pneumatic tires

Abstract

In this pneumatic tire: the thickness of both the first belt layer and the second belt layer in the central portion of the tire does not exceed 1.00 mm; b > a; the length of the first rubber portion in the direction toward the central portion of the tire is greater than the length of the second rubber portion in the direction toward the central portion of the tire; and the reinforcing cord of the belt reinforcement layer is an organic fiber cord with a breaking strength of at least 6.5 cN / dtex, an elongation at break of at least 10%, and an elastic modulus at 7% elongation of at least 6.0 mN / (dtex·%). As shown in the cross-sectional view in the tire width direction, the belt reinforcement layer is arranged in the tire width direction region between at least the end of the first rubber portion on the tire central side and the end of the second belt layer.

Description

Technical Field

[0001] This disclosure relates to an inflatable tire. Background Technology

[0002] Traditionally, in order to achieve both weight reduction and belt end durability in pneumatic tires, a technique is known in which the belt gauge is made relatively thin and inter-belt rubber is arranged at the belt end (see, for example, Patent Documents 1 and 2).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-159250A

[0006] Patent Document 2: Japanese Patent Application Publication No. 2010-163055A Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, in the above structure, the ring effect at the belt end becomes insufficient, and especially during high-speed driving, the radial growth rate at the end of the pneumatic tire becomes greater compared to the central part, which may lead to non-uniformity in the tire width direction.

[0009] Therefore, the object of this disclosure is to provide a pneumatic tire that achieves both weight reduction and belt end durability, and also makes the radial growth rate uniform in the tire width direction.

[0010] Solution for solving the problem

[0011] The key points of the construction disclosed herein are as follows:

[0012] (1) A pneumatic tire, comprising:

[0013] A belt in the tread portion, the belt comprising a first belt layer and a second belt layer disposed radially outward of the first belt layer of the tire;

[0014] and the belt reinforcement layer in the tread portion, the belt reinforcement layer being disposed radially outside the tire of the belt;

[0015] Each of the first belt layer and the second belt layer is formed by multiple belt cords coated with belt rubber.

[0016] The belt reinforcement layer is formed of multiple reinforcing cords coated with reinforcing rubber.

[0017] The thickness of both the first belt layer and the second belt layer at the center of the tire is 1.00 mm or less.

[0018] In the tire width cross-sectional view, when the first imaginary line is defined as a straight line connecting the outermost point of the circumcircle of adjacent belt cords in the first belt layer in the tire radial direction, and the second imaginary line is defined as a straight line connecting the innermost point of the circumcircle of adjacent belt cords in the second belt layer in the tire radial direction, and when the maximum value of the tire radial distance between the first and second imaginary lines at the tire center is defined as 'a', and the minimum value of the length of the line segment connecting the innermost point of the circumcircle of the belt cord located at the outermost position in the tire width direction in the second belt layer to the first imaginary line is defined as 'b',...

[0019] b > a,

[0020] At the end of the belt, a first rubber portion is disposed between the first belt layer and the second belt layer, and a second rubber portion is disposed on the radially outer side of the second belt layer.

[0021] The length of the first rubber portion in the direction toward the center of the tire is longer than the length of the second rubber portion in the direction toward the center of the tire.

[0022] In the cross-sectional view along the tire width, the belt reinforcement layer is disposed at least in the tire width region between the end of the first rubber portion on the tire's central side and the end of the second belt layer.

[0023] Furthermore, the reinforcing cord of the belt reinforcement layer is an organic fiber cord with a breaking strength of 6.5 cN / dtex or greater, a breaking elongation of 10% or greater, and an elastic modulus of 6.0 mN / (dtex·%) or greater at 7% elongation.

[0024] Here, "central part of the tire" refers to the portion within 1 / 4 of the tire's width in the direction of contact with the ground from the tire's equator. "Ground contact width" refers to the distance in the tire's width between the contact points when the tire is unloaded, mounted on a suitable rim, inflated to the specified internal pressure, and without load. "Contact points" refers to the two ends in the tire's width direction of the contact surface that contacts the road surface when the tire is mounted on a suitable rim, inflated to the specified internal pressure, and under maximum load capacity.

[0025] Unless otherwise stated, dimensions such as “thickness,” “(shortest) distance,” and “length” refer to the dimensions described above under no-load conditions.

[0026] "The thickness of the first belt layer and the thickness of the second belt layer at the center of the tire" refers to the thickness measured radially along the tire.

[0027] Here, the breaking strength, breaking elongation, and elastic modulus at 7% elongation are values ​​measured at room temperature (23°C), and the various physical properties of the organic fiber cord can be measured in accordance with JIS L 1013 "Test method for chemical fiber filament yarns".

[0028] The modulus of elasticity at 7% elongation is calculated by converting the slope (N / %) of the tangent at the point on the load elongation curve of the cord corresponding to 7% elongation into a value per 1 dtex.

[0029] In this specification, "applicable rim" refers to a certified rim of an applicable size described or to be described in an industry standard in effect in the region where the tire is manufactured and used. Such industry standards include, for example, the JATMA Yearbook of the Japan Automobile Tire Manufacturers Association (JATMA), the standards manual of the European Tire and Rim Technology Organization (ETRTO), and the Yearbook of the American Tire and Rim Association (TRA). (That is, the term "rim" as used above includes sizes that may be included in the aforementioned industry standards in the future, in addition to current sizes. As an example of "sizes to be described in the future," sizes described as "future developments" in the 2013 edition of ETRTO can be cited.) However, in the case of sizes not described in the aforementioned industry standards, it refers to a rim having a width corresponding to the width of the tire's bead.

[0030] "Specified internal pressure" refers to the air pressure (maximum pressure) corresponding to the maximum load capacity of a single tire of the applicable size and ply rating described in JATMA, etc., and in the case of a size not described in the aforementioned industry standard, "specified internal pressure" refers to the air pressure (maximum pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted.

[0031] "Maximum load" refers to the load corresponding to the maximum load capacity mentioned above.

[0032] The effects of the invention

[0033] According to this disclosure, a pneumatic tire can be provided that achieves both weight reduction and belt end durability, and also makes the radial growth rate uniform in the tire width direction. Attached Figure Description

[0034] In the attached diagram:

[0035] Figure 1 This is a schematic cross-sectional view of a pneumatic tire in the tire width direction according to one embodiment of the present disclosure;

[0036] Figure 2A This is a schematic cross-sectional view showing an example of the end of the belt;

[0037] Figure 2B This is a schematic cross-sectional view showing another example of the end of the belt;

[0038] Figure 3 This is a schematic cross-sectional view of the belt at the center and end portions of a pneumatic tire according to one embodiment of the present disclosure.

[0039] Figure 4 This is a schematic cross-sectional view of the belt at the center of the tire in an inflatable tire according to one embodiment of the present disclosure.

[0040] Figure 5A This is a schematic diagram illustrating a part of the manufacturing process;

[0041] Figure 5B It is based on Figure 5A A schematic cross-sectional view of the end of the belt in a pneumatic tire obtained by the manufacturing method;

[0042] Figure 6A This is a schematic diagram illustrating a part of the manufacturing method of a comparative example pneumatic tire;

[0043] Figure 6B It is based on Figure 6A A schematic cross-sectional view of the end of the belt in a pneumatic tire obtained by the manufacturing method; and

[0044] Figure 7 This is a diagram used to explain the first and second imaginary lines. Detailed Implementation

[0045] In the following, embodiments of the present disclosure will be described and illustrated in detail with reference to the accompanying drawings.

