Engine Cooling Fan Circuit - Toro Groundsmaster 4000-D Service Manual

Engine Cooling Fan Circuit

A four section gear pump is coupled to the piston (trac-
tion) pump. The gear pump section farthest from the pis-
ton pump supplies hydraulic flow for the fan drive
manifold and hydraulic engine cooling fan motor (Fig.
14).
The fan drive 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 drive manifold controls the speed and di-
rection 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 (PRV) in the
fan drive manifold. This valve adjusts fan circuit pres-
sure and flow based on a PWM (Pulse Width Modula-
tion) signal from the TEC--5002 controller. The controller
uses engine 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 and thus, the speed of the cooling fan.
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 drive
manifold will open to keep the motor circuit full of oil so
the fan motor will not cavitate.
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 oil
cooler and oil filter.
Reverse Direction Fan Operation (Fig. 15)
The TEC--5002 controller can reverse the cooling fan to
clean debris from the radiator, oil cooler and rear intake
screen. If hydraulic oil and/or engine coolant tempera-
tures increase to an unsuitable level, a high PWM signal
is sent to the (PRV) valve to slow the cooling fan and di-
rect pump oil flow to the reservoir. The controller then
energizes solenoid valve (S1) in the fan drive manifold
to reverse cooling fan motor oil flow so that the motor
Groundsmaster 4000--D
runs in the reverse direction. A lower PWM signal is sent
to the PRV valve allowing oil flow to return to the fan mo-
tor but in the reverse direction causing the motor and
cooling fan to run in reverse. The controller determines
the length of time that the fan should be run in reverse
before fan rotation is returned to the forward direction.
2
1. Gear pump
REVERSE DIRECTION SHOWN
TO RESERVOIR
M1 M2
P1
TO OIL COOLER
Page 4 - - 25
1
Figure 14
2. Fan drive manifold
TO STEERING TO LIFT/LOWER
CIRCUIT CIRCUIT
L
T P2 FAN DRIVE
MANIFOLD
FROM GEAR PUMP
Figure 15
Hydraulic System