ENGINE AR 4P1085 - Caterpillar

Illustration 1 g00878212
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) Drive pin (12) Springs (13) Shaft spool (14) Crossover relief valve (A) Control section (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.Crossover relief valves (14) protect the steering cylinders from high pressures.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 flow to the steering cylinder in this position. In the NEUTRAL position, the oil that flows into the control section is blocked in passage (3) .The pump has a port for the load sensing signal. The line from this port is connected to the priority valve. Refer to Systems Operation, "Priority Valve" for the operation of the priority valve.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. 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), drive 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 drive pin (11) .This allows shaft spool (13) to turn inside sleeve (8). As the shaft turns, the small holes align with the grooves. The alignment of these holes and grooves provides the path for oil flow to gerotor (6) and to the steering cylinder. Centering springs (12) are compressed, when