Patent Description:
<CIT> discloses a pneumatic tire for use in the winter season. This tire has an outside shoulder land portion divided into outside shoulder blocks by outside shoulder lateral grooves extending in a tire axial direction. The outside shoulder blocks is divided into a first block piece on the outside tread edge side and a second block piece on the inside tread edge side by a first longitudinal narrow groove extending in a tire circumferential direction. Further, the first block piece is provided with first sipes, and the second block piece is provided with second sipes. <CIT> discloses a tire having the features according to the preamble of claim <NUM>.

The sipes formed in the tread block help to improve on-ice performance. On the other hand, each block segment divided by the sipes tends to collapse by the load when contacting with the ground. There is a problem such that, due to such collapse of the block segment piece, strain is concentrated on the bottom of the sipe, and cracks are likely to occur in the bottom. For this reason, in a tire in which sipes are formed in the blocks, the durability of the bottom portion of the sipes against a load (hereinafter, sometimes referred to as "load bearing performance") was required to be improved.

The present invention was made in view of the above circumstances, and
a primary objective thereof is to provide a tire capable of improving the load bearing performance while maintaining the on-ice performance.

The tire according to the present invention comprises the features of claim <NUM>.

Therefore, in the tire according to the present invention, it is possible to improve the load bearing performance, while maintaining the on-ice performance.

An embodiment of the present invention will now be described in detail in conjunction with accompanying drawings.

<FIG> is a developed partial view of a tread portion <NUM> of a tire <NUM> as an embodiment of the present invention.

As shown in <FIG>, the tire <NUM> in the present embodiment is intended for use in the winter season.

The tire <NUM> in the present embodiment is designed for a pneumatic tire for passenger cars. However, the present invention is not limited to the present embodiment, and may be applied, for example, to heavy duty vehicles tires.

The tread portion <NUM> is provided with a plurality of circumferential grooves <NUM> continuously extending in a tire circumferential direction and disposed between two tread edges Te. Thus, the tread portion <NUM> is divided by these circumferential grooves <NUM> into a plurality of land portions <NUM>.

The tread edges Te corresponds to the outermost contact positions in the tire axial direction when the tire <NUM> in its normal state is set on a horizontal flat surface at a camber angle of <NUM> degrees and loaded with <NUM>% of a normal load.

In the case of pneumatic tires for which various standards have been established, the "normal state" of a tire means a state of the tire mounted on a regular rim, and inflated to a regular internal pressure, but loaded with no tire load.

In the case of tires for which various standards are not yet defined or non-pneumatic tires, the "normal state" of a tire means a standard usage condition according to the purpose of use of the tire, which is a condition in which the tire is not mounted on the vehicle and no tire load is applied.

In this specification, unless otherwise noted, the dimensions of each part or position of the tire refer to those measured under the normal state.

Incidentally, known methods can be appropriately applied to the method for measuring the dimensions unless otherwise specified.

The "regular rim" is a wheel rim specified for the tire in a standard system including standards on which the tire is based, for example, "Standard Rim" in JATMA, "Design Rim" in USA, and "Measuring Rim".

The "regular internal pressure" is the air pressure specified for the tire in the standard system including standards on which the tire is based, for example, the "maximum air pressure" in JATMA, the "Inflation Pressure" in ETRTO, and the maximum pressure given in the "Tire Load Limits at various Cold Inflation Pressures" table in TRA or the like.

In the case of pneumatic tires for which various standards have been established, the "normal load" is the tire load specified for the tire in the standard system including standards on which the tire is based, for example, "LOAD CAPACITY" in JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" in ETRTO.

In the case of tires for which various standards have not been established, the "normal load" refers to the maximum load that can be applied when using the tire according to the above-mentioned standa1rds.

In the present embodiment, the tread portion <NUM> is provided with the four circumferential grooves <NUM> including two crown circumferential grooves <NUM> and two shoulder circumferential grooves <NUM>.

The two crown circumferential grooves <NUM> are disposed one on each side of the tire equator C.

The two shoulder circumferential grooves <NUM> are respectively disposed axially outside the two crown circumferential grooves <NUM>.

The present invention is however, not limited to such groove arrangement.

