JP2023072097A - Wear measuring apparatus for tire and buried pin for wear measuring apparatus - Google Patents

Abstract

To provide a wear measuring apparatus for tire that can precisely detect a tire wearing under a less influence of an external magnetic field of terrestrial magnetism etc.SOLUTION: A wear measuring apparatus 10 for a tire 20 that measures a degree of wearing of the tire 20 based upon a magnetic field M1 of a first magnetic body 11 has: a shield part 15 which is buried in a tread part 22 and wears together with the tread part 22; and a first magnetic field detection part 13 which is provided at a position where a magnetic field m1 to be detect, having passed through the shield part 15, of the magnetic field M from the first magnetic body 11 changes as the shield part 15 wears together with the tread part 22.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD 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, grip performance when driving on a road surface and drainage performance for discharging water between the tire and the road surface when driving on a wet road surface deteriorate. Therefore, drivers and vehicle managers visually inspect the worn state of the tread of the tire and replace the tire before the usage limit is exceeded in order to ensure safety. A slip sign or the like provided in the grooves of the tire is used for visual inspection, but the inspection work is complicated and there is a possibility that the evaluation of the wear state is erroneous. If the evaluation is erroneous, tires with degraded performance will continue to be used, which is undesirable from a safety standpoint.
Therefore, methods have been proposed for measuring the degree of tire wear by means other than visual observation. 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 the groove and the deterioration of the tire. there is

U.S. Pat. No. 8,240,198

However, between the inner liner attached to the inner surface of the tire and the tread, a number of steel wire layers are provided, for example, 4 to 5 layers in a truck tire. The problem is that the steel wire layer shields the magnetic field from the magnets embedded in the tread, altering the magnetic field reaching the inside of the tire. However, if the magnetic field of the magnet is strengthened, there is also the problem of attracting unwanted substances such as iron pieces to the tire and increasing the difference in flexibility between the magnet and the tire.

As described above, the shielding cannot greatly increase the magnetic field of the magnets embedded in the tread. Therefore, it can be said that the magnetic field detected by the wear detection device is likely to be affected by an external magnetic field other than the magnetic field from the magnet embedded in the tread. External magnetic fields include, for example, geomagnetism, and the influence of geomagnetism changes from moment to moment depending on the traveling direction of the vehicle, the orientation and rotational position of the tires, and the like. Therefore, if the wear amount of the tire 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 the error with respect to the actual wear amount becomes large. . If the error with respect to the amount of wear increases due to the influence of noise, for example, there is also the problem that the timing suitable for tire rotation (change of position) cannot be detected with high accuracy.
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a tire wear measuring device and an embedded pin for the wear measuring device that can accurately detect tire wear while 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 that can easily detect the timing suitable for tire rotation.

In one aspect of the present invention, there is provided a tire wear measuring device for measuring the degree of wear of a tire based on a magnetic field of a magnet, wherein a shield portion embedded in a tread portion for shielding the magnetic field from the magnet; and a magnetic field detection section provided at a position where the magnetic field from the magnet changes due to wear of the shield section together with the section.
With this configuration, it is possible to measure the degree of wear of the tire based on the magnetic field that changes as the shield portion that wears together with the tread portion of the tire changes.

