JP2017039359A - Run flat tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a run flat tire that allows a heat history of side-reinforcing rubbers during run-flat travelling to be visually checked.SOLUTION: The run flat tire has a side wall part which connects a tread part and a bead part, side reinforcing rubbers provided on an inner surface of the side wall part, and a heat sensitive member, provided at a region including the maximum bent part on the inner surface side of the side reinforcing rubbers, which includes a thermosensitive foamable material and a compressive strain absorbable material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a run flat tire.

As a tire that can puncture a certain distance when the tire punctures during traveling, there is a run flat tire in which a sidewall portion is reinforced with a side reinforcing rubber.
As a run-flat tire, for example, a run-flat tire that makes it possible to later determine the presence or absence of a puncture running history by applying a color-changing material that irreversibly discolors due to a change in temperature due to heat to the inner surface of the sidewall portion of the tire. Has been reported (for example, Patent Document 1).

JP 2013-132989 A

On the other hand, the run-flat tire can be used by repairing the puncture after the run-flat running (punk running). However, if the side reinforcement rubber receives heat above a certain level during run-flat driving, the side reinforcement rubber may have deteriorated. desired.
However, it is difficult to visually determine whether the side reinforcing rubber has received a certain amount of heat during the run-flat running.
Further, for example, in the run flat tire of Patent Document 1, when the tire is bent and deformed by run flat running, the applied discoloration material may be peeled off at a portion where the tire is severely bent and deformed. It is also assumed that the thermal history of the bent part cannot be surely known.

  An object of the present invention is to provide a run flat tire which can check the heat history of the side reinforcement rubber in run flat running in consideration of the above-mentioned matter.

<1> A sidewall portion connecting the tread portion and the bead portion, a side reinforcing rubber disposed on an inner surface of the sidewall portion, and a region including a maximum bent portion on the inner surface side of the side reinforcing rubber, and is heat sensitive. And a temperature indicating member including a foamable material and a compressive strain absorbing material.

In the run flat tire according to <1>, a temperature indicating member having a compressive strain absorbing material and a heat-sensitive foaming material on an inner surface side of a side reinforcing rubber disposed on an inner surface of a sidewall portion connecting the tread portion and the bead portion. The temperature indicating member is bonded to the inner surface of the side reinforcing rubber during normal running. On the other hand, when the side reinforcing rubber formed on the inner surface of the sidewall portion is bent and deformed to increase the temperature, the volume of the heat-sensitive foamable material expands. Due to the expansion of the volume, all or a part of the temperature indicating member is dropped or deformed. Such falling off means that, in the temperature indicating member, for example, when the heat-sensitive foamable material is present in the vicinity of the side reinforcing rubber, the temperature indicating member and the side reinforcing rubber are caused by expansion of the volume of the heat-sensitive foamable material. This may be caused by a decrease in the area of adhesion with the inner surface, or may be caused by a decrease in the compressive strain absorption capacity of the temperature indicating member.
Further, in the temperature indicating member, when the heat-sensitive foamable material is separated from the inner surface of the side reinforcing rubber, the portion including the heat-sensitive foamable material expands due to foaming of the heat-sensitive foamable material, and the portion As a result, the area including the heat-sensitive foamable material falls off or the part deforms due to the reduction of the contact area with the other part.
Therefore, even if the side reinforcement rubber is bent and deformed during run-flat running, if the side reinforcement rubber does not rise above a certain temperature, the temperature indicating member does not deform and adheres to the inside of the side reinforcement rubber. However, during run-flat running, the side reinforcement rubber repeatedly bends greatly, and when the side reinforcement rubber reaches a certain temperature or higher, all or part of the temperature indicating member drops or deforms. The heat history of can be confirmed. It is possible to determine whether or not the side reinforcing rubber has deteriorated due to the thermal history, that is, the degree of durability of the side reinforcing rubber, and to provide effective information for determining whether the tire is repaired or replaced after puncture.

  Here, the temperature indicating member may be provided on the inner surface of the side reinforcing rubber. That is, the temperature indicating member may be arranged directly on the side reinforcing rubber. However, when the inner liner is provided on the inner surface of the side reinforcing rubber, the inner side of the temperature indicating member on the region including the maximum bent portion of the side reinforcing rubber is set. A temperature indicating member is disposed on the inner surface of the side reinforcing rubber via the liner.

  <2> The run flat tire according to <1>, wherein the temperature indicating member includes a layer including the compression strain absorbing material and the heat-sensitive foamable material.

  <3> The temperature indicating member is a laminate in which a compression strain absorbing layer including the compressive strain absorbing material and a temperature indicating layer including the heat-sensitive foamable material are stacked in this order on the inner side of the side reinforcing rubber. The run flat tire according to <1>.

  <4> The run-flat tire according to any one of <1> to <3>, wherein the compressive strain absorbing material includes a silicone resin adhesive.

  <5> The run-flat tire according to any one of <1> to <4>, wherein the thermal conductivity of the temperature indicating member is 0.2 W / m · K or more.

<6> The temperature indicating member according to any one of <1> to <5>, wherein the elastic modulus at 25 ° C. is 1 × 10 ⁶ Pa to 1 × 10 ¹⁰ Pa.

