Document Loe6q31Ezb3jdnRjapKR4eQp3

United States Patent: 4,240,530 Page 1 of 6 USPTO Patent Full-Text and Imaqe Database Home Quick Advanced Pat Num Help Prev. List Hit List Next List Previous Next Bottom View Cart Add to Cart Images (281 of 356) United States Patent Tillenburg 4,240,530 December 23, 1980 Brake pad for disc brakes Abstract A brake pad has friction material bonded to a earner plate The earner plate includes two strengthening parts, of which one is bonded to the friction material and the two are bonded together by a resilient bondmg matenal The two parts have a plurality of aligned recesses and projections to resist shear ^tresses encountered dunng braking Inventors Tillenburg; Johannes (Essen, DE) Assignee Abex Pagid Reibbelag GmbH (Essen, DE) Appl No 035360 Filed May 2,1979 Foreign Application Priority Data May 13,1978[DE] 2821194 Current U.S. Class: Intern'l Class: Field of Search: 188/250E, 188/264G, 188/268 F16D 065/12 188/1 B,73 5,250 B,250 E,264 G 3162271 3490563 References Cited [Referenced Bv] Dec, 1964 Jan, 1970 U.S. Patent Documents Hanson Hahm 188/264. 188/73 'rimary Examiner Reger, Duane A 1'Attorney, Agent or Firm Baker, Jr , Thomas S , Greenlee, David A Claims SCF-ABEX-2435 ABEX-203 25 httn.//natft.usnto eov/netacei/nDh-Parser?Sectl=PT02&Sect2=HITOFF&u=/netahtml/sea 10/18/2003 United States Patent- 4,240,530 Page 2 of 6 What is claimed is 1. A brake pad for disc brakes, in particular disc brakes of motor vehicles, composing a multi-part earner plate and a friction lining pressed thereon, a dampmg layer being provided in each case between two parts of the earner plate to separate the two parts and projections on one part of the earner plate engaging with conespondmg recesses in the other part of the earner plate, charactenzed in that the parts of the earner plate are provided with mating centenng recesses and centenng projections which mutually engage and have oblique centenng surfaces, a slightly compressible thin, vibration-dampmg and heat-insulatmg elastic bonding layer is located between two parts of the carrier plate and the elastic bonding layer consists of a non-swellable matenal which is bonded to the parts of the earner plate under pressure and at the temperature at which the friction lining is bonded to the earner plate. 2 A brake pad according to claim 1, charactenzed in that the penpheral dimensions of the part of the earner plate which is m contact with the brake piston of the disc brake are smaller than those of the other part of the earner plate so that it does not come into contact with the brake housing 3. A brake pad according to claim 1, charactenzed in that the projections on said one part of the earner plate engage said friction lining to help resist shear stress imparted to the friction matenal during braking Description BACKGROUND OF THE INVENTION This invention relates to a brake pad for a disc brake used m a motor vehicle. Such a brake pad customanly includes a composition friction lining which is ngidly attached to a metal earner plate. The earner plate strengthens the brake pad and enables it to withstand the large compressive stresses which are generated dunng the braking process when a piston biases the brake pad against a rotor or brake disc The aforementioned brake pad is economically manufactured m a single working step using a single press die as follows The earner plate is placed in the bottom of a mold. The surface of the earner plate, which receives the friction lining, is coated with an adhesive film Next, the friction lining composition is inserted in the mold Finally, the press die presses the lining mto the mold, which is maintained at a predetermined temperature until the friction matenal is properly shaped and cured Simultaneously with the cunng of the friction matenal, the adhesive is likewise cured and the friction matenal is bonded to the earner plate Dunng the braking process, when the friction lining engages the disc, vibrations occur which are transmitted through the brake pad and the piston to the brake housing or caliper. These vibrations can result in loud, high-pitched squeaking noises Furthermore, friction between the disc and lining dunng the braking process generates large quantities of heat Since friction linings have good heat conductivity, |his heat is transmitted via the earner plate to the brake piston and then to the brake fluid which results nn impaired operability of the brake system In the past, numerous attempts have been made to suppress the braking noises and the heat transfer htto //natft usnto eov/netacei/nnh-Parser?Sect1=PTO?#Sprt?=HTTnFF#ii=/nH-sVihn1/P5i in/i8/onm United States Patent. 