Motor system

Abstract

To provide a motor system equipped with a sliding bearing that uses CO2 refrigerant as a lubricant, the motor system being capable of suppressing leakage of the CO2 refrigerant from between a rotor shaft and a housing.SOLUTION: A motor system S includes a first refrigerant supply passage 18b that communicates with a sliding surface 22 of a sliding bearing 20. The sliding bearing 20 is configured to be lubricated by a supercritical fluid CO2 refrigerant R supplied to the support space 22a through the first refrigerant supply passage 18b. The motor system S further includes a second refrigerant supply passage 18c that extends through at least a housing 15 and communicates with an inner space 15b of the housing 15, and the second refrigerant supply passage 18c includes an expansion chamber 118b for expanding the supercritical fluid CO2 refrigerant R, and is configured to communicate with the inner space 15b of the housing 15 through the vicinity of a seal chamber 50 from the expansion chamber 118b.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a motor system, and more particularly to a motor system having a sliding bearing. [Background technology]

[0002] Conventionally, the rotor shaft of an electric motor is configured to be supported by a rolling bearing or a plain bearing. For example, in the electric motor described in Patent Document 1, the rotor shaft is supported by a rolling bearing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-17291 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, when the rotation speed of an electric motor increases (for example, above 30,000 rpm), rolling bearings suffer from rolling fatigue. To avoid this, such ultra-high-speed rotation motors may use oil-lubricated sliding bearings instead of rolling bearings. In oil-lubricated sliding bearings, oil is supplied to the sliding bearings. However, in this case, the viscosity of the oil causes a problem of stirring resistance loss when the rotor shaft rotates at high speed.

[0005] In recent years, environmentally friendly technologies have been developed for vehicles, etc., using natural refrigerants (such as CO2 refrigerants) in their refrigeration cycles. In a CO2 refrigeration cycle, the CO2 refrigerant changes into one of four states: gas, liquid, gas-liquid mixture, and supercritical fluid, depending on the pressure and temperature.

[0006] The inventors therefore investigated using a CO2 refrigerant instead of oil in a sliding bearing. That is, a CO2 refrigerant (supercritical fluid) is used to lubricate the sliding bearing, and the CO2 refrigerant used for lubrication is then used to cool the coil end. In this case, the CO2 refrigerant (gas) after heat exchange at the coil end has a much lower viscosity than oil, and so the use of such a CO2 refrigerant can significantly reduce agitation resistance loss compared to a liquid oil refrigerant with a certain viscosity.

[0007] However, the inventors discovered a new problem to be solved in this case: if part of the supercritical fluid CO2 refrigerant vaporizes near the sliding bearing, the CO2 gas will leak out through the seal member between the rotor shaft and the housing.To address this problem, it would be possible to use a seal member for gas (for example, a mechanical seal) rather than a seal member for liquid, but this would make the device structure complex and increase manufacturing costs.

[0008] The present invention has been made to solve the problems of the conventional technology described above, and aims to provide a motor system equipped with a sliding bearing that uses a CO2 refrigerant for lubrication, which is capable of preventing CO2 refrigerant from leaking from between the rotor shaft and housing. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a motor system comprising: a rotor shaft extending in the axial direction; a plain bearing that rotatably supports the rotor shaft; a housing that holds the plain bearing; and a seal member that seals between the housing and the end of the rotor shaft extending to the outside of the housing, wherein the housing accommodates the seal member in a seal chamber that communicates with the outside of the housing via a through hole, and holds the plain bearing in a bearing chamber that communicates with the seal chamber and the internal space of the housing; the motor system further comprises a first refrigerant supply passage that extends through the housing and the plain bearing and communicates with a sliding surface of the plain bearing against the rotor shaft, the plain bearing being configured to be lubricated by supercritical CO2 refrigerant supplied to the support space between the plain bearing and the rotor shaft through the first refrigerant supply passage; and the motor system further comprises a second refrigerant supply passage that extends at least through the housing and communicates with the internal space of the housing, the second refrigerant supply passage having an expansion chamber for expanding the supercritical CO2 refrigerant, and is configured to communicate from the expansion chamber through the vicinity of the seal chamber to the internal space of the housing.

