JP2003344205A - Method of detecting abnormality of internal pressure in tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of detecting abnormality of tire internal pressure capable of substituting a conventional tire internal pressure alarm partially or completely, and requiring no battery in a rotational portion of a wheel. <P>SOLUTION: A clearance under an axle (the height of the tire portion just beneath the vehicle axle during traveling) is measured in a real time by a sensor attached to a non-rotational portion of a body side or the axle to detect the abnormality of the internal pressure based on the measured clearance. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a tire internal pressure abnormality for monitoring a tire pressure condition in a vehicle and notifying a driver of the abnormality.

[0002]

2. Description of the Related Art In order to inform a driver of abnormal air pressure,
BACKGROUND ART Conventionally, there is known a tire internal pressure alarm device which is attached to a rim of a vehicle, detects a tire air pressure with a pressure sensor, and transmits information on the air pressure to a receiver provided on the vehicle side by radio waves. Since this tire internal pressure alarm device is attached to the rotating part of the wheel, a power source is provided in the non-rotating part of the vehicle body to supply power for driving the pressure sensor and power for transmitting radio waves. Since it is difficult to do so, a battery is built in the tire internal pressure alarm device, and power is supplied by this battery.

This tire internal pressure alarm device has an original function of checking the internal pressure of the tire to confirm that it is normal. Therefore, the pressure measurement and the transmission of the measurement result must always be performed at intervals of a predetermined time or less. However, in addition to the difficulty in suppressing the power consumption, the tire pressure warning device must be lightweight in order not to disturb the balance of the rotation of the wheels, and there is a limit to the size and capacity of the battery. The early consumption of batteries is a problem. However, every time the battery reaches the end of its life, it is purposely removed from the rim in order to replace the battery of the tire pressure warning device installed in the inner space of the tire surrounded by the tire and the rim. That is not practical. In order to solve this problem, development of battery life extension or tire internal pressure alarm device power saving has been underway, but no satisfactory results have been obtained yet.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and can replace the conventional tire internal pressure alarm device partially or entirely, and further, It is an object of the present invention to provide a tire internal pressure abnormality detection method that does not require a battery for a rotating portion of a wheel.

[0005]

SUMMARY OF THE INVENTION The present invention has been accomplished in order to achieve the above-mentioned object, and its gist structure and operation will be described below.

According to a first aspect of the present invention, there is provided a sensor mounted on a vehicle body side or a non-rotating portion of an axle when a height of a tire portion immediately below an axle of a running vehicle is defined as an axle height. Is used to measure the height under the shaft in real time, and the abnormal state of the internal pressure is detected from the measured value of the height under the shaft.

The below-axis height decreases as the axial load supported by the tire increases and the tire internal pressure decreases. If the axial load itself or the change in the axial load is known, this can be used to estimate the tire internal pressure or the change in the tire internal pressure. The tire internal pressure detection method according to the present invention thus estimates the tire internal pressure or the change in the tire internal pressure, and when this exceeds a predetermined range, it is to detect that the tire internal pressure is abnormal, The conventional tire pressure warning device can be partially or totally replaced. Moreover, according to this tire internal pressure detection method, since the sensor that measures the axial height in real time is attached to the vehicle body side or a non-rotating portion of the axle, the electric power for measurement and the measurement result are measured on the vehicle body side. It is not necessary to provide a battery for supplying electric power for outputting to the alarm display device to the rotating portion of the wheel.

According to a second aspect of the present invention, there is provided a method for detecting a tire internal pressure abnormality according to the first aspect, in which a measured value of an axial height of each tire attached to a pair of left and right wheels of a vehicle is measured. A state in which the difference exceeds a predetermined range is detected as an abnormal state of the internal pressure.

When the tire internal pressure is normal, the difference between the heights of the left and right paired wheels, for example, the left and right front wheels, below the tire axis is known. The height is kept almost constant. And since it is almost impossible that the internal pressures of both tires decrease at the same time, when the internal pressure of one tire decreases, the axial height of this tire becomes smaller, and the difference between the axial height of the other tire occurs. . According to this tire internal pressure abnormality detection method, when the difference between the left and right axial heights of the left and right tires exceeds a predetermined range, it is determined that the tire internal pressure has abnormally decreased, without accurately measuring the axial load. It is possible to easily detect an abnormality in the internal pressure.

