JP5895778B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire requiring uneven wear resistance and WET performance.

  Since pneumatic tires for light trucks stipulated by JATMA are mainly used for local driving, stop-and-go is repeated many times during medium and low speed driving, and excellent wear resistance and grip power (WET performance) are required. The In addition, it is preferable to replace the left and right as well as the left and right in the rotation of the pneumatic tire used mainly for local traveling in order to make the wear uniform and prolong the life, and therefore a symmetrical tread pattern is desired. ing.

  Conventionally, for example, a pneumatic tire described in Patent Document 1 is located in a tread portion at one central circumferential groove located on the tire equatorial plane, and between the central circumferential groove and both tread ends. A total of three lateral circumferential grooves are arranged. These circumferential grooves form four rows of ribs. The rib between the central circumferential groove and the lateral circumferential groove includes a plurality of lateral grooves extending in a direction intersecting the tire circumferential direction from the central circumferential groove, and a first narrow groove extending in the tire circumferential direction communicating with the lateral groove. A groove portion, a first lateral sipe communicating with the first narrow groove portion, a second narrow groove portion communicating with the first lateral sipe and extending in the tire circumferential direction, a second lateral sipe communicating with the second narrow groove portion and the lateral groove, Is provided.

  Conventionally, the pneumatic tire described in Patent Document 2 has one end opened in the lateral circumferential groove and the other end communicated with the second narrow groove portion with respect to the pneumatic tire described in Patent Document 2 described above. An inclined sipe that is continuous with the first lateral sipe and extends in a direction inclined with respect to the tire equatorial plane is further provided.

  Conventionally, in the pneumatic tire described in Patent Document 3, a rib-shaped land portion is defined between three circumferential main grooves disposed in the tread portion, and one rib-shaped land portion is provided on the rib-shaped land portion. A block land portion is defined by arranging a circumferential sub groove, a width direction groove communicating with the circumferential main groove and the circumferential sub groove.

JP 2010-12965 A JP 2010-149761 A JP 2012-86755 A

  The pneumatic tires described in Patent Document 1 to Patent Document 3 described above are provided with circumferential sub-grooves (first narrow groove section and second narrow groove section) in the rib-like land portion (rib), and the circumferential sub-grooves ( A width direction groove (lateral groove) that communicates the first narrow groove portion and the second narrow groove portion) with the central circumferential main groove (central circumferential groove) is provided, and the central circumferential groove (central circumferential groove) Block land portions are defined on both sides in the tire width direction. In the pneumatic tires described in Patent Documents 1 to 3, the block land portions are partitioned on both sides in the tire width direction of the central circumferential groove (central circumferential groove), so that the rigidity of the portion is increased. Therefore, when used mainly in local travel, early wear (center wear wear) tends to occur in the center region of the tread due to repeated stop-and-go during medium and low speed travel. That is, it is difficult to meet the demand for wear resistance.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can improve uneven wear-proof performance and WET performance.

  In order to solve the above-mentioned problems and achieve the object, the pneumatic tire of the first invention has a symmetrical tread pattern on the tread surface of the tread portion that is symmetrical on both sides in the tire width direction with respect to the tire equatorial plane. In the pneumatic tire in which at least four rib-like land portions extending in the tire circumferential direction are formed by at least three circumferential main grooves extending in the tire circumferential direction, the circumferential main When the groove is on the tire equator plane, the circumferential main groove on the tire equator plane is a center main groove, and when the circumferential main groove is not on the tire equator plane, the tire width direction of the tire equator plane is When the circumferential main grooves on both outer sides are combined into a center main groove, and the rib-like land portions adjacent to both outer sides in the tire width direction of the center main groove are side rib-like land portions, Or one side of the tire width direction The lateral rib-shaped land portion extends in the tire circumferential direction within a range of 40% to 60% of the tire width direction dimension, and has a groove depth shallower than the circumferential main groove. The circumferential narrow groove formed on the side rib-shaped land portion and one end thereof communicates with the circumferential main groove adjacent to the outer side in the tire width direction of the side rib-shaped land portion and ends at the other end. Width direction narrow grooves arranged in a plurality of positions in the tire circumferential direction, communicating with the circumferential narrow grooves, extending in a crossing direction in the tire circumferential direction, and having a shallower groove depth than the circumferential main grooves. And a rib shape on the inner side in the tire width direction of the lateral rib-shaped land portion with the circumferential narrow groove as a boundary, and a tire width of the lateral rib-shaped land portion with the circumferential narrow groove as a boundary. The outside in the direction is a block shape.

  According to this pneumatic tire, the circumferential narrow groove has drainage performance in the tire circumferential direction and the lateral narrow groove has drainage performance to the outside in the tire width direction, so that WET performance (operability on wet road surface) And braking performance). In addition, on the inner side in the tire width direction (center main groove side) of the side rib-shaped land portion, the rib shape can suppress a decrease in rigidity more than necessary and improve uneven wear resistance. In particular, when used mainly in local traveling, the occurrence of early wear (center wear wear) in the center region of the tread portion is suppressed by repetition of stop-and-go during medium-low speed traveling. Further, by providing the circumferential narrow groove at substantially the center in the tire width direction which is in the range of 40% to 60% of the tire width direction dimension W of the side rib-shaped land portion, the side rib shape is provided. Since the difference in rigidity in the tire width direction of the land portion is reduced, uneven wear can be suppressed. As a result, it is possible to improve uneven wear resistance and WET performance. Moreover, according to this pneumatic tire, since it has a symmetrical tread pattern, it is possible to replace the front, rear, left and right in rotation, so that the wear can be made uniform and the life can be extended.