[0046] Figure 1 This is a schematic cross-sectional view in the width direction of a pneumatic tire according to one embodiment of the present disclosure. Figure 1 As shown, the pneumatic tire 1 (hereinafter also simply referred to as "tire") of this embodiment includes a pair of bead portions 2, a pair of sidewall portions 3 connected to the bead portions 2, and a tread portion 4 connected between the pair of sidewall portions 3. The tire 1 also includes a carcass 5, which extends annularly between the pair of bead portions 2. The tread portion 4 of the tire 1 includes a belt 6 and a belt reinforcement layer 7 disposed radially outward of the belt 6. The belt 6 includes a first belt layer 6a and a second belt layer 6b disposed radially outward of the first belt layer 6a.

[0047] A bead core 2a is embedded in each bead portion 2. Although not shown, bead filler may be arranged on the radially outer side of the bead core 2a. The bead filler may, for example, have a triangular cross-sectional shape.

[0048] The carcass 5 can be formed from one or more carcass plies. The carcass cords used as the carcass plies can be, for example, organic fiber cords.

[0049] In the example shown, the belt layer consists of two layers, but it can also consist of three or more layers. In this embodiment, the width of the first belt layer 6a in the tire width direction is greater than the width of the second belt layer 6b in the tire width direction. Additionally, the belt reinforcement layer 7 can be arranged to cover only the two ends of the belt 6 in the tire width direction, or it can be arranged to cover the entire belt 6, or as... Figure 1 As shown, a layer arranged to cover the entire belt 6 and a layer arranged to cover only the two ends of the belt 6 can be provided. The belt reinforcement layer 7 arranged to cover only the two ends of the belt 6 is arranged at least in the tire width direction region where the first rubber part 8B is arranged. The width of the belt reinforcement layer 7 arranged to cover the entire belt 6 in the tire width direction is greater than the width of the second belt layer 6b in the tire width direction.

[0050] In the tire 1 of this embodiment, the thickness of the first belt layer 6a and the thickness of the second belt layer 6b at the center of the tire are both 1.00 mm or less. By setting the thickness of each belt layer at the center of the tire to 1.00 mm or less in this way, weight reduction and rolling resistance reduction can be achieved. From the same point of view, it is preferable that the thickness of the first belt layer 6a at the center of the tire is 0.96 mm or less, more preferably 0.90 mm or less. In addition, it is preferable that the thickness of the second belt layer 6b at the center of the tire is 0.96 mm or less, more preferably 0.90 mm or less. To achieve such thicknesses, the diameter of the belt cords embedded in the first belt layer 6a and the second belt layer 6b, as well as the coating thickness of the belt rubber, can be appropriately selected.

[0051] Figure 2A This is a schematic cross-sectional view showing the ends of the belt. As shown, each of the first belt layer 6a and the second belt layer 6b is formed by a plurality of belt cords (61, 62) coated with belt rubber (63, 64). More generally, these belt layers 6a, 6b are formed of rubber-steel hybrid cords, in which the side-by-side aligned steel cords (belt cords 61, 62) are coated with belt rubber (63, 64). Belt layers 6a, 6b can be inclined belt layers where the belt cords intersect each other between layers. Belt cords 61, 62 can extend linearly.

[0052] As shown in the figure, end rubber 8 is arranged at the end of the belt 6 of the tire 1 in this embodiment. In the example shown, at the end of the belt 6, a first rubber portion 8B is arranged between the first belt layer 6a and the second belt layer 6b, and a second rubber portion 8C is arranged on the radially outer side of the second belt layer 6b. In the example shown, at the end of the belt 6, a third rubber portion 8A is also arranged between the tire carcass 5 and the first belt layer 6a, but the third rubber portion 8A can be omitted. By arranging the end rubber 8 at the end of the belt 6 in this way, the durability of the belt end can be improved. That is, the first rubber portion 8B suppresses failures caused by strain between the belt layers, the second rubber portion 8C suppresses failures caused by strain between the second belt layer 6b and the belt reinforcement layer 7, and the third rubber portion 8A suppresses failures caused by strain between the tire carcass 5 and the first belt layer 6a.

[0053] Furthermore, in the tire 1 of this embodiment, as shown in the figure, the first rubber portion 8B has the longest length in the direction toward the center of the tire (which is essentially synonymous with "length in the tire width direction"). In other words, in the tire 1 of this embodiment, when the lengths of the third rubber portion 8A, the first rubber portion 8B, and the second rubber portion 8C in the direction toward the center of the tire are defined as L... A L B and L C (Reference Figure 2A When L A / L B Less than 1.0 and L C / L B Less than 1.0. Furthermore, in the tire 1 of this embodiment, as shown in the figure, among the third rubber portion 8A, the first rubber portion 8B, and the second rubber portion 8C, the first rubber portion 8B is closest to the center of the tire.

[0054] The aforementioned structure of the end rubber 8 can be achieved by manufacturing a tire according to the method for manufacturing a pneumatic tire described later. In the method for manufacturing a pneumatic tire described later, it is difficult to form gaps between the first belt layer 6a and the second belt layer 6b, and between the second belt layer 6b and the belt reinforcement layer 7; this also helps to improve the durability at the belt end.

[0055] In the tire 1 of this embodiment, preferably, L A / L B 0.5 or less, and L C / L B The value is 0.5 or less. In this case, the formation of gaps at the ends of the belt is further suppressed. From the same point of view, more preferably, L A / L B 0.4 or less, and L C / LB It is 0.4 or less.

[0056] exist Figure 2A (as well as Figure 1 , Figure 3 In the tire shown, the third rubber portion 8A, the first rubber portion 8B, and the second rubber portion 8C are integrally arranged as end rubbers 8 at the end of the belt 6, but this integration is not necessary. For example, in the tire of this disclosure, the rubber on the radially inner side of the first belt layer 6a (third rubber portion 8A), the rubber between the first belt layer 6a and the second belt layer 6b (first rubber portion 8B), and the rubber on the radially outer side of the second belt layer 6b (second rubber portion 8C) can be arranged separately. Furthermore, in the tire of this disclosure, as... Figure 2B As shown, the end rubber 8 (rubber sheet) covering the end of the first belt layer 6a and the end rubber 8 (rubber sheet) covering the end of the second belt layer 6b can be in contact (not completely integrated). However, from the viewpoint of further improving the durability of the belt ends, it is preferable that the third rubber portion 8A, the first rubber portion 8B and the second rubber portion 8C are integrated as end rubber 8.

