WO2021201095A1 - Wear measurement device for tire and embedded pin for wear measurement device - Google Patents

Abstract

This wear measurement device 10 for a tire 20 is for measuring the degree of wear of the tire 20 on the basis of the magnetic field M1 of a first magnetic body 11 and comprises a shield part 15 that is embedded in a tread part 22 and wears together with the tread part 22 and a first magnetic field detection unit 13 that is provided at a position where a magnetic field m1 that is within the magnetic field M from the first magnetic body 11 and is detected after passing through the shield part 15 changes as a result of the wear of the shield part 15 together with the tread part 22. As a result, the wear measurement device for a tire is capable of accurately detecting the wear of a tire while suppressing the effect of the magnetic field of the earth and other external magnetic fields.

Description

Embedded pins for tire wear measuring devices and wear measuring devices

The present invention relates to a wear measuring device for detecting tire wear based on a magnetic field and an embedded pin for the wear measuring device.

As tire wear progresses, the grip performance when traveling on a road surface and the drainage performance for draining water between the tire and the road surface when traveling on a wet road surface deteriorate. Therefore, the driver or the vehicle manager visually inspects the worn state of the tread of the tire and replaces the tire before the usage limit is exceeded in order to ensure safety. A slip sign provided in the groove of the tire is used for the visual inspection, but the inspection work is complicated and there is a possibility that the evaluation of the wear state may be erroneous. If the evaluation is incorrect, the tire with deteriorated performance will continue to be used, which is not preferable from the viewpoint of safety.
Therefore, a method of measuring the degree of tire wear by a method other than visual inspection has been proposed. For example, Patent Document 1 describes a method of embedding a magnet in a tread, detecting the magnetic field of the embedded magnet using a magnetic field detection unit arranged in the tire, and evaluating the state of a groove and deterioration of the tire. There is.

U.S. Pat. No. 8240198

However, there are several layers of steel wire between the inner liner attached to the inner surface of the tire and the tread, for example, 4 to 5 layers for truck tires. There is a problem that the steel wire layer shields the magnetic field from the magnet embedded in the tread and changes the magnetic field reaching the inside of the tire. However, if the magnetic field of the magnet is strengthened, it becomes a factor of attracting unnecessary objects such as iron pieces to the tire, and there is also a problem that the difference in flexibility between the magnet and the tire becomes large.

As mentioned above, the magnetic field of the magnet embedded in the tread cannot be made very large by the shield. Therefore, it can be said that the magnetic field detected by the wear detection device is easily affected by an external magnetic field other than the magnetic field from the magnet embedded in the tread. Examples of the external magnetic field include geomagnetism, and the influence of the geomagnetism changes every moment depending on the traveling direction of the vehicle, the direction of the tire, the rotation position, and the like. Therefore, when the tire wear amount is evaluated based on the value of the magnetic flux density measured by one magnetic field detection unit as in the method described in Patent Document 1, there is a problem that an error with respect to the actual wear amount becomes large. .. If the error with respect to the amount of wear becomes large due to the influence of noise or the like, there is also a problem that, for example, it is not possible to accurately detect the timing suitable for tire rotation (position exchange).
Therefore, an object of the present invention is to provide a tire wear measuring device and an embedded pin for the wear measuring device that can accurately detect tire wear by suppressing the influence of an external magnetic field such as geomagnetism.
Another object of the present invention is to provide a tire wear measuring device and an embedded pin for the wear measuring device, which can easily detect a timing suitable for tire rotation.

In one embodiment, in a tire wear measuring device that measures a degree of tire wear based on a magnetic field of a magnet, a shield portion embedded in a tread portion that shields the magnetic field from the magnet and the tread. Provided is a tire wear measuring device characterized by having a magnetic field detecting portion provided at a position where the magnetic field from the magnet changes due to wear of the shield portion together with the portion.
With this configuration, the degree of wear of the tire can be measured based on the magnetic field that changes with the change of the shield portion that wears together with the tread portion of the tire.

The magnetic field detection unit is provided on the inner surface of the tire on the back side of the tread portion, the magnet is provided at a position of the vehicle body facing the tread portion, and the shield portion is the shield portion. It may be provided between the magnetic field detection unit and the magnet.
Further, the magnetic field detection unit is provided at a position of the vehicle body facing the tread portion, the magnet is provided on the inner surface of the tire on the back side of the tread portion, and the shield portion is provided. , May be provided between the magnetic field detection unit and the magnet.
By providing a magnet on the vehicle body instead of the tread portion, it is possible to prevent metals and the like from being attracted to the tire surface. Further, by providing a magnet on the back side of the tread portion, the magnetic field on the tire surface can be suppressed. Therefore, a stronger magnet can be used than when it is embedded in the tread portion. Therefore, the shielding effect of the shield portion changes due to the wear of the shield portion together with the tread portion. Therefore, the magnetic field detected by the magnetic field detection unit also changes, and the progress of tire wear can be accurately measured based on the magnetic field.

