JP3200028B2 - Tire magnetization method and tire magnetic field detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire magnetizing method for magnetically detecting the rotation of a tire for measuring the speed or moving distance of a vehicle such as an automobile, and a method for detecting a tire magnetic field. Things.

[0002]

2. Description of the Related Art A car navigation device (hereinafter, abbreviated as car navigation) used for a current position of a vehicle, road guidance, and the like.
It appeared around 1990 and has become quite popular.

[0003] Car navigation systems have a function of detecting an absolute position by radio waves from artificial satellites by GPS navigation. Recently, however, a car navigation system has a self-sustained status indicating a vehicle movement condition based on angular displacement by a gyro sensor and vehicle speed data from a vehicle body. The number of hybrid systems with built-in navigation has increased and has become mainstream. With this hybrid method, the accuracy of map matching can be improved.

[0004] However, in order to obtain the function of the self-contained navigation, it is necessary to obtain vehicle speed data from the vehicle body, and for this purpose, it is necessary to have a specialized dealer having a wiring diagram of the vehicle body connect the device. . It is difficult for general users to perform this connection work in terms of safety, and the fact that the connection cannot be performed by a specialized dealer and the high cost thereof are becoming obstacles for the further spread of car navigation systems in the future.

[0005]

The above problem can be solved by detecting the rotation or the number of rotations of the tires for measuring the vehicle speed or moving distance and supplying a sensor which can be easily attached to the vehicle. It is most suitable as a practical detection method if the rotation or the rotation speed of the tire can be detected in a non-contact manner.

Therefore, the present inventor has paid attention to the fact that steel radial tires have become the mainstream in recent tires, and in this tire, a steel belt is included inside the outer periphery. The steel belt itself has a weak but remanent magnetization and emits a magnetic field outside the tire.

FIG. 10 shows an example of actually measuring the magnetic field by rotating the tire once. The measurement was taken along the outer circumference at a distance of 15 cm from the tire, but it was found that there were multiple distinct peaks corresponding to one rotation of the tire, and magnetic detection of tire rotation was possible. It turns out.

However, the fact that a plurality of peaks are present during one rotation of the tire in the magnetic field pattern requires that the peaks be counted and the number of rotations of the tire be corrected by a factor of an integer. Since the number of peaks differs individually, it is necessary to set a correction value for each tire.

Therefore, if a signal corresponding to a certain number, for example, one pulse, is obtained per rotation by controlling the magnetization of the tire, magnetic detection of the rotation of the tire becomes easy.

An object of the present invention is to provide a method of magnetizing a tire suitable for detecting the magnetic rotation of a tire. In particular, a change in a magnetic field accompanying the rotation of the tire can be maximized. The purpose is to clarify the magnetization range angle. Another object of the present invention is to provide a method for obtaining a stable output waveform in a method for detecting a magnetic field of a tire.

[0011]

According to the present invention, in order to solve the above-mentioned problems, according to the present invention, a magnetic field due to the remanent magnetization of the steel belt of a tire having a steel belt embedded in the outer peripheral portion is detected from the outside, and the tire is mounted on the tire. A method of magnetizing a tire for detecting rotation, wherein a magnetizing magnet is brought into contact with or close to the outer peripheral surface of the tire so that a magnetic field generated by the magnet follows a circumferential direction of the tire. A first magnetizing step in which the magnet is relatively moved along the circumferential direction of the tire to continuously magnetize in one direction along the circumferential direction over the entire circumference of the outer peripheral portion of the tire; and Is reversed in the circumferential direction of the tire, and the magnet is relatively moved along the circumferential direction of the tire by bringing the magnet into contact with or near the outer circumferential surface of the tire, thereby reducing the predetermined angle smaller than 360 ° of the outer circumferential portion of the tire. Corner He was employed magnetizing method of the tire comprising a second magnetizing step of re-magnetized in the direction opposite the direction of extent of the continuously.

According to this method, the first magnetization step resets the random remnant magnetization initially applied to the steel belt of the tire, and then sets the remnant magnetization within a predetermined angle range in the second magnetization step. By doing so, a stable magnetic field pattern can be obtained. In particular, the smaller angle in the respective angle ranges of the remanent magnetization in the direction opposite to the one direction on the outer peripheral portion of the tire magnetized in the first and second magnetization steps is 30 ° to 1 °.
If the angle is set within the range of 80 °, more preferably within the range of 55 ° to 105 °, the determination range in setting the threshold value of the magnetic sensor output for detecting the rotation of the tire can be widened, It can be made strong against the level fluctuation of the magnetic sensor output due to the external disturbance magnetic field at the time of the detection operation.