  The pneumatic tire according to a second aspect is the pneumatic tire according to the first aspect, wherein the circumferential narrow groove and the width narrow groove have a maximum groove depth relative to a groove depth of the circumferential main groove. It is characterized by being in the range of 10 [%] or more and 40 [%] or less.

  According to this pneumatic tire, if the maximum groove depth of the circumferential narrow groove and the width narrow groove is 10% or more with respect to the groove depth of the circumferential main groove, the drainage performance is further exhibited. The effect of improving the WET performance can be remarkably obtained. Moreover, if the maximum groove depth of the circumferential narrow groove and the width narrow groove is 40% or less with respect to the groove depth of the circumferential main groove, the rigidity reduction of the lateral rib-shaped land portion is further suppressed. The effect of improving uneven wear resistance can be obtained remarkably. As a result, the effect of improving uneven wear resistance and the effect of improving WET performance can be obtained remarkably.

  The pneumatic tire of the third invention is characterized in that, in the first or second invention, a groove bottom sipe is formed at the groove bottom of either the circumferential narrow groove or the width narrow groove. To do.

  According to this pneumatic tire, since the circumferential narrow groove and the lateral narrow groove are formed with a shallower groove depth than the circumferential main groove, the difference in the groove depth is compensated by the groove bottom sipes. By maintaining the rigidity of the rib shape of the side rib-shaped land portion uniformly in the tire width direction and maintaining the block shape rigidity of the side rib-shaped land portion uniform in the tire width direction and the tire circumferential direction, uneven wear can be prevented. Can be suppressed. As a result, the effect of improving uneven wear resistance can be obtained remarkably.

  The pneumatic tire according to a fourth aspect of the present invention is the pneumatic tire according to the third aspect, wherein a groove bottom sipe formed at the groove bottom of the widthwise narrow groove communicates with the circumferential main groove. It extends in the range of 40 [%] or more and 60 [%] or less of the distance from the groove to the circumferential narrow groove.

  According to this pneumatic tire, the drainage from the width direction narrow groove to the circumferential direction main groove can be improved by communicating the groove bottom sipe with the circumferential direction main groove. Moreover, by making the groove bottom sipe 40% or more of the distance from the circumferential main groove to the circumferential narrow groove, the drainage improvement effect can be remarkably obtained, and it should be 60% or less. Thus, the effect of keeping the block-shaped rigidity of the side rib-like land portion uniform in the tire width direction and the tire circumferential direction can be remarkably obtained. As a result, the effect of improving uneven wear resistance and the effect of improving WET performance can be obtained remarkably.

  Moreover, the pneumatic tire of the fifth invention is the pneumatic tire according to the third invention, wherein the groove bottom sipe formed on the groove bottom of the circumferential narrow groove is a portion where the width narrow groove communicates with the circumferential narrow groove. It is characterized by being arranged in the range of 60 [%] to 90 [%] of the interval.

  According to this pneumatic tire, the drainage improvement effect can be remarkably obtained by setting the groove bottom sipe to 60% or more of the interval between the portions where the width direction narrow grooves communicate with the circumferential direction narrow grooves. , 90% or less, the effect of keeping the rigidity of the rib shape and block shape of the side rib-shaped land portion uniform in the tire width direction and the tire circumferential direction can be significantly obtained. As a result, the effect of improving uneven wear resistance and the effect of improving WET performance can be obtained remarkably.

  The pneumatic tire according to a sixth aspect of the present invention is the pneumatic tire according to any one of the third to fifth aspects, wherein the groove bottom sipe sets a maximum groove depth from the tread surface to a groove depth of the circumferential main groove. It is characterized by being in the range of 60 [%] or more and 90 [%] or less.

  By setting the maximum groove depth from the tread surface of the groove bottom sipe to 60 [%] or more with respect to the groove depth of the circumferential main groove, the drainage improvement effect can be remarkably obtained, and 90 [% ] By making the following, the effect of maintaining the rigidity of the rib shape and block shape of the side rib-shaped land portion uniformly in the tire width direction and the tire circumferential direction can be remarkably obtained. As a result, the effect of improving uneven wear resistance and the effect of improving WET performance can be obtained remarkably.

  The pneumatic tire according to a seventh aspect of the present invention is the pneumatic tire according to any one of the first to sixth aspects, wherein the circumferential main groove and the circumferential narrow groove forming the center main groove are the same distance in the tire width direction. It is characterized by being bent or curved in the tire width direction while maintaining the above.

  According to this pneumatic tire, the circumferential main groove forming the center main groove is formed by bending or bending, so that it has edge components in both the tire width direction and the tire circumferential direction, and has a WET performance. Can be improved. In this case, since the circumferential narrow groove and the circumferential main groove maintain the same distance in the tire width direction, the rib shape of the side rib-shaped land portion and the tire width direction dimension of the block shape are uniform in the tire circumferential direction. The effect of maintaining the rigidity of the rib shape and block shape of the side rib-shaped land portion in the tire width direction and the tire circumferential direction can be remarkably obtained.

  The pneumatic tire according to an eighth aspect of the present invention is the pneumatic tire according to any one of the first to seventh aspects, wherein the center main groove has a groove width of 3 [mm] in the tire width direction from the tire equatorial plane to the ground contact end. %] And 15 [%] or less, and each circumferential main groove provided between the center main groove and the lateral rib-shaped land portion is located at the tire equatorial plane. It is characterized by being in the range of 50 [%] or more and 60 [%] or less of the dimension in the tire width direction from the ground to the ground contact end.

