JP6888366B2 - tire - Google Patents

Description

The present invention relates to a tire capable of suppressing so-called stone biting in which a stone is caught in a shoulder main groove and the state is maintained.

In order to suppress stone biting, for example, in Patent Document 1 below, the inner groove wall of the shoulder main groove has a concave wall portion that moves away from the groove center of the shoulder main groove and a convex wall portion that approaches the groove center of the shoulder main groove. A tire has been proposed in which and is alternately included in the tire circumferential direction. Although such a shoulder main groove has a certain effect in suppressing stone biting, there is room for further improvement.

Japanese Unexamined Patent Publication No. 2016-005950

The present invention has been devised in view of the above problems, and based on improving the inner groove wall of the shoulder main groove, a tire capable of more reliably suppressing stone biting into the shoulder main groove can be obtained. Its main purpose is to provide.

The present invention is a tire having a tread portion, and the tread portion is provided with a shoulder main groove that extends continuously in the tire circumferential direction on the tread end side, and the shoulder main groove is inside the inside in the tire axial direction. The inner groove wall has a side groove wall, and the inner groove wall has a concave wall portion that moves away from the groove center of the shoulder main groove by repeatedly increasing and decreasing the angle with respect to the tread normal in the groove cross section in the tire circumferential direction. Convex wall portions approaching the center of the shoulder main groove are alternately included in the tire circumferential direction, and the inner end portion of the concave wall portion in the tire axial direction is locally recessed inward in the tire axial direction and the tread portion. It is characterized by being provided with a recess that opens at the tread surface of the tire.

In the tire of the present invention, it is desirable that the width of the recess in the tire circumferential direction gradually decreases toward the inside in the tire axial direction, at least on the tread surface.

In the tire of the present invention, it is desirable that the recess extends from the tread to the bottom of the groove.

In the tire of the present invention, the shoulder main groove has an outer groove wall on the outer side in the tire axial direction, and the outer groove wall periodically increases or decreases the angle with respect to the tread normal in the groove cross section in the tire circumferential direction. By repeating the process, a convex wall portion facing the concave wall portion of the inner groove wall and approaching the groove center of the shoulder main groove, and a concave portion facing the convex wall portion of the inner groove wall and moving away from the groove center of the shoulder main groove. It is desirable to include the wall portion alternately in the tire circumferential direction.

In the tire of the present invention, the outer groove wall and the inner groove wall are respectively inclined in a direction away from the groove center toward the outside in the tire radial direction from the groove bottom surface, and can be seen in any groove cross section of the shoulder main groove. It is desirable that the angle of the outer groove wall with respect to the tread normal is larger than the angle of the inner groove wall with respect to the tread normal.

In the tire of the present invention, the tread portion is provided with a middle land portion adjacent to the inside of the shoulder main groove in the tire axial direction, and the middle land portion is connected to the recess and the middle land portion. It is desirable that a middle lateral groove is provided across the portion.

In the tire of the present invention, the middle lateral groove includes a main body portion that opens on the tread side of the land portion and a sipe portion that extends inward in the tire radial direction from the bottom portion of the main body portion with a width smaller than that of the main body portion. Is desirable.

In the tire of the present invention, it is desirable that the sipe wall on one side of the sipe portion in the tire circumferential direction is smoothly continuous with the groove wall on one side of the main body portion in the tire circumferential direction.

In the tire of the present invention, it is desirable that the recess includes a pair of first groove walls connected to the inner groove wall and a second groove wall extending between the pair of first groove walls in the tire circumferential direction.

In the tire of the present invention, the shoulder main groove has an outer groove wall on the outer side in the tire axial direction, and in the groove cross section of the shoulder main groove, the inner groove wall and the outer groove wall are respectively from the groove bottom surface. The main body portion that inclines toward the outside in the tire radial direction toward the outside from the groove center of the shoulder main groove, and the main body portion that is connected to the outer side in the tire radial direction and inclines at an angle larger than the main body portion with respect to the tread normal. It is desirable to have an outer portion to be used.

In the tire of the present invention, it is desirable that the maximum depth of the outer portion is 0.30 to 0.50 times the maximum depth of the shoulder main groove.

