In response to regulations implemented by the United States government, automotive manufacturers are starting to provide new vehicles with tire pressure monitoring equipment. Initiated in the year 2000, Congress passed the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act, which related to issues concerned with the operation of a vehicle with substantially under-inflated tires. Under-inflated tires can result in a tire separation/blowout, which adds to the potential for a loss of control of a vehicle. Additionally, under-inflated tires shorten tire life and increase fuel consumption.
Section 12 of the TREAD Act directed the Department of Transportation (DOT) to complete a rule requiring that new motor vehicles must include a warning system that indicates if tires are under-inflated. Ever further, in response to Section 12 of the TREAD Act, the National Highway Traffic Safety Administration's (NHTSA) National Center for Statistics and Analysis (NCSA) conducted the Tire Pressure Special Study (TPSS), which was designed to assess to what extent passenger vehicle operators are aware of the recommend tire pressures for their vehicles, the frequency and the means they use to measure their tire pressure, and how significantly actual measured tire pressure differs from the manufacturers recommend tire pressure.
As a result of the TPSS, the NHTSA favored a direct system using monitors in each wheel to determine whether tires are properly inflated so as to alert drivers when tire pressure is low. In early 2002, the NHTSA issued a regulation mandating the implementation of tire pressure monitoring systems in new vehicles beginning with the 2004 model year. Under that rule, tire pressure monitors had to warn motorists when tire pressure fell 25% or 30% below the vehicle manufacturer's recommended level. The new standard applies to passenger cars, trucks, multipurpose passenger vehicles, and buses with a gross vehicle weight rating of 10,000 pounds or less, except those vehicles with dual wheels on an axle.
Referring now to FIG. 1, a conventional tire pressure monitoring system is shown generally at 1 within a vehicle, V, shown in phantom. As seen in the Figure, a receiver 2 detects wireless tire pressure signals 3a-3d that originate from each of the four in-use tires 4a-4d located at each corner of the vehicle, V. As known in the art, each wireless tire pressure signal 3a-3d is individually recognized by the receiver 2 to properly indicate if a particular in-use tire 4a-4d is not properly inflated. Although the receiver 2 may individually recognize the inflation level of each in-use tire 4a-4d, the tire pressure monitoring system 1 may be affected by a signal other than that of a signal originating from an in-use tire 4a-4d, which is shown generally at 5 in FIG. 2. As such, the signal 5, which is hereinafter referred to as an interfering signal 5, may result in an incorrect reading by the receiver 2.
The interfering signal 5 may be transmitted unintentionally, for example, by an in-use tire 6 operating in conjunction with a tire pressure monitoring system of a nearby vehicle, V2. In another situation, an operator of the vehicle, V2, may intentionally transmit the interfering signal 5 to the vehicle, V, in an attempt to cause the operator of the vehicle, V, to think that the in-use tires 4a-4d are losing pressure. Subsequently, the driver of the vehicle, V, may pull over on the shoulder, S, of the road to manually inspect the in-use tires 4a-4d for pressure loss. Additionally, if one of the in-use tires 4a-4d is swapped with a spare tire 4e, which is shown located in the trunk area of the vehicle, V, the swapped-out in-use tire 4a-4d may unintentionally transmit a false signal from the trunk area of the vehicle, V, to the receiver 2 even though the tire 4a-4d is no longer loaded by the vehicle.
Accordingly, it is therefore desirable to provide an improved tire pressure monitoring system that detects and reacts to a signal other than that of a signal originating from an in-use tire of the tire pressure monitoring system.