Manufacturing method for insulated rolling bearings
By measuring and controlling resin quantity based on intermediate product dimensions, the method addresses unstable molding issues, achieving consistent resin layer thickness and improved bearing quality.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NSK LTD
- Filing Date
- 2025-01-10
- Publication Date
- 2026-07-23
AI Technical Summary
Existing methods for manufacturing insulated rolling bearings face issues with unstable molding quality due to variations in intermediate product dimensions, leading to short shots, overpacking, and burrs, which affect the integrity and consistency of the resin layer.
A method involving weight measurement, volume calculation, and controlled resin injection during insert molding to ensure the correct amount of resin is applied, followed by grinding or cutting to achieve uniform resin layer thickness and high dimensional accuracy.
Prevents short shots and burrs, ensuring stable molding quality and high precision of the resin layer thickness, thereby enhancing the reliability of insulated rolling bearings.
Smart Images
Figure 2026121157000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing an insulated rolling bearing.
Background Art
[0002] For example, in bearings used in motors, generators, etc., if electric discharge occurs between the rolling elements and the outer ring raceway surface or between the rolling elements and the inner ring raceway surface, electric erosion may occur at the discharge part, which may significantly affect the bearing life. For example, in Patent Document 1, by defining the components of the resin layer composition of the resin layer formed on the outer circumferential surface of the outer ring, etc., a method for manufacturing an insulated rolling bearing is disclosed, which aims to achieve both heat dissipation and mechanical strength of the resin layer while maintaining good moldability.
Prior Art Documents
Patent Documents
[0003] [[ID=?]] [[ID=?]]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] [[ID=?]] However, the gap between the cavity of the insert mold into which the resin is injected and the intermediate product depends on the size of the intermediate product, and since the injection amount of the resin is constant, if the dimensions of the intermediate product vary, short shots may cause underfilling, or overpacking may cause burrs, etc., and there was a risk that the quality after molding would not be stable. [[ID=?]] In the insulated rolling bearing described in Patent Document 1, it was difficult to prevent underfilling due to short shots, generation of burrs due to overpacking, and difficulty in detaching the resin layer from the mold, etc., which were caused by variations in the dimensions of the intermediate product during insert molding. [[ID=?]] [[ID=?]]
[0005] [[ID=?]] It should be noted that the tags with "?" in the above translation are the original tags that seem to be incomplete or have some unclear parts in the original text, and they are directly retained as they are according to the requirements.This invention has been made in view of the aforementioned problems, and its purpose is to provide a method for manufacturing insulated rolling bearings with stable molding quality by preventing the occurrence of short shots, overpacking, and burrs that may occur during insert molding due to variations in the dimensions of intermediate products. [Means for solving the problem]
[0006] Therefore, the above objective of the present invention is achieved by the configuration described below [1] relating to a method for manufacturing an insulated rolling bearing. [1] A method for manufacturing an insulating rolling bearing comprising an inner ring and an outer ring, each having a raceway groove, and a plurality of rolling elements arranged to roll freely between the raceway grooves of the inner ring and the outer ring, wherein an electrically insulating resin layer is formed by insert molding on the circumferential surface and axial end face on the side opposite to the raceway groove and on the opposite side of the raceway groove of at least one of the inner ring and the outer ring, The aforementioned insert molding is A weight measurement step for measuring the weight of a ring-shaped metal intermediate product having the shape of the aforementioned raceway groove, A volume calculation step in which the volume of the intermediate product is calculated from the measured weight and density of the intermediate product, A resin quantity calculation step involves calculating the amount of resin required for insert molding by subtracting the volume of the intermediate product from the volume of the cavity of an insert mold for insert molding the resin layer into the intermediate product, An injection molding process in which the amount of resin calculated by controlling the injection molding machine that performs insert molding is injected to form the resin layer on the circumferential surface on the side opposite the raceway groove and on the axial end surface, A method for manufacturing an insulated rolling bearing equipped with [a specific feature]. [Effects of the Invention]
