Housing for a thrust ball bearing and thrust ball bearing with such a housing

Abstract

Housing (1) for a thrust ball bearing, wherein the housing (1) has a plurality of recesses (2) configured to rollably hold balls (5) and arranged in a circumferential direction, wherein an inner surface of a recess (2) has a cylindrical surface (11) and a bearing surface (12) which is formed continuously with the cylindrical surface (11) and which is configured to contact a ball (5) in an axial direction, wherein the cylindrical surface (11) is formed with two projecting portions (13) at an equal distance in a circumferential direction of the recess (2), the two projecting portions (13) protruding from the cylindrical surface (11) on a ball insertion side of the recess (2) which is opposite to the support surface (12) in the axial direction, wherein the projecting portions (13) have circular arc surfaces (13a) projecting from the cylindrical surface (11) in the direction of the center of the recess (2) with a predetermined height and are designed to prevent the ball (5) from falling out of a ball insertion side opening (2a) of the recess (2), characterized in that the housing (1) is a copper alloy housing (1), the projecting portions (13) are elastically deformed or elastically-plastically deformed by the ball (5) during insertion of the ball (5) into the recess (2), and that when an inner diameter of a virtual circle (I) formed from the circular arc surfaces (13a) of the projecting portions (13) is denoted as X, a diameter of the sphere (5) is denoted as Da and a total interference value of the two projecting portions (13) with the sphere (5) in the radial direction is denoted as δ = Da - X, the relationship 0.001 Da < δ < 0.015 Da is satisfied.

Description

Technical field

[0001] The present invention relates to a housing for a thrust ball bearing and a thrust ball bearing with such a housing. A housing with the preamble features of claim 1 is known, for example, from CN 102 817 918 A. A similar housing made of a copper alloy is known from DE 266 093 A. Similar housings made of a synthetic resin are known from JP 2000 - 2 245 A, JP 2006 - 77 964 A, and JP 2008 - 2 652 A. State of the art

[0002] Since a thrust ball bearing is designed such that a shaft washer and a housing washer are separable from each other, it must be ensured that the balls do not easily fall out of the housing for ease of handling, such as attaching and detaching the bearing to and from a device.

[0003] A housing is a machined copper alloy housing used in a thrust ball bearing. As in Fig. As shown in Fig. 7, a conventional machined copper alloy housing 100 has a shape in which one side of a recess 101 holds a ball 102 in a truncated cone shape, and the other side of the recess 101 is cylindrical. Since the ball 102 is likely to fall out in this state when the ball is inserted into the recess 101 from the cylindrical side, the edge of the recess 101 is pressed at four positions P after the ball 102 is placed in the housing 100 to prevent the ball 102 from falling out.

[0004] Furthermore, a resin package has been proposed in which an entrance diameter of a package recess is set smaller than a ball diameter and in which the ball is arranged by elastic deformation (see, for example, Patent Document 1 and Patent Document 2). Citation list

[0005] Patent document 1: JP 2006 - 77 964 A; Patent document 2: JP 2008 - 2 652 A Summary of the inventionProblems to be solved

[0006] Furthermore, for a thrust ball bearing with an outer diameter exceeding approximately 300 mm, a resin housing is unsuitable in terms of shape and strength, and a pressed steel plate housing is also inferior to a machined copper alloy housing in terms of size limitations, rotational accuracy, high-speed performance, and the like. Furthermore, in the case of low production volume, it is desirable to use a machined copper alloy housing in terms of cost.

[0007] On the other hand, in the Fig. In the machined copper alloy housing 100 shown in FIG. 7, a pressing step is performed using a press machine or by hand with a hammer or the like when the size is large. Therefore, various problems such as a large workload and time, low productivity, unevenness in the pressing degree, deterioration in the accuracy of the recess shape, and defects in the external appearance occur.

[0008] Patent Documents 1 and 2 cover resin packages, but do not consider machined copper alloy packages.

