JP2016215939A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can improve wet performance while enhancing rigidity of a land part in a tire circumference direction of a tread part.SOLUTION: The pneumatic tire comprises: at a tread surface at least two circumferential main grooves extending continuously in a tire circumference direction; and at least one rib-like land part which is partitioned and formed by the two circumferential main grooves adjacent to each other. The rib-like land part has a sipe with one end opened, one end of which is opened to the circumferential main grooves and the other end of which is terminated inside the rib-like land part, and a sipe with both ends closed, both ends of which are terminated inside the rib-like land part. A relation of a depth of the sipe with one end opened, a depth of the sipe with both ends closed and depths of the circumferential main grooves satisfies a relation: the depths of the circumferential main grooves≥the depth of the sipe with both ends closed>the depth of the sipe with one end opened.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire.

  Conventionally, in a pneumatic tire, by improving the rigidity in the tire circumferential direction (circumferential rigidity) with respect to a land portion partitioned by a circumferential main groove or a width direction groove of the tread portion, It has been proposed to improve performance (for example, Patent Document 1).

JP-A-11-147407

  Here, by improving the land portion rigidity in the tire circumferential direction in the tread portion, for example, braking performance, drivability, wear resistance, and the like can be improved. In such a tire, wet performance is further improved. It is demanded.

  Then, an object of this invention is to provide the pneumatic tire which can improve wet performance, improving the land part rigidity of the tire circumferential direction in a tread part.

The pneumatic tire of the present invention is formed on the tread tread with at least one circumferential main groove extending continuously in the tire circumferential direction and at least one circumferential main groove adjacent to each other. A rib-shaped land portion, wherein the rib-shaped land portion has one end opening sipe having one end opened in the circumferential main groove and the other end terminated in the rib-shaped land portion. , Both ends closed sipe that ends both ends in the rib-like land portion, and the relationship between the depth of the one end opening sipe, the depth of the both ends closed sipe, and the depth of the circumferential main groove,
The depth of the circumferential main groove ≧ the depth of the closed sipe at both ends> the depth of the open sipe at one end.
According to the pneumatic tire of the present invention, it is possible to improve the wet performance while enhancing the land portion rigidity in the tire circumferential direction in the tread portion.

In the present invention, “sipe” means that a tire is mounted on a rim and an internal pressure of 30 kPa, which is a pressure sufficient to maintain the shape of the tire, is applied (hereinafter referred to as “the tire is mounted on the rim, In the “no-load state in which an internal pressure of 30 kPa, which is a pressure to maintain the shape, is applied” is also referred to as “low-pressure no-load state”), the opening width to the tread surface is 2 mm or less. The “groove” refers to a groove whose opening width to the tread surface exceeds 2 mm in a low-pressure no-load state.
Hereinafter, unless otherwise specified, the dimensions and the like of each element of the tread tread are measured on the development view of the tread tread in a low-pressure no-load state.
The above-mentioned “rim” is an industrial standard effective for the area where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) JATMA YEAR BOOK, and in Europe, ETRTO (The European Tire and RIM Technical Organization's STANDARDDS MANUAL, TRA (The Tire and Rim Association, Inc.) YEAR BOOK, etc. in the United States, etc. Rim, TRA's YEAR BOOK (Design Rim) (i.e., the above "rim" refers to the industry standard in the future in addition to the current size) Examples of “sizes to be described in the future” include the sizes described as “FUTURE DEVELOPMENTS” in STANDARDDS MANUAL 2013 edition of ETRTO.) In the case of a size not described in the standard, it means a rim having a width corresponding to the tire bead width.

Further, in the present invention, the “rib-shaped land portion” refers to a land portion where both ends open to a circumferential main groove that defines the land portion, and no groove is provided across the land portion.
In the present invention, the “depth” of the sipe or the circumferential main groove is the average of the depths measured along the extending direction if the sipe or the circumferential main groove depth is changed. If it is a circumferential main groove, it indicates the depth at the portion where the one-end opening sipe opens.

  Here, in the pneumatic tire of the present invention, it is preferable that the both-end closed sipes are small circular holes as viewed from the tread surface. According to this configuration, the wet performance can be improved while further increasing the rigidity of the land portion in the tire circumferential direction in the tread portion.

  In the present invention, the “small hole” refers to one that extends from the tread and opens to the tread surface.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can improve wet performance can be provided, improving the land part rigidity of the tire circumferential direction in a tread part.

It is a tire width direction schematic sectional drawing of the tire width direction half part of the pneumatic tire which concerns on the 1st Embodiment of this invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. 1. It is a figure which shows the cross section which follows the a-a 'line | wire of the pneumatic tire of FIG. FIG. 3 is a development view showing a tread pattern in which the arrangement pitch of sipes is changed in the tire circumferential direction in the tread pattern of the pneumatic tire shown in FIG. 2. FIG. 5 is a development view showing a modification of the tread pattern of the pneumatic tire shown in FIG. 4. It is a perspective view of the pneumatic tire shown in FIG. (A) It is a figure for demonstrating the wet performance of a wide radial tire, (b) It is a figure for demonstrating the wet performance of a radial radial tire. It is a tire width direction schematic sectional drawing of the tire width direction half part of the pneumatic tire which concerns on the 2nd Embodiment of this invention. It is a schematic plan view showing an example of a belt structure. It is a schematic plan view which shows the other example of a belt structure. It is a schematic plan view which shows another example of a belt structure. It is a tire width direction schematic sectional drawing of the tire width direction half part of the pneumatic tire which concerns on the 3rd Embodiment of this invention. It is a tire width direction schematic partial sectional drawing of the tire width direction half part of the pneumatic tire which concerns on the 4th Embodiment of this invention.

  Hereinafter, the pneumatic tire according to the first embodiment of the present invention (hereinafter also simply referred to as “tire”) will be described in detail with reference to the drawings. The following description and drawings are examples for explaining a tire according to the present invention, and the present invention is not limited to the described and illustrated forms.

As shown in FIG. 1, the pneumatic tire 1 according to the present invention includes, for example, a carcass 22 composed of a carcass ply of a radial arrangement cord straddling a toroidal shape between a pair of bead portions 21, and an outer side in the tire radial direction of the carcass 22. And a tread rubber 23 provided at the front.
More specifically, the tread portion 24, the pair of sidewall portions 25 extending inward in the tire radial direction continuously to the side portions of the tread portion 24, and the inner end of each sidewall portion 25 in the tire radial direction are continuous. A bead portion 21 and a carcass 22 made of one or more carcass plies that extend in a toroidal shape from one bead portion 21 to the other bead portion 21 and reinforce each of the above portions. A bead core is embedded in the bead portion 21. Further, as a reinforcing member for the bead portion 21, a rubber chafer is provided on the outer surface of the bead portion 21, and a belt 26 composed of one or more belt layers is provided on the crown portion of the carcass 22. A tread rubber 23 is provided on the outer side in the tire radial direction of the crown portion of the carcass 22.

  2 and 6, the tread surface T is provided with at least two circumferential main grooves 3 extending continuously in the tire circumferential direction. In the example shown in the figure, two circumferential main grooves 3 extending in a straight line in the development view along the tire circumferential direction are provided, but three or more circumferential main grooves 3 may be provided. . Further, in FIG. 2, the circumferential main groove 3 shows an extending form extending linearly along the tire circumferential direction, but the circumferential main groove 3 may be continuously extended in the tire circumferential direction. Well, for example, it can be an extended form such as a zigzag shape or a wave shape.

  Further, in this embodiment, at least one rib-like land portion 4 that is partitioned by two circumferential main grooves 3 adjacent to each other is provided. In the illustrated example, one rib-like land is provided. The portion 4 is located at the center of the tread tread T, and specifically, the center in the width direction of the rib-like land 4 is located on the tire equatorial plane CL. Further, a shoulder land portion 5 located on the shoulder side of the tread tread T, which is defined by the circumferential main groove 3 located on the outermost side in the tire width direction of the circumferential main groove 3 and the tread ground contact end E, is provided.

  Here, in this embodiment, the rib-like land portion 4 is continuous in the tire circumferential direction, and specifically, the rib-like shape having both ends open to the circumferential main groove 3 that defines the land portion. There is no groove that crosses the land portion 4. Further, from the viewpoint of securing the circumferential rigidity of the rib-shaped land portion, the rib-shaped land portion 4 crosses the rib-shaped land portion 4 whose both ends open to the circumferential main groove 3 that defines the land portion. It is preferable not to have a sipe. Moreover, it is more preferable that the rib-like land portion 4 has neither a groove nor a sipe extending including the center line in the width direction of the rib-like land portion 4.