However, in this case, the precondition is that the abnormality in the internal pressure is determined based on the under-axis height measured while the vehicle is traveling straight. This is, for example, the hydraulic pressure of the steering wheel or the operation of the steering wheel. This precondition can be validated by detecting the amounts and making the abnormality determination of the internal pressure only when they are within the predetermined range.

According to a third aspect of the present invention, there is provided a method for detecting a tire internal pressure abnormality, wherein the time reduction rate of the measured value of the axial height is equal to or more than a predetermined value. Is detected as an abnormal state of internal pressure.

In general, when the tire is flat and an abnormal internal pressure occurs, the internal pressure decreases at a high rate, and therefore the time reduction rate of the measured value of the axial height increases, while the vehicle travels. Inside, the shaft load does not change abruptly if the variable factors due to the vibration of the vehicle are removed. According to this tire internal pressure abnormality detection method, when the time decrease rate of the measured value of the axial height becomes equal to or more than a predetermined value, it is determined that the internal pressure is abnormal, so that the tire internal pressure sharply decreases due to puncture or the like. Can be detected and the driver can be informed of the sign of a dangerous state.

According to a fourth aspect of the present invention, there is provided a tire internal pressure abnormality detecting method as set forth in any one of the first to third aspects, in which a relational expression of an axial height, a tire internal pressure and an axial load is prepared in advance, Separately, the internal pressure is calculated from the axial load measured in real time and the measured value of the under-axis height, and the state where the calculated internal pressure is below a predetermined value is detected as an abnormal state of the internal pressure.

Since the under-shaft height changes depending on the tire internal pressure and the axial load, as described above, the relational expressions of the under-shaft height, the tire internal pressure and the axial load are prepared in advance. be able to. This tire internal pressure abnormality detection method measures the axial load in real time and measures the axial load.
The tire internal pressure is obtained by measuring the tire internal pressure in real time by a method other than the method obtained from the axial height, and by substituting these measured values into the relational expression, it is possible to accurately measure the tire internal pressure, and thus with high accuracy. It is possible to detect an abnormality in the tire internal pressure.

According to a fifth aspect of the present invention, there is provided a tire internal pressure abnormality detecting method as set forth in any one of the first to fourth aspects, wherein the measured values of the axial height are averaged among those measured within a predetermined time. It is the value after the conversion processing.

When the vehicle vibration generated while the vehicle is running is large, the axial load also vibrates, and the measured value of the axial height in this state also fluctuates in a short period. If an abnormality in the tire internal pressure is detected directly from the measured value of the height, the detection accuracy will decrease. According to this tire internal pressure abnormality detection method, since the measured value of the axial height is the value after averaging those measured within a predetermined time, the axial height after averaging The measured value may be one in which the factor of vibration has been removed, and an abnormality in the tire internal pressure can be accurately detected.

A tire internal pressure abnormality detecting method according to a sixth aspect of the present invention is the method according to any one of the first to fifth aspects, wherein when the internal pressure is determined to be in an abnormal state from the measured value of the axial height, the tire The measurement of the internal pressure by the pressure sensor that directly detects the internal pressure is started, and after the pressure value measured by the pressure sensor falls within the normal range, the measurement of the internal pressure by the pressure sensor is stopped after a predetermined time.

This tire internal pressure abnormality detection method preliminarily detects an abnormality in the tire internal pressure based on the measured value of the axial height,
When the abnormality is preliminarily detected, the detection of the tire internal pressure by the pressure sensor is started for the first time, and the main detection of the abnormality of the tire internal pressure is performed.According to this tire internal pressure detection method, the main detection is performed for the tire. Since it is performed by the pressure sensor that directly detects the internal pressure, it is possible to improve the pressure detection accuracy, and it is not necessary to operate the pressure sensor when the pressure is determined to be almost normal, so it is possible to prevent battery consumption. it can.

According to a seventh aspect of the present invention, there is provided a tire internal pressure abnormality detecting method as set forth in any one of the first to sixth aspects, wherein the axis of the magnetization pattern formed in the tread portion of the tire is measured when measuring the axial height. The magnetic flux density of the magnetic field generated from the portion directly below is measured by a magnetic sensor attached to the non-rotating portion of the axle on which this tire is mounted, and the height below the axle is obtained from this measured value.

In this tire internal pressure abnormality detection method, the distance between the portion directly below the axis of the tread portion of the tire and the magnetic sensor attached to the non-rotating portion of the axle is determined by measuring the change in magnetic flux density, and the distance from the rim Since the length under the axle is subtracted from the length of the portion that does not change due to internal pressure such as the radius, the distance between the axle and the tread portion of the tire under the axle can be accurately measured, and other electrical It is possible to provide a method of measuring the axial height that is less affected by the environment as compared with the method and the optical method.

