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 particularly to a motor system having a bearing portion.

Background Art

[0002] Conventionally, there has been known a technique of cooling coil ends by injecting oil onto the coil ends wound around a stator of an electric motor (see, for example, Patent Document 1). In the electric motor of Patent Document 1, oil is introduced into a hollow rotor shaft of the electric motor, and the oil is ejected to the outside of the rotor shaft through a through-hole formed in a peripheral surface of the rotor shaft. The ejected oil is directed toward the coil ends via a member attached to the rotor shaft, so as to cool the coil ends.

[0003] Further, in general, a rotor shaft of an electric motor is configured to be supported by rolling bearings or slide bearings. In the electric motor of Patent Document 1, the rotor shaft is supported by rolling bearings.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

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, exceeding 30,000 rpm), rolling fatigue becomes a problem in rolling bearings. To avoid this, such an ultra-high-speed rotation motor may employ an oil-lubricated slide bearing instead of a rolling bearing. In an oil-lubricated slide bearing, oil is supplied to the slide bearing. However, in this case, in an ultra-high-speed rotation motor, stirring resistance loss during high rotation of the rotor shaft becomes a problem due to the viscosity of the oil.

[0006] The present invention was made to solve the problems of the prior art described above, and aims to provide a motor system that can achieve both a reduction in stirring resistance loss during high-speed rotation and cooling of the stator coils. [Means for solving the problem]

[0007] To achieve the above objective, 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 sliding bearing that rotatably supports the rotor shaft and has a rotor end face facing the rotor in the axial direction, and a housing that holds the sliding bearing, further comprising a refrigerant supply passage communicating with the sliding surface of the sliding bearing relative to the rotor shaft, at least through the housing, and a guide member attached to the rotor shaft so as to be adjacent to the rotor end face of the sliding bearing, wherein the sliding bearing is configured to be lubricated by a CO2 refrigerant supplied to the support space between the sliding bearing and the rotor shaft through the refrigerant supply passage, and the guide member has a guide surface that faces the rotor end face with a predetermined gap, and the guide surface is formed to guide the CO2 refrigerant toward the coil wound around the stator when the CO2 refrigerant is ejected 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 surface of the sliding bearing by supplying CO2 refrigerant to the support space between the sliding 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. At this time, the CO2 refrigerant is directed towards the stator coil by the guide surface of the guide member provided on the rotor shaft 13, thereby cooling the coil, which is the high-temperature part of the motor. Thus, in the present invention, it is possible to use CO2 refrigerant for both lubrication of the sliding bearing and cooling of the motor. Therefore, the motor system of the present invention can achieve both a reduction in stirring resistance loss during high-speed rotation and cooling of the stator coil.

[0009] In this invention, the CO2 refrigerant can be in the form of a supercritical fluid when supplied to the sliding bearing. This supercritical fluid expands when it is ejected from the support space through a predetermined gap into the housing 15, and displaces into a gas-liquid mixture state. Furthermore, this gas-liquid mixture evaporates by exchanging heat with the coil 12b of the stator 12, and displaces into a gas.

[0010] Furthermore, in the present invention, preferably, the guide surface has an inclined surface that widens in diameter as it moves from the sliding bearing toward the rotor. With the present invention configured in this way, the CO2 refrigerant flowing from the support space can be directed by the inclined surface and released into the internal space of the housing.

[0011] Furthermore, the present invention preferably further includes a refrigerant circulation system that supplies CO2 refrigerant to a refrigerant supply passage and recovers the CO2 refrigerant from within the housing. With the present invention configured in this way, a motor system comprising a refrigerant circulation system and a motor can be mounted, for example, on a vehicle.

