Patent ID: 6508740
Filing Date: 2003-01-21
Classification: F16H,Y10T

Abstract:
A control system for an automatic transmission used in a vehicle, said transmission comprising a torque converter with a lock-up mechanism and being disposed in a power transmission path between an engine and driving wheels;said automatic transmission further comprising a plurality of frictionally engaging elements, which are actuated for engagement upon receiving a hydraulic pressure to establish selectively a plurality of speed ratios, a shift from an off-going speed ratio to an on-coming speed ratio being executed by a controlled release of the hydraulic pressure from the frictionally engaging element used for said off-going speed ratio and by a controlled supply of the hydraulic pressure to the frictionally engaging element used for said on-coming speed ratio; said control system comprising: an off-going pressure releasing valve, which releases the hydraulic pressure from the frictionally engaging element used for said off-going speed ratio during said shift from said off-going speed ratio to said on-coming speed ratio; a plurality of lock-up control valves, which control engaging capacity of said lock-up mechanism; and an actuation control valve, which comprises a linear solenoid valve that supplies a control pressure to both said off-going pressure releasing valve and said lock-up control valves and controls operation of said off-going pressure releasing valve and said lock-up control valves; â€ƒwherein: said lock-up control valves comprise a lock-up shift valve, a lock-up control valve, a lock-up timing valve and a lock-up switch solenoid valve; said lock-up shift valve is actuated by a hydraulic pressure from said lock-up switch solenoid valve to switch a condition for engaging said lock-up mechanism and for releasing said lock-up mechanism; while said lock-up shift valve is set by the hydraulic pressure from said lock-up switch solenoid valve in said condition for engaging said lock-up mechanism, said supply of said control pressure from said actuation control valve to said off-going pressure releasing valve is restricted, but said control pressure is supplied to said lock-up control valve and said lock-up timing valve for controlling operation of said lock-up mechanism; and while said lock-up shift valve is set by the hydraulic pressure from said lock-up switch solenoid valve in said condition for releasing said lock-up mechanism, said control pressure is supplied to said off-going pressure releasing valve, so that said actuation control valve controls the release of the hydraulic pressure from the frictionally engaging element used for said off-going speed ratio.