JP2007090972A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve riding comfort performance, while maintaining steering stability at the time of high speed traveling with a pneumatic tire. <P>SOLUTION: This pneumatic tire for a two wheeler is provided with a bead core, a carcass, a spiral belt layer provided by winding a spiral cord 50 in the tire peripheral direction at the tire radial direction outside of the carcass, and a tread. The spiral cord 50 is formed by winding one or a plurality of cords 52 on string rubber 54. The spiral cord 50 is capable of maintaining the steering stability to suppress expansion of the tread 28 in the tire radial direction at the time of high speed traveling, and absorbing impact and improving the riding comfort performance since the cord 50 softly and locally deforms according to ruggedness of a road surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire excellent in steering stability performance at high speed traveling, and more particularly to a pneumatic tire excellent in ride comfort performance.

  In a high-performance pneumatic tire, since the rotational speed of the tire becomes high, the influence of centrifugal force is large, and the tread portion of the tire expands outward, which may impair steering stability performance. For this reason, a tire structure has been developed in which an organic fiber or steel reinforcing member (spiral member) is wound around the tread portion of the tire so as to be substantially parallel to the tire equatorial plane. Nylon fiber, aromatic polyamide (Kevlar: trade name), steel, or the like is used as a reinforcing member wound in a spiral shape along the tire equator plane. Among them, aromatic polyamide and steel are attracting attention because they can suppress expansion of the tread portion without stretching even at high temperatures. When these members are wound around the crown portion of the tire, the so-called “tangle” effect (the tire's centrifugal force is applied even when the tire is rotated at a high speed by pressing the crown portion of the tire like a bathtub). Many patents characterized by disposing the spiral member on the crown of the tire have been filed. (For example, Patent Documents 1, 2, 3, 4, 5)

  It is known that a tire around which these spiral members are wound is excellent in handling stability performance at high speed running and has very high traction performance. However, when the effect of the tire is increased, the bending rigidity of the tread reinforcement is greatly increased, so that the riding comfort is generally deteriorated.

On the other hand, in order to solve the above-mentioned problems, many patents have been filed aiming to achieve both the steering stability performance and the ride comfort performance at the time of high speed traveling by combining the material of the spiral member. (For example, Patent Documents 6, 7, and 8)
JP 2004-067059 A JP 2004-067058 A JP 2003-011614 A JP 2002-316512 A JP 09-226319 A JP-A-10-278508 Japanese Patent Laid-Open No. 07-096710 JP 2002-019413 A

By the way, in order to secure the steering stability performance at the time of high-speed driving, it is necessary to suppress the deformation (expansion) of the tire to the outer side in the tire radial direction due to the centrifugal force with the spiral member having the “taiga” effect as described above. is there. This requires the overall rigidity of the spiral member (here, the rigidity for suppressing the spiral member from extending in the tire circumferential direction, that is, the circumferential rigidity of the spiral member).
On the other hand, in order to ensure riding comfort performance, it is necessary to mitigate or absorb the input of non-uniform and discontinuous force (impact) in the tire circumferential direction such as an uneven pattern on the road surface. When this force is input, bending deformation inward in the tire radial direction occurs in the region where the force of the spiral member is input. For this reason, by reducing the local rigidity of the spiral member (here, the bending rigidity of the spiral member), the input of this force can be relaxed or absorbed.
That is, in order to achieve both the steering stability performance and the ride comfort performance during high-speed traveling, it is necessary to reduce the local rigidity while maintaining the overall rigidity of the spiral member.

  An object of the present invention is to improve the riding comfort performance while maintaining the steering stability performance of the pneumatic tire during high-speed traveling in consideration of the above fact.

