GB2175658A

GB2175658A - A disc brake

Info

Publication number: GB2175658A
Application number: GB08611680A
Authority: GB
Inventors: Manfred Brandenstein
Original assignee: SKF GmbH
Current assignee: SKF GmbH
Priority date: 1985-05-25
Filing date: 1986-05-13
Publication date: 1986-12-03
Also published as: JPS61278633A; FR2582367B1; IT8621903V0; IT8620485A1; IT1189529B; FR2582367A1; DE8515563U1; IT8620485A0; GB8611680D0

Abstract

A sleeve 21 for use in a disc brake has a tubular portion 22 and a flange 23, and apertures 24 for the flow of fluid therethrough, which apertures extend into the tubular portion and the flange. The disc brake can be operated hydraulically or mechanically, and, in the former mode, will effect wear adjustment. <IMAGE>

Description

SPECIFICATION A disc brake This invention is concerned with a sleeve for use in a disc brake and also with a disc brake having the sleeve.

Gebrauchsmuster Specification DE 8328618 discloses a disc brake with an automatic adjustment device. The disc brake comprises a housing; a first piston which is positioned in the housing and is to be actuated by fluid pressure; a second piston which is positioned in the housing in alignment with the first piston and is to be actuated mechanically; a spindle which is connected to the first piston; first sleeve which is arranged to be acted upon by the second piston, the spindle extending in the bore of the first sleeve, the spindle and first sleeve having co-operating screw-threads; a rolling bearing which supports the first sleeve for rotation about its longitudinal axis; a spring urging the bearing in the direction from the first piston to the second piston; and a second sleeve surrounding the first sleeve and having a flange, which second sleeve is fixed in the housing by means of the flange, which second sleeve also prevents the bearing from moving in the direction from the first piston to the second piston.

Actuation of the brake by fluid pressure causes movement of the first piston and the spindle and thus rotation of the first sleeve.

This compensates for any increase in play between the first and second pistons caused by, for example, wear of the brake pads.

For the fluid to act on the first piston, the second sleeve has a number of apertures in its flange for the flow of fluid therethrough.

With relatively small sizes of piston, there is a correspondingly small flange and consequently only small apertures can be provided in the flange. However, such a brake can be operated abruptly and with considerable force, and small apertures result in high fluid velocities. Also, small apertures restrict the free flow of the fluid. High fluid velocities can lead to turbulence at the outlets of the apertures, a rise in temperature and degradation of the fluid. Thus turbulence can give rise to gradual pressure differences in the fluid with the result that the brake feels spongy or soft.

The subjection of the invention is a second sleeve which, in a disc brake, is able to provide a harder feel to the brake.

The invention provides a sleeve for use in a disc brake, the sleeve having a tubular portion and a flange, the flange having apertures therein for the flow of fluid therethrough, wherein the apertures extend into the tubular portion of the sleeve.

Since the apertures extend into the tubular portion of the sleeve, this allows the apertures to be larger than if they did not. Even with a relatively small flange, the sleeve can have relatively large apertures. For the same mass flow rate, the velocity of the fluid can thus be lower, reducing turbulence and temperature increase so reducing or eliminating the spongy feel of the brake.

Each aperture may have flat parallel sides extending longitudinally of the tubular portion; and each aperture may extend radially in the flange the same distance as it extends longitudinally in the tubular portion.

The result of these two features is that the flow of fluid through the apertures is at an angle of about 45" to the longitudinal axis of the sleeve, the two end surfaces of each aperture having approximately the same influence on the flow of the fluid as each other.

The two end surfaces of each aperture can be parallel to each other and to the direction of flow and inclined to the longitudinal axis of the sleeve. However, each aperture may be bounded at one end by a flat longitudinally extending surface in the flange and by a flat radially extending surface in the tubular portion. The two end surfaces of each aperture are thus inclined with respective to each other and to the direction of flow resulting in a constricted portion which is only relatively short in the direction of flow. The degree of inclination can exert a considerable influence on the behaviour of the fluid flowing through the apertures and can be optimised as regards velocity and turbulence of the fluid.

An embodiment of the invention will now be described by way of example, reference being made to the accompanying drawings, of which: Figure 1 is a longitudinal section through part of a hydraulically operated disc brake with a piston for actuation by a hand brake lever; Figure 2 is an end view of the second sleeve shown in Figure 1; and Figure 3 is part of a longitudinal section through the second sleeve.

The device shown in Figure 1 comprises a housing 10, a first piston 11 which has an annular skirt, is positioned in the housing and is to be actuated by hydraulic pressure and a second piston 12 which is aligned with the first piston and is to be actuated mechanically.

The housing 10 has an inlet part 13 for hydraulic fluid. Also positioned in the housing 10 is an offset shaft 14, connected for example to a hand or parking brake lever (not shown), and a push rod 15 which engages in recesses in the shaft 14 and piston 12.

A spindle 16 is connected to the inner face of the first piston 11. A first sleeve 17 is disposed within the housing 10. The spindle 16 extends within the bore of the sleeve 17 and the spindle and sleeve have co-operating screw-threads of a relatively large pitch. At the end nearer the second piston 12, the first sleeve 17 has a radiatly outwardly extending annular flange 18 lying outside of the skirt of the first piston 11. The second piston 12 and the flange 18 of the sleeve 17 have corresponding frustro-conical spaced surfaces 19 and 20 respectively which, when engaged, form a coupling preventing rotation of one with respect to the other.

