Patent Description:
<CIT> discloses a pneumatic tire in which shoulder blocks are specifically designed to prevent the vehicle from overturning when turning.

In this tire, the loss tangent and the lateral rigidity of the shoulder blocks are adjusted in order to reduce the cornering force by the shoulder blocks when the vehicle rolls largely, thereby preventing the overturning.

<CIT> discloses a tire according to the preamble of claim <NUM>. other related tires are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

when the cornering force by the shoulder blocks is reduced in order to improve the resistance to vehicle overturning as in the above-mentioned pneumatic tire, wear resistance of the shoulder blocks is liable to reduce.

The present invention was made in view of the above circumstances, and
a primary objective of the present invention is to provide a tire in which the resistance to vehicle overturning can be effectively improved, while maintaining wear resistance of shoulder blocks.

The present invention is defined by a tire having the features of claim <NUM>.

In the present invention, therefore, the tire can exhibit excellent resistance to vehicle overturning while maintaining the wear resistance of the shoulder blocks.

The present invention is suitably applied to pneumatic tires for passenger cars, but the present invention may be applied to pneumatic tires for heavy duty vehicles such as trucks and buses, as well as non-pneumatic tires so called airless tire.

Taking a pneumatic tire for a passenger car as an example, an embodiment of the present invention will be described in detail in conjunction with accompanying drawings.

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

The tire <NUM> comprises a tread portion <NUM> having a first tread edge T1 and a second tread edge T2.

The tread portion <NUM> is provided with circumferential grooves <NUM> disposed between the first tread edge T1 and the second tread edge T2 and extending continuously in the tire circumferential direction.

The tread portion <NUM> comprises land portions <NUM> axially divided by the circumferential grooves <NUM>.

In the present embodiment, the tread portion <NUM> is provided with four circumferential grooves <NUM>, and thereby, divided into five land portions <NUM> as shown in <FIG>.

The present invention is however, not limited to such tread pattern. For example, the tread portion <NUM> may be divided into four land portions <NUM> by three circumferential grooves <NUM>.

In the present embodiment, the tire <NUM> is bidirectional, and not specified which side should be outboard when the tire is attached to a vehicle.

For convenience, in each of the figures herein, the first tread edge T1 is shown as the tread edge on the left side of the tire equator C, and the second tread edge T2 is shown as the tread edge on the right side of the tire equator C.

It is preferable that a half of the tread portion <NUM> between the first tread edge T1 and the tire equator C has substantially the same configuration as a half of the tread portion <NUM> between the second tread edge T2 and the tire equator C.

It is preferable that the tread portion <NUM> has a point-symmetrical tread pattern.

The first tread edge T1 and the second tread edge T2 correspond to the axially outermost edges of the ground contacting patch of the tire <NUM> when the tire <NUM> under its normal state is loaded by a normal load and the tread portion <NUM> is contacted with a flat horizontal surface at a camber angle of <NUM> degrees.

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

In the case of tires for which no standard is established such as airless tires, the "normal state" means a standard usage state according to the purpose of use of the tire, which is not mounted on the vehicle and loaded with no load.

In the present invention, unless otherwise noted, dimensions, positions and the like of the tire refer to those under the normal state.

The normal rim is a wheel rim officially approved or recommended for the tire by standards organizations, i.e. JATMA (Japan and Asia), T&RA (North America), ETRTO (Europe), TRAA (Australia), STRO (Scandinavia), ALAPA (Latin America), ITTAC (India) and the like which are effective in the area where the tire is manufactured, sold or used.

The normal pressure is the air pressure officially approved or recommended for the tire by standards organizations, i.e. JATMA (Japan and Asia), T&RA (North America), ETRTO (Europe), TRAA (Australia), STRO (Scandinavia), ALAPA (Latin America), ITTAC (India) and the like which are effective in the area where the tire is manufactured, sold or used.

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

In the case of tires for which no standard is established, the "normal load" refers to the maximum load applicable to the tire.

The circumferential grooves <NUM> include two shoulder circumferential grooves <NUM> and two crown circumferential grooves <NUM>.

The two shoulder circumferential grooves <NUM> are disposed adjacently to the first tread edge T1 and second tread edge T2, respectively.

The two crown circumferential grooves <NUM> are disposed between the shoulder circumferential grooves <NUM>, and one on each side of the tire equator.

