TIRE WEAR MEASURING DEVICE

Abstract

Tire wear measuring device (10) which detects wear of a tire (20) based on a magnetic field (M) from a magnet (30) embedded in the tire (20), the device comprising: at least one magnetic sensor (12); and a magnetic collecting element (11) suitable for transmitting the magnetic field from the magnet (30), the magnetic collecting element (11) having an outer edge (11e) from which the magnetic field of the magnet (30) is emitted as an emission magnetic field, wherein the at least one magnetic sensor (12) is arranged in a position at which the emission magnetic field can be detected by the at least one magnetic sensor (11), further comprising: a magnetic field guiding element (13) which guides the emission magnetic field, wherein the magnetic collecting element (11) is a button cell battery, and wherein, in a plan view in a direction along a normal to an electrode surface of the button cell battery (11), one end of the magnetic field guiding element (13a, 13b) adjacent to the at least one magnetic sensor (12) is arranged outside the outer edge (11a) of the button cell battery (11), and the at least one magnetic sensor (12) is arranged between the button cell battery (11) and the end of the magnetic field guiding element (13a, 13b).

Description

Technical area

[0001] The present invention relates to a tire wear measuring device that detects wear of a tire based on a magnetic field from a magnet embedded in the tire, and relates to a power generating device. background

[0002] DE 10 2008 028 967 A1 describes a method with which a profile depth or tread wear of a tire of a vehicle and / or a tire property is determined.

[0003] JP 2019-64 432 A describes a pneumatic tire that can detect a tire's wear condition.

[0004] JP H08-75 403 A describes a detector for small changes in position that detects small displacements of an object in the micrometer range, such as the thickness of paper or a sheet.

[0005] JP 2017-114 438 A describes a tire sensor configured to easily detect a direction in which acceleration is detected by a G-sensor.

[0006] JP 2006 - 290 315 A describes a tire structure and a chemical composition of a bicycle as a vehicle as well as a structure of a power generating device and a headlight.

[0007] The progressive wear of a tire reduces its grip when driving on a road and its water drainage ability to channel water between the tire and the road when driving on a wet road. A driver or fleet manager visually inspects tire treads for wear and replaces a worn tire to ensure safety before the tire becomes excessively worn and unsafe. For example, skid marks placed in a tire's grooves are used for visual inspection. An inspection process is complicated. A wear condition can be incorrectly determined. Some users may never perform the inspection. If a tire's wear is incorrectly determined, the tire may continue to be used with reduced capabilities, which is not preferable from a safety perspective.

[0008] A sensor module has been developed to measure the degree of tire wear by a method other than visual observation. For example, PTL 1 discloses a sensor module including a magnetic sensor that detects the magnetic flux density of a magnetic field in a direction along the radius of a tire in a tread portion. The sensor module is configured to measure the wear of the tread portion based on the magnetic flux density detected by the magnetic sensor.

[0009] PTL 2 discloses an in-tire power generation device that supplies power to other devices within a tire. The power generation device includes rotating elements, each including a magnet, a base supporting the rotating elements, and coils located within the base. The magnets rotate with the rotation of the tire, thus generating electrical power. Citation listPatent literature PTL 1: Japanese unexamined patent application JP 2019 - 203 831 A PTL 2: Japanese unexamined patent application JP 2011 - 239 510 A Summary of the inventionTechnical problem

[0010] The sensor module disclosed in PTL 1 is intended to measure the strength of a magnetic field that changes with wear in order to accurately determine the wear condition of a tire at all times. Consequently, PTL 1 does not describe a configuration aimed at reducing the size and weight of the sensor module. The sensor module is mounted on a tire during use. A large or heavy sensor module may cause the tire to become unbalanced while rotating. Therefore, it is necessary for the sensor module to be as small and light as possible. The device described in PTL 2, which is a sophisticated power generation system, tends to increase in weight. A tire with such a device may become unbalanced while rotating.

[0011] The invention is defined in the appended claims.

[0012] The present invention aims to provide a tire wear measuring device capable of accurately detecting tire wear and achieving a reduction in size and weight, and to provide a power generating device mountable in a tire. Solution to the problem

[0013] The present invention provides a tire wear measuring device that detects the wear of a tire based on a magnetic field from a magnet embedded in the tire. The device includes at least one magnetic sensor and a magnetic collecting element capable of transmitting the magnetic field from the magnet. The magnetic collecting element has an outer edge from which the magnetic field from the magnet is emitted as an emission magnetic field. The at least one magnetic sensor is arranged in a position where the emission magnetic field is detectable by the at least one magnetic sensor.

[0014] In the above configuration, the emission magnetic field of the magnetic collector is detected. Such a configuration eliminates the need to dispose the at least one magnetic sensor near the magnet embedded in the tire. This leads to greater flexibility in the design of the at least one magnetic sensor. This enables a simplification of the structure of the tire wear measuring device and leads to a reduction in the size and weight of the device, as well as higher detection accuracy.

[0015] Preferably, the tire wear measuring device further includes a magnetic field guide element that guides the emitted magnetic field. In this case, the magnetic collecting element may be a button cell battery. Preferably, in a plan view in a direction along a normal to an electrode surface of the button cell battery, an end of the magnetic field guide element adjacent to the at least one magnetic sensor is disposed outside the outer edge of the button cell battery, and the at least one magnetic sensor is disposed between the button cell battery and the end of the magnetic field guide element.

[0016] Such a configuration enables the at least one magnetic sensor to efficiently detect the emission magnetic field guided by the magnetic field guide element, resulting in improved detection accuracy of the at least one magnetic sensor. Specifically, the emission magnetic field guided by the magnetic field guide element is formed between the button cell battery and the end of the magnetic field guide element. The emission magnetic field guided by the magnetic field guide element enables an increase in the magnetic flux density. Therefore, the at least one magnetic sensor arranged between the button cell battery and the end of the magnetic field guide element can accurately detect the emission magnetic field.

