SYSTEM / Control System Torque Reduction Control Purpose: Effectively utilizing engine horsepower by changing pump flow in response to increase or decrease of the engine speed due to traveling load Operation: 1. When accelerator pedal is stepped, MC makes arithmetic operation of the target engine speed. 2. MC makes arithmetic operation, using the target engine speed and signals from the main pump delivery pressure sensor , torque converter input speed sensor, and torque converter output speed sensor, and figures out the pump maximum tilting angle most suitable to each time to transmit it to the pump torque control solenoid valve. 3.
Pump torque control solenoid valve transmits pilot pressure corresponding to the amplitude of signal to the main pump regulator, and controls the pump flow rate. 4. If load applied to the engine becomes large and decreases the actual engine speed than the target speed, the pump tilting angle is decreased to reduce delivery flow. Thus, maneuverability of the vehicle body is improved. NOTE: In case the accelerator pedal becomes abnormal, the back-up control of the accelerator controls and fixes the engine speed at 1000 min -1 . 5. MC makes arithmetic operation of the actual engine speed, receiving signal from the torque converter input speed sensor. NOTE:
In case signal from either the main pump delivery pressure sensor , torque converter input speed sensor, or torque converter output speed sensor is not transmitted to the MC, it does not make torque reduction control, but makes pump control by the standard-torque control. NOTE: In case the pump torque control solenoid valve becomes abnormal, neither standard-torque control nor torque reduction control is made. T2-1-18 Q P-Q Line Flow Pressure P