GB2192033A

GB2192033A - Disc brake for motor vehicles

Info

Publication number: GB2192033A
Application number: GB08714306A
Authority: GB
Inventors: Erhard Czich
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1986-06-28
Filing date: 1987-06-18
Publication date: 1987-12-31
Anticipated expiration: 2007-06-18
Also published as: GB8714306D0; FR2600734B1; FR2600734A1; DE3621712A1; GB2192033B

Abstract

In a re-adjusting device for a disc brake a horizontally adjustable thrust member (23) is provided which comprises a re-adjusting spindle (25) and a re-adjusting nut (24) in engagement with one another through a self-locking thread. A rotatably disposed actuating member (14) and a means (16-18) for translating a rotary movement into an axial movement are provided, with an axially movable part (17) of the latter means engaging the horizontally adjustable thrust member to force the latter axially against a brake actuating piston (4); a rotatable follower (44) is in engagement with the actuating member through a backlash (or lost motion) connection (61,62) and, via clutch means (43) and a shaft (41), with the movable part (25) of the thrust member. The clutch means permits adjustment of the thrust member to be effected during brake actuation until that member encounters an axial force in excess of a predetermined value at which the clutch means permits slipping of the follower (44) relative to the clutch plate (45). Alternative forms of clutch means are disclosed. <IMAGE>

Description

SPECIFICATION Disc brake for motor vehicles The present invention is concerned with a readjusting device for a disc brake, in particular for an automotive vehicle, of the kind comprising a horizontally adjustable thrust member provided with a re-adjustable spindle and a readjusting nut in engagement with one another through a self-locking thread, a pivotally disposed actuating member, means for translating a rotary movement into an axial movement, including an axially movable part engaging the horizontally adjustable thrust member to force the latter axially against an actuating member, a rotable follower in engagement with the actuating member through a Oacklash connection, and comprising a unidirectionally acting clutch for transferring the rotation of the follower to the movable portion of the thrust member.

A re-adjusting means of the afore-described kind is known from DE-OS No. 25 07 012.

That device accommodates, in a housing forming part of a brake caliper, a bipartite sleeve configured as a cylindrical helix sleeve and received in a bore of the housing. A part of the sleeve is fixed to the housing through a stay bolt provided in the rear wall of the housing, while a second part of the sleeve is adjustable relative to the first sleeve part in the axial direction through a complementary helical formation of the facing ends of the two sleeve portions. Disposed between the two sleeve portions is a split roller bearding, with a header radially emerging from the adjustable sleeve portion to pass through the side wall of the housing. The header can be coupled, through a connecting rod linkage, to an actuating unit.Through movement of the header in the circumferential direction, the adjustable sleeve portion can be rotated relative to the other sleeve portion and because of the helical configuration of the ends of the sleeve portions, facing one another, the adjustable sleeve portion is moved in the axial direction so as to cause brake shoes to be forced to opposite front faces of the brake disc. For that purpose, the front end of the adjustable sleeve portion, through a roller bearing, extends to the thrust member unit composed of two equi-axial parts (re-adjustable spindle and re-adjustable nut). The re-adjustable spindle is screwed into the re-adjustable nut and, being prevented from performing a rotating movement, is effective to force a brake shoe against a brake disc.

Moreover, this prior art device comprises a thrust sleeve disposed between the one-piece sleeve and the re-adjusting nut and being in communication therewith through a unidirectionally switching clutch. Formed in a radial end flange of the thrust sleeve are axially di rected locks at an intermediate space in the circumferential direction. A follower fixed by a rotatable sleeve portion is accommodated in one of the locks. If, upon applying the brake, the sleeve portion is not rotated to such an extent that the follower covers the full width of the path of adjustment determined by a lock, no re-adjustment will take place. However, upon wear of the friction pads, the follower will come into abutment with one side of the lock and, through the uni-directionally switching clutch, will turn the thrust member relative to the external portion of the thrust member unit.During release of the brake, a restoring spring in the actuating unit will cause the follower to support itself at the other side of the lock and to rotate the thrust member along with the outer portion of the thrust member unit. This rotation involves an increase in the efficient length of the thrust member unit since the re-adjusting spindle, for example, as a result of its abutting against a brake shoe, is precluded from adjusting itself.

