PULLEY 6I4713 - Caterpillar

Load Sense Signal, Example Using Left Turn Steering
Illustration 1 g03591692
Armed, Left TurnThis example uses the left hand steer function. This load sense example is typical for all valve functions. (1) Tilt cylinders (2) Tilt-in solenoid (3) Tilt-out solenoid (4) Lift cylinders (5) Manual lower valve (6) Lift solenoid (7) Lower solenoid (8) To pilot manifold port "LS VLV" (9) Steer-right solenoid (10) Steer-left solenoid (11) Steering cylinders (12) Thermal bypass manifold (13) Hydraulic oil cooler (14) Hydraulic oil filter (15) From oil fill pump (16) From fan manifold "T" (17) Line relief and makeup valves (18) Compensator spool (19) Control spool (20) Resolver (21) Pilot accumulator (22) Accumulator charging valve (23) Margin relief valve (24) Load-sensing relief valve (25) From loading manifold port "P1" (26) Resolver (27) Control spool (28) Steering priority valve (29) From loading manifold port "LX"This example uses the left hand steer function. This load sense example is typical for all valve functions.When steer-left solenoid (10) is energized, the spool of the solenoid creates a passage for pilot oil to flow to control spool (27) in the steering valve section.The pilot oil causes control spool (27) to shift. The shifted spool directs oil into the signal network and directs oil out port "A" of the steering valve. From port "A" oil flows into the head end of right steering cylinder (11) and the rod end of the left steering cylinder.The pressure in the line from port "A" of the steering valve increases. This pressure is felt in the signal line. The pressure in the signal line acts against resolver (26) in the steering valve and also acts against steering priority valve (28), in conjunction with a spring. The steering priority valve ensures that the steering circuit receives sufficient pump flow to execute the desired turn.The resolver (26) in the steering valve compares the signal pressure in the steering circuit to signal pressure (29) from the loading manifold. This resolver directs the higher of the two pressure signals to the next resolver. The resolvers in the implement circuit are connected in series. The first resolver in the series is located in the steering section of the implement control valve. The series of resolvers continues through the lift section and tilt section of the implement control valve. From there, the signal continues to the resolver network of the attachment sections of the implement control valve.Note: Refer to System Operation, "Work Tool System" for additional information about the attachment sections.Each successive resolver in the series compares the highest pressure from the previous resolvers in the series to the pressure requirements at the current valve section. Ultimately, the highest signal pressure acts on the following components:
load-sensing relief valve (24)
margin relief valve (23)
compensator spool (18) in each valve sectionLoad-sensing relief valve (24) limits the load-sensing signal to a maximum of 24,200 kPa (3510 psi). Margin relief valve (24) limits the maximum pressure differential between the pump outlet pressure and signal pressure to 4000 kPa (580 psi).This load-sensing signal transfers out port