JP5536492B2 - Composite, method for producing the composite, bead core and tire using the composite, and method for producing the tire - Google Patents

Description

The present invention relates to a bead core and a tire using a rubber-steel cord composite having high shape stability , and a method for manufacturing the tire.

  Rubber and steel cord composites are used in a variety of applications. One of the uses is a pneumatic tire. In a pneumatic tire, a bead core for a pneumatic tire, which is generally formed by continuously winding a bead wire made of a steel cord, is embedded in a bead portion, thereby fitting the tire to a rim. For these rubber-steel cord composites, there is a demand for a technique that does not cause deformation due to rubber flow even when high-temperature heat is applied when rubber is vulcanized.

  For example, in Patent Document 1, regarding a pneumatic radial tire belt for a construction vehicle, a steel cord and a coating rubber coated with a thin layer are previously vulcanized or semi-vulcanized and integrated with unvulcanized rubber. Structural composites are disclosed. Patent Document 2 discloses a pneumatic tire in which a precured rubber is disposed around a bead core.

International Publication No. 2003/055697 JP 2004-155096 A

However, in the conventional rubber / steel cord composite, high temperature heat acts when vulcanizing the rubber, and therefore, when the unvulcanized rubber flows, deformation or the like occurs during vulcanization (see FIG. 2b). There is a problem that there was. In particular, in pneumatic tires, when rubber is vulcanized, the shape is stable even when high-temperature heat is applied, the gauge is stable, the bead does not deform, the rim fit is high, and the uniformity is high. A steel cord composite is desired (see FIG. 2a). However, with the conventional technique, it has been difficult to suppress deformation and the like (see FIG. 2b).
For example, in the bead core, due to deformation during vulcanization or flow deformation, the fitting force and fitting pressure of the bead core with respect to the rim during rim assembly vary in the position in the tire circumferential direction. There is a problem that the fitting to the rim becomes insufficient, and the RFV after the rim assembly sometimes deteriorates compared to the RFV level of the tire alone. Here, RFV (radial force variation: variation in vertical force) is a force in the tire radial direction (z-axis direction) generated while a tire receiving a load makes one rotation at a certain radius. This is the size of the fluctuation. When RFV increases, uniformity may be impaired and vibration may occur during traveling. In particular, there is a problem that riding comfort may be difficult to stabilize on a flat road.

  Furthermore, with the conventional technology, it has been difficult to improve the overall fitting characteristics by achieving both the fitting pressure of the pneumatic tire and the rim and the bead unseating resistance (JIS D4230: rim detachment resistance). The fitting pressure and bead unseating resistance of pneumatic tires and rims are greatly affected by the bead core rigidity. However, this also increases the fitting pressure. On the other hand, when the use amount of the bead wire constituting the bead core is reduced, the fitting pressure is lowered, but at the same time, there is a problem that the bead unseating resistance value is also lowered. That is, in the conventional technology, the rim fit property is not improved, the fitting of the tire to the rim is insufficient, and the RFV after the rim assembly may deteriorate compared to the RFV level of the tire alone. There is a problem.

Further, in the belt structure of a pneumatic radial tire for construction vehicles obtained in Patent Document 1, since the rubber has an unvulcanized portion when viewed as a whole as a rubber-steel cord composite, the shape maintaining effect as a whole is small. Further, Patent Document 2 is a technology for arranging rubber subjected to electron beam irradiation around a bead core, which is a technology related to a pre-cured rubber and a steel cord composite, a semi-vulcanized rubber and a steel cord. There is no description or suggestion of a bead insulation rubber technology in which a steel cord is coated with a composite, particularly semi-vulcanized rubber. Furthermore, when vulcanization in the vicinity of the surface proceeds excessively, it is difficult to perform integral molding by vulcanization, and thus there is a problem that an advanced semi-vulcanization process such as electron beam irradiation is required.
Further, the bead core is not vulcanized as usual, and the rubber coating around the bead core is unvulcanized, so that the bead shape tends to collapse. There is a problem.

This invention is made | formed in view of the said problem, and makes it a subject to provide the bead core and tire which used the rubber-steel cord composite with favorable shape stability , and the manufacturing method of this tire.

  As a result of intensive studies to solve the above problems, the present inventor can obtain a rubber / steel cord composite having high shape stability by making all the rubber of the rubber / steel cord composite into a semi-vulcanized state. As a result, the present invention has been completed.

That is , the bead core of the present invention is a bead core for a pneumatic tire formed into an annular shape by continuously winding a bead wire covering formed by coating one or more steel cord bead wires with unvulcanized rubber, after forming the bead core shape, the unvulcanized rubber covering the bead wire, semi pressurized and vulcanized, also the bead wire is in the range below 0.2 D or 0.4 D relative to the rim diameter D of the standard rim It is characterized by being brazed with a curvature radius R.

