Tire air pressure determining apparatus and method of determining tire air pressure

• US 6,575,023 B2
• Filed: 04/20/2001
• Issued: 06/10/2003
• Est. Priority Date: 04/20/2000
• Status: Expired due to Fees

• Current Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.), DENSO Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.), DENSO Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Umeno, Takaji, Mori, Yukio, Inoue, Yuichi, Ohashi, Hideki, Taguchi, Takeyasu, Yonetani, Masahiro
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): JENKINS, JERMAINE L
• Application Number:
  US09/838,291
• Publication Number:
  US 20010032500A1
• Time in Patent Office: 781 Days
• Field of Search: 731/46--468, 340/442-447
• 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

Abstract

A variable value (dynamic load radial deviation β) for making determination of a tire air pressure is calculated from pulse number cumulative values PFL, PFR, PRL and PRR that are cumulated for individual wheels when a predetermined condition is fulfilled. The calculated variable value is stored as a reference variable value, and a speed of a vehicle at the time when the reference variable value is calculated is stored as a reference vehicle speed associated with the reference variable value. If the value is newly calculated, it is determined whether or not a vehicle speed at that moment is within a predetermined vehicle speed range determined by the reference vehicle speed. If it is determined that the vehicle speed is within the predetermined vehicle speed range, it is determined, based on a difference between the newly calculated variable value and the reference variable value associated with the reference vehicle speed, whether or not the tire air pressure is normal.

Thus, even if the vehicle is fitted with one or more tires that depend greatly on vehicle speed, the possibility of erroneously determining that a tire air pressure is not normal can be eliminated.

Claims

1. A tire air pressure determining apparatus comprising:

wheel speed pulse generating means that generates a pulse every time wheels of a vehicle rotate by a predetermined angle and that is provided for each of the wheels;

vehicle speed detecting means that detects a speed of the vehicle as a vehicle speed;

variable value calculating means that calculates a variable value for making determination of a tire air pressure based on the pulse generated by the wheel speed pulse generating means when a predetermined condition is fulfilled;

reference variable value storing means that stores the calculated variable value as a reference variable value;

reference vehicle speed storing means that stores the vehicle speed at the time when the reference variable value is calculated as a reference vehicle speed associated with the reference variable value;

vehicle speed condition determining means that determines whether or not the vehicle speed at the time when the variable value calculating means newly calculates the variable value is within a predetermined vehicle speed range determined by the reference vehicle speed; and

air pressure determining means that determines, based on a difference between the newly calculated variable value and the reference variable value associated with the reference vehicle speed, whether or not the tire air pressure is normal, if it is determined that the vehicle speed at the time when the variable value calculating means newly calculates the variable value is within the predetermined vehicle speed range determined by the reference vehicle speed.

2. The tire air pressure determining apparatus according to claim 1, further comprising:

tire determining means that determines, based on the newly calculated variable value, whether or not the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed, if it is determined that the vehicle speed at the time when the variable value calculating means newly calculates the variable value is not within the predetermined vehicle speed range determined by the reference vehicle speed.

3. The tire air pressure determining apparatus according to claim 2, wherein

the tire determining means calculates a difference between the newly calculated variable value and a last-calculated variable value as a variable value difference, calculates a difference between the vehicle speed at the time when the variable value is newly calculated and a vehicle speed at the time when the last variable value is calculated as a vehicle speed difference, and determines, based on a ratio between the variable value difference and the vehicle speed difference, whether or not the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

4. The tire air pressure determining apparatus according to claim 3, wherein

the tire determining means determines whether or not the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed, if the vehicle speed difference is greater than a predetermined value.

5. The tire air pressure determining apparatus according to claim 3, wherein

the reference variable value storing means newly stores the newly calculated variable value as a reference variable value different from the reference variable value, if the vehicle speed difference is equal to or smaller than a predetermined value, and

the reference vehicle speed storing means newly stores the vehicle speed at the time when the variable value is newly calculated as a reference vehicle speed associated with the variable value.

6. The tire air pressure determining apparatus according to claim 3, wherein

the air pressure determining means determines whether or not the tire air pressure is normal, if the tire determining means determines that the wheels are not fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

7. The tire air pressure determining apparatus according to claim 3, wherein

the reference variable value storing means newly stores the newly calculated variable value as a reference variable value different from the reference variable value, if the tire determining means determines that the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed, and

the reference vehicle speed storing means newly stores the vehicle speed at the time when the variable value is newly calculated as a reference vehicle speed associated with the variable value.

