Creep preventing hydraulic control circuit for vehicle automatic transmission

Claim 1

In a hydraulic control circuit for a vehicle automatic transmission of the type having a hydraulic pressure source, pressure regulating means to regulate the hydraulic pressure from said source, a plurality of shift control valves which selectively transmit hydraulic fluid to a plurality of frictional elements to cause engagement and disengagement of said elements to change the output gear ratio of said transmission, the improved creep-preventing mechanism comprising: a. a first fluid flow control means; b. a second fluid flow control means; c. a third fluid flow control means; d. means connecting said first, second and third flow control means in series; e. electric means to control said first fluid control means in response to the position of the vehicle throttle such that said first fluid control means allows hydraulic fluid to pass therethrough only when said throttle is in a predetermined position; f. means to control said second flow control means in response to the vehicle throttle such that said second fluid flow control means allows hydraulic fluid to pass to said third fluid flow control means only when said throttle is in a predetermined position; and g. means to control said third fluid flow control means in response to a manually controllable gear selector valve such that said third fluid flow control means allows fluid to pass therethrough only when said gear selector valve is in a predetermined position.