JP2019064432A - Pneumatic tire, method for manufacturing pneumatic tire and method for determining wear state of pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that can detect a wear state of a tire not depending on visual inspection irrespective of use conditions.SOLUTION: A pneumatic tire 1 capable of detecting a wear state of a tire includes a tread part 100a formed with a tread surface 12a that comes into contact with a road surface. The tread part 100a has a ferromagnet member 13 that is disposed on a center side in a tire radial direction relative to the tread surface 12a. The ferromagnet member 13 is disposed in a bottom part of a longitudinal groove 11 that is formed in a circumferential direction in the tread part 100a.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire capable of detecting a worn state of a tire, a method of manufacturing the pneumatic tire, and a method of determining a worn state of the pneumatic tire.

  In the pneumatic tire, in order to fully exhibit its function and performance, it is desirable to always know the wear state of the tire. For example, in a pneumatic tire, a groove is formed in a tread portion in order to improve the traction performance in a state where the road surface is wet. In order to maintain sufficient traction performance, although a certain groove depth is required, the use of the pneumatic tire causes the groove to become gradually shallower as the wear of the rubber constituting the tread portion progresses. Therefore, a slip sign is provided at the bottom of the groove in order to grasp the worn state of the tire. The driver, the vehicle manager, etc. can visually check the appearance of the slip sign on the surface of the tread portion to grasp the worn state of the tire and to determine the replacement time of the tire.

  However, there is a possibility that a driver or a vehicle manager who is not accustomed to check visually may be late in noticing the timing of replacing the tire. In addition, depending on the use situation, the time until the slip sign appears on the surface of the tread may be very long. In such a case, it is necessary to repeat visual confirmation over a long period of time, and it can be said that the time and effort is large. In addition, when the use period of the tire becomes long, even if the slip sign does not appear, the tread portion may deteriorate over time, and safety may not be secured. Therefore, attempts have been made to sense the worn state of the tire without relying on visual inspection.

  For example, an apparatus has been developed which predicts the wear of a tire using the temperature rise of the tread portion of a running tread (see, for example, Patent Document 1). In Patent Document 1, a tire is caused to travel in contact with a drum, and the temperature of the tread portion of the tread at that time is measured by thermography.

  In addition, a device has been developed to create wear data that indicates the wear state according to the running state of the vehicle, and predict the wear rate from the wear data and the information on the running state and the wear state acquired during actual travel (See, for example, Patent Document 2). In the device of Patent Document 2, in order to obtain information on the wear state during actual traveling, the magnetic powder rubber formed in a cylindrical shape is embedded in the tire tread so that the axial direction of the cylindrical shape is along the tire radial direction. A method is used in which a change in the magnetic field due to wear of the magnetic powder rubber is used as information on the wear state during actual traveling.

JP 2001-264041 A JP, 2006-327368, A

  However, the device of Patent Document 1 predicts wear on the assumption that the temperature rise of the tread portion when the tire is in contact with the drum for test running is all due to frictional heat. Therefore, it is difficult to apply to wear prediction during actual driving on a general road affected by the road surface temperature.

  Moreover, the apparatus of patent document 2 performs wear prediction of a race tire, and does not assume driving | running | working on a general road. The method of embedding the magnetic powder rubber formed in a cylindrical shape in the tire tread is a continuous change of the magnetic field when the wear rate is extremely high like a race tire (slick tire) used for running at high speed. Can be properly measured, but it is difficult to apply to pneumatic tires used for traveling on general roads.

  As described above, in the conventional device, a technique capable of easily detecting the worn state of the pneumatic tire without relying on visual observation has not yet been sufficiently established.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a pneumatic tire which can detect the worn state of the tire without depending on visual observation regardless of the use condition. Furthermore, it aims at providing the manufacturing method of the pneumatic tire concerned, and the wear state judging method of a pneumatic tire.

The characteristic configuration of the pneumatic tire according to the present invention for solving the above problems is as follows:
A pneumatic tire capable of detecting the wear state of the tire,
A tread portion having a tread surface formed in contact with the road surface;
The tread portion has a ferromagnetic member disposed on the center side in the tire radial direction with respect to the tread surface.

  According to the pneumatic tire of this configuration, since the ferromagnetic member is disposed on the center side in the tire radial direction with respect to the tread surface, the ferromagnetic member may be directly affected by the road surface at the beginning of use of the tire. Instead, the deformation of the ferromagnetic member during traveling can be suppressed. Therefore, the change of the magnetic field in the vicinity of the ferromagnetic member becomes minute at this time. However, when the wear of the tire progresses and the ferromagnetic member is exposed to the surface of the tread portion, the deformation of the ferromagnetic member and the wear of the ferromagnetic member itself occur while traveling. Further, when the aged deterioration of the tire progresses, the elasticity and restoring force of the tread portion decrease, and the ferromagnetic member is pulled by the tread portion and easily deformed. Therefore, the change of the magnetic field in the vicinity of the ferromagnetic member becomes relatively large at this time. Thus, the use period of the pneumatic tire of this configuration is divided into two periods in which the aspect of the magnetic field change is significantly different. Therefore, by setting the depth of the ferromagnetic member from the tread surface appropriately, it is necessary to replace the tire regardless of the conditions of use of the tire such as test running on a drum and actual running on a general road. It becomes possible to detect that the wear has occurred by means of a magnetic sensor or the like without relying on visual observation.

  In the pneumatic tire according to the present invention, preferably, the ferromagnetic member is disposed at a bottom of a longitudinal groove formed in the tread portion in the circumferential direction.

  According to the pneumatic tire of this configuration, since the ferromagnetic member is disposed at the bottom of the longitudinal groove, when the longitudinal groove becomes shallow enough to require replacement of the tire due to wear, the surface of the tread portion is formed. The ferromagnetic member can be configured to be exposed. Therefore, it is possible to easily detect a worn state requiring tire replacement by a magnetic sensor or the like.

  In the pneumatic tire according to the present invention, the tread portion has a plurality of the ferromagnetic members, and the plurality of ferromagnetic members are arranged along the tire circumferential direction and / or the tire width direction. Is preferred.

  According to the pneumatic tire of this configuration, by arranging the ferromagnetic members along the circumferential direction of the tire, it is possible to detect the entire worn state of the tire by a magnetic sensor or the like. In addition, since the ferromagnetic members are arranged along the tire width direction, when the ferromagnetic members are exposed on the surface of the tread portion at any position in the width direction, uneven wear is caused by a magnetic sensor or the like. It becomes possible to detect.

  In the pneumatic tire according to the present invention, the tread portion has a plurality of the ferromagnetic members, and at least two of the plurality of ferromagnetic members are from the tread surface along the tire radial direction. Preferably, the depths are configured to be different from one another.

  The difference in depth from the tread surface along the radial direction of the tire causes a shift in the time of exposure to the tread surface, so that the magnetic field changes in the vicinity of all the ferromagnetic members during the service period of the pneumatic tire of this configuration It is divided into three periods: a minute period, a period in which the magnetic field change is large only in the vicinity of the ferromagnetic member having a shallow depth from the tread surface, and a period in which the magnetic field change in the vicinity of both ferromagnetic members is large. Therefore, by appropriately setting the depths of the respective ferromagnetic members from the tread surface, not only the state in which the tire needs to be replaced but also, for example, the state a little before that is not relied on visual observation Can be detected by a magnetic sensor or the like.

  In the pneumatic tire according to the present invention, preferably, the ferromagnetic member is configured such that the hardness measured in accordance with JIS K 6253 is smaller than the hardness of the tread surface.

  According to the pneumatic tire of this configuration, since the hardness of the ferromagnetic member measured according to JIS K 6253 is smaller than the hardness measured on the tread surface, the ferromagnetic member is a tread surface due to the progress of wear. In the case where the surface of the ferromagnetic member is exposed, when the force is applied directly in contact with the road surface, the ferromagnetic member deforms well and the change of the magnetic field becomes remarkable. Therefore, it can be easily detected by a magnetic sensor or the like that the worn state requiring tire replacement has been reached.

