JP2004322821A - Tire air pressure lowering alarm device and method, and tire air pressure lowering alarm program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide tire air pressure lowering alarm device and method for accurately detecting natural leakage of air at the inside of a tire corresponding to a change of a vehicle condition, etc., and a tire air pressure lowering alarm program. <P>SOLUTION: An alarm is given when detecting the number of rotation of the tire mounted on the vehicle and detecting lowering of air pressure of the tire based on the detected number of rotation. This device is provided with a decision means for making a relation of an elapsed time or a traveling distance after mounting the tire on the vehicle, or filling air in the tire and estimated air pressure as a function, and deciding lowering of tire air pressure due to natural leakage when tire air pressure is reduced from the obtained coefficient together with time or the traveling distance and the reduced amount exceeds a prescribed value, and an alarm means for giving the alarm of lowering of air pressure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４８】
以上の結果より、比較例では条件によって検出のばらつきが見られるのにに対し、実施例はばらつきが少ないことがわかる。とくに、空気補充を行なうケース３の場合では、比較例では２２％の空気圧低下で誤検出したのに対し、本発明の方式による実施例では誤検出しなかった。
【００４９】
【発明の効果】
本発明によれば、個々のタイヤ内部の空気の自然漏れの度合の違い、またはタイヤ装着後にこまめに空気充填する場合など、種々の車両条件の変化などに対応して精度よくタイヤ空気の自然漏洩を検知することが可能になる。
【図面の簡単な説明】
【図１】本発明のタイヤ空気圧低下警報装置の一実施の形態を示すブロック図である。
【図２】本発明のタイヤ空気圧低下警報方法で用いられる時間と推定空気圧との関係をあらわす回帰直線の一例を示すグラフである。
【図３】本発明のタイヤ空気圧低下警報方法の一実施の形態である空気圧推定処理のステップを示すフローチャートである。
【図４】本発明のタイヤ空気圧低下警報方法の一実施の形態である空気圧推定処理のステップを示すフローチャートである。
【図５】図３の走行距離演算処理のステップを示すフローチャートである。
【図６】図３の移動演算処理のステップを示すフローチャートである。
【図７】本発明のタイヤ空気圧低下警報方法で用いられる時間と推定空気圧との関係をあらわす回帰直線の他の例を示すグラフである。
【符号の説明】
１ 車輪速センサ
２ 制御ユニット
３ 表示器
４ 初期化スイッチ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tire pressure drop warning device and method, and a tire pressure drop warning program. More specifically, the present invention relates to a tire pressure drop warning device and method capable of accurately detecting a natural leak of air inside a tire in response to a change in vehicle conditions and the like, and a tire pressure drop warning program.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various systems for detecting a decrease in air pressure due to natural leakage of a tire using wheel speed information have been developed and put into practical use. Among these, there is a well-known device for estimating the absolute air pressure of a tire from the resonance frequency of the tire. Also, paying attention to the fact that when the air inside the tire decreases, the dynamic load radius of the tire decreases, and by comparing the absolute speed of the vehicle with the wheel speed, the change in the dynamic load radius of the tire is detected, and natural air leakage is detected. A device for estimating is also being studied.
[0003]
However, none of these detection methods can cope with a change in vehicle conditions or the like, and there is a problem that the detection accuracy is low. That is, the air pressure of the tire changes depending on the outside air temperature, the road surface temperature, and the heat generated during running. Further, both the tire resonance frequency and the dynamic load radius are affected by the vehicle loading condition, the tire wear degree, the running condition, the road surface condition, and the like. Therefore, it is not possible to distinguish the change due to these factors only from the change amount of the tire resonance frequency or the dynamic load radius, and a false alarm may be issued even if the air pressure is normal.
[0004]
Therefore, in order to increase the detection accuracy of the decrease in tire air pressure, the elapsed time or the running distance after filling the air is used as the tire use history, and the longer the use history, the higher the possibility that the tire air pressure has decreased. There has been proposed a tire pressure abnormality determination device for determining (see Patent Document 1).
