Shaft grounding member and rolling bearing unit for rolling bearings
The shaft grounding member with a spring plate and bent pieces addresses wear and space issues in rolling bearings, ensuring stable conductivity and preventing corrosion and noise, making it compatible with existing designs.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NSK WARNER
- Filing Date
- 2025-04-18
- Publication Date
- 2026-05-15
AI Technical Summary
Existing technologies for preventing electric erosion and electromagnetic noise in rolling bearings generate wear particles, contaminate lubricating oil, damage mating materials, and require additional space, while also failing to adequately suppress temperature rise and ensure stable conductivity.
A shaft grounding member with a spring plate made of a thin conductive material, featuring an annular portion and an elastic portion with bent pieces that apply a pressing force to the outer ring, ensuring stable conductivity and minimizing wear and space requirements.
The solution effectively reduces shaft voltage, prevents electrolytic corrosion, and dissipates electromagnetic noise without generating wear particles, while being versatile and space-efficient, compatible with existing bearings.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a shaft grounding member for a rolling bearing, which is mounted to prevent the occurrence of electric erosion or electromagnetic noise of a rolling bearing in a rolling bearing unit, and a rolling bearing unit equipped with the shaft grounding member for a rolling bearing.
Background Art
[0002] In recent years, the practical application of electric vehicles that drive wheels by arranging an electric motor as a drive source inside or near the wheels has been progressing. Such a drive motor is generally called an in-wheel motor. The structure of a general in-wheel motor is such that a stator (stator) is fixed to a motor housing, and a rotor (rotor) is arranged with a gap in the radial direction on the inner diameter side of the stator, which is a so-called inner rotor type motor. Further, as a drive method of an in-wheel motor, a brushless DC motor driven by an inverter is widely used in consideration of the performance and control performance of the motor.
[0003] In a method driven by an inverter, a potential difference occurs between the stator and the rotor due to a parasitic capacitance or the like between the stator and the rotor. Due to this potential difference, so-called shaft voltage and shaft current are generated. When this shaft current passes through a rolling bearing that supports the rotor, a phenomenon called "electric erosion" that damages the rolling bearing occurs. Specifically, a current flows locally at the contact portion between the rolling surfaces of the outer ring and the inner ring of the rolling bearing and the rolling elements, the raceway surface or the rolling surface melts or the like to generate irregularities, whereby the rolling surface and the surface of the rolling elements of the bearing are roughened, which not only causes noise and vibration, but also affects the life of the bearing when excessive electric erosion occurs.
[0004] In order to prevent electric erosion of a rolling bearing, a conductive member is also interposed. For example, in Patent Documents 1 and 2, it is composed of a contact body for electrically connecting to the rotor of the motor, an elastic body for pressing the contact body toward the rotor side, and a storage portion for housing the contact body and the elastic body. It is proposed to provide the storage portion in the motor housing and electrically connect to the motor stator through the motor housing.
[0005] Furthermore, Patent Document 3 proposes an earthing device in which the tip of a broom-shaped conductive fiber is brought into contact with the outer surface of a rotating shaft.
[0006] Furthermore, Patent Document 4 proposes an electrolytic corrosion prevention device in which an annular seat portion that contacts the end face of the bearing outer ring is bent into a wave washer shape, and an elastic conductor having a contact piece that extends from the inside of the annular seat portion and contacts the vicinity of the center of the end face of the rotating shaft is used, and the annular seat portion is superimposed on the end face of the bearing outer ring fitted into the bearing housing, and the contact piece is in contact with the vicinity of the center of the end face of the rotating shaft fitted into the bearing inner ring, and the surface of the annular seat portion is pressed by the lid-shaped wall of the bearing housing to make it electrically conductive.
[0007] Furthermore, Patent Document 5 proposes housing a rod-shaped conductive brush in a support hole provided in one of the two raceway rings, and using an elastic member to bias the tip of the conductive brush toward the other raceway ring, thereby electrically connecting the two raceway rings.
[0008] Patent Document 6 proposes providing a carbon filament shaft grounding brush with its tip in contact with the extension shaft to ground and remove the shaft voltage generated on the shaft, thereby preventing electrolytic corrosion that occurs in the bearing.
[0009] Incidentally, bearings require measures to counter electromagnetic noise generated by electromagnetic interference, and various devices have been proposed to suppress the generation of electromagnetic noise. For example, Patent Document 7 proposes housing a conductive rod-shaped carbon brush between an inner ring and a metal ring, and biasing the tip of the carbon brush, which is attached to the metal ring by a spring, against the inner ring to bring it into sliding contact. This imparts conductive properties to the conductive bearing and also allows the current flowing through the conductive bearing to flow out of the system via the metal ring and brush, thereby eliminating electromagnetic noise.
[0010] Patent Document 8 proposes a conductive device that can dissipate electromagnetic noise by suppressing the formation of an oil film between a conductive rubber lip and a metal housing attached to a rotating shaft using centrifugal force, or by controlling the thickness of the oil film. By suppressing the formation of the oil film or reducing its thickness, the electrical resistance of the oil film is reduced, making it possible to dissipate electromagnetic noise from the rotating shaft to the housing.
[0011] Patent Document 9 proposes improving electromagnetic noise prevention and electrolytic corrosion prevention by ensuring a path for electric charge by having conductive rolling elements roll between the outer and inner rings while the oil film is broken, thereby significantly reducing the impedance between the outer and inner rings, or the entire bearing.
