JPH1191322A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve maneuvering stability and air sealing ability without using hard rubber composition. SOLUTION: In this tire, a bead base 6 is constituted with plural taper angles tilting to an axial line A in the tire rotational axis direction, taper angle is maximum in the region F from a position P of 1/3-2/3 of a bead base width W in the view from a bead heel H to a bead toe T, and the maximum taper angle α is in a range of 30-40 deg.. In this case, JIS-A hardness of rubber composition composing a bead toe part 7 is in a range of 50-80.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having an improved fit to a rim, and more particularly, to an improvement in steering stability and air sealability without using a hard rubber composition. Related to pneumatic tires.

[0002]

2. Description of the Related Art In a pneumatic tire, a bead base has a function of fixing the tire to a rim while ensuring air sealing. The bead base is generally composed of one or a plurality of taper angles inclined with respect to the axis of the tire rotation axis connecting the left and right bead heels, and the maximum taper angle is set to about 20 °.

[0003] Further, by disposing a hard rubber composition in a bead toe portion with respect to the bead base configured as described above, it is possible to enhance the fitting force of the bead portion to the rim to improve the steering stability. Is being done. However, when disposing the hard rubber composition in the bead toe portion, it is necessary to add a complicated and extra step for inserting the hard rubber composition into the bead toe portion in the tire molding step, and the material of the hard rubber composition There is a problem that the cost increases the manufacturing cost of the tire.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire capable of improving steering stability and air sealability without using a hard rubber composition.

[0005]

A pneumatic tire according to the present invention for achieving the above object comprises a bead base having a plurality of taper angles inclined with respect to the tire rotation axis direction, and the bead base is viewed from the bead heel. 1/3 to 2 of width
The taper angle is maximized in the region from the position of / 3 to the bead toe, the maximum taper angle is in the range of 30 to 40 °, and the J of the rubber composition constituting the bead toe portion is set.
The IS-A hardness is in the range of 50 to 80.

[0006] As described above, the bead base is constituted by a plurality of taper angles inclined with respect to the tire rotation axis direction, and the maximum taper angle is 30 to 40 ° in a specific region on the bead toe side.
Even if the bead toe portion is made of a rubber composition having a JIS-A hardness of 50 to 80, the steering stability is improved because the bead heel fits deep into the rim. Since the bead base is strongly pressed against the rim by being compressed, the contact area is increased and the air sealing property is improved.

Further, according to the present invention, it is not necessary to use a hard rubber composition for improving the steering stability, so that a complicated and extra work for inserting the hard rubber composition into the bead toe portion in the tire molding process is required. The number of steps can be reduced, and material costs can be reduced. In the present invention, the bead toe portion means a portion inside the bead core in the tire rotation axis direction, having the bead toe as a lower end and an upper end at a position of 10 to 20 mm in the tire radial direction from the outer end of the bead core. The JIS-A hardness of the rubber composition was measured at a temperature of 20 ° C.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 illustrates a pneumatic tire according to an embodiment of the present invention, and FIG. 2 illustrates a bead portion thereof in an enlarged manner. In the figure, a carcass layer 2 is mounted between a pair of left and right bead portions 1, 1, and both end portions in the tire width direction of the carcass layer 2 are wound around a bead core 3 from the inside of the tire to the outside. Also, the carcass layer 2 in the tread portion 4
A plurality of belt layers 5 composed of a plurality of reinforcing cords inclined with respect to the tire circumferential direction are arranged outside the tire so that the reinforcing cords intersect each other between the layers.

The bead base 6 has left and right bead heels H.
And a plurality of taper angles inclined with respect to the axis A in the tire rotation axis direction. This bead base 6
Is maximum in a region F from a position P of 1/3 to 2/3 of the bead base width W from the bead heel H to the bead toe T. The maximum taper angle α in the region F is set in a range of 30 to 40 °.

On the other hand, in a region on the bead heel side of the position P, the taper angle β is set in a range of 0 to 15 °. As described above, the bead base 6 may be configured with two or more steps of taper angles. The rising angle γ of the bead portion 1 from the bead heel H to the rim cushion side is 90 ° with respect to the axis A in the tire rotation axis direction.
It is set to ± 5 °.

In the bead portion 1, a bead toe portion 7 located near the bead core 3 inside the tire from the carcass layer 2
Is composed of a rubber composition having a JIS-A hardness of 50 to 80. As the rubber composition forming the bead toe portion 6, for example, the same rubber composition as the inner liner rubber can be used, and it is not necessary to use a hard rubber composition having a JIS-A hardness of more than 80.

As described above, the bead base 6 is constituted by a plurality of taper angles inclined with respect to the tire rotation axis direction.
1/3 to 2 of bead base width W viewed from bead heel H
By setting the taper angle to the maximum in the region F from the position P of / 3 to the bead toe T and setting the maximum taper angle α in the range of 30 to 40 °, for example, the tire is mounted on a rim having a rim base with a taper angle of 5 °. When mounted, the bead heel H fits all the way into the rim to improve steering stability, and the bead toe portion 7 is compressed to strongly press the bead base 6 against the rim, increasing the contact area. Air sealability is improved.

As described above, the bead toe portion 7 is
Even if it is composed of a rubber composition having an SA hardness of 50 to 80, the steering stability can be improved. Therefore, a hard rubber composition having a JIS-A hardness of more than 80 as in the prior art is used for the bead toe portion 7. It is not necessary to dispose, and a complicated process for inserting the hard rubber composition into the bead toe portion 7 in the tire molding process can be reduced, and the material cost can be reduced.

