tire

Abstract

The present invention provides a tire capable of improving muddy performance without compromising noise performance. The tire (1) includes a tread portion (2). The tread portion (2) is provided with a groove (3) including a pair of groove walls (4). The surface (4s) of the groove wall (4) includes a pattern portion (7) formed with a plurality of micro protrusions (8). The pattern portion (7) is formed with a plurality of micro protrusions (8) per 1 mm. 2 The groove wall area is provided with micro protrusions (8) at a density of 1 to 5.

Description

Technical Field

[0001] The present invention relates to tires. Background Art

[0002] Patent Document 1 below describes a tire with a first middle transverse groove in the middle land portion. The first middle transverse groove includes an outer groove extending axially inward from the shoulder main groove. The groove width of the outer groove increases smoothly and gradually toward the shoulder main groove. Such an outer groove can firmly compact mud, improving muddy performance.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-147473

[0004] However, increasing the groove width increases the volume of the groove, which in turn causes a problem of increased noise during running. Summary of the Invention

[0005] The present invention has been made in view of the above-mentioned actual situation, and a main object of the present invention is to provide a tire capable of improving mud performance without impairing noise performance.

[0006] The present invention is a tire comprising a tread portion, wherein the tread portion is provided with a groove, the groove comprising a pair of groove walls, and the surface of at least one of the pair of groove walls comprising a pattern portion having a plurality of micro protrusions formed thereon, the pattern portion being arranged at a rate of 1 mm. 2 The micro protrusions are provided at a density of 1 to 5 per the groove wall area.

[0007] In the tire of the present invention, it is preferable that the pattern portion is provided on both sides of the pair of groove walls.

[0008] In the tire of the present invention, the grooves preferably include circumferential grooves extending in the tire circumferential direction and transverse grooves extending in the tire axial direction, and the pattern portions are provided on groove walls of the circumferential grooves and the transverse grooves.

[0009] In the tire of the present invention, the pattern portion is preferably formed within a range of 20% to 60% of the groove depth of the groove from the outer end of the groove wall in the tire radial direction toward the inner side in the tire radial direction.

[0010] In the tire of the present invention, preferably, the microprotrusions have a protrusion height of 0.1 mm to 0.5 mm.

[0011] In the tire of the present invention, the outer diameter of the fine protrusions is preferably 0.1 mm to 0.5 mm.

[0012] In the tire of the present invention, the fine protrusions preferably have a truncated cone shape.

[0013] In the tire of the present invention, the fine protrusions preferably have recessed portions at their tops.

[0014] In the tire of the present invention, it is preferable that the depth of the recessed portion is 70% to 100% of the protrusion height of the fine protrusion.

[0015] In the tire of the present invention, it is preferable that the opening area of the recessed portion decreases toward the inner side in the projection height direction.

[0016] In the tire of the present invention, it is preferable that the opening shape of the recessed portion is circular.

[0017] In the tire of the present invention, preferably, the groove includes a groove bottom, and the pattern portion is not formed on the groove bottom.

[0018] The tire of the present invention, by adopting the above-mentioned structure, can improve mud performance without impairing noise performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a plan view of a tread portion of a tire according to one embodiment of the present invention.

[0020] Figure 2 (a) is Figure 1 (b) is a three-dimensional view of the groove, and (a) is a cross-sectional view of (b).

[0021] Figure 3 It is a plan view of a tiny protrusion.

[0022] Figure 4 It is a three-dimensional image of a tiny protrusion.

[0023] Figure 5 (a) is a perspective view of a groove according to another embodiment, and (b) is a perspective view of a microprotrusion according to another embodiment.

[0024] Description of labels

[0025] 1: tire; 2: tread; 3: groove; 4: groove wall; 4s: surface; 7: pattern; 8: microprotrusion. DETAILED DESCRIPTION

[0026] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0027] Figure 1 : is a plan view of the tread portion 2 of the tire 1 of this embodiment. Figure 1 1, as a preferred embodiment, the tread portion 2 of the pneumatic tire 1 for a passenger car is shown. However, the present invention can also be applied to, for example, a pneumatic tire 1 for heavy loads or other types of tires 1.

[0028] like Figure 1As shown, the tread portion 2 of this embodiment is provided with a groove 3. In this specification, a groove refers to a groove-shaped body having a width of 1.5 mm or more.

