Method of controlling a dual clutch transmission

A method of controlling torque transferred across each of the two clutches of a dual clutch transmission when the transmission is performing an upshift during an application of positive torque and wherein the first of the two clutches is an off-going clutch and the second of the two clutches is an on-coming clutch, said method includes the steps of:

• determining when a shift has been commanded;
• performing a preparatory clutch pressure fill without a transfer of torque to the on-coming clutch;
• performing a predetermined nominal reduction in the pressure applied to the off-going clutch to cause a slight slip in preparation of disengaging the off-going clutch;
• sensing the speed of a driven member of the off-going clutch;
• determining a desired clutch torque and slip profile for the changeover of the clutches;
• performing a predetermined nominal increase to the pressure applied to the on-coming clutch to cause a slight torque transfer across the on-coming clutch;
• sensing the speed of a driven member of the on-coming clutch;
• determining a first time period during which a torque output of the transmission is changed over from the off-going clutch to the on-coming clutch based on an engine throttle position and the speed of the driven member the off-going clutch;
• determining a first target engine speed profile based on the speed of the driven member of the on-coming clutch and a length of the first time period for completing the clutch change over;
• simultaneously controlling the torque transfer across each clutch so that the torque transferred across the off-going clutch is linearly decreased while the torque transferred across the on-coming clutch is linearly increased at an inversely proportional rate to follow the clutch torque and slip profile and to cause the engine to track the target engine speed profile during the first time period;
• determining a length of a second time period, once the on-coming clutch is transferring all of the output torque in a higher gear, during which the engine speed will be reduced to maintain vehicle speed by increasing the pressure applied to the on-coming clutch;
• determining a second target engine speed profile based on the speed of the on-coming clutch and the length of the second time period for completing the reduction in engine speed;
• increasing the pressure applied to the on-coming clutch to cause the engine to track the second target engine speed profile so that vehicle speed is maintained in the higher gear;
• and
• decreasing the pressure applied to the on-coming clutch a small predetermined amount to allow the engine and vehicle to further accelerate in the higher gear in response to the engine throttle position once the engine and engaged clutch speeds are essentially equal.

A method of controlling a torque transferred across each of the two clutches of a dual clutch transmission during a downshift during an application of negative torque, wherein the first of the two clutches is an off-going clutch and the second of the two clutches is an on-coming clutch, said method includes the steps of:

• determining when a shift has been commanded;
• performing a preparatory clutch pressure fill without a transfer of torque to the on-coming clutch;
• performing a predetermined nominal reduction in the pressure applied to the off-going clutch to cause a slight slip in preparation of disengaging the off-going clutch;
• sensing the speed of a driven member of the off-going clutch;
• determining a desired clutch torque and slip profile for the changeover of the clutches;
• performing a predetermined nominal increase to the pressure applied to the on-coming clutch to cause a slight torque transfer across the on-coming clutch;
• sensing the speed of a driven member of the on-coming clutch;
• determining a length of a first time period during which a torque output of the transmission will be changed over from the off-going clutch to the on-coming clutch based on the clutch speeds and the clutch torque and slip profile;
• determining a first target engine speed profile based on the speed of the driven member of the on-coming clutch and the length of the first time period for completing the clutch change over;
• and
• simultaneously controlling the torque transfer across each clutch so that the torque transferred across the off-going clutch is linearly decreased while the torque transferred across the on-coming clutch is linearly increased at an inversely proportional rate to follow the clutch torque and slip profile and to cause the engine to track the first target engine speed profile during the first time period;
• determining a length of a second time period, once the on-coming clutch is transferring all of the output torque in a higher gear, during which the engine speed will be increased to maintain vehicle speed by decreasing the pressure applied to the on-coming clutch;
• determining a second target engine speed profile based on the speed of the on-coming clutch and the length of the second time period for completing the increase in engine speed;
• increasing the pressure applied to the on-coming clutch to cause the engine to track the second target engine speed profile so that vehicle speed is further reduced in a lower gear.