[0005]
That is, the tire pressure abnormality determination device described in Patent Literature 1 is based on the use history of the tire including the traveling distance of the vehicle and the like, and the pressure drop possibility estimating unit that estimates the possibility that the tire pressure is reduced. And a predetermined low pressure determination condition, a condition that is more easily satisfied when the air pressure drop possibility estimating unit estimates that the possibility that the air pressure is decreasing is high when the possibility is estimated to be low. And a low-pressure determination condition changing unit that changes the condition to a low-pressure determination condition.
[0006]
This device can determine that the possibility of natural air leakage is higher as the elapsed time after filling with air is longer.Therefore, as the elapsed time is longer, the detection time is shortened and the detection frequency is increased. I have to.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 8-22221 (Japanese Patent No. 3339949)
[0008]
[Problems to be solved by the invention]
However, the tire pressure abnormality determination device described in Patent Literature 1 has a problem that it does not cope with a difference in the degree of natural air leakage between individual tires. That is, in general, natural air leakage of a tire differs depending on the structure and material of the tire, how to assemble the rim, and the state of the valve. Therefore, depending on the standard tire, the elapsed time that is likely to increase the possibility of spontaneous leakage is set, and even if the detection frequency is increased after that, depending on the tire, air may flow faster than the standard. Some of them escape, and conversely, some of them are harder to escape than the standard. Therefore, when a certain period elapses after the tire is filled with air, if the vehicle conditions change significantly, it may be erroneously determined to be a natural leak even though the air has not decreased.
[0009]
On the other hand, it is not possible to cope with a case in which the air decreases more quickly than a standard tire, such as when the valve is loosely tightened or the rim is poorly assembled. Furthermore, it is not possible to cope with a case where tires are frequently filled with air pressure. For example, if air pressure filling is performed every few days, it is possible to maintain substantially the same air pressure over a long period of time.However, this method simply judges that natural leakage continues over time, so false detection is possible. The nature becomes high. Further, even if it is possible to determine whether or not air is charged, it is considered that the determination is almost impossible if air pressure is frequently charged.
[0010]
In other words, in the method described in Patent Document 1, the possibility of erroneous detection increases as the elapsed time after pneumatic filling increases, and when the elapsed time is short, the undetected state is relatively lower than when the elapsed time is long. More time (no detection).
[0011]
The present invention has been made to solve such a problem, and a tire pressure drop warning device and method capable of accurately detecting natural leakage of air inside a tire in response to changes in vehicle conditions and the like, and a tire An object of the present invention is to provide a low air pressure warning program.
[0012]
[Means for Solving the Problems]
The tire pressure drop warning device of the present invention detects the rotation speed of a tire mounted on a vehicle, and, based on the detected rotation speed, issues a warning when a decrease in tire pressure is detected. An alarm device,
After the tires are mounted on the vehicle, or after the tires are filled with air, the elapsed time or mileage, and the relationship between the estimated air pressure is made a function, and the tire pressure decreases with time or mileage from the obtained coefficient. And, when the decrease amount exceeds a predetermined threshold value, determining means for determining that there is a decrease in tire pressure due to natural leakage,
Warning means for issuing a warning of a decrease in air pressure. The functioning can be performed by regression calculation or the like.
[0013]
Preferably, the estimated air pressure is estimated based on a travel distance and a travel distance.
[0014]
The tire pressure drop warning method of the present invention detects a rotation speed of a tire mounted on a vehicle, and based on the detected rotation speed, issues a warning when a decrease in tire pressure is detected based on the detected rotation speed. A warning method,
After the tires are mounted on the vehicle, or after the tires are filled with air, the elapsed time or mileage, and the relationship between the estimated air pressure is made a function, and the tire pressure decreases with time or mileage from the obtained coefficient. When the decrease amount exceeds a predetermined threshold value, it is determined that there is a decrease in the tire air pressure due to natural leakage, and a warning of the decrease in the air pressure is issued. The functioning can be performed by regression calculation or the like.
[0015]
Preferably, the estimated air pressure is estimated based on a travel distance and a travel distance.
