Pneumatic Tire and Method for Producing the Same

Abstract

When providing a pneumatic tire and a method for manufacturing the same that enable improvement in riding comfort when providing a sealant layer on the inner surface of the tire in the tread portion. In a pneumatic tire including a tread portion 1 that extends in the tire circumferential direction and forms 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 inner side in the tire radial direction 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 inner surface 10 of the tire in the tread portion 1 is formed, the starting point P1 and the ending point P2 of the strip 21 are spaced apart from each other in the tire circumferential direction, and the angle β on the narrow angle side formed by the starting point P1 and the ending point P2 of the strip 21 around the tire central axis O is larger than the angle α on the narrow angle side formed by both end points X1, X2 in the tire circumferential direction of the grounding area around the tire central axis.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire provided with a sealant layer on the inner surface of the tire in the tread portion and a method for manufacturing the same, and more particularly to a pneumatic tire and a method for manufacturing the same that enable an improvement in riding comfort.

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 common (see, for example, Patent Documents 1 to 3). Examples of 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 heated to a high temperature and softened (see, for example, Patent Document 4). More specifically, a sealant layer is formed by arranging a strip material of the sealant in a softened state by heating to a high temperature in a spiral shape along the tire circumferential direction on the inner surface of the tire.

[0004] However, according to the findings of the present inventor, in a sealant layer having a structure in which the strip material of the sealant is arranged in a spiral shape along the tire circumferential direction, if the starting point and the ending point of the strip material are simultaneously present within the contact surface, this becomes a factor that deteriorates the riding comfort.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] An object of the present invention is to provide a pneumatic tire and a method for manufacturing the same, which enable improvement of the riding comfort when providing a sealant layer on the inner surface of the tire in the tread portion. [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, the start point and the end point of the strip are separated from each other in the tire circumferential direction, and an angle β on the narrow angle side formed by the start point and the end point of the strip around the tire central axis in a state where the pneumatic tire is assembled to a regular rim and filled with a regular internal pressure is larger than an angle α on the narrow angle side formed by both end points in the tire circumferential direction of the grounding area measured when a regular load is applied with the pneumatic tire assembled to the regular rim and filled with the regular internal pressure and placed vertically on a plane.

[0008] The method for manufacturing a pneumatic tire of the present invention for achieving the above object is, after manufacturing 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, A sealant layer is formed by spirally applying a sealant strip along the tire circumferential direction on the inner surface of the tire in the tread portion. The starting point and the ending point of the strip are spaced apart from each other in the tire circumferential direction. With the pneumatic tire assembled on a standard rim and filled with a standard internal pressure, the angle β on the narrow angle side formed by the starting point and the ending point of the strip around the tire central axis is made larger than the angle α on the narrow angle side formed by both end points in the tire circumferential direction of the contact area measured when the pneumatic tire is assembled on a standard rim, filled with a standard internal pressure, and vertically placed on a plane and a standard load is applied.

Advantages of the Invention

[0009] In the present invention, in a pneumatic tire provided with 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, the starting point and the ending point of the sealant strip are spaced apart from each other in the tire circumferential direction, and the angle β on the narrow angle side formed by the starting point and the ending point of the strip around the tire central axis is set larger than the angle α on the narrow angle side formed by both end points in the tire circumferential direction of the contact area. Since the starting point and the ending point of the strip do not exist in the contact surface at the same time, the riding comfort can be improved.

[0010] In the present invention, it is preferable that the angle β is in the range of 60° to 180°. By setting the angle β within the above range, the riding comfort can be effectively improved.

[0011] 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 at the outermost side in the tire radial direction. By increasing the width of the sealant layer in this way and arranging the starting point and the ending point of the sealant strip more outward in the tire width direction, the riding comfort can be effectively improved. Also, by making the width of the sealant layer sufficiently large, good sealing performance can be ensured.

[0012] In the present invention, it is preferable that the storage elastic modulus G' of the sealant at 100°C is 20 kPa or less. Since the vibration of the sealant layer is suppressed due to the small storage elastic modulus G' of the sealant at 100°C, the riding comfort is improved.

