JP2021049958A - tire - Google Patents

Abstract

To improve wet performance and the durability of land parts, in a five-rib tire.SOLUTION: A tire has a tread portion 2. The tread portion 2 is formed by four peripheral grooves 3, and five land parts 4. The five land parts are made from two shoulder land parts 9, two middle land parts 8, and a crown land part 7. The shoulder land part 9 is a rib that is not provided with a lateral groove with a depth of 2 mm or more. The crown land part 7 is provided with a plurality of crown sipes 10. The middle land part 8 is provided with a middle sipe 11. The crown sipe 10 and the middle sipe 11 include a sipe body portion 12 extending in a wave-shape in a tire radial direction, and a bottom part 13 arranged on the inner side in the tire radial direction of the sipe body portion, on a cross-section orthogonal to a length direction thereof. The bottom part 13 extends in the tire radial direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a tire.

Various tires (hereinafter, may be referred to as "5-rib tires") in which the tread portion is formed by five land portions divided by a circumferential groove have been proposed. (For example, see Patent Document 1 below.).

Japanese Unexamined Patent Publication No. 2017-043208

In general, 5-rib tires tend to have a small width in each land area. Further, in a 5-rib tire, when traveling, a large contact pressure tends to act on three land parts (crown land part and middle land parts on both sides thereof) excluding the land parts on both outer sides in the tire axial direction. Therefore, the three land parts are easily deformed during traveling. On the other hand, if sipes are provided on the three land parts in order to improve wet performance, these land parts are more likely to be deformed, which may cause uneven wear and cracks at the bottom of the sipes. there were.

The present invention has been devised in view of the above problems, and a main object of the present invention is to improve wet performance and durability of land parts (crown land part and middle land part) in a 5-rib tire.

The present invention is a tire having a tread portion, and the tread portion is formed by four circumferential grooves extending continuously in the tire circumferential direction and five land portions divided by the circumferential grooves. , The five land parts include two shoulder land parts, two middle land parts provided between the two shoulder land parts, and a crown land part provided between the two middle land parts. The shoulder land portion is a rib having no lateral groove having a depth of 2 mm or more, and the crown land portion is provided with a plurality of crown sipes that cross the crown land portion, and the middle land portion is provided. A plurality of middle sipe crossing the middle land portion are provided in the portion, and the crown sipe and the middle sipe have a sipe main body portion extending in a wavy shape in the tire radial direction in a cross section orthogonal to the length direction thereof, and the sipe. The bottom portion includes a bottom portion arranged inside in the tire radial direction of the main body portion, and the bottom portion extends along the tire radial direction.

In the tire of the present invention, it is desirable that the crown sipe and the middle sipe extend in a wavy shape in the sipe length direction on the tread tread.

In the tire of the present invention, it is desirable that the bottom portion extends linearly in the sipe length direction.

In the tire of the present invention, the length of the bottom portion in the tire radial direction is preferably 10% to 30% of the maximum sipe depth.

In the tire of the present invention, the circumferential groove includes a crown circumferential groove between the crown land portion and the middle land portion, and the depth of the crown sipe and the middle sipe is the depth of the crown circumferential groove. It is preferably 40% to 90% of the tire.

In the tire of the present invention, the crown sipe and the middle sipe have a width of 2.0 mm or less, and the crown land portion and the middle land portion are not provided with grooves having a groove width larger than 2.0 mm. Is desirable.

In the tire of the present invention, it is desirable that the crown sipe and the middle sipe are inclined in opposite directions with respect to the tire axial direction.

In the tire of the present invention, it is desirable that the angle of the middle sipe with respect to the tire axial direction is larger than the angle of the crown sipe with respect to the tire axial direction.

In the tire of the present invention, it is desirable that the length of one pitch of the plurality of crown sipes in the tire circumferential direction is 80% to 150% of the width of the crown land portion in the tire axial direction.

