Heavy-duty tires, green tires for heavy-duty tires, and methods for manufacturing heavy-duty tires.

Abstract

The present invention provides a heavy-duty tire, a green tire for heavy-duty tires, and a method for manufacturing heavy-duty tires, which reduce the mixing rate of different types of rubber in the tread rubber portion (removed rubber) that is removed by grooving. [Solution] The heavy-duty tire 1 has a tread rubber 7 comprising a cap layer 7c and a base layer 7b positioned on the inner circumference side of the tire relative to the cap layer 7c. The cap layer 7c comprises a cap surface layer 7c1 and a cap intermediate layer 7c2 positioned on the inner circumference side of the tire relative to the cap surface layer 7c1 and made of a different type of rubber than the rubber constituting the cap surface layer 7c1. In at least one half of the tire Q with respect to the tire equatorial plane CL, the thickness of the cap intermediate layer 7c2 between a predetermined tire width direction position X, which is a predetermined distance from the tire equatorial plane CL, and a tire width direction position D of the contact end TE is thinner than the thickness of the cap intermediate layer 7c2 positioned inward in the tire width direction from the predetermined tire width direction position X.

Description

Technical Field

[0003]

[0001] The present invention relates to a heavy-duty tire, a green tire for a heavy-duty tire, and a method for manufacturing a heavy-duty tire.

Background Art

[0002] Conventionally, in the manufacture of heavy-duty tires, before vulcanization molding, there are cases where the tread rubber portion in a region substantially corresponding to the region where lug grooves are to be formed in the tread rubber of the green tire is removed by grooving (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since heavy-duty tires are large, the amount of the tread rubber portion removed by grooving (also referred to as "removed rubber" in this specification) also increases. Therefore, it is considered preferable from the viewpoint of reducing waste of resources, etc., to recover the removed rubber and reuse it when manufacturing another tire. However, when the tread rubber has three layers, namely a cap surface layer, a cap intermediate layer, and a base layer, there is a high possibility that the removed rubber will contain not only the rubber constituting the cap surface layer (cap surface layer rubber), but also rubber of a different type from the cap surface layer rubber (particularly, the rubber constituting the cap intermediate layer (cap intermediate layer rubber)). If the mixing rate of the different-type rubber in the removed rubber is high, for example, when the removed rubber is reused for the cap surface layer of another heavy-duty tire, there is a possibility that the physical properties of the cap surface layer of the other heavy-duty tire will be significantly different from the expected ones.

[0005] The present invention aims to provide a heavy-duty tire, a green tire for heavy-duty tires, and a method for manufacturing heavy-duty tires that can reduce the mixing rate of different types of rubber in the tread rubber portion (removed rubber) that is removed by grooving. [Means for solving the problem]

[0006] The above objectives will be achieved by the following means.

[0007] [1] The tread rubber is The cap layer and A base layer is positioned on the inner circumference side of the tire, It has, The aforementioned cap layer is The surface of the cap and A cap intermediate layer is positioned on the inner circumference side of the tire, and is made of a different type of rubber than the rubber that constitutes the cap surface layer. It has, A heavy-duty tire wherein, in at least one half of the tire with respect to the tire's equatorial plane, the thickness of the intermediate cap layer between a predetermined tire widthwise position at a predetermined distance from the tire's equatorial plane and the tire widthwise position of the contact end is thinner than the thickness of the intermediate cap layer inward in the tire widthwise direction than the predetermined tire widthwise position.

[0008] [2] The heavy-duty tire according to [1], wherein in at least one half of the tire, the predetermined tire width direction position is located between a 3 / 8 point, which is 3 / 8 times the contact width from the tire equatorial plane, and the tire width direction position of the contact end.

[0009] [3] The heavy-duty tire according to [1] or [2], wherein in at least one half of the tire, the thickness of the cap intermediate layer decreases substantially in a stepped manner as it moves outward in the tire width direction, over the tire width region between the predetermined tire width direction position and the tire width direction position of the contact end.

[0010] [4] A heavy-duty tire according to any one of [1] to [3], wherein in at least one half of the tire, the outer surface of the cap intermediate layer extends inward in the tire radial direction in a substantially stepped manner as it moves outward in the tire width direction, over a tire width region between the predetermined tire width direction position and the tire width direction position of the contact end.

[0011] [5] The heavy-duty tire according to [1] or [2], wherein in at least one half of the tire, the thickness of the cap intermediate layer decreases substantially smoothly towards the outside in the tire width direction over the tire width region between the predetermined tire width direction position and the tire width direction position of the contact end.

[0012] [6] The heavy-duty tire according to [1], [2], or [5], wherein in at least one half of the tire, the outer surface of the cap intermediate layer extends substantially linearly inward in the tire radial direction as it moves outward in the tire width direction, over a tire width region between the predetermined tire width direction position and the tire width direction position of the contact end.

[0013] [7] The heavy-duty tire according to [1], [2], or [5], wherein in at least one half of the tire, the outer surface of the cap intermediate layer extends radially inward along a curved line that is convex radially outward as it moves outward in the tire width direction, over a tire width region between the predetermined tire width direction position and the tire width direction position of the contact end.

[0014] [8] The heavy-duty tire according to any one of [1] to [7], wherein the cap surface layer, the cap intermediate layer, and the base layer each extend over the entire tire widthwise region between the tire widthwise positions of a pair of contact ends.

