河南理工大学毕业设计英文翻译

The machine piston connecting rod set- detailed

exposition of piston

The piston connecting rod set is composed of the piston, piston wreath, piston pin, connecting rod, connecting rod axle bush, etc. Ⅰ. effect: The effect of the piston is to bear the air pressure, and pass to connecting rod to drive the bent axle to revolve through connecting rod axle bush, the piston coping is still a part of the burning room. The work condition: Piston works under the condition of heat, high pressure, high speed, and bad lubrication .Piston directly contacts with the heat air. The temperature can amount to above 2500 Ks in a moment .The piston is heated severely, but the condition of spreading the hot is bad .So while the piston works, the temperature is very high and the coping is up to the 600-700 Ks: And the temperature distributes asymmetrically; The piston coping bears great air pressure, especially the pressure is greatest in the route of doing efficacy. The gasoline machine is up to the 3-5MPas, the diesel engine is up to the 6-9MPas.This makes the piston produce pound,

and bear the function of the side pressure. Therefore, the piston should have enough heat-proof, try to decrease the heating area,, strengthen the cooling of the piston, to make the highest temperature of the coping descend .The piston moves at very high speed(8-12 ms/ s) back and forth in the air cylinder, and speed changes constantly, This produces very great inertial dint, making the piston bear great additional load working under such bad condition, the piston will become deformed heating power. At the same time ,it slitters the chemical corrosive power of the burning gas .In order to descend the inertial dint of back and forth, we must ease the weight of the piston as possible .Piston works under the condition of the heat, high pressure, high speed(the average speed can amount to the 101115 m/ s), and its lubricant condition is bad and the frication between the piston and the air cylinder wall is very great. In order to descend the friction, the surface of the piston surface must be wear-resistant..

Request:

(1) To have enough rigidity and strength, and the reliable dint;

(2) Transmit heat well, bear the high pressure, bear the heat and

bear to wear away;

(3) the quantity is small, the weight is light, descend the inertial dint of back and forth as possible

The aluminum metal alloy material satisfies the top requests basically, therefore, the piston generally adopts the high strength aluminum metal alloy, but some low speed diesel engines adopt high class iron casting or heat-proof steel

Ⅱ, structure: The piston can be divided into three parts, piston coping, the piston head and piston skirt departments.

1. The piston coping

The piston coping bears the air pressure, it is a part of the burnable room .Its shape, position, size are relevant to the concrete from of the burnable room. They are made to satisfy the combustible hybrid spirit formation and burnable requests. Its coping shape can be divided into four major types, a flat coping piston, a convex coping piston, a concave coping piston and model piston.

A convex coping piston is usually used on the two blunt distance I.C. engines, It is good to improve the process exchanging the gas .Modern four blunt the distance gasoline machine also adopts

the convex coping piston in order to strengthen the effect of pushing the gas or extend the ratio of compressing .Convex of a piston coping presents a form of ball, its coping strength is high, having an effect of leading, being advantageous to improve the process of exchanging the gas, two route of travel gasoline machines often adopt the convex coping piston

A piston coping presents the hollow form, the shape and positions of the cave pit must be advantageous to the combustion of the combustible and hybrid gas, having a pair of eddies concave pit ball, concave pit, U concave pit, and so on.

2.Piston head

The piston refers to the first piston wreath to the part above the piston pin.It has several wreath slots, which are used to install the piston wreath and have an effect of sealing completely. It is also called the leak proof department .The diesel engine’s compress ratio is high, and generally have four wreath slots, The three upper wreaths are used to install, the lower part installs the oil wreath. The gasoline machine has three wreath slots generally, which are two jet of gas wreath slots and an oil wreath slots. At the bottom

of oil wreath slot many paths toward eyelet are drilled to make the quilt oil wreath flow from the air cylinder wall to the oil bottom hull through these eyelets. The working condition of the wreath slot is the worst and should leave the coping generally a little farther.

Above the gas wreath, a narrow insulating slot is usually set to cut off the heat flow which is spread from the piston coping to the first gas wreath and make parts of calories from a piston wreath spread, thus easing the hot burden of the first gas wreath. On some engines small wreathe slots are often made between the coping head and the first gas wreathe, sometimes till a few more wreath. This kind of small wreath can adsorb the lubricant because it accumulates the carbon. It can keep piston and the air cylinder walls from biting to match when it work in the condition of losing oil, so it is called accumulating the carbon slot.

The calories that the piston coping absorbs also mainly passes the air cylinder wall through the piston wreath to leak proof department, again spread by the cool water.In a word, the function of the piston head is in addition to install the piston wreath, still

seal completely function and transmit heat function, sealing completely the air cylinder together with the piston wreath, keeping combustible admixture spirit from leak crankcase, at the same time pass the(70-80)%calories to the air cylinder wall through the piston wreath.