  In the pneumatic tire according to the present invention, it is preferable that the pneumatic tire further includes a detection unit that is disposed on the back side of the tread portion to face the ferromagnetic member and detects a change in magnetic field.

  According to the pneumatic tire of this configuration, since the detection unit is disposed at a position close to the ferromagnetic member, it is possible to detect the change of the magnetic field due to the deformation of the ferromagnetic member with high accuracy.

  In the pneumatic tire according to the present invention, it is preferable to further include a magnetic coupling member disposed opposite to the ferromagnetic member on the back side of the tread portion and forming a magnetic circuit with the ferromagnetic member. .

  According to the pneumatic tire of this configuration, the magnetic coupling member cooperates with the ferromagnetic member to form a magnetic circuit in the vicinity of the arrangement position of the detection unit, so that the detection accuracy of the detection unit can be further improved. it can.

  In the pneumatic tire according to the present invention, it is preferable that the magnetic coupling member be disposed closer to the center in the tire radial direction than the detection portion.

  According to the pneumatic tire of this configuration, the magnetic flux is concentrated at the position of the detecting portion by locating the detecting portion between the ferromagnetic member and the magnetic coupling member, thereby further improving the detection accuracy of the detecting portion be able to.

The characteristic configuration of the method for manufacturing a pneumatic tire according to the present invention for solving the above problems is as follows:
A method for producing a pneumatic tire, comprising the steps of: curing a material filled in a mold to produce a tire;
A first step of disposing a ferromagnetic rubber material at a position closer to the center in the tire radial direction than a position at which the tread surface of the tire is formed in the mold;
A second step of filling a green tire containing unvulcanized rubber in the mold in which the ferromagnetic rubber material is disposed;
A third step of integrating the green tire and the ferromagnetic rubber material by heating in the mold;
To include.

  According to the method of manufacturing a pneumatic tire of this configuration, the ferromagnetic rubber is located at the center side in the tire radial direction with respect to the position where the tread surface of the tire is formed in the mold without largely changing the conventional tire manufacturing process. It is possible to manufacture a pneumatic tire in which the ferromagnetic member is disposed on the center side in the tire radial direction with respect to the tread surface only by performing the step of disposing the material.

In the method of manufacturing a pneumatic tire according to the present invention,
The ferromagnetic rubber material includes unvulcanized rubber,
Preferably, the green tire and the ferromagnetic rubber material are vulcanized by heating in the third step.

  According to the method of manufacturing a pneumatic tire of this configuration, the rubber of the pneumatic tire and the ferromagnetic rubber material can be firmly integrated after vulcanization molding.

In the method of manufacturing a pneumatic tire according to the present invention,
The ferromagnetic rubber material is coated with an adhesive on the side on which the green tire is disposed,
It is preferable that the green tire and the ferromagnetic rubber material be bonded with the adhesive by heating in the third step.

  According to the method of manufacturing a pneumatic tire of this configuration, a ferromagnetic rubber material composed of a non-vulcanizable rubber material such as a rubber material which does not use sulfur for crosslinking reaction and a non-crosslinkable rubber material is It can be bonded and integrated with an adhesive at the time of vulcanization.

The characteristic configuration of the method for manufacturing a pneumatic tire according to the present invention for solving the above problems is as follows:
A method for producing a pneumatic tire, comprising the steps of: curing a material filled in a mold to produce a tire;
A first step of disposing a ferromagnetic rubber material at a position where a longitudinal groove is formed on a tread surface of a green tire containing unvulcanized rubber;
A second step of filling the mold with the green tire in which the ferromagnetic rubber material is disposed;
A third step of integrating the green tire and the ferromagnetic rubber material by heating in the mold;
To include.

  According to the method of manufacturing the pneumatic tire of the present configuration, the center of the tire radial direction from the tread surface can be obtained only by performing the step of arranging the ferromagnetic rubber material at the position where the longitudinal groove is formed on the tread surface of the green tire. A pneumatic tire having a ferromagnetic member disposed on the side can be manufactured.

The characteristic configuration of the method of determining the worn state of a pneumatic tire according to the present invention for solving the above-mentioned problems is as follows:
A method of determining the wear state of a pneumatic tire, comprising
The pneumatic tire includes a tread portion in which a tread surface in contact with a road surface is formed, and the tread portion includes a ferromagnetic member disposed on a radial center side of the tread surface.
Detecting the change of the magnetic field in the vicinity of the ferromagnetic member;
A determination step of determining a wear state of the tread portion according to a change in the detected magnetic field;
To include.

  At the beginning of use of the pneumatic tire, the ferromagnetic member is not directly affected by the road surface, and the deformation of the ferromagnetic member during traveling is suppressed, so the vicinity of the ferromagnetic member detected at this time is The change in the magnetic field becomes minute. However, if the wear of the pneumatic tire progresses and the ferromagnetic member is exposed on the surface of the tread portion, or if the elasticity and resilience of the tread portion decrease due to the aged deterioration of the pneumatic tire, then during running Because deformation of the ferromagnetic member or abrasion of the ferromagnetic member itself occurs, the change in the magnetic field in the vicinity of the ferromagnetic member detected at this time is relatively large. Thus, the use period of the pneumatic tire is divided into two periods in which the aspect of the magnetic field change detected in the detection step is significantly different. Therefore, according to the wear state determination method of the pneumatic tire of the present configuration, it is determined based on the change of the magnetic field in the vicinity of the ferromagnetic member, without relying on visual observation, that the wear state requiring tire replacement has been achieved. It becomes possible.

  In the wear state determination method of a pneumatic tire according to the present invention, a plurality of the ferromagnetic members configured to have different depths from the tread surface in the tire radial direction are arranged in the pneumatic tire. In the detection step, the change in the magnetic field in the vicinity is detected for each of the plurality of ferromagnetic members, and in the determination step, the change in the detected magnetic field among the plurality of ferromagnetic members is detected. It is preferable to determine the wear state of the tread portion according to the amount beyond the fixed amount.

  As the wear of the tread portion of the pneumatic tire progresses, the ferromagnetic members having a shallower depth from the tread surface are sequentially exposed to the tread surface, and the change of the magnetic field in the vicinity becomes larger than a predetermined amount. That is, the present wear amount can be determined depending on which ferromagnetic member in the vicinity of which change in the magnetic field exceeds a predetermined amount. Therefore, according to the wear state determination method of the pneumatic tire of the present configuration, the wear state of the tread portion can be appropriately determined.

FIG. 1 is a partially cutaway perspective view of a pneumatic tire according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the pneumatic tire according to the first embodiment of the present invention taken along the circumferential direction. FIG. 3 is an explanatory view of a ferromagnetic member. FIG. 4 is a cross-sectional view taken along the width direction of a part of the tread portion of the pneumatic tire according to the first embodiment of the present invention. FIG. 5 is a cross-sectional view of a part of a tread portion of a pneumatic tire according to a second embodiment of the present invention taken along the width direction. FIG. 6 is a cross-sectional view of a part of a tread portion of a pneumatic tire according to a third embodiment of the present invention taken along the width direction. FIG. 7 is a cross-sectional view along the width direction of a tread portion of a pneumatic tire according to a fifth embodiment of the present invention. FIG. 8 is a cross-sectional view taken along the width direction of a tread portion of a pneumatic tire according to a sixth embodiment of the present invention. FIG. 9 is a graph showing temporal changes in detection results of the first magnetic sensor and the second magnetic sensor. FIG. 10 is a flowchart showing the processing procedure of the method of determining the worn state of a pneumatic tire according to the seventh embodiment of the present invention. FIG. 11 is an explanatory view of another embodiment. FIG. 12 is an explanatory diagram of another embodiment.

  The pneumatic tire according to the present invention is obtained by disposing a ferromagnetic member on the center side in the tire radial direction from the tread surface in the tread portion of various pneumatic tires (pneumatic radial tires, pneumatic bias tires, etc.) conventionally known. is there.

