JP2014213835A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which can suppress eccentric wear even at wear terminal stage.SOLUTION: In a pneumatic tire, a circumferential fine groove 5 extending to a tire circumferential direction is formed at a land part 4 which is defined between a circumferential main groove 3 and a tread grounding end TG, an annular groove 6 extending to the tire circumferential direction while continuing thereto is formed at a groove wall 5wi inside the tire width direction of the circumferential fine groove 5 from an opening end 5oi inside the tire width direction of the circumferential fine groove 5 up to the innermost end 5oi of the tire radial direction of the circumferential fine groove 5, and a contour of the circumferential fine groove 5 has first to fourth circles having R1 to R4 in curvature radii, a distance L1 in the tire width direction from the innermost end 6wi in the tire width direction of a groove wall 6w of the annular groove 6 up to the outside of the tire width direction of the fine groove 6 is 5.7 to 6.5 mm, and an angle θ with respect to a tread stepping surface of the groove wall 5wi inside the tire width direction of the circumferential fine groove is smaller than 90°.

Description

  In particular, the present invention relates to a pneumatic tire capable of suppressing uneven wear not only at the initial stage of wear but also at the end stage of wear.

  As a pneumatic tire that suppresses uneven wear that occurs in the tread, the tire circumference is formed in a land section defined between a circumferential main groove provided on the tread tread surface that extends continuously in the tire circumferential direction and the tread grounding end. A circumferential narrow groove extending continuously in the direction is provided, where the circumferential narrow groove tire extends from the opening end of the circumferential narrow groove in the tire width direction to the innermost end in the tire radial direction of the circumferential narrow groove. A pneumatic tire is known in which an annular groove extending continuously in the tire circumferential direction is provided on a groove wall on the inner side in the width direction (see Patent Document 1).

  In the conventional pneumatic tire described above, since the circumferential narrow groove is provided, wear generated in a portion on the outer side in the tire width direction than the circumferential narrow groove in the land portion (hereinafter also referred to as “width direction outer land portion portion”). It is possible to prevent the tire from extending to the inner portion in the tire width direction (hereinafter also referred to as “inner land portion in the width direction”) from the circumferential narrow groove of the land portion, and to suppress uneven wear occurring in the pneumatic tire. Can do. In addition, since the circumferential narrow groove is provided with an annular groove, it is possible to prevent the strain generated in the land portion at the time of tire contact at the initial stage of wear from concentrating on the groove bottom of the circumferential narrow groove. Occurrence can be suppressed. Furthermore, since the outline of the circumferential narrow groove has a first arc to a fourth arc, it is possible to suppress the occurrence of stone biting, tearing, and cracks in the circumferential narrow groove.

International Publication No. 2008/111582

  However, in the conventional pneumatic tire described above, the annular groove provided in the circumferential narrow groove is exposed on the tread surface at the end portion of the wear in the widthwise inner land portion. The effect of suppressing wear is lost.

  Therefore, an object of the present invention is to provide a pneumatic tire capable of suppressing uneven wear not only in the early stage of wear but also in the last stage of wear.

The inventors have earnestly studied the conventional pneumatic tire described above, and obtained the following knowledge.
The annular groove provided in the circumferential narrow groove in the conventional pneumatic tire also has an effect of reducing the contact pressure in the widthwise inner land portion. By reducing the contact pressure, the shear force in the tire width direction applied to the widthwise inner land portion is reduced, and uneven wear in the land portion is suppressed. Here, the conventional pneumatic tire at the end of wear is obtained by having an annular groove in the widthwise inner land portion, because the annular groove provided in the circumferential narrow groove is exposed on the tread surface. The effect of reducing the contact pressure in the inner land portion and thus suppressing uneven wear is lost.

In addition, the groove wall on the inner side in the tire width direction of the annular groove is located on the inner side in the tire width direction compared to the groove wall on the inner side in the tire width direction of the circumferential narrow groove portion where the annular groove is not provided. At the end of wear when exposed to the tread surface, the width in the tire width direction of the inner land portion in the width direction becomes smaller than that in the initial wear.
For this reason, the area of the land portion to which a load is applied during rolling of the tire is relatively reduced, and the contact pressure in the widthwise inner land portion is increased. This increase in contact pressure increases the shear strain in the tire width direction of the widthwise inner land portion, and promotes partial wear of the pneumatic tire.
Further, the decrease in the width in the tire width direction of the land portion in the inner side in the width direction increases the bulge of the rubber in the tire width direction in this portion, while the bulge in the tire circumferential direction of the rubber in this portion decreases. Therefore, the inner land portion in the width direction is easily slipped in the tire circumferential direction, and uneven wear of the pneumatic tire is further promoted.

