JP5803859B2 - 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 specified by JATMA are mainly used for local driving, stop-and-go is repeated many times during medium and low-speed driving, and excellent uneven wear resistance and grip power (WET performance) are required. Is done.

  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 uneven 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-described problems and achieve the object, the pneumatic tire of the first invention extends in the tire circumferential direction by 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 are formed, when the circumferential main groove is an odd number, the central circumferential main groove is a center main groove and the circumferential main groove is an even number. When the two main circumferential grooves on the center side are combined as 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 shallower groove depth than the circumferential main groove, One end is provided in the lateral rib-shaped land portion and ends in communication with the circumferential main groove adjacent to the outer side in the tire width direction of the lateral rib-shaped land portion, and the other end penetrates the circumferential narrow groove. A widthwise narrow groove extending in the tire circumferential direction while terminating in the side rib-shaped land portion, having a groove depth shallower than the circumferential main groove, and a plurality of widthwise narrow grooves arranged in the tire circumferential direction. And a circumferential groove bottom sipe formed along the extending direction of the circumferential narrow groove at the groove bottom of the circumferential narrow groove, and the lateral rib-shaped land with the circumferential narrow groove as a boundary The inner side in the tire width direction of the portion is formed in a rib shape, and the outer side in the tire width direction of the side rib-shaped land portion with the circumferential narrow groove as a boundary is formed in 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, the circumferential narrow groove 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 of the side rib-shaped land portion. Since the difference in rigidity in the tire width direction of the portion becomes small, uneven wear can be suppressed. In addition, since the circumferential narrow groove is formed with a shallower groove depth than the circumferential main groove, the rib of the side rib-shaped land portion is compensated by compensating the difference in the groove depth with the circumferential groove bottom sipe. Uneven wear can be suppressed by keeping the rigidity of the shape uniform in the tire width direction. As a result, it is possible to improve uneven wear resistance and WET performance.

  The pneumatic tire according to a second aspect of the present invention further includes, in the first aspect, a widthwise groove bottom sipe formed along the extending direction of the widthwise narrow groove at the groove bottom of the widthwise narrow groove. It is characterized by that.

  According to this pneumatic tire, the widthwise narrow groove is formed with a shallower groove depth than the circumferential main groove. The block-shaped rigidity of the rib-like land portion can be kept uniform in the tire width direction and the tire circumferential direction, and uneven wear can be suppressed. As a result, the effect of improving uneven wear resistance can be obtained remarkably.

  In the first or second invention, the pneumatic tire of the third invention extends from the other end of the widthwise narrow groove toward the center main groove and terminates in the lateral rib-shaped land portion. A tread surface sipe is further included.

  According to this pneumatic tire, in the rib shape inside the tire width direction of the side rib-shaped land portion, the other end of the width direction narrow groove is terminated, and the tread surface sipe is extended from there to be While maintaining the uneven wear resistance performance due to the rib shape of the rib-like land portion, the drainage can be further improved to improve the WET performance.

  The pneumatic tire according to a fourth aspect of the present invention is the pneumatic tire according to the second or third aspect, wherein the width direction groove bottom sipe is formed except for an intersection where the width direction narrow groove penetrates the circumferential direction narrow groove. It is characterized by that.

  If the width direction groove bottom sipe penetrates the intersection where the width direction narrow groove penetrates the circumferential direction narrow groove, the rigidity of the block shape and rib shape near the intersection tends to decrease locally, so this part By providing the width direction groove bottom sipe except for the above, it is possible to suppress the lowering of the rigidity of the side rib-shaped land portion more than necessary and improve the uneven wear resistance.

  In the pneumatic tire according to a fifth aspect of the present invention, in any one of the second to fourth aspects, the width direction groove bottom sipe is formed in communication with the tread surface sipe.

