Abstract
The valve train is one of the main sources of engine vibration, and its dynamic performance is crucial for output power and fuel consumption. The flexibilities of slender bars and beams should be emphasised in the design of valve trains to develop high-power and high-speed engines with industrial applications. A flexible dynamic model of a valve train system is proposed. In the proposed model, the components, except the cam and gear bodies, are modelled as flexible bodies with multidirectional deformations. The gyroscopic effects of the camshaft, cams and gear discs are also considered to predict dynamic responses at high speeds accurately. Gear meshing, the friction of the cam–tappet pair, the centrifugal force of the cams and valve clearance are also considered. Experiments on housing vibration and pushrod stress are conducted to validate the proposed model. Results show that the proposed model can predict the dynamic stress of the flexible components well and predict the trend shown by the housing vibration. The proposed model shows that excessive cam rotation speed and valve clearance will cause intense bounce and jump phenomena. The proposed model can be an important reference for designing engine work speed, adjusting valve clearance and improving component durability.
Highlights
The valve train system is one of the most important engine parts
A flexible dynamic model with the gyroscopic effect and valve clearance impact was developed in this work
The camshaft and rocker arm were modelled as flexible bodies that are based on Timoshenko beam elements, whereas the slender pushrod, valve and tappet were modelled by using bar elements
Summary
The valve train system is one of the most important engine parts. It consists of a series of components that are prone to deformation. Teodorescu et al [3,4] proposed a dynamic valve train model with two equivalent masses by using the lumped parameter method These studies disregard contact deformation between components and the elastic deformation of slender components. The gyroscopic effect of the rotor disc [22], the presence of eccentricity [23] and the multidirection vibrations of the camshaft [17,24] have been considered in the dynamic models of valve trains. A flexible dynamic model with the gyroscopic effect and valve clearance impact was developed in this work. Experiments on the housing vibration and pushrod stress were conducted to validate the proposed model and the effects of the cam speed and valve clearance on jump and bounce phenomena were investigated
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