GB2147672A

GB2147672A - Automatic adjusting device fore disc brake

Info

Publication number: GB2147672A
Application number: GB08423684A
Authority: GB
Inventors: Rudolf Thiel
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1983-10-05
Filing date: 1984-09-19
Publication date: 1985-05-15
Also published as: GB8423684D0; DE3336120C2; DE3336120A1; FR2553167A1; GB2147672B; FR2553167B1

Abstract

An automatic adjusting device (1) for a disc brake comprises an extensible adjusting member which is interposed between a brake piston (8) and a mechanical actuating device (28, 36) and which has two adjusting elements (14, 20) interconnected through a thread without self-locking engagement, a friction clutch (24, 26) for fixing one of the adjusting elements on mechanical actuation, and a spring (54) which is supported on a stop (76) formed fast with the housing, on the one hand, and on a roller bearing (46). on the other hand, the latter being seated on one of the adjusting elements (20). For adjusting the operational clearance between the friction surfaces of the friction clutch in a simple, fast, reliable and inexpensive manner, compensating spacers (80) are provided. In alternative embodiments other arrangements of spacers are used or the components (28, 39, 36) of the actuating device are varied in length. <IMAGE>

Description

SPECIFICATION Automatic adjusting device for a disc brake This invention relates to an automatic adjusting device for a disc brake, of the kind wherein the disc brake comprises a brake piston which is arranged slidably in a brake cylinder for the purpose of actuation of a brake shoe and which is actuatable by virtue of a hydraulic actuating device and a mechanical actuating device, and which comprises an extensible adjusting member which is interposed between the brake piston and the mechanical actuating device and which has two adjusting elements interconnected through a thread without self-locking engagement, one of the adjusting elements abutting on a stop formed fast with the housing, and a friction clutch for fixing one of the adjusting elements on mechanical actuation.

An automatic adjusting device of this kind is known from German printed and published patent application 21 43 575. In this known adjusting device, the adjusting nut is of an outwardly stepped design. Arranged on the step is an axial bearing which is urged by a helical spring against the nut.

The other end of the helical spring bears against a sleeve-shaped stop that is formed fast with the housing. With its end remote from the brake piston, the adjusting nut abuts on a second axial bearing which is supported on the bottom of the cylinder bore. In this arrangement, a hand brake clearance remains between a cone surface disposed at the adjusting nut and a brake piston which are parts of the mechanical actuating device.

It is of decisive importance for the proper functioning of the adjusting device that the predetermined operational clearance will be maintained precisely during the assembly and subsequently.

It is therefore an object of the invention to provide an automatic adjusting device of the kind referred to, wherein a precisely preset clearance will be safeguarded by simple means.

According to the invention in its broadest aspect, an automatic adjusting device for a disc brake, of the kind referred to is characterised in that there is provided at least one compensating spacer for the adjustment of the operational clearance between the friction surfaces of the friction clutch.

According to another aspect of the invention, an automatic adjusting device for a disc brake, of the kind referred to is characterised in that functional components of corresponding length are employed for the adjustment of the operational clearance between the friction surfaces of the friction clutch.

The straightforwardly designed thrust boit of the mechanical actuating device can be used for this purpose in a very simple and economical fashion.

According to a further aspect of the invention, an automatic adjusting device for a disc brake, of the kind referred to is characterised in that a hand brake piston variable in length is provided for the adjustment of the operational clearance between the friction surfaces of the friction clutch.

A device according to the invention permits in a straightforward and inexpensive way the length compensation which becomes necessary as a result of the sum of tolerances of the individual components to be carried out in series production, while the stability of the device is not impaired.

Favourable embodiments of the present invention provide that the compensating spacer is located between the housing and the part formed with the stop at the housing or between the roller bearing and the stop formed fast with the housing.

If the stop is constituted by a sleeve-shaped component coupled to the housing, the compensating spacer will be suitably arranged between a mounting portion of the sleeve-shaped component and the housing.

In another embodiment, the compensating spacer is arranged between the roller bearing and the adjusting element on which the roller bearing is seated. In this embodiment, a circlip which is axially rigidly coupled to the adjusting nut will be provided as a supplement on the side of the bearing that is remote from the compensating washer.

In this arrangement, the roller bearing can be disposed in a snug fit on the adjusting nut, while the circlip is arranged thereon in a sliding fit, or viceversa. Additionally, the circlip can be caulked. Coupling of the circlip with the adjusting nut by means of a thread has likewise proved to be expedient.