[0017] Preferably, the electrode surface of the button cell battery faces the magnet. Such a configuration allows the entire outer edge of the button cell battery to emit the emitting magnetic field. The at least one magnetic sensor, located near the outer edge, can detect the emitting magnetic field.

[0018] The magnetic field guiding element may be an antenna that acts as a waveguide and transmits and receives electromagnetic waves. Using a communication antenna as the magnetic field guiding element allows for a reduction in the size and weight of the tire wear measuring device.

[0019] A direction in which the emitted magnetic field can be detected by the at least one magnetic sensor can be parallel to the electrode surface of the button cell battery. The end of the magnetic field guiding element and the at least one magnetic sensor can be arranged on the same plane parallel to the electrode surface of the button cell battery.

[0020] Such a configuration enables the emission magnetic field detected by the at least one magnetic sensor to include more components parallel to the electrode surface of the button cell battery, resulting in efficient detection of the emission magnetic field.

[0021] The at least one magnetic sensor may include a first sensor and a second sensor. The first sensor may be arranged on one side of the coin cell battery in a direction parallel to the electrode surface of the coin cell battery, and the second sensor may be arranged on the other side of the coin cell battery in this direction. Tire wear may be detected based on an output of the first sensor and an output of the second sensor.

[0022] In this case, the electrode surface of the button cell battery, in a plan view in the direction along the normal to the electrode surface of the button cell battery, preferably has a center point aligned with the magnet embedded in the tire and arranged on a straight line connecting the first sensor and the second sensor.

[0023] The outputs of the first and second sensors can be used to compensate for the influence of noise, such as an external magnetic field. A magnetic field on one side of the coin cell battery and a magnetic field on the other side are oriented in opposite directions. For example, using the difference between the outputs provides an output approximately twice the magnitude of a magnetic sensor, resulting in improved sensing accuracy.

[0024] In the tire wear measuring device including a magnetic field guiding member that guides the emission magnetic field, the at least one magnetic sensor may include a first sensor and a second sensor, the magnetic field guiding member may have a first end and a second end adjacent to the at least one magnetic sensor, the magnetic collecting member may be a button cell battery, the first sensor and the first end may be arranged on one side of the button cell battery in a direction parallel to an electrode surface of the button cell battery, and the second sensor and the second end may be arranged on the other side of the button cell battery in this direction, and the wear of the tire may be detected based on an output of the first sensor and an output of the second sensor.

[0025] Such a configuration enables the emission magnetic field guided by the magnetic field guiding element to be efficiently detected by the at least one magnetic sensor, resulting in improved accuracy of tire wear measurement.

[0026] The tire wear measuring device may further include a coil disposed within a range of the magnet's magnetic field, and an induced current generated in the coil may be available as an operating power source. In this case, the coil is preferably disposed between the magnetic collecting element and the magnet.

[0027] Since the relative positional relationship between the magnet and the coil changes with the rotation of the tire, the density of the magnetic flux flowing through the coil also changes. Placing the coil between the magnetic collecting element and the magnet increases the density of the magnetic flux flowing through the coil, resulting in improved power generation efficiency. Therefore, the electrical energy generated by the coil can be used to operate the tire wear gauge while keeping the tire wear gauge small in external dimensions (size).

[0028] Not belonging to the present invention, a power generation device is further provided, which includes a magnet embedded in a tire and a coil disposed within a magnetic field range of the magnet. In this device, the relative positional relationship between the magnet and the coil changes with the rotation of the tire, and power is generated due to a change in the density of the magnetic flux flowing through the coil caused by a change in the relative positional relationship. Preferably, the power generation device further includes a magnetic element, and the coil is disposed between the magnetic element and the magnet.

[0029] Such a configuration makes it possible to use an induced current generated due to a change in the density of the magnetic flux flowing through the coil caused by the rotation of the tire to generate electricity. Advantageous effects of the invention

[0030] The tire wear measuring device according to the present invention is configured to detect the magnetic field of the magnetic collecting element. This configuration provides greater flexibility in arranging the at least one magnetic sensor. This reduces the size and weight of the device and enables accurate measurement of tire wear. In addition, the configuration including the coil allows an induction current generated due to a change in the magnetic flux density of a magnetic field passing through the coil caused by the rotation of the tire to be utilized for power generation without causing an increase in the size of the device. Brief description of the drawings [ Fig. 1] Fig.1 is a schematic cross-sectional view of the configuration of a tire wear measuring device according to an embodiment of the present invention. [ Fig. 2] (a) is a vector map showing a magnetic field in the tire wear device of Fig. 1, and (b) is a contour map showing sensor-detectable components of the magnetic field in the tire wear measuring device of Fig. 1 represents. [ Fig. 3] (a) is a contour map showing sensor-detectable components of the magnetic field in the tire wear measuring device of Fig. 1, and (b) is a contour map showing sensor-detectable components of a magnetic field in a tire wear measuring device of Fig. 8 shows. [ Fig. 4] Fig.4 is a schematic diagram showing the positional relationship between a magnet, a button cell battery, magnetic sensors, and ends of an antenna in the tire wear measuring device of Fig. 1 represents. [ Fig. 5] Fig. 5 is a schematic cross-sectional view of the configuration of a modification of the tire wear measuring device. [ Fig. 6] (a) is a vector map showing a magnetic field in a tire wear measuring device of Fig. 5, and (b) is a contour map showing sensor-detectable components of the magnetic field in the tire wear measuring device of Fig. 5 represents. [ Fig. 7] Fig. 7 is a schematic sectional view of the tire wear measuring device mounted on a tire. [ Fig. 8] Fig. 8 is a schematic cross-sectional view of the configuration of a prior art tire wear measuring device. [ Fig. 9] (a) is a vector map showing a magnetic field in the tire wear measuring device of Fig. 8, and (b) is a contour map showing sensor-detectable components of the magnetic field in the tire wear measuring device of Fig. 8 shows. [ Fig. 10] Fig. 10 is a schematic cross-sectional view of the configuration of another [ Fig. 11] Fig. 11 is a schematic cross-sectional view of the configuration of a power generation device according to an embodiment of the present invention. [ Fig. 12] (a) is a perspective view illustrating the geometry of the tire wear measuring devices of Example 1 and Example 2, and (b) is a perspective view illustrating the geometry of the tire wear measuring device of Comparative Example 1. [ Fig. 13] Fig.Figure 13 is a graph showing the ratios of the outputs in Examples 1 and 2 to an output in Comparative Example 1. Description of embodiments

