Method for manufacturing resin holder

Abstract

This method for manufacturing a resin cage is provided with: a step in which two or more types of resin materials having different contents of reinforcing fibers are blended such that the amount of reinforcing fibers contained in a molded cage (50) becomes a desired amount of reinforcing fibers; and a step in which the holder (50) is molded using a resin material obtained by blending two or more types of resin materials, and molding is performed such that the amount of reinforcing fibers contained in the molded holder (50) is uniform over the entire holder (50).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a resin cage that achieves an increase in mechanical strength by incorporating reinforcing fibers into a resin material. Background Art

[0002] Conventionally, metal materials such as iron and high-strength brass have been used as cages for rolling bearings. However, with the improvement of the performance of resin materials, resin cages formed by injection molding of resin materials are often used from the viewpoint of weight reduction and the like. In addition, for resin cages, in order to improve mechanical strength, reinforcing fibers such as glass fibers are sometimes incorporated into the resin material.

[0003] Patent Document 1 discloses a cage for a rolling bearing that uses two or more resin materials having different mixing ratios of reinforcing fibers to mold a welded portion and a portion other than the welded portion, and suppresses a decrease in the strength of the welded portion.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent No. 6626255 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] When a cage is injection-molded using a resin material containing reinforcing fibers, and the reinforcing fibers are composed of glass fibers such as glass fiber (グラスファイバー), carbon fibers, etc., the amount of dimensional shrinkage of the resin material varies depending on the content of the reinforcing fibers. Therefore, the mold size is determined in consideration of the dimensional shrinkage amount that varies depending on the content of the reinforcing fibers, so that the size of the molded product becomes the desired size. That is, it is necessary to prepare molding dies with different sizes according to the content of the reinforcing fibers in the resin material used in molding.

[0009] As described above, since the molding die is manufactured in consideration of the dimensional shrinkage amount caused by the content of the reinforcing fibers, when it becomes difficult to obtain a resin material having the content of the reinforcing fibers assumed at the time of manufacturing the molding die, it is necessary to remanufacture an expensive molding die according to the content of the reinforcing fibers of the available resin material, and there is a problem of a large economic burden.

[0010] In addition, the cage for a rolling bearing described in Patent Document 1 is formed by using two or more resin materials to suppress a reduction in the strength of the welded portion. However, the blending ratio of the reinforcing fibers is different between the welded portion and the non-welded portion (in Japanese: other than the welded portion), so the amount of dimensional shrinkage is different between the welded portion and the non-welded portion, the roundness of the inner and outer diameters of the cage deteriorates, and there is a possibility that the rotational accuracy of the cage decreases, leading to vibration and abnormal noise. In addition, it is an invention different from the technique of controlling the dimensional accuracy of a resin cage molded by controlling the content of glass fibers in the entire resin cage, which is the object of the present invention.

[0011] The present invention has been completed in view of the above problems, and an object thereof is to provide a method for manufacturing a resin cage that facilitates the supply of a resin material and can control the dimensional accuracy of the resin cage.

[0012] Means for Solving the Problems

[0013] The above object of the present invention is achieved by the following configuration.

[0014] [1] A method for manufacturing a resin cage, wherein

[0015] the resin cage holds the rolling elements of a rolling bearing so as to be rotatable freely,

[0016] the method for manufacturing the resin cage includes:

[0017] a step of blending two or more resin materials having different contents of reinforcing fibers so that the amount of reinforcing fibers contained in the resin cage after molding becomes a desired amount of reinforcing fibers; and

[0018] a step of molding the resin cage using the resin material obtained by blending the two or more resin materials and molding in such a manner that the amount of the reinforcing fibers contained in the resin cage after molding is uniform over the entire resin cage

[0019] Effects of the Invention

[0020] According to the method for manufacturing a resin cage and the resin cage of the present invention, the supply of the resin material becomes easy, and the dimensional accuracy of the resin cage can be controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a cross-sectional view of a radial ball bearing having the resin cage of the present invention.

[0022] Figure 2 is Figure 1 a perspective view of the resin cage shown. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of a radial ball bearing having the resin cage of the present invention will be described in detail based on the accompanying drawings.

