JP2018016093A - Pneumatic tire and manufacturing method for pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make concavities on a surface of a tire caused due to an overlapping part of a carcass ply layer inconspicuous, without impairing uniformity in weight of the tire in a tire circumferential direction.SOLUTION: In a tire, a carcass ply layer includes a plurality of sheet materials arranged in a tire circumferential direction to contact each other, and has an overlapping part at which end parts in the tire circumferential direction of two sheet materials arranged to contact each other are arranged in a thickness direction to overlap each other. In the overlapping part, a cord of at least one of the two sheet materials, or a first sheet material, is positioned at a side at which the material is separated from the other of the two sheet materials, or a second sheet material, with respect to a center in the thickness direction of the first sheet material. A distance in the thickness direction between a position at which the cord of the first sheet material is arranged and a position at which the cord of the second sheet material is arranged is longer than a half of the total of the thickness of the first sheet material and the thickness of the second sheet material.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire and a method for manufacturing a pneumatic tire.

  A tire generally includes a carcass ply layer as a structure. The carcass ply layer is composed of a sheet-like ply material having a plurality of cords that are aligned with each other and a coat rubber that covers the cords, and extends from the tire center line to the outside in the tire width direction in a cross section in the tire radial direction. The tire is folded from the inner side to the outer side in the tire width direction around the bead core from the tread portion through the sidewall portion. In the tire manufacturing process, the carcass ply layer is formed by winding a sheet-like ply material around a molding drum and bonding the ends of the ply material along the circumference of the molding drum, for example. The ends of the bonded ply materials form overlapping portions that are overlapped with each other in the thickness direction of the ply material.

  Since the cord included in the end portion of the ply material is disposed so as to overlap in the thickness direction in the overlapping portion, the tensile rigidity is higher than that of the portion of the carcass ply layer other than the overlapping portion. For this reason, when the tire is assembled to the rim and internal pressure is applied, the extension amount of the cord at the overlap portion is smaller than the extension amount of the cord portion of the carcass ply layer other than the overlap portion, and the tire surface corresponding to the overlap portion In the region in the tire circumferential direction, a portion where the tire surface is recessed (hereinafter referred to as a recess) is likely to appear. The concave portion is not a problem in the safety of the vehicle, but tends to give a viewer an impression as if it is a defective portion. In particular, the concave portion is easily noticeable when, for example, the thickness of the sidewall portion is reduced in order to reduce the cost of the rubber material of the tire.

  In conventional tires, the intermediate rubber sheet is interposed between the joints of the end portions of the rubberized sheet and between the ends of the rubberized sheet and inside the end portions of the other rubberized sheet. A joining structure of tire shoulder portions joined together is known (Patent Document 1). In this joining structure, the carcass materials are not in contact with each other at the end portion of the joining portion, and since the deformation region of the intermediate rubber sheet layer is large, the concave portion generated at the joining portion of the tire shoulder portion can be improved.

Japanese Patent Laid-Open No. 10-6414

  In the technique of Patent Document 1, by providing an intermediate rubber sheet in addition to the rubberized sheet in the overlapping portion, local changes in shape and rigidity in the tire circumferential direction become large. For this reason, the uniformity at the time of rolling of the tire is deteriorated, and the vibration generated with the rolling of the tire is likely to increase. Moreover, in the technique of patent document 1, since the weight balance in a tire circumferential direction becomes non-uniform | heterogenous by providing an intermediate | middle rubber sheet in an overlap part, it tends to have a bad influence also on the uniformity in a stationary state.

  Accordingly, the present invention provides a pneumatic tire and a pneumatic tire that can make the recesses on the tire surface generated due to the overlapping portions of the carcass ply layers inconspicuous without impairing the uniformity of the tire weight in the tire circumferential direction. It aims at providing the manufacturing method of.

One aspect of the present invention is a pneumatic tire including a carcass ply layer that is folded from the inner side to the outer side in the tire width direction around the bead core from the tread portion through the sidewall portion.
The pneumatic tire is
The carcass ply layer is a plurality of sheet materials having a plurality of cords aligned with each other and a coat rubber covering the cords, and includes a plurality of sheet materials arranged in contact with each other in the tire circumferential direction. ,
The carcass ply layer has an overlapping portion in which two end portions in the tire circumferential direction of the sheet material arranged in contact with each other overlap each other in the thickness direction,
In the overlapping portion, the cord of at least one first sheet material of the two sheet materials is the other of the two sheet materials with respect to the center in the thickness direction of the first sheet material. Located on the side away from the second sheet material,
Thickness of the arrangement position of the cord of the first sheet material in the thickness direction of the first sheet material and the arrangement position of the cord of the second sheet material in the thickness direction of the second sheet material The distance in the direction is longer than half of the total thickness of the first sheet material and the second sheet material.

