Pneumatic Tire and Method for Manufacturing the Same

Abstract

Provided are a pneumatic tire and a method for manufacturing the same, which can suppress peeling of a sealant layer and improve tire balance. In a pneumatic tire including a tread portion 1 extending in the tire circumferential direction and having an annular shape, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed on the tire radial inner side of these sidewall portions 2, a sealant layer 20 having a structure in which a sealant strip 21 is spirally disposed along the tire circumferential direction on the tire inner surface 10 in the tread portion 1 is formed, and at least one end portion of the strip 21 is thinner than the other portion.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire having a sealant layer on the inner surface of the tire in the tread portion and a method for manufacturing the same. More specifically, the present invention relates to a pneumatic tire and a method for manufacturing the same that can suppress peeling of the sealant layer and improve tire balance.

Background Art

[0002] In a pneumatic tire, it has been proposed to provide a sealant layer on the inner side in the tire radial direction of the inner liner layer in the tread portion. In such a pneumatic tire, when a foreign object such as a nail pierces the tread portion, the sealant flows into the through hole, thereby suppressing a decrease in air pressure and enabling driving to be maintained.

[0003] Conventionally, as the sealant constituting the sealant layer, a rubber composition mainly composed of butyl rubber is generally used (see, for example, Patent Documents 1 to 3). Examples of the butyl rubber include halogenated butyl rubbers such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR) in addition to butyl rubber (IIR). Such a sealant is applied to the inner surface of the tire in a state of being softened by heating to a high temperature (see, for example, Patent Document 4). More specifically, a sealant layer is formed by spirally arranging a strip material of the sealant in a softened state by heating to a high temperature along the tire circumferential direction on the inner surface of the tire.

[0004] However, in the sealant layer formed as described above, peeling may occur in the sealant layer starting from the end of the sealant strip material. In addition, since a weight change occurs before and after in the tire circumferential direction with the end of the sealant strip material as a boundary, this becomes a factor deteriorating the tire balance.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] An object of the present invention is to provide a pneumatic tire capable of suppressing peeling of a sealant layer and improving tire balance, and a method for manufacturing the same. [Means for Solving the Problems]

[0007] The pneumatic tire of the present invention for achieving the above object is a pneumatic tire including a tread portion extending in the tire circumferential direction and having an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of these sidewall portions. In the pneumatic tire, a sealant layer having a structure in which a sealant strip is spirally disposed along the tire circumferential direction on the inner surface of the tire in the tread portion is formed, and at least one end portion of the strip is thinner than the other portion.

[0008] The method for manufacturing a pneumatic tire of the present invention for achieving the above object is a method for manufacturing the above-described pneumatic tire. After manufacturing the pneumatic tire excluding the sealant layer, when forming the sealant layer by applying a sealant made of a silicone-based composition to the inner surface of the tire in the tread portion, the temperature of the sealant applied to the inner surface of the tire is made lower than 70°C. [Effects of the Invention]

[0009] In the present invention, a sealant layer having a structure in which a sealant strip is spirally arranged along the tire circumferential direction on the inner surface of the tire in the tread portion is formed, and at least one end of the strip is thinner than the other portion, so that it is possible to suppress the peeling of the sealant layer starting from the end of the strip. Furthermore, it is possible to reduce the weight change occurring before and after in the tire circumferential direction with the end of the strip as a boundary, and to improve the tire balance.

[0010] In the present invention, the strip has a narrow-width portion formed at at least one end and a wide-width portion wider than the narrow-width portion, the length of the narrow-width portion is 30 mm or more, and the average width of the narrow-width portion is preferably in the range of 20% to 97% of the average width of the wide-width portion. By defining the dimensions of the narrow-width portion in this way, it is possible to sufficiently ensure the effect of suppressing the peeling of the sealant layer and the effect of improving the tire balance.

