Abstract: A hydraulic control system for an automatic transmission of an automotive vehicle is provided which has a fail-safe function of preventing unsafe operation of the automatic transmission if a failure occurs in any of solenoid valves which control engagement operations of frictional elements such as clutches and brakes of the transmission. The hydraulic control system includes a hydraulic pressure flow control unit which controls hydraulic pressure flow between at least one of the frictional elements and at least one of the solenoid valves to allow the hydraulic pressure to be supplied to a predetermined combination of the frictional elements to achieve the power transmission at one of given gear ratios. The hydraulic pressure flow control unit restricts the hydraulic pressure flow to an inoperative combination of the frictional elements which provides no power transmission. With these arrangements, the power transmission is established if any of the solenoid valves malfunctions to allow the vehicle to travel.

Abstract: A hydraulic control system for an automatic transmission of automotive vehicles is provided. The hydraulic control system includes a pressure source, a plurality of solenoid valves, and a plurality of directional control valves. Each solenoid valve selectively supplies and release hydraulic pressure to and from one of frictional element of a power train of the automatic transmission according to a given schedule of transmission operation for establishing a given gear ratio. The directional control valves are interposed between the frictional elements of the power train and the solenoid valves, respectively.

Abstract: A rotary flow control valve is provided, that, despite compact design, offers excellent vibration resistance, a high response speed, and superb proportionality of a controlled flow rate to an applied current value. In a channel selector 4 in a rotary flow control valve 1, a guide valve 2 mounted in a hollow of an inner housing 6 is borne by bearings 19 and 20 so that the guide valve 2 can rotate forward or in reverse. Intra-outer housing tubes 10, 11, and 12 are formed in an outer housing 5. In the inner housing 6, communicating channels 13 to 16 are formed in fours at symmetric positions with respect to the rotation center of the guide valve 2. In a torque motor 3, permanent magnets 33 are attached to a lower armature 32 coupled with the guide valve 2 using an adhesive. The magnetic poles at both ends of the permanent magnets 33 are opposed to cylinders 43 about which coils 34 are wound.