tire

Abstract

To exhibit high traction in a mud road or a snow road.SOLUTION: In a tire 1, one groove 3 is provided in a tread part 2. The groove 3 includes a groove bottom 4 defining a groove depth d and a pair of groove walls 5, 5. A pattern part 6 in which a plurality of fine dimples 7 are formed is provided in a part from the groove bottom 4 to a surface 5a of the groove wall 5. An outermost end 6e of the pattern part 6 in a tire radial direction is located in a range of 10% or more and 20% or less of the groove depth d from the groove bottom 4 to the outside of the tire radial direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] The following Patent Document 1 describes a tire provided with grooves. A plurality of minute projections are provided on the groove walls of the grooves in order to enhance the mud performance. These minute projections promote the separation between the groove walls and the mud adhering thereto, and improve the mud performance by suppressing the clogging of the grooves.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, as mud performance and snow performance, it is also required to exhibit greater traction on these soft road surfaces. That is, in the tread contact surface, after the mud and snow are compacted, the groove obtains traction by shearing them. Therefore, it is important that the surface of the groove and the compacted mud and snow do not slip with each other as much as possible while the groove is in contact with the ground. On the other hand, when the groove is separated from the contact surface, the mud and snow in the groove need to be quickly discharged from the groove.

[0005] The present invention has been devised in view of the above actual situation, and the main object thereof is to provide a tire capable of exhibiting high traction on a mud road or a snow road.

Means for Solving the Problems

[0006] The present invention relates to a tire including a tread portion, wherein the tread portion is provided with at least one groove recessed in the radial direction of the tire, the groove includes a groove bottom defining the groove depth and a pair of groove walls, and includes a pattern portion in which a plurality of minute dimples are formed from the groove bottom to the surface of at least one of the pair of groove walls, the outermost end of the pattern portion in the radial direction of the tire is located outside the groove bottom in the radial direction of the tire within a range of 10% or more and 20% or less of the groove depth. [Effects of the Invention]

[0007] By adopting the above configuration, this invention can achieve high traction on muddy and snowy roads. [Brief explanation of the drawing]

[0008] [Figure 1] (a) is a perspective view of the tread portion of a tire according to one embodiment of the present invention, and (b) is a cross-sectional view of the groove. [Figure 2] (a) is a plan view of the pattern section, and (b) is a cross-sectional view of (a) along line AA. [Figure 3] (a) and (b) are cross-sectional views of micro-protrusions in other embodiments. [Figure 4] This is a cross-sectional view of the groove. [Figure 5] This is a plan view of the tread section. [Figure 6] (a) is a perspective cross-sectional view of the circumferential groove and transverse groove of another embodiment, and (b) is a cross-sectional view of the groove of another embodiment. [Modes for carrying out the invention]

[0009] One embodiment of the present invention will be described below with reference to the drawings. The drawings contain exaggerations and representations that differ from the actual structural dimensional ratios in order to aid in understanding the invention. Furthermore, where there are multiple embodiments, the same reference numerals are used throughout the specification for identical or common elements, and redundant descriptions are omitted.

[0010] Figure 1(a) is a perspective cross-sectional view of the tread portion 2 of one embodiment of the tire 1 of the present invention. The present invention is used in a pneumatic tire 1 for passenger cars. The present invention may also be used, for example, in a heavy-duty tire 1.

[0011] In this specification, unless otherwise specified, the dimensions of each part of tire 1 are measured under normal conditions. "Normal conditions" means that tire 1 is mounted on a normal rim (not shown), filled with normal internal pressure, and under no load.

[0012] A "standard rim" is the rim defined for each tire within the standards system that the tire is based on. For example, it is the "standard rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0013] "Regular internal pressure" refers to the air pressure specified for each tire by each standard within the tire standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0014] As shown in Figure 1(a), the tread portion 2 of this embodiment is provided with at least one groove 3 that is recessed in the radial direction of the tire. In this specification, the groove refers to a concave body with a width of 1.5 mm or more.

[0015] Figure 1(b) is a cross-sectional view of the groove 3. As shown in Figure 1, the groove 3 in this embodiment includes a groove bottom 4 that defines the groove depth d, and a pair of groove walls 5, 5. The groove bottom 4 is the position in the cross-section of the groove 3 where the groove depth is greatest. Each groove wall 5 connects the groove bottom 4 to the contact surface 2a of the tread portion 2.

