tire

Abstract

To provide a tire capable of improving the grounding property of a block-like land part while suppressing a deterioration in wear performance.SOLUTION: A land part is divided into block-like parts by first-width-direction sipes. The first-width-direction sipes are extended in the state of being at least partially inclined with respect to a tire width direction. The tire-width-direction width of the block-like part is 25% or more of ground width. The first-width-direction sipe has a broken part provided in a part in the extension direction of the first-width-direction sipe.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire, particularly a high-performance tire having high drainage performance, braking performance, and turning performance.

Background Art

[0002] Conventionally, in tires, particularly high-performance tires, techniques for improving the ground contact property of the block-shaped land portions have been proposed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the tires as described above, the wear performance may deteriorate.

[0005] Therefore, an object of the present invention is to provide a tire that can improve the ground contact property of the block-shaped land portions while suppressing a decrease in wear performance.

Means for Solving the Problems

[0006] The gist configuration of the present invention is as follows. (1) A tire including one or only two circumferential main grooves extending in the tire circumferential direction on the tread surface of the tread portion, and a plurality of land portions partitioned by between the circumferential main grooves or between the tread end and the circumferential main groove, wherein the land portion is partitioned into block-shaped portions by a first width-direction sipe extending in the tire width direction and communicating between the two circumferential main grooves partitioning the land portion or between the tread end and the circumferential main groove, wherein at least a part of the first width-direction sipe extends obliquely with respect to the tire width direction, The width of the aforementioned block-shaped portion in the tire width direction is 25% or more of the contact width. A tire characterized in that the first widthwise sipe has a break in a part of the extending direction of the first widthwise sipe. Here, the "tread surface" of the tread refers to the entire circumferential portion of the tread surface that comes into contact with the road surface when the tire is mounted on the applicable rim, filled to the specified internal pressure, and subjected to the maximum load (hereinafter referred to as the maximum load state). Furthermore, "circumferential main groove" refers to a groove that extends in the circumferential direction of the tire and has a groove width (opening width) of 2 mm or more. When "circumferential main groove" is described as "extending in the circumferential direction of the tire," it includes not only cases where it extends in the circumferential direction of the tire, but also cases where it extends at an inclination angle of 5° or less relative to the circumferential direction of the tire. In addition, it includes not only cases where it extends straight in the circumferential direction of the tire, but also cases where it extends in a zigzag or curved manner. Furthermore, "tread edge" refers to the outer edge in the tire width direction of the contact surface under the maximum load conditions described above. Furthermore, the "sipe" in "first widthwise sipe" refers to an extremely narrow groove that closes within the tread contact surface when the tire rolls. "Width of the block-shaped portion in the tire width direction" refers to the width (maximum width) of the tire in the tire width direction when the tire is mounted on the applicable rim, filled to the specified internal pressure, and unloaded (hereinafter referred to as the standard condition). "Contact width" refers to the width (maximum width) of the contact surface in the tire width direction under the above maximum load condition.

[0007] In this specification, "applicable rim" refers to the standard rim for the applicable size (Measuring Rim in the ETRTO STANDARDS MANUAL, Design Rim in the TRA YEAR BOOK) which is an industrial standard valid in the region where the tire is produced and used, and which is listed or will be listed in the future in publications such as the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States. (That is, the above "rim" includes not only current sizes but also sizes that may be included in the above industrial standards in the future. An example of a "size to be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the ETRTO 2013 edition.) However, in the case of a size not listed in the above industrial standards, it refers to a rim with a width corresponding to the tire bead width. Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating as described in JATMA, etc. For sizes not listed in the above industrial standards, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, "maximum load capacity" refers to the load corresponding to the above maximum load capacity.

[0008] (2) The tire according to (1) above, wherein the interrupted portion is located between the outer end of the first widthwise sipe when mounted on a vehicle and a position separated from the end by a distance of 25% of the width of the block-shaped portion in the tire width direction along the extending direction of the first widthwise sipe.

[0009] (3) The tire according to (1) or (2) above, wherein the land portion having the first widthwise sipe is the center land portion located on the tire's equatorial plane.

