JP2012131280A - Pneumatic tire and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can reduce volume of a conductive part buried in the tread rubber, while suppressing making of the conductive path long distance, and to provide a method for manufacturing the pneumatic tire.SOLUTION: In the pneumatic tire wherein a conductive part 13 which is formed with conductive rubber and reaches from a grounding surface to a bottom face of the tread rubber 10 is buried in the tread rubber 10 formed with non-conductive rubber: the conductive part 13 has, an inside conductive lane 40 in which the conductive rubbers extending along the tire circumferential direction line up in the tire width direction with spacing, and an outside conductive lane 50 which contacts the inside conductive lane 40 from the outside of the tire radial direction, and in which the conductive rubbers extending along the tire circumferential direction line up in the tire width direction with spacing; and a region in which the inside conductive lane 40 and the outside conductive lane 50 intersect is prepared in at least a part of the tire circumferential direction, and in the intersection region, a zigzag conductive path that has the amplitude of the tire circumferential direction is extended to the tire width direction.

Description

  The present invention relates to a pneumatic tire capable of discharging static electricity generated in a vehicle body or a tire to a road surface, and a method for manufacturing the pneumatic tire.

  In recent years, pneumatic tires in which tread rubber is highly compounded with silica have been proposed for the purpose of reducing rolling resistance of tires that are closely related to fuel efficiency. However, such tread rubber has a higher electrical resistance than those with a high carbon black content, and since it inhibits the discharge of static electricity generated in the car body and tires to the road surface, it has a problem of easily causing problems such as radio noise. there were.

  Therefore, a pneumatic tire has been developed in which a conductive portion made of a conductive rubber compounded with carbon black or the like is provided on a tread rubber made of non-conductive rubber compounded with silica or the like so as to exhibit a current-carrying performance. . For example, in the pneumatic tires described in Patent Documents 1 and 2 below, the tread rubber is extended to the inner side in the tire radial direction from the contact surface to the non-conductive tread rubber and extends in the tire width direction between the cap portion and the base portion. A conductive portion reaching the bottom of the rubber is provided to form a conductive path for discharging static electricity.

  However, in the above tread rubber, the conductive portion having an L-shaped cross section continuous in the tire circumferential direction spreads in a uniform sheet shape and has a volume corresponding thereto. It was found that there is a possibility of improvement. In addition, as in the pneumatic tire described in Patent Document 3 below, a structure in which a conductive portion is continuously spiraled along the tire circumferential direction is also known. A means capable of suppressing the long distance is desired.

JP 2009-126291 A International Publication No. 2009/066605 JP 2004-136808 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire capable of reducing the volume of a conductive portion embedded in a tread rubber while suppressing a long distance of a conductive path, and its pneumatic It is providing the manufacturing method of a tire.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is an air in which a tread rubber formed of non-conductive rubber is formed of conductive rubber and has a conductive portion embedded from the ground surface to the side surface or bottom surface of the tread rubber. In the entering tire, the conductive portion includes an inner conductive lane in which conductive rubber extending along the tire circumferential direction is arranged at intervals in the tire width direction, and is in contact with the inner conductive lane from the outer side in the tire radial direction. And a conductive rubber extending along the tire width direction, and an outer conductive lane arranged at intervals in the tire width direction, and a region where the inner conductive lane and the outer conductive lane intersect is provided in at least a part of the tire circumferential direction. A zigzag conductive path having an amplitude in the tire circumferential direction is extended in the tire width direction at the intersection region.

  In this pneumatic tire, the conductive portion embedded in the tread rubber has the inner conductive lane and the outer conductive lane as described above, and is formed to include a large number of missing portions, so that the conductive portion spreads in a uniform sheet shape. The volume can be effectively reduced as compared with. Also, in the crossing region between the inner conductive lane and the outer conductive lane, a zigzag conductive path having an amplitude in the tire circumferential direction extends in the tire width direction, so compared to a structure in which the conductive portion is simply spiral-shaped. , It is possible to suppress the increase in the distance of the conductive path.

  In the pneumatic tire according to the present invention, the tread rubber is formed of non-conductive rubber and forms a ground contact surface, and is formed of non-conductive rubber and joined to the inside of the cap portion in the tire radial direction. The inner conductive lane is formed on the joint surface of the base portion with the cap portion, and the outer conductive lane is formed on the joint surface of the cap portion with the base portion. Those are preferred.

  According to such a configuration, in the tread rubber having a so-called cap-base structure, the inner conductive lane and the outer conductive lane are set at the interface between the cap portion and the base portion, so that the structure of the tread rubber is simplified. This is useful for simplifying the tread rubber molding process.

