Test method for contact stress of engine overhead valve camshaft

Abstract

The invention relates to a method for testing the contact stress of an overhead gas distribution camshaft of an engine. The method includes the following steps that the rotation angle of the camshaft corresponding to the largest contact stress between a cam and a driven member in a work period is determined with a simulation method; the round corner stress of the cam at the rotation angle of the largest contact stress is dynamically tested by means of a bench test; then, the linear relation between the contact force between the cam and the driven member and the round corner stress of the root of the cam is determined, and then the largest contact stress between the cam and the driven member can be obtained through conversion; finally, the contact stress is obtained by solving according to the Hertz formula. With the method, the contact stress of camshafts including any overhead gas distribution mechanism type camshafts can be tested, and test data are highly reliable.

Description

technical field [0001] The invention belongs to the technical field of engine testing, and in particular relates to a method for testing the contact stress of an engine overhead camshaft. Background technique [0002] The camshaft is the core part of the transmission assembly of the engine valve mechanism. In order to ensure the rigidity of the mechanism's power transmission, the design margin of the camshaft's strength is generally large. Under normal circumstances, the camshaft rarely suffers from fracture fatigue failure. On the contrary, the problem of wear and failure of the cam and its follower is more common. The component directly driven by the cam is called a cam follower, which generally refers to a rocker arm, a swing arm or a tappet. Especially with the advent of high power density engines, the friction pair is likely to cause the cam-follower working surface to wear due to severe friction under the action of high temperature, high speed, and variable pressure. ...

AI Technical Summary

Problems solved by technology

[0005] In the prior art, the indirect test method of contact stress can only be aimed at the middle or bottom thruster rocker valve mechanism, choose to arrange strain gauges in the axial direction on the surface of the push rod to obtain the bearing load of the push rod, and then convert to get For the contact force of the cam-tappet, the Hertz formula is used to complete the solution of the contact stress. Therefore, the contact stress test of the overhead camshaft valve train type cannot be realized

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