[0010] (4) The tire according to any one of (1) to (3) above, wherein the extended length of the interrupted portion is 10% or less of the width of the land portion in the tire width direction. Here, "width of the block-shaped portion in the tire width direction" refers to the width (maximum width) when the tire is mounted on the applicable rim, filled to the specified internal pressure, and unloaded (hereinafter referred to as the standard condition). [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a tire that can improve the contact of block-shaped land areas while suppressing a decrease in wear performance. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows a portion of the tire tread pattern according to one embodiment of the present invention. [Figure 2A] This is a diagram showing cross-section AA in Figure 1. [Figure 2B] This is a diagram showing the cross-section of BB in Figure 1. [Figure 2C] This is a diagram showing the cross-section of CC in Figure 1. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described in detail below with reference to the drawings. Although a detailed explanation will be omitted, the tire of this embodiment can be fitted with a general tire structure comprising a sidewall portion extending radially outward from a pair of bead portions, a crown portion including a tread portion spanning between the two sidewall portions, a carcass made of plies of organic fiber cords or steel cords extending from one bead portion through the crown portion to the other bead portion, and a belt having a belt layer made of, for example, steel cords, disposed between the carcass and the tread.

[0014] Figure 1 shows a part of the tread pattern of a tire according to one embodiment of the present invention. This tire has a plurality of (two in the illustrated example) circumferential main grooves 2 (2a, 2b) extending in the circumferential direction of the tire on the tread surface 1 of the tread portion. This tire has two shoulder land portions 3b, 3c that are separated by the tread edge and the circumferential main grooves 2, and a center land portion 3a that is located on the tire equatorial plane CL and is separated by the circumferential main grooves 2. In Figure 1, the regions on the outer side in the tire width direction of the two circumferential main grooves 2 (i.e., the shoulder land portions) are partially omitted from the illustration. Although not particularly limited, the groove width (opening width in the above reference state) of the circumferential main grooves 2 can be, for example, 12 to 18 mm, and the groove depth (maximum depth) can be, for example, 5 to 6 mm. In this example, there are only two circumferential main grooves, one of which, 2a, is located on the outside when mounted on a vehicle, and the other, 2b, is located on the inside when mounted on a vehicle. The groove width of the circumferential main groove 2a located on the outside is smaller than the groove width of the circumferential main groove 2b located on the inside when mounted on a vehicle. This suppresses the decrease in compressive rigidity on the outside when mounted on a vehicle and improves the wear performance of the outer part when mounted on a vehicle, which is prone to wear in the center land portion 3a. Note that "groove depth" and "sipe depth" described later refer to the maximum depth of the grooves and sipes in the above-mentioned standard condition.

[0015] In the example shown in Figure 1, the center land portion 3a is divided into a center block-shaped portion 5 by a first widthwise sipe 4 that extends in the tire width direction and connects two circumferential main grooves 2 (2a, 2b) that divide the center land portion 3.

[0016] Although not particularly limited, the sipe width (opening width) of the first widthwise sipe 4 can be, for example, 0.3 to 0.4 mm, and the sipe depth (maximum depth) can be, for example, 3 to 4 mm. The first widthwise sipe 4 extends at least partially (entirely in this example) obliquely with respect to the tire width direction. The inclination angle of the inclined portion of the first widthwise sipe 4 with respect to the tire width direction is not particularly limited but can be, for example, 5 to 15°. By setting it to 5° or more, a circumferential component that becomes a resistance component against the longitudinal force during braking can be provided to improve the wear performance. On the other hand, by setting it to 15° or less, a widthwise component that becomes a resistance component against the lateral force that causes wear is provided, and the corners of the center block-shaped portion 5 are prevented from becoming too acute, thereby improving the wear performance. Since the contribution of the lateral force to the wear performance is greater than that of the longitudinal force, it is preferable to set the inclination angle in the width direction to a relatively small value of 5 to 15°.

[0017] In the present embodiment, the width of the center block-shaped portion 5 in the tire width direction is 25% or more of the contact width. Thereby, the contact width at the center block-shaped land portion 5 can be ensured to obtain sufficient grip performance. Particularly, the effect can be effectively exerted during the high-speed performance of a light-load vehicle. Here, the "contact width" refers to the width (maximum width) in the tire width direction of the contact surface in the above maximum load state.

[0018] As shown in Fig. 1, the first widthwise groove 4 has a cutout portion 4a in a part of the extending direction of the first widthwise groove 4. That is, in this example, the cutout portion 4a is a land portion having the same height as the chamfered portion 4b. The cutout portion 4a can also be a land portion having the same height as the tread surface 1. Thereby, the center block-shaped portion 5 is not completely divided in the tire circumferential direction by the first widthwise groove 4, the compressive rigidity of the center block-shaped portion 5 can be increased, and the deterioration of the wear performance can be suppressed. In this example, the cutout portion 4a is located between the outer end of the first widthwise groove 4 when mounted on the vehicle and a position separated by a distance of 25% of the width in the tire width direction of the center block-shaped portion 5 along the extending direction of the first widthwise groove 4 from the end. By providing the cutout portion 4a on the outer side when mounted on the vehicle with high grounding performance, the adverse effect on the grounding performance due to the increase in compressive rigidity can be alleviated. Also, by setting the separation distance from the outer end when mounted on the vehicle within the above range, the cutout portion 4a can be separated from the portion having the bulging shape described later, and the deterioration of the grounding performance can be alleviated. The extending length of the cutout portion 4a is 10% or less of the width in the tire width direction of the center land portion 3a. Thereby, the deterioration of the grounding performance can be alleviated.