  Further, specifically in this embodiment, the rib-like land portion 4 has one end opening sipe 6 having one end opened in the circumferential main groove 3 and the other end terminating in the land portion, and the rib-like land portion 4 The both ends closed sipes 7 are disposed at both ends. In addition, the one-end opening sipe 6 of this embodiment includes a circumferential sipe portion 62 positioned closer to the center in the width direction of the rib-like land portion 4 than the both-end closed sipe 7, and the circumferential sipe portion 62 extending from the circumferential sipe portion 62. And a width-direction sipe portion 61 opening in the main groove 3.

In this embodiment, a plurality of one-end open sipes 6 and both-end closed sipes 7 are provided in the tire circumferential direction. Specifically, each one-end opening sipe 6 has a pitch length L (to be described later, the pitch length of the one-end opening sipe 6 is referred to as “pitch length L”) in the rib-like land portion 4 in the tire circumferential direction. The both-end closed sipes 7 are arranged side by side in the tire circumferential direction as a set of one (one) or more with respect to one one-end open sipe 6. ing. Further, in the illustrated example, one end opening sipe 6 that opens in the circumferential main groove 3 on one side in the width direction of the rib-like land portion 4 and the circumferential main groove 3 on the other side in the width direction of the rib-like land portion 4 open. A plurality of one-end opening dies 6 are arranged side by side in the tire circumferential direction in one rib-like land portion 4 together with both-end closing sipes 7.
The pitch length L may be constant without changing in the tire circumferential direction, or may not be constant changing in the tire circumferential direction.

One end of the width direction sipe portion 61 is one end of the one end opening sipe 6, and the other end of the width direction sipe portion 61 is more specifically in the rib-shaped land portion 4. Is located in the rib-like land portion 4 on one end side of the width-direction sipe portion 61 from the center in the width direction of the rib-like land portion 4. The width direction sipe portion 61 extends in the rib-like land portion 4 at an angle of preferably 30 ° or less with respect to the tire width direction.
Further, the circumferential sipe portion 62 of the one-end opening sipe 6 has one end of the circumferential sipe portion 62 connected to the other end of the width-direction sipe portion 61, and the other end of the circumferential sipe portion 62 is rib-shaped land. It is located in the portion 4, more specifically, in the rib-like land portion 4 on the one end side of the one-end opening sipe 6 in the tire width direction from the center in the width direction of the rib-like land portion 4. Further, the circumferential sipe portion 62 extends in the rib-like land portion 4 at an angle of preferably 30 ° or less, more preferably 20 ° or less (0 ° in this example) with respect to the tire circumferential direction.
In addition, the width direction sipe portion 61 and the circumferential sipe portion 62 of the one-end opening sipe 6 may be located on the center line in the width direction of the land portion. Specifically, the one-end opening sipe 6 is formed in the rib-shaped land portion. 4 may extend across the width direction center line of the rib-like land portion 4 from one side in the width direction toward the other side.

Further, the both-end closed sipes 7 are not opened directly and indirectly (in communication with the circumferential main groove 3 via other sipes or grooves) with respect to the circumferential main groove 3. The both-end closed sipe 7 is located closer to the circumferential main groove 3 side where the one end opening sipe 6 opens than the circumferential sipe portion 62 of the one end opening sipe 6 (the circumferential sipe portion 62 of the one end opening sipe 6 is It is located on the side of the circumferential main groove 3 opposite to the circumferential main groove 3 where the one-end opening sipe 6 opens, rather than the both-end closed sipes 7.
In this embodiment, the both-end closed sipes 7 are provided with circular sipes, that is, circular small holes as viewed from the tread surface.

  In this embodiment, a set of one-end open sipes 6 and both-end closed sipes 7 disposed on one half of the land portion on one side in the width direction with respect to the center line in the width direction of the rib-like land portion 4, and the width direction One set of one-end opening sipe 6 and both-end closed sipe 7 disposed in the other half of the land portion are displaced from each other in the tire circumferential direction, and one point on the center line in the width direction of the rib-like land portion 4 Although it is point-symmetric with respect to the center, it can be arranged arbitrarily. Further, one end opening sipes 6 and both end closing sipes 7 are arranged in each half of the land portions on both sides in the width direction with respect to the center line in the width direction of the rib-like land portion 4, but one end opening sipes only on one side. 6 and both-end closed sipes 7 may be disposed, and an arbitrary sipes may be disposed on the other side. Furthermore, although the shape of the width direction sipe portion 61 and the circumferential direction sipe portion 62 of the one-end opening sipe 6 of this embodiment is linear in the tread surface view, a curved shape or the like can be made arbitrary.

In this embodiment, the relationship between the depth of the one-end opening sipe 6, the depths of the both-end closed sipe 7, and the depth of the circumferential main groove 3 is
The depth of the circumferential main groove 3 ≧ the depth of the both-end closed sipe 7> the depth of the one-end open sipe 6.
In this embodiment, the depths of the one-end open sipe 6 and the both-end closed sipe 7 can be 1.5 to 7.0 mm and 2.0 to 9.0 mm, respectively, and the rib-like land portion The depth of the circumferential main groove 3 that defines 4 can be set to 5.0 to 9.0 mm.

Here, the operation and effect of the pneumatic tire 1 of this embodiment will be described below.
In the tire 1 of this embodiment, at least one land portion formed on the tread tread T is partitioned by two circumferential main grooves 3 adjacent to each other, and the rib-like land portion 4 is continuous in the tire circumferential direction. Thus, the circumferential rigidity (circumferential shear rigidity) of the land portion 4 can be increased, and for example, performance such as wear resistance, braking performance, drivability, and wet performance can be improved.
In addition, in the rib-like land portion having high circumferential rigidity, the water film between the land portion and the road surface is not sufficiently removed during wet traveling, and the land portion is sufficiently followed by the unevenness of the road surface. Because it is difficult, the actual contact area when the tire touches the road surface tends to decrease. Therefore, the tire 1 of this embodiment has one end opening sipe 6 and both ends closed sipe 7, thereby improving the water film removal property and the road surface following property while maintaining high rigidity, thereby increasing the actual contact area. As a result, wet performance can be improved.
Specifically, the provision of the one-end opening sipe 6 facilitates removal of the water film, and can reduce the compression rigidity (rigidity in the tire radial direction) and improve the road surface followability. In addition, since the sipe which both ends open with respect to the circumferential direction main groove 3 is not arrange | positioned, circumferential direction rigidity is not reduced excessively and circumferential direction rigidity can be maintained. Further, the arrangement of both ends closed sipes 7 can reduce the compression rigidity (rigidity in the tire radial direction) and improve the road surface followability.
Furthermore, since both ends of the closed sipe 7 are not opened in the circumferential main groove 3 at both ends, it is difficult to reduce the circumferential rigidity. Therefore, the depth of the both ends closed sipe 7 is deeper than the depth of the one end opened sipe 6. Can be set. Accordingly, the depth of the one-end opening sipe 6, the depth of the both-end closed sipe 7, and the depth of the circumferential main groove 3 are: depth of the circumferential main groove 3 ≧ depth of both-end closed sipe 7> one-end opening sipe 6. By setting the depth, both ends closed sipe 7 remain even in the late wear stage of tire 1 after tire 1 is worn and the above-described effect due to one-end opening sipe 6 becomes difficult to be achieved, and the effect of improving wet performance is maintained. Can be made. Moreover, since the depth of the both-end closed sipes 6 is not made deeper than the depth of the circumferential main groove 3, the circumferential rigidity of the rib-like land portion 4 is not excessively reduced.
As described above, according to the tire 1 of the present invention, the water-land removal is performed while improving the land rigidity in the circumferential direction of the tread portion 24 and improving the performance such as wear resistance, braking performance, drivability, and wet performance. The wet performance can be improved by reducing the compression rigidity and improving the road surface followability.

  The both-end closed sipes 7 can have any shape, for example, a linear shape or a curved shape with both ends terminating in the land, or a cross-shaped shape with all ends terminating in the land. However, from the viewpoint of suppressing a decrease in the shear shear rigidity in the width direction, the length measured in the direction along the tire circumferential direction of the both-end closed sipe 7 is the tire circumference of the circumferential sipe portion 62 of the one-end opening sipe 6. The length measured in the direction along the direction is preferably shorter, and the both-end closed sipes 7 are more preferably circular small holes as seen in the tread surface as shown in this embodiment.

