Engine Cooling Fan Circuit - Toro Groundsmaster 4700-D Service Manual

Engine Cooling Fan Circuit

A four section gear pump is coupled to the piston (trac-
tion) pump. The gear pump section P4 (farthest from the
piston pump) supplies hydraulic flow for the hydraulic
engine cooling fan motor (Fig. 24).
The fan control manifold controls the operation of the hy-
draulic motor that drives the engine cooling fan in addi-
tion to including the flow divider for the steering and lift
circuits. The electronically controlled proportional relief
valve (TS) in the manifold controls the oil flow to the fan
motor. The fan control manifold controls the speed and
direction of the fan motor based on electrical output from
the TEC--5002 controller.
Oil flow from the gear pump to the cooling fan motor is
controlled by the proportional relief valve (TS) in the fan
control manifold. This valve adjusts fan circuit flow
based on a PWM (Pulse Width Modulation) signal from
the TEC--5002 controller. The controller uses engine
coolant and hydraulic oil temperatures as inputs to de-
termine the proper PWM signal for the TS valve. The fan
circuit flow determines the speed of the cooling fan mo-
tor.
The fan motor runs at half speed until coolant reach-
o
es approximately 165
creases to full speed (approximately 2800 RPM) as
o
coolant reaches 180 F (82
The fan motor automatically reverses if coolant
o o
reaches 203 F (95 C) or hydraulic oil reaches 212
o
(100 C).
If the fan motor is stalled for any reason, the manifold
proportional relief valve (TS) has a secondary function
as a circuit relief to limit fan motor pressure to 3000 PSI
(207 bar).
When the engine is shut off, the over--running inertia
load of the fan blades keeps driving the fan motor and
turns it into a pump. The check valve (CV) in the fan con-
trol manifold will open to keep the motor circuit full of oil
so the fan motor will not cavitate.
NOTE: If PWM current is not available to the fan control
manifold proportional relief valve (TS), the cooling fan
motor will run at full speed in the normal (forward) direc-
tion.
Forward Direction Fan Operation
Oil flow from the gear pump is sent through the de--ener-
gized solenoid valve S1 to rotate the cooling fan motor.
Return flow from the motor re--enters the manifold (port
M2), through the de--energized solenoid valve S1, out of
the manifold (port T) and then is routed through the deck
control manifold, oil cooler and oil filter.
Groundsmaster 4500--D/4700--D
o
F (74 C). The fan motor in-
o
C).
o
Page 4 - - 31
Reverse Direction Fan Operation (Fig. 25)
The TEC--5002 controller can reverse the cooling fan to
clean debris from the rear intake screen. If hydraulic oil
and/or engine coolant temperatures increase to an un-
suitable level or if the engine cooling fan switch is
pressed to manual reverse, a high PWM signal is sent
to the TS valve to slow the cooling fan and direct pump
oil flow away from the fan motor. The controller then en-
ergizes solenoid valve S1 in the fan control manifold to
reverse cooling fan motor oil flow so that the motor runs
in the reverse direction. A lower PWM signal is sent to
the TS valve allowing oil flow to return to the fan motor
but in the reverse direction causing the motor and cool-
ing fan to run in reverse for a short time.
NOTE: The fan reversal process is not designed to
clean the radiator of debris. Refer to Operator's Manual
for radiator cleaning maintenance recommendations.
2
3
F
1. Gear pump
2. Fan control manifold
REVERSE
DIRECTION
TO RESERVOIR
FROM GEAR
PUMP (P4)
4
1
Figure 24
3. Fan circuit supply hose
4. Hydraulic fan motor
TO STEERING
CIRCUIT
TO LIFT/LOWER
CIRCUIT
TS
FROM GEAR
PUMP (P3)
TO OIL COOLER
Figure 25
Hydraulic System