JP3229412B2 - Pneumatic radial tire for heavy loads - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic radial tire for improving air sealing (fitting) when re-inflating after running without deteriorating rim assembly.

[0002]

2. Description of the Related Art In general, pneumatic radial tires for heavy loads such as trucks and buses (hereinafter abbreviated as "heavy load tires"), when the tread wears out over its life due to long-term use, replace only the tread rubber. That is,
The tire body is re-used). Observing the bead portion of the heavy duty tire removed from the rim due to this retread, as shown in FIG.
The cross-sectional shape of the bead toe portion t, which was the shape shown by the solid line when new, is permanently deformed so as to increase in diameter as shown by the dotted line, and is permanently deformed so that the upper region S of the rim flange projects outside the tire. are doing.

For this reason, when the heavy load tire is assembled on the rim again, the adhesiveness (airtightness) of the permanently deformed bead toe portion to the rim is poor, so that air sealing cannot be performed without using an auxiliary jig. As a countermeasure for such a problem, there is a method of reducing the inner diameter of a portion where the bead portion is joined to the rim. However, in this case, there is a problem that fitting to the rim is not uniform in the circumferential direction. As another measure, there is a method of increasing the angle of the bead base to the tire rotation axis that is joined to the rim.However, this method not only deteriorates the rim assemblability, but also has a sharp bead toe portion, which increases rigidity. There was a problem that it fell and was cut off when assembling the rim.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heavy duty tire capable of improving the air sealing property without deteriorating the rim assembly of the tire.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, a bead core buried in a bead portion is formed in a polygonal cross section, and an inner surface of the bead core having a polygonal cross section is formed at substantially the same angle as a rim sheet. In a heavy-duty tire provided with an inclined linear area, the area corresponding to the bead core in the bead base of the bead portion is inclined with respect to the tire rotation axis, and the bead toe side area is more on the tire rotation axis than the bead core corresponding area. The distance from the bead heel side end of the bead core linear area to the bead core corresponding area of the bead base perpendicular to the linear area is set to g.
_1, when the distance drawn from the bead toe end to the bead base of the bead core corresponding region perpendicular to the straight line region and g _2, difference between the distance (g ₂ -g ₁₎ of the linear zone length L 0.50 ≧ (g ₂ −g ₁ ) /L≧0.20 and the length w of the bead base on the bead toe side relative to the total width W of the bead base in the tire rotation axis direction. W / W ≧ 0.20.

As described above, the diameter of the bead toe side forming the bead base of the bead portion is increased, so that the rim assemblability is improved, and the rigidity of the bead toe portion is increased, so that damage to the tow during rim assembling is prevented. Can be prevented. Also, in the bead-based bead core-compatible area,
Since the distance between the bead core and the straight area on the inner side of the bead is thicker on the bead toe side, the interference with the rim is increased on the bead toe side to improve the sealing performance (fitting performance), but the interference on the bead heel side Does not change, so that the problem of non-uniformity of fitting does not occur.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing an example of a bead portion of the tire of the present invention. In the bead portion B, the end of the carcass layer 2 is turned around the bead core 1 having a polygonal cross section from the inside to the outside of the tire, and two reinforcing layers 3 and 6 are arranged outside the end. Above the bead core 1, bead fillers 4 and 5 made of high hardness rubber are provided. The bead base 9 inclines the region 9c corresponding to the bead core 1 with respect to the tire rotation axis direction, forms a region 9t substantially parallel to the tire rotation axis on the bead toe 7 side, and forms an arc-shaped region on the bead heel 8 side. Region 9h.