The known system requires a special mechanism to restore the re-adjusting means to its initial position as needed, for example, for replacement of pads. This is achieved in that the thrust member disposed non-rotationally, during normal operation, is axially displaceable relative to the actuating member, causing the follower pin establishing the non-rotational connection, after axial displacement of the thrust member, to pass into a circumferential groove, and the thrust member thereby to be rotatable relative to the actuating element. This will enable the adjusting nut to be turned in the restoring direction which is precluded, during normal operation, by the unidirectionally switching clutch coupling and the non-rotational connection between the thrust member and the actuating element.As the thrust member is axially displaceable against the force of a spring, restoring of the re-adjusting means requires application of an axial force simultaneously with a rotating movement thereby rendering the restoring process relatively complex.

It is, an object of the present invention to provide a re-adjusting means of the kind referred to wherein the restoring process is simplified. Moreover, the unfavourable influence of the elasticity in the brake housing and on the pad is to be eliminated by means of the readjusting device.

According to one aspect of the invention there is provided a re-adjusting device for a disc brake, in particular, for an automotive vehicle of the kind comprising a horizontally adjustable- thrust member provided with a readjustable spindle-and a re-adjusting nut in engagement with one another through a selflocking thread, a pivotally disposed actuating member, means for translating a rotary movement into an axial movement including an axially movable part engaging the horizontally adjustable thrust member to force the latter axi ally against an actuating member, a rotable follower in engagement with the actuating member through a backlash connection, and comprising a unidirectionally acting clutch for transferring the rotation of the follower to the movable portion of the thrust member, characterised in that there is provided between the unidirectionally switching clutch and the thrust member a ball ramp clutch for transferring moments up to a predetermined magnitude to the thrust member but which, for movements above that magnitude, is ineffective.

According to another aspect of the invention there is provided a re-adjusting device for a disc brake, especially for an automotive vehicle, of the kind comprising a horizontally adjustable thrust member provided with a readjusting spindle and a re-adjusting nut in engagement through a self-locking thread, a rotatably disposed actuating member, means for translating a rotary movement into an axial movement, including an axially movable part engaging the horizontally adjustable thrust member to force the latter axially against a brake actuating member, a rotatable follower in engagement with the actuating member through a backlash connection, and comprising a unidirectionally acting clutch for transferring the rotation of the follower to the movable part of the thrust member, characterised in that there is provided between the unidirectionally acting clutch and the thrust member a spring clutch for transferring moments up to a predetermined magnitude to the thrust member but which, for moments above that magnitude is inef fective.

There is thus provided a re-adjusting means that is simple in construction and wherein the rotating movement required for re-adjustment, in the brake application direction, is transferred through a single coupling to the threaded spindle such that re-adjustment is performed during brake application. During development of the braking force, an increasing frictional moment is built up in the thread of the thrust member which, in the stretch area, exceeds the moment transferrable by the coupling thereby rendering the coupling ineffective and discontinuing transfer of the rotating movement as initiated. Hence, the re-adjusting process is shifed to the abutment area prior to commencement of the stretch thereby precluding re-adjustment of the stretch travel. Restoring of the threaded spindle during pad replacement can be effected by simply turning the re-adjusting spindle.

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 section through a first embodiment of a disc brake comprising a re-adjusting means; Figure 2 is a sectional view along the line A-A in Figure 1; Figure 3 is a longitudinal section through a second embodiment of a disc brake comprising a re-adjusting means; Figure 4 is a longitudinal section through a third embodiment of a disc brake comprising a re-adjusting unit; Figure 5 is a longitudinal section through a fourth embodiment of a disc brake comprising a re-adjusting unit; Figure 6 is a sectional view along the line A-A in Figure 5; Figure 7 is a longitudinal section through a fifth embodiment of a disc brake, comprising a re-adjusting unit, and Figure 8 is a sectional view along the line B B in Figure 7.