[0024] As Figure 1 shown, the radial ball bearing 10 according to this embodiment includes: an outer ring 20 having an outer ring raceway 21 on its inner peripheral surface; an inner ring 30 having an inner ring raceway 31 on its outer peripheral surface and arranged concentrically with the outer ring 20; and a plurality of balls 40 that are rotatably provided between the outer ring raceway 21 and the inner ring raceway 31. Each ball 40 is held at equal intervals in the circumferential direction and rotatably in a pocket 51 provided in the cage 50.

[0025] As Figure 2 shown, the cage 50 is a resin cage called a so-called crown cage formed by injection molding of a synthetic resin, and is integrally formed as a whole. The cage 50 includes an annular base portion 52 and a plurality of column portions 53 that project axially at equal intervals in the circumferential direction from one axial side surface of the base portion 52 ( Figure 2 the upper side surface). And, the portions surrounded by the opposing circumferential side surfaces of each pair of adjacent column portions 53 in the circumferential direction and the axial one side surface of the base portion 52 are respectively used as the pockets 51.

[0026] When the radial ball bearing 10 is used, as each ball 40 rolls, the outer ring 20 and the inner ring 30 rotate relative to each other. At this time, each ball 40 rotatably held by the cage 50 revolves around the inner ring 30 while rotating on its own axis. In addition, the cage 50 rotates around the inner ring 30 at the same speed as the revolution speed of each of the above-mentioned balls 40.

[0027] The cage 50 is formed, for example, by injecting a thermoplastic resin such as polyamide resin (PA), polyphenylene sulfide resin (PPS), or polyacetal resin (POM) into the cavity of a molding die. In this thermoplastic resin, the mechanical strength is improved by mixing reinforcing fibers such as glass fibers.

[0028] As described above, in order to obtain the desired dimensional accuracy, the cage 50 is manufactured by a molding die that takes into account the dimensional shrinkage of the thermoplastic resin for injection molding. In addition, the dimensional shrinkage of the thermoplastic resin mixed with glass fibers after molding varies depending on the glass fiber content. Therefore, in a molding die designed and manufactured for a thermoplastic resin with a certain glass fiber content, if a thermoplastic resin with a different glass fiber content is used to mold the cage 50, there will be a difference in the dimensional accuracy of the cage 50 as a product.

[0029] If the dimensional accuracy of the formed cage 50 results in a small clearance between the pocket 51 and the ball 40, the pocket 51 will strongly restrict the ball 40, which becomes the main cause of early ablation. In addition, if the clearance between the pocket 51 and the ball 40 is large, the revolution behavior of the cage 50 becomes large, which becomes the main cause of abnormal noise and vibration. Moreover, even if the cage 50 is designed not to interfere with the outer ring 20 and the inner ring 30, if the deviation of the outer inner diameter dimension of the cage is large, it may also interfere with each other, resulting in wear and early ablation of the cage 50. That is, the dimensional accuracy of each part of the cage 50 needs to converge within a certain dimensional tolerance.

[0030] On the other hand, the molding die is made considering the dimensional shrinkage caused by the glass fiber content. Therefore, when it becomes difficult to obtain a resin material with the glass fiber content assumed when making the molding die, in order to maintain the dimensional accuracy of the cage 50, it is necessary to remanufacture the molding die according to the resin material with the glass fiber content that can be obtained. In particular, when such cages 50 involve multiple varieties, the cost increase caused by remanufacturing multiple molding dies becomes a major problem.

[0031] Therefore, the manufacturing method of the resin cage of the present embodiment proposes an effective method in the case where it becomes difficult to obtain the resin material with the desired glass fiber content as described above. That is, by mixing multiple resin materials with different glass fiber contents, as the resin material with the desired glass fiber content, the conventional molding die can be used.

[0032] In addition, by appropriately mixing multiple resin materials with different glass fiber contents and controlling the glass fiber content of the resin material, it is possible to use the same molding die to mold resin cages with different dimensional accuracies.

[0033] Specifically, for a molding die designed and manufactured for a resin material with a glass fiber content of A%, when it is difficult to obtain a resin material with a glass fiber content of A%, by appropriately mixing a resin material with a glass fiber content of B% that is more than the glass fiber content of A% and a resin material with a glass fiber content of C% that is less than the glass fiber content of A%, the overall glass fiber content is controlled to make a resin material with a glass fiber content of A%.

