JP2008126745A - Bead part structure for pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bead part structure for a pneumatic tire capable of effectively preventing oxygen deterioration of a bead part constitution member by effectively suppressing the permeation of oxygen into the bead part. <P>SOLUTION: In the tire bead part provided with a pair of bead cores 1; a carcass 2 troidally extending between these bead cores and having both side part areas wound and returned around the respective bead cores; a rubber chafer 3 for dividing a bead base 4 at an inner peripheral side of the bead core 1; and an inner liner 5 for dividing an inner surface of the tire, at an inner surface side of the tire, a part of the rubber chafer 3 is inserted and arranged between the inner liner 5 and the carcass 2, and an adhesion rubber 7 containing at least one of butyl and halogenated butyl is interposed between the inner liner 5 and the rubber chafer 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bead portion structure of a pneumatic tire, and in particular, proposes a technique capable of effectively preventing oxygen deterioration of a bead portion constituent member caused by oxygen permeating into the bead portion. It is.

  For example, as shown in a schematic perspective view in FIG. 5 (a), an inner liner rubber, a rubber chafer rubber, and the like formed in a cylindrical shape with a uniform diameter on the band drum 50 are included in forming a raw tire. The carcass band 51 is transferred from the band drum 50 onto the molding drum, where both end portions of the carcass band 51 have an inner diameter D as illustrated in FIG. 5B by a radial sectional view including the central axis. In the case where the inner diameter d is reduced to the rewinding portion inner diameter d and the end portions thereof are rewound and locked around the bead core 52 fitted thereto, the inner liner rubber 53, the chafer rubber 54 and the When the carcass band 51 is formed by sequentially laminating the carcass 55 and the like, the inner part is deformed when the diameter of the end portion of the carcass band 51 is reduced. -Between the end portion of the liner rubber 53 and the chafer rubber 54 laminated thereon, a relative displacement in the radial direction and the axial direction occurs at the reduced diameter portion, and this relative displacement may impair the adhesion between them. In addition to the above, the edge of the inner liner rubber 53 was often located at a radially deformed portion and shifted radially outward from the position corresponding to the tip of the bead toe portion of the product tire.

  When the adhesion between the inner liner rubber 53 and the chafer rubber 54 is once lost due to such reduced diameter deformation of the carcass band 51, both of them are formed by vulcanization formation of the finished raw tire in the vulcanization mold. Even when vulcanized under pressure, the inner liner rubber 53 has a composition containing 80% or more of bromobutyl rubber with an emphasis on gas barrier properties, etc., and rim scuff resistance, rim slip resistance, and sag resistance In addition to the low adhesiveness of the chafer rubber 54, which is composed of almost half the composition of natural rubber and butadiene rubber, and the low adhesion between them at the start of vulcanization, vulcanization In other words, after the bonding is completed, the inner liner and the rubber chafer cannot be bonded with sufficient strength in the product tire. In this case, oxygen in the air filled in the product tire permeates into the bead part, promotes oxygen deterioration of the bead part component, and improves the durability of the bead part. There was a problem of lowering.

  In addition, as described above, the edge of the inner liner rubber 53 is shifted radially outward from the position corresponding to the tip of the bead toe portion of the product tire at the reduced diameter deformed portion of the carcass band 51. When a rubber chafer with low gas barrier properties is directly exposed to the air filled in the tire when the rim-assembled tire is filled with air pressure, oxygen is used regardless of whether the inner liner and the rubber chafer are separated or not. However, there is a problem that oxygen penetrates into the bead portion through the rubber chafer and causes the components to undergo oxygen deterioration.

  The present invention has been made in order to solve such a problem, and the object of the present invention is to effectively prevent the penetration of oxygen into the bead part and to cause oxygen deterioration of the bead part constituting member. It is in providing the bead part structure of the pneumatic tire which can prevent effectively.