A second sleeve 21, comprising a tubular part 22 and a radially outwardly extending annular flange 23 at one end, is fixed in the housing. The second sleeve 21 has apertures 24 for the flow of is connected to the inside of one end of a third sleeve 25, the other end of the third sleeve having a radially inwardly extending flange 26. The tubular part 22 of the second sleeve 21 and the third sleeve 25 lie inside the skirt of the first piston 11. A deep groove radial ball bearing 27, comprising an outer race ring 28 and an annular row of balls 29, is positioned inside the third sleeve 25. One end face of the outer race ring 28 abuts the free end of the tubular part 22 of the second sleeve 21. Between the other end face of the outer race ring 28 and the flange 26 of the third sleeve 25 is a helical spring 30, which is under compression so urging the bearing towards the second piston 12.The inner race way groove for the balls 29 is provided by the outer surface of the first sleeve 17 so that the first sleeve is supported for rotation about its longitudinal axis by the bearing 27.

With hydraulic operation of the brake, increasing pressure of the fluid in a chamber 31, defined in part by the flanges 18 and 23 of the sleeves 17 and 21 respectively, effects movement of the first piston 11 in the direction away from the second piston 12. The spindle 16 moves with the piston 11 and brings the sleeve 17 and bearing 27 with it.

However, longitudinal movement of the sleeve 17 is resisted by the spring 30 acting on the outer ring 28 of the hearing 27 so the sleeve moves partly longitudinally and partly rotationally because of the co-operating screw-threads of the spindle 16 and the sleeve 17. The longitudinal movement of the sleeve 17 and bearing 27 produces a slight gap between the end face of the outer ring 28 and the free end of the tubular part 22 of the second sleeve 21. When the pressure is relieved, the spring 30 forces the bearing 27, the first sleeve 17, the spindle 16 and the first piston 11 back longitudinally. Since return movement of the sleeve 17 is not resisted as in the forward movement, the sleeve does not rotate on the return stroke, so bringing the sleeve closer to the second piston 12. Thus wear of, for example, the brake pads is automatically compensated for.

Operation of the hand-brake lever (not shown) causes the offset shaft 14 to rotate anti-clockwise, causing the push rod 15 to effect movement of the second piston 12 towards the first piston 11. After taking up any clearance between the second piston 12 and the flange 18 of the first sleeve 17, the conical surfaces 19 and 20 engage each other in a manner precluding relative rotation. Longitudinal movement of the second piston 12 produces longitudinal movement of the first sleeve 17 and thus the first piston 11 against the action of the spring 30 without rotational movement of the first sleeve.

The shape and relative size of the apertures 24 in the second sleeve 21 are shown clearly in Figures 2 and 3. The second sleeve 21 comprises the tubular part 22 and the annular flange 23 and the apertures 24 not only extend in the flange 23 but also in the tubular portion 22. Each aperture 24 has flat parallel sides 32 extending longitudinally of the tubular portion 22 and generally radially. Each aperture 24 also extends radially in the flange 23 the same distance as it extends longitudinally in the tubular portion 22 and is bounded at one end by a flat longitudinally extending surface 33 in the flange 23 and by a flat radially extending surface 34 in the tubular portion 22.

The direction of flow through the apertures 24 is indicated by the double arrowed line 35 and is about 45" to the longitudinal axis of the tubular portion 22. Each aperture 24 is constricted on the inner corner and widens considerably towards the outer corner. The apertures need not be of the shape described and illustrated. For example, the end surfaces 33 and 34 may extend parallel with each other and with the direction of flow. Also, the apertures may be circular bores extending parallel to the direction of flow.

Claims

1. A sleeve for use in a disc brake, the sleeve having a tubular portion and a flange, the flange having apertures therein for the flow of fluid therethrough, wherein the apertures extend into the tubular portion of the sleeve.

2. A sleeve as claimed in Claim 1, wherein each aperture has flat parallel sides extending longitudinally of the tubular portion.

3. A sleeve as claimed in Claim 1 or 2, wherein each aperture extends radially in the flange the same distance as it extends longitudinally in the tubular portion.

4. A sleeve as claimed in any preceding claim, wherein each aperture is bounded at one end by a flat longitudinally extending surface in the flange and by a flat radially extending surface in the tubular portion.

5. A sleeve for use in a disc brake substantially as herein described with reference to and as shown in the accompanying drawings.

6. A disc brake comprising a housing; a first piston which is positioned in the housing and is to be actuated by fluid pressure; a second piston which is positioned in the housing in alignment with the first piston and is to be actuated mechanically; a spindle which is connected to the first piston; a first sleeve which is arranged to be acted upon by the second piston, the spindle extending in the bore of the first sleeve, the spindle and first sleeve having co-operating screw-threads; a rolling bearing which supports the first sleeve for rotation about its longitudinal axis; a spring urging the bearing in the direction from the first piston to the second piston; and a second sleeve surrounding the first sleeve and having a flange, which second sleeve is fixed in the housing by means of the flange, which second sleeve also prevents the bearing from moving in the direction from the first piston to the second piston, wherein the second sleeve is a sleeve as claimed in any preceding claim.

7. A disc brake substantially as herein described with reference to and as shown in the accompanying drawings.