Abstract:
A caliper disk brake of a vehicle with a brake disk, a brake caliper, a brake anchor plate, a force transmission element guided and supported in a shaft of the brake caliper or of the brake anchor plate, a holding-down spring for holding down the force transmission element, and a holding-down device held and supported on the caliper by a holding device, pretensions the holding-down spring radially against the force transmission device and pretensions the holding-down spring tangentially in the direction of rotation against the force transmission device during forwards travel. The holding device has a center line parallel to the axis of rotation of the brake disk. The tangential pre-tensioning is at least partially attributed to the dimensions of the holding-down device, as measured in the tangential direction from the center line, being larger at least in sections on the disk exit side than on the disk entry side.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a caliper disk brake of a vehicle, such as a commercial vehicle. 
     BACKGROUND OF THE INVENTION 
     Conventionally, a caliper disk brake includes a brake disk having an axis of rotation, a brake caliper, a back plate assembly, a force transmission element, such as a brake-pad plate and/or a pressure plate (which is guided and supported in a channel of the brake caliper or the back plate assembly), a hold-down spring for holding down the force transmission element and a hold-down device, which is held and supported on the caliper by a holding device having a centerline lying parallel to the axis of rotation. The hold-down device pre-stresses the hold-down spring radially against the force transmission device and pre-stresses the hold-down spring against the force transmission device tangentially in the direction of rotation in forward travel of the vehicle. Brakes of this general type under consideration are disclosed, for example, in EP 694 707 B3. A characteristic feature of such brakes is the axial offset of the hold-down yoke by way of an eccentric interlocking support in the brake caliper, in order to exert not only radial but also tangential pre-stressing on the brake linings via the positively interlocking engagement in the hold-down springs formed for this purpose. 
     The basic principle of radial and tangential pre-stressing has proved its worth and should be retained. However, there is a need for design and functional modifications to the brake caliper and to the relevant parts of the hold-down system to afford greater efficiency and greater versatility. 
       FIGS. 1 and 2  herein show the brake according to EP 694 707 B3.  FIG. 1  shows a brake lining  11 , which is guided and supported radially inwards and on both sides in a circumferential direction in a channel guide of the brake caliper or back plate assembly, and on the radially outer edge of which lining a hold-down spring is supported, which is symmetrically formed to both sides of its center axis. Centrally, the hold-down spring comprises a radially deeper center area  3 , from which the higher spring legs  6 ,  7  extend outwards on both sides along the outer edge of the lining, in order for the ends to then exert a spring action on the brake lining when a likewise symmetrically formed hold-down yoke  1  engages with a positive interlock in the here radially inward formed center area. 
     The hold-down yoke  1  is formed from round material. The spring pre-stressing occurs when the hold-down yoke  1 , as in  FIG. 2 , is anchored on the actuation side in interlock openings of the brake caliper, and on the other side is then fixed firmly but detachably by means of bolts to a bearing block of the brake caliper on the wheel-rim side. The hold-down yoke extends over a caliper opening serving for the fitting/removal of brake linings, supported on both sides of the brake disk, and in a direction towards the brake or center axis A. 
     In the axial direction of the brake linings, the hold-down springs are coupled to the brake lining, because radial shoulders  12 ,  14  of the outer edge of the brake lining pass through elongated openings  8 ,  9 ,  10  in the spring. At the ends, the spring legs bear against further radial shoulders  13 ,  13  of the outer edge of the brake lining. The hold-down springs are embodied as leaf springs. 
     The radial and tangential pre-stressing acting on the brake lining by means of the hold-down spring is generated in that the hold-down yoke  1  engages with a positive interlock in the radially formed center area  3  of the hold-down spring and in turn is supported by positive interlock in actuation and wheel rim-side anchorages of the brake caliper, always offset towards the brake disk run-out side by an axial offset x relative to the center or brake axis A, in the direction of rotation of the brake disk in forward travel. As a result, the corresponding spring leg is also forced in a tangential direction. For the eccentric positively interlocking support of the hold-down yoke  1 , the requisite design shapes must be provided at corresponding positions in the brake caliper casting, and these design shapes then still have to undergo machining operations. The bearing points for the hold-down yoke  1  are therefore formed asymmetrically on/in the brake caliper. 
     The relevant brakes are fitted on both sides of the axle, so that they too need to be of mirror-symmetrical design. This means that different casting pattern designs are required for a left-hand brake and a right-hand brake in order to produce the asymmetrical support and holding areas. Accordingly, the positions of the subsequent machining operation for the support and holding areas in the case of a left-hand brake are different from those in that of a right-hand brake. 
     Owing to the aforementioned asymmetry, this principle with different caliper designs is an obstacle to economic and cost-efficient production of the brake calipers mass-produced by casting and machining. 
