Hydraulic control system for automatic transmission of multiple clutch type

摘要

In a hydraulic control system for an automatic transmission of multiple clutch type for use in a motor vehicle, a shift valve (2, 8) which inverts the supply and cutoff of working oil for a hydraulic actuator (20, 22) serving to change-over gear shift stages is provided with a spool valvule (4, 10) and a clutch-oil-pressure supply port (2a, 8a as shown in Fig. 1). Even when a solenoid valve 8 (14, 18) for controlling the shift valve (2, 8) has failed, a clutch oil pressure is supplied from the clutch-oil-pressure supply port (2a, 8a) so as to hold the switchover position of the spool valvule (4, 10) and to keep the gear shift stage already established. Thus, the hydraulic control system prevents an engine speed from rising or the motor vehicle from locking due to the failure of the solenoid valve (14, 18).