[0012] Patent Document 10 proposes an electromagnetic noise suppression device that electrically connects the metal case of the electric motor and the rotating shaft inside the electric motor using conductive means such as a sliding contact member, thereby diverting electromagnetic noise induced on the rotating shaft to a metal electric motor housing grounded to the vehicle body. [Prior art documents] [Patent Documents]
[0013] [Patent Document 1] Japanese Patent Publication No. 2011-135720 [Patent Document 2] Japanese Patent Publication No. 2011-135722 [Patent Document 3] Japanese Patent Publication No. 2020-127257 [Patent Document 4] Japanese Patent Publication No. 2002-146568 [Patent Document 5] Japanese Utility Model Publication No. 4-8820 [Patent Document 6] Japanese Patent Publication No. 2017-060401 [Patent Document 7] Japanese Patent Publication No. 2024-130948 [Patent Document 8] Japanese Patent Publication No. 2023-018214 [Patent Document 9] Japanese Patent Publication No. 2022-139252 [Patent Document 10] Japanese Patent Publication No. 2000-244180 [Overview of the project] [Problems that the invention aims to solve]
[0014] However, in all the technologies described in the patent documents, wear particles generated from the conductive member may contaminate the lubricating oil or grease composition sealed inside for lubrication, potentially damaging the rolling surface. Furthermore, the conductive member may damage the mating material, generating wear particles from that material as well.
[0015] To explain in more detail, in Patent Documents 1 and 2, the contact body, elastic body, and housing are made of metal, and metal powder is generated when these slide against each other due to the vibration of the motor. In addition, the contact body, elastic body, and housing need to be installed in the motor housing, and space is required for this.
[0016] Furthermore, in Patent Document 3, the tip of the broom-shaped conductive fiber is brought into contact with the outer surface of the rotating shaft. However, in order to increase the contact area between the tip of the broom-shaped conductive fiber and the rotating shaft compared to simply bringing them into contact, the broom-shaped conductive fiber is brought into contact with the outer surface of the rotating shaft in a bent state. That is, the tip of the broom-shaped conductive fiber is in contact with the outer surface of the rotating shaft with a certain degree of strong pressure, and wear particles are generated. At the same time, the outer surface of the rotating shaft, which is the mating material of the broom-shaped conductive fiber, is also damaged.
[0017] Furthermore, in Patent Document 4, both the elastic conductor and the rotating shaft are made of metal, and metal powder is generated when the two come into contact. At the same time, the end face of the rotating shaft, which is the mating material of the elastic conductor, is damaged.
[0018] In Patent Document 5, since the tip of the rod-shaped conductive brush is in contact with the other track wheel in a biased state, wear powder of the conductive brush is generated. At the same time, the other track wheel, which is the mating material of the conductive brush, is also damaged. Furthermore, it is necessary to form a support hole for accommodating the conductive brush and the elastic member in the track wheel, which imposes a large load on the track wheel.
[0019] In Patent Document 6, since the tip of the shaft grounding brush made of carbon filaments is provided to abut against the extension shaft, wear powder of the shaft grounding brush is generated. At the same time, the extension shaft, which is the mating material of the shaft grounding brush, is also damaged.
[0020] Furthermore, in the bearings shown in Patent Documents 1 to 9, frictional heat may be generated due to the sliding contact between the conductive member and the mating material during use, which reduces the durability of the bearing. In addition, with the recent improvement in the performance of motors, the peripheral speed of the rotating member has also increased, so further suppression of temperature rise is required.
[0021] Regarding Patent Document 10, although a wear-resistant member is selected as the sliding contact member, the effect of reducing wear is not sufficient.
[0022] Furthermore, a different material from the bearing material such as aluminum may be used for the housing into which the outer ring, which is a fixed ring, fits. In that case, there is a possibility that creep or loosening of the fit may occur between the fixed ring and the fixing member due to temperature changes. In an environment where such creep or loosening of the fit may occur, even when a conductive member is used, it is required to ensure the electrical contact of the conductive member and obtain stable conductivity.
[0023] Therefore, an object of the present invention is to suppress the generation of wear powder from the conductive member or wear powder accompanying the sliding contact between the conductive member and the mating material, suppress damage to the mating material, stably ensure excellent conductivity, not form new processing on the bearing, have no limitation on the type of bearing, be compatible with existing bearings, provide a space-saving and inexpensive shaft grounding member, and a rolling bearing unit equipped with the shaft grounding member. [Means for solving the problem]
[0024] The above objective of the present invention is achieved by the configuration described below [1] relating to the shaft grounding member for rolling bearings.
[0025] [1] A shaft grounding member to be mounted on a rolling bearing unit which has an inner ring rotating type rolling bearing in which the outer ring is fixed to the housing and a shaft directly connected to the motor is fitted into the inner ring, A spring plate made of a thin sheet of conductive material is composed of an annular portion and an elastic portion that extends from the inner circumference end of the annular portion to the center of the annular portion, A soft conductive member is mounted on the side of the elastic portion facing the rolling bearing, In addition to being equipped, The soft conductive member is capable of contacting the end face of the shaft, The spring plate is provided with a plurality of bent portions that are bent in the axial direction on the annular portion facing the side surface of the outer ring, and which apply a pressing force to the outer ring by deforming themselves. A shaft grounding member for rolling bearings characterized by the following.
