Motor system

Abstract

To provide a motor system that can achieve both of reduction of stirring resistance loss during high-speed rotation and cooling of a stator coil.SOLUTION: A motor system S includes: refrigerant supply passages 18 each communicating with a sliding surface 22 of a bearing 20 with respect to a rotor shaft 13; and guide members 30 attached to the rotor shaft 13 so as to be each adjacent to a rotor end surface 24 of the bearing 20. Each of the bearings 20 is configured to be lubricated by CO2 refrigerant R supplied to a support space 22a between the bearing 20 and the rotor shaft 13. The guide member 30 has a guide surface 31 that opposes the rotor end surface 24 across a predetermined-distance gap. The guide surface 31 is formed so as to guide the CO2 refrigerant R toward a coil 12b wound around a stator 12 when the CO2 refrigerant R is ejected from the support space 22a into a housing 15 through the predetermined gap.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A conventional technique for cooling the coil ends by injecting oil onto the coil ends wound around the stator of an electric motor is known (see, for example, Patent Document 1). In the electric motor of Patent Document 1, oil is introduced into the hollow rotor shaft of the electric motor, and the oil is ejected to the outside of the rotor shaft from through holes formed in the circumferential surface of the rotor shaft. The ejected oil is directed toward the coil ends via a member attached to the rotor shaft, thereby cooling the coil ends.

[0003] In general, the rotor shaft of an electric motor is configured to be supported by a rolling bearing or a sliding bearing. In the electric motor of Patent Document 1, the rotor shaft is supported by a rolling bearing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-17291 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, when the rotation speed of an electric motor becomes high (for example, above 30,000 rpm), rolling fatigue becomes a problem for rolling bearings. 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. In this case, however, in ultra-high speed rotation motors, the viscosity of the oil causes a problem of stirring resistance loss at high rotation speeds of the rotor shaft.

[0006] The present invention has been made to solve the problems of the conventional technology described above, and aims to provide a motor system that can achieve both reduced agitation resistance loss during high-speed rotation and cooling of the stator coil. [Means for solving the problem]

[0007] In order to achieve the above object, the motor system of the present invention comprises a stator, a rotor, a rotor shaft fixed to the rotor and extending in the axial direction, a plain bearing rotatably supporting the rotor shaft and having a rotor end face facing the rotor in the axial direction, and a housing for holding the plain bearing, and further comprises a refrigerant supply passage that passes through at least the housing and communicates with the sliding surface of the plain bearing relative to the rotor shaft, and a guide member attached to the rotor shaft so as to be adjacent to the rotor end face of the plain bearing, wherein the plain bearing is configured to be lubricated by CO2 refrigerant supplied to a support space between the plain bearing and the rotor shaft through the refrigerant supply passage, and the guide member has a guide surface that faces the rotor end face across a predetermined gap, and the guide surface is formed to guide the CO2 refrigerant towards the coil wound around the stator when the CO2 refrigerant sprays from the support space through the predetermined gap into the housing.

[0008] In the present invention configured as described above, the motor system can lubricate the sliding surfaces of the plain bearing by supplying CO2 refrigerant to the support space between the plain bearing and the rotor shaft. The motor system also ejects the lubricated CO2 refrigerant from the support space into the internal space of the housing. The guide surface of the guide member attached to the rotor shaft 13 directs the CO2 refrigerant toward the stator coil, cooling the coil, which is a high-temperature part of the motor. This allows the present invention to use CO2 refrigerant to both lubricate the plain bearing and cool the motor. Therefore, the motor system of the present invention can simultaneously reduce agitation resistance loss during high-speed rotation and cool the stator coil.

[0009] In the present invention, the CO refrigerant can be in a supercritical fluid state when supplied to the sliding bearing. This supercritical fluid expands and changes to a gas-liquid mixed state when it is ejected from the support space through a specified gap into the housing 15. This gas-liquid mixed fluid then evaporates and changes to a gas through heat exchange with the coil 12b of the stator 12.

[0010] In the present invention, the guide surface preferably has an inclined surface that increases in diameter from the sliding bearing toward the rotor. According to the present invention configured in this manner, the CO refrigerant flowing from the support space can be directed by the inclined surface and released into the internal space of the housing.

[0011] Preferably, the present invention further includes a refrigerant circulation system that supplies a CO2 refrigerant to the refrigerant supply passage and recovers the CO2 refrigerant from within the housing. According to the present invention configured in this manner, a motor system including the refrigerant circulation system and a motor can be installed in, 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 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] Furthermore, the present invention preferably further comprises a position adjustment mechanism for variably adjusting the relative axial distance between the guide member and the sliding bearing. According to the present invention configured in this manner, by adjusting the relative axial distance, it is possible to adjust the flow rate of CO2 refrigerant released from the sliding bearing into the internal space of the housing.

