JP2011126338A - Pneumatic tire - Google Patents

Abstract

Disclosed is a method for discharging static electricity generated in a vehicle to a road surface while increasing the ratio of natural materials other than petroleum in a tire.
A main portion constituting a main portion of a carcass, a belt layer, and a band layer, a cap rubber portion forming a main portion of a tread grounding surface, and a base rubber disposed on the inner side in the tire radial direction. The outer surface rubber portion 16 that forms the outer surfaces of the portion 12 and the sidewall portion 3 is formed of a non-conductive material, and is disposed on the inner side in the tire radial direction of the through portion 14 exposed on the tread contact surface and the base rubber portion 12. And an undertread rubber portion 13 having a width larger than the belt layer 7 and extending in the tire axial direction and having at least one end portion in the tire axial direction connected to the conductive end portion 10, and at least the tire portion 9 in the tire axial direction. The conductive end portion 10 disposed on one end side, the inner rubber portion 15 disposed on the inner side in the tire axial direction of the outer surface rubber portion 16, and the clinch rubber 4G contacting the rim R are electrically conductive. It is formed of a material.
[Selection] Figure 1

Description

  The present invention relates to a pneumatic tire capable of discharging static electricity generated in a vehicle to a road surface while increasing the usage ratio of natural materials other than petroleum.

  Many of the tires currently on the market are made of petroleum materials that use more than 50% by mass of petroleum. However, it is necessary to suppress the emission of CO2 in order to attach importance to recent environmental problems, in particular to prevent global warming. For this reason, it is required to manufacture tires using non-petroleum natural materials that do not use petroleum as a raw material. Non-petroleum natural materials are non-petroleum raw materials that are not based on petroleum, such as metals, natural rubber, inorganic fillers and / or biofillers, natural fats and oils, natural resins, natural waxes, natural fibers, or their processing. It is a concept that includes things.

  In order to increase the use ratio of natural materials other than petroleum in tires, it is effective to use natural rubber and silica, which are natural materials other than petroleum, for rubber and its reinforcing agent that have a relatively large proportion of the total mass of the tire. is there. In particular, a tire using silica as a reinforcing material for tread rubber has an advantage of achieving both wet grip performance and low rolling resistance performance.

  However, inorganic reinforcing agents such as silica have high electrical insulation. Therefore, the rubber material rich in silica tends to increase the electrical resistance of the tire and tend to accumulate static electricity in the vehicle. Such accumulation of static electricity causes radio wave interference such as radio noise and electrical malfunction.

  As means for preventing static electricity accumulated in the vehicle, as shown in FIG. 9, a base layer b made of a conductive rubber material b1 and a non-conductive cap rubber a extending from the base layer b outward in the tire radial direction. A tread rubber having a through portion k that passes through the surface and is exposed on the tread surface t has been proposed (Patent Document 1 below).

  However, the tread rubber has a clinch rubber (not shown) in contact with the rim, a carcass e or sidewall rubber layer (not shown) in contact with the clinching rubber, and a belt to guide the vehicle-side static electricity to the base layer b. It is necessary to use a conductive rubber material for the layer d. For this reason, in the tire of patent document 1, there exists a problem that it is difficult to enlarge the ratio (henceforth "the non-petroleum natural material rate") which uses a natural material other than petroleum of a tire.

JP 10-175403 A

  The present invention has been devised in view of the above problems, and the ratio of the use of petroleum materials such as carbon black is suppressed to a minimum to increase the ratio of non-oil natural materials in tires, and also due to accumulation of static electricity. The main object of the present invention is to provide a pneumatic tire capable of preventing electrical failure and the like.