[0016]
The tire pressure drop warning program of the present invention, a computer that determines the tire pressure drop, the elapsed time or running distance after the tire is mounted on the vehicle or after the tire is filled with air, and the estimated air pressure When the tire pressure is decreasing with time or mileage from the obtained coefficient, and the amount of decrease exceeds a predetermined threshold value, it is determined that there is a decrease in tire pressure due to natural leakage. It is characterized by functioning as a judging means. The functioning can be performed by regression calculation or the like.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, a tire pressure drop warning device and method and a tire pressure drop warning program of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the tire pressure drop warning device of the present invention, and FIG. 2 shows an example of a regression line representing the relationship between time and estimated air pressure used in the tire pressure drop warning method of the present invention. 3 and 4 are flowcharts showing steps of a tire pressure estimating process according to an embodiment of the tire pressure drop warning method of the present invention, FIG. 5 is a flowchart showing steps of a mileage calculating process in FIG. 3, and FIG. FIG. 7 is a flowchart showing the steps of the movement calculation processing in FIG. 3, and FIG. 7 is a graph showing another example of a regression line representing the relationship between the time and the estimated air pressure used in the tire pressure drop warning method of the present invention.
[0018]
As shown in FIG. 1, the tire pressure drop warning device according to one embodiment of the present invention is configured such that the tire pressures of four tires W ₁ , W ₂ , W _3, and W ₄ provided in a four-wheel vehicle are reduced. A normal wheel speed sensor 1 is provided for detecting whether or not the vehicle speed has decreased, and is provided in association with each of the tires W ₁ , W ₂ , W ₃ and W ₄ . The output of the wheel speed sensor 1 is given to the control unit 2. The control unit 2, a liquid crystal display device for informing a tire W _i whose pneumatic pressure drops, plasma display elements or CRT and a display unit 3 composed of, and the initialization switch 4 which can be operated by a driver is connected ing.
[0019]
Wherein the vehicle speed sensor 1, a pulse signal (hereinafter, referred to as wheel speed pulses) corresponding to the rotational speed of the tire W _i is output, the control unit 2, based on the wheel speed pulse outputted from the wheel speed sensor 1, a predetermined sampling period, for example, the wheel rotational speed of each tire W _i every second is calculated, the control unit 2 calculates the travel distance of the vehicle using the wheel rotation speed.
[0020]
Although not shown, the air pressure drop warning device of the present embodiment includes a moving distance measuring unit such as a GPS for measuring the moving distance of the vehicle.
[0021]
The control unit 2 according to the present embodiment controls the relationship between the elapsed time after the tire is mounted on the vehicle or after the tire is filled with air and the estimated air pressure estimated based on the travel distance and the travel distance of the vehicle. Therefore, it functions as a determination unit for determining that there is a natural leak of air inside the tire. In addition, although the accuracy is slightly reduced, the traveling distance can be used instead of the time information.
[0022]
The relationship between the elapsed time and the estimated air pressure is quantitatively obtained, for example, as a slope (regression coefficient) of a regression line between the elapsed time and the estimated air pressure shown in FIG.
[0023]
In the present invention, as in the conventional determination device, the determination is made not only based on the elapsed time after the air pressure filling, but based on the relationship between the elapsed time and the estimated air pressure, whether the air pressure naturally decreases with time. There is a feature in judging whether or not.
[0024]
That is, first, the estimated air pressure is y, and the time (hour) is x. The estimated air pressure is obtained from the average of the effective data every several minutes to several tens of minutes, and the time is set to be 0 at the time of the driver's initialization start operation, and thereafter added, for example, on an hourly basis.
[0025]
In the method of obtaining the slope by regression, when y = ax + b, the slope a of the regression line is obtained by the following equation.
[0026]
a = {nΣxy- (Σx) (Σy)} / ｛nΣx ^2- (Σx) ² } (1)
(N: number of data)
[0027]
The product of the slope obtained by this and the elapsed time from the air pressure filling to the present time, that is, the estimated air pressure reduction amount, corresponds to the difference between the initial air pressure and the current estimated air pressure and is considerably large (the predetermined pressure). When it is determined that the air pressure exceeds the threshold, it is determined that the air pressure is gradually decreasing with the passage of time and the amount of the air pressure is significantly reduced, and a warning of an air pressure drop is issued.