  Therefore, the inventors have conceived that by appropriately adjusting the width in the tire width direction of the annular groove provided in the circumferential narrow groove, uneven wear of the pneumatic tire is suppressed not only in the initial stage of wear but also in the end stage of wear. The present invention has been completed.

The gist of the present invention is as follows.
The pneumatic tire of the present invention is provided with a circumferential narrow groove in a land portion defined between a circumferential main groove provided on a tread tread and a tread grounding end. An annular groove is provided in a groove wall on the inner side in the tire width direction of the circumferential narrow groove from the opening end on the inner side in the tire width direction of the narrow groove in the tire to the innermost end in the tire radial direction of the circumferential narrow groove. In the cross section, the contour of the circumferential narrow groove is such that the center of curvature is between the opening end of the circumferential narrow groove in the tire width direction and the opening end of the circumferential narrow groove in the tire width direction outside. A first arc having a radius of curvature R1 on the part side, a second arc having a curvature center on the circumferential narrow groove side and having a curvature radius R2, and a curvature radius R3 having a curvature center on the circumferential narrow groove side. The third circular arc and the center of curvature is on the circumferential narrow groove side A pneumatic tire having a fourth arc having a diameter R4, and a groove wall on the outer side in the tire width direction of the circumferential narrow groove from the innermost end in the tire width direction of the groove wall of the annular groove in a cross section in the tire width direction. The tire width direction distance is 5.7 to 6.5 mm, and the angle θ formed with respect to the tread surface of the groove wall on the inner side in the tire width direction of the circumferential narrow groove in the tire width direction cross section is 90 ° It is characterized by being less than.
According to the pneumatic tire of the present invention, uneven wear can be suppressed not only at the initial stage of wear but also at the end stage of wear.

  In the pneumatic tire of the present invention, the angle θ is preferably 80 ° or more. If it is set as the said structure, generation | occurrence | production of the crack in a circumferential direction fine groove can be suppressed.

  According to the pneumatic tire of the present invention, uneven wear can be suppressed not only at the initial stage of wear but also at the end stage of wear.

(A) is a figure which shows the tire width direction cross section of the pneumatic tire of an example of this invention before abrasion about a tire half, (b) is the tire width of the circumferential direction narrow groove which the tire of (a) has It is a direction expanded sectional view.

Hereinafter, embodiments of the pneumatic tire of the present invention will be described with reference to the drawings.
FIG. 1A shows a tire width direction cross-sectional view of a pneumatic tire according to an example of the present invention, which is attached to an applicable rim, has a specified internal pressure, and is in an unloaded state, with respect to the tire half.
The pneumatic tire 1 (hereinafter also referred to as “tire 1”) according to an example of the present invention is a heavy-duty pneumatic tire that is used in heavy-duty vehicles such as trucks and buses. The tire 1 includes a tread 2, and further includes, for example, a pair of sidewall portions (not shown) extending inward in the tire radial direction from the side portion of the tread 2, and an inner radial direction from the sidewall portion. And a pair of bead portions (not shown) extending in the direction.

The tire 1 has a circumferential main groove 3 (3a) continuously extending in the tire circumferential direction on the tread 2 and the circumferential main groove 3 (3a) is landed between the tread ground contact end TG. Section 4 (4a) is defined. And the land part 4 has the circumferential direction fine groove 5 extended continuously in a tire circumferential direction.
The “tread surface” is a tire that comes into contact with the road surface when the tire that is assembled to the applicable rim and filled with the specified internal pressure is rolled with a load corresponding to the maximum load capacity applied. Refers to the outer peripheral surface of the entire circumference. Incidentally, the “applicable rim” is a standard rim defined in the following standard according to the tire size (specified as “Design Rim” in the following TRA YEAR BOOK. ), “Specified internal pressure” refers to the air pressure defined in accordance with the maximum load capacity in the following standards, and “maximum load capacity” is allowed to be applied to the tire according to the following standards: Refers to the maximum mass that can be played. The standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, in the United States, “THE TIRE AND RIM ASSOCIATION INC. (TRA)” “YEAR BOOK” In Europe, it is “STANDARDS MANUAL” of “The European Tire and Rim Technical Organization (ETRTO)”, and in Japan it is “JATMA YEAR BOOK” of “Japan Automobile Tire Association (JATMA)”.
In addition, “extending continuously in the tire circumferential direction” does not mean that the tire extends in a direction parallel to the tire circumferential direction and goes around the tread, but has a component in the tire circumferential direction. It also means that it goes around and goes around the tread.
Furthermore, the “tread grounding end” refers to the end in the tire width direction of the tread surface.
And unless otherwise indicated, the dimensions of the pneumatic tire of the present invention refer to the dimensions when the tire is mounted on an applicable rim, set to a specified internal pressure, and in a no-load state.