  A pneumatic tire according to claim 1 of the present invention includes a bead core embedded in a pair of left and right bead portions, a toroidal shape extending from one bead portion to the other bead portion, and an end portion wound around the bead core. It is formed of at least one carcass locked to the bead core, and a covering rubber that is disposed on the outer side in the tire radial direction of the carcass and covers one or more cords wound spirally. A pneumatic tire comprising at least one spiral belt layer and a tread portion disposed on the outer side in the tire radial direction of the spiral belt layer, wherein the cord includes one organic fiber strand and a plurality of strands. At least one of the organic fiber cords in which the organic fiber strands are twisted advances in a spiral shape, and rubber is disposed in the spiral central portion.

Next, the effect of the pneumatic tire according to claim 1 will be described.
In claim 1, the spiral belt layer includes at least one organic fiber cord formed by twisting one organic fiber strand and a plurality of organic fiber strands in a spiral shape, and a spiral center portion. One or a plurality of cords in which rubber is arranged are substantially spirally formed in the circumferential direction of the tire and formed by winding the entire tire. Here, although clearly stated, the cord of the present invention is an existing twisted cord (for example, at least one organic fiber cord obtained by twisting one organic fiber strand and a plurality of organic fiber strands). This is a fundamentally different invention. The existing twisted cord is formed by twisting the above-described organic fiber cord or the like around its own cord center, but the cord of the present invention is such that the above-described organic fiber cord or the like has a space in the center of the spiral. It is characterized by being formed by spiraling a vortex. Further, in order to clearly distinguish between the cord of the present invention and the existing twisted cord, the claims define that rubber is disposed at the center of the spiral shape. Hereinafter, the cord of the present invention is referred to as a spiral cord.

First, the feature of this spiral cord is that it is flexible against local deformation while maintaining the overall rigidity.
The existing twisted cord is wound around the crown portion of the tire in a state like a taut thread in order to suppress deformation (expansion) of the tire tread portion toward the outer side in the tire radial direction during high-speed running. For this reason, for example, a force (impact) that deforms the local part of the tire inward in the tire radial direction, such as vibration caused by unevenness on the road surface or vibration due to a pattern, that is, a force that locally deforms the twisted cord inward in the tire radial direction is input. In this case, since the twisted cord is tight, it has a high rigidity against this force. As a result, the flexibility of the tire is impaired and the riding comfort performance is deteriorated.

  However, since the spiral cord is formed by spirally vortexing, it has a feature that it is easily loosened in a direction perpendicular to the longitudinal direction of the spiral cord. Therefore, the spiral cord can be flexibly bent and deformed against the force that locally bends and deforms the spiral cord inward in the tire radial direction, and this force can be relaxed or absorbed. Further, the rubber disposed at the center of the spiral can be bent (elastically deformed) following the local deformation of the spiral cord. Therefore, the spiral cord of the present invention can improve riding comfort performance by relaxing or absorbing the input of force that causes local deformation.

  In addition, for the deformation that occurs overall, in this case, the deformation that extends the spiral cord in the tire circumferential direction, the spiral cord is spiral, so it tries to extend in the tire circumferential direction. In order to stretch the spiral, it is necessary to reduce the inner diameter of the spiral. However, since the deformation of reducing the inner diameter of the spiral of the spiral cord is restrained by the incompressibility of the rubber disposed at the center of the spiral shape, the extension of the spiral cord in the tire circumferential direction is suppressed. That is, the rigidity in the tire circumferential direction is maintained. Therefore, it is possible to maintain the steering stability performance by suppressing the deformation of the tire tread portion toward the outer side in the tire radial direction during high-speed traveling.

  From the above, when the spiral cord of the present invention is used, the ride comfort performance can be improved while maintaining the steering stability performance of the pneumatic tire during high speed running.