As a magnetizing method different from the above, there is a first method.
In the magnetizing step, the outer peripheral portion of the tire is magnetized continuously in one direction along the circumferential direction at a predetermined angle smaller than 360 °, and in the second magnetizing step, at least the first outer peripheral portion of the tire is formed in the outer peripheral portion of the tire. An unmagnetized portion that has not been magnetized in the magnetizing step may be magnetized continuously in the direction opposite to the one direction.

Further, according to the present invention, the entire circumference of the outer peripheral portion of the tire is divided into four ranges of 90 °, and the respective ranges are alternately arranged in opposite directions along the circumferential direction of the tire. A method of magnetizing a tire to be magnetized was also adopted.

In the case of this method, specifically, the first method
And the second magnetization step is performed, and the angle of the range of magnetization in the second magnetization step is set to 90 °. After the second magnetizing step, a 90 ° range that is point-symmetrical to the 90 ° range magnetized in the second magnetizing step at the outer peripheral portion of the tire is formed in the same manner as the second magnetizing step. A third magnetization step of continuously re-magnetizing in the direction opposite to the one direction is performed.

According to this magnetizing method, a magnetic field pattern having two peaks per rotation can be formed without reducing the amount of change in the magnetic field accompanying the rotation of the tire. A two-pulse signal can be generated stably.

According to the present invention, there is provided a tire magnetic field detecting method for differentially detecting a magnetic field due to residual magnetization of a steel belt of a tire magnetized by each of the above magnetizing methods using two magnetic detecting elements from outside. In the differential detection, the magnetic field detection directions of the two magnetic detection elements are both parallel to the side surface of the tire, and the two magnetic detection elements are perpendicular to the side surface of the tire. The method of arranging in parallel in the direction was adopted.

According to such a magnetic field detection method, even if the detection position is slightly different, the waveform and phase of the detection output corresponding to the magnetic field pattern from the tire do not change so much, and the optimum magnetic field setting can be directly output. Can be reflected.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a tire magnetizing method and a tire magnetic field detecting method according to the present invention.

[Embodiment of Tire Magnetization Method] First, an embodiment of a tire magnetization method will be described. In the magnetizing method according to the present embodiment, first, as a first magnetizing step, one direction along the circumferential direction continuously over the entire circumference of the outer peripheral portion of the tire 10 including the steel belt inside the outer peripheral portion shown in FIG. Magnetized.

For this purpose, as shown in FIG.
A magnetizing magnet 12 is brought into contact with or close to the outer peripheral surface of
The magnet 12 is rotated 360 times along the circumferential direction of the tire 10.
相 対 Relative movement is required. That is, the magnet 12 itself is moved one or more turns along the outer peripheral surface of the tire 10, or the tire 10 is rotated one or more turns without moving the magnet 12. Here, as shown in the enlarged view of FIG.
The S pole is arranged so as to extend in the circumferential direction of the tire 10, that is, in the direction of relative movement, so that the magnetic field Hw generated by the magnet 12 is applied to the steel belt below the tire outer peripheral portion along the circumferential direction of the tire 10.

Preferably, the tire 10 is magnetized over the entire width of the outer peripheral surface. Therefore, when the width of the magnet 12 arranged as shown in FIGS. 1 and 2 is smaller than the width of the outer peripheral surface of the tire 10, the magnet 12 is moved in the width direction of the outer peripheral surface of the tire 10 as indicated by an arrow in FIG. (The axial direction of the tire 10), and the magnet 12 is moved relative to the tire 10 by at least two rotations in the circumferential direction.
The magnet is magnetized over the entire width of the outer peripheral surface of the tire 10. However,
It is not always necessary to magnetize over the entire width of the tire outer peripheral surface, and it is possible to magnetize a portion of the tire outer peripheral surface, for example, about の of the full width near the magnetic sensor described later.

The relative movement direction of the magnet 12 and the tire 10 may be one direction along the circumferential direction of the tire 10 or may be reciprocated in both directions as two directions along the circumferential direction.

