JP6194151B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a reinforcing layer in a bead portion. The present invention particularly relates to a pneumatic tire capable of achieving both high-speed durability and steering stability.

  Conventionally, in pneumatic tires mainly for high-speed running, steel cords or organic fiber cords are used in the bead part for the purpose of improving the steering stability by suppressing the deformation of the tire from the sidewall part to the bead part during high-speed running. A reinforcement layer made of a rubber coating layer is inserted.

  Patent Document 1 describes a pneumatic radial tire having an inner reinforcing layer made of a plurality of organic fiber cords and an outer reinforcing layer made of a plurality of steel cords. This tire has a two-ply carcass structure, and the inner carcass layer has a main body part extending between a pair of bead cores, and both ends are wound around the bead cores from the inner side to the outer side in the tire width direction, and the turn-up part The outer carcass layer has a 1-1 high turnup structure that is disposed outside the turnup portion of the inner carcass layer. The inner reinforcing layer made of organic fiber cord is arranged between the beet filler and bead core and the inner carcass layer, and the outer reinforcing layer made of steel cord is arranged between the turn-up portion of the inner carcass layer and the outer carcass layer. doing.

  Patent Document 2 describes a pneumatic radial tire having an inner reinforcing layer made of steel cord and an outer reinforcing layer made of aromatic polyamide fiber cord. This tire also has a carcass structure composed of two plies as in Patent Document 1, and the carcass cord is made of organic fibers such as nylon and rayon. The inner reinforcing layer and the outer reinforcing layer are disposed between the turn-up portion of the inner carcass layer and the outer carcass layer.

JP 2000-43517 A JP 2000-62416 A

  However, when a reinforcing layer made of a rubber cord layer of steel cord or organic fiber cord is inserted into the bead portion, the steering stability is improved, but due to the difference in rigidity between the cord constituting the reinforcing layer and the rubber around the reinforcing layer. The present inventors have found that there is a problem that separation occurs between the reinforcing layer and the surrounding rubber, and durability during high-speed running is impaired. This phenomenon becomes more prominent as there is a portion having a large rigidity step in the bead portion. Here, it is common to use hard rubber for the bead filler. In addition, metal cords such as steel cords have a higher tensile elastic modulus than organic fiber cords, so the reinforcement layer formed by rubber-coating steel cords is more than the reinforcement layer formed by rubber-coating organic fiber cords. The rigidity is high. Therefore, in the tires described in Patent Document 1 and Patent Document 2 described above, it is inevitable that a portion having a large rigidity step is generated in the bead portion.

  That is, in the tire of Patent Document 1, an inner reinforcing layer made of an organic fiber cord having a smaller tensile elastic modulus than that of a steel cord is disposed closest to the bead filler made of hard rubber. For this reason, we are anxious about a comparatively big rigid level | step difference arising between a bead filler and an inner side reinforcement layer.

  Moreover, in the tire of patent document 2, the carcass layer formed by rubber-covering a carcass cord made of a low elastic fiber such as nylon is disposed closest to the bead filler made of hard rubber. For this reason, a big rigidity level | step difference arises between a bead filler and this carcass layer. In addition, the turn-up part of the inner carcass layer is adjacent to the inner reinforcement layer made of steel cord, and the nylon cord and steel cord have greatly different tensile elastic modulus. There is a large rigidity step in between.

  As described above, in a conventional pneumatic tire having a reinforcement layer in the bead portion, it is recognized that the high-speed durability is improved by reducing the rigidity step generated in the bead portion, and the arrangement relation of the carcass and the reinforcement layer for that purpose. There is no idea of devising. On the other hand, with the recent improvement in performance of high-speed traveling vehicles, pneumatic tires are required to have higher high-speed durability and steering stability. Conventional pneumatic tires such as those described above satisfy this requirement. I could not meet.

  Then, in view of the said subject, this invention aims at providing the pneumatic tire which can make high speed durability and steering stability which are not in the past compatible.