  A bead portion structure of a pneumatic tire according to the present invention includes a pair of bead cores and a toroidal extension between the bead cores, with both side regions directed around the respective bead cores, for example, from the inner side to the outer side in the tire width direction. A carcass that can be made to have a radial structure, a rubber chafer that divides a bead base as a contact surface to the bead seat of the wheel rim, and an inner liner that divides the inner surface of the tire A portion of the rubber chafer is placed between the inner liner and the carcass on the inner surface side of the tire, and at least one of butyl and butyl halide is disposed between the inner liner and the rubber chafer. It is formed by interposing an adhesive rubber containing.

  Here, preferably, the adhesive rubber is constituted by a rubber composition containing at least one of butyl and butyl halide of 50% by mass or less of the rubber component.

  Preferably, the adhesive rubber is disposed in a radial region of 40 mm or less from the tip of the bead toe portion along the inner liner, and is ½ of the bead base width from the tip of the bead toe portion along the bead base. Within the width direction region within.

In this case, the adhesive rubber can be disposed so as to be exposed from the inner liner in the vicinity of the tip of the bead toe portion in the radial arrangement region of the adhesive rubber.
Here, “near the tip” means a range from the tip of the bead toe to 10 mm measured radially outward along the tire inner surface.
Thus, in this case, the inner end of the inner liner in the radial direction is located radially outward from the tip of the bead toe portion and is present within a range of 10 mm radially outward from the tip.

  In the bead portion structure according to the present invention, in particular, in a product tire after vulcanization formation of a raw tire, an adhesive rubber containing at least one of butyl and halogenated butyl is interposed between the inner liner and the rubber chafer. , Adhesive rubber Under the original function, the inner liner and rubber chafer can be vulcanized and bonded sufficiently firmly, effectively preventing unintended peeling of both of them over a long period of time, The risk of oxygen degradation can be effectively removed.

  On the other hand, the adhesive rubber is subjected to an inner liner rubber and a chafer rubber at the time of the diameter reduction deformation as illustrated in FIG. 5B of the end portion of the carcass band in the green tire molding process before vulcanization thereof. In addition to restraining the relative displacement in the radial direction of the carcass with its inherent adhesive force, etc., it also functions to effectively maintain the adhesion between the two. The risk of lowering the adhesion between the liner rubber and the chafer rubber is advantageously suppressed, and at the same time, the inner edge of the inner liner rubber is effectively restrained to a position corresponding to the tip of the bead toe portion of the product tire. be able to.

Thus, according to this bead portion structure, there is a risk of oxygen deterioration of the bead portion constituting member, sufficient vulcanization adhesion between the inner liner and the rubber chafer, and the bead toe portion in the product tire at the inner edge of the inner liner. This can be effectively prevented by restraining the tip or the vicinity thereof.
Here, as described above, the vicinity of the tip of the bead toe portion means a range from the tip of the bead toe portion to 10 mm as measured radially outward along the tire inner surface.

  In such a bead part structure, when the adhesive rubber is constituted by a rubber composition containing at least one of butyl and butyl halide of 50% by mass or less of the rubber component, the adhesive rubber itself is butyl-based and It can be vulcanized and bonded sufficiently firmly to each of the natural rubber systems. For example, the inner liner rubber is mainly composed of bromobutyl rubber as described above, and the chafer rubber is also as described above. Even if the main component is natural rubber and butadiene rubber, the adhesive strength between them can be sufficiently increased.

  In addition, regarding the arrangement area of the adhesive rubber, the adhesive rubber is arranged in a radial region within 40 mm along the inner liner from the tip of the bead toe portion, and along the bead base from the tip of the bead toe portion. When it is arranged in the width direction region within 1/2 of the bead base width, it is in a portion where a plurality of types of components are concentrated, and if a tire is slightly molded, Even if an attachment error or the like may occur, the adhesion as expected can be sufficiently secured.

  By the way, since the adhesive rubber containing at least one of butyl and halogenated butyl can exhibit an excellent oxygen barrier property by itself, for example, in relation to the molding accuracy of a raw tire, Even if the adhesive rubber is exposed from the inner liner in the vicinity of the tip of the bead toe part in the radial arrangement area, the internal oxygen deterioration of the bead portion constituting member is coupled with the increase in the adhesive strength due to the adhesive rubber. Can be effectively suppressed.

