GB2262145A - Floating-caliper spot-type disc brake for high-powered vehicles - Google Patents

Abstract

A brake shoe, for a floating caliper spot-type disc brake, comprises a friction lining 40, 41 and a backplate 38, 39 formed with a projection 42 which projects from the plane of the backplate and is widened towards its free end. The backplate may also be provided with a pair of spaced parallel oblong webs 63, 64. The projections may be pressed into (Fig. 11), welded to (Fig. 12) or formed integrally with (Fig. 13), the back plate. In use, the shoe is fixed to a piston or a caliper by a spring biasing projection 42 into engagement with a recess (47, Fig. 6, or 43, Fig. 11-13). <IMAGE>

Description

FLOATING-CALIPER SPOT-TYPE DISC BRAKE FOR HIGH-POWERED VEHICLES The present invention relates to a floating-caliper spot-type disc brake designed for a high brake power.

Automotive vehicles which reach high driving speeds need more and more powerful brakes. High-performance brakes require, among other things, as large as possible a brake disc diameter. On the other hand, the diameters of the vehicle wheels ought not to be increased. By these two conditions the mounting space for the brake is being extremely restricted between the external edge of the brake disc and the wheel rim. The brake caliper of a disc brake customarily straddles the external edge of the brake disc, the radial dimensions of a bridge of the brake caliper positioned in the forementioned mounting space limiting the maximum diameter of the brake disc. The caliper bridge must, on the other hand, present a determined minimum thickness because it transmits the clamping forces which are required for braking action.

From the European patent specification, No.

0,412,541 a disc brake suitable for a high brake power is known whose brake caliper is designed in the shape of a floating frame which is axially slidingly guided at a brake carrier being firmly coupled to the steering knuckle of the vehicle by means of pin guides and which extends in axial direction beyond the external edge of the brake disc. Said floating frame encloses four brake shoes which are disposed on either side of the brake disc and transmits the clamping force. The circumferential forces are transmitted by the brake shoes to the brake carrier. Said brake carrier is coupled to the vehicle on the axially internal side of the wheel. In order to be able to also absorb the circumferential forces of the two axially external brake shoes, the brake carrier is furnished with a carrier arm which straddles the external edge of the brake disc.

High-performance brakes require large friction areas of the brake shoes. An increase in size of the brake shoes, in particular in the circumferential direction of the brake disc, has, however, the disadvantage that the friction area is no longer uniformly pressed against the brake disc, neither if and when instead of one, two brake cylinders arranged side by side are used. Beyond this, large brake shoes favour the generation of braking noises and of rubbing, especially when the circumferential force which occurs during braking is transmitted by the brake shoe to the brake housing on the leaving side of the brake disc.

For this reason, two short-size brake shoes are used which are pressed against the brake disc separately from each other by two brake pistons which are arranged one aside the other.

It is another requirement a high-performance brake has to meet that its weight is to be as low as -possible.

Indeed, heavy brakes stage a particular problem because the unsprung masses at the vehicle wheels are increased by them.

This, in turn, has negative effects on the driving behaviour of the vehicle. The brake power cannot for this reason be increased simply by increasing the brake in size.

Preferably the present invention provides a floating-caliper spot-type disc brake with high brake power; a comfortable behaviour of the brake as to the generation of noise and rubbing being aimed at.

According to the present invention there is provided a floating-caliper spot-type disc brake for automotive vehicles; the brake having a brake carrier which is rigidly anchored to the steering knuckle of the vehicle; having a floating caliper which extends beyond the external edge of a brake disc and which is axially slidingly guided at the said brake carrier by means of pin guides; having brake shoes which are disposed on either side of the brake disc and of which a first one and a second one are arranged on the axial internal side of the brake disc and at a distance from each other in the latter's circumferential direction and are supported at the said brake carrier; and having a hydraulic actuating unit which is intended for urging the said brake shoes against the brake disc and which is positioned on the axially internal side of the said floating caliper and is comprised of at least two brake cylinders with brake pistons sliding therein; wherein a third said brake shoe is disposed on the external axial side of the brake disc and is fixed to the said floating caliper; and the friction area point of gravity of the said third brake shoe is situated in the circumferential direction of the brake disc substantially in the middle between the friction area points of gravity of the said two first and second brake shoes being positioned on the internal axial side.

