llllllllllllllIlllllllllllllllllllll!!!)llllllllllllllllllllllllllllll United States Patent [19] [11] Patent Number: 5,593,005 Kullmann et al. [45] Date of Patent: Jan. 14, 1997 [54] CALIPER-TYPE DISC BRAKE WITH 4,811,822 3/1989 Estaque. STEPPED ROTOR 4,930,606 6/1990 Sporzynski et a1. 5,010,985 4/1991 Russell et a1. [75] Inventors: Bernhard Kullmann, Rochester Hills; 510221500 6/1991 Wang - Mich.;Joerg Scheibel,Larry Masserant, Auburn Hills’ Frankfurt, both of FOREIGN PATENTEmmons DOCUMENTS............................... .. Germany; Daniel Keck, Westland; Werner Gottschalk, Auburn Hills’ both 1336878 of 1962 France ................................ .. 188/724 of Mich 0329831 8/1989 Germany ............................ .. 188/73.1 199785 3/1966 U.S.S.R. _ . 0199785 7/1967 U.S.S.R. [73] Assrgnee. ITThAutomotlve, Inc., Auburn Hills, 1019094 2/1966 United Kingdom _ MIC - 1108916 10/1968 United Kingdom. [21] AppL NOJ 486,457 Primary Examiner--Robert J. 0138116111161‘ Assistant Examiner—Chris Schwartz [22] Filed: Jun. 7, 1995 Attorney, Agent, or Firm-Thomas N. Tworney; J. Gordon [51] Int. Cl.6 ........................... .. F16D 55/22; F16D 65/12 Lew“ [52] US. Cl. ........................................ .. 188/724; 188/731 [57] ABSTRACT [58] Fleld of searlcgs Adisc brake for the wheel of a motor vehicle includes a rotor ' ’ '1’92/65 ’85 AA’ 66 70 15’ mounted to the wheel, and a caliper straddling the rotor and ’ ’ ’ ' supporting a brake pad on either side thereof. In order to R f C-t d accommodate packaging constraints within the wheel’s rim, [56] e erences l e the outboard pad and the rotor’s outboard friction surface are US. PATENT DOCUMENTS both positioned radially inwardly of the inboard pad and . inboard rotor friction surface. A hydraulic piston located in 5:31:10“ ' the inboard portion of the caliper ?rst urges the inboard pad 3,312,316 4/1967 Burnett ................................. .. 188/718 al‘mg the PiSt‘m’S l‘mgimdinal “is in“) initial engagement 3:378:114 4/1968 Homns _ with the rotor’s inboard friction surface, whereupon the 3,517,777 6/1970 B61161‘ ................................... .. 188/731 piston acts through the caliper’s bridge and ?nger area to 3,983,969 10/1976 Colpaert et a1. urge the outboard pad into engagement with the rotor’s 3,993,173 11/1976 Hoffman . outboard friction surface. The effective radius of each pad is 4,289,216 9/1981 Shirai et a1. ......................... .. 188/722 less than the radial o?set of the piston’s longitudinal axis ?ick et all from the rotational axis of the wheel and rotor so as to reduce 4,460,070, , 7,1984 Meyersema et e a1‘ . 188/731 the bending. moment applied_ to the rotor upon braking._ 4,533,025 8/1985 Carré .......... ., 188/731 4,712,654 12/1987 Temple et a1. ....................... .. 188/718 5 Claims, 1 Drawing Sheet 26 42 38 4O 12 IO\ 30 28 = If 44 56\ E ‘I ‘1' ~_ 24 .A I 1 , ‘T54 52- Ml ’;5o 8, < l _. \66 //1.|4 32 48 58 K/22 l8 '— 2O 36 34 I“ ll 1 llll “\16 {/‘46 5,593,005 1 2 CALIPER-TYPE DISC BRAKE WITH application of a bending moment to the rotor and, corre STEPPED ROTOR spondingly, uneven brake pad wear. This, in turn, results in a loss over time of vehicle braking performance, oifsetting TECHNICAL FIELD any potential gains which might otherwise have resulted from the increased swept area achieved by the radially-outer The present invention relates to an improved caliper-type inboard pad. disc brake for applying a braking torque to a wheel of a What is needed, then, is an improved caliper-type disc motor vehicle. More speci?cally, the invention relates to brake for the wheel of a motor vehicle which maximizes use caliper-type disc brakes which seek to maximize vehicle of available packaging space within the wheel’s inner rim to braking performance within the physical con?nes of the boost vehicle braking performance while minimizing wheel’s inner rim. applied moments and, correlatively, the uneven wear likely to result therefrom. BACKGROUND OF THE INVENTION The prior art teaches disc brakes for motor vehicles SUMMARY OF THE INVENTION generally comprising a circular disc or rotor mounted to a wheel for rotation therewith about an axis. An anchor Under the present invention, a disc brake for applying a member, rigidly mounted to the axle which supports the net braking torque to a wheel of a motor vehicle which wheel, also provides rigid support for a caliper which rotates about a ?rst axis comprises a rotor mounted to the otherwise straddles a portion of the periphery of the rotor. wheel, with the rotor having a ?rst, inboard side and a Brake linings or “pads” supported by the caliper on either second, outboard side de?ning an inboard annular friction side of the disc are urged into engagement with frictional surface and an outboard annular frictional surface, respec surfaces on the opposite faces of the rotor to generate tively. The outer peripheral edge of the rotor’s outboard braking torque, as by supplying pressurized hydraulic ?uid friction surface is also radially inward of the outer peripheral to a piston housed within one or both ends of the caliper. edge of the rotor’s inboard friction surface, thereby maxi 25 Typically, these prior art disc brakes utilize like-sized mizing the potential swept area on the rotor’s inboard brake pads on either side of the rotor. Each brake pad is friction surface while accommodating the lesser radial clear likewise provided with substantially the same eifective ance afforded by the wheel’s inner rim on the rotor’s radius, that is, the braking force generated by each brake pad outboard side. upon being urged against its respective mating rotor surface 30 The present disc brake also comprises a caliper straddling is effectively offset the same radial distance from the rota the rotor along a portion of its outer edge. The caliper tional axis of the wheel/rotor assembly. The contact area of supports a ?rst, inboard brake pad in opposition with the each brake pad is typically “aligned” with, i.e., is centered rotor’s inboard friction surface and a second, outboard brake about, the longitudinal axis of the piston operating to urge pad in opposition with the rotor’s outboard friction surface. that pad towards its mating rotor surface. The normal forces 35 Typically, due to the packaging constraints of current exerted by the brake pads on both rotor surfaces will thus production wheels, the radially-outermost edge of the out~ likewise be axially aligned and, hence, application of an board brake pad is radially inward of the radially-outermost undesirable moment on the brake rotor will be avoided (the edge of the inboard brake pad. The caliper also has a means, art has recognized that application of such moments are such as a hydraulically-operated piston, operating along a undesirable, for example, given the likelihood of uneven second axis substantially parallel to the rotational axis of the wear of the brake pads). wheel and rotor, for urging the inboard and outboard brake However, in at least one prior art design for a “?xed”-type pads into engagement with the inboard and outboard rotor caliper—that is, a nonswinging dual-opposed-piston cali friction surfaces, respectively. per—the pad located on the side of the rotor nearest the hub Signi?cantly, under the present invention, the effective of the wheel (hereinafter “the outboard pad”) is deliberately 45 radii of the ?rst and second brake pads, when urged into positioned nearer the wheel’s rotational axis than its coun engagement with their respective opposed rotor friction terpart on the other side of the rotor (hereinafter the “inboard surfaces, are each less than the radial offset of the second pad”). This is an attempt to provide a maximum effective axis from the ?rst axis. By requiring that the eifective radius radius/swept area for each individual pad while otherwise of each brake pad—and, particularly, the inboard pad upon accommodating those wheels whose inner rims provide less which the piston directly operates—be less than the radial radial clearance for the outboard pad than for the inboard distance between the wheel’s rotational axis and the opera pad. In such a design, the outboard portions of the caliper, tional axis of the piston, the bending moment applied to the including its outboard piston’s longitudinal axis, are like rotor upon braking will be markedly reduced as compared to wise displaced radially inwardly, relative to the inboard the prior art dual-opposed-piston caliper brake described portions of the caliper, towards the wheel’s rotational axis. 55 above (with its outboard piston and pad deliberately posi As might be expected, under this approach, each like-sized tioned nearer the wheel’s rotational axis than their inboard brake pad is maintained in alignment with the longitudinal counterparts). Stated another way, under the present inven axis of its respective piston. tion, it is desirable to radially outwardly distance the piston’ s Unfortunately, while affording greater radial clearance centerline from the effective radius of the inboard pad upon between the wheel rim and the periphery of the brake which the piston directly operates. caliper—particularly along its outboard end-the radially Even more preferably, under the present invention, the inward displacement of the outboard pad and its driving inner peripheral edge of the rotor’s inboard friction surface piston correlatively reduces the pad’s effective radius. Since is extended radially inward toward the rotational axis of the the effective radius of the inboard pad remains unchanged, wheel and rotor, such that the inner peripheral edge of the the resulting disparity between the eifective radius of each 65 rotor’s inboard friction surface is nearer the rotational axis pad, coupled with the lack of alignment between the longi than the inner peripheral edge of the rotor’ s outboard friction tudinal axes of the inboard and outboard pistons, results in surface.