Method for determining tire inflation status

• US 5,962,779 A
• Filed: 03/27/1998
• Issued: 10/05/1999
• Est. Priority Date: 01/29/1997
• Status: Expired due to Term

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Bass, Ronald Marshall
• Primary Examiner(s): NOORI, MAX H
• Application Number:
  US09/049,969
• Time in Patent Office: 557 Days
• Field of Search: 73/146.3, 73/146.2, 73/146, 73/146.4, 73/146.5
• US Class Current: 73/146.5
• CPC Class Codes: G01L 17/005 using a sensor contacting the exterior surface, e.g. for measuring deformation

Abstract

The inflation status of a vehicle tire is determined while the tire is installed on the vehicle by recording a first signal representing the weight (Y) on a scale plate with respect to time when the tire is rolling on the scale plate; recording a second signal representing the weight (X) on a deformation bar with respect to time when the tire is rolling over the deformation bar; determining the maximum Y of the first signal and the maximum X of the second signal; calculating a ratio R by dividing the maximum X of the second signal by the maximum Y of the first signal; and comparing the calculated ratio R (=X/Y) with a predetermined value for the ratio R pertaining to the maximum Y of the first signal and giving an underinflation signal if the calculated ratio is below the predetermined value. Predetermined values for the ratios are obtained by determining, for a large number of combinations of vehicles and tires, the ratio R as a function of tire pressure; calculating a threshold for each combination of vehicles and tires; and fitting a curve of predetermined values for the ratios R through points having as coordinates the corresponding maximum value Y of the weight on the scale plate with respect to time when the tire is rolling on the scale plate and the corresponding ratio pertaining to the threshold. The curve of predetermined values is fitted so as to define a smooth curve that is an envelope which lies below all threshold data but is as close to the data as possible.

Claims

1. A method for determining the inflation status of a vehicle tire while said tire is installed on said vehicle, comprising the steps of:

recording a first signal representing the weight (Y) on a scale plate with respect to time when said tire is rolling on said scale plate;

recording a second signal representing the weight (X) on a deformation bar with respect to time when said tire is rolling over said deformation bar;

determining the maximum Y of said first signal and the maximum X of said second signal;

calculating a ratio R by dividing the maximum X of said second signal by the maximum Y of said first signal; and

comparing said calculated ratio R (=X/Y) with a predetermined value for the ratio R pertaining to said maximum Y of said first signal and giving an underinflation signal if said calculated ratio is below said predetermined value.

2. The method according to claim 1, wherein the method for obtaining said predetermined value for said ratio comprises the steps of

determining for a large number of combinations of vehicles and tires said ratio R as a function of tire pressure;

calculating for each combination of vehicles and tires a threshold; and

fitting a curve of predetermined values for said ratios R through points having as coordinates the corresponding maximum value Y of the weight on said scale plate with respect to time when said tire is rolling on said scale plate, and the corresponding ratio pertaining to said threshold.

3. The method according to claim 2 wherein said curve of predetermined values is fitted so as to define a smooth curve that is an envelope which lies below all threshold data.

4. The method according to claim 3 wherein said envelope lies as close to said data as possible.