  The invention according to claim 1 of the present invention includes a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a belt layer disposed outside the carcass in the tire radial direction and inside the tread portion. A belt layer covering the outer side of the belt layer in the tire radial direction; a tread rubber disposed on the outer side of the band layer; and a sidewall rubber disposed on the outer side of the carcass in the sidewall portion and extending inward and outward in the tire radial direction. And a pneumatic tire including a conductive clinch rubber that is disposed outside the carcass at the bead portion and contacts the rim when attached to the rim, wherein the carcass and the belt layer are non-conductive. The band layer is made of a non-conductive material and includes a main part that constitutes a main part of the band layer. The tread rubber is arranged at least on one end side in the tire axial direction of the main portion and protrudes outward in the tire axial direction from the outer end of the belt layer and made of a conductive material, and the tread rubber has a width of the tread portion. A non-conductive cap rubber part that extends in the direction and forms the main part of the tread ground surface, a non-conductive base rubber part that is arranged on the inner side in the tire radial direction, and an inner side in the tire radial direction of the base rubber part A conductive undertread rubber portion that is arranged and extends in the tread width direction and at least one end portion in the tire axial direction is connected to the conductive end portion of the band layer, and one end connected to the outer surface of the undertread rubber portion And the other end includes a conductive penetrating portion that penetrates the base rubber portion and the cap rubber portion and is exposed at the tread ground surface, The rubber wheel includes a non-conductive outer surface rubber portion that forms the outer surface of the sidewall portion, and a conductive inner rubber portion that is disposed on the inner side in the tire axial direction of the outer surface rubber portion, and the inner rubber portion includes: The outer end in the tire radial direction is connected to the conductive end portion of the band layer, and the inner end in the tire radial direction is connected to the clinch rubber.

  According to a second aspect of the present invention, the main parts of the carcass, the belt layer, and the band layer are each coated with a cord material with a topping rubber in which silica is blended with a rubber polymer mainly composed of natural rubber. The pneumatic tire according to claim 1.

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the under-tread rubber part has a thickness of 0.5 to 1.5 mm and the smallest thickness among the tread rubbers. .

  According to a fourth aspect of the present invention, the inner rubber portion of the sidewall rubber has a thickness of 0.1 to 2 mm and extends in the tire radial direction, and is connected to the outer side of the central portion in the tire radial direction. 4. A cushion part extending inward in the tire radial direction of the belt layer, and the cushion part has a substantially triangular cross section that gradually decreases after the thickness gradually increases toward the end part. This is a pneumatic tire.

  The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 4, wherein 90% by mass or more of the total mass of the tire is made of a non-petroleum natural material not based on petroleum.

  The pneumatic tire of the present invention includes a clinch rubber that contacts a rim, an inner rubber portion in a sidewall rubber that has an inner end in the tire radial direction connected to the clinch rubber, and a band layer that is connected to the inner rubber portion. A conductive end portion constituting one end side in the tire axial direction, an under tread rubber portion having one end in the tire axial direction connected to the conductive end portion, and one end connected to the outer surface of the under tread rubber portion and the other end The penetrating portion that penetrates the base rubber portion and the cap rubber portion of the tread rubber and is exposed at the tread ground surface is formed of a conductive material. As a result, a conductive path is formed from the rim to the tread ground surface through the clinch rubber, the inner rubber portion, the conductive end portion, the under tread rubber portion, and the through portion, and the static electricity generated in the vehicle is reliably discharged to the tread ground surface. Can do.

  On the other hand, the carcass, the belt layer, the main part of the band layer, the cap rubber part, the base rubber part, and the outer surface rubber part of the side wall rubber are all formed of a non-conductive material. Therefore, the pneumatic tire of the present invention can increase the natural material ratio outside petroleum to the maximum. In particular, since the band layer is composed of a non-conductive main portion and a conductive end portion disposed on one end side in the tire axial direction, the conductive portion can be made smaller and the natural material ratio outside petroleum can be further increased. it can.