[0016] The groove 3 includes a pattern portion 6 in which a plurality of minute dimples 7 are formed extending from the groove bottom 4 over the surface 5a of at least one of the pair of groove walls 5, 5. Such a pattern portion 6 with minute dimples 7 formed thereon reduces the contact area with snow or mud (hereinafter referred to as "mud etc."), thus promoting the peeling of mud etc. from the groove 3 and enhancing the traction on a muddy road or a snowy road. Also, since the minute dimples 7 do not reduce the groove volume of the groove 3, the shearing force can be maintained at a high level. In this specification, the performance related to traction on a muddy road is referred to as mud traction performance, and the performance related to traction on a snowy road is referred to as snow traction performance.

[0017] The outermost end 6e of the pattern portion 6 in the tire radial direction is located in a range T of 10% or more and 20% or less of the groove depth d on the outer side in the tire radial direction from the groove bottom 4. At a position less than 10% of the groove depth d on the outer side in the tire radial direction from the groove bottom 4, when the groove 3 is in contact with the ground (hereinafter referred to as "when grounded"), a relatively large compressive force acts on the mud etc. Therefore, even when the groove 3 separates from the ground (hereinafter referred to as "when separated"), the mud etc. is likely to be in a clogged state. Thus, by setting the outermost end 6e of the pattern portion 6 to be 10% or more on the outer side in the tire radial direction from the groove bottom 4, the soil discharging property and snow discharging property at the time of separation can be enhanced. Also, at a position in a range exceeding 20% of the groove depth d on the outer side in the tire radial direction from the groove bottom 4, even at the time of grounding, the compacted mud etc. is likely to slide relative to the groove 3. Therefore, by setting the outermost end 6e of the pattern portion 6 to be 20% or less on the outer side in the tire radial direction from the groove bottom 4, at the time of grounding, the sliding between the mud etc. and the groove 3 can be suppressed and high traction can be exhibited. Thus, the tire 1 of the present invention can improve the mud traction performance and the snow traction performance.

[0018] The pattern portion 6 is provided on both of the pair of groove walls 5, 5 of the present embodiment. In other words, the pattern portion 6 of the present embodiment is provided on the groove bottom 4 and both groove walls 5. Thereby, the above-described actions are effectively exerted.

[0019] Fig. 2(a) is a plan view of the pattern portion 6, and (b) is a cross-sectional view taken along line A-A of (a). As shown in Fig. 2, in this embodiment, the micro dimples 7 are formed in a hemispherical shape. Such micro dimples 7 can suppress a decrease in the rigidity of the groove 3 and exert a large shearing force. Thus, for the micro dimples 7, for example, it is desirable that the opening area decreases from the surface 5a of the groove wall 5 toward the bottom 7s of the micro dimples 7.

[0020] Figs. 3(a) and (b) are cross-sectional views of the micro dimples 7 of other embodiments (the same cross-section as Fig. 2(b)). As shown in Figs. 3(a) and (b), the micro dimples 7 may be, for example, frustum of a cone shape or frustum of a regular pyramid shape. In the case of frustum of a regular pyramid shape, for example, it is desirable that it is frustum of a regular quadrangular pyramid shape.

[0021] As shown in Fig. 2, the outer diameter R of the hemispherical or frustum of a cone-shaped micro dimple 7 is preferably 0.05 mm or more, more preferably 0.1 mm or more, preferably 0.5 mm or less, and more preferably 0.3 mm or less. Since the outer diameter R is 0.05 mm or more, the soil discharge property and snow discharge property can be ensured. Since the outer diameter R is 0.5 mm or less, a decrease in the rigidity near the groove 3 is suppressed, and a large shearing force can be obtained against mud or the like.

[0022] The depth da of the hemispherical or frustum of a cone-shaped micro dimple 7 is preferably 20% or more of the outer diameter R of the micro dimple 7, more preferably 30% or more, preferably 70% or less, and more preferably 60% or less. Since the depth da of the micro dimple 7 is 20% or more of the outer diameter R of the micro dimple 7, the soil discharge property and snow discharge property are exhibited. Since the depth da of the micro dimple 7 is 70% or less of the outer diameter R of the micro dimple 7, the rigidity near the groove 3 is maintained high. <00001​​In the pattern section 6, the distance h between adjacent minute dimples 7 is preferably 0.5 times or more the outer diameter R of the minute dimple 7, more preferably 0.7 times or more, more preferably 2 times or less, and more preferably 1.8 times or less. Since the distance h is 0.5 times or more the outer diameter R, the decrease in rigidity of the groove 3 is suppressed. Since the distance h is 2 times or less the outer diameter R, the reduction in the contact area between the groove 3 and mud, etc., is maintained.

