Resin retainer for rolling bearing and rolling bearing

Abstract

To provide a resin retainer that undergoes little dimensional change and does not hinder assembly work of rolling elements.SOLUTION: In a resin retainer 1 for a rolling bearing, a ratio of dimensional change is less than 0.16%, and polyacetal (POM) is a preferable form of the resin. A rolling bearing is provided with the resin retainer 1 for the rolling bearing, and is suitable for use as a speed reduction mechanism used in a joint portion of a robot arm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resin cage for a rolling bearing, and to a rolling bearing including such a cage. [Background technology]

[0002] In rolling bearings, a cage is installed between the outer ring and the inner ring to hold multiple rolling elements in an evenly distributed manner, and a resin cage is also used from the viewpoints of weight reduction, productivity, etc. Furthermore, for resin cages, a resin composition that uses polyamide as a base resin and is mixed with reinforcing fibers such as glass fibers, as described in Patent Document 1, for example, is often used because of its high heat resistance and high strength. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-55412 Summary of the Invention [Problem to be solved by the invention]

[0004] However, polyamide has a high water absorption rate and undergoes significant dimensional changes due to water absorption, which can cause dimensional changes during storage and transportation, making it impossible to assemble the rolling elements.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a resin cage which has a small amount of dimensional change and does not impede the assembly work of the rolling elements. [Means for solving the problem]

[0006] As a result of intensive research into solving the above problems, the inventors discovered that when the dimensional change rate is 0.16% or more, it becomes impossible to assemble the rolling elements, and thus completed the present invention. That is, the above object of the present invention is achieved by the following configuration [1] related to a resin cage for a rolling bearing.

[0007] [1] A plastic cage for a rolling bearing, A resin cage for a rolling bearing, characterized in that the resin cage has a dimensional change rate of less than 0.16%.

[0008] Further, preferred embodiments of the present invention relating to a resin cage for a rolling bearing relate to the following [2] and [3].

[0009] [2] A resin cage for a rolling bearing according to [1], characterized in that it is for a rolling bearing having a bearing temperature of 100°C or less. [3] A plastic retainer for a rolling bearing according to [1] or [2], characterized in that it is made of a plastic material containing polyacetal (POM), or a plastic material containing polyamide (PA) and 30 mass% or more of reinforcing fibers.

[0010] The above object of the present invention is achieved by the rolling bearing having the following configuration [4].

[0011] [4] A rolling bearing in which a number of rolling elements are held between an outer ring and an inner ring by a cage so as to be freely rollable at equal intervals, A rolling bearing, wherein the retainer is the resin retainer for a rolling bearing according to any one of [1] to [3].

[0012] Furthermore, preferred embodiments of the present invention relating to the rolling bearing relate to the following [5] and [6]. [5] A rolling bearing according to [4], characterized in that the bearing temperature is 100°C or less. [6] A rolling bearing as described in [4] or [5], characterized in that it is for use in a reduction mechanism used in a joint portion of a robot arm. Effect of the Invention

[0013] The resin cage for rolling bearings of the present invention has a dimensional change rate of less than 0.16%, so that the assembling work of the rolling elements can be carried out without any trouble.

[0014] Furthermore, since the rolling bearing of the present invention is equipped with a resin cage with a dimensional change rate of less than 0.16%, assembly work can be performed smoothly and productivity is high. In particular, it is suitable as a rolling bearing for applications such as reduction gears in the spectator parts of robot arms that rotate at low speeds, have low loads, and do not experience high bearing temperatures, enabling stable rotation. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a side cross-sectional view showing an example of a resin cage for a rolling bearing according to the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a main portion of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and can be modified and implemented as desired without departing from the gist of the present invention.

[0017] [Resin cage for rolling bearings] Fig. 1 is a side cross-sectional view showing an example of a plastic cage for rolling bearings of the present invention (hereinafter simply referred to as a "plastic cage"), showing a plastic cage 1 for a tapered roller bearing for a reduction mechanism used in a joint of a robot arm. Fig. 2 is an enlarged cross-sectional view of a main part of Fig. 1, and Fig. 2 is an enlarged cross-sectional view of the plastic cage for rolling bearings 1 shown in Fig. 1, particularly showing the periphery of the area where main body 10, tapered rollers 20 (rolling elements) and inner ring 30 are arranged.

[0018] As shown in Figs. 1 and 2, there is no limitation on the shape of the resin cage 1, and as shown in Fig. 2, a plurality of pockets 15 are opened at equal intervals along the circumferential direction of the annular main body 10.

[0019] Tapered rollers 20 are held in each pocket 15, but as a result of extensive research by the inventors, it was found that if the dimensional change rate of the resin cage 1 becomes greater than or equal to 0.16%, the claws of the pockets 15 will come into contact with the tapered rollers 20, making assembly impossible. Therefore, in the present invention, the resin cage 1 is manufactured from a resin material with a dimensional change rate of less than 0.16%. Note that the resin material constituting the resin cage 1 preferably has a dimensional change rate of less than 0.16%, more preferably a dimensional change rate of less than 0.1%, and even more preferably a dimensional change rate of less than 0.05%. In this embodiment, the "dimensional change rate" refers to the dimensional change rate at room temperature (RT) of 23°C.