[0007] According to the method for manufacturing insulated rolling bearings of the present invention, it is possible to prevent short shots, overpacking, and burrs that may occur during insert molding due to variations in the dimensions of intermediate products, thereby obtaining insulated rolling bearings with stable molding quality. [Brief explanation of the drawing]
[0008] [Figure 1] Figure 1 is a process diagram illustrating the procedure for forming the outer ring of an insulated rolling bearing, and the assembly obtained by assembling the inner ring and balls to the formed outer ring. [Figure 2] Figure 2(a) is a cross-sectional view of an outer ring in which a resin layer of uniform thickness is insert-molded on the circumferential surface on the side opposite the raceway groove and on the axial end face using an insert mold and intermediate product of appropriate dimensions; Figure 2(b) is an enlarged view of the main part of Figure 2(a); Figure 2(c) is an enlarged view of the main part of an outer ring in which a resin layer is insert-molded into a large intermediate part; and Figure 2(d) is an enlarged view of the main part of an outer ring in which a resin layer is insert-molded into a small intermediate part. [Figure 3] Figure 3 is a process diagram illustrating the process of insert molding a resin layer into the raceway ring of an insulated rolling bearing according to the present invention. [Modes for carrying out the invention]
[0009] Hereinafter, one embodiment of the method for manufacturing an insulated rolling bearing according to the present invention will be described in detail with reference to the drawings. Figure 1 is a process diagram showing the procedure for forming an outer ring having a resin layer, and an assembly in which an inner ring and balls are assembled to the formed outer ring.
[0010] As shown in Figure 1 (Completed Assembly Diagram), the insulated rolling bearing 100 comprises an inner ring 11, an outer ring 13, and a plurality of balls (rolling elements) 15. The inner ring 11 and outer ring 13 are made of metal such as steel, and the ball 15 is made of steel or ceramic material. An inner ring raceway groove (raceway groove) 11a is formed on the outer circumferential surface of the inner ring 11, and an outer ring raceway groove (raceway groove) 13a is formed on the inner circumferential surface of the outer ring 13. Multiple balls 15 are arranged to roll freely between the inner ring raceway groove 11a and the outer ring raceway groove 13a.
[0011] On the outer ring 13, an electrically insulating resin layer 17 is formed over its entire circumference on the circumferential surface (circumferential surface) 13b on the side opposite the outer ring raceway groove 13a, and on the axial end faces 13c at both axial ends. At both axial ends of the outer ring raceway groove 13a, groove shoulders 13d are formed projecting radially inward. The groove shoulders 13d have an inner circumferential surface (groove shoulder circumferential surface) 13e at their projecting tips. The resin layer 17 is formed to wrap around from the axial end face 13c inward inwards, up to a portion of the outer circumference of the groove shoulder end face 13f on the axially outer side of the groove shoulder 13d. In other words, the resin layer 17 is formed to cover the outer circumference of the outer ring 13, which is the anti-raceway groove side circumferential surface 13b and the axial end face 13c.
[0012] For example, epoxy resin, fluororesin, polyamide, etc., can be used as the resin constituting the resin layer 17. A curing agent may be added to the resin film, such as epoxy resin or polyamide-imide resin. The thickness of the resin layer 17 can be, for example, 0.5 mm or more, with a minimum resin thickness of 0.3 mm. It may also be 2 mm or more depending on the conditions.
[0013] First, the procedure for forming the outer ring 13 will be explained. As shown in Figure 1, a metal intermediate product 21 is prepared (ST11) which is formed into a ring shape corresponding to the shape of the outer ring 13 by turning or the like. The intermediate product 21 has a groove shape that will become the outer ring raceway groove 13a, and groove shoulder shapes on both sides of the groove shape that are the same as the groove shoulders 13d of the outer ring 13. This intermediate product 21 is subjected to heat treatment such as quenching and annealing (ST12).