  As described above, the present inventors diligently studied to further improve the high-speed durability of a pneumatic tire having a reinforcing layer in the bead portion. As a result, the rigidity difference between the members constituting the bead portion such as the bead filler, the carcass, and the reinforcing layer. As a result, it has been recognized that the separation generated in the bead portion is a cause of impairing the high-speed durability. Therefore, for the reinforcing layer and the carcass folded portion disposed on the outer side in the tire width direction of the bead filler, members that constitute the bead portion are arranged in order from the side closer to the bead filler made of hard rubber. Inspired to minimize the difference in rigidity between them and suppress the separation generated in the bead portion, it was found that the above problem can be solved by making a pneumatic tire having the following configuration, and the present invention has been completed. .

That is, in view of the above problems, the gist of the present invention is as follows.
(1) a ply main body extending in a toroidal shape between a pair of bead cores, and a ply folded portion extending from the inner side of the tire width direction around each of the bead cores and folded outward from the ply core. A carcass having at least one ply formed by coating a ply cord with rubber;
A bead filler that tapers from the top of the bead core toward the outer side in the tire radial direction between the ply body and the ply turn-up portion;
Between the ply turn-up portion and at least the bead filler, the first reinforcing layer formed by rubber coating the first cord and the second cord, which are disposed in order from the inner side in the tire width direction, are coated with rubber. A second reinforcing layer;
A third reinforcing layer made of rubber disposed on the tire width direction outer side of the ply folded portion,
The first cord, the second cord, and the ply cord have a large tensile elastic modulus in this order,
The rubber constituting the third reinforcing layer has a smaller dynamic elastic modulus than the rubber constituting the bead filler,
The second reinforcing layer has a folded portion that is folded inward from the outer side in the tire width direction around the bead core, and a tire radial direction outer end portion on the outer side in the tire width direction is a tire radial direction on the inner side in the tire width direction. Positioned on the outer side in the tire radial direction from the outer end, and viewed in a cross section in the tire width direction, the outer end in the tire radial direction of the third reinforcing layer and the outer end in the tire radial direction on the outer side in the width direction of the second reinforcing layer The outer end portion in the tire radial direction of the first reinforcing layer and the outer end portion in the tire radial direction of the bead filler are located on the outer side in the tire radial direction in this order, and the first cord is a metal cord or an organic fiber cord. A pneumatic tire characterized in that the second cord and the ply cord are organic fiber cords.

(2) The pneumatic tire according to the above (1) is the first code is a metal cord.

(3) It further has at least one belt layer located on the outer peripheral side of the crown portion of the carcass and formed by rubber-covering the cord,
Of the plies constituting the carcass, at least one ply has a structure in which a folded end of a ply folded portion is positioned between the belt layer and a crown portion of the carcass. The described pneumatic tire.

  (4) The pneumatic tire according to any one of (1) to (3), wherein the carcass is configured by a single ply.

(5) the first code is a steel cord, the second cord is an aromatic polyamide fiber cords, the ply cord according to any one of the rayon cord (2) to (4) Pneumatic tire.
(6) Any of the above (1) to (5), wherein an angle of the first reinforcing layer with respect to a tire radial direction of the first cord is smaller than an angle of the second reinforcing layer with respect to a tire radial direction of the second cord. The pneumatic tire according to Crab.

  In the pneumatic tire of the present invention, by arranging the members having high rigidity in order from the one close to the bead filler made of hard rubber, the rigidity step between the members constituting the bead portion is minimized, and the bead portion is generated. Since separation can be suppressed, it has become possible to achieve both high-speed durability and handling stability, both of which have not been achieved before.

FIG. 3 is a half cross-sectional view in the tire width direction in a no-load state in which the pneumatic tire 100 according to the present invention is mounted on an applied rim and filled with a predetermined air pressure.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. In principle, the same components are denoted by the same reference numerals, and description thereof is omitted.

