Data processing: measuring – calibrating – or testing – Measurement system – Pressure
Reexamination Certificate
1998-08-11
2001-01-30
Assouad, Patrick (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Pressure
C702S140000, C340S444000, C701S070000
Reexamination Certificate
active
06182021
ABSTRACT:
BACKGROUND OF THE INVENTION
According to the results of one survey, of vehicles running on the highway, the percentage of tires with substandard maintenance, when compared with the drive train, and the substandard maintenance percentage of other vehicle systems, is unexpectedly high. Breaking down that percentage, unsuitable tire air pressure covers more than half, and is the top cause, followed by lack of tire tread, and continuing with abnormal tire abrasion/wear and tear. Moreover, there are many drivers who have experienced a tire blowout while driving on the highway, and also as a result of the fear of a blowout while driving on the highway, the desire to equip cars with a tire air pressure warning device, or an equivalent device as standard equipment is rising, and, if tire air pressure warning devices can become less expensive, there are also requests to additionally equip cars in present use with tire air pressure warning devices.
On vehicles, including freight trucks, sensors that detect the air pressure of each individual tire have been provided. By way of slipping, electric waves, magneto-electric induction methods, systems that detect the tire air pressure of a rotating tire in real-time are known. According to these systems, an attempt to inform the driver of tire air pressure abnormalities, such as resulting from a tire puncture etc., is carried out. The above system, which detects the tire air pressure in real time, directly detects the tire air pressure, and has high reliability as an advantage, but the slipping, electric wave, electro-magnetic induction methods have the drawback such as, in order to transmit the air pressure information, the entire system is large scale, moreover, becomes very expensive, and has a problem that the actual use of the system is rather poor.
Also, along with the electrical devices becoming inexpensive in recent years, 4 wheel ABS devices and TRC (Traction Control) devices have come into use on passenger cars. In the case of providing 4 wheel ABS devices, and the like, a device for detecting the number of tire revolutions, a tire revolution detection device, is individually provided. It is made-up of a control system, consisting of individual brake and brake hydraulic devices, and utilizing the vehicle behavior, applies appropriate control.
With this, as described in Japanese Patent laid open 63-305011, a detection method for detecting an abnormal tire air pressure is proposed, in which the number of tire revolutions is summed in the diagonal direction, and it is judged as to whether or not the value of the difference between the sum of the two diagonal pairs of the number of tire revolutions and the difference between the number of revolutions between each tire is greater than that of a prescribed value. In order to eliminate the need for extra additional hardware added to the vehicle, for the aforementioned 4 wheel ABS equipped vehicles, by means of the already provided tire revolution detection device, it is thought that the detected number of tire revolutions can be used effectively to realize a tire air pressure warning device and the like.
That is to say, when running in a straight line, if a specific tire suffers a puncture and the air pressure in that tire rapidly decreases, as a result of the punctured tire's outer diameter becoming smaller than that of the other normal tires, the number of revolutions of the tire increases (because when traveling the same distance, the tire with the smaller diameter will revolve much more rapidly) as compared to the other normal tires. From this, detection of a tire that suffers a puncture, or loss in air pressure becomes possible.
SUMMARY OF THE INVENTION
Thus, it would be preferable to make the judgment of the difference of the number of tire revolutions on the tire air pressure warning apparatus side, but, because in order to make this judgment, at the very least, the number of tire revolutions for 4 tires, at all times, detected by individual units would have to be processed at a very high speed, making the control complicated, some kind of processing becomes necessary.
Furthermore, in order to judge the difference in the number of tire revolutions at the tire pressure warning device as mentioned above, the judgment must be carried out when the car is running in a straight line and all four tires are at the same condition. On one hand, when the car is stopped, the tires are not all at the same condition, the air pressure of each varies, moreover, directly after the tire is changed after a tire puncture, or directly after the tire is changed to a smaller emergency spare tire, the difference in the number of tire revolutions cannot be accurately judged by the tire air pressure warning device. In other words, in the case where all four tires are not at the same conditions, judging the difference in the number of tire revolutions by means of the tire air pressure warning device is prohibitive.
Therefore, considering the aforementioned problems, as an object of the present invention, in order to make a tire air pressure warning device in which the difference in the number of tire revolutions is judged by the tire warning device, at the very least, the number of revolutions for 4 tires are detected by separate units, can be processed, and when the four wheels all are in the same condition the processing can be performed.
It is preferable for the difference on the number of revolutions of a tire to be judged by the tire air pressure warning device, but, because for this judgment, at the very least the number of revolutions of 4 tires must be detected constantly by separate units, the control becomes complicated, and there is a need for some processing. Because of this, after adding the number of revolutions of the tires located diagonally, determining the difference between the diagonal pairs, and, after dividing by double the average value of the number of tire revolutions, a deviation value is found, and the deviation value is compared to a prescribed comparison value (a deviation width), and in the case when this value is exceeded, it can be thought that the tire air pressure can be judged to be abnormal.
However, if this comparative value is fixed, it becomes impossible to suitably make a judgment in regards to the vehicle running conditions. In other words, for example, if the vehicle velocity is large, it is obvious that the result of the number of revolutions is large, and because the change in the deviation valueincreases, it becomes greater than the prescribed comparison value, and an accurate judgment of the tire air pressure becomes unfeasible.
Therefore, as a result of the previous problem, a further goal of the present invention, in the case of a tire air pressure warning device in which the difference in the number of tire revolutions is judged by the tire air pressure warning device, the vehicle running conditions are utilized and suitable tire air pressure judgment is performed.
Moreover, in the case where the difference of the number of tire revolutions is judged by the tire air pressure warning device, in order to make a decision, because, at the least, the number of tire revolutions for four tires must be constantly, by separate units, processed at a high speed, some kind of processing becomes necessary. Because of this, after the number of tire revolutions for tires that are located diagonally are added, the difference in the number of revolutions between the diagonal pairs is determined, then is divided by double the average value of tire revolutions, to obtain the deviation value, which is then compared with a comparative value (the deviation width), and in the case when it exceeds this prescribed value, it can be thought that a tire air abnormality has occurred.
However, when the comparison with this comparative value is performed, because the deviation value is not stable, there are cases when the tire abnormal air pressure cannot be judged. In short, due to noise, caused by variations in road conditions and vehicle running conditions, etc., as the prime factor,
Edahiro Takeshi
Izumi Tomoji
Tachihata Tetsuya
Assouad Patrick
Mazda Motor Corporation
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