In the present embodiment, each of the circumferential grooves <NUM> is a straight groove extending in parallel with the tire circumferential direction.

However, all of or some of the circumferential grooves <NUM> may be non-straight grooves, for example, zigzag or wavy grooves.

It is preferable that the groove width w1 of each of the circumferential grooves <NUM> is at least <NUM>.

Further, it is preferable that the groove width w1 of each of the circumferential grooves <NUM> is set in a range from <NUM>% to <NUM>% of the tread width TW.

The tread width TW is the distance in the tire axial direction between the first tread edge T1 and the second tread edge T2 in the normal state.

The land portions <NUM> include two shoulder land portions <NUM>. The two shoulder land portions <NUM> comprise the first tread edge T1 and the second tread edge T2, respectively, and are defined on the axially outside of the respective shoulder circumferential grooves <NUM>.

The two shoulder land portions <NUM> have substantially the same configuration.

The land portions <NUM> further include two middle land portions <NUM> and one crown land portion <NUM>.

The two middle land portions <NUM> are positioned adjacently to the respective shoulder land portions <NUM> via the shoulder circumferential grooves <NUM>.

The two middle land portions <NUM> are respectively defined between the crown circumferential groove <NUM> and the respective shoulder circumferential grooves <NUM>.

The two middle land portions <NUM> have substantially the same configuration.

The crown land portion <NUM> is defined between the two crown circumferential grooves <NUM> and positioned on the tire equator C.

<FIG> shows the shoulder land portion <NUM> and the middle land portion <NUM> which are disposed on the first tread edge T1 side of the tire equator C.

As shown in <FIG>, the shoulder land portion <NUM> is provided with lateral grooves <NUM> extending from the shoulder circumferential groove <NUM> to the first tread edge T1.

Thereby, the shoulder land portion <NUM> is circumferentially divided into shoulder blocks <NUM> by the shoulder lateral grooves <NUM>.

In the present invention, the width w2 in the tire axial direction of the ground contacting top surface of each of the shoulder blocks <NUM> is set in a range from <NUM>% to <NUM>% of a half tread width TWh.

The half tread width TWh is the distance in the tire axial direction from the tire equator C to the first tread edge T1 under the normal state of the tire, and corresponds to a half of the above-mentioned tread width TW.

<FIG> shows three of the shoulder lateral grooves <NUM> and two of the shoulder blocks <NUM>.

As shown in <FIG>, the ground contacting top surface of each of the shoulder blocks <NUM> is provided with one or more shoulder sipes <NUM> extending in the tire circumferential direction.

The term "sipe" means an incision having a small width and having two opposite side walls, the two opposite side walls extend substantially parallel to each other, and the width w2 between the two opposite side walls is <NUM> or less.

Further, the expression "substantially parallel" means that the angle between the two opposite side walls is <NUM> degrees or less. Preferably, the width W2 of the sipe is <NUM> to <NUM>, more preferably <NUM> to <NUM>.

In the present embodiment, the width w2 of the sipe is constant from the opening to the bottom thereof.

However, the present invention is not limited to such constant width. For example, the width of the sipe may be increased near the open top of the sipe by providing a chamfer for the sipe edge or edges.

Further, the width of the sipe may be increased near the bottom of the sipe so as to have a flask-shaped cross sectional shape. Further, the expression "the shoulder sipe <NUM> extending in the tire circumferential direction" means that the maximum angle of the center line of the shoulder sipe <NUM> with respect to the tire circumferential direction is not more than <NUM> degrees in its top view.

Further, the expression "the ground contacting top surface of each of the shoulder blocks <NUM> is provided with one or more shoulder sipes <NUM>" means that the ground contacting top surface of each of the shoulder blocks <NUM> is not provided with a locally depressed portion such as groove, sipe and recess, except for the shoulder sipe or sipes <NUM>.

In the tire <NUM> according to the present invention, by adopting the above configuration, it is possible to exhibit excellent resistance to vehicle overturning while maintaining the wear resistance of the shoulder blocks <NUM>. The mechanism is as follows.

In the tire <NUM> of the present invention, since the axial width W2 of the ground contacting top surface of each of the shoulder blocks <NUM> is in a range from <NUM>% to <NUM>% of the half tread width TWh, the rigidity of the shoulder blocks <NUM> is optimized. As a result, it is possible to improve the resistance to vehicle overturning while maintaining the wear resistance of the shoulder blocks <NUM>.