     SUMMARY OF THE INVENTION 
     Generally speaking it is an object of the present invention to improve upon the brake described in EP 694 707 B3, particularly with respect to its manufacture in a more efficient and more versatile manner. According to embodiments of the present invention, this object can be achieved in a caliper disk brake of the general type under consideration where the tangential pre-stressing is at least partially attributable to the dimensions of the hold-down device, measured in a tangential direction from the centerline, being at least in part greater on the disk run-out side than on the disk run-in side. 
     The holding device for the hold-down device, that is the support areas for a hold-down yoke on the caliper, can be designed symmetrically if the tangential pre-stressing of the hold-down spring originates not from an asymmetry of the caliper, but rather an asymmetry of the hold-down device. Advantageously, the brake calipers of mirror-symmetrical design in the holding and support areas for the hold-down device on each axle in this respect no longer require different molds to form the casting design shape. Furthermore, the subsequent machining can be standardized. 
     Consequently, besides the relevant brake itself, the present invention also contemplates a cast brake caliper, the holding device of which for holding and supporting the hold-down device is symmetrical in relation to a radial plane containing the centerline, in so far as its contour is predefined by the casting process. As used herein, the term symmetry predefined by casting signifies that one mold of correspondingly symmetrical contour is used for the entire production of the contour of the holding device, whereas asymmetries originating from machining operations performed after casting, such as the asymmetrical introduction of one or more bored holes and/or asymmetrical machining operations for processing of the surface, are within the scope of the inventive embodiments. 
     According to an embodiment of the present invention, the holding device may comprise a projection extending in the direction of the axis of rotation, the lateral flanks of which serve to absorb tangential forces and the radially inner flank of which serves to absorb radial forces. Furthermore, the projection is preferably of roof edge-like design. That is, according to this embodiment, there is a positively interlocking holding area for the hold-down device. It is formed as a positively interlocking block in the casting and towards the side of the brake disk or the hold-down device comprises a roof edge-like projection, against which the corresponding end of the hold-down yoke is radially supported when bilateral lugs also correspondingly engage around the outer faces of the interlocking block. In the fitted position, the positive interlock is thereby established symmetrically. The projection of the holding device is preferably on the actuation side. 
     According to another embodiment, the holding device may comprise a coding device. This serves to ensure that only one hold-down device matching the brake caliper is fitted to the caliper. The coding device may comprise a shoulder. Such a shoulder can be left as a protrusion when machining the face. The shape and positioning of the shoulder are in principle quite arbitrary. For coding in such a case, a corresponding aperture is formed in a corresponding position on the associated hold-down device, so that only this hold-down device fits onto the brake or matches the caliper. It is thereby possible to create a coding, which ensures the correct hold-down device is assigned to the left-hand or right-hand brake and/or ensures the correct hold-down device in view of the size of the brake to be equipped. 
     Additionally or alternatively, gripper hooks can be formed extensively between the support block contour and formed on the hold-down yoke. If these parts and connection areas correspond congruently it is thereby likewise possible to ensure the correct assignment. 
     According to an embodiment, the holding device preferably comprises a threaded connection device. This creates an especially simple design type. 
     According to an embodiment, the coding device and/or the threaded connection device may be situated on the wheel rim-side. If they are not formed by casting, neither the coding device nor the threaded connection device needs to be of symmetrical design in relation to the radial plane containing the centerline. 
     The inventive embodiments can be applied both to a fixed caliper and to a sliding caliper. 
     Still other objects and advantages of the present invention will in part be obvious and will in part be apparent from the specification. 