  A typical pneumatic tire 100 according to the present invention will be described with reference to FIG. Although FIG. 1 does not show the applicable rim for the sake of clarity, FIG. 1 shows the tire mounting posture in a no-load state in which the pneumatic tire 100 is mounted on the applied rim and filled with a predetermined air pressure. The tire width direction half section is shown. The arrangement relationship and dimensional relationship of the tire of the present invention described below are assumed to be in this tire mounting posture. In this embodiment, a pneumatic tire 100 includes a pair of bead portions 1 (only one side is shown) in which a bead core 4 is embedded, and a pair of sidewall portions 2 (only one side is shown) extending from the bead portion 1 to the tire radial direction outside. And a tread portion 3 (only a half portion is shown) extending between the sidewall portions. The bead core typically consists of a steel cord.

  The pneumatic tire of the present invention has a carcass having at least one ply formed by covering a ply cord with rubber. In the pneumatic tire 100 of the present embodiment, the carcass 6 is composed of one ply 5. The ply 5 is a ply body portion 5a extending in a toroidal shape between the pair of bead cores 4, and extends from the ply body portion 5a and is folded back outwardly from the inside in the tire width direction W around each of the bead cores 4 (a pair of plies 5). Ply turn-up portion 5b. In the present invention, when the carcass is composed of a plurality of plies, each ply has a main body portion and a folded portion. The carcass 6 is a radial carcass. In this case, a plurality of ply cords arranged in parallel to each other are arranged at an angle of 70 ° to 90 ° with respect to the tire equator CL plane. The ply cord and the covering rubber will be described later.

  In the present specification, the “predetermined air pressure” means an air pressure corresponding to a maximum load (maximum load capacity) of a single wheel in an application size described in the following standard. Further, the “predetermined load condition” means applying a load of the maximum load (maximum load capacity) of a single wheel in the application size described in the same standard. The “applied rim” is a standard rim (or “Approved Rim” or “Recommended Rim”) in the applicable size described in the standard. As for such industrial standards, standards that are effective in regions where tires are produced or used are defined. For example, “Year Book of The Tire and Rim Association Inc.” in the United States, “STANDARDS MANUAL of The European Tire and Rim Technical Organization” in Europe, and “JATMA Year Book” of the Japan Automobile Tire Association in Japan. It is.

The pneumatic tire 100 includes a pair of bead fillers 7 (only one side is shown) extending from the bead core 4 toward the outer side in the tire radial direction between the ply main body portion 5a and the ply turn-up portion 5b. The bead filler 7 has a substantially triangular cross section and is made of hard rubber having a dynamic elastic modulus of 80 to 180 MPa. The height H _7a from the rim diameter line RL in the tire radial direction outer end portion 7a of the bead filler 7 is preferably positioned 20 to 50% of the tire section height from the rim diameter line. Here, the “rim diameter line” is a tire axial line that determines the rim diameter defined by the rim standards of JATMA (Japan Automobile Tire Association), TRA (American Tire and Rim Association) and ETRTO (European Tire and Rim Technical Organization). Is defined as

  The pneumatic tire 100 includes a pair of first reinforcing layers 8 that are disposed in order from the inner side in the tire width direction W between the ply turn-up portion 5b and at least the bead filler 7, and are formed by rubber coating a first cord. It has a pair of 2nd reinforcement layer 9 formed by rubber-coating a 2nd code | cord | chord (only one side is shown in figure, respectively). The pneumatic tire 100 includes a pair of third reinforcing layers 10 (only one side is shown) made of rubber and disposed outside the tire width direction W of the ply folded portion 5b.

The characteristic configuration of the present invention is that the first cord used for the first reinforcing layer 8, the second cord used for the second reinforcing layer 9, and the ply cord used for the ply 5 have a large tensile elastic modulus in this order, In addition, the rubber constituting the third reinforcing layer 10 has a smaller dynamic elastic modulus than the rubber constituting the bead filler 7.

