JP6946658B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

For example, the pneumatic tire described in Patent Document 1 has a sipe extending in the tire width direction and juxtaposed in the tire circumferential direction on the shoulder block, and a secondary groove intersecting the sipe and extending in the tire circumferential direction to divide the shoulder block. And are provided. Since the auxiliary groove divides the shoulder block, drainage is improved and steering stability on a wet road surface is improved.

Japanese Unexamined Patent Publication No. 2013-189128

By the way, if the sipe is separated in the tire width direction in the center of the land portion, it is possible to secure the block rigidity and prevent the sipe from being clogged with snow or ice. However, in the part where the sipe is separated, the ground pressure is locally higher than in the part where the sipe is provided, and cracks occur from the separated sipe end or the separated sipe end is chipped. As a result, there is a problem that the load durability performance deteriorates.

In the pneumatic tire described in Patent Document 1, the above problem tends to be alleviated by providing the sub-groove, but since the contact pressure peaks at the edge portion of the sub-groove, the deterioration of the load durability performance is improved. It's difficult.

The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of improving load durability while ensuring performance on ice and snow.

In order to solve the above-mentioned problems and achieve the object, the pneumatic tire according to one aspect of the present invention includes a tread portion, a plurality of circumferential grooves extending along the tire circumferential direction and a plurality of circumferential grooves arranged in the tire width direction. A plurality of land portions formed by at least the circumferential grooves and lined up in the tire width direction, a circumferential fine groove provided on the tread surface of the land portion in a longitudinal direction along the tire circumferential direction, and the above. A plurality of sipe provided on the tread surface of the land portion in the areas on both sides of the circumferential narrow groove in the tire width direction and extending along the tire width direction and arranged side by side in the tire circumferential direction, and the circumferential thin groove. It is provided with chamfers provided on at least the opening edges on both sides of the groove in the lateral direction.

The part between the separated sipes has higher rigidity than the part where the sipes are formed, and the ground pressure received from the road surface at the time of touchdown is locally higher, so that the ends of the separated sipes are cut or chipped. It becomes easier and the load durability performance decreases. On the other hand, according to the pneumatic tire according to one aspect of the present invention, in the tread surface of the land portion, a circumferential groove is formed in a longitudinal direction in the tire circumferential direction in the portion between the separated sipes. Therefore, the circumferential groove lowers the rigidity and lowers the ground pressure. However, at least at the opening edge in the lateral direction of the circumferential groove, the contact pressure increases at the edge portion of the opening edge as compared with the others, and a peak of the contact pressure occurs at the edge portion. Therefore, according to the pneumatic tire according to one aspect of the present invention, the chamfered portions are formed at least on both sides of the circumferential groove in the lateral direction, so that the contact pressure peaks at the edge portion. It is possible to improve the load endurance performance because the ground pressure can be made uniform over the entire land area. Moreover, by providing the circumferential groove, the edge component increases along the tire circumferential direction due to the opening edge of the circumferential groove and the drainage property is improved, so that the performance on ice (steering stability performance on ice road surface). Can be improved. Moreover, it has snow performance (steering stability performance on snow road surface) due to sipes. As a result, the load endurance performance can be improved while ensuring the performance on ice and the performance on snow.

In the pneumatic tire according to one aspect of the present invention, the shoulder land portion in which the circumferential groove and the land portion provided with the sipe and the chamfer portion are arranged on the outermost side in the tire width direction in the tread portion. Is preferable.

The shoulder land area has a higher contact pressure than other land areas, especially when changing lanes or cornering, and the contact pressure is higher during the separation of the sipes and at the edge on the short side of the circumferential groove. .. Therefore, according to the pneumatic tire according to one aspect of the present invention, it is possible to remarkably obtain the effect of improving the load durability performance while ensuring the performance on ice and the performance on snow in such a shoulder land portion.

In the pneumatic tire according to one aspect of the present invention, the groove width W0 in the lateral direction of the circumferential narrow groove satisfies 0.5 mm ≦ W0 ≦ 3.0 mm, and the ground contact width D0 of the land portion and the land. It is preferable that the tire width direction distance D1 between the circumferential groove for partitioning the portion and the circumferential narrow groove satisfies the relationship of 0.4 × D0 ≦ D1 ≦ 0.6 × D0.

According to this pneumatic tire, if the groove width W0 of the circumferential groove is 0.5 mm or more, the opening area of the circumferential groove is secured and water between the road surface and the tread surface is sufficiently removed at the time of touchdown. can do. On the other hand, by setting the groove width W0 of the circumferential groove to 3.0 mm or less, the ground contact area of the tread surface of the land portion is secured, the ground contact property between the road surface and the tread surface is improved at the time of ground contact, and the performance on ice is deteriorated. It can be suppressed. Moreover, since the ground pressure tends to be high in the vicinity of the center of the land portion in the tire width direction due to high rigidity, the relationship of 0.4 × D0 ≦ D1 ≦ 0.6 × D0 is satisfied and the circumferential groove is landed. By arranging it near the center of the part, the contact pressure near the center in the tire width direction of the land part can be reduced and the contact pressure of the land part can be made uniform, and the effect of improving the load durability performance can be remarkably obtained. Can be done.

In the pneumatic tire according to one aspect of the present invention, it is preferable that the sipe does not communicate with the circumferential groove.

