JP7353580B2 - pneumatic tires - Google Patents

Description

The present invention relates to pneumatic tires for vehicles such as automobiles.

BACKGROUND ART As a pneumatic tire (hereinafter also simply referred to as a "tire") mounted on a vehicle is driven, the tread portion that contacts the ground wears out, and the tread groove gradually becomes shallower. If the depth of the tread groove becomes shallower than the wear limit, slipping may occur during driving, increasing the risk of an accident. For this reason, it has been established that the amount of wear on the tread should be managed so as not to exceed the wear limit, and when the wear limit is reached, the tire should be replaced as soon as possible to ensure safety while driving. ing.

To specifically check the wear condition of the tread, generally a mark such as a slip sign is provided on the tread, and when this mark appears, it is determined that the amount of wear has reached the wear limit. There is. However, we cannot expect too much from general users that they will be able to reliably check this mark, so instead of visual confirmation by users, we can technically understand the wear condition of the tires and help users determine when it is time to replace them. Techniques have been proposed that can accurately recognize when a person has arrived.

For example, by burying a detection object made of magnetic material in a location where wear reaches the wear limit, and using a magnetic sensor as a detection means to detect the detection object exposed due to wear, the tire can reach the wear limit. A tire wear limit detection device (for example, Patent Document 1) that detects wear, and a magnetic material buried in the tread groove or inside the tire changes shape as the tread wears, and the strength of the magnetic field increases. A tire wear measurement method (for example, Patent Document 2) has been developed in which the wear state of a tire is measured by detecting a change using a detection means such as a magnetic sensor.

Utility Model Publication No. 62-83704 Patent No. 4054196

However, in both the tire wear limit detection device of Patent Document 1 and the tire wear measurement method of Patent Document 2, a detection means such as a magnetic sensor is provided on the vehicle body side, for example, in a tire house. For this reason, the magnetic body provided on the rotating tire side can only be detected when the magnetic body is close to the detection means, and only intermittent measurements can be made. In addition, the positional relationship between the detection means and the magnetic material can easily change depending on factors such as the inclination of the vehicle body, the nature of the road surface during driving, and tire pressure, so it is necessary to stably and accurately measure the strength of the magnetic field. I can't. For this reason, in line with the strong demand for vehicle safety in recent years, there is a need for technology that can more accurately determine the state of tire wear.

As a result of studying a method to solve the above problems and measure the strength of the magnetic field more stably and accurately, the inventors of the present invention discovered that the above problem could be solved by arranging a magnetic sensor in the inner cavity of the tire itself, which is equipped with a magnetic material. I found that I could solve the problem. However, when we tested the measurement of tire wear by actually driving a vehicle equipped with such tires and detecting the wear of the magnetic material, we found that the tires with the above configuration were stable and sufficient in terms of detection sensitivity. It was found that there are cases where it is not possible to obtain adequate detection sensitivity.

Therefore, the present invention provides a pneumatic tire in which the wear state of the tire can be accurately grasped at all times by accurately measuring the strength of the magnetic field, which changes due to wear, in a stable manner and with sufficient detection sensitivity. The task is to do so.

As a result of intensive studies to solve the above-mentioned problems, the present inventor found that the above-mentioned problems could be solved by the invention described below, and completed the present invention.

The invention according to claim 1 includes:
In a tread portion in which a pattern is formed by convex portions and concave grooves, one or more of the convex portions is provided with a through hole that extends from the ground contact surface side toward the inner cavity surface in the radial direction, and the through hole A magnetic material is embedded and enclosed in the
A magnetic sensor that detects the magnetic flux density of a magnetic field formed by the magnetic body is disposed close to a radially inner end of the magnetic body,
The magnetic material is formed by dispersing powder or granules of a hard magnetic material in a polymeric material and is magnetized in one direction, and is enclosed so that the direction of magnetization matches the radial direction of the tire. It is a pneumatic tire characterized by

The invention according to claim 2 is
The pneumatic tire according to claim 1, wherein the position where the magnetic sensor is arranged is on the surface of the inner cavity.

The invention according to claim 3 is
3. The pneumatic tire according to claim 1, wherein a magnetic flux density of the magnetic field formed by the magnetic material on the surface of the magnetic material is 0.05 mT or more.