  <7> The run flat tire according to any one of <1> to <6>, wherein a plurality of the temperature indicating members are arranged.

  <8> The run flat tire according to <7>, wherein the plurality of temperature indicating members are arranged at intervals of 4 mm or more in at least one of a tire circumferential direction and a tire radial direction.

  <9> The region including the maximum bent portion is a region within 80% of the length from the lower end of the side reinforcing rubber to the upper end of the side reinforcing rubber in the tire radial direction of the side reinforcing rubber. The run flat tire according to any one of 8>.

  <10> The run-flat tire according to any one of <1> to <9>, wherein the heat-sensitive foamable material foams at a temperature of 80 ° C to 150 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the run flat tire which can confirm the heat history of the side reinforcement rubber | gum in run flat driving | running can be provided.

It is sectional drawing which shows the shape of the cross section along the tire width direction of the run flat tire which concerns on 1st Embodiment. It is sectional drawing which shows the change of the curvature radius in the largest bending part of the tire bent and deform | transformed by puncture. (A) shows the bent state of the tire during normal running, and (B) shows the bent state of the tire during run flat running. It is sectional drawing which shows the temperature indicating member in the tire of 1st Embodiment. (A) It is the schematic diagram which cut | disconnected the tire of 1st Embodiment along the tire circumferential direction and observed the inner surface of the tire from the tire side surface side. (B) It is the perspective view which expanded a part of inner surface of the tire of 1st Embodiment.

The run flat tire of the present invention includes a sidewall portion that connects the tread portion and the bead portion, a side reinforcing rubber disposed on the inner surface side of the sidewall portion, and a maximum bent portion on the inner surface side of the side reinforcing rubber. A temperature indicating member disposed in the region and including a heat sensitive foamable material and a compressive strain absorbing material.
According to the run flat tire of the present invention, it is possible to determine the degree of durability or the like of the side reinforcing rubber by checking the heat history of the side reinforcing rubber after the run flat running (puncture running).
“Confirmation” of the thermal history means confirmation of “presence / absence or deformation” of the temperature indicating member. The confirmation method includes not only a visual method but also a tactile method.
Details will be described below.

[First Embodiment]
The run flat tire 10 according to the first embodiment will be described with reference to FIG. Note that the present invention is not limited to the first embodiment.
FIG. 1 is a cross-sectional view showing a cross-sectional shape along the tire width direction of the run-flat tire according to the first embodiment. In addition, the arrow W in the drawing indicates the width direction of the run flat tire 10, and the arrow R indicates the tire radial direction of the run flat tire 10. Reference sign CL indicates a center line passing through the center of the run-flat tire 10 in the width direction.

A run-flat tire 10 according to the first embodiment (hereinafter referred to as “tire 10”) includes a pair of left and right bead portions 12 (only one bead portion 12 is shown in FIG. 1), and the pair of bead portions 12. A pair of bead cores 14 embedded therein, a carcass layer 16 extending in a toroidal shape between the pair of bead cores 14, a belt layer 18 provided radially outward of the tire 10 from the carcass layer 16, and the belt layer 18, a tread portion 20 provided radially outside the tire 10, a sidewall portion 22 that connects the bead portion 12 and the tread portion 20, an inner liner 25, and a side formed on the inner surface of the sidewall portion 22. And a reinforcing rubber 26.
In some cases, the tire 10 does not have the inner liner 25. In this case, the temperature indicating member 28 described later is directly bonded to the surface of the side reinforcing rubber 26. Therefore, the temperature indicating member 28 in the present invention is adhered to the inner surface of the side reinforcing rubber 26 or the surface of the inner liner 25.

  The carcass layer 16 is composed of one or a plurality of carcass plies. In the present embodiment, as an example, it is composed of two carcass plies. The carcass ply is formed by coating a plurality of cords (for example, an organic fiber cord or a metal cord) with a covering rubber. Further, the end portion of the carcass layer 16 is folded from the inside of the tire 10 to the outside around the bead core 14.

  The belt layer 18 is constituted by a plurality of belt plies as an example (may be constituted by one belt ply). The belt ply is formed by covering a plurality of cords (for example, an organic fiber cord, a metal cord, etc.) with a covering rubber.

  A plurality of circumferential grooves 24 extending in the circumferential direction of the tire 10 are formed in the tread portion 20. The tread portion 20 is formed with a plurality of width direction grooves (not shown) extending in a direction intersecting the circumferential direction.

  A side reinforcing rubber 26 is installed on the inner side in the tire axial direction of the sidewall portion 22, and constitutes a part of the inner wall of the tire 10. An inner liner 25 is provided on the inner wall of the tire 10 including the inner wall surface of the side reinforcing rubber 26. An upper end portion 26 </ b> A of the side reinforcing rubber 26 extends to the tread portion 20, and a lower end portion 26 </ b> B of the side reinforcing rubber 26 extends to the vicinity of the bead portion 12. Further, the side reinforcing rubber 26 becomes thinner as it goes to the upper end portion 26A and the lower end portion 26B. Further, the side reinforcing rubber 26 is made of rubber harder than the rubber constituting the sidewall portion 22, and even if the tire 10 is punctured, the side reinforcing rubber 26 supports the weight of the vehicle and the occupant. It is configured to allow flat travel (puncture travel).

