JP6729809B2 - Pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire, and more specifically to a pneumatic tire capable of suppressing uneven shoulder wear of a tread portion and improving riding comfort.

A pneumatic tire is generally a tread portion that extends in the tire circumferential direction and forms an annular shape, a pair of sidewall portions that are arranged on both sides of the tread portion, and a tire radial direction inner side of these sidewall portions. And a pair of bead portions, and a structure including a carcass layer mounted between the pair of bead portions and a plurality of belt layers arranged on the tire radial direction outer side of the carcass layer in the tread portion. doing.

In such a pneumatic tire, improvement of wear characteristics is required as a permanent problem. As a method for improving the wear characteristics, for example, it has been proposed to increase the hardness of the cap tread rubber to increase the rigidity of the tread portion (see, for example, Patent Document 1). However, if the hardness of the cap tread rubber is simply increased, there is a problem that the impact received from the road surface during traveling increases with the increase in the rigidity of the tread portion, and the riding comfort (mild feeling) deteriorates. Therefore, it is necessary to balance the wear characteristics and the riding comfort, which are in a trade-off relationship.

By the way, the technique of improving various performances of a pneumatic tire by defining the ground contact shape of a pneumatic tire is proposed (for example, refer to patent documents 2-4). However, these techniques do not attempt to achieve both wear characteristics and riding comfort.

Japanese Patent Laid-Open No. 2017-203080 Japanese Patent Laid-Open No. 6-8710 Japanese Patent Laid-Open No. 8-108710 Japanese Unexamined Patent Publication No. 2009-78790

An object of the present invention is to provide a pneumatic tire capable of suppressing uneven wear of the shoulder of the tread portion and improving riding comfort.

The pneumatic tire of the present invention for achieving the above-mentioned object, a tread portion that extends in the tire circumferential direction and forms an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and these sidewall portions. In a pneumatic tire having a pair of bead portions arranged on the inner side in the tire radial direction,
The maximum contact length in the tire circumferential direction when the pneumatic tire is filled with an air pressure of 230 kPa and the tire is grounded under the conditions that loads of 40%, 75%, and 100% of the maximum load capacity defined by the standard are applied. Let LA1, LB1, LC1 be the maximum ground contact width in the tire width direction be WA1, WB1, WC1, respectively, and at the position of 40% of the maximum ground contact width WA1, WB1, WC1 from the tire center position toward the tire width direction outer side. When the external ground contact lengths in the tire circumferential direction are LA2, LB2, LC2, respectively, the maximum ground contact lengths LA1, LB1, LC1 and the external ground contact lengths LA2, LB2, LC2 are 1.02≦(LB2/LB1)/(LA2 /LA1)≦1.25, 1.00≦(LC2/LC1)/(LB2/LB1)≦1.20,
When the tread portion is divided into a central region having a width corresponding to 53% of the maximum ground contact width WB1 centering on the tire equator and an outer region within the maximum ground contact width WB1 that is outside the central region in the tire width direction. The groove area Sc of the central region and the groove area Ss of the outer region satisfy the relationship of 1.01≦Sc/Ss≦1.50.

In the present invention, the groove area Sc in the central region and the groove area Ss in the outer region satisfy the relationship of 1.01≦Sc/Ss≦1.50, and the sufficient groove area Sc in the central region is ensured. By lowering the rigidity in the central region of the tread portion, the input from the road surface can be alleviated and the riding comfort (mild feeling) can be improved. On the other hand, by reducing the groove area Ss in the outer region, it is possible to secure the rigidity in the outer region of the tread portion and suppress the shoulder uneven wear of the tread portion. Further, the maximum ground lengths LA1, LB1, LC1 and the external ground lengths LA2, LB2, LC2 are 1.02≦(LB2/LB1)/(LA2/LA1)≦1.25, 1.00≦(LC2/LC1)/ By satisfying the relationship of (LB2/LB1)≦1.20 and defining the ground contact shape in consideration of load fluctuation, the effect of suppressing shoulder uneven wear and the effect of improving riding comfort can be further enhanced.

In the present invention, it is preferable that the maximum ground contact length LB1 and the external ground contact length LB2 satisfy the relationship of 0.65≦LB2/LB1≦0.95. The maximum ground lengths LA1, LB1, LC1 and the external ground lengths LA2, LB2, LC2 may satisfy the relationship of (LC2/LC1)/(LB2/LB1)≦(LB2/LB1)/(LA2/LA1). preferable. Thereby, the riding comfort can be improved based on the ground contact shape.

