JP5481973B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire. More specifically, the present invention improves the braking performance on ice in a tire having a sipe formed on a tread surface, and is good according to the required performance of the tire after having finished its role as a winter tire. The present invention relates to a pneumatic tire that can ensure a good wet performance or improve a steering stability performance on a dry road 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 the case of Patent Document 1, although the water absorption of the tread surface can be improved to some extent, there is a limit that it is difficult to maintain steering stability if the number of sipes is further increased to increase the water absorption. Further, in the case of Patent Document 2, since the twist angle is set to a size of 135 ° or more, the releasability from the mold after tire molding vulcanization is deteriorated, and the tread surface is damaged. There is a problem that it is easy to make.

In addition, a studless tire having a sipe provided on the tread surface may be used as a summer tire after the wear has progressed and has finished its role as a winter tire. Thus, depending on the required performance of the tire after completing its role as winter tires, or to secure and to how the steering stability in de line the road surface has become an important issue.

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

An object of the present invention is to improve the braking performance on ice in the tire forming a sipe on the tread surface, according to the required performance of the tire after finishing the role as winter tires, steering stability on de Rye road It is in providing the pneumatic tire which enabled improvement of.

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 a notch is disposed, and a helical twist is applied to the notch of the closed sipe in a depth direction around the virtual axis. The range of the torsion angle given is 10 ° or more and less than 135 ° , and 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 sipe , and the number of cuts is closed. It is characterized by being increased on the tread surface side than on the bottom surface side in the depth direction of the sipe .

Furthermore, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(3) .

(1) The number of the cuts is 3 to 6 on the tread surface side.

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

(3) 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. Since a torsion of 10 ° or more is given to the head in the depth direction centered on the virtual axis, the water absorption performance is enhanced by the increase in volume accompanying the torsion of the notch, and the braking performance on ice can be improved. Furthermore, since the torsion angle of the cut is less than 135 ° in the depth direction, it is possible to improve the water absorption without impairing the mold releasability from the mold and improve the braking performance on ice. it can.

Moreover, by varying the number incisions in the tread surface side and the bottom side in the depth direction of the closed sipes, since the number in the tread surface than the bottom surface of the notch number, the better the releasability from the mold while, in order to land portion stiffness is ensured in the wear late, it is possible to improve the steering stability on a dry road surface after completing its role as winter tires.

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. (A) and (b) respectively show the outer wall shape of the closed sipe according to the embodiment of FIG. FIG. FIG. 3 is a plan view corresponding to FIG. 1 showing an example of a closed sipe according to another embodiment of the present invention. is there. 1 is a plan view showing a part of a tread surface of a pneumatic tire according to an embodiment of the present invention. The The top view which shows a part of tread surface of the pneumatic tire by other embodiment of this invention. It is. 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 within a square frame, and FIGS . 2 (a) and 2 (b) are outer walls of the closed sipe shown in FIG. It is a perspective view which shows a shape.

  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.

And in the closed sipe 5 of this invention, each notch 4 is helically formed toward the depth direction of the land part 3 around the virtual axis 2 so that it may illustrate in Fig.2 (a) and (b) . A tread in the depth direction of the closed sipe 5 is provided with a torsion, and the range of the twist angle from the surface to the bottom of the closed sipe 5 is 10 ° or more and less than 135 °, preferably 90 to 120 °. The number of the cuts 4 is different between the surface side and the bottom surface side. Incidentally, the number of 4 cuts in FIGS. 2 (a) to five at the tread surface side, and illustrates a case where the three at the bottom surface side, FIG. 2 (b), the notch 4 number a tread surface side of the In the example, the number is four and the number is two on the bottom side .

  In this manner, the land portion 3 formed on the tread surface 1 is closed with a plurality of cuts 4 extending in the radial direction and terminating in the land portion 3 with respect to the virtual axis 2 extending in the depth direction of the land portion 3. Since the sipe 5 is provided and the notches 4 are twisted by 10 ° or more in the depth direction centered on the virtual axis, the water absorption performance is enhanced by the increase in the volume accompanying the twist of the notches 4 and braking on ice is performed. Performance can be improved. Furthermore, since the torsion angle of the notch 4 is less than 135 ° in the depth direction, the water absorption is improved without impairing the mold releasability from the mold, and the braking performance on ice is improved. Can do.