[0015] [9] The tread rubber The cap layer and A base layer is positioned on the inner circumference side of the tire, It has, The cap layer has a cap surface layer and a cap intermediate layer which is disposed on the inner circumferential side of the tire relative to the cap surface layer and is made of a rubber of a type different from the rubber constituting the cap surface layer, and in at least one tire half with respect to the tire equatorial plane, the thickness of the cap intermediate layer between a predetermined tire width direction position separated by a predetermined distance from the tire equatorial plane and the tire width direction position of the grounding end is thinner than the thickness of the cap intermediate layer on the inner side in the tire width direction from the predetermined tire width direction position, the green tire for heavy-duty tires

[0016] 〔10〕A method for manufacturing a heavy-duty tire for manufacturing a heavy-duty tire, including a step of manufacturing a pre-grooving green tire for manufacturing a pre-grooving green tire, a grooving step of grooving the pre-grooving green tire to obtain a grooved green tire, and a vulcanization molding step of vulcanization molding the grooved green tire with a vulcanization molding die to obtain a vulcanized heavy-duty tire, The pre-grooving green tire has a tread rubber a cap layer and a base layer disposed on the inner circumferential side of the tire relative to the cap layer, The cap layer has a cap surface layer and a cap intermediate layer which is disposed on the inner circumferential side of the tire relative to the cap surface layer and is made of a rubber of a type different from the rubber constituting the cap surface layer, and in at least one tire half with respect to the tire equatorial plane, the thickness of the cap intermediate layer between a predetermined tire width direction position separated by a predetermined distance from the tire equatorial plane and the tire width direction position of the grounding end is thinner than the thickness of the cap intermediate layer on the inner side in the tire width direction from the predetermined tire width direction position,​​​​ In the grooving step, a tread rubber portion in a region substantially corresponding to a region where lug grooves are to be formed in the vulcanization molding step among the tread rubber of the pre-grooving green tire is removed by the grooving, a method for manufacturing a heavy-duty tire.

[0017] 〔11〕The method for manufacturing a heavy-duty tire according to 〔10〕, wherein the tread rubber portion removed by the grooving in the grooving step has a mixing ratio of a different type of rubber from the rubber constituting the cap surface layer of 10% by mass or less.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a heavy-duty tire, a green tire for a heavy-duty tire, and a method for manufacturing a heavy-duty tire, in which the mixing ratio of different types of rubber in a tread rubber portion (removed rubber) removed by grooving can be reduced.

Brief Description of the Drawings

[0019] [Figure 1] It is a cross-sectional view in the tire width direction schematically showing a green tire for a heavy-duty tire and a heavy-duty tire according to an embodiment of the present invention, which can have the configuration of the tread rubber in any embodiment of the present invention. [Figure 2] It is a cross-sectional view in the tire width direction schematically showing the tread rubber in a green tire for a heavy-duty tire and a heavy-duty tire according to a first embodiment of the present invention. [Figure 3] It is a cross-sectional view in the tire width direction schematically showing the tread rubber in a green tire for a heavy-duty tire and a heavy-duty tire according to a second embodiment of the present invention. [Figure 4] It is a cross-sectional view in the tire width direction schematically showing the tread rubber in a green tire for a heavy-duty tire and a heavy-duty tire according to a third embodiment of the present invention. [Figure 5] It is a schematic diagram for explaining a grooving step in a method for manufacturing a heavy-duty tire according to an embodiment of the present invention. [Figure 6] This is a very schematic view of one of the multiple pieces of rubber removed by grooving in the grooving step illustrated in Figure 5, as seen in the direction of the arrow S in Figure 5. [Modes for carrying out the invention]

[0020] The heavy-duty tire, the green tire for heavy-duty tires, and the method for manufacturing heavy-duty tires according to the present invention can be suitably used for any type of heavy-duty tire, and are particularly suitable for tires for construction and mining vehicles (off-the-road tires).

[0021] Hereinafter, embodiments of the heavy-duty tire, the green tire for the heavy-duty tire, and the method for manufacturing the heavy-duty tire according to the present invention will be described with reference to the drawings. Common components and parts in each figure are denoted by the same reference numeral. In this specification, for convenience, heavy-duty tires are also simply referred to as "tires," and raw tires for heavy-duty use are also simply referred to as "raw tires." In this specification, a tire is a pneumatic tire. In this specification, unless otherwise specified, "heavy-duty tire" or "tire" refers to a tire that has been vulcanized and molded, and is distinguished from a "raw tire" that is in its unvulcanized state.

[0022] For the sake of clarity, this specification will describe in parallel the configurations of various embodiments of the present invention, namely the green tires R1B, R1A, and tire 1. Strictly speaking, the green tires R1B and R1A before vulcanization and the tire 1 after vulcanization may differ in various configurations, such as shape. However, for convenience, Figures 1 to 4 show the configurations of various embodiments of the present invention, namely the green tires R1B, R1A, and tire 1, in a very schematic manner using common drawings. As will be explained in detail later, Figure 1 shows the green tire R1B before grooving, while Figures 2 to 4 show the green tire R1B before grooving and the green tire R1A after grooving.

[0023] Figure 1 is a schematic cross-sectional view in the tire width direction showing a raw tire R1B and a heavy-duty tire 1 for heavy-duty use according to one embodiment of the present invention, which may have the configuration of the tread rubber 7 in any embodiment of the present invention described herein. The green tire R1B and tire 1 in the embodiment shown in Figure 1 are configured as green tires and tires for construction and mining vehicles (off-the-road use), respectively. However, the green tires R1B, R1A and tire 1 in each embodiment of the present invention described herein may be configured as green tires and tires for any type of heavy load.

[0024] Unless otherwise specified, the positional relationships and dimensions of each element shall be measured under standard conditions, with the raw tire R1B, R1A, or tire 1 mounted on the applicable rim, filled to the specified internal pressure, and unloaded. Furthermore, when a green tire R1B, R1A, or tire 1 is mounted on the applicable rim, filled to the specified internal pressure, and subjected to the maximum load, the width of the contact surface in the tire width direction that contacts the road surface is called the "contact width TW," and the end of the contact surface in the tire width direction is called the "contact end TE."

