Patent Description:
Patent Document <NUM> describes a tire having a plurality of straight circumferential grooves and a plurality of lateral grooves are formed in a tread section, a shoulder land region is partitioned into a plurality of shoulder blocks, and a three-dimensional sipe is formed in the shoulder blocks. According to such tire, driving performance on ice and on snow may be improved. Attention is also drawn to the disclosures of <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

However, in the conventional tire, a drainage from the sipe to a circumferential main groove, which mainly handles the drainage of a ground surface, on an icy road surface may be suppressed by a water flow flowing in the circumferential main groove. Therefore, in the conventional tire, the drainage by the sipe in the tread surface may be insufficient, and further improvement in the drainage performance is desired.

Moreover, a block, partitioned by a plurality of the circumferential main grooves and the plurality of lateral grooves formed in the tread section, is desired to reduce rolling resistance further by suppressing deformation due to contact pressure of the tire.

An object of the present invention is to provide a tire that may improve on-ice driving performance by improving drainage from a sipe to a circumferential main groove while reducing rolling resistance of the tire.

A tire according to the present invention is provided as claimed in claim <NUM>.

According to the above-described configuration, a tire that may improve on-ice driving performance by improving drainage from a sipe to a circumferential main groove while reducing rolling resistance of the tire is provided.

Embodiments will be described below with reference to the drawings. It should be noted that the same functions and configurations are denoted by the same or similar reference numerals, and the description thereof is appropriately omitted.

<FIG> is a partial plan view illustrating a tread pattern of a tread section <NUM> of a tire according to present embodiment. <FIG> is a partial enlarged plan view of a shoulder land region SR including a circumferential main groove <NUM>. <FIG> is an enlarged perspective view of a part including an inclined surface <NUM> of one groove wall <NUM> forming a shoulder lateral groove <NUM>. <FIG> is an enlarged end view perpendicular to a tire axial direction TA, which illustrates a part of the inclined surface <NUM> of the groove wall <NUM> at the tire-widthwise-inner position. <FIG> is an enlarged end view perpendicular to the tire axial direction TA, which illustrates a part of the inclined surface <NUM> of the groove wall <NUM> at a tire-widthwise-outer position. <FIG> is an enlarged perspective view of a part of a groove wall <NUM> according to a variant, the part including an inclined surface 32A. <FIG> are enlarged end views perpendicular to the tire axial direction TA, each of which illustrates a part including the inclined surface 32A of the groove wall <NUM> according to the variant.

The tread section <NUM> is formed with a tread pattern in accordance with a performance required for the tire. In this embodiment, the tire is a studless tire that can be suitably used for trucks and buses (TB). The studless tire may be referred to as a snow tire or a winter tire. Alternatively, the tire may be a so-called all-season tire usable not only in winter but also in all seasons.

The tire is not necessarily used for a truck or a bus, but may be used for other types of vehicles, for example, a passenger automobile, a van, and a light-duty truck.

The tire according to the present embodiment includes a tread section <NUM> having a pair of circumferential main grooves <NUM> extending in the tire circumferential direction TC. The tread section <NUM> includes a center land region CR partitioned by the pair of circumferential main grooves <NUM>, and a shoulder land region SR positioned outside a tire width direction TW of the center land region CR partitioned by one circumferential main groove <NUM> of the pair of circumferential main grooves <NUM> and a tread end TE. The center land region CR forms a dense structure in which no main groove extending along the tire circumferential direction TC is formed. The shoulder land region SR includes a block <NUM> partitioned by a plurality of shoulder lateral grooves <NUM> crossing the shoulder land region SR in the tire width direction TW. A sipe <NUM> extending in the tire width direction TW and having one end communicating with the circumferential main groove <NUM> is formed in the block <NUM>. On a corner part <NUM> of the block <NUM> at an intersection of the one circumferential main groove <NUM> and a first shoulder lateral groove <NUM>, a first groove wall <NUM> of the one circumferential main groove <NUM> is provided with a projection <NUM> projecting inward in the tire width direction TW. The first shoulder lateral groove <NUM> is a width direction groove included in the plurality of shoulder lateral grooves <NUM>. The configuration of the tire according to the present embodiment will be described in detail below.

