Load condition preemption of scheduled gearshifts in an automatic transmission

A system for controlling gearshifts in an automatic transmission for an automotive vehicle, comprising:

• multiple ratio gearing and pressure-operated friction elements selectively engaged and released to produce multiple gear ratios through said gearing;
• a pressurized valve system having multiple shift control valves in a valve circuit that communicates with said friction elements;
• solenoid valve means in said circuit for distributing selectively to said shift control valves a fluid pressure signal actuating said friction elements;
• an electronic processor having a memory accessible to the processor stored with shift control information for a current gear ratio including a predetermine function relating current throttle position and a minimum vehicle acceleration at which an upshift from the corresponding current gear ratio can occur and a predetermined function relating current throttle position and minimum vehicle speed at which an upshift from the corresponding current gear ratio can occur;
• means communicating with said processor for generating a throttle position signal representing the current position of the engine throttle;
• means communicating with said processor for generating a vehicle speed signal representing current vehicle speed;
• means for determining current vehicle acceleration from the current vehicle speed;
• means communicating with said processor for generating a gear signal representing the currently engaged gear ratio;
• means for comparing the current vehicle acceleration to said minimum vehicle acceleration and the current vehicle speed to said minimum vehicle speed;
• and
• means for energizing and deenergizing the solenoid valve means to produce a change in gear ratio by selectively engaging and releasing the friction elements in response to the result of said comparisons.

In an automotive vehicle powertrain comprising a multiple speed automatic transmission having multiple gear ratio gearing and pressure-operated friction elements electively engaged and released to produce multiple gear ratios through said gearing, a hydraulic circuit having multiple shift control valves and flow path switching means for selectively engaging and releasing said friction elements, and an internal combustion engine having a variable-position throttle, a method for preventing powertrain hunting comprising the steps of:

• determining current position of the engine throttle;
• determining current vehicle speed;
• determining current vehicle acceleration from the current vehicle speed;
• determining the currently engaged gear ratio;
• establishing for a current gear ratio a predetermined function relating the current throttle position and a minimum vehicle acceleration at which an upshift from the corresponding current gear ratio can occur and a predetermined function relating the current throttle position and a minimum vehicle speed at which a gear ratio upshift from the corresponding current gear ratio can occur;
• comparing the current vehicle acceleration to said minimum vehicle acceleration and the current vehicle speed to said minimum vehicle speed;
• and
• producing a change in gear ratio by selectively engaging and releasing the friction elements in response to the result of said comparisons.

In an automotive vehicle driveline comprising a multiple speed automatic transmission having multiple gear ratio gearing, pressure-operated friction elements selectively engaged and released to produce multiple gear ratios through the gearing, a pressurized valve system having multiple shift control valves in a valve circuit that communicates with the friction elements, solenoid valves in said circuit for distributing selectively to said shift control valves a fluid pressure signal actuating said friction elements, an electronic processor and memory accessible to the processor, and an engine having a variable-position throttle, a method for preventing powertrain hunting comprising the steps of:

• generating and transmitting to said processor a throttle position signal representing current position of the engine throttle;
• generating and transmitting to said processor a vehicle speed signal representing current vehicle speed;
• determining current vehicle acceleration from the current vehicle speed;
• generating and transmitting to said processor a gear signal representing the currently engaged gear ratio;
• storing in said memory shift control information for a current gear ratio including a predetermined function relating the current throttle position and a minimum vehicle acceleration at which a gear ratio upshift from the corresponding current gear ratio can occur and a predetermined function relating the current throttle position and a minimum vehicle speed at which a gear ratio upshift from the corresponding current gear ratio can occur;
• comparing, for the current throttle position, the current vehicle acceleration to said minimum vehicle acceleration and the current vehicle speed to said minimum vehicle speed;
• and
• energizing and deenergizing the solenoid valves to produce a change in gear ratio by selectively engaging and releasing the friction elements in response to the result of said comparisons.