中马力拖拉机发动机罩的减振研究

拖拉机行驶时，其发动机罩受到来自发动机和路面的振动激励，往往会发生相当严重的振动响应，从而直接影响某些零部件的疲劳强度、寿命和仪表、灯具的正常工作。该文通过对国产某中马力拖拉机发动机罩的振动测试和模态试验，对其振动特性进行了分析。在此基础上针对具体情况，专门设计了减振结构，改刚性支承为弹性支承，使发动机罩的振动得到了有效的控制，振动水平明显降低，仪表灯具的工作环境大大改善。

Vibration control of an engine hood on a medium-sized tractor

Generally, engine is a main vibration source for a tractor. Under its excitation, engine hoods on tractors may vibrate seriously, because most hoods are connected rigidly to tractor bodies or frames. As a result, some accessories and lights equipped on the hoods may be damaged or can not work well. In order to control the hood vibration, an engine hood on a wheeled medium-sized tractor is investigated here. At first, the vibration transmission path was studied. Then the hood vibration was tested and analyzed with the technique of frequency analysis. And the natural vibration characteristics analysis of the hood was also conducted with the technique of experimental modal analysis. The vibration spectra showed us that the highest peak was located at the second order frequency of the working engine, which indicated that the second unbalanced inertial force and/or the explosive combustion force are the dominant exciting source for the engine hood. The experimental modal analysis shows that the third and the forth vibration modes of the hood may be one of the main factors which affect the vibration of the engine hood. Considering the characteristics of the exciting forces and the natural properties of the engine hood, some measures for reducing the vibration could be applied. But for economy and convenience, a kind of special elastic supporting members (vibration insulating structures) was designed. The further tests indicated that the specially designed supporting structures work well, and the hood vibration was reduced obviously, and its vibration situation was improved noticeably.