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Question

1 噪声的控制
根据噪声产生和传播的机理,可以把噪声控制技术分为以下三类:一是对噪声源的控制,二是对噪声传播途径的控制,三是对噪声接受者的保护。其中对噪声源的控制是最根本、最直接的措施,包括降低噪声的激振力及降低发动机部位对激振力的响应等,即改造振源和声源。但是对噪声源难以进行控制时,就需要在噪声的传播途径中采取措施,例如吸声、隔声、消声、减振及隔振等措施。汽车的减振降噪水平与整车的动力性、经济性、可靠性及强度、刚度、质量、制造成本和使用密切相关。
1.1 发动机的振动与噪声
降低发动机噪声是汽车噪声控制的重点。发动机是产生振动和噪声的根源。发动机的噪声是由燃料燃烧,配气机构、正时齿轮及活塞的敲击噪声等合成的。
(1) 发动机本体噪声
降低发动机本体噪声就要改造振源和声源,包括用有限元法等方法分析设计发动机,选用柔和的燃烧工作过程,提高机体的结构刚度,采用严密的配合间隙,降低汽缸盖噪声。例如在油底壳上增设加强筋和横隔板,以提高油底壳的刚度,减少振动噪声。另外,给发动机涂阻尼材料也是一个有效的办法。阻尼材料能把动能转变成热能。进行阻尼处理的原理就是将一种阻尼材料与零件结合成一体来消耗振动能量。它有以下几种结构:自由阻尼层结构、间隔自由阻尼层结构、约束阻尼层结构和间隔约束阻尼层结构。它的采用明显地减少了共振的幅度,加快了自由振动的衰减,降低各个零件的传振能力,增加了零件在临界频率以上的隔振能力。
目前,已有一些国家的专家设计了一种发动机主动隔振系统,用于减少发动机振动,以达到降低噪声的目的。
(2) 进气噪声
进气噪声是发动机的主要噪声源之一,系发动机的空气动力噪声,随发动机转速的提高而增强。非增压式发动机的进气噪声主要成分包括周期性压力脉动噪声、涡流噪声、汽缸的亥姆霍兹共振噪声等。增压式柴油机的进气噪声主要来自增压器的压气机。二冲程发动机的噪声源于罗茨泵。对此,最有效的方法是采用进气消声器。类型有阻性消声器(吸声型) 、抗性消声器(膨胀型、共振型、干涉型和多孔分散型) 和复合型消声器。将其与空气滤清器结合起来(即在空滤器上增设共振腔和吸声材料,例R3238 型) 就成为最有效的进气消声器,消声量可超过20dBA。

Answer 1

1 Yawp control
Can is divided into the following to the yawp control technique according to the mechanism of[with] the yawp creation and the dissemination three types of:a is to the control of the yawp source, two is the control that spreads path to the yawp, three is the protection that accepts to the yawp.BE the most basic and the most direct measure to the control of the yawp source among them, include to lower yawp to arouse to flap dint and lower to launch the machine part to arouse to flap dint to respond to etc., then the reformation flaps a source harmony source.But is hard to carry on a control to the yawp source, need in the yawp dissemination path to adopt measure, for example absorb a voice,separate a voice,eliminate a voice and reduce to flap and separate to flap etc. measure.The reduce of automobile flaps the motive,economy,credibility and strength of decline the yawp level and the whole car,just degree,quality,manufacturing cost and use closely related.
1.1 Launch the vibration and the yawp of the machine
Lower to launch the point that the machine yawp is the automobile yawp control.Launch the machine is the creation vibration and yawp source.Launch the yawp of the machine is burn by the fuel, go together with spirit organization,positive hour the wheel gear and piston pound what yawp etc. synthesize.
(1) Launch machine essence yawp
Lowering to launch the machine essence yawp will reform to flap the source harmony source, including to use a limited dollar method etc. method analysis design to launch machine, choosing to use soft burnable work process, the structure that raises the machine body just degree, adopt tight match cleft, lower cylinder cover yawp.For example increase to establish to strengthen 筋 on the oil bottom hull with horizontal separate plank, with exaltation the oil bottom hull just degree, reduce vibration yawp.Moreover give to launch damping material of machine is also a valid way.The damping material can become the thermal energy to the kinetic energy change.The principle that carries on the damping processing is to combine a kind of damping material and spare parts integral whole to consume vibration energy.It has the following a few structure: free damping layer structure,partition freedom damping layer structure,control the damping layer structure and partition to control the damping layer structure.Its adoption reduced the range of the resonance clearly, speeding a freedom the attenuation of the vibration, lowering each spare parts to spread the ability of flap, increasing spare parts to separate the ability of flap above in the critical frequency.
There has been some experts of nations design currently a kind of launch machine to separate to flap system actively, used for reducing to launch the machine vibration to attain a purpose of lower the yawp.
(2) Enter spirit yawp
Enter the spirit yawp is one of the main yawp sources that launches machine, fastenning the air motive yawp of launch the machine, with launch machine to turn to raise but strengthen soon.Increase a press type to launch machine not of into annoy main composition of yawp to include haimuhuozi resonance yawp etc. of the periodic pressure pulsation yawp,backset yawp,cylinder.Increase the press type diesel engine of Be mainly come from increasing to press a machine to press spirit machine into the spirit yawp.Two blunt distances launch the yawp of the machine to come from the 茨 pump.To this, the most valid method is an adoption to enter spirit to eliminate a machine.The type has 阻 to eliminate a machine(absorb a type),anti- sex to eliminate a machine(inflation type,resonance type,the interference type with many bore dispersion types) and the compound type to eliminate a machine.Put together(increase to establish a resonant cavity and absorb a material on the empty colander, example R3238 types) with the air cleaner knot and then become it the most valid of eliminate a machine into the spirit, eliminate the amount of voice can over 20 dBAs.