JP7140659B2 - pneumatic tire - Google Patents

Description

The present invention relates to pneumatic tires.

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

JP-A-6-297913

By the way, a pneumatic pneumatic tire in which two types of blocks are alternately arranged in the tire circumferential direction to form a row of blocks between a main groove extending in the tire circumferential direction and a ground contact end (a tire width direction end of a ground contact area of a tread portion). Tires are present. In such a pneumatic tire, since the shapes and sizes of the two types of blocks are different, there is a problem that only one of the blocks is easily worn. In particular, when the main grooves adjacent to the row of blocks are zigzag-shaped, the blocks have many corners and the edges of the blocks are long, so that the blocks are easily worn, and only one of the two types of blocks is worn. There was a notable problem of ease.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire in which the wear difference between two types of blocks forming a row of blocks on the ground contact side is small.

A pneumatic tire according to an embodiment is 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 edge. wherein the contour of the tread surface in the cross section in the tire width direction is composed of a plurality of arcs, at least one of the connection points of adjacent arcs is a concave connection point forming a recess in the tread surface, and the concave connection point is the zigzag It is located at the position of the main groove, and the radius of curvature of the arc of the zigzag main groove on the ground contact edge side is larger than the curvature radius of the arc of the zigzag main groove on the tire equator side.

According to the pneumatic tire of the embodiment, the radius of curvature of the arc on the side of the ground contact of the zigzag main groove is large, and the concave connecting point connecting the arcs on both sides of the zigzag main groove is located at the zigzag main groove. The contact area between the zigzag main groove and the contact edge is widened, the contact pressure is lowered, and the wear amount and the wear difference between the two types of blocks between the zigzag main groove and the contact edge are reduced.

Embodiment tread pattern. 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 a tread pattern of FIG. In this figure, the shape is exaggerated for explanation. FIG. 4 is a cross-sectional view in the width direction of the zigzag main groove when the concave connecting point between the arcs 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 based on the drawings. The description regarding the shape of the pneumatic tire in the following description describes the shape of the pneumatic tire when mounted on a normal rim and filled with a normal internal pressure. Here, the regular rim means "standard rim" in the JATMA standard, "DesignRim" in the TRA standard, or "MeasuringRim" in the ETRTO standard. The normal internal pressure is the maximum air pressure in JATMA standards, the maximum value of "TIRELOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA standards, or "INFLATION PRESSURE" in ETRTO standards.

In the following description, the term "grounding" refers to a state in which a pneumatic tire mounted on a regular rim and inflated to a regular internal pressure touches the 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 "TIRELOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or "LOAD CAPACITY" in the ETRTO standard.

A 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 carcass plies are folded back from the inner side to the outer side in the tire width direction to wrap the bead portions and form the skeleton of the pneumatic tire. A plurality of belts are provided outside the carcass ply in the tire radial direction, and a tread portion having a contact area is provided outside the belts in the tire radial direction. 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 includes not only straight grooves but also zigzag grooves. In this 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 edge E (the edge in the tire width direction of the ground-contact area 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 grooves 16 . The first block 20 and the second block 21 have different shapes. The first block 20 has the first inclined groove 14, whereas the second block 21 does not have such an inclined groove. 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 inside the first block 20 , and the right end of the first inclined groove 14 opens into 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 obliquely with respect to the tire circumferential direction. The left end of the second inclined groove 15 opens into the zigzag main groove 10 , and the right end of the second inclined groove 15 is closed inside the first rib 22 . The second inclined groove 15 gradually becomes thicker toward the opening end to the zigzag main groove 10 .

The first inclined groove 14 is on the extension line 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 straight main groove 13 on the right side and the grounding end E. As shown in FIG. 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 grounding end E. As shown in FIG.

In such a tread pattern, the groove area ratio on the left side in the tire width direction (that is, on the left side of the tire equator EL) is higher than that on the right side in the tire width direction (that is, on the right side of the tire equator EL). Here, the groove area ratio is the area of the ground contact area including the groove (in other words, the sum of the area of the land part, such as the block, and the area of the groove) in the ground contact area. It is the ratio of the area of the groove portion.

However, the tread pattern of FIG. 1 is only 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 surface in the cross section in the tire width direction consists of a plurality of arcs C1 to C4. Normally, the radius of curvature of the arc near the tire equator is large, and the radius of curvature of the arc becomes smaller toward the outside in the tire width direction, that is, toward the ground contact edge. However, in this embodiment, with the zigzag main groove 10 interposed therebetween, the arc C1 is on the ground contact edge E side, and the arc C2 is on the tire equator EL side. , the radius of curvature R2 of the arc C2 of the zigzag main groove 10 on the side of the tire equator EL. That is, on both sides of the zigzag main groove 10, the magnitude relationship of the radius of curvature of the arc is opposite to that of a normal pneumatic tire.

In the case where the contour of the tread surface consists of 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 larger, and the arc closer to the zigzag main groove 10 has a higher curvature. Small radius. 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 consists of an arc C2 with a radius of curvature R2, an arc C3 with a radius of curvature R3, and an arc C4 with a radius of curvature R4. , arc C3, and arc C4 are closest to the zigzag main groove 10, for example, the relationship of R2<R3<R4 is established.

