Tire air pressure warining device

• US 5,826,210 A
• Filed: 03/29/1994
• Issued: 10/20/1998
• Est. Priority Date: 03/29/1993
• Status: Expired due to Term

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Tachihata, Tetsuya, Izumi, Tomoji, Edahiro, Takeshi
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): PHAN, THAI Q
• Application Number:
  US08/220,361
• Time in Patent Office: 1,666 Days
• Field of Search: 73/146.5, 73/146.2, 340/442, 340/444, 702/140, 702/148, 701/70
• US Class Current: 701/70
• 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 permitting 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 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, comprising:

a deviation width changing means for changing the prescribed width of a deviation width wherein, the tire air pressure abnormality is judged by a comparison between a deviation value which is determined from a prescribed equation based on the difference between the number of revolutions of each tire, and the average number of tire revolutions, and deviation width having a prescribed width; and

prescribed value change means for judging tire air pressure abnormality by comparing the deviation value with a deviation width having a prescribed maximum value and a prescribed minimum value, and changing the prescribed maximum and minimum values in accordance with the vehicle running conditions,

wherein, if the tire temperature is beyond a prescribed temperature, the prescribed width of said deviation width is changed to a fixed value, and further increase said prescribed width as a temperature of the tire increases until said prescribed width reaches a predetermined value.

2. 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 each tire of a vehicle, and outputs a warning signal, comprising:

a judgment means for judging a tire air pressure abnormality by performing a comparison, within a prescribed period of time, between a deviation value, which is obtained from a prescribed equation having factors of the difference between the number of revolutions of each tire, and the average number of tire revolutions, acquired as either a positive or a negative value determined by a prescribed equation based upon a difference in the number of revolutions of each tire, and a differential width, having a prescribed width, and judging a tire air pressure abnormality when within said prescribed period of time, the area of an integral value that said positive or negative value has surpassed said differential width, becomes larger than a prescribed value;

a warning means for informing said judgment results; and

a warning means, for informing said specified tire.

3. A tire air pressure warning device according to claim 2 wherein, within said prescribed period of time, after said positive or negative value has surpassed one limit of said deviation width, and if surpasses the other limit, the process returns to the initial step in which the tire air pressure is judged to be abnormal.

4. A tire air pressure warning device according to claim 2 wherein, within said prescribed period of time, said positive or negative value has surpassed one limit of said deviation width by said means, the tire air pressure has been judged to be abnormal, and if surpasses the other limit of the deviation width and the tire air pressure is judged to be abnormal, then a system error is determined.

5. A tire air pressure warning device according to claim 2 wherein, when said air pressure is judged to be abnormal, the attached device gain attached to the vehicle is changed to safe side.

6. A tire air pressure warning device according to claim 2,

wherein the prescribed equation is based upon the difference in the number of revolutions of each tire.

7. A tire air pressure warning device according to claim 2, further comprising:

a wheel velocity detection means for detecting the four wheel velocities;

a tire air pressure judgment means, for judging a decrease in the tire air pressure using wheel velocity detected by said wheel velocity detection means;

a specific condition detection means for detecting a specific condition that is not suitable for the tire air pressure judgment that detects wheel velocity by regarding said vehicle and/or road surface; and

a prohibiting means for prohibiting the tire air pressure judgment of the tire air pressure judgment means by said tire air pressure judgment means when a specific condition has been detected by said specific condition detection means.

8. A tire air pressure warning device according to claim 7, wherein said specific conditions include the state of acceleration or deceleration.

9. A tire air pressure warning device according to claim 7, wherein said specific conditions include the state when the vehicle is climbing up a hill.

10. A tire air pressure warning device according to claim 7, wherein said specific conditions include the condition when the drive wheels are spinning.

11. A tire air pressure warning device according to claim 7, wherein said specific conditions include the condition when the vehicle is stuck.

12. A tire air pressure warning device according to claim 7, wherein said specific conditions include the state when the road is canted.

13. A tire air pressure warning device according to claim 7, wherein said specific conditions include the state when the wheel velocity of the left/right drive wheels, when compared to the free wheel velocity is consistently low.

14. A tire air pressure warning device according to claim 7, wherein said specific conditions include the state when the wheel velocity of the left/right free wheels, when compared to the drive wheel velocity is consistently low.

