JP5808200B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that can discharge static electricity generated in a vehicle body or a tire to a road surface.

  In recent years, pneumatic tires with high silica content in tread rubber have been proposed for the purpose of reducing rolling resistance, which is closely related to lower fuel consumption of vehicles, and improving braking performance (wet braking performance) on wet road surfaces. Yes. However, such tread rubber has a higher electrical resistance than those with a high carbon black content, and inhibits the release of static electricity generated in the vehicle body and tires to the road surface, which is likely to cause problems such as radio noise. there were.

  Therefore, a tread rubber made of non-conductive rubber compounded with silica or the like is provided with a conductive part made of conductive rubber compounded with carbon black or the like, so that current-carrying performance can be exhibited by a conductive path through the conductive part. Pneumatic tires have been developed. Further, in order to increase the rolling resistance reduction effect, non-conductive rubber may be used not only for the tread rubber but also for the sidewall rubber and the topping rubber of the belt.

  Patent Document 1 describes a pneumatic tire in which a tread rubber or a sidewall rubber is formed of a non-conductive rubber, and a conductive path is formed through a conductive portion embedded in the tread rubber and a topping rubber of a carcass ply. Yes. However, it has been found that there are still conductive rubbers that can be reduced without affecting the current-carrying performance, and that there is a possibility of further improving the performance by reducing such conductive rubbers.

  In recent years, there has been a tendency to reduce the weight of tires. It will cause deterioration. Therefore, in order to satisfactorily exhibit steering stability performance and riding comfort performance, a structure that can suppress a decrease in tire rigidity as much as possible is desired.

JP 2009-6975 A

  The present invention has been made in view of the above circumstances, and the purpose thereof is to secure a current-carrying performance while reducing conductive rubber, and to suppress a decrease in tire rigidity and to improve steering stability performance and riding comfort performance. It is in providing the pneumatic tire which can be exhibited.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a wound-up portion wound from the inner side to the outer side in the tire width direction around the bead core embedded in the bead portion in the main body portion from the tread portion through the sidewall portion to the bead portion. A tread annular body that contacts the carcass ply from the outer side in the tire radial direction, including a tread rubber that forms a contact surface, and a belt that is disposed on the inner side in the tire radial direction of the tread rubber. And a rim strip rubber disposed in the bead portion and capable of contacting a rim, wherein the carcass ply includes an aligned carcass cord and an outer topping that covers the carcass cord from the tire outer surface side. The rubber and the carcass cord are covered from the inner surface of the tire, and the rim strip is formed at the winding portion. An inner topping rubber that is in contact with the rubber, and the outer topping rubber has an outer interface that contacts a different rubber on the main body portion of the sidewall portion or the bead portion, and from the outer interface to the winding portion. A portion extending from the outer interface to a contact portion with the tread annular body is formed of a conductive rubber having a hardness higher than that of the nonconductive rubber, and the inner topping rubber is The main body portion of the sidewall portion or the bead portion has an inner interface with which different rubber contacts, and a portion extending from the inner interface to the outer side in the tire radial direction is formed of non-conductive rubber, and the rim strip extends from the inner interface. The part reaching the adjacent part with the rubber is formed of conductive rubber having higher hardness than the non-conductive rubber, and the outer interface is more than the inner interface. Located on the inner side in the tire radial direction, the conductive rubber of the outer topping rubber is connected to the conductive rubber of the inner topping rubber, and the tread annular body reaches the conductive rubber of the outer topping rubber from the ground contact surface. A conductive path is formed, and the rim strip rubber is formed with a conductive path from the conductive rubber of the inner topping rubber to the contact point with the rim.

  According to the pneumatic tire of the present invention, static electricity generated in the vehicle body or the tire can be discharged to the road surface through the conductive path through the conductive rubber of the outer topping rubber and the conductive rubber of the inner topping rubber. In addition, since the portion extending from the outer interface of the outer topping rubber to the winding portion and the portion extending from the inner interface of the inner topping rubber to the outer side in the tire radial direction are each formed of non-conductive rubber, the electric conductivity included in the carcass ply is included. Energizing performance can be ensured while reducing the amount of rubber.

