ENGINE-RPM-DEPENDENT ARREST DEVICE TO PREVENT NON-PERMITTED DOWN SHIFTS IN MOTOR VEHICLE GEARBOXES

摘要

PCT No. PCT/EP90/00531 Sec. 371 Date Sep. 27, 1991 Sec. 102(e) Date Sep. 27, 1991 PCT Filed Apr. 5, 1990 PCT Pub. No. WO90/12228 PCT Pub. Date Oct. 18, 1990.An engine-rpm-dependent arrest device to prevent non-permitted down shifts in motor vehicle transmissions containing a pilot valve (1) and a control valve (2), both having two shift positions. One shift position of the control valve (2) is engaged by the pressure acting upon a piston surface (36) of the control-valve piston (31) and exceeding a given value of an engine-rpm-dependent low-pressure pump (20). The control valve (2) is exclusively in contact with the pressure medium conveyed by the low-pressure pump (20) and controls the large end surface (40) and the annular surface (41) of a pilot-valve piston (38) designed as stepped piston. If when the high gear is engaged and the engine rpm is above a certain limit value, the gear-shift valve (7) is moved to its position for low gear, then an actuation of the actuation device (15) for the low gear is prevented via the pilot valve (1). At the same time the activation device (16) for the high gear remains actuated with shift pressure so that the high gear remains loaded.