范例[柴油机喷油泵之供油提前角调整]1
目 录
柴油机喷油泵之供油提前角调整„„„„„„„„„„„„„„„„„„„„„„„„„2 摘要„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„2 1 概述„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„3 1.1 柴油机现状简介„„„„„„„„„„„„„„„„„„„„„„„„„„„„„3 1.2 柴油机燃料供给系的组成„„„„„„„„„„„„„„„„„„„„„„„„„3 1.3 调速器„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„5 2 喷油泵„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„6 2.1 喷油泵总成介绍„„„„„„„„„„„„„„„„„„„„„„„„„„„„„6 2.2 喷油泵的结构与功能„„„„„„„„„„„„„„„„„„„„„„„„„„„6 2.3 喷油泵的工作原理„„„„„„„„„„„„„„„„„„„„„„„„„„„„8 2.4 转子分配式喷油泵(V E 泵) „„„„„„„„„„„„„„„„„„„„„„„„8 2.5 单体式喷油泵„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„9 3 供油提前角 „„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„10 3.1 喷油提前角与供油提前角的概念 „„„„„„„„„„„„„„„„„„„„„10 3.2 供油提前角的调整方案 „„„„„„„„„„„„„„„„„„„„„„„„„10 3.3 供油正时的检查与调整 „„„„„„„„„„„„„„„„„„„„„„„„„16 4 VE 型喷油泵调试经验点滴 „„„„„„„„„„„„„„„„„„„„„„„„„„20 4.1 最大供油量的调整 „„„„„„„„„„„„„„„„„„„„„„„„„„„20 4.2 调速器的调整 „„„„„„„„„„„„„„„„„„„„„„„„„„„„„20 4.3 喷油正时的整 „„„„„„„„„„„„„„„„„„„„„„„„„„„„„20 5 供油提前角排放的影响 „„„„„„„„„„„„„„„„„„„„„„„„„„„21 6 喷油泵的维护与保养 „„„„„„„„„„„„„„„„„„„„„„„„„„„„22 7 结论 „„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„23 谢辞 „„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„24 附录 „„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„24 参文献 „„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„25 英文资料—Diesel Fuel Injection„„„„„„„„„„„„„„„„„„„„„„„27 中文翻译—柴油机燃油喷射 „„„„„„„„„„„„„„„„„„„„„„„„„„33
柴油机喷油泵之供油提前角调整
摘要:喷油泵是柴油机的重要组成部分,它在柴油机上的作用是按照柴油机的工作顺序,将低压燃油压缩成高压燃油,定时、定量地通过喷油器将雾状燃油喷入燃烧室内燃烧做功,并能根据操作人员的要求及柴油机工作负荷的变化,自动控制和调整喷油泵供油量。因此,柴油机工作性能的好坏,在很大程度上取决于喷油泵是否在正常工作。供油提前角是指喷油泵第1缸柱塞开始供油时到该缸活塞行至上止点时曲轴转动的角度。供油提前角过大或过小都会影响发动机的工作性能。过大或过小会造成喷油泵喷油时间过早或过晚:喷油时间过早则燃油燃烧不充分,过晚则会冒白烟,燃油也会燃烧不充分,这就使燃烧过程不是处于最佳状态。汽车行驶一定里程或在维修中喷油泵检修后经过调试重新安装时,必须检查与调整供油正时,以保证柴油机经常在最佳或接近最佳供油提前角情况下工作。
关键词:柴油机 喷油泵 喷油器 正时标记 供油提前角
Abstract :The fuel injection pump is an important part of the diesel engine. Its function on the diesel engine is to compress the low pressure fuel into the high pressure one according to the working order of the diesel engine, and atomize the fuel through the injector with a given time and amount into the combustion chamber for burning. And it can automatically control and adjust the fuel amount based on the operator’s requirements and the working load change of the diesel engine. Therefore, the work performance of the diesel engine will depend to a large extent on whether the pump can regularly work or not. The advanced angle for the oil supply timing is referred to the one that the crankshaft rotates from the time when the piston in the cylinder 1 of oil injection pump begins to eject oil to the one when the piston moves to the TDP. Too big or too small advanced angle for the oil supply can affect the work performance of engine. That will cause too early or too late oil injection time : too early oil injection will lead to not combust amfully. Too late oil injection will bring smoke and make fuel not combust amfully. These make combustion not to be the best state. The fuel supply timing must be check and adjust when the fuel injection pump is installed after being check and adjust when the vehicle run for a few miles or is in the repair. It can ensure diesel engine to work in the best or almost best fuel supply advanced angle.