In the present invention, in the tread portion, a central main groove extending in the tire circumferential direction, an outer main groove extending in the tire circumferential direction at a position outside the central main groove in the tire width direction, and a tire width larger than the outer main groove. It is possible to employ a tread pattern in which a plurality of outer lateral grooves extending in the tire width direction are formed at positions outside in the direction.

In this case, in order to secure the rigidity in the outer region of the tread portion and suppress the shoulder uneven wear of the tread portion, the following structure may be adopted. That is, it is preferable that the inclination angle θsl formed by the side wall of the outer lateral groove with respect to the normal line of the tread surface satisfies the relation of 0°≦θsl≦10°. The groove depth Dsl of the outer lateral groove preferably satisfies the relationship of 0.20≦Dsl/GDs≦0.90 with respect to the groove depth GDs of the outer main groove. The outer lateral groove has a raised bottom portion in a part of its longitudinal direction, and the groove depth Db at the raised portion has a relationship of 0.30≦Db/Dsl≦0.90 with respect to the groove depth Dsl of the outer lateral groove. It is preferable to be satisfied. The groove depth GDs of the outer main groove preferably satisfies the relationship of 0.80≦GDs/GDc≦1.00 with respect to the groove depth GDc of the central main groove. Further, when a plurality of central lateral grooves extending in the tire width direction are formed in the tire width direction inner side of the outer main groove in the tread portion, the groove depth Dsl of the outer lateral groove is smaller than the groove depth Dcl of the central lateral groove. It is preferable that the relationship of 0.50≦Dsl/Dcl≦1.00 is satisfied. Furthermore, it is preferable that all of the outer lateral grooves formed outside the outer main groove in the tire width direction have a groove width of 1.0 mm or less.

In the present invention, the tread portion includes a plurality of belt cords that are inclined with respect to the tire circumferential direction, and when a plurality of belt layers in which the belt cords cross each other between layers are embedded, at the tire center position of the belt cords. It is preferable that the inclination angle α with respect to the tire circumferential direction satisfies the relation of 21°≦α≦30°. By not making the inclination angle α of the belt cord at the tire center position extremely low, it is possible to suppress the increase in the rigidity of the belt layer and improve the riding comfort.

Further, the inclination angle α of the belt cord with respect to the tire circumferential direction at the tire center position and the inclination angle β of the belt cord with respect to the tire circumferential direction at the belt end position satisfy the relationship of 18°≦β<α≦30°. Is preferred. By setting the inclination angle β of the belt cord at the belt end position to be small, uneven wear of the shoulder can be effectively suppressed.

The pneumatic tire of the present invention is preferably a passenger car tire having an aspect ratio of 0.65 or less. ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to make both uneven wear resistance and riding comfort compatible in the tire for passenger cars for which improvement of riding comfort is strictly required.

In the present invention, the ground contact shape of the tread portion is measured under the condition that a tire is assembled on a regular rim and is placed vertically on a plane with a predetermined air pressure filled and a predetermined load is applied. The “regular rim” is a rim that is defined for each tire in a standard system including a standard on which the tire is based. For example, JATMA is a standard rim, and TRA is a “Design Rim” or ETRTO. If so, it is set to “Measuring Rim”. The air pressure is 230 kPa. Further, the predetermined load is a load of 40%, 75% or 100% of the maximum load capacity defined for each tire in each standard in the standard system including the standard on which the tire is based.

FIG. 1 is a meridian sectional view showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. FIG. 3 is a plan view showing a ground contact shape (40% load) of the pneumatic tire of FIG. FIG. 4 is a plan view showing a ground contact shape (75% load) of the pneumatic tire of FIG. FIG. 5 is a plan view showing a ground contact shape (100% load) of the pneumatic tire of FIG. FIG. 6 is a cross-sectional view showing a central main groove, an outer main groove, and an outer lateral groove (lug groove) formed in the tread portion of the pneumatic tire of FIG. FIG. 7 is a cross-sectional view showing outer lateral grooves (lug grooves) formed in the tread portion of the pneumatic tire of FIG. FIG. 8 is a cross-sectional view showing a central lateral groove (lug groove) formed in the tread portion of the pneumatic tire of FIG. FIG. 9 is a development view showing a tread pattern of a pneumatic tire according to another embodiment of the present invention. FIG. 10 is a cross-sectional view showing outer lateral grooves (sipe) formed in the tread portion of the pneumatic tire of FIG. FIG. 11 is a cross-sectional view showing a modified example of the outer lateral groove (sipe). FIG. 12 is a development view showing a belt layer constituting the pneumatic tire of the present invention.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 show a pneumatic tire according to an embodiment of the present invention. In FIG. 2, CL is the tire center position, Tc is the tire circumferential direction, and Tw is the tire width direction.