[0014] Furthermore, in the present invention, preferably the guide member includes a magnetic material and is attached so as to be axially movable relative to the rotor shaft, the position adjustment mechanism comprises biasing means that biases the guide member in a first axial direction toward the rotor, and an electromagnet that magnetically attracts the magnetic material in a second axial direction toward the sliding bearing, and the motor system S further comprises a controller that controls the supply of electricity to the electromagnet so as to adjust the position of the guide member relative to the sliding bearing. According to the present invention configured in this manner, the axial distance between the guide member and the sliding bearing can be adjusted by adjusting the axial position of the guide member on the rotor shaft.

[0015] In the present invention, specifically, the biasing means is disposed within the rotor shaft, and the electromagnet is attached to the housing or the plain bearing.

[0016]

[0023] Also, in the present invention, preferably, the motor system is configured such that the rotor rotates in one direction relative to the stator, the guide member is threadedly engaged with the rotor shaft so as to be axially movable, and is attached so as to be movable back and forth from a reference axial position on the rotor shaft in a first axial direction toward the rotor and a second axial direction toward the plain bearing by rotation relative to the rotor shaft, the position adjustment mechanism includes a biasing means that applies a biasing force to the guide member in a direction returning the guide member to the reference position as the guide member rotates relative to the rotor shaft and moves away from the reference position in the axial direction L, the guide member moves from the reference position in the first axial direction against the biasing force of the biasing means when the rotor shaft rotates at an accelerated rate, remains in the reference position when the rotor shaft rotates at a constant speed, and moves from the reference position in the second axial direction against the biasing force of the biasing means when the rotor shaft rotates at a decelerated rate. According to the present invention configured in this manner, when the motor is operating, the axial position of the guide member on the rotor shaft is automatically adjusted in accordance with the positive and negative rotational acceleration of the rotor shaft 13, thereby making it possible to adjust the axial distance between the guide member and the plain bearing.

[0017] In the present invention, more specifically, the biasing means is a spring member that connects the rotor shaft and the guide member.

[0018] Furthermore, in the present invention, preferably the sliding bearing includes a magnetic material and is attached so as to be axially movable relative to the housing, the position adjustment mechanism comprises an electromagnet that can electromagnetically selectively attract the magnetic material in a first axial direction toward the guide member and a second axial direction away from the guide member, and the motor system further comprises a controller that controls the supply of electricity to the electromagnet so as to adjust the relative position of the guide member with respect to the sliding bearing. According to the present invention configured in this way, the axial distance between the guide member and the sliding bearing can be adjusted by adjusting the axial position of the sliding bearing with respect to the housing (i.e., the guide member).

[0019] In the present invention, specifically, the electromagnet is attached to the housing or the sliding bearing.

[0020] Furthermore, the present invention preferably further comprises a flow rate adjustment valve that adjusts the flow rate of CO2 refrigerant flowing through the refrigerant supply passage. According to the present invention configured in this manner, by adjusting the aperture of the flow rate adjustment valve, it is possible to adjust the flow rate of CO2 refrigerant supplied to the plain bearing and to adjust the spray flow rate of CO2 refrigerant released into the internal space of the housing via the plain bearing. [Effects of the Invention]

[0021] The motor system according to the present invention can achieve both a reduction in agitation resistance loss during high-speed rotation and cooling of the stator coil. [Brief explanation of the drawings]

[0022] [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] 5A and 5B are explanatory diagrams of a guide portion according to an embodiment of the present invention. [Figure 4] 1 is an explanatory diagram of a bearing structure according to a first embodiment of the present invention. [Figure 5A] FIG. 6 is an explanatory diagram of a bearing structure according to a second embodiment of the present invention. [Figure 5B] 6A to 6C are explanatory views of the operation of the bearing structure according to the second embodiment of the present invention. [Figure 5C] 6A to 6C are explanatory views of the operation of the bearing structure according to the second embodiment of the present invention. [Figure 6] FIG. 6 is an explanatory diagram of a bearing structure according to a third embodiment of the present invention. [Figure 7] FIG. 10 is an explanatory diagram of a bearing structure according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] 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.

[0024] 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.

[0025] [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.

[0026] [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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The motor 1 also has a guide member 30 for spraying the refrigerant R provided for lubricating the bearings 20 onto high-temperature parts inside the motor 1. The motor 1 also has a position adjustment mechanism 40 for controlling the position of the guide member 30. The guide member 30 and the position adjustment mechanism 40 will be described later.

[0032] [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).

[0033] 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).

[0034] 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.

[0035] 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).

