JP7451920B2 - pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire having a serration region on the surface of a sidewall portion.

The rubber on the sidewalls of pneumatic tires is thin, and uneven appearance defects (hereinafter referred to as ``bulge dents'') occur due to the seams of the carcass, which is the internal structural material, and residual air. Cheap.

In order to make such bulge dents less noticeable (concealing effect), serration regions in which a plurality of ridges are arranged in parallel have been conventionally formed on the surface of the sidewall portion.

On the other hand, in order to improve the fuel efficiency of vehicles, it is strongly desired to reduce the air resistance of rolling tires.

To this end, Patent Document 1 listed below proposes providing a large number of dimple-shaped depressions with an equivalent diameter of 3 to 15 mm on the surface of the sidewall portion. This recess can move the separation of air near the tire surface as far as possible to the rear, thereby suppressing the generation of vortices and reducing pressure resistance.

Japanese Patent Application Publication No. 04-297310

However, the tire proposed above does not have a sufficient effect of concealing bulge dents. Furthermore, since the dimple-like depressions are large, there is a problem that the design is poor and the degree of freedom in design is reduced.

An object of the present invention is to provide a pneumatic tire that can reduce air resistance of the tire while ensuring a bulge dent concealment effect.

The present invention is a pneumatic tire including a sidewall portion,
A reference surface arranged on the surface of the sidewall portion has a plurality of grooves extending in the tire radial direction and arranged in the tire circumferential direction, and a plurality of grooves formed between the adjacent grooves and extending in the tire radial direction. a serrated area including a ridge;
The groove depth D of the groove from the reference surface becomes smaller toward the outer side in the tire radial direction.

In the pneumatic tire according to the present invention, it is preferable that the groove width W of the groove increases toward the outer side in the tire radial direction.

In the pneumatic tire according to the present invention, the groove depth D of the groove is preferably 0.1 to 0.5 mm.

In the pneumatic tire according to the present invention, the groove width W of the groove is preferably 0.6 to 1.8 mm.

In the pneumatic tire according to the present invention, it is preferable that the grooves are connected to circumferential ribs that protrude from the reference surface and extend continuously in the tire circumferential direction.

In the pneumatic tire according to the present invention, the serration region is divided into a plurality of region portions in the tire radial direction, and the groove depths D of the grooves arranged in each region portion are equal to each other, and the tire radius It is preferable that the groove depth D is made smaller in a region located on the outer side in the direction.

The pneumatic tire of the present invention includes a serration region on the reference surface disposed on the surface of the sidewall portion. The serration region includes a plurality of grooves extending in the tire radial direction and arranged in the tire circumferential direction, and a ridge formed between adjacent grooves and extending in the tire radial direction.

The grooves can move the separation of air near the surface of the sidewall portion to the rear side, thereby suppressing the generation of vortices. Therefore, the pressure resistance can be reduced and the air resistance of the tire can be reduced.

Further, as a result of the research conducted by the present inventors, it was confirmed that by making the grooves shallower and wider, the effect of moving the air separation position toward the rear side becomes higher.

Here, in the sidewall portion, since the rotational speed is faster toward the outer side in the tire radial direction, air separation is more likely to occur. However, in the present invention, the groove depth of the grooves is made smaller toward the outside in the tire radial direction, thereby increasing the effect of moving the air separation position toward the rear side. Therefore, the air resistance of the tire can be reduced more effectively.

Furthermore, by reducing the groove depth of the grooves, light is more likely to be reflected, resulting in a disadvantage that the concealment effect of the bulge dent is reduced. However, since the thickness of the rubber increases from the vicinity of the tire maximum width position toward the outside in the tire radial direction, the bulge dent gradually becomes less noticeable. Therefore, it is possible to suppress the influence on the bulge dent concealment effect by reducing the groove depth of the grooves toward the outside in the tire radial direction.

That is, the present invention can achieve both the effect of concealing the bulge dent and the effect of reducing air resistance while ensuring the designability and freedom of design.

1 is a sectional view showing an embodiment of a pneumatic tire of the present invention. FIG. 3 is a partial front view of a sidewall portion showing a serration region. (a) and (b) are a sectional view taken along the line AA and sectional view taken along the line BB in FIG. 2, showing grooves and ridges. FIG. 7 is a partial front view of the sidewall portion showing another example of grooves and ridges. FIG. 7 is a partial front view of a sidewall portion showing another example of a serration region. (a) is a partial side view schematically showing the air flow around the tire during running, and (b) is a cross-sectional view taken along line DD.

