tire

Abstract

To provide a tire improved in mud property without deteriorating noise performance.SOLUTION: A tire includes a tread portion 2. The tread portion 2 is provided with grooves 3 each having a pair of groove walls 4. A surface 4s of the groove walls 4 includes a pattern portion 7 having a plurality of micro-protrusions 8 formed thereon. The pattern portion 7 is provided with the micro-protrusions 8 at density of 1 to 5 per 1 mm2 of groove wall area.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] The following Patent Document 1 describes a tire in which a first middle lateral groove is provided in the middle land portion. The first middle lateral groove includes an outer groove extending axially inward from the shoulder main groove. The outer groove has a groove width that smoothly increases toward the shoulder main groove. Such an outer groove is said to be able to strongly compact mud, improving mud performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-147473 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, increasing the groove width increases the volume of the groove, which in turn increases noise during running.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire that can improve mud performance without impairing noise performance. [Means for solving the problem]

[0006] The present invention relates to a tire including a tread portion, the tread portion being provided with a groove, the groove including a pair of groove walls, and a pattern portion having a plurality of minute protrusions formed on a surface of at least one of the pair of groove walls, the pattern portion being a groove wall area of ​​1 mm2 or less. 2 It is desirable that the minute projections are provided at a density of 1 to 5 per unit area.

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

[0008] In the tire according to the present invention, it is preferable that the grooves include a circumferential groove extending in a tire circumferential direction and a lateral groove extending in an axial direction of the tire, and the pattern portion is provided on a groove wall of the circumferential groove and a groove wall of the lateral groove.

[0009] In the tire according to the present invention, it is preferable that the pattern portion is formed in 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 to the inner side in the tire radial direction.

[0010] In the tire according to the present invention, it is preferable that the minute projections have a projection height of 0.1 to 0.5 mm.

[0011] In the tire according to the present invention, it is preferable that the small projections have an outer diameter of 0.1 to 0.5 mm.

[0012] In the tire according to the present invention, it is desirable that the small projections have a truncated cone shape.

[0013] In the tire according to the present invention, it is preferable that the small projections have recesses at their tops.

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

[0015] In the tire according to the present invention, it is preferable that the recess has an opening area that decreases toward the inside in the projection height direction.

[0016] In the tire according to the present invention, it is preferable that an opening shape of the recess is circular.

[0017] In the tire according to the present invention, it is preferable that the groove includes a groove bottom, and the pattern portion is not formed in the groove bottom. Effect of the Invention

[0018] By employing the above-mentioned configuration, the tire of the present invention can improve muddy road performance without impairing noise performance. [Brief description of the drawings]

[0019] [Figure 1] 1 is a plan view of a tread portion of a tire according to one embodiment of the present invention. [Diagram 2] 2(a) is a perspective view of the groove in FIG. 1, and (b) is a cross-sectional view of (a). [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. 13(a) is a perspective view of a groove according to another embodiment, and FIG. 13(b) is a perspective view of a micro-projection according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a plan view of a tread portion 2 of a tire 1 of this embodiment. Fig. 1 shows the tread portion 2 of a pneumatic tire 1 for passenger cars as a preferred embodiment. However, the present invention may also be applied to, for example, a pneumatic tire 1 for heavy loads or tires 1 of other categories.

[0021] As shown in Fig. 1, a tread portion 2 of this embodiment is provided with grooves 3. In this specification, a groove refers to a groove-shaped body having a width of 1.5 mm or more.

[0022] Fig. 2(a) is a perspective view of the groove 3 in Fig. 1. Fig. 2(b) is a cross-sectional view of Fig. 2(a). As shown in Figs. 2(a) and 2(b), the groove 3 of this embodiment includes a pair of groove walls 4, 4. The groove 3 also includes a groove bottom 5 connecting the inner ends of the pair of groove walls 4, 4 in the tire radial direction. The groove wall 4 extends from the tread surface 2a of the tread portion 2 toward the inner side in the tire radial direction. The groove bottom 5 is an area within 10% of the groove depth D from the maximum depth portion 3e of the groove 3.

[0023] At least one of the pair of groove walls 4, 4 has a surface 4s including a pattern portion 7 on which a plurality of minute protrusions 8 are formed. The pattern portion 7 has a groove wall area of ​​1 mm 2 The minute protrusions 8 are provided at a density of 1 to 5 per groove. The minute protrusions 8 increase the scratching force, shear force, and friction force on the mud that has entered the grooves 3, thereby improving mud performance. The minute protrusions 8 also transmit the vibration of the tread portion 2 during running to the mud that has adhered to the groove walls 4, promoting separation of the mud from the groove walls 4. This allows the tire 1 of this embodiment to suppress clogging of the grooves 3 with mud, and ultimately maintains excellent mud performance for a long period of time while running. Furthermore, since the above-mentioned action is achieved without increasing the groove volume, the tire 1 of this embodiment does not impair noise performance.

