JP6064639B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire with a reduced electric resistance value of a tire tread.

  A technique for reducing the electrical resistance value of a tire tread is known (see, for example, Patent Documents 1 to 3). Each of the techniques disclosed in Patent Documents 1 to 3 is a technique in which an earth tread rubber is formed in a tire radial direction region from the tread surface to the belt layer to reduce the electric resistance value of the tire tread.

Japanese Patent No. 3287795 Japanese Patent No. 3763640 JP 2000-118212 A

  In recent years, in various types of vehicle tires, cap tread rubber has been made high-silica in order to improve the handling stability performance on dry road surfaces and the drainage performance on wet road surfaces at a high level. According to this high-silicaization, the volume resistivity of the cap tread rubber is increased, so that the electrical resistance value of the tire tread is increased, and as a result, the effect of discharging static electricity from the tire tread to the outside is reduced. Accordingly, there is a demand for the development of a technique that can reduce the electrical resistance value of a tire tread even when the cap tread rubber is made high-silica.

  This invention is made in view of the said situation, Comprising: Even if it is a case where cap tread rubber is made into high silica, providing the pneumatic tire which can reduce the electrical resistance value of a tire tread is provided. Objective.

The pneumatic tire according to the present invention includes a carcass layer, a belt layer formed on the outer side in the tire radial direction of the carcass layer, a belt cover layer formed on the outer side in the tire radial direction of the belt layer and including a nylon cord, A tread rubber layer formed on the outer side in the tire radial direction of the belt cover layer. The tread rubber layer is located on the outermost side in the tire radial direction and has a volume resistivity of 10 ⁸ [Ω · cm] or more; an undertread rubber located on the inner side in the tire radial direction of the cap tread rubber; And an earth tread rubber that penetrates at least a part of the cap tread rubber from the tread surface inward in the tire radial direction and has a volume resistivity of 10 ⁶ [Ω · cm] or less. The belt cover layer has a region where the average arrangement density of nylon cords is lower than other regions and includes rayon cords in a certain range in the tire width direction. The range in the tire width direction of the region includes at least the range in the tire width direction in which the earth tread rubber is formed.

  In the pneumatic tire according to the present invention, the arrangement density distribution of the organic fibers (nylon and rayon) cord in the belt cover layer and the positional relationship between the belt cover layer and the earth tread rubber are improved. As a result, the pneumatic tire according to the present invention can reduce the electrical resistance value of the tire tread even when the cap tread rubber is made high-silica.

FIG. 1 is a tire meridian cross-sectional view showing a region near the tire equatorial plane with respect to a tread portion of a pneumatic tire according to an embodiment of the present invention.

  Hereinafter, embodiments of the pneumatic tire according to the present invention (basic form and additional forms 1 and 2 shown below) will be described in detail with reference to the drawings. Note that these embodiments do not limit the present invention. In addition, the constituent elements of the above embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Furthermore, various forms included in the above-described embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Basic form]
Below, the basic form is demonstrated about the pneumatic tire which concerns on this invention. In the following description, the tire radial direction means a direction orthogonal to the rotational axis of the pneumatic tire, the tire radial inner side is the side toward the rotational axis in the tire radial direction, and the tire radial outer side is in the tire radial direction. The side away from the rotation axis. The tire circumferential direction refers to a circumferential direction with the rotation axis as a central axis. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction means the side toward the tire equatorial plane CL (tire equator line) in the tire width direction, and the outer side in the tire width direction means the tire width direction. Is the side away from the tire equatorial plane CL. The tire equatorial plane CL is a plane that is orthogonal to the rotational axis of the pneumatic tire and passes through the center of the tire width of the pneumatic tire.

  FIG. 1 is a tire meridian cross-sectional view showing a region near the tire equatorial plane with respect to a tread portion of a pneumatic tire according to an embodiment of the present invention. The pneumatic tire shown in the figure includes an inner liner layer 12, a carcass layer 14, a belt layer 16, a belt cover layer 18 and a tread rubber layer 20 in order from the inner side to the outer side in the tire radial direction in the tread portion 10. .

  The inner liner layer 12 is a member that keeps tire air from leaking and maintains a predetermined air pressure. The carcass layer 14 has a cord that forms a skeleton of the tire, and is a member that mainly determines the strength of the tire. The belt layer 16 is composed of two layers of belts 16a and 16b. The belt layer 16 gives a predetermined rigidity to the tread portion 10, generates driving force, turning force and braking force for the pneumatic tire, and absorbs an impact from the road surface. In addition, the tire plays a role of withstanding the centrifugal force. The belt cover layer 18 includes a plurality of nylon cords, and is a member for particularly ensuring high-speed durability performance of the tire. Among these, for the inner liner layer 12, the carcass layer 14, and the belt layer 16 (16a, 16b), conventionally used members can be used.