[0057] Figure 3 This is a schematic cross-sectional view of the belt 6 at the center and end of the tire 1 in this embodiment. Figure 3 The end of the belt 6 in the middle corresponds to Figure 2A The part shown. Figure 7 This is a diagram used to illustrate the first and second imaginary lines. For example... Figure 3 and Figure 7 As shown in the cross-sectional view along the tire width, the first imaginary line 21 is defined as a straight line connecting the outermost points of the tire's radial direction of the circumcircle of adjacent belt cords 61 in the first belt layer 6a, and the second imaginary line 22 is defined as a straight line connecting the innermost points of the tire's radial direction of the circumcircle of adjacent belt cords 62 in the second belt layer 6b. The maximum value of the tire's radial distance between the first imaginary line 21 and the second imaginary line 22 at the tire's center is defined as a (in... Figure 7 In the illustration, a1 and a2 are given as examples (the maximum value among countless such tire radial distances), and the minimum value among the lengths of the line segments connecting the innermost point of the tire radial direction of the circumcircle of the belt cord 62 located at the outermost position in the tire width direction of the second belt layer 6b and the first imaginary line 21 is defined as b (in Figure 7In the illustration, b1, b2, and b3 are given as examples (the minimum of a plurality of such tire radial distances). In this case, in tire 1 of this embodiment, b > a. If b ≤ a, strain causing belt edge separation cannot be sufficiently suppressed. In this embodiment, a ratio b / a of 2.0 or greater and 8.0 or less is more preferred. By setting the ratio b / a to 2.0 or greater, the durability at the belt end, especially the belt edge separation durability, can be further improved. By setting the ratio b / a to 8.0 or less, sufficient low rolling resistance required by the tire can be ensured. Furthermore, from the same point of view, a ratio b / a of 2.0 or greater and 6.0 or less is more preferred, and particularly preferred to be 4.1 or greater and 6.0 or less.

[0058] Figure 4 This is a schematic cross-sectional view of the central portion of the belt 6 in the tire 1 of this embodiment, and is Figure 3 The portion enclosed by the dotted line. In the tire 1 of this embodiment, the distance from the interface of the first belt layer 6a to the belt cord 61 at the center of the tire (i.e., the distance c1 from the upper surface to the belt cord 61 and the distance c2 from the lower surface to the belt cord 61) is 0.19 mm or less, and preferably, the distance from the interface of the second belt layer 6b to the belt cord 62 at the center of the tire (i.e., the distance c3 from the upper surface to the belt cord 62 and the distance c4 from the lower surface to the belt cord 62) is 0.19 mm or less. By adopting this structure, the low rolling resistance characteristics of the tire 1 can be further significantly improved. From the same point of view, more preferably, the distance between the interface of the first belt layer 6a and the belt cord 61 at the center of the tire, and the distance between the interface of the second belt layer 6b and the belt cord 62 at the center of the tire, are both 0.17 mm or less, and more preferably 0.14 mm or less.

[0059] Furthermore, the belt reinforcement layer 7 is formed of multiple reinforcing cords coated with reinforcing layer rubber. In this embodiment, the reinforcing cords of the belt reinforcement layer 7 are organic fiber cords with a breaking strength of 6.5 cN / dtex or greater, an elongation at break of 10% or greater, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or greater. If the elastic modulus at 7% elongation is less than 6.0 mN / (dtex·%), the ring effect of reinforcing the belt cannot be sufficiently demonstrated. Furthermore, if the breaking strength is less than 6.5 cN / dtex or the elongation at break is less than 10%, the reinforcing cords of the belt reinforcement layer 7 have low durability, and there is a risk that the ring effect of reinforcing the belt cannot be achieved due to cord breakage, etc. In the example shown, the belt reinforcement layer 7 is a so-called capping layer, but it could also be a layer disposed only at the ends of the belt.

[0060] As described above, in the tire 1 of this embodiment, the thickness of both the first belt layer and the second belt layer at the central portion of the tire is 1.00 mm or less, b > a, and the length of the first rubber portion in the direction toward the central portion of the tire is longer than the length of the second rubber portion in the direction toward the central portion of the tire, thereby achieving both weight reduction and durability at the belt end. Furthermore, since the belt reinforcement layer 7 is arranged radially outward of the belt 6, and the reinforcing cord of the belt reinforcement layer 7 is an organic fiber cord having a breaking strength of 6.5 cN / dtex or greater, an elongation at break of 10% or greater, and an elastic modulus of 6.0 mN / (dtex·%) or greater at 7% elongation, the ring effect of the belt (especially at the belt end) can be enhanced, and the radial growth difference between the central portion and the end portion in the tire width direction can also be suppressed. Thus, the tire 1 according to this embodiment achieves both weight reduction and durability at the belt end, and the radial growth rate in the tire width direction can be made uniform. Furthermore, plunger durability and steering stability can also be improved.

[0061] The tire disclosed herein is not particularly limited to a specific tire structure or material, as long as the construction around the belt 6 and belt reinforcement layer 7 is as described above. For example, in the first belt layer 6a and the second belt layer 6b, multiple belt cords embedded in the belt rubber can be arranged at an angle of, for example, 15° to 40° relative to the tire circumference. Furthermore, in the carcass 5, organic fiber cords extending in a direction substantially perpendicular to the tire circumference (e.g., at an angle of 70° to 90°) can be used. Furthermore, in the tire 1 shown, the carcass 5 can not only have a structure folded around the bead core 2a as shown, but also a structure wound and locked around the bead core 2a (not shown), or a structure locked by being clamped from both sides by bead threads (not shown). Furthermore, in the tire of this disclosure, a tread pattern can be formed on the surface of the tread portion 4. Furthermore, in the tire of this disclosure, an inner liner (not shown) can be formed as the innermost layer. As the gas to be filled into the tire of this disclosure, ordinary air, air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used. The tire disclosed herein is suitable for use as a pneumatic tire for passenger vehicles.

[0062] Next, details of the components used in the tire 1 of this embodiment will be described. It should be noted that the compounds described in this specification may be derived partially or entirely from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires. They may also be derived from any mixture of two or more of fossil resources, biological resources, and recycled resources.

[0063] (Coated rubber (belt rubber))

[0064] The belt rubbers 63 and 64 used for the first belt layer 6a and the second belt layer 6b are not particularly limited, as long as they are general rubber compositions capable of coating the belt cords 61 and 62. Diene-based rubbers are cited as examples of rubber components, with natural rubber or isoprene rubber being particularly preferred. Furthermore, the belt rubbers 63 and 64 may contain fillers such as carbon black, as long as they do not affect the properties of the coating rubber, such as adhesion and durability. HAF-type carbon black is preferred as the carbon black, and the carbon black content in the belt rubbers 63 and 64 may be 50 to 70 parts by weight per 100 parts by weight of the rubber component. In addition to the components mentioned above, the belt rubbers 63 and 64 may appropriately contain, for example: crosslinking agents such as vulcanization accelerators, sulfur, and zinc oxide; adhesion accelerators such as cobalt compounds containing cobalt salts; antioxidants; oils; resins, etc. As antioxidants, amine antioxidants such as 6PPD and bisphenol antioxidants such as o-MBp14 can be mentioned, and these antioxidants can be used alone or in combination of two or more.

[0065] The natural rubber used in the belt belt rubber can be modified. For example, in the case of modified natural rubber, the nitrogen content is preferably 0.1% to 0.3% by mass. Furthermore, the modified natural rubber is preferably natural rubber from which proteins have been removed by centrifugation, enzymatic treatment, or urea treatment. Additionally, the modified natural rubber preferably has a phosphorus content greater than 200 ppm and less than or equal to 900 ppm. The carbon black used in the belt belt rubber can be recycled carbon black.

