JPH11208224A - Pneumatic tubeless tire for heavy loads - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate rim assembly without catching on the rim flange, prevent the bead toe portions from breaking off, and improve air filling performance before and after running. SOLUTION: The bottom surface 5 of a bead portion directly below a bead core 1 on the longitudinal cross-section of a tire is composed of a non-protrusive arc 51 formed with a convex curvature. An angle α, forming a straight line L which connects a point of origin A on the side of the bead toe 31 of the arc 51 and a point of origin B on the side of the bead heal 41 and the rotational axis, forms an angle that strictly follows the rim. Assuming that the center point of the arc 51 where a vertical line bisecting the straight line L, which connects the point of origin A on the side of the bead toe 31 of the arc 51 and the point of origin B on the side of the bead head 41, intersects with the arc 51 is designated a point C, the point C which is then center point of the arc 51 is located within the range of the bead core maximum width W that falls vertical to the rotational axis of the tire from both ends of the bead core maximum width W.

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 tubeless tire, and more particularly to a heavy-duty pneumatic tubeless tire having improved rim assembly workability while improving air filling before and after running.

[0002]

2. Description of the Related Art Heavy duty tires, unlike consumer tires for passenger cars, are production goods, so that tube tires with low cost have been frequently used. In the case of a tube tire, since air was injected into a rubber tube in the tire, the workability of air filling was good. In the case of a heavy duty tube tire, the rim has a 5 ° taper angle. This is similar to a standard passenger car tubeless tire with a 5 ° taper angle with a hump. However, in the case of a heavy load tubeless tire, a rim shape having a taper angle of 15 ° different from these is used in order to prevent the bead from going over the flange due to high internal pressure filling.

[0003] Conventionally, there has been provided a heavy-load tubeless tire which is fitted to a rim of such a heavy-load tire.
For example, as shown in FIG. 2, a two-step tapered surface 6 is formed so that the bead bottom surface 6 in the meridian section of the tire is concave.
An air-fillable pneumatic tubeless tire having an air-filling property constituted of the tires 1 and 62 is provided. In the figure, 7 is a bead core, 8 is a bead toe, and 9 is a bead heel. Β is the angle of the bead taper 61 on the bead heel 9 side, γ is the angle of the bead taper 62 on the bead toe 8 side, E is the point of the bead taper 61 on the bead heel 9 side, F is the bead taper 61 on the bead heel 9 side and the bead toe 8 side. , 62 is a point of the bead taper 62 on the bead toe 8 side. W is the maximum width of the bead core.

[0004]

In the case of this kind of tire, since the bead bottom surface 6 has two-stage tapered surfaces 61 and 62 so as to be concave, as shown in FIG. Rim flange 11 with flat rim taper surface 10
When the rim is assembled to the rim 12 for a heavy-duty tire provided with a bead toe 8 having a small inner diameter, the bead taper 61 on the bead heel 9 contacts the rim taper 10 surface.
Since the bead taper 62 on the side also contacts the rim taper surface 10, the air filling property before and after traveling is considered to be good.

However, in the case of this tire, FIGS.
As shown in the figure, the bead tapers 61, 6
When the tip of the rim flange 11 is caught by the second concave portion 63 and the rim assembling is continued by expanding the annular bead core from the inside in this state, a contraction effect of the hoop (HOOP) tension occurs, and the concave portions 6 in the bead tapers 61 and 62 are generated.
3 bites increase, and rim assembly becomes very difficult.
In addition, the bead toe portion 8 may be broken due to excessive force applied by the rim assembly, and when the tire is run after the rim assembly, moisture may permeate through the bead toe portion 8 and the steel ply cord may be broken. .

An object of the present invention is to provide a heavy-duty pneumatic tubeless tire that can be easily assembled on a rim without being caught on a rim flange, prevents chipping of a bead toe portion, and improves air filling before and after traveling. .

[0007]

As a result of intensive studies to solve the above-mentioned problems, the present invention provides a non-projecting arc by forming a bottom surface of a bead portion immediately below a bead core in a meridional section of a tire with a convex curvature. An angle α between a straight line connecting the start point A on the bead toe side of the arc and the start point B on the bead heel side and the tire rotation axis is an angle that is in close contact with the rim, and the start point A on the bead toe side of the arc is If the center point of the arc at which the perpendicular bisector of the straight line connecting the two ends of the starting point B and the bead heel side intersects the arc is point C, the bead core which is lowered perpendicularly to the tire rotation axis from both ends of the maximum width of the bead core We have developed a heavy duty pneumatic tubeless tire in which the center point C of the arc is located within a large range.