Further, since the ground contacting top surface of each of the shoulder blocks <NUM> is provided with one or more shoulder sipes <NUM> extending in the tire circumferential direction, the rigidity in the tire axial direction of the shoulder blocks <NUM> is reduced, and thereby the resistance to vehicle overturning is improved. On the other hand, the rigidity in the tire circumferential direction of the shoulder blocks <NUM> is not reduced by the shoulder sipes <NUM> and is maintained, so the wear resistance of the shoulder blocks <NUM> can be maintained.

In the present invention, owing to such mechanism, the resistance to vehicle overturning can be improved while maintaining the wear resistance of the shoulder blocks <NUM>.

Hereinafter, the present embodiment will be described in more detail.

Each configuration described below shows a specific example for the present embodiment.

Therefore, even if the tire does not have the configuration described below, the tire will exert the above-mentioned effects of the present invention.

Further, even if any one of the configurations described below is independently applied to the tire having the above-mentioned configurations of the present invention, improvement in performance according to the applied configuration can be expected.

Further, when some of the configurations described below are applied in combination, to the tire having the above-mentioned configurations of the present invention, multiple effect according to the applied configurations on the improvement in performance can be expected.

It is preferable that the width w2 (shown in <FIG>) in the tire axial direction of the ground contacting top surface of each of the shoulder blocks <NUM> is set in a range from <NUM>% to <NUM>% of the half tread width TWh.

Further, the length L4 in the tire circumferential direction of the ground contacting top surface of each of the shoulder blocks <NUM> is smaller than the width W2 in the tire axial direction of the ground contacting top surface.

Specifically, the length L4 is in a range from <NUM>% to <NUM>% of the width w2.

Thus, the ground contacting top surface of the shoulder block <NUM> is long in the tire axial direction. Preferably, the ground contacting top surface has a rectangular shape.

The shoulder lateral grooves <NUM> in this example are arranged at an angle of not more than <NUM> degrees, preferable not more than <NUM> degrees, more preferably not more than <NUM> degrees with respect to the tire axial direction.

Most preferably, and in the present embodiment, the shoulder lateral grooves <NUM> extend parallel with the tire axial direction. Thereby, wear of the shoulder block <NUM> is suppressed.

In order to maintain the wear resistance of the shoulder blocks <NUM>, the shoulder lateral groove <NUM> extends in the tire axial direction with a constant groove width from the shoulder circumferential groove <NUM> to the first tread edge T1.

Further, it is preferable that the groove width w4 of the shoulder lateral groove <NUM> is smaller than the groove width w3 of the shoulder circumferential groove <NUM>.

Specifically, the groove width w4 of the shoulder lateral groove <NUM> is in a range from <NUM>% to <NUM>% of the groove width W3 of the shoulder circumferential groove <NUM>.

<FIG> shows a cross-sectional view taken along line A-A of <FIG>.

The shoulder lateral grooves <NUM> include a tie-bar-equipped shoulder lateral groove <NUM> which is, as shown in <FIG>, provided with tie bars <NUM> raising from the groove bottom so as to connect between two of the shoulder blocks <NUM> adjacent to each other through the tie-bar-equipped shoulder lateral groove <NUM>.

such tie bars <NUM> can further improve the wear resistance.

In <FIG>, the tie bars <NUM> are omitted from the shoulder lateral grooves <NUM> for the sake of simplicity.

In this example, the tie bars <NUM> include an axially inner tie bar <NUM>, an axially outer tie bar <NUM> and an intermediate tie bar <NUM>.

The axially inner tie bar <NUM> is disposed axially inside a center position in the tire axial direction of the tie-bar-equipped shoulder lateral groove <NUM>, wherein the center position is that of the center between the axially inner end at the shoulder circumferential groove <NUM> and the axially outer end at the first tread edge.

Preferably, the axially inner tie bar <NUM> is disposed at the axially inner end of the tie-bar-equipped shoulder lateral groove <NUM>.

Such inner tie bar <NUM> serves for suppressing uneven wear occurring near the axially inner end portion of the tie-bar-equipped shoulder lateral groove <NUM>.

The axially outer tie bar <NUM> is disposed axially outside the above-mentioned center position of the tie-bar-equipped shoulder lateral groove <NUM>.