The technical significance of adopting the above characteristic configuration of the present invention will be described together with the effects. As described above, the present invention is based on the technical idea of minimizing the rigidity step between the members constituting the bead portion. Here, attention is focused on the outer side of the bead filler 7 in the tire width direction.
For the first reinforcing layer 8, the second reinforcing layer 9, and the ply turn-up portion 5b, which are cord rubber coating layers, the tensile elastic modulus of the cord greatly contributes to the rigidity of the entire layer. In the pneumatic tire 100, since the first cord used for the first reinforcing layer 8, the second cord used for the second reinforcing layer 9, and the ply cord used for the ply 5 have a large tensile elastic modulus in this order, The rigidity as a whole also increases in the order of the first reinforcing layer 8, the second reinforcing layer 9, and the ply turn-up portion 5b.
In the present invention, the member closest to the bead filler 7 made of hard rubber is the first reinforcing layer 8 having the highest rigidity as the entire layer among the first reinforcing layer 8, the second reinforcing layer 9, and the ply folded portion 5b. The second reinforcing layer 9 and the ply turn-up portion 5a were sequentially arranged on the outer side. For this reason, on the outer side in the tire width direction of the bead filler 7, members having higher rigidity are sequentially arranged from the inner side to the outer side, and the rigidity step between the members can be minimized. As a result, separation generated in the bead portion can be suppressed, so that high-speed durability that is unprecedented can be realized. In addition, according to the configuration of the present invention in which a layer having lower rigidity is arranged on the outer side in the tire width direction, the lateral rigidity is increased, and the center grounding property is improved as well as the lateral spring property, so that the driving stability is further improved. Is also possible.

The third reinforcing layer 10 is a reinforcing layer made of rubber having no cord as a reinforcing element. Therefore, if the rubber constituting the third reinforcing layer 10 has a smaller dynamic elastic modulus than the rubber constituting the bead filler 7 (the reinforcing layers 8 and 9 and the ply folded 5a), the reinforcing layer including the cord It is clear that the rigidity of the entire layer is lower than that of 8, 9 and the ply turn-up 5a.
Here, the 3rd reinforcement layer 10 is arrange | positioned by the tire width direction outer side of the ply | turnback part 5a. Therefore, adjacent to the third reinforcing layer 10 is the first reinforcing layer 8, the second reinforcing layer 9, and the ply folded portion 5a having the lowest rigidity as the entire layer among the ply folded portions 5b. Therefore, a large rigidity step does not occur between the adjacent ply turn-up portions 5a and the third reinforcing layer 10, which also contributes to the realization of high high-speed durability. Moreover, according to the structure of this invention which arrange | positions a reinforcement layer further on the tire width direction outer side of the carcass 5, it will also improve steering stability more.

  In the pneumatic tire 100, the example in which the first to third reinforcing layers 8, 9, and 10, which are at least three reinforcing layers, are arranged has been described. However, the present invention is not limited to this, and the bead filler is used. As long as the rigidity relationship described above is not lost with respect to the outer side in the tire width direction, a further reinforcing layer may be arranged.

  The first reinforcing layer 8, the second reinforcing layer 9, the third reinforcing layer 10, and the ply 5 are not particularly limited as long as they satisfy the characteristic configuration of the present invention, and can be exemplified as follows. .

(First reinforcing layer 8)
The first cord used for the first reinforcing layer 8 preferably has a tensile modulus of 3200 N / mm ² or more and 4000 N / mm ² or less. The cord material is not particularly limited, and a metal cord, an organic fiber cord, and the like can be used. However, since the tensile elastic modulus is larger than that of the second cord and the ply cord, the first cord is a metal cord such as a steel cord. It is preferable that The first reinforcing layer 8 (wire insert) is preferably a rubber coating layer in which a plurality of first cords are arranged in parallel to each other. In this case, the angle θ1 of the first cord with respect to the tire radial direction is preferably in the range of 30 ° to 60 °.