Referring to the drawings, Figure 1 illustrates a part of a disc brake housing 1 in which is located an actuating means comprising a re-adjusting unit for a brake piston 2.

The brake piston 2 of cup-shaped configuration is axially displaceable in an axial bore 3 of the brake housing 1, with the closed end 4 of the brake piston 2 facing an intermediate member 5 in abutting relationship. The intermediate member 5 is, in turn, in abutment with the back plate 6 of a brake pad 7 such that the latter, during axial displacement of the brake piston 2, is axially displaced through the intermediate member 5 in order to be forced against a brake disc (not shown). When applying the brake pad 7 to the brake disc, a reaction force is developed displacing the brake housing 1 in the opposite direction, causing a leg of the brake housing 1 (not shown) to force a brake pad (not shown), provided on the other side of the brake disc, against the other side of the brake disc.To protect the bore 3 against contamination, a protective cap or gaiter 8 is provided which is fixed in grooves of the brake housing 1 and of the brake piston 2.

Screwed to the brake housing 1 is a pin 9 radially extending into an axial recess 10 of the brake piston 2 thereby rendering the latter non-rotational relative to the brake housing 1.

For applying the brake, an actuating member 12 is rotatably disposed in a bore 11 at the right hand end of the brake housing 1. The actuating element 12 comprises a cylindrical bearing section 13 and an actuating lever 14.

The cylindrical bearing section 13 extends through the bore 11 into the bore 3 and its side remote from the actuating element 12 is in abutting relationship with a means 15 serving to translate the rotary movement of the actuating member 12 into an axial movement.

The means 15, in this instance, is a roller ramp comprising two ramp elements 16,17 between which are located rollers 18. The ramp element 16 nearer to the actuating member 12, is connected thereto through bolts 19 whereby rotary movement of the actuating element 12 results in a corresponding rotary movement of the ramp element 16.

The second ramp element 17 is held non rotationally which is achieved in that the pin 9 engages a corresponding recess 20 of the ramp element 17. The recess 20 is axially extended so that the ramp element 17 is able pad 7 to the brake disc, a reaction force is developed displacing the brake housing 1 in the opposite direction, causing a leg of the brake housing 1 (not shown) to force a brake pad (not shown), provided on the other side of the brake disc, against the other side of the brake disc. To protect the bore 3 against contamination, a protective cap or gaiter 8 is provided which is fixed in grooves of the brake housing 1 and of the brake piston 2.

The second ramp element 17 is held nonrotationally which is achieved in that the pin 9 engages a corresponding recess 20 of the ramp element 17. The recess 20 is axially extended so that the ramp element 17 is able to perform an axial movement although unable to perform a rotating movement. Provided between a disc 21, disposed at an end of the bore 3, and the ramp element 16 is a roller bearing 22.

The roller ramp 15 acts through the ramp element 17 upon a horizontally adjustable thrust member 23 formed by a re-adjusting nut 24 and a re-adjusting spindle 25 which, through a seif locking thread 26, are in engagement with one another. The re-adjusting nut 24 comprises an axially extending shaft section 27 and a radially extending flange section 28. Also, the readjusting spindle 25 comprises an axial shaft section 29 and a radial flange section 30. The flange sections 28, 30 of the re-adjusting nut and of the re-adjusting spindle are facing the closed end 4 of the brake piston 2. The flange section 30 of the re-adjusting spindle 25 has its front side 31 in abutting relationship with the closed end 4 of the brake piston 2 and, through a break-off preventing mechanism 32, is fixed to the brake piston.The shaft sections 27,29 of the re-adjusting nut 24 and the re-adjusting spindle 25 extend through central bores 33, 34 provided in the ramp elements 16, 17 toward the actuating member 12, with the ends thereof remote from the flanges located in a cylindrical recess 35 of the actuating member 12. Provided at the circumference of the shaft section 27 of the re-adjusting nut 24 is an annular groove 36 in which a ring 37 is seated. Supported on this ring is a compression spring 38 the other end of which is in abutment with a shoulder 39 of the ramp element 16 thereby causing facing surfaces of the flange sections 28, 30 of the re-adjusting nut and re-adjusting spindle to remain in abutting relationship.

