STRUCTURE, FUNCTION, & MAINTENANCE STANDARD HYDRAULIC PUMP 2. When signal current is very small (coil ener- gized) When a very small signal current flows to coil (5), coil (5) is energized, and a propulsion force is gen- erated which pushes plunger (6) to the left. Push pin (4) pushes spool (2) to the left, and pres- surized oil flows from port PEPC to port PSIG(PM) . When the pressure at port PSIG(PM) rises and the load of spring (3) + the force acting on surface a of spool (2) becomes greater than the propulsion force of plunger (6), spool (2) is pushed to the right. The circuit between port PEPC and port PSIG(PM) is shut off, and at the same time, port PSIG(PM) and port PT are connected.
As a result, spool (2) is moved up or down until the propulsion force of plunger (6) is balanced with the load of spring (3) + pressure of port PSIG(PM) . Therefore, the circuit pressure between the EPC valve and the LS valve is controlled in proportion to the size of the signal current. 08891 3. When signal current is maximum (coil ener- gized) When the signal current flows to coil (5), coil (5) is energized. When this happens, the signal current is at its max- imum, so the propulsion force of plunger (6) is also at its maximum. For this reason, spool (2) is pushed fully to the left by push pin (4).
As a result, the maximum flow of pressurized oil from port PEPC flows to port PSIG(PM) , and the circuit pressure between the EPC valve and LS valve becomes the maximum. At the same time, port PT closes and stops the oil from flowing to the tank. 08892 10-50 PC210/240-7K