Patent Publication Number: US-2023142188-A1

Title: Pneumatic tire

Description:
This application is based on and claims the benefit of priority from Japanese Patent Application No. 2021-181391, filed on 5 Nov. 2021, the content of which is incorporated herein by reference. 
     FIELD 
     The present invention relates to a pneumatic tire. 
     BACKGROUND 
     Generally, a pneumatic tire has a structure made by coating a backbone structure bridging a carcass ply between a pair of beads arranged at both end inner circumferential parts in the tire width direction, with tread rubber, sidewall rubber, etc. Conventionally, a pneumatic tire has been known in which arranges reinforcement layers that suppress separation from the carcass ply are respectively arranged at both sides in the tire-width direction of a bead filler constituting the beads (for example, refer to Japanese Unexamined Patent Application, Publication No. 2004-130881, etc.). 
     SUMMARY 
     The above-mentioned reinforcement layers arranged at both sides in the tire-width direction of the bead filler in Japanese Unexamined Patent Application, Publication No. 2004-130881 are both shorter than the length in the tire-radial direction of the bead filler. For this reason, upon the tire receiving lateral force, it is assumed that so-called side rigidity resisting this lateral force becomes insufficient, and thus there is room for improvement. 
     Therefore, the present invention has an object of providing a pneumatic tire capable of an improvement in side rigidity over convention. 
     A pneumatic tire according to the present invention includes: a pair of beads having a bead core and a bead filler extending from the bead core to an outer side in a tire-radial direction; a pair of sidewalls extending from each of the pair of beads to an outer side in the tire-radial direction; a tread disposed between the pair of sidewalls; a carcass ply bridged between the pair of beads; an internal side reinforcement layer disposed at an inner side in a tire-width direction of the bead filler; and an external side reinforcement layer disposed at an outer side in the tire-width direction of the bead filler, in which the internal side reinforcement layer is disposed more to an inner side in the tire-radial direction than a tire-radial direction outer end of the bead filler, and the external side reinforcement layer has an outside extending part which extends from the tire-radial direction outer end of the bead filler to an outer side in the tire-radial direction. 
     According to the present invention, it is possible to provide a pneumatic tire capable of an improvement in side rigidity over convention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a view showing a half section in a tire-width direction of a pneumatic tire according to an embodiment; 
         FIG.  2    is a partially enlarged view of  FIG.  1   ; and 
         FIG.  3    is a view for explaining the configuration of an external side reinforcement layer and internal side reinforcement layer of a tire according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be explained while referencing the drawings.  FIG.  1    shows a half section in a tire-width direction of a tire  1 , which is a pneumatic tire according to the present embodiment.  FIG.  2    is a cross-sectional view enlarging a part of  FIG.  1   , showing a portion spanning from a bead  10  to a sidewall  20  described later. 
     The tire  1  according to the present embodiment is a pneumatic tire for passenger vehicles, for example. It should be noted that the tire  1  according to the present embodiment can be adopted for various vehicles such as light trucks, trucks and buses, in addition to passenger vehicles. 
     The specific structure of the tire  1  is left/right symmetrical in a cross section in the tire-width direction.  FIG.  1    is a view showing a half section of the right half of the tire  1 , and the left half (not illustrated) is the same structure. In  FIG.  1   , reference symbol S 1  is a tire equatorial plane. The tire equatorial plane S 1  is a plane intersecting a tire rotational axis (tire meridian axis), and is positioned at the center in the tire-width direction. 
     It should be noted that the cross-sectional view of  FIG.  1    shows an unloaded state in which the tire  1  is mounted to a standard rim and filled with standard internal pressure. It should be noted that standard rim indicates a rim serving as a standard decided by JATMA corresponding to the tire size. In addition, standard internal pressure is 180 kPa in the case of the tire  1  being for a passenger vehicle, for example. 
     Herein, tire-width direction is a direction parallel to the tire rotational axis, and is the left/right direction in the paper plane of  FIG.  1   . In  FIG.  1   , it is illustrated as the tire-width direction X. The tire-width direction inner side is a direction near the tire equatorial plane S 1 , and is the left side in the paper plane of  FIG.  1   . Tire-width direction outer side is a direction distanced from the tire equatorial plane S 1 , and is the right side in the paper plane of  FIG.  1   . 
     In addition, tire-radial direction is a direction perpendicular to the tire rotational axis, and is the vertical direction in  FIG.  1   . In  FIG.  1   , it is illustrated as the tire-radial direction Y. A tire-radial direction outer side is a direction distanced from the tire rotational axis, and is an upper side in the paper plane of  FIG.  1   . Tire-radial direction inner side is a direction approaching the tire rotational axis, and is a lower side in the paper plane of  FIG.  1   . It should be noted that the same also applies for  FIG.  2    described later. 