[0009] The present invention has been conceived in view of the above problems, and it is an object of the present invention to provide a machined housing for a thrust ball bearing in which a ball can be easily inserted into a recess and in which a ball is difficult to fall out of the recess without deteriorating the functions of a machined copper alloy housing, a method of constructing the same, and a thrust ball bearing having the housing. Means to solve the problems

[0010] The object of the present invention is achieved by a housing for a thrust ball bearing according to one of claims 1 to 4 and a thrust ball bearing according to claim 5. Effects of the present invention

[0011] According to the machined housing for a thrust ball bearing of the present invention, an inner surface of a recess includes a cylindrical surface, a seating surface formed continuously with the cylindrical surface and contacting a ball in an axial direction, and the cylindrical surface is provided with two protruding portions spaced at an equal distance in a circumferential direction of the recess on a ball insertion side of the recess, which is opposite to the seating surface in the axial direction. Furthermore, the protruding portions are configured to prevent the ball from falling out of a ball insertion-side opening of the recess and are elastically deformable or elastically plastically deformable by the ball during insertion of the ball into the recess.Accordingly, the insertion of a ball into the recess is facilitated and the ball is difficult to fall out of the recess without compromising the functions of a machined copper alloy housing. Short description of the drawings Fig. 1 shows a cross-sectional view of a machined housing for a thrust ball bearing according to an embodiment of the present invention. Fig. 2 shows a partial plan view of the machined housing for a thrust ball bearing of the Fig. 1. Fig. 3A shows an enlarged cross-sectional view of the machined housing for a thrust ball bearing, and Fig. 3B shows an enlarged top view of the same. Fig. 4 is a diagram showing an FEM analysis of a relationship between an inner diameter of a protruding portion and a load when inserting and removing a ball into and from the housing. Fig. 5 is a diagram showing an FEM analysis of a relationship between a width of a protruding portion and a load when inserting and removing a ball into and from the housing. Fig. 6 shows a cross-sectional view of a machined housing for a thrust ball bearing according to a modification example of the present invention. Fig. 7A shows a cross-sectional view of a conventional machined copper alloy housing for a thrust ball bearing, and Fig. 7B shows an enlarged surface view of a main portion thereof. Description of the embodiments

[0012] Hereinafter, an embodiment of a machined housing for a thrust ball bearing according to the present invention and a thrust ball bearing having the machined housing for a thrust ball bearing will be described in detail with reference to the drawings.

[0013] As in Fig. 1 and Fig. As shown in Figure 2, a thrust ball bearing of the present embodiment includes a plurality of balls 5 and a machined copper alloy housing 1 having a plurality of recesses 2 that rollably support the balls 5 and are arranged at an equal interval in a circumferential direction. The plurality of balls 5 roll between a shaft washer and a housing washer, which are not shown in the drawings.

[0014] An inner surface of each recess 2 of the machined housing 1 includes a cylindrical surface 11 and a truncated conical bearing surface 12 formed continuously with the cylindrical surface 11, gradually and continuously decreasing in diameter, and contacting the ball 5 in the axial direction. The inner surface of the recess 2 is formed with protruding portions 13 at two positions on an inner diameter side and an outer diameter side of the housing 1, respectively. The protruding portions 13 protrude from the cylindrical surface 11 toward a center of the recess 2 at a ball insertion side of the recess 2 (closer to a ball insertion side opening of the cylindrical surface 11) located opposite the bearing surface 12 in the axial direction.

[0015] As in Fig. 3, in the present embodiment, the protruding portions 13 have a circular arc surface 13a while protruding from the cylindrical surface 11 toward the center of the recess 2 at a predetermined height, and have a predetermined width Y in a direction perpendicular to a radial direction of the housing 1. The protruding portions 13 have a predetermined axial length Z from a ball insertion-side end surface 1a of the housing 1, and seating-surface-side tip ends of the protruding portions 13 are inclined by an angle α.

[0016] The protruding portions 13 prevent the ball 5 from falling out of an opening side of the recess 2 and are configured to be elastically plastically deformed (a deformation comprising elastic deformation and plastic deformation) by the ball 5 during insertion of the ball 5 into the recess 2. Accordingly, the ball 5 is inserted into the recess 2 from the opening side of the recess 2 by elastically plastically deforming the protruding portions 13 while the protruding portions 13 are compressed.

