JP5375376B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that improves the braking performance on ice in a tire having a sipe formed on a tread surface.

  In general, braking performance on wet road surfaces and on-ice road surfaces is greatly affected by the presence of a water film on the road surface, so it is widely practiced to improve water absorption by providing sipes on the tread surface. However, if too many sipes are arranged on the tread surface, the tread rigidity is lowered and the steering stability and braking performance are deteriorated. Therefore, many proposals have conventionally been made regarding the form of the sipes and their arrangement ( For example, see Patent Documents 1 and 2).

  Among these, in Patent Document 1, two or more sipes extending in different directions are crossed and arranged on the block surface to improve on-ice stability while preventing sipe cracking failure and chunk-out failure. Has proposed. Further, Patent Document 2 proposes to improve riding comfort while ensuring steering stability and wet braking performance by forming a sipe with a torsion around a torsion shaft extending in the tire radial direction. doing.

  However, in Patent Document 1, although the water absorption of the tread surface can be improved to some extent, if the number of sipes is further increased to increase the water absorption, there is a limit that it becomes difficult to maintain steering stability due to a decrease in tread rigidity. . Further, in Patent Document 2, since the torsion angle is set to a size exceeding 135 °, the releasability from the mold after tire molding vulcanization is deteriorated, and the tread surface is likely to be damaged. There is.

  Under such a background, the present applicant provides a closed sipe composed of a plurality of cuts extending radially in the center of a small hole extending in the tire radial direction and terminating at the land portion in the land portion of the tread surface, A proposal was made to improve the braking performance on the road surface on ice by giving a twist to each notch around the small hole and setting the twist angle within a predetermined range (Japanese Patent Application No. 2009-127469). ). However, with this proposal, it has been found that there is a limit to the effect of improving the braking performance on ice, and the present application has been filed.

JP-A-9-263111 JP 2006-27306 A

  An object of the present invention is to provide a pneumatic tire in which braking performance on ice in a tire having a sipe formed on a tread surface is improved.

In order to achieve the above object, a pneumatic tire according to the present invention includes a plurality of tires extending in a radial direction with respect to a virtual axis extending in a depth direction of the land portion and terminating in the land portion formed on a tread surface. In a pneumatic tire provided with a closed sipe in which an incision is arranged and spirally twisted toward the incision of the closed sipe in a depth direction around the imaginary axis, the imaginary axis of the incision Forming a widened portion that locally widens the cut width at least at one point from the end to the end portion, and setting a twist angle from the surface of the cut to the bottom to 90 to 120 ° , and The width is 2.0 to 5.0 times the width of the cut .

Furthermore, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(6) .

(1) The length of the cut in the radial direction is made different between the tread surface side and the bottom surface side in the depth direction of the closed sipes. In this case, the radial length of the cut may be shortened gradually or stepwise from the tread surface to the bottom surface of the closed sipe.

(2) The width of the cut is made different between the tread surface side and the bottom surface side in the depth direction of the closed sipe. In this case, the width of the cut may be increased gradually or stepwise from the tread surface to the bottom surface of the closed sipe.

(3) The number of the cuts is made different between the tread surface side and the bottom surface side in the depth direction of the closed sipes. In this case, the number of the cuts may be larger on the tread surface side in the depth direction of the closed sipe than on the bottom surface side.

(4) The number of the cuts is 2-6.

(5) The end of the cut on the virtual axis side is connected to the virtual axis or is not continuous. In the former case, a small hole may be formed along the virtual axis in the depth direction of the closed sipe.

(6) A linear sipe extending in the tire width direction together with the closed sipe is provided on the land portion. In this case, when the land portion is a block, the closed sipes may be arranged along the tire width direction at the front end portion and / or the rear end portion in the tire circumferential direction of the block.

According to the present invention described above, a closed sipe in which a plurality of cuts extending in a radial direction with respect to a virtual axis extending in the depth direction and terminating in the land portion is provided in the land portion formed on the tread surface, and these cuts are provided. A spiral twist is applied to the core in the depth direction around the imaginary axis, and the twist angle is set to 90 to 120 ° , so that the tread rigidity is reduced without affecting the releasability from the mold. While suppressing the above, it is possible to improve the water absorption performance and increase the braking performance on ice by increasing the volume accompanying the twisting of the cut.