The temperature indicating member 28 is disposed in a region 29 ′ including the maximum bent portion on the inner surface side of the side reinforcing rubber 26, that is, the surface of the side reinforcing rubber 26 on the inner side in the tire axial direction (inner side in the tire width direction). As will be described later, the temperature indicating member 28 includes a compression strain-absorbing material and a heat-sensitive foaming material, and is disposed on the surface of the side reinforcing rubber 26. In the tire 10, heat generated by the bending generated around the maximum bent portion 29 of the side reinforcing rubber 26 is transmitted to the temperature indicating member 28. Further, since the temperature indicating member 28 includes a compressive strain absorbing material, the maximum bending of the side reinforcing rubber 26 is achieved even when the side reinforcing rubber 26 of the tire 10 is bent and deformed during normal running or run flat running. When the region including the portion does not rise to a certain temperature or higher, the temperature indicating member 28 is not easily peeled off from the side reinforcing rubber 26 or the inner liner 25.
In the tire 10, when the run flat running is continued, the side reinforcing rubber 26 of the tire 10 repeatedly bends greatly, and heat of a certain temperature or more is generated around the maximum bent portion 29 of the side reinforcing rubber 26. This heat is transmitted to the temperature indicating member 28 disposed in the region 29 ′ including the maximum bent portion 29, and the heat-sensitive foaming material in the temperature indicating member 28 expands, so that the temperature indicating member 28 expands and the temperature indicating member 28 As a result that the adhesion to the side reinforcing rubber 26 cannot be maintained, the temperature indicating member 28 is peeled off from the side reinforcing rubber 26 or the inner liner 25. For this reason, the heat history of the side reinforcing rubber 26 can be confirmed by the presence or absence of the temperature indicating member 28 after the run flat running.

  In the first embodiment, the temperature indicating member 28 is disposed in a region 29 ′ including the maximum bent portion 29 on the inner surface of the side reinforcing rubber 26 of the tire 10.

Here, the “maximum bending portion” of the side reinforcing rubber means a portion where the bending of the side reinforcing rubber is maximum during run-flat running. The maximum bent portion of the side reinforcing rubber is determined as follows, for example. First, as shown in FIGS. 2 (A) and 2 (B), in the cross section in the tire width direction, the side reinforcing rubber is disposed at 0.5 cm intervals from the tire width direction center (CL) toward the bead portion 31 at the innermost circumference of the tire. A group of regions at regular intervals that divides the plane is determined (in FIG. 2, each region is indicated by a region 35). Next, the amount of change in the radius of curvature due to bending in each of the regions 35 at predetermined positions from CL, that is, the radius of curvature (r1) in a normal running tire (load 0 kN, internal pressure 200 kPa) in each region 35, and the run flat The radius of curvature (r2) of the running tire (load 8.5 kPa, internal pressure 50 kPa) is measured, and the amount of change (| r1-r2 |) is calculated.
As described above, the region 35 having the largest calculated amount of change on the inner surface of the side reinforcing rubber layer is referred to as a maximum bent portion (see 32 in FIG. 2A and 33 in FIG. 2B).
The curvature radius under each of the above conditions can be measured by image processing and measuring a cross-sectional image obtained by X-ray CT.

  As shown in FIGS. 2A and 2B, when the tire is punctured, the side reinforcing rubber 26 is greatly bent and deformed by a load in the tire radial direction. Since the tire 10 is rolling, the side reinforcing rubber 26 is continuously bent and deformed over the entire circumference. At this time, as shown in FIG. 2B, a maximum bent portion 33 having a radius r2 is generated. In this case, the location of the maximum bent portion is often near the maximum width of the tire regardless of the tire diameter, and often occurs at a certain position of the thickest portion of the side reinforcing rubber of the tire.

Next, the temperature indicating member 28 will be described.
The temperature indicating member 28 of the first embodiment is disposed in a region (region 29 ′ in FIG. 1) including the maximum bent portion on the surface of the side reinforcing rubber 26 formed on the inner surface of the sidewall portion.
FIG. 3 is a diagram illustrating a cross section of the temperature indicating member. As shown in FIG. 3, the temperature indicating member 28 disposed on the surface of the inner liner 25 has a layer containing a compressive strain absorbing material and a heat-sensitive foaming material.
The temperature indicating member 28 includes a compressive strain absorbing material, and absorbs compressive strain due to bending deformation from the side reinforcing rubber 26 and adheres to the surface of the inner liner 25 until the tire begins to bend greatly by continuing run-flat running. Keep doing.
Thereafter, when the side reinforcing rubber 26 repeatedly begins to bend greatly and the temperature of the inner surface of the side reinforcing rubber 26 rises, the heat-sensitive foaming material is fired by heat, and the temperature indicating member 28 expands rapidly. As a result, the temperature indicating member 28 Will not continue to adhere and will fall off the surface of the inner liner 25. The thermal history after run-flat traveling can be easily confirmed by the presence or absence of this dropout. Further, even if the temperature indicating member 28 does not fall off, the heat history can be easily confirmed in this case as well. Note that the arrow H in FIG. 3 indicates the height of the temperature indicating member 28, and the arrow L indicates the length of the temperature indicating member 28 in the tire width direction.

