Motor bearing system

Abstract

To perform switching between a rolling bearing and a sliding bearing by a simple configuration.SOLUTION: A motor bearing system 20 includes: a bearing 4 having an outer ring 6 provided so as to surround the outer periphery of a rotation shaft 2 of a motor 1, an inner ring 7 provided through a gap with the rotation shaft, and a plurality of rolling elements 5 interposed between the outer ring and the inner ring; and a clutch 10 provided on the outer periphery of the rotation shaft and arranged in parallel with the bearing along the axial direction of the rotation shaft, which can switch the state between a fixed state in which the inner ring of the bearing is fixed to the rotation shaft and a released state in which the inner ring is released from the rotation shaft. The bearing functions as a rolling bearing in the fixed state and as a sliding bearing in the released state. The clutch is provided so as to be rotatable with the rotation shaft, and movable in the axial direction, and forms the fixed state by moving to the bearing side in the axial direction while forming the released state by moving to a side opposite to the bearing in the axial direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a bearing system for a motor.

Background Art

[0002] Conventionally, for example, rolling bearings and sliding bearings have been used as bearings for supporting the rotating shafts of power sources (engines and motors) of vehicles. A rolling bearing has low friction in a low rotation region, while a sliding bearing has high friction in a low rotation region. On the other hand, a rolling bearing has a finite life due to rolling fatigue, while a sliding bearing has a permanent life under appropriate lubrication conditions.

[0003] Here, a technique has been proposed in which a system is configured to have both a rolling bearing and a sliding bearing, and the bearing to be applied is switched according to the characteristics of each bearing as described above. For example, Patent Document 1 describes a sliding bearing that supports a rotating body housed in a housing, a rolling bearing that is arranged in parallel with the sliding bearing and supports the rotating body, and a moving mechanism that switches the bearing that functions to support the rotating body by axially moving the inner ring or outer ring of the rolling bearing. In particular, in this system, the radial clearance of the rolling bearing is changed by relatively moving the inner ring or outer ring axially by driving a moving device. When the radial clearance of the rolling bearing is larger than the radial clearance of the sliding bearing, only the sliding bearing functions, while when the radial clearance of the rolling bearing is smaller than the radial clearance of the sliding bearing, only the rolling bearing functions.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technique described in Patent Document 1 mentioned above, both a sliding bearing and a rolling bearing configured separately were used, and the rolling bearing and the sliding bearing were switched by relatively moving the inner ring or the outer ring of the rolling bearing in the axial direction, so the configuration of the system was complicated.

[0006] The present invention has been made to solve the above-described problems of the prior art, and an object thereof is to provide a bearing system for a motor capable of switching between a rolling bearing and a sliding bearing with a simple configuration.

Means for Solving the Problems

[0007] To achieve the above object, the present invention is a bearing system for a motor applied to a vehicle, including an outer ring provided so as to surround the outer periphery of the rotating shaft of the motor, an inner ring disposed inside the outer ring and provided with a gap between the inner ring and the rotating shaft, and a plurality of rolling elements interposed between the outer ring and the inner ring, a bearing configured to support the rotating shaft, and a clutch provided on the outer periphery of the rotating shaft and arranged in parallel with the bearing along the axial direction of the rotating shaft, the clutch being configured to be capable of switching between a first state in which the inner ring of the bearing is fixed to the rotating shaft and a second state in which the inner ring is released from the rotating shaft. The bearing functions as a rolling bearing in the first state and as a sliding bearing in the second state. The clutch is provided so as to be rotatable with the rotating shaft and axially movable on the rotating shaft. By moving axially toward the bearing side and biasing the bearing, the first state is formed, while by moving axially to the side opposite to the bearing and separating from the bearing, the second state is formed.

[0008] In the present invention configured as described above, by axially moving the clutch on the rotating shaft to change the fixing (first state) and release (second state) of the inner ring of the bearing with respect to the rotating shaft, the bearing can be switched between a rolling bearing and a sliding bearing to function. Therefore, according to the present invention, unlike the technique described in Patent Document 1 above, a separately configured sliding bearing and rolling bearing are not used, and the inner ring or outer ring of the rolling bearing is not axially relatively moved. Thus, the switching between the rolling bearing and the sliding bearing can be performed with a simple configuration.

