Patent ID: 8857382

Claim:
An apparatus for controlling a continuously variable transmission having a drive pulley connected to a prime mover installed in a vehicle and movable in an axial direction when hydraulic oil is supplied to a first hydraulic actuator, a driven pulley connected to driven wheels and movable in an axial direction when hydraulic oil is supplied to a second hydraulic actuator, and a power transmissible element wound around the drive pulley and driven pulley and configured to vary a gear ratio continuously variable by controlling supply of hydraulic oil to the first and second actuators to vary the winding radius of the power transmissible element, comprising: a first oil passage that connects the first hydraulic actuator and a reservoir for retaining hydraulic oil; a second oil passage that connects the second hydraulic actuator and the reservoir; a single electric reversible hydraulic pump installed at a common portion of the first oil passage and the second oil passage and capable of pumping hydraulic oil retained in the reservoir and delivering to the first oil passage or the second oil passage; a first check valve installed in the first oil passage between the reservoir and the hydraulic pump for blocking flow of hydraulic oil from the hydraulic pump to the reservoir; a second check valve installed in the second oil passage between the reservoir and the hydraulic pump for blocking flow of hydraulic oil from the hydraulic pump to the reservoir; a first bypass passage formed in the first oil passage between the hydraulic pump and the first hydraulic actuator; a second bypass passage formed in the second oil passage between the hydraulic pump and the second hydraulic actuator; a control valve installed between the first bypass passage and the second bypass passage and capable of varying the flow passage and pressure of hydraulic oil flowing through the first bypass passage and the second bypass passage; a third check valve installed in the first bypass passage for blocking flow of hydraulic oil from the control valve to the hydraulic pump; a fourth check valve installed in the second bypass passage for blocking flow of hydraulic oil from the control valve to the hydraulic pump; and a controller for controlling operation of the hydraulic pump and the control valve.