  Moreover, an example of arrangement | positioning of the temperature indicator 28 is shown to (A) and (B) of FIG. FIG. 4A is a schematic diagram in which the tire 10 is cut along the tire circumferential direction and the inside of the tire 10 is observed from the side surface of the tire 10. FIG. 4B is an enlarged perspective view of a part of the inner surface of the tire 10. As shown in FIG. 4A, a temperature indicating member 28 is disposed on the inner surface of the side reinforcing rubber 26 via an inner liner 25. A plurality of the temperature indicating members 28 are arranged in a region including the maximum bent portion of the side reinforcing rubber 26 so as to be along the serration line 6 decorated in a stripe shape along the tire radial direction on the inner surface of the tire 10. As shown in FIG. 4B, the temperature indicating member 28 has a dome-shaped structure as a whole. When the temperature indicating member 28 is observed from above, it has a circular shape as shown in FIGS. However, the shape of the temperature indicating member 28 is not particularly limited. For example, the shape when observed from above the temperature indicating member 28 is a circle (including an ellipse), a polygon (for example, a triangle, a square, a rhombus, It may be a pentagon, hexagon, star, or the like. The overall shape of the temperature indicating member 28 is not limited to a dome shape, and may be a cone shape such as a columnar shape, a prismatic shape, or a pyramid shape.

  The temperature indicating member 28 is disposed in a region including the maximum bent portion of the side reinforcing rubber 26. As a result, heat from the maximum bending portion of the side reinforcing rubber whose temperature rises most due to the deformation of the tire is directly transmitted, while for the compressive strain from the tire, side reinforcement until the temperature of the side reinforcing rubber rises. It can be made hard to receive the compressive strain by the bending of rubber.

Here, the “region including the maximum bent portion” refers to the region including the maximum bent portion 29 on the inner surface of the tire 10 from the lower end of the side reinforcing rubber to the upper end of the side reinforcing rubber in the tire radial direction of the side reinforcing rubber. A region within at least 80% of the length, that is, the length from the side reinforcing rubber end 26A to the side reinforcing rubber end 26B in FIG.
In addition, from the viewpoint of efficiently transferring the heat from the maximum bent portion to the temperature indicating member 28, the above region is preferably within 50%, and particularly preferably within 30%.

The temperature indicating member 28 preferably has an elastic modulus at 25 ° C. of 1 × 10 ⁶ Pa to 1 × 10 ¹⁰ Pa. When the elastic modulus at 25 ° C. is 1 × 10 ⁶ Pa or more, the adhesive strength of the temperature indicating member 28 to the side reinforcing rubber 26 or the inner liner is increased, and when it is 1 × 10 ¹⁰ Pa or less, the temperature indicating member 28 It is possible to further promote the dropout during expansion. Further, the elastic modulus at 25 ° C., is preferably ^{1 × 10 7 Pa~1 × 10 9} Pa, particularly preferably ^{1 × 10 7 Pa~1 × 10 8} Pa.

  The elastic modulus of the temperature indicating member 28 can be calculated using a universal compression tester. For example, a resin piece containing a heat-sensitive foaming material and a compressive strain-absorbing material constituting the temperature indicating member is molded into a 3 cm × 1 cm × 50 μm sheet by a known method, and the obtained sheet is measured by a viscoelasticity measuring device ( Measured with a test speed of 5 mm / min with DMS7100) manufactured by Hitachi High-Tech Science Co., Ltd., a compression stress-strain curve can be prepared from the measured value, and the calculation can be performed based on this.

  The compressive strain absorbing material is not particularly limited as long as it can absorb the bending deformation of the side reinforcing rubber 26 and has an adhesive force on the inner surface of the side reinforcing rubber 26 or the surface of the inner liner 25. Among them, from the viewpoint of a flexible adhesive having an appropriate elastic modulus and little change in elastic modulus with respect to temperature, for example, a polyolefin-based adhesive, a chlorinated rubber-based adhesive, an acrylic-based adhesive [for example, Y610 (Cemedine) Manufactured)], epoxy adhesive [eg EP138 (made by Cemedine), polyurethane adhesive [eg UM700 (made by Cemedine)], nitrile rubber adhesive [eg, Cemedine 521 (made by Cemedine)], vinyl chloride Adhesives [for example 201 (made by Cemedine)], vinyl acetate-based adhesives [for example 195 (made by Cemedine)], polyester-based adhesives [for example R820 (made by Cemedine)], phenolic adhesives [for example METALOC UB, Metallok U-20 (for example, manufactured by Toyo Chemical Laboratory Co., Ltd.)], silicone resin adhesive [for example, KR-28 2, KR-311 (manufactured by Shin-Etsu Chemical Co., Ltd.)], modified silicone resin adhesive [for example, PM100 (manufactured by Cemedine)] and the like. Among these, silicone resin adhesives and modified silicone resin adhesives, which are silicone resin adhesives, are preferable, and among the modified silicone resin adhesives, acrylic modified silicone resin adhesives are more preferable.

