JP2018044653A - Bearing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent occurrence of electric corrosion in a bearing.SOLUTION: In a bearing structure which includes a shaft member connected to a motor, a pair of bearings disposed on the shaft member at an interval in the axial direction, and a housing relatively rotatably disposed to the shaft member through the pair of bearings, and in which an inner ring as a bearing ring inside of the bearing is fitted to an outer peripheral face of the shaft member, an outer ring as a bearing ring outside of the bearing is fitted to an inner peripheral face of the housing, and metallic rolling elements are disposed between the inner ring and the outer ring, the bearing ring of one of the inner ring and the outer ring in at least one of the pair of bearings, is disposed relatively movably in an axial direction to the shaft member or the housing as the fitting member to which one of the bearing rings is fitted, the fitting member is provided with an opposite face opposed to a side face of one of the bearing rings, and an expansion member capable of pressing one of the bearing rings along the axial direction by thermal expansion, is disposed between the side face of one of the bearing rings and the opposite face of the fitting member.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a bearing structure.

  2. Description of the Related Art Conventionally, drive systems that operate by transmitting rotational power output from a motor as a power source have been used in various devices. In the drive system, specifically, the rotational power output from the motor is transmitted through 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 inverter control. Thereby, a potential difference is generated between the inner ring and the outer ring of the bearing that rotatably supports the shaft member. The potential difference is likely to increase as the load applied to the motor increases. When the potential difference reaches a voltage that can cause dielectric breakdown in the oil film inside the bearing when the load on the motor is relatively high, an excessive current flows between the inner ring and the outer ring of the bearing, Electric corrosion occurs at Thereby, abnormal noise and vibration can occur in the bearing.

  Therefore, techniques for preventing the occurrence of electrolytic corrosion in the bearing have been proposed. Specifically, a technique has been proposed in which an excessive current is prevented from flowing by making it difficult for 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 in a bearing box of a bracket, and the bearing is supported via the insulating material, thereby making it difficult for current to flow between the inner ring and the outer ring of the bearing. A technique for preventing the occurrence of electrolytic corrosion is disclosed.

Japanese Patent Laying-Open No. 2015-082906

  However, there are cases where it is difficult to prevent the occurrence of electrolytic corrosion in the bearing with a technique that makes it difficult for current to flow between the inner ring and the outer ring of the bearing. For example, in the technique using the insulating material described above, the performance of insulating the bearing and the member supporting the bearing with the insulating material can be reduced due to wear or deterioration with time of the insulating member. In addition to the technique using the insulating material described above, it is conceivable to use a technique that makes it difficult for current to flow between the inner ring and the outer ring of the bearing by grounding the shaft member with an earth brush. However, in this technique, the performance of grounding the shaft member with the ground brush can be reduced due to wear or deterioration with time of the ground brush. Therefore, in these techniques, an excessive current may flow between the inner ring and the outer ring of the bearing. Therefore, it can 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 capable of more effectively preventing the occurrence of electrolytic corrosion in the bearing. To provide a structure.

  In order to solve the above-described problems, according to an aspect of the present invention, a shaft member coupled to a motor, a pair of bearings disposed on the shaft member with an interval in the axial direction, and the shaft member In contrast, an inner ring, which is a race ring inside the bearing, is fitted to the outer peripheral surface of the shaft member, and a housing provided relatively rotatably via the pair of bearings. In the bearing structure, an outer ring, which is a raceway outside the bearing, is fitted to an 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 of the bearings, one of the inner ring and the outer ring has the shaft ring with respect to the shaft member or the housing as a fitting member to which the one race ring is fitted. Provided relatively movable in the direction, The joint member is provided with a facing surface that faces the side surface of the one bearing ring, and the thermal expansion between the side surface of the one bearing ring and the facing surface of the fitting member causes the A bearing structure is provided in which an expansion member capable of pressing one of the race rings along the axial direction is provided.

  In at least one of the pair of bearings, the outer ring as the one race ring is provided to be relatively movable in the axial direction with respect to the housing as the fitting member, The housing is provided with a housing extending portion extending radially inward from the inner peripheral surface to which the outer ring is fitted, and an end surface on the outer ring side of the housing extending portion is used as the facing surface. The expansion member may be provided between a side surface of the outer ring and an end surface on the outer ring side of the housing extension portion, facing the side surface of the outer ring.

  The housing extension is positioned opposite to the other bearing side with respect to the outer ring, and the outer ring side end surface of the housing extension faces the side surface opposite to the other bearing side of the outer ring. May be.

  The housing extension may be positioned on the other bearing side with respect to the outer ring, and the end surface on the outer ring side of the housing extension may face the side surface on the other bearing side of the outer ring.

  In at least one of the pair of bearings, the inner ring as the one race ring is provided to be relatively movable in the axial direction with respect to the shaft member as the fitting member, The shaft member is provided with a shaft member extending portion extending radially outward from the outer peripheral surface to which the inner ring is fitted, and the end surface on the inner ring side of the shaft member extending portion is the opposing surface. As opposed to the side surface of the inner ring, the expansion member may be provided between the side surface of the inner ring and the end surface of the shaft member extending portion on the inner ring side.

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

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

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

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

  A rotor of the motor may be integrally connected to the shaft member so as to be rotatable.

  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.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<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 rotationally 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 a vehicle in, for example, an electric vehicle (EV) or a hybrid vehicle (HEV). And the bearing structure 11 can be applied to the drive system which operate | moves by transmitting the rotational power output from the motor 80 in these vehicles. The application of the motor 80 described above is merely an example, and the bearing structure 11 can be applied to a drive system for motors of various applications.

  As shown in FIG. 1, the motor 80 includes a stator 810 and a rotor 820. The stator 810 and the rotor 820 have, for example, a substantially cylindrical shape and are provided to face each other with a gap. Further, the center axes of the stator 810 and the rotor 820 substantially coincide.