Keywords :Diesel engine fuel injection pump injector timing mark advanced angle for the oil supply
1 概述
1.1 柴油机现状简介
笨重、噪音大、喷黑烟,令许多人对柴油机的直观印象不佳,加上柴油机的构造比较复杂,不少人对柴油机缺乏了解,尤其对现代先进的柴油机缺乏了解,因此柴油机汽车在一些城市成了“被限制的对象”,受到种种歧视。其实经过多年的研究和新技术应用,现代柴油机的现状已与往日不可同喻。现代先进的汽车柴油机一般采用电控喷射、共轨、涡轮增压中冷等技术,在重量、噪音、烟度等方面已取得重大突破,达到了汽油机的水平。目前,柴油机主要用于重型汽车,尤其是超重型汽车,国外轻型汽车用柴油机也日益普遍,奔驰、大众、宝马、雷诺、沃尔沃等欧洲名牌车都有采用柴油发动机的车型。
柴油机使用的燃料是柴油,由于柴油比汽油粘度大,蒸发性差,所以在柴油机工作时,必须采用高压喷射的方法,在压缩行程接近上止点时,将柴油以雾状喷入燃烧室,直接在汽缸内部形成可燃混合气,并借助汽缸内空气的高温自行发火燃烧。
与汽油机比较,柴油机具有转速慢,扭矩大,油耗低、负荷高及重量大等特点,多用在大中型汽车上。1976年德国大众汽车公司开发出第一台高速小型化柴油机,使轿车应用柴油机进入实用化,现在西欧约有30%的轿车和90%的商务车采用柴油机。目前轿车柴油机采用每缸4气门, 电控喷射系统,使柴油机排放达到欧洲Ⅱ号标准。这里要提一下的是,在柴油机上应用电控技术比汽油机要困难得多。因为柴油机是高压喷射,对于直喷式柴油机的高压油管,其喷射压力一般高达30-100MPa ,而汽油机上的喷射压力只需0.3MPa ,起码相差100倍,因此汽油机喷射量的控制只需通过电磁阀就可以控制,而像柴油机这样的高压喷射状态用电磁阀控制是难以办到的,所以现有的柴油机电控燃油系统还要加装一个电子控制的执行器来达到控制的目的。
1.2 柴油机燃料供给系的组成
柴油机通过压燃柴油做功,汽油机通过点燃汽油做功,一个“压燃”一个“点燃”,就是两者的根本区别点。汽油机的燃料是在进气行程中与空气混合后进入汽缸,然后被火花塞点燃做功;柴油机的燃料则是在压缩行程接近终了时直接喷注入汽缸,在压缩空气中被压燃做功。这个区别造成了柴油机在燃料供给系统的结构有其自己的特点。一般柴油机燃料供给系, 通常由柴油箱、柴油滤清器、输油泵、喷油泵、喷油器及油管等部件组成。其中柴油机的燃料喷射系统是由喷油泵、喷油器、高压油管及一些附属辅助件组成。
喷油器是柴油机燃料供给系的又一个重要部件,燃油的雾化质量和混合气的良好形成,均与喷油器有直接关系。它是燃油喷射装置的终端部件,直接安装在柴油机汽缸盖上。其作用有两个:一是使一定数量的高压燃油得到良好的雾化,促进燃油着火和燃烧。二是使燃油的喷射按燃烧室类型合理分布,使燃油与空气得到迅速而完善的混合,形成均匀的可燃混合气。喷油器按结构形式可分为开式和闭式两大类。在这里暂不作详细讨论。
图1 喷油器示意图
柴油机燃料输送的简单过程( 如下图2) 是:输油泵将柴油从燃油箱中吸出送到滤清器(柴油压力被提高到0.15~0.30Mpa 左右),过滤后进入喷油泵(为了保证充足的燃料并保持一定的压力,要求输油泵的供油量比喷油泵的需要量要大得多,多余的柴油就经低压油管回到油箱),喷油泵又将柴油压力进一步提高至10Mpa 以上,再经过高压油管进入喷油器直接以雾状喷入汽缸燃烧室中与空气混合后压燃。输油泵供给的多余柴油以及喷油器顶部回油孔流出的少量柴油,都经回油管流回燃油箱(示意图是柴油机燃料供给系统,鲜红色管路是高压输油管、黄褐色管路是低压输油管、紫红色管路是回油管)。
图2 燃料输送的简单过程
为了使柴油机能在怠速稳定工作和限制柴油机超速,在喷油泵上还带有调速器.
1.3 调速器
调速器在VE 型分配泵的上部,是保障柴油机的低速运转和对最高转速的限制,确保喷油量与转速之间保持一定关系的部件,因为它具有在怠速、高速和满载工况下控制发动机转速的功能,因此被看作发动机的“大脑”。它的作用是根据柴油机负荷的变化,自动地调节喷油泵的供油量,以达到稳定怠速、限制超速、或保证发动机在工作转速范围内的任一选定的转速下稳定工作。
3 供油提前角
3.1 喷油提前角与供油提前角的概念
喷油提前角是指喷油器开始喷油至活塞到达上止点之间的曲轴转角。它的大小对柴油机工作过程有很大影响。若喷油提前角过大,喷油时汽缸内空气温度较低,混合气形成条件差,备燃期长,导致发动机工作粗暴,若喷油提前角过小,大部分柴油是在上止点以后,活塞处于下行状态时燃烧的,是最高工作压力降低,热效率也显著下降,导致发动机功率降低,排气冒白烟。因此为保证发动机具有良好的使用性能,必须选择最佳的喷油提前角。
喷油提前角实际上是由喷油泵的供油提前角来保证的。
对于柴油机,不同工况的最佳供油提前角是不同的。汽车柴油机的工作转速和负荷变化范围比较宽,相应的最佳供油提前角变化也较大。
供油提前角是指喷油泵第1缸柱塞开始供油时到该缸活塞行至上止点时曲轴转动的角度。一般柴油机供油提前角为10~16°,供油提前角过大或过小都会影响发动机的工作性能。
为使喷油器喷入汽缸内的柴油能够混合均匀并完全燃烧,必须定期检查、调整喷油泵供油提前角的大小。若供油时间过早,会使柴油机启动困难,出现敲缸、振动加大等故障;若供油时间过迟,则会导致排气管冒黑烟、机油温度过高和油耗上升等不良后果。
3.2 供油提前角的调整方案
供油提前角过大或过小会造成油泵喷油时间过早或过晚(喷油时间过早则燃油燃烧不充分,过晚则会冒白烟,燃油也会燃烧不充分),使燃烧过程不是处于最佳状态(柴油机功率不足的原因之一) 。此时应检查喷油传动轴接合器螺钉是否松动,如果松动,则应重新按照要求调整供油提前角,并拧紧螺钉。
