bearings

Abstract

The present invention provides a bearing that can suppress creep while preventing a decrease in rigidity and cracking of the fixed ring. [Solution] The bearing 100 according to the present invention comprises an inner ring 102, an outer ring 104, and a plurality of rolling elements 106 interposed between the inner ring and the outer ring, wherein one of the inner ring and the outer ring is a rotating ring and the other is a stationary ring, and a compressive stress layer 116 is formed on a part 114a of the outer peripheral surface 114 of the outer ring, which is the stationary ring, that is in contact with the housing 108, which is the mating member to which the outer ring is attached.

Description

Technical Field

[0001] The present invention relates to a bearing in which one of an inner ring and an outer ring is a rotating ring and the other is a fixed ring.

Background Art

[0002] A bearing includes an inner ring, an outer ring, and a plurality of rolling elements. In a structure where the outer ring of the bearing is attached to a housing by clearance fitting and a shaft is press-fitted into the inner ring so that the inner ring rotates together with the shaft, the inner ring is a rotating ring and the outer ring is a fixed ring. In such a bearing, outer ring creep may occur.

[0003] [[ID=!16]]For example, when an external force Fr is generated on the bearing, strain (elongation) occurs in the outer ring due to the rolling element load (contact reaction force Q) within the load zone, and the position of the strain also moves (propagates) along with the revolution motion of the rolling elements. Such strain propagation causes the outer ring to move relative to the housing, which is what is called outer ring strain creep.

[0004] Patent Document 1 describes a bearing device. This bearing device has a structure in which an inner raceway ring (inner ring) is attached to a shaft and rotates integrally with the shaft, and an outer raceway ring (outer ring) is clearance-fitted to a housing. As a result, the outer ring, which is the fixed ring, and the mating member, the housing, have a fitting surface extending in the circumferential direction. Further, a relief surface that divides the fitting surface over the entire width is formed on a part of the outer peripheral surface of the outer ring so as not to contact the housing on the relief surface.

[0005] In this bearing device, when the relief surface enters the load zone due to creep, a gap is formed between the outer peripheral surface of the outer ring and the housing. Therefore, even if the outer peripheral surface of the outer ring is deformed in a wave shape, it does not contact the housing due to the relief surface. For this reason, it is stated that the wave-like deformation of the outer peripheral surface of the outer ring does not act as a traveling wave that creeps the outer ring, and creep is suppressed thereafter.

Prior Art Documents

Patent Documents

[0006] Note: There seems to be a typo in the original text at line 16 where "いわゆる外輪歪クリープと呼ばれるものである" is translated as "いわゆる外輪歪クリープと呼ばれるものである" in the English version. It should be something like "which is what is called outer ring strain creep". I've corrected it in the translation above. [Patent Document 1] Patent No. 7152916 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in Patent Document 1, a gap is formed between the outer ring and the housing by a relief surface formed on a part of the outer circumference of the outer ring, so there is no mating member (housing) that receives the load of the rolling elements at the location of the relief surface. As a result the outer ring becomes more prone to deformation, which can reduce the overall rigidity of the bearing, and repeated deformation may cause the outer ring to crack.

[0008] In view of these problems, the present invention aims to provide a bearing that can suppress creep while preventing a decrease in rigidity and cracking of the fixed ring. [Means for solving the problem]

[0009] To solve the above problems, a typical bearing configuration according to the present invention comprises an inner ring, an outer ring, and a plurality of rolling elements interposed between the inner ring and the outer ring, wherein one of the inner ring and the outer ring is a rotating ring and the other is a stationary ring, and a compressive stress layer is formed on a part of the contact surface of the stationary ring that contacts the mating member to which the stationary ring is attached.

[0010] Preferably, the above-mentioned compressive stress layer extends across the entire width in the axial direction of the fixed wheel and covers 50% or more of the load area in the circumferential direction.

[0011] The above-mentioned compressive stress layer is preferably formed by shot peening or WPC. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a bearing that can suppress creep while preventing a decrease in rigidity and cracking of the fixed ring. [Brief explanation of the drawing]

[0013] [Figure 1] This figure illustrates a bearing in an embodiment of the present invention. [Figure 2] This diagram illustrates the forces acting on the bearing shown in Figure 1. [Figure 3] Figure 2 is a schematic diagram illustrating the principle of creep occurring in the bearing. [Figure 4] This figure illustrates the function of the compressive stress layer formed on the outer ring of the bearing in Figure 1. [Figure 5] This figure illustrates how creep is suppressed by the bearing shown in Figure 1. [Modes for carrying out the invention]

[0014] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values ​​shown in these embodiments are merely examples to facilitate understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustrations.