[0010] In the present invention configured as described above, the motor system can supply CO2 refrigerant to the support space between the plain bearing and the rotor shaft through the first refrigerant supply passage. The CO2 refrigerant supplied to the support space can lubricate the sliding surface of the plain bearing. The CO2 refrigerant then sprays from the support space into the internal space of the housing and can flow from the support space into the seal chamber. When sprayed into the internal space of the housing, the CO2 refrigerant expands, becoming a low-temperature, low-pressure gas-liquid mixture, cooling the inside of the motor. The CO2 refrigerant that flows into the seal chamber fills the seal chamber. The seal chamber is then pressurized by the CO2 refrigerant in the support space. Meanwhile, the supercritical fluid CO2 refrigerant flows through the second refrigerant supply passage and expands in the expansion chamber, becoming a low-temperature, low-pressure gas-liquid mixture. This low-temperature CO2 refrigerant passes near the seal chamber, cooling the refrigerant in the seal chamber. In this way, the refrigerant in the seal chamber is maintained in a pressurized and cooled state. This prevents the refrigerant in the seal chamber from gasifying and maintains it as a supercritical fluid during motor operation. Therefore, in the present invention, the sliding bearing can be lubricated using CO2 refrigerant, and leakage of CO2 refrigerant to the outside of the housing through the seal member between the rotor shaft and the housing can be prevented.

[0011] The present invention preferably further includes a refrigerant circulation system that supplies a supercritical fluid CO refrigerant to the first refrigerant supply passage and the second refrigerant supply passage. According to the present invention configured in this manner, a motor system including the refrigerant circulation system and a motor can be mounted on, for example, a vehicle.

[0012] In the present invention, the refrigerant circulation system preferably includes a compressor that compresses gaseous CO2 refrigerant recovered from the housing to generate a supercritical CO2 refrigerant, and a condenser that condenses the CO2 refrigerant output from the compressor, exchanges heat with the external environment, and supplies the supercritical CO2 refrigerant to the first refrigerant supply passage and the second refrigerant supply passage. According to the present invention configured in this manner, the gaseous CO2 refrigerant after heat exchange in the motor is compressed by the compressor to generate a high-temperature, high-pressure supercritical fluid (compression stroke). Next, the compressed CO2 refrigerant is condensed in the condenser to generate a medium-temperature, high-pressure CO2 refrigerant (condensation stroke). The condensed CO2 refrigerant is then expanded in the motor to generate a low-temperature, low-pressure gas-liquid mixture (expansion stroke). Finally, the CO2 refrigerant is evaporated by heat exchange in the motor to generate a high-temperature, low-pressure gaseous CO2 refrigerant (evaporation stroke). This is how the present invention forms a refrigeration cycle.

[0013] In the present invention, the sealed chamber is preferably configured to hold CO2 refrigerant supplied through the first refrigerant supply passage and the support space. According to the present invention configured in this manner, the sealed chamber in which the seal member is disposed can be filled with CO2 refrigerant.

[0014] In the present invention, the refrigerant circulation system preferably recovers at least the gaseous CO2 refrigerant from inside the housing. According to the present invention configured in this way, the CO2 refrigerant in a gas-liquid mixed state sprayed out from the support space at an appropriate flow rate is vaporized by heat exchange inside the motor, so the refrigerant circulation system can recover the gaseous CO2 refrigerant.

[0015] In the present invention, the first refrigerant supply passage and the second refrigerant supply passage are preferably formed to branch off from a main refrigerant supply passage that extends through the housing. According to this configuration of the present invention, the CO2 refrigerant branches off from the main refrigerant supply passage to the first refrigerant supply passage and the second refrigerant supply passage, and is used to lubricate the sliding bearing, cool the motor components, and cool the seal chamber, respectively.

[0016] In the present invention, the seal preferably includes an annular stationary seal fixed to the seal chamber so as to surround the through hole, and an annular rotary seal fixed to the rotor shaft, the stationary seal and the rotary seal sliding against each other when the rotor shaft rotates. According to the present invention configured in this manner, the seal can seal the supercritical fluid CO refrigerant in the seal chamber by the sliding between the stationary seal and the rotary seal. [Effects of the Invention]

[0017] The electric motor system according to the present invention can provide a motor system equipped with a sliding bearing that uses a CO2 refrigerant for lubrication, which can prevent the CO2 refrigerant from leaking from between the rotor shaft and the housing. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic configuration diagram of a motor system according to an embodiment of the present invention. [Figure 2] 1 is an explanatory diagram of a refrigeration cycle of a refrigerant according to an embodiment of the present invention. [Figure 3] 1 is an explanatory diagram of a bearing structure according to an embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory diagram of a bearing structure according to a comparative example of the present invention. [Figure 5] 10A and 10B are explanatory diagrams of a bearing structure according to a modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a motor system according to an embodiment of the present invention will be described with reference to the accompanying drawings. [Overall configuration] First, the overall configuration of a motor system according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram of a motor system according to this embodiment. The motor system S shown in Fig. 1 is mounted on a vehicle such as an electric vehicle, and can provide rotational driving force to the vehicle.