[0066] (End rubber)

[0067] There are no particular limitations on the end rubber 8 (third rubber part 8A, first rubber part 8B, second rubber part 8C), but for example, the same rubber composition as the belt rubbers 63, 64 of the first belt layer 6a and the second belt layer 6b can be used.

[0068] (with cord binding)

[0069] In the first belt layer 6a and the second belt layer 6b, multiple cords 61 and 62 are typically arranged side-by-side. These belt cords 61 and 62 are typically steel cords. Furthermore, there are no particular limitations on the structure of such belt cords. However, from the viewpoint of effectively achieving improved tire durability and low rolling resistance, it is preferable that the belt cord has a 1×N structure formed by twisting N filaments (where N is an integer selected from 2 to 6). In particular, in tires with a load index less than 100, a 1x2 structure is more preferred, and in tires with a load index of 100 or greater, a 1x5 structure is more preferred. Furthermore, from a similar viewpoint, it is preferable that the cords are monofilaments arranged side-by-side without being twisted together. In the case of the 1×N structure described above, the cord can also have a 1×N open structure in which the filaments are twisted together and spaced apart so that the filaments do not contact each other. Compared to cords in which the filaments are twisted together in contact with each other, open-structure cords exhibit superior fatigue resistance. A 1×N open-structure cord can be formed by inserting uncured rubber between the filaments and twisting them together, or by coating the surface of the filaments with uncured rubber and then twisting them together. Furthermore, such filaments can be pre-shaped before twisting. When pre-forming, the forming pitch of the filaments is preferably in the range of 8 mm or greater and 16 mm or less. If the forming pitch is within this range, rubber permeability is enhanced, and durability can be further improved. Furthermore, the ratio of the filament cross-sectional area Sf to the area Sc of the circumcircle of the cord cross-section, Sf / Sc, is preferably in the range of 0.4 or greater and 0.7 or less. If Sf / Sc is within this range, rubber permeability is enhanced, and durability can be further improved. The filaments constituting the belt cords 61 and 62 can have their surfaces surface-treated during the drawing process. In this case, preferably, the amount of phosphoric acid on the surface of the filament after surface treatment is 2.0 mg / m. 2 Or less. If the amount of phosphoric acid on the surface of the filament is 2.0 mg / m 2 If the amount is less, the adhesion between the filament and the coated rubber becomes advantageous.

[0070] The filaments of the belt cords 61 and 62 used in the first belt layer 6a and the second belt layer 6b are preferably classified as ST grade (ultra-high tensile strength cord) or UT grade (super-high tensile strength cord) as defined in ISO 17832:2009, and are particularly preferably classified as UT grade. In this case, both improved tire durability and low rolling resistance can be effectively achieved. From a similar point of view, preferably, when the diameter of the filaments constituting the belt cords is X (mm) and the tensile strength of the filaments is Y (MPa), the belt cords 61 and 62 satisfy the following mathematical formula (1):

[0071] 4000-2000X≤Y≤4500-2000X...(1)

[0072] Regarding the filaments constituting the aforementioned belt cords 61 and 62, from the viewpoint of fatigue resistance, the hardness of the surface layer is preferably 90% to 110% relative to the hardness of the inner layer, more preferably 100%. Here, the surface layer of the filament refers to the layer (region) extending to a depth of 0.01 mm from the outermost surface of the filament, while the inner layer of the filament refers to the layer (region) inside the aforementioned surface layer. The aforementioned hardness can be measured, for example, as Vickers hardness. The hardness of the surface layer of the filament can be measured at a depth of 0.005 mm from the outermost surface of the filament, and the hardness of the inner layer of the filament can be measured in a region deeper than 0.04 mm from the outermost surface of the filament. There are no particular limitations on the manufacturing method of the filaments constituting the aforementioned belt cords 61 and 62. For example, the aforementioned filaments can be obtained by refining and drawing iron ore, refining and drawing scrap iron, or recycling steel taken from tires.

[0073] In the first belt layer 6a and the second belt layer 6b, preferably, the cord density of the belt cords 61 and 62 is 50 cords / dm or greater and 250 cords / dm or less. In this case, improved tire durability and low rolling resistance can be effectively achieved. Specifically, when the aforementioned belt cords have a 1×N structure (where N is an integer selected from 2 to 6), it is preferable that the cord density of the belt cords is 60 cords / dm or greater and 95 cords / dm or less. On the other hand, when the aforementioned cords are monofilaments, it is preferable that the cord density of the cords is 180 cords / dm or greater and 240 cords / dm or less.

[0074] The diameters of the belt cords 61 and 62 used in the first belt layer 6a and the second belt layer 6b are preferably 0.2 mm or larger and 1.2 mm or smaller. In this case, improved tire durability and low rolling resistance can be effectively achieved. Specifically, when the belt cords have a 1×N structure (where N is an integer selected from 2 to 6), the diameter of the cords is preferably 0.4 mm or larger and 1.2 mm or smaller, and more preferably 0.5 mm or larger and 1.0 mm or smaller. On the other hand, when the belt cords are monofilaments, the diameter of the belt cords is preferably 0.24 mm or larger and 0.28 mm or smaller.

[0075] (Belt reinforcement layer)

[0076] As described above, in the tire 1 of this disclosure, a belt reinforcement layer 7 is provided on the radially outer side of the belt 6. The belt reinforcement layer 7 is a component formed by coating reinforcing cords (organic fiber cords) configured substantially parallel to the tire circumference (e.g., at an angle of 0° to 5° relative to the tire circumference) with reinforcing layer rubber (elastomer). The belt reinforcement layer 7 can be formed by continuously spirally winding a narrow strip made of elastomer-coated organic fiber cords along the tire circumference.

[0077] Organic fiber cords suitable for belt reinforcement layers are organic fiber cords with a breaking strength of 6.5 cN / dtex or greater, a breaking elongation of 10% or greater, and an elastic modulus of 6.0 mN / (dtex·%) or greater at 7% elongation.

[0078] Organic fiber cords with a breaking strength of 6.5 cN / dtex or greater, an elongation at break of 10% or greater, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or greater exhibit high breaking strength, large elongation at break, and high elastic modulus at 7% elongation. By applying such organic fiber cords to the belt reinforcement layer 7 to supplement the rigidity of the belt 6, it is possible to suppress, for example, the reduction in plunger durability due to the application of belt layers containing metal monofilaments, while improving tire steering stability.

[0079] There are no particular limitations on the materials used for the organic fiber cords, and examples include: polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); nylons such as 6-nylon, 6,6-nylon, 4,6-nylon, and 4,10-nylon; and cellulose such as rayon and lyocell fibers. Polyethylene terephthalate is preferred, meaning that the organic fiber cord serving as the reinforcing member of the belt reinforcement layer is preferably a cord made of polyethylene terephthalate (hereinafter sometimes simply referred to as "polyethylene terephthalate cord"). Polyethylene terephthalate cords have higher rigidity than commonly used nylon cords and can improve tire plunger durability and steering stability.