[0036] [Bearing structure] FIG. 3 is an explanatory diagram of the bearing structure of this embodiment. As shown in FIG. 3, bearing 20 rotatably supports the end of rotor shaft 13. Bearing 20 includes a substantially cylindrical main body 21 and an end surface (rotor end surface) 24 facing rotor 11. The inner circumferential surface of main body 21 forms a sliding surface 22 with rotor shaft 13. Rotor end surface 24 has an inclined surface 25 that is truncated into a conical shape. Inclined surface 25 is a thrust surface. Main body 21 is formed with a through-hole 23 that extends from the radially outer side of rotor shaft 13 toward the center, penetrating the outer circumferential surface 26 of main body 21 through the side wall and communicating with sliding surface 22. Through-hole 23 communicates with refrigerant supply passage 18 and forms part of refrigerant supply passage 18. Note that refrigerant supply passage 18 may be directly connected to support space 22a between rotor shaft 13 and bearing 20 without passing through through-hole 23.

[0037] 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. Note that, although it is advantageous for the rotor end surface 24 of the bearing 20 to have the inclined surface 25 in terms of guiding the refrigerant R, the inclined surface 25 is not necessary.

[0038] During operation of the motor 1, the refrigerant circulation system 8 pumps the supercritical fluid refrigerant R through the refrigerant supply passage 18 and the through-hole 23 to the bearing 20. The supercritical fluid refrigerant R maintains a high pressure state, filling the support space 22a between the rotor shaft 13 and the bearing 20 and lubricating the bearing 20. The refrigerant R 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 refrigerant R is further directed along the guide surface 31 of the guide member 30 and guided toward the coil end 12c. The refrigerant R that reaches the coil end 12c cools it. The vaporized refrigerant R exchanges heat with the coil end 12c and is discharged to the outside through the refrigerant discharge passage 19.

[0039] [Flow rate adjustment control] Next, with reference to Figures 4 to 7, various embodiments of flow rate adjustment control of the refrigerant R that cools the coil ends 12c of the stator 12 will be described. Note that in the present embodiments, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted. Also, Figures 4 to 7 show the non-output end of the rotor shaft 13 that is not connected to an external structure (such as a transaxle), but the output end also has a similar configuration.

[0040] In this embodiment, power to support the rotor shaft 13 can be obtained by supplying the supercritical fluid refrigerant R to the bearing 20. However, if the refrigerant R vaporizes in the bearing 20, the desired density and viscosity cannot be ensured, resulting in increased frictional resistance and wear. Furthermore, if the flow rate of the refrigerant R ejected from the bearing 20 into the internal space 15b of the housing 15 is large, the refrigerant R that has not completely vaporized will be supplied to the downstream compressor 81, causing liquid compression. Furthermore, the cooling requirements for the coil end 12c vary depending on the operating state of the motor 1. For this reason, in this embodiment, the flow rate of the refrigerant R ejected from the bearing 20 into the internal space 15b of the housing 15 is appropriately controlled.

[0041] [First embodiment] Flow rate adjustment control according to the first embodiment will be described with reference to Figure 4. Figure 4 shows the bearing structure of the first embodiment. In the first embodiment, the axial position of the guide member 30 relative to the bearing 20 is adjustable by a position adjustment mechanism 40. In the first embodiment, this allows the passage width or distance d of the injection passage 32 to be adjusted, thereby adjusting the injection flow rate of the refrigerant R.

[0042] The position adjustment mechanism 40 includes a biasing means 43 arranged inside the rotor shaft 13, an electromagnet 44 arranged radially outside the rotor shaft 13 and near the bearing 20 (inside the bearing 20 or the housing 15), and a controller 46 that controls the energization of the electromagnet 44. The controller 46 is a computer having a processor or the like, and receives signals (refrigerant temperature, refrigerant pressure, refrigerant flow rate, motor rotation speed, stator temperature, etc.) from various sensors provided in the motor system S, and outputs operation signals to each component of the refrigerant circulation system 8, solenoid valves, electromagnets (electromagnetic solenoids), etc. The controllers of the other embodiments are similar to the controller 46 of the first embodiment.

[0043] The biasing means 43 biases the guide member 30 in the axial direction L in a direction away from the bearing 20. An operating hole 41a extending in the axial direction L and a guide hole 41b communicating with the operating hole 41a and extending in the radial direction to reach the circumferential surface of the rotor shaft 13 are formed inside the rotor shaft 13. The biasing means 43 includes an operating rod 43a arranged in the operating hole 41a, a connecting rod 43b arranged in the guide hole 41b, and a spring member 43c.

[0044] A spring member 43c is connected to the base end of the operating rod 43a, and a connecting rod 43b is connected to the tip end of the operating rod 43a. Both ends of the connecting rod 43b are connected to the guide member 30. Therefore, the connecting rod 43b can move a predetermined distance in the axial direction L within the guide hole 41b together with the guide member 30. The spring member 43c constantly biases the operating rod 43a in the axial direction L toward the rotor 11 (first axial direction), and biases the guide member 30 in a direction away from the bearing 20 via the connecting rod 43b.