汽车行驶一定里程或在维修中喷油泵检修后经过调试重新安装时,必须检查与调整供油提前角,以保证柴油机经常在最佳或接近最佳供油提前角情况下工作。
下面来介绍一下几种调整方法:
(1)拆下喷油泵1缸高压油管,一人摇转曲轴,当快要到达1缸供油提前角位置时,要缓慢摇转曲轴,一人凝视1缸出油阀的出油口油面,当油面刚刚向上一动时,停止摇转曲轴,检查飞轮或曲减震带轮上的供油提前角刻线是否与其对应的指针对上(为以后检查方便,这时可在联轴器和泵壳上补做一对正时记号)。这种方法对单体泵和组合泵都适用,是我们去年在做HFC4GA1 (自然吸气柴油机) 试验过程中调整供油提前角一直所采用的,可是现在已不再采用了。
因为在采用这种方法时,操作较为复杂,且不够准确,如掌握不好,很容易引起较大的误差。产生误差的原因有:由于柱塞副总是有一定的间隙,所以,就存在—定的泄漏;在盘车时,盘车速度的快慢对柱塞副建立油压有一定的影响。在同一台机上:假若盘车速度快,则可发现供油要早一些;若盘车速度慢,则供油要晚一些;若慢到一定程度,偶尔还有不喷油的现象出现,对柱塞副已有一定磨损的旧柴油机更是如此,误差很大。所以,对已经使用较长时间的柴油机不能采用这种方法来检查供油提前角。采用这种方法通常要两个人配合,一个人盘车,一个人观察,若配合好,观察误差一般不大于0.5°曲轴转角。在采用这种方法时,也有采用压力油来进行的。在柴油加压的情况下,可以弥补一部分由盘车速度快慢引起的对供油提前角的影响;但油压的高低对供油提前角检查值的影响还是很大的。我们曾经
作过试验:在同一台机上,试验油压为0.5MPa 和0.7MPa 时,后者比前者略提前l °曲轴转角,所以,在采用压力油检查时,最好应规定检查时的油压值,以减少校查误差。
在采用柴油直接检查的方法时,还有一种方法是断油检查法,这种方法很适宜于单体高压油泵,也适用于组合式高压油泵。所采用的柴油为压力油,且油压应大于高压油泵出油阀的开启压力。对采用上部密封出油阀的高压油泵,其出油阀的开启压力一般为0.5—0.8MPa 。在采用这种方法时,应将高压油泵的回油口堵上,或接上调压阀,以保持一定的压力;将油管接在高压油泵的进油口后,由于油压大于出油阀的开启压力,所以,柴油从高压油泵的出油口流出,这时盘车,当盘车至柱塞将套筒进油口封住时,高压油泵的出油口就断油了,这点就是供油始点。这种方法和前述的方法相比,要准确一些。首先,断油比冒油观察起来要方便;其次,由于断油法是柱塞将进油孔封住而断油,所以盘车快慢对检查结果的影响比较小,可以慢慢地盘车,这样,可以减小观察误差。这种方法也适用于等压式出油阀的高压油泵。
(2)我们现在在试验过程中应用的调整供油提前角的方法是这样的: 先拆下喷油泵四个缸的高压油管,再拆下喷油泵上的放气螺栓,装上一个我们自己根据需要加工的专用转接头,再装上百分表拧紧,转动曲轴,百分表示数即随之变化,当曲轴转到一定角度时,百分表示数将不变,此时对百分表进行调零,之后转动曲轴到一缸上止点(0°)。看百分表的读数。因为喷油泵通过三角形固定板上的3个螺栓固定在柴油机缸体上,所以得松掉三个螺帽之后才能够对喷油泵进行调整:将喷油泵体逆着凸轮轴旋转方向转动一定角度,供油提前角增大;反之,则减小。
通过百分表的示数来读取,调整到需要的角度以后,旋紧三角形固定板上的3个螺栓就可以了。(此调整方法是油泵厂家提供给我们的, 供油提前角的大小以丝计量, 不在用度了)
采用这种方法大大地提高了装配、检查精度和速度。由于这种方法要拆下一些高压油泵零件,所以,在调整完毕重新装配时,要特别注意零件的清洁。
对于不同的供油提前角通过试验所做出的结果是不同的,下面以HFC4DA1-1(增压中冷柴油机)的外特性数据为例(如下表)进行分析:
外特性的试验方法是这样的:油门全开,在柴油机工作转速范围内,按照从高到低的顺序改变转速进行测量。主要采集的数据有:转速、有效功率、有效扭矩、燃油消耗率、冷却水温度、机油压力、机油温度和排气管温度。
试验一:调整供油提前角为120丝
表1.1 供油提前角为120丝时测锝数据
续表1.1
根据数据绘出图形5.1:
图3.1
试验二:调整供油提前角为115丝
表1.2 供油提前角为115丝时测锝数据
续表1.2
根据数据绘出图形5.2:
图3.2
试验三:调整供油提前角为110丝
表1.3 供油提前角为110丝时测锝数据
续表1.3
根据数据绘出图形5.3:
图3.3
试验四:调整供油提前角为100丝
表1.4 供油提前角为100丝时测锝数据
续表1.4
根据数据绘出图形3.4:
图3.4
试验五:调整供油提前角为90丝
表1.5 供油提前角为115丝时测锝数据
续表1.5
根据数据绘出图形3.5:
图3.5
注:此款柴油发动机的额定功率为68KW 。
由以上数据及图形可知,供油提前角的大小对柴油机的功率、扭矩影响很大。通过对功率、油耗、排温、机油压力、尾气等诸多方面的综合分析研究可得出供油提前角为100丝时为最佳供油状态。
3.3 供油正时的检查与调整
3.3.1 供油正时
供油正时是指喷油泵正确的供油时间,一般也用供油提前角表示。一般柴油机供油提前角为10~16°,供油提前角过大或过小都会影响发动机的工作性能。汽车行驶一定里程或在维修中喷油泵检修后经过调试重新安装时,必须检查与调整供油正时,以保证柴油机经常在最佳或接近最佳供油提前角情况下工作。以保证气动力性、经济性及排放要求。
3.3.2 供油正时标记的种类
为了便于检查与调整供油提前角,厂家在制造柴油机时,一般将正时标记做在柴油机和
和喷油泵上都有供油正时标记,一般可分为三种: 1)泵的第一分泵开始供油标记;
喷油泵的相应位置上,不同车型供油正时标记位置及符号也不一样,柴油汽车通常在发动机
多指喷油泵联轴器(或自动提前器)上和喷油泵轴承盖上的定时刻线,只要两刻线对准,便可肯定是喷油泵向第1缸开始供油的时刻.
