大马力拖拉机驾驶室噪声分析与优化

发布时间：2018-09-12 08:25

【摘要】：拖拉机行驶路况差,作业任务重,特别是大马力拖拉机,噪声问题比较突出。随着对拖拉机行车速度、乘车舒适性和驾驶员健康要求的逐步提高,如何有效降低拖拉机驾驶室耳旁噪声是农业机械领域的研究热点。驾驶室耳旁噪声不仅和驾驶室悬置系统的隔振阻尼特性有关,而且与驾驶室表面结构的声学特性有关。因此,驾驶室耳旁噪声既是评估悬置系统隔振阻尼效果的指标,也为选用驾驶室内隔音吸音材料提供重要的指导意义。本文以东风1204大型拖拉机为样机,首先理论分析了驾驶室内耳旁噪声的来源以及其产生机理,分析得到驾驶室耳旁噪声是由空气噪声、混响声和固体噪声组成的。接着采用消元法、覆盖法和表面加速度法等多种试验方法进行试验验证,一方面正确识别了各噪声源自身的噪声声量级,以及各噪声源对驾驶室耳旁噪声的贡献率,从而验证了驾驶室耳旁噪声的理论分析;另一方面借助驾驶室耳旁噪声的频谱分析结果,大致将驾驶室耳旁噪声划分为中高频噪声和低频噪声两大类。高频噪声主要由空气噪声和混响声组成,通过优化组合驾驶室内包装材料可以降低驾驶室耳旁噪声。实验结果表明,优化后的包装材料组合方式使得耳旁噪声声压级下降12.1 dB。低频噪声主要源于发动机的二阶不平衡往复惯性力,超出了包装材料降噪能力,必须通过优化驾驶室悬置系统的刚度和阻尼,从而阻隔传播到驾驶室的低频噪声。首先借助RecurDyn多体动力学仿真软件创建悬置系统穿联结式减振器模型和驾驶室模型,并且使用表面振速法测得的试验数据验证仿真模型的正确性。然后选定减振器的刚度和阻尼为设计变量进行优化设计。试验结果表明,优化后的刚度和阻尼有效提高了“低频”悬置系统的隔振率,进而降低了驾驶室耳旁噪声频段中的低频噪声,使驾驶员的乘车舒适性得到保证。本文最后总结了降低大马力拖拉机驾驶室耳旁噪声的方式方法,主要表现为优化驾驶室内包装材料组合来降低中高频噪声和优化驾驶室悬置参数来降低低频噪音。结果表明本文采取的降噪方式达到了预期的降噪效果,使得样机满足国家关于拖拉机驾驶室耳旁噪声的行业标准。
[Abstract]:The tractor is in poor road condition, heavy duty, especially the high horsepower tractor, the noise problem is prominent. With the improvement of tractor driving speed, ride comfort and driver health requirements, how to effectively reduce the tractor cab ear noise is a research hotspot in the field of agricultural machinery. The noise around the cab ear is not only related to the vibration isolation and damping characteristics of the cab suspension system, but also to the acoustic characteristics of the cab surface structure. Therefore, the noise around the cab ear is not only an index to evaluate the vibration isolation and damping effect of the suspension system, but also an important guide for the selection of sound insulation materials in the cab. Taking Dongfeng 1204 tractor as a prototype, the origin and mechanism of the inner ear noise in the cab are analyzed theoretically, and the results show that the noise is composed of air noise, mixed noise and solid noise. On the one hand, the noise levels of each noise source are correctly identified, and the contribution rate of each noise source to the noise around the cab ear is correctly identified. On the other hand, with the help of the spectrum analysis results of the cab ear noise, the cab ear noise can be divided into two categories: middle and high frequency noise and low frequency noise. The high frequency noise is mainly composed of air noise and reverberation sound. By optimizing the packaging materials of cab, the noise around the cab ear can be reduced. The experimental results show that the sound pressure level of ear noise decreases by 12.1 dB. due to the optimized packaging material combination. The low-frequency noise is mainly caused by the second-order unbalanced reciprocating inertia force of the engine, which is beyond the capability of packaging material noise reduction. It is necessary to optimize the stiffness and damping of the cab suspension system to block the low-frequency noise propagating to the cab. In this paper, RecurDyn multi-body dynamics simulation software is used to establish the suspension system impeller model and cab model, and the experimental data measured by the surface vibration velocity method is used to verify the correctness of the simulation model. Then the stiffness and damping of the damper are selected as the design variables to optimize the design. The experimental results show that the optimized stiffness and damping can effectively improve the vibration isolation rate of the "low-frequency" mounting system, and then reduce the low-frequency noise in the noise frequency band of the cab ear, so that the driver's ride comfort can be guaranteed. In the end of this paper, the methods of reducing the noise around the cab of a high-power tractor are summarized. The main ways are to optimize the inner packaging material of the cab to reduce the mid-high frequency noise and optimize the cab mounting parameters to reduce the low frequency noise. The results show that the noise reduction method adopted in this paper achieves the desired noise reduction effect and makes the prototype meet the national industry standards on tractor cab ear noise.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S219.0

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