Disc brake adjustment device having a blocking device

A wear adjustor is provided for adjusting the wear of brake pads and the brake disc of a pneumatically operated disc brake having a brake application device that can be actuated via a rotary lever. The wear adjustor is able to be inserted into an adjusting spindle of the brake application device. The wear adjustor includes a clutch ring for coupling to a spring sleeve that is in engagement with the adjusting spindle. A blocking device is disposed between the adjusting spindle and the wear adjustor. The blocking device forms a stop for the adjusting spindle in the tangential direction relative to the rotating direction.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to an adjusting device for a disc brake and, in particular, an adjusting device for a pneumatically actuated disc brake having a rotary-lever-actuated brake application device, which adjusting device can preferably be inserted into an adjusting spindle of the brake application device. The adjusting device has a clutch ring for coupling to a spring sleeve which is in engagement with the adjusting spindle.

Adjusting devices or wear adjustors for disc brakes exist in various embodiments. DE 10 2004 037 771 A1 (having U.S. published counterpart application US2009/209890 A1) discloses an adjusting device for a disc brake, the specifications of which are expressly incorporated by reference herein. This adjusting device is suitable for a pneumatically actuated disc brake, in particular one of sliding-caliper design. Furthermore, the adjusting device can however also be used in pneumatically actuated fixed-caliper or pivoting-caliper disc brakes.

Pneumatically actuated disc brakes have over time become standard equipment on heavy commercial vehicles. Such disc brakes require mechanical boosting or “force amplification” in order to produce the demanded brake application force, because the force of the pneumatically charged brake cylinders is restricted on account of the pressure level (at present approximately 10 bar) and the limited structural size of the brake cylinder. Presently known pneumatically actuated disc brakes have boost ratios of between 10:1 and 20:1. The piston strokes of the brake cylinders are in the range from 50 mm to 75 mm, resulting in brake application travels of approximately 4 mm for pressing the brake pads against the brake disc.

The friction material thickness of the brake pads lies in the range of 20 mm, and because two pads are installed, this results in a wear travel of approximately 40 mm, not taking disc wear into consideration. This travel is a multiple greater than the above-mentioned brake application travel. It is therefore necessary for the brake to be adjusted correspondingly to the pad wear by means of a device. The prior art provides automatic wear adjustment by means of which the so-called air play, that is to say the gap between the brake pads and the brake disc in the non-actuated state, is kept constant independently of the wear state and wear behavior of the brake pads.

In commercial vehicles, use is very often made of disc brakes which have an adjuster which is arranged concentrically in the cavity of a threaded spindle and which is driven eccentrically by a rotary lever via a drive element (for example shift finger or toothed wheel). During a braking process, the rotary lever which is coupled to the piston rod of the brake cylinder performs a rotational movement. Before the rotational movement of the lever is introduced into the adjuster via the coupling mechanism of the adjusting means (for example shift fork and shift finger or toothed wheel), a so-called idle travel must be overcome. This travel is decisive of the size of the so-called air play, because during this movement, the adjustment is not activated, and the brake application travel therefore constitutes the air play. After the idle travel is overcome, the adjuster is set in a rotational movement, and an adjusting process is initiated by the coupling to the threaded spindle or tube.

DE 10 2004 037 711 A1 describes an adjuster of this type, which is shown inFIG. 12. The adjuster is composed substantially of the following functional elements: shaft2; bearing disc3; axial bearing5; collar bush, or spacer sleeve19; shift fork, or drive ring6; ball ramp clutch7; cone clutch17; and cylindrical spring12. With regard to the description, reference is made to DE 10 2004 037 711 A1.

The adjusting device must basically perform two functions:

1. the automatic air play adjustment; and

2. the manual restoration or retraction of the adjusting mechanism upon replacement of the brake pads.

When installing new brake pads, thrust pieces which press the pads against the brake disc must be reset. This is carried out by turning back or retracting threaded plungers (threaded tubes or adjusting spindles) which, during use of the brake, have been screwed out by the automatically operating adjusting device according to pad wear.