[0011] In the present invention, the sealant is preferably composed of a silicone-based composition. When the sealant is composed of a rubber composition mainly based on butyl rubber, the sealant cools down before the circumferential portions of the sealant strip material fit well with each other. As a result, the integrality between the circumferential portions of the sealant strip material is not good, and the sealing performance of the sealant layer becomes insufficient. In addition, when the integrality between the circumferential portions of the sealant strip material is insufficient, the sealant layer tends to flow toward the center side of the tread portion due to the centrifugal force generated during tire rotation, which also causes a reduction in the sealing performance. On the other hand, when the sealant is composed of a silicone-based composition, the circumferential portions of the sealant strip material are likely to fit well with each other during the curing reaction process of the silicone-based composition, and the integrality between the circumferential portions of the sealant strip material becomes good. Therefore, the sealing performance of the sealant layer can be improved. In addition, since the integrality between the circumferential portions of the sealant strip material is good, the sealant layer is less likely to flow toward the center side in the tire width direction due to the centrifugal force generated during tire rotation, which also contributes to the improvement of the sealing performance. Furthermore, the sealant composed of a silicone-based composition can be applied at a low temperature. For example, the temperature of the sealant applied to the inner surface of the tire can be lower than 70°C, so there is also an advantage that the influence of heat on the tire can be reduced and the deterioration of tire performance can be avoided.

[0012] In the present invention, the silicone-based composition is preferably a two-component curable silicone. Since the two-component curable silicone has a low viscosity immediately after the two components are mixed, it can be applied even at a low temperature.

[0013] In the present invention, the glass transition temperature of the sealant preferably ranges from -120°C to -40°C. By using a sealant with a low glass transition temperature, the puncture sealing performance in a low-temperature environment can be ensured well.

[0014] In the present invention, it is preferable that the thickness of the sealant layer is in the range of 2.0 mm to 5.0 mm. Thereby, while ensuring puncture sealing performance, it is possible to suppress deterioration of rolling resistance due to an increase in tire weight, and to suppress uneven distribution of the sealant layer caused by the flow of the sealant.

[0015] In the present invention, when a belt layer including a belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion, it is preferable that the width of the sealant layer is 90% or more of the width of the belt layer located on the innermost side in the tire radial direction. In particular, it is preferable that the end portion of the sealant layer is disposed on the outer side in the tire width direction than the end portion of the belt layer located on the innermost side in the tire radial direction. By making the width of the sealant layer sufficiently large, it is possible to effectively prevent a puncture of a pneumatic tire.

[0016] In the present invention, when a belt cover layer including an organic fiber cord oriented in the tire circumferential direction is embedded on the outer peripheral side of the belt layer in the tread portion, it is preferable that the end portion of the sealant layer is disposed on the outer side in the tire width direction than the end portion of the belt cover layer. By making the width of the sealant layer sufficiently large, it is possible to effectively prevent a puncture of a pneumatic tire.

[0017] In the present invention, when a belt layer including a belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion, it is preferable that the inclination direction of the sealant strip with respect to the tire circumferential direction is opposite in phase to the inclination direction of the belt cord of the belt layer located on the innermost side in the tire radial direction. In a pneumatic tire, ply steer occurs due to the orientation of the belt cord of the belt layer, but the orientation of the sealant strip also becomes a factor of ply steer. Therefore, by making the inclination direction of the sealant strip with respect to the tire circumferential direction opposite in phase to the inclination direction of the belt cord of the belt layer located on the innermost side in the tire radial direction, it is possible to reduce ply steer.

[0018] In the present invention, it is preferable that the distance L from the belt layer to the sealant layer is 10 mm or less at all locations of the belt layer located at the innermost side in the tire radial direction. Thereby, when a foreign object such as a nail penetrates the tread portion, the sealant easily flows to the belt layer, so that good puncture sealing performance can be ensured.

[0019] In the present invention, it is preferable that the ratio of the thickness S of the sealant layer to the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer satisfies the relationship of S / L≧0.3. By making the thickness S of the sealant layer sufficiently larger than the distance L, good puncture sealing performance can be ensured.

[0020] In the present invention, it is preferable that the distance in the tire width direction between the center position of the sealant layer in the tire width direction and the tire equator is 10 mm or less. By reducing the distance in the tire width direction between the center position of the sealant layer in the tire width direction and the tire equator, the tire balance can be improved.