  In the pneumatic tire according to the present invention, it is preferable that at least one of the inner conductive lane and the outer conductive lane is formed of a strip-shaped conductive rubber that spirally continues along the tire circumferential direction. This simplifies the structure of the inner conductive lane and the outer conductive lane, which is beneficial for simplifying the tread rubber molding process.

  In the pneumatic tire according to the present invention, the inner conductive lane and the outer conductive lane each locally have a shift portion formed by increasing an inclination angle with respect to the tire circumferential direction, and the inner conductive lane. It is preferable that the shift region and the shift portion of the outer conductive lane are overlapped with each other with the inclination directions opposite to each other. According to such a configuration, the amplitude of the zigzag conductive path provided in the intersecting region can be reduced, and the increase in the distance of the conductive path can be effectively suppressed.

  In the method for manufacturing a pneumatic tire according to the present invention, the tread rubber formed of non-conductive rubber embeds a conductive portion formed of conductive rubber and extending from the ground surface to the side surface or bottom surface of the tread rubber. In the pneumatic tire manufacturing method, the step of forming the tread rubber includes winding the inner conductive lane by winding the belt-shaped conductive rubber spirally along the tire circumferential direction and spaced apart in the tire width direction. And forming the outer conductive lane by winding a belt-shaped conductive rubber spirally along the tire circumferential direction and spaced in the tire width direction so as to contact the inner conductive lane from the outer side in the tire radial direction. Forming a region where the inner conductive lane and the outer conductive lane intersect at least a part of the tire circumferential direction, and the tire circumferential direction at the intersecting region It is intended to include the steps of extending a zigzag conductive path having an amplitude in the tire width direction.

  According to this manufacturing method, the conductive portion embedded in the tread rubber has the inner conductive lane and the outer conductive lane as described above, and is formed to include many missing portions, so that the volume of the conductive portion is effective. Can be reduced. Also, in the crossing region between the inner conductive lane and the outer conductive lane, a zigzag conductive path having an amplitude in the tire circumferential direction extends in the tire width direction, so compared to a structure in which the conductive portion is simply spiral-shaped. , It is possible to suppress the increase in the distance of the conductive path.

  In the method for manufacturing a pneumatic tire according to the present invention, the tread rubber is formed of non-conductive rubber and includes a cap portion that constitutes a ground contact surface, and is formed of non-conductive rubber and is radially inward of the cap portion in the tire radial direction. When the base portion is formed by spirally winding a strip-shaped non-conductive rubber in a case where the base portion is joined to the belt-shaped non-conductive rubber, The inner conductive lane is formed on the joint surface of the base portion with the cap portion by the conductive rubber, and when the cap portion is formed by spirally winding a strip-shaped non-conductive rubber, the band-shaped It is preferable that the outer conductive lane is formed on the joint surface of the cap portion with the base portion by a strip-shaped conductive rubber that constitutes a part of the inner peripheral surface of the non-conductive rubber.

  According to such a manufacturing method, when molding a tread rubber having a so-called cap-base structure, an inner conductive lane can be formed with the formation of the base portion, and an outer conductive lane can be formed with the formation of the cap portion. The tread rubber having the conductive portion as described above can be molded easily and efficiently.

  In the method for manufacturing a pneumatic tire according to the present invention, when the belt-like conductive rubber is wound in the step of forming the inner conductive lane, a shift portion formed by increasing an inclination angle with respect to the tire circumferential direction is locally localized in the tire circumferential direction. When the belt-like conductive rubber is wound in the step of forming the outer conductive lane, a shift portion is provided locally in the tire circumferential direction to increase the inclination angle with respect to the tire circumferential direction. It is preferable that the shift portion of the outer conductive lane is overlapped with the shift portion of the inner conductive lane with the inclination direction reversed. According to this manufacturing method, the amplitude of the zigzag conductive path provided in the intersecting region can be reduced, and the increase in the distance of the conductive path can be effectively suppressed.

Tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention Plan view showing the structure of inner and outer conductive lanes Sectional drawing which expands and shows the interface of a cap part and a base part The top view which shows the structure of the electroconductive part which concerns on another embodiment of this invention. Schematic configuration diagram showing equipment for winding the rubber band Sectional drawing which shows an example of strip | belt-shaped rubber used for formation of a base part Sectional drawing which shows an example of the strip | belt-shaped rubber used for formation of a cap part Sectional view schematically showing the tread rubber molding process Plan view for explaining the formation process of the conductive part The top view for demonstrating the formation process of the electroconductive part which concerns on another embodiment of this invention.

  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. The bead portion 1 is provided with an annular bead 1a formed by covering a converging body such as a steel wire with rubber and a bead filler 1b made of hard rubber.

