Pneumatic tires

Abstract

To provide a pneumatic tire in which a deformation suppression part is formed on an inner surface of the tire so that thicknesses of a sealant layer can be suppressed from locally varying during travelling.SOLUTION: In a pneumatic tire, in which a sealant layer 10 is arranged in a region corresponding to a tread part 1 on an inner surface Ts of the tire, a deformation suppression part 20 extending in a tire circumferential direction is provided in at least one place in a tire width direction of the region corresponding to the tread part 1 on the inner surface Ts of the tire. The sealant layer 10 has a plurality of sealant parts 11-14 partitioned by the deformation suppression part 20. Modulus at 20% extension at 80°C of the deformation suppression part 20 is 1.5 times-1000 times of modulus at 20% extension at 80°C of the sealant layer 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire having a sealant layer disposed on the inner surface of the tire, and more specifically, to a pneumatic tire in which a deformation suppression portion is provided on the inner surface of the tire, thereby making it possible to suppress local changes in thickness of the sealant layer during running. [Background technology]

[0002] As a pneumatic tire having puncture sealing properties, one in which a sealant layer made of an adhesive sealant is disposed in an area corresponding to the tread portion on the inner surface of the tire has been proposed (for example, Patent Document 1). In a pneumatic tire having such a sealant layer, when a foreign object such as a nail penetrates the tread portion, the adhesive sealant clings to the foreign object, and as the foreign object falls off, the adhesive sealant is guided to the puncture hole, thereby exerting a sealing effect.

[0003] Such a sealant layer has fluidity, which causes the sealant layer to move due to deformation of the tire when it comes into contact with the ground during running, resulting in a problem of localized changes in the thickness of the sealant layer. If the thickness of the sealant layer changes locally, not only will the sealing effect deteriorate, but tire vibration will also occur. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-080909 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a pneumatic tire that makes it possible to suppress local changes in thickness of a sealant layer during running by providing a deformation suppression portion on the inner surface of the tire. [Means for solving the problem]

[0006] To achieve the above objectives of The pneumatic tire of the present invention has a sealant layer disposed in a region corresponding to a tread portion on an inner surface of the tire, the deformation suppressing portion extending in a tire circumferential direction is provided in at least one location in the tire width direction of the region corresponding to the tread portion on the inner surface of the tire, the sealant layer has a plurality of sealant portions divided by the deformation suppressing portions, and a modulus of the deformation suppressing portion at 20% elongation at 80°C is 1.5 to 1000 times that of the sealant layer at 20% elongation at 80°C. The deformation suppression portion has a modulus of 0.005 MPa to 0.050 MPa at 20% elongation at 80°C. It is characterized by the above. Effect of the Invention

[0007] In the present invention, a deformation suppression portion extending in the tire circumferential direction is provided at least at one location in the tire width direction in the region corresponding to the tread portion on the inner surface of the tire, the sealant layer has a plurality of sealant portions divided by the deformation suppression portions, and the modulus of the deformation suppression portion at 20% elongation at 80°C is 1.5 to 1000 times that of the sealant layer at 20% elongation at 80°C, so that the rigidity of the deformation suppression portion is higher than that of the sealant layer. Therefore, even if the sealant layer is compressed due to the tire's deformation when it comes into contact with the ground during running, the deformation suppression portion with high rigidity acts to prevent the sealant layer from flowing and the adjacent sealant portions from adhering to each other, and the local thickness change of the sealant layer can be suppressed. This makes it possible to suppress tire vibration caused by the movement of the sealant layer during running.

[0008] In the pneumatic tire of the present invention, the height of the deformation suppressing portion is preferably 0.8 to 2.0 times the thickness of the thicker of the sealant portions adjacent to the deformation suppressing portion, thereby making it possible to effectively suppress local thickness changes in the sealant layer.

[0009] The width of the deformation suppression portion is preferably 0.01 mm to 4.00 mm, which makes it possible to effectively suppress local variations in thickness of the sealant layer.

[0010] The width of each sealant portion is preferably 3 mm to 150 mm, which makes it possible to effectively prevent adjacent sealant portions from adhering to each other even when the tire undergoes significant deformation, such as when the tire goes over a protrusion.

[0011] It is preferable that a barrier layer including a plurality of barrier sections divided by deformation suppression sections is provided between each of the sealant sections and the inner liner layer that forms the tire inner surface, which makes it difficult for liquid components (e.g., oil components) blended in the sealant layer (each sealant section) to migrate to the inner liner layer, thereby suppressing deterioration of tire durability caused by the liquid components in the sealant layer.

