| Assembled camshaft, where shaft tube and cam are separately produced and then assembled, has offered a range of remarkable advantages in cost reduction, weight saving, optimum combination of cam/shaft materials, design and manufacture flexibility and performance improvement over conventional camshafts made from one material. This technology is very important to reduce the automobile cost, lighten the engine weight and improve the engine performance. Assembled camshafts are attracted much attention as competitive products and technologies for camshaft manufacture because of its unique, composite design and special features compared to conventional camshaft. As a novel technology of camshaft manufacture, assembled camshaft has obvious advantages, it is the main developing object of camshaft manufacture.The key technology of assembled camshaft is the joining between the shaft tube and the cam lobe, it also plays an important part in of the camshaft's performance. At the present time, the assembled camshaft connected technology includes the thermal units: welded joint, powder sintering, expanding shaft tube, mechanical assembly knurled interference, etc. Contrasted the differences methods of assembled camshaft machining problems, the current trend of the assembly or joining technology is towards cold-assembly and automatic production with high efficiency. It has much significance to do the research of connection technology and manufacture of its equipment by the knurling interference fit and expanding tube.This dissertation studies the characteristic of the steel ball expanding connection technology, it adopts the way of seamless steel pipe technology, the cam's inner inner surface with keyway and the axle journals are clearance fitted in a certain pre-set phase angle on the sleeves. Then utilize a hydraulic-apparatus to push a bigger steel ball through the stern tube. The extruding force makes the stern tube connected with the camshaft and the axle journal orderly. Compared with other connections, it is simpler, high efficiency, lower cost price.Based on the connect principle, this paper analyzes the connection process, include the optimum combination of cam/shaft materials, fit clearance, magnitude of steel ballinterference, wall thickness of shaft tube and cam lobe width influence the assembly load and joining strength significantly. The major research is summarized as follows:(1) Shows the disquisition of expanding tube by pushing through a ball for assembled camshaft. Analyses the junction principle of the cam's inner surface with keyways. To meet the technical requirements of automobile engine-V348, the paper founds and simplifies the cam-blade model, uses analog method to show the connection of the models and the original peach model.(2) Contrast the surface of the cam type of chip connection strength of the face. Park will be a simple surface model and simplified model for the park's smooth connection analysis and comparison of numerical simulation, compared the stress distribution, strain distribution, press-fit force, the ability to reverse resistance decreases 30.8%. Surface model obtained for the smooth model of torsional capacity of 63.2%. Prove with the inner surface of the cam groove, the connection strength of the impact of better.(3) Using FEM numerical simulation technique, the factors to effect on assembly load and joining strength are analyzed, which provide the basis for the manufacture of assembled camshaft and the design of assembly equipments by expanding tube. The results show that the optimum combination of cam/shaft materials, fit clearance, magnitude of steel ball interference, wall thickness of shaft tube and cam lobe width influence the assembly load and joining strength significantly. The stability of the joining connection by expanding tube mainly depends on the optimal material matching of cam and shaft, the proper choice of fit clearence, augment of magnitude of steel ball interference and cam width will enhance the joining strength of expanding tube. This paper provides an useful references for the following steel ball camshaft expanding experimental research. |
