Abstract:
A disk brake ( 1 ) usually comprises a caliper ( 2 ), a carrier ( 3 ) and friction means ( 8, 9 ). The caliper is slideably mounted on the carrier. To improve the braking performance of such a disk brake while reducing the manufacturing cost, the invention provides that a first friction means is retained rotationally by the carrier while a second friction means is retained rotationally by the caliper. The disk brake according to the present invention is also characterized in that the carrier has at least two guide pins ( 17, 18 ), the caliper being slideably mounted on the carrier via these two pins, the caliper having at least two bores ( 19, 20 ) able to receive one pin each.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a disk brake of a motor vehicle. The object of the invention is to improve the braking performance of disk brakes while reducing the manufacturing cost of such disk brakes. The invention is more particularly intended for the automotive sector but could also be applied in other sectors. 
     A disk brake of a vehicle is usually situated on a hub of at least one wheel of the vehicle which hub receives an axle of the vehicle wheel and supports the disk brake. A disk brake is connected to the wheel of the vehicle in such a way that the wheel imparts a rotational movement to the brake disk. 
     The disk brake comprises a caliper forming a first jaw and a second jaw, the first jaw and the second jaw facing one another on either side of a plane of a brake disk and joining together outside the disk. The first jaw and the second jaw of the caliper are provided with a first brake pad and with a second brake pad, respectively. The brake pads are placed facing one another, on either side of the brake disk, in such a way that their plane of symmetry is coplanar. This caliper is intended to apply the first brake pad and the second brake pad via the first jaw and the second jaw, respectively, against a first face and against a second opposed face of a brake disk. A disk brake also comprises a carrier fixed to the hub of at least one wheel of the vehicle. The carrier supports the caliper and at least partially flanks each brake pad longitudinally with respect to a direction of the rotational movement of the brake disk. 
     During braking, the first brake pad and the second brake pad draw together perpendicularly with respect to a plane of the brake disk via the first jaw and via the second jaw. In order to draw together perpendicularly to the plane of the brake disk, at least one of the brake pads is first pushed toward the brake disk via a piston placed in at least one of the jaws of the caliper. The piston exerts a pressure, for example on the first brake pad, such that the piston tends to draw the first brake pad against the brake disk perpendicularly to the plane of this same brake disk. This piston moves under the action of at least one braking circuit generating a hydraulic pressure on the piston. The braking circuit may comprise a master cylinder of a vehicle, for example. The second brake pad is then directed perpendicularly toward the brake disk by a reaction of the other jaw moving in return toward the disk. 
     The carrier allows the caliper to be maintained straddling the disk. By straddling is meant the fact that the caliper is placed of either side of the plane of the disk while passing over the disk, outside a periphery of the disk. The carrier also allows the caliper to be guided during advancing/retreating movements of this same caliper with respect to the disk. The advancing movements of the caliper are produced during vehicle braking, causing the pads to be drawn together against the disk. The retreating movements of the caliper are produced during vehicle braking disengagement, causing the pads to be separated with respect to the disk. 
     To maintain the caliper in a straddling orientation and to guide the caliper, it is known for the carrier to have bores intended to receive guide pins carried by the caliper, the pins and the bores cooperating to produce the advancing/retreating movements of the caliper with respect to the disk. These pins allow the caliper to be supported by the carrier while facilitating the guiding of the two pads against the disk. The carrier extends above the disk with its bores so that the pins slide in these bores while also passing over the disk. The carrier keeps the two pads in position and it recovers the major part of the braking torque. 
     Document FR 2 747 751 describes a brake disk provided with a carrier and with a caliper. This document describes that the two guide pins are carried by the carrier and that the bores are formed in the caliper. These guide pins are each arranged with an axis parallel to a central axis of the disk. More specifically, these pins are arranged with one having an axis passing beyond the periphery of the disk and extending on either side of the disk and with the other having an axis passing inside this same periphery, the second pin extending on only one side of the disk. This specific arrangement of the axes of the pins makes it possible to substantially reduce the distance between these two axes, thereby resulting in minimum frictional torque. Jamming of the pins is thus minimized, and sliding can take place under optimum conditions. 
     However, this type of disk brake has the disadvantage of having a considerable weight. The braking performance is all the more reduced as a result. 
     SUMMARY OF THE INVENTION 
     To solve this problem, the invention makes provision to reduce the weight of a disk brake while increasing the braking performance. In particular, the invention provides that one of the pads is retained rotationally by the carrier and that the other pad is retained rotationally by the caliper. It is thus possible to provide a half-carrier extending on only one side of the plane of the disk. Such a form of the carrier makes it possible advantageously to reduce the weight of the disk brake and to improve the performance of the disk brake. 
