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Service Manual
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Chapter 9 - Cooling systemCooling System................................................................................................................................................. 9-2
1 Adjusting ........................................................................................................................................... 9-21.1 Specifications ......................................................................................................................... 9-2
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9 Cooling System
On the hydraulic excavator R 9250, the engine coolant is cooled in radiators, which are ventilated by one coo-ling fan.
The cooling fan is driven hydraulically by the pump P6.1 that supplies one hydraulic motor MF1.
The hydraulic oil is cooled in radiators, which are ventilated by one cooling fan.
The cooling fan is driven hydraulically by the pump P6.2 that supplied one hydraulic motor MF2.
General data :
* This data are valid when engine runs at nominal speed.
R 9250Oil cooling
R 9250Water cooling
Cooling pump Type Combi pump A11VO75DRX+A11VO75DRX
Nominal RPM*Pump delivery max*Pump flow max*Pump flow max hydraulically adjusted*
min-1cm
l/minl/min
222674280183
222674280183
Hydraulic motors Nb / Type 1 / FMF 90 1 / FMF 90
Nominal RPM* min-1 1200 1150
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9.1 Schematic
9.1.1 Electric schematic
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Schematic
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A1019
B2
B3
B14
B67
E1038
F148
S74
U16
X1-1
X71
X76
X77
X81
X135
X300
X811
X812
X846
X858
Y10_1
Y10_2
Kl31
+24V
Regulation plate
Transmitter / engine coolant temperature
Transmitter / coolant level
Transmitter / hydraulic oil level
Transmitter / hydraulic oil temperature
Connection box regulation
15A Fuse / A1019
Safety switch engine Flow
Electronic box BST
Connector 24 poles / U16 BST
Connector 24 poles / A1019
Connector 2 poles / A1019
Connector 4 poles / A1019
Connector 7 poles / A1019
Connector 40 poles / U16 BST
Kl31 electronic ground E1005
Connector 2 poles / Y10_1
Connector 2 poles / Y10_2
Connector 31 poles / U18 Quantum
Connector 24 poles / E1038
Solenoid valve / water ventilator
Solenoid valve / oil ventilator
Ground
Circuit 24 V
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Schematic
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9.1.2 Hydraulic
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CP2
CP4
CP5
CP6
MF1
MF2
P3
P6.1
P6.2
SP
SU1
Y10.1
Y10.2
Lower collecting pipe / support control valves
Collecting pipe before oil cooler
Collecting pipe after oil cooler
Collecting pipe for control valves
Oil fan motor
Water fan motor
Working pump Nb. 3
Water cooler fan pump
Oil cooler fan pump
Suction pipe
Servo oil unit
Regulation solenoid valve : water fan
Regulation solenoid valve : hydraulic oil fan
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Location of the components
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9.2 Location of the components
Cooling pumps P6.1 and P6.2
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Regulation solenoid valves Y10.1 and Y10.2
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Location of the components
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Hydraulic motor FMF and cooling fan
Regulation plate (A1019) Transmitter for hydraulic oil level (B14) and tem-perature (B67)
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Electronic box BST (U16)
Regulation connection box (E1038) Hydraulic manual operation (E1004)
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9.3 Functional description
The variable displacement pumps P6.1 and P6.2 supply oil to the constant volume hydraulic motors FMF forcooler fan driven. The control pressure for the pumps displacement regulation is generated by the regulationsolenoid valves Y10.1 and Y10.2.
These valves control the pressure applied on the pressure cut off valve and so the pump angle. The openingof the regulation solenoid valves Y10.1 depends on the engine coolant temperature and others parameters(see next temperature regulation). The opening of the regulation solenoid valves Y10.2 depends on the hy-draulic oil temperature (see next temperature regulation).
Each hydraulic motor FMF is equipped with a suction valve to prevent cavitation and with a pressure cut offvalve to prevent mechanical damages if the corresponding fan is blocked.
9.3.1 Hydraulic pumps
9.3.1.1 DescriptionThe pump A11VO75DRX is described in the hydraulic pump A11VO75DRX
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9.3.1.2 RegulationThe operation of the engine cooling pump and the hydraulic oil cooling pump are the same, and the regulationpressure values are the same too.
The regulation solenoid valves Y10.1 and Y10.2 are installed between the port Fa (replenishing pressure)and the regulators.
We use here the pump P6.2 to describe the functioning.
Pressure regulationThis regulation allows to adjust the pump flow in function of the pump high pressure Hd.
