Variable Geometry Camshaft

1
Variable Geometry Camshaft

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

Sponsor Gary Griffiths
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
• 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

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

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 41 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