轻型货车变速器设计毕业论文

随着国民经济的迅猛发展，汽车产量逐年增加，2006年已达720万辆。我国汽车保有量越来越多，车型也越来越复杂。尤其是高科技的飞速发展，一些新技术、新材料在汽车上的广泛应用后，给汽车故障诊断与排除增加了一定难度。本篇论文重点讨论轿车离合器的故障分析及维修方法。离合器是手动变速汽车必备的一个重要总成。没有离合器手动挡汽车将无法起步，并且难以实现挡位变换。在汽车使用中，离合器难免出现这样、那样的故障，直接影响汽车的正常运行。现在汽车迅速进入家庭，汽车私有化程度提高，所以汽车故障将会影响到我们每一个人。分析研究离合器故障现象、原因、探索离合器故障的排除方法和离合器的维修工艺，具有重大而现实的意义。本文重点通过北京现代轿车离合器故障的探讨，正确认识离合器故障，更好的使用和维护离合器。离合器安装在发动机与变速器之间，用来分离或接合前后两者之间动力联系。其功用是：1）使汽车平稳起步;现今所用的盘片式离合器的先驱的多片盘式离合器，它是直到1925年以后才出现的。多片离合器最主要的优点是，在汽车起步时离合器的接合比较平顺，无冲击。20世纪20年代末，直到进入30年代时，只有工程车辆、赛车和大功率的轿车上使用多片离合器。多年的实践经验和技术上的改进使人们逐渐趋向与首选单片干式摩擦离合器，因为它具有从动部件转动惯量小、散热性好、结构简单、调整方便、尺寸紧凑、分离彻底等优点，而且在结构上采取一定措施，已能做到接合平顺，因此现在广泛用于大、中、小各类车型中。如今单片干式摩擦离合器在结构设计方面相当完善。采用具有轴向弹性的从动盘，提高了离合器接合时的平顺性。离合器从动盘总成中装有扭转减振器，防止了传动系统的扭转共振，减小了传动系噪声和动载荷，随着人们对汽车舒适性要求的提高，离合器已在原有基础上得到不断改进，乘用车上愈来愈多地采用具有双质量飞轮的扭转减振器，能更有效地降低传动系的噪声。汽车离合器有摩擦式离合器、液力偶合器、电磁离合器等几种。液力偶合器靠工作液(油液)传递转矩，外壳与泵轮连为一体，是主动件；涡轮与泵轮相对，是从动件。当泵轮转速较低时，涡轮不能被带动，主动件与从动件之间处于分离状态；随着泵轮转速的提高，涡轮被带动，主动件与从动件之间处于接合状态。电磁离合器靠线圈的通断电来控制离合器的接合与分离。如在主动与从动件之间放置磁粉，则可以加强两者之间的接合力，这样的离合器称为磁粉式电磁离合器。目前，与手动变速器相配合的绝大多数离合器为干式摩擦式离合器，按其从动盘的数目，又分为单盘式、双盘式和多盘式等几种。摩擦式离合器又分为湿式和干式两种。离合器的工作原理离合器的工作原理：离合器的主动部分和从动部分借接触面间的摩擦作用，或是用液体作为传动介质(液力偶合器)，或是用磁力传动(电磁离合器)来传递转矩，使两者之间可以暂时分离，又可逐渐接合，在传动过程中又允许两部分相互转动。目前在汽车上广泛采用的是用弹簧压紧的摩擦离合器(简称为摩擦离合器)。发动机飞轮是离合器的主动件。带有摩擦片的从动盘和从动盘毂借滑动花键与从动轴（变速器主动轴）相连。压紧弹簧将从动盘压紧在飞轮端面上。发动机转矩即靠飞轮与从动盘接触面之间的摩擦作用而传到从动盘，再由此经过从动轴和传动系统中一系列部件驱动车轮。弹簧的压紧力越大，则离合器所能传递的转矩也越大。离合器分离轴承缺油时，将产生“吱吱”声。此时应给分离轴承注油或更换分离轴承。分离杠杆(或膜片弹簧分离指端)不在同一平面时，易使减震弹簧折断，起步时将产生连续打滑，引起振动。此外，离合器弹簧折断、弹力变小，也会发生同样现象。分离杠杆的回位弹簧弹力减弱，会导致离合器分离轴承回位不好，从而造成离合器分离不彻底，产生异响。此时应将分离杠杆的高度调整一致，更换弹簧。从动盘毂或离合器从动轴花键磨损，应更换从动盘或离合器从动轴。离合器、变速器、发动机曲轴主轴颈轴线没对准，应予对准。由于前导向轴承（套）损坏引发的噪声。只要离合器分离必定出现噪声，离合器一旦接合噪声就没有了。有时会把这种噪声误解为分离轴承的失效所致，所以要注意分辨。变速器安装不当，往往使导向轴承额外受力，在离合器使用若干次后就使它损坏，很快出县现噪声。任何类型的分离轴承失效后都会出现尖锐噪声。如果分离轴承有故障，那么噪声将随离合器踏板力的增加而增加。如果噪声在离合器分离后才出现，那就是前导向轴承有故障。离合器完全接合后出现的噪声，会来自于变速器。离合器操纵系统轴承预紧度不够，也能引发噪声。如果变速器在空挡，发动机在运转，可以在车厢内听到“格格”声，这就是变速器中发生的噪声。可以说，这是由于发动机的激励，造成传动系统扭转振动在变速器中引发的噪声。这和离合器从动盘中的扭转减振器结构性能改变有很大关系。

AbstractAn engine speed control system causes an engine, equipped with an automatic transmission which shifts up according to predetermined shift schedules, to reduce its output at a predetermined engine speed so as to protect the engine by preventing the engine from being subjected to "over-revolution." The predetermined engine speed is changed according to engine operating conditions such as a decrease in engine temperature. Simultaneously, a shift-up vehicle speed, at which the automatic transmission shifts itself up, is decreased according to engine operating conditions and, more particularly, engine temperatures and throttle openings. As a result, an up-shift of the automatic transmission properly takes place, even when the vehicle travels at lower speeds.Claims1. An engine speed control system for an automobile engine equipped with an automatic transmission, said engine speed control system comprising: over-revolution prevention means, actuated at a predetermined engine speed so as to decrease engine output, for preventing said engine from being brought into over-revolution while said engine operates under loads; engine operating condition detecting means for detecting an engine operating condition, including at least a throttle opening of an engine throttle valve; speed altering means for altering said predetermined engine speed depending upon said engine operating condition detected by said engine operating condition detecting means; and shift-up vehicle speed shift means for determining a regular shift-up vehicle speed, at which said automatic transmission is shifted up, according to a throttle opening of said engine throttle valve detected by said engine operating condition detecting means, and shifting said regular shift-up vehicle speed in response to a alteration of said predetermined engine speed. 3. An engine speed control system as recited in claim 2, wherein said engine operating condition detecting means also detects an engine temperature, said speed altering means decreasing said predetermined engine speed as an engine temperature detected by said engine operating condition detecting means becomes lower. 4. An engine speed control system as recited in claim 3, wherein said shift-up vehicle speed shift means shifts said regular shift-up vehicle speed by shift coefficients according to engine temperatures detected by said engine operating condition detecting means. 