The pump high pressure is applied on the regulator 24.2 via a disk. The spring is adjusted so that the pressure delivered by the pump drives the motors (and so the fans) at
the prescribed speed. While the nominal value of the pressure is not reached, the regulator 24.2 connects the bottom side of the
control piston 21.1 to the pump high pressure Hd via the regulator 24.2 through the throttle 21.3. Thepump is then swivelled out.
As soon as the nominal pressure value in the circuit is reached, the pump high pressure Hd pushes theregulator 24.2 to the right. The regulator 24.2 connects the bottom side of the control piston 21.2 to thepump high pressure Hd via the regulator 24.2 through the throttle 21.4. The pump is then swivelled in andthe equilibrium is reached.
Flow regulationThis regulation allows to adjust the pump flow in function of the opening of the regulation solenoid valves. Thesolenoid valves receive a regulating current from the BST depending on recorded parameters (the fuel tempe-rature, the coolant temperature and the air intake manifold temperature for Y10.1, the oil temperature forY10.2). See next temperature regulation.
Acting like a variable throttle, the regulation solenoid valve Y10.2 changes the pilot pressure (30 bar) intothe positioning pressure (Pst).
The positioning pressure (Pst) is applied on the regulator via a circle (this surface is bigger as the crownsurface on which the pump high pressure Hd is applied).
Depending on its position (and so on the value of the positioning pressure), the regulator 24.2 makes thevalue of the regulation pressure (Preg) change. It connects the bottom side of the control piston 21.1 orthe control piston 21.2 either with the pump high pressure Hd or with or with the tank pressure. The pumpis then swivelled out or back until a new equilibrium is reached.
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Situation for cold temperature
When the machine is cold, the current on Y10.2 is maximal, Y10.2 is opened. The positioning pressure is maximal and thanks to the high pressure the regulator 24.2 is pushed to the
right. Then the bottom side of the piston 21.2 is connected to the high pressure via the regulator 24.2. As the rode side of the piston 21.2 is connected to the high pressure, the pump swivels to minimum angle. The fan speed is minimal.
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Situation for intermediate temperature
When the temperature of the machine increases, the current on Y10.2 decreases and Y10.2 gets partiallyclosed.
Y10.2 acts as a throttle on the pilot pressure. The pilot pressure applied on regulator 24.2 side decreases. The spring partially pushes the regulator 24.2 to the left. The pressure applied on the bottom side of the
control piston 21.2 decreases. So the piston 21.1 moves to the right, and the piston 21.2 move to the left. The pump swivels out to a greater angle. The fans speed increases until a new balance with the tempe-
rature is reached. The fan speed is intermediate.
Situation for hot temperature
When the temperature of the machine reaches the upper limit, the current on Y10.2 has a minimum value.Y10.2 get completety closed.
The positioning pressure becomes very low. The spring pushes the regulator 24.2 completely to the left. The pressure applied on the bottom side of the control piston 21.2 decreases. So the piston 21.1 moves
completely to the right, and the piston 21.2 move to the left. The pump swivels out to maximum angle. The fan speed reached its maximum value.
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9.3.2 Temperature regulation
9.3.2.1 Hydraulic oilThe hydraulic oil temperature sensor B67 and the hydraulic oil level sensor B14 are situated on top of the hy-draulic tank.
The resistance of the sensor B67 is changing in relation with the hydraulic oil temperature in the tank.
The first BST (U16) receives this resistance value and convert it in a temperature value in C (see graphR=f(T)).
The BST supplies the RSV Y10_2 with a regulating current, which depends directly of the hydraulic oil tempe-rature. The responses I (RSV for Y10_2)=f(T) are pre-programmed in the BST unit U16 (see graph IY10.2 =f(T)).
This current is used to regulate the pump because the solenoid valve Y10.2 acts as a variable throttle and con-trols the pressure applied on the pressure cut off valve. This allows to control the positioning piston and thenthe pump angle. Consequently, the fan speed is directly controlled by the BST.
A green light diode on the regulation connection box E1038 lights up if there is current on Y10.2. This diode isused to check rapidly if there is a problem in the electrical circuit.
At the start, the current supplying Y10.2 is blocked at 500 mA during one minute. The regulation works normallyafter one minute. This makes some oil flow in the cooling circuit at the start.
In case of safety operation (by pushing the switch S74), the relay on the plate A1019 is energised and the cur-rent on RSV Y10_2 is open circuited. The RSV is closed thus the pump swivels out to maximum angle. In thiscase, the fans turn at maximum speed.