  In the overlapping portion, it is preferable that the cord of the second sheet material is located on the side away from the first sheet with respect to the center in the thickness direction of the second sheet material.

  It is preferable that the arrangement position of the cord in the thickness direction of the sheet material is located in a region of 10% to 40% of the thickness of the sheet material from the center in the thickness direction of the sheet material.

  The pneumatic tire is suitable when the folded end of the carcass ply layer is disposed at a position of 5% to 40% of the height of the pneumatic tire from the bead core.

  The pneumatic tire is suitable when the cord is made of an organic fiber material.

  The pneumatic tire is suitable for a small truck tire having a maximum air pressure specified by JATMA of 350 kPa to 600 kPa.

  In the pneumatic tire, the first sheet material and the second sheet material have the same thickness, and the arrangement position of the cord of the first sheet material and the center in the thickness direction of the first sheet material And the distance between the arrangement position of the cord of the second sheet material and the center in the thickness direction of the second sheet material are suitable.

Another aspect of the present invention is a method for manufacturing a pneumatic tire.
The method for manufacturing the pneumatic tire includes a step of arranging a plurality of sheet materials in contact with each other in the tire circumferential direction,
A step of overlapping the end portions in the tire circumferential direction of the two sheet materials in contact with each other in the thickness direction of the sheet material,
The sheet material has a plurality of cords that are aligned with each other, and a coat rubber that covers the cords,
In the arranging step, in the overlapping portion, the cord of at least one of the two sheet materials is the first sheet material with respect to the center in the thickness direction of the first sheet material. Arranging the first sheet material and the second sheet material so as to be located on the side away from the second sheet material arranged in contact with the sheet material;
In the overlapping portion, the arrangement position of the cord of the first sheet material in the thickness direction of the first sheet material, and the arrangement of the cord of the second sheet material in the thickness direction of the second sheet material The distance in the thickness direction with respect to the position is longer than half the total of the thickness of the first sheet material and the thickness of the second sheet material.

  According to the present invention, it is possible to make the concave portion of the tire surface generated due to the overlapping portion of the carcass ply layer inconspicuous without impairing the uniformity of the tire weight in the tire circumferential direction.

It is a tire sectional view showing a section of a part of a pneumatic tire. It is sectional drawing which shows the overlap part of a carcass ply layer. It is sectional drawing which shows the overlap part of the carcass ply layer which concerns on a modification. It is a figure explaining the step which arrange | positions the manufacturing method of a pneumatic tire.

Hereinafter, the pneumatic tire of this invention and the manufacturing method of a pneumatic tire are demonstrated in detail.
(Whole tire description)
Hereinafter, the pneumatic tire of this embodiment will be described. FIG. 1 is a tire cross-sectional view showing a partial cross section of a pneumatic tire (hereinafter referred to as a tire) 1 of the present embodiment.
The tire 1 is, for example, a light truck tire. A light truck tire is a tire defined in Chapter B of JATMA YEAR BOOK 2012 (Japan Automobile Tire Association Standard). In addition, the tire 1 can be applied to a passenger car tire defined in Chapter A and a truck and bus tire defined in Chapter C.

  The tire circumferential direction described below refers to the direction of rotation of the tread surface (both rotational directions) when the tire 1 is rotated about the tire rotation axis, and the tire radial direction refers to the tire rotation axis. A radial direction extending perpendicularly. The outer side in the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction, and the inner side in the tire radial direction refers to the side closer to the tire radial direction toward the tire rotation axis. The tire width direction means a direction parallel to the tire rotation axis direction, and the tire width direction outer side means both sides of the tire 1 away from the tire center line. The tire inner side refers to the side approaching the tire cavity region inside the inner liner (described later), and the tire outer side refers to the side away from the tire cavity region.

  As shown in FIG. 1, the tire 1 has a bead core 7, a carcass ply layer 5, and a belt layer 6 as a skeleton material, and a tread portion 2, a sidewall portion around these skeleton materials. 3 and mainly have a bead filler, a rim cushion rubber, and an inner liner.