4,240,530 Page 3 of 6 One method of suppressing the brake noises is based on the principle that two bodies of different mass possess different characteristic frequencies, such that if the two bodies are bonded together and their 'masses are suitably matched, their vibration frequencies interfere with and impede one another m such a way as to dampen vibration In accordance with this principle, a brake pad has been manufactured where a metallic earner plate has a composition friction matenal on one side and a plastic or aluminum back plate which is bonded using a resin adhesive on the other side. Although good heat insulation can be achieved with the plastic back plate, the vibration damping is not effective It is also known to manufacture brake pads based on the pnnciple of damping or absorbing vibration by interposing an elastic damping element between one surface which is vibrating and a second surface which is to be isolated from the vibration. According to this pnnciple, a brake pad has been manufactured where the earner plate is subdivided into two metal plates with a layer of an elastic, heat insulating matenal, such as rubber, interposed between the two plates A problem with this type of pad is that it is extremely expensive to manufacture, and there is a significant reduction in the mechanical strength of the pad A typical brake pad has a earner plate which is approximately five millimeters thick. Consequently, even after the friction matenal has worn off the earner plate, a portion of the earner plate is retained m the brake housing during braking In other words, a portion of the brake housing supports the earner plate. However, in the case of a brake pad having a multi-layered plate of the type desenbed above, also called a sandwiched lining, it is not desirable to increase the thickness of the earner plate This is because, if the earner plate thickness is increased, the friction lining thickness must be decreased which results m shortening the working life of the pad Consequently, the multi-part earner plate must have a total thickness of approximately five mihmeters Each part of the earner plate must be made two to three millimeters thick However, after the friction lining has worn off, one part of the earner plate is completely outside of the brake housmg dunng braking Only the second part is retained m the brake ^fciousmg. As a result, the elastic bonding layer between the two parts is subjected to the high shear stress ^^dunng braking The layer cannot withstand the stress and one part of the earner plate is displaced relative to the other, i e , the part of the earner plate which engages the disc and is out of the brake housmg will be displaced relative to the other part Under this condition, the part outside of the housmg cannot retract into the housing after braking and the brake can no longer be released. In an extreme case, the protruding part of the earner plate can lock the brake In another brake pad having a multi-part earner plate, a relatively thm self-adhesive, plastic film has been used in place of rubber for the damping-elastic interlayer of the sandwich plate This film is incapable of satisfactonly absorbing the above-desenbed shear stresses and possesses the additional following disadvantages. If the parts of the carrier plate with the plastic film are placed m a mold in the manner initially desenbed in order to simultaneously press the friction lining and bond the lining to the sandwich plate, the film softens and flows from between the parts of the earner plate. This is because the plastic film is unable to withstand the temperature and pressure required to shape and cure the friction lining. It is possible to have friction lining first pressed onto one part of the carrier plate and the parts of the earner plate subsequently bonded in a second die However, this requires an additional working step which adds to the cost of the pad Further, this requires an expensive die which accurately surrounds the parts of the earner plate so that the metal plates are not mutually displaced when the film softens. Customanly, the finished pressed brake pads are ground to exact dimensions on their side faces and are then lacquered at an elevated temperature, in this procedure there is a nsk of the film softening and the metal plates bemg mutually displaced In order to manufacture a brake pad which has a multi-part earner plate in a single working step and ^fcvhich is capable of absorbing the shear forces generated dunng braking, a multi-part earner plate has ^^been made with a plurality of matching through bores and a layer of rubber interposed between the parts of the earner plate When the friction lining is pressed, the earner plate bores are filled with lining composition which bonds the sandwiched layers of the earner plate to one another in a method similar to httn //oatft usnto eov/netacgi/noh-Parser^Sectl=PT02&Sect2=HITOFF&u:=/netahtml/sea . 