[0009] In the present invention, preferably, when viewed in a cross-section along the axial direction, a first inclined surface inclined with respect to the radial direction and the axial direction of the rotating shaft is formed at the end on the inner ring side of the bearing, and the clutch has, when viewed in a cross-section along the axial direction, a second inclined surface inclined with respect to the radial direction and the axial direction so as to be able to contact the first inclined surface of the bearing, formed opposite to the first inclined surface. When the first inclined surface of the bearing and the second inclined surface of the clutch come into contact, the first state is formed, while when the first inclined surface and the second inclined surface are separated, the second state is formed. In the present invention configured as described above, by forming the first state by bringing the first inclined surface and the second inclined surface into contact, compared with the case of bringing non-inclined vertical surfaces into contact, when bringing the first and second inclined surfaces into contact from the separated state, displacement of the axis center of the rotating shaft can be suppressed. In other words, it becomes easier to hold the position of the axis center at a desired position (center position).

[0010] In a preferred example of the present invention, the first inclined surface of the bearing, when viewed in a cross-section along the axial direction, is inclined in a direction away from the rotating shaft as it advances toward the clutch side, and the second inclined surface of the clutch, when viewed in a cross-section along the axial direction, is inclined in a direction approaching the rotating shaft as it advances toward the bearing side.

[0011] In the present invention, preferably, a pair of clutches are provided so as to sandwich the bearing in the axial direction. According to the present invention configured as described above, by sandwiching the bearing with a pair of clutches to form the first state, the inner ring of the bearing can be securely fixed to the rotating shaft.

[0012] In the present invention, preferably, a shaft rotation speed sensor for detecting the rotation speed of the rotating shaft, an actuator configured to be movable to switch the clutch between the first state and the second state, and a control device configured to control the actuator based on the rotation speed detected by the shaft rotation speed sensor are further provided. According to the present invention configured as described above, the rolling bearing and the sliding bearing can be accurately switched according to the rotation speed (motor rotation speed) of the rotating shaft. For example, based on the rotation speed of the rotating shaft, by determining a situation where a gas bearing as a sliding bearing can be realized, the bearing can be switched to the gas bearing in an accurate situation.

[0013] In the present invention, preferably, the control device controls the actuator to set the clutch to the first state when the rotation speed is less than the first speed, controls the actuator to switch the clutch between the first state and the second state when the rotation speed is between the first speed and a second speed higher than the first speed, and controls the actuator to set the clutch to the second state when the rotation speed is higher than the second speed. According to the present invention configured as described above, the rolling bearing and the sliding bearing can be switched more accurately using the threshold values (the first and second speeds) of the rotation speed defined in detail.

Advantages of the Invention

[0014] According to the bearing system of the motor according to the present invention, the switching between the rolling bearing and the sliding bearing can be performed with a simple configuration.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0016] Hereinafter, a bearing system of a motor according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0017] [Device Configuration] FIG. 1 is a schematic configuration diagram of a motor system to which a bearing system of a motor according to an embodiment of the present invention is applied. FIG. 1 is a cross-sectional view of the motor system 100 taken along the axial direction. As shown in FIG. 1, the motor system 100 is a system for driving a vehicle and mainly includes a motor (electric motor) 1 including a rotor 1a and a stator 1b, a rotating shaft 2 of the motor 1, and a pair of bearings 4 (in FIG. 1, only one bearing 4 is shown and the illustration of the other bearing 4 is omitted) that support the rotating shaft 2. These motor 1, rotating shaft 2, and bearing 4 are housed in a housing (not shown).

[0018] The bearing 4 is a radial bearing that supports the rotating shaft 2, and includes an outer ring 6 provided so as to surround the outer circumference of the rotating shaft 2, an inner ring 7 disposed inside (radially inside) the outer ring 6 and provided with a gap between the inner ring 7 and the rotating shaft 2, and a plurality of rolling elements (typically "rollers") 5 interposed between the outer ring 6 and the inner ring 7. Further, the bearing 4 has an inner ring fixing portion 8 provided inside (radially inside) the inner ring 7. The inner ring fixing portion 8 is preferably configured integrally with the inner ring 7, but may be configured separately from the inner ring 7.