[0015] Figure 1 is a diagram illustrating a bearing 100 in an embodiment of the present invention. Figure 2 is a diagram illustrating the forces acting on the bearing 100 in Figure 1. The bearing 100 comprises an inner ring 102, an outer ring 104, and a plurality of rolling elements 106. The rolling elements 106 are interposed between the inner ring 102 and the outer ring 104 and roll between the inner ring 102 and the outer ring 104.

[0016] The bearing 100 is fitted into the housing 108 by clearance fitting, and the shaft 112 is press-fitted into the inner circumferential surface 110 of the inner ring 102. Thus, the bearing 100 is a rotating ring in which the inner ring 102 rotates together with the shaft 112, and a stationary ring in which the outer ring 104 is attached to the mating member (i.e., the housing 108).

[0017] Furthermore, in the bearing 100, as shown in FIG. 1, in a part 114a of the contact surface (outer peripheral surface 114) of the outer ring 104, which is a fixed ring, that contacts the housing 108, a compression stress layer 116 indicated by hatching is formed. The compression stress layer 116 is formed by shot peening or WPC (Wide Peening and Cleaning) (registered trademark), etc., although details will be described later. The WPC treatment is a surface modification technique in which fine particles are made to collide with the surface of a metal part at high speed, and is also referred to as fine particle peening.

[0018] As shown in FIG. 2, the bearing 100 is attached to the housing 108 and has a structure in which the shaft 112 is press-fitted into the inner ring 102. When this bearing 100 receives an external force Fr, the load is grounded from the shaft 112 to the inner ring 102, the rolling elements 106, the outer ring 104, and the housing 108, and a range (load zone A) in which the rolling elements 106 receive a contact reaction force Q (see FIG. 3(b)) is generated. Due to this contact reaction force Q and the rolling of the rolling elements 106, so-called outer ring distortion creep (hereinafter referred to as creep), in which the outer ring 104 moves relatively to the housing 108, may occur (see FIG. 3).

[0019] FIG. 3 is a schematic diagram for explaining the principle of creep occurring in the bearing 100 of FIG. 2. In the bearing 100, due to the contact reaction force Q of the rolling elements 106 generated in the load zone A, as shown in FIG. 3(a), distortion (elongation) occurs on the outer peripheral surface 114 of the outer ring 104. In the figure, a fixed point C between the outer peripheral surface 114 of the outer ring 104 and the housing 108 is shown.

[0020] The outer ring 104 of the bearing 100 receives the contact reaction force Q from the rolling elements 106 that roll in the direction indicated by the arrow D in FIG. 3(b). For this reason, in the outer ring 104, shrinkage due to compression (see the radial arrows Ea, Eb) and elongation (see the circumferential arrow G) occur, and then, shrinkage due to relaxation (see the circumferential arrows Ha, Hb) and elongation (see the radial arrow J) occur.

[0021] In this way, in the outer ring 104, as the rolling elements 106 roll, continuous shrinkage and elongation in the circumferential and radial directions occur, and the position of the strain also moves (propagates). Due to such strain propagation, minute slips (see arrows Ka and Kb) occur between the outer ring 104 and the housing 108, and creep occurs in which the outer ring 104 moves relatively with respect to the housing 108.

[0022] In the bearing 100 of the present embodiment, in order to suppress creep, a compressive stress layer 116 (see FIG. 1) is formed on a part 114a of the outer peripheral surface 114 of the outer ring 104. Further, as shown in FIG. 1, the compressive stress layer 116 is formed over the entire width in the axial direction of the outer ring 104. Furthermore, the compressive stress layer 116 is formed over 50% or more of the range (angle) of the load zone A shown in FIG. 2 in the circumferential direction of the outer ring 104.

[0023] FIG. 4 is a diagram for explaining the function of the compressive stress layer 116 formed on the outer ring 104 of the bearing 100 in FIG. 1. The compressive stress layer 116 is formed by subjecting a part 114a of the outer peripheral surface 114 of the outer ring 104 to shot peening or WPC as shown in FIG. 4(a). However, the compressive stress layer 116 is not limited to shot peening or WPC, and may be formed using other methods such as laser peening.