2)发动机供油提前角标记;
它是第1缸活塞到达压缩行程上止点前供油提前角位置的标记,多指飞轮壳(或其上的检视孔)上的指针和飞轮上该机型要求的供油提前角的角度,个别的是指曲轴前端减震皮带轮上的刻线和机体前齿轮室盖上的指针(这就是我们现在试验过程中调整所依据的);对于多缸柴油机,当指针对上相应角度或刻线,并保证1缸进、排气门都有间隙时,才可肯定该缸在供油提前角位置。
3) 喷油泵与发动机传动齿轮的啮合标记;
有传动齿轮配气正时标记、喷油泵与驱动部分的连接标记。在柴油机大修后将啮合齿轮上相应的正时标记对上即可。个别的机型在安装喷油泵时还注意连接标记。
3.3.3 对供油正时的检查
对柴油机来说,供油正时是一个非常重要的基本参数,供油正时的变化,直接影响柴油机的工作过程,以及爆发压力,油耗等性能参数。所以,每台柴油机在装配时,都要检查和调整供油正时,使实际的供油定时在图纸规定范围之内;在柴油机出现性能方面的故障时,也经常要检查供油正时是否正确。下面就谈一下采用柱塞式高压油泵的柴油机供油正时的检查方法以及影响正确测量供油正时的一些因素。
3.3.3.1 就机检查供油正时
油泵固定在柴油机上,可能因为各种情况造成供油正时不准,这时就需要检查供油 正时:
① 一人摇转曲轴使1缸活塞处于压缩行程(即1缸进、排气门都出现间隙)时,当固定标记正好对准飞轮或曲轴胶带轮上的供油提前角记号时,停止摇转曲轴。
② 对于有喷油泵第一分泵开始供油正时标记的,检查联轴器(或自动提前器)上的定时刻线标记是否与泵壳前端上的刻线记号对上。若两记号正好对上,则说明供油正时正确;若联轴器上的标决还未到泵壳刻线记号,则说明供油时间过晚;反之若联轴器上的标记已超过泵壳刻线记号,则说明供油时间过早。
③ 若喷油泵联轴器从动盘和泵壳前端面上没有刻线记号,可采用以下这种方法: 因4行程发动机完成一个工作行程曲轴要转180°,其曲轴转1°活塞移动的距离应是其行程的1/180,只要知道该车活塞的行程和供油提前角,即可计算出活塞到达该供油提前角的有效活塞行程,或以飞轮的齿数为基础,先数准飞轮的齿数,然后求出转动每个齿相应的曲轴转角,然后求出提前角内共转动几个齿,然后在飞轮或曲轴皮带轮上作好正时标记,为以后进行供油提前角的检查与调整补做一对记号。
④ 在柴油机和高压油泵结构许可的条件下,可以来用百分表来测量供油始点。具体方法如下:将高压油泵的出油阀拆下,在适合的位置上,将百分表支好,使百分表测头接触到柱塞顶面,然后盘车,使柱塞位于升程始点,这时开始正盘,按照图纸设计尺寸,直接用百分表测量柱塞升程。在柱塞升至将套筒进油孔封住的尺寸时,即为图纸设计供油始点。由于这种方法是采用百分表直接读取柱塞的升程值,所以误差很小。其误差的大小主要取决于柱塞副的尺寸精度和装配尺寸误差。这种方法特别适合于来用终点调节式拄塞的单体高压油泵。在我厂HFC4DA1-1系列柴油机上就采用这种方法来检查和调整供油正时。
行检查和调整。
⑤ 还有采用压缩空气代替油来检查供油始点的方法,这种方法需要一套专用工具。以上这些方法,都是对柱塞式高压油泵而言的,对PT 泵和分配泵则应按生产厂家推荐的方法进
采用以上这些方法来检查供油定时,都存在一定的误差,我认为很重要的一点是应避免和减小由于检查方法不同而带来的误差。大家知道,柴油机供油定时的设定通常是在理论计算的基础上,结合实机试验进行优化后确定的。为此,应该使成批生产时所采用的供油定时检查方法和试验时所采用的方法一致,以消除由于方法不同而引起的误差;对设计图纸和技术要求来讲,除了规定供油正时及允许的误差值以外,应规定或推荐相应的检查方法,以便在装配时采用。
3.3.3.2. 装机校准供油正时
柴油机大修和喷油泵检修后重新安装时,必须检查供油正时:
① 顺时针摇转曲轴,使第1缸活塞处于压缩行程上止点前规定的供油开始位置,即固定标记对准飞轮或曲轴胶带轮上的供油提前角记号。
② 转动喷油泵凸轮轴,使喷油泵联轴器(或自动提前器)上的定时刻线标记与泵壳前端上的刻线记号对准。
③ 向前推入喷油泵,使从动凸缘盘的凸块插入联轴器并与之接合,在拧紧主动凸缘盘和中间凸缘盘的两个螺钉时,应使两凸缘盘上的“0”标记对准,这样,即可保证柴油机的供油提前角符合要求。
3.3.4 调整供油正时
在检查供油正时时,如果发现供油提前角过小或过大,就要进行调整,常用的调整方法有:
1)转动喷油泵泵体调整供油提前角
结构特点:用正时齿轮和花键轴头直接插入驱动的喷油泵,大多采用三角形固定板和法兰盘与机体连接,在三角形固定板上有3个螺栓固定在柴油机上,固定板螺栓处有3个弧形长孔。用法兰盘连接的喷油泵,喷油泵体与法兰盘用4个螺栓固定,在喷油泵体螺栓处有4个弧形长孔。
调试方法:调整供油提前角时,先松掉三角形固定板上的3个螺栓,然后将喷油泵体逆着凸轮轴旋转方向转动一定角度,则供油提前角增大;反之,供油提前角减少。调整以后,旋紧三角形固定板上的3个螺栓即可。
2)转动泵轴调整供油提前角
用联轴器驱动的喷油泵,在连接盘上的有2个弧形长孔。调整供油提前角时,可先松开连接盘上的2个固定螺栓,将喷油泵凸轮轴顺旋向转动一个角度,便可增大供油提前角;逆旋向转动一个角度,则可减小供油提前角。调整完后,拧紧连接盘上的2个固定螺栓就行了。
通过检查供油正时,发现实际供油提前角不符合要求时,可通过对微调部位的适当调整来实现供油正时,因柴油机结构不同,其驱动联接的方式也不相同,故调整部位与调整方法也不相同。
3)改变联轴节相对位置调整供油提前角
结构特点:以联轴节驱动的喷油泵,联轴节用两个联接螺栓和主动凸缘盘结合。松开联接螺栓,主动盘就可以带动喷油泵凸轮轴相对于主动凸缘盘转动一个角度。主动盘上的零刻线对准主动凸缘盘或钢片上的定时刻线,是它们的基准位置,向两边转动的极限位置由主动盘上的弧形槽限制。
调试方法:将喷油泵凸轮轴顺驱动轴旋转方向转动一定角度,供油提前角增大;反之,
供油提前角减少。调整以后,旋紧联轴节上的联接螺栓。
注意事项:
1) 供油提前角、出油提前角、喷油提前角是3个性质不同但又有紧密相关的名词术语,从曲轴转角来看(以到达上止点为限):供油提前角大于出油提前角大于喷油提前角。用供油提前角来保证出油提前角和喷油提前角。
2) 供油提前角的调试分为静态调试(粗调试,以对正正时标记为主)和动态调试(微调试)两类,在调试时应先粗调试后微调试,调试完毕应锁紧螺栓。