In the tire of the present invention, each of the main body portions has a concave wall portion that moves away from the groove center of the shoulder main groove by repeatedly increasing and decreasing the angle with respect to the tread normal in the groove cross section in the tire circumferential direction. It is desirable that the convex wall portions approaching the center of the shoulder main groove are alternately included in the tire circumferential direction.

In the tire of the present invention, it is desirable that each of the convex wall portions of the inner groove wall faces the concave wall portion of the outer groove wall.

In the tire of the present invention, it is desirable that the main body portion of the outer groove wall has an angle with respect to the tread normal larger than that of the main body portion of the inner groove wall.

In the tire of the present invention, it is desirable that the difference in angle between the main body portion of the inner groove wall and the main body portion of the outer groove wall with respect to the tread normal is 2 to 13 °.

The inner groove wall of the shoulder main groove of the tire of the present invention has a concave wall portion that moves away from the groove center of the shoulder main groove by repeatedly increasing and decreasing the angle with respect to the tread normal in the groove cross section in the tire circumferential direction. , The convex wall portion that approaches the center of the main groove of the shoulder is alternately included in the tire circumferential direction. The concave wall portion and the convex wall portion greatly change the shape in the groove before and after the main groove touches the ground, and thus helps to promote the discharge of stones.

The inner end of the concave wall portion in the tire axial direction is provided with a concave portion that is locally recessed inward in the tire axial direction and is opened by the tread surface of the tread portion. Such a recess provides a large space locally on the concave wall side, and thus the stone in the shoulder main groove can be reliably discharged. In addition, the main groove is greatly elastically deformed so as to expand after narrowing the groove space from the recess as a starting point when the tire touches the ground and is released from the ground, and discharges stones sandwiched in the shoulder main groove. be able to.

It is a development view of the tread part of the tire of one Embodiment of this invention. It is an enlarged view of the shoulder main groove of FIG. It is the end view of the line AA of FIG. It is a perspective view of the recess of FIG. It is an enlarged view of the middle land part of FIG. (A) is a sectional view taken along line B-B of FIG. 5, (b) is a sectional view taken along line C-C of FIG. It is an enlarged view of the crown land part of FIG. It is an enlarged view of the shoulder main groove of another embodiment of this invention. It is the end view of the DD line of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of the tread portion 2 of the tire 1 of the present embodiment. The tire 1 of the present embodiment can be used for various tires such as pneumatic tires for passenger cars and heavy loads, and non-pneumatic tires in which pressurized air is not filled inside the tires. The tire 1 of the present embodiment is suitably used as, for example, a pneumatic tire for a heavy load having a high contact pressure and easily causing stone biting.

As shown in FIG. 1, the tread portion 2 of the tire 1 is provided with, for example, a pair of shoulder main grooves 5 that extend continuously in the tire circumferential direction on the tread end Te side.

The "tread end Te" is a flat tire 1 with a normal load applied to a tire 1 in a normal state, which is assembled on a normal rim (not shown), is filled with a normal internal pressure, and has no load, and has a camber angle of 0 °. This is the most outer contact position in the tire axial direction when the tire is grounded.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATTA and "Design Rim" for TRA. If it is ETRTO, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in "VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum load capacity", for TRA, the table "TIRE LOAD LIMITS" The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

Each shoulder main groove 5 of the present embodiment is arranged, for example, on the most tread end Te side, and extends linearly. A shoulder land portion 9 is divided between the shoulder main groove 5 and the tread end Te. The middle land portion 7 is adjacent to the inside of the shoulder main groove 5 in the tire axial direction.

In the case of a pneumatic tire for a heavy load, it is desirable that the shoulder main groove 5 has a groove width W1 of, for example, 3.0 to 7.0% of the tread width TW in order to ensure sufficient drainage. The tread width TW is the distance in the tire axial direction between the tread ends Te and Te of the tire 1 in the normal state. From the same viewpoint, the groove depth of the shoulder main groove 5 is preferably 10 to 25 mm, for example.

FIG. 2 shows an enlarged view of the shoulder main groove 5 of FIG. FIG. 3 shows an end view taken along line AA of FIG. As shown in FIGS. 2 and 3, the shoulder main groove 5 has an inner groove wall 11 and an outer groove wall 12.