     As shown in  FIG.  1   , the tire  1  includes: a pair of beads  10  provided at both sides in the tire-width direction; a pair of sidewalls  20  extending from each of the pair of beads  10  to the outer side in the tire-radial direction; tread  30  arranged between the pair of sidewalls  20 ; a carcass ply  40  arranged to bridge between the pair of beads  10 ; an inner liner  50  arranged on the tire inner cavity side of the carcass ply  40 ; and an internal side reinforcement layer  60  and external side reinforcement layer  70  provided to the sidewalls  20 . 
     The bead  10  has a bead core  11 , bead filler  12  extending from the bead core  11  to the outer side in the tire-radial direction, a chafer  13 , and a rim protector  15 . 
     The bead core  11  is an annular member made by bead wires made of rubber-coated metal being wrapped around in the tire-circumferential direction several times. The bead core  11  is a member playing the role of fixing the tire  1  filled with air to the rim. The bead filler  12  takes on a tapered shape as extending from the inner side in the tire-radial direction to the outer side. 
     As shown in  FIG.  2   , the bead filler  12  has an inner surface  12   b  on an inner side in the tire-circumferential direction, an outer surface  12   c  on an outer side in the tire-circumferential direction, a tire-radial direction outer end  12   d  which is a tapered-shape tip, and a tire-radial direction inner end  12   e . The inner surface  12   b  and outer surface  12   c  of the bead filler  12  both gently curve so as to widen to the outer side in the tire-width direction as approaching the outer side in the tire-radial direction, and converge at the tire-radial direction outer end  12   d . The tire-radial direction inner end  12   e  of the bead filler  12  adheres to the tire-radial direction outer end  11 A of the bead core  11 . 
     The tire-width direction dimension of the tire-radial direction inner end  12   e  of the bead filler  12  is smaller than the tire-width direction dimension of the tire-radial direction outer end  11 A of the bead core  11 . At the inner side in the tire-width direction of the tire-radial direction outer end  11 A of the bead core  11 , a step part  11   b  facing the outer side in the tire-radial direction without being covered by the tire-radial direction inner end  12   e  of the bead filler  12  is formed. At the outer side in the tire-width direction of the tire-radial direction outer end  11 A of the bead core  11 , a step part  11   c  facing the outer side in the tire-radial direction without being covered by the tire-radial direction inner end  12   e  of the bead filler  12  is formed. 
     The bead filler  12  is provided to raise the rigidity of a circumferential portion of the bead  10 , and ensure high maneuverability and stability. The bead filler  12 , for example, is configured from rubber having higher hardness than the surrounding rubber members. 
     The chafer  13  is provided to the inner side in the tire-radial direction of the carcass ply  40  provided around the bead core  11 . The rim protector  15  includes rim strip rubber  14 . The rim strip rubber  14  is arranged on the outer side in the tire-width direction of the chafer  13  and carcass ply  40 . An apex part  14   a  following the tire-circumferential direction is formed at the outer surface of the rim strip rubber  14 . The rim strip rubber  14  contacts with an inner side portion of the rim on which the tire  1  is mounted. The rim protector  15  is continuous in a ring shape in a tire-circumferential direction. The rim protector  15  has a function of protecting the rim from external injury. 
     The sidewall  20  includes sidewall rubber  21  arranged on the outer side in the tire-width direction of the carcass ply  40 . The sidewall rubber  21  configures an outer wall surface of the tire  1 . The sidewall rubber  21  is a portion which bends the most upon the tire  1  exhibiting a cushioning action, and usually flexible rubber having fatigue resistance is adopted therein. 
     The tread  30  includes an endless belt  31  and cap ply  32 , and tread rubber  33 . 
     The belt  31  is arranged at an outer side in the tire-radial direction of the carcass ply  40 . The cap ply  32  is arranged at an outer side in the tire-radial direction of the belt  31 . The belt  31  is a member reinforcing the tread  30 . The belt  31  in the embodiment is a two-layer structure including an inner side belt  311  and outer side belt  312 . The inner side belt  311  and outer side belt  312  both have a structure in which a plurality of cords such as steel cords is covered with rubber. 
     In the belt  31  of two-layer structure of the present embodiment, the inner side belt  311  is wider than the outer side belt  312 . Therefore, the tire-width direction outer end  311 A of the inner side belt  311  is positioned more to the outer side in the tire-width direction than the tire-width direction outer end  312 A of the outer side belt  312 . By providing the belt  31 , the rigidity of the tire  1  is ensured, and the ground contact property of the tread  30  to the road surface improves. It should be noted that the belt  31  is not limited to a two-layer structure, and may have a structure of one layer, or three or more layers. 
     The cap ply  32  is a member reinforcing the tread  30  together with the belt  31 . The cap ply  32 , for example, has a structure in which a plurality of organic fiber cords having an insulation property such as polyimide fibers is covered with rubber. A tire-width direction outside end  32 A of the cap ply  32  is positioned more to the outer side in the tire-width direction than the tire-width direction outer end  311 A of the inner side belt  311 . An end part  33   b  on the outer side in the tire-width direction of the cap ply  32  covers and adheres the end part  311   b  on the outer side in the tire-width direction of the inner side belt  311 . The outer side belt  312  thereby enters a state sandwiched by the cap ply  32  and inner side belt  311 . By providing the cap ply  32 , it is possible to achieve an improvement in durability and a reduction in road noise during travel. 
