 performs control to close pressure reducing valve 34 in order to end the reduction in atmospheric pressure by pressure reducing device 10, and also performs control to gradually decrease the opening degree of oil flow control valve 33 while gradually increasing the opening degrees of first and second flow control valves 30, 31 in order to reduce the viscosity of the refrigerant supplied from refrigerant passage 22 to sliding bearing 14.

[0058] [flowchart] Next, a flowchart showing basic control according to this embodiment will be described with reference to Fig. 8. This flow is repeatedly executed at a predetermined cycle by the control device 80. In detail, the processor 80a in the control device 80 reads out a program stored in the memory 80b and executes the program, thereby realizing the control according to this flow.

[0059] First, in step S10, the control device 80 acquires various pieces of information from the above-mentioned sensors 40 to 48 and the external information acquisition device 49. 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] Next, a flowchart showing collision avoidance control according to this embodiment will be described with reference to Fig. 9. This flow is also repeatedly executed at a predetermined cycle by the control device 80. In detail, the processor 80a in the control device 80 reads out a program stored in the memory 80b and executes the program, thereby realizing the control related to this flow.

[0068] First, in step S30, the control device 80 acquires various pieces of information from the above-mentioned sensors 40 to 48 and the external information acquisition device 49. Then, the control device 80 proceeds to step S31, and determines whether or not there is a possibility that the rotating shaft 13 of the motor 1 will come into contact with the sliding bearing 14, based on the acceleration detected by the acceleration sensor 47 and the external information acquired by the external information acquisition device 49.

[0069] In one example, the control device 80 determines that there is a possibility that the rotating shaft 13 will come into contact with the plain bearing 14 when the acceleration of the vehicle 200 in the longitudinal, lateral, yaw, roll, or pitch direction detected by the acceleration sensor 47 (including multiple sensors) is equal to or greater than a threshold. In another example, the control device 80 determines that there is a possibility that the rotating shaft 13 will come into contact with the plain bearing 14 when external information acquired by the external information acquisition device 49 (typically a camera or radar) indicates that the vehicle 200 may collide with an obstacle (another vehicle, a step, etc.) on the travel path. In yet another example, the control device 80 determines that there is a possibility that the rotating shaft 13 will come into contact with the plain bearing 14 when external information acquired by the external information acquisition device 49 (typically a navigation system) indicates a travel path on which acceleration equal to or greater than a threshold (such as acceleration in the yaw direction due to turning) may occur due to the travel of the vehicle 200.

[0070] If the control device 80 determines that there is a possibility that the rotating shaft 13 will come into contact with the sliding bearing 14 (step S31: Yes), the process proceeds to step S32. If the control device 80 does not determine that there is a possibility that the rotating shaft 13 will come into contact with the sliding bearing 14 (step S31: No), the control device 80 terminates the control related to this flow. In step S32, the control device 80 executes contact avoidance control to avoid contact between the rotating shaft 13 and the sliding bearing 14. Specifically, the control device 80 performs control to open the pressure reducing valve 34 of the pressure reducing device 10 (first control) and also performs control to quickly fully open the oil flow rate adjustment valve 33 and quickly fully close the first and second flow rate adjustment valves 30, 31 (second control) in order to quickly improve the load capacity of the sliding bearing 14 by reducing the pressure of the refrigerant between the rotating shaft 13 and the sliding bearing 14 and causing the oil in the refrigerant to precipitate.

[0071] The control device 80 then proceeds to step S33 and determines whether the refrigerant pressure detected by the pressure sensor 40 (the pressure of the refrigerant supplied to the sliding bearing 14) is within a target range. This target range is set based on the liquefaction pressure (supercritical pressure) of the refrigerant at which oil can be separated out. As a result of step S33, if the control device 80 determines that the refrigerant pressure is within the target range (step S33: Yes), the control device 80 proceeds to step S34. In this case, to end contact avoidance control, the control device 80 closes the pressure reduction valve 34 of the pressure reduction device 10 in step S34 and then ends the control related to this flow. At this time, as described above ( FIG. 7 ), the control device 80 gradually decreases the aperture of the oil flow control valve 33 while gradually increasing the apertures of the first and second flow control valves 30, 31 in order to reduce the viscosity of the refrigerant supplied to the sliding bearing 14. On the other hand, if the control device 80 does not determine that the refrigerant pressure is within the target range (step S33: No), the control device 80 returns to step S32. In this case, the control device 80 continues the contact avoidance control until the pressure of the refrigerant falls within the target range.