In addition, since the widened part that locally widens the cut width is formed at least at one point from the virtual axis of the cut to the end part, the width of the cut is widened by the tread contact pressure that accompanies the contact of the tire when running on the road on ice. Since the water on the road surface on ice is easy to flow into the widened part and the water that has flowed into the widened part is efficiently diffused toward each cut, the water intake and drainage function is promoted. Thus, the braking performance on ice can be further improved.
In addition, in the present invention, since the width of the widened portion described above is 2.0 to 5.0 times the width of the notch, the occurrence of uneven wear around the widened portion is maintained while maintaining the effect of improving braking performance on ice. It is possible to suppress a decrease in steering stability accompanying a decrease in rigidity of the land portion.

It is a top view which shows an example of the closed sipe formed in the tread surface of the pneumatic tire by embodiment of this invention. It is a perspective view which shows the outer wall shape of the closed sipe of FIG. (A) And (b) is a top view equivalent to FIG. 1 which shows an example of the closed sipe by other embodiment of this invention, respectively. It is a perspective view equivalent to FIG. 2 which shows an example of the outer wall shape of the closed sipe by other embodiment of this invention. It is a perspective view equivalent to FIG. 2 which shows an example of the outer wall shape of the closed sipe by other embodiment of this invention. (A) And (b) is a top view equivalent to FIG. 1 which shows an example of the closed sipe by further another embodiment of this invention, respectively. It is a top view equivalent to FIG. 1 which shows an example of the closed sipe by other embodiment of this invention. It is a top view which shows a part of tread surface of the pneumatic tire by embodiment of this invention. It is a top view which shows a part of tread surface of the pneumatic tire by other embodiment of this invention. It is a partial top view which shows the tread surface of the pneumatic tire employ | adopted in the Example.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a plan view showing an example of a closed sipe formed on a tread surface of a pneumatic tire according to an embodiment of the present invention in a square frame, and FIG. 2 is a perspective view showing an outer wall shape of the closed sipe shown in FIG. is there.

  In FIG. 1, the land portion 3 formed on the tread surface 1 of the pneumatic tire of the present invention extends in the radial direction with respect to the virtual axis 2 extending in the depth direction of the land portion 3 and terminates in the land portion 3. A closed sipe 5 in which a plurality of (three in the figure) cuts 4 are arranged is provided.

In the closed sipe 5 of the present invention, the widened portion 6 that locally widens the cut width is formed in at least one place (one place in the figure) between the virtual axis 2 of each cut 4 and the end portion 4z. The notch 4 of the closed sipe 5 is helically twisted in the depth direction about the virtual axis 2 as shown in FIG. Then, has set twist angle of from 4 surface cut up to the bottom surface 9 0 to 120 °. In the figure, W indicates the cut width of the widened portion 6.

As described above, the land portion 3 formed on the tread surface 1 is provided with a plurality of cuts 4 extending in the radial direction with respect to the virtual axis 2 extending in the depth direction of the land portion 3 and terminating in the land portion 3. A closed sipe 5 is provided, and a spiral twist is given to the incisions 4 in the depth direction around the virtual axis 2, and the twist angle is set to 90 to 120 °. Without causing any trouble, it is possible to increase the water absorption performance by increasing the volume associated with the twisting of the notch 4 and to improve the braking performance on ice while suppressing the decrease in the tread rigidity.

  Moreover, since the widened portion 6 that locally widens the cut width is formed at least at one point between the virtual axis 2 of the cut 4 and the end portion 4z, the cut is caused by the tread contact pressure accompanying the ground contact of the tire when traveling on an icy road surface. The width of 4 widens in the width direction around the widened portion 6 so that the water on the ice surface can easily flow into the widened portion 6, and the water that has flowed into the widened portion 6 efficiently diffuses toward each notch 4. Therefore, the suction / drainage function is promoted, and the braking performance on ice can be further improved.

Here, if the twist angle of the notch 4 is less than 90 ° , the effect of improving water absorption is not sufficiently obtained, and the effect of improving braking performance on ice is insufficient, and if it exceeds 120 ° , the vulcanized tire The mold releasability at the time of taking out from the mold deteriorates, and the tread surface 1 is easily damaged.