In the tire of the present invention, it is desirable that the length of one pitch of the plurality of middle sipe in the tire circumferential direction is 80% to 150% of the width of the middle land portion in the tire axial direction.

In the tire of the present invention, it is desirable that the shoulder land portion is a smooth rib having no groove.

The tread portion of the tire of the present invention includes two shoulder land portions, two middle land portions provided between the two shoulder land portions, and a crown land portion provided between the two middle land portions. It is formed of five land areas consisting of. The shoulder land portion is composed of ribs having a depth of 2 mm or more and not provided with a lateral groove. Such a shoulder land portion is made highly rigid, the amount of deformation in the tire radial direction when touching the ground is small, and the contact pressure acting on the crown land portion and the middle land portion is reduced. Such an action helps to suppress wear and damage of the crown land portion and the middle land portion.

The crown land portion is provided with a plurality of crown sipes that cross the crown land portion, and the middle land portion is provided with a plurality of crown sipes that cross the middle land portion. Each such sipe helps improve wet performance.

The crown sipe and the middle sipe include a sipe main body portion extending in a wavy shape in the tire radial direction and a bottom portion arranged inside the tire radial direction of the sipe main body portion in a cross section orthogonal to the length direction thereof. When the sipe main body is grounded, the sipe walls facing each other mesh with each other to suppress the opening of the sipe, and thus damage to the land portion can be suppressed. Further, since the bottom portion extends along the radial direction of the tire, stress is unlikely to be concentrated on the bottom portion even when the sipe is opened, and the occurrence of cracks can be effectively suppressed.

It is a development view of the tread part of the tire of one Embodiment of this invention. It is an enlarged view of the crown land part and the middle land part of FIG. FIG. 2 is a cross-sectional view taken along the line AA of FIG. It is an enlarged perspective view which shows the sipe wall of a crown sipe and a middle sipe. It is sectional drawing of the tire sipe of the comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a developed view of a tread portion 2 of a tire 1 showing an embodiment of the present invention. As shown in FIG. 1, the tire 1 of the present invention is suitably used as, for example, a pneumatic tire for a heavy load. However, the present invention is not limited to such usage.

The tread portion 2 is formed by four circumferential grooves 3 that extend continuously in the tire circumferential direction and five land portions 4 divided by the circumferential grooves 3.

The circumferential groove 3 is composed of two crown circumferential grooves 5 and two shoulder circumferential grooves 6. The crown circumferential grooves 5 are arranged on both sides of the tire equator C, for example. The shoulder circumferential groove 6 is provided between the crown circumferential groove 5 and the tread end Te.

The "tread end Te" is the most when a normal load is applied to a tire 1 in a normal state, which is rim-assembled on a regular rim and is filled with a regular internal pressure, and is grounded on a flat surface at a camber angle of 0 degrees. This is the ground contact position on the outside in the tire axial direction. Unless otherwise specified, the dimensions and the like of each part of the tire are values measured in a normal state.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATTA, "Design Rim" for TRA, and ETRTO. If so, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in "VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum load capacity", for TRA, the table "TIRE LOAD LIMITS" The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

The crown circumferential groove 5 and the shoulder circumferential groove 6 extend linearly in the tire circumferential direction, for example.

It is desirable that the distance L1 in the tire axial direction from the tire equator C to the groove center line of the crown circumferential groove 5 is, for example, 0.08 to 0.15 times the tread width TW. It is desirable that the distance L2 in the tire axial direction from the tire equator C to the groove center line of the shoulder circumferential groove 6 is, for example, 0.25 to 0.35 times the tread width TW. However, the arrangement of the crown circumferential groove 5 and the shoulder circumferential groove 6 is not limited to such a range. The tread width TW is the distance in the tire axial direction between the tread ends Te and Te in the normal state.

The groove width of each circumferential groove is preferably, for example, 3 to 6% of the tread width TW. In the case of the heavy-duty tire of the present embodiment, the depth of each circumferential groove is preferably 10 to 20 mm, for example.