  In addition, the portion from the outer interface of the outer topping rubber to the contact portion with the tread annular body and the portion from the inner interface of the inner topping rubber connected to the adjacent portion to the rim strip rubber are relatively hard. Since it is made of high rubber, the rigidity (particularly longitudinal rigidity) of the tire can be effectively ensured. In addition, since the portion wound around the bead core from the inner side in the tire width direction to the outer side is also formed of a rubber having a high hardness, the rigidity (particularly the lateral rigidity) of the tire can be effectively ensured. Therefore, it is possible to suppress the decrease in tire rigidity and to satisfactorily exhibit steering stability performance and riding comfort performance.

  In the present invention, the outer topping rubber has a tread side interface in contact with a different rubber on the inner side in the tire radial direction of the tread annular body, and a portion extending from the tread side interface to the outer interface is formed of conductive rubber. The portion extending inward in the tire width direction from the tread side interface is formed of non-conductive rubber, and the inner topping rubber is formed of non-conductive rubber in the portion positioned on the outer side in the tire radial direction from the inner interface. Those are preferred.

  According to such a configuration, since the topping rubber of the carcass ply disposed in the tread portion is mainly formed of non-conductive rubber, the conductive rubber included in the carcass ply can be further reduced. Nevertheless, since the conductive rubber having relatively high hardness is arranged as described above so as to suppress the decrease in the rigidity of the tire as much as possible, the steering stability performance and the riding comfort performance can be exhibited well.

  In the present invention, the outer topping rubber is formed of a non-conductive rubber from the outer interface to the tip of the rolled-up portion, and the inner topping rubber has a rim-side interface where a different rubber is in contact with the rolled-up portion. Preferably, the portion from the rim side interface to the inner interface is made of conductive rubber, and the portion from the rim side interface to the tip of the rolled-up portion is made of non-conductive rubber.

  According to such a configuration, since the topping rubber of the carcass ply in the winding portion is mainly formed of non-conductive rubber, the conductive rubber included in the carcass ply can be further reduced. Since the tension acting on the carcass cord is small near the tip of the hoisting part and the effect on the tire stiffness is small, even if the conductive rubber is reduced at this part, steering stability performance and riding comfort performance can be demonstrated well. it can.

  In the present invention, from the viewpoint of increasing the rigidity of the tire, it is preferable that the conductive rubber included in the carcass ply has a JISA hardness of 56 ° or more and the non-conductive rubber has a JISA hardness of less than 56 °. Moreover, it is preferable that the said outer interface and the said inner interface are each located in the range of the height used as 60% of tire cross-section height centering on a tire maximum width position.

The tire meridian half sectional view showing an example of a pneumatic tire according to the present invention A diagram conceptually showing the topping rubber of a carcass ply 2 is a cross-sectional view of the carcass ply of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A pneumatic tire T shown in FIG. 1 includes a pair of bead portions 1, sidewall portions 2 extending outward in the tire radial direction from each of the bead portions 1, and tire radial direction outer ends of the sidewall portions 2. And a tread portion 3 that is connected to the tread. An annular bead core 1a formed by covering a converging body such as a steel wire with rubber is embedded in the bead portion 1, and a bead filler 1b made of hard rubber is disposed on the outer side in the tire radial direction of the bead core 1a.

  Further, in the tire T, a body portion 71 extending from the tread portion 3 to the bead portion 1 through the sidewall portion 2 to the bead portion 1 is provided with a series of winding portions 72 wound around the bead core 1a from the inner side to the outer side in the tire width direction. A carcass ply 7 is provided. The carcass ply 7 is formed in a toroidal shape as a whole, and a bead core 1 a and a bead filler 1 b are sandwiched between a main body 71 and a winding part 72. An inner liner rubber 5 for maintaining air pressure is provided inside the carcass ply 7.

  The tread portion 3 includes a tread rubber 10 constituting a ground contact surface and a belt 6 disposed on the inner side in the tire radial direction of the tread rubber 10, and a tread annular body that contacts the carcass ply 7 from the outer side in the tire radial direction. 20 is provided. The tread annular body 20 of the present embodiment further includes a belt reinforcing material 8, a rubber pad 11, and a wing rubber 12 in addition to the tread rubber 10 and the belt 6. Further, the tread rubber 10 is provided with a conductive portion 13, and in FIG. 1, the conductive portion 13 is colored black for easy discrimination on the drawing.

