1., the main hazards of noise

Noise pollution not only has a negative impact on people’s sense of self and work ability, but also can lead to serious health disorders, fatigue, early deafness, hypertension, neurological diseases and so on.

Formation and Countermeasure of engine noise for 2. vehicles

The noise of Baotou North Benz parts mainly includes combustion noise, mechanical noise, intake and exhaust noise, noise from cooling fans and other components.

Noise is the noise produced by the explosion of a combustible mixture when the gas pressure in the cylinder rises sharply and impacts the engine components. If the sixteen alkane in diesel oil is not suitable or the injection time is too advanced, it will cause the engine to work rough and make the noise increase dramatically. Due to overheating, poor gasoline quality and excessive ignition advance angle, the high frequency explosion and knocking of the gasoline engine are caused by the gasoline engine.

The noise generated by the combustion process and structure vibration of Baotou Benz parts inside the engine, is connected through the outer surface of the engine vibration structure and engine outer surface of rigid to atmospheric radiation, so it is called the engine surface noise. According to the mechanism of engine surface noise, it can be divided into combustion noise and mechanical noise. The combustion noise is mainly due to cyclical changes in pressure inside the cylinder, closely related with combustion engine and combustion speed; the periodic change of mechanical noise is when the engine works among all moving parts and moving parts and fixed parts between the force caused by it, and the excitation force and the structure of the engine dynamic characteristics and other factors. Generally speaking, combustion noise dominates at low speed, and mechanical noise dominates at high speed.

To reduce combustion noise, it is necessary to improve combustion conditions and improve combustion quality so as to achieve smooth pressure waveform. The most effective combustion can be achieved by the proper arrangement of spark plugs and valves, as well as proper chamber type and cooling method. For diesel engine, it is necessary to choose a suitable sixteen alkane diesel fuel. If it fails to do so, the ignition accelerator can be added to improve the ignition quality, so that the noise caused by fuel combustion can be effectively prevented.

Mechanical noise includes piston knock, valve impact, timing gear movement and so on. Reduce the piston slap, can be taken to reduce the gap between the piston and the cylinder wall and piston pin and crank center center offset method. The magnitude of the impact noise of the valve mechanism is determined by the clearance of the valve. The valve clearance is too small to make the seal poor. It is too large to cause a great impact on the opening and closing of the valve, causing strong noise and increasing wear and tear. In use, the valve clearance should be adjusted frequently to make it in the required clearance, usually by adding a buffer to the front of the camshaft in order to minimize impact or to use hydraulic tappet. The vibration and noise of a serious lack of rigid push rod and rocker and valve in the transmission mechanism will cause the valve movement, even the valve out of control; pulse valve spring will produce noise, so the valve spring requirements of high quality, elastic foot, and installed to give certain pre tightening force.

The operation of the timing gear noise is a noise source greatly in the diesel engine, the assembly should be the timing gear mark alignment, using different materials (such as plastic, fabric etc.) manufacturing timing gear can greatly reduce the noise, the chain transmission ratio of gear drive can effectively reduce transmission noise.

The way to control the intake and exhaust noise is the same. In the case of ensuring that the output power of the engine is not reduced, the intake and exhaust noise can be reduced by improving the engine valve mechanism or the exhaust mechanism. The widely used paper air filter and exhaust muffler can effectively reduce inlet and exhaust noise.

In order to reduce the noise of high speed engine fan, a fan with hydraulic coupling or variable speed angle can be used, and water temperature induction electric clutch fan can also be adopted. When the fan material is changed into nylon, it also has some effect on reducing the fan noise.

3. vibration noise

The main solutions to vibration and noise are as follows: vibration reduction. It is mainly used in vibration source to reduce the amplitude of vibration wave. In order to reduce the vibration source, vibration isolator is installed in the way of vibration wave transmission. Most of the modern structures are complex multi degree of freedom systems, which are mostly broadband excitation. Increasing damping can effectively suppress vibration. The commonly used methods are damping free layer treatment and constrained layer damping treatment.

4. noise control and identification of noise sources

The ways of noise control are sound source control, noise transmission, path control and personal protection measures. Sound source control is the most basic way to control the mechanical noise, and the control of noise transmission is the most effective and the most commonly used way to reduce noise. The common measures are sound absorption, sound insulation, noise elimination, vibration isolation and so on.

Noise generated by the two ways to spread outward, one is directly through the media of air and noise pollution caused by noise, the air is called air sound; the other is directly through the source adjacent solid component vibration, the vibration in the form of elastic waves propagation in adjacent components, and radiation the larger noise into the air in the weak point, the noise propagation is called solid solid sound. The main technical measure to control solid sound is vibration isolation, that is, the rigid connection between the vibration source and the foundation or other objects is changed into an elastic connection, so as to weaken or impede the transmission of vibration energy and achieve the purpose of noise reduction.

Noise control measures of 5. vehicle engines

Specific methods are: engine noise absorption, absorb sound by microwell plate and foam; vibration dampers – vibration source and structure isolation; closed – enclosures or other noise insulation closed, so it is difficult to spread; damping – mechanical energy into heat and dissipate.

Selection of materials must meet the requirements of sound insulation, sound absorption, vibration reduction and heat insulation. The engine for processing sound insulation and damping are: by installing the damping pad on the engine and radiator is fixed on the bracket, the mechanical energy is converted into heat energy; the internal engine should avoid uneven, can be used with porous material damping layer; take measures to be closed on the body all the skeleton of the slit, so as to avoid wave diffraction.

To solve the noise of vehicle engine is a technical problem that involves all aspects of the whole machine, including the structure, material, quality distribution, process level, assembly sealing, etc. of the Benz engine in the northern part of Baotou. The manufacturer in the vehicle engine structure including positive measures to prevent noise by vibration, sound insulation technology, improvement of automobile structure, in the distance from the sound source is arranged in the insulation plate, muffler, on the bus with rear engine, improved muffler structure etc..