【摘要】：變速器是汽車(chē)的重要部件,而處于常嚙合狀態(tài)的變速器主減速齒輪對(duì),作為變速器的重要零件,它承受著汽車(chē)傳動(dòng)的全部扭矩。同時(shí)因?yàn)槠?chē)頻繁的換檔和車(chē)速變化,造成變速器主減速齒輪對(duì)的壽命縮短。主減速齒輪價(jià)格昂貴,不可隨意調(diào)換,制造精度比較高。而齒輪的承載能力主要受接觸強(qiáng)度和彎曲強(qiáng)度的限制,因此,對(duì)主減速齒輪副的彎曲應(yīng)力和接觸應(yīng)力進(jìn)行科學(xué)的分析,就顯得十分必要。 本文根據(jù)某企業(yè)提供的汽車(chē)手動(dòng)變速器主減速齒輪對(duì)的結(jié)構(gòu)及機(jī)械性能參數(shù),實(shí)現(xiàn)了主減速斜齒輪的三維參數(shù)化精確建模。盡管很多研究人員在有關(guān)CAD/CAM/CAE軟件上實(shí)現(xiàn)了“參數(shù)化”的斜齒輪建模,但這個(gè)“參數(shù)化”是在“事先手動(dòng)參與”后的實(shí)現(xiàn)的“參數(shù)化”,并不是完全的全過(guò)程參數(shù)化。另外很多研究文獻(xiàn)忽略了齒輪根部的精確造型,而這是進(jìn)行輪齒根部彎曲強(qiáng)度有限元計(jì)算的重要前提。本文建立斜齒輪的完整的實(shí)用的數(shù)學(xué)模型,所謂“完整”,既包括漸開(kāi)線齒廓,也包括過(guò)渡曲線齒廓;所謂“實(shí)用”,是指以齒厚中心線為對(duì)稱(chēng)軸建立了齒廓的數(shù)學(xué)模型,這有利于三維CAD建模。并基于APDL語(yǔ)言實(shí)現(xiàn)了斜齒輪的三維參數(shù)化精確建模。 本文對(duì)變速器在發(fā)動(dòng)機(jī)最大輸出扭矩(變速器最大輸入扭矩)時(shí),齒輪副的受載和約束情況進(jìn)行了分析,重點(diǎn)介紹了漸開(kāi)線斜齒輪嚙合最?lèi)杭虞d線的定義,并根據(jù)此定義對(duì)變速器主減速齒輪副的最?lèi)杭虞d線進(jìn)行了計(jì)算,利用最?lèi)杭虞d線對(duì)齒輪施加載荷。求解計(jì)算后,分別對(duì)主動(dòng)和從動(dòng)齒輪的彎曲應(yīng)力分布狀況進(jìn)行了研究,得出齒輪中較危險(xiǎn)彎曲應(yīng)力的位置,在實(shí)際的齒輪設(shè)計(jì)中可以作為理論參考,同時(shí)在齒輪制造和熱處理過(guò)程中可以對(duì)彎曲應(yīng)力最大的地方考慮特殊處理,以增加齒輪的壽命和可靠性。傳統(tǒng)計(jì)算公式與有限元法算的結(jié)果相比較,計(jì)算公式得到的彎曲應(yīng)力值偏小些,說(shuō)明工程中,按有限元法進(jìn)行設(shè)計(jì)和校核,是偏安全的。用有限元分析結(jié)果對(duì)彎曲強(qiáng)度進(jìn)行了校核,應(yīng)力最大值比材料彈性許用應(yīng)力小,得出齒輪彎曲強(qiáng)度儲(chǔ)備較大。這與主減速齒輪實(shí)際使用中很少發(fā)生彎曲折斷的結(jié)論是一致的。 本文為使齒輪副非線性接觸分析的計(jì)算速度加快,結(jié)果更精確,對(duì)齒輪副嚙合模型做簡(jiǎn)化,取大齒輪的四個(gè)齒和小齒輪的三個(gè)齒進(jìn)行接觸有限元分析。建立接觸對(duì)(指定接觸面和目標(biāo)面、創(chuàng)建目標(biāo)面和接觸面單元、調(diào)整接觸初始條件),計(jì)算在載荷和約束作用下的應(yīng)力值,得出直觀的齒輪副接觸面上接觸應(yīng)力變化云圖。從圖分析知等效接觸應(yīng)力最大值為929.6 MPa,齒面接觸應(yīng)力成線形分布,即沿接觸線分布,分布不均,兩端靠近中間的位置接觸應(yīng)力相對(duì)較大,中間位置相對(duì)較小,最大的接觸應(yīng)力出現(xiàn)在節(jié)線附近靠近齒根處。分析得出的齒輪中較危險(xiǎn)接觸應(yīng)力位置,在實(shí)際的齒輪設(shè)計(jì)中可以作為理論參考,同時(shí)在齒輪制造和熱處理過(guò)程中可以對(duì)接觸應(yīng)力最大的地方考慮特殊處理,以增加齒輪的壽命和可靠性。與彎曲應(yīng)力計(jì)算結(jié)果比較分析相似,計(jì)算公式得到的接觸應(yīng)力值偏小些,說(shuō)明工程中,按有限元法進(jìn)行設(shè)計(jì)和校核,是偏安全的。對(duì)接觸強(qiáng)度進(jìn)行了校核,其結(jié)果得到了合作企業(yè)的認(rèn)可,精度較高。 綜上所述,本文對(duì)MT21變速器主減速齒輪副的彎曲強(qiáng)度和接觸強(qiáng)度進(jìn)行了詳盡的分析,掌握了該齒輪副應(yīng)力分布,對(duì)強(qiáng)度進(jìn)行了校核,分析結(jié)果經(jīng)設(shè)計(jì)方認(rèn)證,認(rèn)為具有較高的精度。本文的研究工作為齒輪的結(jié)構(gòu)優(yōu)化、輪齒修形、多物理場(chǎng)耦合分析等奠定了基礎(chǔ)。鑒于齒輪強(qiáng)度計(jì)算的復(fù)雜性,應(yīng)當(dāng)說(shuō)本文的研究仍屬于基礎(chǔ)性的工作。在本文研究基礎(chǔ)上,可以方便地進(jìn)一步研究齒輪的結(jié)構(gòu)優(yōu)化、輪齒修形、多物理場(chǎng)禍合分析、概率設(shè)計(jì)(可靠性設(shè)計(jì))等。
[Abstract]:Transmission is an important part of automobile, and the main gear pair of transmission in constant meshing state, as an important part of transmission, it bears all the torque of automobile transmission. It is necessary to scientifically analyze the bending stress and contact stress of the main reducer gear pair.
According to the structure and mechanical performance parameters of the main reducer gear pair of the automobile manual transmission provided by an enterprise, this paper realizes the accurate three-dimensional parametric modeling of the helical gear pair of the main reducer. The parameterization after participation is not a complete parameterization of the whole process. In addition, many research papers neglect the precise modeling of the root of the gear, which is an important prerequisite for the finite element calculation of the bending strength of the root of the gear. Linear tooth profile also includes transition curve tooth profile; the so-called "practical" refers to the establishment of a mathematical model of tooth profile with the center line of tooth thickness as the symmetrical axis, which is conducive to three-dimensional CAD modeling.