  Although the content rate (mass%) with respect to the total mass of the temperature indicating member 28 of the compressive strain absorbing material that can be included in the temperature indicating member 28 is appropriately set, it is preferably 10% by mass to 95% by mass. By being 10 mass% or more, it becomes easier to ensure the adhesion between the temperature indicating member 28 and the side reinforcing rubber 26 or the inner liner 25 at a temperature equal to or lower than the temperature at which the temperature indicating member 28 starts to expand, and is 95 mass% or less. Thus, when the temperature indicating member 28 is expanded, the temperature indicating member 28 can be more reliably detached from the side reinforcing rubber 26 or the inner liner 25. Furthermore, it is more preferable that it is 40 mass%-90 mass%, and it is especially preferable that it is 50 mass%-80 mass%.

  The temperature indicating member 28 may include a heat conductive material in order to efficiently transfer heat generated at the maximum bent portion 29 to the heat-sensitive foamable material when the tire 10 is bent and deformed. By including the heat conductive material, heat due to the temperature rise of the maximum bending portion of the tire can be more reliably and efficiently transmitted. From such a viewpoint, the thermal conductivity of the temperature indicating member 28 is preferably 0.2 W / m · K or more, more preferably 0.5 W / m · K or more, and particularly preferably 1.5 W / m · K. That's it.

As said heat conductive material, a heat conductive filler is mentioned, for example. Examples of the thermally conductive filler include thermally conductive metal oxides, nitrides, metal powders, and carbides (carbon nanotubes, graphite, carbon fibers, etc.).
Examples of the metal oxide include aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, and silicon oxide. Examples of the nitride include boron nitride, aluminum nitride, and silicon nitride. Examples of the carbide include silicon carbide and boron carbide. Examples of the metal powder include silver, gold, copper, and aluminum. As the heat conductive material, one or two or more of them can be used. The heat conductive material is preferably carbon, carbon nanotube, graphite, or carbon fiber.

The temperature indicating member 28 of the first embodiment includes a heat-sensitive foaming material that foams due to a temperature change. The heat-sensitive foaming material means a material that foams by absorbing heat, and is a material that irreversibly expands the temperature indicating member.
Although it does not specifically limit as a heat-sensitive foamable material foamed by a temperature change, A well-known heat-sensitive foamable material is mentioned. Among them, a heat-sensitive foamable material that is microencapsulated (hereinafter referred to as a heat-expandable microcapsule) is preferable.
The heat-expandable microcapsule is formed of, for example, a liquid foaming agent and a polymer shell encapsulating the liquid foaming agent. When heated, the polymer shell softens and the encapsulated liquid shell is encapsulated. Since the foaming agent is changed to a gas, the capsule has a characteristic that the capsule expands to several tens to several hundred times the previous volume at that pressure. For this reason, the volume of the temperature indicating member 28 can be expanded by increasing the temperature by including a certain amount of such heat-sensitive foamable material in the temperature indicating member 28. Thus, the polymer shell that expands depending on the temperature is not particularly limited, and examples thereof include thermoplastic resins such as vinylidene chloride resins, acrylonitrile resins, and acrylic resins. Among these, acrylic resins are used. preferable.
As the foaming agent, various known inorganic foaming agents and organic foaming agents can be used. Moreover, a foaming agent can be used individually or in combination of 2 or more types.

As the thermally expandable microcapsule, for example, a microencapsulated thermal foaming agent described in JP2013-79322A can be used.
As the thermally expandable microcapsules, commercially available ones may be purchased or appropriately prepared. As a preparation method, it describes in Unexamined-Japanese-Patent No. 2013-79322, for example. Examples of commercially available products include “Matsumoto Microsphere F-36”, “Matsumoto Microsphere F-36LV”, “Matsumoto Microsphere F-48”, “Matsumoto Microsphere FN-80GS”, and “Matsumoto Microsphere F- 50 ”(manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) and trade names“ Expanscel Microsphere WU ”and“ Expansel Microsphere DU ”(manufactured by Nippon Philite Co., Ltd.).
The average particle diameter of the thermally expandable microcapsule is preferably 1 μm to 100 μm, and more preferably 3 μm to 50 μm from the viewpoint of dispersibility and thin layer formation.

  The content of the heat-sensitive foamable material with respect to the total amount of the temperature indicating member 28 is preferably 5% by mass to 90% by mass. By being 5 mass% or more, the thermal expansibility of the temperature indicating member 28 can be increased, and when the temperature rises, it can be more reliably caused to drop from the inner surface of the side reinforcing rubber 26 or the surface of the inner liner 25 of the temperature indicating member 28. . By being 90 mass% or less, sufficient adhesiveness with the side reinforcement rubber 26 or the inner liner 25 and more appropriate compressive strain absorption ability can be ensured. Furthermore, the content is more preferably 10% by mass to 60% by mass, and particularly preferably 20% by mass to 50% by mass.