The inner groove wall 11 is formed inside the groove center 5c in the tire axial direction. The inner groove wall 11 is formed between the groove edge 18 on the inner side in the tire axial direction and the groove bottom surface 10. The outer groove wall 12 is formed on the outer side of the groove center 5c in the tire axial direction. The outer groove wall 12 is formed between the groove edge 19 on the outer side in the tire axial direction and the groove bottom surface 10. As used herein, the groove center 5c means a virtual surface extending in the depth direction of the groove through a central position between a pair of groove edges 18 and 19 in a tread plan view. The inner groove wall 11 and the outer groove wall 12 are respectively inclined in the groove cross section in a direction away from the groove center 5c from the groove bottom surface 10 toward the outside in the tire radial direction.

In addition, in FIG. 2, the inner groove wall 11 and the outer groove wall 12 are colored so that the invention can be easily understood. Further, in FIGS. 1 and 2, the inner groove bottom edge 13 where the groove bottom surface 10 of the shoulder main groove 5 and the inner groove wall 11 intersect, and the outer side where the groove bottom surface 10 of the shoulder main groove 5 and the outer groove wall 12 intersect. The bottom edge 14 of the lateral sulcus is indicated by a chain double-dashed line.

As shown in FIGS. 2 and 3, in the inner groove wall 11, the angle θ1 with respect to the tread normal in the groove cross section repeats increasing and decreasing periodically in the tire circumferential direction. As a result, the inner groove wall 11 alternately includes the concave wall portion 16 away from the groove center of the shoulder main groove 5 and the convex wall portion 17 approaching the groove center of the shoulder main groove 5 in the tire circumferential direction. The concave wall portion 16 and the convex wall portion 17 of the present embodiment each have a smoothly curved outer surface. The concave wall portion 16 and the convex wall portion 17 greatly change the shape in the groove before and after the main groove touches the ground, which is useful for promoting the discharge of stones.

The inner groove wall 11 of the present embodiment is formed between the groove edge 18 on the tread side extending linearly along the tire circumferential direction and the inner groove bottom edge 13 extending wavy in the tire circumferential direction. The linear groove edge 18 helps to suppress its uneven wear. The wavy inner groove bottom edge 13 can be expected to discharge stones that have penetrated to the vicinity of the groove bottom surface 10.

It is desirable that the inner groove bottom edge 13 extends in a sinusoidal shape, for example. When stress acts on the tread portion 2, the inner groove bottom edge 13 can flex smoothly as a whole, disperses the stress on the groove bottom surface, and tears and damages the shoulder land portion 9 (hereinafter, "" It may be called "rib tier").

The minimum value of the angle θ1 of the inner groove wall 11 is preferably, for example, 5 to 8 °. The maximum value of the angle θ1 is preferably, for example, 9 to 12 °. It is desirable that the angle θ1 of the inner groove wall 11 changes periodically in the tire circumferential direction, for example, in the range of 7 ° to 10 °. Such an inner groove wall 11 is useful for suppressing stone biting while maintaining drainage.

From the same viewpoint, it is desirable that the pitch P1 of the concave wall portion 16 or the convex wall portion 17 in the tire circumferential direction is, for example, 0.10 to 0.20 times the tread width TW (shown in FIG. 1). The pitch P1 is indicated by, for example, the distance between the outer ends 17t of the convex wall portions 17 adjacent to each other in the tire circumferential direction in the tire axial direction.

The inner end of the concave wall portion 16 in the tire axial direction is provided with a concave portion 20 that is locally recessed inward in the tire axial direction and is opened by the tread surface of the tread portion 2. Such a recess 20 provides a large space locally on the concave wall portion 16 side, and as a result, the stone in the shoulder main groove 5 can be reliably discharged. Further, the main groove is greatly elastically deformed so as to expand after narrowing the groove space from the recess 20 as a starting point when the tire touches the ground and is released from the ground, and the stone sandwiched in the shoulder main groove 5 is formed. Can be discharged.

FIG. 4 shows a perspective view of the recess 20. As shown in FIG. 4, in order to further exert the above-mentioned effect, it is desirable that the recess 20 extends from the tread surface to the bottom surface of the groove. Such a recess 20 can be expected to discharge stones that have penetrated to the vicinity of the bottom surface 10 of the groove.