[0017] As in Fig. 2, the plurality of recesses 2 are formed such that the ball insertion side openings 2a of the recesses 2 alternately face one side in the axial direction of the housing 1 and the other side in the axial direction. Thus, the bearing surfaces 12, as shown in Fig. 1 located on one side and the other side in the axial direction, are brought into contact with the balls 5, the machined housing 1 being formed so as not to contact a wave washer and a housing washer not shown in the drawings.

[0018] Herein, the projecting portions 13 of the present embodiment are configured to be defined depending on the ball diameter Da as shown below. (a) Inner diameter X (superposition) of the above sections 13

[0019] If, as in Fig. 3A, the inner diameter of a virtual circle 1 formed by circular arc surfaces 13a of the two protruding portions 13 is denoted as X and the total overlap amount of the two protruding portions 13 with the sphere diameter Da in the radial direction is denoted as δ (= Da - X), the inner diameter X of the protruding portions 13 is defined such that the relationship 0.001 Da < δ < 0.015 Da is satisfied.

[0020] Although preferably the inner diameter X is formed such that the projecting portions 13 are within an elastic deformation range when the ball 5 is inserted into the recess 2 of the housing 1, this is difficult in terms of productivity considering the tolerances of the ball 5, which is a steel ball, so that the inner diameter X, δ is defined in the manner described above.

[0021] It is sufficient that the force required to remove the ball 5 from the recess 2 (a withdrawal force) is large enough so that the inserted ball 5 does not easily slip out of the housing 1, and thus δ can be set to a larger value. However, if δ is set to a value that is too large, the force required to insert the ball 5 into the recess 2 (a plugging force) increases, so that it becomes more difficult to insert the ball, the ball is damaged, and the amount of plastic deformation increases, so that the problem of deterioration of the external appearance occurs.

[0022] Fig. Figure 4 shows an FEM analysis of the ball insertion and removal load for a thrust ball bearing housing with 19 balls, which has an inner diameter of 170 mm and an outer diameter of 215 mm. The horizontal axis shows a relationship between δ and the ball diameter Da, and the vertical axis shows a relationship between the withdrawal force and the insertion force. In this analysis, as described below, the width Y of the protruding portions 13 is set to 0.15 Da < Y < 0.70 Da. Since the ratio of the insertion force and the withdrawal force decreases with increasing δ, the efficiency of increasing δ for the sake of the withdrawal force is poor. The decrease in the ratio of the insertion force and the withdrawal force occurs due to the increasing plastic deformation value as δ increases, and thus the protruding portions 13 are compressed more, so the external appearance deteriorates. Therefore, the upper limit of δ is set to δ < 0.015 Da.

[0023] Furthermore, since the withdrawal force is small and the probability of the ball 5 falling out of the casing 1 during handling is high when δ is 0.001 Da or less, the lower limit δ is set to 0.001 Da < δ. (b) Width Y of the preceding sections 13

[0024] The width Y of the projecting portions 13 with respect to the ball diameter Da is defined such that the relationship 0.15 Da < Y < 0.70 Da is satisfied, and preferably defined such that the relationship 0.15 Da < Y < 0.40 Da is satisfied.

[0025] Fig. Figure 5 shows an FEM analysis of the loads during ball insertion and removal in and out of a housing for a 19-ball thrust ball bearing having an inner diameter of 170 mm and an outer diameter of 215 mm. The horizontal axis shows a relationship between the width Y and the ball diameter Da, and the vertical axis shows a relationship between the withdrawal force and the insertion force. In this analysis, the inner diameter X of the protruding portions 13 is set to a value that satisfies the aforementioned range of δ. The relationship between the withdrawal force and the insertion force is large when the width Y satisfies the relationship 0.15 Da < Y < 0.70 Da. However, when the width Y is set to 0.4 Da or more, the insertion force itself increases, and thus insertion becomes more difficult. Therefore, it is preferable to define the width Y as 0.15 Da < Y < 0.40 Da.

