Variable Geometry Camshaft

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Variable Geometry Camshaft

• Scott Lake
• Matt Phillips
• Zachary Lightner
• Ryan Kowalewski
• Matt Griffey

Sponsor Gary Griffiths
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Outline

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

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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

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Engineering Requirements

• Increased volumetric efficiency
• 41 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

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Jaguar XJ6 Series 2 Engine
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Jaguar XJ6 Series 2 Engine
Current Timing Chain
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VGC Components

• New Components
• Baseplate
• Tappet and tappet guide
• Fulcrum and bushings
• Camshaft

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Design Considerations Base Plate
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Design Considerations Gear Train
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Final Design
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Dynamic Analysis
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Dynamic Analysis

• Standard Spring

• Stiff Spring

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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)

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Materials
Component Material Yield Strength (GPa)
Base Plate, Cylinder Head Aluminum Alloy 296 69
Camshaft, Fulcrums, Rocker Arms, Tappets, Tappet Guides Cast Iron (ASTM 60) 150
Rocker Arm Supports, Rocker Arm Pins 1020 Steel 200
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Mesh Statistics
Number of Parts Number of Nodes Number of Elements
Cam Portion (Impact Load) 10 51,755 25,903
Cam Portion (Step Load) 10 51,789 25,951
Rocker Arm Portion (Impact Load) 7 15,102 6,607
Rocker Arm Portion (Step Load) 7 15,080 6,609
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Loading Conditions
Impact Load
0.016 seconds 2956 N
Maximum Load
0.0160 seconds 2956 N
0.0186 seconds 5617 N
0.0206 seconds 6452 N
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Cam Portion Von Mises Stresses
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Cam Portion Life Cycles
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Cam Portion Safety Factor
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Rocker Arm Portion Deformation
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Rocker Arm Portion Impact Position
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Rocker Arm Portion Life Cycles
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Rocker Arm Portion Safety Factor
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Recommendation

• Redesign of VGC system to be located outboard of
  tappet guide assembly
• Reduce generated forces by reducing separation
  distance, cam inertia
• Explore alternate 41 gear ratio designs
• Component Refinement Redesign of high-stress
  components

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Questions?
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Appendix
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Patent Figures
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Patent Figures
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Cam Contact
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Patent Figures
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Patent Figures
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Dynamic Analysis
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Rocker Arm Portion Maximum Load
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Rocker Arm Portion Maximum Load