Recess 20 has a first wall 31 of the pair leading to the inner groove wall 11, the second groove wall 32 between the first groove wall 31 of the pair. The first groove wall 31 of the pair, for example, extend diagonally from the inner groove wall 11 in the tire axial direction. Second groove wall 32, extends between the first groove wall 31 of the pair in the circumferential direction of the tire. Such a recess 20 helps to suppress an excessive decrease in rigidity of the middle land portion 7.

As shown in FIG. 2, it is desirable that the width of the recess 20 in the tire circumferential direction gradually decreases toward the inside in the tire axial direction, at least on the tread surface. The width of the recess 20 of the present embodiment gradually decreases toward the inside in the tire axial direction over the entire area from the tread surface to the bottom surface of the groove. Such a recess 20 can be opened and closed more greatly when the tire is running, and stones can be discharged more positively.

The width W3 of the recess 20 in the tire axial direction is, for example, 0.05 to 0.12 times the width W2 of the middle land portion 7 in the tire axial direction (shown in FIG. 1 and the same applies hereinafter). Is desirable. It is desirable that the width W4 of the recess 20 in the tire circumferential direction is, for example, 0.08 to 0.15 times the width W2 of the middle land portion 7. Such a recess 20 can obtain the above-mentioned effect while maintaining the rigidity of the middle land portion 7.

Similar to the inner groove wall 11, the outer groove wall 12 also has an angle θ2 with respect to the tread normal in the groove cross section periodically increasing and decreasing in the tire circumferential direction. As a result, the outer groove wall 12 alternately includes the convex wall portion 22 that approaches the groove center of the shoulder main groove 5 and the concave wall portion 21 that moves away from the groove center of the shoulder main groove 5 in the tire circumferential direction. The concave wall portion 21 and the convex wall portion 22 of the outer groove wall 12 also have a smoothly curved outer surface, respectively.

In the present embodiment, the convex wall portion 22 of the outer groove wall 12 faces the concave wall portion 16 of the inner groove wall 11. The concave wall portion 21 of the outer groove wall 12 faces the convex wall portion 17 of the inner groove wall 11. Such an outer groove wall 12, together with the inner groove wall 11, helps to suppress stone biting.

The outer groove wall 12 of the present embodiment is formed between the groove edge 19 on the tread side extending linearly along the tire circumferential direction and the outer groove bottom edge 14 extending wavy in the tire circumferential direction.

It is desirable that the outer groove bottom edge 14 extends in the tire circumferential direction in the same phase as the inner groove bottom edge 13, for example. As a more desirable embodiment, the outer groove bottom edge 14 of the present embodiment extends in a sinusoidal shape in the tire circumferential direction with an amplitude larger than that of the inner groove bottom edge 13. Such an outer groove bottom edge 14 can further promote the discharge of stones, disperse stress on the groove bottom surface 10, and effectively suppress rib tiers.

It is desirable that the angle θ2 of the outer groove wall 12 is larger than the angle θ1 of the inner groove wall 11. As a further preferred embodiment, in this embodiment, in both of the groove cross-section of the shoulder main groove 5, the angle θ2 of the outer groove wall 12 is larger than the angle theta 1 of the inner groove wall 11. As a result, rib tier is more reliably suppressed.

The minimum value of the angle θ2 of the outer groove wall 12 is preferably, for example, 10 to 14 °. The maximum value of the angle θ2 is preferably 18 to 22 °, for example. It is desirable that the angle θ2 of the outer groove wall 12 changes periodically in the tire circumferential direction, for example, in the range of 12 ° to 20 °. Such an outer groove wall 12 can suppress stone biting and rib tier without impairing wet performance.

It is desirable that the difference between the angle θ2 of the outer groove wall 12 and the angle θ1 of the inner groove wall 11 is, for example, 2 to 13 °. Such outer groove walls 12 and inner groove walls 11 help to uniformly wear the groove edges 18 and 19.

As shown in FIG. 1, the tread portion 2 is further provided with a crown main groove 6. The crown main groove 6 is provided inside the shoulder main groove 5 in the tire axial direction. For example, one crown main groove 6 of the present embodiment is provided on each side of the tire equator C. One crown main groove 6 may be provided on the tire equator C, for example. The crown main groove 6 has, for example, a groove width and a groove depth similar to those of the shoulder main groove 5 described above.

