JP2010058671A - Pneumatic tire - Google Patents

Abstract

The present invention relates to a pneumatic tire with improved bead durability and tire handling stability.
A first carcass ply 31 winds up only a first bead 11 and is folded and terminated. A first bead 11 has a cross-sectional height H1, a second bead 21 has a cross-sectional height H2, and a first carcass ply 31. H1 <H2 <H3 where the cross-sectional height of the end portion 31a of the first carcass ply is H3 <H2 <H3, and the second carcass ply 32 is disposed on the outer side in the width direction of the hoisting portion 31b of the first carcass ply 31 without winding the second bead 21 The end portion 32a of the second carcass ply 32 is a pneumatic tire that terminates on an imaginary line L1 connecting the upper end of the first bead core 12 and the upper end of the second bead core 12 or radially inward from L1.
[Selection] Figure 1

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire with improved bead portion durability and bead portion rigidity.

  Since the tire bead portion is a portion that securely fixes the tire to the rim and maintains the air pressure in the tire, durability of the bead portion is required. In order to ensure the durability of the bead part, a pneumatic tire is known in which two sets of beads each having a bead core and a bead filler are arranged (Patent Document 1). Further, if the rigidity of the bead portion is low, the steering stability of the tire is lowered, and therefore it is necessary to ensure the rigidity of the bead portion of a certain value or more.

JP 2007-182167 A

  The bead portion repeatedly bends as the tire rotates. If the carcass ply on which the bead is wound is terminated at a portion where distortion is likely to occur due to such repeated bending, the rubber and the carcass ply are easily separated from the portion. This separation causes a tire failure. Further, if the rigidity of the bead portion is low, the steering stability of the tire is lowered, and therefore it is necessary to ensure the rigidity of the bead portion of a certain value or more.

  Accordingly, an object of the present invention is to provide a pneumatic tire in which the durability of the bead portion and the rigidity of the bead portion are improved.

The pneumatic tire of the present invention includes a first bead including a first bead core and a first bead filler, a first carcass ply that winds up the first bead to form a toroidal shape,
A second bead core and a second bead filler; a second bead disposed on the outer side in the width direction of the first bead; and a second carcass ply having a toroidal shape disposed on the outer side of the first carcass ply. A pneumatic tire,
The first carcass ply is wound and terminated only by winding up the first bead,
With the first bead mounted on a specified rim, the first bead has a cross-sectional height H1, the second bead has a cross-sectional height H2, and the end of the first carcass ply has a cross-sectional height H3. H1 <H2 < H3,
The second carcass ply is disposed on the outer side in the width direction of the winding portion of the first carcass ply without winding up the second bead,
The end portion of the second carcass ply terminates on an imaginary line L1 connecting the upper end of the first bead core and the upper end of the second bead core or radially inward from L1.

  The pneumatic tire of the present invention includes two sets of beads and ensures the rigidity of the bead portion. Further, the second carcass ply on the outer side in the width direction is arranged on the outer side in the width direction of the winding portion of the first carcass ply without winding up the second bead 21. Moreover, the end portion of the second carcass ply terminates on an imaginary line L1 connecting the upper end of the first bead core and the upper end of the second bead core or radially inward from L1. As a result, since the end portion of the second carcass ply ends in a region where the strain does not concentrate, it is difficult for the end portion to peel off from the rubber, and the durability of the bead portion is ensured. is there.

  Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a bead portion of a pneumatic tire according to the present invention, and FIG. 2 is an enlarged view of the vicinity of a bead core.

  The bead unit 1 includes two beads, a first bead 11 and a second bead 21. The first bead 11 includes a first bead core 12 and a first bead filler 13. Similarly, the second bead 21 includes a second bead core 22 and a second bead filler 23 and is disposed on the outer side in the width direction of the first bead 11. The cross-sectional height H2 of the second bead 21 is the cross-sectional height of the first bead 11 so that the upper end 23a of the second bead filler 23 is located further radially outward than the upper end 13a of the first bead filler 13. It is higher than H1. Thus, the rigidity of bead part 1 is secured by arranging two sets of beads.

  The first carcass ply 31 has a toroidal shape, and only the first bead 11 is wound up and folded to terminate. The end portion 31 a of the first carcass ply 31 is located further radially outward than the upper end 13 a of the first bead filler 13 and the upper end 23 a of the second bead filler 23. Therefore, since the end portion 31a of the first carcass ply 31 is away from the position where the distortion concentrates, the durability of the bead portion 1 is ensured.

