JP2020100298A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that can exert excellent low fuel consumption performance and yet suppress deterioration in noise performance, while preventing deterioration in durability.SOLUTION: A tread rubber 5 forming an outer surface of a tread part 3 has a cap rubber 51 forming a grounding surface and a base rubber 52 provided inside in a tire radial direction of the cap rubber 51. A tan δ is lower than a tan δ of a side wall rubber 6. The base rubber 52 is extended up to the side wall part 2, where a height H52 of an extending end 52E of the base rubber 52 with a bead base line BL as a reference is below 80% of a tire cross section height H. The base rubber 52 is provided so as not to contact a rim strip rubber 7.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pneumatic tire.

The outer surface of the sidewall portion of the pneumatic tire is formed of sidewall rubber having excellent cut resistance (external scratch resistance) and weather resistance. In recent years, tires in which the thickness of sidewall rubber is reduced have been proposed in order to reduce rolling resistance and reduce fuel consumption. However, when the thickness of the sidewall rubber is reduced, the deformation due to the vibration of the secondary mode of the cross section tends to be large, and there is a problem that the road noise in the medium frequency band (250 to 400 Hz) due to this deformation is deteriorated.

In the pneumatic tire disclosed in Patent Document 1, the sidewall rubber has an inner and outer two-layer structure, and the inner layer sidewall continuously extends to the tread portion. Since the inner side wall constitutes a conductive path for discharging static electricity to the road surface, the inner side wall is provided so as to be in contact with both the conductive rubber provided on the tread portion and the rim strip rubber (clinch rubber) provided on the bead portion. To be Therefore, if there is a large difference in rubber hardness between the inner side wall and the rim strip rubber, stress due to repeated deformation during running tends to concentrate at the interface between them, which may cause deterioration of durability.

In the pneumatic tire described in Patent Document 2, the height of the rim strip rubber forming the outer surface of the bead portion is larger than usual and is extended outward in the tire radial direction. In the sidewall portion, an extension portion of the rim strip rubber is arranged inside the sidewall rubber in the tire width direction. In Patent Document 2, the improvement effect on rolling resistance is positioned as an effect obtained by relatively reducing the thickness of the rim strip rubber at the tire maximum width position.

JP, 2014-218096, A JP, 2008-010393, A

The present invention has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire capable of exhibiting good fuel economy performance while preventing deterioration of durability and suppressing deterioration of noise performance. It is in.

The pneumatic tire according to the present invention includes a carcass extending from a tread portion to a bead portion through a sidewall portion, a tread rubber forming an outer surface of the tread portion, and a sidewall rubber forming an outer surface of the sidewall portion. And a rim strip rubber that forms an outer surface of the bead portion, wherein the tread rubber has a cap rubber that forms a ground contact surface, and a base rubber that is provided on a tire radial direction inner side of the cap rubber. The tan δ of the base rubber is lower than the tan δ of the sidewall rubber, the base rubber is extended to the sidewall portion, and the height of the extension end of the base rubber based on the bead base line is the tire cross section. The height is 80% or less, and the base rubber is provided so as not to contact the rim strip rubber.

With such a configuration, in the sidewall portion, the base rubber having a relatively low tan δ (loss tangent) is arranged inside the sidewall rubber in the tire width direction, so that the rolling can be performed without reducing the thickness of the sidewall rubber. The resistance can be reduced. Further, since the base rubber does not contact the rim strip rubber, an interface having a large rubber hardness difference is not formed between them, and deterioration of durability can be prevented. As a result, it is possible to exhibit good fuel economy performance while preventing deterioration of durability, and to suppress deterioration of noise performance.

The carcass has a winding portion that is wound to the outside in the tire radial direction via a bead core provided in the bead portion, and the extension end of the base rubber is arranged inside the tire radial direction from the tip of the winding portion. Is preferably provided. As a result, it is possible to suppress heat generation in the winding portion where stress tends to concentrate and improve durability. Further, the base rubber extends so long that it overlaps with the rolled-up portion of the carcass in the tire width direction, which is convenient for exhibiting good fuel economy performance.

It is preferable that the rim strip rubber extends beyond the maximum tire width position and extends outward in the tire radial direction. As a result, the reduction in tire rigidity due to the base rubber being arranged in the sidewall portion can be compensated by the rim strip rubber, and the steering stability performance can be maintained and improved.

The height of the rim strip rubber based on the bead baseline is preferably 50% or more of the tire cross-sectional height. As a result, the reduction in tire rigidity due to the base rubber being arranged in the sidewall portion can be compensated by the rim strip rubber, and the steering stability performance can be maintained and improved.

