GB1433968A - Pressure system for a motor vehicle - Google Patents

Abstract

1433968 Change speed control AUTOMOBILWERK EISENACH VEB 2 May 1974 [5 July 1973] 19218/74 Heading F2D Fluid delivered through a conduit 5 to operating means in an automatic transmission of a motor vehicle and controlled as to its pressure P by a valve 4 is supplied either from an enginedriven pump 1 or a road speed responsive pump 2 depending upon which at any instant delivers the higher pressure. As shown, the pressure from pump 1 is higher so that a valve 3 is displaced to the right and the pump 1 discharges through conduits 12, 312, 5 and, through a restriction 51, to an end surface 405 of the valve 4, leftward displacement of this valve against the loadings of a spring 43 and a piston 41 limiting pressure by connecting a passage 11 with exhaust R 1 . One side 413 of the piston 41 is subject to a load responsive pressure P d controlled, e.g. in accordance with engine throttle opening or inlet depression, and the other side is exhausted through a passage 414 and the valve 3. A higher pressure P is determined by the valve 4 when low ratio or reverse is selected by admission of pressure P or P d to a surface 409. When the valve 3 is displaced to the left, as pressure from pump 2 exceeds that from pump 1, the pump 2 is connected to the conduit 5, the conduit 312 is cut off [from the pump 1, and the loading applied by the piston 41 to the valve 4 is reduced by connection of the passage 414 to a road speed responsive pressure P v instead of to exhaust R 3 . The valve 4 then connects the pump 1 to exhaust R 1 and governs pressure in the conduit 5 by controlling a passage to exhaust R 2 .