[0020] An example of the resin material is polyacetal (POM). The dimensional change rate of polyacetal (POM) is 0.1% or less, which is extremely small. In addition, it has excellent wear resistance and impact resistance, and has a low coefficient of friction with metal rolling elements due to its self-lubricating properties, making it suitable for the resin retainer 1. Polyacetal (POM) may be used alone or may contain reinforcing fibers such as glass fibers. That is, the resin material may be polyacetal (POM) alone or may be polyacetal (POM) containing a predetermined amount of reinforcing fibers. The content of the reinforcing fibers is appropriately selected depending on the type and application of the rolling bearing in which the resin retainer 1 is incorporated, and is, for example, 10% by mass or more, preferably 15% by mass or more, and more preferably 25% by mass or more, based on the total amount of materials constituting the resin retainer 1 for bearing.

[0021] In addition, polyamide (PA) has a high water absorption rate and a dimensional change rate of 0.16% or more, but the dimensional change rate can be reduced by adding a specified amount of reinforcing fibers, so that the dimensional change rate can be reduced to less than 0.16% by adding 30 mass% or more, preferably 40 mass% or more, and more preferably 50 mass% or more of reinforcing fibers to the total amount of material constituting the resin cage 1 for bearings.

[0022] In order to prevent deterioration due to heat during molding and use, the resin material may contain additives such as iodide-based heat stabilizers and amine-based antioxidants, either alone or in combination. EXAMPLES

[0023] Example 1 Polyacetal (POM) was used alone as the resin material to create a resin cage for tapered roller bearings as shown in Figures 1 and 2. The water absorption rate of polyacetal (POM) is approximately 0.2% (23°C, 50% RH, 24 hr), and the dimensional change rate is 0.1% or less. When the tapered rollers were assembled using the resin cage created, there was no interference between the tabs and the tapered rollers, and the process was easy.

[0024] Example 2 Polyamide containing 30% by mass of glass fiber (Polyamide 610, Asahi Kasei Corporation) was used as the resin material to manufacture a resin cage for tapered roller bearings as shown in Figure 1. This polyamide has a water absorption rate (23°C, 50% RH, 24 hr) of 0.9% and a dimensional change rate of 0.18%, but by setting the dimensional tolerance during processing to be 0.02% smaller, the assembly work of the tapered rollers could be carried out without any problems.

[0025] Comparative Example 1 Using polyamide 66 as the resin material, we produced a resin cage for tapered roller bearings as shown in Figures 1 and 2. This polyamide 66 had a water absorption rate (23°C, 50% RH, 24 hr) of 2.5% and a dimensional change rate of 0.5%, making it difficult to assemble the tapered rollers.

[0026] Comparative Example 2 Polyamide 66 containing 25% by mass of glass fiber was used as the resin material to manufacture a resin cage for tapered roller bearings as shown in Figure 1. This polyamide 66 containing 25% by mass of glass fiber had a water absorption rate (23°C, 50% RH, 24 hr) of 1.9% and a dimensional change rate of 0.4%, making the assembly of tapered rollers difficult.

[0027] [Rolling bearings] The present invention also relates to a rolling bearing in which a plurality of rolling elements (tapered rollers 20) are held by a cage between an outer ring and an inner ring so as to be freely rollable at equal intervals, the rolling bearing including the above-mentioned resin cage 1. There is no limitation on the type of rolling bearing, but the rolling bearing is particularly suitable for a rolling bearing of a reduction mechanism used in a joint part of a robot arm. As described above, polyacetal (POM) is suitable as a resin with small dimensional change, but since the heat resistance temperature of polyacetal (POM) is about 100°C, when polyacetal (POM) is used, a rolling bearing with a bearing temperature of 100°C or less is preferable. The joint part of a robot arm rotates forward and backward at a low speed, the load applied to the bearing is small, and the bearing temperature is generally 100°C or less, so the resin cage 1 of the present invention can be preferably used.

[0028] The present invention is not limited to the above-described embodiment and modified examples, and can be modified, improved, etc. as appropriate. For example, in the above embodiment, a tapered roller bearing is used as an example of a rolling bearing, but the present invention is not limited to a tapered roller bearing, and can be applied to other types of rolling bearings, such as a cylindrical roller bearing. [Explanation of symbols]

[0029] 1 Plastic cage 10 Main body 15 Pocket 20 Tapered roller 30 Inner Circle

Claims

1. A resin cage for a rolling bearing, A resin cage for a rolling bearing, characterized in that the resin cage has a dimensional change rate of less than 0.16%.

2. 2. The resin cage for a rolling bearing according to claim 1, which is for a rolling bearing having a bearing temperature of 100° C. or less.

3. 2. The resin cage for a rolling bearing according to claim 1, characterized in that it is made of a resin material containing polyacetal (POM) or a resin material containing polyamide (PA) and 30 mass % or more of reinforcing fibers.

4. A rolling bearing in which a plurality of rolling elements are held by a cage between an outer ring and an inner ring so as to be freely rollable at equal intervals, A rolling bearing, wherein the cage is the resin cage for rolling bearings according to any one of claims 1 to 3.

5. 5. The rolling bearing according to claim 4, characterized in that the bearing temperature is 100° C. or less.

6. 5. The rolling bearing according to claim 4, which is for use in a reduction mechanism used in a joint portion of a robot arm.

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