Data processing: measuring – calibrating – or testing – Measurement system – Speed
Reexamination Certificate
2003-03-17
2004-09-07
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Speed
C702S138000, C073S146200, C340S443000, C340S444000
Reexamination Certificate
active
06789038
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2002-085706 filed on Mar. 26, 2002 including the specification, drawings and abstract incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an art for estimating a tire condition amount in a vehicle, in particular, it relates to an art for estimating the tire condition amount based upon a rotational speed of that tire.
2. Description of Related Art
An art that estimates tire condition amounts such as tire pressure for purposes including the discovery of tire abnormalities in a vehicle while the vehicle is running already exists.
In an example of this art, a wheel speed sensor is fixed to a vehicle body side and used to detect a vehicle wheel speed of a vehicle wheel consisting of a tire fixed to a disc wheel. A tire condition amount is estimated by the wheel speed sensor.
More specifically, a reflected value that reflects the tire condition amount based upon the vehicle wheel speed detected by the wheel speed sensor is obtained, and the tire condition amount is estimated based upon the obtained reflected value.
As specific systems that estimate tire pressure as a tire condition amount, a dynamic load tire radius system and a tire vibration system are known.
In addition, a resonance frequency system, a disturbance observer system and the like are known tire vibration systems. In a case where the resonance frequency system is employed, the tire resonance phenomenon does not appear as conspicuously within a high speed region where a vehicle wheel speed or a vehicle speed is high, as in a low speed region.
Therefore, in Japanese Patent Laid-Open Publication No. 10-129222, the following type of art is disclosed for obtaining a resonance frequency of a rear vehicle wheel not only in a condition where the vehicle speed is in a low speed region, i.e. a condition where the resonance frequency detected for the rear vehicle wheel does not reach a detection limit, but also in a condition where the vehicle speed is in a high speed region, i.e. a condition where the resonance frequency detected for the rear vehicle wheel has reached a detection limit.
In that art, the resonance frequency of each vehicle wheel and the dynamic load radius reflected value that reflects a dynamic load radial difference between a front vehicle wheel and a rear vehicle wheel is used to determine the presence of abnormalities in the tire pressure condition.
Specifically, when the resonance frequency of the rear vehicle wheel does not exceed the detection limit, the resonance frequency of the rear vehicle wheel is detected, and the presence of abnormalities in the rear wheel tire pressure condition is determined based upon the detected resonance frequency.
On the contrary, when the resonance frequency of the rear vehicle wheel exceeds a detection limit, the resonance frequency of the rear vehicle wheel is estimated based upon the dynamic load radius reflected value at that time, and a previously detected resonance frequency for the rear vehicle wheel during a state in which the detection limit of the resonance frequency regarding the rear vehicle wheel was not exceeded.
Thus, according to the art disclosed in Japanese Patent Laid-Open Publication No. 10-129222, the resonance frequency of the rear vehicle wheel after exceeding the detection limit is estimated based upon the rear wheel resonance frequency prior to exceeding the detection limit, and the dynamic load radius reflected value after exceeding the detection limit.
Therefore, in this art, to estimate the rear wheel resonance frequency during an estimating period after the detection limit has been exceeded, an obtained resonance frequency for any one of the vehicle wheels cannot be used in a period corresponding to the estimating period.
Namely, according to this art, the resonance frequency detected before the estimating period is used in order to estimate the resonance frequency of the rear vehicle wheel in an estimating period after the detection limit has been exceeded.
Furthermore, according to this art, data obtained during a period corresponding to the estimating period is also used in order to estimate the resonance frequency of the rear vehicle wheel in an estimating period after the detection limit has been exceeded; that data is the dynamic load radius reflected value.
The physical type of the dynamic load radius reflected value is different from that of the resonance frequency that needs to be estimated for the rear vehicle wheel. Therefore, mutual conversion therebetween is necessary.
Also, since the dynamic load radius reflected value is generally obtained as one value representing all vehicle wheels in the vehicle, it is a physical amount with which it is difficult to reflect the tire pressure condition of each tire independent from the other tires.
Therefore, with this art there is a limit to improving the accuracy of estimating the resonance frequency of the rear vehicle wheel after the detection limit has been exceeded.
In other words, with this art it is difficult to accurately obtain a reflected value that reflects a tire condition amount of a vehicle wheel for which it is difficult to accurately obtain the reflected value among plural vehicle wheels in a vehicle.
SUMMARY OF THE INVENTION
It is an object of the invention to accurately obtain using other data, a reflected value that reflects a tire condition amount of a vehicle wheel for which is it difficult to accurately obtain the reflected value among plural vehicle wheels in a vehicle.
A first aspect of the invention relates to an apparatus that estimates the tire condition amount of each vehicle wheel, and is provided in a vehicle equipped with vehicle wheels formed with air enclosed under pressure in an inside portion of a tire mounted to a disc wheel. The apparatus includes a plurality of wheel speed sensors which detect a vehicle wheel speed of each vehicle wheel, a respective one of the sensors being provided in relation to a respective one of the plurality of vehicle wheels, and an estimating unit that obtains a reflected value reflecting a tire condition amount of each of the plurality of vehicle wheels based upon the vehicle wheel speed detected by each of the plurality of wheel speed sensors, and estimates the tire condition amount of each of the plurality of vehicle wheels based upon the obtained reflected value. The estimating unit estimates a reflected value of a first vehicle wheel for which it is relatively difficult to accurately obtain the reflected value based upon a vehicle wheel speed of the first vehicle wheel among the plurality of vehicle wheels, during a first period corresponding to a second period for obtaining the reflected value of the first vehicle wheel, based upon a reflected value obtained for a second vehicle wheel for which it is relatively easy to accurately obtain the reflected value based upon the vehicle wheel speed of the second vehicle wheel, in order to obtain the reflected value of the first vehicle wheel.
In the art disclosed in Japanese Patent Laid-Open Publication No. 10-129222 mentioned above, a resonance frequency of a rear vehicle wheel that is the first vehicle wheel, for which it is difficult to accurately obtain the reflected value that reflects the tire condition amount based upon the vehicle wheel speed, is estimated before the obtaining period using an obtained resonance frequency of a front vehicle wheel that is the second vehicle wheel, for which it is easier to accurately obtain the reflected value that reflects the tire condition amount based upon the vehicle wheel speed.
Therefore, in the art of Japanese Patent Laid-Open Publication No. 10-129222, the resonance frequency of the rear vehicle wheel cannot be estimated using the resonance frequency of the front vehicle wheel obtained during a period corresponding to the period when the resonance frequency of the rear vehicle wheel needs to be obtained.
Meanwhile, knowledge acquired through the research of the inventors of the invention
Mori Yukio
Nakashima Seiichi
Barlow John
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
Walling Meagan
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