In this embodiment, it is more preferable that the rib-like land portion 4 has neither a groove nor a sipe extending including the center line in the width direction of the rib-like land portion 4. Thereby, a shear stress can be made uniform in the tire width direction of the rib-like land part 4, and wet performance can be improved.
Specifically, the rib-like land portion is crushed by a load at the time of tire contact, and the tread rubber of the rib-like land portion bulges into the circumferential main groove (crushing), and the end portion in the width direction of the rib-like land portion The stress is concentrated on the side, and therefore, the shear stress in the width direction is large at the end portion in the width direction.
Here, if the circumferential rigidity of the rib-shaped land portion is uniform in the width direction, for example, when braking the tire, the shear stress in the tire circumferential direction is uniformly applied in the tire width direction, but the rib-shaped land portion Since the shear stress in the tire width direction is relatively higher on the width direction end side than on the center side, the resultant force of the shear stress in the tire width direction and the tire circumferential direction is on the width direction end side of the rib-like land portion. It was larger than the center side. That is, the width direction end portion side of the rib-like land portion is such that the resultant force of the shear stress is more likely to exceed the maximum frictional force compared to the central side. For example, on a wet road surface, the end portion in the width direction of the rib-like land portion It was easy to slip because of the side (it could not be said that the slip limit of the rib-like land was large).
On the other hand, the rib-like land portion 4 has neither a groove nor a sipe extending including the center line in the width direction of the rib-like land portion 4 and is wider than the center in the width direction of the rib-like land portion 4 By having the one end opening sipe 6 and the both ends closing sipe 7 on the outer side in the direction, the rigidity at the center in the width direction of the rib-like land portion 4 can be relatively increased. And the width direction edge part side of the rib-like land part 4 becomes relatively smaller than the center side in the width direction of the rib-like land part 4, for example, and the shear stress in the tire circumferential direction at the time of braking of the tire 1 is reduced. Since the shear stress in the tire width direction is relatively higher at the width direction end portion side of the rib-like land portion 4 than the center side by the crushing of the rib-like land portion 4, the resultant force of the shear stress in the tire width direction and the tire circumferential direction is expressed in a rib shape. The land portion 4 can be made uniform in the tire width direction. Therefore, it is difficult for the resultant force of the shear stress to exceed the maximum frictional force in the width direction of the rib-like land portion 4, for example, even when the road surface is wet, triggered by the width direction end portion side of the rib-like land portion 4. Slip can be suppressed, that is, the slip limit can be increased.

  In this embodiment, as shown in FIG. 2, it is preferable that the one-end opening sipe 6 is composed of a width-direction sipe portion 61 and a circumferential-direction sipe portion 62. The actual ground contact area can be improved. Further, in such a case, from the viewpoint of suppressing the decrease in the shear rigidity in the width direction, the circumferential sipe portion 62 of the one-end opening sipe 6 is at a distance of 25% or more of the land width W of the rib-like land portion 4. It is preferable that the part 4 is located away from the width direction end.

  Further, as shown in FIG. 2, it is preferable that the both-end closed sipe 7 is located on the side of the circumferential main groove 3 where the one-end opening sipe 6 opens, rather than the circumferential sipe portion 62 of the one-end opening sipe 6. Thereby, the fall of the width direction shear rigidity of the rib-like land part 4 can be suppressed more, for example, the fall of cornering power can be suppressed more. In such a case, the both-end closed sipes 7 are preferably disposed within the range in the tire circumferential direction where the one-end open sipes 6 are located in the rib-like land portion 4. When the both-end closed sipes 7 are arranged outside the range in the tire circumferential direction where the one-end open sipe 6 is located, one end-opened sipes adjacent to each other in the tire circumferential direction can be obtained, although the compression rigidity reduction effect by the both-end closed sipes 7 can be obtained. This is because there is a possibility that the effect of removing the water film by the one-end opening sipe 6 is not sufficient, and it is difficult to sufficiently improve the wet property.

Here, in this embodiment, as described above, the plurality of one-end opening sipes 6 arranged in the tire circumferential direction are arranged side by side in the tire circumferential direction with the pitch length L in the rib-like land portion 4. The one end opening sipe 6 is disposed with a pitch length L, and the tire circumferential direction of one pitch length L and one end opening sipe 6 and both ends closed sipe 7 disposed within the range of one pitch length L. The relationship with the sipe component total length Ls is
L ≦ Ls ≦ 3L
It is preferable that According to this configuration, the compression rigidity can be sufficiently reduced and the cornering power can be sufficiently maintained.
The “pitch length L” means from one end in the tire circumferential direction of one end opening sipe 6 to the corresponding one end in the tire circumferential direction of one end opening sipe 6 adjacent to the one end opening sipe 6 in the tire circumferential direction. The length on the development measured along the tire circumferential direction. Further, “the tire circumferential direction sipe component total length Ls of the one end opening sipe 6 and the both ends closed sipe 7 disposed in the range of one pitch length L” means that one pitch length L in the rib-like land portion 4. Is a length measured along the tire circumferential direction by projecting the one-end open sipe 6 and the both-end closed sipe 7 arranged in the tire width direction, and there is an overlapping portion in the projected sipe Means the length obtained by adding the overlapped portions by the overlapped amount.
In addition, from the viewpoint of reducing the compression rigidity and maintaining the cornering power, as shown in FIG. 2, one end opening sipes 6 are respectively provided for the two circumferential main grooves 3 that define the rib-like land portions 4. At the same time, the length of the one end opening sipe 6 measured along the tire circumferential direction is the pitch length L, and the length of the both ends closed sipe 7 measured along the tire circumferential direction is half or less of the pitch length L. It is preferable.

Further, as in this embodiment, when the plurality of one-end opening sipes 6 arranged in the tire circumferential direction are arranged side by side in the tire circumferential direction with a pitch length L in the rib-like land portion 4, The relationship between the land portion width W of the portion 4 and the tire width direction sipe component total length Ws of the one end opening sipe 61 in the land portion 4 disposed within the range of one pitch length L is as follows.
0.6W ≦ Ws ≦ 1.2W
It is preferable that
According to this configuration, it is possible to improve wet performance while suppressing a decrease in circumferential rigidity. Specifically, by increasing the total width Ws of the sipe component in the tire width direction within one pitch length L to 0.6 times or more the land width W, the wet performance is improved as the water film removability increases. By making the land width W 1.2 times or less, it is possible to suppress a decrease in circumferential rigidity.
“Land width W” refers to the length of the rib-like land 4 measured along the tire width direction. Further, “the tire width direction sipe component total length Ws of the one-end opening sipe 61 in the land portion 4 arranged in the range of one pitch length L” is arranged in the range of one pitch length L. It is the length measured along the tire width direction by projecting the one-end opening sipe 61 in the land portion 4. When the one-end opening sipe 61 in the range is projected in the tire circumferential direction, for example, If there is an overlapping portion in the projected sipe due to the presence of a plurality of pieces or the sipe being bent, the length is obtained by adding the overlapping portion to the overlapped portion.

  As described above, in the rib-like land portion 4, by making the tire circumferential direction sipe component total length Ls equal to or greater than the pitch length L, the compression rigidity of the rib-like land portion 4 can be sufficiently reduced, and the tire circumference By making the directional sipe component total length Ls not more than three times the pitch length L, the cornering power can be sufficiently maintained.

Moreover, in this one-end opening sipe 6, as in this embodiment, the relationship between one pitch length L and the land portion width W of the rib-like land portion 4 is
0.5W ≦ L ≦ 1.5W
It is preferable that According to this configuration, it is possible to improve wet performance while suppressing a decrease in circumferential rigidity.