When magnetizing the tire with the tire mounted on the vehicle, the target tire is floated by a jack, a magnet for magnetizing is applied to the tire outer peripheral surface, and the tire is rotated by hand. The magnet can be easily magnetized by first rubbing the magnet on the outer peripheral surface of the tire other than the ground contact portion with a magnet without jacking up, and then moving the vehicle a little and rubbing the remaining portion to magnetize. .

As described above, by the first magnetizing step,
The tire is continuously magnetized in one direction along the circumferential direction over the entire circumference of the outer peripheral portion of the tire, and the residual magnetization originally held by the tire is re-magnetized in one direction and reset.

Here, there is a method of completely demagnetizing the initial remanent magnetization by applying an AC attenuating magnetic field to the tire. However, the completely demagnetized steel belt portion is easily magnetized, and the magnetism is randomly magnetized by an external magnetic field. It is not suitable because noise caused by the generation is a problem.

Next, as a second magnetizing step, as shown in FIG. 3, the polarity of the magnetizing magnet 12 is reversed with respect to the circumferential direction of the tire 10 so that the magnet 12 abuts on the outer peripheral surface of the tire 10. By causing the tire 10 to approach and relatively move along the circumferential direction of the tire 10, a range of a predetermined angle θ smaller than 360 ° of the outer peripheral portion of the tire 10 is continuously formed in a direction opposite to the magnetization direction of the first magnetization step. Re-magnetize. Thereby, magnetization for detecting the rotation of the tire 10 can be performed magnetically, and a magnetic field which can be easily detected by the magnetic sensor can be generated.

Here, the angle θ of the second magnetization influences the pattern and magnitude of the generated magnetic field, and there is an optimum angle. The result of studying the optimum value will be described below.

First, in the study, the angle θ of the second magnetization was set to 2
The magnetic field along the circumferential direction at a distance of 20 cm from the outer periphery of the tire was measured by changing the angle by 2.5 ° and rotating the tire magnetized at each angle, and the pattern was examined. The magnets used had an NS pole spacing of 2 mm and a magnetizing magnetic field Hw of about 200 Gauss at a location 10 mm from the magnetized facing surface. FIG. 4 shows the results. The horizontal axis of the data is the time axis, and the rotation of the tire at the time of measurement varies because it is not constant, but one rotation can be recognized from a periodic pattern.

Looking at the magnetic field pattern, when the angle θ is 90 ° or less, it has a sharp peak below, and when θ = 90 °, the change in the magnetic field is largest. As a matter of course, if the polarity of the magnetization is reversed, the peak will be sharpened upward. 9 more
When the angle exceeds 0 °, a sharp peak is dented, and the concavity becomes deeper as the angle increases.

To detect the magnetic field generated from the tire and to detect the rotation of the tire, a predetermined threshold value is set. However, considering that a level variation occurs in the magnetic field pattern from the tire due to the external magnetic field, It is necessary that the setting range of the threshold can be set widely. The discrimination width, which is a range suitable for setting the threshold, is such that when the magnetization angle θ is about 90 ° or less, the distance between the lower peak and the bottom of the upper dent is L.
(See the figure of 67.5 °), and when the magnetization angle exceeds 90 ° and a dent occurs in the peak that is pointed downward, L ′ (see the figure of 157.5 °) between the upper and lower dents It becomes the discrimination width.

FIG. 5 is a graph showing the discrimination widths L and L '. From this graph, it can be seen that 90 ° is the optimum magnetization angle. Also, considering the practical range,
In the region where the magnetization angle θ is small, the magnetic field generated from the tire is small and the influence of the disturbance magnetic field is large. Therefore, if the practical range is 50% of the maximum discrimination width, the magnetization angle θ is 30 ° to 180 °. Are suitable. Furthermore, if the optimum range is set to 80% of the maximum discrimination width, the range from 55 ° to 105 ° corresponds, and a more stable magnetic field can be obtained.

Although the angle range has been described up to 180 °, the second magnetization angle θ is 180 °.
Is exceeded, it is symmetrical only by reversing the polarity.
The angle 360 ° -θ of the remanent magnetization of the first magnetization in which the second magnetization was not performed can be considered in the same manner as described above. That is, the range of the optimum magnetization angle described above is the first range.
And the smaller of the angles of the remanent magnetization in the direction opposite to the one direction and the direction of the residual magnetization in the outer peripheral portion of the tire magnetized in the second magnetizing step.