[0012] Furthermore, in the present invention, preferably, the refrigerant circulation system includes a compressor that compresses gaseous CO2 refrigerant recovered from the housing to produce supercritical fluid CO2 refrigerant, and a condenser that condenses the CO2 refrigerant output from the compressor, exchanges heat with the external environment, and supplies the supercritical fluid CO2 refrigerant to the refrigerant supply passage. With the present invention configured in this way, the gaseous CO2 refrigerant after heat exchange in the motor is compressed by the compressor to form a high-temperature, high-pressure supercritical fluid (compression stroke). Next, the compressed CO2 refrigerant is condensed in the condenser to a medium-temperature, high-pressure state (condensation stroke). Furthermore, the condensed CO2 refrigerant is expanded in the motor to a low-temperature, low-pressure gas-liquid mixture state (expansion stroke). Finally, it is evaporated by heat exchange in the motor to produce high-temperature, low-pressure gaseous CO2 refrigerant (evaporation stroke). In the present invention, a refrigeration cycle can be formed in this way.

[0013] Furthermore, the present invention preferably includes a position adjustment mechanism for adjusting the relative axial distance between the guide member and the sliding bearing. With the present invention configured in this way, the flow rate of CO2 refrigerant released from the sliding bearing into the internal space of the housing can be adjusted by adjusting the relative axial distance.

[0014] Furthermore, in the present invention, preferably, the guide member includes a magnetic material and is mounted so as to be axially movable with respect to the rotor shaft, the position adjustment mechanism comprises a biasing means for biasing the guide member in a first axial direction toward the rotor, and an electromagnet for magnetically attracting 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 power to the electromagnet to adjust the relative position of the guide member with respect to the sliding bearing. With 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 guide member on the rotor shaft.

[0015] Furthermore, in this invention, specifically, the biasing means is arranged within the rotor shaft, and the electromagnet is attached to the housing or sliding bearing.

[0016] Furthermore, 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 screwed onto the rotor shaft so as to be movable in the axial direction, and is mounted so as to be able to move back and forth in a first axial direction toward the rotor and a second axial direction toward the sliding bearing from an axial reference position on the rotor shaft by rotating relative to the rotor shaft, the position adjustment mechanism includes a biasing means that applies a biasing force to the guide member in the direction of 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 is rotating at an accelerating speed, remains at the reference position when the rotor shaft is rotating 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 is rotating at a decelerating speed. With the present invention configured in this way, when the motor is operating, the axial position of the guide member on the rotor shaft is automatically adjusted according to 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 sliding bearing.

[0017] Furthermore, in this invention, 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 mounted axially movable relative to the housing, the position adjustment mechanism comprises an electromagnet capable of electromagnetically selectively attracting 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 power to the electromagnet to adjust the relative position of the guide member with respect to the sliding bearing. With 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] Furthermore, in this invention, specifically, the electromagnet is mounted on a housing or a sliding bearing.

[0020] Further, in the present invention, it is preferable to further comprise a flow rate adjustment valve that adjusts the flow rate of the CO₂ refrigerant flowing through the refrigerant supply passage. According to the present invention configured as described above, by adjusting the opening degree of the flow rate adjustment valve, the flow rate of the CO₂ refrigerant supplied to the plain bearing can be adjusted, and the injection flow rate of the CO₂ refrigerant discharged into the inner space of the housing via the plain bearing can be adjusted.

Effects of the Invention

[0021] According to the motor system of the present invention, both reduction of stirring resistance loss during high-speed rotation and cooling of the stator coils can be achieved.

Brief Description of Drawings

[0022] [Figure 1] It is a schematic configuration diagram of a motor system according to an embodiment of the present invention. [Figure 2] It is an explanatory diagram of a refrigerant refrigeration cycle according to an embodiment of the present invention. [Figure 3] It is an explanatory diagram of a guide portion according to an embodiment of the present invention. [Figure 4] It is an explanatory diagram of a bearing structure according to a first embodiment of the present invention. [Figure 5A] It is an explanatory diagram of a bearing structure according to a second embodiment of the present invention. [Figure 5B] It is an explanatory diagram of the operation of the bearing structure according to the second embodiment of the present invention. [Figure 5C] It is an explanatory diagram of the operation of the bearing structure according to the second embodiment of the present invention. [Figure 6] It is an explanatory diagram of a bearing structure according to a third embodiment of the present invention. [Figure 7] It is an explanatory diagram of a bearing structure according to a fourth embodiment of the present invention.

