JPH0640222A - Bead part structure of pneumatic tire - Google Patents

Abstract

PURPOSE:To embody the improvement of wheel uniformity so as to suppress RFV effectively. CONSTITUTION:A tire bead part 2 is provided with a swollen heel 9. The rubber hardness of the swollen heel 9 is to be 65 or harder in JIS hardness, and the number of stages in the bead part height direction of bead cores 5 embedded in the bead part 2 is to be not less than the number of cords disposed parallelly in the width direction of the bead part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention provides a tire with a rim, that is, a wheel with excellent uniformity.
Regarding the bead structure of pneumatic tires, especially JATMA, such as split rims, deep rims, wide deep rims, etc.
Rim whose standard is defined by etc. (hereinafter referred to as "standard rim")
By improving the uniformity of the assembled wheels, the radial runout (hereinafter referred to as "RRO") is reduced.
It effectively suppresses radial force variation (hereinafter referred to as "RFV").

[0002]

2. Description of the Related Art Conventionally, for the purpose of reducing the RFV of a wheel, the RFV of the tire itself is measured over the entire circumference thereof, and the position where the measured value becomes maximum is the outer peripheral runout of the rim on which the tire is mounted. It has been widely practiced to assemble the rim so as to match the smallest position of the rim.

[0003]

However, in recent years, the rim processing accuracy has been greatly improved, so that the RFV of the wheel cannot be effectively reduced even by the above-mentioned method, and rather, , RFV of the wheel,
Often, the difference between the maximum and minimum values was greater than a similar difference in the RFV of the tire itself.

This means that the RRO as a wheel does not become small even when a tire having a good RRO is mounted on a rim with high processing accuracy.
It is believed that the cause is eccentric mounting when assembling the tire rim. That is, in the conventional tire, when the tire is assembled to the rim, as illustrated in FIG.
A relatively large gap 25 is formed between the portion 24 and the portion 24, and the position and size of the gap 25 are variously changed in the tire circumferential direction.
It is considered to be a major factor in the deterioration of O.

Therefore, in order to reduce the variation of the gap 25 in the tire circumferential direction, in Japanese Patent Laid-Open No. 3-189201, RRO at the shoulder portion of the wheel is measured on the circumference and the value is large. Spacers are installed between the bead of the tire and the flange of the rim at the location, but this makes it necessary to reverse the rim assembly and the internal pressure filling operation, resulting in poor workability. In addition to
There has been a problem that a large external force acts on the wheel, which changes the relative position between the tire and the rim, and requires re-correction. The present invention has been made to solve the above problems of the prior art, and when assembling the tire to the rim, particularly between the tire bead portion and the rounded corner recess of the rim. The present invention provides a bead structure for a pneumatic tire, which is capable of concentrically mounting tires to improve the uniformity of the wheels and effectively reduce the RFV of the tires by preventing the occurrence of the gap.

[0006]

According to the bead structure of a pneumatic tire of the present invention, an inclined bead seat, a rounded corner recess successively extending outward in the width direction of the inclined bead seat, and an outwardly curved inward bend. A standard rim having a curved flange, in a pneumatic tire in which a bead portion of a tire is tightly fitted to the inclined bead sheet, in the bead portion,
Prior to contact between the curved flange of the rim and the outer surface of the bead portion facing the curved flange of the rim, a bulging heel is provided in close contact with the rounded corner concave portion of the rim over the entire circumference, and the rubber hardness of the bulging heel is JIS hardness. The number of stacked cords in the height direction of the bead portion of the bead core embedded in the bead portion is 65 degrees or more and is equal to or more than the number of parallel cords in the width direction of the bead portion.