[0012] In the present invention, the modulus at 20% elongation at 80° C. is measured in accordance with JIS-K6251. [Brief description of the drawings]

[0013] [Figure 1] 1 is a meridian cross-sectional view showing an example of a pneumatic tire according to an embodiment of the present invention. [Diagram 2] 2 is an enlarged cross-sectional view showing a main part of the pneumatic tire of FIG. 1. [Diagram 3] 1(a) and 1(b) are cross-sectional views showing a state in which the thickness of the sealant layer is non-uniform. [Figure 4] FIG. 4 is a meridian cross-sectional view showing a modified example of a pneumatic tire according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which: Figures 1 and 2 show a pneumatic tire according to an embodiment of the present invention.

[0015] As shown in Figures 1 and 2, the pneumatic tire of this embodiment has a tread portion 1 extending circumferentially around the tire to form a ring, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged radially inward of the sidewall portions 2.

[0016] A carcass layer 4 is installed between a pair of bead portions 3, 3. This carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around a bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5. Furthermore, an inner liner layer 9 is arranged along the carcass layer 4 on the tire inner surface Ts.

[0017] 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 reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to, for example, a range of 10° to 40°. As the reinforcing cords of the belt layers 7, steel cords are preferably used. On the outer peripheral side of the belt layers 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. As the reinforcing cords of the belt cover layer 8, organic fiber cords such as nylon and aramid are preferably used.

[0018] It should be noted that the above-described tire internal structure shows a typical example of a pneumatic tire, but is not limited thereto.

[0019] In the above pneumatic tire, a sealant layer 10 is disposed along the tire circumferential direction in a region corresponding to the tread portion 1 on the tire inner surface Ts. Furthermore, the sealant layer 10 has a plurality of sealant portions 11-14 divided by the deformation suppression portions 20 described later. In FIG. 1, the sealant layer 10 is divided into four sealant portions 11-14 by three deformation suppression portions 20. The sealant layer 10 (sealant portions 11-14) is made of an adhesive sealant material. Any adhesive composition can be used as the sealant material. By using such a sealant material, it becomes possible to adhere to the tire inner surface Ts due to the adhesiveness of the sealant material. Note that the sealant portions 11-14 may be made of sealant materials made of the same adhesive composition, or sealant materials made of different adhesive compositions may be used.

[0020] In addition, a deformation suppressing portion 20 extending in the tire circumferential direction is provided in at least one location in the tire width direction in a region of the tire inner surface Ts corresponding to the tread portion 1. The deformation suppressing portion 20 suppresses the sealant layer 10 from flowing from the shoulder portion side toward the center portion side when the sealant layer 10 is compressed due to the tire's contact deformation during running. The deformation suppressing portion 20 can be made of vulcanized rubber, a resin film, or a resin.

[0021] Such a deformation suppression portion 20 is fixed to the tire inner surface Ts and is formed in a ring shape in the tire circumferential direction. The deformation suppression portion 20 protrudes from the tire inner surface Ts toward the tire radially inward. In addition, it is preferable that the deformation suppression portion 20 is arranged so as to include a position corresponding to an end of the belt layer 7 on the tire inner surface Ts. In addition, it is preferable that the deformation suppression portion 20 is arranged in a region excluding the lower region of the main groove formed in the tread portion 1 and excluding a range within 2 mm from each of both ends of the main groove in the tire width direction toward the outer side in the tire width direction. In other words, it is preferable that the deformation suppression portion 20 is arranged in a region below the land portion formed in the tread portion 1, where the distance in the tire width direction from the end of the land portion in the tire width direction exceeds 2 mm.

[0022] In the above pneumatic tire, the modulus of the deformation suppression portion 20 at 20% elongation at 80° C. is 1.5 to 1000 times the modulus of the sealant layer 10 at 20% elongation at 80° C. In this case, the modulus of the deformation suppression portion 20 at 20% elongation at 80° C. is preferably in the range of 0.005 MPa to 0.050 MPa.