[0026] Furthermore, preferred embodiments of the present invention relating to shaft grounding members for rolling bearings are described in the following [2] to [9].
[0027] [2] Each of the bent portions is a cut-out piece formed by folding in the axial direction between a pair of notches cut out from the outer edge of the annular portion. [1] The shaft grounding member for rolling bearings.
[0028] [3] The plurality of bent portions have a portion between a pair of notches cut out from the outer edge of the annular portion that is bent in one direction in the axial direction and a portion that is bent in the other direction in the axial direction. [1] The shaft grounding member for rolling bearings.
[0029] [4] Each of the bent portions is a folded piece formed by folding back in the axial direction a portion between a pair of notches cut out from the outer edge of the annular portion, or a portion extending radially from the outer edge of the annular portion. [1] The shaft grounding member for rolling bearings.
[0030] [5] The plurality of bent portions have a portion between a pair of notches cut out from the outer peripheral edge of the annular portion, or a portion extending radially from the outer peripheral edge of the annular portion, which has one folded piece folded back to one side in the axial direction and the other folded piece folded back to the other side in the axial direction. [1] The shaft grounding member for rolling bearings.
[0031] [6] The annular portion is pressed against the side surface of the outer ring with a spacer in between. A shaft grounding member for rolling bearings as described in any one of [1] to [5].
[0032] [7] The soft conductive member is a resin-impregnated nonwoven fabric, a nonwoven fabric, a resin-impregnated woven fabric, a woven fabric, It consists of at least one selected from a resin-impregnated soft porous material and a soft porous material. A shaft grounding member for rolling bearings as described in any one of [1] to [6].
[0033] [8] The elastic portion of the spring plate is bent in the middle. A shaft grounding member for rolling bearings as described in any one of [1] to [7].
[0034] [9] The elastic portion of the spring plate is formed flush with the annular portion, A shaft grounding member for rolling bearings as described in any one of [1] to [7].
[0035] The above objective of the present invention is achieved by the following configuration
[10] relating to the rolling bearing unit.
[0036]
[10] The rolling bearing has an inner ring that rotates, with the outer ring fixed to the housing and the inner ring into which a shaft directly connected to the motor is fitted, A rolling bearing unit characterized by being fitted with a rolling bearing shaft grounding member described in any one of [1] to [9].
[0037] Hereafter, "shaft grounding member for rolling bearings" will simply be referred to as "shaft grounding member," and "rolling bearing unit" will simply be referred to as "bearing unit." [Effects of the Invention]
[0038] In this invention, the spring plate of the shaft grounding member is provided with multiple bent portions that are bent axially in the annular portion facing the side surface of the fixed ring and apply a pressing force between itself and the fixed ring by deforming. Therefore, stable conductivity with the fixed ring and housing can be ensured without providing separate components such as disc springs or wave springs. Consequently, a decrease in conductivity due to loosening of the shaft grounding member's fixing or vibration can be suppressed, reducing the shaft voltage, which is the potential difference between the rotating member and the fixed member, thereby preventing electrolytic corrosion of the rolling bearing and allowing electromagnetic noise to escape through the space between the rotating member and the fixed member. Furthermore, creep in the rolling bearing can be prevented.
[0039] The shaft grounding member of the present invention consists of a soft conductive member attached to the elastic portion of a spring plate, which is in contact with the end face of the shaft. The biasing force exerted by the spring plate on the end face of the shaft of the soft conductive member is not very strong, so wear particles are less likely to be generated. Moreover, since the soft conductive member is made of a soft material, damage to the shaft, which is the mating material, is also minimized.
[0040] Furthermore, it is highly versatile as it requires no processing of the rolling bearing, has no restrictions on the type of rolling bearing, and can be applied to existing rolling bearings. In addition, the spring plate is thin, which minimizes the increase in space required for the bearing unit it is installed in.
