JP2020090122A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire configured so that a difference in abrasion between two kinds of blocks forming a block row at a ground-contact end side is reduced.SOLUTION: In a pneumatic tire in which a zigzag main groove 10 extending zigzag in a tire circumferential direction is formed and two kinds of blocks 20 and 21 are arranged alternately in the tire circumferential direction between the zigzag main groove 10 and a ground-contact end E, a contour of a tread surface in a cross section in a tire width direction is formed of a plurality of circular arcs, at least one of connection points in the adjacent circular arcs is a concave connection point P forming a concave part in the tread surface, and the concave connection point is at the position of the zigzag main groove 10, where a curvature radius R1 of the circular arc C1 at the ground-contact end side of the zigzag main groove 10 is larger than a curvature radius R2 of the circular arc C2 at a tire equator side of the zigzag main groove 10.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pneumatic tire.

For example, as described in Patent Document 1, when the tread portion of the pneumatic tire is viewed in a cross section in the width direction, the tread surface is formed by a plurality of arcs. Usually, the radius of curvature of the circular arc near the equator of the tire is large, and the radius of curvature of the circular arc becomes smaller toward the outer side in the tire width direction.

JP 6-297913 A

By the way, between the main groove extending in the tire circumferential direction and the ground contact end (the tire width direction end of the ground contact region of the tread portion), two types of blocks are alternately arranged in the tire circumferential direction to form a block row. There are tires. In such a pneumatic tire, since the two types of blocks have different shapes and sizes, there is a problem that only one block is easily worn. In particular, when the main groove adjacent to the block row has a zigzag shape, the block has many corners and the edge of the block becomes long, so that the block is easily worn, and only one of the two types of blocks is worn. The problem of being easy was prominent.

Therefore, it is an object of the present invention to provide a pneumatic tire having a small difference in wear between two types of blocks forming a block row on the ground contact end side.

The pneumatic tire of the embodiment has a zigzag main groove extending in a zigzag shape in the tire circumferential direction, and two types of blocks are alternately arranged in the tire circumferential direction between the zigzag main groove and the ground contact end. In, the contour of the tread tread in the tire width direction cross section is composed of a plurality of arcs, at least one of the connecting points of adjacent arcs is a concave connecting point forming a recess in the tread tread, and the concave connecting point is the zigzag. The radius of curvature of the arc on the ground contact end side of the zigzag main groove is larger than the radius of curvature of the arc on the tire equator side of the zigzag main groove.

According to the pneumatic tire of the embodiment, the radius of curvature of the arc on the grounding end side of the zigzag main groove is large, and furthermore, since the concave connecting points that connect the arcs on both sides of the zigzag main groove are located in the zigzag main groove, The ground contact area between the zigzag main groove and the ground contact end is widened to reduce the ground contact pressure, and the wear amount and the wear difference between the two types of blocks between the zigzag main groove and the ground contact end are reduced.

The tread pattern of the embodiment. In this figure, the vertical direction is the tire circumferential direction and the horizontal direction is the tire width direction. Sectional drawing of the tire width direction left side of the tread part which has the tread pattern of FIG. In this figure, the shape is exaggerated for the sake of explanation. FIG. 6 is a cross-sectional view in the width direction of the zigzag main groove when the concave connection point of the arc and the arc is located at the center position in the width direction of the zigzag main groove.

The structure of the pneumatic tire of the embodiment will be described with reference to the drawings. In the following description regarding the shape of the pneumatic tire, the shape of the pneumatic tire when mounted on the regular rim and filled with the regular internal pressure is described. Here, the regular rim is a “standard rim” in the JATMA standard, a “DesignRim” in the TRA standard, or a “MeasuringRim” in the ETRTO standard. Further, the normal internal pressure is the maximum value of "maximum air pressure" in the JATMA standard, the maximum value of "TIRELOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or "INFLATION PRESSURE" in the ETRTO standard.

Further, grounding in the following description means grounding in a state where a pneumatic tire mounted on a regular rim and filled with a regular internal pressure is in contact with a road surface and a regular load is applied thereto. Here, the normal load is the "maximum load capacity" in the JATMA standard, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or "LOAD CAPACITY" in the ETRTO standard.

The rough cross-sectional structure of the pneumatic tire of this embodiment is as follows. First, bead portions are provided on both sides in the tire width direction, and a carcass ply is folded back from the tire width direction inner side to the outer side to wrap the bead portion and form a skeleton of a pneumatic tire. A plurality of belts are provided on the tire radial direction outer side of the carcass ply, and a tread portion having a grounding region is provided on the tire radial direction outer side of the belt. Further, sidewalls are provided on both sides of the carcass ply in the tire width direction. In addition to these members, a plurality of members are provided according to the functional needs of the tire.

A tread pattern as shown in FIG. 1 is formed on the tread portion. This tread pattern is asymmetric with respect to the tire equator EL.

