pneumatic tires

Abstract

To improve noise performance in a pneumatic tire comprising a serration portion on an outer surface of sidewall portions.SOLUTION: A pneumatic tire comprises a tread portion 2, a pair of sidewall portions 3, a pair of bead portions 4, a carcass 6 extending between the pair of bead portions 4, and an inner rubber 10 extending between the pair of bead portions 4 on an inner side of the carcass 6. The inner rubber 10 comprises a first portion 11 extending in the tread portion 2 with a first thickness t1, and a second portion 12 extending in the pair of sidewall portions 3 with a second thickness t2. The first thickness t1 is greater than the second thickness t2. An outer surface of at least one of the pair of sidewall portions 3 comprises a serration portion 30. The serration portion 30 comprises a plurality of grooves 31 and a plurality of ridges 32. Each of the grooves 31 comprises an outer end portion 33 in the tire radial direction, and has a depth of 0.2 mm or less in the outer end portion 33.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire. [Background Art]

[0002] The following Patent Document 1 proposes a pneumatic tire including a serration region including a plurality of grooves and a plurality of ridges in a sidewall portion. The serration region helps to make small irregularities in the sidewall portion (hereinafter referred to as "bulge dent") less noticeable. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2021-54301 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In recent years, with the popularization of hybrid vehicles that use both an engine and a motor, and EV vehicles that run only on a motor, noise during vehicle travel has been significantly reduced. For this reason, there is a demand for improved noise performance even for tires provided with a serration portion on the outer surface of a sidewall portion.

[0005] The present invention has been devised in view of the actual circumstances described above, and a main object of the present invention is to improve noise performance in a pneumatic tire provided with a serration portion on the outer surface of a sidewall portion. [Means for Solving the Problem]

[0006] The present invention relates to a pneumatic tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions, a carcass extending between the pair of bead portions, and an inner rubber extending inside the carcass between the pair of bead portions, wherein the inner rubber comprises a first portion extending the tread portion with a first thickness and a second portion extending the pair of sidewall portions with a second thickness, the first thickness being greater than the second thickness, and the outer surface of at least one of the pair of sidewall portions includes a serration portion, the serration portion includes a plurality of grooves extending in the radial direction of the tire and arranged in the circumferential direction of the tire, and a plurality of ridges divided into the plurality of grooves, each of the plurality of grooves including an outer end in the radial direction of the tire, and the depth at the outer end being 0.2 mm or less. [Effects of the Invention]

[0007] The pneumatic tire of the present invention can improve noise performance by adopting the above configuration. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of a tire according to one embodiment of the present invention. [Figure 2] Figure 1 is an enlarged cross-sectional view of the tread area. [Figure 3] Figure 1 is an enlarged perspective view of the sidewall section. [Figure 4] This is an enlarged perspective view of region A in Figure 3. [Figure 5] Figure 4 is a cross-sectional view along the length of the groove. [Figure 6] This is a cross-sectional view perpendicular to the longitudinal direction of the grooves and ridges in Figure 4. [Figure 7] This is a magnified cross-sectional view of the bead area when a tire is mounted on a standard rim. [Figure 8] This is an enlarged cross-sectional view of the first end of the first part of Figure 2. [Figure 9] These are enlarged cross-sectional views of the first and second parts of another embodiment of the present invention. [Figure 10]These are enlarged cross-sectional views of the first and second parts of yet another embodiment of the present invention. [Figure 11] This is an enlarged cross-sectional view of the sidewall portion of yet another embodiment of the present invention. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Figure 1 shows a cross-sectional view of a pneumatic tire 1 (hereinafter sometimes simply referred to as "tire 1") showing one embodiment of the present invention. Figure 1 is a cross-sectional view including the axis of rotation of tire 1 in its normal state. As shown in Figure 1, tire 1 of this embodiment is suitably used, for example, as a pneumatic tire for a passenger car. However, the present invention is not limited to this embodiment and may be applied, for example, to a pneumatic tire for heavy loads.

[0010] "Normal condition" refers to the state in the case of pneumatic tires for which various standards are defined, where the tire is mounted on a normal rim, filled to the normal internal pressure, and under no load. In the case of tires for which various standards are not defined, the normal condition means the standard operating condition according to the intended use of the tire, where it is not mounted on a vehicle and under no load. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured under the normal condition. Furthermore, the dimensions of components that cannot be measured under the normal condition (for example, the internal material of tire 1) are values ​​measured with tire 1 in a state that approximates the normal condition as much as possible.