Here, the "magnetization pattern" represents the magnetic flux density of a component of a magnetic field emitted from the surface of a magnetized object, which is perpendicular to the surface, along a predetermined direction on the surface. Specifically, a magnetic sensor such as a Gauss meter, which is brought close to the surface of the object, is moved by controlling its posture so that the magnetic field lines whose detection direction is perpendicular to the surface of the object are captured. The magnitude of the magnetic flux density appearing on the sensor is plotted on the vertical axis, and the predetermined direction is plotted on the horizontal axis, which is the magnetization pattern.

The tire internal pressure abnormality detecting method according to claim 8 is the method according to any one of claims 4 to 7, wherein when the axial load separately measured in real time is measured, the magnetization formed on the tread portion of the tire is measured. The magnetic flux density of the magnetic field generated from the part directly above the axis of the pattern is measured by the magnetic sensor attached to the vehicle body part on the side opposite to the tire holding the suspension of the axle on which this tire is mounted,
The axial load is obtained from this measured value.

This tire internal pressure abnormality detection method measures the change in the magnetic flux density by measuring the distance between the portion directly above the axis of the tread portion of the tire and the magnetic sensor attached to the body portion on the opposite side of the suspension. This distance,
The axial load is calculated from the spring constant of the suspension, and the axial load can be measured independently, and when the distance is measured, it is performed using the magnetic sensor provided on the vehicle body side. It is not necessary to provide a battery in the rotating part of the wheel, and it is possible to measure this with minimal environmental influences compared to other electrical and optical methods.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view showing a tire 1 used in this tire internal pressure abnormality detection method in a state of being mounted on a vehicle. A rim 11 on which the tire 1 is mounted is fixed to a hub 12 which constitutes a rotating portion of an axle 10 of the vehicle, and the hub 12 is axially supported by an axle case 13 which constitutes a non-rotating portion of the axle 10, while M
A magnetic sensor 14 including an I sensor (magnetic impedance sensor) and the like is fixedly connected to the axle case 13. The below-axis height H in FIG. 1 indicates the height of the portion directly below the axis of the tire 1, and the below-axis height H decreases as the axial load increases or the internal pressure of the tire 1 decreases.

The tread portion 2 of the tire 1 is provided with a belt 3 made of a steel cord 5 and arranged around the tire 1, and the belt 3 has a predetermined magnetization whose magnetization changes in the circumferential direction. It is magnetized to have a pattern. FIG. 2 is a perspective view showing the structure of the steel cord 5. The steel cord 5 is formed by, for example, spirally winding a single wire 7 made of a hard magnetic material on the outside of a twisted structure of seven steel wires 6. Can carry a high remanence.

In order to impart a predetermined magnetization pattern to the tire 1 having the belt 3, a product tire produced through a normal process is magnetized by using a magnetizer or the like while changing the magnetization in the circumferential direction. Can be done by
The material used for the wire 7 made of a hard magnetic material can be selected from ferrite, rare earth magnet materials such as neodymium iron boron and samarium cobalt, and alnico magnet materials. In order to form thin wires that become strands from materials, in addition to using methods for rolling and sintering depending on the workability of each material, these magnetic materials were mixed and dispersed in resin or rubber. The thin wire may be formed by subjecting the material to extrusion or rolling.

The belt 3 made of the steel cord 5 constructed as described above has a tire 1 having a magnetization pattern having a high peak of magnetization which cannot be obtained by a tire magnetized with a belt made of a steel cord made of a soft magnetic material. Can be given to.

FIG. 3 is a development view showing the arrangement of the magnetic poles when the belt 3 viewed from the inner surface of the tire is developed on a plane. The direction indicated by arrow D is the tire width direction, the direction indicated by arrow C is the tire circumferential direction, and N and S indicate the peak positions of the magnetic poles. In the example shown in FIG. 3, the magnets have a uniform magnetization in the width direction of the tire, and the magnetic poles are arranged in the circumferential direction of the tire so that the polarities are reversed at a predetermined pitch.