[0008] The bead core 1 is wound with a plurality of steel wires 11 or steel strips, and has a hexagonal cross section. A straight area a that is inclined substantially the same as the rim sheet on which the tire is mounted is formed on the inner diameter side. In the above configuration, the linear area a on the inner diameter side of the bead core 1 and the bead core corresponding area 9 of the bead base 9
The distance from the bead heel 8 is thinner on the bead heel 8 side and thicker on the bead toe 7 side. That is, as shown in FIG. 2, the bead heel 8 in the bead core linear area a
The distance g ₁ measured perpendicularly to the straight area a from the side end and the distance g ₂ measured perpendicular to the straight area a from the end of the bead toe 7 are g ₂ > g ₁ and the difference (g) ₂ -g ₁₎ the ratio of the length L of the linear range a in (g ₂ -g ₁₎ / L 0.
It is set to be 20 to 0.50.

If this ratio is smaller than 0.20, it will be difficult to ensure the sealing performance when assembling the rim without a jig. On the other hand, if it is larger than 0.50, even if sealing at the time of re-assembly is possible, variations in fitting will occur in the circumferential direction, and the sealing performance will be impaired. That is, when looking at the deformation of the bead portion when the tire is used, as shown in FIG. 3, the bead core 1 is pulled in the direction of the arrow by the tension of the carcass, rotates the bead toe side around the bead heel side, and rotates the bead toe. Bead base 9 using restoring force (elastic modulus of bead core)
Is press-bonded to the rim R, so that air sealing properties can be obtained.
The configuration of g ₂ > g ₁ is achieved by increasing the distance g ₂ on the bead toe side where the bead core 1 has a large elongation.
Since the interference is increased, the fitting property (sealing property) when inflating again after running is improved.

The above-mentioned g ₁ and g ₂ are the lowermost wires 1
The length L is measured as the distance between the centers of the wires 11, 11 arranged on both outer sides. When the bead core is formed from a steel strip, g ₁ and g ₂ can be measured from the lower surface of the lowermost steel strip, and the length L can be measured as the distance between both ends.

Further, the bead toe region 9 of the bead base 9
t is formed to be parallel to the tire rotation axis direction over the length w, or to be a slope that is gentler than the slope of the bead core corresponding region 9c (a slope smaller than the tire rotation axis direction). By forming the bead toe region 9t having such an inclination, the inner diameter of the bead portion joined to the rim is increased, so that the rim assemblability can be improved.

The length w of the bead toe region 9t is w / w with respect to the total width W of the bead base 9 in the tire rotation axis direction.
W is set to 0.20 or more, preferably 0.20 to 0.40. By having such a sufficient width, the rigidity of the bead toe portion is improved, and it is possible to prevent toe breakage during rim assembly. The diameter D of the bead toe region 9t is preferably larger than the rim diameter × 0.96. The bead heel region 9h is formed in an arc shape with a radius r, and the range r is desirably 8 to 10 mm.

[0013]

【Example】

Example 1 The tire size was 11R22.5, the bead core structure was as shown in FIG. 1, the length L of the straight area a of the bead core was 12 mm, the total width W of the bead base was 32 mm, and the length w of the bead toe area was 8 mm (w / W 0.25), and the ratio (g ₂ −g ₁ ) / L is set to 0, 0.10, 0.18, 0.
Seven types of radial tires for heavy loads were manufactured, which were changed to 25, 0.35, 0.50 and 0.6.

With respect to these seven types of tires, the possibility of inflation at the time of re-assembly and the variation in fitting after inflation were evaluated by the following method, and the results shown in FIG. 4 were obtained. From FIG. 4, (g ₂ -g
₁ ) In the case of a tire having a value of / L of 0.20 or more, inflation was possible without using a jig when assembling the rim again. However, it can be seen that a tire exceeding 0.5 has a large variation in fitting in the tire circumferential direction.

[0015]How to evaluate inflatability when re-rimming
Law: 2 tires of size 11R22.5 14PR
Assemble on 2.5 × 7.50 rim, 7kgf / mm^Twosky of
Filled with air and attached to a truck with a nearly constant load, 70,000k
After traveling m, bleed air and then inflate
Was. In Fig. 4, the mark ● indicates inflation unless a jig is used.
○ means that it could not be done.
This means that inflation was possible.

