JP2023025555A - tire - Google Patents

Abstract

To provide a tire that can prevent a crack from developing larger in a groove bottom part of a groove that is provided in a tread part.SOLUTION: A tire includes a tread part 2. The tread part 2 is provided with at least one groove 10 for draining water. A plurality of fine grooves 20 is provided in a groove bottom part 11 of the groove 10. A groove width W1 of the fine grooves 20 is 200 μm or less.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to tires.

For example, Patent Literature 1 below proposes a tire having a tread portion provided with a plurality of drainage grooves.

JP 2020-125046 A

Cracks may occur in the bottom of grooves provided in the tread due to aging of the tire. In particular, when a single scratch is formed on the bottom of the groove during use of the tire, distortion of the tread portion during running of the tire concentrates on the scratch, and a crack tends to grow larger starting from the scratch. was there.

The present disclosure has been devised in view of the above circumstances, and a main object thereof is to provide a tire capable of suppressing large crack growth at the bottom of grooves provided in the tread.

The present disclosure is a tire having a tread portion, wherein the tread portion is provided with at least one drainage groove, a groove bottom portion of the groove is provided with a plurality of fine grooves, and the plurality of fine grooves are provided in a groove bottom portion of the groove. The tire has a groove width of 200 μm or less.

By adopting the above configuration, the tire of the present disclosure can effectively suppress large crack growth at the groove bottom of the groove provided in the tread.

It is a meridian cross-sectional view of the tire of this embodiment. Figure 2 is an enlarged perspective view of the groove of Figure 1; 3 is an enlarged cross-sectional view of the fine groove of FIG. 2; FIG. 3 is an enlarged plan view of the groove bottom of FIG. 2; FIG.

An embodiment of the present disclosure will be described below with reference to the drawings. FIG. 1 is a meridional cross-sectional view of a tire 1 in a normal state, showing an embodiment of the present disclosure. As shown in FIG. 1, the present disclosure is preferably applied to pneumatic tires for passenger cars, for example. However, the present disclosure is not limited to such an aspect, and may be applied to tires for motorcycles and heavy loads, for example.

In the case of a pneumatic tire defined by various standards, the "normal state" is a state in which the tire is mounted on a normal rim, filled with a normal internal pressure, and in a no-load state. In the case of tires for which various standards have not been established, the normal condition means a standard usage condition according to the purpose of use of the tire, which is a condition in which the tire is not mounted on the vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are the values measured in the normal condition.

A "regular rim" is a rim defined for each tire in a standard system that includes standards on which tires are based. For ETRTO, it is "Measuring Rim".

"Regular internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standards on which tires are based. Maximum value described in VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

Inside the tire 1 of this embodiment, tire constituent members such as a carcass 6 and a belt layer 7 are arranged. Known aspects are appropriately adopted for these tire constituent members.

The carcass 6 extends from the bead portion 4 on one side through the sidewall portion 3 on one side, the tread portion 2, the sidewall portion 3 on the other side, and the bead portion 4 on the other side. The carcass 6 of this embodiment is composed of, for example, one carcass ply 6A. The carcass ply 6A is composed of, for example, carcass cords made of organic fibers arranged at an angle of 75 to 90 degrees with respect to the tire circumferential direction.

The belt layer 7 is composed of, for example, two belt plies 7A and 7B. The belt plies 7A and 7B are composed of, for example, belt cords arranged at an angle of 10 to 45 degrees with respect to the tire circumferential direction. Organic fiber cords, for example, may be employed for the belt cords. In other embodiments, a tread reinforcing layer such as a band layer may be further arranged outside the belt layer 7 .

At least one drainage groove 10 is provided in the tread portion 2 . The tread portion 2 of the present embodiment is provided with a plurality of circumferential grooves continuously extending in the tire circumferential direction as drainage grooves 10 . The grooves 10 are not limited to such an aspect, and include, for example, lateral grooves extending in the tire axial direction.

The drainage groove 10 is a groove at least partially arranged in the ground contact surface of the tread portion 2, and during wet running, drains water between the contact surface of the tread portion 2 and the road surface to the outside of the tire. It means a groove that can expect the function of discharging. In the passenger car tire 1 of this embodiment, the groove width of the groove 10 is, for example, 1.5 to 15 mm, preferably 3 to 10 mm. The depth of the groove 10 is, for example, 3-15 mm, preferably 5-10 mm. The angle of the groove wall surface of the groove 10 with respect to the tire radial direction is, for example, 0 to 15°. However, the dimensions of the groove 10 are not limited to such an aspect.

