JP4387381B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire including a tread pattern having a land portion in which at least one sipe is formed, and is particularly useful as a studless tire.

  Conventionally, studless tires are provided with incisions called sipe in the land such as blocks and ribs, and this sipe provides an edge effect even on road surfaces with a low coefficient of friction, so stable running on ice road surfaces is possible. It becomes possible. As such a sipe, a so-called two-dimensional sipe whose shape does not change in the depth direction is known, and a flat sipe having a flat sipe inner wall surface or a concavo-convex row in the normal direction ND of the tread as shown in FIG. An extended corrugated sipe 20 has been put into practical use.

  In recent years, the number of sipes tended to increase in order to enhance the edge effect, but if the number of sipes was increased too much, the number of edges increased, but the rigidity of the land part decreased and collapsed excessively, conversely There arises a problem that the edge effect is reduced and the ice performance is lowered. For this reason, a so-called three-dimensional sipe in which the shape of the sipe is changed in the depth direction to suppress collapse is attracting attention.

  Various types of three-dimensional sipe shapes have been proposed. For example, the waveform sipe amplitude is changed in the depth direction (see Patent Document 1 below), and the concavo-convex rows of the sipe inner wall surface are in the normal direction of the tread surface. Inclined (see Patent Document 2 below). Further, there is a sipe 30 as shown in FIG. 4 in which the concavo-convex row on the sipe inner wall surface is inclined in the sipe longitudinal direction to form a zigzag shape (see Patent Documents 3 and 4 below). In any of these cases, when the land portion falls, the sipe inner wall surface extending in the oblique direction engages with the ridges and the ridges, thereby suppressing excessive falling.

However, the sipe described in Patent Document 1 below has a problem that it is difficult to incline the concavo-convex row as a whole, and the engaging action is small. In addition, as in the sipe described in Patent Document 2 below, when the concavo-convex row is inclined only in one direction within the inner wall surface of the sipe, the land portion is easily deformed in a shearing manner with respect to the load from the reverse inclination direction. As a result, there is a problem that ice performance and uneven wear resistance performance cannot be sufficiently improved. In the sipe described in Patent Documents 3 and 4 below, the oblique component for engaging the ridge and the groove is small, and there is room for further improvement in order to sufficiently suppress the falling of the land portion.
JP 59-199306 A Japanese Patent Laid-Open No. 10-258615 Japanese Patent No. 3504632 Specification JP 2006-27558 A

  This invention is made | formed in view of the said situation, The objective is to provide the pneumatic tire which can fully suppress the fall of a land part and can improve ice performance.

The above object can be achieved by the present invention as described below. That is, the pneumatic tire of the present invention is a pneumatic tire provided with a tread pattern having a land portion where at least one sipe is formed, and the sipe inner wall surface of the sipe is inclined with respect to the normal direction of the tread. In addition, the first concavo-convex row in which the ratio of the length of the ridge to the sipe or the length of the sipe in the sipe longitudinal direction is 0.25 or more, and the second concavo-convex row inclined in the direction opposite to the first concavo-convex row The length of the ridge or groove in the sipe longitudinal direction is obtained on the basis of the side edge of the ridge or groove, and when the sipe depth is D, at least The first concavo-convex row and the second concavo-convex row are provided in an intermediate portion of 0.15D to 0.9D from the tread surface. In the intermediate portion, the first concavo-convex row is provided at the approximate center of the sipe inner wall surface in the sipe longitudinal direction. 1 uneven row is arranged, the rest on both sides It is characterized in that the second concave-convex rows are arranged.

  According to the pneumatic tire of the present invention, the sipe inner wall surface of the sipe is provided with the first concavo-convex row in which the ratio of the length of the ridges or ridges in the sipe longitudinal direction to the sipe is 0.25 or more. When the land part falls down, the oblique component for engaging the ridges and the concave stripes becomes large, and the land part's fall-down suppressing effect is fully exerted, resulting in braking performance and uneven wear resistance performance on the ice road surface. Can be improved. Moreover, since the second concavo-convex row inclined in the direction opposite to the first concavo-convex row is provided on the inner wall surface of the sipe, the shear deformation of the land portion can be suppressed, and the land portion is appropriately collapsed. It is possible to effectively improve the ice performance.

