Heavy duty tire

Abstract

In the heavy duty tire (1), the tread rubber (7) has a cap layer (7c) and a base layer (7b) disposed closer to the inner periphery of the tire than the cap layer, the cap layer is provided with a cap surface layer (7c1) and a cap intermediate layer (7c2), and the tan delta of the cap surface layer is greater than the tan delta of the cap intermediate layer in a tensile test under the conditions of room temperature of 24 DEG C, amplitude of 2% and 50 Hz, and the tan delta of the cap intermediate layer is greater than the tan delta of the cap surface layer. And the difference between the tan [delta] of the cap surface layer in a tensile test at room temperature of 24 DEG C, amplitude of 2% and 50 Hz and the tan [delta] of the cap intermediate layer in a tensile test at room temperature of 24 DEG C, amplitude of 2% and 50 Hz is 0.06 or more.

Description

Technical Field

[0001] The present disclosure relates to heavy-duty tires.

[0002] This application claims priority from patent application No. 2022-102135 filed in Japan on June 24, 2022, the entire contents of which are incorporated herein by reference. Background Art

[0003] There is already a heavy load tire in which the tread rubber has a cap layer and a base layer (Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-137411 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] Generally speaking, heavy-duty tires are required to have two main performance characteristics: wear resistance and heat resistance (and therefore durability). However, these performance characteristics are in a trade-off relationship, and it is not easy to achieve both.

[0009] There is room for improvement in achieving both wear resistance and heat resistance in conventional heavy load tires.

[0010] An object of the present disclosure is to provide a heavy load tire capable of achieving both wear resistance and heat resistance at a higher level.

[0011] Solutions for solving problems

[0012] The above objectives can be achieved through the following means.

[0013] [1] A heavy-duty tire, wherein:

[0014] The tread rubber has:

[0015] Caprock; and

[0016] a base layer, which is on the inner circumference side of the tire of the cover layer,

[0017] The cap layer comprises:

[0018] Cover surface layer; and

[0019] Cover the middle layer,

[0020] In a tensile test at room temperature 24° C., an amplitude of 2% and 50 Hz, the cover surface layer has a larger tan δ than the cover intermediate layer, and

[0021] The difference between tan δ of the cover surface layer in a tensile test at room temperature 24°C, amplitude 2% and 50 Hz and tan δ of the cover intermediate layer in a tensile test at room temperature 24°C, amplitude 2% and 50 Hz is 0.06 or more.

[0022] Effects of the Invention

[0023] According to the present disclosure, it is possible to provide a heavy load tire capable of achieving both wear resistance and heat resistance at a higher level. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] [ Figure 1 ] Figure 1 1 is a cross-sectional view in the tire width direction schematically illustrating a heavy load tire according to one embodiment of the present disclosure.

[0025] [ Figure 2 ] Figure 2 It's a picture. Figure 1 An enlarged view of a portion of a heavy-duty tire.

[0026] [ Figure 3 ] Figure 3 The analysis results for several tire models are provided. DETAILED DESCRIPTION

[0027] The heavy-duty tire according to the present disclosure may be suitable for use in any type of heavy-duty tire, and is particularly suitable for use in construction and mining vehicle tires (off-road tires).

[0028] Hereinafter, embodiments of a heavy load tire according to the present disclosure will be described with reference to the drawings.

[0029] In the various figures, like parts and components are designated by like reference numerals / symbols.

[0030] In this specification, for convenience, a heavy-duty tire or the like is also simply referred to as a "tire." In this specification, a tire is a pneumatic tire.

[0031] Figure 1 and Figure 2 1 is a diagram for explaining a heavy load tire 1 according to one embodiment of the present disclosure. Figure 1 1 is a cross-sectional view in the tire width direction schematically illustrating a heavy load tire according to one embodiment of the present disclosure. Figure 2 It's a picture. Figure 1 An enlarged view of a portion of a heavy-duty tire.

[0032] Figure 1 and Figure 2The heavy-duty tire 1 of the embodiment illustrated in FIG. 1 is configured as a construction and mining vehicle tire (off-road tire). However, the heavy-duty tire 1 may be configured as any type of heavy-duty tire.