[0014] Next, a resin layer 17 is insert-molded around the entire circumference of the ring in the area of the intermediate product 21, from the anti-raceway groove side circumferential surface 13b, the axial end surface 13c, and the groove shoulder end surface 13f on the axial side from the axial end surface 13c (ST13). Specifically, the intermediate product 21 is placed in the cavity of the insert mold 25, and heated resin material is injected and solidified into the gap between the circumferential surface 13b on the side of the anti-raceway groove, the axial end face 13c, and the mold surface facing the region from the axial end face 13c to the groove shoulder end face 13f of the intermediate product 21.
[0015] At this time, as shown in FIGS. 2(a) and 2(b), if the dimensions of both the intermediate product 21 and the mold (cavity) 25 are appropriate, a resin layer 17 with a uniform wall thickness t is insert-molded. However, when the intermediate product 21 is formed by machining such as turning, generally the dimensional accuracy of the intermediate product 21 is not necessarily high-precision, about 0.1 mm, and there is a large variation.
[0016] Therefore, as shown in FIG. 2(c), when the dimension of the intermediate product 21 is large, the thickness t1 of the resin layer 17 at that part becomes thin. In addition, since the volume of the gap between the cavity and the intermediate product 21 becomes small, there is a risk of overpacking or burrs due to an excessive amount of injected resin relative to the gap volume.
[0017] On the other hand, as shown in FIG. 2(d), when the dimension of the intermediate product 21 is small, the thickness t2 of the resin layer 17 at that part becomes thick. In addition, since the volume of the gap between the cavity and the intermediate product 21 becomes large, it becomes a factor of short shot due to insufficient amount of injected resin relative to the gap volume. Thus, due to the variation in the dimension of the intermediate product 21, there is a variation in the thickness t of the resin layer 17, and there is a risk that a stable molding quality with a uniform thickness t of the resin layer 17 cannot be obtained. In addition, it becomes a cause of overpacking, burrs, and short shot.
[0018] In order to solve such problems, in the manufacturing method of the insulating rolling bearing of the present embodiment, insert molding is performed according to the procedure shown in FIG. 3.
[0019] First, as shown in FIG. 3, the weight of the machined metal intermediate product 21 is measured (ST13-1, weight measurement step).
[0020] Next, the measured weight of the intermediate product 21 is divided by the density of the constituent material of the intermediate product 21 (metal such as steel material in the present embodiment) to calculate the volume of the intermediate product 21 (ST13-2, volume calculation step).
[0021] Then, the volume of the cavity of the insert mold 25 is determined in advance (ST13-3), and then the volume of the intermediate product 21, which was determined in the volume calculation step, is subtracted from the volume of the cavity to calculate the volume of resin (resin amount) required for insert molding (ST13-4, resin amount calculation step).
[0022] Next, the required stroke of the cylinder is calculated by dividing the calculated volume of resin by the cross-sectional area of the injection molding machine's cylinder (ST13-5). Subsequently, the operation of the injection molding machine is controlled to activate the cylinder by the calculated required stroke to inject resin, thereby insert molding a resin layer 17 around the entire circumference of the ring in the area from the axial end face 13b on the non-raceway groove side of the intermediate product 21, to the axial end face 13c, and from the axial end face 13c to the axially inward groove shoulder end face 13f (ST13-6, injection molding process).
[0023] In this way, by controlling the amount of resin injected according to the size (volume) of each intermediate product 21, insert molding can be performed with the correct amount of resin, preventing overpacking, burrs, and short shots.
[0024] As shown in Figure 1, after insert molding the insulating resin, the resin layer 17 formed on the axial end face 13c of the intermediate product 21 is ground or cut to finish it to a predetermined width (ST14). Similarly, the outer diameter of the resin layer 17 formed on the circumferential surface 13b of the intermediate product 21 on the side opposite the raceway groove is also finished to a predetermined outer diameter by grinding or cutting (ST15).
[0025] For grinding the resin layer 17, it is preferable to use a grinding wheel that has a porous structure with gaps between the abrasive grains contained within it. By using such a porous grinding wheel, resin clogging of the grinding wheel during resin grinding can be prevented, and the lifespan of the grinding wheel can be extended.
[0026] Subsequently, the outer ring raceway groove 13a is further ground (ST16). The insulating rolling bearing 100 is completed by assembling the outer ring 13, inner ring 11, and ball 15 into an assembly.
