| 摘要 |
<p>A system for controlling a lock-up clutch of a torque converter (12) comprises a lock-up control valve (60), and a shuttle valve (130). The lock-up control valve includes a spool (102) having a first (100b) and a second (100a) pressure acting areas. The shuttle valve delivers an output hydraulic pressure when at least one of two inlet ports (134, 138) is pressurized. One (134) of the inlet ports is subject to a first hydraulic pressure (136) which builds up at a band brake (B/B) during operation with the fourth speed ratio, while the other inlet port (138) is subject to a second hydraulic pressure (140) which builds up at an overrun clutch (O/C) during operation with the third, second, and first speed ratios when an engine brake operation range is selected. The output hydraulic pressure (128) of the shuttle valve is transmitted to the lock-up control valve to act on the second pressure acting area. The first pressure acting area is subject to a third hydraulic pressure which builds up at a high clutch (H/C) during operation with each of the third and fourth speed ratios. The lock-up control valve include a spring (104) biasing the spool toward a first position where the lock-up clutch is released. The spring allow movement of the spool toward a second position where the lock-up clutch is engaged when the first and second pressure acting areas are both subject to the hydraulic pressures.</p> |