Accordingly, in the tire of the present invention, the whole or a part of the bottom surface of the bead portion immediately below the bead core in the meridian cross section of the tire is formed in a non-projecting shape with a convex curvature to form a so-called gentle arc. The rim flange does not get caught and bite when the rim is assembled.

In addition, since the angle α between the straight line connecting the start point A on the bead toe side and the start point B on the bead heel side of the arc and the rotation axis of the tire is set to the angle that is in close contact with the rim, Once the tip of the rim flange spreads the bead's annular bead core from the inside, it once overcomes the non-protruding arc that constitutes the bead bottom surface against the contraction effect of the hoop (HOOP) tension generated.
The rim can be easily assembled by the contraction force of the above hoop (HOOP) tension, and the bead bottom surface is in close contact with the tapered surface of the rim flange on the circular arc surface, and the sealing performance is excellently exhibited by the contraction force of the above hoop (HOOP) tension I do.

In addition, when the center point of the arc at which the perpendicular bisector of the straight line connecting both ends of the bead toe side start point A and the bead heel side start point B intersects with the arc is point C, the bead core Since the point C, which is the center point of the arc, is located within the range of the maximum width of the bead core dropped vertically from both ends of the tire perpendicularly to the tire rotation axis, the center point of the seal is located immediately below the bead core with the least deformation during traveling. Because it is located, air filling properties are good even after traveling.

[0011]

FIG. 1 is an enlarged sectional view of a main part of a bead portion showing an embodiment of a heavy-load pneumatic tubeless tire according to the present invention.

In FIG. 1, reference numeral 1 denotes a bead core, reference numeral 2 denotes a bead base portion showing a lower region of the bead core 1, reference numeral 3 denotes a bead toe portion forming one side of the bead base portion 2, and reference numeral 4 denotes a bead base portion on the other side. It is a bead heel part to constitute. 31 is a bead toe and 41 is a bead heel. Reference numeral 5 denotes a bottom surface of the bead portion, that is, a bottom surface of the bead base portion 2.

In the tire of the present embodiment, as shown in the figure, the bead bottom surface 5 immediately below the bead core 1 in the tire meridian section is formed with a convex curvature to form a smooth non-projecting arc 51. The distance between a straight line L (virtual straight line) connecting both ends of the start point A on the bead toe 31 side and the start point B on the bead heel 41 side exceeds the maximum width W of the bead core and forms the bead portion bottom surface 5. And the arc 51
An angle α formed between a straight line L connecting both ends of the start point A on the bead toe 31 side and the start point B on the bead heel 41 side and the tire rotation axis is an angle that makes close contact with the rim. Therefore,
This is different from the conventional tire having a concave two-step tapered surface in that the center of the seal is located at the center position of the circular arc 51 and substantially the entire bead bottom surface 5 forming the circular arc has sealing properties. It is also conceivable that the conventional two-stage tapered surface is made into a convex two-stage tapered surface. In this case, if the angle of one tapered surface is set to an angle close to the rim, the seal is formed on the one tapered surface. As a result, the angle of the other tapered surface is in a non-contact state, the contact area of the bottom surface of the bead portion is reduced, and it is not always preferable in terms of stable fitting (rim fitting) during running.
Further, the rim assembling operation is extremely easy as compared with a tire in which the bead bottom surface 5 is formed in a protruding arc.

Specifically, it is preferable that the angle α is not less than the angle of the rim taper and not more than 30 °. When the angle α exceeds 30 °, it is difficult to assemble the rim with a tire in which the bead bottom surface 5 has a convex arc. If the angle α is smaller than the angle of the rim taper, the rim can be easily assembled, but the air filling property is reduced.

In the case of the tire of this embodiment, as shown in the figure, a perpendicular bisector of a straight line L connecting both ends of the starting point A on the bead toe 31 side and the starting point B on the bead heel 41 side of the arc 51 is the arc 51. When the center point of the arc 51 intersecting with the point C is point C, the point C which is the center point of the arc 51 is located within the range of the maximum width W of the bead core lowered perpendicularly to the tire rotation axis from both ends of the maximum width W of the bead core. doing. Therefore, the center point of the seal is located immediately below the bead core 1 with the least amount of deformation during traveling, so that the air filling property is good even after traveling.

The tire of the present embodiment is replaced with the tire shown in FIGS.
When the rim is mounted on a rim for a heavy duty tire having a rim flange having a flat rim taper surface on both sides as shown in (1), the front end of the rim flange is not caught and bitten by the bottom surface of the bead portion. In addition, during the rim assembly process, if the tip of the rim flange spreads over the bead's annular bead core from the inside, it will overcome the arc of the bottom of the bead once it resists the contraction effect of the hoop tension generated by the hoop (HOOP) tension. (HOOP) The rim can be easily assembled by the contraction force of the tension, and the hoop (HOOP)
Due to the contraction force of the tension, the bottom surface of the bead portion comes into close contact with the tapered surface of the rim flange on the circular arc surface, so that the sealing performance is excellently exhibited.