Further, in the rib-like land portion 4, the arrangement pitch length L of the one-end opening sipes 6 is preferably 0.5 to 3.0% of the tire circumferential length at the center in the width direction of the rib-like land portion 4. More preferably, it is 1.0 to 2.5%. Moreover, it is preferable that the land part width W of a rib-like land part is 15 to 35% of the tread width TW, More preferably, it is 18 to 22%.
Here, the “tire circumference” is a length measured in a low-pressure no-load state, and the “tread width” is defined for each vehicle in which the tire 1 is incorporated in the rim and the tire is mounted. Is the length measured along the tire width direction between the tread grounding ends E on both sides with the internal pressure filled, and the “tread grounding end” is the outermost position of the tread tread surface T in the tread width direction. The “tread tread” is the tire 1 that is incorporated in the rim described above and filled with the internal pressure specified for each vehicle on which the tire is mounted, and the tire 1 is applied with a load of 75% of the maximum load capacity. It is an outer peripheral surface over the entire circumference of the tire 1 that comes into contact with the road surface when rolling. In addition, the state of “filling the internal pressure specified for each vehicle on which a tire is mounted” is simply described in JATMA YEAR BOOK (JATMA), etc. The air pressure (maximum air pressure) corresponding to the maximum load capacity of the wheel. Further, the “maximum load capacity” refers to the maximum load capacity of a single wheel in the applicable size / ply rating described in JATMA or the like or described in the future.
In the case of a size not described in the industry standard, the “tire circumference” is a length measured in a low-pressure no-load state, and the “tread width” is the tire 1 on the rim described above. It is the length measured along the tire width direction between the tread grounding ends E on both sides with the internal pressure specified for each vehicle equipped with tires installed, and the “tread grounding end” is the tread. The tread tread is the outermost position of the tread T in the tread width direction. The “tread tread” is assumed to be the maximum number of occupants of the tire 1 that is incorporated in the rim described above and applies the internal pressure specified for each vehicle on which the tire is mounted. The entire circumference of the tire 1 that comes into contact with the road surface when the tire 1 is rolled with a load of 75% of the load applied to the most heavily loaded tire among the four wheels. It is the outer peripheral surface. In addition, the state of “filling the internal pressure defined for each vehicle on which a tire is mounted” means that the air pressure corresponding to the load applied to the tire that is most loaded among the four wheels when the maximum number of passengers is assumed. Refers to the state.
The air here can be replaced with an inert gas such as nitrogen gas or the like.

Further, in the present invention, when the both-end closed sipes 7 are small holes as shown in this embodiment, at least one small hole is disposed within one pitch length L in the rib-like land portion 4. In addition, the opening area S (mm ² ) of one small hole to the tread surface T is preferably in the range of 0.1 ≦ S ≦ 4.
In the illustrated example, in the rib-like land portion 4, the small holes are the width direction sipe portion 61 and the circumferential sipe portion 62 of the one end opening sipe 6, and the one end opening sipe adjacent to the one end opening sipe 6 in the tire circumferential direction. Two pieces are arranged in the land portion surrounded by 6.

In the land half, at least one small hole is disposed within one pitch length L, and the opening area S (mm ² ) of one small hole to the tread surface T is 0.1 ≦ S. By setting it within the range of ≦ 4, the compression rigidity can be further reduced while maintaining the circumferential rigidity of the land portion, and therefore the wettability can be further improved. Specifically, since the opening area S of the small hole is 0.1 mm ² or more, the compression rigidity can be sufficiently reduced. In addition, since the opening area S is 4 mm ² or less, it is possible to prevent the area of the land portion of the rib-like land portion 4 and thus the actual ground contact area from being lowered, and the reduction in the wet performance due to the decrease in the actual ground contact area. Can be prevented.
When a plurality of small holes are arranged within the range of one pitch length L, the opening area S (mm ² ) of one small hole is an average value of the plurality of small holes.

  In the rib-like land portion 4, the number of the small holes is not particularly limited. However, in the land half portion of the rib-like land portion 4, the pitch length L (mm) and one pitch length L ( mm) is preferably 0.1 ≦ N / L ≦ 0.3 in relation to the number N of small holes arranged in the range of mm). By making N / L (pieces / mm) 0.1 or more, the compression rigidity can be sufficiently reduced, and by making N / L (pieces / mm) 0.3 or less, rib-like land The area of the portion 4 can be prevented from decreasing, and the cornering power can be prevented from decreasing.

Here, the cross-sectional shape in the tire width direction of the rib-like land portion 4 of the present embodiment will be described.
3, the half part of the cross section (tire width direction cross section) shape along aa 'of the rib-shaped land part 4 shown in FIG. 2 is shown.
In this embodiment, the outer contour (tread tread surface T side) of the rib-like land portion 4 has a different radius of curvature R and can be formed by a plurality of arcs convex in the tire radial direction (in the illustrated example). Two arcs). Moreover, the said some circular arc can make curvature radius R1, R2 small from the width direction center side of the rib-shaped land part 4 toward the width direction end side. In addition, the connecting portion 81 between the outer contour of the rib-like land portion 4 and the groove wall of the circumferential main groove 3 can be smoothly curved, but as shown in FIG. From the viewpoint of increasing the size, it is preferable that the corner is formed to be angular.

  The groove wall of the circumferential main groove 3 that defines the rib-like land portion 4 has a groove wall of 0 ° to the direction perpendicular to the tread surface so that the groove width increases from the groove bottom to the opening. It is preferable to incline at an angle θ of 20 °. Moreover, it is preferable that the connection part 82 connected with the groove bottom and groove wall of the circumferential direction main groove 3 is a tire width direction cross section, and is smoothly connected with the convex shape inside the tire radial direction.

By the way, in this embodiment, when the one-end opening sipes 6 are arranged in the tire circumferential direction with the pitch length L, as shown in FIG. 4, the pitch length L of the one-end opening sipes 6 is set on the tire circumference. The pattern can be changed. Specifically, the tread pattern shown in FIG. 4 is a rib-like land portion 4 and one-end opening sipes 6 arranged at a pitch length L satisfy L ≦ Ls ≦ 3L in all the following patterns P1 to P3. However, the pitch length L is changed. The patterns P1 to P3 each have a relatively long pitch length L, and the tread pattern shown in FIG. 4 is provided with the patterns P1 to P3 repeatedly in order. In the patterns P1 and P2, two small holes are arranged in the range of one pitch length L, whereas in the pattern P3, three small holes are arranged in the range of one pitch length L. Individually arranged.
In the example of FIG. 4, three types of patterns in which the pitch length L is changed in the tire circumferential direction are shown, but it is arbitrary to use two types or four or more types of patterns. Moreover, although the patterns P1 to P3 are repeatedly provided in order, the pattern arrangement order is arbitrary. For example, after only one pattern is repeatedly arranged a plurality of times, another pattern can be arranged once or a plurality of times. .

  Further, in the tire 1 shown in FIG. 4, two circumferential main grooves 3 are provided on the tread surface T, and one rib-like land portion 4 defined by the two circumferential main grooves 3 is provided. However, as shown in FIG. 5, the tread tread surface T is provided with three or more circumferential main grooves 3 (three in the example of FIG. 5) and is partitioned by the three or more circumferential main grooves 3. Applying the sipe configuration of the present invention to all of the plurality of land portions as the rib-like land portion 4, or using the sipe configuration of the present invention as a part of the plurality of land portions as the rib-like land portion 4 It can also be applied.

  In addition, a plurality of sipes and small holes are repeatedly arranged in the tire circumferential direction in the shoulder land portion 5, but various sipes and grooves can be arbitrarily disposed in the shoulder land portion 5.

  Here, in this embodiment, the size of the tire is not particularly limited, but is preferably used as a pneumatic radial tire for a passenger car having the following size.

In a no-load state in which the tire is incorporated into the rim and the internal pressure is 250 kPa or more, when the tire cross-sectional width SW is less than 165 (mm), the tire cross-sectional width SW (mm) and the outer diameter OD (mm) When the ratio SW / OD is 0.26 or less and the tire cross-sectional width SW is 165 (mm) or more, the relationship between the tire cross-sectional width SW (mm) and the outer diameter OD (mm) is
2.135 × SW + 282.3 ≦ OD
(Hereinafter, it is also referred to as satisfying the relational expression (1). In addition, the tire size in this relation is also referred to as a narrow-width large-diameter size). Since the tire has the above-described relationship, the tire has a narrow width and a large diameter, can improve the rolling resistance performance of the tire (reduce the rolling resistance value), and can reduce the weight of the tire.
Further, the internal pressure during rolling of the tire is preferably 250 kPa or more, and more preferably 250 to 350 kPa. In a narrow large diameter size, the contact length tends to increase, but by setting it to 250 kPa or more, the increase in the contact length can be suppressed, the deformation amount of the tread rubber can be reduced, and the rolling resistance can be further reduced.
Further, from the viewpoint of reducing the rolling resistance value of the tire and reducing the weight of the tire, when the internal pressure during rolling of the tire is 250 kPa or more, the cross-sectional width SW (mm) and the outer diameter OD ( mm) is preferably −0.0187 × SW ² + 9.15 × SW−380 ≦ OD (hereinafter also referred to as satisfying relational expression (2)).
The “cross-sectional width SW” and “outer diameter OD” of the tire are the cross-sectional widths specified in JIS D 4202-1994, respectively, in a no-load state in which the tire is mounted on the rim and the internal pressure is 250 kPa or more. Refers to the outer diameter.