[0020] The motor system S includes a motor (electric motor) 1 and a refrigerant circulation system 8. The motor 1 provides rotational driving force to the vehicle. The refrigerant circulation system 8 is configured to circulate a refrigerant R in a refrigeration cycle to cool the motor 1. That is, in this refrigeration cycle, the expansion stroke and evaporation stroke of the refrigerant R are carried out within the motor 1, and the compression stroke and condensation stroke of the refrigerant R are carried out in the refrigerant circulation system 8. In this embodiment, it is preferable to use a CO2 refrigerant, which is a natural refrigerant, as the refrigerant R. Note that the refrigerant R may also be a mixture of a natural refrigerant and oil at a predetermined mixing ratio.

[0021] [Configuration of refrigerant circulation system] The refrigerant circulation system 8 includes a compressor 81 for compressing the refrigerant R, a condenser, a fan, etc., and also has a heat exchanger (condenser) 83 for cooling the refrigerant R compressed by the compressor 81, piping 85, and valves (not shown). The motor 1 is incorporated into the refrigerant circulation system 8.

[0022] [Motor configuration] The motor 1 according to this embodiment includes a rotor 11, a stator 12, a rotor shaft (rotating shaft) 13 fixed to the rotor 11 and extending in the axial direction, a pair of bearings (slide bearings) 20 that rotatably support the rotor shaft 13, a housing 15 that accommodates and supports the rotor 11, stator 12, rotor shaft 13, and bearings 20, and a seal member 16 that seals between the housing 15 and the rotor shaft 13. One end of the rotor shaft 13 is connected to a transaxle (not shown) of the vehicle or the like.

[0023] The stator 12, which has a substantially cylindrical shape, is configured by winding a coil 12b around a stator core 12a. As shown in FIG. 1, the coil 12b is wound around the stator core 12a, so that coil ends 12c protrude from both axial ends of the stator core 12a. The rotor 11 has a rotor core and a plurality of permanent magnets attached to the rotor core. The rotor shaft 13 is fixed to the rotor core. The rotor 11 is configured to be rotatable within the stator 12, with the rotor shaft 13 as the rotation axis.

[0024] The seal member 16 seals the gap between the housing 15 and the end of the rotor shaft 13 that protrudes to the outside through a through hole 15a formed in the housing 15, thereby preventing leakage of the refrigerant R from the inside of the housing 15 to the outside.

[0025] The motor 1 also has a refrigerant supply passage 18 that supplies the refrigerant R supplied from the refrigerant circulation system 8 to the bearing 20, and a refrigerant discharge passage 19 that returns the refrigerant R from inside the motor 1 to the refrigerant circulation system 8. More specifically, the refrigerant supply passage 18 supplies the refrigerant R to the gap between the rotor shaft 13 and the bearing 20. As a result, the refrigerant R is supplied to the sliding surface of the bearing 20 relative to the rotor shaft 13 and is used to lubricate the bearing 20. In this embodiment, the refrigerant R, which is a high-pressure supercritical fluid, is used as a lubricant for the bearing 20. The refrigerant R used as a lubricant leaves the bearing 20 and enters the housing 15, where it is vaporized by heat exchange with the motor components, and then returns to the refrigerant circulation system 8 through the refrigerant discharge passage 19.

[0026] The motor 1 is an ultra-high-speed motor and is configured to operate at high rotational speeds, for example, exceeding 30,000 rpm. Therefore, if a rolling bearing were used for the bearing 20, rolling fatigue would be a problem. Furthermore, if a typical oil-lubricated sliding bearing were used, the rotor shaft 13 would suffer from significant oil agitation resistance losses. Therefore, in this embodiment, instead of oil, a sliding bearing using a supercritical fluid refrigerant R with significantly lower viscosity than oil is used as the bearing 20. In this embodiment, by supplying the supercritical fluid refrigerant R, which has a higher density and viscosity than the gaseous refrigerant R, to the bearing 20, the necessary liquid film can be provided on the sliding surface. This eliminates problems such as rolling fatigue and oil agitation resistance.

[0027] The motor 1 also has a guide member 30 for blowing the refrigerant R provided for lubricating the bearings 20 onto high temperature parts inside the motor 1. The guide member 30 will be described later.