[0025] In this specification, "applicable rim" refers to the standard rim (Measuring Rim in the ETRTO STANDARDS MANUAL, Design Rim in the TRA YEAR BOOK) for applicable sizes, which is listed or will be listed in the industrial standards valid in the region where pneumatic tires are produced and used, such as the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States. However, for sizes not listed in these industrial standards, it refers to a rim with a width corresponding to the bead width of the pneumatic tire. "Applicable rim" includes current sizes as well as sizes that will be listed in the aforementioned industrial standards in the future. An example of "sizes that will be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the ETRTO 2013 edition.

[0026] In this specification, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating as described in the aforementioned industrial standards such as the JATMA YEAR BOOK. For sizes not listed in the aforementioned industrial standards, it refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, in this specification, "maximum load" refers to the load corresponding to the maximum load capacity of a tire of the applicable size as described in the aforementioned industrial standards, or, for sizes not listed in the aforementioned industrial standards, the load corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted.

[0027] In this specification, "tire circumferential direction" refers to the direction in which the tire R1B, R1A, or tire 1 rotates around the central axis (tire rotation axis O) of the tire R1B, R1A, or tire 1; "tire radial direction" refers to the direction perpendicular to the tire rotation axis O; and "tire width direction" refers to the direction parallel to the tire rotation axis O. In some drawings, the tire circumferential direction is indicated by the symbol "CD", the tire radial direction by the symbol "RD", and the tire width direction by the symbol "WD". Furthermore, in this specification, the side of the tire radially that is closer to the tire rotation axis O is referred to as the "inner radial direction (RDI)," and the side of the tire radially that is further from the tire rotation axis O is referred to as the "outer radial direction (RDO)." In addition, in this specification, the side of the tire width that is closer to the tire equatorial plane CL is referred to as the "inner width direction," and the side of the tire width that is further from the tire equatorial plane CL is referred to as the "outer width direction."

[0028] First, the overall structure of the raw tires R1B, R1A, and tire 1 will be described. Note that in Figure 1, the raw tire shown is the raw tire before grooving, which will be described later, and the grooved raw tire R1A, which will be described later, is not shown. However, the grooved raw tire R1A has the same configuration as the raw tire before grooving, except that it has the grooved recess k (Figures 2 to 4) described later. As shown in Figure 1, the green tires R1B, R1A, and tire 1 each comprise a tread portion 1a, a pair of sidewall portions 1b extending radially inward from both ends of the tread portion 1a in the tire width direction, and a pair of bead portions 1c provided at the radially inward ends of each sidewall portion 1b. The bead portions 1c are configured to contact the rim on the radially inward and tire widthward sides when the green tires R1B, R1A, or tire 1 are mounted on the rim. Furthermore, the raw tires R1B, R1A, and tire 1 each comprise a pair of bead cores 4a, a pair of bead fillers 4b, a carcass 5, a belt 6, a tread rubber 7, a side rubber 8, and an inner liner 9.

[0029] Each bead core 4a is embedded in the corresponding bead portion 1c. The bead core 4a comprises a plurality of bead wires, each covered with rubber. The bead wires are preferably made of metal (e.g., steel). The bead wires can be, for example, monofilaments or stranded wires.

[0030] Each bead filler 4b is located radially outward relative to the corresponding bead core 4a. The bead fillers 4b taper outward in the radial direction of the tire. The bead fillers 4b are made of rubber. Generally, bead filler 4b is sometimes called a "stiffener."

[0031] The carcass 5 spans between a pair of bead cores 4a and extends in a toroidal manner. The carcass 5 is composed of one or more (one in the example in Figure 1) carcass plies 5a. Each carcass ply 5a includes one or more carcass cords and a covering rubber covering the carcass cords. The carcass cords can be formed from monofilaments or stranded wires. Carcass 5 is preferably of a radial structure, but may also be of a bias structure.

[0032] The belt 6 is positioned radially outward relative to the crown portion of the carcass 5. The belt 6 comprises one or more belt layers 6a (six layers in the example shown in Figure 1). Each belt layer 6a includes one or more belt cords and a covering rubber covering the belt cords. The belt cords can be made of monofilament or stranded wire. The belt cords are preferably made of metal (e.g., steel), but may also be made of organic fibers such as polyester, nylon, rayon, or aramid.

[0033] The tread rubber 7 is located on the radially outer side of the belt 6 in the tread portion 1a. The tread rubber 7 constitutes the tread tread surface 2, which is the radially outer surface of the tread portion 1a. A tread pattern is formed on the tread tread surface 2 of the tire 1 by grooves and / or sipes. The tread pattern is formed by vulcanization molding of the green tire R1A. Therefore, the green tires R1B and R1A do not have a tread pattern (and consequently, grooves and / or sipes on the tread tread surface 2). For example, in the example shown in Figure 1, the tread surface 2 of tire 1 has multiple lug grooves h formed on at least one side (both sides in the example shown in Figure 1) of the tire half Q with respect to the tire equatorial plane CL. Each lug groove h opens at the contact edge TE, extends inward from the contact edge TE in the tire width direction, and terminates just before reaching the tire equatorial plane CL. On at least one side (both sides in the example shown in Figure 1) of the tire half Q, the multiple lug grooves h are arranged at intervals from each other along the tire circumferential direction. Note that the position and shape of the lug grooves h illustrated in Figure 1 are merely examples, and the position and shape of the lug grooves h formed on tire 1 may differ from those shown in Figure 1. In Figure 1, the illustration of grooves and / or sipes that may be provided on the tread surface 2 other than the lug grooves h is omitted. In the green tires R1B and R1A, the tread rubber 7 is made of raw rubber (unvulcanized rubber). The tread rubber 7 in the green tires R1B and R1A can be molded, for example, by extrusion molding. In tire 1, the tread rubber 7 is made of vulcanized rubber. Further details about tread rubber 7 will be explained later.

