Measuring and testing – Tire – tread or roadway
Reexamination Certificate
2003-06-12
2004-10-12
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Tire, tread or roadway
Reexamination Certificate
active
06802213
ABSTRACT:
BACKGROUND
Motor vehicles are supported by inflatable tires having a desired inflation pressure. Improper inflation of a tire can lead to poor gas mileage and increased tire wear. Maintaining tire inflation within an acceptable range can alleviate these issues. To do so however, requires frequent measuring of tire pressure and evaluation of whether that pressure lies within an acceptable range. Moreover, tire pressure will also vary according to temperature and vehicle load.
There are several advantages to maintaining the pneumatic tires of an automobile at the inflation pressure recommended by the tire or vehicle manufacturer. Vehicle handling characteristics are maintained when all tires are inflated to the condition specified by the vehicle designer. The loss of pressure in one or more tires on the vehicle may result in less than optimum driver control. Inadvertent over-inflation of one or more tires may also result in less than optimum vehicle handling. Operating a vehicle with tire pressures outside the recommended inflation range can also reduce tire life due to excessive flexing and heating and resultant fatigue or wear. Tire pressure monitoring systems have been developed which alert the vehicle operator when the pressure in one or more of the tires fitted to the vehicle is outside a predetermined range.
Indeed, following an increase in public awareness of the potential consequences of operating tires outside the manufacturers recommended pressure range, legislation has been introduced such as proposed FMVSS 138 which requires that a tire pressure monitoring system be installed as original equipment on all new vehicles sold in the United States after November 2003.
While several tire pressure-monitoring methods have been proposed, two general approaches have been favored. One is indirect and relies on the determination of the rolling radius of each hub and tire assembly (and often linked to the anti-lock brake system (ABS) of the vehicle). The second is direct and relies on the wireless transmission of a signal from a transducer module installed in the pressurized cavity of each tire. Such systems work well for their intended purposes, but there are disadvantages.
The rolling radius method relies on the signals generated by wheel rotation sensors, typically installed as part of an anti-lock braking system. The rolling radius represents the actual radius from the center of the tire to the generally flattened area of the tire in contact with the ground. Because of the flattening at the point of contact of the tire and the road or surface, the rolling radius measures smaller than the nominal radius of the tire as manufactured or unloaded, since the nominal radius does not account for variation in pressure within the tire and load on the tire. Since the rotational speed of each wheel is known accurately, the rolling radius of the hub and tire assembly mounted at each wheel can be inferred. This system of tire pressure monitoring (frequently referred to in the art as ABS-tire pressure monitoring) does not, however, provide absolute values of pressure, nor does it provide tire temperature information. If all of the tires on the vehicle were to lose pressure equally over time, such a system may fail to detect a reduction in pressure in any tire. Also, this system requires that data be gathered over some minimum number of wheel rotations in order to allow tire temperatures to equalize to some extent, to determine relative rolling radii, and then to approximate each tire pressure. This type of system is not well suited to anything other than installation as original equipment. While this type of system is a low cost addition to a vehicle equipped with anti-lock brakes, it has many performance shortcomings. One of the major deficiencies of this system is that if all tires are over or under inflated, the differential wheel speed measurements between wheels are not capable of detecting the condition.
The direct sensing method requires the installation of a wireless module in contact with the gas within the pressurized cavity of each tire and hub assembly. A matched receiving module is installed on a fixed portion of the vehicle such that the transmitted data may be processed and presented to the vehicle operator as required. A receiver may be positioned within each wheel well of the vehicle, in which case it is necessary to install one receiver for each monitored tire on the vehicle, or, a single receiver may be placed approximately centrally within the vehicle, such as at the interior rearview mirror location. The significant disadvantage of multiple receivers is the high additional cost. Additionally, installation is difficult unless installed as original equipment.
Thus, there is a need for an improved tire pressure monitoring system that overcomes the above disadvantages.
SUMMARY OF THE INVENTION
Disclosed generally herein is a method and apparatus for determining the pressure of the vehicle tires via the sensed speed of the vehicle wheels and the tire pressure of a single tire. The present invention substantially reduces its susceptibility to false alarms by determining whether a variation in wheel speed is due to some external factor, or is due to a loss in pressure in one or more tires. Further, the present invention discloses a cost effective means for tire pressure monitoring without employing a pressure sensor in each tire, such that using a differential wheel speed algorithm in conjunction with a single tire pressure sensor allows determination of over or under inflation even if all of the tires are over/under inflated to the same level.
To effectively reduce the risk of false alarms in the system caused by external factors, the present invention generally develops predetermined models of the relationship between the individual wheel speed values for a variety of operating scenarios. The scenarios are those that would cause notable wheel speed variations not attributable to loss of tire pressure, such as the above-described external factors. The models thus developed are made available to the routine in accord with the present invention, and are compared to the sensed speed of the individual wheels. Generally, from this comparison, if it is determined that the vehicle is operating in such a manner that the present wheel speed data is not useful for the determination of tire pressure, the data is discarded, and the present iteration of the routine is terminated.
Otherwise, the wheel speed data and single tire pressure data are compared to predetermined models of what the data should resemble if there is at least a threshold loss of pressure in a vehicle tire. If this comparison indicates a sufficient loss of tire pressure, the routine provides an indication thereof to the vehicle operator, who can then take appropriate action.
The above described and other features are exemplified by the following figures and detailed description.
REFERENCES:
patent: 5218862 (1993-06-01), Hurrell, II et al.
patent: 5721374 (1998-02-01), Siekkinen et al.
patent: 6161905 (2000-12-01), Hac et al.
patent: 6369703 (2002-04-01), Lill
patent: 6481806 (2002-11-01), Krueger et al.
patent: 2002/0157461 (2002-10-01), Schmidt et al.
patent: 2003/0030553 (2003-02-01), Schofield et al.
Allen Andr
Delphi Technologies Inc.
Funke Jimmy L.
Lefkowitz Edward
LandOfFree
Method and apparatus for tire pressure monitoring does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for tire pressure monitoring, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for tire pressure monitoring will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3275807