Research On Torsion Vibration Of Four Cylinder Gasoline Engine With Cylinder Deactivation

Vehicle engines work in small load conditions in many cases,the cylinder deactivation means that when the engine is working in small load,at the condition of maintaining the torque output as same as the case before the cylinder deactivation,through the control of fuel injection,ignition and exhaust and other devices,So that some of the cylinders to stop working to improve the load rate of the remaining working cylinders,thereby improving the efficiency of the engine,so as to achieve the purpose of fuel saving.But at the same time of improving the fuel economy,the cylinder deactivation technology also changed the engine ignition interval,so that the ignition angle increases,reduce the frequency of ignition.When the cylinder deactivation is working,the remaining cylinders must be injected more fuel to ensure to output the same torque as the normal condition.The cylinder pressure will change to a great extent,the torque fluctuation of the engine will increase and the torsional vibration will deteriorate.Firstly,through the simulation analysis of the different cylinder deactivation strategies and the number of stopping cylinders,it is concluded that the valve shut off strategy is the best among the three strategies.In this paper,the analysis of the engine deactivated cylinder is carried out,and the torsional vibration model of 2.0VVT four-cylinder gasoline engine crankshaft is established by using the simulation software EXCITE-Designer.The torsional vibration characteristics of the shaft system are calculated and analyzed.Three kinds of different cylinder deactivation strategy are analyzed and compared,and the influence of cylinder deactivation working at different positions is studied.The calculation results show that the free-end torsional vibration amplitude of the crankshaft increases obviously after cylinder deactivation,among which the low harmonic vibration is the main factor.In the three kinds of stopping strategies,Torsional vibration characteristics of the fuel interruption is the best;for different positions of the cylinder to stop working,the more close to the flywheel cylinder end torsional vibration characteristics of the better.In order to improve the torsional vibration characteristics of the crankshaft,the AVL EXCITE Designer Damper Variation was used to determine the range of the parameters of the damper for the engine studied,and the optimum values of the damper parameters.The natural frequencies and the mode shapes and the torsional vibration characteristics are compared and analyzed.At the same time,in order to isolate the torsional vibration between the engine crankshaft and the transmission,the basic structure and working principle of the dual mass flywheel are introduced.The theoretical basis of the isolation torsional vibration and the fluctuation rate of the rotational speed are explained.For the target engine,the main parameters of thedouble mass flywheel are determined.A DMF torsional vibration model was established in EXCITE,and the effect of DMF was evaluated.The calculation results show that the double mass flywheel can effectively reduce the natural frequency of the shafting and isolate the torsional vibrations from the engine to the gearbox.