  A pneumatic tire according to a second aspect of the present invention is the pneumatic tire according to the first aspect, wherein the rubber has a circular cross section and the rubber has a diameter of 0.1 to 2.0 mm. And

Next, the effect of the pneumatic tire of Claim 2 is demonstrated.
If the diameter of the cross section obtained by cutting the rubber arranged at the center of the spiral shape of the spiral cord in a direction perpendicular to the longitudinal direction is less than 0.1 mm, this spiral cord has almost no difference from the existing twisted cord. Because there is no (ie, this spiral cord is almost taut), the effect of locally deforming and relaxing or absorbing the input of the force (impact) from the unevenness of the road surface described above is reduced. Less improvement in comfort performance. Further, if the diameter of the cross section of the rubber is larger than 2.0 mm, the bending rigidity of the rubber is increased. Therefore, the bending rigidity of the spiral cord itself is increased, and it is difficult to deform locally. The effect of relaxing or absorbing the input of force (impact) from the unevenness of the surface is reduced, and the improvement in riding comfort performance is reduced. Therefore, the diameter of the cross section of the rubber is preferably 0.1 to 2.0 mm.

  A pneumatic tire according to a third aspect of the present invention is the pneumatic tire according to the first or second aspect, wherein the pitch length of the cord satisfies 3.0 to 20.0 mm.

Next, the effect of the pneumatic tire according to claim 3 will be described.
If the pitch length of the spiral cord is less than 3.0 mm, even if there is rubber in the spiral central portion of the spiral cord, the spiral cord tends to extend in the tire circumferential direction, and the tire tread portion during high-speed running The effect of suppressing deformation (expansion) to the outer side in the tire radial direction is reduced. Further, if the pitch length is larger than 20.0 mm, there is almost no difference from the existing twisted cord (that is, this spiral cord is almost taut). The spiral cord is flexibly deformed and the effect of mitigating or absorbing the shock input is reduced, and the improvement in riding comfort performance is reduced. Accordingly, the pitch length of the spiral cord preferably satisfies 3.0 to 20.0 mm.

  A pneumatic tire according to a fourth aspect of the present invention is the pneumatic tire according to any one of the first to third aspects, wherein the organic fiber strand is made of an aromatic polyamide fiber.

Next, the effect of the pneumatic tire of Claim 4 is demonstrated.
Aromatic polyamide fiber has high strength and elastic modulus, and excellent heat resistance, so it suppresses deformation (expansion) of the tire tread in the tire radial direction without stretching even at high temperatures that occur in tires during high-speed running. it can. Therefore, the aromatic polyamide fiber is an optimal material for increasing the rigidity in the tire circumferential direction of the spiral belt layer, and the ride comfort performance can be effectively improved by adopting the configuration of the present application.

  The pneumatic tire according to a fifth aspect of the present invention is the pneumatic tire according to any one of the first to fourth aspects, wherein the cord is one organic fiber strand in a string-like unvulcanized rubber. And at least 1 or more of the organic fiber cord which twisted the multiple organic fiber strand was wound and formed, It is characterized by the above-mentioned.

Next, the effect of the pneumatic tire of Claim 5 is demonstrated.
According to a fifth aspect of the present invention, the spiral cord according to any one of the first to fourth aspects advances in the circumferential direction of the tire while spiraling in a spiral shape, and the entire tire is spirally wound to form a spiral belt layer. Form. In order to manufacture the spiral belt layer more easily, the claims define a method for manufacturing the spiral cord. A conventional spiral belt layer is manufactured by winding a belt-like ply in which one or more of the above-described twisted cords are covered with rubber substantially spirally around the tire circumferential direction. Here, as in the present claim, the spiral cord manufactured by wrapping the above-described organic fiber cord or the like around the string-like unvulcanized rubber is the same as the conventional spiral belt layer manufacturing method. A spiral belt layer is formed by spirally winding in the direction. When the spiral belt layer thus formed is vulcanized, the unvulcanized rubber in a string form is integrated with the surrounding covering rubber to form a pneumatic tire. Therefore, the spiral cord of the present invention does not require the operation of covering with a coated rubber unlike the conventional twisted cord, so that the manufacturing process of the pneumatic tire is shortened, thereby reducing the manufacturing time and the manufacturing equipment. Cost reduction, and manufacturing becomes easy.