[0034] The side rubber 8 is located on the sidewall portion 1b. The side rubber 8 constitutes the outer surface of the sidewall portion 1b on the outer side in the tire width direction. The side rubber 8 is located further outward in the tire width direction than the carcass 5. The side rubber 8 is located further outward in the tire width direction than the bead filler 4b. The side rubber 8 is formed integrally with the tread rubber 7. In the raw tires R1B and R1A, the side rubber 8 is made of raw rubber (unvulcanized rubber). In tire 1, the side rubber 8 is made of vulcanized rubber.

[0035] The inner liner 9 is positioned on the inside of the tire of the carcass 5, and may be laminated on the inside of the tire of the carcass 5, for example. The inner liner 9 is made of, for example, a butyl rubber with low air permeability. Butyl rubbers include, for example, butyl rubber and its derivative, halogenated butyl rubber. The inner liner 9 is not limited to butyl rubber and can be made of other rubber compositions, resins, or elastomers.

[0036] Here, with reference to Figures 5 and 6, a method for manufacturing heavy-duty tires according to one embodiment of the present invention will be described. The method for manufacturing heavy-duty tires according to this embodiment can be used to manufacture heavy-duty tires 1 according to any embodiment of the present invention. A method for manufacturing heavy-duty tires includes a pre-grooving green tire manufacturing step, a grooving step, and a vulcanization molding step.

[0037] First, in the pre-grooving tire manufacturing step, the pre-grooving tire R1B is manufactured. The pre-grooving green tire R1B refers to the green tire in the state immediately before the grooving step described later is performed, as shown by the solid and dashed lines in Figure 5. The outer surface of the tread rubber 7 of the pre-grooving green tire R1B may be a substantially cylindrical smooth surface with virtually no recesses. In Figure 1, an example of a pre-grooving tire R1B is schematically shown by a solid line.

[0038] Subsequently, in the grooving step, grooves are applied to the pre-grooving green tire R1B manufactured in the pre-grooving green tire manufacturing step to obtain a grooved green tire R1A. Grooved green tire R1A refers to the green tire immediately after the grooving step has been performed, as shown by the solid line in Figure 5. In the grooving step, the tread rubber portions m of the raw tire R1B before grooving that are located in areas that substantially correspond to the areas where lug grooves h will be formed in the subsequent vulcanization molding step (also referred to as the "planned lug groove formation area hp" in this specification) are removed by grooving. In this specification, the tread rubber portion m that is removed by grooving is also referred to as the "removed rubber m". In the tread rubber 7 of the ungrooved tire R1B, each area from which the removed rubber m has been removed becomes a recess (hereinafter referred to as "grooved recess k"). Therefore, the outer surface of the tread rubber 7 of the grooved ungrooved tire R1A has a plurality of grooved recesses k. Note that the lug groove formation area hp and the grooved area (and consequently the tread rubber portion m removed by grooving, and the grooved recess k) may each exist at multiple positions spaced apart from each other along the circumferential direction of the tire, at least on one half of the tire Q. However, for simplicity, only some of these are shown in Figure 5. Figure 6 is a very schematic view of one of the multiple removed rubber portions m in the grooving step illustrated in Figure 5, as seen in the direction of the S arrow in Figure 5. Grooving may be done using a machine or by hand.

[0039] Subsequently, in the vulcanization molding step, the grooved green tire R1A obtained in the grooving step is vulcanized using a vulcanization molding die to obtain a vulcanized heavy-duty tire 1. Although not shown in the diagram, the molding surface of the vulcanization mold has multiple lug groove forming protrusions, each configured to form lug grooves h in the lug groove formation area hp of the tread rubber 7. In the vulcanization molding step, when the grooved green tire R1A is set into the vulcanization mold, the multiple lug groove forming protrusions of the vulcanization mold are each positioned to fit into the corresponding grooved recess k in the grooved green tire R1A.

[0040] Generally, since heavy-duty tires 1 are large, the tread rubber 7 of the raw tires R1B and R1A for heavy-duty tires tends to be thick. If grooving (grooving step) is not performed, when setting the raw tire R1A in the vulcanization molding die, it is necessary to press the multiple lug groove forming protrusions of the vulcanization molding die into the tread rubber 7 of the raw tire R1A. This can make it difficult to set the raw tire R1A in the desired position in the vulcanization molding die, and the surrounding tread rubber 7 may be pressed by the lug groove forming protrusions, potentially causing undesirable deformation of the tire components in that area. In other words, by performing grooving (grooving step) in advance, the need to press the multiple lug groove forming protrusions of the vulcanizing mold into the tread rubber 7 of the raw tire R1A when setting the raw tire R1A into the vulcanizing mold afterwards can be reduced. Consequently, it becomes easier to set the raw tire R1A in the desired position within the vulcanizing mold, and the risk of undesirable deformation of the tire components near the lug groove forming protrusions can be reduced.

[0041] Preferably, the number of tread rubber portions m (rubber to be removed m) removed by grooving (grooving step) is the same as the number of lug grooves h (and consequently, the area hp where lug grooves are to be formed) formed in the vulcanization molding step. The area of ​​tread rubber m removed by grooving (grooving step) preferably overlaps with the area hp where the corresponding lug grooves are to be formed, but it is not necessary for it to perfectly coincide with the area hp where the corresponding lug grooves are to be formed.

