Shift control device for automatic transmission

摘要

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; and two shift valves controlled by the second solenoid valve; whereby the shift control device performs automatic gear-shifting of an automatic transmission with four forward gears or one with three forward gears and a mechanical drive with a torque converter lock-up clutch engaged.