  Hereinafter, the present invention will be described with reference to FIGS. 1 to 12. In the following embodiments, a pneumatic radial tire (hereinafter, may be simply referred to as a "tire") mounted on a passenger car, a truck, a bus, a two-wheel vehicle or the like will be described as an example. However, the present invention is not intended to be limited to the configurations described in the embodiments and drawings described below.

First Embodiment
FIG. 1 is a partially cutaway perspective view of a pneumatic tire 1 according to a first embodiment of the present invention. As shown in FIG. 1, the pneumatic tire 1 includes a tread portion 100 a in contact with a road surface, shoulder portions 100 b positioned on both sides of the tread portion 100 a, sidewall portions 100 c forming side surfaces of the pneumatic tire 1, and sidewall portions A bead portion 100d is provided on the inner peripheral side (rim side) of 100c.

  The tread portion 100 a has a longitudinal groove 11, a block portion 12 and a ferromagnetic member 13 on the outer surface in the tire radial direction. The longitudinal groove 11 is a groove extending in the circumferential direction, and an example in which four grooves are arranged in the tire width direction W is shown in FIG. A plurality of block portions 12 which are land portions are formed to sandwich the vertical groove 11, and the top portion forms a tread surface 12a as a contact surface in contact with the road surface. The ferromagnetic member 13 is a member including a ferromagnetic material magnetized so that the center side in the tire radial direction is an N pole and the outer side is an S pole, and a plurality of the ferromagnetic members 13 are arranged at the bottom of the longitudinal groove 11 . On the surface in the tire radial direction center side of the tread portion 100a (hereinafter referred to as "the back side of the tread portion 100a"), a plurality of magnetic sensors are disposed at positions facing the respective ferromagnetic members 13 with the longitudinal groove 11 interposed therebetween. 14 is attached. The magnetic sensor 14 detects a magnetic field in the vicinity of the ferromagnetic member 13. Examples of such a magnetic sensor 14 include a reed switch, a magnetoresistive element, a Hall element, a coil, an inductor, an MI element (magnetic impedance element), a flux gate sensor, and the like. Among them, a Hall element is preferable because it has high sensitivity over a wide range and is useful as the magnetic sensor 14.

  FIG. 2 is a cross-sectional view along the circumferential direction of the pneumatic tire 1 according to the first embodiment of the present invention. In FIG. 2, a cross section including the longitudinal groove 11 is illustrated. The ferromagnetic member 13 is formed at the bottom of the longitudinal groove 11 so that the top of the ferromagnetic member 13 is closer to the center in the tire radial direction than the tread surface 12a in contact with the road surface G. In FIG. 2, an example in which nine ferromagnetic members 13 are disposed at the bottom of one longitudinal groove 11 and arranged at an interval of 40 ° with respect to the rotation center O of the pneumatic tire 1 is shown. The number of ferromagnetic members 13 disposed at the bottom of one longitudinal groove 11 may be two or more, and more preferably four to nine. In the pneumatic tire 1, the ferromagnetic member 13 is worn on the surface of the tread portion 100 a due to wear according to the depth Δd along the tire radial direction from the tread surface 12 a in contact with the road surface G to the top of the ferromagnetic member 13. The time to exposure is fixed.

  FIG. 3 is an explanatory view of the ferromagnetic member 13. FIG. 3A is a perspective view of a part of the tread portion 100a. The ferromagnetic member 13 is disposed on the bottom of the longitudinal groove 11 so as to cross the longitudinal groove 11 in the tire width direction, and is in contact with the side surface of the block portion 12. FIG. 3B is a cross-sectional view along the tire circumferential direction of the tread portion 100a when the pneumatic tire 1 is in an unused state. In the unused state, the depth d1 of the longitudinal groove 11 is larger than the height h from the bottom of the longitudinal groove 11 to the top 13a of the ferromagnetic member 13 (hereinafter simply referred to as "height h"). Therefore, the ferromagnetic member 13 does not come in contact with the road surface at the beginning of use of the tire, and the deformation of the ferromagnetic member 13 during traveling can be suppressed. As a result, the change of the magnetic field detected by the magnetic sensor 14 becomes minute.

  FIG. 3C is a cross-sectional view taken along the tire circumferential direction of the tread portion 100a when the wear of the pneumatic tire 1 has progressed. In the state shown in FIG. 3C, the depth d2 of the longitudinal groove 11 matches the height h due to the wear of the block portion 12, and the top portion 13a of the ferromagnetic member 13 is exposed on the surface of the tread portion 100a. ing. Therefore, the ferromagnetic member 13 comes in contact with the road surface, and the deformation of the ferromagnetic member 13 during traveling becomes larger than the state shown in FIG. 3 (b). As a result, in the detection value by the magnetic sensor 14, a waveform (hereinafter referred to as “contact waveform”) appears in which the magnetic field increases and decreases in a cycle in which the ferromagnetic member 13 contacts the road surface during traveling.

  Thus, the detection result by the magnetic sensor 14 is different between the state shown in FIG. 3 (b) and the state shown in FIG. 3 (c). Therefore, by referring to the detection value of the magnetic sensor 14, it is possible to detect a change in the state of the pneumatic tire 1 due to wear without relying on visual observation of the pneumatic tire 1. In particular, the height of the contact waveform in the detection value of the magnetic sensor 14 is made to coincide with the state where the tire needs replacement of the pneumatic tire 1 (hereinafter referred to as "necessary replacement state"). It is preferable to set h to the depth of the longitudinal groove 11 where tire replacement is recommended (ie, the same depth as the position of the slip sign). Specifically, it is preferably 1 to 10 mm, and more preferably 1.5 to 5 mm. If the height h is less than 1 mm, the detection of wear may be delayed. In such a case, the traction performance on a wet road surface becomes insufficient, which may cause safety problems. If the height h is higher than 10 mm, a contact waveform appears in the detection value of the magnetic sensor 14 in a state where the longitudinal groove 11 is still deep enough and there is no problem in the traction performance of the pneumatic tire 1. In such a case, there is a possibility that the driver, the vehicle manager or the like may forego the tire replacement even after the appearance of the contact waveform, and as a result, the appropriate tire replacement time may be missed.

  The ferromagnetic member 13 preferably has a trapezoidal cross-sectional shape along the circumferential direction of the tire, with the top 13 a side as the upper bottom. With such a cross-sectional shape, the area of the top portion 13a in contact with the road surface is small. Therefore, in the state shown in FIG. 3 (c), the ferromagnetic member 13 is compressed and deformed by capturing the force from the road surface. It will be easier. Thereby, the contact waveform can be easily generated. Also, in general, the surface magnetic flux density of the magnet decreases as the length in the magnetization direction decreases. When wear progresses further after the ferromagnetic member 13 is in the state shown in FIG. 3C, the height h along the magnetization direction is reduced, so that the surface magnetic flux density is significantly reduced. Become. Since a significant decrease in the surface magnetic flux density can be detected relatively easily as a decrease in the magnetic flux density detected by the magnetic sensor 14, it is determined whether the ferromagnetic member 13 is exposed on the surface of the tread portion 100a. It can be used. Further, by using the detection of the remarkable decrease of the surface magnetic flux density in combination with the detection of the contact waveform, it is possible to sense the state change of the pneumatic tire 1 due to the wear in more detail. The ferromagnetic member 13 is not limited to a trapezoidal shape in cross section along the circumferential direction of the tire, but in the state shown in FIG. It is preferable that it is a shape which is easily compressively deformed by the force of. For example, the ferromagnetic member 13 may have a cylindrical shape, a conical shape, a truncated cone shape, a polygonal pillar shape, a polygonal pyramid shape, a polygonal truncated pyramid shape, a spherical shape, an elliptical spherical shape, or the like.