15. A tire air pressure warning device according to claim 7, wherein said specific conditions include the state when the left/right rear wheel loading, when compared to both the front wheel loading is large.

16. A tire air pressure warning device according to claim 7, wherein said specific conditions include the state when the four wheel wheel loading is greater than a prescribed value.

17. A tire air pressure warning device according to claim 7, wherein said specific conditions include when, based upon the wheel velocity of the left/right drive wheels, each of both of the bad road judgments judge that a vehicle is driven under a bad road condition.

18. A tire air pressure warning device according to claim 7, wherein said specific conditions include when, based upon the wheel velocity of the left/right free wheels, the bad road judgments judge that a vehicle is driven under a bad road condition.

19. A tire air pressure warning device according to claim 7, wherein said specific conditions include the condition that the parking brake is "on."

20. A tire air pressure warning device according to claim 7, wherein said specific conditions include the state in which the anti-skid brake devices are in operation.

21. A tire air pressure warning device according to claim 7, wherein said specific conditions include the state when the traction control equipment is in operation.

22. A tire air pressure warning device according to claim 2, further comprising:

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

23. A tire air pressure warning device according to claim 22, further comprising a coefficient setting means for setting coefficients to compensate the difference between initial conditions of each of said tires,

wherein said prescribed equation has the coefficients as factor for obtaining said deviation value.

24. A tire air pressure warning device according to claim 2, wherein judgment of tire air pressure abnormality by said judgment means is prohibited when a revolving state of the vehicle is higher than a prescribed value.

25. A tire air pressure warning device as recited in claim 2, further comprising:

a tire air pressure judgment means for judging a decrease in the tire air pressure based upon the difference between revolution of each of said tires; and

an allowance means for allowing judgment of tire air pressure decrease by said tire air pressure judgment means when a vehicle velocity is within a prescribed velocity range.

26. A tire air pressure warning device according to claim 25, further comprising:

a wheel velocity detection means for detecting the four wheel velocities for the vehicle;

a road surface condition detection means for detecting the condition of the road traveled on; and

a vehicle velocity range setting means for establishing the vehicle velocity range in which it is permissible to perform the tire air pressure judgment of the tire air pressure judgment means utilizing the road surface condition detected by said road surface detection means,

wherein said tire air pressure judgment means judges a decrease in the tire air pressure using the wheel velocity detected by said wheel velocity detection means and by a road surface condition detected by said road surface condition detection means.

27. A tire air pressure warning device according to claim 26 wherein said road surface condition detection means has means for detecting a road surface friction state, and wherein said vehicle range setting means sets the vehicle velocity range upper limit value at a low friction state to a value lower than that at a high friction state.

28. A tire air pressure warning device according to claim 26 wherein said road surface condition detection means has means for detecting a bad road surface, and said vehicle range setting means, constructed such that for a bad road state, rather than for a good road state, the vehicle velocity range upper limit value is set lower.

29. A tire air pressure warning device according to claim 26 wherein said road surface condition detection means has means for detection the slope of the road surface, and said vehicle range setting means, constructed such that for an upward slope (climbing a hill), rather than for a flat slope, the vehicle velocity range upper limit value is set lower.

30. A tire air pressure warning device according to claim 26, the tire air pressure judgment means further comprising:

an initial setting establishing process means for establishing a compensation coefficient for a newly attached tire by utilizing the four wheel velocities in order to compensate for the tire manufacturing error; and

a tire air pressure judgment process means for carrying out the tire air pressure judgment process by utilizing the compensation coefficient established in said initial setting process means and the four wheel velocities.

31. A tire air pressure warning device according to claim 30, wherein said vehicle velocity region establishing means, respectively establish the vehicle velocity region, within which the settings process of the initial settings process means is permitted, and the vehicle velocity region, within which the judgment process of the tire air pressure judgment means is permissable.

32. A tire air pressure warning device according to claim 25, further comprising:

a filter for filtering the detected signals from the wheel velocity sensors; and

a setting means for, when the vehicle velocity is high, setting a filtering coefficient to be greater than the filtering coefficient which has been set when the vehicle velocity was low.

33. A tire air pressure warning device according to claim 25, further comprising:

a prohibition means for prohibiting judgment of tire air pressure decrease by said tire air pressure judgment means when running conditions of driving wheels are greater than a slip ratio of a prescribed value.

