Cool throughout the night

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”.

Full life­time 

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.”