When the sipe communicates with the circumferential groove, the sipe becomes continuous in the tire width direction through the circumferential groove, and the rigidity of the land portion tends to decrease, so that the effect of improving the load durability performance is small. Therefore, according to the pneumatic tire according to one aspect of the present invention, since the sipe does not communicate with the circumferential groove, the decrease in the rigidity of the land portion can be suppressed, and the effect of improving the load durability performance is remarkable. Can be obtained.

In the pneumatic tire according to one aspect of the present invention, it is preferable that the sipes do not communicate with the chamfered portion.

When the sipe communicates with the chamfered portion, the end portion of the sipe approaches the circumferential groove, and the rigidity of the land portion tends to decrease, so that the effect of improving the load durability performance is small. Therefore, according to the pneumatic tire according to one aspect of the present invention, the sipe does not communicate with the chamfered portion, so that the end portion of the sipe is arranged away from the circumferential groove to suppress a decrease in the rigidity of the land portion. The effect of improving the load durability performance can be remarkably obtained.

In the pneumatic tire according to one aspect of the present invention, the groove depth H0 of the circumferential fine groove and the groove depth Hg of the circumferential groove that divides the land portion provided with the circumferential fine groove are , 0.05 × Hg ≦ H0 ≦ 0.4 × Hg.

According to this pneumatic tire, if the groove depth H0 of the circumferential groove is 0.05 times or more of the groove depth Hg of the circumferential groove, the situation where the circumferential groove is crushed at the time of touchdown can be suppressed. The ground pressure can be sufficiently reduced by the circumferential groove. On the other hand, if the groove depth H0 of the circumferential groove is 0.4 times or more the groove depth Hg of the circumferential groove, the decrease in the rigidity of the land portion due to the circumferential groove can be suppressed, so that the load durability performance is improved. The effect of

In the pneumatic tire according to one aspect of the present invention, the groove depth H0 of the circumferential fine groove and the depth H1 of the chamfered portion provided in the circumferential fine groove are 0.1 × H0 ≦. It is preferable to satisfy the relationship of H1 ≦ 0.5 × H0.

According to this pneumatic tire, if the depth H1 of the chamfered portion is 0.1 times or more the groove depth H0 of the circumferential groove, the ground contact pressure can be sufficiently lowered by the chamfered portion. On the other hand, if the depth H1 of the chamfered portion is 0.5 times or less of the groove depth H0 of the circumferential groove, the decrease in rigidity of the land portion due to the chamfered portion can be suppressed, so that the effect of improving the load durability performance is achieved. Can be remarkably obtained.

In the pneumatic tire according to one aspect of the present invention, the groove width W0 in the lateral direction of the circumferential narrow groove and the width W1 of the chamfered portion provided in the circumferential narrow groove are 0.1 × It is preferable to satisfy the relationship of W0 ≦ W1 ≦ 0.7 × W0.

According to this pneumatic tire, if the width W1 of the chamfered portion is 0.1 times or more the groove width W0 of the circumferential groove, the ground contact pressure can be sufficiently reduced by the chamfered portion. On the other hand, if the width W1 of the chamfered portion is 0.7 times or less of the groove width W0 of the circumferential groove, the decrease in rigidity of the land portion due to the chamfered portion can be suppressed, so that the effect of improving the load durability performance is remarkable. Can be obtained.

In the pneumatic tire according to one aspect of the present invention, it is preferable that the chamfered portion is formed in a curved shape.

The ground pressure tends to be higher at the corners in the cross section. Therefore, by forming the chamfered portion into a curved surface shape, the ground pressure can be sufficiently reduced.

In the pneumatic tire according to one aspect of the present invention, the land portion communicates with each of the circumferential grooves adjacent in the tire width direction and is divided into blocks in the tire circumferential direction by a plurality of lug grooves arranged in the tire circumferential direction. The circumferential groove is formed so as to include a central portion of the block-shaped land portion in the tire circumferential direction and is provided in a longitudinal shape, and the chamfered portion is a block-shaped land portion in the tire circumferential direction. It is preferable that at least one of the width and the depth is formed larger in the central portion than in the other portion.

Since the rigidity is high near the center of the block-shaped land in the tire circumferential direction, the contact pressure tends to be high. Therefore, according to the pneumatic tire according to one aspect of the present invention, at least one of the width W1 and the depth H1 of the chamfered portion is set in the central portion of the block-shaped land portion in the tire circumferential direction as compared with the other portions. Due to the large shape, it is possible to reduce the contact pressure near the center of the tire circumferential direction in the land portion to make the contact pressure in the land portion uniform, and it is possible to remarkably obtain the effect of improving the load durability performance. ..

The pneumatic tire according to one aspect of the present invention is preferably applied to a studless tire.

Studless tires tend to have a relatively low tread rigidity in order to improve on-ice and snow performance, but studless tires often use sipes to suck up the water film with the road surface on the tread surface. Therefore, the rigidity of the land area becomes low. For this reason, when changing lanes or cornering, the land portion tends to fall in the tire width direction and the steering stability performance deteriorates. Therefore, if the sipes are separated in the tire width direction, the decrease in rigidity is suppressed. However, since the ground contact pressure locally increases while the sipes are separated in the tire width direction, the ground contact pressure can be increased by providing a circumferential groove and a chamfer as in the pneumatic tire according to one aspect of the present invention. Can be homogenized. Therefore, the pneumatic tire according to one aspect of the present invention is suitable for a studless tire because it can improve the load endurance performance while ensuring the performance on snow and the performance on ice.

The pneumatic tire according to the present invention can improve the load durability performance while ensuring the performance on ice and the performance on snow.