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

When the magnet is provided on the back side of the vehicle body or the tread portion, the reference magnetic field detection is provided at a position where the magnetic field from the reference magnet does not change without being affected by the wear of the shield portion together with the reference magnet and the tread portion. It is preferable to have a part and a.
The difference between the first detection value detected by the magnetic field detection unit and the second detection value detected by the reference magnetic field detection unit is taken to remove the influence of the external magnetic field, thereby accurately measuring the progress of tire wear. can be measured.
In this case, it is preferable that the magnetic field detection section and the reference magnetic field detection section are provided at symmetrical positions with respect to the center line of the width of the tire. As a result, the wear measuring devices 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, and the It is embedded in the tread portion together with the first magnet and the second magnet, and the first magnet, the shield portion, and the second magnet are arranged in this order in the radial direction of the tire. may have been
With this configuration, it is possible to easily detect that the degree of wear of the tire has reached a predetermined threshold based on the change in the magnetic field caused by the member exposed on the surface of the tread as the wear of the tire progresses. For example, when the first magnet wears and the shield portion appears, the magnetic field of the magnet detected by the magnetic field detection portion can be eliminated. In this way, it can be detected that the wear of the tread portion has reached a predetermined threshold 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 embedded pin having a storage portion in which the first magnet, the shield portion and the second magnet are stored is located in the tread portion. The storage portion includes a cylindrical portion that stores the first magnet, the shield portion, and the second magnet, and the cylindrical portion includes the The shield part may be arranged between the first magnet and the second magnet. Moreover, the storage portion may include an engaging protrusion projecting from the outer peripheral surface of the cylindrical portion.
By providing the engagement protrusion in the storage portion, the state in which the embedded pin is embedded in the tire can be stably maintained.

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

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

In another aspect, the present invention includes a first magnet, a shield section, a second magnet, and a storage section, and the storage section includes the first magnet, the shield section, and the second magnet. a cylindrical portion containing a magnet, wherein the shield portion is disposed inside the cylindrical portion between the first magnet and the second magnet; An embedded pin for a measuring device is provided.
The storage portion may include an engaging protrusion that protrudes from the outer peripheral surface of the cylindrical portion. The engaging protrusion can stably hold the state in which the embedded 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 as the shield changes as the tread wears.

FIG. 2 is a cross-sectional view illustrating a state in which the wear measuring device according to the first embodiment is provided on a tire; Graph schematically showing the relationship between the amount of tire wear and the detected magnetic field Sectional drawing explaining the modification of a wear measuring apparatus Sectional drawing explaining the modification of a wear measuring apparatus (a) Cross-sectional view for explaining a tire wear measuring device according to a second embodiment, (b) Cross-sectional view for explaining an embedded pin having an accommodating portion in which a first magnet, a shield portion and a second magnet are accommodated. figure Fig. 5(b) shows a state in which the embedded pin has changed due to wear of the tread portion. Sectional view of the state, (c) Sectional view of the state in which the shield part 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) Cross-sectional view of the initial state where the first magnet appears on the surface, (b) Cross-sectional view of the state where the shield part appears on the surface, and (c) The shield part is worn away. Cross-sectional view of the state where the second magnet appears on the surface (a) Graph of output waveforms in the state of FIG. 8(a), (b) Graph of output waveforms in the state of FIG. 8(b), (c) Graph of output waveforms in the state of FIG. 8(c) (a) Cross-sectional view and (b) plan view for explaining a modification of the wear measuring device Graphs of output waveforms in the wear measuring device of FIGS. 10(a) and 10(b) Sectional view for explaining a state in which a conventional tire wear measuring device is provided on a tire

[First embodiment]
Embodiments of the present invention will be described below with reference to the drawings. In each figure, the same members are denoted by the same numbers, and descriptions thereof are 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, the magnetic field detection unit 112 changes to The magnetic field M indicated by the dashed line changes. By detecting the change in the magnetic field M, the wear state of the tread portion 22 is measured.

However, under the environment in which the tire 20 is actually used, in addition to the magnetic field M, there is an external magnetic field G such as geomagnetism. The external magnetic field G or the like becomes noise when measuring the magnetic field M, and causes deterioration in the measurement accuracy of the magnetic field M by the magnetic field detection unit 112 . When the magnetic field detector 112 provided on the inner surface of the tire 20 measures the magnetic field M, the magnetic field M changes due to the steel wire layer 24 inside the tire 20 . Therefore, the influence of the external magnetic field G on 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 detectors in order to eliminate the influence of the external magnetic field G. FIG. The tire wear measuring device of the present invention will be described below.