     The tread rubber  33  is arranged on the outer side in the tire-radial direction of the cap ply  32 . The tread rubber  33  is a member constituting the tire tread  331  which contacts the road surface during travel. A tread pattern  34  configured by a plurality of grooves, for example, is provided in the tire tread of the tread rubber  33 . A high modulus rubber  36  is arranged at the outer side in the tire-width direction of the tread rubber  33 . The high modulus rubber  36  is sandwiched between the tread rubber  33  and sidewall rubber  21 , and is adhered to the tread rubber  33  and sidewall rubber  21 . The high modulus rubber  36  is a belt-like rubber member of comparatively thin thickness, and is configured from rubber of higher modulus (modulus of elasticity of rubber) than the tread rubber  33  and sidewall rubber  21 . 
     The carcass ply  40  configures a ply serving as the backbone of the tire  1 . The carcass ply  40  is embedded within the tire  1 , in a form passing through the pair of sidewalls  20  and the tire inner wall side of the tread  30  between the pair of beads  10 . 
     The carcass ply  40  includes a plurality of carcass cords (not illustrated) serving as the backbone of the tire  1 . The plurality of carcass cords extends in plane along the tire-width direction, for example, and are arranged side by side in the tire-circumferential direction. This carcass cord is configured from an insulative organic fiber cord such as polyester or polyamide, or the like. The plurality of carcass cords is coated by rubber, whereby the carcass ply  40  is configured. 
     The carcass ply  40  has a ply main body part  401 , ply folding part  402 , and an elbow-shaped bend  403 . The ply main body part  401  is a portion extending from the inner side in the tire-width direction of one bead core  11 , through the tread  30  until the inner side in the tire-width direction of the other bead core  11 . The ply folding part  402  is a portion which extends to the outer side in the tire-radial direction on the outer side in the tire-width direction of the bead filler  12 , by being folded back around the bead core  11  from the tire-radial direction inner end of the ply main body part  401 . The elbow-shaped bend  403  is a portion which bends in a U-shape around the bead core  11  from the ply main body part  401 , and linked to the ply folding part  402 . The ply main body part  401  and ply folding part  402  are continuous via the elbow-shaped bend  403 . 
     The ply main body part  401  is arranged at the inner side in the tire-width direction of the bead core  11  and bead filler  12  on the inner side in the tire-radial direction. The ply folding part  402  is arranged at the outer side in the tire-width direction of the bead core  11  and bead filler  12 . The elbow-shaped bend  403  includes an inner most side portion in the tire-radial direction of the carcass ply  40 . 
     The carcass ply  40  of the present embodiment has a two-layer structure in which a first carcass ply  410  and second carcass ply  420  are overlapped. In the ply main body part  401 , the first carcass ply  410  is arranged on the tire inner cavity side of the second carcass ply  420 . 
     The second carcass ply  420  of the ply folding part  402  extends from the inner side in the tire-radial direction to the middle of the sidewall  20 . The end part  421  on the outer side in the tire-radial direction of the second carcass ply  420  of the ply folding part  402  is superimposed on the second carcass ply  420  of the ply main body part  401  arranged at the sidewall  20 . The tire-radial direction outer end  421 A of the second carcass ply  420  of the ply folding part  402  is positioned more to the outer side in the tire-radial direction than the tire-radial direction inner end  36 A of the high modulus rubber  36 . 
     The first carcass ply  410  of the ply folding part  402  extends to the outer side in the tire-radial direction beyond the tire-radial direction outer end  421 A of the second carcass ply  420  from the inner side in the tire-radial direction, and further extends through the sidewall  20  until the end part on the outer side in the tire-width direction of the tread  30 . The end part  411  on the outer side in the tire-radial direction of the first carcass ply  410  of the ply folding part  402  is superimposed with a portion spanning from the sidewall  20  to the tread  30  of the second carcass ply  420  of the ply main body part  401 . The tire-radial direction outer end  411 A of the first carcass ply  410  of the ply folding part  402  is positioned more to the inner side in the tire-width direction than the tire-width direction outer end  312 A of the outer side belt  312 . 
     The carcass ply  40  of the present embodiment is a two-layer structure; however, the carcass ply  40  may be one layer, or may be three or more layers. If the carcass ply  40  is configured from ply of a two-layer structure or more layers than this, it is preferable since the tire  1  is sufficiently suppressed from locally deforming in the vicinity of the rim mounting part. 
     The aforementioned chafer  13  of the bead  10  is provided so as to surround the end part on the inner side in the tire-radial direction of the carcass ply  40  including the elbow-shaped bend  403 . In addition, the rim strip rubber  14  is arranged on the outer side in the tire-width direction of the ply folding part  402  of the carcass ply  40  and the chafer  13 . The end part on the outer side in the tire-radial direction of the rim strip rubber  14  is covered by the sidewall rubber  21 . 