In this paper, the load and restraint of gear pair in the maximum output torque of engine (maximum input torque of transmission) are analyzed. The definition of the worst load line of involute helical gear meshing is introduced emphatically. According to this definition, the worst load line of the main gear pair of transmission is calculated, and the worst load line is used. After calculating, the bending stress distribution of active and driven gears is studied, and the position of dangerous bending stress in gears is obtained. It can be used as a theoretical reference in actual gear design, and special consideration can be given to the place where the bending stress is maximum in gear manufacturing and heat treatment. Comparing with the result of finite element method, the value of bending stress obtained by traditional calculation formula is smaller, which shows that it is safe to design and check according to finite element method in engineering. The allowable stress is small and the reserve of bending strength of the gear is large, which is consistent with the conclusion that the bending fracture of the main reducer gear seldom occurs in actual use.
In order to speed up the calculation of non-linear contact analysis of gear pair and make the result more accurate, the meshing model of gear pair is simplified, and the contact finite element analysis of four teeth of big gear and three teeth of small gear is carried out. By calculating the stress value under load and restraint, the contact stress variation nephogram on the contact surface of gear pair is obtained intuitively. The maximum value of equivalent contact stress is 929.6 MPa, and the contact stress on the tooth surface is linear distribution, that is, along the contact line, the distribution is uneven, the contact stress at the two ends near the middle position is relatively large, and the middle position is relative. The position of the dangerous contact stress in the gear can be used as a theoretical reference in the actual gear design. At the same time, special treatment can be taken into account in the gear manufacturing and heat treatment process to increase the life and reliability of the gear. Similar to the calculation results of bending stress, the contact stress values obtained by the calculation formulas are slightly smaller, which shows that it is safe to design and check the contact strength by finite element method in engineering. The results are approved by the cooperative enterprise and have higher accuracy.
In summary, the bending strength and contact strength of the main reducer gear pair of MT21 transmission are analyzed in detail in this paper, the stress distribution of the gear pair is mastered, and the strength is checked. The analysis result is verified by the designer, and it is considered to have higher precision. In view of the complexity of gear strength calculation, this paper is still a basic work. On the basis of this study, it is convenient to further study gear structure optimization, gear tooth modification, multi-physical field coincidence analysis, probability design (reliability design) and so on.
【學(xué)位授予單位】：江西理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2011
【分類(lèi)號(hào)】：TH132.41

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本文編號(hào)：2231076