[0031] Embodiments of the present invention will be described below with reference to the drawings. The same components are denoted by the same reference numerals throughout the figures, and redundant descriptions will be omitted where appropriate.

[0032] Fig. 7 is a schematic cross-sectional view of a tire wear measuring device according to an embodiment of the present invention mounted on a tire. As shown in Fig.7, a tire wear measuring device 10 is arranged on an inner surface 21 of a tire 20, and a magnetic object 30 is embedded in a tread portion 23 on an outer surface 22. When the magnetic object 30 is worn together with the tread portion 23, the magnetic field M generated in Fig. 7 is shown by dashed lines, of the magnetic object 30. The tire wear measuring device 10 can detect a wear state of the tread portion 23 by measuring the magnetic field M. For example, a wear state of the tire 20 can be detected based on a table in which the changes in the magnetic field M associated with the wear of the magnetic object 30 and a measured value of the magnetic field M are stored.

[0033] Fig. 8 is a schematic cross-sectional view of the configuration of a prior art tire wear measuring device. As shown in Fig.As shown in Figure 8, a tire wear measuring device 100 includes a button cell battery 101. Since the button cell battery 101 includes a casing made of a highly permeable soft magnetic material, a magnetic field generated by the magnetic object 30 embedded in the tread portion 23 of the tire 20 tends to be conducted to the button cell battery 101. For this reason, the button cell battery 101 is not normally disposed between the magnetic object 30 and the magnetic sensors 102A and 102B. The magnetic sensors 102A and 102B are disposed closer to the magnetic object 30 than the button cell battery 101 and are positioned at a sufficient distance from the button cell battery 101.In other words, a distance D1 from the magnetic object 30 to the button cell battery 101 is greater than a distance D2 from the magnetic object 30 to the magnetic sensors 102A and 102B, so that the button cell battery does not affect the magnetic detection by the magnetic sensors 102A and 102B. This arrangement of the button cell battery 101 and the magnetic sensors 102A and 102B in . Fig. 8 results in a complicated structure of the tire wear measuring device 100, which increases the size of the device.

[0034] Fig. 9(a) is a vector map showing a magnetic field in the tire wear measuring device of Fig. 8 shows. Fig. 9(b) is a contour map showing the sensor-detectable components of the magnetic field in the tire wear measuring device of Fig.8. The vector map shows the directions of the magnetic field components and magnetic flux densities using vectors. The contour map shows the magnetic flux densities of the magnetic field components in a direction along the x-axis as shades of gray. A darker shade of gray indicates a higher magnetic flux density.

[0035] As in Fig. As shown in Fig. 9(a), in the prior art tire wear measuring device 100, a region with high magnetic flux density is formed near the magnetic object 30. The magnetic sensors 102A and 102B are arranged in this region to detect the magnetic flux of the magnetic object 30. However, it has been found that a region in which the magnetic flux density of the components in the direction along the X-axis is high is formed near an outer edge 101e of the button cell battery 101 opposite the magnetic object 30, as shown in Fig.9(b). A magnetic field in this region is an emission magnetic field, that is, the magnetic field of the magnetic object 30, which is guided onto the button cell battery 101 and radiated by the button cell battery 101. The emission magnetic field changes when the magnetic field of the magnetic object 30 changes. Therefore, measuring the emission magnetic field makes it possible to detect a change in the magnetic field of the magnetic object 30.

[0036] Specifically, the button cell battery 101 may be arranged closer to the magnetic object 30 than the magnetic sensors 102A and 102B, and the magnetic sensors 102A and 102B may be arranged in a position where the emission magnetic field emitted from the outer edge 101e of the button cell battery 101 can be detected by the sensors. Such a configuration enables measurement of the change in the magnetic field of the magnetic object 30. This configuration makes it possible to use the button cell battery 101 as a magnetic collecting element (pseudo yoke), resulting in a simplified structure of the tire wear measuring device 100. This enables a reduction in the size and weight of the tire wear measuring device 100. Embodiments of the present invention will now be described.

[0037] Fig.1 shows a schematic cross-sectional view of the configuration of the tire wear measuring device according to the embodiment of the present invention. As in Fig. 1, the tire wear measuring device 10 according to the embodiment includes a magnetic sensor 12A, a magnetic sensor 12B and a button cell battery 11, and detects a magnetic field of the magnetic object 30 embedded in the tire 20 to measure the wear of the tire 20.

[0038] The button cell battery 11 is arranged in a position where the button cell battery 11 can transmit the magnetic field of the magnetic object 30. The button cell battery 11 has an outer edge 11e from which the magnetic field of the magnetic object 30 is radiated as an emission magnetic field. In the embodiment, an example is described in which a commercially available button cell battery (button battery) is used as a power source for the tire wear measuring device 10. A magnetic collecting element is not limited to the button cell battery 11. Any magnetic collecting element capable of transmitting a magnetic field from the magnetic object 30 can be used. The term "magnetic collecting element capable of transmitting a magnetic field" used here refers to a component, for example, a magnetic field sensor.a battery that allows the magnetic field of the magnetic object 30 to be radiated as an emission magnetic field therefrom, and that includes a portion made of a highly permeable soft magnetic material. The button cell battery 11 includes a casing (outer) that extends continuously from an electrode surface 11d to the outer edge 11e, and the casing is made of a soft magnetic material. When placed in a position exposed to the magnetic field of the magnetic object 30, the button cell battery 11 transmits the magnetic field of the magnetic object 30 and allows the magnetic field of the magnetic object 30 to be radiated as an emission magnetic field from the outer edge 11e, which is located away from the magnetic object 30.