As illustrated in <FIG>, the pair of circumferential main grooves <NUM> extending along the tire circumferential direction TC is formed in the tread section <NUM>. In this embodiment, the pair of circumferential main grooves <NUM> are straightly formed. However, the pair of circumferential main grooves <NUM> may not necessarily be straight, such as coasting slightly in the tire width direction.

The tread section <NUM> is partitioned into a center land region CR where the tire width direction TW of which is partitioned by the pair of circumferential main grooves <NUM>, and a shoulder land region SR located outside in the tire width direction TW of the center land region CR and partitioned by one circumferential main groove <NUM> of the pair of circumferential main grooves <NUM> and a tread end TE.

In the present embodiment, a circumferential groove having a groove width equal to a groove width of the one circumferential main groove <NUM> or a groove width wider than the groove width of the one circumferential main groove <NUM> is not formed in the center land region CR.

In other words, only a circumferential narrow groove <NUM> extending in the tire circumferential direction and having a groove width narrower than the circumferential main groove <NUM> is formed in the center land region CR. Therefore, in the center land region CR, the distance between adjacent land blocks (which may be called spacing or gap) is narrow. Therefore, in the center land region CR, a plurality of land blocks are densely arranged to form a dense structure with respect to arrangement of land blocks in a general tire of this type.

In the present embodiment, the groove width of the one circumferential main groove <NUM> is about <NUM> to <NUM>, and the groove width of the circumferential narrow groove <NUM> is about <NUM> to <NUM>.

A shoulder lateral groove <NUM> crossing in the tire width direction TW from the circumferential main groove <NUM> to the tread end TE is formed in at least one shoulder land region SR. In this embodiment, a plurality of the shoulder lateral grooves <NUM> are formed in the shoulder land region SR. The shoulder land region SR is partitioned into a plurality of blocks <NUM> by the plurality of the shoulder lateral grooves <NUM>.

A sipe <NUM> extending in the tire width direction TW and communicating with the circumferential main groove <NUM> is formed in each block <NUM> of the shoulder land region SR. Here, the sipe is a narrow groove formed to have a groove width (for example, a groove width of <NUM> to <NUM>), which is configured to close in the ground plane when the tire is grounded. In this embodiment, the sipe <NUM> is a so-called three-dimensional sipe that is bent a plurality of times.

As illustrated in <FIG>, on a surface forming a first groove wall <NUM> of the circumferential main groove <NUM> in each block <NUM>, a projection <NUM> projecting inner side in the tire width direction TW is formed at a corner part <NUM>, where the circumferential main groove <NUM> intersects the shoulder lateral groove <NUM>.

In the present embodiment, the three-dimensional sipe <NUM> is not formed at a tire circumferential position where the projection <NUM> of each block <NUM> is formed. It should be noted that a sipe may be formed on a block <NUM> at a tire circumferential position where the projection <NUM> is formed, if the sipe has an end part in tire width direction TW on the circumferential main groove <NUM> side not opened to the circumferential main groove <NUM> at the projection <NUM>.

Each block <NUM> is formed to have a circumferential narrow groove <NUM> extending in the tire circumferential direction TC and having a groove width narrower than the groove width of the circumferential main groove <NUM>. The groove width of the circumferential narrow groove <NUM> formed in the shoulder land region SR may be the same as the groove width of the circumferential narrow groove <NUM> formed in the center land region CR at an upper limit, and may be the same as the groove width of the sipe at a lower limit. Specifically, the groove width of the circumferential narrow groove <NUM> is <NUM> to <NUM>.