The bead core 7 has an annular shape, and is disposed at the inner end in the tire radial direction at each of both ends in the tire width direction. The bead part 4 including the bead core 7 is disposed on both sides in the tire width direction so as to sandwich the tread part 2 and forms a pair.
The carcass ply layer 5 is wound between a pair of bead cores 7 so as to form a toroidal shape, and is folded from the inner side to the outer side in the tire width direction around the bead core 7 from the tread part 2 through the sidewall part 3. The carcass ply layer 5 will be described in detail later.
Two belt layers 6 are provided in the tire 1 in the illustrated example. All the belt layers 6 are wound in the tire circumferential direction on the outer side in the tire radial direction of the carcass ply layer 5. Each of the belt layers 6 is a member in which a steel cord is covered with rubber. The steel cord of the belt layer 6 is disposed at a predetermined angle, for example, 20 to 30 degrees with respect to the tire circumferential direction. The steel cords of the two belt layers 6 are inclined in directions opposite to each other with respect to the tire circumferential direction and cross each other. The belt layer 6 suppresses the expansion of the carcass ply layer 5 due to the filled air pressure.

A tread portion 2 is provided on the outer side of the belt layer 6 in the tire radial direction. The tread portion 2 is provided with a circumferential groove and a lug groove. Sidewall portions 3 are connected to both ends of the tread portion 2 in the tire width direction. The sidewall portions 3 are arranged so as to sandwich the tread portion 2 to form a pair. On the outer surface in the tire width direction of the sidewall portion 3, an area for displaying information such as the tire rotation direction, size, model number, mark, and country of manufacture is provided.
The tire 1 may further include a belt cover layer (not shown) that covers the outer surface of the belt layer 6 in the tire radial direction. The belt cover layer is made of organic fibers and rubber that covers the organic fibers.

(Carcass ply layer)
FIG. 2 is a cross-sectional view showing a part of the carcass ply layer 5.
The carcass ply layer 5 is composed of a plurality of sheet materials. The number of sheet materials constituting the carcass ply layer 5 may be two, or may be three or four or more. In the following description, the case where the carcass ply layer 5 is composed of two sheet materials of the sheet material 10 (first sheet material) and the sheet material 20 (second sheet material) will be described as an example.

  The sheet materials 10 and 20 are disposed in contact with each other in the tire circumferential direction. Each of the sheet materials 10 and 20 includes a plurality of cords 11 and 21 that are aligned with each other, and coat rubbers 13 and 23 that cover the cords 11 and 21. The cords 11 and 21 extend linearly and are arranged substantially parallel to each other, and the extending direction is inclined by 75 to 90 degrees with respect to the tire circumferential direction. The cords 11 and 21 are made of an organic fiber material or steel. The cord made of an organic fiber material is made of, for example, polyester, nylon, rayon, aromatic polyamide or the like, and a plurality of filaments made of any of these materials are twisted together. The cord made of steel is obtained, for example, by twisting a single steel wire. The cross sections of the cords 11 and 21 are substantially circular in the example shown in FIG.

  The thickness of the sheet material 10 and the sheet material 20 is constant in the tire circumferential direction. Further, each of the sheet material 10 and the sheet material 20 does not have a boundary (interface) in which a plurality of sheet-like members are stacked. The thicknesses of the sheet materials 10 and 20 are preferably 0.5 mm or more and 2 mm or less, respectively. Moreover, it is preferable that the diameter (maximum diameter) of the cords 11 and 21 is 0.1 mm or more and 1 mm or less, respectively. The spacing (space) between two adjacent cords 11 or cords 21 is preferably 0.5 mm or more and 2 mm or less, respectively.