[0011] A "standard rim" is the rim defined for each tire within the standards system that the tire is based on. For example, it is the "standard rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0012] "Normal internal pressure" refers to the air pressure specified for each tire by the relevant standards in the standard system that includes the standards on which the tire is based. For JATMA, it is the "maximum air pressure"; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; for ETRTO, it is "INFLATION PRESSURE".

[0013] The tire 1 includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portions 3 are connected to the outer side of the tread portion 2 in the tire axial direction and extend in the tire radial direction. The bead portions 4 are connected to the inner side of the sidewall portions 3 in the tire radial direction. Further, the tire 1 includes a carcass 6 and an inner rubber 10. The carcass 6 extends between the pair of bead portions 4. In other words, the carcass 6 extends from one bead portion 4, through one sidewall portion 3, the tread portion 2, and the other sidewall portion 3, to the other bead portion 4. The inner rubber 10 is arranged inside the carcass 6 and extends between the pair of bead portions 4. Thereby, the inner rubber 10 forms the tire inner cavity surface 1A. The inner rubber 10 is made of vulcanized rubber and is different from a sealant for puncture prevention.

[0014] The carcass 6 is composed of, for example, one carcass ply 6A. The carcass ply 6A includes, for example, a main body portion 6a and a turned-up portion 6b. The main body portion 6a extends between the pair of bead portions 4, for example. The turned-up portion 6b is connected to the main body portion 6a, for example, and is turned up from the inner side to the outer side in the tire axial direction around the bead core 5.

[0015] The carcass ply 6A includes a plurality of carcass cords and a topping rubber that covers these cords (not shown). For the carcass cords, organic fiber cords such as aramid and rayon are used, for example. It is desirable that the carcass cords are arranged at an angle of 70 to 90° with respect to the tire equator C, for example.

[0016] FIG. 2 shows an enlarged cross-sectional view of the tread portion 2 of FIG. 1. As shown in FIG. 2, the tread portion 2 of the present embodiment includes, for example, a belt layer 7 and a band layer 8 disposed radially outward of a carcass 6 in the tire radial direction. However, the tread portion 2 is not limited to such an embodiment. The belt layer 7 includes a first belt ply 7A adjacent to the carcass 6, and a second belt ply 7B disposed radially outward of the first belt ply 7A in the tire radial direction. Each of the first belt ply 7A and the second belt ply 7B includes a plurality of belt cords arranged at an angle of 15 to 45° with respect to the tire circumferential direction, and a topping rubber covering these belt cords. The belt cords of the first belt ply 7A and the belt cords of the second belt ply 7B are inclined in directions opposite to each other with respect to the tire circumferential direction. This effectively reinforces the tread portion 2.

[0017] It is preferable that the axial length of the second belt ply 7B in the tire axial direction is smaller than the axial length of the first belt ply 7A in the tire axial direction. Accordingly, the outer end 7b of the second belt ply 7B in the tire axial direction is positioned inward in the tire axial direction relative to the outer end 7a of the first belt ply 7A in the tire axial direction.

[0018] The band layer 8 is composed of, for example, one band ply 8A. The band ply 8A includes, for example, a band cord arranged at an angle of 5° or less with respect to the tire circumferential direction, and a topping rubber covering the band cord. The band layer 8 of the present embodiment is disposed so as to cover the entire belt layer 7.

[0019] The tread portion 2 has a ground contact surface 2s. The ground contact surface 2s of the tread portion 2 corresponds to the surface between a first tread end T1 and a second tread end T2 among the outer surface of the tread portion 2. The first tread end T1 and the second tread end T2 each correspond to the outermost ground contact position in the tire axial direction when 70% of the regular load is applied to the tire 1 in the regular state and the tread portion 2 is in contact with a flat surface at a camber angle of 0°.

[0020] "Regular load" refers to the load specified for each tire within the standard system, including the standard on which the tire is based, in the case of pneumatic tires for which various standards are defined. For example, it is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. For tires for which no various standards are defined, "regular load" refers to the maximum load that can be applied when using the tire, in accordance with the above standards.

[0021] In this embodiment, the tire 1 has a specified orientation for mounting on a vehicle. As a result, the first tread end T1 is located on the outside of the vehicle when mounted, and the second tread end T2 is located on the inside of the vehicle when mounted. The orientation for mounting on a vehicle is indicated, for example, by letters or symbols on the outer surface of the sidewall portion 3 (shown in Figure 1). However, the tire 1 of the present invention is not limited to this configuration, and may also be designed without specifying an orientation for mounting on a vehicle.