As shown in FIG. 1, the pneumatic tire according to the present embodiment has a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions 2 and 2 arranged on both sides of the tread portion 1. And a pair of bead portions 3, 3 arranged inside the sidewall portion 2 in the tire radial direction.

A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of carcass cords extending in the tire radial direction, and is folded back from the inside of the tire to the outside of a bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5.

On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of belt cords that are inclined with respect to the tire circumferential direction, and are arranged so that the belt cords intersect each other between the layers. A steel cord is preferably used as the belt cord forming the belt layer 7. On the outer peripheral side of the belt layer 7, at least one belt reinforcing layer 8 including a plurality of band cords oriented in the tire circumferential direction is arranged. It is desirable that the belt reinforcing layer 8 has a jointless structure in which a strip material in which at least one band cord is aligned and covered with rubber is continuously wound in the tire circumferential direction. As the band cord forming the belt reinforcing layer 8, an organic fiber cord such as nylon or aramid is preferably used.

As shown in FIG. 2, the tread portion 1 includes a pair of central main grooves 11, 11 extending in the tire circumferential direction at positions on both sides of the tire center position CL, and a tire width direction outer side than the central main grooves 11, 11. A pair of outer main grooves 12, 12 extending in the tire circumferential direction is formed at the position. The center main groove 11 and the outer main groove 12 may have a straight shape or a zigzag shape. As a result, the center land portion 20 is defined between the central main grooves 11 and 11, the middle land portion 30 is defined between the central main groove 11 and the outer main groove 12, and the outside of the outer main groove 12 is defined. A shoulder land portion 40 is defined in the.

Each of the middle land portions 30 is formed with a plurality of central lateral grooves 31 extending in the tire width direction. The central lateral groove 31 includes a central lug groove 31A having a groove width on the tread surface in the range of 1.1 mm to 9.5 mm and a central sipe 31B having a groove width on the tread surface of 1.0 mm or less. .. The central lug grooves 31A and the central sipes 31B are alternately arranged along the tire circumferential direction. Further, one of the middle land portions 30 is formed with a circumferential narrow groove 32 extending in the tire circumferential direction and having a zigzag shape.

Each of the shoulder land portions 40 is formed with a plurality of outer lateral grooves 41 extending in the tire width direction. The outer lateral groove 41 includes at least one of an outer lug groove 41A having a groove width on the tread surface in the range of 1.1 mm to 9.0 mm and an outer sipe 41B having a groove width on the tread surface of 1.0 mm or less. There is. In the case where both are mixed, the outer lug grooves 41A and the outer sipe 41B are alternately arranged along the tire circumferential direction.

3 to 5 show the ground contact shapes (40% load, 75% load, 100% load) of the pneumatic tire of FIG. 1, respectively. In the above pneumatic tire, the pneumatic tire is filled with an air pressure of 230 kPa and grounded under the condition that the maximum load capacity defined by the standard is 40%, 75%, and 100%, respectively. The maximum contact length in the circumferential direction is LA1, LB1, LC1 (mm), and the maximum contact width in the tire width direction is WA1, WB1, WC1 (mm), respectively, and maximum contact from the tire center position to the outer side in the tire width direction. External contact lengths in the tire circumferential direction at positions of 40% of the widths WA1, WB1, and WC1 are LA2, LB2, and LC2 (mm), respectively.

That is, as shown in FIG. 3, the pneumatic tire is filled with an air pressure of 230 kPa, and the maximum tire circumferential direction is obtained when the tire is grounded under the condition that a load of 40% of the maximum load capacity defined by the standard is applied. The contact length is LA1, the maximum contact width in the tire width direction is WA1, and the outer contact length in the tire circumferential direction at the position of 40% of the maximum contact width WA1 from the tire center position CL toward the outer side in the tire width direction is LA2. .. The external contact length LA2 is an average value of the measured values on both sides of the tire center position CL.

