TUBE AS 3N1328 - Caterpillar

Steering Pump
Illustration 1 g03669062
(1) Steering pump
(2) Pump control valve
(3) Flow control adjustment
(4) High-pressure cutoff adjustmentThe steering pump (1) is a variable displacement, piston-type pump mounted to the front of the torque converter pump drive housing on the right side. The pump contains a single actuator to move the swashplate. Pump control valve (2) controls the pump oil flow. The pump control valve contains the flow control adjustment (3) and the high-pressure cutoff adjustment (4).Steering Pump and Pump Control Valve
Low Pressure - Standby
Illustration 2 g06064996
Low-pressure standby
(1) Flow compensator spool
(2) Actuator piston
(3) Flow from the steering control valve
(4) Bias spring
(5) High-pressure cutoff spoolWhen, the engine is started and the steering pump has no demand for steering oil. The bias spring (4) moves the actuator piston (2), which holds the swashplate at maximum angle. When, the steering control valve (3) is in the "HOLD" position, pump flow is blocked at the steering control valve, and no signal pressure is generated. As the pump produces flow, the system pressure begins to increase. This pressure is felt at the left end of the flow compensator spool (1). The flow compensator spool moves against spring force and permits system oil to flow to the actuator piston.The actuator piston moves the swashplate to the "LOW PRESSURE STANDBY" position. In"LOW PRESSURE STANDBY", the pump produces enough flow to compensate for system leakage at sufficient pressure to provide instantaneous response when the steering control valve is moved.Steering Pump -Upstroke
Illustration 3 g06064998
Upstroke
(1) Flow compensator spool
(2) Actuator piston
(3) Flow from the steering control valve
(4) Bias spring
(5) High-pressure cutoff spoolDuring a turn, signal pressure at the steering control valve (3) increases. This increased pressure causes the force (flow compensator valve spring plus oil pressure) at the right end of the flow compensator spool (1) to become greater than the pump supply pressure at the left end of the spool.The increased pressure at the right end of the flow compensator spool causes the spool to shift left. The spool reduces or blocks pump output oil flow to the actuator piston (2), and opens a passage to drain. Reducing or blocking oil flow to the actuator piston reduces or eliminates the pressure acting against the actuator piston. When the