FIG. 1B shows an enlarged view of the circumferential narrow groove of the pneumatic tire of the example of the present invention shown in FIG.
Here, in the tire width direction cross section shown in FIG. 1B, the tire 1 is from the opening end 5oi on the inner side in the tire width direction of the circumferential narrow groove 5 to the innermost end 5bi in the tire radial direction of the circumferential narrow groove 5. The groove wall 5wi on the inner side in the tire width direction of the circumferential narrow groove 5 has an annular groove 6 that extends continuously in the tire circumferential direction.

  Further, in the tire width direction cross section shown in FIG. 1B, the outline of the circumferential narrow groove 5 of the tire 1 is from the opening end 5oi of the circumferential narrow groove 5 on the inner side in the tire width direction of the groove wall 6w of the annular groove 6. Between the innermost end 6wi in the tire width direction, the first arc C1 having the curvature radius R1 of 1.0 to 12.0 mm and the curvature center O1 on the land portion 4 (4a) side, and the curvature center O2 are in the circumferential direction. A second arc C2 having a radius of curvature R2 of 1.5 to 4.0 mm on the narrow groove 5 side is provided in this order.

  By providing the first arc C1 between the opening end 5oi and the innermost end 6wi, when a foreign substance such as a stone enters the circumferential narrow groove 5, the foreign substance is easily discharged outside without being caught by the groove wall. Thus, it is possible to prevent foreign matter from damaging the groove wall 5w and the groove bottom 5b of the circumferential narrow groove 5. If the radius of curvature R1 is within the above range, this effect can be easily obtained.

  By providing the second arc C2 between the opening end 5oi and the innermost end 6wi, even when a vehicle equipped with a pneumatic tire rides on a road shoulder or a curb, and a relatively large load is applied to the land portion 4, the land It is possible to prevent the distortion generated in the portion 4 from concentrating in the inner part of the annular groove 6, and it is possible to prevent the occurrence of tears and cracks in this portion. If the radius of curvature R2 is within the above range, this effect can be easily obtained.

  Further, the tire 1 has a center of curvature O3 between the innermost end 6i in the tire width direction of the groove wall 6w of the annular groove 6 and the innermost end 5bi in the tire radial direction of the groove bottom 5b of the circumferential narrow groove 5 in the circumferential direction. It has the 3rd circular arc C3 which exists in the narrow groove 5 side, and has the curvature radius R3 of 1.0-6.0 mm.

  By providing the third arc C3 between the innermost end 6wi and the innermost end 5bi, as in the case of the second arc C2, it is possible to prevent the occurrence of tears and cracks in the inner part of the annular groove 6. it can. If the radius of curvature R3 is within the above range, this effect can be easily obtained.

  Further, between the innermost end 5bi in the tire radial direction of the circumferential narrow groove 5 and the opening end 5oo on the outer side in the tire width direction of the groove bottom 5b of the circumferential narrow groove 5, the center of curvature O4 is on the circumferential narrow groove 5 side. There is a fourth arc C4 having a radius of curvature R4 of 2.0 to 16.0 mm. The center of curvature O4 is in the vicinity of the groove bottom 5b of the circumferential narrow groove 5, and is, for example, on the inner side in the tire radial direction from the center of curvature O2 of the second arc C2.

  By providing the fourth arc between the innermost end 5bi and the opening end 5oo, tears and cracks are generated in the inner part of the annular groove 6 as in the case of the second arc C2 and the third arc C3. Can be prevented. If the radius of curvature R4 is within the above range, this effect can be easily obtained.