[0039] In this embodiment, the term "position affected by the magnetic field of the magnetic object 30" refers to a range in which the magnetic flux density of the magnetic field of the magnetic object 30 is detectable. Although a magnetic flux density of more than 0 mT can be detected, a lower magnetic flux density is susceptible to noise. For example, it is preferable to obtain the difference between multiple detection results to compensate for the influence of noise. The term "being arranged in the position acted upon by the magnetic field of the magnetic object 30" refers to a state in which a magnetic field transmitting portion made of a soft magnetic material is arranged in the position affected by the magnetic field.The button cell battery 11 transmits and allows the magnetic field to be emitted as the emission magnetic field from the outer edge 11e as long as a portion of the electrode surface 11d made of the soft magnetic material is located in the position affected by the magnetic field. For this reason, the entire portion made of the soft magnetic material does not need to be located in the position affected by the magnetic field of the magnetic object 30.

[0040] The electrode surface 11d of the button cell battery 11 is arranged to face the magnetic object 30. In other words, the electrode surface 11d is arranged to face the inner surface 21 of the tire 20, so that the direction (normal direction) of a normal line 11L to the electrode surface 11d is along the Y axis. Thus, the button cell battery 11 can efficiently transmit the magnetic field from the magnetic object 30 and allow the magnetic field to be radiated as an emission magnetic field from the outer edge 11e.

[0041] The magnetic sensors 12A and 12B are arranged in a position adjacent to a surface 11f of the button cell battery 11 opposite the magnetic object 30, and in which the emission magnetic field emitted from the outer edge 11e can be detected by the sensors. The magnetic sensors 12A and 12B are arranged on the same plane. The emission magnetic field is Fig.1 is radiated obliquely upward from the outer edge 11e. A region having a higher magnetic flux density than that of its surrounding region is formed near the outer edge 11e. In other words, arranging the magnetic sensors 12A and 12B in the position where the emission magnetic field emitted from the outer edge 11e is detectable enables accurate detection of a change in the magnetic field. In order to detect the emission magnetic field by the magnetic sensors 12A and 12B, for example, a magnetic flux density in a direction in which the emission magnetic field is detectable at the position of each of the magnetic sensors 12A and 12B is preferably 0.4 mT or more. In this embodiment, the term "magnetic flux density" as used herein refers to a magnetic flux density detected when the tire wear measuring device 10 is mounted on a new tire 20 before use.

[0042] In the application of the magnetic object 30 to generate a magnetic field with a surface magnetic flux density of, for example, 26 mT, when the button cell battery 11 is arranged in a position where the distance D1 from the magnetic object 30 to the electrode surface 11d is in the range of about 10 to about 20 mm, the button cell battery 11 can transmit the magnetic field. In order to accurately detect the emission magnetic field from the outer edge 11e by the magnetic sensors 12A and 12B, the magnetic sensors 12A and 12B are arranged such that a distance (LX) along the X-axis from the outer edge 11e of the button cell battery 11 is 2.8 mm or less, preferably 2.5 mm or less, more preferably 2.3 mm or less.For the same purpose, the magnetic sensors 12A and 12B are arranged so that a distance (LY) along the Y-axis from the outer edge 11e of the button cell battery 11 is 3.2 mm or less, preferably 2.9 mm or less, more preferably 2.7 mm or less.

[0043] As in Fig.1, the distance D2 along the Y-axis between the magnetic object 30 and the magnetic sensors 12A and 12B is greater than the distance D1 between the magnetic object 30 and the button cell battery 11. Consequently, the magnetic sensors 12A and 12B do not directly detect the magnetic field from the magnetic object 30. The magnetic sensors 12A and 12B detect the emission magnetic field transmitted through the button cell battery 11 and radiated from the outer edge 11e. In this embodiment, the term "distance between components" as used herein refers to a distance between portions of the components that are closest to each other.

[0044] For the magnetic sensors 12A and 12B, which measure the emission magnetic field from the outer edge 11e, magnetoresistive elements are used, each having a resistance that changes depending on the direction and strength of a magnetic field. Examples of the magnetoresistive element include a giant magnetoresistive element (GMR) and a tunneling magnetoresistive element (TMR). Measurement by the magnetic sensors 12A and 12B does not need to be performed continuously in real time, but can be performed intermittently at regular time intervals. Alternatively, measurement can also be performed in response to an external instruction received via a radio communication unit (not shown). Measuring at regular time intervals or based on a command results in lower power consumption than continuous measurement.Instead of the magnetoresistive elements, Hall elements can be used as the magnetic sensors 12A and 12B to measure a change in the strength of a magnetic flux.

[0045] Magnetoimpedance elements can be used as the magnetic sensors 12A and 12B to measure a change in impedance caused by a change in the magnetic field.

[0046] The magnetic sensors 12A and 12B, which are configured to detect a magnetic flux density in the direction along the X-axis, can accurately detect the emission magnetic field from the outer edge 11e. The detection direction is not limited to the direction along the X-axis. The magnetic sensors 12A and 12B may be configured to detect magnetic fields along three mutually orthogonal axes (i.e., the X, Y, and Z axes). In this case, each of the magnetic sensors 12A and 12B may include three sensor elements, each detecting a magnetic field along one axis. In the embodiment, the magnetic sensors 12A and 12B are GMR sensors, each including a GMR element in a molded package.