  The second carcass ply 32 also has a toroidal shape. The second carcass ply 32 is arranged on the outer side in the width direction of the winding portion 31 b of the first carcass ply 31 without winding up the second bead 21. The end portion 32 a of the second carcass ply 32 terminates in a region 40 on the imaginary line L <b> 1 connecting the upper end of the first bead core 12 and the upper end of the second bead core 22 or radially inward from L <b> 1. Since the bead cores 12 and 22 are composed of a plurality of steel cords, distortion does not concentrate in the region 40. In particular, it is preferable that the end portion 32a terminates on an imaginary line L0 connecting the centers of the bead cores 12 and 22 because the influence of distortion is small. As a result, peeling from the rubber from the end portion 32a hardly occurs, and the durability of the bead portion 1 is ensured.

  The end portion 32a preferably terminates on the imaginary line L2 connecting the lower end of the first bead core 12 and the lower end of the second bead core 22 or on the radially outer side from L2. As shown in FIG. 3, the end portion 32 a of the second carcass ply 32 is bent inward in the radial direction beyond the imaginary line L <b> 2, and the region 50 is sandwiched between the bead cores 12 and 22 and the rim R. You may terminate. Since strain does not concentrate even in the region 50, peeling from the rubber from the end portion 32a hardly occurs, and the durability of the bead portion 1 is ensured.

  Further, as shown in FIG. 4, the end portion 32a may be bent outward in the width direction. In any case, the end portion 32a passes through the center of the bead core 12 and terminates on the imaginary line L3 parallel to the tire equatorial plane (not shown) or on the outer side in the width direction from L3, or passes through the center of the bead core 22 and the tire equatorial plane. It is preferable that it terminates on the imaginary line L4 parallel to the inner side in the width direction from L4. If it terminates in the width direction inside beyond the imaginary line L3, or terminates in the width direction outside beyond the imaginary line L4, peeling from the end portion 32a easily occurs due to distortion.

  The cross-sectional height H1 of the first bead 11 is preferably 10 to 15% of the cross-sectional height H of the tire. If H1 is less than 10%, sufficient rigidity of the bead portion 1 may not be obtained. Conversely, when H1 exceeds 15% of H, the distance from the upper end 13a of the first bead filler 13 to the upper end 23a of the second bead filler 23 becomes short. As a result, since the strain concentrates between the upper end 13a of the first bead filler 13 and the upper end 23a of the second bead filler 23, durability may be reduced.

  The cross-sectional height H2 of the second bead 21 is preferably 150 to 300% of H1. If H2 is less than 150% of H2, sufficient bead portion 1 rigidity may not be obtained. On the contrary, when H2 exceeds 300% of H1, since the strain concentrates in the vicinity of the position where the tire has the maximum tire width, the durability may be lowered.

  Moreover, it is preferable that the difference H1-H2 and H2-H3 of a cross-sectional height are 10 mm or more. When the difference in cross-sectional heights H1-H2 and H2-H3 is less than 10 mm, between the upper end 13a of the first bead filler 13 and the upper end 23a of the second bead filler 23, and the upper end 23a of the second bead filler 23 The strain may concentrate between the end portion 31a of the first carcass ply 31 and the durability may be lowered. In addition, as long as the relationship of H1 <H2 <H3 is maintained, the upper limits of the difference in cross-sectional heights H1-H2 and H2-H3 are not particularly limited. Further, although the upper limit of H3 is not particularly limited, it can be wound up until the end 31a of the first carcass ply 31 is located near the belt layer (not shown). For example, 1 / of the ground contact width of the tread from the ground contact end. It is also possible to terminate the end portion 31a by 3 in the width direction inside.

  In the present invention, the tire dimensions such as the tire cross-sectional height H and the cross-sectional heights H1, H2, and H3 of each member are the dimensions measured from the upper ends of the bead cores 11 and 12 in a state where they are mounted on the specified rim. The specified rim is a standard rim defined by JATMA (Japan Automobile Tire Association) for each tire size.

