Automatic shift control system for automatic transmission

Claim 2

In an automatic transmission for an engine driven vehicle having a torque converter whose input shaft is connected with an output shaft of said engine, a gear unit connected with an output shaft of said torque converter, frictionally engaging means combined with said gear unit for accomplishing selective meshing engagement of gears in said gear unit, and drive means coupled to said frictionally engaging means for actuating said frictionally engaging means to shift gears, the improvement in an automatic shift control system comprising: first means for generating an electrical signal responsive to a load on said engine; second means for generating an electrical signal responsive to a vehicle speed; shift signal generation means including first and second shift signal generator means each of which is connected in circuit with each of said first and second means to generate a lower gear position responsive signal and to generate a higher gear position responsive signal, respectively, when the electrical signals from said first and second means satisfy predetermined conditions, two solenoid means connected in circuit with said first and second shift signal generator means, respectively, to generate output signals when the signal from said first and second shift signal generator means is respectively applied thereto, for applying said output signals to said drive means for actuating said frictionally engaging means, gate means between said second shift signal generator means and the respective solenoid means, and mountainous area circuit means including a brake fluid pressure detecting means for Generating a signal representing a braking pressure, said mountainous area circuit means being connected in circuit with said first and second means and said first shift signal generator means and including means for applying a signal to said gate means so as to prevent said higher gear position responsive signal from being applied to said solenoid means when at least one of the conditions of the electrical signals from said first and second means and the condition of the output signal of said brake fluid pressure detecting means satisfies a first predetermined condition, and for ceasing to generate and apply said signal to said gate means so as to permit said higher gear position responsive signal to be applied to said solenoid means when at least the condition of the lower gear position responsive signal from said first shift signal generating means and the conditions of the signals from said first and second means satisfies a second predetermined condition.

Claim 3

An automatic shift control system for an automatic transmission as in claim 1, in which said mountainous area circuit means comprises a first throttle position discriminating circuit connected in circuit with said first means for generating a signal when the value of the electrical signal responsive to a load on the engine is larger than a preset value, a first vehicle speed discriminating circuit connected in circuit with said second means for generating a signal when the value of the electrical signal responsive to a vehicle speed is smaller than a preset value, a vehicle acceleration discriminating circuit connected in circuit with said second means for generating a signal when a differentiated value of the electric signal responsive to a vehicle speed is smaller than a preset value, a time circuit connected in circuit with said vehicle acceleration discriminating circuit for generating a signal when the signal generated by said vehicle acceleration discriminating circuit continues to appear for more than a predetermined period of time, a first AND circuit connected in circuit with said first throttle position discriminating circuit, said first vehicle speed discriminating circuit and said time circuit for generating a signal upon receipt of all the signals from said first throttle position discriminating circuit, from said first vehicle speed discriminating circuit and from said time circuit, a brake fluid pressure detecting circuit connected in circuit with said brake fluid pressure detecting means for generating a signal when the signal from said brake fluid pressure detecting means satisfies a predetermined condition, a first OR circuit connected in circuit with said first AND circuit and said brake fluid pressure detecting circuit for generating a signal upon receipt of at least one of the signals from said first AND circuit and from said brake fluid pressure detecting circuit, a second throttle position discriminating circuit connected in circuit with said first means for generating a signal when the vlaue of the electric signal responsive to a load on the engine is larger than another preset value, a second vehicle speed discriminating circuit connected in circuit with said second means for generating a signal when the value of the electric signal responsive to a vehicle speed is larger than another preset value, a second AND circuit connected in circuit with said throttle position discriminating circuit and said second vehicle speed discriminating circuit for generating a signal upon receipt of both signals from said second throttle position discriminating circuit and from said second vehicle speed discriminating circuit, a second OR circuit connected in circuit with said second AND circuit and said first shift signal generator means for generating a signal upon receipt of at least one of the signal from said second AND circuit and the lower gear position responsive signal from said first shift signal generator means, and a bistaBle memory circuit connected in circuit with said first and second OR circuits which is placed in one of two stable states thereof and continues to generate a signal upon receipt of the signal from said first OR circuit and which is placed in the other stable state thereof and ceases to generate said signal upon receipt of the signal from said second OR circuit.

Claim 4

An automatic shift control system for an automatic transmission as in claim 2, in which said first throttle position discriminating circuit is constructed to generate a signal when the value of the electrical signal responsive to a load on the engine continues to be larger than the preset value for more than a predetermined period of time.