     The inner liner  50  covers the tire inner surface between the pair of beads  10 . Therefore, the inner liner  50  configures the inner wall surface of the tire  1 . The inner liner  50  covers the inner surface of the tread  30  and the ply main body part  401  in a region spanning from the tread  30  to the sidewall  20 . In addition, the inner liner  50  covers the inner surface of the ply main body part  401  and chafer  13 , in a region spanning from the sidewall  20  to the bead  10 . The inner liner  50  is configured by air permeation resistant rubber, whereby the air inside the tire inner cavity is prevented from leaking to outside. 
     Herein, as the rubber adopted in the bead filler  12 , rubber having higher hardness than at least the sidewall rubber  21  and inner liner  50  is used. The hardness of the rubber is a value (durometer hardness) measured by a type-A durometer based on JIS K6253 in a 23° C. atmosphere. 
     For example, when setting the hardness of the sidewall rubber  21  as a reference, the hardness of the bead filler  12  preferably uses rubber of hardness of about 1.2 to 2.3 times the hardness of the sidewall rubber  21 . The hardness of the rim strip rubber  14  more preferably uses rubber of hardness on the order of 1 to 1.6 times the hardness of the sidewall rubber  21 . By establishing such hardness, it is possible to keep the balance in flexibility as a tire and rigidity in the vicinity of the beads  10 . 
     As shown in  FIG.  2   , the internal side reinforcement layer  60  is arranged on the inner side in the tire-width direction of the bead filler  12 . The internal side reinforcement layer  60  is an annular reinforcement layer along the tire-circumferential direction. The cross-sectional shape in the tire-width direction of the internal side reinforcement layer  60  extends from the inner side to the outer side in the tire-radial direction. 
     The internal side reinforcement layer  60  adheres to the inner surface  12   b  of the bead filler  12 , in a state in which the tire-radial direction inner end  60   a  thereof engages with the step part  11   b  on the inner side of the bead filler  12 . Therefore, the tire-radial direction inner end  60   a  of the internal side reinforcement layer  60  is positioned more to the outer side in the tire-radial direction than the tire-radial direction outer end  11 A of the bead core  11 . The tire-radial direction length L 1  of the internal side reinforcement layer  60  is shorter than the tire-radial direction length L of the bead filler  12 . Therefore, the tire-radial direction outer end  60   b  of the internal side reinforcement layer  60  is positioned more to the inner side in the tire-radial direction than the tire-radial direction outer end  12   d  of the bead filler  12 . In other words, the internal side reinforcement layer  60  is arranged more to the inner side in the tire-radial direction than the tire-radial direction outer end  12   d  of the bead filler  12 . It should be noted that the tire-radial direction inner end  60   a  of the internal side reinforcement layer  60  may contact with the tire-radial direction outer end  11 A of the bead core  11 . 
     In addition, the internal side reinforcement layer  60  adheres to the second carcass ply  420  of the ply main body part  401  of the carcass ply  40 . In other words, the internal side reinforcement layer  60  is sandwiched between the bead filler  12  and ply main body part  401 , and adheres to both this bead filler  12  and second carcass ply  420  of the ply main body part  401 . More specifically, the internal side reinforcement layer  60  may contact with the bead filler  12 . In addition, the internal side reinforcement layer  60  may contact with the ply main body part  401 . Since the tire-radial direction inner end  60   a  and tire-radial direction outer end  60   b  of the internal side reinforcement layer  60  are thereby protected by the carcass ply  40 , the inner liner  50  is avoided from receiving external injury by the internal side reinforcement layer  60 . 
     Herein, it is good for the tire-radial direction outer end  12   d  of the bead filler  12  and tire-radial direction outer end  60   b  of the internal side reinforcement layer  60  not to have matching positions in the tire-radial direction X for manufacturing; however, the tire-radial direction length of the internal side reinforcement layer  60  is preferably as long as possible from the aspect of a rigidity improvement. From this viewpoint, in the present embodiment, the tire-radial direction length L 1  of the internal side reinforcement layer  60  is preferably at least 60% and no more than 90% of the tire-radial direction length L of the bead filler  12 , and more preferably at least 70% and no more than 90%. 
     As shown in  FIG.  2   , the external side reinforcement layer  70  is arranged at the outer side in the tire-width direction of the bead filler  12 . The external side reinforcement layer  70  is an annular reinforcement layer along the tire-circumferential direction. The cross-sectional shape in the tire-width direction of the external side reinforcement layer  70  extends from the inner side to the outer side in the tire-radial direction. 
     The external side reinforcement layer  70  adheres to the outer surface  12   c  of the bead filler  12 , in a state in which the tire-radial direction inner end  70   a  thereof engages with the step part  11   c  on the outer side of the bead filler  12 . Therefore, the tire-radial direction inner end  70   a  of the external side reinforcement layer  70  is positioned more to the outer side in the tire-radial direction than the tire-radial direction outer end  11 A of the bead core  11 . It should be noted that the tire-radial direction inner end  70   a  of the external side reinforcement layer  70  may contact with the tire-radial direction outer end  11 A of the bead core  11 . 