FIG. 1 is a cross-sectional view for explaining a state in which a tire wear measuring device according to the present embodiment is provided on a 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 measures wear of the tread portion 22 of the tire 20 based on the fact that the effect of shielding the magnetic field M1 of the first magnetic body 11 provided on the vehicle body 30 by the shield portion 15 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 changes in the magnetic field M1 of the first magnetic body 11 detected by the first magnetic field detection section 13 .

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

A first magnetic field detector 13 for detecting the magnetic field M1 of the first magnetic body 11 and a second magnetic field detector for detecting the magnetic field M2 of the second magnetic body 12 are provided on the inner side surface 23 of the tire 20, that is, the back side of the tread portion 22. 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 section 15 and therefore is not detected by the first magnetic field detection section 13 . As the wear of the shield portion 15 progresses together with the tread portion 22 and the shielding effect of the shield portion 15 decreases, the magnetic field m1 that has passed through the shield portion 15 of the magnetic field M1 is detected by the first magnetic field detection portion 13 .

The first magnetic field detection unit 13 and the second magnetic field detection unit 14 are located at positions on the inner surface 23 of the tire 20 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. are placed. In this embodiment, the first magnetic field detection section 13 and the second magnetic field detection section 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 section 13 and the second magnetic field detection section 14 are provided at symmetrical positions with respect to the center line C of the tire width (X-axis direction). there is Therefore, the distance in the X-axis direction between the first magnetic body 11 and the second magnetic body 12 can be increased. Therefore, the first magnetic field detection section 13 and the second magnetic body 12 should not be affected by the second magnetic body 12 provided adjacent to the first magnetic body 11 facing the first magnetic field detection section 13 . Keeping distance is easier. Similarly, it becomes easy to secure the distance between the second magnetic field detection section 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 (in the X-axis direction), the maximum distance in the X-axis direction between the first magnetic field detection unit 13 and the second magnetic body 12 is half the tire width. is the distance of On the other hand, by arranging the first magnetic field detection section 13 and the second magnetic field detection section 14 at both ends of the tire width, the distance in the X-axis direction between the first magnetic field detection section 13 and the second magnetic body 12 can be reduced to 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 that attracts unnecessary objects such as iron pieces to the tire 20 . Therefore, since a magnetic field stronger than that of the first magnetic body 111 embedded in the tread portion 22 of the tire 20 in the conventional wear measuring device 100 (see FIG. 12) can be used, the accuracy of wear measurement is improved.

The first magnetic field detection section 13 is positioned so that the magnetic field of the first magnetic body 11 can be detected when the shield section 15 provided between the first magnetic body 11 and the first magnetic field detection section 13 is worn. is provided. The shield portion 15 is embedded in a portion of the tread portion 22 of the outer surface 21 of the tire 20 and wears as the tread portion 22 wears. Therefore, of the magnetic field M1 generated by the first magnetic body 11, the magnetic field m1 measured by the first magnetic field detector 13 increases as the tread portion 22 wears.

On the other hand, since the shield part 15 is not provided between the second magnetic body 12 and the second magnetic field detection part 14, the magnetic field M2 from the second magnetic body 12 is detected by the second magnetic field detection part 14. The applied magnetic field m2 is not affected by the wear of the tread portion 22 and the shield portion 15, 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 portion 13 increases. Therefore, 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 influenced by the external magnetic field G, similarly to 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 detector 13 and the magnetic field m2 detected by the second magnetic field detector 14, the influence of the external magnetic field G can be removed. Therefore, it is possible to suppress deterioration of the detection accuracy due to the influence of the external magnetic field G, and to measure wear of the tread portion 22 of the outer surface 21 of the tire 20 with high accuracy. Note that the first magnetic field detection unit 13 and the second magnetic field detection unit 14 measure the magnetic field using magnetic flux density or magnetic field strength.

The relative positional relationship with respect to the ground between the first magnetic field detection section 13 and the second magnetic field detection section 14 periodically changes as the tire 20 rotates. Therefore, the influence of 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 arranged in the width direction (X-axis direction) of the tire 20 perpendicular to the rotation direction (Z-axis direction) of the tire 20 on the inner surface 23 of the tire 20 . arranged 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 is simultaneously grounded as the tire 20 rotates.