[0024] In particular, the density of the microprojections 8 is set to 1 mm 2 Since the number of micro-projections 8 is one or more per square meter, the vibrations caused by the running of the vehicle can be effectively transmitted to the mud adhering to the groove wall 4. In addition, the density of the micro-projections 8 is set to 1 mm per square meter of groove wall area. 2 Since the number of projections is five or less, the rigidity of the minute projections 8 is maintained high, and the above-mentioned effect is exerted for a long period of time.

[0025] In this specification, the dimensions of each part of the tire 1 are values ​​measured when the tire 1 is mounted on a regular rim (not shown), inflated to the regular internal pressure, and in a regular condition with no load. The "regular rim" is a rim that is determined for each tire by a standard system that includes the standard on which the tire 1 is based, and is, for example, a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO.

[0026] The "normal internal pressure" is the air pressure determined for each tire by each standard in the standard system including the standard on which the tire 1 is based, and is the "maximum air pressure" in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "INFLATION PRESSURE" in the case of ETRTO. If the tire 1 is for a passenger car, the normal internal pressure is 180 kPa.

[0027] In this embodiment, the pattern portion 7 is provided on both of the pair of groove walls 4. This allows the above-mentioned effects to be effectively achieved.

[0028] As shown in Fig. 1, the grooves 3 include, for example, a circumferential groove 10 extending in the tire circumferential direction and a lateral groove 11 extending in the tire axial direction. In this specification, "extending in the tire circumferential direction" refers to extending at an angle of 45 degrees or more with respect to the tire axial direction. Also, "extending in the tire axial direction" refers to extending at an angle of less than 45 degrees with respect to the tire axial direction. Furthermore, for convenience, the grooves 3 in Fig. 1 are shown in color.

[0029] The circumferential groove 10 extends continuously in the tire circumferential direction, for example. The circumferential groove 10 of the present embodiment includes a pair of crown circumferential grooves 10A arranged on both sides of the tire equator C, and a pair of shoulder circumferential grooves 10B arranged on the outer side of the crown circumferential grooves 10A in the tire axial direction.

[0030] The lateral groove 11 of this embodiment includes a crown lateral groove 11A, a middle lateral groove 11B, a shoulder lateral groove 11C, and a shoulder small lateral groove 11D. The crown lateral groove 11A extends, for example, from a pair of crown circumferential grooves 10A toward the inside in the tire axial direction. The middle lateral groove 11B connects, for example, the crown circumferential groove 10A and the shoulder circumferential groove 10B. The shoulder lateral groove 11C connects, for example, the shoulder circumferential groove 10B and the tread edge Te. The shoulder small lateral groove 11D extends, for example, from the tread edge Te toward the inside in the tire axial direction and is formed with a length shorter than that of the shoulder lateral groove 11C. The groove 3 is not limited to such an embodiment, and various embodiments are adopted.

[0031] The tread portion 2 of the present embodiment is provided with sipes 12. The sipes 12 include, 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 outside in the tire axial direction and terminates without connecting 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 inside in the tire axial direction and terminates without connecting to the crown circumferential groove 10A. The fourth sipe 12D extends from the shoulder circumferential groove 10B toward the outside in the tire axial direction. In this specification, the sipe is a notch-like body having a width of less than 1.5 mm.

[0032] The tread edge Te means the axially outermost contact point of the tire when the tire 1 in the normal state is placed on a flat surface with a normal load applied and a camber angle of 0 degrees. The "normal load" is a load determined for each tire by each standard in a system of standards including the standard on which the tire 1 is based, and is the "maximum load capacity" in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO.

[0033] The sipe 12 has a pair of sipe walls 12a. The sipe walls 12a are not formed with the pattern portion 7. In this embodiment, the sipe walls 12a of all the sipes 12 are not formed with the pattern portion 7.

[0034] 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 lateral groove 11. The pattern portion 7 is provided, for example, on the groove wall 13A of the crown circumferential groove 10A and the groove wall 13B of the shoulder circumferential groove 10B. The pattern portion 7 is also provided on the groove wall 14A of the crown lateral groove 11A, the groove wall 14B of the middle lateral groove 11B, the groove wall 14C of the shoulder lateral groove 11C, and the groove wall 14D of the shoulder small lateral groove 11D.

