JP7298240B2 - pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire having beads.

Patent Literature 1 listed below describes a pneumatic tire in which the bead heel portion of the bead portion is chamfered linearly and at a predetermined angle.

Japanese Patent No. 4415460

In recent years, there has been a demand for a pneumatic tire that achieves uniform fitting with a rim. In particular, it is desired that the fitting pressure between the bead portion and the rim of a pneumatic tire is constant in the tire circumferential direction, and such a tire is said to have good circumferentially uniform fitting performance. . A pneumatic tire with good circumferential uniform fitting performance has the advantage of, for example, a small radial force variation (hereinafter sometimes simply referred to as "RFV") and excellent tire uniformity when mounted on a rim.

SUMMARY OF THE INVENTION The present invention has been made in view of the circumstances as described above, and a main object of the present invention is to provide a pneumatic tire capable of improving uniform fitting performance on the circumference.

The present invention is a pneumatic tire having a pair of bead portions, wherein each of the pair of bead portions includes a bead base surface extending axially outward from the bead toe and a tire radially extending portion so as to contact the flange portion of the rim. and a bead heel surface forming a corner portion between the bead base surface and the bead flange surface, wherein in a cross section of the bead portion, the bead heel surface has a major radius of curvature with a large radius of curvature. and a sub-portion having a radius of curvature smaller than that of the main portion, and the main portion is connected to the bead base surface or the bead flange surface via the sub-portion.

In the pneumatic tire according to the present invention, the bead heel surface is composed of the main portion, a first sub-portion connected to the bead base surface side of the main portion, and a second sub-portion connected to the bead flange surface side of the main portion. It is desirable to consist of parts.

In the pneumatic tire according to the present invention, it is desirable that the radius of curvature of the main portion is 9 mm or more.

In the pneumatic tire according to the present invention, it is desirable that the secondary portion has a radius of curvature of 3 to 7 mm.

In the pneumatic tire according to the present invention, the bead base surface has a base outer portion connected to the bead heel surface, and the base outer portion extends linearly in the cross section of the bead portion. is desirable.

In the pneumatic tire according to the present invention, it is desirable that the length of the base outer portion is 3 mm or more.

In the pneumatic tire according to the present invention, the bead flange surface has a flange inner portion connected to the bead heel surface, and the flange inner portion extends linearly in the cross section of the bead portion. is desirable.

In the pneumatic tire according to the present invention, it is desirable that the inner portion of the flange has a length of 3 mm or more.

In the pneumatic tire according to the present invention, the bead base surface has a base outer portion connected to the bead heel surface, and a first imaginary line extending the base outer portion axially outward; The length in the tire axial direction between the intersection of the second imaginary line extending radially inward of the flange inner portion and the axially outer end of the base outer portion is 4.5 to 7.5 mm. is desirable.

In the pneumatic tire according to the present invention, the bead base surface has a base outer portion connected to the bead heel surface, and a first imaginary line extending the base outer portion axially outward; The length in the tire radial direction between the intersection of the second imaginary line extending radially inward of the flange inner portion and the radially inner end of the flange inner portion in the tire radial direction is 4.5 to 7.5 mm. is desirable.

In the pneumatic tire according to the present invention, the bead heel surface includes a second sub-portion continuous with the bead flange surface side of the main portion, and the main portion or the second sub-portion protrudes in the tire axial direction. A protrusion is preferably provided.

In the pneumatic tire according to the present invention, it is desirable that the convex portion is continuous in the tire circumferential direction.

In the pneumatic tire according to the present invention, it is desirable that the width of the protrusion perpendicular to the longitudinal direction is 1.5 mm or less.

In the pneumatic tire according to the present invention, it is desirable that the projection height of the projection is 1.0 mm or less.

In the pneumatic tire according to the present invention, it is desirable that the pneumatic tire is for passenger cars.

In the pneumatic tire of the present invention, in the cross section of the bead portion, the bead heel surface includes a main portion and a sub-portion having a smaller radius of curvature than the main portion, and the main portion passes through the sub-portion, Contiguous with the bead base surface or bead flange surface.