In principle the centres of gravity of the friction areas of brake shoes abutted against different axial sides of the brake disc are arranged not opposite one another but staggered with respect to one another in the circumferential direction of the brake disc.

In one form of the invention there are provided three brake shoes, two of which are positioned on the internal axial side of the brake disc and at a distance from each other in circumferential direction. A third brake shoe is disposed on the other axial side and viewed in projection covers with its friction area the distance of the other two brake shoes. In this configuration, the friction area of the third brake shoe preferably corresponds to the sum of the friction areas of the other two in order to make sure that all three of the brake linings are being abraded in a roughly uniform way.

In another form four brake shoes are provided out of which two are disposed on the internal axial side and two on the external axial side of the brake disc. The first two brake shoes have a smaller distance from each other in circumferential direction than the latter two, as a result whereof a staggered arrangement comes about again.

Experience teaches that the staggered arrangement offers the advantage that any rubbing of the brake or braking noises, such as, for example, squealing, are largely avoided. This is presumably because of the main points of stress being disposed spatially staggered along the brake disc vibratory undulations and changes of thickness of the brake disc from one point of stress to the other having a temporally staggered balancing effect.

In a preferred embodiment of the invention the circumferential force occurring during braking action is transmitted from a brake shoe being fixed on the external axial side to the floating caliper not directly to the brake carrier but indirectly through the floating caliper. In this case, the brake carrier may be of particularly simpledesign and light-weight, since it is not required to extend from one axial side of the brake disc to the other beyond the latter's external edge in order to absorb there directly the circumferential force of an external brake shoe.

A pin guide with a supporting pin which transmits the circumferential force and with an elastically guided guide pin offers the advantage that inaccuracies which are due to manufacturing techniques, for example slightly differing distances between the two pins, can be balanced by the elastic guide.

The supporting pin is preferably disposed symmetrically in the centre of the brake. Thanks to the uniform flux of force at this point and because the pin acts on a zone of the brake carrier which for the rest is not stressed but at a slight extent, the pin guide cannot practically cant in this arrangement and offers, therefore, great ease of movement.

The brake carrier is particularly suitable for integration in the steering knuckle of the vehicle if it comprises a fixing section which extends substantially in the circumferential direction of the brake disc and starting from which a central carrier arm and two carrier arms being positioned externally in the circumferential direction extend radially in the direction of the edge of the brake disc in order to absorb the circumferential forces of the first and of the second brake shoes which are each positioned between the said carrier arms, with the central carrier arm being formed with a bore for the accommodation of the supporting pin and with the two external carrier arms being each formed with a bore for the guide pins.

In particular in case of an integrated brake carrier it is recommended to firmly press the pin into a bore of the brake carrier. Depending on the spatial conditions, it may, however, else be more favourable to firmly press the supporting pin into the floating caliper in the range of the hydraulic unit. The weight of the brake may be reduced still further with the supporting pin being hollow in its axially sliding section.

If the floating caliper is designed in a shell-type construction with recesses through which the brake shoes can be withdrawn radially outwardly or be incorporated and the range of the floating caliper which straddles the external edge of the brake disc is, in particular, designed very narrow, then the caliper has a very small mass in conjunction with an extreme rigidity and affords a large diameter of the brake disc since thanks to its low thickness it requires little mounting space in the range between the external edge of the brake disc and the wheel rim. The requirements of a high-performance brake are, therefore, met particularly well in this instance. This is supplemented by the ease of maintenance because the brake shoes can be mounted and be demounted in an easy way through the recesses of the floating caliper.

