Abstract

 
 
 
 A valvetrain including switchable rocker finger follower is capable of discrete switching between two modes (two cam profiles). The exact moment when switching occurs is called crossover point and this paper reviews the factors that cause the shift of the crossover point from its nominal design position. The range where crossover point can shift is called critical shifting window and its size and factors influencing it will be adressed.
 
 
 
Highlights
Valvetrain mechanism between camshaft and a valve itself allows to transform camshaft rotational movement to the intake and exhaust valve translational movement
The results show the size of CSW can be decreased by proper cam design as well
The presence of critical shifting window is inevitable, and its size is prescribed by the manufacturing tolerances and design of a cam lobe profile during CP
Summary
Valvetrain mechanism between camshaft and a valve itself allows to transform camshaft rotational movement to the intake and exhaust valve translational movement. The valvetrain is no exception and variable valve timing (VVT) and variable valve lift (VVL) are used in vehicles nowadays. Cam phaser is the most common way for VVT implementation. It allows to shift the entire valve lift within the specified range of an engine cycle and it appears in two versions – discrete and continuous timing switching. The axial camshaft shifting or switching the cam that controls the valve using advanced finger followers or rocker arms is used by OEMs. Combination of VVT and VVL is commonly called as variable valve actuation (VVA). The switchable roller finger follower (SRFF) is one of the ways how to implement discrete variable valve lift. Critical Shifting Window in Switchable Rocker Finger Follower PETR KOHOUT, JAN KINDERMANN
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