[0028]
Further, as another embodiment of the determination method of the present invention, for example, a correlation coefficient between the elapsed time and the estimated air pressure is obtained, thereby determining whether or not the correlation between the air pressure reduction rate and the elapsed time is high. A method may be used. That is, when the correlation function is, for example, 0.85 or more, it is determined that the correlation between the decrease in air pressure and time is high, that is, the air pressure naturally decreases with time.
[0029]
If the estimated air pressure does not decrease even after a long period of time, it can be determined that maintenance of the air pressure has been performed. After a long period (approximately one month), if the estimated air pressure is almost in the initial state in the range of ± 10% and it can be determined that the slope of the regression line or the correlation coefficient is a value close to zero, maintenance is performed. Judgment has been made, and the time and integrated value are returned to zero.
[0030]
For example, the regression curve when the tire pressure is replenished for one year and no maintenance is performed thereafter becomes a curve as shown in FIG.
[0031]
The method of determining a decrease in air pressure according to the present invention is executed, for example, according to the steps of the flowcharts of FIGS. 3 to 6 as an embodiment, but the present invention is not limited to this.
[0032]
(1) First, in step S1 in FIG. 3, the vehicle speed, the road condition, the presence or absence of a sudden operation, and the operation state of the GPS are checked, respectively, to determine whether or not the condition for determining a decrease in tire air pressure is satisfied.
[0033]
(2) Next, the traveling distance calculation processing S2 is executed. The traveling distance calculation processing S2 is specifically executed in steps shown in FIG.
[0034]
(3) Next, the moving distance calculation processing S3 is executed. The moving distance calculation processing S3 is specifically executed in the steps shown in FIG.
[0035]
(4) After that, in step S4, a determination value is calculated from the traveling distance and the moving distance. As the determination value, the average of the determination values for m times is adopted (steps S5 to S7).
[0036]
(5) Next, from the relationship between the time x and the judgment value y, the sum of the time Sx, the sum of the judgment values Sy, and the product of the time and the judgment value for obtaining the slope of the regression line of the equation (1). sum Sxy, calculates the sum Sx ² of the square of the time (step S9).
[0037]
(6) It is determined that the processing up to step S9 has exceeded a predetermined number n ₀ (for example, 100 times) (step S10), it is determined that the determination value is not ≒ 1 (step S11), and the determination value is a predetermined value. If an alarm is issued when the pressure is reduced by 30% from the initial air pressure, it is determined that the threshold value is greater than the determination value of the present embodiment = running distance / moving distance of about 1.004 (step S12). ), The slope of the regression line is calculated (step S13). Here, the estimated air pressure decreases with time, but the determination value increases with time, so that the slope becomes> 0.
[0038]
If it is determined in step S11 that the determination value is ≒ 1, it is further determined whether a long period has elapsed (step S16), and whether the slope ≒ 0 or the correlation coefficient ≒ 0 is determined. (Step S17) If both Steps S16 and S17 are Yes, the elapsed time and the variables of Steps S9 to S10 are reset to 0 (Step S18). If any one of Steps S16 and S17 is No, Return as it is.
[0039]
(7) Thereafter, when it is determined that the product of the slope and the time is substantially equal to the determination value −1, that is, within a range of an error of about ± 10% (step S14), a warning is issued to the driver (step S14). S15).
[0040]
【Example】
Next, a judgment test was performed as follows while comparing an example of the tire pressure drop warning method of the present invention with a comparative example.
[0041]
(1) Judgment method (Example) The method of the present invention (determining that there is a natural leak of air inside the tire from the relationship between the elapsed time and the estimated air pressure),
(Comparative example) A method in which the detection time is advanced according to the elapsed time. Here, immediately after the end of the initialization, the time required for the detection is set to 30 minutes, and thereafter, every 10 days, the time is reduced by 1 minute, and 10 minutes (after 200 days) is set as the lower limit.
[0042]
(2) Vehicle used: FF2400cc passenger car tire 215 / 55R16 (Summer tire manufactured by Sumitomo Rubber Industries, Ltd. (name: LM702))
[0043]
The following three cases were set and their detectability was compared. Note that the air pressure drop warning method used here estimates the air pressure drop from the difference between the average of the wheel speeds and the absolute vehicle speed calculated from the vehicle position information obtained from the GPS.