  The ferromagnetic member 13 is made of a rubber material in which a magnetic filler is dispersed. Examples of the magnetic filler include rare earths, irons, cobalts, nickels, oxides, etc., but neodymium or ferrite which is resistant to heat is preferable because higher magnetic force can be obtained. The shape of the magnetic filler is not particularly limited, and may be spherical, flat, needle-like, columnar, or indeterminate. The magnetic filler may be introduced into the rubber material after magnetization but is preferably magnetized after being introduced into the rubber material. By magnetizing after introduction, control of the polarity of the magnet becomes easy, and detection of the magnetic field becomes easy. As a rubber material used for the ferromagnetic member 13, a thermoplastic elastomer, a thermosetting elastomer, or a mixture thereof can be used. Thermosetting elastomers include, for example, diene-based synthetic rubbers such as polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, polychloroprene rubber and nitrile rubber, ethylene-propylene rubber, butyl rubber, acrylic rubber, polyurethane rubber, fluororubber, silicone Although rubber, non-diene synthetic rubber such as epichlorohydrin rubber, and natural rubber can be mentioned, it is preferable to use the same rubber material as the material of the block portion 12. Examples of thermoplastic elastomers include styrene thermoplastic elastomers, polyolefin thermoplastic elastomers, polyurethane thermoplastic elastomers, polyester thermoplastic elastomers, polyamide thermoplastic elastomers, polybutadiene thermoplastic elastomers, polyisoprene thermoplastic elastomers, A fluororubber type thermoplastic elastomer etc. can be mentioned.

  The ferromagnetic member 13 has a hardness (hereinafter simply referred to as "hardness") measured in accordance with JIS K 6253, which is smaller than the hardness of the block portion 12 in contact with the ferromagnetic member 13 Is preferred. Specifically, the hardness of the block portion 12 measured in accordance with JIS K 6253 is preferably 50 to 80, and more preferably 60 to 70. If the hardness of the block portion 12 is 50 to 80, sufficient running performance can be obtained. The hardness of the ferromagnetic member 13 measured according to JIS K 6253 is preferably 35 to 79, and more preferably 50 to 69. If the hardness of the ferromagnetic member 13 is 35 to 79, deformation of the ferromagnetic member 13 can be suppressed before the ferromagnetic member 13 is exposed to the surface of the tread portion 100a. If the hardness of the ferromagnetic member 13 is less than 35, the strength of the ferromagnetic member 13 is insufficient, and the block portion 12 directly in contact with the road surface is used even if it is not exposed to the surface of the tread portion 100a. As a result, the ferromagnetic member 13 may be deformed during traveling. In this case, in order to accurately detect the difference in magnetic field change before and after the state requiring replacement, high accuracy is required for sensing. The use of high precision magnetic sensors can be a cost disadvantage. When the hardness of the ferromagnetic member 13 exceeds 79, the ferromagnetic member 13 can not successfully follow the shape change of the pneumatic tire 11, which may affect the running property, or the ferromagnetic member 13 However, there is a risk that the tire may come off the pneumatic tire 1.

  FIG. 4 is a cross-sectional view of a portion of the tread portion 100 a of the pneumatic tire 1 according to the first embodiment of the present invention taken along the width direction. In FIG. 4, the magnetic field in the vicinity of the ferromagnetic member 13 is indicated by magnetic lines of force. In order to detect the change of the magnetic field due to the deformation of the ferromagnetic member 13 in the magnetic sensor 14, the position of the magnetic sensor 14 disposed across the rubber, ply, inner liner, etc. constituting the tread portion 100a is sufficient. A magnetic flux density is required. Therefore, the surface magnetic flux density of the ferromagnetic member 13 is preferably 0.3 to 50 mT, and more preferably 0.6 to 20 mT. If the surface magnetic flux density of the ferromagnetic member 13 is 0.3 to 50 mT, the magnetic sensor 14 mounted inside the tread portion 100a can sufficiently detect the influence of the ferromagnetic member 13 on the magnetic field. If the surface magnetic flux density is lower than 0.3 mT, the influence of the ferromagnetic member 13 on the magnetic field at the position of the magnetic sensor 14 is weak, and the change of the magnetic field generated by the deformation of the ferromagnetic member 13 is There is a possibility that it can not be detected sufficiently. If the value is higher than 50 mT, the amount of adsorption of iron powder or the like may increase during traveling, which may affect the traveling performance.

  The pneumatic tire 1 is manufactured by filling a tire material in a mold and performing vulcanization molding. In particular, in the method of manufacturing a pneumatic tire according to the first embodiment of the present invention, a ferromagnetic rubber material in which a magnetic filler is dispersed in a rubber material before setting the green tire in a mold that is a vulcanized mold is used. The pneumatic tire 1 can be manufactured only by arranging it in a mold and integrating it with the green tire in the vulcanization process without largely changing the conventional tire manufacturing process.

  More specifically, first, a ferromagnetic rubber material in which a magnetic filler is dispersed in a rubber material is manufactured. Here, in the case of using a rubber material that uses sulfur for the crosslinking reaction of natural rubber, diene-based synthetic rubber, etc., a mixture of unvulcanized rubber material and a magnetic filler that is a ferromagnetic substance such as ferrite powder is used. It can be a ferromagnetic rubber material. When using non-crosslinkable rubber materials such as chlorine-based acrylic rubber, epoxy-based acrylic rubber, silicone rubber, etc. and non-crosslinkable rubber materials such as thermoplastic elastomers, such as rubber materials and ferrite powder What applied a vulcanized adhesive to a part of the surface of a mixture with a magnetic filler which is a ferromagnetic substance can be used as a ferromagnetic rubber material. Next, the manufactured ferromagnetic rubber material is magnetized. At this time, a ferromagnetic rubber material using a rubber material which does not use sulfur for crosslinking reaction or a non-crosslinkable rubber material is magnetized such that the surface coated with the vulcanized adhesive becomes an N pole.

  Next, in a mold having the same shape as that of a mold for producing a pneumatic tire having a slip sign, a ferromagnetic rubber material is disposed at a position where a slip sign is conventionally formed. This position is a position closer to the center in the tire radial direction than the position where the tread surface of the tire is formed in the mold. At this time, the ferromagnetic rubber material is disposed with the N pole facing the center in the tire radial direction and the S pole facing the outside. Further, in a ferromagnetic material using a rubber material which does not use sulfur for crosslinking reaction or a non-crosslinkable rubber material, the surface coated with the vulcanized adhesive is disposed toward the center in the tire radial direction. In the arrangement of the ferromagnetic rubber material in the mold, the ferromagnetic rubber material can be fixed at a desired position by providing a magnet on the outside of the mold. Thereafter, a green tire containing unvulcanized rubber is filled in a mold in which the ferromagnetic rubber material is disposed, and the green tire is heated in the mold to be contained in the green tire and the ferromagnetic rubber material or the vulcanized adhesive. The green tire and the ferromagnetic rubber material are integrated by vulcanization molding with a vulcanized rubber. As a result, the pneumatic tire 1 in which the ferromagnetic member 13 is provided integrally with the tread portion 100a is obtained.

  In the method of manufacturing a pneumatic tire according to the first embodiment of the present invention, the pneumatic tire 1 can also be provided by disposing a ferromagnetic rubber material on the surface of the green tire before setting the green tire in a mold. It can be manufactured. Specifically, first, the ferromagnetic rubber material is disposed at the position where the longitudinal groove of the tread surface of the green tire containing unvulcanized rubber is formed. In the step of arranging the ferromagnetic rubber material on the surface of the green tire, for example, by arranging the ferromagnetic rubber material every time the green tire is rotated by a fixed angle, as in the pneumatic tire 1 shown in FIG. The ferromagnetic members 13 can be provided at equal intervals in the tire circumferential direction. Next, the mold is filled with a green tire having a ferromagnetic rubber material disposed on its surface. Here, a green tire is used so that the mold has a recess formed at a position closer to the center in the tire radial direction than the position at which the tread surface of the tire is formed, and the ferromagnetic rubber material is accommodated in the recess. Position the Thereafter, the green tire and the ferromagnetic rubber material are integrated by heating and curing the green tire and the unvulcanized rubber contained in the ferromagnetic rubber material or the vulcanized adhesive in the mold. . As a result, the pneumatic tire 1 in which the ferromagnetic member 13 is provided integrally with the tread portion 100a is obtained.

