JP4382080B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire including a tread pattern having blocks or ribs formed with at least one corrugated sipe, and is particularly useful as a studless tire.

  Conventionally, studless tires are provided with cuts called sipe in land portions such as blocks and ribs, and the edge component of this sipe enables stable running on an ice road surface having a low friction coefficient. As such a sipe, for example, a wave sipe 30 as shown in FIG. 4 is put into practical use. The wave type sipe has a higher sipe density than the straight sipe, and the ice performance can be improved by increasing the edge component.

  However, it has been found that the conventional wave-shaped sipe does not sufficiently exhibit the edge effect because the top of the wave makes point contact with the road surface during braking, and is insufficient as an improvement effect on ice performance. Moreover, in practice, running performance on a dry road surface is also important, and a pneumatic tire that can achieve both ice performance and dry performance at a high level has been desired.

  In Patent Document 1 below, a corrugated sipe is composed of a short side and a long side, the ratio (short side / long side) is set to 0.25 to 0.75, and the inclination angle of the long side is set to the tire circumference. A pneumatic tire has been proposed in which the angle is 65 to 90 degrees with respect to the direction, the crossing angle between the long side and the short side is 90 to 130 degrees, and the inclination direction between the lateral groove and the long side is reversed. However, this corrugated sipe has a short side with a small length, and its angle greatly allows deviation from the tire circumferential direction. Conceivable.

In the following Patent Document 2, a lateral sipe formed in a block is formed by a bent sipe having a large amplitude in a side area of the block, a sipe having a small amplitude in a central area of the block, and an additional sipe in a central area. A pneumatic tire provided and subdivided into micro blocks has been proposed. However, in this tire, since the central area of the block is subdivided into micro blocks, the rigidity is low, and the block easily falls down on the ice road surface, so the edge effect is reduced and ice performance is reduced. There is a risk.
JP 2000-94909 A JP-A-8-230417

  This invention is made | formed in view of the said situation, The objective is to provide the pneumatic tire which can make ice performance and dry performance compatible in a high dimension.

  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 block or rib in which at least one corrugated sipe is formed, wherein the corrugated sipes are a start point and an end point of the corrugated sipes. A first sipe portion having a wavy shape by repeating a first portion having an angle of ± 10 degrees with respect to a basic line connecting the two and a second portion having an angle with respect to a perpendicular of the basic line of ± 10 degrees; and A second sipe portion having a wavy shape by repeating a third portion having an angle of ± 10 degrees with respect to the intersecting line intersecting at an angle of 45 degrees and a fourth portion having an angle of ± 10 degrees with respect to the perpendicular of the intersecting line. The first sipe portion having one or more periods is formed in a central region in the tire width direction of the block or rib, and both end regions in the tire width direction of the block or rib , In which the second sipe portion of one cycle or more are formed.

  The pneumatic tire of the present invention has a relatively high contact pressure in the center region in the tire width direction of the block or rib on an ice road surface with a low friction coefficient, and a block or rib tire on a dry road surface with a high friction coefficient. It is based on the inventor's knowledge that the contact pressure at both end regions in the width direction is relatively high, and the ice performance is obtained by utilizing the contact pressure distribution of the block or rib that varies depending on the friction coefficient of the road surface. And dry performance at a high level.

  According to this pneumatic tire, the corrugated first sipe portion as described above is formed in the central region of the block or rib in the tire width direction, so that the conventional corrugated sipe as shown in FIG. In comparison, the sipe density in the region where the contact pressure tends to be high on the ice road surface becomes high. In addition, the first sipe portion repeats the first portion along the basic line and the second portion along the perpendicular to the basic line to form a wave, so that the point contact between the top of the wave and the road surface during braking Can be suppressed, and an edge component highly contributing to ice performance can be obtained.

