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Research Papers: Internal Combustion Engines

Addressing Cam Wear and Follower Jump in Single-Dwell Cam-Follower Systems With an Adjustable Modified Trapezoidal Acceleration Cam Profile

[+] Author and Article Information
Forrest W. Flocker

Wade Department of Mechanical and Aerospace Engineering, Trine University, One University Boulevard, Angola, IN 46703flockerf@trine.edu

J. Eng. Gas Turbines Power 131(3), 032804 (Feb 12, 2009) (8 pages) doi:10.1115/1.3030874 History: Received June 18, 2008; Revised June 30, 2008; Published February 12, 2009

Presented is a modified trapezoidal cam profile with an adjustable forward and backward acceleration. The profile is suitable for single-dwell cam and follower applications. The main benefit of the profile is that it allows cam designers to choose easily a value for the maximum forward or maximum backward acceleration to achieve design objectives. An additional benefit of the profile is that it has a continuous jerk curve. Follower acceleration is one of the primary factors affecting cam wear and follower jump, two main concerns of cam designers. Large forward acceleration against a load creates cam-follower interface forces that can cause excessive wear. Backward acceleration tends to reduce the cam-follower interface force, and if the backward acceleration is sufficiently large, separation between the cam and follower (“follower jump”) can occur. The cam profile presented in this paper gives cam designers an easy way to adjust the maximum forward or backward acceleration to prevent these problems.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

A plate cam driving an axial follower

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Figure 2

Follower displacement for a typical single-dwell cam-follower system

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Figure 3

Follower acceleration during the rise and fall interval

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Figure 4

Follower velocity during the rise and fall interval

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Figure 5

Follower jerk during the rise and fall interval

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Figure 6

Effect of the jerk control parameter on follower displacement for R=1

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Figure 7

Effect of the jerk control parameter on follower velocity for R=1

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Figure 8

Effect of the jerk control parameter on follower acceleration for R=1

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Figure 9

Effect of the jerk control parameter on follower jerk for R=1

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Figure 10

Effect of the acceleration ratio parameter on follower displacement for n=2nmin

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Figure 11

Effect of the acceleration ratio parameter on follower velocity for n=2nmin

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Figure 12

Effect of the acceleration ratio parameter on follower acceleration for n=2nmin

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Figure 13

Effect of the acceleration ratio parameter on follower jerk for n=2nmin

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Figure 14

Schematic of an overhead valve train

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Figure 15

Single-degree-of-freedom model of a cam/follower system

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Figure 16

Cam interface force for a typical automotive valve train with R=1

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Figure 17

Cam interface force for a typical automotive valve train with R=5

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Figure 18

Cam interface force for a typical automotive valve train with R=1/5

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Figure 19

Maximum interface force for a typical automotive valve train with three different acceleration profiles

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