tire

Abstract

To provide a tire that can make both motion performance on a dry road surface and on a wet road surface compatible high high-dimensionally, even if a shape of a block is so complicated that a width of the block varies in a tire width direction.SOLUTION: In a pneumatic tire, at least a portion including an outside end in a tire width direction of a grounding surface of a block, on a cross section along the tire width direction and a tire radial direction, is formed in a round shape that goes toward inside in the tire radial direction as going toward outside in the tire width direction. Differences in height between a top part at an outermost side in the tire radial direction of the block and an outside end in the tire width direction of at least one side of the block vary according to widths of the block.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a tire including land blocks having a cross-sectional shape along the tire width direction that is rounded. [Background technology]

[0002] Conventionally, a tire has been known that has land blocks (which may simply be called blocks) with a rounded cross-sectional shape along the tire width direction in order to improve driving performance on wet roads without degrading driving performance on dry roads (Patent Document 1).

[0003] A tire equipped with such blocks can improve drainage without reducing block rigidity, thereby achieving high levels of driving performance on both dry and wet roads. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2014 / 148260 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the block shape is complex, for example when the block width varies in the tire width direction, it is not easy to achieve high levels of driving performance on both dry and wet roads.

[0006] The following disclosure has been made in light of these circumstances, and aims to provide a tire that can achieve high levels of driving performance on both dry and wet roads, even when the block shape is complex, such as when the block width varies in the tire width direction. [Means for solving the problem]

[0007] One aspect of the present disclosure is a tire (pneumatic tire 10) having a tread (tread 20) formed with a plurality of blocks (center blocks 100, second blocks 200, and shoulder blocks 300), in which, in a cross section along the tire width direction and the tire radial direction, at least a portion of the contact surface of the block, including the tire widthwise outer end, is rounded toward the tire radially inward as it moves toward the tire widthwise outer side, and the height difference from the tire radially outermost apex of the block to at least one tire widthwise outer end of the block varies depending on the width of the block. [Effects of the Invention]

[0008] According to the tire described above, even when the block shape is complex, such as when the block width varies in the tire width direction, it is possible to achieve high levels of driving performance on both dry and wet roads. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a partial plan view of the tread of a pneumatic tire 10. FIG. [Figure 2] FIG. 2 is an enlarged plan view of a portion of the tread 20. As shown in FIG. [Figure 3] FIG. 3 is a diagram showing a schematic cross-sectional shape of the center block 100, the second block 200, and the shoulder block 300 along the tire width direction and the tire radial direction. [Figure 4] FIG. 4 is a diagram showing the cross-sectional shape of the tread 20 including the second block 200 (narrow width region 210). [Figure 5] FIG. 5 is a diagram showing the cross-sectional shape of the tread 20 including the second block 200 (wide region 230). DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described with reference to the drawings. Note that the same or similar reference numerals are used to designate the same functions or configurations, and descriptions thereof will be omitted as appropriate.

[0011] (1) Overall tire configuration FIG. 1 is a partial plan view of a tread 20 of a pneumatic tire 10 according to this embodiment. As shown in FIG. 1, the pneumatic tire 10 has a tread 20 in which a plurality of blocks (land blocks) are formed. FIG. 1 shows only one side in the tire width direction based on the tire equator line CL. The pneumatic tire 10 has a symmetrical shape with respect to the tire equator line CL.

[0012] The pneumatic tire 10 can be used for a general four-wheeled passenger vehicle, but can be suitably used for a high-performance vehicle with particularly high maneuverability.

[0013] The tread 20 is the portion that comes into contact with the road surface. The tread 20 has a pattern formed thereon that corresponds to the environment in which the pneumatic tire 10 is used and the type of vehicle on which it is mounted.

[0014] Specifically, circumferential grooves 30, inclined grooves 40, and lug grooves 50 are formed in the tread 20. The circumferential grooves 30 are formed closer to the tire equator line CL. The circumferential grooves 30 are linear grooves extending in the tire circumferential direction.

[0015] The inclined grooves 40 extend at an angle relative to the tire width direction and the tire circumferential direction. The inclination angle of the inclined grooves 40 is not particularly limited, but an appropriate inclination angle may be set in consideration of the drainage performance required of the pneumatic tire 10. The inclined grooves 40 may curve toward the shoulder side of the tread 20 as they move outward in the tire width direction, and the inclined grooves 40 may extend to the shoulder of the tread 20.