FIG. 1 is a plan view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged plan view of a pneumatic tire according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along the line AA in FIG. FIG. 4 is an enlarged plan view of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is a cross-sectional view taken along the line BB in FIG. FIG. 6 is an enlarged plan view of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 7 is a cross-sectional view taken along the line CC in FIG. FIG. 8 is an enlarged cross-sectional view of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 9 is an enlarged plan view of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 10 is an enlarged plan view of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 11 is an enlarged cross-sectional view of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 12 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention. FIG. 13 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components of this embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within a range self-evident by those skilled in the art.

The pneumatic tire according to this embodiment will be described. FIG. 1 is a plan view of a pneumatic tire according to the present embodiment. FIG. 2 is an enlarged plan view of the pneumatic tire according to the present embodiment. FIG. 3 is a cross-sectional view taken along the line AA in FIG. 4 to 11 are views showing another example of the pneumatic tire according to the present embodiment.

In the following description, the tire radial direction means a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the inside in the tire radial direction is the side toward the rotation axis in the tire radial direction and the outside in the tire radial direction. Refers to the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction means a circumferential direction with the rotation axis as a central axis. The tire width direction means a direction parallel to the rotation axis, the inside in the tire width direction is the side toward the tire equatorial plane (tire equatorial line) in the tire width direction, and the outside in the tire width direction is in the tire width direction. The side of the tire away from the equatorial plane. The tire equatorial plane is the central plane in the tire width direction orthogonal to the rotation axis, and the tire equatorial line is a line on the tire equatorial plane along the tire circumferential direction of the pneumatic tire 1.

As shown in FIG. 1, the pneumatic tire 1 of the present embodiment has a tread portion 2. The tread portion 2 is made of a rubber material and is exposed on the outermost side of the pneumatic tire 1 in the tire radial direction, and the surface thereof serves as the tread surface 2a and serves as the contour of the pneumatic tire 1.

The tread portion 2 is provided with a plurality of circumferential grooves 3 extending along the tire circumferential direction (five in the present embodiment) arranged side by side on the tread surface 2a in the tire width direction. The circumferential groove 3 has a groove width of 3 mm or more and 15 mm or less and a groove depth of 5 mm or more and 15 mm or less (dimension from the opening position of the tread surface 2a to the groove bottom).

In the tread portion 2, a plurality of land portions 4 (six in the present embodiment) are formed on the tread surface 2a by the circumferential groove 3 in the tire width direction. In the present embodiment, the land portion 4 on the inner side in the tire width direction with respect to the circumferential groove 3 on both outer sides in the tire width direction is referred to as the inner land portion 4A, and is in the tire width direction with respect to the circumferential groove 3 on both outer sides in the tire width direction. The outer land portion 4 is called the shoulder land portion 4B. In FIG. 1, the shoulder land portion 4B is shown only in the ground contact area, and the outside of the ground contact area is omitted.

Here, in the ground contact region, when the pneumatic tire 1 is rim-assembled on the regular rim, the regular internal pressure is applied, and 70% of the regular load is applied, the tread surface 2a of the tread portion 2 of the pneumatic tire 1 becomes. An area that touches a dry, flat road surface. Both ends of the ground contact region in the tire width direction are referred to as ground contact ends T, and are shown continuously in the tire circumferential direction in FIG. The regular rim is a "standard rim" specified by JATTA, a "Design Rim" specified by TRA, or a "Measuring Rim" specified by ETRTO. The normal internal pressure is the "maximum air pressure" specified by JATTA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. The normal load is the "maximum load capacity" specified by JATTA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO.

The land portion 4 is provided with a lug groove 5 on the tread surface 2a. The lug groove 5 intersects the tire circumferential direction and extends, and the end portion communicates with the circumferential groove 3. The lug groove 5 has a groove width of 1.5 mm or more and 10.0 mm or less and a groove depth of 5 mm or more and 15 mm or less. The land portion 4 has a block B divided in the tire circumferential direction by a circumferential groove 3 and a lug groove 5. Further, the land portion 4 has ribs R that are not divided in the tire circumferential direction by the lug groove 5 and are continuous in the tire circumferential direction. In the pneumatic tire 1 shown in FIG. 1, one of the four inner land portions 4A is a rib R, and the other three are blocks B. The shoulder land portion 4B is all block B.

The land portion 4 is provided with a sipe 6 on the tread surface 2a. A plurality of sipes 6 extend along the tire width direction and are provided side by side in the tire circumferential direction. The sipe 6 has a groove width of 0.3 mm or more and 1.2 mm or less and a groove depth of 3 or less in the circumferential direction. The sipe 6 has a form in which it communicates with the circumferential groove 3 and a form in which it does not communicate with the circumferential groove 3. Further, the sipe 6 is formed in a zigzag shape in which a plurality of openings to the tread surface 2a are continuously bent. In this case, the sipe 6 may be a two-dimensional sipe in which the shape inside the tread portion 2 from the tread surface 2a to the inside in the tire radial direction has a zigzag shape along the zigzag shape of the tread surface 2a. In addition, it may be a further bent three-dimensional sipe. Further, the sipe 6 may have an opening to the tread surface 2a continuously and linearly formed. In this case, the sipe 6 may be a one-dimensional sipe in which the shape of the inside of the tread portion 2 from the tread surface 2a to the inside in the tire radial direction is linear along the straight line of the tread surface 2a. It may be a tread. Therefore, the pneumatic tire 1 of the present embodiment is configured as a studless tire in which the sipe 6 is provided on the tread surface 2a of the land portion 4. Then, in the present embodiment, as shown in FIGS. 1 and 2, the sipe 6 includes a form in which the sipe 6 is separated into two in the middle of extending along the tire width direction in one land portion 4.