The inventors conducted various studies on the cause of the deterioration of the circumferentially uniform fit of the tire. In general, in the rim assembling process of mounting a tire on a rim, first, the bead portion is placed on the rim seat surface of the rim, then the bead portion gradually moves outward in the tire axial direction, and finally, the bead portion moves to the rim flange. is completed by contacting the Here, if the radius of curvature of the bead heel surface is small, the bead heel surface is sharpened, and in the process of assembling the rim, it may fit with the rim locally with a large pressure at some point in the tire circumferential direction. This prevents subsequent movement of the bead portion and, in turn, prevents the fitting pressure between the bead portion and the rim from becoming constant in the tire circumferential direction.

In the present invention, since the main portion of the bead heel surface has a relatively large radius of curvature on the bead heel surface, local large fitting pressure with the rim is suppressed when the bead heel surface is assembled with the rim. On the other hand, if the main portion having a large radius of curvature is provided on the bead heel surface, the bead base surface and the bead flange surface tend to be relatively small. Eliminate points. That is, it is possible to sufficiently maintain the contact length between the bead base surface or the bead flange surface and the rim, thereby suppressing an increase in fitting pressure.

Therefore, in the pneumatic tire of the present invention, the fitting pressure between the bead portion and the rim can be made uniform over the tire circumferential direction.

1 is a cross-sectional view showing an embodiment of a pneumatic tire of the present invention; FIG. FIG. 2 is an enlarged view of the bead portion of FIG. 1; 3 is an enlarged view of the bead heel surface of FIG. 2; FIG. (a), (b) is sectional drawing of the bead part of other embodiment. Furthermore, it is sectional drawing of the bead part of other embodiment. Furthermore, it is sectional drawing of the bead part of other embodiment.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a cross section (tire meridian Cross section). INDUSTRIAL APPLICABILITY The present invention is suitably used for various tires 1 for motorcycles, heavy loads, etc., in addition to the tire 1 for passenger cars. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the tire 1 are values measured in this free state.

As shown in FIG. 1, in this embodiment, the tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead cores 5 of the bead portions 4 on both sides, and A belt layer 7 arranged inside the tread portion 2 is provided. For the carcass 6 and the belt layer 7, known modes are appropriately employed. A rim R (shown in FIG. 2) is attached to the bead portion 4 .

FIG. 2 is an enlarged view of the bead portion 4 of FIG. As shown in FIG. 2, a normal rim RA is used as the rim R, for example. "Regular rim" RA is a rim defined for each tire in the standard system including the standard on which the tire 1 is based. For example, JATMA is a standard rim, TRA is a "Design Rim", or For ETRTO, it is "Measuring Rim".

In the present embodiment, the rim R includes a base portion Ra that contacts the bead toe 4e of the bead portion 4, and a rim R that protrudes from the axially outer end of the base portion Ra while curving smoothly outward in the tire radial direction and axially outward. and a flange portion Rb. The bead toe 4 e is the inner end of the bead portion 4 in the tire radial direction. The base portion Ra has, for example, a hump (not shown) protruding outward in the tire radial direction for preventing the tire 1 from coming off the rim R on the inner side in the tire axial direction.

The bead portion 4 of this embodiment each includes a bead base surface 10 , a bead flange surface 11 and a bead heel surface 12 . In this embodiment, the bead base surface 10 extends axially outward from the bead toe 4e. The bead flange surface 11 extends in the tire radial direction so as to contact the flange portion Rb of the rim R in this embodiment. The bead heel surface 12 forms a corner portion C between the bead base surface 10 and the bead flange surface 11 in this embodiment.

