Motor bearing system

Abstract

To provide a motor bearing system in which switching between a rolling bearing and a slide bearing can be performed with a simple configuration.SOLUTION: A motor bearing system 20 includes: a bearing 3 that includes a plurality of rolling elements 6, an outer ring 5, and a sleeve 7 and supports a rotation shaft 2 of a motor 1; a fixed member 8 that is configured not to rotate in conjunction with rotation of the rotation shaft; and a brake mechanism 9 that is configured to fix the sleeve to the fixed member. In the motor bearing system, when the sleeve is fixed by the brake mechanism, a rolling bearing is realized, and when the sleeve is released by the brake mechanism, a slide bearing is realized because the entire bearing rotates with respect to the fixed member in conjunction with rotation of the rotation shaft in a state where an outer circumferential surface 7s of the sleeve is spaced from an inner circumferential surface 8s of the fixed member. As a result, the sleeve is switched between fixing and releasing of the sleeve by the brake mechanism so that the rolling bearing and the slide bearing can be selectively realized.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a motor bearing system that is switchable between a rolling bearing and a sliding bearing. [Background technology]

[0002] Conventionally, rolling bearings and plain bearings have been used as bearings to support the rotating shaft of, for example, a vehicle's power source (engine or motor). Rolling bearings have low friction in the low rotation range, while plain bearings have high friction in the low rotation range. On the other hand, rolling bearings have a finite lifespan due to rolling fatigue, but plain bearings have an indefinite lifespan under appropriate lubrication conditions.

[0003] Here, a technology has been proposed in which a system is configured to include both rolling bearings and plain bearings, and the bearing to be applied is switched depending on the characteristics of each bearing as described above. For example, Patent Document 1 describes a system that includes a plain bearing that supports a rotating body housed in a housing, a rolling bearing that is arranged in parallel to the plain bearing and supports the rotating body, and a movement mechanism that switches the bearing that functions to support the rotating body by moving the inner ring or outer ring of the rolling bearing in the axial direction. In particular, in this system, the radial clearance of the rolling bearing is changed by driving the movement device to move the inner ring or outer ring relative to the rolling bearing in the axial direction, and only the plain bearing functions when the radial clearance of the rolling bearing is larger than that of the plain bearing, but only the rolling bearing functions when the radial clearance of the rolling bearing is smaller than that of the plain bearing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-19728 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology described in Patent Document 1 above uses both a sliding bearing and a rolling bearing configured as separate bodies, and switches between the rolling bearing and the sliding bearing by relatively moving the inner ring or outer ring of the rolling bearing in the axial direction, resulting in a complex system configuration.

[0006] The present invention has been made to solve the problems of the conventional technology described above, and aims to provide a motor bearing system that can switch between rolling bearings and sliding bearings with a simple configuration. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a motor bearing system comprising: a bearing attached to the outer periphery of a rotating shaft of a motor to support the rotating shaft, the bearing comprising: a plurality of rolling elements arranged circumferentially around the rotating shaft; and an outer ring portion arranged radially outward of the plurality of rolling elements and holding the plurality of rolling elements; a fixing member having an inner circumferential surface that extends along the outer circumferential surface of the outer ring portion of the bearing and is provided with a gap between it and the outer circumferential surface, and configured not to rotate with rotation of the rotating shaft; and a brake mechanism configured to fix the outer ring portion of the bearing to the fixing member; the motor bearing system is characterized in that when the brake mechanism fixes the outer ring portion, the bearing functions as a rolling bearing, but when the brake mechanism releases the outer ring portion, the outer circumferential surface of the outer ring portion is separated from the inner circumferential surface of the fixing member, and the entire bearing rotates relative to the fixing member with rotation of the rotating shaft, thereby forming a sliding bearing; and the motor bearing system is configured to be able to selectively function as a rolling bearing or a sliding bearing by switching between fixing and releasing the outer ring portion using the brake mechanism.

[0008] In the present invention configured as described above, the brake mechanism can alternate between locking and unlocking the outer ring of the bearing, allowing the motor bearing system to switch between the rolling bearing and plain bearing functions. Therefore, unlike the technology described in Patent Document 1, the present invention does not require separately configured plain bearings and rolling bearings, nor does it require the inner or outer ring of the rolling bearing to move relative to one another in the axial direction. This allows for simple switching between the rolling bearing and plain bearing. Furthermore, even if a failure such as seizure occurs between the outer peripheral surface of the outer ring and the inner peripheral surface of the fixed member used to realize the plain bearing, the bearing's rolling bearing function is guaranteed, ensuring the rotation of the motor's rotating shaft. This makes it possible to achieve an accurate fail-safe.