The invention according to claim 4 includes:
2. The hard magnetic material is one or more magnetic powders selected from magnetic powders for producing alnico magnets, ferrite magnets, samarium magnets, and neodymium magnets. A pneumatic tire according to any one of claims 3 to 5.

The invention according to claim 5 includes:
A magnetic sensor that detects the magnetic flux density of a magnetic field formed by the magnetic body, a power source, and a transmitting/receiving means are housed in a sensor module, and the sensor module is close to a radially inner end of the magnetic body. The pneumatic tire according to any one of claims 1 to 4, characterized in that the pneumatic tire is arranged as follows.

According to the present invention, a pneumatic tire is provided in which the wear state of the tire can be accurately grasped at all times by accurately measuring the strength of the magnetic field, which changes due to wear, in a stable manner and with sufficient detection sensitivity. can do.

FIG. 1 is a schematic cross-sectional view illustrating the arrangement of magnetic bodies in a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of the arrangement of magnetic sensors on a tire in an embodiment of the present invention. It is a figure which shows an example of arrangement|positioning of the magnetic body and magnetic sensor in the tire which has a base pen structure. It is a figure explaining the process of forming a base pen structure in manufacture of the tire which has a base pen structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments and with reference to the drawings.

[1] Pneumatic tire according to the present embodiment 1. Outline of the pneumatic tire according to the present embodiment As a result of examining the reasons why detection sensitivity may not be stably and sufficiently obtained, the inventors have found that tires usually include a tread reinforcing layer such as a breaker, a belt, and a carcass. Because tire components are used that have metal cords as constituent materials, if a magnetic sensor is placed on the inner cavity surface side, sufficient detection sensitivity may not be obtained due to magnetic shielding by the metal cords. I understand. For this reason, in this embodiment, the magnetic material is placed in the through hole that reaches the surface of the internal cavity, and as a result, there is no object between the magnetic material and the surface of the internal cavity that shields the magnetic field. A magnetic field with suppressed loss of magnetic flux density is formed even on the surface of the cavity, and stable and sufficient detection sensitivity can be obtained.

In addition, in the tire of this embodiment, since the magnetic sensor is placed in the tire itself, it is possible to continuously detect the amount of change in magnetic flux density, and the wear state of the tire mounted on the vehicle can be monitored over time. can be grasped. In addition, the distance between the two is always maintained constant, allowing the magnetic sensor to detect changes in magnetic flux density in the magnetic material without being affected by the inclination of the vehicle, the nature of the road surface, tire pressure, etc. Therefore, the wear state of the tires can be constantly monitored with high accuracy.

2. Characteristics of the pneumatic tire according to the present embodiment The pneumatic tire according to the present embodiment has a magnetic material formed by dispersing powder particles of a hard magnetic material in a polymeric material in the convex portions of the tread. A magnetic sensor that is embedded and contained in a through hole provided in the magnetic material and detects the magnetic flux density of the magnetic field formed by the magnetic material is placed close to the radially inner end of the magnetic material. It is characterized by Therefore, in the following, first, the positional relationship between the magnetic body and the magnetic sensor will be explained, and then each of the magnetic body and the magnetic sensor will be explained.

(1) Positional relationship between the magnetic body and the magnetic sensor FIG. 1 is a schematic cross-sectional view illustrating the arrangement of the magnetic body in the pneumatic tire according to the present embodiment. It shows two convex parts. In FIG. 1, a tread portion 1 has a convex portion 2 surrounded by a groove 9, and contacts the ground at a ground surface 8. As shown in FIG. A through hole 3 having a predetermined shape is provided in the convex portion 2, and a magnetic material 4 is embedded and contained therein. Further, 5 is a breaker, 6 is a breaker cord, 7 is a surface of the inner cavity, and 10 is a magnetic sensor.

In this embodiment, as shown in FIG. 1, a magnetic body 4 magnetized in one direction is embedded inside the through hole 3 so that the magnetization direction matches the tire radial direction, and a convex A magnetic field of a predetermined strength is formed in the thickness direction of the portion 2. The magnetic sensor 10 is disposed in the inner cavity of the tire close to the radially inner end of the magnetic body 4 .