3) 不同车型其喷油提前角不同,调试方法因车结构而异、因故障现象而异,应举一反三,灵活运用。
4) 单缸柴油机(如190型、1100型等)的调试通过增、减调整垫或旋进(出)螺丝钉来实现,每增(减)一片或旋进(出)螺丝钉一圈,喷油提前角减(增)1.3°。
5) 柴油车的工作状态与众多因素有关(如最佳供油提前角和各缸间供油间隔是否正确)应力求调试准确供油提前角。供油正时的标志为:将汽车预热后以最高挡最低稳定车速行驶,然后将加速踏板踩到底,使汽车急加速运行,此时,若能听到柴油机有轻微的着火敲击声,且随着车速提高短时间后消失。则提前角正确。
7 结论
通过以上诸多的论述、试验、分析,关于柴油机油泵供油提前角的调整可以总结为以下几点:
(1)影响喷油过程的因素相当复杂,良好的喷油过程依赖于各参数合理的选择与匹配。同时,喷油过程还要与燃烧室结构、气流运动等密切配合,以满足柴油机各工况的要求。
(2)柴油机工作性能的好坏,在很大程度上取决于喷油泵是否在正常工作。 (3)喷油泵工作的状态是否最佳取决于供油提前角的大小:供油提前角过大或过小会造成油泵喷油时间过早或过晚,直接影响柴油机的性能:包括经济性、动力性、排放、噪音等。
(4)调整供油提前角的方法很多,关键在于操作最简化、误差最小化、方法实用化。 (5)喷油泵的保养直接影响柴油机的寿命。
毕业论文写到这里基本已告一段落了,通过此篇论文的撰写,我学到了很多知识,最起码对柴油机喷油泵的相关知识有了更深一步的了解。因为这是我在毕业之前的最后一次作业,也是我生平第一次写论文,所以我写的非常认真,态度也比较严谨、端正,在写之前感觉很可怕,觉得深奥不可捉摸,怕自己难以写好,然而通过这两个多月的不懈努力,终于有了一篇崭新的论文摆在了我面前(我会好好地珍惜)。在这两个多月里,我不断的找资料,去图书馆、书店、网吧等各个有可能找到资料的地方,向设计部门的同志借相关专业的书籍,通过各种渠道来充实我的作业,这一万多字虽不是很多,但每个字都凝聚了我的努力,是我辛勤汗水的体现。由此我也深深体会到凡事只要你付出并且用心去做了,总会有回报。
在这期间,我得到了许多老师和单位领导的帮助,特别是我的指导教师卢晓玲老师给了我很多的指导与帮助,不断地给我提出了许多宝贵的意见和建议,激发了我的写作灵感,卢老师严谨治学的教学态度和渊博的知识体系令我无比敬佩,在此,我向她表示深深的感谢和崇高的敬意!同时,我的领导唐昊所长、王永部长、汪旭明、李龙超,师傅孙丁柱、李国柱、洪凤锁,他们也给了我莫大的帮助与支持,工作之余时常传授经验于我,帮我修改不足之处,在思想上给予我启迪和鼓励,使我受益非浅,我深受感动。感谢他们对我孜孜不倦的教导。我也要向以下几位给我提供相关资料的同志们表示感谢,他们是技术研究四部的部长贾杰、设计人员陆荣荣、钱多德、陈园明、李自强、王海洋等,谢谢他们的支持。最后,我要感谢学生科科长郭永胜老师以及我的班主任刘芳老师,他们多次对我们讲述写好论文的重要性和必要性,并及时给我们传递相关信息。谢谢他们的关心与厚爱!
最后, 我要一并向所有给予我帮助的老师、领导、同学、同事表示最衷心的感谢, 没有他们的热心帮助与大力支持, 我要完成这样一篇论文可以说相当困难. 谢谢各位!
毕竟是第一次写论文,没什么经验,所以这其中一定存在着很多的不足和欠妥之处,语言、格式方面可能存在着很多不完善的地方, 恳请各位老师给予指导斧正,不甚感谢!
在此即将毕业之际,我要向三年来培育过我的所有老师表示衷心的感谢。谢谢他们对我无微不至的关怀之情和教导之恩。
南京威孚公司VE型分配泵产品型号含义
NJ VE 4/ 12 F 1900 L 001
r /min
VE型分配泵主要技术参数
缸数:2、3、4、6
旋转方向:左、右旋(从驱动端或法兰端看) 柱塞直径:8——14mm (按发动机要求) 凸轮升程:1. 8——3. 3mm (按发动机要求) 最大供油量:140mm /循环 最大泵端压力:75MPa 最高转速:3000r /min
调速器:机械离心式(全程式或二极式) 提前器:液压活塞式 停油:电磁式或手动式 输油泵型式:滑片式 润滑方式:燃油润滑
安装方式:法兰(三角形或菱形)
3
参考文献:
[1] 赵奎翰 《内燃机工程》 18(1):1~8 1997 [2] 余志生 《汽车理论》北京:机械工业出版社 1992 [3] 蔡兴旺 《高等内燃机学》机械工业出版社 2004.8 [4] 关文达 《汽车构造》 北京:机械工业出版社 1999.9 [5] 《汽车工程手册试验篇》 北京:人民交通出版社 2002.9 [6] 邢文华 《汽车检测与诊断技术》 国防工业出版社 2004.8 [7] 谭正三 《发动机构造》(第2版) 北京:机械工业出版社 1996 [8] 汽车编辑委员会 《汽车问题解答》 北京:人民交通出版让 1999. [9] 王泽九 《重型汽车构造与维修[M] 》 北京:人民交通出版让 1994.[10] 林家让 《汽车构造》 (发动机篇) 北京:电子工业出版社 2004.6 [11] 《工程机械与维修》杂志 [12] 《柴油机燃油系统结构及维修》 [13] 《汽车发动机燃料供给与调节》
[14] 《VE 型分配泵产品说明书》 南京威孚金宁有限公司
2005年6月
Diesel Fuel Injection
The purpose of the fuel injection system is to deliver fuel into the engine cylinders, while precisely controlling the injection timing, fuel atomization, and other parameters. The main types of injection systems include pump-line-nozzle, unit injector, and common rail. Modern injection systems reach very high injection pressures, and utilize sophisticated electronic control methods.