It is sectional drawing of the right half which shows the pneumatic tire of one Embodiment of this invention. It is an enlarged view of the tire axial direction outer side of the tread part of FIG. It is sectional drawing which shows the structure of the band layer of the other Example of this invention. It is an expanded view which shows the arrangement | positioning position of a penetration part. It is a figure which shows the extrusion molded product which tread rubber was integrally combined. It is a figure which shows the extrusion molding which integrally bonded the side wall rubber and the clinch rubber. 1 is a schematic cross-sectional view conceptually showing a tire electrical resistance measuring device. It is sectional drawing which shows the structure of a comparative example. It is sectional drawing of the tire explaining background art.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a pneumatic tire (hereinafter, simply referred to as “tire”) 1 according to this embodiment reaches a bead core 5 of a bead portion 4 from a tread portion 2 through a sidewall portion 3. A carcass 6, a belt layer 7 arranged radially outside the carcass 6 and inside the tread portion 2, a band layer 8 covering the outer side of the belt layer 7 in the tire radial direction, and outside the band layer 8. The tread rubber 2G is disposed, the sidewall rubber 3G is disposed outside the carcass 6 in the sidewall portion 3 and extends inward and outward in the tire radial direction, and is disposed outside the carcass 6 in the bead portion 4. It comprises at least a conductive clinch rubber 4G that comes into contact with the rim R when mounted on the rim R. In this embodiment, a radial tire for passenger cars It is shown. Although only the right half section of the tire is shown in FIG. 1, the tire 1 of the present embodiment has a substantially symmetrical structure with respect to the tire equator C with respect to the internal structure.

  The carcass 6 includes a main body portion 6a straddling a pair of bead cores 5 and 5 in a toroidal manner, and a folded portion 6b which is continuous from both sides of the main body portion 6a and is folded from the inner side to the outer side in the tire axial direction around the bead core 5. And at least one carcass ply 6A (in the present embodiment). In the carcass ply 6A, carcass cords arranged substantially in parallel are covered with topping rubber, and the carcass cords are inclined at an angle of, for example, 75 to 90 ° with respect to the tire equator C direction.

  The bead core 5 has an annular shape formed by, for example, winding a non-stretch bead wire many times. Thereby, fitting with bead part 4 and rim R is fully secured.

  Further, a bead apex rubber 19 made of hard rubber extending from the outer surface of the bead core 5 in the radial direction of the tire and having a substantially triangular cross section is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A. The

  Note that an inner liner rubber 18 having excellent air impermeability is disposed inside the carcass 6.

  The belt layer 7 includes, for example, two outer belt plies 7A and 7B in the tire radial direction, and the inner belt ply 7A is formed wider than the outer belt ply 7B. Each belt ply 7A, 7B has a highly elastic belt cord inclined at an angle of 15 to 35 ° with respect to the tire equator C. The belt plies 7A and 7B are inclined so that the belt cords covered with the topping rubber intersect each other. As a result, the belt layer 7 hooks the carcass 6 over substantially the entire width of the tread portion 2, and the rigidity of the tread portion 2 is enhanced.

  The band layer 8 is composed of at least one ply having a cord, restrains the belt layer 7 and improves handling stability, high-speed durability, and the like. In addition to the cut ply, for example, the band layer 8 includes a belt-like ply in which one or more belt cords are covered with a topping rubber at an angle of 5 degrees or less with respect to the outer side in the tire radial direction of the belt layer 7 and the tire circumferential direction. A so-called jointless band ply formed by winding in a spiral manner may be used.

  In addition, as shown in an enlarged view in FIG. 2, the band layer 8 is disposed on the main portion 9 constituting the main portion of the band layer 8 and at least one end side of the main portion 9 in the tire axial direction. And a conductive end portion 10.

  In the present embodiment, the main portion 9 is made of a full band ply FB arranged over the entire width of the belt layer 7. The conductive end portion 10 is formed of a pair of edge band plies EB disposed on both outer end sides in the tire axial direction of the full band ply FB, and is located on the outer side in the tire axial direction from the outer end of the belt layer 7. Arranged to protrude.

  Further, the band layer 8 of this embodiment has an outer end edge e1 in the tire axial direction of the main portion 9 and a conductive end portion 10 as shown in an enlarged view in a circle surrounded by a chain line in FIG. When the inner end edge e2 abuts each other, the main portion 0 and the conductive end portion 10 are continuously arranged in the tread width direction. Thereby, the conductive end portion 10 is provided at a position further beyond the outer end of the belt layer 7. However, as shown in FIG. 3, the conductive end portion 10 may be disposed such that the inner side portion in the tire axial direction covers and overlaps the outer end portion of the main portion 9 in the tire axial direction. In this embodiment, since the outer end portion of the main portion 9 is restrained by the conductive end portion 10, it is desirable in that the steering stability and the like are maintained high.

