Abstract:
A sliding caliper disc brake for a motor vehicle having a disc, a carrier ( 2 ), a caliper ( 3 ) and pads ( 52 ). The carrier ( 2 ), respectively, provides bearing surfaces ( 61   b   , 63   b ) for the caliper ( 3 ) and pads ( 52 ) having a non-zero angle (Ab) which opposes rotational movement between the caliper ( 3 ) and pads ( 52 ) when the disc turns in a direct sense (D). Thus, a resistance to a braking torque generated during braking is dampened by a shear force developed between the caliper ( 3 ) and pads ( 52 ).

Description:
The present invention relates to a disc brake for a motor vehicle. 
     More specifically, the present invention relates to a disc brake of the type which comprises: a disc which has an inboard face and an outboard face, this disc rotating about a transverse axis in a direct sense of rotation when the vehicle is travelling forward; a carrier comprising an upstream branch and a downstream branch straddling the disc and secured to a common base which is fixed to the vehicle facing the inboard face of the disc, the downstream branch following on from the upstream branch in the direct sense of rotation of the disc, and each branch having an inboard housing and an outboard housing which are situated one on each side of the disc; a caliper straddling the disc and mounted so that it can slide relative to the carrier in a transverse direction parallel to the transverse axis, this caliper comprising a jaw facing towards the outboard face of the disc, and a cylinder facing towards the inboard face of the disc and closed by a piston; guide means provided on the carrier and on the caliper and comprising a bore and a pin sliding in the bore; and a pair of friction pads, this pair being formed of an inboard pad and an outboard pad placed respectively, in the transverse direction, between the piston and the inboard face of the disc, and between the outboard face of the disc and the jaw of the caliper, the inboard pad having an upstream end and a downstream end which are mounted so that they can slide in respective inboard housings in the upstream and downstream branches, and the outboard pad having an upstream end and a downstream end which are mounted so that they can slide in the respective outboard housings of the upstream and downstream branches, the inboard and outboard pads carrying, between their respective ends, respective friction linings facing towards the inboard and outboard faces of the disc and by means of which each pad is urged by the disc in the direct sense of rotation in the event of braking while the vehicle is travelling forward. 
     BACKGROUND OF THE INVENTION 
     Disc brakes of this type are well known in the prior art, as shown, for example, in Patent documents PCT/FR96/00615, PCT/FR94/00174, and EP-0,694,133. 
     One of the many problems which arise when designing disc brakes lies in the difficulty of absorbing the drag forces transmitted to the pads by the disc, without the carrier deformations which necessarily result from this causing resistance that opposes the satisfactory sliding of the caliper relative to the carrier, as such a resistance itself generates abnormal and uneven wear of the pads, risks of brake seizure, increases in brake-fluid absorption, noise, etc. 
     SUMMARY OF THE INVENTION 
     The invention falls within this context and its object is to propose a disc brake capable of absorbing the dragging forces transmitted to the pads by the disc by converting them into shear forces. 
     To this end, the brake of the invention which in other respects conforms to the above preamble, is essentially characterized in that the pin is a single pin and lies on a mid-plane of the caliper, in that the downstream branch of the carrier and the jaw of the caliper have first and second respective contact surfaces capable of coming to bear one on the other in a first oblique plane, in that the downstream branch of the carrier and at least one of the inboard and outboard pads have third and fourth respective contact surfaces capable of coming to bear one on the other in a second oblique plane, and in that the first and second oblique planes form a non-zero angle between them. 
     The disc brake of the invention may also advantageously comprise a spring bearing on the outboard pad and on the jaw of the caliper and exerting an elastic torque tending to make the caliper turn in the direct sense of rotation relative to the outboard pad. 
     In one possible embodiment of the invention, the upstream end of at least one of the inboard and outboard pads is attached to the upstream branch of the carrier. 
     As a preference, the downstream branch of the carrier has a pair of first contact surfaces forming a dihedron of mutual contact between this downstream branch and the jaw, and a pair of third contact surfaces forming a dihedron of mutual contact between this downstream branch and the first pad. 
     In this way, the jaw of the caliper may have, facing the downstream branch of the carrier, a pair of second contact surfaces, each of which is capable of coming to bear on the dihedron of mutual contact between the downstream branch of the carrier and the jaw. 
     Likewise, the downstream end of the first pad may have a pair of fourth contact surfaces, each of which is capable of coming to bear on the dihedron of mutual contact between the downstream branch of the carrier and this first pad. 
     Finally, it may also be advantageous to contrive for the angle formed between the first and second oblique planes to be at least equal to 45 degrees. 
