JP4311719B2 - Pneumatic tire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly, to a pneumatic tire optimized for bead portion performance by improving a carcass ply cord, particularly a heavy-duty pneumatic tire. .
[0002]
[Prior art]
Generally, reinforcement cords having various twisted structures are used for pneumatic tires. For example, as a ply cord used for a carcass of a truck / bus radial tire (hereinafter also referred to as a “TBR tire”), various steel cords obtained by twisting strands of the same wire diameter have been used. As a technique related to the improvement of the cord, Patent Document 1 describes a technique in which the shape of the bead portion is stabilized by plastic deformation of the cord.
[0003]
[Patent Document 1]
US Pat. No. 6,530,401 specification
[Problems to be solved by the invention]
Usually, such a ply cord is formed at the same twist pitch over a pair of bead portions. Therefore, only the same performance can be obtained in all the parts in the tire cross-sectional direction, and the required performance for each part is not satisfied.
[0005]
In particular, since it is necessary to roll up the ply along the bead core at the bead portion, there is a problem that the rigidity of the conventional ply cord is too high and the bead portion shape becomes unstable. That is, the R of the lower base portion of the bead core at the time of winding is increased, the ply cord upper end position of the winding end is uneven, the end tends to jump up when the winding ply cord is returned, the member volume of the winding portion is increased, etc. There was a tendency that it was difficult to ensure the uniformity of the product in terms of both processability and product performance.
[0006]
On the other hand, the shape has been stabilized by combining the size and shape of the bead portion constituting member to ensure the winding shape of the bead core, but in this case, the required shape as the product itself is limited. There is a problem. In addition, since this method is not sufficient in terms of improving the workability, a technique capable of satisfying both the product performance and the workability has been demanded regarding the improvement of the bead portion.
[0007]
Accordingly, an object of the present invention is to eliminate the above-described problems in the bead portion caused by the high rigidity of the ply cord, stabilize the bead portion shape, and achieve both uniform product performance and good workability. The purpose is to provide tires.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventor changed the ply cord twist pitch in one cord using a specific device, and applied the optimum twist pitch in each part, The inventors have found that a pneumatic tire with improved product performance and processability can be realized, and have completed the present invention.
[0009]
That is, the pneumatic tire of the present invention is a carcass that is folded and locked from the inside to the outside of the tire around bead cores embedded in a pair of bead portions, a tread portion that is positioned on the outer periphery of the crown portion of the carcass, In a pneumatic tire comprising a sidewall portion located at a side portion of the carcass and at least one belt layer disposed inside the tread portion,
The ply cords of the carcass, the pitch P _b twisting the folded portion near the bead core is characterized in that is smaller than the twisting pitch P _CL on the tire equatorial plane.
[0010]
In the present invention, the vicinity of the folded portion of the bead core preferably corresponds to at least the apex of the ply cord that is located on the inner side in the tire axial direction and on the outermost side in the tire radial direction in the cross section in the tire axial direction. From the position of 5 mm on the outer side in the tire radial direction than the part to be performed, the region from the position corresponding to the apex located on the outermost side in the tire radial direction and outside in the tire axial direction is included. Moreover, the twisting pitch P _b can be in the 1 / 3-1 / 4 times the range of the twisting pitch P _CL.
[0011]
The pneumatic tire of the present invention is particularly suitable as a heavy-duty pneumatic radial tire such as a TBR tire.
[0012]
In the pneumatic tire of the present invention, by changing the twist pitch of the reinforcing cord of the carcass in the vicinity of the rolled-up portion (folded portion) of the bead portion, both the product performance required for the bead portion and the workability can be achieved. As a result, it is possible to obtain a pneumatic tire ensuring the optimum design.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the pneumatic tire of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a pneumatic radial tire according to an embodiment of the present invention includes a carcass 3 that is folded and locked from a tire inner side to an outer side around a bead core 2 embedded in a bead portion 1, and a carcass. 3, a tread portion 6 positioned at the crown portion, a sidewall portion 8 positioned at the side portion of the carcass 3, and a belt layer 4 disposed inside the tread portion 6. The carcass 3 is formed by arranging ply cords in a direction substantially perpendicular to the circumferential direction, and is constituted by a single carcass ply in the present embodiment. Moreover, the code | symbol 5 in a figure shows a bead filler.