An enlarged perspective view of the groove 10 is shown in FIG. As shown in FIG. 2, the groove bottom 11 of the groove 10 is provided with a plurality of fine grooves 20 . The groove bottom 11 of the groove 10 of the present disclosure includes a bottom surface 13 extending in the groove width direction between two groove wall surfaces 12 extending in the depth direction of the groove 10, and between the bottom surface 13 and the groove wall surface 12. A curved surface 14 is included. In addition, in FIG. 2, the fine grooves 20 are exaggerated and enlarged so that the features of the present disclosure can be easily understood.

An enlarged cross-sectional view of the fine groove 20 is shown in FIG. As shown in FIG. 3, the groove width W1 of the plurality of fine grooves 20 is 200 μm or less. By adopting the configuration described above, the present disclosure can effectively suppress large crack growth at the groove bottom portion 11 of the groove 10 provided in the tread portion 2 . The reason for this is presumed to be the following mechanism.

Conventionally, due to aged deterioration of a tire, cracks may occur at the groove bottoms of grooves provided in the tread portion, and the cracks may grow larger. In particular, when the groove bottom is composed of a smooth outer surface, a single flaw is formed on the groove bottom, and distortion of the tread portion during tire running concentrates on the flaw, which in turn causes the flaw to become a starting point. There was a tendency for cracks to grow large.

In the present disclosure, as described above, since a plurality of fine grooves having a groove width of 200 μm or less are provided in the groove bottom portion 11, the strain and stress of the tread portion 2 during tire running are distributed and act on each fine groove 20. Therefore, cracks do not grow large from the fine grooves 20, and the occurrence of large cracks that are fatal to the use of the tire can be suppressed.

A more detailed configuration of the present embodiment will be described below. Each configuration described below represents a specific aspect of the present embodiment. Therefore, it goes without saying that the present disclosure can exhibit the above effects even if it does not have the configuration described below. Further, even if any one of the configurations described below is applied alone to the tire of the present disclosure having the features described above, an improvement in performance according to each configuration can be expected. Furthermore, when some of the respective configurations described below are applied in combination, it is possible to expect a combined improvement in performance according to each configuration.

If the groove width W1 of the fine groove 20 is large, cracks may grow from the fine groove 20 . Therefore, the groove width W1 of the fine groove 20 is desirably 150 μm or less, more desirably 100 μm or less. On the other hand, when the groove width W1 of the fine groove 20 is small, the strain of the tread portion 2 cannot be dispersed sufficiently, and the effect of suppressing crack growth may deteriorate. Therefore, the groove width W1 of the fine groove 20 is desirably 5 μm or more, more desirably 30 μm or more. By setting the groove width W1 of the fine groove 20 within the above range, the strain of the tread portion 2 can be sufficiently dispersed while suppressing the growth of cracks from the fine groove 20 . Note that even when the groove width W1 of the fine groove 20 is substantially 0 due to the two groove wall surfaces of the fine groove 20 coming into contact with each other, compared with a conventional tire (a tire in which no fine grooves are arranged), the , the effect of suppressing the growth of cracks can be fully expected.

From the same viewpoint as the groove width W1 described above, the depth d1 of the plurality of fine grooves 20 is preferably 10 μm or more, more preferably 30 μm or more, preferably 300 μm or less, more preferably 150 μm or less, and even more preferably 100 μm. It is below. In particular, the fine grooves 20 having a depth d1 of 30 to 100 μm can be expected to have the above effects even when the groove width is greater than 200 μm.

Preferably, the plurality of microgrooves 20 extends along the length of the groove 10, as shown in FIG. Note that this aspect includes aspects in which the angle between the groove 10 and the fine groove 20 is 10° or less. In a more desirable aspect, the groove 10 and the plurality of fine grooves 20 extend parallel. However, it is not limited to such a mode, and the fine grooves 20 may extend in the groove width direction of the grooves 10 .

FIG. 4 shows an enlarged plan view of the groove bottom 11 in which the fine grooves 20 are provided. As shown in FIG. 4, the fine grooves 20 extend linearly in the direction described above, for example. However, it is not limited to such a mode, and the fine grooves 20 may extend in a wavy shape, for example. The length L1 of the plurality of fine grooves 20 (the so-called periphery length along the length direction of the fine grooves 20) is preferably 500 µm or more, more preferably 800 µm or more, and more preferably 3000 µm or less. is 2000 μm or less, more preferably 1500 μm or less. In this embodiment, a plurality of fine grooves 20 having the same shape extend in the same direction.