     Further features and advantages of the invention will emerge clearly from the description thereof given hereafter by way of non-limiting indication with reference to the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view from above and in part section of a known disc brake, of the type to which the present invention applies; 
     FIG. 2 is a view from above and in part section of a disc brake in accordance with the present invention; 
     FIG. 3 is a front-on view of a disc brake in accordance with the invention, seen from the outside of the vehicle which it is mounted; 
     FIG. 4 is a view similar to FIG. 3, representing the brake in another condition; 
     FIG. 5 is a view from above of a carrier of a disc brake in accordance with the invention; and 
     FIG. 6 is a front-on view of a disc brake in accordance with the invention, observed from the angle identified by arrows  6 — 6  in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As FIG. 1 shows, the invention applies to a disc brake for a motor vehicle, of the type which comprises, in the known way, a disc  1 , a carrier  2 , a caliper  3 , guide means  41 ,  42 ,  43 ,  44  provided on the carrier  2  and on the caliper  3 , and a pair of friction pads which is formed of an inboard pad  51  and an outboard pad  52 . 
     For reasons of clarity, the disc is assumed to turn from left to right in all the figures, which means that if FIGS. 1,  2 ,  5  and  6  are assumed to depict a brake mounted on the left-hand side of a vehicle, then FIGS. 3 and 4 must be considered as depicting a brake mounted on the right-hand side of this vehicle. 
     The disc  1  has an inboard face  11  and an outboard face  12  and is rotated, with a wheel of the vehicle, about a transverse axis X in a direct sense of rotation D when the vehicle is travelling forward. 
     The carrier  2  comprises an upstream branch  21  and a downstream branch  22  which both straddle the disc  1  and which are secured to a common base  23  of the carrier, the latter being fixed to the vehicle facing the inboard face  11  of the disc, for example by means of bolts inserted in orifices  231  and  232 . 
     By convention, the downstream branch  22  is here defined as being the one which follows on from the other, known as the “upstream branch  21 ” in the direct sense of rotation D of the disc. 
     Furthermore, as best shown in FIG. 5, each branch has an inboard housing  211 ,  221  and an outboard housing  212 ,  222 , the inboard and outboard housings lying one on either side of the disc  1 . 
     The caliper  3 , which straddles the disc  1  also, is mounted so that it can slide relative to the carrier  2 , in a transverse direction T parallel to the transverse axis X. 
     This caliper  3 , which acts as a gripper, essentially comprises a jaw  32  pointing towards the outboard face  12  of the disc, and a cylinder  31  lying on the same side as the inboard face  11  of the disc and closed by a piston  311 . 
     The guide means  41 ,  42 ,  43  and  44  are formed in pairs, each pair comprising a bore and a pin mounted so that it can slide in this bore. 
     In the prior art illustrated in FIG. 1, the guide means  41  and  43  provided on the carrier consist of two pins, the guide means  42  and  44  provided on the caliper  3  then consisting of two bores. 
     The inboard pad  51  is placed, in the transverse direction T, between the piston  311  and the inboard face  11  of the disc, and has an upstream end  511  and a downstream end  512  which are mounted so that they can slide in the respective inboard housings  211 ,  221  of the upstream and downstream branches  21 ,  22 . 
     Similarly, the outboard pad  52  is placed between the outboard face  12  of the disc and the jaw  32  of the caliper, and has an upstream end  521  and a downstream end  522  which are mounted so that they can slide in respective outboard housings  212 ,  222  of the upstream and downstream branches  21 ,  22 . 
     Moreover, the inboard and outboard pads  51 ,  52  carry, between their respective ends, friction linings  510 ,  520 , the lining  510  of the inboard pad facing towards the inboard face  11  of the disc  1 , and the lining  520  of the outboard pad facing towards the outboard face  12  of the disc. 
     When pressurized brake fluid is injected into the cylinder  31  and pushes the piston  311  towards the disc  1 , this piston presses the pad  51  against the inboard face  11  of the disc, the result of which is that the cylinder  31  is forced away from the disc until the jaw  32  presses the outboard pad  52  onto the outboard face  12  of the disc with an equivalent force. 
     If, during this operation, the vehicle is travelling forwards, the pads  51  and  52  therefore receive from the disc, and via their linings  510  and  520  which rub on the latter, a force which urges them in the direct sense of rotation D and which has to be absorbed by the carrier  2 , the purpose of the invention being precisely to propose special means for facilitating this absorption. 
     To this end, the brake of the invention comprises just one pair of guide means, that is to say a single pin  41  sliding in a single bore  42 , it being possible for the pin  41  and the bore  42  to be provided on the carrier and on the caliper respectively or vice versa with equal ease, provided that they are placed in the mid-plane of the caliper  3 , that is to say in the plane which, in scenarios in which the brake comprises just one single central piston as illustrated, consists of the plane of the line M passing through the axis X of rotation of the disc and through the axis of symmetry of revolution of the piston  311 . 
     Furthermore, the downstream branch  22  of the carrier and the jaw  32  of the caliper have first and second respective contact surfaces such as  61   a ,  62   a  in FIG. 3, and  61   b ,  62   b  in FIG. 4, which when the brake is actuated can come to bear one against the other in a first oblique plane such as P 1   a  in FIG.  3  and P 1   b  in FIG.  4 . 