[0019] In addition, the motor system 100 is configured to be able to switch between a fixed state (first state) in which the inner ring 7 of the bearing 4 is fixed (connected) to the rotating shaft 2 and a released state (second state) in which the inner ring 7 is separated from the rotating shaft 2, and further includes a clutch 10 and a pedestal 12 fixed to the rotating shaft 2 and provided to face the inner ring fixing portion 8 of the bearing 4. In the motor system 100, the bearing system 20 of the motor according to the present embodiment mainly includes the bearing 4 and the clutch 10. The clutch 10 is also provided for the other bearing 4 whose illustration is omitted in FIG. 1.

[0020] Specifically, the clutch 10 is provided on the outer circumference of the rotating shaft 2 and arranged in parallel with the bearing 4 along the axial direction. Further, a pair of clutches 10 are provided so as to sandwich the bearing 4 in the axial direction. The clutch 10 is attached to the rotating shaft 2 so as to rotate together with the rotating shaft 2 and is provided to be axially movable on the rotating shaft 2 (the white arrow in FIG. 1). For example, the clutch 10 moves on a pedestal 12 fixed to the rotating shaft 2. Alternatively, the clutch 10 may be directly moved on the rotating shaft 2 without providing the pedestal 12.

[0021] The clutch 10 configured as described above forms a fixed state in which the inner ring 7 is fixed to the rotating shaft 2 by moving axially toward the bearing 4 side and biasing the bearing 4 (pressed by an actuator 15 described later), while forming a released state in which the inner ring 7 is disengaged from the rotating shaft 2 by moving axially to the side opposite to the bearing 4 and separating from the bearing 4. When the clutch 10 is in the fixed state, the bearing 4 functions as a rolling bearing, and when the clutch 10 is in the released state, the bearing 4 functions as a sliding bearing. In particular, in the present embodiment, the bearing 4 functions as a sliding bearing using gas lubrication in a gas bearing (typically an air bearing). Details thereof will be described later.

[0022] Specifically, the outer wall surface of the clutch 10 facing the bearing 4 abuts against the outer wall surface of the inner ring fixing portion 8 facing the clutch 10, thereby forming a fixed state in which the clutch 10 fixes the inner ring 7 to the rotating shaft 2. More specifically, the bearing 4 has a first inclined surface 8a inclined with respect to the radial direction and the axial direction of the rotating shaft 2 when viewed in a cross section along the axial direction, formed at the end on the inner ring 7 side, that is, at the inner ring fixing portion 8, and the clutch 10 has a second inclined surface 10a inclined with respect to the radial direction and the axial direction so as to be able to abut against the first inclined surface 8a of the bearing 4, formed facing the first inclined surface 8a when viewed in a cross section along the axial direction. Then, a fixed state is formed by the abutment of the first inclined surface 8a of the inner ring fixing portion 8 and the second inclined surface 10a of the clutch 10, and a released state is formed by the separation of the first inclined surface 8a and the second inclined surface 10a.

[0023] FIG. 1 showed a conceptual diagram schematically showing the bearing 4 and the clutch 10, etc. Hereinafter, with reference to FIGS. 2 to 4, the specific configuration of the bearing system 20 of the motor according to the present embodiment will be described. FIG. 2 shows a perspective view of the bearing system 20 of the motor according to the present embodiment, FIG. 3 shows a cross-sectional view of the bearing system 20 of the motor in the released state, and FIG. 4 shows a cross-sectional view of the bearing system 20 of the motor in the fixed state.