[0035] As shown in Figures 2(a) and (b), it is preferable that the pattern portion 7 is not formed on the groove bottom 5. Since the groove bottom 5 is unlikely to come into contact with mud, providing the pattern portion 7 there may not improve mud performance. Also, compared to the groove wall 4, vibrations during travel are less likely to be transmitted to the groove bottom 5. For this reason, providing the minute protrusions 8 on the groove bottom 5 may cause the groove to become clogged with mud, making it difficult to improve mud performance.

[0036] The pattern portion 7 is preferably formed in a range of 20% to 60% of the groove depth D of the groove 3 from the outer end 4e (tread surface 2a) in the tire radial direction of the groove wall 4 to the inner side in the tire radial direction. In other words, since the outer end 7e in the tire radial direction of the pattern portion 7 is located at a position 20% or more of the groove depth D from the outer end 4e, the shear force in the tire radial direction by the outer end 4e (edge ​​of the groove 3) and the shear force, scratching force, and friction force by the minute protrusions 8 are compatible, improving mud performance. In addition, since the inner end 7i in the tire radial direction of the pattern portion 7 is located at a position 60% or less of the groove depth D from the outer end 4e, mud clogging in the groove 3 is effectively suppressed. From this viewpoint, it is more preferable that the outer end 7e of the pattern portion 7 is located at a position 30% or more of the groove depth D from the outer end 4e, and it is more preferable that the inner end 7i of the pattern portion 7 is located at 50% or less.

[0037] In order to effectively exert the above-mentioned effect, the length H of the pattern portion 7 in the tire radial direction is desirably 20% or more of the groove depth D, more desirably 25% or more, desirably 40% or less, and more desirably 35% or more.

[0038] In order to improve mud performance, the pattern portion 7 is preferably formed to 50% or more, and more preferably 70% or more, of the longitudinal length (not shown) of the groove 3. In this embodiment, the pattern portion 7 is formed to 100% of the longitudinal length of the groove 3 (the entire longitudinal length of the groove 3).

[0039] Fig. 3 is an enlarged plan view of the small protrusions 8. Fig. 4 is a perspective view of the small protrusions 8. As shown in Figs. 3 and 4, the small protrusions 8 are frustum-shaped in this embodiment. This allows the small protrusions 8 to maintain high rigidity and to exert shear forces and the like in multiple directions. The shape of the small protrusions 8 is not limited to a frustum-shaped shape, and may be, for example, a cylindrical or pyramidal shape.

[0040] The projection height H1 of the micro-projections 8 is preferably 0.1 to 0.5 mm. Since the projection height of the micro-projections 8 is 0.1 mm or more, shear force and the like are effectively exerted, and mud performance can be improved. Since the projection height of the micro-projections 8 is 0.5 mm or less, adhesion of mud is suppressed, and chipping, cracking, and the like are suppressed, so that mud performance is maintained. From this viewpoint, the projection height H1 of the micro-projections 8 is more preferably 0.15 mm or more, and more preferably 0.45 mm or less.

[0041] The outer diameter φ of the micro-protrusions 8 is preferably 0.1 to 0.5 mm. Since the outer diameter φ of the micro-protrusions 8 is 0.1 mm or more, mud performance can be improved. Since the outer diameter φ of the micro-protrusions 8 is 0.5 mm or less, the durability of the micro-protrusions 8 is maintained and a decrease in mud performance is suppressed. From this viewpoint, the protrusion height of the micro-protrusions 8 is more preferably 0.15 mm or more, and more preferably 0.45 mm or less.

[0042] The distance La between adjacent micro-projections 8, 8 is preferably 0.2 mm or less, more preferably 0.15 mm or less, and even more preferably 0.10 mm or less. By arranging the micro-projections 8 at such a distance La, it is possible to increase the scratching force, shear force, and friction force against the mud that has entered the groove 3.

[0043] The minute projections 8 are provided with recesses 15 at the projection tops 8a. Such recesses 15 are capable of shearing mud within the recesses 15, further improving mud performance.

[0044] The opening shape of the recess 15 is, for example, circular. Such recess 15 suppresses a decrease in the rigidity of the microprotrusion 8. The opening shape of the recess 15 is not limited to this embodiment, and may be, for example, elliptical, triangular, or rectangular.

[0045] The depth d1 of the recesses 15 is desirably 70% to 100% of the projection height H1 of the small projections 8. Since the depth d1 of the recesses 15 is 70% or more of the projection height H1, a large amount of mud can be secured to enter the recesses 15. Since the depth d1 of the recesses 15 is within 100% of the projection height H1, the rigidity of the small projections 8 is maintained high, and therefore the mud performance can be maintained high for a long period of time.