[0080] Preferably, the organic fiber cord has an elastic modulus of 2.5 mN / (dtex·%) or greater at a load of 29.4 N measured at 160 °C. Here, the elastic modulus at 29.4 N measured at 160 °C is calculated by converting the slope (N / %) of the tangent at the point corresponding to the 29.4 N load on the load-elongation curve of the cord measured at 160 °C into a value per dtex. The reason for measuring the elastic modulus at 160 °C is that as the vehicle travels at high speeds, the temperature inside the tire rises, and the temperature of the belt reinforcement layer reaches 160 °C when tire failure occurs during high-speed driving. Specifically, compared to room temperature, polyethylene terephthalate cords exhibit a significant decrease in elastic modulus at high temperatures, and even if the cord has high elasticity at room temperature, it will not exhibit sufficient reinforcement effect on the belt (improved durability against protrusion input and suppression of belt protrusion) if it cannot maintain a high elastic modulus at high temperatures; therefore, the elastic modulus at high temperatures is very important. By setting the elastic modulus of the cord under a load of 29.4 N measured at 160 °C to 2.5 mN / (dtex·%) or greater, the plunger durability of the tire can be improved, the amount of belt protrusion during high-speed driving can be suppressed, the stress during tire compression and decompression can be reduced, and the steering stability of the tire during high-speed driving can be improved.

[0081] To improve the elastic modulus of the organic fiber cord at 160°C, impregnation under high tension is preferred. Furthermore, to fully enhance the cord's elasticity, a tension of 6.9 × 10⁻⁶ is preferably applied during the cord bonding process. -2 N / tex or greater. However, methods for improving the elasticity of the cord are not limited to this, and other methods, such as reducing the twist of the cord, can also be used. Bonding treatment includes drying, heat treatment, normalizing, etc., and is performed by appropriately adjusting the temperature, time, and tension. Bonding treatment can be performed by a single-bath or double-bath method, but a double-bath method is preferred, and it is preferable to apply a 6.9 × 10⁻⁶ N / tex pressure to the cord during the heat treatment of the double-bath method. -2 N / tex or greater tension.

[0082] Organic fiber cords preferably have a twist coefficient α expressed by the following mathematical formula:

[0083] α=T×D 1 / 2

[0084] [In the mathematical formula, α is the twist coefficient, T is the number of twists (turns / 100mm), and D is the total fineness of the cord (dtex)], and the twist coefficient α is preferably between 500 and 2500. When the twist coefficient α of the organic fiber cord is 500 or greater, the bonding strength of the filaments becomes stronger, the adhesion becomes sufficient, and when it is 2500 or less, sufficient elastic modulus can be exhibited to achieve the effect of improving durability against protrusion input and suppressing belt protrusion.

[0085] Furthermore, preferably, the total fineness of the organic fiber cord is between 1000 dtex and 3500 dtex. When the total fineness of the cord is 1000 dtex or greater, it can exhibit sufficient elastic modulus to improve durability against protruding inputs and suppress belt protrusion. When it is 3500 dtex or less, the cords can be tightly packed, ensuring sufficient rigidity per unit width. The raw materials for the aforementioned organic fiber cord are not particularly limited and can be synthetically derived, biologically derived, or mechanically recycled through crushing, melting, and respinning (e.g., PET products from PET bottles), or chemically recycled through depolymerization and repolymerization (e.g., PET products from PET bottles).

[0086] (Coated rubber (reinforcing rubber))

[0087] Preferably, when measured at a temperature of 24°C, an amplitude of ±1%, and a frequency of 52Hz, the reinforcing layer rubber has a storage modulus E' of 6.0MPa or less.

[0088] Furthermore, the loss index L of the coated rubber contained in each 100mm unit width of the belt reinforcement layer is defined by the following formula:

[0089] L=tanδ×((100×D)-π(D / 2)2×N),

[0090] (where tanδ is the loss tangent of the reinforcing layer rubber measured under the conditions of temperature 24℃, initial strain 6%, amplitude ±1%, and frequency 52Hz, D is the diameter (mm) of the circumcircle of the reinforcing cord, and N is the number of reinforcing cords embedded in the belt reinforcing layer (cords / 100 mm)).

[0091] Preferably 4.00 or smaller.

[0092] Furthermore, preferably, the rubber composition used for the reinforcing layer rubber contains natural rubber and styrene-butadiene rubber as rubber components, and contains 70 parts by weight or more of natural rubber per 100 parts by weight of the rubber component. Also preferably, the styrene-butadiene rubber used in the rubber composition used for the reinforcing layer rubber is non-oil-plasticized. Furthermore, preferably, the rubber composition used for the reinforcing layer rubber contains 30 to 60 parts by weight of carbon black per 100 parts by weight of the rubber component, and the carbon black has a nitrogen adsorption specific surface area (N₂SA) of 40 m². 2 / g or less. It is also preferred that the rubber composition used for the reinforcing layer rubber does not contain oil derived from the polymer. Additionally, it is preferred that the oil content in the rubber composition used for the reinforcing layer rubber is 0.2% by mass or less. The natural rubber used for the reinforcing layer rubber may be modified. For example, in the case of modified natural rubber, the nitrogen content is preferably 0.1% to 0.3% by mass. Furthermore, it is preferred that the modified natural rubber is natural rubber from which proteins have been removed by centrifugation, enzymatic treatment, or urea treatment. The phosphorus content of the modified natural rubber is preferably greater than 200 ppm and less than or equal to 900 ppm. The carbon black used for the reinforcing layer rubber may be recycled carbon black.

[0093] In this specification, "recycled carbon black" refers to carbon black obtained by recovering it from recycled waste. Examples of such recycled waste include, for example, used rubber and used tires containing carbon black (especially vulcanized rubber products) and waste oil. "Recycled carbon black" is different from carbon black produced directly from hydrocarbons (such as petroleum or natural gas), i.e., carbon black that is not a recycled product. Note that "used" here includes not only items that have actually been used and then discarded, but also items that were manufactured but discarded without actual use.

[0094] Furthermore, the recycled carbon black used in this embodiment is preferably obtained through the pyrolysis of a vulcanized rubber product containing carbon black. In this case, resource recycling can be achieved, further contributing to improvements in sustainability. Additionally, the recycled carbon black used in this embodiment is preferably obtained from the solid residue generated during the pyrolysis of a vulcanized rubber product containing carbon black. When the rubber product containing carbon black is pyrolyzed, solid residue and volatile components (oil) are obtained, and the recycled carbon black can be recovered from either. However, the recycled carbon black used in this embodiment preferably does not include carbon black recovered from oil.

[0095] Solid residues obtained from pyrolysis waste, such as used rubber and used tires, contain ash in addition to carbon black. The ash originates from non-volatile components contained in the rubber or tires. Therefore, the recycled carbon black obtained from such solid residues has a relatively low carbon black content. On the other hand, considering the various physical properties required for manufacturing tires using recycled carbon black, it is preferable to have the carbon content in the recycled carbon black as high as possible. In the recycled carbon black used in this embodiment, the carbon content is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and particularly preferably 89% by mass or more. The carbon content in the recycled carbon black used in this embodiment is preferably 97% by mass or less. Note that the above carbon content values ​​do not include adsorbed moisture.

