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| Illustration 1 | g01220954 |
Gear Pump (Pilot) (1) Piston pump (Implement, Steering, Brake). (2) Gear pump (pilot). (3) Line to control manifold for pilot and differential locks. | |
Gear pump (2) is located in piston pump (1) . Gear pump (2) supplies pilot oil to the pilot hydraulic system.
Gear pump (2) is a fixed displacement gear pump. Gear pump (2) is driven by piston pump (1) . The output from the pilot pump is approximately 19 L/min (5 US gpm) .
The pilot pump has two internal gears that are tightly fit into the pilot pump housing. The drive gear is connected directly to the input shaft. The idler gear is meshed with the drive gear inside the housing. Both gears rotate with very tight tolerances on all sides.
Each gear has a side plate on both sides. The side plates sandwich the gears. The side plates, drive gear, idler gear, and the pump housing create the pumping chamber.
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| Illustration 2 | g00789321 |
Operation of the Gear Pump (A) Inlet port. (B) Outlet port. (4) Cavity. (5) Idler gear. (6) Drive gear. (7) Pump housing | |
Oil flows into the chamber through inlet port (A) . When the gear teeth separate, a partial vacuum is formed. Oil fills the cavity between the teeth at inlet port (A) . The gears rotate and the gears carry oil from inlet port (A) around the circumference of the pump to outlet port (B) . Oil is carried around the circumference of the pump in cavity (4) which is created between gear teeth and the pump housing. Oil is forced out of the space in the gear teeth as the gears mesh at outlet port (B) .
Note: Oil cannot return to inlet port (A) in cavity (4) . Idler gear (5) and drive gear (6) are interlocked together. This forces all of the oil out of the cavity.