[0013] In the present invention, it is preferable that the loss elastic modulus G" of the sealant at 100°C is 5 kPa or less. Since the heat generation of the sealant layer is suppressed due to the small loss elastic modulus G" of the sealant at 100°C, the influence on durability can be reduced.

[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, the puncture sealing property can be ensured.

[0015] In the present invention, it is preferable that the sealant is composed of a silicone-based composition. When the sealant is composed of a rubber composition mainly composed of butyl rubber, the sealant cools down before the peripheral portions of the sealant strip fit well with each other. As a result, the integrality of the peripheral portions of the sealant strip is not good, and the sealing property of the sealant layer becomes insufficient. Further, when the integrality of the peripheral portions of the sealant strip is insufficient, the sealant layer easily flows 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 property. On the other hand, when the sealant is composed of a silicone-based composition, the peripheral portions of the sealant strip easily fit with each other in the curing reaction process of the silicone-based composition, and the integrality of the peripheral portions of the sealant strip becomes good. Therefore, the sealing property of the sealant layer can be improved. Further, since the integrality of the peripheral portions of the sealant strip is good, the sealant layer hardly flows 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 property. 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 made 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.

[0016] 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 low temperatures.

[0017] In the present invention, the angle α is the angle on the narrow angle side formed by both ends in the tire circumferential direction of the grounding area measured when an inflated tire is assembled on a regular rim, filled with a regular internal pressure, placed vertically on a plane, and a regular load is applied around the tire central axis. The angle β is the angle on the narrow angle side formed by the starting point and the ending point of the belt material around the tire central axis in a state where an inflated tire is assembled on a regular rim and filled with a regular internal pressure. The "regular rim" is the rim defined for each tire in a standard system including the standard on which the tire is based. For example, in the case of JATMA, it is the standard rim; in the case of TRA, it is the "Design Rim"; or in the case of ETRTO, it is the "Measuring Rim". The "regular internal pressure" is the air pressure defined for each tire in a standard system including the standard on which the tire is based. In the case of JATMA, it is the maximum air pressure; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; in the case of ETRTO, it is the "INFLATION PRESSURE". The "regular load" is the load defined for each tire in a standard system including the standard on which the tire is based. In the case of JATMA, it is the maximum load capacity; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; in the case of ETRTO, it is the "LOAD CAPACITY".

[0018] In the present invention, the storage elastic modulus G' and the loss elastic modulus G" of the sealant are measured under the conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ±2%, and a temperature of 100 °C using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS-K6394.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0020] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. Figures 1 and 2 show a pneumatic tire according to an embodiment of the present invention.

[0021] As shown in Figure 1, the pneumatic tire of this 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.

[0022] 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 of the tire 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 circumference of the bead core 5.

[0023] On one side, 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 cross each other between the layers. The plurality of belt layers 7 include a first belt layer 7A located at the innermost side in the tire radial direction and a second belt layer 7B located outside the first belt layer 7A, and the width of the first belt layer 7A is wider than the width of the second belt layer 7B. 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.

[0024] On the outer peripheral side of the belt layer 7, for the purpose of improving high-speed durability, 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. 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.

[0025] Note that 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.

[0026] 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. The sealant layer 20 has a structure in which a sealant strip 21 is arranged spirally along the tire circumferential direction (see FIG. 4). The sealant of the sealant layer 20 may be composed of a rubber composition mainly composed of butyl rubber, but is preferably composed of a silicone-based composition. The silicone-based composition includes a synthetic polymer compound having a main skeleton formed by a siloxane bond.

[0027] The above-described pneumatic tire can be manufactured by the following method. First, a pneumatic tire having a tread portion 1, a pair of sidewall portions 2, and a pair of bead portions 3, and having a belt layer 7 and a belt cover layer 8 embedded in the tread 1 portion is manufactured as described above. Next, a sealant made of, for example, a silicone-based composition is applied to the inner surface 10 of the tread portion 1 to form a sealant layer 20.