By arranging 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 relative to the ground changes as well. 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, which are measured simultaneously, are affected by the external magnetic field G in the same way. to receive. Therefore, by using the difference between the first detected value and the second detected value measured simultaneously, the effect of the external magnetic field G can be removed from the first detected value.

The first magnetic field detection section 13 and the second magnetic field detection section 14 are equipped with a magnetoresistive effect element that measures a magnetic field and whose resistance changes depending on the direction and strength of the magnetic field. A GMR element, a TMR element, or the like can be used as the magnetoresistive element. The measurements by the first magnetic field detection section 13 and the second magnetic field detection section 14 do not need to be performed continuously in real time, and may be performed intermittently at regular time intervals. Alternatively, the measurement may be performed according to an external instruction received via wireless communication means (not shown). By performing the measurement at regular time intervals or in response to an instruction, power consumption can be suppressed more than continuous measurement. Alternatively, a Hall element may be used as the magnetoresistive effect element of the first magnetic field detection section 13 and the second magnetic field detection section 14 to measure the change in magnetic flux intensity.
Alternatively, a magneto-impedance effect element may be used to measure changes in impedance caused by changes in the magnetic field.

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

The first magnetic field detection section 13 and the second magnetic field detection section 14 are arranged on the same plane, and are arranged with their three sensitivity axes directed in the same direction. 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 is obtained for each of the X-axis component, the Y-axis component, and the Z-axis component, and the composite magnetic field of the difference is calculated. and estimate the amount of wear. Thereby, wear of the tread portion 22 of the tire 20 can be detected with high accuracy.

The tire wear measuring device 10 outputs information about wear of the tire 20 based on magnetic field measurements by the first magnetic field detector 13 and the second magnetic field detector 14 to a vehicle side device or the like via wireless communication means or the like. may Via wireless communication, it is possible to transmit information on measurement results by the first magnetic field detection section 13 and the second magnetic field detection section 14 to the vehicle side device, and receive information from the vehicle side device. Transmission and reception of information through 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 for explaining a modification 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 section 13 and the second magnetic field detection section 14 are provided on the vehicle body 30 , and the first magnetic body 11 and the second magnetic body 12 are located on the inner surface 23 of the tire 20 . is different from the wear measuring device 10 of FIG. As with the wear measuring device 10 , the wear measuring device 40 wears the shield portion 15 as well as the tread portion 22 . As the shield portion 15 wears, its shield 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 as the tread portion 22 wears.

[Modification 2]
FIG. 4 is a cross-sectional view illustrating a modification of the tire wear measuring device according to the present embodiment. A tire wear measuring device 50 shown in the figure differs from the wear measuring devices 10 and 40 shown in FIGS.

The control unit 51 measures the degree of wear of the tire 20 based on the magnetic field m1, the magnetic field m2, and a table stored in the storage unit 52. FIG. The control unit 51 is configured by a CPU or the like.
The storage unit 52 stores a table used for calculating the wear amount of the tread portion 22 of the tire 20 from the magnetic field m1 and the magnetic field m2. Used.

[Second embodiment]
In the case of an FF (front-engine, front-drive) vehicle, the front wheels serve as drive wheels and steer wheels, so tires mounted on the front wheels wear more easily than tires mounted on the rear wheels. Also, in the case of FF vehicles, the size of the front and rear tires is often the same. Therefore, the front and rear tires are rotated so that the amount of wear of each tire is uniform. An embodiment of the present invention will be described below as a tire wear measuring device suitable for informing the timing of tire rotation.