  In the manufacturing method in which the ferromagnetic rubber material is disposed in the mold before setting the green tire in the mold, the ferromagnetic rubber material may not be magnetized before being disposed in the mold. In addition, in the manufacturing method in which the ferromagnetic rubber material is disposed on the surface of the green tire before setting the green tire in the mold, the ferromagnetic rubber material is not magnetized before being disposed on the surface of the green tire. May be In these cases, the pneumatic tire 1 can be obtained by magnetizing the portion corresponding to the ferromagnetic member 13 in the pneumatic tire obtained after vulcanization formation. Alternatively, magnetized ferrite powder or the like may be used to manufacture the ferromagnetic rubber material.

  In addition, in the manufacturing method in which the ferromagnetic rubber material is disposed in the mold before setting the green tire in the mold, when using a rubber material that does not use sulfur for the crosslinking reaction or a non-crosslinkable rubber material, The application of the vulcanized adhesive to the ferromagnetic rubber material may be performed after the ferromagnetic rubber material is placed in the mold.

  In addition, a manufacturing method in which the ferromagnetic rubber material is disposed in the mold before setting the green tire in the mold, and a ferromagnetic rubber material disposed on the surface of the green tire before setting the green tire in the mold In any of the manufacturing methods, if the ferromagnetic rubber material is made of a rubber material using sulfur for the crosslinking reaction, the green tire and the ferromagnetic rubber material contain the same unvulcanized rubber material Is preferred. When the ferromagnetic rubber material is composed of a rubber material that does not use sulfur for crosslinking reaction or a non-crosslinkable rubber material, the green tire and the vulcanized adhesive applied to the ferromagnetic rubber material are the same as unvulcanized It is preferable to include a rubber material. In these cases, the rubber of the tread portion 100a and the ferromagnetic member 13 are firmly integrated after vulcanization molding. Furthermore, in the case of forming a ferromagnetic rubber material with a rubber material that does not use sulfur for crosslinking reaction or a non-crosslinkable rubber material, a solvent type adhesive in which the base material is dissolved in a solvent instead of the vulcanized adhesive. It is also possible to use etc. When a solvent type adhesive is used, the solvent can be vaporized by heating in the step of vulcanizing the green tire, and the green tire and the magnetic rubber material can be bonded and integrated.

  As described above, in the pneumatic tire 1 according to the first embodiment, since the ferromagnetic member 13 is disposed closer to the center in the tire radial direction than the tread portion 100a, the ferromagnetic tire 1 is ferromagnetic at the start of use of the tire. The body member 13 is not affected by the contact road surface, and the deformation of the ferromagnetic member during traveling can be suppressed. Therefore, the change of the magnetic field in the vicinity of the ferromagnetic member 13 becomes minute at this time. However, when the wear of the tire progresses and the ferromagnetic member 13 is exposed on the surface of the tread portion 100a, the deformation of the ferromagnetic member 13 and the wear of the ferromagnetic member 13 itself subsequently occur during traveling. In addition, when the aged deterioration of the tire progresses, the elasticity and restoring force of the tread portion 100a decrease, and the ferromagnetic member 13 is pulled by the tread portion 100a and easily deformed. Therefore, the change of the magnetic field in the vicinity of the ferromagnetic member 13 becomes relatively large at this time. Thus, the use period of the pneumatic tire 1 according to the first embodiment is divided into two periods in which the aspect of the magnetic field change is significantly different. Therefore, by setting the height h of the ferromagnetic member 13 appropriately, it is possible to determine that the replacement state is required regardless of the use condition of the tire, based on the detection value of the magnetic sensor 14 without relying on visual observation. It becomes possible to detect.

Second Embodiment
In the second embodiment, a pneumatic tire 1 having a yoke (a yoke) will be described. Here, description is abbreviate | omitted about the structure similar to the pneumatic tire 1 in 1st Embodiment.

  FIG. 5 is a cross-sectional view of a portion of a tread portion 100a of a pneumatic tire 1 according to a second embodiment of the present invention taken along the width direction. In FIG. 5, the magnetic field in the vicinity of the ferromagnetic member 13 is indicated by magnetic lines of force. In the pneumatic tire 1 according to the second embodiment, a yoke 15 that is a magnetic coupling member is provided on the surface of the magnetic sensor 14 on the center side in the tire radial direction. As shown in FIG. 5, the yoke 15 cooperates with the ferromagnetic member 13 to form a magnetic circuit.

  In the pneumatic tire 1 according to the second embodiment having such a configuration, the magnetic flux is concentrated on the magnetic sensor 14 located between the ferromagnetic member 13 and the yoke 15, so the detection accuracy of the magnetic sensor 14 is improved. It can be done. As a result, it becomes possible to detect the contact waveform more accurately, and it is even easier to detect that the pneumatic tire 1 has become in the required replacement state by the detection value of the magnetic sensor 14 without relying on visual observation. become.

Third Embodiment
In the third embodiment, a pneumatic tire 1 in which the ferromagnetic member is a soft magnetic material will be described. Here, description is abbreviate | omitted about the structure similar to the pneumatic tire 1 in 1st Embodiment.

  FIG. 6 is a cross-sectional view of a portion of a tread portion 100a of a pneumatic tire 1 according to a third embodiment of the present invention taken along the width direction. In FIG. 6, the magnetic field in the vicinity of the ferromagnetic member 13 is indicated by magnetic lines of force. In the pneumatic tire 1 according to the third embodiment, the ferromagnetic member 16 is provided at the bottom of the longitudinal groove 11, and the bias magnet 17 as the magnetic coupling member is provided on the surface of the magnetic sensor 14 on the center side in the tire radial direction. It is done. As shown in FIG. 6, the ferromagnetic member 16 cooperates with the bias magnet 17 to form a magnetic circuit.

  The ferromagnetic member 16 is made of a rubber material in which a magnetic filler of a soft magnetic material is dispersed. Examples of soft magnetic fillers include powders of soft magnetic materials such as pure iron, carbon steel, stainless steel, soft ferrite, iron-silicon alloys, iron-nickel alloys, and iron-cobalt alloys. In particular, the use of carbon steel is preferred. The powder of the soft magnetic material may or may not be surface-treated, but is preferably surface-treated from the viewpoint of corrosion resistance and the like. As a rubber material used for the ferromagnetic member 16, a thermoplastic elastomer, a thermosetting elastomer, or a mixture thereof can be used. Examples of thermosetting elastomers include polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, polychloroprene rubber, nitrile rubber, diene-based synthetic rubber such as ethylene-propylene rubber, ethylene-propylene rubber, butyl rubber, acrylic rubber, polyurethane rubber Although non-diene based synthetic rubbers such as fluororubber, silicone rubber, epichlorohydrin rubber, and natural rubber can be mentioned, it is preferable to use the same rubber material as the material of the block portion 12. Examples of thermoplastic elastomers include styrene thermoplastic elastomers, polyolefin thermoplastic elastomers, polyurethane thermoplastic elastomers, polyester thermoplastic elastomers, polyamide thermoplastic elastomers, polybutadiene thermoplastic elastomers, polyisoprene thermoplastic elastomers, A fluororubber type thermoplastic elastomer etc. can be mentioned. The bias magnet 17 is a permanent magnet such as a ferrite magnet disposed so that the center side in the tire radial direction is an N pole and the outer side is an S pole.

  In the pneumatic tire 1 according to the third embodiment having such a configuration, since the magnetic flux is concentrated on the magnetic sensor 14 located between the ferromagnetic member 16 and the bias magnet 17, the detection accuracy of the magnetic sensor 14 can be increased. It can be improved. As a result, it becomes possible to detect the contact waveform more accurately, so that it is possible to easily detect that the pneumatic tire 1 has become in the required replacement state by the detection value of the magnetic sensor 14 without relying on visual observation. it can. Further, since the ferromagnetic member 13 provided on the front side of the tread portion 100a is a soft magnetic material, the adsorption of iron powder or the like during traveling is small, and the traveling performance is not affected.

