Patent ID: 6024671
Filing Date: 2000-02-15
Classification: F16H,Y10S,Y10T

Abstract:
An apparatus for controlling an automatic transmission, comprising:a torque converter;speed change gears to which a power is input from an engine through the torque converter;a plurality of frictional elements for switching power transmitting paths provided in the speed change gears;a hydraulic pressure control circuit provided with a plurality of solenoid valves for controlling a hydraulic pressure supplied to the frictional elements;speed change control means for controlling the solenoid valves so as to establish a target gear stage based on a value related to an engine load and a value related to a vehicle speed;said frictional elements including a first frictional element and a second frictional element, the first frictional element having an engaging hydraulic pressure chamber and a disengaging hydraulic chamber and being engaged when the hydraulic pressure is supplied only into the engaging hydraulic chamber, the second frictional element having a single hydraulic chamber and being engaged when the hydraulic pressure is supplied into the hydraulic chamber, the hydraulic chamber of the second frictional element being communicated with the disengaging hydraulic chamber;said solenoid valves including a first solenoid valve for controlling the hydraulic pressure supplied into the engaging hydraulic chamber of the first frictional element and a second solenoid valve for controlling the hydraulic pressure supplied into both the disengaging hydraulic chamber of the first frictional element and the hydraulic chamber of the second frictional element;said hydraulic pressure control circuit establishing a first gear stage which is located in a low speed side and in which the hydraulic pressure is supplied into the engaging hydraulic chamber of the first frictional element by the first solenoid valve and the hydraulic pressure is not supplied into the disengaging hydraulic chamber of the first frictional element and the hydraulic chamber of the second frictional element by the second solenoid valve, the circuit further establishing a second gear stage which is located in a high speed side and in which the hydraulic pressure is supplied into the engaging hydraulic chamber of the first frictional element by the first solenoid valve and the hydraulic pressure is supplied into the disengaging hydraulic chamber of the first frictional element and the hydraulic chamber of the second frictional element by the second solenoid valve;failure detection means for detecting a failure of the first solenoid valve in which the first solenoid valve is fixed under a condition that the first solenoid valve supplies the hydraulic pressure into the engaging hydraulic chamber; andmeans for increasing more the hydraulic pressure supplied into both the disengaging hydraulic chamber of the first frictional element and the hydraulic chamber of the second frictional element by the second solenoid valve in a case where the failure detection means has detected the failure than in a case where the failure detection means has not detected the failure, when the first gear stage is changed into the second gear stage.