  The stator 810 is positioned on the outer peripheral side of the rotor 820 and is fixed to a 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 composed 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 a 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.

  The rotor 820 is arranged along the circumferential direction so that a plurality of permanent magnets have different polarities alternately. As described above, the rotating magnetic field is generated by the stator 810, so that a 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 fixed to the inner peripheral portion of the rotor 820 while being inserted. Therefore, the rotor 820 of the motor 80 is integrally connected to the shaft member 110 so as to be rotatable. As described above, the shaft member 110 can be directly connected to the motor 80. The shaft member 110 corresponds to an output shaft of the motor 80 that is directly rotated by the motor 80. The shaft member 110 can be formed of, for example, an iron-based material such as cast iron.

  As illustrated 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 motor 80 described above is housed in a housing 150, and the shaft member 110 is rotatably supported by a pair of bearings 130a and 130b. A portion of the shaft member 110 on one side (left side in FIG. 1) from the motor 80 is accommodated in the housing 150, and a portion on the other side (right side in FIG. 1) extends from the inside of the housing 150 toward the outside. . Hereinafter, one side and the other side of the motor 80 are also simply referred to as one side and the other side, respectively. In FIG. 1, the details of the other side of the shaft member 110 outside the housing 150 are not shown, but the other side of the shaft member 110 is, for example, a drive system to which the bearing structure 11 is applied. Are connected to other shaft members constituting a part of the shaft 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 inner rings 131a and 131b that are inner races, outer rings 132a and 132b that are outer races, and inner rings 131a and 131b and outer rings 132a and 132b. 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 rolling elements 133a and 133b rotate. The friction between the members inside the bearings 130a and 130b is reduced.

  Further, lubricating oil is injected into the bearings 130a and 130b, and an oil film is formed between the rolling elements 133a and 133b and the inner rings 131a and 131b and the outer rings 132a and 132b by the lubricating oil. Thereby, reduction of the friction between each member in the inside of bearing 130a, 130b is implement | achieved. Hereinafter, the bearing 130a and the bearing 130b are also simply referred to as the bearing 130 unless otherwise distinguished. 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 also simply referred to as the outer ring 132 unless otherwise distinguished.

  The pair of bearings 130a and 130b are disposed on the shaft member 110 with an interval in the axial direction. In addition, the said axial direction is a direction along the central axis of the shaft member 110, and such a direction is only called an axial direction below. Further, the inner rings 131 a and 131 b of the bearings 130 a and 130 b are fitted to the outer peripheral surface of the shaft member 110. Specifically, in the bearing structure 11, the inner ring 131 a of the bearing 130 a is fitted to the outer peripheral surface 111 at one end of the shaft member 110. On the other hand, the inner ring 131 b of the bearing 130 b is fitted to the outer peripheral surface 113 on the other side of the shaft member 110. In the first embodiment, the relative movement of the inner ring 131 with 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 the outer peripheral surface to 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 extending from the outer peripheral surface 113 to the radially outer side is provided. In the shaft member 110, the extending portion 114 and the extending portion 115 correspond to the above-described shaft member extending portion.

  The extending portion 114 is positioned on the bearing 130b side as the other bearing with respect to the inner ring 131a, and the end surface 116 on the inner ring 131a side of the extending portion 114 is in contact with the side surface on the bearing 130b side of the inner ring 131a. 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 is in contact with the other side surface of the inner ring 131a. Accordingly, 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 positioned on the bearing 130a side as the other bearing with respect to the inner ring 131b, and the end surface 117 on the inner ring 131b side of the extending portion 115 is in contact with the side surface on the bearing 130a side of the inner ring 131b. In other words, the extending portion 115 is positioned on one side with respect to the inner ring 131b, and the end surface 117 is in contact with a side surface on one side of the inner ring 131b. Accordingly, 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. Specifically, the housing 150 accommodates a part of the shaft member 110, the pair of bearings 130a and 130b, and the motor 80. An opening through which the other portion of the shaft member 110 is inserted is provided at the other end of the housing 150. Further, a concave portion 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 than the other parts on the central side in the axial direction.

  Outer rings 132 a and 132 b of bearings 130 a and 130 b are attached to the housing 150. Thereby, the housing 150 is provided so as to be relatively rotatable with respect to the shaft member 110 via the pair of bearings 130a and 130b. Specifically, the outer rings 132 a and 132 b of the bearings 130 a and 130 b are fitted to the inner peripheral surface of the housing 150. More specifically, in the bearing structure 11, the outer ring 132 a of the bearing 130 a is fitted to the inner peripheral surface 152 on one side of the housing 150. On the other hand, the outer ring 132 b of the bearing 130 b 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 to be movable relative to the housing 150 in the axial direction. 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 extending portion that extends radially inward from the inner peripheral surface to which the outer ring 132 is fitted. Specifically, a bottom 151 extending in a direction orthogonal to the axial direction is provided at one end of the housing 150. One side of the internal 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 into 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 to which the outer ring 132b is fitted. In the housing 150, the bottom portion 151 and the extending portion 155 correspond to the housing extending portion. In the first embodiment, the housing extension is located on the opposite side to the other bearing 130 side with respect to the outer ring 132. In addition, an expansion member 170 is provided between the end surface of the housing extension portion on the outer ring 132 side and the side surface of the outer ring 132 as described later.

  Specifically, the bottom 151 is located on the opposite side of 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 opposite to the bearing 130b side. In other words, the bottom portion 151 is positioned on one side with respect to the outer ring 132a, and the end surface 158 faces the side surface on one side of the outer ring 132a. On the other hand, the extending portion 155 is located on the opposite side to 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 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 is opposed to the other side surface of the outer ring 132b. As described above, the housing 150 is provided with the end surface 158 and the end surface 159 corresponding to the facing surfaces facing the side surfaces of the outer ring 132.

