A transmission control device controls a CVT installed in a vehicle. The device has, as modes for the CVT, a CVT mode M1 for changing a transmission gear ratio steplessly based on the operating state of the vehicle, and a stepped transmission mode M2 for changing the transmission gear ratio stepwise based on the operating state of the vehicle. The device includes a transmission mode switching control unit (controller) 12 for controlling switching between the CVT mode M1 and the stepped transmission mode M2 based on an actual accelerator opening. The transmission mode switching control unit (controller) 12 performs switching from the CVT mode M1 to the stepped transmission mode M2, if the actual accelerator opening reaches or exceeds a first threshold value T1 set in a plurality of stages so as to increase stepwise in accordance with an increase in a vehicle speed.

A method of operating a vehicle having an engine, a throttle valve and a throttle operator. A continuously variable transmission operatively connected to the engine has a driving pulley, a driven pulley, and a belt operatively connecting the driving and driven pulleys. A ground engaging member is operatively connected to the driven pulley. A piston is operatively connected to the driving pulley for applying a piston force thereto and thereby changing an effective diameter of the driving pulley. A control unit controls actuation of the piston and the piston force. The method includes detecting a stall condition indicative of the vehicle being stalled, and, responsive to the detection, setting the piston force to be zero.

A method of operating a vehicle having an engine, a throttle valve and a throttle operator. A continuously variable transmission operatively connected to the engine has a driving pulley, a driven pulley, and a belt operatively connecting the driving and driven pulleys. A ground engaging member is operatively connected to the driven pulley. A piston is operatively connected to the driving pulley for applying a piston force thereto and thereby changing an effective diameter of the driving pulley. A control unit controls actuation of the piston and the piston force. The method includes detecting a stall condition indicative of the vehicle being stalled, and, responsive to the detection, setting the piston force to be zero.

A method of operating a vehicle having an engine, a throttle valve and a throttle operator. A continuously variable transmission operatively connected to the engine has a driving pulley, a driven pulley, and a belt operatively connecting therebetween. A ground engaging member is operatively connected to the driven pulley. A piston is operatively connected to the driving pulley for applying a piston force thereto and thereby changing an effective diameter of the driving pulley. A control unit controls actuation of the piston and the piston force. The method includes determining at least one of the throttle operator and throttle valve position, detecting a parking/drive away condition indicative of one of a parking operation and a drive-away operation of the vehicle, and, responsive to the detection, actuating the piston and controlling the piston force based on the at least one of the throttle operator position and the throttle valve position.

A method of operating a vehicle having an engine, a throttle valve and a throttle operator. A continuously variable transmission operatively connected to the engine has a driving pulley, a driven pulley, and a belt operatively connecting therebetween. A ground engaging member is operatively connected to the driven pulley. A piston is operatively connected to the driving pulley for applying a piston force thereto and thereby changing an effective diameter of the driving pulley. A control unit controls actuation of the piston and the piston force. The method includes determining at least one of the throttle operator and throttle valve position, detecting a parking/drive away condition indicative of one of a parking operation and a drive-away operation of the vehicle, and, responsive to the detection, actuating the piston and controlling the piston force based on the at least one of the throttle operator position and the throttle valve position.

A system for conducting a rationality check of a transmission grade sensor includes a controller configured to calculate a change in elevation over time based on a change in barometric pressure. The controller calculates another change in elevation based on an average grade determined from a transmission grade sensor. The controller compares the second change in elevation to the first change in elevation and, if there is a significant discrepancy between them, calculates a grade correction factor. The controller then modifies the shift logic and/or shift schedule of the transmission based on the average grade from the transmission grade sensor and on the grade correction factor.

A method of operating a vehicle having an engine, a throttle valve and a throttle operator. A continuously variable transmission is operatively connected to the engine and has a driving pulley, a driven pulley, and a belt operatively connecting therebetween. At least one ground engaging member is operatively connected to the driven pulley and includes at least one of a wheel and a track. A piston is operatively connected to the driving pulley for applying a piston force to the driving pulley when actuated and thereby changing an effective diameter of the driving pulley. A control unit controls actuation of the piston and the piston force. The method includes determining an engine speed, and controlling the piston force based on the engine speed.

A method of operating a vehicle having an engine, a throttle valve and a throttle operator. A continuously variable transmission is operatively connected to the engine and has a driving pulley, a driven pulley, and a belt operatively connecting therebetween. At least one ground engaging member is operatively connected to the driven pulley and includes at least one of a wheel and a track. A piston is operatively connected to the driving pulley for applying a piston force to the driving pulley when actuated and thereby changing an effective diameter of the driving pulley. A control unit controls actuation of the piston and the piston force. The method includes determining an engine speed, and controlling the piston force based on the engine speed.

A vehicle propulsion system that includes a prime mover having an output shaft, a torque converter including a compressor coupled to the output shaft of the prime mover, a turbine fluidly coupled to the compressor, and a torque converter clutch for selectively mechanically coupling the compressor to the turbine, a continuously variable transmission (CVT) coupled to the turbine of the torque converter, and a controller that is programmed to receive signals indicating operating conditions of the vehicle propulsion system, determine whether the received signals indicate a reduction in ratio in the CVT is impending, determine whether to open the torque converter clutch based upon a determination that a reduction in ratio is impending, and open the torque converter clutch in response to a determination to open the torque converter clutch.

A vehicle propulsion system that includes a prime mover having an output shaft, a torque converter including a compressor coupled to the output shaft of the prime mover, a turbine fluidly coupled to the compressor, and a torque converter clutch for selectively mechanically coupling the compressor to the turbine, a continuously variable transmission (CVT) coupled to the turbine of the torque converter, and a controller that is programmed to receive signals indicating operating conditions of the vehicle propulsion system, determine whether the received signals indicate a reduction in ratio in the CVT is impending, determine whether to open the torque converter clutch based upon a determination that a reduction in ratio is impending, and open the torque converter clutch in response to a determination to open the torque converter clutch.