| Standing wave linear ultrasonic motor is a new type of motor driven by friction.It is very popular because of its simple structure and high driving efficiency.Due to the intermittent and impact contact between the vibrator and the slider of the standing wave linear ultrasonic motor,there is a serious wear problem on the friction interface.It has been shown that the application of hard coating material with good wear resistance to the standing wave linear ultrasonic motor can effectively reduce the wear of the friction interface and improve the performance of the motor.At present,the research on the friction pair of the standing wave linear ultrasonic motor mainly focuses on the combination of hard coating and uncoated materials,while the research on the combination of two hard coatings is less.In this paper,the tribological characteristics of the friction pairs composed by Al Ti N,Ti N,Ti CN and DLC,as well as their application in the standing wave linear ultrasonic motor were studied.Four hard coatings were selected.The hardness,elastic modulus,thickness and surface roughness of the coating were tested by nanoindentation system,ball-crater method and white-light interferometer.The surface morphology of the coating before and after wear test was observed by metallographic microscope and scanning electron microscopy.The tribological characteristics of the 16 kinds of combinations were investigated by using HIT-II ball-on-disc tester.The wear mechanisms of the coating combinations were analyzed by scanning electron microscopy(SEM),Energy-dispersive spectroscopy(EDS)and Raman spectroscopy.The results show that the combinations of Al Ti N balls/different coated discs and DLC discs/different coated balls have smaller wear and friction coefficient.Among them,the wear mechanism of the friction pairs composed of Al Ti N balls and four kinds of coated discs is extremely slight abrasive wear.The wear mechanism of the combinations of DLC discs and the coated balls(except for the Al Ti N ball)is mainly adhesive wear,accompanied by slight abrasive wear.Furthermore,the effects of working parameters and combination mode on friction and wear characteristics were also studied.The coating with high hardness and good wear resistance should be selected as the fixed part with high contact frequency,while the coating with slightly lower hardness and surface roughness is selected as the moving part.Such design principle can ensure good tribological characteristics of coating friction pairs.The test-bed of V-vibrator standing wave linear ultrasonic motor was built.The driving force,average velocity and stability of 7 kinds of coating friction pairs selected from the ordinary friction and wear tests were tested.The results show that the Al Ti N vibrator/Ti CN slider has better motor performance and less wear,and can be used as the coating friction pair of the standing wave linear ultrasonic motor.At the same time,the dynamic contact process and micro wear mechanism of the vibrator and the slider were studied,and some corresponding measures were given to solve the serious wear problem of the slider edge.In addition,the contact characteristics and friction and wear test results of coating friction pairs under ordinary conditions and ultrasonic driven conditions were further discuss.It can be concluded that the ordinary friction and wear test and the ultrasonic driven friction and wear test have the same wear results,but show differences in the friction coefficient.Through the analysis and discussion,the design method of the coating friction pair of the standing wave linear ultrasonic motor was finally obtained. |
PDF Full Text Request