LEDs for the rest of us

Automotive Design & Production, July, 2005

LED lighting is becoming more common, but it is by no means commonplace. One reason is the cost associated with the use of numerous discrete elements in a lighting unit, which makes it a custom design. Not only is the housing unique, so is the array of lights behind it. It's enough to offset the lower power consumption and longevity advantages LEDs hold over incandescent lamps, and make LED lighting something found only in high-end vehicles.

"Joule" is the First standardized LED system solution offered to OEMs in a plug-and-play package," says Dave Hulick, global auxiliary product manager, Osram Sylvania (www.sylvania.com; Hillsboro, NH). Hulick says the Joule isn't as cheap as the incandescent bulbs most vehicles still use, nor is it as expensive as a custom LED array. "It's a solution that moves LEDs into the volume sector while giving car makers the opportunity to upgrade and differentiate the design of their rear combination lamps without resorting to an expensive redesign."

The first thing you notice about the Joule is the wrap-around heat sink base that is the main component of its thermal management system. "That's a critical item," says Fred Peterson, HID Engineering manager, "because LED output drops as the temperature rises." The second thing you notice is the USCAR connector, and the third is the capped chrome pillar rising above the base. The Joule reflects its light along the underside of the cap and down the pillar. "We are selling customer a light pattern as well as a technology," says Peterson, "so that we can upgrade the latter without requiring OEMs or suppliers to change the lamp fixtures. We want this technology to be plug-and-play in every way possible."

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Despite the fact that the Joule light has yet to make it production debut--it's slated to debut on the 2006 Mercury Mountaineer--the second generation is already under development. Made up of 8 pieces instead of the first generation's 11, the design reduces complexity and the number of components, replaces separate LEDs on the pillar with an acrylic light pipe that can be tuned for different focal lengths, and will be capable of combining LEDs to produce amber light as well as red for a combined stop/turn function. Currently, it takes separate Joule units to perform this function. The white backup light will likely remain separate to keep cost and complexity in check.

"The Joule's base will support a number of light designs," says Peterson, "From 3D optic disc designs to fiber optics." An optic disc would allow a car maker like BMW, for example, to copy the "angel eyes" ring that light up around its HID front lighting units with a similar design in the rear without using multiple LEDs. Combining Joule with a separate lens eliminates the need for a reflector, making body color or contrasting taillights a possibility. Osram Sylvania also has shown automakers a fiber optic light that mates moveable light-conducting fibers with the Joule base. "It didn't take the designers long to realize they could arrange the fibers in various ways, from a starburst to a chevron, to get different looks without having to specify separate lighting units." says Peterson.--CAS