GB936282A - Improvements relating to braking apparatus for regulating pressure on motor vehicles - Google Patents

Abstract

936,282. Fluid-pressure brakes. DAIMLER-BENZ A.G. Feb. 23, 1961 [March 3, 1960], No. 6718/61. Class 103 (1). An hydraulic braking system for a motorvehicle having pneumatic springing comprises a regulator so constructed and arranged that the ratio of front wheel braking force to rear wheel braking force is caused to vary in a manner dependent on the vehicle load and the degree of braking, and such that this ratio can follow the curve 12<SP>1</SP> or 13<SP>1</SP>, Fig. 1, and thus approximate closely to the ideal curves 12, 13, for both minimum and maximum load conditions, respectively, where 11 represents front wheel braking force and 10 rear wheel braking force. For this purpose the regulator is arranged to receive pressure from the master cylinder 45, and is responsive both to pneumatic pressure in the bellows 41 of the rear suspension and also to a normally constant but adjustable pressure derived from the pneumatic suspension via a regulating valve 58. The arrangement is such that as the braking pressure rises the regulator maintains equal pressure in both rear and front wheel cylinders 46, 53 until a predetermined pressure is reached, at point 14 or 14<SP>1</SP>, Fig. 1, or intermediately, depending on the pressure in the bellows 41 and the adjustment of the valve 58. At this point the brake pressure, acting on a piston 35 of the regulator in opposition to the pressure in bellows 41 acting on a control piston 30, closes a valve 37 so that instead of brake fluid passing directly to the front wheel cylinders 53 via valve 37, passageway 49, chamber 50 and conduit 52, the piston 28 is moved and, owing to the difference between the area of its face exposed to the brake pressure and the face of its annular part 28<SP>1</SP> in the chamber 50, transmits a higher pressure via the conduit 52 to the front wheel cylinders 53, this higher pressure also being influenced by the air pressure in bellows 41 acting on a piston 25 in opposition to the brake pressure. The point at which the valve 37 is closed and the ratio of higher pressure to brake pressure obtained thereby are modified by the pressure in bellows 41 acting on pistons 30, 25 respectively. The normally constant pressure provided by the valve 58 also acts on both pistons 30, 25, but in opposition to the pressure in bellows 41, via conduit 57, chamber 56 and passageway 59. Extensions 27, 26 of the pistons 28, 25 are in abutting relationship in a housing 20, and a rod 34 extends through apertures in these extensions to interconnect the pistons 35, 30. In use, the valve 58 is adjusted to give an appropriate constant pressure in the chamber 56 according to the load on the vehicle, or the valve 58 may be designed to give the appropriate pressure automatically as the load on the vehicle is changed.