| 摘要 |
<p>An antuomatic transmission comprises a main gearing and an auxiliary gearing drivingly connected to the main gearing. The auxiliary gearing is shiftable from a high gear position (direct drive) to a low gear position (reduction drive) by disengagement of a direct clutch and engagement of a reduction brake. In order to enhance a response to engine braking forward running demand and a response to reverse running deamnd, a bypass line is arranged in parallel to an one-way orifice disposed in a hydraulic fluid line having one end communicating with the reduction brake and an opposite end connected to a shift valve. The shift valve is fluidly disposed between a pressure regulator valve, the opposite end of the hydraulic fluid line, and the direct clutch. A reduction brake timing valve opens the bypass line when a III-range hydraulic pressure or a reverse-select hydraulic pressure is present. The one-way orifice divides the hydraulic fluid line into a first portion extending between the one-way orifice and the reduction brake and a second portion extending between the one-way orifice and the opposite end. An accumulator communicates with the first portion of the hydraulic fluid line. The II-range hydraulic pressure or reverse-select hydraulic pressure is supplied as an accumulator back-up pressure to the accumulator.</p> |
