Crain News Service report
CLERMONT-FERRAND, France (Jan. 7, 2014) — Michelin Group has filed for a patent on the use of polyurethane foam inside a tire to reduce noise.
However, as yet the company has not disclosed whether it's making such tires, whereas both Continental A.G. and Pirelli Tyre S.p.A. have started supplying OE customers with similarly equipped tires.
Michelin filed its patent application with the World Intellectual Property Organization in 2013. The patent, number WO/2013/182477, is published on the organization's website.
According to the filing, "The polyurethane is based on a diphenylmethane diisocyanate (MDI), in particular on 4,4'-diphenylmethane diisocyanate and a polyol which has an ethylene oxide content greater than 50 percent (percent by weight).
"This specific polyurethane formulation makes it possible to obtain a light foam which efficiently absorbs noise. It has the advantage of being simple and inexpensive and of being easy to use by direct casting of the reagents in the tire of the invention."
In the filing, Michelin claims the cavity noise generated by tires equipped with the foam insert was reduced by 2.5 dB (A).
Both Continental and Pirelli Tyre have developed tires for Audi Group that are designed to reduce noise for occupants of the car by using a layer of polymer sponge that is adhered to the inner liner of the tire.
Pirelli claims the innovation—being pitched as "Pirelli Noise Cancelling System"—can reduce the noise heard by those inside the car by 2 to 3 decibels, or roughly half. Conti claims its technology—dubbed "ContiSilent"—can reduce the tire-generated noise level reaching a car's cabin by as much as 9 decibels.
This item is based on reporting by Urethanes Technology, a sister publication of Tire Business, and Tire Business archive research.