  The hydro-browning phenomenon tends to occur starting from the center side in the tire width direction of the tread surface. Therefore, according to this pneumatic tire, the groove width of the center main groove disposed on the center side in the tire width direction is defined, and the position of the circumferential main groove adjacent to the outer side of the center main groove in the tire width direction is the tire width. By disposing on the center side in the direction, the drainage performance on the center side in the tire width direction is improved, so that the WET performance can be further improved.

  In the pneumatic tire according to the ninth invention, in any one of the first to eighth inventions, a JIS hardness at 20 [° C.] of the compound forming the tread portion is in a range of 60 or more and 75 or less. It is characterized by.

  According to this pneumatic tire, by making the JIS hardness at 20 [° C.] of the compound forming the tread part 60 or more, the effect of improving the uneven wear resistance and the effect of improving the WET performance with a moderate hardness are remarkable. Can get to.

  A pneumatic tire according to a tenth aspect of the invention is characterized in that in any one of the first to ninth aspects, the pneumatic tire is applied to a pneumatic tire for a small truck having a specified internal pressure of 600 [kPa] or less.

  According to this pneumatic tire, since it is mainly used in local travel, stop-and-go is repeated many times during medium and low speed travel, and excellent wear resistance and grip power (WET performance) are required. According to this pneumatic tire, it is possible to satisfy the requirements for excellent wear resistance and gripping power as a pneumatic tire for small trucks mainly used in local travel.

  The pneumatic tire according to the present invention can improve uneven wear resistance and WET performance.

FIG. 1 is a plan view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is a partially enlarged cross-sectional view of the pneumatic tire shown in FIGS. 1 and 2. FIG. 4 is a partially enlarged plan view of the pneumatic tire shown in FIGS. 1 and 2. FIG. 5 is a plan view of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 6 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 7 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 8 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 9 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. Further, a plurality of modifications described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

  1 and 2 are plan views of the pneumatic tire according to the present embodiment, FIG. 3 is a partially enlarged sectional view of the pneumatic tire shown in FIGS. 1 and 2, and FIG. FIG. 5 is a partially enlarged plan view of the pneumatic tire shown in FIG. 2, and FIG. 5 is a plan view of another example of the pneumatic tire according to the present embodiment.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side. The term “side away from the rotation axis” in the tire radial direction. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction means the side toward the tire equator plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction means the tire width. The direction away from the tire equatorial plane CL in the direction. The tire circumferential direction is a circumferential direction with the rotation axis as a central axis. The tire equatorial plane CL is a plane that is orthogonal to the rotational axis of the pneumatic tire 1 and passes through the center of the tire width of the pneumatic tire 1. The tire equator line is a line along the circumferential direction of the pneumatic tire 1 on the tire equator plane CL. In the present embodiment, the same sign “CL” as that of the tire equator plane is attached to the tire equator line.

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

  Further, the pneumatic tire 1 of the present embodiment has a symmetric tread pattern in which the both sides in the tire width direction are symmetric with respect to the tire equatorial plane CL in the tread portion 2. Specifically, the tread portion 2 has at least three circumferential main grooves 3 extending in the tire circumferential direction on the tread surface 2a (three in FIG. 1 and three in FIG. 1). (It is four). The tread portion 2 has at least four rib-like land portions 4 extending along the tire circumferential direction by at least three circumferential main grooves 3 on the tread surface 2a (four in FIG. 1). In FIG. 2, there are five). The symmetrical tread pattern indicates that the tread pattern has the same shape when turned over in the tire width direction. Further, the symmetrical tread pattern includes a pattern whose phase is shifted in the tire circumferential direction with respect to the tire equatorial plane CL.

  In this embodiment, as shown in FIG. 1, when the circumferential main groove 3 is on the tire equator plane CL, the circumferential main groove 3 on the tire equator plane CL is used as the center main groove 31. As shown in FIG. 2, when the circumferential main groove 3 is not on the tire equatorial plane CL, the two main circumferential grooves 3 on both outer sides of the tire equatorial plane CL in the tire width direction are combined to form the center main groove 31. And Further, the rib-like land portions 4 adjacent to both outer sides in the tire width direction of the center main groove 31 are referred to as side rib-like land portions 41. Although not clearly shown in the drawing, when there are five circumferential main grooves 3, the circumferential main groove 3 is on the tire equator plane CL, so the circumferential main groove 3 on the tire equator plane CL is the center main groove. 31. The rib-shaped land portions 4 adjacent to the outer sides in the tire width direction of the center main grooves 31 are referred to as side rib-shaped land portions 41.

  The lateral rib-shaped land portion 41 is formed with circumferential narrow grooves 5 and width narrow grooves 6 that are narrower than the circumferential main grooves 3. In the lateral rib-shaped land portion 41, the circumferential narrow groove 5 ranges from one side in the tire width direction to 40 [%] or more and 60 [%] or less of the tire width direction dimension W of the side rib-shaped land portion 41. Thus, it extends along the tire circumferential direction. The circumferential narrow groove 5 is formed with a groove depth D2 (see FIG. 3) shallower than the groove depth D1 (see FIG. 3) of the circumferential main groove 3. Further, in the lateral rib-shaped land portion 41, one end of the width-direction narrow groove 6 communicates with the circumferential main groove 3 adjacent to the outer side in the tire width direction of the lateral rib-shaped land portion 41 and ends at the other end. A plurality of circumferentially extending grooves 5 are provided that extend in a crossing manner in the tire circumferential direction and communicate with the circumferential narrow groove 5. The width direction narrow groove 6 is formed with a groove depth D3 (see FIG. 3) shallower than the groove depth D1 (see FIG. 3) of the circumferential main groove 3.