Preferably, the outer tie bar <NUM> is disposed at the shoulder lateral groove's axially outer end at the first tread edge. specifically, in a cross section of the tie-bar-equipped shoulder lateral groove <NUM> taken along the length direction of the tie-bar-equipped shoulder lateral groove <NUM>, when a zone which extends radially outwardly from the radially outer surface of the outer tie bar <NUM> while keeping a constant width equal to the width of the radially outer surface, is set, the first tread edge T1 is included in this zone.

In other words, the first tread edge T1 is included in the extent of the radially outer surface of the outer tie bar <NUM> in the length direction of the tie-bar-equipped shoulder lateral groove <NUM>.

Such outer tie bars <NUM> serve for suppressing uneven wear occurring near the first tread edge T1.

The intermediate tie bar <NUM> is disposed between both ends in the tire axial direction of the shoulder lateral groove <NUM>, and between the axially outer tie bar <NUM> and the axially inner tie bar <NUM>.

It is preferable that the distance between the intermediate tie bar <NUM> and the axially inner tie bar <NUM> is smaller than the distance between the intermediate tie bar <NUM> and the axially outer tie bar <NUM>.

Such intermediate tie bar <NUM> can effectively suppress the shoulder lateral groove <NUM> from opening excessively, and can further improve the wear resistance.

The shoulder lateral groove <NUM> in the present embodiment is provided with only the axially inner tie bar <NUM>, axially outer tie bar <NUM>, and intermediate tie bar <NUM>.

But, the present invention is not limited to such arrangement. For example, the shoulder lateral groove <NUM> may be provided with only one of these tie bars <NUM>, or only two of these tie bars <NUM>.

The length L6 in the tire axial direction of one tie bar <NUM> is, for example, set in a range from <NUM>% to <NUM>% of the axial width w2 of the ground contacting top surface of the shoulder block <NUM>.

Further, it is preferable that the total axial length of all the tie bars <NUM> disposed in one shoulder lateral groove <NUM> is set in a range from <NUM>% to <NUM>% of the axial width W2 of the ground contacting top surface of the shoulder block <NUM>.

Thereby, the wear resistance and the ride comfort performance are improved in a well-balanced manner.

Here, the axial length of the tie bar <NUM> is measured at the center position in the radial height direction of the tie bar <NUM>.

In the present embodiment, the axially inner tie bar <NUM>, the axially outer tie bar <NUM>, and the intermediate tie bar <NUM> have the same radial height h1.

Preferably, the radial height h1 is set in a range from <NUM>% to <NUM>%, more preferably <NUM>% to <NUM>% of the maximum depth d1 of the shoulder lateral groove <NUM>.

In the present embodiment, as shown in <FIG>, each shoulder sipe <NUM> extends from one of the shoulder lateral grooves <NUM> and ends within the shoulder block <NUM>.

The angle of the shoulder sipe <NUM> with respect to the tire circumferential direction is preferably set in a range from <NUM> to <NUM> degrees.

As a result, while maintaining the rigidity in the tire circumferential direction of the shoulder block <NUM>, the rigidity in the tire axial direction of the shoulder block <NUM> can be relaxed, and the resistance to vehicle overturning performance is further improved.

As shown in <FIG>, the shoulder sipe <NUM> is connected to the shoulder lateral groove <NUM> at the formation position of one of the plurality of tie bars <NUM>.

In the present embodiment, the shoulder sipe <NUM> is connected to the shoulder lateral groove <NUM> at the forming position of the intermediate tie bar <NUM>. Thereby, it is possible to further improve the wear resistance.

The expression "at the formation position of the tie bar <NUM>" means that the shoulder sipe <NUM> is included in a zone, which extends radially outwardly from the radially outer surface of the tie bar <NUM> while keeping a constant width equal to that of the radially outer surface, in the cross section of the tie-bar-equipped shoulder lateral groove <NUM> taken along the length direction of the groove <NUM>. The boundary between the radially outer surface and the other surface of the tie bar <NUM> is lies at the center position of the tie bar <NUM> in the radial height direction.

In the present embodiment, as shown in <FIG>, the above-said at least one shoulder sipe <NUM> includes a first shoulder sipe <NUM> and a second shoulder sipe <NUM>.

Preferably, each of the shoulder blocks <NUM> is provided with one first shoulder sipe <NUM> and one second shoulder sipe <NUM>.