[0023] In the above-mentioned pneumatic tire, the deformation suppression part 20 extending in the tire circumferential direction is provided at least at one location in the tire width direction in the region corresponding to the tread part 1 of the tire inner surface Ts, and the sealant layer 10 has a plurality of sealant parts 11 to 14 divided by the deformation suppression part 20. The modulus of the deformation suppression part 20 at 20% elongation at 80°C is 1.5 to 1000 times that of the sealant layer 10 at 20% elongation at 80°C, so that the rigidity of the deformation suppression part 20 is higher than that of the sealant layer 10. Therefore, even if the sealant layer 10 is compressed due to the tire's contact deformation during running, the deformation suppression part 20 with high rigidity acts to prevent the sealant layer 10 from flowing and the adjacent sealant parts 11 to 14 from adhering to each other, and the local thickness change of the sealant layer 10 can be suppressed. This makes it possible to suppress tire vibration caused by the movement of the sealant layer 10 during running.

[0024] Here, if the modulus of the deformation suppression portion 20 at 20% elongation at 80°C is less than 1.5 times the modulus of the sealant layer 10 at 20% elongation at 80°C, the rigidity of the deformation suppression portion 20 is not sufficiently higher than the rigidity of the sealant layer 10, and local thickness changes of the sealant layer 10 cannot be sufficiently suppressed. Conversely, if the modulus of the deformation suppression portion 20 at 20% elongation at 80°C is more than 1000 times the modulus of the sealant layer 10 at 20% elongation at 80°C, the ride comfort of the tire tends to deteriorate.

[0025] In the above pneumatic tire, the height h of the deformation suppression portion 20 is preferably 0.8 to 2.0 times, and more preferably 1.1 to 2.0 times, the thickness t of the thicker sealant portion 11 to 14 among the sealant portions 11 to 14 adjacent to the deformation suppression portion 20. In this case, the height h of the deformation suppression portion 20 is preferably in the range of 1.6 mm to 8.0 mm. Here, the thickness t of each sealant portion 11 to 14 may be non-uniform in the tire width direction as shown in Figs. 3(a) and 3(b). Specifically, Fig. 3(a) shows a case where the thickness t of the sealant portions 11 to 14 is smaller than the height h of the deformation suppression portion 20, and Fig. 3(b) shows a case where the thickness t of the sealant portions 11 to 14 is larger than the height h of the deformation suppression portion 20. In consideration of this point, the thickness t of each sealant portion 11 to 14 is the average value of thicknesses measured at eight points on the tire circumference at intervals of 30 mm in the tire width direction from the deformation suppression portion 20 along a direction perpendicular to the tire inner surface Ts.

[0026] By appropriately setting the ratio h / t of the height h of the deformation suppressing portion 20 to the thickness t of each of the sealant portions 11 to 14 in this manner, local thickness variations in the sealant layer 10 can be effectively suppressed.

[0027] Here, if the ratio h / t is less than 0.8, it is not possible to sufficiently suppress the flow of the sealant layer 10 when the sealant layer 10 is compressed due to deformation of the tire when it comes into contact with the ground. Conversely, if the ratio h / t is more than 2.0, the deformation suppression section 20 will vibrate during running, which tends to deteriorate the ride comfort of the tire during running.

[0028] The width w of the deformation suppression portion 20 is preferably 0.01 mm to 4.00 mm. The width w of the deformation suppression portion 20 is the length measured at the portion that abuts against the tire inner surface Ts. By appropriately setting the width w of the deformation suppression portion 20 in this manner, local thickness changes in the sealant layer 10 can be effectively suppressed.

[0029] Here, if the width w of the deformation suppression portion 20 is smaller than 0.01 mm, it is difficult to provide the deformation suppression portion 20 on the tire inner surface Ts, resulting in reduced productivity. Conversely, if the width w of the deformation suppression portion 20 is larger than 4.00 mm, when a hole is made in the tire by a nail or the like, the deformation suppression portion 20 undesirably reduces the repairable area.

[0030] The width W of each of the sealant portions 11-14 is preferably 3 mm to 150 mm. The width W of the sealant portions 11-14 is determined by measuring the sealant portions 11-14 along the curvature of the tire inner surface Ts and further measuring each of the sealant portions 11-14 at eight points around the tire circumference, and averaging the widths.

[0031] By appropriately setting the width W of each sealant portion 11-14 in this manner, even if the tire undergoes significant deformation, such as when going over a protrusion, it is possible to effectively prevent adjacent sealant portions 11-14 from adhering to each other. Note that the narrower the width W of each of the sealant portions 11-14, the less likely the sealant layer 10 will flow during driving.