  Moreover, as a content rate with respect to the said compression-strain-absorbing material of the said heat-sensitive foamable material, 5 mass%-90 mass% are preferable. By being 5% by mass or more, the thermal expansion property of the temperature indicating member 28 can be improved, and when the temperature rises, the temperature-increasing member 28 can be more reliably detached from the inner surface of the side reinforcing rubber 26 or the inner liner 25 surface. When the content is 90% by mass or less, sufficient adhesiveness with the side reinforcing rubber 26 or the inner liner 25 and more appropriate compressive strain absorption ability can be ensured. Furthermore, the content is more preferably 20% by mass to 80% by mass, and particularly preferably 30% by mass to 70% by mass.

  The volume when the temperature indicating member 28 is expanded is appropriately adjusted. For example, the volume when the temperature indicating member 28 is expanded most is 1.1 to 3.0 times the volume of the temperature indicating member 28 before expansion. It is preferable that By being 1.1 times or more, the temperature indicating member 28 can be more reliably dropped from the inner surface of the side reinforcing rubber 26 or the surface of the inner liner 25, and by being 3.0 times or less, the temperature indicating member 28 is removed. Therefore, it is possible to secure a more appropriate compressive strain absorption capacity and more economical. The volume is more preferably 1.2 times to 2.5 times, and particularly preferably 1.5 times to 2.0 times.

  Moreover, the temperature which expands the temperature indicating member 28 can be adjusted by changing the kind of heat-sensitive foamable material. The temperature at which the temperature indicating member is expanded is appropriately adjusted according to a desired threshold, but it is preferable to use a heat-sensitive foaming material that foams at an arbitrary temperature of 80 ° C. to 150 ° C. from the viewpoint of the temperature range during run flat running. More preferably, the heat-sensitive foaming material foams at an arbitrary temperature of 90 ° C to 140 ° C.

  The types of compression strain-absorbing material and heat-sensitive foamable material to be included in the temperature indicating member 28 and their contents are 10 mass% to 95 mass% of the silicone resin adhesive with respect to the total mass of the temperature indicating member 28, and As the heat-sensitive foamable material, it is preferable to contain 5% by mass to 90% by mass of thermally expandable microcapsules having a thermoplastic polymer shell made of an acrylic resin and encapsulating a foaming agent. Furthermore, 10% to 60% by mass of a thermally expandable microcapsule containing 40% to 90% by mass of a silicone resin adhesive, having a thermoplastic polymer shell made of an acrylic resin, and encapsulating a foaming agent. % Content is more preferable.

A plurality of temperature indicating members 28 are preferably arranged on the inner surface of the side reinforcing rubber 26 or the surface of the inner liner. In this case, the plurality of temperature indicating members 28 can be provided so as to be aligned in the tire radial direction.
Further, the thickness of the temperature indicating member (see FIG. 3) is preferably 0.1 mm to 10 mm, more preferably 0.1 mm to 5 mm, and more preferably 0.11 mm to 0.11 mm from the viewpoint of adhesiveness and expansibility. Particularly preferred is 3 mm.

  In addition to the above materials, other components can be further added to the temperature indicating member 28. The other components can be appropriately selected according to the purpose and necessity, and examples thereof include pressure-sensitive adhesives, coloring materials and pigments, binders, lubricants, known thermofusible substances, antioxidants, antistatic agents and the like. It is done.

  The temperature indicating member 28 is prepared by, for example, kneading the adhesive as the compressive strain absorbing material, the microbeads as the heat-sensitive foaming material and the binder using a self-revolving mixer or the like, and the obtained mixture is run. It is applied to the side reinforcing rubber 26 of the flat tire with a constant area and a constant thickness. Thereafter, the run flat tire 10 having the temperature indicating member 28 can be prepared by drying the run flat tire at a temperature equal to or lower than the temperature at which expansion of the heat-sensitive foamable material is started.

An example of the arrangement position of the temperature indicating member is shown in FIGS. The plurality of temperature indicating members 28 arranged on the surface of the inner liner 25 are preferably arranged at intervals of 4 mm or more in at least one of the tire circumferential direction (C) and the tire radial direction (R). By setting the interval in at least one of the tire circumferential direction and the tire radial direction to be 4 mm or more, temperature detection can be performed more reliably avoiding contact with each other due to the plurality of temperature indicating members 28 being too close at the time of tire bending deformation. preferable. In addition, by arranging a plurality of temperature indicating members, temperature detection can be performed more accurately even if there is a slight change in the maximum bending portion.
Further, the temperature indicating members 28 in the case of being arranged in a plurality may use heat-sensitive foam materials that foam in the same temperature range, or may use heat-sensitive foam materials that foam at different temperatures. For example, by using a heat-sensitive foaming material that foams in a temperature range higher than that of a temperature-indicating member disposed at a far distance, the heat history of all the temperature-indicating members in a plurality, that is, a temperature indicating member that is close to the maximum bending portion, The thermal history of a wider range of side reinforcing rubber can be known in detail.

Next, the operation of the tire 10 of the first embodiment will be described.
When the tire 10 is punctured while the vehicle is running, air (nitrogen) filled in the tire 10 leaks to the outside of the tire 10 and the air pressure of the tire 10 decreases.
The tire 10 in which air has leaked can run flat for a certain distance because the side reinforcing rubber 26 formed on the inner surface of the sidewall portion 22 supports the weight of the vehicle and the occupant.
During run-flat travel, the side reinforcing rubber 26 close to the tread portion 20 that is in contact with the road surface is greatly bent and deformed by a load in the tire radial direction. Since the tire 10 is rolling, the side reinforcing rubber 26 is continuously bent and deformed over the entire circumference. Thereby, a hysteresis loss increases and the temperature of the side reinforcement rubber 26 rises rapidly. Such a phenomenon does not occur until the side reinforcing rubber 26 is bent several times, and therefore occurs only when the tire 10 is punctured.