[0045] The electromagnet 44 is configured such that an electric wire is wound around a magnetic material, and an electromagnetic force in the axial direction L is generated by energizing the electric wire. The guide member 30 is formed including a magnetic body. For example, the guide member 30 itself is formed of a magnetic material, or the guide member 30 contains a magnetic body therein. Therefore, when the electromagnet 44 generates an electromagnetic force, the guide member 30 is attracted in the direction of the bearing 20 (the second axial direction) by this electromagnetic force, and the distance d becomes smaller than the initial value (reference distance d0) (d < d0).

[0046] The controller 46 can control the energization amount to the electromagnet 44 (that is, the suction force to the guide member 30) based on a sensor signal SR such as the motor rotation speed, and thereby control the distance d between the guide member 30 and the bearing 20. That is, the electromagnet 44 and the guide member 30 form an electromagnetic solenoid.

[0047] For example, when the rotation speed is low (that is, when the cooling requirement for the coil end 12c is small), the controller 46 sets the energization amount to a large value, thereby increasing the movement distance of the guide member 30 and decreasing the distance d (d < d0). Thereby, the refrigerant R is provided to the high-temperature part with a small injection flow rate. On the other hand, when the rotation speed is high (that is, when the cooling requirement is large), the controller 46 sets the energization amount to a small value, thereby decreasing the movement distance of the guide member 30 and increasing the distance d. For example, when the energization amount is zero, the distance d becomes equal to the reference distance d0. Thereby, the refrigerant R is provided to the high-temperature part with a large injection flow rate.

[0048] Also, in the present embodiment, the controller 46 is configured to synchronize the energization to the electromagnet 44 in the two bearings 20 that support both sides of the rotor shaft 13 in the axial direction L. Thereby, in the present embodiment, the guide members 30 on both sides of the rotor shaft 13 move in opposite directions in synchronization in the axial direction L, so that the displacement of the rotor shaft 13 in the axial direction L is prevented. Note that the configuration of synchronizing as described above is the same in other embodiments.

[0049] In this way, in the first embodiment, the controller 46 can adjust the injection flow rate by adjusting the passage width or distance d of the injection passage 32 according to the level of the cooling demand for the motor 1.

[0050] [Second embodiment] Flow rate adjustment control according to the second embodiment will be described with reference to Figures 5A, 5B, and 5C. Figure 5A shows the bearing structure of the second embodiment, and Figures 5B and 5C show the operating state of the bearing structure of the second embodiment. Figure 5B shows the rotor shaft 13 and guide member 30 as viewed from the axial direction L. In the second embodiment, the axial position of the guide member 30 relative to the bearing 20 is automatically adjusted by a position adjustment mechanism 140 in response to changes in the rotation speed (acceleration a) of the motor 1. In the second embodiment, this adjusts the passage width or distance d of the injection passage 32, thereby adjusting the injection flow rate of the refrigerant R. The motor 1 is configured to rotate in one direction.

[0051] 5A, the guide member 30 has a through hole 132 for allowing the rotor shaft 13 to pass therethrough, and a spiral thread groove (female thread) 132a is formed on the inner peripheral surface of the through hole 132. Furthermore, a thread groove (male thread) 113a that threadably engages with the thread groove 132a of the guide member 30 is formed on the outer peripheral surface of the rotor shaft 13. Therefore, the guide member 30 threadably engages with the rotor shaft 13, and can move on the rotor shaft 13 in the axial direction L by rotating. Alternatively, a male thread groove may be formed in the guide member 30, and a female thread groove may be formed in the rotor shaft 13.

[0052] The position adjustment mechanism 140 includes a biasing means 143 that biases the guide member 30 in the circumferential direction relative to the rotor shaft 13. The biasing means 143 includes a spring member 143a, an attachment member 143b fixed to the rotor shaft 13, and an attachment member 143c fixed to the guide member 30. One end of the spring member 143a is connected to the attachment member 143b of the rotor shaft 13, and the other end is connected to the attachment member 143c of the guide member 30. The spring member 143a is expandable and contracts, and exerts a contracting force (when expanded) or an expanding force (when contracted) depending on the positive or negative displacement length from its natural length. The guide member 30 is normally held at a reference position P0 in the axial direction L of the rotor shaft 13. The reference position P0 is determined by the natural length of the spring member 143a. The distance by which the spring member 143a extends or contracts from its natural length can be adjusted by the spring constant of the spring member 143a. Therefore, in this embodiment, the spring constant of the spring member 143a is selected so that the movement distance of the guide member 30 in the axial direction L is set appropriately according to the acceleration a.