In the present embodiment, the carcass ply layer 5 has an overlapping portion 5A and an overlapping portion 5B (see FIG. 4) at positions separated from each other in the tire circumferential direction. Hereinafter, the overlapping portion 5A will be mainly described as a representative. The overlapping portion 5A has an end portion 10a on one side in the tire circumferential direction of the sheet material 10 and an end portion 20a on the other side in the tire circumferential direction of the sheet material 20 in the thickness direction of the sheet materials 10 and 20. It is the part which is arranged overlapping. The end portion 10 a of the sheet material 10 is disposed on the tire outer side of the end portion 20 a of the sheet material 20. In the example shown in FIG. 2, the cord 11 of the sheet material 10 among the sheet materials 10 and 20 is located on the side away from the sheet material 20 with respect to the center in the thickness direction of the sheet material 10. That is, the sheet material 10 is unevenly thickened. On the other hand, the cord 21 of the sheet material 20 is located at the center in the thickness direction of the sheet material 20. That is, the sheet material 20 is not unevenly thickened. Further, the distance (inter-cord distance) d between the arrangement position of the cord 11 in the thickness direction of the sheet material 10 and the arrangement position of the cord 21 in the thickness direction of the sheet material 20 is the thickness of the sheet material 10. The length is longer than half of the total t1 + t2 of the thickness t1 and the thickness t2 of the sheet material 20. That is, the relationship represented by the following formula is satisfied.
d> (t1 + t2) / 2
The arrangement positions of the cords 11 and 21 are the thickness direction positions of the sheet materials 10 and 20 where the central axes of the cords 11 and 21 are located.

  When the tire 1 is assembled to the rim and internal pressure is applied, the bulging of the overlapping portion 5A to the outside of the tire is suppressed compared to the portion of the carcass ply layer 5 other than the overlapping portion 5A. May occur. In the tire 1 of the present embodiment, the sheet material 10 is unevenly thickened, so that the distance between the cords 11 and 21 is larger than that in the case where the sheet material is not unevenly thickened and is disposed between the cords 11 and 21. There is a large amount of coat rubber. For this reason, the tensile stiffness of the carcass ply layer 5 in the overlapping portion 5A is smaller than that in the case where the sheet material is not unevenly thickened, and the difference in tensile stiffness with the portion of the carcass ply layer 5 other than the overlapping portion 5A is reduced. Yes. The tensile rigidity is the tensile rigidity in the direction in which the cords 11 and 21 extend. As a result, the depth of the concave portion generated on the tire surface is reduced, and as a result, the concave portion is less conspicuous.

  In the present embodiment, the arrangement position of the cord 11 in the thickness direction of the sheet material 10 is located in the region of 10% to 40% of the thickness t1 of the sheet material 10 from the center in the thickness direction of the sheet material 10. Preferably it is. If it is located in an area of less than 10%, the amount of the coat rubber between the cords 11 and 21 is not sufficient as compared with the case where the thickness of the sheet material 10 is not uneven, and the effect of making the recesses inconspicuous is reduced. Moreover, if it is located in a region exceeding 40%, the carcass ply layer 5 is repeatedly deformed as the tire 1 rotates, whereby the cord 11 is peeled off from the coat rubber 13 and the durability of the carcass ply layer 5 is deteriorated. There is a case. The arrangement position of the cord 11 is more preferably a region of 15% or more and 30% or less of the thickness t1 of the sheet material 10.

In the tire 1 of the present embodiment, the folded end 5a (see FIG. 1) of the carcass ply layer 5 is disposed at a position of 5% to 40% of the height H (see FIG. 1) of the tire 1 from the bead core 7. It is suitable when it is. That is, it is preferable to satisfy the relationship represented by the following formula.
0.05H <h <0.4H
In the formula, h represents the height from the bead core 7 to the end 5 a of the carcass ply layer 5 along the height 1 direction of the tire 1.
In a region in the tire height direction higher than the height position (turn-up position) of the folded end 5a of the carcass ply layer 5, an effect of suppressing the overlapping portion 5A from expanding to the outside of the tire when internal pressure is applied. Is smaller than the area in the tire height direction below the height of the turn-up position. For this reason, the concave portion generated due to the overlapping portion 5A is likely to have a deeper depth in a region in the tire height direction higher than the turn-up position. In particular, the tire 1 that satisfies the relationship of the above formula has such a problem because the turn-up position is low. In the tire 1 of the present embodiment, since the sheet material 10 of the carcass ply layer 5 is unevenly thickened, the concave portion can be made inconspicuous as described above even when the turn-up position is low.

  In the tire 1 of the present embodiment, in the overlapping portion 5A, contrary to the example shown in FIG. 2, the sheet material 10 is not unevenly thickened, and the sheet material 20 may be unevenly thickened. That is, the cord 11 of the sheet material 10 is located at the center of the sheet material 10 in the thickness direction, and the cord 21 of the sheet material 20 is away from the sheet material 10 with respect to the center of the sheet material 20 in the thickness direction. May be located. In this aspect, because the sheet material 10 located outside the tire is not uneven, the distance between the cord 11 of the sheet material 10 and the surface of the sidewall portion 3 is long, and accordingly, the amount of rubber can be secured. The concave portion of the tire surface that is generated when the internal pressure is applied becomes more inconspicuous.