The bead heel surface 12 includes a main portion 14 having a large radius of curvature and a secondary portion 15 having a smaller radius of curvature than the main portion 14 . The main portion 14 is connected to the bead base surface 10 or the bead flange surface 11 via the secondary portion 15 . As described above, the main portion 14 has a relatively large radius of curvature R1 at the bead heel surface 12, thereby suppressing the occurrence of locally large fitting pressure with the rim R when the main portion 14 is assembled with the rim. . On the other hand, if the main portion 14 with a large radius of curvature is provided on the bead heel surface 12, the bead base surface 10 and the bead flange surface 11 tend to be relatively small, but the secondary portion 15 can be formed with a relatively small radius of curvature R2. eliminates this point. That is, it is possible to sufficiently maintain the contact length between the bead base surface 10 or the bead flange surface 11 and the rim R, thereby suppressing an increase in fitting pressure.

The tire 1 is generally obtained by vulcanizing and molding a raw tire (not shown) made of unvulcanized rubber using a known vulcanizing mold. For the tire 1, for example, if air remains between the vulcanization mold and the green tire during the vulcanization molding, the surface of the tire 1 is dented, which is called bare damage. In this embodiment, since the main portion 14 and the secondary portion 15 are formed in an arc shape having a radius of curvature, the raw tire easily comes into contact with the inner surface of the vulcanization mold that forms the main portion 14 and the secondary portion 15. , air is less likely to remain in the vulcanization mold. Therefore, in the tire 1 of the present embodiment, bare generation is suppressed.

The bead heel surface 12 of the present embodiment is composed of the main portion 14, the first sub-portion 16 that continues to the bead base surface 10 side of the main portion 14, and the second sub-portion 17 that continues to the bead flange surface 11 side of the main portion 14. It is configured. In other words, in this embodiment, the sub-portion 15 is composed of a first sub-portion 16 on the bead base surface 10 side and a second sub-portion 17 on the bead flange surface 11 side. Such a bead heel surface 12 can sufficiently maintain the contact length between the bead base surface 10 and the bead flange surface 11 and the rim R.

The curvature radius R1 of the main portion 14 is preferably 9 mm or more. When the curvature radius R1 of the main portion 14 is less than 9 mm, the fitting pressure between the main portion 14 and the rim R is large, and the fitting pressure between the bead base surface 10 or the bead flange surface 11 and the rim R is uniform. There is a risk that it will not.

The curvature radius R2 of the sub-portion 15 is preferably 3-7 mm. If the radius of curvature R2 is less than 3 mm, the fitting pressure between the sub-portion 15 and the rim R increases, and the fitting pressure between the bead base surface 10 or the bead flange surface 11 and the rim R may not be uniform. There is Moreover, there is a possibility that the occurrence of bares cannot be suppressed. If the radius of curvature R2 exceeds 7 mm, the length of contact between the bead base surface 10 or the bead flange surface 11 and the rim R is reduced, and the fitting pressure therebetween may become excessively large, as described above.

Although not particularly limited, the tire radial length La of the main portion 14 is preferably 50% to 60% of the tire radial length L1 of the bead heel surface 12 . The tire radial length Lb of the first sub-portion 16 is desirably 7% to 15% of the tire radial length L1 of the bead heel surface 12, for example. The tire radial length Lc of the second sub-portion 17 is preferably 30% to 38% of the tire radial length L1 of the bead heel surface 12, for example.

The bead base surface 10 is formed in this embodiment to include a base outer portion 18 connected to the bead heel surface 12 . In this embodiment, the base outer portion 18 extends from the bead toe 4e to the axially inner end 16i of the first subportion 16 of the bead heel surface 12 .

The base outer portion 18 extends linearly. Such a base outer portion 18 helps to keep the fitting pressure between the rim R and the base portion Ra small. In this specification, the above-mentioned "straight line" means not only one straight line but also an arc that is convex to one side with respect to the tire radial direction or tire axial direction and has a radius of curvature of 15 mm or more. It refers to the mode in which The base outer portion 18 is formed by, for example, one straight line.

It is desirable that the length L3 of the base outer portion 18 is 3 mm or more. As a result, the above effects are effectively exhibited.

