【摘要】：拖拉機行駛路況差,作業(yè)任務(wù)重,特別是大馬力拖拉機,噪聲問題比較突出。隨著對拖拉機行車速度、乘車舒適性和駕駛員健康要求的逐步提高,如何有效降低拖拉機駕駛室耳旁噪聲是農(nóng)業(yè)機械領(lǐng)域的研究熱點。駕駛室耳旁噪聲不僅和駕駛室懸置系統(tǒng)的隔振阻尼特性有關(guān),而且與駕駛室表面結(jié)構(gòu)的聲學(xué)特性有關(guān)。因此,駕駛室耳旁噪聲既是評估懸置系統(tǒng)隔振阻尼效果的指標(biāo),也為選用駕駛室內(nèi)隔音吸音材料提供重要的指導(dǎo)意義。本文以東風(fēng)1204大型拖拉機為樣機,首先理論分析了駕駛室內(nèi)耳旁噪聲的來源以及其產(chǎn)生機理,分析得到駕駛室耳旁噪聲是由空氣噪聲、混響聲和固體噪聲組成的。接著采用消元法、覆蓋法和表面加速度法等多種試驗方法進行試驗驗證,一方面正確識別了各噪聲源自身的噪聲聲量級,以及各噪聲源對駕駛室耳旁噪聲的貢獻率,從而驗證了駕駛室耳旁噪聲的理論分析;另一方面借助駕駛室耳旁噪聲的頻譜分析結(jié)果,大致將駕駛室耳旁噪聲劃分為中高頻噪聲和低頻噪聲兩大類。高頻噪聲主要由空氣噪聲和混響聲組成,通過優(yōu)化組合駕駛室內(nèi)包裝材料可以降低駕駛室耳旁噪聲。實驗結(jié)果表明,優(yōu)化后的包裝材料組合方式使得耳旁噪聲聲壓級下降12.1 dB。低頻噪聲主要源于發(fā)動機的二階不平衡往復(fù)慣性力,超出了包裝材料降噪能力,必須通過優(yōu)化駕駛室懸置系統(tǒng)的剛度和阻尼,從而阻隔傳播到駕駛室的低頻噪聲。首先借助RecurDyn多體動力學(xué)仿真軟件創(chuàng)建懸置系統(tǒng)穿聯(lián)結(jié)式減振器模型和駕駛室模型,并且使用表面振速法測得的試驗數(shù)據(jù)驗證仿真模型的正確性。然后選定減振器的剛度和阻尼為設(shè)計變量進行優(yōu)化設(shè)計。試驗結(jié)果表明,優(yōu)化后的剛度和阻尼有效提高了“低頻”懸置系統(tǒng)的隔振率,進而降低了駕駛室耳旁噪聲頻段中的低頻噪聲,使駕駛員的乘車舒適性得到保證。本文最后總結(jié)了降低大馬力拖拉機駕駛室耳旁噪聲的方式方法,主要表現(xiàn)為優(yōu)化駕駛室內(nèi)包裝材料組合來降低中高頻噪聲和優(yōu)化駕駛室懸置參數(shù)來降低低頻噪音。結(jié)果表明本文采取的降噪方式達到了預(yù)期的降噪效果,使得樣機滿足國家關(guān)于拖拉機駕駛室耳旁噪聲的行業(yè)標(biāo)準。
[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.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S219.0

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