[0047] The tire wear measuring device 10 can output information about the wear of the tire 20 based on the measurement of the magnetic field by the magnetic sensors 12A and 12B to an in-vehicle device, for example, via the radio communication unit. The tire wear measuring device 10 can transmit information about the measurement results of the magnetic sensors 12A and 12B to the in-vehicle device and receive information from the in-vehicle device via the radio communication unit. The transmission and reception of information through communication between the tire wear measuring device 10 and external devices is controlled by a central processing unit (CPU) (not shown).

[0048] The tire wear measuring device 10 includes an antenna 13 for external communication. The antenna 13 has opposite ends 13a and 13b positioned near the magnetic sensors 12A and 12B, respectively, so that each end is arranged in a position where the emission magnetic field can be guided from the outer edge 11e to that end. The antenna 13 serves as a waveguide, transmitting and receiving electromagnetic waves. The antenna 13 functions as a magnetic field guide member (yoke) that guides the emission magnetic field from the outer edge 11e of the button cell battery 11. The ends 13a and 13b of the antenna 13 are arranged near the outer edge 11e of the button cell battery 11 and each function as a magnetic field guide member (yoke) that guides the emission magnetic field. The magnetic sensors 12A and 12B are arranged between the outer edge 11e and the ends 13a and 13b.

[0049] Fig. 2(a) is a vector map showing a magnetic field in the tire wear measuring device of Fig. 1 shows. Fig. 2(b) is a contour map showing sensor-detectable components of the magnetic field in the tire wear measuring device of Fig. 1 shows. As in (a) and (b) of Fig.2, the tire wear measuring device 10 is configured such that the button cell battery 11 is disposed in a position where the button cell battery 11 can transmit the magnetic field of the magnetic object 30, and each of the magnetic sensors 12A and 12B is disposed in a position where the emitted magnetic field from the outer edge 11e of the button cell battery 11 can be detected by the sensor. Such a configuration allows the button cell battery 11 to function as a pseudo yoke, and allows the magnetic sensors 12A and 12B to detect the emitted magnetic field from the outer edge 11e. Disposing the button cell battery 11 between the magnetic object 30 and the magnetic sensors 12A and 12B in the manner described above enables a reduction in the size and weight of the tire wear measuring device 10 and an accurate measurement of a magnetic field from the magnetic object 30.

[0050] Fig. 3(a) is a contour map showing sensor-detectable components of the magnetic field in the tire wear measuring device of Fig. 1 shows. Fig. 3(b) is a contour map showing sensor-detectable components of the magnetic field in the tire wear measuring device of Fig. 8 shows.

[0051] As in Fig.As shown in Figure 3(a), in the tire wear measuring device 10 according to the embodiment, regions where the magnetic flux density of components in the X-axis direction is high are formed between the outer edge 11e of the button cell battery 11 and the ends 13a and 13b of the antenna 13. These regions are formed by the emission magnetic field guided from the outer edge 11e of the button cell battery 11 to the ends 13a and 13b of the antenna 13. The arrangement of the magnetic sensors 12A and 12B, each having a sensitivity axis along the X-axis, in these regions enables accurate detection of the magnetic field from the magnetic object 30.Furthermore, since the magnetic sensors 12A and 12B are arranged between the outer edge 11e of the button cell battery 11 and the ends 13a and 13b of the antenna 13, each of the magnetic sensors 12A and 12B is reliably arranged in a position where the emission magnetic field can be detected by the sensor.

[0052] As in Fig. As shown in Figure 3(b), in the prior art tire wear measuring device 100, the magnetic sensors 102A and 102B are arranged closer to the magnetic object 30 than the button cell battery 11 and directly detect the magnetic field of the magnetic object 30. Such a configuration makes it difficult to reduce the size and weight of the device.

[0053] Fig.Fig. 4 is a schematic diagram showing the positional relationship between the magnetic object 30, the button cell battery 11, the magnetic sensors 12A and 12B, and the ends 13a and 13b of the antenna 13 in the tire wear measuring device of Fig. 1. Fig. 4 schematically shows the positional relationship in the plan view in the direction of the Y-axis or in the direction along the normal 11L (see Fig. 1) to the electrode surface 11d of the button cell battery 11. In other words: The electrode surface 11d is visible to the observer from Fig. 4. As in Fig.As shown in Figure 4, the end 13a of the antenna 13 adjacent to the magnetic sensor 12A and the end 13b thereof adjacent to the magnetic sensor 12B are arranged outside the outer edge 11e of the button cell battery 11, or so as not to overlap the button cell battery 11. The magnetic sensor 12A is arranged between the outer edge 11e of the button cell battery 11 and the end 13a of the antenna 13, and the magnetic sensor 12B is arranged between the outer edge 11e of the button cell battery 11 and the end 13b of the antenna 13.

[0054] With reference to Fig.4, in the plan view in the direction along the Y-axis, the outer edge 11e of the button cell battery 11, the magnetic sensor 12A, and the end 13a of the antenna 13 are arranged so that they do not overlap each other, and the outer edge 11e of the button cell battery 11, the magnetic sensor 12B, and the end 13b of the antenna 13 are arranged so that they do not overlap each other. The arrangement in Fig. 4 is an example. The magnetic sensors 12A and 12B only need to be arranged between the outer edge 11e of the button cell battery 11 and the ends 13a and 13b of the antenna 13. For example, in the plan view in the Y-axis direction, the magnetic sensor 12A, the outer edge 11e, and part or all of the end 13a may overlap, and the magnetic sensor 12B, the outer edge 11e, and part or all of the end 13b may overlap.

[0055] The tire wear measuring device 10 includes the magnetic sensor 12A and the magnetic sensor 12B. The magnetic sensor 12A is arranged in the direction along the X-axis on one side of the button cell battery 11 parallel to the electrode surface 11d of the button cell battery 11, and the magnetic sensor 12B is arranged on the other side thereof. In the embodiment as shown in Fig. 4, the electrode surface 11d of the button cell battery 11 has a center point O aligned with the magnetic object 30 embedded in the tire 20 and is arranged on a straight line L connecting the magnetic sensor 12A and the magnetic sensor 12B.

