Lubricant ageing in wet clutch applications

Transcription

1 Lubricant ageing in wet clutch applications Kim Berglund Supervisors: Pär Marklund Roland Larsson Industry partners: BorgWarner Statoil Lubricants Wet clutch - Engaged Input shaft Output shaft 1

2 Wet clutch lubricant Anti-wear Detergents Friction modifiers Antioxidants Wet clutch - Engaged Input shaft Output shaft 2

3 Friction disc surface Lubricant action in between surfaces (1vol%) Friction generates heat Wear of surfaces Friction modification Anti-wear films forming Additive interaction Separator disc surface Lubricant sump (99vol%) Oxidation Keeping contaminants soluble Hydrolysis Interaction between molecules 3

4 Wet clutch degradation Temperature System parameters Contamination ( particles (e.g. Wear Water Wet clutch degradation Wet clutch degradation mechanisms Adhesive/Tribochemical wear Abrasive wear Oxidation Thermal Evaporation degradation Hydrolysis System parameters Temperature Contamination ( particles (e.g. Wear Water 4

5 Wet clutch degradation Wet clutch failure modes Loss of torque transfer Surface failure Degradation of friction characteristics Lubrication failure Wet clutch degradation mechanisms Adhesive/Tribochemical wear Abrasive wear Oxidation Thermal Evaporation degradation Hydrolysis Temperature System parameters Contamination ( particles (e.g. Wear Water Objectives Predict lubricant degradation Define end of life Remaining useful life possible 5

6 Applications Short engagement times High power Continuous slip Low power End of life lubricant Friction coefficient vs. Speed at 70 C Out of antioxidants Decreasing Antioxidant Levels 6

7 End of life - friction characteristics * * Master thesis work of Henrik Lundh at Luleå university of technology in cooperation with BorgWarner (supervisor Pär Marklund, LTU) End of life - friction characteristics 7

8 Prediction of remaining life Wet clutch failure modes Loss of torque transfer Surface failure Degradation of friction characteristics Lubrication failure Wet clutch degradation mechanisms Adhesive/Tribochemical wear Abrasive wear Oxidation Thermal Evaporation degradation Hydrolysis Temperature System parameters Contamination ( particles (e.g. Wear Water ATF oxidation model* *Calcut, B. D.; Sarkar, R. & Linden, J. L. Estimating the Useful Life of an ATF Using an Integrated Bulk Oxidation and Friction Degradation Model SAE Technical Papers,

9 Heat model Heat generation f(μ,v,p) in friction interfaces House and oil sump Surroundings Heat model output Engagement Cooling 9

10 Heat model SUMP: Large part of the lubricant ~99% Remaining life INTERFACE: Small part of the lubricant ~1% Heat model Remaining life 10

11 Consumption of life model [1 engagement] Remaining life=1-consumption of life Significance of interface temperature Remaining life=1-consumption of life 11

12 Engagement vs. cooling phase Cooling is important In conclusion Defined end of life Cooling important Surface temperatures important Prediction model Design process 12

13 Thank you for listening! Thanks to: Industrial partners: BorgWarner Statoil Lubricants Financial support: Swedish foundation for strategic research (SSF- ProViking) VINNOVA, FFI Heat model Heat generation f(μ,v,p) in friction interfaces f(rot speed, (Discs-House temp)) House and oil sump f(air vel, (House-Air temp)) Surroundings 13

14 ln(t)=a+b/t Engagement power Same energy of engagement 14

15 Engagement power Same energy of engagement Energy alone is not sufficient Wet clutch degradation pathways Wet clutch failure Loss of torque transfer Surface failure Degradation of friction characteristics Lubrication failure Lubricant degradation Adhesive/Tribochemical wear Abrasive wear Oxidation Thermal Evaporation Hydrolysis degradation Temperature Contamination ( particles (e.g. Wear Water 15

16 Wet clutch frictional behavior Torque transfer failure Failure!!! Needed torque level 16

17 Torque transfer failure No Failure Needed torque level Large changes in frictional behavior? Desirable Undesirable Shudder Stick slip 17

18 Wet clutch - Disengaged Separator disc Input shaft Output shaft Friction material Core disc Wet clutch - Engaged Input shaft Output shaft 18