  Expansion members 170 a and 170 b 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 side surface on one side of the outer ring 132a and the end surface 158. On the other hand, 170 b is provided between the other side surface of the outer ring 132 b and the end surface 159. The expansion members 170a and 170b can extend along the axial direction during thermal expansion, for example. Therefore, in the first embodiment, the expansion members 170a and 170b can press the outer rings 132a and 132b along the axial direction by thermal expansion. Hereinafter, the expansion member 170a and the expansion member 170b are also simply referred to as the expansion member 170 unless otherwise distinguished.

  Specifically, the expansion member 170 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, a resin having relatively high heat resistance and oil resistance is preferably used. The central axis of the expansion member 170 may substantially coincide with the central axis of the bearing 130. The inner diameter and the outer diameter of the expansion member 170 can substantially match the inner diameter and the outer diameter of the outer ring 132, respectively. Further, the expansion members 170 a and 170 b can be provided in contact with the inner peripheral surfaces 152 and 154 of the housing 150.

  In FIG. 1, the expansion member 170 at a low load when the load applied to the motor 80 is relatively low is indicated by a solid line, and the expansion member 170 at a high load when the load applied to the motor 80 is relatively high is indicated by a broken line. Yes. When the motor 80 has a high load, the amount of heat generated in the motor 80 increases as the current supplied to the motor 80 increases as compared to when the motor 80 has a low load. As a result, when the motor 80 is heavily loaded, the temperature of each member constituting the bearing structure 11 is higher than when the motor 80 is lightly loaded. Therefore, when the motor 80 is heavily loaded, the temperature of the expansion member 170 is relatively high, so that the expansion ring 170 is thermally expanded to press the outer ring 132 along the axial direction. Specifically, the expansion member 170a provided between one side surface of the outer ring 132a and the end surface 158 of the housing 150 thermally expands, thereby pressing the outer ring 132a to the other side. On the other hand, when the expansion member 170b provided between the other side surface of the outer ring 132b and the end surface 159 of the housing 150 is thermally expanded, the outer ring 132b is pressed to one side.

  Incidentally, 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 is heavily loaded, 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, as described above, the shaft member 110 and the housing 150 may be formed of, for example, cast iron and aluminum alloy. Moreover, the thermal expansion coefficient of an aluminum alloy is generally larger than that of cast iron. Therefore, when the motor 80 is under a high load, the distance between the end surface 158 of the bottom portion 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. May be longer than when loaded. Similarly, when the motor 80 is heavily loaded, 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 can be longer than 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 when the motor 80 is heavily loaded. May be insufficient, or the force that presses 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, the outer ring 132 can be more reliably pressed along the axial direction by the expansion member 170 when the motor 80 is heavily loaded. The type and dimensions of the resin forming the expansion member 170 are appropriately set so that the expansion ring 170 can press the outer ring 132 along the axial direction when the motor 80 is heavily loaded. 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 dimensions 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 motor 80 is under a high load, the outer ring 132 is moved 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 moves to one side by being pressed to one side by the expansion member 170b. Thereby, in the bearing 130, the number of the rolling elements 133 which contact both the inner ring | wheel 131 and the outer ring | wheel 132 can be increased. In addition, 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, current can easily flow between the inner ring 131 and the outer ring 132 of the bearing 130.

  Incidentally, the motor 80 is specifically driven by inverter control as described above. The shaft member 110 is connected to the motor 80. Therefore, a voltage can be generated in the shaft member 110 by high frequency induction as the motor 80 is driven. Thereby, 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, current can easily flow between the inner ring 131 and the outer ring 132 of the bearing 130 at the time of high load of the motor 80 in which the potential difference is likely to increase. Can do. As a result, current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage at which dielectric breakdown can occur 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 more effectively prevented.

  Further, when the motor 80 is under a low load, the amount of heat generated in the motor 80 is lower than when the motor 80 is under a high load. Thereby, the temperature of the expansion member 170 becomes relatively low. Therefore, according to the first embodiment, when the motor 80 is under a low load, 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 motor 80 is under a low load when the potential difference generated between the inner ring 131 and the outer ring 132 of the bearing 130 is relatively small, the outer ring 132 is pressed against the expansion member 170 to cause a difference between the members in the bearing 130. An increase in friction can be suppressed.

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

<2. Second Embodiment>
Then, with reference to FIG. 2, the bearing structure 12 which concerns on the 2nd Embodiment of this invention is demonstrated. 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 first embodiment described above, a housing extending portion extending radially inward from an inner peripheral surface to which the outer ring 132 is fitted in the housing 250 is an outer ring 132. Is located on the other bearing 130 side. In the second embodiment, the expansion member 170 is provided between the end surface of the housing extension 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 130 a and 130 b, and a housing 250.

  As in the first embodiment described above, the shaft member 210 is fixed in a state of being inserted through the inner peripheral portion of the rotor 820 of the motor 80, and can rotate integrally with the rotor 820. The shaft member 210 is rotatably supported by a pair of bearings 130a and 130b. Further, a portion on one side of the shaft member 210 is accommodated in the housing 250, and a portion on the other side extends outward from the housing 250.

  Inner rings 131 a and 131 b of the bearings 130 a and 130 b are fitted to the outer peripheral surface of the shaft member 210. Specifically, in the bearing structure 12, the inner ring 131 a of the bearing 130 a is fitted to the outer peripheral surface 211 on one side of the shaft member 210. On the other hand, the inner ring 131 b of the bearing 130 b is fitted to the outer peripheral surface 213 on the other side of the shaft member 210. In the second embodiment, the relative movement of the inner ring 131 with respect to the shaft member 210 in the axial direction is restricted as in the first embodiment described above. 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. A rotor 820 of the motor 80 is fitted on 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 to which the inner ring 131 is fitted. Specifically, an extended portion 214 that extends radially outward from the outer peripheral surface 211 is provided at one end of the shaft member 210. On the other hand, on the other side of the shaft member 210, an extending portion 215 extending outward in the radial direction 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 above-described shaft member extending portion.

