JP2021011917A - Cross roller bearing - Google Patents

Abstract

To provide a cross roller bearing hardly causing edge load and suppressing skew of a roller.SOLUTION: Edge load hardly occurs by combining a projected curve-shaped cross-sectional shape of an outer peripheral surface of a roller and recessed curve-shaped cross-sectional shapes of inclined raceway surfaces of an outer ring and an inner ring, and the inclined raceway surfaces of the outer ring and the inner ring are asymmetric in an axial direction of the roller. On an axial cross-section of the outer ring, an area of a negative clearance δ1 between the inclined raceway surface and an outer peripheral surface of the roller is increased at a shaft end side of the outer ring with respect to an axial center side of the outer ring, and on an axial cross-section of the inner ring, an area of a negative clearance δ2 between the inclined raceway surface and the outer peripheral surface of the roller is increased at an axial center side of the inner ring with respect to a shaft end side of the inner ring, thus an axial distribution of a speed transmitted to the roller from a rotation-side raceway ring is unified, and skew of the roller can be suppressed.SELECTED DRAWING: Figure 3

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 the outer ring and the inner ring (hereinafter, collectively referred to as "track ring") are inclined in accordance with the cylindrical roller. In many cases, the raceway surface is formed linearly in its axial cross section.

FIG. 4 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 orbital surfaces 52a formed so as to be orthogonal to each other so that the inclined directions alternate 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".

However, in the cross roller bearing in which the outer peripheral surface of the roller 53 and the inclined raceway surfaces 51a and 52a on the load side of the raceway rings 51 and 52 are in linear contact with each other, between the outer peripheral surface and the end surface of the roller 53. When the boundary portion (edge) of the raceway ring 51, 52 comes into contact with the inclined raceway surfaces 51a, 52a on the load side, a local excessive surface pressure (edge load) is generated, the raceway wheels 51, 52 are damaged, and the bearing. There is a problem that the life is shortened.

In response to this, the axial cross-sectional shape of the outer peripheral surface of the roller is formed into a convex curve shape, and the axial cross-sectional shape of each inclined raceway surface of the raceway ring is a concave curve corresponding to the convex curve shape of the outer peripheral surface of the roller. It has been proposed that edge loading is less likely to occur by forming the shape (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 9-126233

By the way, the cross roller bearing has a problem of roller skew in addition to the above-mentioned edge load.

That is, to explain the cross roller bearing having the general configuration shown in FIG. 4, the axial dimension of the roller 53 is based on 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. Is also formed small so that a gap is formed between the end surface of the roller 53 and the inclined raceway surface 51a on the non-load side of the outer ring 51 and between the inclined raceway surface 52a on the non-load side of the inner ring 52. Actually, the roller 53 is skewed during the 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 51a on the non-load side of the raceway rings 51 and 52. , 52a may come into contact.

It is considered that the occurrence of this roller skew is caused by 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. 5, when the inner ring 52 rotates, the peripheral speed of the inclined track surface 52a is larger on the shaft end side on the large diameter side than on the axial center side on the small diameter side. There is an axial difference in the speed transmitted by the roller 53 from the inner ring 52, and a moment around the axial center of the roller 53 acts on the roller 53, causing the roller 53 to skew. Similarly, when the outer ring 51 rotates, the peripheral speed of the inclined raceway surface 51a is larger on the axial center side on the large diameter side than on the shaft end side on the small diameter side, so that the roller 53 transmits from the outer ring 51. There is an axial difference in the speed at which the roller 53 is skewed.

When the end surface of the roller 53 comes into contact with the inclined raceway surfaces 51a and 52a on the non-load side of the raceway wheels 51 and 52 due to the skew of the roller 53, the bearing torque becomes large and smooth operation may not be possible.

This roller skew problem cannot be solved by implementing edge load countermeasures as proposed in Patent Document 1.

Therefore, an object of the present invention is to provide a cross roller bearing in which edge load is unlikely to occur and roller skew can be suppressed.

In order to solve the above problems, the present invention presents 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. A plurality of rollers arranged so as to alternately change the inclined direction in the circumferential direction are provided between the inclined track surface of the above and the pair of inclined track surfaces of the inner ring, and the outer peripheral surface of the roller has an axial cross section thereof. The shape is formed into a convex curve shape, and each inclined raceway surface of the outer ring and each inclined raceway surface of the inner ring are formed into a concave curve shape whose axial cross-sectional shape corresponds to the convex curve shape of the outer peripheral surface of the roller. In the cross-roller bearing, the rollers are arranged in a preloaded state between the outer ring and the inner ring, and each inclined orbital surface of the outer ring is negatively connected to the outer peripheral surface of the roller in its axial cross section. The structure is formed so that the clearance area is larger on the axial end side of the outer ring than on the axial center side of the outer ring, and each inclined orbital surface of the inner ring is the outer peripheral surface of the roller in the axial cross section. It is assumed that at least one of the configurations formed so that the area of the negative gap between them is larger on the axial center side of the inner ring than on the axial end side of the inner ring is adopted. The "axial cross-sectional shape" here is also simply referred to as a "cross-sectional shape" in the following description.

