When’s the last time that you checked your car’s tire pressure? If you are like most American motorists, you pay little attention to whether your tires are fully inflated even before you embark on long road trips.
U.S. government studies of the issue indicate that commercial truck drivers feel the same way as everyday commuters. A survey conducted a few years ago by the Federal Motor Carrier Safety Administration found that only 44% of all domestic truck tires are inflated to within 5 psi (34 kPa) of their target pressures. Further, it showed that nearly half are under-inflated by 6 to 19 psi (41 to 131 kPa) while an additional 7% are under-inflated by 20 psi (138 kPa) or more.
The trouble is that chronic tire under-inflation cuts vehicle fuel economy substantially and speeds up tire wear, according to John Kotanides, Jr., Project Manager of the Advanced Concepts Group at the Goodyear Innovation Center in Akron, OH. “Our rule of thumb is that every 10 psi loss in inflation pressure leads to a 1% loss in miles per gallon,” which at current prices costs a typical long-haul truck operator about $600 in extra annual fuel purchases, he said. “In addition, we find that a 10% under-inflation can shorten tire tread life by 9 to 16%.”
Properly inflated tires also help keep a vehicle's handling performance at optimal levels. Under-inflation means less evenly distributed pressure on the road. It also reduces the tread area that is in direct contact with the road and can impact the integrity of the tire casing, which is key to any post-use retreading process.
That’s why Goodyear engineers are developing a passive self-inflation system that automatically tops off the air in commercial truck tires as they roll down the road. The Air Maintenance Technology (AMT) system should help tires to remain inflated at the optimum pressure over the long term, reducing the need for any external pumps or electronics. The commercial application of Goodyear's new AMT system recently made its debut at the 2012 IAA Commercial Vehicles Show in Hanover, Germany.
“Goodyear started working on the technology on the consumer application side in late 2009-2010,” Kotanides recalled, “but then in August 2011 we received a grant of up to $1.5 million over three years from the [U.S.] Department of Energy’s Office of Vehicle Technology to develop a self-inflation system for commercial truck tires.”
Principal investigator on the in-house RD&E project, Robert Benedict, invented the patent-pending passive pumping concept for the self-inflation system, Kotanides said. During the following year the Goodyear team “designed the system, conducted initial testing, and proved out the theory behind the pumping mechanism before delivering a working prototype.”
“The idea was to keep it as simple as possible,” Kotanides said. The AMT system involves a regulator that senses when the tire is at optimal pressure. “If the pressure drops below the target level, an inlet filter in the regulator allows some outside air into the pumping tube which runs circumferentially around the inside of the tire,” he explained. “Deformations of the tube as the tire rolls produce little puffs of air that transfer air from the pumping tube through an inlet valve and into the interior cavity of the tire.”
The purely mechanical system is now undergoing fine-tuning and further tests at Goodyear’s Topeka, KS, manufacturing facility, he said. “We plan to start fleet evaluations in 2013.” The commercial truck AMT system is being designed to perform after the retreading process.
Goodyear has also received a grant from the Luxembourg government for research and development of an AMT system for consumer tires. That work is being conducted at Goodyear’s Innovation Center in Colmar-Berg, Luxembourg.
Commercial trucks pose a different challenge for the AMT system than do cars and light-duty trucks because their tires are larger and feature higher inflation pressures—105 psi (724 kPa) for commercial tires vs. 32 psi (221 kPa) for consumer tires. In addition, they operate over much longer distances, carrying much heavier loads. This poses a significantly more challenging performance requirement for the pump system.
“We believe the Air Maintenance Technology application for commercial vehicle tires will not only enhance the performance of the tire, but will also provide cost savings to fleet owners and operators through the extension of tire tread life and increased fuel economy,” said Goodyear’s Chief Technical Officer, Jean-Claude Kihn. “The progress we continue to make with this technology is very encouraging. We look forward to further testing of this concept.”