HYDRAULIC CONTROL DEVICE FOR AUTOMATIC TRANSMISSION FOR CAR

摘要

PURPOSE:To enable control of a speed change gear even when one side of pressure control valves gets out of order by connecting the drain port of one of the pressure control valves for the output oil pressure control of a pressure regulating valve and the back pressure control of accumulator to the output side of the other pressure control valve. CONSTITUTION:A hydraulic control device is provided with the first pressure control valve 18. to control line pressure sent out from a regulator valve 14 and the second pressure control valve 12 to control the back pressure of an accumulators A1-A4 connected to oil passages for clutches 1-C5. The drain port 18b of the first pressure control valve 18. is connected to an oil passage L20 on the output side of the second pressure control valve 182. When the first pressure control valve 181 is locked in a state where the drain port 18b is opened, the output oil pressure of the second pressure control valve 182, is led from the drain port 18b of the first pressure control valve 18. into its oil passage L39 on the output side. Thus the line pressure can be prevented from lowering.