Method of controlling a hydraulic continuously variable transmission

A vehicle comprising:

• a frame;
• an engine mounted to the frame, the engine having a throttle valve controlling a flow of air to the engine;
• a ground engaging element mounted to the frame for propelling the vehicle;
• a driving shaft extending from the engine and being driven by the engine;
• a driven shaft operatively connected to ground engaging element for driving the ground engaging element;
• a hydraulic fluid reservoir;
• a pump fluidly communicating with the reservoir;
• a continuously variable transmission operatively connecting the driving shaft with the driven shaft, the continuously variable transmission including:
• a driving pulley disposed on the driving shaft for rotation therewith;
• a driven pulley disposed on the driven shaft for rotation therewith;
• and
• a belt operatively connecting the driving pulley with the driven pulley,
• the driving pulley including:
• a fixed sheave disposed on the driving shaft for rotation therewith;
• a movable sheave disposed on the driving shaft for rotation therewith, the belt being disposed between the fixed sheave and the movable sheave;
• a spring biasing the movable sheave away from the fixed sheave;
• and
• a CVT chamber fluidly communicating with the pump, the pump supplying hydraulic fluid from the reservoir to the CVT chamber to create a hydraulic pressure in the CVT chamber, and the hydraulic pressure in the CVT chamber biasing the movable sheave toward the fixed sheave;
• and
• a control unit determining a hydraulic pressure to be created in the CVT chamber,
• the hydraulic pressure determined by the control unit causing the movable sheave to apply a total clamping force onto the belt that is less than a clamping force necessary to cause the belt to rotate synchronously with the driving pulley when a drive ratio of the continuously variable transmission corresponds to a low gear ratio condition.

A method of controlling a hydraulic continuously variable transmission of a vehicle;

• the continuously variable transmission including a driving pulley disposed on a driving shaft for rotation therewith, a driven pulley disposed on a driven shaft for rotation therewith, and a belt operatively connecting the driving pulley with the driven pulley;
• the driving pulley including a fixed sheave, a movable sheave, and a spring biasing the movable sheave away from the fixed sheave;
• the driving shaft being driven by an engine of the vehicle;
• the method comprising:
• determining a vehicle speed;
• and
• controlling a hydraulic pressure applied to the movable sheave to apply a total clamping force onto the belt that is less than a clamping force necessary to cause the belt to rotate synchronously with the driving pulley when the vehicle speed corresponds to a low vehicle speed.