In this way, by arranging the magnetic sensor 10 and the magnetic body 4 facing each other on the inside and outside of one tire in the radial direction, the distance between them is always maintained constant, and the inclination of the vehicle body Since the magnetic sensor 10 can detect changes in the magnetic flux density in the magnetic body 4 without being affected by the road surface properties while driving, the tire air pressure, etc., it is possible to constantly grasp the wear state of the tires with high accuracy. I can do it.

In addition, since the magnetic body 4 is provided from the ground plane to penetrate all tire members that have metal cords, it is not affected by magnetic shielding by metal cords and can measure changes in magnetic flux density with high sensitivity. can do.

The pair of magnetic material and magnetic sensor may be provided in only one convex portion formed in the tread portion 1, or may be provided in a plurality of convex portions. Further, only one pair of the magnetic body and the magnetic sensor may be provided in the circumferential direction of the tire in one convex portion formed on the tread portion 1, or a plurality of pairs may be provided at equal intervals, for example. It may be. In addition, as a pair of a magnetic body and a magnetic sensor, one magnetic sensor may be installed on the inner tire surface corresponding to the buried position of the magnetic body, or a plurality of magnetic sensors may be installed on the tire inner cavity surface corresponding to the buried position of the magnetic body. The magnetic sensor may be installed on the surface of the inner cavity of the tire corresponding to the position where the magnetic material is buried.

(2) Magnetic material The magnetic material 4 is formed by dispersing hard magnetic material particles (magnetic powder) in a polymer material, and is magnetized in one direction, and the magnetization direction is the radius of the tire. It is buried in the tread in an orientation that matches the direction. When a magnetic body is formed using powder of such a hard magnetic material, this magnetic body becomes a permanent magnet by magnetization, so a magnetic field can be formed around it with a predetermined magnetic flux density, After magnetization, it does not easily demagnetize.

In the present embodiment, a magnetic body 4 is embedded inside the through hole 3 to form a magnetic field of a predetermined strength in the thickness direction of the convex portion 2 . Therefore, by knowing the amount of change in the magnetic flux density in the magnetic body 4 that wears out as the tire wears, it is possible to know the wear status of the tire.

The shape of the magnetic body 4 is formed to match the shape of the through hole 3 so that the magnetic body 4 can be embedded in the entire through hole 3 or the above-mentioned region. As the magnetic body 4, an elastic body in which particles of hard magnetic material (magnetic powder) are dispersed in a polymeric material is used.

As magnetic powders, we use alnico magnets whose main components are aluminum, nickel, cobalt, and iron, and ferrite magnets whose main component is iron oxide, because they have a large coercive force after magnetization and are not easily demagnetized. Preferable examples include magnetic materials for producing magnets, samarium, samarium-based magnets containing iron as main components, and neodymium-based magnets containing neodymium, iron, and boron as main components.

Specific alnico magnets include Al-Ni-Co-Fe-Cu, ferrite magnets include Fe ₂ O ₃ -SrO, and samarium magnets include Sm-Co-Fe-Cu and Sm -Fe-N, etc., and neodymium-based magnets include Nd-Fe-B-Dy, Nd-Fe-Nb-B, Nd-Pr-Fe-Nb-B, etc.

In addition, two or more of the magnetic powders described above may be selected and used, for example, a mixture of ferrite magnetic powder and samarium magnetic powder, a mixture of samarium magnetic powder and neodymium magnetic powder, etc. By mixing, a samarium-ferrite-based magnetic material and a samarium-neodymium-based magnetic material can be formed, respectively.

The particle size of the magnetic powder is preferably 400 μm or less, and more preferably 250 μm or less, considering the dispersibility in polymeric materials when forming a magnetic body and the abrasion associated with metal particles. preferable.

In addition, from the viewpoint of fully exhibiting the characteristics of a tire, the polymer material is preferably a resin material or a rubber material that can exhibit elasticity in a hardened state. From the viewpoint that the body wears in the same way as the tread rubber and provides a stable ride, a resin material or a rubber material that can exhibit wear characteristics equivalent to the tread rubber composition after curing is preferred.

