TM 5-3810-300-24 & P2
Steering Control Valve.
Turning effort applied to the steering wheel of the vehicle actuates the steering control valve, which in turn directs
hydraulic fluid from the pump directly to the cylinder located in the steering linkage.
The valve piston is centered automatically by the hydraulic force against the reaction rings. When the operator's effort at
the steering wheel exceeds the hydraulic force at the reaction ring, the control valve is actuated and the hydraulic power
is provided for power steering.
Whenever the valve piston is in center (neutral) position the oil pressure at the cylinder ports of the valve is low. Under
this condition there is no circulation of oil through the lines to the power cylinder. The oil is circulating, however, from the
pump, through the valve and to the reservoir with sufficient pressure only to overcome the resistance due to friction in
the valve, lines, and fittings.
When the effort in turning the steering wheel of the vehicle overcomes the centering effect of the force against the
reaction rings the valve piston is moved axially to restrict the flow of oil to one of the cylinder ports. At the same instant,
the passage in the second cylinder port is opening thus causing an immediate increase in pressure in one of the ports at
the power cylinder which supplies power for steering.
While the oil under pressure is entering one end of the cylinder, the oil from the discharge end of the cylinder is returning
through the first cylinder port in valve and into the return port, back to the reservoir.
Full pressure in the steering system is obtained with a valve piston travel of about thirty-five thousandths (.035) of an
inch. The slightest movement of the piston however, causes a pressure differential at the valve cylinder ports. When the
effort at the steering wheel is released the valve piston returns to center position.
Whenever the steered wheels are subjected to shock loads the movement of the steering linkage tends to actuate the
valve in the drag link momentarily. This action moves the valve piston axially in the appropriate direction thereby
diverting the hydraulic fluid to the proper side of the power cylinder piston to resist the forces of tie shock. This blocking
action prevents "kickbacks" at the steering wheel and stabilizes the steering.
Power Steering Pump.
The power steering pump is capable of pumping power steering fluid to the system. The pump is engine driven, and
produces 8 GPM at 1200 RPM. The pump is of the gear type with a drive gear assembly and driven gear assembly. A
flow control and relief valve is in the pump.
Flow Control Valve and Relief Valve. The primary purpose of the Flow Control and Relief Valve is to limit fluid flow (7
GPM) to the steering control valve.
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