  A toroidal carcass layer 7 is disposed between the pair of bead portions 1 and the ends thereof are locked in a state of being wound up via the beads 1a. The carcass layer 7 is composed of at least one carcass ply (in this embodiment, two), and the carcass ply is formed by covering a cord extending at an angle of approximately 90 ° with respect to the tire equator C with a topping rubber. Has been. An inner liner rubber 5 for maintaining air pressure is disposed on the inner periphery of the carcass layer 7.

  A rim strip rubber 4 in contact with a rim (not shown) is disposed on the outer periphery of the bead portion 1 of the carcass layer 7. Further, a sidewall rubber 9 is disposed on the outer periphery of the sidewall portion 2 of the carcass layer 7. In this embodiment, the topping rubber of the carcass ply, the rim strip rubber 4 and the sidewall rubber 9 are each formed of conductive rubber.

  On the outer periphery of the tread portion 3 of the carcass layer 7, a belt layer 6 composed of a plurality of (two in this embodiment) belt plies is disposed. Each belt ply is formed by covering a cord extending obliquely with respect to the tire equator C with a topping rubber, and the cords are laminated so that the cords cross each other in opposite directions. On the outer periphery of the belt layer 6, there is disposed a belt reinforcing layer 8 formed by covering a cord extending substantially in the tire circumferential direction with a topping rubber, but may be omitted if necessary.

  The tread portion 3 is provided with a tread rubber 10 formed of non-conductive rubber, and a conductive portion 13 formed of conductive rubber and extending from the ground surface to the bottom surface of the tread rubber 10 is embedded in the tread rubber 10. Yes. The tread rubber 10 of the present embodiment includes a cap portion 12 formed of non-conductive rubber and constituting a ground plane, and a base portion 11 formed of non-conductive rubber and joined to the inside of the cap portion 12 in the tire radial direction. With. In addition, the tire T employs a so-called side-on-tread structure in which end portions of the sidewall rubber 9 are mounted on both end portions of the tread rubber 10, but is not limited thereto.

Here, the conductive rubber refers to rubber having a volume resistivity of less than 10 ⁸ Ω · cm. For example, the conductive rubber is produced by blending carbon black as a reinforcing agent in a high ratio with raw material rubber. In addition to carbon black, carbon fibers such as carbon fiber and graphite, and metal-based known conductivity imparting materials such as metal powders, metal oxides, metal flakes, and metal fibers can also be blended. Non-conductive rubber refers to rubber having a volume resistivity of 10 ⁸ Ω · cm or more, and is produced, for example, by blending silica as a reinforcing agent in a high ratio with raw material rubber.

  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.

From the viewpoint of enhancing the durability of the conductive portion 13 and improving the current-carrying performance, the conductive rubber forming the conductive portion 13 is nitrogen adsorption specific surface area: N ₂ SA (m ² / g) × carbon black blending amount (mass) %) Is 1900 or more, preferably 2000 or more, and dibutyl phthalate oil absorption: DBP (ml / 100 g) × carbon black compounding amount (mass%) is 1500 or more, preferably 1700 or more. It is preferable. N ₂ SA is determined according to ASTM D3037-89, and DBP is determined according to ASTM D2414-90.

  In the tire T, since both the base portion 11 and the cap portion 12 are made of non-conductive rubber, the improvement effect by forming the tread rubber 10 with non-conductive rubber (in the case of high silica content) The effect of reducing rolling resistance and the effect of improving braking performance on wet road surfaces can be improved satisfactorily. Static electricity generated in the vehicle body and tires is discharged to the road surface through a conductive path through the rim, rim strip rubber 4, sidewall rubber 9, carcass ply topping rubber, and conductive portion 13.

  The conductive portion 13 is provided so as to be connected to the rim or rubber that can be energized from the rim, and constitutes a conductive path for discharging static electricity to the road surface. In the tire T, any or all of the topping rubber of the carcass ply, the rim strip rubber 4 and the side wall rubber 9 can be formed of non-conductive rubber. In this case, the side wall rubber 9 The conductive portion 13 may be extended to the rim strip rubber 4 or the outer wall surface of the rim strip rubber 4 that contacts the rim. It is also possible to form the topping rubber of the belt layer 6 and the belt reinforcing layer 8 with non-conductive rubber.

  In the present embodiment, the base portion 11 is divided in the tire width direction around the tire equator C where the conductive portion 13 is inclined and exposed to the ground contact surface, and a rubber that forms the cap portion 12 is filled in the depression 14 at the divided portion. is doing. In such a structure, by making the rubber hardness Hc of the cap portion 12 higher than the rubber hardness Hb of the base portion 11, for example, the rubber hardness Hc is 67 ± 5 °, the rubber hardness Hb is 57 ± 5 °, and the hardness difference By setting Hc-Hb to 1 to 20 ° (preferably 3 to 15 °), a large amount of rubber having a high rubber hardness is arranged at a portion where the conductive portions 13 are relatively dense and close to the ground plane, and this portion It is possible to suppress the early wear by increasing the rigidity at. The rubber hardness refers to a value measured at 25 ° C. according to JIS K6253 durometer hardness test (type A).

