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Research Papers: Internal Combustion Engines

# Analysis and Customization of Rocker Arm Joint Sliding Velocity

[+] Author and Article Information
Bruce K. Geist1

Advance Vehicle Engineering, Chrysler LLC, Auburn Hills, MI 48326-2757bg57@chrysler.com

David Eovaldi

Performance Parts and Motorsports Division, Chrysler LLC, Auburn Hills, MI 48326-2757dme5@chrysler.com

$vtr(2)$ is defined as the velocity of a fixed point on surface $Σ2$. The velocity $vtr(2)$ does not include any velocity contribution due to sliding motion along the surface of $Σ2$.

1

Corresponding author.

J. Eng. Gas Turbines Power 131(6), 062801 (Jul 13, 2009) (7 pages) doi:10.1115/1.3078184 History: Received June 24, 2008; Revised July 09, 2008; Published July 13, 2009

## Abstract

This paper examines how the sliding motion between a rocker arm and a valve stem tip can be adjusted by reshaping the rocker pad surface. The valve tip is assumed flat, and the rocker arm and valve stem are assumed to lie in a common plane. It is shown that the rubbing velocity between a rocker arm and a valve stem tip, as well as the curvature of the rocker arm pad, may be determined from two features of the contact: (1) the contact point path between the rocker arm and the valve stem tip and (2) the angle that the valve stem tip makes with the line connecting the rocker pivot to the zero-lift point of contact. An algorithm is presented for determining a rocker arm surface from a prescribed contact point path and valve angle. The derived technique enables customization of rocker arm pad curvature and rocker arm joint sliding velocity.

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## Figures

Figure 1

Diagram of rocker arm and valve when the valve is at zero lift

Figure 2

Calculating translational velocities vtr(1) and vtr(2)

Figure 3

Define γ(s)=arctan(y(s)/x(s)). To produce an approximate surface reconstruction, assume that γ(s) is negligible compared to θ(s).

Figure 4

First axis: derived rocker arm pad shown rotating about its pivot at the origin. Design parameters are r0=43 mm, α=2.73 deg, and valve radius of 4 mm. The target contact point path is shown to the right of a circular arc of radius 43 mm. Second axis: shows a zoom-in of the indicated area from the first axis.

Figure 5

Target versus actual: pivot to contact point distance as a function of contact point angle

Figure 6

First and second axes: target versus actual v(12)/ω as a function of contact point angle. third axis: curvature of constructed surface, piecewise linear because r(θ) is piecewise quadratic

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