JP6751325B2 - Bearing structure - Google Patents

Description

The present invention relates to a bearing structure.

Conventionally, a drive system that operates by transmitting rotational power output from a motor as a power source has been used in various devices. In the drive system, specifically, the rotational power output from the motor is transmitted via the shaft member. Generally, such a shaft member is rotatably supported by a bearing. Here, a voltage may be generated in the shaft member directly or indirectly connected to the motor by high frequency induction resulting from the motor being driven by the inverter control. This causes a potential difference between the inner ring and the outer ring of the bearing that rotatably supports the shaft member. The higher the load on the motor, the easier the potential difference increases. Then, when the load applied to the motor is relatively high and the load reaches a voltage that may cause dielectric breakdown in the oil film inside the bearing, when the potential difference reaches an excessive current flowing between the inner ring and the outer ring of the bearing, Electrolysis occurs at. As a result, abnormal noise or vibration may occur in the bearing.

Therefore, a technique for preventing the occurrence of electrolytic corrosion in the bearing has been proposed. Specifically, there has been proposed a technique for suppressing an excessive current flow by making it difficult for a current to flow between the inner ring and the outer ring of the bearing. For example, in Patent Document 1, an insulating material is fitted into the bearing box of the bracket, and the bearing is supported through the insulating material to prevent current from flowing between the inner ring and the outer ring of the bearing. A technique for preventing the occurrence of electrolytic corrosion in is disclosed.

JP, 2005-082906, A

However, it may be difficult to prevent the occurrence of electrolytic corrosion in the bearing by the technique of making it difficult for the current to flow between the inner ring and the outer ring of the bearing. For example, in the technique using the above-described insulating material, the performance of insulating the bearing from the member supporting the bearing by the insulating material may be deteriorated due to wear of the insulating member or deterioration with time. In addition to the above-described technique using the insulating material, it is conceivable to use a technique for grounding the shaft member with an earth brush to prevent current from flowing between the inner ring and the outer ring of the bearing. However, in this technique, the performance of grounding the shaft member by the ground brush may be deteriorated due to wear of the ground brush and deterioration with time. Therefore, in these techniques, an excessive current may flow between the inner ring and the outer ring of the bearing. Therefore, it may be difficult to prevent the occurrence of electrolytic corrosion in the bearing.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved bearing that can more effectively prevent the occurrence of electrolytic corrosion in the bearing. To provide the structure.

In order to solve the above-mentioned problems, according to one aspect of the present invention, a shaft member connected to a motor, a pair of bearings provided at the shaft member with an interval in the axial direction, and the shaft member. And a housing that is relatively rotatably provided via the pair of bearings, and an inner ring that is an inner race ring of the bearing is fitted to an outer peripheral surface of the shaft member. An outer ring, which is a bearing ring on the outer side of the bearing, is fitted to the inner peripheral surface of the housing, and a metal rolling element is interposed between the inner ring and the outer ring. in at least one bearing of the inner ring relative to the shaft member, the axis direction is provided to freely move relatively, the the shaft member, from the outer peripheral surface of the inner ring is fitted A shaft member extending portion extending outward in the radial direction is provided, an end surface of the shaft member extending portion on the inner ring side faces a side surface of the inner ring, and a side surface of the inner ring and the shaft member extending portion. There is provided a bearing structure in which an expansion member capable of pressing the inner ring along the axial direction by thermal expansion is provided between the inner ring side end surface and the inner ring side end surface .

The shaft member extending portion is located on the side opposite to the other bearing side with respect to the inner ring, and the inner ring side end surface of the shaft member extending portion is a side surface opposite to the other bearing side of the inner ring. You may face with.

The shaft member extending portion may be located on the other bearing side with respect to the inner ring, and the inner ring side end surface of the shaft member extending portion may face the other bearing side surface of the inner ring. ..

The expansion member may be expandable along the axial direction during thermal expansion.

The expansion member may be bendable and deformable in the axial direction during thermal expansion.

A rotor of the motor may be rotatably connected to the shaft member as a unit.

As described above, according to the present invention, it is possible to more effectively prevent the occurrence of electrolytic corrosion in the bearing.

It is sectional drawing which shows an example of a structure of the bearing structure which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows an example of a structure of the bearing structure which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows an example of a structure of the bearing structure which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows an example of a structure of the bearing structure which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows an example of a structure of the bearing structure which concerns on a 1st modification. It is sectional drawing which shows an example of a structure of the expansion member which concerns on a 1st modification. It is a perspective view which shows an example of a structure of the expansion member which concerns on a 1st modification. It is sectional drawing which shows an example of a structure of the bearing structure which concerns on a 2nd modification.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, and duplicate description will be omitted.

<1. First Embodiment>
First, a bearing structure 11 according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing an example of the configuration of the bearing structure 11 according to the first embodiment. Specifically, FIG. 1 is a cross-sectional view of a cross section including the central axis of the shaft member 110 in the bearing structure 11.

The bearing structure 11 is a structure for rotatably supporting the shaft member 110 connected to the motor 80. The motor 80 is a drive motor provided as a drive source for driving the drive wheels of an electric vehicle (EV) or a hybrid vehicle (HEV), for example. The bearing structure 11 can be applied to a drive system that operates by transmitting the rotational power output from the motor 80 in these vehicles. The above-described application of the motor 80 is merely an example, and the bearing structure 11 can be applied to drive systems for motors for various applications.

The motor 80 includes a stator 810 and a rotor 820, as shown in FIG. The stator 810 and the rotor 820 have, for example, a substantially cylindrical shape, and are provided to face each other with a gap therebetween. Further, the central axes of the stator 810 and the rotor 820 are substantially the same.

The stator 810 is located on the outer peripheral side of the rotor 820 and is fixed to the housing 150 described later. A plurality of armatures are arranged on the stator 810 along the circumferential direction. Specifically, the stator 810 is provided with an iron core made of a plurality of laminated copper plates and a coil wound around each of a plurality of slots provided in the inner peripheral portion of the iron core. The armature is formed by such an iron core and coil. The coil of the stator 810 is electrically connected to the battery via the inverter device, and when electric power is supplied to the coil, a rotating magnetic field that rotates along the circumferential direction of the stator 810 is generated.

On the rotor 820, a plurality of permanent magnets are arranged along the circumferential direction so as to have different polarities alternately. When the rotating magnetic field is generated by the stator 810 as described above, the magnetic force acts on the permanent magnet of the rotor 820. Thereby, the rotor 820 can rotate relative to the stator 810. The motor 80 is driven by inverter control. Thereby, the rotation speed of the rotor 820 is controlled. The shaft member 110 is inserted and fixed to the inner peripheral portion of the rotor 820. Therefore, the rotor 820 of the motor 80 is rotatably connected to the shaft member 110 as a unit. In this way, the shaft member 110 can be directly connected to the motor 80. The shaft member 110 corresponds to the output shaft of the motor 80 that is directly driven to rotate by the motor 80. The shaft member 110 can be formed of, for example, an iron-based material such as cast iron.

As shown in FIG. 1, the bearing structure 11 includes the shaft member 110 described above, a pair of bearings 130 a and 130 b, and a housing 150. As shown in FIG. 1, the above-described motor 80 is housed in the housing 150, and the shaft member 110 is rotatably supported by the pair of bearings 130a and 130b. A portion of the shaft member 110 on one side (left side in FIG. 1) of the motor 80 is housed in the housing 150, and a portion of the other side (right side in FIG. 1) of the motor 80 extends from the inside of the housing 150 to the outside. .. In the following, the one side and the other side of the motor 80 are also simply referred to as the one side and the other side, respectively. In FIG. 1, details of the other part of the shaft member 110 outside the housing 150 are omitted, but the other part of the shaft member 110 is, for example, a drive system to which the bearing structure 11 is applied. Is connected to another shaft member that constitutes a part of the above through mechanical elements such as gears and clutches.

Each of the bearings 130a and 130b is specifically a ball bearing. Each of the bearings 130a and 130b is made of a metal that is interposed between the inner races 131a and 131b that are inner races, the outer races 132a and 132b that are outer races, and the inner races 131a and 131b and the outer races 132a and 132b. And rolling elements 133a and 133b. The inner rings 131a and 131b, the outer rings 132a and 132b, and the rolling elements 133a and 133b can be formed of bearing steel such as SUJ material, for example. A plurality of rolling elements 133a and 133b are arranged along the circumferential direction, and when the inner rings 131a and 131b and the outer rings 132a and 132b rotate relative to each other, the plurality of rolling elements 133a and 133b rotate by themselves. The friction between the respective members inside the bearings 130a and 130b is reduced.

