Method and an apparatus for controlling a car equipped with an automatic transmission having a lockup clutch

A method for controlling a car equipped with an automatic transmission having a lockup clutch, comprising the steps of:

• a) setting a target driving torque;
• b) engaging said lockup clutch when the car speed has exceeded a predetermined value;
• c) detecting a variation of a generated torque;
• d) setting a target engine torque lower than the current engine torque when a range of a variation of a generated torque has exceeded a predetermined value;
• e) setting a target throttle valve opening at which an engine efficiency is the optimum from said target engine torque;
• f) deciding a target air-fuel ratio at which said target engine torque can be achieved;
• g) deciding a transmission ratio from said target driving torque and said target engine torque;
• h) deciding a target fuel flow rate from said target air-fuel ratio;
• and
• i) controlling a throttle actuator, a fuel supply unit and said automatic transmission to obtain said target throttle valve opening, said target fuel flow rate and said target speed change rate.

A control unit for a car equipped with an automatic transmission having a lockup clutch, comprising:

• means for controlling an output torque of said engine according to a command value;
• means for changing a transmission ratio of said automatic transmission;
• means for detecting a variation of an engine torque;
• means for deciding a target driving torque;
• means for reducing said command value when a range of said detected variation of said torque has exceeded a predetermined value;
• and
• means for deciding a transmission ratio at which a reduction of the driving torque due to a reduction of said engine torque is to be compensated for.

A control unit for a car equipped with an automatic transmission having a lockup clutch, comprising:

• an accelerator for indicating a driving torque by operation of a driver;
• means for setting a target driving torque according to an indication of said accelerator;
• means for detecting a variation of a generated torque;
• means for setting a target engine torque based on said target driving torque and transmission ratio;
• means for deciding a target throttle valve opening at which an engine efficiency is an optimum based on said target engine torque;
• means for deciding a target air-fuel ratio at which said target engine torque can be achieved;
• means for reducing said target engine torque when said means for detecting a torque variation has detected a torque variation which exceeds a predetermined value;
• means for deciding a target transmission ratio at which a reduction of said target engine torque is compensated for and said target driving torque is generated;
• and
• means for controlling said engine and said automatic transmission to obtain a target throttle valve opening, target air-fuel ratio and target speed change rate.