  The belt 6 includes a plurality (two in this embodiment) of belt plies 6a and 6b. The belt plies 6a and 6b are formed by covering a belt cord that is aligned in a direction inclined with respect to the tire circumferential direction with a topping rubber, and the belt cords are laminated so as to cross each other in opposite directions between the plies. Yes. The belt reinforcing member 8 is formed by covering a reinforcing cord extending substantially in the tire circumferential direction with a topping rubber.

  The rubber pad 11 is disposed on the inner side in the tire radial direction of the belt 6, protrudes outward in the tire width direction from the belt end, and contacts the tread rubber 10. The belt end is a side end of the belt ply 6a which is wide among the belt plies 6a and 6b. The wing rubber 12 is joined to the side of the tread rubber 10. One end of the conductive portion 13 embedded in the tread rubber 10 is exposed to the ground surface, and the other end is connected to the rubber pad 11. The belt reinforcing member 8, the rubber pad 11, and the wing rubber 12 may be omitted.

  The bead portion 1 is provided with a rim strip rubber 4 that can contact a rim (not shown). The rim strip rubber 4 is located on the outer side in the tire width direction of the winding part 72 and is interposed between the rim and the winding part 72 when the rim is mounted. In the sidewall portion 2, sidewall rubber 9 is provided on the outer side of the carcass ply 7 in the tire width direction. In the tire T, a tread-on-side structure in which the end portion of the tread rubber 10 is placed on the end portion of the sidewall rubber 9 is employed, but the present invention is not limited to this.

  In the present embodiment, the tread rubber 10, the topping rubber of the belt 6, the topping rubber of the belt reinforcing member 8, the wing rubber 12, and the sidewall rubber 9 are each formed of non-conductive rubber. Further, the conductive portion 13, the rubber pad 11, and the rim strip rubber 4 provided on the tread rubber 10 are each formed of conductive rubber. As will be described later, the topping rubber of the carcass ply 7 uses a non-conductive rubber and a conductive rubber depending on the part.

  FIG. 2 is a diagram conceptually showing the carcass ply 7 of FIG. 1, and is drawn with an increased thickness for convenience of explanation. 3A to 3E respectively show cross-sectional views taken along arrows AA, BB, CC, DD, and EE in FIG. In FIGS. 2 and 3, the conductive rubber included in the carcass ply 7 is colored black for easy discrimination on the drawings.

  The carcass ply 7 includes an aligned carcass cord 17, an outer topping rubber 18 that covers the carcass cord 17 from the tire outer surface side, and an inner topping rubber 19 that covers the carcass cord 17 from the tire inner surface side. The carcass cords 17 are arranged in a direction substantially orthogonal to the tire circumferential direction, and organic fiber cords or steel cords are preferably used. The inner topping rubber 19 covers the carcass cord 17 from the inner surface of the tire in the main body portion 71 that forms the main body of the carcass ply 7, and contacts the rim strip rubber 4 at the winding-up portion 72.

  The outer topping rubber 18 has an outer interface 31 in contact with a different rubber on the main body 71 in the sidewall portion 2. Nevertheless, the portion from the outer interface 31 to the winding portion 72 is formed of non-conductive rubber, and the portion from the outer interface 31 to the contact portion 20A with the tread annular body 20 is harder than the non-conductive rubber. Is made of highly conductive rubber. At the contact portion 20 </ b> A with the tread annular body 20, the conductive rubber of the outer topping rubber 18 contacts the rubber pad 11 as shown in FIG. 1.

  The inner topping rubber 19 has an inner interface 32 in contact with the main body 71 in the sidewall portion 2 and different rubber. Nevertheless, the portion extending from the inner interface 32 to the outer side in the tire radial direction is made of non-conductive rubber, and the portion extending from the inner interface 32 to the adjacent portion 4A with the rim strip rubber 4 is more than the non-conductive rubber. It is made of conductive rubber with high hardness. At a location 4A adjacent to the rim strip rubber 4, the conductive rubber of the inner topping rubber 19 contacts the rim strip rubber 4 as shown in FIG.