[0009] In the present invention, preferably, the motor bearing system further comprises a gas passage for supplying gas to the gap between the outer peripheral surface of the outer ring portion and the inner peripheral surface of the fixed member, and a pump provided on the gas passage for pressurizing the gas, wherein the pump supplies gas from the gas passage to the gap at least when the brake mechanism releases the outer ring portion, thereby realizing a sliding bearing. According to the present invention configured in this manner, a gas layer is formed in the gap between the outer peripheral surface of the outer ring portion and the inner peripheral surface of the fixed member by the gas supplied from the pump, making it possible to effectively realize a gas bearing as a sliding bearing.

[0010] In the present invention, preferably, when the gas passage is a first gas passage, the motor bearing system further has a second gas passage for supplying gas from the pump to the brake mechanism, and the brake mechanism is configured to fix the outer ring portion by utilizing the pressure of the gas supplied from the pump via the second gas passage. According to the present invention configured as described above, the outer ring portion can be reliably fixed by the brake mechanism using the pressure of the gas supplied from the pump. Furthermore, according to the present invention, since one pump is used both to form a gas layer in the gap between the outer ring portion and the fixing member and to drive the brake mechanism, it is possible to simplify the system configuration and reduce costs.

[0011] In the present invention, preferably, the outer ring portion has a protrusion at its axial end that protrudes radially outward, and the brake mechanism is configured to fix the outer ring portion by applying force to the protrusion of the outer ring portion. According to the present invention configured in this manner, the outer ring portion can be fixed by the brake mechanism with a simple configuration.

[0012] In the present invention, the brake mechanism preferably includes a coil, and is configured to fix the outer ring portion by utilizing an electromagnetic force generated by energizing the coil. According to the present invention configured as described above, the outer ring portion can be reliably fixed by the brake mechanism using the electromagnetic force of the coil.

[0013] In the present invention, preferably, the outer ring portion and the brake mechanism each include a frictional fastening element that fastens to each other, and the outer ring portion is fixed by the brake mechanism when these frictional fastening elements are fastened to each other. According to the present invention configured as described above, the outer ring portion can be reliably fixed by the brake mechanism using the frictional fastening element.

[0014] In the present invention, preferably, the motor bearing system further includes a motor rotation speed sensor that detects the rotation speed of the motor, and a control device configured to control the brake mechanism based on the rotation speed detected by the motor rotation speed sensor, and the control device is configured to control the brake mechanism to fix the outer ring portion when the rotation speed is less than a predetermined value, and to control the brake mechanism to release the outer ring portion when the rotation speed is equal to or greater than the predetermined value. According to the present invention configured in this manner, it is possible to switch appropriately between a rolling bearing and a sliding bearing in accordance with the motor rotation speed. Specifically, by determining the conditions under which a sliding bearing is feasible based on the motor rotation speed, it is possible to switch to a sliding bearing in the appropriate conditions.

[0015] In the present invention, preferably, the motor bearing system further includes a gas passage for supplying gas to the gap between the outer peripheral surface of the outer ring portion and the inner peripheral surface of the fixed member, and a pump provided on the gas passage for pressurizing the gas, and the control device is configured to control the brake mechanism to release the outer ring portion when the rotation speed is equal to or higher than a predetermined value, and to control the pump to supply gas from the gas passage to the gap. According to the present invention configured in this manner, in a situation where a gas bearing can be realized as a sliding bearing, the gas supplied from the pump can form a gas layer in the gap between the outer peripheral surface of the outer ring portion and the inner peripheral surface of the fixed member, thereby making it possible to effectively realize a gas bearing. [Effects of the Invention]

[0016] According to the motor bearing system of the present invention, switching between the rolling bearing and the sliding bearing can be performed with a simple configuration. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of a motor system to which a motor bearing system according to an embodiment of the present invention is applied; [Figure 2] 1 is a cross-sectional view of a motor bearing system according to a first example embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view of a motor bearing system according to a second example embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view of a motor bearing system according to a third example embodiment of the present invention. [Figure 5] FIG. 2 is a block diagram showing the electrical configuration of the motor bearing system according to the embodiment of the present invention. [Figure 6]FIG. 1 is an explanatory diagram illustrating a basic concept of bearing switching control according to an embodiment of the present invention. [Figure 7] 4 is a time chart showing bearing switching control according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

[0019] [Device configuration] First, the basic device configuration of a motor bearing system according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram of a motor system to which a motor bearing system according to this embodiment is applied. Specifically, Fig. 1 is a cross-sectional view of a motor system 100 as viewed along the axial direction.