  As shown in FIGS. 1 and 2, the tread rubber 2G extends in the width direction of the tread portion 2 and is disposed on the inner side in the tire radial direction of the cap rubber portion 11 forming the main portion of the tread grounding surface 2A. A base rubber portion 12, an under tread rubber portion 13 that is disposed on the inner side in the tire radial direction of the base rubber portion 12 and extends in the tread width direction, and one end connected to the outer surface of the under tread rubber portion 13 and the other end The base rubber part 12 and the cap rubber part 11 are formed so as to include at least one through part 14 exposed at the tread ground surface 2A.

  The cap rubber portion 11 is preferably arranged so as to occupy a width of 80% or more of the ground contact width TW, which is the distance in the tire axial direction between the ground contact ends 2e and 2e of the tread portion 2. The cap rubber part 11 of the present embodiment constitutes the entire area of the tread grounding surface excluding the through part 14. Further, the cap rubber portion 11 of the present embodiment is disposed beyond the ground contact end 2e outward in the tire axial direction.

  The “tread contact surface” means a contact surface when a normal load is applied to a tire that is assembled on a normal rim and filled with a normal internal pressure and pressed against a flat surface with a camber angle of 0 degrees. Further, the contact end 2e of the tread portion 2 is the outermost end in the tire axial direction of the tread contact surface.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA. "Or, if ETRTO, means" Measuring Rim ". The “regular internal pressure” is the air pressure defined by the standard for each tire, and is “maximum air pressure” for JATMA, and “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA. The maximum value, ETRTO, means “INFLATION PRESSURE”, but in the case of passenger car tires, it is 180 kPa. Furthermore, the “regular load” is a load defined by the standard for each tire, and is described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for JATMA and “TRAI LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA. If the maximum value of ETRTO, "LOAD CAPACITY".

  The base rubber portion 12 is disposed on the entire inner side in the tire radial direction of the cap rubber portion 11. Moreover, the base rubber part 12 of this embodiment is comprised by about 5-20% of the thickness of the cap rubber part 11, and small thickness.

  The under tread rubber portion 13 is configured with a smaller thickness than the base rubber portion 9. The under tread rubber portion 13 has at least one end portion in the tire axial direction (in this embodiment, both outer end portions in the tire axial direction) extends to the conductive end portion 10 of the band layer 8, and the tire radius of the conductive end portion 10 Connected to the outer surface of the direction.

  Further, in the tread rubber 2G of the present embodiment, wing rubber portions 20 having a substantially triangular cross section are disposed on both outer sides in the tire axial direction. The outer ends of the cap rubber part 11 and the base rubber part 12 are connected to the wing rubber part 20, respectively. Needless to say, the members 11 to 14 and 20 are made of rubber materials having different compositions. Such a tread rubber 2G is formed by, for example, extruding the rubber parts 11, 12, 13, 14 and 20 integrally as shown in FIG. 4 by using a five-screw extruder having five extrusion heads. The extruded product is preferably used.

  Further, the side wall rubber 3G is made of a relatively low elasticity rubber excellent in cut resistance and flexibility, and can flex flexibly following the deformation of the carcass 6 during tire running. The sidewall rubber 3 </ b> G of the present embodiment includes an outer surface rubber portion 16 that forms the outer surface 3 </ b> A of the sidewall portion 3, and an inner rubber portion 15 that is disposed on the inner side in the tire axial direction of the outer surface rubber portion 16.

  The outer surface rubber portion 16 has an outer end in the tire radial direction connected to an inner surface in the tire radial direction of the wing rubber portion 20. On the other hand, the inner end of the outer surface rubber portion 16 in the tire radial direction is connected to the clinch rubber 4G.

  Further, the outer end of the inner rubber portion 15 in the tire radial direction passes through the inner side of the conductive end portion 10 of the band layer 8 in the tire radial direction, and terminates between the belt layer 7 and the carcass 6. As a result, the outer end of the inner rubber portion 15 is connected to the inner surface of the conductive end portion 10 of the band layer 8.

  Thus, the sidewall rubber 3G of the present embodiment has a so-called TOS (tread over sidewall) structure in which the outer end portion is covered with the outer end portion in the tire axial direction of the tread rubber 2G. It is not limited to such an aspect.