Here, the tire 1 has a groove wall 5wo on the outer side in the tire width direction of the circumferential narrow groove 5 from the innermost end 6wi in the tire width direction of the groove wall 6w of the annular groove 6 in the cross section in the tire width direction shown in FIG. The tire width direction distance L1 is required to be 5.7 to 6.5 mm.
The distance L1 indicates a linear distance between the innermost end 6wi and the point P when the intersection point between the straight line passing through the innermost end 6wi and parallel to the tire width direction and the groove wall 5wo is a point P.

  In the tire 1, since the circumferential narrow groove 5 includes the annular groove 6, the distortion generated in the land portion 4 (4 a) at the time of tire contact is prevented from concentrating on the groove bottom 5 b of the circumferential narrow groove 5 at the initial stage of wear. Can do. Further, the contact pressure in the widthwise inner land portion 4ai of the land portion 4 (4a) is reduced.

  When the distance L1 is less than 5.7 mm, the effect of reducing the contact pressure by the annular groove 6 is not sufficient, and the effect of suppressing the uneven wear of the pneumatic tire cannot be sufficiently obtained.

  In the tire 1, the width in the tire width direction of the inner land portion 4 ai in the width direction is smaller than that in the initial stage of wear at the end of wear. Therefore, the contact pressure in the width direction inner land portion 4ai is increased, the shear strain in the tire width direction of the width direction inner land portion 4ai is increased, and uneven wear of the pneumatic tire is easily promoted. Furthermore, the bulging of the rubber in the tire circumferential direction of the width direction inner land portion 4ai is reduced, and the portion 4ai is easily slipped in the tire circumferential direction, and uneven wear of the pneumatic tire is easily promoted.

  When the distance L1 is more than 6.5 mm, the width in the tire width direction of the widthwise inner land portion 4ai becomes too small at the end of wear compared to the initial wear, and the ground contact in the widthwise inner land portion 4ai occurs. The pressure increases too much. Therefore, the shear strain in the tire width direction in the width direction inner land portion 4ai increases, and uneven wear of the pneumatic tire is promoted. Furthermore, due to an excessive decrease in the width in the tire width direction of the width direction inner land portion 4ai, the bulging of the rubber in the portion 4ai outward in the tire radial direction is excessively reduced, and the tire circumferential direction becomes more slippery, Uneven wear of the pneumatic tire is promoted.

  For the above reasons, according to the pneumatic tire of the present invention in which the distance L1 is 5.7 to 6.5 mm, uneven wear can be suppressed not only in the initial stage of wear but also in the end stage of wear.

  The distance L1 is preferably 6.1 to 6.5 mm. If the distance L1 is within this range, it is possible to enhance the effect of suppressing uneven wear not only in the early stage of wear but also in the late stage of wear.

Here, in the tire width direction cross section shown in FIG. 1B, the angle θ formed with respect to the tread surface of the tread 2 of the groove wall 5wi on the inner side in the tire width direction of the circumferential narrow groove 5 may be less than 90 °. I need.
Note that “the angle θ formed with respect to the tread 2 on the tread 2 of the groove wall 5wi on the inner side in the tire width direction of the circumferential narrow groove 5” means that the width direction inner land portion 4ai is on the inner side in the tire width direction of the circumferential narrow groove 5 The angle formed at the open end 5oi of the. Here, when the contour of the groove wall 5wi is a curve, it indicates an angle formed by the tread 2 with respect to the tread 2 of the tangent line of the groove wall 5wi at the opening end 5oi on the inner side in the tire width direction of the circumferential narrow groove 5.

In general, the tread rubber near the groove wall flows by bulging in a direction orthogonal to the direction of the groove wall under load when the tire rolls.
When the angle θ is less than 90 °, the bulge (rubber flow) of the tread rubber in the tire width direction at the time of load is smaller than when θ is 90 °. Therefore, the amount of bulging of the tread rubber in the tire circumferential direction is increased by the amount that does not bulge in the tire width direction. Therefore, the driving force in the tire circumferential direction can be sufficiently exerted from the initial stage of wear to the end stage of wear, and uneven wear of the pneumatic tire can be further suppressed.
On the other hand, when the angle θ is 90 ° or more, the tread rubber bulges in the tire width direction under load becomes larger than that when θ is 90 ° by a mechanism opposite to the above. Therefore, the amount of bulging in the tire width direction is reduced by the amount of bulging in the tire width direction. For this reason, the driving force in the tire circumferential direction cannot be sufficiently exerted from the beginning of wear to the end of wear, and the effect of suppressing the uneven wear of the pneumatic tire cannot be obtained.