[0042] The configuration of the tread rubber 7 in each of the green tires R1B, R1A, and tire 1 according to various embodiments of the present invention will be described in more detail below. Unless otherwise specified, the configuration of the tread rubber 7 described herein can be applied to each of the green tires R1B, R1A, and tire 1 according to any embodiment of the present invention. In Figure 1, the solid line shows the ungrooved tire R1B, and the solid line and the dashed line (showing lug grooves h) show the (vulcanized) tire 1. Figures 2 to 4 are cross-sectional views in the tire width direction, showing the tread rubber 7 in the green tires R1B, R1A, and tire 1, respectively, according to the first to third embodiments of the present invention, in a more schematic manner than in Figure 1. In Figures 2 to 4, the solid lines show the tread rubber 7 of the green tire R1B before grooving, the solid lines and dashed lines (showing grooved recesses k) show the tread rubber 7 of the grooved green tire R1A, and the solid lines and dashed lines (showing lug grooves h) show the tread rubber 7 of the (vulcanized) tire 1. In the following, for the sake of clarity, various embodiments of the present invention, including the first to third embodiments, will be described in parallel.

[0043] As shown in Figures 1 to 4, the tread rubber 7 has a cap layer 7c and a base layer 7b. The base layer 7b is positioned on the inner circumference side of the tire compared to the cap layer 7c. The cap layer 7c comprises two layers: a cap surface layer 7c1 and a cap intermediate layer 7c2. In each embodiment shown in Figures 1 to 4, the cap consists of these two layers. The cap intermediate layer 7c2 is positioned on the inner circumference side of the tire, relative to the cap surface layer 7c1. The cap intermediate layer 7c2 is made of a different type of rubber (in this specification, the rubber making up the cap intermediate layer 7c2 is also referred to as "cap intermediate layer rubber 7c2r") than the rubber making up the cap surface layer 7c1 (also referred to as "cap surface rubber 7c1r"). Therefore, the physical properties of the cap surface rubber 7c1r may differ from those of the cap intermediate layer rubber 7c2r. The outer surface of the cap surface layer 7c1 on the tire's outer circumference constitutes the tread surface 2. The base layer 7b is made of a different type of rubber than the cap surface rubber 7c1r and the cap intermediate layer rubber 7c2r (in this specification, the rubber constituting the base layer 7b is also referred to as "base layer 7b rubber"). Therefore, the physical properties of the base layer 7b may differ from those of the cap surface rubber 7c1r and the cap intermediate layer rubber 7c2r. In each embodiment shown in Figures 1 to 4, the tread rubber 7 consists of three layers: a cap surface layer 7c1, a cap intermediate layer 7c2, and a base layer 7b.

[0044] The cap surface layer 7c1, the cap intermediate layer 7c2, and the base layer 7b each extend across the entire tire widthwise region between the tire widthwise positions D of the pair of contact ends TE.

[0045] As shown in Figures 2 to 4, in at least one side (both sides in each embodiment of Figures 2 to 4) of the tire half Q with respect to the tire equatorial plane CL, the thickness of the cap intermediate layer 7c2 between a predetermined tire width direction position X and the tire width direction position D of the contact end TE is thinner than the thickness of the cap intermediate layer 7c2 inside the tire width direction from the predetermined tire width direction position X. The predetermined tire width direction position X is a position in the tire width direction that is a predetermined distance away from the tire equatorial plane CL in the tire width direction. That is, in the at least one side of the tire half Q, the thickness of the cap intermediate layer 7c2 is thinner outside the tire width direction than inside the tire width direction. By making the thickness of the cap intermediate layer 7c2 relatively thin on the outer side in the tire width direction, compared to a case where the thickness of the cap intermediate layer 7c2 is not relatively thin on the outer side in the tire width direction, the proportion of the cap surface layer rubber 7c1r in the tread rubber portion m (removed rubber m) removed by grooving (grooving step) during manufacturing becomes higher, and the mixing rate of different types of rubber (especially the cap intermediate layer rubber 7c2r) can be reduced (see Figures 2 to 4 and Figure 6). Specifically, for example, it becomes possible to reduce the mixing rate of different types of rubber in the removed rubber m to 10% by mass or less (or 5% by mass or less) per green tire. Therefore, for example, when the removed rubber m is reused as the cap surface layer 7c1 of another heavy-duty tire 1, the risk that the physical properties of the cap surface layer 7c1 of that other heavy-duty tire 1 will differ significantly from what was intended can be reduced. Furthermore, by making the thickness of the cap intermediate layer 7c2 relatively thicker on the inner side in the tire width direction, it is possible to increase the amount of the cap intermediate layer 7c2 compared to the case where the thickness of the cap intermediate layer 7c2 is thin across the entire width of the tire, thereby effectively utilizing the performance of the cap intermediate layer 7c2 and improving tire performance.

[0046] From the same viewpoint as above, as shown in Figures 2 to 4, it is preferable that the thickness of the cap surface layer 7c1 between a predetermined tire width direction position X and the tire width direction position D of the contact end TE in at least one side (both sides in each embodiment of Figures 2 to 4) of the tire half Q is thicker than the thickness of the cap surface layer 7c1 inside the tire width direction from the predetermined tire width direction position X.

[0047] In this specification, the thickness of the tread rubber 7 and the thickness of each layer constituting the tread rubber 7 (cap layer 7c, cap surface layer 7c1, cap intermediate layer 7c2, and base layer 7b) shall be measured parallel to the tire diameter direction.

[0048] The thickness of the tread rubber 7 may be substantially constant along the tire width direction between the tire width direction positions D of the pair of contact ends TE, or it may vary along the tire width direction. The thickness of the cap layer 7c may be substantially constant along the tire width direction between the tire width direction positions D of the pair of contact ends TE, or it may vary along the tire width direction. The thickness of the base layer 7b may be substantially constant along the tire width direction between the tire width direction positions D of the pair of contact ends TE, or it may vary along the tire width direction.