The circumferential grooves <NUM> may adopt various modes such as those extending linearly in the tire circumferential direction and those extending in a zigzag shape in the tire circumferential direction.

<FIG> shows a cross section of the tread portion <NUM>, wherein the sipes and the lateral grooves observed in the plan view of the tread portion <NUM> are omitted here.

It is preferable that the groove widths of the circumferential grooves <NUM> are not less than <NUM> as shown in <FIG>.

The maximum groove width W1 of the circumferential grooves <NUM> is, for example, <NUM>% to <NUM>% of the tread width TW (shown in <FIG>).

The maximum depth d1 of the circumferential groove <NUM> is, for example, <NUM> to <NUM>.

Incidentally, the tread width TW corresponds to the distance in the tire axial direction between the tread edges Te under the normal state.

As shown in <FIG>, the tread portion <NUM> in the present embodiment is divided into five land portions <NUM> by the four circumferential grooves <NUM> described above.

The five land portions <NUM> are one crown land portion <NUM>, two middle land portions <NUM> and two shoulder land portions <NUM>.

The crown land portion <NUM> is defined between the two circumferential crown grooves <NUM>.

Each of the middle land portions <NUM> is defined between the crown circumferential groove <NUM> and one of the shoulder circumferential grooves <NUM>.

Each of the shoulder land portions <NUM> is defined between one of the shoulder circumferential grooves <NUM> and the adjacent tread edge Te.

The tread portion <NUM> in the present embodiment is provided with a plurality of lateral grooves <NUM>. Thereby, each of the five land portions <NUM> is circumferentially divided by the lateral grooves <NUM> into a plurality of blocks <NUM> in a row.

The above-said plurality of blocks <NUM> includes at least one first block <NUM>.

In the present embodiment, the shoulder land portion <NUM> includes a plurality of the first blocks <NUM> arranged in the tire circumferential direction. The plurality of first blocks <NUM> constitute the tread edge Te.

there is shown an enlarged view of the plurality of first blocks <NUM>.

The plurality of first blocks <NUM> shown in <FIG> are included in the shoulder land portion <NUM> on the left side of <FIG>.

As shown in <FIG>, the plurality of sipes <NUM> extending in the tire axial direction are arranged in the ground contacting top surface <NUM> at intervals in the tire circumferential direction.

The term "sipe" means a narrow groove having a width not more than <NUM> between two opposite side walls, inclusive of a cut having no substantial width.

A chamfer may be provided at the edge of the opening of the sipe.

Further, the bottom 15d of the sipe <NUM> may be communicated with a wide portion as described later.

<FIG> is an enlarged perspective view showing the internal space of the sipe <NUM>.

As shown in <FIG>, the internal space are lightly dotted.

<FIG> shows a cross-sectional view of the sipe <NUM> perpendicular to the sipe length direction.

<FIG> is a cross-sectional view including a first wide portion <NUM>, and corresponds to the cross-sectional view taken along line AA in <FIG>. The first wide portion <NUM> will be described later,.

<FIG> is a cross-sectional view of the sipe <NUM> taken along a plane parallel to the ground contacting top surface <NUM> of the first block <NUM>.

The cross-sectional view of <FIG> includes a tie bar <NUM> which will be described later.

In the present embodiment, as shown in <FIG> and <FIG>, each of the sipes <NUM> includes a zigzag-shaped portion in a cross section orthogonal to the sipe length direction.

Further, as shown in <FIG> and <FIG>, each of the sipes <NUM> includes a zigzag portion in a cross section parallel to the ground contacting top surface <NUM>.

Here, the expression "include a zigzag-shaped portion" means that the part which vibrates in a zigzag is formed in at least one position.

In the present embodiment, as a preferable example, in both the cross section orthogonal to the sipe length direction and the cross section parallel to the ground contacting top surface <NUM>, the sipe is zigzag-shaped as a whole.

<FIG> is a cross-sectional view of the sipe <NUM> taken along the length direction of the sipe <NUM>.

The cross-sectional view of <FIG> corresponds to the cross-sectional view taken along line BB of <FIG>.

In <FIG>, double-dots chain lines <NUM> corresponding mountain lines and valley lines of concavities and convexities formed in the opposite side walls of the sipe.