  According to this pneumatic tire, the effect of the above-described tread surface sipe can be remarkably obtained by communicating the width direction groove bottom sipe with the tread surface sipe. That is, while maintaining the uneven wear resistance performance due to the rib shape of the side rib-shaped land portion, it is possible to further improve the drainage and improve the WET performance.

  The pneumatic tire according to a sixth aspect of the present invention is the pneumatic tire according to any one of the first to fifth aspects, wherein the sipe sets a maximum groove depth from the tread surface to a groove depth of the circumferential main groove. On the other hand, the range is from 60% to 90%.

  According to this pneumatic tire, the maximum groove depth from the tread surface of the sipe is set to 60% or more with respect to the maximum groove depth of the circumferential main groove. By setting the ratio to 90 [%] or less, 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 is the pneumatic tire according to any one of the first to sixth aspects, wherein the widthwise narrow groove is along each linear component having at least two angles with respect to the tire circumferential direction. It is formed by bending.

  According to this pneumatic tire, since the widthwise narrow grooves are formed along the linear component, the effect of improving drainage can be remarkably obtained, and the WET performance can be further improved.

  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 widthwise narrow groove includes a groove width W1 on one end side communicating with the circumferential main groove, and the side. The groove width W2 at the other end that terminates in the rib-like land portion satisfies the relationship W2 <W1, and is formed by gradually changing the groove width between the one end and the other end. And

  According to this pneumatic tire, the groove width W1 at one end communicating with the circumferential main groove is larger than the groove width W2 at the other end terminating at the side rib-shaped land portion, and at one end and the other end. Therefore, the drainage from the side rib-shaped land portion to the circumferential main groove side can be improved.

  The pneumatic tire according to a ninth aspect of the present invention is the pneumatic tire according to any one of the first to eighth aspects, wherein the circumferential narrow groove and the width narrow groove have a maximum groove depth that is the circumferential main groove. It is characterized by being in the range of 10 [%] to 40 [%] with respect to the groove depth.

  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 according to a tenth aspect of the invention is the pneumatic tire according to any one of the first to ninth aspects, wherein the center main groove has a groove width dimension of 3 [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 an eleventh aspect, in any one of the first to tenth aspects, the outermost rib-like land portion in the tire width direction is 10 with respect to the groove depth of the circumferential main groove. [%] It is characterized by not disposing narrow grooves or sipes.

  According to this pneumatic tire, uneven wear resistance is prevented by disposing 10% or more narrow grooves and sipes with respect to the groove depth of the circumferential main groove in the outermost rib-like land portion in the tire width direction. The performance improvement effect can be obtained more remarkably.

  In the pneumatic tire of the twelfth invention, in any one of the first to eleventh 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 thirteenth aspect is characterized in that, in any one of the first to twelfth 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 uneven wear resistance and grip power (WET performance) are required. According to this pneumatic tire, as a pneumatic tire for small trucks mainly used in local running, it is possible to satisfy the requirements for excellent uneven wear resistance and gripping power.

  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 chart showing the results of the performance test of the pneumatic tire according to the example 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.

  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. 3 is a partially enlarged plan view of the pneumatic tire shown in FIG. 2.

  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, in the pneumatic tire 1 of the present embodiment, the tread portion 2 has at least three circumferential main grooves 3 extending along the tire circumferential direction on the tread surface 2a (3 in FIG. 1). (4 in FIG. 2). 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). In the pneumatic tire 1 of the present embodiment, the tread pattern of the tread surface 2a is preferably a symmetrical tread pattern in which both sides in the tire width direction are symmetrical with respect to the tire equatorial plane CL. The symmetrical tread pattern indicates that the tread pattern has the same shape when turned over in the tire width direction. 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 an odd number, the central circumferential main groove 3 is used as the center main groove 31 (in FIG. 1, the central circumferential main groove 3 3 is on the tire equatorial plane CL). As shown in FIG. 2, when the circumferential main grooves 3 are an even number, the two circumferential main grooves 3 on the center side (both outer sides in the tire width direction) are combined to form a center main groove 31. Although not clearly shown in the figure, when there are five circumferential main grooves 3, the circumferential main grooves 3 are odd numbers, so the central circumferential main groove 3 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. It extends through the circumferential narrow groove 5 to extend in the tire circumferential direction while terminating in the side rib-shaped land portion 41, and a plurality of tires are arranged in the tire circumferential direction. 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 the range of 7 [mm] to 12 [mm] and a groove width of 8 [mm] to 14 [mm]. mm] or less. Further, the circumferential narrow grooves 5 and the width narrow grooves 6 have the groove depths D2 and D3 within the specified range, and the groove widths within a range of 2 [mm] to 4 [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.