[0072] [Action and effect] Next, the operation and effects of the refrigerant circulation system 100 according to this embodiment will be described.

[0073] In this embodiment, the refrigerant circulation system 100, which circulates a refrigerant (CO2 refrigerant) containing oil in CO2, includes a compressor 3 that compresses the refrigerant, a rotor 11 and a stator 12, a rotating shaft 13 connected to the rotor 11, a motor 1 equipped with a plain bearing 14 that is lubricated with the liquid refrigerant compressed by the compressor 3 and supports the rotating shaft 13, a refrigerant passage 22 for supplying the refrigerant to the plain bearing 14 of the motor 1, a pressure reducing device 10 configured to reduce the pressure of the refrigerant supplied from the refrigerant passage 22 to the plain bearing 14, an acceleration sensor 47 configured to determine the possibility of the rotating shaft 13 in the motor 1 coming into contact with the plain bearing 14, an external information acquisition device 49, and a control device 80, and the control device 80 is configured to control the operation of the pressure reducing device 10 when it is determined that there is a possibility that the rotating shaft 13 will come into contact with the plain bearing 14.

[0074] Thus, in this embodiment, when there is a possibility that the rotating shaft 13 may come into contact with the sliding bearing 14, the control device 80 activates the pressure reducing device 10, thereby reducing the pressure (ambient pressure) inside the motor 1 and reducing the pressure of the refrigerant between the rotating shaft 13 and the sliding bearing 14 below the liquefaction pressure. As a result, the liquid CO2 in the refrigerant evaporates, causing the highly viscous oil in the refrigerant to precipitate. The precipitated oil adheres to the outer circumferential surface of the rotating shaft 13 and the inner circumferential surface of the sliding bearing 14. As a result, an oil film (a refrigerant with a 100% oil content, i.e., oil itself) is formed on the outer circumferential surface of the rotating shaft 13 and the inner circumferential surface of the sliding bearing 14, which quickly improves the load capacity of the sliding bearing 14. Therefore, this embodiment accurately prevents physical contact between the rotating shaft 13 and the sliding bearing 14.

[0075] 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 pressure reducing device 10 includes a pressure reducing tank 7 for storing negative pressure, a pressure reducing passage 27 connected to the refrigerant passage 24 and in which the pressure reducing tank 7 is provided, and a pressure reducing valve 34 provided on the pressure reducing passage 27, and the control device 80 is configured to open the pressure reducing valve 34 of the pressure reducing device 10 when it is determined that there is a possibility that the rotating shaft 13 will come into contact with the sliding bearing 14. In this way, the pressure inside the motor 1 can be quickly reduced by using the negative pressure stored in the pressure reducing tank 7.

[0076] Furthermore, according to this embodiment, the pressure reducing device 10 is configured to store the negative pressure created by the operation of the compressor 3 in the pressure reducing tank 7. This allows the negative pressure to be efficiently stored in the pressure reducing tank 7.

[0077] Furthermore, according to this embodiment, the refrigerant circulation system 100 further includes a refrigerant passage 21 that communicates with the refrigerant passage 22 and allows refrigerant from the compressor 3 to flow into the refrigerant passage 22, an oil passage 25 that communicates with the refrigerant passage 22 and allows oil to flow into the refrigerant passage 22, a first flow control valve 30 provided in the refrigerant passage 21, and an oil flow control valve 33 provided in the oil passage 25. The control device 80 is configured to control the pressure reduction device 10 to operate, fully close the first flow control valve 30, and fully open the oil flow control valve 33 when it is determined that the rotating shaft 13 may come into contact with the plain bearing 14. This makes it possible to further reduce the pressure of the refrigerant supplied from the refrigerant passage 22 to the plain bearing 14 when the pressure reduction device 10 reduces the pressure (ambient pressure) inside the motor 1. This makes it possible to more quickly reduce the pressure of the refrigerant between the rotating shaft 13 and the plain bearing 14 below the liquefaction pressure, enabling the oil in the refrigerant to precipitate more effectively.