It is desirable that the crown main groove 6 is provided with, for example, a plurality of protrusions 23 protruding from the bottom surface of the groove in the tire circumferential direction. Such protrusions can effectively suppress stone biting in the crown main groove 6. Further, in the present embodiment, by providing the protrusion 23 in the crown main groove 6, the stone biting in the crown main groove 6 on which a large contact pressure acts is surely suppressed, and the shoulder main groove 5 is not provided with the protrusion. As a result, the groove volume is secured and the wet performance is improved.

The shoulder main groove 5 and the crown main groove 6 of the present embodiment are provided with a plurality of lug sipes 30 having one end connected to the main groove and the other end interrupted in the land portion. The length L1 of the lug sipe 30 in the tire axial direction is, for example, 0.5 to 5.0% of the tread width TW. Such a lag sipe 30 is useful for suppressing distortion of the groove edge of each main groove at the time of contacting the ground, and thus suppressing uneven wear thereof.

By providing the shoulder main groove 5 and the crown main groove 6 in the tread portion 2, the crown land portion 8 is divided in addition to the shoulder land portion 9 and the middle land portion 7. The crown land portion 8 is provided between, for example, a pair of crown main grooves 6.

FIG. 5 shows an enlarged view of the middle land portion 7. As shown in FIG. 5, the middle land portion 7 is divided between the crown main groove 6 and the shoulder main groove 5. The middle land portion 7 is provided with, for example, the above-mentioned recess 20 and a plurality of middle lateral grooves 25 that are connected to the recess 20 and cross the middle land portion 7. In the present embodiment, a similar recess 24 is provided at the end of the middle lateral groove 25 on the crown main groove 6 side. As a result, stone biting in the crown main groove 6 can be further suppressed.

In the tread plan view, it is desirable that each middle lateral groove 25 is curved in an arc shape. Such a middle lateral groove 25 is useful for dispersing the stress acting on the groove edge and suppressing uneven wear of the land portion starting from the groove edge.

As shown in FIG. 1, in the present embodiment, the middle lateral groove 25 provided in the middle land portion 7 on one side of the tire equator C and the middle lateral groove provided in the middle land portion 7 on the other side of the tire equator C. It is desirable that 25 is convex in the opposite direction to each other. Such an arrangement of the middle lateral grooves 25 exerts an edge effect regardless of the rotation direction of the tire.

FIG. 6A shows a cross-sectional view taken along the line BB of FIG. As shown in FIG. 6A, the middle lateral groove 25 includes a main body portion 26 and a sipe portion 27. The main body 26 is opened on the tread side of the land portion and has a groove width W5 of 2.0 mm or more. The sipe portion 27 extends inward in the tire radial direction from the bottom portion of the main body portion 26 with a width W6 smaller than that of the main body portion 26. The width W6 of the sipe portion 27 is, for example, 0.5 to 1.5 mm. The depth d1 from the tread to the bottom of the sipe portion is, for example, 0.50 to 0.60 times the depth of the shoulder main groove 5.

The sipe wall 27w on one side of the sipe portion 27 of the present embodiment in the tire circumferential direction is smoothly continuous with, for example, the groove wall 26w on one side of the main body portion 26 in the tire circumferential direction.

As shown in FIG. 5, in the present embodiment, the sipe wall on one side (upper side in FIG. 5) of the sipe portion 27 in the tire circumferential direction and the groove wall on one side in the tire circumferential direction of the main body portion 26 are continuous. The first middle lateral groove 25a, the sipe wall on the other side (lower side in FIG. 5) of the sipe portion 27 in the tire circumferential direction, and the groove wall on the other side in the tire circumferential direction of the main body 26 are continuous to each other in the second middle lateral groove 25b. And are provided alternately in the tire circumferential direction. As a result, the rigidity of each block between the middle lateral grooves 25 is slightly different, and as a result, the striking sound when the middle land portion 7 touches the ground becomes white noise.

FIG. 6B shows a sectional view taken along line CC of the middle lateral groove 25 of FIG. As shown in FIG. 6B, the sipe portion 27 includes a central portion 28 and an end portion 29 having different depths. In this embodiment, the end portions 29 are arranged on both sides of the central portion 28 and have a depth smaller than that of the central portion 28. As a result, excessive opening of the sipe portion 27 is suppressed, and steering stability is enhanced.