  Further, the circumferential narrow groove 5 is formed with a circumferential groove bottom sipe 7 at the groove bottom. The circumferential groove bottom sipe 7 is formed from the groove bottom of the circumferential narrow groove 5 toward the inside in the tire radial direction, and extends along the extending direction of the circumferential narrow groove 5 (tire circumferential direction). ing. The circumferential groove bottom sipe 7 has a groove width of 1.0 [mm] or less. The circumferential groove bottom sipe 7 is formed at the center of the circumferential narrow groove 5 in FIG. The circumferential groove bottom sipe 7 is not limited to this, but may be formed along the groove wall of the circumferential narrow groove 5 toward the inside in the tire radial direction, though not explicitly shown in the drawing. Further, when the circumferential groove bottom sipe 7 is formed along the groove wall of the circumferential narrow groove 5, the circumferential groove bottom sipe 7 may be formed on either one or both of the both circumferential groove grooves 5.

  According to the pneumatic tire 1 as described above, the circumferential narrow groove 5 has the drainage performance in the tire circumferential direction, and the lateral narrow groove 6 has the drainage performance to the outer side in the tire width direction. It is possible to improve operability and braking performance on the road surface. 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. In addition, since the circumferential narrow groove 5 is formed with a shallower groove depth than the circumferential main groove 3, the difference in the groove depth is compensated by the circumferential groove bottom sipe 7, so that the lateral rib-like land 5 The rigidity of the rib shape of the portion 41 can be kept uniform in the tire width direction, and uneven wear can be suppressed. As a result, it is possible to improve uneven wear resistance and WET performance.

  The pneumatic tire 1 preferably has a symmetric tread pattern, and can be exchanged in the front / rear and left / right directions in rotation, so that the wear can be made uniform and the life can be extended. .

  Further, in the pneumatic tire 1 of the present embodiment, as shown in FIGS. 3 and 4, a width direction groove bottom sipe 8 is formed on the groove bottom of the width direction narrow groove 6. The width direction groove bottom sipe 8 is formed from the groove bottom of the width direction narrow groove 6 toward the inside in the tire radial direction, and is provided along the extending direction of the width direction narrow groove 6. The width direction groove bottom sipe 8 has a groove width of 1.0 [mm] or less. Moreover, the width direction groove bottom sipe 8 is formed at the center of the groove bottom of the width direction narrow groove 6 in FIG. The width direction groove bottom sipe 8 is not limited to this, but may be formed along the groove wall of the width direction narrow groove 6 although not shown in the drawing. Further, when the width direction groove bottom sipe 8 is formed along the groove wall of the width direction narrow groove 6, the width direction groove bottom sipe 8 may be formed on either or both of the both wall surfaces of the width direction narrow groove 6.

  According to this pneumatic tire 1, the width direction narrow groove 6 is formed with a shallower groove depth than the circumferential direction main groove 3, so that the difference in groove depth is compensated by the width direction groove bottom sipe 8. Thus, the block-shaped rigidity of the side rib-shaped land portion 41 can be kept uniform in the tire width direction and the tire circumferential direction, thereby suppressing uneven wear. As a result, the effect of improving the uneven wear resistance can be remarkably obtained.