Also, the pneumatic tire of the present invention is formed in an annular shape by continuously winding a bead wire covering formed by coating one or more steel cord bead wires with unvulcanized rubber. in buried to a pneumatic tire comprising, after forming the bead core shape, the unvulcanized rubber covering the bead wire, semi-vulcanized, the bead wire, 0.2 D or more with respect to the rim diameter D of the standard rim 0 .4 characterized by being brazed with a radius of curvature R in the range of D or less .

The pneumatic tire manufacturing method of the present invention is a pneumatic tire manufacturing method in which an annular bead core is embedded in a bead portion, wherein one or more steel cord bead wires are coated with unvulcanized rubber. A step of continuously winding the bead wire covering to form an annular shape, a step of semi-vulcanizing the unvulcanized rubber covering the bead wire after forming the bead core shape, and the bead wire with respect to a rim diameter D of a standard rim. characterized in that it comprises the step of attaching habit with a radius of curvature R in the range below 0.2 D or 0.4 D Te.

  The “standard rim” used here is a standard rim (JATMA, TRA, ETRTO, etc.) for an applicable size specified in industrial standards and standards effective in the area where the tire is manufactured, sold, or used. Or “Approved Rim”, “Recommended Rim”).

  Moreover, the curvature radius of the brazing of the bead wire embedded in the pneumatic tire is specified by the following procedure. That is, after disassembling the tire and taking out the bead core so as not to damage the bead wire, the bead wire for two rounds is cut out from the end of the bead wire disposed on the outer side in the tire radial direction so as not to be damaged. Next, the cut-out bead wire is left on a flat plate, and the inner diameter of the annular body formed by the bead wire in a natural state is measured at eight positions that are evenly spaced on the circumference, and a half of the average value is defined as a curvature radius R.

According to the present invention, by previously semi-vulcanized, the vulcanization of such a tire, since the flow of rubber is suppressed, bead cores and tire shape stability with good rubber-steel cord composite In addition, a method for manufacturing the tire can be provided.

It is a tire width direction sectional view of the right half part of the pneumatic tire according to this invention, and shows the state attached to the standard rim. It is sectional drawing of 1 aspect of the bead core of this invention and the prior art bead core, (a) It is sectional drawing of 1 aspect of the bead core excellent in the shape stability of this invention, (b) Because unvulcanized rubber was used It is sectional drawing of 1 aspect of the deformed prior art bead core.

Hereinafter, the present invention will be described in detail .

[Semi-vulcanized rubber / steel cord composite]
The semi-vulcanized rubber / steel cord composite used in the present invention is a composite composed of a semi-vulcanized rubber and a steel cord, and by pre-half vulcanization, the flow of rubber is suppressed during vulcanization, Good shape stability. In particular, in pneumatic tires, when rubber is vulcanized, the shape is stable even when high-temperature heat is applied, the gauge is stable, the bead is not deformed, the rim fit is high, and the uniformity is high. Steel cord composite.
Here, the composite consisting of semi-vulcanized rubber and steel cord means that the bead member rubber occupies 100% of the bead cross section of the bead member rubber, and the bead member rubber This eliminates the use of a vulcanized rubber or an unvulcanized rubber in a part that is not related, that is, a part not related to the shape deformation of the composite.

[Steel cord]
The steel cord used for this invention is not specifically limited, For example, the steel cord used for a normal tire is suitable.

[Semi-vulcanized rubber]
The semi-vulcanized rubber used in the present invention is not particularly limited. For example, a rubber that is used for a normal tire and is semi-vulcanized is suitable. The semi-vulcanized state refers to a state in which the treatment is stopped before the unvulcanized (vulcanization degree 0%) rubber compound is completely vulcanized (vulcanization degree 100%) at a predetermined vulcanization temperature. Vulcanized rubber is rubber that has been subjected to such preliminary vulcanization. The semi-vulcanized state can be defined by the degree of vulcanization determined from the vulcanization degree curve (JIS K6300-2).
Furthermore, it is preferable that the vulcanization degree of the rubber is in the range of 20% to 80%. When the degree of vulcanization is less than 20%, the composite may flow and deform due to high temperature heat during rubber vulcanization. When the degree of vulcanization exceeds 80%, the subsequent vulcanization This is because vulcanization integration may be insufficient as a rubber composite.
Here, the “degree of vulcanization” is a scale indicating the reaction state (degree of SS crosslinking reaction) determined by the vulcanization time and vulcanization temperature when vulcanized at a certain vulcanization temperature. It can be measured experimentally by instrumental analysis such as NMR, and the vulcanization behavior (relationship between heating temperature-heating time-torque) can be ascertained by the curlastometer method according to JIS K6300-2: 2001. Can be predicted. When completely vulcanized, the softness of the rubber is lost, the rubber hardness is increased, the rubbers are not vulcanized and bonded together, and the vulcanization cannot be integrated. Therefore, in practical management at a site such as a factory, vulcanization degree management by rubber hardness can be suitably used.