In the tire magnetizing method described so far, the description has been made on the assumption that the tire is magnetized with a magnetic field along the circumferential direction of the tire. There is a concern that optimal conditions for magnetization by the circumferential magnetic field may be maintained due to the fact that the magnetization is not necessarily in the circumferential direction and the magnetic field direction changes depending on the detection position due to the arc shape of the magnetization. However, according to the results of the actual study, the optimal conditions observed in the magnetization by the circumferential magnetic field were
It has been found that it can be applied even under the conditions actually used. The details of the study will be described below.

When the magnetic field from the tire is detected by a magnetic sensor, it is considered that a suitable place for installing the sensor is a trunk room on the back side of the tire in the case of an ordinary passenger car. It is conceivable to arrange the sensor on the XY plane as shown in b).

In the study, a tire having a diameter of 60 cm was used, and X
Height H from the Y plane to the tire top is 10 cm, XZ
The distance S between the plane and the tire side was set to 15 cm. Also,
In the magnetization of the tire, the angle range θ of the smaller one of the two residual magnetizations at the outer periphery of the tire in the first and second magnetization steps was set to 90 ° by the method described above. The magnetic field detection direction is the Z-axis direction, and is indicated by A, B, C, D, and E on the X-axis in the figure.
The state of the magnetic field change due to the rotation of the tire was measured at each point at 0 cm intervals.

The result is shown in FIG. 7, and when compared with the data of the angle θ = 90 ° described in FIG. 4, the waveform at point A is such that the phase is differentiated by 90 °. As the point approaches the outer point D, the magnetic field and the waveform in the outer peripheral direction become similar. Thus, it is understood that the phase change is influenced by the angle between the magnetization direction of the tire outer peripheral portion closest to the measurement point and the Z-axis direction which is the magnetic field detection direction.

At points A to E, there is a change in phase in the waveform, but the peak at the lower end is stably output once per revolution, and the discrimination width L between the peak and the upper peak is small. Obtained stably. This indicates that the optimum condition of the magnetization viewed from the circumferential magnetic field is maintained.

Therefore, the method of magnetizing with the magnetic field along the circumferential direction of the tire is effective for any position where the actual sensor is installed and the magnetic field detecting direction.

As described above, a method of magnetizing a tire that generates an optimal magnetic field for detecting rotation of a tire having a steel belt embedded in the outer peripheral portion is established, and an optimal angle range of magnetization is set. Was completed.

In the magnetizing method according to the above embodiment, the tire is magnetized continuously in one direction along the circumferential direction in the first magnetizing step over the entire circumference of the tire outer peripheral portion. Thus, a range of a predetermined angle smaller than 360 ° at the tire outer peripheral portion is continuously re-magnetized in the direction opposite to the one direction. On the other hand, as a second magnetizing method, the arrangement of magnetizing magnets,
The direction of the generated magnetic field, the relative movement, the method of reversing the polarity of the magnet, and the like are the same as described above, and in the first magnetization step, a range of a predetermined angle smaller than 360 ° of the outer peripheral portion of the tire is continuously circumferentially set. In the second magnetizing step, the non-magnetized portion which has not been magnetized in the first magnetizing step is continuously formed in the outer peripheral portion of the tire in the direction opposite to the one direction. It may be magnetized. However, since it is not easy to accurately magnetize only the unmagnetized portion, the magnetized portion may be magnetized including the portion adjacent to the unmagnetized portion. Also in the second magnetization method, the setting of the optimum angle range of 30 ° to 180 °, particularly 55 ° to 105 ° for the smaller angle of the residual magnetization in the two directions described above applies.

However, the magnetizing operation is easier and more efficient with the method of the embodiment described above than with the second magnetizing method.

[Embodiment of Tire Magnetic Field Detecting Method] Next, an embodiment of a tire magnetic field detecting method for detecting a magnetic field of a tire magnetized by the above-described magnetizing method according to the present invention will be described. In particular, the optimum arrangement of the magnetic detection elements when detecting the magnetic field of the tire with the magnetic sensor will be described.

As an element for detecting a magnetic field from a tire, any of a flux gate sensor, a magnetic impedance element, a Hall element and the like may be used as long as it has a practical sensitivity of about several milligauss. Because of the influence of external magnetic field, for example, the magnetic field from an adjacent passing vehicle, the magnetic field from the residual magnetization of the reinforcing steel around the road, the steel frame, etc., only the magnetic field from the tire can be generated by the differential operation of the two magnetic detecting elements. Only be able to detect. However, in this differential detection, if the two magnetic detection elements are not properly arranged, the phase will greatly change due to the detection of the magnetic field from the tire, making it difficult to set the threshold value and making it difficult to handle.