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

  The housing 250 accommodates 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 through which the other part of the shaft member 210 is inserted is provided at the other end of the housing 250. In addition, 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 than the other portions on the central side in the axial direction. Further, a bottom portion 251 extending in a direction orthogonal to the axial direction is provided at one end of the housing 250. One side of the internal space of the housing 250 is separated from the outside by the bottom 251. The outer rings 132a and 132b of the bearings 130a and 130b are attached to the housing 250. Thereby, the housing 250 is provided so as to be relatively rotatable with respect to the shaft member 210 via the pair of bearings 130a and 130b.

  The outer rings 132 a and 132 b of the bearings 130 a and 130 b are fitted to the inner peripheral surface of the housing 250. Specifically, in the bearing structure 12, the outer ring 132 a of the bearing 130 a is fitted to the inner peripheral surface 252 on one side of the housing 250. On the other hand, the outer ring 132 b of the bearing 130 b is fitted to the inner peripheral surface 254 on the other side of the housing 250. In the second embodiment, as in the first embodiment described above, the outer ring 132 is provided so as to be movable relative to the housing 250 in the axial direction. 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 extending portion that extends radially inward from the inner peripheral surface to 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 to which the outer ring 132b is fitted. In the housing 250, the extending part 255 and the extending part 256 correspond to the housing extending part. In the second embodiment, unlike the first embodiment, the housing extension is located on 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 extension 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 with respect to the outer ring 132a, and the end surface 258 faces the other side surface of the outer ring 132a. On the other hand, the extension part 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 positioned on one side with respect to the outer ring 132b, and the end surface 259 faces the side surface on one side of the outer ring 132b. As described above, the housing 250 is provided with the end surface 258 and the end surface 259 corresponding to the facing surfaces facing the side surfaces of the outer ring 132.

  Expansion members 170 a and 170 b 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 outer ring 132a and end surface 258. On the other hand, 170b is provided between the side surface on one side of the outer ring 132b and the end surface 259. Therefore, in the second embodiment, as in the first embodiment described above, the expansion member 170 can press the outer ring 132 along the axial direction by thermal expansion.

  In FIG. 2, the expansion member 170 when the motor 80 is under a low load is indicated by a solid line, and the expansion member 170 when the motor 80 is under a high load is indicated by a broken line. When the motor 80 is under a high load, the temperature of the expansion member 170 is relatively high, so that the outer ring 132 is pressed along the axial direction when the expansion member 170 is thermally expanded. Specifically, the expansion member 170a provided between the other side surface of the outer ring 132a and the end surface 258 of the housing 250 is thermally expanded, whereby the outer ring 132a is pressed to one side. On the other hand, the expansion member 170b provided between one side surface of the outer ring 132b and the end surface 259 of the housing 250 is thermally expanded, whereby the outer ring 132b is pressed to the other side.

  In the bearing structure 12 according to the second embodiment, the outer ring 132 is provided to be relatively movable in the axial direction with respect to the housing 250 as described above. Therefore, when the motor 80 is under a high load, the outer ring 132 is moved 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 moves 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, 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 is likely to increase. Current can easily flow between the inner ring 131 and the outer ring 132 of the bearing 130. As a result, current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage at which dielectric breakdown can occur 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 more effectively prevented.

  Further, according to the second embodiment, as in the first embodiment described above, when the motor 80 is under a low load, the outer ring 132 is not pressed by the expansion member 170 or the force that presses the outer ring 132 is relatively low. Get smaller. Therefore, when the motor 80 is under a low load when the potential difference generated between the inner ring 131 and the outer ring 132 of the bearing 130 is relatively small, the outer ring 132 is pressed against the expansion member 170 to cause a difference between the members in the bearing 130. An increase in friction can be suppressed.

  In the above description, an example in which the outer ring 132 is provided so as to be relatively movable in the axial direction with respect to the housing 250 in both the pair of bearings 130a and 130b has been described. However, similarly to the above-described first embodiment. The bearing 130 in which the outer ring 132 is provided so as to be relatively movable in the axial direction relative to the housing 250 may be either one of the pair of bearings 130a and 130b. Even in such a case, it is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of one of the bearings 130 when the load is high. It can prevent more effectively.

<3. Third Embodiment>
Subsequently, a bearing structure 13 according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a cross-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 first embodiment described above, the inner ring 131 is provided so as to be relatively movable in the axial direction with respect to the shaft member 310. In the third embodiment, the shaft member extending portion extending radially outward from the outer peripheral surface to which the inner ring 131 is fitted in the shaft member 310 is between the end surface on the inner ring 131 side and the side surface of the inner ring 131. An inflatable member 170 is provided.

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

  The shaft member 310 is fixed in a state of being inserted into the inner peripheral portion of the rotor 820 of the motor 80 and can be rotated integrally with the rotor 820 as in the first embodiment described above. The shaft member 310 is rotatably supported by a pair of bearings 130a and 130b. Further, one side portion of the shaft member 310 is accommodated in the housing 350, and the other side portion extends outward from the housing 350.

  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 through which the other side portion of the shaft member 310 is inserted is provided at the other end portion of the housing 350. In addition, a concave portion 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 than the other portions on the central side in the axial direction. In addition, 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 internal space of the housing 350 is separated from the outside by the bottom portion 351. Outer rings 132a and 132b of bearings 130a and 130b are attached to the housing 350. Thereby, the housing 350 is provided so as to be relatively rotatable with respect to the shaft member 310 via the pair of bearings 130a and 130b.