(Semi-vulcanization method)
In the semi-vulcanization treatment, after the steel cord is coated with the unvulcanized rubber, the heating device is not particularly limited, but the unvulcanized rubber is preferably semi-vulcanized in advance using an electric kettle or an electric furnace. A semi-vulcanization treatment is performed by heat treatment at a predetermined vulcanization temperature for a predetermined vulcanization time while predicting from the vulcanization behavior or controlling the hardness.
Further, after forming the bead core shape and unvulcanized rubber and steel cord, you half vulcanized unvulcanized rubber. This is because vulcanization is less likely to occur when vulcanized after assembling to some extent.

(Production method of composite)
The method for producing a composite includes a step of coating a steel cord with unvulcanized rubber, and a step of semi-vulcanizing the unvulcanized rubber after coating. In the molding process, the apparatus is not particularly limited. For example, a bead insulation apparatus for covering a steel cord with a tire bead core rubber is a preferable example. In the semi-vulcanization step, the semi-vulcanization treatment is performed by performing heat treatment at a predetermined vulcanization temperature for a predetermined vulcanization time while predicting from the vulcanization behavior or controlling the hardness. The composite is further vulcanized and integrated .

[Use of composite of semi-vulcanized rubber and steel cord]
Complex of semi-vulcanized rubber and the steel cord of the present invention is used in Bidoko A, also used in pneumatic tires, in particular, when used in a pneumatic tire, high temperature heat when vulcanizing rubber Even if this works, the shape is stable, the gauge is stable, the bead is not deformed, the rim fit is high, and the uniformity is high.

(Bead wire and tire)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a tire widthwise section of the right half of a pneumatic tire (hereinafter referred to as “tire”) according to the present invention attached to a standard rim, and FIG. 2a is a sectional view of the bead core of the tire shown in FIG. It is. Since a bead core, which is a composite of semi-vulcanized rubber and steel cord, is used for a tire, the cross-sectional shape is maintained even by vulcanization, and a bead core cross-sectional shape having a rectangular outer shape without deformation is exhibited as shown in FIG. Therefore, the deformation is observed in the entire bead core shown in FIG. 2b, and can be distinguished from the bead core in which the influence of the deformation is seen in the bead core or the bead wire (bead steel cord) of the prior art tire having a substantially rhombus outer shape.

  A tire 1 shown in FIG. 1 includes a tread portion 2 that contacts a road surface, a pair of sidewall portions 3 that extend inward in the tire radial direction from both side portions of the tread portion 2, and a tire radial direction inner side of each sidewall portion 3. A pair of bead portions 5 provided and fitted to the standard rim 4. A toroidal carcass 6 is mounted between the pair of bead parts 5, and an end part thereof is folded from the inner side in the tire width direction toward the outer side in the tire width direction around the bead core 7 embedded in the bead part 5. ing. Further, a belt 8 formed by covering a reinforcing element with rubber is disposed on the outer periphery of the crown portion of the carcass 6.

As shown in FIG. 2a, the bead core 7 has a multilayer structure in which bead wires 9 made of steel cord are laminated in the tire radial direction, and further forms a composite with semi-vulcanized rubber. The bead wire 9, with respect to the rim diameter D of the pre-standard rim 4 0. Continuous brazing is performed with a radius of curvature R in the range of 2D to 0.4D. Here, the reason why the radius of curvature R is 0.2 D or more is that it is difficult to make the radius of curvature R less than 0.2 D, and the rigidity of the bead wire 9 is too low, and the rim assembly is improved. This is because the fitting pressure of the object becomes too low, and the amount of change in RFV after rim assembly increases. On the other hand, if the radius of curvature R is 0.4 D or less , if it exceeds 0.4, the rigidity of the bead wire 9 is not sufficiently lowered, and the rim assembly property is not sufficiently improved. This is because the amount of change in RFV increases.

The bead core 7 is formed by spirally winding a coating of unvulcanized rubber continuously in the circumferential direction while shifting the position in the tire width direction with one bead wire 9 subjected to such brazing. One of the layers constitute constitute a plurality of layers in the same procedure on this layer can be formed by semi-vulcanized after bead molding further. Alternatively, a plurality of bead wires 9 subjected to such brazing are arranged in parallel in the tire width direction with a coating of unvulcanized rubber, and simultaneously wound in the circumferential direction to form one layer. configure multiple layers in the same procedure above may be formed by semi-vulcanized after bead molding further. By semi-vulcanized after configuration and bead molded bead core with a coating of unvulcanized rubber, it is possible to prevent the bead type collapse during vulcanization, whereby a gap of the bead rear portion is eliminated, bead fit And RFV is improved.