Mode for Carrying Out 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 the motor system according to this embodiment will be described with reference to Figure 1. Figure 1 is a schematic diagram of the motor system according to this embodiment. The motor system S shown in Figure 1 can be mounted on a vehicle such as an electric vehicle and provide rotational driving force to the vehicle.

[0024] The motor system S comprises 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 refrigerant R in a refrigeration cycle to cool the motor 1. That is, in this refrigeration cycle, the expansion and evaporation strokes of refrigerant R are performed in the motor 1, and the compression and condensation strokes of refrigerant R are performed in the refrigerant circulation system 8. In this embodiment, it is preferable to use a natural refrigerant such as CO2 as refrigerant R. Alternatively, a mixture of natural refrigerant and oil in a predetermined mixing ratio may be used as refrigerant R.

[0025] [Refrigerant circulation system configuration] The refrigerant circulation system 8 includes a compressor 81 for compressing the refrigerant R, a heat exchanger (condenser) 83 which includes a condenser and fan 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 (sliding bearings) 20 that rotatably support the rotor shaft 13, a housing 15 that houses and supports the rotor 11, stator 12, rotor shaft 13, and bearings 20, and a sealing member 16 that seals the space between the housing 15 and the rotor shaft 13. One end of the rotor shaft 13 is connected to a vehicle transaxle (not shown) or the like.

[0027] The roughly cylindrical stator 12 is constructed by winding a coil 12b around a stator core 12a. As shown in Figure 1, the coil 12b is wound around the stator core 12a, so that coil ends 12c protrude from both ends of the stator core 12a in the axial direction. 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 rotate within the stator 12 with the rotor shaft 13 as its axis of rotation.

[0028] The sealing member 16 seals the space between the end of the rotor shaft 13, which protrudes to the outside through the through hole 15a formed in the housing 15, and the housing 15, thereby preventing the leakage of refrigerant R from the inside of the housing 15 to the outside.

[0029] Furthermore, the motor 1 has a refrigerant supply passage 18 that supplies 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. Specifically, the refrigerant supply passage 18 supplies 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 used for lubrication of the bearing 20. In this embodiment, 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 exits the bearing 20 and enters the housing 15, vaporizes through heat exchange with motor components, and then returns to the refrigerant circulation system 8 through the refrigerant discharge passage 19.

[0030] Motor 1 is an ultra-high-speed rotating motor, configured to operate at high rotational speeds exceeding, for example, 30,000 rpm. Therefore, if a rolling bearing were to be used for bearing 20, rolling fatigue would become a problem. Furthermore, if a typical oil-lubricated sliding bearing using oil were to be used, the loss due to oil stirring resistance by the rotor shaft 13 would be significant. Therefore, in this embodiment, a sliding bearing using a supercritical fluid refrigerant R, which has significantly lower viscosity than oil, is used as bearing 20 instead of oil. In this embodiment, by supplying a supercritical fluid refrigerant R, which has higher density and viscosity than gaseous refrigerant R, to bearing 20, a necessary liquid film can be provided on the sliding surface. This eliminates problems such as rolling fatigue and oil stirring resistance.

[0031] Furthermore, the motor 1 has a guide member 30 for blowing the coolant R, which is provided for lubricating the bearing 20, onto the high-temperature parts inside the motor 1. In addition, the motor 1 is equipped with 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, with reference to Figure 2, the refrigeration cycle of the refrigerant R in this embodiment will be described. Figure 2 is a pH diagram of the CO2 refrigerant, with the horizontal axis representing enthalpy and the vertical axis representing pressure. The viscosity (μPa·s) of the CO2 refrigerant is also shown in Figure 2. When the pressure and temperature of the CO2 refrigerant are increased from the ambient environment (room temperature, 1 atmosphere) to reach the critical point (31°C, 7.4 MPa), it becomes a supercritical fluid.

[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 high-temperature, high-pressure CO2 refrigerant R (point B), exchanges heat with the external environment (cold air, cooling water, etc.), and generates medium-temperature, high-pressure CO2 refrigerant R (supercritical fluid) (point C). The medium-temperature, high-pressure CO2 refrigerant R is supplied to the bearing 20 of the motor 1 and lubricates the bearing 20.