Further, the land portion 4 is provided with a circumferential groove 7 on the tread surface 2a. The circumferential groove 7 is provided so as to extend longitudinally along the tire circumferential direction while the plurality of sipes 6 arranged in the tire circumferential direction are separated. Therefore, the sipes 6 are separated in the regions on both sides of the circumferential groove 7 in the tire width direction on the tread surface 2a of the land portion 4, extend along the tire width direction, and are provided side by side in the tire circumferential direction. There is. Further, the sipe 6 is provided with the separated end portion 6a communicating with the circumferential groove 7 in FIGS. 1 to 3. As shown in FIG. 1, the circumferential narrow groove 7 is provided at both ends in the longitudinal direction in the block B of the land portion 4 so as to communicate with the lug groove 5. In addition, although not explicitly shown in the drawing, the circumferential narrow groove 7 is provided in the block B of the land portion 4 so that at least one end in the longitudinal direction does not communicate with the lug groove 5 and is terminated in the land portion 4. You may. Further, as shown in FIG. 1, the circumferential groove 7 is continuously provided in the longitudinal direction at the rib R of the land portion 4. In addition, although not explicitly shown in the drawing, the circumferential groove 7 may be provided by dividing the rib R of the land portion 4 in the longitudinal direction and terminating both ends within the land portion 4.

Further, the land portion 4 is a tread surface 2a, and a chamfer portion 8 is provided at the opening edge of the circumferential groove 7. The chamfered portion 8 may be provided at least on the opening edges on both sides in the lateral direction along at least the longitudinal shape of the circumferential groove 7, and is provided at the end of the circumferential groove 7 in the longitudinal direction. May be good.

Such a form having a sipe 6, a circumferential groove 7, and a chamfered portion 8 is applied to the inner land portion 4A and the shoulder land portion 4B in the land portion 4, and is applied to the block B and the rib R.

As described above, the pneumatic tire 1 of the present embodiment is formed in the tread portion 2 by a plurality of circumferential grooves 3 extending along the tire circumferential direction and lining up in the tire width direction, and at least the circumferential groove 3. A plurality of land portions 4 arranged in the tire width direction, a circumferential groove 7 provided on the tread surface 2a of the land portion 4 in a longitudinal direction along the tire circumferential direction, and a tread surface 2a of the land portion 4. Sipe 6 separated in the regions on both sides of the circumferential tread 7 in the tire width direction and extending along the tire width direction and provided side by side in the tire circumferential direction, and at least the lateral direction of the circumferential tread 7. It is provided with chamfering portions 8 provided on the opening edges on both sides of the tire.

The portion between the separated sipes 6 has higher rigidity than the portion where the sipes 6 is formed, and the contact pressure received from the road surface at the time of touchdown is locally higher. Chips are likely to occur and load durability is reduced. On the other hand, according to the pneumatic tire 1 of the present embodiment, in the tread surface 2a of the land portion 4, a circumferential groove 7 is formed longitudinally in the tire circumferential direction in the portion between the separated sipes 6. Therefore, the circumferential groove 7 lowers the rigidity and lowers the ground pressure. However, at least at the opening edge in the lateral direction of the circumferential groove 7, the ground contact pressure increases at the edge portion of the opening edge as compared with the others, and a peak of the ground pressure occurs at the edge portion. Therefore, according to the pneumatic tire 1 of the present embodiment, the chamfered portions 8 are formed on the opening edges on both sides of the circumferential groove 7 in the lateral direction at least, so that the contact pressure peaks at the edge portion. It is possible to improve the load endurance performance because the ground pressure can be made uniform in the entire land portion 4 by preventing the situation where Moreover, since the circumferential groove 7 is provided, the edge component is increased along the tire circumferential direction due to the opening edge of the circumferential groove 7 and the drainage property is improved. Performance) can be improved. Moreover, the sipe 6 has performance on snow (stability of steering on a snowy road surface). As a result, the load endurance performance can be improved while ensuring the performance on ice and the performance on snow.

Further, in the pneumatic tire 1 of the present embodiment, the land portion 4 provided with the circumferential groove 7, the sipe 6, and the chamfer portion 8 is arranged on the outermost side in the tire width direction in the tread portion 2. It is preferably 4B.

The shoulder land portion 4B has a higher contact pressure than the other land portions 4 especially when changing lanes or cornering, and touches the edge portion on the short side of the circumferential groove 7 while the sipe 6 is separated. The pressure increases. Therefore, according to the pneumatic tire 1 of the present embodiment, in such a shoulder land portion 4B, the effect of improving the load durability performance while ensuring the performance on ice and the performance on snow can be remarkably obtained.

Further, in the pneumatic tire 1 of the present embodiment, as shown in FIGS. 3, 5, 7, and 11, the groove width W0 in the lateral direction of the circumferential narrow groove 7 is 0.5 mm ≦ W0 ≦ 3. The contact width D0 of the land portion 4 (4B) that satisfies 0 mm and the tire width direction distance D1 between the circumferential groove 3 and the circumferential fine groove 7 that divide the land portion 4 (4B) are 0.4 × D0. It is preferable to satisfy the relationship of ≦ D1 ≦ 0.6 × D0.

