Method and system for determining tire pressure imbalances

• US 6,684,691 B1
• Filed: 01/17/2003
• Issued: 02/03/2004
• Est. Priority Date: 09/19/2000
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Rosseau, James R.
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Ellington, Alandra
• Application Number:
  US10/347,151
• Time in Patent Office: 382 Days
• Field of Search: 731/46, 731/462, 340/442, 340/444
• US Class Current: 73/146
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00
• CPC Class Codes: B60T 2240/07 Tire tolerance compensation

Abstract

A tire deflation warning system is based solely on the measured distance traveled by each tire of a: vehicle. The vehicle is equipped with a sensor which generates pulses representative of the distance traveled by each wheel such as generated by an ABS brake system. The system accumulates the pulses in the controller to determine whether the vehicle is stable. If the vehicle is stable, it performs a test to cover individual tires, opposing diagonal tires or any combination of three tires using an average of the diagonal ratio. These tests are performed by utilizing the pulses generated by each wheel representing the distance traveled by the wheel.

Claims

1. A method of detecting tire pressure imbalances in a set of tires of a vehicle, the vehicle having four wheels, a right front wheel, a left front wheel, a right rear wheel and a left rear wheel, each of the four wheels having a sensor generating a pulse for a predetermined amount of distance traveled by the respective wheel, said method comprising the steps of:

initiating a calibration mode;

accumulating a number of pulses generated by each sensor during a predetermined calibration time interval;

storing the number of pulses generated by each sensor during a measured interval equal in length to the calibration interval into an individual account for each sensor in a storage device;

computing a stability check using the number of pulses stored in the individual accounts, discarding the numbers stored in the individual accounts if the stability check is unsatisfactory;

summing the number of pulses in each of the accounts for a comparison total for each measured interval not discarded;

comparing the comparison total to the calibration standard; and

triggering an alarm when the comparison total is less than the calibration standard for a predetermined number of measured intervals.

2. The method of claim 1, wherein the stability step includes checking for slippage by comparing a front axle sum of the accounts for the right front wheel and left front wheel with a rear axle sum of the accounts for the left rear wheel and right rear wheel, discarding the numbers in the account if the sum of the front axle differs by more than a predetermined amount from the rear axle sum.

3. The method of claim 2, wherein the checking step further includes computing a diagonal ratio by comparing a first diagonal sum of the accounts for the right front wheel and the account for the left rear wheel with a second diagonal sum of the accounts for the left front wheel and the account for the right rear wheel for the measured interval;

and discarding the numbers in the accounts if the diagonal ratio is above a predetermined amount.

4. The method of claim 3 wherein the checking step further includes computing a longitudinal ratio by comparing the front axle sum to the rear axle sum and discarding the numbers in the accounts if the longitudinal ratio is above a predetermined amount.

5. The method of claim 2 wherein the checking step further includes computing a lateral ratio by comparing the sum of accounts for one side with the sum of the accounts for all wheels, the sum of accounts for one side being the front left wheel and the left rear wheel or the sum of pulses for the right front wheel and the right rear wheel, and discarding the numbers in the accounts if the longitudinal ratio is above a predetermined amount.

6. The method of claim 4 wherein the checking step further includes discarding the numbers in the accounts if the longitudinal ratio is above a predetermined amount and the diagonal ratio is within a predetermined range.

7. The method of claim 5 wherein the calibration step includes computing a calibration lateral ratio by comparing the sum of the accounts of one side during the calibration step, the one side being the left front wheel and the rear left wheel or the front right wheel and the rear right wheel, with the sum of the numbers in the four accounts;

and issuing an alarm if the lateral ratio for the measured interval remains in a predetermined range which is greater than a predetermined amount from the calibration lateral ratio.

8. The method of claim 4 herein the calibration step includes computing a calibration longitudinal ratio by comparing the front axle sum to the rear axle sum during the calibration interval, and the step of issuing an alarm if the longitudinal ratio computed during the measured interval is more than a predetermined amount from the calibration longitudinal ratio.

9. The method of claim 1 wherein the measured interval is one millisecond.

10. A tire pressure detection system for a vehicle having a plurality of wheels comprising:

providing a pulse generating sensor for each wheel of the vehicle to generate a pulse sum for each wheel as each wheel rotates;

adding the pulse sums from the pulse generating sensors of each wheel to generate a total sum of pulses for all the pulse generating sensors;

comparing the total sum of pulses to a calibrated pulse sum;

comparing the pulse sum of at least one wheel to an individual wheel calibrated pulse sum when the total sum of pulses is equal to the calibrated pulse sum;

triggering an indicator when the pulse sum of the at least one wheel is not equal to the individual wheel calibrated pulse sum.

11. The system of claim 10 further comprising:

generating a ratio of pulse sums for two wheels;

comparing the ratio of pulse sums to a calibrated ratio of sums for two wheels when the total sum of pulses is equal to the calibrated pulse sum; and

triggering an indicator when the ratio of pulse sums is not equal to the calibrated ratio of sums.