[0029] Figure 2 (a) is Figure 1 A three-dimensional view of the slot 3. Figure 2 (b) is Figure 2 (a) is a cross-sectional view of. Figure 2 As shown in Figures (a) and (b), the groove 3 of this embodiment includes a pair of groove walls 4, 4. Furthermore, the groove 3 includes a groove bottom 5 connecting the radially inner ends of the pair of groove walls 4, 4. The groove walls 4 extend radially inward from the tread surface 2a of the tread portion 2. The groove bottom 5 is the region within 10% of the groove depth D from the maximum depth portion 3e of the groove 3.

[0030] The surface 4s of at least one of the pair of groove walls 4 and 4 includes a pattern portion 7 formed with a plurality of fine protrusions 8. The pattern portion 7 is formed with a plurality of fine protrusions 8 per 1 mm. 2 The groove wall area is provided with micro-protrusions 8 at a density of 1 to 5. The micro-protrusions 8 can increase the traction, shearing force and friction force on the mud entering the groove 3, and can improve the mud performance. In addition, the micro-protrusions 8 transmit the vibration of the tread portion 2 during driving to the mud attached to the groove wall 4, promoting the separation of the groove wall 4 and the mud. As a result, the tire 1 of this embodiment can suppress the mud clogging of the groove 3 and thus continue to maintain excellent mud performance for a long time during driving. In addition, the above-mentioned effect is obtained without increasing the groove volume, so the tire 1 of this embodiment will not damage the noise performance.

[0031] In particular, since the density of the microprotrusions 8 is 2 The groove wall area is more than one, so the vibration during driving can be effectively transmitted to the mud attached to the groove wall 4. In addition, since the density of the micro-protrusions 8 is 1 mm 2 Since there are 5 or less of the micro-protrusions 8 in the groove wall area, the rigidity of the micro-protrusions 8 is maintained high and the above-mentioned effect can be exerted for a long time.

[0032] In this specification, the dimensions of various parts of the tire 1 are values measured in a normal, unloaded state, with the tire 1 assembled on a normal rim (not shown) and inflated to a normal internal pressure. The term "normal rim" refers to a rim whose specifications are determined for each tire within the standard system that includes the standards to which the tire 1 conforms. For example, in the case of JATMA, this is referred to as a "standard rim," in the case of TRA, it is referred to as a "design rim," and in the case of ETRTO, it is referred to as a "measuring rim."

[0033] The "normal internal pressure" mentioned above refers to the air pressure determined for each tire within the standard system that includes the standard to which tire 1 conforms. For JATMA, this is the "maximum air pressure," for TRA, it is the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table, and for ETRTO, it is the "INFLATION PRESSURE." For tire 1 intended for passenger cars, the normal internal pressure is 180 kPa.

[0034] In this embodiment, the pattern portion 7 is provided on both sides of the pair of groove walls 4. This effectively exhibits the above-mentioned function.

[0035] like Figure 1 As shown, the groove 3 includes, for example, a circumferential groove 10 extending in the tire circumferential direction and a transverse groove 11 extending in the tire axial direction. In this specification, "extending in the tire circumferential direction" means extending at an angle of 45 degrees or more relative to the tire axial direction. In addition, "extending in the tire axial direction" means extending at an angle of less than 45 degrees relative to the tire axial direction. In addition, for convenience, Figure 1 Slot 3 is shown in shaded form.

[0036] The circumferential grooves 10 extend continuously along the tire circumferential direction, for example. The circumferential grooves 10 of this embodiment include a pair of crown circumferential grooves 10A disposed on both sides of the tire equator C, and a pair of shoulder circumferential grooves 10B disposed axially outward of the crown circumferential grooves 10A.

[0037] The transverse grooves 11 of this embodiment include a crown transverse groove 11A, an intermediate transverse groove 11B, a shoulder transverse groove 11C, and a shoulder small transverse groove 11D. The crown transverse groove 11A, for example, extends from a pair of crown circumferential grooves 10A toward the inner side of the tire in the axial direction. The intermediate transverse groove 11B, for example, connects the crown circumferential groove 10A and the shoulder circumferential groove 10B. The shoulder transverse groove 11C, for example, connects the shoulder circumferential groove 10B and the tread end Te. The shoulder small transverse groove 11D, for example, extends from the tread end Te toward the inner side of the tire in the axial direction and is formed with a length smaller than that of the shoulder transverse groove 11C. The groove 3 is not limited to this method and various methods can be used.