[0020] As shown in Fig. 1, the motor system 100 mainly comprises a motor (electric motor) 1 including a rotor 1a and a stator 1b, a rotating shaft 2 connected to the rotor 1a, and a pair of motor bearing systems 20 (only one of which is shown in Fig. 1, the other is omitted) that support the rotating shaft 2. The motor 1, rotating shaft 2, and motor bearing system 20 are housed in a housing (not shown). The motor system 100 is used to drive a vehicle (not shown), such as an electric car.

[0021] Specifically, the motor bearing system 20 has a bearing (rolling bearing) 3 including an inner ring 4 fixed to the outer periphery of the rotating shaft 2, an outer ring 5 arranged radially outward of the inner ring 4 with a gap between it and the inner ring 4, a plurality of rolling elements (balls or rollers) 6 interposed between the inner ring 4 and the outer ring 5, and a sleeve 7 fixed to the outer periphery of the outer ring 5. The sleeve 7 has an outer peripheral surface 7s and a protrusion (in other words, a flange portion) 7p provided at an end in the axial direction and protruding radially outward. The outer ring 5 and sleeve 7 of the bearing 3 correspond to an example of an "outer ring portion" in the present invention.

[0022] The motor bearing system 20 also includes a fixed member 8 that surrounds the bearing 3 and is configured not to rotate with the rotation of the rotating shaft 2, and a brake mechanism 9 that is fixed to the fixed member 8 and configured to fix the sleeve 7 of the bearing 3 to the fixed member 8. The fixed member 8 is formed, for example, from the housing (case) of the motor 1, and includes an inner circumferential surface 8s that extends along the outer circumferential surface 7s of the sleeve 7 and is provided with a small gap SP between it and the outer circumferential surface 7s. The brake mechanism 9 also includes an actuator (not shown) that applies a force (braking force) to the protruding portion 7p of the sleeve 7, thereby fixing the sleeve 7 to the fixed member 8 so that it does not rotate with the rotating shaft 2. In this case, the outer ring 5 fixed to the sleeve 7 is also fixed to the fixed member 8.

[0023] Additionally, the fixed member 8 is formed with a portion of a gas passage 11 for supplying gas (typically air) to a gap SP between an inner peripheral surface 8s of the fixed member 8 and an outer peripheral surface 7s of the sleeve 7. A pump 12 for pumping the gas is provided on the gas passage 11.

[0024] In the motor bearing system 20 according to this embodiment, when the brake mechanism 9 fixes the sleeve 7, the outer ring 5 is fixed via the sleeve 7, and the bearing 3 functions as a rolling bearing (the original function of the bearing 3). In contrast, when the brake mechanism 9 releases the sleeve 7, the entire bearing 3 (including the sleeve 7) rotates together with the rotating shaft 2, thereby providing a sliding bearing, particularly a gas bearing (gas-lubricated bearing). When this sliding bearing is provided, the bearing 3 rotates relative to the fixed member 8 with the outer peripheral surface 7s of the sleeve 7 spaced apart from the inner peripheral surface 8s of the fixed member 8. In addition, in this embodiment, when the brake mechanism 9 releases the sleeve 7, gas from the pump 12 is supplied to the gap SP between the sleeve 7 and the fixed member 8, forming a gas layer in this gap SP, thereby providing a sliding bearing (gas bearing).

[0025] As described above, the motor bearing system 20 according to this embodiment is configured to be able to selectively implement a rolling bearing or a sliding bearing by switching between fixing and releasing the sleeve 7 using the brake mechanism 9.

[0026] Next, specific embodiments (first to third embodiments) of the motor bearing system 20 described above will be described with reference to FIGS.

