Patent ID: 8157681

Claim:
A continuously variable transmission without using a primary pulley pressure sensor comprising: an input side primary pulley which varies a groove width according to a first oil pressure; an output side secondary pulley which varies a groove width according to a second oil pressure; a belt looped around the primary pulley and the secondary pulley, having a contact radius for the primary pulley and a contact radius for the secondary pulley, the contact radius of the primary pulley and the contact radius of the secondary pulley varying in accordance with the groove width of the primary pulley and the groove width of the secondary pulley; a speed change control mechanism constituted by a speed change link, one end portion of which is connected to a movable sheave of the primary pulley and another end portion of which is connected to a step motor, and a speed change control valve connected to a center of the speed change link, which controls the first oil pressure in accordance with an operating position of the step motor, and a controller, which: stores a speed ratio at a stopping time of a vehicle; initializes the step motor, whereby the operation position of the step motor is shifted to a home position during activation of the vehicle when the speed ratio at the stopping time of the vehicle could not be stored; sets the first oil pressure to substantially zero, increases the second oil pressure to a predetermined oil pressure, and shifts a ratio between the contact radius with the primary pulley and the contact radius with the secondary pulley to a ratio corresponding to a lowest speed ratio, after the step motor is initialized and when the speed ratio at the stopping time of the vehicle could not be stored and the primary pulley and the secondary pulley do not rotate during activation of the vehicle; and stores a position of the primary pulley following shifting to the ratio corresponding to the lowest speed ratio as a position corresponding to the home position of the step motor.