10/18/2003 United States Patent- 4,240,530 Page 4 of 6 rivets or bolts. A problem with this construction is that the rigid structures of the friction lining material ^which pass through the bores in the carrier plate prevent mutual displacement of the earner plate parts, ^n>ut also prevent free oscillation of the earner plate parts relative to each other Consequently, the rubber matenal interposed between the earner plate parts cannot operate. The result is that the earner plate operates as a one-piece unit. In another brake pad having a multi-part earner plate, recesses have been pressed into one part of the earner plate and projections have been pressed into the other part of the earner plate and the parts aligned such that the projections mate with the recesses The mutually engaging projections and recesses enable the multi-part earner plate to withstand the shear forces generated dunng braking and prevent displacement of the relative parts However, as a result of the metal-to-metal contact of the projections and recesses, vibrations are transmitted between the parts of the carrier plate and the damping effect of the elastic layer interposed between the parts is adversely affected It is desired to provide a brake pad having a multi-part earner plate in which a damping layer of resilient matenal is provided between the parts of the earner plate and projections on one part of the earner plate engage corresponding recesses in the other part of the earner plate. However, the earner plate must be constructed m such a way that the two parts of the earner plate are isolated from one another and vibration in one of the parts cannot be transmitted to the other part directly It is also desired to provide a brake pad compnsing a multi-part earner plate which can be manufactured in a single working step, such that simultaneously with production of a multi-part sandwich earner plate, the friction lining can be pressed onto the earner plate ^SUMMARY OF THE INVENTION The brake pad of the instant invention provides a multi-part earner plate in which the parts have corresponding centering projections and recesses which mutually engage and have oblique centenng surfaces A thin, slightly compressible vibration damping and heat-insulatmg elastic bonding layer is interposed between the two parts of the earner plate. The elastic bonding layer consists of a nonswellable matenal which, under the pressure and temperature of pressing and cunng the friction lining, is permanently bonded to the parts of the earner plate. DESCRIPTION OF THE DRAWINGS FIG 1 shows a brake pad according to the instant invention, FIG 2 is a sectional view along the line II--II of FIG l,and FIG 3 is a sectional view along the lines III--III of FIG 1 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS 1-3, the brake pad of the instant invention consists of a multi-part earner plate 1 and a friction lining 5. The earner plate 1 consists of two metal parts 2 and 3 which have a resilient bonding and damping material 4 interposed therebetween A portion of part 3 of the earner plate, which is adjacent the friction matenal 5, projects laterally beyond the friction matenal 5 and has a pair of bores 6 Jfhe bores 6 provide a means for attaching the brake pad to a brake housing or caliper A plurality of calotte-shaped embossings 8 are formed on the outer part 2 of the earner plate 1 Likewise, a plurality of calotte-shaped embossings 7 are formed on the inner part 3 of the earner plate 1 httn //natft usnto eov/netacei/nnh-Parser?Sect1 =PT02&.Sect2=HTT0FF#n=/nftahtm1/cpn 1 n/1 8/900'* United States Patent 4,240,530 Page 5 of 6 The calotte-shaped embossings 7 and 8 in parts 3 and 2, respectively, are axially aligned. The part 3 is fcpnnged so that the raised portion of the embossings 7 engage the friction matenal and the recessed portion of the embossings face part 2 Part 2 of the carrier plate 1 is arranged so that the raised portion of the embossings 8 are received in the recessed portion of the embossings 7 m part 3 In this manner the raised portions of the embossings 7 on part 3 project into the friction matenal 5 and help resist shear stress imparted to the friction matenal 5 dunng braking Likewise, the nested relationship of the embossings 7 and 8 enable the earner plate 1 to resist the shear stresses imparted to part 3 dunng braking. Refemng to FIG 2, it can be seen that a thin bonding matenal 4 is inserted between and permanently bonded to parts 2 and 3 of the earner plate 1 In this way, parts 2 and 3 are joined to form the carrier plate 1. The matenal 4 is slightly compressible, vibration-damping, heat-insulating, elastic and nonswellable. A brake pad according to the instant invention can be manufactured as follows. Part 3 of the earner plate 1 which is closest to the friction matenal 5 is constructed from a steel plate three millimeters thick. Part 2 of the earner plate 1 is constructed from a steel plate 1 2 millimeters thick. Part 2 can also have the same length and width as part 3 and have bores coaxial with the bores 6 in part 3. A plurality of calotte shaped, axially aligned embossings 7 and 8 are formed on parts 3 and 2, respectively. The embossings have oblique centenng surfaces which are approximately eight millimeters in diameter and one millimeter m depth. After embossing the two metallic plates are degreased in the customary manner and an adhesive is put on both sides of part 3 and on the side of part 