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9.3.2.2 Engine coolantThe QUANTUM system receives several parameters from censors located on the engine. Three parametersare used to regulate the fan speed :
the fuel temperature the coolant temperature the air intake manifold temperature
The QUANTUM system calculates a pulse wide modulated signal (PWM) depending on the values of themeasured parameters.
If the temperature is below the low regulation limit (fan on with low speed), the PWM is equal to the maximum(95%).
Between the two regulation limits (low and high), the signal decreases in relation with the most important pro-portion between the measured value and the low and high limits in all the three temperature ranges. It meansthat the QUANTUM system calculates the lower PWM of the measured parameters.
Above the high limit value (fan on with full speed), the PWM signal is equal to 5%.
The lower PWM (which corresponds to the most unfavourable parameter of the three measured parameters)is then sent to the regulation plate A1019. This plate converts the PWM signal in an analogical signal. The va-riation of the intensity of this signal is proportional to the PWM between 5% and 95%. This signal is then am-plified by the BST and is sent via the plate A1019 to the regulation solenoid valve Y10.1.
At the start, the current supplying Y10.1 is blocked at 500 mA during one minute. The regulation works normallyafter one minute. This makes oil flow in the cooling circuit at the start.
In case of safety operation (by pushing the switch S74), the relay on the plate A1019 is energised and the cur-rent on RSV Y10_1 is open circuited. The RSV is closed and thus the pump swivels out to maximum angle. Inthis case, fans turn at maximum speed.
Schematic of the temperature regulation
Fuel tem-perature
Coolant tem-perature
Air intake mani-fold temperature
PWM 24V/256Hz A1019 Y10_1
Low regulation value / 86 C 54 C 95 % 18 mA 880 mA
High regulation value 68 C 94 C 83 C 5 % 1 mA 250 mA
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Relation between measured values and PWM
Pulse Wide Modulated 5%Warning : the values of this graphic are indicative
Pulse Wide Modulated 95%Warning : the values of this graphic are indicative
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Relation between PWM and IA1019 and IY10.1
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Troubleshooting
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9.4 Troubleshooting
9.4.1 Overheating in the hydraulic oil cooling circuit
The fan turn at the nominal speed
NY Check the cooling circuit (oil level, exchanger core dirty,
fan blades, ...). The air circulation is disturbed.
Disconnect the regulation solenoid valve(RSV). Fan should now turn at nominalspeed.
N
Y Reconnect the RSV and check the intensity at the RSV. Therelation between intensity and temperature is correct (seecurve I(RSV)=f(T)).
NY
Replace the RSV
Check the transmitter resistance. The relation between tem-perature and transmitter resistance is correct, see curveR=f(T) for oil transmitter.
N Y
The transmitter is defec-tive. Replace the trans-mitter
Check the BST.Replace the BST if neces-sary
Check the maximum oil pressure of thepump and compare it with the valuegiven in the schedule Specifications(see 5). The pressure is well adjusted.
YN
Adjust the pressure at the prescribed value (see 5)
Close off Fa port on the pump. The fanspeed increases to the right value
NY Regulating solenoid valve is defective or leaking. Replace
the RSV.
Measure the oil flow in the circuit. Therelation between this oil flow and the fanspeed is correct (see curve Q=f(N)).
NY The hydraulic pump volumetric efficiency is poor. Change
the pump if necessary.
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9.4.2 Overheating in the engine cooling circuit
The hydraulic motor volumetric effi-ciency is poor if the point is below andright of the wear limit line (curve Q=f(N)).Change the motor if necessary
The fan turn at the nominal speed
N
Y Check the cooling circuit (coolant level, exchanger core dirty, fan blades, ...) The coolant flow in the exchanger is disturbed (for example, the thermostat on the engine
can be defectuous). The air circulation is disturbed.
Disconnect the regulation solenoidvalve (RSV). Fan should now turnat nominal speed
Y Reconnect the RSV and check the intensity at the RSV. The intensityvalue is approx. 250 mA.
NY
Replace the RSV
Check the square signal from the Quantum with an oscilloscope or a voltmeter in direct cur-rent. The value is approx. 5%24 = 1,2V.
N
Y
Check the intensity at A1019 output. The value is approx.1mA.
N Y
Check the BST andreplace it if necessary
Check the plate A1019plate and replace it ifnecessary
The trouble was cause by the Quantum or the censors. Replace the Quantum or the sen-sors or get the engine monitoring system repaired by a Cummins representative.
Check the maximum oil pressure of thepump and compare it with the value given inthe schedule Specifications (see 5).The pressure is well adjusted.