[0014]
In the pneumatic tire of the present invention, the ply cords of the carcass 3, the pitch P _b twisting the folded portion near the bead core, is characterized in that is smaller than the pitch P _CL twist on the tire equatorial plane. That is, the number of twists in the vicinity of the folded portion of the bead core is increased more than on the tire equatorial plane. This reduces the rigidity of the carcass ply cord in the vicinity of the folded portion of the bead core to improve the bending workability, so that the ply along the bead core can be improved without causing problems as in the prior art. Can be easily rolled up, and the bead portion shape can be stabilized. In addition, since there is no restriction on the bead part constituent member, it is possible to improve the ability to respond to the required shape and required performance design for the product, and at the same time, it is possible to remove unnecessary extravagant parts in the bead part The balance between them can be improved. Furthermore, since manufacturing defects can be reduced, the product quality can be stabilized. Furthermore, since the accuracy of folding the ply cord to the bead core is improved, it is possible to reduce the variation in the ply end position in the folded portion, and to improve the ply end separation, which is the main failure of the bead portion, and to improve the durability. It is also possible to plan.
[0015]
In the present invention, the vicinity of the folded portion of the bead core that changes the twist pitch is preferably located at least on the inner side in the tire axial direction and on the outermost side in the tire radial direction of the bead core 2 in the cross section in the tire axial direction. From the position X of 5 mm on the outer side in the tire radial direction from the portion corresponding to the apex to the portion Y corresponding to the apex located on the outer side in the tire axial direction and on the outermost side in the tire radial direction. At least by the smaller than the pitch P _CL twist twisting pitch of the range on the tire equatorial plane, it is possible to reliably obtain the effect of the present invention to stabilize such a bead portion shape.
[0016]
Pitch P _b twisting the folded portion near the bead core, relative to the pitch P _CL twist on the tire equatorial plane, is made smaller than this, but reduced the stiffness can be obtained the desired effect of the present invention , Specifically, for example, it is within 1 / 3-1 / 4 times the range of the twisting pitch P _CL. By the pitch P _b twisting the folded portion near the bead core is within this range, to optimize the stiffness in the folded portion near the bead core ply cord, it is possible to obtain the effect of the present invention more appropriately.
[0017]
Incidentally, the twisting pitch of the ply cord has a pitch P _b twisting the folded portion at least near the bead core, as long as the pitch P _CL twist on the tire equatorial plane as the condition is satisfied, and how the other parts It may be set to and is not particularly limited. That is, the fluctuation region of the twist pitch may exist in any part of the cord, and the specific twist pitch of the part other than the above can be appropriately determined and is not particularly limited.
[0018]
In the present invention, as long as the twist angle of the outermost layer filament of the carcass satisfies the above-described conditions, the configuration of each part of the other tire, the material used, and the like are not particularly limited. For example, the carcass 3 cord is preferably a steel cord when used as a heavy-duty tire, but is not limited thereto, and may be a cord made of an organic fiber material, or a cord and an organic fiber are twisted together. A complex may also be used. In the illustrated embodiment, the belt layer 4 includes a single inclined belt layer 4A in which a plurality of steel cords extending obliquely with respect to the tire equatorial plane CL are arranged, and the belt layer 4 is positioned on the inclined belt layer 4A. The circumferential belt layer 4B in which a plurality of steel cords intersecting with the steel cords is arranged, but the number and configuration of the belt layers 4 are not particularly limited, and the use and type of the tire It may be determined appropriately according to.
[0019]
The means for changing the twisting pitch in one cord is not particularly limited, but a molding machine and a twisting wire machine that can change the twisting angle of the cord, which has been considered difficult so far. Has recently been developed, and the present applicant has previously filed a patent application for the twister (Japanese Patent Application No. 2002-341037). Therefore, this twister will be described in detail below.
