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Wheels:
Car horns go the capacitive-touch route; fewer components required

New car owners of the near future might yell, "What the beep?!" when they try to pound their horns.

TRW Automotive Holdings Corp. is developing a new electronic horn system (EHS) that is activated by gently touching a conductive area on the steering wheel airbag cover.

The technology aims to offer a number of benefits, including improved visual appearance, enhanced functionality, lower actuation forces, and fewer components compared with conventional horn systems.

"Classic vehicle horn systems can be bulky and expensive," says Guido Hirzmann, TRW's group leader, new technology, mechatronic. "Our new EHS includes a significant reduction of components like springs, silver contact, screws, fixation clips, and more. There are no moving parts, allowing the driver airbag to be fixed directly into the steering wheel -- resulting in an improved fit and symmetry."

Special coatings enable the airbag cover to be turned into a 3D electrical conductive surface. This can detect the position of a finger or hand and send a signal to an ECU, resulting in the horn actuation. No force is required to activate the system.

The unique design of the cover also helps to prevent the horn being activated by accident. The system is a 3D design spanning the entire airbag cover, with the sensor integrated into a defined area. Using smaller sensor fields connected to the ECU, it is possible to detect if the driver's hand approaches the cover from the side (accidentally) or from the top (purposeful activation by the driver).

"We have chosen this capacitive solution partly because more and more electronic devices are using the technology, making it very familiar to many users, including younger occupants," says Hirzmann. "A similar concept could also be integrated into surfaces near to the fingers of the driver to incorporate a 'greeting horn,' or into multifunction switches or any other function. Several vehicle manufacturers are showing interest."

TRW expects that its EHS unit will be ready for production in 2014.

Source: TRW

Published September 2012

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