Among the above-mentioned polymeric materials, a rubber material having the same composition as the tread rubber composition used for the tread portion is preferable, considering that the location where the magnetic body is provided is the tread portion. That is, the magnetic material is preferably formed by dispersing magnetic powder in a rubber material having the same formulation as the tread rubber composition. For example, some fillers in the formulation of the tread rubber composition are replaced with magnetic powder. It may be mixed in the form. The amount of magnetic powder contained in the magnetic material is preferably 10 to 70% by mass, more preferably 30 to 70% by mass, and even more preferably 40 to 70% by mass.

The magnetic material can be magnetized using a known magnetizing device, for example, a capacitor-type magnetizing power supply, a magnetizing coil, a magnetizing yoke, or the like. Note that the timing for magnetizing may be performed before being embedded in the tread portion or after being embedded in the tread portion. When magnetizing, from the viewpoint of sufficiently detecting the magnetic flux density formed by the magnetic body with the magnetic sensor, it is necessary to magnetize it in the direction toward the magnetic sensor and form dense lines of magnetic force toward the magnetic sensor. preferable.

In addition, in the case of a method of embedding a separately molded magnetic body 4 in the through hole 3, if the magnetic body 4 is magnetized after being molded and before being embedded in the through hole 3, a large magnetizing device is not required, and more than one magnetic body can be used at the same time. Since the magnetic body 4 can be magnetized, the magnetic body 4 can be efficiently manufactured.

The magnetic material must be configured to have a magnetic flux density of 0.05 mT or more at the measurement position where the magnetic sensor is placed, from the viewpoint that the magnetic flux density of the magnetic material can be reliably measured without being affected by earth's magnetism. is preferred. In consideration of such a point of view, it is preferable that the magnetic body is configured to have a magnetic flux density of 0.05 mT or more on the surface of the magnetic body.

On the other hand, from the viewpoint of preventing the magnetic force of the magnetic material from adversely affecting other electronic devices installed in the vehicle, it is preferable that the surface magnetic flux density of the magnetic material is 600 mT or less, so that it does not fall onto the road surface when driving on the road. From the viewpoint of preventing adsorption of metal pieces such as nails, the surface magnetic flux density of the magnetic body is more preferably 60 mT or less. Note that the surface magnetic flux density of a magnetic material is a value measured by bringing a Tesla meter into direct contact with the surface of a magnetized magnetic material.

(3) Magnetic Sensor The magnetic sensor is provided to measure the magnetic flux density of the magnetic material, which changes as the magnetic material is worn out in accordance with the wear of the tread portion. In this embodiment, as shown in FIG. 1, it is arranged close to the radially inner end of the magnetic body.

In this way, the magnetic sensor is placed close to the radially inner end of the magnetic material, and the magnetic sensor detects the magnetic lines of force that are densely formed in one direction toward the magnetic sensor. Magnetic flux density, which continuously changes due to wear, can be measured stably and accurately at all times.

Specific examples of magnetic sensors include Hall elements, magnetoresistive elements (MR), and other magnetic sensors that are small in size and can be attached to the surface of the inner cavity of a tire and can withstand vibrations and deformation of a rotating tire. Preferable examples include magnetic impedance (MI) elements, and among these, magnetoresistive elements are more preferable from the viewpoint of measurement accuracy.

As shown in FIG. 2, the sensor module 11, together with this magnetic sensor, has a receiving section that receives detected data, and sends the received data to a wear state determination device provided in the vehicle body by wire or wireless. The transmitter, accompanying antenna, power supply, etc. are housed inside the housing.

In addition to the magnetic sensor, this sensor module 11 may also house a pressure sensor that detects the internal pressure of the tire, a temperature sensor that measures temperature, an acceleration sensor that detects acceleration, etc. By using this sensor, in addition to magnetic flux density, it is possible to acquire tire internal pressure, tire temperature, acceleration data, etc. in real time. By comprehensively analyzing the data acquired by these multiple sensors, it is possible to understand the condition of the tires in more detail, which is expected to be effective in the automatic driving control of vehicles expected in the future. It can be used for.

