Design And Research On The Test RIG For CAM Elastohydrodynamic Lubrication Film Thickness

Cam mechanism is widely used in automatic or semi-automatic machinery. The contact between cam and its follower is a single point or line contact. During the transmission of cam mechanism, the load, the entraining velocity and radius of curvature are varying with the cam angle, which causes a strong nonsteady feature of EHL between cam and its follower. This has caused considerable difficulties in analyzing EHL of cam mechanism. At present, most of the research in this area has focused on the simplified steady state problem by making many assumptions about EHL of the cam mechanism. However, the theoretical analysis is still not fully experimentally validated, because of the slow development of laboratory techniques about cam mechanism lubrication. So, it has a great significance to research the test rig for cam EHL film thickness and explore the EHL characteristics of cam mechanism.Through the analysis of each test method of EHL and the motion characteristics of cam mechanism, this paper holds that it will occurs many great difficulties to measure the film thickness of cam mechanism, despite good results that most of test methods have been obtained in measuring steady state EHL film thickness. By measuring the follower displacements on the conditions of dry friction and oil lubrication, this paper uses the displacement method to indirectly determine the oil film thickness between cam and its follower. Taking the cam/tappet pair as the research object, on the basis of EHL theory, this paper analyzed the influence of contact load, speed, cam curve and cam base circle radius on the oil film thickness, providing theoretical dates for the whole scheme design of test rig.The test rig mechanical structure part is mainly composed of the design of cam mechanism, spindle system, loading device and structure of box and the selection of electrical motor. According to the design parameters, three dimension solid models of the components and assemblies are completed, and then the components drawings are finished, which were sent to factory for machining parts. The data acquisition system of the test rig is designed by using virtual instrument technology and the LabVIEW software. In this part, the sensor’s selection method is introduced, and an application of the data acquisition system is designed, which contains the functions of data’s acquisition, processing, storage and display, etc.