34. A tire air pressure warning device according to claim 33, further comprising a detection means for detecting occurrence of the slipping condition due to running on an upslope.

35. A tire air pressure warning device according to claim 34, wherein if slip rate of the driving wheels is a prescribed value or greater when velocity changes of front and rear wheels are in the same direction and velocity change of each of said tires are a prescribed value or less, said detection means detects occurrence of the slipping condition due to running on the upslope.

36. A tire air pressure warning device according to 2, further comprising:

a prohibition means for judging whether or not the vehicle is in a normal running condition based on the detected signals from the wheel velocity sensors, and until current running condition has changed from abnormal running condition to the normal running condition, judgment of tire air pressure decrease by said tire air pressure judgment means is prohibited, using wheel velocity data in a prescribed period from a point where the current running condition has become the normal running condition.

37. A tire air pressure warning device according to claim 36, wherein said prohibition means prohibits the judgment of tire air pressure decrease by said tire air pressure of judgment means, using wheel velocity data in a prescribed period before the current running condition has become from the abnormal running condition to the normal running condition.

38. A tire air pressure warning device according to claim 37, wherein said prohibition means prohibits accumulation of wheel velocity data.

39. A tire air pressure warning device according to claim 36, wherein said prohibition means prohibits the judgment of tire air pressure decrease by said tire air pressure judgment means, when the current running condition has become from a straight running condition to the turning condition.

40. A tire air pressure warning device according to claim 36, wherein said prohibition means prohibits the judgment of tire air pressure decrease by said tire air pressure judgment means, when the current running condition has become from an unbraked condition to a braked condition.

41. A tire air pressure warning device according to claim 36, wherein said prohibition means prohibits the judgment of tire air pressure decrease by said tire air pressure judgment means, when the current running condition has become from a high μ

running condition to a low μ

running condition.

42. A tire air pressure warning device which outputs a warning when a decrease in the tire air pressure is detected, using the four wheel velocities of the vehicle, comprising:

a wheel velocity detection means for detecting the four wheel velocities;

an initial settings process means for carrying out initial settings processing range using the wheel velocities detected in said wheel velocity detection means, for a specified first vehicle velocity range, in order to compensate for the initial different conditions of the four tires;

an air pressure judgment process means for carrying out the tire air pressure judgment process for a second vehicle velocity range, broader than the first vehicle velocity range, wherein receiving the wheel velocities detected in said wheel velocity detection means and the process results of the initial settings process means, according to the initial settings process means, after the initial settings process for a specified period of time or a specified distance.

43. A tire air pressure warning device according to claim 42, wherein said initial settings process means initializes the compensation coefficient in order to correct for the initial different conditions of the four times.

44. A tire air pressure warning device according to claim 43, wherein said tire air pressure judgment process means determines tire air pressure judgment variable based on said compensation coefficient and the four wheel velocities, and by comparing said tire air pressure judgment variable to a judgment threshold value, a decrease in the tire air pressure is determined.

45. A tire air pressure warning device according to claim 42, wherein said tire air pressure judgment process means is constructed to multiply divide said first vehicle velocity range, in order to correct the judgment threshold value in the air pressure judgment process, a correction value is established and the correction value is placed into said multiply divided vehicle velocity range.

46. A tire air pressure warning device according to claim 42, wherein said tire air pressure judgment process means is constructed to multiply divide said second vehicle velocity range, in order to correct the judgment threshold value in the air pressure judgment process, a correction value is established and the correction value is placed into said multiply divided vehicle velocity range.

47. A tire air pressure warning device according to claim 42, wherein said tire air pressure judgment process means determines a learned control coefficient, by a result of tire pressure, so that the reduction of air pressure is not misjudged by learned control coefficient.

48. A tire air pressure warning device according to claim 42, wherein said air pressure judgment process means carries out the tire air pressure judgment by receiving the four wheel velocities and calculation result by said initial settings process means so as to obtain a deviation value by a predetermined calculation based on differences among revolution numbers of the four wheels, an average revolution number, and results of initial setting calculation of the four wheels, and by comparing the deviation value with a predetermined deviation value.

