Toro 03781, Service Manual

Page: 95 / 468

Reelmaster 7000−D Hydraulic System Page 5 − 25
Engine Cooling Fan Circuit
A four section gear pump is coupled to the piston (trac-
tion) pump. The gear pump section P5 (farthest from the
piston pump) supplies hydraulic flow for the hydraulic
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 (FD) for the steering and
lift circuits. The electronically controlled proportional re-
lief valve (PRV) in the fan control manifold TS port con-
trols the oil flow to the fan motor. The fan control
manifold controls the speed and direction of the fan mo-
tor based on electrical output from the Toro Electronic
Controller (TEC).
Oil flow from the gear pump to the cooling fan motor is
controlled by the proportional relief valve (PRV) in the
fan control manifold TS port. This valve adjusts fan cir-
cuit flow based on a PWM (Pulse Width Modulation) sig-
nal from the TEC. The controller uses engine coolant
and hydraulic oil temperatures as inputs to determine
the proper PWM signal for the proportional relief valve.
The fan circuit flow determines the speed of the cooling
fan motor.
The fan motor runs at reduced speed until engine
coolant temperature reaches approximately 165F
(74C), or hydraulic oil temperature reaches 170F
(77C). The fan motor increases to full speed (approx-
imately 2800 RPM) as engine coolant temperature
reaches 180F (82C), or hydraulic oil temperature
reaches 195F (91C).
The fan motor automatically slows down and then re-
verses direction if engine coolant temperature
reaches 203F (95C) or hydraulic oil temperature
reaches 212F (100C).
If the fan motor is stalled for any reason, the manifold
proportional relief valve (PRV) 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 (fill with air).
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.
Fan Operation (forward/pull)
In the forward direction, the fan pulls air from outside the
engine compartment through the radiator and oil cooler.
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 manifold port M2,
passes through the de−energized solenoid valve S1,
out manifold port T, and then is routed through the mow
control manifold, oil cooler and return oil filter.
Fan Operation (reverse/push) (Fig. 17)
The TEC can reverse the cooling fan to push air from in-
side the engine compartment through the radiator and
oil cooler to clean debris from the rear intake screen. If
hydraulic oil and/or engine coolant temperatures in-
crease to an unsuitable level or if the engine cooling fan
switch is pressed to manual reverse, 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 energizes solenoid valve S1 in the fan control man-
ifold to reverse cooling fan motor oil flow so that the mo-
tor 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
the rear intake screen (not the radiator) of debris. Refer
to Operator’s Manual for radiator cleaning maintenance
recommendations.
Figure 17
REVERSE
DIRECTION
0.51 CID
T
TS
S1
CV
FD
P2 P1
ST
L
M1
50/50 SPLIT
FAN CONTROL
MANIFOLD
G2
G1
FAN
M2
MOTOR
Hydraulic
System