In the present invention, when the sipe depth is D, the first concavo-convex row and the second concavo-convex row are provided at least in an intermediate portion of 0.15D to 0.9D from the tread surface . With such a configuration, it is possible to sufficiently secure a region where the first concavo-convex row and the second concavo-convex row are provided, appropriately exhibiting the effect of suppressing the collapse of the land portion, and to reliably improve the ice performance.

In the present invention, in the intermediate portion, the first concavo-convex row is arranged in the approximate center of the sipe inner wall surface in the sipe longitudinal direction, and the second concavo-convex row is arranged in the remaining portions on both sides thereof . With such a configuration, a relatively large oblique component can be arranged at the approximate center of the inner wall surface of the sipe, and the land collapse can be effectively suppressed in the longitudinal direction of the sipe. Deformation can be sufficiently suppressed, and ice performance can be appropriately improved.

  In the above, it is preferable that at least one of the tread surface portion which is the tread surface side and the bottom portion which is the bottom side of the intermediate portion is formed by a two-dimensional sipe whose shape does not change in the depth direction. Since the tread surface portion of the sipe is formed in a two-dimensional sipe, the uneven portion extending in the oblique direction is not exposed to the tread surface in the initial wear state where the land portion is relatively easy to fall down, so that an acute angle portion is formed in the land portion piece. The occurrence of uneven wear can be suppressed without any problems. In addition, since the bottom of the sipe is formed by a two-dimensional sipe, local stress concentration at the groove bottom of the sipe can be prevented and the occurrence of cracks and the like can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of a land portion of a pneumatic tire according to the present invention, and shows an enlarged part of a block as a land portion. FIG. 2 is a plan view of the sipe formed in the block and a front view of the sipe inner wall surface. In the figure, “+” indicates a ridge, and “−” indicates a ridge, and these irregularities are based on a sipe reference plane F (a virtual plane passing through the center of the amplitude) (see FIG. 3 described above). The same applies to 4.)

  The pneumatic tire according to the present invention includes a tread pattern having a land portion in which at least one sipe is formed. In the present embodiment, as shown in FIG. 1, an example in which three sipes 10 are formed in a block 1 is shown. The sipe 10 extends in a wavy shape on the tread surface 1a, and is formed as a double-sided open sipe in which the sipe longitudinal direction is parallel to the tire width direction WD and both ends thereof are opened on the side wall surface 1b of the block 1. .

  In the present embodiment, as shown in FIG. 2, the first concavo-convex row 11 inclined to the sipe inner wall surface 1 c of the sipe 10 with respect to the normal direction ND of the tread surface 1 a and the first concavo-convex row 11 are opposite to each other. And a second concavo-convex row 12 inclined to each other. And when the length of the sipe 10 in the sipe longitudinal direction of the sipe 10 is L1, and the length of the ridge 11a of the first concavo-convex row 11 in the sipe longitudinal direction is L2, the ridge 11a or the groove 11b with respect to the sipe 10 The length ratio L2 / L1 in the sipe longitudinal direction is set to 0.25 or more. The illustrated length L2 is the length of the concave strip 11b in the sipe longitudinal direction.

  For this reason, when the oblique component for engaging the ridges 11a and the ridges 11b is increased and a longitudinal force is generated along the tire circumferential direction PD, the effect of suppressing the collapse of the block 1 is sufficiently exhibited. Thus, braking performance and uneven wear resistance performance on ice road surfaces can be improved. In such a first concavo-convex row 11, the block 1 tends to be deformed in a shearing manner with respect to a load from the reverse inclination direction, but the second concavo-convex row 12 is provided in the reverse direction on the sipe inner wall surface 1 c. Therefore, the shear deformation of the block 1 can be suppressed, and the ice performance can be effectively enhanced by appropriately suppressing the collapse of the block 1.

  L2 / L1 is set to 0.25 or more as described above, but it should be 0.3 or more from the viewpoint of increasing an oblique component for engaging the ridges 11a and the ridges 11b. Preferably, 0.4 or more is more preferable. When L2 / L1 is less than 0.25, the oblique component is reduced, so that the effect of suppressing the collapse of the block 1 is reduced and the effect of improving the ice performance is small.

  The inclination angle θ1 of the first concavo-convex row 11 with respect to the normal direction ND is preferably 10 to 80 degrees, and more preferably 30 to 60. If θ1 is less than 10 degrees, it becomes substantially difficult to set L2 / L1 to 0.25 or more. On the other hand, if θ1 exceeds 80 degrees, the inclination angle becomes too large to substantially set the concavo-convex row.