  Further, the tread rubber layer 20 positioned on the outermost side in the tire radial direction of the tread portion 10 includes cap tread rubbers 20a and 20a that are divided into right and left at the center in the tire width direction, and the tire radial direction of the cap tread rubbers 20a and 20a. An under tread rubber 20b located on the inner side and an earth tread rubber 20c located between the cap tread rubbers 20a and 20a and extending from the tread surface TS to the under tread rubber 20b are configured.

The cap tread rubber 20a can be made into a rubber composition in which silica as a reinforcing material is richer than carbon black and, for example, 2 to 4 parts by weight of an antioxidant is blended with 100 parts by weight of a rubber component. The volume resistivity of the cap tread rubber 20a is larger than 10 ⁸ [Ω · cm].

The undertread rubber 20b can be made into a rubber composition in which carbon black is blended richly and, for example, 1 to 3 parts by weight of an antioxidant is blended with 100 parts by weight of a rubber component. The volume resistivity of the undertread rubber 20b is 10 ⁸ [Ω · cm] or less.

The earth red rubber 20c is a rubber composition containing carbon black richly and containing a larger amount of anti-aging agent than the cap tread rubber 20a, for example, 4 to 7 parts by weight of the anti-aging agent in 100 parts by weight of the rubber component. It can be set as the compounded rubber composition. The volume resistivity of the earth red rubber 20c is 10 ⁶ [Ω · cm] or less.

  It is preferable to form the columnar shape shown in FIG. 1 continuously in the tire circumferential direction because the electrostatic discharge effect is high, but the earth tread rubber 20c may be intermittently formed in the tire circumferential direction. Further, in FIG. 1, the earth tread rubber 20c is formed so that the center in the tire width direction coincides with the tire equatorial plane CL, but if it is in the tire width direction position included in the tire ground contact region during vehicle travel. Any position may be used.

  Further, the innermost side in the tire radial direction of the earth tread rubber 20c can be designed to contact the undertread rubber 20b as shown in FIG. However, even if the innermost side in the tire radial direction is separated from the undertread rubber 20c without being completely in contact, the distance between the undertread rubber 20b and the earth tread rubber 20c is within a range of 0.8 mm. Can be maintained.

  On the other hand, although not shown, it is possible to design the earth tread rubber 20c so as to penetrate not only the cap tread rubber 20a but also the under tread rubber 20b so that the innermost side in the tire radial direction is in contact with the belt cover layer 18. preferable. When the tire rolls, static electricity is generated particularly when the carcass layer 14 rubs against an adjacent layer in the tire radial direction. When the innermost side in the tire radial direction of the earth tread rubber 20c is adjacent to the belt cover layer 18, the earth red rubber 20c having a relatively low volume resistivity is brought closer to the carcass layer 14 expected as a static electricity generation region. . As a result, discharge of static electricity from the periphery of the carcass layer 14 to the tread surface TS can be made easier.

  Under the premise as described above, in the present embodiment, as shown in FIG. 1, the belt cover layer 18 has an average density of nylon cords in a certain range WB in the tire width direction as compared with other ranges. And has a region R (hatched portion in FIG. 1) including a rayon cord. Here, the average arrangement density of the nylon cord (rayon cord) is a nylon cord (rayon cord) per unit area of the belt cord layer 18 in a certain range in the tire width direction of the belt cover layer 18 in the tire meridional section view. ) A value defined by the number of arrangement. Therefore, for example, the average arrangement density of nylon cords (rayon cords) in the region R is the number of nylon cords (rayon cords) arranged per unit area in the region R of FIG.

  In the present embodiment, the tire width direction range WB of the region R includes at least the tire width direction range WC in which the earth tread rubber 20c is formed. Here, the tire width direction range WB in the region R includes the tire width direction range WC means that the minimum tire width direction size in the region R is equal to or greater than the maximum tire width direction size of the earth tread rubber 20c. To do. In the example shown in FIG. 1, the minimum dimension in the tire width direction of the region R is equal to the maximum dimension in the tire width direction of the earth tread rubber 20c.