  The outer interface 31 is located on the inner side in the tire radial direction than the inner interface 32, and the conductive rubber of the outer topping rubber 18 is connected to the conductive rubber of the inner topping rubber 19. Therefore, the conductive rubber included in the carcass ply 7 continuously extends from the contact portion 20A with the tread annular body 20 to the adjacent portion 4A with the rim strip rubber 4, and electrically connects the rubber pad 11 and the rim strip rubber 4. Conduct.

  The tread annular body 20 has a conductive path from the ground surface to the conductive rubber of the outer topping rubber 18. In the present embodiment, the tread rubber 10 is formed of non-conductive rubber, but a conductive path is constituted by the conductive portion 13 and the rubber pad 11. The rim strip rubber 4 has a conductive path from the conductive rubber of the inner topping rubber 19 to the contact portion 4B with the rim. In the present embodiment, the rim strip rubber 4 is formed of a conductive rubber, and energization via the rim strip rubber 4 is possible.

  Static electricity generated in the vehicle body or the like is from the rim to the conductive path formed in the rim strip rubber 4, the conductive rubber in the inner topping rubber 19, the conductive rubber in the outer topping rubber 18, and the conductive path formed in the tread annular body 20. Through the road surface. In the present embodiment, the conductive path configured in the rim strip rubber 4 is the rim strip rubber 4 itself, and the conductive paths configured in the tread annular body 20 are the rubber pad 11 and the conductive portion 13. Such a conductive path from the rim to the ground plane may be provided on at least one side in the tire width direction.

The conductive rubber is a rubber having a volume resistivity of less than 10 ⁸ Ω · cm, and examples thereof include a raw material rubber compounded with carbon black as a reinforcing agent in a high ratio. The carbon black is blended in an important part of 30 to 100 with respect to 100 parts by weight of the rubber component, for example. In addition to carbon black, the conductive rubber can be blended with carbon fiber, graphite or other carbon-based materials, and metal-based known conductivity imparting materials such as metal powders, metal oxides, metal flakes, and metal fibers. can get.

The non-conductive rubber is a rubber having a volume resistivity of 10 ⁸ Ω · cm or more, and is exemplified by a raw rubber blended with a high ratio of silica as a reinforcing agent. The silica is blended, for example, in 30 to 100 important parts with respect to 100 parts by weight of the rubber component. As silica, wet silica can be preferably used, but those commonly used as reinforcing materials can be used without limitation. The nonconductive rubber may be prepared by blending calcined clay, hard clay, calcium carbonate, or the like, in addition to silicas such as precipitated silica and anhydrous silicic acid.

  Examples of the raw rubber include natural rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), and butyl rubber (IIR). These may be used alone or in combination of two or more. Used. A vulcanizing agent, a vulcanization accelerator, a plasticizer, an anti-aging agent and the like are appropriately blended with the raw rubber.

  In the topping rubber of the carcass ply 7, the conductive rubber has a higher hardness than the nonconductive rubber. For this reason, relatively hard rubber is disposed from the bead portion 1 to the buttress portion, and the vertical rigidity of the tire T is effectively ensured. The buttress portion is the outer portion in the tire radial direction of the sidewall portion 2 that is not grounded during normal running on a flat road, and greatly contributes to the longitudinal rigidity. Further, since the hard rubber is disposed around the bead core 1a, particularly on the outer side in the tire width direction of the bead filler 1b, the lateral rigidity of the tire T is effectively ensured. As a result, a reduction in tire rigidity can be suppressed, and steering stability performance and riding comfort performance can be satisfactorily exhibited.

  In the topping rubber of the carcass ply 7, from the viewpoint of increasing the rigidity of the tire T, the JISA hardness of the conductive rubber (value measured at 25 ° C according to JISK6253 durometer hardness test (type A)) is 56 ° or more. The non-conductive rubber preferably has a JISA hardness of less than 56 °. Further, it is more preferable that the conductive rubber has a JISA hardness of 60 ° or more. The difference in hardness between the conductive rubber and the non-conductive rubber included in the carcass ply 7 is, for example, 4 ° or more in JISA hardness.