Hereinafter, this will be described more specifically with reference to FIG. In the figure, 1 is a tire, 2 is a bead portion thereof, and 3 is a bead portion 2 of the tire 1.
Shows a standard rim for fitting. Reference numeral 4 denotes a sidewall portion of the tire, and reference numeral 5 denotes a bead core embedded in the bead portion 2. Here, the standard rim 3 is, for example, an inclined bead seat 6 inclined at an angle of 5 ° ± 1 °.
And a rounded corner concave portion 7 continuous to the outside in the width direction of the inclined bead sheet 6, and a curved flange 8 continuously curved outward to the outside thereof. And in this invention,
The bead portion 2 is provided with a bulging heel 9 that comes into close contact with the rounded corner concave portion 7 of the rim 3. The bulging margin d of the bulging heel 9 during vulcanization molding of the tire is a straight line 1 obtained by extending the inclined bead seat 6 to the rounded corner recess side within the widthwise cross section of the rim 3 as shown in the drawing. The curved flange 8 continuous with the corner round recessed portion 7 is contacted and passes through a base point Q on the bead portion, which is planned in the tire design, corresponding to an intersection P with a straight line m orthogonal to the central axis of the rim 3, Is defined with reference to a vertical line n extending from the tire center axis to the swelling margin d of 2 mm or more.

In such a bead portion 2, at least the bulging heel 9 is formed of hard rubber having a JIS hardness of 65 ° or more, and the bead core 5 embedded in the bead portion 2 has a high bead portion height. The number of stacked cords in the vertical direction is equal to or more than the number of parallel cords in the width direction of the bead portion.

[0009]

In general, the tire 1 has a bead portion having an appropriate tightening margin with respect to a rim diameter D defined by a diameter of a circle whose radius is the distance from the intersection point P of the straight line 1 and the straight line m to the rim center axis line. It is assigned to 2.

A tire 1 having such a bead portion 2
Of the bead portion 2 on the rim,
It is carried out by partially overcoming it around the curved flange 8 of the standard rim 3, and the subsequent assembly of the tire 1 is carried out by filling the tire with internal pressure until the specified internal pressure is reached. This is done by pushing the part 2 outward along the inclined bead seat 6 until the bead outer surface contacts the curved flange 8.

Referring to the progress of the rim assembly for the conventional tire shown in FIG. 3, the bead portion 21 has a higher degree of tight fitting as it moves outward on the inclined bead seat. Since the frictional resistance of the bead portion 21 that hinders this movement is not always uniform over the entire circumference, many portions of the outer surface of the bead portion first come into contact with the curved flange 24 of the rim 22,
This contact state varies depending on the circumferential position of the outer surface of the bead portion. Once such a contact state occurs, the gap between the outer surface of the bead portion and the rim 22
The air contained in 25 will limit the further outward movement of the bead portion 21 along the inclined bead seat by increasing its pressure, so that the radial position, size, etc. of the gap 25 are Due to the difference depending on the position in the tire circumferential direction, even if the tire itself is vulcanized and molded with sufficient uniformity, RRO as a wheel becomes large, and as a result, RFV becomes large.

On the other hand, according to the present invention, when the rim assembly as described above is advanced, first, the bulging heel 9 is
Adheres to the rounded corner recessed portion 7 of the rim 3 and then, under the compression deformation of the bulging heel 9, the outer surface of the bead portion comes into contact with the curved flange 8. Therefore, the above-mentioned between the outer surface of the bead portion and the rim is described. The occurrence of such a gap 25 is sufficiently prevented, and the tire 1
The center axis of the wheel will be easily and highly accurately aligned with the center axis of the standard rim 3, and therefore the RRO of the wheel can be reduced and the RFV can be effectively suppressed.

Here, the bulging margin d of the bulging heel 9 has a size sufficient to fill the above-mentioned gap 25, and in the case of a typical passenger car tire, it is preferable to be in the range of 2 mm to 4 mm.

Further, at least the bead portion has a rubber hardness of 65 degrees or more in JIS hardness at least in the bulging heel 9, so that the bulging heel 9 and thus the tire 1 can be firmly fixed to the corner rounded recess 7. Further, it is possible to advantageously lead the uniform contact of the bulging heel 9 with the rounded corner concave portion 7 over the entire circumference, but it is preferable that the hardness is up to 80 degrees.