When a magnet is provided on the vehicle body or the back side of the tread portion, the reference magnetic field detection provided at a position where the reference magnet and the shield portion together with the tread portion are not affected by wear and the magnetic field from the reference magnet does not change. It is preferable to have a portion.
By taking the difference between the first detected value detected by the magnetic field detector and the second detected value detected by the reference magnetic field detector and removing the influence of the external magnetic field, the progress of tire wear can be accurately measured. Can be measured.
In this case, it is preferable that the magnetic field detection unit and the reference magnetic field detection unit are provided at positions symmetrical with respect to the center line of the width of the tire. As a result, the wear measuring device can be arranged in a well-balanced manner, so that the wheel balance can be easily stabilized.

In the wear measuring device, the magnet has a first magnet and a second magnet, and the shield portion is sandwiched between the first magnet and the second magnet. The first magnet and the second magnet are embedded in the tread portion, and the first magnet, the shield portion, and the second magnet are arranged side by side in the radial direction of the tire in this order. It may have been done.
With this configuration, it is possible to easily detect that the tire wear degree has reached a predetermined threshold value based on the change in the magnetic field due to the member exposed on the surface of the tread portion as the tire wear progresses. For example, when the first magnet is worn and the shield portion appears, the magnetic field of the magnet detected by the magnetic field detection unit can be eliminated. In this way, it is possible to detect that the wear of the tread portion has reached a predetermined threshold value depending on whether or not the magnetic field from the magnet is detected.

When the magnet has a first magnet and a second magnet, the tread portion is an embedded pin having the first magnet, the shield portion, and the accommodating portion in which the second magnet is housed. The storage portion is provided with a tubular portion for accommodating the first magnet, the shield portion, and the second magnet, and the inside of the tubular portion is the said. The shield portion may be arranged between the first magnet and the second magnet. Further, the storage portion may include an engaging protrusion that protrudes from the outer peripheral surface of the tubular portion.
By providing the engaging protrusion in the storage portion, the state in which the embedded pin is embedded in the tire can be stably maintained.

The magnetic pole on the shield portion side of the first magnet and the magnetic pole on the shield portion side of the second magnet may be the same.
With this configuration, it is possible to detect whether the first magnet or the second magnet is exposed on the surface of the tire by the direction of the magnetic field. Therefore, it becomes possible to more clearly measure the degree of progress of tire wear.

Further, the wear measuring device may include a plurality of the embedded pins.
By using a plurality of embedded pins, the reliability of the wear measuring device can be improved, and the wear state of the tire at different positions can be measured.

In another aspect of the present invention, the present invention includes a first magnet, a shield portion, a second magnet, and a storage portion, and the storage portion is the first magnet, the shield portion, and the second. A tubular portion for accommodating a magnet is provided, and inside the tubular portion, the shield portion is arranged between the first magnet and the second magnet. An embedded pin for a measuring device is provided.
The accommodating portion may include an engaging protrusion that protrudes from the outer peripheral surface of the tubular portion. The engaging protrusion can stably hold the state in which the buried pin is embedded in the tire.

The tire wear measuring device of the present invention can accurately measure tire wear by detecting a magnetic field that changes with a change in the shield due to wear of the tread portion.

A cross-sectional view illustrating a state in which the wear measuring device according to the first embodiment is provided on the tire. A graph schematically showing the relationship between the amount of tire wear and the detected magnetic field A cross-sectional view illustrating a modified example of the wear measuring device. A cross-sectional view illustrating a modified example of the wear measuring device. (A) A cross-sectional view illustrating the tire wear measuring device according to the second embodiment, (b) A cross-sectional view illustrating an embedded pin having a storage portion in which a first magnet, a shield portion, and a second magnet are housed. figure FIG. 5 (b) shows a state in which the embedded pin has changed due to wear of the tread portion, (a) a cross-sectional view in an initial state in which the first magnet appears on the surface, and (b) a shield portion appears on the surface. Cross-sectional view of the state, (c) Cross-sectional view of the state where the shield portion is worn and the second magnet appears on the surface. (A) Graph of output waveform in the state of FIG. 6 (a), (b) Graph of output waveform in the state of FIG. 6 (b), (c) Graph of output waveform in the state of FIG. 6 (c). A modified example of the embedded pin will be described (a) a cross-sectional view in an initial state where the first magnet appears on the surface, (b) a cross-sectional view in a state where the shield portion appears on the surface, and (c) the shield portion is worn. Cross-sectional view of the second magnet appearing on the surface (A) Graph of output waveform in the state of FIG. 8 (a), (b) Graph of output waveform in the state of FIG. 8 (b), (c) Graph of output waveform in the state of FIG. 8 (c). (A) Cross-sectional view, (b) Plan view for explaining a modified example of the wear measuring device. Graphs of output waveforms in the wear measuring devices of FIGS. 10 (a) and 10 (b). A cross-sectional view illustrating a state in which a conventional tire wear measuring device is provided on a tire.