[0021] In the present invention, it is preferable that a sound-absorbing material is installed along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer. The sealant layer can be used as an adhesive layer for the sound-absorbing material. In particular, when the sealant is composed of a silicone-based composition, the sound-absorbing material can be installed with respect to the sealant layer applied at a low temperature, so that damage to the sound-absorbing material can be avoided and its sound-absorbing effect can be maintained well.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0023] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 to 3 show a pneumatic tire according to an embodiment of the present invention.

[0024] As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and forms an annular shape, a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3, 3 disposed on the inner side in the tire radial direction of these sidewall portions 2.

[0025] A carcass layer 4 is mounted between the pair of bead portions 3, 3. This carcass layer 4 includes a plurality of carcass cords extending in the tire radial direction, and is folded back from the inner side to the outer side around a bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0026] On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of belt cords inclined with respect to the tire circumferential direction, and are arranged such that the belt cords intersect each other between the layers. In the belt layer 7, the inclination angle of the belt cord with respect to the tire circumferential direction is set in the range of, for example, 10° to 40°. As the belt cord of the belt layer 7, a steel cord is preferably used.

[0027] On the outer peripheral side of the belt layer 7, at least one belt cover layer 8 is arranged in which reinforcing cords are arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction for the purpose of improving high-speed durability. It is desirable that this belt cover layer 8 has a jointless structure in which a strip material formed by rubber-coating at least one reinforcing cord aligned is continuously wound at substantially 0° with respect to the tire circumferential direction. As the reinforcing cord of the belt cover layer 8, organic fiber cords such as nylon and polyethylene terephthalate (PET) are preferably used.

[0028] In addition, the above-described tire internal structure shows a typical example in a pneumatic tire, but is not limited thereto. In the tread portion 1, various grooves including a plurality of main grooves 11 extending in the tire circumferential direction are formed.

[0029] In the above pneumatic tire, a sealant layer 20 is formed on the inner surface 10 of the tread portion 1 so as to be continuous in the tire circumferential direction. It is preferable that the center position of the sealant layer 20 in the tire width direction coincides with the tire equator CL, but the center position may be shifted toward either one side in the tire width direction from the tire equator CL. The distance in the tire width direction between the center position of the sealant layer 20 in the tire width direction and the tire equator CL is preferably 10 mm or less, more preferably 5 mm or less. Thereby, the sealant layer 20 does not adversely affect the tire balance. As shown in FIG. 3, the sealant layer 20 has a structure in which a sealant strip material 21 is arranged in a spiral shape along the tire circumferential direction. The sealant of the sealant layer 20 may be composed of a rubber composition mainly based on butyl rubber, but is preferably composed of a silicone-based composition. The silicone-based composition includes a synthetic polymer compound having a main skeleton by a siloxane bond.

[0030] The pneumatic tire described above can be manufactured by the following method. First, a pneumatic tire is manufactured which includes a tread portion 1, a pair of sidewall portions 2, and a pair of bead portions 3 as described above, and in which a belt layer 7 and a belt cover layer 8 are embedded in the tread portion 1. Next, a sealant made of, for example, a silicone-based composition is applied to the inner surface 10 of the tire in the tread portion 1 to form a sealant layer 20.

[0031] FIG. 4 shows a specific manufacturing method of the pneumatic tire of FIG. 1, and FIG. 5 shows a sealant layer formed on the inner surface of the tire in the tread portion. In FIG. 4, a sealant extruding device 31 mixes the sealant supplied from pumps 32 and 33, and continuously discharges the mixed sealant from a nozzle 34 as a strip material 21. This sealant extruding device 31 is configured such that the position of the nozzle 34 is displaceable. Therefore, by moving the nozzle 34 in the tire axial direction while rotating the tire from a state where the nozzle 34 is close to the inner surface 10 of the tire, the strip material 21 of the sealant can be spirally arranged on the inner surface 10 of the tire while being inclined with respect to the tire circumferential direction Tc (see FIG. 5). The circumferential portions of the strip material 21 of the sealant arranged in a spiral shape are in close contact with each other. The strip material 21 of the sealant arranged in this spiral shape is integrated to form a sealant layer 20. In this sealant layer 20, at least one end portion (both end portions in FIG. 5) of the strip material 21 of the sealant is thinner than the other portions. Note that the thickness of the strip material 21 can be arbitrarily adjusted based on the relative rotational speed of the tire with respect to the nozzle 34.