  In the tire 1 of the present embodiment, as shown in FIG. 3, it is preferable that both the sheet material 10 and the sheet material 20 are unevenly formed in the overlapping portion 5 </ b> A. That is, the cord 11 of the sheet material 10 is located on the side away from the sheet material 20 with respect to the center of the sheet material 10 in the thickness direction, and the cord 21 of the sheet material 20 is centered in the thickness direction of the sheet material 20 However, it is preferable to be located on the side away from the sheet material 10. FIG. 3 is a cross-sectional view showing an overlapping portion 5A of the carcass ply layer 5 according to a modification. In this aspect, since the inter-cord distance d is large and the amount of coat rubber between the cords 11 and 21 is large, the tensile rigidity of the carcass ply layer 5 in the overlapping portion 5A is tensile with the portion of the carcass ply layer 5 other than the overlapping portion 5A. The difference in stiffness is even smaller. For this reason, the recessed part of the tire surface which generate | occur | produces when an internal pressure is added becomes more inconspicuous. In the modification shown in FIG. 3, the arrangement position of the cord 21 in the thickness direction of the sheet material 20 is in the region of 10% to 40% of the thickness t2 of the sheet material 20 from the center in the thickness direction of the sheet material 20. Preferably it is located. Further, the distance between the center in the thickness direction of the sheet material 20 and the arrangement position of the cord 21 is the same as the distance between the center in the thickness direction of the sheet material 10 and the arrangement position of the cord 11. Also good.

  The carcass ply layer 5 shown in FIG. 3 may be manufactured using sheet materials having different sheet structures as the sheet materials 10 and 20, or may be manufactured using sheet materials having the same sheet structure. In the carcass ply layer 5 manufactured using the sheet material having the same sheet structure, specifically, the sheet material 10 and the sheet material 20 have the same thickness, and the arrangement position of the cord 11 of the sheet material 10 in the overlapping portion 5A. And the distance between the center of the sheet material 10 in the thickness direction and the distance between the arrangement position of the cord 21 of the sheet material 20 and the center of the sheet material 20 in the thickness direction are equal. When the sheet material having the same sheet structure is used, the material cost of the carcass ply layer 5 can be reduced. Furthermore, when the sheet material is manufactured using the same sheet structure, the lengths of the sheet material in the tire circumferential direction may be different from or equal to each other. When manufactured using sheet materials having the same length in the tire circumferential direction, the overlapping portions 5A and 5B can be arranged at equal intervals in the tire circumferential direction, so that the uniformity of the tire weight in the tire circumferential direction can be improved. .

  In the tire 1 of the present embodiment, as described above, the sheet material 10 is unevenly thickened, and the amount of coat rubber between the cords 11 and 21 is increased, so that the tensile rigidity of the carcass ply layer 5 in the overlapping portion 5A. The difference in tensile rigidity of the portion of the carcass ply layer 5 other than the overlapping portion 5A is small. For this reason, when the tire 1 is assembled to the rim and an internal pressure is applied, the recess depth of the recess on the tire surface caused by the overlapping portion 5A becomes small, and the recess can be made inconspicuous. In the tire 1 of the present embodiment, the sheet material 10 and the sheet material 20 are in contact with each other in the overlapping portion 5 </ b> A, and no other rubber sheet is interposed between the sheet material 10 and the sheet material 20. For this reason, changes in the local shape and rigidity in the tire circumferential direction are suppressed, deterioration of uniformity at the time of tire rolling is suppressed, and an increase in vibration generated due to tire rolling is suppressed. The Further, since no other rubber sheet is interposed between the sheet material 10 and the sheet material 20, it is possible to suppress uneven weight balance in the tire circumferential direction, and to adversely affect uniformity in a stationary state. It is suppressed.

  In the present embodiment, it is preferable that both the sheet material 10 and the sheet material 20 are unevenly thickened. In this aspect, since the inter-cord distance d is large and the amount of coat rubber between the cords 11 and 21 is large, the tensile rigidity of the carcass ply layer 5 in the overlapping portion 5A is tensile with the portion of the carcass ply layer 5 other than the overlapping portion 5A. The difference in stiffness is even smaller. For this reason, the recessed part of the tire surface which generate | occur | produces when an internal pressure is added becomes more inconspicuous.