The base outer portion 18 smoothly joins the first sub-portion 16 in this embodiment. The "smoothly" means that the angle θ1 between the tangential line 16t at the axially inner end 16i of the first sub-portion 16 and the base outer portion 18 is ±5 degrees or less. In this embodiment, the angle θ1 is 0 degrees.

FIG. 3 is an enlarged view of the corner portion C of the bead portion 4. As shown in FIG. As shown in FIG. 3 , in this embodiment, the bead flange surface 11 includes a flange inner portion 21 connected to the bead heel surface 12 and a flange outer portion 22 disposed radially outward of the flange inner portion 21 . contains.

The flange inner portion 21 extends linearly in this embodiment. The flange inner portion 21 is formed, for example, by one straight line.

It is desirable that the length L2 of the flange inner portion 21 is 3 mm or more. As a result, the fitting pressure between the flange inner portion 21 and the flange portion Rb of the rim R is reduced.

The flange inner portion 21 continues smoothly with the second sub-portion 17 in this embodiment. The "smoothly" means that the angle θ2 between the tangent line 17t at the tire radial direction outer end 17e of the second sub-portion 17 and the flange inner portion 21 is ±5 degrees or less. In this embodiment, the angle θ2 is 0 degrees.

The second sub-portion 17 of the present embodiment is provided with a protrusion 25 protruding in the axial direction of the tire. In order to discharge the air between the vulcanization mold and the green tire, the vulcanization mold may be provided with, for example, a hole-shaped vent channel connecting the inner surface and the outer surface thereof. Further, in order to form the convex portion 25, a groove-like portion having a reverse pattern of the convex portion 25 is formed on the inner surface of the vulcanization mold. By connecting one end of the vent channel to the groove-shaped portion and providing the other end on the outer surface, the air can be smoothly discharged to the outside of the vulcanization mold. In this way, the protrusions 25 are useful in suppressing the occurrence of bareness. Further, the convex portion 25 abuts on the flange portion Rb (shown in FIG. 2) of the rim R, thereby improving the airtightness of the tire cavity when the rim is assembled and facilitating the rim assembly by filling the internal pressure. The convex portion 25 may be provided on the main portion 14, for example. Also, the convex portion 25 may be provided across the second sub-portion 17 and the main portion 14, for example.

It is desirable that the convex portion 25 is continuous in the tire circumferential direction. As a result, the effect of suppressing the generation of bears is exhibited continuously in the tire circumferential direction.

It is desirable that the axially outer end 25e of the protrusion 25 be formed axially inward of a second imaginary line 21c extending radially inward of the flange inner portion 21 . Since such a convex portion 25 suppresses an excessive increase in the fitting pressure with the flange portion Rb, the uniform fitting performance on the circumference is maintained at a high level.

It is desirable that the width wa of the projection 25 perpendicular to its longitudinal direction is 1.5 mm or less, for example. Moreover, it is desirable that the protrusion height ha of the protrusion 25 is 1.0 mm or less. When the width wa of the protrusion 25 exceeds 1.5 mm, or when the protrusion height ha of the protrusion 25 exceeds 1.0 mm, the fitting pressure between the protrusion 25 and the flange Rb becomes excessively large. Uniform mating performance is degraded.

A point of intersection K1 between a first imaginary line 18c extending axially outward of the base outer portion 18 and a second imaginary line 21c and an axially outer end 18e of the base outer portion 18 in the tire axial direction. The length L4 of is preferably 4.5 to 7.5 mm. If the length L4 is less than 4.5 mm, the fitting pressure between the first sub-portion 16 or the base outer portion 18 and the rim R may increase. If the length L4 exceeds 7.5 mm, the contact length between the bead base surface 10 and the rim R may not be sufficiently maintained, and the fitting pressure may become excessively large.

In order to effectively enhance the above action, the tire radial length L5 between the intersection point K1 and the tire radial inner end 21i of the flange inner portion 21 is preferably 4.5 to 7.5 mm. desirable.