  In addition, the twist angle of the notch 4 mentioned above does not need to be the same in each notch 4 which comprises the closed sipe 5. FIG. That is, the case where the interval between the notches 4 adjacent to each other in the single closed sipe 5 is allowed is allowed. Further, the twist angle of the notch 4 may be changed non-linearly with respect to the depth direction in addition to changing linearly with respect to the depth direction.

  The pneumatic tire of the present invention configured as described above is formed by a plurality of incisions 4 in which the closed sipes 5 are twisted around the virtual axis 2 extending in the depth direction of the land portion 3. When removing the vulcanized tire from the mold, the tread surface 1 is likely to be damaged by the forming blade of the notch 4. From this point of view, the inner surface of the mold for vulcanizing and molding the pneumatic tire of the present invention is provided with a molding blade of a notch 4 that is rotatable about the virtual axis 2 and is vulcanized by this mold. It is good to do.

  In the embodiment of FIG. 1, the case where the planar shape of the widened portion 6 formed in the notch 4 is formed in a circular shape is shown, but the planar shape of the widened portion 6 is not limited to this, and an elliptical shape or It can be formed into a polygon. In this case, from the viewpoint of preventing cracks from occurring due to stress concentration on the wall surface of the widened portion 6, the wall surface shape is preferably a shape having a curvature.

Further, in the present invention, the width W of the widened portion 6 described above is set to 2 . It is set to 0 to 5.0 times . If the width W of the widened portion 6 is less than 2.0 times the width of the notch 4, the effect of improving the braking performance on ice cannot be obtained, and if it exceeds 5.0 times , uneven wear tends to occur around the widened portion 6. In addition, the steering stability is reduced due to a decrease in rigidity of the land portion 3.

  The width of the notch 4 is not particularly limited, but it is usually preferable to set it to about 0.3 to 2.0 mm. The width W of the widened portion 6 is preferably set within the above-described range and the upper limit thereof is set to about 8 mm according to the type and size of the tire. However, in the case of large tires used for construction vehicles, the size may be set larger than this.

  In the embodiment of FIG. 1, the case where one widened portion 6 is provided for each of the three cuts 4 constituting the closed sipe 5 has been described. However, in the closed sipe 5 of the present invention, FIG. As illustrated in 3 (a) and (b), two or more widened portions 6 may be formed for each notch 4. In addition to this, the widening portion 6 can be provided at the terminal portion of the notch 4, and as illustrated in FIG. 3B, the lengths of the notches 4 can be changed from each other, In some cases, the planar shapes of the widened portions 6 formed in the notches 4 may be mutually changed.

  In the present invention, the radial lengths of the cuts 4 constituting the closed sipe 5 can be made different between the tread surface 1 side and the bottom surface side. FIG. 4 shows a case where the radial length of the notch 4 is formed longer on the tread surface 1 side than on the bottom surface side. As a result, the release property from the mold of the tire after vulcanization is made smooth, and the tread rigidity is enhanced with the progress of wear, so in the late stage of wear after finishing the role as a winter tire, Steering stability on dry roads can be improved.

  On the other hand, when the length of the cut 4 in the radial direction is formed shorter on the tread surface 1 side than on the bottom surface side, it takes some effort to release the vulcanized tire from the mold, but wear progressed. Even if it is a case, since the volume of the notch 4 can be ensured, wet performance can be improved in the latter stage of wear after having finished the role as a winter tire.

  In the pneumatic tire of the present invention, from the viewpoint of emphasizing the releasability from the mold of the vulcanized tire, the radial length of the notch 4 is changed from the tread surface 1 side to the bottom surface as shown in FIG. It is good to change so that it may become short or gradually toward the side.

  Here, the radial lengths of the cuts 4 at the tread surface 1 and the bottom surface of the closed sipe 5 are appropriately set according to the required performance of the tire, but the release from the tire mold after vulcanization is performed. From the standpoint of ensuring a good balance between stability and good steering stability, the relationship between the radial length L2 on the bottom surface of the notch 4 and the radial length L1 on the tread surface 1 is 0.05 ≦ L2 / L1 ≦ 0. It is good to adjust so that it may become .5.