The tire thickness in the buttress region of the sidewall portion is preferably 125% or more of the tire thickness at the tire maximum width position. Thereby, the thickness of the sidewall rubber can be appropriately secured, and the deterioration of noise performance can be favorably suppressed.

A tire meridian sectional view showing an example (first embodiment) of a pneumatic tire according to the present invention. A tire meridian sectional view showing a second embodiment of a pneumatic tire. A tire meridian sectional view showing a third embodiment of a pneumatic tire

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, a pneumatic tire T according to the present embodiment includes a pair of bead portions 1, sidewall portions 2 that extend outward in the tire radial direction from each of the bead portions 1, and each of the sidewall portions 2. And a tread portion 3 connected to the outer end in the tire radial direction. The bead portion 1 is provided with an annular bead core 1a and a bead filler 1b provided on the outer side of the bead core 1a in the tire radial direction. The bead core 1a is formed by covering a converging body such as a steel wire with rubber. The bead filler 1b is made of hard rubber that extends outward in the tire radial direction and has a triangular cross section.

The pneumatic tire T further has a carcass 4 extending from the tread portion 3 to the bead portion 1 via the sidewall portion 2, a tread rubber 5 forming an outer surface of the tread portion 3, and an outer surface of the sidewall portion 2. The side wall rubber 6 and the rim strip rubber 7 forming the outer surface of the bead portion 1 are provided. The tread portion 3 is provided with a belt 8 laminated on the tire radial direction outer side of the carcass 4 and a belt reinforcing member 9 laminated on the tire radial direction outer side of the belt 8 and covered with the tread rubber 5. ing. Although not shown, a tread pattern is formed on the surface of the tread rubber 5 according to the required tire performance and usage conditions. The inner surface of the tire T is formed of the inner liner rubber 10.

The carcass 4 is formed of a carcass ply in which a plurality of cords arranged in a direction substantially orthogonal to the tire circumferential direction are covered with rubber. A metal such as steel or an organic fiber such as polyester, rayon, nylon or aramid is preferably used as a material for the cord. The number of carcass plies forming the carcass 4 is not limited to one and may be plural. The carcass 4 is wound up (that is, turned up) to the outside in the tire radial direction via the bead core 1a. In other words, the carcass 4 has a body portion 41 extending from the tread portion 3 through the sidewall portion 2 to the bead portion 1, and a series of winding portions 42 arranged outside the bead core 1a and the bead filler 1b in the tire width direction. is there.

The tread rubber 5 includes a cap rubber 51 that forms a ground contact surface and a base rubber 52 that is provided inside the cap rubber 51 in the tire radial direction. The base rubber 52 is formed of rubber having a heat generation lower than that of the cap rubber 51. The tan δ (loss tangent) of the base rubber 52 is lower than the tan δ of the cap rubber 51 and lower than the tan δ of the sidewall rubber 6. The tan δ of the base rubber 52 is, for example, 0.1 to 0.3. In the present specification, tan δ shall mean the value measured at 35°C. Specifically, tan δ is measured under the conditions of a frequency of 50 Hz, a static strain of 10%, a dynamic strain of 2% and a temperature of 35° C. using a Rheometer E4000 manufactured by USM.

In the present embodiment, an example in which the cap rubber 51 is made of conductive rubber is shown, but the present invention is not limited to this. Examples of the conductive rubber include rubbers having a volume resistivity of less than 10 ⁸ Ω·cm. The conductive rubber is produced, for example, by blending the raw material rubber with carbon black as a reinforcing agent at a high ratio. In addition to carbon black, it is possible to use a known carbon-based conductivity-imparting material such as carbon fibers and graphite, and metal-based materials such as metal powder, metal oxides, metal flakes, and metal fibers. Examples of the raw material rubber include natural rubber and styrene-butadiene rubber.

The sidewall rubber 6 is made of rubber having excellent cut resistance and weather resistance. In this embodiment, the tan δ of the sidewall rubber 6 is lower than the tan δ of the cap rubber 51. The tire T has a so-called sidewall on tread (SWOT) structure in which the end portion of the sidewall rubber 6 on the outer side in the tire radial direction is placed on the side portion of (the cap rubber 51 of) the tread rubber 5. It is adopted. In the tire meridian section, the sidewall rubber 6 extends inward in the tire radial direction from the buttress region 2b and reaches the rim strip rubber 7 via the tire maximum width position 2m.

