JP7528705B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

Generally, the sidewall of a tire is covered with a thin layer of rubber. For this reason, localized irregularities called bulges and dents are likely to appear on the outer surface of the sidewall due to the seams of the carcass, which is the internal structural material of the tire. For this reason, for example, Patent Document 1 below proposes a tire with a decorative pattern on the outer surface of the sidewall to prevent the irregularities from being noticeable.

On the other hand, vulcanization molds for tire molding are provided with many vent holes for discharging gas from within the mold cavity. These vent holes help prevent molding defects in pneumatic tires by discharging air and gas generated during vulcanization from within the mold cavity, while vent holes provided in positions corresponding to the sidewalls of the pneumatic tire suck up the plasticized rubber together with the gas, forming whisker-like so-called spews (see, for example, Patent Document 2 below).

JP 2020-131763 A JP 2002-264145 A

To make the decorative portion more prominent on the outer surface of the sidewall, it is possible to form a decorative portion and a smooth portion. In this case, if many vent holes are provided in the vulcanization mold at positions corresponding to the smooth portion, many spews are formed in the smooth portion of the sidewall. Such spews tend to generate air resistance when the tire rotates, which in turn increases the rolling resistance of the tire.

The present invention was devised in consideration of the above-mentioned circumstances, and its main objective is to reduce rolling resistance while suppressing vulcanization molding defects in pneumatic tires in which decorative parts are formed on the outer surface of the sidewall part.

The present invention is a pneumatic tire having a pair of sidewall portions, and a pattern portion extending in a band shape in the tire circumferential direction is configured on the outer surface of at least one of the pair of sidewall portions, and the pattern portion includes a plurality of smooth portions aligned in the tire circumferential direction and a boundary portion that defines the smooth portions, and the boundary portion includes a pair of ribs that protrude outside the tire beyond the outer surface of the smooth portions and extend around the smooth portions, and an uneven portion provided between the pair of ribs, and the outer surface of the smooth portions is not provided with spews.

In the pneumatic tire of the present invention, it is preferable that the uneven portion includes a plurality of ridges extending between the pair of ribs.

In the pneumatic tire of the present invention, it is preferable that the pattern portion includes three or more of the smooth portions.

In the pneumatic tire of the present invention, it is preferable that the uneven portion has a top surface that is flush with the pair of ribs.

In the pneumatic tire of the present invention, it is desirable that the depth of the region between the pair of ribs is smaller than the maximum height of the boundary portion.

In the pneumatic tire of the present invention, it is preferable that the areas of the plurality of smooth portions decrease toward one side in the tire circumferential direction.

In the pneumatic tire of the present invention, the boundary portion includes a first boundary portion extending along the tire circumferential direction, and the pair of ribs at the first boundary portion includes an outer rib and an inner rib arranged radially inward of the outer rib in the tire, and it is preferable that the maximum height of the inner rib from the reference sidewall surface is greater than the maximum height of the outer rib from the reference sidewall surface.

In the pneumatic tire of the present invention, it is preferable that a spew is formed in the first boundary portion.

By adopting the above-mentioned configuration, the pneumatic tire of the present invention can reduce rolling resistance while suppressing vulcanization molding defects.

FIG. 2 is an enlarged view of the outer surface of the sidewall portion of the tire of the present embodiment. FIG. 2 is an enlarged perspective view of a smooth portion and a boundary portion of FIG. 1 . 2 is a cross-sectional view taken along line AA in FIG. 1. 2 is a cross-sectional view taken along line BB in FIG. 1.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Fig. 1 is an enlarged view of the outer surface of a sidewall portion 3 when a pneumatic tire (hereinafter, sometimes simply referred to as a "tire") 1 of this embodiment is viewed from the side. In Fig. 1, the contour extending in an arc corresponds to the outer surface 2s of a tread portion 2. As shown in Fig. 1, the tire 1 of this embodiment is a tire for passenger cars, and has a pair of sidewall portions 3 on both sides of the tread portion 2. However, the present invention is not limited to such an embodiment, and may be applied to, for example, tires for motorcycles and tires for heavy loads.