[0028] [Refrigerant refrigeration cycle] Next, the refrigeration cycle of refrigerant R in this embodiment will be described with reference to Figure 2. Figure 2 is a pH diagram of CO2 refrigerant, with the horizontal axis representing enthalpy and the vertical axis representing pressure. Figure 2 also shows the viscosity (μPa·s) of CO2 refrigerant. CO2 refrigerant becomes a supercritical fluid when the pressure and temperature are increased from the ambient environment (room temperature, 1 atmosphere) and it reaches its critical point (31°C, 7.4 MPa).

[0029] First, in the refrigeration cycle (ABCD) of this embodiment, a compression stroke (AB) is performed by the compressor 81. The compressor 81 is a rotary type, and receives high-temperature, low-pressure CO2 refrigerant R (gas) from the motor 1 via piping 85 (point A), compresses the received refrigerant R, and discharges high-temperature, high-pressure CO2 refrigerant R (supercritical fluid) (point B).

[0030] Next, a condensation process (BC) is performed by the heat exchanger 83. The heat exchanger 83 receives the high-temperature, high-pressure CO2 refrigerant R (point B) and exchanges heat with the external environment (cold air, cooling water, etc.) to generate a medium-temperature, high-pressure CO2 refrigerant R (supercritical fluid) (point C). The medium-temperature, high-pressure CO2 refrigerant R is supplied to the bearings 20 of the motor 1 to lubricate the bearings 20.

[0031] Furthermore, an expansion stroke (CD) takes place inside the motor 1. The CO2 refrigerant R passes through the annular support space between the bearing 20 and the rotor shaft 13 and the injection passage, and enters the internal space 15b of the housing 15. At this time, the CO2 refrigerant R expands as it moves from the narrow space to the wide space, becoming a low-temperature, low-pressure CO2 refrigerant R (gas-liquid mixture) (point D). Furthermore, an evaporation stroke (DA) takes place inside the motor 1. The low-temperature, low-pressure CO2 refrigerant R evaporates within the housing 15 by exchanging heat with the high-temperature parts of the motor 1, becoming a high-temperature, low-pressure CO2 refrigerant R (gas). This high-temperature, low-pressure CO2 refrigerant R is returned to the compressor 81 (point A).

[0032] [Bearing structure] The bearing structure of this embodiment will be described with reference to Figures 3 and 4. Figure 3 is an explanatory diagram of the bearing structure of this embodiment, and Figure 4 is an explanatory diagram of a bearing structure according to a comparative example. In this embodiment, as shown in Figure 3, a through hole 15a provided in the housing 15 and extending in the axial direction L connects the outside of the housing 15 with an internal space 15b. Note that the diameter of the through hole 15a is reduced on the outer surface side of the housing 15 by an extension wall 15c.

[0033] The through hole 15a has a seal chamber 50, which is a space adjacent to the extension wall 15c, and a bearing chamber 52, which is a space that communicates with the seal chamber 50 and the internal space 15b. The bearing 20 is fitted into and attached to the bearing chamber 52. That is, the seal chamber 50 extends in the axial direction L between the bearing 20 and the extension wall 15c.

[0034] The seal member 16 is disposed within the seal chamber 50. The seal member 16 includes an annular stationary seal member 16a fixed to the extension wall 15c and an annular rotary seal member 16b fixed to the rotor shaft 13. When the rotor shaft 13 rotates, the rotary seal member 16b and the stationary seal member 16a slide against each other to seal between the housing 15 and the rotor shaft 13.

[0035] As shown in FIG. 3 , bearing 20 rotatably supports the end of rotor shaft 13. Bearing 20 includes a substantially cylindrical main body 21, an end face (rotor end face) 24a facing rotor 11, and an end face (seal end face) 24b facing seal member 16. The inner circumferential surface of main body 21 is a sliding surface 22 with rotor shaft 13. Rotor end face 24a has an inclined surface 25 cut into a conical shape. Inclined surface 25 is a thrust surface. Main body 21 is formed with a through-hole 23 extending from the radially outer side of rotor shaft 13 toward the center, penetrating the side wall from the outer circumferential surface 26 of main body 21 to communicate with sliding surface 22. Through-hole 23 communicates with refrigerant supply passage 18 and forms part of refrigerant supply passage 18.