[0032] Here, if the width W of each of the sealant portions 11-14 is smaller than 3 mm, when a hole is made in the tire by a nail or the like, the area that can be repaired by the sealant layer 10 is reduced, which is undesirable. Conversely, if the width W of each of the sealant portions 11-14 is larger than 150 mm, when the sealant layer 10 is compressed due to deformation of the tire in contact with the ground, local deformation of the sealant layer 10 is likely to occur, which is undesirable.

[0033] FIG. 4 shows a modified example of a pneumatic tire according to an embodiment of the present invention. As shown in FIG. 4, a barrier layer 15 is provided between the inner liner layer 9 forming the tire inner surface Ts and each of the sealant portions 11 to 14. The barrier layer 15 has a plurality of barrier portions 16 to 19 divided by a deformation suppression portion 20. The barrier layer 15 suppresses the migration of liquid components (e.g., oil components) blended in the sealant layer 10 (sealant portions 11 to 14) to the inner liner layer 9. The adhesive composition constituting the sealant layer 10 preferably contains an oil component in an amount of 25% by weight to 75% by weight of the total amount of the adhesive composition. Examples of the oil component contained in the adhesive composition include aromatic oil, paraffin oil, and polybutene oil. The barrier layer 15 and the sealant layer 10 are laminated in this order from the inner liner layer 9 toward the tire radial direction inward.

[0034] The barrier layer 15 can be made of rubber or resin that has low affinity with the liquid component blended in the sealant layer 10. Examples of materials that have low affinity with the liquid component of the sealant layer 10 include rubbers such as nitrile rubber and fluororubber, and resins such as polyethylene, polypropylene, and vinyl chloride. In particular, the barrier layer 15 is preferably made of resin, and in this case, the barrier layer 15 can have excellent barrier properties and productivity. It is also preferable to blend talc or clay in the barrier layer 15, and blending these can enhance the effect of suppressing the migration of the liquid component of the sealant layer 10 to the inner liner layer 9. In addition, the thickness of the barrier layer 15 is preferably 0.01 mm to 1.0 mm. The width of the barrier layer 15 is configured to be equal to or greater than the width of each of the sealant parts 11 to 14. In particular, the width of the barrier layer 15 is preferably in the range of 100% to 130% of the width of the sealant parts 11 to 14, and more preferably in the range of 110% to 120%. The width of the barrier layer 15 is the length measured along the curvature of the tire inner surface Ts.

[0035] The barrier layer 15 can be formed on the tire inner surface Ts by attaching it to a green tire and vulcanizing it together with the tire, applying rubber or resin to a vulcanized tire, spraying rubber or resin onto a vulcanized tire, or attaching a sheet-like rubber or resin to a vulcanized tire via an adhesive. When rubber or resin is applied to a vulcanized tire, the unevenness of the tire inner surface Ts formed by the bladder during vulcanization is flattened, increasing the bonding area between the sealant layer 10 and the barrier layer 15 and improving adhesion, which is preferable.

[0036] In the pneumatic tire of the present embodiment, a barrier layer 15 that suppresses migration of liquid components blended in the sealant layer 10 to the inner liner layer 9 is provided between the inner liner layer 9 and the sealant layer 10 that form the tire inner surface Ts, so that the liquid components (e.g., oil components) blended in the sealant layer 10 are less likely to migrate to the inner liner layer 9, thereby suppressing deterioration of tire durability due to the liquid components of the sealant layer 10. In addition, the barrier layer 15 does not affect the adhesion or fluidity of the sealant layer 10, so that the sealant layer 10 can exhibit its inherent sealing performance.

[0037] 4 shows an embodiment in which the barrier layer 15 has a plurality of barrier portions 16-19 separated by the deformation suppression portion 20, but the present invention is not limited to this. Alternatively, the deformation suppression portion 20 and the barrier layer 15 can be integrally molded to use a barrier layer provided with the deformation suppression portion 20.

[0038] 1 and 4 show an example in which each of the sealant portions 11 to 14 has the same thickness t, but each may have a different thickness t. Also, while Fig. 1 and 4 show an example in which three deformation suppressing portions 20 are provided in the region corresponding to the tread portion 1 of the tire inner surface Ts, the number of deformation suppressing portions 20 is not limited thereto and may be, for example, in the range of 2 to 70. EXAMPLES

[0039] For pneumatic tires having a tire size of 235 / 40R18 and a sealant layer disposed on the inner surface of the tread portion, tires of a conventional example, comparative examples 1 and 2, and examples 1 to 10 were manufactured with the presence or absence of a deformation suppression portion, the number of deformation suppression portions, the number of sealant portions, the modulus ratio, the ratio h / t, the width w of the deformation suppression portion, the width W of each sealant portion, and the presence or absence of a barrier layer set as shown in Table 1.