  FIG. 1 is a cross-sectional view in the tire width direction showing an embodiment of the present invention in one rim assembly posture in a rim assembly posture. In the figure, 1 is a bead core and 2 is a toroidal extension between a pair of bead cores 1. The carcass made of one or more carcass plies each having a radial structure or a bias structure in which both side regions are wound around the respective bead cores 1 from the inner side to the outer side in the tire width direction are shown. .

  In the figure, reference numeral 3 denotes a rubber chafer disposed on the inner peripheral side of the bead core 1, and the rubber chafer 3 defines a bead base 4 in surface contact with the bead seat BS of the wheel rim R. Reference numeral 5 denotes an inner liner that partitions the inner surface of the tire and has excellent gas barrier properties.

  Further, here, the rubber chafer 3 that contributes to the section of the bead base 4 in surface contact with the bead sheet BS is located between the inner liner 5 and the carcass 2 on the bead toe side, and is radially outward from the bead core 1. And a hard rubber portion 3b on the bead heel side and extending radially outward from the rim flange RF, and at the bead toe portion 6, the inner liner 5 and the rubber chafer 3 more directly. Is interposed between the soft rubber portion 3a and an adhesive rubber 7 containing at least one of butyl and halogenated butyl, preferably at a ratio of 50% by mass or less of the rubber component.

  Reference numeral 8 in the figure denotes a wire chafer disposed around the bead core 1 along the carcass 2 and between the carcass 2 and the rubber chafer 3.

  According to such a bead portion structure, as described above, in the product tire that has been vulcanized and molded under the original function of the adhesive rubber 7, for example, the inner liner 5 mainly composed of bromobutyl rubber. Also, for example, the soft rubber portion 3a of the rubber chafer 3 mainly composed of natural rubber and butadiene rubber can be vulcanized and bonded sufficiently firmly.

  In addition, the adhesive rubber 7 assists the adhesion between the inner liner rubber and the chafer rubber when the green tire is molded under the action of the viscous force inherent to the adhesive rubber material before vulcanization. And, since the edge of the inner liner rubber is constrained to a predetermined position, it ensures effective adhesion between the inner liner rubber and the chafer rubber when molding the raw tire, and the inner edge of the inner liner rubber is The positional deviation from the position corresponding to the tip of the bead toe portion 6 of the product tire can be advantageously suppressed, and as a result, the oxygen of the bead portion constituting member is obtained under the oxygen barrier properties of both the inner liner 5 and the adhesive rubber 7. The possibility of deterioration can be effectively removed.

  In the bead portion structure as described above, the area where the adhesive rubber 7 is disposed is within the radial region where the distance a measured along the tire inner surface, in the drawing, along the inner liner 5 from the tip of the bead toe portion 6 is within 40 mm. In addition, it is preferable that the distance b measured from the tip of the bead toe portion 6 to the bead heel portion 9 side along the bead base 4 is within a width direction region within 1/2 of the bead base width w.

  FIG. 2 is a cross-sectional view of the principal part illustrating this, particularly when the arrangement area of the adhesive rubber in the radial direction is changed. FIG. 2A shows the adhesive rubber 7 with the bead toe. The portion 6 is continuously disposed in a region within 40 mm from the position corresponding to the tip of the portion 6 toward the outer side in the radial direction.

  2 (b) shows that the arrangement area of the adhesive rubber 7 in the radial direction is within 40 mm from the position corresponding to the tip of the bead toe portion 6, but the inner end of the adhesive rubber itself in the radial direction. i is positioned radially outward from the tip position p of the bead toe portion 6.

  FIG. 3 is a cross-sectional view showing another example of the arrangement of the adhesive rubber. The adhesive rubber 7 is measured along the bead base 4 from the position corresponding to the tip of the bead toe portion 6, and 1 of the bead base width w. / 2 on the other hand, the area where the adhesive rubber 7 is disposed in the radial direction is measured from the position corresponding to the tip of the bead toe portion 6 and shown in FIG. As shown in FIG. 3 (b), the distance a in the radial direction is set as the distance b in the width direction as a relatively narrow range toward the outer side in the radial direction. It is a smaller one.