12. The system of claim 10 further comprising receiving the pulse sums from an anti-lock brake system.

13. The system of claim 10 further comprising the anti-lock brake system transmitting the pulse sums periodically.

14. A method of detecting tire pressure imbalances in a set of tires of vehicle, the vehicle having four wheels, and each wheel having a sensor generating a pulse for a predetermined amount of distance traveled by the wheel, the method comprising:

entering a calibration mode;

accumulating a number of pulses from each sensor and adding the number of pulses from each sensor to generate a calibrated total pulse count in the calibration mode;

storing the individual pulse sums of each said sensor used to generate the calibrated total pulse count as individual pulse sum calibration values;

storing the calibrated total pulse count;

exiting the calibration mode;

accumulating a number of pulses from each sensor to generate operating individual pulse sums and adding the number of operating individual pulse sums to generate an operating pulse count;

determining if the operating pulse count is equal to the calibrated total pulse count;

comparing at least one of the operating individual pulse sums to the individual pulse sum calibration values when the operating pulse count is equal to the calibrated total pulse count; and

triggering an indicator if at least one of the operating individual pulse sums is not equal to the individual pulse sum calibrations.

15. The method of claim 14 further comprising:

generating a ratio of operating individual pulse sums for at least two wheels;

comparing the ratio of operating individual pulse sums to a ratio of individual pulse sum calibration values for the at least two wheels; and

triggering an indicator when the ratios are not equal.

16. A system for detecting tire pressure imbalance in a vehicle comprising:

a plurality of wheels coupled to the vehicle;

a plurality of pulse generating sensors operatively coupled to said plurality of wheels, each said pulse generating sensor generating a pulse for a predetermined amount of distance traveled by each said wheel;

a controller for receiving said pulses generated by said plurality of pulse generating sensors;

wherein said controller accumulates individual pulse sums from each of said pulse generating sensors pulses to generate a sum of total pulses;

wherein said controller stores said individual pulse sums and said sum of total pulses;

wherein said controller compares said sum of total pulses to a calibrated pulse total;

wherein when said sum of total pulses is equal to said calibrated pulse total, said controller compares at least one of said individual pulse sums to a calibrated individual pulse sum for a specific wheel; and

wherein when at least one of said individual pulse sums is not equal to said calibrated individual;

. pulse sum for a specific wheel an indicator will be triggered.

17. The system of claim 16 wherein said individual pulse sums from at least two wheels are used to generate a ratio;

wherein said ratio is compared to a calibrated ratio; and

wherein an indicator is triggered when said ratio is not equal to a calibrated ratio.

18. The system of claim 16 wherein said pulse generating sensors are coupled to an anti-lock brake system and said anti-lock brake system transmits said pulses to said controller.

19. A system for detecting tire pressure imbalance comprising:

a vehicle;

a plurality of wheels coupled to said vehicle;

a plurality of sensors operatively coupled to said plurality of wheels, each said sensor sensing one of said plurality of wheels, said sensors generating pulses indicative of distance traveled by each said wheel;

a controller for receiving said pulses generated by said sensors;

wherein said controller accumulates individual pulse sums from each of said pulse generating sensors pulses to generate a sum of total pulses;

wherein said controller;

stores said individual pulse sums and said sum of total pulses;

wherein said controller compares said sum of total pulses to a calibrated pulse total;

wherein when said sum of total pulses is equal to said calibrated pulse total, said individual pulse sums from at least two wheels are used to generate a ratio;

wherein said ratio is compared to a calibrated ratio; and

wherein an indicator is triggered when said ratio is not equal to a calibrated ratio.

20. The system of claim 19 wherein said plurality of sensors are coupled to an anti lock brake system and said anti-lock brake system transmits said pulses to said controller.

21. A method of calibrating for tire pressure imbalances in a set of tires of vehicle, the vehicle having four wheels, and each wheel having a sensor generating a pulse for a predetermined amount of distance traveled by the wheel, the method comprising:

entering a calibration mode;

accumulating a number of pulses from each sensor and adding the number of pulses from each sensor to generate a calibrated total pulse count in the calibration mode;

storing the individual pulse sums of each sensor used to generate the calibrated total pulse count as individual pulse sum calibration values;

storing the calibrated total pulse count; and

exiting the calibration mode.

22. The method of claim 21 further comprising rejecting the calibrated total pulse count and individual pulse sum calibration values if a ratio of individual pulse sums is not equal to a calibrated value.

23. The method of claim 21 further comprising rejecting the calibrated total pulse count and individual pulse sum calibration values if the vehicle is turning.

24. A method of detecting tire pressure imbalances in a set of tires of vehicle, the vehicle having four wheels, and each wheel having a. sensor generating a pulse for a predetermined amount of distance traveled by the wheel, the method comprising:

entering a calibration mode;

accumulating a number of pulses from each sensor and adding the number of pulses from each sensor to generate a calibrated total pulse count in the calibration mode;

storing the individual pulse sums of each sensor used to generate the calibrated total pulse count as individual pulse sum calibration values;

generating at least one ratio of the individual pulse sum calibration values;

storing the at least one. ratio of the individual pulse sum calibration values;

storing the calibrated total pulse count;

exiting the calibration mode;

accumulating a number of pulses from each sensor to generate operating individual pulse sums and adding the number of operating individual pulse sums to generate an operating pulse count;

determining if the operating pulse count is equal to the calibrated total pulse count;

generating a ratio of operating individual pulse sums for at least two wheels;

comparing the ratio of operating individual pulse sums to the at least one ratio of individual pulse sum calibration values for the at least two wheels when the operating pulse count is equal to the calibrated total pulse count; and

triggering an indicator when the ratios are not equal.