[0022] As shown in Figure 2, the tread portion 2 of this embodiment includes a plurality of circumferential grooves 20 that extend continuously in the circumferential direction of the tire on the contact surface 2s, and a plurality of land portions 25 divided by the plurality of circumferential grooves 20. In the tire 1 of this embodiment, the tread portion 2 is divided into five land portions 25 by four circumferential grooves 20. However, the present invention is not limited to this embodiment.

[0023] The multiple circumferential grooves 20 include a first shoulder circumferential groove 21, a second shoulder circumferential groove 22, a first crown circumferential groove 23, and a second crown circumferential groove 24. The first shoulder circumferential groove 21 is provided between the first tread edge T1 and the tire equator C, and in this embodiment, it is positioned furthest towards the first tread edge T1 among the multiple circumferential grooves 20. The second shoulder circumferential groove 22 is provided between the second tread edge T2 and the tire equator C, and in this embodiment, it is positioned furthest towards the second tread edge T2 among the multiple circumferential grooves 20. The first crown circumferential groove 23 is provided between the first shoulder circumferential groove 21 and the tire equator C. The second crown circumferential groove 24 is provided between the second shoulder circumferential groove 22 and the tire equator C.

[0024] The axial distance L1 from the tire equator C to the groove centerline of the first shoulder circumferential groove 21 or the second shoulder circumferential groove 22 is preferably, for example, 25% to 35% of the tread width TW. The axial distance L2 from the tire equator C to the groove centerline of the first crown circumferential groove 23 or the second crown circumferential groove 24 is preferably, for example, 5% to 15% of the tread width TW. The tread width TW is the axial distance from the first tread end T1 to the second tread end T2 in the normal state.

[0025] In this embodiment, each circumferential groove 20 extends linearly parallel to the tire's circumferential direction (not shown). Each circumferential groove 20 may also extend in a wavy pattern, for example.

[0026] The groove width of each circumferential groove 20 should preferably be at least 3 mm. Furthermore, the groove width of each circumferential groove 20 should preferably be, for example, 4.0% to 8.5% of the tread width TW. The sum of the groove widths of multiple circumferential grooves 20 should preferably be, for example, 20% to 30% of the tread width TW, and more preferably 20% to 25%. This reduces external noise while improving handling stability on dry surfaces.

[0027] The depth of each circumferential groove 20 is preferably, for example, 5 to 10 mm, in the case of pneumatic tires for passenger cars.

[0028] As shown in Figure 1, the inner rubber 10 includes a first portion 11 and a second portion 12. The first portion 11 extends the tread portion 2 with a first thickness t1. The second portion 12 extends a pair of sidewall portions 3 with a second thickness t2. Note that the first thickness t1 and the second thickness t2 refer to the thickness from the inner surface 6i of the carcass 6 to the inner surface 1A of the tire, and do not include the topping rubber of the carcass ply 6A.

[0029] In this invention, the first thickness t1 is greater than the second thickness t2. Here, the statement that the first thickness t1 is greater than the second thickness t2 means that the average value of the first thickness t1 is greater than the average value of the second thickness t2. The average value of the first thickness t1 corresponds to the value obtained by dividing the cross-sectional area of ​​the first portion 11 in the tire meridian section by the length of the first portion 11 along the inner surface 1i of the tire. The same applies to the average value of the second thickness t2. In a preferred embodiment, in this embodiment, the above-described thickness relationship is maintained over the entire circumference of the tire. However, the present invention is not limited to this embodiment.

[0030] Figure 3 shows an enlarged perspective view of the outer surface of the sidewall portion 3. As shown in Figure 3, in the present invention, at least one outer surface of a pair of sidewall portions 3 includes the serration portion 30. In this embodiment, both outer surfaces of the pair of sidewall portions 3 include the serration portion 30. In Figure 3, dots are marked in the area where the serration portion 30 is located. The serration portion 30 occupies at least a portion of the outer surface of the sidewall portion 3. The serration portion 30 may be arranged intermittently in the circumferential direction of the tire, or it may be arranged continuously around the entire circumference of the tire.

[0031] Figure 4 shows an enlarged perspective view of area A in Figure 3. In Figure 4, arrow A1 corresponds to the tire radial direction, and arrow A2 corresponds to the tire circumferential direction. As shown in Figure 4, the serration section 30 includes a plurality of grooves 31 extending in the tire radial direction and aligned in the tire circumferential direction, and a plurality of ridges 32 divided into the plurality of grooves 31. Each ridge 32 is formed between two adjacent grooves 31 and extends in a ridge-like manner. Note that a groove 31 extending in the tire radial direction means that the maximum angle of the center line of the groove 31 with respect to the tire radial direction is less than 45°.