Therefore, in the present embodiment, it is intended to define the positional relationship when detecting the magnetic field of the tire with respect to the two magnetic detecting elements upon differential detection.

The conditions regarding the arrangement of the elements are as follows: (1) One large positive or negative sharp peak is obtained for one rotation of the tire in the detection output.

(2) The judgment width L for setting the above-mentioned threshold value in the detection output can be widened.

(3) The conditions (1) and (2) do not greatly vary depending on the installation position of the magnetic sensor composed of two magnetic detecting elements.

(1) and (2) are for maintaining the optimum conditions for the magnetization of the tire, and (3) is for the purpose of simplifying the installation of the magnetic sensor without requiring precision in the installation position. is there.

The optimization of the arrangement of the two magnetic sensing elements was determined by the following study.

In examining the arrangement of the two magnetic detecting elements for differential detection, the magnetic sensors are placed at the measurement points A, B, C, and D in the positional relationship of the coordinates described with reference to FIGS. And the two magnetic sensing elements used in the sensor are separated by 3
The comparison was made between an arrangement arranged in parallel along the X-axis direction and an arrangement arranged in parallel along the Y-axis direction.
A magnetic impedance element was used as the magnetic detection element used in the study, and was configured to have a magnetic field detection sensitivity in the Z direction, that is, a direction parallel to the side surface of the tire 10.

FIG. 8 shows the results. In the case where the detection output waveforms are arranged in parallel along the X-axis direction, the phase of the detected output waveform changes drastically at each point from A to D, the waveform changes, and the threshold value is changed. The determination width L to be set is not constant and needs to be adjusted according to the installation location of the magnetic sensor, which is not practical.

Compared with this, when arranged in parallel in the Y-axis direction, that is, in the direction perpendicular to the side surface of the tire, the peak at the lower end of the detected output waveform is stable at each measurement point, and the influence of the phase change is the same. Only the magnitude of the peak appearing in the threshold value changes, the determination width L for setting the threshold value is stable.
This indicates that the optimum condition of magnetization by the magnetic field along the circumferential direction is maintained, and it is not necessary to finely adjust the threshold value depending on the installation location of the magnetic sensor, and it is extremely easy to handle.

Therefore, as shown in the perspective view of FIG. 9, using the tire 10 magnetized by the above-described magnetizing method according to the present invention, the magnetic field emitted from the tire 10 to the outside is detected by two magnetic sensors 14. When the differential detection is performed by the magnetic detection elements 16, the magnetic field detection directions of the two magnetic detection elements 16 are both parallel to the side surface of the tire 10, and the two magnetic detection elements 16 are By arranging the magnetic sensors 14 in parallel along the direction perpendicular thereto, it is clear that the magnetic sensors 14 can be easily installed, and that the discrimination width for setting the threshold value in the detected output waveform can be widened and stably obtained. Became.

[Other Embodiments of Tire Magnetization Method] The above-described embodiment of the tire magnetization method aims at supplying one pulse signal to the car navigation body for one rotation of the tire. If two pulses are output in one rotation of the tire, the unit of one pulse is 1 from one rotation of the tire.
Since the rotation is equivalent to / 2 rotation, an error due to an output pulse error due to an external magnetic field which becomes a disturbance, a tire vibration, an impact, or the like can be reduced. For example, for a tire with a diameter of 60 cm,
The accuracy of measuring the moving distance by one pulse is improved from 1.88 m to 0.94 m. In addition, when the moving distance is obtained by speed calculation in the car navigation body, for example, when the speed calculation process is obtained by the number of pulses per second, the error increases when the number of pulses per rotation is small, and the error increases when driving at low speed. However, this point can also contribute to improvement in accuracy.

Therefore, a method of magnetizing a tire that enables stable generation of a two-pulse signal for one rotation of the tire has been considered. The embodiment will be described below.