  Further, in the pneumatic tire of the present invention, the width of the cut 4 constituting the closed sipe 5 can be made different between the tread surface 1 side and the bottom surface side in the depth direction of the closed sipe 5. In this case, the width of the notch 4 may be changed gradually or stepwise from the tread surface 1 to the bottom surface of the closed sipe 5. Thereby, since the volume of the notch 4 can be adjusted according to progress of wear, the use according to the required performance of the tire becomes possible in the late stage of wear after finishing the role as a winter tire.

  The width of the notch 4 described above has little influence on the releasability from the mold. Therefore, from the viewpoint of placing importance on ensuring wet performance in the latter stage of wear, the width of the notch 4 is changed from the tread surface 1 side to the bottom surface side. It is good to change so that it may become wide gradually or stepwise.

  Thereby, since the volume of the notch 4 can be secured even when the wear progresses, the wet performance can be improved in the late stage of wear after the role as the winter tire is finished.

  Here, the widths of the cuts 4 in the tread surface 1 and the bottom surface of the closed sipe 5 are appropriately set according to the required performance of the tire, but the release property from the mold of the tire after vulcanization and good From the viewpoint of ensuring the wet performance in a well-balanced manner, the relationship between the width W2 on the bottom surface of the notch 4 and the width W1 on the tread surface 1 may be adjusted so that 0.3 ≦ W1 / W2 ≦ 0.7.

  Furthermore, in the pneumatic tire of the present invention, the number of the cuts 4 can be made different between the tread surface 1 side and the bottom surface side in the depth direction of the closed sipe 5. FIG. 5 shows a case where the number of the cuts 4 is larger on the tread surface 1 side in the depth direction of the closed sipe 5 than on the bottom surface side. As a result, the release property from the mold of the tire after vulcanization is made smooth, and the tread rigidity is enhanced with the progress of wear, so in the late stage of wear after finishing the role as a winter tire, Steering stability on dry roads can be improved.

  On the other hand, when the number of the cuts 4 is smaller on the tread surface 1 side than on the bottom surface side, it is necessary to devise when releasing the vulcanized tire from the mold, but even if wear progresses Since the volume of the notch 4 can be secured, wet performance can be improved in the late stage of wear after the role as a winter tire has been completed.

  However, in the pneumatic tire of the present invention, from the viewpoint of emphasizing the releasability from the mold of the tire after vulcanization, the number of the cuts 4 is set on the tread surface 1 side from the bottom surface side as shown in FIG. It is good to increase as well.

  In the present invention, the boundary position between the tread surface 1 side and the bottom surface side that changes the number of the cuts 4 in the depth direction of the closed sipe 5 is not particularly limited, and the boundary position between the tread surface 1 side and the bottom surface side depends on the required performance of the tire. Set appropriately each time. Further, depending on the required performance of the tire, the number of the cuts 4 can be changed also in an intermediate region between the tread surface 1 side and the bottom surface side. In this case, it is preferable that the number of the notches 4 is configured to gradually change with respect to the depth direction of the closed sipe 5.

  In the embodiment of FIGS. 1 to 4 described above, the case where the number of the cuts 4 constituting the closed sipe 5 is three is shown, but the number of the cuts 4 constituting the closed sipe 5 in the present invention is limited to this. It is good to comprise 2-6 according to the form of a tread pattern instead of a thing. If the number of the cuts 4 is 7 or more, cracks are likely to occur on the tread surface 1 during tire running.

  In the above-described embodiment, the case where the end portions of the cuts 4 on the virtual axis 2 side are respectively connected to the virtual axis 2 is shown, but in the pneumatic tire of the present invention, as illustrated in FIG. The end 4a on the virtual axis 2 side of the cut 4 constituting the closed sipe 5 may be discontinuously arranged with respect to the virtual axis 2 in some cases. The effect in this case is not different from the case according to the above-described embodiment.

  In the present invention, when the ends of the cuts 4 on the virtual axis 2 side are connected to the virtual axis 2 respectively, they are closed along the virtual axis 2 as illustrated in FIGS. 6A and 6B. The small hole 7 can be formed toward the depth direction of the sipe 5. As a result, the water absorption on the icy road surface is further increased, and the braking performance during traveling on the icy road surface can be further improved.