  In the present embodiment, the arrangement position of the cord 11 in the thickness direction of the sheet material 10 is located in the region of 10% to 40% of the thickness t1 of the sheet material 10 from the center in the thickness direction of the sheet material 10. Therefore, the amount of the coated rubber between the cords 11 and 21 is sufficiently secured to increase the effect of making the concave portion inconspicuous, and the carcass ply layer 5 is repeatedly deformed as the tire 1 rotates. This is preferable in that deterioration of durability of the layer 5 can be suppressed.

  In the tire 1 of the present embodiment, since the sheet material 10 of the carcass ply layer 5 is unevenly thickened, even when the turn-up position satisfies the relationship of the above formula and is low, the concave portion is not easily noticeable. Can do.

  When the cord of the sheet material is made of an organic fiber material, the effect of suppressing the bulge of the overlapping portion to the outside of the tire when the internal pressure is applied is small compared to the case where the cord is made of steel. Cheap. In the tire 1 of the present embodiment, as described above, the sheet material 10 is unevenly thickened, and the amount of coat rubber between the cords 11 and 21 is increased, so that the concave portion is not easily noticeable. For this reason, the tire 1 of this embodiment is suitable when the cords 11 and 21 are made of an organic fiber material.

  Small truck tires having a maximum air pressure of 350 kPa to 600 kPa as defined by JATMA are more susceptible to large loads than those of passenger car tires, and concavities generated due to overlapping portions are easily noticeable. As described above, the tire 1 of the present embodiment is suitable when the above-described small truck tire is an application target because the concave portion due to the overlapping portion is less noticeable.

  The sheet material 10 and the sheet material 20 are equal in thickness, and the distance between the arrangement position of the cord 11 of the sheet material 10 and the center of the sheet material 10 in the thickness direction, the arrangement position of the cord 21 of the sheet material 20 and the sheet The carcass ply layer 5 having the same distance from the center in the thickness direction of the material 20 can be manufactured using the same sheet material. Thereby, the material cost of the carcass ply layer 5 can be reduced.

Next, the manufacturing method of the tire of this embodiment is demonstrated.
Here, the case where the tire 1 described above is manufactured will be described as an example. Further, the case where the sheet material 10 is unevenly thickened and the sheet material 20 is not unevenly thickened will be described as an example.
The tire manufacturing method includes a step of arranging the sheet material 10 and the sheet material 20 so as to contact each other in the tire circumferential direction (arranging step), and end portions 10a and 20a in the tire circumferential direction of the sheet materials 10 and 20 contacting each other. And overlapping each other in the thickness direction of the sheet materials 10 and 20 to form overlapping portions 5A and 5B (forming step). In the placing step, as shown in FIG. 4, the cord 11 of the sheet material 10 is positioned on the side away from the sheet material 20 with respect to the center in the thickness direction of the sheet material 10 in the overlapping portions 5A and 5B. Thus, the sheet material 10 and the sheet material 20 are arranged.

The arranging step and the forming step are performed using a forming drum 30 (see FIG. 4). FIG. 4 is a diagram illustrating the steps of arranging the tire manufacturing method.
Prior to the arranging step and the forming step, an inner liner is wound once around the surface of the forming drum 30 in advance, and ends in the circumferential direction are joined to each other. In FIG. 4, the illustration of the inner liner is omitted.
The placing step and the forming step are performed in parallel. Specifically, these steps are performed by first winding the sheet material 20 around a predetermined circumferential region of the forming drum 30 around which the inner liner is wound, and then the circumferential end 10a of the sheet material 10; The sheet material 10 is wound around an area on the periphery of the forming drum 30 around which the sheet material 20 is not wound so that the sheet material 20 is overlapped with the circumferential ends 20a and 20b of the sheet material 20 from the outside in the radial direction. In the example shown in FIG. 4, the sheet material 10 and the sheet material 20 have the same length along the circumference of the forming drum 30. For this reason, the overlapping portions 5 </ b> A and 5 </ b> B are formed so as to be positioned on a straight line passing through the rotation center of the forming drum 30.