[0028] FIG. 3 shows a specific manufacturing method of the pneumatic tire of FIG. 1, and FIG. 4 shows a sealant layer formed on the inner surface of the tire in the tread portion. In FIG. 3, the sealant extruding device 31 mixes the sealant supplied from the pumps 32 and 33, and continuously discharges the mixed sealant from the nozzle 34 as a strip material 21. The sealant extruding device 31 is configured such that the position of the nozzle 34 can be displaced. 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. 4). 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 such a spiral shape is integrated to form the sealant layer 20.

[0029] When forming the sealant layer 20 by spirally applying the strip material 21 of the sealant along the tire circumferential direction to the inner surface 10 of the tire in the tread portion 1, as shown in FIG. 4, the starting point P1 and the ending point P2 of the strip material 21 are separated from each other in the tire circumferential direction Tc, and the angle β on the narrow angle side formed by the starting point P1 and the ending point P2 of the strip material 21 around the tire central axis O is made larger than the angle α on the narrow angle side formed by both end points X1 and X2 in the tire circumferential direction of the grounding area of the pneumatic tire around the tire central axis O. The angle α is the angle on the narrow angle side formed by both end points X1 and X2 in the tire circumferential direction of the grounding area measured when the pneumatic tire is assembled on a standard rim, filled with the standard internal pressure, placed vertically on a plane, and a standard load is applied, as shown in FIG. 5(a). The angle β is the angle on the narrow angle side formed by the starting point P1 and the ending point P2 of the strip material 21 around the tire central axis O when the pneumatic tire is assembled on a standard rim and filled with the standard internal pressure, as shown in FIG. 5(b).

[0030] In the pneumatic tire described above, in a pneumatic tire having a sealant layer 20 with a structure in which a sealant strip 21 is spirally arranged along the tire circumferential direction on the tire inner surface 10 in the tread portion 1, the starting point P1 and the ending point P2 of the sealant strip 21 are separated from each other in the tire circumferential direction, and the angle β on the narrow angle side formed by the starting point P1 and the ending point P2 of the strip 21 around the tire central axis O is set to be larger than the angle α on the narrow angle side formed by both end points X1 and X2 in the tire circumferential direction of the grounding area around the tire central axis O. As a result, the starting point P1 and the ending point P2 of the strip 21 do not exist in the ground contact surface at the same time, so the riding comfort can be improved.

[0031] In the above pneumatic tire, the angle β is preferably in the range of 60° to 180°, more preferably in the range of 90° to 180°. By setting the angle β within the above range, the riding comfort can be effectively improved. If the angle β is too small, the effect of improving the riding comfort will decrease. On the other hand, the angle α is generally in the range of 20° to 50°. Also, it is desirable that the difference between the angle β and the angle α satisfies the relationship β - α ≧ 60°.

[0032] In the pneumatic tire described above, a plurality of belt layers 7 including belt cords inclined with respect to the tire circumferential direction are embedded in the tread portion 1, and the belt cords are arranged so as to cross each other between the layers. When these belt layers 7 include a first belt layer 7A located on the innermost side in the tire radial direction and a second belt layer 7B located on the outermost side in the tire radial direction, 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 7B located on the outermost side in the tire radial direction. In particular, it is preferable that the end portion of the sealant layer 20 is arranged on the outer side in the tire width direction than the end portion of the belt layer 7A located on the innermost side in the tire radial direction. By making the width Ws of the sealant layer 20 sufficiently larger than the width Wb of the belt layer 7B and arranging the starting point P1 and the ending point P2 of the sealant strip 21 on the outer side in the tire width direction, the riding comfort can be effectively improved. Also, by making the width Ws of the sealant layer 20 sufficiently large, good sealing performance can be ensured. Here, if the width Ws of the sealant layer 20 is smaller than 90% of the width Wb of the belt layer 7B, the effect of improving the riding comfort is reduced, and the puncture sealing performance is also reduced.

