Patent Publication Number: US-2003221919-A1

Title: Disc brake

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a disc brake, and more particularly to a disc brake in which a layered shim for preventing generation of squeal during braking (hereinafter referred to as an “anti-squeal layered shim”) is attached to a backing plate of a pad so as to be interposed between the backing plate of the pad and a press member for pressing the pad toward a disc rotor.  
       [0003] 2. Description of the Related Art  
       [0004] A disc brake of the above-mentioned type is disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. 6-129451. In such a disc brake, a press member presses a pad against a disc rotor via a layered shim in order to generate braking force. The layered shim employed in the disc brake disclosed in the above-mentioned publication consists of a first shim (a press-member-side shim) to be attached to the backing plate of the pad, and a second shim (a pad-side shim) which has a slit for holding lubricant and which is to be interposed between the backing plate and the first shim. In some layered shims, a rubber coated shim is employed as the pad-side shim, and/or the pad-side shim and the press-member-side shim are joined and fixed together by means of adhesive.  
       [0005] In the above-described conventional disc brake, squeal generated during braking is reduced through absorption of vibration and stabilization of surface pressure distribution, which are achieved by the layered shim disposed between the backing plate of the pad and the press member. However, in the conventional disc brake, the pad may move in the direction of rotation of the disc rotor during braking, whereby relative movement may occur between the pad-side shim and the press-member-side shim of the layered shim. In such a case, the absorption of vibration and the stabilization of surface pressure distribution, which are achieved by the layered shim, are impaired, possibly resulting in failure of the layered shim to sufficiently attain the squeal prevention effect.  
       SUMMARY OF THE INVENTION  
       [0006] In view of the foregoing, an object of the present invention is to provide a disc brake in which joint between the pad-side shim and the press-member-side shim of a layered shim can be reliably maintained, whereby absorption of vibration and stabilization of surface pressure distribution, which are achieved by the layered shim, can be achieved for a long period of time without any impairment, so that the layered shim can consistently attain the squeal prevention effect over a long period of time.  
       [0007] In order to achieve the above object, the present invention provides a disc brake comprising a disc rotor, a pad having a backing plate, a press member for pressing the pad toward the disc rotor, and an anti-squeal layered shim attached to the backing plate and disposed between the press member and the backing plate of the pad. The layered shim includes a pad-side shim and a press-member-side shim. A depression is provided on a surface of the pad-side shim, the surface facing toward the press member. A projection is provided on the press-member-side shim, the projection being fitted into the depression in order to restrict relative movement between the pad-side shim and the press-member-side shim along a pressing surface.  
       [0008] By virtue of the above-described configuration, even when relative movement is about to occur between the pad-side shim and the press-member-side shim of the layered shim upon movement of the pad in the rotational direction of the disc rotor during braking, such relative movement is prevented by means of fitting engagement between the above-described depression and projection. Therefore, the joint between the pad-side shim and the press-member-side shim of the layered shim is reliably maintained, whereby absorption of vibration and stabilization of surface pressure distribution, which are achieved by the layered shim, can be achieved over a long period of time without any impairment, and thus the layered shim can consistently attain the squeal prevention effect over a long period of time.  
       [0009] The projection may be formed through formation of a depression on a surface of the press-member-side shim, the surface facing toward the press member, and the depression may be provided in such a manner that at least a portion of the depression overlaps a pressing surface of the press member. In this case, the depression formed on the surface of the press-member-side shim facing toward the press member can be used as surface pressure adjustment means (means for reducing surface pressure).  