The five land areas 4 are the two shoulder land areas 9, the two middle land areas 8 provided between the two shoulder land areas 9, and the crown land area provided between the two middle land areas 8. It consists of 7. The land portion 7 of the crown is divided between the two circumferential grooves 5 of the crown. The middle land portion 8 is divided into a crown land portion 7 and a shoulder land portion 9. The shoulder land portion 9 is divided between the shoulder circumferential groove 6 and the tread end Te.

The shoulder land portion 9 is a rib having a depth of 2 mm or more and not provided with a lateral groove. Such a shoulder land portion 9 has a small amount of deformation in the tire radial direction when the tire touches the ground, and reduces the load acting on the crown land portion 7 and the middle land portion 8. Such an action helps to suppress wear and damage of the crown land portion 7 and the middle land portion 8.

In order to further enhance the above-mentioned action, the shoulder land portion 9 of the present embodiment is a smooth rib without a groove.

FIG. 2 shows an enlarged view of the crown land portion 7 and the middle land portion 8. As shown in FIG. 2, the width W1 of the crown land portion 7 in the tire axial direction and the width W2 of the middle land portion 8 in the tire axial direction are, for example, the tread width TW (shown in FIG. 1, and so on. It is 0.10 to 0.20 times.

The crown land portion 7 is provided with a plurality of crown sipes 10 that cross the crown land portion 7. The middle land portion 8 is provided with a plurality of crown sipes 10 that cross the middle land portion 8. Such a crown sipe 10 and a middle sipe 11 are useful for ensuring wet performance. In addition, in this specification, a sipe means a notch having a width of 2.0 mm or less.

FIG. 3 shows a cross-sectional view taken along the line AA of the crown sipe 10 of FIG. 2 as a diagram showing the cross-sectional shapes of the crown sipe 10 and the middle sipe 11. As shown in FIG. 3, the crown sipe 10 and the middle sipe 11 are arranged inside the sipe main body 12 in the tire radial direction and the sipe main body 12 extending in a wavy shape in the tire radial direction in a cross section orthogonal to the length direction thereof. Includes the bottom portion 13 that has been removed. Further, the bottom portion 13 extends along the radial direction of the tire. In this embodiment, the bottom portion 13 extends parallel to the tire radial direction.

When the sipe main body 12 is in contact with the ground, the sipe walls facing each other mesh with each other to suppress the opening of the sipe, and thus damage to the land portion can be suppressed. Further, since the bottom portion 13 extends along the radial direction of the tire, stress is unlikely to be concentrated on the bottom portion 13 even when the sipe is opened, and the occurrence of cracks can be effectively suppressed.

The maximum sipe depth d1 of the crown sipe 10 and the middle sipe 11 is, for example, 40% to 90% of the depth of the crown circumferential groove 5, preferably 60% to 80%.

The length L3 of the sipe main body 12 in the tire radial direction is, for example, 70% to 90% of the maximum sipe depth d1.

The sipe body 12 may extend in a zigzag shape in the radial direction of the tire, for example. In the cross section orthogonal to the sipe length direction, the amplitude amount A1 (peak-to-peak amplitude amount, the same applies hereinafter) of the sipe main body portion 12 is, for example, 0.5 to 2.5 mm, which is desirable. Is 1.0 to 2.0 mm. As a result, molding defects during tire vulcanization are suppressed, and sipe opening is suppressed.

The length L4 of the bottom portion 13 in the tire radial direction is, for example, 10% to 30%, preferably 15% to 20% of the maximum sipe depth d1. Such a bottom portion 13 can effectively suppress cracks in the land portion.

The width of the bottom portion 13 is the same as the width of the sipe main body portion 12. However, the width of the bottom portion 13 is not limited to such an aspect, and the width of the bottom portion 13 may be larger than the width of the sipe main body portion 12.

FIG. 4 shows an enlarged perspective view showing the sipe wall 20 of the crown sipe 10 and the middle sipe 11. As shown in FIG. 4, the bottom portion 13 extends linearly in the sipe length direction. That is, at the bottom portion 13, the sipe wall 20 is formed in a flat shape. Such a bottom portion 13 is unlikely to be the starting point of a crack and is useful for increasing the durability of the land portion.