Further, as shown in FIG. 4, the pneumatic tire is filled with an air pressure of 230 kPa, and the maximum tire circumferential direction when the tire is grounded under the condition that a load of 75% of the maximum load capacity defined by the standard is applied. The contact length is LB1, the maximum contact width in the tire width direction is WB1, and the external contact length in the tire circumferential direction at a position of 40% of the maximum contact width WB1 from the tire center position CL toward the outside in the tire width direction is LB2. .. The external contact length LB2 is an average value of the measured values on both sides of the tire center position CL.

Further, as shown in FIG. 5, the pneumatic tire is filled with an air pressure of 230 kPa, and the maximum tire circumferential direction is obtained when the tire is grounded under the condition that a load of 100% of the maximum load capacity defined by the standard is applied. The contact length is LC1, the maximum contact width in the tire width direction is WC1, and the outer contact length in the tire circumferential direction at the position of 40% of the maximum contact width WC1 from the tire center position CL to the outside in the tire width direction is LC2. .. The external contact length LC2 is an average value of the measured values on both sides of the tire center position CL.

Here, the maximum ground lengths LA1, LB1, LC1 and the external ground lengths LA2, LB2, LC2 satisfy the following relationship.
1.02≦(LB2/LB1)/(LA2/LA1)≦1.25
1.00≦(LC2/LC1)/(LB2/LB1)≦1.20

Further, as shown in FIG. 4, the tread portion 1 is located in the central region Xc having a width corresponding to 53% of the maximum ground contact width WB1 centered on the tire equator (that is, the tire center position CL) and the maximum ground contact width WB1. The groove area Sc (mm ² ) of the central area Xc and the groove area Ss (mm ² ) of the outer area Xs satisfy the following relationship when divided into the outer area Xs which is on the outer side in the tire width direction from the central area Xc. ..
1.01≦Sc/Ss≦1.50

The groove area Sc of the central region Xc means the total area of the groove components formed in the central region Xc on the tire circumference, and the groove area Ss of the outer region Xs of the groove components formed in the outer region Xs on the tire circumference. It means the total area. When the groove component has a chamfer, the area of the chamfer is included in the total area of the groove component.

In the pneumatic tire described above, the groove area Sc of the central region Xc and the groove area Ss of the outer region Xs satisfy the relationship of 1.01≦Sc/Ss≦1.50, and the groove area Sc in the central region Xc is By sufficiently securing the rigidity, the rigidity in the central region Xc of the tread portion 1 can be lowered to reduce the input from the road surface and improve the riding comfort (mild feeling). On the other hand, by reducing the groove area Ss in the outer region Xs, the rigidity of the outer region Xs of the tread portion 1 can be ensured and uneven shoulder wear of the tread portion 1 can be suppressed.

Here, if Sc/S is smaller than 1.01, the groove area Sc in the central region Xc becomes insufficient, so that the effect of improving the riding comfort becomes insufficient, and conversely, if Sc/Ss is larger than 1.50. Since the groove area Ss in the outer region Xs becomes too large, the effect of suppressing shoulder uneven wear becomes insufficient. In particular, it is desirable to satisfy the relationship of 1.05≦Sc/Ss≦1.30, and further 1.13≦Sc/Ss≦1.30.

In the pneumatic tire described above, the maximum ground contact lengths LA1, LB1, LC1 and the external ground contact lengths LA2, LB2, LC2 are 1.02≦(LB2/LB1)/(LA2/LA1)≦1.25, 1.00. By satisfying the relationship of ≦(LC2/LC1)/(LB2/LB1)≦1.20 and defining the ground contact shape in consideration of load fluctuation, the effect of suppressing shoulder uneven wear and the effect of improving riding comfort are further enhanced. be able to. That is, in a general vehicle with the engine mounted in the front, (LB2/LB1)/(LA2/LA1) is set within a predetermined range in consideration of the load fluctuation of the rear-mounted tire having a relatively small load. By setting (LC2/LC1)/(LB2/LB1) within a predetermined range in consideration of the load variation of the front mounted tire having a relatively large load, the effect of suppressing shoulder uneven wear and the ride comfort can be improved. The improvement effect can be optimized.