[0096] Specifically, ash includes zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, magnesium oxide, etc. In the case of producing recycled carbon black from solid residues obtained through pyrolysis waste, various ash removal processes can be performed, but a certain amount of ash remains. In this embodiment, the recycled carbon black is allowed to contain ash. The lower limit of the ash content of the recycled carbon black used in this embodiment can be 0.5% by mass. On the other hand, considering the various physical properties required for tires and the quality of the recycled carbon black, it is preferable that the ash content in the recycled carbon black is 20% by mass or less, more preferably 15% by mass or less, and even more preferably 5.0% by mass or less. If the ash content in the recycled carbon black is 20% by mass or less, various physical properties of rubber products using rubber compositions can be improved. Here, in this specification, the ash content of carbon black is calculated from the mass of the non-combustible component (ash) after ashification by burning carbon black at 550°C ± 25°C.

[0097] Furthermore, recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975 references "Rubber Chemistry and Technology", Vol. 85, No. 3, pp. 408–449 (2012), particularly pp. 438, 440 and 442, and describes that it can be obtained by pyrolysis of organic materials under anaerobic conditions at 550°C to 800°C or by vacuum pyrolysis at relatively low temperatures (paragraph

[0027] ). Carbon black obtained by such a pyrolysis process typically lacks functional groups on its surface, as mentioned in paragraph

[0004] of Japanese Patent No. 6856781 ("Comparison of Surface Morphology and Chemical Properties of Pyrolytic Carbon Black and Commercial Carbon Black", Electric Power Technology 160 (2005) 190-193).

[0098] The recycled carbon black can be recycled carbon black lacking functional groups on its surface, or it can be recycled carbon black that has been treated to include functional groups on its surface. The treatment to include functional groups on the surface of the recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained by a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent No. 6856781, carbon black obtained by a pyrolysis process is treated with an amino acid compound containing at least one thiol or dithio group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes carbon black that has been treated to include such functional groups on its surface.

[0099] (Adhesive)

[0100] Preferably, the reinforcing cord (organic fiber cord) of the belt reinforcement layer 7 is bonded to the reinforcing layer rubber with an adhesive. From an environmental protection point of view, it is preferable to use an impregnation treatment solution that does not contain resorcinol or formaldehyde as the adhesive composition for the organic fiber cord. As such an impregnation treatment solution, for example, a composition containing a rubber latex having an unsaturated diene (a) and at least one compound (b) selected from the following compounds: a compound having a skeleton structure composed of polyether and containing amine functional groups, a compound having an acrylamide structure, a polypeptide, polylysine, and carbodiimide. In addition, as such an impregnation treatment solution, for example, in addition to the rubber latex having an unsaturated diene (a) and compound (b) mentioned above, a composition containing at least one of an aqueous compound (c) having a (thermally dissociable-terminated) isocyanate group, a polyphenol (d), and a polyvalent metal salt (e) may also be mentioned.

[0101] Furthermore, as an impregnation treatment solution that does not contain resorcinol or formaldehyde, compositions containing polyphenols (I) and aldehydes (II) may also be mentioned. In addition to polyphenols (I) and aldehydes (II), such compositions may also contain at least one of isocyanate compounds (III) and rubber latex (IV).

[0102] By including polyphenols (I) and aldehydes (II) in the adhesive composition used to treat (coat) organic fiber cords, good adhesion can be exhibited even when resorcinol is not used, taking into account environmental impact.

[0103] [Polyphenols (I)]

[0104] By including a polyphenol (I) as a resin component in the adhesive composition, the adhesion to organic fiber cords can be enhanced. Here, the polyphenol (I) is typically a water-soluble polyphenol, and there are no particular limitations as long as it is a polyphenol other than resorcinol. The number of aromatic rings or hydroxyl groups in the polyphenol (I) can be appropriately selected.

[0105] From the viewpoint of achieving or even better adhesion, it is preferred that the polyphenol (I) has two or more hydroxyl groups, and more preferably three or more hydroxyl groups. When the polyphenol has three or more hydroxyl groups, the polyphenol or its condensate dissolves in water in the aqueous adhesive composition (impregnation treatment solution). Therefore, the polyphenol can be uniformly distributed in the adhesive composition, thereby achieving or even better adhesion. Furthermore, when the polyphenol (I) is a polyphenol containing multiple (two or more) aromatic rings, two or three hydroxyl groups are present at the ortho, meta, or para positions in each of these aromatic rings.

[0106] As polyphenols (I), polyphenolic compounds such as those described in WO 2022 / 130879 can be used. These polyphenols (I) can be used alone or in combination of two or more.

[0107] [Aldehydes (II)]

[0108] By including an aldehyde (II) as a resin component in addition to the polyphenol (I) described above, high adhesion can be achieved together with the polyphenol (I). Here, the aldehyde (II) is not particularly limited and can be appropriately selected according to the desired performance. Note that in this specification, aldehyde (II) also includes aldehyde derivatives derived from aldehydes.

[0109] As aldehydes (II), examples include monoaldehydes such as formaldehyde, acetaldehyde, butyraldehyde, acrolein, propionaldehyde, chloroform, butyraldehyde, hexanal, and allylaldehyde, or aliphatic dialdehydes such as glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, and adipaldehyde, as well as aromatic ring-containing aldehydes and dialdehyde starch. These aldehydes (II) can be used alone or in combination of two or more.

[0110] Preferably, aldehyde (II) is or includes aldehydes containing an aromatic ring. This is because even better adhesion can be obtained. Furthermore, it is preferred that aldehyde (II) is formaldehyde-free. Here, "formaldehyde-free" means, for example, that the formaldehyde content is less than 0.5% by mass of the total mass of the aldehydes.

[0111] In the adhesive composition, polyphenols (I) and aldehydes (II) are in a condensation state, and preferably the mass ratio of polyphenols to aromatic aldehydes (aromatic aldehyde content / polyphenol content) is 0.1 or greater and 3 or less. In this case, the hardness and adhesiveness of the resin, which is the product of the condensation reaction between polyphenols and aromatic aldehydes, become more suitable. From the same point of view, it is more preferable that the mass ratio of polyphenols to aromatic aldehydes in the adhesive composition (aromatic aldehyde content / polyphenol content) is 0.25 or greater and more preferably 2.5 or less.

[0112] Note: The above mass ratios are based on the mass of the dried material (solid content ratio).

[0113] Furthermore, the total content of polyphenols (I) and aldehydes (II) in the adhesive composition is preferably 3% to 30% by mass. In this case, even better adhesion can be ensured without deteriorating workability, etc. From the same point of view, it is more preferable that the total content of polyphenols (I) and aldehydes (II) in the adhesive composition is 5% by mass or more, and more preferably 25% by mass or less.

[0114] Note: The total content mentioned above is based on the weight of the dried material (solid content ratio).

[0115] [Isocyanate compound (III)]

[0116] Preferably, in addition to the polyphenols (I) and aldehydes (II) mentioned above, the adhesive composition also contains isocyanate compounds (III). In this case, the adhesiveness of the adhesive composition can be further enhanced due to the synergistic effect with the polyphenols (I) and aldehydes (II).

[0117] Here, the isocyanate compound (III) is a compound that promotes adhesion to resin materials (e.g., phenol / aldehyde resin obtained by condensing polyphenols (I) and aldehydes (II)) as adhesive compositions, and is a compound having an isocyanate group as a polar functional group. These isocyanate compounds (III) can be used alone or in combination of two or more.

