JP2001047817A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent performance decrement of a tire resulting from a spew formed according to a vent hole of a mold for vulcanization. SOLUTION: In a pneumatic radial tire intended for an ultra-fast automobile and substantially having no pattern on the surface of a tread, the tire is provided with a plurality of projecting parts 2 arranged like pear skin on the whole tread surface, and so dense that a negative ratio (per unit ground contact area (non-projecting part area)/(non-projecting part area + projecting part area) × 100% per unit tread area) ranging from 25 to 75%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire suitable for being mounted on an ultra-high-speed passenger vehicle, and more particularly to a tire having a spew, which has conventionally been inevitable in the vulcanization molding of a tire, and has a high durability. It is intended to effectively avoid deterioration in maneuverability.

[0002]

2. Description of the Related Art A mold used for vulcanization of a tire is provided with a plurality of vent holes having a diameter of about 1.5 mm to discharge air remaining in the mold during vulcanization. Since the rubber is extruded here during the vulcanization molding, the product tire taken out of the mold has a spew (Spew) as shown in FIGS. 3A and 3B corresponding to the hole. Generally, a plurality of rubber projections t are attached to each other.

[0003] In order to ship a vulcanized tire having the above spew as a product, it is necessary to remove the spew. Conventionally, a plurality of V-shaped grooves are formed while the tire is rotated. The spew was cut off by pushing it off using a comb-shaped cutter.

[0004]

In the cutting of the spew by such a cutter, it is desired to completely remove the spew from the surface of the tire. However, in practice, some uncut parts are left from the viewpoint of reducing the manufacturing cost. The spew was cut off with a comb-shaped cutter as described above, but the spew was cut with the support of the spew falling down at the moment the cutter hit the spew. Since the spew was cut off, an inclined surface having an angle with respect to the tread surface of the tire was formed at the tip that remained when the spew was cut off,
When there is such a residual spew, the contact pressure distribution of the tread becomes non-uniform, and the shear force becomes locally large, causing problems such as uneven wear around the spew.
In a tire having an extremely thin tread rubber, such as a tire mounted on an ultra-high-speed passenger vehicle, there is a concern that the tire may break down from the belt due to the tread rubber.

An object of the present invention is to propose a new pneumatic radial tire that can solve the conventional problems caused by the spew described above.

[0006]

SUMMARY OF THE INVENTION The present invention is a pneumatic radial tire for an ultra-high-speed passenger vehicle having substantially no pattern on the surface of the tread, wherein the tire is arranged in a satin pattern over the entire surface of the tread surface. Having a plurality of convex portions having a density of 25 to 75% at a negative rate (negative rate: (non-convex area) / (non-convex area + convex area) × 100%) per unit ground contact area. It is a pneumatic radial tire characterized by the following.

In the present invention, the rubber forming the tread preferably has a hardness at room temperature of 50 ° or less.
The tread thickness is desirably 2 to 6 mm.

[0008] In the pneumatic radial tire having the above structure, the height of the convex portion is 0.1 to 0.5 mm.
It is preferable that the contact area be 0.25 to ⁴ mm ² .

The protruding portion has a dome shape whose tip has an arc shape, and has a ground contact surface radius of 0.1 to 0.5.
mm, and it is desirable to arrange ribs connecting the convex portions along the width direction of the tread.

The height of the rib and the width of the ground plane rib are 0.1 to
It can be 0.5 mm.

In the present invention, the tread surface has a convex portion satisfying the above conditions, but has substantially no trace of a spew formed corresponding to a mold air vent during vulcanization molding of a tire. I do.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to the drawings. FIGS. 1 (a) and 1 (b) show the configuration of a pneumatic radial tire according to the present invention in a developed tread and its cross section. In FIG. Are convex portions arranged in a satin pattern.

In order to maintain sufficient running performance as a tire applicable to an ultra-high-speed passenger vehicle, the convex portion 2 is (non-convex area) / (non-convex area + convex area) per unit contact area. × 100% is defined as the negative rate, 2
It shall have a density of 5 to 75%.

The convex portion 2 is provided over the entire tread contact surface in a state where the negative ratio has a density of 25 to 75%. The convex portion 2 is provided at a position corresponding to the tread of the tire vulcanization molding die under the above conditions. Satisfactory concave portions are provided and formed at the time of vulcanization molding of a tire.

The concave portion of the vulcanization molding die that forms the matte-shaped convex portion 2 is positioned between the portions corresponding to the tread portion of the green tire inserted in the die until the portion is pressed to the die. Most of the mold is discharged outside the mold before the mold is completely sealed in order to disperse the air remaining in between, so that the so-called bear failure that occurs on the tread surface is avoided.

The height h of the projection 2 is 0.1 to 0.5 mm,
The contact area was 0.25 to ⁴ mm ² ,
By defining the size of the convex portion 2 within this range, air remaining in the vulcanizing mold can be effectively discharged, and if the upper limit of the convex portion 2 is exceeded, the convex portion 2
This is because there is a disadvantage that the distribution of the contact pressure in the vicinity of the tire becomes uneven and the performance of the tire is adversely affected by a local increase in the shearing force.

The convex portion 2 can be formed in a dome shape having a circular arc at its tip in order to efficiently discharge the residual air in the mold. In this case, the radius of the ground contact surface is set for the same reason as described above. The shape is 0.1 to 0.5 mm, but the shape is not limited to this, and various shapes such as a square shape can be applied, as long as the ground area defined in the present invention is satisfied.

