SYSTEM / Control System Horsepower Control Purpose: Controls delivery flow rate of each main pump and uses engine power effectively so that sum of pump torques divided to two main pumps and fan pump does not ex- ceed the engine output torque. Operation: 1. In normal, delivery pressure difference between main pumps 1 and 2 occurs with two pumps op- erated. 2. Larger load is applied to the main pump with higher delivery pressure and smaller load is ap- plied to that with lower delivery pressure. 3. The pump delivery pressure sensor and pump regulator pressure sensor detect this status and send the signal to MC. 4.
MC calculates the maximum target pump dis- placement angle according to the signals from two main pump delivery pressure sensors so that sum of pump torques of main pumps 1, 2 and fan pump does not exceed the engine output power. NOTE: Delivery flow rate of the fan pump is con- trolled by the fan pump flow rate control regardless with engine output power. (Re- fer to T2-2-38.) 5. MC compares actual pump displacement angle detected by the pump regulator pressure sensor with the target pump displacement angle. 6.
MC activates the pump control solenoid valve at the side with larger load in order to compensate for the difference between the actual and target pump displacement angles, and increases deliv- ery flow rate of the main pump with larger load. Pump 1 Delivery Pressure Sensor Pump 2 Delivery Pressure Sensor Engine Control Dial Pump 1 Regulator Pressure Sensor Pump 2 Regulator Pressure Sensor T1J1-02-02-038 Pump 1 Control Solenoid Valve Pump 2 Control Solenoid Valve T2-2-28