  The outer rings 132 a and 132 b of the bearings 130 a and 130 b are fitted to the inner peripheral surface of the housing 350. Specifically, in the bearing structure 13, the outer ring 132 a of the bearing 130 a is fitted to the inner peripheral surface 352 on one side of the housing 350. On the other hand, the outer ring 132 b of the bearing 130 b 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 relative to the housing 350 in the axial direction 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 that extends radially inward from the inner peripheral surface to 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, an extension portion 356 is provided on the other side of the housing 350 and extends radially inward from the inner peripheral surface 354 to which the outer ring 132b is fitted. In the housing 350, the extending portion 355 and the extending portion 356 correspond to the housing extending portion.

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

  Inner rings 131 a and 131 b of the bearings 130 a and 130 b are fitted to the outer peripheral surface of the shaft member 310. Specifically, in the bearing structure 13, the inner ring 131 a of the bearing 130 a is fitted to the outer peripheral surface 311 on one side of the shaft member 310. On the other hand, the inner ring 131 b of the bearing 130 b is fitted to the outer peripheral surface 313 on the other side of the shaft member 310. In the third embodiment, unlike the first embodiment described above, 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. A 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 the outer peripheral surface to which the inner ring 131 is fitted. Specifically, an extending portion 314 that extends radially outward from the outer peripheral surface 311 is provided at one end of the shaft member 310. On the other hand, on the other side of the shaft member 310, an extending portion 315 extending from the outer peripheral surface 313 to the radially outer side is provided. In the shaft member 310, the extending portion 314 and the extending portion 315 correspond to the above-described shaft member extending portion. In the third embodiment, the shaft member extending portion is located on the opposite side to the other bearing 130 side with respect to the inner ring 131. Further, an 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 opposite side of the bearing 130b 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 positioned on one side with respect to the inner ring 131a, and the end surface 316 is opposed to a side surface on one side of the inner ring 131a. On the other hand, the extending portion 315 is located on the opposite side of the bearing 130a 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 opposite to the bearing 130a side. In other words, the extending portion 315 is positioned on the other side with respect to the inner ring 131b, and the end surface 317 is opposed to the other side surface of the inner ring 131b. As described above, the shaft member 310 is provided with the end surface 316 and the end surface 317 corresponding to the facing surfaces facing the side surfaces of the inner ring 131.

  In the third embodiment, expansion members 170 a and 170 b 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 side surface on one side 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 extend along the axial direction during thermal expansion. Therefore, in 3rd Embodiment, the expansion member 170 can press the inner ring | wheel 131 along an axial direction by thermally expanding. In the third embodiment, the inner diameter and the outer diameter of the expansion member 170 can substantially match the inner diameter and the outer diameter of the inner ring 131, respectively. Further, the expansion members 170 a and 170 b can be provided so as to circumscribe the outer peripheral surfaces 311 and 313 of the shaft member 310.

  In FIG. 3, the expansion member 170 when the motor 80 is under a low load is indicated by a solid line, and the expansion member 170 when the motor 80 is under a high load is indicated by a broken line. When the motor 80 is under a high load, the temperature of the expansion member 170 is relatively high, so that the inner ring 131 is pressed along the axial direction when the expansion member 170 is thermally expanded. Specifically, the expansion member 170a provided between the side surface on one side of the inner ring 131a and the end surface 316 of the shaft member 310 thermally expands, thereby pressing the inner ring 131a to the other side. On the other hand, 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 is thermally expanded, whereby the inner ring 131b is pressed 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 motor 80 is under a high load, 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. Thereby, in the bearing 130, the number of the rolling elements 133 which contact both the inner ring | wheel 131 and the outer ring | wheel 132 can be increased. In addition, 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, as in the first embodiment described above, 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 is likely to increase. Current can easily flow between the inner ring 131 and the outer ring 132 of the bearing 130. As a result, current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage at which dielectric breakdown can occur 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 more effectively prevented.

  Further, according to the third embodiment, when the motor 80 is under a low load, the inner ring 131 is not pressed by the expansion member 170 or the force that presses the inner ring 131 is relatively small. Therefore, when the motor 80 is under a low load when the potential difference generated between the inner ring 131 and the outer ring 132 of the bearing 130 is relatively small, the inner ring 131 is pressed against the expansion member 170, so An increase in friction can be suppressed.

  In the above description, the example 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 in both the pair of bearings 130a and 130b has been described. However, as in the first embodiment described above. 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, it is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of one of the bearings 130 when the load is high. It can prevent more effectively.

<4. Fourth Embodiment>
Subsequently, a bearing structure 14 according to a fourth embodiment of the present invention will be described with reference to FIG. 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, in the fourth embodiment, unlike the above-described third embodiment, the shaft member extending portion extending radially outward from the outer peripheral surface to which the inner ring 131 is fitted in the shaft member 410 is the inner ring. It is located on the other bearing 130 side with respect to 131. 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.

  The shaft member 410 is fixed in a state of being inserted through the inner peripheral portion of the rotor 820 of the motor 80 and can be rotated integrally with the rotor 820, as in the third embodiment described above. The shaft member 410 is rotatably supported by a pair of bearings 130a and 130b. In addition, a portion on one side of the shaft member 410 is accommodated in the housing 450, and a portion on the other side extends outward from the housing 450.

  The housing 450 accommodates 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. In addition, an opening through which the other part of the shaft member 410 is inserted is provided at the other end of the housing 450. In addition, 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 than the other portions on the central side in the axial direction. In addition, a bottom portion 451 extending in a direction orthogonal to the axial direction is provided at one end of the housing 450. One side of the inner space of the housing 450 is separated from the outside by a bottom portion 451. The outer rings 132a and 132b of the bearings 130a and 130b are attached to the housing 450. Thereby, the housing 450 is provided so as to be relatively rotatable with respect to the shaft member 410 via the pair of bearings 130a and 130b.