[0026] In the above configuration of the inner diameter X and the width Y, the FEM analysis is performed using a housing for a thrust ball bearing having an outer diameter of 215 mm, but the inner diameter X and the width Y specified depending on a ball diameter Da can be used when the thrust ball bearing has an outer diameter exceeding about 100 mm. (c) Axial length Z of the protruding sections 13

[0027] As described above, the plurality of recesses 2 are formed such that the ball insertion-side openings of the recesses 2 alternately face one side in the axial direction of the housing 1 and the other side in the axial direction, and the seating surfaces 12 located on one side and the other side in the axial direction are brought into contact with the balls 5, so that the machined housing 1 does not contact the shaft washer and the housing washer. In order to support the ball 5 by the truncated cone-shaped seating surface 12 and not contact the protruding portions 13, the axial length Z of the protruding portions 13 extending from the ball insertion-side end surface 1a of the housing 1 is defined so as to satisfy the following expression.

[0028] That is, if a distance from an axial end surface 1b of a seating surface side of the housing 1 to a height of the ball 5 protruding from the ball insertion side opening 2a of the recess 2 when the ball 5 contacts the seating surface 12 is denoted as S, a ball diameter is denoted as Da, and an inner diameter of a virtual circle I formed by the circular arc shapes 13a of the protruding portions 13 is denoted as X, and an axial length Z of the protruding portions 13 satisfies the formula (1). Incidentally, it is sufficient if a lower limit of Z 0 < Z. [Formula] Z <S−Da2−Da2−X22

[0029] In the present embodiment, the two protruding portions 13 are provided on the outer diameter side and the inner diameter side of the housing 1. The insertion force and withdrawal force of the balls 5 are affected, in addition to the shape of the protruding portions 13, by the wall thickness of portions in which the protruding portions 13 are provided. Since, as shown in Fig. 2, a wall thickness in the circumferential direction is determined based on the inner and outer diameters of the bearing, the ball diameter, and the number of balls, the insertion force and withdrawal force are greatly affected by the size of the bearing even in a housing using the balls 5 with the same ball diameter. Meanwhile, the wall thicknesses b and c of the inner diameter side and the outer diameter side are determined based on the ball diameter Da and the inner and outer diameters of the housing 1. The inner and outer diameters of the housing 1 can be arbitrarily selected with restrictions on the strength and size of the bearing, and the wall thickness W in the radial direction of the housing 1 is set to 1.2 Da < W < 1.5 Da, taking into account the restrictions on the strength and size of the bearing.Even if the dimensions of the bearings are different due to the specified wall thicknesses, it is possible to form the same recess shape as long as the wall thicknesses b and c are set to the same value and the same ball diameter is used, and thus it is possible to standardize the tools for machining the recesses 2, which can reduce the cost.

[0030] Thus, in the present embodiment, the two projecting portions 13 are provided on the outer diameter side and the inner diameter side of the housing 1, while the central positions thereof in the circumferential directions are arranged on a line L extending along the radial direction of the housing 1.

[0031] Furthermore, the material cost can be equal to that of a conventional housing by using the shape of the protruding portions 13 that do not protrude from the housing width. According to the machined housing 1 configured as described above, although the machining cost of the recesses 2 increases due to the complexity of the recess shapes, it is possible to omit a pressing process of the recesses 2, thereby ultimately reducing costs.

[0032] According to the machined housing 1 for a thrust ball bearing of the present embodiment, as described above, the inner surface of the recess 2 includes the cylindrical surface 11 and the seating surface 12 formed continuously with the cylindrical surface 11 and contacting the ball 5 in the axial direction. The cylindrical surface 11 is provided with two protruding portions 13 at equal intervals in a circumferential direction of the recess 2, which protrude from the cylindrical surface 11 on a ball insertion side of the recesses 2, which is opposite to the seating surface 12 in the axial direction. Further, the protruding portions 13 are formed to prevent the ball 5 from falling out of the ball insertion-side opening of the recess 2 and are elastically and plastically deformed by the ball 5 during insertion of the ball 5 into the recess 2.For this reason, without sacrificing the functions of the machined copper alloy housing 1, it becomes easier to insert the ball 5 into the recess 2, and the ball 5 is difficult to fall out of the recess 2.

[0033] Furthermore, according to the method of designing the machined housing 1 for a thrust ball bearing of the present embodiment, since the axial length Z and / or the inner diameter X and / or the width Y of the protruding portions 13 is / are defined depending on the ball diameter Da, it is possible to achieve an improvement in the insertion properties of the ball 5 into the recess 2 regardless of the size of the bearing and to prevent the ball 5 from falling out of the recess 2.

