Tire air pressure warning device

• US 6,182,021 B1
• Filed: 08/11/1998
• Issued: 01/30/2001
• Est. Priority Date: 03/29/1993
• Status: Expired due to Fees

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Tachihata, Tetsuya, Izumi, Tomoji, Edahiro, Takeshi
• Primary Examiner(s): ASSOUAD, PATRICK J
• Application Number:
  US09/132,308
• Time in Patent Office: 903 Days
• Field of Search: 702/138, 702/140, 702/148, 701/70, 731/462, 731/463, 731/464, 731/465, 340/442, 340/443, 340/444, 340/445
• US Class Current: 702/138
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00

Abstract

When the difference between the number of revolutions of each tire of a vehicle is judged by the tire air pressure warning device must be made under the condition that the number of revolutions of the four wheels must constantly be detected by different units, and processed at a high speed, and where the vehicle is travelling in a straight line, and at a point in time when all four wheels become at the same condition. In the case that all four wheels do not reach the same condition, the judgment of the difference in the number of tire revolutions at the tire air pressure warning device is prohibited. Also, using the vehicle running conditions, the most suitable tire air pressure judgment is carried out, and various noise generate when the vehicle is travelling do not have any effect, and the tire air pressure abnormality is detected with good accuracy, the detected signal from the wheel velocity sensors is carefully selected, and the reliability and accuracy of the tire air pressure judgment is improved. When the vehicle and/or the road surface is in a specific condition, by prohibiting the tire air pressure judgment, the reliability and accuracy of the tire air pressure judgment is increased. By permiting the tire air pressure judgment when within a vehicle velocity region, that is established using the road conditions, the reliability and accuracy of the tire air pressure judgment is improved.

Claims

1. A tire air pressure warning device which judges tire air pressure abnormality based on detected signals from wheel velocity sensors that detect a revolving state of respective tires of a vehicle, and outputs a warning signal, comprising:

a coefficient setting means for setting coefficients to compensate a difference between initial conditions of respective said tires, based upon the detected signals from the wheel velocity sensors;

a judgment means for judging tire air pressure abnormality by comparing a deviation value obtained from a prescribed equation based on a difference between a number of revolutions of each tire and a deviation width having a prescribed width; and

a prohibiting means for prohibiting judgment of tire air pressure abnormality by said judgment means when the coefficients do not satisfy a prescribed condition.

2. A tire air pressure warning device according to claim 1, wherein said prescribed equation has the coefficients as factors for obtaining said deviation value.

3. A tire air pressure warning device that judges a tire air pressure abnormality utilizing detected signals from wheel velocity sensors that separately detect a revolving state of respective tires of a vehicle, and outputs a warning signal, comprising:

a judgment means for judging tire air pressure abnormality by comparing a deviation value obtained from a prescribed equation based on a difference between a number of revolutions of each tire and an average tire rotation and a deviation width having a prescribed maximum value and a prescribed minimum value;

a vehicle velocity detecting means for detecting a vehicle velocity;

a deviation width changing means for changing the prescribed maximum value and the prescribed minimum value according to the velocity of said vehicle, wherein the deviation width changing means changes the prescribed maximum value and prescribed minimum value such that a tire air pressure abnormality judgement is more likely the greater the velocity.

4. A tire air pressure warning device according to claim 3, wherein said deviation width changing means increases a difference between the prescribed maximum value and the prescribed minimum value as the vehicle velocity increases.

5. A tire air pressure warning device which outputs a warning when a decrease in tire air pressure is detected in respective four wheels of a vehicle, comprising:

wheel velocity sensors which output a number of pulse signals per one revolution of the respective four wheels of the vehicle, the wheel velocity sensors including a plurality of detecting portions provided on a disk which rotates with the wheel, and electromagnetic pickups to detect the detecting portions and to output the same number of pulse signals per one revolution;

a data collection means for counting the number of pulse signals output from the respective wheel velocity sensors, and for measuring a time required to output the number of pulse signals for each respective wheel velocity sensor, thus obtaining the wheel velocity data of each wheel; and

a first reset means for resetting a counter number in a counter of the data collection means when the pulse signals from the respective wheel velocity sensors are not output within a first prescribed time period, after an output signal is initially output from any of the wheel velocity sensors when the operation of the tire air pressure warning device is started.

6. A tire air pressure warning device according to claim 5, wherein after the counter is reset, the first reset means re-starts counting of the pulse signal by the data collection means.