[0035] Furthermore, an expansion stroke (CD) takes place inside the motor 1. The CO2 refrigerant R enters the internal space 15b of the housing 15 through the annular support space between the bearing 20 and the rotor shaft 13, and through the injection passage. At this time, the CO2 refrigerant R expands as it moves from a narrow space to a wider 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 part 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] Figure 3 is an explanatory diagram of the bearing structure of this embodiment. As shown in Figure 3, the bearing 20 rotatably supports the end of the rotor shaft 13. The bearing 20 comprises a substantially cylindrical body portion 21 and an end face (rotor end face) 24 facing the rotor 11. The inner circumferential surface of the body portion 21 is the sliding surface 22 with respect to the rotor shaft 13. The rotor end face 24 has an inclined surface 25 that is cut out in a conical shape. The inclined surface 25 is the thrust surface. The body portion 21 has a through hole 23 that extends from the radially outer side of the rotor shaft 13 toward the center, passing through the side wall from the outer circumferential surface 26 of the body portion 21 and communicating with the sliding surface 22. The through hole 23 communicates with the refrigerant supply passage 18 and forms part of the refrigerant supply passage 18. The refrigerant supply passage 18 may be directly connected to the support space 22a between the rotor shaft 13 and the bearing 20 without passing through the through hole 23.

[0037] The guide member 30 is an umbrella-shaped member and has a conical guide surface (inclined surface) 31 that widens in diameter 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 approximately 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 apart by a predetermined distance d in the axial direction L to form an annular injection passage 32. The injection passage 32 defines 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 part, is located on its extension. Although having an inclined surface 25 on the rotor end surface 24 of the bearing 20 is advantageous for the guidance of the refrigerant R, it is not necessary for the rotor end surface 24 of the bearing 20 to have an inclined surface 25.

[0038] During operation of motor 1, the refrigerant circulation system 8 pumps the supercritical fluid refrigerant R to the bearing 20 through the refrigerant supply passage 18 and through hole 23. The supercritical fluid refrigerant R maintains a high-pressure state and lubricates the bearing 20 by filling the support space 22a between the rotor shaft 13 and the bearing 20. The refrigerant R flows axially L through the narrow support space 22a toward the guide member 30, and is then injected into the internal space 15b of the housing 15 through the narrow injection passage 32. The refrigerant R expands as it enters the wider 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. Upon reaching the coil end 12c, the refrigerant R cools the coil end 12c. The refrigerant R that has vaporized after heat exchange with the coil end 12c is discharged to the outside through the refrigerant discharge passage 19.

[0039] [Flow rate adjustment control] Next, referring to Figures 4 to 7, each embodiment of flow rate adjustment control for the refrigerant R that cools the coil ends 12c of the stator 12 will be described. In this embodiment, the same reference numerals are used for the same elements, and redundant explanations are omitted. Also, in Figures 4 to 7, the non-output ends of the rotor shaft 13 that are not connected to external structures (transaxle, etc.) are shown, but a similar configuration is provided at the output end.

[0040] In this embodiment, power to support the rotor shaft 13 can be obtained by supplying a 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 secured, leading to 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 does not vaporize completely will be supplied to the downstream compressor 81, causing liquid compression. In addition, the cooling requirements for the coil ends 12c differ 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] The flow rate adjustment control according to the first embodiment will be explained 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 configured to be adjustable by the position adjustment mechanism 40. In the first embodiment, the flow rate of the refrigerant R is adjusted by adjusting the passage width or distance d of the injection passage 32.

