乘用车变速器设计【捷达汽车变速器】
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附 录Manual transmission Overview Manual transmissions often feature a driver-operated clutch and a movable gear selector. Most automobile manual transmissions allow the driver to select any forward gear ratio (gear) at any time, but some, such as those commonly mounted on motorcycles and some types of racing cars, only allow the driver to select the next-higher or next-lower gear. This type of transmission is sometimes called a sequential manual transmission. Sequential transmissions are commonly used in auto racing for their ability to make quick shifts.Manual transmissions are characterized by gear ratios that are selectable by locking selected gear pairs to the output shaft inside the transmission. Conversely, most automatic transmissions feature epicyclic (planetary) gearing controlled by brake bands and/or clutch packs to select gear ratio. Automatic transmissions that allow the driver to manually select the current gear are called Manumatics. A manual-style transmission operated by computer is often called an automated transmission rather than an automatic.Contemporary automobile manual transmissions typically use four to six forward gears and one reverse gear, although automobile manual transmissions have been built with as few as two and as many as eight gears. Transmission for heavy trucks and other heavy equipment usually have at least 9 gears so the transmission can offer both a wide range of gears and close gear ratios to keep the engine running in the power band. Some heavy vehicle transmissions have dozens of gears, but many are duplicates, introduced as an accident of combining gear sets, or introduced to simplify shifting. Some manuals are referred to by the number of forward gears they offer (e.g., 5-speed) as a way of distinguishing between automatic or other available manual transmissions. Similarly, a 5-speed automatic transmission is referred to as a 5-speed automaticThe earliest form of a manual transmission is thought to have been invented by LouisRen Panhard and Emile Levassor in the late 19th century. This type of transmission offered multiple gear ratios and, in most cases, reverse. The gears were typically engaged by sliding them on their shaftshence the term shifting gears, which required a lot of careful timing and throttle manipulation when shifting, so that the gears would be spinning at roughly the same speed when engaged; otherwise, the teeth would refuse to mesh. These transmissions are called sliding mesh transmissions and sometimes called a crash box. Most newer transmissions instead have all gears mesh at all times but allow some gears to rotate freely on their shafts; gears are engaged using sliding-collar dog clutches; these are referred to as constant-mesh transmissions.In both types, a particular gear combination can only be engaged when the two parts to engage (either gears or dog clutches) are at the same speed. To shift to a higher gear, the transmission is put in neutral and the engine allowed to slow down until the transmission parts for the next gear are at a proper speed to engage. The vehicle also slows while in neutral and that slows other transmission parts, so the time in neutral depends on the grade, wind, and other such factors. To shift to a lower gear, the transmission is put in neutral and the throttle is used to speed up the engine and thus the relevant transmission parts, to match speeds for engaging the next lower gear. For both