YN
Adjust the pressure at the prescribed value (see 5).
Close off Fa port on the pump. The fanspeed increases to the right value.
NY
Regulating solenoid valve is defective or leaking. Replace the RSV.
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Troubleshooting
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Measure the oil flow in the circuit. The rela-tion between this oil flow and the fan speedis correct (see curve Q=f(N)).
NY
The hydraulic pump volumetric efficiency is poor. Change the pump if necessary.
The hydraulic motor volumetric efficiency ispoor if the point is below and right of thewear limit line (curve Q=f(N)). Change themotor if necessary
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9.5 Adjusting
9.5.1 Specifications
Maximum pressure P6.1 (engine cooling) bar 250
Maximum pressure P6.2 (oil cooling) bar 250
Fan speed for engine cooling RPM 1200
Fan speed for oil cooling RPM 1200
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9.6 Components description
9.6.1 Hydraulic pump A11VO75DRXThe variable displacement pump A11VO75DRX comprises two units arranged in tandem and designed as axialis piston swash plate pumps. It is used to supply hydraulically auxiliary circuit (such as the cooler fan motorson excavator R 9250).
Axial piston pumps are energy converters : they transform mechanical energy into hydraulic energy by theiraxially directed pistons in a cylinder housing.
The pistons with glide shoes rotate on the swash plate. Because of the adjustable inclination of the gliding sur-face, a corresponding piston stroke in the cylinder is created, and thus the adjustable flow of the hydraulicpump.
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9.6.1.1 Construction of variable displacement pump A11VOThe variable displacement pump A11VO comprises two units arranged in tandem and designed as axial pistonswash plate pumps.
The pump is consisting of six main parts :
The central housing 3.0 with suction and pressure ports also contains the control pistons 20.1 and 21.1 forthe both pump units.
The both complete pump gears 20 and 21. The both pump regulators 23 and 24, which are mounted to the connector housing 3.0. The closing flange 11.
The pumps gears (shaft, cylinder and pistons) are driven by the Diesel engine via the coupling.
The variable displacement pumps are supplied with hydraulic oil via the suction ports S in the central housing3.0. It delivers hydraulic oil into the working circuits via connection A.
The leak oil from the pumps flows via the leak oil connection T to the tank.
The regulators 23 / 24 control the swivel angle, and thus the oil delivery of the pump units via the positioningpiston 20.1 / 20.2 / 21.1 / 21.2. The position of these pistons depends on the pump high pressure, and also onexternal control pressures, which are connected to the regulator. These external control pressures are differentaccording to the regulation type.
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3.0
11
20
21
23
24
Central housing
Closing flange
First pump
Second pump
First pump regulator
Second pump regu-lator
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9.6.1.2 Function of hydraulic pump
Function of the pump power gearThe input shaft 1.10, with bearing mounting in the pump gear 11, drives the cylinder 1.11. Nine pistons 1.9 aremounted parallel around the driving shaft in the cylinder.The piston bottoms are ball shaped and set in the slideshoes 1.16. They are held by return plate 1.14 and return ball 1.13 on the swivelling, but not rotating swivelcrossbar 1.2 with thrust washer 1.15.
The slide shoes 1.16, mounted hydraustatically on the thrust washer 1.15 (via bore holes in the pistons andslide shoes) reduce the large sliding surface between the slide shoes and the thrust washer to a minimum.
When not under pressure, the cylinder 1.11 is pressed against the control lens 1.12 by the springs 1.17, ins-talled in the return ball 1.13. As pressure increases, cylinder and control lens are so well balanced by hydraulicforces, that even at high loads an oil film is maintained on the surfaces of the control lens, while at the sametime leak oil is kept to a minimum. Part of the leak oil is used to lubricate all moving parts and then flows exter-nally to the tank.
If the cylinder 1.11 turns, the pistons 1.9 move in a double stroke from the lower to the upper limit and thenreverse. The stroke is carried out in relations to the swivel angle of the swivel crossbar 1.2 and is responsiblefor the flow volume.
The axial piston unit moves the oil via kidney shaped control inlets in the control lens 1.12. Four of the movingpistons draw oil through the kidney shaped oil inlets on the suction side of the pump. The other four pistonsdisplace the oil which is supplied via the kidney shaped oil outlets to the pressure side of the pump, moving oilvia connection A into the hydraulic system. A ninth piston is moving either at the upper or the lower limit, atdead center, i.e. just changing directions.