  The size and the cross-sectional shape of the small hole 7 formed along the virtual axis 2 are not particularly limited. However, as illustrated in FIG. ), It may be formed into a polygon or a star corresponding to the number of cuts 4 according to the number of cuts 4 constituting the closed sipe 5.

  In the above-described embodiment, the case where the cuts 4 constituting the closed sipes 5 are linearly extended in the radial direction has been described. However, the planar form of the cuts 4 in the present invention is not limited to this, and a curved line is used. It can be formed into a shape, a wave shape or a zigzag shape.

  In the pneumatic tire of the present invention, it is preferable that the above-described closed sipes 5 are dispersed and arranged over the entire land portion 3 formed on the tread surface 1. In this case, it is preferable to arrange the cuts 4 constituting the closed sipe 5 so as not to approach each other from the viewpoint of uniformly maintaining the rigidity distribution of the land portion 3 and suppressing uneven wear.

  Further, as illustrated in FIGS. 8 and 9, a linear sipe 8 that extends in the tire width direction together with the closed sipe 5 can be provided in the land portion 3 according to the required characteristics of the tire. Thereby, the increase in the edge effect accompanying the arrangement of the linear sipe 8 makes it possible to achieve both the steering stability on the road surface on ice and the braking performance on ice at a high level.

  In the embodiment of FIG. 8, a plurality of closed sipes 5 arranged in parallel on the surface of the rib 9 formed on the tread surface 1 and a linear sipe 8 extending zigzag in the tire width direction are arranged in the tire circumferential direction T. However, the shape of the linear sipes 8 and the arrangement thereof are not limited to this, and can be changed as appropriate according to the shape of the tread pattern. Examples of the shape of the linear sipe 8 include a substantially linear or wavy shape and a three-dimensional shape.

  Further, when the land portion 3 is a block, as illustrated in FIG. 9, the block 10 is partitioned by a linear sipe 8 extending in the tire width direction, and the closed sipe 5 is disposed on the tire kicking side and It is good to arrange | position in parallel along the tire width direction of the front-end part and / or rear-end part (a front-end part and rear-end part in a figure) of the block 10 equivalent to the stepping side.

  In particular, the linear sipe 8 extending in the tire width direction is formed as much as possible in the region at the front end portion and / or the rear end portion corresponding to approximately 30% or less of the tire circumferential direction length of the block 10. The closed sipes 5 may be arranged in parallel along the tire width direction. As a result, the block rigidity at the front end portion and / or the rear end portion of the block 10 is ensured, and while ensuring good steering stability while efficiently suppressing the occurrence of uneven wear, the water absorption is further increased and The braking performance can be improved.

As described above, the pneumatic tire according to the present invention has a closed structure in which a plurality of cuts extending in a radial direction with respect to a virtual axis extending in the depth direction and terminating in the land portion are arranged in a land portion formed on a tread surface. A sipe is provided, and a widened portion that locally widens the cut width is formed at least at one point between the imaginary axis of the cut and the terminal portion, and the width of the widened portion is set to 2.0 to 5. Along with 0 times, a spiral twist is given to each incision in the depth direction centered on the virtual axis, and the twist angle is set to 90 to 120 ° , so that the mold can be released from the mold. Studless tie used on icy and snowy road surfaces because it improves braking performance on ice while suppressing the decrease in tread rigidity without causing any hindrance and has an excellent effect with a simple configuration. It can be widely applied to.

  The tire size is 195 / 65R15 91Q, the tire pattern is FIG. 10, and the form of the closed sipe 5 is composed of three notches 4 extending radially from the virtual axis 2 extending in the tire radial direction and terminating in the land portion 3. The tires according to the present invention (Examples 1 and 2) in which each widening portion 6 is formed in each incision 4 as shown in FIG. 1 and the twist angle of the incision 4 is varied as shown in Table 1. After forming the small hole 7 along the virtual axis 2 without forming the widened portion 6 in each notch 4, a comparative tire (Comparative Example 1) in which the twist angle of the notch 4 was 90 ° was produced. .