upshifts and downshifts, the clutch is released (engaged) while in neutral. Some drivers use the clutch only for starting from a stop, and shifts are done without the clutch. Other drivers will depress (disengage) the clutch, shift to neutral, then engage the clutch momentarily to force transmission parts to match the engine speed, then depress the clutch again to shift to the next gear, a process called double clutching. Double clutching is easier to get smooth, as speeds that are close but not quite matched need to speed up or slow down only transmission parts, whereas with the clutch engaged to the engine, mismatched speeds are fighting the rotational inertia and power of the engine.Even though automobile and light truck transmissions are now almost universally synchronised, transmissions for heavy trucks and machinery, motorcycles, and for dedicated racing are usually not. Non-synchronized transmission designs are used for several reasons. The friction material, such as brass, in synchronizers is more prone to wear and breakage than gears, which are forged steel, and the simplicity of the mechanism improves reliability and reduces cost. In addition, the process of shifting a synchromesh transmission is slower than that of shifting a non-synchromesh transmission. For racing of production-based transmissions, sometimes half the teeth (or dogs) on the synchros are removed to speed the shifting process, at the expense of greater wear. Shafts Like other transmissions, a manual transmission has several shafts with various gears and other components attached to them. Typically, a rear-wheel-drive transmission has three shafts: an input shaft, a countershaft and an output shaft. The countershaft is sometimes called a layshaft.In a rear-wheel-drive transmission, the input and output shaft lie along the same line, and may in fact be combined into a single shaft within the transmission. This single shaft is called a mainshaft. The input and output ends of this combined shaft rotate independently, at different speeds, which is possible because one piece slides into a hollow bore in the other piece, where it is supported by a bearing. Sometimes the term mainshaft refers to just the input shaft or just the output shaft, rather than the entire assembly.In some transmissions, its possible for the input and output components of the mainshaft to be locked together to create a 1:1 gear ratio, causing the power flow to bypass the countershaft. The mainshaft then behaves like a single, solid shaft, a situation referred to as direct drive.Even in transmissions that do not feature direct drive, its an advantage for the input and output to lie along the same line, because this reduces the amount of torsion that the transmission case has to bear. Most front-wheel-drive transmissions for transverse engine mounting are designed differently. For one thing, they have an integral final drive and differential. For another, they usually have only two shafts; input and countershaft, sometimes called input and output. The input shaft runs the whole length of the gearbox, and there is no separate input pinion. At the end of the second (counter/output) shaft is a pinion gear that mates with the ring gear on the differential. Front-wheel and rear-wheel-drive transmissions operate similarly. When the transmission is in neutral, and the clutch is disengaged, the input shaft, clutch disk and countershaft can continue to rotate under their own inertia. In this state, the engine, the input