[0019] In the example shown in Fig. 1, the first widthwise groove 4 has a chamfered portion 4b provided in the opening. Thereby, the compressive rigidity in the vicinity of the first widthwise groove 4 can be moderately reduced, and the grounding performance can be further improved. In the illustrated example, the chamfered portion 4b is provided in the openings on both sides in the tire circumferential direction of the first widthwise groove 4, but it can also be provided on either one side, or a configuration without the chamfered portion 4b can be adopted.

[0020] Figure 2A shows the AA cross-section of Figure 1, Figure 2B shows the BB cross-section of Figure 1, and Figure 2C shows the CC cross-section of Figure 1. As shown in Figures 2A to 2C, each of the center block-shaped portions 5 has a shape that rises from all four sides toward the center (following an arc in the cross-sections shown in Figures 2A and 2C). Here, in Figure 2A, P1 and P2 indicate the starting positions of the rising portion from the tread surface 1 in the circumferential direction of the tire. Also, in Figure 2C, Q1 and Q2 indicate the starting positions of the rising portion from the tread surface 1 in the width direction of the tire. In this example, the radius of curvature between P1 and P2 is larger than the radius of curvature of the region outside the block from P1 and outside the block from P2, and the radius of curvature between Q1 and Q2 is larger than the radius of curvature of the region outside the block from Q1 and outside the block from Q2. Here, the "starting point of drop" in the tire circumferential direction refers to the point closest to the apex in the tire profile area where the drop height (distance inward in the tire radial direction) from the apex is 1 / 6 or more of the groove depth (maximum depth) of the adjacent circumferential main groove in the tire width direction, in the circumferential cross-section of the tire before rim assembly (cross-section passing through the apex of the tread profile (outermost point in the tire radial direction)). Similarly, the "starting point of drop" in the tire width direction refers to the point closest to the apex in the tire profile area where the drop height (distance inward in the tire radial direction) from the apex is 1 / 6 or more of the groove depth (maximum depth) of the adjacent circumferential main groove in the tire width direction, in the tire width cross-section (cross-section passing through the apex). If there are two adjacent circumferential main grooves with different groove depths, the maximum depth of the deeper groove shall be used.

[0021] Returning to Figure 1, this tire has a second widthwise sipe 6 (one in the illustrated example) on each of the center block-shaped portions 5, which extends across the tire equatorial plane CL in the tire width direction and terminates at both ends within the center block-shaped portion 5. In this example, the extending length of the second widthwise sipe 6 is 50% or more of the width of the center block-shaped portion 5 in the tire width direction. The sipe width (opening width) of the second widthwise sipe 6 can be, for example, 0.3 to 0.4 mm, and the sipe depth (maximum depth) can be, for example, 3 to 4 mm. At least a portion (in this example, the entirety) of the second widthwise sipe 6 extends at an inclination with respect to the tire width direction. In the illustrated example, the second widthwise sipe 6 extends approximately parallel to the first widthwise sipe 4. The inclination angle of the inclined portion of the second widthwise sipe 6 with respect to the tire width direction is not particularly limited, but can be, for example, 0 to 15°. The second lateral sipe 6 may extend in the tire width direction (without being inclined).

[0022] In this example, both ends of the second widthwise sipe 6 are located on the central side of the center block-shaped portion 5 in the tire circumferential direction, relative to the starting points P1 and P2 where the raised portion begins to drop from the tread surface 1. This reduces the compressive stiffness of the raised portion, further improving contact with the ground. In addition, both ends of the second widthwise sipe 6 are located on the outside of the center block-shaped portion 5 (towards the end of the center block-shaped portion 5) in the tire width direction, relative to the starting points Q1 and Q2 where the raised portion begins to drop from the tread surface 1. In this example, in the tire circumferential direction, the positional relationship between both ends of the second widthwise sipe 6 and the starting points P1 and P2 is as described above. Therefore, in the tire width direction, the positional relationship is as described above to ensure uniform contact pressure across the entire center block-shaped portion 5, so that the compressive stiffness of the raised portion does not decrease too much.