  The outer interface 31 and the inner interface 32 are each preferably located within a height range (within the range of the region X shown in FIG. 1) that is 60% of the tire cross-section height with the tire maximum width position as the center. Further, the outer interface 31 or the inner interface 32 may be set in the main body 71 in the bead unit 1. In order to ensure the connection between the conductive rubber of the outer topping rubber 18 and the conductive rubber of the inner topping rubber 19 while reducing the conductive rubber in the carcass ply 7, the overlap allowance W thereof is, for example, 1 to 40 mm. Is set. In order to suppress the decrease in rigidity, it is more preferable to set the overlap margin W to 1 to 15 mm.

  In the present embodiment, the outer topping rubber 18 has a tread side interface 33 in contact with a different rubber on the inner side in the tire radial direction of the tread annular body 20. Nevertheless, the portion from the tread side interface 33 to the outer interface 31 is made of conductive rubber, and the portion extending inward in the tire width direction from the tread side interface 33 is made of nonconductive rubber. The inner topping rubber 19 is formed of a non-conductive rubber at a portion located on the outer side in the tire radial direction from the inner interface 32.

  According to this configuration, since the topping rubber of the carcass ply 7 disposed in the tread portion 3 is mainly formed of non-conductive rubber, the conductive rubber included in the carcass ply 7 can be further reduced. Nevertheless, the conductive rubber having a relatively high hardness is arranged as described above so that the decrease in rigidity of the tire T can be suppressed as much as possible, so that the steering stability performance and the riding comfort performance can be exhibited well. .

  The conductive rubber in the outer topping rubber 18 preferably extends to the inner side in the tire width direction from the belt end so that a contact area with the tread annular body 20 is ensured. Further, when the outer topping rubber 18 has the tread side interface 33, the tread side interface 33 is formed in a range that is within 20% of the belt width from the belt end to the inside in the tire width direction from the viewpoint of reducing the conductive rubber. It is preferable. The belt width is measured as a distance in the tire width direction between the belt ends.

  In this embodiment, the inner topping rubber 19 has a rim-side interface 34 in contact with a different rubber at the winding portion 72. Nevertheless, the portion from the rim side interface 34 to the inner interface 32 is formed of conductive rubber, and the portion from the rim side interface 34 to the tip of the winding portion 72 is formed of nonconductive rubber. The outer topping rubber 18 is formed of a non-conductive rubber at a portion from the outer interface 31 to the tip of the winding part 72. In a portion adjacent to the sidewall rubber 9, the topping rubber of the winding portion 72 is formed of non-conductive rubber.

  According to such a configuration, the topping rubber of the carcass ply 7 in the winding portion 72 is mainly formed of non-conductive rubber, so that the conductive rubber included in the carcass ply 7 can be further reduced. Since the tension acting on the carcass cord 17 is small in the vicinity of the tip of the winding portion 72, particularly on the outer side in the tire radial direction from the rim strip rubber 4, there is little influence on the rigidity of the tire. Stable performance and ride performance can be exhibited well.

  In the present embodiment, the conductive portion 13 extends inward in the tire radial direction from the ground contact surface and extends in the tire width direction (right side in FIG. 1) and is connected to the rubber pad 11, but the rubber pad 11 is omitted. The conductive portion 13 may be directly connected to the conductive rubber of the outer topping rubber 18. Such a configuration is particularly useful when a side-on-tread structure in which the end portion of the sidewall rubber is placed on the end portion of the tread rubber is employed. If it is a side-on-tread structure, the wing rubber 12 can also be simply omitted.

  The tread portion 3 where the ground contact surface from which one end of the conductive portion 13 is exposed is assembled to a regular rim, the tire is placed vertically on a flat road surface filled with a regular internal pressure, and is grounded to the road surface when a regular load is applied. Refers to the 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, a standard rim is used for JATMA, “Design Rim” is used for TRA, and “Measuring” is used for ETRTO. Rim ".