In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are measured in a normal state. In the case of pneumatic tires for which various standards are established, the "normal state" refers to a state in which the tire is mounted on a normal rim, inflated to a normal internal pressure, and no load is applied. In the case of tires for which various standards are not established or non-pneumatic tires, the normal state refers to a standard usage state according to the intended use of the tire, and a state in which no load is applied.

A "genuine rim" is a rim that is specified for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

"Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. For JATMA, it is the "maximum air pressure." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "INFLATION PRESSURE."

In the tire 1 of this embodiment, a pattern portion 5 extending in a band shape in the tire circumferential direction is configured on the outer surface of at least one of the pair of sidewall portions 3. The pattern portion 5 includes a plurality of smooth portions 8 aligned in the tire circumferential direction and a boundary portion 10 that defines the smooth portions 8.

2 shows an enlarged perspective view of the smooth portion 8 and the boundary portion 10. As shown in FIG. 2, the boundary portion 10 includes a pair of ribs 15 that protrude outward from the outer surface of the smooth portion 8 and extend around the smooth portion 8, and an uneven portion 18 provided between the pair of ribs 15. Furthermore, no spew is provided on the outer surface of the smooth portion 8. In this specification, the term "spew" refers to a thin, whisker-like piece of rubber that is sucked up during vulcanization molding by a vent hole provided in the mold.

By adopting the above-mentioned configuration, the tire 1 of the present invention can reduce rolling resistance while suppressing vulcanization molding defects. The following mechanism is presumed to be the reason for this.

Conventionally, when a sidewall portion is provided with multiple smooth portions and boundary portions that define them, the boundary portions are often recessed further than the smooth portions. This is presumably determined in consideration of the workability and maintainability of the molding surfaces of the vulcanization mold that correspond to the smooth portions and boundary portions. However, the inventors have reexamined these conventional circumstances and the effects of recessed boundary portions and the provision of spews on the smooth portions, leading to the completion of the present invention.

In the present invention, the ribs of the boundary portion 10 protrude beyond the smooth portion 8, so that the area constituting the boundary portion 10 is concave on the molding surface of the corresponding mold. This makes it difficult for air pockets to form in the smooth portion 8 during vulcanization molding. Even if a bare spot occurs due to air pockets, it occurs between a pair of ribs 15, so the impact on the appearance of the tire is small. This prevents vulcanization molding defects.

In addition, generally, when a tire rotates, the smooth portion of the sidewall has a relatively high speed of air flowing over its surface, which is thought to have a large effect on the tire's air resistance. In the present invention, since no spew is provided on the smooth portion 8, it is thought that the air resistance of the tire can be reduced, and therefore the rolling resistance of the tire can be reduced.

The following describes the configuration of this embodiment in more detail. Each of the configurations described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-mentioned effects even if it does not have the configurations described below. Furthermore, even if any one of the configurations described below is applied alone to a tire of the present invention having the above-mentioned characteristics, an improvement in performance corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, a composite improvement in performance corresponding to each configuration can be expected.

As shown in FIG. 1, the pattern portion 5 of the sidewall portion 3 includes, for example, three or more smooth portions 8. The areas of the multiple smooth portions 8 become smaller toward one side in the tire circumferential direction. The pattern portion 5 having such smooth portions 8 can reliably make bulges and dents in the sidewall portion 3 less noticeable (hereinafter, this effect may be referred to as "improved concealment performance").

In a more desirable embodiment, the smooth portion 8 includes a large smooth portion 8a that is relatively long in the tire circumferential direction and a small smooth portion 8b that is relatively short in the tire circumferential direction. The circumferential length of the large smooth portion 8a in this embodiment is, for example, 4% to 7% of the total circumferential length of the ground contact surface of the tread portion 2. The circumferential length of the small smooth portion 8b in this embodiment is, for example, 3% or less of the total circumferential length of the ground contact surface of the tread portion 2. In this embodiment, 5 to 15 small smooth portions 8b are lined up on one side of one large smooth portion 8a in the tire circumferential direction. This arrangement of the smooth portions 8 further improves the concealing performance.