Pump displacementThe control pistons 20.1 and 20.2, connected with the swivel crossbar 1.2, displace the pump from maximumto minimum swivel angle. The regulator 23 controls the displacement of the control piston 20.1 and 20.2 whileconnecting their large surface either with high pressure of the pump, or with tank pressure.
According to the regulation type, the control procedure of the pump swivel angle by the control piston is diffe-rent. For exact description, refer to part cooling system.
11.11.21.91.101.111.121.131.141.151.161.171.191.231.241.251.261.27
Pump gear completePump housingCrossbarPiston with glide shoeDriving shaftCylinderControl lensReturn ballReturn plateSlide plateSlide shoeSpringPlugO-ringAdjustable stopHex. head nutAdjustable stopHex. head nut
1111.111.2
20.120.1020.1120.12
20.220.2020.2120.22
2323.123.2
Closing flangeO-ringO-ring
Control pistonControl piston (first part)Pin (second part)Spring
Control pistonControl piston (first part)Pin (second part)Spring
RegulatorRegulator solenoid valvePlug
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9.6.1.3 Function of hydraulic pump
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9.6.2 Hydraulic fixed displacement motor FMF
Oil motor - type FMF 90
Max. oil volumeMax. permissible leak oil quantity
at 320 barat 150 bar
90 cm
//
Torques values :Allen head screw 14 620 Nm
(M20 10.9)
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9.6.2.1 DescriptionThe FMF fixed displacement motor is used to drive cooling fans. The axial piston motor is designeed as aswash plate type motor.
Axial piston motors are energy converters : they transform hydraulic energy into mechanical energy by theiraxially directed pistons in a cylinder housing.
The pistons with glide shoes rotate on the swash plate. Because of the inclination of the gliding surface, a pistonstroke is created in the cylinder, and thus the constant flow volume of the oil motor.
9.6.2.2 Function of oil motor, see diagrammHousing 12 contains nine pistons, which are located parellel in relation to the output shaft 3. The pistons arecontained in cylinder 4, which is connected by gears to the output shaft 3. The end of each piston 5 is designedas a ball joint, which is mounted in glide shoe 5.1. They are held against the fixed swash plate 6 by the retainerplate 7 and the return ball 8.
The hydrostatic support (oil film) between the glide shoes 5.1 and the fixed swash plate 6 (due to drillings inpiston 5 and glide shoes 5.1) reduces surface pressure between the glide shoe and the swash plate.
In a no load or pressureless condition, the cylinder 4 is pressed against the control lens 9 by spring 8.1, whichis installed in return ball 8. As the system pressure increases, cylinder 4 and control lens 9 are so well balancedby hydraulic forces that even at high loads an oil film is maintained on the surfaces of the control lens as wellas on the glide shoes. At the same time, leak oil kept to a minimum. Part of the leak oil is used for lubricationof all moving parts and then returned to the tank via an external line.
If pressurized oil enters at connection A or B, four pistons 5 are pressurized via kidney shaped inlets in thecontrol lens 9. On the opposite side, four more pistons 5 push the low pressure return oil through kidney shapedinlets in control lens 9 and connection A or B to the tank. A ninth piston is at dead center, which means at thepoint or reversing direction.
Once the oil pressure reaches the four pistons on the pressure side, a certain force is created by oil pressureand piston surface. This force is transferred via piston 5 and glide shoe 5.1 onto the swash plate 6.
This radial force, which uses cylinder 4 as a lever, created the torque, which is transferred via cylinder 4 to theoutput shaft 3. The amount of torque is in direct proportion to the system pressure, which means high pressure= high torque. By applying oil to the opposite port (connection A or B), the torque and direction of the hydraulicmotor is reversed (right or left turn).
During a complete revolution of cylinder 4, pistons 5 perform a dual stroke from the lower dead center to thetop dead center and reverse. This stroke depends on the inclination of the swash plate 6 and influences the oilquantity.
The displacement of the hydraulic motor remains the same until the oil supply from the variable flow pumpschanges.
9.6.2.3 Maintenance and repairsLiebherr hydraulic motors are maintenance free.
For resealing and repair work see the Repair instructions for Liebherr fixed displacement oil motors FMF.
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23455.16788.19101213
Roller bearingDrive shaftCylinderPistonGlide shoeSwash plateRetainer plateReturn ballSpringControl lensDowel pinHousingConnector plate
141516171819222324262728
Allen head screwCover ringShaft sealO-ringO-ringO-ringSnap ringSnap ringPinNeedle bearingSpacerSpacer
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