[0027] (First Example) First, FIG. 2 is a cross-sectional view of a motor bearing system according to a first example of this embodiment. As shown in FIG. 2, in a motor bearing system 20a according to the first example, a sleeve 7a has a plate-shaped frictional fastening element 7a1 (corresponding to the protruding portion 7p described above) provided at an end in the axial direction and protruding radially outward. The brake mechanism 9a also has an attachment portion 9a1 for attaching the brake mechanism 9a to the fixed member 8, two plate-shaped frictional fastening elements 9a2 attached to the inner circumferential surface of the fixed member 8 so as to fasten with the frictional fastening element 7a1 of the sleeve 7a, a piston 9a3 driven by an actuator (not shown) for pressing the frictional fastening element 9a2, and an elastic portion (e.g., rubber) 9a4 provided between the attachment portion 9a1 and the piston 9a3 for biasing the piston 9a3 in the direction opposite to the pressing direction. The brake mechanism 9a is configured as a dry clutch.

[0028] In the motor bearing system 20a according to the first embodiment, the piston 9a3 in the brake mechanism 9a is driven by an actuator to press the frictional fastening element 9a2, which then fastens the frictional fastening element 9a2 to the frictional fastening element 7a1 of the sleeve 7a, thereby fixing the sleeve 7a by the brake mechanism 9a. This allows the sleeve 7a to be reliably fixed by the brake mechanism 9a using the frictional fastening elements 7a1 and 9a2.

[0029] (Second Example) Next, Fig. 3 is a cross-sectional view of a motor bearing system according to a second example of this embodiment. As shown in Fig. 3, in a motor bearing system 20b according to the second example, a sleeve 7b is provided at an end in the axial direction and has two plate-shaped frictional fastening elements 7b1 (corresponding to the protruding portions 7p described above) that protrude radially outward. Furthermore, a brake mechanism 9b has an attachment portion 9b1 for attaching the brake mechanism 9b to a fixed member 8, three plate-shaped frictional fastening elements 9b2 attached to the inner circumferential surface of the fixed member 8 so as to fasten with the frictional fastening elements 7b1 of the sleeve 7b, and a piston 9b3 for pressing the frictional fastening elements 9b2. This brake mechanism 9b is configured with a dry multi-plate clutch.

[0030] A gas passage 9b4, to which gas is supplied from the pump 12, is connected to the brake mechanism 9b. In this case, a portion of the gas passage 9b4 is formed in the mounting portion 9b1 of the brake mechanism 9b. For example, the gas passage 9b4 is connected to a portion of the gas passage 11 downstream of the pump 12. In this brake mechanism 9b, the piston 9b3 is driven to press the frictional engagement element 9b2 by the pressure of the gas supplied from the pump 12 through the gas passage 9b4. The brake mechanism 9b also has a return spring (not shown) that urges the piston 9b3 in the direction opposite to the pressing direction.

[0031] In the motor bearing system 20b according to the second embodiment, the piston 9b3 of the brake mechanism 9b presses the frictional fastening element 9b2 by the pressure of the gas supplied from the pump 12, and this frictional fastening element 9b2 fastens with the frictional fastening element 7b1 of the sleeve 7b, thereby fixing the sleeve 7b by the brake mechanism 9b. This allows the sleeve 7b to be reliably fixed by the brake mechanism 9b by utilizing the pressure of the gas supplied from the pump 12. Furthermore, according to the second embodiment, a single pump 12 is used both to form a gas layer in the gap SP between the sleeve 7b and the fixed member 8 and to drive the brake mechanism 9b, which makes it possible to simplify the system configuration and reduce costs.

[0032] (Third Example) Next, Fig. 4 is a cross-sectional view of a motor bearing system according to a third example of this embodiment. As shown in Fig. 4, in a motor bearing system 20c according to the third example, a sleeve 7c is fixed to an axial end and has a protrusion 7c1 that protrudes radially outward and an armature 7c2 attached to the protrusion 7c1 (these correspond to the protrusion 7p described above). A brake mechanism 9c also has a mounting portion 9c1 for mounting the brake mechanism 9c to a fixed member 8, a coil 9c2 fixed to the mounting portion 9c1 that generates an electromagnetic force for attracting the armature 7c2 of the sleeve 7c, and a lining (friction material) 9c3 provided opposite the armature 7c2. This brake mechanism 9c is configured as an electromagnetic brake.

[0033] In the motor bearing system 20c according to the third embodiment, the brake mechanism 9c is configured such that the coil 9c2 is energized to generate an electromagnetic force, which attracts the armature 7c2 of the sleeve 7c and causes it to abut against the lining 9c3, thereby fixing the sleeve 7c with the brake mechanism 9c. This allows the sleeve 7c to be reliably fixed with the brake mechanism 9c by utilizing the electromagnetic force of the coil 9c2.

