Tire air pressure estimating apparatus

• US 20020059826A1
• Filed: 09/28/2001
• Published: 05/23/2002
• Est. Priority Date: 09/29/2000
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Umeno, Takaji, Ono, Eiichi, Asano, Katsuhiro
• Granted Patent: US 6,668,637 B2
• Time in Patent Office: Days
• US Class Current: 73/146.5
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00
• CPC Class Codes: B60C 23/062 Frequency spectrum analysis of wheel speed signals, e.g. using Fourier transformation

Abstract

Tire air pressure during high speed travel is estimated without a sensor for detecting the tire air pressure directly. An apparatus is constituted by a wheel speed sensor, road surface friction state estimator for estimating a friction state estimation value representing friction between the tire and a road surface from wheel speed detected by the wheel speed sensor, tire air pressure estimator for estimating any reduction in the tire air pressure based on the friction state estimation value, and a display for displaying the estimated reduction in the tire air pressure.

Claims

1. A tire air pressure estimating apparatus comprising:

a wheel speed sensor for detecting a wheel speed;

a road surface friction state estimator for estimating a friction state estimation value which represents friction state between a road surface and a tire on the basis of the wheel speed detected by the wheel speed sensor; and

a tire air pressure estimator for estimating pressure of the tire on the basis of the friction state estimation value estimated by the road surface friction state estimator.

2. A tire air pressure estimating apparatus comprising:

a wheel speed sensor for detecting a wheel speed of a single wheel;

a road surface friction state estimator for estimating a friction state estimation value, which represents friction state between a tire and a road surface, based on the wheel speed detected by the wheel speed sensor; and

a tire air pressure estimator for estimating pressure of the tire on the basis of the friction state estimation value estimated by the road surface friction state estimator.

3. A tire air pressure estimating apparatus according to claim 2, wherein the road surface friction state estimator estimates, as the friction state estimation value, a change in frequency cut off characteristics in a frequency range including frequency lower than a torsional resonance frequency, which is attributable to an increase in ground contact length, in a wheel speed frequency characteristics.

4. A tire air pressure estimating apparatus according to claim 2, wherein the road surface friction state estimator estimates, as the friction state estimation value, at least one of:

(a) in a transmission characteristics, from road surface disturbance to the wheel speed, approximated to a low order model,

a frequency, at which gain changes from a value in a predetermined range to a value out of the predetermined range, in a gain diagram representing a frequency response of the approximated model; and

(b) one of a difference or ratio between a characteristic quantity in a low frequency range including frequency lower than a torsional resonance frequency and a characteristic quantity in a high frequency range which is higher than the low frequency range, in a gain diagram representing a frequency response of a transmission characteristics, from the road surface disturbance to the wheel speed.

5. A tire air pressure estimating apparatus according to claim 4, wherein the both characteristic quantities are vibration levels of a wheel speed signal.

6. A tire air pressure estimating apparatus according to claim 3, wherein the tire air pressure estimator estimates the tire air pressure by comparing the friction state estimation value with a reference value.

7. A tire air pressure estimating apparatus according to claim 2, wherein the road surface friction state estimator estimates, as the friction state estimation values, vibration levels of a wheel speed signal in a plurality of frequency bands.

8. A tire air pressure estimating apparatus according to claim 7, wherein the tire air pressure estimator estimates the tire air pressure by comparing the vibration levels of the wheel speed signal in the plurality of frequency bands.

9. A tire air pressure estimating apparatus comprising:

a wheel speed sensor for detecting wheel speed of a single wheel;

a tire air pressure estimator for estimating pressure of a tire, on the basis of the wheel speed detected by the wheel speed sensor, from a change in frequency cut off characteristics in a frequency range including frequency lower than a torsional resonance frequency, in a wheel speed frequency characteristics.

10. A tire air pressure estimating apparatus comprising:

wheel speed sensors for detecting respective wheel speeds of a plurality of wheels,

road surface friction state estimators for, on the basis of the respective wheel speeds of the plurality of wheels detected by the wheel speed sensors, estimating a friction state estimation values, which represent friction states between a tire and a road surface; and

a tire air pressure estimator for estimating pressures of the tires on the basis of the friction state estimation values estimated by the road surface friction state estimators.