  Here, in the pneumatic tire 1 of the present embodiment, the circumferential main groove 3 has a groove depth D1 in a range of 7 [mm] to 12 [mm] and a groove width of 8.0 [mm] or more. The range is 15.0 [mm] or less. Further, the circumferential narrow grooves 5 and the width narrow grooves 6 have the groove depths D2 and D3 within the above specified range, and the groove width within the range of 1.0 [mm] to 5.0 [mm]. .

  And the side rib-shaped land part 41 is formed into a rib shape on the inner side in the tire width direction (center main groove 31 side) with the circumferential narrow groove 5 as a boundary by the circumferential narrow groove 5 and the lateral narrow groove 6. The outer side in the tire width direction with the circumferential narrow groove 5 as a boundary is formed into a block shape by a plurality of narrow grooves 6 in the width direction.

  According to such a pneumatic tire 1, according to such a pneumatic tire 1, the circumferential narrow groove 5 has a drainage property in the tire circumferential direction, and the width-direction narrow groove 6 has an outer side in the tire width direction. By having drainage, it is possible to improve WET performance (operability and braking performance on wet road surfaces). Further, on the inner side in the tire width direction of the side rib-shaped land portion 41 (on the center main groove 31 side), it is possible to suppress a decrease in rigidity more than necessary due to the rib shape and to improve uneven wear resistance. In particular, when used mainly in local traveling, the occurrence of early wear (center wear wear) in the center region of the tread portion 2 is suppressed by repetition of stop-and-go during medium-low speed traveling. In addition, the circumferential narrow groove 5 is provided at substantially the center in the tire width direction, which is in the range of 40% to 60% of the tire width direction dimension W of the lateral rib-shaped land portion 41. Since the difference in rigidity in the tire width direction of the rib-like land portion 41 is reduced, it is possible to suppress uneven wear. As a result, it is possible to improve uneven wear resistance and WET performance. Moreover, according to this pneumatic tire 1, since it has a symmetrical tread pattern, it is possible to replace the front, rear, left and right in rotation, so that the wear can be made uniform and the life can be extended. Become.

  In addition, as shown in FIG. 3, the pneumatic tire 1 of the present embodiment has the maximum groove depths D <b> 2 and D <b> 3 of the circumferential narrow grooves 5 and the width narrow grooves 6, and the groove depth D <b> 1 of the circumferential main grooves 3. In contrast, it is preferable to be in the range of 10% to 40%.

  According to this pneumatic tire 1, if the maximum groove depths D <b> 2 and D <b> 3 of the circumferential narrow groove 5 and the widthwise narrow groove 6 are 10% or more with respect to the groove depth D <b> 1 of the circumferential main groove 3. In addition, the drainage performance can be further exerted, and the improvement effect of the WET performance can be remarkably obtained. If the maximum groove depths D2 and D3 of the circumferential narrow groove 5 and the widthwise narrow groove 6 are 40% or less with respect to the groove depth D1 of the circumferential main groove 3, the lateral rib-shaped land portion is formed. Thus, it is possible to remarkably obtain the effect of improving uneven wear resistance by further suppressing the rigidity reduction of 41. As a result, the effect of improving the uneven wear resistance and the effect of improving the WET performance can be remarkably obtained. Note that the maximum groove depths D2 and D3 of the circumferential narrow grooves 5 and the widthwise narrow grooves 6 are set to be the groove depths of the circumferential main grooves 3 in order to obtain the effect of improving uneven wear resistance and the WET performance. More preferably, it is in the range of 20% to 30% with respect to the thickness D1.

  In the pneumatic tire 1 of the present embodiment, as shown in FIGS. 3 and 4, groove bottom sipes 7 and 8 are formed on the groove bottom of either the circumferential narrow groove 5 or the width narrow groove 6. It is preferable.

  As shown in FIG. 4, the pneumatic tire 1 of the present embodiment has a tread surface that has one end communicating with the circumferential main groove 3 and the other end terminating in the rib-like land portion 4 and opening in the tread surface 2 a. It has a sipe 9. The sipe 7, 8, 9 has a groove width of 1.0 [mm] or less. Further, the pneumatic tire 1 of the present embodiment has a narrow groove of 10% or more with respect to the groove depth D1 of the circumferential main groove 3 on the tread surface 2a of the rib-like land portion 4 on the outermost side in the tire width direction. Or sipe is not arranged.

  The groove bottom sipe 7 is formed from the groove bottom of the circumferential narrow groove 5 toward the inner side in the tire radial direction, and extends along the extending direction of the circumferential narrow groove 5 (tire circumferential direction). . In addition, the groove bottom sipe 7 is formed along the groove wall of the circumferential narrow groove 5 in FIG. 4. However, the groove bottom sipe 7 is not limited to this, but may be formed at the center of the groove bottom of the circumferential narrow groove 5. Further, when the groove bottom sipe 7 is formed along the groove wall of the circumferential narrow groove 5, the groove bottom sipe 7 may be formed on one or both of the both groove walls of the circumferential narrow groove 5. The groove bottom sipe 8 is formed from the groove bottom of the width-direction narrow groove 6 toward the inner side in the tire radial direction, and extends along the extending direction of the width-direction narrow groove 6. Moreover, the groove bottom sipe 8 is formed along the groove wall of the width direction narrow groove 6 in FIG. However, the groove bottom sipe 8 is not limited to this, but may be formed at the center of the groove bottom of the width direction narrow groove 6. Further, when the groove bottom sipe 8 is formed along the groove wall of the width direction narrow groove 6, the groove bottom sipe 8 may be formed on either or both of the both groove walls of the width direction narrow groove 6.

