Shift control system and shift control method for continuously variable transmission

摘要

A maximum flow calculating unit (166) calculates a maximum amount (Qmax) of hydraulic fluid that can flow into or out of an input-side hydraulic cylinder (42c) when a shift control command signal (S T ) is set to a reference DUTY value, based on an estimated valve pressure difference (”P) calculated by an estimated pressure difference calculating unit (156), and a post-guard target sheave position setting unit (170) performs a guard process for restricting the amount of change of the sheave position, using a guard value (”Xg) calculated by a guard value calculating unit (168) based on the maximum flow amount (Qmax), so as to set a post-guard target sheave position (Xtg). Since the thus set target sheave position (Xtg) does not undergo excessive large changes nor excessively small changes during shifting, a target value for shifting is set so that a feedforward controlled variable determined based on the amount of change of the target sheave position (Xtg) becomes an appropriate value.