JP2020159498A - Cross roller bearing - Google Patents

Abstract

To provide a cross roller bearing in which operation trouble is unlikely to occur due to skewing of a roller.SOLUTION: Crowning surfaces 3a, 3b on both sides of a roller 3 in an axial direction are formed asymmetrically so that in an axial cross section of the roller 3, an area between a virtual cylindrical surface C having a maximum diameter of the roller 3 and an outer peripheral surface of the roller 3 is larger on one end side (S1) of the roller 3 than on the other end side (S2), and the roller 3 is arranged so that the one end side is inclined toward an outer peripheral side of a bearing. Consequently, compared to the conventional one in which the outer peripheral surface of a roller is in linear contact with an inclined raceway surface on a load side of a raceway ring, the axial distribution of a speed transmitted from the raceway ring on a rotation side of the roller 3 is made uniform, the skewing of the roller 3 is suppressed, and smooth operation can be performed for a long period of time.SELECTED DRAWING: Figure 2

Description

The present invention relates to a cross roller bearing in which rollers are incorporated so that the inclination direction alternately changes in the circumferential direction between the outer ring and the inner ring.

A cross-roller bearing has a plurality of rollers bearing between a pair of inclined race planes formed on the inner peripheral surface of the outer ring and a pair of inclined race planes formed on the outer peripheral surface of the inner ring. It is arranged so that the inclination direction changes alternately in the circumferential direction, and is widely used in industrial machines such as reduction gears for robots as a bearing capable of supporting a large radial load, thrust load, and moment load.

For such a cross roller bearing, a cylindrical roller, which has a large production volume and is advantageous in terms of cost, is used as a roller, and in accordance with this, each inclination of the outer ring and the inner ring (hereinafter, collectively referred to as "track ring") is used. In many cases, the raceway surface is formed linearly in its axial cross section (see, for example, Patent Document 1).

Japanese Patent No. 3739056

FIG. 5 shows an example of a cross roller bearing using the above-mentioned roller made of cylindrical rollers. In this cross roller bearing, the outer ring 51 and the inner ring 52 are integrally formed, and the pair of inclined raceway surfaces 51a formed so as to be orthogonal to the inner peripheral surface of the outer ring 51 and the outer peripheral surface of the inner ring 52. Rollers 53 made of cylindrical rollers are arranged between the pair of inclined raceway surfaces 52a formed so as to be orthogonal to each other so that the inclined directions change alternately in the circumferential direction.

The pair of inclined orbital surfaces 51a of the outer ring 51 extend linearly to both sides in the axial direction from the relief groove 51b formed in the central portion of the inner peripheral surface of the outer ring 51 in the axial direction in the axial cross section, and one of them. The inclined track surface 51a is in linear contact with the outer peripheral surface of the roller 53. Similarly, the pair of inclined orbital surfaces 52a of the inner ring 52 extend linearly on both sides in the axial direction from the relief groove 52b formed in the central portion in the axial direction of the outer peripheral surface of the inner ring 52 in its axial cross section. One inclined track surface 52a is in linear contact with the outer peripheral surface of the roller 53. In the following description, among the inclined raceway surfaces of the raceway rings (outer ring and inner ring), the one that contacts the outer peripheral surface of the roller in the axial cross section is the "load side", and the one that does not contact the outer peripheral surface of the roller is ". It is called "non-load side".

Further, the axial dimension of the roller 53 is formed to be smaller than the distance between the inclined raceway surface 51a of the outer ring 51 and the inclined raceway surface 52a of the inner ring 52 facing each other, and the end surface of the roller 53 and the non-load side of the outer ring 51 are formed. A gap is formed between the inclined raceway surface 51a and the inclined raceway surface 52a on the non-load side of the inner ring 52.

However, in reality, the roller 53 is skewed during bearing operation (the rotation axis of the roller is tilted in the bearing circumferential direction), and the outer peripheral portion of the end surface of the roller 53 is the inclined raceway surface on the non-load side of the raceway rings 51 and 52. It may come into contact with 51a and 52a. It is considered that the occurrence of the skew of the roller 53 is due to the difference in peripheral speed in the axial direction on the inclined raceway surface of the raceway ring on the rotating side. That is, for example, as shown in FIG. 6, in the case of 52 rotations of the inner ring, the peripheral speed of the inclined raceway surface 52a is larger on the shaft end side on the large diameter side than on the shaft center side on the small diameter side, so that the roller 53 There is an axial difference in the speed transmitted from the inner ring 52, and a moment around the axial center of the roller 53 acts on the roller 53 to skew the roller 53. Similarly, in the case of 51 rotations of the outer ring, the peripheral speed of the inclined raceway surface 51a is larger on the shaft center side on the large diameter side than on the shaft end side on the small diameter side, so that the roller 53 is transmitted from the outer ring 51. There is an axial difference in speed and the roller 53 skews.

