| 摘要 |
PROBLEM TO BE SOLVED: To suppress overload on an electric pump supplying a hydraulic pressure to a friction coupling element during idle stop of an engine and furthermore to reduce a capacity of the electric pump, in an automatic transmission including the electric pump.SOLUTION: A hydraulic control device for an automatic transmission is provided which includes a mechanical pump 6 driven by an engine, an electric pump 106 operated during automatic stop of an engine, friction coupling elements 40, 60 coupled upon starting a vehicle, and a hydraulic circuit 100 for controlling supply of hydraulic pressure to the friction coupling elements, the hydraulic circuit 100 being provided with a switching valve 120 capable of switching a first condition in which the mechanical pump 6 is functioned as a hydraulic pressure supply source to the friction coupling elements 40, 60, and a second condition in which the electric pump 106 is functioned as the hydraulic pressure supply source. In the hydraulic control device, the hydraulic circuit 100 is constituted in such a way that discharge oil from the electric pump 106 is drained from a prescribed draining portion 154 when the switching valve 120 is in the first condition, and when the switching valve 120 is in the second condition, the draining is suppressed in comparison with that in the first condition.SELECTED DRAWING: Figure 3 |
