(1) Work tool pump
(2) Hydrostatic pump
(3) Gear pump (charge oil)
The gear pump (charge oil) (3) is a fixed displacement gear pump. The gear pump (charge oil) supplies hydraulic oil to the fan motor, hydrostatic system, work tool control valve, and the accumulator for the work tool control valve. The gear pump (charge oil) will also supply oil to the quick coupler control if the machine is equipped with a quick coupler.
The gear pump (charge oil) (3) is mounted to the work tool pump (1). The work tool pump (1) is mounted to the front section of the hydrostatic pump (2).
When the pump is viewed from the drive end, the pump shaft rotates in a clockwise direction.
Typical Fixed Displacement Gear Pump
(4) Drive gear
(5) Idler gear
(A) Outlet (High pressure)
(B) Inlet (Low pressure)
A gear pump carries oil from inlet port (B) to outlet port (A) in the spaces between the gear teeth.
The drive shaft turns drive gear (4). The drive gear forces idler gear (5) to rotate. When the gear teeth separate, a partial vacuum is formed. Oil fills in the spaces between the teeth inlet port (B). The gears carry oil around the circumference of the pump to outlet port (A). A seal is formed by the gear teeth against the pump housing. Oil is forced out of the spaces between the gear teeth as the gear teeth mesh together at outlet port (A). Oil will not return to inlet port (B) because the meshing of the gears will fill the spaces between the gear teeth.
The flow rate of oil that is supplied by the pump is controlled by the rate of rotation of the shaft. The rotation rate of the shaft is in direct correlation to engine speed.