  The outer rings 132 a and 132 b of the bearings 130 a and 130 b are fitted to the inner peripheral surface of the housing 450. Specifically, in the bearing structure 14, the outer ring 132 a of the bearing 130 a is fitted to the inner peripheral surface 452 on one side of the housing 450. On the other hand, the outer ring 132 b of the bearing 130 b is fitted to the inner peripheral surface 454 on the other side of the housing 450. In the fourth embodiment, similar to the third embodiment described above, the relative movement of the outer ring 132 relative 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 that extends radially inward from the inner peripheral surface to 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 orthogonally to the other end surface of the bottom portion 451. On the other hand, an extended portion 456 extending radially inward from an inner peripheral surface 454 to which the outer ring 132b is fitted is provided at the other end portion of the housing 450. In the housing 450, the extending portion 455 and the extending portion 456 correspond to the housing extending portion.

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

  Inner rings 131 a and 131 b of the bearings 130 a and 130 b are fitted to the outer peripheral surface of the shaft member 410. Specifically, in the bearing structure 14, the inner ring 131 a of the bearing 130 a is fitted to the outer peripheral surface 411 at one end of the shaft member 410. On the other hand, the inner ring 131 b of the bearing 130 b is fitted to the outer peripheral surface 413 on the other side of the shaft member 410. In the fourth embodiment, as in the third embodiment described above, the inner ring 131 is provided so as to be movable relative to the shaft member 410 in the axial direction. 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. A 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 the outer peripheral surface to which the inner ring 131 is fitted. Specifically, on one side of the shaft member 410, an extending part 414 extending 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 extending outward in the radial direction 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 above-described 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, an 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 other side surface 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 positioned on one side with respect to the inner ring 131b, and the end surface 417 is opposed to a side surface on one side of the inner ring 131b. As described above, the shaft member 410 is provided with the end surface 416 and the end surface 417 corresponding to the facing surfaces facing the side surfaces of the inner ring 131.

  In the fourth embodiment, expansion members 170 a and 170 b 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 inner ring 131a and end surface 416. On the other hand, 170b is provided between the side surface on one side of the inner ring 131b and the end surface 417. Therefore, in the fourth embodiment, as in the third embodiment described above, the expansion member 170 can press the inner ring 131 along the axial direction by thermal expansion. In the fourth embodiment, as in the third embodiment described above, the inner diameter and the outer diameter of the expansion member 170 can substantially match the inner diameter and the outer diameter of the inner ring 131, respectively. Further, the expansion members 170 a and 170 b can be provided so as to circumscribe the outer peripheral surfaces 411 and 413 of the shaft member 410.

  In FIG. 4, the expansion member 170 when the motor 80 is under a low load is indicated by a solid line, and the expansion member 170 when the motor 80 is under a high load is indicated by a broken line. When the motor 80 is under a high load, the temperature of the expansion member 170 is relatively high, so that the inner ring 131 is pressed along the axial direction when the expansion member 170 is thermally expanded. Specifically, when 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 is thermally expanded, the inner ring 131a is pressed to one side. On the other hand, when 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 is thermally expanded, the inner ring 131b is pressed to the other side.

  In the bearing structure 14 according to the fourth embodiment, the inner ring 131 is provided so as to be relatively movable in the axial direction with respect to the shaft member 410 as described above. Therefore, when the motor 80 is under a high load, 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 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, as in the first embodiment described above, 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 is likely to increase. Current can easily flow between the inner ring 131 and the outer ring 132 of the bearing 130. As a result, current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage at which dielectric breakdown can occur 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 more effectively prevented.

  Further, according to the fourth embodiment, as in the third embodiment described above, when the motor 80 is under a low load, the inner ring 131 is not pressed by the expansion member 170 or the force that presses the inner ring 131 is relatively low. Get smaller. Therefore, when the motor 80 is under a low load when the potential difference generated between the inner ring 131 and the outer ring 132 of the bearing 130 is relatively small, the inner ring 131 is pressed against the expansion member 170, so An increase in friction can be suppressed.

  In the above description, an example 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 in both the pair of bearings 130a and 130b has been described. However, as in the first embodiment described above. 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, it is possible to facilitate the flow of current between the inner ring 131 and the outer ring 132 of one of the bearings 130 when the load is high. It can prevent more effectively.

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

(5-1. First Modification)
First, a bearing structure 60 according to a first modification will be described with reference to FIGS. FIG. 5 is a cross-sectional view showing an example of the configuration of the bearing structure 60 according to the first 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. In addition, in FIG. 5, illustration of the other side part of the bearing structure 60 is abbreviate | omitted. FIG. 6 is a cross-sectional view showing an example of the configuration of the expansion member 670 according to the first modification. FIG. 7 is a perspective view showing an example of the configuration of the expansion member 670 according to the first 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 modification, as in the first embodiment described above, relative movement of the inner ring 131 with 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. The end surface 158 of the bottom 151 on the outer ring 132a side faces the side surface on one side of the outer ring 132a. The expansion member 670 is provided between one side surface of the outer ring 132 a and the end surface 158 of the housing 150.

  In FIG. 5, the expansion member 670 when the motor 80 is under a low load is indicated by a solid line, and the expansion member 670 when the motor 80 is under a high load is indicated 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 to the other side when the motor 80 is under a low load. A large diameter portion 675 corresponding to one end portion of the expansion member 670 contacts the end surface 158 of the housing 150, and a small diameter portion 676 corresponding to the other end portion of the expansion member 670 corresponds to the one side surface of the bearing 130a. Abut.