  When the temperature of the side reinforcing rubber 26 rises and the surface temperature of the side reinforcing rubber 26 reaches 80 ° C. to 90 ° C., for example, the temperature indicating member 28 disposed on the inner surface of the side reinforcing rubber 26 or the inner liner 25 is The expansion starts in response to the heat transmitted from the side reinforcing rubber 26. Further, the side reinforcing rubber 26 generates heat by continuously bending and deforming. When the surface temperature of the side reinforcing rubber 26 rises, the temperature indicating member 28 expands, so that the adhesiveness between the temperature indicating member 28 and the inner surface of the side reinforcing rubber 26 or the surface of the inner liner 25 cannot be maintained. Peel off. For this reason, even if time has elapsed since the end of the run-flat travel, the heat history of the side reinforcing rubber 26 can be confirmed by the presence or absence of the temperature indicating member 28.

  Here, since the temperature indicating member 28 disposed on the inner surface of the side reinforcing rubber 26 or the surface of the inner liner 25 includes a compressive strain absorbing material, until the side reinforcing rubber 26 is repeatedly greatly bent and the temperature rises, The temperature indicating member 28 is not easily missing from the inner surface of the side reinforcing rubber 26 or the surface of the inner liner 25.

  After the tire 10 has run flat for a certain distance, the punctured tire 10 is removed from the rim, and it is confirmed whether the temperature indicating member 28 exists. At this time, if the temperature indicating member 28 is not present, it can be determined that the temperature of the side reinforcing rubber 26 has reached a certain temperature, so it can be determined whether the tire can be repaired and used. .

  For example, as a result of checking the temperature indicating member 28, the temperature of the side reinforcing rubber 26 has not reached a constant temperature if the temperature indicating member 28 is present despite the run-flat running. In this case, since the side reinforcing rubber 26 has not deteriorated, the tire 10 can be used again if the punctured portion is repaired and filled with air.

Conversely, if the temperature indicating member 28 is not present, the surface temperature of the side reinforcing rubber 26 has reached a certain temperature, and the side reinforcing rubber 26 may be altered, and the support It can be estimated that there is a risk that the strength has decreased. In this case, the tire 10 is replaced with a new tire without being reused.
As described above, the thermal history of the tire 10 can be determined by arranging the temperature indicating member 28 that expands as the temperature of the side reinforcing rubber 26 increases.

[Other Embodiments]
As another embodiment, the temperature indicating member is a laminate in which a compression strain absorbing layer including a compressive strain absorbing material and a temperature indicating layer including a heat-sensitive foamable material are stacked in this order on the inner side of the side reinforcing rubber. You may comprise. The compressive strain absorbing layer is a layer that absorbs compressive strain from the side reinforcing rubber 26 and, like the temperature indicating member 28 of the first embodiment, the maximum bent portion of the surface of the side reinforcing rubber 26 on the inner side in the tire axial direction. Arranged in the containing region 29 '.
The temperature indicating layer refers to a layer showing a heat history due to a temperature rise. The temperature indicating layer receives heat from the side reinforcing rubber 26 via the compression strain absorbing layer, or the compression strain absorbing layer and the inner liner 25, and expands when the temperature rises above a certain temperature to cause a volume change, and then drops off, Or it deforms greatly. For this reason, the thermal history can be confirmed by the presence or absence of the temperature indicating layer or the presence or absence of deformation of the temperature indicating layer. The temperature indicating layer may be provided directly on the surface of the compression strain absorbing layer, or another layer such as an adhesive layer may be further provided between the temperature indicating layer and the compression strain absorbing layer as long as the effect of the present invention is not affected. You may have.

By using a layer structure in which the compression strain absorbing layer and the temperature indicating layer are separated as in the temperature indicating member, a desired function can be easily provided in advance for each layer. In other words, in the compressive strain absorbing layer, since there is no need to consider the influence by not including the heat-sensitive foamable material in the layer, the elastic modulus and adhesive force necessary to maintain the compressive strain absorbing ability. Therefore, it is easy to select a compressive strain absorbing material or the like in advance and set a necessary content. Further, in the temperature indicating layer, since it is not necessary to consider the influence by not including a compressive strain absorbing material in the layer, a heat-sensitive foaming material or the like necessary for having a desired coefficient of thermal expansion is used. It is easy to pre-select and set the required content.
Further, since the temperature indicating layer is attached to the inner surface of the side reinforcing rubber 26 or the inner liner 25 via the compression strain absorbing layer, the thermal foaming in the temperature indicating layer is increased until the side reinforcing rubber rises above a certain temperature. The foaming material can be prevented from foaming, and the temperature indicating layer can be prevented from dropping or greatly deforming.

  The present invention will be specifically described by the following examples, but the present invention is not limited thereto.