shaft and clutch, and the output shaft all rotate independently.Shift modeMain article: Gear stickA 5 speed gear lever In many modern passenger cars, gears are selected by manipulating a lever connected to the transmission via linkage or cables and mounted on the floor of the automobile. This is called a gear stick, shift stick, gearshift, gear lever, gear selector, or shifter. Moving the lever forward, backward, left, and right into specific positions selects particular gears. An aftermarket modification of this part is known as the installation of a short shifter which can be combined with an aftermarket shift knob or Weighted Gear Knob. A sample layout of a four-speed transmission is shown below. N marks neutral, the position wherein no gears are engaged and the engine is decoupled from the vehicles drive wheels. In reality, the entire horizontal line is a neutral position, although the shifter is usually equipped with springs so that it will return to the N position if not moved to another gear. The R marks reverse, the gear position used for moving the vehicle rearward. This layout is called the shift pattern. Because of the shift quadrants, the basic arrangement is often called an H-pattern.While the layout for gears one through four is nearly universal, the location of reverse is not. Depending on the particular transmission design, reverse may be located at the upper left extent of the shift pattern, at the lower left, at the lower right, or at the upper right. There is usually a mechanism that only allows selection of reverse from the neutral position, to reduce the likelihood that reverse will be inadvertently selected by the driver. This is the most common five-speed shift pattern:This layout is reasonably intuitive because it starts at the upper left and works left to right, top to bottom, with reverse at the end of the sequence and toward the rear of the car.This is another five-speed shift pattern, which can be found in Saabs, BMWs, some Audis, Volvos, Volkswagens, Opels, Hyundais, most Renaults, some diesel Fords, and more:Dog-leg first shift patterns are used on many race cars and on older road vehicles with three-speed transmissions: The name derives from the up-and-over path between first and second gears. Its use is common in race cars and sports cars, but is diminishing as six speed and sequential gearboxes are becoming more common. This is a typical shift pattern for a six-speed transmission: Though eight-speed transmissions do exist, six forward speeds is widely considered to be the maximum that can be contained within a variation of the H shift pattern. In such a case, Reverse is placed outside of the H, with a canted shift path, to prevent the shift lever from intruding too far into the drivers space (in left-hand drive cars) when reverse is selected. This is the most common layout for a six-speed manual transmission. Most front-engined, rear-wheel drive cars have a transmission that sits between the driver and the front passenger seat. Floor-mounted shifters are often connected directly to the transmission. Front-wheel drive and rear-engined cars often require a mechanical linkage to connect the shifter to the transmission.References1.Synchronizers; graphic illustration of how they work. http:/www.howstuffworks.com/transmission3.htm. Retrieved 2007-07-18.2. a b U.S. Department of Energy vehicle fuel economy website3.An Overview of Current Automatic, Manual and Continuously Variable Transmission Efficiencies and Their Projected Future Improvements, Kluger and Long, SAE 1999-01-12594.An Investigation into The Loss Mechanisms associated with a Pushing Metal V-Belt Continuously Variable Transmission, Sam Akehurst, 2001, Ph. D Thesis, University of Bath.5.Rick Steves Europe: Driving in Europe6.Why Dual Clutch Technology Will Be Big Business. Dctfacts.com. http:/www.dctfacts.com/archive/2008/why-dual-clutch-technology-big-business.aspx. Retrieved 2010-02-07.