Fourth Embodiment
The pneumatic tire 1 according to the fourth embodiment is a tire that assumes use for sensing the state of a running tire and / or the state of a road surface in addition to the worn state of the tire and the tire replacement time. In the pneumatic tire 1 according to the first embodiment, the deformation of the ferromagnetic member 13 after being in direct contact with the road surface is suppressed by suppressing the deformation of the ferromagnetic member 13 until the ferromagnetic member 13 is in direct contact with the road surface. It was configured to be clearly detectable. On the other hand, in the pneumatic tire 1 according to the fourth embodiment, the ferromagnetic member 13 is configured to be easily deformed even when not in direct contact with the road surface. In such a configuration, the ferromagnetic member 13 is disposed adjacent to the block portion 12 and the hardness (a) of the ferromagnetic member 13 measured in accordance with JIS K 6253 and the JIS K 6253 It can be realized by setting the hardness ratio (a / b) to the hardness (b) of the block portion 12 to be measured to an appropriate value.

  In the pneumatic tire 1 according to the fourth embodiment, the block portion 12 preferably has a hardness (b) of 50 to 80, more preferably 60 to 70, which is measured in accordance with JIS K 6253. preferable. If the hardness (b) of the block portion 12 is 50 to 80, sufficient running performance can be obtained.

  The ferromagnetic member 13 is preferably integrally formed adjacent to the block portion 12 on both sides in the tire width direction at the bottom of the longitudinal groove 11. The ferromagnetic member 13 preferably has a hardness (a) of 15 to 60, more preferably 30 to 50, which is measured in accordance with JIS K 6253. If the hardness (a) of the ferromagnetic member 13 is 15 to 60, the ferromagnetic member 13 has sufficient flexibility, and the block portion depending on the state of the running tire and / or the road surface When 12 is deformed, the shape of the ferromagnetic member 13 is easily deformed by the pressure from the block 12. If the hardness of the ferromagnetic member 13 is less than 15, the strength of the ferromagnetic member 13 is insufficient, and excessive deformation of the ferromagnetic member 13 may make accurate sensing difficult. Also, the hardness of the ferromagnetic member 13 increases as the compounding amount of the magnetic filler increases. Therefore, when the hardness of the ferromagnetic member 13 is less than 15, the amount of the magnetic filler that can be filled is small, and the magnetic force necessary for sensing may not be obtained. When the hardness of the ferromagnetic member 13 exceeds 60, sufficient flexibility can not be obtained for the ferromagnetic member 13 and the ferromagnetic member 13 is applied even when a force is applied via the block portion 12 in direct contact with the road surface. There is a risk that 13 does not deform sufficiently.

  The hardness ratio (a / b) of the hardness (a) of the ferromagnetic member 13 to the hardness (b) of the block portion 12 is preferably 0.1875 or more and less than 1, and is 0.45 or more. , Less than 0.7 is more preferable. When the hardness ratio (a / b) is at least 0.1875 and less than 1, a force is applied via the block portion 12 in direct contact with the road surface while maintaining sufficient running performance by appropriate hardness of the block portion 12 Thus, the ferromagnetic member 13 is deformed during traveling. Therefore, by detecting the magnetic field change due to the deformation of the ferromagnetic member 13 with the magnetic sensor 14, it is possible to sense the road surface condition as well as the tire condition from the beginning of use of the tire. If the hardness ratio (a / b) is less than 0.1875, excessive deformation of the ferromagnetic member 13 may make accurate sensing difficult. When the hardness ratio (a / b) is 1 or more, sufficient flexibility is not obtained for the ferromagnetic member 13 and the ferromagnetic member is obtained even when a force is applied via the block portion 12 in direct contact with the road surface. There is a possibility that 13 does not deform. As a result, in a state where the ferromagnetic member 13 is not exposed on the surface of the tread portion 100a, it is difficult to sense the state of the tire and / or the state of the road surface.

  In the pneumatic tire 1 according to the fourth embodiment, although direct effects such as force and temperature from the road surface are received by the block portion 12 in contact with the road surface, the hardness measured by the block portion 12 according to JIS K 6253 Since the ferromagnetic members 13 configured to be smaller are arranged adjacent to each other, the deformation of the block 12 depending on the state of the road surface, the state of the block 12 itself such as wear, etc. The change in shape of the magnetic member 13 is reflected. In addition, when the aged deterioration of the tire progresses, the elasticity and restoring force of the block portion 12 decrease, and the ferromagnetic member 13 is pulled by the block portion 12 and easily deformed. Therefore, by detecting the change in the magnetic field in the vicinity of the ferromagnetic member 13 with the magnetic sensor 14, it is possible to sense the state of the tire or the road surface.

  For example, when the block portion 12 is deformed so as to be crushed in the tire radial direction by a force from the road surface, the ferromagnetic member 13 is compressed and deformed by receiving pressure from the block portion 12 adjacent to both side surfaces. The compressive deformation from the side of the ferromagnetic member 13 causes the particles of the magnetic filler dispersed in the rubber material of the ferromagnetic member 13 to coagulate, diffuse or rotate. A magnetic field pulse is formed by repeating aggregation and diffusion of the particles of the magnetic filler, and concentration or cancellation of the magnetic pole occurs by rotation of the particles of the magnetic filler, so these can be easily detected by the magnetic sensor 14. Furthermore, since the ferromagnetic member 13 is integrally formed with the block portion 12, when the block portion 12 is deformed so as to be squeezed in the tire radial direction by the force from the road surface, the block portion 12 is dragged and deformed. It also deforms in the tire radial direction. By such deformation, the position of the magnetic filler dispersed in the rubber material of the ferromagnetic member 13 can be displaced in the tire radial direction. The displacement of the magnetic filler in the tire radial direction causes a change in distance from the magnetic sensor 14, which can be easily detected by the magnetic sensor 14. As described above, by detecting the shape change of the ferromagnetic member 13 with the magnetic sensor 14, it is possible to sense the slip, acceleration, jerk, vibration, etc. of the pneumatic tire 1 with respect to the road surface from the strength, period, etc. It becomes possible. The ferromagnetic member 13 is also compressed and deformed by receiving pressure from the block portions 12 adjacent to both side surfaces by deformation of the pneumatic tire 1 due to road surface contact. Therefore, it is possible to sense the air pressure of the pneumatic tire 1 by detecting the change in shape of the ferromagnetic member 13 with the magnetic sensor 14.

  In addition, since the tire or road surface condition is not directly sensed from the block 12, there is no need to change the configuration of the block 12 from the conventional tire, and the travel performance such as traction performance realized by the block 12 is impaired. Absent. Furthermore, since the hardness of the ferromagnetic member 13 is smaller than the hardness of the block portion 12, when the ferromagnetic member 13 is exposed to the tread surface 12a by the progress of wear, the ferromagnetic member 13 is blocked by the force from the road surface. The deformation is larger than that of the part 12, and the change of the magnetic field becomes remarkable. Therefore, the magnetic sensor 14 can easily detect that the worn state requiring tire replacement has been reached.

Fifth Embodiment
In the fifth embodiment, a pneumatic tire 1 having a plurality of ferromagnetic members arranged so as to have different magnetization directions will be described. Here, description is abbreviate | omitted about the structure similar to the pneumatic tire 1 in 4th Embodiment.

  FIG. 7 is a cross-sectional view taken along the width direction of the tread portion 100 a of the pneumatic tire 1 according to the fifth embodiment of the present invention. In FIG. 7, magnetic fields in the vicinity of the ferromagnetic members 113 a to 113 d in the cross section in the width direction of the tread portion 100 a are indicated by magnetic lines of force.

