JP3249673B2 - Pneumatic tire and method for manufacturing pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire and a pneumatic tire.
TECHNICAL FIELD The present invention relates to a method for manufacturing a tire including a tire .

[0002]

2. Description of the Related Art With the recent increase in speed of vehicles, flattening of pneumatic tires has progressed, and one of the resulting problems is the problem of drainage on wet road surfaces. Conventionally, this countermeasure has been mainly made by improving the pattern applied to the tread portion. For example, a so-called rib pattern in which a land portion is divided by a groove substantially along the tire equatorial plane, an arrow-shaped groove extending from the vicinity of the tire equatorial plane to the tire circumferential direction and axially outward and opening outside the ground contact surface, A so-called directional pattern that determines the tire rotation direction,
Alternatively, a pattern in which a concave portion which is wider and deeper than a normal groove extending in the circumferential direction of the tire near the equatorial plane of the tire is provided, and the groove is combined with the above-mentioned arrow-shaped groove is such.

The inventor has studied a technique which can be applied to these patterns and further improves drainage. First, the inventor of the present invention ran a pneumatic tire having three straight grooves on the tread portion substantially along the tire equatorial plane at a high speed on a stagnant road surface, and observed the flow of the grooves on the ground contact surface. As a result, even with this tire having a straight groove,
Turbulence was generated on the kicking side, which was considered to be one of the factors limiting drainage.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the drainage performance by suppressing the above-mentioned turbulence phenomenon.

[0005]

According to a first aspect of the present invention, a pair of bead portions, sidewall portions extending radially outward from the bead portions in the tire radial direction, and straddling the sidewall portions are provided. A pneumatic tire having an annular tread portion and the tread portion divided into a plurality of land portions by grooves, wherein a silicon-based mold release agent, a lubricant, or a polyethylene oxide is formed on a groove wall surface of the groove. Since the linear polymer material is applied, a difference in height between peaks of irregularities on the surface of the groove wall is a smooth surface of 10 μm or less. The invention according to claim 2 includes a pair of beads, a sidewall extending radially outward from the beads, and a tread extending annularly across the sidewall. In the method for manufacturing a pneumatic tire in which the tread portion is divided into a plurality of land portions by grooves, a polyethylene polymer sheet is placed at a groove assumed position in the tread portion of the green tire before vulcanization, and the tire is mounted. Together with a vulcanization step to obtain a smooth surface having a height difference between peaks of irregularities on the surface of the groove wall of 10 microns or less. The invention according to claim 3 includes a pair of beads, a sidewall extending radially outward from the beads, and a tread extending annularly across the sidewall. Then, in the method for manufacturing a pneumatic tire in which the tread portion is divided into a plurality of land portions by grooves, vulcanization molding is performed using a vulcanization mold having a fine surface finish, and peaks of irregularities on the surface of the groove wall are obtained. It is characterized in that the height difference between them is a smooth surface of 10 microns or less.

Here, a groove having a height difference between peaks of irregularities on the groove wall surface of 10 μm or less refers to a groove substantially along the tire equatorial plane, a groove having a small inclination angle with respect to the tire equatorial plane, and Everything that drains, such as grooves extending from the tire equatorial plane to the tire circumferential direction and axially outward and opening outside the ground contact surface, and near the tire equatorial plane to wider recesses that are wider and deeper than normal grooves extending in the tire circumferential direction near the tire equatorial plane Grooves are included.

[0007] And all the grooves of the tread portion are
The surface does not have to be
Mainly on the groove bottom surface or groove side wall surface
Irregularities or irregularities on the groove bottom surface and groove side wall surface
If the height difference between peaks is less than 10 microns
Just fine.