The couplings provided according to the invention are also disposed in recess 35 of the actuating member 12. Located in the hollow re-adjusting spindle 25 is a spline-shaft connection 40 comprising a partially longitudinallysplined shaft 41 inside the correspondingly splined interior of the shaft section 29 of the spindle 25. In this manner, the shaft 41 can move axially within the spindle 25 but is locked to it for rotation therewith, the shaft 41 has a bearing section 42 protruding from the hollow re-adjusting spindle 25 toward the actuating member 12.

Disposed on the bearing section 42 of the shaft 41 is a ball ramp coupling 43 comprising a re-adjusting sleeve 44 rotatably disposed on the bearing section 42 of the shaft 41 and forming part of a follower means to be described in greater detail in the following. Disposed opposite the re-adjusting sleeve 44 is a coupling disc 45 non-rotationally connected to the bearing section 42. The outer diameter of the disc 45 corresponds to that of the readjusting sleeve 44. The coupling disc 45, on the side facing the re-adjusting sleeve 44, comprises ball ramps one of which is designated by numberal 46. Respectively disposed in the ball ramps 46 are balls 47 held in a ball cage 48. The ball ramp coupling 43 is located in a re-adjusting housing 49 positioned with low clearance in the cylindrical recess 35 of the actuating member 12.Also disposed in the re-adjusting housing 49 is a cup-spring package 50 seated on an axial extension of the coupling disc 45. The cup-spring package 50 is on the one hand, in abutment with the coupling disc 45 and, on the other hand, with a ring 51, which, via a safety ring 52, is held in the re-adjusting housing 49.Supported on ring 51, on the other side thereof, is a spring 53 located in a recess 54 of the adjusting nut 24. Located on an axial extension 55 of the re-adjusting sleeve 44 is a slip ring 56 cooperating with sliding faces formed on the re adjusting sleeve 44 and on an inwardly protruding flange portion of the re-adjusting hous ing 49.A pre-loaded spring 57 is provided on the extension 55, one end section 58 of which engages a radial bore 59 of the readjusting sleeve 44 and the other section 60 of which is tied to a pin 61 whose free end, protruding from the actuating member 12, can move between the ends of a recess 62 extending for a small distance in a circumferential direction in the sleeve 44.

The way of operation of the disc brake and the re-adjusting unit, respectively, as illustrated in Figures 1 and 2 will now be described as follows: In the resting position, pin 61, under the influence of the torsion spring 57, is in abutment with the right hand end of recess 62 of the re-adjusting sleeve 44 as shown in Figure 2. After a short (clockwise) travel of the lever 14 (lost travel), the recess 62 has been reached pin 61 attached to the actuating member 12 moves to the left hand end of the recess 62 (Figure 2) and the load on the torsion spring 57 is increased beyond its preloading. Continued movement of the actuating member (abutment travel) causes re-adjustment sleeve 44 to be entrained and similarly moved. During that actuating phase, clutch disc 45, cup-spring package 50, re-adjusting housing 49 and splined shaft 41 will all be entrained and similarly moved.As a result thereof, also the re-adjusting spindle 25 will rotate so as to cause a re-adjusting process.

During another actuating phase, the re-adjusting forces will reach a value such that the coupling force is exceeded. The clutch disc 45 and the splined shaft 41 will thereby come to a standstill, although the re-adjusting sleeve 44 will continue to rotate thereby causing the balls in the cage 48 to be entrained. The balls will move up the ramps 46 along the clutch disc 45 thereby necessarily increasing the spring bias of the cup-spring package 50 which, however, has no bearing on the function. It should be noted that the cup-spring bias will increase only until as the balls 47 have reached the end of the ball ramps 46 and are continuing to run along a planar path.

During the whole of this phase of movement (brake clamping travel) the re-adjustment process is discontinued.

