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Friday, January 25, 2013

797B Off-Highway Truck Fan Drive Hydraulic System: Fan Drive Hydraulic System


Hydraulic System


Fan drive hydraulic system
(1) Fan drive motor
(2) Makeup valve
(3) Fan drive pump
(4) Pump drive
(5) Pressure reducing valve (fan drive)
(6) Oil filter (case drain)
(7) Solenoid and relief valve
(8) Oil filter (steering and fan drive)
(9) Oil cooler (steering and fan drive)(10) Hydraulic tank

Location of Components

JSM1-168
Left side view of fan drive lines
(2) Makeup valve
(3) Fan drive pump
(4) Pump drive
(5) Pressure reducing valve (fan drive)
(6) Oil filters (case drain)
(7) Solenoid and relief valve(10) Hydraulic tank
JSM169-UP
Left side view of fan drive lines
(2) Makeup valve
(3) Fan drive pump
(4) Pump drive
(5) Pressure reducing valve (fan drive)
(6) Oil filters (case drain)
(7) Solenoid and relief valve(10) Hydraulic tank
Rear view of fan drive lines
(1) Fan drive motor
(2) Makeup valve(11) Radiator

Operation

Oil flows from fan drive pump (3) through makeup valve (2) to fan drive motor (1). Oil flows from the motor through makeup valve (2). The oil flows from makeup valve (2) through oil filters (8) and oil cooler (9). The oil flows from oil cooler (9) to hydraulic tank (10) for the steering and fan drive.
Fan drive motor (1) is a fixed displacement motor. The fan speed is determined by the amount of flow from fan drive pump (3). Fan drive pump (3) is a variable displacement piston pump that is controlled by the Brake/Cooling ECM.
Case drain oil flows from fan drive motor (1) and fan drive pump (3) through oil filter (6) to the steering and fan drive hydraulic tank.
If the supply oil to the fan stops suddenly, the fan and the motor may continue to rotate because of the mass of the fan. Makeup valve (2) allows the oil in the circuit to flow from the return side to the supply side. This prevents a vacuum in the lines on the supply side.
Pressure reducing valve (5) utilizes steering system pressure in order to keep the fan speed below 10 rpm in cold weather. The fan speed should never be 0 rpm.
Fan speed is controlled by the Brake/Cooling ECM. Fan speed will vary depending on many inputs.
The minimum fan speed will be below 10 rpm. The minimum fan speed will occur when all of the temperature inputs are cold.
The following inputs determine the fan speed:

  • Jacket water coolant temperature
  • Aftercooler coolant temperature
  • Transmission lube temperature
  • Torque converter outlet oil temperature
  • Brake oil temperature
  • Brake status
  • Ground speed
  • Output status of the hoist system
Table 1
Standard Fan Speed Control Limits (RPM)
106 Inch Fan    
Engine Speed    Non-Retarding Fan Speed Limit    Retarding Fan Speed Limit    
1250 or Less    339    525    
1300    353    525    
1450    394    525    
1500    407    525    
1600    434    525    
1700    461    525    
1750 or more
   		475    525    

Refer to Table 1 for the fan speed limits that are based on the temperature sensor inputs, the ground speed and the retarding/braking inputs.
Table 2
Engine Fan Control, Non-Retarding Or Retarding Below 4 MPH
106 Inch Fan (1)    
Aftercooler Temperature    Jacket Water Coolant Temperature    Transmission Lube Temperature    TC Out Temperature    Brake Oil Temperature    Fan Control    
Priority 1    2    3    4    5       
<
65 °C (149 °F)    		<
88 °C (190 °F)    		<
88 °C (190 °F)    		<
88 °C (190 °F)    		<
102 °C (215 °F)    		Off    
<
65 °C (149 °F)    		<
99 °C (210 °F)
>
88 °C (190 °F)    		<
96 °C (204 °F)
>
88 °C (190 °F)    		<
102 °C (216 °F)
>
88 °C (190 °F)    		<
107 °C (225 °F)
>
102 °C (215 °F)    		Modulate By Priority    
>
65 °C (149 °F)    		>
99 °C (210 °F)    		>
96 °C (204 °F)    		>
102 °C (215 °F)    		>
107 °C (225 °F)    		"Limit Chart"    
( 1 )When you use Retarding/Braking 4 mph and above 4 mph will set the fan speed to the "limit chart".

Refer to Table 2. If all of the temperature sensors are below the lower limits, then the fan control is turned off and the fan speed could be near 0 rpm. If the temperatures are between the sensor's lower limits and the sensor's upper limits, then the fan speed will be modulated by priority. If any of the temperatures are above the upper limits, the fan speed will be set to the limits that are shown in Table 1.
Note: When the body is being raised or lowered, the fan speed will be 200 rpm in order to reduce the load on the pump drive.



If you need more information, You can visit:
http://www.cat.com

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