[0053] 5B(b) and 5C(b) show a state in which the motor 1 is rotating at a constant speed (i.e., acceleration a = 0). When the motor rotation speed is constant, no force is applied between the rotor shaft 13 and the guide member 30. Therefore, the spring member 143a is at its natural length, and the guide member 30 is maintained at the reference position P0. Therefore, the passage width (distance d) of the injection passage 32 has the reference distance d0 (d = d0), and the injection flow rate of the refrigerant R is maintained at the reference flow rate.

[0054] Figures 5B(a) and 5C(a) show the state where the motor 1 is accelerating (i.e., acceleration a>0). When the motor rotation speed is increasing, the guide member 30 is accelerated slower than the rotor shaft 13 due to inertia force, and the guide member 30 rotates relative to the rotor shaft 13 slightly. In this embodiment, when such relative rotation occurs, the spiral directions of the screw groove 132a and the screw groove 113a are oriented such that the guide member 30 moves away from the bearing 20. At this time, the spring member 143a is compressed from its natural length. When the guide member 30 moves in the first axial direction and moves away from the bearing 20, the passage width (distance d) of the injection passage 32 becomes wider than the reference distance d0 (d>d0), so the injection flow rate of the refrigerant R is increased compared to the reference flow rate. When the motor rotation speed becomes constant, the force (the force to extend) for the spring member 143a to return to its natural length rotates the guide member 30 in the returning direction and returns the guide member 30 to the reference position P0.

[0055] Figures 5B(c) and 5C(c) show the state where the motor 1 is decelerating (i.e., acceleration a<0). When the motor rotation speed is decreasing, the guide member 30 is decelerated slower than the rotor shaft 13 due to inertia force, and the guide member 30 rotates relative to the rotor shaft 13 slightly. In this embodiment, when such relative rotation occurs, the spiral directions of the screw groove 132a and the screw groove 113a are oriented such that the guide member 30 approaches the bearing 20. At this time, the spring member 143a is stretched from its natural length. When the guide member 30 moves in the second axial direction and approaches the bearing 20, the passage width (distance d) of the injection passage 32 becomes narrower than the reference distance d0 (d<d0), so the injection flow rate of the refrigerant R is decreased compared to the reference flow rate. When the motor rotation speed becomes constant, the force (the force to contract) for the spring member 143a to return to its natural length rotates the guide member 30 in the returning direction and returns the guide member 30 to the reference position P0.

[0056] Thus, in the second embodiment, the injection flow rate can be automatically adjusted according to the magnitude of the cooling requirement for the motor 1 (i.e., the cooling requirement is high when the motor 1 is accelerating and low when it is decelerating).

[0057] [Third embodiment] Flow rate adjustment control according to the third embodiment will be described with reference to Fig. 6. Fig. 6 shows the bearing structure of the third embodiment. In the third embodiment, the axial position of the bearing 20 relative to the guide member 30 is adjustable by a position adjustment mechanism 240. In the third embodiment, the passage width or distance d of the injection passage 32 is thereby adjusted, thereby adjusting the injection flow rate of the refrigerant R.

[0058] As shown in FIG. 6 , in this embodiment, a bottomed mounting hole 51 for mounting the bearing 20 is formed in the housing 15. A thread groove (female thread) 51a is formed on the inner peripheral surface of the mounting hole 51. Furthermore, a thread groove (male thread) 21a that threadably mates with the thread groove 51a of the mounting hole 51 is formed on the outer peripheral surface 26 of the main body 21 of the bearing 20. Therefore, the bearing 20 threadably mates with the mounting hole 51 of the housing 15, and can move back and forth in the axial direction L relative to the mounting hole 51 by rotating. Alternatively, a male thread groove may be formed in the housing 15, and a female thread groove may be formed in the bearing 20. Furthermore, other configurations may be used as long as the bearing 20 can move back and forth relative to the housing 15. For example, a configuration in which a slider provided on the bearing 20 slides on a guide rail provided in the mounting hole 51 of the housing 15 may be used.

[0059] The position adjustment mechanism 240 includes a pair of electromagnets 244a, 244b arranged inside the housing 15 or the bearing 20 on the radial outside of the rotor shaft 13, and a controller 246 that controls the energization of these electromagnets 244a, 244b. The electromagnets 244a, 244b are arranged spaced apart by a predetermined length in the axial direction L. The electromagnets 244a, 244b are configured such that an electric wire is wound around a magnetic material, and generate an electromagnetic force when an electric current is passed through the electric wire.

[0060] Also, the bearing 20 is formed to include a magnetic body 21b between a pair of electromagnets 244a and 244b in the axial direction L. Therefore, when the electromagnets 244a and 244b are selectively energized to generate an electromagnetic force in the axial direction L, the bearing 20 is attracted toward the energized electromagnet by this electromagnetic force. Due to this attractive force, the bearing 20 rotates the thread groove 51a of the mounting hole 51 and slightly moves in the axial direction L.