The coupling force is dependent on the spring bias of the cup-spring package 50 and the slope of the ball ramps. However, the latter will have to be at an angle which is sufficiently small to enable the balls 47 to be carried along through the re-adjusting sleeve 44 by friction. The coupling force is increased by the friction force of the sealing ring 56 disposed between the re-adjusting housing 49 and the re-adjusting sleeve 44. In general, the coupling force must exceed the re-adjusting force.

During the return (anti-clockwise) movement of the actuating lever 14, there is first a last motion phase in which the clamping load is decreased, with pin 61 returning to the right hand end of the recess 62. Thereafter, the readjusting sleeve 44 containing the recess is carried round until the balls have reached their initial position in the spherical surface of the ramp.

Subsequently, during the residual travel of the lever 14 the one coupling half, with coupling disc 45, comes to a standstill and readjusting sleeve 44 forming the second coupling half, is caught by the lever until the latter is again in its initial position. The combined resultant frictional moments occurring between the balls 47 and the re-adjusting sleeve 44, and between the re-adjusting sleeve 44 and the slip ring 56, are required to be lower than the re-adjusting moments as otherwise the piston is restored. During replacement of pads, the coupling moment must be manually overcome by rotation of the splined shaft 41, with the balls 47 overriding.

During restoring of the piston the moment is lower, as in that case, only frictional forces will have to be overcome.

Figure 3 shows another form of embodiment of a spot-type disc brake comprising a re-adjusting unit. To the extent that the latter as well as the associated disc brakes and readjusting units are identical with those of the embodiment shown in Figures 1 and 2, identical reference numerals have been employed.

To avoid repetitions, a description of such parts has been omitted.

The re-adjusting unit according to Figure 3 comprises a re-adjusting housing 70 of a multiple-step configuration. Disposed in a smaller diameter section 72 of the re-adjusting housing, is a section of a re-adjusting sleeve 73. In a larger diameter section 71 is disposed the coupling disc 45. Located on a radially projecting section 74 of the re-adjusting sleeve 73 is a sliding ring 75 cooperating with a radially inwardly projecting section 74 of the re-adjusting housing 70. Between the sliding ring 75 and the friction surface disposed opposite the ring-shaped surface of the re-adjusting housing is a space 'a'. A torsion spring of the type provided in the example of embodiment according to Figures 1 and 2 is not required in this embodiment of the readjusting unit.

The way of operation of the re-adjusting unit shown in Figure 3 largely corresponds to that of the one according to Figures 1 and 2,exhibiting the following characteristics: The "lost travel" of the actuating lever 14 determining the size of the pad clearance is controlled by clearance "a" between the sliding ring 75 and re-adjusting housing 70. In the return travel of lever 14, the frictional moments arising from the combined sliding friction between balls 47 and re-adjusting sleeve 73 and between re-adjusting sleeve and actuating lever 14 are very low. The statements relative to the embodiment shown in Figures 1 and 2 are also applicable to the forward and backward rotation of the brake piston 2 during replacement of pads which, however, pro vides an additional advantage.The whole of the coupling package can be unlocked in that the toothed shaft 40 is forced forward meaning, however, that adequate space is required between the coupling and the re-adjusting nut 24.

Figure 4 shows a third embodiment of a readjusting means wherein, again, only the dif ferences from the embodiment in Figures 1 and 2 have been illustrated. In this re-adjusting unit, the ball cage 79 comprises a spring flag 80 bent in the axial direction and engaging a recess 81 of the clutch disc 82, with cams 83 disposed in that recess. A cupspring package 84, on one side, is supported through a safety ring inserted into the re-adjusting housing 49 and, on the other side, is supported on a ring 85 displaceable with the clutch disc 82.

The lost travel, in this re-adjusting unit is provided in the recess on the re-adjusting sleeve 44. The ball cage 79, through the spring flag 80, always places the balls into an abutting position on the ramp in that the spring flag 80, through cams 83, slides along the clutch disc 82. This re-adjusting unit has the advantage of low moments of return travel.