(Second reinforcing layer 9)
The second cord used for the second reinforcing layer 9 preferably has a tensile modulus of 170 to 300 cN / dtex. The cord material is not particularly limited, and a metal cord, an organic fiber cord, or the like can be used. However, since the tensile elastic modulus is smaller than the first cord and larger than the ply cord, the second cord has a relatively high elasticity. The organic fiber cord is preferably used. Specific examples include wholly aromatic polyester fibers such as aromatic polyamide fibers (aramid fibers) and polyarylate fibers, polyvinyl alcohol fibers, carbon fibers, polyparaphenylene benzoxazole (PBO) fibers, and lyocell fibers. it can. The lyocell fiber is a cellulose fiber obtained from a raw material cellulose by a solvent spinning method. For example, as described in Japanese Patent Publication No. 60-28848 and Japanese Patent Publication No. 11-504995, A solution containing cellulose and a non-solvent such as water is spun into air or a non-precipitating medium, and at that time, the fiber-forming solution exiting from the spinneret is pulled at a speed higher than the speed at which it is fed. It can obtain by extending | stretching by the draw ratio more than double, and processing with a non-solvent. As the second cord, a composite cord formed by twisting a plurality of types of organic fibers having different elastic moduli may be used. In this case, the organic fibers to be combined are not limited to highly elastic fibers, but are nylon fibers and polyester fibers (excluding wholly aromatic polyester fibers) such as polyethylene terephthalate (PET) fibers and polyethylene naphthalate (PEN) fibers. In addition, a relatively low elasticity organic fiber such as polytrimethylene terephthalate (PTT) fiber, polyvinyl alcohol fiber, aliphatic polyketone (PK) fiber, or the like may be included. The second reinforcing layer 9 is preferably a rubber coating layer in which a plurality of second cords are arranged in parallel to each other. In this case, the angle θ2 of the second cord with respect to the tire radial direction is preferably in the range of 0 ° to 45 °.

(Ply 5)
The ply cord used for the ply 5 preferably has a tensile elastic modulus of 4.7 cN / dtex or more. The cord material is not particularly limited, and a metal cord, an organic fiber cord, and the like can be used. However, since the tensile elastic modulus is smaller than that of the first cord and the second cord, an organic fiber cord having a relatively low elasticity. It is preferable that As a specific material, the above-mentioned low elastic fiber can be used, and the same is true in that a composite cord formed by twisting a plurality of types of organic fibers having different elastic moduli may be used.

Although the covering rubber which comprises the 1st reinforcement layer 8, the 2nd reinforcement layer 9, and the ply 5 is not specifically limited, It is preferable to comprise from the rubber | gum whose dynamic elastic modulus is 30-150 MPa, and all coating rubbers are the same material. A rubber having the same value of dynamic elastic modulus is preferable.

(Third reinforcing layer 10)
The rubber constituting the third reinforcing layer 10 is not particularly limited as long as it has a smaller dynamic elastic modulus than the rubber constituting the bead filler 7. For example, the rubber is composed of rubber having a dynamic elastic modulus of 50 to 150 MPa. It is preferable to do.

  As a most typical example of the cords included in the first reinforcing layer 8, the second reinforcing layer 9, and the ply 5, in the pneumatic tire 100 of the present embodiment, the first cord is a steel cord, and the second cord is Aromatic polyamide fiber cord (Kevlar: registered trademark) and ply cord are rayon.

The “tensile elastic modulus” and “ dynamic elastic modulus ” of the organic fiber cord in this specification are measured by the following methods. First, the tensile elastic modulus is obtained by taking out the belt reinforcing layer without damaging the cord from a pneumatic tire that is not running and is in a new state. At this time, excess rubber adhering to the cord of the belt reinforcing layer is carefully removed with scissors or the like. Furthermore, a tensile load-elongation curve is drawn at room temperature (25 ° C. ± 2 ° C.) with an autograph (Shimadzu Corporation) according to JIS (L1017). The load axis of the load-elongation curve is converted to a value obtained by dividing the load axis by the total number of detex (dtex) of the cord before tension, and the stress-elongation curve is rewritten. Subsequently, a tangent line is drawn at a load point of 7.94 mN / dtex (0.9 g / d) in this curve diagram, and the inclination of the tangent line is obtained. A value obtained by multiplying this value (the inclination) by (0.981 × the specific gravity of the organic fiber) is the tensile elastic modulus (GPa) here. Next, the dynamic elastic modulus was measured using a spectrometer manufactured by Toyo Seiki Co., Ltd. at an initial load of 100 g, a strain of 1%, a measurement frequency of 50 Hz, and a measurement temperature of 25 ° C.