[0032] In the pneumatic tire described above, a sealant layer 20 having a structure in which a strip material 21 of the sealant is spirally arranged along the tire circumferential direction is formed on the inner surface 10 of the tire in the tread portion 1, and at least one end portion of the strip material 21 is thinner than the other portions, whereby peeling of the sealant layer 20 starting from the end portion of the strip material 21 can be suppressed, and furthermore, weight changes occurring before and after in the tire circumferential direction with the end portion of the strip material 21 as a boundary can be reduced, and the tire balance can be improved.

[0033] In the pneumatic tire described above, the belt material 21 has a narrow-width portion 21X formed at at least one end portion thereof and a wide-width portion 21Y thicker than the narrow-width portion 21X. The length X of the narrow-width portion 21X is 30 mm or more, and the average width of the narrow-width portion 21X is set in the range of 20% to 97% of the average width of the wide-width portion 21Y. The narrow-width portion 21X may be gradually narrowed toward the tip side, or may be gradually tapered toward the tip side. By defining the dimensions of the narrow-width portion 21X in this way, it is possible to sufficiently ensure the effect of suppressing the peeling of the sealant layer 20 and the effect of improving the tire balance.

[0034] Here, when the length X of the narrow-width portion 21X is less than 30 mm, the effect of suppressing the peeling of the sealant layer 20 and the effect of improving the tire balance are reduced. In particular, it is desirable that the length X of the narrow-width portion 21X is 50 mm or more, and the upper limit thereof is desirably set to 1 / 8 of the inner peripheral length of the tire. Also, when the average width of the narrow-width portion 21X is less than 20% of the average width of the wide-width portion 21Y, it becomes difficult to form the sealant layer 20, and conversely, when it is more than 97%, the effect of suppressing the peeling of the sealant layer 20 and the effect of improving the tire balance are reduced. In particular, it is preferable that the average width of the narrow-width portion 21X is in the range of 20% to 50% of the average width of the wide-width portion 21Y.

[0035] In the above pneumatic tire, it is preferable that the sealant is composed of a silicone-based composition. A sealant layer 20 having a structure in which a strip material 21 of the sealant is spirally arranged along the tire circumferential direction on the tire inner surface 10 in the tread portion 1 is formed. Since the sealant is composed of a silicone-based composition, the circumferential portions of the sealant strip material 21 are easily adapted to each other in the curing reaction process of the silicone-based composition, and the integrality of the circumferential portions of the sealant strip material 21 becomes good. Therefore, the sealing performance by the sealant layer 20 can be improved. Further, since the integrality of the circumferential portions of the sealant strip material 21 is good, it becomes difficult for the sealant layer 20 to flow toward the center side in the tire width direction due to the centrifugal force generated during tire rotation, and this also contributes to the improvement of the sealing performance. Furthermore, when a silicone-based composition is used as the sealant of the sealant layer 20, it has the advantages of excellent weather resistance and low temperature dependence of physical properties.

[0036] Since the silicone-based composition has good fluidity even at low temperatures, it is preferable that the temperature of the sealant applied to the tire inner surface 10 is lower than 70°C. Thereby, the influence of heat on the tire can be reduced, and the deterioration of tire performance can be avoided. When this temperature is 70°C or higher, the influence of heat on the tire becomes large, which becomes a factor for deteriorating tire performance. In particular, it is desirable that the temperature of the sealant applied to the tire inner surface 10 is 35°C or lower. Also, from the viewpoint of the fluidity of the silicone-based composition, it is preferable that the lower limit value of the temperature of the sealant applied to the tire inner surface 10 is 20°C.