  According to the pneumatic tire 1, the circumferential narrow groove 5 and the width narrow groove 6 are formed with a shallower groove depth than the circumferential main groove 3. , 8 to keep the rib-shaped rigidity of the side rib-shaped land portion 41 uniform in the tire width direction, and the block-shaped rigidity of the side rib-shaped land portion 41 to the tire width direction and the tire circumferential direction. It is possible to suppress uneven wear while maintaining the same. As a result, the effect of improving the uneven wear resistance can be remarkably obtained.

  Moreover, in the pneumatic tire 1 of this embodiment, as shown in FIG. 4, the groove bottom sipe 8 formed in the groove bottom of the width direction narrow groove 6 is connected to the circumferential main groove 3, and the circumferential direction It is preferable that the distance S1 from the main groove 3 to the circumferential narrow groove 5 extends in the range of 40% to 60%.

  According to this pneumatic tire 1, the drainage performance from the width direction narrow groove 6 to the circumferential direction main groove 3 can be improved by communicating the groove bottom sipe 8 with the circumferential direction main groove 3. In addition, by setting the groove bottom sipe 8 to 40 [%] or more of the distance S1 from the circumferential main groove 3 to the circumferential narrow groove 5, it becomes possible to obtain a remarkable effect of improving the drainage performance. %] Or less, the effect of keeping the block-shaped rigidity of the side rib-shaped land portion 41 uniform in the tire width direction and the tire circumferential direction can be significantly obtained. As a result, the effect of improving the uneven wear resistance and the effect of improving the WET performance can be remarkably obtained. In order to obtain the effect of improving uneven wear resistance and the improvement of WET performance, the groove bottom sipe 8 is not less than 45% of the distance S1 from the circumferential main groove 3 to the circumferential narrow groove 5 and not less than 55%. It is more preferable to extend in the following range.

  Further, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 4, the groove bottom sipe 7 formed on the groove bottom of the circumferential narrow groove 5 has the width narrow groove 6 communicating with the circumferential narrow groove 5. It is preferable to arrange in the range of 60 [%] or more and 90 [%] or less of the interval S2 of the locations to be performed. In FIG. 4, a plurality of groove bottom sipes 7 are arranged at intervals S <b> 2 where the width direction narrow grooves 6 communicate with the circumferential direction narrow grooves 5, and the total is intended.

  According to this pneumatic tire 1, the drainage improvement effect is remarkable by setting the groove bottom sipe 7 to 60 [%] or more of the interval S2 of the part where the width direction narrow groove 6 communicates with the circumferential direction narrow groove 5. By making it 90% or less, the effect of maintaining the rigidity of the rib shape and block shape of the side rib-shaped land portion 41 uniformly in the tire width direction and the tire circumferential direction is remarkably obtained. It becomes possible. As a result, the effect of improving the uneven wear resistance and the effect of improving the WET performance can be remarkably obtained. In addition, in order to obtain the effect of improving uneven wear resistance and the effect of improving WET performance more than 70 [%] of the interval S2 of the groove bottom sipe 7 where the width direction narrow groove 6 communicates with the circumferential direction narrow groove 5 It is more preferable to arrange within a range of 80% or less.

  In the pneumatic tire 1 of the present embodiment, as shown in FIG. 3, the groove bottom sipes 7 and 8 have the maximum groove depth D4 from the tread surface 2a and the maximum groove depth D1 of the circumferential main groove 3. In contrast, it is preferable to be in the range of 60 [%] to 90 [%].

  By making the maximum groove depth D4 from the tread surface 2a of the groove bottom sipes 7 and 8 60% or more with respect to the maximum groove depth D1 of the circumferential main groove 3, the drainage improvement effect is remarkably achieved. By making it 90% or less, the effect of maintaining the rigidity of the rib shape and block shape of the side rib-shaped land portion 41 uniformly in the tire width direction and the tire circumferential direction can be significantly obtained. Is possible. As a result, the effect of improving the uneven wear resistance and the effect of improving the WET performance can be remarkably obtained. Note that the maximum groove depth D4 from the tread surface 2a of the groove bottom sipes 7 and 8 is set to the maximum groove depth D1 of the circumferential main groove 3 in order to obtain the effect of improving uneven wear resistance and the improvement of WET performance. On the other hand, it is more preferable that the range be 70% or more and 80% or less.

  In the pneumatic tire 1 of the present embodiment, as shown in FIG. 5, the circumferential main groove 3 and the circumferential narrow groove 5 forming the center main groove 31 are maintained in the tire width direction while maintaining the same distance in the tire width direction. It is preferable to be bent or curved. FIG. 5 shows the case where the circumferential main groove 3 is on the tire equatorial plane CL. In this case, the circumferential main groove 3 on the tire equatorial plane CL is used as the center main groove 31. Although not clearly shown in the figure, when the circumferential main groove 3 is not on the tire equatorial plane CL, the two main circumferential grooves 3 on both outer sides of the tire equatorial plane CL in the tire width direction are combined to form the center main groove 31. Therefore, the two center main grooves 31 are formed to be bent or curved in the tire width direction.

  According to the pneumatic tire 1, the circumferential main groove 3 forming the center main groove 31 is formed by being bent or curved, and thus has edge components in both the tire width direction and the tire circumferential direction, It becomes possible to improve the WET performance. In this case, the circumferential narrow groove 5 and the circumferential main groove 3 maintain the same distance in the tire width direction, so that the rib shape of the side rib-shaped land portion 41 and the tire width direction dimensions of the block shape are uniform in the tire circumferential direction. Therefore, the effect of maintaining the rigidity of the rib shape and block shape of the side rib-shaped land portion 41 uniformly in the tire width direction and the tire circumferential direction can be significantly obtained.

