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Variable Geometry Camshaft

Sponsor: Gary Griffiths. Variable Geometry Camshaft. Scott Lake Matt Phillips Zachary Lightner Ryan Kowalewski Matt Griffey. Outline. Background of Invention Jaguar XJ6 Series 2 Engine CAD Model Development Dynamic Analysis. Background. A standard cam has a single profile

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Variable Geometry Camshaft

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  1. Sponsor: Gary Griffiths Variable Geometry Camshaft Scott Lake Matt Phillips Zachary Lightner Ryan Kowalewski Matt Griffey

  2. Outline • Background of Invention • Jaguar XJ6 Series 2 Engine • CAD Model Development • Dynamic Analysis

  3. Background • A standard cam has a single profile • Profile dictates valve lift and duration • Optimal performance at one particular engine speed • Optimal valve lift and duration vary throughout engine RPM range

  4. Engineering Requirements • Increased volumetric efficiency • 4:1 Gear ratio mechanism for transferring torque from the input gear to the camshaft • 180° of crankshaft rotation resulting in 90° of valve duration • 240° of crankshaft rotation resulting in 120° of valve duration • Fulcrum Rotation of no more than 24° • Translational movement of rocker tower

  5. Jaguar XJ6 Series 2 Engine

  6. Jaguar XJ6 Series 2 Engine Current Timing Chain

  7. VGC Components New Components • Baseplate • Tappet and tappet guide • Fulcrum and bushings • Camshaft

  8. Design Considerations – Base Plate

  9. Design Considerations – Gear Train

  10. Final Design

  11. Dynamic Analysis

  12. Dynamic Analysis Standard Spring Stiff Spring 2900 mm N 50,000 mm N

  13. Approach • Divide model into two portions at cam – rocker arm interface • Observe deformation and Von Mises stresses at two distinct times: • Impact position (Cam initially makes contact with rocker arm) • Maximum Load position (Maximum normal force between cam and rocker arm)

  14. Materials

  15. Mesh Statistics

  16. Loading Conditions Impact Load: Maximum Load:

  17. Cam Portion – Von Mises Stresses

  18. Cam Portion – Life Cycles

  19. Cam Portion – Safety Factor

  20. Rocker Arm Portion – Deformation

  21. Rocker Arm Portion – Impact Position

  22. Rocker Arm Portion – Life Cycles

  23. Rocker Arm Portion – Safety Factor

  24. Recommendation • Redesign of VGC system to be located outboard of tappet guide assembly • Reduce generated forces by reducing separation distance, cam inertia • Explore alternate 4:1 gear ratio designs • Component Refinement – Redesign of high-stress components

  25. Questions?

  26. Appendix

  27. Patent Figures

  28. Patent Figures

  29. Cam Contact

  30. Patent Figures

  31. Patent Figures

  32. Dynamic Analysis

  33. Rocker Arm Portion – Maximum Load

  34. Rocker Arm Portion – Maximum Load

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