Moreover, by varying the number of 4 cuts in the tread surface 1 side and the bottom side in the depth direction of the closed sipe 5, since the number of the notch 4 and a number in the tread surface 1 side than the bottom surface side, from the mold Since the rigidity of the land portion 3 in the latter stage of wear is ensured while making the mold release property good , the steering stability on the dry road surface after finishing the role as a winter tire can be improved.

  If the torsion angle is less than 10 °, the effect of improving water absorption is not sufficiently obtained, and the effect of improving braking performance on ice is insufficient, and if it is 135 ° or more, the vulcanized tire is removed from the mold. The releasability at the time of taking out deteriorates and the tread surface 1 is easily damaged.

  In the present invention, the twist angle of the cuts 4 described above may not be the same in each cut 4 constituting the closed sipe 5. 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.

  Since the pneumatic tire of the present invention configured as described above is formed by a plurality of cuts 4 in which the closed sipe 5 is provided with a twist around the virtual axis 2 extending in the depth direction of the land portion 4. 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. 2 to the aforementioned (a), 5 present the number of cuts 4 constitute a closed sipe 5 is the tread surface side, shows a case where the three at the bottom side, in the embodiment of FIG. 2 (b) The case where the number of the cuts 4 constituting the closed sipe 5 is four on the tread surface side and the number of the cuts 4 constituting the closed sipe 5 in the present invention is limited to this. It is good to use 3-6 on the tread surface side according to the tread pattern. If the number of cuts 4 on the tread surface side is 2 or less, it is difficult to obtain good braking performance on ice, and if it is 7 or more, cracks are likely to occur on the tread surface 1 during tire running.

  In the present invention, the boundary position between the tread surface 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 each time according to the required characteristics of the tire. Set as appropriate. Further, depending on the required characteristics of the tire, the number of the cuts 4 can be changed also in an intermediate region between the tread surface side and the bottom surface side. In this case, it is preferable that the number of the cuts 4 is gradually increased or decreased with respect to the depth direction of the closed sipe 5.

As described above, in the pneumatic tire of the present invention, as illustrated in FIGS. 2A and 2B , the number of the cuts 4 constituting the closed sipe 5 is made larger on the tread surface side than on the bottom surface side. I have to.

  As described above, when the number of the cuts 4 is larger on the tread surface 1 side than on the bottom surface side, it is advantageous for releasability from the mold after vulcanization molding, and at the same time wear has progressed to some extent. Since the land rigidity can be ensured, the steering stability can be improved. Therefore, the present invention can be preferably applied to a studless tire oriented to ensure steering stability on a dry road surface after finishing the role as a winter tire.

In the embodiment shown in FIG. 1 described above, the case where the end portions on the virtual axis 2 side of the cuts 4 are connected to the virtual axis 2 is illustrated, but the pneumatic tire of the present invention is illustrated in FIG. As described above, 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 operational effects in this case are not different from those according to the embodiment shown in FIG.

In the present invention, when the end of the cut 4 on the virtual axis 2 side is connected to the virtual axis 2 as in the embodiment shown in FIG. 1 , the depth direction of the closed sipe 5 along the virtual axis 2 A small hole can be formed toward. 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. Furthermore, the thickness of the cut 4 and the length in the radial direction can be changed with respect to the depth direction. Thereby, the rigidity of the land portion 3 and the volume of the closed sipe 5 can be appropriately adjusted according to the required characteristics of the tire.

In the embodiment shown in FIGS. 1 to 3 described above, the case where the cuts 4 constituting the closed sipes 5 are linearly extended in the radial direction has been described, but the form of the cut direction of the cuts 4 in the present invention is this. Without being limited thereto, it can be formed in a wavy or zigzag form.

  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 FIG. 4 and FIG. 5 , a linear sipe 6 that extends in the tire width direction together with the closed sipe 5 can be provided on 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 6 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. 4 , a plurality of closed sipes 5 arranged in parallel on the surface of the rib 7 formed on the tread surface 1 and a linear sipe 6 extending zigzag in the tire width direction are arranged in the tire circumferential direction T. However, the shape of the linear sipes 6 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 form of the linear sipe 6 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. 5 , the block 8 is partitioned by a linear sipe 6 extending in the tire width direction, and then 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 8 equivalent to the stepping side.

