JP2000006619A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wet grip performance, brake on the ice, driving performance and uneven wear resisting performance by restraining a pneumatic tire from having its grounding property deterioration when the number of sipes are increased. SOLUTION: A block-shaped land part 18 is formed with a plurality of sipes 20 zigzag extending along the tire in the cross direction. The sipes 20 being varied of its amplitude in the depth direction, the sipe wall contacting area becomes larger as compared with the sipes extending straight in the depth direction. Also because the amplitude of the sipe 20 is varied, the opposing sipe walls easily come into contact with each other only by the block-shaped land part 18 receiving compressional deformation by the sipe walls inclining. For this reason, sipe contacting force comes still more stronger when the block deforms and the block-shaped land part 18 can be restrained from collapsing more effectively than the conventional ones at the time of braking drive when the number of sipes are increased, which serve to improve wet grip performance, on-the-ice-braking and uneven wear resisting performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to an improvement of a pneumatic tire having excellent running performance on ice and snow roads.

[0002]

2. Description of the Related Art With the ban on the use of spike tires, various improvements in treads have been made in search of better studless tires.

[0003] As a feature almost common to this studless tire, a large number of sipes extending straight in the depth direction are provided on the tread.

The sipe divides the tread surface into a number of blocks, and the shape of the sipe in the width direction has been studied in order to improve the friction coefficient (μ) on ice (edge effect) by the corners of the blocks.

[0005]

In order to achieve a higher friction coefficient on ice in the prior art, there are a method of increasing the number of sipes and a method of improving the water removal function.

[0006] If the number of sipes is increased in the prior art, the grounding property is deteriorated due to a decrease in the block rigidity, so that such an effect cannot be expected. In addition, uneven wear (heel and toe wear) due to deterioration of the grounding property occurs.

[0007] The present invention has been made in view of the above-mentioned problems, and it is possible to suppress deterioration of the grounding property when the number of sipes is increased, thereby improving wet grip performance, braking drive performance on ice, and uneven wear resistance. It is an object of the present invention to provide a pneumatic tire that can be used.

[0008]

According to the first aspect of the present invention,
Including a plurality of circumferentially extending main grooves and a block-shaped land portion divided by a number of lug grooves intersecting these main grooves,
In the pneumatic tire provided with a tread in which each of the block-shaped land portions has a plurality of sipes, the sipes have an amplitude in a direction orthogonal to a longitudinal direction of the sipe at least at any position in a depth direction, and have a sipe depth. It is characterized in that the amplitude changes at one or a plurality of locations in the direction position into large, small, large or small and large.

Next, the operation of the pneumatic tire according to the first aspect will be described.

In general, since the groove width of the sipe is narrow, when the block-shaped land portion comes into contact with the ground during driving braking or the like, the sipe wall surfaces come into contact with each other and the fall of the small land portion divided by the sipe is suppressed to some extent. Is done.

Since the sipe of the pneumatic tire according to the first aspect has an amplitude in the sipe width direction at any position in the depth direction, the sipe of the pneumatic tire is compared with a sipe of a conventional shape extending straight in the depth direction. And the contact area of the sipe wall increases,
It is highly effective in suppressing the falling of the block-shaped land portion during the braking drive.

Also, since the amplitude of the sipe changes in the depth direction, the sipe cross-sectional shape (perpendicular to the longitudinal direction) is substantially bent in the depth direction, and the block-shaped land portion is compressed. The sipe walls that oppose each other are easily in contact with each other even if they are deformed, so the sipe contact force during block deformation is even stronger, compared to a conventional block-shaped land part that has a sipe that extends straight in the depth direction. The effect of suppressing the falling of the block-like land portion is enhanced.

[0013] In the pneumatic tire according to the first aspect, the contact area of the sipe wall surface is increased by having the amplitude, and
Due to the increase in sipe contact force when subjected to compressive deformation,
Even when the number of sipes is increased, in the case of a sipe extending in the tire width direction, the fall of the block-shaped land portion (tire circumferential direction) during braking drive or the like can be suppressed more than before, and the sipe extending in the tire circumferential direction can be suppressed. In the case of (1), the fall of the block-shaped land portion (in the tire width direction) during cornering can be suppressed as compared with the conventional case.