3. Piston skirt department

The piston skirt department refers to the parts from the bottom of the oil wreathe slot. It includes the pin which is used to pack the piston. The piston skirt department exercises to rise to lead to the function to the piston in the back and forth in the air cylinder, and bear the side pressure. The length of the skirt department is decided by the size and the piston diameter of the side pressure. The so-called side pressure mean in the compression route of travel and make route of travel of efficacy .The level component of the gas pressure which take effect on the piston coping presses the piston to the air cylinder wall. Compress the route of travel and make the side pressure direction of the efficacy route of travel air exactly the opposite, because of the combustion pressure consumedly high in compress the pressure, so, make the side in

the route of travel of efficacy pressure also consumedly high in compress the side in the route of travel pressure. Two on the sides that bear the side pressure of the piston skirt department be called to push the dint to face, they be placed in to sell the mutually perpendicular direction of the stalk line with piston up.

Structure characteristics:

(1) make into oval in advance:

The wall thick of the piston skirt department is bigger along the direction of the pin and the hot inflation have great capacity. While working under the common function of hot burden and the side pressure the skirt ministry becomes the oval pillar form. Following the piston to pin direction it has the elongation slightly, but the perpendicularity pin direction it has slightly short. In order to make piston in working condition still keep the cylinder form and prevent from resulting in piston choked to death or the part wore away big because of oval transform, the piston skirt department processes generally and in advance oval, its major axis and pistons sell the stalk direction perpendicular. In order to reduce the heat transform around the piston, we can also make the

surface of skirt cast into bottom to sink the 0.5-1 mms

In order to make both sides of skirt bear the air pressure and keeping with air cylinder small but safety of cleft, while working the piston must have right of cylinder form. But, because the thickness of the piston skirt department is very asymmetry, the piston pin the metals of a bore part thick, be subjected to the hot inflation to have great capacity, follow the piston to sell a stalk line direction of transform to have great capacity in other directions. Moreover, the function that bears the air side pressure, causes the piston to transform the more perpendicular piston of quantity pin the direction big.

Thus, if the piston in cold state hour skirt department is a circular, while working the piston will become on oval, making a circumference cleft of the piston and air cylinder not equal, resulting in piston block in the air cylinder and the machine can't work normally. Therefore, while processing we make the piston skirt department into the oval shape in advance. The direction of oval major axis is perpendicular with the pin. The direction of the minoraxis follows the direction of the pin. Thus while working the

piston work tend the near positive circle.

(2)The temperate of the piston along the direction of the length is very asymmetry. The temperature of the upper part of the piston is high, the lower part is low, it is upper part that the inflation quantity also correspond big, the lower part is small. In order to make the piston top and bottom diameter tend equal, that is to say the cylinder form, must make the piston into the top smaller the bottom the big stairs form in advance, taper.

(3) In order to reduce the calories of the piston skirt department ,we usually open the hot slot horizontally in the skirt department. In order to compensa the skirt department after be subjected to the heat of transform the quantity, the skirt department opens lengthways of inflation slot. The shape of the sl ot contain" T" form or" Π " form slots. The horizontal slot opens generally under most the underneath of a wreath slot, both the edge pin sides ( also opened in the oil wreath slot) of on the skirt department so as to reduce the head calories delivered toward the skirt department, so it is called separating the hot slot. The vertical slot will make the skirt department have the certain flexibility so

as to the possibly small cleft with the air cylinder while thus making piston assemble, but at hot state have the in expiation of function again, result in piston choked to death in the air cylinder unlikely, past be called vertical slot inflation slot. The skirt department will make it open a side of the slot after open the vertical slot just the degree diminish, bearing the side a side that pressure is smaller in assemble should make it locate make route of travel of efficacy .The diesel engine piston is subjected to the dint big, the skirt department does not open the slot generally.

(4) In order to ease the weight some pistons slice one part in both sides that opens the bore or is free from the side pressure to the skirt department, to eliminate the inertial dint, to reduce neighborhood of heat transform the quantity, and form drag along the plank type piston or short piston.The flexibility between of the plank structure skirt is good, the quantity is small, the matching cleft between the piston and air cylinder is smaller, so it is applicable to the high speed engine.

(5)In order to reduce the hot inflation degree of the aluminum metal alloy piston skirt department, some gasoline machine

piston imbeds the steel slice in the piston skirt department or pin. The structure characteristics of the permanent model steel is as the permanent model steel is the low carbon iron nickel metal alloy with33% ～ 36% nickel, its coefficient of expansion is only 1/10 of that of aluminum metal alloy. But pin through the permanent model steel slice and the skirt departments connect with each other and curb the degree of the coefficient of expansion.