[0024] As shown in FIG. 2, the bearing system 20 of the motor further has an actuator 15 configured to be movable to switch the clutch 10 between a fixed state and a released state (in FIGS. 3 and 4, for convenience of explanation, the illustration of the actuator 15 is omitted). Specifically, the actuator 15 moves the clutch 10 to switch it between the fixed state and the released state, and operates to press the clutch 10 against the bearing 4 in the fixed state, that is, generates a pressing force. Also, the actuator 15 is provided in a pair facing each other on the outer periphery of the rotating shaft 2, and another pair is provided with this pair sandwiching the bearing 4, and each of the pair of clutches 10 is configured to be axially movable. Note that various known mechanisms can be applied to the actuator 15 as a mechanism for axially moving the clutch 10.

[0025] Also, as shown in FIG. 2, the bearing system 20 of the motor has a detent 17 for reliably fixing the clutch 10 to the rotating shaft 2. Typically, this detent 17 is constituted by a convex portion and a concave portion provided on each of the clutch 10 and the rotating shaft 2, and these convex portion and concave portion are engageable with each other and are formed to be relatively slidable in the axial direction. With the detent 17 configured in this way, the clutch 10 can rotate together (interlockingly) with the rotating shaft 2, while being axially movable on the rotating shaft 2.

[0026] Next, as shown in FIGS. 3 and 4, the inner ring fixing portion 8 of the bearing 4 is formed in a substantially cylindrical shape as a whole so as to surround the rotating shaft 2, and when viewed in a cross-section along the axial direction, on the surfaces (i.e., both end faces) facing each of the pair of clutches 10, the above-described first inclined surface 8a is formed. This first inclined surface 8a, when viewed in a cross-section along the axial direction, is inclined in a direction away from the rotating shaft 2 as it progresses toward the clutch 10 side. Further, each of the pair of clutches 10 is formed in a substantially cylindrical shape (in other words, substantially annular shape) as a whole so as to surround the rotating shaft 2, and when viewed in a cross-section along the axial direction, on the surface facing the bearing 4, the above-described second inclined surface 10a is formed. This second inclined surface 10a, when viewed in a cross-section along the axial direction, is inclined in a direction approaching the rotating shaft 2 as it progresses toward the bearing 4 side. As shown in FIG. 4, the first inclined surface 8a of the inner ring fixing portion 8 and the second inclined surface 10a of the clutch 10 are in contact with each other without a gap, and by the contact of these first inclined surface 8a and second inclined surface 10a, a fixed state of the bearing 4 by the clutch 10 is formed. In this case, due to the pressing force applied from the actuator 15 to the clutch 10, the second inclined surface 10a is biased against the first inclined surface 8a. Incidentally, if the angles of the first inclined surface 8a and the second inclined surface 10a with respect to the axial direction are set to relatively large angles (i.e., steep inclinations), it is advantageous in ensuring the load capacity of the gas bearing described later.

[0027] Next, with reference to FIG. 5, the electrical configuration of the bearing system 20 of the motor according to this embodiment will be described. As shown in FIG. 5, the bearing system 20 of the motor includes various sensors indicated by reference numerals 31 to 40, a control device 50 into which various signals are input from these various sensors, and an actuator 15 that is controlled by a control signal supplied from the control device 50. The control device 50 is composed of a computer including one or more processors 50a (typically a CPU), a memory 50b such as a ROM and a RAM that stores various programs (including basic control programs such as an OS and application programs that are launched on the OS and realize specific functions) and various data interpreted and executed on the processor 50a. Note that the control device 50 controls not only the actuator 15 but also the motor 1 via an inverter (not shown).

[0028] Specifically, the bearing system 20 of the motor mainly includes a vehicle speed sensor 31 that detects the speed of the vehicle (vehicle speed), an acceleration sensor 32 that detects the acceleration of the vehicle, an accelerator opening sensor 33 that detects the accelerator opening corresponding to the depression amount of the accelerator pedal, a brake sensor 34 that detects the depression amount of the brake pedal, a shaft rotation speed sensor 35 that detects the rotation speed (unambiguously the number of revolutions) of the rotating shaft 2 of the motor 1, a bearing rotation speed sensor 36 that detects the rotation speed (unambiguously the number of revolutions) of the bearing 4, a shaft center position sensor 37 that detects the position in the radial direction of the center axis of the rotating shaft 2, a shaft load sensor 38 that detects the load applied to the rotating shaft 2, an outer bearing load sensor 39 that detects the load applied to the outer ring 6 of the bearing 4, and an inner bearing load sensor 40 that detects the load applied to the inner ring 7 of the bearing 4.