[0024] Specifically, by projecting a projection material (spherical particles 118) toward a part 114a of the outer peripheral surface 114 of the outer ring 104, the crystal structure is dislocated, compressive stress (see arrows La and Lb) is generated, and work hardening (surface treatment) of the yield region 120 occurs. Further, surface defects are improved (the pores and recesses in the metal structure are made uniform) by the depressions 122 formed by the spherical particles 118. In this way, a highly rigid compressive stress layer 116 is formed on a part 114a of the outer peripheral surface 114 of the outer ring 104.

[0025] In the bearing 100, as shown in Figure 4(b), a highly rigid compressive stress layer 116 formed on a portion 114a of the outer circumferential surface 114 of the outer ring 104 cancels out the strain generated in the outer ring 104 with the compressive stress indicated by arrow Lc, thereby reducing the strain generated on the outer circumferential surface 114 of the outer ring 104. As a result, the strain on the outer circumferential surface 114 of the outer ring 104 is reduced in the bearing 100.

[0026] Figure 5 illustrates how creep is suppressed by the bearing 100 shown in Figure 1. Figure 5(a) shows the state in which the hardened compressive stress layer 116 of the bearing 100 is located in the unloaded area B and outside the loaded area A at the start of rotation. In the bearing 100 shown in Figure 5(a), in the loaded area A, the circumferential displacement that acts as a traveling wave in the range Ma on the load area inlet side of the outer ring 104 is greater than the circumferential displacement that acts as a retreating wave in the range Mb on the load area outlet side. As a result, creep occurs in the bearing 100 shown in Figure 5(a), and the outer ring 104 moves in the rotational direction of the inner ring 102.

[0027] Next, in bearing 100, the outer ring 104 rotates due to creep, and as shown in Figure 5(b), the range Mc of the compressive stress layer 116 enters the load zone A. In this case, in the load zone A of bearing 100, the strain of the outer ring 104 is reduced in the range Mc of the compressive stress layer 116 within the range Ma on the load zone inlet side (see Figure 5(a)).

[0028] As a result, in the outer ring 104, a circumferential displacement that acts as a traveling wave occurs in the range Md (=Ma-Mc), which is the range Ma on the load zone inlet side minus the range Mc of the compressive stress layer 116. When the traveling wave in range Md becomes smaller than the retreating wave in range Mb, the rotation of the outer ring 104 stops and creep is suppressed.

[0029] In other words, in bearing 100, even if the compressive stress layer 116 is outside the load zone A at the start of rotation, when the outer ring 104 moves forward due to creep and approaches the load zone A, the traveling and retreating waves balance out, suppressing (stopping) the creep.

[0030] Therefore, with bearing 100, creep can be suppressed by forming a highly rigid compressive stress layer 116 on a part 114a of the outer circumferential surface 114 of the outer ring 104. In addition, bearing 100 does not form a gap between the outer circumferential surface 114 of the fixed ring outer ring 104 and the mating member housing 108, thus preventing a decrease in rigidity and cracking of the outer ring 104.

[0031] Furthermore, in the bearing 100, the compressive stress layer 116 is formed in the circumferential direction of the outer ring 104 over 50% of the load zone A. Therefore, when the outer ring 104 moves due to creep and the compressive stress layer 116 enters the load zone A, the strain generated on the outer circumferential surface 114 of the outer ring 104 can be sufficiently reduced by the compressive stress layer 116. In addition, since the compressive stress layer 116 extends across the entire width in the axial direction of the outer ring 104, the generation of strain can be reduced across the entire width in the axial direction of the outer ring 104 in the load zone A.

[0032] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these examples. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. [Industrial applicability]

[0033] This invention can be used as a bearing in which one of the inner ring and outer ring is a rotating ring and the other is a stationary ring. [Explanation of Symbols]

[0034] 100...bearing, 102...inner ring, 104...outer ring, 106...rolling element, 108...housing, 110...inner surface of inner ring, 112...shaft, 114...outer surface of outer ring, 114a...part of outer surface of outer ring, 116...compressive stress layer, 118...spherical particles, 120...yield region, 122...recess

Claims

1. In a bearing comprising an inner ring, an outer ring, and a plurality of rolling elements interposed between the inner ring and the outer ring, wherein one of the inner ring and the outer ring is a rotating ring and the other is a stationary ring, A bearing characterized in that a compressive stress layer is formed on a part of the contact surface of the fixed ring that contacts the mating member to which the fixed ring is attached.

2. The bearing according to claim 1, characterized in that the compressive stress layer is formed over the entire width in the axial direction of the fixed ring and over 50% or more of the load area in the circumferential direction.

3. The bearing according to claim 1 or 2, characterized in that the compressive stress layer is formed by shot peening or WPC (registered trademark).

Images