By next month, all new cars are required to have tire-pressure-monitoring systems. But, of course, there’s still a disconnect between noticing a squashed sidewall or a glowing idiot light and finding the time and gumption to pull over at a gas station, dig out a couple quarters (remember when air was free?), and bring the pressures up to spec. Lazy motorists, rejoice! Goodyear may soon relieve you of that messy, fussy task.
In August, the Akron, Ohio, company was awarded a $1.5-million Department of Energy grant to develop tires for commercial vehicles that keep themselves pumped up, and, in July, Goodyear’s European operations obtained a similar grant to develop a consumer version there. Company reps are not divulging details on how their Air Maintenance Technology system works, but after studying U.S. Patent 643243, it appears the concept is forehead-smackingly simple.
The “pump” is designed right into the rubber of the tire sidewall and works like many heart-lung machine blood pumps do: A loop of tubing is flattened by a roller or some other device, pushing a volume of fluid (here, it’s air) ahead of it and sucking in new fluid behind it. In the case of a rolling tire, the road serves to compress a tube mounted in a cavity in the sidewall up near the wheel rim while spring-loaded ball valves admit the pressurized air into the tire cavity if the pressure has dropped, or vent it back out the inlet hole if the tire is properly aired up (thereby purging the inlet filter). As illustrated, the tube and check valves are designed to be pressed into a cavity formed in the tire mold, and all the check valves operate in axial (parallel to axle and ground) channels so they’re unaffected by centrifugal forces.
The system is designed only to counteract a tire’s natural leakage rate of 1 to 3 percent per month–it won’t compensate for a puncture, so TPMS is still required. It seems hard to believe nobody thought of this before the December 21, 2009, patent filing date, right?
Actually, on February 21, 2008, Czech firm Coda Development SRO filed an application for a design that looks mighty similar to these non-patent-lawyerly eyes. A more elaborate system of check valves seems to allow users to alter the pressure level to be maintained, for example, to allow a higher pressure for autobahn speeds/high loads. Neither company would comment on the record, but I’m guessing the Goodyear patent particulars pertain to the simpler commercial-vehicle application (which would always operate at the same pressure), and the European-developed consumer design may incorporate some provision for altering the pressure.
It’s a great idea, and the government investment probably makes sense in the face of quoted statistics — annually, roughly 30 percent of vehicles have at least one tire 25 percent underinflated, and such underinflation contributes to $3.7 billion in wasted fuel, the premature replacement of 4.5 million tires, and 660 tire-related crash fatalities. But I have to wonder, with lubed-for-life suspensions, 100,000-mile transmission and spark-plug service intervals, oil that lasts 15,000 miles, and now tires that air themselves up, how will anybody bond with the maintenance-free cars of the future?
Illustrator: Rob Warnick
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