Simulation of the Clutch Hill Start Test - gtisoft.com · the clutch type) the pressure plate away from the flywheel to remove the diaphragm spring fingers’ pressure from the clutch

Simulation of the Clutch Hill Start Test

Cem Erbaş 20.10.2014

Contents 1 Purpose of the Simulation 2 Operation Principle of Clutch 3 Testing and Procedure 4 Theory 5 Simulation 6 Assumptions 7 Test and Simulation Results 8 DOE 9 Conclusions

1 Purpose of the Simulation 2 Operation Principle of Clutch 3 Testing and Procedure 4 Theory 5 Simulation 6 Assumptions 7 Test and Simulation Results 8 DOE 9 Conclusions

The simulation targets to determine and optimize the parameters that heavily influence the heat dissipation in the clutch during the vehicle launch.

The simulation aims to prevent possible thermal damages in the clutch without performing the vehicle tests. The preparations and expenses throughout the test are high.

Purpose of the Simulation

Procedures and preparations for the test are complicated. There was no tool available to simulate the test within Ford.

2 Operation Principle of Clutch 3 Testing and Procedure 4 Theory 5 Simulation 6 Assumptions 7 Test and Simulation Results 8 DOE 9 Conclusions

1 Purpose of the Simulation

Operation Principle of Clutch

When the driver depresses the clutch pedal, the clutch release system actuates and the clutch release bearing pushes (or pulls, depending on the clutch type) the pressure plate away from the flywheel to remove the diaphragm spring fingers’ pressure from the clutch disc. This allows the clutch disc to run free, and disengages the engine from the transmission.



• It is made sure all equipments work properly before the test.

• The driveline properties are selected to ensure that the wheel

traction force is at a minimum.

• The test is performed on a hill.

• Thermocouples are placed in the clutch housing. The test

begins when the air within the clutch housing is at 80 celsius.

• The driver changes the gears (first gear), drives the vehicle,

stops it, and waits for 60 seconds. Then runs the vehicle again.

• This cycle is repeated with certain cycles.

• The temperature from the sensors are measured at each step

and evaluated at the end of the test.

Testing and Procedure

Thermocouples inside clutch housing

PROCEDURE

Testing and Procedure

Type Road Truck – Vehicle 1 Mixer – Vehicle 2 Tractor – Vehicle 3

Test date [dd.mm.yyyy] 01.11.2013 28.02.2014 19.03.2014

Drive 8x2 8x4 4x2

Wheelbase [mm] 5500 5100 3600

Outside temperature [°C] 10 10 21

Trailer No No Yes

Max engine torque [Nm] 1300 2000 2300

Max power [PS] 330 420 460

Engine displacement [L] 9 11.3 12.7

Number of cylinders 6 6 6

GTM [kg] 35500 41000 43000

Final drive ratio 4.63 3.76 2.85

First gear ratio 9.48 13.8 13.8

Slope [%] 10 10 10

Dynamic tire radius [mm] 524 524 526



Theory • The torque that a clutch can transmit from the engine is obtained by the equation below:

• The resistance torque caused by the driveline and the vehicle during the vehicle launch is:

• Due to the difference between the engine torque and the resistance torque, slipping occurs,

and heat energy is generated. The thermal energy heats up the frictional components. The

dissipated energy heats the air within the clutch housing, and the clutch housing in return.



Simulation

Basic Model The complete model consists of five sections mainly, each one is linked to each other accordingly.

Simulation

Clutch Clutch frictional mass Clutch housing mass Clutch surface area Clutch housing surface area Material types Clutch sizes Clutch lining’s friction coefficient vs temperature Heat transfer coefficients Clutch inertias

INPUTS

Vehicle Transmission gear ratios Driveshaft Halfshafts Differential - FDR Gross total mass of the vehicle Driveline inertias Tyre properties – tyre sizes Center of gravity of the vehicle Aerodynamics Rolling force

Driver Driveaway duration Gas & clutch pedal modulation Driver’s aggression

Environment Road type & grade Ambient temperature Wind, rain etc.

