Pneumatic tire

Abstract

To provide a pneumatic tire that can improve quietness while suppressing rolling resistance from increasing.SOLUTION: A pneumatic tire according to the present invention has tire oblateness of 10-65, where a thickness of a side wall part in a region in a tire radial direction between positions separated, by a distance equal to 15% of a height of a tire cross section, from a maximum width position of the tire to inside and to outside in the tire radial direction in a reference state is larger by 1.0-4 mm than a thickness of a thinnest portion of the side wall part.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, due to the increasing concern about environmental problems, the quietness of tires has been increasingly demanded. In response to this, techniques have been proposed to improve the quietness of tires by suppressing vibrations by thickening the sidewall portion or providing a protruding portion on the sidewall portion (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in consideration of environmental problems, while it is also required to improve the fuel efficiency of tires, if the thickness of the sidewall is increased, there is a risk that the rolling resistance will increase due to the increase in weight and the fuel efficiency will decrease. Further, when the thickness is partially increased by providing a protruding portion as in Patent Documents 1 and 2, although the influence on the rolling resistance can be suppressed as much as possible, there is a risk that the effect of improving the quietness will become insufficient. Thus, it has generally been difficult to achieve both an improvement in quietness and a suppression of an increase in rolling resistance.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire capable of improving quietness while suppressing an increase in rolling resistance.

Means for Solving the Problems

[0006] The gist configuration of the present invention is as follows. (1) A pneumatic tire with an aspect ratio of 10 to 65, when the pneumatic tire is mounted on an applicable rim, filled with a specified internal pressure, and in a no-load state, which is defined as the reference state, the thickness of the sidewall portion in the tire radial region between positions separated by 15% of the tire cross-sectional height from the maximum width position of the tire in the radial direction inside and outside of the tire in the reference state is 1.0 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion. The pneumatic tire is characterized by this.

[0007] In this specification, the "applicable rim" refers to an industrial standard effective in the region where the tire is produced and used. In Japan, it is the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Association), in Europe, it is the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation), and in the United States, it is the YEAR BOOK of TRA (The Tire and Rim Association, Inc.). It refers to the standard rim (Measuring Rim in the ETRTO's STANDARDS MANUAL and Design Rim in the TRA's YEAR BOOK) in the applicable size described therein or to be described in the future (that is, the above "rim" includes sizes that may be included in the above industrial standards in the future in addition to the current sizes. Examples of "sizes to be described in the future" include the sizes described as "FUTURE DEVELOPMENTS" in the 2013 edition of ETRTO). This can be done.) In the case of a size not described in the above industrial standards, it refers to a rim with a width corresponding to the bead width of the tire. Also, the "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 described in the above JATMA, etc. In the case of a size not described in the above industrial standards, the "specified internal pressure" shall refer to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Here, the "thickness of the sidewall portion" means the thickness measured in a direction perpendicular to the carcass line in the cross-section in the tire width direction. Further, the statement that the thickness of the sidewall portion in the tire radial direction region is "1.0 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion" means that the average thickness of the sidewall portion in the tire radial direction region is "1.0 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion". When a convex portion is formed in the tire radial direction region, the thickness includes the height of the convex portion.

[0008] (2) The pneumatic tire according to (1) above, wherein the thickness of the sidewall portion at the maximum tire width position is 120% to 200% of the thickness of the thinnest portion of the sidewall portion.

[0009] (3) The pneumatic tire according to (1) or (2) above, wherein a rubber member is attached to the tire radial direction region.

[0010] (4) The pneumatic tire according to (3) above, wherein the rubber member is attached to the inner surface of the tire.

[0011] (5) The pneumatic tire according to (3) above, wherein the rubber member is attached to the outer surface of the tire.

[0012] (6) The pneumatic tire according to (3) above, wherein the rubber member is disposed inside the tire.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a pneumatic tire that can improve quietness while suppressing an increase in rolling resistance.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be exemplified and described in detail with reference to the drawings.