  The normal 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. The maximum air pressure is JATMA, and the table is TRA. “INFLATION PRESSURE” for the maximum value described in “ETRTO”, but 180 KPa when the tire is for a passenger car. In addition, the normal load is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. If it is JATMA, it is the maximum load capacity, and if it is TRA, the maximum load described in the above table. If the value is ETRTO, it is “LOAD CAPACITY”, but if the tire is for a passenger car, the load is 85% of the corresponding load at an internal pressure of 180 KPa.

  The shape of the conductive portion is not particularly limited as long as a required conductive path is configured in the tread annular body 20. For example, a conductive portion in which one end is exposed to the ground surface and the other end is connected to the belt reinforcing member 8 on the bottom surface of the tread rubber 10 may be used. In this case, the topping rubber of each of the belt reinforcing member 8 and the belt 6 is formed of a conductive rubber, and the belt 6 is brought into contact with the conductive rubber of the rubber pad 11 or the outer topping rubber 18 so that the outer topping is removed from the ground surface. A conductive path to the conductive rubber of the rubber 18 can be configured.

  In the present embodiment, an example in which the rim strip rubber 4 is formed of a conductive rubber has been shown, but it is also possible to form the rim strip rubber 4 from a nonconductive rubber. In this case, for example, a conductive portion formed of conductive rubber is embedded in the rim strip rubber 4, and one end of the conductive portion is connected to the conductive rubber of the inner topping rubber 19, and the other end is in contact with the rim 4B. By exposing to the rim, a conductive path from the conductive rubber of the inner topping rubber 19 to the contact portion 4B with the rim can be configured.

  The thickness ratio between the outer topping rubber 18 and the inner topping rubber 19 can be variously changed. However, from the viewpoint of reducing the conductive rubber in the carcass ply 7 while ensuring the energization performance, the ratio of the thickness of the conductive rubber to the thickness of the entire ply is preferably 2 to 50%.

  In the present embodiment, an example in which one carcass ply 7 is provided is shown, but a plurality (for example, two) may be provided. In this case, for example, the conductive path in the carcass ply can be configured by making the overlap margin W between the conductive rubber of the outer topping rubber 18 and the conductive rubber of the inner topping rubber 19 adjacent in the thickness direction of the carcass ply.

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

  Examples that specifically show the structure and effects of the present invention will be described below. Each performance evaluation of the tire was performed as follows.

(1) Longitudinal rigidity With the air pressure specified by the vehicle, when the load corresponding to the load of the actual vehicle is applied, the deflection when the vertical compression force is further applied to the tire is measured, and the reciprocal is calculated. . The result of Comparative Example 1 is evaluated as an index with the value of 100, and the larger the value, the greater the longitudinal rigidity.

(2) Lateral rigidity With the air pressure specified by the vehicle, the displacement when a lateral force in the width direction was further applied to the tire was measured and the reciprocal was calculated in a state where a load corresponding to the actual vehicle load was applied. . The result of Comparative Example 1 is evaluated as an index with the value of 100, and the larger the value, the greater the longitudinal rigidity.

(3) Steering stability performance Tires were mounted on the actual vehicle to achieve the air pressure specified by the vehicle, and straight running and cornering running were performed and evaluated by a sensory test of the driver. The result of Comparative Example 1 is evaluated as an index with the value of 100, and the larger the value, the better the steering stability performance.

(4) Ride comfort performance (feeling of damping)
The actual vehicle was fitted with tires to achieve the air pressure specified by the vehicle, traveled over the protrusions on the road surface, and evaluated by a driver's sensory test. The result of Comparative Example 1 is evaluated as an index with the value of 100, and the larger the value, the better the steering stability performance.

(5) Electric resistance (energization performance)
A predetermined load was applied to the tire mounted on the rim, and an electric resistance value was measured by applying an applied voltage (500 V) from a shaft supporting the rim to a metal plate to which the tire contacts the ground.

(6) Rolling resistance The rolling resistance of the tire was measured by a drum running test using a rolling resistance tester. The result of Comparative Example 1 is evaluated as an index with the value of 100, and the smaller the value, the better the rolling resistance.