手动变速器 概述手动变速器通常设有一个司机操纵离合器和一个可移动的齿轮选择器。大多数汽车手动变速器,让驾驶者选择任何前进齿轮比(“齿轮”在任何时间),但有些如,常用于摩托车和赛车某些类型的安装,只允许司机选择下一个更高或下一个较低的齿轮。这种传送方式有时也被称为顺序手动变速器。顺序传输,通常用于赛车,使他们迅速转变。 手动变速器的特点是传动比通过锁定到内部齿轮对传动输出轴的选择。相反,大多数自动变速器的特点行星齿轮由刹车带传动和控制/或离合器选择齿轮比。自动变速器,让驾驶者手动选择当前齿轮被称为Manumatics。手动式变速器由计算机操作通常被称为半自动变速器,而不是自动变速箱。 现代汽车手动变速器,通常使用4至6个前进档和一个倒档,虽然汽车手动变速器,已建成以尽可能少的两个和多达8对齿轮。重型卡车和其他重型设备的传输通常有至少9对这样的齿轮传动,可以同时提供一个广泛和密切的齿轮传动比,以保持发动机的功率的正常运行。一些重型汽车变速器齿轮有几十个,但很多是重复的,作为一个齿轮组相结合,以简化或变速转向时发生意外。有些手册所提到的数目,如前进档,他们提供(例如,5速自动之间的一种可手动变速器或其他识别方式)。同样,一个5速自动变速器被称为一个“5速自动”。手动变速器最早的形式被认为是由圣路易斯的勒内潘哈德和埃米尔勒瓦索尔发明于19世纪。这种传送方式提供多种传动比,齿轮是典型的沿着他们的轴滑动,因此所谓“换档齿轮”,这需要时间和油门的精心操纵,使齿轮将在大致相同的旋转速度时进行,否则,齿轮会拒绝啮合。这些传动被称为“滑动啮合”的传动,大多数较新的变速器,不是在任何时候都啮合,但允许一些齿轮齿轮轴自由转动;这被称为“常啮合”的传动。在这两种类型,一个特定的齿轮组合,在同一速度只能进行两部分运动。转移到一个更高的齿轮,传动放在空挡位置,并允许缓慢降速,直到下一个齿轮传动部件在适当的速度下进行啮合。由于空挡和其他传动部件,车辆减速。所以在空挡时间取决于技巧水平,操作,和其他此类因素。转移到低档的齿轮,传动放在空挡和油门是用来加速,从而使有关的传动部件,以配合参与下一个低档的齿轮速度。对于这两个加减档,离合器分离,有些司机于从一开始只用空挡而停止离合器和离合器的变化是没有做。其他司机会分离(脱离)离合器,转向空挡,然后进行短暂的分离,迫使传动部件,发动机转速匹配,然后再压低离合器转移到下一个齿轮,这个过程被称为双离合。双离合是比较容易得到顺利换挡,因为速度是相当比较接近,但不匹配时需要加快或减慢传动部分,从离合器到发动机,不匹配的速度与转动惯量和发动机功率相冲突。尽管汽车和轻型卡车变速器现在几乎普遍同步,但是重型卡车和摩托车变速器,以及专用赛车通常不是。有几个原因使用非同步传输的设计。摩擦材料,如黄铜,在同步器中更容易磨损;齿轮比,简单提高可靠性和降低成本。此外,实现同步器传输过程是一个较缓慢移动,而非同步器变速箱,对于赛车的生产为基础的传输,有时一半的啮合齿环都被去掉,以加换挡速度,但要更多的磨损费用。轴像其他变速器一样,手动变速器有齿轮和附加到轴的其他零件。通常情况下,后轮驱动传动有三个轴:输入轴,一个副轴和输出轴。该副轴有时被称为中间轴。在后轮驱动的变速器中,输入和输出轴沿同一路线,事实上在变速器中可合并为一个单轴传动。这种单轴称为主轴。输入和输出两端这种组合轴以不同的速度独立旋转,这是可能的,因为一件轴滑入另一个轴的轴心,它是由轴承支承。有时这个词是指主轴,包括输入轴输出轴。在某些变速器中,输入和输出的主轴组件可能被固定,共同创造一个1:1齿轮比,使功率传动到中间轴。该主轴然后像一个单一实心轴传动,这种情况被称为直接驱动。甚至在不直接驱动的变速器中,输入轴和输出轴沿一条直线这是一种优势,因为这减少了变速器要承担的扭转量。大多数前轮驱动的横置发动机变速器装配设计不同。一方面,他们有一个很完整的驱动力。另一方面,他们通常只有两轴,输入和副轴,有时也被称为输入轴和输出轴。输入轴齿轮箱运行的整个长度中也没有独立的输入小齿轮。在输出轴中是一个小齿轮轴端齿轮与输入轴齿轮的配合。前轮和后轮驱动变速器的操作方式相似。当变速器是空挡时,是脱离离合器,输入轴,离合器盘和副轴旋转可以继续根据自己的惰性。在这种状态下,发动机,输入轴和离合器,输出轴都独立地自转。换挡方式主要文章:换挡杆一个5速变速杆在许多现代轿车,选择齿轮操纵或通过安装在汽车地盘上电缆连接的换挡杆联动。这就是所谓的排档杆,换档杆,换档,换档杆,齿轮选择器。移动换挡杆向前,向后,左,右到具体位置选择特定齿轮。这部分是售后众所周知的一段,可与售后市场的换档把手或加权齿轮旋钮组合安装。一个四速传动样本布局如下。N标志着空挡位置,其中没有齿轮活动和发动机与汽车的驱动车轮没有关系。实际上,整个水平线是一个中立的位置,如果不移动到另一个挡位换档时后由回位弹簧使其返回到N的位置。相反的R标记,是倒档。这个布局被称为换挡模式。由于换挡象限,基本方式是通常被称为一个H -格局。虽然这个布局对齿轮1到4几乎是普遍的,但没有倒档的位置。根据特定的传动设计,倒档也许位于换挡模式的左上部,在左下角,右下角,或在右上方。通常有一种装置,只允许倒档的选择从空挡选,减少的无意中挂错倒档的可能性。这是最共同的五速度转移模式:因为它开始在左上部并且传动由左到右,由上至下,与倒档在序列的结尾和向汽车的后方,这种布局是合理的。这是另一个五速度换挡模式,可以在Saabs, BMWs,某一Audis, Volvos, Volkswagens, Opels, Hyundais,多数Renaults,一些柴油论坛,或者其他地方找到:这种换挡模式首先使用在许多赛车和三速度传输的更旧的公路车辆:这个名字源于向上及以上第一和第二齿轮之间的道路,它常用语赛车和跑车,由于六速连续变速器的频繁使用,这种换挡模式在逐渐减少。这是六速变速器的一个典型的换挡模式:虽然8速变速器的确存在,6个前进的速度被广泛认为是可以在一个的“H”的格局转变中的最大变化。在这种情况下,倒档放在“H”的外面,有斜移路径,以防止侵入驾驶员挂档时,倒档被选中。这是一个六速手动变速器最常见的布局。大多数前置后驱轿车,变速器安装在司机和前排乘客座位之间。地盘安装换挡杆通常是直接连接到变速器中。前轮驱动和后置发动机汽车往往需要一个机械连杆连接的变速器来传输。参考文献1.Synchronizers;graphicillustrationofhow they work. http:/www.howstuffworks.com/transmission3.htm. Retrieved 2007-07-18.2. a b U.S. Department of Energy vehicle fuel economy website3.An Overview of Current Automatic, Manual and Continuously Variable Transmission Efficiencies and Their Projected Future Improvements, Kluger and Long, SAE 1999-01-12594. An Investigation into The Loss Mechanisms associated with a Pushing Metal V-Belt Continuously Variable Transmission, Sam Akehurst, 2001, Ph. D Thesis, University of Bath.5.Rick Steves Europe: Driving in Europe6.Why Dual Clutch Technology Will Be Big Business. Dctfacts.com. http:/www.dctfacts.com/archive/2008/why-dual-clutch-technology-big-business.aspx. Retrieved 2010-02-07.14SY-025-BY-5毕业设计(论文)中期检查表填表日期2010. 