[0034] In the following, the motor bearing systems 20a to 20c, sleeves 7a to 7c, and brake mechanisms 9a to 9c shown in the first to third embodiments will be collectively referred to as "motor bearing system 20," "sleeve 7," and "brake mechanism 9," respectively, as in Figure 1.

[0035] [Electrical configuration] Next, the electrical configuration of the motor bearing system 20 according to this embodiment will be described with reference to Fig. 5. As shown in Fig. 5, in addition to the motor 1, brake mechanism 9, and pump 12 described above, the motor bearing system 20 includes various sensors indicated by reference numerals 31 to 36, a control device 50 to which various signals are input from these various sensors, and a display device 40 that displays various information via the control device 50. The control device 50 is configured as a computer that includes one or more processors 50a (typically a CPU) and memory 50b such as ROM and RAM that stores various programs (including basic control programs such as an OS and application programs that are run on the OS to realize specific functions) that are interpreted and executed by the processor 50a, and various data.

[0036] Specifically, the motor bearing system 20 mainly includes a motor rotation speed sensor 31 that detects the motor rotation speed (the rotation speed of the rotor 1a, the rotating shaft 2, which is synonymous with rotational speed) of the motor 1, a sleeve rotation speed sensor 32 that detects the sleeve rotation speed (synonymous with rotational speed) of the sleeve 7, a vibration sensor 33 that detects vibration of the bearing 3 (including the sleeve 7), a vehicle speed sensor 34 that detects the speed of the vehicle (vehicle speed), an acceleration sensor 35 that detects the acceleration occurring in the vehicle, and an accelerator opening sensor 36 that detects the accelerator opening corresponding to the amount of depression of the accelerator pedal in the vehicle.

[0037] The control device 50 controls the motor 1, the brake mechanism 9, the pump 12, the display device 40, etc., based on detection signals from the various sensors 31 to 36. In particular, in this embodiment, the control device 50 controls the brake mechanism 9 to switch between locking and releasing the sleeve 7, so that the bearing 3 can function by switching between a rolling bearing and a sliding bearing, based on the motor rotation speed detected by the motor rotation speed sensor 31 (hereinafter, this control will be referred to as "bearing switching control"). Furthermore, during this bearing switching control, the control device 50 controls the pump 12 to supply gas from the gas passage 11 to the gap SP between the sleeve 7 and the fixed member 8, at least when the brake mechanism 9 releases the sleeve 7.

[0038] [Bearing switching control] Next, the bearing switching control according to this embodiment will be specifically described.

[0039] First, the basic concept of bearing switching control according to this embodiment will be described. Conventionally, rolling bearings and plain bearings have been used as bearings to support the rotating shaft of a vehicle's power source. Rolling bearings have low friction in low rotational speed ranges, while plain bearings have high friction in low rotational speed ranges. On the other hand, rolling bearings have a finite lifespan due to rolling fatigue, while plain bearings have a permanent lifespan under appropriate lubrication conditions. In a typical engine (internal combustion engine), it is effective to use plain bearings in high rotational speed ranges. These plain bearings typically use fluid lubrication with lubricating oil. However, in a motor 1 that operates at a higher rotational speed than an engine, using such plain bearings in the high rotational speed range of the motor 1 increases the fluid friction and resistance of the lubricating oil, resulting in a problem of reduced motor power consumption.

[0040] For this reason, in this embodiment, a gas bearing (typically an air bearing) lubricated by a gas with a lower viscosity than lubricating oil is used as the sliding bearing. To achieve this gas bearing, a gas layer must be reliably formed in the gap SP between the sleeve 7 and the fixed member 8 to prevent the sleeve 7 and the fixed member 8 from coming into contact without ensuring the load capacity of the gas bearing. In this embodiment, to reliably form this gas layer, gas is supplied to the gap SP between the sleeve 7 and the fixed member 8 by a pump 12, and the wedge effect and throttling effect that occur in this gap SP are utilized. Because these wedge and throttling effects are only obtainable in the high-speed rotation range of the motor 1, methods that attempt to utilize these effects may not ensure sufficient load capacity of the gas bearing in the low-speed rotation range of the motor 1, resulting in contact between the sleeve 7 and the fixed member 8.

[0041] In view of the above, in this embodiment, the control device 50 performs bearing switching control to switch between locking and releasing the sleeve 7 by the brake mechanism 9 depending on the motor rotation speed, as described above, so that the bearing 3 functions as a rolling bearing in the low rotation range, while the bearing 3 functions as a sliding bearing (gas bearing) in the high rotation range.