       [0010] Further, the pad-side shim and the press-member-side shim may be joined and fixed together by means of adhesive. In this case, the function of the adhesive, which joins and fixes the pad-side shim and the press-member-side shim together, is maintained over a long period of time, and the layered shim can consistently attain the squeal prevention effect over a long period of time. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] Various other objects, features and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiments when considered in connection with the accompanying drawings, in which:  
     [0012]FIG. 1 is a vertical cross-sectional view of a disc brake according to one embodiment of the present invention;  
     [0013]FIG. 2 is a front view of a layered shim shown in FIG. 1, as viewed from the pad side;  
     [0014]FIG. 3 is an enlarged cross-sectional view taken along line A-A of FIG. 2;  
     [0015]FIG. 4 is a front view corresponding to FIG. 2 and showing another embodiment of the present invention;  
     [0016]FIG. 5 is an enlarged cross-sectional view taken along line B-B of FIG. 4; and  
     [0017]FIG. 6 is a front view corresponding to FIG. 2 and showing still another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0018] Embodiments of the present invention will now be described with reference to the drawings. FIGS.  1  to  3  show a disc brake according to an embodiment of the present invention. In this disc brake, an inner pad  12  and an outer pad  13 , which press-hold and brake a disc rotor  11 , are mounted to a mounting  14  so as to be movable over a predetermined distance in the direction of the rotor axis (the left-right direction in FIG. 1) and to be slightly movable in the circumferential direction of the rotor (in the rotational direction, more precisely, the tangential direction, of the disc rotor  11 ). Further, a movable caliper  15  is mounted to the mounting  14  to be movable in the direction of the rotor axis.  
     [0019] The inner pad  12  includes a backing plate  12   a  and a lining  12   b . The inner pad  12  is pressed and moved toward the disc rotor  11  by means of a piston  16 , which is accommodated in a cylinder portion  15   a  of the movable caliper  15  to be movable in the direction of the rotor axis. Further, an anti-squeal layered shim  20  is attached to the backing plate  12   a  of the inner pad  12 , so that the anti-squeal layered shim  20  is interposed between the backing plate  12   a  and the piston  16 .  
     [0020] Meanwhile, the outer pad  13  includes a backing plate  13   a  and a lining  13   b . The outer pad  13  is pressed and moved toward the disc rotor  11  by means of a reaction arm portion  15   b  of the movable caliper  15 , which portion is formed to overhang the pads  12  and  13 . Further, an anti-squeal layered shim  20  is attached to the backing plate  13   a  of the outer pad  13 , so that the anti-squeal layered shim  20  is interposed between the backing plate  13   a  and the reaction arm portion  15   b.    
     [0021] As shown in FIGS. 2 and 3, each of the layered shims  20  is composed of a rubber-coated shim  21  attached to the back surface (rear surface) of the backing plate  12   a  or  13   a  of the corresponding pad  12  or  13 , and an SUS shim  22  which is joined and fixed to the back surface of the rubber-coated shim  21  by use of adhesive  23 . The rubber-coated shim  21  is a layered plate consisting of a base plate  21   a  made of mild steel (SPCC), and a heat-resistant rubber layer (a layer of NBR rubber)  21   b  laminated on a surface of the base plate  21   a . The SUS shim  22  is a plate made of stainless steel (SUS).  
     [0022] The disc brake having the above-described configuration operates as follows. During braking, pressurized oil is supplied to the cylinder portion  15   a  of the movable caliper  15 , whereby the pressurized oil causes the piston  16  to press the inner pad  12  toward the disc rotor  11  via the layered shim  20 , with generation of a reaction force which causes the reaction arm portion  15   b  of the movable caliper  15  to press the outer pad  13  toward the disc rotor  11  via the layered shim  20 . Therefore, the inner pad  12  and the outer pad  13  are pressed against the disc rotor  11 , so that the inner pad  12  and the outer pad  13  press-hold the disc rotor  11  to thereby generate a braking force.  
     [0023] In the disc brake of the present embodiment, as shown in FIGS. 2 and 3, two circular through-holes  21   c  are formed in the rubber coated shim  21  of the layered shim  20 ; and two circular projections  22   a  are formed on the SUS shim  22  of the layered shim  20 . Each of the circular projections  22   a  has four inclined connecting portions  22   a   1 , which are located at the upper, lower, left, and right sides, respectively, in FIG. 2, and is fitted into the corresponding circular through-hole  21   c  (a depression provided on the rubber coated shim  21 ). This configuration restricts relative movement between the rubber coated shim  21  and the SUS shim  22  of the layered shim  20  along a pressing surface (the back surface of the SUS  22 , with which the piston  16  or the reaction arm portion  15   b  of the movable caliper  15  comes into contact).  