1.Introduction
The performance of diesel engines is heavily influenced by their injection system design. In fact, the most notable advances achieved in diesel engines resulted directly from superior fuel injection system designs. While the main purpose of the system is to deliver fuel to the cylinders of a diesel engine, it is how that fuel is delivered that makes the difference in engine performance, emissions, and noise characteristics.Unlike its spark-ignited engine counterpart, the diesel injection system delivers fuel under extremely high injection pressures. This aspect implies that the system component designs and materials should be selected to withstand higher stresses, while still performing for extended durations matching the engine’s durability targets. Grea ter manufacturing precision and tight tolerances are also required for the system efficient function. In addition to expensive materials and manufacturing costs, diesel injection systems are characterized by more intricate control requirements. All these features add up to a system whose cost may represent as much as 30% of the total cost of the engine.
This and the following papers will review the basic diesel fuel injection system and its components, the various types of injection systems, and how they meter and deliver fuel into the cylinders of a diesel engine. The mechanical function of these systems will be described with emphasis on their mixture formation role. Various injection timing and metering schemes will be described.
Many specialized terms are used to describe the components and the operation of fuel injection systems. The following are definitions of selected, more common terms .
Nozzle refers to the part of the nozzle body/needle assembly which interfaces with the combustion chamber of the engine. Terms like P-Type, M-Type, or S-Type nozzle refer to standardized dimensions of nozzle parameters, as per ISO specifications.
Nozzle holder or injector body refers to the part the nozzle is mounted on. In conventional injection systems this part mainly served the nozzle mounting and nozzle needle spring preloading purpose. In common rail system, it contains the main functional parts: the servo-hydraulic circuit and the hydraulic actuator (electromagnetic or piezoelectric).
Injector commonly refers to the nozzle holder and nozzle assembly.
Rate of injection is the mass flow of fuel out of the nozzle, typically shown
angle.
over a time axis. Start of injection and end of injection refer to the start and end of flow from the nozzle, often referred to with reference to the engine crank
Opening rate and closing rate refers to the gradients in the rate of injection during needle nozzle opening and closing, respectively.Injection pressure is not used consistently in the literature. It may refer to the mean pressure in the hydraulic system for common rail systems, or to the maximum pressure during an injection (peak injection pressure) in conventional systems.
2.Purposes of Fuel Injection System
As stated above, the main purpose of the fuel injection system is to deliver fuel into the cylinders of an engine. While this may be the general purpose of the system, two specific objectives of a fundamental importance may be described by the following functions:
(1)Timely introduction of the fuel into the cylinder, that is, injection timing and its control.
(2)Delivery of an accurate amount of fuel to meet power requirement, that is, injection metering and its control.
To deliver an accurately metered amount of fuel at the proper time to achieve good combustion. How well this delivered fuel mixes with the inducted air is of major importance.
Therefore, fuel atomization, i.e., how small the fuel particle size is and how dispersed it is in the cylinder, should be a primary design objective for a successful diesel fuel injection system. Yet, even a properly atomized, accurately metered, and well timed fuel delivery may not provide the desired combustion efficiency. Another important parameter in this respect is the quality of the mixture (fuel and air). While good atomization goes a long way toward improving combustion efficiency, how well the available air is used is also an indicator of high combustion efficiency. To achieve this objective, better air utilization must be achieved. This parameter can be accomplished through a combination of fuel penetration into the dense air that is compressed in the cylinder, and equally dividing the total fuel among the cylinders of an engine. The primary purposes of the diesel fuel injection system
are graphically represented in Figure 6.
Figure 6 Functions of Diesel Fuel Injection System
To accomplish the described functions is no small task, and to do it effectively
requires the collective experience of many experts specialized in the disciplines of materials, mechanical design, hydraulics and fluid dynamics, as well as combustion systems. As more limits were imposed on emissions from diesel engines, and pressures were felt from customers for better performance, the need for additional fuel injection system functions became apparent. Indeed the modern diesel injection system must perform the tasks of metering, timing, and atomizing as well as contribute to good air and fuel mixing. In addition, experience gained since the mid-1970’s has shown that scheduli ng of the metered fuel into the cylinder is very important to the performance, emissions, and noise characteristics of the combustion process. A general term describing the scheduling of injected fuel is rate shaping . Yet, modern systems are not only concerned with how much fuel is delivered per crank angle degree, but also with the number of injections per combustion cycle.
3.Types of Diesel Fuel Injection Systems
Diesel fuel injection systems can be classified into three categories, as follows:
(1)Pump-Line-Nozzle
(2)Unit Injector
(3)Common Rail
P-L-N configurations and components are discussed inPump-Line-Nozzle Injection System
Figure 7. Pump-Line-Nozzle System Principle
Pump-Line-Nozzle System Principle Pump-line-nozzle (P-L-N) is a fuel system using central injection pump driven off the engine geartrain, Figure 7. The injection pump feeds separate injection nozzles located in the cylinder head above each cylinder. Lines—which must be of exactly equal length—link the pump with the nozzles. In the case of the in-line pump, the central pump incorporates a number of separate plunger/barrel pumping elements (such as that shown in Figure 7), each serving one injector. Each nozzle incorporates a needle valve and the orifices which provide fuel atomization.
The P-L-N fuel system used to be the most common type of diesel injection, dominating most diesel engine applications. In addition to the in-line pump design, where each injector is fed by a separate pumping element, several other configurations that have been developed, including the distributor/rotary pump. Both types of pump systems and their components are discussed in more detail in the Pump-Line-Nozzle Injection System paper.
More details are available in Common Rail Fuel Injection .
