Automatic transmission control system for automobile

Claim 1

An automatic transmission control system for a vehicle having wheels connected through an automatic transmission having gears to an engine with an accelerator pedal and an electromagnetic valve unit with a plurality of electromagnetic valves having respective solenoids, comprising a wheel r.p.m. detector for generating an output at frequency proportional to the vehicle wheel speed; an ac to dc voltage converter connected to said detector for converting the output thereof into a corresponding dc voltage; a throttle switch adapted to cooperate with the accelerator pedal and having a plurality of contacts successively made upon further depression of the accelerator pedal; a throttle circuit connected to said throttle switch and having an output terminal to provide outputs of various values corresponding to respective contacts of the throttle switch; a plurality of gear shift signal generators connected to said converter and throttle circuit and having predetermined shifting characteristics and comparing the output signal from said ac to dc converter with the output signal from said throttle circuit; a logic circuit connected to said gear shift signal generators for producing output signals according to the output signals of said gear shift signal generators; a memory circuit connected to said logic circuit for holding the signal immediately before the disappearance of the output signals of said logic circuit; an electromagnetic valve drive circuit connected to and controlled by said memory circuit to feed said solenoids of said electromagnetic valves to change a gear position; and switching means having off and on positions respectively for flat road operation of said vehicle and for upward slope operation thereof, slope-ascending circuit means connected between said switching means and said throttle circuit and operative only when said switching means is in its said on position for applying an electrical signal to said throttle circuit to develop therefrom for said signal generators a said throttle circuit output corresponding to full depression of said accelerator pedal regardless of the actual position of said pedal, said slope-ascending circuit means being further connected to one of said gear shift generators and having means operative only when said switching means is in its said on position for developing and applying a second electrical signal to said one gear shift generator so as to cause in conjunction with said full depression throttle circuit output a change in the said predetermined shifting characteristics for aiding said upward slope operation by said vehicle.