Valve spring

其功用是保證氣門在關(guān)閉時(shí)能壓緊在氣門座上，而在運(yùn)動(dòng)時(shí)使傳動(dòng)件保持相互接觸，不致因慣性力的作用而相互脫離，產(chǎn)生沖擊和噪聲。所以氣門彈簧在安裝時(shí)就有較大的預(yù)緊力，同時(shí)有較大的剛度。

Its function is to ensure that the valve can be pressed on the valve seat when it is closed, and keep the transmission parts in contact with each other during movement, so as not to separate from each other due to the action of inertial force, resulting in impact and noise. Therefore, the valve spring has greater preload and stiffness during installation.

氣門彈簧的材料通常為高碳錳鋼、硅錳鋼和鎳鉻鋼的鋼絲，用冷繞成型后，經(jīng)熱處理而成。為了提高彈簧的疲勞強(qiáng)度，一般用噴丸或噴砂表面處理，氣門彈簧的形狀多為圓柱形螺旋彈簧。

The material of valve spring is usually high carbon manganese steel, silicon manganese steel and nickel chromium steel wire, which is formed by cold winding and heat treatment. In order to improve the fatigue strength of the spring, shot blasting or sand blasting surface treatment is generally used. The shape of the valve spring is mostly cylindrical coil spring.

氣門彈簧在工作時(shí)可能發(fā)生共振。當(dāng)氣門彈簧的固有振動(dòng)頻率與凸輪軸轉(zhuǎn)速或氣門開閉的次數(shù)成倍數(shù)關(guān)系時(shí)，就會(huì)產(chǎn)生共振。共振會(huì)使氣門彈簧加速疲勞損壞，配氣機(jī)構(gòu)也無法正常工作，因而應(yīng)盡力防止。

Valve springs may resonate during operation. When the natural vibration frequency of the valve spring is a multiple of the camshaft speed or the number of valve opening and closing, resonance will occur. Resonance will accelerate the fatigue damage of valve spring, and the valve mechanism can not work normally, so every effort should be made to prevent it.

通過增加彈簧剛度來提高固有頻率是防止共振的措施之一。但剛度增加，凸輪表面的接觸應(yīng)力加大，使磨損加快，曲軸驅(qū)動(dòng)配氣機(jī)構(gòu)所消耗的功也增加。有的內(nèi)燃機(jī)采用變螺距彈簧來防止共振。工作時(shí)，彈簧螺距較小的一端逐漸疊合，有效圈數(shù)不斷減少，因而固有頻率也不斷增加。這種氣門彈簧在安裝時(shí)，應(yīng)將螺距較小的一端靠近氣門座。

Increasing the natural frequency by increasing the spring stiffness is one of the measures to prevent resonance. However, with the increase of stiffness, the contact stress on the cam surface increases, which speeds up the wear, and the work consumed by the crankshaft driven valve train also increases. Some internal combustion engines use variable pitch springs to prevent resonance. When working, the end with small spring pitch is gradually overlapped, the number of effective turns is decreasing, and the natural frequency is also increasing. When installing this valve spring, the end with smaller pitch should be close to the valve seat.

不少柴油發(fā)電機(jī)組采用兩根氣門彈簧來防止共振。內(nèi)、外兩根氣門彈簧同心地安裝在一個(gè)氣門們上。采用雙彈簧的優(yōu)點(diǎn)除了可以防止共振外，同時(shí)當(dāng)一根彈簧折斷時(shí)，另一根還可繼續(xù)維持工作，不致產(chǎn)生氣門落入汽缸的事故。此外，在保證相同彈力的條件下，雙彈簧的高度可比一根彈簧的小，因而可降低整機(jī)高度。采用雙彈簧時(shí)，內(nèi)、外彈簧的螺旋方向應(yīng)相反，以避免當(dāng)一根彈簧折斷時(shí)，折斷部分卡入另一根彈簧中。

Many diesel generator sets use two valve springs to prevent resonance. The inner and outer valve springs are concentrically installed on one valve. In addition to preventing resonance, the use of double springs can also keep the other spring working when one spring is broken, so as not to cause the accident that the valve falls into the cylinder. In addition, under the condition of ensuring the same elastic force, the height of the double spring can be smaller than that of one spring, so the height of the whole machine can be reduced. When double springs are used, the spiral direction of the inner and outer springs shall be opposite, so as to avoid that when one spring is broken, the broken part is clamped into the other spring.

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