The plurality of fine grooves 20 includes two fine grooves 20 adjacent to each other with a first interval t1 in the groove width direction of the fine grooves 20 . In this embodiment, the plurality of fine grooves 20 are arranged in the groove width direction of the fine grooves 20 with the first interval t1 therebetween. From the viewpoint of sufficiently exhibiting the crack growth suppression effect, the first interval t1 is preferably 100 μm or more, more preferably 150 μm or more, and preferably 1000 μm or less, more preferably 500 μm or less, and still more preferably 300 μm or less. .

The plurality of fine grooves 20 includes two fine grooves 20 adjacent to each other with a second interval t2 in the length direction of the fine grooves 20 . In this embodiment, the plurality of fine grooves 20 are linearly aligned in the longitudinal direction of the fine grooves 20 with a second interval t2 to form a row. From the same viewpoint as the first interval t1, the second interval t2 is preferably 100 μm or more, more preferably 150 μm or more, and preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less.

The plurality of microgrooves 20 includes first microgrooves 21 and second microgrooves 22 extending in the same direction. Also, the first fine groove 21 and the second fine groove 22 overlap in the length direction. In this embodiment, the row of the first fine grooves 21 arranged linearly in the length direction of the fine grooves 20 and forming a row, and the row arranged linearly in the length direction of the fine grooves 20 are configured. The rows of the second fine grooves 22 are adjacent to each other, and the first fine grooves 21 and the second fine grooves 22 are arranged so as to overlap in the length direction. The overlapping length L2 of the first fine groove 21 and the second fine groove 22 is preferably 10% or more, more preferably 20% or more, of the maximum length of the first fine groove 21 or the second fine groove 22. It is preferably 30% or more, preferably 50% or less, more preferably 45% or less. As a result, the stress is distributed to each of the fine grooves 20, and the stress is more likely to act, and the occurrence of cracks is further reliably suppressed.

The number of fine grooves 20 provided per 1 cm ² of the surface of the groove bottom 11 is preferably 20 or more, more preferably 100 or more, still more preferably 200 or more, and preferably 1550 or less, more preferably. It is 700 or less, more preferably 500 or less. Thereby, crack generation can be suppressed while maintaining the durability of the groove bottom portion 11 .

As shown in FIG. 2 , in this embodiment, a plurality of fine grooves 20 are provided not only on the bottom surface 13 of the groove 10 but also on the curved surface 14 between the bottom surface 13 and the groove wall surface 12 . However, it is not limited to such a mode, and for example, the fine grooves 20 may be provided only on the bottom surface 13 of the groove 10 .

The strain and stress of the tread portion 2 are more likely to act on the curved surface 14 than on the bottom surface 13 . Therefore, it is desirable that the groove width or depth of the fine grooves 20 provided on the curved surface 14 is smaller than the groove width or depth of the fine grooves 20 provided on the bottom surface 13 . The number of fine grooves 20 provided per 1 cm ² of the curved surface 14 is preferably smaller than the number of fine grooves 20 provided per 1 cm ² of the bottom surface 13 . This reduces the strain and stress acting on the curved surface 14, further suppressing the occurrence of cracks.

Since a large strain does not act on the groove wall surface 12 of the groove 10, the groove wall surface 12 of the groove 10 of this embodiment is not provided with the fine grooves 20 described above. Thereby, the durability of the groove wall surface 12 is maintained.

The fine grooves 20 described above can be obtained by a known manufacturing method. For example, unevenness corresponding to a plurality of fine grooves 20 is arranged by laser processing or the like on the outer surface of the convex portion of the vulcanization mold corresponding to the grooves 10 described above, and this vulcanization mold is used to form the tread portion of the tire. The tire of the present disclosure can be manufactured by molding the The tire of the present disclosure can also be manufactured by forming the above-described grooves 10 and fine grooves 20 in the tread portion 2 by hand cutting, for example, without being limited to such a mode.

Although the tire according to one embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the above-described specific embodiments, and can be implemented with various modifications.

As an example tire, a pneumatic tire of size 215/55R17 shown in FIG. 1 was manufactured. The tire of the example has the basic structure of FIG. 1, and as shown in FIG. 2, fine grooves are provided on the groove bottom of the groove. As a comparative example, a pneumatic tire was manufactured in which the groove bottom portion was not provided with fine portions. The tire of the comparative example is substantially the same as the tire of the example except for the above items. These test tires were run under certain conditions, and the number of cracks generated in the groove bottom was measured. A specific test method is as follows.