  The pneumatic tire of the present invention preferably further includes at least one belt layer that is located on the outer peripheral side of the crown portion of the carcass and is formed by covering the cord with rubber. The pneumatic tire 100 of the present embodiment is a belt layer that is a two-layer cord rubber coating layer that is formed by sequentially laminating cords on the outer periphery of the crown portion 6a of the carcass 6 so that the cords cross each other across the tire equator CL. The cross belt 11 includes 11a and 11b. Examples of the cord include a steel cord and an organic fiber cord. Further, the pneumatic tire 100 is disposed on the outer side in the tire radial direction of the cross belt 11 so as to cover the entire width of the cross belt 11, and a plurality of cords arranged substantially parallel to the tire equator CL are covered with rubber. The cap layer 12 is a belt reinforcing layer. Although one wide belt reinforcing layer is shown as the cap layer in FIG. 1, the present invention is not limited to this, and a plurality of layers may be arranged.

(Carcass structure)
The pneumatic tire 100 has a so-called envelope structure in which the folded end 5c of the ply folded portion 5a of the ply 5 constituting the carcass 6 is located between the belt layer 11 and the crown portion 6a of the carcass 6. According to the envelope structure, it is possible to obtain the same handling stability as that of the 1-1 high turn-up structure having two plies. Furthermore, it is preferable that the carcass is composed of one ply in that the weight can be reduced as compared with the case of two plies.

(Disposition range and disposition relationship of the first to third reinforcing layers 8, 9, 10)
Hereinafter, a preferable arrangement range and arrangement positional relationship of the reinforcing layer will be described. As shown in FIG. 1, the tire radial direction outer end portion 10a of the third reinforcement layer 10, the tire radial direction outer end portion 9a of the second reinforcement layer 9, the tire radial direction outer end portion 8a of the first reinforcement layer 8, and The tire radial direction outer end portion 7a of the bead filler 7 is preferably located on the outer side in the tire radial direction in this order as seen in the cross section in the tire width direction. The upper end of the reinforcing layer is a place where distortion concentrates due to repeated deformation of the tire due to load rolling during high-speed running, but in this way, by dispersing the height of the upper end of the three reinforcing layers, Strain concentration can be suppressed, and high-speed durability can be further improved. In addition, by arranging the upper ends of the three reinforcing layers so as to be higher toward the outer side in the tire width direction, highly rigid members gather at the upper end of the tire, and the actual vehicle performance can be further improved.

As shown in FIG. 1, the heights from the rim diameter line RL of the outer ends in the tire radial direction of the third reinforcing layer 10, the second reinforcing layer 9, and the first reinforcing layer 8 are respectively H _10a , H _9a , H _8a . From the viewpoint of dispersing the end portions in order to suppress strain concentration, H _10a -H _9a , H _9a -H _8a , and H _8a -H _7a are each preferably 5 mm or more.

In addition, the tire radial direction inner end portion 10 b of the third reinforcement layer 10 is preferably located on the tire radial direction outer side than the tire radial direction inner end portion 8 b of the first reinforcement layer 8. This is because, by separating from the bead, local concentration of stress is suppressed, and the structure around the bead is simplified to improve the fit to the rim as much as possible. Then, assuming that the heights of the end portions 10b and 8b from the rim diameter line RL are H _10b and H _8b , respectively, from the viewpoint of dispersing the end portions in order to suppress strain concentration, H _10b -H _8a It is preferable to be 5 mm or more.