4.18迄今已进行 8 周剩余 8 周学生姓名李 威系部汽车与交通工程学院专业、班级车辆工程B06-2班指导教师姓名苏清源职称副教授从事专业车辆工程是否外聘是否题目名称乘用车变速器设计学生填写毕业设计(论文)工作进度已完成主要内容待完成主要内容(1)各挡传动比的计算;(2)各挡齿轮设计计算;(3)输入轴输出轴的设计及校核;(4)变速器操纵机构及箱体设计;(5)完成装配图。(1)完成零件图;(2)撰写设计说明书。存在问题及努力方向存在问题:由于输出轴4挡与5挡齿轮设计成一体,导致输出轴拆卸不方便;努力方向:把4挡与5挡设计成普通斜齿,中间用套筒定位,这样就可以解决输出轴拆卸不方便的问题。学生签字: 指导教师意 见 指导教师签字: 年 月 日教研室意 见教研室主任签字: 年 月 日乘用车变速器设计第1章 绪 论1.1 概述 本文以捷达汽车变速器为研究对象,变速器用来改变发动机传到驱动轮上的转矩和转速,目的是在原地起步,爬坡,转弯,加速等各种行驶工况下,使汽车获得不同的牵引力和速度,同时使汽车在最有利的工况范围内工作。变速器设有空挡和倒档。需要时,变速器还有动力输出功能。一 对变速器如下基本要求:1. 保证汽车有必要的动力性和经济型。2. 设置空挡。用来切断发动机动力向驱动轮的传输。3. 设置倒档,使汽车能倒退行驶。4. 设置动力传输装置,需要时进行功率输出。5. 换挡迅速、省力、方便。6. 工作可靠,汽车行驶过程中,变速器不得有跳挡、乱挡以及换挡冲击等现象发生。7. 变速器应有高的工作效率。8. 变速器的工作噪声低。除此之外,变速器还应该满足轮廓尺寸和质量小、制造成本低、拆装容易、维修方便等要求。满足汽车必要的动力性和经济性指标,这与变速器挡数、传动比范围和各挡传动比有关。汽车工作的道路条件越复杂、比功率越小,变速器传动比范围越大。二 变速器的类型:(1) 按传动比变化 变速器可分为有级式、无级式、和综合式三种。1.有级式变速器 具有若干个数值一定的传动比,传动比的变化呈阶梯式或跳跃式。有级式变速器应用最为广泛,传动方式采用齿轮传动(包括轴线固定的普通齿轮传动和部分齿轮轴线旋转的行星齿轮传动)。目前,轿车和轻、中型载货汽车装用的有级式变速器多为36个前进挡和一个倒档。2.无级式变速器 无级式变速器的传动比可以在一定范围内连续变化。有电力式和液压式无级变速器两种。传动部分分为直流串励电动和液力变矩器。3.综合式变速器 综合式变速器由液力变矩器和齿轮式有级变速器组成的液力机械式变速器,其传动比可以在最大值与最小值之间的几个间断的范围内作无级变化。目前应用较多。(2)按操纵方式 变速器可分为强制操纵式变速器、自动操纵式变速器和半自动操纵式变速器三种。1.强制操纵式变速器 靠驾驶员直接操纵变速换挡。2.自动操纵式变速器 传动比的选择和换挡是自动进行的,驾驶员只需操纵加速踏板,变速器就可以根据发动机的负荷信号和车速信号来控制执行元件,实现挡位的变换。3.半自动操纵式变速器 分为两类:一类是部分挡位自动换挡,部分挡位手动换挡;另一类是预先按钮选定挡位,在踩下离合器踏板或松开加速踏板时,由执行机构自动换挡。三 变速器的工作原理普通齿轮变速器也叫定轴式变速器,它由一个变速器壳、轴线固定的几根轴和若干齿轮等零件组成,可实现变速、变扭和改变旋转方向。1. 变速原理一对齿数不同的齿轮啮合传动时,设主动齿轮的转速为,齿数为,从动齿轮的转速为,齿数为。若小齿轮带动大齿轮时,转速就降低了;若大齿轮带动小齿轮时,转速即升高。在相同的时间内啮合的齿数相等,即=。齿轮的传动比为=/=/。齿轮传动机构的传动比定义为主动齿轮的转速与从动齿轮的转速之比,它也等于从动齿轮的齿数与主动齿轮的齿数之比,即这就是齿轮传动的变速原理。汽车变速器就是根据这一原理利用若干大小不同的齿轮副传动而实现变速的。2. 变向原理汽车发动机在工作过程中是不能逆转的。为了能使汽车倒退行驶,在变速器中设置了倒挡(R)。倒挡传动机构是在主动齿轮与从动齿轮之间增加一个中间齿轮,利用中间齿轮来改变输出轴的转动方向,因此,这个中间齿轮油称之为倒挡换挡齿轮。1.1.1 变速器的发展现状 变速器作为传递动力和改变车速的重要装置,国外对其操纵的方便性和挡位等方面的要求越来越高。目前对4挡特别是5挡变速器的应用有日渐增多的趋势,同时,6挡变速器的装车率也在上升。中国汽车变速器(汽车变速器市场调研)市场正处于高速发展期。2009年中国汽车销售1364万辆,同比增长46.15%,2015年汽车销售规模将达到4000万辆。在汽车行业市场规模高速增长的情况下,中国变速器(变速器行业分析)行业面临着重大机遇。2009年中国汽车变速器(汽车变速器市场调研)市场规模达520亿元人民币,并且以每年超过20%的速度增长,预计2015年有望达到1500亿元。由于近年来乘用车市场增长迅速,2007年中国乘用车变速器需求量在600万件以上,其中大部分为手动变速器,但是自动变速器的需求比例不断提高。与此同时随着商用车市场快速发展,2007年商用车变速器的市场需求量有200万件,其中轻型货车用变速器占市场主流,然而重型车变速器市场有望成为未来的新亮点。在手动变速器领域,国产品牌已占主导地位。但技术含量更高的自动变速器市场却是进口产品的天下,2007年中国变速器产品(变速器产品进口统计)进口额达到30亿美元。国内变速器企业未来面临严峻挑战。1.1.2 研究的目的、依据和意义随着汽车工业的迅猛发展,车型的多样化、个性化已经成为汽车发展的趋势。而变速器设计是汽车设计中重要的环节之一。它是用来改变发动机传到驱动轮上的转矩和转速,因此它的性能影响到汽车的动力性和经济性指标,对轿车而言,其设计意义更为明显。在对汽车性能要求越来越高的今天,车辆的舒适性也是评价汽车的一个重要指标,而变速器的设计如果不合理,将会使汽车的舒适性下降,使汽车的运行噪声增大。通过本题目的设计,学生可综合运用汽车构造、汽车理论、汽车设计、机械设计、液压传动等课程的知识,达到综合训练的效果。由于本题目模拟工程一线实际情况,学生通过毕业设计可与工程实践直接接触,从而可以提高学生解决实际问题的能力。1.1.3 研究的方法本次设计主要是通过查阅近几年来有关国内外变速器设计的文献资料,结合所学专业知识进行设计。通过比较不同方案和方法选取最佳方案进行设计,通过排量选择变速器中心距;各档传动比的计算;计算变速器的齿轮的结构参数并对其进行校核计算;计算选择轴与轴承,同时对其进行校核,对同步器、换挡操纵机构等结构件进行分析计算;另外,对现有传统变速器的结构进行改进、完善。第2章 变速器主要参数的选择与计算2.1设计初始数据 最高车速:=180Km/h 发动机功率:=74KW 转矩:=150 总质量:=1500Kg 转矩转速:=3800r/min 车轮:185/60R14 2.2变速器各挡传动比的确定初选传动比: = 0.377 (2.1) 式中: 最高车速 发动机最大功率转速 车轮半径 变速器最小传动比 乘用车取0.85 主减速器传动比 =9549 (转矩适应系数=1.11.3) (2.2) 所以,=9549=5653.008r/min/ =1.42.0 符合=0.377=0.377=4.026 (2.3)双曲面主减速器,当6时,取=90%最大传动比的选择:满足最大爬坡度。 (2.4) 式中:G作用在汽车上的重力,汽车质量,重力加速度,=15000N;发动机最大转矩,=150N.m;主减速器传动比,=4.026传动系效率,=90%;车轮半径,=0.289m;滚动阻力系数,对于货车取=0.01651+0.01(-50)=0.03795;爬坡度,取=16.7带入数值计算得 满足附着条件: (2.5)为附着系数,取值范围为0.50.6,取为0.6为汽车满载静止于水平面,驱动桥给地面的载荷,这里取70%mg ;计算得3.283 ; 由得2.5513.283 ; 取=3.2 ;校核最大传动比 ;在3.04.5范围内,故符合。其他各挡传动比的确定: 按等比级数原则,一般汽车各挡传动比大致符合如下关系: (2.6)式中:常数,也就是各挡之间的公比;因此,各挡的传动比为: ,=1.337所以其他各挡传动比为: =3.2, =2.390,=1.788,=1.337 ,=0.852.3变速器传动方案的确定图2-1a为常见的倒挡布置方案。图2-1b所示方案的优点是换倒挡时利用了中间轴上的一挡齿轮,因而缩短了中间轴的长度。但换挡时有两对齿轮同时进入啮合,使换挡困难。图2-1c所示方案能获得较大的倒挡传动比,缺点是换挡程序不合理。图2-1d所示方案针对前者的缺点做了修改,因而取代了图2-1c所示方案。图2-1e所示方案是将中间轴上的一,倒挡齿轮做成一体,将其齿宽加长。图2-1f所示方案适用于全部齿轮副均为常啮合齿轮,换挡更为轻便。为了充分利用空间,缩短变速器轴向长度,有的货车倒挡传动采用图2-61所示方案。其缺点是一,倒挡须各用一根变速器拨叉轴,致使变速器上盖中的操纵机构复杂一些。本设计采用图2-1f所示的传动方案。图2-1 变速器倒档传动方案 因为变速器在一挡和倒挡工作时有较大的力,所以无论是两轴式变速器还是中间轴式变速器的低档与倒挡,都应当布置在在靠近轴的支承处,以减少轴的变形,保证齿轮重合度下降不多,然后按照从低档到高挡顺序布置各挡齿轮,这样做既能使轴有足够大的刚性,又能保证容易装配。倒挡的传动比虽然与一挡的传动比接近,但因为使用倒挡的时间非常短,从这点出发有些方案将一挡布置在靠近轴的支承处。图2.2变速器传动示意图1. 输入轴五挡齿轮 2.输出轴五挡齿轮 3.输入轴四挡齿轮 4.输出轴四挡齿轮5. 输入轴三挡齿轮 6.输出轴三挡齿轮 7.输入轴二挡齿轮 8.输出轴二挡齿轮9. 输入轴一挡齿轮 10.输出轴一挡齿轮 11.倒挡齿轮 12.输入轴倒挡齿轮13.输出轴倒挡齿轮2.4中心距A的确定初选中心距:发动机前置前驱的乘用车变速器中心距A,可根据发动机排量与变速器中心距A的统计数据初选,A=66mm2.5齿轮参数2.5.1 模数对货车,减小质量比减小噪声更重要,故齿轮应该选用大些的模数;从工艺方面考虑,各挡齿轮应该选用一种模数。啮合套和同步器的接合齿多数采用渐开线。由于工艺上的原因,同一变速器中的接合齿模数相同。其取值范围是:乘用车和总质量在1.814.0t的货车为2.03.5mm;总质量大于14.0t的货车为3.55.0mm。选取较小的模数值可使齿数增多,有利于换挡。 表2.1汽车变速器齿轮法向模数车型乘用车的发动机排量V/L货车的最大总质量/t1.0V1.61.6V2.56.01414.0模数/mm2.252.752.753.003.504.504.506.00表2.2汽车变速器常用齿轮模数一系列1.001.251.502.002.503.004.005.006.00二系列1.752.252.753.253.503.754.505.50 发动机排量为1.6L,根据表2.2.1及2.2.2,齿轮的模数定为2.252.75mm。2.5.2 压力角理论上对于乘用车,为加大重合度降低噪声应取用14.5、15、16、16.5等小些的压力角;对商用车,为提高齿轮承载能力应选用22.5或25等大些的压力角。国家规定的标准压力角为20,所以变速器齿轮普遍采用的压力角为20。2.5.3 螺旋角 实验证明:随着螺旋角的增大,齿的强度也相应提高。在齿轮选用大些的螺旋角时,使齿轮啮合的重合度增加,因而工作平稳、噪声降低。斜齿轮传递转矩时,要产生轴向力并作用到轴承上。乘用车两轴式变速器螺旋角:20252.5.4 齿宽直齿,为齿宽系数,取为4.58.0,取7.0;斜齿,取为6.08.5。采用啮合套或同步器换挡时,其接合齿的工作宽度初选时可取为24mm,取4mm。2.5.5 齿顶高系数在齿轮加工精度提高以后,包括我国在内,规定齿顶高系数取为1.00. 2.6本章小结通过初始数据,首先确定变速器的最大传动比,然后根据最大传动比,确定挡数及各挡传动比的大小,然后根据变速器中心距A与发动机排量的关系,初选变速器的中心距。然后确定齿轮的模数,压力角,螺旋角,齿宽等参数,为下一章齿轮参数的计算做准备。第3章 齿轮的设计计算与校核3.1齿轮的设计与计算 3.1.1 各挡齿轮齿数的分配一挡齿轮为斜齿轮,模数为2.5,初选=22一挡传动比为 (3.1) 为了求,的齿数,先求其齿数和, 斜齿 (3.2) =48.96取整为49即=11.65 取12 =49-12=37对中心距进行修正因为计算齿数和后,经过取整数使中心距有了变化,所以应根据取定的和齿轮变位系数重新计算中心距,再以修正后的中心距作为各挡齿轮齿数分配的依据。=66.06mm (3.3)对一挡齿轮进行角度变位:端面啮合角 : tan=tan/cos=0.392 (3.4) =21.42啮合角 : cos=0.932 (3.5) =21.29变位系数之和 (3.6) =-0.11查变位系数线图得: 计算一挡齿轮9、10参数:分度圆直径 =2.512/cos22=32.356mm =2.537/22=99.764mm齿顶高 =3.74mm =1.415mm式中: =(66-66.06)/2.5=-0.024 = -0.11+0.024 = -0.086齿根高 =2.1mm =4.425mm齿顶圆直径 =39.836mm =102.062mm齿根圆直径 =28.156mm =90.914mm 当量齿数 =15.056 =46.424二挡齿轮为斜齿轮,模数为2.25,初选=24 =53.59 取整为54=15.81,取整为17 =37则,=2.1765=2.390对二挡齿轮进行角度变位:理论中心距 =66.499mm端面压力角 tan=tan/cos =21.574端面啮合角 = 变位系数之和 = -0.216查变位系数线图得: -0.216 =0.35 =二挡齿轮参数:分度圆直径 =41.870mm =91.128mm齿顶高 =3.029mm =0.9675mm式中: = -0.22 =-0.004齿根高 =2.025mm =4.086mm齿顶圆直径 =47.928mm =93.063mm齿根圆直径 =37.370mm =82.956mm 当量齿数 =22.298 =49.843三挡齿轮为斜齿轮,初选=22模数为2.25 =1.649 =54.39, 取整为55得=19.727取整为21,=34 = =1.619=1.788对三挡齿轮进行角度变为:理论中心距 =66.734mm端面压力角 tan=tan/cos=0.388 =21.218端面啮合角 =0.9426 变位系数之和 = -0.31查变位系数线图得: =0.19 = -0.50三挡齿轮5、6参数:分度圆直径 =50.916mm =82.508mm齿顶高 =2.642mm =1.089mm式中: = -0.326 =0.016齿根高 =2.385mm =3.938mm齿顶圆直径 =56.245mm =84.686mm齿根圆直径 =46.191mm =74.633mm 当量齿数 =26.389 =42.660四挡齿轮为斜齿轮,初选=24模数=2.5 = 取整为49 =20.614,取整为23 =26 则: = =1.1304=1.377对四挡齿轮进行角度变位:理论中心距 =67.064mm端面压力角 tan=tan/cos=0.3922 =21.42端面啮合角 =0.946 变位系数之和 = -0.39查变位系数线图得: = -0.03 = -0.36四挡齿轮3、4参数:分度圆直径 =62.942mm =71.151mm齿顶高 =2.375mm =1.55mm式中: =-0.41 =-0.02齿根高 =3.2mm =4.025mm齿顶圆直径 =67.692mm =74.251mm齿根圆直径 =56.542mm =63.101mm 当量齿数 =30.168 =34.103五挡齿轮为斜齿轮,初选=22模数=2.25 = 取整为55 =29.4,取整为31 =24 则: = =0.774=0.85对五挡齿轮进行角度变位:理论中心距 =66.734mm端面压力角 tan=tan/cos=0.388 =21.218端面啮合角 =0.9426 变位系数之和 = -0.31查变位系数线图得: = 0.19 = -0.50五挡齿轮1、2参数:分度圆直径 =75.228mm =80.512mm齿顶高 =2.642mm =1.089mm式中: =-0.326 =-0.086齿根高 =2.385mm =3.938mm齿顶圆直径 =80.512mm =60.419mm齿根圆直径 =70.458mm =50.365mm 当量齿数 =38.896 =30.112确定倒挡齿轮齿数倒挡齿轮选用的模数与一挡相同,倒挡齿轮的齿数一般在2123之间,初选后,可计算出输入轴与倒挡轴的中心距。