Engine Cooling Fan Circuit - Toro Groundsmaster 4500-D Service Manual

Engine Cooling Fan Circuit

A four section gear pump is coupled to the piston (trac-
tion) pump. The final gear pump section (farthest from
the piston pump) supplies hydraulic flow for the hydrau-
lic engine cooling fan motor.
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 (PRV) 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 section to the cooling fan
motor is controlled by the proportional relief valve (PRV)
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 en-
gine coolant and hydraulic oil temperatures as inputs to
determine the proper PWM signal for the PRV valve.
The fan circuit flow determines the speed of the cooling
fan motor.
The fan motor runs at half speed until coolant reach-
o
es approximately 165 F (74
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 cooling fan motor is stalled for any reason, the
manifold proportional relief valve (PRV) has a secon-
dary 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 (PRV), 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 section is sent through the
de--energized solenoid valve S1 to rotate the cooling fan
motor. Return flow from the motor re--enters the man-
ifold (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
C). The fan motor in-
o
C).
o
F
Page 4 - - 31
Reverse Direction Fan Operation (Fig. 24)
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 a manual fan reversal is requested via
the InfoCenter display, a high PWM signal is sent to the
PRV valve to slow the cooling fan and direct pump oil
flow away from the fan motor. The controller then ener-
gizes solenoid valve S1 in the fan control manifold to re-
verse cooling fan motor oil flow so that the motor runs in
the reverse direction. A lower PWM signal is sent to the
PRV valve allowing oil flow to return to the fan motor but
in the reverse direction causing the motor and cooling
fan to run in reverse for a short time.
NOTE: The fan reversal process is designed to clean
debris from the rear screen but not the radiator. Refer to
Operator's Manual for radiator cleaning maintenance
recommendations.
TO RESERVOIR
M1 M2
S1
CV
G2
G1
PRV
P1 T
FROM GEAR
TO OIL
PUMP SECTION COOLER
Figure 24
REVERSE
DIRECTION
TO STEERING
CIRCUIT
ST
50/50 FLOW
DIVIDER
FD
L
TO LIFT/LOWER
CIRCUIT
P2
FAN CONTROL
MANIFOLD
FROM GEAR
PUMP SECTION
Hydraulic System