     Thus, during vehicle braking the piston causes a first pad to move toward the disk, this first pad being retained rotationally by the carrier, while a second pad can be applied against the other face of the disk by reaction of the caliper while being retained rotationally by the caliper. 
     The movement of the caliper with respect to the carrier is brought about by cooperation of the pins and the respective bores. In the invention, provision is made for the pins to be carried by the carrier and for the bores to be formed by the caliper. 
     The caliper may advantageously have at least one window cut into it, thereby promoting better heat dissipation from the caliper. This also makes it possible to increase the arch width of the caliper and also to advantageously increase the stiffness of the caliper for an equivalent weight. Finally, this also makes it possible to reduce the weight of the caliper. 
     The brake pads may be fixed to the caliper and to the carrier by securing means, including screwing, attachment by at least one block, or by at least one spring. 
     The invention also makes it possible to increase a diameter of the disk for one and the same wheel. 
     More specifically, the subject of the invention is a disk brake for a motor vehicle, comprising a disk brake caliper, which caliper is provided with a hydraulic cylinder having a piston which is slideably mounted in this cylinder and with a nose, the caliper having a shape intended for straddling a disk, a carrier secured to the vehicle, the caliper being mounted so that it can move on the carrier, the disk being intended to be arranged between the nose and the piston and to rotate there, two frictional means arranged on either side of the disk and able to be applied against opposed faces of the disk by means of the piston and the nose, respectively, characterized in that a first friction means is retained rotationally by the carrier, and a second friction means is retained rotationally by the caliper. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood on reading the description below and from examining the accompanying figures. These are presented only by way of indication and without any limitation on the invention. In the figures: 
         FIG. 1  shows a partial sectional view of a disk brake passing through a plane perpendicular to a plane formed by a brake disk, according to the invention. 
         FIG. 2  shows a profile view of a disk brake, according to the invention. 
         FIG. 3  shows a perspective view of a disk brake, according to the invention. 
         FIG. 4  shows a schematic representation of a friction means connected to a caliper, according to the invention. 
         FIGS. 5   a ,  5   b ,  6  and  7  show schematic representations of a friction means connected to the caliper or to the carrier, according to variants of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a disk brake  1  for a motor vehicle, according to the invention. The disk brake  1  comprises a caliper  2  and a carrier  3 . The caliper  2  is provided with a hydraulic cylinder  4  having a piston  5  which is slideably mounted in this cylinder. The caliper  2  also has a nose  7 . The carrier  3  is secured to the vehicle and the caliper is mounted so that it can move on the carrier. A disk  6  is interposed between the nose  7  of the caliper  2  and the piston  5  of this same caliper  2  while being intended to rotate. The caliper has a shape intended to straddle the disk  6 . As mentioned above, by straddling is meant the fact that the caliper  2  is positioned on either side of a plane of the disk while being connected over the disk, outside a periphery of the disk. The disk  6  delimits, on either side of the plane of the disk, an external side (E) and an internal side (I), the external side being remote from a hub (not shown) of the vehicle and the internal side being in proximity to this same hub. The disk brake also comprises two friction means  8  and  9  arranged on either side of the plane of the disk  6 . These friction means  8  and  9  are able to be applied against the opposed faces  10  and  11  of the disk via the piston  5  and the nose  7  of the caliper  2 , respectively. 
     According to the invention, a first friction means  8  is retained rotationally by the carrier  3  and a second friction means  9  is retained rotationally by the nose  7  of the caliper  2  ( FIGS. 2 and 3 ). The carrier  3  forms a yoke having an intermediate part  12 , a first arm  13  and a second arm  14 , the first arm  13  and the second arm  14  being connected by the intermediate part  12  ( FIG. 3 ). In the preferred example of the invention ( FIGS. 2 and 3 ), the carrier forms a half-carrier. The carrier extends in a plane parallel to a plane formed by the disk. It is not placed on either side of the plane of the disk. 
     The two arms  14  and  13  and the intermediate part  12  of the carrier  3  form a space  16  inside which is arranged the first friction means  8  ( FIG. 3 ). A friction means  8 ,  9  is formed by a brake pad  8 . 1 ,  9 . 1  and by a pad support  8 . 2 ,  9 . 2  ( FIG. 3 ). The pad support connects the corresponding pad to the nose of the caliper or to the carrier. 
     Each brake pad  8 . 1  and  9 . 1  has an inner face  21 ,  22  and an outer face  23  and  24 , respectively, each of the outer faces being opposed to the disk and each of the inner faces being placed facing the disk. 
     The caliper  2  straddles the disk  6  while having a generally U-shaped form ( FIG. 2 ). The caliper forms a first branch  15  of the U and a second branch  7  of the U. The second branch  7  forms the nose  7  of the caliper. The second friction means  9  is carried by the nose  7  of the caliper  2 . The other branch  15  comprises the hydraulic cylinder  4  with the piston  5  slideably mounted in this same cylinder. The piston  5  is able to move the first friction means  8  toward the disk  6 . 