[0029] In this embodiment, based on the detection signals from the various sensors 31 to 40 described above, the control device 50 controls the actuator 15 to switch the clutch 10 between the fixed state and the released state so as to cause the bearing 4 to function by switching between a rolling bearing and a sliding bearing (hereinafter, this control is referred to as "motor shaft restricted control"). Typically, the control device 50 executes such motor shaft restricted control based on the rotational speed of the rotating shaft 2 of the motor 1 detected by the shaft rotational speed sensor 35 (hereinafter, appropriately referred to as "motor rotational speed").

[0030] [Motor shaft restricted control] Next, the motor shaft restricted control according to this embodiment will be specifically described.

[0031] First, the basic concept of the motor shaft restricted control according to this embodiment will be described. Conventionally, rolling bearings and sliding bearings have been used as bearings for supporting the rotating shaft of a vehicle's power source. A rolling bearing has low friction in the low rotation region, while a sliding bearing has high friction in the low rotation region. On the other hand, a rolling bearing has a finite lifespan due to rolling fatigue, while a sliding bearing has a permanent lifespan under appropriate lubrication conditions. In a general engine (internal combustion engine), it is effective to apply a sliding bearing in the high rotation region. Usually, fluid lubrication with lubricating oil is used for this sliding bearing. However, in the motor 1 that operates at a higher rotation speed than the engine, if such a sliding bearing is applied in the high rotation region of the motor 1, there is a problem that the fluid friction and resistance of the lubricating oil increase, resulting in a decrease in the motor's power consumption.

[0032] Therefore, in the present embodiment, an attempt was made to apply a gas bearing (typically an air bearing) that uses lubrication with a gas having a lower viscosity than the lubricating oil as a sliding bearing. In order to realize this gas bearing, it is necessary to surely form a gas layer between the bearing 4 and the rotating shaft 2 in order to prevent contact between them. In the present embodiment, in order to surely form such a gas layer, the so-called wedge effect and throttling effect generated between the bearing 4 and the rotating shaft 2 are utilized. However, since the wedge effect and the throttling effect can basically be obtained only in the high rotation region of the motor 1, in the method of utilizing these effects, there is a possibility that the bearing 4 and the rotating shaft 2 may come into contact with each other in the low rotation region of the motor 1. From the above, in the present embodiment, the control device 50 switches the above-described clutch 10 between the fixed state and the released state according to the motor rotation speed so that the bearing 4 functions as a rolling bearing in the low rotation region and functions as a gas bearing (sliding bearing) in the high rotation region (FIGS. 3 and 4).

[0033] Next, with reference to FIG. 6, the basic concept of the motor shaft control according to the present embodiment will be described more specifically. Here, the motor shaft control according to the present embodiment and the motor shaft control according to the comparative example will be described in comparison. FIG. 6 shows the motor rotation speed on the horizontal axis and the shaft frictional torque on the vertical axis.

[0034] In the motor shaft control according to the comparative example, the bearing that functions to support the rotating shaft of the motor is switched between a rolling bearing and a sliding bearing that uses fluid lubrication with lubricating oil. Specifically, in the comparative example, in the region R11 (low rotation region) where the motor rotation speed is low, a rolling bearing is applied as the bearing that functions to support the rotating shaft 2, while in the region R12 where the motor rotation speed is higher than the region R11, a sliding bearing is applied as the bearing that functions to support the rotating shaft 2. This control corresponds to the technique described in Patent Document 1.

[0035] In FIG. 6, graph G11 shows the shaft friction torque generated in a rolling bearing, that is, the boundary lubrication friction due to direct contact, and graph G12 shows the shaft friction torque generated in a sliding bearing using fluid lubrication with lubricating oil, that is, the fluid lubrication friction of the lubricating oil. Therefore, the shaft friction torque generated in the motor shaft control according to the above-described comparative example is the sum of the shaft friction torque shown in graph G11 and the shaft friction torque shown in graph G12, that is, the one shown in graph G21. In this case, the reason why the shaft friction torque increases significantly as the motor rotation speed increases in region R12 is due to the increase in friction caused by the deformation of the rolling elements in the rolling bearing as shown in graph G13.