When turning back the adjusting spindles, it must be ensured that the spindles are not turned against a delimitation with too high a force. If this were to occur, there is the risk of the adjustment being inoperative after replacing the brake pads because the force with which the adjusting spindles are jammed against the delimitation is greater than the adjusting force generated by the adjuster.

As mentioned above, when installing new brake pads, the adjusting spindles are reset by manually turning the adjuster. Since it is not possible to visually check the end position of the adjusting spindles, a mechanical, clearly perceptible turn-back delimitation is required.

It is therefore the object of the present invention to provide an adjusting device with a turn-back delimitation, with the above disadvantages being eliminated or significantly reduced, and further advantages being obtained.

This and other objects are achieved by an adjusting device for adjusting for wear of the brake pads and the brake disc of a pneumatically actuated disc brake having a rotary-lever-actuated brake application device, which adjusting device can preferably be inserted into an adjusting spindle. The adjusting device has a clutch ring for coupling to a spring sleeve which is in engagement with the adjusting spindle. A blocking device is arranged between the adjusting device, which can be inserted into the adjusting spindle, and the adjusting spindle. The blocking device forms a stop in the tangential direction relative to the direction of rotation for the adjusting spindle. In this way, it is advantageously obtained that, during the resetting of the adjusting spindle by the adjusting device, the adjusting spindle is prevented by the blocking device from becoming jammed, because the stop in the tangential direction halts the rotational movement.

Since the turning back of the adjusting spindle is carried out by use of the adjusting device, and the adjuster or the adjusting device is in direct engagement with the adjusting spindle, the turn-back delimitation can be realized by way of the adjuster, such that no complex modifications are necessary.

When the adjusting spindle has reached the pad installation position, the adjuster is retracted into the adjusting spindle to a maximum extent. The adjusting spindle performs a rotational movement relative to the clutch ring of the adjuster. A deformable or displaceable profiled blocking element is arranged between the end side of the adjusting spindle and the adjuster. The clutch ring of the adjuster preferably has a corresponding, for example a sawtooth-like crown, toothing adapted to the blocking element.

If the adjusting spindle is now turned back, it comes into contact with the blocking element at the end of the adjustment path. The blocking element is deformed or displaced axially by the end side of the adjusting spindle until the profile engages in the toothing of the clutch ring. Since the clutch ring is fixed to the disc brake, for example to the brake caliper thereof, by means of a collar bush and a bearing disc of the adjuster, the adjusting spindle can be turned back no further. A turn-back stop which acts in the circumferential direction is thereby realized. Jamming of the adjusting spindle can thereby be prevented. When the brake is actuated, the adjusting spindle can be turned away from the stop by the adjuster without the need to overcome a high friction force or jamming force.

An alternative embodiment provides a crown toothing on the adjusting spindle. Here, when the pad installation position is reached, the adjusting spindle engages with the end-side toothing directly into the end-side toothing of the clutch ring on the adjuster. As a result, the adjusting spindle can be turned back no further. Since it is the case in this solution too that the stop acts in the tangential direction, no jamming occurs. It is therefore possible for the adjusting spindle to be turned away from the stop with little force expenditure. The automatic adjustment function is thereby ensured without restriction.

Axial mobility of the blocking element is made possible for example by means of at least one lug which engages with a recess of the spring sleeve. The blocking element may have resilient hooks which are provided to engage with corresponding recesses of the clutch ring.

A disc brake, in particular a pneumatically actuated disc brake, has the above-described adjusting device.

DETAILED DESCRIPTION OF THE DRAWINGS

Elements with the same or similar functions are provided with the same reference numerals in the figures.

With regard to the design and function of a pneumatic disc brake according toFIG. 13, reference is made to the corresponding description of DE 197 29 024 C1, the specification of which is expressly incorporated by reference herein. The following components are indicated inFIG. 13: disc brake20, brake disc21, brake caliper22, brake pads23, bridge24, adjusting spindles25and26, thrust pieces27, sprockets28, chain29, eccentric30and rotary lever31, which has a drive element32interacting with a shift fork of an adjusting device1. The adjusting device1is in this case arranged in the adjusting spindle25. An adjusting device1will now be explained in more detail. The adjusting device1would also be suitable for an electromotively actuated disc brake.

