JP7081998B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

Conventionally, a sipe has been formed on the land portion of a tread of a pneumatic tire for the purpose of improving control drive performance. However, when the extension-direction end of the sipe is blocked in the land, stress is concentrated on the extension-direction end of the sipe, so that cracks are likely to occur starting from that end.

Therefore, as described in Patent Document 1, it has been proposed to form a branch sipe, which is a form in which the sipe is branched into two or more in a plan view, at the end in the extension direction of the sipe. This branch sipe disperses the stress applied to the end in the extension direction of the sipe, and is effective in preventing the occurrence of cracks.

Japanese Unexamined Patent Publication No. 2006-341688

However, there is a problem that the rigidity of the land portion of the tread becomes low as a result of the formation of the branch sipe at the end in the extension direction of the sipe. The low rigidity of the land part of the tread causes wear of the land part and the like.

Therefore, it is an object of the present invention to provide a pneumatic tire in which cracks are less likely to occur starting from the end in the extension direction of the sipe and the rigidity of the land portion of the tread is not so low.

In the pneumatic tire of the embodiment, a sipe is formed on the land portion of the tread, and at least one of the extending directions of the sipe is a closed portion that is closed in the land portion, and the sipe is a main sipe and the main sipe. In a pneumatic tire consisting of two auxiliary sipes that branch off from the end on the closed portion side, the auxiliary sipes are connected to the main sipes from the end to the bottom and gradually gradually toward the depth direction. It is characterized in that the end of the auxiliary sipe opposite to the main sipe is warped toward the inside of the auxiliary sipe .

In the pneumatic tire of the embodiment, since the two auxiliary sipes are branched from the end portion of the main sipes and the land portion is deformed, the stress is not concentrated on the end portion of the main sipes but is distributed to the auxiliary sipes. And cracks are less likely to occur. Also, since the auxiliary sipe gradually shortens toward the depth, the rigidity of the land area does not decrease so much.

The tread pattern of the embodiment. Top view of the block of the embodiment. Sectional drawing of the sipe of embodiment in the depth direction and the extension direction. FIG. 2 is a cross-sectional view taken along the line AA in FIG. Cross-sectional view of the modified example sipes in the depth and extension directions. FIG. 2 is a cross-sectional view at a position corresponding to AA in FIG. Cross-sectional view of the modified example sipes in the depth and extension directions. FIG. 2 is a cross-sectional view at a position corresponding to AA in FIG. Cross-sectional view of the modified example sipes in the depth and extension directions. FIG. 2 is a cross-sectional view at a position corresponding to AA in FIG. Cross-sectional view of the modified example sipes in the depth and extension directions. FIG. 2 is a cross-sectional view at a position corresponding to AA in FIG. Cross-sectional view of the three-dimensional auxiliary sipe of the modified example in the depth direction and the extension direction. The figure which looked at the 3D auxiliary sipe of the modification example from the extension direction of the main sipe. The figure seen from the arrow C direction of FIG. Top view of the modified sipes. (A) is a modified example in which two auxiliary sipes form a U shape. (B) is a modified example in which two auxiliary sipes form a C shape.

The structure of the pneumatic tire of the embodiment will be described with reference to the drawings. Unless otherwise stated, new pneumatic tires that are not worn will be described below. Further, in the following description, the plan view means that the tread is viewed from the outside in the radial direction of the tire.

The pneumatic tire of the present embodiment assumes, for example, a heavy-duty tire mounted on a truck, a bus, or the like. Further, the pneumatic tire of the present embodiment assumes, for example, a studless tire mounted when traveling on an ice road surface.

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 the carcass ply is folded back from the inside to the outside in the tire width direction to wrap the bead portion and form a skeleton of a pneumatic tire. A plurality of belts are provided on the outer side of the carcass ply in the tire radial direction, and a tread having a ground contact surface is provided on the outer side of the belt in the tire radial direction. In addition, 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 as required for the function of the tire.

