CONTROL GP-MONITOR 1419780 - Caterpillar

Illustration 1 g01279669
Typical example of the metering pump for the steering
(A) Control section
(B) Pump section
(1) Outlet to tank
(2) Metering pump inlet check valve
(3) Inlet from pump
(4) Crossover relief valve
(5) Drive
(6) Stator
(7) Rotor The 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 (4) 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 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 a check valve and flows into the metering pump through inlet (3). The oil flows into the gerotor pump (B). As the steering wheel turns, gerotor pump (B) turns. 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) and drive (5) also start to turn. Sleeve (8) does not start to turn at the same time.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 (B) and to the steering cylinder. Centering springs are compressed, when the spool moves in relation to the sleeve.When the steering wheel is not turning, centering springs move the spool and centering springs move the sleeve to a NEUTRAL position. When the rotation of the steering wheel is stopped, the wheels stay in that position.The steering wheel must be turned in the opposite direction in order to make a left turn. The steering wheel must be turned in the opposite direction for travel that is straight.When the steering wheel is turned for a left turn, oil flows into inlet (3). Oil flows to the gerotor pump (B). Oil flows from gerotor