  The second reinforcing layer 9 preferably has a folded portion 9 c that is folded from the outside in the tire width direction W to the inside around the bead core 7. By folding back the second reinforcing layer 9 around the bead core 7, it is possible to prevent the tire from coming off during load rolling and improve the rigidity of the bead portion 1. On the other hand, the first reinforcing layer 8 is preferably configured not to be rolled up around the bead core 7. Since the first reinforcing layer 8 has higher rigidity than the second reinforcing layer 9, if the structure is wound up, the rigidity of the bead portion 1 becomes too high, and the fit with the rim may be impaired. is there.

  By using the pneumatic tire 100 of the present invention as a passenger car (PSR) tire, the effects of the present invention can be obtained more remarkably. In addition, when used for high speed traveling at 290 km / h or higher, the effect of improving durability can be obtained more remarkably.

  The present invention is an invention of a pneumatic tire characterized by the internal structure of the bead portion, and since any other tire structure and tread pattern of the tread portion 3 do not require modification, any one can be used.

  Next, in order to further clarify the effects of the present invention, a comparative evaluation performed using pneumatic tires according to the following examples and comparative examples will be described.

(Example tire)
The tire shown in FIG. 1 was used as an example tire. The tire size was 265 / 50R19. The internal structure of the tire was as follows.
Bead filler: Hard rubber having a dynamic elastic modulus of 120 MPa. The height H _7a of the end portion 7a from the rim diameter line RL is located at 34% of the tire cross-sectional height from the rim diameter line.
First reinforcing layer 8: Steel cords as a first cord were arranged in parallel to each other, covered with soft rubber, and arranged such that the cord had an angle of 0 ° with respect to the tire radial direction. The heights H _8a and H _8b of the end portions 8a and 8b from the rim diameter line RL are located at 40% and 2% of the tire cross-section height from the rim diameter line, respectively.
Second reinforcing layer 9: As a second cord, Kevlar (registered trademark) fiber cords are arranged in parallel to each other, covered with the soft rubber, and arranged such that the cord has an angle of 45 ° with respect to the tire radial direction. . The height H _9a of the end portion 9a from the rim diameter line RL is located at 45% of the tire cross-section height from the rim diameter line, and the lower portion of the second reinforcing layer 9 is around the bead core from the outside in the tire width direction. The end 9b was extended to the lower periphery of the bead filler 7 by folding back inside.
Carcass 6: As a ply cord, rayon cords were radially arranged and covered with the above soft rubber to obtain an envelope structure carcass composed of one ply.
Third reinforcing layer 10: Hard rubber having a dynamic elastic modulus of 100 MPa. The heights H _10a and H _10b of the end portions 10a and 10b from the rim diameter line RL are located at 50% and 12% of the tire cross-sectional height from the rim diameter line, respectively.

Only the arrangement order of the first to third reinforcing layers or the presence / absence of the arrangement of the example tires was changed to obtain comparative example tires shown below.
(Comparative tire 1)
A tire similar to the example tire was designated as comparative example tire 1 except that the first to third reinforcing layers were not disposed.

(Comparative tire 2)
A tire similar to the example tire was used as the comparative example tire 2 except that the third reinforcing layer was not disposed.

(Comparative tire 3)
A tire similar to the example tire was used as the comparative example tire 3 except that the arrangement order of the first reinforcing layer and the second reinforcing layer was changed.

(Comparative tire 4)
A tire similar to the example tire was used as the comparative example tire 4 except that the arrangement order of the second reinforcing layer and the ply turn-up portion was changed.

(Comparative tire 5)
A tire similar to the example tire was used as the comparative tire 5 except that the arrangement order of the ply turn-up portion and the third reinforcing layer was changed.

<High speed durability>
After each tire is assembled on the rim and adjusted to an internal pressure of 290 kPa, the vehicle starts running at a speed of 220 km / h, and the speed is gradually increased by 10 km / h every 20 minutes to measure the speed when a failure occurs. Then, the failure occurrence speed of Comparative Example 1 was taken as 100 and indicated as an index. The larger the index value, the higher the endurance limit speed and the higher the durability at high speed. The results are shown in Table 1.