Here, the angle θ is preferably 80 ° or more.
If the angle θ is less than 80 °, the width in the tire width direction of the circumferential narrow groove 5 (the groove width of the circumferential narrow groove 5) increases toward the inner side in the tire radial direction. Therefore, when a foreign substance such as a stone enters the circumferential narrow groove 5, the foreign substance is not easily discharged to the outside. This makes it easier for foreign matter to damage the groove wall 5w and the groove bottom 5b of the circumferential narrow groove 5. Therefore, if the angle θ is 80 ° or more, the occurrence of cracks in the circumferential narrow groove can be suppressed.

  The angle θ is more preferably 85 ° to 90 °. If the angle θ is within this range, the effect of suppressing the occurrence of cracks while suppressing uneven wear of the pneumatic tire can be enhanced.

Here, in the tire width direction cross section shown in FIG. 1 (b), the tire is formed by the groove wall 5wi on the inner side in the tire width direction of the circumferential narrow groove 5 and the innermost end 6wi in the tire width direction of the groove wall 6w of the annular groove 6. When the width direction distance is L2, and the tire width direction width of the circumferential narrow groove 5 is w, it is preferable to satisfy the relationship of 1.0 ≦ L2 / w ≦ 5.0.
The distance L2 refers to a distance in the tire width direction between the opening end 5oi on the inner side in the tire width direction of the circumferential narrow groove 5 and the innermost end 6wi in the tire width direction of the groove wall 6w of the annular groove 6.

  When L2 / w ≧ 1.0, the contact pressure applied to the widthwise inner land portion 4ai can be reduced, and uneven wear of the pneumatic tire can be further suppressed. If L2 / w ≦ 5.0, the occurrence of tears and cracks in the inner part of the annular groove 6 can be effectively prevented.

  More preferably, L2 and w satisfy the relationship of 1.6 ≦ L2 / w ≦ 2.3. When L2 / w is within this range, it is possible to enhance the effect of suppressing a decrease in durability while suppressing uneven wear of the pneumatic tire.

The distance L2 is preferably 3.5 to 6.0 mm.
If L2 is 3.5 mm or more, the driving force in the tire circumferential direction at the end of the widthwise inner land portion 4ai can be increased. If L2 is 6.0 mm or less, it is possible to effectively suppress the occurrence of tears and cracks in the inner part of the annular groove 6.

  The distance L2 is more preferably 4.0 to 5.8 mm. If it is the said range, the effect of preventing generation | occurrence | production of a tear and a crack effectively can be heightened, increasing the driving force of the tire circumferential direction in the edge part of the width direction inner side land part 4ai.

The width w of the circumferential narrow groove 5 is preferably 0.3 to 5.0 mm.
If w is 0.3 mm or more, the effect of suppressing uneven wear can be significantly obtained. If w is 5.0 mm or less, tears and cracks in the groove bottom 5b of the circumferential narrow groove 5 can be obtained. Generation | occurrence | production can be prevented effectively.

  The w is more preferably 1.0 to 2.5 mm. When the w is in this range, the effect of effectively preventing the occurrence of tears and cracks can be enhanced while significantly obtaining the effect of suppressing uneven wear of the pneumatic tire.

Here, when the depth of the circumferential narrow groove 5 is d and the depth of the circumferential main groove 3a (3) on the outermost side in the tire width direction is D, 0.3 ≦ d / D ≦ 1. It is preferable that the relationship 5 is satisfied.
The “depth d of the circumferential narrow groove 5” refers to the intersection of the straight line passing through the tire radial innermost end 5bi of the circumferential narrow groove 5 and parallel to the tire radial direction and the tread surface of the tread 2 as a point Q. The distance between the innermost end 5bi and the point Q is shown. The “depth D of the circumferential main groove 3” refers to the intersection of a straight line passing through the innermost end 3ai in the tire radial direction of the circumferential main groove 3 and parallel to the tire radial direction and the tread 2 tread contour. The distance between the innermost end 3ai and the point R when R is indicated.

  If d / D ≧ 0.3, the effect of suppressing the occurrence of uneven wear of the pneumatic tire by providing the annular groove 6 can be significantly obtained, and if d / D ≦ 1.5, Generation of cracks at the groove bottom 5b of the circumferential narrow groove 5 can be effectively prevented.

