Patent ID: 7553256

Claim:
A hydraulic control apparatus of a belt-drive CVT for a vehicle, controlling a transmission ratio by changing respective effective rotation radii of a belt, linking driving and driven pulleys, by working fluid pressure, comprising: vehicle information sensors that detect vehicle information; hydraulic actuators that adjust each displacement position in moving direction of the driving and driven pulleys, and change the respective effective rotation radii of the belt wound around the driving and driven pulleys in accordance with the working fluid pressure; a control unit that determines each fluid pressure command value provided for the driving and driven pulleys based on the vehicle information detected by the vehicle information sensors, and controls the hydraulic actuators responsively to each control command value corresponding to the respective fluid pressure command values; the control unit comprising: an actual displacement amount acquisition section for acquiring an amount of actual displacement of one of the driving and driven pulleys; a target displacement amount set section for setting an amount of target displacement of one of the driving and driven pulleys based on the vehicle information detected by the vehicle information sensors at a time of speed change to a limit of speed change; a fluid pressure rapidly changing quantity estimate section for estimating a rapidly changing amount of the working fluid pressure, occurring at close to an end of the speed change, from a flowing working fluid quantity of a fluid chamber of the one pulley, which is obtained from the actual displacement amount of the one of the pulleys acquired by the actual displacement amount acquisition section, and a modulus of volume elasticity of the working fluid, at the speed change; and a correction operation section for correcting the fluid pressure command value by the rapidly changing amount of the working fluid pressure at a time when a rate of the actual displacement amount with respect to the target displacement amount has reached a predetermined rate α 0 , at the speed change.