[First Embodiment]
An embodiment of the present invention will be described below with reference to the drawings. In each figure, the same member is assigned the same number, and the description thereof will be omitted as appropriate.

FIG. 12 is a cross-sectional view illustrating a state in which a conventional tire wear measuring device is provided on a tire. As shown in the figure, in the tire wear measuring device 100, as the magnetic field detection unit 112 wears the first magnetic body 111 embedded in the tread portion 22 on the outer surface 21 of the tire 20, the tire wear measuring device 100 is shown in the drawing. The magnetic field M indicated by the broken line changes. By detecting the change in the magnetic field M, the wear state of the tread portion 22 is measured.

However, in an environment where the tire 20 is actually used, an external magnetic field G such as geomagnetism exists in addition to the magnetic field M. The external magnetic field G or the like becomes noise when measuring the magnetic field M, and causes a decrease in the measurement accuracy of the magnetic field M by the magnetic field detection unit 112. When the magnetic field detection unit 112 provided on the inner surface of the tire 20 measures the magnetic field M, the magnetic field M is changed by the steel wire layer 24 inside the tire 20. Therefore, the influence of the external magnetic field G in the measurement of the magnetic field M becomes large.

Therefore, the tire wear measuring device of the present embodiment is provided with two magnetic field detection units in order to eliminate the influence of the external magnetic field G. Hereinafter, the tire wear measuring device of the present invention will be described.

FIG. 1 is a cross-sectional view illustrating a state in which the tire wear measuring device according to the present embodiment is provided on the tire. As shown in the figure, the tire wear measuring device 10 includes a shield portion 15. The shield portion 15 is embedded in the tread portion 22 of the tire 20 and wears together with the tread portion 22. The wear measuring device 10 wears the tread portion 22 of the tire 20 based on the fact that the shielding effect of the first magnetic body 11 provided on the vehicle body 30 by the shield portion 15 on the magnetic field M1 changes with wear. Measure the degree. In other words, the wear measuring device 10 measures the degree of wear of the tread portion 22 of the tire 20 based on the change in the magnetic field M1 of the first magnetic body 11 detected by the first magnetic field detecting unit 13.

The first magnetic body 11 and the second magnetic body 12 are provided at positions facing the tread portion 22 on the vehicle body 30 and at positions symmetrical with respect to the center line C of the tire width (X-axis direction). By arranging the plurality of magnetic materials at equal intervals in this way, the wheel balance is further stabilized. Further, by using a plurality of magnetic materials, the redundancy of the wear measuring device 10 is improved.

Then, on the inner surface 23 of the tire 20, that is, the back side of the tread portion 22, a first magnetic field detection unit 13 for detecting the magnetic field M1 of the first magnetic body 11 and a second magnetic field for detecting the magnetic field M2 of the second magnetic body 12 are detected. A detection unit 14 is provided. However, in the initial state, the magnetic field M1 of the first magnetic body 11 is shielded by the shield unit 15, so that it is not detected by the first magnetic field detection unit 13. Then, as the shield portion 15 wears along with the tread portion 22 and the shielding effect of the shield portion 15 decreases, the magnetic field m1 of the magnetic field M1 that has passed through the shield portion 15 is detected by the first magnetic field detection unit 13.

The first magnetic field detection unit 13 and the second magnetic field detection unit 14 are located on the inner surface 23 of the tire 20 at positions that are strongly affected by the magnetic field M1 generated by the first magnetic body 11 and the magnetic field M2 generated by the second magnetic body 12, respectively. Have been placed. In the present embodiment, the first magnetic field detection unit 13 and the second magnetic field detection unit 14 are arranged directly above the first magnetic body 11 and the second magnetic body 12, that is, at positions where they overlap when viewed from the Y-axis direction.

Like the first magnetic body 11 and the second magnetic body 12, the first magnetic field detection unit 13 and the second magnetic field detection unit 14 are provided at positions symmetrical with respect to the center line C of the tire width (X-axis direction). There is. Therefore, the distance between the first magnetic body 11 and the second magnetic body 12 in the X-axis direction can be increased. Therefore, the first magnetic field detection unit 13 and the second magnetic body 12 are combined so that the first magnetic field detection unit 13 is not affected by the second magnetic body 12 provided adjacent to the first magnetic body 11 facing the first magnetic field detection unit 13. It becomes easy to secure the distance. Similarly, it becomes easy to secure the distance between the second magnetic field detection unit 14 and the first magnetic body 11.