     The tire-radial direction length L 2  of the external side reinforcement layer  70  is longer than the tire-radial direction length L of the bead filler  12 . The external side reinforcement layer  70  has an inside extending part  71  on the inner side in the tire-radial direction adhering to the outer surface  12   c  of the bead filler  12 , and an outside extending part  72  extending more to the outer side in the tire-radial direction than the tire-radial direction outer end  12   d  of the bead filler  12 . The leading end of the outside extending part  72 , i.e. tire-radial direction outer end  70   b  of the external side reinforcement layer  70 , is at substantially the same position as the widest position W 1  of the tire  1  in the tire-radial direction, or between the widest position W 1  of the tire  1  and the tire-radial direction outer end  12   d  of the bead filler  12 . 
     The entirety of the external side reinforcement layer  70 , i.e. inside extending part  71  and outside extending part  72 , all adhere to the second carcass ply  420  of the ply folding part  402  of the carcass ply  40 . Herein, the inside extending part  71  is sandwiched between the bead filler  12  and ply folding part  402 , and adheres to both this bead filler  12  and second carcass ply  420  of the ply folding part  402 . In other words, the inside extending part  71 , which is part of the external side reinforcement layer  70 , is sandwiched between the bead filler  12  and ply folding part  402 . More specifically, the external side reinforcement layer  70  may contact with the bead filler  12 . In addition, the external side reinforcement layer  70  may contact with the second carcass ply  420  of the ply folding part  402 . 
     On the other hand, the outside extending part  72  which is a portion extending to the outer side in the tire-radial direction beyond the tire-radial direction outer end  12   d  of the bead filler  12  is sandwiched between the second carcass ply  420  on the side of the ply main body part  401  and the second carcass ply  420  on the side of the ply folding part  402 . In other words, the outside extending part  72  is sandwiched between the ply main body part  401  and ply folding part  402 . In other words, the outside extending part  72  is disposed at an outer side in the tire-width direction of the ply main body part  401 . The outside extending part  72  adheres to both the second carcass ply  420  on the side of the ply main body part  401  and the second carcass ply  420  on the side of the ply folding part  402 . The tire-radial direction outer end  70   b  of the external side reinforcement layer  70  is thereby suppressed from forming a step at the outer surface of the sidewall  20 , and thus a favorable appearance characteristic is retained. In addition, since the tire-radial direction outer end  70   b  of the external side reinforcement layer  70  is protected by the carcass ply  40 , the inner liner  50  is avoided from receiving external injury by the external side reinforcement layer  70 . 
     In the present embodiment, the tire-radial direction length L 2  of the external side reinforcement layer  70  is preferably at least 110% and no more than 170% the tire-radial direction length L of the bead filler  12 , and is more preferably at least 120% and no more than 160%. 
     In the present embodiment, the tire-radial direction outer end  60   b  of the inside inner reinforcement layer  60  is positioned more to the inner side in the tire-radial direction than the tire-radial direction outer end  12   d  of the bead filler  12 . In addition, the tire-radial direction outer end  70   b  of the external side reinforcement layer  70  is positioned more to the outer side in the tire-radial direction than the tire-radial direction outer end  12   d  of the bead filler  12 . In this way, by the tire-radial direction outer end of each of the internal side reinforcement layer  60  and external side reinforcement layer  70  shifting to the tire-radial direction, without aligning with the tire-radial direction outer end of the bead filler  12 , stress concentration hardly occurs. As a result thereof, an improvement in durability is achieved. 
     As shown in  FIG.  2   , the outside end part  61  in the tire-radial direction of the aforementioned internal side reinforcement layer  60  points to the external side reinforcement layer  70 . A virtual extension line  611  extending in a pointing direction of this outside end part  61  from the outside end part  61  in the tire-radial direction of the internal side reinforcement layer  60  intersects the external side reinforcement layer  70 . 
     In the internal side reinforcement layer  60  and external side reinforcement layer  70  in the present embodiment, the metal fiber cord layer containing metal fibers is favorably used.  FIG.  3    is a view showing a part of the external side reinforcement layer  70  from a metal fiber cord layer, and is a virtual diagram when viewing the external side reinforcement layer  70  arranged within the tire  1  from the outer side in the tire-width direction towards the inner side in the tire-width direction. It should be noted that the internal side reinforcement layer  60  is also configured by a metal fiber cord layer similarly to the external side reinforcement layer  70 . Therefore, herein, the structures for both the internal side reinforcement layer  60  and external side reinforcement layer  70  are described later on behalf of the external side reinforcement layer  70 , according to  FIG.  3   . 
     The external side reinforcement layer  70  is configured to include a plurality of metal cords  81  formed by intertwining a plurality of metal fibers, and topping rubber  82  integrated by coating the plurality of metal cords  81 . 