A floating-caliper housing which is divided into two parts is recommended for manufacturing technique reasons because the brake cylinder bores can so be tooled in an easy manner. By coupling of the housing parts by means of three screws the weight of the brake can be reduced still further with respect to the use of four screws which are otherwise customary. Moreover, the vibration behaviour of the brake will be favourably influenced by the centrally disposed screw coupling.

On the other hand, the floating caliper may, however, alternatively be designed one-part. In this case, the brake cylinder bores would have to be carried out from the outside and the hydraulic cylinders subsequently be closed by cover lids.

In case of the customary mode of fixing of the brake shoes as is, indeed, also known from the European patent specification, No. 0,412,541, viz. to retaining pins which are disposed in the range between the wheel rim and the external edge of the brake disc the maximum possible diameter of the brake disc might be restricted. Moreover, special tools are required for mounting and for demounting of the brake shoes.

In a recommendable further development of the invention these disadvantages do not turn up. The fixing means are positioned on the reverse of the brake shoes and in the internal range of the brake, and they do not restrict the brake disc diameter. For mounting, a brake shoe is inserted from the outside through a recess of the floating caliper, is urged radially against a spring and is locked at the floating caliper or at a brake piston with a projection of the backplate. Mounting and demounting will allow to be carried out safely and quickly manually.

There are various preferred design versions of the brake shoes with regard to the mentioned fixing means. A conical shape of the projection of the backplate safeguards that the brake shoe is being urged against the brake piston or against the floating caliper free of rattling,. A spring being intended for prestressing of a brake shoe which is abutted against the brake piston can be simply configurated and be locked at the brake carrier. A simple-design spring for prestressing of the brake shoe can be fixed to the floating frame.

The inventive disc brake will allow still to be improved as to its noise behaviour by a combination of further features. Webs can serve for transmitting the circumferential force from a brake shoe disposed on the external axial side to the floating frame. It can be safeguarded by the arrangement and particularly by the distances of webs and grooves relative to one another that the circumferential force is always transmitted through the web being disposed on the entering side of the brake disc.

According to experience such a "dragged" brake shoe will not be excited to perform noise-generating vibrations.

Leaf springs and brake shoes which are intended for use in a disc brake according to the present invention and which are configurated accordingly, are also features of the present invention.

Constructional embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 shows a top view of disc brake according to the present invention with three brake shoes.

Figure 2 shows a perspective total view of the disc brake; Figure 3 shows a representation of the points of gravity of the friction areas being disposed in a staggered arrangement; Figure 4 shows a back view of the disc brake as seen from the direction A in Figure 1; Figure 5 shows a partly sectioned front view of the disc brake as seen from the direction B in Figure 1; Figure 6 shows a cross section along the line C-C in Figure 1, with a supporting pin which is pressed into the brake carrier; Figure 7 shows a sectioned partial view as in Figure 6, with a supporting pin which is pressed into the floating caliper; Figure 8 shows a perspective representation of the brake carrier; Figure 9 shows a perspective representation of a brake shoe which is intended to be fixed to the floating caliper; Figure 10 shows a perspective representation of a brake shoe which is intended to be fixed to the brake carrier and to the brake piston; Figure 11 shows a sectioned detail of the brake shoe fixing means with a pin which is pressed into a bore of the backplate of a brake shoe; Figure 12 as in Figure 11, with a pin which is welded to the backplate; and Figure 13 as in Figure 11, with a buttonhead through projection which is shaped out of the backplate.

In Figures 1 and 2 above all a floating caliper 1 is visible which is realised in a shell-type construction with three large recesses 2, 3, 4 through which three brake shoes 5, 6, 7 can be incorporated and be withdrawn. The floating caliper 1 extends beyond the external edge of a brake disc 10 (Figure 6) and is provided on the inner axial side with a hydraulic unit which is comprised of brake cylinders 11, 12 being positioned side by side and of two brake pistons 13, 14.