[0008]

In general, it has been observed that irregularities having no direction are numerous on the surface of a groove wall of a tire, and the difference in height between peaks is several hundred microns or less, but exceeds 10 microns. Due to the unevenness, the drainage efficiency of water passing through the groove was reduced by shear resistance generated near the surface of the groove wall, and a turbulent flow phenomenon occurred on the kicking side of the contact surface. On the other hand, in the present invention, since the height difference between the peaks of the irregularities is a smooth low friction surface of 10 μm or less, the above-mentioned shear resistance is extremely small, and the drainage property can be improved. Various means for making such a surface are conceivable, and examples thereof are described below.
First, a means for applying a silicon-based release agent, a lubricant, or a linear polymer material of polyethylene oxide to the surface of the groove wall can be considered. Further, a polymer sheet of polyethylene may be placed at an assumed position of a groove in a tread portion of a green tire before vulcanization and subjected to a vulcanization step together with the tire. Further, a means for making the surface finish of the vulcanization mold fine may be used.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a development view of a tread portion 2 of a pneumatic tire 1 according to the present invention. This tire is size 2
A 25 / 50R16 pneumatic radial tire for a passenger car, comprising: a pair of beads; a sidewall extending radially outward from the bead; and a tread extending annularly across the sidewall. However, only the tread portion is shown here.

The tread portion 2 is provided with three grooves 3 each having a width of 8 mm and a depth of 8 mm and extending substantially along the tire equatorial plane E, each having a distance of 30 mm in the tire axial direction.
FIG. 2 shows an enlarged view of the groove wall surface of the groove 3, which is formed by applying a silicone-based release agent to the groove surface of a normal tire after vulcanization to reduce the surface. The surface was finished to have a smooth friction surface.

For comparison with the above-mentioned inventive tire, a conventional tire which is different from the inventive tire only in that the above-mentioned silicone release agent is not applied was prepared. FIG. 3 shows an enlarged view of the groove wall surface of the groove of the tire. As described above, conventionally, the surface of the groove wall of the tire has countless irregularities having no directionality, and the height of the peaks of the irregularities is large. Is greater than 10 microns.

These test tires are assembled on a rim of size 71 / 2JJ, which is one of the applicable rims, filled with an internal pressure of 2.0 kgf / cm ² and mounted on an actual vehicle, and subjected to a water retention test at a depth of 10 mm. The vehicle traveled straight on the road and the speed at which the hydroplaning phenomenon occurred was measured.

As a result, in the conventional tire, the speed is 77
In contrast to km / h, the difference in height between peaks of the unevenness is up to 5 by applying the silicone release agent once.
In the invention tire 1 suppressed to a micron, the speed is 80
The above-mentioned speed was 82 km / h in the inventive tire 2 in which the height difference between the peaks of the unevenness was suppressed to almost 0 μm by applying the silicone release agent twice at km / h.

[0014]

According to the present invention, the drainage performance can be improved.

[Brief description of the drawings]

FIG. 1 is a development view of a tread portion of an inventive tire.

FIG. 2 is an enlarged view of a groove wall surface of a groove in a tread portion of the invention tire.

FIG. 3 is an enlarged view of a groove wall surface of a groove in a tread portion of a conventional tire.

[Brief description of reference numerals]

 1 pneumatic tire 2 tread 3 groove

Claims (3)

(57) [Claims] 1. A tread comprising: a pair of beads; a sidewall extending radially outward from the beads; and a tread extending annularly across the sidewall. In a pneumatic tire in which a portion is divided into a plurality of land portions by grooves, a silicon-based release agent, a lubricant, or a linear polymer material of polyethylene oxide is applied to a groove wall surface of the groove. A pneumatic tire having a smooth surface having a height difference between peaks of irregularities on the surface of the groove wall of 10 microns or less. 2. The tread having a pair of beads, a sidewall extending radially outward from the beads, and a tread extending annularly across the sidewall. A method for manufacturing a pneumatic tire in which a portion is divided into a plurality of land portions by grooves, wherein a vulcanizing step is carried out together with a tire by placing a polyethylene polymer sheet at an assumed groove position in a tread portion of a green tire before vulcanization. Wherein the difference in height between peaks of irregularities on the surface of the groove wall is made a smooth surface of 10 μm or less. 3. The tread, comprising: a pair of bead portions; sidewall portions each extending outward in the tire radial direction from the bead portions; and a tread portion extending annularly across the sidewall portions. In a method of manufacturing a pneumatic tire in which a portion is divided into a plurality of land portions by grooves, vulcanization molding is performed using a vulcanization mold having a fine surface finish, and the height of peaks of irregularities on the surface of the groove wall is set. A pneumatic tire having a smooth surface having a difference of 10 μm or less.