[0036] On the other hand, in the present embodiment, as described above, the control device 50 controls the actuator 15 to switch the clutch 10 between the fixed state and the released state in order to switch the bearing 4 that supports the rotating shaft 2 of the motor 1 between a rolling bearing and a gas bearing. First, in region R11 where the motor rotation speed is low, since almost no wedge effect and throttling effect can be obtained, the control device 50 sets the clutch 10 in the fixed state so that the bearing 4 functions as a rolling bearing.

[0037] Subsequently, when the motor rotation speed exceeds region R11, that is, when entering region R12 that is higher than region R11, a certain degree of wedge effect and throttling effect can be obtained. Therefore, the control device 50 attempts to make the bearing 4 function as a gas bearing. Specifically, in region R13 on the low rotation side in region R12, since the wedge effect and throttling effect are not sufficient, the control device 50 changes the clutch 10 between the fixed state and the released state so as to switch the bearing 4 between a rolling bearing and a gas bearing. Then, in region R14 on the high rotation side in region R12, since the wedge effect and throttling effect are sufficient, the control device 50 sets the clutch 10 in the released state so that the bearing 4 functions as a gas bearing.

[0038] In FIG. 6, graph G14 shows the shaft friction torque generated by the gas bearing, that is, the gas lubrication friction. The shaft friction torque generated in the motor shaft control according to the above-described embodiment is the sum of the shaft friction torque shown in graph G11 and the shaft friction torque shown in graph G14, that is, the one shown in graph G22. When comparing the shaft friction torque according to this embodiment shown in graph G22 with the shaft friction torque according to the comparative example shown in graph G21, it can be seen that according to this embodiment, the shaft friction torque is significantly reduced. Therefore, according to this embodiment, it can be said that the electricity cost can be effectively improved as compared with the comparative example.

[0039] Next, with reference to FIG. 7, the motor shaft control according to this embodiment will be specifically described. FIG. 7 is a time chart showing the motor shaft control according to this embodiment. FIG. 7 shows, in order from the top, the motor rotation speed, the rotation speed when bearing 4 is regarded as a rolling bearing, the rotation speed when bearing 4 is regarded as a gas bearing (sliding bearing), and the state (fixed state or released state) of clutch 10. In FIG. 7, the "first speed" is the motor rotation speed corresponding to the lower limit value of region R13 in FIG. 6 (in other words, the upper limit value of region R11), and the "second speed" is the motor rotation speed corresponding to the lower limit value of region R14 in FIG. 6 (in other words, the upper limit value of region R13). FIG. 7 assumes a situation where the motor rotation speed increases from the first speed to the second speed and the vehicle accelerates.

[0040] Before time t0, the motor rotation speed is less than the first speed (that is, the motor rotation speed is within region R11), the clutch 10 is in a fixed state, and the bearing 4 functions as a rolling bearing. Then, from time t0, the motor rotation speed begins to exceed the first speed (that is, the motor rotation speed enters region R12). The control device 50 starts to control the actuator 15 from the subsequent time t1 so that the clutch 10 shifts from the fixed state to the released state. As a result, while the rotation speed when the bearing 4 is regarded as a rolling bearing decreases, the rotation speed when the bearing 4 is regarded as a gas bearing begins to increase. After that, at time t2, the clutch 10 is completely switched from the fixed state to the released state, and the control device 50 controls the actuator 15 to maintain the clutch 10 in the released state. After this time t2, while the rotation speed when the bearing 4 is regarded as a rolling bearing becomes very small, the rotation speed when the bearing 4 is regarded as a gas bearing becomes stable at a large speed, that is, the bearing 4 stably functions as a gas bearing. After that, at time t3, the motor rotation speed reaches the second speed.