[0040] In Table 1, "modulus ratio" refers to the ratio of the modulus of the deformation suppression part at 20% elongation at 80°C to the durus of the sealant layer at 20% elongation at 80°C. "Ratio h / t" refers to the ratio of the height h [mm] of the deformation suppression part to the thickness t [mm] of the thicker sealant part adjacent to the deformation suppression part. "Width W of each sealant part" means that when one numerical value is listed (except for Example 8), each sealant part has the same width as listed, and when two numerical values ​​are listed (Example 8), each sealant part has the respective width as listed.

[0041] For these test tires, the difference in sealant layer thickness after running and the ride comfort were evaluated by the following test methods. The results are also shown in Table 1.

[0042] Difference in sealant layer thickness after running: Each test tire was mounted on a wheel with a rim size of 18 x 8.5J, and run for hours using a drum test machine under the following conditions: air pressure of 150kPa, 120% of the maximum load of JATMA, running speed of 80km / h, slip angle of ±1°, while varying the slip angle with a 1Hz square wave. After running, the thickness of the sealant layer was measured by CT scanning with an air pressure of 200kPa applied, and the difference [mm] between the maximum and minimum thicknesses of the sealant layer was calculated.

[0043] Ride comfort: Each test tire was mounted on a wheel with a rim size of 18 x 8.5J, and the air pressure was set to 250kPa, and the tire was mounted on a front-wheel drive vehicle. A sensory evaluation was carried out by a test driver on a test course consisting of a circular circuit with a smooth road surface. The evaluation results were expressed as an index with the conventional example being set at 100. The higher the index value, the better the ride comfort.

[0044] [Table 1]

[0045] As can be seen from Table 1, in Examples 1 to 10, the variation in the difference in thickness of the sealant layer after driving was small while maintaining ride comfort compared to the conventional examples, and therefore local changes in thickness of the sealant layer were suppressed.

[0046] On the other hand, in Comparative Example 1, the ratio of the modulus of the deformation suppression part at 20% elongation at 80°C to the durus of the sealant layer at 20% elongation at 80°C was set lower than the range specified in the present invention, so the difference in thickness of the sealant layer after driving fluctuated greatly and local thickness changes in the sealant layer could not be sufficiently suppressed.In Comparative Example 2, the ratio of the modulus of the deformation suppression part at 20% elongation at 80°C to the durus of the sealant layer at 20% elongation at 80°C was set higher than the range specified in the present invention, so local thickness changes in the sealant layer could be suppressed but the ride comfort of the tire deteriorated. [Explanation of symbols]

[0047] 1 Tread section 2 Sidewall 3 Bead section 9 Inner liner layer 10 Sealant Layer 11~14 Sealant section 20 Deformation suppression section Ts Tire inner surface CL Tire centerline

Claims

1. In a pneumatic tire having a sealant layer disposed in an area corresponding to a tread portion on an inner surface of the tire, A pneumatic tire characterized in that a deformation suppressing portion extending in a tire circumferential direction is provided in at least one location in the tire width direction of a region corresponding to a tread portion on the tire inner surface, the sealant layer has a plurality of sealant portions divided by the deformation suppressing portions, the modulus at 20% elongation at 80°C of the deformation suppressing portion is 1.5 to 1000 times that of the sealant layer at 20% elongation at 80°C, and the modulus at 20% elongation at 80°C of the deformation suppressing portion is in the range of 0.005 MPa to 0.050 MPa.

2. The pneumatic tire according to claim 1, characterized in that the height of the deformation suppressing portion is 0.8 to 2.0 times the thickness of the thicker of the sealant portions adjacent to the deformation suppressing portion.

3. The pneumatic tire according to claim 1 or 2, characterized in that the deformation suppression portion has a width of 0.01 mm to 4.00 mm.

4. The pneumatic tire according to any one of claims 1 to 3, characterized in that each of the sealant portions has a width of 3 mm to 150 mm.

5. The pneumatic tire according to any one of claims 1 to 4, characterized in that a barrier layer including a plurality of barrier portions separated by the deformation suppression portion is provided between an inner liner layer forming the tire inner surface and each of the sealant portions.

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