     The present invention accordingly comprises the features of construction, combination of elements, and arrangement of parts, all as exemplified in the constructions herein set forth, and the scope of the invention will be indicated in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is discussed in more detail below on the basis of preferred exemplary embodiments, referring to the accompanying drawings, in which: 
         FIGS. 1 and 2  show conventional caliper disk brakes; 
         FIGS. 3 and 4  are diagrammatic top views of a caliper disk brake according to one exemplary embodiment of the present invention; 
         FIG. 5  is a diagrammatic, perspective view of the brake according to  FIGS. 3 and 4 ; 
         FIG. 6  is a diagrammatic, sectional view of the brake according to  FIGS. 3 and 4 ; 
         FIG. 7  diagrammatically shows a hold-down yoke of the brake according to  FIGS. 3 and 4 ; 
         FIGS. 8 and 9  show the interaction of the hold-down yoke with the brake caliper; 
         FIG. 10  is a perspective, partial view of a holding area of the brake caliper for the hold-down yoke; 
         FIG. 11  is a diagrammatic, partial view of another holding area of the caliper for the hold-down yoke; 
         FIGS. 12 and 13  show two different embodiments of the fastening of the hold-down yoke on the wheel rim-side of the caliper; 
         FIGS. 14 to 18  show different views of hold-down springs for the brake according to  FIGS. 3 and 4 ; and 
         FIGS. 19 and 20  show sectional views of the interaction of the hold-down yoke with the hold-down spring according to one exemplary embodiment of the present invention and according to the state of the art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An exemplary embodiment of a caliper disk brake according to the present invention comprises a brake disk, the axis of rotation of which is denoted by A. The direction of rotation in forward vehicle travel is denoted by an arrow D. The brake comprises a brake caliper  20  and a back plate assembly  22 , the brake caliper gripping around the brake disk like a frame. A wheel rim-side brake lining, comprising a metal backing plate with friction lining, is denoted by the reference numeral  24 , an actuation-side brake lining, comprising a metal backing plate with friction lining, by the reference numeral  26  and a pressure plate by the reference numeral  28 . The elements specified are force transmission elements. They are held down by hold-down springs  30 ,  32  and  34 , that is they are pre-stressed in a radial direction. As is explained further below, the brake lining  26  and the pressure plate  28  are also pre-stressed in a tangential direction. 
     A hold-down device in the form of a hold-down yoke  36 , which extends over a caliper opening for the fitting/removal of the brake linings supported on both side of the brake disk, serves to hold down the hold-down springs  30 ,  32  and  34 . Here, the hold-down yoke  36  is responsible not only for the radial pre-stressing of the hold-down springs  30 ,  32  and  34  but also for the tangential pre-stressing of the hold-down springs  32  and  34 . By contrast, only a radial pre-stressing, but not a tangential pre-stressing, acts on the hold-down spring  30  and the brake lining  24 . Moments originating from a tangential pre-stressing of the hold-down spring  30  and the brake lining  24 , which are detrimental to the operation of the brake and which effect the free sliding of the sliding caliper, are thereby avoided. 
     The brake caliper  20 , which in the exemplary embodiment represented in the drawings is a sliding caliper, comprises a holding device for holding and supporting the hold-down yoke  36 . This holding device comprises two areas, that is a wheel rim-side area  38  and an actuation-side area  40 . In top view, both areas are formed symmetrically about a centerline M, which lies parallel to the axis of rotation A. They are also symmetrical in relation to a radial center plane ME, which is spanned by the axis of rotation A and the centerline M. This symmetry means that the contour of the holding device is such that one and the same mold can be used for casting the caliper, irrespective of whether the caliper is designed for a right-hand or a left-hand brake. 
     Forming part of the actuation-side area  40  of the holding device is a projection  42  of roof edge-like design. Its lateral flanks  44 ,  46  serve to absorb tangential forces. Its radially inner flank  48  serves to absorb radial forces. 
     On the actuation side, the hold-down yoke  36  is designed to match the projection  42 . For example, it comprises a recess  50 , which in the assembled state accommodates the projection  42 . Lateral flanks  52  and  54  of the recess  50  serve to transmit tangential forces. A radially outer face  56  serves to transmit radial forces. In the fitted state, it bears on the flank  48  of the projection  42  facing the brake disk. 
     In the wheel rim-side area  38 , the caliper  20  comprises a threaded hole  58 , into which a bolt  60  is screwed for fixing the hold-down yoke  36 . Like the actuation-side area  40 , the wheel rim-side area  38  of the holding device is designed symmetrically in relation to the centerline M and the center plane ME. Only the threaded hole  58  is not symmetrically situated, in order to prevent a hold-down yoke for a right-hand (left-hand) brake being fitted to a left-hand (right-hand) brake. It is not formed by casting but rather is made by means of a drill and/or a thread cutter after the actual casting of the caliper. 
     A coding device is provided in the area  38  of the holding device. For this purpose, according to  FIGS. 11 and 12 , a protrusion  62  may be left during the machining, so that, according to  FIG. 12 , only one such hold-down yoke  36  can be fitted, which has an aperture  64  matching the protrusion  62 . Like the threaded hole  58 , the protrusion  62  is not formed by casting and can therefore be arranged asymmetrically. 
     In addition or alternatively, the hold-down yoke  36  according to  FIG. 13  may comprise lugs, which grip around corresponding structures on the caliper  20 . This again ensures that only one matching hold-down yoke  36  can be fitted. 
     The protrusion  62 , the aperture  64  and the lugs  66  and  68  are therefore coding devices, which ensure that only one matching hold-down yoke is ever fitted to the caliper. 
     The hold-down yoke is asymmetrical in two different respects. Firstly it comprises tangential shoulders  70  and  72  only on the actuation side, not on the wheel-rim side. Secondly its dimensions V 1 , V 2  measured in a tangential direction from the centerline M are greater in the area of the first projection  70 , that is on the disk run-out side, than in the area of the projection  72 , that is on the disk run-in side. 
