Patent ID: 7811187

Claim:
A continuously variable transmission comprising: a primary pulley having a primary movable sheave that is capable of moving to change a groove width of said primary pulley; a secondary pulley having a secondary movable sheave that is capable of moving to change a groove width of said secondary pulley; a belt engaged with said primary pulley and said secondary pulley to transmit torque therebetween; a control valve unit that is capable of producing a first fluid pressure and a second fluid pressure to supply to a first fluid pressure chamber and a second fluid pressure chamber, respectively, of at least one of said primary pulley and said secondary pulley, said first and second fluid pressure chambers being fluid-tight; a control unit that outputs a command to said control valve unit to obtain target fluid pressures of the first fluid pressure and the second fluid pressure; and a thrust applying mechanism that is capable of applying a resultant force to the movable sheave of the at-least one of said primary and secondary pulleys so as to narrow the groove width thereof, wherein the resultant force contains a spring force of a spring, a first fluid pressure force obtained based on the first fluid pressure and acting in the same direction as the spring force, and a second fluid pressure force based on the second fluid pressure and acting in a direction opposite to the spring force and the first fluid pressure force, and wherein the first fluid pressure force and the second fluid pressure force are set such that the spring force is set to be larger than a thrust which is necessary to obtain one of a low speed ratio by said primary pulley and a high speed ratio by said secondary pulley.