[0032] Such serrated sections 30 help to make the bulge dents in the sidewall section 3, which are unavoidable in tire manufacturing, less noticeable. Hereafter, this effect may be referred to as "improved appearance." On the other hand, the serrated sections 30 tend to generate noise (wind noise) when the vehicle is in motion.

[0033] Figure 5 shows a cross-sectional view of the groove 31 of the serration section 30 along its length. As shown in Figure 5, each of the multiple grooves 31 includes an outer end 33 and an inner end 34 in the tire radial direction. The outer end 33 is the end of the groove 31 on the tread section 2 (shown in Figure 1) side, and the inner end 34 is the end of the groove 31 on the bead section 4 (shown in Figure 1) side. In this embodiment, the outer end 33 and inner end 34 each have an inner wall 31a extending in the depth direction of the groove 31. In the present invention, each of the multiple grooves 31 has a depth d1 of 0.2 mm or less at the outer end 33.

[0034] The present invention can improve noise performance by having a large first thickness t1 (shown in Figure 1) of the first portion 11 of the inner rubber 10, and by defining the depth of the multiple grooves 31 at their outer ends 33. The reason for this is as follows.

[0035] Generally, when serrations are provided on the sidewall, noise (wind noise) tends to be generated due to friction between the air and the serrations during tire movement. Furthermore, the outer ends of the grooves constituting the serrations in the radial direction of the tire experience a higher air velocity during tire movement compared to other parts of the grooves, making them more prone to generating the aforementioned noise. In this invention, by setting the depth of the outer end 33 of the grooves 31 constituting the serrations 30 to 0.2 mm or less, the aforementioned noise can be reduced, thereby reducing both external and internal vehicle noise.

[0036] Furthermore, as described above, the first thickness t1 (shown in Figure 1) of the first portion 11 of the tire 1 of the present invention is large, allowing the tread portion 2 to effectively absorb vibrations from the road surface, thereby further reducing in-vehicle noise. For these reasons, the tire 1 of the present invention can exhibit excellent noise performance.

[0037] The configuration of this embodiment will be described in more detail below. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-described effects even without the configurations described below. Furthermore, even if any one of the configurations described below is applied individually to a tire of the present invention having the above-described features, an improvement in performance corresponding to each configuration can be expected. Moreover, if several of the configurations described below are applied in combination, a combined improvement in performance corresponding to each configuration can be expected.

[0038] As shown in Figure 4, the grooves 31 and ridges 32 of the serrated portion 30 extend, for example, in a straight line. The grooves 31 and ridges 32 of the serrated portion 30 extend at an angle of preferably 15° or less, and more preferably 5° or less, with respect to the tire radial direction. However, the present invention is not limited to such embodiments.

[0039] As shown in Figure 5, it is desirable that the depth of the groove 31 decreases from the inner end 34 to the outer end 33. In the desirable embodiment, the depth of the groove 31 decreases continuously. Therefore, the depth d2 of the inner end 34 constitutes the maximum depth of the groove 31. A serrated section 30 having such grooves 31 can improve both appearance performance and noise performance in a balanced manner. Furthermore, a serrated section 30 composed of such grooves 31 also helps to reduce the air resistance of the tire.

[0040] The depth d2 of the inner end portion 34 is, for example, 0.3 mm or more. Furthermore, the depth d2 of the inner end portion 34 is preferably 1.0 mm or less, more preferably 0.8 mm or less, and even more preferably 0.5 mm or less. Also, the depth d2 of the inner end portion 34 is preferably 1.5 times or more, more preferably 3.0 times or more, even more preferably 5.0 times or more, preferably 10.0 times or less, more preferably 9.0 times or less, and even more preferably 8.0 times or less of the depth d1 of the outer end portion 33. A groove 31 having such an outer end portion 33 and inner end portion 34 can improve appearance performance and noise performance in a well-balanced manner.

[0041] In a more desirable embodiment, the d2 of the inner end portion 34 is smaller than the difference between the average value of the first thickness t1 (shown in Figure 1) of the first portion 11 of the inner rubber 10 and the average value of the second thickness t2 (shown in Figure 1) of the second portion 12. As a result, the vibration absorption capacity of the tread portion 2 becomes sufficiently large compared to the noise generated by the serration portion 30, and noise performance can be further improved.

[0042] Figure 6 shows cross-sectional views perpendicular to the longitudinal direction of multiple grooves 31 and ridges 32. As shown in Figure 6, the groove width W1 of the grooves 31 is, for example, 0.6 to 1.8 mm. This improves both appearance performance and noise performance in a balanced manner.

