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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
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
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
Forward Direction Fan Operation
Oil flow from the gear pump is sent through the
Reverse Direction Fan Operation (Fig. 15)
The
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 |
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 | Page 4 | Hydraulic System |