The ground contact width D0 shown in FIG. 3 is the distance between the ground contact end T and the opening edge of the circumferential groove 3 arranged on the outermost side in the tire width direction in the tire width direction in the shoulder land portion 4B. Although not explicitly shown in the drawing, the ground contact width D0 in the inner land portion 4A is the distance between the opening edges in the tire width direction of each circumferential groove 3 on both sides in the tire width direction for partitioning the inner land portion 4A.

When the groove width W0 of the circumferential fine groove 7 is 0.5 mm or more, the opening area of the circumferential fine groove 7 can be secured and water between the road surface and the tread surface 2a can be sufficiently removed at the time of touchdown. On the other hand, by setting the groove width W0 of the circumferential narrow groove 7 to 3.0 mm or less, the ground contact area of the tread surface 2a of the land portion 4 is secured, and the ground contact between the road surface and the tread surface 2a is improved at the time of ground contact, and the ground contact property is improved on ice. It is possible to suppress the deterioration of performance. Moreover, since the ground portion 4 (4B) near the center in the tire width direction has high rigidity, the ground pressure tends to be high, so that the relationship of 0.4 × D0 ≦ D1 ≦ 0.6 × D0 is satisfied and the circumferential direction is satisfied. By arranging the narrow groove 7 near the center of the land portion 4 (4B), the contact pressure near the center of the land portion 4 (4B) in the tire width direction is reduced and the contact pressure of the land portion 4 (4B) is made uniform. The effect of improving the load durability performance can be remarkably obtained.

Further, as shown in FIGS. 4 and 5, in the pneumatic tire 1 of the present embodiment, it is preferable that the sipe 6 does not communicate with the circumferential groove 7. 4 and 5 show a form in which the end portion 6a of the sipe 6 is terminated in the chamfered portion 8 without communicating with the circumferential groove 7.

When the sipe 6 communicates with the circumferential groove 7, the sipe 6 is continuous in the tire width direction via the circumferential groove 7, and the rigidity of the land portion 4 (4B) tends to decrease. The improvement effect is small. Therefore, according to the pneumatic tire 1, since the sipe 6 does not communicate with the circumferential groove 7, the decrease in the rigidity of the land portion 4 (4B) can be suppressed, and the effect of improving the load endurance performance can be obtained. It can be obtained remarkably.

Further, as shown in FIGS. 6, 7 to 11, it is preferable that the sipe 6 does not communicate with the chamfered portion 8 in the pneumatic tire 1 of the present embodiment. 6 and 7 to 11 show a form in which the end portion 6a of the sipe 6 is terminated in the tread surface 2a of the land portion 4 (4B) without communicating with the circumferential groove 7 and the chamfered portion 8. There is.

When the sipe 6 communicates with the chamfered portion 8, the end portion 6a of the sipe 6 approaches the circumferential groove 7, the rigidity of the land portion 4 (4B) tends to decrease, and the load durability performance is improved. small. Therefore, according to the pneumatic tire 1, the sipe 6 does not communicate with the chamfered portion 8, so that the end portion 6a of the sipe 6 is arranged away from the circumferential groove 7 and the rigidity of the land portion 4 (4B) is increased. It is possible to suppress the decrease in load durability, and the effect of improving the load durability performance can be remarkably obtained. In order to obtain this effect, as shown in FIGS. 7, 8 and 11, the distance between the end portion 6a of the sipe 6 and the edge portion of the chamfered portion 8 (the edge portion leading to the tread surface 2a). G is preferably in the range of 0.5 mm or more and 2.0 mm or less.

Further, as shown in FIGS. 3, 5, 7, and 11, in the pneumatic tire 1 of the present embodiment, the groove depth of the circumferential narrow groove 7 (the dimension from the opening position of the tread surface 2a to the groove bottom). ) H0 and the groove depth (dimension from the opening position of the tread surface 2a to the bottom of the groove) Hg of the circumferential groove 3 for partitioning the land portion 4 (4B) provided with the circumferential groove 7 are 0. It is preferable to satisfy the relationship of 05 × Hg ≦ H0 ≦ 0.4 × Hg.

The circumferential groove 3 shown in FIGS. 3, 5, 7, and 11 is a circumferential groove 3 arranged on the outermost side in the tire width direction for partitioning the shoulder land portion 4B. In the inner land portion 4A, the one having the deeper groove depth Hg among the circumferential grooves 3 on both sides in the tire width direction for partitioning the inner land portion 4A is used as the comparison with the groove depth H0 of the circumferential narrow groove 7.

If the groove depth H0 of the circumferential groove 7 is 0.05 times or more the groove depth Hg of the circumferential groove 3, it is possible to suppress the situation where the circumferential groove 7 is crushed at the time of touchdown. Therefore, the ground pressure can be sufficiently lowered. On the other hand, if the groove depth H0 of the circumferential groove 7 is 0.4 times or more the groove depth Hg of the circumferential groove 3, the decrease in rigidity of the land portion 4 (4B) due to the circumferential groove 7 can be suppressed. Therefore, the effect of improving the load durability performance can be remarkably obtained. In addition, in order to sufficiently reduce the ground contact pressure by the circumferential groove 7 and to obtain the effect of improving the load durability performance remarkably, the groove depth Hg of the circumferential groove 3 is set to the above-mentioned range of 5 mm or more and 15 mm or less. It is preferable that the groove depth H0 of the circumferential narrow groove 7 is 0.3 mm or more and 4.0 mm or less.

