Abstract
Interference joint is one of the most advanced assembly methods for camshaft. The joining force in the assembly process and the connection strength after assembly are the key aspects of the camshaft assembly system. In this paper, the mechanism of joining force and connection strength are analyzed from two aspects of elasticity and plasticity using thick-wall cylinder model. Joining and torsion experiments are done to determine the joining force and connection strength. Joining forces fluctuating increase in the joining process, which is composed by friction force Fs and shearing force Ff. Fs is 0.87 KN, and Ff is 6.23 KN when the assembly interference is 0.15mm. Joining force linear increases with the interference, and torque exponential increases with it. The empirical formulas between the torque capacity, joining force, and interference of the camshaft are provided by the experiment results. The assembly interference limit of 0.3mm is estimated for the case of this paper. Metallographic observation reveals the changes of metal flow line of the knurled tube. The top of knurled tooth turns over and an inverted triangle formed after joining process.
Highlights
As the key part of the engine valve, camshaft has an important influence on the volume of intake air, dynamic performance, and gas emission of the engine [1]
The joining force and connection strength of the assembly camshaft depends on many factors, including interference, geometric parameters and material properties [9, 10]
The results show that the tube chamfer angle has a crucial influence on the joining forces as well as the push out forces
Summary
As the key part of the engine valve, camshaft has an important influence on the volume of intake air, dynamic performance, and gas emission of the engine [1]. Interference assembly of knurled cam and tube has been widely used in camshafts manufacturing because of high connection strength, and no thermal deformation etc [7, 8]. The joining force and connection strength of the assembly camshaft depends on many factors, including interference, geometric parameters and material properties [9, 10]. Larger shaft chamfer angles lead to lesser joining force. It is almost certain that the interference has an important influence on the connection strength It determines the joining force and working reliability of camshaft. For the camshaft with knurled tube and cam, the relationship between the interference and the joining force as well as connection strength is not analyzed fully. Stress and strain of knurled tube are analyzed systematically by metallographic observation and FEM
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