  The inclination angle θ2 of the second concavo-convex row 12 with respect to the normal direction ND is preferably 10 to 80 degrees, and more preferably 30 to 60. In addition, θ2 is preferably substantially the same angle (± 10 degrees) as θ1, thereby effectively suppressing shear deformation of the block 1 against a load from a direction opposite to the first concavo-convex row 11. be able to.

  When the sipe depth is D, 0.15D to 0.9D from the tread surface 1a is the intermediate portion 4, the tread surface 1a side is the tread surface portion 3, and the bottom side is the bottom portion 5, in the present invention, It is preferable that the second concavo-convex row 12 is provided at least in the intermediate portion 4. In this embodiment, an example in which the first concavo-convex row 11 and the second concavo-convex row 12 are provided in the intermediate portion 4 and the bottom portion 5 is shown.

  The intermediate portion 4 is entirely occupied by the first concavo-convex row 11 and the second concavo-convex row 12, and the central portion in the sipe longitudinal direction of the first concavo-convex row 11 is the central portion in the sipe longitudinal direction of the sipe inner wall surface 1c. Located in the vicinity. That is, the first concavo-convex row 11 is arranged at the approximate center of the sipe inner wall surface 1c in the sipe longitudinal direction, and the second concavo-convex rows 12 are arranged at the remaining portions on both sides thereof. Thereby, the largest diagonal component is arrange | positioned in the approximate center of the sipe inner wall surface 1c, and the fall-suppressing effect of the block 1 can be exhibited with sufficient balance in the sipe longitudinal direction.

  The 2nd uneven | corrugated row | line | column 12 is extended so that the protruding item | line 12a and the recessed item | line 12b may intersect with the protruding item | line 11a or the recessed item | line 11b of the 1st uneven | corrugated row | line | column 11, and it combines with the protruding item | line 11a or the protruding item | line 11b, and protrudes. A v-shaped portion (or y-shaped portion) of a strip or a concave strip is formed. Thereby, the shear deformation of the block 1 can be more effectively suppressed, and even when a lateral force is generated in the block 1 as in turning, the deformation can be suppressed to ensure the ice performance. From this point of view, θ2 is preferably substantially the same angle as θ1, and in this embodiment, θ1 = θ2 = 45 degrees.

  In the present embodiment, an example in which the first concavo-convex row 11 and the second concavo-convex row 12 are also formed on the bottom 5 has been shown, but a configuration in which the bottom 5 is formed by a two-dimensional sipe is also a preferred embodiment of the present invention. Can be mentioned. In particular, when the bottom portion 5 is formed by a plane sipe, local stress concentration at the groove bottom of the sipe 10 can be effectively prevented, and block-out (breaking, dropping) of the block piece can be prevented.

  The tread surface portion 3 is formed of a corrugated sipe (an example of a two-dimensional sipe) in which the concavo-convex row extends along the normal direction ND, and the concavo-convex row extending in the oblique direction is not exposed on the tread surface 1a. Therefore, in the initial wear state where the block 1 is relatively easy to fall down, excellent uneven wear resistance performance can be exhibited without forming an acute angle portion on the block piece. In addition, when the sipe 10 extends linearly on the tread surface 1a, the tread surface portion 3 may be formed by a plane sipe, and this configuration is useful as a summer tire.

  The first unevenness row 11 and the second unevenness row 12 are formed in synchronization with the unevenness row of the tread surface portion 3. That is, the protrusions 11 a and the protrusions 12 a of the intermediate portion 4 are connected to the protrusions of the tread surface portion 3, and the recesses 11 b and the recesses 12 b are connected to the recesses of the tread surface portion 3. The sipe inner wall surface 1c has a shape in which a part of the concavo-convex row is inclined as the first concavo-convex row and the remaining portion is inclined in the reverse direction as the second concavo-convex row except for the tread portion of the corrugated sipe 20 shown in FIG. It has become.

  Thus, in this embodiment, the 1st uneven | corrugated row | line | column 11 and the 2nd uneven | corrugated row | line | column 12 are formed with the pitch according to the wave shape in the tread 1a. In such a case, the ratio L2 / λ of the length L2 to the wavelength λ of the wave shape of the tread 1a is 1.2 from the viewpoint of securing the size of the oblique component for engaging the ridges 11a and the ridges 11b. The above is preferable.

