Abstract:
An anchor having first and second rails to align first and second friction members with a rotor. The first and second friction members are moved into engagement with the rotor to effect a brake application. The anchor has projections that extend from the first and second rails and are aligned with the rotor. The thickness of a friction member is reduced by wear through the engagement with the rotor. Each friction member is attached to a carrier by a first inwardly projecting lip on a first end and a second inwardly projecting lip on a second end that has a length that corresponds to an initial thickness of a friction pad plus one-half the width of a projection. During a brake application the lips either engage projections on the first rail or projections on the second rail such that braking forces are communicated into the anchor without the introduction of a moment that could effect the uniform application of force from the friction member on the rotor.

Description:
BACKGROUND OF INVENTION 
     This invention relates to a disc brake having carrier members associated with first and second friction pads in which reaction forces are carried through point contacts into an anchor along first and second planes that are aligned with the radial surfaces on a rotor during a brake application to substantially eliminate lateral forces that may contribute to non-uniform wear patterns in the first and second friction pads. 
     Disc brakes such as illustrated in U.S. Pat. Nos. 4,044,864; 4,219,106; 4,335,806 and 5,551,537 have an anchor with support surfaces or rails that are spaced apart from each other to receive and guide first and second friction pads toward a rotor during a brake application. In such disc brakes, the first and second friction pads each have a carrier member that is retained in first and second rails on an anchor. Reaction forces developed during a brake application are communicated from the carriers into the anchor during a brake application. While the shape of the carrier member may be different as illustrated in U.S. Pat. Nos. 5,111,914 and 6,039,155 all such carrier members are off-set with respect to a radial engagement surface of the rotor and as a result a moment is generated by transmission of a friction force into the anchor. Even though this moment is small it contributes to uneven force and the distribution of pressure on the friction pad against the rotor that may create noise and ultimately uneven wear of the friction pad. 
     SUMMARY OF INVENTION 
     It is a primary object of this invention to substantially eliminate the introduction of a moment into a carrier member of a friction pad during a brake application by providing for the inline transmission of reaction forces generated during a brake application directly into a support member. 
     According to this invention, a disc brake has a support member fixed to a housing on a vehicle with first and second rails that align first and second carrier members in parallel planes on opposite sides of a rotor. Friction pads on the first and second carrier members are respectively moved into engagement with first and second radial surfaces on the rotor to develop a brake force that is communicated into the anchor to opposes the rotation of the rotor and thereby effect a brake application. The support member or anchor has first and second projections that extend from the first rail and first and second projections that extend from the second rail. The first projections are located in a first plane that is aligned with the first radial surface of the rotor while the second projections are located in a second plane that is aligned with the second radial surface of the rotor. An initial thickness of the friction pads is continually reduced by wear through the engagement with the rotor during a brake application. Each friction pad is attached to a carrier member and defined by a first inwardly projecting lip on a first end and a second inwardly projecting lip on a second end. The length of each of the first and second inwardly projecting lips is equal to an initial thickness of a friction pads plus one-half the width of a projection that extends from a rail. During a brake application and depending on the rotational direction of the rotor, an inwardly projection lip engages either the first and second projections on the first rail or the first and second projections on the second rail along the first and second planes to-transmit braking forces into the anchor without the introduction of a moment that may effect the uniform application of an actuation force between the pad and rotor and ultimately uneven wear of a friction pad. 
     An advantage of this invention resides in a carrier for first friction member having a inwardly projecting lip that engages a projection that extends from an anchor in a plane that is aligned with a radial rotor surface such that reaction forces are transmitted into an anchor in a same plane as where the reaction force are generated. 
     A further object of this invention relates to a carrier member for a friction pad wherein an inwardly projecting lip has a length that corresponds to an initial thickness of a friction pad plus at least one-half the width of a projection that extends from a rail on a rotor such that a reaction force is carried through a point contact with the projection with changes in a thickness of the friction pad. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a schematic illustration of a disc brake made according to the present invention having support rails in an anchor with projections aligned with first and second radial surface on a rotor through which braking forces are transmitted into the anchor during a brake application. 
     FIG. 2 is a sectional view taken along lines  2 — 2  of FIG. 1 showing a relationship between the first and second carriers for the first and second friction members and anchor with an initial thickness of the friction pads; 
     FIG. 3 is a sectional view taken along lines  3 — 3  showing a relationship between the end of a carrier and rail of the anchor; and 
     FIG. 4 is a sectional view taken along lines  2 — 2  of the first and second carriers and anchor after the friction pads have worn through the engagement with the rotor. 