[0118] There are no particular limitations on the isocyanate compound (III), but from the viewpoint of further improving adhesion, it is preferable to include an aromatic compound containing (terminated) isocyanate groups. By including an aromatic compound containing (terminated) isocyanate groups in the adhesive composition, the aromatic compound containing (terminated) isocyanate groups is distributed near the interface between the organic fiber cord and the adhesive composition, thereby producing a further adhesion-promoting effect, and due to this effect, the adhesion of the adhesive composition to the organic fiber cord can be further enhanced.

[0119] As aromatic compounds containing (terminated) isocyanate groups, those described in Japanese Patent Application No. 2023-040157 and those described in Japanese Patent Application No. 2023-030762 can be used.

[0120] There is no particular limitation on the content of isocyanate compound (III) in the adhesive composition, but from the viewpoint of more reliably ensuring excellent adhesion, it is preferably 5% to 65% by mass. From the same viewpoint, it is preferred that the content of isocyanate compound (III) in the adhesive composition is 10% by mass or more, and more preferably 45% by mass or less.

[0121] Note: The above content is based on the mass of the dried material (solid content ratio).

[0122] [Rubber Latex (IV)]

[0123] In addition to the polyphenols (I), aldehydes (II), and isocyanate compounds (III) mentioned above, the adhesive composition may further substantially contain rubber latex (IV). Therefore, the adhesive composition can further enhance the adhesion to rubber components.

[0124] Here, there are no particular limitations on the rubber latex (IV), and examples include synthetic rubbers such as polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR), or vinylpyridine-styrene-butadiene copolymer rubber (Vp), in addition to natural rubber (NR). These rubber latexes (IV) can be used alone or in combination of two or more.

[0125] When preparing an adhesive composition containing rubber latex (IV), it is preferable to mix the rubber latex (IV) with phenols (I) and aldehydes (II) before adding the isocyanate compound (III).

[0126] The content of rubber latex (IV) in the adhesive composition is preferably 20% by mass or more, more preferably 25% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less.

[0127] There are no particular limitations on the method of manufacturing the adhesive composition, but for example, methods of mixing and maturing raw materials such as polyphenols (I), aldehydes (II), and rubber latex (IV) can be mentioned, or methods of mixing and maturing polyphenols (I) and aldehydes (II), and then further adding and maturing rubber latex (IV). When the raw materials include isocyanate compounds (III), the method may involve adding and maturing rubber latex (IV), and then adding isocyanate compounds (III).

[0128] (Method for manufacturing pneumatic tires)

[0129] The method for manufacturing a tire (hereinafter sometimes simply referred to as the "manufacturing method") is a method for manufacturing the pneumatic tire 1 of the present invention described above, and includes the step of laminating the first belt layer 6a and the second belt layer 6b (lamination step). Furthermore, in the manufacturing method of this embodiment, before the lamination step, the ends of the first belt layer 6a are covered with a first rubber sheet, and the ends of the second belt layer 6b are covered with a second rubber sheet. At this time, for both the first and second rubber sheets, when laminating, the length of the rubber sheet portion on the side facing the other belt layer is longer than the length of the rubber sheet portion on the opposite side, thereby the ends of each belt layer are covered in an alternating manner. According to this manufacturing method, the formation of gaps between the first belt layer 6a and the second belt layer 6b, and between the second belt layer 6b and the reinforcing layer 7, can be effectively suppressed while manufacturing the pneumatic tire 1 described above.

[0130] The mechanism for suppressing gap formation described above in this embodiment will now be described in detail.

[0131] Figure 5A This is a schematic diagram illustrating the lamination steps in the manufacturing method of this embodiment. As shown, in the lamination step, for example, the first belt layer 6a, the second belt layer 6b, and other layers 16 (including the belt reinforcement layer 7 and other rubber layers, adhesive layers, etc. (not shown)) are laminated in this order, and while pressing the roller 15 from above, the roller is moved from the center of the tire toward the ends of each layer, thereby bonding the first belt layer 6a, the second belt layer 6b, and the other layers 16 together. At this time, the ends of the first belt layer 6a are covered with a first rubber sheet beforehand, and the ends of the second belt layer 6b are covered with a second rubber sheet. At this time, as... Figure 5A As shown, the first rubber sheet covering the end of the first belt layer 6a is configured such that the length of the rubber sheet portion on the side facing the second belt layer 6b when the layers are stacked (the length in the tire width direction, which also applies thereafter) (L) B1’ ) than the length of the rubber sheet portion located on the opposite side (L) A’ The length is such that it covers the ends of the first belt layer 6a in an alternating manner. Similarly, as Figure 5AAs shown, the second rubber sheet covering the end of the second belt layer 6b is configured such that when the layers are stacked, the length (L) of the rubber sheet portion on the side facing the first belt layer 6a is such that... B2’ ) than the length of the rubber sheet portion located on the opposite side (L) C’ The length is such that it covers the ends of the second belt layer 6b in an alternating manner. If such a configuration of rubber sheets is used to perform lamination and bonding, then as Figure 5B As schematically shown, it is difficult to form gaps between the first belt layer 6a and the second belt layer 6b at the belt end, and between the second belt layer 6b and other layers 16.

[0132] On the other hand, traditionally, such as Figure 6A As shown, the first rubber sheet covering the end of the first belt layer 6a and the second rubber sheet covering the end of the second belt layer 6b are both symmetrically wrapped around the ends (i.e., L...). A′ ≈L B1′ L B2′ ≈L C′ When lamination and bonding are performed using such a rubber sheet configuration, the first belt layer 6a, the second belt layer 6b, and the other layers 16 cannot deform until they are in close contact with each other, and as a result, Figure 6B As shown, large gaps (air pockets) may be formed at the ends of the belt between the first belt layer 6a and the second belt layer 6b, and between the second belt layer 6b and other layers 16.

[0133] The other layers 16 mentioned above may include, for example, belt reinforcement layers, and may also be tire-forming components such as rubber layers.

[0134] The first and second rubber sheets mentioned above can be, for example, rectangular rubber sheets.

[0135] In the above-mentioned lamination step, it is preferable to laminate the first belt layer 6a and the second belt layer 6b so that the first rubber sheet and the second rubber sheet are in contact with each other.

[0136] In the manufacturing method of this embodiment, when stacking the first belt layer 6a and the second belt layer 6b, preferably, the ends of the first rubber sheet and the second rubber sheet located between the first belt layer 6a and the second belt layer 6b do not overlap. In other words, preferably, the distance Lx' (distance in the tire width direction) between the end of the first rubber sheet and the end of the second rubber sheet located between the first belt layer 6a and the second belt layer 6b (refer to...) Figure 5A The value is greater than 0. This further suppresses the formation of gaps at the ends of the belt. In this case, the end of the first rubber sheet of the first belt layer 6a can be closer to the center of the tire, or as... Figure 5AAs shown, the end of the second rubber sheet in the second belt layer 6b can be closer to the center of the tire. However, from the viewpoint of more effectively suppressing gap formation, it is preferable to... Figure 5A As shown, the end of the second rubber sheet of the second belt layer 6b is closer to the center of the tire.

