Modeling of Clutch Housing and Facing Temperature for Estimating Clutch Life of a Manual Transmission Vehicle Presented by: P Srinivasan Co-Authors: Dr. Saravanan Muthiah Vehicle Performance Simulation (VPS-COE) Powertrain Division (PTD) Mahindra & Mahindra Ltd 1
Introduction & Motivation Poor clutch life is a major issue for some vehicle models. Clutch overheating is the primary cause for clutch failure. The reasons include: Vehicle Overloading Heavy Traffic Riding of Clutch Pedal Incorrect Gear Selection Poor Low end torque 2
Impact of Clutch Temperature: Safe Zone High Clutch Wear Temp Clutch Failure Slip Torque Transfer Friction 3
Impact of Clutch Temperature: High Wear Rate Source: Technical Handbook, Valeo Transmission Systems. 4
Objective & Scope of the Study Estimate temperature rise on clutch facing & clutch housing. Objective: Optimize Clutch Design at an early stage of Product Development in conjunction with supplier provided data (facing temperature vs wear ratio) for different clutch materials. 5
Theory Behind the Simulation Model Torque Loss Transmitting torque from the engine (T) Resistance Torque (τ drv ) Drive Torque Clutch Slip T High Engine CSC (T Avg) T Low GB Clutch Housing Convection Dissipated Energy Thermal Energy Housing Dissipates Some Heat to Ambient Heats Up Air Within Clutch Housing Heats Up Frictional Components Heat Energy Generated 6
Theory Behind the Simulation Model Step (1): The torque that a clutch can transfer from an engine is obtained by the equation below: T. FOS = N f. R m. µ. F a T = Transmitting torque from the engine FOS = Factor of safety is 1.3 N f R m = Number of sliding surfaces (Single clutch=2; Twin clutch=4) = Clutch mean or effective radius µ = Friction coefficient of the clutch linings F a = Clamping load LuGre Friction Model This friction model is based on the idea of intermeshing bristles that transmit the friction load between contacting bodies. The bristle model captures micro slip and also the drop in friction as the sliding speed is increased. Clamp Load The load exerted by the diaphragm to clamp the clutch disc between pressure plate & flywheel 7
Theory Behind the Simulation Model Step (2): Resistance torque generated by the driveline & vehicle during vehicle launch is obtained by: τ drv = I trans1 + I trans2 R t 2 + F aer + F rol + F grd R d R t + I dsh R t 2 + + r whl I axl R 2 2 + M vehr whl d R t R 2 2 d R t 2 dω drv dt τ drv = Resistance torque dω drv = Angular speed of input shaft I trans = Transmission inertia R t = Transmission ratio I dsh I axl = Driveshaft inertia = Axle inertia R d F aer F rol = Final drive ratio = Aerodynamic resistance force = Rolling resistance force M veh = Vehicle mass F grad = Gradient resistance force r whl = Wheel dynamic rolling radius 8
Theory Behind the Simulation Model Due to clutch slip, heat energy is generated which increases the clutch facing temperature. The dissipated energy also heats the air within the clutch housing, which can be measured easily using thermocouple. Step (3): Clutch energy is calculated by using the below equation E = ti tc T t. ω t. dt E = Clutch energy; ti = Initial temperature tc = Critical temperature; T t = Torque range ω t = Angular speed bet n engine & gearbox Power = E t D = Outer diameter of clutch; d = Inner diameter of clutch Step (4): Clutch temperature is calc. by using thermal conductance Thermal Conductance = W m 2. K Area = π (D2 d 2 4. N f 9
Theory Behind the Simulation Model Step (5): Clutch wear is calculated by using the below equation: Sample Total volume worn off mm 3 = Friction energy dissipation MJ. Wear rate mm3 MJ 10
Theory Behind the Simulation Model Step (6): Clutch useful volume is calculated by using below equation Clutch useful volume mm 3 = Clutch area mm 2. Clutch useful thickness mm Step (7): Finally, Clutch life is obtained by using below equation No of cycles = Clutch useful volume Total volume worn off Clutch life km = Drive cycle distance km. No ofcycles 11
Input Data Requirements 12
Clutch Drive Cycle Input Data Drive cycle data (~27 km) was collected in Chennai city during peak traffic ~ 30 repeated launches in 1200 sec was observed (~1.2 km), which means every 40 sec/launch occurs. 13
Clutch Thermal Simulation Model 14
Clutch Thermal Simulation Model Convection Convection Clutch Housing Ambient Conduction 15
Simulation Model 16
Vehicle Testing Cross Section View of Clutch Engine GB Passenger Vehicle (SUV) was used for testing. The thermocouple was inserted in Clutch housing & temperature was measured. Test data collection was started once the air within the clutch housing reached 80 deg. C. Clutch Housing 17
Vehicle/Engine Speed Comparisons 18
Clutch Temperature Simulation Results Simulation model predicts both clutch facing and housing temperatures Out of which the clutch housing temperature can be measured easily during testing 19
Simulation Vs Test Results Clutch temperature simulation model shows an excellent correlation (> 90%) with the test results. 20
Sensitivity Analysis Results Final Drive Ratio Vehicle Weight Road Grade Better FE Better High Speed NVH Better In-Gear Elasticity Better Clutch Life Better Launch NVH Better In-Gear Acceleration Better Gradeability Right Trade-Off Tyre Size 21
Clutch Life Estimation (Example) Cumulative Wear (mm 3 ) 170 Clutch Useful Volume (mm 3 ) 43982 Number of Cycles 258 Cycle Distance (km) 0.71 Total Distance (km) 183 22
Applications Different Facing Material Optimize the Target Performance based on Benchmark Optimize the Clutch Design 23
Conclusion Clutch overheating is the primary cause for clutch failure. By using 1-D thermal modeling, clutch facing & housing temperature are simulated. Simulation results show an excellent correlation (> 90%) with the test data. FDR has a huge impact on Clutch wear, FE, Drivability & NVH. Hence, doing a right trade-off is very critical at an early design stage. 24
References T. K. Garrett, K. Newton & W. Steeds., The Motor Vehicle, 13th Edition, ISBN 07506-4449-4: 750-759, 2001. Bosch Automotive Handbook, 6th Edition, SAE, Robert Bosch GmbH, ISBN 0-7680-1513-8, 2004. Virendra Kumar, Gopal Sahu, Prakash, Ritesh, Shailendra, Review on Wear Analysis of Different Types of Clutch Material, International Journal of Research in Advent Technology, E-ISSN: 2321-9637, 2015. Shaohua Sun, Yulong Lei, Yao Fu, Cheng Yang and ShunBo Li, Analysis of Thermal Load for Dry Clutch under the Frequent Launching Condition, SAE Technical Paper 2013-01-0814. K.C. Lathiya, N.P. Badola, C.L. Unhad, B.D. Dhamecha, A Literature Review on Failure in Single Plate Clutch System, International Journal for Scientific Research & Development, ISSN: 2321-0613, 2014. Technical Handbook, Valeo Transmission Systems. GT-SUITE User Guide, GT-ISE v2016. Ricardo Victorino Coelho, Tulio Gustavo Lima, Clutch 430 Heavy Duty, SAE Technical Paper 2011-36- 0257. 25
Acknowledgements GT Support Team (North America) / ESI-Group (Pune) Clutch Team Engine Calibration Team 26
Thank you for your attention! 27