FIG. 4 is a chart showing the magnetization pattern along the straight line L1 shown in FIG. This magnetization pattern is
The tire has four N-pole and S-pole peaks during one round of the tire. FIG. 5 is an arrangement diagram showing an arrangement of magnetic force lines coming in and out of each magnetic pole on the belt 3 and a magnetic sensor 14 for detecting the magnetic force lines as seen from the axial direction of the tire. The magnetic sensor 14 has a tread portion 2 immediately below the axle.
It is located directly below the axle so as to detect changes in the magnetic field from.

The lines of magnetic force extend parallel to the equatorial plane of the tire 1, and the magnetic sensor 14 is also provided in such a posture as to detect the lines of magnetic force in this direction. At the rotational position of the tire 1 in which the sensor 14 is located on the same radius, the magnetic flux density detected by the magnetic sensor 14 is the smallest, and the tire 1 in which the midpoint between the adjacent magnetic poles and the magnetic sensor 14 are located on the same radius. The magnetic flux density becomes maximum at the rotational position of.

FIG. 6A is a graph showing the change over time in the magnetic flux density detected by the magnetic sensor 14. The curve M1 is
The magnetic flux density change when the internal pressure of the tire 1 is normal is represented, and the curve M2 represents the magnetic flux density change when the internal pressure of the tire 1 is decreased.

While the tire 1 makes one revolution, four peaks of the magnetic flux density detected by the magnetic sensor 14 appear corresponding to the number of poles of the belt 3 for each of the N pole and the S pole. When the internal pressure of the tire 1 decreases, the axial height H of the tire 1 decreases, so the distance between the magnetic sensor 14 and the axial magnetic poles of the tire 1 decreases, and as a result, the detected magnetic flux density increases,
The magnitude of the peak N1 of the magnetic flux density is larger than that of the curve M1 representing the magnetic flux density when the internal pressure of the tire 1 is normally maintained by ΔF, as indicated by the curve M2. Then, in the relational expression between the axial height and the magnetic flux density peak value prepared in advance, the peak value of the measured magnetic flux density is substituted to obtain the axial height, and the axial height becomes equal to or less than a predetermined value. When this happens, the driver can be notified of this by determining that the internal pressure has dropped abnormally. Alternatively, when the difference ΔF between the peak of the magnetic flux density and the normal internal pressure becomes larger than a predetermined range, it is possible to determine that the internal pressure has abnormally decreased and issue a warning to the driver.

However, the internal pressure abnormality detection method described above can accurately detect the internal pressure abnormality when the axial load applied to the tire is constant. In addition to the internal pressure, it is greatly affected by the axial load.In addition, the axial load changes not only with the weight of the vehicle and the number of occupants, but also with the vibration during running of the vehicle, the state of steering of the vehicle or the state of acceleration / deceleration. Since it also fluctuates, in reality, further devising is necessary.
These ideas will be described.

An orthodox method for completely eliminating the influence of the axial load is a method of measuring the axial load in real time on the basis of an amount other than the height below the shaft, and measuring the axial load in this way. The tire internal pressure can be calculated in real time by substituting the load and the measured value of the axial height for the three-dimensional relational expressions of the axial height, the tire internal pressure, and the axial load prepared in advance.

An example of a specific method for measuring the axial load in this case is shown below. As shown in FIG. 1, the fender 16
The magnetic sensor 15 is fixedly provided at a position just above the axis of the tire 1. FIG. 6B is a graph showing the change over time in the magnetic flux density detected by the magnetic sensor 15. Curve R1
Represents the change in the magnetic flux density when the axial load of the tire 1 is small, and the curve R2 represents the change in the magnetic flux density when the axial load of the tire 1 is large.

While the tire 1 makes one revolution, four peaks of the magnetic flux density detected by the magnetic sensor 15 also appear corresponding to the number of poles of the belt 3 for each of the N pole and the S pole. When the axial load increases, the suspension bends in proportion to the axial load and the distance between the magnetic sensor 15 and the shaft center decreases, while the axial height of the tire 1 does not change.
The distance D between the tire 5 and the upper surface of the tire 1 decreases. as a result,
As the axial load increases, the magnetic flux density detected by the magnetic sensor 15 increases, and the magnitude of the peak N1 of the magnetic flux density is ΔG larger than that of the curve M1 when the axial load is small, as shown by the curve R2. Only grows. Then, by preparing a relational expression between the axial load and the peak value of the magnetic flux density in advance, the axial load can be obtained from the measured peak value of the magnetic flux density.