Here, if (LB2/LB1)/(LA2/LA1) is less than 1.02, the effect of improving the riding comfort is insufficient, and conversely, if it is greater than 1.25, the effect of suppressing shoulder uneven wear is unsatisfactory. Will be enough. Similarly, if (LC2/LC1)/(LB2/LB1) is less than 1.00, the riding comfort improving effect is insufficient, and conversely, if it is more than 1.20, the shoulder uneven wear suppressing effect is insufficient. Will be enough. In particular, it is desirable to satisfy the relations of 1.03≦(LB2/LB1)/(LA2/LA1)≦1.15 and 1.02≦(LC2/LC1)/(LB2/LB1)≦1.10.

In the above pneumatic tire, it is preferable that the maximum ground contact length LB1 and the external ground contact length LB2 satisfy the relationship of 0.65≦LB2/LB1≦0.95. By controlling the ground contact shape under the condition that a load of 75% of the maximum load capacity is applied, good riding comfort can be exhibited during steady running. In particular, in the range of 0.70≦LB2/LB1≦0.88, the envelope characteristics of the tread portion 1 are improved and the riding comfort is effectively improved.

In the above pneumatic tire, the maximum contact lengths LA1, LB1, LC1 and the external contact lengths LA2, LB2, LC2 have a relationship of (LC2/LC1)/(LB2/LB1)≦(LB2/LB1)/(LA2/LA1). Good to be satisfied. In this way, the ride comfort can be improved by optimizing the ground contact shapes of the rear-mounted tire and the front-mounted tire.

As described above, in the tread portion 1, the central main groove 11 extending in the tire circumferential direction, the outer main groove 12 extending in the tire circumferential direction at a position outside the central main groove 11 in the tire width direction, and the outer main groove 12 are provided. In a pneumatic tire having a tread pattern in which a plurality of outer lateral grooves 41 extending in the tire width direction are formed at a position on the outer side in the tire width direction, the rigidity in the outer region Xs of the tread portion 1 is ensured and the tread portion is secured. In order to suppress the uneven wear of the shoulder 1, the structure as shown in FIGS. 6 to 8 can be adopted.

That is, as shown in FIG. 7, the inclination angle θsl formed by the side wall of the outer lateral groove 41 (particularly, the outer lug groove 41A) with respect to the normal line of the tread surface preferably satisfies the relationship of 0°≦θsl≦10°. By setting the inclination angle θsl of the outer lateral groove 41 in the above range, the rigidity of the outer region Xs of the tread portion 1 can be secured. Here, if θsl is smaller than 0° and the side wall has an overhang shape, the rigidity in the outer region Xs is lowered, and conversely, if it is larger than 10°, drainage is adversely affected. In particular, it is desirable to satisfy the relationship of 1°≦θsl≦8°.

As shown in FIG. 6, the groove depth Dsl of the outer lateral groove 41 preferably satisfies the relationship of 0.20≦Dsl/GDs≦0.90 with respect to the groove depth GDs of the outer main groove 12. As a result, the rigidity of the outer region Xs of the tread portion 1 can be secured. Here, if Dsl/GDs is smaller than 0.20, the drainage is adversely affected, and conversely, if it is larger than 0.90, the rigidity in the outer region Xs is reduced.

The outer lateral groove 41 (particularly, the outer lug groove 41A) has a raised bottom portion 42 in a part of its longitudinal direction, and the groove depth Db at the raised bottom portion 42 is 0. It is preferable to satisfy the relationship of 30≦Db/Dsl≦0.90. Here, the raised bottom portion 42 is arranged at a position adjacent to the outer main groove 12 and opening. By providing such a raised bottom portion 42, rigidity in the outer region Xs of the tread portion 1 can be secured. Here, if Db/Dsl is larger than 0.90, the influence on the rigidity becomes small, and conversely, if it is smaller than 0.30, the drainage property is adversely affected.

The groove depth GDs of the outer main groove 12 may satisfy the relationship of 0.80≦GDs/GDc≦1.00 with respect to the groove depth GDc of the central main groove 11. As a result, the rigidity of the outer region Xs of the tread portion 1 can be secured. Here, if GDs/GDc is smaller than 0.80, the drainage is adversely affected, and conversely, if it is larger than 1.00, it becomes difficult to secure the rigidity in the outer region Xs of the tread portion 1. ..