[0038] In addition, the tread portion 2 of the present embodiment is provided with a sipe 12. The sipe 12 includes, for example, a first sipe 12A, a second sipe 12B, a third sipe 12C, and a fourth sipe 12D. The first sipe 12A extends from the crown circumferential groove 10A toward the outer side in the tire axial direction and terminates in a manner not connected to the shoulder circumferential groove 10B. The second sipe 12B connects the crown circumferential groove 10A and the shoulder circumferential groove 10B. The third sipe 12C extends from the shoulder circumferential groove 10B toward the inner side in the tire axial direction and terminates in a manner not connected to the crown circumferential groove 10A. The fourth sipe 12D extends from the shoulder circumferential groove 10B toward the outer side in the tire axial direction. In addition, in this specification, a sipe is a cut-shaped body having a width of less than 1.5 mm.

[0039] The tread end Te is the axially outermost point of contact when a normal load is applied to the tire 1 in the normal state and the tire contacts a flat surface at a camber angle of 0 degrees. "Normal load" refers to the load determined for each tire within the standard system, including the standard to which the tire 1 conforms. For JATMA, this is the "maximum load capacity," for TRA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table, and for ETRTO, it is "LOAD CAPACITY."

[0040] The sipe 12 has a pair of sipe walls 12a. The sipe walls 12a do not have the pattern portion 7 formed thereon. In the present embodiment, the sipe walls 12a of all the sipes 12 do not have the pattern portion 7 formed thereon.

[0041] In this embodiment, the pattern portion 7 is provided on the groove wall 13 of the circumferential groove 10 and the groove wall 14 of the transverse groove 11. For example, the pattern portion 7 is provided on the groove wall 13A of the crown circumferential groove 10A and the groove wall 13B of the shoulder circumferential groove 10B. Furthermore, the pattern portion 7 is provided on the groove wall 14A of the crown transverse groove 11A, the groove wall 14B of the middle transverse groove 11B, the groove wall 14C of the shoulder transverse groove 11C, and the groove wall 14D of the shoulder small transverse groove 11D.

[0042] like Figure 2 As shown in (a) and (b), it is preferable that the tread portion 7 not be formed on the groove bottom 5. Because the groove bottom 5 is less likely to come into contact with mud, even if the tread portion 7 is provided there, muddy performance may not be improved. Furthermore, compared to the groove wall 4, the groove bottom 5 is less susceptible to transmission of vibrations during driving. Therefore, providing the micro-protrusions 8 on the groove bottom 5 is more likely to cause mud clogging, potentially failing to improve muddy performance.

[0043] The tread portion 7 is preferably formed within a range of 20% to 60% of the groove depth D of the groove 3 from the radially outer end 4e (tread surface 2a) of the groove wall 4 toward the radially inner side. In other words, since the radially outer end 7e of the tread portion 7 is located at or above 20% of the groove depth D from the outer end 4e, it is possible to balance the radial shear force exerted by the outer end 4e (the edge of the groove 3) with the shear force exerted by the micro-protrusions 8, traction, and friction, thereby improving muddy performance. Furthermore, since the radially inner end 7i of the tread portion 7 is located at or below 60% of the groove depth D from the outer end 4e, mud clogging within the groove 3 is effectively suppressed. From this perspective, it is more preferable that the outer end 7e of the tread portion 7 is located at or above 30% of the groove depth D from the outer end 4e, and it is even more preferable that the inner end 7i of the tread portion 7 is located at or below 50%.

[0044] To effectively exert the above-mentioned effects, the length H of the pattern portion 7 in the tire radial direction is preferably 20% or more of the groove depth D, more preferably 25% or more, and preferably 40% or less, more preferably 35% or less.

[0045] To improve muddy performance, the tread portion 7 is preferably formed to occupy at least 50% of the longitudinal length (not shown) of the groove 3, and more preferably at least 70%. In this embodiment, the tread portion 7 is formed to occupy 100% of the longitudinal length of the groove 3 (the entire longitudinal length of the groove 3).