[0056] The straight line L connecting the magnetic sensor 12A and the magnetic sensor 12B is parallel to the X-axis. Each of the ends 13a and 13b of the antenna 12 is arranged on the straight line L. The magnetic sensors 12A and 12B are arranged symmetrically with respect to the center point O of the electrode surface 11d of the button cell battery 11. The ends 13a and 13b of the antenna 13 are arranged symmetrically with respect to the center point O of the electrode surface 11d of the button cell battery 11.

[0057] The magnetic sensor 12A and the end 13a are arranged on one side of the button cell battery 11, and the magnetic sensor 12B and the end 13b are arranged on the other side. The button cell battery 11 is superimposed with the magnetic object 30 in the direction along the X-axis.

[0058] The above-described configuration causes an emission magnetic field Ma detected by the magnetic sensor 12A and an emission magnetic field Mb detected by the magnetic sensor 12B to have the same magnetic flux density and be oriented opposite to each other. Therefore, the wear of the tire 20 is detected based on an output of the magnetic sensor 12A and an output of the magnetic sensor 12B, resulting in improved redundancy of the tire wear measuring device 10.

[0059] The magnetic sensors 12A and 12B are similarly affected by an external magnetic field, which serves as noise in the measurement. Therefore, the difference between the outputs of these two sensors can be used to eliminate the influence of the external magnetic field. Since the outputs of the two sensors are based on magnetic fields oriented in opposite directions, using the difference between the outputs provides an output whose magnitude is twice that of an output from one sensor, in addition to eliminating the influence of noise. Therefore, the influence of noise such as an external magnetic field can be eliminated, and an output can be increased in magnitude, thereby achieving an accurate measurement of the wear of the tire 20.

[0060] The magnetic object 30 includes a polymer material and a hard magnetic particulate material (magnetic particles) dispersed in the polymer material and magnetized in one direction. The magnetic object 30 is embedded in the tread portion such that the direction of magnetization is aligned with a radial direction of the tire. As the polymer material, a rubber material having the same composition as that of a tread rubber composition for the tread portion is preferably used.

[0061] The magnetic object 30 preferably has a magnetic flux density of 1 mT or more on its surface. To achieve reliable measurement of the magnetic flux density of the magnetic object without being influenced by the earth's magnetism, the magnetic object 30 preferably has a magnetic flux density of 0.05 mT or more, more preferably 0.5 mT or more, at measurement positions where the magnetic sensors 12A and 12B are arranged.

[0062] To prevent the magnetic force of the magnetic object 30 from adversely affecting, for example, other in-vehicle electronic devices, the magnetic object 30 preferably has a surface magnetic flux density of 600 mT or less. To prevent the magnetic object 30 from attracting a metal piece, such as a nail, on a road during road travel, the magnetic object 30 further preferably has a surface magnetic flux density of 60 mT or less. The surface magnetic flux density of the magnetic object is a value measured in teslameters in direct contact with the magnetized magnetic object 30. <modifikation>

[0063] Fig. 5 is a schematic cross-sectional view of the configuration of a modification of the tire wear measuring device according to the embodiment. A tire wear measuring device 50 of Fig. 5 is configured such that the magnetic sensors 12A and 12B and the ends 13a and 13b of the antenna 13 are disposed on a surface 51d of a substrate 51 facing the button cell battery 11. The tire wear measuring device 50 differs from the tire wear measuring device 10 in the configuration described above. In other words, the tire wear measuring device 50 includes the magnetic sensors 12A and 12B and the ends 13a and 13b of the antenna 13, which are disposed on the same plane of the substrate 51 parallel to the electrode surface 11d of the button cell battery 11.

[0064] Fig. 6(a) is a vector map showing a magnetic field in the tire wear measuring device of Fig. 5 shows. Fig. 6(b) is a contour map showing the sensor-detectable component of the magnetic field in the tire wear measuring device of Fig. 5 shows. As in (a) and (b) of Fig. As shown in Figure 6, such a configuration in which the magnetic sensors 12A and 12B and the ends 13a and 13b of the antenna 13 are arranged on the same plane allows an emission magnetic field to be guided from the outer edge 11e of the button cell battery 11 to the ends 13a and 13b of the antenna 12 and to be oriented in the direction along the X-axis in which the emission magnetic field is detectable by the magnetic sensors 12A and 12B on the substrate 51. This leads to higher detection accuracy of the tire wear measuring device 50.

[0065] Fig. 10 is a schematic cross-sectional view of the configuration of another modification of the tire wear measuring device according to the present invention. As in Fig. 10, a tire wear measuring device 60 includes a coil 61 disposed within the range of a magnetic field from the magnetic object 30 and capable of utilizing, as an operating power source, an induced current generated in the coil 61 by rotation of the tire 20. The tire wear measuring device 60 differs from the tire wear measuring device 10 (see Fig. 1) in the configuration described above. The magnetic object 30 embedded in the tread portion 23 of the tire 20 is displaced due to deformation of the tire 20 associated with its rotation. The tire wear measuring device 60 utilizes the displacement of the magnetic object 30 to generate electrical energy.

[0066] The coil 61 is arranged between the button cell battery 11, which also serves as a magnetic collecting element, and the magnetic object 30 embedded in the tread portion 23 of the tire 20. The magnetic flux density of a magnetic field from the magnetic object passing through the coil 61 changes due to deformation of the tire 20 associated with the rotation of the tire 20. A change in the magnetic flux density in the direction along the Y-axis, which is Fig. 10, indicated by a bordered double-headed arrow, causes an induction current in coil 61, which in turn produces an electromotive force. The electromotive force is used as a power source of the tire wear measuring device 60, e.g., to activate the tire wear measuring device 60 or for communication.