7. A tire air pressure warning device which outputs a warning when a decrease in the tire air pressure is detected in respective four wheels of a vehicle, comprising:

wheel velocity sensors which output a number of pulse signals per one revolution of each of the four wheels of the vehicle, the wheel velocity sensors including a plurality of detecting portions provided on a disk which rotates with the wheel, and electromagnetic pickups to detect the detecting portions and to output the same number of pulse signals per one revolution;

a data collection means for counting the number of the pulse signals output from the respective wheel velocity sensors, and for measuring a time required to output the number of pulse signals for each respective wheel velocity sensor, thus obtaining the wheel velocity data of each wheel; and

a second reset means for resetting a counter number in a counter of the data collection means, after the number of pulse signals from any of the wheel velocity sensors is output, if the number of pulse signals from the respective wheel velocity sensors is not output from the respective wheel velocity sensors within a second prescribed time period after the operation of the tire air pressure warning device is in operation.

8. A tire air pressure warning device which outputs a warning when a decrease in the tire air pressure is detected in respective four wheels of a vehicle, comprising:

wheel velocity sensors which output a number of pulse signals per one revolution of each of the four wheels of the vehicle, the wheel velocity sensors including a plurality of detecting portions provided on a disk which rotates with the wheel, and electromagnetic pickups to detect the detecting portions and to output the same number of pulse signals per one revolution;

a data collection means for counting a number of the pulse signals output from the respective wheel velocity sensors, and for measuring a time required to output the number of pulse signals for each respective wheel velocity sensor, thus obtaining the wheel velocity data of each wheel;

a first reset means for resetting a counter number in a counter of the data collection means when the pulse signals from the respective wheel velocity sensors are not output within a first prescribed time period, after an output signal is initially output from any of the wheel velocity sensors when the operation of the tire air pressure warning device is started; and

a second reset means for resetting a counter number in a counter of the data collection means, after the number of pulse signals from any of the wheel velocity sensors is output, if the plurality of pulse signals from the respective wheel velocity sensors is not output from the respective wheel velocity sensors within a second prescribed time period, after the operation of the tire air pressure warning device is in operation.

9. A tire air pressure warning device which outputs a warning when a decrease in the tire air pressure is detected using detected signals from wheel velocity sensors from respective four wheels of a vehicle, comprising:

a tire pressure judging means for judging a decrease of the tire pressure based on differences between respective tire rotations;

a detecting means for judging whether the vehicle is in a normal running condition or in an abnormal running condition; and

a prohibition means for prohibiting the judgement of the tire pressure by the tire air pressure warning device, when the vehicle is in an abnormal running condition, or until a current running condition has changed from the abnormal running condition to the normal running condition within a prescribed time.

10. A tire air pressure warning device according to claim 9, further comprising:

a data erasing means which erases a detected output from the wheel velocity sensors when the vehicle changes from a normal running condition to an abnormal running condition, thus prohibiting the detected outputs obtained just before changing from the normal running condition to the abnormal running condition from being used for controlling the tire air pressure warning device.

11. A tire air pressure warning device according to claim 9, wherein the detecting means detects that the vehicle is in the normal running condition when the vehicle is running straight, and detects that the vehicle is in the abnormal running condition when the vehicle is turning.

12. A tire air pressure warning device according to claim 9, wherein the detecting means detects that the vehicle is in the normal running condition when the vehicle is not braked, and detects that the vehicle is in the abnormal running condition when the vehicle is braked.

13. A tire air pressure warning device according to claim 9, wherein the detecting means detects that the vehicle is in the normal running condition when the vehicle is running on a high friction surface, and detects that the vehicle is in the abnormal running condition when the vehicle is running on a low friction surface.

14. A tire air pressure warning device that judges a tire air pressure abnormality utilizing detected signals from wheel velocity sensors that separately detect the revolving state of respective tires of a vehicle, and outputs a warning signal to a driver, comprising:

a tire chain detecting means for detecting if tire chains are attached to said respective tires based on the detected signals from the wheel velocity sensors; and

a prohibition means for prohibiting the detection of tire pressure decrease when said tire chain detecting means detects attached tire chains.

15. A tire air pressure warning device that judges a tire air pressure abnormality utilizing detected signals from wheel velocity sensors that separately detect the revolving state of respective tires of a vehicle, and outputs a warning signal to a driver, comprising:

a tire chain detecting means for detecting a condition that a tire chain is attached when a velocity of right and left rear wheels is smaller than a velocity of right and left front wheels; and

a prohibition means for prohibiting the detection of tire pressure decrease when said tire chain detecting means detects an attached tire chain.

16. A tire pressure warning device that judges a tire air pressure abnormality utilizing detected signals from wheel velocity sensors that separately detect the revolving state of each tire of a vehicle, and outputs a warning signal to a driver, comprising:

a tire chain detecting means for detecting a condition that a tire chain is attached when a velocity of right and left front wheels is smaller than a velocity of right and left rear wheels; and

a prohibition means for prohibiting the detection of tire pressure decrease when said tire chain detecting means detects an attached tire chain.