[0016] FIG. 1 is a partial cross-sectional view in the tire width direction of a pneumatic tire according to an embodiment of the present invention. FIG. 1 shows only one half in the tire width direction with the tire equatorial plane CL as a boundary, but the other half has the same configuration. Further, FIG. 1 is a partial cross-sectional view in the tire width direction in the above reference state.

[0017] As shown in FIG. 1, this pneumatic tire (hereinafter, also simply referred to as a tire) 1 has a pair of bead portions 2, a pair of sidewall portions 6 continuous with the bead portions 2, and a tread portion 5 continuous with the pair of sidewall portions 6.

[0018] In this example, the bead portion 2 has a bead core 2a and a bead filler 2b. The bead core 2a includes, in this example, a plurality of bead wires coated with rubber around the periphery. The bead wires are formed of steel cords in this example. The bead filler 2b is made of rubber or the like and is located on the outer side in the tire radial direction of the bead core 2a. In this example, the bead filler 2b has a substantially triangular cross-sectional shape with a decreasing thickness toward the outer side in the tire radial direction. On the other hand, the bead core 2a and the bead filler 2b are not limited to the above example and can have various configurations, and it is also possible not to have the bead core 2a or the bead filler 2b.

[0019] As shown in FIG. 1, the tire 1 has a carcass 3 composed of one or more carcass plies extending toroidally across a pair of bead portions 2. The carcass 3 has a carcass main body portion 3a disposed between the bead cores 2a and a carcass folded-back portion 3b formed by folding back from the inner side in the tire width direction to the outer side in the tire width direction around the bead core 2a. In this example, the end of the carcass folded-back portion 3b is located on the inner side in the tire radial direction from the tire maximum width position, but the extending length of the carcass folded-back portion 3b from the inner side in the tire width direction to the outer side in the tire width direction can be set as appropriate. The carcass 3 can also have a structure without the carcass folded-back portion 3b, or can have a structure in which the carcass folded-back portion 3b is wound around the bead core 2a. The carcass ply can be formed by coating organic fibers with rubber.

[0020] On the outer side in the tire radial direction of the crown portion of the carcass 3, a belt 4 and tread rubber constituting the tread portion 5 are provided. The belt 4 can be constituted by, for example, a plurality of belt layers laminated in the tire radial direction. In this example, the belt 4 is an inclined belt composed of two belt layers in which the belt cords cross each other between the layers. The belt cord can be, for example, a steel cord. Note that the number of belt layers, the inclination angle of the belt cord, the width in the tire width direction of each belt layer, etc. are not particularly limited and can be set as appropriate.

[0021] The tire 1 has an inner liner (not shown) on the inner surface 8 of the tire.

[0022] Here, for the tire of the present embodiment, the tire aspect ratio is 10 to 65 (preferably 35 to 55). In addition, it is preferable that the tire has a configuration without side reinforcing rubber.

[0023] Further, as shown in FIG. 1, in the above reference state, a tire radial region between positions separated by 15% of the tire section height SH from the tire maximum width position P in the tire radial direction inside and outside is defined as R. At this time, the thickness of the sidewall portion in the tire radial region R is 1.0 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion. In this example, in the tire radial region R (only in the tire radial region R), by attaching a rubber member (a rubber sheet in this example) 7 to the surface of the sidewall portion, the thickness is made to be within the above range. Hereinafter, the operation and effect of the pneumatic tire of the present embodiment will be described.

[0024] The inventors of the present invention studied the phenomenon in which noise is generated due to the vibration of the tire, and obtained the knowledge that the tire maximum width position and its vicinity are the bellies (portions where the displacement amount of the amplitude becomes large) at 800 Hz to 1000 Hz. Then, the inventors of the present invention locally increase the thickness in the tire radial region R between positions separated by 15% of the tire section height SH (0.15×SH vertically in the drawing) from the tire maximum width position P in the tire radial direction inside and outside, thereby reducing the amplitude at 800 Hz to 1000 Hz and improving the quietness of the tire. And it was found that the increase in thickness can be made local and the increase in tire weight can be suppressed as much as possible.