When the end face of the roller 53 comes into contact with the inclined raceway surfaces 51a and 52a on the non-load side of the raceway rings 51 and 52 due to the skew of the roller 53, the oil film may run out between the two, and the bearing may not be operated smoothly. ..

Therefore, an object of the present invention is to provide a cross roller bearing in which operation troubles due to roller skew are unlikely to occur.

In order to solve the above problems, the present invention has an outer ring having a pair of inclined orbital surfaces orthogonal to each other on the inner peripheral surface, an inner ring having a pair of inclined orbital surfaces orthogonal to each other on the outer peripheral surface, and a pair of the outer rings. In a cross roller bearing provided with a plurality of rollers arranged so as to alternately change the inclination direction in the circumferential direction between the inclined raceway surface and the pair of inclined raceway surfaces of the inner ring, the outer peripheral surface of the roller is , Asymmetric crowning is applied to the plane orthogonal to the axial direction at the axial center position of the roller, and the crowning has a virtual outer peripheral surface of the roller and the maximum diameter of the roller in the axial cross section of the roller. The area between the roller and the cylindrical surface is formed to be larger on one end side of the roller than on the other end side, and the roller adopts a configuration in which one end side is tilted toward the outer peripheral side of the bearing. did.

According to the above configuration, with respect to the load-side inclined raceway surface of the rotating raceway ring, one end side of the roller comes into contact with the side where the peripheral speed of the inclined raceway surface is large, and the contact surface pressure is the inclined raceway surface. It becomes smaller than the contact surface pressure between the side with the smaller peripheral speed and the other end side of the roller, and the non-uniformity of the speed transmitted from the raceway ring on the rotating side of the roller is alleviated. Skew is suppressed, and the end surface of the roller is less likely to come into contact with both the inclined raceway surface on the non-load side of the outer ring and the inclined raceway surface on the non-load side of the inner ring, so that the stability of bearing operation can be improved.

Here, the processing cost can be reduced by assuming that the roller is not crowned at the other end side.

As described above, the cross roller bearing of the present invention is provided with asymmetric crowning on the outer peripheral surface of the roller so that the axial distribution of the speed transmitted from the raceway ring on the rotating side of the roller is made uniform. Therefore, the skew of the rollers is suppressed, and smooth operation can be performed for a long period of time.

Longitudinal front view of the main part of the cross roller bearing of the embodiment (A) is a front view of the roller of FIG. 1, and (b) is an explanatory view of the asymmetry of the outer peripheral surface shape of the roller of (a). Explanatory drawing of roller behavior seen from above except for the outer ring of FIG. Front view showing a modified example of the outer peripheral surface shape of the roller Longitudinal front view of the main part of the conventional cross roller bearing Explanatory drawing of roller behavior seen from above except for the outer ring of FIG.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4. This cross roller bearing is an inner ring rotation type incorporated in a speed reducer for a robot, and as shown in FIG. 1, an outer ring 1 having a pair of inclined raceway surfaces 1a orthogonal to each other on the inner peripheral surface and an outer ring 1 on the outer peripheral surface. The inclination direction is alternately changed in the circumferential direction between the inner ring 2 having a pair of inclined raceway surfaces 2a orthogonal to each other and the pair of inclined raceway surfaces 1a of the outer ring 1 and the pair of inclined raceway surfaces 2a of the inner ring 2. It is provided with a plurality of rollers 3 to be arranged. The outer ring 1 and the inner ring 2 are integrally formed, and the rollers 3 are arranged in a state of being in contact with adjacent objects, that is, in a so-called full roller state.

The outer ring 1 and the inner ring 2 have the same configuration as the conventional one shown in FIG. 5, and the pair of inclined raceway surfaces 1a of the outer ring 1 have an axial center of the inner peripheral surface of the outer ring 1 in the axial cross section thereof. A pair of inclined raceway surfaces 2a of the inner ring 2 extending linearly from the relief groove 1b formed in the portion to both sides in the axial direction also have a relief formed in the central portion in the axial direction of the outer peripheral surface of the inner ring 2 in its axial cross section. It extends linearly from the groove 2b to both sides in the axial direction.