[0042] Next, the basic concept of the bearing switching control according to this embodiment will be explained in more detail with reference to Fig. 6. Here, the bearing switching control according to this embodiment will be compared with the bearing switching control according to a comparative example. In Fig. 6, the horizontal axis represents the motor rotation speed, and the vertical axis represents the shaft friction torque.

[0043] In the bearing switching 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 region R11 (low rotation region) where the motor rotation speed is low, a rolling bearing is used as the bearing that functions to support the rotating shaft 2, while in region R12 where the motor rotation speed is higher than region R11, a sliding bearing is used as the bearing that functions to support the rotating shaft 2. This control corresponds to the technology described in Patent Document 1.

[0044] In Figure 6, graph G11 shows the axial friction torque generated in a rolling bearing, i.e., boundary lubrication friction due to direct contact, and graph G12 shows the axial friction torque generated in a sliding bearing that uses fluid lubrication with lubricating oil, i.e., fluid lubrication friction of lubricating oil. Therefore, the axial friction torque generated in the bearing switching control of the above-mentioned comparative example is the sum of the axial friction torque shown in graph G11 and the axial friction torque shown in graph G12, i.e., the torque shown in graph G21. In this case, the axial friction torque increases significantly as the motor rotation speed increases in region R12. This is due to increased friction caused by deformation of the rolling elements in the rolling bearing, as shown in graph G13.

[0045] In contrast to this, in this embodiment, as described above, the control device 50 controls the brake mechanism 9 to switch between locking and releasing the sleeve 7 so that the bearing 3 can be switched between functioning as a rolling bearing and a sliding bearing (gas bearing). First, in the region R11 where the motor rotation speed is low, the wedge effect and throttle effect cannot be obtained, so the control device 50 locks the sleeve 7 using the brake mechanism 9 to cause the bearing 3 to function as a rolling bearing, that is, to cause the bearing 3 to perform its original function (function as a rolling bearing).

[0046] Next, when the motor rotation speed exceeds region R11, that is, when it enters region R12 which is higher than region R11, the wedge effect and throttle effect gradually begin to be obtained, so control device 50 causes bearing 3 to function as a gas bearing. Specifically, control device 50 releases sleeve 7, which had been fixed by brake mechanism 9, and supplies gas from pump 12 to gap SP between sleeve 7 and fixed member 8, thereby causing bearing 3 to function as a gas bearing and not as a rolling bearing. In this case, outer peripheral surface 7s of sleeve 7 is separated from inner peripheral surface 8s of fixed member 8, and a gas bearing is realized in which the entire bearing 3 (including sleeve 7) rotates together relative to fixed member 8.

[0047] In Figure 6, graph G14 shows the shaft friction torque generated in the gas bearing, i.e., gas-lubricated friction. The shaft friction torque generated in the bearing switching control according to the present embodiment described above is the sum of the shaft friction torque shown in graph G11 and the shaft friction torque shown in graph G14, i.e., the torque shown in graph G22. When comparing the shaft friction torque according to the present embodiment shown in graph G22 with the shaft friction torque according to the comparative example shown in graph G21, it can be seen that the shaft friction torque is significantly reduced according to the present embodiment. Therefore, it can be said that the present embodiment can effectively improve electricity consumption compared to the comparative example.

[0048] Next, the flow of bearing switching control according to this embodiment will be described with reference to Fig. 7. Fig. 7 is a time chart showing bearing switching control according to this embodiment. From top to bottom, Fig. 7 shows the motor rotation speed, on / off of the brake mechanism 9, and on / off of the pump 12. Note that in Fig. 7, the "predetermined value" of the motor rotation speed is the motor rotation speed corresponding to the lower limit of region R12 in Fig. 6 (in other words, the upper limit of region R11). Also, Fig. 7 assumes a situation in which the motor rotation speed increases and the vehicle accelerates.

[0049] 7, between times t0 and t1 when the motor rotation speed is below a predetermined value, the control device 50 turns on the brake mechanism 9 to fix the sleeve 7 and turns off the pump 12, causing the bearing 3 to function as a rolling bearing. Then, from time t1 when the motor rotation speed reaches or exceeds a predetermined value, the control device 50 turns off the brake mechanism 9 to release the sleeve 7 and turns on the pump 12 to supply gas into the gap SP between the sleeve 7 and the fixed member 8, thereby switching the bearing 3 from a rolling bearing to a sliding bearing (gas bearing).