Further, as shown in <FIG>, the sipe <NUM> is provided with only one tie bar <NUM>.

The tie bar <NUM> locally protrudes outward in the tire radial direction from the bottom 18d of the sipe, and terminates without reaching the ground contacting top surface <NUM> of the first block <NUM>.

<FIG> is an enlarged top view of the first block <NUM>, wherein the positions of the tie bars <NUM> of the respective sipes <NUM> are indicated by hatched circles.

In the present embodiment, as shown in <FIG>, the sipes <NUM> provide in one first block <NUM> include at least.

Here, two tie bars located at different axial positions means that the center 18c in the sipe length direction of the tie bar <NUM> of the first sipe <NUM> is displaced from that of the second sipe <NUM>.

Thus, in the present embodiment, it is possible that, in the top view of the first block <NUM>, a virtual zone <NUM> (dotted in <FIG>), which is formed by extending the axial extent of the tie bar <NUM> of the first sipe <NUM> toward the second sipe <NUM> in parallel with the tire circumferential direction, may partially overlaps with the tie bar <NUM> of the second sipe <NUM>.

The tire <NUM> of the present embodiment can improve the load bearing performance while maintaining the on-ice performance by adopting the above-described configuration. The reason is as follows.

In the present embodiment, as shown in <FIG> and <FIG>, each of the sipes <NUM> has the zigzag-shaped portion in the cross section orthogonal to the sipe length direction, and also has the zigzag-shaped portion in the cross section parallel to the ground contacting top surface <NUM> of the first block <NUM>. Further, as shown in <FIG>, each of the sipes <NUM> is provided with at least one tie bar <NUM>.

When a load from the ground acts on the first block <NUM>, the side walls of the sipes <NUM> facing each other are strongly engaged with each other so as to maintain the apparent rigidity of the first block <NUM>. Further, the tie bars <NUM> maintain the rigidity of the first block <NUM>.

As a result, the collapse of the first block <NUM> is effectively suppressed, and the strain at the bottom of the first sipe <NUM> can be suppressed, therefore, the load bearing performance is improved.

In addition, as shown in <FIG>, in the present embodiment, as the tie bars <NUM> of the first sipe <NUM> and the second sipe <NUM> are located at different axial positions, the first block <NUM> is surely prevented from falling down. and the load bearing performance is further improved.

In addition, since the tie bars <NUM> described above suppress local falling down of the block, even if a large shear stress acts on the first block <NUM>, for example, during braking on ice, the entire edges of the first sipe <NUM> and the second sipe <NUM> exerts a large frictional force to maintain the on-ice performance.

For the above reasons, the tire <NUM> can improve the load bearing performance while maintaining the on-ice performance.

Hereinafter, the present embodiment will be described in more detail. Each configuration described below represents a specific aspect of the present embodiment. Therefore, the present invention can exhibit the above effects even if it does not have the configuration described below. Further, even if any one of the configurations described below is applied singly to the tire of the present invention having the features described above, an improvement in performance corresponding to each configuration can be expected. Furthermore, when some of the respective configurations described below are applied in combination, it is possible to expect a combined improvement in performance according to each configuration.

As shown in <FIG>, when the tread portion <NUM> is axially divided into four equal parts: two outer parts 2A, which are regions on the tread edge Te side, and two inner parts 2B, which are regions on the tire equator C side, the plurality of first blocks <NUM> is preferably arranged in the land portion <NUM> included in the outer part 2A.

In the present embodiment, the plurality of first blocks <NUM> is included in the shoulder land portion <NUM>, and the plurality of first blocks <NUM> forms the tread edge Te.

Thereby, since the sipes <NUM> are arranged in the shoulder land portion <NUM> where ground contact pressure tends to become high, the load bearing performance is reliably improved.

Preferably, <NUM> to <NUM> sipes <NUM> are disposed per one first block <NUM>. In the present embodiment, as shown in <FIG>, five sipes <NUM> are disposed per one first block <NUM>, and each sipe <NUM> crosses the first block <NUM> in the tire axial direction. Further, in the present embodiment, except for the sipes <NUM>, the first block <NUM> is not provided with recesses such as grooves. However, the present invention is not limited to such arrangement. For example, the first block <NUM> may be provided with a narrow groove extending in the tire circumferential direction.