  Further, in this pneumatic tire, the sipe density in the region where the contact pressure tends to be high on the dry road surface because the wave-like second sipe portion as described above is formed in both end regions of the block or rib in the tire width direction. Can be made smaller than the central area of the block, thereby providing excellent dry performance. As a result, while improving the ice performance by the first sipe part described above on the ice road surface, the ice performance and the dry performance are improved by expressing the dry performance improvement effect by the second sipe part on the dry road surface. It is possible to achieve both dimensions.

  In the above, the corrugated sipe is formed in a block or a rib provided in a region that is within one third of the ground contact width from the contact end toward the tire equator, and the corrugated sipes have the first sipes. It is preferable that the amplitude of the part is set larger than the amplitude of the second sipe part.

  In the above pneumatic tire, the phenomenon that the contact pressure at the both ends of the block or rib increases on the dry road surface is particularly remarkable in the vicinity of the contact end, and the block or rib provided in the vicinity of the contact end improves the dry performance. It was made based on the knowledge that the contribution of the mortar is large, and by utilizing these skillfully, the dry performance is mainly improved, and as a result, the ice performance and the dry performance are balanced at a higher level.

  According to this pneumatic tire, by forming the wave sipe as described above in the block or rib near the ground contact end, the amplitude of the second sipe portion is set to be relatively small in the block or rib that contributes to the dry performance. By doing so, the rigidity of the region where the contact pressure tends to be high on the dry road surface can be increased, and the dry performance can be improved. Further, by setting the amplitude of the first sipe portion to be relatively large in the block or rib, the edge component in the region where the contact pressure tends to be high on the ice road surface can be increased, and the ice performance can be improved. As a result, ice performance and dry performance can be achieved at a higher level.

  In the above, it is preferable that the basic line extends at an angle of ± 10 degrees with respect to the tire width direction. According to the said structure, the edge component of the 1st part and 2nd part which a 1st sipe part has becomes a thing with high contribution to ice performance more reliably, and the improvement effect of ice performance is expressed favorably.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing an example of a tread surface of a pneumatic tire according to the present invention. FIG. 2 is an enlarged view of a main part of a block provided on the tread surface and a corrugated sipe formed in the block.

  As shown in FIG. 1, the pneumatic tire according to the present embodiment includes a tread pattern T having a plurality of blocks 1 each having a corrugated sipe 10 formed therein. Each block 1 is divided into rectangles by a circumferential groove 2 extending in the tire circumferential direction and a lateral groove 3 extending in the tire width direction, and five rows of blocks 1 are arranged symmetrically with respect to the tire equator C.

  As shown in FIG. 2 (a), the corrugated sipe 10 is a double-sided open sipe that extends so that the basic line SL and the tire width direction WD are parallel to each other and whose both ends are open on the side wall of the block 1. Is formed. The basic line SL is a virtual straight line that connects the start point SP and the end point GP of the corrugated sipe 10. The corrugated sipe 10 includes a first sipe portion 11 and a second sipe portion 12, and the second sipe portion 12, the first sipe portion 11, and the second sipe portion 12 are arranged in this order along the tire width direction WD. Has been.

  As shown in FIG. 2B, the first sipe portion 11 includes a first portion 11a having an angle of ± 10 degrees with respect to the basic line SL and a first portion 11a having an angle of ± 10 degrees with respect to the perpendicular PLs of the basic line SL. The first portion 11a and the second portion 11b are repeated to form a wave shape. The angle is determined with reference to the center line of the sipe groove width of the corrugated sipe 10 (the same applies to the second sipe portion 12 described later).

  The “wave shape” of the first sipe part 11 is not limited to a rectangular wave as in the present embodiment, and if the angle relationship between the first part 11 a and the second part 11 b described above is satisfied, the wavy line is It may extend in a zigzag or bend while being bent.

  The first sipe portion 11 is formed in the central region 1a of the block 1 in the tire width direction WD. Therefore, in the region where the contact pressure tends to be high on the ice road surface, the conventional corrugation as shown in FIG. The sipe density is higher than the sipe. Moreover, since the first portion 11a along the basic line SL and the second portion 11b along the vertical line PLs are repeatedly waved, point contact between the top of the wave and the road surface during braking can be suppressed, and the ice Edge components that contribute to performance can be obtained.