[0016] The lug grooves 50 extend along the tire width direction and are shorter than the oblique grooves 40. The lug grooves 50 need not necessarily extend parallel to the tire width direction as long as they are aligned along the tire width direction rather than the tire circumferential direction. The lug grooves 50 may also extend to the shoulders of the tread 20.

[0017] The tread 20 has a plurality of blocks formed therein, each of which is partitioned by a circumferential groove 30, an oblique groove 40, and a lug groove 50. Specifically, the tread 20 has a center block 100, a second block 200, and a shoulder block 300 formed therein.

[0018] The center block 100 is a rib-shaped block formed in an area including the tire equator line CL. The center block 100 is defined by circumferential grooves 30.

[0019] The second blocks 200 are formed on the outer sides in the tire width direction of the center blocks 100. The second blocks 200 are defined by the circumferential grooves 30 and the oblique grooves 40.

[0020] The shoulder blocks 300 are formed on the outer sides in the tire width direction of the second blocks 200. The shoulder blocks 300 are defined by the oblique grooves 40 and the lug grooves 50.

[0021] Although not shown, the pneumatic tire 10 may be configured with a carcass, intersecting belts, various belt reinforcing layers, bead portions, etc. The belt reinforcing layer may have a structure in which a cord made of polyethylene terephthalate is wound spirally continuously in the tire circumferential direction, and the cord has a diameter of 6.9 × 10 -2 It is preferable that the adhesive is applied by applying a tension of 29.4 N / tex or more, and that the modulus of elasticity measured at 160°C under a load of 29.4 N is 2.5 mN / dtex·% or more.

[0022] 2 is a partially enlarged plan view of the tread 20. As described above, the second blocks 200 are defined by the circumferential grooves 30 and the oblique grooves 40, and therefore the width of the second blocks 200 varies in the tire circumferential direction.

[0023] Specifically, the second block 200 has a narrow region 210 , a medium width region 220 , and a wide width region 230 .

[0024] The narrow-width region 210 is a region within the second block 200 where the width (block width) along the tire width direction is narrow. The narrow-width region 210 may be a region with a width of a predetermined width (W1) or less.

[0025] The medium-width region 220 is a region within the second block 200 where the block width is medium. The medium-width region 220 may be a region with a width of a predetermined width (W2) or less.

[0026] The wide-width region 230 is a region within the second block 200 where the block width is wide. The wide-width region 230 may be a region with a width of a predetermined width (W3) or less.

[0027] The narrow-width region 210, the medium-width region 220, and the wide-width region 230 may be classified based on the block width. For example, a region with a block width of less than 30 mm may be the narrow-width region 210, a region with a block width of 30 mm or more and 45 mm or less may be the medium-width region 220, and a region with a block width of 45 mm or more may be the wide-width region 230.

[0028] Note that W1, W2, and W3 have the relationship of W1 < W2 < W3, and may be the average width in each region or the width at a specific position in the tire circumferential direction of each region.

[0029] (2) Cross-sectional shape of the block Next, the cross-sectional shape of the block, specifically, the cross-sectional shapes of the center block 100, the second block 200, and the shoulder block 300 will be described.

[0030] FIG. 3 is a schematic diagram of the cross-sectional shape of the block according to the present embodiment. Specifically, FIG. 3 shows the schematic cross-sectional shapes of the center block 100, the second block 200, and the shoulder block 300 (hereinafter, the block is appropriately omitted) along the tire width direction and the tire diameter direction.

[0031] As shown in FIG. 3, the grounding surface (tread surface) of the block is round. Specifically, as shown in FIG. 3, in a cross section along the tire width direction and the tire diameter direction, at least a part including the outer end of the grounding surface of the block in the tire width direction is round and slopes inward in the tire diameter direction as it goes outward in the tire width direction.

[0032] That is, in a cross section along the tire width direction and the tire diameter direction, the outer contour shape of the block has a top P that is the outermost position in the tire diameter direction and is convex outward in the tire diameter direction.

