Research On Process Ptimization For Contactresistance Of Sealed Electromagnetic Relay

Electromagnetic relay is a kind of automatic switch which realizes smaller current,lower voltage signal to control larger current and higher voltage circuit.The main components of electromagnetic relay usually include coils,armature,yoke,contacts,etc.Contacts are used to realize switching function,that is,to control the current in the output circuit through the connection and disconnection of contacts.Therefore,the contact is one of the most important components to ensure the normal function of the relay.Electromagnetic relay may fail because contacts cannot be effectively connected and disconnected.According to the statistics of the failure phenomena of electromagnetic relays used in military equipment such as aerospace,aviation,weapons and ships,remainder and contact resistance are two main problems leading to the failure of relays.Among them,the contact resistance problem accounts for more than 20% of all fault problems.In order to improve the reliability of relays and ensure the application requirements of key models,this paper studies the mechanism and conditions of contact resistance variation of relays,in order to find effective methods and measures to control contact resistance over-tolerance.In this paper,the influence of the surface plating quality of the contact on the contact resistance is studied.By using pulse plating and optimizing the process to improve the density of the coating on the contact surface,the porosity in the middle and surface of the coating is reduced,and finally the amount of impurities remaining in the pores is reduced;The time of the cold-water cleaning and the ultrasonic cleaning of deionized water was studied.By optimizing the cleaning time,the post-treatment quality of the parts electroplating was improved,and the purpose of completely removing the residual salt of the plating solution in the parts was achieved.The improvement of the plating quality of the contact surface is advantageous for increasing the contact conductivity between the contacts and reducing the failure rate of the contact resistance.According to the coil structure of electromagnetic relay,the volatile materials generated by various non-metallic materials under high temperature conditions are analyzed.It is confirmed that the pollution source causing the change of contact resistance mainly comes from two aspects.One is that the coil enameled wire is in production.Paraffin wax which acts as a lubricant in the process,paraffin wax volatilizes carbon element in high temperature environment,and condenses on the contact surface at normal temperature to increase the contact resistance;secondly,the cleaning agent and flux are adsorbed between the layers after the coil is wound.If the impurities remain,they cannot be effectively discharged,and the decomposition at high temperature forms a contaminated film attached to the surface of the contact,resulting in an increase in contact resistance.By studying the outgassing conditions of the coil material and the winding under various temperature,vacuum and time conditions,the weight loss curve is drawn to determine the specific temperature,vacuum and the coil in the case where the volatile matter of the organic substance tends to be stable and small enough.The time parameter value is optimized and the optimal parameters are selected to achieve the purpose of effective gas release.In this paper,the internal parts cleaning of relays is studied for the problem that the contact resistance increases due to the adhesion of fine particles to the contact surface.Through the application of automatic cleaning equipment,the effects of frequency,power,time and other parameters on the cleaning effect are studied,and the optimal parameters suitable for the cleaning of electromagnetic relay parts are found.By studying the cleaning process,different types are selected according to the classification of cleaning objects.The cleaning process is optimized and optimized to meet the characteristics of high-frequency ultrasonic and gas-phase cleaning technology for relay cleaning.The application of cleaning effect evaluation methods has clarified the target for ionic pollutants,non-ionic pollutants and insoluble particles.The evaluation method for the cleaning effect of the three types of pollutants of the excess material ensures the quality of the cleaning of the relay parts.Finally,prototype processing and testing are carried out.According to the requirements of the national military standard grade of electromagnetic relay,high and low temperature operation,medium current,life and other tests are carried out to monitor the test process.The electrical parameters tested before and after the tests meet the requirements of the national military standard of products.The test results show that reasonable high vacuum gas release parameters,good contact condition and strict process flow are necessary to improve contact performance.Aiming at the problem of high contact resistance in relay products during test and use,this paper systematically studies three main factors affecting contact resistance: surface quality of contacts,volatilization control of polluted atmosphere and quality control of cleaning process.According to theoretical guidance and experimental verification,several key technologies such as improving contact surface coating are studied.Breakthroughs have been made in tightness,volatilization control of non-metallic materials in relay,influence of baking parameters on gas release of components,application of automatic cleaning equipment and optimization of cleaning process.The application of control measures in product production can improve the qualified rate of contact resistance and achieve the purpose of the research.The conclusions obtained in this paper can be used for reference for similar products such as switches and controllers.