  Further, as shown in FIGS. 3 and 4, the pneumatic tire 1 of the present embodiment extends from the other end of the width-direction narrow groove 6 to the center main groove 31 side, and in the side rib-shaped land portion 41. A tread surface sipe 9 that terminates is formed. The tread surface sipe 9 is provided along the extending direction of the widthwise narrow groove 6 at one end of the widthwise narrow groove 6. The tread surface sipe 9 has a groove width of 1.0 [mm] or less.

  According to this pneumatic tire 1, in the rib shape inside the tire width direction of the side rib-shaped land portion 41, the other end of the width direction narrow groove 6 is terminated, and the tread surface sipe 9 is extended therefrom. Thus, while maintaining the uneven wear resistance performance due to the rib shape of the lateral rib-like land portion 41, it is possible to further improve the drainage and improve the WET performance. The tread surface sipe 9 may be formed along the extending direction of the other end of the widthwise narrow groove 6 or may be formed away from the extending direction of the other end of the widthwise narrow groove 6. However, it is possible to further improve the drainage performance if it is formed along the extending direction of the other end of the width direction narrow groove 6. The tread surface sipe 9 preferably has a groove length extending from one end of the widthwise narrow groove 6 of 2 [mm] or more and 8 [mm] or less in order to obtain the above-described effect remarkably.

  Moreover, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 4, the width direction groove bottom sipe 8 is formed except for the intersection X where the width direction narrow groove 6 penetrates the circumferential direction narrow groove 5. It is preferable.

  When the width direction groove bottom sipe 8 penetrates the intersection X where the width direction narrow groove 6 penetrates the circumferential direction narrow groove 5, the rigidity of the block shape or rib shape near the intersection X tends to decrease locally. Therefore, by providing the width direction groove bottom sipe 8 except for this portion, it is possible to suppress a reduction in rigidity of the side rib-shaped land portion 41 more than necessary and to improve uneven wear resistance. In addition, it is more preferable to form the circumferential groove bottom sipe 7 excluding the intersecting portion X in order to suppress the local decrease in the rigidity of the block shape and the rib shape in the portion close to the intersecting portion X.

  Further, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 3, the width direction groove bottom sipe 8 is preferably formed in communication with the tread surface sipe 9.

  According to this pneumatic tire 1, by making the width direction groove bottom sipe 8 communicate with the tread surface sipe 9, the effect of the above-described tread surface sipe 9 can be remarkably obtained. That is, it is possible to further improve the drainage and improve the WET performance while maintaining the uneven wear resistance performance due to the rib shape of the side rib-shaped land portion 41.

  Moreover, in the pneumatic tire 1 of this embodiment, as shown in FIG. 3, the above-described sipe (circumferential groove bottom sipe 7, width direction groove bottom sipe 8, and tread surface sipe 9) is from the tread surface 2a. It is preferable that the maximum groove depths D4, D5, and D6 be in the range of 60% to 90% with respect to the groove depth D1 of the circumferential main groove 3.

  By setting the maximum groove depth D4, D5, D6 from the tread surface 2a of the sipe 7, 8, 9 described above to 60 [%] or more with respect to the maximum groove depth D1 of the circumferential main groove 3, drainage performance is achieved. As a result, the rigidity of the rib shape and the block shape of the side rib-shaped land portion 41 is kept uniform in the tire width direction and the tire circumferential direction. The effect can be obtained remarkably. 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 D4, D5, and D6 from the tread surface 2a of the sipes 7, 8, and 9 are set to the maximum of the circumferential main groove 3 in order to obtain the effect of improving uneven wear resistance and the effect of improving WET performance. More preferably, it is in the range of 70 [%] to 80 [%] with respect to the groove depth D1.

  Further, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 4, the widthwise narrow groove 6 is bent along each linear component having at least two angles (α, β) with respect to the tire circumferential direction. Preferably formed.