As illustrated in <FIG>, an outer end of the three-dimensional sipe <NUM> in the tire width direction TW may communicate with the circumferential narrow groove <NUM>. A groove depth of the circumferential narrow groove <NUM> may be shallower than a groove depth of the shoulder lateral groove <NUM> as illustrated in <FIG>.

As illustrated in <FIG>, a groove wall <NUM> on the shoulder lateral groove <NUM> side at the corner part <NUM> of the block <NUM> may be formed in protruding shape protruding in the tire circumferential direction TC, the corner part <NUM> being a part where the projection <NUM> is formed. That is, the corner part <NUM> of the block <NUM> including the protruding shape protruding in the tire circumferential direction TC may protrude toward inner side in the tire width direction TW (toward an tire equatorial line side) and toward the tire circumferential direction TC side at the groove walls of the circumferential main groove <NUM> and the shoulder lateral groove <NUM>. In the present embodiment, only one groove wall of the shoulder lateral groove <NUM> is formed to include the protruding shape protruding in the tire circumferential direction TC.

As illustrated in <FIG>, in the second groove wall <NUM> of the circumferential main groove <NUM>, a recess <NUM> recessed in the tire width direction TW is formed at a position opposed to the tire circumferential position of the first groove wall <NUM> where the projection <NUM> is formed. The intersection P between the second groove wall <NUM> and an extension line of the three-dimensional sipe <NUM> extending in the tire width direction TW is located in the recess <NUM>, including an end part in the tire circumferential direction TC of the recess <NUM>. The extension line of the three-dimensional sipe <NUM> extending in the tire width direction TW is illustrated by a broken line in <FIG>.

As illustrated in <FIG>, the groove wall <NUM> of the shoulder lateral groove <NUM>, which partitions the shoulder land region SR into a plurality of blocks <NUM>, includes an inclined surface <NUM> with curved shape. In the cross section perpendicular to the tire axial direction, the inclination angle θ of the inclined surface <NUM>, which has curved shape, with respect to the tire radial direction TR gradually increases from the inner side in the tire width direction TW to the outer side in the tire width direction TW. The inclination angle θ of the inclined surface <NUM> is an inclination angle from the groove bottom <NUM> to the tread surface <NUM>.

For example, the inclination angle θ1 at the inner end of the curved inclined surface <NUM> in the tire width direction TW illustrated in <FIG> is <NUM>° to <NUM>°. The inclination angle θ2 at the outer end of the curved inclined surface <NUM> in the tire width direction TW illustrated in <FIG> is <NUM>° to <NUM>°. However, the inclination angle θ of the curved inclined surface <NUM> is selected in a range satisfying a condition that the inclination angle θ is gradually increased from the inclination angle θ1 at the inner end in the tire width direction TW to the inclination angle θ2 at the outer end in the tire width direction TW.

Although the contents of the present invention have been described in accordance with embodiments, it will be apparent to those skilled in the art that the present invention is not limited to these descriptions but is defined by the appended claims.

In the end surface perpendicular to the tire axial direction illustrated in <FIG> of the present embodiment, the inclined surface <NUM> is inclined linearly from the groove bottom <NUM> of the groove wall <NUM> to the surface <NUM> of the tread section <NUM>. However, the inclined surface <NUM> with curved shape is not limited to the embodiment illustrated in <FIG> as long as the surface from the groove bottom <NUM> to the surface <NUM> of the tread section <NUM> is inclined. For example, as in a variant illustrated in <FIG>, an inclined surface 32A with curved shape may have an end face, the end face perpendicular to the tire axial direction, inclined from a groove bottom 33A of the groove wall <NUM> to a tread surface 35A and curved to be convex downward, as illustrated in <FIG>.

Further, as illustrated in <FIG>, the tread pattern formed on the tread section <NUM> of the tire according to the present embodiment has a pattern in which the tire rotation direction is designated so that the effect is remarkably exhibited during driving. However, the tread pattern is not limited to this. For example, in a case where it is desirable to have a structure that exhibits the effect in a good balance between driving and braking, a pattern inverted at the tire equatorial line CL may be used.

