GB2207957A

GB2207957A - Cross roller bearing

Info

Publication number: GB2207957A
Application number: GB08719256A
Authority: GB
Inventors: Hiroshi Teramachi
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-08-14
Filing date: 1987-08-14
Publication date: 1989-02-15
Also published as: DE3727543A1; FR2619606A1; GB8719256D0

Description

1 g 1 1 MH 52-044 CROSS ROLLER BEARING 2 1f2 0 7 9 5 '7 1 The present

invention relates to a cross roller bearing used frequently, for example, in the swinging, articulated and manipulator rotating portions of industrial robots and in medical devices, and to a process for manufacturing a cross roller bearing.

In a conventional cross roller bearing known in the art, as shown in Fig. 6, an outer race 1 has its inner circumference 2 formed with an inwardly facing V-shaped groove 3 which extends in the circumferential direction and opens inwardly, and an inner race 1 has its outer circumference 5 formed with an outwardly facing V-shaped groove 3 which extends in the circumferential direction and faces the aforementioned inward V-shaped groove 3. The aforementioned outer race 1 comprises of a pair of members la and lb which are split along the bottom line 3c of its inward V-shaped groove 3. For assembly of the cross roller bearing, rollers 7 such as cylindrical or spherical rollers and not-shown spacer-retainers are fitted between the outward V-shaped groove 6 of the aforementioned inner race 4 and one outer race member la or lb. Next, the other outer race member lb or la is fitted between the inner race 4 and one outer race member la or lb. These paired outer race members la and lb are mated at their mating faces 8a and 8b and are fastened by bolts 9a and nuts 9b.

In the cross roller bearing thus constructed according to the prior art, however, the paired members la and lb comprising the outer race 1 are machined separately of each other. This makes it necessary to machine the mating faces 8a and 8b, which are to be joined for assembly, separately of each other. It is remarkably difficult to machine the separately machined mating faces 8a and 8b so accurately that-they will completely mate with each other. Even if possible, the machining cost required will be very high. Furthermore, rolling faces 3a and 3b forming the inward V- shaped groove 3, on which the rollers will roll, have to be machined after they have been temporarily assembled at the aforementioned mating faces 8a and 8b. Without these mating faces 8a and 8b being accurately finished, the rolling faces 3a and 3b can not be accurately machined. This raises a problem that the swinging motions of the inner and outer races 1 and 4 through the rollers 7 cannot be accomplished smoothly and accurately.

Even if, however, both the aforementioned mating faces 8a and 8b and the rolling faces 3a and 3b forming the inward-V-shaped groove 3 were accurately machined, the paired outer race members la and lbwould be displaced with slight slackness being established, if any, between the bolts 9a and the nuts 9b, because there is a clearance between each of the bolts 9a fastening the paired outer race members la and lb and each bolt hole 10 through which the corresponding bolt 9a extends. As a result, a deviation is established between the outer circumference and the rolling faces 3a and 3b forming the inward V-shaped groove 3 and between the individual rolling faces 3a and 3b, thus causing the problem that high accuracy is difficult to hold thereby eliminating the smooth swinging motions.

In the prior art, still moreover, the process for manufacturing the cross roller bearing requires a number of steps including: (1) the step of roughly machining the paired members la and lb comprising the outer race 1; (2) the step of hardening and annealing the individual outer race members la and lb; (3) the step of grinding the mating faces

IS 8a and 8b; (4) the step of joining the mating faces Ba and 8b to temporarily assemble the two outer races members la and lb by the bolts 9a and the nuts 9b to grind the outer circumference of the outer race 1; (5) the step of grinding the rolling faces 3a and 3b comprising the inward V-shaped groove 3 in the temporary assembled state; (6) the step of removing the bolts 9a and the nuts 9b used for the temporary assembly and assembling the rollers 7 and the (not shown) spacer retainers between the inner circumference of one of the outer race members la or lb and the inner race 4 in which the rolling faces 6a and 6b comprising the outward V- shaped groove 6 have been ground; and (7) the step of fitting the other outer race member la or lb between the aforementioned outer race member la or lb and the inner race 4 and fastening the paired outer race members la and lb by the bolts 9a and nuts 9b. in addition, when the outer circumference and sides of the outer race 1 and the rolling faces 8a and 8b are to be ground in the temporarily assembled state, the paired outer race members la and lb are deviated from each other to raise a further problem in that it is difficult to accurately grind members la and lb.