  Specifically, the expansion member 670 is a bimetal formed by bonding two types of metal members having different thermal expansion coefficients. For example, as shown in FIGS. 6 and 7, the expansion member 670 is formed by laminating a first metal member 671 located on the outer peripheral side and a second metal member 672 located on the inner peripheral side. . The first metal member 671 and the second metal member 672 have different thermal expansion coefficients, and the inner periphery of the first metal member 671 and the outer periphery of the second metal member 672 are bonded to each other. Specifically, the second metal member 672 has a larger thermal expansion coefficient than the first metal member 671. Therefore, when the motor 80 is heavily loaded, the small diameter portion 676 can be bent and deformed in the direction away from the large diameter portion 675 due to the temperature increase 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 is subjected to a high load corresponding to the thermal expansion. Therefore, the expansion member 670 can press the outer ring 132a along the axial direction by thermally expanding. Therefore, in the first modification, when the motor 80 is under a high load, the outer ring 132 is moved in the axial direction by being pressed in the axial direction by the expansion member 670. Thereby, according to the 1st modification, it is possible to show the same effect as a 1st embodiment mentioned above.

  In the above description, the example in which the expansion member 170 in the bearing structure 11 according to the first embodiment is replaced with the expansion member 670 that can be bent and deformed in the axial direction during thermal expansion has been described. 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 Modification)
Subsequently, a bearing structure 70 according to a second modification will be described with reference to FIG. FIG. 8 is a cross-sectional view showing an example of the configuration of the bearing structure 70 according to the second 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. In FIG. 8, the expansion member 170 when the motor 80 is under a low load is indicated by a solid line, and the expansion member 170 when the motor 80 is under a high load is indicated by a broken line. In the second modification, 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 130 a and 130 b, and a housing 750.

  The shaft member 710 is rotatably supported in the housing 750 by a pair of bearings 130a and 130b. Further, one side portion and the other side portion of the shaft member 710 extend outward from the inside of the housing 750. Therefore, openings on one side and the other side of the housing 750 are provided with openings through which the one side portion and the other side portion of the shaft member 710 are inserted. In FIG. 8, the details of one side portion of the shaft member 710 outside the housing 750 are not shown, but for example, the one side portion of the shaft member 710 is a drive system to which the bearing structure 70 is applied. Are connected to other shaft members constituting a part of the shaft through mechanical elements such as gears and clutches.

  Further, the other side of the shaft member 710 outside the housing 150 is connected to the output shaft 910 of the motor 80 via, for example, a clutch C10. Thus, the shaft member 710 according to the second modification is indirectly connected to the motor 80. The motor 80 is accommodated 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 modification, the relative movement of the inner ring 131 with respect to the shaft member 710 in the axial direction is restricted as in the first embodiment described above. Specifically, the inner ring 131a and the inner ring 131b are fitted into the outer peripheral surface 711 on one side and the outer peripheral surface 713 on the other side, respectively, in a tight fit state. In addition, on one side and the other side of the shaft member 710, there are provided 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. The inner ring 131 a and the inner ring 131 b are positioned in contact with 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.

  Further, 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 respectively fitted to the inner peripheral surface 752 on one side of the housing 750 and the inner peripheral surface 754 on the other side in a clearance fit state. Further, at one end and the other end of the housing 750, there are provided an inner peripheral surface 752 and an extending portion 755 and an extending portion 756 extending radially inward from the inner peripheral surface 754, respectively. The extending part 755 and the extending part 756 face one side surface of the outer ring 132a and the other side surface of the outer ring 132b. In addition, an expansion member 170a and an expansion member 170b are provided between the extending portion 755 and one side surface of the outer ring 132a and between the extending portion 756 and the other side surface of the outer ring 132b, respectively. Note that the extending portion 755 and the extending portion 756 correspond to a housing extending portion that extends radially inward from an inner peripheral surface to which the outer ring 132 is fitted in the housing 750.

  In the second modification, the shaft member 710 is indirectly connected to the motor 80 as described above. Even in such a case, as the motor 80 is driven, a potential difference may be generated between the inner ring 131 and the outer ring 132 of the bearing 130 that rotatably supports the shaft member 710. Further, since the shaft member 710 is connected to the motor 80 via the output shaft 910 and the clutch C10, the temperature of each member constituting the bearing structure 70 is higher when the motor 80 is heavily loaded than when the load is low. Can be expensive. Therefore, since the temperature of the expansion member 170 becomes relatively high when the motor 80 is under a high load, the outer ring 132 is pressed along the axial direction by the expansion of the expansion member 170 as shown in FIG. . Therefore, when the motor 80 is under a high load, the outer ring 132 is moved in the axial direction by being pressed in the axial direction by the expansion member 170. Thereby, according to the 2nd modification, it is possible to show the same effect as a 1st embodiment mentioned above.

  In the above description, the example in which the housing extension is positioned on the opposite side of the other bearing 130 with respect to the outer ring 132 has been described. However, the housing extension is positioned on the other bearing 130 side with respect to the outer ring 132. May be. Even in that case, the same effects as those of the first embodiment described above can be obtained. In the above description, the example in which the outer ring 132 is provided so as to be relatively movable in the axial direction with respect to the shaft member 710 has been described. However, 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. Accordingly, it is possible to achieve the same effect as that of the first embodiment described above.

<6. Conclusion>
As described above, according to each embodiment, in at least one bearing 130 of the pair of bearings 130a and 130b, one of the inner ring 131 and the outer ring 132 is fitted with the one of the bearing rings. 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 combined. Further, the fitting member is provided with a facing surface that faces the side surface of the one race ring. In addition, an expansion member 171 is provided between the side surface of the one raceway and the facing surface of the fitting member so as to press the one raceway along the axial direction by thermal expansion.