Embodiments of the present invention will be described in detail below.
As conceptually shown in FIGS. 1 and 2, the pneumatic tire 1 of this embodiment (hereinafter, may simply be referred to as "tire 1") has a serration area on the surface 2S of the sidewall portion 2. Includes 3. The radially outer end 3E of the serration region 3 is preferably disposed radially outside the tire maximum width position K (shown in FIG. 1) and radially inside the circumferential protrusion J.

The circumferential protrusion J is a rib formed at a dividing position between the tread mold and the side mold in the vulcanization mold. This circumferential protrusion J is formed as an inverted shape of the circumferential groove provided in the vulcanization mold to prevent rubber from biting between the tread mold and the side mold when the mold is closed, and to vent air.

The serration region 3 is a band-shaped body extending in the tire circumferential direction around the tire rotation axis i. In this example, a case is shown in which the serration region 3 has an annular shape that extends continuously in the tire circumferential direction. In the serration area 3 of this example, a mark 4 such as letters, symbols, or figures is formed to represent, for example, the tire manufacturer's name, brand name, size, or the like.

However, the invention is not limited to this, and for example, as conceptually shown in FIG. 5, the serration region 3 may have an arc shape formed in a part of the tire circumferential direction. In the case of an arcuate shape, it is preferable to arrange a plurality of serration regions 3 in the tire circumferential direction. At this time, it is preferable that the length of each serration region 3 in the tire circumferential direction is 90 degrees or more in terms of the central angle α around the tire rotation axis i. Further, the mark 4 may be formed in the area between the serration areas 3 . In the serration region 3 of FIG. 5, grooves 6 and ridges 7, which will be described later, are omitted.

3(a) and 3(b) show a cross section taken along line AA and line BB in FIG. 2. As shown in FIGS. 2 and 3, the serration region 3 includes a plurality of grooves 6 recessed in the reference plane X disposed on the surface 2S, and ridges formed between adjacent grooves 6, 6. and a ridge 7 having a shape. The lines in FIG. 2 indicate the upper ends of the ridges 7.

The reference plane X is a plane on which the serration region 3 is formed, and is substantially equal to a virtual plane joining the upper end of the ridge 7. In this example, the reference surface X is formed at a position lower than the surface 2S by, for example, 0.1 to 0.5 mm, but the reference surface X may be formed at the same height as the surface 2S.

As shown in FIG. 2, the grooves 6 extend in the tire radial direction and are arranged in the tire circumferential direction. Therefore, the ridge 7 formed between the grooves 6, 6 also extends in the tire radial direction.

Extending in the radial direction of the tire includes extending in the radial direction of the tire and extending at an angle θ of less than 45 degrees with respect to the radial direction of the tire (as shown in FIG. 4). In the case of inclination, the angle θ is preferably 30 degrees or less, more preferably 15 degrees or less, and even more preferably 10 degrees or less. Note that the tire radial direction is a direction along a radial line extending from the tire rotation axis i. In this example, the grooves 6 are shown extending in the tire radial direction. That is, the grooves 6 in this example are formed radially.

It is preferable that the groove 6 is connected to a circumferential protrusion 11 that is raised from the reference plane X and extends continuously in the tire circumferential direction. In this example, the outer end of the groove 6 in the tire radial direction is connected to the first circumferential protrusion 11 . Further, the inner end portion of the groove 6 in the tire radial direction is connected to the second circumferential protrusion 11 . The first circumferential protrusion 11 is the circumferential protrusion J disposed at the above-described dividing position of the mold. Further, the second circumferential protrusion 11 is formed as an inverted shape of an exhaust vent groove provided in the vulcanization mold. In this case, air between the mold surface and the sidewall portion 2 during vulcanization can be made to exit the mold through the grooves 6 and the first and second circumferential protrusions 11. Benefits arise. The groove 6 may be connected to the circumferential protrusion 11 at the center in the longitudinal direction.

As shown in FIG. 3(b), the groove depth D of the groove 6 from the reference surface X becomes smaller toward the outer side in the tire radial direction.

FIGS. 6(a) and 6(b) schematically show the air flow around the tire during running. During running, air that hits the tread surface a from the front side in the traveling direction F branches to both sides in the tire axial direction, forming an airflow b that flows rearward along the surface 2S of the sidewall portion 2. At this time, when serrations are arranged on the surface 2S of the sidewall portion 2, air is caught in the unevenness, producing the effect of suppressing separation from the surface 2S. The air whose separation is suppressed passes through the tread end and flows around to the tread surface a side, increasing the pressure on the tire back surface C, thereby reducing air resistance such as reducing pressure resistance.

