【正文】 ngine block. The block is an iron or aluminum casting that contains engine cylinders and passages called water jackets for coolant circulation. The top of the block is covered with the cylinder head, which forms the bustion chamber. The bottom of the block is covered with an oil pan or oil sump. 天津職業(yè)技術(shù)師范大學(xué) 2021屆本科生畢業(yè)設(shè)計(jì) Power is produced by the linear motion of a piston in a cylinder. However, this linear motion must be changed into rotary motion to turn the wheels of cars and trucks. The piston is attached to the top of a connecting rod by a pin, called a piston pin or wrist pin. The bottom of the connecting rod is attached to the crankshaft. The connecting rod transmits the upanddown motion of the piston to the crankshaft, which changes it into rotary motion. The connecting rod is mounted on the crankshaft with large bearings called rod bearings. Similar bearings, called main bearings, are used to mount the crankshaft in the block. The diameter of the cylinder is called the engine bore. Displacement and pression ratio are two frequently used engine specifications. Displacement indicates engine size, and pression ratio pares the total cylinder volume to pression chamber volume. The term “stroke” is used to describe the movement of the piston within the cylinder, as well as the distance of piston travel. Depending on the type of engine the operating cycle may require either two or four strokes to plete. The 4 stroke engine is also called Otto, who first applied the principle in 1876. In the 4 stroke engine, four strokes of the piston in the cylinder are required to plete one full operating cycle. Each stroke is named after the action it performs intake, pression, power, and exhaust in that order. （ 1） Intake stroke As the piston moves down, the vaporized mixture of fuel and air enters the cylinder through the open intake valve. To obtain the maximum filling of the cylinder the intake valve opens about 10176。 they go up and down on the pedals, providing power. Pedals are like the connecting rods。after b. d . c. to take advantage of ining mixture. （ 2） Compression stroke The piston turns up, the intake valve closes, the mixture is pressed within the bustion chamber, while the pressure rise to about 1Mpa depending on various factors including the pression ratio, throttle opening and engine speed. Near the top of the stroke the mixture is ignited by a spark which bridges the gap of the spark plug. （ 3） Power stroke The expanding gases of bustion produces a rise in pressure of the gas to some Mpa, and the piston is forced down in the cylinder. The exhaust valve opens near the bottom of the stroke. （ 4） Exhaust stroke The piston moves back up with the exhaust valve open some 50176。已經(jīng)幾乎統(tǒng)治壟斷了汽車的領(lǐng)域，其它類型的發(fā)動機(jī)，如柴油機(jī)在以后再敘述。 (5)燃料，機(jī)油，維修的經(jīng)濟(jì)性。 發(fā)動機(jī)的燃料 內(nèi)燃機(jī)能被制造或依靠幾乎任務(wù)東西運(yùn)行的，只要這些東西能轉(zhuǎn)換或燃料的氣體。 往復(fù)式發(fā)動機(jī) 在這種類型汽車的發(fā)動機(jī)里，活塞在各自的汽缸里往復(fù)運(yùn)動。 發(fā)動機(jī)的部件 典型的汽車的發(fā)動機(jī)是由許多必須的部件組成的，這些部件被設(shè)計(jì)成用來提供發(fā)動機(jī)運(yùn)行的可靠性和高效率性。 （ 4）活塞環(huán)。 （ 8）氣閥結(jié)構(gòu)。它包括汽缸體本身和環(huán) 繞在周圍的水套。 柴油機(jī)用的發(fā)動機(jī)與汽油機(jī)用的非常相似。鋁也是一種金屬，重量比鑄鐵要輕很多，并天津職業(yè)技術(shù)師范大學(xué) 2021屆本科生畢業(yè)設(shè)計(jì) 且鋁的導(dǎo)熱速度比鑄鐵的要快。 一些制造商制造的鋁制氣缸也沒有氣缸。然后給它們涂上一層化學(xué)制劑，把表面上的鋁腐蝕掉?；钊且粋€圓柱狀放在氣缸內(nèi)的物體。 活塞在氣缸中就像你在騎自行車時的腿。 反過來，活塞與連桿連著，連桿連在曲軸上。這個銷子用來連接連桿小頭的。 連桿和連桿軸瓦的間隙是在制造中造好的。通常，連桿蓋上都印有數(shù)字。如果曲軸旋轉(zhuǎn)，軸瓦可能由于間隙不符合要求而發(fā)生過早磨損或失效。這將破壞發(fā)動機(jī)。旋轉(zhuǎn)運(yùn)動通過傳動系將動力傳給車輪。 發(fā)動機(jī)工作原理 大多數(shù)發(fā)動機(jī)是四沖程往復(fù)式內(nèi)部燃燒，但也有的是兩沖程的發(fā)動機(jī)，包括一些柴油機(jī)和一些旋轉(zhuǎn)的機(jī)器。機(jī)體是用鐵或鋁鑄造成的，里面包含著氣缸和水套，水套是為了冷卻水在里面循環(huán)。然而，這個直線運(yùn)動必須要變?yōu)檐囕喌仔D(zhuǎn)運(yùn)功。連桿通過一個叫連桿軸承的零件裝在曲軸上。排量表示發(fā)動機(jī)的大小，壓縮比是整個氣缸容積與發(fā)動機(jī)燃燒室容積的比值。在四沖程發(fā)動機(jī)中，活塞需要在一個工作循環(huán)完成四個沖程。 開啟，并有 20176。 （ 2）壓縮沖程 活塞向上運(yùn)動，進(jìn)氣門關(guān)閉，混合氣被壓縮在燃燒室內(nèi)，壓力 迅速上升到 MPa，這是和壓縮比，節(jié)氣門開啟度和發(fā)動機(jī)轉(zhuǎn)速等有關(guān)。 打開，允許氣缸內(nèi)的氣體排出，并準(zhǔn)備為下一次進(jìn)氣沖程做準(zhǔn)備。然而，進(jìn)氣和壓縮兩個 動作被合并為一個沖程，做功和排氣被合并為一個沖程。 一個多缸發(fā)動機(jī)有三種布置形式。大多數(shù) V 型發(fā)動機(jī)有 6 缸或 8 缸，但也有 4 缸機(jī)和 12 缸機(jī)也用這種排