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

[0043] The biasing means 43 biases the guide member 30 away from the bearing 20 in the axial direction L. Inside the rotor shaft 13, there is an operating hole 41a extending in the axial direction L, and a guide hole 41b communicating with the operating hole 41a and extending radially to reach the circumferential surface of the rotor shaft 13. The biasing means 43 includes an operating rod 43a disposed in the operating hole 41a, a connecting rod 43b disposed 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 of the operating rod 43a. Both ends of the connecting rod 43b are connected to the guide member 30. Therefore, the connecting rod 43b, together with the guide member 30, is movable within the guide hole 41b by a predetermined length in the axial direction L. The spring member 43c constantly biases the operating rod 43a in the axial direction L toward the rotor 11 (first axial direction), and via the connecting rod 43b, biases the guide member 30 toward the bearing 20.

[0045] The electromagnet 44 has a configuration in which an electric wire is wound around a magnetic material, and generates electromagnetic force in the axial direction L when the electric wire is energized. The guide member 30 is formed containing a magnetic material. For example, the guide member 30 itself is made of a magnetic material, or the guide member 30 contains a magnetic material therein. Therefore, when the electromagnet 44 generates electromagnetic force, the electromagnetic force attracts the guide member 30 toward the bearing 20 (the second axial direction), and the distance d becomes smaller than the initial value (reference distance d0) (d<d0).

[0046] The controller 46 can control the distance d between the guide member 30 and the bearing 20 by controlling the amount of energization to the electromagnet 44 (that is, the attraction force applied to the guide member 30) based on a sensor signal SR such as the motor rotation speed. 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 demand for the coil end 12c is small), the controller 46 sets the energization amount to a large value, thereby increasing the moving distance of the guide member 30 and decreasing the distance d (d<d0). Accordingly, the refrigerant R is supplied to the high-temperature portion with a small injection flow rate. On the other hand, when the rotation speed is high (that is, when the cooling demand is large), the controller 46 sets the energization amount to a small value, thereby reducing the moving distance of the guide member 30 and increasing the distance d. For example, when the energization amount is zero, the distance d is equal to the reference distance d0. Accordingly, the refrigerant R is supplied to the high-temperature portion with a large injection flow rate.

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

[0049] Thus, 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 magnitude of the cooling requirement for the motor 1.

[0050] [Second Embodiment] The flow rate adjustment control according to the second embodiment will be explained 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 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 the position adjustment mechanism 140 in accordance with the change in the rotational speed (acceleration a) of the motor 1. In the second embodiment, the flow rate of the refrigerant R is adjusted by adjusting the passage width or distance d of the injection passage 32. The motor 1 is configured to rotate in one direction.

[0051] As shown in Figure 5A, the guide member 30 is provided with a through hole 132 for the rotor shaft 13 to pass through, and a helical screw groove (female thread) 132a is formed on the inner circumferential surface of the through hole 132. In addition, a screw groove (male thread) 113a is formed on the outer circumferential surface of the rotor shaft 13 that engages with the screw groove 132a of the guide member 30. Therefore, the guide member 30 is screwed to the rotor shaft 13 and can move along the rotor shaft 13 in the axial direction L by rotating. Alternatively, the guide member 30 may have a male screw groove and the rotor shaft 13 may have a female screw groove.

[0052] The position adjustment mechanism 140 includes a biasing means 143 that biases the guide member 30 circumferentially relative to the rotor shaft 13. The biasing means 143 comprises a spring member 143a, a mounting member 143b fixed to the rotor shaft 13, and a mounting member 143c fixed to the guide member 30. One end of the spring member 143a is connected to the mounting member 143b of the rotor shaft 13, and the other end is connected to the mounting member 143c of the guide member 30. The spring member 143a is expandable and contractible, and acts as a compressive force (when extended) and an elongating force (when compressed) depending on the positive and negative displacement lengths from its natural length. Normally, the guide member 30 is 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 axial travel distance L of the guide member 30 is appropriately set according to the acceleration a.

[0053] Figures 5B(b) and 5C(b) show the motor 1 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 held at the reference position P0. Consequently, the passage width (d) of the injection passage 32 has a reference distance d0 (d=d0), and the injection flow rate of the refrigerant R is maintained at the reference flow rate.