The crown sipe 10 and the middle sipe 11 extend in a wavy shape in the sipe length direction on the tread tread. The crown sipe 10 and the middle sipe 11 of the present embodiment are configured as a so-called 3D sipe in which the sipe main body 12 extends in a wavy manner in the sipe length direction and the sipe depth direction. In such a sipe, the sipe walls facing each other can be firmly engaged with each other, and the above-mentioned effect can be further enhanced.

As shown in FIG. 2, the amplitude amount A2 of the crown sipe 10 and the middle sipe 11 in the tread plane view is, for example, 1.0 to 3.5 mm, preferably 1.5 to 3.0 mm. As a result, molding defects during tire vulcanization are suppressed, and sipe opening is suppressed.

It is desirable that the crown sipe 10 and the middle sipe 11 are inclined with respect to the tire axial direction, respectively. As a result, frictional force in the tire axial direction is provided during wet running, and wet performance is improved.

As a preferred embodiment, the crown sipe 10 and the middle sipe 11 of the present embodiment are inclined in opposite directions with respect to the tire axial direction. Such a sipe arrangement helps to control one-sided tire flow.

The angle θ1 of the crown sipe 10 with respect to the tire axial direction is, for example, 5 to 15 °. The angle θ2 of the middle sipe 11 with respect to the tire axial direction is, for example, 10 to 20 °. It is desirable that the angle θ2 of the middle sipe 11 is larger than the angle θ1 of the crown sipe 10. As a result, frictional force is obtained in multiple directions by the edges of each sipe, and wet performance is improved. When the sipe extends in a wavy shape, the angle is measured at the center line of the amplitude of the sipe.

It is desirable that the one-pitch length P1 of the plurality of crown sipes 10 in the tire circumferential direction is 80% to 150% of the width W1 of the crown land portion 7 in the tire axial direction. Further, it is desirable that the one-pitch length P2 of the plurality of middle sipes 11 in the tire circumferential direction is 80% to 150% of the width W2 of the middle land portion 8 in the tire axial direction. Such a sipe arrangement enhances the wet performance and the durability of the land in a well-balanced manner.

It is desirable that the end portion 11a of the middle sipe 11 on the crown circumferential groove 5 side is displaced from the end portion 10a of the crown sipe 10 on the crown circumferential groove 5 side in the tire circumferential direction. The amount of displacement L5 between the end portion 11a of the middle sipe 11 and the end portion 10a of the crown sipe 10 in the tire circumferential direction is, for example, 0.25 to 0.45 times the width W2 of the middle land portion 8 in the tire axial direction. Is. As a result, uneven wear around the crown circumferential groove 5 is suppressed.

The crown sipe 10 includes a non-overlapping portion extending outside the first region 15 in which any one of the middle sipe 11 is projected parallel to the tire axial direction. The non-overlapping portion is preferably 50% or more of the length of the crown sipe 10. As a more desirable embodiment, the crown sipe 10 of the present embodiment is entirely arranged outside the first region 15.

It is desirable that the middle sipe 11 arranged on one middle land portion 8 includes an overlapping portion extending within the first region 15 of any one of the middle sipe 11 arranged on the other middle land portion 8. The overlapping portion is preferably 50% or more of the length of the middle sipe. As a more desirable embodiment, the middle sipe 11 of the present embodiment is entirely arranged in the first region 15. Such an arrangement of sipes, in combination with the arrangement of the crown sipes 10 described above, can suppress uneven wear on land.

It is desirable that the crown sipe 10 and the middle sipe 11 communicate with, for example, the recesses 25 in which the side walls of the land portions at both ends are recessed. This further improves the wet performance.

It is desirable that the crown land portion 7 and the middle land portion 8 are not provided with grooves having a groove width larger than 2.0 mm. This further improves the durability of each land area.