For example, when the first magnetic field detection unit 13 is arranged at the center position of the tire width (X-axis direction), the distance between the first magnetic field detection unit 13 and the second magnetic body 12 in the X-axis direction is at most half the tire width. Is the distance. On the other hand, by arranging the first magnetic field detection unit 13 and the second magnetic field detection unit 14 at both ends of the tire width, the distance between the first magnetic field detection unit 13 and the second magnetic body 12 in the X-axis direction can be increased. It becomes possible to make it about the same as the width of the tire 20.

Since the first magnetic body 11 and the second magnetic body 12 are provided on the vehicle body 30, they do not become a factor of attracting unnecessary objects such as iron pieces to the tire 20. Therefore, since it is possible to use a material having a stronger magnetic field than the first magnetic material 111 embedded in the tread portion 22 of the tire 20 in the conventional wear measuring device 100 (see FIG. 12), the accuracy of wear measurement is improved.

The first magnetic field detection unit 13 is located at a position where the magnetic field of the first magnetic body 11 can be detected when the shield unit 15 provided between the first magnetic body 11 and the first magnetic field detection unit 13 is worn. It is provided. The shield portion 15 is embedded in a part of the tread portion 22 on the outer surface 21 of the tire 20, and wears as the tread portion 22 wears. Therefore, of the magnetic field M1 formed by the first magnetic body 11, the magnetic field m1 measured by the first magnetic field detection unit 13 increases with the wear of the tread portion 22.

On the other hand, since the shield portion 15 is not provided between the second magnetic body 12 and the second magnetic field detection unit 14, the second magnetic field detection unit 14 of the magnetic field M2 from the second magnetic body 12 detects the magnetic field M2. The magnetic field m2 to be generated is not affected by the wear of the shield portion 15 together with the tread portion 22, and does not change as the wear of the tread portion 22 progresses.

FIG. 2 is a graph schematically showing the relationship between the amount of tire wear and the detected magnetic field. As shown in the figure, as the wear of the tread portion 22 progresses, the magnetic field m1 detected by the first magnetic field detection unit 13 increases. Therefore, the wear of the tread portion 22 can be measured based on the change in the magnetic field m1. However, the magnetic field m1 is also affected by the external magnetic field G.

Therefore, the tire wear measuring device 10 of the present embodiment measures the magnetic field m2 affected by the external magnetic field G as in the magnetic field m1, and measures the wear of the tread portion 22 using the difference between the magnetic field m1 and the magnetic field m2. By doing so, the accuracy of wear measurement is improved. By using the difference between the magnetic field m1 detected by the first magnetic field detection unit 13 and the magnetic field m2 detected by the second magnetic field detection unit 14, the influence of the external magnetic field G can be removed. Therefore, it is possible to suppress a decrease in detection accuracy due to the influence of the external magnetic field G and accurately measure the wear of the tread portion 22 on the outer surface 21 of the tire 20. The first magnetic field detection unit 13 and the second magnetic field detection unit 14 measure the magnetic field using the magnetic flux density or the magnetic field strength.

The relative positional relationship between the first magnetic field detection unit 13 and the second magnetic field detection unit 14 with respect to the ground changes periodically with the rotation of the tire 20. Therefore, the influence of the geomagnetism on the detected value also changes periodically. Therefore, the first magnetic field detection unit 13 and the second magnetic field detection unit 14 are in the width direction (X-axis direction) of the tire 20 orthogonal to the rotation direction (Z-axis direction) of the tire 20 on the inner surface 23 of the tire 20. It is provided in parallel. Therefore, the opposite surface (outer surface 21) of the installation location of the first magnetic field detection unit 13 and the second magnetic field detection unit 14 comes into contact with the ground at the same time as the tire 20 rotates.

By providing the first magnetic field detection unit 13 and the second magnetic field detection unit 14 in parallel in the direction orthogonal to the rotation direction of the tire 20 as described above, the first magnetic field detection unit 13 and the second magnetic field detection unit 14 are provided. The relative positional relationship with the ground with respect to 14 changes in the same manner. Therefore, the first detection value (magnetic field m1) of the first magnetic field detection unit 13 and the second detection value (magnetic field m2) of the second magnetic field detection unit 14 measured at the same time have the same influence of the external magnetic field G. To receive. Therefore, by using the difference between the first detected value and the second detected value measured at the same time, the influence of the external magnetic field G can be removed from the first detected value.

The first magnetic field detection unit 13 and the second magnetic field detection unit 14 are provided with a magnetoresistive element that measures a magnetic field and changes the resistance depending on the direction and strength of the magnetic field. Examples of the magnetoresistive element include a GMR element and a TMR element. The measurement by the first magnetic field detection unit 13 and the second magnetic field detection unit 14 does not have to be performed continuously in real time, and may be performed intermittently at regular time intervals. Alternatively, the measurement may be performed in response to an external instruction received via a wireless communication means (not shown). By performing the measurement at regular time intervals or in response to instructions, power consumption can be suppressed as compared with continuous measurement. Further, a Hall element may be used as the magnetoresistive element which is the first magnetic field detection unit 13 and the second magnetic field detection unit 14, and the change in the strength of the magnetic flux may be measured.
Further, a magnetic impedance effect element may be used to measure the change in impedance due to the change in the magnetic field.