  The size of the tire used for the evaluation is 195 / 65R15, and the tire structure and the rubber composition in each example are common except for the configuration of the carcass ply. The configuration and evaluation results of the carcass ply are as shown in Table 1. In Comparative Examples 1 to 3, the topping rubber of the carcass ply is formed of one kind of rubber, and in Comparative Example 4, a non-conductive rubber and a conductive rubber are arranged opposite to FIG.

  As shown in Table 1, although Comparative Examples 1 and 3 have energization performance, the rolling resistance is relatively high. Moreover, Comparative Examples 2 and 4 do not have energization performance. On the other hand, in Examples 1-3, rolling resistance is low by reducing conductive rubber, and steering stability performance and riding comfort performance can be satisfactorily exhibited while ensuring energization performance.

DESCRIPTION OF SYMBOLS 1 Bead part 1a Bead core 2 Side wall part 3 Tread part 4 Rim strip rubber 6 Belt 7 Carcass ply 10 Tread rubber 11 Rubber pad 13 Conductive part 17 Carcass cord 18 Outer topping rubber 19 Inner topping rubber 20 Tread annular body 31 Outer interface 32 Inner interface 33 Tread side interface 34 Rim side interface 71 Main body 72 Winding part

Claims (5)

A carcass ply provided with a series of winding portions wound from the inner side to the outer side in the tire width direction around the bead core embedded in the bead portion on the main body portion from the tread portion through the sidewall portion to the bead portion,
Including a tread rubber constituting a contact surface, and a belt disposed on the inner side in the tire radial direction of the tread rubber, and a tread annular body that contacts the carcass ply from the outer side in the tire radial direction;
In a pneumatic tire provided with a rim strip rubber arranged in the bead portion and capable of contacting the rim,
The carcass ply has an aligned carcass cord, an outer topping rubber that covers the carcass cord from the tire outer surface side, and the carcass cord from the tire inner surface side, and contacts the rim strip rubber at the winding portion. With an inner topping rubber,
The outer topping rubber has an outer interface in contact with a different rubber on the main body portion in the sidewall portion or the bead portion, and a portion from the outer interface to the rolled-up portion is formed of a non-conductive rubber, The portion from the outer interface to the contact portion with the tread annular body is formed of conductive rubber having a higher hardness than non-conductive rubber,
The inner topping rubber has an inner interface in contact with a different rubber on the main body portion in the sidewall portion or the bead portion, and a portion extending from the inner interface to the tire radial direction outer side is formed of a non-conductive rubber, A portion from the inner interface to the adjacent portion with the rim strip rubber is formed of conductive rubber having a higher hardness than non-conductive rubber,
The outer interface is located on the inner side in the tire radial direction with respect to the inner interface, and the conductive rubber of the outer topping rubber is connected to the conductive rubber of the inner topping rubber. A conductive path leading to the conductive rubber of the outer topping rubber is configured, and the conductive path from the conductive rubber of the inner topping rubber to the contact point with the rim is configured in the rim strip rubber. Pneumatic tire. The outer topping rubber has a tread side interface in contact with different rubber on the inner side in the tire radial direction of the tread annular body, and a portion extending from the tread side interface to the outer interface is formed of a conductive rubber, and the tread side The portion extending from the interface to the inside in the tire width direction is formed of non-conductive rubber,
The pneumatic tire according to claim 1, wherein the inner topping rubber is formed of a non-conductive rubber at a portion extending from the inner interface to the outer side in the tire radial direction. The outer topping rubber is formed of a non-conductive rubber in a portion from the outer interface to the tip of the rolled-up part,
The inner topping rubber has a rim-side interface with which a different rubber is in contact with the rolled-up portion, and a portion extending from the rim-side interface to the inner interface is formed of a conductive rubber. The pneumatic tire according to claim 1 or 2, wherein a portion reaching the tip is formed of non-conductive rubber.   The pneumatic tire according to any one of claims 1 to 3, wherein the conductive rubber included in the carcass ply has a JISA hardness of 56 ° or more, and the non-conductive rubber has a JISA hardness of less than 56 °.   The pneumatic tire according to any one of claims 1 to 4, wherein the outer interface and the inner interface are each positioned within a height range that is 60% of a tire cross-section height with the tire maximum width position as a center.

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