The floating caliper 1 is composed of two housing parts 8, 9 which are coupled together by three screws 15, 1 & , 17. One screw 16 is positioned in the centre of the housing and two screws 15, 17 are arranged in line with the axes of the brake pistons (Figure 4) at the marginal ranges of the floating caliper 1 as seen in the circumferential direction of the brake disc 10. This arrangement guarantees that the screws 15, 16, 17 transmit no or only slight bending moments and substantially undergo exclusively tensile stresses. They do not, therefore, require to be dimensioned strongly. The bridge 18 which is coupled by the screw 16 contributes to the stiffening of the floating caliper 1. On the whole, the floating caliper 1 is optimised for a high-performance brake as to strength and weight thanks to its shell-type construction with the recesses 2, 3, 4 and thanks to the arrangement of the screws 15, 16, 17.

In Figure 8 a brake carrier 19 is illustrated which is formed with two bores 20, 21 for the passage of two anchor screws serving to anchor it to the steering knuckle of the vehicle which is not shown in the drawing. A central carrier arm 24 and two externally disposed carrier arms 23, 25 start from the fixing section 22 of the brake carrier 19.

Between said carrier arms 23, 24, 25 two brake shoes 5, 7 are axially slidingly arranged, the carrier arms 23, 24, 25 absorbing the circumferential forces from the brake shoes 5, 7 during braking action. The central carrier arm 24 is furnished with a bore 26 to accommodate a supporting pin 27 (Figure 6), and the two external carrier arms 23, 25 are formed with bores 28, 29 for two guide pins 30, 31.

On the pins 27, 30, 31 the floating caliper 1 is axially slidingly guided at the brake carrier 19. As is best seen in Figure 6, the brake shoe 6 which is disposed on the external axial side of the brake disc 10 is fixed to the floating caliper 1. The circumferential force which occurs during braking at the brake shoe 6 will be transmitted through the floating caliper 1 to the internal axial side and there to the supporting pin 27 which takes support at the brake carrier 19. Said supporting pin 27 is dimensioned particularly strongly and is firmly pressed intot he bore 26 of the brake carrier 19. It slides practically without play within a bore 32 of the floating caliper 1. For protection against dust, said bore 32 is closed by a cover lid 33, and an elastic sleeve 34 is positioned around the supporting pin 27 between the floating caliper 1 and the brake carrier 19.

In another embodiment which is illustrated in Figure 7 the supporting pin 27 is pressed into the bore 32 of the floating caliper 1, whereas it axially slides in the bore 26 of the brake carrier 19. The section of the supporting pin 27 which is pressed in in each instance is designed solidly for reasons of strength while the sliding section is hollow in order to save weight.

The guide pins 30, 31 slide in two elastic bearings 67, 68 in this embodiment. They do not transmit any circumferential forces but are intended exclusively for the elastic guidance of the floating caliper 1 and are, therefore, weakly dimensioned. The guide presents a play due to the elasticity of the bearings 67, 68 by which inaccuracies allow to be balanced which are due to the manufacturing technique.

As is visible in Figures 1 and 3, the brake shoes 5, 6, 7 are disposed staggered in the circumferential direction of the brake disc 10. The friction area point of gravity 36 of the brake shoe 6 is positioned, in the projection (Figure 3), in the middle between the friction area points of gravity 35, 37 of the brake shoes 5, 7. The friction area of the brake shoe 6 corresponds to the sum of the friction areas of the brake shoes 5, 7 and overlaps with the latter as is outlined by shading in Figure 3.

In Figures 9 and 10 the brake shoes 5, 6, 7 are shown once more singly. Each of them is substantially comprised of a backplate 38 or 39 and of a friction lining 40 or 41. On the side of the backplate 38, 39 facing away from the friction lining 40, 41 a pin 42 is pressed in which is intended for fixing of the brake shoe 5, 6, 7 in the brake. As is shown in Figure 11 by example of the brake shoe 5, 7, the pin 42 is conically widened toward its free end and engages a hollow brake piston 13, 14 where it is locked in a circumferential annular groove 43 and is in abutment with a conical section 44 of the annular groove 43.