  The rubber sheets to be the sheet materials 10 and 20 are prepared in advance by supplying unvulcanized rubber from both sides of a plurality of cords aligned with each other and covering the cord with unvulcanized rubber, for example. The The rubber sheet to be the sheet material 10 is configured such that the amount of unvulcanized rubber supplied from one side of the plurality of cords (for example, above the plurality of cords aligned in the horizontal direction) is supplied to the other side (for example, horizontal It is produced by making it different from the supply amount of the unvulcanized rubber from below the plurality of cords aligned in the direction. The supply amount of the unvulcanized rubber is adjusted by adjusting the flow rate of the unvulcanized rubber. On the other hand, the rubber sheet used as the sheet material 20 is produced by equalizing the amount of unvulcanized rubber supplied from both sides of a plurality of cords.

  A belt layer 6 is further formed on the carcass ply layer 5 formed in this way, and after tread rubber or the like is wound, the raw tire is vulcanized to become the tire 1. The cords 11 and 21 of the sheet materials 10 and 20 are chemically bonded to the coat rubbers 13 and 23 by vulcanization. The circumferential ends 20a, 20b of the sheet material 20 and the circumferential ends 10a, 10b of the sheet material 10 are chemically bonded to each other by vulcanization.

[Example]
In order to confirm the effects of the present invention, the tires of Examples 1 to 11 having the specifications shown in Table 1 and Table 2 below and the conventional tires were produced and used in a vehicle (a small truck with a maximum load of 2 t and a displacement of 2000 cc). The tire was mounted and filled with an air pressure of 350 kPa, and the difficulty of seeing the recesses on the tire surface was evaluated according to the following procedure. The tire size was 145R12 6PR. Except for the specifications shown in Tables 1 and 2 and the following specifications, the specifications of the manufactured tire are the same as those of FIG. 1 and the tire 1 described above.
The carcass ply layer was produced using two sheet materials having the same length in the tire circumferential direction. The thickness of each sheet material was 1 mm. The cord diameter was 0.5 mm in all cases, and the interval (space) between the cords was 1 mm in all cases. In the conventional example, the carcass ply layer was produced using two sheet materials that were not unevenly thickened.
The ratio of the height h from the bead core to the turn-up position with respect to the tire cross-section height H was 40%.

  In Tables 1 and 2, the “cord placement position” is the ratio (%) of the distance from the center in the thickness direction to the center of the cord in the thickness of each sheet material in each of the sheet materials 10 and 20. Represent. Further, regarding “cord material”, “PE” represents polyester. This cord is a cord formed by twisting 3 to 5 filaments made of polyester at a twist pitch of 5 mm. The steel cord is a cord formed by twisting a single steel wire at a twist pitch of 5 mm.

[Difficult to see recesses]
According to 10 panelists, it is difficult to see the recess when looking at the tire surface from the side of the tire in a three-bright indoor environment at a distance of 5 m in the direction along the tire rotation axis. Sensory evaluation was performed. The case where the concave portion was visually recognized was 10 points, and the case where the concave portion was not visually recognized was 0 points, and the total score of all panelists was calculated. The results are shown in Tables 1 and 2. When the evaluation score was 50 points or more, it was evaluated that the recess was difficult to see in the brightness.
The three types of brightness (1) to (3) were as follows.
(1) Brightness outdoors in the daytime in fine weather (2) Brightness outdoors in the daytime in cloudy weather (3) Brightness when illuminated with electric light in the garage The surface of the tire to be observed is on the tread surface Of the region (buttress region) extending from the ground contact end toward the sidewall portion and extending from 0 to 40% of the contact width, the tire side region extends from the tread end to the sidewall portion. . Note that the ground contact ends are both ends in the tire width direction of the ground contact surface when the tire 1 is assembled to a regular rim, filled with a regular internal pressure, and grounded on a horizontal plane under the condition that 88% of the regular load is a load load. The regular rim is a “measurement rim” defined in JATMA. The normal internal pressure is the “maximum air pressure” defined by JATMA. The normal load is the “maximum load capacity” defined in JATMA.

  When the conventional example and Examples 1 to 11 are compared, the cord of the sheet material 10 is located on the side away from the sheet material 20 with respect to the center of the sheet material 10 in the thickness direction, and the sheet material 10 and the sheet material 20 The distance between the cords is larger than half of the total thickness of the sheet materials 10 and 20, so that the concave portion generated on the tire surface due to the overlapping portion is at least the brightness of sunlight outdoors in the daytime in fine weather It turns out to be difficult to see under. Further, when Examples 2 to 4 are compared with Example 1, the cord arrangement position of the sheet material 10 is in the region of 10 to 40% in the thickness direction from the center of the sheet material 10 (Examples 2 to 4). Further, it can be seen that the concave portion is difficult to see.