Figures 5 and 6 show a fourth embodiment of a re-adjusting means, wherein a re-adjusting sleeve 90 is rotatably disposed on the bearing section 42 of a splined shaft 41. The re-adjusting sleeve comprises an axially extending cylindrical section 91 and a radially extending section 92. Provided in the radially extending section 92 of the re-adjusting sleeve 90 is a recess 93 which extends across a part of the circumference of section 92 and which is engaged by a pin 94 fixed to the actuating member 12.

Provided on the cylindrical section 91 of the re-adjusting sleeve 90 is a unidirectionally switching clutch 98 which, in this instance, is formed by a needle roller freewheel. The outer clutch ring 99 of coupling 98 comprises a friction cone 100 cooperating with a friction cone 101 provided on a coupling member 102 to form a friction clutch 103. The coupling member 102, through a pressure connection 104, is non-rotationally disposed on the splined shaft 41.

Coupling member 102 is held, in the axial direction, by a re-adjusting housing 105 which, by flange sections 106, 107, engages, on the one hand, cqrresponding recesses in the coupling member and, on the other hand, the re-adjusting sleeve 90. Located between sections 91, 92 of the re-adjusting sleeve 90 and the clutch ring 99 is a cup-spring package 108 forcing the clutch ring against the coupling member 102 to produce frictional engagement between cone 100 and cone 101.

A compression spring 109 is disposed in a recess 110 provided on the inner side of the re-adjusting nut 24 and, on the one hand, is supported on a shoulder of the re-adjusting nut and, on the other hand, on the coupling member. Provided on the end of the bearing section 42 of the splined shaft 41 is a recess 95 comprising an internal hexagon for insertion of a corresponding tool to rotate the shaft 41. A compression spring 111 is provided in the embodiment as shown in Figures 5 and 6 as it is in the one according to Figures 1 and 2, which compression spring, on the one hand, is in communication with pin 94 and, on the other hand, with a re-adjusting sleeve 90.

The way of operation of the re-adjusting unit shown in Figures 5 and 6 is as follows: In the resting position, pin 94, as a result of the clamping forces of the torsion spring 111, is in abutment with the right hand end of the recess 92 of the re-adjusting sleeve 90. After a short travel of the lever (lost motion), the torsion spring 111 continues to be loaded and pin 94 moves within the recess of the readjusting sleeve 90 until it is in abutment with the left hand end of the recess. When the lever continues to travel (abutment travel) the readjusting sleeve 90 is entrained. As the freewheeling of the sleeve in that direction is blocked, the clutch ring 99 and, hence, the coupling member and the coupling disc 102, respectively, are caught through frictional resistance.Frictional resistance exists between the clutch ring 99 and the clutch disc 102 as a result of the force of the cup-spring package 108. The splined shaft 41 is moved along with the clutch disc as these two parts are in communication by compression. Consequently, also the re-adjusting spindle 25 is moved thereby causing a re-adjusting process. Re-adjustment is effected by screwing out the readjusting spindle 25 of the re-adjusting nut 24. Re-adjustment and screwing out the readjusting spindle is effected until the pads come into abutment with the brake discs. During abutment of the pad, the "abutment force" now exerted on the actuating lever 14, results in an increase in the frictional forces between the re-adjusting spindle 25 and the brake piston 2 and between thelre-adjusting spindle 25 and the re-adjusting nut 24 (thread friction).The torque thus prevailing on the readjusting spindle 25 exceeds the limited torque caused by frictional resistance between the parts of the re-adjusting coupling, i.e. the clutch ring 99 and the clutch disc 102, and between the clutch disc 102 and the re-adjusting housing; as a result of a continued travel of the lever (clamping travel), the splined shaft will come to a standstill thereby causing slippage on the re-adjusting coupling. No further re-adjustment can thus be effected.