Lubricating oil is injected into the bearings 130a and 130b, and the lubricating oil forms an oil film between the rolling elements 133a and 133b and the inner rings 131a and 131b and the outer rings 132a and 132b, respectively. Thereby, reduction of friction between the respective members inside the bearings 130a and 130b is realized. In the following, the bearing 130a and the bearing 130b will be simply referred to as the bearing 130 unless otherwise specified. Further, the inner ring 131a and the inner ring 131b are also simply referred to as the inner ring 131 unless otherwise distinguished. Further, the outer ring 132a and the outer ring 132b are simply referred to as the outer ring 132 unless otherwise specified.

The pair of bearings 130a and 130b are arranged on the shaft member 110 at intervals in the axial direction. In addition, the said axial direction is a direction along the central axis of the shaft member 110, and below, such a direction is only called an axial direction. The inner rings 131a and 131b of the bearings 130a and 130b are fitted to the outer peripheral surface of the shaft member 110. Specifically, in the bearing structure 11, the inner ring 131a of the bearing 130a is fitted to the outer peripheral surface 111 at one end of the shaft member 110. On the other hand, the inner ring 131b of the bearing 130b is fitted to the outer peripheral surface 113 on the other side of the shaft member 110. In the first embodiment, relative movement of the inner ring 131 with respect to the shaft member 110 in the axial direction is restricted. Specifically, the inner rings 131a and 131b are fitted to the outer peripheral surfaces 111 and 113 of the shaft member 110 in a tight fit state. The rotor 820 of the motor 80 is fitted to the outer peripheral surface 112 on the center side of the shaft member 110.

The shaft member 110 is provided with a shaft member extending portion that extends radially outward from an outer peripheral surface into which the inner ring 131 is fitted. Specifically, on one side of the shaft member 110, an extending portion 114 that extends radially outward from the outer peripheral surface 111 is provided. On the other hand, on the other side of the shaft member 110, an extending portion 115 that extends radially outward from the outer peripheral surface 113 is provided. In the shaft member 110, the extending portion 114 and the extending portion 115 correspond to the shaft member extending portion.

The extending portion 114 is located on the bearing 130b side as the other bearing with respect to the inner ring 131a, and the end surface 116 of the extending portion 114 on the inner ring 131a side contacts the side surface of the inner ring 131a on the bearing 130b side. In other words, the extending portion 114 is located on the other side with respect to the inner ring 131a, and the end surface 116 contacts the side surface on the other side of the inner ring 131a. Thereby, the bearing 130a can be positioned in the axial direction with respect to the shaft member 110. On the other hand, the extending portion 115 is located on the bearing 130a side as the other bearing with respect to the inner ring 131b, and the end surface 117 of the extending portion 115 on the inner ring 131b side contacts the side surface of the inner ring 131b on the bearing 130a side. In other words, the extending portion 115 is located on one side with respect to the inner ring 131b, and the end surface 117 abuts on one side surface of the inner ring 131b. Thereby, the bearing 130b can be positioned in the axial direction with respect to the shaft member 110.

The housing 150 is a member that accommodates various members. The housing 150 can be formed of, for example, an aluminum alloy. The housing 150 specifically accommodates a part of the shaft member 110, the pair of bearings 130 a and 130 b, and the motor 80. The other end of the housing 150 is provided with an opening through which the other part of the shaft member 110 is inserted. Further, a recess 153 having a shape corresponding to the shape of the motor 80 is provided on the center side of the housing 150. Therefore, the inner diameter of the housing 150 is larger on the central side in the axial direction than on the other portions.

Outer rings 132a and 132b of bearings 130a and 130b are attached to the housing 150. Accordingly, the housing 150 is provided rotatably relative to the shaft member 110 via the pair of bearings 130a and 130b. The outer rings 132a and 132b of the bearings 130a and 130b are specifically fitted to the inner peripheral surface of the housing 150. More specifically, in the bearing structure 11, the outer ring 132a of the bearing 130a is fitted to the inner peripheral surface 152 on one side of the housing 150. On the other hand, the outer ring 132b of the bearing 130b is fitted to the inner peripheral surface 154 on the other side of the housing 150. In the first embodiment, the outer ring 132 is provided so as to be relatively movable in the axial direction with respect to the housing 150. Specifically, the outer rings 132a and 132b are fitted to the inner peripheral surfaces 152 and 154 of the housing 150 in a clearance fit state.

Further, the housing 150 is provided with a housing extension portion that extends inward in the radial direction from the inner peripheral surface into which the outer ring 132 is fitted. Specifically, a bottom portion 151 extending in a direction orthogonal to the axial direction is provided at one end of the housing 150. One side of the inner space of the housing 150 is separated from the outside by the bottom 151. The bottom portion 151 extends radially inward from the inner peripheral surface 152 with which the outer ring 132a is fitted. On the other hand, the other end of the housing 150 is provided with an extending portion 155 that extends radially inward from the inner peripheral surface 154 into which the outer ring 132b is fitted. In the housing 150, the bottom portion 151 and the extension portion 155 correspond to the above-mentioned housing extension portion. In the first embodiment, the housing extension portion is located on the side opposite to the other bearing 130 side with respect to the outer ring 132. Further, an expansion member 170 is provided between the end surface of the housing extending portion on the outer ring 132 side and the side surface of the outer ring 132, as described later.

Specifically, the bottom portion 151 is located on the side opposite to the bearing 130b as the other bearing with respect to the outer ring 132a. Therefore, the end surface 158 of the bottom portion 151 on the outer ring 132a side faces the side surface of the outer ring 132a on the side opposite to the bearing 130b side. In other words, the bottom portion 151 is located on one side of the outer ring 132a, and the end surface 158 faces one side surface of the outer ring 132a. On the other hand, the extending portion 155 is located on the opposite side of the bearing 130a as the other bearing with respect to the outer ring 132b. Therefore, the end surface 159 of the extending portion 155 on the outer ring 132b side faces the side surface of the outer ring 132b on the side opposite to the bearing 130a side. In other words, the extending portion 155 is located on the other side with respect to the outer ring 132b, and the end surface 159 faces the side surface on the other side of the outer ring 132b. In this way, the housing 150 is provided with the end surfaces 158 and 159 corresponding to the facing surfaces that face the side surfaces of the outer ring 132.

Expansion members 170a and 170b are provided between the side surface of the outer ring 132 and each of the end surfaces 158 and 159 of the housing 150. Specifically, 170a is provided between the one side surface of the outer ring 132a and the end surface 158. On the other hand, 170b is provided between the other side surface of the outer ring 132b and the end surface 159. The expansion members 170a and 170b are expandable along the axial direction during thermal expansion, for example. Therefore, in the first embodiment, the expansion members 170a and 170b are capable of pressing the outer rings 132a and 132b along the axial direction by thermal expansion. In addition, below, the expansion member 170a and the expansion member 170b are also simply referred to as the expansion member 170 unless otherwise distinguished.

The expansion member 170 specifically has a substantially cylindrical shape and can be formed of a resin such as polyimide resin or nylon. As the resin forming the expansion member 170, it is preferable to use a resin having relatively high heat resistance and oil resistance. The central axis of the expansion member 170 may be substantially coincident with the central axis of the bearing 130. The inner diameter and the outer diameter of the expansion member 170 may substantially match the inner diameter and the outer diameter of the outer ring 132, respectively. The expansion members 170a and 170b may be provided so as to be in contact with the inner peripheral surfaces 152 and 154 of the housing 150.

In FIG. 1, the expansion member 170 when the load applied to the motor 80 is relatively low is shown by a solid line, and the expansion member 170 when the load applied to the motor 80 is relatively high is shown by a broken line. There is. When the load of the motor 80 is high, the amount of heat generated in the motor 80 increases due to an increase in the current supplied to the motor 80 as compared to when the load is low. As a result, when the motor 80 has a high load, the temperature of each member forming the bearing structure 11 becomes higher than that when the load is low. Therefore, when the motor 80 has a high load, the temperature of the expansion member 170 becomes relatively high, so that the expansion member 170 thermally expands to press the outer ring 132 along the axial direction. Specifically, the outer ring 132a is pressed to the other side by thermal expansion of the expansion member 170a provided between the one side surface of the outer ring 132a and the end surface 158 of the housing 150. On the other hand, thermal expansion of the expansion member 170b provided between the other side surface of the outer ring 132b and the end surface 159 of the housing 150 causes the outer ring 132b to be pressed to one side.