The interval "ta" between two sipes <NUM> adjacent in the tire circumferential direction (corresponds to the distance in the tire circumferential direction between the sipe center lines) is, for example, <NUM> to <NUM>, preferably <NUM> to <NUM>. Thereby, it is possible to exhibit excellent on-ice performance while suppressing uneven wear of the first block <NUM>.

In the present embodiment, as shown in <FIG>, the sipe <NUM> is provided with only one tie bar <NUM> at a position other than the ends in the sipe length direction.

In the present embodiment, as shown in <FIG>, the tie bar <NUM> extends in the tire radial direction with a constant width W5 except for the radially outer end portion 18a which has an arcuate outer surface convex toward the ground contacting top surface <NUM>.

The constant width W5 of the tie bar <NUM> in a cross section along the length direction of the sipe <NUM> is, for example, in a range from <NUM> to <NUM>.

The height h1 in the tire radial direction from the bottom of the first wide portion <NUM> which will be described later, to the radially outer end of the tie bar <NUM>, is preferably set in a range from <NUM>% to <NUM>% of the maximum depth d3 from the ground contacting top surface <NUM> of the first block <NUM> to the bottom of the first wide portion <NUM>.

such tie bars <NUM> serve to improve the load bearing performance and the on-ice performance in a well-balanced manner.

As shown in <FIG>, the tie bar <NUM> is preferably disposed in a center region of each sipe <NUM> in its longitudinal direction.

Therefore, when the first sipe <NUM> is divided into three equal parts in the sipe length direction, it is preferable that the above-said first position is located in the central part. Similarly, when the second sipe <NUM> is divided into three equal parts in the sipe length direction, it is preferable that the above-said second position is located in the central part.

That is, the center 18c of each tie bar <NUM> in the sipe length direction is located within the central part.

Thereby, the central part of the first block <NUM> in the tire axial direction is effectively reinforced.

As long as the center 18c is located within the central part, a portion of the tie bar <NUM> may be outside the central part.

In <FIG>, the boundary lines <NUM> between three equal parts are indicated by double-dots chain line.

The plurality of sipes <NUM> provided in one first block <NUM> are not limited to the first sipe <NUM> and the second sipe <NUM> only.

In the present embodiment, in addition to the first sipe <NUM> and the second sipe <NUM>, a third sipe <NUM>, a fourth sipe <NUM>, and a fifth sipe <NUM> provided per one first block <NUM>.

In <FIG> , the first sipe <NUM> to the fifth sipe <NUM> are arranged in order from one side to the other side in the tire circumferential direction.

Further, in <FIG>, the positions at which the tie bars <NUM> of the sipes <NUM> to <NUM> are provided are indicated by hatched circles.

The third sipe <NUM> has the tie bar <NUM> at a third position in the tire axial direction different from the first position and the second position.

The fourth sipe <NUM> has the tie bar <NUM> at a fourth axial position in the tire axial direction.

The fifth sipe <NUM> has the tie bar <NUM> at a fifth position in the tire axial direction.

The fourth position is different from the first to third positions.

The fifth position is different from the first to fourth positions.

The second position is between the first position and the third position in the tire axial direction.

Thereby, the on-ice performance and the load bearing performance are further improved.

The first position and the second position are on one side in the tire axial direction of the third position.

The fourth position and the fifth position are on the other side in the tire axial direction of the third position.

The fourth position is between the third position and the fifth position in the tire axial direction.

Thereby, it is possible to suppress uneven wear in the region where these sipes <NUM> are provided, while obtaining the above-described effects.

In the present embodiment, for each sipe <NUM> provided in the first block <NUM>, the tie bar <NUM> is located in the central part when the sipe <NUM> is divided into three equal parts in the sipe length direction as described above.

It is preferable that, for every two of the sipes <NUM> adjacent to each other in the tire circumferential direction,
a virtual zone, which is formed by extending the axial extent of the tie bar <NUM> of one of the two sipes toward the other of the two sipes in parallel with the tire circumferential direction, partially overlaps with the tie bar of the other of the two sipes.

Thereby, the central portion of the first block <NUM> in the tire axial direction is effectively reinforced, and the load-bearing performance is improved.