[0037] As the silicone-based composition constituting the sealant of the sealant layer 20, one-part curable silicone or two-part curable silicone can be used, but it is particularly preferable to use two-part curable silicone. Examples of one-part curable silicone include moisture-curable silicone. Two-part curable silicone is composed of a first liquid and a second liquid. By mixing these first and second liquids, the curing reaction starts, and stability as the sealant layer 20 is ensured after curing. In the above-described apparatus, the first and second liquids of two-part curable silicone are supplied from pumps 32 and 33, respectively. Since two-part curable silicone has a low viscosity immediately after the two liquids are mixed, it can be applied even at low temperatures. In particular, two-part curable silicone preferably has a period of 5 days or more until complete curing.

[0038] Two-part curable silicone is composed of, for example, a condensation-curable silyl-terminated polymer, a silane crosslinking agent, a condensation catalyst, a filler, etc. Examples of the condensation-curable silyl-terminated polymer include polydialkylsiloxane, alkylphenylsiloxane, an organic polymer having a silyl group (e.g., silyl polyether, silyl acrylate), polyisobutylene having a silyl group, etc. Examples of the silane crosslinking agent include alkoxy-functional silane, oximosilane, acetoxysilane, enoxysilane, etc. Examples of the filler include iron oxide, titanium dioxide, carbon black, talc, etc. Examples of the condensation catalyst include titanate, zirconate, etc. These condensation-curable silyl-terminated polymer, silane crosslinking agent, condensation catalyst, and filler are stored in a state divided into the first and second liquids in a combination in which the curing reaction does not proceed, and are mixed at the time of use. Examples of two-part curable silicone include those described in Japanese Patent Application Laid-Open No. 2018-503725 and Japanese Patent Application Laid-Open No. 2022-550962. As a commercially available product of two-part curable silicone, for example, SST-2650 manufactured by Dow can be used.

[0039] In the pneumatic tire described above, it is preferable that the glass transition temperature of the sealant in the sealant layer 20 is in the range of -120°C to -40°C. By using a sealant with a low glass transition temperature, it is possible to ensure good puncture sealing performance in a low-temperature environment. If the glass transition temperature of the sealant is higher than -40°C, the puncture sealing performance in a low-temperature environment will deteriorate.

[0040] In the pneumatic tire described above, as shown in FIG. 2, it is preferable that the thickness S of the sealant layer 20 is in the range of 2.0 mm to 5.0 mm. Thereby, while ensuring puncture sealing performance, it is possible to suppress the deterioration of rolling resistance due to an increase in tire weight and to suppress the uneven distribution of the sealant layer 20 caused by the flow of the sealant. Here, if the thickness S of the sealant layer 20 is less than 2.0 mm, the puncture sealing performance will deteriorate. Conversely, if it is greater than 5.0 mm, the rolling resistance will deteriorate due to an increase in tire weight, and there is a risk of uneven distribution of the sealant layer 20 due to the flow of the sealant. The thickness S of the sealant layer 20 is the overall average thickness. Such an average thickness of the sealant layer 20 can be calculated, for example, by photographing the tire meridian cross-section at 8 locations on the tire circumference using a CT scan, and measuring the thickness of the sealant layer 20 at 5 points in each of the photographed images, namely, the tire equator position, the outer edge positions (both sides) 10 mm inward in the tire width direction from the edge of the sealant layer 20, and the intermediate positions (both sides) between the tire equator position and the outer edge positions, and then calculating from the measured values at a total of 40 points.

[0041] In the pneumatic tire, as shown in FIG. 3, when a belt layer 7 (7A, 7B) including belt cords inclined with respect to the tire circumferential direction is embedded in the tread portion 1, it is preferable that the inclination direction of the sealant strip 21 with respect to the tire circumferential direction is out of phase with the inclination direction of the belt cords of the belt layer 7A located at the innermost side in the tire radial direction. In a pneumatic tire, ply steer occurs due to the orientation of the belt cords of the belt layer 7, and the orientation of the sealant strip 21 also becomes a factor of ply steer. Therefore, by setting the inclination direction of the sealant strip 21 with respect to the tire circumferential direction to be out of phase with the inclination direction of the belt cords of the belt layer 7A located at the innermost side in the tire radial direction, it becomes possible to reduce ply steer.

