JP-7856205-B1 - Rolling bearings

Abstract

[Problem] To provide a rolling bearing that can prevent cracks and damage by sufficiently reducing bearing vibration, thereby improving durability. [Solution] The rolling bearing 10 comprises a pair of raceway rings (outer ring 1, inner ring 3) having a pair of opposing raceway surfaces (outer ring raceway surface 1a, inner ring raceway surface 3a), and a plurality of rolling elements 5 that are held to roll freely between the pair of raceway surfaces (outer ring raceway surface 1a, inner ring raceway surface 3a). The rolling elements 5 are made of alumina-zirconia ceramics. When the wobble component of the rolling elements 5 is separated into low band, medium band, and high band bands, the webbing values are LB(npc), MB(npc), and HB(npc), respectively, the webbing value LB is 100 npc or less, the webbing value MB is 100 npc or less, and the webbing value HB is 250 npc or less. [Selection Diagram] Figure 1

Inventors

• 坂井 祐太

Assignees

• 日本精工株式会社

Dates

Publication Date

20260511

Application Date

20250926

Claims (3)

1. A rolling bearing comprising a pair of raceway rings having a pair of opposing raceway surfaces, and a plurality of rolling elements held to roll freely between the pair of raceway surfaces, The rolling element is made of alumina-zirconia ceramics. When the wobble component of the rolling element is separated into low-band, medium-band, and high-band bandwidths, the resulting webiness values are denoted as LB(npc), MB(npc), and HB(npc), respectively. The webiness value LB is 100 npc or less, the webiness value MB is 100 npc or less, and the webiness value HB is 250 npc or less . A rolling bearing characterized in that the rolling elements contain 70% to 95% by volume of alumina, and a total of 5% to 30% by volume of zirconia and its stabilizer, wherein the content of the stabilizer is 2.0 mol% to 5.0 mol% relative to the content of the zirconia .
2. The rolling bearing according to claim 1, characterized in that the arithmetic mean roughness Ra of the rolling elements is 0.01 μm or less.
3. The rolling bearing according to claim 1 or 2 , characterized in that the stabilizer contains yttria.

Description

This invention relates to a rolling bearing that is mounted on rotating shafts of, for example, motors and generators, and is particularly suitable for mounting in areas where electric current may flow. Conventionally, in equipment with rotating bodies, metal bearings are fitted to the rotating shaft to reduce the frictional resistance caused by the rotation. For example, in motors that rotate a rotating body (so-called rotor) using electromagnetic force, and in generators that generate electricity by rotating a rotating body (so-called turbine) using hydraulic power, bearings are fitted to the rotating shaft of the rotating body. These motors and generators have a problem where current leaks into the bearings, leading to corrosion (electrolytic corrosion) caused by the current flow. Therefore, bearings using ceramic rolling elements are used not only to improve electrolytic corrosion resistance and corrosion resistance, but also for high-speed rotating devices and to improve wear resistance and acoustic resistance. Silicon nitride is a ceramic material used in bearings, exhibiting excellent rolling fatigue characteristics. In bearing components made of steel or silicon nitride, damage and cracks do not propagate. However, when alumina is used as the material for ceramic rolling elements, damage and cracks propagate because alumina has low toughness. Therefore, in recent years, bearings using ceramic materials with improved strength have been proposed by combining alumina ( Al₂O₃ ) with zirconia ( ZrO₂ ) . For example, Patent Document 1 proposes a rolling bearing in which at least the rolling surfaces of the inner ring, outer ring, and rolling elements are formed from a composite ceramic material, and the composite ceramic has main components made of alumina and zirconia. Patent Document 1 states that by specifying the content of alumina and zirconia in the main components, it is possible to obtain a composite ceramic material that is extremely corrosion-resistant, has excellent surface workability and mechanical strength, and has little strength reduction due to the crystal transformation of zirconia in water. Furthermore, Patent Document 2 discloses a rolling bearing in which at least one of the outer ring, inner ring, and rolling elements is made of a ceramic material mainly composed of Al₂O₃ and ZrO₂ . Patent Document 2 states that durability and mechanical strength can be improved by specifying the aggregate particle size of ZrO₂ in the ceramic material. Japanese Patent Application Publication No. 11-153142Japanese Patent Publication No. 2000-319064 Figure 1 is a cross-sectional view showing an example of a rolling bearing according to an embodiment of the present invention.Figure 2 is a micrograph showing the surface of the rolling element of the inventive example and comparative example. As a result of diligent research by the inventors of this invention, it has been discovered that by controlling the webiness value for each wobble component of the rolling elements, vibrations in rolling bearings can be sufficiently reduced, thereby preventing the occurrence of cracks and damage. The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below. [Rolling bearings] Figure 1 is a cross-sectional view showing an example of a rolling bearing according to an embodiment of the present invention. As shown in Figure 1, the rolling bearing 10 has a steel outer ring 1 having an outer ring raceway surface 1a on its inner circumferential surface, and a steel inner ring 3 having an inner ring raceway surface 3a on its outer circumferential surface. When the outer ring 1 and the inner ring 3 are combined, a raceway ring having a pair of opposing raceway surfaces is formed. In addition, a plurality of rolling elements 5 are arranged between the pair of raceway rings (between the outer ring raceway surface 1a and the inner ring raceway surface 3a). Each of these rolling elements 5 is held to roll freely by a cage 7 while being arranged at equal intervals in the circumferential direction. Furthermore, sealing members 9 are attached to both axial sides of the outer ring 1 and the inner ring 3, and these sealing members 9 hold the lubricating oil sealed between the outer ring 1 and the inner ring 3. <Rolling element> The rolling elements of the rolling bearing according to this embodiment will be described in detail below. (Composition: Alumina-zirconia ceramics) The rolling element 5 is made of alumina-zirconia ceramics. Unlike steel, ceramics are materials that hardly undergo plastic deformation. When steel rolling elements are used, any localized abnormal roughness (protrusions) disappear due to plastic deformation caused by "break-in" that occurs during the initial use of the bearing. However, in the case of ceramic rolling elements, since they do not undergo plastic deformation, there is a risk of minute damage or cracks occ