[0041] Because the bearing unit of the present invention is equipped with the shaft grounding member of the present invention, the generation of wear particles and damage to the mating material are suppressed, and furthermore, it is highly versatile and does not increase the space required. [Brief explanation of the drawing]
[0042] [Figure 1] Figure 1(A) is a perspective view showing an example of the axial grounding member of the present invention, and Figure 1(B) is a front view thereof. [Figure 2] Figure 2(A) is a cross-sectional view AA of Figure 1(B), and Figure 2(B) is an enlarged cross-sectional view showing the bent portion between the annular part and the elastic part. [Figure 3] Figure 3 is an enlarged cross-sectional view corresponding to Figure 2(B), showing another example of a cut and bent piece. [Figure 4] Figure 4(A) is a cross-sectional view showing the state when the shaft grounding member shown in Figure 1 is attached to the housing, before the cut and bent piece is pressed against the outer ring side, and Figure 4(B) is a cross-sectional view showing the state when the shaft grounding member shown in Figure 1 is attached to the bearing unit. [Figure 5] Figure 5(A) is a perspective view showing a first modified example of the axial grounding member according to an embodiment of the present invention, and Figure 5(B) is a front view thereof. [Figure 6] Figure 6 is a cross-sectional view of BB in Figure 5(B). [Figure 7] Figure 7 shows the process of attaching the shaft grounding member shown in Figure 5 to the housing. Figure 7(A) is a cross-sectional view showing the state before one cut-up piece is pressed against the outer ring side. Figure 7(B) is a cross-sectional view showing the state before the other cut-up piece is pressed against the outer ring side. Figure 7(C) is a cross-sectional view showing the state in which one cut-up piece is pressed against the outer ring side via a spacer and the shaft grounding member is attached to the bearing unit. Figure 7(D) is a cross-sectional view showing the state in which the other cut-up piece is pressed against the outer ring side via a spacer and the shaft grounding member is attached to the bearing unit. [Figure 8] Figure 8(A) is a perspective view showing a second modified example of the axial grounding member according to an embodiment of the present invention, and Figure 8(B) is a front view thereof. [Figure 9] Figure 9 is a cross-sectional view of CC in Figure 8(B). [Figure 10] Figure 10(A) is a cross-sectional view showing the state when the shaft grounding member shown in Figures 8 and 9 is attached to the housing, before the folded piece is pressed against the outer ring side, and Figure 10(B) is a cross-sectional view showing the state in which the folded piece is pressed against the outer ring side via the spacer and the shaft grounding member is attached to the bearing unit. [Figure 11] Figure 11 is a diagram showing a third modified example of the axial grounding member according to an embodiment of the present invention, and is a cross-sectional view corresponding to Figure 2(A). [Figure 12] Figure 12 is a cross-sectional view showing an example of a bearing unit with the shaft grounding member shown in Figure 11 attached. [Modes for carrying out the invention]
[0043] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below, and can be modified and implemented as appropriate without departing from the spirit of the invention.
[0044] As shown in Figure 1, the shaft grounding member 1 comprises a spring plate 10 consisting of an annular portion 11 and a single elastic portion 13 extending from the inner circumference end 12 of the annular portion 11 toward the center of the annular portion 11. As shown in Figures 2 and 4, the elastic portion 13 is bent toward the right in the figures, starting from the elastic base portion 14, so that when mounted on the bearing unit 100, it approaches the end face 60a side of the shaft 60 which is fitted into the inner ring 52 of the rolling bearing 50.
[0045] The spring plate 10 is made entirely of a thin sheet of a conductive material such as metal. When the conductive material is metal, stainless steel is preferred because it is easy to process and less prone to rusting.
[0046] A soft conductive member 20 is attached to the tip portion of the elastic portion 13, that is, the central portion of the annular portion 11, on the side facing the end face 60a of the shaft 60 that is fitted into the rolling bearing 50. The spring plate 10 and the soft conductive member 20 constitute the shaft grounding member 1. The soft conductive member 20 is attached to the elastic portion 13 using adhesive.
[0047] As the flexible conductive member 20, a flexible base material into which a conductive material is mixed or supported, or commercially available products referred to as "conductive sheets" can be used. As the flexible base material, at least one selected from porous materials and resin-impregnated porous materials can be used. As the porous material, paper, cloth, nonwoven fabric, resin sheet, or a soft porous material such as sponge can be used. Of these, it is preferable to use at least one selected from soft porous materials such as nonwoven fabric, woven fabric and sponge, and resin-impregnated soft porous materials such as resin-impregnated nonwoven fabric, resin-impregnated woven fabric and sponge as the base material. When a resin-impregnated porous material is used as the base material for the flexible conductive member 20, the resin coats its skeleton, allowing the flexible conductive member 20 to be strengthened to the desired level while maintaining its flexible properties. Therefore, it is more preferable to use at least one selected from resin-impregnated nonwoven fabrics, resin-impregnated woven fabrics, and resin-impregnated soft porous materials such as sponges as the base material.
[0048] Furthermore, when using a resin-impregnated porous material as the base material, it is preferable to use a thermosetting resin as the resin to impregnate the porous material. Any thermosetting resin that can be impregnated into the base material and is thermosetting is acceptable, and examples include phenolic resin, modified phenolic resin, epoxy resin, modified epoxy resin, polyimide resin, silicone resin, polyester resin, polyurethane resin, and rubber resin.
[0049] As the conductive material to be mixed into or supported on the soft substrate, it is preferable to use at least one selected from metal fibers such as silver, copper, gold, aluminum, and stainless steel, and their pulverized or powdered forms, as well as conductive carbon fibers, and their pulverized or powdered forms.
[0050] Furthermore, as shown in Figure 2(B), the bending angle θ1 between the annular portion 11 and the elastic portion 13 is appropriately set so that the soft conductive member 20 contacts the end face 60a of the shaft 60 when mounted on the bearing unit 100. The biasing force of the soft conductive member 20 on the end face 60a of the shaft 60 can also be adjusted by the bending angle θ1; the biasing force can be increased by decreasing the bending angle θ1, and conversely, the biasing force can be decreased by increasing the bending angle θ1.
[0051] There are no restrictions on the planar shape of the flexible conductive member 20; in addition to the circular shape shown in Figure 1, it may also be rectangular or made up of multiple small pieces. The flexible conductive member 20 preferably contacts the end face 60a of the shaft 60 near the center of the shaft, as the peripheral speed is low near the center of the shaft, making it less likely for wear particles to be generated.
