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| Illustration 1 | g06301871 |
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Implement pump | |
The implement pump is a variable displacement axial piston pump that supplies hydraulic oil to the lift cylinders and the tilt cylinder. The pump operates between minimum displacement and maximum displacement.
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| Illustration 2 | g06302417 |
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Partial schematic of implement pump | |
The implement pump uses a swashplate that is driven by a single actuator (4) with two cylinders. The end of small cylinder (7) is connected to system pressure (A) from the discharge of the pump. In addition, small cylinder (7) has a bias spring (6) that assists in up-stroking the pump during low discharge pressure. The end of large cylinder (8) sees the modulated pilot pressure that is controlled by control spool (9) of the piston pump. The pilot pressure that is used to control large cylinder (8) is externally supplied. The pump displacement is controlled by a proportional current from the implement ECM to coil assembly (3) of the pump control valve.
The implement ECM supplies current to coil assembly (3). The current is proportional to the command from the lift control lever or the tilt control lever.
When a stall is detected and the lift function is active, the implement pump will de-stroke to 10% displacement. When a stall is detected and the tilt function is active, the implement pump will de-stroke to 10% displacement. This procedure is for stall conditions when a single function is active.
At full current that is approximately 1.8 amp, coil assembly (3) is fully energized. Control spool (9) is shifted to all the way to the left. Oil that is behind large cylinder (8) is vented to the case drain of the pump. The force that is developed by the pressure in small cylinder 7 shifts actuator (4) to the right. Swashplate (12) will upstroke to the maximum angle. At 1.8 amp of current to coil assembly (3), the pilot control valve will shift in order to develop maximum displacement.
While the engine is starting, implement ECM will send the maximum amount of current to coil assembly (3). The float solenoid valve will also be energized. This procedure sends implement pump flow to the tank to reduce the hydraulic load on the engine. After 11 seconds, implement ECM will provide normal implement control.
The inlet oil is charged by the super charger impeller. In addition, the pump has internal case flushing. Charged oil flows from the inlet to the case through orifice (5). Due to case flushing, flow of case drain oil from the pump depends on oil temperature, pump speed, and pressure differential between inlet pressure and case pressure. An increase in pump speed, an increase in oil temperature, or an increase of differential oil will increase the flow of case drain oil.