(Example 1)
≪Preparation of test run flat tire≫
The components shown in composition 1 below were kneaded using a self-revolving mixer to obtain a mixture for preparing a temperature indicating member.
<Composition 1>
Compressive strain absorbing material: 66% by mass of silicone-modified acrylic resin (Cemedine)
・ Heat-sensitive foaming material: Matsumoto Microsphere F-48 (Matsumoto Yushi Seiyaku Co., Ltd.) 33% by mass
Next, a run-flat tire (size: 255 / 35R18) similar to the tire shown in the first embodiment, the region including the maximum bending portion on the inner side of the side reinforcing rubber, that is, the maximum bending portion on the inner liner The above-mentioned mixture was applied to a region including, using a mold or the like, and cured at 23 ° C. for 24 hours to obtain a run-flat tire having a dome-shaped temperature indicating member having a diameter of 3 mm and a height of 1.5 mm.
Further, the temperature indicating members were arranged at an interval of 5 mm in the R direction (see FIG. 4B) in a region including the maximum bent portion on the inner liner.
As described above, the maximum bend in the run-flat tire is calculated by calculating the absolute value of the amount of change between the radius of curvature of the run-flat tire during normal running and the radius of curvature during run-flat running. It was determined by specifying the place to have. Further, the radius of curvature during the run-flat running was measured by processing and measuring a cross-sectional image obtained by X-ray CT (Y. MTIS, manufactured by YXLON).
≪Running test≫
The run flat tire having the temperature indicating member prepared above was attached to a drum type running test machine, and running was performed under the following conditions.
<Condition>
・ Tire internal pressure: 50kPa
・ Total load: 7kN
・ Speed: 120km / h
・ Mileage: 180km
After the run flat running under the above conditions, the state of the temperature indicating member was confirmed.

(Example 2)
In Example 1, the presence or absence of the temperature indicating member was confirmed after running (normal running) in the same manner as in Example 1 except that the tire internal pressure under the conditions in the test method was 260 kPa.

(Comparative Example 1)
In Example 1, run-flat running was performed in the same manner as in Example 1 except that the composition 1 of the mixture used for preparing the temperature indicating member was changed to the following composition 2, and the state of the temperature indicating member was confirmed.
<Composition 2>
・ Compressive strain absorbing material: 100% by mass of silicone-modified acrylic resin (Cemedine)
・ Thermosensitive foaming material: None << Result >>

From the results shown in Table 1, in Example 1, the temperature indicating member was peeled off by run-flat running, and in Example 2, the temperature indicating member was not peeled off by normal running. For this reason, in a run flat tire equipped with a temperature indicating member containing a heat-sensitive foamable material, it was shown that the heat history of the side reinforcing rubber in the run flat traveling can be confirmed by the presence or absence of the temperature indicating member.
On the other hand, in Comparative Example 1, the temperature indicating member was not peeled even by run-flat running. For this reason, in a run flat tire equipped with a temperature indicating member that does not include a heat-sensitive foamable material, it was not possible to confirm the heat history of the side reinforcing rubber during run flat running.

10 run-flat tires, 12, 31 bead parts, 20 tread parts, 22 sidewall parts, 25 inner liners, 26 side reinforcement rubbers, 28 temperature indicating members, 29 maximum bent parts, 29 'areas including maximum bent parts, 35 areas

Claims (10)

A sidewall portion connecting the tread portion and the bead portion;
A side reinforcing rubber disposed on the inner surface of the sidewall portion;
A temperature indicating member that is disposed in a region including the maximum bending portion on the inner surface side of the side reinforcing rubber, and includes a heat-sensitive foaming material and a compressive strain absorbing material;
Run flat tire with   The run-flat tire according to claim 1, wherein the temperature indicating member includes a layer including the compression strain absorbing material and the heat-sensitive foamable material.   The temperature indicating member is a laminate in which a compression strain absorbing layer including the compressive strain absorbing material and a temperature indicating layer including the heat-sensitive foamable material are stacked in this order on the inner side of the side reinforcing rubber. 2. The run flat tire according to 1.   The run-flat tire according to any one of claims 1 to 3, wherein the compressive strain absorbing material includes a silicone resin-based adhesive.   The run-flat tire according to any one of claims 1 to 4, wherein the temperature indicating member has a thermal conductivity of 0.2 W / m · K or more. The run-flat tire according to any one of claims 1 to 5, wherein the temperature indicating member has an elastic modulus at 25 ° C of 1 x 10 ⁶ Pa to 1 x 10 ¹⁰ Pa.   The run flat tire according to any one of claims 1 to 6, wherein a plurality of the temperature indicating members are arranged.   The run-flat tire according to claim 7, wherein the plurality of temperature indicating members are arranged at intervals of 4 mm or more in at least one of the tire circumferential direction and the tire radial direction.   The region including the maximum bent portion is a region within 80% of the length from the lower end of the side reinforcing rubber to the upper end of the side reinforcing rubber in the tire radial direction of the side reinforcing rubber. The run flat tire according to any one of the above items.   The run-flat tire according to any one of claims 1 to 9, wherein the heat-sensitive foamable material foams at a temperature of 80 ° C to 150 ° C.