8. The tire air pressure determining apparatus according to claim 4, wherein

the reference variable value storing means newly stores the newly calculated variable value as a reference variable value different from the reference variable value if the vehicle speed difference is equal to or smaller than the predetermined value, and

the reference vehicle speed storing means newly stores a vehicle speed at the time when the variable value is newly calculated as a reference vehicle speed associated with the variable value.

9. The tire air pressure determining apparatus according to claim 4, wherein

the air pressure determining means determines whether or not the tire air pressure is normal, if the tire determining means determines that the wheels are not fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

10. The tire air pressure determining apparatus according to claim 4, wherein

the reference variable value storing means newly stores the newly calculated variable value as a reference variable value different from the reference variable value, if the tire determining means determines that the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed, and

the reference vehicle speed storing means newly stores the vehicle speed at the time when the variable value is newly calculated as a reference vehicle speed associated with the variable value.

11. The tire air pressure determining apparatus according to claim 8, wherein

the air pressure determining means determines whether or not the tire air pressure is normal, if the tire determining means determines that the wheels are not fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

12. The tire air pressure determining apparatus according to claim 8, wherein

the reference variable value storing means newly stores the newly calculated variable value as a reference variable value different from the reference variable value, if the tire determining means determines that the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed, and

the reference vehicle speed storing means newly stores the vehicle speed at the time when the variable value is newly calculated as a reference vehicle speed associated with the variable value.

13. The tire air pressure determining apparatus according to claim 11, wherein

the reference variable value storing means newly stores the newly calculated variable value as a reference variable value different from the reference variable value, if the tire determining means determines that the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed, and

the reference vehicle speed storing means newly stores the vehicle speed at the time when the variable value is newly calculated as a reference vehicle speed associated with the variable value.

14. The tire air pressure determining apparatus according to claim 1, wherein

the variable value is a difference between a sum of a pulse number cumulative value PFL of a front-left wheel and a pulse number cumulative value PRR of a rear-right wheel and a sum of a pulse number cumulative value PFR of a front-right wheel and a pulse number cumulative value PRL of a rear-left wheel, i.e., (PFL+PRR)−

(PFR+PRL) or (PFR+PRL)−

(PFL+PRR).

15. The tire air pressure determining apparatus according to claim 1, wherein

the variable value is a ratio between a sum of a pulse number cumulative value PFL of a front-left wheel and a pulse number cumulative value PRR of a rear-right wheel and a sum of a pulse number cumulative value PFR of a front-right wheel and a pulse number cumulative value PRL of a rear-left wheel, i.e., (PFL+PRR)/(PFR+PRL) or (PFR+PRL)/(PFL+PRR).

16. The tire air pressure determining apparatus according to claim 1, wherein

the variable value is a difference between a ratio between a rotational speed VFL of a front-left wheel and a rotational speed VFR of a front-right wheel and a ratio between a rotational speed VRL of a rear-left wheel and a rotational speed VRR of a rear-right wheel, i.e., (VFR/VFL)−

(VRR/VRL) or (VRR/VRL)−

(VFR/VFL).

17. A tire air pressure determining apparatus comprising:

wheel speed pulse generating means that generates a pulse every time wheels of a vehicle rotate by a predetermined angle and that is provided for each of the wheels;

vehicle speed detecting means that detects a speed of the vehicle as a vehicle speed;

variable value calculating means that calculates a variable value for making determination of a tire air pressure based on the pulse generated by the wheel speed pulse generating means when a predetermined condition is fulfilled;

vehicle speed range specifying means that specifies to which one of a plurality of divided ranges the vehicle speed at the time when the variable value is calculated belongs;

reference variable value storing means that stores the calculated variable value as a reference variable value of the range to which the vehicle speed at the time when the variable value is calculated belongs; and

air pressure determining means that determines, based on a difference between the newly calculated variable value and the stored reference variable value, whether or not the tire air pressure is normal, if the range to which the vehicle speed at the time when the variable value calculating means newly calculates the variable value belongs is the same as the range to which the vehicle speed of the stored reference variable value belongs.

18. The tire air pressure determining apparatus according to claim 17, further comprising:

tire determining means that determines, based on the newly calculated variable value, whether or not the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed, if the range to which the vehicle speed at the time when the variable value calculating means newly calculates the variable value belongs is different from the range to which the vehicle speed of the stored reference variable value belongs.