    
    
     DETAILED DESCRIPTION 
     In this description a same number may be used for a feature in describing a same component when used in a different locations or it necessary&#39; may be added to the original number. 
     The disc brake  10  shown in drawings for use in a brake system of a vehicle is basically of a type known in the prior art as disclosed in U.S. Pat. No. 5,810,122. 
     The disc brake  10  as shown in FIG. 1 includes an anchor or support member  12  that is fixed to a stationary frame  14  of a vehicle in a manner as disclosed in U.S. Pat. No. 5,988,761 and an integral caliper  16  is connected to the support member  12  through guide pins  44  and  50 . The integral caliper  16  of disc brake  10  includes an actuation section  18  that is connected by a bridge  22  to u-shaped arms  20 , 20 ″. The actuation section  18  as best illustrated in FIG. 2 has a bore  24 , 24 ′ therein for the retention of pistons  26 , 26 ′ to define an actuation chambers  28 , 28 ′. A first friction member  30  is associated with pistons  26 , 26 ′ while a second friction member  32  is associated with arms  20 , 20 ′. The first friction member  30  includes a backing plate or carrier  34  and a friction pad  36  while the second friction member  32  also includes a backing plate or carrier  38  and friction pad  40 . The backing plate or carrier  34  has a first projection  34   a  that is located in a slot  31  that defines a first rail of the support member or anchor  12  and a second projection  34   b  that is located in slot  33  that defines a second rail of the support member  12 . Similarly, backing plate or carrier  38  has a first projection  38   a  that is located in slot  31  of the first rail and a second projection  38   b  that is located in slot  33  of the second rail of support member or anchor  12 . Slots  31  and  33  in support member or anchor  12  are parallel to each other and when the support member or anchor  12  is fixed to a vehicle, the slots  31 , 33  are positioned in a perpendicular relationship with rotor  42  such that the engagement faces on the first  36  and second  40  friction pads are respectively positioned in parallel planes that are adjacent a first radial face  42   a  and a second radial face  42   b  of a rotor  42  that rotates with an axle of the vehicle. The caliper  16  is connected to the support member or anchor  12  by the first guide pin  44  that extends through an opening in an ear  46  that extends from the actuation section  18  and the second guide pin  50  that extends through an ear  52  that extends from the actuation section  18 . The first  44  and second  50  guide pins are respectively mounted to slide in corresponding first and second bores in the support member or anchor  12 . The first and second bores in support member or anchor  12  are spaced apart and parallel to each other to respectively align the first guide pin  44  and the second guide pin  50  in a parallel relationship with the first slot  31  in the first guide rail and second slot  33  in the second guide rails to assist in maintaining the perpendicular relationship between the radial face  42   a  on rotor  42  and the face on the first friction member  36  and radial face  42   b  on rotor  42  and the face on the second friction member  40 . During a brake application, the caliper  16  slides with respect to the support member or anchor  12  and the first  44  and second  50  guide pins correspondingly move in the first and second bores in the support member or anchor  12  to maintain the parallel relationship between the friction pads  36  and  40  and corresponding radial surfaces  42   a  and  42   b  on rotor  42 . Caliper  16  moves with respect to support member or anchor  12  as a reaction to pressurized fluid being supplied to chambers  28 , 28 ′ that acts pistons  26 , 26 ′ to move the backing plate or carrier  34  to move friction pads  36  and  40  toward rotor  42 . As backing plate or carrier  34  moves, the first projection  34   a  slides in slot  31  and the second projection  34   b  slides in slot  33  while at the same time the first projection  38   a  on backing plate  38  slides in slot  31  and the second projection  38   b  slides in slot  33 . During a brake application, the engagement of the face of friction pad  36  with rotor face  42   a  and the engagement of the face of friction pad  40  with rotor face  42   b  create first and second reaction forces that are carried into anchor  12  by way of either the first rail or the second rail (depends on the rotational direction of the rotor) to oppose the rotation of the rotor  42 . When the actuation force acting on the pistons  26 , 26 ′ and arms  20 , 20 ′ is equal to the brake forces created through the frictional engagement of the friction pads  36  and  40  with radial rotor faces  42   a  and  42   b , the rotor  42  will come to a stop. 