As shown in FIG. 1, the bead portion 4 is provided with a rubber chafer 8 made of, for example, hard rubber having excellent abrasion resistance. The rubber chafer 8 includes, for example, a central portion 8a that forms the bead base surface 10, an inner piece portion 8b that extends radially inward and outward in the tire axial direction inside the central portion 8a, and an outer portion that forms the bead flange surface 11. It is formed with a substantially U-shaped cross section having a piece 8c. Such a rubber chafer 8 can prevent problems such as damage due to friction with the rim R and deviation of the rim.

FIG. 4(a) is a cross-sectional view of the bead portion 4 of another embodiment, and FIG. 4(b) is a cross-sectional view of the bead portion 4 of still another embodiment. Components that are the same as those of this embodiment are given the same reference numerals, and detailed descriptions thereof are omitted. As shown in FIG. 4( a ), in the bead portion 4 of this embodiment, the sub-portion 15 is formed only by the first sub-portion 16 . In this embodiment, the flange inner portion 21 and the main portion 14 are smoothly connected. Even in such an embodiment, the circumferentially uniform fitting performance is improved.

As shown in FIG. 4(b), in the bead portion 4 of this embodiment, the sub-portion 15 is formed only by the second sub-portion 17. As shown in FIG. In this embodiment, the base outer portion 18 and the main portion 14 are smoothly connected.

5 and 6 are cross-sectional views of the bead portion 4 of still another embodiment. Components that are the same as those of this embodiment are given the same reference numerals, and detailed descriptions thereof are omitted. As shown in FIG. 5, in the bead portion 4 of this embodiment, the main portion 14 is formed in a straight line (curvature radius R1 is ∞). Such a main portion 14 is also suppressed from being sharpened, and thus serves to reduce the fitting pressure between the main portion 14 and the rim R.

As shown in FIG. 6 , in the bead portion 4 of this embodiment, the bead base surface 10 is composed of a base outer portion 18 and a base inner portion 19 connected to the base outer portion 18 . In this embodiment, the base inner portion 19 includes a bead toe 4e. The base inner portion 19 is formed, for example, in an arcuate shape concave inward in the tire radial direction. Such a base inner portion 19 also improves the circumferentially uniform fitting performance. The curvature radius R4 of the base inner portion 19 is preferably 3 to 10 mm, for example.

Although the particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be modified in various ways.

Pneumatic tires for passenger cars of size 245/45R18 having the basic structure shown in Fig. 1 were prototyped based on the specifications shown in Table 1, and bare bead portions generated at this time were confirmed. The uniform mating performance was tested. In addition, the secondary part is not provided in the comparative example 1. FIG. The test method is as follows.

<Bear occurrence rate>
A test tire was manufactured by vulcanizing and molding a raw tire with a vulcanizing mold having a well-known structure. Then, the percentage of sample tires in which bare bead portions occurred was calculated. Results are given as percentages. The smaller the numerical value, the smaller the bare occurrence rate and the better. A raw tire is molded by a well-known molding method.

<Uniform fitting performance on circumference>
The RFV (Radial Force Variation) of the sample tire was measured. The measurement was performed twice for each tire using a tire uniformity tester in accordance with JASO C607:2000 "Uniformity test method for automobile tires". The second measurement was performed after removing the rim and reassembling the rim after the first measurement. The result is expressed by the waveform difference (difference (N) between the maximum value and the minimum value) of these primary waveforms calculated by Fourier transforming the first and second RFV measurement values. The smaller the numerical value, the better the uniform fitting performance on the circumference.
Rim: Regular rim Internal pressure: 200kPa
Load: 4.88kN
Running speed: 7km/h
The results of the tests are shown in Table 1.

As is clear from Table 1, it was confirmed that the tire of the example had a smaller occurrence of bears than the tire of the comparative example, and was excellent in uniform fitting performance on the circumference.

