COMPONENT OPERATION / Pump Device PUMPS 1, 2 CONTROL SOLENOID VALVE, FAN PUMP CONTROL SOLENOID VALVE The pump control solenoid valve is quipped with the regulator for pumps 1, 2 and fan pump. The pump control solenoid valve supplies the flow rate control pressure to the regulator and controls the pump delivery flow rate. Operation 1. In neutral, port Pi and the output port are blocked by spool (1). The output port is connected to port T through the notch in spool (1). 2. When current from MC (main controller) flows to solenoid (4), solenoid (4) is excited and pushes spring 2 (3). 3. Spring 2 (3) pushes spool (1) to the left.
Port Pi is connected to the output port through the notch in spool (1). Therefore, pressure in the output port increases. 4. There is the pressure receiving area difference in the notch in spool (1). The area of right side (B) is larger than that of left side (A). 5. When pressure in the output port starts to in- crease, Pi1 Ч A + S2 (force pushing spool (1) to the left) becomes stronger than Pi1 Ч B + S1 (force pushing spool (1) to the right). Therefore, spool (1) moves to the left. 6. When pressure in the output port increase further, Pi1 Ч B + S1 (force pushing spool (1) to the right) becomes stronger than Pi1 Ч A + S2 (force pushing spool (1) to the left).
Therefore, spool (1) returns to the right. 7. Consequently, as port Pi and the output port are blocked by spool (1), pressure in the output port stops increasing. Pi1: Pressure in the output port A, B: Pressure receiving area on spool (1) S1: Spring 1 (2) force (Force pushing spool (1) to the left side) S2: Spring 2 (3) force (Force pushing spool (1) to the right side) T3-1-28