[0137] In this manufacturing method, as long as the arrangement of the rubber sheets surrounding the first belt layer 6a and the second belt layer 6b is as described above, and the structure of the pneumatic tire 1 of this embodiment is obtained, there are no particular limitations on other specific manufacturing conditions. For example, the lengths (L) of the third rubber portion 8A, the first rubber portion 8B, and the second rubber portion 8C in the laminated tire 1 are... A L B and L C The relative positional relationship corresponds to the length (L) of each rubber sheet portion in this manufacturing method. A’ L B1’ To L B2’ and L C’ Therefore, those skilled in the art can adjust them accordingly. In addition, for example, in order to adjust the spacing between the belt cords of the first belt layer 6a and the second belt layer 6b in the tire 1 of this embodiment (and thus make b > a), the thickness of the first rubber sheet covering the end of the first belt layer 6a and / or the thickness of the second rubber sheet covering the end of the second belt layer 6b can be adjusted appropriately.

[0138] Example

[0139] The tire of the present invention will now be described in more detail using examples.

[0140] Using a belt structure as shown in Tables 1 to 3 below and having Figure 2A The tires with schematic structures of the belt ends shown in the figure were evaluated for belt edge separation durability and rolling resistance. The dimensions of the tires used for testing are shown in Tables 1 to 3, and the cords in each belt layer of each tire were configured to intersect at an angle of ±30° relative to the tire circumference. Furthermore, in Tables 1 to 3, the cord density, cord diameter, filament diameter, thickness of the first and second belt layers at the center of the tire, and the distance between the interface of the first and second belt layers at the center of the tire and the cords are values ​​specified during tire design. Values ​​indicated by 'a' indicate twice the distance between the interface of the belt layers at the center of the tire and the cords. Values ​​indicated by 'b' indicate values ​​actually measured by dissecting and manufacturing the tire.

[0141] (Belt edge separation durability)

[0142] After degradation, each example tire was inflated and mounted on a test passenger vehicle, and then run on BES rollers while a constant lateral force (SF) was repeatedly applied. The tire was then dissected and the length of the cracks generated at the ends of the belt layers was measured. The crack length of each example was compared to that of a conventional example; if the difference in crack length was less than 0.5 mm, it was evaluated as equivalent to the conventional example, and if the crack length was 0.5 mm or more shorter than the conventional example, it was evaluated as good. The results are shown in Tables 1 to 3.

[0143] [Table 1]

[0144]

[0145] [Table 2]

[0146]

[0147] [Table 3]

[0148]

[0149] (Effect of the belt reinforcement layer)

[0150] In the tires of Invention Examples 1 to 4 shown in Tables 1 to 3, by arranging a belt reinforcement layer (which is formed by coating cords made of polyethylene terephthalate with an elastomer having a breaking strength of 6.5 cN / dtex or greater, an elongation at break of 10% or greater, and an elastic modulus at an elongation of 7% or greater of 6.0 mN / (dtex·%)) can the radial growth rate in the tire width direction be made uniform, and the improved plunger durability and steering stability of the tire are further confirmed.

[0151] (The effect of the interlayer rubber)

[0152] In the tires of Invention Examples 1 to 4 shown in Tables 1 to 3, by arranging a belt reinforcement layer (which is formed by coating a cord made of polyethylene terephthalate with an elastomer, the cord having a breaking strength of 6.5 cN / dtex or greater, an elongation at break of 10% or greater, and an elastic modulus at an elongation of 7% of 6.0 mN / (dtex·%) or greater) on the radially outer side of the belt, and by arranging interlayer rubber at the belt end (between the end of the first belt layer and the end of the second belt layer) such that b > a, it was confirmed that strain at the belt end was suppressed and the durability of the belt end of the tire was improved.

[0153] [Contributions to the UN-led Sustainable Development Goals (SDGs)]

[0154] The SDGs have been advocated for achieving a sustainable society. One implementation of this disclosure may be a technology that contributes to, for example, “7. Affordable and Clean Energy,” “12. Responsible Consumption and Production,” and “13. Climate Action.”

[0155] [List of reference numerals]

[0156] 1. Pneumatic tire,

[0157] 2: Bead area,

[0158] 3: Side wall portion,

[0159] 4: Fetal face.

[0160] 5: Fetus,

[0161] 6: Belt,

[0162] 7: Belt reinforcement layer,

[0163] 8: End rubber,

[0164] 15: Roller

[0165] 16: Other layers

Claims

1. A pneumatic tire, comprising: A belt in the tread portion, the belt comprising a first belt layer and a second belt layer disposed radially outward of the first belt layer of the tire; and the belt reinforcement layer in the tread portion, the belt reinforcement layer being disposed radially outward of the belt on the tire. Each of the first belt layer and the second belt layer is formed by multiple belt cords coated with belt rubber. The belt reinforcement layer is formed of multiple reinforcing cords coated with reinforcing rubber. The thickness of both the first belt layer and the second belt layer at the center of the tire is 1.00 mm or less. In the tire width cross-sectional view, when the first imaginary line is defined as a straight line connecting the outermost point of the circumcircle of adjacent belt cords in the first belt layer in the tire radial direction, and the second imaginary line is defined as a straight line connecting the innermost point of the circumcircle of adjacent belt cords in the second belt layer in the tire radial direction, and when the maximum value of the tire radial distance between the first and second imaginary lines at the tire center is defined as 'a', and the minimum value of the length of the line segment connecting the innermost point of the circumcircle of the belt cord located at the outermost position in the tire width direction in the second belt layer to the first imaginary line is defined as 'b',... b > a, At the end of the belt, a first rubber portion is disposed between the first belt layer and the second belt layer, and a second rubber portion is disposed on the radially outer side of the second belt layer. The length of the first rubber portion in the direction toward the center of the tire is longer than the length of the second rubber portion in the direction toward the center of the tire. In the cross-sectional view along the tire width, the belt reinforcement layer is disposed at least in the tire width region between the end of the first rubber portion on the tire's central side and the end of the second belt layer. Furthermore, the reinforcing cord of the belt reinforcement layer is an organic fiber cord with a breaking strength of 6.5 cN / dtex or greater, a breaking elongation of 10% or greater, and an elastic modulus of 6.0 mN / (dtex·%) or greater at 7% elongation.

2. The pneumatic tire according to claim 1, wherein in a cross-sectional view along the tire width direction, the belt reinforcement layer is disposed at least in the tire width direction region in which the second belt layer is disposed.

3. The pneumatic tire according to claim 1 or 2, wherein, In the central portion of the tire, for each of the first belt layer and the second belt layer, the distance between the interface of the first belt layer and the second belt layer and the belt cord is 0.19 mm or less.

4. The pneumatic tire according to any one of claims 1 to 3, wherein each of the belt cords has a 1×N structure formed by twisting N filaments, and N is an integer selected from 2 to 6.

5. The pneumatic tire according to any one of claims 1 to 4, wherein the cord density of the belt cord is 60 cords / dm or greater and 95 cords / dm or less.

6. The tire according to any one of claims 1 to 5, wherein the diameter of each of the belt cords is 0.5 mm or greater and 1.0 mm or less.

7. The pneumatic tire according to any one of claims 1 to 6, wherein the ratio b / a is 2.0 or greater and 8.0 or less.

8. The pneumatic tire according to any one of claims 1 to 7, wherein the organic fiber cord serving as the reinforcing cord is a cord made of polyethylene terephthalate.

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