19. The tire air pressure determining apparatus according to claim 18, wherein

the tire determining means calculates a difference between the newly calculated variable value and a last-calculated variable value as a variable value difference, and determines, based on the variable value difference, whether or not the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

20. The tire air pressure determining apparatus according to claim 18, wherein

the reference variable value storing means stores a variable value first stored as the reference variable value as a reference variable value of the range to which the vehicle speed at the time when the variable value calculating means newly calculates the variable value belongs, if the tire determining means determines that the wheels are not fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

21. The tire air pressure determining apparatus according to claim 18, wherein

the reference variable value storing means stores the newly calculated variable value as a reference variable value of the range to which the vehicle speed at the time when the variable value is calculated belongs, if the tire determining means determines that the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

22. The tire air pressure determining apparatus according to claim 19, wherein

the reference variable value storing means stores a variable value first stored as the-reference variable value as a reference variable value of the range to which the vehicle speed at the time when the variable value calculating means newly calculates the variable value belongs, if the tire determining means determines that the wheels are not fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

23. The tire air pressure determining apparatus according to claim 19, wherein

the reference variable value storing means stores the newly calculated variable value as a reference variable value of the range to which the vehicle speed at the time when the variable value is calculated belongs, if the tire determining means determines that the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

24. The tire air pressure determining apparatus according to claim 22, wherein

the reference variable value storing means stores the newly calculated variable value as a reference variable value of the range to which the vehicle speed at the time when the variable value is calculated belongs, if the tire determining means determines that the wheels are fitted with tires that are different in dependency of dynamic load radius on vehicle speed.

25. The tire air pressure determining apparatus according to claim 17, wherein

the variable value is a difference between a sum of a pulse number cumulative value PFL of a front-left wheel and a pulse number cumulative value PRR of a rear-right wheel and a sum of a pulse number-cumulative value PFR of a front-right wheel and a pulse number cumulative value PRL of a rear-left wheel, i.e., (PFL+PRR)−

(PFR+PRL) or (PFR+PRL)−

(PFL+PRR).

26. The tire air pressure determining apparatus according to claim 17, wherein

the variable value is a ratio between a sum of a pulse number cumulative value PFL of a front-left wheel and a pulse number cumulative value PRR of a rear-right wheel and a sum of a pulse number cumulative value PFR of a front-right wheel and a pulse number cumulative value PRL of a rear-left wheel, i.e., (PFL+PRR)/(PFR+PRL) or (PFR+PRL)/(PFL+PRR).

27. The tire air pressure determining apparatus according to claim 17, wherein

the variable value is a difference between a ratio between a rotational speed VFL of a front-left wheel and a rotational speed VFR of a front-right wheel and a ratio between a rotational speed VRL of a rear-left wheel and a rotational speed VRR of a rear-right wheel, i.e., (VFR/VFL)−

(VRR/VRL) or (VRR/VRL)−

(VFR/VFL).

28. A tire air pressure determining apparatus comprising:

a wheel speed pulse generating device that generates a pulse every time wheels of a vehicle rotate by a predetermined angle and that is provided for each of the wheels;

a vehicle speed detecting device that detects a speed of the vehicle as a vehicle speed;

a variable value calculating device that calculates a variable value for making determination of a tire air pressure based on the pulse generated by the wheel speed pulse generating device when a predetermined condition is fulfilled;

a reference variable value storing device that stores the calculated variable value as a reference variable value;

a reference vehicle speed storing device that stores the vehicle speed at the time when the reference variable value is calculated as a reference vehicle speed associated with the reference variable value;

a vehicle speed condition determining device that determines whether or not the vehicle speed at the time when the variable value calculating device newly calculates the variable value is within a predetermined vehicle speed range determined by the reference vehicle speed; and

an air pressure determining device that determines, based on a difference between the newly calculated variable value and the reference variable value associated with the reference vehicle speed, whether or not the tire air pressure is normal, if it is determined that the vehicle speed at the time when the variable value calculating device newly calculates the variable value is within the predetermined vehicle speed range determined by the reference vehicle speed.

29. A tire air pressure determining apparatus comprising:

a wheel speed pulse generating device that generates a pulse every time wheels of a vehicle rotate by a predetermined angle and that is provided for each of the wheels;

a vehicle speed detecting device that detects a speed of the vehicle as a vehicle speed;

a variable value calculating device that calculates a variable value for making determination of a tire air pressure based on the pulse generated by the wheel speed pulse generating device when a predetermined condition is fulfilled;

a vehicle speed range specifying device that specifies to which one of a plurality of divided ranges the vehicle speed at the time when the variable value is calculated belongs;

a reference variable value storing device that stores the calculated variable value as a reference variable value of the range to which the vehicle speed at the time when the variable value is calculated belongs; and

an air pressure determining device that determines, based on a difference between the newly calculated variable value and the reference variable value associated with the reference vehicle speed, whether or not the tire air pressure is normal, if it is determined that the vehicle speed at the time when the variable value calculating device newly calculates the variable value is within a predetermined vehicle speed range determined by the reference variable value.