AutoFarm A5 - Theory of Operation

Hardware Installation Guide 11
2
Theory of Operation
This Theory of Operation chapter contains descriptions of AutoFarm component functional operations and their interactions
when implemented in Compact Valve Closed Center installations.
• AutoSteer Valve
• Oil Supply
• Right and left Steering Circuit
• Manual Override Sensor
• Load Sense
• Plugs and Orifices
• Closed Center Valve Installations Overview
• Closed Center Load Sense Installation
• Closed Center Power Beyond Installation
• Wheel Angle Sensor
AutoSteer Valve
Oil Supply
The steering valve receives high pressure oil from the pump at the PRESS port and returns low pressure oil back to tank
through the TANK port. A Load Sense pilot signal is sent out through the LS OUT port for stroking up a pump or priority
valve on machines that have variable flow pumps or a steering priority valve. A built-in Load Sense relief valve protects the
pump from over-pressure by limiting the maximum LS pressure signal from the AutoFarm valve.
Right and left Steering Circuit
A 12 volt proportional valve directs oil to either the Right or Left valve port for steering the vehicle. To make a left turn, an
electrical signal is sent to the “left” coil on the proportional valve. The spool inside the proportional valve then allows oil flow
between the PRESS port and the LEFT port while also allowing return oil flow from the RIGHT port to the TANK port.
To make a right turn, an electrical signal is sent to the “right” coil on the proportional valve. The proportional valve then
allows oil flow between the PRESS port and the RIGHT port while also allowing return flow from the LEFT port to the TANK
port. Steering speed is controlled by the voltage or PWM (pulse width modulation) signal sent to the proportional valve coils.
Higher voltages or higher PWM signals result in more spool movement and a higher oil flow through the proportional valve
and a faster steering speed.
Pilot operated check valves are present at the right and left steer ports, holding the vehicle’s steering cylinder in a fixed
position between steering commands while also isolating the valve’s LS circuit from the manual steering pressures while
manually steering.