  Further, the inner end of the inner rubber portion 15 in the tire radial direction extends to the bead portion 4 and ends between the clinch rubber 4G and the carcass 6. Thereby, the inner rubber part 15 is connected to the clinch rubber 4G with a sufficient length.

  Further, in the present embodiment, the inner rubber portion 15 has a central portion 15a having a thickness t1 of 0.1 to 2 mm and extending in the tire radial direction, and is connected to the outer side of the central portion 15a in the tire radial direction, and the belt layer. 7 and a cushion portion 15b extending inward in the tire radial direction. The cushion portion 15b is formed in a generally triangular cross section that gradually decreases after the thickness gradually increases toward the outer end in the tire axial direction so as to absorb the difference in curvature between the belt layer 7 and the carcass 6. .

  The clinch rubber 4G is made of a highly elastic rubber excellent in wear resistance, and is bled outward from the bead heel in the tire radial direction. Accordingly, the clinch rubber 4G can contact at least the rim flange Rf when the rim is assembled to the rim.

  Further, the side wall rubber 3G and the clinch rubber 4G are extruded by, for example, using a triaxial extruder and the outer surface rubber portion 16, the inner rubber portion 15 and the clinch rubber 4G are integrally extruded as shown in FIG. Use of a molded product is desirable from the viewpoint of productivity and adhesion between the sidewall rubber 3G and the clinch rubber 4G.

  In the present embodiment, a chafer rubber 17 is provided on the bead portion 4. The chafer rubber 17 is formed in a substantially U-shaped cross section having a base portion 17b exposed on the bottom surface of the bead and outer and inner rising portions 17a and 17c extending outward in the tire radial direction from both ends in the tire axial direction. Has been.

  Further, in the present embodiment, in order to increase the ratio of natural materials other than oil of the tire 1, the rubber members (tread rubber 2G, sidewall rubber 3G, clinch rubber 4G, chafer rubber 17, inner liner rubber occupying most of the mass of the tire). 18, the bead apex rubber 19, and the main one (topping rubber used for each ply), it is desirable to use a rubber compound containing a larger amount of non-petroleum natural materials.

  Each of the rubber members includes a rubber polymer and an additive blended therein. Therefore, in order to enhance the non-petroleum natural material of the rubber member, it is desirable that all or the main part of the rubber polymer and all or the main part of the additive are formed of the non-petroleum natural material.

  Natural rubber (including modified products) is preferably used as the rubber for non-petroleum natural materials. Examples of modified natural rubber include epoxidized natural rubber. This epoxidized natural rubber tends to be particularly excellent in grip properties, low rolling resistance, and resistance to flex cracking. Therefore, by blending natural rubber and epoxidized natural rubber in an appropriate blend, the required characteristics can be obtained. It is desirable that all the different types of tire rubber members or at least 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, and particularly preferably 80% by mass or more are suitably adopted.

  Examples of the additive compounded in the tire rubber member include a reinforcing agent, a softening agent, a vulcanizing agent, a vulcanization accelerator, an antiaging agent, and a tackifier. Among these additives, reinforcing agents, softening agents, and vulcanizing agents are essential, but others are added to the rubber component as necessary.

  As the reinforcing agent, carbon black using petroleum as a raw material has been widely used. However, in this embodiment, it is desirable that silica, which is a natural material other than petroleum, is used for all or the main part of the reinforcing agent. In particular, tires using silica as a reinforcing material for tread rubber maintain a high hysteresis loss on the low temperature side, so that they exhibit excellent wet grip performance, while the hysteresis loss on the high temperature side is low, so rolling resistance There is an advantage that both low rolling resistance performance and wet grip performance are achieved.

  Moreover, as said softener, it is desirable to use the natural vegetable oil which is the softener of the natural material other than petroleum for the whole or the main part. In particular, vegetable oils and fats having a low degree of unsaturation are preferable as softeners, semi-drying oils having an iodine value (grams of iodine that can be added to 100 g of oils and fats) of 100 to 130, and non-drying properties having an iodine value of 100 or less. Oil or solid fat is preferred.

  Other additives, such as vulcanizing agents, vulcanization accelerators, anti-aging agents, and tackifiers, are very small compared to reinforcing agents and softening agents, but on the physical properties of rubber. Since the influence is large, the same one as before can be used.

