pneumatic tires

Abstract

We provide a pneumatic tire that can reduce rim flange wear caused by chafers. [Solution] The pneumatic tire according to the embodiment is equipped with a chafer made of a composite of nonwoven fabric and rubber in the bead portion, and the difference in thickness between the thickest and thinnest parts of the nonwoven fabric is less than 0.08 mm.

Description

[Technical Field]

[0001] This invention relates to a pneumatic tire. [Background technology]

[0002] The bead area of ​​a pneumatic tire is equipped with a chafer as a reinforcing layer to protect the carcass ply from friction with the wheel rim. Generally, a composite of plain weave fabric and rubber is used as the chafer. The plain weave fabric is used to support a sufficient amount of rubber, preventing the bead core from being exposed due to rim slippage.

[0003] Patent Document 1 discloses the use of a short-fiber reinforced rubber ply in which two types of short fibers are oriented in a predetermined direction as a chafer for a pneumatic tire, and also discloses chafers made of corded fabric and nonwoven fabric as comparative examples. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 50-25206 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In chafers made of a composite of plain weave fabric and rubber, the unevenness of the fabric becomes visible on the tire surface in the bead area, causing friction during tire operation and resulting in wear on the rim flange. Although Patent Document 1 discloses the application of nonwoven fabric to chafers as a comparative example, as described above, it does not mention the uniformity of the surface.

[0006] In view of the above, the embodiments of the present invention aim to provide a pneumatic tire that can suppress wear of the rim flange. [Means for solving the problem]

[0007] An embodiment of the present invention provides a chafer made of a composite of nonwoven fabric and rubber in the bead portion, wherein the difference in thickness between the thickest and thinnest parts of the nonwoven fabric is less than 0.08 mm. [Effects of the Invention]

[0008] According to embodiments of the present invention, friction of the rim flange can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] A cross-sectional view of the bead portion and its vicinity of a pneumatic tire according to one embodiment. [Figure 2] A schematic cross-sectional view showing the structure of a plain weave fabric related to a comparative example. [Modes for carrying out the invention]

[0010] The pneumatic tire according to this embodiment is equipped with a chafer made of a composite of nonwoven fabric and rubber (hereinafter also simply referred to as the composite) as a reinforcing layer in the bead portion. The nonwoven fabric used to constitute the composite has a thickness difference of less than 0.08 mm between its thickest part (hereinafter also referred to as the thickest part) and its thinnest part (hereinafter also referred to as the thinnest part).

[0011] Unlike plain woven fabrics, nonwoven fabrics do not have a clear distinction between warp and weft threads, and have a structure in which fibers are uniformly dispersed. Due to this characteristic, it is thought that the surface of nonwoven fabrics is easier to make smoother than that of plain woven fabrics. Therefore, by using a nonwoven fabric with a uniform surface instead of plain woven fabric as the fiber material for the chafer, the contact area with the rim flange is increased, and the pressure on the contact surface is reduced, thereby suppressing wear of the rim flange due to friction and thus reducing the abrasion of the rim flange. For this reason, in this embodiment, a nonwoven fabric is used in which the difference in thickness between the thickest and thinnest parts (hereinafter also referred to as the maximum thickness difference) is less than 0.08 mm. Preferably, the maximum thickness difference of the nonwoven fabric is 0.07 mm or less, and more preferably 0.06 mm or less.

[0012] Here, the maximum thickness difference of the nonwoven fabric is measured as follows. For measurement, the nonwoven fabric is used in its base material state before the composite with rubber is made. For a 20 cm square piece of nonwoven fabric, the thickness is measured at five points that are at least 10 cm apart from each other. The largest value among these is taken as the thickness of the thickest part, and the smallest value is taken as the thickness of the thinnest part. The difference between these two values ​​is used to determine the maximum thickness difference. The thickness of each of the five points is measured using a thickness measuring instrument in accordance with JIS L1096:2010, Method 8.4 A, under constant time (10 seconds) and constant pressure (23.5 kPa).

[0013] The thickness of the nonwoven fabric is not particularly limited; for example, it may be 0.20 to 1.10 mm, 0.30 to 0.80 mm, or 0.40 to 0.60 mm. Here, the thickness of the nonwoven fabric is the average of the thicknesses of the five locations mentioned above.