[0052] Furthermore, the annular portion 11 has multiple notches 16 formed from the outer edge toward the inner circumference, and between adjacent notches 16, 16, a cut-out piece 18 (bent portion) is formed, bent from the starting point 17. The cut-out piece 18 is bent axially so that its tip slopes toward the back of the paper in Figure 1(B), that is, it is bent in the opposite direction to the axial direction in which the elastic portion 13 bends. The tip of the cut-out piece 18 is formed in a straight line and is located on the inner diameter side of the imaginary circle connecting multiple arc-shaped portions whose outer circumferences are not arc-shaped and on which the cut-out piece 18 is not formed.
[0053] Furthermore, the cut-out pieces 18 may be bent axially so that their tips are angled toward the front of the paper in Figure 1(B). Also, although the cut-out pieces 18 are formed at four equally spaced locations in Figure 1, there is no limit to the number. In addition, although the multiple cut-out pieces 18 are formed alternately with multiple arc portions as shown in the figure, they are not limited to this arrangement and may be formed around the entire circumference of the annular portion 11.
[0054] As shown in Figure 2(B), there is no restriction on the cutting angle θ2 of the cutting piece 18 relative to the annular portion 11, and it is set appropriately according to the desired biasing force (pressing force). By reducing the cutting angle θ2, the biasing force can be weakened, and conversely, by increasing the cutting angle θ2, the biasing force can be increased.
[0055] In Figure 2(B), the cut and bent piece 18 is formed by a single bending process and has a flat surface. However, as shown in Figure 3, it may be folded multiple times (twice in the example shown) to form a stepped cross-section.
[0056] Furthermore, such a spring plate 10 can be formed, for example, by blanking, wire cutting, or laser processing to create a predetermined shape, followed by bending using a press or the like, but the manufacturing method is not limited to these.
[0057] Figure 4 shows a bearing unit 100 with the shaft grounding member 1 configured in this way. The rolling bearing 50 has a plurality of rolling elements (balls) 53 between the outer ring 51 and the inner ring 52, and the plurality of rolling elements 53 are held in place by a cage 54 so as to be able to roll, and the plurality of rolling elements 53 are lubricated with lubricating oil or grease composition. Here, the rotating ring is the inner ring 52, and a shaft 60 directly connected to a motor (not shown) is fitted into it. The shaft 60 is fitted so that its end face 60a is flush with the end face 52a of the inner ring 52. The outer ring 51 is a fixed ring and is fixed to the housing 70. Note that the configuration of the rolling bearing 50 is not limited to this and may have other configurations.
[0058] As shown in Figure 4(A), when attaching the shaft grounding member 1 to the bearing unit 100, the conductive spacer 30 is first fitted into the inner diameter side of the housing 70, and then the shaft grounding member 1 is fitted into the inner diameter side of the housing 70. After that, the conductive retaining member 80 is fitted into the inner diameter side of the housing 70 and the retaining member 80 is pressed against the outer ring 51. As a result, the annular portion 11 of the shaft grounding member 1 is pressed against the side surface of the outer ring 51 via the conductive spacer 30. Here, the cut and bent portion 18 of the shaft grounding member 1 is elastically deformed by the retaining member 80, so an axial spring reaction force acts on the spacer 30 and the retaining member 80, and as a result the pressing force against the side surface 51a of the outer ring 51 via the spacer 30 also increases.
[0059] The thickness of the spacer 30 should be determined considering the amount of pressure applied by the spring plate 10 and the thickness of the soft conductive member 20. Alternatively, the annular portion 11 of the shaft grounding member 1 may directly contact the side surface of the outer ring 51 without the spacer 30.
[0060] In an inner-ring rotating type bearing unit 100 that does not incorporate a shaft grounding member 1, current from the motor usually flows through the shaft 60 to the inner ring 52, energizing the rolling elements 53 and the outer ring 51 inside the bearing, causing electrolytic corrosion of the rolling bearing 50. In contrast, in the present invention, the soft conductive member 20 of the shaft grounding member 1 is mounted in the housing 70 so as to abut against the end face 60a of the shaft 60. Furthermore, the annular portion 11 of the spring plate 10 is electrically connected to the side surface of the outer ring 51 via a conductive spacer 30, and is also electrically connected to a conductive retaining member 80.
[0061] As a result, the current from the shaft 60 flows from the soft conductive member 20 to the elastic portion 13 and annular portion 11 of the spring plate 10, and then flows to the housing 70 via the cut-and-bent piece 18 of the annular portion 11, the outer edge of the arc portion of the annular portion 11, the retaining member 80, the spacer 30 and the outer ring 51. Note that because the outer ring 51 has a large contact area with the housing 70, the current that flows through the outer ring 51 does not pass through the rolling elements 53 and flows to the housing 70.
[0062] In this way, the shaft grounding member 1 grounds the rotating member, the shaft 60, and the fixed member, the housing 70, so that current does not flow inside the bearing, and the shaft voltage, which is the potential difference between the rotating member and the fixed member, can be significantly reduced. Therefore, electrolytic corrosion of the rolling bearing 50 can be prevented, and electromagnetic noise can be dissipated through the space between the rotating member, the shaft 60, and the fixed member, the housing 70.
[0063] In this embodiment, the outer edge of the arc portion of the annular portion 11 and the spacer 30 are in contact with the housing 70. However, it is also possible to configure it so that it does not contact the housing 70, but is instead held between the outer ring 51 and the retaining member 80. In that case, the current flowing through the annular portion 11 flows to the housing 70 via the outer ring 51 and the retaining member 80.
