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EP-4542067-B1 - ELECTROLYTIC CORROSION PREVENTION MEMBER FOR ROLLING BEARING AND ELECTROLYTIC CORROSION PREVENTION ROLLING BEARING UNIT

EP4542067B1EP 4542067 B1EP4542067 B1EP 4542067B1EP-4542067-B1

Inventors

  • FURUYA, Masatomo
  • SETOI, MUTSUMI
  • MURAMATSU, FUMIMASA

Dates

Publication Date
20260513
Application Date
20240620

Claims (5)

  1. An electrolytic corrosion prevention member (1) for a rolling bearing (50), the electrolytic corrosion prevention member (1) being mounted on a rolling bearing unit (100) including the inner ring rotating type rolling bearing (50) in which an outer ring (51) is fixed to a housing (70) and a shaft (60) directly connected to a motor is fitted to an inner ring (52) in order to prevent electrolytic corrosion of the rolling bearing (50), the electrolytic corrosion prevention member (1) comprising: a spring plate (10) including an annular portion (11) and an elastic portion (13) that extends continuously from an inner peripheral side end portion (12) of the annular portion (11) to a center of the annular portion (11) and being formed of a thin plate of a conductive material; and a soft conductive member (20) mounted on a surface of the elastic portion (13) on a side facing the rolling bearing (50), wherein the soft conductive member (20) is capable of abutting against an end surface (60a) of the shaft (60), and wherein the soft conductive member (20) is made of at least one selected from a resin-impregnated non-woven fabric, a resin-impregnated woven fabric, and a resin-impregnated soft porous body.
  2. The electrolytic corrosion prevention member (1) for a rolling bearing (50) according to claim 1, wherein the annular portion (11) is pressed against a side surface of the outer ring (51) with a spacer (30) interposed therebetween.
  3. The electrolytic corrosion prevention member (1) for a rolling bearing (50) according to claim 1, wherein the elastic portion (13) of the spring plate (10) is bent halfway.
  4. The electrolytic corrosion prevention member (1) for a rolling bearing (50) according to claim 1, wherein the elastic portion (13) of the spring plate (10) is flush with the annular portion (11).
  5. An electrolytic corrosion prevention rolling bearing unit (100) comprising: an inner ring rotating type rolling bearing (50) in which an outer ring (51) is fixed to a housing (70) and a shaft (60) directly connected to a motor is fitted to an inner ring (52); and the electrolytic corrosion prevention member (1) for a rolling bearing (50) according to any one of claims 1 to 4.

Description

BACKGROUND 1. Field of the Invention The present disclosure relates to an electrolytic corrosion prevention member for a rolling bearing that prevents electrolytic corrosion of a rolling bearing in a rolling bearing unit, and an electrolytic corrosion prevention rolling bearing unit provided with the electrolytic corrosion prevention member for a rolling bearing. 2. Description of the Related Art In recent years, there has been a progress in practical use of an electric vehicle in which an electric motor serving as a drive source is provided inside or in the vicinity of the wheels to drive the wheels. Such a drive motor is generally called an in-wheel motor. The general in-wheel motor has a structure in which a stator is fixed to a motor housing and a rotor is provided on the inner diameter side of the stator with a gap in the radial direction, and is a so-called inner rotor type motor. As a drive method for the in-wheel motor, a brushless DC motor driven by an inverter is often used in consideration of the performance and the control performance of the motor. In the method of driving with the inverter, a potential difference occurs between the stator and the rotor due to the parasitic capacitance between the stator and the rotor. This potential difference generates a so-called shaft voltage and shaft current, and when this shaft current passes through the rolling bearing that supports the rotor, a phenomenon called "electrolytic corrosion" occurs that damages the rolling bearing. Specifically, the current flows locally in the contact portion between the raceway surfaces of the outer ring and the inner ring of the rolling bearing and the rolling elements, and the raceway surface or the rolling surface is melted and becomes uneven. This not only roughens the rolling surface and the rolling element surface of the bearing, causing the noise and the vibration, but also affects the life of the bearing if excessive electrolytic corrosion occurs. In order to prevent the electrolytic corrosion of the rolling bearing, a conductive member is sometimes used. For example, JP2011-135720A and JP2011-135722A propose a conductive member including a contact body that electrically conducts with the rotor of the motor, an elastic body that presses the contact body toward the rotor, and a storage portion that stores the contact body and the elastic body, in which the storage portion is provided in a motor housing and electrically connected to the motor stator via the motor housing. JP2020-127257A proposes a grounding device in which the distal end portion of a broom-shaped conductive fiber is brought into contact with the outer peripheral surface of a rotating shaft. Further, JP2002-146568A proposes an electrolytic corrosion prevention device in which an annular seat portion in contact with the end surface of a bearing outer ring is bent into a wave washer shape, an elastic conductor including a contact piece that is extended from the inner side of the annular seat portion and that is in contact with the vicinity of the end surface center portion of the rotating shaft is used, and the surface of the annular seat portion is pressed by the lid-shaped wall of a bearing housing and electrically conducted in the state in which the contact piece abuts against the vicinity of the end surface center portion of the rotating shaft fitted to the bearing inner ring, and in which the annular seat portion is overlapped with the end surface of the bearing outer ring fitted in the bearing housing. Further, JPH04-8820U proposes that a rod-shaped conductive brush is accommodated in a support hole formed in either one of two bearing rings, the distal end of the conductive brush is biased toward the other bearing ring and is brought into sliding contact with the other bearing ring by the elastic member, and the two bearing rings are electrically conducted. However, in the technique described above, the abrasion powder generated from the conductive member may contaminate the lubricating oil or the grease composition sealed for lubrication and may damage the raceway surface or the rolling surface. The mating member of the conductive member may be damaged and the abrasion powder may be generated. Specifically, in JP2011-135720A and JP2011-135722A, the contact body, the elastic body, and the storage body are metal members, and are brought into sliding contact with one another due to the vibration of the motor, so that the metal powder is generated. It is necessary to provide the contact body, the elastic body, and the storage body in the motor housing, and a space therefor is also required. In JP2020-127257A, the distal end portion of broom-shaped conductive fiber is brought into contact with the outer peripheral surface of the rotating shaft. However, in order to increase the contact area between the distal end portion of the broom-shaped conductive fiber and the rotating shaft as compared to when the distal end portion of the broom-shaped conductiv