[0041] [Operation and Effect] Next, the operation and effects of the bearing system 20 of the motor according to this embodiment will be described. In this embodiment, the bearing system 20 of the motor applied to a vehicle includes an outer ring 6 provided so as to surround the outer periphery of the rotating shaft 2 of the motor 1, an inner ring 7 disposed inside the outer ring 6 and provided with a gap between the inner ring 7 and the rotating shaft 2, and a plurality of rolling elements 5 interposed between the outer ring 6 and the inner ring 7. The bearing system 20 further includes a bearing 4 configured to support the rotating shaft 2, and a clutch 10 provided on the outer periphery of the rotating shaft 2 and arranged in parallel with the bearing 4 along the axial direction of the rotating shaft 2. The clutch 10 is configured to be able to switch between a fixed state in which the inner ring 7 of the bearing 4 is fixed to the rotating shaft 2 and a released state in which the inner ring 7 is released from the rotating shaft 2. The bearing 4 functions as a rolling bearing in the fixed state and as a sliding bearing in the released state. The clutch 10 is provided so as to be rotatable with the rotating shaft 2 and axially movable on the rotating shaft 2. By moving axially toward the bearing 4 side to urge the bearing 4, a fixed state is formed, while by moving axially to the side opposite to the bearing 4 to separate from the bearing 4, a released state is formed.

[0042] According to such an embodiment of the present invention, by axially moving the clutch 10 on the rotating shaft 2 to change the fixed state and the released state of the inner ring 7 of the bearing 4 with respect to the rotating shaft 2, the bearing 4 can be switched between a rolling bearing and a sliding bearing to function. Therefore, according to this embodiment, unlike the technique described in Patent Document 1 above, a separately configured sliding bearing and rolling bearing are not used, and the inner or outer ring of the rolling bearing is not axially relatively moved. Thus, the switching between the rolling bearing and the sliding bearing can be performed with a simple configuration.

[0043] Further, according to the present embodiment, when viewed in a cross-section along the axial direction, the bearing 4 has a first inclined surface 8a inclined with respect to the radial direction and the axial direction formed at the end on the inner ring 7 side (inner ring fixing portion 8), and the clutch 10 has a second inclined surface 10a inclined with respect to the radial direction and the axial direction so as to be able to contact the first inclined surface 8a of the bearing 4 when viewed in a cross-section along the axial direction, and the second inclined surface 10a is formed to face the first inclined surface 8a. When the first inclined surface 8a of the bearing 4 and the second inclined surface 10a of the clutch 10 are in contact with each other, a fixed state is formed, while when the first inclined surface 8a and the second inclined surface 10a are separated from each other, a released state is formed. By forming a fixed state by bringing the first inclined surface 8a and the second inclined surface 10a into contact with each other in this way, when the first and second inclined surfaces 8a and 10a are brought into contact from a separated state, compared with the case of bringing non-inclined vertical surfaces into contact with each other, displacement of the axis of the rotating shaft 2 can be suppressed. In other words, it becomes easier to hold the position of the axis at a desired position (central position).

[0044] Further, according to the present embodiment, a pair of clutches 10 are provided so as to sandwich the bearing 4 in the axial direction. Thereby, by sandwiching the bearing 4 with the pair of clutches 10 to form a fixed state, the inner ring 7 of the bearing 4 can be reliably fixed to the rotating shaft 2.

[0045] Further, according to the present embodiment, the bearing system 20 of the motor further includes a shaft rotation speed sensor 35 that detects the rotation speed of the rotating shaft 2 (motor rotation speed), an actuator 15 configured to be movable to switch the clutch 10 between a fixed state and a released state, and a control device 50 configured to control the actuator 15 based on the motor rotation speed. Thereby, according to the motor rotation speed, the rolling bearing and the sliding bearing (gas bearing) can be accurately switched. Specifically, based on the motor rotation speed, by determining a situation in which a gas bearing as a sliding bearing can be realized, the bearing 4 can be switched to a gas bearing in an accurate situation.