(Action etc.)
As described above, when the tire rolls, static electricity is generated particularly when the carcass layer 14 rubs against an adjacent layer in the tire radial direction. If this static electricity is left inside the tire, the static electricity may become a source of interference in an electronic circuit in a vehicle including a wireless receiver. In addition, the occurrence of sparks due to static electricity may deteriorate the safety during refueling, and further, when the vehicle gets on and off, the static electricity may pass through the human body and cause discharge.

  In order to make it easier to discharge the static electricity generated inside the tire to the outside in view of these undesired situations, in the present embodiment, as shown in FIG. 1, the belt cover layer 18 is constant in the tire width direction. The area WB is provided with a region R in which the average arrangement density of the nylon cord is lower than that of the other ranges and includes the rayon cord. This is based on the knowledge that when a certain number of organic fiber cords are included in the rubber layer, the volume resistivity of the rubber layer is lower when the rayon cord is included than when the nylon cord is included. Therefore, in the present embodiment, a region having a low volume resistivity is provided in a part of the belt cover layer 18 in the tire width direction in the discharge route of static electricity from the periphery of the carcass layer 14 to the tread surface TS. Become.

  Further, in the present embodiment, as shown in FIG. 1, the tire width direction range WB of the region R includes at least the tire width direction range WC in which the earth tread rubber 20c is formed. That is, in the meridional section of the tire, a region R having a low volume resistivity of the belt cover layer 18 is necessarily located immediately below the region where the earth tread rubber 20c is formed.

  The carcass layer 14, the belt layer 16, and the belt cover layer 18 are arranged according to the arrangement density distribution of the organic fibers (nylon and rayon) cord in the belt cover layer and the positional relationship between the belt cover layer and the earth tread rubber. A path for easily discharging static electricity to the outside of the tire is formed, consisting of the region R, the under tread rubber 20b and the earth tread rubber 20c. In other words, according to the pneumatic tire of the present embodiment, the electrical resistance value of the tire tread can be reduced even when the cap tread rubber is made high-silica. As a result, it is possible to suppress adverse effects on the electronic circuit inside the vehicle due to static electricity, deterioration of safety during refueling, and discharge to the human body when getting on and off the vehicle, which can occur when static electricity is left inside the tire.

  In addition, in the example illustrated in FIG. 1, the region R including the rayon cord of the belt cover layer 18 has a tire extending inward in the tire width direction from the boundary B with the other region (both outer sides in the tire width direction). It is preferable to gradually reduce the nylon cord arrangement density and gradually increase the rayon cord arrangement density to the equator plane CL. According to the combination of the gradually increasing arrangement mode of the nylon cord and the gradually decreasing arrangement mode of the rayon cord in the tire width direction of the region R, the rigidity of the belt cover layer 18 gradually changes in the tire width direction. It is possible to suppress deterioration of steering stability performance and the like.

  In addition, although not shown in figure, the pneumatic tire of this embodiment shown above has the same meridian cross-sectional shape as the conventional pneumatic tire. Here, the meridional cross-sectional shape of the pneumatic tire refers to a cross-sectional shape of the pneumatic tire that appears on a plane perpendicular to the tire equatorial plane CL. The pneumatic tire of the present embodiment has a bead portion, a sidewall portion, and a tread portion from the inner side in the tire radial direction toward the outer side in a tire meridional cross-sectional view. And this pneumatic tire is provided with wing chip rubber on both sides of a rubber layered product by cap tread rubber and under tread rubber, for example in tire meridional section view. The wing tip rubber can be the same rubber composition as the above-mentioned earth red rubber.

  In addition, the pneumatic tire of the present embodiment includes normal manufacturing processes, that is, a tire material mixing process, a tire material processing process, a green tire molding process, a vulcanization process, and an inspection process after vulcanization. It is obtained through the process. When manufacturing the pneumatic tire of the present embodiment, in particular, in the green tire molding process, a rubber layer including a nylon cord that is a constituent member of the belt cover layer is disposed in the vicinity of the tire equatorial plane CL (region R). It winds relatively sparsely, but winds relatively densely in other areas. Further, in the green tire molding process, a rubber layer including a rayon cord, which is a constituent member of the belt cover layer, is wound only near the tire equatorial plane CL (region R). This controls the distribution density distribution of the organic fiber cord in the belt cover layer. Further, in the green tire molding process, the position in the tire width direction of the earth tread rubber is accommodated in the position in the tire width direction in the region including the rayon cord in the belt cover layer, and the belt cover layer and the earth red rubber are arranged. Control the positional relationship.

[Additional form]
Next, additional embodiments 1 and 2 that can be optionally implemented with respect to the basic embodiment of the pneumatic tire according to the present invention will be described.