     This configuration makes it possible to impress a tangential pre-stressing on the actuation-side brake lining  26  and the pressure plate  28  situated on the actuation side, without the need for the brake caliper  20  to have a correspondingly asymmetrical design in the areas  38  and  40  of its holding device for the hold-down yoke  36  and without a disadvantageous tangential pre-stressing acting on the wheel rim-side brake lining  24 . 
     It is also possible, by applying different spring pre-stresses, purposely to control the variety of interactions with the hold-down springs. This can be done in that, according to  FIG. 7 , it is only necessary to adjust the width V 1  of the hold-down yoke in the direction of the dashed lines to the disk run-out. For this purpose, it is only necessary to shape the sheet-metal pressing accordingly. Through interaction with the abovementioned codings it is then possible to make a precise assignment to the corresponding brake and its conditions of use, without having to make adaptations to the cast areas of the brake caliper in order to do this. 
     The hold-down yoke  36  is preferably produced as a shaped, sheet-metal pressing and comprises a bead, which is offset in relation to the centerline M and the radial plane R according to the difference between the dimensions V 1  and V 2 . The bead is denoted by the reference numeral  74 . In the assembled state it bears flatly on the respective hold-down spring  30 ,  32  and  34  and impresses the radial pre-stressing, cf.  FIG. 19 . In the configuration according to  FIG. 20 , by contrast, which corresponds to the state of the art, there is only a linear bearing contact. Such a linear bearing contact imposes a considerably greater load on the hold-down spring than the flat bearing contact according to  FIG. 19 . 
     Design configurations of the hold-down spring in the form of a leaf spring can be gleaned, in particular, from  FIGS. 14 to 18 . It comprises two identical spring legs  76 ,  78  and a trapezoidal center area  80  situated between them, which projects radially inwards. In the relaxed state, the two legs of the trapezoidal area  80  each enclose an angle α of more than 95° with its base. In the exemplary embodiment represented in the drawing these angles are 117°. With each of the two adjacent spring legs  76 ,  78  they enclose an angle β of less than 850. In the exemplary embodiment shown the angle β is 74°. 
     In the side view, the springs are not angular. Rather, in the relaxed state they are each curved with a radius in each case of 10 mm to 16 mm in the transitional area between the two legs of the trapezoidal area  80  and its base, in the exemplary embodiment shown 13 mm, and in the transitional area between the trapezoidal area  80  and the spring legs  76 ,  78  they are curved with a radius of 4 mm to 9.5 mm, in the exemplary embodiment shown 7 mm. 
     The spring legs  76 ,  78  may be of straight design according to  FIGS. 14 to 16 . They may also be of convex or concave design, however, as can be seen from  FIGS. 17 and 18 . 
     That area of the projection  70 , which bears on the hold-down spring  32  is denoted in  FIG. 19  by the reference numeral  82 . Its center M 82  is separated from the center M 74  by the distance H in a radial direction and by the distance E in a tangential direction, where H&lt;E. By contrast the corresponding bearing contact lines  15  and  16  in the state of the art are such that H=E, cf.  FIG. 20 . 
     In the exemplary embodiment represented in the drawings, the site P of the greatest (compressive) stress lies in the hold-down spring  32 , which is situated in the transitional area between the center area  74  and the spring leg  76 , removed from the (extensive) area of the greatest wear due to friction or to the radial impact of the brake lining or the pressure plate in the contact areas. 
     By contrast, under similar conditions of use, as specified above, according to the state of the art in  FIG. 20 , only a linear bearing contact occurs in the radial contact area, so that, here, the site of the greatest wear in the radial area with the linear bearing contact (see arrow) then directly and closely adjoins the area P of the greatest (compressive) stress in the hold-down spring, so that here H=E. 
     As can be seen from  FIG. 19  in particular, the hold-down yoke  36  in cross section has a trough-like configuration, sloping away on the outside, that is at the ends of the projections  70 ,  72 . This allows slight relative movements (sliding) during reversing movements of the hold-down spring. In the state of the art according to  FIG. 20  with the round material, which bears against perpendicular spring portions, this is not the case. The inventive design reduces the stress loads in the critical zones. 
     Here too, as in the state of the art according to  FIG. 1 , the hold-down springs are coupled to the brake lining in the axial direction of the brake linings, because radial shoulders  12  of the outer edge of the brake lining pass through elongated openings  8 ,  9  in the two lateral spring legs of the spring. At the ends the spring legs bear against further radial shoulders  13 ,  13  of the outer edge of the brake lining. The hold-down springs are embodied as leaf springs. 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.