GB1473254A - Control valve for an automobile transmission system of an automobile - Google Patents

Abstract

1473254 Change-speed control AUTOMOBILWERKE EISENACH VEB 28 July 1975 [26 Aug 1974] 31441/75 Heading F2D A valve for controlling the rates of pressurization and depressurization of hydraulic actuators of a brake and a clutch which establish second and third speed ratios in an automatic change-speed transmission of a vehicle comprises a spool valve element 4 controlling flow of fluid to and from a third speed clutch K, and a spool valve element 5 loaded by a spring 3 and controlling flow to and from a second speed brake B. The valve elements are shown in the positions they occupy when conduits 1, 2 connected respectively with 2-3 and 1-2 shift valves (not shown) are vented, the transmission then operating in low ratio. When the 1-2 shift valve selects second speed it supplies a load-dependent principal pressure to the conduit 2 which communicates with the brake actuator through an unrestricted path 22, 221, 231, 23 and parallel paths with restrictions 223, 21. At the same time a reservoir R1, comprising a spring-loaded differential piston loaded by the principal pressure, is charged. When the pressure which acts in a chamber 55, reaches a value to overcome the spring 3 the valve element 5 is displaced to a position in which an abutment 52 engages the end wall of the chamber 6 and the unrestricted passage 231 is closed so that further build up of pressure is controlled by the restrictions 223, 21. Progression to third speed is initiated when the shift valves pressurize and vent, respectively, the conduits 1, 2. The clutch actuator and a reservoir R2 connected through a restriction 132 are then filled through passages 12, 13 and a parallel passage with restriction 11, and when pressure acting on a surface 42 of the valve element 4 overcomes the pressure in the chamber 55, which falls as the brake actuator is vented through the restrictions 223, 21 and a parallel restriction 234 controlled by a non-return valve 235, the valve element 4 moves to close the passage 12 and the passage leading to the restriction 223. Build up of pressure in the clutch actuator and reservoir R2 then takes place solely through the restriction 11. In the 3-2 shift the brake actuator is pressurized solely through the restriction 21 and the clutch actuator is exhausted solely through the restriction 11 until the falling clutch pressure acting on the surface 42 is overcome by the rising brake pressure in the chamber 55 whereupon the valve element 4 is displaced to open the unrestricted passage 12 and the passage with the restriction 223. Due to the employment of the load responsive principal pressure, to which both reservoirs R1, R2 are subjected, the rates of clutch and brake operation and the engagement pressures are load responsive, being highest during kick-down.