[0042] In the pneumatic tire, as shown in FIG. 1, it is preferable that the width Ws of the sealant layer 20 is 90% or more of the width Wb of the belt layer 7A located at the innermost side in the tire radial direction. In particular, it is preferable that the end portion of the sealant layer 20 is disposed outside the end portion of the belt layer 7A located at the innermost side in the tire radial direction in the tire width direction. By making the width Ws of the sealant layer 20 sufficiently larger than the width Wb of the belt layer 7A, it is possible to effectively prevent a puncture of the pneumatic tire. Here, if the width Ws of the sealant layer 20 is smaller than 90% of the width Wb of the belt layer 7A, the puncture sealing performance deteriorates.

[0043] For the same reason, when a belt cover layer 8 including organic fiber cords oriented in the tire circumferential direction is embedded on the outer peripheral side of the belt layer 7 in the tread portion 1, it is preferable that the end portion of the sealant layer 20 is disposed outside the end portion of the belt cover layer 8 in the tire width direction. By making the width of the sealant layer 20 sufficiently large, it is possible to effectively prevent a puncture of the pneumatic tire.

[0044] In the pneumatic tire described above, as shown in FIG. 2, it is preferable that the distance (shortest distance) L from the belt layer 7A to the sealant layer 20 is 10 mm or less at all locations of the belt layer 7A located at the innermost side in the tire radial direction. As a result, when a foreign object such as a nail penetrates the tread portion 1, the sealant easily flows to the belt layer 7A, so that good puncture sealing performance can be ensured. If there is a portion where the distance L from the belt layer 7A to the sealant layer 20 is greater than 10 mm, the puncture sealing performance in that portion may become insufficient.

[0045] In the pneumatic tire described above, it is preferable that the ratio of the thickness S of the sealant layer 20 to the distance L from the belt layer 7A located at the innermost side in the tire radial direction to the sealant layer 20 satisfies the relationship of S / L≧0.3. By making the thickness S of the sealant layer 20 sufficiently large with respect to the distance L, good puncture sealing performance can be ensured. If the ratio S / L is less than 0.3, the puncture sealing performance will deteriorate.

[0046] FIG. 6 shows a pneumatic tire according to another embodiment of the present invention. In FIG. 6, a sound absorbing material 40 is installed along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer 20. The sound absorbing material 40 is composed of a porous material having continuous bubbles and has predetermined sound absorbing characteristics based on its porous structure. It is preferable to use foamed polyurethane as the porous material of the sound absorbing material 40. The sound absorbing material 40 is adhered onto the sealant layer 20 based on the adhesiveness of the sealant layer 20 after the formation of the sealant layer 20. In particular, when the sealant of the sealant layer 20 is composed of a silicone-based composition, since the sound absorbing material 40 is installed with respect to the sealant layer 20 applied at a low temperature, damage to the sound absorbing material 40 can be avoided and its sound absorbing effect can be maintained well.

Examples

[0047] In a pneumatic tire having a tire size of 255 / 45R19 and including a tread portion, a pair of sidewall portions, and a pair of bead portions, a sealant layer having a structure in which a sealant strip is spirally arranged along the tire circumferential direction on the inner surface of the tire in the tread portion is formed. The constituent material of the sealant layer, the presence or absence of narrow-width portions formed at both ends of the strip, the length of the narrow-width portions, the ratio of the average width of the narrow-width portions to the average width of the wide-width portions, the thickness S of the sealant layer, the ratio of the width of the sealant layer to the width of the belt layer, the inclination direction of the sealant strip, the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer, and the ratio S / L were varied in various ways as shown in Table 1 to produce tires of Comparative Examples 1 to 2 and Examples 1 to 8. Also, a tire of a conventional example without a sealant layer on the inner surface of the tire in the tread portion was prepared.

[0048] Regarding the inclination direction of the sealant strip, when the inclination direction of the sealant strip with respect to the tire circumferential direction is in the same phase as the inclination direction of the belt cord of the belt layer located at the innermost side in the tire radial direction, it is indicated as "same", and when the inclination direction of the sealant strip with respect to the tire circumferential direction is in the opposite phase to the inclination direction of the belt cord of the belt layer located at the innermost side in the tire radial direction, it is indicated as "reverse".