In the magnetizing method of this embodiment, first, the first and second magnetizing steps in the embodiment of the tire magnetizing method described above are sequentially performed. However, the angle of the re-magnetization range in the second magnetization step is 90 °. Further, as described above, in the first magnetizing step, the unmagnetized portion is not magnetized over the entire outer periphery of the tire, and the unmagnetized portion is magnetized in the second magnetizing process. However, in this case, the angle of the range of magnetization in the first magnetizing step is set to an angle larger than 270 ° and smaller than 360 °, and in the second magnetizing step, all of the unmagnetized portion is Magnetize the range of 90 ° including it.

Next, a third magnetizing step is performed. In this step, the outer circumference of the tire is rotated by 180 ° on the opposite side of the center of the tire from the 90 ° range magnetized in the second magnetization step. The 90 ° range that is point-symmetric with respect to the 90 ° range magnetized in the magnetizing step is continuously formed along the circumferential direction in the same manner as the second magnetizing step in the same direction as the second magnetizing step, that is, Re-magnetization is performed in a direction opposite to the magnetization direction of the first magnetization step. The magnetization is completed in the third magnetization step.

FIG. 11 shows the magnetized state of the tire after magnetizing by such a magnetizing method. According to the magnetization method of the present embodiment, as shown here, the entire circumference of the outer peripheral portion of the tire 10 is set to 9 by indicating the range and direction of the residual magnetization in the first to third magnetization steps.
It is divided into four ranges of 0 °, and a magnetized state is formed in which the respective ranges are alternately magnetized in the opposite direction along the circumferential direction of the tire.

Next, based on the measurement results of the magnetic field along the circumferential direction of the outer periphery of the tire magnetized in the above embodiment, the magnetic field pattern of the tire after the completion of the second magnetization step and the end of the third magnetization step The subsequent magnetic field patterns are shown in FIGS.

The magnetic field pattern after the completion of the third magnetizing step is
Although the heights of the peaks are slightly different, the waveform has two peaks for one rotation of the tire. The magnitude of the change in the magnetic field is almost the same as that after the completion of the second magnetization step, and it can be seen that good magnetization is possible.

According to the magnetizing method of the present embodiment, in detecting the magnetic rotation of the tire magnetized by this method, it is possible to stably generate a signal of two pulses for one rotation of the tire. Becomes Therefore, it is possible to reduce the error of the measurement of the moving distance of the vehicle by detecting the rotation of the tire, and to improve the accuracy of the self-contained navigation of the car navigation.

When a magnetic field is detected for detecting the rotation of a tire magnetized by the method of the present embodiment, the arrangement of the two magnetic detecting elements in the above-described embodiment of the tire magnetic field detecting method is optimal. Of course, the detection method of the embodiment can be applied as it is.

[0064]

As is apparent from the above description, according to the present invention, the rotation of the tire is detected by externally detecting the magnetic field due to the residual magnetization of the steel belt of the tire having the steel belt embedded in the outer peripheral portion. A magnetizing method for the tire, wherein the magnetizing magnet is brought into contact with or close to the outer peripheral surface of the tire so that the magnetic field generated by the magnet is along the circumferential direction of the tire, and the magnet is moved in the circumferential direction of the tire. The first magnetizing step continuously magnetizes the entire circumference of the outer peripheral portion of the tire in one direction along the circumferential direction, and then performs the second magnetizing step. The magnetizing method for re-magnetizing a range of a predetermined angle smaller than 360 ° of the outer peripheral portion of the tire continuously in the direction opposite to the one direction, and the first magnetizing step allows the outer peripheral portion of the tire to be rotated 360 °. Smaller predetermined angle range After being continuously magnetized in one direction along the circumferential direction, a non-magnetized portion not magnetized in at least the first magnetizing step is continuously formed on the outer peripheral portion of the tire by the second magnetizing step. Since the magnetizing method of magnetizing in the one direction and the opposite direction is employed, a periodic magnetic field can be generated from the tire stably for one rotation of the tire. In the rotation detection, it is possible to stably obtain a signal of one pulse for one rotation of the tire, and it is possible to provide a magnetization method suitable for detecting the magnetic rotation of the tire.

In the above magnetizing method, in particular, the first
And the smaller angle in the respective angle ranges of the remanent magnetization in the direction opposite to the one direction of the outer peripheral portion of the tire magnetized by the second magnetizing step is in the range of 30 ° to 180 °, more preferably 55 °. By setting the angle to be within the range of 105 °, a wide margin can be set in setting the threshold value of the magnetic sensor output for detecting the rotation of the tire, and the magnetic sensor against external disturbance magnetic field during the detection operation can be set. It can be made strong against output level fluctuation.