The boundary portion 10 includes two first boundary portions 11 extending along the tire circumferential direction and a plurality of second boundary portions 12 connected between them. The two first boundary portions 11 extend parallel to each other at a distance in the tire radial direction. The plurality of second boundary portions 12 are provided at a distance in the tire circumferential direction. Each second boundary portion 12 extends, for example, at an incline with respect to the tire circumferential direction. In this embodiment, one smooth portion 8 is defined by the two first boundary portions 11 and the two second boundary portions 12.

The second boundaries 12 are arranged, for example, such that their angle with respect to the tire circumferential direction becomes larger toward one side in the tire circumferential direction. In other words, the more the second boundaries 12 included in one pattern section 5 are located on one side in the tire circumferential direction, the larger their angle with respect to the tire circumferential direction. In addition, the second boundaries 12 are arranged such that the distance between two second boundaries 12 in the tire circumferential direction becomes smaller toward one side in the tire circumferential direction. This further improves the concealing performance.

Figure 3 shows a cross-sectional view of line A-A in Figure 1 as a cross-sectional view showing an example of the boundary portion 10. As shown in Figure 3, the maximum height h1 of the boundary portion 10 from the reference sidewall surface 3s is, for example, 0.2 to 1.0 mm. The width W1 of the boundary portion 10 is, for example, 2.0 to 5.0 mm. However, the boundary portion 10 is not limited to this dimensional range, and it is sufficient that the boundary portion 10 is capable of defining the smooth portion 8 when the sidewall portion 3 is observed with normal attention while the tire is stationary.

The pair of ribs 15 at the boundary portion 10 are, for example, flattened triangular shapes with a top surface 15t on the tire outer surface side. The width W2 of the top surface 15t is, for example, 0.2 to 0.4 mm. This prevents vulcanization molding defects at the boundary portion 10 and reduces the air resistance at the boundary portion 10.

The depth d1 of the area between the pair of ribs 15 is, for example, smaller than the maximum height h1 of the boundary portion 10, and is preferably 70% to 90% of the maximum height h1. This prevents vulcanization molding defects and increases the contrast between the area and the smooth portion 8.

As shown in FIG. 2, the uneven portion 18 provided between the pair of ribs 15 includes a plurality of ridges 25 extending between the pair of ribs 15. The ridges 25 have, for example, a top surface on the outer surface side of the tire. This increases the contrast between the boundary portion 10 and the smooth portion 8, resulting in excellent concealment performance. However, the uneven portion 18 may be in any form that creates a contrast with the smooth portion 8, and may, for example, be a form in which a plurality of columnar protrusions are arranged.

As shown in FIG. 3, it is preferable that the uneven portion 18 has a top surface 18t that is flush with the pair of ribs 15. This configuration means that the top surfaces of the ribs 15 and the top surface 18t of the uneven portion 18 are disposed at the same height relative to the reference sidewall surface 3s. This further increases the contrast between each top surface 18t and the rest of the surface, further improving the concealing performance.

Figure 4 shows a cross-sectional view of line B-B in Figure 2 as a cross-sectional view illustrating another aspect of the boundary portion 10. As shown in Figure 4, the pair of ribs 15 of the first boundary portion 11 includes an outer rib 16 and an inner rib 17 arranged radially inward of the outer rib 16.

The maximum height h3 of the inner rib 17 from the reference sidewall surface 3s is greater than the maximum height h2 of the outer rib 16 from the reference sidewall surface 3s. Specifically, the maximum height h3 of the inner rib 17 is 110% to 140% of the maximum height h2 of the outer rib 16. The first boundary portion 11 having such inner ribs 17 and outer ribs 16 has high releasability during vulcanization molding, and can effectively suppress vulcanization molding defects.