[0049] For these test tires, the peel resistance, tire balance, rolling resistance, ply steer, and puncture sealability of the sealant layer were evaluated by the following test methods, and the results are shown together in Table 1.

[0050] Peel resistance of the sealant layer: Each test tire was assembled onto a wheel with a rim size of 19×8.5J, the air pressure was set to 230 kPa, and it was mounted on an indoor drum tester (drum diameter 1707 mm). The ambient temperature was controlled at 38 ± 3 °C, and the driving test was continued at a driving speed of 80 km / h until the driving distance reached 2500 km while bearing a load of 88% of the JATMA maximum load. After the test, the peeling of the sealant layer starting from the end of the belt material was examined. The evaluation results were indicated as "◎" when there was no peeling at all, "○" when the peeling of the belt material was more than 0 mm and 3 mm or less, "△" when the peeling of the belt material was more than 3 mm and 10 mm or less, and "×" when the peeling of the belt material was more than 10 mm.

[0051] Tire balance: Each test tire was assembled onto a wheel with a rim size of 19×8.5J and mounted on a rolling resistance tester. With the air pressure set to 210 kPa, the radial force variation (RFV) was measured in accordance with JIS-D4233. The evaluation results were shown as an index with the reciprocal of the measured value, taking the conventional example as 100. The larger this index value, the better the tire balance.

[0052] Rolling resistance: Each test tire was assembled onto a wheel with a rim size of 19×8.5J and mounted on a rolling resistance tester. With the air pressure set to 210 kPa, the rolling resistance was measured in accordance with JIS-D4234. The evaluation results were shown as an index with the reciprocal of the measured value, taking the conventional example as 100. The larger this index value, the smaller the rolling resistance.

[0053] Pull steer: Each test tire was assembled onto a wheel with a rim size of 19×8.5J and mounted on a uniformity tester. With the air pressure set to 200 kPa, the pull steer was measured in accordance with JIS-D4233. The evaluation results were shown as an index with the reciprocal of the measured value, taking the conventional example as 100. The larger this index value, the smaller the pull steer.

[0054] Puncture sealability: Each test tire was assembled onto a wheel with a rim size of 19×8.5J, and the initial air pressure was set to 250 kPa. A nail with a diameter of 4.0 mm was driven into the tread part, and after leaving the tire for 1 hour with the nail pulled out, the air pressure was measured again, and the pressure drop rate relative to the initial air pressure was determined. Regarding the evaluation results, when the pressure drop rate was 2% or less, it was indicated as "◎", when the pressure drop rate exceeded 2% and was 7% or less, it was indicated as "○", when the pressure drop rate exceeded 7% and was 20% or less, it was indicated as "△", and when the pressure drop rate exceeded 20%, it was indicated as "×".

[0055]

Table 1

[0056] As can be seen from this Table 1, for the tires of Examples 1 to 8, the peel resistance of the sealant layer was good for all of them, and the tire balance was also good. In addition, for the tires of Examples 1 to 8, good results were also obtained regarding rolling resistance, ply steer, and puncture sealability. On the other hand, for the tires of Comparative Examples 1 and 2, since narrow-width portions were not formed at both ends of the belt material of the sealant, the peel resistance of the sealant layer was insufficient, and the tire balance was also deteriorated.

Explanation of Signs

[0057] 1 Tread part 2 Sidewall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt cover layer 10 Tire inner surface 20 Sealant layer 21 Sealant belt material 21X Narrow-width portion 21Y Wide-width portion 40 Sound-absorbing material

Claims

1. In a pneumatic tire having a tread portion extending in the tire circumferential direction and forming an annulus, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of these sidewall portions, a sealant layer having a structure in which a sealant strip is spirally disposed along the tire circumferential direction on the inner surface of the tire in the tread portion is formed, and at least one end of the strip is thinner than the other portion, a pneumatic tire, characterized in that the distance in the tire width direction between the center position in the tire width direction of the sealant layer and the tire equator is 10 mm or less.