Viewed from a first broad aspect there is herein disclosed a method of forming a cross roller bearing comprising the steps of: forming an inwardly facing V-shaped groove in the inner circumference of an outer race and extending in the circumferential direction thereof, forming an outwardly facing V-shaped groove in the outer circumference of an inner race and extending in the circumferential direction thereof and facing the inward V-shaped groove of said outer race; splitting said outer race to form radial split faces, expanding said outer race at said split faces and fitting rollers between said inward V-shaped groove and said outward V-shaped groove.

By means of this method, at least in preferred forms, it is possible to provide a cross roller bearing having, by forming radial split faces in the outer race, accurately machined roller rolling faces comprising the inward V-shaped groove and having no deviation during use between the outer circumference and the inward V-shaped groove and between the individual rolling faces comprising the inward V-shaped groove.

In a preferred embodiment, said outer race is split by forming a radial notch in said outer race and breaking said outer race by applying a force to said notch. This notch is sufficient if its depthwise direction is oriented generally in the radial direction of the outer race, and may extend either all over or partially of the split line, on which the split faces are to be formed. It is, however, preferable that the notch be formed in the inner circumference of the outer race, in which concentration of stress takes place when the outer race is split by means of a press or the like. By thus forming the split faces of the cut faces, the split faces can be joined in a completely mating manner after the outer race has been expanded at the split faces to allow the rollers and so on to be assembled between the inner and outer races, the faces being held together in use by the resiliency of the outer race. Even if a slightclearance is left between the split faces while the cross roller bearing is not used, the split faces come into completely mating engagement while ensuring the roundness of the outer race when the cross roller bearing is assembled for use in a machine element such as a swinging member.

Viewed from another broad aspect there is herein disclosed a cross roller bearing comprising: an outer race having an inwardly facing V-shaped 1 lk- groove formed in its inner circumference and extending in the circumferential direction, an inner race having an outwardly facing Vshaped groove formed in its outer circumference and extending in the circumferential direction and facing the V-shaped groove of said outer race; and rollers fitted between the V-shaped groove of said outer race and the V-shaped groove of said inner race, wherein said outer race is split to form radial split faces whereby said outer race may be expanded at said radial split faces to allow said rollers to be fitted between said races.

Since the cross roller bearing is constructed by splitting the outer race in the radial direction, the roller rolling faces comprising the inward V-shaped groove of the outer race can be accurately ground but do not lose their accuracy. Furthermore, since the split faces are cut to completely mate each other, the outer race can retain its roundness when it is assembled IPto a machine such as a swinging member, even if the radial split faces have a slight clearance.

By means of the present invention, at least in its preferred forms, the roller rolling faces forming the inward V-shaped groove of the outer race can be ground easily and accurately. Moreover, the outer race can be made remarkably simply because it is not divided into two parts.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- Fig. 1 is a top plan view showing a cross roller bearing according to one embodiment of the present invention; Fig. 2 is a section taken from Fig. 1; Fig. 3 is a perspective view showing the relations between rollers and spacer-retainers to be assembled between inner and outer races; Fig. 4 is a perspective view showing the outer race of Fig. 1; Fig. 5 is an enlarged view showing a portion of Fig. 4; and Fig. 6 is a sectional view showing the cross roller bearing of the prior art already described.