A tread pattern as shown in FIG. 1 is formed on the tread. In this exemplified tread pattern, four main grooves 10 extending in the tire circumferential direction are formed. The depth of the main groove 10 is not limited, but is, for example, 17 mm or more and 22 mm or less. Then, as the region defined by the main groove 10, the shoulder between the center region 12 through which the center line C in the tire width direction passes, the tire ground contact end E which is both ends of the ground contact surface of the tread in the tire width direction, and the main groove 10. A region 14 and a mediate region 16 between the center region 12 and the shoulder region 14 are formed.

Further, in the center region 12, the shoulder region 14, and the mediate region 16, the blocks 18 as the land portion defined by the plurality of lateral grooves 11 extending in the tire width direction are arranged in the tire circumferential direction, respectively.

However, this tread pattern is only an example. The number of main grooves, the presence or absence of lateral grooves, the degree of inclination of each groove with respect to the tire circumferential direction and the tire width direction, etc. are not limited to the form shown in FIG. The land portion of each region may be a rib extending in the tire circumferential direction without being divided by the lateral groove, but the land portion of each region will be described below as a block 18.

As shown in FIGS. 1 and 2, one or more sipes 20 are formed in these blocks 18. Although the sipe 20 extends in the tire width direction in the plan view in FIGS. 1 and 2, the sipe 20 may extend in an inclined direction with respect to the tire width direction in the plan view, or may extend in the tire circumferential direction. ..

In the present embodiment, both sides of the sipe 20 in the extension direction are closed portions in the block 18. However, only one of the extension directions of the sipe 20 may be a closed portion blocked in the block 18, and the other may be opened from the block end to the main groove 10 or the like.

The sipe 20 includes a main sipe 21 extending in one direction and two auxiliary sipe 23 branching from the closed end side of the main sipe 21 (referred to as the main sipe end 22). In this embodiment, two auxiliary sipes 23 extend from both ends of the main sipes 21. However, when both sides of the sipe 20 in the extension direction are closed portions in the block 18, the auxiliary sipe 23 may extend only from the main sipe end 22 on the one closed portion side. It is assumed that the main sipe end 22 continues from the open end of the main sipe 21 to the bottom.

Although the main sipe 21 is drawn as a straight line in a plan view in FIG. 2, it may be a wavy or zigzag shape in a plan view. Further, when a plurality of sipes 20 are formed in each block 18, the main sipes 21 of the plurality of sipes 20 may extend in parallel in a plan view as shown in FIG. It is assumed that the extension direction of the main sipe 21 coincides with the extension direction of the sipe 20.

Specific numerical values of the length, width, and depth of the main sipe 21 are not limited. As an example, the width of the main sipe 21 is 0.3 mm or more and 0.8 mm or less, and the depth of the main sipe 21 is 50% or more and 70% or less of the depth of the main groove 10.

Further, the auxiliary sipe 23 of the present embodiment is linear in a plan view. Two auxiliary sipes 23 extending from one main sipe end 22 form a V shape. It is preferable that the angle θ in the extension direction of the auxiliary sipe 23 with respect to the extension direction of the main sipe 21 is 50 ° or more and 70 ° or less, respectively. Therefore, the angle 2θ formed by the two auxiliary sipes 23 is preferably 100 ° or more and 140 ° or less.

As shown in FIG. 3, the auxiliary sipe 23 gradually shortens toward the depth direction. That is, the length of the auxiliary sipe 23 in the extension direction (direction of arrow B in FIGS. 2 and 3) becomes shorter as the position of the auxiliary sipe 23 becomes deeper. As shown in FIG. 3, the auxiliary sipe 23 is connected to the main sipe 21 from the opening end 24 to the ground plane side to the bottom 25. Therefore, the auxiliary sipe 23 gradually becomes shorter toward the main sipe 21 as it gets deeper.

As shown in FIG. 3, in the present embodiment, in the cross section of the auxiliary sipe 23 in the depth direction and the extension direction, the end portion of the auxiliary sipe 23 opposite to the main sipe 21 (referred to as the auxiliary sipe end 26) has a straight line. It is drawn, and the cross-sectional shape of the auxiliary sipe 23 in the depth direction and the extension direction is a triangle. It is assumed that the auxiliary sipe end 26 continues from the opening end 24 of the auxiliary sipe 23 to the bottom 25.