A rubber used for the tread section <NUM> may be made of an appropriate material in consideration of on-snow driving performance and wear resistance, and is not particularly limited. However, a material that may contribute to a reduction of rolling resistance (RR) of the tire may be used. Specifically, the rolling resistance coefficient (RRC) is preferably <NUM> or less.

In this embodiment, as illustrated in <FIG>, a dense structure, in which a plurality of land blocks are densely arranged in the center land region CR, is formed. This structure is a structure in which the center land region CR is partitioned by the circumferential narrow grooves <NUM>. Therefore, the blocks or ribs partitioned by the circumferential narrow grooves <NUM> support each other along the tire width direction TW during deformation, and deformation of the blocks or ribs in the tire width direction TW is suppressed. Therefore, uneven wear resistance in the center land region CR can be improved. Further, the rolling resistance of the tire can be reduced.

When the center land region CR has the dense structure, in which a plurality of land blocks are densely arranged, deformation of the center land region CR in the tire width direction TW is suppressed. As a result, the ground pressure in the shoulder land region SR is relatively increased. Accordingly, deformation of the shoulder land region SR becomes large. For this reason, in a tire in which the center land region CR has a dense structure in which a plurality of land blocks are densely arranged, it is important to improve the performance of draining water generated from an ice surface in contact with the shoulder land region SR in order to improve the on-ice driving performance of the tire.

In this embodiment, as illustrated in <FIG> and <FIG>, the three-dimensional sipe <NUM> extending in the tire width direction TW and having one end communicating with the circumferential main groove <NUM> is formed in the block <NUM> formed in the shoulder land region SR, and the projection <NUM> projecting inward in the tire width direction TW is formed on the first groove wall <NUM> of the circumferential main groove <NUM> at the corner part <NUM> of the block <NUM> where the circumferential main groove <NUM> and the shoulder lateral groove <NUM> intersect.

According to this configuration, the three-dimensional sipe <NUM> absorbs water generated from the ice road surface. The water absorbed by the three-dimensional sipe <NUM> is drained into the circumferential main groove <NUM>. However, even when the three-dimensional sipe <NUM> is formed, if the water flow in the circumferential main groove <NUM> is fast, there is a possibility that the drainage from the three-dimensional sipe <NUM> to the circumferential main groove <NUM> may become insufficient. In contrast, in the present embodiment, the projection <NUM> is formed on the first groove wall <NUM> of the circumferential main groove <NUM> in the corner part <NUM> of the block <NUM>. With this configuration, the water flow in the circumferential main groove <NUM> is moderated, and the drainability from the three-dimensional sipe <NUM> to the circumferential main groove <NUM> is sufficiently secured.

Thus, in the present embodiment, wear resistance and uneven wear resistance can be improved while reducing the rolling resistance of the tire. Further, the on-ice driving performance of the tire can be improved.

In this embodiment, the sipe <NUM> is a three-dimensional sipe. When the sipe <NUM> is a three-dimensional sipe, the water absorbing performance of the sipe improves and water generated between the shoulder land region SR and the road surface can be absorbed more quickly.

Further, as illustrated in <FIG>, in the tire according to the present embodiment, the three-dimensional sipe <NUM> is not formed in the tire circumferential direction position of the block <NUM> where the projection <NUM> is formed. That is, sipes opening to the circumferential main grooves <NUM> are not formed in the projections <NUM>. According to this configuration, the rigidity of the projection <NUM> is secured, and the water flow in the circumferential main groove <NUM> can be moderated more reliably.