The method described above detects abnormal tire internal pressure by accurately obtaining the tire internal pressure from the measured values of the axial height and the axial load, respectively. Another way to detect is: One is to consider the curve M1 shown in FIG. 6 (a) when the tire internal pressure is normal as the counterpart of the pair of left and right wheels. According to this method, the curve M1 is attached to these wheels. When each tire bears the load evenly on the left and right, when the internal pressure is normal, the axial height of each tire is almost the same, so ΔF is zero, but the internal pressure of one tire decreases. Then, since ΔF changes, an alarm is issued when it exceeds a predetermined range, so that an abnormality in the internal pressure can be detected.

This method is premised on the condition that the left and right tires bear the load evenly. Therefore, if this premise is not satisfied, this can be done by, for example, the hydraulic pressure of the steering wheel or the steering amount of the steering wheel. By detecting and transmitting a signal indicating that the internal pressure abnormality is not detected, the detected state of the internal pressure can be transmitted to the driver more accurately than in the case where no signal is transmitted.

As a more simple method for detecting an abnormality in the internal pressure, it is also possible to detect an abnormality in the internal pressure by issuing an alarm when the rate of decrease in the internal pressure per a predetermined time becomes larger than a predetermined threshold value. In this case, although the axial load fluctuates up and down during normal traveling, it does not suddenly and simply decrease. Therefore, by appropriately selecting the threshold value, the axial load fluctuation and the abnormal decrease in internal pressure can be distinguished. it can.

Further, in each of the above-mentioned methods, it is preferable to eliminate the influence of the fluctuation of the axial load due to the vibration when the vehicle travels, in order to improve the accuracy of detecting the abnormality in the tire internal pressure. For example, the measured value of the height below the axis may be a value obtained by averaging the values measured within a predetermined time. For example, if the cycle of normal vehicle vibration is 1 second or less, the current measured value of the axial height may be the time average value of the axial height from 1 second before to the present.

The method of obtaining the axial height when detecting the abnormality in the tire internal pressure has been described above for the case where the magnetic poles on the belt 3 are arranged as shown in FIG. The present invention is not limited to this, and another example of the arrangement of magnetic poles is shown below. FIG. 7 is a development view showing the magnetized belt 3 when it is developed on a plane as viewed from the inner surface of the tire. The direction indicated by arrow D is the tire width direction, the direction indicated by arrow C is the tire circumferential direction, and N and S indicate the peak positions of the magnetic poles. In this tire 1, the N pole is arranged on one side in the width direction and the S pole is arranged on the other side, and the strength of each magnetic pole is changed along the circumferential direction,
The changes are provided in synchronization with each other.

8 (a), 8 (b) and 8 (c)
8A and 8B are charts showing magnetization patterns along straight lines L2, L3, and L4 in FIG. 7, respectively. In addition, FIG.
9A and 9A are arrangement diagrams showing the arrangement of magnetic force lines emitted from the respective magnetic poles on the belt 3 and the magnetic sensor 14 for detecting the magnetic force lines on the tire meridian section, and FIG.
9A shows a state where the peak of the magnetic pole on the belt 3 is located directly below the axle, and FIG. 9B shows a state where the valley of the magnetic pole is located directly below the axle. Further, the magnetic sensor 14 is arranged directly below the axle so as to detect a change in the magnetic field from the tread portion 2 immediately below the axle.

As shown in FIGS. 9 (a) and 9 (b), the lines of magnetic force extend parallel to the meridian plane of the tire 1, and the magnetic sensor 14 is also in a position to detect the lines of magnetic force in this direction. When the tire 1 is rotated, the magnetic flux density detected by the magnetic sensor 14 is the largest at the rotational position of the tire 1 where the peak of the magnetic pole and the magnetic sensor 14 are located on the same radius when the tire 1 is rotated. The magnetic flux density is smallest at the rotational position of the tire 1 where the magnetic sensor 14 and the magnetic sensor 14 are located on the same radius.

The description of the method for determining the axial height of the tire 1 using the tire 1 and the magnetic sensor 14 arranged in this way is the same as the case of the magnetic pole arrangement shown in FIG. This is omitted.

Further, in the above description, the magnetization pattern of the tire 1 was formed by magnetizing the belt 3 made of steel cord containing strands of hard magnetic material, but instead, as shown in FIG. In addition, the belt 3a is made of a normal steel belt, and a magnetic rubber sheet 4 made by mixing and dispersing magnetic particles made of a hard magnetic material is attached to the inner side of the inner liner 8 in the radial direction to form a tire. After vulcanization, the tire can be magnetized to form a predetermined pattern.

