GB916856A - Motor vehicle disc brake assembly - Google Patents

Abstract

916,856. Disc brakes. GENERAL MOTORS CORPORATION. March 15, 1961 [April 6, 1960 (3)], No. 9459/61. Class 103 (1). [Also in Group XXVI] A liquid-cooled disc brake is similar to that disclosed in Specification 905,058, but includes temperature-responsive means whereby the pump is operated at a slow speed when the brake is released and has cooled down, and at a higher speed when the brake is hot immediately after release, following an application, the speed being progressively reduced to the slow speed as the brake cools. As shown, the arrangement of the braking discs 32, 34 and pump body 78 is similar to that of the disclosure referred to but an annular chamber 86 is formed on the side of the pump body opposite to that of the chamber 82 in which the braking discs are arranged, a restricted annular passage 83 connecting the chamber 86 to the chamber 82, whilst the friction material 85 on the reaction member 22 is made porous and an annular groove 87 is provided in the reaction member and connected with the pump inlet by a passage 88. As a result, the pressure in chamber 84 is reduced a predetermined amount below that of the chamber 82, causing the pump body to be urged towards the reaction member with a light force sufficient to maintain a slowpumping action when the brake is not applied. This force is increased when the brake is hot, i.e. immediately after release, following an application, by the provision of a temperatureresponsive element comprising thermally-expansible material 95 acting on a diaphragm forming one wall of a casing 94 mounted within the pump body, movement of the diaphragm being transmitted by a rod 90 to a cap 91 which is thus moved against the action of a light spring 98 into engagement with an end disc 57 of the assembly. This causes a reaction force, determined by springs 100, 101 acting on the casing 94, to urge the pump body towards the reaction member 22. The disclosure also includes a modification of the release mechanism to effect automatic adjustment for wear, and of the linings used for the discs. The former consists of two springs 53, 58, Fig. 4, which act respectively between the applying piston 37 and a sleeve 55, and between a shoulder 54 on a rod 51 and a fixed member 59. The function of the sleeve 55 is merely to locate the end disc 57 when the brake is released. A longitudinally split sleeve 48 is fitted tightly on the rod 51 and fits less tightly in an aperture 50 in the piston 37. When the brake is applied the springs 53, 58 are compressed and the rod 51 is moved towards the fixed member 59 but does not normally reach it. When wear of the linings 36 on the discs 34 increases beyond a certain point the rod 51 contacts the member 59 on application of the brake and the sleeve 48 is pushed further within the aperture 50 in the piston 37 to compensate for the wear. The linings 36 on the discs 34 have grooves 125, Fig. 6, formed therein to allow the cooling fluid to pass from their outer peripheries to the space surrounding the axle 2, there being apertures 63 in the discs 34 to enable the fluid to flow axially in this space.