The lighting effect of automobile headlamp affect the driving at night?
Datetime: 2020-11-19 17:14:05 Views: 452
Because the lighting effect of the automobile headlamp has a great influence on the safety of driving at night, the lighting standards of the headlamp are regulated by law in many countries in the world. The basic requirements are as follows:
First, the headlamp shall ensure bright and uniform lighting in front of the vehicle, so that the driver can see the objects on the road within 100m in front of the vehicle. With the continuous improvement of the driving speed of modern vehicles, the requirements for the headlamp are also higher and higher. The lighting distance of the headlamp of modern high-speed vehicles should reach 200-250m.
Second, the headlamp should prevent glare to avoid the other driver from dazzle when the two cars meet at night, resulting in traffic accidents.
(2) Structure of headlight
The headlamp consists of a reflector, a light distribution mirror and a bulb, as shown in Figure 4.1.
The mirror is used to maximize the light from the bulb into a strong beam to increase the distance of the light. It is generally paraboloid, the inner surface is chromium, aluminum or silver, and then polished. At present, vacuum aluminum plating is widely used. The filament is located at the focal point of the reflector, and most of the light is reflected and then it becomes a parallel beam and is shot far away, with a distance of 150 meters or more, as shown in Figure 4.2.
Figure 4.1 composition of headlamp
Figure 4.2 principle of reflector
2) Light distribution mirror
The light distribution mirror is also called astigmatic glass. Before it is installed, the reflected beam can be diffused and distributed, so that the lighting of the road section is more uniform. The light distribution mirror is a combination of prism and lens made of transparent glass. As shown in Figure 4.3.
Figure 4.3 optical distribution mirror
At present, there are two kinds of lamps for automobile headlamp, namely incandescent bulb and tungsten halogen bulb. The filament of both kinds of lamps is made of tungsten wire. Because of the evaporation loss of tungsten wire, the service life of the bulb is shortened. In order to prolong its life, the air in the glass bubble is extracted and then filled with other gases. If the gas filled in the glass bubble is inert gas, it is incandescent bulb; if the halogen element (iodine or bromine is generally filled) is filled, it is tungsten halide bulb, as shown in Figure 4.4. Most of the production in China is tungsten bromide lamp.
Figure 4.4 bulb
The halogen bulb is made by the principle of tungsten halide regeneration and cycle reaction. The principle of tungsten halogen regeneration and recycling reaction refers to the vapor tungsten evaporated from the filament, which reacts with halogen to produce a volatile tungsten halide. It spreads to the high temperature area near the filament and decomposes it, which makes the tungsten return to the tungsten wire. The released halogen continues to diffuse and participates in the next cycle reaction. Thus, it circulates repeatedly to prevent the evaporation of tungsten and the blackening of tungsten bulb Phenomenon. Therefore, tungsten halide bulb has the characteristics of long life and large brightness compared with incandescent bulb.