(Additional form 1)
In the basic configuration, the tire in the region R including the rayon cord of the belt cover layer 18 has a tire width direction dimension of the earth tread rubber 20c shown in FIG. 1 of 0.3 [mm] or more and 3.0 [mm] or less. It is preferable that the width direction dimension is larger than the tire width direction dimension of the earth tread rubber 20c (additional form 1).

  By setting the tire width direction dimension of the earth tread rubber 20c to 0.3 [mm] or more, a sufficient arrangement area of the earth tread rubber 20c having a relatively low volume resistivity is secured, and the electric resistance value of the tire tread is secured. Can be further reduced. Further, since the earth tread rubber 20c has a lower hardness than the cap tread rubber 20a, the earth tread rubber 20c wears out first on the ground contact surface. When the dimension in the tire width direction is 3.0 [mm] or less, The deterioration of the steering stability performance can be suppressed without excessively increasing the local wear point.

  In order to efficiently form a path for discharging static electricity to the outside, the tire width direction dimension of the region R of the belt cover layer 18 and the tire width direction dimension of the earth tread rubber 20c are made the same, and the region R It is preferable to completely match the positions in the tire width direction of the earth tread rubber 20c. However, when the tire width direction dimension is the same as the tire width direction dimension, in the product tire, the tire width direction arrangement position of the region R and the tire width direction arrangement position of the earth tread rubber 20c are completely matched. This is not an easy task in view of various operations in the green tire molding process.

  For this reason, in the additional form 1, the member in the green tire corresponding to the earth tread rubber 20c of the product tire is accurately positioned with respect to the region in the green tire corresponding to the region R of the product tire when the green tire is molded. It is intended to give these regions and members as much dimensional relationships as possible. And as a result of giving such a dimensional relationship, in the additional form 1, it is prescribed | regulated that the tire width direction dimension of the area | region R is larger than the tire width direction dimension of the earth red rubber 20c in the product tire. doing. As a result, the arrangement position of the earth tread rubber 20c in the tire width direction can be reliably stored within the tire width direction range WB of the region R, and the positional relationship between the belt cover layer 18 and the earth tread rubber 20c is reliably controlled. As a result, a path for discharging static electricity to the outside can be formed efficiently.

(Additional form 2)
In the basic form and the form obtained by adding the additional form 1 to the basic form, the tire width direction dimension of the region R including the rayon cord of the belt cover layer 18 shown in FIG. 1 is 1 [mm] or more and 30 [mm] or less. (Additional form 2) is preferred.

  By setting the dimension in the tire width direction of the region R including the rayon cord of the belt cover layer 18 to 1 [mm] or more, the belt cover layer 18 has a sufficient region R in which the volume resistivity is reduced, so that the tire tread The electric resistance value can be further reduced. In addition, when a certain number of nylon cords and rayon cords are included in the rubber layer, the rigidity of the rubber layer becomes lower as the region where the nylon cord (rayon cord) is disposed is lower (higher). By setting the tire width direction dimension of the region R to 30 [mm] or less, it is possible to suppress a reduction in the rigidity of the belt cover layer 18, and in particular, it is possible to suppress deterioration in steering stability performance and high-speed durability performance.

  The tire size is 225 / 65R17, and the tread portion 10 having the structure shown in FIG. 1 is provided. In particular, the belt cover layer 18 is in a certain range WB in the tire width direction, and the average density of nylon cords compared to other ranges The air of Examples 1 to 4 has a region R including a rayon cord that is low and the tire width direction range WB of the region R includes at least the tire width direction range WC in which the earth tread rubber 20c is formed. Each tire was prepared. Further, the pneumatic tire of the conventional example has the same structure as each example except that the nylon cord arrangement density of the belt cover layer 18 is uniform in the entire region in the tire width direction and does not include the rayon cord. It was created. The conditions for the pneumatic tires (test tires) of Examples 1 to 4 and Conventional Example 1 are as shown in Table 1.

  For each test tire produced in this way, the electrical resistance value and steering stability performance of the tire tread were evaluated. These results are also shown in Table 1.

(Electric resistance value)
A tire when applying a measurement voltage of 500 V using a model HP4339A high resistance meter manufactured by Hured Packard with a pneumatic pressure of 200 kPa applied to each test tire and a load of 6.67 kN in accordance with JATMA. The electrical resistance value of the tread was measured.