[0064] Furthermore, since the end face 60a of the shaft 60 is in contact with the soft conductive member 20, the end face 60a of the shaft 60 will not be damaged, and a decrease in the rotational torque of the shaft 60 can be suppressed. If the base material of the flexible conductive member 20 is porous, it has oil-absorbing and oil-retaining properties, so oil is easily discharged between adjacent spring plates 10 when the shaft rotates, making it difficult for an oil film to form, and the conductivity is good even when used in oil. Furthermore, by making the base material of the flexible conductive member 20 porous, the coefficient of friction is suppressed even when used in environments other than oil, and the reduction in the rotational torque of the inner ring 52 can be suppressed.
[0065] Furthermore, the spring plate 10 of the shaft contact member 1 is a thin plate, which minimizes the increase in space required for the bearing unit 100. Also, there are no restrictions on the rolling bearing 50, and no processing is required, so it can be applied to existing rolling bearings, making it extremely versatile.
[0066] As described above, by increasing the contact area between the soft conductive member 20 of the shaft grounding member 1 and the end face 60a of the shaft 60 of the rolling bearing 50, the axial voltage between the rotating member and the stationary member can be stably reduced. Since the spring plate 10 is an elastic member made of a thin plate that is bent as a whole, by pressing the annular portion 11 of the shaft grounding member 1 against the outer ring 51, the elastic force due to the pressing acts on the elastic portion 13, causing it to expand so that the bending angle θ1 shown in Figure 2(B) becomes larger, and the entire elastic portion 13 moves towards the rolling bearing 50. Accordingly, in Figure 4, the portion of the soft conductive member 20 that was away from the end face 60a of the shaft 60 also moves towards the rolling bearing 50, and almost the entire soft conductive member 20 comes into contact with the end face 60a of the shaft 60. This improves the conductivity between the soft conductive member 20 and the inner ring 52, and more effectively prevents electrolytic corrosion of the rolling bearing 50 and reduces electromagnetic noise.
[0067] Furthermore, the cut-out piece 18 increases the pressing force on the side surface of the outer ring 51 of the shaft grounding member 1. As a result, even if axial play occurs between the outer ring 51 and the housing 70, the shaft grounding member 1 remains fixed, and electrical contact between the annular portion 11 and the side surface of the outer ring 51 via the conductive spacer 30, as well as electrical contact with the conductive retaining member 80, is maintained. Therefore, the aforementioned shaft voltage can be reduced more stably, thereby preventing electrolytic corrosion and reducing electromagnetic noise.
[0068] Furthermore, the cut-and-bent piece 18 increases the pressing force on the side surface of the outer ring 51 of the shaft contact member 1. Therefore, even if the fit between the outer ring 51 and the housing 70 becomes loose, the outer ring 51 can be fixed to the housing 70, thereby suppressing creep of the rolling bearing 50.
[0069] In particular, in a bearing unit 100 in which the housing 70 is made of aluminum and the housing 70 and the outer ring 51 are made of different materials, the dimensional change due to the difference in thermal expansion coefficients between the housing 70 and the outer ring 51 is large, making it more susceptible to creep and loosening of the fit. Therefore, an increase in the pressing force at the mounting portion of the shaft contact member 1 by the cut and bent piece 18 becomes more significant.
[0070] Furthermore, while disc springs and wave springs are commonly used in rolling bearing units to suppress creep and axial play, the inclusion of a cut-and-bent piece 18 in the shaft contact member 1 eliminates the need for disc springs and wave springs, thereby reducing the cost of the rolling bearing unit.
[0071] (First variation) In the axial grounding member 1 of the above embodiment, all cut-up pieces 18 are bent to one side in the axial direction. However, as shown in Figures 5 and 6, one cut-up piece 18A bent to one side in the axial direction and the other cut-up piece 18B bent to the other side in the axial direction may be formed alternately.
[0072] In this case as well, as shown in Figure 7, when the annular portion 11 of the shaft grounding member 1 is pressed against the side surface of the outer ring 51 via the conductive spacer 30 by the conductive pressing member 80, the cut and bent pieces 18A and 18B of the shaft grounding member 1 are elastically deformed by the pressing member 80, and an axial spring reaction force acts on the spacer 30 and the pressing member 80. As a result, the pressing force against the side surface 51a of the outer ring 51 via the spacer 30 is also increased, the fixing of the shaft grounding member 1 is maintained more reliably, and the same effects as in the above embodiment can be achieved. Furthermore, the cut-up pieces 18A and 18B are not limited to being formed alternately; either cut-up piece 18A or 18B may be formed at any position.
[0073] (Second variation) Furthermore, as shown in Figures 8 and 9, the axial grounding member 1 may have multiple folded pieces 22 (bent portions) instead of the multiple cut-up pieces 18 which are the biasing portions in the above embodiment.
[0074] The annular portion 11 has multiple notches 16 formed from the outer edge toward the inner circumference, and between adjacent notches 16, 16, a folded piece 22 is formed, folded back from the starting point 17. The tip of the folded piece 22 is folded back toward the far side of the paper in Figure 8(B), that is, it is folded back in the opposite direction to the axial direction in which the elastic portion 13 bends. The starting point 17 of the folded piece 22 is located on the inner diameter side of the imaginary circle connecting multiple arc-shaped portions whose outer circumferences are not arc-shaped and for which the folded piece 22 is not formed.