In Figs. 1 to 3, there is shown a cross roller bearing according to an embodiment of the present invention. In this cross roller bearing, an annular outer race 1 is formed in its inner circumference 2 with an inwardly facing V-shaped groove 3 which extends in the circumferential direction and opens inwardly. An inner race 4 is formed in its outer circumference 5 with an outwardly facing V-shaped groove which extends in the circumferential direction and faces the aforementioned inward V-shaped groove 3. Rollers 7 are fitted between the aforementioned inward and outward V-shaped grooves 3 and 6. The outer race 1 thus formed has radial split faces 8a and 8b which are formed by splitting the outer race 1 in a suitable position so that it can be expanded at the split-faces 8a and 8b in the directions of arrows A, as shown in Fig. 4. In this embodiment, the rollers 7 to be assembled between the outer race 1 and the inner race 4 are assembled with spacer-retainers 11, as shown in Fig. 3, so that their skewness may be prevented.

In this embodiment, moreover, the split faces 8a and 8b of the outer race 1 are formed, as shown in Figs. 4 and 5, by applying an external force by means of a press to a notch 12 which is formed in a corner defined by the inner circumference 2 and the side of the outer race 1. Thus, the split faces 8a and 8b are cut faces capable of completely mating each other.

The process for manufacturing the cross roller bearing of this embodiment comprises the following sequential steps of: (1) roughly machining the 1 outer race 1 having an inwardly facing V-shaped groove 3; (2) forming the radial notch 12 in the corner defined by the inner circumference 2 and the side of the outer race 1; (3) hardening and annealing the outer race 1; (4) grinding the outer circumference, the sides and the rolling faces 3a and 3b forming the inward V-shaped groove 3; (5) applying an external force by a press to split the outer race 1 from the side, at which the notch 12 is formed, to the other side along the center line extending from the notch 12; and (6) expanding the outer race 1 at its cut split faces 8a and 8b and fitting the rollers 7 and the spacer-retainers 11 in the gap between the outer race 1 and the inner race 4.

In this cross roller bearing manufacturing process, when the outer race 1 is to be expanded at its split faces 8a and 8b to allow the rollers 7 and the spacer-retainers 11 to be fitted in the gap between the outer and inner races 1 and 4, for example, a suitable jig is arranged at the outer side of the inner race 4 and used to assemble the rollers 7 and the spacer-retainers 11 in the outward V- shaped groove 6 of the inner race 4.

The outer race 1 expanded at its split faces 8a and 8b is fitted in this state. Then, the jig is removed to assemble the rollers 7 and the spacerretainers 11 between the outer and inner races 1 and 4.

Claims

CLAIMS:

1. A method of forming a cross roller bearing comprising the steps of: forming an inwardly facing v-shaped groove in the inner circumference of an outer race and extending in the circumferential direction thereof, forming an outwardly facing V-shaped groove in the outer circumference of an inner race and extending in the circumferential direction thereof and facing the inward V-shaped groove of said outer race; splitting said outer race to form radial split faces, expanding said outer race at said split faces and fitting rollers between said inward V-shaped groove and said outward V-shaped groove.

2. A method according to claim 1 wherein said outer race is split by forming a radial notch in said outer race and breaking said outer race by applying a force to said notch.

3. A method of forming a cross roller bearing substantially as hereinbefore described with reference to Pigs. 1 to 5 of the accompanying drawings.

4. A cross roller bearing formed by a method according to any preceding claim.

5. A cross roller bearing comprising: an outer race having an inwardly facing V-shaped groove formed in its inner circumference and extending in the circumferential direction, an inner race having an outwardly facing V-shaped groove formed in its outer circumference and extending in the circumferential direction and facing the V-shaped groove of said outer race; and rollers fitted between the V- shaped groove of said outer race and the ii V-shaped groove of said inner race, wherein said outer race is split to form radial split faces whereby said outer race may be expanded at said radial split faces to allow said roller to be fitted 5 between said races.

i

6. A cross roller bearing substantially as hereinbefore described with reference to Pigs 1 to 5 of the accompanying drawings.

Published 1988 at The Patent Wice. State House 66 71 High Holborn. London WC1R 4TP- Flirther copies may be obtained from The Patent Office, Sales Branch, St Mazy Cray. Orpington, Kent BR5 3RD Printed by Multiplex techniques ITd, St Mary Cray. Kent Cor. 1 87