That is, in a cross roller bearing in which edge load is less likely to occur by combining the convex curved cross-sectional shape of the outer peripheral surface of the roller and the concave curved cross-sectional shape of each inclined raceway surface of the raceway ring, the raceway ring on the rotating side For the inclined track surface on the load side, the contact surface pressure between the roller and the side with a large peripheral speed of the inclined track surface should be smaller than the contact surface pressure between the inclined track surface with a small peripheral speed and the roller. As a result, the non-uniformity of the speed transmitted from the rotating race wheel in the axial direction of the roller can be alleviated, and the skew of the roller can be suppressed.

Here, either one of the outer ring and the inner ring may be divided in the axial direction, or both may be integrally formed. Further, the rollers may be arranged by a cage at equal intervals in the circumferential direction, or may be arranged in a state of being in contact with adjacent objects, that is, in a so-called full roller state.

As described above, the cross roller bearing of the present invention combines the convex curved cross-sectional shape of the outer peripheral surface of the roller with the concave curved cross-sectional shape of each inclined raceway surface of the raceway ring to make edge load less likely to occur. At the same time, by making the distribution of the negative clearance between the inclined raceway surface of the raceway ring and the outer peripheral surface of the roller asymmetric, the axial distribution of the speed transmitted from the raceway ring on the rotating side of the roller is made uniform, and the roller Since the skew is suppressed, 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) and (b) are explanatory views of the cross-sectional shape of the inclined raceway surface of the outer ring and the inner ring of FIG. 1, respectively. (A) and (b) are explanatory views of the axial distribution of the negative clearance between the roller of FIG. 1 and the outer ring and the inner ring, respectively. Longitudinal front view of the main part of the conventional cross roller bearing Explanatory drawing of the behavior of the roller 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 3. This cross roller bearing is of 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 cross-sectional shape of the outer peripheral surface of the roller 3 is formed into a convex curve shape. The pair of inclined raceway surfaces 1a of the outer ring 1 extend from the relief grooves 1b formed in the central portion of the inner peripheral surface of the outer ring 1 in the axial direction in the axial cross section thereof, and extend to both sides in the axial direction. It is formed in a concave curve shape corresponding to the convex curve shape of the surface. Similarly, the pair of inclined raceway surfaces 2a of the inner ring 2 also extend in both axial directions from the relief groove 2b formed in the axial center portion of the outer peripheral surface of the inner ring 2 in the axial cross section thereof, and are the outer peripheral surfaces of the roller 3, respectively. It is formed in a concave curve shape corresponding to the convex curve shape of. In FIG. 1 and FIG. 2 described later, the shapes of the inclined raceway surfaces 1a and 2a of the raceway rings (outer ring 1 and inner ring 2) and the outer peripheral surfaces of the rollers 3 are exaggerated.

Here, as shown in FIGS. 2A and 2B, the cross-sectional shapes of the inclined raceway surfaces 1a and 2a of the raceway rings 1 and 2 come into contact with the axially central portion of the outer peripheral surface of the roller 3 in the assembled state, respectively. The R shape is the base of the region to be formed, and the R shapes having different radii of curvature are continuous on both sides thereof. Among them, the cross-sectional shape of the inclined raceway surface 1a of the outer ring 1, the smallest radius of curvature R ₁₀ of the base of the R shape, the radius of curvature R _1a in the axial center of the R shape of the outer ring 1 in the axial end of the outer ring 1 It is formed to be smaller than the radius of curvature R _1b of the R shape (FIG. 2 (a)). Further, as for the cross-sectional shape of the inclined raceway surface 2a of the inner ring 2, the radius of curvature R ₂₀ of the base R shape is the smallest, and the radius of curvature R _2a of the R shape on the axial center side of the inner ring 2 is on the shaft end side of the inner ring 2. It is formed larger than the radius of curvature R _2b of the R shape (FIG. 2 (b)).

On the other hand, the cross-sectional shape of the outer peripheral surface of the roller 3 is an R shape having a constant radius of curvature before being assembled. Then, the roller 3 is in a preload state between the outer ring 1 and the inner ring 2, that is, a state in which a gap between the outer peripheral surface of the roller 3 and the inclined raceway surfaces 1a and 2a on the load side of the raceway rings 1 and 2 is inflicted. It is built in.

Then, by setting the radius of curvature of each R shape formed by the cross-sectional shapes of the inclined raceway surfaces 1a and 2a of the raceway rings 1 and 2 and the outer peripheral surface of the roller 3 as described above, the roller 3 and the raceway in the embedded state are set. The roller axial distributions of the negative clearances δ ₁ and δ ₂ as shown in FIGS. 3 (a) and 3 (b) are formed between the wheels 1 and ₂ . Also in FIG. 3, the negative gaps δ ₁ and δ ₂ are exaggerated.