  The pneumatic tire of the present invention can improve riding comfort performance while maintaining steering stability performance during high-speed traveling.

[First Embodiment]
Next, a first embodiment of the pneumatic tire of the present invention will be described with reference to FIG. In addition, the pneumatic tire of this embodiment is the pneumatic tire 10 for two-wheeled vehicles for the rear of a two-wheeled vehicle, and a tire size is 190 / 50ZR17.
As shown in FIG. 1, a pneumatic tire 10 for a motorcycle includes a first carcass ply 12 and a second carcass ply 14 in which a cord extending in a direction intersecting the tire equatorial plane CL is embedded. 16 is provided.

(Carcass)
Both ends of the first carcass ply 12 and the second carcass ply 14 are wound around the bead core 20 embedded in the bead portion 18 from the tire inner side toward the outer side.

  The first carcass ply 12 is formed by embedding a plurality of radially extending cords (for example, organic fiber cords such as nylon) in parallel in the covering rubber. In the present embodiment, the first carcass ply 12 has a tire equatorial plane CL. The angle of the cord with respect to the tire equatorial plane CL is set to 80 degrees. The second carcass ply 14 is also one in which a plurality of radially extending cords (for example, organic fiber cords such as nylon) are embedded in parallel in the covering rubber, and in this embodiment, the tire equatorial plane CL The angle of the cord with respect to the tire equatorial plane CL is set to 80 degrees. Further, the cord of the first carcass ply 12 and the cord of the second carcass ply 14 intersect each other and are inclined in opposite directions with respect to the tire equatorial plane CL. In the present embodiment, the first carcass ply 12 and the second carcass ply 14 are made of nylon.

(Spiral belt layer)
A spiral belt layer 22 is provided outside the carcass 16 in the tire radial direction. The spiral belt layer 22 is formed by spirally winding one or more spiral cords 50 around the carcass 16, and the direction of the spiral cord 50 is substantially the tire circumferential direction.
The spiral cord 50 is formed by spirally winding one or a plurality of cords 52 around a string rubber 54 which is a string-like rubber having a circular cross section cut in a direction perpendicular to the longitudinal direction. When the cord 52 is wound around the string rubber 54, the shape of the string rubber 54 may be deformed from a circle. In this embodiment, the string rubber 54 is circular. However, in other embodiments, it may be a circular shape, and in the case of a circular shape, the circular major axis is replaced with a diameter L described later. The configuration.
The cord 52 is composed of an organic fiber cord obtained by twisting one organic fiber strand 60 or a plurality of organic fiber strands 60.

  In addition, as shown in FIG. 2A, the spiral cord 50 of the present embodiment includes a cord 52 made of one organic fiber strand 60 (for example, an aramid fiber strand made of an aromatic polyamide fiber strand). Two pieces of cord rubber 54, which is the same material as the coating rubber used for a conventional general belt layer, is formed by spirally wrapping each half-phase phase.

Further, the string rubber 54 of the present embodiment is made of the same material as the coating rubber used for a conventional general belt layer, but in other embodiments, a different rubber may be used.
In addition, although the spiral cord 50 of this embodiment was set as the said structure, in other embodiment, as shown to FIG. 4 (A) and (B), the 1 thru | or plurality which consists of the one organic fiber strand 60 The cord 52 may be arranged around the string rubber 54. Also, as shown in FIGS. 4C and 4D, the cord 52 is made of an organic fiber cord in which a plurality of organic fiber strands 60 are twisted. One or a plurality of cords 52 may be arranged around the string rubber 54. 4 is a locus of the outer contour of the cord 52 when the cord 52 spirals.

Moreover, when the diameter of the string rubber 54 is L, the range of L preferably satisfies 0.1 to 2.0 mm. (See Fig. 3 (A))
Further, when the pitch length of the cord 52 is P, the range of P preferably satisfies 3.0 to 20.0 mm. (See Fig. 2 (A))
Moreover, it is preferable that the organic fiber strand 60 consists of an aromatic polyamide fiber.