[0033] Unless otherwise specified, the positions and dimensions of the various elements shall be measured under the reference condition of the tire 1 mounted on the applicable rim, filled to the specified internal pressure and without load.

[0034] In addition, when the tire is mounted on an applicable rim, filled with a specified internal pressure and loaded with a maximum load, the width of the ground contact surface in the tire width direction that contacts the road surface is referred to as the "ground contact width (TW)", and the end of the ground contact surface in the tire width direction is referred to as the "ground contact end (TE)".

[0035] As used in this specification, the term "applicable rim" refers to a standard rim of an applicable size that has been recorded or will be recorded in the future in the industry standards effective in the region where the tire is produced or used (the measurement rim in the ETRTO (European Tire and Rim Technical Organization) standard manual and the design rim in the TRA (Tire and Rim Association) yearbook). Examples of industry standards include the JATMA Yearbook of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the ETRTO Standard Manual in Europe, and the TRA Yearbook in the United States. For sizes not recorded in these industry standards, the term "applicable rim" refers to a rim having a width corresponding to the bead width of the pneumatic tire. "Applicable rim" includes current sizes and future sizes that will be recorded in the above-mentioned industry standards. An example of "sizes to be recorded in the future" may be sizes recorded as "FUTURE DEVELOPMENTS" in the 2013 edition of ETRTO.

[0036] As used in this specification, "specified internal pressure" means the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel at the applicable size and ply grade recorded in the industrial standards such as the above-mentioned JATMA Yearbook. In the case of a size not recorded in the above-mentioned industrial standards, "specified internal pressure" means the air pressure (maximum air pressure) corresponding to the maximum load capacity determined according to the vehicle on which the tire is mounted. In addition, as used in this specification, the term "maximum load" means a load corresponding to the maximum load capacity of the tire of the applicable size recorded in the above-mentioned industrial standards, or, for a size not recorded in the above-mentioned industrial standards, means a load corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted.

[0037] First, the overall structure of the tire 1 will be described.

[0038] like Figure 1As shown, the tire 1 includes 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 radial inner ends of each sidewall portion 1b. The bead portions 1c are configured so that when the tire 1 is mounted on the rim, the bead portions 1c contact the rim radially inward and outward in the tire width direction.

[0039] Furthermore, the tire 1 includes a pair of bead cores 4 a , a pair of bead fillers 4 b , a carcass 5 , a belt 6 , a tread rubber 7 , a sidewall rubber 8 , and an inner liner 9 .

[0040] Each bead core 4a is buried in the corresponding bead portion 1c. The bead core 4a includes a plurality of bead wires covered with rubber. The bead wires are suitably made of metal (eg, steel). The bead wires may be, for example, monofilaments or twisted wires.

[0041] Each bead filler 4b is located at the outer side of the corresponding bead core 4a in the tire radial direction. The bead filler 4b gradually becomes thinner toward the outer side of the tire radial direction. The bead filler 4b is made of rubber.

[0042] In general, bead fillers are sometimes referred to as "reinforcements".

[0043] The carcass 5 spans between a pair of bead cores 4a and extends in a toroidal shape. Figure 1 In the example of the embodiment, a carcass ply 5a is formed. Each carcass ply 5a contains one or more carcass cords and a coating rubber covering the carcass cords. The carcass cords may be monofilaments or twisted wires.

[0044] The carcass 5 is preferably of a radial structure, but may also be of a bias structure.

[0045] The belt 6 is arranged on the outer side in the tire radial direction relative to the crown of the carcass 5. The belt 6 includes one or more belt layers 6a (in Figure 1 In the example of the belt layer 6a, 6 layers are provided. Each belt layer 6a includes one or more belt cords and a coating rubber covering the belt cords. The belt cords may be monofilaments or twisted wires. The belt cords are most preferably made of metal (e.g., steel), but may also be made of organic fibers such as polyester, nylon, rayon, or aramid.

[0046] The tread rubber 7 is located in the tread portion 1a on the outer side of the belt 6 in the tire radial direction. The tread rubber 7 constitutes the tread 2, which is the surface of the tread portion 1a on the outer side in the tire radial direction. A tread pattern is formed on the tread 2 by grooves and / or sipes. However, for simplicity, Figure 1 The grooves and / or sipes provided on the tread 2 are omitted. Figure 2, examples of grooves g that may be provided in the tread 2 are illustrated in dotted lines for reference.