  In the pneumatic tire 1 of the present embodiment, as shown in FIG. 1, FIG. 2, or FIG. 5, the center main groove 31 has a groove width direction dimension L from the tire equatorial plane CL to the ground contact end T. 3 [%] to 15 [%], and each circumferential main groove 3 provided adjacent to the center main groove 31 with the side rib-shaped land portion 41 in between is the tire equatorial plane CL. Is preferably in the range of 50% to 60% of the tire width direction dimension L from the tire equatorial plane CL to the contact end T.

  Each circumferential main groove 3 provided apart from the tire equator plane CL is a position at the center of the groove width of the circumferential main groove 3 from the tire equator plane CL.

  Here, the contact end T is the contact area (when the pneumatic tire 1 is assembled to a regular rim and filled with a regular internal pressure and 70% of the regular load is applied, the tread portion 2 of the pneumatic tire 1 is applied. These are the outermost ends in the tire width direction of the region where the tread surface 2a is in contact with the road surface). In FIGS. 1, 2, and 5, the contact end T is shown continuously in the tire circumferential direction. Moreover, in the pneumatic tire 1 of the present embodiment in which the interval in the tire width direction of the ground contact edge T is set as the ground contact width TW and has a symmetrical tread pattern, the tire width direction dimension L from the tire equatorial plane CL to the ground contact edge T is This corresponds to 1/2 of the grounding width TW.

  The regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  The hydrobrunning phenomenon tends to occur starting from the center side of the tread surface 2a in the tire width direction. Therefore, according to the pneumatic tire 1, the groove width of the center main groove 31 disposed on the center side in the tire width direction is defined, and the circumferential main groove 3 adjacent to the outer side of the center main groove 31 in the tire width direction is defined. By disposing the position on the center side in the tire width direction, drainage performance on the center side in the tire width direction is improved, so that it is possible to further improve the WET performance.

  Moreover, it is preferable that the pneumatic tire 1 of this embodiment is the range whose JIS hardness in 20 [degreeC] of the compound which makes the tread part 2 is 60 or more and 75 or less.

  According to this pneumatic tire 1, by making the JIS hardness at 20 [° C.] of the compound forming the tread portion 2 60 or more, the effect of improving the uneven wear resistance and the effect of improving the WET performance with an appropriate hardness. Can be obtained remarkably. When the JIS hardness at 20 [° C.] of the compound forming the tread portion 2 is 75, this is the maximum value used for a general pneumatic tire. In addition, in order to obtain the effect of improving uneven wear resistance and the effect of improving WET performance more remarkably, it is preferable to set the JIS hardness at 20 [° C.] of the compound forming the tread portion 2 in the range of 65 to 70.

  Moreover, it is preferable that the pneumatic tire 1 of this embodiment is applied to the pneumatic tire for small trucks with a specified internal pressure of 600 [kPa] or less.

  Since pneumatic tires for light trucks are mainly used for local travel, stop-and-go is repeated many times during medium and low speed travel, and excellent wear resistance and grip power (WET performance) are required. According to the pneumatic tire 1 of the present embodiment, it is possible to satisfy the requirements of excellent wear resistance and gripping power as a small truck pneumatic tire mainly used in local travel.

  6 to 9 are tables showing the results of the performance test of the pneumatic tire according to this example. In this example, performance tests on uneven wear resistance and WET performance (WET braking performance) were performed on multiple types of pneumatic tires with different conditions.

  In this performance test, a pneumatic tire of a tire size 205 / 85R16 117 / 115L LTR rib tire was assembled to a regular rim, filled with a regular internal pressure, and mounted on a test vehicle (3 [t] stacked light truck).

  The evaluation method of uneven wear resistance performance is the uneven wear that occurred in the rib-like land portion after traveling 50,000 [km] at an average speed of 60 [km / h] on the test vehicle (side rib-like land portion and other The difference in the amount of wear on the tread surface from the rib-like land is measured. Based on this measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This evaluation indicates that the larger the value, the better the uneven wear resistance performance.

  The WET performance is evaluated by measuring the braking distance from an initial speed of 60 [km / h] on a test course on a wet road surface with a water depth of 10 ± 1 [mm] using the test vehicle. Based on this measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This evaluation shows that the larger the value, the better the WET performance.

  6 and 7 show a pneumatic tire in which four circumferential main grooves are arranged in a tread portion and five rib-like land portions are partitioned. That is, the circumferential main groove is not on the tire equatorial plane. The pneumatic tire of Conventional Example 1 has a rib-like land portion (side rib-shaped land portion) adjacent to both sides in the tire width direction of each circumferential main groove (center main groove) on both sides in the tire width direction of the tire equatorial plane. Each end communicates with the circumferential main grooves on both sides of the tire width direction, and a plurality of narrow grooves in the width direction formed with a shallower depth than the circumferential main grooves are arranged to block the side rib-shaped land portions It is said. Moreover, the pneumatic tire of Comparative Example 1 is a rib-like land portion (side rib-shaped land portion) adjacent to both sides in the tire width direction of each circumferential main groove (center main groove) on both sides in the tire width direction of the tire equatorial plane. The circumferential ribs extending in the tire circumferential direction and having a groove depth shallower than the circumferential main groove are arranged so that the side rib-shaped land portion has two rib shapes. Further, the pneumatic tire of Comparative Example 2 is connected to the circumferential ribs on both sides in the tire width direction in the side rib-shaped land portion, and the groove depth is larger than the circumferential main groove with respect to the pneumatic tire of Comparative Example 1. A plurality of narrow grooves formed in the width direction are arranged to form a side rib-like land portion in a block shape. In the pneumatic tires of Conventional Example 1, Comparative Example 1, and Comparative Example 2, narrow grooves are not formed in other rib-like land portions. Note that Comparative Example 1 and Comparative Example 2 are evaluated based on Conventional Example 1.