[0014] The basis weight of the nonwoven fabric is not particularly limited; for example, 50-150 g / m². 2 However, often 80-130g / m 2 However, often 90-120g / m 2 But that's fine. The weight of the nonwoven fabric is 50g / m². 2 As a result, the reinforcing effect as a chafer can be enhanced. Also, 150g / m 2 The following factors make it easier to calender the composite.

[0015] Here, the basis weight of a nonwoven fabric is the mass per unit area of ​​the nonwoven fabric, and is calculated by dividing the mass of the nonwoven fabric by the area of ​​the nonwoven fabric (the area of ​​the plane when the nonwoven fabric is considered as a plane), and is also called surface density (the same applies to the basis weight of composites and the basis weight of rubber in composites).

[0016] The material of the non-woven fabric is not particularly limited, but organic fibers are preferred. For example, polyester fibers, aliphatic polyamide fibers (nylon fibers), aromatic polyamide fibers (aramid fibers), polyvinyl alcohol-based fibers, carbon fibers, etc. can be mentioned, and they can be either short fibers or long fibers. Any one of these may be used, or two or more of them may be used in combination.

[0017] The thickness of the fibers constituting the non-woven fabric is not particularly limited. For example, the fiber diameter may be 10 to 50 μm, or may be 15 to 40 μm. The fiber diameter can be determined by electron microscope observation, and can be determined as the average value of the diameters of 10 arbitrarily selected fibers.

[0018] The manufacturing method of the non-woven fabric is not particularly limited, and it can be formed by a known method. For example, methods of forming a web by a carding method, a papermaking method, an air-laying method, a melt blowing method, a spunbond method, and a needle punching method, etc. can be mentioned. As methods of bonding fibers in a web other than the melt blowing method and the spunbond method, there are a thermal fusion method, a method using a binder, a water flow entanglement method of entangling fibers by the force of water flow or a needle, a needle punching method, etc. Among these manufacturing methods, the melt blowing method and the spunbond method are preferred.

[0019] The rubber constituting the composite is not particularly limited, and generally, a rubber composition used for a chafer, for example, a composition obtained by blending a filler, a vulcanizing agent, etc. into a diene-based rubber can be used. Examples of the diene-based rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), etc. Any one of these may be used, or two or more of them may be used in combination. The diene-based rubber preferably contains natural rubber, and more preferably contains 50% by mass or more with natural rubber as the main component.

[0020] Examples of fillers include carbon black and / or silica, with carbon black being preferred. The content of the filler (preferably carbon black) is not particularly limited, but is preferably 40 to 100 parts by mass, and more preferably 50 to 80 parts by mass, per 100 parts by mass of diene rubber.

[0021] Sulfur is commonly used as a vulcanizing agent, and its content is not particularly limited, but it may be 1 to 8 parts by mass or 3 to 6 parts by mass.

[0022] In addition to the above components, the rubber composition may contain various additives commonly used in rubber compositions, such as zinc oxide, stearic acid, antioxidants, oils, waxes, resins, and vulcanization accelerators.

[0023] Rubber compositions can be prepared by kneading in accordance with conventional methods using commonly used mixers such as Banbury mixers, kneaders, and rolls. That is, for example, in the first mixing stage, additives other than the vulcanizing agent and vulcanization accelerator are added to the diene rubber and mixed, and then, in the final mixing stage, the vulcanizing agent and vulcanization accelerator are added to the resulting mixture and mixed to prepare the rubber composition.

[0024] The composite comprises a nonwoven fabric and rubber, with the nonwoven fabric coated with rubber. The method for manufacturing the composite is not particularly limited; for example, an unvulcanized composite can be obtained by pressing an unvulcanized rubber composition onto the nonwoven fabric from both sides or one side using a press or heat roll. An unvulcanized tire (green tire) can be manufactured by combining the obtained unvulcanized composite with other tire components. Subsequently, a pneumatic tire can be manufactured by vulcanizing and molding at, for example, 140-180°C. Therefore, the composite is incorporated into the tire in a vulcanized state.