[0036] The guide member 30 is an umbrella-shaped member and has a conical guide surface (inclined surface) 31 whose diameter increases in the axial direction L from the bearing 20 toward the rotor 11. The guide surface 31 of the guide member 30 and the inclined surface 25 of the bearing 20 have substantially the same inclination angle with respect to the axial direction L so that they can slide against each other. The guide member 30 is attached to the rotor shaft 13 so as to be in close proximity to the bearing 20. Specifically, the guide surface 31 and the inclined surface 25 are spaced a predetermined distance d in the axial direction L to form an annular injection passage 32. The injection passage 32 determines the injection direction and also functions as an expansion valve. The guide surface 31 of the guide member 30 is formed so that the coil end 12c of the stator 12, which is a high-temperature portion, is located on its extension. Incidentally, having the inclined surface 25 on the rotor end surface 24a of the bearing 20 is advantageous for guiding the refrigerant R, but the inclined surface 25 is not necessary.

[0037] Refrigerant supply passage 18 is connected to heat exchanger 83 by piping 85 (see FIG. 1). Within housing 15, refrigerant supply passage 18 includes main refrigerant supply passage 18a connected to piping 85, and first refrigerant supply passage 18b and second refrigerant supply passage 18c branching off from main refrigerant supply passage 18a upstream of through-hole 23. First refrigerant supply passage 18b communicates with through-hole 23 of bearing 20.

[0038] The second refrigerant supply passage 18c includes an inlet passage 118a branching from the main refrigerant supply passage 18a, an expansion chamber 118b, and a cooling passage 118c that communicates with the expansion chamber 118b through the vicinity of the seal chamber 50 and into the internal space 15b of the housing 15. The inlet passage 118a has a small flow path cross-sectional area, similar to the main refrigerant supply passage 18a and the first refrigerant supply passage 18b, and communicates with the expansion chamber 118b. The expansion chamber 118b has a relatively large internal space. Therefore, in this embodiment, the inlet passage 118a functions as an expansion valve. The cooling passage 118c is configured to pass through the vicinity of the seal chamber 50 (for example, through a circumferential side portion of the seal chamber 50 having a cylindrical cross section and / or the extension wall 15c).

[0039] When the motor 1 is operating, the refrigerant circulation system 8 pressure-feeds the medium-temperature, high-pressure supercritical fluid refrigerant R through the first refrigerant supply passage 18b and the through-hole 23 to the bearing 20. The supercritical fluid refrigerant R maintains a high pressure state and fills the narrow support space 22a between the rotor shaft 13 and the bearing 20, lubricating the bearing 20. The medium-temperature, high-pressure refrigerant R in the support space 22a flows in the axial direction L through the narrow support space 22a toward the guide member 30 and then passes through the narrow injection passage 32 to be injected into the internal space 15b of the housing 15. The refrigerant R expands upon entering the large internal space 15b of the housing 15, becoming a gas-liquid mixture. The expanded low-temperature, low-pressure refrigerant R is further directed along the guide surface 31 of the guide member 30 and guided toward the coil end 12c. Upon reaching the coil end 12c, the refrigerant R cools the coil end 12c. The high-temperature, low-pressure refrigerant R that has been vaporized through heat exchange with the coil end 12c passes through the refrigerant discharge passage 19 and is discharged to the outside.

[0040] Furthermore, the medium-temperature, high-pressure refrigerant R in the support space 22a flows in the axial direction L and also flows into the seal chamber 50, filling the seal chamber 50 after the motor 1 is started. For example, when the motor 1 is started, the supercritical fluid refrigerant R is not depressurized to the expansion pressure (point D in FIG. 2) in the expected refrigeration cycle when it flows into the seal chamber 50, but it is slightly expanded or depressurized, and supercritical fluid refrigerant R or refrigerant R in a gas-liquid mixed state can be generated at a moderate pressure (pressure between points C and D).

[0041] Meanwhile, the supercritical fluid refrigerant R enters the inlet passage 118a of the second refrigerant supply passage 18c. As the refrigerant R flows through the inlet passage 118a and into the expansion chamber 118b, it expands and becomes a low-temperature, low-pressure gas-liquid mixture. This low-temperature, low-pressure refrigerant R cools the seal chamber 50 from the surroundings as it passes through the cooling passage 118c. This gas-liquid mixture refrigerant R releases cold energy as it flows through the cooling passage 118c and vaporizes, and is released as low-temperature, low-pressure refrigerant R into the internal space 15b from the opening 118d.

