Driving force control system for a vehicle

A driving force control system for a vehicle which controls an automatic transmission system of the vehicle having a torque converter connected to an output shaft of an engine, a stepped automatic transmission mechanism connected to an output shaft of the torque converter, and a hydraulic circuit for actuating the stepped automatic transmission mechanism, and by which line pressure control means for controlling an oil line pressure in the hydraulic circuit is supplied with a line pressure command value so as to control said stepped automatic transmission for controlling a torque of a driving axle connected to the stepped automatic transmission mechanism;

• comprising:
• shift signal output means for delivering a shift signal which indicates a gear shift position of said stepped automatic transmission mechanism;
• engine r.p.m. detection means for detecting r.p.m. of said engine shall be also termed "engine r.p.m.");
• torque-converter output shaft r.p.m. detection means for detecting r.p.m. of said output shaft of said torque converter (hereinbelow, the r.p.m. shall be also termed "torque-converter output shaft r.p.m.");
• input torque calculation means for calculating an input torque of said stepped automatic transmission mechanism on the basis of the engine r.p.m. detected by said engine r.p.m. detection means, the torque-converter output shaft r.p.m. detected by said torque-converter output shaft r.p.m. detection means, and torque converter characteristics prepared beforehand;
• shift start recognition means for recognizing an actual mechanical shift start timing of said stepped automatic transmission mechanism in accordance with a change of the input torque calculated by said input torque calculation means, on condition that the shift signal delivered from said shift signal output means has changed;
• shift end recognition means for recognizing a timing which is earlier than an actual mechanical shift end timing of said stepped automatic transmission mechanism, as a shift end;
• a standard line pressure calculation portion for calculating that oil line pressure in said hydraulic circuit which is required for performing a gear shift operation, in accordance with said input torque at the change of said shift signal;
• target axle torque setting means for setting a target axle torque of said driving axle, at least, under the gear shift operation dependent on a situation of said vehicle;
• axle torque determination means for determining an actual axle torque of said driving axle;
• axle torque deviation calculation means for calculating a deviation between the target axle torque and the actual axle torque during said gear shift operation;
• line-pressure correction magnitude calculation means for calculating a correction magnitude of said oil line pressure in said hydraulic circuit in accordance with the deviation calculated by said axle torque deviation calculation means;
• and
• a command line pressure calculation portion which adds up the oil line pressure calculated by said standard line pressure calculation portion and the correction magnitude calculated by said line-pressure correction magnitude calculation means, and which supplies said line pressure control means with a sum value of the addition as the line pressure command value for a time period from the shift start timing to the shift end timing such that said oil line pressure in said hydraulic circuit becomes the sum value.