caution - Toro

Engine Cooling Fan Circuit
A four section gear pump is coupled to the piston (traction)
pump. The gear pump section farthest from the piston
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 hydraulic
motor that drives the engine cooling fan in addition
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 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 (PRV) in the
fan drive manifold. This valve adjusts fan circuit pressure
and 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 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--energized
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.
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. 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 2. Fan drive manifold
TO RESERVOIR
1
Figure 14
REVERSE DIRECTION SHOWN
TO STEERING
CIRCUIT
M1 M2 L
TO LIFT/LOWER
CIRCUIT
Hydraulic
System
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 temperatures
increase to an unsuitable level, a high PWM signal
is sent to the (PRV) valve to slow the cooling fan and direct
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
P1
TO OIL COOLER
T
Figure 15
P2
FAN DRIVE
MANIFOLD
FROM GEAR PUMP
Groundsmaster 4100--D
Page 4 - 25
Hydraulic System