(6) the gasoline that have is on board, the center line of the piston pin is to deviate the piston center line flat surface, subjected to the main side in the route of travel of efficacy a square of the pressure partial to move the 1-2 mms. This kind of structure can make piston compare in from compress route of travel go to make route of travel of efficacy mildly from press toward air cylinder of a the noodles transfer to press toward air cylinder of another one side, reducing the sound of knocking the urn. While installing, the direction that this kind of piston pin is partial to place can't pack anti-, otherwise change to pound the dint and will enlarge, making the skirt department damaged

中文翻译：

发动机活塞连杆组—活塞详解

活塞连杆组由活塞、活塞环、活塞销、连杆、连杆轴瓦等组成。

一、功用：

活塞的功用是承受气体压力，并通过活塞销传给连杆驱使曲轴旋转，从而气缸里面的吸气、排气等过程。活塞顶部还是燃烧室的组成部分。

活塞的工作条件：活塞在高温、高压、高速、润滑不良的条件下工作。活塞直接与高温气体接触，瞬时温度可达2500K 以上，因此，受热严重，而散热条件又很差，所以活塞工作时温度很高，顶部高达600～700K ，且温度分布很不均匀；活塞顶部承受气体压力很大，特别是作功行程压力最大，汽油机高达3～5MPa ，柴油机高达6～9MPa ，这就使得活塞产生冲击，并承受侧压力的作用，因此，活塞应有足够的耐热性，要尽量减小活塞的受热面，加强活塞的冷却，适当增大传热面，使活塞顶部的最高温度下降，以便保护活塞头。活塞在气缸内以很高的速度(8～12m/s)往复运动，且速度在不断地变化，这就产生了很大的惯性力，使

活塞受到很大的附加载荷。活塞在这种恶劣的条件下工作，会产生变形并加速磨损，还会产生附加载荷和热应力，同时受到燃气的化学腐蚀作用。因此， 为了减小往复惯性力，必须尽可能地减轻活塞的重量。活塞是在高温、高压、高速（活塞平均速度可达101115m/s）的条件下工作的，其润滑条件较差，活塞与气缸壁间摩擦严重。为减小摩擦，活塞表面必须光滑、耐磨。

要求：(1) 要有足够的刚度和强度，传力可靠；

(2) 导热性好，耐高压、耐高温、耐磨损；

(3) 质量小，重量轻，尽可能减小往复惯性力。

铝合金材料基本上满足上面的要求，因此，活塞一般都采用高强度铝合金，但在一些低速柴油机上采用高级铸铁或耐热钢也符合要求。

二、构造：

活塞可分为三部分，活塞顶部、活塞头部和活塞裙部。

1.活塞顶部

活塞顶部承受气体压力，它是燃烧室的组成部分，其形状、位置、大小都和燃烧室的具体形式有关，都是为满足可燃混合气形成和燃烧的要求，其顶部形状可分为四大类，平顶活塞、凸顶活塞、凹顶活塞和成型顶活塞。

加工最简单的是平顶活塞，它的顶部是一个平面，结构简单，制造

起来较容易，受热面积小，加工简单，顶部应力分布较为均匀，一般用在汽油机上，柴油机很少采用。

凸顶活塞多用于二冲程内燃机上，它有利于改善换气过程。现代四冲程汽油机为了增强挤气效果或增大压缩比也有采用凸顶活塞。凸顶活塞顶部凸起呈球顶形，其顶部强度高，起导向作用，有利于改善换气过程，二行程汽油机常采用凸顶活塞。

凹顶活塞顶部呈凹陷形，凹坑的形状和位置必须有利于可燃混合气的燃烧，从而提高燃料的利用率。他的内型有双涡流凹坑、球形凹坑、U 形凹坑等等。

1. 活塞头部

活塞头部是活塞环槽以上的部分。其主要作用是承受气体压力，并传给连杆；与活塞环一起实现对气缸的密封；将活塞顶所吸收的热量通过活塞环传给气缸壁。 它有数道环槽，用以安装活塞环，起密封作用，又称为防漏部。柴油机压缩比高，一般有四道环槽，上部三道安装气环，下部安装油环。汽油机一般有三道环槽，其中有两道气环槽和一道油环槽，在油环槽底面上钻有许多径向小孔，使被油环从气缸壁上刮下的机油经过这些小孔流回油底壳。第一道环槽工作条件最恶劣，一般应离顶部较远些。

在第一道气环的上方往往开有一道较窄的隔热槽，隔断由活塞顶部传向第一道气环的热流，使部分热量由第二、三道活塞环传出，从而减轻第一道气环的热负荷。有的发动机，在活塞顶面至第一道环槽之间，有时一直到以下几道环槽处，常加工出细小的环行槽。这种细小的环行槽可以因积碳而吸附润滑油，在失油工作时可防止活塞与气缸壁的咬合，故称之为积碳槽。