Engine Engine inertia 3D torque map Engine speed

Acceleration pedal and clutch pedal (Clutch modulation)

Simulation

• 3D engine lookup map (engine rpm vs gas pedal vs engine torque) is

inserted into engine section. According to the pedal inflection, the clutch

benefits the torque.

• According to the given clutch & gas modulation time, the heat energy

dissipation may change and it can be seen whether the engine stalls.

Engine Torque Map

Simulation

3D engine lookup map (engine rpm vs gas pedal vs engine torque)

Clutch mechanical section

Simulation

Engine side and transmission side inertias, clutch dimension, friction

properties

Clutch mechanical section

Improvement

Simulation

The coefficient of the friction of the clutch linings was considered constant

in the previous versions of GT-SUITE (before V7.3).

The variation of the friction coefficient with respect to temperature has

been implemented by GT upon request by Ford Otosan.

This variation is crucial for the dissipated heat energy in the clutch.

Clutch thermal section

Simulation

Clutch mass and surface areas, clutch housing mass and surface areas,

heat transfer coefficients.

Vehicle section

Simulation

Complete powertrain, including brakes and road.

Control section

Simulation

The model is controlled by a GT-Driver model. The Driver targets a certain speed,

brakes, stops and waits. This step is repeated multiple times according to Ford

Otosan Inhouse Test Procedure



Assumptions

The gas pedal inflection percentage is considered approximately at 80%, which was also observed during various tests around the same level

The clutch housing’s surface area and mass are approximated to their actual values, slight changes have been made for the correlation.

The conductive and convective heat transfer coefficients are kept constant according to the approximate temperature value

Engine speed has a range such that it gives approximately around the maximum amount of torque for the given gas pedal position, due to the fact that it was observed during various tests.



Test and simulation results



DOE

DOE evaluation is carried out from the correlated model in GT-SUITE.

The driveline equation (vehicle side torque of the clutch) is as follows. Balances vehicle side output torque from clutch with inertia of the entire driveline and retarding forces on the vehicle.

DOE setup is constructed such that the parameters having square of the factors have three levels to catch the parabolic curve for the best result. 432 cycles are performed in DOE as a result.

Factor Unit Min Median Max # of Levels 1st gear ratio - 12.8 13.8 14.8 3

FDR - 2.7 2.85 3 3 GVM kg 40000 45000 2 Grade % 10 - 12 2 Tyre size mm 458 492 526 3

Ambient temp. °C 10 - 30 2 Max. clutch torque Nm 2040 - 2240 2

DOE

The effects of the vehicle properties on the clutch housing temperatures can be seen in the main effects plot. The contribution of the ambient temperature has the least effect on the clutch housing temperatures.

Main Effects Plot

DOE

It can be seen that the transmission ratio effects the energy dissipation in the clutch the most.

Pareto Chart

DOE

The combined effects of the parameters on the clutch housing temperatures are seen in the interaction plot

Interaction Plot



Conclusions

The expenses and preparations made for the test are eliminated with virtual development. Therefore; physical vehicle tests are no longer required and thermal risks are eliminated before the validation

The robustnesses of different clutch types are now able to be compared w/o vehicle testing to predict optimal design solution at further development activities Driveline properties like final drive ratio; gear

ratios can be optimized while controlling the dissipated heat in the clutch. Their effects of magnitutes are calculated in DOE. This will yield less fuel consumption as a result.

Software can be updated to predict impact torques applied to driveline system since clutch pedal vs acceleration pedal response modelled. (Bump stop test; etc)

Various driver profiles are created to predict the effect of a driver abuse. AMT (Automated transmissions) strategy present optimal torque build up and clutch lift off during pullaway which minimize clutch energies. This model consider AMT strategy as a professional driver to achieve optimal energies.

The tool is implemented to heavy trucks. But can also be implemented to passenger cars as well, which is less complicated and take less time.

Acknowledgments

Çağkan Kocabaş (Ford) Nikolaos Papadopoulos (Gamma Technologies) Jonathan Zeman (Gamma Technologies)

Thank You

We Care

Simulation of the Clutch Hill Start Test - gtisoft.com · the clutch type) the pressure plate away from the flywheel to remove the diaphragm spring fingers’ pressure from the clutch

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