  In particular, the linear sipes 6 extending in the tire width direction as much as possible are not formed 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 8, and 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 8 is ensured, 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. Sipes are provided, and a spiral twist is given to these cuts in the depth direction centered on the virtual axis, and the twist angle is set to 10 ° or more and less than 135 °, so that the mold can be released from the mold. Without causing any problems, the water absorption is improved to improve the braking performance on ice, and the number of cuts on the tread surface side and the bottom surface side in the depth direction of the closed sipe is made different , and this number of cuts is reduced to the bottom side. by increasing the tread surface than while improving the releasability from the mold, one that enables the improvement of the steering stability on de line road surface after finishing the role as winter tires ,Simple Since it has an excellent effect while having a simple structure, it can be widely applied to studless tires used on icy and snowy road surfaces.

< Conventional Examples, Examples 1 and 2, Comparative Examples 1 and 2 >
The tire size is 195 / 65R1591Q, the tire pattern is FIG. 6 , and the number of cuts constituting the closed sipe provided on the land portion is 5 on the tread surface side, and the intermediate position in the depth direction of the closed sipe is the boundary. Conventional tire (conventional example) and comparative tire (comparative examples 1 and 2) having the same number of cuts on the tread surface side and the bottom surface side, and tires of the present invention (examples 1 and 2) having three on the bottom side Were prepared. In each tire, the twist angle of the cut was varied as shown in Table 1 , the closed sipe depth was 7 mm, the radial length of the cut was 2 mm, and the thickness of the cut was 0.5 mm.

With respect to these five types of tires, the release properties when the vulcanized tires are taken out from the mold are evaluated, and the following test methods are used to evaluate the braking performance on ice at the time of new products and the steering stability performance in the late wear phase. Evaluation was performed and the results are shown in Table 1 . Regarding the releasability from the mold of the tire after vulcanization, those with no damage on the tread surface are indicated by “○”, and those with damage on the tread surface are indicated by “X”. .

  In addition, the evaluation of the steering stability performance in the later stage of wear was performed in advance until the remaining groove depth of the main groove (maximum depth: 8.9 mm) formed on the tread surface reached 40% of the depth when new. Was worn and evaluated in that state.

[Evaluation of braking performance on ice]
Each tire except the comparative example 2 where the tread surface was damaged was assembled in a rim of size 15 × 6 JJ, filled with air pressure of 230 kPa and mounted on the front and rear wheels of a 2000 cc domestic passenger car. A braking test was conducted at a speed of 40 km / h, and the braking performance on ice was evaluated by the reciprocal of the braking stop 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.

[Evaluation of steering stability]
Each tire except the comparative example 2 in which the tread surface is damaged is assembled in a rim of size 15 × 6 JJ, filled with air pressure of 230 kPa and mounted on front and rear wheels of a domestic passenger car with a displacement of 2000 cc. The test course was run at a speed of 60 to 100 km / h, and sensory evaluation was performed by a five-point method using Comparative Example 1 as “3” by three skilled test drivers. The results are shown in Table 1 on average. The larger the value, the better the steering stability performance.

From Table 1 , it can be seen that the tire of the present invention is superior in braking performance on ice when it is new compared to the conventional tire and the comparative tire. In Comparative Example 2 in which the twist angle of cutting was set to 140 °, it was confirmed that the releasability from the mold deteriorates.

  Furthermore, the tire of the present invention in which the number of cuts on the bottom surface side is smaller than that on the tread surface side has improved steering stability performance compared to conventional tires and comparative tires in which the number of cuts does not change in the depth direction in the late stage of wear. It was confirmed.

DESCRIPTION OF SYMBOLS 1 Tread surface 2 Virtual axis 3 Land part 4 Cut 5 Closed sipe 6 Linear sipe 7 Rib 8 Block

Claims (7)

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,
The range of the torsion angle given to the cut of the closed sipe is set to 10 ° or more and less than 135 °, and 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 sipe , A pneumatic tire in which the number of cuts is greater on the tread surface side than on the bottom surface side in the depth direction of the closed sipes . The pneumatic tire according to claim 1, wherein the number of the cuts is 3 to 6 on the tread surface side. The pneumatic tire according to claim 1 or 2, wherein an end of the notch on the virtual axis side is connected to the virtual axis. The pneumatic tire according to claim 3, 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 4, 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 5 , wherein a linear sipe extending in the tire width direction is provided in the land portion together with the closed sipe. The pneumatic tire according to claim 6, 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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