Study On The Sealing Of Matched Surfaces Between Cylinder Block And Head

Sealing is one of the important indexes to assess engine quality and performance during engine manufacturing and assembly. With the rapid development of engine technology, more and more demands of dynamic performance and fuel economy are needed, and also bring great challenges to sealing. The engine sealing performance is poor will cause to leak water,oil and gas, which not only can cause loss of engine power, service life reduced, but also cause pollution, energy waste. This paper mainly focuses on leakage between matched surfaces of the engine cylinder block and head, which is comprehensive effect between of manufacturing precision of matched surfaces, gasket, friction coefficient of cylinder head bolt, tightening sequence, consistency of bolt preload, material properties of parts. The solution to leakage of matched surfaces is usually to replace the parts, restart to assembly, which not only cost a lot of human and material resources, but also seriously affect production capacity, which is one of the key assembly problems to be solved urgently during production process. It is urgent to find a scientific method to assess the influence of manufacturing accuracy of matched surfaces, tightening sequence and torque to the sealing.Through the numerical analytical method the relationship between manufacturing precision of matched surfaces and leakage and the finite element numerical simulation analysis. The influence of manufacture accuracy and assembly process to the sealing performance is investigated. The main research works are as follows:(1) Mechanism analysis about seal of gasket connection systemResearch on the mechanism of gasket seal, process and its leakage form, analyzes the main influence factors of gasket seal, and derivative the metal gasket model based on fractal theory.(2) Study on the relationship between sealing performance and precision of surface manufacturingAnalysis the Hertz contact model and statistics contact model of rough surface, measure the matched surfaces by the Coherix infrared laser profile apparatus, summarize the processing regularity of matched surfaces. Derive the cloud points according to the measured results, after denoising, mass data for digital processing, research the relationship between manufacture accuracy and sealing performance.(3) Simulation analysis of matched surface between block and cylinder head by FEASimulate the engine assembly by FEA, load by torque control method according to bolt assembly process and the actual bolt tighten sequence, assess the leakage by the stress distribution of gasket.(4) Simulation and quality evaluation of the assembly processQuality evaluation of bolt tightening sequence and torque during the existing bolt torque range. Six bolt-tightening sequences are compared, in order to find out the stress distribution of which is more uniform.