[0042] If refrigerant R in a gas-liquid mixed state is present in the seal chamber 50, the refrigerant R in the gas-liquid mixed state is cooled at a predetermined moderate pressure by the cooling passage 118c. As a result, the refrigerant R in the gas-liquid mixed state is removed from the refrigeration cycle (see FIG. 2) line and becomes a liquid state. The refrigerant R that has undergone a phase transition to a liquid is pressurized by the refrigerant R in the support space 22a, and therefore undergoes a further phase transition to a supercritical fluid. Furthermore, if refrigerant R in a supercritical fluid state is present in the seal chamber 50, the refrigerant R in the supercritical fluid state is cooled at a predetermined moderate pressure by this cooling. As a result, the refrigerant R in the supercritical fluid state is removed from the refrigeration cycle line but remains a supercritical fluid and is further pressurized by the refrigerant R in the support space 22a.

[0043] During operation of the motor 1, the seal chamber 50 is filled with refrigerant R and is maintained at a high pressure by the refrigerant R in the support space 22a. In this state, the supercritical fluid refrigerant R in the seal chamber 50 is cooled and maintained at a low temperature by the low-temperature, low-pressure refrigerant R in the cooling passage 118c. That is, the supercritical fluid refrigerant R filled in the seal chamber 50 is maintained at a high pressure by the refrigerant R in the support space 22a and maintained at an appropriate low temperature by the refrigerant R passing through the cooling passage 118c. This effectively prevents the refrigerant R in the seal chamber 50 from gasifying. Therefore, in this embodiment, the seal member 16 arranged in the seal chamber 50 can keep the refrigerant R in a supercritical fluid state within the seal chamber 50 without leaking it to the outside.

[0044] 3, a communication passage 50a may be formed to communicate between the seal chamber 50 and the internal space 15b. In this case, the supercritical fluid refrigerant R filling the seal chamber 50 passes through the communication passage 50a and is released into the internal space 15b of the housing 15. At this time, the refrigerant R expands and becomes a gas-liquid mixture, similar to the refrigerant R that has passed through the injection passage 32. In this case, the seal chamber 50 receives the supercritical fluid refrigerant R sequentially supplied from the first refrigerant supply passage 18b, making it easier to maintain the refrigerant R in a supercritical state within the seal chamber 50. The communication passage 50a also functions as a gas vent hole for the seal chamber 50.

[0045] In contrast to the bearing structure of FIG. 3, the bearing structure of the comparative example shown in FIG. 4 does not include the second refrigerant supply passage 18c. Therefore, when the motor 1 is operating, the refrigerant circulation system 8 supplies the medium-temperature, high-pressure supercritical fluid refrigerant R to the support space 22a through the refrigerant supply passage 18 and the through-hole 23. In this case, the refrigerant R passes through the support space 22a and flows into the injection passage 32 and the seal chamber 50. The supercritical fluid refrigerant R may expand to a gas-liquid mixed state when flowing from the very narrow support space 22a to the relatively larger seal chamber 50. However, since the second refrigerant supply passage 18c is not included, the gas-liquid mixed refrigerant R in the seal chamber 50 is not liquefied and may be heated by the surrounding environment and vaporize. Therefore, in the comparative example of FIG. 4, the refrigerant R may leak through the seal member 16.

[0046] 5, the second refrigerant supply passage 18c may be configured to communicate with the support space 22a. The refrigerant supply passage 18 (first refrigerant supply passage 18b) is also configured to communicate with the support space 22a. In this modified example, the bearing 20 has, in addition to the through-hole 23, a through-hole 23a that penetrates the side wall from the outer circumferential surface 26 of the main body 21 to communicate with the sliding surface 22. The inlet passage 118a of the second refrigerant supply passage 18c is configured to communicate with the through-hole 23a and receive the supercritical fluid refrigerant R from the support space 22a and supply it to the expansion chamber 118b. Therefore, when the refrigerant R flows from the inlet passage 118a into the expansion chamber 118b, it expands or reduces its pressure, becoming a low-temperature, low-pressure refrigerant R. Even with this configuration, the second refrigerant supply passage 18c can cool the refrigerant R in the seal chamber 50 by allowing the low-temperature, low-pressure refrigerant R generated in the expansion chamber 118b to flow through the downstream cooling passage 118c. Note that the communication passage 50a may also be provided in the example of FIG. 5.