According to another embodiment, the sleeveshaped component is of bipartite design, a first sleeve part comprising a flange for securement in the housing and forming an abutment surface for the roller bearing. A second thin-walled sleeve part is of substantially cylindrical configuration and forms an abutment surface for the spring. Both sleeve parts are suitably interconnected by a rolling or caulking engagement or by spot-welding. In addition, there is the possibility of precisely setting the spring force by virtue of the length ratio of the sleeve parts prior to caulking.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section through a part of a disc brake incorporating an adjusting device, only one side of the brake, however, being partially illustrated without pad and without disc; Figure 2 is a longitudinal cross-section similar to that one of Figure 1, however, showing a second embodiment of the adjusting device; Figure 3 is a longitudinal cross-section similar to that one of Figure 1, however, showing a third embodiment of the adjusting device; and Figure 4 is a longitudinal cross-section similar to that one of Figure 1, however, showing a fourth embodiment of the adjusting device.

Firstly, Figure 1 will be referred to which shows a longitudinal cross-section through a part of a disc brake with an adjusting device 1. A brake housing 2 is furnished with a cylinder bore 4 which is substantially stepped three times. In the bore portion 6 of largest diameter, a brake piston 8 is axially slidably contained. The brake piston 8 is of bowl-type design, its open end being located in the cylinder bore 4, while its closed end projects from the cylinder bore 4 to press against a brake shoe (not shown). With a view to sealing the brake piston 8 in relation to the cylinder bore, a so-called roll-back seal 10 known per sue is arranged in an annular groove 12 of the brake housing 2, the seal 10 likewise effecting the resetting of the brake piston 8.

Fitted to the bottom of the brake piston 8 in a torsionally secured manner is an adjusting spindle 14 which extends coaxially through the hollow space formed by the brake piston and into a bore portion 16 of reduced diameter. The adjusting spindle 14 comprises a multiple thread 18 without self-locking engagement. An adjusting nut 20 disposed on the adjusting spindle 14 is provided with a corresponding thread. The adjusting nut is substantially of cylindrical configuration. However, it has at its end remote from the piston a radial projection 22 which forms a conical friction surface 24.

Coacting with said conical friction surface 24 is another conical friction surface 26 which latter is provided at a hand brake piston 28. The adjusting nut 20 and the hand brake piston 28 thus represent two parts of a friction clutch. The hand brake piston 28 is composed of a cylindrical portion 30 which is slidably arranged in a reduced-diameter bore portion 32, as well as of a flange portion 34 which extends substantially radially and whereat the friction surface 26 is disposed. The flange portion 34 of the hand brake piston 28 encompasses the radial projection 22 of the adjusting nut 20 from the outside, the operational clearance S remaining between the friction surfaces 24, 26.

Beside the hand brake piston 28, the mechanical actuating device further includes an eccentric device 36 which acts via a tappet 39 upon the hand brake piston 28. The eccentric device 36 comprises a shaft 38 which is rotatably supported in a bore 40 extending transversely to the cylinder bore 4, and to which a hand brake lever is fixed (in a manner not shown). Contained in the shaft 38 is a recess 42 in which an end of the tappet 39 is arranged. The other end of this tappet is located in a recess 44 contained in the hand brake piston 28.

The part of the adjusting nut 20 that faces the brake piston 8 carries a three-point or four-point roller bearing 46, whose inner bearing ring is herein formed by the adjusting nut 20 itself. The outer bearing ring 48 of the roller bearing 46, which ring is divided into two parts along a plane that extends vertically to the axis of rotation, abuts on a shoulder 50 of a sleeve 52 which is secured in the brake housing 2 and which extends in an axial direction between the adjusting nut 20 and the wall of the brake piston 8. Bearing against the other side of the outer bearing ring 48 is a helical spring 54, the other end of which is supported on a flange 76 which is formed at the end of the sleeve 52. Instead of the helical spring, it is also possible to use a cup spring or a cup spring assembly, or another elastic member which deliver a specific force (for instance a rubber sleeve).

The sleeve 52 illustrated herein is of bipartite design and comprises a first sleeve part 64 which forms a radially extending flange 66 that is secured in an annular groove 68 of the housing 2. The first sleeve part 64 constitutes at its end an abutment surface 70 for the roller bearing 46, against which abutment surface the latter is urged by the helical spring 54. A second sleeve part 72 is substantially of thin-walled cylindrical configuration and is connected to the first sleeve part by a rolling or caulking engagement. To this end, the first sleeve part 64 contains at least one recess 74 into which the material of the second sleeve part will be deformed during the rolling or caulking process, welding process or the like. To this end, the second sleeve part 72 will be slid on the outer periph ery of the first sleeve part 64.This way, there will be accomplished a favourable method of adjusting the force of the spring, as a result whereof improvement of the efficiency of adjustment may be attained. The end of the helical spring 54 which is remote from the roller bearing 46 abuts on an inwardly projecting flange portion 76 that is designed at the second sleeve part 72.