More specifically, in this embodiment, at least the cap rubber part 11, the base rubber part 12, the outer surface rubber part 16 of the sidewall rubber 3G, the topping rubber of the carcass 6, the topping rubber of the belt layer 7, and the band layer 8 The topping rubber of the main part 9 is a non-conductive rubber having a volume resistivity of 1 × 10 ⁸ Ωcm or more by blending an inorganic filler such as silica as a reinforcing agent with a rubber polymer mainly composed of natural rubber. Is used. As a result, not only the rubber parts but also the cord / rubber composites such as the carcass 6, the belt layer 7 and the main part 9 of the band layer 8 are covered with the non-conductive rubber material. No non-conductivity. As a particularly preferable embodiment for increasing the ratio of non-petroleum natural materials, the rubber members of the chafer rubber 17, the wing rubber portion 20, the inner liner rubber 18 and the bead apex rubber 19 may be formed of the non-conductive rubber material.

  Here, the “volume resistivity” is measured using an ADVANTESTER 8340A electrical resistance measuring instrument using a rubber sample 15 cm square and 2 mm thick under the conditions of an applied voltage of 500 V, an air temperature of 25 ° C., and a humidity of 50%. Value.

On the other hand, the through portion 14, the under tread rubber portion 13, the topping rubber of the conductive end portion 10, the inner rubber portion 15 and the clinch rubber 4G are formed of a conductive rubber material having a volume specific resistance of 1 × 10 ⁵ Ωcm or less. Is done.

  As the conductive rubber material, in addition to a material containing more carbon black as a reinforcing agent, for example, an ion conductive material such as lithium salt or a metal material such as iron or nickel may be used. As described above, the conductive end portion 10 is a cord / rubber composite composed of a band cord and a topping rubber covering the band cord. At least the topping rubber constituting the outer peripheral surface of the conductive end portion 10 is a conductive material. It shows the electroconductivity which conducts electricity substantially by comprising.

  As described above, in the tire 1 of the present embodiment, the metal rim R, the clinch rubber 4G, the inner rubber portion 15 of the sidewall rubber 3G, the conductive end portion 10 of the band layer 8, the under tread rubber portion 13 and the through portion 14 are used. Therefore, the static electricity generated in the vehicle can be reliably discharged to the road surface through the conductive path.

  In particular, when the carcass 6 and the belt layer 7 are made of a non-conductive material as in the present invention, if the width of the belt layer 7 is increased in order to enhance high-speed durability, the inner rubber 15 and the under tread rubber There is a possibility that the belt layer 7 extends between the portion 13 and the contact between them is hindered. However, as in the tire 1 of the present invention, the band layer 8 is provided with the conductive end portion 10 that protrudes outward in the tire axial direction from the outer end of the belt layer 7, and the inner rubber 15 and the under rubber via the conductive end portion 10 are provided. By connecting the tread rubber portion 13 to the tread rubber portion 13, it is possible to ensure a conductive path. Moreover, the band layer 8 is also useful for increasing the ratio of non-petroleum natural materials because the main portion 9 covering the entire width of the belt layer 7 is formed of non-petroleum natural materials.

  From the viewpoint as described above, the width BW of the conductive end portion 10 in the tire axial direction is preferably 1 mm or more, more preferably 5 mm or more. On the other hand, if the length BW of the conductive end portion 10 in the tire axial direction is increased, the outer end may approach the buttress portion and become a starting point of damage. Therefore, the width BW is preferably 12 mm or less, more preferably Is preferably 9 mm or less.

  The through portion 14 is preferably formed continuously in the tire circumferential direction, but a part of the through portion 14 may be interrupted by a lateral groove provided in the tread portion 2. Further, it is preferable that the penetrating portion 14 is disposed near the center of the tread portion 2. Thereby, the penetration part 14 can be earth | grounded on a road surface irrespective of the progress state of turning of a vehicle, a straight advance, and the abrasion of a tire, and can ensure favorable discharge. Further, as shown in FIG. 6A, one through portion 14 may be provided, or two or more through portions 14 may be provided at a distance in the tire axial direction as shown in FIG. 6B. good. In the latter case, providing symmetrically with respect to the tire equator C is preferable in that deterioration of tire uniformity can be prevented.

