Research On Balance Beam Of CBK200 Motorcycle Engine

China is the big motorcycle manufacturing country in world, but China’s motorcycle technology level is still rather low, the independent development ability is still poor, and especially the core technology is still at the imitation stage in engine design where there be existing many problems in its development process, such as the very important vibration problems of motorcycle engine, which restricts the Chinese to improve the level of motorcycle industry. Therefore, the key to improve the overall quality of motorcycles is to weaken the motorcycle vibration,which is also the urgent problem that needs to be solved.Based on the research and development needs on a motorcycle enterprise, which developed a section balance shaft body of SHS162FMJ(CBK200)engine. Firstly, the inertia force which can cause engine vibrate has been analyzed and calculated theoretically based on the research project of a motorcycle enterprise about weakening vibration, a method named single shaft balance to eliminate the main inertia force has been put forward. The first-order reciprocating inertia force and rotary inertia force which causes vibration can be eliminated by this method, and the geometrical shape of the balance shaft and auxiliary units connected with balance auxiliary device are designed and assembled; Secondly, through calculation and test analysis of key parts of the engine crankshaft in the assembly, and considering the characteristics of engine balance shaft mechanism, the motorcycle engine and its mechanism are designed and improved; Thirdly, the device with this balance shaft is modeled with the three-dimensional modeling software Pro/E. Then the model is imported into ANSYS and conduct the modal analysis and structural stress analysis to verify feasibility of the design through simulation results and theoretical research for the feasibility of this design; Fourthly, the contrast tests of durable and vibration of common engine and engine with balance shaft are implemented respectively, and the advantage and disadvantage of the latter are acquired for directing practical production.The testing result and theoretical analysis show that the lowest frequency of the balance shaft is a value of 5196.7Hz which is much higher than the natural frequency of the engine, and the balance shaft will not cause resonance with engine;The factor of the static strength safety is 8.5, higher than the industry standard value4.0, which proves that the strength and stiffness of the balance shaft meet design requirements.At the same time, according to test method of the vibration comfort ofmotorcycle,the road comfort test shows that the vibration of the engine with one balance shaft has been improved obviously. The final results show that the one shaft balance method applied to the engine can reduce the first order reciprocating inertial force and inertial force caused by vibration, and offer an obvious effect on the similar model of motorcycle. The conclusion of study provides a valuable reference method and program for research of vibration, design and evaluation to motorcycle engine.