GB1253329A - Liquid-cooled disc brakes - Google Patents

Abstract

1,253,329. Liquid cooling of multi-disc disc brakes. GENERAL MOTORS CORP. 21 May, 1970 [2 June, 1969 (2)], No. 24586/70. Heading F2E. [Also in Division F1] A liquid-cooled multi-disc disc brake includes a pump drive disc having opposed side friction surfaces and a drive gear formed on it; this drive disc is located between, and frictionally engageable with, two of the rotatable brake discs, and is clutched in driving relation with these when the disc pack is compressed; a driven gear is in mesh with the drive gear, and drives a pump when the drive gear is rotated. As shown in Fig. 1, vehicle wheel 10, hub 12, brake discs 36 and cap 26 are rotative, while support member 20 and housing 22 are stationary, and actuating piston 52 and brake discs 34 are axially slidable. A disc 42 is provided to drive, by gear teeth 46 on its periphery, a pump drive gear 48 connected to a pump impeller 50 in a cooling-liquid pump assembly. The inner periphery 44 of disc 42 fits around the splines 40 of hub 12. Cooling liquid is retained between hub 12 and housing 22 and between the brake discs by seals 24, 27. In the brakes off position, drive disc 42 is not in frictional contact with the two discs 36 rotating one on each side of it, but it is caused to rotate at a relatively low speed by the viscous shear action of the intervening cooling liquid, and thus drives impeller 50. Immediately the brakes are applied, the pump drive disc 42 is frictionally engaged by the two discs 36 at its sides, and it thereupon drives impeller 50 at a speed considerably higher than its former speed and also the speed of rotation of the wheel and hub. Wear compensating.-For brake application, piston 52 is moved to the right by provision of fluid pressure in chamber 54; the piston 52 has press fitted to its inner periphery a cylinder 72 with flange 80, the flange 80 being accommodated between a retaining ring 86 and a housing shoulder 84. If, during application flange 80 reaches shoulder 84 while, due to wear of the brake discs, the piston 52 still has some distance to travel, the fluid pressure causes the piston to slip relative to the cylinder 72. On brake release, leftward movement of piston 52 and cylinder 72 is again limited by ring 86. In the modification in Fig. 2 (not shown), the pump drive disc 42 is in two concentric parts, the main outer part (60) having the gear teeth, and a smaller inner part (62) having splines engaging the splines 40 of hub 12, the two parts meeting at bearing surfaces, so that during the low speed rotation the two parts can rotate at different speeds. Also, the faces of part (60) have channel-like areas to facilitate the viscous shear drive. A modified actuator and wear-compensating structure is shown in Fig. 4. Pressure fluid is supplied to chamber 90 behind piston 92, and cylinder 98 is press fitted to the outside of piston 92. During brake actuation, a Belleville spring 66, whose outer periphery always engages housing shoulder 68, is completely flattened against the shoulder by the edge of cylinder 98. Thereafter, piston 92 is forced to slip longitudinally inside cylinder 98 if brake disc wear has occurred.