[0033] More specifically, the outer contour shape of the block may be composed of a plurality of parts with different radii of curvature. Such a block may be particularly called a multi-round block (MRB).

[0034] In the MRB, the convex shape of the grounding surface of the block consists of a convex curve in which a plurality of curved portions having a predetermined curvature are smoothly connected. When the curvature of the central curve portion including the central portion of the grounding surface (the region including the block equator line CL B is defined as Rc and the curvature of the end curve portion including the end of the grounding surface is defined as Re, it may be defined that Rc < Re and the curvature of the curve portion located between the central curve portion and the end curve portion is within the range of Rc to Re.

[0035] Also, in the present embodiment, the height difference D from the top P, which is the outermost position of the block in the tire diameter direction, to at least one outer end of the block in the tire width direction varies according to the width of the block (such as W1, W2, W3 shown in FIG. 2). The position of the top P may vary in the tire width direction according to the block width, but the position of the top P does not necessarily change abruptly according to the block width and may change gently in order to avoid becoming a wear core.

[0036] The height difference D may be interpreted as the difference in height from the groove bottom of the groove adjacent to the block along the tire radial direction. The height difference D may also be called the drop amount of the block (MRB drop amount). The height difference D may be expressed as the sum of the height difference D1 in the Rc region and the height difference D2 in the Re region. In addition, the sidewall of the block may be inclined at a predetermined angle (φ) with respect to the tire radial direction.

[0037] Fig. 4 shows the cross-sectional shape of the tread 20 including the second blocks 200 (narrow regions 210). Fig. 5 shows the cross-sectional shape of the tread 20 including the second blocks 200 (wide regions 230).

[0038] The height difference D varies depending on the width of the blocks. Specifically, the height difference D may increase as the width of the blocks increases. The specific value of the height difference D is not particularly limited, and may be determined depending on the curvature of the MRB, the level of drainage performance required of the pneumatic tire 10, the tire life (groove depth of the circumferential grooves 30 and the inclined grooves 40, etc.), etc. Generally, the height difference D may be set within a range of several millimeters or less.

[0039] As shown in Fig. 4, when the width of a block is equal to or less than a predetermined value (for example, W1), the height difference D may be constant regardless of the width of the block. Also, as shown in Fig. 4, when the width of a block (narrow width region 210) is equal to or less than a predetermined value, the block (narrow width region 210) may be rounded over the entire block in the tire width direction. That is, in the narrow width region 210, the block equator line CL B The position of this curve is the apex P, and a curvature (MRB set width in the drawing) may be imparted to the entire block in the tire width direction.

[0040] On the other hand, when the width of the block exceeds a predetermined value (for example, W3), the block (wide region 230) may be rounded in a part of the block including the outer end of the block's contact surface in the tire width direction. BThe region of a predetermined width including the position is the apex P, and a curvature may be imparted to a part of the block on the outer side in the tire width direction (MRB set width in the drawing). B When the region of the predetermined width including the position is the apex P, the MRB set width may be based on the outer end of the block of the apex P in the tire width direction.

[0041] Furthermore, when the block width is equal to or greater than a predetermined value (e.g., W2), the elevation difference D may be constant regardless of the block width. Furthermore, the elevation difference D may vary depending on the width of the rounded portion of the block along the tire width direction. In other words, the elevation difference D may vary depending on the MRB set width.

[0042] The MRB may also be set for the center block 100 and the shoulder blocks 300 based on the same technical concept as for the second block 200. For example, the same MRB setting as for the narrow width region 210 may be applied to the center block 100, and the same MRB setting as for the medium width region 220 may be applied to the shoulder blocks 300. Alternatively, the MRB setting may not be applied to the second block 200, and may be applied only to the center block 100 and / or the shoulder blocks 300.

[0043] (3) Actions and Effects In the pneumatic tire 10 described above, the height difference D from the apex P of the block at the outermost position in the tire radial direction to at least one outer end of the block in the tire width direction varies depending on the width of the block. Specifically, the height difference D may vary depending on the width of the rounded portion of the block along the tire width direction.

[0044] More specifically, the height difference D increases as the block width (for example, W1, W2, W3, etc. shown in FIG. 2) increases.