[0025] The thickness of the composite is not particularly limited, but is preferably 1.0 to 1.5 mm, and more preferably 1.15 to 1.35 mm. The thickness of the composite is measured by the same method as described above for the thickness of the nonwoven fabric.

[0026] The amount of rubber in the composite is not particularly limited; for example, the basis weight of the rubber can be 800-1600 g / m². 2 But often, 1000-1400g / m 2 But that's fine. The basis weight of the rubber can be calculated from the difference between the basis weight of the composite and the basis weight of the nonwoven fabric.

[0027] Figure 1 is a cross-sectional view showing the bead portion 10 and its vicinity of a pneumatic tire according to one embodiment. In Figure 1, the right side is the outer side in the tire axial direction, the left side is the inner side in the tire axial direction, the upper side is the outer side in the tire radial direction, and the lower side is the inner side in the tire radial direction. The tire axial direction refers to the direction parallel to the tire rotation axis, the inner side in the axial direction refers to the direction approaching the tire equator, and the outer side in the axial direction refers to the direction away from the tire equator. The tire radial direction refers to the direction perpendicular to the tire rotation axis, the outer side in the radial direction refers to the direction away from the rotation axis, and the inner side in the radial direction refers to the direction approaching the rotation axis. The tire circumferential direction refers to the direction of rotation around the tire rotation axis.

[0028] The pneumatic tire has a pair of annular bead portions 10 on both sides in the tire width direction. The bead portion 10 has a bead core 12 made of bundled steel wires covered with rubber, and a bead filler 14 which is a rubber member provided radially outside the bead core 12.

[0029] The pneumatic tire has a carcass ply 16 formed by a plurality of ply cords covered with rubber. The carcass ply 16 bulges toroidally between a pair of bead portions 10 to form the framework of the tire shape, and on both sides in the tire axial direction, it is folded back from the inside to the outside in the tire axial direction around the bead portions 10 and wound up outward in the tire radial direction.

[0030] An inner liner 18, made of rubber, is attached to the inside of the toroidal portion of the carcass ply 16 (i.e., the inside of the tire). A sidewall rubber 20 is attached to the outer side of the carcass ply 16 in the axial direction of the tire. Although not shown in the diagram, multiple belts are laminated around the outer circumference of the crown portion of the toroidal carcass ply 16. Each belt consists of multiple cords, such as steel, covered in rubber. A tread rubber with a contact surface is provided on the outer circumference of the belts.

[0031] In the above configuration, in this embodiment, a chafer 22 made of the composite material is provided on the bead portion 10. As shown in Figure 1, the chafer 22 is provided so as to cover the folded portion of the carcass ply 16 from the inside in the radial direction of the tire, and is provided with a constant cross-section over the entire circumference in the circumferential direction of the tire. The chafer 22 is a reinforcing layer for protecting the carcass ply 16 from friction with the rim flange R of the wheel. In this example, the chafer 22 forms the inner circumferential surface of the bead portion 10 that contacts the rim flange R, and extends radially outward from the bead core 12 on both sides of the bead portion 10 in the tire axial direction (both left and right sides of the bead portion 10 in Figure 1). The chafer 22 made of the composite material is installed on at least one of the pair of bead portions 10, but preferably it is installed on both sides of the bead portion 10.

[0032] Examples of tires according to this embodiment include pneumatic tires of various uses and sizes, such as passenger car tires and large tires for trucks and buses. Passenger car tires are preferred. [Examples]

[0033] The following are examples of the present invention, but the present invention is not limited to these examples.

[0034] [Comparison of the maximum thickness difference between nonwoven fabrics and plain woven fabrics] For nonwoven fabrics and plain woven fabrics, the difference in thickness between the thickest and thinnest parts was measured. For the plain woven fabric, a nylon 6 plain woven fabric, commonly used in tire chafers, was used. For the nonwoven fabric, Unitika Ltd.'s spunbond nonwoven fabric "Marrix AX" (fiber diameter 28 μm, basis weight 103.0 g / m²) was used. 2 ) was used.

