Pressure reducing control device for the hydraulic control circuit of an automatic transmission

Claim 1

In a hydraulic control circuit for an automatic transmission of the type wherein a plurality of shift control valves selectively deliver hydraulic fluid to a plurality of frictional elements to cause engagement and disengagement of said frictional elements, having a hydraulic pressure source, a primary pressure regulating valve interposed between said pressure source and said shift control valves to regulate the pressure of the hydraulic fluid supplied to said shift control valves a manually controllable gear selector valve with an inlet connected to said hydraulic pressure source and a plurality of outlets, the improvements comprising: a. a first speed pressure reducing valve interposed between a first shifT control valve and a first frictional element to reduce the pressure of the fluid supplied to the first frictional element when the shift control valve is in a first position and the manually controllable gear selector valve is in a position selecting the lowest forward speed; and b. a second speed pressure reducing valve interposed between a second shift control valve and a second firctional element to reduce the pressure supplied to said second frictional element when said first shift control valve is in a second position and when said manually controllable gear selector valve is in a position allowing the transmission to shift into its second lowest forward speed but no higher.