[0047] [Action and effect] Next, the operation and effects of the motor system S according to this embodiment will be described. The motor system S according to this embodiment comprises a rotor shaft 13 extending in the axial direction L, a plain bearing 20 that rotatably supports the rotor shaft 13, a housing 15 that holds the plain bearing 20, and a seal member 16 that seals between the housing 15 and an end of the rotor shaft 13 that extends to the outside from the housing 15. The housing 15 accommodates the seal member 16 in a seal chamber 50 that communicates with the outside of the housing 15 via a through hole 15a, and holds the plain bearing 20 in a bearing chamber 52 that communicates between the seal chamber 50 and an internal space 15b of the housing 15. The motor system S further comprises a first refrigerant supply passage 18b that extends through the housing 15 and the plain bearing 20 and communicates with a sliding surface 22 of the plain bearing 20 relative to the rotor shaft 13. The plain bearing 20 is connected to the rotor shaft 13 via the first refrigerant supply passage 18b. The motor system S is configured to be lubricated by a supercritical fluid CO2 refrigerant R supplied to the support space 22a between the motor system S and the shaft 13, and the motor system S further includes a second refrigerant supply passage 18c extending at least through the housing 15 and communicating with the internal space 15b of the housing 15, and the second refrigerant supply passage 18c includes an expansion chamber 118b for expanding the supercritical fluid CO2 refrigerant R, and is configured to communicate from the expansion chamber 118b through the vicinity of the seal chamber 50 to the internal space 15b of the housing 15.

[0048] In this embodiment, the motor system S can supply CO2 refrigerant R to the support space 22a between the plain bearing 20 and the rotor shaft 13 via the first refrigerant supply passage 18b. The CO2 refrigerant R supplied to the support space 22a can lubricate the sliding surface 22 of the plain bearing 20. The CO2 refrigerant R is then ejected from the support space 22a into the internal space 15b of the housing 15 and can flow from the support space 22a into the seal chamber 50. When ejected into the internal space 15b of the housing 15, the CO2 refrigerant R expands to a low-temperature, low-pressure gas-liquid mixture, cooling the inside of the motor. The CO2 refrigerant R that flows into the seal chamber 50 fills the seal chamber 50. The seal chamber 50 is then pressurized by the CO2 refrigerant R in the support space 22a. Meanwhile, the supercritical fluid CO2 refrigerant R flows through the second refrigerant supply passage 18c and expands in the expansion chamber 118b to a low-temperature, low-pressure gas-liquid mixture. This low-temperature CO2 refrigerant R passes near the seal chamber 50 and cools the refrigerant R inside the seal chamber 50. In this way, the refrigerant R inside the seal chamber 50 is maintained in a pressurized and cooled state. This prevents the refrigerant R inside the seal chamber 50 from gasifying and is maintained as a supercritical fluid while the motor 1 is in operation. For this reason, in this embodiment, the CO2 refrigerant R can be used to lubricate the sliding bearing 20, and can also be prevented from leaking outside the housing 15 through the seal member 16 between the rotor shaft 13 and the housing 15.

[0049] Furthermore, this embodiment further includes a refrigerant circulation system 8 that supplies supercritical fluid CO refrigerant R to the first refrigerant supply passage 18b and the second refrigerant supply passage 18c. In this embodiment, a motor system S including the refrigerant circulation system 8 and the motor 1 can be mounted on, for example, a vehicle.

[0050] According to this embodiment, the refrigerant circulation system 8 includes a compressor 81 that compresses the gaseous CO refrigerant R recovered from the housing 15 to generate a supercritical CO refrigerant R, and a condenser (heat exchanger) 83 that condenses the CO refrigerant R output from the compressor 81, exchanges heat with the external environment, and supplies the supercritical CO refrigerant R to the first refrigerant supply passage 18b and the second refrigerant supply passage 18c. In this embodiment, the gaseous CO refrigerant R after heat exchange within the motor 1 is compressed by the compressor 81 to generate a high-temperature, high-pressure supercritical fluid (compression stroke). Next, the compressed CO refrigerant R is condensed by the condenser 83 to generate a medium-temperature, high-pressure CO refrigerant R (condensation stroke). The condensed CO refrigerant R is then expanded within the motor 1 to generate a low-temperature, low-pressure gas-liquid mixture (expansion stroke). Finally, the CO refrigerant R is evaporated by heat exchange within the motor 1 to generate a high-temperature, low-pressure gaseous CO refrigerant R (evaporation stroke). This embodiment forms a refrigeration cycle.

[0051] Furthermore, according to this embodiment, the sealed chamber 50 is configured to hold the CO2 refrigerant R supplied through the first refrigerant supply passage 18b and the support space 22a. In this embodiment, the sealed chamber 50 in which the seal member 16 is disposed can be filled with the CO2 refrigerant R.

