Jacobsen AR3, Техническое руководство по ремонту

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5-4 4181384 First Edition
HYDROSTATIC POWER TRAIN
5
Theory of Operation and
Sub-Circuit Schematics
Traction Circuit Forward Schematic
and Theory of Operation
See Figure 5-3.
System Conditions:
• Engine running
• Mow valve off
• Park brake released
• Traction pedal depressed (forward position)
Charge Pressure Circuit
Operating pressure oil from the cutting unit pump enters
the mow and brake valve at port “CP” and is directed to
the pilot line circuits of the relief valve, mow solenoid
valve, and the load control valve.
Operating pressure oil flows through the valve and exits
the mow and brake valve at port “MP” and flows to the
hydraulic oil filter. Oil flows through the oil filter, enters the
traction drive pump at port “E,” and is routed to the pilot
line of the charge pressure relief valve and to the traction
drive circuit/pump. The charge pressure relief valve
regulates the charge pressure applied to the traction
drive circuit/pump. If the incoming charge pressure oil
reaches 160 psi (11 bar), the charge pressure relief valve
will open, releasing excess flow to the hydraulic tank.
Park Brake Circuit
The front wheel motors are equipped with multi-disk wet
brakes. The brakes are spring-applied, and released with
charge pressure oil controlled by the brake solenoid valve
in the mow and brake valve.
The park brake circuit is equipped with a lever-operated
park brake release valve to allow the release of the
brakes with a dead engine for towing purposes. The park
brake release valve is normally in the operating position,
directing the charge oil from the mow and brake valve to
the brake pistons in the front wheel motors to release the
parking brakes.
When the park brake release lever is moved to the
released position, the oil passage from the mow and
brake valve is closed, and the passage is opened to the
steering cylinder. This oil pathway provides a means to
release the parking brakes with the engine off by turning
the steering wheel, routing oil from the steering circuit to
the parking brake to release the brakes.
Traction Pump Circuit
The traction drive pump receives a supply of filtered,
charge pressure oil from the charge pressure circuit.
When the traction pedal is moved to the forward position,
the engine-driven traction pump supplies operating
pressure oil in parallel to the front wheel motors, and in
series to the rear wheel motor from port “B” of the traction
drive pump, resulting in full time three-wheel drive. Oil
from the rear wheel motor returns to the traction drive
pump through port “A” and back into the closed-loop
traction pump circuit. The traction drive circuit is
protected by a system relief valve. This valve will open,
venting excess oil flow to the hydraulic tank if the
pressure rises to 3046 psi (210 bar).
Flushing Valve
The flushing valve is used to remove hot oil from the
closed-loop traction drive circuit when moving forward.
Oil lost due to venting through the flushing valve is
replenished by the incoming charge pressure oil at port
“E” of the traction drive pump.
When driving forward, operating pressure oil is routed to
the pilot line of the flushing valve, shifting the valve spool
and opening the valve. Hot oil from traction drive pump
port “A” and the wheel motors flows through the flushing
valve, through the orifice, and is routed through the oil
cooler and back to the hydraulic oil tank.