[0027] In this way, by grinding the outer ring raceway groove 13a after processing the resin layer 17 on the non-raceway groove side circumferential surface 13b of the intermediate product 21, the coaxiality between the outer ring raceway groove 13a and the surface of the resin layer 17 on the non-raceway groove side circumferential surface 13b can be made highly accurate. Furthermore, even if the thickness of the resin layer 17 after insert molding is uneven, the resin layer 17 can be finished to high dimensional accuracy by grinding the formed resin layer 17.
[0028] Furthermore, the present invention is not limited to the embodiments described above, and can be modified, improved, and so on as appropriate.
[0029] As described above, the following matters are disclosed in this specification: (1) A method for manufacturing an insulating rolling bearing comprising an inner ring and an outer ring, each having a raceway groove, and a plurality of rolling elements arranged to roll freely between the raceway grooves of the inner ring and the outer ring, wherein an electrically insulating resin layer is formed by insert molding on the circumferential surface and axial end face on the side opposite to the raceway groove and on the opposite side of the raceway groove of at least one of the inner ring and the outer ring, The aforementioned insert molding is A weight measurement step for measuring the weight of a ring-shaped metal intermediate product having the shape of the aforementioned raceway groove, A volume calculation step in which the volume of the intermediate product is calculated from the measured weight and density of the intermediate product, A resin quantity calculation step involves calculating the amount of resin required for insert molding by subtracting the volume of the intermediate product from the volume of the cavity of an insert mold for insert molding the resin layer into the intermediate product, An injection molding process in which the amount of resin calculated by controlling the injection molding machine that performs insert molding is injected to form the resin layer on the circumferential surface on the side opposite the raceway groove and on the axial end surface, Equipped with, A method for manufacturing insulated rolling bearings. This configuration prevents short shots, overpacking, and burrs that may occur during insert molding, even if the dimensional accuracy of the intermediate product varies.
[0030] (2) The process further comprises grinding or cutting the resin layer formed on the circumferential surface on the side opposite the raceway groove and the axial end surface of the intermediate product, and grinding the raceway groove formed in the intermediate product. (1) A method for manufacturing an insulated rolling bearing. With this configuration, even if the thickness of the resin layer after insert molding is uneven, the dimensional accuracy of the raceway can be achieved with high precision. [Explanation of symbols]
[0031] 11 Inner circle 13 Outer ring 13a Outer ring raceway groove (raceway groove) 13b Counter raceway groove side circumferential surface 13c Axial end face 15 Balls (rolling elements) 17 Resin layer 21 Intermediate Products 25 Insert molds 100 Insulated Rolling Bearings
Claims
1. A method for manufacturing an insulating rolling bearing comprising an inner ring and an outer ring, each having a raceway groove, and a plurality of rolling elements arranged to roll freely between the raceway grooves of the inner ring and the outer ring, wherein an electrically insulating resin layer is formed by insert molding on the circumferential surface and axial end surface on the side opposite to the raceway groove and on the opposite side of the raceway groove of at least one of the inner ring and the outer ring. The aforementioned insert molding is A weight measurement step for measuring the weight of a ring-shaped metal intermediate product having the shape of the aforementioned raceway groove, A volume calculation step in which the volume of the intermediate product is calculated from the measured weight and density of the intermediate product, A resin quantity calculation step involves calculating the amount of resin required for insert molding by subtracting the volume of the intermediate product from the volume of the cavity of an insert mold for insert molding the resin layer into the intermediate product, An injection molding process in which the amount of resin calculated by controlling the injection molding machine that performs insert molding is injected to form the resin layer on the circumferential surface on the side opposite the raceway groove and on the axial end surface, Equipped with, A method for manufacturing insulated rolling bearings.
2. The process further comprises grinding or cutting the resin layer formed on the circumferential surface and axial end surface of the intermediate product opposite the raceway groove, and grinding the raceway groove formed in the intermediate product. A method for manufacturing an insulated rolling bearing according to claim 1.