When the tire is a tire having a small width and a large diameter having the tire cross-sectional width SW and the outer diameter OD, the dynamic storage elastic modulus E ′ at 30 ° C. of the tread rubber is 6.0 to 12. It is preferably 0 MPa. In a tire having a narrow width and a large diameter, by setting the dynamic storage elastic modulus E ′ of the tread rubber within the specific range, the wet friction coefficient μ can be improved, so that the wet performance can be improved. . In addition, by setting the dynamic storage elastic modulus E ′ as described above, it is possible to improve cornering power during cornering and improve steering stability. In addition, from the same viewpoint, the dynamic storage elastic modulus E ′ is more preferably 7.9 to 12.0 MPa, and further preferably 8.0 to 11.0 MPa.
When the tire has a narrow width and a large diameter, the loss tangent tan δ at 60 ° C. of the tread rubber is preferably 0.05 to 0.15. Thereby, rolling resistance performance can be improved.

The dynamic storage elastic modulus E ′ (MPa) and loss tangent tan δ (ratio of dynamic loss elastic modulus (E ″) and dynamic storage elastic modulus (E ′) (E ″ / E ′)) Is a value measured on the vulcanized rubber under the conditions of initial load: 160 g, initial strain: 1%, vibration frequency: 50 Hz on a test piece of thickness: 2 mm, width: 5 mm, length: 20 mm, The dynamic storage elastic modulus E ′ is a value measured at a temperature of 30 ° C. unless otherwise specified (hereinafter, “dynamic storage elastic modulus E ′ at 30 ° C.” is simply referred to as “dynamic storage elastic modulus E ′. The loss tangent tan δ is a value measured at a temperature of 60 ° C. unless otherwise specified (hereinafter, “loss tangent tan δ at 60 ° C.” may be simply referred to as “loss tangent tan δ”). ).
The “tread rubber” means a rubber that does not include a member such as a belt that is arbitrarily included in the tread portion.

Tread rubber is a rubber containing arbitrarily known fillers, anti-aging agents, vulcanizing agents, vulcanization accelerators, process oils, scorch preventing agents, zinc white, stearic acid and the like in addition to conventionally known rubber components. The composition can be formed by kneading and vulcanizing according to a conventional method.
The kneading conditions are not particularly limited, and using a Banbury mixer, roll, internal mixer, etc., depending on the compounding formulation, the input volume to the kneading apparatus, etc., the rotational speed of the rotor, ram pressure, kneading temperature, as appropriate. The kneading time may be adjusted.
Moreover, as conditions at the time of vulcanizing a rubber composition, vulcanization temperature can be 100-190 degreeC, for example. The vulcanization time can be, for example, 5 to 80 minutes.

Examples of the rubber component of the tread rubber include modified or unmodified styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), polyisoprene rubber (IR), isobutylene isoprene rubber (IIR), and halogenated butyl rubber. , Synthetic rubbers such as styrene-isoprene copolymer rubber (SIR) and chloroprene rubber (CR), and natural rubber (NR).
A method for modifying a conjugated diene polymer such as SBR and BR is not particularly limited, and a conventionally known method can be used. For example, a method described in International Publication No. 2008/050845 (conjugated diene polymer) And the like, a method in which a modifier is reacted with the active terminal and a condensation reaction involving the modifier in the presence of a titanium-based condensation accelerator is used.
As the conjugated diene polymer, for example, a copolymer of 1,3-butadiene and styrene is preferably exemplified.
Examples of the modifier include N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane, N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane, 1-trimethylsilyl-2-ethoxy-2-methyl-1- Aza-2-silacyclopentane is preferred.
Examples of the titanium-based condensation accelerator include tetrakis (2-ethyl-1,3-hexanediolato) titanium, tetrakis (2-ethylhexoxy) titanium, titanium di-n-butoxide (bis-2,4-pentanedionate). Are preferable.
You may use the rubber component mentioned above individually by 1 type or in combination of 2 or more types.

Examples of the filler include conventionally known carbon black, silica, calcium carbonate, talc, and clay. You may use said filler individually by 1 type or in combination of 2 or more types.
When the tire has a narrow large diameter size, the tire includes a rubber composition that forms tread rubber at least including a rubber component and a filler. In the rubber composition, with respect to 100 parts by mass of the rubber component, It is preferable that 50-100 mass parts of fillers are contained. Thereby, there exists an advantage that it is excellent in abrasion resistance and workability. From the viewpoint of wear resistance and workability, the filler is more preferably contained in an amount of 55 to 85 parts by mass, and more preferably 75 to 85 parts by mass with respect to 100 parts by mass of the rubber component. . Moreover, it is more preferable that 50-90 mass parts of fillers are contained with respect to 100 mass parts of diene polymer (diene rubber).

When the tire has a narrow large diameter size, the tire preferably contains silica, and the silica is contained in an amount of 25 to 100 parts by mass with respect to 100 parts by mass of the rubber component. Thereby, there exists an advantage that it is excellent in wet performance. From the viewpoint of wet performance, the silica is more preferably contained in an amount of 50 to 75 parts by mass, and more preferably 60 to 75 parts by mass with respect to 100 parts by mass of the rubber component.
When silica is used as the filler, the silica may be treated with a silane coupling agent.

By the way, in order to set E ′ to 6.0 to 12.0 MPa as described above, for example, among the diene polymer 100 phr, the modified S-SBR is in the range of 20 to 70 phr, and the filler 50 to 50 Of 80 phr, silica may be appropriately changed within the range of 30 to 80 phr.
In order to set tan δ to 0.05 to 0.15 as described above, for example, among 100 phr of the diene polymer, NR is in the range of 0 to 20 phr, and the modified S-SBR is in the range of 20 to 70 phr. And silica should just be suitably changed in the range of 30-80 phr among the fillers 50-80 phr.
“Phr” refers to the amount (parts by mass) of various components based on 100 parts by mass of the rubber component.

  When the tire has a narrow large diameter, the tire size of the pneumatic radial tire for passenger cars is specifically 105 / 50R16, 115 / 50R17, 125 / 55R20, 125 / 60R18, 125 / 65R19, 135 / 45R21, 135 / 55R20, 135 / 60R17, 135 / 60R18, 135 / 60R19, 135 / 65R19, 145 / 45R21, 145 / 55R20, 145 / 60R16, 145 / 60R17, 145 / 60R18, 145 / 60R19, 145 / 65R19, 155 / 45R18, 155 / 45R21, 155 / 55R18, 155 / 55R19, 155 / 55R21, 155 / 60R17, 155 / 65R13, 155 / 65R18, 155 / 70R17, 155 / 70R19, 1 5 / 45R22, 165 / 55R16, 165 / 55R18, 165 / 55R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 45R23, 175 / 55R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 175 / 65R15, 185 / 45R22, 185 / 50R16, 185 / 50R20, 185 / 55R19, 185 / 55R20, 185 / 60R17, 185 / 60R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, 195 / 60R19, 195 / 65R17, 205 / 50R21, 205 / 55R16, 205 / 55R20, 205 / 60R16, 205 / 60R18, 215 / 0R21,215 / 60R17,225 / 65R17 are mentioned as examples.

Here, when the tire has a narrow width and a large diameter, it is preferable to reduce the amount of grooves occupying the tread from the viewpoint of achieving both wet performance and other performance. Specifically, the groove volume ratio (groove volume V2 / tread rubber volume V1) is preferably 20% or less, and the negative ratio (ratio of groove area to tread tread area) is 20% or less. It is preferable. These values are lower than the standard values for conventional size pneumatic radial tires for passenger cars.
In order to improve the wet performance, it is a general idea to increase the groove amount. However, a pneumatic radial for a passenger car having a narrow and large diameter that satisfies the above relational expression (1) and / or (2). In the case of a tire, since the width W of the ground contact surface is narrowed, water is easily discharged in the tire width direction as shown in FIG. 7B in comparison with FIG. 7A. For this reason, even if the groove amount is reduced, the wet performance is maintained, and other performance such as cornering power can be improved by improving the rigidity of the land portion.
The groove volume ratio is, for example, the tire diameter at the center in the tire width direction at the inner side in the tire width direction from the both ends in the width direction of the maximum width belt layer having the maximum width in the tire width direction of the belt layer. When the volume of the tread rubber on the outer side in the tire radial direction from the outermost reinforcing member (belt layer and belt reinforcing layer) is V1, and the total volume of grooves formed on the tread surface is V2, the ratio is defined as V2 / V1. Is done.

  Here, when the tire has a narrow width and a large diameter and the vehicle mounting direction of the tire is specified, between the tire mounting direction half of the vehicle mounting inner side and the vehicle mounting outer side with the tire equatorial plane CL as a boundary. A difference may be provided in the negative rate.