FIG. 7 shows an enlarged view of the crown land portion 8 of FIG. As shown in FIG. 7, the crown land portion 8 is provided with a plurality of crown lateral grooves 33. The crown lateral grooves 33 communicate with each other, for example, between the crown main grooves 6. The crown lateral groove 33 is, for example, a linear shape inclined at an angle θ3 of 10 to 40 ° with respect to the tire axial direction.

At both ends of the crown lateral groove 33, for example, recesses 34 similar to those described above are connected. As a result, the stone biting of the crown main groove 6 is further suppressed.

As a preferred embodiment, the crown transverse groove 33 of the present embodiment has substantially the same cross-sectional shape as the middle transverse groove 25 shown in FIGS. 6A and 6B, for example. That is, the crown lateral groove 33 includes, for example, a main body portion having a groove width of 2.0 mm or more and a sipe portion extending inward in the tire radial direction from the bottom portion of the main body portion (not shown).

As shown in FIG. 1, it is desirable that each crown lateral groove 33 and each middle lateral groove 25 are displaced from each other in the tire circumferential direction. Since the crown lateral groove 33 and the middle lateral groove 25 do not touch the ground at the same time, they are useful for suppressing the maximum sound pressure of the pumping sound.

As a more desirable embodiment, each crown lateral groove 33 of the present embodiment is arranged at a position smoothly continuous with the middle lateral grooves 25 on both sides via the crown main groove 6. As a result, the water in the crown lateral groove 33 is easily discharged to the outside in the tire axial direction during wet running.

The shoulder land portion 9 is a semi-plain rib having no groove or sipe, except for the lug sipe 30 described above. Such a shoulder land portion 9 can provide excellent steering stability.

FIG. 8 shows an enlarged view of the shoulder main groove 5 of another embodiment of the present invention. FIG. 9 shows an end view of the shoulder main groove 5 of FIG. 8 along the DD line. In FIGS. 8 and 9, the elements common to the above-described embodiments are designated by the same reference numerals, and the description thereof is omitted here.

As shown in FIGS. 8 and 9, in this embodiment, in the cross section of the shoulder main groove 5, the inner groove wall 11 and the outer groove wall 12 have a main body portion 35 and an outer portion 36, respectively. There is. The main body 35 is inclined from the bottom surface 10 of the groove toward the outside in the radial direction of the tire in a direction away from the center 5c of the shoulder main groove 5. The outer portion 36 is connected to the outer side of the main body portion 35 in the radial direction of the tire. The outer portion 36 is inclined with respect to the tread normal at an angle larger than that of the main body portion. Such a shoulder main groove 5 can easily discharge the bitten stone. In FIG. 8, the main body portion 35 and the outer portion 36 are colored so that the invention can be easily understood, and the boundary 39 between the main body portion 35 and the outer portion 36 is indicated by a two-dot chain line.

As shown in FIG. 9, it is desirable that the maximum depth d3 of the outer portion 36 is, for example, 0.30 to 0.50 times the maximum depth d2 of the shoulder main groove 5. Such an outer portion 36 can exert the above-mentioned effect while ensuring wet performance.

It is desirable that the outer portion 36 of the inner groove wall 11 is inclined at an angle θ4 of 15 to 25 ° with respect to the tread normal, for example. Such an inner groove wall 11 can suppress stone biting while ensuring the width of the middle land portion 7 and maintaining the wear resistance performance.

From the same viewpoint, it is desirable that the outer portion 36 of the outer groove wall 12 is inclined with respect to the tread normal at an angle θ5 larger than that of the outer portion 36 of the inner groove wall 11. Specifically, it is desirable that the angle θ5 of the outer portion 36 of the outer groove wall 12 is, for example, 25 to 35 °.

As shown in FIG. 8, in each main body 35, the angle with respect to the tread normal in the groove cross section repeats increasing and decreasing periodically in the tire circumferential direction. As a result, each main body portion 35 alternately includes a concave wall portion 37 away from the groove center of the shoulder main groove 5 and a convex wall portion 38 approaching the groove center of the shoulder main groove 5 in the tire circumferential direction. In the present embodiment, each convex wall portion 17 of the inner groove wall 11 faces the concave wall portion 21 of the outer groove wall 12. Each convex wall portion 22 of the outer groove wall 12 faces the concave wall portion 16 of the inner groove wall 11.