In <FIG>, tie bar arrangement lines <NUM> are indicated by double-dot chain lines.

Each of the tie bar arrangement lines <NUM> is an imaginary line connecting the centers of two of the tie bars <NUM> adjacent in the tire circumferential direction.

In the present embodiment, in a top view of the first block, each of the tie bar arrangement lines <NUM> is inclined in one direction with respect to the tire circumferential direction. The angle θ1 of each tie bar arrangement line <NUM> with respect to the tire circumferential direction is, for example, <NUM> to <NUM> degrees.

As a result, uneven wear resistance and the load bearing performance are improved in a well-balanced manner.

In the present invention, the tie bar arrangement is not limited to the above example, and various arrangements can be adopted.

<FIG> each show a top view of the first block <NUM> as another example of the tie bar arrangement.

In <FIG>, the same reference numerals are given to elements that are common to the above-described example, and the above-described configurations can be applied thereto.

In the examples shown in <FIG>, the tie bar <NUM> of each sipe <NUM> is arranged in a central part when the sipe <NUM> is divided into three equal parts in the longitudinal direction. And the tie bar arrangement lines <NUM> extend in a zigzag pattern.

In the examples shown in <FIG> and <FIG>, in the top view of the first block <NUM>, tie bar center lines 18v extending parallel to the tire circumferential direction through the respective centers 18c of the tie bars <NUM>, are displaced in the tire axial direction. such arrangement of the tie bars <NUM> helps to further improve the load bearing performance.

In the examples shown in <FIG> and <FIG>, it is preferable that the tie bar centerlines 18v of the tie bars <NUM> are respectively placed on virtual lines which are drawn in parallel to the tire circumferential direction at substantially equal spacings L2.

The "substantially equal spacing" means that the difference between the minimum value and the maximum value of the spacings L2 between the tie bar center lines 18v is not more than <NUM>% of the maximum value.

For example, The spacings L2 are in a range from <NUM>% to <NUM>% of the maximum width W5 of the tie bars <NUM>.

As a result, the above effects can be reliably obtained.

In the example shown in <FIG>, in a top view of the first block <NUM>, a virtual zone (not shown), which is formed by extending the axial extent of the tie bar <NUM> of the second sipe <NUM> toward the third sipe <NUM> in parallel to the tire circumferential direction, overlaps with the tie bar <NUM> of the third sipe <NUM>.

Further, in the top view of the first block <NUM>, a virtual zone (not shown), which is formed by extending the axial extent of the tie bar <NUM> of the third sipe <NUM> toward the fourth sipe <NUM> in parallel to the tire circumferential direction, overlaps with the tie bar <NUM> of the fourth sipe <NUM>.

such arrangement of the tie bars <NUM> helps to further increase the load bearing performance.

In the example shown in <FIG>, in a top view of the first block <NUM>, a virtual area (not shown), which is formed by extending the axial extent of the tie bar <NUM> of the second sipe <NUM> toward the third sipe <NUM> in parallel to the tire circumferential direction, does not overlap with the tie bar <NUM> of the third sipe <NUM>.

Further, in the top view of the first block <NUM>, a virtual zone (not shown), which is formed by extending the axial extent of the tie bar <NUM> of the third sipe <NUM> toward the fourth sipe <NUM> in parallel to the tire circumferential direction, does not overlap with the tie bar <NUM> of the fourth sipe <NUM>.

As a result, the reinforcing effect by the tie bars <NUM> acts over a wide range, and uneven wear of the first block <NUM> can be suppressed.

In the example shown in <FIG>, among the first to fifth sipes <NUM> to <NUM> arranged from one side to the other side in the tire circumferential direction, the tie bar <NUM> of the third sipe <NUM> and the tie bar <NUM> of the fifth sipe <NUM> are located at the same axial position as the first position of the first sipe <NUM>. That is, the third sipe <NUM> and the fifth sipe <NUM> are configured as "the first sipe <NUM> having the tie bar <NUM> at the first position in the tire axial direction".

On the other hand, the tie bar <NUM> of the fourth sipe <NUM> is located at the same axial position as the second position of the second sipe <NUM>. That is, the fourth sipe <NUM> is configured as "the second sipe <NUM> having the tie bar <NUM> at the second position in the tire axial direction".

