Lock-up clutch control valve assembly

Claim 1

A control for a lock-up clutch for an engine driven automatic transmission having a plurality of forward speed ratios including a lowest speed ratio and a highest speed ratio, comprising: first fluid pressure providing means for providing a first fluid pressure when each of the plurality of speed ratios except the lowest speed ratio is established in the transmission; second fluid pressure providing means for providing a second fluid pressure when a predetermined speed ratio between the highest and lowest speed ratios is established in the transmission; a lock-up control valve operatively connected with the lock-up clutch and being movable to first and second positions for controlling the disengagement and engagement respectively of the lock-up clutch, said lock-up valve including a first pressure acting area adapted to communicate with said first fluid pressure providing means, and a second pressure acting area in fluid communication with said second fluid pressure providing means to be biased toward said second position thereof; a lock-up timing valve operatively connected between said first fluid pressure providing means and said lock-up valve and being movable to a first position for communicating said first fluid pressure to said first pressure acting area to bias said lock-up valve means toward said second position thereof and to a second position to exhaust the bias pressure acting on said first pressure acting area, said lock-up timing valve means including a pressure acting area in fluid communication with said second fluid pressure providing means and being biased by said second fluid pressure toward said second position thereof; first resistive means for resisting a movement of said lock-up timing toward said second position thereof until said second fluid pressure increases above a first predetermined value; and second resistive means for resisting a movement of said lock-up valve toward said second position thereof until said second fluid pressure increases above a second predetermined value, said second predetermined value being higher than said first predetermined value.