[0047] Further details of the tread rubber 7 will be described later.

[0048] The sidewall rubber 8 is located in the sidewall portion 1b. The sidewall rubber 8 constitutes the outer surface of the sidewall portion 1b in the tire width direction. The sidewall rubber 8 is located outside the tire width direction of the carcass 5. The sidewall rubber 8 is located outside the tire width direction of the bead filler 4b. The sidewall rubber 8 is formed integrally with the tread rubber 7.

[0049] The inner liner 9 is arranged on the inner side of the tire of the carcass 5, and can be laminated on the inner side of the tire of the carcass 5, for example. The inner liner 9 is made of, for example, butyl rubber having low air permeability. Butyl rubber includes, for example, butyl rubber and its derivatives, halogenated butyl rubber. The inner liner 9 can be made not only of butyl rubber, but also of other rubber compositions, resins or elastomers.

[0050] The following is a more detailed description of the tread rubber 7.

[0051] like Figure 1 and Figure 2 As shown, the tread rubber 7 has a cap layer 7c and a base layer 7b. The base layer 7b is arranged closer to the inner peripheral side of the tire than the cap layer 7c.

[0052] The cap layer 7c includes two layers: a cap surface layer 7c1 and a cap intermediate layer 7c2, and in the present embodiment, it is composed of these two layers. The cap intermediate layer 7c2 is arranged closer to the inner peripheral side of the tire than the cap surface layer 7c1. The surface of the cap surface layer 7c1 on the outer peripheral side of the tire constitutes the tread 2.

[0053] The tread rubber 7 is composed of three layers: a cap surface layer 7c1, a cap intermediate layer 7c2, and a base layer 7b.

[0054] The cap surface layer 7c1, the cap intermediate layer 7c2, and the base layer 7b are present over the entire area in the tire width direction between the tire width direction positions D of the pair of ground contact ends TE.

[0055] In the tensile test at room temperature 24°C, amplitude 2% and 50Hz, the cover surface layer 7c1 has a larger tanδ than the cover intermediate layer 7c2. The difference between the tanδ of the cover surface layer 7c1 in the tensile test at room temperature 24°C, amplitude 2% and 50Hz and the tanδ of the cover intermediate layer 7c2 in the tensile test at room temperature 24°C, amplitude 2% and 50Hz is 0.06 or more. As a result, the cover surface layer 7c1 has higher wear resistance than the cover intermediate layer 7c2, and the cover intermediate layer 7c2 has higher heat resistance than the cover surface layer 7c1.

[0056] As described above, in the tire 1, the cover layer 7c of the tread rubber 7 includes two layers: a cover surface layer 7c1 and a cover middle layer 7c2; in a tensile test at room temperature 24°C, an amplitude of 2% and 50Hz, the cover surface layer 7c1 has a larger tanδ than the cover middle layer 7c2; the difference between the tanδ of the cover surface layer 7c1 in the tensile test at room temperature 24°C, an amplitude of 2% and 50Hz and the tanδ of the cover middle layer 7c2 in the tensile test at room temperature 24°C, an amplitude of 2% and 50Hz is 0.06 or more.

[0057] Through repeated examinations and analyses, the inventors of the present disclosure newly discovered that such a configuration of the tire 1 makes it possible to have higher wear resistance than conventional tires while ensuring heat resistance (and thus durability).

[0058] In this way, according to the tire 1, a higher level of compatibility between wear resistance and heat resistance can be achieved.

[0059] Note that in the base layer 7b, even if tanδ in the tensile test at room temperature 24°C, amplitude 2% and 50Hz is 0.03 or more lower than tanδ of the cover intermediate layer 7c2, it is suitable. This makes it possible to achieve a higher level of compatibility between wear resistance and heat resistance.