In each of the shoulder blocks <NUM>, the first shoulder sipe <NUM> is connected to one of the tie-bar-equipped shoulder lateral grooves <NUM> which is positioned on one side of the shoulder block <NUM> in the tire circumferential direction (lower side in <FIG>), and
the second shoulder sipe <NUM> is connected to one of the tie-bar-equipped shoulder lateral grooves <NUM> which is positioned on the other side of the shoulder block <NUM> in the tire circumferential direction (upper side in <FIG>).

Further, both the first shoulder sipe <NUM> and the second shoulder sipe <NUM> are connected to the respective tie-bar-equipped shoulder lateral grooves <NUM> at the respective formation positions of the intermediate tie bars <NUM>.

Thereby, the ride comfort performance is improved, while the above-mentioned effects are exhibited.

It is preferable that the first shoulder sipe <NUM> and the second shoulder sipe <NUM> are disposed axially inside a center line 10a of the shoulder block <NUM> in the tire axial direction (in <FIG>, the center line is indicated by alternate long and short dash line).

More specifically, the edges of the first shoulder sipe <NUM> and the edges of the second shoulder sipe <NUM> are completely positioned axially inside the center line 10a.

Therefore, the rigidity of the shoulder block <NUM> is relaxed in its axially inside region, and as a result, the ride comfort performance is further improved.

On the other hand, if the first shoulder sipe <NUM> and the second shoulder sipe <NUM> are disposed excessively close to the shoulder circumferential groove <NUM>, there is a possibility that uneven wear occurs on the shoulder block <NUM>.

Therefore, the axial distance L3 from the connecting position 16a of the first shoulder sipe <NUM> with the shoulder lateral groove <NUM> to the axially inner end of the shoulder lateral groove <NUM> is preferably set in a range from <NUM>% to <NUM>% of the axial width w2 of the ground contacting top surface of the shoulder block <NUM>.

And the axial distance L3 from the connecting position 17a of the second shoulder sipe <NUM> with the shoulder lateral groove <NUM> to the axially inner end of the shoulder lateral groove <NUM> is preferably set in a range from <NUM>% to <NUM>% of the axial width W2 of the ground contacting top surface of the shoulder block <NUM>.

It is preferable that the connecting position 17a of the second shoulder sipe <NUM> with the shoulder lateral groove <NUM> is displaced in the tire axial direction from the connecting position 16a of the first shoulder sipe <NUM> with the shoulder lateral groove <NUM>.

The distance L9 in the tire axial direction between the connecting position 16a and the connecting position 17a is preferably set in a range from <NUM>% to <NUM>% of the axial width w2 of the ground contacting top surface of the shoulder block <NUM>. Thereby, it becomes possible to further improve the wear resistance of the shoulder blocks <NUM>.

In order to further improve the wear resistance of the shoulder blocks <NUM>, it is preferred that the first shoulder sipe <NUM> and the second shoulder sipe <NUM> are inclined in the same direction with respect to the tire circumferential direction.

In the present embodiment, the first shoulder sipe <NUM> and the second shoulder sipe <NUM> are inclined at the same angle with respect to the tire circumferential direction.

Preferably, the angle θ1 between the shoulder lateral groove <NUM> and the shoulder sipe <NUM> is set in a range from <NUM> to <NUM> degrees.

In each of the shoulder blocks <NUM>, the first shoulder sipe <NUM> and the second shoulder sipe <NUM> are arranged such that the first shoulder sipe <NUM> and the second shoulder sipe <NUM> are positioned within a narrow zone <NUM>.

The narrow zone <NUM> is shown in <FIG> by shading with small dots. As shown, the narrow zone <NUM> extends with a constant width and is inclined in the substantially same direction as the first shoulder sipe <NUM> and the second shoulder sipe <NUM> in the top view of the shoulder block <NUM>.

The constant width of the narrow zone <NUM> is preferably not more than <NUM>.

In this example, in order to further improve the ride comfort performance, the first shoulder sipe <NUM> and the second shoulder sipe <NUM> are arranged so as to extend substantially on a straight line. In this case, the width of the narrow zone <NUM> can be the substantially same as the width of the sipes <NUM> and <NUM>.

It is preferable that each shoulder sipe <NUM> (<NUM>, <NUM>) ends within the shoulder block <NUM> without crossing the center line 10b of the shoulder block <NUM> in the tire circumferential direction (indicated by the alternate long and short dash line in <FIG>).