By the way, the shaft member 110 and the housing 150 are fixed to the motor 80 on the center side of the bearing structure 11, for example. Therefore, when the motor 80 has a high load, the shaft member 110 and the housing 150 can thermally expand in a direction away from the motor 80 on one side and the other side. Here, the shaft member 110 and the housing 150 may be respectively formed of, for example, cast iron and an aluminum alloy, as described above. Further, the coefficient of thermal expansion of an aluminum alloy is generally larger than that of cast iron. Therefore, when the motor 80 has a high load, the distance between the end surface 158 of the bottom 151 of the housing 150 and the side surface on one side of the outer ring 132a is low due to the difference in thermal expansion coefficient between the shaft member 110 and the housing 150. It can be longer than under load. Further, when the motor 80 has a high load, similarly, the distance between the end surface 159 of the extending portion 155 of the housing 150 and the other side surface of the outer ring 132b may be longer than that when the load is low.

Therefore, if the thermal expansion coefficient of the expansion member 170 provided between each end surface of the housing 150 and the side surface of the outer ring 132 is excessively small, the outer ring 132 is pressed by the expansion member 170 during high load of the motor 80. Not performed, or the force pressing the outer ring 132 may be insufficient. Here, since the expansion member 170 of the bearing structure 11 according to the first embodiment is specifically formed of resin as described above, it has a relatively large coefficient of thermal expansion. Therefore, when the load of the motor 80 is high, the expansion member 170 can more reliably press the outer ring 132 along the axial direction. The type and size of the resin forming the expansion member 170 are appropriately set so that the outer ring 132 can be pressed by the expansion member 170 along the axial direction when the motor 80 has a high load. Specifically, the type and size of the resin forming the expansion member 170 can be appropriately set based on the material forming the shaft member 110 and the housing 150, the size of the shaft member 110 and the housing 150, and the like.

In the bearing structure 11 according to the first embodiment, the outer ring 132 is provided so as to be relatively movable in the axial direction with respect to the housing 150, as described above. Therefore, when the load of the motor 80 is high, the outer ring 132 moves in the axial direction by being pressed in the axial direction by the expansion member 170. Specifically, the outer ring 132a moves to the other side by being pressed to the other side by the expansion member 170a. On the other hand, the outer ring 132b is moved to one side by being pressed to one side by the expansion member 170b. As a result, in the bearing 130, the number of rolling elements 133 in contact with both the inner ring 131 and the outer ring 132 can be increased. Further, the film thickness of the oil film interposed between the rolling element 133 and each of the inner ring 131 and the outer ring 132 can be reduced. Therefore, it is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of the bearing 130.

By the way, specifically, the motor 80 is driven by the inverter control as described above. Further, the shaft member 110 is connected to the motor 80. Therefore, a voltage may be generated in the shaft member 110 by high frequency induction when the motor 80 is driven. As a result, a potential difference is generated between the inner ring 131 and the outer ring 132 of the bearing 130 that rotatably supports the shaft member 110.

Here, according to the first embodiment, as described above, when the load of the motor 80 in which the potential difference is likely to increase is high, it is easy for the current to flow between the inner ring 131 and the outer ring 132 of the bearing 130. You can As a result, a current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage that may cause dielectric breakdown in the oil film inside the bearing 130. Therefore, it is possible to appropriately prevent an excessive current from flowing between the inner ring 131 and the outer ring 132 of the bearing 130. Therefore, the occurrence of electrolytic corrosion in the bearing 130 can be prevented more effectively.

Further, when the load of the motor 80 is low, the amount of heat generated by the motor 80 is lower than that when the load is high. As a result, the temperature of the expansion member 170 becomes relatively low. Therefore, according to the first embodiment, when the load of the motor 80 is low, the outer ring 132 is not pressed by the expansion member 170, or the force pressing the outer ring 132 is relatively small. Therefore, when the load of the motor 80 in which the potential difference between the inner ring 131 and the outer ring 132 of the bearing 130 is relatively small becomes small, the outer ring 132 is pressed by the expansion member 170 so that the internal components of the bearing 130 are separated from each other. It is possible to suppress an increase in friction.

In the above description, an example in which the outer ring 132 is provided in both the pair of bearings 130 a and 130 b so as to be movable in the axial direction relative to the housing 150 has been described. The bearing 130 provided so as to be relatively movable with respect to each other may be either one of the pair of bearings 130a and 130b. Even in such a case, in one bearing 130, it is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of the bearing 130 at the time of high load, so that the occurrence of electrolytic corrosion in the bearing 130. It can be prevented more effectively. Further, in such a case, the housing extension portion and the expansion member 170 may not be provided for the bearing 130 in which the relative movement of the outer ring 132 in the axial direction with respect to the housing 150 is restricted. From the viewpoint of improving the effect of preventing the occurrence of electrolytic corrosion, the outer ring 132 is provided in both the pair of bearings 130a and 130b so as to be relatively movable in the axial direction with respect to the housing 150, and the bearings 130a and 130b. More preferably, the housing extension and the expansion member 170 are provided for both.

<2. Second Embodiment>
Next, with reference to FIG. 2, a bearing structure 12 according to a second embodiment of the present invention will be described. FIG. 2 is a cross-sectional view showing an example of the configuration of the bearing structure 12 according to the second embodiment. Specifically, FIG. 2 is a cross-sectional view of a cross section including the central axis of the shaft member 210 in the bearing structure 12. In the second embodiment, the configuration around the bearing 130 is different from that of the first embodiment described with reference to FIG. Specifically, in the second embodiment, unlike the above-described first embodiment, the housing extending portion that extends radially inward from the inner peripheral surface of the housing 250 to which the outer ring 132 is fitted has an outer ring 132. Is located on the other bearing 130 side. Further, in the second embodiment, the expansion member 170 is provided between the end surface of the housing extending portion on the outer ring 132 side and the side surface of the outer ring 132.

As shown in FIG. 2, the bearing structure 12 includes a shaft member 210, a pair of bearings 130a and 130b, and a housing 250.

Similar to the first embodiment described above, the shaft member 210 is fixed while being inserted into the inner peripheral portion of the rotor 820 of the motor 80, and is rotatable integrally with the rotor 820. The shaft member 210 is rotatably supported by the pair of bearings 130a and 130b. A portion of the shaft member 210 on one side is housed in the housing 250, and a portion on the other side extends from the inside of the housing 250 toward the outside.

Inner rings 131a and 131b of the bearings 130a and 130b are fitted to the outer peripheral surface of the shaft member 210. Specifically, in the bearing structure 12, the inner ring 131a of the bearing 130a is fitted to the outer peripheral surface 211 on one side of the shaft member 210. On the other hand, the inner ring 131b of the bearing 130b is fitted to the outer peripheral surface 213 on the other side of the shaft member 210. Further, in the second embodiment, similarly to the above-described first embodiment, relative movement of the inner ring 131 with respect to the shaft member 210 in the axial direction is restricted. Specifically, the inner rings 131a and 131b are fitted to the outer peripheral surfaces 211 and 213 of the shaft member 210 in a tight fit state. The rotor 820 of the motor 80 is fitted to the outer peripheral surface 212 on the center side of the shaft member 210.

The shaft member 210 is provided with a shaft member extending portion that extends radially outward from the outer peripheral surface into which the inner ring 131 is fitted. Specifically, the one end of the shaft member 210 is provided with an extending portion 214 that extends radially outward from the outer peripheral surface 211. On the other hand, on the other side of the shaft member 210, an extending portion 215 that extends radially outward from the outer peripheral surface 213 is provided. In the shaft member 210, the extending portion 214 and the extending portion 215 correspond to the shaft member extending portion.

The extending portion 214 is located on the side opposite to the bearing 130b side as the other bearing with respect to the inner ring 131a, and the end surface 216 of the extending portion 214 on the inner ring 131a side is a side surface of the inner ring 131a opposite to the bearing 130b side. Abut. In other words, the extending portion 214 is located on one side with respect to the inner ring 131a, and the end surface 216 abuts on one side surface of the inner ring 131a. As a result, the bearing 130a can be positioned in the axial direction with respect to the shaft member 210. On the other hand, the extending portion 215 is located on the side opposite to the bearing 130a side as the other bearing with respect to the inner ring 131b, and the end surface 217 of the extending portion 215 on the inner ring 131b side is opposite to the bearing 130a side of the inner ring 131b. Abut the side surface of. In other words, the extending portion 215 is located on the other side of the inner ring 131b, and the end surface 217 is in contact with the other side surface of the inner ring 131b. Thereby, the bearing 130b can be positioned in the axial direction with respect to the shaft member 210.