The first magnetic field detection unit 13 and the second magnetic field detection unit 14 are configured to be capable of detecting magnetic fields in three axial directions (X-axis, Y-axis, and Z-axis) that are orthogonal to each other. The first magnetic field detection unit 13 and the second magnetic field detection unit 14 may be configured by using three sensors for uniaxial detection.

The first magnetic field detection unit 13 and the second magnetic field detection unit 14 are arranged on the same plane, and their three sensitivity axes are arranged so as to face the same direction. For the magnetic field m1 detected by the first magnetic field detection unit 13 and the magnetic field m2 detected by the second magnetic field detection unit 14, differences are taken for each of the X-axis component, the Y-axis component, and the Z-axis component, and the combined magnetic magnetic field of the difference is obtained. Obtain and estimate the amount of wear. As a result, the wear of the tread portion 22 of the tire 20 can be detected with high accuracy.

The tire wear measuring device 10 outputs information on tire wear based on the measurement of the magnetic field by the first magnetic field detecting unit 13 and the second magnetic field detecting unit 14 to the vehicle side device or the like via wireless communication means or the like. You may. Information on the measurement results of the first magnetic field detection unit 13 and the second magnetic field detection unit 14 can be transmitted to the vehicle-side device or information from the vehicle-side device can be received via wireless communication. Information transmission / reception by communication between the tire wear measuring device 10 and an external device is controlled by a CPU (not shown).

[Modification 1]
FIG. 3 is a cross-sectional view illustrating a modified example of the tire wear measuring device according to the present embodiment. In the wear measuring device 40 shown in the figure, the first magnetic field detection unit 13 and the second magnetic field detection unit 14 are provided on the vehicle body 30, and the first magnetic body 11 and the second magnetic body 12 are the inner surface 23 of the tire 20. The configuration provided in the above is different from that of the wear measuring device 10 of FIG. Like the wear measuring device 10, the wear measuring device 40 wears the shield portion 15 together with the tread portion 22. As the shield portion 15 wears, its shielding effect is reduced. The wear measuring device 40 can measure the wear of the tire 20 by using the difference between the magnetic field m1 that changes as the shielding effect of the shield portion 15 decreases and the magnetic field m2 that does not change due to the wear of the tread portion 22.

[Modification 2]
FIG. 4 is a cross-sectional view illustrating a modified example of the tire wear measuring device according to the present embodiment. The tire wear measuring device 50 shown in the figure is different from the wear measuring devices 10 and 40 shown in FIGS. 1 and 3 in that it includes a control unit 51 and a storage unit 52.

The control unit 51 measures the degree of wear of the tire 20 based on the magnetic field m1, the magnetic field m2, and the table stored in the storage unit 52. The control unit 51 is composed of a CPU and the like.
The storage unit 52 stores a table used for calculating the amount of wear of the tread portion 22 of the tire 20 from the magnetic field m1 and the magnetic field m2, and a ROM (Read Only Memory) such as a mask ROM, EEPROM, or flash memory is used. Used.

[Second Embodiment]
In the case of an FF (front engine / front drive) vehicle, since the front wheels double as drive wheels and steering wheels, the tires mounted on the front wheels are more likely to wear than the tires mounted on the rear wheels. Further, in the case of an FF vehicle, the tire sizes of the front wheels and the rear wheels are often the same. Therefore, the tires of the front wheels and the rear wheels are rotated so that the amount of wear of each tire is adjusted to be equal. Hereinafter, embodiments of the present invention will be described as a tire wear measuring device suitable for notifying the timing of tire rotation.

FIG. 5A is a cross-sectional view illustrating the tire wear measuring device according to the present embodiment. As shown in the figure, in the wear measuring device 60 of the present embodiment, the shield portion 61 sandwiched between the magnetic material (first magnet) 62A and the magnetic material (second magnet) 62B is the tread of the tire 20. The magnetic field M generated by the magnetic body 62A and the magnetic body 62B, which is embedded in the unit 22, is detected by the magnetic field detection unit 63 provided in the vehicle body 30. The magnetic body 62A, the shield portion 61, and the magnetic body 62B are arranged side by side in the radial direction (Y-axis direction) of the tire 20 in this order. Therefore, as the tread portion 22 wears, the portions appearing on the surface of the tire 20 change in the order of the magnetic body 62A, the shield portion 61, and the magnetic body 62B. As will be described later, since the magnetic field M changes with the change of the member appearing on the surface of the tire 20, the magnetic field M can be detected by the magnetic field detection unit 63, and the wear of the tread portion 22 can be measured accurately.