11. A tire air pressure estimating apparatus according to claim 10, wherein the road surface friction state estimator estimates, as the friction state estimation value, one of:

a change in frequency cut off characteristics in a frequency range including frequency lower than a torsional resonance frequency, which is attributable to an increase in ground contact length, in a wheel speed frequency characteristics, and

a change in vibration suppression characteristics in the frequency range including frequency lower than the torsional resonance frequency, which is attributable to the increase in the ground contact length.

12. A tire air pressure estimating apparatus according to claim 10, wherein the road surface friction state estimation section estimates, as the friction state estimation value, for each of the plurality of the wheels, at least one of:

(a) in a transmission characteristics, from road surface disturbance to the wheel speed, approximated to a low order model,

a frequency, at which gain changes from a value in a predetermined range to a value out of the predetermined range, in a gain diagram representing a frequency response of the approximated model;

(b) a vibration level of a wheel speed signal in a special frequency band; and

(c) a vibration level of the wheel speed signal in a special frequency range, the wheel speed signal being obtained by processing using frequency-weighted filter which makes gain high at a higher frequency range of the special frequency range.

13. A tire air pressure estimating apparatus according to claim 12, wherein the tire air pressure estimator estimates the tire air pressure by one of:

(1) comparing a difference or ratio between the estimated frequencies, at which gain changes from the value in the predetermined range to the value out of the predetermined range, in the gain diagram representing the frequency response of the approximated model, with a reference value, and

(2) comparing a difference or ratio between the estimated vibration levels of the wheel speed signals in the special frequency band, with a reference value; and

(3) comparing a difference or ratio between the estimated vibration levels of the wheel speed signals in the special frequency range, the wheel speed signal being obtained by processing using frequency-weighted filter which makes gain high at the higher frequency range of the special frequency range, with a reference value.

15. A tire air pressure estimating apparatus according to claim 14, wherein the tire air pressure estimator compares a difference or ratio between the characteristic quantities of the wheel speed signal in the low frequency range and the high frequency range, with a reference value, so as to relatively compare the characteristic quantities.

19. A tire air pressure estimating apparatus according to claim 18, wherein the tire air pressure estimator compares a difference or ratio between the characteristic quantities of the wheel speed signal with a reference value, so as to relatively compare the characteristic quantities.

20. A tire air pressure estimating apparatus according to claim 14, wherein the characteristic quantities are vibration levels.

14. A tire air pressure estimating apparatus comprising:

a wheel speed sensor for detecting wheel speed of a single wheel;

a detection section for detecting, based on a wheel speed signal that is output by the wheel speed sensor, a characteristic quantity of the wheel speed signal in a low frequency range including frequency lower than a torsional resonance frequency and a characteristic quantity of the wheel speed signal in a high frequency range which is higher than the low frequency range,

a tire air pressure estimator for estimating pressure of a tire by relatively comparing the characteristic quantities detected by the detection section.

16. A tire air pressure estimating apparatus comprising:

wheel speed sensors for detecting respective wheel speeds of a plurality of wheels;

tire air pressure estimator for estimating pressures of tires, based on the respective wheel speeds of the plurality of wheels that are detected by the wheel speed sensors, from one of;

a change in frequency cut off characteristics in a frequency range including frequency lower than a torsional resonance frequency of wheel speed frequency characteristics, and

a change in vibration suppression characteristics in the frequency range including frequency lower than the torsional resonance frequency.

17. A tire air pressure estimating apparatus comprising:

a wheel speed sensor for detecting a wheel speed of a single wheel;

a detection section for detecting, based on a wheel speed signal that is output from the wheel speed sensor, characteristic quantities of the wheel speed signal in each of a plurality of frequency ranges; and

a tire air pressure estimator for estimating pressure of a tire by comparing the plurality of characteristic quantities detected by the detection section.

18. A tire air pressure estimating apparatus comprising:

wheel speed sensors for detecting respective wheel speeds of a plurality of wheels;

detection sections for detecting, based on the respective wheel speeds of the plurality of wheels detected by the wheel speed sensors, for each of the plurality of the wheels, at least one of;

characteristic quantities of the wheel speed signal in a plurality of frequency bands, or

a characteristic quantity of the wheel speed signal in a special frequency range, the wheel speed signal in the special frequency range being obtained by processing the wheel speed signal using a frequency-weighted filter which makes gain high at a higher frequency range of the special frequency range; and

a tire air pressure estimator for estimating pressures of tires by relatively comparing the respective characteristic quantities of the wheel speed signal detected by the detection section.