  Among the land portions, various configurations can be adopted for the shoulder land portion that can be formed into a rib shape that is divided by the outermost circumferential main groove in the tire width direction and the tread ground contact end E. For example, in the tire in which the vehicle mounting direction is specified, the width in the tire width direction of the shoulder land portion on the outer side and the inner side of the vehicle mounting can be changed. In consideration of steering stability, it is preferable that the width in the tire width direction of the shoulder land portion outside the vehicle mounting is larger than the width in the tire width direction of the shoulder land portion inside the vehicle mounting.

In the case of a tire having a narrow large diameter, as shown in FIG. 8, a straight line parallel to the tire width direction passing through the point P on the tread surface in the tire equatorial plane CL in the tire width direction cross section is m1, When the straight line parallel to the tire width direction passing through the contact edge E ′ is m2, the distance in the tire radial direction between the straight line m1 and the straight line m2 is the height _LCR , and the tire tread width is TW ′, the ratio L _CR / TW ′ is preferably 0.045 or less. By setting the ratio L _CR / TW ′ within the above range, the crown portion of the tire is flattened (flattened), the contact area increases, the input (pressure) from the road surface is relaxed, and the tire radial direction It is possible to reduce the deflection rate of the tire and improve the durability and wear resistance of the tire.
Here, the “grounding end E ′” refers to each vehicle on which a tire is mounted on a rim, filled with a maximum air pressure specified for each vehicle on which the tire is mounted, and placed vertically on a flat plate. It refers to both end points in the tire width direction on the contact surface with the flat plate when a weight corresponding to the specified maximum load is applied.

  In the case of a tire having a narrow width and a large diameter, the tread rubber may be formed by laminating a plurality of different rubber layers in the tire radial direction. As the plurality of rubber layers, those having different tangent loss, modulus, hardness, glass transition temperature, material and the like can be used. Moreover, the ratio of the thickness in the tire radial direction of the plurality of rubber layers may be changed in the tire width direction, or only the circumferential main groove bottom or the like may be a rubber layer different from the periphery thereof.

  The tread rubber may be formed of a plurality of rubber layers different in the tire width direction. As the plurality of rubber layers, those having different tangent loss, modulus, hardness, glass transition temperature, material and the like can be used. In addition, the ratio of the width in the tire width direction of the plurality of rubber layers may be changed in the tire radial direction, and only in the vicinity of the circumferential main groove, only in the vicinity of the tread ground contact E, only in the shoulder land portion, in the center land portion. Only a limited part of the region, such as only, may be a rubber layer different from its surroundings.

  The tire having a narrow width and a large diameter preferably has an inclined belt layer formed of a rubberized layer of a cord extending in an inclined manner with respect to the tire circumferential direction. In this case, the inclined belt layer may be only one layer. . However, in the case of a tire having a narrow and large diameter, if only one inclined belt layer is used, the shape of the ground contact surface at the time of turning tends to be distorted. Therefore, an inclined belt layer extending in a direction in which cords cross each other between two or more layers is used. A belt structure in which two belt layers form an inclined belt layer is most preferable.

  In a tire having a narrow width and a large diameter, the width in the tire width direction of the maximum width inclined belt layer having the largest width in the tire width direction is preferably 90% to 115% of the tread width TW. % To 105% is particularly preferred.

  In a tire having a narrow width and a large diameter, a metal cord, particularly a steel cord is most commonly used as a belt cord of the inclined belt layer, but an organic fiber cord can also be used. The steel cord is mainly composed of steel and can contain various trace contents such as carbon, manganese, silicon, phosphorus, sulfur, copper, and chromium.

  In a tire having a narrow width and a large diameter, a monofilament cord or a cord obtained by twisting a plurality of filaments can be used as the belt cord of the inclined belt layer. Various designs can be adopted for the twist structure, and various cross-sectional structures, twist pitches, twist directions, and distances between adjacent filaments can be used. Furthermore, the cord which twisted the filament of a different material can also be used, and it does not specifically limit as a cross-sectional structure, Various twisted structures, such as a single twist, a layer twist, a double twist, can be taken.

  In a narrow-width large-diameter tire, the inclination angle of the belt cord of the inclined belt layer is preferably 10 ° or more with respect to the tire circumferential direction.

In a tire having a narrow and large diameter, the inclination angle of the belt cord of the inclined belt layer is a high angle, specifically, 35 ° or more with respect to the tire circumferential direction, and particularly in a range of 55 ° to 85 ° with respect to the tire circumferential direction. It is preferable that
This is because by setting the inclination angle to 35 ° or more, the rigidity in the tire width direction can be increased, and in particular, the steering stability performance during cornering can be improved. Moreover, it is because the rolling resistance performance can be improved by reducing the shear deformation of the interlayer rubber.

A tire having a narrow width and a large diameter may have a circumferential belt composed of one or more circumferential belt layers outside the inclined belt layer in the tire radial direction.
When the inclination angles θ1 and θ2 of the belt cords of the inclined belt layer are 35 ° or more, the circumferential belt has a tire circumferential rigidity per unit width of the central region C including the tire equatorial plane CL, and other regions. It is preferably higher than the tire circumferential rigidity per unit width.
FIG. 9 schematically shows an example of a belt structure, in which circumferential belt layers 53 and 114 are laminated on the outer side in the tire radial direction of the inclined belt layers 111 and 112, and in the central region C, the circumferential belt layers 113 and 114 overlap each other in the tire radial direction.
For example, as shown in FIG. 9, by increasing the number of circumferential belt layers in the central region C as compared with other regions, the tire circumferential rigidity per unit width of the central region C is determined as the unit of other regions. It can be higher than the tire circumferential rigidity per width.
Many of the tires in which the belt cord of the inclined belt layer is inclined at 35 ° or more with respect to the tire circumferential direction are in a high frequency range of 400 Hz to 2 kHz in vibration modes such as primary, secondary and tertiary in the cross-sectional direction Since the tread surface has a shape that vibrates greatly uniformly, a large radiated sound is generated. Therefore, locally increasing the tire circumferential rigidity of the tread tire width direction center region makes it difficult for the tread tire width direction center region to spread in the tire circumferential direction, and the tread tread surface spread in the tire circumferential direction is suppressed. As a result, radiated sound can be reduced.
Further, as described above, in a tire having increased rigidity in the tire circumferential direction in the central region including the tire equatorial plane CL, the tread has a land portion continuous in the tire circumferential direction in the region including at least the tire equatorial plane CL of the tread surface. It is preferable to have. If the circumferential main groove is disposed on or near the tire equator plane CL, the rigidity of the tread in the region may be reduced, and the contact length in the land portion defining the circumferential main groove may be extremely short. Therefore, it is preferable to dispose land portions (rib-shaped land portions) continuous in the tire circumferential direction over a certain region including the tire equatorial plane CL from the viewpoint of improving noise performance without reducing cornering power.

FIG. 10 schematically shows another example of the belt structure, in which one circumferential belt layer 123 is laminated on the outer side in the tire radial direction of the two inclined belt layers 121 and 122.
In the case of a tire having a narrow width and a large diameter, as in the example shown in FIG. 10, when the inclination angle of the belt cord of the inclined belt layer is 35 ° or more, the inclined belt layer has a width in the tire width direction. An inclination angle θ1 with respect to the tire circumferential direction of a cord that includes at least two different inclined belt layers and forms the widest inclined belt layer, and an inclination angle θ2 with respect to the tire circumferential direction of a cord that forms the narrowest inclined belt layer 35 ° ≦ θ1 ≦ 85 °, 10 ° ≦ θ2 ≦ 30 °, and θ1> θ2 are preferably satisfied.
Many tires having an inclined belt layer having a belt cord inclined at an angle of 35 ° or more with respect to the tire circumferential direction are vibration modes such as primary, secondary, and tertiary in the cross-sectional direction in a high frequency range of 400 Hz to 2 kHz. Since the tread surface has a shape that vibrates greatly uniformly, a large radiated sound is generated. Therefore, if the tire circumferential direction rigidity of the tread tire width direction central region is locally increased, the tread tire width direction central region becomes difficult to spread in the tire circumferential direction, and the spread of the tread surface in the tire circumferential direction is suppressed. As a result, radiated sound can be reduced.