[0023] Here, the center block-shaped portion 5 is provided with circumferential shallow grooves 7 that extend in the circumferential direction of the tire and have a groove depth shallower than the sipe depth of the first widthwise sipe 4. This moderately relaxes the compressive rigidity of the center block-shaped portion 5, improving contact with the road surface, especially during the initial stages of driving. In this example, the circumferential shallow grooves 7 are located on the inside when mounted on the vehicle. This is because relaxing the compressive rigidity on the inside when mounted on the vehicle, which is less prone to wear, allows for a balance between wear performance and the aforementioned contact with the road surface. Here, the groove width (opening width) of the circumferential shallow grooves 7 is not particularly limited, but can be, for example, 1 mm or less, and the groove depth (maximum depth) of the circumferential shallow grooves 7 can be, for example, 1 / 3 to 1 / 2 of the sipe depth of the first widthwise sipe 4, and is not particularly limited, but can be, for example, 1 to 2 mm.

[0024] The following describes the effects and benefits of the tire according to this embodiment. In this embodiment, the center block-shaped portion 5 of the tire is demarcated by the first widthwise sipes 4. Compared to the case where the land portion is completely demarcated by widthwise grooves (without sipes), the compressive rigidity of the center land portion 3a is higher, allowing it to exhibit performance suitable for high-performance tires. Furthermore, since the tire in this embodiment has only one or two (only two in this example) circumferential main grooves 2, sufficient grip performance can be ensured by providing a wide contact width for the center land portion 3a. This is particularly effective when performing at high speeds on lightly loaded vehicles. In this embodiment, the width of the center block-shaped portion 5 in the tire width direction is 25% or more of the contact width. This ensures sufficient contact width at the center block-shaped land portion 5 and provides sufficient grip performance. In addition, in this embodiment, since the first widthwise sipes 4 are inclined with respect to the tire width direction, a circumferential component that acts as a resistance component against longitudinal forces during braking can be provided, improving wear performance. Furthermore, in this embodiment, since the first widthwise sipe 4 has a break 4a in a part of the extending direction of the first widthwise sipe 4, the center block-shaped portion 5 is not completely divided in the tire circumferential direction by the first widthwise sipe 4, thereby increasing the compressive rigidity of the center block-shaped portion 5 and suppressing a decrease in wear performance. As described above, the tire of this embodiment can improve the contact of the block-shaped ground portion while suppressing a decrease in wear performance.

[0025] In the above embodiment, in the center block-shaped portion 5 of the center land portion 3a partitioned between the two circumferential main grooves, at least a portion of the first widthwise sipe 4 extends inclined with respect to the tire width direction, the width of the center block-shaped portion 5 in the tire width direction is 25% or more of the contact width, and the first widthwise sipe 4 has a break 4a in part of the direction of extension of the first widthwise sipe 4. However, in the block-shaped portion of the shoulder land portion 3b partitioned between the circumferential main groove 2 and the tread edge, at least a portion of the first widthwise sipe 4 extends inclined with respect to the tire width direction, the width of the block-shaped portion in the tire width direction is 25% or more of the contact width, and the first widthwise sipe 4 may have a break 4a in part of the direction of extension of the first widthwise sipe 4.

[0026] As described above, it is preferable that the discontinued portion is located between the outer end of the first widthwise sipe when mounted on a vehicle and a position separated from that end by a distance of 25% of the width of the block-shaped portion in the tire width direction along the extending direction of the first widthwise sipe. By providing the discontinued portion on the outer side when mounted on a vehicle, where ground contact is high, the adverse effect on ground contact due to increased compressive rigidity can be mitigated. Furthermore, by setting the distance from the outer end when mounted on a vehicle within the above range, the discontinued portion can be separated from the portion having a raised shape, thereby mitigating the deterioration of ground contact.

[0027] Here, the land portion having the first widthwise sipe is preferably the center land portion located on the tire's equatorial plane. This is because achieving both contact and wear resistance in the center land portion is particularly suitable for high-performance tires.

[0028] Furthermore, it is preferable that the extended length of the interrupted section be 10% or less of the width of the tire in the width direction of the ground section. This can mitigate the deterioration of ground contact.

[0029] Furthermore, it is preferable that each block-shaped portion has a second widthwise sipe that extends across the tire's equatorial plane in the tire's width direction and terminates at both ends within the block-shaped portion. This further reduces the compressive rigidity of the block-shaped portion and improves its contact with the road surface. Since both ends of such second widthwise sipes terminate within the block-shaped portion, the occurrence of breakage or other damage to the block-shaped portion can also be suppressed.