[0045] For this reason, even if the block width varies in the tire width direction, a sufficient load can be applied near the block apex P, effectively suppressing loss of ground contact pressure. If there is not a sufficient height difference D (drop amount), the wider the block width, after the pneumatic tire 10 is filled with internal pressure, the greater the deformation of the tread rubber in the thin gauge parts due to the difference in rigidity caused by the difference in tread rubber gauge between the grooves and the block (land portion) ends, and the more likely ground contact pressure will concentrate on the edge parts of the blocks.

[0046] With the pneumatic tire 10, the concentration of ground pressure at the edge portions of the blocks can be reduced regardless of the block width, thereby suppressing loss of ground pressure. This increases the ground pressure near the apex P, suppressing the retention of a water film between the tire and the road surface when traveling on wet roads. As a result, high drainage performance can be ensured regardless of the block width.

[0047] That is, the pneumatic tire 10 can achieve high levels of driving performance on both dry and wet roads even when the block shape is complex, such as when the block width varies in the tire width direction.

[0048] In this embodiment, when the block width is equal to or smaller than a predetermined value (for example, W1), the height difference D may be constant regardless of the block width. This is because if the height difference D is too large when the block width is narrow, the effect of suppressing loss of ground contact pressure may be reduced.

[0049] Furthermore, when the block width is equal to or less than a predetermined value (for example, W1), the block may be rounded over the entire block in the tire width direction, which can effectively increase the ground contact pressure near the apex P.

[0050] On the other hand, if the width of the block exceeds a predetermined value (for example, W3), the block may be rounded in part, including the outer end of the block's contact surface in the tire width direction. This allows for a sufficient area of ​​the top P, which is not curved and is flat, to be secured in the case of a wide block, thereby improving ground contact and drainage.

[0051] In this embodiment, if the width of the block is equal to or greater than a predetermined value (for example, W2), the height difference D may be constant regardless of the width of the block. This is because if the height difference D is too large when the block width is wide, the block's contact area will be reduced, which will in turn impair ground contact and drainage.

[0052] (4) Other embodiments Although the embodiments have been described above, it will be obvious to those skilled in the art that the present invention is not limited to the description of the embodiments and that various modifications and improvements are possible.

[0053] For example, the pneumatic tire 10 has the circumferential grooves 30, the oblique grooves 40, and the lug grooves 50 formed therein, but some of these grooves may not be formed. In other words, the MRB setting described above may be applied to any pneumatic tire having blocks formed therein whose block widths vary in the tire circumferential direction.

[0054] Furthermore, the pneumatic tire 10 has a tread pattern that is symmetrical with respect to the tire equator line CL, but is not limited to such a tread pattern, and a tread pattern that is asymmetrical with respect to the tire equator line CL may also be applied.

[0055] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure. [Explanation of symbols]

[0056] 10 Pneumatic tires 20 Tread 30 Circumferential groove 40 Slant groove 50 lug grooves 100 Center Block 200 Second Block 210 Narrow area 220 Intermediate width area 230 Wide Area 300 Shoulder Block CL tire equator line P Top

Claims

1. A tire having a tread formed with a plurality of blocks, In a cross section along the tire width direction and the tire radial direction, at least a part of the contact surface of the block including an outer end in the tire width direction has a rounded shape that approaches the inner side in the tire radial direction as it approaches the outer side in the tire width direction, a difference in elevation from an outermost apex of the block in the tire radial direction to at least one outer end of the block in the tire width direction varies in the tire circumferential direction according to a width of the block along the tire width direction, A tire in which the position of the apex of each block in the tire width direction varies in the tire circumferential direction depending on the width of the block.

2. The tire according to claim 1 , wherein the height difference increases as the width of the block increases.

3. A tire as described in claim 1, wherein, with respect to the portion of the block where the width is 30 mm or less, the height difference is the same as the height difference when the width is 30 mm, regardless of the width of the block, and does not change in the circumferential direction of the tire.

4. A tire as described in claim 1, wherein when the width of the block is 45 mm or more, the height difference is the same as the height difference when the width is 45 mm regardless of the width of the block, and does not change in the circumferential direction of the tire.

5. A tire as described in claim 1, wherein the height difference of the blocks varies depending on the width of the rounded portion along the tire width direction.

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