  The grounding surface from which the conductive portion 13 is exposed is assembled with a rim on a regular rim, and the tire is placed vertically on a flat road surface filled with a regular internal pressure, and the surface of the tread portion that contacts the road surface when a regular load is applied. Point to. 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. “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 conductive portion 13 extends from the ground contact surface inward in the tire radial direction and reaches the outer peripheral surface of the base portion 11. The conductive portion 13 is provided continuously to the first conductive portion 13 a and extends in the tire width direction (this embodiment). In the embodiment, it has a second conductive portion 13b extending in the right direction in FIG. 1 and reaching the bottom surface of the tread rubber 10. In the present embodiment, the first conductive portion 13a is inclined in the vicinity of the tire equator C and exposed to the ground surface, and its tip portion is extended in the tire width direction to ensure the exposure frequency on the ground surface. To increase the degree of freedom of pattern design.

  FIG. 2 is a plan view of the second conductive portion 13 included in the conductive portion 13. The conductive portion 13 includes an inner conductive lane 40 and an outer conductive lane 50 that is in contact with the inner conductive lane 40 from the outside in the tire radial direction. The conductive lanes 40 and 50 each have a conductive property extending along the tire circumferential direction CD. The elastic rubber 90 is configured by being arranged at intervals in the tire width direction WD. In the illustrated example, the conductive rubber 90 constituting the inner conductive lane 40 is inclined in the upward direction, and the conductive rubber 90 constituting the outer conductive lane 50 is inclined in the downward direction. For convenience of explanation, the former is denoted by 90a and the latter is denoted by 90b.

  As described above, the portion composed of the inner conductive lane 40 and the outer conductive lane 50 (second conductive portion 13b in the present embodiment) is formed in a mesh shape including a number of missing portions 60. The volume of the conductive portion 13 is greatly reduced as compared with the conductive portion spreading in a uniform sheet shape. And the non-conductive rubber which forms the base part 11 or the cap part 12 is distribute | arranged to the missing part 60 by the part which this volume was reduced, and, thereby, the improvement effect mentioned above (the reduction effect of rolling resistance, a wet road surface, etc.) The effect of improving the braking performance in the vehicle is enhanced.

  Further, in a region CA where the inner conductive lane 40 and the outer conductive lane 50 intersect (hereinafter referred to as the intersecting region CA), as indicated by an arrow in FIG. 2, a zigzag conductive path having an amplitude in the tire circumferential direction CD. Is provided so as to extend in the tire width direction WD. This makes it possible to suppress the increase in the distance of the conductive path as compared with a structure in which the conductive portions are simply continuous in a spiral shape, which is advantageous in ensuring energization performance. The intersection area CA is provided in at least a part in the tire circumferential direction, and can be provided over the entire area in the tire circumferential direction.

  In order to suppress the increase in the distance of the conductive path, as in the present embodiment, the conductive rubber 90a constituting the inner conductive lane 40 and the conductive rubber 90a constituting the outer conductive lane 50 in the intersection area CA are as follows. It is preferable to incline with respect to the tire circumferential direction CD, respectively, and to reverse the inclination direction. The inclination angle θ of the conductive rubbers 90a and 90b with respect to the tire circumferential direction CD is set to, for example, 5 to 27 °.

  From the viewpoint of suppressing the long distance of the conductive path, the amplitude A of the zigzag conductive path in the intersection area CA is preferably 200 mm or less, and the wavelength L of the zigzag conductive path is the width of the tread rubber 10 of 10 W It is preferable that it is 10% or less. In order to simplify the molding process of the tread rubber 10, the amplitude A is preferably 20 mm or more, and the wavelength L is preferably 5% or more of the width 10W. The amplitude A and the wavelength L are measured at the center of the width of the band-shaped conductive rubber 90.

  As shown in an enlarged view in FIG. 3, in this embodiment, an inner conductive lane 40 is formed on the joint surface of the base portion 11 with the cap portion 12, and an outer conductive lane is formed on the joint surface of the cap portion 12 with the base portion 11. 50 is formed. With this configuration, it is not necessary to embed the inner conductive lane 40 or the outer conductive lane 50 inside the base portion 11 or the cap portion 12, so that the structure of the tread rubber 10 is simplified and the molding process of the tread rubber 10 is performed. Useful for simplification.

