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| Illustration 1 | g01596393 |
General Hydraulic System (1) Line to forward return manifold (2) Line to port "A" of cooler manifold (3) Generator motor (4) Flow control valve (5) Generator control solenoid (6) Generator manifold (7) Relief valve (8) Line to tee on right propel pump (9) Displacement piston cavity (10) Line from hydraulic tank port "2" (11) Bias piston cavity (12) Generator pump (13) Pressure compensator spool (14) Flow compensator spool | |
When the engine is not operating, the bias piston spring forces the swashplate in the generator pump to the maximum angle. When the engine is started, the pump begins to produce flow. Supply oil is sent to the pressure compensator spool. Supply oil is sent to the flow compensator spool. The pressure compensator spool and the flow compensator spool are inside the pump. Supply oil is also sent out of port "B" from the pump to port "P" of the generator manifold.
When the generator is not operating, the generator control solenoid is de-energized. In this situation, supply oil is blocked at the spool of the generator control solenoid. As pressure increases in the system, supply pressure forces the flow compensator spool to shift against the combined force of the margin spring and signal pressure. Oil is then sent into the displacement piston cavity which causes the pump to destroke. As the swashplate angle decreases, the displacement piston uncovers a passage for oil to flow from the displacement piston cavity and into the pump case.
At this point, supply pressure decreases, and the combined force from the margin spring and signal pressure causes the flow compensator spool to shift. This shift closes the passage for supply oil to the displacement piston cavity, and the swashplate angle increases. Eventually, the load sensing spool reaches equilibrium, and the pump operates at low pressure standby. At low pressure standby, there is enough pump flow to make up for the leakage in the system. System pressure at low pressure standby is equal to signal pressure plus margin pressure.
Note: Low pressure standby is not independently adjustable. Low pressure standby may vary from one machine to another machine. Also, low pressure standby may vary in the same pump as system leakage or pump leakage increases.
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| Illustration 2 | g01596394 |
Generator Hydraulic System (1) Line to forward return manifold (2) Line to port "A" of cooler manifold (3) Generator motor (4) Flow control valve (5) Generator control solenoid (6) Generator manifold (7) Relief valve (8) Line to tee on right propel pump (9) Displacement piston cavity (10) Line from hydraulic tank port "2" (11) Bias piston cavity (12) Generator pump (13) Pressure compensator spool (14) Flow compensator spool | |
When the generator control switch is in the ON position, the generator control solenoid is energized. Pump supply oil flows through the flow control valve and across the generator control spool. The flow control valve can be adjusted in order to control the frequency of the generator.
Downstream from the generator control spool, supply oil is sent out of port "LS" to the pump controls. Supply oil is also sent out of port "A" from the generator valve to the generator motor. As the pump supply oil attempts to overcome the restriction of the generator motor, the pressure in the load sensing line increases. The increased signal pressure is sent to the flow compensator spool in the pump which causes the spool to shift. The shift closes the passage for supply oil to the displacement piston cavity, and the swashplate angle increases.
The generator motor begins to turn. Generator operation produces power in the high voltage circuits. Eventually, the system reaches equilibrium. At this point, the pump flow is held at a level which is adequate to fulfill the system load and the system flow requirements.
If the signal pressure reaches the setting of the pressure compensator spring, the pressure compensator pilot valve opens. The compensator pressure is set at 25000 ± 690 kPa (3630 ± 100 psi). When this valve opens, the load sensing pressure is limited. This action causes the pump to destroke until equilibrium is again established.
If the pressure reaches 30300 kPa (4400 psi) during operation, the relief valve opens. This relief valve is a fast acting valve. The valve quickly relieves pressure in the system. The valve prevents the generator from surging.