Assemled Hollow Camshaft Trial-manufacure

Since the entry of 21th century, with the rapid development of industrial economy, the demand of oil became lager and larger. the oil is non-reproducible, with the repertory reducing, the oil price will become higher and higher. As a major consumer of oil, the quantity of the automobile has exploded, the gasoline and diesel oil used in automobile becomes scarce. The cost of oil of automobile increases day by day.For saving fuel and reducing exhaust emission, the structure lighting of automobile become more important. Reducing 10% of weight can save 8%-10% of oil consuming, and reduce exhaust emission at the same time. There are two ways for structure weight lighting: one is the adoption lighting alloys such as Al alloy, Mg alloy, Ti alloy, engineering plastic and composite materials, the other is to adopt hollow varying section structure, it can reduce the weight, also can save the materials and make full use of intensity and rigidity of materials.Engine is the power source of automobile, no matter petro engine or diesel engine, reducing friction loss is an important way to save energy. The friction loss of valve transmission structure is closely connect to its initial force. So, it can advance the efficiency of engine and reduction of oil consuming by lighten valve transmission structure components moving quality.Camshaft as an important part of valve transmission system impacts a lot on gas engine performance. To solve tradition camshaft disadvantage like high weight, low utilization, high process cost and so on, the countries around the world devote many manpower and material resources to do some research and development on this new materials and new technics.Far from 80 years of 19th century, someone have developed a new method on camshaft manufacture in foreign countries, that is assembly camshaft. This one is achieved by changing structure and manufacture process.The assembly camshaft is consisted by cam, shaft and shaft neck, which can be assembled, optimize materials and fine machine the parts, at the end use welding, mechanical assembling, powder metallurgy sinter to obtain integer joint.Now, assembly camshaft has develop 20 years, the welding camshaft, sinter camshaft and mechanical enlarging tube connect camshaft came out successively. Apply composite materials have been developed energetically. Jilin university and Haerbin Institute of technology have developed the research on assembly camshaft manufacture technology, but it has not applied on batch production yet. Some domestic joint venture automobile works and a lot of automobile works abroad have adopt this kind technics and achieve bath production.The content related in this paper is to trial-produce the assembly hollow camshaft products fulfilling the performance requirements, it can also accumulate the data for engine designer and supply the reference for manufacture technics. According to analyze the disadvantages of traditional casting and forging camshaft, this paper illustrates the advantage of assembly camshaft manufacture.This paper emphasizes on the joint technology on assembly camshaft, reveal the joint mechanism on every method and its advantage and disadvantage. This paper confirms the trial-produce technology on assembly hollow camshaft through mechanical enlarging tube method.Through the process of press forming, the punch which's diameter is a little bigger than the shaft tube push the tube to produce plastic deformation along the radial direction, the outer of the shaft tube crush into the spline of cam and shaft neck, realize the joint through spline and friction of elastic deformation.The benefit of machine spline on the inner hole of camshaft and shaft neck is: the spline is working of multi-tooth, well bearing, guiding and keeping centric well, the teeth root is flat, the shaft and hub be weakened little, at the same time, machine of spline is simple. The final joint result of cam and shaft depends on punch diameter, spline dimension and the matching of them. the front of punch is inducting section, then the guiding section, the guiding section and inner hole of shaft tube is interference-fit, at the end is forming ligament. The spline adopts small modulus, large press angle, through carry out single joint experiment with different punch dimension, obtained the forming tonnage comparatively to forming extent.Check the joint intensity through whisht wrest testing, In the case of 0.15mm plastic deformation of shaft tube at single side, the maximum torque is 1.26KN, yielding torque is 1.18KN, it is far beyond 0.2KN that required in usual camshaft design. Analysis the cut section of this case, we found that it had not been fulfill. But the whisht wrest has already meet the intensity requirement.The working condition of camshaft is cyclic torque transmission; generally speaking, the joint intensity of assembly camshaft should be lager than 200Nm. The deformation of camshaft can separate into bending deformation and twist deformation. For spline joint, the major invalidation is tooth face push down, some times it can be tooth root breaking. So it is only necessary to calculate the spline joint extrusion intensity. The extrusion intensity in this case is far below the permission joint stress 35MPa. Through the cut section of destruct experimental part, twist invalidation is the interface of shaft and cam spline, bringing slippage, the spline tooth fall off and extruded flat. Because the shaft tube and the thin wall of camshaft is weak in wrest, the distortion of shaft tube and cam hole appear. For the joint method explained above, the avoiding of fracture is conquering elastic deformation and extrusion flat spline tooth.The assembly camshaft consist of many kinds parts which have complicate shape, it require that the forming tooling should be fine located, easy assembled, so we adopt insert fission casing structure.The inner diameter of Cam and shaft neck is a little bigger than the shaft outer diameter, assure the shaft can easily pass through the inner hole of cam and shaft neck, the gap is about 0.2mm on both side. According to grind experimental result, the allowance of all parts are 0.5mm, then can machine the qualify components.This paper have developed the self-determination knowledge property right of the joint technic and parameters of camshaft. Developed reasonable forming technic and related tooling on assembly hollow camshaft, have trial-manufactured qualify hollow camshaft parts; now, the technic is applying for national patent.After this technic applied to production, it is can efficiently reduce camshaft weight, vibration and noise, advance engine performance, reduce oil consuming and save production cost. The technic will have a wide application in the future market.