     In a first exemplary embodiment, the caliper  2  is a one-piece component. In a variant, the caliper is formed in two parts (not shown), a first part carrying the piston and a second part carrying one of the friction means. The first part is connected to the second part by fixing means such as bolts. 
     The carrier  3  comprises two pins  17  and  18  which extend perpendicularly to the plane formed by the disk  6  ( FIG. 1 ). These pins  17  and  18  are carried by the first arm  13  and by the second arm  14  of the carrier, respectively. The first pin and the second pin can be at least partially threaded in order to be introduced into a corresponding internally threaded cavity, which cavity is formed in a corresponding arm of the carrier. Such pins can be produced by stamping the material or by rolling. 
     Each pin  17 ,  18  extends along an axis  44  and  45 , respectively, each of these axes being parallel to an axis  46  of rotation of the disk and perpendicular to the plane of the disk ( FIGS. 1 ,  2 ). The first pin and the second pin are intended to slide through a corresponding bore  19  and  20 . The first bore  19  and the second bore  20  are formed in the caliper  2  and are able to receive one pin each. 
     As represented in broken lines in  FIG. 1 , the bores are advantageously through bores such that each of these bores emerges at two opposed ends toward the internal side ( 1 ) and toward the external side (E). The first bore  19  emerges at a first end  19 . 1  toward the internal side (I) and at a second first end  19 . 2  toward the external side (E). The second bore  20  emerges at a first second end  20 . 1  towards the internal side (I) and at a second end  20 . 2  towards the external side (E). 
     Such through bores passing through two ends advantageously facilitate the machining of the caliper. It is no longer necessary to set a machining depth for the bores. It is thus intended to plug the second ends  19 . 2 ,  20 . 2  using a plug (not shown) which is screwed inside the corresponding bore. 
     On the other hand, such through bores can advantageously allow the caliper to slide with respect to the pins via one of the two ends in proximity to the internal side (I) on the one hand and, on the other hand, to fix by screwing the second friction means  9  via the other end remote from the internal side (not shown). It is the pad support  9 . 2  of this second friction means  9  which can be fixed to one of the ends of the bore that is remote from the internal side (I). Fixing this pad support  9 . 2  to such a bore end advantageously makes it possible to avoid having to plug the bores. 
     Finally, such emerging bores can advantageously facilitate removal of the disk brake from outside the vehicle. Specifically, at least one of the pins is provided at one of its free ends with a means for receiving an unscrewing tool, for example an Allen key. 
     As shown in  FIG. 1 , the caliper is able to slide during braking and brake disengagement by an efficient length  53  with respect to the pins. By efficient length  53  is meant a caliper sliding length with respect to the pins during vehicle braking. The efficient length  53  can be measured along an axis parallel to the axis of a pin. The bores of the caliper have an insertion length  55  greater than the efficient length  53  increased by the sum of the tolerable wear lengths  54  of the pads and the disk. In one example, the brake pads measure 2 centimeters thick and the columns can therefore be introduced into their corresponding bore by a length of 3 to 5 centimeters. The wear lengths  54  of the pads and the disk are measured along an axis parallel to the axis  46  of rotation of the disk or to the axis  44  of a pin. 
     Each brake pad can be connected to the corresponding support by small attachment studs formed by each of the pads intended to be inserted into corresponding cavities formed by the support. In the example shown in  FIG. 4 , the second pad  9 . 1  can be connected to the second pad support  9 . 2  by insertion of the studs such as  28 , which are formed by the second pad  9 . 1  and are inserted in corresponding cavities  29  formed in the second pad support  9 . 2 . The second pad  9 . 1  can be joined together with the second pad support  9 . 2  by pressing each of the studs  28  into a corresponding cavity  29 . The studs and the cavities are represented in broken lines in  FIG. 4 . 
     At least one friction means can be connected to the nose of the caliper and/or to the carrier via projections and slots, the projections  30 ,  31  being able to engage in a slot  32 ,  33  formed in the carrier or in the nose of the caliper, the associated slots and projections forming means for securing the friction means to the carrier or to the caliper nose. The slots and the projections are produced in such a way that the corresponding pad hardly moves with respect to the caliper. The slots and the projections are also produced in such a way that there is virtually no axial clearance between the pad support and the caliper nose. 