[0043] The cross-sectional shape of the ridge 32 is, for example, triangular. However, the cross-sectional shape of the ridge 32 is not limited to this form, and various forms such as trapezoidal or semicircular shapes can be adopted. The apex angle θ1 of the ridge 32 is, for example, 60 to 90°.

[0044] As shown in Figure 3, the outer surface of the sidewall portion 3 includes at least one mark portion 35 containing at least one letter, figure, or symbol. In Figure 3, an example of a mark portion 35 is shown, consisting of the letters "ABC". In this embodiment, the mark portion 35 is located inside the serrated portion 30. It is desirable that this mark portion 35 is composed of fine grooves 36 with a depth smaller than the inner end portion 34 of the groove 31 (shown in Figure 5). Specifically, the depth of the fine grooves 36 is, for example, 0.2 to 0.8 mm. This creates a contrast between the mark portion 35 and the serrated portion 30, which can improve the visibility of the mark portion 35.

[0045] The outer surface of the sidewall portion 3 may have a stepped portion 38 that extends in the circumferential direction of the tire and has a minute height in the direction normal to the outer surface of the tire. This stepped portion 38 corresponds to the split position between the tread segment and the side plate during vulcanization molding. In Figure 3, this step is shown with a thin line, and the height that appears in the cross-section is omitted. It is desirable that the height of this stepped portion 38 be 0.7 mm or less. This reduces the air resistance generated by this stepped portion 38, and in addition to improving noise performance, improvements in fuel efficiency can be expected.

[0046] In another embodiment, the stepped portion 38 may be located at the boundary portion 39 between the serrated portion 30 and the other portion. This can further improve the appearance of the sidewall portion 3.

[0047] Figure 7 shows an enlarged view of the bead portion 4 in its normal state when the tire 1 is mounted on a normal rim R. As shown in Figure 7, at least one of the pair of bead portions 4 in this embodiment includes a rim guard 40. In a preferred embodiment, both of the pair of bead portions 4 include a rim guard 40. The rim guard 40 is a triangular-shaped rubber member that protrudes outward in the tire axial direction from the carcass 6. The rim guard 40 effectively prevents the rim flange Rf from contacting a curb or the like when the tire is running.

[0048] In this embodiment, the tire radial distance L9 from the outer edge of the rim flange Rf of the regular rim R in the tire radial direction to the vertex 40a of the rim guard 40 in the tire axial direction is 1.0 to 10.0 mm. This protects the rim flange Rf while reducing air turbulence between the rim guard 40 and the rim flange Rf, potentially improving noise performance.

[0049] As shown in Figure 2, the first portion 11 includes a first end 13 on the first tread end T1 side and a second end 14 on the second tread end T2 side. The first end 13 has a first thickness t1 that continuously decreases toward the outer end 11a on the first tread end T1 side of the first portion 11. The second end 14 has a first thickness t1 that continuously decreases toward the outer end 11b on the second tread end T2 side of the first portion 11. In this embodiment, the position where the above-described decrease in the first thickness t1 ends corresponds to the outer end 11a in the tire axial direction of the first portion 11.

[0050] From the viewpoint of reliably reducing in-vehicle noise, the outer end 11a of the first portion 11 of this embodiment on the first tread end T1 side is located, for example, on the first tread end T1 side of the first crown circumferential groove 23, and more preferably on the first tread end T1 side of the first shoulder circumferential groove 21.

[0051] Figure 8 shows an enlarged cross-sectional view of the first end 13 of the first portion 11. As shown in Figure 8, it is desirable that the outer end 11a of the first portion 11 on the first tread end T1 side be at the same position in the tire axial direction as the outer end 7b of the second belt ply 7B, or that it be located inward in the tire axial direction than the outer end 7b of the second belt ply 7B. In a more desirable embodiment, the distance L3 in the tire axial direction between the outer end 11a of the first portion 11 and the outer end 7b of the second belt ply 7B is set to 10 mm or less. This ensures sufficient length of the first portion 11 in the tire axial direction, while the deformation around the outer end 11a of the first portion 11 during tire running can be suppressed by the belt layer 7, and consequently, the peeling of the inner rubber 10 around the outer end 11a can be suppressed.

[0052] Furthermore, the first end portion 13 is connected to a portion that extends with a constant first thickness t1 on the tire equator C (shown in Figure 1). The length L4 of the first end portion 13 in the tire axial direction is 2.0% to 4.0% of the tread width TW (shown in Figure 1). This prevents abrupt changes in the thickness of the inner rubber 10 and suppresses damage such as delamination of the inner rubber 10.

