Variable geometry camshaft
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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

Sponsor:

Gary Griffiths

Variable Geometry Camshaft

Scott Lake

Matt Phillips

Zachary Lightner

Ryan Kowalewski

Matt Griffey


Outline
Outline

  • Background of Invention

  • Jaguar XJ6 Series 2 Engine

  • CAD Model Development

  • Dynamic Analysis


Background
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


Engineering requirements
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



Jaguar xj6 series 2 engine1
Jaguar XJ6 Series 2 Engine

Current Timing Chain


Vgc components
VGC Components

New Components

  • Baseplate

  • Tappet and tappet guide

  • Fulcrum and bushings

  • Camshaft






Dynamic analysis1
Dynamic Analysis

Standard Spring

Stiff Spring

2900 mm N

50,000 mm N


Approach
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)




Loading conditions
Loading Conditions

Impact Load:

Maximum Load:


Cam portion von mises stresses
Cam Portion – Von Mises Stresses








Recommendation
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












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