When reversing the lever travel (releasing direction) first a return travel of pin 94 is performed within the recess 93 in the initial position (return lost travel). If the lever continues to move until the resting position is reached (residual return travel), the re-adjusting sleeve 90 is entrained with almost no force applied as the sleeve freewheel now in the freewheeling position does not effect a force transfer to the coupling ring 99, in other words, the actuating phase is subdivided into three stages: 1. Lost travel 2. Abutment travel 3. Clamping travel The lost travel determines the size of the pad clearance; re-adjustment is discontinued. During the abutment travel, pad wear is set of f by re-adjustment of the piston. During the clamping travel, the force for deceleration is applied; re-adjustment is discontinued.The releasing phase is subdivided into return travel and residual return travel; re-adjustment is discontinued in either case. In pad replacement, the toothed shaft 40 is manually restored, with the sleeve freewheel being in the blocking direction. This means that the coupling moment and the readjusting moment (friction between the re-adjusting spindle 25 and piston and thread friction between re-adjusting spindle 25 and readjusting nut 24) must be applied. When restoring the piston by hand, only the re-adjusting moment will have to be produced as the sleeve freewheel is in the freewheeling position.

Figures 7 and 8 show a fifth embodiment of a re-adjusting device, with the re-adjusting coupling, in this instance, being configured as a spring clutch, with a re-adjusting sleeve 115 being provided on the splined shaf t 41. Disposed between shaft 41 and the re-adjusting sleeve is a sleeve freewheel 116. A coupling ring 117 is rotatably seated on the re-adjusting sleeve 115. The rotary movement of the coupling ring 11 7 on the re-adjusting sleeve 115 is limited by means of a pin 118 located in the coupling ring 117, the pin 118 protruding into a recess 119 in the re-adjusting sleeve 115. The rotary movement of the coupling ring 117 over the actuating lever 14 is limited by an axially extending pin 120 attached to the actuating lever and engaging a recess 121 extending across a predetermined area along the circumference of the coupling ring 117.A torsion spring 122 is disposed concentrically in relation to the coupling ring 117, with the radially extending ends thereof engaging corresponding bores provided in the re-adjusting sleeve 115 and in the coupling ring 117. The re-adjusting sleeve 115 is disposed between two rings 123, 124 seated in grooves of the toothed shaft 40, with a cupspring package 125 being provided between the ring 124 and the re-adjusting sleeve. A spring 126 in abutment with the re-adjusting nut 24, on the other side, is in abutment with a radial extension of the re-adjusting sleeve 115.

The re-adjusting device illustrated in Figures 7 and 8 is similar to the one shown in Figures 5 and 6 except for the substantial difference that the re-adjusting coupling is in the form of a spring clutch.

In a first actuating phase (lost travel), pin 120 moves within the recess 121 of the coupling ring 117; re-adjustment is discontinued during that phase. During the second actuating phase (abutment travel), the coupling ring 117 is caused to be entrained.Thanks to the load on the torsion spring 122, the re-adjusting sleeve 115 is entrained. The latter, through, the sleeve freewheel 116, carries along the splined shaft 41; re-adjustment is effected by rotation of the re-adjusting spindle 25 in the manner already described. During the third actuating phase (clamping travel), the friction moment on the re-adjusting spindle 25 attains a value high enough to overcome the loading of the torsion spring 122.The re-adjusting sleeve 115 then comes to a standstill whereas the coupling ring 117 continues to be entrained through the actuating lever 14 in such a way that the load of the torsion spring increases which, however, is of no influence; re-adjustment is discontinued.

During the releasing operation, the conditions of movement are reversed. During a first phase (decrease in the clamping load), the coupling ring 117 travels in the opposite direction until pin 118 comes into abutment with the wall confining the recess 119. During the second phase (lost travel), the pin 120 moves within the recess 121 in the coupling ring 117 in the initial position. The coupling ring 117, through friction of the cup-spring package 125, via re-adjusting sleeve 115, is held in the resting position. During the third phase (residual travel), the lever 14 is restored to the resting position, with the component parts coupling ring 117 and the re-adjusting sleeve 115 being entrained without rotation of the splined shaft 41 as the sleeve freewheel is turned to the direction of freewheeling. A sliding sleeve 127 located between the re-adjusting sleeve 115 and the coupling ring 117 provides for minimum friction between these parts. In pad replacement, the splined shaf t 41 is engaged against the low spring force of spring 126 and the re-adjustment disengaged from the pin 120. Now, the brake piston can be restored or advanced with a small torque on the gear shaft.