[0053] As shown in Figure 2, the first portion 11 has the same configuration on the second tread end T2 side as on the first tread end T1 side. That is, the outer end 11b of the first portion 11 on the second tread end T2 side is located, for example, on the second tread end T2 side of the second crown circumferential groove 24, and more preferably on the second tread end T2 side of the second shoulder circumferential groove 22. Furthermore, it is desirable that the outer end 11b of the first portion 11 on the second tread end T2 side is in the same position in the tire axial direction as the outer end 7b of the second belt ply 7B in the tire axial direction, or that it is located inward in the tire axial direction than the outer end 7b of the second belt ply 7B. Also, the distance in the tire axial direction between the outer end 11b of the first portion 11 and the outer end 7b of the second belt ply 7B is 10 mm or less. The second end 14 also has the same configuration as the first end 13.

[0054] With the outer ends 11a and 11b of the first part 11 arranged as described above, it is desirable that the axial length L5 of the first part 11 in this embodiment be 90% to 110% of the tread width TW. This makes it possible to reliably reduce in-vehicle noise while suppressing an increase in tire weight.

[0055] In this embodiment, the first portion 11 has a first length L6 from the tire equator C to the outer end 11a on the first tread end T1 side and a second length L7 from the tire equator C to the outer end 11b on the second tread end T2 side that are substantially the same. More specifically, the difference between the first length L6 and the second length L7 is 5% or less of the first length L6. This improves the uniformity of the tire. In another embodiment, for example, the second length L7 may be greater than the first length L6. Specifically, the second length L7 is 105% to 110% of the first length L6. In such an embodiment, the length of the first portion 11 is sufficiently secured on the second tread end T2 side, which is on the inside of the vehicle when mounted, so that in-vehicle noise can be further reduced.

[0056] The first portion 11 extends between the first end 13 and the second end 14 with a constant first thickness t1. As a result, the first thickness t1 is substantially the same at the tire equator C and at a position on the first tread end T1 side of the first shoulder circumferential groove 21. In a preferred embodiment, the first thickness t1 is substantially the same from the tire equator C to a position beyond the first shoulder circumferential groove 21. Note that "substantially the same" means that unavoidable errors in rubber products such as tires are permissible, and includes embodiments in which the difference between the maximum and minimum thickness is 5% or less of the maximum value.

[0057] The first portion 11 may have a region extending with a constant first thickness t1 to the first tread edge T1. In other words, the first thickness t1 may be substantially the same from the position of the tire equator C to the position of the first tread edge T1 (an imaginary line extending parallel to the tire radial direction through the first tread edge T1). In this case, the outer edge 11a of the first portion 11 is located outward in the tire axial direction from the first tread edge T1. Such an embodiment can further reduce in-vehicle noise.

[0058] It is desirable that the first portion 11 has the same configuration as described above between the tire equator C and the second tread edge T2. That is, the first thickness t1 is substantially the same at the position of the tire equator C and at a position on the second tread edge T2 side of the second shoulder circumferential groove 22. In a preferred embodiment, the first thickness t1 is substantially the same from the position of the tire equator C to a position beyond the second shoulder circumferential groove 22. In another embodiment, the first portion 11 may have a region extending with a constant first thickness t1 that extends to the second tread edge T2.

[0059] The average value of the first thickness t1 is preferably 1.5 to 3.5 times the average value of the second thickness t2 (shown in Figure 1, and the same applies hereafter). Specifically, the average value of the first thickness t1 is preferably 1.5 times or more, more preferably 1.75 times or more, even more preferably 1.9 times or more, preferably 3.5 times or less, more preferably 2.7 times or less, and even more preferably 2.2 times or less of the average value of the second thickness t2. This makes it possible to reliably reduce in-vehicle noise while suppressing the weight increase of tire 1.

[0060] From a similar viewpoint, the average value of the first thickness t1 is preferably 2.0 mm or more, more preferably 2.5 mm or more, preferably 4.5 mm or less, more preferably 4.0 mm or less, and even more preferably 3.5 mm or less. On the other hand, the average value of the second thickness t2 is, for example, greater than 0.5 mm and less than 2.0 mm. In a preferred embodiment, the average value of the second thickness t2 is 1.0 to 1.5 mm. In this embodiment, the second part 12 extends from the first part 11 to the bead part 4 (shown in Figure 1), and the second thickness t2 is constant throughout the entire part. However, the second part 12 is not limited to this embodiment.