  That is, since the edge component of the first portion 11a extends along the tire width direction WD, an edge effect in the front-rear direction useful for ice braking performance is exhibited, and the edge component of the second portion 11b is Since it extends along direction PD, the edge component of the 1st part 11a can be enlarged, and the horizontal edge effect useful for ice turning performance is also expressed. In order to ensure the effect of improving the ice performance, the first sipe portion 11 having one or more cycles is formed in the central area 1a of the block 1. Note that one cycle of the first sipe portion 11 corresponds to the pitch P1.

  In the present embodiment, the basic line SL is parallel to the tire width direction WD and the perpendicular line PLs is parallel to the tire circumferential direction PD, but the present invention is not limited to this. However, it is preferable that the basic line SL extends at an angle of ± 10 degrees with respect to the tire width direction WD, more preferably at an angle of ± 5 degrees, from the viewpoint of more surely expressing the above-described improvement effect of ice performance. Preferably, it is further parallel to the tire width direction WD. In addition, the angle of the first portion 11a with respect to the basic line SL is more preferably ± 5 degrees, and the angle of the second portion 11b with respect to the perpendicular PLs is more preferably ± 5 degrees.

  In the present embodiment, the first portion 11a and the second portion 11b are connected via a connecting portion 11c formed of an arc, thereby improving the wear resistance of the portion where the first sipe portion 11 is bent. It is increasing. In addition, the connection part 11c does not need to be formed only by the circular arc, and may be an elliptical arc or a part of a parabola.

  In the first sipe portion 11, there are few portions whose angle with respect to the tire width direction WD is around 45 degrees, and therefore it is difficult for the block pieces to open when a longitudinal force or a lateral force is generated in the block 1 on the ice road surface. Thereby, the block piece can be prevented from falling down, and the occurrence of step wear of the block piece adjacent to the corrugated sipe 10 can be suppressed.

  The first sipe part 11 preferably includes the first part 11a in a length of 20 to 70% within one period, thereby increasing the number of edge components that express the edge effect in the front-rear direction and suitable for ice braking performance. To improve. Moreover, it is preferable to include the 2nd part 11b by 20 to 70% of length in 1 period, and thereby, the edge component which expresses the edge effect of a horizontal direction increases, and ice turning performance improves suitably.

  In the above, from the viewpoint of securing both performances to a certain level or higher while improving the balance between ice braking performance and ice turning performance, the second portion 11a is included in the length of 40 to 60% in one cycle. More preferably, the portion 11b is included in a length of 40 to 60%.

  Furthermore, in order to improve both the ice braking performance and the ice turning performance in a well-balanced manner, the ratio of the lengths of the first portion 11a and the second portion 11b (first portion / second portion) is 0.8 to 1.. 2 is preferable, and 0.9 to 1.1 is more preferable. In addition, when the 1st sipe part 11 is formed exceeding 1 period, it is preferable to repeat the 1st part 11a and the 2nd part 11b with the same period.

  As shown in FIG. 2C, the second sipe portion 12 includes a third portion 12a having an angle with respect to the intersecting line CL of ± 10 degrees and an angle with respect to the perpendicular PLc of the intersecting line CL of ± 10 degrees. 4 portions 12b, and the third portion 12a and the fourth portion 12b are repeated to form a wave shape. The intersection line CL is a virtual straight line that intersects the basic line SL at an angle of 45 degrees (θ = 45 degrees).

  The “wavy shape” of the second sipe portion 12 is not limited to the one similar to the sine wave as in the present embodiment, but the one in which the wavy line is bent and extends in a zigzag, or the straight line and the curve are alternately combined. included.