49. 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 each tire of a vehicle, and outputs a warning signal, comprising:

a deviation width changing means for changing the prescribed width of a deviation width wherein, the tire air pressure abnormality is judged by a comparison between a deviation value which is determined from a prescribed equation based on the difference between the number of revolutions of each tire, and the average number of tire revolutions, and deviation width having a prescribed width; and

prescribed value change means for judging tire air pressure abnormality by comparing the deviation value with a deviation width having a prescribed maximum value and a prescribed minimum value, and changing the prescribed maximum and minimum values in accordance with the vehicle running conditions,

wherein said prescribed equation has unsettled coefficients as factor for obtaining said deviation value.

50. A tire air pressure warning device according to claim 49, wherein said coefficient setting means sets the coefficients based on the detected signals from the wheel velocity sensors, and wherein judgment of tire air pressure abnormality is prohibited until the coefficients satisfy a prescribed condition which is a normal driving condition.

51. A tire air pressure warning device which outputs a warning when a decrease in the tire air pressure is detected, using the four wheel velocities of the vehicle, comprising:

a wheel velocity detection means for detecting the four wheel velocities;

an initial settings process means, wherein using the wheel velocities detected in said wheel velocity detection means, when specified coefficient calculation conditions are established, the initial settings, where compensation coefficients are calculated in order to compensate for the four wheel tire initial conditions, are carried out;

an initial settings start switch means, for giving the start order for the initial settings in the initial settings process; and

a condition mitigation means for mitigating said coefficient calculation conditions, after the start command is input by said initial settings start switch means, at prescribed timing, even if the initial settings have not been completed.

52. A tire air pressure warning device according to claim 51,

wherein said condition mitigation means mitigates said coefficient calculation conditions, after the start command is input by said initial settings start switch means, even if the specified period of time has elapsed, and the initial settings have not been completed.

53. A tire air pressure warning device according to claim 51,

wherein said condition mitigation means mitigates said coefficient calculation condition, after the start command is input by said initial settings start switch means, when even if vehicle has traveled the specified distance, and the initial settings have not been completed.

54. A tire air pressure warning device according to claim 51,

wherein said condition mitigation means mitigates said coefficient calculation conditions, after the start command is input by said initial settings start switch means, when the start command is input once again.

55. A tire air pressure warning device according to the claims 52, 53 or 54, wherein said coefficient calculation conditions include the condition that, based on the wheel velocity, the temporary tire condition is judged.

56. A tire air pressure warning device according to claim 55, wherein said condition mitigation means is made-up such that the condition threshold value, that judges the condition of an attached temporary tire, is increased.

57. 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 each tire of a vehicle, and outputs a warning signal, comprising:

a deviation width changing means for changing the prescribed width of a deviation width wherein, the tire air pressure abnormality is judged by a comparison between a deviation value which is determined from a prescribed equation based on the difference between the number of revolutions of each tire, and the average number of tire revolutions, and deviation width having a prescribed width;

prescribed value change means for judging tire air pressure abnormality by comparing the deviation value with a deviation width having a prescribed maximum value and a prescribed minimum value, and changing the prescribed maximum and minimum values in accordance with the vehicle running conditions;

a wheel velocity detection means for detecting four wheel velocities;

a tire air pressure judgment means, for judging a decrease in the tire air pressure using wheel velocity detected by said wheel velocity detection means;

a specific condition detection means for detecting a specific condition that is not suitable for the tire air pressure judgment that detects wheel velocity by regarding said vehicle and/or road surface; and

a prohibiting means for prohibiting the tire air pressure judgment of the tire air pressure judgment means by said tire air pressure judgment means when a specific condition has been detected by said specific condition detection means.

58. 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 each tire of a vehicle, and outputs a warning signal, comprising:

a deviation width changing means for changing the prescribed width of a deviation width wherein, the tire air pressure abnormality is judged by a comparison between a deviation value which is determined from a prescribed equation based on the difference between the number of revolutions of each tire, and the average number of tire revolutions, and deviation width having a prescribed width; and

prescribed value change means for judging tire air pressure abnormality by comparing the deviation value with a deviation width having a prescribed maximum value and a prescribed minimum value, and changing the prescribed maximum and minimum values in accordance with the vehicle running conditions,

wherein judgment of tire air pressure abnormality by said judgment means is prohibited when a revolving state of the vehicle is higher than a prescribed value.