  The under tread rubber portion 13 has the smallest thickness in the tread rubber 2G. This is useful for securing a large volume of the cap rubber portion 11 and the base rubber portion 12 and increasing the natural material ratio outside petroleum. From such a viewpoint, the thickness t2 of the undertread rubber portion 13 is preferably 0.1 mm or more, more preferably 0.5 mm or more, and preferably 1.5 mm or less, more preferably 1.2 mm or less. desirable.

  The chafer rubber 17 may be formed of the conductive rubber material, although it does not increase the ratio of non-petroleum natural materials. In this case, as shown in FIG. 1, the inner end in the tire radial direction of the central portion 15a of the inner rubber portion 15 is also connected to the chafer rubber 17, so that the vehicle side static electricity can be more reliably received from the rim. Useful.

  Further, in order to increase the ratio of non-oil natural materials, it is preferable that all or the main part of the tire cords are made of non-oil natural material cords. For example, natural fiber cords are suitably used for carcass cords and band cords in order to suppress a decrease in fuel efficiency due to an increase in mass.

  As the natural fiber cord, a cord of regenerated cellulose fiber or purified cellulose fiber is preferable. In particular, refined cellulose fibers have high crystallinity and high orientation between crystalline and non-crystalline parts, so that moisture does not easily enter between the cellulose chains, and the strength and stability of humidity are high. Have. Therefore, by using the cord of this purified cellulose fiber for a carcass cord and / or a band cord, the strength against humidity and the stability of elongation are enhanced. This is useful for improving high-speed durability and high-speed steering stability compared to conventional tires using nylon cords or polyester cords. For heavy duty tires, metal cords made of metal such as steel cords may be used for the carcass cords, belt cords, etc., but in such cases, metal cords are used in the same way as before. Good to do. For the belt cord and the bead wire, a metal cord and a metal wire are used in order to ensure necessary rigidity.

  By accumulating the improvements as described above, the tire 1 of the present embodiment is formed of 90% by mass or more, more preferably 95% by mass or more of the total mass of the natural material other than petroleum. Thereby, what is called an eco-friendly tire can be provided.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.

A pneumatic tire (size: 195 / 65R15) having the internal structure shown in FIGS. 1 and 8 was prototyped based on the use of Table 1, and the electrical resistance of each tire was measured. The material of each rubber member and each tire cord is shown below. The carcass topping rubber, belt layer topping rubber, and band main part topping rubber of Comparative Example 2 are made of a conductive material.
Cap part, base rubber part, outer surface rubber part, carcass topping rubber, belt layer topping rubber, chafer rubber, wing rubber part, inner liner rubber and bead apex rubber: 100% by mass of natural rubber and predetermined silica are blended Non-conductive material.
Penetration part, under tread rubber part, topping rubber of conductive end part, inner rubber part and clinch rubber: conductive material in which rubber polymer is blended with 100% by mass of natural rubber and predetermined carbon black.
Belt cords and bead wires: Metal wires and metal cords (natural materials other than petroleum).
Carcass cord: Rayon cord (natural material other than petroleum)
Band cord: Rayon cord (natural material other than petroleum)
The non-conductive material of rubber has a volume specific resistance value of 1 × 10 ⁸ Ωcm ± 10%, and the conductive material has a volume specific resistance value of 1 × 10 ⁵ Ωcm ± 10%.
The test method is as follows.

<Electric resistance of tire>
As shown in FIG. 7, a metal plate 26 (electric resistance value is 10 Ω or less) whose surface is polished and placed on an insulating plate 25 (electric resistance value is 10 ¹² Ω or more), and a tire / rim assembly. The electrical resistance value of the assembly of the test tire and the rim J was measured in accordance with JATMA regulations using a measuring device including a conductive tire mounting shaft 27 that holds the tire and an electrical resistance measuring device 28. Each test tire T was a tire in which the surface release agent and dirt were sufficiently removed in advance and were sufficiently dried. Other conditions are as follows.
Rim material: Aluminum alloy Rim size: 15 × 6.5-J
Internal pressure: 200 kPa
Load: 5.3kN
Test environment temperature (test room temperature): 25 ° C
Humidity: 50%
Measuring range of electric resistance measuring device: 10 ^{3 to} 1.6 × 10 ¹⁶ Ω
Test voltage (applied voltage): 1000V