According to the present invention, in the method for magnetizing a tire, the entire circumference of the outer peripheral portion of the tire is divided into four ranges of 90 ° each, and each range is alternately arranged along the circumferential direction of the tire. Since the method of magnetizing in the opposite direction is adopted, a magnetic field pattern having two peaks for one rotation of the tire can be generated in a change in the magnetic field according to the rotation of the tire. In detecting the magnetic rotation of the tire, it becomes possible to stably obtain a signal of two pulses for one rotation of the tire, thereby reducing the measurement error of the moving distance of the vehicle due to the detection of the rotation of the tire, and enabling auto navigation of the car navigation system. Accuracy can be improved.

Further, according to the present invention, a tire magnetic field detecting method for differentially detecting a magnetic field due to residual magnetization of a steel belt of a tire magnetized by each of the above-described magnetizing methods using two magnetic detecting elements from outside. In the differential detection, the magnetic field detection directions of the two magnetic detection elements are both parallel to the side surface of the tire, and the two magnetic detection elements are perpendicular to the side surface of the tire. Because the method of arranging in parallel in the direction was adopted, even if the detection position is slightly different,
The waveform and phase of the detection output do not change much, and the margin for setting the above threshold can be stably obtained.
Installation of a magnetic sensor including two magnetic detection elements can be facilitated.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a first magnetization step in an embodiment of a tire magnetization method according to the present invention.

FIG. 2 is an enlarged view in which main parts of FIG. 1 are enlarged.

FIG. 3 is a perspective view illustrating a second magnetizing step in the embodiment.

FIG. 4 is a waveform chart showing respective generated magnetic field patterns of the tire according to the difference in the magnetization angle θ in the second magnetization step.

FIG. 5 is a graph showing discrimination widths L and L ′ for setting a rotation detection threshold value of a magnetic field detection output according to the magnetization angle θ.

6A and 6B are a top view and a side view showing respective positions of magnetic field measurement points with respect to a tire in a study of the effectiveness of the magnetizing method of the embodiment with respect to the actual arrangement of the magnetic sensors.

FIG. 7 is a waveform chart showing a magnetic field change due to tire rotation at each measurement point in FIG.

FIG. 8 is a waveform chart of a table showing a relationship between the arrangement of elements and a detection output waveform when differential detection is performed by two magnetic detection elements, according to an embodiment of the tire magnetic field detection method according to the present invention. is there.

FIG. 9 is a perspective view showing an arrangement of two magnetic sensing elements determined in the same embodiment.

FIG. 10 is a waveform diagram showing a result of measuring a magnetic field change accompanying rotation of a naturally magnetized steel radial tire.

FIG. 11 is an explanatory view showing a magnetized state of a tire in another embodiment of the tire magnetizing method according to the present invention.

FIG. 12 is a waveform chart showing a magnetic field pattern of a tire after completion of a second magnetization step and after completion of a third magnetization step of the embodiment.

[Explanation of symbols]

 Reference Signs List 10 tire 12 magnetizing magnet 14 magnetic sensor 16 magnetic detecting element

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 19/00

Claims (8)