The specific numerical values of the length, width, and depth of the auxiliary sipe 23 are not limited. The width of the auxiliary sipe 23 may be the same as the width of the main sipe 21, but may be narrower than the width of the main sipe 21 or wider than the width of the main sipe 21. Further, the depth of the auxiliary sipe 23 is preferably 1/3 or more of the depth of the main sipe 21 and less than or equal to the depth of the main sipe 21. The depth of the auxiliary sipe 23 is the length from the opening end 24 to the bottom 25.

In the present embodiment, the length, width, and depth of all the auxiliary sipes 23 included in one sipes 20 are the same. However, at least one of the length, width, and depth of the auxiliary sipe 23 may be different for each auxiliary sipe 23.

As shown in FIGS. 1 and 2, another sipe does not have to exist at locations on both sides of the sipe 20 in the extension direction of the auxiliary sipe 23.

In the present invention, the main sipe 21 and the auxiliary sipe 23 are narrow grooves, and more accurately, the pneumatic tire mounted on the regular rim and filled with the regular internal pressure touches the ground, and the regular load is applied to the ground contact. A groove that closes the opening to the ground plane under loaded conditions.

Here, the regular rim is a "standard rim" in the JATMA standard, a "Design Rim" in the TRA standard, or a "Measuring Rim" in the ETRTO standard. The normal internal pressure is the "maximum air pressure" in the JATMA standard, the maximum value of "TIRELOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard. 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 the "LOAD CAPACITY" in the ETRTO standard.

As described above, in the present embodiment, since the sipe 20 is composed of the main sipe 21 and the two auxiliary sipe 23 branched from the main sipe end 22 and extending from the main sipe end 22, the stress is the main sipe when the block 18 is deformed. It is dispersed in the auxiliary sipe 23 without being concentrated on the end 22, and cracks are unlikely to occur. Further, since the auxiliary sipe 23 is connected to the main sipe 21 from its opening end 24 to the bottom 25, the auxiliary sipe 23 does not separate from the main sipe 21 even if the block 18 wears.

Further, the auxiliary sipe 23 is gradually shortened toward the depth direction. Therefore, the rigidity of the block 18 is not so low as compared with the case where the length of the auxiliary sipe is constant in the depth direction (that is, the cross-sectional shape in the depth direction and the extension direction of the auxiliary sipe is rectangular).

By the way, since the auxiliary sipe 23 is gradually shortened toward the depth direction, the auxiliary sipe 23 becomes shorter as the wear of the block 18 progresses. Therefore, it seems that the effect of the auxiliary sipe 23 to disperse the stress becomes smaller as the wear of the block 18 progresses. However, as the block 18 wears and becomes lower, the amount of deformation of the block 18 when the tire rolls becomes smaller, so that the stress applied to the main sipe end 22 becomes smaller. Therefore, even if the block 18 is worn and the auxiliary sipe 23 is shortened, the stress applied to the main sipe end 22 can be sufficiently dispersed by the auxiliary sipe 23.

Further, if the angle of the extension direction of the auxiliary sipe 23 with respect to the extension direction of the main sipe 21 is 50 ° or more and 70 ° or less, the three sipe formed at the intersection of the main sipe 21 and the two auxiliary sipe 23. The angles of the corners are almost even. Therefore, the three corners are worn almost evenly.

Further, if the depth of the auxiliary sipe 23 is 1/3 or more of the depth of the main sipe 21 and equal to or less than the depth of the main sipe 21, the auxiliary sipe 23 can sufficiently disperse the stress.

Next, an example of modification of the above embodiment will be described. However, various changes are possible in addition to the following modification examples, and the scope of the invention is not limited to the scope of the above embodiment and the following modification examples.

The cross-sectional shape of the auxiliary sipe in the depth direction and the extension direction is not limited to the shape shown in FIG. 3, and may be, for example, the shape shown in FIGS. 4 to 7.

In the auxiliary sipe 123a of FIG. 4, the auxiliary sipe end 126a, which is the end opposite to the main sipe 21, is warped in a direction of reducing the volume of the auxiliary sipe 123a (that is, toward the inside of the auxiliary sipe 123a). In other words, the auxiliary sipe end 126a is a curved surface (curved in FIG. 4 which is a cross-sectional view) convex inward of the auxiliary sipe 123a. Since the volume of the auxiliary sipe 123a becomes small due to the warping of the auxiliary sipe end 126a in this way, the rigidity of the block 18 does not become so low. The broken line in FIG. 4 indicates the auxiliary sipe end 26 of the auxiliary sipe 23 of the above embodiment.