When a plurality of central lateral grooves 31 extending in the tire width direction are formed in the tread portion 1 at positions on the inner side of the outer main groove 12 in the tire width direction, the groove depth Dsl of the outer lateral grooves 41 is the groove depth of the central lateral groove 31. It is preferable to satisfy the relationship of 0.50≦Dsl/Dcl≦1.00 with respect to Dcl (see FIGS. 7 and 8). As a result, the rigidity of the outer region Xs of the tread portion 1 can be secured. Here, if Dsl/Dcl is smaller than 0.50, the drainage property is adversely affected, and conversely, if it is larger than 1.00, it becomes difficult to secure the rigidity in the outer region Xs of the tread portion 1. ..

FIG. 9 shows a tread pattern of a pneumatic tire according to another embodiment of the present invention. 9, the same parts as those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 9, all of the outer lateral grooves 41 formed on the outer side in the tire width direction with respect to the outer main groove 12 are composed of outer sipe 41B having a groove width of 1.0 mm or less. In this way, by setting all of the outer lateral grooves 41 to be the outer sipes 41B having a groove width of 1.0 mm or less, it is possible to secure the rigidity in the outer region Xs of the tread portion 1 and suppress shoulder uneven wear. In FIG. 9, all of the central lateral grooves 31 formed on the inner side in the tire width direction with respect to the outer main groove 12 are composed of central sipes 31B having a groove width of 1.0 mm or less.

The outer sipe 41B may have a constant groove width from the tread surface to the groove bottom as shown in FIG. 10, or as shown in FIG. 11, the chamfered portion 43 at the opening to the tread surface. May have. A similar structure can be adopted for the central sipe 31B.

In the pneumatic tire described above, when the tread portion 1 includes a plurality of belt cords C that are inclined with respect to the tire circumferential direction, and a plurality of belt layers 7 in which the belt cords C intersect each other between layers are embedded, As shown in FIG. 12, the inclination angle α of the belt cord C at the tire center position CL with respect to the tire circumferential direction may satisfy the relationship of 21°≦α≦30°. By not making the inclination angle α of the belt cord C at the tire center position CL extremely low, it is possible to suppress the increase in the rigidity of the belt layer 7 and improve the riding comfort. Here, when the inclination angle α is smaller than 21°, the rigidity of the belt layer 7 is increased, so that the effect of improving the riding comfort is deteriorated. Not at all.

Further, the inclination angle α of the belt cord C at the tire center position CL with respect to the tire circumferential direction and the inclination angle β of the belt cord C with respect to the tire circumferential direction at the belt end position BE are in a relationship of 18°≦β<α≦30°. Be satisfied with. By lowering the inclination angle β of the belt cord C at the belt end position BE, it is possible to effectively suppress shoulder uneven wear, and moreover, to reduce the inclination angle α of the belt cord C at the tire center position CL. By not making the angle extremely low, it is possible to suppress an increase in the rigidity of the belt layer 7 in the central region Xc of the tread portion 1 and maintain a good riding comfort. In particular, the difference between the inclination angle α and the inclination angle β is preferably 3° or more. A structure in which the inclination angle β of the belt cord C with respect to the tire circumferential direction at the belt end position BE is smaller than the inclination angle α of the belt cord C with respect to the tire circumferential direction at the tire center position CL is preferable. The belt cord C may be inclined at a constant angle with respect to the tire circumferential direction over the entire width, and the inclination angles α and β may be set to the same value, or α<β.

As shown in FIG. 12, the belt layer 7 has a high angle area Ac on the center side where the inclination angle of the belt cord C is α±1° and a shoulder where the inclination angle of the belt cord C is β±1°. And the width Lc of the high angle area Ac is 1/2 or more of the total width L of the belt layer 7, and the width Ls of each low angle area As is 1 of the total width L of the belt layer 7. /8 or more is preferable. By setting the high-angle area Ac on the center side and the low-angle area As on the shoulder side of the belt layer 7 as described above, the rigidity distribution of the tread portion 1 can be optimized. Here, if the width Lc of the high angle region Ac is smaller than 1/2 of the total width L of the belt layer 7, the function as the belt layer 7 is deteriorated, and the width Ls of the low angle region As is the total width of the belt layer 7. If it is smaller than 1/8 of L, the rigidity in the tire circumferential direction in the outer region Xs of the tread portion 1 cannot be sufficiently increased. The width Lc of the high angle region Ac and the width Ls of the low angle region As are set based on the total width L of each belt layer 7.