[0052] Furthermore, according to this embodiment, the refrigerant circulation system 8 recovers at least the gaseous CO2 refrigerant R from inside the housing 15. In this embodiment, the CO2 refrigerant R in a gas-liquid mixed state, ejected at an appropriate flow rate from the support space 22a, is vaporized by heat exchange inside the motor 1, so the refrigerant circulation system 8 can recover the gaseous CO2 refrigerant R.

[0053] Furthermore, according to this embodiment, first refrigerant supply passage 18b and second refrigerant supply passage 18c are formed to branch off from main refrigerant supply passage 18a, which extends through housing 15. In this embodiment, CO2 refrigerant R branches off from main refrigerant supply passage 18a to first refrigerant supply passage 18b and second refrigerant supply passage 18c, and is used to lubricate sliding bearing 20, cool motor components, and cool seal chamber 50, respectively.

[0054] Furthermore, according to this embodiment, the seal member 16 includes an annular stationary seal member 16a fixed to the seal chamber 50 so as to surround the through hole 15a, and an annular rotary seal member 16b fixed to the rotor shaft 13, and the stationary seal member 16a and the rotary seal member 16b slide against each other when the rotor shaft 13 rotates. In this embodiment, the seal member 16 can seal the supercritical fluid CO refrigerant R within the seal chamber 50 through the sliding between the stationary seal member 16a and the rotary seal member 16b. [Explanation of symbols]

[0055] 1 motor 11 rotor 12 stator, 12b coil, 12c coil end 13 rotor shaft 15 housing, 15a through hole, 15b internal space 16 seal member, 16a stationary seal member, 16b rotating seal member 18 refrigerant supply passage, 18a main refrigerant supply passage 18b first refrigerant supply passage, 18c second refrigerant supply passage 118a inlet passage, 118b expansion chamber 118c cooling passage, 118d opening 19 Refrigerant discharge passage 20 bearing, 22 sliding surface, 22a support space 30 guide member, 31 guide surface 32 Injection passage 50 seal chamber, 52 bearing chamber 8 Refrigerant circulation system 81 Compressor 83 Heat exchanger L axis direction R refrigerant S Motor System d distance

Claims

1. A motor system comprising: a rotor shaft extending in an axial direction; a plain bearing that rotatably supports the rotor shaft; a housing that holds the plain bearing; and a seal member that seals between the housing and an end of the rotor shaft that extends outward from the housing, the housing accommodates the seal member in a seal chamber that communicates with the outside of the housing via a through hole, and holds the sliding bearing in a bearing chamber that communicates with the seal chamber and an internal space of the housing, The motor system further includes a first refrigerant supply passage that extends through the housing and the plain bearing and communicates with a sliding surface of the plain bearing relative to the rotor shaft, and the plain bearing refrigerates a supercritical fluid CO 2 supplied through the first refrigerant supply passage to a support space between the plain bearing and the rotor shaft. 2 configured to be lubricated by a refrigerant; The motor system further includes a second refrigerant supply passage extending through at least the housing and communicating with an interior space of the housing, the second refrigerant supply passage supplying the CO 2 of the supercritical fluid. 2 A motor system comprising an expansion chamber for expanding a refrigerant, the expansion chamber communicating with an interior space of the housing through a vicinity of the seal chamber.

2. The CO of the supercritical fluid 2 The motor system of claim 1 , further comprising a coolant circulation system that supplies coolant to the first coolant supply passage and the second coolant supply passage.

3. The refrigerant circulation system includes: The CO gas recovered from the housing 2 The refrigerant is compressed to produce the supercritical fluid CO 2 a compressor for generating a refrigerant; The CO output from the compressor 2 The refrigerant is condensed and heat exchanged with the external environment, and the CO 2 3. The motor system of claim 2, further comprising: a condenser that supplies refrigerant to the first refrigerant supply passage and the second refrigerant supply passage.

4. The seal chamber is provided with the CO refrigerant supplied through the first refrigerant supply passage and the support space. 2 The motor system of claim 1 configured to hold a coolant.

5. The refrigerant circulation system includes at least the gaseous CO 2 The motor system of claim 2 , wherein the refrigerant is recovered from within the housing.

6. 2. The motor system according to claim 1, wherein the first coolant supply passage and the second coolant supply passage are formed so as to branch off from a main coolant supply passage that extends through the housing.

7. the seal member includes an annular stationary seal member fixed to the seal chamber so as to surround the through hole, and an annular rotary seal member fixed to the rotor shaft, The motor system according to claim 1 , wherein the stationary seal member and the rotary seal member slide against each other when the rotor shaft rotates.

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