     The plurality of metal cords  81  are arranged with an interval in the tire-circumferential direction C in a sloped state extending to slope relative to the radial direction R of the tire  1 . The interval between the plurality of metal cords  81  aligned in the tire-circumferential direction C widens as approaching the outer side in the tire-radial direction. 
     The angle θ formed by the radial direction R of the tire  1  and the extending direction of the metal cord  81  of the external side reinforcement layer  70  is preferably at least 10° and no more than 40°. It should be noted that, in the present embodiment, the ply cord constituting the carcass ply  40  is arranged radially (radial direction R) from the center of the tire  1 . Consequently, in the present embodiment, the angle θ formed by the extending direction of the ply cord of the carcass ply  40  and the extending angle of the metal cords  81  of each of the internal side reinforcement layer  60  and external side reinforcement layer  70  is at least 10° and no more than 40°. The sloping direction of the metal cords  81  of the internal side reinforcement layer  60  may be the opposite direction to the sloping direction of the metal cords  81  of the external side reinforcement layer  70 . 
     In this way, by having the ply cords of the carcass ply  40  and the metal cords  81  of each of the internal side reinforcement layer  60  and external side reinforcement layer  70  intersect in a side view, it is possible to raise the rigidity of the portion at which the internal side reinforcement layer  60  and external side reinforcement layer  70  overlap with the carcass ply  40 . 
     As the metal constituting the metal cord  81 , a metal cord material having flexibility while being high strength, and having high fatigue resistance is preferable, and steel cord is more preferably used, for example. In the case of steel cord, for example, cord made by intertwining several to several tens of wires consisting of high carbon steel on the order of φ0.1 to φ0.5 mm, and conducting plating to raise the adhesive property with the rubber as necessary can be used. As the metal cords  81  of the present embodiment, those having an outside diameter (cord diameter) of at least 0.5 mm and no more than 1.2 mm are preferably used, for example. 
     It should be noted that the internal side reinforcement layer  60  and external side reinforcement layer  70  may be reinforcement layers in which a plurality of organic fiber cords having an insulation property such as polyamide fibers are covered with rubber, similarly to the cap ply  32 , for example. 
     According to the tire  1  of the present embodiment, upon the tire  1  receiving lateral force during cornering or the like, the external side reinforcement layer  70  strongly resists this lateral force, and exerts sufficient side rigidity. In addition, upon receiving lateral force, the internal side reinforcement layer  60  effectively suppresses deflection of the bead filler  12 , whereby sufficient side rigidity is exhibited. Therefore, the side rigidity drastically rises by the internal side reinforcement layer  60  and external side reinforcement layer  70 , a result of which an improvement in cornering performance is possible. 
     As in the present embodiment, when the tire-radial direction length L 1  of the internal side reinforcement layer  60  is at least 60% and no more than 90% of the tire-radial direction length L of the bead filler  12 , it is particularly preferable in the internal side reinforcement layer  60  suppressing deflection of the bead filler  12 . 
     Herein, three types of analysis models of tires including the same configurations as the present embodiment but with different tire-radial direction lengths L 1  of the internal side reinforcement layer  60  relative to the tire-radial direction length L of the bead filler  12  were prepared, and the characteristics related to the rigidity of these tires were measured by simulation. In addition, for comparison, a tire having only the external side reinforcement layer  70  without the internal side reinforcement layer  60  was prepared as a model 0, and the characteristics related to rigidity were measured by simulation in the same way. The results thereof are shown in Table 1. 
     As shown in Table 1, for models 1 to 3 of the tire, the proportion L 1 /L (%) of the tire-radial direction length L 1  of the internal side reinforcement layer  60  relative to the tire-radial direction length L of the bead filler  12  were respectively 50%, 70% and 80%. The characteristics measured by simulation were measured, as rigidity values, the three types of “front/rear rigidity”, which is the resistance to load received from a front/rear direction during acceleration and during deceleration, “lateral rigidity” against the load from a lateral direction, and “vertical rigidity” against vertical load applied from above to below. In Table 1, the rigidity improvement rate indicating how much the rigidity of each of the models 1 to 3 improves relative to model 0 without the internal side reinforcement layer  60  is written jointly with the rigidity value. 
     It should be noted that the tires of the respective measured models correspond to rims of 19×10.0J (19 inch rim diameter, 10 inch rim width, flange shape: J), and the internal pressure in a state mounted to this rim was measured at 220 kpa. In addition, the vertical load on the tire was set as 680 kg, the front/rear load was set as 204 kg, and the horizontal load was set as 204 kg, and each load was applied to the tire. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Model 1 (50%) 
                 Model 2 (70%) 
                 Model 3 (80%) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Rigidity 
                   