FIG. 5A is a cross-sectional view for explaining 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 body (first magnet) 62A and the magnetic body (second magnet) 62B is the tread of the tire 20. A magnetic field detector 63 provided in the vehicle body 30 is embedded in the portion 22 and detects the magnetic field M generated by the magnetic bodies 62A and 62B. 62 A of magnetic bodies, the shield part 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 wear of the tread portion 22 progresses, the portion appearing on the surface of the tire 20 changes in the order of the magnetic body 62A, the shield portion 61, and the magnetic body 62B. As will be described later, the magnetic field M changes with changes in the members appearing on the surface of the tire 20, so the magnetic field M can be detected by the magnetic field detector 63 and wear of the tread portion 22 can be accurately measured.

FIG. 5(b) is a cross-sectional view for explaining the embedded pin 65 in which the magnetic body 62A, the shield part 61 and the magnetic body 62B are housed in the housing part. As shown in the figure, the buried pin 65 is formed by housing a magnetic body 62A, a magnetic body 62B, and a shield portion 61 in a housing portion 64, and is buried in the tread portion 22. As shown in FIG. By integrating the magnetic body 62A, the magnetic body 62B, and the shield part 61 as the embedding pin 65, the tread part 22 is reduced compared to the case where the magnetic body 62A, the magnetic body 62B, and the shield part 61 are individually embedded in the tread part 22. can be easily embedded in

Also, the method of embedding the embedding pin 65 in the tread portion 22 is not particularly limited. Compared to the case where the embedded pin 65 is embedded in the tread portion 22 during molding of the tire 20, since it is not necessary to hold the embedded pin 65 in the mold, the tire 20 can be manufactured by a method that is substantially the same as the conventional and proven method. It has the advantage that it can be manufactured with The embedded pin 65 can be driven by the same technique as driving the non-slip rivets of a studded tire.

The storage portion 64 includes a tubular portion 641 that can accommodate the magnetic bodies 62A, 62B, and the shield portion 61, and an engaging protrusion 642 that protrudes from the outer peripheral surface of the tubular portion 641 on one end side. I have. Here, the one end side refers to the end in the Y-axis direction farther from the outer surface 21 of the tire 20 (the rotation center side of the tire 20 ) when 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 projection 642 prevents the embedded pin 65 from falling off from the tread portion 22 by engaging with the tread portion 22 inside the tread portion 22 . In addition, in the present embodiment, the engaging protrusion 642 is provided at the end of the tubular portion 641, but the position at which it is provided is not limited to the end. However, when the embedding pin 65 is driven and embedded in the tread portion 22 after the tire 20 is manufactured, providing it at the end facilitates alignment with the recessed portion provided on the tread portion 22 side, so that it does not come off. become difficult.

6(a) to 6(c) are cross-sectional views showing states in which the embedded pin 65 shown in FIG. FIG. 6(a) shows the initial state (new state) in which the magnetic body 62A appears on the surface of the tread portion 22, and FIG. 6(c) 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 has progressed further). As shown in these figures, as the tread portion 22 wears and the embedded pin 65 wears, the member appearing on the surface of the tread portion 22 changes.

7(a) to 7(c) schematically show graphs of output waveforms of the magnetic field detector 63 in the states of FIGS. 6(a) to 6(c).
In the state where the magnetic body 62A is exposed as shown in FIG. 6A, the magnetic field M of the magnetic body 62A is detected by the magnetic field detection section 63. Since the magnetic field detector 63 detects the magnetic field M when the embedded pin 65 passes through the position facing the magnetic field detector 63, the output from the magnetic field detector 63 accompanying the rotation of the tire 20 is shown in FIG. square wave.

When the magnetic body 62A shown in FIG. 6B is completely worn away and the shield part 61 is exposed, the magnetic field of the magnetic body 62B is shielded by the shield part 61. The output from has a waveform indicating no magnetic field as shown in FIG. 7(b).

When the shield portion 61 is completely worn away and the magnetic body 62B is exposed as shown in FIG. 6C, the magnetic field M of the magnetic body 62B is detected by the magnetic field detection section 63. The output from the section 63 becomes a rectangular wave shown in FIG. 7(c).