  For comparison, a comparative tire (Comparative Example 2) in which the notch 4 was not formed with the widened portion 6 and the small hole 7 and the twist angle of the notch 4 was 140 ° was produced. In each tire, the width of the notch 4 was 0.5 mm, the width of the widened portion 6 was 1.8 mm, the diameter of the small hole 7 was 1.8 mm, and the depth of the closed sipe 5 was 7 mm.

  These four types of tires were evaluated for releasability when the vulcanized tire was removed from the mold, and on-ice braking performance was evaluated by the test method described below. In addition, regarding the releasability from the mold of the tire after vulcanization, in Table 1, “O” indicates that the tread surface was not damaged, and “X” indicates that the tread surface was damaged. Displayed. Then, the evaluation of the braking performance on ice was performed by excluding those in which the tread surface was damaged.

[Test on braking performance on ice]
Each tire is assembled in a rim of size 15 x 6 JJ, filled with air pressure of 230 kPa and mounted on the front and rear wheels of a domestic passenger car with a displacement of 2000 cc, and then a braking test is performed from the initial speed of 40 km / h on the ice surface. The braking performance on ice was evaluated by the reciprocal of the stopping distance. The results are also shown in Table 1 using an index with Comparative Example 1 as 100. The larger the value, the better the braking performance on ice.

  From Table 1, the tire of the present invention in which the widened portion 6 is formed in each of the cuts 4 constituting the closed sipes 5 is formed with only the small holes 7 along the virtual axis 2 without forming the widened portions 6 in the respective cuts 4. It can be seen that the braking performance on ice is superior to that of the comparative tire (Comparative Example 1). In Comparative Example 2 in which the twist angle of the notch 4 was set to 140 °, it was confirmed that the releasability from the mold deteriorates.

DESCRIPTION OF SYMBOLS 1 Tread surface 2 Virtual axis 3 Land part 4 Notch 4z End part 5 Closed sipe 6 Wide part 7 Small hole 8 Linear sipe 9 Rib 10 Block

Claims (13)

The land portion formed on the tread surface is provided with a closed sipe in which a plurality of cuts extending in a radial direction with respect to a virtual axis extending in the depth direction of the land portion and terminating in the land portion are disposed. In a pneumatic tire in which a spiral twist is given to the incision in the depth direction around the virtual axis,
A widened portion that locally widens the cut width is formed at least at one point between the virtual axis and the end portion of the cut, and the twist angle from the surface to the bottom of the cut is set to 90 to 120 ° . A pneumatic tire in which the width of the widened portion is 2.0 to 5.0 times the width of the cut . 2. The pneumatic tire according to claim 1, wherein the radial lengths of the cuts are made different between a tread surface side and a bottom surface side in the depth direction of the closed sipes. The pneumatic tire according to claim 2, wherein a length of the cut in a radial direction is gradually or stepwise shortened from a tread surface to a bottom surface of the closed sipe. The pneumatic tire according to any one of claims 1 to 3, wherein a width of the cut is made different between a tread surface side and a bottom surface side in the depth direction of the closed sipes. The pneumatic tire according to claim 4, wherein the width of the cut is increased gradually or stepwise from the tread surface to the bottom surface of the closed sipe. The pneumatic tire according to any one of claims 1 to 5, wherein the number of the cuts is made different between a tread surface side and a bottom surface side in the depth direction of the closed sipes. The pneumatic tire according to claim 6, wherein the number of the cuts is greater on the tread surface side in the depth direction of the closed sipe than on the bottom surface side. The pneumatic tire according to any one of claims 1 to 7, wherein the number of the cuts is 2 to 6. The pneumatic tire according to any one of claims 1 to 8, wherein an end of the notch on the virtual axis side is connected to the virtual axis. The pneumatic tire according to claim 9, wherein a small hole is formed in the depth direction of the closed sipe along the virtual axis. The pneumatic tire according to any one of claims 1 to 8, wherein an end of the notch on the virtual axis side is discontinuous with respect to the virtual axis. The pneumatic tire according to any one of claims 1 to 11 , wherein a linear sipe extending in the tire width direction together with the closed sipe is provided in the land portion. The pneumatic tire according to claim 12, wherein the land portion is a block, and the closed sipes are arranged along a tire width direction at a front end portion and / or a rear end portion in the tire circumferential direction of the block.

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