     [0024] Therefore, even when relative movement is about to occur between the rubber coated shim  21  and the SUS shim  22  of the layered shim  20  along the pressing surface upon movement of the pad  12  or  13  in the rotational direction of the disc rotor  11  during braking, such relative movement is prevented by means of fitting engagement between the two circular through-holes  21   c  and the two circular projections  22   a . Therefore, the joint between the rubber coated shim  21  and the SUS shim  22  of the layered shim  20  is reliably maintained, whereby absorption of vibration and stabilization of surface pressure distribution, which are achieved by the layered shim  20 , can be achieved over a long period of time without any impairment, and thus the layered shim  20  can consistently attain the squeal prevention effect over a long period of time.  
     [0025] Further, in the disc brake of the present embodiment, as shown in FIG. 3, each of the circular projections  22   a  is formed through formation of a depression  22   b  on the back surface of the SUS shim  22  (on the side toward the piston  16  or the reaction arm portion  15   b ; i.e., on the side toward the press member); and, as indicated by an imaginary line in FIG. 2, the depression  22   b  is provided in such a manner that at least a portion of the depression  22   b  overlaps the pressing surface of the reaction arm portion  15   b  (or the piston  16 ). Therefore, the depression  22   b  formed on the back surface of the SUS shim  22  can be used as surface pressure adjustment means (means for reducing surface pressure).  
     [0026] Further, in the disc brake of the present embodiment, since the above-described configuration (fitting engagement between the two circular through-holes  21   c  and the two circular projections  22   a ) restricts relative movement between the rubber coated shim  21  and the SUS shim  22  of the layered shim  20  along the pressing surface, the function of the adhesive  23 , which joins and fixes the rubber coated shim  21  and the SUS shim  22  together, is maintained over a long period of time, and the layered shim  20  can consistently attain the squeal prevention effect over a long period of time.  
     [0027] In the above-described embodiment, relative movement between the rubber coated shim  21  and the SUS shim  22  of the layered shim  20  along the pressing surface is suppressed by means of fitting engagement between the two circular through-holes  21   c  and the two circular projections  22   a . However, the relative movement can be suppressed by means of fitting engagement between a single rectangular (non-circular) through-hole  21   c  and a single rectangular projection  22   a  as shown in FIGS. 4 and 5, or fitting engagement between a single cruciform (non-circular shape) through-hole  21   c  and a single cruciform projection  22   a  as shown in FIG. 6.  
     [0028] In the embodiments shown in FIGS. 4 and 6, the projection  22   a  has four inclined connecting portions  22   a   1 , which are located at the upper, lower, left, and right sides, respectively, and is fitted into the through-hole  21   c  (a depression provided on the rubber coated shim  21 ). This configuration restricts relative movement between the rubber coated shim  21  and the SUS shim  22  of the layered shim  20  along the pressing surface. Further, as indicated by broken lines in FIG. 5, the upper, lower, left, and right cut end surfaces of the projections  22   a  restrict such relative movement.  
     [0029] In the above-described embodiments, a through-hole  21   c  of a circular, rectangular, or cruciform shape is employed as a depression provided on the rubber coated shim  21  (a depression into which the projection  22   a  of the SUS shim  22  is fitted). However, a bottomed hole of a circular, rectangular, or cruciform shape which is open toward the SUS shim  22  may be employed as a depression provided on the rubber coated shim  21 .  
     [0030] In the above-described embodiments, the present invention is applied to a disc brake which employs the above-described layered shim  20  in which the rubber coated shim  21  and the SUS shim  22  are joined and fixed together by use of the adhesive  23 . However, the present invention can be applied to a disc brake which employs a layered shim in which a rubber coated shim and an SUS shim are merely brought into contact with each other, with or without a modification.  
     [0031] Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.