As an alternative to this, a modified pin 45 may else be welded to the backplate 38 or 39 as is shown in Figure 12, most simply by friction welding. In a design version which is illustrated in Figure 13 there is no separate pin. In this instance, the backplate 38 or 39 is formed with a buttonhead through projection 46 whose projecting end has a conical shape.

For fixing of the brake shoe 6 the floating caliper 1 is provided with a stepped bore 47 which is engaged by the pin 42 (Figure 6).

In order that a brake shoe 5, 6, 7 is firmly locked with its pin 42 in the annular groove 43 or in the stepped bore 47, it has to be prestressed in radial direction 48.

Two leaf springs 49, 50 are fixed to the brake carrier 19 (Figures 4, 5) for the prestressing of the brake shoes 5, 7.

Each of the leaf springs 49, 50 has two anchor tongues 51, 52 with which they encircle the section 22 of the brake carrier 19 and lock there. The free end of the anchor tongue 52 which is bent over loop-shaped is utilised as a spring tongue 53 which is in abutment against the radially narrow side 54 of the brake shoe 5, 7 and urges it into the radial direction 48. The other brake shoe 6 is prestressed by another leaf spring 55 which is fixed at its central section 56 by means of a screw 57 to the floating caliper 1.

The leaf spring 55 is formed with two spring arms 58, 59 which, starting from the central section 56, point in opposite directions and are abutted against two points 60, 61 of the radially narrow side of the brake shoe 6.

At their radially external narrow sides each of the backplates 38, 39 of the brake shoes 5, 6, 7 is furnished with an ear 62 which serves to facilitate mounting. If, for example, a brake shoe 5, 6, 7 clamps it will be possible to make grip with a suitable tool at the ear 62 in order to be able to pull more firmly.

The backplate 38 of the brake shoe 6 is provided with two webs 63, 64 which extend at right angle to the circumferential direction of the brake disc 10 and parallel to each other. The webs 63, 64 engage associated grooves 65, 66 of the floating caliper 1. The width and the distance of the grooves 65, 66 are slightly larger than those of the webs 63, 64 so that the circumferential force will always be transmitted from the brake shoe 6 to the floating caliper 1 through the web which is positioned on the entering side of the brake disc.

Claims (8)

CLAIMS:

1. A brake shoe for use in a spot-type disc brake, with a friction lining (40, 41) and with a backplate (38, 39); wherein on the side facing away from the said friction lining (40, 41) the said backplate (38, 39) is formed with a projection (42, 45, 46) which projects from the plane of the said backplate (38, 39) and which is widened toward its free end.

2. A brake shoe as claimed in claim 1, wherein the said projection (42, 45) is formed by a pin (42, 45) or a bolt which is welded to the said backplate (38, 39) or pressed into a bore of the said backplate (38, 39).

3. A brake shoe as claimed in claim 1 or 2, wherein the said projection (46) is formed by a buttonhead through projection (46) which is shaped out of the said backplate (38, 39).

4. A brake shoe as claimed in any one of claims 1 to 3, wherein the said projection (42, 45, 46) comprises a conical section whose diameter increases toward the free end.

5. A brake shoe as claimed in any one of claims 1 to 4, wherein the other radially narrow side of the said backplate (38, 39) is furnished with an ear (62).

6. A brake shoe as claimed in any one of claims 1 to 5, which is intended for fixing to a floating caliper (1) on the latter's external axial side, wherein the said backplate (38) is furnished on the side facing away from the said friction lining (40) with two oblong webs (63, 64j which extend along the said backplate (38) at a distance from each other and parallel to each other.

7. A brake shoe as claimed in claim 6, wherein the said webs (63, 64) are shaped out of the said backplate (38).

8. A brake shoe substantially as described herein with reference to Figure 9 of the accompanying drawings.