SYSTEM / Control System Overheat Prevention Control Purpose: Prevents the engine from overheating by reducing the main pump maximum flow rate and pump torque, reducing the load applied to the engine when coolant and hydraulic oil temperatures increase beyond the specified level. Operation: 1. The signal from coolant temperature sensor is sent to MC via ECM and CAN. 2. When coolant temperature is 99 ° C (210 ° F) or higher, MC calculates the target pump displace- ment angle according to the signal from the pump delivery pressure sensor. MC compares the ac- tual pump displacement angle detected by the pump regulator pressure sensor with the target pump displacement angle. 3.
MC activates the pump control solenoid valve in order to compensate the difference between the actual and target displacement angels, and de- creases 7 % of pump torque. 4. The signal from the hydraulic oil temperature sensor is sent to MC 5. When coolant temperature is 100 ° C (212 ° F) or higher, MC calculates the target pump displace- ment angle according to the signal from the pump delivery pressure sensor. MC compares the ac- tual pump displacement angle detected by the pump regulator pressure sensor with the target pump displacement angle. 6.
MC activates the pump control solenoid valve in order to compensate the difference between the actual and target displacement angels, and de- creases maximum flow rate and 7 % of pump torque. Completion Condition for Overheat Control Coolant temperature 95 ° C (203 ° F) or lower Hydraulic oil temperature: 95 ° C (203 ° F) or lower Q Flow Rate Pressure P Q Flow Rate Pressure P T2-2-32