Claims

1. A re-adjusting device for a disc brake, in particular, for an automotive vehicle of the kind comprising a horizontally adjustable thrust member provided with a re-adjustable spindle and a re-adjusting nut in engagement with one another through a self-locking thread, a pivotally disposed actuating member, means for translating a rotary movement into an axial movement including an axially movable part engaging the horizontally adjustable thrust member to force the latter axially against an actuating member, a rotable follower in en gagement with the actuating member through a backlash connection, and comprising a unidirectionally acting clutch for transferring the rotation of the follower to the movable portion of the thrust member, characterised in that there is provided between the unidirectionally switching clutch and the thrust member (23) a ball ramp clutch (43) for transferring moments up to a predetermined magnitude to the thrust member (23) but which, for movements above that magnitude, is ineffective.

2. A re-adjusting device according to claim 1, characterised in that a rotatable part (44) of the follower is an intergral part of the ball ramp clutch (43).

3. A re-adjusting device according to claims 1 or 2, characterised in that the ball ramp clutch (43) comprises a coupling disc (45) with ball ramps (46) located therein.

4. A re-adjusting device according to claims 2 or 3, characterised in that the rotatable part (44) of the follower and the clutch disc (45) are located on a common shaft (40).

5. A re-adjusting device according to claim 4, characterised in that the ball ramp clutch (43) is disposed in a re-adjusting housing (49).

6. A re-adjusting device according to claim 5, characterised in that a slip ring (56) is provided between the ball ramp clutch (43) and the re-adjusting housing (49).

7. A re-adjusting device according to claims 5 or 6, characterised in that a defined clearance (a) determining the size of the pad clearance is provided between the re-adjusting housing (49) and a rotatable part of the follower forming part of the ball ramp clutch (43).

8. A re-adjusting device according to any one of the preceding claims, characterised in that the balls (47) of the ball ramp clutch (43) are provided in a ball cage (48).

9. A re-adjusting device according to claim 8, characterised in that a ball ramp clutch (43) includes an actuating means (79, 80, 83) to maintain the ball cage and the balls, respectively, in a position of abutment relative to the ramp.

10. A re-adjusting device in accordance with any one of the preceding claims, characterised in that a torsion spring (57) is provided, the one end of which is rigidly connected to the housing and the other end of which engages a rotatable part (44) of the follower means.

11. A re-adjusting device according to claim 10, characterised in that the torsion spring (57) is located on an extension of the rotatable part.

12. A re-adjusting device for a disc brake, especially for an automotive vehicle, of the kind comprising a horizontally adjustable thrust member provided with a re-adjusting spindle and a re-adjusting nut in engagement through a self-locking thread, a rotatably disposed actuating member, means for translating a rotary movement into an axial movement, including an axially movable part engaging the horizontally adjustable thrust member to force the latter axially against a brake actuating member, a rotatable follower in engagement with the actuating member through a backlash connection, and comprising a unidirectionally acting clutch for transferring the rotation of the follower to the movable part of the thrust member, characterised in that there is provided between the unidirectionally acting clutch and the thrust member a spring clutch (122) for transferring moments up to a predetermined magnitude to the thrust member but which, for moments above that magnitude, is ineffective.

13. A re-adjusting device according to claim 12, characterised in that the spring clutch comprises a torsion spring (122) engaging, with one end thereof, a rotatable part (44) of the follower.

14. A re-adjusting device according to claim 13, characterised in that the other end of the torsion spring (122) engages a rotatably disposed portion (115) connectible to a part of the thrust member.

15. A re-adjusting device according to claim 14, characterised in that the rotatably disposed part (115) is located on a shaft 41, and that a unidirectionally acting clutch (116) is provided between the shaft and the rotatable part.

16. A re-adjusting device for a disc brake substantially as described with reference to the accompanying drawings.