FIG. 11 schematically shows another example of the belt structure, in which one circumferential belt layer 133 is laminated on the outer side in the tire radial direction of the two inclined belt layers 131 and 132.
In a tire having a narrow width and a large diameter, the circumferential belt layer is preferably highly rigid. More specifically, the circumferential belt layer includes a rubberized layer of a cord extending in the tire circumferential direction, and the Young's modulus of the cord is expressed as Y (GPa). When the number of driving is n (lines / 50 mm), the circumferential belt layer is m layers, and X = Y × n × m, it is preferable that 1500 ≧ X ≧ 750. In the case of a tire having a narrow width and a large diameter, local deformation occurs in the tire circumferential direction with respect to the input when turning from the road surface, and the ground contact surface is substantially triangular, that is, the contact length in the circumferential direction depends on the position in the tire width direction. Tends to be a shape that changes greatly. On the other hand, by using a highly rigid circumferential belt layer, the ring rigidity of the tire is improved, and deformation in the tire circumferential direction is suppressed. Deformation is also suppressed, and the ground contact shape is less likely to change. In addition, the eccentric rigidity is promoted by improving the ring rigidity, and the rolling resistance is simultaneously improved. The effect of improving the rolling resistance is particularly large in a narrow-width large-diameter tire.

  Further, when a highly rigid circumferential belt layer is used as described above, the inclination angle of the inclined belt layer with respect to the tire circumferential direction of the belt cord is preferably a high angle, specifically 35 ° or more. When a highly rigid circumferential belt layer is used, the contact length may be reduced depending on the tire due to the increased rigidity in the tire circumferential direction. Therefore, by using a high-angle inclined belt layer, it is possible to reduce the out-of-plane bending rigidity in the tire circumferential direction, increase the elongation in the tire circumferential direction of the rubber when the tread surface is deformed, and suppress the decrease in the contact length. it can.

  Further, in a tire having a narrow large diameter, a wavy cord may be used for the circumferential belt layer in order to increase the breaking strength. Similarly, in order to increase the breaking strength, a high elongation cord (for example, an elongation at break of 4.5 to 5.5%) may be used.

  Furthermore, various materials can be used for the circumferential belt layer in a tire having a narrow width and a large diameter. Typical examples include rayon, nylon, polyethylene naphthalate (PEN), and polyethylene terephthalate (PET). Aramid, glass fiber, carbon fiber, steel, etc. can be used. From the viewpoint of weight reduction, an organic fiber cord is particularly preferable.

  Here, in the case of a tire having a narrow width and a large diameter, the cord of the circumferential belt layer can be a monofilament cord, a cord in which a plurality of filaments are combined, or a hybrid cord in which filaments of different materials are combined. .

  In the case of a tire having a narrow width and a large diameter, the number of driving in the circumferential belt layer can be in a range of 20 to 60 pieces / 50 mm, but is not limited to this range.

  Furthermore, a tire having a narrow width and a large diameter can have a distribution of rigidity, material, number of layers, driving density, etc. in the tire width direction, for example, the number of layers of the circumferential belt layer only at the end in the tire width direction. On the other hand, the number of circumferential belt layers can be increased only in the center portion.

  Further, in a tire having a narrow large diameter, the circumferential belt layer can be designed to be wider or narrower than the inclined belt layer. For example, the width in the tire width direction can be 90% to 110% of the maximum width inclined belt layer having the largest width in the tire width direction among the inclined belt layers.

  Here, it is particularly advantageous from the viewpoint of manufacturing that the circumferential belt layer is configured as a spiral layer.

  In the case of a tire having a narrow width and a large diameter, it is possible not to provide a circumferential belt layer.

  Various structures can be employed for the carcass line in a tire having a narrow width and a large diameter. For example, in the tire radial direction, the carcass maximum width position can be brought closer to the bead portion side or closer to the tread side. For example, the carcass maximum width position can be provided in the range of 50% to 90% in comparison with the tire cross-section height from the bead base portion to the outer side in the tire radial direction.

  In addition, in a tire having a narrow width and a large diameter, the carcass can adopt various structures. For example, the number of driving carcass can be in the range of 20 to 60 pieces / 50 mm, but is not limited thereto.

  Furthermore, for example, the folded end of the carcass can be positioned on the inner side in the tire radial direction of the end of the bead filler in the tire radial direction, and the folded end of the carcass is positioned in the tire radial direction from the outer end of the bead filler in the tire radial direction or the maximum tire width position. It can be located on the outer side, and in some cases, it can extend to the inner side in the tire width direction from the end in the tire width direction of the inclined belt layer. Furthermore, when the carcass is constituted by a plurality of carcass plies, the position of the carcass folded end in the tire radial direction can be varied. In addition, a structure in which a plurality of bead core members are sandwiched or wound around a bead core without using a carcass folded portion can be employed.

In a tire having a narrow width and a large diameter, it is preferable to make the tire side portion thinner. “To thin the tire side portion” means, for example, that the cross-sectional area S1 of the bead filler in the tire width direction is 1 to 4 times the cross-sectional area S2 of the bead core in the tire width direction. Further, the ratio Ts / Tb between the gauge Ts of the sidewall portion at the tire maximum width portion and the bead width Tb at the tire radial direction center position of the bead core can be 15% or more and 40% or less. Further, the ratio Ts / Tc between the gauge Ts of the sidewall portion in the tire maximum width portion and the diameter Tc of the carcass cord can be set to 5 or more and 10 or less.
The gauge Ts is the sum of the thicknesses of all members such as rubber, a reinforcing member, and an inner liner. In the case where the bead core is divided into a plurality of small bead cores by the carcass, the distance between the innermost end in the width direction and the outermost end of all the small bead cores is Tb.

  In a tire having a narrow large diameter, the tire maximum width position can be provided in the range of 50% to 90% in comparison with the tire cross-section height from the bead base portion to the outer side in the tire radial direction.

  A tire having a narrow width and a large diameter may have a structure having a rim guard.

  The tire of a narrow-width large-diameter tire may have a structure without a bead filler.

  In a tire having a narrow width and a large diameter, the bead core can adopt various structures such as a circular cross section and a polygonal cross section. In addition to a structure in which the carcass is wound around the bead core, a structure in which the carcass is sandwiched between a plurality of bead core members may be employed.

  In a tire having a narrow width and a large diameter, a rubber layer, a cord layer, or the like can be further provided in the bead portion for the purpose of reinforcement or the like. Such additional members can be provided at various positions with respect to the carcass and the bead filler.

In the case of a tire having a narrow width and a large diameter, it is preferable to increase the thickness of the inner liner from the viewpoint of reducing in-vehicle noise of 80-100 Hz. Specifically, it is preferably about 1.5 mm to 2.8 mm thicker than usual (about 1.0 mm).
It has been found that narrow-width and large-diameter tires tend to deteriorate 80-100 Hz in-vehicle noise especially when high internal pressure is used. By increasing the thickness of the inner liner, it is possible to improve vibration damping and reduce 80-100 Hz in-vehicle noise. In addition, since the loss which contributes to rolling resistance is small compared with other members, such as a tread, an inner liner can improve noise performance, suppressing deterioration of rolling resistance to the minimum.

  In a tire having a narrow width and a large diameter, the inner liner can be formed by a film layer mainly composed of a resin in addition to a rubber layer mainly composed of butyl rubber.

  In the case of a tire having a narrow width and a large diameter, in order to reduce cavity resonance noise, a porous member can be disposed on the tire inner surface, or electrostatic flocking can be performed.

  A tire having a small width and a large diameter may be provided with a sealant member for preventing air leakage during puncture on the tire inner surface.

  The tire having a narrow width and a large diameter may be a side-reinforced run-flat tire having a crescent-shaped reinforcing rubber in the tire side portion.

In the case of a side-reinforced run-flat tire in a narrow-width large-diameter tire, both the run-flat durability and the fuel efficiency can be realized by the structure in which the side portion is simplified. This is because, in the case of a pneumatic radial run flat tire for a passenger car having a narrow width and a large diameter, the deformation of the side portion and the tread portion is relatively small during the run flat running, while the relative deformation from the shoulder portion to the buttress portion. This is based on the knowledge that deformation increases. This deformation is in contrast to the relatively large deformation at the side portion in the conventional size.
Due to such a characteristic deformation of the narrow width and large diameter size, the run-flat durability can be sufficiently secured even with the simplified structure, and the fuel efficiency can be further improved.
A specific simplification technique can be achieved by satisfying at least one of the following conditions (i) to (iii).
FIG. 12 is a tire width direction cross-sectional view of a tire according to an embodiment of the present invention when the tire of the present invention is a run-flat tire having a narrow width and a large diameter.
(I) As shown in FIG. 12, the folded end A of the carcass folded portion is located on the inner side in the tire radial direction from the tire maximum width position P. (ii) The tire is assembled in the rim, filled with a predetermined internal pressure, The maximum tire radial direction length of the side reinforcing rubber 141 in the tire width direction cross section in the reference state as a load is H1, and the outermost point in the tire radial direction of the bead filler is connected to the outermost point in the tire radial direction of the bead core. When the length of the line segment is H2, 1.8 ≦ H1 / H2 ≦ 3.5 is satisfied. (Iii) A standard state in which a tire is incorporated into a rim, a predetermined internal pressure is filled, and no load is applied. When the maximum length in the tire radial direction of the side reinforcing rubber 141 in the tire width direction cross section at this time is H1 (mm), the relational expression 10 (mm) ≦ (SW / OD) × H1 ≦ 20 (mm) is satisfied. Fulfill.