[0061] As shown in Figure 2, the first portion 11 and the second portion 12 of the inner rubber 10 are formed of an air-impermeable rubber material. For example, butyl-based or halogenated butyl-based rubber materials may be used as the rubber material. In this embodiment, the first portion 11 and the second portion 12 are formed of the same rubber material.

[0062] However, the present invention is not limited to these embodiments. Figure 9 shows enlarged cross-sectional views of the first part 11 and the second part 12 of another embodiment of the present invention. As shown in Figure 9, the first part 11 of the inner rubber 10 of this embodiment includes an inner liner layer 16 made of an air-impermeable rubber material (hereinafter referred to as the first rubber material) and an additional layer 17 disposed between the inner liner layer 16 and the carcass 6. This additional layer 17 is made of a second rubber material different from the first rubber material. For example, an air-permeable rubber material may be used as the second rubber material. That is, the first part 11 of this embodiment is formed by combining an air-impermeable rubber material and an air-permeable rubber material.

[0063] In this embodiment, the inclusion of an additional layer 17 in the first portion 11 can improve various performance aspects. For example, the second rubber material constituting the additional layer 17 may be a rubber material with a larger loss tangent tanδ than the first rubber material constituting the inner liner layer 16. In such an embodiment, the tread portion 2 can absorb vibrations from the road surface even more effectively, further reducing in-vehicle noise. The loss tangent tanδ is measured using a viscoelastic spectrometer under the following conditions, in accordance with the provisions of JIS-K6394. Initial distortion: 5% Amplitude: ±1% Frequency: 10Hz Deformation mode: Tension Measurement temperature: 70℃

[0064] The placement of the additional layer 17 is not limited to the configuration shown in Figure 9. Figure 10 shows enlarged cross-sectional views of the first part 11 and the second part 12 of yet another embodiment of the present invention. As shown in Figure 10, the additional layer 17 may be positioned radially inward of the inner liner layer 16. Alternatively, the additional layer 17 may constitute a part of the inner surface 1A of the tire.

[0065] Furthermore, as shown in Figures 9 and 10, even in the configuration in which an additional layer 17 is included in the first portion 11 of the inner rubber 10, the first thickness t1 corresponds to the thickness from the inner surface 6i of the carcass 6 in the tread portion 2 to the inner surface 1A of the tire.

[0066] Figure 11 shows an enlarged cross-sectional view of the sidewall portion 3 of another embodiment of the present invention. As shown in Figure 11, the second portion 12 of this embodiment includes an inner liner layer 16 made of a first rubber material that is air-impermeable, and an intermediate layer 18 disposed between the inner liner layer 16 and the carcass 6. In Figure 11, the intermediate layer 18 is dotted. The intermediate layer 18 is made of a rubber material different from the first rubber material. The intermediate layer 18 may be made of the same second rubber material as the additional layer 17 of the first portion 11 described in Figures 9 and 10. By including such an intermediate layer 18 in the second portion 12, the transmission of vibrations generated in the tread portion 2 to the vehicle side can be further suppressed. The intermediate layer 18 may be made of a rubber material further different from the first rubber material and the second rubber material.

[0067] The intermediate layer 18 overlaps, for example, with the band layer 8 in the tire axial direction. In a preferred embodiment, the intermediate layer 18 overlaps with the belt layer 7 in the tire axial direction. The intermediate layer 18 may also be connected to the first portion 11 of the inner rubber 10. Furthermore, it is preferable that the intermediate layer 18 extends radially inward from the radially outer end of the folded portion 6b of the carcass 6. Such an intermediate layer 18 helps to further reduce in-vehicle noise.

[0068] Although a tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiments described above and can be implemented in various modified forms.

[0069] [Note] The present invention includes the following embodiments.