FIG. 5B is a cross-sectional view illustrating the embedded pin 65 in which the magnetic body 62A, the shield portion 61, and the magnetic body 62B are housed in the storage portion. As shown in the figure, the embedded pin 65 has a magnetic body 62A, a magnetic body 62B, and a shield portion 61 housed in a storage portion 64, and is embedded in a tread portion 22. By integrating the magnetic body 62A, the magnetic body 62B, and the shield portion 61 as the embedding pin 65, the tread portion 22 is compared with the case where the magnetic body 62A, the magnetic body 62B, and the shield portion 61 are individually embedded in the tread portion 22. It can be easily buried in.

The method of burying the buried pin 65 in the tread portion 22 is not particularly limited, but for example, the buried pin 65 can be embedded in the tread portion 22 after the tire 20 is manufactured. Compared to the case where the buried pin 65 is embedded in the tread portion 22 when molding the tire 20, it is not necessary to hold the buried pin 65 in the molding die. There are merits such as being able to manufacture with. The buried pin 65 can be driven by the same technique as driving a non-slip stud on a studded tire.

The storage portion 64 includes a cylindrical tubular portion 641 capable of accommodating the magnetic body 62A, the magnetic body 62B, and the shield portion 61, and an engaging protrusion 642 protruding from the outer peripheral surface on one end side of the tubular portion 641. I have. Here, the one end side means the end in the Y-axis direction on the far side (the rotation center side of the tire 20) from the outer surface 21 of the tire 20 in a state where the storage portion 64 is embedded in the tread portion 22. Inside the tubular portion 641, the magnetic body 62B, the shield portion 61, and the magnetic body 62A are arranged in this order from the engaging protrusion 642 side. The engaging protrusion 642 engages with the tread portion 22 inside the tread portion 22 to prevent the embedded pin 65 from falling off from the tread portion 22. In the present embodiment, the engaging protrusion 642 is provided at the end of the cylindrical portion 641, but the position where it is provided is not limited to the end. However, when the buried pin 65 is driven into the tread portion 22 after the tire 20 is manufactured, the tire 20 is provided at the end portion so that the tire 20 can be easily aligned with the recess provided on the tread portion 22 side and falls off. It becomes difficult.

6 (a) to 6 (c) are cross-sectional views showing a state in which the buried pin 65 of FIG. 5 (b) is worn for each degree of wear of the tread portion 22. FIG. 6A shows an initial state (new state) in which the magnetic body 62A appears on the surface of the tread portion 22, and FIG. 6B shows a state in which the shield portion 61 appears on the surface of the tread portion 22 (wear). The advanced state) is shown, and FIG. 6C shows a state in which the shield portion is worn and the magnetic body 62B appears on the surface of the tread portion 22 (a state in which the wear is further advanced). As shown in these figures, as the wear of the buried pin 65 progresses with the wear of the tread portion 22, the members appearing on the surface of the tread portion 22 change.

7 (a) to 7 (c) schematically show a graph of the output waveform of the magnetic field detection unit 63 in the states of FIGS. 6 (a) to 6 (c).
In the state where the magnetic body 62A shown in FIG. 6A is exposed, the magnetic field M of the magnetic body 62A is detected by the magnetic field detection unit 63. Since the magnetic field detection unit 63 detects the magnetic field M when the buried pin 65 passes the position facing the magnetic field detection unit 63, the output from the magnetic field detection unit 63 accompanying the rotation of the tire 20 is shown in FIG. 7A. It becomes a square wave.

When the magnetic body 62A shown in FIG. 6B is completely worn and the shield portion 61 is exposed, the magnetic field of the magnetic body 62B is shielded by the shield portion 61, so that the magnetic field detection unit 63 accompanying the rotation of the tire 20 The output from is a waveform showing no magnetic field as shown in FIG. 7 (b).

In a state where the shield portion 61 shown in FIG. 6C is completely worn and the magnetic body 62B is exposed, the magnetic field M of the magnetic body 62B is detected by the magnetic field detection unit 63, so that the magnetic field detection accompanying the rotation of the tire 20 is detected. The output from the unit 63 is a rectangular wave shown in FIG. 7 (c).

As for the magnetic field M, it is sufficient if it can detect whether or not there is no magnetic field, and it is not necessary to detect the magnitude of the magnetic field M. Less susceptible to change. Further, since the magnetic field M does not have to be increased, the risk of attracting unnecessary objects such as iron pieces to the surface of the tire 20 can be reduced.