<Number of cracks generated>
After storing the test tire in the following storage method, run it on a drum tester under the following running conditions, and cracks that occur at the bottom of the groove (length of 5.0 mm or more and opening width of 0.5 mm or more) ) was measured.
Storage method: Stored for 20 days in a storage room at a temperature of 80°C and a humidity of 80%. Running conditions: Tires are mounted on regular rims, filled with regular internal pressure, and subjected to 80% of the maximum tire load on a drum tester. Tables 1 to 4 show the test results of running the tire at 100 km/h for 20,000 km.

As shown in Tables 1 to 4, the comparative example had 21 cracks, while the examples had 0 to 8 cracks. That is, it was confirmed that the present disclosure could significantly suppress crack growth.

[Appendix]
The present disclosure includes the following aspects.

[Present Disclosure 1]
A tire having a tread portion,
The tread portion is provided with at least one drainage groove,
A plurality of fine grooves are provided in the groove bottom of the groove,
The groove width of the plurality of fine grooves is 200 μm or less,
tire.
[Disclosure 2]
The tire according to the present disclosure 1, wherein the groove width is 5 μm or more.
[Disclosure 3]
The tire according to present disclosure 1 or 2, wherein the depth of the plurality of fine grooves is 10 to 300 μm.
[Disclosure 4]
4. The tire according to any one of present disclosures 1 to 3, wherein the plurality of fine grooves have a length of 500 to 3000 μm.
[Disclosure 5]
5. The tire according to any one of the present disclosures 1 to 4, wherein the plurality of fine grooves extend along the length direction of the grooves.
[Disclosure 6]
6. The tire according to any one of the present disclosures 1 to 5, wherein 20 to 1550 fine grooves are provided per 1 cm ² of the surface of the groove bottom.
[Present Disclosure 7]
The plurality of fine grooves includes two fine grooves adjacent to each other with a first interval in the groove width direction of the fine grooves,
7. The tire according to any one of the present disclosure 1 to 6, wherein the first spacing is 100-1000 μm.
[Disclosure 8]
The plurality of microgrooves includes two microgrooves adjacent to each other with a second spacing in the length direction of the microgrooves,
The tire according to any one of the present disclosure 1 to 7, wherein the second spacing is 100-1000 μm.
[Disclosure 9]
The plurality of fine grooves include first fine grooves and second fine grooves extending in the same direction,
The first fine groove and the second fine groove overlap in their length direction,
8. Any one of 1 to 7 of the present disclosure, wherein the overlapping length of the first fine groove and the second fine groove is 10% to 45% of the maximum length of the first fine groove or the second fine groove The tire described in
[Disclosure 10]
A tire having a tread portion,
The tread portion is provided with at least one drainage groove,
A plurality of fine grooves are provided in the groove bottom of the groove,
The depth of the plurality of fine grooves is 30 to 100 μm,
tire.

2 tread portion 10 groove 11 groove bottom 20 fine groove W1 groove width of fine groove

Claims (10)

A tire having a tread portion,
The tread portion is provided with at least one drainage groove,
A plurality of fine grooves are provided in the groove bottom of the groove,
The groove width of the plurality of fine grooves is 200 μm or less,
tire. The tire according to claim 1, wherein the groove width is 5 µm or more. The tire according to claim 1 or 2, wherein the depth of said plurality of fine grooves is 10 to 300 µm. The tire according to any one of claims 1 to 3, wherein the length of said plurality of fine grooves is 500-3000 µm. 5. A tire according to any preceding claim, wherein the plurality of microgrooves extends along the length of the grooves. The tire according to any one of claims 1 to 5, wherein 20 to 1550 fine grooves are provided per 1 cm ² of the surface of the groove bottom. The plurality of fine grooves includes two fine grooves adjacent to each other with a first interval in the groove width direction of the fine grooves,
A tire according to any one of the preceding claims, wherein said first spacing is between 100 and 1000 µm. The plurality of microgrooves includes two microgrooves adjacent to each other with a second spacing in the length direction of the microgrooves,
A tire according to any one of the preceding claims, wherein said second spacing is between 100 and 1000 µm. The plurality of fine grooves include first fine grooves and second fine grooves extending in the same direction,
The first fine groove and the second fine groove overlap in their length direction,
Any one of claims 1 to 8, wherein the overlapping length of the first fine groove and the second fine groove is 10% to 45% of the maximum length of the first fine groove or the second fine groove. or the tire according to item 1. A tire having a tread portion,
The tread portion is provided with at least one drainage groove,
A plurality of fine grooves are provided in the groove bottom of the groove,
The depth of the plurality of fine grooves is 30 to 100 μm,
tire.

Images