As shown in FIGS. 2 (a) and 2 (b), a rib 3 is provided so as to connect the convex portion 2 along the width direction of the tread, and this is extended toward the buttress region and connected to the annular rib. In a corresponding vulcanizing mold, air remaining in the mold can be communicated with an exhaust groove for positively exhausting air, thereby enabling more efficient exhaust. The ribs 3 can be provided in the direction in which the tire rotates in order to improve the exhaust efficiency and maintain a balance in steering stability.

The height h _{1 of the} rib 3 and the width L of the contact pressure rib are set to 0.1 to 0.5 mm. By avoiding performance degradation.

As the rubber forming the tread, a rubber having a hardness at room temperature of 50 ° or less is used in order to exert a sufficient grip during actual running.

According to the present invention, a vulcanization mold is provided with a concave portion at a position corresponding to the tire tread surface, and a plurality of convex portions are provided on the tread surface of the vulcanized tire. The spew corresponding to the vent hole is formed in the mold, of course, there is no trace, etc.There is no such thing as the unevenness of the contact pressure distribution and the local increase of the shearing force due to the conventional spew. Absent. The pitch P between the adjacent protrusions 2 in the protrusions 2 is preferably 0.5 to 1 mm.

[0022]

EXAMPLE A dome-shaped convex part having a height of 0.3 mm was formed on a tread surface of a tire (tread rubber thickness 5 mm, dread rubber hardness at room temperature of 49 °) having a size of 235 / 45R 17 by 1 cm ^3. A pneumatic radial tire having a smooth pattern as shown in FIG. 1 provided so as to have a density of 100 pieces (a negative rate of 50%) per tire was manufactured, and the durability of the tire with an HSP drum was examined. .

The results are shown in a conventional tire in which three rows of air vent spews (1.8 mm in diameter) are arranged at equal intervals around the tire at the center and at the end of the tire tread, and a bent tire of the same size is used. The results are shown in Table 1 together with the results of a survey on comparative tires without pews (without bleeding the mold).

In the HSP drum test, a drum having a diameter of 2 m was used, and each of the tires was subjected to a regular rim (8J × 17).
2.5 kgf / cm ² the embedded internal pressure, 300 kg applied load
(Camber angle CA = 0, sideslip angle SA =
0) at 150 km / h to 10 km / h at 10 minute intervals
The speed was increased by h.

[0025]

[Table 1]

As shown in Table 1, in the conventional tire, although there is no particular problem regarding the vulcanization non-uniformity of the tread surface, fatigue occurs due to repetitive input near the remaining spew (removal mark of the spew), and the tread becomes chunky. Out and tire failure was inevitable. Further, in the comparative tire, since no air was removed from the mold, an unvulcanized portion was formed on the tread surface, and chunk out from the unvulcanized portion in the drum test. On the other hand, the conformable tire according to the present invention was uniformly vulcanized on the tread surface and had no particular problem, and it was confirmed that no chunk-out was observed even in the drum test and the tire was completed.

[0027]

According to the present invention, since there is substantially no spew formed corresponding to the mold air vent in the vulcanization molding of the tire, the unevenness of the contact pressure distribution and the localization of the shearing force caused by the spew are substantially eliminated. In particular, it is possible to stabilize the performance of a pneumatic radial tire for an ultra-high-speed passenger vehicle, which is greatly affected by the spew.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a configuration of a pneumatic radial tire according to the present invention, wherein (a) shows a tread developed and (b) shows a cross section of the tread.

FIGS. 2A and 2B are views showing another example of the pneumatic radial tire according to the present invention.

FIG. 3 is a view showing a conventional pneumatic radial tire having a smooth pattern, in which (a) shows a tread developed and (b) shows a cross section of the tread.

[Explanation of symbols]

 1 tread 2 convex part 3 rib t spew

Claims (8)

[Claims] 1. A pneumatic radial tire for an ultra-high-speed passenger vehicle having substantially no pattern on the tread surface, wherein the tire is arranged in a satin pattern over the entire area of the tread surface, and has a negative rate (negative rate: unit). (Non-convex area) / (Non-convex area + convex area) × 100 per contact area
%), Having a plurality of convex portions having a density of 25 to 75%. 2. The pneumatic radial tire according to claim 1, wherein the rubber forming the tread has a hardness at room temperature of 50 ° or less. 3. The pneumatic radial tire according to claim 1, wherein the tread has a thickness of 2 to 6 mm. 4. The pneumatic pneumatic pump according to claim 1, wherein the convex portion has a height of 0.1 to 0.5 mm and a ground contact area of 0.25 to 4 mm ^2. Radial tire. 5. The pneumatic radial tire according to claim 1, wherein the projection has a dome shape having a circular arc-shaped tip, and a radius of the ground contact surface is 0.1 to 0.5 mm. . 6. The pneumatic radial tire according to claim 1, further comprising a rib connecting a convex portion along a width direction of the tread. 7. The rib has a height and a tread rib width of 0.1.
The pneumatic radial tire according to claim 6, which has a thickness of 0.5 mm. 8. The pneumatic radial tire according to claim 1, wherein the tread surface has substantially no trace of a spew formed corresponding to a mold air vent during vulcanization molding of the tire. .