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Evaluation of a 4-stroke 4-cylinder Diesel Engine Valve-train for Replacement of a Solid Camshaft with a Hollow Camshaft
Abstract:
The use of hydroforming technique is commonly used for the manufacturing of BIW, chassis and suspension components. For low weight and cost effective solutions it is also finding application in powertrain components mainly in the engine camshafts.
Weight of the valvetrain parts plays a vital role for enhancing the engine response and performance. Hollow camshafts are produced by assembling aggregate parts, i.e., cam lobes, journals, sprockets etc. on a tubular shaft. Compared to conventional solid cast or forge camshafts, hollow camshafts provide opportunities for weight reduction exceeding 60%, design flexibility to improve performance of engine and valve train because of reduced rotational inertia.
In order to obtain the above benefits the valve train of an existing 4-cylinder 4-stroke diesel engine is modified by replacing the solid forged camshaft with a hollow camshaft. The main consideration in carrying out the change is that the valve train performance should be enhanced. For this, the basic requirement of the camshaft torsional and bending rigidity should be same as that of the solid camshaft.
Physical validation of such a system on an engine dynamometer would involve investment in tooling for the camshaft and the lobes, journals and sprocket. This is also a time taking process, as the development would require tuning at various levels.
In order to reduce the development time and cost, a numerical model of the valve train is developed. The valve train is then analyzed and the performance is compared with the solid camshaft. Once the valve train parameters are optimized, the hollow camshaft is evaluated for durability.