By the way, the number of cords of the bead core 5 embedded in the bead portion 2 is naturally limited in relation to the cross-sectional area of the bead core 5 and the like. However, when the number of cords is constant, the bead portion height is high. By setting the number of stacked cords in the depth direction to be equal to or more than the number of parallel cords in the width direction of the bead portion, the high pressure contact area between the outer surface of the bead portion and the rounded corner recesses 7 and the curved flanges 8 is sufficiently widened, It further reduces the RRO of the wheels and ensures continuous suppression of RFV.

[0016]

[Examples] The effects on RRO (mm) and RFV (kgf) when the bulging amount of the bulging heel, the rubber hardness of the bulging heel, and the cord arrangement of the bead cord are changed will be described below. . A tubeless tire for passenger cars, the size of which is 205/65 R15, and the applicable rim is 15 × 6JJ. In a wheel, the bulging heel 9 has a rubber hardness of 70 degrees and the bead core 5 has a cord arrangement. 2, the bulge amount d of the bulge heel 9 was changed in the range of 0 mm to 4 mm with 5 rows and 5 columns. Table 1 shows the measured values of RRO and RFV at this time.

[0017]

[Table 1]

From Table 1, it is understood that both RRO and RFV are remarkably improved by setting the bulge amount d to 2.0 mm or more.

Further, in the above-mentioned place, the tire 1
RRO and RFV are shown when the swelling amount d of the swelling heel 9 is 2.0 mm, the bead arrangement is 5 steps and 5 rows, and the rubber hardness of the swelling heel 9 is changed in the range of 50 degrees to 80 degrees. It became as shown in 2.

[0020]

[Table 2]

From this, it is clear that RRO and RFV are particularly reduced at a rubber hardness of 65 degrees or more.

Further, the bulge amount d of the bulge heel 9 is 2.0 mm.
Table 3 shows the RRO and RFV when the JIS hardness of the bulging heel 9 is set to 70 degrees and the code arrangement of the bead core 5 is changed to 4 rows 6 rows, 5 rows 5 rows and 6 rows 4 rows. Became.

[0023]

[Table 3]

It is clear from Table 3 that the effect of improving RRO and RFV is great when the number of stages is equal to or more than the number of columns.

[0025]

As described above, according to the present invention, the conventional rim shape is not changed, and the rim assembling operation can be performed without any special consideration in the rim assembling operation. Accurate seating is performed, so the RRO of the wheel with the rim assembled
Can be reduced to effectively suppress RFV.
Moreover, here, by setting the JIS hardness of the bulging heel to 65 degrees or more, the bulging heel can be evenly and firmly fixed to the rounded corner recesses, and the bead arrangement of the bead core can be specified. This increases the high pressure contact area of the outer surface of the bead to the rim, and increases the RR of the wheel.
O, and by extension, further improve RFV,
V can be suppressed over a long period of time.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention before and after assembling a rim.

FIG. 2 is a diagram showing an example of a bead core code sequence.

FIG. 3 is a partial cross-sectional view showing a rim assembled state of a conventional tire.

[Explanation of symbols]

 1 Tire 2 Bead Part 3 Standard Rim 4 Sidewall Part 5 Bead Core 6 Inclined Bead Seat 7 Corner Rounded Recess 8 Curved Flange 9 Swelling Heel

Claims (1)

[Claims] 1. A standard rim having an inclined bead seat, a rounded corner recess that is sequentially connected to the outside in the width direction of the inclined bead seat, and a curved flange that bends outwardly. In a pneumatic tire in which a bead part is tightly fitted, in the bead part, prior to contact between the curved flange of the rim and the outer surface of the bead part opposite to the curved flange of the rim, the bead part is closely adhered to the rounded corner recess of the rim. Providing a swelling heel to
The rubber hardness of the swelled heel is 65 degrees or more in JIS hardness, and the number of stacked cords in the bead core in the height direction of the bead core is equal to or more than the number of parallel cords in the bead width direction. Bead structure of various pneumatic tires.