[0024] Figure 4 is a cross-sectional view of the groove 3. As shown in Figure 4, each groove wall 5 includes an arc-shaped connecting portion 11 that connects to the groove bottom 4, and a base portion 12 that extends with a radius of curvature R2 (including R2 being infinite) that is larger than the radius of curvature R1 of the connecting portion 11. The connecting portion 11, formed with a relatively small radius of curvature R1, is prone to clogging with mud and other debris. For this reason, it is desirable to form a pattern portion 6 on the connecting portion 11. Also, if a pattern portion 6 is formed on the base portion 12, mud and other debris may be easily discharged from inside the groove 3 when it comes into contact with the ground, and shear force may not be obtained. For this reason, it is desirable that no pattern portion 6 is formed on the base portion 12. The radius of curvature of the base portion 12 is preferably R2, which is 200 mm or more.

[0025] Figure 5 is a plan view of the tread portion 2 between the tread ends Te, Te. The tread end Te corresponds to the outermost contact point in the tire axial direction when the tire 1 in the normal state is subjected to a normal load and makes contact with a plane at a camber angle of 0°.

[0026] "Regular load" refers to the load specified for each tire within the standard system, including the standard on which the tire is based, in the case of pneumatic tires for which various standards are defined. For JATMA, this is the "maximum load capacity," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "LOAD CAPACITY."

[0027] As shown in Figure 5, the tread portion 2 of this embodiment is provided with a plurality of grooves 3. The grooves 3 include circumferential grooves 8 extending in the tire circumferential direction and transverse grooves 9 extending in the tire axial direction. In this specification, circumferential grooves 8 refer to grooves 3 that extend parallel to the tire circumferential direction or that are inclined at an angle of less than 45 degrees with respect to the tire circumferential direction. Transverse grooves 9 refer to grooves 3 that are inclined at an angle of 45 degrees or more with respect to the tire circumferential direction.

[0028] In this embodiment, the circumferential groove 8 extends continuously in the circumferential direction of the tire. The circumferential groove 8 may also include a discontinuous groove (not shown) that terminates at the contact surface 2a. In this embodiment, the lateral groove 9 includes a first lateral groove 9A that connects adjacent circumferential grooves 8, 8 in the axial direction of the tire, and a second lateral groove 9B that has one end connected to the circumferential groove 8 and the other end terminated at the contact surface 2a. The lateral groove 9 may also include grooves (not shown) that terminate at both ends at the contact surface 2a.

[0029] In this embodiment, the pattern section 6 is provided in both the circumferential grooves 8 and the transverse grooves 9. This enhances the ability to remove soil, snow, and shear force against mud and other debris in each groove 3. The pattern section 6 may be provided in, for example, all circumferential grooves 8 and all transverse grooves 9, or in at least one circumferential groove 8 or at least one transverse groove 9.

[0030] Figure 6(a) is a perspective cross-sectional view of a circumferential groove 8 and a transverse groove 9 in another embodiment. As shown in Figure 6(a), in this embodiment, the micro-dimples 7B formed on the groove bottom 4B and groove wall 5B of the transverse groove 9 are larger than the micro-dimples 7A formed on the groove bottom 4A and groove wall 5A of the circumferential groove 8. The transverse groove 9 is more prone to clogging with mud and other debris than the circumferential groove 8. Therefore, it is desirable to make the micro-dimples 7 of the transverse groove 9 relatively larger to improve the soil and snow removal capabilities compared to the circumferential groove 8. Specifically, the outer diameter R of the micro-dimples 7 of the transverse groove 9 is larger than that of the micro-dimples 7 of the circumferential groove 8. At this time, it is desirable that the number of micro-dimples 7 per unit area of ​​the pattern portions 6A and 6B of the circumferential groove 8 and the transverse groove 9 be the same.

[0031] Figure 6(b) is a cross-sectional view of the groove 3 in another embodiment. As shown in Figure 6(b), in this embodiment, the micro-dimples 7y formed in the connecting portion 11 are larger than the micro-dimples 7x formed in the groove bottom 4. The connecting portion 11 is relatively more prone to clogging with mud and other debris than the groove bottom 4. Therefore, it is desirable to make the micro-dimples 7y of the connecting portion 11 relatively larger to improve the ability to remove soil and snow compared to the groove bottom 4. Specifically, the outer diameter R of the micro-dimples 7y of the connecting portion 11 is larger than that of the micro-dimples 7x of the groove bottom 4. At this time, it is desirable that the number of micro-dimples 7 per unit area of ​​the pattern portions 6x and 6y of the groove bottom 4 and the connecting portion 11 be the same.