5. An engine speed control system as recited in claim 4, wherein said shift-up vehicle speed shift means decreases said regular shift-up vehicle speed in response to a decrease in said predetermined engine speed. 6. An engine speed control system as recited in claim 5, wherein said shift-up vehicle speed shift means decreases said regular shift-up vehicle speed in response to a decrease in said predetermined engine speed only while said engine operates at certain engine loads. 7. An engine speed control system as recited in claim 6, wherein said shift-up vehicle speed shift means increases said regular shift-up vehicle speed in response to an increase in said predetermined engine speed while said engine operates at other engine loads. 8. An engine speed control system as recited in claim 3, wherein said shift-up vehicle speed shift means includes means for limiting a throttle opening of said engine throttle valve detected by said engine operating condition detecting means to a predetermined guard opening. 9. An engine speed control system as recited in claim 8, wherein said shift-up vehicle speed shift means decreases said regular shift-up vehicle speed in response to a decrease in said predetermined engine speed. 10. An engine speed control system as recited in claim 9, wherein said shift-up vehicle speed shift means decreases said regular shift-up vehicle speed in response to a decrease in said predetermined engine speed only while said engine operates at certain engine loads. 11. An engine speed control system as recited in claim 10, wherein said shift-up vehicle speed shift means decreases said regular shift-up vehicle speed in response to an increase in said predetermined engine speed while said engine operates at other engine loads. 12. An engine speed control system for an automobile engine equipped with an automatic transmission which shifts up at predetermined shift-up vehicle speeds according at least to throttle openings, said engine speed control system comprising: over-revolution prevention means, actuated at a predetermined engine speed so as to decrease engine output, for preventing said engine from being brought into over-revolution while said engine operates under loads; engine temperature detecting means for detecting an engine operating temperature of said engine; speed altering means for decreasing said predetermined engine speed with a decrease in engine temperature detected by said engine temperature detecting means; and shift-up vehicle speed shift means for decreasing a predetermined shift-up vehicle speed in response to a decrease of said predetermined engine speed. 13. An engine speed control system as recited in claim 12, wherein said shift-up vehicle speed shift means decreases said predetermined shift-up vehicle speed in response to a decrease of said predetermined engine speed only while said engine operates at certain engine loads. 14. An engine speed control system as recited in claim 13, wherein said shift-up vehicle speed shift means increases said predetermined shift-up vehicle speed in response to a decrease of said predetermined engine speed while said engine operates at other engine loads. 15. An engine speed control system for an automobile engine equipped with an automatic transmission which shifts up at predetermined shift-up vehicle speeds according at least to throttle openings, said engine speed control system comprising; over-revolution prevention means, actuated at a predetermined engine speed so as to decrease engine output, for preventing said engine from being brought into over-revolution while said engine operates under loads; engine temperature detecting means for detecting an engine operating temperature of said engine; speed altering means for decreasing said predetermined engine speed with a decrease in engine temperature detected by said engine temperature detecting means; throttle valve opening detecting means for detecting a throttle opening of an engine throttle valve; and shift-up vehicle speed shift means for limiting the throttle opening of said engine throttle valve to a predetermined guard opening according to which a predetermined shift-up vehicle speed is restrictively determined when said engine temperature detecting means detects a predetermined engine temperature. 