[0020]
Such a twisting machine has a rotating body that twists a plurality of supplied wires to form a twisted wire, and unloading means for unloading the twisted wire from the rotating body, and the twisted wire side before and after the twisting point. Or it is the twist machine which has open | released either one of the wire side. Here, the term “open” means that one end of the twist point can be rotated in accordance with the twist rotation.
[0021]
Specifically, a twisting machine 22 of the type shown in FIG. 2 can be suitably used. FIG. 2 is a side view showing the configuration of the twisting machine 22 provided in the cord production line 10. The cord manufacturing line 10 includes a plurality of bobbins 14A to C each having a wire wound thereon, tension control units 16A to 16C for controlling the tension of the wires 18A to 18C wound from the bobbins 14A to C, A twisting machine 22 that twists the strands 18A to 18C via the tension control units 16A to 16C into the cord 20 is provided. The twisting machine 22 is a feed / rotation integrated device that twists the strands 18 </ b> A to 18 </ b> C to manufacture one cord 20.
[0022]
The twisting machine 22 includes a wrinkling part (molding part) 24 that attaches wrinkles (molds) to the strands 18A to 18C, a twisting point forming part 28 that forms a twisting point 26, and a downstream side of the twisting point forming part 28. And a motor 34 for applying a rotational force to the rotary body 30 and a feeding force for feeding the cord 20 from the rotary body 30. The rotating body 30 is rotatably held by bearing portions 36 </ b> A and B provided in the twisting machine 22.
[0023]
As shown in FIGS. 2 and 3, on the downstream side of the rotary body 30, a rotary drive pulley 42 is fixed to a rotary drive shaft portion 40 extending from the housing 31 of the rotary body 30 in a short cylindrical shape. An endless belt 46 is hung on the rotation driving pulley 42 and the first rotating plate 44 attached to the motor 34.
[0024]
An elongated cylindrical feed driving shaft member 50 that transmits the feeding force of the cord 20 is supported on the rotating body 30 by the insertion bearing portion 51 so that the rotating shafts coincide with each other. . A feed driving pulley 52 fixed to the feed driving shaft member 50 is provided downstream of the rotation driving pulley 42, and the second rotation attached to the feed driving pulley 52 and the motor 34. An endless belt 56 is hung on the plate 54.
[0025]
A feed mechanism 58 that feeds the cord 20 is provided in the housing 31. The feed mechanism 58 includes a first gear 60 that is fixed to the distal end side on the same axis as the feed drive shaft member 50, and a second gear 62 that meshes with the first gear 60. A small gear portion 64 having a small diameter is provided at the rotation center of the second gear 62. The feed mechanism 58 has a winding portion 66 around which the cord 20 is wound several times and a multistage winding capstan 68 having a large gear portion 67 that meshes with the small gear portion 64, and a multistage winding capstan 68 in contact with the cord. And a pinch roller 70 that presses 20 against the winding portion 66. Further, the feed mechanism 58 has a multi-stage winding dummy pulley 72 around which the cord 20 wound around the multi-stage winding capstan 68 is further wound several times.
[0026]
The diameters of the multistage winding capstan 68 and the multistage winding dummy pulley 72 are set such that the diameters, materials, etc. of the strands 18A to 18C are not disturbed in terms of straightness when using the cord 20 fed from the rotating body 30. It is decided in consideration.
[0027]
Further, the twisting machine 22 is provided with a cord discharge pipe guide 74 that guides the cord 20 unwound from the multistage winding dummy pulley 72 through the feed driving shaft member 50 to the downstream side of the rotating body 30. Yes.
[0028]
The diameter of the first rotating plate 44 is slightly larger than that of the second rotating plate 54, and the ratio between the rotating speed of the rotating body 30 (twisting speed of the stranded wire) and the feeding speed of the cord 20 is adjusted. .
[0029]
As described above, in this embodiment, the rotational drive shaft portion 40 and the feed drive shaft member 50 are coaxially arranged, and the twisting machine 22 is compared with the case where a feed drive motor is further provided on the rotating body 30. The configuration is simple.
