Hello everyone. I am coming. IMDS was introduced in the previous issue. In this issue, we introduce the issue of fogging of car lights.
We conduct research from the following aspects
The source of moisture in car lights
The principle of fogging
solution
Why do car lights fog up in the first place?
The source of moisture in car lights
1. Exchange with outside air through holes
2. Release of water molecules in materials
The principle of fogging of car lights
Principle: When the temperature of the inner surface of the lampshade is lower than the dew point of the nearby air, condensation (fogging) will occur.
Dew point: The dew point temperature refers to the temperature corresponding to when the moist air reaches saturation when the steam partial pressure remains constant.
Saturation water vapor pressure: At a certain temperature, if the water vapor pressure increases to a certain limit value, the water vapor in the air will reach saturation, which is the saturated water vapor pressure.
Humidity: The amount of water vapor contained in the air. At a certain temperature, the more water vapor there is, the more humid the air is.
solution
1. Use anti-fog treatment on the inner surface of the lamp housing, but the cost is too high.
2. Open ventilation holes
The fog will dissipate quickly, but it will not effectively prevent dust and water from entering the lamp.
3. Breathable cover and breathable membrane
It can effectively prevent dust and water, but the fog will take longer to dissipate.
4. Improve the temperature field and flow field inside the lamp
When the car lights are turned on, there will be natural convection in the lights, resulting in an uneven temperature field, and the flow in local areas is slow, which can easily cause condensation.
Consider heat-flow design: ensure temperature uniformity as much as possible and avoid dead zones.
Okay, that’s it for introducing the general principles and solutions to lamp fogging. Fogging is a problem that is difficult to solve and avoid in the automotive lighting industry. Later, we will do a separate issue to specifically introduce the causes and solutions of fogging. thank you all
