GB1230690A - - Google Patents

Abstract

1,230,690. Hydrodynamic brakes combined with other brakes; trailer brakes; fluid control. DAIMLER-BENZ A.G. 7 Aug., 1969 [8 Aug., 1968], No. 39565/69. Headings F2E and F2F. In continuous braking apparatus for a commercial vehicle or a tractor-trailer unit, maximum continuous braking retardation is provided by the effects of an engine brake, a controllable retarder and, in the case of a tractortrailer unit, the trailer brakes, and the retardation is controllable in a graduated manner by bringing the braking components into action one after another in dependence on the displacement of the brake lever (pedal or manual). As shown, when pedal 14 is depressed, an electromagnetic clutch 18 is first engaged by the supply of current to it via a contact 31 in a switching device 30, this contact being the first to be encountered on movement of the pedal. The rotor of the hydrodynamic retarder 2 thus begins to be driven by the vehicle engine through flywheel 12 and gearing. Next, a valve 15 is actuated to open a relay valve 16 whereby compressed air from a reservoir 8 forces oil from a reservoir 13 into the retarder casing. Braking thus commences and proceeds linearly as the filling of the retarder proceeds. Before filling of the retarder is complete, contact 32 is encountered, whereupon solenoid 28 is energized at a low voltage (e.g. 12 volts) to urge plunger 27 of valve 26 to the left until the extremity of the valve makes contact with a spring-loaded stop 29. In this position a compressed air reservoir 22 on the trailer is connected via a pressure limiter 24, limiting the pressure to, e.g., 0À3 atmosphere, to the brake cylinders 23 of the trailer brakes 3. Next, contact 33 is encountered, whereby solenoid valve 9 is energized to admit compressed air to a piston 6 to close butterfly valve 5 in an exhaust pipe elbow 4 constituting an engine brake 1. At the beginning of this stage filling of the retarder 2 is completed, and its braking effect reaches maximum value. Finally, contact 34 is encountered, whereupon the full voltage (e.g. 24 volts) is applied to solenoid 28. Plunger 27 is thereby moved further to the left, overcoming the force of spring 29, pressure limiter 24 is disconnected, and pressure limiter 25, which permits the pressure to rise to, e.g., 0À6 atmosphere, is interposed between reservoir 22 and trailer brake cylinders 23. On release of pedal 14 braking is relieved in reverse sequence. When the pedal is fully released, retarder 2 empties itself by centrifugal force.