活塞顶部吸收的热量主要也是经过防漏部通过活塞环传给气缸壁，

再由冷却水传出去。总之，活塞头部的作用除了用来安装活塞环外，还有密封作用和传热作用，与活塞环一起密封气缸，防止可燃混合气漏到曲轴箱内，同时还将(70～80)%的热量通过活塞环传给气缸壁，以免气缸内的温度过高，减小对缸体材料所产生的不利。

2.活塞裙部

活塞裙部指从油环槽下端面起至活塞最下端的部分，它包括装活塞销的销座孔。活塞裙部对活塞在气缸内的往复运动起导向作用，并承受缸体的侧压力。裙部的长短取决于侧压力的大小和活塞直径。所谓侧压力是指在压缩行程和作功行程中，作用在活塞顶部的气体压力的水平分力使活塞压向气缸壁。压缩行程和作功行程气体的侧压力方向正好相反，由于燃烧压力大大高于压缩压力，所以，作功行程中的侧压力也大大高于压缩行程中的侧压力。活塞裙部承受侧压力的两个侧面称为推力面，它们处于与活塞销轴线相垂直的方向上。

结构特点：

(1）预先做成椭圆形：

活塞裙部沿销座方向壁厚较大，热膨胀量大。工作时在热负荷和侧压力的共同作用下裙部会变成椭圆柱形，沿活塞销轴方向略有伸长，而垂直销轴方向略有所短。为了使活塞在工作状态下仍保持圆柱形，防止因椭圆变形而造成活塞卡死或局部磨损过大，活塞裙部一般预先加工成椭圆形，其长轴与活塞销轴方向垂直。为了减小活塞销座附近的热变形，还可以将销座的裙部表面铸成下陷0.5—1mm 。

为了使裙部两侧承受气体压力并与气缸保持小而安全的间隙，要求活塞在工作时具有正确的圆柱形。但是，由于活塞裙部的厚度很不均匀，活塞销座孔部分的金属厚，受热膨胀量大，沿活塞销座轴线方向的变形量大于其他方向。另外，裙部承受气体侧压力的作用，导致沿活塞销轴

向变形量较垂直活塞销方向大。这样，如果活塞冷态时裙部为圆形，那么工作时活塞就会变成一个椭圆，使活塞与气缸之间圆周间隙不相等，造成活塞在气缸内卡住，发动机就无法正常工作。因此，在加工时预先把活塞裙部做成椭圆形状。椭圆的长轴方向与销座垂直，短轴方向沿销座方向。这样活塞工作时趋近正圆，从而减小活塞与缸体的摩擦力。

(2）预先做成预先做成阶梯形、锥形

活塞沿高度方向的温度很不均匀，活塞的温度是上部高、下部低，膨胀量也相应是上部大、下部小。为了使工作时活塞上下直径趋于相等，即为圆柱形，就必须预先把活塞制成上小下大的阶梯形、锥形，有利于活塞的运动。

(3）为了减小活塞裙部的受热量，通常在裙部开横向的隔热槽，为了补偿裙部受热后的变形量，裙部开有纵向的膨胀槽。槽的形状有"T" 形或" Π" 形槽。横槽一般开在最下一道环槽的下面，裙部上边缘销座的两侧(也有开在油环槽之中的) ，以减小头部热量向裙部传递，故称为隔热槽。竖槽会使裙部具有一定的弹性，从而使活塞装配时与气缸间具有尽可能小的间隙，而在热态时又具有补偿作用，不致造成活塞在气缸中卡死，故将竖槽称为膨胀槽。裙部开竖槽后，会使其开槽的一侧刚度变小，在装配时应使其位于作功行程中承受侧压力较小的一侧。柴油机活塞受力大，裙部一般不开槽。

（4）有些活塞为了减轻重量，在裙部开孔或把裙部不受侧压力的两边切去一部分，以减小惯性力，减小销座附近的热变形量，形成拖板式活塞或短活塞。拖板式结构裙部弹性好，质量小，活塞与气缸的配合间隙较小，适用于高速发动机。短板式结构裙一般用于低速发动机。

（5）为了减小铝合金活塞裙部的热膨胀量，有些汽油机活塞在活塞裙部或销座内嵌入钢片。恒范钢片式活塞的结构特点是，由于恒范钢为含镍33%～36%的低碳铁镍合金，其膨胀系数仅为铝合金的1/10，而销座通过恒范钢片与裙部相连，牵制了裙部的热膨胀变形量，有利于保持活塞的基本尺寸，减小摩擦。

（6）有的汽油机上，活塞销孔中心线是偏离活塞中心线平面的，向作功行程中受主侧压力的一方偏移了1～2mm 。这种结构可使活塞在从压缩行程到作功行程中较为柔和地从压向气缸的一面过渡到压向气缸的另一面，以减小敲缸的声音。在安装时，这种活塞销偏置的方向不能装反，否则换向敲击力会增大，使裙部受损。