Patent ID: 8275510

Claim:
A failure determining device of a continuously variable transmission mounted on a vehicle, wherein said continuously variable transmission includes a drive pulley, a driven pulley and a belt, said belt is wound around said drive and driven pulleys, a speed ratio is continuously changed by changing winding radii of said belt around said pulleys, said pulleys have groove widths being changeable by actuators supplied with a hydraulic pressure regulated by a regulator valve, and said regulator valve includes a first regulator valve for regulating a hydraulic pressure supplied to the actuator of said drive pulley and a second regulator value for regulating the hydraulic pressure supplied to the actuator of said driven pulley; said failure determining device comprises: a sensing unit for sensing a physical quantity corresponding to a running state of said vehicle, and a determining unit connected to said sensing unit; said determining unit determines whether said first regulating valve is abnormal in a region where the hydraulic pressure supplied to the actuator of said driven pulley is higher than the hydraulic pressure supplied to the actuator of said drive pulley, or not, at the time of changing speed ratio in a first region of the speed ratio based on a degree of change of an actual speed ratio calculated based on a running state corresponding to said sensed physical quantity and the target speed ratio; said determining unit determines whether said second regulating valve is abnormal in a region where the hydraulic pressure supplied to the actuator of said driven pulley is lower than the hydraulic pressure supplied to the actuator of said drive pulley, or not, at the time of changing speed ratio change in a second region on a speed increase side with respect to said first region, based on the degree of change of the actual speed ratio calculated based on said running state and the target speed ratio; and said first and second regions do not overlap together, and each of said first and second regions allows the change of speed ratio when said second regulating valve is abnormal.