Control system for automatic transmission using torque converter speed ratio to determine the on-time for a solenoid controlled 3-2 timing valve

A shift control system for controlling a shift operation of an automatic transmission having a torque converter through which a transmission gear mechanism is connected to engine output means, said transmission gear mechanism having a plurality of frictional coupling elements which are selectively locked and unlocked by hydraulic control means to perform an automatic shift operation of said automatic transmission into desired gears, said shift control system comprising:

• valve means, included in said hydraulic control means, for connecting and disconnecting a supply of hydraulic pressure to said frictional coupling elements so that said frictional coupling elements are locked and unlocked;
• time regulating means for regulating a duration time for which said valve means is kept actuated and, in turn, a speed at which at least one of said frictional coupling elements is locked;
• input and output detecting means for detecting a first rotational speed input to and a second rotational speed output from said torque converter;
• and
• control means for calculating a conversion efficiency based on said first rotational speed and said second rotational speed detected by said input and output detecting means and for controlling said time regulating means so as to shorten said duration time when said control means calculates a conversion efficiency which is lower than a predetermined low conversion efficiency and increase said duration time when said control means calculates a conversion efficiency which is higher than a predetermined high conversion efficiency.

A shift control system for controlling a shift operation of an automatic transmission having a torque converter through which a transmission gear mechanism is connected to an engine output means, said transmission gear mechanism having a plurality of frictional coupling elements which are selectively locked and unlocked by hydraulic control means for controlling the frictional coupling elements to perform an automatic shift operation of said automatic transmission into desired gears, said shift control system comprising:

• valve means, included in said hydraulic control means, for connecting and disconnecting a supply of hydraulic pressure to said frictional coupling elements so that said frictional coupling elements are locked and unlocked;
• time regulating means for regulating a duration time for which said valve means is kept actuated and, in turn, a speed at which at least one of said frictional coupling elements is locked;
• detecting means for detecting a first rotational speed input to and a second rotational speed output from said torque converter;
• conversion efficiency calculating means for calculating a conversion efficiency of said torque converter based on the first and second rotational speeds detected by said detecting means;
• speed change calculating means for calculating a speed change of an input speed supplied to said transmission gear mechanism;
• learning value calculating means for calculating a learning value of said duration time by comparing the speed change of the input speed to a predetermined value so as to increase the learning value when the speed change is smaller than the predetermined value and to decrease the learning value when the speed change is larger than the predetermined value;
• predetermined value changing means for increasing the predetermined value when the conversion efficiency is larger than a second predetermined value and decreasing the predetermined value when the conversion efficiency is smaller than the second predetermined value;
• and
• control means for controlling said time regulating means so as to variably regulate the duration time based on the learning value.