- Underground Articulated Truck:
- AD55B (S/N: JNW1-UP)
The hydraulic fan system information in the above manual is incorrect for AD55B (S/N: JNW117-127). Include the following information with the existing information.
Hydraulic Fan System
 | |
| Illustration 1 | g01937393 |
Hydraulic fan system schematic (1) Fan speed sensor (2) Hydraulic fan motor (3) Anti-cavitation valve (4) Fan demand valve (5) Case drain oil filter (6) Pump control valve (7) Pressure tap (8) Hydraulic fan pump (9) Hydraulic tank (10) Cat Monitoring System (11) Engine ECM (12) Power Train/Chassis ECM | |
The cooling system has a hydraulically driven fan, that is controlled by the hydraulic fan system.
The main components of the hydraulic fan system are; fan speed sensor (1), hydraulic fan motor (2), fan demand valve (4), case drain oil filter (5), pump control valve (6), hydraulic fan pump (8), hydraulic tank (9), Engine Electronic Control Module (ECM) (11) and Power Train/Chassis Electronic Control Module (ECM) (12).
 | |
| Illustration 2 | g01913814 |
Hydraulic fan pump (8) is mounted to the brake and pilot section of the hoist, brake and pilot pump.
Hydraulic fan pump (8) is a variable displacement piston pump.
Hydraulic fan pump (8) adjusts the fan speed in order to match the cooling demands of the system. Hydraulic fan piston pump (8) adjusts the fan speed by controlling oil flow to hydraulic fan motor (2) .
The hydraulic fan system controls the fan speed in order to provide the required amount of cooling air. During heavy machine usage or high ambient temperatures the hydraulic fan system will increase the fan speed. During light usage and lower ambient temperature the hydraulic fan system will maintain a lower fan speed. The hydraulic fan system controls the speed of the fan through the use of hydraulic fan pump (8) .
The oil flow from hydraulic fan pump (8) is controlled by fan demand valve (4) and pump control valve (6). Engine ECM (11) sends a Pulse Width Modulated (PWM) signal to the solenoid on fan demand valve (4). Fan demand valve (4) will control pump control valve (6). Pump control valve (6) will control the oil flow from hydraulic fan piston pump (8) proportionally.
Note: Maximum PWM signal results in minimum pump output. Minimum PWM signal results in maximum controlled pump output. No PWM signal results in maximum mechanical pump output.
The Engine ECM uses the hydraulic oil temperature sensor, the engine coolant temperature sensor, the engine intake air temperature sensor and the fan speed sensor to determine the PWM signal sent to the solenoid on fan demand valve (4) .
Maximum Fan Speed Operation
 | |
| Illustration 3 | g01913815 |
Hydraulic fan system (maximum speed) (1) Hydraulic fan piston pump (2) Case drain (3) Solenoid (4) Pump control valve (5) Spring (6) Suction (7) Spring (8) Outlet (9) Signal passage (10) Plunger (11) Fan demand valve (12) Signal line (13) Signal passage (14) Bias spring (15) Swashplate (16) Actuator piston (17) Pressure control spool (18) Pump control spool (19) Pump pressure line (BB) Cutaway section (CC) Component surface (FF) Activated components (GG) Tank oil (JJ) High pressure oil | |
When maximum fan speed is required, the Engine ECM sends minimum PWM signal to solenoid (3). Plunger (10) blocks signal passage (13). The force of spring (5) plus signal pressure in passage (9) holds pump control spool (18) downward.
When pump control spool (18) is held downward, the passage to actuator piston (16) is open to case drain (2). Case drain oil flows through the case drain oil filter to the hydraulic tank. The force of bias spring (14) moves swashplate (15) toward the maximum angle.
The maximum amount of oil flows from hydraulic fan pump (1) through outlet (8) to the hydraulic fan motor. The maximum oil flow to the hydraulic fan motor causes the fan to rotate at the maximum speed.
Pressure control spool (17) limits the maximum pressure in the hydraulic fan system. If the oil pressure overcomes spring (7), pressure control spool (17) moves upward. High pressure oil is allowed to flow to actuator piston (16) causing hydraulic fan pump (1) to destroke.
Minimum Fan Speed Operation
 | |
| Illustration 4 | g01937453 |
Hydraulic fan system (minimum fan speed) (1) Hydraulic fan pump (2) Case drain (3) Solenoid (4) Pump control valve (5) Spring (6) Suction (7) Spring (8) Outlet (9) Signal passage (10) Plunger (11) Fan demand valve (12) Signal line (13) Signal passage (14) Bias spring (15) Swashplate (16) Actuator (17) Pressure control spool (18) Pump control spool (19) Pump pressure line (BB) Cutaway section (CC) Component surface (FF) Activated components (GG) Tank oil (KK) Pressure reduction oil | |
When the engine is first started or when the machine is working in a cold climate, the required fan speed for cooling is low. Maximum PWM signal is sent to solenoid (3) .
When a slower fan speed is required, the Engine ECM increases the PWM signal to solenoid (3). Plunger (10) moves upward. When plunger (10) moves upward, signal passage (13) is opened to case drain (2). Case drain oil flows through the case drain oil filter to the hydraulic tank. The pressure in signal passage (9) at the top of pump control spool (18) reduces. The pressure at the bottom of pump control spool (18) overcomes the force of spring (5). Pump control spool (18) shifts upward. This allows pressure oil to flow to actuator piston (16) .
When pressure oil flows into actuator piston (16) the force of bias spring (14) is overcome. Swashplate (15) moves toward the minimum angle until equilibrium is reached between the pressure in actuator piston (16) and the force of bias spring (14) .
A decreased amount of oil flows from hydraulic fan pump (1) through outlet (8) to the hydraulic fan motor. The decreased amount of oil flow to the hydraulic fan motor causes the fan to rotate at a slower speed.
Hydraulic Fan Motor
 | |
| Illustration 5 | g01913817 |
Rear of the engine radiator (1) Anti-cavitation valve (2) Case drain (3) Hydraulic fan motor (4) Fan speed sensor | |
Hydraulic fan motor (3) is a fixed displacement piston motor. Hydraulic fan motor (3) is operated by pressure oil from the hydraulic fan pump. Hydraulic fan motor (3) is directly attached to the fan. Anti-cavitation valve (1) is installed in the hydraulic lines. Anti-cavitation valve (1) allows hydraulic fan motor (3) to stop gradually when the engine is stopped.
Fan speed sensor (4) provides an input signal to the Engine ECM. The Engine ECM uses this input in order to maintain fan speed between 0 and 1150 rpm.
 | |
| Illustration 6 | g01913818 |
(5) Housing | |
The oil inside housing (5) is used to lubricate all the bearings and the moving parts. This oil drains from housing (5) through case drain (2). Oil from case drain (2) flows through the case drain oil filter. Oil from the case drain oil filter flows back to the hydraulic tank.