The pneumatic tire described above is suitable as a passenger car tire having an aspect ratio of 0.65 or less. In a tire for a passenger car for which improvement of riding comfort is strictly required, it becomes possible to achieve both uneven wear resistance and riding comfort.

Although the tread pattern including four main grooves in the tread portion has been described in the above-described embodiment, the present invention has a tread pattern including three main grooves in the tread portion and a V-shaped main groove in the tread portion. It can also be applied to a tread pattern including the above.

With a tire size of 205/55R16 91V, a carcass layer is mounted between a pair of bead portions, two belt layers are embedded in the tread portion on the tire radial outside of the carcass layer, and extend in the tire circumferential direction on the tread portion. A pair of central main grooves, a pair of outer main grooves extending in the tire circumferential direction at positions outside the central main groove in the tire width direction, and a pair of outer main grooves extending in the tire width direction at positions inside the tire width direction. In a pneumatic tire having a plurality of central lateral grooves and a plurality of outer lateral grooves extending in the tire width direction at a position outside the outer main groove in the tire width direction, a tire circumference at a tire center position of a belt cord. Inclination angle α, inclination angle β of the belt cord with respect to the tire circumferential direction at the belt end position, inclination angle θsl of the sidewall of the outer lateral groove, groove depth GDs of the outer main groove, groove depth Dsl of the outer lateral groove, ratio Dsl /GDs, groove depth Db at the raised portion of the outer lateral groove, ratio Db/Dsl, groove depth GDc of the central main groove, ratio GDs/GDc, groove depth Dcl of the central lateral groove, ratio Dsl/Dcl, outer lateral groove Groove width, ratio Sc/Ss of the groove area Sc of the central region to the groove area Ss of the outer region, (LB2/LB1)/(LA2/LA1), (LC2/LC1)/(LB2/LB1), LB2/LB1( Tires of Comparative Examples 1 to 3 and Examples 1 to 9 in which the rectangular ratio) was set as shown in Table 1 were manufactured.

With respect to these test tires, uneven wear resistance (shoulder region), riding comfort and wet performance were evaluated by the following test methods, and the results are also shown in Table 1.

Uneven wear resistance (shoulder area):
Each test tire was mounted on a wheel with a rim size of 16×6.5J and mounted on a friction energy measuring tester, and the average friction energy in the shoulder area of the tread was measured under the conditions of an air pressure of 230 kPa and a load of 4.5 kN. did. The measured value is obtained by measuring the frictional energy at a total of 4 points of 2 places in the tire width direction×2 places in the tire circumferential direction at intervals of 10 mm in each region and averaging them. The evaluation results are shown by an index using Comparative Example 2 as 100, using the reciprocal of the measured value. The larger the index value, the better the uneven wear resistance.

Ride:
Each test tire was mounted on a wheel with a rim size of 16×6.5J, mounted on a front-wheel drive vehicle with a displacement of 2 liters, filled with the designated air pressure of the vehicle, and a paneler on a test course with projections on the road surface. A running test was conducted by using a sensory evaluation of riding comfort (mild feeling) in consideration of the input of protrusions. The evaluation results are shown by an index with Comparative Example 1 being 100. The larger the index value, the better the riding comfort.

Wet performance:
Each test tire was mounted on a wheel with a rim size of 16×6.5J, mounted on a front-wheel drive vehicle with a displacement of 2 liters, filled with the designated air pressure of the vehicle, and a running test was conducted by a paneler on a sprinkled test course. A sensory evaluation on steering stability on wet road surface was performed. The evaluation results are shown by an index with Comparative Example 1 being 100. The larger the index value, the better the wet performance.

As can be seen from Table 1, the tires of Examples 1 to 9 were excellent in uneven wear resistance, riding comfort, and wet performance in comparison with Comparative Example 1. On the other hand, the tires of Comparative Examples 2 and 3 were not always sufficient in the effect of improving these performances.