FIG. 1shows a partial section illustration of a brake caliper22of a disc brake20having an adjusting spindle25and an adjusting device according to the invention, which is inserted in the adjusting spindle25. The adjusting spindle25is provided at the bottom with a thrust piece27(see alsoFIG. 13), with the adjusting spindle being shown here in an initial position for installation or exchange of a brake pad.

The adjusting device1has the following components, which are not all shown here: a spindle, having a drive journal at its upper end; a bearing disc3for fastening the adjusting device1in the brake caliper22; a collar bush4which is rotationally fixedly coupled to the bearing disc3and has an upper collar with a running surface arranged therebelow for balls of an axial bearing; a drive ring which is connected to a shift fork which is coupled to a rotary lever31; a ball ramp clutch having a clutch ring8which interacts with a spring sleeve14; and a cylindrical spring which is arranged in the spring sleeve14and which is supported on a profiled disc. The general function of the adjusting device1is described in detail in DE 10 2004 037 771 A1 with regard toFIG. 5, to which reference is hereby made.

Reference is now made toFIGS. 2,4,6and8, in which are respectively shown, in partial section illustration, a first, second, third and fourth exemplary embodiment of an adjusting device1according to the invention with a first, second, third and fourth exemplary embodiment of a blocking element5according to the invention.

A blocking device is arranged between the underside of the clutch ring8and the top side of the adjusting spindle25. In these present examples, the blocking device has in each case one deformable or displaceable profiled blocking element5. The clutch ring8of the adjuster1preferably has a sawtooth-like crown toothing adapted to the blocking element5. If the adjusting spindle25is now turned back, it comes into contact with the blocking element5at the end of the adjustment path. The blocking element5is deformed or displaced axially by the end side of the adjusting spindle25until the profile engages in the toothing of the clutch ring8. Since the clutch ring8is fixed by means of the collar bush and the bearing disc3of the adjuster1, the adjusting spindle25can be turned back no further. A turn-back stop which acts in the circumferential direction is thereby realized. Jamming of the adjusting spindle25can thereby be prevented. When the brake is actuated, the adjusting spindle25can be turned away from the stop by the adjuster1without the need to overcome a high friction force or jamming force.

The different blocking elements5have in each case lugs6situated on an inner periphery for rotationally fixed connection to recesses33, which run in the axial direction, of the spring sleeve14. In this way, the blocking elements5are in each case axially displaceable along the spring sleeve14.

The blocking element5, according to the first exemplary embodiment inFIG. 3has, on its outer circumference, resilient hooks7that engage with corresponding recesses of the clutch ring8.

FIG. 5shows an alternative in a second embodiment of the blocking element5, with the hooks7being attached in each case to spring lugs9.

FIG. 7illustrates a further alternative in a third embodiment of the blocking element5. Here, there are teeth of a toothed profile10on the outer circumference, and restoring spring elements11situated at the inside for interaction with the adjusting spindle25.

FIG. 9shows yet a further alternative in a fourth embodiment of the blocking element5. Here, teeth of the toothed profile10are arranged on the outer circumference. The blocking element5is, for example, a rigid ring.

A further possible solution is for a crown toothing to be formed on the adjusting spindle25, and this is shown, as a fifth exemplary embodiment, inFIGS. 10 and 11. In this solution, when the brake pad installation position is reached, the adjusting spindle25engages, with an end-side toothing12integrally formed thereon, directly into a corresponding end-side toothing of the clutch ring8on the adjuster1. As a result, the adjusting spindle can be turned back no further. Since it is the case in this solution too that the stop acts in the tangential direction, no jamming occurs, and it is therefore possible for the adjusting spindle25to be turned away from the stop with little force expenditure. The automatic adjustment function is thereby ensured without restriction.

TABLE OF REFERENCE NUMERALS

11Restoring spring element