TURBOCHARGER GP 7C9392 - Caterpillar

Illustration 1 g00557813
Typical example of the metering pump for the steering (1) Outlet to tank, (2) Metering pump inlet check valve, (3) Inlet from pump, (4) Passage, (5) Passage from Gerotor, (6) Gerotor, (7) Passage to Gerotor, (8) Sleeve, (9) Makeup valve, (10) Drive, (11) Pin, (12) Springs, (13) Shaft spool, (A) Control section and (B) Pump sectionThe metering pump (steering) has two main sections, control section (A) and pump section (B). These two sections work together in order to send oil to the steering cylinder. The metering pump is located in the front of the cab behind a panel near the steering column.Both the direction of a turn and the speed of a turn are controlled by the metering pump. As the steering wheel is turned faster, there is an increase in the flow of oil to the steering cylinder. The increased flow of oil to the steering cylinder causes the steering cylinder to move farther. The increased flow of oil also causes the steering cylinder to move faster. This causes the machine to turn faster.When the steering wheel is not being turned, control section (A) is in the NEUTRAL position. The metering pump is a closed center valve so there is no alignment between the passages in the spool and orifices in the sleeve in this position. In the NEUTRAL position, the oil that flows into control section (A) flows through orifices to the hydraulic tank. This allows cooler oil to enter the metering pump.The pump has a port for the load sensing signal. The line from this port is connected to the priority valve. Some of the flow of the inlet oil that is in the NEUTRAL position also flows back to the priority valve. This oil keeps the spool in the priority valve slightly open. This oil keeps the spool ready for a quick response to steering demands.When the steering wheel is turned for a right turn, pump oil opens check valve (2) and flows into the metering pump through inlet (3) and passage (4). The oil flows from passage (4) into gerotor (6) through passage (7). As the steering wheel turns, gerotor pump (6) turns. This causes the flow of oil from the pump. The oil flows through passage (5). The oil is then directed to the steering cylinders through the right turn port.As the oil flows out to the cylinder through the right port for a right turn, return oil from the cylinder is coming back into the metering pump through the left port. This oil is sent to the tank through outlet (1) .When the steering wheel starts to turn, shaft spool (13), pin (11) and drive (10) also start to turn. Sleeve (8) does not start to turn at the same time as the spool because the diameter of the holes in the sleeve are slightly larger than the diameter of pin (11) .This allows shaft spool (13) to turn inside sleeve (8). As the shaft turns, the small holes align