  According to this pneumatic tire 1, since the widthwise narrow grooves 6 are formed along the linear component, it is possible to obtain a remarkable effect of improving drainage and further improve the WET performance. It becomes possible.

  In addition, as shown in FIG. 4, the width direction narrow groove 6 is bent and formed along each linear component α1, β1 having two angles α, β with respect to the tire circumferential direction. The angles α and β of the linear components α1 and β1 are preferably 30 [°] or more with respect to the tire circumferential direction in order to improve drainage. In order to further improve drainage performance, the continuous linear components α1 and β1 are 30 ° or more and 90 ° or less so that the angles α and β are oriented in the same direction with respect to the tire circumferential direction. preferable. The continuous linear components α1 and β1 preferably have an angle difference between the angles α and β of 10 [°] or more and 40 [°] or less in order to further improve drainage. The continuous linear components α1 and β1 indicate that the relation between the angle α on the outer side in the tire width direction and the angle β on the inner side in the tire width direction is β <α. It is preferable for improving the drainage performance. When the number of linear components (number of angles) increases, it approaches a circular arc. Therefore, the number of linear components (number of angles) is preferably 2 or more and 4 or less in order to improve drainage.

  Further, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 4, the widthwise narrow groove 6 is composed of a groove width W1 on one end side communicating with the circumferential main groove 3 and a side rib-shaped land portion 41. It is preferable that the groove width W2 on the other end side that terminates satisfies the relationship of W2 <W1, and the groove width is gradually changed between the one end side and the other end side.

  According to this pneumatic tire 1, the groove width W <b> 1 at one end communicating with the circumferential main groove 3 is larger than the groove width W <b> 2 at the other end terminating at the side rib-shaped land portion 41, and one end side and the other. Since the groove width is gradually changed from the end side, drainage performance from the side rib-shaped land portion 41 to the circumferential main groove 3 side can be improved.

  The groove width W2 at the other end that terminates at the side rib-shaped land portion 41 has a ratio W2 / W1 with respect to the groove width W1 at one end communicating with the main groove of 0.7 to 0.9. It is preferable for improving drainage. Further, the groove width W1 on one end side of the width-direction narrow groove 6 communicating with the circumferential main groove 3 is the width of each virtual line along both opening edges in the extending direction of the width-direction narrow groove 6 on the tread surface 2a. This is the shortest distance between the intersections intersecting the imaginary line along the opening edge of the circumferential main groove 3 with which the directional fine groove 6 communicates. When the chamfered portion 10 is formed in a portion where the width direction narrow groove 6 communicates with the circumferential main groove 3, the chamfered portion 10 is ignored. On the other hand, the groove width W2 on the other end side of the widthwise narrow groove 6 that terminates in the side rib-shaped land portion 41 is an imaginary line along both opening edges in the extending direction of the widthwise narrow groove 6 on the tread surface 2a. Is the shortest distance between the portions away from the narrow groove 6 in the width direction. When the other end of the width direction narrow groove 6 terminates with an arc, it is the shortest distance between the inflection points of the arc.

  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.

  Further, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 1 or FIG. 2, the center main groove 31 has a groove width 3 [L] in the tire width direction dimension L from the tire equatorial plane CL to the ground contact end T. %] And 15 [%] or less, and each circumferential main groove 3 provided adjacent to the center main groove 31 with the lateral rib-shaped land portion 41 in between is a position from the tire equatorial plane CL. Is preferably in the range of 50 [%] or more and 60 [%] or less of the tire width direction dimension L from the tire equatorial plane CL to the ground contact edge 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 a region where the tread surface 2a is in contact with the road surface). In FIGS. 1 and 2, 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, a 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.

  Further, in the pneumatic tire 1 according to the present embodiment, the outermost rib-like land portion 4 in the tire width direction has 10% or more narrow grooves and sipes with respect to the groove depth D1 of the circumferential main groove 3. Preferably not.