  The thickness T of the ridges 11a and the ridges 11b of the first concavo-convex row 11 is preferably 0.5 to 2.5 mm, and if this is smaller than 0.5 mm, the block piece tends to fall down and 2.5 mm. If it is larger, it tends to be difficult to sufficiently arrange the uneven rows. In addition, the amplitude (the sum of the heights of the tops on both sides) of the first uneven row 11 is preferably 1 to 2 mm. The thickness and amplitude of the ridges 12a and the ridges 12b of the second concavo-convex row 12 are preferably equivalent to those of the first concavo-convex row 11, but may be different.

  The groove width of the sipe 10 may be the same width or slightly different in each part, but is preferably 0.2 to 0.7 mm in order to exhibit a sufficient edge effect. Further, the sipe depth D is preferably 30 to 80% of the main groove depth.

  The portion of the tread pattern other than the block 1 may be any pattern. For example, a block provided with blocks and ribs on the left and right sides of the block 1 is exemplified. The block 1 is not limited to the rectangular shape as described above, and may be any of a parallelogram, a V shape, a polygon, or a curved line.

  In the present invention, instead of a block as a land portion, a rib extending linearly or zigzag along the tire circumferential direction PD may be adopted, and the sipe inner wall surface of the sipe formed in the rib By providing such a concavo-convex row, it is possible to sufficiently exhibit the fall-in suppressing effect and improve the ice performance.

In the present invention, the effect of suppressing the collapse of the block 1 is great, and therefore the edge effect can be further enhanced by increasing the number of edges by increasing the number of sipes 10 and increasing the sipe density. From such a viewpoint, in the present invention, the sipe density is preferably 0.05 to 0.2 mm / mm ² . The sipe density is a value obtained by dividing the total length of all sipes by the area of the tread.

  Usually, a plurality of sipes are formed for one block or one rib, but adjacent sipes may have the same shape or different wave shapes, inclination angles, period of unevenness, and amplitude. However, in order to improve the demoldability after vulcanization molding, it is preferable that adjacent sipes have the same shape.

  In the present invention, the sipe structure as described above can be applied to all land portions in the tread pattern, but may be applied only to some land portions in the tread pattern.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that sipes as described above are formed on land portions such as blocks and ribs, and conventionally known materials, shapes, structures, manufacturing methods, etc. Either can be employed in the present invention.

  INDUSTRIAL APPLICABILITY The present invention is useful for a tire having a block-based tread pattern because it has a great effect of suppressing the falling of the land portion, and can improve ice performance, so that it is particularly useful as a studless tire (winter tire). is there.

[Other Embodiments]
(1) The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention. For example, the sipe is formed by one-side open sipe or closed sipe. Or the number of the first concavo-convex rows may be increased. Further, the length in the sipe longitudinal direction of the ridges or grooves in the second concavo-convex row is not particularly limited, and is not limited to be shorter than the length L2.

  (2) In the above-described embodiment, the reference surface F of the sipe 10 is formed so as to be substantially parallel to the normal line of the tread surface 1a. However, the present invention is not limited to this, and the sipe 10 The reference surface may be slightly inclined (for example, 15 ° or less) with respect to the normal line of the tread surface.

  (3) In the above-described embodiment, an example in which the sipe longitudinal direction is formed so as to be substantially parallel to the tire width direction is shown, but the present invention is not limited to this, and the sipe longitudinal direction is in the tire width direction. In this case, the inclination angle is preferably within 45 °.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Ice braking performance A tire was mounted on a real vehicle (domestic 3000cc class FR sedan), and the vehicle was driven on an ice road under the load condition of one passenger, and the ABS was operated by applying braking force at a speed of 40km / h. The braking distance was evaluated with an index. The evaluation is indicated by an index when the conventional product (Comparative Example 1) is set to 100, and the larger the numerical value, the better the ice braking performance.

(2) Uneven wear resistance performance The amount of step wear (step difference between sipe and sipe due to wear) when traveling on a paved road for 8000 km was measured and evaluated by an index. The evaluation is indicated by an index when the conventional product (Comparative Example 1) is 100, and the larger the value, the better the uneven wear resistance.