[0035] The difference in thickness between the thickest and thinnest parts of a plain weave fabric was determined as follows. The structure of the plain weave fabric is shown in Figure 2, with the thickest part being where the warp and weft threads overlap. On the other hand, the thinnest part can be considered to be equal to the cord gauge of the thinner of the warp or weft threads. Therefore, the difference in thickness between the thickest and thinnest parts of a plain weave fabric was considered to be equal to the cord gauge of the thicker of the warp or weft threads. The cord gauge was measured using a stand-type dial gauge (leg diameter 9.5 ± 0.03 mm, load 1666 ± 29.4 mN, accuracy 0.01 mm) in accordance with JIS L1017:2002.

[0036] On the other hand, the difference in thickness between the thickest and thinnest parts of the nonwoven fabric was measured at five locations at least 10 cm apart for a 20 cm square piece of nonwoven fabric. The difference between the largest and smallest values ​​was used. The thickness was measured in accordance with JIS L1096:2010, Method 8.4 A, using a stand-type dial gauge (leg diameter 9.5 ± 0.03 mm, load 1666 ± 29.4 mN, accuracy 0.01 mm) under a constant time (10 seconds) and constant pressure (23.5 kPa).

[0037] The results are shown in Table 1 below. It was found that the difference in thickness between the thickest and thinnest parts (maximum thickness difference) of the above nonwoven fabric was smaller than that of plain woven fabric. From these results, it is expected that using such a nonwoven fabric as a chafer will increase the contact area with the rim flange and reduce the pressure on the contact surface, thereby suppressing wear of the rim flange due to friction. [Table 1]

[0038] [Example 1] Using a Banbury mixer, a rubber composition was prepared according to a conventional method. The formulation of the rubber composition was 60 parts by mass of carbon black ("Seast 300" manufactured by Tokai Carbon Co., Ltd.), 5 parts by mass of zinc oxide ("Zinc Oxide No. 3" manufactured by Mitsui Mining & Smelting Co., Ltd.), 2 parts by mass of stearic acid ("Lunac S20" manufactured by Kao Corporation), 2 parts by mass of an antioxidant ("Antigen 6C" manufactured by Sumitomo Chemical Co., Ltd.), 5 parts by mass of oil ("Process NC-140" manufactured by ENEOS Corporation), 4.5 parts by mass of sulfur ("Powder Sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.), and 1 part by mass of a vulcanization accelerator ("Soxeal CZ" manufactured by Sumitomo Chemical Co., Ltd.) with respect to 100 parts by mass of natural rubber (RSS#3), and these were mixed together.

[0039] Using a calendar roll, the rubber composition was formed into a sheet with a thickness of 0.6 mm, and the obtained unvulcanized rubber sheet was pressure-bonded and laminated (topping) to the above non-woven fabric ("Marlex AX", a spunbond non-woven fabric made of polyester fibers manufactured by Unitika Ltd., basis weight 103.0 g / m 2 ) to obtain a composite with a thickness of 1.26 mm. In the obtained composite, the basis weight of the rubber was 1224 g / m 2 .

[0040] The obtained unvulcanized composite was used in a chafer, and according to a conventional method, a pneumatic radial tire of Example 1 (tire size: 205 / 60R16 92H) was prototyped by vulcanization molding. For the obtained prototype tire, the wear against the rim flange was evaluated.

[0041] [Comparative Example 1] As the non-woven fabric, a spunbond non-woven fabric (fiber diameter 28 μm) made of polyester fibers with a basis weight of 248.3 g / m 2 was used, and the thickness of the unvulcanized rubber sheet was set to 0.5 mm, and the preparation of the composite of Comparative Example 1 was attempted in the same manner as in Example 1. When the maximum thickness difference in the base material state was measured for the non-woven fabric used in Comparative Example 1, it was as shown in Table 3 below, and the maximum thickness difference was 0.16 mm.

[0042] In Comparative Example 1, increasing the thickness difference between the thickest and thinnest parts of the nonwoven fabric resulted in the entire nonwoven fabric becoming bulkier. Consequently, the rubber did not penetrate sufficiently into the nonwoven fabric during calendering, and a good composite of nonwoven fabric and rubber could not be obtained. Therefore, no prototype tires were manufactured.

