IMPLEMENT AND STEERING HYDRAULIC SYSTEM CONTINUED
Control Valve (Winch)
Winch Control Valve (Reel In)
When the machine is equipped with a winch, the winch control valve is at the top of the valve stack. The winch
control valve controls the operation of the winch motor. The control valve is equipped with these components:
control valve spool, resolver, flow control valve, and load check valve.
The winch control valve is spring centered. The control valve spool is a closed center spool and a pilot operated
spool with three positions: REEL IN, HOLD, and REEL OUT. A spring keeps the spool in HOLD position when the
winch motor is not active. Movement of the spool is controlled by the pilot control system. The pilot control system
connects the winch control lever to the control valve spool.
The resolver is a double check valve. The flow control valve limits the maximum flow of oil to the winch motor. The
functions of the resolver and of the control valve spool are described in the sections on positions of the control
valve. The description of the function of the load check valve is in a separate section.
a. Load Check Valve
The load check valve prevents reverse oil flow in the winch motor, which can cause circuit drift or load loss. The
load check valve does not open until pump oil pressure in chamber #3 becomes greater than the combined forces
of the spring for the load check valve and of the oil pressure in the passage.
b. HOLD Position
When all the control valve spools are in the HOLD position, pump oil fills the parallel oil passages of the control
valves. The pump maintains oil pressure at 435 psi (3,000 kPa). Signal oil passage, chamber #1, and resolver are
drained. Reel out passage, reel in passage, and passage are blocked.
c. REEL IN Position
When pilot control pressure causes the control valve spool to move to the REEL IN position, signal oil passage is
opened to reel in passage. Winch oil from the reel in passage flows through the signal oil passage to chamber #1.
The oil functions as signal oil. Part of the signal oil flows to chamber #2 behind the flow control valve. The signal oil
opens the flow control valve. The rest of the signal oil flows through the resolver to the inlet manifold.
The increase of pump oil flow to the inlet passage flows through the primary metering holes into chamber #3.
The pump oil opens and directs oil through the load check valve. The oil flows through the passage, around the
control valve spool, and through the passage to the winch motor. The winch then reels in the cable.
Return oil from the winch motor flows through the reel out passage, around the control valve spool, and through the
outlet passage to the tank.