Comparative example 1 (conventional product)
A radial tire (size 205 / 65R15) having a tread pattern having square blocks (30 mm long, 30 mm wide, open sipes on both sides) on the entire surface (5 rows) having a corrugated sipe shown in FIG. The sipe depth was 8 mm, the groove width was 0.3 mm, the sipe interval was 5 mm, and the sipe amplitude was 1.2 mm.

Comparative Example 2
A radial tire that is the same as Comparative Example 1 was used as Comparative Example 2 except that a concavo-convex row that was inclined in the sipe longitudinal direction and formed in a zigzag shape was provided as in the sipe 30 shown in FIG. In addition, the inclination angle of the concavo-convex row with respect to the normal direction of the tread was set to 45 degrees.

Comparative Example 3
A radial tire that was the same as Comparative Example 1 was used as Comparative Example 3, except that a concavo-convex row that was inclined only in one direction was provided in the sipe inner wall surface as in the sipe 40 shown in FIG. In addition, the inclination angle of the concavo-convex row with respect to the normal direction of the tread was set to 45 degrees.

Examples 1 and 2
Example 1 and Example 2 are radial tires that are the same as Comparative Example 1 except that the uneven rows as shown in FIG. Note that L2 / L1 was 0.43 in Example 1 and 0.57 in Example 2. In Example 1, θ1 was 45 degrees and θ2 was 45 degrees. In Example 2, θ1 was 53.1 degrees and θ2 was 53.1 degrees.

Comparative Example 4
A radial tire that was the same as Example 1 was used as Comparative Example 4 except that L2 / L1 was 0.1, θ1 was 13 degrees, and θ2 was 13 degrees. The evaluation results of each example are shown in Table 1.

  From Table 1, in Examples 1 and 2, the ice braking performance and uneven wear resistance performance are improved as compared with Comparative Examples 1 to 4, and the first unevenness row and the second unevenness row provided on the sipe inner wall surface, It turns out that the fall of the block can fully be suppressed. In Comparative Example 3, although the size of the oblique component is not different from that in Example 1, the ice performance is not greatly improved because the block is easily deformed in a shearing manner and the fall-down suppressing effect is not sufficient.

The perspective view which shows an example of the land part which concerns on the pneumatic tire of this invention The top view of the sipe which concerns on the pneumatic tire of this invention, and the front view of a sipe inner wall surface Plan view of sipe and front view of sipe inner wall surface related to conventional pneumatic tire Plan view of sipe and front view of sipe inner wall surface related to conventional pneumatic tire Plan view of sipe and front view of sipe inner wall surface related to conventional pneumatic tire

Explanation of symbols

1 block (land)
DESCRIPTION OF SYMBOLS 1a Tread surface 1c Sipe inner wall surface 3 Tread surface part 4 Intermediate | middle part 5 Bottom part 10 Sipe 11 1st uneven | corrugated row 11a 1st uneven | corrugated row | line | column 11b 1st uneven | corrugated row | line | column 12nd 2nd uneven | corrugated row | line | column 12a 12b Concave strip D of second concavo-convex row Sipe depth L1 Length sipe longitudinal direction L2 of sipe Length sipe longitudinal direction ND of first concavo-convex row ND Normal direction of tread surface

Claims (2)

In a pneumatic tire provided with a tread pattern having a land portion forming at least one sipe,
The sipe inner wall surface of the sipe is inclined with respect to the normal direction of the tread surface, and a first concavo-convex row in which the ratio of the length of the convex or concave sipe to the sipe in the longitudinal direction of the sipe is 0.25 or more, A second concavo-convex row inclined in a direction opposite to the first concavo-convex row is provided ,
The length in the sipe longitudinal direction of the ridge or groove is obtained on the basis of the side edge of the ridge or groove,
When the sipe depth is set to D, at least the first concavo-convex row and the second concavo-convex row are provided in an intermediate portion that is 0.15D to 0.9D from the tread surface,
The pneumatic tire according to claim 1, wherein in the intermediate portion, the first concavo-convex row is disposed substantially at the center of the sipe inner wall surface in the sipe longitudinal direction, and the second concavo-convex rows are disposed on the remaining portions on both sides thereof . 2. The pneumatic tire according to claim 1 , wherein at least one of a tread portion that is a tread surface side and a bottom portion that is a bottom side of the intermediate portion is formed by a two-dimensional sipe whose shape does not change in the depth direction.

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