The arc on the bottom surface of the bead portion is particularly limited as long as it is formed on all or a part of the bottom surface of the bead portion so that the bottom surface of the bead portion is formed in a non-projecting shape with a gentle convex curvature. It is not something to be done. Further, a plurality of arcs may be formed on the bottom surface of the bead portion. However, if the curvature of the arc on the bottom surface of the bead portion is too large, the rim assembly is good, but the rim assembly is not much different from the planar configuration. As a result, the air seal deteriorates, which is not preferable as a heavy load tubeless tire. on the other hand,
If the arc at the bottom of the bead is too small, it will be a kind of protrusion even if the air filling property is good, and it will be very difficult to get over this protrusion with respect to the rim flange, and the rim assembly will be more difficult than the conventional tire . Considering the radius of curvature of the arc on the bottom surface of a suitable bead portion,
00 mm is preferable, and among them, it has been found that it is optimal to set the range to 80 to 200 mm. When the radius of curvature of the arc is less than 30 mm, it is difficult to assemble the rim even if the air seal is good. If the radius of curvature of the arc exceeds 200 mm, the air seal deteriorates. Also, even within the above-mentioned range of curvature, if the distance between the start point A on the bead toe side and the start point B on the bead heel side of the arc is too small, the arc becomes a so-called protruding shape and, as described above, on the rim Since assembling becomes difficult, it is important to use a bead bottom surface that forms a non-projecting arc. In this sense, it is important to define both ends of the start point A on the bead toe side and the start point B on the bead heel side of the arc so that the optimal arc on the bead bottom surface extends over almost the entire bead bottom surface as much as possible. Specifically, the starting point A on the bead toe side and the starting point B on the bead heel side of the arc
Is desirably designed so that the distance of a straight line connecting both ends thereof exceeds the maximum width W of the bead core. However, in the present invention, the starting point A on the bead toe side of the arc is
This applies even if the distance between the straight line connecting both ends of the starting point B on the bead heel side does not exceed the bead core maximum width W. Also, as described above, a plurality of arcs may be formed on the bottom surface of the bead portion immediately below the bead core in the meridian section of the tire.
In such a case, if the center point of the arc at which the perpendicular bisector of the straight line connecting the start point A on the bead toe side and the start point B on the bead heel side of each arc intersects the arc is point C, the maximum width of the bead core The point C, which is the center point of each arc, may be located within the range of the maximum width of the bead core vertically lowered from both ends of the tire rotation axis.

In the tire of the present invention, the bead toe inner diameter d is 95.0 to 97.0 of the nominal diameter D (that is, the nominal rim diameter).
% Is preferable. If the bead toe inner diameter d is designed to exceed 97.0% of the nominal diameter D, the bead toe does not come into contact with the rim taper portion, so that it is not preferable because stable air filling properties cannot be secured. If the bead toe inner diameter d is less than 95.0% of the nominal diameter D, rim assembly work becomes difficult.

The heavy duty tire to which the present invention is applied means a series tire having a tire diameter of 17.5 to 24.5. Therefore, the various numerical values specified in the present invention are numerical values applied to tires having the above-described common diameter range.

[0020]

FIG. 1 shows a tire size 11R under the following conditions.
A 22.5 14PR heavy load tubeless tire was prototyped, and the air filling property and rim assembling workability of a new tire before running and a used tire after running were evaluated, respectively.

(Example tire) Angle α: 20 ° Curvature radius of arc: 100 mm Bead toe inner diameter d: 96% of nominal diameter D Bead core maximum width W: 18 mm Distance between bead toe and bead heel: 26 mm C point: Bead core maximum width W 2mm from the center position to the bead toe side Point A: 16mm from the center position of the bead core maximum width W to the bead toe side B point: 10mm from the center position of the bead core maximum width W to the bead heel side

(Comparative tire) For comparison, a conventional tire was also evaluated as a comparative tire. The comparative tire is the tire shown in FIG. 2 and is as follows. Angle of the bead taper on the bead heel side: 19 ° Angle of the bead taper on the bead toe side γ: 29 ° Point of the bead taper on the bead heel side E: 13 mm from the center position of the maximum width W of the bead core to the bead heel side and the bead on the bead heel side and the bead toe side Point of intersection F of taper: 2 mm on the bead toe side from the center position of the bead core maximum width W Point of bead taper on the bead toe side G: 16 mm on the bead toe side from the center position of the bead core maximum width W

The conditions of the test tire are as follows: internal pressure: 900 kP
a, Load: JATMA 88%, running speed 80
Km / h, mileage 35,000 km, rim 22.5 ×
7.50 was used.