The buttress region 2b is a region outside the sidewall portion 2 in the tire radial direction, and is a region that does not contact the ground during normal traveling on a flat paved road. Since the buttress region 2b serves as an antinode of the cross-section secondary mode vibration, by securing the mass of this region, road noise mainly in the middle frequency band (280 to 400 Hz) can be reduced. The tire maximum width position 2m is a position where the profile line on the outer surface of the tire T in the sidewall portion 2 is farthest from the tire equator (not shown) in the tire width direction. The profile line is a contour of the outer surface of the sidewall main body excluding protrusions such as rim protectors, and usually has a tire meridian cross-sectional shape defined by smoothly connecting a plurality of arcs.

The rim strip rubber 7 is formed of rubber having excellent abrasion resistance. The rim strip rubber 7 is provided at a portion in contact with a rim (not shown) on which the tire T is mounted. The rubber hardness of the rim strip rubber 7 is higher than the rubber hardness of the sidewall rubber 6 and the base rubber 52. The rubber hardness of the rim strip rubber 7 is, for example, 60 to 70 degrees. The rubber hardness of the sidewall rubber 6 is, for example, 55 to 65 degrees. The rubber hardness of the base rubber 52 is, for example, 50 to 55 degrees. In the present specification, the rubber hardness refers to a value (durometer hardness) measured using a type A durometer in an atmosphere of 23° C. according to JIS K6253.

In the present embodiment, the height H7 of the rim strip rubber 7 based on the bead base line BL is, for example, 15 to 55% of the tire cross-section height HT. From the viewpoint of reducing road noise in the low frequency band (80 to 100 Hz), the height H7 is preferably 50% or less of the tire cross-section height HT. As a result, compared with the structure in which the rim strip rubber 7 is extended outward in the tire radial direction (see FIG. 3), the increase in tire rigidity is suppressed and the primary characteristic value can be decreased.

The bead base line BL is a virtual straight line in the tire width direction that defines the rim diameter of the standard rim. The outer diameter line DL is a virtual straight line in the tire width direction that passes through the tire outer diameter position (not shown). The tire cross-section height HT is obtained as the height of the tire outer diameter position based on the bead base line BL. The height H7 of the rim strip rubber 7 is smaller than the winding height H4 of the carcass 4. The winding height H4 indicates the height of the winding portion 42 (the position of the tip 4E) based on the bead base line BL. The winding height H4 is, for example, 25 to 80% of the tire cross-section height HT. The winding height H4 is larger than the height H1b of the bead filler 1b based on the bead base line BL, but is not limited to this.

The belt 8 is formed of a belt ply having a plurality of cords arranged in a direction inclined with respect to the tire circumferential direction and covered with rubber. The belt 8 is composed of a plurality of (two in the present embodiment) belt plies, and the cords are laminated so that the cords cross each other in opposite directions. Steel is preferably used as the material of the cord. The belt reinforcing member 9 is formed of a reinforcing ply formed by coating a cord extending substantially in the tire circumferential direction with rubber. Organic fibers are preferably used as the material of the cord. By reinforcing the belt 8 with the belt reinforcing material 9, high-speed durability performance can be improved.

In the tire T, the base rubber 52 extends to the sidewall portion 2. The base rubber 52 is interposed between (the main body portion 41 of the carcass 4) and the sidewall rubber 6 and extends along the tire radial direction while curving. The extended end 52E of the base rubber 52 is arranged inside the side end 51E of the cap rubber 51 in the tire radial direction. The height H52 of the extension end 52E of the base rubber 52 based on the bead base line BL is 80% or less of the tire cross-section height HT, and the base rubber 52 is provided so as not to contact the rim strip rubber 7. .. The structure of the base rubber 52 may be applied to at least the sidewall portion 2 on one side, and is preferably applied to both sides in order to enhance the improvement effect.

According to this configuration, in the sidewall portion 2, the base rubber 52 having a low tan δ is arranged inside the sidewall rubber 6 in the tire width direction. Therefore, even if the thickness of the sidewall rubber 6 is not reduced, for example, even if the tire thickness T2m at the tire maximum width position 2m is 5.0 mm or more, the rolling resistance can be reduced. From the viewpoint of improving fuel economy performance, it is preferable that the extension end 52E be located inside the tire maximum width position 2m in the tire radial direction. Similarly, the height H52 is preferably 80% or less of the tire cross-section height HT, and more preferably 50% or less, from the viewpoint of improving fuel economy performance.

