在壓縮和燃燒過程中，氣門必須保證嚴(yán)密的密封，不能出現(xiàn)漏氣現(xiàn)象，否則柴油發(fā)電機(jī)組的功率會(huì)下降，嚴(yán)重時(shí)柴油發(fā)電機(jī)組由于壓縮終了溫度和壓力太低，一直不能著火啟動(dòng)。氣門在漏氣情況下工作，高溫燃?xì)忾L時(shí)間的沖刷進(jìn)氣門，使氣門過熱、燒損。
In the process of compression and combustion, the valve must be tightly sealed without air leakage, otherwise the power of the diesel generator set will decrease. In serious cases, the diesel generator set cannot be started on fire because the temperature and pressure at the end of compression are too low. The valve works under the condition of air leakage, and the high-temperature gas washes the inlet valve for a long time, causing the valve to overheat and burn.
氣門是在高溫、高機(jī)械負(fù)荷及冷卻潤滑困難的條件下工作的，氣門頭部還承受氣體壓力的作用，排氣門還要受到高溫廢氣的沖刷，經(jīng)受廢氣中的硫化物的腐蝕。因此，要求氣門具有足夠的強(qiáng)度、耐高溫、耐腐蝕和耐磨損的能力。
The valve works under the conditions of high temperature, high mechanical load and difficult cooling and lubrication. The valve head also bears the role of gas pressure. The exhaust valve is also scoured by high-temperature exhaust gas and corroded by sulfide in the exhaust gas. Therefore, the valve is required to have sufficient strength, high temperature resistance, corrosion resistance and wear resistance.
氣門分為進(jìn)氣門和排氣門兩種。頂置式氣門配氣機(jī)構(gòu)有每缸二氣門（一個(gè)進(jìn)氣門、一個(gè)排氣門）、三氣門（兩個(gè)進(jìn)氣門、一個(gè)排氣門）、四氣門（兩個(gè)進(jìn)氣門、兩個(gè)排氣門）和五氣門（三個(gè)進(jìn)氣門、兩個(gè)排氣門）之分。二汽門多用于中小功率的柴油發(fā)電機(jī)組；后三者用于強(qiáng)化程度較高的中、大型柴油發(fā)電機(jī)組，并以四氣門的居多。
Valves are divided into inlet valve and exhaust valve. The overhead valve train can be divided into two valves per cylinder (one inlet valve and one exhaust valve), three valves (two inlet valves and one exhaust valve), four valves (two inlet valves and two exhaust valves) and five valves (three inlet valves and two exhaust valves). The second steam valve is mostly used for diesel generator sets with medium and small power; The latter three are used for medium and large diesel generator sets with high strengthening degree, and most of them are four valve.
進(jìn)氣門由于工作溫度稍低，一般采用普通合金鋼；排氣門普遍采用熱合金鋼。為了節(jié)約成本，有時(shí)桿部選用一般合金鋼，而頭部采用熱合金，然后將兩者接在一起。
Because the working temperature of the intake valve is slightly lower, it is generally made of ordinary alloy steel; Hot alloy steel is widely used for exhaust valves. In order to save cost, sometimes the rod is made of general alloy steel, and the head is made of hot alloy, and then the two are connected together.
氣門錐面是氣門與氣門之間的配合面，氣門的密封性就是依靠?jī)蓚€(gè)表面嚴(yán)密貼合來保證的。此外，氣門接受燃?xì)獾募訜崃康?5％要通過錐面?zhèn)鞒?。從有利于傳熱的觀點(diǎn)出發(fā)，氣門錐面與氣門座接觸的寬度應(yīng)越寬越好，但是接觸面越寬，密封的可靠性就越低，因?yàn)楣ぷ髅嫔系谋葔簻p小，雜物和硬粒不易被碾碎和排走，所以通常要求氣門錐面密封環(huán)帶的寬度在1～2mm之間即可。
The valve cone is the mating surface between the valve and the valve. The tightness of the valve depends on the close fitting of the two surfaces. In addition, 75% of the heating amount received by the valve is transmitted through the conical surface. From the point of view conducive to heat transfer, the wider the contact width between the valve cone and the valve seat, the better. However, the wider the contact surface, the lower the reliability of the seal. Because the specific pressure on the working surface is reduced, and the sundries and hard particles are not easy to be crushed and discharged, it is usually required that the width of the valve cone seal ring should be between 1 ~ 2mm.