  In general, when a tire rim is assembled, particularly in the case of a rim with a hump, it is necessary to expand the diameter of the bead portion 5 and set the bead seat portion of the rim 4. Since the bead wire 9 constituting it has a low rigidity, the diameter can be increased even with a relatively small force, so that the bead portion can be uniformly fitted (fitted) on the circumference. Further, after the rim assembly, the bead core 7 tries to reduce the diameter by the action of the bead wire 9 having the curvature radius R smaller than the rim diameter D, so that the fitting pressure of the bead portion 5 to the rim 4 is improved.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. . According to the present invention, since the bead wire is brazed with a relatively small radius of curvature to reduce the rigidity of the bead wire, the force required for the tire rim assembly is reduced, and therefore the tire rim assembly performance is improved, and consequently the tire It is possible to reduce the amount of RFV in the rim assembly.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
[Examples 1 to 4]

  Next, tires according to the present invention were prototyped and performance evaluations were performed, which will be described below.

  The tires of Examples 1 to 4 are steel radial tires for passenger cars having a tire size of 205 / 55R16, and have a 4 × 4 strand bead core made of a bead wire having a diameter of 1.3 mm. The bead wires of the tires of these examples are composites treated under the semi-vulcanized conditions shown in Table 1 so that the semi-cured state predicted from the vulcanization curve is obtained, and the rim diameter D of the standard rim (6.5JJ). Is brazed with a radius of curvature R shown in Table 1.

  For comparison, the brazing of the bead wire is 2R / D = 0.8, 1.2, and the same configuration as in Examples 1 to 4 except that a composite of semi-vulcanized rubber and steel cord is used. A tire of a conventional example having a tire was also prototyped.

  The following items were evaluated for each of the test tires.

[Evaluation method]
(Rim fit)
Mount the test tire on the rim to make a tire wheel, observe the bead part with an internal pressure of 220 kPa, measure the gap between the rim and the bead part, and determine the rim fit based on the total value of the gaps at 10 points on the circumference Evaluated. The tire value of the comparative example is expressed as an index with the value of 100, and the smaller the value, the better the rim fit property.

(RFV)
The test tire is assembled on a rim of 6.5 JJ × 16, and RFV (N) is measured in accordance with the “Automotive Tire Uniformity Test Method” of Automotive Regulations JASOC607. evaluated. The smaller the numerical value, the smaller the RFV and the better the tire performance.

  From the results shown in Table 1, it can be seen that the tires of Examples 1 to 4 have significantly improved rim fit and RFV as compared with the conventional tires. Therefore, the tires of Examples 1 to 4 are excellent in overall fitting characteristics, and the amount of change in RFV after rim assembly can be minimized.

  It has become possible to provide rubber-steel cord composites with excellent shape stability. In particular, the present invention provides a pneumatic tire that improves the rim fit of a tire by minimizing the amount of change in RFV after rim assembly by semi-vulcanizing unvulcanized rubber after forming a bead core shape. It became possible.

1 Tire 2 Tread 3 Sidewall 4 Rim 5 Bead 6 Carcass 7 Bead Core 8 Belt 9 Bead Wire (Steel Cord)
10 Semi-cured rubber 11 Unvulcanized rubber D Rim diameter

Claims (3)

In a bead core for a pneumatic tire formed into an annular shape by continuously winding a bead wire covering made of one or more steel cords coated with unvulcanized rubber,
After forming the bead core shape, the unvulcanized rubber covering the bead wire is semi-vulcanized, and the bead wire has a radius of curvature R in the range of 0.2D to 0.4D with respect to the rim diameter D of the standard rim. A bead core for a pneumatic tire, characterized by being continuously brazed with. In a pneumatic tire in which a bead core is embedded in a bead part, which is formed in an annular shape by continuously winding a bead wire covering made of one or more steel cords coated with unvulcanized rubber,
After forming the bead core shape, the unvulcanized rubber covering the bead wire, semi-vulcanized, the bead wire, the curvature in the range of not less than 0.2 D or 0.4 D relative to the rim diameter D of the standard rim A pneumatic tire characterized by being continuously brazed with a radius R. In the manufacturing method of the pneumatic tire formed by embedding an annular bead core in the bead part,
A step of continuously winding a bead wire covering formed by coating one or more steel cord bead wires with unvulcanized rubber to form an annular shape;
A step of semi-vulcanizing the unvulcanized rubber covering the bead wire after forming the bead core shape;
The pneumatic tire manufacturing method, characterized by comprising the step of attaching continuously habit with a radius of curvature R in the range below 0.2 D or 0.4 D relative to the rim diameter D of the standard rim the bead wire .

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