Further, as shown in FIGS. 3, 5, 7, 8, and 11, in the pneumatic tire 1 of the present embodiment, the groove depth of the circumferential narrow groove 7 (from the opening position of the tread surface 2a to the groove bottom). H0 and the depth of the chamfer 8 provided in the circumferential groove 7 (dimension from the opening position of the tread surface 2a to the groove bottom) H1 are 0.1 × H0 ≦ H1 ≦ It is preferable to satisfy the relationship of 0.5 × H0.

If the depth H1 of the chamfered portion 8 is 0.1 times or more the groove depth H0 of the circumferential narrow groove 7, the ground contact pressure can be sufficiently lowered by the chamfered portion 8. On the other hand, if the depth H1 of the chamfered portion 8 is 0.5 times or less of the groove depth H0 of the circumferential narrow groove 7, the decrease in rigidity of the land portion 4 (4B) due to the chamfered portion 8 can be suppressed. The effect of improving the load durability performance can be remarkably obtained. In addition, in order to sufficiently reduce the ground pressure by the chamfered portion 8 and to obtain the effect of improving the load durability performance remarkably, the groove depth H0 of the circumferential narrow groove 7 is 0.3 mm or more and 4.0 mm or less as described above. It is preferable that the depth H1 of the chamfered portion 8 is 0.1 mm or more and 2.0 mm or less with respect to the range.

Further, as shown in FIGS. 3, 5, 7, 8, and 11, in the pneumatic tire 1 of the present embodiment, the groove width W0 in the lateral direction of the circumferential narrow groove 7 and the circumferential narrow groove 7 are obtained. It is preferable that the width W1 of the chamfered portion 8 provided in the groove 7 satisfies the relationship of 0.1 × W0 ≦ W1 ≦ 0.7 × W0.

If the width W1 of the chamfered portion 8 is 0.1 times or more the groove width W0 of the circumferential narrow groove 7, the chamfered portion 8 can sufficiently reduce the ground contact pressure. On the other hand, if the width W1 of the chamfered portion 8 is 0.7 times or less of the groove width W0 of the circumferential narrow groove 7, the decrease in rigidity of the land portion 4 (4B) due to the chamfered portion 8 can be suppressed, so that the load durability The effect of improving the performance can be remarkably obtained. In addition, in order to sufficiently reduce the ground pressure by the chamfered portion 8 and to obtain the effect of improving the load durability performance remarkably, the groove width W0 of the circumferential narrow groove 7 is set to a range of 1.0 mm or more and 3.0 mm or less. The width W1 of the chamfered portion 8 is preferably 0.2 mm or more and 2.0 mm or less.

Further, as shown in FIG. 8, it is preferable that the chamfered portion 8 is formed in a curved surface shape.

When the chamfered portion 8 has a curved surface shape, the width W1 and the depth H1 are inflection points with respect to the groove wall of the tread surface 2a and the circumferential narrow groove 7 (the point at which the curvature changes from the tread surface 2a (the meridional cross section)). In the case of, it is a point, but it appears as a line on the tread surface 2a))) as a reference.

The ground pressure tends to be higher at the corners in the cross section. Therefore, by forming the chamfered portion 8 into a curved surface shape, the ground pressure can be sufficiently reduced. Even if the cross section of the chamfered portion 8 is formed with a plurality of corners so that the corners are as close to a curved surface as possible, it can contribute to sufficiently reducing the ground contact pressure.

Further, as shown in FIGS. 9 to 10, in the pneumatic tire 1 of the present embodiment, a plurality of land portions 4 (4B) communicate with each circumferential groove 3 adjacent in the tire width direction and are lined up in the tire circumferential direction. It is formed in a block shape divided in the tire circumferential direction by the lug groove 5, and the circumferential fine groove 7 is provided in a longitudinal shape including the central portion of the block-shaped land portion 4 (4B) in the tire circumferential direction. It is preferable that at least one of the width and the depth of the chamfered portion 8 is formed in the central portion of the block-shaped land portion 4 (4B) in the tire circumferential direction as compared with the other portions.

The chamfered portion 8 shown in FIG. 9 has a small width W1 formed at both ends of the circumferential groove 7 penetrating the land portion 4 (4B) in the tire circumferential direction, and has a width at the central portion of the land portion 4 (4B). W1 is formed large. In this case, it is assumed that the depth H1 of the chamfered portion 8 is constant from the tread surface 2a in the longitudinal direction (extending direction: tire peripheral direction) of the circumferential groove 7.

Further, the chamfered portion 8 shown in FIG. 10 has a gradual width from both ends toward the central portion of the land portion 4 (4B) with respect to the circumferential groove 7 penetrating the land portion 4 (4B) in the tire circumferential direction. W1 is formed large. In this case, it is assumed that the depth H1 of the chamfered portion 8 is constant from the tread surface 2a in the longitudinal direction (extending direction: tire peripheral direction) of the circumferential groove 7.

Further, the chamfered portion 8 shown in FIG. 11 has a small depth H1 formed at both ends of the circumferential groove 7 penetrating the land portion 4 (4B) in the tire circumferential direction, and is formed at the center of the land portion 4 (4B). A large depth H1 is formed in the portion. In this case, the width W1 of the chamfered portion 8 is assumed to have a constant distance from the lateral edge of the circumferential groove 7 in the longitudinal direction (extending direction: tire circumferential direction) of the circumferential groove 7. ..

Further, although not clearly shown in the drawing, the chamfered portion 8 has a larger width W1 and depth H1 of the chamfered portion 8 than other portions in the central portion of the land portion 4 (4B) in the tire circumferential direction. It may have been.