That is, in the pneumatic tire according to the first aspect, an increase in the amount of deformation of the block-shaped land portion when the number of sipes is increased can be reduced. Can be suppressed, the wet grip performance, the braking drive performance on ice, and the uneven wear resistance performance can be improved, and in the case of a sipe extending in the tire circumferential direction, the cornering performance can be improved.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the sipe has a portion where the amplitude becomes zero at a position on the bottom side of the tread.

Next, the operation of the pneumatic tire according to claim 2 will be described.

In a sipe extending linearly in the tire width direction, the water film between the sipe and the road surface cannot be cut sufficiently because the edge length appearing on the tread surface is not sufficient.

On the other hand, in a sipe having an amplitude on the block surface and having a constant amplitude in the depth direction (for example, a general zigzag sipe), a water film is cut in the amplitude shape of the block surface, and a road surface is formed inside the sipe. Although it is possible to suck up the water between the block, the water sucked up particularly at the center of the block cannot be smoothly drained to the outside of the block.

That is, comparing a sipe having an amplitude like a zigzag sipe and a straight sipe extending linearly, the straight sipe has a smoother flow of water in the sipe (the longitudinal direction of the sipe), Water can be drained smoothly from the side of the block.

In the sipe for a pneumatic tire according to the second aspect, when the sipe extends in the width direction of the tire, the amplitude of the sipe changes in the depth direction, thereby cutting off a water film on the block surface, and the inside of the sipe. It is possible to smoothly drain the water sucked up to the main groove from the side surface of the block via the portion where the amplitude of the sipe becomes zero and the vicinity thereof.

According to a third aspect of the present invention, in the pneumatic tire according to the second aspect, a depth A of a portion where the amplitude becomes zero at a position on the bottom side of the tread surface of the sipe, and a depth of the sipe. It is characterized in that the relation with B is 1/10 <A / B <1/2.

Next, the operation of the pneumatic tire according to the third aspect will be described.

In the case of a sipe extending along the tire width direction, when A / B <1/10, the portion where the amplitude becomes zero in the early stage of wear disappears.
There is a possibility that the water sucked into the sipe cannot be drained smoothly from the block side into the main groove.

On the other hand, if 1/2 <A / B, the rigidity of only the base portion (base) of the land portion divided by the sipe decreases, and the deformation concentrates near the base, so that the block shape is obtained. The falling deformation of the land cannot be suppressed. Therefore, heel-and-toe wear may occur from the beginning of wear.

Therefore, it is preferable that 1/10 <A / B <1/2.

According to a fourth aspect of the present invention, in the pneumatic tire according to the first aspect, the sipe has an amplitude of zero on a tread surface.

Next, the operation of the pneumatic tire according to claim 4 will be described.

In the pneumatic tire according to the fourth aspect, the sipe contact force generated inside the block-shaped land portion is stronger than the sipe of the second aspect because of the larger contact area. Thereby, the deformation of the block-shaped land portion is suppressed, and the contact property is improved.

According to a fifth aspect of the present invention, in the pneumatic tire according to the fourth aspect, a depth A of a portion where the amplitude is maximum at a position on the bottom side of the tread surface of the sipe, and a depth of the sipe. It is characterized in that the relationship with B is 1/10 <A / B <2/3.

Next, the operation of the pneumatic tire according to claim 5 will be described.

If A / B <1/10, the portion where the amplitude becomes maximum in the early stage of wear disappears.
The effect of suppressing deformation of the block-shaped land portion according to claim 4 cannot be obtained.

On the other hand, when 2/3 <A / B, the rigidity of only the root portion of the small land portion divided by the sipe is reduced, and deformation near the root portion is concentrated. This makes it impossible to suppress the falling deformation of the vehicle.