[0067] In the tire wear measuring device 60, a change in the magnetic flux density of the magnetic field from the magnetic object 30 associated with the rotation or vibration of the tire 20 is used to generate an induced current in the coil 61, thus generating electrical energy. Therefore, the tire wear measuring device 60 can be made small and lightweight, and the generated electrical energy can be used for various applications. As described above, a change in the relative positional relationship between the magnetic object 30 and the coil 61 caused by the rotation of the tire 20 is converted into electrical energy and used as electrical energy. This reduces the power consumption burden of the button cell battery 11.

[0068] For a magnetic field between the magnetic object 30 and the button cell battery 11, the surface of the button cell battery 11 collects the magnetic field and thus increases the magnetic flux density of the component in the direction along the Y-axis of the magnetic field. As a typical magnetic flux passing through a coil, when the magnetic flux density of the component (components in the direction along the Y-axis in Fig. 10) of the magnetic flux orthogonal to the coil is higher, the magnetic flux through the coil changes more significantly, so a larger induction current is generated in the coil. For this reason, when viewed from the magnetic object 30, the coil 61 is arranged adjacent to the button cell battery 11 and positioned closer to the magnetic object 30 than the button cell battery 11. This increases an induction current generated in the coil 61 with the rotation of the tire 20, thus allowing efficient generation of electrical power.

[0069] An electromotive force produced in the coil 61 changes depending on the magnitude or degree of change in the magnetic flux density of a magnetic field from the magnetic object 30. In other words, an electromotive force produced in the coil 61 reflects a state of the tire 20. For this reason, an electromotive force produced in the coil 61 can be used to detect a state of the tire 20. For example, when the magnetic object 30 embedded in the tread portion 23 decreases in size due to wear of the tire 20, the magnetic flux density of the magnetic field from the magnetic object 30 decreases, so a change in the magnetic flux density of the magnetic field from the magnetic object 30 related to the rotation of the tire 20 also decreases.Therefore, an electromotive force (induction current) produced in the coil 61 changes depending on the degree of wear of the tire 20. For this reason, the wear of the tire 20 can be detected based on an electromotive force produced in the coil 61. In this case, the tire wear measuring device 60 may include the magnetic sensors 12A and 12B in . Fig. 10 exclude.

[0070] The coil 61 is electrically connected to an energy storage component (not shown). The energy storage component includes a rectifier circuit and a charging circuit, and allows an induction current generated due to a change in magnetic flux density to be charged in a capacitor. As the rectifier circuit, for example, a rectifying element having a circuit that rectifies an induction current (alternating current) generated in the coil 61 can be used. As the charging circuit, for example, a capacitive capacitor that stores electrical charge of an induction current can be used. Using electrical energy stored in the capacitor to activate the tire wear measuring device 60 or for communication reduces the load on the button cell battery 11, thus extending a period (operating time) during which the tire wear measuring device 60 can be continuously used.When the button cell battery 11 is a secondary battery, the button cell battery 11 can be used as an energy storage component, and the capacitor described above can be omitted.

[0071] In this case, the energy storage component includes a charging and discharging circuit instead of the charging circuit.

[0072] Fig. 10 shows an exemplary configuration in which the magnetic object 30 deforms when the tire 20 deforms. The configuration is not limited to this example. The tire wear measuring device 60 may have any configuration as long as the deformation of the tire 20 causes a change in the magnetic flux density of a magnetic field from the magnetic object 30 in the coil 61. For example, the tire wear measuring device 60 may have a configuration in which the deformation of the tire 20 causes the coil 61, rather than the magnetic object 30, to deform to cause a change in the magnetic flux density of the magnetic field from the magnetic object 30 in the coil 61.

[0073] Fig. 11 is a schematic cross-sectional view of the configuration of a power generation device according to an embodiment of the present invention. As shown in Fig. As shown in Fig. 11, a power generation device 70 includes the magnetic object 30 embedded in the tire 20 and the coil 61 disposed within the range of a magnetic field from the magnetic object 30. A relative positional relationship between the magnetic object 30 and the coil 61 changes with the rotation of the tire 20. A change in the relative positional relationship causes a change in the magnetic flux density of the magnetic field passing through the coil 61, thus generating electrical power.

[0074] The power generation device 70 further includes the button cell battery 11 as a secondary battery serving as a magnetic element. The coil 61 is arranged between the button cell battery 11 and the magnetic object 30. Such a configuration can increase an induction current generated in the coil 61 with the rotation of the tire 20, resulting in efficient power generation.

[0075] Although the antenna 13 in Fig. As shown in Figure 11, the antenna 13 can be removed from the configuration when not required. For example, the power generation unit 70 can supply power to a sensor separately from the power generation unit 70, and the sensor can have an antenna for communication.

[0076] The above-described embodiments are intended for a simple understanding of the present invention and are not intended to limit the scope of the present invention. Therefore, the components disclosed in the above embodiments are intended to be interpreted so that all design changes and equivalents belong to the technical scope of the present invention. For example, the power generation unit 70 may be made of Fig. 11 may include a measuring unit that measures a change in amplitude or frequency of an electromotive force produced in the coil 61, and detects a tire condition including a wear condition based on a signal received from the measuring unit. When an electromotive force produced in the coil 61 is a signal source to be measured by the measuring unit, the power generation device 70 may serve as a detecting device that outputs information about a tire condition. Although the button cell battery 11 functions as a magnetic element in the power generation unit 70, a magnetic element other than the button cell battery 11 may be provided. When the power generation unit 70 functions as a detecting device, the button cell battery 11 may be excluded or omitted. EXAMPLES

[0077] In order to determine how much higher an output in the tire wear measuring device 10 according to the present invention is compared to the Fig. 1 and an output in the tire wear measuring device without the antenna 13 are different from those in the tire wear measuring device 100 of the prior art from Fig. 8, the outputs were measured and compared. The setup included the magnetic object 30 with a surface magnetic flux density of 26 mT.