For the adjustment of the operational clearance S, first the hand brake piston 28 will be fitted into the housing during the assembly. Thereafter, the distance between a reference point on the friction surface 26 and the radially extending wall 78 of the groove 68 will be measured. The resulting differential value in respect of a nominal size will be compensated for by inserting at least one corresponding spacer 80 into the annular groove 68 between the wall 78 and the flange 66. The abutment surface 70 of the first sleeve part 64 and thus the axial position of the roller bearing 46 and of the adjusting nut 20, respectively, will thus be displaced in an axial direction to the predetermined nominal size. The compensating spacers 80 are graded is size so that normally there is need to insert the one spacer.If required, however, the necessary size compensation can likewise be obtained by combination of several spacers. This also applies to the embodiments described hereinbelow, insofar as compensating spacers are used therein.

Figure 2 will now be referred to which shows an arrangement similar to that of Figure 1. Therefore, oniy those features will be described herein which differ from those of Figure 1. In contrast to Figure 1, the adjusting device of Figure 2 includes an adjusting nut 82 in whose outer periphery a step 84 is machined. In the event of there being no need for compensating spacers, the roller bearing 46 will bear against the radially extending wall of the step 84. If, however, compensating spacers 86 are required, these will be arranged between the step 84 and the inner bearing ring of the roller bearing 46, as shown. The roller bearing 46 is secured onto the adjusting nut 82 by means of a snug fit.

The embodiment illustrated in Figure 3 corresponds basically to that of Figure 2, the adjusting nut 82 comprising herein again a step 84 and with a compensating spacer 86 being disposed between this step 84 and the roller bearing 46. The roller bearing 46 is seated on the adjusting nut 82 is a slide fit in this embodiment. Adjacent to the roller bearing 46, a circlip 92 is mounted onto the adjusting nut 82 in a snug fit. The circlip 92 abuts with its end face 94 close to the roller bearing 46 on the inner bearing ring of the roller bearing 46. Alternatively, the roller bearing 46 can be arranged in a snug fit and the circlip 92 in a sliding fit. In this case, the circlip 92 is secured in an axial direction by way of a beaded or caulking engagement 96.

The invention likewise permits the circlip 92 to be screwed to the adjusting nut 82. In this event, the circlip and the adjusting nut are provided with a special thread.

In the embodiment illustrated in Figure 4, the adjustment of the operational clearance S will be brought about by the provision of a two-part hand brake piston 98. The hand brake piston 98 is composed of a piston part 100 and a flange part 102 which are screwed to one another through a special thread 104. This special thread 104 enables an axial displacement of the flange part 102 to be obtained in relation to the piston part 100 for clearance adjustment. After the adjustment, the flange part 102 will be fixed on the piston part 100. Figure 4 shows another possibility of arranging a compensating spacer 88. This compensation method, in which the spacer 88 is located between the outer bearing ring 90 of the bearing 91 and the first sleeve part 64, can be employed as an alternative to the compensation method by means of the extensible hand brake piston shown in Figure 4.

Another possibility for adjusting the operational clearance consists in the utilisation of parts 39 of varying length. Thus, for instance, the tappet 39 which is arranged between the eccentric shaft 38 and the hand brake piston 98 can be made use of in graded lengths depending on the operational clearance required.

In all the embodiments (Figure 1 to Figure 4), there is, beside the axial tolerance compensation with a view to avoiding compulsive forces which may result in impaired ease of motion of and jamming of the adjusting device. This will be accomplished according to the invention in that there is the provision of a distance (A) between the sleeve part 72 and the outer rings of the bearing 46, which distance is so dimensioned as to allow compensation of discrepancies from the coaxialities occuring during manufacture and assembly.

Claims

1. An automatic adjusting device for a disc brake, of the kind wherein the disc brake comprises a brake piston which is arranged slidably in a brake cylinder for the purpose of actuation of a brake shoe and which is actuatable by virtue of a hydraulic actuating device and a mechanical actuating device, and which comprises an extensible adjusting member which is interposed between the brake piston and the mechanical actuating device and which has two adjusting elements interconnected through a thread without self-locking engagement, one of the adjusting elements abutting on a stop formed fast with the housing, and a friction clutch for fixing one of the adjusting elements abutting on a stop formed fast with the housing, and a friction clutch for fixing one of the adjusting elements on mechanical actuation, characterised in that there is provided at least one compensating spacer (80, 86, 88) for the adjustment of the operational clearance S between the friction surfaces (24, 26) of the friction clutch.