[0078] Furthermore, according to this embodiment, the refrigerant circulation system 100 further includes an oil tank 6 that is connected to the oil passage 25 and stores oil, and the oil tank 6 is configured to separate the oil contained in the refrigerant and store the oil. This allows the oil to be appropriately recovered from the refrigerant and stored in the oil tank 6.

[0079] [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]

[0080] 1 motor 3 Compressor 5 Heat exchanger 6. Oil Tank 7. Decompression Tank 10 Pressure reducing device 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 47 Accelerometer 49 External information acquisition device 80 Control device 100 Refrigerant Circulation System 200 vehicles

Claims

1. CO 2 A refrigerant circulation system that circulates a refrigerant containing oil, a compressor that compresses the refrigerant; a motor including a rotor, a stator, a rotating shaft connected to the rotor, and a sliding bearing that supports the rotating shaft and is lubricated using the liquid refrigerant compressed by the compressor; a refrigerant passage for supplying the refrigerant to the sliding bearing of the motor; a pressure reducing device configured to reduce the pressure of the refrigerant supplied from the refrigerant passage to the sliding bearing; a contact determination device configured to determine the possibility of the rotating shaft of the motor coming into contact with the sliding bearing; a control device configured to perform control to activate the pressure reducing device when it is determined by the contact determination device that there is a possibility that the rotating shaft will come into contact with the sliding bearing; and A refrigerant circulation system comprising:

2. 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 pressure reducing device includes a pressure reducing tank that stores negative pressure, a pressure reducing passage connected to the second refrigerant passage and in which the pressure reducing tank is provided, and a pressure reducing valve provided on the pressure reducing passage, The control device is configured to open the pressure reducing valve of the pressure reducing device when the contact determination device determines that there is a possibility that the rotating shaft will come into contact with the sliding bearing. The refrigerant circulation system of claim 1 .

3. The refrigerant circulation system according to claim 2 , wherein the pressure reducing device is configured to store a negative pressure created by the operation of the compressor in the pressure reducing tank.

4. If the refrigerant passage is a first refrigerant passage, the refrigerant circulation system further includes: a third refrigerant passage communicating with the first refrigerant passage and allowing the refrigerant from the compressor to flow into the first refrigerant passage; an oil passage communicating with the first refrigerant passage and allowing the oil to flow into the first refrigerant passage; a refrigerant flow rate control valve provided on the third refrigerant passage; and an oil flow rate control valve provided on the oil passage. The control device is configured to, when the contact determination device determines that there is a possibility that the rotating shaft will contact the sliding bearing, perform control to operate the pressure reduction device, and perform control to fully close the refrigerant flow rate adjustment valve and fully open the oil flow rate adjustment valve. The refrigerant circulation system according to claim 1 or 2.

5. 5. The refrigerant circulation system according to claim 4, further comprising an oil tank connected to the oil passage and configured to store the oil, the oil tank being configured to separate the oil contained in the refrigerant and store the oil.

6. The refrigerant circulation system is mounted on a vehicle, The contact determination device is configured to include one or more sensors that detect acceleration occurring in at least one of a longitudinal direction, a lateral direction, a yaw direction, a pitch direction, and a roll direction in the vehicle, and to determine the possibility of the rotating shaft coming into contact with the sliding bearing based on the output of the one or more sensors. The refrigerant circulation system according to claim 1 or 2.

7. The refrigerant circulation system is mounted on a vehicle, The contact determination device is configured to include an external information acquisition device that acquires external information about the vehicle, and to determine the possibility of the rotating shaft coming into contact with the sliding bearing based on the external information acquired by the external information acquisition device. The refrigerant circulation system according to claim 1 or 2.

Images