In the present embodiment, the recess <NUM> recessed in the tire width direction TW is formed at the tire circumferential position on the second groove wall <NUM> of the circumferential direction main groove <NUM> opposed to the tire circumferential position where the projection <NUM> is formed on the first groove wall <NUM>. The intersection P between the second groove wall <NUM> and the extension line of the three-dimensional sipe <NUM> extending in the tire width direction TW is located in the recess <NUM>, including the end part in the tire circumferential direction TC of the recess <NUM>.

According to this configuration, the water flow in the circumferential main groove <NUM> can be moderated without reducing an amount of water flowing in the circumferential main groove <NUM>. That is, according to this configuration, the drainage performance can be further improved.

In the present embodiment, a circumferential narrow groove <NUM> extending in the tire circumferential direction TC is formed in the block <NUM>, and the other end of the three-dimensional sipe <NUM> communicates with the circumferential narrow groove <NUM>. Since the circumferential narrow groove <NUM> is formed on the block <NUM>, the block <NUM> can be deformed in the tire circumferential direction. Therefore, according to the present embodiment, the uneven wear resistance of the tire may be improved. Further, drainage from the other end of the three-dimensional sipe <NUM> to the shoulder lateral groove <NUM> is made possible, and drainage performance may be further improved.

In the present embodiment, a groove wall of the shoulder lateral groove <NUM> at the corner part <NUM> of the block <NUM> may be formed in protruding shape protruding in the tire circumferential direction TC, the corner part <NUM> being a part where the projection <NUM> is formed. According to this configuration, an intrusion of water from the circumferential main groove <NUM> into the shoulder lateral groove <NUM> is suppressed, and the water flow in the shoulder lateral groove <NUM> drained from the circumferential main groove <NUM> side to the tread end TE side can be moderated. Thus, drainability from the circumferential narrow groove <NUM> to the shoulder lateral groove <NUM> is secured.

Claim 1:
A tire comprising a tread section (<NUM>) including a pair of circumferential main grooves (<NUM>) extending in a tire circumferential direction (TC), wherein
the tread section (<NUM>) includes: a center land region (CR) partitioned by the pair of circumferential main grooves (<NUM>); and a shoulder land region (SR) located outside in a tire width direction (TW) of the center land region (CR) and partitioned by one circumferential main groove (<NUM>) of the pair of circumferential main grooves (<NUM>) and a tread end (TE),
the center land region (CR) forms a dense structure, in which no main groove extending along the tire circumferential direction is formed and only a circumferential narrow groove (<NUM>) extending in the tire circumferential direction and having a groove width narrower than the circumferential main groove (<NUM>) is formed in the center land region (CR),
the shoulder land region (SR) includes a block (<NUM>) partitioned by a plurality of shoulder lateral grooves (<NUM>) crossing the shoulder land region (SR) in the tire width direction (TW),
the block (<NUM>) is provided with a sipe (<NUM>) extending in the tire width direction (TW) and having one end communicating with the one circumferential main groove (<NUM>), and
on a corner part (<NUM>) of the block (<NUM>) at an intersection of the one circumferential main groove (<NUM>) and a first shoulder lateral groove (<NUM>) included in the plurality of shoulder lateral grooves (<NUM>), a first groove wall (<NUM>) of the one circumferential main groove (<NUM>) is provided with a projection (<NUM>) projecting inward in the tire width direction (TW), wherein
the sipe (<NUM>) is not formed at a tire circumferential position of the block (<NUM>) where the projection (<NUM>) is formed,
at a tire circumferential position on a second groove wall (<NUM>) of the one circumferential main groove (<NUM>) corresponding to a tire circumferential position where the projection (<NUM>) is formed, a recess (<NUM>) recessed inward in the tire width direction (TW) is formed,
an intersection (P) between the second groove wall (<NUM>) and an extension line of the sipe (<NUM>) extending in the tire width direction (TW) is arranged in the recess (<NUM>), including an end part in the tire circumferential direction (TC) of the recess (<NUM>), and
there is no sipe opening to the one circumferential main groove (<NUM>) formed in the projection (<NUM>).