[0046]

As is apparent from the above description,
According to the present invention, the sensor mounted on the vehicle body side or the non-rotating portion of the axle measures the in-axis height in real time, and the abnormal internal pressure is detected from the measured in-axis height. The tire pressure alarm device can be partially or completely replaced, and the battery for supplying electric power for measuring and outputting the measurement result to the alarm display device on the vehicle body It is not necessary to provide it on the rotating part of

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire used in a tire internal pressure abnormality detection method according to an embodiment of the present invention.

FIG. 2 is a perspective view of a steel cord.

FIG. 3 is a development view showing a magnetic pole arrangement of a belt.

FIG. 4 is a chart showing a magnetization pattern of a belt.

FIG. 5 is an arrangement diagram showing an arrangement of magnetic poles and magnetic sensors.

FIG. 6 is a graph showing a change over time in the magnetic flux density detected by the magnetic sensor.

FIG. 7 is a development view showing the magnetic pole arrangement of the belt.

FIG. 8 is a chart showing a magnetization pattern of a belt.

FIG. 9 is an arrangement diagram showing an arrangement of magnetic poles and magnetic sensors.

FIG. 10 is a cross-sectional view of another tire used in the method for detecting abnormality in tire internal pressure.

[Explanation of symbols]

1 tire 2 tread section 3,3a belt 4 Magnetic rubber sheet 5 steel cord 6 Steel wire 7 Wire made of hard magnetic material 8 Inner liner 10 axles 11 rims 12 hubs 13 axle case 14, 15 Magnetic sensor 16 fenders

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B60C 23/06 B60C 23/06 D (72) Inventor Takahisa Shizuku 3-1-1 Ogawahigashi-cho, Kodaira-shi, Tokyo F-term in Bridgestone Technology Center of stock company (reference) 2F055 AA12 BB20 CC14 DD20 EE27 FF31 FF45 GG11

Claims (8)

[Claims] 1. When a height of a tire portion immediately below an axle of a running vehicle is set as an under-axle height, a sensor attached to a vehicle body side or a non-rotating portion of the axle is used to measure the under-axle height in real time. A tire internal pressure abnormality detection method that measures and detects an abnormal state of internal pressure from the measured value of the height under the shaft. 2. A state in which a difference in measured values of under-axis heights of respective tires attached to a pair of left and right wheels of a vehicle exceeds a predetermined range is detected as an internal pressure abnormal state. The method for detecting a tire internal pressure abnormality according to. 3. The tire internal pressure abnormality detection device according to claim 1, wherein a state in which the time reduction rate of the measured value of the axial height is equal to or higher than a predetermined value is detected as an abnormal state of the internal pressure. 4. A relational expression of the axial height, the tire internal pressure and the axial load is prepared in advance, and the internal pressure is calculated from the axial load separately measured in real time and the measured value of the axial height, The tire internal pressure abnormality detection method according to any one of claims 1 to 3, wherein a state in which the calculated internal pressure becomes equal to or lower than a predetermined value is detected as an abnormal state of the internal pressure. 5. The measured value of the under-axis height is a value obtained by averaging the measured values within a predetermined time.
5. The method for detecting abnormality in tire internal pressure according to any one of 4 to 4. 6. When it is determined that the internal pressure is in an abnormal state from the measured value of the height below the shaft, the internal pressure measurement by a pressure sensor that directly detects the internal pressure of the tire is started, and the pressure value measured by the pressure sensor is normal. The tire internal pressure abnormality detection method according to claim 1, wherein the measurement of the internal pressure by the pressure sensor is stopped after a predetermined time has passed after entering the range. 7. A magnetic flux density of a magnetic field generated from a portion immediately below an axis of a magnetization pattern formed on a tread portion of a tire when measuring an under-axle height is attached to a non-rotating portion of an axle on which the tire is mounted. 7. The method for detecting abnormality in tire internal pressure according to claim 1, wherein the axial height is measured by a magnetic sensor and the height below the axis is obtained from the measured value. 8. When measuring the axial load separately measured in real time, the magnetic flux density of the magnetic field generated from the portion directly above the axis of the magnetization pattern formed on the tread portion of the tire is measured by the suspension of the axle on which the tire is mounted. 8. A magnetic sensor attached to a vehicle body portion on the side opposite to the sandwiched tire is used for measurement, and the axial load is determined from the measured value.
The method for detecting abnormality in tire internal pressure according to any one of 1.