[0061] The controller 246 can control the energization (for example, on / off) to the electromagnets 244a and 244b (that is, the attractive force to the bearing 20) based on a sensor signal SR such as the motor rotation speed, and control the distance d between the guide member 30 and the bearing 20. That is, the electromagnets 244a and 244b and the bearing 20 form a double electromagnetic solenoid.

[0062] For example, when the rotation speed is low (that is, when the cooling requirement for the coil end 12c is small), the controller 46 energizes the electromagnet 244a for a predetermined time to move the bearing 20 in the direction of the guide member 30 (the first axial direction), thereby reducing the distance d below the reference distance d0 (d < d0). As a result, the refrigerant R is supplied to the high-temperature part with a small injection flow rate. On the other hand, when the rotation speed is high (that is, when the cooling requirement is large), the controller 46 energizes the electromagnet 244b for a predetermined time to move the bearing 20 in the direction away from the guide member 30 (the first axial direction), thereby increasing the distance d above the reference distance d0 (d > d0). As a result, the refrigerant R is supplied to the high-temperature part with a large injection flow rate.

[0063] Thus, in the third embodiment, the controller 46 can adjust the injection flow rate by adjusting the passage width of the injection passage 32 or the distance d according to the magnitude of the cooling requirement for the motor 1.

[0064] [Fourth Embodiment] Flow rate adjustment control according to the fourth embodiment will be described with reference to Fig. 7. Fig. 7 shows the bearing structure of the fourth embodiment. The fourth embodiment is configured to adjust the flow rate of refrigerant R supplied to bearing 20. For such flow rate adjustment control, the fourth embodiment is provided with a flow rate adjustment valve 340 provided in refrigerant supply passage 18 and a controller 346 that controls flow rate adjustment valve 340.

[0065] Therefore, in the fourth embodiment, unlike the other embodiments, the bearing 20 and the guide member 30 are not movable in the axial direction L. In the fourth embodiment, instead of fixing the guide member 30, which is a separate member, to the rotor shaft 13, a conical guide surface that functions as the guide surface 31 of the guide member 30 may be formed at the tip portion of the rotor shaft 13.

[0066] Based on the sensor signal SR of the motor rotation speed, etc., the controller 346 can increase the flow rate by increasing the opening of the flow rate adjustment valve 340 when the cooling demand for the motor 1 is large, and can decrease the opening of the flow rate adjustment valve 340 to decrease the flow rate when the cooling demand is small. As a result, in the fourth embodiment, it is possible to appropriately adjust the injection flow rate from the bearing 20 to the coil end 12c according to the cooling demand.

[0067] [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 includes a stator 12, a rotor 11, a rotor shaft 13 fixed to the rotor and extending in the axial direction L, a plain bearing 20 that rotatably supports the rotor shaft 13 and has a rotor end surface 24 that faces the rotor 11 in the axial direction L, and a housing 15 that holds the plain bearing 20. The motor system S further includes a refrigerant supply passage 18 that passes through at least the housing 15 and communicates with a sliding surface 22 of the plain bearing 20 relative to the rotor shaft 13, and a guide member 30 attached to the rotor shaft 13 so as to be adjacent to the rotor end surface 24 of the plain bearing 20. The plain bearing 20 is configured to be lubricated by CO2 refrigerant R supplied through the refrigerant supply passage 18 to the support space 22a between the plain bearing 20 and the rotor shaft 13, and the guide member 30 has a guide surface 31 that faces the rotor end face 24 via a predetermined gap (an injection passage 32 with a distance d), and the guide surface 31 is formed to guide the CO2 refrigerant R toward the coil 12b wound around the stator 12 when the CO2 refrigerant R is sprayed from the support space 22a through the predetermined gap into the housing 15.

[0068] In this embodiment, the motor system S supplies CO2 refrigerant R to the support space 22a between the plain bearing 20 and the rotor shaft 13, thereby lubricating the sliding surface 22 of the plain bearing 20. The motor system S also ejects the lubricated CO2 refrigerant R from the support space 22a into the internal space 15b of the housing 15. At this time, the CO2 refrigerant R is directed toward the coil 12b of the stator 12 by the guide surface 31 (inclined surface) of the guide member 30 provided on the rotor shaft 13, thereby cooling the coil 12b, which is a high-temperature part of the motor 1. This makes it possible to use the CO2 refrigerant R to both lubricate the plain bearing 20 and cool the motor 1. Therefore, the motor system S of this embodiment can achieve both reduced agitation resistance loss during high-speed rotation and cooling of the coil 12b of the stator 12.

[0069] In this embodiment, the CO2 refrigerant R can be in a supercritical fluid state when supplied to the sliding bearing 20. This supercritical fluid expands and changes to a gas-liquid mixed state when it is ejected from the support space 22a through a specified gap into the housing 15. Furthermore, this gas-liquid mixed fluid evaporates as it exchanges heat with the coil 12b of the stator 12, changing to a gas.