As shown in FIG. 2, when spews are arranged in the patterned portion 5, it is preferable that the spews are provided at the boundary portion 10 (the spews are omitted in FIG. 2). In other words, it is preferable that vent holes are provided at the molding surface of the vulcanizing mold where the boundary portion 10 is molded. This makes it possible to reduce the number of spews while suppressing the occurrence of bare spots.

In addition, since the first boundary 11 has a large length in the tire circumferential direction, providing vent holes in this area increases the efficiency of gas exhaust. Also, the spews arranged at the first boundary 11 tend to have less air resistance than the spews arranged at the second boundary 12. From this perspective, in a more desirable embodiment, it is desirable that a spew is formed at the first boundary 11 and that no spew is formed at the second boundary 12. This reliably suppresses vulcanization molding defects and further reduces rolling resistance.

The above describes in detail a particularly preferred embodiment of the present invention, but the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways.

A tire of size 225/55R19 including the sidewall portion shown in FIG. 1 was manufactured. As a comparative example, a tire was manufactured in which the smooth portion protruded beyond the boundary portion and a spew was arranged in the smooth portion. The comparative tire was substantially the same as the example tire except for the above-mentioned points. Each test tire was tested for the presence or absence of vulcanization molding defects and rolling resistance. The common specifications and test method of the test tires are as follows.
Rim: 19x7J
Tire pressure: 200kPa

<Presence or absence of vulcanization molding defects>
Each test tire was evaluated for the occurrence of dents (B/S) in the sidewall due to defective vulcanization. The results were rated on the following five-level scale.
A: B/S is not detected by visual inspection or palpation. B: B/S is not detected by visual inspection. C: B/S is detected by visual inspection, but is barely noticeable. D: B/S is detected by visual inspection. E: B/S is very noticeable and improvement is necessary.

<Rolling resistance>
The rolling resistance of each test tire was measured when it was run at a constant speed using a drum tester. The results were expressed as an index with the reciprocal of the rolling resistance of the comparative example taken as 100, and the larger the index, the lower the rolling resistance and the better the result.
The results of the tests are shown in Table 1.

As shown in Table 1, the test results confirmed that the tires of the embodiment had reduced rolling resistance while suppressing vulcanization molding defects.

3 Sidewall portion 5 Pattern portion 8 Smooth portion 10 Boundary portion 15 Rib 18 Concave-convex portion

Claims (8)

A pneumatic tire having a pair of sidewall portions,
At least one of the pair of sidewall portions has an outer surface formed with a pattern portion extending in a band shape in the tire circumferential direction,
The pattern portion includes a plurality of smooth portions arranged in a tire circumferential direction and a boundary portion that defines the smooth portions,
the boundary portion includes a pair of ribs that protrude toward an outer side of the tire than an outer surface of the smooth portion and extend around the smooth portion, and an uneven portion provided between the pair of ribs,
The outer surface of the smooth portion is not provided with a spew.
Pneumatic tires. The pneumatic tire of claim 1, wherein the uneven portion includes a plurality of ridges extending between the pair of ribs. The pneumatic tire according to claim 1 or 2, wherein the pattern portion includes three or more of the smooth portions. The pneumatic tire according to any one of claims 1 to 3, wherein the uneven portion has a top surface that is flush with the pair of ribs. The pneumatic tire according to any one of claims 1 to 4, wherein the depth of the region between the pair of ribs is smaller than the maximum height of the boundary portion. The pneumatic tire according to any one of claims 1 to 5, wherein the areas of the plurality of smooth portions decrease toward one side in the tire circumferential direction. the boundary portion includes a first boundary portion extending along a tire circumferential direction,
The pair of ribs of the first boundary portion includes an outer rib and an inner rib disposed radially inward of the outer rib,
The pneumatic tire according to claim 1 , wherein a maximum height of the inner rib from a reference sidewall surface is greater than a maximum height of the outer rib from the reference sidewall surface. The pneumatic tire according to claim 7, wherein a spew is formed in the first boundary portion.

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