A plurality of main grooves are formed in the tread portion. The main groove is a thick groove extending in the tire circumferential direction, and not only a straight shape but also a zigzag shape is included in the main groove. In the present embodiment, a zigzag main groove 10 extending in the tire circumferential direction is formed on the left side of the tire equator EL. Two straight main grooves 12 and 13 extending in the tire circumferential direction are formed on the right side of the tire equator EL.

First blocks 20 and second blocks 21 are alternately arranged in the tire circumferential direction between the left ground contact end E (the tire width direction end of the ground contact region of the tread portion) and the zigzag main groove 10. The first block 20 and the second block 21 are separated by the first lateral groove 16. The first block 20 and the second block 21 have different shapes. The first block 20 has the first inclined groove 14 formed therein, whereas the second block 21 has no such inclined groove formed. Therefore, the first block 20 has lower rigidity than the second block 21. The first inclined groove 14 extends obliquely with respect to the tire circumferential direction. The left end of the first inclined groove 14 is closed in the first block 20, and the right end of the first inclined groove 14 is open to the zigzag main groove 10.

A first rib 22 as a land portion is formed between the zigzag main groove 10 and the left straight main groove 12. A plurality of second inclined grooves 15 are formed in the first rib 22. The second inclined groove 15 extends while inclining with respect to the tire circumferential direction. The left end of the second inclined groove 15 is open to the zigzag main groove 10, and the right end of the second inclined groove 15 is closed in the first rib 22. The second inclined groove 15 is gradually thickened toward the opening end to the zigzag main groove 10.

The first inclined groove 14 is on an extension of the second inclined groove 15, and the first inclined groove 14 and the second inclined groove 15 form one inclined groove.

A second rib 23 as a land portion is formed between the left straight main groove 12 and the right straight main groove 13. The second rib 23 is formed with a second lateral groove 17 whose left end is closed inside the second rib 23 and whose right end is open to the right straight main groove 13.

A third rib 24 as a land portion is formed between the right straight main groove 13 and the ground contact end E. The third rib 24 is formed with a third lateral groove 18 whose left end is closed inside the third rib 24 and whose right end is open to the ground end E.

In such a tread pattern, the groove area ratio on the left side in the tire width direction (that is, the left side from the tire equator EL) is higher than the groove area ratio on the right side in the tire width direction (that is, the right side from the tire equator EL). Here, the groove area ratio refers to the area of the grounding area including the groove (in other words, the total of the area of the land portion, that is, the area of the block or the like to be grounded and the area of the groove portion) in the grounding area. It is the ratio of the area of the groove portion.

However, the tread pattern of FIG. 1 is merely an example. The number of main grooves, the presence or absence of lateral grooves, the inclination angle of each groove with respect to the tire circumferential direction, and the like are not limited to those shown in FIG.

As shown in FIG. 2, the contour of the tread tread in the tire width direction cross section includes a plurality of arcs C1 to C4. Usually, the radius of curvature of the arc near the equator of the tire is large, and the radius of curvature is smaller toward the outer side of the tire width direction, that is, the arc near the ground contact end. However, in the present embodiment, there is an arc C1 on the ground contact end E side and an arc C2 on the tire equator EL side across the zigzag main groove 10, and the radius of curvature R1 of the arc C1 on the ground contact end E side of the zigzag main groove 10 is , Larger than the radius of curvature R2 of the arc C2 of the zigzag main groove 10 on the tire equator EL side. That is, the magnitude relationship of the curvature radii of the arcs on both sides of the zigzag main groove 10 is opposite to that of a normal pneumatic tire.

In the case where the contour of the tread surface comprises a plurality of arcs in the range from the zigzag main groove 10 to the tire equator EL, for example, the radius of curvature of the arc near the tire equator EL is large, and the arc closer to the zigzag main groove 10 has a larger curvature. The radius is small. That is, as shown in FIG. 2, in the range from the zigzag main groove 10 to the tire equator EL, the contour of the tread surface comprises an arc C2 having a radius of curvature R2, an arc C3 having a radius of curvature R3, and an arc C4 having a radius of curvature R4. , Arc C3, arc C4 in the order of zigzag main groove 10, the relationship of R2<R3<R4 holds, for example.

Adjacent arcs of the tread tread contour are connected at connection points. There are a plurality of such connecting points. The adjacent arcs may be directly connected to each other or may be connected via a small rounded portion. When adjacent arcs are connected to each other via a small rounded portion, the central point in the length direction along the rounded portion is set as the connecting point.

Then, some or all of the plurality of connecting points are concave connecting points forming a recess on the tread surface. In the present embodiment, at least the connecting point of the arcs C1 and C2 is the concave connecting point P. On the other hand, at the connection point between the arcs C2 and C3 and the connection point between the arcs C3 and C4, for example, as shown in FIG. 2, the contour of the tread surface is smoothly connected without forming a recess.