(tread)
On the outer side of the spiral belt layer 22 in the tire radial direction, a tread rubber 30 forming a tread 28 is disposed in order.

As shown in FIG. 1, the belt layer of the present embodiment is only the spiral belt layer 22, but other belt layers may be added. (For example, a cross belt layer where the cords cross each other)
Although the groove is not formed in the tread 28 shown in FIG. 1, the groove | channel for drainage required at the time of wet road surface travel may be formed.
The pneumatic tire according to the present embodiment is a pneumatic tire for a motorcycle. However, in any other type of pneumatic tire such as a passenger car, a truck, and a bus, a conventional twisted cord or a spiral belt using a monofilament cord is used. Applicable to tires with layers.

(Function)
Since the spiral cord 50 is formed by spirally vortexing, the spiral cord 50 has a characteristic that it is easily loosened in a direction perpendicular to the longitudinal direction of the spiral cord 50. Therefore, the spiral cord 50 can be flexibly bent and deformed with respect to the force that locally bends and deforms the spiral cord 50 inward in the tire radial direction, and this force can be relaxed or absorbed. Further, the string rubber 54 disposed at the center of the spiral shape can be bent and deformed (elastically deformed) following the local deformation of the spiral cord 50. Therefore, the spiral cord 50 can relax or absorb an input of a force that causes local deformation to improve riding comfort performance.

  In addition, for the deformation that occurs as a whole, in this case, the deformation in which the spiral cord 50 is stretched in the tire circumferential direction, the spiral cord 50 has a spiral shape and therefore tends to stretch in the tire circumferential direction. In order to extend in the tire circumferential direction, it is necessary to reduce the inner diameter of the spiral. However, the deformation of the spiral cord 50 that reduces the inner diameter of the spiral is restrained by the incompressibility of the string rubber 54 disposed at the center of the spiral shape, so that the extension of the spiral cord 50 in the tire circumferential direction is suppressed. . That is, the rigidity in the tire circumferential direction is maintained. Therefore, it is possible to maintain the steering stability performance by suppressing the deformation of the tire tread portion toward the outer side in the tire radial direction during high-speed traveling.

  From the above, when the spiral cord 50 is used, the riding comfort performance can be improved while maintaining the steering stability performance when the pneumatic tire 10 is traveling at a high speed.

  Further, if the diameter L of the cross section obtained by cutting the string rubber 54 in the direction perpendicular to the longitudinal direction is less than 0.1 mm, the spiral cord 50 has almost no difference from the existing twisted cord (that is, this spiral). Since the cord 50 is almost taut), the effect of locally deforming and relaxing or absorbing the input of force (impact) from the road surface unevenness is reduced, and the improvement in riding comfort performance is reduced. Further, if the diameter L of the cross section of the string rubber 54 is larger than 2.0 mm, the bending rigidity of the string rubber 54 is increased. Therefore, the bending rigidity of the spiral cord 50 itself is increased, and it is difficult to deform locally. The effect of relaxing or absorbing the input of the force (impact) from the road surface unevenness described above is reduced, and the improvement in ride performance is reduced. Therefore, the diameter of the cross section of the string rubber 54 is preferably 0.1 to 2.0 mm.

  Further, if the pitch length P of the spiral cord 50 is less than 3.0 mm, even if the cord rubber 54 is disposed on the spiral cord 50, the spiral cord 50 is easily stretched in the tire circumferential direction, and at the time of high speed running. The effect of suppressing deformation (expansion) of the tread 28 to the outer side in the tire radial direction is reduced. Also, if the pitch length P is greater than 20.0 mm, there is almost no difference from the existing twisted cord (that is, the spiral cord 50 is almost taut), and therefore the force from the road surface unevenness ( The spiral cord 50 is flexibly deformed and the effect of mitigating or absorbing the input is reduced, and the improvement in ride comfort performance is reduced. Accordingly, the pitch length P of the spiral cord 50 preferably satisfies 3.0 to 20.0 mm.