The housing 250 houses a part of the shaft member 210, the pair of bearings 130a and 130b, and the motor 80, as in the first embodiment described above. Further, an opening portion through which the other side portion of the shaft member 210 is inserted is provided at the other end portion of the housing 250. A recess 253 having a shape corresponding to the shape of the motor 80 is provided on the center side of the housing 250. Therefore, the inner diameter of the housing 250 is larger on the central side in the axial direction than on the other portions. Further, at one end of the housing 250, a bottom portion 251 extending in a direction orthogonal to the axial direction is provided. One side of the inner space of the housing 250 is separated from the outside by the bottom portion 251. Outer rings 132a and 132b of the bearings 130a and 130b are attached to the housing 250. As a result, the housing 250 is provided rotatably relative to the shaft member 210 via the pair of bearings 130a and 130b.

Outer rings 132a and 132b of the bearings 130a and 130b are fitted to the inner peripheral surface of the housing 250. Specifically, in the bearing structure 12, the outer ring 132a of the bearing 130a is fitted to the inner peripheral surface 252 on one side of the housing 250. On the other hand, the outer ring 132b of the bearing 130b is fitted to the inner peripheral surface 254 on the other side of the housing 250. In the second embodiment, similarly to the above-described first embodiment, the outer ring 132 is provided so as to be relatively movable in the axial direction with respect to the housing 250. Specifically, the outer rings 132a and 132b are fitted to the inner peripheral surfaces 252 and 254 of the housing 250 in a clearance fit state.

The housing 250 is provided with a housing extension portion that extends radially inward from an inner peripheral surface into which the outer ring 132 is fitted. Specifically, on one side of the housing 250, an extending portion 255 that extends radially inward from the inner peripheral surface 252 is provided. On the other hand, on the other side of the housing 250, an extending portion 256 is provided that extends radially inward from the inner peripheral surface 254 with which the outer ring 132b is fitted. In the housing 250, the extending portion 255 and the extending portion 256 correspond to the above housing extending portion. In the second embodiment, unlike the first embodiment, the housing extension portion is located on the other bearing 130 side with respect to the outer ring 132. Further, the expansion member 170 is provided between the end surface of the housing extending portion on the outer ring 132 side and the side surface of the outer ring 132.

Specifically, the extending portion 255 is located on the bearing 130b side as the other bearing with respect to the outer ring 132a. Therefore, the end surface 258 of the extending portion 255 on the outer ring 132a side faces the side surface of the outer ring 132a on the bearing 130b side. In other words, the extending portion 255 is located on the other side of the outer ring 132a, and the end surface 258 faces the other side surface of the outer ring 132a. On the other hand, the extending portion 256 is located on the bearing 130a side as the other bearing with respect to the outer ring 132b. Therefore, the end surface 259 of the extending portion 256 on the outer ring 132b side faces the side surface of the outer ring 132b on the bearing 130a side. In other words, the extending portion 256 is located on one side of the outer ring 132b, and the end surface 259 faces one side surface of the outer ring 132b. In this way, the housing 250 is provided with the end surface 258 and the end surface 259 corresponding to the facing surfaces facing the side surface of the outer ring 132.

Expansion members 170a and 170b are provided between the side surface of the outer ring 132 and each of the end surfaces 258 and 259 of the housing 250. Specifically, 170a is provided between the other side surface of the outer ring 132a and the end surface 258. On the other hand, 170b is provided between the one side surface of the outer ring 132b and the end surface 259. Therefore, in the second embodiment, similarly to the above-described first embodiment, the expansion member 170 can thermally pressurize the outer ring 132 along the axial direction.

In FIG. 2, the expansion member 170 when the motor 80 has a low load is shown by a solid line, and the expansion member 170 when the motor 80 has a high load is shown by a broken line. When the load of the motor 80 is high, the temperature of the expansion member 170 becomes relatively high, and therefore the outer ring 132 is pressed along the axial direction by the thermal expansion of the expansion member 170. Specifically, the outer ring 132a is pressed to one side by thermal expansion of the expansion member 170a provided between the other side surface of the outer ring 132a and the end surface 258 of the housing 250. On the other hand, thermal expansion of the expansion member 170b provided between the one side surface of the outer ring 132b and the end surface 259 of the housing 250 causes the outer ring 132b to be pressed to the other side.

In the bearing structure 12 according to the second embodiment, the outer ring 132 is provided so as to be relatively movable in the axial direction with respect to the housing 250, as described above. Therefore, when the load of the motor 80 is high, the outer ring 132 moves in the axial direction by being pressed in the axial direction by the expansion member 170. Specifically, the outer ring 132a moves to one side by being pressed to one side by the expansion member 170a. On the other hand, the outer ring 132b is moved to the other side by being pressed to the other side by the expansion member 170b.

Therefore, according to the second embodiment, similarly to the above-described first embodiment, when the electric load of the motor 80 in which the potential difference generated between the inner ring 131 and the outer ring 132 of the bearing 130 is easily increased is high, It is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of the bearing 130. As a result, a current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage that may cause dielectric breakdown in the oil film inside the bearing 130. Therefore, it is possible to appropriately prevent an excessive current from flowing between the inner ring 131 and the outer ring 132 of the bearing 130. Therefore, the occurrence of electrolytic corrosion in the bearing 130 can be prevented more effectively.

Further, according to the second embodiment, similarly to the above-described first embodiment, when the load of the motor 80 is low, the outer ring 132 is not pressed by the expansion member 170, or the force pressing the outer ring 132 is relatively small. Get smaller. Therefore, when the load of the motor 80 in which the potential difference between the inner ring 131 and the outer ring 132 of the bearing 130 is relatively small becomes small, the outer ring 132 is pressed by the expansion member 170 so that the internal components of the bearing 130 are separated from each other. It is possible to suppress an increase in friction.

Note that, in the above, an example in which the outer ring 132 is provided in both the pair of bearings 130a and 130b so as to be relatively movable in the axial direction with respect to the housing 250 has been described, but similar to the above-described first embodiment. The bearing 130, in which the outer ring 132 is axially movable relative to the housing 250, may be either one of the pair of bearings 130a and 130b. Even in such a case, in one bearing 130, it is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of the bearing 130 at the time of high load, so that the occurrence of electrolytic corrosion in the bearing 130. It can be prevented more effectively.

<3. Third Embodiment>
Next, with reference to FIG. 3, a bearing structure 13 according to a third embodiment of the present invention will be described. FIG. 3 is a sectional view showing an example of the configuration of the bearing structure 13 according to the third embodiment. Specifically, FIG. 3 is a cross-sectional view of a cross section including the central axis of the shaft member 310 in the bearing structure 13. In the third embodiment, the configuration around the bearing 130 is different from that of the first embodiment described with reference to FIG. Specifically, in the third embodiment, unlike the above-described first embodiment, the inner ring 131 is provided so as to be relatively movable in the axial direction with respect to the shaft member 310. Further, in the third embodiment, between the end surface on the inner ring 131 side of the shaft member extending portion that extends radially outward from the outer peripheral surface of the shaft member 310 to which the inner ring 131 is fitted, and the side surface of the inner ring 131. An expansion member 170 is provided.

As shown in FIG. 3, the bearing structure 13 includes a shaft member 310, a pair of bearings 130a and 130b, and a housing 350.

Similar to the first embodiment described above, the shaft member 310 is fixed while being inserted into the inner peripheral portion of the rotor 820 of the motor 80, and is rotatable integrally with the rotor 820. The shaft member 310 is rotatably supported by the pair of bearings 130a and 130b. A portion of the shaft member 310 on one side is housed in the housing 350, and a portion on the other side thereof extends from the inside of the housing 350 toward the outside.

The housing 350 houses a part of the shaft member 310, the pair of bearings 130a and 130b, and the motor 80, as in the first embodiment described above. Further, an opening portion through which the other side portion of the shaft member 310 is inserted is provided at the other end portion of the housing 350. A recess 353 having a shape corresponding to the shape of the motor 80 is provided on the center side of the housing 350. Therefore, the inner diameter of the housing 350 is larger on the central side in the axial direction than on the other portions. A bottom portion 351 extending in a direction orthogonal to the axial direction is provided at one end of the housing 350. One side of the inner space of the housing 350 is separated from the outside by the bottom portion 351. Outer rings 132a and 132b of the bearings 130a and 130b are attached to the housing 350. As a result, the housing 350 is relatively rotatably provided to the shaft member 310 via the pair of bearings 130a and 130b.