Since the rigidity of the block-shaped land portion 4 (4B) near the center in the tire circumferential direction is high, the contact pressure tends to be high. Therefore, according to the pneumatic tire 1 of the present embodiment, as described above, the width W1 of the chamfered portion 8 in the central portion of the block-shaped land portion 4 (4B) in the tire circumferential direction as compared with other portions. And since at least one of the depth H1 is formed to be large, it is possible to reduce the contact pressure of the land portion 4 (4B) near the center in the tire circumferential direction and make the contact pressure of the land portion 4 (4B) uniform. Therefore, the effect of improving the load durability performance can be remarkably obtained.

Further, the pneumatic tire 1 of the present embodiment is preferably applied to a studless tire.

In studless tires, the rigidity of the tread portion 2 tends to be relatively low in order to improve the performance on ice and snow, but in the studless tire, the sipe 6 is used to suck up the water film with the road surface on the tread surface 2a. Since it is used frequently, the rigidity of the land portion 4 becomes low. For this reason, when the land portion 4 is likely to fall in the tire width direction during lane change or cornering, the steering stability performance is deteriorated. Therefore, if the sipe 6 is separated in the tire width direction, the decrease in rigidity is suppressed. However, since the ground contact pressure locally increases while the sipe 6 is separated in the tire width direction, the ground contact pressure is provided by providing the circumferential groove 7 and the chamfered portion 8 as in the pneumatic tire 1 of the present embodiment. Can be homogenized. Therefore, the pneumatic tire 1 of the present embodiment is suitable for a studless tire because it can improve the load durability performance while ensuring the performance on snow and the performance on ice.

In the above-described embodiment, the circumferential narrow groove 7 is formed so that the groove width W0 does not change in its own longitudinal direction (extending direction: tire circumferential direction) and is constant. Not limited to this, although not explicitly shown in the drawing, the circumferential narrow groove 7 may be formed by changing its groove width W0 in its own longitudinal direction (extending direction: tire circumferential direction). For example, in the pneumatic tire 1 of the present embodiment, the land portion 4 (4B) communicates with each circumferential groove 3 adjacent in the tire width direction and is divided in the tire circumferential direction by a plurality of lug grooves 5 arranged in the tire circumferential direction. The circumferential groove 7 is formed in a block shape, and the circumferential groove 7 has at least a groove width W0 and a groove depth H0 in the central portion of the block-shaped land portion 4 (4B) in the tire circumferential direction as compared with other portions. It is preferable that one is formed large.

Specifically, although not explicitly shown in the drawing, the circumferential groove 7 includes the central portion of the land portion 4 (4B) in the tire circumferential direction and is provided in the longitudinal direction in the same manner as the chamfered portion 8 described above. The groove width W0 is formed small at both ends of the tire, and the groove width W0 is formed large at the central portion of the land portion 4 (4B). In this case, it is assumed that the groove depth H0 of the circumferential narrow groove 7 has a constant distance from the tread surface 2a in the longitudinal direction (extending direction: tire circumferential direction).

Further, although not clearly shown in the drawing, the circumferential groove 7 is provided with the land portion 4 (4B) including the central portion in the tire circumferential direction in the longitudinal direction, similarly to the chamfered portion 8 described above. A gradual groove width W0 is formed from the portion toward the central portion of the land portion 4 (4B). In this case, it is assumed that the groove depth H0 of the circumferential narrow groove 7 has a constant distance from the tread surface 2a in the longitudinal direction (extending direction: tire circumferential direction).

Further, although not clearly shown in the drawing, the circumferential groove 7 has a groove at both ends of the land portion 4 (4B) including the central portion in the tire circumferential direction in a longitudinal direction, similarly to the chamfered portion 8 described above. The depth H0 is formed small, and the groove depth H0 is formed large in the central portion of the land portion 4 (4B). In this case, it is assumed that the groove width W0 of the circumferential narrow groove 7 is constant in the longitudinal direction (extending direction: tire circumferential direction).

Further, although not explicitly shown in the drawing, the circumferential groove 7 has a groove width W0 and a groove width W0 in the central portion of the land portion 4 (4B) in the tire circumferential direction as compared with other portions, similarly to the chamfered portion 8 described above. The groove depth H0 may be formed to be large.

Since the rigidity of the block-shaped land portion 4 (4B) near the center in the tire circumferential direction is high, the contact pressure tends to be high. Therefore, according to the pneumatic tire 1 of the present embodiment, as described above, the groove of the circumferential narrow groove 7 in the central portion of the block-shaped land portion 4 (4B) in the tire circumferential direction is compared with other portions. Since at least one of the width W0 and the groove depth H0 is formed to be large, the contact pressure of the land portion 4 (4B) near the center in the tire circumferential direction is reduced to make the contact pressure of the land portion 4 (4B) uniform. The effect of improving the load durability performance can be remarkably obtained.

In this embodiment, performance tests on ice performance, snow performance, and load durability performance were performed on a plurality of types of pneumatic tires under different conditions (see FIGS. 12 and 13).

In this performance test, a pneumatic tire (test tire), which is a studless tire with a tire size of 195 / 65R15, was rim-assembled on a regular rim of 15 × 6J.

