System for notifying person of level of danger of occurrence of tire failure

• US 6,744,355 B2
• Filed: 06/21/2002
• Issued: 06/01/2004
• Est. Priority Date: 06/26/2001
• Status: Expired due to Fees

• Current Assignee: Yokohama Rubber Company Limited
• Original Assignee: Yokohama Rubber Company Limited
• Inventors: Tozawa, Yukio, Kogure, Tomohiko
• Primary Examiner(s): TONG, NINA C
• Application Number:
  US10/176,048
• Publication Number:
  US 20020196138A1
• Time in Patent Office: 711 Days
• Field of Search: 340/442, 340/444, 340/447, 340/446, 340/448, 340/445, 731/464, 731/465
• US Class Current: 340/442
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver

Abstract

A system for notifying a driver in a vehicle of a level of danger of an occurrence of tire failure according to the present invention has a danger level assessment device which calculates a danger level assessment value indicating an index showing a probability of the occurrence of the failure from a measured tire inflation pressure and a measured tire running speed, using a characterized danger level assessing function to assess the danger level according to the calculated value. The characterized assessing function is a function of a tire running speed and of a tire inflation pressure, in which a value of the function monotonously increases as the tire running speed increase and as the tire inflation pressure decreases. The danger level assessment value is obtained by adding a cumulative value determined according to usage history of the tire to a value calculated from the danger level assessing function with the measured tire running speed and the measured tire inflation pressure.

Claims

1. A system for assessing a level of danger of an occurrence of failure of a mounted tire to a vehicle, and notifying a person of the level of the danger according to a result of the assessment, the system comprising:

a tire inflation pressure measuring device for monitoring a tire inflation pressure of the mounted tire;

a tire running speed measuring device for monitoring a tire running speed of the mounted tire;

a danger level assessment device for, at least in a case where the tire running speed obtained by the monitoring is higher than a given reference speed, calculating a danger level assessment value indicating an index showing a probability of the occurrence of the failure of the mounted tire from the tire inflation pressure obtained by the monitoring by the tire inflation pressure measuring device and from the tire running speed obtained by the monitoring by the tire running speed measuring device, based on a danger level assessing function, and assessing the danger level of the occurrence of the tire failure of the mounted tire from the danger level assessment value; and

a notification device for notifying a person of the danger level of the occurrence of the failure of the mounted tire, according to a result of the assessment of the danger level,

wherein the danger level assessing function is a function of the tire running speed and of the tire inflation pressure, in which, at least when the tire running speed is in a speed range above the given reference speed, a value of the function monotonically increases as the tire running speed increases, and the value of the function increases as the tire inflation pressure decreases.

2. The system according to claim 1, wherein the danger level assessing function has a first linear function defined in a speed range equal to or below the reference speed in which a value of the function remains fixed regardless of increase in the tire running speed, or increases linearly with the tire running speed, and a second linear function defined in a speed range above the reference speed in which a value of the function increases linearly with the tire running speed;

and

wherein the first linear function and the second linear function connect at the reference speed and a gradient of the second linear function with respect to the tire running speed is greater than a gradient of the first linear function with respect to the tire running speed.

3. The system according to claim 2, wherein the gradient of the first linear function and the gradient of the second linear function are determined by the tire inflation pressure.

4. The system according to claim 3,

wherein the gradient of the first linear function is equal to or above 0, and is equal to or less than 0.02 times a calculated value produced from the first linear function at a tire running speed 0 under a condition of a tire inflation pressure to be set of the mounted tire;

and

the gradient of the second linear function is greater than 0.02 times, and equal to or less than 1.0 times, the calculated value produced from the first linear function at the tire running speed 0 under the condition.

5. The system according to claim 1, wherein the danger level assessment device adds a cumulative value determined according to a usage history of the mounted tire to a calculated value from the danger level assessing function, whereby the danger level assessment value is calculated.

6. The system according to claim 5, wherein the danger level assessment device multiplies a duration of time for which the mounted tire is used by a function assessment reference value calculated from the danger level assessing function at a tire running speed that is produced by multiplying the reference speed by the given value greater than 1, whereby the cumulative value is obtained.

7. The system according to claim 5, wherein the danger level assessment device multiplies a sum of calculated values in a past for the mounted tire from the danger level assessing function by a function assessment reference value calculated from the danger level assessing function at a tire running speed that is produced by multiplying the reference speed by the given value greater than 1, whereby the cumulative value is obtained.

8. The system according to claim 5, wherein the danger level assessment device calculates a weighted average between:

a value produced by multiplying a product of a duration of time for which the mounted tire is used and a function assessment reference value calculated from the danger level assessing function at a tire running speed that is produced by multiplying the reference speed by a given value greater than 1, by a given number of times; and

a value produced by multiplying a product of a sum of calculated values in a past for the mounted tire from the danger level assessing function and the function assessment reference value by a given number of times, whereby the cumulative value is obtained.

9. The system according to claim 1, wherein the danger level assessing function with respect to the tire running speed when the tire inflation pressure is at a fixed level is a function obtained by approximating a characteristic function of a rolling resistance value that indicates a dependency of the mounted tire'"'"'s rolling resistance on the tire running speed using two straight-line or curved-line functions which are connected to each other at the reference speed, and multiplying each of these straight-line or curved-line functions by a given coefficient;

and

a value of the coefficient used in the speed range above the reference speed is a value equivalent to or greater than a value of the coefficient used in the speed range that is equal to or below the reference speed.

10. The system according to claim 1, wherein sensitivity coefficients which indicate gradients of the danger level assessing function with respect to the tire running speed, and which include a first sensitivity coefficient for the speed range equal to or below the reference speed and a second sensitivity coefficient for the speed range above the reference speed, decrease linearly as the tire inflation pressure increases.

11. The system according to claim 1, further comprising a load measuring device for monitoring a tire load while the vehicle runs,

wherein the danger level assessment device calculates a tire load ratio based on a load obtained from the load measuring device by the monitoring, and adjusts a calculated value produced from the danger level assessing function based on the tire load ratio.