[0078] Fig. 12(a) is a perspective view showing the appearance and schematic internal structures of tire wear measuring devices of Example 1 and Example 2. Fig. 12(b) is a perspective view showing the appearance and schematic internal structures of a tire wear measuring device of Comparative Example 1. Table 1 and Fig. 13 shows the measured outputs. [Table 1] Table 1 Example 1 Example 2 Comparison example 1 without yoke with yoke D1 (mm) 16.0 16.0 20.7 D2 (mm) 21.2 21.2 17 Size (mm) 28 × 36 × 15 28 × 36 × 15 36 × 47 × 24 Volume ratio (%) 37.2 37.2 100.0 Weight (g) 21 21 42 Weight ratio (%) 50.0 50.0 100.0 Output ratio (%) 123.0 145.7 100.0

[0079] As shown in Table 1 and Fig. As shown in Figure 13, the configuration in which the button cell battery transmits a magnetic field from the magnetic object and the magnetic sensors detect an emission magnetic field radiated from the outer edge of the button cell battery enables a remarkable reduction in volume and weight compared with the prior art configuration, and also achieves improved detection accuracy due to a larger output. Industrial applicability

[0080] The present invention is applicable to a tire wear measuring device capable of measuring a wear state of a tire without visual inspection. List of reference symbols 10, 50, 60 Tire wear measuring device 11 Button cell battery (battery, magnetic collecting element, magnetic element) 11L Normal 11d Electrode surface 11e outer edge 11f surface 12A magnetic sensor (first sensor) 12B magnetic sensor (second sensor) 13 Antenna 13a End (first end, end adjacent to the magnetic sensor) 13b End (second end, end adjacent to the magnetic sensor) 20 tires 21 inner surface 22 exterior surface 23 Tread section 30 magnetic object (magnet) 51 Substrat 51d surface 61 coil 70 power generation facility 100 tire wear measuring device 101 button cell battery 101e outer edge 102A, 102B magnetic sensor M magnetic field Ma, Mb emission magnetic field O center D1, D2 distance< / modifikation>

Claims

[1] Tire wear measuring device (10) which detects wear of a tire (20) based on a magnetic field (M) from a magnet (30) embedded in the tire (20), the device comprising: at least one magnetic sensor (12); and a magnetic collecting element (11) suitable for transmitting the magnetic field from the magnet (30), the magnetic collecting element (11) having an outer edge (11e) from which the magnetic field of the magnet (30) is emitted as an emission magnetic field, wherein the at least one magnetic sensor (12) is arranged in a position at which the emission magnetic field can be detected by the at least one magnetic sensor (11), further comprising: a magnetic field guiding element (13) which guides the emission magnetic field, wherein the magnetic collecting element (11) is a button cell battery, and wherein, in a plan view in a direction along a normal to an electrode surface of the button cell battery (11), one end of the magnetic field guiding element (13a, 13b) adjacent to the at least one magnetic sensor (12) is arranged outside the outer edge (11a) of the button cell battery (11), and the at least one magnetic sensor (12) is arranged between the button cell battery (11) and the end of the magnetic field guiding element (13a, 13b). [2] Tire wear measuring device (10) according to claim 1, wherein the electrode surface (11d) of the button cell battery (11) faces the magnet (30). [3] The tire wear measuring device (10) according to claim 1, wherein the magnetic field guiding member (13) is an antenna serving as a waveguide and radiating and receiving electromagnetic waves. [4] Tire wear measuring device (10) according to claim 1 or 2, wherein a direction in which the emission magnetic field can be detected by the at least one magnetic sensor (12) is parallel to the electrode surface (11d) of the button cell battery (11), and wherein the end of the magnetic field guiding element (13a, 13b) and the at least one magnetic sensor (12) are arranged on the same plane parallel to the electrode surface (11d) of the button cell battery (11). [5] Tire wear measuring device (10) according to claim 1, wherein the at least one magnetic sensor (12) includes a first sensor (12A) and a second sensor (12B), wherein the first sensor (12A) is arranged in a direction parallel to the electrode surface (11d) of the button cell battery (11) on one side of the button cell battery (11), and the second sensor (12B) is arranged in the direction on another side of the button cell battery (11), and wherein wear of the tire is detected based on an output of the first sensor (12A) and an output of the second sensor (12B). [6] The tire wear measuring device (10) according to claim 5, wherein, in a plan view in the direction along the normal to the electrode surface (11d) of the button cell battery (11), the electrode surface (11d) of the button cell battery (11) has a center aligned with the tire-embedded magnet (30) and is arranged on a straight line connecting the first sensor (12A) and the second sensor (12B). [7] Tire wear measuring device (10) according to claim 1, wherein the at least one magnetic sensor (12) includes a first sensor (12A) and a second sensor (12B), wherein the magnetic field guiding element (13) has a first end (13a) and a second end (13b) adjacent to the at least one magnetic sensor (12); wherein the first sensor (12A) and the first end (13a) are arranged in a direction parallel to an electrode surface (11d) of the button cell battery (11) on one side of the button cell battery (11), and the second sensor (12B) and the second end (13b) are arranged in the direction on another side of the button cell battery (11), and wherein wear of the tire is detected based on an output of the first sensor (12A) and an output of the second sensor (12B). [8] Tire wear measuring device (10) according to claim 1, further comprising: a coil (61) arranged within a region of the magnetic field of the magnet (30), wherein an induction current generated in the coil (61) due to rotation of the tire (20) is available as an operating power source. [9] Tire wear measuring device (10) according to claim 8, wherein the coil (61) is arranged between the magnetic collecting element (13) and the magnet (30).

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