Search

EP-4481216-B1 - RESIN-MADE BALL BEARING RETAINER AND BALL BEARING

EP4481216B1EP 4481216 B1EP4481216 B1EP 4481216B1EP-4481216-B1

Inventors

  • SUZUKI HIRONORI
  • OKAZAKI Yamato

Dates

Publication Date
20260506
Application Date
20230207

Claims (6)

  1. A resin cage for a ball bearing, the resin cage comprising: at least one circular ring portion; and a plurality of column portions extending in an axial direction from the circular ring portion, wherein balls of a ball bearing are rotatably holdable by cylindrical or partially cylindrical pockets formed between the column portions adjacent to each other, and the circular ring portion has a guide surface guided by an inner circumferential surface of an outer ring or an outer circumferential surface of an inner ring of the ball bearing, a roundness of the guide surface is 5 µm or less, differences between angles formed by centers of the pockets adjacent to each other and 360°/number of pockets are all within ± 0.1°, and orientations of centers of all the pockets are oriented toward one side in a circumferential direction and one side in the axial direction from an outer diameter side toward an inner diameter side.
  2. The resin cage for a ball bearing according to claim 1, wherein a sum of differences between angles, which are formed by a center of any one of the pockets and centers of the pockets adjacent to the one pocket on both sides, and 360°/number of pockets is within ± 0.1°.
  3. The resin cage for a ball bearing according to claim 1 or 2, wherein the orientations of the centers of all the pockets are within 1°.
  4. The resin cage for a ball bearing according to any one of claims 1 to 3, wherein a variation in bottom thicknesses of the pockets is 10 µm or less.
  5. The resin cage for a ball bearing according to any one of claims 1 to 4, wherein the resin cage is a crown cage or a double circular ring cage including a pair of the circular ring portions.
  6. A ball bearing comprising: an outer ring whose inner circumferential surface is formed with an outer ring raceway groove; an inner ring whose outer circumferential surface is formed with an inner ring raceway groove; a plurality of balls rollably disposed between the outer ring raceway groove and the inner ring raceway groove; and the resin cage for a ball bearing according to any one of claims 1 to 5.

Description

TECHNICAL FIELD The present invention relates to a resin cage for a ball bearing and a ball bearing, and for example, relates to a resin cage for a ball bearing and a ball bearing used in a dental air turbine, a cleaner, an electric tool, or the like in high-speed rotation. BACKGROUND ART In general, a resin cage applied to a ball bearing is produced by injection molding. Specifically, the cage is produced by forming a ring-shaped cavity corresponding to the cage in a mold, injecting a molten resin material (thermoplastic resin) from a resin injection gate provided in a peripheral edge portion of the cavity, cooling and solidifying the resin material. Patent Literature 1 discloses, as a resin cage, a crown cage including a spherical pocket and a double circular ring cage including a cylindrical pocket. In addition, in an angular contact ball bearing disclosed in Patent Literature 2, there is disclosed a resin cage including a pocket in which a cylindrical portion and a diameter-reduced portion are combined. CITATION LIST PATENT LITERATURE Patent Literature 1: JP2020-46069APatent Literature 2: JPH07-4439A Z P Patent Literature 3: DE 10 2015 214851 A1 SUMMARY OF INVENTION TECHNICAL PROBLEM In the resin cages disclosed in Patent Literatures 1, 2 and 3, it is generally indicated that pockets are equally distributed in a circumferential direction, but in practice, angles between the pockets vary, and the equal distribution is extremely slightly disrupted. In a case of a cylindrical pocket, it is generally indicated that a center of each pocket is also oriented to a bearing center, but in practice, the center of each pocket is oriented to the bearing center with the center of each pocket oriented in varying directions. For this reason, when the resin cage having variations in pocket disposition angles and pocket orientations as described above is used in high-speed rotation of, for example, dmn 1,000,000 or more, vibration of the cage may be large and a bearing life may be shortened. The present invention has been made in view of the above-described problems, and an object thereof is to provide a resin cage for a ball bearing and a ball bearing that can reduce vibration of a cage during bearing rotation and improve a bearing life. SOLUTION TO PROBLEM The above object of the present invention is obtained by a resin cage according to appended claim 1. ADVANTAGEOUS EFFECTS OF INVENTION According to the resin cage for a ball bearing and the ball bearing according to the present invention, the roundness of the guide surface is 5 µm or less, the differences between the angles formed by the centers of the adjacent pockets and 360°/number of pockets are all within ± 0.1°, and the orientations of the centers of all the pockets are oriented to the one side in the circumferential direction and the one side in the axial direction from the outer diameter side toward the inner diameter side, whereby vibration of the cage during bearing rotation can be reduced and a bearing life can be improved. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a vertical cross-sectional view of a main portion of a deep groove ball bearing in which a double circular ring cage according to a first embodiment of the present invention is incorporated.FIG. 2 is a perspective view of the double circular ring cage shown in FIG. 1.FIG. 3 is a schematic view showing a pocket orientation of the double circular ring cage.FIGS. 4A to 4D are schematic views showing four aspects of the pocket orientation of the double circular ring cage.FIG. 5 is a schematic view of the double circular ring cage, which shows a pocket equal distribution angle difference between pockets and the pocket orientation.FIG. 6 is a graph showing the pocket equal distribution angle difference between pockets in three cages according to the present embodiment.FIG. 7 is an unfolded view of the double circular ring cage showing a variation in bottom thicknesses of pockets.FIG. 8 is a schematic view of a double circular ring cage according to a comparative example, which shows a pocket equal distribution angle difference between pockets and a pocket orientation.FIG. 9 is a graph showing the pocket equal distribution angle difference between pockets in three cages as comparative examples.FIG. 10 is a graph showing a relationship between a roundness and a rotation life time.FIG. 11 is a graph showing a relationship between a maximum value of the pocket equal distribution angle difference between pockets, the number of pocket misorientations, and the rotation life time.FIG. 12 is a graph showing a relationship between a maximum value of a pocket orientation angle and the rotation life time.FIG. 13 is a perspective view of a crown cage as a modification. DESCRIPTION OF EMBODIMENTS Hereinafter, a resin cage for a ball bearing and a ball bearing in which the resin cage is incorporated according to an embodiment of the present invention will be described in detail with reference to the drawings. As shown