Here, in the sidewall portion 2, since the rotational speed is faster toward the outer side in the tire radial direction, air is more easily separated. However, in the serration region 3 of this embodiment, the groove depth D of the groove 6 is made smaller toward the outside of the tire, thereby delaying the separation of air and moving the separation position toward the rear (toward the tread end). Therefore, the effect of causing air to flow around to the tread surface a side is enhanced, and the pressure on the tire back surface C is increased, making it possible to reduce air resistance more effectively.

On the other hand, the small groove depth D of the grooves 6 causes a disadvantage in that the effect of concealing the bulge dent is reduced. However, since the thickness of the rubber increases from the vicinity of the tire maximum width position K toward the outside in the tire radial direction, the bulge dent gradually becomes less noticeable. Therefore, it is possible to suppress the effect on the bulge dent concealment effect by decreasing the groove depth D toward the outside in the tire radial direction.

That is, the serration region 3 makes it possible to achieve both the effect of concealing the bulge dent and the effect of reducing air resistance while ensuring aesthetic quality and freedom of design.

It is also preferable that the groove width W of the groove 6 increases toward the outer side in the tire radial direction. This also increases the effect of moving the air separation position to the rear side (toward the tread end side), making it possible to more effectively reduce the air resistance of the tire 1.

The groove depth D of the grooves 6 is preferably 0.1 to 0.5 mm. If the groove depth D is less than 0.1 mm, the concealing effect of the bulge dent will not be sufficiently exhibited. On the other hand, if the groove depth D exceeds 0.5 mm, the effect of moving the separation position toward the rear (toward the tread end) tends to decrease.

The groove width W of the groove 6 is preferably 0.6 to 1.8 mm. If the groove width W exceeds 1.8 mm, the effect of concealing the bulge dent will not be sufficiently exerted. On the other hand, when the groove width W is less than 0.6 mm, the effect of moving the peeling position toward the rear (toward the tread end) tends to decrease.

The cross-sectional shape of the ridge 7 is not particularly limited, but a triangular cross-sectional shape with an apex angle β in the range of 60 to 120 degrees, particularly 75 to 105 degrees, or a trapezoidal cross-sectional shape with the apex removed is preferably adopted. sell.

In this example, a case is shown in which the groove depth D of the grooves 6 continuously decreases toward the outer side in the tire radial direction. However, the present invention is not limited to this, and the groove depth D may become smaller intermittently.

Another embodiment of the serration region 3 is shown in FIG.

In this example, the serration region 3 is divided into a plurality of region portions 10 in the tire radial direction. The groove depths D of the grooves 6 arranged in each region 10 are equal to each other, and the groove depth D is smaller as the region 10 is located on the outer side in the tire radial direction.

Specifically, in this example, a case is shown in which the serration region 3 is divided into two regions: an inner region portion 10A and an outer region portion 10B. The grooves 6A arranged in the inner region portion 10A have the same groove depth DA (not shown). Further, the grooves 6B arranged in the outer region portion 10B have the same groove depth DB (not shown). The groove depth DB in the outer region portion 10B is smaller than the groove depth DA in the inner region portion 10A.

Even with this configuration, similar effects can be obtained. Note that the number of divisions can be appropriately selected from 2 or more.

Although FIG. 4 shows a case where the grooves 6 extend at an angle θ smaller than 45 degrees with respect to the radial direction of the tire, the grooves 6 extend in the radial direction of the tire, that is, at an angle θ=0. It may be degree.

Although 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 and implemented in various ways.

1 Pneumatic tire 2 Sidewall portion 2S Surface 3 Serration region 6 Groove 7 Ridge 10 Region portion 11 Circumferential rib X Reference surface

Claims (4)

A pneumatic tire including a sidewall portion,
A reference surface arranged on the surface of the sidewall portion has a plurality of grooves extending in the tire radial direction and arranged in the tire circumferential direction, and a plurality of grooves formed between adjacent grooves and extending in the tire radial direction. a serrated area including a ridge;
The serration area is divided into a plurality of area parts in the tire radial direction,
The grooves formed in the plurality of regions are spaced apart from each other,
The groove depths of the grooves arranged in each region are equal to each other,
The groove depth of the groove in the area portion located on the outside in the tire radial direction is smaller than the groove depth of the groove in the area portion located on the inside in the tire radial direction.
pneumatic tires. The pneumatic tire according to claim 1 , wherein the groove depth D of the groove is 0.1 to 0.5 mm . The pneumatic tire according to claim 1 or 2, wherein the groove width W of the groove is 0.6 to 1.8 mm. The pneumatic tire according to any one of claims 1 to 3, wherein the groove is connected to a circumferential rib that protrudes from the reference surface and extends continuously in the tire circumferential direction .

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