[0044]
1. Standard case: When the tires are filled with normal pressure air and air is not refilled (leakage rate 2% / month)
2. A case where the air pressure drops quickly: After filling the air with the normal pressure, the valve is slightly loosened so that the air leaks faster than usual (leakage rate 10% / month)
3. Case where air replenishment was performed: Air pressure replenishment was performed for one year and maintenance was not performed after that (leakage rate 0 → 2% / month)
[0045]
Do this for two years. In order to shorten the test period, the time lapse was set to 10 times (actual test period: about 70 days).
[0046]
(3) Test result [0047]
[Table 1]

[0048]
From the above results, it can be seen that in the comparative example, the detection variation is observed depending on the condition, whereas in the example, the variation is small. In particular, in case 3 in which air replenishment was performed, an erroneous detection was performed with a 22% reduction in air pressure in the comparative example, but no erroneous detection was performed in the example according to the method of the present invention.
[0049]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the natural air leak of a tire air accurately respond | corresponds to the change of various vehicle conditions, such as the difference of the degree of the natural air leak of the inside of each tire, or the case where air is frequently filled after mounting the tire. Can be detected.
[Brief description of the drawings]
FIG. 1 is a block diagram showing one embodiment of a tire pressure drop warning device of the present invention.
FIG. 2 is a graph showing an example of a regression line representing a relationship between time and an estimated air pressure used in the tire pressure drop warning method of the present invention.
FIG. 3 is a flowchart showing steps of a tire pressure estimation process which is one embodiment of the tire pressure drop warning method of the present invention.
FIG. 4 is a flowchart showing steps of a tire pressure estimation process which is one embodiment of the tire pressure drop warning method of the present invention.
FIG. 5 is a flowchart showing steps of a traveling distance calculation process of FIG. 3;
FIG. 6 is a flowchart showing steps of a movement calculation process in FIG. 3;
FIG. 7 is a graph showing another example of a regression line representing a relationship between time and an estimated air pressure used in the tire pressure drop warning method of the present invention.
[Explanation of symbols]
1 wheel speed sensor 2 control unit 3 display 4 initialization switch

Claims (5)

An air pressure drop warning device that detects a rotation speed of a tire mounted on a vehicle and, based on the detected rotation speed, issues an alarm when a decrease in tire air pressure is detected.
After the tires are mounted on the vehicle, or after the tires are filled with air, the elapsed time or mileage, and the relationship between the estimated air pressure is made a function, and the tire pressure decreases with time or mileage from the obtained coefficient. And, when the decrease amount exceeds a predetermined threshold value, determining means for determining that there is a decrease in tire pressure due to natural leakage,
An alarm device for alarming a decrease in tire air pressure, comprising alarm means for issuing an alarm of a decrease in air pressure. The apparatus of claim 1, wherein the estimated air pressure is estimated based on a travel distance and a travel distance. A method for detecting a rotation speed of a tire mounted on a vehicle, based on the detected rotation speed, when a decrease in tire air pressure is detected, an alarm method for lowering air pressure that issues an alarm,
After the tires are mounted on the vehicle, or after the tires are filled with air, the elapsed time or mileage, and the relationship between the estimated air pressure is made a function, and the tire pressure decreases with time or mileage from the obtained coefficient. And when the amount of decrease exceeds a predetermined threshold value, it is determined that there is a decrease in tire air pressure due to spontaneous leakage, and a warning of a decrease in tire air pressure is issued. . The method of claim 3, wherein the estimated air pressure is estimated based on a mileage and a travel distance. A computer that determines the decrease in tire air pressure, a function of the relationship between the elapsed time or mileage after the tire is mounted on the vehicle or after the tire is filled with air and the estimated air pressure, and the obtained coefficient is used as a function. When the tire pressure decreases with time or mileage and the amount of decrease exceeds a predetermined threshold value, the air pressure for functioning as a judging means for determining that the tire pressure has decreased due to natural leakage. Drop alert program.

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