     The example shown in  FIG. 4  schematically represents the second friction means  9  connected to the nose  7  of the caliper  2 . This second friction means  9  comprises a brake pad  9 . 1  and a pad support  9 . 2 . The second friction means  9  is connected to the nose of the caliper via the pad support  9 . 2 . The pad support  9 . 2  has a first projection  30  and a second projection  31 . Correspondingly, the caliper nose  7  has a first slot  32  and a second slot  33  receiving said projections  31  and  30 . The slots and the projections are formed in such a way that the pad support provided with the pad is joined to the nose. 
     The caliper nose  7  carrying the second friction means  9  can be cut away in its center to form an orifice  34  which delimits, on either side of this same orifice, a first extension  35  and a second extension  36  ( FIGS. 3 and 4 ). Such a shape of the caliper  2  makes it possible to reduce the weight of the disk brake according to the invention. 
     To retain the friction means on the nose of the caliper or on the carrier, a spring such as  41  can be fixed to a corresponding pad support while being placed in bearing contact against the caliper or the carrier. Specifically, in the example in  FIG. 4 , such a spring  41  intended to maintain the second friction means on the nose  7  of the caliper is formed by a metal strip  41  which can be placed from the first extension to the second extension while bearing against the first extension, against the second extension and against the corresponding pad support. This spring  41  extends parallel to the plane formed by the disk. This spring  41  allows the second friction means to be retained on the nose of the caliper while maintaining the second friction means in a floating configuration with respect to the nose. 
     The spring  41  connects the first extension to the second extension while attaching itself to the second friction means by way of securing means. Specifically, this spring  41  is formed from a metal plate which is locally deformed in its center to form a reception housing  42  ( FIG. 2 ). This reception housing  42  receives a boss  43  formed correspondingly by the pad support  9 . 2 . By being on the boss  43 , the spring  41  bears on the one hand against the first extension  35  and against the second extension  36  on the other hand. The metal plate formed by the spring  41  tends to curve between the reception housing  42  and each of the locations where the spring  41  bears on the corresponding extensions. 
     In one variant, at least one support of a friction means is provided with at least a first recess  38  and the caliper nose and/or the carrier is provided with a second recess  39 . At least one removable block  37  is partially housed in the first recess and in the second recess. In the example in  FIGS. 5   a  and  5   b , the second friction means can be connected to the nose of the caliper by the block  37  housed partially in the first recess  38  formed by the pad support  9 . 2  of the second friction means  9  and housed partially in the second recess  39  formed in the caliper nose. The block  37  can first be inserted in one of the two recesses  38  or  39 , and then either the second friction means or the caliper is applied to this same second block  37  so as to imbricate this block  37  between the caliper nose and the second friction means. In this latter case, these recesses  38  and  39  are advantageously non-emerging. 
     According to another variant of the invention, the second friction means can be connected to the nose of the caliper and/or to the carrier via at least one bolt  47  and one nut  48  ( FIG. 6 ). 
     Each friction means has a first lug  25 , a second lug  26  and a central body  27 . In the example in  FIG. 4 , the second friction means  9  has a first lug  25  and a second lug  26  and a central body  27 . According to another variant of the invention in  FIG. 7 , the lugs  25  and  26  of the corresponding friction means are prolonged to form a hook  50 . The hook  50  is represented in broken lines in  FIG. 7 . This hook  50  delimits, together with the body  27  of the friction means, an insertion housing  51  inside which the carrier  3  or the nose  7  of the caliper  2  is inserted in a floating manner. To this end, the carrier or the caliper nose forms a protuberance  52  of complementary shape to the insertion housing. The housing  51  and the protuberance  52  are produced in such a way that the friction means is inserted in a floating manner in the carrier or in the caliper. The friction means thus floating is of the “pull push” type and thus takes up some of the braking torque and contributes to the stiffness of the carrier. In the example in  FIG. 7 , the first friction means is placed in the space  16 . It is the intermediate part  12  which forms at least one protuberance  52  of complementary shape to the insertion housing. 
     To facilitate dissipation of heat from the disk brake according to the invention, the caliper can have at least one window such as  49  ( FIG. 1 ). This window makes it possible to reduce the weight of such a disk brake and also makes it possible to promote a release of heat produced during vehicle braking resulting from the friction of the pads against the disk. 
     The disk has a center and a periphery, the center being a location of the disk at which the axis of rotation  46  of the disk is situated perpendicularly to the plane of the disk. The periphery of the disk delimits the disk. The material formed by the caliper can be distributed to a greater quantity in the vicinity of a first location and in the vicinity of a second location, the first location and the second location being placed along the periphery of the disk and opposing one another, than in the vicinity of a center of this same caliper likewise situated along the periphery of the disk. More precisely, the material formed by the caliper can be distributed with a larger quantity of material at a first location where the first bore is formed and at a second location where the second bore is formed than at a location corresponding to the center of this same caliper. Such a distribution of the material forming the caliper advantageously makes it possible to gain up to 20% braking absorption.