In the auxiliary sipe 123b of FIG. 5, the bottom portion 125b is parallel to the opening end 124b and forms a step with the main sipe 21. Further, the auxiliary sipe 123c of FIG. 6 has a constant length in the extension direction in the portion from the opening end 124c to the predetermined depth position 127c, and gradually shortens in the depth direction in the portion deeper than the predetermined depth position 127c. There is. Further, in the auxiliary sipe 123d of FIG. 7, the length in the extension direction is constant in the portion from the opening end 124d to the predetermined depth position 127d, and gradually shortens in the depth direction in the portion deeper than the predetermined depth position 127d. Further, a step portion parallel to the opening end 124d is formed at a predetermined depth position 127d. Even when these auxiliary sipes 123b, 123c, and 123d are formed, cracks are less likely to occur from the main sipes end 22, and the rigidity of the block 18 is not so low.

Further, at least one of the main sipe and the auxiliary sipe may be a so-called three-dimensional sipe whose shape changes along the depth direction. The specific shape of the three-dimensional sipe is not limited, and for example, various conventionally known shapes can be applied. Further, it can be said that the auxiliary sipe 123e shown in FIGS. 8 and 9 is also one form of the three-dimensional sipe. The auxiliary sipe 123e of FIGS. 8 and 9 is bent at the position of the broken line in FIG. 8, and the portion on the opening end 124e side of the bent portion is inclined with respect to the tire radial direction. Note that the auxiliary sipes 123e in FIGS. 8 and 9 look the same as in FIG. 2 in a plan view.

Further, the shapes of the two auxiliary sipes extending from the one main sipe end 22 in a plan view may be as shown in FIGS. 10 (a) and 10 (b). The two auxiliary sipes 123f in FIG. 10A form a U-shape. Further, the two auxiliary sipes 123g in FIG. 10B form a C shape.

Further, it is preferable that the shape of the auxiliary sipe in the plan view and the cross-sectional shape in the depth direction are the same on both sides of the sipe 20 in the extension direction. However, at least one of the shape of the auxiliary sipe in the plan view and the cross-sectional shape in the depth direction may be different on both sides of the extension direction of the sipe 20.

C ... Tire width direction center line, E ... Tire ground contact end, 10 ... Main groove, 11 ... Horizontal groove, 12 ... Center area, 14 ... Shoulder area, 16 ... Mediate area, 18 ... Block, 20 ... Sipe, 21 ... Main Sipe, 22 ... Main sipe end, 23 ... Auxiliary sipe, 24 ... Open end, 25 ... Bottom, 26 ... Auxiliary sipe end, 123a, 123b, 123c, 123d, 123e, 123f, 123g ... Auxiliary sipe, 124b, 124c, 124d , 124e ... Open end, 125b ... Bottom, 126a ... Auxiliary sipe end, 127c, 127d ... Predetermined depth position

Claims (4)

A sipe is formed on the land portion of the tread, and at least one of the extending directions of the sipe is a closed portion in the land portion, and the sipe is from the main sipe and the end portion of the main sipe on the closed portion side. In a pneumatic tire consisting of two branched and extended auxiliary sipes
The auxiliary sipe is connected to the main sipe from the end to the bottom, and gradually shortens toward the depth direction .
A pneumatic tire, characterized in that the end of the auxiliary sipe opposite to the main sipe is warped toward the inside of the auxiliary sipe . The pneumatic tire according to claim 1, wherein the auxiliary sipes are linear in a plan view. The pneumatic tire according to claim 2, wherein the angle of the auxiliary sipe in the extension direction with respect to the extension direction of the main sipe is 50 ° or more and 70 ° or less. The pneumatic tire according to any one of claims 1 to 3, wherein the depth of the auxiliary sipe is 1/3 or more of the depth of the main sipe and equal to or less than the depth of the main sipe.

Images