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Thermal insulation effect on EHL of coated cam/tappet contact during start up

Xianghui Meng (State Key Laboratory of Mechanical System and Vibration, Shanghai Jiaotong University, Shanghai, China and School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai, China)
Changya Yu (State Key Laboratory of Mechanical System and Vibration, Shanghai Jiaotong University, Shanghai, China and School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai, China)
Youbai Xie (State Key Laboratory of Mechanical System and Vibration, Shanghai Jiaotong University, Shanghai, China and School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai, China)
Benfu Mei (Pan Asia Technical Automotive Center Co., Ltd, Shanghai, China)

Industrial Lubrication and Tribology

ISSN: 0036-8792

Article publication date: 2 July 2018

Issue publication date: 17 August 2018

132

Abstract

Purpose

This paper aims to investigate the lubrication performance of cam/tappet contact during start up. Especially, the thermal insulation effects of coating on the lubrication performance during cold start up process and warm start up process are studied.

Design/methodology/approach

A numerical model for the analysis of thermal elastohydrodynamic lubrication of coated cam/tappet contact is presented. In this model, the Reynolds equation and the energy equations are discretized by the finite difference method and solved jointly.

Findings

During start up, the contact force at cam nose-to-tappet contact decreases with increasing time, while the absolute entrainment velocity has the upward trend. The minimum film thickness, maximum average temperature and friction power loss increase with increasing time, while the coefficient of friction decreases during start up. Because of the thermal insulation effect, the coating can significantly increase the degree of temperature rise. Compared with the uncoated case, the coated cam/tappet results in a lower friction power loss. Generally, the friction power loss in the cold start up process is much higher than that in the warm start up process.

Originality/value

By this study, the lubrication performance and the kinematics and the dynamics of the cam/tappet during start up process are investigated. Meanwhile, the thermal insulation effect of coating is also illustrated. The difference of lubrication performance between cold start up process and warm start up process is analyzed. The results and thermal elastohydrodynamic lubrication method presented in this study can be a guidance in the design of the coated cam/tappet.

Keywords

Acknowledgements

The authors would like to thank the National Natural Science Foundation of China (No. 51375300, 51575342) and the Research Project of State Key Laboratory of Mechanical System and Vibration (No. MSVZD201401) for supporting this work.

Citation

Meng, X., Yu, C., Xie, Y. and Mei, B. (2018), "Thermal insulation effect on EHL of coated cam/tappet contact during start up", Industrial Lubrication and Tribology, Vol. 70 No. 6, pp. 917-926. https://doi.org/10.1108/ILT-03-2016-0065

Publisher

:

Emerald Publishing Limited

Copyright © 2018, Emerald Publishing Limited

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