Therefore, it is preferable that 1/10 <A / B <2/3.

According to a sixth aspect of the present invention, in the pneumatic tire according to any one of the first to fifth aspects,
The sipe extends in the tire width direction.

Next, the operation of the pneumatic tire according to claim 6 will be described.

In the case where a sipe extending along the tire width direction is provided on the block-shaped land portion as in the pneumatic tire according to the sixth aspect, the small land portion divided by the sipe may extend in the tire circumferential direction. The fall can be suppressed, and the performance when traveling straight ahead, specifically, the wet grip performance, the braking drive performance on ice, and the uneven wear resistance performance can be improved.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of a pneumatic tire according to the present invention will be described below with reference to FIGS.

The internal structure of the pneumatic tire 10 of the present embodiment is the structure of a general radial tire, so that the description of the internal structure will be omitted.

As shown in FIG. 2, the tread 12 of the pneumatic tire 10 of the present embodiment has a tire circumferential direction (arrow S).
), And a plurality of lug grooves 16 intersecting with the main grooves 14 are formed, and the block-shaped land portion 18 is divided by these main grooves 14 and the lug grooves 16. I have.

In the present embodiment, both the main groove 14 and the lug groove 16 are straight, but the main groove 14 is a well-known groove continuous in the tire circumferential direction at a predetermined interval left and right such as a zigzag shape or a crank shape. Similarly, the lug groove 16 may have another shape such as a crank shape or a concave groove.

As shown in FIGS. 1 and 2, the block-shaped land portion 18 of this embodiment has a square shape in which the length L1 in the tire circumferential direction and the length L2 in the tire width direction (direction of arrow W) are set to be the same. The shape may be other shapes such as a rectangle.

As shown in FIG. 2, a plurality of sipes 20 extending in the tire width direction and crossing the block-shaped land portion 18 are formed on the block-shaped land portion 18, and each block-shaped land portion 18 It is divided into a plurality of small blocks (land areas) 18B by a plurality of sipes 20.

As shown in FIG. 1, the sipe 2 of the present embodiment
0 is a zigzag shape (triangular wave shape) on the tread surface 18, and its amplitude a gradually decreases toward the bottom side and becomes zero at the central portion in the depth direction (A = 0.5B), and from the central portion in the depth direction. It gradually increases toward the bottom.

The shape that appears on the tread surface 18A of the sipe 20 is not limited to the zigzag shape, but may be another shape such as a sine curve.

In this embodiment, the sipe depth B of each sipe 20 is all set to be the same, and the dimension A up to the position where the amplitude a closest to the tread surface 18A becomes zero is all set to the same size. ing.

The relationship between the sipe depth B and the dimension A is as follows.
1/10 <A / B <2/3.

Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

In the sipe 20 of the pneumatic tire 10 of the present embodiment, the contact area of the sipe wall surface is increased as compared with a sipe of a conventional shape extending straight in the depth direction (condition of the same depth as the sipe 20), and braking is performed. Block-shaped land part 18 when driving
It is highly effective in suppressing the falling of

Further, in the sipe 20, since the amplitude a changes in the depth direction, the sipe 20 has a substantially sipe cross-sectional shape (perpendicular to the longitudinal direction) bent in the depth direction.
A conventional block having a sipe extending straight in the depth direction because the opposing sipe walls easily come into contact with each other even if the block-shaped land portion 18 is only subjected to compression deformation, so that the sipe contact force at the time of block deformation is further increased. The block-shaped land portion 18 of the present embodiment is less likely to fall as compared with the land portion.

In the pneumatic tire 10 of the present embodiment, when the number of sipe is increased, the increase in the contact area of the sipe wall surface due to the amplitude a and the increase in the sipe contact force when subjected to compressive deformation. Also, the falling of the block-shaped land portion 18 during the braking drive can be suppressed as compared with the related art.