  At least one of the inner conductive lane 40 and the outer conductive lane 50 is preferably formed of a strip-shaped conductive rubber that spirally continues along the tire circumferential direction. In the present embodiment, as will be described later in the description of the manufacturing method, the conductive rubber 90a constituting the inner conductive lane 40 and the conductive rubber 90b constituting the outer conductive lane 50 are both along the tire circumferential direction CD. It is formed of a strip-like conductive rubber that is spirally continuous. With such a configuration, the structure of the conductive lanes 40 and 50 is simplified, which is useful for simplifying the molding process of the tread rubber 10.

  The first conductive portion 13a can be composed of the conductive lanes 40 and 50 in the same manner as the second conductive portion 13b. However, the proportion of the volume in the entire conductive portion 13 is smaller than that of the second conductive portion 13b, and wear is also caused. Since it is also an exposed part, in this embodiment, the 1st electroconductive part 13a is formed in the uniform sheet form. Thus, it is preferable that the conductive part 13 has the conductive lanes 40 and 50 as described above at least in the second conductive part 13b.

  FIG. 4 is an example in which the intersection area CA is locally provided in the tire circumferential direction. In this example, the inner conductive lane 40 and the outer conductive lane 50 each have shift portions 40a and 50a each having an increased inclination angle with respect to the tire circumferential direction CD in the tire circumferential direction CD, and the shift portion 40a. And the shift portion 50a overlap each other with the inclination directions opposite to each other. In areas before and after the intersection area CA, the conductive lanes 40 and 50 extend substantially parallel to the tire circumferential direction CD.

  According to this configuration, the conductive rubber 90 constituting the inner conductive lane 40 and the outer conductive lane 50 can be greatly inclined, and the amplitude of the zigzag conductive path provided in the intersection area CA can be reduced to reduce the conductive path. Can be effectively suppressed. In this case, the inclination angle of the conductive rubbers 90a and 90b with respect to the tire circumferential direction CD in the intersection area CA can be set to, for example, 10 to 30 °, and the conductive rubbers 90a and 90b with respect to the tire circumferential direction CD in the areas before and after that. The inclination angle can be set to 0 to 5 °, for example.

  Next, an example of a method for manufacturing the pneumatic tire T will be described. Since the tire T can be manufactured in the same manner as the conventional tire manufacturing process except for the point related to the tread rubber 10, the description will focus on the tread rubber molding process. In the present embodiment, an example in which the tread rubber 10 is molded by a so-called ribbon winding method is shown. The ribbon winding method is a method of forming a rubber member having a desired cross-sectional shape by winding a narrow, unvulcanized belt-like rubber spirally in the tire circumferential direction.

  The band-shaped rubber can be molded and wound using equipment such as that illustrated in FIG. This facility includes a belt-like rubber supply device 30 capable of co-extrusion of two types of rubber to form a multilayered belt-like rubber 20, a rotating support 31 around which the belt-like rubber 20 supplied from the belt-like rubber supply device 30 is wound, A belt-like rubber supply device 30 and a control device 32 that controls the operation of the rotary support 31. The rotary support 31 is configured to be capable of rotating in the R direction around the shaft 31a and moving in the axial direction.

  The extruder 33 includes a hopper 33a, a screw 33b, a barrel 33c, a drive device 33d for the screw 33b, and a head portion 33e incorporating a gear pump. Similarly, the extruder 34 includes a hopper 34a, a screw 34b, a barrel 34c, a driving device 34d, and a head portion 34e. At the front ends of the pair of extruders 33 and 34, a rubber unit 35 to which a base 36 is attached is provided.

  When non-conductive rubber, which is a rubber material, is put into the hopper 33a and conductive rubber, which is a rubber material, is put into the hopper 34a, each rubber is fed forward while being kneaded by the screws 33b and 34b, and the head portions 33e and 34e. Then, they are united in a predetermined shape at the rubber uniting part 35 and extruded from the discharge port 36a as a multilayer rubber band 20. The molded belt-like rubber 20 is fed forward by a roll 37 and wound around the rotary support 31 while being pressed by a roller 38.

  FIG. 6A shows a multilayer rubber band 20 used for forming the base portion 11, and the lower side in FIG. 6 is the inner peripheral side facing the rotation support 31 during winding. The band-shaped rubber 20 includes a band-shaped non-conductive rubber 21 and a band-shaped conductive rubber 90 constituting a part of the outer peripheral surface of the band-shaped non-conductive rubber 21. The strip-shaped conductive rubber 90 constitutes the inner conductive lane 40 as will be described later. FIG. 6B shows an example in which the conductive rubber 90 is formed by shifting from the center. The cross section of the belt-like rubber 20 is not limited to a triangular shape, and may be another shape such as an elliptical shape.