[0070] Furthermore, according to this embodiment, guide surface 31 has an inclined surface whose diameter increases from sliding bearing 20 toward rotor 11. In this embodiment, CO2 refrigerant R flowing from support space 22a can be directed by guide surface 31 and released into internal space 15b of housing 15.

[0071] Moreover, according to this embodiment, the system further includes a refrigerant circulation system 8 that supplies CO2 refrigerant R to the refrigerant supply passage 18 and recovers the CO2 refrigerant R from inside the housing 15. In this embodiment, the motor system S, which includes the refrigerant circulation system 8 and the motor 1, can be mounted on, for example, a vehicle.

[0072] 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 refrigerant supply passage 18. 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). Furthermore, the condensed CO refrigerant R is 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). In this manner, a refrigeration cycle can be formed in this embodiment.

[0073] Furthermore, according to the present embodiment, the device is further provided with a position adjustment mechanism 40, 140, 240 for variably adjusting the relative axial distance d between the guide member 30 and the sliding bearing 20. In this embodiment, by adjusting the relative axial distance d, it is possible to adjust the flow rate of CO2 refrigerant R released from the sliding bearing 20 into the internal space 15b of the housing 15.

[0074] Moreover, according to the present embodiment, the guide member 30 includes a magnetic material and is attached so as to be movable in the axial direction L relative to the rotor shaft 13, the position adjustment mechanism 40 comprises biasing means 43 that biases the guide member 30 in a first axial direction toward the rotor 11, and an electromagnet 44 that magnetically attracts the magnetic material in a second axial direction toward the sliding bearing 20, and the motor system S further comprises a controller 46 that controls the supply of electricity to the electromagnet 44 so as to adjust the relative position of the guide member 30 with respect to the sliding bearing 20. In this embodiment, the axial distance d between the guide member 30 and the sliding bearing 20 can be adjusted by adjusting the axial position of the guide member 30 on the rotor shaft 13.

[0075] Furthermore, according to this embodiment, specifically, the biasing means 43 is disposed inside the rotor shaft 13 , and the electromagnet 44 is attached to the housing 15 or the plain bearing 20 .

[0076] Furthermore, according to this embodiment, the motor system S is configured such that the rotor 11 rotates in one direction relative to the stator 12, and the guide member 30 is threadedly engaged with the rotor shaft 13 so as to be movable in the axial direction L, and is attached so as to be movable back and forth from a reference position P0 on the rotor shaft 13 in the axial direction L in a first axial direction toward the rotor 11 and a second axial direction toward the sliding bearing 20 by rotating relative to the rotor shaft 13. The position adjustment mechanism 140 adjusts the position of the guide member 30 relative to the rotor shaft 13. and biasing means 143 that applies a biasing force to guide member 30 in a direction returning guide member 30 to reference position P0 in response to rotor shaft 13 rotating relative to the rotor shaft 13 and moving away from reference position P0 in the axial direction L, and when rotor shaft 13 rotates at an accelerated speed, guide member 30 moves in the first axial direction from reference position P0 against the biasing force of biasing means 143, when rotor shaft 13 rotates at a constant speed, guide member 30 remains in reference position P0, and when rotor shaft 13 rotates at a decelerated speed, guide member 30 moves in the second axial direction from reference position P0 against the biasing force of biasing means 143. In this embodiment, when motor 1 is operating, the axial position of guide member 30 on rotor shaft 13 is automatically adjusted in response to the positive and negative rotational acceleration of rotor shaft 13, making it possible to adjust the axial distance d between guide member 30 and sliding bearing 20.

[0077] According to this embodiment, the biasing means 143 is specifically a spring member 143a that connects the rotor shaft 13 and the guide member 30.

[0078] Moreover, according to the present embodiment, the sliding bearing 20 includes a magnetic material and is attached so as to be movable in the axial direction L relative to the housing 15, the position adjustment mechanism 240 comprises electromagnets 244a, 244b that can electromagnetically selectively attract the magnetic material in a first axial direction toward the guide member 30 and a second axial direction away from the guide member 30, and the motor system S further comprises a controller 246 that controls the supply of electricity to the electromagnets 244a, 244b so as to adjust the relative position of the guide member 30 with respect to the sliding bearing 20. In this embodiment, the axial distance d between the guide member 30 and the sliding bearing 20 can be adjusted by adjusting the axial position of the sliding bearing 20 with respect to the housing 15 (i.e., the guide member 30).

[0079] Furthermore, according to this embodiment, specifically, the electromagnets 244a and 244b are attached to the housing 15 or the sliding bearing 20.