[0046] Also, according to this embodiment, when the motor rotation speed is less than the first speed, the control device 50 controls the actuator 15 to set the clutch 10 in a fixed state. When the motor rotation speed is between the first speed and a second speed higher than the first speed, the control device 50 controls the actuator 15 to switch the clutch 10 between the fixed state and the released state. When the motor rotation speed is higher than the second speed, the control device 50 controls the actuator 15 to set the clutch 10 in the released state. Thereby, by using the threshold values (the first and second speeds) of the motor rotation speed defined in detail, the rolling bearing and the sliding bearing (gas bearing) can be switched more accurately.

[0047] [Modification Example] In the above-described embodiment, the bearing 4 operates as a sliding bearing (gas bearing) using gas lubrication. However, in other examples, the bearing 4 may operate as a sliding bearing using fluid lubrication with lubricating oil (grease or oil).

[0048] Also, in the above-described embodiment, the inner ring 7 of the bearing 4 and the clutch 10 are in contact with each other at inclined surfaces (the first inclined surface 8a and the second inclined surface 10a). However, the inner ring 7 of the bearing 4 and the clutch 10 may be configured to be in contact with each other at substantially perpendicular surfaces without using such inclined surfaces.

Explanation of Reference Numerals

[0049] 1 Motor 2 Rotating Shaft 4 Bearing 5 Rolling Element 6 Outer Ring 7 Inner Ring 8 Inner Ring Fixing Portion 10 Clutch 8a First Inclined Surface 10a Second Inclined Surface 15 Actuator 20 Bearing System of Motor 50 Control Device 100 Motor System

Claims

1. A bearing system for a motor applied to a vehicle, comprising: An outer ring provided to surround the outer periphery of the rotating shaft of the motor, an inner ring disposed inside the outer ring and provided with a gap between the inner ring and the rotating shaft, and a plurality of rolling elements interposed between the outer ring and the inner ring, and a bearing configured to support the rotating shaft; A clutch provided on the outer periphery of the rotating shaft and arranged in parallel with the bearing along the axial direction of the rotating shaft, the clutch being configured to be able to switch between a first state in which the inner ring of the bearing is fixed to the rotating shaft and a second state in which the inner ring is released from the rotating shaft; having; The bearing functions as a rolling bearing in the first state and functions as a sliding bearing in the second state; The clutch is provided so as to be rotatable with the rotating shaft and movable in the axial direction on the rotating shaft, and forms the first state by moving toward the bearing side in the axial direction and biasing the bearing, while forming the second state by moving to the side opposite to the bearing in the axial direction and separating from the bearing. A bearing system for a motor, characterized in that.

2. When viewed in a cross-section along the axial direction, a first inclined surface inclined with respect to the radial direction and the axial direction of the rotating shaft is formed at an end portion on the inner ring side of the bearing; When viewed in a cross-section along the axial direction, a second inclined surface inclined with respect to the radial direction and the axial direction is formed opposite to the first inclined surface of the bearing so as to be able to contact the first inclined surface of the bearing; The first state is formed by the first inclined surface of the bearing and the second inclined surface of the clutch coming into contact with each other, while the second state is formed by the first inclined surface and the second inclined surface being separated from each other. The bearing system for a motor according to claim 1.

3. When viewed in a cross-section along the axial direction, the first inclined surface of the bearing is inclined in a direction away from the rotation axis as it advances toward the clutch side. When viewed in a cross-section along the axial direction, the second inclined surface of the clutch is inclined in a direction approaching the rotation axis as it advances toward the bearing side. The bearing system for a motor according to claim 2.

4. The bearing system for a motor according to claim 1 or 2, wherein a pair of the clutches are provided so as to sandwich the bearing in the axial direction.

5. A shaft rotation speed sensor for detecting the rotation speed of the rotation shaft, An actuator configured to be movable to switch between the first state and the second state of the clutch, A control device configured to control the actuator based on the rotation speed detected by the shaft rotation speed sensor, The bearing system for a motor according to claim 1 or 2, further comprising:

6. The control device is configured to control the actuator to set the clutch to the first state when the rotation speed is less than a first speed, control the actuator to switch the clutch between the first state and the second state when the rotation speed is between the first speed and a second speed higher than the first speed, and control the actuator to set the clutch to the second state when the rotation speed is higher than the second speed. The bearing system for a motor according to claim 5.

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