As can be seen from FIG. 3A, the area of the negative clearance δ ₁ between the outer peripheral surface of the roller 3 and the inclined raceway surface 1a of the outer ring 1 is closer to the shaft end side of the outer ring 1 than the axial center side of the outer ring 1. Is getting bigger. Further, as can be seen from FIG. 3B, the area of the negative clearance δ ₂ between the outer peripheral surface of the roller 3 and the inclined raceway surface 2a of the inner ring 2 is in the axial direction of the inner ring 2 with respect to the axial end side of the inner ring 2. It is larger on the center side.

Further, as shown in FIG. 1, the axial dimension of the roller 3 is formed to be smaller than the distance between the inclined raceway surface 1a of the outer ring 1 and the inclined raceway surface 2a of the inner ring 2 facing each other, and the end surface and the outer ring of the roller 3 are formed. A gap is formed between the inclined raceway surface 1a on the non-load side of 1 and the inclined raceway surface 2a on the non-load side of the inner ring 2.

This cross roller bearing has the above configuration, the cross-sectional shape of the outer peripheral surface of the roller 3 is formed into a convex curve shape, and the cross-sectional shape of the inclined raceway surfaces 1a and 2a of the raceway rings 1 and 2 is the outer peripheral surface of the roller 3. Since it is formed in a concave curve shape corresponding to the convex curve shape, edge load is less likely to occur as compared with the conventional one in which the outer peripheral surface of the roller is in linear contact with the inclined raceway surface on the load side of the raceway ring.

Moreover, since the negative clearances δ ₁ and δ ₂ between the roller 3 and the raceway wheels 1 and ₂ have an asymmetric roller axial distribution as shown in FIGS. 3 (a) and 3 (b), they rotate. Regarding the inclined orbital surface 2a on the load side of the inner ring 2 which is the side orbital ring, the contact surface pressure between the inclined orbital surface 2a on the side having a large peripheral speed (shaft end side) and the roller 3 is the peripheral speed of the inclined orbital surface 2a. It becomes smaller than the contact surface pressure between the small side (center side in the axial direction) and the roller 3, the non-uniformity of the speed transmitted from the inner ring 2 of the roller 3 in the axial direction is alleviated, and the skew of the roller 3 is suppressed. Be done.

Therefore, in this cross roller bearing, the bearing wheels 1 and 2 are damaged by the edge load, or the roller 3 comes into contact with the inclined raceway surfaces 1a and 2a on the non-load side of the raceway wheels 1 and 2 due to skew, and the bearing torque increases. It is hard to slip and can be operated smoothly for a long period of time.

Further, since the end face of the roller 3 is less likely to come into contact with the inclined raceway surfaces 1a and 2a on the non-load side of the raceway wheels 1 and 2, the surface processing of the end surface of the roller 3 may be changed from the conventional grinding process to turning processing. It can be omitted to reduce the roller manufacturing cost.

The depth of the recesses of the inclined raceway surfaces 1a and 2a of the raceway rings 1 and 2 and the height of the convex portion of the outer peripheral surface of the roller 3 are exaggerated in FIGS. 1 and 2, but are actually several μm. Since the above effect is exhibited even with a degree, it is possible to easily process by setting conditions according to the size of the bearing, the preload amount, and the like.

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 not by the above description but by the scope of claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims are included.

For example, in the embodiment, the cross-sectional shapes of the inclined raceway surface 1a of the outer ring 1 and the inclined raceway surface 2a of the inner ring 2 are asymmetrical shapes that suppress the skew of the roller 3, but the inclined raceway surface of the outer ring One of the cross-sectional shapes of the inclined orbital surface of the inner ring is formed as in the embodiment, and the cross-sectional shape of the other is symmetrical with respect to a line that passes through the axial center of the roller and is orthogonal to the axial direction of the roller. It may be formed.

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 the rollers are arranged at equal intervals in the circumferential direction by the 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

Claims (3)

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. A plurality of rollers arranged so as to alternately change the inclination direction in the circumferential direction are provided between the two, and the outer peripheral surface of the roller is formed in an axial cross-sectional shape having a convex curved shape, and each of the outer rings. The inclined raceway surface and each inclined raceway surface of the inner ring are formed in a cross roller bearing whose axial cross-sectional shape is formed into a concave curved shape corresponding to the convex curved shape of the outer peripheral surface of the roller.
The roller is arranged between the outer ring and the inner ring in a preloaded state, and the area of the gap between each inclined raceway surface of the outer ring and the outer peripheral surface of the roller in the axial cross section thereof is the axis of the outer ring. The structure formed so as to be larger on the shaft end side of the outer ring than on the direction center side, and the area of the gap between each inclined raceway surface of the inner ring and the outer peripheral surface of the roller in the axial cross section thereof. A cross roller bearing characterized in that at least one of the configurations formed so as to be larger on the axial center side of the inner ring than on the shaft end side of the inner ring is adopted. The cross roller bearing according to claim 1, wherein the outer ring and the inner ring are integrally formed. The cross roller bearing according to claim 1 or 2, wherein the rollers are arranged so as to be in contact with adjacent objects.

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