The pitch P2 of the concave wall portions 16 and 21 or the convex wall portions 17 and 22 in the tire circumferential direction (in FIG. 8, the pitch between the outer ends 17t of the convex wall portion 17 of the inner groove wall 11 is shown). It is preferably 0.10 to 0.20 times the tread width TW, and more preferably 0.15 to 0.18 times the tread width TW. Such a main body 35 is useful for suppressing stone biting while maintaining drainage.

As shown in FIG. 9, it is desirable that the main body 35 of the inner groove wall 11 periodically changes in the tire circumferential direction in an angle θ6 with respect to the tread normal, for example, in the range of 7 to 10 °.

It is desirable that the main body 35 of the outer groove wall 12 has, for example, an angle θ7 with respect to the tread normal periodically changing in the tire circumferential direction in the range of 12 to 20 °.

It is desirable that the angle θ7 of the main body 35 of the outer groove wall 12 is larger than, for example, the angle θ6 of the main body 35 of the inner groove wall 11. As a more desirable embodiment, in the present embodiment, the angle θ7 of the main body 35 of the outer groove wall 12 is larger than the angle θ6 of the main body 35 of the inner groove wall 11 in any of the groove cross sections of the shoulder main groove 5. large. The difference in angle between the main body 35 of the inner groove wall 11 and the main body 35 of the outer groove wall 12 with respect to the tread normal is preferably 2 to 13 °, for example. Thereby, for example, even when the shoulder main groove 5 bites the stone, the shoulder land portion 9 is appropriately bent and the stone can be quickly discharged.

Although the tire of one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and may be modified to various embodiments.

Table 1 shows a heavy-duty pneumatic tire of size 295 / 75R22.5 having the basic tread pattern of FIG. 1 and having the inner and outer gutter walls of the shoulder main grooves shown in FIGS. 2 and 3. It was prototyped based on the specifications of. As a comparative example, a tire having the basic tread pattern of FIG. 1 and having the angles of the inner groove wall and the outer groove wall constant over the entire circumference of the tire was prototyped. The stone biting performance and wet performance of each test tire were tested. The common specifications and test methods for each test tire are as follows.
Mounting rim: 22.5 x 8.25
Tire internal pressure: 830kPa
Test vehicle: 10t truck, 50% of standard load capacity is loaded in the center of the loading platform Test tire mounting position: All wheels

<Stone biting performance>
After traveling 16000 km on a general road with the above test vehicle, the weight of the stone sandwiched between the shoulder main grooves of each test tire was measured. The result is an index with the tire of the comparative example as 100, and the smaller the value, the more the occurrence of stone biting is suppressed.

<Wet performance>
On an asphalt road surface having a water film with a thickness of 3 mm, the test vehicle traveled while accelerating from 50 km / h, and the speed when the hydroplaning phenomenon occurred was measured. The result is an index with a comparative example of 100, and the larger the value, the better the wet performance.
The test results are shown in Table 1.

As a result of the test, it was confirmed that the tire of the example effectively suppressed stone biting. Further, it was confirmed that the tire of the embodiment maintained the wet performance.

Table 2 shows the heavy-duty pneumatic tires of size 295 / 80R22.5 having the basic tread pattern of FIG. 1 and having the inner and outer gutter walls of the shoulder main grooves shown in FIGS. 8 and 9. It was prototyped based on the specifications of. Each test tire was tested for the above stone biting performance and wet performance as well as the following uneven wear resistance.

<Uneven wear resistance>
After traveling 48,000 km with the above test vehicle, the difference in the amount of wear on both sides of the shoulder main groove was measured. The result is an index in which the difference in the amount of wear in the comparative example is 100, and the smaller the value, the smaller the difference in the amount of wear and the more the uneven wear is suppressed.
The test results are shown in Table 2.

As a result of the test, it was confirmed that the tire of the example effectively suppressed stone biting. Further, it was confirmed that the tire of this embodiment maintains the wet performance and the uneven wear resistance performance.