DESCRIPTION OF SYMBOLS 1 tread part 2 sidewall part 3 bead part 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt reinforcing layer 11 central main groove 12 outer main groove 31 central lateral groove 31A central lug groove 31B central sipe 41 outer lateral groove 41A outer lug groove 41B Outside sipe

Claims (13)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged on the tire radial inner side of these sidewall portions. In the provided pneumatic tire,
The maximum contact length in the tire circumferential direction when the pneumatic tire is filled with an air pressure of 230 kPa and the tire is grounded under the conditions that loads of 40%, 75%, and 100% of the maximum load capacity defined by the standard are applied. Let LA1, LB1, LC1 be the maximum ground contact width in the tire width direction be WA1, WB1, WC1, respectively, and at the position of 40% of the maximum ground contact width WA1, WB1, WC1 from the tire center position toward the tire width direction outer side. When the external ground contact lengths in the tire circumferential direction are LA2, LB2, LC2, respectively, the maximum ground contact lengths LA1, LB1, LC1 and the external ground contact lengths LA2, LB2, LC2 are 1.02≦(LB2/LB1)/(LA2 /LA1)≦1.25, 1.00≦(LC2/LC1)/(LB2/LB1)≦1.20,
When the tread portion is divided into a central region having a width corresponding to 53% of the maximum ground contact width WB1 centering on the tire equator and an outer region within the maximum ground contact width WB1 that is outside the central region in the tire width direction. The pneumatic tire, wherein the groove area Sc of the central region and the groove area Ss of the outer region satisfy the relationship of 1.01≦Sc/Ss≦1.50. The pneumatic tire according to claim 1, wherein the maximum ground contact length LB1 and the external ground contact length LB2 satisfy the relationship of 0.65≦LB2/LB1≦0.95. The maximum ground lengths LA1, LB1, LC1 and the external ground lengths LA2, LB2, LC2 satisfy the relationship of (LC2/LC1)/(LB2/LB1)≦(LB2/LB1)/(LA2/LA1). The pneumatic tire according to claim 1 or 2, which is characterized. In the tread portion, a central main groove extending in the tire circumferential direction, an outer main groove extending in the tire circumferential direction at a position outside the central main groove in the tire width direction, and a position outside the outer main groove in the tire width direction. 4. The pneumatic tire according to claim 1, wherein a plurality of outer lateral grooves extending in the tire width direction are formed. The pneumatic tire according to claim 4, wherein an inclination angle θsl formed by a side wall of the outer lateral groove with respect to a normal line of the tread surface satisfies a relationship of 0°≦θsl≦10°. The groove depth Dsl of the outer lateral groove satisfies the relationship of 0.20≦Dsl/GDs≦0.90 with respect to the groove depth GDs of the outer main groove. Pneumatic tires. The outer lateral groove has a raised bottom portion in a part of its longitudinal direction, and the groove depth Db at the raised portion is 0.30≦Db/Dsl≦0.90 with respect to the groove depth Dsl of the outer lateral groove. The pneumatic tire according to any one of claims 4 to 6, which satisfies the relationship. 8. The groove depth GDs of the outer main groove satisfies the relationship of 0.80≦GDs/GDc≦1.00 with respect to the groove depth GDc of the central main groove. Pneumatic tire described in Crab. In the tread portion, a plurality of central lateral grooves extending in the tire width direction at a position on the inner side in the tire width direction of the outer main groove is formed, and the groove depth Dsl of the outer lateral grooves is the groove depth Dcl of the central lateral groove. On the other hand, the pneumatic tire according to any one of claims 4 to 8, which satisfies a relationship of 0.50 ≤ Dsl/Dcl ≤ 1.00. The pneumatic tire according to any one of claims 4 to 9, wherein all of the outer lateral grooves formed outside the outer main groove in the tire width direction have a groove width of 1.0 mm or less. The tread portion includes a plurality of belt cords that are inclined with respect to the tire circumferential direction, and a plurality of belt layers in which the belt cords intersect each other between layers are embedded, and the tire circumferential direction at the tire center position of the belt cords. The pneumatic tire according to any one of claims 1 to 10, wherein the inclination angle α with respect to the angle satisfies the relation of 21°≦α≦30°. The inclination angle α of the belt cord with respect to the tire circumferential direction at the tire center position and the inclination angle β of the belt cord with respect to the tire circumferential direction at the belt end position satisfy the relationship of 18°≦β<α≦30°. The pneumatic tire according to claim 11, wherein: The pneumatic tire according to claim 1, wherein the pneumatic tire is a passenger car tire having an aspect ratio of 0.65 or less.

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