  The second sipe portion 12 is formed in both end regions 1b of the block 1 in the tire width direction WD. Therefore, in a region where the contact pressure tends to be high on the dry road surface, the sipe density is smaller than that in the central region 1a. This setting has a high contribution to dry performance. In order to ensure the effect of improving the dry performance, the second sipe portion 12 having one cycle or more is formed in each end region 1b of the block 1. One cycle of the second sipe part 12 corresponds to the pitch P2.

  From the viewpoint of surely exhibiting the above effects, it is preferable that the angle of the third portion 12a with respect to the intersection line CL is ± 5 degrees and the angle of the fourth portion 12b with respect to the perpendicular PLc is ± 5 degrees. For the same reason that the first sipe part 11 has the connecting part 11c, the second sipe part 12 has the third part 12a and the fourth part 12b interposed with the connecting part 12c formed by an arc. It is connected.

  The second sipe portion 12 preferably includes the third portion 12a with a length of 20 to 70% within one cycle and the fourth portion 12b with a length of 20 to 70% within one cycle. More preferably, the third portion 12a is included in the length of 40 to 60% and the fourth portion 12b is included in the length of 40 to 60%. Thereby, an increase in the sipe density in both end regions 1b can be suppressed to ensure dry performance.

  Further, the ratio of the length of the third portion 12a and the fourth portion 12b (third portion / fourth portion) is preferably 0.8 to 1.2, and preferably 0.9 to 1.1. Is more preferable. When the 2nd sipe part 12 is formed exceeding 1 period, it is preferable to repeat the 3rd part 12a and the 4th part 12b with the same period.

  As shown in FIG. 2A, when the length in the tire width direction of the block 1 is H, the tire width direction length H1 of the central region 1a in which the first sipe portion 11 is disposed is at least H / 3. It is preferable that Thereby, the improvement effect of the ice performance by the 1st sipe part 11 mentioned above can be expressed favorably. Further, from the viewpoint of expressing the ice performance and the dry performance in a high dimension with a good balance, the tire width direction length H1 of the central region 1a and the tire width direction lengths H2 of both end regions 1b are approximately H / 3, respectively. More preferably.

  In the present embodiment, the corrugated sipe 10 has linear portions 13 along the tire width direction WD at both ends thereof. Thereby, the angle with respect to the side wall of the block 1 is not reduced, and breakage of the block piece in the vicinity of the sipe end can be prevented. In order to appropriately exhibit such an effect, it is preferable that the straight portion 13 extends at an angle of ± 20 degrees with respect to the tire width direction WD.

  In the example shown in FIG. 1, five corrugated sipes 10 are formed for each block 1, but in the present invention, plural corrugated sipes 10 are formed for one block 1 in this way. May be. In addition, it is preferable that the adjacent wave-shaped sipes 10 synchronize a period like this embodiment, and the demolding property of the blade after a vulcanization molding becomes favorable.

  In the present embodiment, the sipe depth and the sipe groove width of the first sipe part 11 and the second sipe part 12 are equal to each other, which makes it easy to manufacture and remove the blade. In order for the corrugated sipe 10 to exhibit a sufficient edge effect, the sipe depth is preferably 30-80% of the depth of the main groove (circumferential groove 2), and the sipe groove width is 0.2-0. 7 mm is preferred.

  In the present invention, the pitch P1 (wavelength, one cycle) of the first sipe part 11 is ensured by appropriately changing the sipe density between the central region 1a and the both end regions 1b to ensure the effect of improving ice performance and dry performance. The ratio of the tire width direction length) to the pitch P2 of the second sipe part 12 (pitch P1 / pitch P2) is preferably 0.8 to 1.2, and preferably 0.9 to 1.1. Is more preferable, and 1.0 is still more preferable.

  In the present invention, instead of the block 1, a rib extending linearly or zigzag along the tire circumferential direction PD may be adopted, and the above-described wave sipe may be formed on the rib. In the present invention, the sipe structure as described above can be adopted for all land portions in the tread pattern, but may be adopted only for some land portions in the tread pattern. .

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the sipes as described above are formed on the blocks or ribs, and any conventionally known material, shape, structure, manufacturing method, etc. Can be adopted.