Outer rings 132a and 132b of the bearings 130a and 130b are fitted to the inner peripheral surface of the housing 350. Specifically, in the bearing structure 13, the outer ring 132a of the bearing 130a is fitted to the inner peripheral surface 352 on one side of the housing 350. On the other hand, the outer ring 132b of the bearing 130b is fitted to the inner peripheral surface 354 on the other side of the housing 350. In the third embodiment, unlike the above-described first embodiment, the relative movement of the outer ring 132 in the axial direction with respect to the housing 350 is restricted. Specifically, the outer rings 132a and 132b are fitted to the inner peripheral surfaces 352 and 354 of the housing 350 in a tight fit state.

The housing 350 is provided with a housing extension portion that extends radially inward from an inner peripheral surface into which the outer ring 132 is fitted. Specifically, on one side of the housing 350, an extending portion 355 that extends radially inward from the inner peripheral surface 352 is provided. On the other hand, on the other side of the housing 350, an extending portion 356 that extends radially inward from the inner peripheral surface 354 with which the outer ring 132b is fitted is provided. In the housing 350, the extending portion 355 and the extending portion 356 correspond to the above housing extending portion.

The extending portion 355 is located on the bearing 130b side as the other bearing with respect to the outer ring 132a, and the end surface 358 of the extending portion 355 on the outer ring 132a side contacts the side surface of the outer ring 132a on the bearing 130b side. In other words, the extending portion 355 is located on the other side of the outer ring 132a, and the end surface 358 abuts on the other side surface of the outer ring 132a. On the other hand, the extending portion 356 is located on the bearing 130a side as the other bearing with respect to the outer ring 132b, and the end surface 359 of the extending portion 356 on the outer ring 132b side contacts the side surface of the outer ring 132b on the bearing 130a side. In other words, the extending portion 356 is located on one side of the outer ring 132b, and the end surface 359 abuts on one side surface of the outer ring 132b. Thereby, the bearing 130b can be positioned with respect to the housing 350 in the axial direction.

Inner rings 131a and 131b of the bearings 130a and 130b are fitted to the outer peripheral surface of the shaft member 310. Specifically, in the bearing structure 13, the inner ring 131a of the bearing 130a is fitted to the outer peripheral surface 311 on one side of the shaft member 310. On the other hand, the inner ring 131b of the bearing 130b is fitted to the outer peripheral surface 313 on the other side of the shaft member 310. Further, in the third embodiment, unlike the above-described first embodiment, the inner ring 131 is provided so as to be relatively movable in the axial direction with respect to the shaft member 310. Specifically, the inner rings 131a and 131b are fitted to the outer peripheral surfaces 311 and 313 of the shaft member 310 in a clearance fit state. The rotor 820 of the motor 80 is fitted on the outer peripheral surface 312 on the center side of the shaft member 310.

The shaft member 310 is provided with a shaft member extending portion that extends radially outward from an outer peripheral surface into which the inner ring 131 is fitted. Specifically, the one end of the shaft member 310 is provided with an extending portion 314 that extends radially outward from the outer peripheral surface 311. On the other hand, on the other side of the shaft member 310, an extending portion 315 that extends radially outward from the outer peripheral surface 313 is provided. In the shaft member 310, the extending portion 314 and the extending portion 315 correspond to the shaft member extending portion. In the third embodiment, the shaft member extending portion is located on the side opposite to the other bearing 130 side with respect to the inner ring 131. Further, the expansion member 170 is provided between the end surface of the shaft member extending portion on the inner ring 131 side and the side surface of the inner ring 131.

Specifically, the extending portion 314 is located on the side opposite to the bearing 130b side as the other bearing with respect to the inner ring 131a. Therefore, the end surface 316 of the extending portion 314 on the inner ring 131a side faces the side surface of the inner ring 131a opposite to the bearing 130b side. In other words, the extending portion 314 is located on one side of the inner ring 131a, and the end surface 316 faces one side surface of the inner ring 131a. On the other hand, the extending portion 315 is located on the side opposite to the bearing 130a side as the other bearing with respect to the inner ring 131b. Therefore, the end surface 317 of the extending portion 315 on the inner ring 131b side faces the side surface of the inner ring 131b on the side opposite to the bearing 130a side. In other words, the extending portion 315 is located on the other side of the inner ring 131b, and the end surface 317 faces the other side surface of the inner ring 131b. In this way, the shaft member 310 is provided with the end surfaces 316 and 317 corresponding to the facing surfaces that face the side surfaces of the inner ring 131.

In the third embodiment, the expansion members 170a and 170b are provided between the side surface of the inner ring 131 and each of the end surfaces 316 and 317 of the shaft member 310. Specifically, 170a is provided between the one side surface of the inner ring 131a and the end surface 316. On the other hand, 170b is provided between the other side surface of the inner ring 131b and the end surface 317. Here, as described above, the expansion member 170 can expand along the axial direction at the time of thermal expansion. Therefore, in the third embodiment, the expansion member 170 can thermally pressurize the inner ring 131 along the axial direction. In addition, in the third embodiment, the inner diameter and the outer diameter of the expansion member 170 may substantially match the inner diameter and the outer diameter of the inner ring 131, respectively. The expansion members 170a and 170b may be provided so as to circumscribe outer peripheral surfaces 311 and 313 of the shaft member 310.

In FIG. 3, the expansion member 170 when the load of the motor 80 is low is shown by a solid line, and the expansion member 170 when the load of the motor 80 is high is shown by a broken line. Since the temperature of the expansion member 170 becomes relatively high when the motor 80 has a high load, the inner ring 131 is pressed along the axial direction by thermal expansion of the expansion member 170. Specifically, the expansion member 170a provided between the one side surface of the inner ring 131a and the end surface 316 of the shaft member 310 thermally expands, so that the inner ring 131a is pressed to the other side. On the other hand, thermal expansion of the expansion member 170b provided between the other side surface of the inner ring 131b and the end surface 317 of the shaft member 310 pushes the inner ring 131b to one side.

In the bearing structure 13 according to the third embodiment, the inner ring 131 is provided so as to be relatively movable in the axial direction with respect to the shaft member 310, as described above. Therefore, when the load of the motor 80 is high, the inner ring 131 moves in the axial direction by being pressed in the axial direction by the expansion member 170. Specifically, the inner ring 131a moves to the other side by being pressed to the other side by the expansion member 170a. On the other hand, the inner ring 131b moves to one side by being pressed to one side by the expansion member 170b. As a result, in the bearing 130, the number of rolling elements 133 in contact with both the inner ring 131 and the outer ring 132 can be increased. Further, the film thickness of the oil film interposed between the rolling element 133 and each of the inner ring 131 and the outer ring 132 can be reduced.

Therefore, according to the third embodiment, similarly to the above-described first embodiment, at the time of high load of the motor 80 in which the potential difference generated between the inner ring 131 and the outer ring 132 of the bearing 130 tends to increase, It is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of the bearing 130. As a result, a current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage that may cause dielectric breakdown in the oil film inside the bearing 130. Therefore, it is possible to appropriately prevent an excessive current from flowing between the inner ring 131 and the outer ring 132 of the bearing 130. Therefore, the occurrence of electrolytic corrosion in the bearing 130 can be prevented more effectively.

According to the third embodiment, when the motor 80 has a low load, the expansion member 170 does not press the inner ring 131, or the force pressing the inner ring 131 is relatively small. Therefore, when the load of the motor 80 in which the potential difference between the inner ring 131 and the outer ring 132 of the bearing 130 becomes relatively small is low, the inner ring 131 is pressed by the expansion member 170, so that the internal components of the bearing 130 are separated from each other. It is possible to suppress an increase in friction.

Note that, in the above, an example in which the inner ring 131 is provided in both the pair of bearings 130a and 130b so as to be relatively movable in the axial direction with respect to the shaft member 310 has been described, but similar to the above-described first embodiment. In addition, the bearing 130 in which the inner ring 131 is provided so as to be relatively movable in the axial direction with respect to the shaft member 310 may be either one of the pair of bearings 130a and 130b. Even in such a case, in one bearing 130, it is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of the bearing 130 at the time of high load, so that the occurrence of electrolytic corrosion in the bearing 130. It can be prevented more effectively.