16. An engine speed control system for an automobile engine equipped with an automatic transmission, said engine speed control system comprising: over-revolution prevention means, actuated at a predetermined engine speed so as to decrease engine output, for preventing said engine from being brought into over-revolution while said engine operates under loads; engine operating condition detecting means for detecting an engine operating condition, including at least an engine load on said engine; speed altering means for altering said predetermined engine speed depending upon said engine operating condition detected by said engine operating condition detecting means; and shift-up vehicle speed shift means for determining a regular shift-up vehicle speed, at which said automatic transmission is shifted up, according to the engine load detected by said engine operating condition detecting means, and shifting said regular shift-up vehicle speed in response to an alteration of said predetermined engine speed.Description of Related Art In order to prevent an automotive engine from operating in an "over-revolution" condition, i.e., at rotational speeds beyond a specific rotational speed for which the engine is rated, it is typical to establish an upper critical speed for the automotive engine so as to prohibit an undesirable rise in rotational speed beyond the upper critical speed. Such an upper critical speed is referred to as an over-revolution restrictive speed in this specification. Prohibiting such an undesirable speed rise is performed by interrupting or cutting fuel supply to the engine, by controlling fuel ignition, or by controlling the rate at which intake air is admitted into the engine. An engine speed control system having an over-revolution prevention feature is known from, for instance, Japanese Unexamined Utility Model No. 59-194,550. On the other hand, because engine lubrication qualitatively deteriorates with a decrease in engine temperature, it has been proposed to lower the over-revolution restrictive speed, depending on a decrease in engine temperature, so as to realize reliable engine lubrication over allowable engine speeds. Automotive engines require a certain speed control so that an over-revolution restrictive speed becomes lower for low engine temperatures. Such a speed control is hereafter referred to as an over-revolution prevention control, and is provided to protect the engine against deterioration of engine lubrication at low engine temperatures. Executing the over-revolution prevention control at low engine temperatures, however, may cause an automatic transmission to fail to up-shift in response to a requirement for quick acceleration. Moreover, an over-revolution prevention control system for an engine equipped with an automatic transmission may also have the disadvantage of letting the engine operate too sluggishly in speed for a long period of time to cause an up-shift, even if quick acceleration is needed. This is because the engine is normally forced to maintain a higher speed while operating at lower temperatures. This causes the shift-up vehicle speed to become higher, thereby heating up the engine. However, since the over-revolution restrictive speed established for lower engine temperatures remains low, although the shift-up vehicle speed is changed so that it becomes higher, no up-shift of the automatic transmission takes place, even though the engine operates at full throttle. 这是英文原文，瑞士的～希望对楼主有用！您还可以参考以下网站：

拨叉零件的工艺规程及夹具设计1前言 机械制造工艺学课程设计使我们学完了大学的全部基础课、技术基础课以及大部分专业课之后进行的.这是我们在进行毕业设计之前对所学各课程的一次深入的综合性的总复习,也是一次理论联系实际的训练,因此,它在我们四年的大学生活中占有重要的地位。 就我个人而言，我希望能通过这次课程设计对自己未来将从事的工作进行一次适应性训练，从中锻炼自己分析问题、解决问题的能力，为今后参加祖国的建设打下一个良好的基础。 由于能力所限，设计尚有许多不足之处，恳请各位老师给予指导。2零件的分析2.1零件的作用 题目所给的零件是CA6140车床的拨叉。它位于车床变速机构中，主要起换档，使主轴回转运动按照工作者的要求工作，获得所需的速度和扭矩的作用。零件上方的φ22孔与操纵机构相连，二下方的φ55半孔则是用于与所控制齿轮所在的轴接触。通过上方的力拨动下方的齿轮变速。两件零件铸为一体，加工时分开。2.2零件的工艺分析零件的材料为HT200，灰铸铁生产工艺简单，铸造性能优良，但塑性较差、脆性高，不适合磨削，为此以下是拨叉需要加工的表面以及加工表面之间的位置要求：2.2.1小头孔以及与此孔相通的的锥孔、螺纹孔2.2.2大头半圆孔Ф2.2.3拨叉底面、小头孔端面、大头半圆孔端面，大头半圆孔两端面与小头孔中心线的垂直度误差为0.07mm，小头孔上端面与其中心线的垂直度误差为0.05mm。 由上面分析可知，可以粗加工拨叉底面，然后以此作为粗基准采用专用夹具进行加工，并且保证位置精度要求。再根据各加工方法的经济精度及机床所能达到的位置精度，并且此拨叉零件没有复杂的加工曲面，所以根据上述技术要求采用常规的加工工艺均可保证。......