[0033] In the pneumatic tire described above, it is preferable that the sealant is composed of a silicone-based composition. A sealant layer 20 having a structure in which a sealant strip 21 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 21 are easily compatible with each other in the curing reaction process of the silicone-based composition, and the integrality of the circumferential portions of the sealant strip 21 becomes good. Therefore, the sealing performance of the sealant layer 20 can be improved. Also, since the integrality of the circumferential portions of the sealant strip 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, which 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.

[0034] Since the silicone-based composition has good fluidity even at low temperatures, it is preferable to keep the temperature of the sealant applied to the inner surface 10 of the tire below 70°C. This can reduce the influence of heat on the tire and avoid deterioration of tire performance. If this temperature is 70°C or higher, the influence of heat on the tire increases, which becomes a factor in deteriorating tire performance. In particular, it is desirable that the temperature of the sealant applied to the inner surface 10 of the tire be 35°C or lower. Also, from the perspective of the fluidity of the silicone-based composition, the lower limit of the temperature of the sealant applied to the inner surface 10 of the tire is preferably 20°C.

[0035] As the silicone-based composition constituting the sealant of the sealant layer 20, one-component curable silicone or two-component curable silicone can be used, but it is particularly preferable to use two-component curable silicone. Examples of one-component curable silicone include moisture-curable silicone. Two-component 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 liquid and the second liquid of the two-component curable silicone are supplied from pumps 32 and 33, respectively. Since two-component curable silicone has a low viscosity immediately after the two liquids are mixed, it can be applied even at low temperatures. In particular, it is preferable that the period until complete curing of the two-component curable silicone is 5 days or more.

[0036] Two-component 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 a first liquid and a second liquid in a combination where the curing reaction does not proceed, and are mixed at the time of use. Examples of two-component 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-component curable silicone, for example, SST-2650 manufactured by Dow can be used.

[0037] In the pneumatic tire described above, it is preferable that the storage elastic modulus G' of the sealant at 100°C is 20 kPa or less. Since the vibration of the sealant layer 20 is suppressed due to the small storage elastic modulus G' of the sealant at 100°C, the riding comfort is improved. If the storage elastic modulus G' of the sealant at 100°C is greater than 20 kPa, the effect of improving the riding comfort decreases. In particular, it is desirable that the storage elastic modulus G' of the sealant at 100°C is in the range of 5 kPa to 15 kPa.

[0038] In the pneumatic tire described above, it is preferable that the loss elastic modulus G" of the sealant at 100°C is 5 kPa or less. Since the heat generation of the sealant layer 20 is suppressed due to the small loss elastic modulus G" of the sealant at 100°C, the influence on durability can be reduced. If the loss elastic modulus G" of the sealant at 100°C is greater than 5 kPa, the effect of improving durability decreases. In particular, it is desirable that the loss elastic modulus G" of the sealant at 100°C is in the range of 1 kPa to 3 kPa.

[0039] In the above pneumatic tire, as shown in FIG. 2, the thickness S of the sealant layer 20 is preferably 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 that the sealant layer 20 will be unevenly distributed 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: 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. The measurement value is calculated from a total of 40 points.

[0040] In the above pneumatic tire, as shown in FIG. 2, at all locations of the belt layer 7A located at the innermost side in the tire radial direction, the distance (shortest distance) L from the belt layer 7A to the sealant layer 20 is preferably 10 mm or less. Thereby, 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.

[0041] In the above pneumatic tire, 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 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.

[0042] 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 air 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.

Example

[0043] 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 strip of sealant is spirally arranged along the tire circumferential direction on the inner surface of the tire in the tread portion is formed. Tires of Comparative Examples 1 to 2 and Examples 1 to 8 were manufactured in which the constituent material of the sealant layer, the angle α on the narrow angle side formed by both end points in the tire circumferential direction of the grounding area around the tire central axis, the angle β on the narrow angle side formed by the starting point and the ending point of the strip around the tire central axis, the ratio (Ws / Wb×100%) of the width of the sealant layer to the width of the belt layer, the storage elastic modulus G' of the sealant at 100°C, the loss elastic modulus G" of the sealant at 100°C, and the thickness S of the sealant layer were varied as shown in Table 1.