With such sipe arrangement, this example can be said that the first sipe <NUM> having the tie bar <NUM> at the first position in the tire axial direction, and the second sipe <NUM> having the tie bar <NUM> at the second position in the tire axial direction are alternately arranged in the tire circumferential direction.

As a result, the tie bar arrangement lines <NUM> form a zigzag line extending in the tire circumferential direction.

In such example, as the tie bars <NUM> adjacent in the tire circumferential direction are separated from each other in the tire axial direction, uneven wear of the first block <NUM> can be further suppressed.

In this example, in a top view of the first block <NUM>, a virtual zone <NUM>, which is formed by extending the axial extent of the tie bar <NUM> of the first sipe <NUM> toward the second sipe <NUM> in parallel with the tire circumferential direction, does not overlap with the tie bar <NUM> of the second sipe <NUM>.

On the other hand, the first position is located in a central part when the first sipe <NUM> is divided into three equal parts in the longitudinal direction of the sipe.

Also, the second position is located in a central part when the second sipe <NUM> is divided into three equal parts in the longitudinal direction of the sipe.

The positions of the tie bars <NUM> are not limited to the above examples.

As a modified example of that shown in <FIG>, it may be possible that:.

In such modified example, since no tie bar <NUM> is arranged in a central part of the sipe <NUM>, each sipe <NUM> can exhibit high water absorption performance, thereby exhibiting excellent on-ice performance.

As a further modified example of that shown in <FIG>, it may be possible that the centers 18c of the tie bars <NUM> are axially displaced from each other. Thereby, uneven wear of the first block <NUM> is suppressed.

<FIG> shows a top view of the first block <NUM> as another example of the tie bar arrangement.

In this first block <NUM>, the first sipe <NUM> to the fifth sipe <NUM> are arranged in order from one side to the other side in the tire circumferential direction.

Each sipe <NUM> is divided into five equal parts in the longitudinal direction of the sipe, namely, a first part <NUM>, a second part <NUM>, a third part <NUM>, a fourth part <NUM> and a fifth part <NUM>.

The first part <NUM> is arranged closest to the tread edge Te.

The second part <NUM> is adjacent to the first part <NUM> on the tire equator C side.

The third part <NUM> is adjacent to the second part <NUM> on the tire equator C side.

The fourth part <NUM> is adjacent to the third part <NUM> on the tire equator C side.

The fifth part <NUM> is adjacent to the fourth part <NUM> on the tire equator C side. That is, the fifth part <NUM> is positioned closest to the tire equator C among the five regions.

In the example shown in <FIG>, the first position is located in the third part <NUM> of the first sipe <NUM>, the second position is located in the fourth part <NUM> of the second sipe <NUM>, the third position is located in the third part <NUM> of the third sipe <NUM>, the fourth position is located in the second part of the fourth sipe <NUM>, and the fifth position is located in the third part <NUM> of the fifth sipe <NUM>.

As a result, the tie bar arrangement lines <NUM> oscillate and extend in a wavy shape.

such arrangement of the sipes <NUM> helps to improve the on-ice performance and the load-bearing performance in a well-balanced manner.

As a modified example of that of <FIG>, it may be possible that the centers 18c of the tie bars <NUM> are axially displaced from each other. Thereby, uneven wear of the first block <NUM> is suppressed.

<FIG> shows a top view of the first block <NUM> as still another example of the tie bar arrangement.

In this example, the first position is located in the first part <NUM> of the first sipe <NUM>, the second position is located in the third part <NUM> of the second sipe <NUM>, the third position is located in the fifth part <NUM> of the third sipe <NUM>, the fourth position is located in the third part of the fourth sipe <NUM>, and the fifth position is located in the first part <NUM> of the fifth sipe <NUM>.

As a result, the tie bar arrangement lines <NUM> are bent convexly toward the tire equator C.

In such arrangement of the sipes <NUM>, since two tie bars <NUM> on the most tread edge Te side (the tie bar <NUM> of the first sipe <NUM> and the tie bar <NUM> of the fifth sipe <NUM>), are separated in the tire circumferential direction, improvement in wandering performance can be expected while obtaining the above effects.