  According to the pneumatic tire 1, the rib-like land portion 4 on the outermost side in the tire width direction is not provided with a narrow groove or sipe of 10% or more with respect to the groove depth D1 of the circumferential main groove 3. Further, the effect of improving the uneven wear resistance can be obtained more remarkably. 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 10.

  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 frequently repeated at medium and low speed travel, and excellent uneven wear resistance and gripping power (WET performance) are required. According to the pneumatic tire 1 of the present embodiment, it is possible to satisfy the requirements of excellent uneven wear resistance and gripping force as a small truck pneumatic tire mainly used in local travel.

  5-8 is a table | surface which shows the result of the performance test of the pneumatic tire which concerns on a present 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. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. 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. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation shows that the larger the value, the better the WET performance.

  FIG. 5 and FIG. 6 are pneumatic tires in which four circumferential main grooves are arranged in the tread portion to define five rib-like land portions. 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.

  On the other hand, as shown in FIGS. 5 and 6, the pneumatic tires of Examples 1 to 26 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 penetrates the circumferential narrow groove and terminates in the lateral rib-shaped land portion and extends across the tire circumferential direction, and extends from the circumferential main groove. Are formed with a shallow groove depth, a plurality of width direction narrow grooves arranged in the tire circumferential direction, and the circumferential direction narrow grooves on the groove bottom of the circumferential direction narrow groove. A circumferential groove bottom sipe formed along the existing 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, with the circumferential narrow groove as a boundary. The outer side in the tire width direction of the side rib-shaped land portion has a block shape. In the pneumatic tires of Examples 1 to 26, no narrow grooves are formed in other rib-like land portions. In the pneumatic tires of Examples 5 to 26, a groove bottom sipe is formed on the groove bottom of the narrow groove in the width direction. In the pneumatic tires of Examples 9 to 26, a tread surface sipe is formed at the other end of the narrow groove in the width direction. In the pneumatic tires of Example 7, Example 8, and Examples 11 to 26, the width direction groove bottom sipe and the circumferential direction groove bottom sipe are not arranged at the intersection of the narrow grooves. In the pneumatic tires of Examples 13 to 26, the width direction groove bottom sipe communicates with the tread surface sipe. In the pneumatic tires of Example 4, Example 6, Example 10, Example 8, Example 12, Example 14 to Example 26, the sipe groove depth is within a specified range. In the pneumatic tires of Examples 19 to 26, the narrow grooves in the width direction are bent along the linear component. In the pneumatic tires of Examples 20 to 26, the relationship between the groove widths at both ends of the narrow groove in the width direction is defined. In the pneumatic tires of Examples 21 to 26, the groove depth of the narrow grooves is within a specified range. In the pneumatic tire of Example 26, the groove width of the center main groove and the position of the adjacent circumferential main groove are satisfied.

  FIGS. 7 and 8 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 2 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. 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 3 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 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.

  On the other hand, as shown in FIGS. 7 and 8, the pneumatic tires of Examples 27 to 52 are provided on 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. 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 penetrates the circumferential narrow groove and terminates in the lateral rib-shaped land portion and extends across the tire circumferential direction, and extends from the circumferential main groove. Are also formed with a narrow groove depth and a plurality of narrow grooves in the circumferential direction of the tire, and the circumferential narrow grooves at the bottom of the circumferential narrow grooves. A circumferential groove bottom sipe formed along the extending 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, with the circumferential narrow groove as a boundary. The outer side in the tire width direction of the side rib-shaped land portion thus formed is made into a block shape. In the pneumatic tires of Examples 27 to 52, no narrow grooves are formed in the other rib-like land portions. In the pneumatic tires of Examples 31 to 52, a groove bottom sipe is formed at the groove bottom of the width direction narrow groove. In the pneumatic tires of Examples 35 to 52, a tread surface sipe is formed at the other end of the widthwise narrow groove. In the pneumatic tires of Example 33, Example 34, and Examples 37 to 52, the width direction groove bottom sipe and the circumferential direction groove bottom sipe are not arranged at the intersections of the narrow grooves. In the pneumatic tires of Examples 39 to 52, the width direction groove bottom sipe communicates with the tread surface sipe. In the pneumatic tires of Example 30, Example 32, Example 34, Example 36, Example 38, and Examples 40 to 52, the sipe groove depth is within a specified range. In the pneumatic tires of Examples 45 to 52, the narrow grooves in the width direction are bent along the linear component. In the pneumatic tires of Examples 46 to 52, the relationship between the groove widths at both ends of the narrow groove in the width direction is defined. In the pneumatic tires of Examples 47 to 52, the groove depth of the narrow grooves is within a specified range. In the pneumatic tire of Example 52, the groove width of the center main groove and the position of the adjacent circumferential main groove are satisfied.