In this tire T, since the base rubber 52 and the rim strip rubber 7 do not come into contact with each other and no interface is formed between them, deterioration of durability can be prevented. In the present embodiment, the extension end 52E and the outer end 7E of the rim strip rubber 7 are arranged apart from each other in the tire radial direction so that the base rubber 52 and the rim strip rubber 7 do not contact (that is, do not form an interface). , The height H7 is smaller than the height H52. Such a configuration is convenient for reducing air entering in the manufacturing process. Further, since the base rubber 52 is extended and disposed in the sidewall portion 2 instead of separately adding a rubber member having a low tan δ, the tire T is repeatedly deformed without unnecessarily increasing the rubber interface. Stress concentration due to is suppressed.

As described above, in the tire T, the rolling resistance is reduced without depending on the thinning of the sidewall portion 2, and the deterioration of the noise performance can be suppressed. From the viewpoint of securing the mass of the buttress region 2b and reducing the road noise in the medium frequency band, it is preferable to appropriately increase the tire thickness T2b in the buttress region 2b. Specifically, the tire thickness T2b is preferably 125% or more of the tire thickness T2m, more preferably 130% or more, still more preferably 150% or more. The tire thickness T2b is measured at a position where the height H2b based on the outer diameter line DL is 20% of the tire cross-section height HT. In view of low fuel consumption performance, the tire thickness T2b can be suppressed within the range of 100 to 125% of the tire thickness T2m.

Each dimension such as height and thickness of the pneumatic tire T is measured in a non-loaded state in which the tire is mounted on a standard rim and a regular internal pressure is filled. A standard rim is a rim that is defined for each tire in a standard system including standards on which a tire is based. For example, a standard rim for JATMA, "Design Rim" for TRA, or ETRTO for ETRTO. Call it "Measuring Rim". The regular internal pressure is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure is used, and for TRA, the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION" is used. If it is the maximum value described in "PRESSURES" or ETRTO, it is "INFLATION PRESSURE".

The interface of the rubber member as shown in the figure can be specified in the tire cross section after vulcanization molding. For example, by cutting the tire with a sharp blade, it is determined by the properties of the rubber interface thinly observed in the cross section. be able to.

[Second Embodiment]
Next, a second embodiment will be described with reference to FIG. The second embodiment has the same configuration as the first embodiment except for the configuration described below, and therefore common points will be omitted and differences will be mainly described. The same configurations as the configurations described in the first embodiment are denoted by the same reference numerals, and duplicated description will be omitted. The third embodiment described later is also similar to this.

The carcass 4 has a winding-up portion 42 that is wound up to the outside in the tire radial direction via a bead core 1a provided in the bead portion 1. In the present embodiment, the extension end 52E of the base rubber 52 is arranged inside the tip 4E of the winding portion 42 in the tire radial direction. Therefore, the height H52 of the extension end 52E is smaller than the winding height H4. In the example of FIG. 2, the extension end 52E is arranged on the inner side in the tire width direction of the winding portion 42, but it is not limited to this, and may be arranged on the outer side in the tire width direction of the winding portion 42.

Since the extension end 52E is arranged on the inner side in the tire radial direction with respect to the tip 4E in this manner, heat generation of the winding portion 42 where stress tends to concentrate can be suppressed and durability can be improved. Further, since the base rubber 52 is extended to such an extent that it overlaps the winding portion 42 of the carcass 4 in the tire width direction, it is convenient for exhibiting good fuel economy performance. In the present embodiment, the height H52 of the extension end 52E is, for example, 20 to 75% of the tire section height HT, and the hoisting height H4 is, for example, 25 to 80% of the tire section height HT.

[Third Embodiment]
Next, a third embodiment will be described with reference to FIG. When the rubber hardness of the base rubber 52 is lower than the rubber hardness of the sidewall rubber 6 (for example, the rubber hardness difference is 2 degrees or more), extending the base rubber 52 to the sidewall portion 2 lowers the tire rigidity. The steering stability may deteriorate. Therefore, in the present embodiment, the rim strip rubber 7 having a relatively high rubber hardness is extended outward in the tire radial direction to compensate for the decrease in tire rigidity due to the base rubber 52 with the rim strip rubber 7 to improve the steering stability performance. We are trying to maintain and improve.

In the present embodiment, the rim strip rubber 7 extends outward in the tire radial direction beyond the maximum tire width position 2 m. That is, the outer end 7E of the rim strip rubber 7 is disposed outside the tire maximum width position 2m in the tire radial direction. In the present embodiment, the height H7 of the rim strip rubber 7 is preferably 50% or more of the tire cross-section height HT. From the viewpoint of avoiding the formation of the interface between the base rubber 52 and the rim strip rubber 7, the height H7 is preferably less than 80% of the tire cross-section height HT.