  When Examples 1 to 5 and Examples 6 to 10 are compared, the cord of the sheet material 20 is located on the side away from the sheet material 10 with respect to the center in the thickness direction of the sheet material 20. It turns out that a recessed part becomes difficult to see. Further, when Examples 7 to 9 are compared with Example 6, the cord arrangement position of the sheet material 20 is in the region of 10 to 40% in the thickness direction from the center of the sheet material 20 (Examples 7 to 9). ), It can be seen that the concave portion is difficult to see. Further, when Example 8 is compared with Example 11, it can be seen that even when the cord is made of an organic fiber material (Example 8), it is possible to achieve a high level of difficulty in seeing the concave portion.

  As described above, the pneumatic tire and the manufacturing method of the pneumatic tire according to the present invention have been described in detail. However, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention. Of course.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 5 Carcass ply layer 5
5A, 5B Overlapping part 5a The folded end 7 of the carcass ply layer 7 Bead core 10 Sheet material (first sheet material)
10a, 10b End portion 20 of sheet material 10 Sheet material (second sheet material)
20a, 20b End portion 11, 21 of cord material 20, cord 13, 23 Coat rubber

Claims (8)

A pneumatic tire provided with a carcass ply layer that is folded from the inner side to the outer side in the tire width direction around the bead core from the tread part through the sidewall part,
The carcass ply layer is a plurality of sheet materials having a plurality of cords aligned with each other and a coat rubber covering the cords, and includes a plurality of sheet materials arranged in contact with each other in the tire circumferential direction. ,
The carcass ply layer has an overlapping portion in which two end portions in the tire circumferential direction of the sheet material arranged in contact with each other overlap each other in the thickness direction,
In the overlapping portion, the cord of at least one first sheet material of the two sheet materials is the other of the two sheet materials with respect to the center in the thickness direction of the first sheet material. Located on the side away from the second sheet material,
Thickness of the arrangement position of the cord of the first sheet material in the thickness direction of the first sheet material and the arrangement position of the cord of the second sheet material in the thickness direction of the second sheet material The pneumatic tire is characterized in that the distance in the direction is longer than half the total thickness of the first sheet material and the second sheet material.   2. The cord according to claim 1, wherein in the overlapping portion, the cord of the second sheet material is located on the side away from the first sheet with respect to the center in the thickness direction of the second sheet material. Pneumatic tire.   The arrangement position of the cord in the thickness direction of the sheet material is located in a region of 10% to 40% of the thickness of the sheet material from the center in the thickness direction of the sheet material. 2. The pneumatic tire according to 2.   The pneumatic end according to any one of claims 1 to 3, wherein the folded end of the carcass ply layer is disposed at a position of 5% to 40% of the height of the pneumatic tire from the bead core. tire.   The pneumatic tire according to any one of claims 1 to 4, wherein the cord is made of an organic fiber material.   The pneumatic tire according to any one of claims 1 to 5, wherein a tire for a small truck having a maximum air pressure defined by JATMA of 350 kPa to 600 kPa is applied.   The first sheet material and the second sheet material are equal in thickness, and the distance between the arrangement position of the cord of the first sheet material and the center in the thickness direction of the first sheet material, The pneumatic tire according to any one of claims 1 to 6, wherein a distance between the arrangement position of the cord of the second sheet material and the center in the thickness direction of the second sheet material is equal. Arranging a plurality of sheet materials so as to contact each other in the tire circumferential direction;
A step of overlapping the end portions in the tire circumferential direction of the two sheet materials in contact with each other in the thickness direction of the sheet material,
The sheet material has a plurality of cords that are aligned with each other, and a coat rubber that covers the cords,
In the arranging step, in the overlapping portion, the cord of at least one of the two sheet materials is the first sheet material with respect to the center in the thickness direction of the first sheet material. Arranging the first sheet material and the second sheet material so as to be located on the side away from the second sheet material arranged in contact with the sheet material;
In the overlapping portion, the arrangement position of the cord of the first sheet material in the thickness direction of the first sheet material, and the arrangement of the cord of the second sheet material in the thickness direction of the second sheet material A method of manufacturing a pneumatic tire, characterized in that the distance in the thickness direction from the position is longer than half the total thickness of the first sheet material and the second sheet material.

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