[0054] Figs. 5B(a) and 5C(a) show a state where the motor 1 is accelerating (that is, acceleration a > 0). When the motor rotation speed is increasing, the speed of the guide member 30 increases later than that of the rotor shaft 13 due to inertial force, and the guide member 30 slightly rotates relative to the rotor shaft 13. In the present embodiment, when such relative rotation occurs, the helical 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 separates from the bearing 20, the passage width (distance d) of the injection passage 32 becomes larger 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 of the spring member 143a returning to its natural length (expansion force) rotates the guide member 30 in the returning direction, and returns the guide member 30 to the reference position P0.

[0055] Figs. 5B(c) and 5C(c) show a state where the motor 1 is decelerating (that is, acceleration a < 0). When the motor rotation speed is decreasing, the speed of the guide member 30 decreases later than that of the rotor shaft 13 due to inertial force, and the guide member 30 slightly rotates relative to the rotor shaft 13. In the present embodiment, when such relative rotation occurs, the helical 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 smaller 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 of the spring member 143a returning to its natural length (compression force) rotates the guide member 30 in the returning direction, and returns the guide member 30 to the reference position P0.

[0056] As described above, in the second embodiment, the injection flow rate can be automatically adjusted according to the level of the cooling demand for the motor 1 (that is, the cooling demand is high when the motor 1 is accelerating, and the cooling demand is low when the motor 1 is decelerating).

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

[0058] As shown in Figure 6, in this embodiment, the housing 15 has a bottomed mounting hole 51 for mounting the bearing 20. A screw groove (female thread) 51a is formed on the inner circumferential surface of the mounting hole 51. In addition, a screw groove (male thread) 21a is formed on the outer circumferential surface 26 of the main body portion 21 of the bearing 20, which engages with the screw groove 51a of the mounting hole 51. Therefore, the bearing 20 is screwed into the mounting hole 51 of the housing 15 and can move forward and backward in the axial direction L relative to the mounting hole 51 by rotation. Alternatively, the housing 15 may have a male screw groove and the bearing 20 may have a female screw groove. Furthermore, other configurations may be used as long as the bearing 20 can move forward and backward relative to the housing 15. For example, a slider provided on the bearing 20 may slide on a guide rail provided in the mounting hole 51 of the housing 15.

[0059] The position adjustment mechanism 240 comprises a pair of electromagnets 244a and 244b arranged radially outward from the rotor shaft 13 within the housing 15 or bearing 20, and a controller 246 that controls the energization of these electromagnets 244a and 244b. The electromagnets 244a and 244b are spaced apart by a predetermined length in the axial direction L. The electromagnets 244a and 244b have a configuration in which an electric wire is wound around a magnetic material, and an electromagnetic force is generated by energizing the electric wire.

[0060] Further, the bearing 20 is formed to include a magnetic body 21b between the pair of electromagnets 244a and 244b in the axial direction L. Accordingly, 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 along the thread groove 51a of the mounting hole 51 and slightly moves in the axial direction L.

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

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

[0063] As described above, 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 in accordance with the magnitude of the cooling demand for the motor 1.

[0064] [Fourth Embodiment] Referring to Figure 7, the flow rate adjustment control according to the fourth embodiment will be described. Figure 7 shows the bearing structure of the fourth embodiment. In the fourth embodiment, the flow rate of the refrigerant R supplied to the bearing 20 is adjusted. In the fourth embodiment, for this flow rate adjustment control, a flow rate adjustment valve 340 is provided in the refrigerant supply passage 18, and a controller 346 controls the 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 of a separate component 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 sensor signals SR such as motor rotation speed, the controller 346 can increase the flow rate by opening the flow control valve 340 when the cooling requirement for the motor 1 is high, and decrease the flow rate by opening the flow control valve 340 when the cooling requirement is low. In this fourth embodiment, it is possible to appropriately adjust the injection flow rate from the bearing 20 to the coil end 12c in accordance with the cooling requirement.