The evaluation method of performance on ice is to run a test course on an ice road surface with a test vehicle (front drive vehicle with a displacement of 1.5 L) equipped with the above test tires filled with an air pressure of 230 kPa, and a professional test driver controls the drive. Feeling evaluation is performed regarding performance, lane change performance, cornering performance, etc. This evaluation is an index evaluation based on the conventional example (100). This evaluation shows that the higher the index, the better the performance on ice.

The evaluation method of snow performance is to run a test course on a snowy road surface with a test vehicle (front drive vehicle with a displacement of 1.5 L) equipped with the above test tires filled with an air pressure of 230 kPa, and a professional test driver controls the drive. Feeling evaluation is performed regarding performance, lane change performance, cornering performance, etc. This evaluation is an index evaluation based on the conventional example (100). This evaluation shows that the higher the index, the better the performance on snow.

The load durability performance is evaluated by filling each tire with an air pressure of 180 kPa, using an indoor drum tester (drum diameter: 1707 mm), controlling the ambient temperature to 38 ± 3 ° C, and then performing the maximum load specified by JATTA. A load corresponding to 88% of the tire is applied, the tire is run at a speed of 81 km / h for 2 hours, and then the load is increased by 13% every 2 hours, and the running time when the tire is broken is measured. .. Then, based on this measurement result, an index evaluation is performed using the conventional example as a reference (100). This evaluation shows that the higher the index, the better the load endurance performance.

In FIG. 12, the conventional pneumatic tire does not have a circumferential groove and a chamfered portion in the pattern of the tread portion having the sipes shown in FIG. Further, the pneumatic tire of the comparative example has a circumferential groove in the pattern of the tread portion having a sipe shown in FIG. 1, but does not have a chamfered portion. In FIGS. 12 and 13, the pneumatic tires of Examples 1 to 20 have a circumferential groove and a chamfered portion in the pattern of the tread portion having the sipes shown in FIG. Then, as shown in the test results of FIGS. 12 and 13, it can be seen that the pneumatic tires of Examples 1 to 20 have improved load endurance performance while ensuring performance on snow and on ice.

1 Pneumatic tire 2 Tread part 2a Tread surface 3 Circumferential groove 4 Land part 4A Inner land part 4B Shoulder land part 5 Rug groove 6 Sipe 6a End part 7 Circumferential narrow groove 8 Chamfered part D0 Land contact width D1 Circumference Direction Groove tire width Directional distance G Distance between the end of the sipe and the edge of the chamfer H0 Circumferential groove depth H1 Chamfer depth Hg Circumferential groove depth T Grounding end W0 Circumferential narrow groove width W1 Chamfer width

Claims (10)

In the tread part, there are multiple circumferential grooves that extend along the tire circumferential direction and are lined up in the tire width direction.
At least a land portion formed by the circumferential groove and lined up in the tire width direction,
Circumferential narrow grooves provided on the tread surface of the land portion in a longitudinal direction along the tire circumferential direction,
A plurality of sipes provided on the tread surface of the land portion in the tire circumferential direction separated by regions on both sides of the circumferential narrow groove in the tire width direction and extending along the tire width direction.
Chamfered portions provided at least on both sides of the circumferential groove in the lateral direction, and
Equipped with a,
The land portion communicates with each of the circumferential grooves adjacent to each other in the tire width direction, and is formed in a block shape divided in the tire circumferential direction by a plurality of lug grooves arranged in the tire circumferential direction.
The circumferential groove includes a block-shaped central portion of the land portion in the tire circumferential direction, and is continuously provided in the tire circumferential direction of the land portion.
The chamfered portion is continuously provided in the tire circumferential direction of the land portion, and at least one of the width and the depth is larger in the central portion of the land portion in the tire circumferential direction than the other portion. that has been formed, the pneumatic tire. The pneumatic tire according to claim 1, wherein the land portion provided with the circumferential groove and the sipe and the chamfer portion is a shoulder land portion arranged on the outermost side in the tire width direction in the tread portion. .. The groove width W0 in the lateral direction of the circumferential narrow groove satisfies 0.5 mm ≦ W0 ≦ 3.0 mm, and the ground contact width D0 of the land portion, the circumferential groove for partitioning the land portion, and the circumferential direction. The pneumatic tire according to claim 1 or 2, wherein the distance D1 in the tire width direction from the narrow groove satisfies the relationship of 0.4 × D0 ≦ D1 ≦ 0.6 × D0. The pneumatic tire according to any one of claims 1 to 3, wherein the sipe does not communicate with the circumferential groove. The pneumatic tire according to any one of claims 1 to 4, wherein the sipe does not communicate with the chamfered portion. The groove depth H0 of the circumferential groove and the groove depth Hg of the circumferential groove that divides the land portion provided with the circumferential groove are 0.05 × Hg ≦ H0 ≦ 0.4. The pneumatic tire according to any one of claims 1 to 5, which satisfies the relationship of × Hg. The groove depth H0 of the circumferential fine groove and the depth H1 of the chamfered portion provided in the circumferential fine groove satisfy the relationship of 0.1 × H0 ≦ H1 ≦ 0.5 × H0. The pneumatic tire according to any one of claims 1 to 6. The relationship between the groove width W0 in the lateral direction of the circumferential narrow groove and the width W1 of the chamfered portion provided in the circumferential narrow groove is 0.1 × W0 ≦ W1 ≦ 0.7 × W0. The pneumatic tire according to any one of claims 1 to 7, which satisfies. The pneumatic tire according to any one of claims 1 to 8, wherein the chamfered portion is formed in a curved surface shape. The pneumatic tire according to any one of claims 1 to 9 , which is applied to a studless tire.

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