  Although the present invention can be applied to so-called summer tires, it is particularly useful as a studless tire (winter tire) because ice performance and dry performance can be achieved at a high level.

[Other Embodiments]
(1) In the above-described embodiment, an example in which the wave-shaped sipe 10 having a constant amplitude is uniformly formed in the entire tread surface is shown. However, the present invention is not limited to this, and the tread surface region is not limited to this. Correspondingly, the shape of the corrugated sipe may be varied. For example, in FIG. 1, a corrugated sipe 20 as shown in FIG. 3 is formed in the block 1 in a region Sh that is within 1/3 of the contact width W from the contact end E of the tread surface toward the tire equator C. Thus, a more preferable improvement effect can be obtained.

  This wave sipe 20 is equivalent to the wave sipe 10 of FIG. 2 except that the amplitude A1 of the first sipe part 21 is set larger than the amplitude A2 of the second sipe part 22. As described above, the ground pressure in the both end regions 1b of the block 1 becomes relatively high on the dry road surface, but this phenomenon becomes remarkable in the region Sh. Further, the block 1 provided in the vicinity of the ground contact E has a larger contribution to the dry performance than the blocks provided in other regions.

  Therefore, by forming the corrugated sipe 20 in the block 1 provided in the region Sh, it is possible to increase the sipe interval in the both end regions 1b where the contact pressure becomes high on the dry road surface, thereby increasing the rigidity, and excellent dry performance. Can be demonstrated. Further, in the central area 1a where the contact pressure becomes high on the ice road surface, the ice performance is improved by forming the first sipe portion 21 having a large amplitude, and the ice performance is particularly improved because it is provided in the block 1 near the contact end E. Ice turning performance can be improved.

  The contact width W is a distance in the tire width direction WD between the contact ends E. The contact end E is a road surface when a tire loaded with a rim is placed perpendicular to a plane with normal internal pressure filled and a normal load is applied. This is the outermost position in the tire width direction WD that contacts the ground. Here, the normal load and the normal internal pressure are the maximum load (design normal load in the case of passenger car tires) defined in JIS D4202 (specifications of automobile tires) and the air pressure corresponding thereto.

  (2) In the present invention, the corrugated sipe may be formed by one-sided open sipe or closed sipe, but from the viewpoint of enhancing the edge effect by appropriately defeating the block piece, both-side open sipe as in the above-described embodiment It is preferable to be formed as. In addition, the first sipe portion and the second sipe portion may be formed discontinuously. However, from the viewpoint of the edge effect and the sipe formability, the first sipe portion and the second sipe portion are the same as in the above-described embodiment. It is preferable that the part is continuous.

  (3) In the above-described embodiment, an example is shown in which the wave-shaped sipes as described above are formed on the block 1 that is rectangular in plan view. However, the shape of the block is not limited to this, and a V-shaped, polygonal, or curved tone is used. Anything may be used. It is preferable that both end regions of the block or rib in which the second sipe portion is formed are provided substantially uniformly from the side wall of the block or rib, thereby improving the improvement effect by the first sipe portion and the second sipe portion. It can be expressed in a balanced manner.

  (4) In the above-described embodiment, the first portion 11a and the second portion 11b of the first sipe portion 11, and the third portion 12a and the fourth portion 12b of the second sipe portion 12 respectively extend substantially linearly. Although an example has been shown, these may be curved and extended. In such a case, the angle with respect to each line such as the basic line SL can be determined by using a tangent at the center in the extending direction of each part.

  (5) In the present invention, all or part of the corrugated sipe can be provided as a so-called three-dimensional sipe in which the shape changes along the sipe depth direction and the inner wall surfaces of the sipe are engaged with each other. Examples of the three-dimensional sipe include those in which concave and convex portions that engage with each other are formed on the inner wall surface of the sipe, and examples of the shape of the concave and convex portions include a hemispherical shape and a pyramid shape. Such a three-dimensional sipe has a great effect of suppressing the falling of the land portion and can secure an edge effect. Therefore, it is preferable that the three-dimensional sipe is provided in a region that has a large contribution to ice performance and has a ground contact width that is ½ of the ground contact width.