On the other hand, as shown in FIG. 2A, the roller 3 is subjected to crowning that is asymmetric with respect to a surface orthogonal to the axial direction at the axial center position on the outer peripheral surface thereof. Among them, the crowning surface 3a on one end side is a single R shape having an axial cross-sectional shape having a radius of curvature R, and is formed between the vicinity of the axial center of the roller 3 and the slanted surface 3c at the axial end. The crowning surface 3b on the other end side is the same as the crowning surface 3a on the one end side in that the axial cross-sectional shape is a single R shape having a radius of curvature R, but the axis is from the axial center of the roller 3. It is formed in a range of about half of the range up to the end sloping surface 3c on the shaft end side.

Therefore, as shown in FIG. 2B, considering the virtual cylindrical surface C having the maximum diameter of the roller 3 in the axial cross section of the roller 3, between the virtual cylindrical surface C and the outer peripheral surface of the roller 3. area, towards the area S ₁ of one end of the roller 3 is larger than the area S ₂ of the other end. In FIG. 2B, the gap between the virtual cylindrical surface C and the outer peripheral surface of the roller 3 is exaggerated.

Then, as shown in FIG. 1, the rollers 3 are arranged so that one end side thereof is inclined toward the outer peripheral side of the bearing, and the rollers 3 are arranged on the shaft end side (the side having a large peripheral speed) of the inclined raceway surface 2a on the load side of the inner ring 2. The contact surface pressure is set to be smaller than the contact surface pressure between the shaft center side (small peripheral speed side) of the inclined track surface 2a on the load side and the other end side of the roller 3. As a result, as shown in FIG. 3, the axial distribution of the velocity transmitted by the roller 3 from the inner ring 2 is when the outer peripheral surface of the roller is in linear contact with the inclined raceway surface on the load side of the raceway ring (FIG. 6). Compared to (see), it is more uniform.

This cross roller bearing has the above configuration, and the outer peripheral surface of the roller 3 is subjected to asymmetric crowning so that the axial distribution of the speed transmitted from the inner ring 2 of the roller 3 is made uniform. The skew of 3 is suppressed. Therefore, it is difficult for the end surface of the roller 3 to come into contact with both the inclined raceway surface 1a on the non-load side of the outer ring 1 and the inclined raceway surface 2a on the non-load side of the inner ring 2, and smooth operation can be performed for a long period of time.

Here, in the above-described examples of FIGS. 1 to 3, the crowning surfaces 3a and 3b are asymmetrically formed on one end side and the other end side of the outer peripheral surface of the roller 3, but as in the modified example shown in FIG. The crowning surface 3a may be formed only on one end side of the outer peripheral surface of the roller 3 without crowning the other end side (the side arranged on the outer side of the bearing) of the roller 3. If this modification is performed, the processing cost of the roller 3 can be reduced as compared with the examples of FIGS. 1 to 3.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

For example, the axial cross-sectional shape of the crowning surface of the roller is not limited to a single R shape as in the embodiment, and the area between the outer peripheral surface of the roller and the virtual cylindrical surface having the maximum diameter of the roller is one end of the roller. It suffices that the side is formed so as to be larger than the other end side, and a plurality of R shapes in succession or the like can be adopted.

Further, the cross roller bearing of the present invention is not limited to the inner ring rotation type in which the outer ring and the inner ring are integrally formed and the rollers are arranged in a fully roller state as in the embodiment, and either the outer ring or the inner ring is the shaft. Of course, it can also be applied to those which are divided in the direction, those in which rollers are arranged at equal intervals in the circumferential direction by a cage, and those in which the outer ring rotates.

1 Outer ring 1a Inclined track surface 1b Escape groove 2 Inner ring 2a Inclined track surface 2b Escape groove 3 Roller 3a, 3b Crowning surface 3c Slow surface C Virtual cylindrical surface

Claims (2)

An outer ring having a pair of inclined orbital surfaces orthogonal to each other on the inner peripheral surface, an inner ring having a pair of inclined orbital surfaces orthogonal to each other on the outer peripheral surface, a pair of inclined orbital surfaces of the outer ring, and a pair of inclined orbital surfaces of the inner ring. In a cross-roller bearing provided with a plurality of rollers arranged so as to alternately change the inclination direction in the circumferential direction.
The outer peripheral surface of the roller is subjected to crowning that is asymmetric with respect to the plane orthogonal to the axial direction at the axial center position of the roller, and the crowning is the outer peripheral surface of the roller in the axial cross section of the roller. The area between the roller and the virtual cylindrical surface having the maximum diameter is formed so as to be larger on one end side of the roller than on the other end side, and the roller is in a state where one end side is tilted toward the outer peripheral side of the bearing. A cross roller bearing characterized by being arranged. The cross roller bearing according to claim 1, wherein the roller is not crowned at an end portion on the other end side.

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