In the present invention, it is necessary to maximize the taper angle in a region F from a position P of 1/3 to 2/3 of the bead base width W to the bead toe T as viewed from the bead heel H. If this position P is less than 1/3 of the bead base width W when viewed from the bead heel H, the bead toe portion 7 becomes excessively large and the rim assemblability decreases, and conversely, 2/3 of the bead base width W.
If it exceeds, the compressing action of the bead toe portion 7 at the time of assembling the rim becomes small.

The maximum taper angle α of the bead base 6
Is in the range of 30 to 40 °, more preferably 30 to 36 °. If the maximum taper angle α is less than 30 °, the bead toe portion 7 cannot be compressed when the rim is assembled,
Conversely, if the angle exceeds 40 °, the rim assemblability of the bead toe portion 7 is reduced. Further, the rising angle γ of the bead portion 1 from the bead heel H to the rim cushion side is preferably set to 90 ± 5 ° with respect to the axis in the tire rotation axis direction. By making the rising angle γ close to 90 ° in this manner, the fitting property of the bead portion 1 to the rim flange becomes good with respect to the maximum taper angle α of the bead base 6.

[0016]

EXAMPLES Conventional tires 1 and 2 having the following structure and a tire of the present invention were manufactured with the same tire size as 195 / 55R15. Conventional tire 1 As shown in FIG. 3, the bead base 6 is constituted by a two-step taper angle inclined with respect to the axis A in the tire rotation axis direction, and as viewed from the bead heel H, 2/3 of the bead base width W.
The taper angle α in the region F from the position to the bead toe T is 20 °, and the taper angle β on the bead heel side is 1
At 0 °, the rubber composition constituting the bead toe portion 7 is made common with the inner liner rubber, and the JIS-A
The hardness was set to 60. The rising angle γ of the bead portion 1 from the bead heel H toward the rim cushion was set to 90 ° with respect to the axis A in the tire rotation axis direction.

The tire composition of the conventional tire 2 was the same as that of the conventional tire 1 except that the JIS-A hardness of the rubber composition constituting the bead toe portion 7 was 90 and the rubber composition was inserted separately from the inner liner rubber. As shown in FIG. 2 of the present invention tire , the bead base 6 has a two-step taper angle inclined with respect to the axis A in the tire rotation axis direction, and is 2/3 of the bead base width W viewed from the bead heel H.
The taper angle α in the region F from the position of the to the bead toe T is 35 °, and the taper angle β on the bead heel side is 1
At 0 °, the rubber composition constituting the bead toe portion 7 is made common with the inner liner rubber, and the JIS-A
The hardness was set to 60. The rising angle γ of the bead portion 1 from the bead heel H toward the rim cushion was set to 90 ° with respect to the axis A in the tire rotation axis direction.

The test tires were evaluated for steering stability, fitting force and air sealability by the following test methods.
The results are shown in Table 1. Driving stability: Each test tire is mounted on a rim with a rim size of 15 × 6JJ and mounted on a passenger car, and the air pressure is 200 kP.
As a, the steering stability was evaluated by performing a feeling test with five test drivers at the circuit. The evaluation results were obtained by calculating an average evaluation value by five test drivers, and expressed as an index with the conventional tire 1 being 100. The larger the index value, the better the steering stability.

Fitting force: Each test tire was rim size 15 ×
The fitting force was measured by a Hoffman fitting measuring device after assembling to a 6JJ rim. The evaluation results were indicated by an index with the conventional tire 1 being 100. The larger the index value, the higher the fitting force. Air sealability: Each test tire is rim size 15 × 6JJ
7 rim with an initial air pressure of 2.3 kPa
After 2 hours, the air pressure was measured to evaluate the degree of air leakage. The evaluation results were indicated by an index with the conventional tire 1 being 100. The larger the index value, the better the air sealing property.

[0020]

As is clear from Table 1, the tire of the present invention has a higher fitting force, better steering stability and better air sealability than the conventional tire 1. Also,
In the conventional tire 2, the hard rubber composition was arranged in the bead toe portion, so each performance was excellent as in the tire of the present invention, but the hard rubber composition was inserted in the bead toe portion separately from the attachment of the inner liner rubber during tire molding. In addition, a hard rubber composition has required a complicated process, and the material cost has increased.

[0022]

As described above, according to the present invention, the bead base is constituted by a plurality of taper angles inclined with respect to the tire rotation axis direction, and is 1/3 to 2/2 of the width of the bead base as viewed from the bead heel. The bead toe portion is made of a rubber composition having a JIS-A hardness of 50 to 80 by maximizing the taper angle in a region from the position 3 to the bead toe and setting the maximum taper angle in a range of 30 to 40 °. Even so, the bead heel fits deep into the rim, so that steering stability can be improved. In addition, the bead toe portion is compressed, and the bead base is strongly pressed against the rim, so that air sealing can be improved. .

Further, according to the present invention, it is not necessary to use a hard rubber composition for improving the steering stability, so that a complicated and extra work for inserting the hard rubber composition into the bead toe portion in the tire molding process is required. The number of steps can be reduced, and material costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a meridian half sectional view illustrating a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a bead part of FIG. 1;

FIG. 3 is a sectional view showing a bead portion of a conventional tire.

[Explanation of symbols]

 Reference Signs List 1 Bead portion 2 Carcass layer 3 Bead core 6 Bead base 7 Bead toe portion A Axis line in tire rotation axis direction H Bead heel W Bead base width T Bead toe α Maximum taper angle

Claims (1)

[Claims] 1. A bead base comprising a plurality of taper angles inclined with respect to a tire rotation axis direction, wherein said taper is formed in a region from a position of 1/3 to 2/3 of a bead base width from a bead heel to a bead toe. The angle is maximized, the maximum taper angle is in the range of 30 to 40 °, and the JIS-A hardness of the rubber composition constituting the bead toe portion is 5
A pneumatic tire in the range of 0 to 80.