2 which faces part 3 A layer of cychzed rubber having a thickness of 0.15 millimeters is placed between the parts 2 and 3 of the earner plate 1. The parts 2 and 3 of the earner plate 1 are placed in a mold with the layer 4 therebetween. A friction jlining composition 5 is then poured into the mold Subsequently, the pressing process is earned out at a pressure between 500 and 700 kp/cm sup 2 and at a temperature between 150 degree, and 210 degree C for a cunng time of 2-12 minutes This is done in a smgle press die and in a single step The friction lining composition is shaped and formed to give the friction lining 5 and simultaneously the lining 5 is bonded to the earner plate 1 and the bonding layer 4 is bonded to the parts 2 and 3 to produce the unitized earner plate 1 Using this method, it has been found that the bonding layer 4 is non-swellable, that is to say, nonflowable, and the matenal is not pressed out from between the parts 2 and 3 dunng the pressing operation. Further, it has been found that dunng the pressing operation, the projections and recesses of the calotte-shaped embossings 7 and 8 precisely center parts 2 and 3 and prevent relative displacement of the parts. It has also been found that the bonding matenal 4 not only forms a vibration-dampmg and heat-insulating layer, but is also forms a wall having a uniform thickness between the parts 2 and 3. In this manner, metal-to-metal contact of the parts 2 and 3 is prevented at all places including adjacent the calotte-shaped embossings, with the result that no bndges are formed which can transmit vibration or heat. Since the bonding matenal 4 is very thin, it has been found that using the aforementioned dimensions the projections and recesses of the embossmgs 7 and 8 adequately engage each other and reliably absorb the shear forces ansing dunng braking, and that mutual displacement of the parts 2 and 3 is prevented. In actual tests in which the brake pad was stressed by sheanng forces which acted parallel to the contact surfaces, the shear forces reached 1870-2000 kp before failure These forces are considerably higher |han those customanly demanded by brake manufacturers and car manufacturers A vanety of matenals suitable for bonding layer 4 have been found One suitable matenal is rubbermodified asbestos having a thickness of 0 5 millimeters Another matenal is linen-fabnc impregnated http //oatft usnto eov/netacei/nnh-Parser?Sectl=PT02&Sect2=HTTOFF&u=/netahtrn1/<;ea 10/18/7003 United States Patent 4,240,530 Page 6 of 6 with synthetic latex and pre-dned, such as is employed as the raw material m the manufacture of fabric|>ased laminates Another material is a rubber-modified epoxide resin film This matenal gives Extremely high shear values, e.g., on the order of 3000 kp It has also been found that the earner plate 1 can be assembled utilizing three parts joined by two bondmg layers 4 Refemng to FIG. 1, it is seen that part 2 of the earner plate, l e, the part which is contacted by the brake piston, is not as long as part 3 Moreover, it has been found desirable to make the width of part 2 one millimeter less than the width of the friction lining 5 and part 3 When this is done, part 2 does not extend to the two lateral edges of the brake pad which, dunng braking, lie against the brake housing. Consequently, part 2 does not come into contact with the brake housing and does not form a bridge by means of which vibrations and heat can be transferred from part 3 to the brake housing and brake piston via part 2. It has also been found that embossings eight millimeters wide and one millimeter m depth can be formed m parts 2 and 3 of the carrier plate 1 m place of the calotte-shaped embossings 7 and 8 shown m FIGS. 1-3. One of the embossings is located parallel to the cut line II--II of FIG. 1 which is parallel to the two lateral edges of the brake pad A third embossing is located in the middle of part 3 of the earner plate 1 in the direction of the line III--III of FIG. 1. To obtain oblique centering surfaces like those present in the calotte-shaped embossings, the centering recesses and projections are sphencally curved at their ends in the longitudinal direction and provided with a rounded cross-section in the transverse direction. This results m the same centenng effect as m the calotte-shaped embossings. fcfrom the above it can be seen that the calotte-shaped embossings provide centenng recesses and projections with oblique centenng surfaces which permit accurate alignment of the parts 2 and 3 of the earner plate 1 and also permit an elastic bonding layer 4 having a uniform thickness. Consequently, the brake pad of the instant invention has a earner plate 1 with a high shear strength but in which metal-tometal contact of the shear plate parts is avoided, with the result that the shear plate parts are isolated from each other for excellent vibration damping and heat insulation * * ie ie ie http //oatft usoto gov/netacei/nDh-Parser`?Sectl=PT02&Sect2=HITOFF&u=/netahtml/sea 10/18/2003