Experimental Study On Assembly Technology Of Connecting Bolt Of Engine Main Bearing Cap Based On The Method Of Controlling Torque And Angle

With the rapid development of the automotive industry,people have put forward higher requirements for the safety performance of automobiles.The engine as the heart of the car,its reliable and smooth operation takes on the most important tasks.To ensure the normal operation of the engine,the reasonable fastening of the connections structure on the engine is one of the important preconditions.In recent years,the failure of connection bolts has caused numerous automobile accidents.Therefore,it is necessary to study the assembly quality of bolts.Most engines are assembled in a threaded connection,because the threaded connection can provide a large preload,as a standard part,it is interchangeable and easy to assemble.However,in order to control the assembly quality of the bolts,it is necessary to study the assembly process factors of the bolts.Based on the school-enterprise cooperation project and aiming at solving practical problems of the enterprise,this paper focuses on improving the quality of bolt assembly,analyzing various factors that will affect the assembly quality,summarizing the rules,applying them to the assembly engineering,and tests them to check the rationality of the solution.The main research contents of this paper are as follows:First of all,the importance of the bolted connection structure of the main bearing cap is analyzed,and the alternating load on the bolt is analyzed,so as to determine the maximum preload and the minimum preload of the bolt under the working condition;The evaluation standard of bolt assembly quality and the engineering method of assembly quality evaluation are introduced.Second,Carry out tests according to the original process plan,determine that the final preload and torque are not within the qualified range,and then analyze the factors that may affect the dispersion of preload force,find out the main influencing factors according to the actual situation;This paper mainly studies three factors including assembly method,tightening specification and surface treatment,finds out the influence rule according to theoretical analysis and experiment,and improves the assembly process plan according to the influence rule.Third,According to the previous experimental data,it was found that the friction coefficient dispersion of zinc salt phosphating treatment was too large,failing to meet the requirements;further study the phosphating solution formula,find the best formula that makes the friction coefficient more stable,and then carry on assembly experiment of the best phosphating solution formula;the effect has a large improvement but still fails to meet the eligibility criteria;Finally,the parameters of the torque Angle method were optimized and tested.,the optimal parameters of the Torque-Angle method were selected by comparing multiple parameter optimization schemes.Then,the qualified assembly process scheme was determined by combining with the tightening specifications previously determined.