[0030] As described above, it is preferable that the width of the block-shaped portion in the tire width direction be 25% or more of the contact width, thereby ensuring sufficient contact width on the block-shaped land portion and obtaining sufficient grip performance. Furthermore, as described above, the extension length of the second widthwise sipe is preferably 50% or more of the width of the block-shaped portion in the tire width direction, thereby achieving a sufficient effect of uniformizing the ground pressure.

[0031] Furthermore, as described above, it is preferable that both ends of the second widthwise sipes are located closer to the center of the block-shaped portion than the starting points P1 and P2 of the raised portion's descent from the tread surface in the tire circumferential direction. This is because it can alleviate the compressive rigidity of the raised portion and improve contact with the ground. Also, it is preferable that both ends of the second widthwise sipes are located further outward (towards the end of the block-shaped portion) of the block-shaped portion than the starting points Q1 and Q2 of the raised portion's descent from the tread surface in the tire width direction. This is because it can equalize the contact pressure across the entire block-shaped portion.

[0032] Furthermore, as mentioned above, when there are only two circumferential main grooves, it is preferable that one circumferential main groove is located on the outside when mounted on the vehicle, and the other circumferential main groove is located on the inside when mounted on the vehicle, and that the groove width of the circumferential main groove located on the outside when mounted on the vehicle is smaller than the groove width of the circumferential main groove located on the inside when mounted on the vehicle. This suppresses a decrease in compressive rigidity on the outside when mounted on the vehicle and improves the wear performance of the outer part when mounted on the vehicle, which is prone to wear.

[0033] Furthermore, as described above, it is preferable that the block-shaped portion is provided with shallow circumferential grooves that extend in the circumferential direction of the tire and whose groove depth is shallower than the sipe depth of the first widthwise sipes. This allows for a moderate reduction in the compressive rigidity of the block-shaped portion, thereby improving contact with the road surface.

[0034] Furthermore, as mentioned above, it is preferable that the circumferential shallow grooves be located on the inside when mounted on a vehicle. This is because, by mitigating the compressive rigidity on the inside when mounted on a vehicle, which is less prone to wear, it is possible to achieve both wear performance and the aforementioned contact performance, especially in the initial stages of driving.

[0035] Furthermore, by having only one second widthwise sipe in each block-shaped portion, the compressive rigidity of the block-shaped portion can be prevented from decreasing excessively.

[0036] It is preferable to have only two circumferential main grooves. This ensures sufficient contact width on block-shaped land areas, thereby providing adequate grip performance. This is particularly effective when lightly loaded vehicles are performing at high speeds.

[0037] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above. [Explanation of Symbols]

[0038] 1: Tread surface, 2: Main grooves in the circumferential direction, 3: Land area, 4: First widthwise sipe, 5: Center block-shaped section, 6: Second widthwise sipe, 7: Circumferential shallow groove, CL: Tire equatorial plane

Claims

1. A tire comprising, on the tread surface of the tread portion, one or two circumferential main grooves extending in the circumferential direction of the tire, and a plurality of land areas partitioned by the spaces between the circumferential main grooves or between the tread edge and the circumferential main grooves, The land portion is divided into block-shaped sections by a first widthwise sipe extending in the tire width direction, which connects the two circumferential main grooves that define the land portion or the tread edge with the circumferential main groove. The first lateral sipe extends at least inclined with respect to the tire width direction, The width of the aforementioned block-shaped portion in the tire width direction is 25% or more of the contact width. The first widthwise sipe has a break in a part of the direction of extension of the first widthwise sipe, The land portion having the first widthwise sipe is the center land portion located on the tire's equatorial plane, Each of the aforementioned block-shaped portions has a shape that rises from all four sides toward the center, The interrupted portion is located between the outer end of the first widthwise sipe when mounted on a vehicle and a position separated from the end by a distance of 25% of the width of the block-shaped portion in the tire width direction along the extending direction of the first widthwise sipe. A tire characterized in that the first widthwise sipe extends linearly from one end to the other, straddling the interrupted portion.

2. The tire according to claim 1, wherein the extended length of the interrupted portion is 10% or less of the width of the land portion in the tire width direction.

3. The tire according to claim 1 or 2, wherein the center land portion has second widthwise sipes whose ends terminate within the block-shaped portion.

4. The tire according to claim 3, wherein both ends of the second widthwise sipe are located in the circumferential direction of the tire, on the central side of the block-shaped portion, more than the point where the raised portion begins to drop from the tread surface.

5. The tire according to claim 3, wherein both ends of the second widthwise sipe are located outside the block-shaped portion in the tire width direction, beyond the starting point of the raised portion from the tread surface.

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