[0049] In the grooving step, the rubber to be removed by grooving (Figure 6) preferably contains a different type of rubber (particularly the intermediate layer rubber 7c2r) from the rubber constituting the cap surface layer 7c1 (cap surface layer rubber 7c1r) at a mixing rate of 10% by mass or less, and more preferably 5% by mass or less, per fresh tire. This effectively reduces the risk that, for example, when the removed rubber m is reused as the cap surface layer 7c1 of another heavy-duty tire 1, the physical properties of the cap surface layer 7c1 of that other heavy-duty tire 1 may differ significantly from those intended.

[0050] From the viewpoint of reducing the amount of different types of rubber mixed in the rubber to be removed m and ensuring the amount of the cap intermediate layer 7c2, it is preferable that, as shown in each embodiment of Figures 2 to 4, the predetermined tire width direction position X in at least one half of the tire Q is located between the 3 / 8 point C and the tire width direction position D of the contact end TE.

[0051] In this specification, as shown in Figures 2 to 4, a pair of tire widthwise positions A located 1 / 8 times the contact width TW from the tire equatorial plane CL are referred to as "1 / 8 point A", a pair of tire widthwise positions B located 1 / 4 times the contact width TW from the tire equatorial plane CL are referred to as "1 / 4 point B", and a pair of tire widthwise positions C located 3 / 8 times the contact width TW from the tire equatorial plane CL are referred to as "3 / 8 point C".

[0052] From the viewpoint of reducing the amount of different types of rubber mixed in the rubber to be removed m and ensuring the amount of the cap intermediate layer 7c2, as shown in the embodiments of Figures 2 to 4, it is preferable that in at least one side (both sides in the embodiments of Figures 2 to 4), in the tire half Q, the maximum thickness of the cap intermediate layer 7c2 between a predetermined tire width direction position X and the tire width direction position D of the contact end TE is thinner than the minimum thickness of the cap intermediate layer 7c2 located inside the tire width direction from the predetermined tire width direction position X (the thickness at the tire width direction position where the thickness is minimum). From a similar viewpoint, as shown in the embodiments of Figures 2 to 4, it is preferable that the average thickness of the cap intermediate layer 7c2 between a predetermined tire widthwise position X and a tire widthwise position D of the contact end TE in at least one side (both sides in the embodiments of Figures 2 to 4) of the tire half Q is thinner than the average thickness of the cap intermediate layer 7c2 inside the tire widthwise direction from the predetermined tire widthwise position X.

[0053] From the viewpoint of reducing the mixing rate of different types of rubber in the rubber to be removed m and ensuring the amount of the cap intermediate layer 7c2, it is preferable that, as shown in the embodiments of Figures 2 to 4, in at least one side (both sides in the embodiments of Figures 2 to 4) of the tire half Q, the thickness of the cap intermediate layer 7c2 gradually decreases towards the outside in the tire width direction over the tire width region between a predetermined tire width direction position X and the tire width direction position D of the contact end TE. In this specification, "gradual decrease" is a concept that includes cases where the decrease is constant in part, but not limited to cases where it is always (smooth and / or stepwise), but does not include cases where it increases.

[0054] As shown in the embodiments of Figures 2 to 3, in at least one side (both sides in the embodiments of Figures 2 to 3) of the tire half Q, the thickness of the cap intermediate layer 7c2 may be substantially constant along the tire width direction over a tire width region that is inward in the tire width direction from a predetermined tire width direction position X. As shown in the embodiments of Figures 2 to 3, in at least one side (both sides in the embodiments of Figures 2 to 3) of the tire half Q, the outer surface 7c2s of the cap intermediate layer 7c2 on the tire circumferential side may extend substantially linearly along the tire width direction over a tire width region that is inward in the tire width direction from a predetermined tire width direction position X.

[0055] Alternatively, as shown in the embodiment of Figure 4, in at least one side (both sides in the embodiment of Figure 4), the thickness of the cap intermediate layer 7c2 may gradually decrease towards the outside in the tire width direction in a tire width region that is inward in the tire width direction from a predetermined tire width direction position X in the tire width direction. As shown in the embodiment of Figure 4, in at least one half of the tire Q (both sides in the embodiment of Figure 4), the outer surface 7c2s of the cap intermediate layer 7c2 on the tire circumferential side may gradually extend inward in the tire radial direction as it moves outward in the tire width direction, over a tire width region that is inward in the tire width direction from a predetermined tire width direction position X.

[0056] As shown in the embodiment of Figure 2, in at least one half of the tire Q (both sides in the embodiment of Figure 2), the thickness of the cap intermediate layer 7c2 may decrease in a substantially stepped manner towards the outside in the tire width direction over the tire width region between a predetermined tire width direction position X and the tire width direction position D of the contact end TE.

[0057] In this specification, the reason for using terms such as "approximately" or "nearly" in descriptions of thickness and shape is to take into account minute irregularities and other variations that may occur during manufacturing; however, the use of "approximately" or "nearly" is optional.

[0058] As shown in the embodiment of Figure 2, in at least one half of the tire Q (both sides in the embodiment of Figure 2), the outer surface 7c2s of the cap intermediate layer 7c2 on the tire circumferential side may extend inward in the tire radial direction in a substantially stepped manner as it moves outward in the tire width direction, over a tire width direction region between a predetermined tire width direction position X and a tire width direction position D of the contact end TE. For example, as shown in the embodiment of Figure 2, in at least one half of the tire Q (both sides in the embodiment of Figure 2), the outer surface 7c2s of the cap intermediate layer 7c2 on the tire circumferential side may have a vertical portion 7c2sb extending substantially linearly outward in the tire width direction from a predetermined position X in the tire width direction, and a horizontal portion 7c2sc extending substantially linearly from the outer end of the vertical portion 7c2sb in the tire width direction to the tire width direction position D of the contact end TE. The angle made by the vertical portion 7c2sb with respect to the tire width direction is greater than the angle made by the horizontal portion 7c2sc with respect to the tire width direction. The angle made by the vertical portion 7c2sb with respect to the tire width direction is preferably greater than 45°, and may be, for example, 90°. The angle made by the horizontal portion 7c2sc with respect to the tire width direction is preferably less than 45°, and may be, for example, 0°.