<4. Fourth Embodiment>
Next, with reference to FIG. 4, a bearing structure 14 according to a fourth embodiment of the present invention will be described. FIG. 4 is a cross-sectional view showing an example of the configuration of the bearing structure 14 according to the fourth embodiment. Specifically, FIG. 4 is a cross-sectional view of a cross section including the central axis of the shaft member 410 in the bearing structure 14. In the fourth embodiment, the configuration around the bearing 130 is different from that in the third embodiment described with reference to FIG. Specifically, unlike the above-described third embodiment, in the fourth embodiment, the shaft member extending portion that extends radially outward from the outer peripheral surface of the shaft member 410 into which the inner ring 131 is fitted has an inner ring. It is located on the other bearing 130 side with respect to 131. Further, in the fourth embodiment, the expansion member 170 is provided between the end surface of the shaft member extending portion on the inner ring 131 side and the side surface of the inner ring 131.

As shown in FIG. 4, the bearing structure 14 includes a shaft member 410, a pair of bearings 130 a and 130 b, and a housing 450.

Similar to the third embodiment described above, the shaft member 410 is fixed while being inserted into the inner peripheral portion of the rotor 820 of the motor 80, and is rotatable integrally with the rotor 820. The shaft member 410 is rotatably supported by the pair of bearings 130a and 130b. Further, a portion of the shaft member 410 on one side is housed in the housing 450, and a portion on the other side extends from the inside of the housing 450 toward the outside.

The housing 450 houses a part of the shaft member 410, the pair of bearings 130a and 130b, and the motor 80, as in the third embodiment described above. Further, an opening portion through which the other side portion of the shaft member 410 is inserted is provided at the other end portion of the housing 450. Further, a concave portion 453 having a shape corresponding to the shape of the motor 80 is provided on the center side of the housing 450. Therefore, the inner diameter of the housing 450 is larger on the central side in the axial direction than on the other portions. Further, at one end of the housing 450, a bottom portion 451 extending in a direction orthogonal to the axial direction is provided. One side of the inner space of the housing 450 is separated from the outside by the bottom portion 451. Outer rings 132a and 132b of the bearings 130a and 130b are attached to the housing 450. As a result, the housing 450 is rotatably provided relative to the shaft member 410 via the pair of bearings 130a and 130b.

The outer rings 132a and 132b of the bearings 130a and 130b are fitted to the inner peripheral surface of the housing 450. Specifically, in the bearing structure 14, the outer ring 132a of the bearing 130a is fitted to the inner peripheral surface 452 on one side of the housing 450. On the other hand, the outer ring 132b of the bearing 130b is fitted to the inner peripheral surface 454 on the other side of the housing 450. In the fourth embodiment, similarly to the above-described third embodiment, the relative movement of the outer ring 132 with respect to the housing 450 in the axial direction is restricted. Specifically, the outer rings 132a and 132b are fitted to the inner peripheral surfaces 452 and 454 of the housing 450 in a tight fit state.

The housing 450 is provided with a housing extension portion that extends radially inward from an inner peripheral surface into which the outer ring 132 is fitted. Specifically, on one side of the housing 450, an extending portion 455 that extends radially inward from the inner peripheral surface 452 is provided. More specifically, the extending portion 455 is provided such that the inner peripheral surface is connected to the end surface on the other side of the bottom portion 451 at right angles. On the other hand, at the other end of the housing 450, an extending portion 456 that extends radially inward from the inner peripheral surface 454 into which the outer ring 132b is fitted is provided. In the housing 450, the extending portion 455 and the extending portion 456 correspond to the above housing extending portion.

The extending portion 455 is located on the side opposite to the bearing 130b side as the other bearing with respect to the outer ring 132a, and the end surface 458 of the extending portion 455 on the outer ring 132a side is a side surface of the outer ring 132a opposite to the bearing 130b side. Abut. In other words, the extending portion 455 is located on one side of the outer ring 132a, and the end surface 458 abuts on one side surface of the outer ring 132a. On the other hand, the extending portion 456 is located on the opposite side to the bearing 130a side as the other bearing with respect to the outer ring 132b, and the end surface 459 of the extending portion 456 on the outer ring 132b side is opposite to the bearing 130a side of the outer ring 132b. Abut the side surface of. In other words, the extending portion 456 is located on the other side of the outer ring 132b, and the end surface 459 abuts on the other side surface of the outer ring 132b. Thereby, the bearing 130b can be positioned with respect to the housing 450 in the axial direction.

Inner rings 131a and 131b of the bearings 130a and 130b are fitted to the outer peripheral surface of the shaft member 410. Specifically, in the bearing structure 14, the inner ring 131a of the bearing 130a is fitted to the outer peripheral surface 411 at one end of the shaft member 410. On the other hand, the inner ring 131b of the bearing 130b is fitted to the outer peripheral surface 413 on the other side of the shaft member 410. In the fourth embodiment, similarly to the above-described third embodiment, the inner ring 131 is provided so as to be relatively movable in the axial direction with respect to the shaft member 410. Specifically, the inner rings 131a and 131b are fitted to the outer peripheral surfaces 411 and 413 of the shaft member 410 in a clearance fit state. The rotor 820 of the motor 80 is fitted to the outer peripheral surface 412 on the center side of the shaft member 410.

The shaft member 410 is provided with a shaft member extending portion that extends radially outward from an outer peripheral surface into which the inner ring 131 is fitted. Specifically, on one side of the shaft member 410, an extending portion 414 that extends radially outward from the outer peripheral surface 411 is provided. On the other hand, on the other side of the shaft member 410, an extending portion 415 that extends radially outward from the outer peripheral surface 413 is provided. In the shaft member 410, the extending portion 414 and the extending portion 415 correspond to the shaft member extending portion. In the fourth embodiment, the shaft member extending portion is located on the other bearing 130 side with respect to the inner ring 131. Further, the expansion member 170 is provided between the end surface of the shaft member extending portion on the inner ring 131 side and the side surface of the inner ring 131.

Specifically, the extending portion 414 is located on the bearing 130b side as the other bearing with respect to the inner ring 131a. Therefore, the end surface 416 of the extending portion 414 on the inner ring 131a side faces the side surface of the inner ring 131a on the bearing 130b side. In other words, the extending portion 414 is located on the other side with respect to the inner ring 131a, and the end surface 416 faces the side surface on the other side of the inner ring 131a. On the other hand, the extending portion 415 is located on the bearing 130a side as the other bearing with respect to the inner ring 131b. Therefore, the end surface 417 of the extending portion 415 on the inner ring 131b side faces the side surface of the inner ring 131b on the bearing 130a side. In other words, the extending portion 415 is located on one side of the inner ring 131b, and the end surface 417 faces one side surface of the inner ring 131b. In this way, the shaft member 410 is provided with the end surfaces 416 and 417 corresponding to the facing surfaces that face the side surfaces of the inner ring 131.

In the fourth embodiment, the expansion members 170a and 170b are provided between the side surface of the inner ring 131 and each of the end surfaces 416 and 417 of the shaft member 410. Specifically, 170a is provided between the other side surface of the inner ring 131a and the end surface 416. On the other hand, 170b is provided between the one side surface of the inner ring 131b and the end surface 417. Therefore, in the fourth embodiment, similarly to the above-described third embodiment, the expansion member 170 can thermally pressurize the inner ring 131 along the axial direction. In addition, in the fourth embodiment, the inner diameter and the outer diameter of the expansion member 170 may substantially match the inner diameter and the outer diameter of the inner ring 131, respectively, as in the above-described third embodiment. The expansion members 170a and 170b may be provided so as to circumscribe outer peripheral surfaces 411 and 413 of the shaft member 410.

In FIG. 4, the expansion member 170 when the load of the motor 80 is low is shown by a solid line, and the expansion member 170 when the load of the motor 80 is high is shown by a broken line. Since the temperature of the expansion member 170 becomes relatively high when the motor 80 has a high load, the inner ring 131 is pressed along the axial direction by thermal expansion of the expansion member 170. Specifically, the inner ring 131a is pressed to one side by thermal expansion of the expansion member 170a provided between the other side surface of the inner ring 131a and the end surface 416 of the shaft member 410. On the other hand, the inner ring 131b is pressed toward the other side by thermal expansion of the expansion member 170b provided between the side surface on one side of the inner ring 131b and the end surface 417 of the shaft member 410.