<Steering stability>
Each tire was attached to the vehicle, and the driving stability such as turning ability and lane changeability when running on the test course was evaluated by a professional driver. The evaluation results were displayed as an index with Comparative Example 1 as 100. The larger the index, the better the steering stability. The results are shown in Table 1.

  From Table 1, in Example, compared with Comparative Examples 1-5, it was able to make high-speed durability and steering stability compatible. Specifically, in Comparative Examples 3 to 5, where the arrangement order of the first to third reinforcing layers and the ply turn-up portion is not in the order of high rigidity from the side closer to the bead filler, a place where a high rigidity step occurs There is. For this reason, it is inferior to high-speed durability compared with an Example. Moreover, the comparative example 2 does not arrange | position the 3rd reinforcement layer, and is inferior to an Example in terms of steering stability.

  In the pneumatic tire of the present invention, by arranging the members having high rigidity in order from the one close to the bead filler made of hard rubber, the rigidity step between the members constituting the bead portion is minimized, and the bead portion is generated. Since separation can be suppressed, it has become possible to achieve both high-speed durability and handling stability, both of which have not been achieved before.

DESCRIPTION OF SYMBOLS 100 Pneumatic tire 1 Bead part 2 Side wall part 3 Tread part 4 Bead core 5 Ply 5a Ply main-body part 5b Ply return part 5c Ply return end 6 Carcass 6a Crown part of a carcass 7 Bead filler 8 1st reinforcement layer 9 2nd reinforcement layer 10 Third reinforcing layer 11 Cross belt (11a, 11b belt layer)
12 Cap layer

Claims (6)

A ply main body portion extending in a toroid between a pair of bead cores, and a ply folded portion extending from the ply main body portion and folded back from the inside in the tire width direction around each of the bead cores. A carcass having at least one ply made of rubber; and
A bead filler that tapers from the top of the bead core toward the outer side in the tire radial direction between the ply body and the ply turn-up portion;
Between the ply turn-up portion and at least the bead filler, the first reinforcing layer formed by rubber coating the first cord and the second cord, which are disposed in order from the inner side in the tire width direction, are coated with rubber. A second reinforcing layer;
A third reinforcing layer made of rubber disposed on the tire width direction outer side of the ply folded portion,
The first cord, the second cord, and the ply cord have a large tensile elastic modulus in this order,
The rubber constituting the third reinforcing layer has a smaller dynamic elastic modulus than the rubber constituting the bead filler,
The second reinforcing layer has a folded portion that is folded inward from the outer side in the tire width direction around the bead core, and a tire radial direction outer end portion on the outer side in the tire width direction is a tire radial direction on the inner side in the tire width direction. Located on the outside in the tire radial direction from the outer edge,
A tire radial direction outer end of the third reinforcing layer, a tire radial outer end of the second reinforcing layer on the outer side in the width direction of the second reinforcing layer, and an outer end of the first reinforcing layer in the tire radial direction when viewed in a cross section in the tire width direction. Part, and the tire radial direction outer end of the bead filler are located on the outer side in the tire radial direction in this order,
The pneumatic tire according to claim 1, wherein the first cord is a metal cord or an organic fiber cord, and the second cord and the ply cord are organic fiber cords.   The pneumatic tire according to claim 1, wherein the first cord is a metal cord. It is located on the outer peripheral side of the crown portion of the carcass, further comprising at least one belt layer formed by rubber-covering the cord,
3. The air according to claim 1, wherein at least one of the plies constituting the carcass has a structure in which a folded end of a ply folded portion is located between the belt layer and a crown portion of the carcass. Enter tire.   The pneumatic tire according to any one of claims 1 to 3, wherein the carcass is constituted by a single ply.   The pneumatic tire according to any one of claims 2 to 4, wherein the first cord is a steel cord, the second cord is an aromatic polyamide fiber cord, and the ply cord is a rayon cord.   6. The angle according to claim 1, wherein an angle of the first reinforcing layer with respect to a tire radial direction of the first cord is smaller than an angle of the second reinforcing layer with respect to a tire radial direction of the second cord. Pneumatic tire.