[0060] Figure 3 The results of FEM analysis performed on four tire models 1 to 4 are provided. Figure 3 As shown, tire models 1 to 4 have different tire sizes. In each of tire models 1 to 4, as shown in FIG. Figure 1 and Figure 2 As shown in the example of , the tread rubber 7 has a cap layer 7c and a base layer 7b, and the cap layer 7c is composed of a cap surface layer 7c1 and a cap middle layer 7c2 (however, this does not include the case where the ratio of the thickness t7c1 of the cap surface layer 7c1 to the thickness t7c of the cap layer 7c is 0% or 100%). As the physical property values ​​used in the FEM calculation, in the tensile test at room temperature of 24°C, amplitude of 2% and 50Hz, the tanδ of the cap surface layer 7c1 is 0.25, and is made of rubber having a total filler content (total amount of carbon and silicon) of 65 parts. As the physical property values ​​used in the FEM calculation, in the tensile test at room temperature of 24°C, amplitude of 2% and 50Hz, the tanδ of the cap middle layer 7c2 is 0.14, and is made of rubber having a total filler content (total amount of carbon and silicon) of 50 parts. For tire models 1 to 4, the thickness t7c1 ( Figure 2 ) and the thickness t7c of the cap layer 7c ( Figure 2 ) ratio is almost constant.

[0061] exist Figure 3 In the graph of , the horizontal axis is the ratio (%) of the thickness t7c1 of the cover surface layer 7c1 to the thickness t7c of the cover layer 7c for each tire model. Figure 3 In the graph of FIG. 1 , the vertical axis is the relative temperature (° C.) compared to a given reference temperature, which occurs in the target analysis portion X ( Figure 2 ). Figure 2 As shown in the figure, the target analysis portion X is a portion located approximately 3.5 mm from the outermost belt layer 6a in the belt 6 on the outer peripheral side of the tire, and is located near the tire equatorial plane CL in the tire width direction. The above-mentioned reference temperature is the temperature (° C.) occurring in the portion of the tire where the target analysis portion X is located when the above-mentioned specified operation is performed on a given tire as in the past. For example, the given tire is such a tire that includes a cap layer consisting of only one layer and is made of a rubber having a tan δ of 0.19 in a tensile test under the conditions of room temperature 24° C., amplitude 2% and 50 Hz, and a total filler content (total amount of carbon and silicon) of 55 parts as the physical properties used in the FEM calculation.

[0062] The above-mentioned reference temperature can be used as an indicator of the heat resistance of the conventional tire. In addition, the relative temperature of the target analysis portion X of the tire model can be used as an indicator of the heat resistance of the tire model. If the relative temperature of the target analysis portion X is 0°C, the heat resistance of the tire model is equivalent to that of the conventional tire, and the lower the relative temperature of the target analysis portion X, the higher the heat resistance of the tire model.

[0063] As from Figure 3 It can be seen from the analysis results that the degree of heat resistance and wear resistance of the tire 1 can be adjusted by adjusting the ratio of the thickness t7c1 of the cover surface layer 7c1 to the thickness t7c of the cover layer 7c, and then adjusting the ratio of the thickness t7c1 of the cover surface layer 7c1 to the thickness t7c2 of the cover middle layer 7c2.

[0064] In this specification, "the thickness t7c of the cap layer 7c", "the thickness t7c1 of the cap surface layer 7c1" and "the thickness t7c2 of the cap intermediate layer 7c2" should be measured parallel to the tire radial direction, such as Figure 2 shown.

[0065] The ratio t7c1 / t7c of the thickness t7c1 of the cover surface layer 7c1 to the thickness t7c of the cover layer 7c, and the ratio t7c1 / t7c2 of the thickness t7c1 of the cover surface layer 7c1 to the thickness t7c2 of the cover middle layer 7c2 can be constant along the tire width direction or vary along the tire width direction between the tire width direction positions D of a pair of ground contact ends TE.

[0066] For tire 1, in the cover layer 7c, in the portion between the tire width direction positions D of a pair of ground contact ends TE (i.e., the portion from the tire width direction position D of one ground contact end TE to the tire width direction position D of the other ground contact end TE), it is suitable that the average value of the ratio of the thickness t7c1 of the cover surface layer 7c1 to the thickness t7c of the cover layer 7c is 85% or less, and more suitable that it is 80% or less.

