Pressure control system and control method for a multiple-ratio transmission with pre-staged ratio shifts

A pressure control system for a multiple-ratio, geared, power transmission mechanism for an automotive vehicle powertrain including an engine and a torque output shaft drivably connected to vehicle traction wheels, the transmission mechanism having pressure-operated friction elements for selectively activating multiple torque flow paths through the transmission mechanism and actuators for selectively actuating and deactivating the friction elements;

• an electronic controller for developing a desired gear ratio in the transmission mechanism in response to driveline operating variables and driver commanded operating variables, the controller including memory registers for storing transmission control algorithms and a processor unit for executing the control algorithms to establish a desired destination gear ratio in a ratio change sequence in response to the operating variables;
• the electronic controller including a first subsystem with algorithms for processing changes in the desired destination gear by identifying active friction elements and by timing of the start and completion of each ratio change;
• a second subsystem with algorithms for specifying the pressure control action required to apply or release a friction element during a ratio change and during a friction element engagement, the second subsystem comprising a library of pressure profiles required to complete all ratio changes and engagements;
• the first subsystem determining and commanding the ratio change needed to effect the desired destination gear from a current gear state, the needed ratio change being configured from a pre-selectable set of shift events;
• and
• a third subsystem storing a collection of pressure calculations and algorithms accessible by the first and second subsystems for calculating an appropriate pressure for each friction element.

A pressure control system for a multiple-ratio, geared, power transmission mechanism for an automotive vehicle powertrain including an engine and a torque output shaft drivably connected to vehicle traction wheels, the transmission mechanism having pressure-operated friction elements for selectively activating multiple torque flow paths through the transmission mechanism and actuators for selectively actuating and deactivating the friction elements;

• an electronic controller for developing a desired gear ratio in the transmission mechanism in response to driveline operating variables and driver commanded operating variables, the controller including memory registers for storing transmission control algorithms and a processor unit for executing the control algorithms to establish a desired destination gear ratio in a ratio change sequence in response to the operating variables;
• the electronic controller including a first subsystem with algorithms for processing changes in the desired destination gear by identifying active friction elements and by timing of the start and completion of each ratio change;
• a second subsystem with algorithms for specifying the pressure control action required to apply or release a friction element during a ratio change and during a friction element engagement, the second subsystem comprising a library of pressure profiles required to complete all ratio changes and engagements;
• the first subsystem determining and commanding the ratio change needed to effect the desired destination gear from a current gear state, the needed ratio change being configured from a pre-selected set of shift patterns;
• a third subsystem storing a collection of pressure calculations and algorithms accessible by the first and second subsystems for calculating an appropriate pressure for each friction element;
• the first subsystem having buffer portions that receive desired friction element data including shift identification, friction element identification, friction element status and pressure profiles for a current shift in a first buffer stage of a gear shift sequence and buffer portions that receive desired friction element data for a forthcoming shift in a second buffer stage of a gear shift sequence whereby the control system compensates for hydraulic and electronic system delays during ratio changes as friction elements involved in activating the forthcoming gear are prepared for state changes to improve system response.

A method for controlling a multiple-ratio, geared, power transmission mechanism for an automotive vehicle powertrain including an engine and a torque output shaft drivably connected to vehicle traction wheels, the transmission mechanism having pressure-operated friction elements for selectively activating multiple torque flow paths trough the transmission mechanism and actuators for selectively activating and deactivating the friction elements, the method comprising the steps of:

• developing a desired gear ratio in the transmission mechanism in response to driveline operating variables and driver commanded operation variables;
• storing transmission control algorithms;
• executing the control algorithms to establish a desired destination gear ratio in a ratio change sequence in response to the operating variables;
• processing changes in the desired destination gear by identifying active friction elements and by timing the start and completion of each ratio change;
• specifying the pressure control action required to apply or release a friction element during a ratio change and during a friction element engagement;
• storing a library of pressure profiles required to complete all ratio changes or engagements;
• and
• storing a collection of pressure calculations and algorithms accessible for calculating an appropriate pressure for each friction element.