[0032] Although a tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiments described above and can be implemented in various modified forms. [Examples]

[0033] A 275 / 65R20 size tire with the basic pattern shown in Figure 5 was prototyped based on the specifications in Table 1, and the mud traction and snow traction performance of each test tire was tested. The common specifications and test methods for each test tire are as follows.

[0034] <Mud traction performance, Snow traction performance> Each test tire was mounted on all wheels of the vehicle under the following conditions. A test driver then drove the vehicle on test courses with muddy and snowy surfaces. The test driver subjectively evaluated the driving characteristics, including steering response, traction, and grip. The results are shown on a scale where Comparative Example 1 is rated at 100. A higher number indicates better performance. The test results are shown in Tables 1 and 2. Internal pressure (all wheels): 230kPa Vehicle: Four-wheel drive passenger car (SUV) Vehicle engine displacement: 2500cc In the table, "Position of the outermost edge of the pattern (%)": Distance in the radial direction of the tire between the groove bottom and the outermost edge of the pattern / Groove depth × 100

[0035] [Table 1]

[0036] [Table 2]

[0037] The test results confirmed that the tires in the example demonstrated improved mud traction and snow traction performance. Passing noise was also tested, and the results were the same for all of the comparative and example examples.

[0038] [Note] The present invention includes the following embodiments.

[0039] [Invention 1] A tire including a tread portion, The tread portion is provided with at least one groove that is recessed in the radial direction of the tire. The groove includes a groove bottom that defines the groove depth and a pair of groove walls. The groove bottom extends to the surface of at least one of the pair of groove walls, and includes a patterned portion in which a plurality of minute dimples are formed. The outermost edge of the pattern portion in the tire radial direction is located outside the groove bottom in the tire radial direction, within a range of 10% or more and 20% or less of the groove depth. tire. [Invention 2] The tire according to the present invention 1, wherein the pattern portion is provided on both of the pair of groove walls. [Invention 3] The groove includes a circumferential groove extending in the direction of the tire circumference and a transverse groove extending in the direction of the tire axis. The tire according to invention 1 or 2, wherein the pattern portion is provided in both the circumferential groove and the transverse groove. [4th Invention] The tire according to any one of inventions 1 to 3, wherein the minute dimples are hemispherical, frustoconical, or regular polygonal frustoconical. [5th ​​Invention] The tire according to claim 4 of the present invention, wherein the outer diameter of the hemispherical or frustoconical minute dimples is 0.05 to 0.5 mm. [Invention 6] The tire according to invention 4 or 5, wherein the depth of the hemispherical or frustoconical micro-dimples is 20% to 70% of the outer diameter of the micro-dimples. [7th Invention] The tire according to any one of invention 1 to 6, wherein in the pattern portion, the distance between adjacent minute dimples is 0.5 to 2 times the outer diameter of the minute dimple. [Explanation of symbols]

[0040] 1 tire 2 Tread section 3 grooves 4 Groove bottom 5. Trench wall 5a surface 6 Pattern section 6e outermost edge 7. Microscopic dimples d Groove depth

Claims

1. A tire including a tread portion, The tread portion is provided with at least one groove that is recessed in the radial direction of the tire. The groove includes a groove bottom that defines the groove depth and a pair of groove walls. The groove bottom extends to the surface of at least one of the pair of groove walls, and includes a patterned portion in which a plurality of minute dimples are formed. The outermost edge of the pattern portion in the tire radial direction is located outside the groove bottom in the tire radial direction, within a range of 10% or more and 20% or less of the groove depth. tire.

2. The tire according to claim 1, wherein the pattern portion is provided on both of the pair of groove walls.

3. The groove includes a circumferential groove extending in the direction of the tire circumference and a transverse groove extending in the direction of the tire axis. The tire according to claim 1 or 2, wherein the pattern portion is provided in both the circumferential groove and the transverse groove.

4. The tire according to claim 1 or 2, wherein the minute dimples are hemispherical, frustoconical, or regular frustoconical.

5. The tire according to claim 4, wherein the outer diameter of the hemispherical or frustoconical minute dimples is 0.05 to 0.5 mm.

6. The tire according to claim 4, wherein the depth of the hemispherical or frustoconical minute dimple is 20% to 70% of the outer diameter of the minute dimple.

7. The tire according to claim 4, wherein in the pattern portion, the distance between adjacent minute dimples is 0.5 to 2 times the outer diameter of the minute dimple.

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