  When the belt-shaped rubber 20 is extruded, the rotation of the gear pump in the head portion 34e is stopped, and if necessary, the rotation of the screw 34b is also stopped, and the extrusion of the conductive rubber 90 is stopped. A single-layered belt-like rubber 20 formed only of the non-conductive rubber 21 as shown in FIG. The operation of the gear pump and the screws 33b and 34b in the head portions 33e and 34e is controlled by the control device 32, and switching between a single layer and multiple layers in the belt-like rubber 20 can be performed.

  The width 90W of the conductive rubber 90 is preferably 10 to 50%, more preferably 10 to 30% of the total width 20W of the belt-like rubber 20. When this ratio is 10% or more, the width dimension of the conductive rubber 90 can be secured and the occurrence of disconnection can be suppressed, which is beneficial in maintaining the energization performance. Moreover, when this ratio is 50% or less, the volume of the conductive rubber can be satisfactorily reduced.

  FIG. 7A shows a multilayer rubber band 20 ′ used for forming the cap portion 12. The band-shaped rubber 20 ′ is composed of a band-shaped nonconductive rubber 22 and a band-shaped conductive rubber 90 constituting a part of the inner peripheral surface of the band-shaped nonconductive rubber 22. The strip-shaped conductive rubber 90 constitutes the outer conductive lane 50 as described later. FIG. 7B shows a belt-like rubber 20 ′ formed by shifting the conductive rubber 90, and FIG. 7C shows a single-layer belt-like rubber 20 ′ formed only by the non-conductive rubber 22. . The band-shaped rubber 20 ′ can be molded in the same manner as the band-shaped rubber 20, and the preferred width ratio is also as described above.

  In the molding process of the tread rubber 10, a belt-like non-conductive rubber 21 is spirally wound around the outer peripheral surface of the rotary support 31 along the tire circumferential direction, thereby forming the base portion 11 as shown in FIG. To do. At this time, the belt-like rubber 20 to be used is a single layer (see FIG. 6C) when the left portion 11L of the base portion 11 is formed, and a multilayer (see FIG. 6A or FIG. 6B) when the right half 11R is formed. Reference). The base part 11 does not necessarily need to be completely divided into right and left, and may be connected at one place in the tire circumferential direction according to the winding of the belt-shaped rubber.

  The belt-like rubber 20 is wound with belt-like rubbers adjacent to each other in the tire width direction overlapping with each other as shown in FIG. 9A or with the edges facing each other. As the belt-shaped rubber 20 is wound, the belt-shaped conductive rubber 90a is wound spirally along the tire circumferential direction and spaced in the tire width direction, whereby the inner conductive lane 40 is formed. 9 and 10, the conductive rubber 90 is colored so that it can be distinguished from the non-conductive rubbers 21 and 22.

  Next, the belt-like non-conductive rubber 22 is spirally wound along the tire circumferential direction, thereby forming the left half 12L of the cap portion 12 as shown in FIG. 8B. In the formation of the left half 12L, the single-layered rubber band 20 'shown in FIG. 7C is used. The slope 16 is formed in order to mount the first conductive portion 13a in a later process.

  Subsequently, as shown in FIG. 8C, one end is exposed to the ground plane, and the other end is the inner conductive lane 40 or the outer conductive lane 50 (however, in this embodiment, the outer conductive lane 50 is still formed. A first conductive portion 13a is formed by providing a conductive rubber connected to the first conductive portion 13a. Any of the conductive rubber and the inner conductive lane 40 and the outer conductive lane 50 may be formed first. The 1st electroconductive part 13a can be formed by arrangement | positioning of the rubber sheet which consists of electroconductive rubber besides the ribbon winding method.

  Then, the belt-like non-conductive rubber 22 is spirally wound along the tire circumferential direction, thereby forming the right half 12R of the cap portion 12 as shown in FIG. 8D. At this time, in the vicinity of the joint surface with the base portion 11, the multilayer rubber band 20 ′ shown in FIG. 7 (A) or (B) is used. Along with the winding of the belt-shaped rubber 20 ′, the belt-shaped conductive rubber 90b is wound spirally along the tire circumferential direction and spaced apart in the tire width direction, and the outer conductive lane 50 as shown in FIG. 9B. Is formed.

  The outer conductive lane 50 is formed so as to be in contact with the inner conductive lane 40 from the outer side in the tire radial direction, and the conductive rubber 90b constituting the outer conductive lane 50 is opposite to the conductive rubber 90a constituting the inner conductive lane 40. The intersection area CA is provided by wrapping around. The intersection area CA is provided in at least a part in the tire circumferential direction, and as described with reference to FIG. 2, the zigzag conductive path having an amplitude in the tire circumferential direction extends in the tire width direction.