In the bearing structure 14 according to the fourth embodiment, the inner ring 131 is provided so as to be movable in the axial direction relative to the shaft member 410, as described above. Therefore, when the load of the motor 80 is high, the inner ring 131 moves in the axial direction by being pressed in the axial direction by the expansion member 170. Specifically, the inner ring 131a is moved to one side by being pressed to one side by the expansion member 170a. On the other hand, the inner ring 131b moves to the other side by being pressed to the other side by the expansion member 170b.

Therefore, according to the fourth embodiment, similarly to the above-described first embodiment, when the electric load of the motor 80 in which the potential difference generated between the inner ring 131 and the outer ring 132 of the bearing 130 easily increases, It is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of the bearing 130. As a result, a current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage that may cause dielectric breakdown in the oil film inside the bearing 130. Therefore, it is possible to appropriately prevent an excessive current from flowing between the inner ring 131 and the outer ring 132 of the bearing 130. Therefore, the occurrence of electrolytic corrosion in the bearing 130 can be prevented more effectively.

Further, according to the fourth embodiment, like the above-described third embodiment, when the load of the motor 80 is low, the inner ring 131 is not pressed by the expansion member 170, or the force pressing the inner ring 131 is relatively small. Get smaller. Therefore, when the load of the motor 80 in which the potential difference between the inner ring 131 and the outer ring 132 of the bearing 130 becomes relatively small is low, the inner ring 131 is pressed by the expansion member 170, so that the internal components of the bearing 130 are separated from each other. It is possible to suppress an increase in friction.

Note that, in the above, an example in which the inner ring 131 is provided so as to be movable in the axial direction relative to the shaft member 410 in both the pair of bearings 130a and 130b has been described, but the same as in the above-described first embodiment. In addition, the bearing 130 in which the inner ring 131 is provided so as to be relatively movable in the axial direction with respect to the shaft member 410 may be either one of the pair of bearings 130a and 130b. Even in such a case, in one bearing 130, it is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of the bearing 130 at the time of high load, so that the occurrence of electrolytic corrosion in the bearing 130. It can be prevented more effectively.

<5. Modification>
Next, various modifications will be described with reference to FIGS. 5 to 8.

(5-1. First Modification)
First, a bearing structure 60 according to a first modification will be described with reference to FIGS. 5 to 7. FIG. 5: is sectional drawing which shows an example of a structure of the bearing structure 60 which concerns on a 1st modification. Specifically, FIG. 5 is a cross-sectional view of a cross section including the central axis of the shaft member 110 in the bearing structure 60. Note that, in FIG. 5, the illustration of the other side portion of the bearing structure 60 is omitted. FIG. 6 is a sectional view showing an example of the configuration of the expansion member 670 according to the first modification. FIG. 7: is a perspective view which shows an example of a structure of the expansion member 670 which concerns on a 1st modification. In the first modification, the configuration of the expansion member 670 is different from that of the first embodiment described with reference to FIG. Therefore, the expansion member 670 will be mainly described below.

In the first modified example, similarly to the above-described first embodiment, relative movement of the inner ring 131 with respect to the shaft member 110 in the axial direction is restricted. Specifically, the inner ring 131a is fitted to the outer peripheral surface 111 of the shaft member 110 in a tight fit state. The outer ring 132 is provided so as to be relatively movable in the axial direction with respect to the housing 150. Specifically, the outer ring 132a is fitted to the inner peripheral surface 152 of the housing 150 in a clearance fit state. An end surface 158 of the bottom portion 151 on the outer ring 132a side faces a side surface on one side of the outer ring 132a. The expansion member 670 is provided between the one side surface of the outer ring 132a and the end surface 158 of the housing 150.

In FIG. 5, the expansion member 670 when the load of the motor 80 is low is shown by a solid line, and the expansion member 670 when the load of the motor 80 is high is shown by a broken line. As shown in FIG. 5, the expansion member 670 according to the first modification can be bent and deformed in the axial direction during thermal expansion. The expansion member 670 has, for example, a tapered tube shape whose diameter decreases from one side toward the other side when the motor 80 has a low load. The large diameter portion 675 corresponding to one end of the expansion member 670 abuts the end surface 158 of the housing 150, and the small diameter portion 676 corresponding to the other end of the expansion member 670 forms a side surface of the bearing 130a. Abut.

The expansion member 670 is specifically a bimetal formed by bonding two kinds of metal members having different thermal expansion coefficients. For example, the expansion member 670 is formed by stacking a first metal member 671 located on the outer peripheral side and a second metal member 672 located on the inner peripheral side, as shown in FIGS. 6 and 7. .. The first metal member 671 and the second metal member 672 have different coefficients of thermal expansion, and the inner peripheral portion of the first metal member 671 and the outer peripheral portion of the second metal member 672 are bonded to each other. Specifically, the second metal member 672 has a larger coefficient of thermal expansion than the first metal member 671. Therefore, when the motor 80 has a high load, the small diameter portion 676 may be bent and deformed in the direction away from the large diameter portion 675 due to the temperature rise of the expansion member 670, as shown in FIGS. 6 and 7.

Therefore, as shown in FIG. 5, the expansion member 670 can be bent and deformed in the axial direction when the motor 80 has a high load corresponding to the time of thermal expansion. Therefore, the expansion member 670 can press the outer ring 132a in the axial direction by thermal expansion. Therefore, in the first modified example, when the motor 80 has a high load, the outer ring 132 moves in the axial direction by being pressed in the axial direction by the expansion member 670. Thereby, according to the first modified example, it is possible to obtain the same effect as that of the above-described first embodiment.

In addition, although the example which replaced the expansion member 170 in the bearing structure 11 which concerns on 1st Embodiment with the expansion member 670 which can be bent and deformed in the axial direction at the time of thermal expansion was demonstrated above, the 2nd-4th implementation. The expansion member 170 in the bearing structures 12 to 14 according to the embodiment may be replaced with the expansion member 670. Even in such a case, it is possible to achieve the same effect as when the expansion member 170 in the bearing structure 11 according to the first embodiment is replaced with the expansion member 670.

(5-2. Second modified example)
Next, with reference to FIG. 8, a bearing structure 70 according to the second modification will be described. FIG. 8: is sectional drawing which shows an example of a structure of the bearing structure 70 which concerns on a 2nd modification. Specifically, FIG. 8 is a cross-sectional view of a cross section including the central axis of the shaft member 710 in the bearing structure 70. Further, in FIG. 8, the expansion member 170 when the motor 80 has a low load is shown by a solid line, and the expansion member 170 when the motor 80 has a high load is shown by a broken line. In the second modified example, unlike the first embodiment described with reference to FIG. 1, the shaft member 710 is indirectly connected to the motor 80.

As shown in FIG. 8, the bearing structure 70 includes a shaft member 710, a pair of bearings 130a and 130b, and a housing 750.

The shaft member 710 is rotatably supported in the housing 750 by a pair of bearings 130a and 130b. Further, the one side portion and the other side portion of the shaft member 710 extend from the inside of the housing 750 to the outside. Therefore, the one end and the other end of the housing 750 are provided with openings through which the one end and the other end of the shaft member 710 are inserted, respectively. In FIG. 8, the details of the portion on one side of the shaft member 710 outside the housing 750 are omitted, but for example, the portion on the one side of the shaft member 710 is a drive system to which the bearing structure 70 is applied. Is connected to another shaft member that constitutes a part of the above through mechanical elements such as gears and clutches.

Further, the other portion of the shaft member 710 outside the housing 150 is connected to the output shaft 910 of the motor 80 via, for example, the clutch C10. In this way, the shaft member 710 according to the second modification is indirectly connected to the motor 80. The motor 80 is housed in the case 920, and the output shaft 910 is directly connected to the rotor 820. The rotational power output from the motor 80 is transmitted to the shaft member 710 via the output shaft 910 and the clutch C10.

In the second modified example, similar to the above-described first embodiment, relative movement of the inner ring 131 with respect to the shaft member 710 in the axial direction is restricted. Specifically, the inner ring 131a and the inner ring 131b are fitted to the outer peripheral surface 711 on one side and the outer peripheral surface 713 on the other side of the shaft member 710, respectively, in a state of tight fit. In addition, on one side and the other side of the shaft member 710, an extending portion 714 and an extending portion 715 that extend radially outward from the outer peripheral surface 711 and the outer peripheral surface 713, respectively, are provided. The inner ring 131 a and the inner ring 131 b are positioned by abutting against the end surface 716 on one side of the extending portion 714 and the end surface 717 on the other side of the extending portion 715.