[0059] Alternatively, as shown in the embodiments of Figures 3 and 4, in at least one half of the tire Q (both sides in the embodiments of Figures 3 and 4), the thickness of the cap intermediate layer 7c2 may decrease substantially smoothly towards the outside in the tire width direction across the tire width region between a predetermined tire width direction position X and the tire width direction position D of the contact end TE.

[0060] As shown in the embodiment of Figure 3, in at least one half of the tire Q (both sides in the embodiment of Figure 3), the outer surface 7c2s of the cap intermediate layer 7c2 on the tire circumferential side may extend substantially linearly inward in the tire radial direction as it moves outward in the tire width direction, over a tire width direction region between a predetermined tire width direction position X and a tire width direction position D of the contact end TE.

[0061] Alternatively, as in the embodiment of Figure 4, in at least one half of the tire Q (both sides in the embodiment of Figure 4), the outer surface 7c2s of the cap intermediate layer 7c2 on the tire circumferential side may extend inward in the tire radial direction along a curved line that is convex outward in the tire radial direction as it moves outward in the tire width direction, over a tire width direction region between a predetermined tire width direction position X and the tire width direction position D of the contact end TE.

[0062] Furthermore, as shown in the embodiment of Figure 4, in at least one half of the tire Q (both sides in the embodiment of Figure 4), the outer surface 7c2s of the cap intermediate layer 7c2 on the tire circumferential side may extend in a substantially crescent shape toward the tire radially inward, substantially along a curved line that is convex outward in the tire radially direction, as it moves toward the outside in the tire width direction, over the tire width direction region between the tire equatorial plane CL and the tire width direction position D of the contact end TE.

[0063] In a tensile test conducted at room temperature of 24°C, 2% amplitude, and 50Hz, the tanδ of the cap surface layer 7c1 is greater than that of the cap intermediate layer 7c2. The difference between the tanδ of the cap surface layer 7c1 and the tanδ of the cap intermediate layer in the same tensile test may be 0.03 or greater. In this case, the cap surface layer 7c1 has higher abrasion resistance than the cap intermediate layer 7c2, and the cap intermediate layer 7c2 has higher heat resistance than the cap surface layer 7c1. This configuration of the cap layer 7c allows for a high level of both abrasion resistance and heat resistance.

[0064] In a tensile test conducted at room temperature of 24°C, 2% amplitude, and 50Hz, the tanδ of the cap surface layer 7c1 is greater than that of the cap intermediate layer 7c2. The difference between the tanδ of the cap surface layer 7c1 and the tanδ of the cap intermediate layer 7c2 in the same tensile test may be 0.06 or greater. In this case, the cap surface layer 7c1 has higher abrasion resistance than the cap intermediate layer 7c2, and the cap intermediate layer 7c2 has higher heat resistance than the cap surface layer 7c1. This configuration of the cap layer 7c allows for a high level of both abrasion resistance and heat resistance.

[0065] The tanδ of the base layer 7b in a tensile test under conditions of room temperature (24°C), 2% amplitude, and 50 Hz may be 0.03 or more lower than that of the cap intermediate layer 7c2. In this case, a higher level of both abrasion resistance and heat resistance can be achieved.

[0066] The inner end of each lug groove h (and by extension, the planned lug groove formation area hp) in the tire width direction may be at any position. For example, as shown in the examples in Figures 2 to 4, it may be located between the 3 / 8 point C and the tire width direction position D of the contact end TE, or it may be located between the 1 / 4 point B and the 3 / 8 point C.

[0067] As shown in Figures 2 to 4, in the grooved green tire R1A, each grooved recess k opens at the contact edge TE, extends inward from the contact edge TE in the tire width direction, and terminates just before reaching the tire equatorial plane CL. In a grooved raw tire R1A, the inner end of each grooved recess k in the tire width direction may be located outside the inner end of the corresponding lug groove h (and thus the planned lug groove formation area hp) in the tire width direction, as shown in the examples in Figures 2 to 4, or it may be located at the same position in the tire width direction as the inner end of the corresponding lug groove h (and thus the planned lug groove formation area hp). In a grooved green tire R1A, the inner end of each grooved recess k in the tire width direction may be located between the 3 / 8 point C and the tire width direction position D of the contact end TE, as shown in the examples in Figures 2 to 4. In a grooved raw tire R1A, the inner end of each grooved recess k in the tire radial direction may be located radially outward from the inner end of the corresponding lug groove h (and thus the planned lug groove formation area hp), as shown in the examples in Figures 2 to 4, or it may be located at the same radial position as the inner end of the corresponding lug groove h (and thus the planned lug groove formation area hp).