2. The pneumatic tire according to claim 1, characterized in that the strip has a narrow-width portion formed at the at least one end and a wide-width portion thicker than the narrow-width portion, the length of the narrow-width portion is 30 mm or more, and the average width of the narrow-width portion is in the range of 20% to 97% of the average width of the wide-width portion.

3. The pneumatic tire according to claim 1 or 2, characterized in that the sealant is composed of a silicone-based composition.

4. The pneumatic tire according to claim 3, characterized in that the silicone-based composition is a two-component curable silicone.

5. The pneumatic tire according to claim 1 or 2, characterized in that the glass transition temperature of the sealant is in the range of -120°C to -40°C.

6. The pneumatic tire according to claim 1 or 2, characterized in that the thickness of the sealant layer is in the range of 2.0 mm to 5.0 mm.

7. The pneumatic tire according to claim 1 or 2, characterized in that a belt layer including belt cords inclined with respect to the tire circumferential direction is embedded in the tread portion, and the width of the sealant layer is 90% or more of the width of the belt layer located innermost in the tire radial direction.

8. The pneumatic tire according to claim 7, characterized in that the end of the sealant layer is disposed outside the end of the belt layer located innermost in the tire radial direction in the tire width direction.

9. In a pneumatic tire having a tread portion extending in the tire circumferential direction and forming an annulus, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of these sidewall portions, A sealant layer having a structure in which a belt-like material of a sealant is spirally arranged along the tire circumferential direction is formed on the inner surface of the tire in the tread portion, and at least one end portion of the belt-like material is thinner than the other portion, and a belt layer including a belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion, the width of the sealant layer is 90% or more of the width of the belt layer located at the innermost side in the tire radial direction, and the end portion of the sealant layer is arranged on the outer side in the tire width direction than the end portion of the belt layer located at the innermost side in the tire radial direction, a belt cover layer including an organic fiber cord oriented in the tire circumferential direction is embedded on the outer peripheral side of the belt layer in the tread portion, and the end portion of the sealant layer is arranged on the outer side in the tire width direction than the end portion of the belt cover layer. A pneumatic tire characterized by this.

10. In a pneumatic tire including a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged on the inner side in the tire radial direction of these sidewall portions, A sealant layer having a structure in which a belt-like material of a sealant is spirally arranged along the tire circumferential direction is formed on the inner surface of the tire in the tread portion, and at least one end portion of the belt-like material is thinner than the other portion, and a belt layer including a belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion, and the inclination direction of the belt-like material of the sealant with respect to the tire circumferential direction is in a reverse phase to the inclination direction of the belt cord of the belt layer located at the innermost side in the tire radial direction. A pneumatic tire characterized by this.

11. In a pneumatic tire including a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged on the inner side in the tire radial direction of these sidewall portions, A sealant layer having a structure in which a belt-like material of a sealant is spirally arranged along the tire circumferential direction is formed on the inner surface of the tire in the tread portion, and at least one end portion of the belt-like material is thinner than the other portion, and a belt layer including a belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion, and the width of the sealant layer is 90% or more of the width of the belt layer located at the innermost side in the tire radial direction, A pneumatic tire, characterized in that at all positions of the belt layer located at the innermost in the tire radial direction, the distance L from the belt layer to the sealant layer is 10 mm or less.

12. The pneumatic tire according to claim 11, characterized in that the ratio of the thickness S of the sealant layer to the distance L from the belt layer located at the innermost in the tire radial direction to the sealant layer satisfies the relationship S / L≥0.

3.

13. The pneumatic tire according to claim 1 or 2, characterized in that a sound-absorbing material is installed along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer.

14. A method for manufacturing a pneumatic tire according to any one of claims 1, 9, 10, and 11, after manufacturing a pneumatic tire excluding the sealant layer, when forming the sealant layer by applying a sealant made of a silicone-based composition to the inner surface of the tire in the tread portion, the temperature of the sealant applied to the inner surface of the tire is made lower than 70°C. A method for manufacturing a pneumatic tire, characterized by this.

15. The method for manufacturing a pneumatic tire according to claim 14, characterized in that a sound-absorbing material is installed along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer.

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