氣門頂面上有時(shí)還銑出一條較窄的凹槽、主要用于研磨氣門時(shí)能將工具插入槽中旋轉(zhuǎn)氣門，氣門和氣門座配對(duì)進(jìn)行研磨，研磨后氣門即不能互換。
Sometimes a narrow groove is milled on the top surface of the valve, which is mainly used for grinding the valve. The tool can be inserted into the groove to rotate the valve. The valve and valve seat are paired for grinding, and the valves cannot be interchanged after grinding.
氣門錐面的角一般為30或45，也有少數(shù)柴油發(fā)動(dòng)機(jī)做成60?或15?錐角的，錐角愈小，單位面積上的壓力也愈小，氣門與氣門座之間的相對(duì)滑動(dòng)位移也較小，從而使氣門的磨損減輕。因此，有的柴油發(fā)電機(jī)組進(jìn)氣門錐面的錐角為30?。
The angle of valve cone is generally 30 or 45, and a few diesel engines are made of 60? Or 15? The smaller the cone angle, the smaller the pressure per unit area, and the smaller the relative sliding displacement between the valve and the valve seat, so as to reduce the wear of the valve. Therefore, the cone angle of the intake valve cone of some diesel generator sets is 30 °?.
排氣門曲于高溫廢氣不斷流過錐面，廢氣中的炭煙微粒容易沉積附著在錐面上，影響密封性，因此，排氣門要求面上的比壓要高些，以利于積炭的排除，氣門大多采用45的錐角，為了制造和維修的方便，不少柴油發(fā)電機(jī)組進(jìn)、排氣門錐角都采用45。
The exhaust valve is bent at high temperature, and the exhaust gas continues to flow through the conical surface. The soot particles in the exhaust gas are easy to deposit and adhere to the conical surface, affecting the sealing. Therefore, the specific pressure on the exhaust valve surface is required to be higher to facilitate the elimination of carbon deposition. Most valves adopt a cone angle of 45. For the convenience of manufacturing and maintenance, the cone angles of inlet and exhaust valves of many diesel generator sets adopt 45.
氣門座的錐角有時(shí)比氣門角大0.5～1，使兩者接觸面積更小，可以提高工作面的比壓，從而提高其密封的可靠性。
The cone angle of the valve seat is sometimes 0.5 ~ 1 larger than the valve angle, so that the contact area between the two is smaller, which can improve the specific pressure of the working face and improve the reliability of its sealing.
氣門座的直徑對(duì)氣流的阻力影響較大。頭部直徑愈大，因而阻力減小。但直徑的大小受氣缸頂面的限制?？紤]到進(jìn)氣阻力對(duì)柴油發(fā)電機(jī)組性能的影響比排氣阻力更大，所以一般都使進(jìn)氣門的直徑比排氣門稍大。有些柴油發(fā)電機(jī)組的進(jìn)、排氣門直徑相同，以便于制造和維修，但如果兩者材料不同，則必須打上標(biāo)記，以免裝錯(cuò)。
The diameter of valve seat has a great influence on the resistance of air flow. The larger the diameter of the head, the lower the resistance. However, the diameter is limited by the cylinder top surface. Considering that the influence of intake resistance on the performance of diesel generator set is greater than exhaust resistance, the diameter of intake valve is generally slightly larger than that of exhaust valve. The inlet and exhaust valves of some diesel generator sets have the same diameter to facilitate manufacturing and maintenance, but if they are made of different materials, they must be marked to avoid wrong installation.
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