  Example tires according to the present invention and conventional tires were prototyped and evaluated. Table 1 shows the cross-sectional heights H1 and H2 of the beads 11 and 12 and the cross-sectional height H3 of the end portion 31a of the first carcass ply 31 of the tires of Examples and Conventional Examples. Example 1 was a tire in which the end portion 32a of the second carcass ply 32 is terminated on an imaginary line L0 connecting the centers of the bead cores 12 and 22, as shown in FIG. Examples 2 and 3 were tires in which the end portion 32a ended on the imaginary lines L1 and L2. Examples 4 and 5 were tires in which the end portion 32a was bent beyond the imaginary line L2 and terminated on the imaginary lines L3 and L4. The conventional example is different from the example in that the second carcass ply 32 ends by winding up the second bead 21 (the sectional height of the end position of the end portion 32a was 70% of H).

  Comparative Example 1 was a tire in which the second carcass ply 32 did not wind up the second bead 21, but the end portion 32a was terminated radially outside by 5 mm from the virtual line L1. The comparative example 2 was a tire in which the end portion 32a was bent beyond the imaginary line L3 and terminated at the inner side in the width direction by 5 mm from the imaginary line L3. Comparative Example 3 was a tire in which the end portion 32a was bent beyond the imaginary line L4 and terminated outside in the width direction by 5 mm from the imaginary line L4.

  The tire sizes of the example, comparative example, and conventional example were LT235 / 85 120Q, mounted on a standard rim having a rim diameter of 16 inches and a rim width of 6.5 inches, and evaluated at an air pressure of 550 kPa specified by JATMA.

  The results are shown in Table 1. In Table 1, the durability is a distance traveled until the tire breaks by a test using a test method based on JIS D4230, and is expressed as an index with the conventional example being 100. Is high. Lateral stiffness is measured by applying a lateral force of 30% of the reference load to the tire and measuring the amount of lateral deflection with the standard load specified by JATMA applied to the tire. It is a value divided by the amount of deflection, and is represented by an index with the conventional example being 100. The larger the number, the higher the lateral stiffness of the tire.

  According to Table 1, it can be seen that the rigidity of the bead portion is increased and the durability is improved in any of the tires.

It is sectional drawing which shows the bead part of the pneumatic tire which concerns on this invention. It is an enlarged view near the bead core of the pneumatic tire concerning the present invention. It is an enlarged view near the bead core of the pneumatic tire concerning the present invention. It is an enlarged view near the bead core of the pneumatic tire concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 11 1st bead 12 1st bead core 13 1st bead filler 21 2nd bead 22 2nd bead core 23 2nd bead filler 31 1st carcass ply 32 2nd carcass ply R rim

Claims (5)

A first bead comprising a first bead core and a first bead filler; a first carcass ply that rolls up the first bead to form a toroidal shape;
A second bead core and a second bead filler; a second bead disposed outside the first bead in the width direction; and a second carcass ply disposed outside the first carcass ply and having a toroidal shape. A pneumatic tire,
The first carcass ply is wound and terminated only by winding up the first bead,
With the first bead mounted on a specified rim, the first bead has a cross-sectional height H1, the second bead has a cross-sectional height H2, and the end of the first carcass ply has a cross-sectional height H3. H1 <H2 < H3,
The second carcass ply is disposed on the outer side in the width direction of the winding portion of the first carcass ply without winding up the second bead,
An end portion of the second carcass ply terminates on an imaginary line L1 connecting the upper end of the first bead core and the upper end of the second bead core or radially inward from L1.   2. The pneumatic tire according to claim 1, wherein an end portion of the second carcass ply terminates on an imaginary line L <b> 2 connecting the lower end of the first bead core and the lower end of the second bead core or radially outward from L <b> 2. . The end portion of the second carcass ply is bent radially inward over an imaginary line L2 connecting the lower end of the first bead core and the lower end of the second bead core,
2. The pneumatic tire according to claim 1, wherein the pneumatic tire terminates on an imaginary line L <b> 3 passing through the center of the first bead core and parallel to the tire equatorial plane or on the outer side in the width direction from L <b> 3. The end of the second carcass ply is bent radially outward beyond a virtual line L2 connecting the lower end of the first bead core and the lower end of the second bead core,
2. The pneumatic tire according to claim 1, wherein the pneumatic tire terminates on an imaginary line L <b> 4 passing through the center of the second bead core and parallel to the tire equatorial plane or inward in the width direction from L <b> 4.   The sectional height H1 of the first bead is 10 to 15% of the sectional height H of the tire, the sectional height H2 of the second bead is 150 to 300% of H1, and the difference in sectional height H1. The pneumatic tire according to any one of claims 1 to 4, wherein -H2 and H2-H3 are 10 mm or more.

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