[0068] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is considered to be a technology that can contribute to "No. 8 - Decent Work and Economic Growth" and "No. 13 - Climate Action," among others. [Industrial applicability]

[0069] The heavy-duty tire, the green tire for heavy-duty tires, and the method for manufacturing heavy-duty tires according to the present invention can be suitably used for any type of heavy-duty tire, and are particularly suitable for tires for construction and mining vehicles (off-the-road tires). [Explanation of Symbols]

[0070] 1: Heavy-duty tires (tires), R1B: Ungrooved raw tire (raw tire), R1A: Grooved raw tire (raw tire) 1a: Tread section, 1b: Sidewall section, 1c: Bead section, 2: Tread surface, 4a: Bead core, 4b: Bead filler, 5: Carcass, 5a: Carcass ply, 6: Belt, 6a: Belt layer, 7: Tread rubber, 7c: Cap layer, 7c1: Cap surface layer, 7c1r: Cap surface rubber, 7c2: Cap intermediate layer, 7c2r: Cap intermediate layer rubber, 7c2s: Outer surface of the cap intermediate layer, 7c2sb: Longitudinal part, 7c2sc: Lateral part, 7b: Base layer, 8: Side elastic, 9: Inner liner, CL: Tire equatorial plane, TW: Contact width, TE: Contact edge A: 1 / 8 point, B: 1 / 4 point, C: 3 / 8 point, D: Position of the tire's contact edge in the tire's width direction. Q: Half of the tire Q, X: Position in the specified tire width direction, h: lug groove, hp: Area where lug grooves are planned to be formed. k: Grooved recess, m: Rubber to be removed (tread rubber portion), O: Tire rotation axis, CD: Circumferential direction of the tire, WD: Width direction of the tire, RD: Radial direction of the tire, RDO: Outer radial direction of the tire, RDI: Inner radial direction of the tire

Claims

1. The tread rubber The cap layer and A base layer is positioned on the inner circumference side of the tire, It has, The aforementioned cap layer is The surface of the cap and A cap intermediate layer is positioned on the inner circumference side of the tire, and is made of a different type of rubber than the rubber that constitutes the cap surface layer. It has, A heavy-duty tire wherein, in at least one half of the tire with respect to the tire's equatorial plane, the thickness of the intermediate cap layer between a predetermined tire widthwise position at a predetermined distance from the tire's equatorial plane and the tire widthwise position of the contact end is thinner than the thickness of the intermediate cap layer inward in the tire widthwise direction than the predetermined tire widthwise position.

2. The heavy-duty tire according to claim 1, wherein in at least one half of the tire, the predetermined tire width direction position is located between a 3 / 8 point, which is 3 / 8 times the contact width from the tire equatorial plane, and the tire width direction position of the contact end.

3. The heavy-duty tire according to claim 1, wherein in at least one half of the tire, the thickness of the cap intermediate layer decreases substantially in a stepped manner as it moves outward in the tire width direction, over a tire width region between the predetermined tire width direction position and the tire width direction position of the contact end.

4. The heavy-duty tire according to claim 1, wherein in at least one half of the tire, the outer surface of the cap intermediate layer extends inward in the tire radial direction in a substantially stepped manner as it moves outward in the tire width direction, over a tire width region between the predetermined tire width direction position and the tire width direction position of the contact end.

5. The heavy-duty tire according to claim 1, wherein in at least one half of the tire, the thickness of the cap intermediate layer decreases substantially smoothly towards the outside in the tire width direction over a tire width region between the predetermined tire width direction position and the tire width direction position of the contact end.

6. The heavy-duty tire according to claim 1, wherein in at least one half of the tire, the outer surface of the cap intermediate layer extends substantially linearly inward in the tire radial direction as it moves outward in the tire width direction, over a tire width region between the predetermined tire width direction position and the tire width direction position of the contact end.

7. The heavy-duty tire according to claim 1, wherein in at least one half of the tire, the outer surface of the cap intermediate layer extends radially inward along a curved line that is convex radially outward as it moves outward in the tire width direction, over a tire width region between the predetermined tire width direction position and the tire width direction position of the contact end, as it moves outward in the tire width direction.

8. The heavy-duty tire according to any one of claims 1 to 7, wherein the cap surface layer, the cap intermediate layer, and the base layer each extend over the entire tire widthwise region between the tire widthwise positions of a pair of contact ends.

9. The tread rubber The cap layer and A base layer is positioned on the inner circumference side of the tire, It has, The aforementioned cap layer is The surface of the cap and A cap intermediate layer is positioned on the inner circumference side of the tire, and is made of a different type of rubber than the rubber that constitutes the cap surface layer. It has, A raw tire for heavy loads, wherein, in at least one half of the tire with respect to the tire's equatorial plane, the thickness of the intermediate cap layer between a predetermined tire widthwise position at a predetermined distance from the tire's equatorial plane and the tire widthwise position of the contact end is thinner than the thickness of the intermediate cap layer inward in the tire widthwise direction than the predetermined tire widthwise position.

10. A method for manufacturing heavy-duty tires, Grooving pre-raw tire manufacturing step, Grooving step: Grooving is performed on the aforementioned ungrooved tire to obtain a grooved tire. The grooved green tire is vulcanized using a vulcanization mold to obtain a vulcanized heavy-duty tire, a vulcanization molding step, Includes, The aforementioned pre-grooving tire has a tread rubber that The cap layer and A base layer is positioned on the inner circumference side of the tire, It has, The aforementioned cap layer is The surface of the cap and A cap intermediate layer is positioned on the inner circumference side of the tire, and is made of a different type of rubber than the rubber that constitutes the cap surface layer. It has, In the aforementioned ungrooved tire, in at least one half of the tire with respect to the tire equator, the thickness of the cap intermediate layer between a predetermined tire width direction position a predetermined distance from the tire equator and the tire width direction position of the contact end is thinner than the thickness of the cap intermediate layer inward in the tire width direction from the predetermined tire width direction position. A method for manufacturing a heavy-duty tire, wherein in the grooving step, the portion of the tread rubber of the raw tire before grooving that is in a region substantially corresponding to the region in which lug grooves will be formed in the vulcanization molding step is removed by grooving.

11. The method for manufacturing a heavy-duty tire according to claim 10, wherein the tread rubber portion removed by grooving in the grooving step contains a different type of rubber from the rubber constituting the cap surface layer, with a mixing rate of 10% by mass or less.

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