     Also, the downstream branch  22  of the carrier and at least one of the pads, for example the outboard pad  52 , have third and fourth respective contact surfaces such as  63   a ,  64   a  in FIG. 3, and  63   b ,  64   b  in FIG. 4, which when the brake is actuated, can come to bear one on the other in a second oblique plane such as P 2   a  in FIG. 3, and P 2   b  in FIG.  4 . 
     Finally, as FIGS. 3 and 4 show, the first and second oblique planes such as P 1   a  and P 2   a , or P 1   b  and P 2   b , form a non-zero angle such as Aa or Ab between them, preferably at least equal to 45 degrees. 
     A spring  7 , for example fixed to the outboard pad  52  and bearing in notches  321  and  322  of the jaw  32  of the caliper, is preferably designed to exert an elastic torque tending to make the caliper  3  turn in the direct sense of rotation D relative to the outboard pad  52 . 
     An examination of FIGS. 3 and 4, which deal with the same brake observed in different phases of braking, allows a better understanding of the invention. 
     As shown in FIG. 3, which corresponds to actuation of the brake with a low braking torque, the caliper is forced, if driven in the direct sense of rotation indicated by the arrow D, to follow a rotational movement in this direct sense D by the bearing of the contact surface  62   a  on the contact surface  61   a , while the outboard pad  52  is forced, if driven in the direct sense D, to follow a rotational movement in the opposite sense to this direct sense D by the bearing of the contact surface  64   a  on the contact surface  63   a.    
     However, as the caliper  3  grips the outboard pad  52 , it actually has a pronounced tendency to follow the movements of this pad. 
     This being the case, the natural driving of the caliper  3  by the pad  52  and the opposing effects of the caliper  3  and of the outboard pad  52  bearing on the carrier  2  generate a shear force between the caliper  3  and the pad  52 , and this results in easier absorption of the braking torque. 
     Likewise, as shown by FIG. 4 which corresponds to brake actuation with a high braking torque, the caliper is forced, if driven in the direct sense of rotation indicated by the arrow D, to follow a rotational movement in the opposite sense to the direct sense D by the bearing of the contact surface  62   b  on the contact surface  61   b , while the outboard pad  52  is forced, if driven in the direct sense D, to follow a rotational movement in this same direct sense D by the bearing of the contact surface  64   b  on the contact surface  63   b.    
     In the latter case, the natural driving of the caliper  3  by the pad  52  and the opposing effects of the caliper  3  and of the outboard pad  52  bearing on the carrier  2  therefore also generate a shear force between the caliper  3  and the pad  52 , and allows better absorption of the braking torque. 
     As it is advantageous to combine the effects obtained by the invention in the case of relatively gentle braking torques and in the case of relatively high braking torques, it may be beneficial, as shown in FIGS. 3 and 4, to contrive for the downstream branch  22  of the caliper to have a pair  61   a ,  62   b  of first contact surfaces forming a dihedron P 1   a , P 1   b  of mutual contact between the downstream branch and the jaw  32 , and a pair  63   a ,  63   b  of third contact surfaces forming a dihedron P 2   a , P 2   b  of mutual contact between the downstream branch and the outboard pad  52 . 
     This being the case, the jaw  32  of the caliper preferably has, facing the downstream branch  22  of the carrier, a second pair of contact surfaces  62   a ,  62   b  each of which is capable of coming to bear on the dihedron P 1   a , P 1   b  of mutual contact between the downstream branch  22  of the carrier and the jaw  32 . 
     Likewise, it is advantageous to contrive for the downstream end  522  of the outboard pad  52  to have, facing the downstream branch  22  of the carrier, a pair of fourth contact surfaces  64   a ,  64   b , each of which is capable of coming to bear on the dihedron P 2   a , P 2   b  of mutual contact between the downstream branch  22  of the carrier and this outboard pad  52 . 
     Brake balance can furthermore be improved by arranging the contact surfaces  61   a ,  61   b  of the carrier  2 , and  62   a ,  62   b  of the jaw  3 , exclusively on the outboard part  220  (FIG. 5) of the carrier and on the corresponding outboard part  320  (FIG. 2) of the jaw. 
     The effectiveness of the arrangement proposed may also be enhanced by attaching the upstream end  511 ,  521  of at least one of the inboard  51  and outboard  52  pads, and preferably of both pads, to the upstream branch  21  of the carrier, for example by means of complementary respective reliefs such as  212   a  and  521   a  (FIG.  4 ). 
     Finally, the effects of the invention may also be enhanced by contriving for the inboard pad  52  itself also to have a pair of contact surfaces capable of coming to bear on the carrier, these surfaces then being symmetric with respect to the disc  1  with the contact surfaces  64   a ,  64   b  of the outboard pad  52 .