  On the other hand, as shown in FIGS. 6 and 7, the pneumatic tires of Examples 1 to 41 are provided on both sides in the tire width direction of the circumferential main grooves (center main grooves) on both sides of the tire equatorial plane in the tire width direction. For adjacent rib-shaped land portions (side rib-shaped land portions), from one side in the tire width direction of the side rib-shaped land portions to 40 [%] or more and 60 [%] of the tire width direction dimension of the side rib-shaped land portions. %] A circumferential narrow groove extending along the tire circumferential direction and having a groove depth shallower than the circumferential main groove in the following range, and one end of the lateral rib-shaped land portion on the outer side in the tire width direction. The other end communicates with the circumferential narrow groove and terminates and extends across the tire circumferential direction, and the groove depth is shallower than the circumferential main groove. A plurality of widthwise narrow grooves formed in the tire circumferential direction, and a tire width of a side rib-shaped land portion with the circumferential narrow groove as a boundary Countercurrent inner and ribs, the tire width direction outer side rib-like land portion in which the circumferential narrow groove as a boundary is a block shape. In the pneumatic tires of Examples 1 to 41, no narrow grooves are formed in other rib-like land portions. In the pneumatic tires of Examples 4 to 8, the groove depth of the narrow grooves is defined. In the pneumatic tires of Examples 9 to 18, a groove bottom sipe is formed at the groove bottom of the widthwise narrow groove. In the pneumatic tires of Examples 19 to 28, a groove bottom sipe is formed at the groove bottom of the circumferential narrow groove. In the pneumatic tires of Examples 29 to 38, groove bottom sipes are formed on the groove bottoms of the width direction narrow grooves and the circumferential direction narrow grooves. In the pneumatic tires of Example 39 and Example 41, the circumferential main groove and the circumferential narrow groove are bent (see FIG. 5). The pneumatic tires of Example 40 and Example 41 satisfy the regulation of the groove width of the center main groove and the position of the adjacent circumferential main groove. In addition, Examples 1 to 41 are evaluated based on Conventional Example 1.

  FIGS. 8 and 9 are pneumatic tires in which three circumferential main grooves are arranged in a tread portion and four rib-like land portions are partitioned. That is, the circumferential main groove is disposed on the tire equatorial plane. In the pneumatic tire of Conventional Example 2, the rib-shaped land portions (side rib-shaped land portions) adjacent to both sides in the tire width direction of the circumferential main groove (center main groove) on the tire equatorial plane are both sides in the tire width direction. Each of the ends communicates with the circumferential main groove, and a plurality of narrow grooves in the width direction formed with a groove depth shallower than the circumferential main groove are arranged to form the side rib-shaped land portion in a block shape. In the pneumatic tire of Comparative Example 3, the circumferential direction of the circumferential main groove (center main groove) on the tire equatorial plane is adjacent to both sides in the tire width direction, and the circumferential direction of the tire is in the tire circumferential direction. The lateral rib-like land portion is formed in two rib shapes by disposing a circumferential narrow groove formed to extend in the direction of the groove and having a groove depth shallower than the circumferential main groove. Further, the pneumatic tire of Comparative Example 4 is connected to the circumferential ribs on both sides in the tire width direction on the side rib-shaped land portion, and the groove depth of the pneumatic tire of Comparative Example 4 is larger than that of the circumferential main groove. A plurality of narrow grooves formed in the width direction are arranged to form a side rib-like land portion in a block shape. In the pneumatic tires of Conventional Example 2, Comparative Example 3, and Comparative Example 4, no narrow grooves are formed in other rib-like land portions. The conventional example 2 is an index based on the conventional example 1, and the comparative example 3 and the comparative example 4 are evaluated based on the conventional example 2.

  On the other hand, as shown in FIGS. 8 and 9, the pneumatic tires of Examples 42 to 82 are rib-like land adjacent to both sides in the tire width direction of the circumferential main groove (center main groove) on the tire equator plane. For the portion (side rib-shaped land portion), a range from 40% to 60% of the tire width direction dimension of the side rib-shaped land portion from one side in the tire width direction of the side rib-shaped land portion. And a circumferential narrow groove extending along the tire circumferential direction and having a groove depth shallower than the circumferential main groove, and one circumferential end adjacent to the outer side in the tire width direction of the side rib-shaped land portion. The other end communicates with the circumferential groove and terminates and extends across the tire circumferential direction, and has a groove depth shallower than the circumferential main groove. A plurality of widthwise narrow grooves arranged in the direction, and a rib-shaped inner side in the tire width direction of the side rib-shaped land portion with the circumferential narrow groove as a boundary And then, the tire width direction outer side rib-like land portion in which the circumferential narrow groove as a boundary is a block shape. In the pneumatic tires of Examples 42 to 82, no narrow grooves are formed in other rib-like land portions. In the pneumatic tires of Examples 45 to 49, the groove depth of the narrow groove is defined. In the pneumatic tires of Examples 50 to 59, a groove bottom sipe is formed at the groove bottom of the narrow groove in the width direction. In the pneumatic tires of Examples 60 to 69, a groove bottom sipe is formed at the groove bottom of the circumferential narrow groove. In the pneumatic tires of Examples 70 to 79, groove bottom sipes are formed at the groove bottoms of the width direction narrow grooves and the circumferential direction narrow grooves. In the pneumatic tires of Example 80 and Example 82, the circumferential main groove and the circumferential narrow groove are bent (see FIG. 5). The pneumatic tires of Example 81 and Example 82 satisfy the regulation of the groove width of the center main groove and the position of the adjacent circumferential main groove. In addition, Examples 42 to 82 are evaluated based on Conventional Example 2.

