Control system and strategies for a double acting secondary sheave servo for a continuously variable transmission

A continuously variable transmission system to provide transmission of torque from a torque input means to a torque output means, comprising:

• rotatable input and output shafts;
• drive means for drivingly coupling said input shaft with said output shaft, said drive means including a first variable pulley rotatable with said input shaft, a second variable pulley rotatable with said output shaft, and a belt means coupling said first and second variable pulleys, each of said first and second variable pulleys having a fixed sheave and a movable sheave;
• first biasing means for continuously biasing together said fixed and movable sheaves of said first variable pulley, second biasing means for continuously biasing together said fixed and movable sheaves of said second variable pulley;
• said first biasing means including at least one fluid chamber having fluid access to a source of pressurized hydraulic fluid via a primary line;
• said second biasing means including a plurality of fluid chambers including first, second, and third fluid chambers having fluid access to a source of pressurized hydraulic fluid via a secondary line, addition and exhaustion of fluid from said fluid chambers being effective to cause relative movement of said movable sheave;
• and
• a valve means for regulation of fluid flow to said plurality of fluid chambers of said secondary pulley in communication with said source of pressurized hydraulic fluid, said valve means operative to regulate the secondary line pressure below the pressure of said source and distinct from the primary line pressure, with the first and third chambers being in fluid communication with the valve means.

A continuously variable transmission system with a primary coupling means and primary line in fluid communication therewith, a secondary coupling means and secondary line in fluid communication therewith, said secondary coupling means including a closed balance means in fluid communication with an intermediate line, and a general line in fluid communication with the primary line, the secondary line, and intermediate line, and means for controlling the clamping force of said secondary coupling means in response to the input torque, drive ratio, engine speed, and downshift strategy employed, said means for controlling the clamping force of said secondary coupling means comprising:

• means for ascertaining a required secondary line pressure for the input torque, drive ratio, engine speed, downshift strategy employed, and pressure of the secondary balance means in the continuously variable transmission;
• means for ascertaining a required primary line pressure for the input torque, drive ratio, engine speed, and downshift strategy employed in the continuously variable transmission;
• means for substantially setting the general line pressure to the required primary line pressure responsive to said required primary line pressure greater than or equal to said required secondary pressure;
• and
• means for substantially setting the secondary line pressure to the required secondary line pressure responsive to said required primary line pressure greater than or equal to said required secondary line pressure.

A continuously variable transmission system with a primary coupling means and primary line in fluid communication therewith, a secondary coupling means and secondary line in fluid communication therewith, said secondary coupling means including a balance means in fluid communication with an intermediate line, and a general line in fluid communication with the primary line, the secondary line, and intermediate line, and means for controlling the clamping force of said secondary coupling means in response to the input torque, drive ratio, engine speed, and downshift strategy employed, said means for controlling the clamping force of said secondary coupling means comprising:

• means for ascertaining a required secondary line pressure for the input torque, drive ratio, engine speed, downshift strategy employed, and pressure of the secondary balance means in the continuously variable transmission;
• means for ascertaining a required primary line pressure for the input torque, drive ratio, engine speed, and downshift strategy employed in the continuously variable transmission;
• and
• means responsive to the required secondary line pressure greater than the required primary line pressure for substantially setting the general line pressure to the required secondary line pressure and for substantially setting the secondary line pressure to the general line pressure.

A continuously variable transmission system with a primary coupling means and primary line in fluid communication therewith, a secondary coupling means and secondary line in fluid communication therewith, said secondary coupling means including a balance means in fluid communication with an intermediate line, a general line in fluid communication with the primary line, the secondary line, and intermediate line, and means for controlling the clamping force of said secondary coupling means in response to the input torque, drive ratio, engine speed, and downshift strategy employed, said means for controlling the clamping force of said secondary coupling means comprising:

• means for ascertaining a first required secondary line pressure for the input torque, drive ratio, engine speed, and downshift strategy employed in the continuously variable transmission;
• means for comparing the first required secondary line pressure with a switching pressure setpoint;
• means responsive to the first required secondary pressure greater than the switching pressure setpoint for substantially exhausting the secondary balance means;
• means responsive to the first required secondary pressure greater than the switching pressure setpoint for substantially setting the general line pressure to the first secondary pressure;
• means responsive to the first required secondary pressure greater than the switching pressure setpoint for substantially setting the secondary line pressure to the general line pressure;
• means responsive to the first required secondary pressure lesser than or equal to the switching pressure setpoint for substantially setting the secondary balance means pressure to the intermediate line pressure;
• means for ascertaining a second required secondary line pressure for the input torque, drive ratio, engine speed, downshift strategy employed, and secondary balance means pressure in the continuously variable transmission;
• means for ascertaining a required primary line pressure for the input torque, drive ratio, engine speed, and downshift strategy employed in the continuously variable transmission;
• means for comparing the second required secondary line pressure with the required primary line pressure;
• means responsive to the required primary line pressure greater than o equal to said second required secondary pressure for substantially setting the general line pressure to the required primary line pressure;
• and
• means responsive to the required primary line pressure greater than or equal to said second required secondary pressure for substantially setting the secondary line pressure to the second required secondary line pressure.

A continuously variable transmission system with a primary coupling means and primary line in fluid communication therewith, a secondary coupling means and secondary line in fluid communication therewith, said secondary coupling means including a balance means in fluid communication with an intermediate line, a general line in fluid communication with the primary line, the secondary line, and intermediate line, and means for controlling the clamping force of said secondary coupling means in response to the input torque, drive ratio, engine speed, and downshift strategy employed, said means for controlling the clamping force of said secondary coupling means comprising:

• means for ascertaining a first required secondary line pressure for the input torque, drive ratio, engine speed, and downshift strategy employed in the continuously variable transmission;
• means for comparing the first required secondary line pressure with a switching pressure setpoint;
• means responsive to the first required secondary pressure greater than the switching pressure setpoint for substantially exhausting the secondary balance means;
• means responsive to the first required secondary pressure greater than the switching pressure setpoint for substantially setting the general line pressure to the first secondary pressure;
• means responsive to the first required secondary pressure greater than the switching pressure setpoint for substantially setting the secondary line pressure to the general line pressure;
• means responsive to the first required secondary pressure lesser than or equal to the switching pressure setpoint for substantially setting the secondary balance means pressure to the intermediate line pressure;
• means for ascertaining a second required secondary line pressure for the input torque, drive ratio, engine speed, downshift strategy employed, and secondary balance means pressure in the continuously variable transmission;
• means for ascertaining a required primary line pressure for the input torque, drive ratio, engine speed, and downshift strategy employed in the continuously variable transmission;
• means for comparing the second required secondary line pressure with the required primary line pressure;
• means responsive to the required primary line pressure lesser than said second required secondary pressure for substantially setting the general line pressure to the second required secondary line pressure;
• and
• means responsive to the required primary line pressure lesser than said second required secondary pressure for substantially setting the secondary line pressure to the general line pressure.