[0080] Moreover, according to this embodiment, there is also provided a flow rate adjustment valve 340 that adjusts the flow rate of CO2 refrigerant R flowing through the refrigerant supply passage 18. In this embodiment, by adjusting the aperture of the flow rate adjustment valve 340, it is possible to adjust the flow rate of CO2 refrigerant supplied to the plain bearing 20 and adjust the injection flow rate of CO2 refrigerant R released into the internal space 15b of the housing 15 via the plain bearing 20. [Explanation of symbols]

[0081] 1 motor 11 rotor 12 stator, 12b coil, 12c coil end 13 rotor shaft 15 housing, 15b internal space 18 refrigerant supply passage, 19 refrigerant discharge passage 20 bearing, 22 sliding surface, 22a support space 24 rotor end face, 25 inclined face 30 guide member, 31 guide surface 32 Injection passage 40, 140, 240 position adjustment mechanism 43, 143 energizing means 44, 244a, 244b electromagnet 8 Refrigerant circulation system 81 Compressor 83 Heat exchanger 340 Flow control valve L axis direction P0 reference position R refrigerant S motor system d distance

Claims

1. A motor system including: a stator; a rotor; a rotor shaft fixed to the rotor and extending in an axial direction; a plain bearing rotatably supporting the rotor shaft and having a rotor end surface facing the rotor in the axial direction; and a housing holding the plain bearing, a refrigerant supply passage that passes through at least the housing and communicates with a sliding surface of the plain bearing relative to the rotor shaft; a guide member attached to the rotor shaft so as to be adjacent to the rotor end surface of the sliding bearing; Further provided with The sliding bearing is configured to circulate the CO refrigerant supplied through the refrigerant supply passage to a support space between the sliding bearing and the rotor shaft. 2 configured to be lubricated by a refrigerant; The guide member has a guide surface that faces the rotor end surface with a predetermined gap therebetween, and the guide surface 2 When the refrigerant is ejected from the support space through the predetermined gap into the housing, 2 A motor system configured to direct refrigerant toward coils wound around the stator.

2. The motor system according to claim 1 , wherein the guide surface has an inclined surface whose diameter increases from the sliding bearing toward the rotor.

3. The CO 2 A refrigerant is supplied to the refrigerant supply passage, and the CO 2 The motor system of claim 1 , further comprising a coolant circulation system that recovers coolant from within the housing.

4. 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 4. The motor system according to claim 3, further comprising: a condenser that supplies refrigerant to the refrigerant supply passage.

5. The motor system according to claim 1 , further comprising a position adjustment mechanism for variably adjusting a relative axial distance between the guide member and the sliding bearing.

6. the guide member includes a magnetic body and is attached to the rotor shaft so as to be movable in the axial direction; the position adjustment mechanism includes a biasing means that biases the guide member in a first axial direction toward the rotor, and an electromagnet that magnetically attracts the magnetic body in a second axial direction toward the sliding bearing, The motor system according to claim 5 , further comprising a controller that controls energization of the electromagnet so as to adjust the relative position of the guide member with respect to the sliding bearing.

7. The motor system according to claim 6 , wherein the biasing means is disposed within the rotor shaft, and the electromagnet is attached to the housing or the plain bearing.

8. the motor system is configured such that the rotor rotates in one direction relative to the stator; the guide member is threadedly engaged with the rotor shaft so as to be axially movable, and is attached so as to be movable back and forth from a reference axial position on the rotor shaft in a first axial direction toward the rotor and a second axial direction toward the sliding bearing, the position adjustment mechanism includes a biasing means that applies a biasing force to the guide member in a direction returning the guide member to the reference position in response to the guide member rotating relative to the rotor shaft and moving away from the reference position in the axial direction, 6. The motor system according to claim 5, wherein the guide member moves from the reference position in the first axial direction against the biasing force of the biasing means when the rotor shaft rotates at an accelerated speed, remains at the reference position when the rotor shaft rotates at a constant speed, and moves from the reference position in the second axial direction against the biasing force of the biasing means when the rotor shaft rotates at a decelerated speed.

9. 9. The motor system according to claim 8, wherein the biasing means is a spring member connecting the rotor shaft and the guide member.

10. the sliding bearing includes a magnetic body and is attached to the housing so as to be axially movable, the position adjustment mechanism includes an electromagnet that can electromagnetically selectively attract the magnetic body in a first axial direction toward the guide member and a second axial direction away from the guide member, The motor system according to claim 5 , further comprising a controller that controls energization of the electromagnet so as to adjust the relative position of the guide member with respect to the sliding bearing.

11. The motor system according to claim 10 , wherein the electromagnet is attached to the housing or the plain bearing.

12. The CO flowing through the refrigerant supply passage 2 The motor system according to claim 1 , further comprising a flow control valve for controlling the flow rate of the coolant.

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