(Maneuvering stability)
Assembled each test tire on a 17x7J rim at an air pressure of 230 kPa, mounted on a sedan type vehicle (front engine / front drive system) with a displacement of 2400 CC, and evaluated the functionality by the paneler when traveling on a dry road surface at a maximum speed of 240 km / h Carried out. And based on this measurement result, the index evaluation which made the conventional example the reference | standard (100) was performed. This evaluation shows that the larger the index, the higher the steering stability performance.

  According to Table 1, the distribution density distribution of the organic fiber (nylon and rayon) cords in the technical scope of the present invention and the positional relationship between the belt cover layer and the earth red rubber are predetermined. For the pneumatic tires of Examples 1 to 4 (which are within the range), the tire tread has a lower electrical resistance value than the conventional pneumatic tires that do not belong to the technical scope of the present invention. I understand.

  Further, according to Table 1, it can be seen that the pneumatic tires of Examples 1 to 4 maintain the same level of steering stability performance as the conventional example. In general, when the belt cover layer is provided with a region where the average arrangement density of nylon cords is low and the rayon cords are included (region R in FIG. 1), the rigidity of the belt cover layer is lowered, and steering stability performance is improved. There is concern about deterioration. However, according to the present invention, even if the region R is provided, it is understood that an excellent electrical resistance value can be exhibited without deteriorating the steering stability performance by appropriately changing the design of other tread structures. .

  The present invention includes the following aspects.

(1) A carcass layer, a belt layer formed on the outer side in the tire radial direction of the carcass layer, a belt cover layer formed on the outer side in the tire radial direction of the belt layer and including a nylon cord, and a tire of the belt cover layer A tread rubber layer formed on the outer side in the radial direction, the tread rubber layer positioned on the outermost side in the tire radial direction and having a volume resistivity of 10 ⁸ [Ω · cm] or more, and the cap An under tread rubber located inside the tread rubber in the tire radial direction and at least a part of the cap tread rubber from the tread surface toward the inside in the tire radial direction, and a volume resistivity of 10 ⁶ [Ω · cm] or less The belt cover layer is in a certain range in the tire width direction compared with other ranges. Lower average arrangement density of Nkodo, and has an area containing a rayon cord, the tire width direction range of the area, a pneumatic tire including the tire width direction range which is at least the ground tread rubber formed.

  (2) The tire width direction dimension of the earth red rubber is 0.3 [mm] or more and 3.0 [mm] or less, and the tire width direction dimension of the region including the rayon cord of the belt cover layer is the above The pneumatic tire according to the above (1), which is larger than the tire width direction dimension of the earth red rubber.

  (3) The pneumatic tire according to (1) or (2), wherein a tire width direction dimension of a region including the rayon cord of the belt cover layer is 1 [mm] or more and 20 [mm] or less.

10 tread portion 12 inner liner layer 14 carcass layer 16 belt layer 16a, 16b belt 18 belt cover layer 20 tread rubber layer 20a cap tread rubber 20b under tread rubber 20c earth tread rubber B boundary between region R and other regions CL tire equator Surface R Area where the average arrangement density of the organic fiber cords 18a of the belt cover layer 18 is low TS Tread surface WB Tire width direction constant range of the belt cover layer 18 WC Tire width direction range where the earth tread rubber 20c is formed

Claims (3)

A carcass layer; a belt layer formed on the outer side in the tire radial direction of the carcass layer; a belt cover layer formed on the outer side in the tire radial direction of the belt layer and including a nylon cord; and an outer side in the tire radial direction of the belt cover layer And a tread rubber layer formed on
A cap tread rubber in which the tread rubber layer is positioned on the outermost side in the tire radial direction and has a volume resistivity of 10 ⁸ [Ω · cm] or more; an under tread rubber positioned on the inner side in the tire radial direction of the cap tread rubber; An earth tread rubber that penetrates at least a part of the cap tread rubber from the tread surface toward the inner side in the tire radial direction and has a volume resistivity of 10 ⁶ [Ω · cm] or less.
The belt cover layer has a region in which the average arrangement density of nylon cords is low compared to other ranges in a certain range in the tire width direction and includes rayon cords,
A pneumatic tire in which the range in the tire width direction of the region includes at least the range in the tire width direction in which the earth tread rubber is formed.   The tire width direction dimension of the earth tread rubber is 0.3 [mm] or more and 3.0 [mm] or less, and the tire width direction dimension of the region including the rayon cord of the belt cover layer is that of the earth red rubber. The pneumatic tire according to claim 1, wherein the pneumatic tire is larger than a tire width direction dimension.   The pneumatic tire according to claim 1 or 2, wherein a tire width direction dimension of a region including the rayon cord of the belt cover layer is 1 [mm] or more and 30 [mm] or less.

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