As for the magnetic field M, it is sufficient to detect whether or not there is no magnetic field, and it is not necessary to detect the magnitude of the magnetic field. Less susceptible to change. Moreover, since the magnetic field M does not need to be increased, the risk of attracting unwanted 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 a change in the magnetic field M associated with a change in the member exposed as the tread portion 22 wears, using the magnetic field detection portion 63 . The embedded pin 65 embedded in the tread portion 22 has the shield portion 61 provided between the magnetic bodies 62A and 62B. Therefore, since the magnetic field M is no longer detected when the tread portion 22 reaches the predetermined worn state, it can be easily detected that the tread portion 22 has reached the predetermined worn state. By setting the above-described predetermined wear state to a time suitable for rotation of the tire 20, the wear measuring device 60 can accurately notify the time suitable for rotation of the tire 20. FIG. Further, for example, by setting the timing at which the magnetic material 62B is exposed on the surface of the tread portion 22 to such an extent that the wear of the tread portion 22 progresses 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]
8(a) to 8(c) are cross-sectional views illustrating modifications of the embedded pin. The embedded pin 67 shown in FIGS. 8A to 8C has the same magnetic pole on the shield part 61 side of the magnetic body 62A and the magnetic pole of the magnetic body 62B on the shield part 61 side. In other words, it differs from the embedded pin 65 in that the magnetic poles on the surface side of the tread portion 22 are different. By reversing the direction of the magnetic field 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 part 61 is completely worn and the magnetic body 62B appears. The output waveform of the detection result of the magnetic field M by the magnetic field detection unit 63 (see FIG. 5(a)) can be differentiated and distinguished easily.

As shown in FIGS. 9A to 9C, the magnetic body 62A in FIG. 8A appears on the surface of the tread portion 22, and the shield portion 61 in FIG. and the state in which the second magnetic material appears on the surface of the tread portion 22 due to wear of the shield portion shown in FIG. Therefore, for example, if the shield portion 61 shown in FIG. 8B is made to appear on the surface when the tread portion 22 is in a worn state requiring rotation of the tire 20, based on the pattern of the output waveform, It is possible to easily detect whether it is before the rotation timing of the tire 20 (Fig. 9(a)), the rotation timing (Fig. 9(b)), or after the rotation timing (Fig. 9(c)). It is also possible to notify the time when the tire needs to be replaced based on the detected state of the buried pin 67 .

As for the magnetic field M, it is sufficient to detect whether there is no magnetic field and the direction of the magnetic pole (north pole or south pole), and it is not necessary to detect the magnitude. Therefore, it is less likely to be affected by changes in the magnetic field M, and the magnetic field M does not need to be increased, so the risk of attracting unwanted substances such as iron pieces to the tire surface can be reduced.

[Modification]
FIG. 10(a) is a cross-sectional view illustrating a modification of the wear measuring device according to the present embodiment, and FIG. 10(b) is a plan view of the tire 20 viewed from the outer surface 21 side. As shown in these figures, the present invention can be implemented as a wear measuring device 70 having a plurality of embedded pins 65A-65C (hereinafter referred to as embedded pins 65 when not distinguished). By using a plurality of embedded 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 for each location where the embedded pins 65 are embedded. Therefore, for example, uneven wear of the tire 20 can be detected.

As shown in FIG. 10B, in the wear measuring device 70, among the plurality of embedded pins 65A to 65C, the embedded pins 65B and 65C are arranged on the same straight line in the width direction (X-axis direction) of the tire 20. is provided in The magnetic field detectors 63A to 63C are arranged on the same straight line in the width direction of the tire 20 (X-axis direction). When the tire 20 rotates in the direction (Z-axis direction) indicated by the white arrow in FIG. It will pass through positions facing the detectors 63B and 63C.

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

Further, as shown in FIG. 10(b), the directions of the magnetic bodies 62A and 62B are opposite between the embedded pin 65B and the embedded 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 detected simultaneously by the magnetic field detectors 63B and 63C can be distinguished by the direction of the magnetic field M. FIG. That is, when a plurality of embedded pins 65 are arranged side by side in the X-axis direction, the magnetic field M of each embedded pin 65 is separated by differentiating the exposed magnetic poles of the adjacent embedded pins 65, thereby improving the measurement accuracy. can be improved.