(57) [Claims] 1. A method of magnetizing a tire for detecting rotation of the tire by externally detecting a magnetic field due to residual magnetization of the steel belt of a tire including a steel belt on an outer peripheral portion, the method comprising: The magnet is brought into contact with or close to the outer peripheral surface of the tire, and the magnetic field generated by the magnet is moved along the circumferential direction of the tire, and the magnet is relatively moved along the circumferential direction of the tire. A first magnetizing step of continuously magnetizing in one direction along the circumferential direction over the entire circumference of the portion, and after the step, reversing the polarity of the magnet in the circumferential direction of the tire, By relatively moving along the circumferential direction of the tire by contacting or approaching the outer circumferential surface, a range of a predetermined angle smaller than 360 ° of the outer circumferential portion of the tire is continuously re-magnetized in a direction opposite to the one direction. Second wear Magnetizing method of tire characterized by comprising the step. 2. A method of magnetizing a tire for detecting rotation of the tire by externally detecting a magnetic field due to residual magnetization of the steel belt of a tire having a steel belt embedded in an outer peripheral portion, the method comprising: The magnet is brought into contact with or close to the outer peripheral surface of the tire, and the magnetic field generated by the magnet is moved along the circumferential direction of the tire, and the magnet is relatively moved along the circumferential direction of the tire. A first magnetizing step of continuously magnetizing a predetermined angle range smaller than 360 ° of the portion in one direction along the circumferential direction, and after the step, reversing the polarity of the magnet with respect to the circumferential direction of the tire, The magnet is brought into contact with or close to the outer peripheral surface of the tire and relatively moved along the circumferential direction of the tire, so that at least the first magnetizing step has not performed the non-magnetization on the outer peripheral portion of the tire. Part of Magnetizing method of the tire, characterized in that continuously and a second magnetized step of magnetizing the one direction and the opposite direction. 3. The smaller angle in the respective angle ranges of the remanent magnetization in the direction opposite to the one direction on the outer peripheral portion of the tire magnetized in the first and second magnetization steps is 30 ° to 180 °.
2. The method according to claim 1, wherein the angle is within the range of ゜.
Or the method of magnetizing a tire according to 2. 4. An outer peripheral portion of the tire magnetized in the first and second magnetizing steps, wherein the smaller angle in the respective angle ranges of the remanent magnetization in the direction opposite to the one direction is from 55 ° to 105 °.
2. The method according to claim 1, wherein the angle is within the range of ゜.
Or the method of magnetizing a tire according to 2. 5. A method of magnetizing a tire for detecting rotation of the tire by externally detecting a magnetic field due to residual magnetization of the steel belt of a tire having a steel belt included in an outer peripheral portion, the method comprising: A method of magnetizing a tire, comprising dividing an entire circumference of an outer peripheral portion into four ranges of 90 °, and magnetizing the respective ranges so as to be alternately in opposite directions along a circumferential direction of the tire. 6. A magnetizing magnet is brought into contact with or close to the outer peripheral surface of the tire, and the generated magnetic field of the magnet is arranged along the circumferential direction of the tire. A first magnetizing step in which the magnet is continuously moved in one direction along the circumferential direction over the entire circumference of the outer peripheral portion of the tire; and after the first magnetizing step, the polarity of the magnet is changed to the tire By inverting with respect to the circumferential direction, the magnet is brought into contact with or close to the outer circumferential surface of the tire and relatively moved along the circumferential direction of the tire, so that the 90 ° range of the outer circumferential portion of the tire is continuously A second magnetizing step of re-magnetizing in the direction opposite to the one direction, and after the second magnetizing step, the outer peripheral portion of the tire has a 90 ° range re-magnetized in the second magnetizing step. A 90 ° range that is point-symmetric is continuously formed in the same manner as in the second magnetizing step. Magnetizing method of tire according to claim 5, characterized in that it consists of a third magnetizing step of re-magnetized in one direction and the opposite direction. 7. A magnetizing magnet is brought into contact with or close to the outer peripheral surface of the tire, and the generated magnetic field of the magnet is arranged along the circumferential direction of the tire. A first magnetization step of continuously magnetizing a range of an angle greater than 270 ° and smaller than 360 ° in the outer peripheral portion of the tire in one direction along the circumferential direction by moving the tire; After the step, the polarity of the magnet is reversed with respect to the circumferential direction of the tire, and the magnet is brought into contact with or close to the outer circumferential surface of the tire and relatively moved along the circumferential direction of the tire, so that in the outer circumferential portion of the tire, 9 including all non-magnetized portions not magnetized in the first magnetizing step
A second magnetization step of continuously magnetizing a range of 0 ° in the direction opposite to the one direction, and after the second magnetization step, magnetizing the outer peripheral portion of the tire in the second magnetization step. A third magnetization step of continuously re-magnetizing the 90 ° range point-symmetric to the 90 ° range in the direction opposite to the one direction by the same method as the second magnetization step. The tire magnetization method according to claim 5, characterized in that: 8. A magnetic field due to residual magnetization of a steel belt of a tire magnetized by the method for magnetizing a tire according to any one of claims 1 to 7, which is differentially detected by two magnetic detecting elements from outside. A method for detecting a magnetic field of a tire to be detected, wherein at the time of the differential detection, magnetic field detection directions of the two magnetic detection elements are both parallel to a side surface of the tire, and the two magnetic detection elements are A method for detecting a magnetic field of a tire, wherein the tires are arranged in parallel in a direction perpendicular to a side surface of the tire.