[0046] Figure 3 It is an enlarged plan view of the microprotrusion 8. Figure 4 It is a three-dimensional diagram of the micro protrusion 8. Figure 3 、 Figure 4 As shown, in this embodiment, the microprotrusions 8 are truncated cone-shaped. This maintains high rigidity and enables the microprotrusions 8 to exert shear forces in multiple directions. Furthermore, the shape of the microprotrusions 8 is not limited to a truncated cone; for example, they may be cylindrical or pyramidal.

[0047] The protrusion height H1 of the microprotrusions 8 is preferably 0.1 mm to 0.5 mm. A protrusion height of 0.1 mm or greater effectively exerts shear force, improving muddy performance. A protrusion height of 0.5 mm or less not only prevents mud from adhering, but also prevents chipping and cracking, maintaining muddy performance. From this perspective, the protrusion height H1 of the microprotrusions 8 is more preferably 0.15 mm or greater, and more preferably 0.45 mm or less.

[0048] The outer diameter φ of the microprotrusions 8 is preferably 0.1 mm to 0.5 mm. When the outer diameter φ of the microprotrusions 8 is 0.1 mm or greater, muddy performance can be improved. When the outer diameter φ of the microprotrusions 8 is 0.5 mm or less, the durability of the microprotrusions 8 is maintained, suppressing degradation of muddy performance. From this perspective, the protrusion height of the microprotrusions 8 is more preferably 0.15 mm or greater, and more preferably 0.45 mm or less.

[0049] The distance La between adjacent microprotrusions 8 is preferably 0.2 mm or less, more preferably 0.15 mm or less, and further preferably 0.10 mm or less. Disposing the microprotrusions 8 at such a distance La can increase the traction, shearing, and frictional forces on the soil entering the groove 3 .

[0050] The micro-protrusions 8 are provided with recesses 15 at the protrusion tops 8a. Such recesses 15 can shear the mud inside the recesses 15, thereby further improving muddy performance.

[0051] The opening shape of the recess 15 is, for example, circular. Such a recess 15 suppresses a decrease in the rigidity of the microprotrusion 8. The opening shape of the recess 15 is not limited to this form, and may be, for example, elliptical, triangular, or rectangular.

[0052] The depth d1 of the recess 15 is preferably between 70% and 100% of the protrusion height H1 of the microprotrusion 8. Since the depth d1 of the recess 15 is at least 70% of the protrusion height H1, a large amount of mud can be ensured to enter the recess 15. Since the depth d1 of the recess 15 is within 100% of the protrusion height H1, the rigidity of the microprotrusion 8 is maintained high, thereby maintaining high mud performance over a long period of time.

[0053] In this embodiment, the opening area A of the recess 15 decreases toward the inner side in the protrusion height direction. Such a recess 15 not only helps maintain the rigidity of the microprotrusion 8 higher, but also facilitates the discharge of soil buried in the recess 15.

[0054] In order to effectively play such a role, the ratio (A2 / A1) of the opening area A2 at the inner end 15i of the recess 15 in the direction of the protrusion height to the opening area A1 at the outer end 15e (protrusion top 8a) of the recess 15 in the direction of the protrusion height is preferably greater than 20%, more preferably greater than 30%, preferably less than 60%, and further preferably less than 50%.

[0055] The width w1 of the protrusion top 8a, excluding the recess 15, is preferably 0.03 mm to 0.08 mm. A width w1 of 0.03 mm or greater maintains high rigidity of the microprotrusion 8. A width w1 of 0.08 mm or less ensures a secure opening area A, increasing the shear force on the soil.

[0056] Figure 5 (a) is a perspective view of the groove 3 of another embodiment. The same components as those in this embodiment are marked with the same reference numerals and their descriptions are omitted. Figure 5 As shown in (a), in this embodiment, the pattern portion 7 is formed by providing a plurality of micro-protrusion groups 9 composed of a plurality of micro-protrusions 8. Each micro-protrusion group 9 is arranged so as to have a gap S that is larger than the outer diameter φ of the micro-protrusion 8. This pattern portion 7 suppresses the reduction in the groove volume of the groove 3, thereby being able to exert shear force, friction force, and traction force on a larger amount of mud.

