Method and apparatus for tire pressure monitoring

Abstract

The relative speed of each of the tires of a vehicle is monitored as an indication of the operating state of the vehicle, wherein if the vehicle is not operating in one of a number of predetermined states, the relative speed is monitored as an indication of relative pressure of the vehicle tires, and further wherein differences in relative speed not related to the predetermined states, and not related to differences in relative pressure, are accounted for. In addition, a single tire pressure sensor is employed to account for over or under inflation of substantially equal proportion in the tires.

Description

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 wit...

AI Technical Summary

Benefits of technology

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.

Problems solved by technology

Improper inflation of a tire can lead to poor gas mileage and increased tire wear.

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.

Such systems work well for their intended purposes, but there are disadvantages.

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.

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.

This type of system is not well suited to anything other than installation as original equipment.

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 significant disadvantage of multiple receivers is the high additional cost.

Additionally, installation is difficult unless installed as original equipment.

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