  In the pneumatic tire 1 according to the fifth embodiment, four longitudinal grooves 11a to 11d aligned in the tire width direction are formed in the tread portion 100a, and ferromagnetic members 113a to 113d are disposed at the bottoms of the tread portions 100a. There is. The ferromagnetic member 113a disposed at the bottom of the longitudinal groove 11a has an S pole at the center in the tire radial direction, and the ferromagnetic member 113b disposed at the bottom of the longitudinal groove 11b has an N pole at the tire radial center. is there. With such an arrangement, the ferromagnetic members 113a and the ferromagnetic members 113b adjacent to each other form a magnetic circuit. The ferromagnetic member 113c disposed at the bottom of the longitudinal groove 11c has an N pole at the center in the tire radial direction, and the ferromagnetic member 113d disposed at the bottom of the longitudinal groove 11d has an S at the center in the tire radial direction. The ferromagnetic member 113c and the ferromagnetic member 113d form a magnetic circuit. On the other hand, although the ferromagnetic member 113b and the ferromagnetic member 113c are adjacent to each other, no magnetic circuit is formed because the magnetization directions are the same.

  Inside the tread portion 100a, the magnetic sensor 14 is provided at a position corresponding to between the ferromagnetic member 113a and the ferromagnetic member 113b and at a position corresponding to between the ferromagnetic member 113c and the ferromagnetic member 113d. Is attached. At each position of the magnetic sensor 14, the magnetic flux is concentrated by the magnetic circuit formed by the ferromagnetic member 113a and the ferromagnetic member 113b and the magnetic circuit formed by the ferromagnetic member 113c and the ferromagnetic member 113d. Therefore, the detection accuracy of the magnetic sensor 14 can be improved. Therefore, in the pneumatic tire 1 according to the fifth embodiment, the magnetic sensor 14 can detect the magnetic field change due to the deformation of the ferromagnetic members 113a to 113d with high accuracy. Thereby, the condition of the tire and / or the condition of the road surface can be sensed with high accuracy from the beginning of use of the tire.

Sixth Embodiment
In the sixth embodiment, a pneumatic tire 1 having two types of ferromagnetic members having different depths from the tread surface along the tire radial direction will be described. Here, description is abbreviate | omitted about the structure similar to the pneumatic tire 1 in 1st Embodiment.

  FIG. 8 is a cross-sectional view taken along the width direction of the tread portion 100 a of the pneumatic tire 1 according to the sixth embodiment of the present invention. FIGS. 8A and 8B respectively show cross sections at different angles in the circumferential direction with respect to the rotation center O of the pneumatic tire 1.

  At the position shown in FIG. 8A, the ferromagnetic member 13L is disposed at the bottom of the longitudinal groove 11. The ferromagnetic member 13L is configured such that the height h1 from the bottom of the longitudinal groove 11 matches the depth of the longitudinal groove 11 recommended for tire replacement, and the pneumatic tire 1 is in a state requiring replacement. When exposed to the surface of the tread portion 100a. Therefore, the first magnetic sensor 14a facing the ferromagnetic member 13L detects a contact waveform after the tire is in a state requiring replacement, and outputs this.

  At the position shown in FIG. 8 (b), the ferromagnetic member 13 H is disposed at the bottom of the longitudinal groove 11. The height h2 of the ferromagnetic member 13H from the bottom of the longitudinal groove 11 is set higher than the height h1 of the ferromagnetic member 13L, and the tread portion 100a is formed before the pneumatic tire 1 is in the state of needing replacement. Exposed on the surface of Therefore, the second magnetic sensor 14b facing the ferromagnetic member 13H detects a contact waveform before the tire needs to be replaced, and outputs this.

  FIG. 9 is a graph showing temporal changes in detection results of the first magnetic sensor 14a and the second magnetic sensor 14b. The output of the magnetic sensor such as a Hall element is a voltage (V) according to the magnetic flux density (T). However, in FIG. 9, the output of each magnetic sensor at the start of use of the tire is An arbitrary unit (au) as a reference is used. In addition, although the output of the magnetic sensor produces minute fluctuations even when the contact waveform does not appear, its amplitude is extremely small compared to the amplitude of the contact waveform, and it is easy to distinguish from the contact waveform. is there. Therefore, in FIG. 9, the output of the magnetic sensor in the state where the contact waveform does not appear is drawn flat.

  During the period from the start of tire use to the time when the ferromagnetic member 13H is exposed on the surface of the tread portion 100a (first period), the contact waveform is applied to any of the outputs of the first magnetic sensor 14a and the second magnetic sensor 14b. Does not appear.

  However, as the wear of the block portion 12 progresses, the ferromagnetic member 13H is exposed on the surface of the tread portion 100a and the ferromagnetic member 13L is on the surface of the tread portion 100a due to the difference in height from the bottom of the longitudinal groove 11. State (hereinafter, referred to as "attention required state"). The wear of the block 12 further progresses from the time when the caution state is reached, and the period (second period) until the ferromagnetic member 13L is also exposed to the surface of the tread 100a is the output of the second magnetic sensor 14b. The contact waveform appears only, and the contact waveform does not appear at the output of the first magnetic sensor 14a. Further, in the second period, since the ferromagnetic member 13H also wears, the magnetic flux density at the position of the second magnetic sensor 14b is attenuated along with the wear of the ferromagnetic member 13H, and the detected value also decreases.

  In the period (third period) after the ferromagnetic member 13L is exposed to the surface of the tread portion 100a and in a state requiring replacement (a third period), the contact waveforms are output from the outputs of both the first magnetic sensor 14a and the second magnetic sensor 14b. Appear. Further, in the third period, since the ferromagnetic members 13H and 13L also wear, the magnetic flux density at the position of the first magnetic sensor 14a and the second magnetic sensor 14b along with the wear of the ferromagnetic members 13H and 13L It attenuates and their detected values also decrease.

  As described above, in the pneumatic tire 1 according to the sixth embodiment, the difference in height between the ferromagnetic members 13H and 13L causes a time shift at the time of exposure on the surface of the tread portion 100a, and hence the air During the use period of the tire 1, the contact waveform does not appear in any of the outputs of the first magnetic sensor 14a and the second magnetic sensor 14b. In the first period, the contact waveform appears only in the output of the second magnetic sensor 14b. It is divided into two periods, and three periods in which a contact waveform appears in both outputs. Therefore, it becomes possible to detect not only the state in which the tire needs to be replaced but also, for example, the state a little before that, based on the detection result of the magnetic sensor without relying on visual observation.

Seventh Embodiment
In the seventh embodiment, a method of determining a worn state of a pneumatic tire for warning a driver of a worn state of a vehicle in a vehicle will be described. FIG. 10 is a flowchart showing the processing procedure of the method of determining the worn state of a pneumatic tire according to the seventh embodiment of the present invention. The wear state determination method of the pneumatic tire according to the seventh embodiment obtains the outputs of the first magnetic sensor 14a and the second magnetic sensor 14b on the vehicle side with the pneumatic tire 1 according to the sixth embodiment as a determination target Used for wear condition determination.

  In the wear state determination method of the pneumatic tire according to the seventh embodiment, first, an output of a unit time (for example, 1 second) of the first magnetic sensor 14a is acquired as continuous data (step 1), and a contact waveform appears It is determined whether it is (step 2). The determination of the appearance of the touch waveform can be made, for example, based on whether or not the amplitude of the output value exceeds a threshold in continuous data of unit time. When the contact waveform appears in the output of the first magnetic sensor 14a (Step 2: Yes), the pneumatic tire 1 is in the replacement required state, and a tire change signal is issued (Step 3).

  When the contact waveform does not appear in the output of the first magnetic sensor 14a (Step 2: No), the output of the unit time of the second magnetic sensor 14b is acquired as continuous data (Step 4), and the contact waveform appears. It is determined (step 5). When the contact waveform appears in the output of the second magnetic sensor 14b (step 5: Yes), the pneumatic tire 1 approaches the state requiring replacement and is in the caution state, so an alert signal is issued ( Step 6). When the contact waveform does not appear in the output of the second magnetic sensor 14 b (Step 5: No), the determination is ended.