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

[0068] In this embodiment, the motor system S can lubricate the sliding surface 22 of the sliding bearing 20 by supplying CO2 refrigerant R to the support space 22a between the sliding bearing 20 and the rotor shaft 13. 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 towards 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. Thus, in this embodiment, the CO2 refrigerant R can be used for both lubrication of the sliding bearing 20 and cooling of the motor 1. Therefore, the motor system S of this embodiment can achieve both a reduction in stirring 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 the form of a supercritical fluid when supplied to the sliding bearing 20. This supercritical fluid expands and displaces into a gas-liquid mixture state when it is ejected from the support space 22a through a predetermined gap into the housing 15. Furthermore, this gas-liquid mixture evaporates and displaces into a gas by exchanging heat with the coil 12b of the stator 12.

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

[0071] Furthermore, according to this embodiment, a refrigerant circulation system 8 is provided 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, for example, on a vehicle.

[0072] Furthermore, according to this embodiment, the refrigerant circulation system 8 includes a compressor 81 that compresses the gaseous CO2 refrigerant R recovered from the housing 15 to produce a supercritical fluid CO2 refrigerant R, and a condenser (heat exchanger) 83 that condenses the CO2 refrigerant R output from the compressor 81, exchanges heat with the external environment, and supplies the supercritical fluid CO2 refrigerant R to the refrigerant supply passage 18. In this embodiment, the gaseous CO2 refrigerant R after heat exchange in the motor 1 is compressed by the compressor 81 to form a high-temperature, high-pressure supercritical fluid (compression stroke). Next, the compressed CO2 refrigerant R is condensed in the condenser 83 to a medium-temperature, high-pressure state (condensation stroke). Furthermore, the condensed CO2 refrigerant R is expanded in the motor 1 to a low-temperature, low-pressure gas-liquid mixture state (expansion stroke). Finally, it is evaporated by heat exchange in the motor 1 to produce a high-temperature, low-pressure gaseous CO2 refrigerant R (evaporation stroke). In this embodiment, a refrigeration cycle can be formed.

[0073] Furthermore, this embodiment includes position adjustment mechanisms 40, 140, and 240 for adjusting the relative axial distance d between the guide member 30 and the sliding bearing 20. In this embodiment, the flow rate of the CO2 refrigerant R released from the sliding bearing 20 into the internal space 15b of the housing 15 can be adjusted by adjusting the relative axial distance d.

[0074] Furthermore, according to this embodiment, the guide member 30 includes a magnetic material and is mounted so as to be movable in the axial direction L relative to the rotor shaft 13. The position adjustment mechanism 40 includes a 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. The motor system S further includes a controller 46 that controls the supply of power to the electromagnet 44 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 arranged inside the rotor shaft 13, and the electromagnet 44 is attached to the housing 15 or the sliding 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 screwed onto the rotor shaft 13 so as to be movable in the axial direction L, and is mounted so as to be able to move back and forth in a first axial direction toward the rotor 11 and a second axial direction toward the sliding bearing 20 from a reference position P0 in the axial direction L on the rotor shaft 13 by rotating relative to the rotor shaft 13, and the position adjustment mechanism 140 is such that the guide member 30 is on the rotor shaft 13 In contrast, the motor 1 is equipped with a biasing means 143 that applies a biasing force to the guide member 30 in the direction of returning it to the reference position P0 as it rotates and moves away from the reference position P0 in the axial direction L. The guide member 30 moves from the reference position P0 in the first axial direction against the biasing force of the biasing means 143 when the rotor shaft 13 is rotating at an accelerating speed, remains at the reference position P0 when the rotor shaft 13 is rotating at a constant speed, and moves from the reference position P0 in the second axial direction against the biasing force of the biasing means 143 when the rotor shaft 13 is rotating at a decelerating speed. In this embodiment, when the motor 1 is operating, the axial position of the guide member 30 on the rotor shaft 13 is automatically adjusted according to the positive and negative rotational acceleration of the rotor shaft 13, thereby allowing adjustment of the axial distance d between the guide member 30 and the sliding bearing 20.

