Research On A Valve Tappet Production Technology And Improvement

A kind of high speed light engine in cars was developed in recent years。 The engine has the advantages of compact construction, light weight, good power performance. Its valve train was designed with overhead camshaft, no push rod, thin-walled cup-shaped valve tappet; it also can adjust the valve clearance with the adjusting shim to meet the requirements of high performance, low emission and large power. This is a kind of ideal car. The processing technology of thin-walled cup-shaped valve tappet in the engine was mainly discussed in this paper; we studied, improved and implemented the key processing technology based on the traditional process to improve technique of production and technological level of the valve tappet.Firstly, refining blank technique was used in the production of the valve tappet. There were many kinds of part blank and its production technology, international trend of manufacturing technique is refining blank technique,it is a technique to reduce cutting or avoid cutting. The blank of the thin-walled cup-shaped valve tappet in this paper was made by multi-position cold squeeze technique, one-step formed, so the inner hole and end face and the arc link of the ledges do not need to be cut. It is not only ensure good metal fibrous streamline to achieve the physical mechanics performance requirements when using the products, but also reduce the cutting allowance, which can reduce cutting processing workload and the production cost, shorten production period, and enhance production efficiency. In recent decades, cold extrusion blank processing technology is a relatively advanced blank processing technology, and makes the blank produce plastic deformation by strong pressure from three directions in the extrusion. Cold extrusion blank processing technology has several characteristics:extruding in normal temperature and do not need to heat which make the operation simple and cost less;squeezing out various shapes, complex deep hole, thin wall, and shaped profile;high precision of the size; good mechanical performance because of the continuous fibrous tissue after extrusion deformation in the internal parts;high material utilization and production efficiency. But, the annealing treatment must be conducted because it exits lot of internal stress after blank extrusion deformation.Secondly, the thin-walled cup-shaped valve tappet whose thickness is always lmm more or less, deforms easily when it is quenched. So we complete carburizing and quenching process in the Net Belt Sealed Controlled Atmosphere Multi-purpose Furnace. The Multi-purpose Furnace is sealed, continuous heating (The processes of preheating, heating, quenching and tempering are completed in the same furnace.), carburizing and quenching with gas protection, which ensure the deformation is small. Its characteristic is:high-accuracy, small deformation on component because of the processes completed in the same furnace, non-oxidation because of the gas protection and high efficiency because of continuous production. The Mesh Belt Quenching Furnace can not only improve the production efficiency greatly, but also make the components small deformation and high accuracy. Thus we can reduce heat treatment after finishing the allowance.Thirdly, the thin-walled cup-shaped valve tappet such as this type will cause large deformation after heat treatment. And it increases the processing difficulty because of the high product size precision and geometric tolerance requirements, also because of cylindrical straightness and parallel degree requirements of0.005mm. Through repeated researches, we set aside little but enough machining allowance before heat treatment and high precision cylindrical grinding machine after heat treatment. At the same time, we adjust the parameters of grinding machine to the best fit, and improve the cylindrical surface size precision and the geometric tolerance precision by multiple grinding. Thus we guarantee the product performance.At last, the technologies above, such as refined blank, advanced heat treatment process, advanced numerical control lathe and grinding machine for process focus, make the technological process of the thin-walled cup-shaped valve tappet improve a lot than the traditional process technology:high utilization rate of raw materials, high precision of heat treatment, high precision products, line brief, high production efficiency and products with low cost. The technology of the product is very high and it is a leading domestic level, close to the world advanced level.