[0057] Figure 5 (b) is a perspective view of a micro protrusion 8 of another embodiment. The same components as those of this embodiment are marked with the same reference numerals and their descriptions are omitted. Figure 5 As shown in (b), in this embodiment, the opening area A of the recessed portion 15 of the micro-protrusion 8 is formed uniformly in the protrusion height direction. Such a recessed portion 15 can shear a large amount of mud, thereby improving muddy performance.

[0058] As mentioned above, the tire according to one embodiment of the present invention has been described in detail, but the present invention is not limited to the above-mentioned specific embodiment and can be implemented in various modified forms.

[0059] [Example]

[0060] Based on the specifications in Table 1, we have produced Figure 1 The basic tread pattern of the tire is 265 / 65R18, and the mud performance and noise performance of each test tire are tested. The basic structure of the tread is as follows Figure 2 The common specifications and test methods of each test tire are as follows. In addition, the test tire is a so-called all-season tire for SUVs.

[0061] Mud performance

[0062] Each test tire was mounted on all wheels of a vehicle under the following conditions. A test driver then drove the vehicle on a muddy test course. The test driver sensory-evaluated driving characteristics, including steering responsiveness, traction, and grip. The results were expressed as a score, with Comparative Example 1 being 100. Higher values are considered better.

[0063] Internal pressure (all wheels): 230kPa

[0064] Vehicle: 4-wheel drive passenger car (SUV)

[0065] Vehicle displacement: 2500cc

[0066] Height of micro protrusion: 0.3mm

[0067] Outer diameter of tiny protrusion: 0.3mm

[0068] <Noise performance>

[0069] A test driver drove the vehicle at 70 km / h on a dry asphalt road. The driver evaluated the noise level using their senses. The results were expressed as a score, with Comparative Example 1 being 100. A higher score indicates better noise performance.

[0070] The test results are shown in Table 1.

[0071] [Table 1]

[0072]

[0073] In Table 1, “the distance from the outer end of the groove wall” refers to the ratio relative to the groove depth D in units of “%”.

[0074] As a result of the test, it was confirmed that the tire of the example improved mud performance without impairing noise performance.

Claims

1. A tire comprising a tread portion, wherein: A groove is provided in the tread portion. The groove comprises a pair of groove walls, A surface of at least one of the pair of groove walls includes a pattern portion having a plurality of micro protrusions formed thereon, The pattern portion is 1 mm 2 The micro protrusions are provided at a density of 1 to 5 in the groove wall area, The pattern portion includes a plurality of micro-protrusion groups, each micro-protrusion group is composed of a plurality of the micro-protrusions, and a gap is provided between the plurality of micro-protrusion groups adjacent to each other, and the gap is larger than the outer diameter of each micro-protrusion. In each pair of micro-protrusions adjacent to each other, the distance between the micro-protrusions is smaller than the outer diameter of each micro-protrusion in each micro-protrusion group, and the micro-protrusion groups are arranged in a repeated manner in the pattern portion.

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

3. The tire according to claim 1 or 2, wherein: The grooves include circumferential grooves extending in the tire circumferential direction and transverse grooves extending in the tire axial direction. The pattern portion is provided on the groove wall of the circumferential groove and the groove wall of the transverse groove.

4. The tire according to claim 1 or 2, wherein: The pattern portion is formed in a range of 20% to 60% of a groove depth of the groove from an outer end of the groove wall in the tire radial direction toward an inner side in the tire radial direction.

5. The tire according to claim 1 or 2, wherein: The micro-protrusions have a protrusion height of 0.1 mm to 0.5 mm.

6. The tire according to claim 1 or 2, wherein: The outer diameter of the micro protrusion is 0.1 mm to 0.5 mm.

7. The tire according to claim 1 or 2, wherein: The micro protrusion is in the shape of a truncated cone.

8. The tire according to claim 1 or 2, wherein: The micro-protrusions are provided with recessed portions at the tops of the protrusions.

9. The tire according to claim 8, wherein: The depth of the recess is 70% to 100% of the height of the microprotrusion.

10. The tire according to claim 8, wherein The opening area of the recessed portion decreases toward the inner side in the height direction of the protrusion.

11. The tire according to claim 8, wherein The opening shape of the recess is circular.

12. The tire according to claim 1 or 2, wherein: The tank comprises a tank bottom, The pattern portion is not formed on the groove bottom.

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