The wear measuring device 60 measures the wear of the tread portion 22 by detecting the change of the magnetic field M due to the change of the exposed member due to the wear of the tread portion 22 by the magnetic field detecting unit 63. The buried pin 65 embedded in the tread portion 22 is provided with a shield portion 61 between the magnetic body 62A and the magnetic body 62B. Therefore, the magnetic field M is not detected when the tread portion 22 reaches a predetermined wear state, so that it can be easily detected that the tread portion 22 has reached a predetermined wear state. By setting the above-mentioned predetermined wear state at a time suitable for the rotation of the tire 20, the wear measuring device 60 can accurately notify the time suitable for the rotation of the tire 20. Further, for example, by setting the timing at which the magnetic body 62B is exposed on the surface of the tread portion 22 to the extent that the tread portion 22 is worn and the tire needs to be replaced, it is possible to notify the time when the tire needs to be replaced. It is possible.

[Modification example]
8 (a) to 8 (c) are cross-sectional views illustrating a modified example of the buried pin. The embedded pins 67 shown in FIGS. 8A to 8C have the same magnetic poles on the shield portion 61 side of the magnetic body 62A and the magnetic poles on the shield portion 61 side of the magnetic body 62B. In other words, it differs from the buried pin 65 in that the magnetic poles on the surface side of the tread portion 22 are different. By reversing the directions of the magnetic fields of the magnetic body 62A and the magnetic body 62B, the initial state before the magnetic body 62A is worn and the state where the shield portion 61 is completely worn and the magnetic body 62B appears can be obtained. The output waveform of the detection result of the magnetic field M by the magnetic field detection unit 63 (see FIG. 5A) can be differentiated and easily distinguished.

As shown in FIGS. 9A to 9C, the magnetic body 62A of FIG. 8A appears on the surface of the tread portion 22, and the shield portion 61 of FIG. 8B is the tread portion 22. An output waveform having a different pattern can be obtained between the state of appearing on the surface of the tread portion 22 and the state of the shield portion of FIG. 8C being worn and the second magnetic material appearing on the surface of the tread portion 22. Therefore, for example, if the shield portion 61 shown in FIG. 8B appears on the surface when the tread portion 22 is in a wear state in which the tire 20 should be rotated, the pattern of the output waveform can be used. It is possible to easily detect whether the tire 20 is before the rotation time (FIG. 9 (a)), after the rotation time (FIG. 9 (b)), or after the rotation time (FIG. 9 (c)). It is also possible to notify when the tire needs to be replaced based on the detected state of the buried pin 67.

Regarding the magnetic field M, it is sufficient if it is possible to detect whether or not there is a magnetic field and the direction of the magnetic poles (N pole or S pole), and it is not necessary to detect the magnitude. Therefore, it is not easily affected by the change of the magnetic field M, and the magnetic field M does not have to be increased, so that the risk of attracting unnecessary objects such as iron pieces to the tire surface can be reduced.

[Modification example]
FIG. 10A is a cross-sectional view illustrating a modified example of the wear measuring device according to the present embodiment, and FIG. 10B is a plan view seen from the outer surface 21 side of the tire 20. As shown in these figures, the present invention can be implemented as a wear measuring device 70 provided with a plurality of buried pins 65A to 65C (hereinafter, when these are not distinguished, they are referred to as buried pins 65). By using a plurality of buried pins 65, the redundancy of the wear measuring device 70 is improved, and the wear of the tread portion 22 of the tire 20 can be measured at each place where the buried pins 65 are buried. Therefore, for example, it becomes possible to detect uneven wear of the tire 20.

As shown in FIG. 10B, in the wear measuring device 70, among the plurality of buried pins 65A to 65C, the buried pins 65B and 65C are aligned on the same straight line in the width direction (X-axis direction) of the tire 20. It is provided in. The magnetic field detection units 63A to 63C are provided side by side on the same straight line in the width direction (X-axis direction) of the tire 20. When the tire 20 rotates in the direction indicated by the white arrow in FIG. 10B (Z-axis direction), the buried pins 65B and 65C simultaneously move into a magnetic field after the buried pin 65A passes a position facing the magnetic field detection unit 63A. It will pass through the positions facing the detection units 63B and 63C.

The magnetic field MA of the buried pin 65A and the magnetic fields MB and MC of the buried pins 65B and 65C can be distinguished by the detection timing. That is, the magnetic field M of each buried pin 65 can be separated by changing the position of the buried pin 65 adjacent to the X-axis direction in the Z-axis direction (rotational direction of the tire 20). In the following, when the magnetic field MA, the magnetic field MB, and the magnetic field MC are not distinguished, these are referred to as the magnetic field M.