[0024] The air-filling property of the two types of tires, a new one assembled on a rim and a tire after running under the above conditions, was changed from a state in which insects were not inserted into the valve in a vertical position, with only an original air pressure of 7.0 kg / cm ^2. It was checked whether air filling was possible. ○
Required no auxiliary work for air filling. × required auxiliary work for air filling.

The rim assembling workability is performed by a lever mechanism used in a general market. In addition, since a truck tire usually requires 6 to 8 rim assembling operations, an evaluation was made based on the operator's feeling while taking this fact into account. ○ is 6 ~
A level at which continuous operation of eight lines is considered to be possible, and a level at which continuous operation of six to eight lines is considered to be difficult.

Table 1 shows the evaluation results of the air filling property and the rim assembling workability of each tire of the example and the comparative example at the time of a new article and after running.

[0027]

[Table 1]

As shown in Table 1, the comparative example tire had good air filling properties when new, but poor rim assembly workability, and chipping occurred in the bead toe portion due to excessive force applied during rim assembly. . When the vehicle was run using this tire, the air filling property deteriorated. On the other hand, the tires of the examples of the present invention had good air filling properties and rim assembly workability both when new and after running.

[0029]

According to the present invention, the whole or a part of the bottom surface of the bead portion immediately below the bead core in the meridional section of the tire is formed as a non-projecting arc by forming a convex curvature, and the starting point of the arc on the bead toe side. The angle α between the straight line connecting A and both ends of the start point B on the bead heel side and the rotation axis of the tire is an angle that is in close contact with the rim, and both ends of the start point A on the bead toe side and the start point B on the bead heel side of the arc. When the center point of the arc at which the perpendicular bisector of the straight line intersects the arc is point C, the center of the arc is within the range of the maximum width of the bead core vertically lowered from both ends of the maximum width of the bead core to the tire rotation axis. Since this is a heavy-load pneumatic tubeless tire where point C is located, it is more likely to be caught by the rim flange than a conventional tire in which the bottom surface of the bead portion has a concave two-step tapered surface. Easily can be rim to Razz, after new time and traveling even rim workability is improved.

Further, chipping and cracking of the bead toe portion can be prevented. Further, especially for a rim flange for a heavy duty tire having a flat rim taper surface on both sides, the bead portion bottom surface is centered on the arc of the bead bottom surface. , A stable fit (rim fit) is exerted between the bead portion bottom surface and the rim taper surface before and after traveling.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part of a bead portion showing an embodiment of a heavy-load pneumatic tubeless tire according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of a bead portion showing an example of a conventional pneumatic tubeless tire for heavy load.

FIG. 3 is a schematic sectional view showing a rim assembly state of the tire shown in FIG. 2;

FIG. 4 is an enlarged schematic cross-sectional view of a main part showing a rim assembly state in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core 2 Bead base 3 Bead toe 31 Bead toe 4 Bead heel 41 Bead heel 5 Bead bottom 51 Arc

Claims (5)

[Claims] 1. A bead bottom surface immediately below a bead core in a meridional cross section of a tire is formed as a non-projecting circular arc with a convex curvature, and a starting point A on the bead toe side and a starting point B on the bead heel side of the circular arc. The angle α between the straight line connecting both ends and the tire rotation axis is set as the angle to be in close contact with the rim, and the perpendicular bisector of the straight line connecting both ends of the start point A on the bead toe side and the start point B on the bead heel side of the arc If the center point of the arc that intersects the arc is point C, point C, which is the center point of the arc, is located within the range of the bead core maximum width vertically lowered from both ends of the bead core maximum width to the tire rotation axis. Heavy duty pneumatic tubeless tires. 2. The pneumatic tubeless tire for heavy loads according to claim 1, wherein the radius of curvature of the arc at the bottom of the bead portion is 30 to 1000 mm. 3. The pneumatic tubeless tire for heavy loads according to claim 1, wherein a straight line connecting both ends of the start point A on the bead toe side and the start point B on the bead heel side of the arc exceeds the maximum width W of the bead core. 4. An angle α between a straight line connecting both ends of a bead toe side start point A and a bead heel side start point B of a circular arc on the bead bottom surface and the tire rotation axis is in a range of not less than 30 ° and not more than a rim taper angle. The pneumatic tubeless tire for heavy loads according to claim 1 or 2. 5. The bead toe inner diameter d is set to 9 of the nominal diameter D.
The pneumatic tubeless tire for heavy loads according to any one of claims 1 to 4, wherein the content is 5.0 to 97.0%.