  In addition, since the aromatic polyamide fiber has high strength and elastic modulus and is excellent in heat resistance, the tread 28 is not deformed (expanded) in the tire radial direction without being stretched even at a high temperature generated in the tire during high-speed running. Can be suppressed. Therefore, the aromatic polyamide fiber is an optimal material for increasing the rigidity in the tire circumferential direction of the spiral belt layer 22, and the ride comfort performance can be effectively improved with the configuration of the present application.

  Further, as shown in FIGS. 2A and 3A, a cord 52 is wound around an unvulcanized string rubber 54 to produce a spiral cord 50, and the spiral cord 50 is spiraled in the tire circumferential direction. The spiral belt layer 22 was formed by winding in a shape. When the spiral belt layer 22 thus formed is vulcanized, the string rubber 54 is integrated with the surrounding covering rubber to form the pneumatic tire 10 as shown in FIGS. 2 (B) and 3 (B). . From this, the spiral cord 50 does not require an operation of covering with a coated rubber unlike a conventional twisted cord, so that the manufacturing process of the pneumatic tire 10 is shortened, thereby reducing the manufacturing time and the manufacturing equipment. Costs are reduced and manufacturing becomes easy.

(Test Example 1)
In order to confirm the performance improvement effect of the pneumatic tire of the present invention, one type of pneumatic tire for a motorcycle according to an example according to the first embodiment and one type of pneumatic tire for a motorcycle according to a comparative example are prepared and an actual vehicle is used. The pilot performance comparison test was conducted. Since these pneumatic tires for motorcycles (hereinafter simply referred to as tires) were rear tires, only the rear tires were replaced, and actual vehicle tests were performed. The front tire was always fixed with a conventional tire. The evaluation method is as follows.

  In the test, the test tire was mounted on a 1000cc sports-type motorcycle, and the vehicle was driven on the test course. The steering stability when turning the vehicle (cornering performance), the ride performance when driving straight, and the steering stability The evaluation was centered on performance, and a comprehensive evaluation was performed using a 10-point method based on the feeling of the test rider. The test driver's evaluation comments are also included and the results are shown below.

(Comparative example)
Structure: The tire of the comparative example has a steel cord in which the spiral belt layer of the tire according to the first embodiment shown in FIG. 1 is formed by twisting two parallel steel single wires having a diameter of 0.21 mm in a 1 × 3 type. It is formed by winding a belt-like ply embedded in the covering rubber in a spiral shape in the tire rotation axis direction.
Riding comfort: 5 points Straight braking, traction performance: 7 points Steering steering stability performance: 4 points Overall steering stability performance overall points: 6 points Rider Comments: Riding comfort feels when tires are stiff and straight running Is not so good. Feels sensitive to road surface irregularities. The tire feels rigid during traction, and traction and braking are good. When turning, the tire has sufficient lateral rigidity but feels like slipping. However, this is an acceptable range.

(Example)
Structure: In the tire of the example, the spiral cord 50 of the tire according to the first embodiment shown in FIG. The cord 52 is a twisted cord having a diameter of 0.51 mm in which aramid fiber strands are twisted by 1 × 2 type, and the string rubber 54 is the same kind of rubber as the coating rubber of the spiral belt layer of the comparative example. The diameter L of the cross section cut in the perpendicular direction is 0.50 mm. The spiral cord 50 is formed by winding two cords 52 spirally around a string rubber 54 with a pitch length P of 20.0 mm and a half-cycle phase shifted from each other.
Ride comfort when going straight: 8 points Braking and traction performance when going straight: 8 points Steering stability performance when turning: 5 points Overall points of overall steering stability performance: 7 points Rider Comments: Ride comfort when traveling straight ahead is better than Comparative Example 1 Remarkably good. The thrust from the road surface is no longer felt, especially in the fine vibration region. The tire feels a little dull even during traction, but it feels like a high limit and a grip. When turning, the tires are equally stable against lateral deformation, and I think they have a grip. The tire feels softer than the comparative example.