The sensor module 11 is not limited to the configuration described above, and may include a storage section that stores verification data indicating the relationship between the amount of wear and magnetic flux density, which will be described later, and a storage section that stores verification data stored in the storage section. The vehicle is equipped with a measurement unit that measures the state of wear of the tread based on the magnetic flux density detected by the magnetic sensor, and a transmission unit that transmits data on the state of wear measured by the measurement unit to a device installed in the vehicle body. It may be configured as follows.

As a method of attaching the sensor module 11 to the tire, for example, a method of attaching it to a socket provided on the surface of the inner cavity of the tire, a method of directly adhering it to the surface of the inner cavity of the tire, a method of embedding it in the tire, etc. may be adopted as appropriate. Of these, attachment of the sensor module to a socket provided on the surface of the inner cavity of the tire is particularly preferable because attachment and replacement are easy.

[2] Method for manufacturing a pneumatic tire according to the present embodiment The pneumatic tire according to the present embodiment includes a through-hole forming process and a magnetic material embedding process in addition to the normal pneumatic tire manufacturing process. It can be manufactured by a manufacturing method provided. The through-hole forming step and magnetic material embedding step will be explained below.

1. Through-hole formation process This process involves forming a through-hole for embedding a magnetic material in one or more of the convex parts of the tread of a vulcanized pneumatic tire, radially inward from the ground contact side. This is the process of

Specifically, one or more of the tread parts of a vulcanized pneumatic tire is drilled radially inward from the ground contact side using a drilling jig such as a cork borer, drill, or hole cutter. By doing so, a through hole is formed. Among these drilling jigs, a cork borer is preferred in view of ease of drilling work.

2. Magnetic material embedding step This step is a step of embedding a magnetic material into the through hole formed in the through hole forming step. The magnetic material may be produced separately, or may be produced by pouring a polymeric material in which a hard magnetic material is dispersed into the through hole and hardening it. In the following, first, the production of the magnetic material will be explained, and then the embedding of the magnetic material will be explained.

When using a separately produced magnetic material, the magnetic material using magnetic powder is prepared by appropriately selecting the magnetic powder and polymeric material, mixing them appropriately, and kneading them into a predetermined shape, i.e., the magnetic material. It can be manufactured by forming it into a shape suitable for embedding and then magnetizing it. Thereafter, the magnetized magnetic material is embedded in the through hole. After embedding the magnetic material, a sensor module is installed near the magnetic material.

In addition, when producing a magnetic material in a through-hole, the above-mentioned magnetic powder and polymeric material are appropriately selected, and the magnetic powder is dispersed in a liquid polymeric material at a predetermined mixing ratio, and the mixture is appropriately mixed and kneaded. A method may be used in which a liquid or viscous magnetic material is injected into the through hole 3 to fill it before hardening, and then hardened. After curing, the magnetic material is magnetized and a sensor module is installed near the magnetic material.

[3] Tire Wear Measuring Method Next, a tire wear measuring method according to the present embodiment will be described.

In this embodiment, the wear state of the pneumatic tire described above is measured according to the following procedure.

1. Preliminary data acquisition Prior to measurement, the magnetic flux density of the magnetic field, which changes due to wear of the magnetic material, is measured in advance for the same type of tire as the measurement target using a magnetic sensor installed on the inner cavity surface, and data is acquired. do.

Specifically, first, we measure the magnetic flux density in a new tire (the same type of tire as the measurement target) immediately after manufacture, and then use a tire abrasion drum tester to test this tire until it exceeds the wear limit. , wear out the tires. Then, the device is stopped at predetermined intervals during the process, and the wear amount and magnetic flux density at that point are measured.

At this time, the magnetic sensor is placed at a radially inward position corresponding to the magnetic material inside the tire, and the positional relationship between the magnetic sensor and the magnetic material is maintained constant, so changing magnetic flux density can be suppressed. Can be measured stably and accurately.

After that, data for verification showing the relationship between the amount of wear and magnetic flux density is created based on the amount of wear and magnetic flux density measured at each point in time, and the created data is used to determine the wear state installed in the vehicle body. Store it in the device.