[0030]
In order to use the twisting machine 22, when the motor 34 is rotated at a predetermined number of revolutions, the feed driving pulley 52 rotates, and the first gear 60, the second gear 62, the multistage winding capstan 68, and the multistage winding dummy pulley 72 are rotated. Rotational force is transmitted sequentially. As a result, the strands 18 </ b> A to 18 </ b> C that have passed through the twist point forming unit 28 are sent out from the rotating body 30 at a predetermined sending speed.
[0031]
Further, the rotational driving dummy pulley 72 rotates, and the rotating body 30 rotates at a predetermined rotational speed. Accordingly, the strands 18 </ b> A to 18 </ b> C are twisted while being drawn out from the twist point forming part 28, and are sent out from the rotating body 30 as a cord 20.
[0032]
In this way, the feed drive of the cord 20 is performed by rotating the feed drive shaft member 50 relative to the rotary drive shaft portion 40 on the rotating body 30, that is, the rotational speed of the feed drive shaft. The feed speed is determined by the difference from the rotational speed of the rotating body 30.
[0033]
The rotational speed ratio between the rotational drive shaft portion 40 and the feed drive shaft member 50 may be a variable speed structure, or the above two shafts may be separately driven to set the rotational speed to an arbitrary speed. Thus, the twist pitch can be freely changed each time. Thereby, a twist pitch can be changed also in one continuous cord, and a twist pitch can be changed according to the conditions concerning the present invention.
[0034]
Conventionally, it has been very difficult to use a cord manufactured using a twister having such a variable pitch function for a tire. Therefore, in order to make full use of this function, it is preferable that the position where the twister is provided be close to the tire member or the device for manufacturing the tire itself, in order to facilitate positioning with the use site of the tire. It is desirable to be able to operate in combination with this device.
[0035]
The cord that can be manufactured by the twisting machine 22 is not limited to a steel cord, and a cord made of an organic fiber material can also be manufactured, and the same effect can be obtained. Further, a composite in which the cord and the organic fiber are twisted, a composite in which the cord and the cord-like rubber are twisted, and a composite in which the cord, the organic fiber and the cord-like rubber are twisted are manufactured. It is possible to provide a reinforcing material suitable for the required tire quality.
[0036]
The material of the wire is not particularly limited, and the wire may be a strand or a strand. The twisting method is not particularly limited, such as single twisting, double twisting, and layer twisting. When the wire is a strand, a strand is manufactured (for example, when the material of the strand is steel, a strand made of steel is manufactured by a twister).
[0037]
In the twisting machine 22, the rotating body 30 includes a rotation driving shaft portion 40 for rotationally driving the entire rotation body, and a feed driving shaft held coaxially with the rotation driving shaft portion 40 by a bearing portion 51. These two shafts are rotationally driven by a single motor 34. Thereby, the structure of the twister 22 can be remarkably simplified. In order to generate the driving force of the feed mechanism 58, the rotary body 30 may be provided with an electric motor or the like. However, in order to make the device simpler, the feed drive shaft is coaxial with the rotary shaft of the rotary body 30. The feed mechanism 58 in the rotating body 30 is driven.
[0038]
Further, since the cord 20 is pulled out from the twist point forming portion 28 by the multi-stage winding capstan 68 and the multi-stage winding dummy pulley 72 and fed out from the rotating body 30, it is not necessary to press the cord 20 with a very high force by the pinch roller 70. . In addition, the winding direction of the multi-stage winding capstan 68 and the multi-stage winding dummy pulley 72 is reversed, and the cord 20 does not have to be wound on the reel, so that the cord 20 with greatly improved straightness can be manufactured. it can.