[0070] [Invention 1] It is a pneumatic tire, The tread section and A pair of sidewall sections, A pair of bead sections, A carcass extending between the pair of bead portions, The carcass includes an inner rubber extending between the pair of bead portions inside the carcass, The inner rubber includes a first portion extending the tread portion with a first thickness and a second portion extending the pair of sidewall portions with a second thickness. The first thickness is greater than the second thickness. At least one of the pair of sidewall portions has an outer surface including a serrated portion. The serration portion includes a plurality of grooves extending in the radial direction of the tire and arranged in the circumferential direction of the tire, and a plurality of ridges divided into the plurality of grooves. Each of the aforementioned multiple grooves includes an outer end in the radial direction of the tire, and the depth at the outer end is 0.2 mm or less. Pneumatic tires. [Invention 2] The pneumatic tire according to the present invention 1, wherein the plurality of grooves include inner ends in the radial direction of the tire, and the depth decreases from the inner ends to the outer ends. [Invention 3] The pneumatic tire according to the present invention, wherein the depth at the inner end is 0.3 to 1.0 mm. [4th Invention] The pneumatic tire according to the present invention, wherein the depth at the inner end is 5.0 to 8.0 times the depth at the outer end. [5th ​​Invention] The outer surface of the sidewall portion includes at least one mark portion comprising at least one letter, figure, or symbol, The pneumatic tire according to any one of claims 1 to 4 of the present invention, wherein the mark portion is composed of fine grooves having a depth smaller than the inner end of the groove. [Invention 6] The pneumatic tire according to the present invention, wherein the depth of the aforementioned fine grooves is 0.2 to 0.8 mm. [7th Invention] A stepped portion is formed on the outer surface of the sidewall portion, having a height in the direction normal to the outer surface of the tire and extending in the circumferential direction of the tire. The pneumatic tire according to any one of claims 1 to 6 of the present invention, wherein the height of the stepped portion is 0.7 mm or less. [8th Invention] At least one of the pair of bead portions includes a rim guard that protrudes outward in the tire axial direction from the carcass, When the aforementioned pneumatic tire is mounted on a standard rim and filled to the standard internal pressure, in an unloaded, standard state, The pneumatic tire according to any one of claims 1 to 7 of the present invention, wherein the distance in the tire radial direction from the outer end of the rim flange of the regular rim in the tire radial direction to the vertex of the rim guard in the tire axial direction is 1.0 to 10.0 mm. [Invention 9] The pneumatic tire according to any one of claims 1 to 8 of the present invention, wherein the first thickness is 1.5 to 3.5 times the second thickness. [Invention 10] The first thickness is 2.0 to 4.5 mm, the pneumatic tire according to any one of claims 1 to 9 of the present invention. [Explanation of Symbols]

[0071] 2 Tread section 3. Sidewall section 4. Bead section 6 Carcass 10 Inner rubber 11 Part 1 12 Part 2 30 Serrated section 31 grooves 32 Ridge 33 Outer end t1 First thickness t2 Second thickness

Claims

1. It is a pneumatic tire, The tread section and A pair of sidewall sections, A pair of bead sections, A carcass extending between the pair of bead portions, The carcass includes an inner rubber extending between the pair of bead portions inside the carcass, The inner rubber includes a first portion extending the tread portion with a first thickness and a second portion extending the pair of sidewall portions with a second thickness. The first thickness is greater than the second thickness. At least one of the pair of sidewall portions has an outer surface including a serrated portion. The serration portion includes a plurality of grooves extending in the radial direction of the tire and arranged in the circumferential direction of the tire, and a plurality of ridges divided into the plurality of grooves. Each of the aforementioned plurality of grooves includes an outer end in the radial direction of the tire, and the depth at the outer end is 0.2 mm or less. Pneumatic tires.

2. The pneumatic tire according to claim 1, wherein the plurality of grooves include inner ends in the radial direction of the tire, and the depth decreases from the inner ends to the outer ends.

3. The pneumatic tire according to claim 2, wherein the depth at the inner end is 0.3 to 1.0 mm.

4. The pneumatic tire according to claim 3, wherein the depth at the inner end is 5.0 to 8.0 times the depth at the outer end.

5. The outer surface of the sidewall portion includes at least one mark portion which includes at least one letter, figure, or symbol. The pneumatic tire according to claim 1, wherein the mark portion is composed of fine grooves having a depth smaller than the depth of the inner end of the groove in the tire radial direction.

6. The pneumatic tire according to claim 5, wherein the depth of the fine grooves is 0.2 to 0.8 mm.

7. A stepped portion is formed on the outer surface of the sidewall portion, having a height in the direction normal to the outer surface of the tire and extending in the circumferential direction of the tire. The pneumatic tire according to claim 1 or 2, wherein the height of the stepped portion is 0.7 mm or less.

8. At least one of the pair of bead portions includes a rim guard that protrudes outward in the tire axial direction from the carcass, When the aforementioned pneumatic tire is mounted on a standard rim and filled to the standard internal pressure, in an unloaded, standard state, The pneumatic tire according to claim 1 or 2, wherein the distance in the tire radial direction from the outer end of the rim flange of the regular rim in the tire radial direction to the vertex of the rim guard in the tire axial direction is 1.0 to 10.0 mm.

9. The pneumatic tire according to claim 1 or 2, wherein the first thickness is 1.5 to 3.5 times the second thickness.

10. The pneumatic tire according to claim 1 or 2, wherein the first thickness is 2.0 to 4.5 mm.

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