2. An automatic adjusting device as claimed in claim 1, characterised in that the compensating spacer (80) is located between the housing (2) and the part (62) forming the stop at the housing.

3. An automatic adjusting device as claimed in claim 1, wherein the stop (66) formed fast with the housing is constituted by a sleeve-shaped component (52) coupled to the housing, characterised in that the compensating spacer (80) is arranged between a mounting portion of the sleeve-shaped component (52) and the housing (2).

4. An automatic adjusting device as claimed in claim 1, characterised in that the spacer is arranged between the roller bearing (46) and the stop formed fast with the housing.

5. An automatic adjusting device as claimed in claim 1, characterised in that the compensating spacer (86) is arranged between the roller bearing (46) and the adjusting element (82) on which the roller bearing is seated.

6. An automatic adjusting device as claimed in claim 5, characterised in that, on the side of the roller bearing (46) remote from the compensating spacer (86), a circlip (92) is seated on the adjusting nut (82) which is axially rigidly coupled to the adjusting nut.

7. An automatic adjusting device as claimed in claim 6, characterised in that the roller bearing (46) is disposed in a snug fit on the adjusting nut and the circlip (92) is arranged in a sliding fit thereon, or vice-versa.

8. An automatic adjusting device as claimed in claim 6, characterised in that the circlip (92) is connected with the adjusting nut by means of a thread.

9. An automatic adjusting device as claimed in claim 3, characterised in that the sleeve-shaped component (52) is of bipartite design.

10. An automatic adjusting device as claimed in claim 9, characterised in that a first sleeve part (64) comprises a flange (66) for securement in the housing (2) and forms an abutment surface (70) for the roller bearing.

11. An automatic adjusting device as claimed in claim 9, characterised in that a second sleeve part (72) is of substantially cylindrical configuration and forms an abutment surface (76) for the spring (54).

12. An automatic adjusting device as claimed in any one of claims 9 to 11, characterised in that the sleeve parts (64, 72) are interconnected by a rolling or caulking engagement or by spot-welding.

13. A method for the manufacture of an automatic adjusting device as claimed in any one of the preceding claims, characterised in that the actual size between a first reference point on one of the friction surface and a second reference point on the housing or on the second friction surface is measured, and in that at least one compensating washer is inserted between the respective parts for compensation until attainment of the nominal size.

14. An automatic adjusting device for a disc brake, of the kind wherein the disc brake comprises a brake piston which is arranged slidably in a brake cylinder for the purpose of actuation of a brake shoe and which is actuatable by virtue of a hydraulic actuating device and a mechanical actuating device, and which comprises an extensible adjusting member which is interposed between the brake piston and the mechanical actuating device and which has two adjusting elements interconnected through a thread without self-locking engagement, one of the adjusting elements abutting on a stop formed fast with the housing, and a friction clutch for fixing one of the adjusting elements on mechanical actuation, characterised in that functional components of corresponding length are employed for the adjustment of the operational clearance between the friction surfaces (24, 26) of the friction clutch.

15. An automatic adjusting device as claimed in claim 14, characterised in that the functional component is a tappet (39) provided in the mechanical actuating device.

16. An automatic adjusting device for a disc brake, of the kind wherein the disc brake comprises a brake piston which is arranged slidably in a brake cylinder for the purpose of actuation of a brake shoe and which is actuatable by virtue of a hydraulic actuating device and a mechanical actuating device, and which comprises an extensible adjusting member which is interposed between the brake piston and the mechanical actuating device and which has two adjusting elements abutting on a stop formed fast with the housing, and a friction clutch for fixing one of the adjusting elements on mechanical actuation, characterised in that a hand brake piston (98) variable in length is provided for the adjustment of the operational clearance between the friction surfaces (24, 26) of the friction clutch.

17. An automatic adjusting device as claimed in claim 16, characterised in that the hand brake piston is of bipartite design, the two parts (100, 102) being interconnected through a special thread (104).

18. An automatic adjusting device as claimed in any one of claims 3 to 12, characterised in that, between the sleeve part (72) and the outer part of the bearing (46), there is provided a distance (A) which is so large as to allow compensation of the tolerance and centricity variations ensuing from manufacture and assembly of the individual components and to prevent the occurrence of compulsive forces which impair ease of motion of the bearing and of the adjusting elements (20, 14).

19. An automatic adjustment device for a disc brake, substantially as described with reference to the accompanying drawings.