| 摘要 |
<p>PURPOSE:To provide a sure fail-safe function with a simple structure by control ling a transmission part and a clutch part by means of a control valve operated by a solenoid valve, detecting abnormality in the solenoid valve of speed change control part, and operating the clutch part so as to interrupt the connection between an engine and wheels. CONSTITUTION:Failure in a solenoid valve 23 is judged based on solenoid pressure, and the solenoid pressure is computed so that a speed change control valve 21 generates a required control pressure if there is no failure in the valve 23, and then the valve 23 is modulation controlled in its pulse width. Similarly, if there is no failure in a solenoid valve 24 it is subjected to pulse width modulation control. If there is failure in the valve 23 or 24, a solenoid valve 32 is made off and the solenoid pressure is made a specified value or less, and then line pressure of a changeover valve 7 is supplied to a shift valve 8. In the case of D range, clutch pressure is not supplied to backward and forward clutches 12b, 12a from output ports 81b, 81c, and the connection between an engine and a transmission part 11 is interrupted by the clutches 12b, 12a. Fail-safe function works accordingly.</p> |