It is preferable that the length L5 in the tire circumferential direction of the shoulder sipe <NUM> is set in a range from <NUM>% to <NUM>% of the length L4 in the tire circumferential direction of the shoulder block <NUM>.

Such shoulder sipes <NUM> serve for improving the wear resistance and the ride comfort performance in a well-balanced manner.

Each of the middle land portions <NUM> is provided with middle lateral grooves <NUM> as shown in <FIG>.

The middle lateral grooves <NUM> extend across the entire axial width of the middle land portion <NUM>. Thereby, the middle land portion <NUM> is circumferentially divided into middle blocks <NUM>.

It is preferable that the width w5 in the tire axial direction of the ground contacting top surface of the middle block <NUM> is smaller than the width W2 in the tire axial direction of the ground contacting top surface of the shoulder block <NUM>.

Specifically, the axial width w5 of the ground contacting top surface of the middle block <NUM> is in a range from <NUM>% to <NUM>% of the axial width w2 of the ground contacting top surface of the shoulder block <NUM>.

As a result, the progress of wear of the shoulder blocks <NUM> and that of the middle blocks <NUM> becomes uniform, and uneven wear thereof is suppressed.

The middle lateral grooves <NUM> in the present embodiment are inclined with respect to the tire axial direction.

The angle θ2 of the middle lateral grooves <NUM> with respect to the tire axial direction is larger than the angle of the shoulder lateral grooves <NUM> with respect to the tire axial direction.

In the middle lateral grooves <NUM> in the present embodiment, the angle θ2 with respect to the tire axial direction increases toward the inside in the tire axial direction, wherein, the angle θ2 is in a range from <NUM> to <NUM> degrees, for example.

As a result, the middle lateral grooves <NUM> are curved convexly toward one side in the tire circumferential direction (lower side in <FIG>) on the first tread edge T1 side of the tire equator.

such middle lateral grooves <NUM> can enhance the wet performance in addition to the improvement of the wear resistance and the ride comfort performance.

In the present embodiment, the groove width W6 of the middle lateral grooves <NUM> is larger than the groove width w4 of the shoulder lateral grooves <NUM>.

Specifically, the groove width w6 of the middle lateral grooves <NUM> is in a range from <NUM>% to <NUM>% of the groove width w4 of the shoulder lateral grooves <NUM>.

Thereby, the progress of wear of the shoulder land portion <NUM> and that of the middle land portion <NUM> become uniform, and uneven wear these portions is suppressed.

<FIG> shows a cross-sectional view taken along line B-B of <FIG>.

The middle lateral grooves <NUM> include a tie-bar-equipped middle lateral groove <NUM> which is, as shown in <FIG>, provided with at least one middle tie bar <NUM> raising from the groove bottom so as to connect between two of the middle blocks <NUM> adjacent to each other through the tie-bar-equipped middle lateral groove <NUM>. Preferably, and in the present embodiment, each of the middle lateral grooves <NUM> is provided with only one middle tie bar <NUM>. The middle tie bar <NUM> serves for increasing the rigidity of the middle land portion <NUM> in the tire circumferential direction and improving the wear resistance.

In the present embodiment, only one middle tie bar <NUM> is disposed between both ends in the tire axial direction of the middle lateral groove <NUM>.

However, the present invention is not limited to such arrangement. For example, a plurality of middle tie bars <NUM> may be disposed in one middle lateral groove <NUM>.

The length L7 in the tire axial direction of the single middle tie bar <NUM> is, for example, set in a range from <NUM>% to <NUM>% of the width W5 (shown in <FIG>) in the tire axial direction of the middle block <NUM>.

The maximum height h2 of the middle tie bar <NUM> is set in a range from <NUM>% to <NUM>% of the maximum depth d2 of the middle lateral groove <NUM>.

Further, in the present embodiment, the middle tie bar <NUM> is disposed so as to extend across the center position in the tire axial direction of the middle lateral groove <NUM>. Thereby, the wear resistance and the ride comfort performance are improved in a well-balanced manner.

It is preferable that, when the axial lengths of the tie bars are compared, the middle tie bar <NUM> is larger than any of the axially inner tie bar <NUM>, the outer tie bar <NUM> and the middle tie bar <NUM> provided in the shoulder lateral groove <NUM>.