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

[0078] Furthermore, according to this embodiment, the sliding bearing 20 includes a magnetic material and is mounted to the housing 15 so as to be movable in the axial direction L, and the position adjustment mechanism 240 includes 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 includes a controller 246 that controls the supply of power to the electromagnets 244a, 244b 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] Furthermore, according to this embodiment, a flow control valve 340 is provided to adjust the flow rate of the CO2 refrigerant R flowing through the refrigerant supply passage 18. In this embodiment, by adjusting the opening degree of the flow control valve 340, the flow rate of the CO2 refrigerant supplied to the sliding bearing 20 can be adjusted, and the injection flow rate of the CO2 refrigerant R released into the internal space 15b of the housing 15 via the sliding bearing 20 can be adjusted. [Explanation of Symbols]

[0081] 1 motor 11 rotors 12 Stator, 12b Coil, 12c Coil terminal 13 Rotor shaft 15 Housing, 15b Interior space 18 Refrigerant supply passage, 19 Refrigerant discharge passage 20 Bearing, 22 Sliding surface, 22a Support space 24 Rotor end face, 25 Inclined surface 30 Guide member, 31 Guide surface 32 Injection passage 40, 140, 240 position adjustment mechanism 43, 143 Biasing 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 comprising a stator, a rotor, a rotor shaft fixed to the rotor and extending in the axial direction, a sliding bearing that rotatably supports the rotor shaft and has a rotor end face facing the rotor in the axial direction, and a housing that holds the sliding bearing, A refrigerant supply passage that communicates with the sliding surface of the sliding bearing relative to the rotor shaft, at least through the housing, A guide member is attached to the rotor shaft so as to be adjacent to the rotor end face of the sliding bearing, Furthermore, The sliding bearing receives CO2 supplied through the refrigerant supply passage into the support space between the sliding bearing and the rotor shaft. 2 It is configured to be lubricated by a refrigerant. The guide member has a guide surface that faces the rotor end face with a predetermined gap between them, and the guide surface is the CO 2 When the refrigerant is ejected from the support space through the predetermined gap into the housing, the CO 2 A motor system configured to guide a refrigerant toward a coil wound around the stator.

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

3. The aforementioned CO 2 The refrigerant is supplied to the refrigerant supply passage, and the CO 2 The motor system according to claim 1, further comprising a refrigerant circulation system for recovering refrigerant from within the housing.

4. The refrigerant circulation system is The CO gas recovered from the housing 2 The refrigerant is compressed to form a supercritical fluid CO 2 A compressor that generates a refrigerant, The CO output from said compressor 2 refrigerant is condensed to exchange heat with the external environment, and the CO in the supercritical fluid 2 a condenser that supplies refrigerant to the refrigerant supply passage; the motor system according to claim 3, comprising the condenser.

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

6. The guide member includes a magnetic material and is mounted so as to be movable in the axial direction relative to the rotor shaft. The position adjustment mechanism comprises a biasing means for biasing the guide member in a first axial direction toward the rotor, and an electromagnet for magnetically attracting the magnetic material in a second axial direction toward the sliding bearing. The motor system according to claim 5, further comprising a controller that controls the supply of current to the electromagnet in order 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 arranged within the rotor shaft, and the electromagnet is attached to the housing or the sliding bearing.

8. The motor system is configured such that the rotor rotates in one direction relative to the stator. The guide member is screwed onto the rotor shaft so as to be movable in the axial direction, and is mounted so as to be able to move back and forth in a first axial direction toward the rotor and a second axial direction toward the sliding bearing, from an axial reference position on the rotor shaft by rotating relative to the rotor shaft. The position adjustment mechanism includes a biasing means that applies a biasing force to the guide member in the direction of returning the guide member to the reference position as the guide member rotates relative to the rotor shaft and moves axially away from the reference position. 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 is rotating at an accelerating speed, remains in the reference position when the rotor shaft is rotating 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 is rotating at a reduced speed.

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 material and is mounted to the housing so as to be movable in the axial direction. The position adjustment mechanism comprises an electromagnet capable of electromagnetically selectively attracting the magnetic material 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 the supply of current to the electromagnet in order 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 sliding bearing.

12. The CO2 flowing through the refrigerant supply passage 2 The motor system according to claim 1, further comprising a flow control valve for adjusting the flow rate of refrigerant.

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