As a modified example of that shown in <FIG>, it is possible that the center 18c of the tie bar <NUM> of the first sipe <NUM> and the center 18c of the tie bar <NUM> of the fifth sipe <NUM> are displaced from each other in the tire axial direction.

Further, it is possible that the center 18c of the tie bar <NUM> of the second sipe <NUM> and the center 18c of the tie bar <NUM> of the fourth sipe <NUM> are displaced from each other in the tire axial direction.

Thereby, uneven wear of the first block <NUM> is suppressed.

Hereinafter, the features of one sipe <NUM> will be described in more detail. The features described below are applicable to the first sipe <NUM> through fifth sipe <NUM> described above.

As shown in <FIG>, the sipe <NUM> is divided into at least a first portion <NUM> and a second portion <NUM> in the sipe length direction by one tie bar <NUM>.

In the region between the tie bar <NUM> and the ground contacting top surface <NUM> of the first block <NUM>, the boundary between the first portion <NUM> and the second portion <NUM> is an imaginary line (not shown) which is obtained by extending the center line in the width direction of the tie bar <NUM> toward the outside in the tire radial direction.

The bottom 16d of the first portion <NUM> communicates with a first wide portion <NUM> having a circular cross section.

The first wide portion <NUM> has a groove width larger than the sipe width in the first portion <NUM> as shown in <FIG>.

The first wide portion <NUM> extends linearly along the sipe length direction of the first portion <NUM> over its entire length as shown in <FIG>.

Similarly, the bottom 17d of the second portion <NUM> communicates with a second wide portion <NUM> having a circular cross section as shown in <FIG> and <FIG>.

The second wide portion <NUM> has a groove width larger than the sipe width in the second portion <NUM>.

The second wide portion <NUM> extends linearly along the sipe length direction of the second portion <NUM> over its entire length.

The first wide portion <NUM> and the second wide portion <NUM> do not communicate with each other.

since the above-described sipe <NUM> comprises the first wide portion <NUM> and the second wide portion <NUM>, which are not in communication with each other.

Even if the first block <NUM> collapses, strain is dispersed at the bottom of the sipe <NUM>, and damage to the sipe can be suppressed. In addition, since the first wide portion <NUM> and the second wide portion <NUM> exhibit excellent water absorption performance, the on-ice performance can be further improved.

The shape of the cross section of the first wide portion <NUM> and the second wide portion <NUM> is not limited to circular, and may be triangular, for example.

As shown in <FIG>, in the cross section of the sipe <NUM>, the sipe <NUM> extends in the tire radial direction with a constant width w2.

Further, as shown in <FIG>, the sipe <NUM> extends in its length direction while maintaining the constant width W2 described above. That is, the sipe <NUM> extends with the constant width W2 over its entirety.

For example, the width W2 is preferably not more than <NUM>, more preferably <NUM> to <NUM>.

As a result, the load bearing performance and the on-ice performance are improved in a well-balanced manner.

The present invention is however, not limited to such configuration. Further, inevitable errors occurs in rubber products such as tires can be allowed. Therefore, the width of the sipe <NUM> may vary depending on its measurement position.

In this case, it is preferable that the ratio W2M/W2m between the maximum value W2M and the minimum value W2m (not shown) of the width of the sipe <NUM> is not more than <NUM>.

The maximum value W2M is preferably <NUM> to <NUM>.

The minimum value W2m is desirably <NUM> to <NUM>.

As shown in <FIG>, the maximum depth d3 from the ground contacting top surface <NUM> of the first block <NUM> to the bottom of the first wide portion <NUM> is <NUM> to <NUM>.

The maximum depth d4 from the ground contacting top surface of the first block <NUM> to the bottom of the second wide portion <NUM> is <NUM> to <NUM>.

As a result, the load bearing performance and the on-ice performance can be improved in a well-balanced manner. Preferably, the depth d3 is the same as the depth d4.

As shown in <FIG>, the first wide portion <NUM> extends linearly in the sipe length direction of the sipe <NUM> while maintaining a circular area in the cross section.

As a result, the first wide portion <NUM> is configured in a columnar shape except for the communicating portion with the sipe <NUM>.