  The d / D is more preferably 0.9 ≦ d / D ≦ 1.1. When the above d / D is in this range, it is possible to enhance the effect of effectively preventing the occurrence of cracks while significantly obtaining the effect of suppressing uneven wear of the pneumatic tire.

In the example pneumatic tire shown in FIG. 1 (a), with respect to the tire half, one circumferential main groove 3b on the tire equator, and between the circumferential main groove 3b and the tread ground contact end TG. Although one circumferential main groove 3a is provided, the pneumatic tire of the present invention is not limited to this, and a plurality of circumferential main grooves can be provided for a half of the tire.
In the example pneumatic tire shown in FIG. 1A, a land portion 4b is also defined between the circumferential main groove 3a and the circumferential main groove 3b.

The circumferential main groove 3a on the outermost side in the tire width direction is preferably in the range of 50 to 65% of the tread grounding half width Tv from the tire equator CL.
If it is 50% or more, it is possible to achieve both the balance of uneven wear of the widthwise inner land portion 4ai and the land portion 4b. If it is 65% or less, the shear rigidity in the tire width direction of the width direction inner land portion 4ai can be ensured, and the effect of suppressing the uneven wear of the width direction inner land portion 4ai can be significantly obtained.
The “tread grounding half width Tv” refers to a half value of the tread grounding width. Here, the tread contact width indicates the maximum linear distance in the tire axial direction of the tread surface.

  The circumferential main groove 3a on the outermost side in the tire width direction is more preferably in the range of 53 to 61% of the tread grounding half width Tv from the tire equator CL. If it is set as the said range, the effect which suppresses the uneven wear of the land part 4b can be obtained significantly, ensuring the uneven wear resistance of the width direction outer side land part 4ao.

Further, the circumferential narrow groove 5 is preferably in the range of 90 to 98% of the tread grounding half width Tv from the tire equator CL.
If it is 90% or more, the shear rigidity of the land portion 4a on the outer side in the tire width direction becomes sufficiently small, the wear on the land portion 4a is promoted, and the uneven wear on the land portion 4b on the inner side in the tire width direction is suppressed. Can do. If it is 98% or less, the baldness and chipping of the land portion 4a on the outer side in the tire width direction can be prevented.

  The circumferential narrow groove 5 is more preferably in the range of 92 to 97.5% of the tread grounding half width Tv from the tire equator CL. If it is set as the said range, the baldness and notch | chip of the land part 4b can be prevented, suppressing the partial wear of the land part 4b.

The pneumatic tire of the example of the present invention shown in FIG. 1 has a structure similar to the structure of the illustrated tire half with respect to the tire half (not shown) symmetrically with respect to the tire equatorial plane. In the pneumatic tire, the tire half not shown may not have the same structure as the tire half shown.
In addition, the pneumatic tire of the present invention can be suitably used for a tire having a size of 295 / 60R22.5 to 11R24.5 and a tire having a tread grounding half width Tv of 110 to 123 mm.

  In the pneumatic tire of the example of the present invention shown in FIG. 1, the height in the tire radial direction of the width direction outer land portion 4ao is smaller than that of the width direction inner land portion 4ai. According to this configuration, self-excited wear of the width direction outer land portion 4ao can be promoted, and uneven wear generated in the width direction inner land portion 4a can be suppressed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

In this example, a tire having a tire size of 295 / 75R22.5 was used. As the example tire 1, tires having specifications shown in Table 1 were produced.
The prepared tire was mounted on an applicable rim (8.25) defined in JATMA standard, and a rim assembled tire was manufactured.

Uneven Wear Resistance Test In the drum testing machine, the tire assembled with the rim was run for 100,000 km under conditions of an internal pressure of 690 kPa and a normal load. And the amount of wear at the tire width direction inner end of the width direction inner land portion 4ai before and after traveling, that is, the tire radial depth (A) of the tread rubber lost due to wear, and the width direction inner land portion 4ai. The amount of wear at the outer end in the tire width direction, that is, the average value of the difference (AB) from the tire radial depth (B) of the tread rubber lost due to wear was calculated. The average wear resistance of the pneumatic tire was evaluated from the average value. The evaluation results are shown in Table 1. It shows that the effect which suppresses uneven wear is so high that a value is small.