Further, as shown in FIG. 10B, the directions of the magnetic body 62A and the magnetic body 62B are opposite to each other in the buried pin 65B and the buried pin 65C. That is, the directions of the magnetic poles appearing on the surface of the tread portion 22 are reversed. Therefore, the magnetic field MB and the magnetic field MC simultaneously detected by the magnetic field detection units 63B and 63C can be distinguished by the direction of the magnetic field M. That is, when a plurality of buried pins 65 are arranged side by side in the X-axis direction, the magnetic fields M of each buried pin 65 are separated by different magnetic poles of the magnetic materials exposed in the adjacent buried pins 65, and the measurement accuracy is improved. Can be improved.

FIG. 11 is a graph of output waveforms showing detection of magnetic fields MA to MC by the wear measuring device 70 shown in FIGS. 10 (a) and 10 (b). As shown in the figure, since the magnetic field MA, the magnetic field MB, and the magnetic field MC are obtained as outputs having different patterns, it is possible to suppress that one becomes noise of the other. Therefore, the measurement accuracy of each part of the tire 20 provided with the buried pins 65A to 65C is improved.

The number and burial positions of the burial pins 65 shown in FIGS. 10 (a) and 10 (b) are examples, and configurations other than these may be used. For example, two or four or more buried pins 65 may be buried, or all the buried pins 65 may be buried side by side on the same straight line in the X-axis direction.

The present invention can be applied to a tire wear measuring device capable of measuring a tire wear state without visual inspection.

10, 40, 50, 60, 70: Wear measuring device 11: First magnetic material (magnet)
12: Second magnetic material (reference magnet)
13: First magnetic field detection unit (magnetic field detection unit)
14: Second magnetic field detection unit (reference magnetic field detection unit)
15: Shield part 20: Tire 21: Outer surface 22: Tread part 23: Inner side surface 24: Steel wire layer 30: Body 51: Control part 52: Storage part 61: Shield part 62A: Magnetic material (first magnet)
62B: Magnetic material (second magnet)
63, 63A, 63B, 63C :: Magnetic field detection unit 64: Storage unit 65, 65A, 65B, 65C, 67: Embedded pin 100: Wear measuring device 111: First magnetic body 112: Magnetic field detection unit 641: Cylindrical unit 642 : Engagement protrusion C: Center line G: External magnetic field M, M1, M2, MA, MB, MC: Magnetic field m1: Magnetic field (first detected value)
m2: Magnetic field (second detected value)

Claims (12)

1. In a tire wear measuring device that measures the degree of tire wear based on the magnetic field of a magnet,
   A shield portion embedded in the tread portion that shields the magnetic field from the magnet, and a shield portion.
   A tire wear measuring device comprising a magnetic field detection unit provided at a position where the magnetic field from the magnet changes due to wear of the shield portion together with the tread portion.
2. The magnetic field detecting portion is provided on the inner surface of the tire on the back side of the tread portion.
   The magnet is provided at a position of the vehicle body facing the tread portion.
   The wear measuring device according to claim 1, wherein the shield portion is provided between the magnetic field detecting portion and the magnet.
3. The magnetic field detection unit is provided at a position on the vehicle body facing the tread unit.
   The magnet is provided on the inner surface of the tire on the back side of the tread portion.
   The wear measuring device according to claim 1, wherein the shield portion is provided between the magnetic field detecting portion and the magnet.
4. With reference magnet,
   2. Wear measuring device.
5. The wear measuring device according to claim 4, wherein the magnetic field detection unit and the reference magnetic field detection unit are provided at positions symmetrical with respect to the center line of the width of the tire.
6. The magnet has a first magnet and a second magnet.
   The shield portion is embedded in the tread portion together with the first magnet and the second magnet in a state of being sandwiched between the first magnet and the second magnet.
   The wear measuring device according to claim 1, wherein the first magnet, the shield portion, and the second magnet are arranged side by side in the radial direction of the tire in this order.
7. An embedded pin having a first magnet, a shield portion, and a storage portion in which the second magnet is housed is embedded in the tread portion.
   The accommodating portion includes a tubular portion for accommodating the first magnet, the shield portion, and the second magnet.
   The wear measuring device according to claim 6, wherein the shield portion is sequentially arranged between the first magnet and the second magnet inside the tubular portion.
8. The wear measuring device according to claim 7, wherein the storage portion has an engaging protrusion protruding from the outer peripheral surface of the tubular portion.
9. The wear measuring device according to claim 7, wherein the magnetic pole on the shield portion side of the first magnet and the magnetic pole on the shield portion side of the second magnet are the same.
10. The wear measuring device according to claim 7, further comprising the plurality of embedded pins.
11. It has a first magnet, a shield, a second magnet, and a storage section.
    The accommodating portion includes a tubular portion for accommodating the first magnet, the shield portion, and the second magnet.
    An embedded pin for a wear measuring device in which the shield portion is arranged between the first magnet and the second magnet inside the tubular portion.
12. The embedded pin for a wear measuring device according to claim 10, wherein the storage portion has an engaging protrusion protruding from the outer peripheral surface of the tubular portion.

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