Abstract: This unit is equipped with a solenoid valve which is installed in an oil passage and exhausts the oil pressure from the oil passage at an appointed time in accordance with the output of an electric control circuit, and with a shift transition control valve controlled by said solenoid having two independent oil chambers in which the oil pressures supplied to hydraulic servos in forward and reverse drives respectively are regulated. Shift valves are installed between the shift transition control valve and the hydraulic servos, and the oil pressure adjusted by the shift transition control valve is supplied to the appointed oil pressure servos through each shift valve from the start to the completion of a shift. When the shift is completed, the oil pressure supplied to the hydraulic servo is changed to line pressure. The timing function required for a clutch-to-clutch shift is controlled by a timing device composed of a pressure hold valve and a flow control valve.

Abstract: A system for controlling the hydraulic pressure of a hydraulic control circuit of an automatic, variable speed transmission during a shift operation is provided. The hydraulic control circuit includes a plurality of hydraulic pressure control valves, a plurality of flow path switching means and a plurality of solenoid valves for controlling the engagement and disengagement of clutches and brakes in the transmission. The energization of the solenoid valves disposed in the hydraulic control circuit is controlled by an electronic system, which comprises a large scale integrated semiconductor logic unit, a semiconductor read-only memory, a semiconductor read-write memory and as required, input/output ports.

Abstract: The control device for automatic transmissions with an overdrive mechanism engages the brake of the overdrive mechanism while the shift control valve of the hydraulic control device is in the N-position (neutral), so that when the shift lever is shifted from the N-position to the D-position or R-position, the overdrive mechanism is momentarily set for overdrive thereby reducing shocks upon manually shifting.

Abstract: A shift control device for an automatic transmission comprises a pressure hold valve equipped with a pressure oil and an oil chamber wherein said pressure oil is connected to an oil passage being between a shift valve and an oil servo and equipped line pressure is supplied to said oil chamber, and a flow control valve which restricts exhausting of the pressure oil of said pressure hold valve; wherein oil is exhausted through a fore-stage shift valve after the oil pressure of the oil pressure servo to be released is held in the appointed times at the shift where fore-stage engaging elements are disengaged and other engaging elements are allowed to operate without passing through the one-way clutch of an automatic transmission.

Abstract: An electronic system for controlling an automatic transmission having an hydraulic control circuit comprises a large scale integrated semiconductor logic unit, a semiconductor read-only memory, a semiconductor read-write memory and input and output ports as required.

Abstract: A system for controlling the hydraulic pressure of a hydraulic control circuit associated with an automatic, variable speed transmission is provided. The hydraulic control circuit comprises a plurality of hydraulic pressure control valves, a plurality of flow path switching means and a plurality of solenoid valves, and operates to control the engagement and disengagement of the clutches and brakes disposed within the transmission. The energization of the solenoid valves of the hydraulic control circuit is controlled by an electronic system, which comprises a large scale integrated semiconductor logic unit, a semiconductor read-only memory, a semiconductor read-write memory and as required, input/output ports.

Abstract: A shift control device for an automatic transmission relating to this invention comprises: an electric control circuit comprising a means for generating an electric signal in accordance with the running conditions of the vehicle and a logic circuit for receiving the signals from said means and generating an electric output signal corresponding to one of the gears; a first solenoid to supply and discharge fluid pressure in fluid passages, said first solenoid acting in response to said electric output signal; a first shift valve operable between upshift and down-shift positions, the position of said first shift valve controlled by said first solenoid; a second solenoid to supply and discharge fluid pressure in fluid passages, said second solenoid acting in response to said electric output signal; and second and third shift valves operable between upshift and downshift positions, the positions of said second and third shift valves controlled by said second solenoid and by the position of said first shift valve;