     The communication of the brake forces into the support member or anchor  12  according to this invention is achieve through the relationship developed between backing plate or carrier  34  and backing plate or carrier  38  and the first slot or rail  31  or the second slot or rail  33  in anchor  12 . The physical structure of each backing plate or carrier and the rail of the support member  12  are identical and function in a same manner. In order to eliminated redundancy, only backing plate or carrier  34  and the first rail  31  of support member  12  will hereinafter be described in specific detail unless necessary to further define the operation of the disc brake  10 . 
     Support member or anchor  12  has a first projection  70  and a second projection  72  that extends from the first rail  31  and a first projection  74  and a second projection  76  that extends from the second rail  33 . The first projections  70  and  74  have a width “W” with the a center  73 , 73 ′ thereof located along a first plane that is parallel with the radial face  42   a  on rotor  42  while the second projections  72  and  76  also have a width “W” with a center  75 , 75 ′ thereof is located in a second plane that is parallel with the radial face  42   b  on rotor  42 . The anchor is made of a cast member and as a result may not possess a desired resistance to wear when engaged with another member. To protect a rubbed or engaged surface and in particular the guide surfaces of slots  31  and  33 , a first surface protection member  78  (made of stainless steel) is located in slot  31  and attached to anchor  12  and a second surface protection member  80  is located in slot  33  and attached to anchor  12 . The first and second surface protection members  78  and  80  each have a profile that matches the first and second rails to protect the support member or anchor (cast metal) from frictional wear. 
     The backing plate or carrier  34  is characterized by a flat plate with a first projection  34   a  defined by an inwardly projection lip  82  and a second projection  34   b  defined by an inwardly projecting lip  84 . Lips  82  and  84  each have a length that is equal to an initial thickness of friction pad  36  plus one-half W of a projection  70 . As best illustrated in FIG. 3 for lip  82 ′, each lip  82  has a top  86  and bottom  88  that is located in either slot  31  or slot  33  to provide radial retention and maintain the friction pad  36  in alignment with radial surface  42   a.    
     In disc brake  10 , during a brake application, a leading edge ( 36   a  and  40   a  or  36   b  and  40   b ) for the friction pads  36  and  40  is defined by the rotation of rotor  42  and is first surface to engage the rotor  42 . When  36   a  and  40   a  are the leading edges of the friction pads  36  and  40 , inwardly projecting lip  82  on backing plate or carrier  34  engages the first projection  70  and inwardly projecting lip  82 ′ on backing plate or carrier  38  engages the second projection  72  on the first rail  31  and when edges  36   b  and  40   b  are the leading edge, inwardly projecting lip  84  on backing plate or carrier  34  engages the first projection  74  and inwardly projecting lip  84 ′ engages the second projection  76  on the second rail  33  to transmit frictional engagement forces developed during a brake application into the anchor or support member  12 . The actuating pressurized fluid is supplied to chambers  28 , 28 ′ that act on pistons  26 , 26 ′ and housing  19  uniformly move the friction members  30  and  42  toward the rotor  42  and on engagement of the face of friction member  36  with rotor face  42   a  and the face of friction member  40  with rotor face  42   b  the resulting reaction forces are carried through the point of contact between the inwardly projecting lips on the carrier members  34  and  38  with the projections  70 , 72 , 74 , 76  on the rails along planes that are inline with the plane of frictional engagement. Since the reactions forces are in-line with the frictional engagement forces and directly transmitted into the support member  12  no moment is introduced that effects the uniform application of the actuation force derived from the pressurized fluid. Thus, the actuation force is uniformly applied across an entire carrier member  34 , 38  to bring the friction pads  36  and  40  into engagement with the rotor  42  in planes that are substantially parallel to the radial faces  42   a  and  42   b  of the rotor  42  and as a result the development of noise is substantially reduced or eliminated. 
     Over a period of time, the frictional engagement of friction pads  36  and  40  with radial faces  42   a  and  42   b  of rotor  42  cause the thickness of the friction pads  36  and  40  to be reduced in a manner as illustrated in FIG.  4 . However, the point contact relationship between the inwardly projecting lips  82 , 82 ′ and projections  70 , 72  on the first rail  31  and inwardly projecting lips  84 , 84 ′ and projections  74 , 76  on the second rail  33  remain along in planes aligned with the radial surfaces  42   a  and  42   b  of rotor and as a result an actuation force is uniformly applied to move the face of friction pads  36  and  40  into engagement with the rotor  42 .