[0039]
In the twisting machine 22, a twisted wire can be formed by twisting a plurality of single wires and carrying them out of the rotating body, and a twisting machine that does not have to wind the twisted wire from the rotating body as in the prior art is realized. This makes it possible to realize a compact twister that can form a twisted wire with excellent rotation and straightness. Compared to conventional twisters that are generally used in the manufacture of steel cords, the space The price can be reduced to 1/10 or less. Moreover, when manufacturing a strand wire using this twister, selection of a wire can be performed arbitrarily. For example, by supplying a plurality of strands as a core and a plurality of strands as a sheath as wire rods, a layer twisted cord with a compact structure in which the core and the sheath are twisted in the same direction and the same pitch It may be manufactured. Alternatively, a plurality of strands as a core may be unwound in a state where they are already twisted and supplied to a twister to produce a layer twist cord having a different pitch with the sheath. Further, a strand in which 2 to 7 strands are already twisted may be used as a wire to be unwound and supplied to manufacture a double twisted cord. Moreover, you may make the material of the strand wire to manufacture into 2 or more types by making non-identical the material of the several strand as a wire to supply. In addition, a composite of a cord and rubber may be manufactured by twisting together a wire coated with rubber or a processed rubber made into a string simultaneously with steel and other strands.
[0040]
【Example】
Hereinafter, the present invention will be described based on examples.
As test tires, ply cords of the carcass, the pitch P _b to 4.5mm twisting the folded portion near the bead core were prepared TBR tire set the pitch P _CL to 15.5mm twist on the tire equatorial plane. Here, the vicinity of the folded portion of the bead core whose twist pitch has been changed is a portion of the ply cord corresponding to the apex located on the inner side in the tire axial direction and on the outermost side in the tire radial direction of the bead core in the tire axial cross section. A range from a position X of 5 mm on the outer side in the tire radial direction to a portion Y corresponding to the apex located on the outer side in the tire axial direction and on the outermost side in the tire radial direction (see FIG. 1). The test tires are tire size: 275 / 70R22.5, rim size: 22.5 inches, internal pressure: 900 kPa, ply cord twist structure: 3 + 9 + 15 × 0.165 (mm), number of shots: 9.7 Book / 50 mm.
[0041]
When manufacturing the test tire, the rigidity of the ply cord in the vicinity of the folded portion of the bead core is low, so the ply can be easily rolled up along the bead core, and a stable bead portion shape with excellent balance between the members can be obtained. Could be realized. Moreover, since there is no restriction | limiting with respect to a bead part structural member, it was confirmed that the response | compatibility with respect to the required shape and required performance design with respect to a product can fully be aimed at. Furthermore, it is possible to reduce the variation in the ply end position in the folded portion.
[0042]
【The invention's effect】
As described above, according to the present invention, the problem in the bead portion caused by the high rigidity of the ply cord is solved, the bead portion shape is stabilized, and uniform product performance and good workability are achieved. It is possible to realize a pneumatic tire that satisfies both requirements.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a pneumatic radial tire according to an embodiment of the present invention.
FIG. 2 is a side sectional view showing a configuration of a twister.
3 is a cross-sectional plan view of the twister shown in FIG. 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bead part 2 Bead core 3 Carcass 4 Belt layer 5 Bead filler 6 Tread part 8 Side wall part 18A-C Strand 20 Cord 22 Twisting machine 30 Rotating body 58 Feed mechanism

Claims (4)

A carcass that is folded and locked from the inside to the outside of the tire around a bead core embedded in each of the pair of bead portions, a tread portion that is positioned on the outer periphery of the crown portion of the carcass, and a sidewall that is positioned on a side portion of the carcass In a pneumatic tire comprising a portion and at least one belt layer disposed inside the tread portion,
The ply cords of the carcass, the pitch P _b twisting the folded portion near the bead core, the pneumatic tire characterized in that it is smaller than the pitch P _CL twist on the tire equatorial plane. Near the turn-up portion of the bead core is at least on the outer side in the tire radial direction from the portion corresponding to the apex located on the inner side in the tire axial direction and on the outermost side in the tire radial direction of the bead core in the cross section in the tire axial direction of the ply cord. 2. The pneumatic tire according to claim 1, comprising a position from 5 mm to a portion corresponding to an apex located on the outer side in the tire axial direction and on the outermost side in the tire radial direction. The twisting pitch P _b The pneumatic tire according to claim 1 or 2, wherein a 1 / 3-1 / 4 times the range of the twisting pitch P _CL. The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is a heavy-duty pneumatic radial tire.

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