Textron Jacobsen SLF530, Repair Manual

Page: 213 / 352

HYDRAULICS
673831-Rev A 6-19
6
Mow Circuit (On) Schematic and
Theory of Operation
System Conditions:
• Engine running at fast idle
• Cutting units lowered
• Mow switch in the on position
• Backlap not active on the LDU
• Parking brake switch in the off position (parking brake
disengaged)
NOTES
• See (See “Mow/Backlap Circuit—Theory of
Operation” on page 4-29.) for the electrical operation
of this circuit.
• The function of each reel valve is the same, except
where noted.
Oil Supply to Reel Valves
Oil is drawn from the hydraulic tank through a 100-mesh
screen, and enters the gear pump, supplying oil to all
three pump sections. Sections 2 (rear reel) and 3 (front
reel) supply operating pressure oil to port “P” of the
corresponding reel valves.
Mow Circuit
Operating pressure oil supplied by sections 2 and 3 of the
gear pump enters the reel valve bodies at port “P” and is
routed to the pilot lines of the 2200 psi (152 bar) relief
valves, against the relief valves, and to the solenoid
valves. With the mow switch in the on position, the
solenoid valves shift, routing operating pressure oil
through port “A” to the reel motors in series, driving the
motors.
Circuit Relief
The mow circuit is protected by the 2200 psi (152 bar)
pilot-operated relief valves. The relief valve for the front
and center reel motors will open if the oil pressure in the
circuit reaches 2200 psi (152 bar), routing oil through the
front reel valve to the oil cooler, and then the hydraulic
tank. The relief valve for the rear reel motors will open if
the oil pressure in the circuit reaches 2200 psi (152 bar),
routing oil through the rear reel valve to the charge filter.
Oil Return
Oil returning from the motors enters the reel valves at
port “B” and flows through the solenoid valves, exiting the
valves at port “T.”
Front Reels: The oil from the front reel motors is routed
through the oil cooler to the hydraulic tank.
Rear Reels: The oil from the rear reel motors is routed to
the brake valve port “CHG” and the charge filter.
When the parking brake switch is in the OFF position, the
MCU will energize the brake valve solenoid coil, shifting
the solenoid valve. This allows charge pressure oil to flow
through the needle valve, against the 507 psi (35 BAR)
brake relief valve and hand pump check valve. Charge
pressure oil also flows out brake valve Port PB2 to the left
and right front wheel motors Port X. The charge pressure
oil will cause the brake piston to compress the brake
spring in the wheel motors, releasing the pressure on the
friction discs, allowing the wheel motors to rotate.
The charge filter is used to remove debris from the oil. If
the charge filter becomes plugged, the 25 psi (1.7 bar)
crack bypass will open, allowing oil to bypass the charge
filter.
Oil from the charge filter is routed to the traction pump to
fill the closed-loop traction circuit. Once filled, the
200 psi (14 bar) charge pressure relief valve will open,
allowing oil to return to the hydraulic tank.
Hydraulic oil is used to lubricate the internal components
of the reel motors.