On the other hand, it is preferable that the axial length L7 of the middle tie bar <NUM> is smaller than the total axial length of the axially inner tie bar <NUM>, the outer tie bar <NUM> and the intermediate tie bar <NUM>.

Thereby, the rigidity distribution of the shoulder land portion <NUM> and the middle land portion <NUM> is optimized, and the wear resistance is further improved.

Each of the middle blocks <NUM> is provided with at least one middle sipe <NUM> as shown in <FIG>.

The middle sipe <NUM> is connected to at least one of the two middle lateral grooves <NUM> located on both sides in the tire circumferential direction of the middle blocks <NUM>.

In the present embodiment, the middle sipe <NUM> is connected to the two middle lateral grooves <NUM> located on both sides in the tire circumferential direction. That is, the middle sipe <NUM> completely crosses the middle block <NUM> in the tire circumferential direction.

Further, it is preferable that each of the both ends in the tire circumferential direction of the middle sipe <NUM> is connected to a central portion of the middle lateral groove <NUM> when the middle lateral groove <NUM> is divided into three equal parts in the length direction.

Such middle sipe <NUM> serves for relaxing the rigidity in the tire axial direction of the middle block <NUM> and improving the ride comfort performance.

The middle sipe <NUM> in this example is inclined with respect to the tire circumferential direction.

It is preferable that the middle sipe <NUM> is inclined in the same direction as the shoulder sipe <NUM>.

The angle θ3 between the middle sipe <NUM> and the middle lateral groove <NUM> is, for example, set in a range from <NUM> to <NUM> degrees. Such middle sipe <NUM> serves for improving the wear resistance and the ride comfort performance in a well-balanced manner.

Preferably, that the number Ns of the shoulder lateral grooves <NUM> disposed in each shoulder land portion <NUM> is larger than the number Nm of the middle lateral grooves <NUM> disposed in each middle land portion <NUM>.

As a result, the length in the tire circumferential direction of each shoulder block <NUM> can be made relatively small, and the overall wear resistance of the land portions and various dynamic performances including steering stability can be maintained while improving the resistance to vehicle overturning.

More preferably, the number Ns is not more than <NUM>% of the number Nm. Thereby, the above-mentioned performance is improved in a well-balanced manner.

It is preferable that the middle sipe <NUM> is connected to the middle lateral groove <NUM> at the same forming position as the middle tie bar <NUM> as shown in <FIG>.

Thereby, the connecting position between the middle lateral groove <NUM> and the middle sipe <NUM> is reinforced by the middle tie bar <NUM>, and uneven wear near the connecting position is suppressed.

In the present embodiment, as shown in <FIG>, each of the middle blocks <NUM> is not provided with a groove or a sipe except for the middle sipe <NUM>. Thereby, the above-mentioned effect can be further enhanced.

<FIG> is a top view of a part of the crown land portion <NUM>.

It is preferable that the width w7 in the tire axial direction of the crown land portion <NUM> is set in a range from <NUM>% to <NUM>% of the tread width TW (shown in <FIG>).

It is preferable that the width w7 of the crown land portion <NUM> is smaller than the width w2 in the tire axial direction of the shoulder block <NUM>.

The crown land portion <NUM> is provided with first crown lateral grooves <NUM> and second crown lateral grooves <NUM>.

The first crown lateral grooves <NUM> extend from the crown circumferential groove <NUM> on one side in the tire axial direction (left side in <FIG>) of the crown land portion <NUM>, toward the tire equator C, and ends within the crown land portion <NUM>.

The second crown lateral grooves <NUM> extend from the crown circumferential groove <NUM> on the other side in the tire axial direction (right side in <FIG>) of the crown land portion <NUM>, toward the tire equator C, and ends within the crown land portion <NUM>.

The first crown lateral grooves <NUM> and the second crown lateral grooves <NUM> can enhance the wet performance, while maintaining the rigidity of the crown land portion <NUM>.

In order to improve the wear resistance and the ride comfort in a well-balanced manner, the axial length L8 of the first crown lateral groove <NUM> and the axial length L8 of the second crown lateral groove <NUM> are preferably set in a range from <NUM>% to <NUM>% of the axial width W7 of the crown land portion <NUM>.

The first crown lateral grooves <NUM> are curved convexly toward one side in the tire circumferential direction (upper side in <FIG>), whereas.

the second crown lateral grooves <NUM> are curved convexly toward the other side in the tire circumferential direction (lower side in <FIG>). Thereby, uneven wear of the crown land portion <NUM> is further suppressed.