The outer ring 132 is provided so as to be relatively movable in the axial direction with respect to the housing 750. Specifically, the outer ring 132a and the outer ring 132b are fitted to the inner peripheral surface 752 on one side and the inner peripheral surface 754 on the other side of the housing 750, respectively, with a clearance fit. In addition, an extending portion 755 and an extending portion 756, which extend inward in the radial direction from the inner peripheral surface 752 and the inner peripheral surface 754, respectively, are provided at one end and the other end of the housing 750. The extending portion 755 and the extending portion 756 face a side surface on one side of the outer ring 132a and a side surface on the other side of the outer ring 132b. An expansion member 170a and an expansion member 170b are provided between the extending portion 755 and the side surface on one side of the outer ring 132a and between the extending portion 756 and the side surface on the other side of the outer ring 132b. The extending portion 755 and the extending portion 756 correspond to the housing extending portion that extends radially inward from the inner peripheral surface of the housing 750 in which the outer ring 132 is fitted.

In the second modification, the shaft member 710 is indirectly connected to the motor 80, as described above. Even in such a case, a potential difference may occur between the inner ring 131 and the outer ring 132 of the bearing 130 that rotatably supports the shaft member 710, as the motor 80 is driven. Further, since the shaft member 710 is connected to the motor 80 via the output shaft 910 and the clutch C10, when the motor 80 has a high load, the temperature of each member forming the bearing structure 70 is lower than that when the load is low. Can be high. Therefore, when the load of the motor 80 is high, the temperature of the expansion member 170 becomes relatively high, so that the expansion member 170 thermally expands as shown in FIG. 8, and the outer ring 132 is pressed along the axial direction. .. Therefore, when the load of the motor 80 is high, the outer ring 132 moves in the axial direction by being pressed in the axial direction by the expansion member 170. Thereby, according to the second modified example, it is possible to achieve the same effect as that of the above-described first embodiment.

In the above description, the example in which the housing extension portion is located on the side opposite to the other bearing 130 side with respect to the outer ring 132 has been described, but the housing extension portion is located on the other bearing 130 side with respect to the outer ring 132. May be. Even in that case, the same effect as that of the above-described first embodiment can be obtained. Further, in the above, an example in which the outer ring 132 is provided so as to be movable in the axial direction relative to the shaft member 710 has been described, but the inner ring 131 is relatively movable in the axial direction with respect to the shaft member 710. May be provided. In that case, the expansion member 170 is provided between the end surface of the shaft member extending portion on the inner ring 131 side and the side surface of the inner ring 131. Thereby, it is possible to achieve the same effect as that of the above-described first embodiment.

<6. Conclusion>
As described above, according to each embodiment, in at least one bearing 130 of the pair of bearings 130a and 130b, either one of the inner race 131 and the outer race 132 is fitted with the one race. It is provided so as to be relatively movable in the axial direction with respect to a shaft member or a housing as a fitting member to be fitted. Further, the fitting member is provided with a facing surface facing the side surface of the one bearing ring. Further, between the side surface of the one bearing ring and the facing surface of the fitting member, an expansion member 171 capable of pressing the one bearing ring in the axial direction by thermal expansion is provided.

Therefore, at the time of high load of the motor 80 in which the temperature of the expansion member 170 becomes relatively high, the one expansion ring 170 is thermally expanded and the one bearing ring is pressed in the axial direction. In each embodiment, as described above, the one bearing ring is provided so as to be relatively movable in the axial direction with respect to the fitting member. Therefore, when the load of the motor 80 is high, the one race ring is moved in the axial direction by being pressed in the axial direction by the expansion member 170. As a result, in the bearing 130, the number of rolling elements 133 in contact with both the inner ring 131 and the outer ring 132 can be increased. Further, the film thickness of the oil film interposed between the rolling element 133 and each of the inner ring 131 and the outer ring 132 can be reduced. Therefore, it is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of the bearing 130.

Therefore, a current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage that may cause dielectric breakdown in the oil film inside the bearing 130. Therefore, it is possible to appropriately prevent an excessive current from flowing between the inner ring 131 and the outer ring 132 of the bearing 130. Therefore, the occurrence of electrolytic corrosion in the bearing 130 can be prevented more effectively.

Further, according to each embodiment, when the motor 80 has a low load, the expansion member 170 does not press the one bearing ring, or the force pressing the one bearing ring is relatively small. Therefore, when the load of the motor 80 in which the potential difference between the inner ring 131 and the outer ring 132 of the bearing 130 is relatively small becomes small, the outer ring 132 is pressed by the expansion member 170 so that the internal components of the bearing 130 are separated from each other. It is possible to suppress an increase in friction.

In addition, in 1st Embodiment and 2nd Embodiment, the outer ring 132 corresponds to said one bearing ring, and a housing corresponds to the said fitting member. Therefore, in the first embodiment and the second embodiment, the occurrence of electrolytic corrosion is more effectively generated in the bearing 130 used in the bearing structure in which the outer ring 132 is provided so as to be relatively movable in the axial direction with respect to the housing. Can be prevented. On the other hand, in the third and fourth embodiments, the inner ring 131 corresponds to the above-mentioned one bearing ring, and the shaft member corresponds to the above-mentioned fitting member. Therefore, in the third embodiment and the fourth embodiment, the occurrence of electrolytic corrosion is more effective in the bearing 130 used in the bearing structure in which the inner ring 131 is provided so as to be relatively movable in the axial direction with respect to the shaft member. Can be prevented.

Although the expansion members 170 and 670 have been described above with reference to the drawings, the expansion member provided between the side surface of the one bearing ring and the facing surface of the fitting member is not limited to the above. The present invention is not limited to the example, and may have another configuration as long as the one bearing ring can be pressed in the axial direction by thermal expansion.

Moreover, although the example in which each bearing structure includes the pair of bearings 130a and 130b has been described above, each bearing structure may include another bearing different from the bearings 130a and 130b, and the shaft member includes the other bearing. It may be rotatably supported by.

Further, in the above, each component of each bearing structure has been described with reference to each drawing, but the shape of each component is not limited to an example corresponding to each drawing, and the shape shown in the drawings is only an example. Absent. For example, the shape of each component does not need to be symmetrical about the axial direction, and may not be rotationally symmetrical about the central axis. Moreover, each component may be formed by a plurality of members.

Although the preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to the examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various modifications or applications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

11, 12, 13, 14, 14, 60, 70 Bearing structure 80 Motor 110, 210, 310, 410, 710 Shaft member 130, 130a, 130b Bearing 131, 131a, 131b Inner ring 132, 132a, 132b Outer ring 133, 133a, 133b Rolling Moving body 150, 250, 350, 450, 750 Housing 170, 170a, 170b, 670 Expansion member 671 First metal member 672 Second metal member 675 Large diameter part 676 Small diameter part 710 Shaft member 810 Stator 820 Rotor 910 Output shaft 920 Case

Claims (6)

A shaft member connected to the motor,
The shaft member, a pair of bearings arranged at intervals in the axial direction,
A housing provided so as to be rotatable relative to the shaft member via the pair of bearings;
Equipped with
An inner ring, which is a bearing ring inside the bearing, is fitted to the outer peripheral surface of the shaft member,
An outer ring, which is an outer race ring of the bearing, is fitted to an inner peripheral surface of the housing,
A metal rolling element is interposed between the inner ring and the outer ring,
In the bearing structure,
In at least one of the pair of bearings, the inner ring is provided so as to be relatively movable in the axial direction with respect to the shaft member ,
The shaft member is provided with a shaft member extending portion that extends radially outward from the outer peripheral surface into which the inner ring is fitted,
An end surface of the shaft member extending portion on the inner ring side faces a side surface of the inner ring,
And a side surface of the inner ring, between the inner ring side end surface of the shaft member extending portion, it can press the expansion member is provided along the inner ring in the axial direction by thermal expansion,
Bearing structure. The shaft member extending portion is located on the opposite side to the other bearing side with respect to the inner ring,
The inner ring side end surface of the shaft member extending portion faces a side surface of the inner ring opposite to the other bearing side,
The bearing structure according to claim 1 . The shaft member extending portion is located on the other bearing side with respect to the inner ring,
The inner ring-side end surface of the shaft member extending portion faces the other bearing-side side surface of the inner ring,
The bearing structure according to claim 1 . The inflatable member is, at the time of thermal expansion can be extended along the axial direction, the bearing structure according to any one of claims 1-3. The inflatable member is, at the time of thermal expansion is deformable bent into the axial direction, the bearing structure according to any one of claims 1-3. Wherein the shaft member, the rotor of the motor is rotatably integrally connected, a bearing structure according to any one of claims 1-5.

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