The total common rail system includes a low pressure supply pump that draws fuel from the tank and feeds it to the high pressure pump. High pressure fuel delivered into the rail may bring along pressure pulsations, therefore the volume of the common rail should be designed to dampen those pulsations. These pulsations result from the delivery characteristics of the multi-plungers radial fuel pump. Driving the pump at engine speed increases fuel pumping capacity and improves the potential for high injection pressure. Control of fuel metering and injection timing is similar to that in the in-line pump and unit injector systems. In spite of the availability of these desirable features in common rail systems, it needs to be emphasized that such systems could not attain their potential without the help from electronic controls. In fact, electronics were introduced in all types of fuel injection systems to expand their capabilities and improve their performance.
For each of the above injection system categories there are a number of sub-categories that will be detailed in the following papers. However, there are some generalized comments that can be made at this stage to further clarify how quickly these three very general categories can branch out into many unique and distinct designs. For instance, pump-line-nozzle systems include in-line, distributor (rotary), as well as unit pumps. Not only could we differentiate them as such, but we can also separate between them on the basis of whether they are mechanically- or electronically-controlled. Similarly, unit injectors can be mechanically- or electronically-controlled. Unit injector systems can also be designed to deliver extremely high injection pressures, in which case they may feature mechanical intensifiers in the form of plungers having two different diameters. They may also be actuated by brute force imparted to the top of the injector by a large cam such as the Cummins pressure-time controlled (PT) system. The common rail category enjoys a similar variety of design details. The evolution of the diesel injection systems from the old
mechanically-controlled P-L-N designs to the modern electronically-controlled unit
injector and accumulator designs, driven in general by the need of achieving tighter injection control and lower emissions, follows one distinct trend: increased injection pressures. In fact, this trend continued through the last century. For heavy-duty applications, it accelerated in the 1970’s to meet the demand for cleaner, as well as more fuel efficient engines. Eventually the high speed, passenger car market adopted the same philosophy, and even though it started a decade after the heavy-duty applications, both light-duty and heavy-duty applications have now similar injection pressures.
4.Electronic Control in Fuel Injection
Overview
The need to meet emission regulations was one of the most important —if not the most important — reason for modernizing the diesel fuel injection system. Customer demand for better engine response and driveability also played a major role in advancing the fuel system’s state -of-the-art. Diesel engine designers and builders were not just satisfied with its superior fuel economy, but sought to continue to improve it to maintain its lead over its competition. Not only was the goal to improve its fuel economy standing, but to achieve this objective while also meeting the tough emission regulations that were imposed in the 1980’s and 1990’s, as well as early in the 21 Century.