  In the present embodiment, when the band-shaped rubber 20 is wound, by extension, the band-shaped non-conductive rubber 21 is spirally wound to form the base portion 11, the band-shaped conductive rubber 90 a causes the base portion 11 to An inner conductive lane 40 is formed on the joint surface with the cap portion 12. Further, when the band-shaped rubber 20 ′ is wound, the band-shaped non-conductive rubber 22 is spirally wound to form the cap portion 12, and the base portion of the cap portion 12 is formed by the band-shaped conductive rubber 90b. The outer conductive lane 50 is formed on the joint surface with the first electrode 11. Therefore, compared with the case where the strip | belt-shaped electroconductive rubber 90 is wound alone, shaping | molding efficiency is improved favorably.

  In the molding of the tread rubber 10, an extrusion molding method may be employed as appropriate, and a combined use with a ribbon winding method is also possible. The extrusion molding method is a method of extruding an unvulcanized rubber member having a predetermined cross-sectional shape and jointing the end portions to form an annular shape.

  Although not shown in FIG. 8, the belt layer 6 and the belt reinforcing layer 8 are disposed on the inner periphery of the tread rubber 10, and the tread rubber 10 is used as the carcass layer 7, the sidewall rubber 9, and the like. The pneumatic tire T shown in FIG. 1 can be manufactured by combining with the tire constituent members. The tire T manufactured in this way is vulcanized in the vulcanization molding process, and a tread pattern is provided on the surface of the tread rubber 10.

  When the conductive portion 13 shown in FIG. 4 is provided, at the stage where the inner conductive lane 40 is formed, a belt-shaped conductive rubber 90a is wound around as shown in FIG. At the stage of forming the conductive lane 50, as shown in FIG. 10 (B), a belt-shaped conductive rubber 90b is wound to provide a shift portion 50a, and the shift portion 50a is overlapped with the shift portion 40a with the inclination direction reversed. Just do it.

[Another embodiment]
(1) In the above-described embodiment, an example in which the base portion is divided into left and right has been shown. However, the present invention is not limited to this, and the base portion may be formed continuously. In the above-described embodiment, an example in which the conductive portion reaches the bottom surface of the tread rubber has been described. However, the conductive portion may reach the side surface of the tread rubber and be connected to the sidewall rubber.

  (2) When the inner conductive lane and the outer conductive lane are not set at the interface between the cap portion and the base portion, the strip-shaped non-conductive rubber having the strip-shaped conductive rubber constituting the inner conductive lane and the outer conductive lane The belt-like non-conductive rubber having the belt-like conductive rubber constituting the same rubber may be the same rubber. In this case, for example, after forming the inner conductive lane 40 using the belt-like rubber 20 shown in FIG. 6A, the belt-like rubber 20 is turned over to be the same as the belt-like rubber 20 ′ shown in FIG. It is also possible to form the outer conductive lane 50 using such a posture.

  Examples that specifically show the structure and effects of the present invention will be described below. The size of the tire used for the evaluation is 245 / 55R19, and the tire structure and the rubber composition in each example are common except for the structure of the conductive portion described below.

The evaluation items are as follows.
Current-carrying performance: The presence or absence of current-carrying performance was evaluated based on the presence or absence of a conductive path.
Rolling resistance: The rolling resistance was measured with a rolling resistance tester. The index evaluation is performed with the result of Comparative Example 1 being 100, and the smaller the value, the smaller the rolling resistance.
Braking performance: On a wet road surface, the braking distance when the traveling speed was reduced from 100 km / h to 0 km / h was measured, and the reciprocal was calculated. The index evaluation is made with the result of Comparative Example 1 being 100, and the larger the value, the better the braking performance.

  Comparative Example 1 except that a conductive portion having an L-shaped cross section that is continuous in the tire circumferential direction is the same as Example 1, and Comparative Example 2 that is the same as Example 1 except that the conductive portion is not provided. It was. Further, in the tire having the structure shown in FIG. 1, Examples 1 and 2 have conductive portions each having an inner conductive lane and an outer conductive lane as shown in FIG. 2. Further, Comparative Example 3 was the same as Example 1 except that the inner conductive lane and the outer conductive lane extended in parallel around the entire circumference and no crossing region was provided. The evaluation results are shown in Table 1.