Although the tire of one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and may be modified to various embodiments.

A pneumatic tire of size 275 / 80R22.5 for heavy loads having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, as shown in FIG. 5, a tire was prototyped in which each sipe a extends parallel to the radial direction of the tire and does not have a sipe main body extending in a wavy shape. The tire of the comparative example is the same as the basic pattern shown in FIG. 1, except for the above configuration. The wet performance and land durability of each test tire were tested. The common specifications and test methods for each test tire are as follows.
Mounting rim: 7.50 x 22.5
Tire internal pressure: 900kPa
Test vehicle: 5t loaded on 10t truck (2-D vehicle) Tire mounting position: All wheels

<Wet performance>
With the above test vehicle, a sudden start was made on an asphalt road surface having a water film with a water depth of 1 mm, and the time required to travel 20 m was measured. The result is the reciprocal of the time of the comparative example, and is shown by an exponent with the value of the comparative example as 100. The larger the value, the better the wet performance.

<Durability of land>
The appearance of wear on land when the test vehicle was run for a certain distance was visually evaluated. The result is a score with the appearance of the comparative example as 100, and the larger the value, the better the durability of the land area.
The test results are shown in Table 1.

As a result of the test, it was confirmed that the tire of the example had improved wet performance and durability on land.

2 Tread part 3 Circumferential groove 4 Land part 7 Crown land part 8 Middle land part 9 Shoulder land part 10 Crown sipe 11 Middle sipe 12 Sipe body part 13 Bottom part

Claims (11)

A tire with a tread
The tread portion is formed by four circumferential grooves extending continuously in the tire circumferential direction and five land portions divided by the circumferential grooves.
The five land parts consist of two shoulder land parts, two middle land parts provided between the two shoulder land parts, and a crown land part provided between the two middle land parts. Become
The shoulder land portion is a rib having no lateral groove having a depth of 2 mm or more.
A plurality of crown sipes that cross the crown land portion are provided on the crown land portion.
The middle land portion is provided with a plurality of middle sipes that cross the middle land portion.
The crown sipe and the middle sipe include a sipe body portion extending in a wavy shape in the tire radial direction and a bottom portion arranged inside the tire radial direction in a cross section orthogonal to the length direction thereof.
The bottom portion extends along the radial direction of the tire.
tire. The tire according to claim 1, wherein the crown sipe and the middle sipe extend in a wavy shape in the sipe length direction on the tread tread. The tire according to claim 1 or 2, wherein the bottom portion extends linearly in the sipe length direction. The tire according to any one of claims 1 to 3, wherein the length of the bottom portion in the tire radial direction is 10% to 30% of the maximum sipe depth. The circumferential groove includes a crown circumferential groove between the crown land portion and the middle land portion.
The tire according to any one of claims 1 to 4, wherein the depth of the crown sipe and the middle sipe is 40% to 90% of the depth of the crown circumferential groove. The crown sipe and the middle sipe have a width of 2.0 mm or less and have a width of 2.0 mm or less.
The tire according to any one of claims 1 to 5, wherein the crown land portion and the middle land portion are not provided with a groove having a groove width larger than 2.0 mm. The tire according to any one of claims 1 to 6, wherein the crown sipe and the middle sipe are inclined in opposite directions with respect to the tire axial direction. The tire according to any one of claims 1 to 7, wherein the angle of the middle sipe with respect to the tire axial direction is larger than the angle of the crown sipe with respect to the tire axial direction. The tire according to any one of claims 1 to 8, wherein the length of one pitch of the plurality of crown sipes in the tire circumferential direction is 80% to 150% of the width of the land portion of the crown in the tire axial direction. The tire according to any one of claims 1 to 9, wherein one pitch length of the plurality of middle sipe tires in the tire circumferential direction is 80% to 150% of the width of the middle land portion in the tire axial direction. The tire according to any one of claims 1 to 10, wherein the shoulder land portion is a smooth rib having no groove.

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