(Verification of results)
Consider the results of the comparative example and the example. In the example, the rider has an impression that the tire is particularly soft, and feels that the tire absorbs the road surface unevenness and the ride comfort is improved. This is considered to be because the followability to local deformation by the spiral cord is improved. Along with this, the handling stability is also improved. This is thought to be due to the improved trackability on the road surface and improved ground contact as a tire and more grip.

It is sectional drawing along the rotating shaft of the pneumatic tire which concerns on 1st Embodiment. (A) It is the side view which looked at the spiral cord 50 before the vulcanization | cure of the pneumatic tire which concerns on 1st Embodiment from the direction orthogonal to a longitudinal direction. (B) It is the side view which looked at the spiral cord 50 after the vulcanization of the pneumatic tire which concerns on 1st Embodiment from the direction orthogonal to a longitudinal direction (string rubber 54 abbreviation). (A) It is sectional drawing which cut the spiral cord 50 before the vulcanization | cure of the pneumatic tire which concerns on 1st Embodiment in the orthogonal | vertical direction with respect to the longitudinal direction. (B) It is sectional drawing cut in the direction orthogonal to the longitudinal direction of the spiral cord 50 after the vulcanization of the pneumatic tire concerning a 1st embodiment. (A) It is sectional drawing which cut | disconnected the spiral cord 50 in which the cord 52 before the vulcanization | cure of the pneumatic tire which concerns on 1st Embodiment consists of the one organic fiber strand 60 in the orthogonal direction with the longitudinal direction. (B) It is sectional drawing which cut | disconnected the spiral cord 50 which consists of three organic fiber strands 60 of (A) in the direction orthogonal to a longitudinal direction. (C) The cord 52 before vulcanization of the pneumatic tire according to the first embodiment has a spiral cord 50 made of one organic fiber cord twisted by three organic fiber strands 60 and a direction perpendicular to the longitudinal direction. FIG. (D) It is sectional drawing which cut the spiral cord 50 which consists of three organic fiber cords of (C) in the direction orthogonal to the longitudinal direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 16 Carcass 18 Bead part 20 Bead core 22 Spiral belt layer 28 Tread 50 Spiral cord (cord)
52 Code 54 String rubber (string-like unvulcanized rubber)
60 Organic fiber

Claims (5)

A bead core embedded in a pair of left and right bead parts;
At least one carcass straddling in a toroid form from one bead portion to the other bead portion, and having an end portion wound around the bead core and locked to the bead core;
At least one spiral belt layer formed from a covering rubber that covers one or more cords that are disposed on the outer side in the tire radial direction of the carcass and wound spirally;
A tread portion disposed on the outer side in the tire radial direction of the spiral belt layer, and a pneumatic tire comprising:
In the cord, at least one of an organic fiber strand and an organic fiber cord obtained by twisting a plurality of organic fiber strands advances in a spiral shape, and rubber is disposed in the spiral central portion. A pneumatic tire characterized by   The pneumatic tire according to claim 1, wherein the rubber has a circular cross section, and the rubber has a diameter of 0.1 to 2.0 mm.   The pneumatic tire according to claim 1 or 2, wherein a pitch length of the cord satisfies 3.0 to 20.0 mm.   The pneumatic tire according to any one of claims 1 to 3, wherein the organic fiber strand is made of an aromatic polyamide fiber.   The cord is formed by spirally winding at least one organic fiber cord in which one organic fiber strand and a plurality of organic fiber strands are twisted around a string-like unvulcanized rubber. The pneumatic tire according to any one of claims 1 to 4, wherein:

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