In the present embodiment, the concave connecting point P between the circular arc C1 and the circular arc C2 exists at the position of the zigzag main groove 10. In other words, the respective extension lines of the arc C1 appearing in the first block 20 and the second block 21 and the arc C2 appearing in the first rib 22 intersect at the position of the zigzag main groove 10.

As a preferable form, a concave connecting point P between the circular arc C1 and the circular arc C2 passes through the apex T1 (see FIG. 1) of the protrusion of the first rib 22 into the zigzag main groove 10 and extends in the tire circumferential direction (see FIG. 1). 1)) or a straight line L2 (see FIG. 1) that extends in the tire circumferential direction through the apex T2 (see FIG. 1) of the protrusion of the first block 20 and the second block 21 into the zigzag main groove 10. In particular, it is preferable that the concave connecting point P between the circular arc C1 and the circular arc C2 be located at the position of the straight line L2 near the ground contact end E.

In addition, the apex T1 of the protrusion of the first rib 22 to the zigzag main groove 10 is the end portion of the first rib 22 on the ground contact end E side in other words. In addition, in other words, the apex T2 of the protrusion of the first block 20 and the second block 21 into the zigzag main groove 10 is the end portion of the first block 20 and the second block 21 on the tire equator EL side. is there.

By the way, when the concave connecting point P between the circular arc C1 and the circular arc C2 is not located at the position of the straight line L1 or the straight line L2, for example, when the pneumatic tire is manufactured so as to be at the center position in the width direction of the zigzag main groove 10, As shown in FIG. 3, there is a possibility that a concave portion 19 similar to the shape in the vicinity of the concave connection point P of the circular arc C1 and the circular arc C2 is formed at the groove bottom of the zigzag main groove 10. Then, the dread rubber may become thin at the position of the recess 19.

The above configuration has the following operational effects. As described above, the first block 20 and the second block 21 having different shapes are alternately arranged between the zigzag main groove 10 and the ground contact end E in the tire circumferential direction. Will wear out. However, in the present embodiment, the radius of curvature R1 of the arc C1 on the ground contact end E side of the zigzag main groove 10 (that is, the arc of the contour of the tread surface of the block row) is the curvature radius of the arc C2 of the zigzag main groove 10 on the tire equator EL side. Greater than radius R2. Therefore, the ground contact area of the first block 20 and the second block 21 forming the block row is expanded, and the ground pressure is reduced. As a result, the amount of wear of the first block 20 and the second block 21 decreases, and the difference in wear of the first block 20 and the second block 21 decreases.

Here, although not shown, in the case where the connecting point connecting the circular arcs in the contour of the tread surface is a concave connecting point forming a concave portion, and the concave connecting point is on a land portion such as a block or a rib. In this case, the contact area may be reduced near the concave connection point and the contact pressure may increase. However, in the present embodiment, as shown in FIG. 2, since the concave connecting point P between the circular arc C1 and the circular arc C2 is at the position of the zigzag main groove 10, the concave connecting point P has an influence on the width of the ground contact area. small. Therefore, despite the existence of the concave connecting point P, the ground contact area of the first block 20 and the second block 21 is not narrowed, and it is possible to prevent the ground pressure from increasing. The wear of the second block 21 can be suppressed.

Further, the concave connecting point P between the circular arc C1 and the circular arc C2 is defined by the straight lines L1 and L2 passing through the apexes T1 and T2 of the protrusions of the land portions 20, 21 and 22 on both sides of the zigzag main groove 10 into the zigzag main groove 10. If it is in the position, it is possible to prevent the tread rubber from becoming thin at the groove bottom of the zigzag main groove 10 as shown in FIG.

The above embodiment is an example, and the scope of the invention is not limited to this. Various modifications, substitutions, omissions, etc. can be made to the above embodiments without departing from the spirit of the invention.

C1, C2, C3, C4... Arc, E... Ground contact end, EL... Tire equator, P... Concave connecting point, 10... Zigzag main groove, 12, 13... Straight main groove, 14... First inclined groove, 15... Second inclined groove, 16... First lateral groove, 17... Second lateral groove, 18... Third lateral groove, 19... Recessed portion, 20... First block, 21... Second block, 22... First rib, 23... Second rib , 24... Third rib

Claims (2)

In a pneumatic tire in which a zigzag main groove extending in a zigzag shape in the tire circumferential direction is formed, and two types of blocks are alternately arranged in the tire circumferential direction between the zigzag main groove and the ground contact end,
The contour of the tread surface in the tire width direction cross section is composed of a plurality of arcs, and at least one of connection points of adjacent arcs is a concave connection point forming a recess on the tread surface, and the concave connection point is the zigzag main groove. In the position of
A pneumatic tire in which the radius of curvature of the arc on the ground contact end side of the zigzag main groove is larger than the radius of curvature of the arc on the tire equator side of the zigzag main groove. The concave connection point at the position of the zigzag main groove is at a straight line position extending in the tire circumferential direction through the apex of the protrusion of the land portion on both sides of the zigzag main groove to the zigzag main groove. The pneumatic tire according to 1.