Increasing use is being made of full LED headlights for both main and dipped beam operation in motor vehicles. These are compact, bright and efficient and with a colour temperature similar to daylight do not strain motorists’ eyes. But there is one problem manufacturers have to tackle: How to dissipate the heat. The intense luminance in a very small area generates heat which in the long term would damage the semiconductor. If a certain limit temperature is exceeded, the efficiency of the LEDs drops dramatically. The strength of the light dwindles and the service life is drastically reduced. Without the cooling system developed by ebm-papst, it would not be possible to achieve the performance required from a full LED headlight.
It all comes down to the ball bearings
The fans are integrated directly into the headlight. The air is blown onto the heat sinks of the LED array. This creates a turbulent but nonetheless controlled flow which ensures efficient heat transfer. At the same time the warm air is put to good use as it stops condensate misting up the inside of the headlight. “The ventilation must function just as well at winter starting temperatures of minus 40 degrees centigrade to prevent misting as at the maximum operating temperature of 120 degrees to cool the system. It was an enormous challenge to find a ball bearing grease capable of coping with this temperature span without solidifying or turning to liquid”, says Johannes Hirt, the Automotive Fans project manager. In the course of numerous trials, the engineers at ebm-papst came up with the ideal combination of ball bearing type and a highly specific grease.
Fit for motor vehicle use
Even without very high or low temperatures, it’s a hard life being an automotive component: Engine vibration, potholes and wet conditions all take their toll. To make their fans fit for motor vehicle use, the engineers at ebm-papst employ a special fan mounting system combining soft and hard suspension. This prevents the mutual intensification of natural vibration, engine vibration and impact – the so-called rebound effect. Optimum rotor and stator clearance is maintained. “The greatest asset is however the material. We make use of a special plastic which is crack-proof, temperature-resistant, stable and suitable for intricate geometry”, explains Hirt. “And there is hardly any outgassing. That’s an important aspect as it could cloud the lens”.
LED fans also need plenty of stamina. “The headlights are solid-state components. You can’t just quickly change the bulb”, as Johannes Hirt points out. Like the gearbox, they are designed to last for the full 15-year lifetime of the vehicle. “That’s why motor vehicle engineers used to be so reluctant to fit a permanently integrated rotating and potentially problematic component like a fan. It took fans from ebm-papst to convince the automotive industry.”