[0075] The folded-over piece 22 may also be formed by folding its tip towards the front of the paper in Figure 8(B). Furthermore, although the folded-over piece 22 is formed at four equally spaced locations in Figure 8, there is no limit to the number of pieces. Additionally, while the multiple folded-over pieces 22 are formed alternately with multiple arc portions as shown in the figure, they are not limited to this arrangement and may be formed around the entire circumference of the annular portion 11.
[0076] As shown in Figure 9, there is no restriction on the bending angle θ3 of the folded piece 22 relative to the annular portion 11, and it can be set appropriately according to the desired biasing force (pressing force). By reducing the bending angle θ3, the biasing force can be weakened, and by increasing the bending angle θ3, the biasing force can be increased.
[0077] In this case as well, as shown in Figure 10, when the annular portion 11 of the shaft grounding member 1 is pressed against the side surface of the outer ring 51 via the conductive spacer 30 by the conductive pressing member 80, the folded portion 22 of the shaft grounding member 1 is elastically deformed by the pressing member 80, so that an axial spring reaction force acts on the spacer 30 and the pressing member 80. As a result, the pressing force against the side surface 51a of the outer ring 51 via the spacer 30 is also increased, the fixing of the shaft grounding member 1 is maintained more reliably, and the same effects as in the above embodiment can be achieved.
[0078] In the second modified example, the folded portion 22 is formed by folding back the portion between adjacent notches 16, 16 in the axial direction, but it may also be formed by folding back the portion extending radially from the outer edge of the annular portion 11 in the axial direction.
[0079] Furthermore, in the folded portion of the second modified example, similar to the cut-out portion of the first modified example, the portion between the pair of notches 16, 16 cut out from the outer peripheral edge of the annular portion 11, or the portion extending radially from the outer peripheral edge of the annular portion 11, may be configured to have one folded portion folded back to one side in the axial direction and the other folded portion folded back to the other side in the axial direction.
[0080] It should be noted that the present invention is not limited to the embodiments described above, and can be modified and improved as appropriate. For example, in the above embodiment, its first and second modified examples, the elastic portion 13 of the spring plate 10 is configured to bend midway. However, in a third modified example, it may be configured to be formed flush with the annular portion 11 without bending at the elastic base portion 14. That is, as shown in Figure 11, the annular portion 11 and the elastic portion 13 are linearly continuous in a side view. In Figure 2(A), the cut-up pieces 18 are formed in two opposing pairs of regions, but the positions where the cut-up pieces 18 are formed can be set arbitrarily. For example, as shown in Figure 11, the areas where the cut-up pieces 18 are formed and the areas where the cut-up pieces 18 are not formed may be opposite each other.
[0081] Therefore, in the bearing unit 100 shown in Figure 12, when the annular portion 11 of the shaft grounding member 1 is sandwiched between the flange portion 71 of the housing 70 and the side surface of the outer ring 51, the elastic portion 13 of the shaft grounding member 1 elastically deforms by the thickness of the soft conductive member 20, and the bending reaction force of the spring plate 10 causes the soft conductive member 20 to come into contact with the end face 60a of the shaft 60. This makes it possible to perform the same function as in the above embodiment.
[0082] In this case, bending of the spring plate 10 is unnecessary, so the shaft grounding member 1 can be manufactured at a low cost, and the spring plate 10 and the soft conductive member 20 can be easily bonded together.
[0083] Furthermore, in this embodiment, the spring plate is configured to have one elastic portion extending toward the center of the annular portion, but it may also be configured to have multiple elastic portions extending radially toward the center of the annular portion.
[0084] Furthermore, the axial grounding member of the present invention can also be suitably used when only one of the following is required: prevention of electrolytic corrosion and suppression of electromagnetic noise generation.
[0085] Furthermore, when the primary objective is to prevent galvanic corrosion, the term "shaft grounding member" in this specification may be replaced with "galvanic corrosion prevention member," and the term "rolling bearing unit" may be replaced with "galvanic corrosion prevention rolling bearing unit." Specifically, this is as follows.
[0086] (1) A corrosion prevention member to be mounted on a rolling bearing unit which has an inner ring rotating type rolling bearing in which the outer ring is fixed to the housing and a shaft directly connected to the motor is fitted into the inner ring, A spring plate made of a thin sheet of conductive material is composed of an annular portion and an elastic portion that extends from the inner circumference end of the annular portion to the center of the annular portion, A soft conductive member is mounted on the side of the elastic portion facing the rolling bearing, In addition to being equipped, The soft conductive member is capable of contacting the end face of the shaft, The spring plate is provided with a plurality of bent portions that are bent in the axial direction on the annular portion facing the side surface of the outer ring, and which apply a pressing force to the outer ring by deforming themselves. A corrosion-preventing member for rolling bearings characterized by the following.
[0087] (2) Each of the bent portions is a cut-out piece formed by folding in the axial direction between a pair of notches cut out from the outer edge of the annular portion. (1) The anti-corrosion member for rolling bearings described in (1).
[0088] (3) The plurality of bent portions have a portion between a pair of notches cut out from the outer edge of the annular portion that is bent in one direction in the axial direction and a portion that is bent in the other direction in the axial direction. (1) The anti-corrosion member for rolling bearings described in (1).