[0067] As from Figure 3 As can be seen from the analysis results provided, this makes it easier to ensure the thickness t7c2 of the cover intermediate layer 7c2, and thus, to ensure at least approximately the same degree of heat resistance as before. Therefore, a higher level of compatibility between wear resistance and heat resistance can be achieved.

[0068] For the tire 1, in the cover layer 7c, in the portion between the tire width direction positions D of a pair of ground contact ends TE (i.e., the portion from the tire width direction position D of one ground contact end TE to the tire width direction position D of the other ground contact end TE), it is appropriate that the average value of the ratio of the thickness t7c1 of the cover surface layer 7c1 to the thickness t7c of the cover layer 7c is 60% or more, and more appropriate that it is 70% or more.

[0069] This allows the thickness t7c1 of the cover surface layer 7c1 to be increased, significantly extending the service life before the cover intermediate layer 7c2 with lower wear resistance is exposed. Therefore, a higher level of compatibility between wear resistance and heat resistance can be achieved.

[0070] Note that each groove g ( Figure 2 ) in the groove bottom of the deepest groove g (the innermost end of the groove g in the tire radial direction) is as follows Figure 2 It is suitable that the groove bottom is located in the cover layer 7c, and it is more suitable that the groove bottom is located in the cover intermediate layer 7c2. The same applies to the knife groove.

[0071] Industrial Applicability

[0072] The heavy-duty tire according to the present disclosure may be suitable for use in any type of heavy-duty tire, and is particularly suitable for use in construction and mining vehicle tires (off-road tires).

[0073] Description of Reference Numerals

[0074] 1 Heavy load tire (tire)

[0075] 1a Tread

[0076] 1b Side wall

[0077] 1c Bead

[0078] 2 tread

[0079] 4a Bead core

[0080] 4b tire bead filler

[0081] 5. Carcass

[0082] 5a Carcass ply

[0083] 6 belt harness

[0084] 6a Belt

[0085] 7. Tread rubber

[0086] 7c cap layer

[0087] 7c1 cover surface layer

[0088] 7c2 cover middle layer

[0089] 7b Base

[0090] 8 sidewall rubber

[0091] 9 Lining layer

[0092] CL Tire equatorial plane

[0093] TW Ground Width

[0094] TE Ground Terminal

[0095] A 1 / 8 point

[0096] B 1 / 4 point

[0097] C 3 / 8 points

[0098] D The tire width position of the ground contact end

[0099] X Target Analysis Section

[0100] g Groove

Claims

1. A heavy-duty tire, wherein: The tread rubber has: Cap layer; and a base layer arranged on the inner circumference of the tire of the cover layer, The cap layer comprises: Cover surface layer; and Cover the middle layer, In a tensile test at room temperature 24° C., an amplitude of 2% and 50 Hz, the cover surface layer has a larger tan δ than the cover intermediate layer, and The difference between tan δ of the cover surface layer in a tensile test at room temperature 24°C, amplitude 2% and 50 Hz and tan δ of the cover intermediate layer in a tensile test at room temperature 24°C, amplitude 2% and 50 Hz is 0.06 or more.

2. The heavy load tire according to claim 1, wherein: In a tensile test under conditions of room temperature 24° C., amplitude 2%, and 50 Hz, tan δ of the base layer is lower than tan δ of the cover intermediate layer by 0.03 or more.

3. The heavy load tire according to claim 1, wherein: In the cap layer, an average value of a ratio of a thickness of the cap surface layer to a thickness of the cap layer in a portion between tire width direction positions of a pair of ground contact ends is 85% or less.

4. The heavy load tire according to claim 1, wherein: In the cap layer, in a portion between tire width direction positions of a pair of ground contact ends, an average value of a ratio of a thickness of the cap surface layer to a thickness of the cap layer is 60% or more.

5. The heavy load tire according to claim 1, wherein: In the cap layer, in a portion between tire width direction positions of a pair of ground contact ends, an average value of a ratio of a thickness of the cap surface layer to a thickness of the cap layer is 60% to 85%.

6. The heavy load tire according to any one of claims 1 to 5, wherein: The cap surface layer, the cap intermediate layer, and the base layer are present over the entire area in the tire width direction between the tire width direction positions of a pair of ground contact ends.

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