2. Attaching the tires to be measured to an actual vehicle and driving Next, the tires to be measured are attached to an actual vehicle and the vehicle is driven. As the vehicle runs, the magnetic material wears out along with the tread portion, so the magnetic flux density detected by the magnetic sensor changes.

Then, by comparing the change in magnetic flux density measured by the magnetic sensor with pre-stored verification data in the wear condition determination device received from the magnetic sensor, it is possible to determine to what extent the change in the magnetic flux density in the tire being measured. It can be determined whether wear is progressing.

When measuring magnetic flux density, the influence of changes in magnetic flux density (disturbances) caused by changes in external magnetic fields can be considered, but these effects are due to the gradual change in magnetic flux density due to gradual tire wear. Unlike this, these disturbances appear as large changes, so these disturbances can be eliminated by performing statistical processing.

As described above, in the tire according to the present embodiment, by applying the above-described wear measurement method, the positional relationship between the magnetic sensor and the magnetic body is maintained constant, and the magnetic flux changes in accordance with wear. Since the density can be measured stably and accurately at all times, the wear state of the tire can be measured more accurately and stably.

Next, application technology of the above-mentioned wear measurement technology will be described.

In recent years, tires with a base pen structure in which a conductive layer is provided on the tread have been manufactured in order to release static electricity accumulated in the vehicle to the road surface. Since there are major restrictions on the placement of magnetic materials and detection means when trying to detect It is preferable to arrange it at an inward position to detect tire wear.

That is, in a tire having a base pen structure, in a tread portion in which a pattern is formed by convex portions and concave grooves, a base pen formed of a magnetic material is embedded in one or more of the convex portions. A magnetic sensor that detects the magnetic flux density of the magnetic field formed by the magnetic material is placed at a radially inward position corresponding to the magnetic material. The magnet is formed and magnetized in one direction, and is enclosed in the tread portion so that the magnetization direction and the tire radial direction coincide.

At this time, the magnetized magnetic material is a hard magnetic material with conductivity, so if such a base pen is embedded and a magnetic field is formed in the thickness direction of the convex part, it will be different from a conventional base pen. Similarly, in addition to being able to release static electricity accumulated in the vehicle to the road surface, it is also possible to detect changes in the magnetic flux density of the magnetic field caused by the deformation of the magnetic material as the convex parts wear. The degree of wear until the wear limit is reached can be continuously detected.

Since the magnetic sensor that measures changes in magnetic flux density is placed in a radially inward position corresponding to the magnetic material inside the tire, that is, in the tire itself, the tire is able to detect changes in the slope of the vehicle body and the nature of the road surface while driving. , even when affected by tire air pressure, the positional relationship between the magnetic sensor and the magnetic body can be maintained constant, and changes in magnetic flux density can be measured stably and accurately. It is possible to grasp the wear condition with high accuracy.

Since the base pen is formed from a magnetic material, conventional base pen formation technology can be applied when embedding the magnetic material, and there is no need to create a new process for arranging the magnetic material, making it more efficient. It is possible to manufacture tires and increase productivity.

FIG. 3 is a diagram showing an example of the arrangement of magnetic bodies and magnetic sensors in a tire having such a base pen structure, and shows one convex portion 2 formed surrounded by a groove. In FIG. 3, the tread portion 1 includes a base pen formed of a magnetic material 13, one end of which is exposed to the ground plane 8, and the other end of which is in contact with the radially inward breaker 5 of the tire member, which is a conductive member. is embedded.

The magnetic body 13 forming the base pen is magnetized in one direction, and is enclosed in the tread portion so that the direction of magnetization coincides with the radial direction of the tire. The magnetic sensor is provided radially inward of the tire corresponding to the position of the convex portion in which the magnetic body 13 is embedded.

Here, as the magnetic material, the above-mentioned magnetic materials can be used, but since it is used as a base pen, it is preferable that the magnetic material has the following characteristics.

First, in order for the magnetic body 13 to function as a base pen, the specific resistance of the magnetic body 13 is preferably 1×10 ⁸ Ω·cm or less, more preferably 1×10 ⁶ Ω·cm or less. .

