Control system for a hydraulically-operated transmission of a vehicle

A control system for a hydraulically-operated transmission for a vehicle, said transmission being connected to a crankshaft of an internal combustion engine and having a plurality of friction engagement elements, said control system changing a shift position by switching engagement states of said friction engagement elements, and comprising:

• a working oil temperature sensor for detecting a working oil temperature of said transmission;
• a cooling water temperature sensor for detecting a cooling water temperature of said engine;
• a plurality of sensors for detecting an operating condition of said transmission;
• a working oil temperature estimating module for calculating an estimated value of the working oil temperature on the basis of the detected cooling water temperature and the detected operating condition of said transmission;
• a weighting factor calculating module for calculating a weighting factor according to the working oil temperature detected by said working oil temperature sensor or the estimated working oil temperature calculated by said working oil temperature estimating module;
• an actual working oil temperature calculating module for calculating a weighted average value of the working oil temperature detected by said working oil temperature sensor and the estimated working oil temperature calculated by said working oil temperature estimating module, by using the weighting factor calculated by said weighting factor calculating module, and outputting the calculated weighted average value as an actual working oil temperature;
• and
• a hydraulic pressure control module for controlling a hydraulic pressure of the working oil according to the actual working oil temperature outputted from said actual working oil temperature calculating module.

A control method for a hydraulically-operated transmission for a vehicle, said transmission being connected to a crankshaft of an internal combustion engine and having a plurality of friction engagement elements, a shift position of said transmission being changed by switching engagement states of said friction engagement elements, said control method comprising the steps of:

• a) detecting a working oil temperature of said transmission by a working oil temperature sensor;
• b) detecting a cooling water temperature of said engine by a cooling water temperature sensor;
• c) detecting an operating condition of said transmission by a plurality of sensors;
• d) calculating an estimated value of the working oil temperature on the basis of the detected cooling water temperature and the detected operating condition of said transmission;
• e) calculating a weighting factor according to the detected working oil temperature or the estimated working oil temperature;
• f) calculating a weighted average value of the detected working oil temperature and the estimated working oil temperature by using the weighting factor, as an actual working oil temperature;
• and
• g) controlling a hydraulic pressure of the working oil according to the actual working oil temperature.