PNEUMATIC TIRE

A tread portion has a pin hole with a stud pin being mounted. In the periphery of the pin hole a recess is formed that gradually deepens as the recess extends toward radially outside and that has a depth of 10% or less of the depth of the pin hole.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority based on Japanese Patent Application No. 2017-215877 filed on Nov. 8, 2017, the contents of which are incorporated herein by this reference.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to a pneumatic tire.

Related Art

Conventionally, a pneumatic tire has been known in which a plurality of recessed parts extending in the outer diameter direction are formed in the periphery of each pin hole with a stud pin being mounted (for example, see Japanese Patent No. 5452588).

However, in the conventional pneumatic tire, a recessed part having substantially the same depth as the pin hole is arranged near the pin, and the holding strength of the pin hole with respect to the stud pin is not sufficient.

SUMMARY

An object of the present invention is to provide a pneumatic tire capable of ensuring an anti-detachment property of a stud pin and improving ice performance.

The present invention provides, as a means for solving the above problem, a pneumatic tire including a tread portion having a pin hole with a stud pin being mounted, in which in a periphery of the pin hole a recess is formed that gradually deepens as the recess extends toward radially outside and that has a depth of 10% or less of a depth of the pin hole.

With this configuration, the recess formed in the periphery of the pin hole does not adversely affect the holding strength of the pin hole with respect to the stud pin. Moreover, an edge formed by the recess acts so as to bite into an ice and snow surface. Accordingly, excellent ice performance is exerted by the stud pin firmly held and an edge effect of the recess.

It is preferable that the recess is one of a plurality of recesses.

With this configuration, the number of edges formed by the recesses increases, and further excellent ice performance can be exerted.

It is preferable that the recesses are arranged evenly in a circumferential direction around the pin hole.

With this configuration, an edge effect can be obtained in any direction around the stud pin, thus exhibiting excellent ice performance not only, for example, during straight running but also during turning.

It is preferable that the recesses increase in width from a center of the pin hole toward radially outside.

With this configuration, an edge length can be increased on an outer diameter side of the pin hole, where a holding state of the stud pin is hardly affected. This makes it possible to exert further excellent ice performance.

According to the present invention, in the periphery of a pin hole a recess is formed that gradually deepens as the recess extends toward radially outside and that has a depth of 109 or less of a depth of the pin hole, so that it is possible to improve ice performance while maintaining a good holding state of the pin hole with respect to the stud pin.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described bel with reference to the accompanying drawings. It should be noted that the following description is merely exemplary in nature and is not intended to limit the invention, its applicable objects, and its applications.

FIG. 1is a partial development view of a tread portion1of a pneumatic tire according to the present embodiment. A center rib2is formed at the center in the tire width direction of the tread portion1. On both sides of the center rib2in the tire width direction, inclined blocks4defined by inclined grooves3extend. As a result, the inclined blocks4are arranged at predetermined intervals in the tire circumferential direction.

The inclined groove3includes a wide first inclined groove3A and a narrow second inclined groove3B. Portions of both side edges of the first inclined groove3A are formed in a zigzag shape.

Longitudinal grooves communicating substantially orthogonally with the first inclined groove3A and the second inclined groove3B on both sides midway in the inclined blocks4are formed. The longitudinal grooves5are alternately displaced between the inclined blocks4arranged in the tire circumferential direction on the center side and the lateral sides in the tire width direction. As a result, the inclined block4is separated into a center block6and a shoulder block7. The center block6includes a short first center block6aand a long second center block6b. The shoulder block7includes a long first shoulder block7afollowing the first center block6aand a short second shoulder block7bfollowing the second center block6b.

In the center rib2and the center block6following the center rib2, first sipes8are formed radially around the center rib2side. Two or three second sipes9are formed in the shoulder block7along the longitudinal direction of the shoulder block. The sipes8and9each have a waveform. One end of the first sipe8communicates with the inclined groove3, and the other end of the first sipe8terminates in the center rib2or the center block6. One end of the second sipe9communicates with the longitudinal groove5, and the other end of the second sipe9terminates in the shoulder block7. However, a pin region10is formed in each of the blocks6and7as described later, and the sipes8and9are not formed in this pin region10.

The pin regions10are formed in the center rib2, the center blocks6and the shoulder blocks7. The pin regions10are respectively formed on the center rib2, the end portion of the first center block6awhich is located on the tire width direction side, the center portion of the second center block6b, the end portion of the second center block6bwhich is located on the tire width direction side, the center side of the first shoulder block7a, and the center portion of the second shoulder block7b. This is because when the tread portion1is divided into the center region along the center rib2, the mediate regions on both sides of the center region, and the shoulder region on the outer side in the tire width direction, the number of pin regions10is substantially even in each region. Further, the pin regions10are arranged so as to be substantially even in the tire circumferential direction.

As shown inFIG. 2, a pin hole11is formed in the center portion of each pin region10, and a stud pin12is mounted in the pin hole. Three recesses13are formed at equal angular intervals in the periphery of each pin hole11. Each of the recesses13extends so as to gradually increase in width toward radially outside around the pin hole11. An inner edge13aof the recess13is formed concentrically with the pin hole11, and both side edges include an inner arcuated edge13bwhich increases the width of the recess13with a radius R1, and a linear outer edge13cextending further radially outside. The outer edge of the recess13includes an outer arcuated edge13dwith a radius R2, an inner edge13eextending parallel to both side edges from the outer arcuated edge13d, and an outermost edge13flocated outermost in radial direction. The bottom surface of the recess13includes an inclined surface13ggradually deepens from the inner edge to the concentric circle contacting the outer arcuated edge13don radially outside and a flat surface13hsurrounded by the outer edge13c, the inner edge13e, and the outermost edge13fand having the same depth. The depth of the deepest flat surface of the recess13is set to 10% or less this case, 0.8 mm) of the depth of the pin hole11. Note that a region where the inclined surface13gis formed gives a fan-shaped portion13A of the recess13and a region where the flat surface13his formed gives a branch portion13B of the recess13.

The pneumatic tire with the pin regions10each having the above configuration has the following advantages.

(1) The recess13formed in the periphery of the stud pin12is 10% or less of the depth of the pin hole11, so that even if the ground contact pressure acts, the holding strength of the pin hole11with respect to the stud pin12is not reduced. In particular, since the recess13is formed so as to gradually decrease in depth toward the center of the pin hole11, the holding strength of the pin hole11can be further increased.

(2) The recess13increases in width toward radially outside with respect to the center of the pin hole11and the distal end portion of the recess13is bifurcated, so that the length of the edge to be formed can be increased. Therefore, a scratching effect (edge effect) is obtained When the tire contacts the ice and snow surface.

Note that the present invention is not limited to the configuration described in the above embodiment, and various modifications can be made.

In the above embodiment, the number of recesses13for one pin region10is three, but the number is not limited to this and can be set to one, two, or four or more.

In the above embodiment, the recess13has two branch portions13B, but the branch portion13B may be three or more.