In the case of a side-reinforced run-flat tire in a narrow-width large-diameter tire, by arranging the outer circumferential main groove on the outermost side in the tire width direction from the tire equatorial plane CL in the tire width direction, Further improvement in durability can be realized. This is because, in the case of a pneumatic radial run flat tire for a passenger car having a narrow width and a large diameter, the deformation of the side portion and the tread portion is relatively small during the run flat running, while the relative deformation from the shoulder portion to the buttress portion. This is based on the knowledge that deformation increases. This deformation is in contrast to the relatively large deformation at the side portion in the conventional size. For such a deformation characteristic of the narrow and large diameter, the outermost circumferential main groove in the tire width direction is arranged closer to the tire equatorial plane CL, so that the buttress can be lifted from the shoulder land during run-flat running. The ground contact property over the part can be improved, and the contact pressure is relieved. As a result, run flat durability can be further improved.
FIG. 13 is a tire width direction cross-sectional view of a tire according to another embodiment of the present invention when the tire of the present invention is a run-flat tire having a narrow width and a large diameter.
Specifically, the tire has a maximum width in the tire width direction among one or more belt layers in a cross section of the tire width direction in a reference state in which the tire is incorporated into the rim, filled with a predetermined internal pressure, and is unloaded. The half width in the tire width direction of the belt layer is WB, and the outer circumferential main groove 151 on the outermost side in the tire width direction among one or more circumferential main grooves from the tire width direction end of the belt layer having the largest width in the tire width direction. When the distance in the tire width direction to the center position in the tire width direction is WG, it is preferable that the relational expression 0.5 ≦ WG / WB ≦ 0.8 is satisfied.

  As mentioned above, although one Embodiment of this invention was described with reference to drawings, the pneumatic tire of this invention is not limited to said example, A change can be added suitably.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

  In order to confirm the effect of the present invention, tires of the following Examples 1 to 3 and Comparative Examples 1 to 7 were respectively prototyped.

[Example 1]
The tire of Example 1 is a radial tire having a tire size of 165 / 60R19 as shown in FIG. 5, and has the configuration shown in Table 1 and includes three main circumferentially on the tread surface T. A groove is provided. Further, in the tire of Example 1, a plurality of small holes as one end opening sipes and both end closing sipes are arranged in the tire circumferential direction in the two rib-like land portions defined by the three circumferential main grooves. ing. The circumferential main groove has a groove width of 7.5 mm and a groove depth of 7 mm, the one-end opening sipe has a width of 0.7 mm and a depth of 4 mm, and the both-end closed sipes have a diameter of 1.5 mm. The depth is 5 mm.
[Example 2]
The tire of Example 2 is the same as the tire of Example 1 except that the depth of the circumferential main groove is changed from 7 mm to 5 mm.
[Example 3]
The tire of Example 3 is the same as the tire of Example 1 except that the small holes serving as both-end closed sipes existing in the range of the pitch length L are changed to one straight line (vertical groove). The longitudinal groove is a sipe extending along the tire circumferential direction, and has a width of 0.7 mm and a depth of 6 mm.
[Comparative Example 1]
The tire of Comparative Example 1 is a radial tire having a tire size of 195 / 65R15, and has the specifications shown in Table 1. The tread tread T has three circumferential main grooves. . Further, in the tire of Comparative Example 1, in two land portions that are defined by the circumferential main groove, a communication groove that traverses the land portion having both ends opened to the circumferential main groove is disposed, and one end opening sipes and None of the ends are closed. The circumferential main groove has a groove width of 9 mm and a groove depth of 6.5 mm.
[Comparative Example 2]
In the tire of Comparative Example 2, in two rib-like land portions that are defined by three circumferential main grooves, communication grooves that traverse the land portions that are open at both ends in the circumferential main groove are disposed. The tire is the same as that of the tire of Example 1 except that neither the opening sipe nor the both-end closed sipe is provided. The communication groove has a groove width of 2 mm and a groove depth of 5 mm.
[Comparative Examples 3 and 4]
In the tires of Comparative Examples 3 and 4, the two rib-like land portions defined by the three circumferential main grooves were changed in the presence or absence of the one-end opening sipes and the both-end closed sipes. This is the same as tire No. 1.
[Comparative Examples 5 to 7]
The tires of Comparative Examples 5 to 7 are the same as the tire of Example 1 except that the depth of the one-end opening sipe and the both-end closed sipe are changed as shown in Table 1.

Each of the above test tires was evaluated by the following method.
[Wet performance]
Each of the above test tires was mounted on a rim under the following conditions, filled with internal pressure, mounted on the vehicle, and then traveled on a wet road surface at a speed of 80 km / h. Then, after running in the above state, the stop distance (m) when full braking is performed is measured, and the average deceleration (m / s ² ) (average deceleration a, initial speed v, mass m, stop at this time When the distance ^L, from mv 2/2 = maL, can be calculated as ^{a =} v 2 / 2L) was calculated. The evaluation results are indicated by an index with the tire described in Comparative Example 1 as 100, with the value for each test tire being the reciprocal. A larger index value means better wet performance.
Examples 1 to 3, Comparative Examples 2 to 7: Rim size 5.5 J-19, internal pressure 300 kPa
Comparative Example 1: Rim size 6.5 J-15, internal pressure 220 kPa
[Rolling resistance performance]
Each of the above test tires is mounted on the rim under the same conditions as the wet performance measurement conditions, filled with the internal pressure, loaded with the maximum load specified for each tire, and adjusted to a drum rotation speed of 100 km / h. The rolling resistance value was measured.
The evaluation results are indicated by an index with the tire described in Comparative Example 1 as 100, with the value for each test tire being the reciprocal. It means that rolling resistance performance is so good that this index value is large.
[Cornering power]
The cornering power was measured using a flat belt type cornering tester. Specifically, each of the above test tires was mounted on a rim and filled with internal pressure under the same conditions as the wet performance measurement conditions, and measurement was performed by attaching a flat belt cornering tester. The cornering force was measured with a belt speed of 100 km / h and a slip angle (SA) between the rolling direction of the tire and the circumferential direction of the drum of 1 °.
The evaluation results are shown as an index with the cornering force of Comparative Example 1 as 100. The larger the index value, the better the cornering force at the slip angle, that is, the cornering power at the slip angle.

  From Table 1, it can be seen that Examples 1 to 3 have improved wet performance compared to the tires of Comparative Examples 1 to 7.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can improve wet performance can be provided, improving the land part rigidity of the tire circumferential direction in a tread part.

1: pneumatic tire, 21: bead part, 22: carcass, 23: tread rubber, 24: tread part, 25: sidewall part, 26: belt, 3: circumferential main groove, 4: rib-like land part, 5 : Shoulder land part, 6: one end opening sipe, 61: width direction sipe part, 62: circumferential sipe part, 7: both ends closed sipe part, 81: connecting part, 82: connecting part, 111, 112, 121, 122, 131 132: Inclined belt layer, 113, 114, 123, 133: Circumferential belt layer, 141: Side reinforcing rubber, 151: Circumferential main groove, E: Tread grounding end, L: Pitch length, P1 to P3: Pattern, R1, R2: radius of curvature, T: tread surface, TW: tread width, W: land width of rib-like land

Claims (2)

On the tread surface, at least two circumferential main grooves extending continuously in the tire circumferential direction, and at least one rib-like land portion defined by the two circumferential main grooves adjacent to each other, A pneumatic tire provided,
The rib-shaped land portion has one end opening sipe having one end opened in the circumferential main groove and the other end terminating in the rib-shaped land portion, and both end closed sipes terminated at both ends in the rib-shaped land portion. Have
The relationship between the depth of the one end opening sipe, the depth of the both ends closed sipe and the depth of the circumferential main groove is as follows:
A pneumatic tire characterized in that the depth of the circumferential main groove ≧ the depth of the closed sipe at both ends> the depth of the open sipe at one end.   The pneumatic tire according to claim 1, wherein the both-end closed sipes are circular small holes as viewed from the tread surface.