1 pneumatic tire 4 bead portion 4e bead toe 10 bead base surface 11 bead flange surface 12 bead heel surface 14 main portion 15 secondary portion R rim Rb flange portion

Claims (13)

A pneumatic tire having a pair of beads,
Each of the pair of bead portions includes a bead base surface extending axially outward from the bead toe, a bead flange surface extending in the tire radial direction so as to contact the flange portion of the rim, the bead base surface and the bead flange surface. and a bead heel surface forming a corner between
In the cross section of the bead portion, the bead heel surface includes a main portion having a large radius of curvature and a secondary portion having a smaller radius of curvature than the main portion,
the main portion is connected to the bead base surface or the bead flange surface via the secondary portion ;
the radius of curvature of the sub-portion is 3-7 mm;
pneumatic tires. A pneumatic tire having a pair of beads,
Each of the pair of bead portions includes a bead base surface extending axially outward from the bead toe, a bead flange surface extending in the tire radial direction so as to contact the flange portion of the rim, the bead base surface and the bead flange surface. and a bead heel surface forming a corner between
In the cross section of the bead portion, the bead heel surface includes a main portion having a large radius of curvature and a secondary portion having a smaller radius of curvature than the main portion,
the main portion is connected to the bead base surface or the bead flange surface via the secondary portion;
the bead flange surface having a flange inner portion connected to the bead heel surface;
In the cross section of the bead portion, the flange inner portion extends linearly,
the bead base surface has a base outer portion connected to the bead heel surface;
The intersection of a first imaginary line extending the base outer portion axially outward and a second imaginary line extending the flange inner portion radially inward, and the intersection of the base outer portion in the tire axial direction. The axial length of the tire between the outer end is 4.5 to 7.5 mm,
pneumatic tires. A pneumatic tire having a pair of beads,
Each of the pair of bead portions includes a bead base surface extending axially outward from the bead toe, a bead flange surface extending in the tire radial direction so as to contact the flange portion of the rim, the bead base surface and the bead flange surface. and a bead heel surface forming a corner between
In the cross section of the bead portion, the bead heel surface includes a main portion having a large radius of curvature and a secondary portion having a smaller radius of curvature than the main portion,
the main portion is connected to the bead base surface or the bead flange surface via the secondary portion;
the bead flange surface having a flange inner portion connected to the bead heel surface;
In the cross section of the bead portion, the flange inner portion extends linearly,
the bead base surface has a base outer portion connected to the bead heel surface;
A first imaginary line extending axially outward of the base outer portion and a second imaginary line extending radially inward of the flange inner portion and the intersection of the flange inner portion in the tire radial direction. The length in the tire radial direction between the inner end is 4.5 to 7.5 mm,
pneumatic tires. 2. The bead heel surface is composed of the main portion, a first sub-portion connected to the bead base surface side of the main portion, and a second sub-portion connected to the bead flange surface side of the main portion . 4. The pneumatic tire according to any one of 3 . The pneumatic tire according to any one of claims 1 to 4 , wherein said main portion has a radius of curvature of 9 mm or more . the bead base surface has a base outer portion connected to the bead heel surface;
The pneumatic tire according to any one of claims 1 to 5 , wherein the base outer portion extends linearly in a cross section of the bead portion . 7. The pneumatic tire according to claim 6 , wherein the base outer portion has a length of 3 mm or more . 4. The pneumatic tire according to claim 2 or 3 , wherein the flange inner portion has a length of 3 mm or more . the bead heel surface includes a second sub-portion continuous with the bead flange surface side of the main portion;
The pneumatic tire according to any one of claims 1 to 8 , wherein the main portion or the second sub-portion is provided with a convex portion projecting in the tire axial direction . The pneumatic tire according to claim 9 , wherein the convex portion is continuous in the tire circumferential direction . The pneumatic tire according to claim 9 or 10 , wherein the width perpendicular to the longitudinal direction of the projection is 1.5 mm or less . 12. The pneumatic tire according to any one of claims 9 to 11 , wherein the projection height of said projection is 1.0 mm or less . The pneumatic tire according to any one of claims 1 to 12 , wherein the pneumatic tire is for passenger cars .

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