[0025] If the position where the thickness is increased is outside or inside the tire radial direction than the tire radial region R, the effect of reducing the amplitude of the vibration mode cannot be sufficiently obtained, and the effect of improving the quietness of the tire cannot be sufficiently obtained. If the thickness of the sidewall portion in the tire radial region R is less than 1.0 mm greater than the thickness of the thinnest part of the sidewall portion, the effect of suppressing the above-described vibration cannot be sufficiently enhanced, and the quietness of the tire cannot be improved. On the other hand, if it is more than 4 mm thick, the thickness in the vicinity of the tire maximum width position P becomes locally too large, resulting in a large weight bias, and there is a risk of flowing or shifting during vulcanization of the tire.

[0026] And in a tire having the aspect ratio within the above range, since it is possible to make the sidewall portion relatively thin, it is particularly suitable for achieving both a reduction in rolling resistance due to thinning of the sidewall portion and a reduction in vibration and thus noise due to a local weight increase in the tire radial region R. That is, if the aspect ratio of the tire is less than 10, it becomes easy to pick up road surface vibrations, and in addition, the sidewall portion where a local weight portion can be provided becomes small, so it is difficult to obtain the sufficient effect of the invention. On the other hand, if the aspect ratio of the tire is more than 65, the weight of the tire itself becomes large, and thus the rolling resistance cannot be reduced.

[0027] For the same reason as above, it is more preferable that the thickness of the sidewall portion in the tire radial region R is 1.5 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion. Note that the tire radial width of the portion where the thickness of the sidewall portion in the tire radial region R is 1.0 to 4 mm (preferably 1.5 to 4 mm) thicker than the thickness of the thinnest part of the sidewall portion is preferably 7% or more of the tire cross-sectional height, and more preferably 10% or more. This is because the above effects can be sufficiently obtained. Also, in the tire radial region R, it is most preferable that a weight portion (protrusion) is provided in an annular shape at the maximum width position of the sidewall portion, but it may be interrupted on the circumference, and it is preferably arranged in a total of 50% or more of one circumference on the circumference.

[0028] Further, it is preferable that the thickness of the sidewall portion at the maximum tire width position P is 110% to 200% of the thickness of the thinnest portion of the sidewall portion. By setting it to 110% or more, the effect of suppressing the above-described vibration can be further enhanced, and the quietness of the tire can be further improved. On the other hand, by setting it to 200% or less, it is possible to suppress the situation where the weight at the maximum tire width position P becomes locally too large and the weight bias becomes large, and the tire flows or shifts during vulcanization.

[0029] In the tire radial region R(10%) between the positions spaced 10% of the tire cross-sectional height from the maximum tire width position P toward the inner and outer sides in the tire radial direction in the above reference state, the thickness of the sidewall portion is preferably 1.0 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion. This is because the vibration can be more effectively reduced and the quietness of the tire can be further improved. For the same reason, it is more preferable that the thickness of the sidewall portion in the tire radial region R(10%) is 1.0 to 3 mm thicker than the thickness of the thinnest portion of the sidewall portion.

[0030] FIG. 2 is a partial cross-sectional view in the tire width direction of a pneumatic tire according to a first modification. FIG. 3 is a partial cross-sectional view in the tire width direction of a pneumatic tire according to a second modification. When locally increasing the thickness in the tire radial region R (or R(10%)), as shown in FIG. 2 it is also possible to dispose the rubber member (rubber sheet) 7 inside the sidewall portion 6, or, as shown in FIG. 3, to attach the rubber member (rubber sheet) 7 to the tire inner surface 8 (either inside or outside the inner liner when having an inner liner). However, when the rubber member (rubber sheet) 7 is attached to the tire inner surface 8, the energy loss of the inner liner becomes large. Therefore, it is more preferable to attach the rubber member (rubber sheet) 7 to the tire outer surface or dispose it inside the sidewall portion (inside the sidewall rubber). In FIGS. 1 to 3, an example in which the rubber member is a rubber sheet is shown, but the rubber member in the sheet shape is not limited to this, and it can be various shapes such as a protruding shape with a semi-circular cross section or a rectangular cross section.

