JP2005035331A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for improving plunger resistance without changing a generation ratio of cracks at an end of a tire belt. <P>SOLUTION: This pneumatic tire is provided with at least a sheet of belt layer 4 arrayed with a plurality of cords extending to be inclined to tire equatorial plane on an outer periphery of a crown part of a toroidal carcass 3 by stretching between at least a pair of bead cores 2 and a tread part 6 provided at the tire radial direction outside of the belt layer 4. Twist pitch of the cord arrayed within at least a sheet of the belt layer 4 of the belt layers 4 is changed from small pitch to large pitch from a tire center part toward the end of the belt. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４２】
【表２】

【００４３】
【発明の効果】
以上説明してきたように、本発明の空気入りタイヤにおいては、タイヤベルト端での亀裂の発生率を変えずに耐プランジャー性を向上させることができ、その結果、タイヤの重量およびコストを下げることができる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る空気入りラジアルタイヤの断面図である。
【図２】ベルト層のコード配列を示す説明図である。
【図３】撚り機の構成を示す側面断面図である。
【図４】図３に示す撚り機の平面断面図である。
【符号の説明】
１ ビード部
２ ビードコア
３ カーカス
４ ベルト層
５ ビードフィラー
６ トレッド部
８ サイドウォール部
１８Ａ〜Ｃ 素線
２０ コード
２２ 撚り機
３０ 回転体
５８ 送り機構[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire improved in plunger resistance without changing the rate of occurrence of cracks at the end of a tire belt, particularly a pneumatic radial tire for heavy loads.
[0002]
[Prior art]
Conventionally, steel cords of various twisted structures have been used as reinforcing materials in pneumatic tires, particularly heavy duty pneumatic radial tires. For example, various steel cords obtained by twisting strands of the same wire diameter have been used as steel cords used for the belt layer of heavy duty pneumatic tires.
[0003]
[Problems to be solved by the invention]
However, until now, the twist pitch is always uniform in one belt layer, and it has been practically impossible to change the twist pitch in the tire width direction due to a problem in the tire manufacturing technology.
[0004]
For this reason, in conventional tires, in one belt layer, cracks at the belt end that tend to occur when the cord twist pitch is small, and decrease in plunger resistance that tends to occur when the cord twist pitch increases. It was not possible to reconcile the contradictory matters.
[0005]
Accordingly, an object of the present invention is to provide a pneumatic tire that solves the problems of the prior art and has improved plunger resistance without changing the occurrence rate of cracks at the end of the tire belt.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventor changed the cord twist pitch in one belt layer using a specific device. The inventors have found that the plunger resistance can be improved without changing, and have completed the present invention.
[0007]
That is, in the pneumatic tire of the present invention, at least one cord in which a plurality of cords extending at an inclination with respect to the tire equatorial plane is arranged on the outer periphery of a crown portion of a carcass that forms a toroid shape between at least a pair of bead cores. In a pneumatic tire including a belt layer and a tread portion provided on the outer side in the tire radial direction of the belt layer,
The twist pitch of the cords arranged in at least one belt layer among the belt layers changes from small to large from the tire central portion toward the belt end.
[0008]
In the pneumatic tire according to the present invention, in particular, the heavy-duty pneumatic radial tire, the at least one belt layer has a region from the tire central portion to at least 50% of the region S from the tire central portion to the belt end. In Sa, it is preferable that the twist pitch of the cord is smaller than that in the other region Sb, and the at least one belt layer is in the region Sc from the belt end to at least 10 mm in the tire central direction. It is preferable that the twist pitch of the cord is larger than that of the other region Sd. Furthermore, the cord twist pitch PC at the tire central portion and the twist pitch PS at the belt end of the at least one belt layer are represented by the following formulas:
PS / 5 ≦ PC ≦ PS / 1.2
It is preferable to satisfy the relationship represented by these.
[0009]
Compared to a conventional pneumatic tire in which the cord twist pitch is uniform in one belt layer, in the pneumatic tire of the present invention, the crack at the belt end is generated without changing the strength of the center portion of the tire. As a result, the weight and cost of the tire can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, 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 around a bead core 2 embedded in a bead portion 1 from the inside of the tire to the outside, and a carcass 3. The bead filler 5 disposed between the main body 3A and the winding part 3B, the tread part 6 located at the crown part of the carcass 3, the sidewall part 8 located at the side part of the carcass 3, and the tread part 6 The belt layer 4 of the two layers arrange | positioned inside is provided. The carcass 3 has a cord arranged in a direction substantially perpendicular to the circumferential direction, and in the present embodiment, is constituted by a single carcass ply.
[0011]
The belt layer 4 according to the present embodiment is located on the inclined belt layer 4A, one 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 steel cord And an inclined belt layer 4B in which a plurality of steel cords crossing each other are arranged. The number of belt layers 4 is not particularly limited, and may be appropriately determined according to the use and type of the tire.
[0012]
In the present invention, the twisting pitch of the steel cords arranged in at least one of the inclined belt layer 4A and the inclined belt layer 4B can be changed from small to large from the center of the tire toward the belt end. is important. Specifically, at least one of the inclined belt layer 4 </ b> A and the inclined belt layer 4 </ b> B is disposed in the region Sa from the tire central portion to at least 50% of the region S from the tire central portion to the belt end. The cord twist pitch is made smaller than that in the region Sb (see FIG. 2). Or at the same time, at least one belt layer of the inclined belt layer 4A and the inclined belt layer 4B is compared with the other regions Sd in the region Sc from the belt end to at least 10 mm in the tire center direction. Make it bigger. By doing in this way, compared with the case where the twist pitch of all the steel cords is uniform, it becomes possible to suppress generation | occurrence | production of the crack of a belt end, without changing the intensity | strength of a tire center part.
[0013]
The amount of change in the twist pitch of the steel cords arranged in one belt layer is determined by the cord twist pitch at the center of the tire being PC and the cord at the belt end in order to achieve the intended purpose of the present invention. When the twist pitch of PS is PS,
PS / 5 ≦ PC ≦ PS / 1.2
It is preferable to satisfy the relationship represented by these. More preferably, the following formula:
PS / 3 ≦ PC ≦ PS / 1.2
Satisfies the relationship expressed by
[0014]
The inclination angles of the steel cords of the inclined belt layer 4A and the inclined belt layer 4B with respect to the tire equatorial plane CL are preferably in the range of 15 ° to 45 ° and −15 ° to −45 °, respectively. The number of steel cords driven in the inclined belt layer 4A and the inclined belt layer 4B is preferably in the range of 15 to 50 per 50 mm.
[0015]
The cord of the belt layer 4 is not limited to a steel cord, and may be a cord made of an organic fiber material. The core is a steel cord and the surrounding first and / or second sheath is an organic fiber. A composite formed by twisting organic fibers may be used.
[0016]
The means for changing the twisting pitch of the cord is not particularly limited, but a twisting machine that can change the twisting pitch of the cord, which has been difficult so far, has recently been developed, and the applicant of the present application A patent application has already been filed for the twisting machine (Japanese Patent Application No. 2002-341037). Therefore, this twister will be described in detail below.
[0017]
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.
[0018]
Specifically, a twister 22 of the type shown in FIG. 3 can be suitably used. FIG. 3 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.
[0019]
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.
[0020]
As shown in FIGS. 3 and 4, on the downstream side of the rotator 30, a rotation drive pulley 42 is fixed to a rotation drive shaft portion 40 extending from the housing 31 of the rotator 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.
[0021]
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.
[0022]
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.
[0023]
The diameters of the multi-stage winding capstan 68 and the multi-stage winding dummy pulley 72 are the same as the diameters, materials, etc. of the strands 18A to 18C so that there is no problem in terms of straightness when using the cord 20 fed from the rotating body 30. It is decided in consideration.
[0024]
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.
[0025]
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. .
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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 member, and a twist pitch can be changed according to the belt layer which concerns on this invention.
[0031]
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.
[0032]
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.
[0033]
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).
[0034]
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.
[0035]
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.
[0036]
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.
[0037]
【Example】
Hereinafter, the present invention will be described based on examples.
As test tires, the tires of Examples 1 and 2 and the tires of Conventional Examples 1 and 2 were prepared, and the plunger resistance and the belt end crack length were compared and evaluated.
[0038]
For all the test tires, the tire size is 295 / 75R22.5, the rim size is 8.25 inches, the internal pressure is 705 kPa, and only the number of twists of the steel cord of the outermost belt of the belt layer (3.5 belt structure) is as follows. It was made to fluctuate as shown in Table 1. The conditions of the other belt layers were all the same, the twisted structure: 1 + 6 × 0.34 (mm), and the number of driving: 14/50 mm.
[0039]
The plunger resistance test was based on the test method described in JIS-D4230 with a plunger diameter of 38 mm. It represents with the index which sets the prior art example 2 to 100, and it is excellent in plunger resistance, so that a numerical value is large.
[0040]
The belt end crack length was measured by running 4000 km on a drum to which a load was applied at a constant speed of 65 km / h. As shown in Table 1 below, the load was applied under a step load condition that changes with time. The result is represented by an index with Conventional Example 1 being 100, and the larger the value, the lower the crack occurrence rate at the end of the tire belt.
[0041]
[Table 1]