  Therefore, at the time of high load of the motor 80 in which the temperature of the expansion member 170 is relatively high, the expansion member 170 is thermally expanded to press the one track ring along the axial direction. In each embodiment, as described above, the one track ring is provided so as to be relatively movable in the axial direction with respect to the fitting member. Therefore, when the motor 80 is under a high load, the one raceway is moved in the axial direction by being pressed in the axial direction by the expansion member 170. Thereby, in the bearing 130, the number of the rolling elements 133 which contact both the inner ring | wheel 131 and the outer ring | wheel 132 can be increased. In addition, 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, current can easily flow between the inner ring 131 and the outer ring 132 of the bearing 130.

  Accordingly, current can flow between the inner ring 131 and the outer ring 132 of the bearing 130 before the potential difference reaches the voltage at which dielectric breakdown can occur 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 more effectively prevented.

  Further, according to each embodiment, when the motor 80 is under a low load, the one raceway ring is not pressed by the expansion member 170, or the force that presses the one raceway ring is relatively small. Therefore, when the motor 80 is under a low load when the potential difference generated between the inner ring 131 and the outer ring 132 of the bearing 130 is relatively small, the outer ring 132 is pressed against the expansion member 170 to cause a difference between the members in the bearing 130. An increase in friction can be suppressed.

  In the first embodiment and the second embodiment, the outer ring 132 corresponds to the one raceway, and the housing corresponds to the fitting member. Therefore, in the first embodiment and the second embodiment, the occurrence of electrolytic corrosion in the bearing 130 used in the bearing structure in which the outer ring 132 is provided to be relatively movable in the axial direction with respect to the housing is more effectively generated. Can be prevented. On the other hand, in 3rd Embodiment and 4th Embodiment, the inner ring | wheel 131 corresponds to said one track ring, and a shaft member corresponds to said fitting member. Therefore, in the third embodiment and the fourth embodiment, it is more effective to generate electric corrosion in the bearing 130 used in the bearing structure in which the inner ring 131 is provided to be movable relative to the shaft member in the axial direction. Can be prevented.

  In the above description, the expansion members 170 and 670 have been described with reference to the drawings. However, the expansion member provided between the side surface of the one raceway ring and the facing surface of the fitting member It is not limited to an example, and may have another configuration as long as it can press the above-mentioned one raceway along the axial direction by thermal expansion.

  In the above description, an example in which each bearing structure includes a pair of bearings 130a and 130b has been described. However, each bearing structure may include another bearing different from the bearings 130a and 130b, and the shaft member may be the other bearing. May be supported by rotation.

  In the above description, each component of each bearing structure has been described with reference to each drawing. However, the shape of each component is not limited to the example corresponding to each drawing, and the shape shown in the drawing is only an example. Absent. For example, the shape of each component does not have to be symmetric with respect to the axial direction, and may not be rotationally symmetric with respect to the central axis. Each component may be formed of a plurality of members.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can make various modifications or application examples 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, 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 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 portion 676 Small diameter portion 710 Shaft member 810 Stator 820 Rotor 910 Output shaft 920 Case

Claims (10)

A shaft member connected to the motor;
A pair of bearings disposed on the shaft member at intervals in the axial direction;
A housing that is relatively rotatable with respect to the shaft member via the pair of bearings;
With
An inner ring that is an inner race of the bearing is fitted to the outer peripheral surface of the shaft member,
An outer ring that is an outer race of the bearing is fitted to the 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, one of the inner ring and the outer ring has a bearing ring with respect to the shaft member or the housing as a fitting member into which the one race ring is fitted. And relatively movable in the axial direction,
The fitting member is provided with a facing surface that faces the side surface of the one raceway ring,
Between the side surface of the one race ring and the facing surface of the fitting member, an expansion member is provided that can press the one race ring along the axial direction by thermal expansion.
Bearing structure. In at least one of the pair of bearings, the outer ring as the one race ring is provided to be relatively movable in the axial direction with respect to the housing as the fitting member,
The housing is provided with a housing extending portion extending radially inward from the inner peripheral surface to which the outer ring is fitted,
An end surface on the outer ring side of the housing extending portion is opposed to a side surface of the outer ring as the facing surface,
The expansion member is provided between a side surface of the outer ring and an end surface on the outer ring side of the housing extension portion.
The bearing structure according to claim 1. The housing extension is located on the opposite side to the other bearing side with respect to the outer ring,
An end surface on the outer ring side of the housing extension portion faces a side surface on the opposite side to the other bearing side of the outer ring,
The bearing structure according to claim 2. The housing extension is located on the other bearing side with respect to the outer ring,
An end surface on the outer ring side of the housing extension portion faces a side surface on the other bearing side of the outer ring,
The bearing structure according to claim 2. In at least one of the pair of bearings, the inner ring as the one race ring is provided to be relatively movable in the axial direction with respect to the shaft member as the fitting member,
The shaft member is provided with a shaft member extending portion extending radially outward from the outer peripheral surface to which the inner ring is fitted,
The end surface on the inner ring side of the shaft member extending portion faces the side surface of the inner ring as the facing surface,
The expansion member is provided between a side surface of the inner ring and an end surface on the inner ring side of the shaft member extending portion.
The bearing structure according to claim 1. The shaft member extending portion is located on the opposite side to the other bearing side with respect to the inner ring,
An end surface on the inner ring side of the shaft member extending portion is opposed to a side surface opposite to the other bearing side of the inner ring,
The bearing structure according to claim 5. The shaft member extending portion is located on the other bearing side with respect to the inner ring,
An end surface on the inner ring side of the shaft member extending portion is opposed to a side surface on the other bearing side of the inner ring,
The bearing structure according to claim 5.   The bearing structure according to claim 1, wherein the expansion member is extendable along the axial direction during thermal expansion.   The bearing structure according to claim 1, wherein the expansion member can be bent and deformed in the axial direction during thermal expansion.   The bearing structure according to any one of claims 1 to 9, wherein a rotor of the motor is connected to the shaft member so as to be integrally rotatable.

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