Adjacent arcs of the tread footprint profile are connected at connection points. There are multiple such connection points. Adjacent circular arcs may be directly connected, or may be connected via a small rounded portion. When adjacent circular arcs are connected via a small radius portion, the longitudinal center point along the radius is taken as the connecting point.

Some or all of the plurality of connecting points are concave connecting points that form recesses in the tread surface. In this embodiment, at least the connection point between the arc C1 and the arc C2 is the concave connection point P. As shown in FIG. On the other hand, at the connection point between the arc C2 and the arc C3 and the connection point between the arc C3 and the arc C4, the contour of the tread surface is smoothly connected without forming a concave portion, as shown in FIG. 2, for example.

In this embodiment, the concave connecting point P between the arc C1 and the arc C2 is located at the zigzag main groove 10. As shown in FIG. In other words, extension lines of the arc C<b>1 appearing in the first block 20 and the second block 21 and the arc C<b>2 appearing in the first rib 22 intersect at the position of the zigzag main groove 10 .

As a preferred form, the concave connection point P between the arc C1 and the arc C2 is a straight line L1 (see FIG. 1) extending in the tire circumferential direction through the apex T1 (see FIG. 1) of the projection of the first rib 22 into the zigzag main groove 10. 1), or on a straight line L2 (see FIG. 1) extending in the tire circumferential direction through the apex T2 (see FIG. 1) of the projection of the first block 20 and the second block 21 into the zigzag main groove 10. In particular, it is preferable that the concave connection point P between the arc C1 and the arc C2 is located on the straight line L2 near the ground edge E.

In other words, the apex T1 of the projection of the first rib 22 into the zigzag main groove 10 is the edge of the first rib 22 on the side of the contact edge E. As shown in FIG. 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 of the first block 20 and the second block 21 on the tire equator EL side. be.

Incidentally, if the pneumatic tire is manufactured so that the concave connection point P between the arc C1 and the arc C2 is not located on the straight line L1 or the straight line L2, but is located, for example, in the center of the zigzag main groove 10 in the width direction, As shown in FIG. 3, there is a possibility that a recessed portion 19 similar in shape to the vicinity of the recessed connecting point P between the arcs C1 and C2 is formed in 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 effects. As described above, the first blocks 20 and the second blocks 21 having different shapes are alternately arranged in the tire circumferential direction between the zigzag main groove 10 and the ground contact edge E. wear out. However, in the present embodiment, the curvature radius R1 of the arc (that is, the arc of the contour of the tread surface of the block row) C1 on the ground contact edge E side of the zigzag main groove 10 is the curvature radius of the arc C2 on the tire equator EL side of the zigzag main groove 10. greater than radius R2. Therefore, the contact areas of the first blocks 20 and the second blocks 21 forming the block row are widened, and the contact pressure is lowered. As a result, the wear amount of the first block 20 and the second block 21 is reduced, and the wear difference between the first block 20 and the second block 21 is reduced.

Here, although not shown, the connection point connecting the arcs in the contour of the tread surface is a concave connection point that forms a recess, and the concave connection point is on a land portion such as a block or rib. In this case, there is a risk that the ground contact area will be narrowed near the concave connecting point and the contact pressure will increase. However, in this embodiment, as shown in FIG. 2, the concave connection point P between the arcs C1 and C2 is located at the zigzag main groove 10, so the influence of the concave connection point P on the width of the contact area is small. small. Therefore, despite the presence of the concave connection point P, the contact area of the first block 20 and the second block 21 does not decrease, and the contact pressure can be prevented from increasing. Wear of the second block 21 can be suppressed.

Further, the concave connecting point P between the arc C1 and the arc C2 is the straight line L1, L2 passing through the apexes T1, T2 of the protrusions of the land portions 20, 21, 22 on both sides of the zigzag main groove 10 into the zigzag main groove 10. If it is in this 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 embodiments are examples, and the scope of the invention is not limited thereto. Various modifications, substitutions, omissions, and the like can be made to the above embodiments without departing from the scope of the invention.

C1, C2, C3, C4... circular arc, E... ground contact edge, EL... tire equator, P... concave connection 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 Recess 20 First block 21 Second block 22 First rib 23 Second rib , 24... third rib

Claims (2)

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 a ground contact edge,
The contour of the tread surface in the cross section in the tire width direction is composed of a plurality of arcs, at least one of the connection points of the adjacent arcs is a concave connection point forming a recess in the tread surface, and the concave connection point is the zigzag main groove. is located at
A pneumatic tire, wherein the radius of curvature of the arc of the zigzag main groove on the side of the ground contact is greater than the radius of curvature of the arc of the zigzag main groove on the side of the tire equator. 3. The concave connection point at the position of the zigzag main groove is at the position of a straight line extending in the tire circumferential direction through the apexes of protrusions of the land portions on both sides of the zigzag main groove into the zigzag main groove. 1. The pneumatic tire according to 1.

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