初选=21,=13,则:=42.5mm为保证倒挡齿轮的啮合和不产生运动干涉,齿轮12和13的齿顶圆之间应保持有0.5mm以上的间隙,则齿轮13的齿顶圆直径应为 =2662.5(13+2)1=93.5mm =2=35.4为了保证齿轮12和13的齿顶圆之间应保持有0.5mm以上的间隙,取=34计算倒挡轴和输出轴的中心距 = =68.75mm计算倒挡传动比 =2.6153.1.2齿轮材料的选择原则1、满足工作条件的要求 不同的工作条件,对齿轮传动有不同的要求,故对齿轮材料亦有不同的要求。但是对于一般动力传输齿轮,要求其材料具有足够的强度和耐磨性,而且齿面硬,齿芯软。2、合理选择材料配对 如对硬度350HBS的软齿面齿轮,为使两轮寿命接近,小齿轮材料硬度应略高于大齿轮,且使两轮硬度差在3050HBS左右。为提高抗胶合性能,大、小轮应采用不同钢号材料。3、考虑加工工艺及热处理工艺 变速器齿轮渗碳层深度推荐采用下列值:渗碳层深度0.81.2 时渗碳层深度0.91.3时渗碳层深度1.01.3表面硬度HRC5863;心部硬度HRC3348对于氰化齿轮,氰化层深度不应小于0.2;表面硬度HRC。对于大模数的重型汽车变速器齿轮,可采用25CrMnMO,20CrNiMO,12Cr3A等钢材,这些低碳合金钢都需随后的渗碳、淬火处理,以提高表面硬度,细化材料晶面粒。3.1.3计算各轴的转矩发动机最大扭矩为192N.m,齿轮传动效率99%,离合器传动效率98%,轴承传动效率96%。输入轴 =150N.m输出轴 =15096%99%=142.56N.m 输出轴一挡 =142.563.2=456.129N.m 输出轴二挡 =142.562.297=334.351N.m输出轴三挡 =142.561.649=240.028N.m输出轴四挡 =142.561.184=172.343N.m输出轴五挡 =142.560.85=123.726N.m倒挡 =15030.85=372.849N.m3.2轮齿的校核3.2.1轮齿弯曲强度计算1、倒档直齿 轮弯曲应力图3.1 齿形系数图 (3.8) 式中:弯曲应力(MPa);计算载荷(N.mm);应力集中系数,可近似取=1.65;摩擦力影响系数,主、从动齿轮在啮合点上的摩擦力方向不同,对弯曲应力的影响也不同;主动齿轮=1.1,从动齿轮=0.9;齿宽(mm);模数;齿形系数,如图3.1。当计算载荷取作用到变速器第一轴上的最大转矩时,一、倒挡直齿轮许用弯曲应力在400850MPa,货车可取下限,承受双向交变载荷作用的倒挡齿轮的许用应力应取下限。计算倒挡齿轮11,12,13的弯曲应力 ,=21,=13,=34,=0.141,=0.145,=0.162,=372.849N.m,=142.56N.m=719.114MPa400850MPa =735.948MPa400850MPa = = 512.219MPa400850MPa2、 斜齿轮弯曲应力 (3.9) 式中:计算载荷,Nmm;法向模数,mm;齿数;斜齿轮螺旋角,;应力集中系数,=1.50;齿形系数,可按当量齿数在图中查得;齿宽系数重合度影响系数,=2.0。当计算载荷取作用到变速器第一轴上的最大转矩时,对乘用车常啮合齿轮和高挡齿轮,许用应力在180350MPa范围,对货车为100250MPa。(1)计算一挡齿轮9,10的弯曲应力 ,=12,=37,=0.118,=0.155,=456.129N.m,=150N.m,=316.37MPa180350MPa =344.001MPa180350MPa(2)计算二挡齿轮7,8的弯曲应力=17,=37,=0.164,=0.122,=334.351N.m,=150N.m, =294.47MPa180350MPa =345.728MPa180350MPa(3)计算三挡齿轮5,6的弯曲应力=21,=34,=0.152,=0.121,=240.028N.m,=150N.m =261.042MPa180350MPa =283.588MPa180350MPa(4)计算四挡齿轮3,4的弯曲应力=23,=26,=0.145,=0.125,=172.343N.m,=150N.m =147.791MPa180350MPa =185.136MPa180350MPa(5)计算五挡齿轮1,2的弯曲应力=31,=24,=0.156,=0.148,=150N.m,=123.726N.m = =172.301MPa180350MPa = =217.892MPa180350MPa3.2.2轮齿接触应力j (3.10) 式中:轮齿的接触应力,MPa;计算载荷,N.mm;节圆直径,mm;节点处压力角,齿轮螺旋角,;齿轮材料的弹性模量,MPa;齿轮接触的实际宽度,mm; 、主、从动齿轮节点处的曲率半径,mm,直齿轮、,斜齿轮、; 、主、从动齿轮节圆半径(mm)。将作用在变速器第一轴上的载荷作为计算载荷时,变速器齿轮的许用接触应力见表3.2。弹性模量=20.6104 Nmm-2,齿宽表3.2变速器齿轮的许用接触应力齿轮渗碳齿轮液体碳氮共渗齿轮一挡和倒挡190020009501000常啮合齿轮和高挡13001400650700(1)计算一挡齿轮9,10的接触应力=456.192N.m,=150N.m, , =31.429mm, =u=100.573 mm=6.434mm=19.838mm = =1445.184MPa19002000MPa =1342.598MPa19002000MPa(2)计算二挡齿轮7,8的接触应力=334.351N.m,=150N.m,=40.036mm,=91.964mm=18.672mm=8.579mm = =1212.385MPa13001400MPa =1132.459MPa13001400MPa(3)计算三挡齿轮5,6的接触应力=240.028N.m,=150N.m,=49.830mm,=84.412mm=17.003mm=10.134mm = =1060.116MPa13001400MPa =987.396MPa13001400MPa(4)计算四挡齿轮3,4的接触应力=172.343N.m,=150N.m,=60.440mm,=71.560mm=14.579mm=12.897mm = =873.056MPa13001400MPa =740.923MPa13001400MPa(5)五挡齿轮1,2的接触应力=150N.m,=123.726N.m,=71.351mm,=60.649mm=14.476mm=11.796mm = =833.087MPa13001400MPa = 783.954MPa13001400MPa(6)计算倒挡齿轮11,12,13的接触应力=372.849N.m,=150N.m, mm mm mm =5.558mm =14.536mm =8.978mm = =564.157MPa19002000MPa =1604.646MPa19002000MPa = =12303150MPa19002000MPa3.3本章小结本章首先根据所学汽车理论的知识计算出主减速器的传动比,然后计算出变速器的各挡传动比;接着确定齿轮的参数,如齿轮的模数、压力角、螺旋角、齿宽、齿顶高系数;介绍了齿轮变位系数的选择原则,并根据各挡传动比计算各挡齿轮的齿数,根据齿数重新计算各挡传动比,同时对各挡齿轮进行变位。然后简要介绍了齿轮材料的选择原则,即满足工作条件的要求、合理选择材料配对、考虑加工工艺及热处理,然后计算出各挡齿轮的转矩。根据齿形系数图查出各齿轮的齿形系数,计算轮齿的弯曲应力和接触应力。