Vehicle pneumatic tires typically include a rubber tire mounted on a metal rim with a valve protruding through the rim. The valve includes internal components that permit a gas to be introduced into and purged from the tire. The tire generally includes multiple layers of rubber and reinforcement with a tire liner on the inside and a tread on a generally cylindrical outer surface. Vehicle pneumatic tires are typically filled with compressed air. The air is compressed by an air compressor and stored or diverted to the tires. However, this compressed air will generally have condensed moisture from the atmosphere and may also have oils that become entrained in the compressed air within the air compressor.
Atmospheric air at sea level typically includes about 78.1% nitrogen gas (N2) and about 20.9% oxygen gas (O2). The remaining 1% of this air is water vapor and other gasses (hydrocarbons, argon, carbon dioxide, . . . ). As mentioned, compressing this air may result in oil entrained in the compressed air. This compressed air may also contain water droplets that condense as the air is compressed. While dryers may be added to air compressors to separate out water, some water vapor will be present in compressed air that may have been dried. This water vapor within the compressed air will be introduced into a vehicle tire when the tire is pressurized with the compressed air. However, water vapor will escape through a vehicle tire at a rate that is greater than the rate that N2 will escape through the tire. Additionally, the water vapor may undesirably react with the tire, the rim, and the valve internal components to degrade these components and cause further leakage of gasses from the tire.
The O2 component of the compressed air within the tire will escape through a vehicle tire at a rate that is greater than the rate that N2 will escape through the tire. Furthermore, the O2 component of the compressed air within the tire may damage the reinforcement and the rubber compound of the tire liner resulting in a degraded tire.
The aforementioned leakages prevent the vehicle tire from remaining at an optimum tire pressure for fuel economy, safety, and tire wear. Also, it has been found that a vehicle tire that operates with at least about 92% N2 will operate at a lower temperature, thereby increasing tire life.
Compressed gasses that do not contain O2 may be used to pressurize a vehicle tire, however these gasses may not be readily available for distribution or may be contained in very high pressure (greater than 2000 pounds pre square inch (psi)) containers that require special handling. Additionally, since many tires are pressurized with compressed air, purging the air and pressurizing the tire with an alternate gas may be time consuming and expensive. What is needed, therefore, is a cost effective apparatus and method for purging vehicle tires, and other components, and pressurizing the tires with gasses that do not contain undesirable amounts of O2 and water.