Hydraulic control for automatic transmission wherein sequential clutch engagement is controlled by an accumulator

Claim 1

A hydraulic control for an automatic transmission which comprises, in combination: a source of operating fluid; at least first and second friction coupling members which are each capable of assuming one of released and coupled positions at a time; a valving means interposed between the operating fluid source and both of the first and second friction coupling members and operable to selectively interrupt and effectuate the supply of the operating fluid from the operating fluid source to both of the first and second friction coupling members; a first fluid passage for supplying the operating fluid to one of the friction coupling members for causing said one of the first and second friction coupling members to assume the coupled position; a second fluid passage for supplying the operating fluid to the other of the first and second friction coupling members for causing said other of the first and second friction coupling members to assume the coupled position; and an accumulator having a working chamber fluid-connected with the first fluid passage, said accumulator comprising a piston and a spring for urging the piston in one direction, said piston comprising a switching member which controls the supply of operating fluid to said second fluid passage, said switching member being operable to establish the second fluid passage when the operating fluid supplied into the working chamber attains a predetermined value required to displace the piston against the spring to regulate the pressure of the operating fluid for minimizing a shock which would result when said one of the first and second friction coupling members is brought into the coupled position, said switching member being also operable to close the second fluid passage when and so long as the pressure of the operating fluid supplied into the working chamber is lower than the predetermined value, whereby the timing at which said other of the first and second friction coupling members is brought into the coupled position is delayed relative to the timing at which said one of the first and second friction coupling members is brought into the coupled position.