FIG. 11 is a graph of output waveforms showing detection of the magnetic fields MA to MC by the wear measuring device 70 shown in FIGS. 10(a) and 10(b). As shown in the figure, the magnetic field MA, the magnetic field MB, and the magnetic field MC are obtained as outputs of different patterns, so that one can be suppressed from becoming noise of the other. Therefore, the measurement accuracy is improved for each portion of the tire 20 provided with the embedded pins 65A-65C.

The number of embedded pins 65 and the embedded positions shown in FIGS. 10(a) and 10(b) are merely examples, and configurations other than these are also possible. For example, a configuration in which two or four or more embedded pins 65 are embedded, or a configuration in which all embedded pins 65 are embedded on the same straight line in the X-axis direction may be employed.

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

10, 40, 50, 60, 70: wear measuring device 11: first magnetic body (magnet)
12: Second magnetic body (reference magnet)
13: first magnetic field detection unit (magnetic field detection unit)
14: Second magnetic field detector (reference magnetic field detector)
15: Shield portion 20: Tire 21: Outer surface 22: Tread portion 23: Inner surface 24: Steel wire layer 30: Car body 51: Control unit 52: Memory unit 61: Shield unit 62A: Magnetic material (first magnet)
62B: Magnetic body (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 part 642 : Engagement projection 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)

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 magnetic field detection section provided at a position where the magnetic field from the magnet changes due to wear of the shield section together with the tread section. The magnetic field detection unit is provided on the back side of the tread portion on the inner surface of the tire,
The magnet is provided at a position facing the tread portion on the vehicle body,
The wear measuring device according to claim 1, wherein the shield section is provided between the magnetic field detection section and the magnet. The magnetic field detection unit is provided at a position facing the tread portion in the vehicle body,
The magnet is provided on the back side of the tread portion on the inner surface of the tire,
The wear measuring device according to claim 1, wherein the shield section is provided between the magnetic field detection section and the magnet. a reference magnet;
4. The reference magnetic field detector according to claim 2 or 3, which is not affected by wear of the shield part together with the tread part and is provided at a position where the magnetic field from the reference magnet does not change. wear measuring device. 5. The wear measuring device according to claim 4, wherein the magnetic field detection section and the reference magnetic field detection section are provided at symmetrical positions with respect to the center line of the width of the tire. the magnets comprise 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 sandwiched between the first magnet and the second magnet,
2. The wear measuring device according to claim 1, wherein the first magnet, the shield portion, and the second magnet are arranged in this order in the radial direction of the tire. embedded in the tread portion is an embedded pin having a storage portion in which the first magnet, the shield portion and the second magnet are stored;
The storage unit comprises a cylindrical tubular portion that stores the first magnet, the shield portion, and the second magnet,
7. The wear measuring device according to claim 6, wherein said shield part is arranged in order between said first magnet and said second magnet inside said cylindrical part. 8. The wear measuring device according to claim 7, wherein the storage portion has an engaging protrusion projecting from the outer peripheral surface of the cylindrical portion. 8. The wear measuring device according to claim 7, wherein the magnetic pole of the first magnet on the side of the shield portion and the magnetic pole of the second magnet on the side of the shield portion are the same. 8. The wear measuring device according to claim 7, comprising a plurality of said embedded pins. comprising a first magnet, a shield portion, a second magnet, and a storage portion;
The storage unit comprises a cylindrical tubular portion that stores the first magnet, the shield portion, and the second magnet,
An embedded pin for a wear measuring device, wherein the shield part is arranged inside the cylindrical part between the first magnet and the second magnet. 11. The embedded pin for a wear measuring device according to claim 10, wherein said accommodating portion has an engaging protrusion projecting from an outer peripheral surface of said cylindrical portion.

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