2 Tread part 5 Shoulder main groove 11 Inner groove wall 16 Concave wall part 17 Convex wall part 20 Recessed Te tread end

Claims (15)

A tire with a tread
The tread portion is provided with a shoulder main groove that extends continuously in the tire circumferential direction on the tread end side.
The shoulder main groove has an inner groove wall on the inner side in the tire axial direction.
The inner groove wall is formed between a groove edge on the tread side extending linearly along the tire circumferential direction and an inner groove bottom edge extending wavy in the tire circumferential direction.
The inner groove wall has a concave wall portion that moves away from the groove center of the shoulder main groove and a groove of the shoulder main groove by repeatedly increasing and decreasing the angle with respect to the tread normal in the groove cross section in the tire circumferential direction. Convex walls that approach the center are included alternately in the tire circumferential direction.
A tire in which the inner end portion of the concave wall portion in the tire axial direction is provided with a concave portion that is locally recessed inward in the tire axial direction and is opened at the tread surface of the tread portion. The tire according to claim 1, wherein the recessed portion has a width in the tire circumferential direction gradually decreasing inward in the tire axial direction, at least on the tread surface. The tire according to claim 1 or 2, wherein the recess extends from the tread surface to the bottom surface of the groove. The shoulder main groove has an outer groove wall on the outer side in the tire axial direction.
The outer groove wall faces the concave wall portion of the inner groove wall and approaches the groove center of the shoulder main groove by repeatedly increasing and decreasing the angle with respect to the tread normal in the groove cross section in the tire circumferential direction. The tire according to any one of claims 1 to 3, wherein the convex wall portion and the concave wall portion facing the convex wall portion of the inner groove wall and away from the groove center of the shoulder main groove are alternately included in the tire circumferential direction. The outer groove wall and the inner groove wall are inclined from the bottom surface of the groove toward the outside in the radial direction of the tire in a direction away from the center of the groove.
The tire according to claim 4, wherein the angle of the outer groove wall with respect to the tread normal is larger than the angle of the inner groove wall with respect to the tread normal in any of the groove cross sections of the shoulder main groove. The tread portion is provided with a middle land portion adjacent to the inside of the shoulder main groove in the tire axial direction.
The tire according to any one of claims 1 to 5, wherein the middle land portion is provided with the recess and a middle lateral groove that is connected to the recess and crosses the middle land portion. The tire according to claim 6, wherein the middle lateral groove includes a main body portion that opens on the tread side of the land portion and a sipe portion that extends inward in the radial direction of the tire with a width smaller than that of the main body portion from the bottom portion of the main body portion. The tire according to claim 7, wherein the sipe wall on one side in the tire circumferential direction of the sipe portion is smoothly continuous with the groove wall on one side in the tire circumferential direction of the main body portion. The recess according to any one of claims 1 to 8, wherein the recess includes a pair of first groove walls connected to the inner groove wall and a second groove wall extending between the pair of first groove walls in the tire circumferential direction. Tires. The shoulder main groove has an outer groove wall on the outer side in the tire axial direction.
In the groove cross section of the shoulder main groove,
The inner groove wall and the outer groove wall are connected to a main body portion that inclines toward the outside in the tire radial direction from the bottom surface of the groove in a direction away from the groove center of the shoulder main groove and the outer side in the tire radial direction of the main body portion, respectively. The tire according to claim 1, further comprising an outer portion that is inclined at an angle larger than that of the main body portion with respect to the tread normal. The tire according to claim 10, wherein the maximum depth of the outer portion is 0.30 to 0.50 times the maximum depth of the shoulder main groove. Each of the main body portions has a concave wall portion that moves away from the groove center of the shoulder main groove and a groove of the shoulder main groove by repeatedly increasing and decreasing the angle with respect to the tread normal in the groove cross section in the tire circumferential direction. The tire according to claim 10 or 11, wherein convex wall portions approaching the center are alternately included in the tire circumferential direction. The tire according to claim 12, wherein each convex wall portion of the inner groove wall faces the concave wall portion of the outer groove wall. The tire according to claim 12 or 13, wherein the main body portion of the outer groove wall has an angle with respect to a tread normal larger than that of the main body portion of the inner groove wall. The tire according to claim 14, wherein the difference in angle between the main body portion of the inner groove wall and the main body portion of the outer groove wall with respect to the tread normal is 2 to 13 °.

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