[0043] [Comparative Example 2] Using the plain woven fabric described above instead of the nonwoven fabric, and with an unvulcanized rubber sheet thickness of 0.6 mm, a composite of plain woven fabric and rubber (thickness 1.25 mm) according to Comparative Example 2 was prepared in the same manner as in Example 1. The obtained unvulcanized composite was used in a chafer, and a prototype pneumatic radial tire (tire size: 205 / 60R16 92H) of Comparative Example 2 was fabricated by vulcanization molding according to a conventional method. The wear of the obtained prototype tire against the rim flange was evaluated.

[0044] [Comparative Example 3] Instead of nonwoven fabric, a plain weave nylon 6 fabric with the warp and weft cord gauges shown in Table 3 below was used, and the thickness of the unvulcanized rubber sheet was set to 0.6 mm. The rest of the process was the same as in Example 1 to produce a composite of plain weave fabric and rubber (thickness 1.25 mm) according to Comparative Example 3. The obtained unvulcanized composite was used as a chafer, and an attempt was made to prototype a pneumatic radial tire (tire size: 205 / 60R16 92H) of Comparative Example 2 by vulcanization molding according to a conventional method. However, in order to reduce the difference between the thickest and thinnest parts, the threads constituting the plain weave fabric became too thin, and the chafer could not withstand the expansion during tire molding, causing it to tear, and a normal tire could not be produced.

[0045] The method for measuring the basis weight of nonwoven fabrics and rubber was as follows: Three or more pieces of nonwoven fabric measuring 20 cm square were cut out, the weight of the nonwoven fabric under standard conditions was measured, and the basis weight of the nonwoven fabric was calculated as the mass per unit area using the following formula. Weight [g / m 2 ] = (mass of nonwoven fabric [g]) / (area of ​​nonwoven fabric [m²]) 2 ]) The rubber basis weight was calculated by determining the basis weight of the composite in the same way as the basis weight of the nonwoven fabric, and then subtracting the basis weight of the nonwoven fabric from the resulting composite basis weight.

[0046] The thickness of the composite was measured in accordance with JIS L1096:2010, Method 8.4 A, similar to the thickness of the nonwoven fabric.

[0047] The method for evaluating wear on the rim flange is as follows. Drum tests were conducted on the prototype tires of Example 1 and Comparative Example 2 under the conditions shown in Table 2 below. [Table 2]

[0048] After the drum test was completed, the surface roughness of the rim flange was measured to determine the arithmetic mean surface roughness, and the degree of rim wear was evaluated.

[0049] (1) Arithmetic mean surface roughness A Mitutoyo SURFTEST SJ-210 surface roughness meter was used, and the arithmetic mean roughness (Ra) was measured using the ISO 4287:1997 standard. Five measurement points were taken on the rim flange, separated by at least 10 cm from each other, and the average value was calculated.

[0050] (2) Rim wear The amount of damage was evaluated by visual inspection using a 10-point scale over a 5cm circumferential area of ​​the rim flange. A score of 0 indicated no damage at all, while 10 indicated that damage was present throughout the entire measurement area without any gaps.

[0051] [Table 3]

[0052] The details of the arithmetic mean surface roughness of the rim flange before and after the test are shown in Table 4 below. [Table 4]

[0053] The results are shown in Tables 3 and 4. When comparing Example 1 and Comparative Example 2, in which wear on the rim flange was evaluated, Example 1, which used a nonwoven fabric with a small maximum thickness difference, showed a smaller arithmetic mean surface roughness on the rim flange after the drum test compared to Comparative Example 2, which used a plain weave fabric. Visual evaluation of rim wear also showed that damage to the rim flange was suppressed. Therefore, it was shown that wear on the rim flange can be suppressed by using a nonwoven fabric with a small maximum thickness difference.

[0054] Furthermore, the various numerical ranges described in this specification can be any combination of their upper and lower limits, and all such combinations are described herein as preferred numerical ranges. Also, the description of a numerical range as "X~Y" means X or greater and Y or less. [Explanation of symbols]

[0055] 10...Bead section, 12...Bead core, 14...Bead filler, 16...Carcass ply, 18...Inner liner, 20...Sidewall rubber, 22...Chafer, R...Rim flange

Claims

[Claim 1] A pneumatic tire having a chafer made of a composite of nonwoven fabric and rubber in the bead portion, wherein the difference in thickness between the thickest and thinnest parts of the nonwoven fabric is less than 0.08 mm.

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