  As shown in the test results of FIGS. 5 to 8, it can be seen that the pneumatic tires of Examples 1 to 52 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 Circumferential groove bottom sipe 8 Width direction Groove bottom sipe 9 Tread surface sipe T Grounding end

Claims (13)

In the pneumatic tire in which at least four rib-like land portions extending in the tire circumferential direction are formed on the tread surface of the tread portion by at least three circumferential main grooves extending in the tire circumferential direction.
When the circumferential main groove is an odd number, the central circumferential main groove is a center main groove, and when the circumferential main groove is an even number, the two circumferential main grooves on the center side are combined. When the center main groove and the rib-shaped land portion adjacent to both outer sides in the tire width direction of the center main groove is a side rib-shaped land portion,
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 is provided in the lateral rib-shaped land portion and ends in communication with the circumferential main groove adjacent to the outer side in the tire width direction of the lateral rib-shaped land portion, and the other end penetrates the circumferential narrow groove. A widthwise narrow groove extending in the tire circumferential direction while terminating in the side rib-shaped land portion, having a groove depth shallower than the circumferential main groove, and a plurality of widthwise narrow grooves arranged in the tire circumferential direction. ,
A circumferential groove bottom sipe formed on the groove bottom of the circumferential narrow groove along the extending direction of the circumferential narrow groove;
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 A pneumatic tire characterized by having a block shape.   The pneumatic tire according to claim 1, further comprising a widthwise groove bottom sipe formed along the extending direction of the widthwise narrow groove at the groove bottom of the widthwise narrow groove.   3. The pneumatic system according to claim 1, further comprising a tread surface sipe extending from the other end of the width direction narrow groove toward the center main groove side and terminating in the side rib-shaped land portion. tire.   4. The pneumatic tire according to claim 2, wherein the width direction groove bottom sipe is formed except for an intersecting portion where the width direction narrow groove penetrates the circumferential direction narrow groove.   The pneumatic tire according to any one of claims 2 to 4, wherein the width direction groove bottom sipe is formed in communication with the tread surface sipe.   The sipe has a maximum groove depth from the tread surface in a range of 60% to 90% with respect to a groove depth of the circumferential main groove. The pneumatic tire according to any one of 5.   The pneumatic tire according to any one of claims 1 to 6, wherein the narrow groove in the width direction is formed by bending along each linear component having at least two angles with respect to the tire circumferential direction. .   In the width direction narrow groove, the groove width W1 on one end side communicating with the circumferential main groove and the groove width W2 on the other end side terminating on the side rib-shaped land portion satisfy the relationship of W2 <W1. The pneumatic tire according to any one of claims 1 to 7, wherein a groove width is gradually changed between one end side and the other end side.   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 any one of claims 1 to 8.   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 9, wherein   11. The outermost rib-like land portion in the tire width direction does not include a narrow groove or sipe of 10% or more with respect to the groove depth of the circumferential main groove. The pneumatic tire according to one.   The pneumatic tire according to any one of claims 1 to 11, wherein 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.   The pneumatic tire according to any one of claims 1 to 12, 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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