  As described above, in the processing procedure of the method of determining the worn state of the pneumatic tire according to the seventh embodiment, the change of the magnetic field in the vicinity of the ferromagnetic member 13L without relying on visual observation that the tire is in the required replacement state. It is possible to make a determination based on Moreover, it is possible to determine not only the state in which the tire needs to be replaced, but also, for example, the critical state just before that based on the change of the magnetic field in the vicinity of the ferromagnetic member 13H without relying on visual observation. .

  When the pneumatic tire 1 according to the first embodiment is used as a determination target in the method of determining the worn state of the pneumatic tire, only the steps 1 to 3 in the flowchart shown in FIG. 10 should be performed. Thus, it becomes possible to determine that the tire needs to be replaced based on the change in the magnetic field in the vicinity of the ferromagnetic member 13 without relying on visual observation.

  Further, the wear state determination method of the pneumatic tire according to the seventh embodiment may be performed by, for example, providing a computer on a vehicle and causing a computer to execute a computer program in which the processing procedure of the flowchart shown in FIG. It is possible.

[Another embodiment]
The pneumatic tire according to the present invention has the above-described first embodiment, as long as it exhibits the effect of the present invention that the worn state requiring tire replacement is detected by a magnetic sensor without relying on visual observation. It is also possible to change the configuration described in the seventh embodiment. Several such modifications are described as alternative embodiments. 11 and 12 are explanatory diagrams of another embodiment.

Another Embodiment 1
In the pneumatic tire 1 according to the first embodiment described above, as shown in FIG. 11A, a film-like flexibility is provided between the surface (inner liner) on the back side of the tread portion 100a and the sensor component 14 It is possible to provide a sexing member 700. In this configuration, there is no need to attach the plurality of magnetic sensors 14 one by one to the inside of the tire after molding in the manufacture of the pneumatic tire 1, and the flexible member 700 in a state in which the plurality of magnetic sensors 14 are fixed on the upper surface. The plurality of magnetic sensors 14 can be attached collectively to the tire by pasting the rear side of the tread portion 100a. Therefore, it is possible to improve the workability in the manufacture of the pneumatic tire 1. Furthermore, a feed circuit to the magnetic sensor 14, a transmission circuit for transmitting the detection result of the magnetic sensor 14 to the outside of the pneumatic tire 1 or the like may be formed on the flexible member 700.

  Further, as shown in FIG. 11B, the flexible member 700 has a first portion 700a of a long shape along the tire circumferential direction passing through the center of the tread portion 100a or the vicinity thereof, and a first portion 700a. It is also possible to configure in a shape having a second portion 700b extending laterally from the first portion 700a orthogonal to the longitudinal direction. In this configuration, when sticking on the back side of the tread portion 100a, the flexible member 700 is unlikely to be wrinkled or overlapped, and the magnetic sensor 14 can be attached more accurately.

Another Embodiment 2
The magnetic sensor 14 does not necessarily have to be provided on the pneumatic tire 1. For example, as shown in FIG. 12, by providing the magnetic sensor 14 in a tire house of a vehicle attached with the pneumatic tire 1, it is possible to detect the magnetic field in the vicinity of the ferromagnetic member 13. In such a configuration, it is not necessary to provide the pneumatic tire 1 with a transmission circuit or the like for transmitting the detection result of the magnetic sensor 14 to the outside of the pneumatic tire 1. For example, it is possible to output the detection value of the magnetic sensor 14 directly to the computer 20 mounted on the vehicle. By causing the computer 20 to execute a program including the processing procedure of the flowchart shown in FIG. 10 and displaying the determination result on the monitor 30, it is possible to warn the driver that it is necessary to change the tire.

  The pneumatic tire 1 according to the present invention is useful in applications such as passenger cars, trucks, buses, motorcycles, etc. for detecting worn states of tires without relying on visual observation, and in addition to conventional vehicles operated by a driver. The invention is also applicable to a vehicle provided with a driving support function or an automatic driving function.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 11, 11a-d Vertical groove 12a Tread surface 13, 13L, 13H, 113a-d, 16 Ferromagnetic member 14 Magnetic sensor (detection part)
15 Yoke (magnetic coupling member)
17 Bias magnet (magnetic coupling member)
100a tread

Claims (14)

A pneumatic tire capable of detecting the wear state of the tire,
A tread portion having a tread surface formed in contact with the road surface;
The said tread part is a pneumatic tire which has a ferromagnetic material member arrange | positioned on the tire radial direction center side with respect to the said tread surface.   The pneumatic tire according to claim 1, wherein the ferromagnetic member is disposed at a bottom of a longitudinal groove formed in the tread portion in the circumferential direction. The tread portion has a plurality of the ferromagnetic members.
The pneumatic tire according to claim 1 or 2, wherein the plurality of ferromagnetic members are arranged along the tire circumferential direction and / or the tire width direction. The tread portion has a plurality of the ferromagnetic members.
The depth according to any one of claims 1 to 3, wherein at least two of the plurality of ferromagnetic members are different in depth from the tread surface in the tire radial direction. Pneumatic tire.   5. The pneumatic material according to claim 1, wherein the ferromagnetic member is configured such that the hardness measured in accordance with JIS K 6253 is smaller than the hardness of the tread surface. tire.   The pneumatic tire according to any one of claims 1 to 5, further comprising: a detection unit disposed on the back side of the tread portion to face the ferromagnetic member and detecting a change in a magnetic field.   The pneumatic tire according to claim 6, further comprising: a magnetic coupling member disposed on the back side of the tread portion opposite to the ferromagnetic member and forming a magnetic circuit with the ferromagnetic member.   The pneumatic tire according to claim 7, wherein the magnetic coupling member is disposed closer to the center in the tire radial direction than the detection portion. A method for producing a pneumatic tire, comprising the steps of: curing a material filled in a mold to produce a tire;
A first step of disposing a ferromagnetic rubber material at a position closer to the center in the tire radial direction than a position at which the tread surface of the tire is formed in the mold;
A second step of filling a green tire containing unvulcanized rubber in the mold in which the ferromagnetic rubber material is disposed;
A third step of integrating the green tire and the ferromagnetic rubber material by heating in the mold;
A method of manufacturing a pneumatic tire, including: The ferromagnetic rubber material includes unvulcanized rubber,
The method for manufacturing a pneumatic tire according to claim 9, wherein the green tire and the ferromagnetic rubber material are vulcanized by heating in the third step. The ferromagnetic rubber material is coated with an adhesive on the side on which the green tire is disposed,
The method for manufacturing a pneumatic tire according to claim 9, wherein the green tire and the ferromagnetic rubber material are adhered by the adhesive by heating in the third step. A method for producing a pneumatic tire, comprising the steps of: curing a material filled in a mold to produce a tire;
A first step of disposing a ferromagnetic rubber material at a position where a longitudinal groove is formed on a tread surface of a green tire containing unvulcanized rubber;
A second step of filling the mold with the green tire in which the ferromagnetic rubber material is disposed;
A third step of integrating the green tire and the ferromagnetic rubber material by heating in the mold;
A method of manufacturing a pneumatic tire, including: A method of determining the wear state of a pneumatic tire, comprising
The pneumatic tire includes a tread portion in which a tread surface in contact with a road surface is formed, and the tread portion includes a ferromagnetic member disposed on a radial center side of the tread surface.
Detecting the change of the magnetic field in the vicinity of the ferromagnetic member;
A determination step of determining a wear state of the tread portion according to a change in the detected magnetic field;
A method of determining the wear state of a pneumatic tire, including: In the pneumatic tire, a plurality of the ferromagnetic members are arranged such that the depths from the tread surface along the tire radial direction are different from each other,
In the detection step, a change in the magnetic field in the vicinity is detected for each of the plurality of ferromagnetic members;
The wear of the pneumatic tire according to claim 13, wherein in the determination step, the wear state of the tread portion is determined according to one of the plurality of ferromagnetic members in which a change in a detected magnetic field exceeds a predetermined amount. State determination method.

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