SHIELD 7N4476 - Caterpillar

Illustration 1 g06056161
(1) Hydraulic oil cooler
(2) Joystick control
(3) Implement Valve
(4) Lift cylinder
(5) Tilt cylinder
(6) Implement pump pressure sensor
(7) Pilot Valve
(8) Accumulator
(9) Hydraulic tank and filter
(10) Implement pump
(11) Brake charge/pilot pump
(12) Cooler bypass valveThe implement hydraulic system controls the operation of the blade.The implement hydraulic system is composed of the following systems: the implement electronic control system, the pilot hydraulic system, and the hydraulic system.The hydraulic tank is common to all the systems.For more detailed component locations refer to System Operation, "Location of Components (Hydraulic System)"The basic operation of the hydraulic system works in the following manner.The operator turns the key start switch to start the machine. The implement pump and the pilot/brake pump supply hydraulic oil for the implement system.The operator enables the implement pilot system with the implement lockout switch that is on the right-hand console. When the pilot system is enabled, the implement is ready to operate.When the operator moves the electrohydraulic control (2), a PWM (Pulse Width Modulated) signal is sent to the electronic control module. The Electronic Control Module (ECM) sends a PWM driver to the appropriate solenoid valve on the implement valve (3). The PWM driver activates the solenoid valve to vent pilot oil from the pilot control actuator.When the pilot oil is supplied to the pilot control actuator, the spool in the implement valve (3) will shift. When the spool shifts, oil that flows from the implement pumps will flow to the respective hydraulic circuit.When the position of the electrohydraulic control (2) is changed, the PWM signal that is sent to the ECM will also change. The ECM changes the corresponding PWM driver to control the corresponding solenoid on the implement valve (3). The change of PWM driver will result in a change of position for the spool in the main control valve.Implement Electronic Control SystemThe implement electronic control system performs the following functions:
The implement electronic control system electronically controls the implement valve solenoids.
The implement electronic control system allows communication between the electronic control modules.
The implement electronic control system displays information to the operator.The implement electronic control system is made up of the following components: electrohydraulic control (2), implement electronic control module , Caterpillar data link, Caterpillar Monitoring System, pilot on/off solenoid valve, implement solenoid valves and pressure/temperature sensors.Reference: For additional information on the implement electronic control system, refer to System Operation, "Electronic Control (Hydraulic System)".Pilot Hydraulic SystemThe pilot hydraulic system provides pilot oil to the main control valve to actuate the spools of the main control valve.The pilot hydraulic system is made up of the following components: the pilot/brake pump, pressure reducing valve (Pilot Oil), hydraulic oil filter and implement solenoid valves.Reference: For additional information on the pilot hydraulic system, refer to Systems Operation, "Pilot System Implement" for the machine that is being serviced.Main Hydraulic SystemThe main hydraulic system supplies hydraulic oil that is used to power the cylinders that move the implements.The main hydraulic system is made up of the following components: main control valve, lift cylinder, tilt cylinder, main relief