Variable transmission system for vehicle

A variable transmission system for a vehicle, the variable transmission system omprising:

• a primary pulley including a first moving sheave, the first moving sheave being configured to be non-rotatable relative to a first fixed sheave and an input shaft, the first moving sheave configured to move in an axis direction, the first fixed sheave being fixed to the input shaft;
• a secondary pulley including a second moving sheave, the second moving sheave being configured to be non-rotatable relative to a second fixed sheave and an output shaft, the second moving sheave configured to move in the axis direction, the second fixed sheave being fixed to the output shaft;
• a chain belt wound on the primary pulley and the secondary pulley;
• a tensioner mechanism including a hydraulic pressure sensor, a head, and an actuator,
• the tensioner mechanism being configured to press a chord portion only when the chain belt extends by a predetermined amount or more, the chord portion being a part of the chain belt, the part being not wound on the pulleys,
• the hydraulic pressure sensor being configured to detect a magnitude of a hydraulic pressure to move the second moving sheave in the axis direction,
• the head being placed so as to be opposed to the chord portion,
• the actuator being configured to move the head in a direction where the chord portion is pressed;
• and
• an electronic control unit configured to continuously change a driving torque on an input-shaft side and to output the driving torque toward an output-shaft side by continuously changing respective winding radiuses of the chain belt with respect to the pulleys,
• when the magnitude of the hydraulic pressure detected by the hydraulic pressure sensor is a first predetermined value or more, the electronic control unit being configured to operate the actuator to press the chord portion such that the winding radiuses of the chain belt are maintained and a raceway length of the chain belt is made longer than a raceway length of the chain belt before the pressing by a predetermined amount or more,
• the predetermined amount being a circumferential extension amount of the chain belt when the magnitude of the hydraulic pressure is the first predetermined value.