  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 performance A tire was mounted on an actual vehicle (domestic 3000cc class FR sedan), and the braking distance was measured when the ABS was operated by applying braking force from a speed of 40 km / h while traveling on an ice road surface. The evaluation is indicated by an index when the comparative example 1 is set to 100, and the larger the numerical value, the better the ice braking performance.

(2) Dry performance Tires were mounted on all the wheels of the above-mentioned actual vehicle, and straight running, turning, braking, etc. were performed on the dry road surface, and handling performance was evaluated by a driver's sensory test. Evaluation is shown by an index when Comparative Example 1 is set to 100, and the larger the value, the better the dry performance.

Comparative Example 1
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) shown in FIG. The sipe depth was 8 mm, the groove width was 0.3 mm, the sipe interval was 5 mm, the amplitude was 2 mm, and the pitch (wavelength) was 5 mm.

Example 1
Instead of the corrugated sipe shown in FIG. 4, a radial tire which is the same as the comparative example 1 except that the corrugated sipe shown in FIG.

Example 2
A radial tire that is the same as that of Example 1 except that the corrugated sipe shown in FIG. In the wave sipe formed in the block near the ground end, the amplitude of the first sipe part was 3 mm and the amplitude of the second sipe part was 1 mm.

  From the results shown in Table 1, in Example 1, the ice performance is greatly improved while ensuring the dry performance by forming the corrugated sipe having the first sipe portion and the second sipe portion as described above. I understand that. In the second embodiment, both the ice performance and the dry performance are greatly improved by forming a wave-shaped sipe in which the amplitude of the first sipe portion is larger than the amplitude of the second sipe portion in the block near the grounding end. I understand that From this, it can be seen that in Examples 1 and 2, the ice performance and the dry performance are compatible at a high level.

The top view which shows an example of the tread surface of the pneumatic tire which concerns on this invention Enlarged view of main parts of block and corrugated sipe The principal part enlarged view which shows the block in another embodiment of this invention. Enlarged view of the main part showing a block in which a conventional corrugated sipe is formed

Explanation of symbols

1 Block 1a Central area 1b Block both ends area 10 Wave type sipe 11 1st sipe part 11a 1st part 11b 2nd part 12 2nd sipe part 12a 3rd part 12b 4th part C Tire equator CL Crossing line E Grounding End GP Wave type sipe end point PLc Cross line perpendicular PLs Basic line perpendicular SL Basic line SP Wave type sipe start point T Tread pattern W Ground contact width WD Tire width direction

Claims (3)

In a pneumatic tire provided with a tread pattern having blocks or ribs forming at least one corrugated sipe,
The wave sipe is
A first part having an angle of ± 10 degrees with respect to the basic line connecting the start point and the end point of the corrugated sipe and a second part having an angle with respect to the normal of the basic line of ± 10 degrees are repeatedly formed into a wavy shape. 1 sipe part,
A second portion having a wavy shape by repeating a third portion having an angle of ± 10 degrees with respect to the intersecting line intersecting the basic line at an angle of 45 degrees and a fourth portion having an angle of ± 10 degrees with respect to the perpendicular of the intersecting line. Having a sipe part,
The first sipe portion having one cycle or more is formed in the central region in the tire width direction of the block or rib, and the second portion having one cycle or more is formed in each end region of the block or rib in the tire width direction. A pneumatic tire, wherein a sipe portion is formed.   The corrugated sipe is formed in a block or a rib provided in a region that is within 1/3 of the ground contact width from the ground contact end toward the tire equator, and the amplitude of the first sipe portion of the corrugated sipe The pneumatic tire according to claim 1, wherein is set larger than an amplitude of the second sipe portion.   The pneumatic tire according to claim 1, wherein the basic line extends at an angle of ± 10 degrees with respect to the tire width direction.

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