As the magnetic material used for the magnetic body 13, a conductive magnetic material is preferably used because it functions as a base pen without adding a conductive material. Such conductive magnetic materials include metal magnets such as alnico magnets, samarium magnets, and neodymium magnets, or non-magnetic polymers made from magnetic polymers with a tetracyanoquinodimethane structure on a polyaniline skeleton. Examples include metal magnets.

Further, from the viewpoint of ensuring sufficient conductivity as a base pen, carbon black may be added to the material forming the magnetic body 13 as necessary. The carbon black to be added should have aggregate characteristics such that the maximum frequency diameter (Dmod) of the Stokes equivalent diameter distribution curve is 43 to 79 nm, and the half of the distribution curve with respect to Dmod, from the viewpoint of exhibiting ground contact and antistatic function over a long period of time. Carbon black having a value range (ΔD50) ratio (ΔD50/Dmod) of 0.78 to 2.5 is preferably used.

The magnetic body 13 can be formed by the base pen forming step in the manufacturing process of a pneumatic tire having a normal base pen structure also serving as the magnetic body forming step.

As an example, a magnetic material formed by dispersing hard magnetic material particles in a polymeric material is formed using co-extrusion, which is a known method of forming the base pen in the process of extruding the tread part. can do. Specifically, for example, it is formed by integrally extruding the base layer, cap layer, and magnetic material (base pen) using a three-screw extruder, and then magnetizing the magnetic material in a predetermined direction.

Further, as another method, for example, it can be formed using a strip wind method. That is, in the tread ring forming process, a rubber strip made of a rubber composition for forming a magnetic body is wound around the base pen forming position on the breaker 5 instead of a rubber strip made of a rubber composition for forming a normal base pen. Thus, a magnetic body (base pen) 13 is formed.

FIG. 4 is a diagram illustrating the process of forming a base pen structure in manufacturing a tire having a base pen structure, and the base pen is formed according to the steps (a) to (c). First, as shown in FIG. 4(a), rubber strips are laminated to form the tread layer 14. Next, as shown in FIG. 4B, magnetic materials are laminated along the tread layer 14 to form a base pen made of the magnetic material 15. Thereafter, as shown in FIG. 4C, the tread layer 14 is again formed on the outside of the base pen formed from the magnetic material 15. As a result, a tread having a base pen made of a magnetic material is formed.

Note that for magnetization, as described above, a known magnetization device such as a capacitor type magnetization power supply device, a magnetization coil, a magnetization yoke, etc. is used.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments. Various changes can be made to the above embodiments within the same and equivalent scope as the present invention.

1 Tread portion 2 Convex portion 3 Through hole 4 Magnetic body 5 Breaker 6 Breaker cord 7 Inner cavity surface 8 Ground surface 9 Concave groove 10 Magnetic sensor 11 Sensor module 13, 15 Magnetic body (base pen)
14 Tread layer

Claims (5)

In a tread portion in which a pattern is formed by convex portions and concave grooves, one or more of the convex portions is provided with a through hole that extends from the ground contact surface side toward the inner cavity surface in the radial direction, and the through hole A magnetic material is embedded and enclosed in the
A magnetic sensor that detects the magnetic flux density of a magnetic field formed by the magnetic body is disposed close to a radially inner end of the magnetic body,
The magnetic material is formed by dispersing powder or granules of a hard magnetic material in a polymeric material and is magnetized in one direction, and is enclosed so that the direction of magnetization matches the radial direction of the tire. A pneumatic tire characterized by: The pneumatic tire according to claim 1, wherein the position where the magnetic sensor is arranged is on the surface of the inner cavity. The pneumatic tire according to claim 1 or 2, wherein the magnetic flux density of the magnetic field formed by the magnetic material on the surface of the magnetic material is 0.05 mT or more. 2. The hard magnetic material is one or more magnetic powders selected from magnetic powders for producing alnico magnets, ferrite magnets, samarium magnets, and neodymium magnets. The pneumatic tire according to claim 3. A magnetic sensor that detects the magnetic flux density of a magnetic field formed by the magnetic body, a power source, and a transmitting/receiving means are housed in a sensor module, and the sensor module is close to a radially inner end of the magnetic body. The pneumatic tire according to any one of claims 1 to 4, characterized in that the pneumatic tire is arranged as follows.

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