  As shown in the test results of FIGS. 6 to 9, it can be seen that the pneumatic tires of Examples 1 to 82 have improved uneven wear resistance and WET performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2a Tread surface 3 Circumferential main groove 31 Center main groove 4 Rib-like land part 41 Side rib-like land part 5 Circumferential narrow groove 6 Width-direction narrow groove 7, 8 Groove bottom sipes 9 Tread surface Sipe CL Tire Equatorial Surface T Grounding End

Claims (7)

The tread surface of the tread portion has a symmetrical tread pattern that is symmetrical on both sides in the tire width direction with respect to the tire equatorial plane, and has at least three circumferential main grooves extending along the tire circumferential direction. In the pneumatic tire in which at least four rib-like land portions extending in the direction are formed,
When the circumferential main groove is on the tire equator plane, the circumferential main groove on the tire equator plane is a center main groove, and when the circumferential main groove is not on the tire equator plane, the tire equator plane When the circumferential main grooves on both outer sides in the tire width direction are combined into a center main groove, and the rib-like land portions adjacent to both outer sides in the tire width direction of the center main groove are side rib-shaped land portions,
Extending along the tire circumferential direction from one side of the lateral rib-shaped land portion in the tire width direction to a range of 40% to 60% of the tire width direction dimension of the lateral rib-shaped land portion. And a circumferential narrow groove formed with a groove depth shallower than the circumferential main groove,
One end of the side rib-shaped land portion is connected to the circumferential main groove adjacent to the outer side in the tire width direction of the side rib-shaped land portion, and the other end communicates with the circumferential narrow groove. Extending in the tire circumferential direction and terminating, the groove depth is shallower than the circumferential main groove, a plurality of width direction narrow grooves arranged in the tire circumferential direction,
A rib-shaped inner side in the tire width direction of the lateral rib-shaped land portion with the circumferential narrow groove as a boundary, and an outer side in the tire width direction of the lateral rib-shaped land portion with the circumferential narrow groove as a boundary The block shape,
A groove bottom sipe is formed on the groove bottom of the widthwise narrow groove, the groove bottom sipe communicates with the circumferential main groove, and a distance of 40 [ %] And a pneumatic tire extending in a range of 60 [%] or less. The tread surface of the tread portion has a symmetrical tread pattern that is symmetrical on both sides in the tire width direction with respect to the tire equatorial plane, and has at least three circumferential main grooves extending along the tire circumferential direction. In the pneumatic tire in which at least four rib-like land portions extending in the direction are formed,
When the circumferential main groove is on the tire equator plane, the circumferential main groove on the tire equator plane is a center main groove, and when the circumferential main groove is not on the tire equator plane, the tire equator plane When the circumferential main grooves on both outer sides in the tire width direction are combined into a center main groove, and the rib-like land portions adjacent to both outer sides in the tire width direction of the center main groove are side rib-shaped land portions,
Extending along the tire circumferential direction from one side of the lateral rib-shaped land portion in the tire width direction to a range of 40% to 60% of the tire width direction dimension of the lateral rib-shaped land portion. And a circumferential narrow groove formed with a groove depth shallower than the circumferential main groove,
One end of the side rib-shaped land portion is connected to the circumferential main groove adjacent to the outer side in the tire width direction of the side rib-shaped land portion, and the other end communicates with the circumferential narrow groove. Extending in the tire circumferential direction and terminating, the groove depth is shallower than the circumferential main groove, a plurality of width direction narrow grooves arranged in the tire circumferential direction,
A rib-shaped inner side in the tire width direction of the lateral rib-shaped land portion with the circumferential narrow groove as a boundary, and an outer side in the tire width direction of the lateral rib-shaped land portion with the circumferential narrow groove as a boundary The block shape,
A groove bottom sipe is formed at the groove bottom of the circumferential narrow groove, and the groove bottom sipe is not less than 60% and not more than 90% of the interval between the widthwise narrow grooves communicating with the circumferential narrow groove. Pneumatic tire characterized by being arranged in the range.   The circumferential narrow groove and the width narrow groove have a maximum groove depth in the range of 10% to 40% with respect to the groove depth of the circumferential main groove. The pneumatic tire according to claim 1 or 2.   The groove bottom sipe has a maximum groove depth from the tread surface in a range of 60% to 90% with respect to the groove depth of the circumferential main groove. The pneumatic tire according to any one of 1 to 3.   2. The circumferential main groove and the circumferential narrow groove forming the center main groove are formed to be bent or curved in the tire width direction while maintaining the same distance in the tire width direction. 4. The pneumatic tire according to any one of 4.   The center main groove has a groove width in a range of 3 [%] to 15 [%] of the tire width direction dimension from the tire equatorial plane to the ground contact edge, and the side main rib is shaped like the side rib. Each of the circumferential main grooves provided between the land portions has a position from the tire equatorial plane in the range of 50% to 60% of the tire width direction dimension from the tire equatorial plane to the ground contact edge. The pneumatic tire according to any one of claims 1 to 5, wherein: The pneumatic tire according to any one of claims 1 to 6 , which is applied to a pneumatic tire for a small truck having a specified internal pressure of 600 [kPa] or less.

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