[0042]
[Table 2]

[0043]
【The invention's effect】
As described above, in the pneumatic tire of the present invention, the plunger resistance can be improved without changing the crack occurrence rate at the end of the tire belt, and as a result, the weight and cost of the tire are reduced. be able to.
[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 an explanatory diagram showing a cord arrangement of a belt layer.
FIG. 3 is a side sectional view showing a configuration of a twister.
4 is a cross-sectional plan view of the twister shown in FIG. 3. 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 Feeding mechanism

Claims (5)

At least one belt layer in which a plurality of cords extending obliquely with respect to the tire equatorial plane are arranged on the outer periphery of the crown portion of the carcass forming a toroidal shape straddling between at least a pair of bead cores, and the belt layer In a pneumatic tire provided with a tread portion provided on the outer side in the tire radial direction,
A pneumatic tire characterized in that a twist pitch of cords arranged in at least one belt layer among the belt layers changes from small to large from the tire central portion toward the belt end. The at least one belt layer has a cord twist pitch smaller in the region Sa from the tire central portion to at least 50% of the region S from the tire central portion to the belt end than in the other regions Sb. The heavy duty pneumatic tire according to claim 1. 3. The pneumatic structure according to claim 1, wherein the at least one belt layer has a larger cord twist pitch than the other regions Sd in a region Sc of at least 10 mm from the belt end toward the center of the tire. tire. The twist pitch PC of the cord at the center of the tire of the at least one belt layer and the twist pitch PS of the cord at the belt end are represented by the following formulas:
PS / 5 ≦ PC ≦ PS / 1.2
The pneumatic tire according to any one of claims 1 to 3, which satisfies a relationship represented by: It is a pneumatic radial tire for heavy loads, The pneumatic tire as described in any one of Claims 1-4.

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