Also in this embodiment, the base rubber 52 is provided so as not to contact the rim strip rubber 7. In the example of FIG. 3, the rim strip rubber 7 extending outward in the tire radial direction overlaps the base rubber 52 in the tire width direction, and the height H7 is larger than the height H52. However, since the winding portion 42 is interposed between the base rubber 52 and the rim strip rubber 7, they are not in contact with each other. In such a configuration, the hoisting height H4 is equal to or greater than the height H7, and is set to, for example, 25 to 80% of the tire cross-section height HT.

The pneumatic tire of the present invention can be configured in the same manner as a normal pneumatic tire except that the sidewall portion is configured as described above, and any conventionally known material, shape, manufacturing method and the like can be adopted in the present invention.

The present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention.

In order to specifically show the constitution and effect of the present invention, the following evaluations (1) to (4) were carried out and will be described.

(1) Low Fuel Consumption Performance The rolling resistance was measured under ISO conditions, the reciprocal of the measurement result was calculated, and indexed using Comparative Example as 100. The larger the value, the smaller the rolling resistance and the better the fuel efficiency.

(2) Road noise in the middle frequency band (noise performance)
A microphone was installed near the ears of the driver's seat, and the sound pressure in the medium frequency band (315 Hz band) when running on a rough road surface at a speed of 60 km/h was measured and indexed as 100 as a comparative example. The higher the value, the lower the sound pressure level and the better the noise performance.

(3) Road noise in the low frequency band A microphone was installed near the ear of the driver's seat, and the sound pressure in the low frequency band (80 Hz band) was measured when running on a rough road surface at a speed of 60 km/h, and a comparative example. Was indexed as 100. The higher the value, the lower the sound pressure level.

(4) Steering stability performance Tires were mounted on a test vehicle, and turning, braking, and acceleration tests were performed in actual vehicle running to perform sensory evaluation by the driver, and a comparative example was set to 100 and indexed. The larger the value, the better the steering stability.

The size of the tire used for the test was 195/65R15, and the tire was mounted on a standard rim of the size specified by JATMA, and the air pressure was set to 240 kPa. As shown in Table 1, the height (H52) of the extension end of the base rubber, the carcass winding height (H4), the height of the rim strip rubber (H7), and the tire thickness (T2b) in the buttress region are variously changed. Comparative example and Examples 1 to 6 are made different from each other and the other configurations are common. The comparative example is provided with a normal base rubber that is not extended to the sidewall portion.

As shown in Table 1, in Examples 1 to 6, good fuel economy performance was exhibited, and deterioration of road noise (noise performance) in the middle frequency band was suppressed. Further, in Examples 1 and 4, the road noise in the low frequency band can be reduced by lowering the primary eigenvalue. In Examples 2 and 6, steering stability performance can be maintained and improved by compensating for the decrease in tire rigidity with the rim strip rubber.

1 bead part 1a bead core 2 sidewall part 2b buttress area 2m tire maximum width position 3 tread part 4 carcass 5 tread rubber 6 sidewall rubber 7 rim strip rubber 51 cap rubber 52 base rubber 52E extended end BL bead base line HT tire cross section height Sa T Pneumatic tire

Claims (5)

Carcass from the tread portion through the sidewall portion to the bead portion, the tread rubber forming the outer surface of the tread portion, the sidewall rubber forming the outer surface of the sidewall portion, and the outer surface of the bead portion With a rim strip rubber to form,
The tread rubber has a cap rubber forming a ground contact surface, and a base rubber provided on the tire radial direction inner side of the cap rubber, tan δ of the base rubber is lower than tan δ of the sidewall rubber,
The base rubber is extended to the sidewall portion, the height of the extension end of the base rubber based on the bead base line is 80% or less of the tire cross-sectional height, and the base rubber is the rim strip rubber. Pneumatic tires are provided so that they do not come into contact with. The carcass has a winding-up portion that is wound up to the outside in the tire radial direction via a bead core provided in the bead portion,
The pneumatic tire according to claim 1, wherein the extended end of the base rubber is arranged inside the tire radial direction with respect to the tip end of the winding portion. The pneumatic tire according to claim 1 or 2, wherein the rim strip rubber extends beyond the tire maximum width position and extends outward in the tire radial direction. The pneumatic tire according to any one of claims 1 to 3, wherein a height of the rim strip rubber based on a bead baseline is 50% or more of a tire cross-sectional height. The pneumatic tire according to any one of claims 1 to 4, wherein a tire thickness in a buttress region of the sidewall portion is 125% or more of a tire thickness at a tire maximum width position.

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