The centers of the circular cross sections of the first wide portion <NUM> collectively form a central axis of the first wide portion <NUM>, and this central axis extends linearly.

The same applies to the second wide portion <NUM>.

However, the first wide portion <NUM> and the second wide portion <NUM> are not limited to such linearly extending shape, and the central axis may extend in a zigzag shape.

As shown in <FIG>, the diameter L1 in the cross section of the first wide portion <NUM> is preferably not less than <NUM> times, more preferably not less than <NUM> times, but preferably not more than <NUM> times, more preferably not more than <NUM> times the width W2 of the sipe <NUM> in the cross section.

As a result, the above effects can be obtained while demonstrating excellent dimoldability during tire production.

In addition, the above-mentioned "width in the cross section of the sipe <NUM>" means the constant width W2 in this embodiment, and means the maximum width when the width varies depending on the measurement position.

From a similar point of view, the diameter of the second wide portion <NUM> in its cross section is preferably not less than <NUM> times, more preferably not less than <NUM> times, but preferably not more than <NUM> times, more preferably not more than <NUM> times the width of the sipe <NUM> in its cross section.

As shown in <FIG>, the tread portion <NUM> in the present embodiment comprises a cap tread rubber layer Cg and a base tread rubber layer Bg.

The cap tread rubber layer Cg forms a ground contacting surface of the tread portion <NUM>.

The base tread rubber layer Bg is disposed radially inside the cap tread rubber layer Cg.

The rubber hardness of the cap tread rubber layer Cg is, for example, in a range from <NUM> to <NUM> degrees.

The base tread rubber layer Bg has a rubber hardness greater than that of the cap tread rubber layer Cg.

The rubber hardness of the base tread rubber layer Bg is, for example, in a range from <NUM> to <NUM> degrees.

In this specification, the rubber hardness means the type-A durometer hardness measured at <NUM> deg. according to Japanese Industrial Standard (JIS) K6253.

In the present embodiment, the distance t2 in the tire radial direction from the ground contacting surface of the tread portion <NUM> to the boundary <NUM> between the cap tread rubber layer Cg and the base tread rubber layer Bg, is in a range from <NUM>% to <NUM>% of the total thickness t1 of the tread rubber.

On the other hand, as shown in <FIG>, the minimum distance t3 in the tire radial direction from the boundary <NUM> to the bottoms of the first wide portion <NUM> and the second wide portion <NUM> is not less than <NUM>, preferably from <NUM> to <NUM>.

This effectively suppresses rubber separation at the boundary <NUM> due to deformation of the first wide portion <NUM> and the second wide portion <NUM>.

Claim 1:
A tire comprising a tread portion (<NUM>) provided with a plurality of blocks (<NUM>) including at least one first block (<NUM>) provided with a plurality of sipes (<NUM>) extending in a tire axial direction and arranged at intervals in a tire circumferential direction, wherein
each of the plurality of sipes (<NUM>) has a zigzag portion in a cross section perpendicular to the length direction of the sipe (<NUM>), and
a zigzag portion in a cross section parallel to the ground contacting top surface (<NUM>) of the first block (<NUM>),
characterized in that each of the plurality of sipes (<NUM>) is provided with only one tie bar (<NUM>) protruding radially outwardly from a bottom (15d) of the sipe (<NUM>) and terminating without reaching the ground contacting top surface (<NUM>),
the plurality of sipes (<NUM>) includes
a first sipe (<NUM>) having the tie bar (<NUM>) at a first position in the tire axial direction, and
a second sipe (<NUM>) having the tie bar (<NUM>) at a second position in the tire axial direction different from the first position, the first position of the first sipe (<NUM>) is located in a central part when the first sipe (<NUM>) is divided into three equal parts in the sipe length direction, the second position of the second sipe (<NUM>) is located in a center part when the second sipe (<NUM>) is divided into three equal parts in the sipe length direction, and in a top view of the first block (<NUM>), a virtual zone (<NUM>), which is formed by extending an axial extent of the tie bar (<NUM>) of the first sipe (<NUM>) toward the second sipe (<NUM>) in parallel with the tire circumferential direction, partially overlaps with the tie bar (<NUM>) of the second sipe (<NUM>).