Apparatus for controlling the pressure of a fluid fed to a clutch of a transmission

Claim 1

In combination, a source of pressure fluid, friction engaging apparatus adapted for connection with said source for being operated by said pressure fluid, and a valve means between said source and said friction apparatus for controlling the flow of the pressure fluid to said friction engaging apparatus to provide an initial high rate of supply of pressure fluid during which the friction engaging apparatus takes up slack followed by a reduced rate during which the friction engaging apparatus is rendered operative, said valve means comprising a valve member, an outlet passage leading from the valve member to the friction engaging apparatus and a feedback circuit connected between the outlet passage and the valve member and responsive to the fluid pressure being supplied to the friction apparatus for controlling the valve member, said valve member being initially operated to pass pressure fluid at a maximum rate, said feedback circuit including means to apply the pressure of a portion of the fluid which is supplied to the friction apparatus to said valve member to partially close the same and reduce the flow of the fluid supplied to the friction apparatus, said valve member including two individually displaceable elements which are also displaceable relative to one another, and resilient means between said displaceable elements, one of said elements regulating the flow of pressure fluid to said friction engaging apparatus and having a lesser cross-section than that of the other of said elements, said means of the feedback circuit for applying the pressure fluid to the valve member comprising first and second pressure chambers respectively communicating with said displaceable elements, and fluid passages connecting said outlet passage to the respective chambers in parallel for supply thereto of pressure fluid which is fed to the friction apparatus for urging said elements towards one another in opposition to said resilient means, and means for delaying the supply of pressure fluid to the chamber associated with the displaceable element of larger cross-section, comprising a restriction in the passage leading to the chamber associated with the displaceable element of larger cross-section, the latter chamber being enlarged with respect to the other chamber to further delay supply of pressure fluid thereto, said friction engaging apparatus having initial slack, said fluid pressure being supplied at an initial high rate to take up said slack whereafter the fluid pressure in the chamber associated with said element of smaller cross-section increases relative to the fluid pressure in the chamber associated with the element of larger cross-section whereby said element of smaller cross-section is displaced and the flow of pressure fluid to the friction engaging apparatus is reduced, the pressure of the fluid supplied to the chamber associated with the element of larger cross-section gradually increasing whereby the rate of flow of pressure fluid to said friction apparatus also gradually increases.