[0031] Here, the mass of the sidewall portion in the tire radial direction region R (or R(10%)) is preferably 0.5% to 5% of the total mass of the pneumatic tire 1, and more preferably 1.5% to 5%. By setting it to 0.5% or more (more preferably 1.5% or more), the effect of suppressing the vibration described above can be further enhanced, and the quietness of the tire can be further improved. On the other hand, by setting it to 5% or less, it is possible to suppress the situation where the weight becomes locally too large and the weight bias becomes large near the tire maximum width position P, and the tire flows or shifts during vulcanization. For the same reason, the mass of the sidewall portion in the tire radial direction region R(10%) is more preferably 1.5% to 4.5% of the total mass of the pneumatic tire, and even more preferably 1.8% or more.

[0032] In the above tire radial direction region R (or R(10%)), the thickness of the sidewall portion is preferably 5 mm to 15 mm. By setting it to 5 mm or more, the effect of suppressing vibration and improving quietness can be further enhanced. On the other hand, by setting it to 15 mm or less, an increase in weight can be suppressed as much as possible.

[0033] Incidentally, the specific gravity of the rubber member (e.g., rubber sheet) 7 is preferably 1.05 times or more, more preferably 1.1 times or more, the specific gravity of the sidewall rubber. This is because it is suitable for locally increasing the weight. On the other hand, in order to prevent the weight bias from becoming too large, the specific gravity of the rubber member (e.g., rubber sheet) 7 is preferably 2 times or less the specific gravity of the sidewall rubber. The specific gravity can be adjusted, for example, by adjusting the compounding amount of the filler. The filler is not particularly limited, and for example, silica, aluminum hydroxide, calcium carbonate, basic magnesium carbonate, clay, diatomaceous earth, recycled rubber and powdered rubber, carbon black, etc. can be used.

[0034] In the above example, the rubber member was arranged to locally increase the weight of the radial region R, but various other methods are also possible. For example, in the tire radial region R, it is also preferable to have a weight member made of metal or fiber (metal fiber or non-metal fiber). As the metal and fiber, steel (linear metal having iron as the main component (the mass of iron exceeds 50% by mass of the total mass of the metal filaments)), or it may be composed of only iron, or may contain metals other than iron, such as zinc, copper, aluminum, tin, etc. Steel, copper, and alloys containing them can also be exemplified. A plating treatment may be performed to enhance the adhesion to the rubber. Incidentally, according to the above embodiment in which the rubber member is arranged in the tire radial region R, there is an advantage that the durability against repeated deformation is high.

[0035] Here, the gauge of the tread rubber is preferably 2 to 15 mm. By setting it to 2 mm or more, the quietness can be further enhanced. On the other hand, by setting it to 15 mm or less, the rolling resistance can be reduced by weight reduction. In order to achieve both a reduction in rolling resistance and quietness at a higher level, the gauge of the tread rubber is preferably 8 mm or less and more preferably so. The "tread rubber gauge" refers to the tire radial thickness from the tread surface to the outermost reinforcing member in the tire radial direction at the tire equatorial plane in the above reference state (for example, the outermost belt layer in the tire radial direction. When a belt reinforcing layer is arranged on the outer side of the belt in the tire radial direction, it is the outermost belt reinforcing layer in the tire radial direction). However, when grooves are arranged at the tire equatorial plane, it is considered assuming there are no grooves.

[0036] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments at all.

Embodiment

[0037] (Example 1) In the above tire radial region R of a tire of size 205 / 55R16, as shown in FIG. 1, three prototypes were made by changing the weight with mass added to the surface at the maximum width position (Inventive Examples 1 to 3). Also, a conventional one without mass added at the maximum width position was prepared (Comparative Example 1). In Inventive Example 1, 55 g of mass was added, in Inventive Example 2, 105 g of mass was added, and in Inventive Example 3, 165 g of mass was added. As a result, in Inventive Examples 1, 2, and 3, the mass of the sidewall portion in the above tire radial region R became 0.5%, 1%, and 2% of the total mass of the pneumatic tire, respectively. Also, in Inventive Examples 1, 2, and 3, the thickness of the sidewall portion in the above tire radial region R became 0.5 mm, 1 mm, and 2 mm thicker than the thickness of the thinnest part of the sidewall portion, respectively.

[0038] For these tires, the vibration mode in the above tire radial region R was measured by simulation using FEM. The measurement results are shown in FIG. 4.

[0039] As shown in FIG. 4, it can be seen that in Inventive Examples 1 to 3, the amplitude in the range of 800 Hz to 1000 Hz is reduced compared to Comparative Example 1.

[0040] (Example 2) Next, the effects of the present invention were confirmed by varying the positions where the weight was increased. In Invention Example 4, a tire was prototyped with a mass of 130 g added to the maximum width position. In Invention Example 4, the mass of the sidewall portion in the tire radial region R was 1.1% of the total mass of the pneumatic tire. Also, in Invention Example 4, the thickness of the sidewall portion in the tire radial region R was 1 mm thicker than the thickness of the thinnest portion of the sidewall portion. Further, in Comparative Example 2, a mass of 130 g was added to the surface of the sidewall portion in a region outside the tire radial region R in the tire radial direction. Also, in Comparative Example 3, a mass of 130 g was added to the surface of the sidewall portion in a region inside the tire radial region R in the tire radial direction. In Comparative Example 4, a mass of 130 g was added so as to cover the entire sidewall portion.

[0041] For these tires, the vibration modes at the rubber sheet attachment positions were measured by simulation using FEM. The measurement results of Invention Example 4 and Comparative Examples 2 and 3 are shown in FIG. 5. Also, the measurement results of Invention Example 4 and Comparative Example 4 are shown in FIG. 6.

[0042] As shown in FIG. 5, it can be seen that in Invention Example 4, the amplitude in the range of 800 Hz to 1000 Hz is reduced compared to Comparative Examples 2 and 3. Also, as shown in FIG. 6, it can be seen that in Invention Example 4, the amplitude in the range of 800 Hz to 1000 Hz is reduced compared to Comparative Example 4.

[0043] Also, in Invention Examples 1 to 3, the weight increases were 0.5%, 1%, and 2% respectively, without causing excessive weight increase. When a rubber sheet corresponding to such a mass was attached no rubber flow or displacement occurred during vulcanization.

Explanation of Reference Numerals

[0044] 1: Pneumatic tire, 2: Bead portion, 3: Carcass, 4: Belt, 5: Tread portion, 6: Sidewall part, 7: Rubber member, 8: Tire inner surface

Claims

1. A pneumatic tire having a tire aspect ratio of 10 to 65, when the pneumatic tire is mounted on an application rim, filled with a specified internal pressure, and set to an unloaded state as a reference state, the thickness of the sidewall portion in the tire radial region between positions separated by 15% of the tire cross-sectional height from the tire maximum width position toward the inner and outer sides in the tire radial direction in the reference state is 1.0 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion, the gauge of the tread rubber is 2 to 8 mm, and a rubber member is attached only to the tire radial region. A pneumatic tire characterized by this.

2. The pneumatic tire according to claim 1, wherein the thickness of the sidewall portion at the tire maximum width position is 120% to 200% of the thickness of the thinnest portion of the sidewall portion.

3. The pneumatic tire according to claim 1, wherein the rubber member is attached to the inner surface of the tire.

4. The pneumatic tire according to claim 1, wherein the rubber member is attached to the outer surface of the tire.

5. The pneumatic tire according to claim 1, wherein the rubber member is disposed inside the tire.

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