Variation of fitting : In the evaluation of inflatability, the distance between the contact point between the bead heel portion of the tire and the rim flange and the rim check line is measured along the tire circumferential direction, and the maximum value and the minimum value are measured. The difference (mm) was expressed. Example 2 The point that the tire size is 11R22.5, the bead core structure is FIG. 1 and L is 12 mm are common, and the ratio (g ₂ −
g ₁ ) / L, W, and the ratio w / W were changed as shown in Table 1 to produce tires 1 and 2 of the present invention and comparative tires 1 and 2 respectively. Further, as a conventional tire, the linear region a of the bead core having the ratio (g ₂ −g ₁ ) / L of 0.1 and the ratio w / W of 0.063 is substantially parallel to the bead base portion. A tire was manufactured in which the bead core corresponding region of the bead base portion and the bead toe portion had substantially the same inclination. With respect to these five types of tires, the inflatability at the time of re-assembly was evaluated by the above method, and the toe breaking durability at the time of rim assembly was evaluated by the following method. Table 1 shows the results.

Toe breaking durability when assembling the rim : Three test tires were repeatedly assembled on the rim 10 times repeatedly, and the broken (cut) portions of the bead toe portion were visually counted. The larger the number, the more likely the bead toe portion is to be cut during rim assembly, and the lower the durability.

[0018] Table 1 shows that the tires 1 and 2 of the present invention have improved inflatability when re-assembled and improved toe breaking durability when assembled on the rim, as compared with the conventional tires.
It can be seen that, although the inflation property is improved, the tow breaking durability when the rim is assembled is deteriorated.

[0019]

According to the present invention, the diameter of the bead toe side forming the bead base of the bead portion is increased, so that the rim assembling property is improved, and the rigidity of the bead toe portion is increased. Breakage can also be prevented. Further, in the bead core corresponding region of the bead base, the distance between the bead core and the linear region on the radially inner side of the bead is increased toward the bead toe side, and the interference with the rim is increased, so that the sealing performance (fitting performance) can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a bead portion of the tire of the present invention.

FIG. 2 is an explanatory diagram showing a dimensional relationship of the bead portion.

FIG. 3 is a cross-sectional view showing a deformed state of a bead portion during internal pressure filling.

FIG. 4 is a graph showing the relationship between the ratio (g ₂ −g ₁ ) / L and the inflatability during re-rim assembly.

FIG. 5 is a cross-sectional view showing deformation of a bead portion of a conventional heavy duty tire.

[Explanation of symbols]

1 Bead core 7 Bead toe 8 Bead heel 9 Bead base 9c Bead core corresponding area 9t Bead toe area a Linear area

Claims (1)

(57) [Claims] 1. A heavy-duty pneumatic radial tire in which a bead core embedded in a bead portion is formed in a polygonal cross section, and a linear region inclined at substantially the same angle as a rim sheet is provided on the inner diameter side of the polygonal cross section bead core. While inclining the corresponding region of the bead base and the bead core with respect to the tire rotation axis,
The bead toe-side region is formed to be more gently inclined with respect to the tire rotation axis than the bead core corresponding region or formed in parallel with the tire rotation axis, and the bead is perpendicular to the linear region from the bead heel side end of the bead core linear region. When the distance lowered to the bead core corresponding region of the base is g ₁ and the distance lowered to the bead core corresponding region of the bead base from the bead toe side end perpendicular to the straight line region is g ₂ , the difference between the two distances (g
_2- g ₁ ) is set to 0.50 ≧ (g ₂ −g ₁ ) /L≧0.20 with respect to the length L of the linear region, and the length w of the bead toe side region of the bead base is set to: A heavy duty pneumatic radial tire in which w / W ≧ 0.20 with respect to the total width W of the bead base in the tire rotation axis direction.