[0050] [Action and effect] Next, the operation and effect of the motor bearing system 20 according to this embodiment will be described. As described above, in this embodiment, when the brake mechanism 9 locks the sleeve 7, the motor bearing system 20 uses the bearing 3 to form a rolling bearing, whereas when the brake mechanism 9 releases the sleeve 7, the outer peripheral surface 7s of the sleeve 7 is spaced from the inner peripheral surface 8s of the fixed member 8, and the entire bearing 3 rotates relative to the fixed member 8 in conjunction with the rotation of the rotating shaft 2, thereby forming a sliding bearing. As a result, the motor bearing system 20 is configured to be able to selectively function as a rolling bearing or a sliding bearing by switching between locking and releasing the sleeve 7 using the brake mechanism 9.

[0051] According to this embodiment, the brake mechanism 9 can switch between locking and unlocking the outer ring 5 of the bearing 3 via the sleeve 7, thereby enabling the motor bearing system 20 to switch between the rolling bearing and plain bearing functions. Therefore, unlike the technology described in Patent Document 1, this embodiment does not use a plain bearing and a rolling bearing configured as separate components, nor does it require the inner or outer ring of the rolling bearing to move relative to one another in the axial direction. Therefore, switching between the rolling bearing and plain bearing can be performed with a simple configuration. Furthermore, according to this embodiment, even if a failure occurs, such as seizure between the outer peripheral surface 7s of the sleeve 7 and the inner peripheral surface 8s of the fixed member 8, the function of the rolling bearing provided by the bearing 3 is guaranteed, thereby ensuring the rotation of the rotating shaft 2 of the motor 1. This makes it possible to achieve an appropriate fail-safe.

[0052] In this embodiment, a configuration is employed in which the rolling bearing is disposed radially inward and the plain bearing is disposed radially outward ( FIG. 1 ). However, a configuration in which the rolling bearing is disposed radially outward and the plain bearing is disposed radially inward (hereinafter referred to as a “comparative example configuration”) is also conceivable. However, in the comparative example configuration, a mechanism (such as a clutch or actuator) for switching between the rolling bearing and the plain bearing is provided on the rotating shaft, which results in high rotation speeds. Therefore, the comparative example configuration is relatively difficult to implement. In contrast, in this embodiment, a mechanism for switching between the rolling bearing and the plain bearing, i.e., a brake mechanism 9, is not provided on the rotating shaft 2, so the comparative example configuration is not as difficult to implement as the comparative example configuration.

[0053] Furthermore, according to the present embodiment, motor bearing system 20 further includes gas passage 11 for supplying gas to gap SP between outer peripheral surface 7s of sleeve 7 and inner peripheral surface 8s of fixed member 8, and pump 12 provided on gas passage 11 for pumping the gas, and pump 12 supplies gas from gas passage 11 to gap SP at least when brake mechanism 9 releases sleeve 7, thereby realizing a sliding bearing. This makes it possible to accurately form a gas layer in gap SP between sleeve 7 and fixed member 8, making it possible to effectively realize a gas bearing as a sliding bearing.

[0054] Furthermore, according to this embodiment, the sleeve 7 has a protrusion 7p that protrudes radially outward at an end in the axial direction, and the brake mechanism 9 is configured to fix the sleeve 7 by applying force to the protrusion 7p of the sleeve 7. This allows the brake mechanism 9 to fix the sleeve 7 with a simple configuration.

[0055] Furthermore, according to this embodiment, the motor bearing system 20 further includes a motor rotation speed sensor 31 that detects the motor rotation speed, and a control device 50 configured to control the brake mechanism 9 based on this motor rotation speed. The control device 50 is configured to control the brake mechanism 9 to lock the sleeve 7 when the motor rotation speed is below a predetermined value, and to control the brake mechanism 9 to release the sleeve 7 when the motor rotation speed is equal to or greater than the predetermined value. This allows for appropriate switching between a rolling bearing and a sliding bearing (gas bearing) depending on the motor rotation speed. Specifically, by determining the conditions under which a gas bearing can be used as a sliding bearing based on the motor rotation speed, it is possible to switch to a gas bearing in appropriate conditions.

[0056] Furthermore, according to this embodiment, control device 50 is configured to control brake mechanism 9 to release sleeve 7 when the motor rotation speed is equal to or greater than a predetermined value, and to control pump 12 to supply gas to gap SP between sleeve 7 and fixed member 8. As a result, in a situation where a gas bearing can be realized as a sliding bearing, a gas layer can be accurately formed in gap SP between sleeve 7 and fixed member 8, making it possible to effectively realize a gas bearing as a sliding bearing.