  FIG. 4 is a cross-sectional view of an essential part showing another embodiment, which particularly shows a case where a high oxygen barrier property is used in addition to the excellent adhesive property of the adhesive rubber.

This is because the adhesive rubber itself is in contact with the air filled in the tire and can still effectively prevent the penetration of oxygen into the bead portion. The inner end of the liner 2 in the radial direction is positioned in the vicinity of the tip position p of the bead toe portion 6 so that the adhesive rubber 7 is exposed from the inner liner 2 in the vicinity thereof.
In this case, in the narrow area where the adhesive rubber 7 is exposed from the inner liner 2, the adhesive rubber itself functions to prevent oxygen deterioration of the bead portion constituting member.

Here, what is shown in FIG. 4A is an adhesive rubber 7 disposed so as to cover the entire inner surface side of the rubber chafer 3, and what is shown in FIG. 4B is a rubber chafer. 3, the adhesive rubber 7 is disposed so as to cover the rubber chafer 3 over the range from the inner surface side to the bead base side through the tip position p of the bead toe portion 6.
In any of these cases, the arrangement area of the adhesive rubber 7 satisfies the above distance condition.

For truck and bus tires of size 11R22.5, the respective bead structure shown in FIGS. 2 (a) and 4 (a) is adopted, the thickness of the adhesive rubber is 0.5 mm, and the distance a is 40 mm. In addition, each of Example tires 1 and 2 in which the composition of the adhesive rubber is chlorobutyl rubber / natural rubber = 50/50 and Comparative Example tires 1 and 2 each having a bead portion structure in which the adhesive rubber is omitted from the example tire When the oxygen barrier property of the bead part was measured under the following conditions, the results shown in Table 1 as indices were obtained.
The index values in the table indicate better results as the values are smaller.
In this test, the tire was filled with oxygen and maintained at a constant temperature of 60 ° C. for 30 days, and then the oxygen barrier property was evaluated by measuring the degree of oxygen deterioration of the rubber on the carcass surface. went.

  According to the results shown in Table 1, it can be seen that all of the example tires can exhibit excellent oxygen barrier properties under the action of adhesive rubber.

It is a tire width direction sectional view of one bead part showing an embodiment of this invention. It is sectional drawing similar to FIG. 1 which shows a modification. It is sectional drawing similar to FIG. 1 which shows another modification. It is tire width direction sectional drawing of one bead part which shows other embodiment. It is explanatory drawing which shows the example of a shaping | molding of the raw tire with high possibility of oxygen deterioration of a bead part.

Explanation of symbols

1 Bead core 2 Carcass 3 Rubber chafer 3a Soft rubber part 3b Hard rubber part 4 Bead base 5 Inner liner 6 Bead toe part 7 Adhesive rubber 8 Wire chafer 9 Bead heel part R Wheel rim BS Bead sheet RF Rim flange a, b Distance p Tip position i Inner edge w Bead base width

Claims (4)

A pair of bead cores, a carcass extending in a toroidal manner between these bead cores, with both side regions rolled back around each bead core, a rubber chafer that divides the bead base on the inner peripheral side of the bead core, and an inner surface of the tire In the tire bead portion comprising an inner liner that
A part of the rubber chafer is placed between the inner liner and the carcass on the inner surface side of the tire, and an adhesive rubber containing at least one of butyl and halogenated butyl is interposed between the inner liner and the rubber chafer. The pneumatic tire bead structure.   The bead part structure of a pneumatic tire according to claim 1, wherein the adhesive rubber is constituted by a rubber composition containing at least one of butyl and butyl halide of 50% by mass or less of the rubber component.   Adhesive rubber is disposed in the radial region within 40 mm along the inner liner from the tip of the bead toe portion, and in the width direction within ½ of the bead base width from the tip of the bead toe portion along the bead base. The bead portion structure of a pneumatic tire according to claim 1 or 2, wherein the bead portion structure is disposed in the region.   The bead of a pneumatic tire according to any one of claims 1 to 3, wherein the adhesive rubber is disposed so as to be exposed from the inner liner in the vicinity of the tip of the bead toe portion in the radial arrangement region of the adhesive rubber. Part structure.

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