[0046] In this embodiment, the recesses 15 have an opening area A that decreases toward the inside in the projection height direction. Such recesses 15 are useful for maintaining the rigidity of the small projections 8 at a higher level, and also facilitate the discharge of mud buried in the recesses 15.

[0047] In order to effectively exert such an effect, the ratio (A2 / A1) of the opening area A1 at the outer end 15e (protrusion top 8a) of the recess 15 in the protrusion height direction to the opening area A2 at the inner end 15i of the recess 15 in the protrusion height direction is preferably 20% or more, more preferably 30% or more, more preferably 60% or less, and even more preferably 50% or less.

[0048] The width w1 of the projection top 8a of the recess 15 is preferably 0.03 to 0.08 mm. Since the width w1 is 0.03 mm or more, the rigidity of the minute projections 8 is maintained high. Since the width w1 is 0.08 mm or less, the opening area A is secured and the shear force against the mud is increased.

[0049] FIG. 5(a) is a perspective view of a groove 3 of another embodiment. The same components as those in this embodiment are given the same reference numerals and their description is omitted. As shown in FIG. 5(a), in this embodiment, the pattern portion 7 is formed so that a plurality of micro-projection groups 9 each consisting of a plurality of micro-projections 8 are provided. Each micro-projection group 9 is arranged with a gap S larger than the outer diameter φ of the micro-projection 8. Such a pattern portion 7 suppresses the reduction in the groove volume of the groove 3, and can exert shear force, friction force, and scratching force on a larger amount of mud.

[0050] Fig. 5(b) is a perspective view of the small protrusions 8 of another embodiment. The same components as those of this embodiment are given the same reference numerals and their description will be omitted. As shown in Fig. 5(b), in this embodiment, the recesses 15 of the small protrusions 8 are formed with the same opening area A in the protrusion height direction. Such recesses 15 can shear a large amount of mud, thereby improving mud performance.

[0051] Although the tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the above specific embodiment and can be modified and carried out in various aspects. EXAMPLES

[0052] Tires of size 265 / 65R18 having the basic pattern of Figure 1 were prototyped based on the specifications in Table 1, and the mud performance and noise performance of each sample tire were tested. The basic structure of the pattern part is shown in Figures 2(a) and (b). The common specifications and test methods of each sample tire are as follows. The sample tires are so-called all-season tires for SUVs.

[0053] <Mud performance> Each sample 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 sensorily evaluated the driving characteristics related to steering response, traction, grip, etc. The results are shown as a score with Comparative Example 1 being 100. The higher the score, the better the result. Internal pressure (all wheels): 230kPa Vehicle: 4-wheel drive passenger car (SUV) Vehicle displacement: 2500cc Micro-protrusion height: 0.3 mm External diameter of micro projection: 0.3 mm

[0054] <Noise performance> A test driver drove the vehicle on a dry asphalt road at a speed of 70 km / h. The test driver evaluated the noise generated by the vehicle sensorily. The results are shown as a score based on Comparative Example 1 being 100. The higher the score, the better the noise performance. The test results are shown in Table 1.

[0055] [Table 1]

[0056] As a result of the test, it was confirmed that the tires of the embodiment had improved mud performance without impairing noise performance. [Explanation of symbols]

[0057] 1 Tire 2 Tread section 3 grooves 4. Groove Wall 4s surface 7 Pattern section 8 Microprotrusions

Claims

1. A tire including a tread portion, The tread portion is provided with a groove, The groove includes a pair of groove walls; At least one of the pair of groove walls includes a pattern portion having a plurality of minute protrusions formed on a surface thereof, The pattern portion has a groove wall area of ​​1 mm ２ the microprotrusions are provided at a density of 1 to 5 per The microprotrusions have recesses at their tops. tire.

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

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

4. 4. The tire according to claim 1, 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 to an inner side in the tire radial direction.

5. 5. The tire according to claim 1, wherein the minute projections have a projection height of 0.1 to 0.5 mm.

6. 6. The tire according to claim 1, wherein the small projections have an outer diameter of 0.1 to 0.5 mm.

7. 7. A tire according to any one of claims 1 to 6, wherein the microprojections are frustoconical.

8. A tire as described in any one of claims 1 to 7, wherein the depth of the recess is 70% to 100% of the protrusion height of the microprotrusions.

9. A tire as described in any one of claims 1 to 8, wherein the recess has an opening area that decreases toward the inside in the protrusion height direction.

10. A tire as described in any one of claims 1 to 9, wherein the opening shape of the recess is circular.

11. The groove includes a groove bottom, The tire according to claim 1 , wherein the pattern portion is not formed in the groove bottom.

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