Research On Key Technology Of Piston And Cylinder Liner Friction Testing Machine Based On IMEP Method

In the internal combustion engine,the friction characteristics of piston-cylinder liner have a great influence on the mechanical loss and engine life.How to reduce friction,improve fuel economy,and engine efficiency have always been a key problem in engine research.It is very necessary to simulate the friction state of piston and cylinder liner of engine by using friction testing machine,in order to verify the mechanical efficiency and friction property of material surface,and improve the structure life.It has very important practical significance to improve the performance of internal combustion engine.To solve the problem of sensor excitation and signal transmission of friction testing machine under the condition of high-speed rotation and the problem of decoupling of multi-cylinder friction force in multi-station test,a multi-station piston-cylinder liner friction measurement simulation test machine based on wireless signal transmission and wireless power supply technology was designed by means of IMEP method.The related theory and key technology of testing machine were studied emphatically.The main research contents are as follows:(1)Lagrange multiplier method was used to establish the dynamic equation,which relates inertia force,internal force of connecting rod,load force and friction force,and the analytical mathematical model of IMEP method was established.The model not only considered the influence of the axial internal force on the friction force of the connecting rod,but also considered the coupling action of the tangential force and the additional bending moment on the cross section of the connecting rod.The quasi-analytical expression of piston velocity was derived,which can describe the mathematical relationship between the sliding block velocity and the crankshaft velocity under the condition of motor driving.This provides a theoretical basis for the accurate calculation of the piston-cylinder friction force.(2)The overall structure of high-speed multi-station piston ring-cylinder friction testing machine based on wireless power supply and wireless signal transmission was designed.A new detachable wedge-shaped lobe loading mechanism was applied in the piston ring loading structure,which can effectively reduce the load of motor driving system.On the one hand,the structure reduces the unnecessary energy loss of the friction testing machine,on the other hand,it reduces the speed fluctuation of the motor drag system,which is helpful to ensure the test accuracy.In addition,the finite element transient analysis of multi-flexible body dynamics of connecting rod and piston was carried out,and the influence law of axial force and tangential force of connecting rod on the measurement precision of friction force was emphatically analyzed.(3)The electrical system and software system involved were designed in general,and the test data synchronization technique based on location relationship was proposed.