Toro 4100-D service manual Engine Cooling Fan Circuit, Forward Direction Fan Operation

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

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.

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1

Figure 14

1. Gear pump 2. Fan drive manifold

	REVERSE DIRECTION SHOWN
TO RESERVOIR
	TO STEERING		TO LIFT/LOWER
	CIRCUIT		CIRCUIT
M1	M2		L
P1	T	P2	FAN DRIVE
			MANIFOLD
			FROM GEAR PUMP
TO OIL COOLER

Figure 15

Hydraulic System

Groundsmaster 4100--D Page 4 -- 25 Hydraulic System