In the present embodiment, as shown in <FIG>,.

By arranging the lateral grooves in this way, the progress of wear in each land portion becomes uniform, and uneven wear in each land portion is suppressed.

While detailed description has been made of a preferable embodiment of the present invention, the present invention can be embodied in various forms without being limited to the illustrated embodiment.

Based on the tread pattern shown in <FIG>, pneumatic tires of size <NUM>/60R17C (rim size 17x6. OJ) having specifications shown in Table <NUM> were experimentally manufactured as test tires (working examples Ex. <NUM> and comparative examples Ref.<NUM>-Ref.<NUM>), and tested for the wear resistance of the shoulder blocks and the resistance to vehicle overturning as follows.

Each test tire mounted on a wheel rim of size <NUM>×<NUM>. 0J and inflated to <NUM> kPa, was run on a simulated road surface of a tire test drum for a predetermined distance under certain conditions, and then, the remaining radial heights of the shoulder blocks were measured to obtain the average value.

The results are indicated in Table <NUM> by an index based on comparative Example Ref.<NUM> being <NUM>, wherein the larger the value, the better the wear resistance of the shoulder blocks.

A test car (3000cc 4WD car) with the same test tires mounted on all wheels and inflated to <NUM> kPa was entered into an asphalt paved test course at a speed of <NUM>/h and, with sharp steering operation, the steering wheel was rotated in one direction at a predetermined steering angle, and then immediately the steering wheel was turned in the opposite direction at the same steering angle. And it was observed whether the tires were lifted from the road surface more than <NUM> due to the roll of the vehicle body. The results are shown in Table <NUM>.

As shown in Table <NUM>, in the working examples, the wear resistance was improved, and at the same time, the tire lifting more than <NUM> did not occur and thus the resistance to vehicle overturning was improved.

On the other hand, in the comparative example Ref.<NUM> in which the width of the ground contacting top surface of the shoulder block was small, the wear resistance of the shoulder blocks was low. In the comparative example Ref.<NUM> in which the width of the ground contacting top surface of the shoulder block was large, the tire lifting more than <NUM> occurred.

Claim 1:
A tire (<NUM>) comprising
a tread portion (<NUM>) having a first tread edge (T1), and provided with a shoulder circumferential groove (<NUM>) disposed adjacently to the first tread edge (T1) and extending continuously in the tire circumferential direction, so as to define a shoulder land portion (<NUM>) between the shoulder circumferential groove (<NUM>) and the first tread edge (T1), wherein
the shoulder land portion (<NUM>) is provided with shoulder lateral grooves (<NUM>) extending from the shoulder circumferential groove (<NUM>) to the first tread edge (T1), so as to circumferentially divide the shoulder land portion (<NUM>) into shoulder blocks (<NUM>), and
the shoulder lateral grooves (<NUM>) include a tie-bar-equipped shoulder lateral groove (<NUM>) provided with at least one tie bar (<NUM>) rising from the groove bottom so as to connect between two of the shoulder blocks (<NUM>) adjacent to the tie-bar-equipped shoulder lateral groove (<NUM>),
characterized in that the width (w2) in the tire axial direction of the ground contacting top surface of each of the shoulder blocks (<NUM>) is in a range from <NUM> % to <NUM> % of a half tread width (Twh) between the first tread edge (T1) and the tire equator (c),
each of the shoulder blocks (<NUM>) is provided with one or more shoulder sipes (<NUM>) each extending from one of the shoulder lateral grooves (<NUM>) and ending within the shoulder block (<NUM>),
the ground contacting top surface of each of the shoulder blocks (<NUM>) is provided with one or more shoulder sipes (<NUM>) extending in the tire circumferential direction,
the shoulder lateral grooves (<NUM>) include a tie-bar-equipped shoulder lateral groove (<NUM>) provided with tie bars (<NUM>) raising from the groove bottom so as to connect between two of the shoulder blocks (<NUM>) adjacent to each other through the tie-bar-equipped shoulder lateral groove (<NUM>), and
in the case of the shoulder sipe (<NUM>) connected to the tie-bar-equipped shoulder lateral groove (<NUM>), the shoulder sipe (<NUM>) is connected at a formation position of one of said tie bars (<NUM>) in the tire axial direction.