797B Off-Highway Truck Fan Drive Hydraulic System: Makeup Valve (Fan Motor)

Location of the makeup valve for the piston motor for the fan drive (1) Pressure tap (2) Makeup valve for the piston motor for the fan drive (3) Supply line from the piston pump for the fan drive(4) Return line

The makeup valve (2) for the piston motor is mounted behind the lower right section of the radiator.

Makeup valve for the piston motor for the fan drive (5) Return port (6) Passage (7) Check valve (8) Supply port from the cooling piston pump (9) Passage(10) Spring

The supply oil flows from the piston pump through the makeup valve to the piston motor. Return oil also flows from the piston motor through the makeup valve.
Return oil from the piston motor is used as makeup oil. When the fan stops operating, the makeup oil is used to prevent a vacuum condition in the piston motor.
When the control valve for the piston pump signals the piston pump to destroke, the supply of oil to the piston motor is reduced. The piston motor continues to rotate due to the mass of the fan blade assembly. Continued rotation of the piston motor creates a vacuum at passage (9) of makeup valve (2). This vacuum lowers the pressure in passage (9). The combined force of the pressure in passage (9) and the force of spring (10) is less than the force of the pressure that is in passage (6). Check valve (7) will open.
When check valve (7) is open, return oil from passage (6) flows to passage (9). The return oil enters the piston motor through line (8). This makeup oil circuit eliminates the possibility of cavitation in the piston motor.
The same process occurs when the machine is shut down.
A pressure tap (1) is located on makeup valve (2). The pressure tap is used in order to measure the pressure of the piston pump.

Piston Motor (Fan Drive)

Back of the engine radiator (1) Fan motor(2) Speed sensor (fan drive)

Fan motor (1) is a fixed displacement axial piston motor. The fan motor is operated by the pressure oil from the variable displacement piston pumps. The fan motor is directly attached to the fan.
Fan speed sensor (2) provides an input signal to the Brake/Cooling ECM. The Brake/Cooling ECM uses this input in order to maintain the fan speed between 0 and 817 rpm.

(3) Speed sensor (4) Port to case drain (5) Plate (6) Piston (7) Center pin (8) Port plate (9) Shaft (10) Housing (11) Barrel(12) Plate

The components of the motor that turn are shaft (9) , plate (5) , pistons (6) , and barrel (11) . The parts that do not turn are plate (12) , housing (10) , and port plate (8) .
Pump oil flows through the inlet control slot in plate (12) to port plate (8) then into the piston bores in barrel (11) . Barrel (11) rotates about center pin (7) which is at a fixed angle of 40 degrees to the axis of shaft (9) .
The oil inside housing (10) is used to lubricate all the bearings and the moving parts. This oil drains from housing (10) through case drain line (2) .

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797B Off-Highway Truck Fan Drive Hydraulic System: Makeup Valve (Fan Motor) 2013-01-25T19:44:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown