Pneumatic tire

Abstract

To provide a pneumatic tire that can improve quietness while suppressing rolling resistance from increasing.SOLUTION: In a pneumatic tire according to the present invention, mass of a side wall part in a regions 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 equal to 1.5%-5% of total mass of the pneumatic tire.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, such as thickening the sidewall portion or providing protrusions 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, increasing the thickness of the sidewall may increase the rolling resistance due to the increase in weight and thus reduce the fuel efficiency. In addition, when the thickness is partially increased by providing protrusions 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, When the pneumatic tire is mounted on an applicable rim, filled with a specified internal pressure, and set to an unloaded state as a reference state, A pneumatic tire, characterized in that the mass 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 in the radial direction inside and outside of the tire in the reference state is 1.5% to 5% of the total mass of the pneumatic tire.

[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.), etc. It refers to the standard rim (Measuring Rim in the ETRTO STANDARDS MANUAL, Design Rim in the TRA YEAR BOOK) in the applicable size described 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 sizes described as "FUTURE DEVELOPMENTS" in the 2013 edition of ETRTO). 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.

[0008] (2) In the tire radial region between positions that are each 10% of the tire cross-sectional height away from the tire maximum width position in the radial inner and outer directions in the reference state, the mass of the sidewall portion is 1.5% to 5% of the total mass of the pneumatic tire, the pneumatic tire according to (1) above.

[0009] (3) In the tire radial region, a rubber member is disposed, the pneumatic tire according to (1) or (2) above.

[0010] (4) The specific gravity of the rubber member is 1.05 times or more the specific gravity of the sidewall rubber, the pneumatic tire according to (3) above.

[0011] (5) In the tire radial region, it has a weight member made of metal or fiber, the pneumatic tire according to (1) or (2) above.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a pneumatic tire capable of improving quietness while suppressing an increase in rolling resistance.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be exemplified and described in detail with reference to the drawings.

[0015] FIG. 1 is a partial cross-sectional view of a pneumatic tire according to an embodiment of the present invention in the tire width direction. 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.

[0016] 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.

[0017] 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 whose peripheries are covered with rubber. The bead wire is formed of a steel cord 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 thickness decreasing 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.

[0018] As shown in FIG. 1, the tire 1 has a carcass 3 composed of one or more carcass plies that extend toroidally across a pair of bead portions 2. The carcass 3 has a carcass main body portion 3a disposed between bead cores 2a, and a carcass folded-back portion 3b that is folded 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 radially inward of the maximum tire width position, but the length of the carcass folded-back portion 3b extending from the inner side 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 configured by coating an organic fiber with rubber.

[0019] 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 composed of, 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. As the belt cord, for example, a steel cord can also be used. 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.

[0020] The tire 1 has an inner liner (not shown) on the inner surface 8 of the tire.

[0021] Here, as shown in FIG. 1, in the above reference state, a tire radial region between positions separated by 15% of the tire cross-sectional height SH from the maximum tire width position P both radially inward and outward is defined as R. At this time, the mass of the sidewall portion in the tire radial region R is 1.5% to 5% of the total mass of the pneumatic tire 1. In this example, in the tire radial region R (only in the tire radial region R), a rubber member (rubber sheet in this example) 7 is attached to the surface of the sidewall portion so as to be within the above mass range. The effects of the pneumatic tire of the present embodiment will be described below.

[0022] When the inventors studied the phenomenon of noise generation due to tire vibration, they obtained the finding that the maximum tire width position and its vicinity are the bellies (parts where the displacement amount of the amplitude becomes large) at 800 Hz to 1000 Hz. Then, the inventors locally increased the mass in the tire radial region R between positions separated by 15% of the tire section height SH (0.15×SH up and down 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 also found that the increase in mass can be made local and the increase in tire weight can be suppressed as much as possible.

[0023] If the position for increasing the weight is outside or inside the tire radial direction rather than the tire radial region R, the effect of reducing the amplitude at 800 Hz to 1000 Hz and improving the quietness of the tire cannot be sufficiently obtained. Also, if the mass of the sidewall portion in the tire radial region R is less than 1.5% of the total mass of the pneumatic tire, the effect of suppressing the above-described vibration cannot be sufficiently exerted, and the quietness of the tire cannot be sufficiently improved. On the other hand, if the mass of the sidewall portion in the tire radial region R exceeds 5% of the total mass of the pneumatic tire, the weight near the tire maximum width position P becomes locally too large and the weight bias becomes large, and there is a risk of flowing or shifting during vulcanization of the tire. For the same reason, it is more preferable that the mass of the sidewall portion in the tire radial region R is 1.8% to 4.5% of the total mass of the pneumatic tire.

[0024] It is more preferable that the mass of the sidewall portion in the tire radial region R(10%) between positions separated by 10% of the tire section height from the tire maximum width position P in the tire radial direction inside and outside in the above reference state is 1.5% to 5% of the total mass of the pneumatic tire. This is because the vibration can be more effectively reduced and the quietness of the tire can be further improved. Also in this case, for the same reason, it is more preferable that the mass of the sidewall portion in the tire radial direction region R (10%) is 1.8% to 4.5% of the total mass of the pneumatic tire.

[0025] FIG. 2 is a partial cross-sectional view in the tire width direction of the pneumatic tire according to the first modified example. FIG. 3 is a partial cross-sectional view in the tire width direction of the pneumatic tire according to the second modified example. When locally increasing the mass in the tire radial direction region R (or R (10%)), as shown in FIG. 2, the rubber member (rubber sheet) 7 can also be disposed inside the sidewall portion 6, or as shown in FIG. 3, the rubber member (rubber sheet) 7 can be attached 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 increases. Therefore, it is more preferable that the rubber member (rubber sheet) 7 is attached to the tire outer surface or disposed inside the sidewall portion (inside the sidewall rubber). In FIGS. 1 to 3, an example where the rubber member is a rubber sheet is shown, but it is not limited to the sheet-shaped rubber member, and it can be various shapes such as a protruding shape with a semicircular cross-section or a rectangular cross-section.

[0026] Here, it is preferable that the thickness of the sidewall portion in the tire radial direction region R (or R (10%)) is 1.0 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion. By being 1.0 mm or thicker, 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 making it 4 mm or less, the thickness in the vicinity of the tire maximum width position P becomes locally too large and the weight bias becomes large, and it is possible to suppress the flow or displacement during vulcanization of the tire. Here, the "thickness of the sidewall portion" means the thickness measured in the direction perpendicular to the carcass line in the tire width direction cross-section. Also, the statement that the thickness of the sidewall portion in the tire radial direction region R (or R(10%)) is "1.0 to 4 mm thicker than the thickness of the thinnest part 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 part of the sidewall portion". When a convex portion is formed in the above tire radial direction region, the thickness includes the height of the convex portion.

[0027] For the same reason, it is more preferable that the thickness of the sidewall portion in the tire radial direction region R (or R(10%)) is 1.5 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion.

[0028] It is preferable to change the weight by changing the specific gravity of the material in the tire radial direction region R (or R(10%)). By creating a local weight addition site only by the specific gravity and reducing the unevenness, the structural stress concentration site can be reduced, and the durability of the tire can be improved. Also, the thickness of the sidewall portion at the tire maximum width position P can be set to 120% to 200% of the thickness of the thinnest part of the sidewall portion. By setting it to 120% or more, the effect of suppressing the above-mentioned 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 tire maximum width position P becomes locally too large and the weight bias becomes large, and the tire flows or shifts during vulcanization.

[0029] 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, the weight increase can be suppressed as much as possible.

[0030] 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 1.3 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, powder rubber, carbon black, etc. can be used.

[0031] 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). The metal and fiber may be composed of only steel (linear metal with iron as the main component (the mass of iron exceeds 50% of the total mass of the metal filament)) or 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 of high durability against repeated deformation.

[0032] Here, the gauge of the tread rubber is preferably 2 to 30 mm, more preferably 2 to 15 mm. By setting it to 2 mm or more, the quietness can be further enhanced, while by setting it to 30 mm or less, the rolling resistance can be reduced by weight reduction. The "tread rubber gauge" refers to the tire radial thickness from the tread surface to the outermost reinforcing member in the tire equatorial plane (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) under the above reference state. However, when grooves are arranged in the tire equatorial plane, it is considered assuming that there are no grooves.

[0033] The tire aspect ratio is preferably 20 to 80, more preferably 20 to 65, and even more preferably 35 to 55. In a tire having an 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 the thinning of the sidewall portion and a reduction in vibration and thus noise due to a local weight increase in the above tire radial region R. That is, when the tire aspect ratio is 20 (preferably 35) or more, radiated noise can be reduced. On the other hand, when the tire aspect ratio is 80 (preferably 65, more preferably 55) or less, it becomes easier to reduce the weight and the rolling resistance can be reduced. Note that it is preferably configured without side reinforcing rubber.

[0034] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments at all.

Embodiment

[0035] (Example 1) In the tire radial direction region R of a tire with a tire size of 205 / 55R16, as shown in Fig. 1, three prototypes were made with different weights by adding mass to the maximum width position (Inventive Examples 1 to 3). Also, a conventional tire without adding mass to 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 tire radial direction 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 tire radial direction region R became 0.5 mm, 1 mm, and 2 mm thicker than the thickness of the thinnest part of the sidewall portion, respectively.

[0036] For these tires, the vibration mode in the tire radial direction region R was measured by simulation using FEM. The measurement results are shown in Fig. 4.

[0037] 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.

[0038] (Example 2) Next, the position where the weight was increased was varied to confirm the effect of the present invention. In Inventive Example 4, a prototype tire with 130 g of mass added to the maximum width position was made. In Inventive Example 4, the mass of the sidewall portion in the tire radial direction region R became 1.1% of the total mass of the pneumatic tire. Also, in Inventive Example 4, the thickness of the sidewall portion in the tire radial direction region R became 1 mm thicker than the thickness of the thinnest part of the sidewall portion. Also, in Comparative Example 2, 130 g of mass was added to the surface of the sidewall portion in a region outside the tire radial direction region R. In Comparative Example 3, 130 g of mass was added to the surface of the sidewall portion in a region inside the tire radial direction region R. In Comparative Example 4, 130 g of mass was added so as to cover the entire sidewall portion.

[0039] 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.

[0040] 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.

[0041] In addition, 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, there was no occurrence of rubber flow or displacement during vulcanization.

Explanation of Reference Numerals

[0042] 1: Pneumatic tire, 2: Bead portion, 3: Carcass, 4: Belt, 5: Tread portion, 6: Sidewall portion, 7: Rubber member, 8: Inner surface of tire

Claims

Claim 1 A pneumatic tire, when the pneumatic tire is mounted on an applicable rim, filled with a specified internal pressure, and set to an unloaded state as a reference state, the mass of the sidewall portion in the tire radial direction region between positions spaced 15% of the tire section height from the tire maximum width position in the tire radial direction inside and outside in the reference state is 1.5% to 5% of the total mass of the pneumatic tire, and a rubber member is disposed only in the tire radial direction region. The pneumatic tire is characterized by this. Claim 2 The pneumatic tire according to claim 1, wherein the mass of the sidewall portion in the tire radial direction region between positions spaced 10% of the tire section height from the tire maximum width position in the tire radial direction inside and outside in the reference state is 1.5% to 5% of the total mass of the pneumatic tire. Claim 3 The pneumatic tire according to claim 1 or 2, wherein the specific gravity of the rubber member is 1.05 times or more the specific gravity of the sidewall rubber.

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