[0089] (4) Each of the bent portions is a folded piece formed by folding back in the axial direction a portion between a pair of notches cut out from the outer edge of the annular portion, or a portion extending radially from the outer edge of the annular portion. (1) The anti-corrosion member for rolling bearings described in (1).
[0090] (5) The plurality of bent portions have a portion between a pair of notches cut out from the outer peripheral edge of the annular portion, or a portion extending radially from the outer peripheral edge of the annular portion, which has one folded piece folded back to one side in the axial direction and the other folded piece folded back to the other side in the axial direction. (1) The anti-corrosion member for rolling bearings described in (1).
[0091] (6) The annular portion is pressed against the side surface of the outer ring with a spacer in between. A corrosion-preventing member for rolling bearings as described in any one of (1) to (5).
[0092] (7) The soft conductive member is a resin-impregnated nonwoven fabric, a nonwoven fabric, a resin-impregnated woven fabric, a woven fabric, It consists of at least one selected from a resin-impregnated soft porous material and a soft porous material. A corrosion-preventing member for rolling bearings as described in any one of (1) to (6).
[0093] (8) The elastic portion of the spring plate is bent in the middle. A corrosion-preventing member for rolling bearings as described in any one of (1) to (7).
[0094] (9) The elastic portion of the spring plate is formed flush with the annular portion, A corrosion-preventing member for rolling bearings as described in any one of (1) to (7).
[0095] (10) The inner ring is a rotating type rolling bearing in which the outer ring is fixed to the housing and the shaft directly connected to the motor is fitted into the inner ring, A rolling bearing unit that prevents electrolytic corrosion, characterized by being fitted with an electrolytic corrosion prevention member for rolling bearings described in any one of (1) to (9).
[0096] Furthermore, when the primary objective is to suppress the generation of electromagnetic noise, the term "shaft grounding member" in this specification may be replaced with "electromagnetic noise suppression member," and the term "rolling bearing unit" may be replaced with "electromagnetic noise suppression rolling bearing unit." [Explanation of Symbols]
[0097] 1. Axis grounding member 10 Spring Plates 11 Annular section 12 Inner circumference end 13,14 Elastic part 17 Starting point 18 Cut and bent piece (bent section) 20 Flexible conductive material 22 Folded-over piece (bent section) 30 Spacers 50 bearings 51 Outer ring 52 Inner Ring 52a,60a end face 53 Rolling element 54 Cage 60 shaft 70 Housing 80 Retaining member 100 bearing unit
Claims
1. A shaft grounding member to be mounted on a rolling bearing unit that has an inner ring rotating type rolling bearing in which the outer ring is fixed to the housing and a shaft directly connected to the motor is fitted into the inner ring, A spring plate made of a thin sheet of conductive material is composed of an annular portion and an elastic portion that extends from the inner circumference end of the annular portion to the center of the annular portion, A soft conductive member is mounted on the side of the elastic portion facing the rolling bearing, In addition to being equipped, The soft conductive member is capable of contacting the end face of the shaft, The spring plate is provided with a plurality of bent portions that are bent in the axial direction on the annular portion facing the side surface of the outer ring, and which apply a pressing force to the outer ring by deforming themselves. A shaft grounding member for rolling bearings characterized by the following.
2. Each of the aforementioned bent portions is a cut-out piece formed by bending in the axial direction between a pair of notches cut out from the outer edge of the annular portion. The shaft grounding member for a rolling bearing according to claim 1.
3. Each of the aforementioned bent portions has a portion between a pair of notches cut out from the outer peripheral edge of the annular portion, which consists of one cut-out piece bent in one axial direction and another cut-out piece bent in the other axial direction. The shaft grounding member for a rolling bearing according to claim 1.
4. Each of the aforementioned bent portions is a folded piece formed by folding back in the axial direction a portion between a pair of notches cut out from the outer peripheral edge of the annular portion, or a portion extending radially from the outer peripheral edge of the annular portion. The shaft grounding member for a rolling bearing according to claim 1.
5. Each of the aforementioned bent portions has a portion between a pair of notches cut out from the outer peripheral edge of the annular portion, or a portion extending radially from the outer peripheral edge of the annular portion, which has one folded piece folded back to one side in the axial direction and the other folded piece folded back to the other side in the axial direction. The shaft grounding member for a rolling bearing according to claim 1.
6. The annular portion is pressed against the side surface of the outer ring with a spacer in between. The shaft grounding member for a rolling bearing according to claim 1.
7. The flexible conductive member is composed of at least one selected from a resin-impregnated nonwoven fabric, a nonwoven fabric, a resin-impregnated woven fabric, a woven fabric, a resin-impregnated flexible porous body, and a flexible porous body. The shaft grounding member for a rolling bearing according to claim 1.
8. The elastic portion of the spring plate is bent in the middle. The shaft grounding member for a rolling bearing according to claim 1.
9. The elastic portion of the spring plate is formed flush with the annular portion. The shaft grounding member for a rolling bearing according to claim 1.
10. It features an inner ring rotating type rolling bearing in which the outer ring is fixed to the housing and the shaft directly connected to the motor is fitted into the inner ring, A rolling bearing unit characterized by being fitted with a rolling bearing shaft grounding member according to any one of claims 1 to 9.