最后计算出各挡齿轮所受的力,为下章对轴及轴承进行校核做准备。第4章 轴的设计与计算及轴承的选择与校核4.1轴的设计计算4.1.1 轴的工艺要求倒挡轴为压入壳体孔中并固定不动的光轴。变速器第二轴视结构不同,可采用渗碳、高频、氰化等热处理方法。对于只有滑动齿轮工作的第二轴可以采用氰化处理,但对于有常啮合齿轮工作的第二轴应采用渗碳或高频处理。第二轴上的轴颈常用做滚针的滚道,要求有相当高的硬度和表面光洁度,硬度应在HRC5863,表面光洁度不低于8。对于做为轴向推力支承或齿轮压紧端面的轴的端面,光洁度不应低于7,并规定其端面摆差。一根轴上的同心直径应可控制其不同心度。对于采用高频或渗碳钢的轴,螺纹部分不应淬硬,以免产生裂纹。对于阶梯轴来说,设计上应尽量保证工艺简单,阶梯应尽可能少。4.1.2 初选轴的直径传动轴的强度设计只需按照扭转强度进行计算,输入轴轴颈 =103=24.27mm 取整后d=25mm (4.1)图4.1 轴的示意图4.1.3 轴的强度计算轴的刚度验算若轴在垂直面内挠度为,在水平面内挠度为和转角为,可分别用式计算 (4.2) (4.3) (4.4) 式中:齿轮齿宽中间平面上的径向力(N);齿轮齿宽中间平面上的圆周力(N);弹性模量(MPa),=2.1105MPa;惯性矩(mm4),对于实心轴,;轴的直径(mm),花键处按平均直径计算;、齿轮上的作用力距支座、的距离(mm);支座间的距离(mm)。轴的全挠度为mm。 (4.5)轴在垂直面和水平面内挠度的允许值为=0.050.10mm,=0.100.15mm。齿轮所在平面的转角不应超过0.002rad。变速器中一挡所受力最大,故只需校核一挡处轴的刚度与挠度输入轴刚度 图4.2 输入轴受力分析图一挡齿轮所受力N,Nmm,mm mm (4.6)=0.035mm (4.7)=0.090=-0.000323rad0.002rad (4.8)输出轴刚度图4.3 输出轴受力分析图N,Nmm,mm mm=0.020mm =0.052=0.00019rad0.002rad输入轴的强度校核 图4.4 输入轴的强度分析图一挡时挠度最大,最危险,因此校核。 1)竖直平面面上得 =1062.39N竖直力矩=164971.09N.mm2)水平面内上、和弯矩由以上两式可得=6483.79N,=1004987.02N.mm按第三强度理论得: N.mm输出轴强度校核 1)竖直平面面上得 =1048.05N竖直力矩=162447.93N.mm2)水平面内上、和弯矩由以上两式可得=5653.89N,=873562.59N.mm按第三强度理论得: N.mm4.2轴承的选择及校核4.2.1输入轴的轴承选择与校核 由工作条件和轴颈直径初选输入轴的轴承型号,30205(左右),由机械设计手册查得代号为30205的圆锥滚子轴承 , ,e=0.37,Y=1.6;轴承的预期寿命:=103008=24000h 校核轴承寿命)、求水平面内支反力、和弯矩+=由以上两式可得=2572.99N,=1062.39N )、内部附加力、,由机械设计手册查得Y=1.6 (4.9) (4.10) )、轴向力和 由于 所以左侧轴承被放松,右侧轴承被压紧 )、求当量动载荷 查机械设计课程设计得 故右侧轴承X=0.67 左侧轴承X=0.4径向当量动载荷 (4.11) =1.2(0.672572.99+1.6322.62)=2688.11N 校核轴承寿命 预期寿命 ,为寿命系数,对球轴承=3;对滚子轴承=10/3。(4.12) =55229.2h=24000h合格4.2.2 输出轴轴承校核 初选输出轴的轴承型号,30206(左右),由机械设计手册查得代号为30206的圆锥滚子轴承 , ,e=0.37,Y=1.6;轴承的预期寿命:=103008=24000h 校核轴承寿命)、求水平面内支反力、和弯矩+=由以上两式可得=2538.25N,=1048.05N )、内部附加力、,由机械设计手册查得Y=1.6 )、轴向力和 由于 所以右侧轴承被放松,左侧轴承被压紧 )、求当量动载荷 查机械设计课程设计得 故右侧轴承X=0.67 左侧轴承X=0.4径向当量动载荷 =1.2(0.672538.25+1.6327.52)=2669.59N 校核轴承寿命 预期寿命 ,为寿命系数,对球轴承=3;对滚子轴承=10/3; =150426.9h=24000h 故该轴承合格4.3本章小结本章首先简要介绍了轴的工艺要求,即满足工作条件的要求。通过计算,确定轴的最小轴颈,通过轴承等确定轴的轴颈和各阶梯轴的长度,然后对轴进行刚度和强度的验算校核。通过轴颈,选择合适的轴承,通过轴向力的大小对轴承进行寿命计算。 结 论本次设计的变速器是以捷达参数为依据,乘用车两轴变速器,通过排量选择中心距的大小,齿轮的模数等,确定倒挡的布置形式,确定齿轮的压力角,螺旋角,齿宽,齿形系数等,然后计算变速器的各挡传动比,各齿轮的参数,通过变为系数图查找计算变为系数,然后对各挡齿轮进行变位。然后简要的介绍了齿轮材料的选择原则,对齿轮进行校核。通过最小轴颈的计算,选择轴承,确定轴各段的长度和轴颈大小。对轴和轴承进行校核计算。 对于本次设计的变速器来说,其特点是:扭矩变化范围大可以满足不同的工况要求,结构简单,易于生产、使用和维修,价格低廉,而且采用结合套挂挡,可以使变速器挂挡平稳,噪声降低,轮齿不易损坏。在设计中采用了5+1档手动变速器,通过较大的变速器传动比变化范围,可以满足汽车在不同的工况下的要求,从而达到其经济性和动力性的要求;变速器挂档时用同步器,虽然增加了成本,但是使汽车变速器操纵舒适度增加,齿轮传动更平稳。本着实用性和经济性的原则,在各部件的设计要求上都采用比较开放的标准,因此,安全系数不高,这一点是本次设计的不理想之处。 参考文献1郝京顺.汽车变速器的发展J.知识讲座,2000(6)2杨通顺变速器的黄金时代J汽车与配件,20033王尚军.DC6J80T六档变速器设计J.大同齿轮集团有限责任公司,2002(1)4林绍义.一种汽车变速器设计J.机电技术,2004(1)5吴修义.国内组合式机械变速器的现状与发展J.现代零部件,2005(1)6吴修义.机械变速器系列化及与车辆的匹配J.变通世界,1999(9)7殷浩东.工程机械驱动桥、变速器产品现状与发展分析J.工程机械与维修, 2006(4)8张洪欣变速器优化设计J哈尔滨工业大学出版社,20039王望予.汽车设计M.北京:机械工业出版社,200310陈家瑞.汽车构造M.北京:机械工业出版社,200511吴际璋汽车构造M北京:人民交通出版社,200412张阳,席军强,陈慧岩.半挂牵引车自动变速器换档策略研究J.北京理工大学机械与车辆工程学院,2006(2)13余志生.汽车理论M北京:机械工业出版社,200014刘惟信.汽车设计M.北京:清华大学出版社,200115王三民.诸问俊.机械原理与设计M.北京:机械工业出版社,200116王世刚,张秀亲,苗淑杰.机械设计实践M.哈尔滨:哈尔滨工程大学出版社,200117Nakayama T, Suda 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The present and future of electric power steering. Int. J. Of Vehicle Design, 1994, 15(3,4,5):243234.18Yasuo Shimizu ,Toshitake Kawai. Development of Electric Power Steering. SAE Paper No. 910014.致 谢通过本次设计,使我对变速器有了更多的了解,明白了变速器设计的重要性对变速器的现状及未来有了更深刻的了解,综合运用了汽车构造、汽车理论汽车设计、机械设计、液压传动等课程知识,巩固了所学知识。在本次毕业设计中,指导老师苏清源一直关注着我的每一步进展,并给了我很多的意见和建议,同时也对我提出了严格的要求,我能够顺利的完成毕业设计,和苏老师的指导师分不开的,在此特别感谢苏老师对我指导与帮助。另外,在这次毕业设计时,遇到很多问题,车辆工程老师和同学也给了我很大帮助,非常感谢帮助过我的老师与同学。42
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