                 Rigidity 
                   
                 Rigidity 
               
               
                   
                 Rigidity value 
                 Rigidity 
                 improvement 
                 Rigidity 
                 improvement 
                 Rigidity 
                 improvement 
               
               
                   
                 of model 0 
                 value 
                 rate 
                 value 
                 rate 
                 value 
                 rate 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 front/rear 
                 582.5 
                 600.5 
                 3.10% 
                 606.6 
                 4.14% 
                 602.0 
                 3.35% 
               
               
                 rigidity 
               
               
                 lateral 
                 338.0 
                 340.9 
                 0.85% 
                 344.9 
                 2.02% 
                 341.4 
                 0.99% 
               
               
                 rigidity 
               
               
                 Vertical 
                 380.5 
                 382.5 
                 0.51% 
                 381.6 
                 0.28% 
                 382.0 
                 0.39% 
               
               
                 rigidity 
               
               
                   
               
            
           
         
       
     
     According to Table 1, all the tires having the internal side reinforcement layer  60  had improved rigidity, and the rigidity improvement effect of the internal side reinforcement layer  60  was confirmed. However, model 1 had lower lateral rigidity and higher vertical rigidity than model 2 and model 3. This concerns a decline in ride quality due to model 1 having relatively low side rigidity against lateral force, and high vertical rigidity. Therefore, the tire-radial direction length L 1  of the internal side reinforcement layer  60  is preferably at least 50% relative to the tire-radial direction length L of the bead filler  12 . In addition, if the tire-radial direction length L 1  of the internal side reinforcement layer  60  is similar to the tire-radial direction length L of the bead filler  12 , the tire-radial direction outer ends of both will be aligned; however, this leads to stress concentration on this portion, and there is concern over causing a decline in durability. For these reasons, the proportion L 1 /L of the tire-radial direction length L 1  of the internal side reinforcement layer  60  relative to the tire-radial direction length L of the bead filler  12  is considered preferably at least 60% and no more than 90%. 
     According to the tire  1  of the present embodiment, the following effects are exerted. 
     (1) The tire  1  according to the present embodiment includes: a pair of beads  10  having a bead core  11  and a bead filler  12  extending from the bead core  11  to an outer side in the tire-radial direction; a pair of sidewalls  20  extending from each of the pair of beads  10  to the outer side in the tire radial direction; tread  30  arranged between the pair of sidewalls  20 ; the carcass ply  40  bridging between the pair of beads  10 ; the internal side reinforcement layer  60  arranged at the inner side in the tire-width direction of the bead filler  12 ; and the external side reinforcement layer  70  arranged at the outer side in the tire-width direction of the bead filler  12 , in which the internal side reinforcement layer  60  is arranged more to the inner side in the tire-radial direction than the tire-radial direction outer end of the bead filler  12 , and the external side reinforcement layer  70  has an outside extending part  72  extending from the tire-radial direction outer end of the bead filler  12  to the outer side in the tire-radial direction. 
     It thereby becomes possible to achieve an improvement in side rigidity over convention, a result of which an improvement in cornering performance becomes possible. 