[0057] [Variations] In the above-described embodiment, the "outer ring portion" of the present invention is composed of separate members, namely the outer ring 5 and the sleeve 7, but in other examples, this "outer ring portion" may be composed of a member in which the outer ring 5 and the sleeve 7 are integrated.

[0058] Furthermore, in the above-described embodiment, a gas bearing using gas lubrication was shown as the sliding bearing, but in other examples, a sliding bearing using fluid lubrication with lubricating oil (grease or oil) may also be used. [Explanation of symbols]

[0059] 1 motor 2 rotation axes 3. Bearings 4. Inner Circle 5 outer ring 6 rolling elements 7 Sleeve 7p protrusion 7s outer surface 8 Fixing member 8s Inner surface 9 Brake mechanism 9b4 Gas passage (second gas passage) 11 Gas passage (first gas passage) 12 Pump 20 Motor Bearing System 50 Control device 100 Motor System

Claims

1. 1. A motor bearing system comprising: a bearing attached to an outer periphery of a rotating shaft of a motor so as to support the rotating shaft, the bearing comprising: a plurality of rolling elements provided along a circumferential direction of the rotating shaft; and an outer ring portion provided radially outward of the plurality of rolling elements and holding the plurality of rolling elements; a fixed member having an inner peripheral surface that extends along an outer peripheral surface of the outer ring portion of the bearing and is provided with a gap between the inner peripheral surface and the outer peripheral surface, and configured not to rotate in accordance with rotation of the rotating shaft; a brake mechanism configured to fix the outer ring portion of the bearing to the fixing member; and the motor bearing system When the brake mechanism fixes the outer ring portion, the bearing functions as a rolling bearing, whereas when the brake mechanism releases the outer ring portion, the outer peripheral surface of the outer ring portion is spaced from the inner peripheral surface of the fixed member, and the entire bearing rotates relative to the fixed member in conjunction with rotation of the rotating shaft, thereby forming a sliding bearing. The brake mechanism is configured to selectively realize the rolling bearing and the sliding bearing by switching between fixing and releasing the outer ring portion.

1. A motor bearing system comprising:

2. the motor bearing system further includes a gas passage for supplying gas to the gap between the outer peripheral surface of the outer ring portion and the inner peripheral surface of the fixed member, and a pump provided on the gas passage for pumping the gas, The pump supplies the gas from the gas passage to the gap at least when the brake mechanism releases the outer ring portion, thereby realizing the sliding bearing. The motor bearing system of claim 1 .

3. the gas passage is a first gas passage, the motor bearing system further includes a second gas passage for supplying the gas from the pump to the brake mechanism; The brake mechanism is configured to fix the outer ring portion by utilizing the pressure of the gas supplied from the pump via the second gas passage.

3. The motor bearing system of claim 2.

4. the outer ring portion includes a protrusion protruding radially outward at an end portion in the axial direction, The brake mechanism is configured to apply a force to the protrusion of the outer ring portion to fix the outer ring portion.

3. The motor bearing system according to claim 1 or 2.

5. 3. The motor bearing system according to claim 1, wherein the brake mechanism includes a coil and is configured to fix the outer ring portion by utilizing an electromagnetic force generated by energizing the coil.

6. 3. The motor bearing system according to claim 1, wherein the outer ring portion and the brake mechanism each have a frictional fastening element that fastens to each other, and the outer ring portion is fixed by the brake mechanism when these frictional fastening elements are fastened to each other.

7. the motor bearing system further includes a motor rotation speed sensor that detects a rotation speed of the motor; and a control device that controls the brake mechanism based on the rotation speed detected by the motor rotation speed sensor, 3. The motor bearing system according to claim 1, wherein the control device is configured to control the brake mechanism to fix the outer ring portion when the rotation speed is less than a predetermined value, and to control the brake mechanism to release the outer ring portion when the rotation speed is equal to or greater than the predetermined value.

8. the motor bearing system further includes a gas passage for supplying gas to the gap between the outer peripheral surface of the outer ring portion and the inner peripheral surface of the fixed member, and a pump provided on the gas passage for pumping the gas, 8. The motor bearing system according to claim 7, wherein the control device is configured to control the brake mechanism to release the outer ring portion when the rotational speed is equal to or greater than the predetermined value, and to control the pump to supply the gas from the gas passage to the gap.

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