[0034] In addition, it is also possible to appropriately mix a resin material with a glass fiber content of B% that is more than A% and a resin material without glass fiber (glass fiber content of 0%) to make a resin material with an overall glass fiber content of A%. In addition, the resin materials to be mixed are not limited to 2 types, and may also be 3 types or more.

[0035] In this way, by combining a variety of resin materials with different glass fiber contents, a resin material with a glass fiber content of A% is produced, and a forming mold designed for use with the resin material with a glass fiber content of A% is used to injection-mold the cage 50. It should be noted that a variety of resin materials with different glass fiber contents are preferably mixed as evenly as possible during the mixing of the resin materials (before injection molding), so that the amount of glass fiber in the molded cage 50 can be evenly formed over the entire cage 50.

[0036] As a result, over the entire cage 50, the resin material and the amount of glass fiber are evenly formed, and the dimensional deviation of the molded cage 50 in the circumferential direction is small, and good roundness can be maintained.

[0037] As described above, by combining a variety of resin materials with different glass fiber contents to produce a resin material with a desired glass fiber content, even when the supply of the resin material with the desired glass fiber content becomes difficult, it is possible to replace the supply of the resin material, improving the supplyability of the resin material. In addition, there is no need to manufacture a new forming mold, reducing the supply burden of the forming mold.

[0038] In addition, by controlling the glass fiber content of the resin material by using the manufacturing method of the resin cage of the present invention, it is possible to control the dimensions of the cage 50 using the same forming mold, and it is also possible to handle cages 50 with slightly different internal design dimensions.

[0039] In addition, the present invention is not limited to the above-described embodiments, and can be appropriately deformed, improved, etc. For example, in the above-described embodiment, a crowned cage used in a ball bearing is described, but it is not limited thereto, and it can also be similarly applied to other types of resin cages used in cylindrical roller bearings, tapered roller bearings, needle roller bearings, etc.

[0040] Moreover, in the above-described embodiment, as the reinforcing fiber, a type of glass fiber, i.e., glass fiber (グラスファイバー), is described, but it is not limited thereto, and it can also be similarly applied to resin cages containing other reinforcing fibers such as carbon fiber.

[0041] As described above, the following matters are disclosed in this specification.

[0042] (1) A method for manufacturing a resin cage that rotatably holds rolling elements of a rolling bearing, wherein,

[0043] The method for manufacturing the resin cage includes:

[0044] A step of combining two or more resin materials having different contents of reinforcing fibers in such a manner that the amount of reinforcing fibers contained in the resin cage after molding becomes the desired amount of reinforcing fibers; and

[0045] A step of molding the resin cage using the resin material combined with the two or more resin materials and molding in such a manner that the amount of the reinforcing fibers contained in the resin cage after molding is uniform over the entire resin cage.

[0046] According to this structure, by combining two or more resin materials having different contents of reinforcing fibers and molding in such a manner that the amount of reinforcing fibers contained in the resin cage after molding is uniform over the entire resin cage, it is possible to improve the supplyability of the resin material and to control the dimensional accuracy of the resin cage.

[0047] According to this structure, even for resin materials having different contents of reinforcing fibers, it is possible to obtain a resin cage with controlled dimensional accuracy.

[0048] As described above, various embodiments have been described, but the present invention is of course not limited to this example. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and these modification examples or correction examples also of course belong to the technical scope of the present invention. In addition, within the scope not departing from the gist of the invention, the constituent elements in the above-described embodiments can be arbitrarily combined.

[0049] In addition, this application is based on a Japanese patent application filed on December 16, 2022 (Japanese Patent Application No. 2022-201398), the content of which is incorporated herein by reference.

[0050] Explanation of Reference Numerals

[0051] 10 Radial ball bearing (rolling bearing)

[0052] 40 Ball (rolling element)

[0053] 50 Cage

Claims

1. A method for manufacturing a resin cage, characterized in that: The resin cage holds the rolling elements of a rolling bearing so as to be rotatable freely; The method for manufacturing the resin cage comprises: A step of mixing two or more resin materials having different contents of reinforcing fibers so that the amount of reinforcing fibers contained in the resin cage after molding becomes a desired amount of reinforcing fibers; And A step of molding the resin cage using the resin material obtained by mixing the two or more resin materials, and molding the resin cage so that the amount of the reinforcing fibers contained in the resin cage after molding is uniform over the entire resin cage.

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