[0034] However, the present invention is not limited to the above-described embodiment and modification examples, and appropriate modifications, improvements, and the like may be made.

[0035] In the above-described embodiment, the support surface 12 of the recess 2 has a truncated cone shape, but the present invention is not limited thereto. For example, the support surface 12 may have a shape such as the mortar-shaped support surface 12 as shown in Fig. 6, as long as it contacts the ball 5 in the axial direction and the ball 5 does not slip out of the side opposite to the opening side of the recess 2.

[0036] Furthermore, two projecting portions are preferably provided on the inner diameter side and the outer diameter side of the housing 1, respectively, but another arrangement may be made as long as the projecting portions are provided at the same interval in the circumferential direction of the recess 2.

[0037] Furthermore, the machined housing for a thrust ball bearing of the present invention can also be applied to a single or double thrust ball bearing.

[0038] Further, the projecting portions 13 are elastically-plastically deformed by the ball 5 when the ball 5 is inserted into the recess 2, but if it is possible to form the tolerances of the balls 5 and the inner diameter X of the projecting portions 13 with a smaller value, a structure in which the ball 5 is inserted by elastic deformation may be used.

[0039] Furthermore, the material of the balls 5 is not limited to a steel ball of the previously described embodiment and may also comprise, for example, a ceramic ball.

[0040] This application is based on Japanese Prior Art Patent Application No. 2014-53726 filed on March 17, 2014. List of reference symbols 1 Machined housing for a thrust ball bearing 2 recess 5 balls 11 Cylinder surface 12 support surface 13 Previous section X inner diameter Y Width Z axial length

Claims

[1] Housing (1) for a thrust ball bearing, wherein the housing (1) has a plurality of recesses (2) configured to rollably hold balls (5) and arranged in a circumferential direction, wherein an inner surface of a recess (2) has a cylindrical surface (11) and a bearing surface (12) which is formed continuously with the cylindrical surface (11) and which is configured to contact a ball (5) in an axial direction, wherein the cylindrical surface (11) is formed with two projecting portions (13) at an equal distance in a circumferential direction of the recess (2), the two projecting portions (13) protruding from the cylindrical surface (11) on a ball insertion side of the recess (2) which is opposite to the support surface (12) in the axial direction, wherein the projecting portions (13) have circular arc surfaces (13a) projecting from the cylindrical surface (11) in the direction of the center of the recess (2) with a predetermined height and are designed to prevent the ball (5) from falling out of a ball insertion side opening (2a) of the recess (2), characterized by , that the housing (1) is a copper alloy housing (1), the projecting portions (13) are elastically deformed or elastically-plastically deformed by the ball (5) during insertion of the ball (5) into the recess (2), and that when an inner diameter of a virtual circle (I) formed from the circular arc surfaces (13a) of the projecting portions (13) is denoted as X, a diameter of the sphere (5) is denoted as Da and a total interference value of the two projecting portions (13) with the sphere (5) in the radial direction is denoted as δ = Da - X, the relationship 0.001 Da < δ < 0.015 Da is satisfied. [2] A housing (1) for a thrust ball bearing according to claim 1, wherein the two projecting portions (13) are provided on an inner diameter side and an outer diameter side of the housing (1). [3] A housing (1) for a thrust ball bearing according to claim 1 or 2, wherein the plurality of recesses (2) are formed such that the ball insertion side openings (2a) of the recesses (2) alternately face one side in the axial direction of the housing (1) and the other side in the axial direction, and wherein, when a distance from an axial end face (1b) of a seating surface side of the housing (1) to a height of the ball (5) protruding from the ball insertion side opening (2a) of the recess (2) when the ball (5) contacts the seating surface (12) is defined as S, and an axial length Z of the protruding portions (13) extending from a ball insertion side end face of the housing satisfies formula (1). [Formula 1] Z <s−da2−da2−x22[4] A housing (1) for a thrust ball bearing according to any one of claims 1 to 3, wherein when a width of the projecting portions (13) is designated as Y, the relationship 0.15 Da < Y < 0.70 Da is satisfied. [5] Thrust ball bearing with a housing (1) according to one of claims 1 to 4.

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