  As comparative tires 1 to 6 and example tires 2 to 4, tires having specifications shown in Table 1 were produced, and the uneven wear resistance test was performed in the same manner as in example 1.

  By comparing Examples 1 to 4 and Comparative Examples 1 to 6, it can be seen that if θ is less than 90 °, uneven wear can be suppressed not only in the initial stage of wear but also in the end stage of wear.

  According to the pneumatic tire of the present invention, uneven wear can be suppressed not only at the initial stage of wear but also at the end stage of wear.

  DESCRIPTION OF SYMBOLS 1; Pneumatic tire of an example of this invention, 2; Tread, 3 (3a, 3b); Circumferential main groove, 3ai; Tire radial direction innermost end of the circumferential main groove, 4 (4a, 4b); 4ai; widthwise inner land portion, 4ao; widthwise outer land portion, 5; circumferential narrow groove, 5b; groove bottom of circumferential narrow groove, 5bi; tire radial innermost end of circumferential narrow groove, 5w; groove wall of circumferential narrow groove, 5wi; groove wall inside tire width direction of circumferential narrow groove, 5wo; groove wall outside tire width direction of circumferential narrow groove, 5oi; tire width direction of circumferential narrow groove Inner opening end, 5oo; circumferential narrow groove opening end on the outer side in the tire width direction, 6; annular groove, 6w; annular groove groove wall, 6wi; annular groove groove wall innermost end in the tire width direction, C1; 1st circular arc, C2; 2nd circular arc, C3; 3rd circular arc, C4; 4th circular arc, L1; groove of annular groove Tire width direction distance from the innermost end in the tire width direction to the groove wall outside the tire width direction of the circumferential narrow groove, L2: the groove wall inside the tire width direction of the circumferential narrow groove, and the tire of the groove wall of the annular groove R1; radius of curvature of the first arc, R2: radius of curvature of the second arc, R3: radius of curvature of the third arc, R4: radius of curvature of the fourth arc, O1; Center of curvature of the first arc, O2: Center of curvature of the second arc, O3: Center of curvature of the third arc, O4: Center of curvature of the fourth arc, d: Depth of circumferential narrow groove, w: Circumferential narrow groove D: Depth of circumferential main groove, TG: Tread ground contact end, θ: Angle formed with respect to tread of tread of groove wall inside tire width direction of circumferential narrow groove

Claims (2)

A circumferential main groove continuously extending in the tire circumferential direction provided on the tread surface and a land portion defined between the tread grounding end and a circumferential narrow groove extending continuously in the tire circumferential direction are provided,
In the cross section in the tire width direction, on the groove wall on the inner side in the tire width direction of the circumferential narrow groove from the opening end on the inner side in the tire width direction of the circumferential narrow groove to the innermost end in the tire radial direction of the circumferential narrow groove, An annular groove extending continuously in the tire circumferential direction is provided,
In the cross section in the tire width direction, the contour of the circumferential narrow groove is such that the center of curvature is between the opening end on the inner side in the tire width direction of the circumferential narrow groove and the innermost end in the tire width direction of the annular groove. A first arc having a radius of curvature R1 of 1.0 to 12.0 mm on the side and a second arc having a radius of curvature R2 of 1.5 to 4.0 mm with the center of curvature being on the circumferential narrow groove side. Between the innermost end in the tire width direction of the groove wall of the annular groove and the innermost end in the tire radial direction of the circumferential narrow groove, and the center of curvature is on the circumferential narrow groove side. A third arc having a radius of curvature R3 of 0.0 mm, and the center of curvature is between the innermost end in the tire radial direction of the circumferential narrow groove and the opening end on the outer side in the tire width direction of the circumferential narrow groove. Air having a fourth arc on the side of the circumferential narrow groove and having a radius of curvature R4 of 2.0 to 16.0 mm Ri is a tire,
In the tire width direction cross section, the distance in the tire width direction from the innermost end in the tire width direction of the groove wall of the annular groove to the groove wall on the outer side in the tire width direction of the circumferential narrow groove is 5.7 to 6.5 mm ,
A pneumatic tire characterized in that an angle θ formed with respect to a tread surface of a groove wall on the inner side in the tire width direction of the circumferential narrow groove is less than 90 ° in a cross section in the tire width direction.   The pneumatic tire according to claim 1, wherein the angle θ is 80 ° or more.

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