     (2) In the tire  1  according to the present embodiment, it is preferable for the carcass ply  40  to have: the ply main body part  401  extending between the tread  30  and an inner side in the tire-width direction of the bead  10 ; and the ply folding part  402  extending to an outer side in the tire-radial direction at an outer side in the tire-width direction of the bead filler  12 , by being folded back around the bead core  11  from the tire-radial direction inner end of the ply main body part  401 , and for the internal side reinforcement layer  60  to be sandwiched between the bead filler  12  and ply main body part  401 , and a part of the external side reinforcement layer  70  to be sandwiched between the bead filler  12  and ply folding part  402 . 
     It is thereby possible to obtain a drastic improvement effect in side rigidity by cooperation of the carcass ply  40  with the internal side reinforcement layer  60  and external side reinforcement layer  70 . In addition, during manufacture of the tire  1 , since it is possible to bring the internal side reinforcement layer  60  and external side reinforcement layer  70  into contact with the bead filler  12 , positioning of the internal side reinforcement layer  60  and external side reinforcement layer  70  is easy to do, and manufacturing is facilitated. 
     (3) In the tire  1  according to the present embodiment, the tire-radial direction inner end  60   a  of the internal side reinforcement layer  60  and the tire-radial direction inner end  70   a  of the external side reinforcement layer  70  are both preferably positioned more to the outer side in the tire-radial direction than the tire-radial direction outer end of the bead core  11 . 
     It thereby becomes possible to sufficiently exhibit a deflection suppression effect of the bead filler  12  by each of the internal side reinforcement layer  60  and the external side reinforcement layer  70  without being inhibited by the bead core  11 , and thus possible to precisely improve the side rigidity. 
     (4) In the tire  1  according to the present embodiment, the outside extending part  72  of the external side reinforcement layer  70  is preferably sandwiched between the ply main body part  401  and ply folding part  402 . 
     It is thereby possible to obtain a drastic improvement effect in the side rigidity by cooperation between the carcass ply  40  and the outside extending part  72  of the external side reinforcement layer  70 . In addition, the outside extending part  72  of the external side reinforcement layer  70  is protected by the carcass ply  40 , and negative influences on the tire outer surface and tire inner surface is avoided by the outside extending part  72 . 
     (5) In the tire  1  according to the present embodiment, the tire-radial direction length L 1  of the internal side reinforcement layer  60  is preferably at least 60% and no more than 90% of the tire-radial direction length L of the bead filler  12 . 
     It is thereby possible to precisely obtain the deflection suppression effect of the bead filler  12  by the internal side reinforcement layer  60 . 
     (6) In the tire  1  according to the present embodiment, the outside end part  61  in the tire-radial direction of the internal side reinforcement layer  60  points to the external side reinforcement layer  70 , and the virtual extension line  611  extending in the pointing direction of this outside end part  61  preferably intersects the external side reinforcement layer  70 . 
     It is thereby possible to more effectively suppress deformation in which the external side reinforcement layer  70  bends to the inner side in the tire-width direction by the internal side reinforcement layer  60 , upon receiving strong lateral force, whereby an even greater improvement in side rigidity becomes possible. 
     It should be noted that the present invention is not limited to the above-mentioned embodiment, and even if performing modifications, improvements, etc. in a scope which can achieve the object of the present invention, it will be encompassed in the scope of the present invention. 
     For example, the internal side reinforcement layer  60  and external side reinforcement layer  70  may not be adhered to the bead filler  12 , and a separate rubber layer may be interposed between each of the internal side reinforcement layer  60  and external side reinforcement layer  70 , and the bead filler  12 . 
     So long as the outside extending part  72  of the external side reinforcement layer  70  is extending more to the outer side in the tire-radial direction than the bead filler  12 , the length thereof is not limited, and may extend from the sidewall  20  over the tread  30 , instead of the ply folding part  402  of the carcass ply  40 , for example.