[0044] Regarding these test tires, the ride comfort and puncture sealing performance were evaluated by the following test methods, and the results are also shown in Table 1.

[0045] Ride comfort: Each test tire was assembled onto a wheel with a rim size of 19×8.5J and mounted on a test vehicle (SUV) with a displacement of 2400 cc. With the air pressure set at 210 kPa and the load at 100% of the maximum impossible force, a driving test was conducted by a test driver, and a sensory evaluation of the ride comfort was performed. The evaluation results were shown as an index with Comparative Example 1 set as 100. The larger this index value, the better the ride comfort.

[0046] Puncture sealability: Each test tire was assembled onto a wheel with a rim size of 19×8.5J, the initial air pressure was set at 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. The evaluation results were indicated as "◎" when the pressure drop rate was 2% or less, "○" when the pressure drop rate was more than 2% and 7% or less, "△" when the pressure drop rate was more than 7% and 20% or less, and "×" when the pressure drop rate was more than 20%.

[0047]

Table 1

[0048] As can be seen from Table 1, in addition to the good puncture sealability of the tires of Examples 1 to 8, the ride comfort was excellent in comparison with Comparative Examples 1 and 2.

Explanation of symbols

[0049] 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 Band material of sealant 40 Sound-absorbing material P1 Starting point of band material End point of the P2 strip Both end points in the tire circumferential direction of the X1 and X2 grounding regions

Claims

1. A pneumatic tire comprising a tread portion extending in a tire circumferential direction to form 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 tire radially inner sides of the sidewall portions, a sealant layer having a structure in which a strip of sealant is spirally arranged along the circumferential direction of the tire formed on the inner surface of the tread portion, the start point and end point of the strip being spaced apart from each other in the circumferential direction of the tire, and a narrow angle β formed by the start point and end point of the strip around the tire center axis when the pneumatic tire is mounted on a normal rim and inflated to a normal internal pressure is larger than a narrow angle α formed by both end points of the tire circumferential direction of the contact patch around the tire center axis when the pneumatic tire is mounted on a normal rim and inflated to a normal internal pressure and placed vertically on a flat surface and a normal load is applied.

2. 2. The pneumatic tire according to claim 1, wherein the angle β is in the range of 60° to 180°.

3. 3. The pneumatic tire according to claim 1, wherein a belt layer including belt cords inclined relative 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 outermost position in the tire radial direction.

4. 3. The pneumatic tire according to claim 1, wherein the sealant has a storage modulus G' at 100° C. of 20 kPa or less.

5. 3. The pneumatic tire according to claim 1, wherein the sealant has a loss modulus G" at 100°C of 5 kPa or less.

6. 3. The pneumatic tire according to claim 1, wherein the sealant layer has a thickness in the range of 2.0 mm to 5.0 mm.

7. 3. The pneumatic tire according to claim 1, wherein the sealant is made of a silicone-based composition.

8. 8. The pneumatic tire according to claim 7, wherein the silicone-based composition is a two-component curing silicone.

9. After manufacturing a pneumatic tire having a tread portion extending in the tire circumferential direction to form 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 tire radially inner sides of the sidewall portions, a sealant layer is formed on the inner surface of the tire in the tread portion in a spiral pattern along the tire circumferential direction, a start point and an end point of the sealant layer are spaced apart from each other in the tire circumferential direction, and a narrow angle β formed by the start point and the end point of the strip around the tire center axis when the pneumatic tire is mounted on a normal rim and inflated to a normal internal pressure is made larger than a narrow angle α formed by both end points of the tire circumferential direction of the contact patch around the tire center axis when the pneumatic tire is mounted on a normal rim and inflated to a normal internal pressure and placed vertically on a flat surface and a normal load is applied.

Images