  As shown in Table 1, in Comparative Example 1, the rolling resistance is relatively high and the braking performance is relatively inferior. Moreover, since the comparative example 2 does not comprise an electroconductive part, electricity supply performance is not exhibited. On the other hand, in Examples 1 and 2, the rolling resistance and braking performance are improved as the volume of the conductive portion can be reduced while maintaining the energization performance. In Example 1, the band-shaped conductive rubber constituting the conductive portion is narrow, and Example 2 is preferable from the viewpoint of preventing disconnection. In Comparative Example 3, since the intersection region between the inner conductive lane and the outer conductive lane is not provided, the energization performance is not exhibited.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 10 Tread rubber 11 Base part 12 Cap part 13 Conductive part 13a First conductive part 13b Second conductive part 21 Strip-shaped nonconductive rubber 22 Strip-shaped nonconductive rubber 40 Inner conductive lane 40a Shift portion 50 Outer conductive lane 50a Shift portion 60 Missing portion 90 Band-shaped conductive rubber CA Intersection region

Claims (7)

In a pneumatic tire in which a tread rubber formed of a non-conductive rubber is formed of a conductive rubber and has a conductive portion embedded from the ground surface to the side surface or bottom surface of the tread rubber,
The conductive portion includes an inner conductive lane in which conductive rubber extending along the tire circumferential direction is arranged at intervals in the tire width direction, and contacts the inner conductive lane from the outer side in the tire radial direction and extends along the tire circumferential direction. An outer conductive lane in which conductive rubber is arranged at intervals in the tire width direction; and
A region where the inner conductive lane and the outer conductive lane intersect is provided in at least a part of the tire circumferential direction, and a zigzag conductive path having an amplitude in the tire circumferential direction extends in the tire width direction at the intersecting region. A pneumatic tire characterized by being made. The tread rubber includes a cap portion formed of non-conductive rubber and constituting a ground contact surface, and a base portion formed of non-conductive rubber and joined to the inside of the cap portion in the tire radial direction,
The pneumatic tire according to claim 1, wherein the inner conductive lane is formed on a joint surface of the base portion with the cap portion, and the outer conductive lane is formed on a joint surface of the cap portion with the base portion. .   The pneumatic tire according to claim 1 or 2, wherein at least one of the inner conductive lane and the outer conductive lane is formed of a strip-shaped conductive rubber that spirally continues along a tire circumferential direction.   The inner conductive lane and the outer conductive lane each have a shift portion formed by increasing an inclination angle with respect to the tire circumferential direction locally in the tire circumferential direction, and the shift portion of the inner conductive lane and the outer conductive lane The pneumatic tire according to any one of claims 1 to 3, wherein the crossing region is provided by overlapping a shift portion with an inclination direction opposite to each other. In the manufacturing method of the pneumatic tire, in which the tread rubber formed of the non-conductive rubber is embedded in the conductive portion formed of the conductive rubber and reaching the side surface or the bottom surface of the tread rubber from the ground surface.
Forming the tread rubber,
Forming an inner conductive lane by winding a belt-shaped conductive rubber spirally along the tire circumferential direction and spaced in the tire width direction; and
An outer conductive lane is formed by winding a belt-shaped conductive rubber spirally along the tire circumferential direction and spaced in the tire width direction so as to contact the inner conductive lane from the outer side in the tire radial direction. Providing a region where the inner conductive lane and the outer conductive lane intersect in at least a part of the direction, and extending a zigzag conductive path having an amplitude in the tire circumferential direction in the intersecting region in the tire width direction; The manufacturing method of the pneumatic tire characterized by including. The tread rubber includes a cap portion formed of non-conductive rubber and constituting a ground contact surface, and a base portion formed of non-conductive rubber and joined to the inside of the cap portion in the tire radial direction,
When forming the base portion by spirally winding a strip-shaped non-conductive rubber, the cap in the base portion is formed by the strip-shaped conductive rubber constituting a part of the outer peripheral surface of the strip-shaped non-conductive rubber. Forming the inner conductive lane on the joint surface with the portion,
When the cap portion is formed by spirally winding a strip-shaped non-conductive rubber, the strip-shaped conductive rubber constituting a part of the inner peripheral surface of the strip-shaped non-conductive rubber is used to form the cap portion in the cap portion. The method for manufacturing a pneumatic tire according to claim 5, wherein the outer conductive lane is formed on a joint surface with the base portion. When winding the belt-shaped conductive rubber in the step of forming the inner conductive lane, a shift portion is provided locally in the tire circumferential direction to increase the inclination angle with respect to the tire circumferential direction,
When the belt-like conductive rubber is wound in the step of forming the outer conductive lane, a shift portion having a large inclination angle with respect to the tire circumferential direction is locally provided in the tire circumferential direction, and the outer conductive lane The method for manufacturing a pneumatic tire according to claim 5 or 6, wherein the shift portion is overlapped with the shift portion of the inner conductive lane so that the inclination direction is reversed.

Images