As already mentioned, some of the early gains in the evolution of the modern diesel injection system were realized through increasing injection pressures. However, engine designers felt their hands were tied and were unable to make other gains until they were able to introduce electronic control into the injection system. Introducing this technology made other advances easier to achieve. It was easier to customize torque outputs from the same base engine to meet the demands of several applications in the heavy-duty market. It was also easy to include many value added features such as limiting maximum road speed for fleets where fuel consumption is directly related to driving habits. For the first time injected fuel quantity was trimmed according to fuel temperature for consistent power output regardless of fuel temperature, within certain limits. Electronics brought along the promise of reduced cost through simplifying many of the functions otherwise provided by cumbersome mechanical devices, and allowed the implementation of full-authority parameter control strategies. For instance, a drive-by-wire system allowed the implementation of low- or no-smoke strategies versus systems where the injection was solidly connected to the accelerator pedal. In addition to smoke-free strategies, electronic controls facilitated flexibility in injection timing and metering control, and reduced cycle-to-cycle, and cylinder-to-cylinder variability.
柴油机燃油喷射 燃油喷射系统的目的是将燃油输送到发动机缸体内,同时精确地控制喷射正时、燃油雾化和其他参数。喷射系统的主要类型包括泵-管-嘴、单体泵和共轨。现代喷射系统可达到很高的喷射压力,使用的是复杂的电子控制系统。
1. 介绍
柴油发动机的性能受喷射系统设计的影响很大。实际上,柴油发动机的先进性直接体现在高级喷射系统的设计上。喷射系统的主要目的是将燃油输送给柴油发动机的缸体。怎样输送燃油才能使发动机的性能、排放和噪音等特性,不象点燃式发动机,柴油喷射系统可在很高的喷射压力下输送燃油。这意味着系统零部件的设计和材料应当选择能抵抗高压力,同时能提高发动机可靠性指标。为满足系统功效,需要较高的生产精度和较小的公差。除了昂贵的材料和生产成本,柴油发动机喷射系统以具有更复杂的控制要求为特征。所有的这些特点组成系统,其成本可占到发动机总成本的30%。
下面将回顾基本的柴油喷射系统和与它相关的附件,以及其他各种类型的喷射系统,还有他们如何测量和输送燃油给柴油机的缸体的。这些系统的机械功能的重点在于混合物的形成。各种不同的喷射正时和测量策略将被介绍。
许多专用术语用于描述零部件和燃油喷射系统的运行。下面是所选得更为普及的一些术语。
喷嘴是指喷嘴壳体和针的装配体,他与发动机的燃烧室相接触。如P 型、M 型和S 型喷嘴之累的术语是指喷嘴参数的标准尺寸,如ISO 标准规范。
喷嘴支撑或喷射器壳体是指安放喷嘴的部件。在传统的喷射系统中,这个部件主要用于安放喷嘴和预加载荷的喷嘴针阀弹簧。在共轨系统中,它包含主要的功能部件:伺服液压电路和液压激励(电磁或压电)。喷射器通常是指喷嘴支撑和喷嘴的组合体。喷射率是燃油出喷嘴的质量流量,典型地显示在时间坐标上。喷射的开始和结束是指柴油从喷嘴出来的开始和结束时刻,经常参照发动机的曲轴转角。
开启和关闭速率分别指针阀开启和关闭之间喷射率的梯度。喷射压力并不是一贯使用在文献中,它是指支持共轨系统的液压系统的平均压力或传统系统中喷射过程的最大压力(峰值压力)
2. 燃油喷射系统的作用
如上所述,燃油喷射系统的主要作用是将燃油输送进发动机的缸体。而这是系统的一般作用,两个特别的目的如下所述:
(1)燃油进缸体的时刻介绍,即喷射正时和它的控制。
(2)输送精确的燃油量以满足功率的需要,即喷射计量和它的控制。
然而,它仍然不足以满足精确测量燃油,在合适的时刻进行输送,从而达到好的燃烧效果。怎样将燃油混合物,含有吸进的空气,输送缸体是主要的。因此,燃油雾化,无论燃油颗粒尺寸多么小以及在缸内如何分散,是成功的柴油喷射系统主要的设计指标。然而,一个合适的雾化、精确的计量和良好的正时时刻,可能也不会提供想要的燃烧效率。另外一个重要的参数就是混合物的质量(燃油和空气)。然而,雾化好对提高燃烧效率是有利的,还有所吸入的空气的质量也是高效燃烧的一个指标。为达到这个指标,要有高质量的空气,这个
油。柴油机燃油喷射系统的主要作用如下图6所示。
方面可通过压入汽缸中的空气中渗入进来的燃油的混合,并且等分配在发动机汽缸内的燃
图6 柴油燃油喷射系统的功能
要完成功能介绍是一个不小的任务,这需要许多专家集体的经验,特别在材料规范、机械设计、液压和流体动力,还有燃烧系统等方面。由于柴油发动机的排放存在更多的限制,以及来自消费者对更好性能需求的压力,对附增喷射系统功能的需要明显了。事实上,现代柴油喷射系统必须进行计量任务、正时、雾化和充分的空气燃油混合。此外,自二十世纪七十年代中期以来,所获取的经验显示进入缸体计量燃油的控制,对于性能、排放和燃烧过程的噪音特性是非常重要的。燃油喷射控制的一般描述是速率修正。然而,现代系统不仅仅关于每个曲轴转角的送油量,而且也涉及了每个燃烧循环的喷射次数。
3. 柴油机燃油喷射系统的分类
柴油燃油喷射系统可以分为3类,如下所示:
(1)泵—管—嘴
(2)单体泵
(3)共轨
泵—管—嘴结构和组件将在泵—管—嘴喷射系统做以讨论。
图7 泵—管—嘴系统原理图
泵—管—嘴系统原理:泵—管—嘴系统是一种采用单体泵通过发动机齿轮驱动的燃油系统,喷油泵供燃油给每一个单独的喷油器,这些喷油器位于缸盖的上端。油管必须准确保证相同长度,油管用来连接喷油泵和喷油器。泵的核心包括几个独立的柱塞/泵的基本元素(如图7所示),每一个柱塞对应一个喷油器。每一个喷油器包括一个针阀和数个孔用来产生雾化的燃油。
泵—管—嘴燃油喷射系统过去是柴油机燃油喷射系统最基本的一种,在当时是柴油机燃油喷射系统的主流。此外还有直列泵的设计,每个喷油器都有自己的供给要素,其它一些结构需要开发,包括分配泵/旋转泵,关于这两种泵的系统合组件介绍将在泵—管—嘴系统中作详细讨论。
下面是关于共轨燃油系统的具体介绍:
共轨系统总体包括一个低压供给泵,用来从燃油箱吸入燃油供给高压泵。高压燃油进入共轨管时可能会产生压力的波动,因此在设计共轨管的容积时应注意防止这种波动。这种波动的产生是由于燃油泵多个柱塞的供给特性决定的。在发动机转速下驱动泵增加了泵的泵油量并且提高了高压喷射的潜力。控制燃油的测定和喷油时刻与直列泵和单体泵相似。尽管在高压共轨系统有众多有效的特性,但必须强调的是这种系统如果没有电控的话也很难发挥其应有的潜力。实际上电子控制系统在各种燃油喷射系统中都有运用,以提高它们的能力和性能。
对于以上介绍的燃油喷射系统种类中都有一定数量的子种类,这在以后的章节中会做详细介绍。然而,在目前有一些一般评论可以进一步说明这三种喷射泵分支出不同设计思路的便捷性。例如,泵—管—嘴系统包括直列,分配(旋转),还有单体泵。这并不是它们区别的唯一特征,同样我们可以根据它们是否采用电控或者是采用机械控制来区分。同样道理单体泵也可以采用机械控制或者电子控制。单体泵系统可以设计成供给较高的喷射压力,如果这样则可能采用不同的柱塞直径形式。也可能通过施加力于喷油器,这种喷油器通过一个大的凸轮控制压力。共轨系统也同样可以采用相似的设计细节。
柴油喷射系统的演变过程是从传统的泵—管—嘴系统到现代的电子控制的单体泵和混合设计,所有这些都是为了更严密的喷射控制和低排放,但又一个趋势:提高喷射压力,实际上这种趋势贯穿了上个世纪。对于重型车,从十九世纪七十年代这种趋势有加速迹象以满足更好的清洁,更好的燃油经济性。最终高速乘用车也采用了相同的理念,即使这样在重型车应用之后它们也开辟了新的章程,今天对于轻型车和重型车都有相似的喷射压力。
4. 电控燃油喷射系统
总览
对于现代柴油燃油喷射系统满足排放要求是很重要的内容之一。用户要求更好的发动机响应,驾驶性同样在现代燃油系统中起着重要的角色。柴油发动机设计师和制造商并不满意优良的燃油经济性,仍然继续改进并维持他们的领导地位。不仅仅是把提高燃油经济性作为目标,同样也要满足排放法规限制,这些法规的发布是在十九世纪八、九十年代,以及二十一世纪初期
在前面已经提及到,现代柴油喷射系统演化的早期成果认为是在于提高燃油喷射压力。然而,发动机设计师认为他们现在束手无策除非采用电子控制。引进这种技术要做别的改进也显得相对容易些。这样也更容易做到从同一基本型发动机定制出扭矩以满足重型车市场的不同需求。同样更便于实现更多的特性,例如车队的最大道路速度,在那里燃油消耗和驾驶习惯有直接关系。首次燃油喷射量和不同输出功率的燃油温度相平衡而不管燃油温度,除了
一些限制外。电子化使费用降低成为可能,否则通过机械装置,同时实现了全参数控制。例如有线驾驶系统允许有烟和无烟策略的实现,在这种系统中喷射固定地连接到加速踏板上。此外自由烟度,电子控制在燃油喷射正时和测量有了更大的灵活性,减少了反复循环,以及缸体—缸体的可变性。