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Technical Briefs

Electrohydraulic Fully Flexible Valve Actuation System With Internal Feedback

[+] Author and Article Information
Zongxuan Sun

Department of Mechanical Engineering, University of Minnesota, Twin Cities Campus, Minneapolis, MN 55455

J. Dyn. Sys., Meas., Control 131(2), 024502 (Feb 04, 2009) (8 pages) doi:10.1115/1.3072146 History: Received August 13, 2007; Revised October 15, 2008; Published February 04, 2009

Fully flexible valve actuation (FFVA) system, often referred to as camless valvetrain, employs electronically controlled actuators in place of the camshaft to drive the intake or exhaust valves for internal combustion engines (ICEs). This system offers significant fuel economy benefits, emissions reduction, and better torque output performance for the ICE. It could also enable a number of advanced combustion concepts, such as homogeneous charge compression ignition. It further provides a common platform that incorporates the functions of cam phasing, two/three step cam or continuously variable lift, cylinder deactivation, port deactivation, etc. Therefore it is desirable to develop FFVA systems for future engines. In this paper, we first outline the technical barriers for developing production-viable FFVA systems. To address those challenges, a new electrohydraulic valve actuation concept with the “internal feedback” mechanism is presented. Key technical issues, such as dynamic range capability, valve motion performance, and energy consumption, are analyzed. Experimental results based on a prototype system are shown to demonstrate the capabilities and performance of the proposed system.

FIGURES IN THIS ARTICLE
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Copyright © 2009 by American Society of Mechanical Engineers
Topics: Engines , Valves , Feedback
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References

Figures

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Figure 1

Structure of the valve actuation system

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Figure 2

Control block diagram of the valve actuation system

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Figure 3

Relationship between minimum valve lift and engine valve speed during opening

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Figure 4

Hydraulic force and associated fluid deflection as a function of seating distance with valve velocity at 4 m/s

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Figure 5

Closing timing variation versus seating velocity at 700 rpm engine speed

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Figure 6

Closing timing variation versus seating velocity at 7000 rpm engine speed

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Figure 7

Desired valve profile during the engine valve closing event

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Figure 8

IFS area schedule, flow rate, and pressure drop during the valve closing event

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Figure 9

Frequency response of the IFS

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Figure 10

Engine valve lift, velocity, solenoid displacement, and on/off valves triggering timing (bottom left: lift control on/off valve and bottom right: seating control on/off valve) at 5000 rpm engine speed

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Figure 11

Picture of the electrohydraulic FFVA system

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Figure 12

Variable valve-lift control (top: valve position, middle: current to VCM, bottom left: lift control on/off valve triggering timing, and bottom right: seating control on/off valve triggering timing)

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Figure 13

Engine valve seating control (zoom in plot at the valve seat is shown on the right) (top: valve position, middle: current to VCM, and bottom: seating control on/off valve triggering timing)

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Figure 14

Engine valve transient control (top: valve position, middle: current to VCM, bottom: lift control on/off valve triggering timing, and seating control on/off valve triggering timing)

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