The test procedure is as follows.
(1) A test tire T is mounted on a rim to prepare a tire / rim assembly. At this time, soapy water is used as a lubricant at the contact portion between the two.
(2) The tire / rim assembly is left in the test room for 2 hours and then attached to the tire mounting shaft 27.
(3) The tire / rim assembly is loaded with the load for 0.5 minutes, and further for 0.5 minutes after being released and for 2 minutes after being released.
(4) When the test voltage is applied and 5 minutes have passed, the electrical resistance value between the tire mounting shaft 27 and the metal plate 26 is measured by the electrical resistance measuring device 28. The measurement is performed at four positions at 90 ° intervals in the tire circumferential direction, and the maximum value among them is taken as the electrical resistance value (measured value) of the tire T.
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that the tire of the example has a lower electrical resistance than the comparative example.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2A Tread ground surface 2G Tread rubber 3 Side wall part 3G Side wall rubber 4 Bead part 4G Clinch rubber 5 Bead core 6 Carcass 7 Belt layer 8 Band layer 9 Main part 10 Conductive end part 11 Cap rubber part 12 Base Rubber part 13 Under tread rubber part 14 Through part 15 Inner rubber part 16 Outer rubber part R Rim

Claims (5)

A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, a belt layer disposed outside the carcass in the tire radial direction and inside the tread portion, and a band covering the outer side of the belt layer in the tire radial direction Layer, a tread rubber disposed outside the band layer, a sidewall rubber disposed outside the carcass in the sidewall portion and extending inward and outward in the tire radial direction, and disposed outside the carcass in the bead portion. And a pneumatic tire including a conductive clinch rubber that comes into contact with the rim when mounted on the rim,
The carcass and the belt layer are formed of a non-conductive material;
The band layer is made of a non-conductive material and constitutes a main part of the band layer, and is arranged at least on one end side in the tire axial direction of the main part and is arranged on the tire shaft more than the outer end of the belt layer. Including a conductive end portion that protrudes outward in the direction and made of a conductive material,
The tread rubber extends in the width direction of the tread part and forms a main part of the tread ground surface, and a non-conductive cap rubber part;
A non-conductive base rubber portion disposed inside the tire radial direction;
A conductive undertread rubber portion that is arranged on the inner side in the tire radial direction of the base rubber portion and extends in the tread width direction and at least one end portion in the tire axial direction is connected to the conductive end portion of the band layer;
One end is connected to the outer surface of the under tread rubber portion and the other end includes a conductive through portion that penetrates the base rubber portion and the cap rubber portion and is exposed at the tread ground surface,
The sidewall rubber includes a non-conductive outer surface rubber portion that forms an outer surface of the sidewall portion, and a conductive inner rubber portion that is disposed on the inner side in the tire axial direction of the outer surface rubber portion. The pneumatic tire is characterized in that the outer end in the tire radial direction is connected to the conductive end of the band layer and the inner end in the tire radial direction is connected to the clinch rubber.   2. The pneumatic tire according to claim 1, wherein main parts of the carcass, the belt layer, and the band layer are each coated with a cord material with a topping rubber in which silica is mixed with a rubber polymer mainly composed of natural rubber.   The pneumatic tire according to claim 1 or 2, wherein the under-tread rubber portion has a thickness of 0.5 to 1.5 mm and the smallest thickness among the tread rubbers. The inner rubber portion of the sidewall rubber has a thickness of 0.1 to 2 mm and extends in the tire radial direction, and is connected to the outer side in the tire radial direction of the central portion and inward in the tire radial direction of the belt layer. Including a cushion part that extends,
The pneumatic tire according to any one of claims 1 to 3, wherein the cushion portion has a substantially triangular cross section that gradually decreases after the thickness gradually increases toward the end portion.   The pneumatic tire according to any one of claims 1 to 4, wherein 90% by mass or more of the total mass of the tire is made of a non-petroleum natural material not based on petroleum.

Images