As described above, in the pneumatic tire 10 of the present embodiment, the increase in the amount of deformation of the block-shaped land portion 18 when the number of sipes is increased can be reduced, and deterioration of the contact property can be suppressed. The braking drive performance on ice and the uneven wear resistance performance can be improved.

If A / B <1/10, the portion where the amplitude becomes zero in the early stage of wear (the portion where the amplitude changes in the present invention) disappears, and the effect of the present invention is lost. In the middle stage, heel-and-toe wear occurs due to a decrease in block rigidity.

On the other hand, when 2/3 <A / B, sipe 2
The rigidity of only the base portion (base portion) of the small block divided by 0 is reduced, and the deformation concentrates near the base, so that the falling deformation of the block-like land portion 18 cannot be suppressed. For this reason, heel-and-toe wear occurs from the beginning of wear.

In general, a sipe that is linear in the tire width direction cannot cut the water film sufficiently because the edge length is not sufficient. On the other hand, in a sipe with a constant amplitude in the depth direction, it is possible to cut the water film in a zigzag shape on the block tread and suck up the water inside the sipe. Cannot drain.

However, the pneumatic tire 10 of the present embodiment
Then, as the amplitude a changes in the depth direction, the tread surface 18A
To smoothly drain the water sucked into the sipe from the side surface of the block-shaped land portion 18 (the longitudinal end of the sipe 20) to the main groove 14 through a portion where the amplitude a is zero or small. Is possible, thereby improving the rejection water performance.

In order to smoothly drain the water sucked into the sipe through the portion where the amplitude a of the sipe 20 is zero or small, the relationship between the sipe depth B and the dimension A is expressed by 1 /. It is preferable to set 10 <A / B <1/2.

When A / B <1/10, the effect is lost in the early stage of wear, and when 1/2 <A / B, the sipe 20 cannot sufficiently suck up water, so that such an effect cannot be expected.

In this embodiment, the block-like land portion 1 is used.
8, four or more sipes 20 may be formed on one block-shaped land portion 18, and the number of the sipes 20 formed on one block-shaped land portion 18 may be less than four. The number of embodiments is not limited.

Further, the sipe 20 does not cross the block-shaped land portion 18 as shown in FIG. It is also possible to use a so-called transverse sipe such as the sipe 20 and a dead end sipe as appropriate. [Second Embodiment] Next, a second embodiment of the pneumatic tire of the present invention will be described.
Will be described with reference to FIG. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 3, sipe 2 of the present embodiment
Reference numeral 4 denotes a zigzag shape on the tread surface 18, and its amplitude a becomes zero at a certain depth (A) gradually decreasing toward the bottom side, and gradually increases toward the bottom side from there. A + λ), the amplitude becomes the same as that of the tread surface 18A, and further gradually decreases from there toward the bottom, and becomes zero at the bottom.

In the sipe 24 of the present embodiment, the first
Since the contact area of the sipe wall surface is increased as compared with the sipe of the conventional shape extending straight in the depth direction (the condition of the same depth as the sipe 24) similarly to the embodiment of FIG. The effect of suppressing is high.

In the sipe 24 as well, since the amplitude a changes in the depth direction, the sipe cross-sectional shape (perpendicular to the longitudinal direction) is substantially bent in the depth direction, and the block-shaped land portion is formed. Even when the slab 18 is only subjected to compressive deformation, the opposing sipe walls easily come into contact with each other, so that the sipe contact force at the time of block deformation is further increased, and the conventional sipe land portion having a sipe extending straight in the depth direction is formed. In comparison, the block-shaped land portion 18 of the present embodiment is less likely to fall.

Therefore, also in the present embodiment, the increase in the contact area of the sipe wall surface due to having the amplitude a
Due to the increase in sipe contact force when subjected to compressive deformation,
Even when the number of sipes is increased, the falling of the block-shaped land portion 18 during the braking drive can be suppressed as compared with the conventional case, and the wet grip performance, the braking drive performance on ice, the partial wear resistance performance as in the first embodiment. Can be improved.

Incidentally, like the sipe 24 of the present embodiment,
If the amplitude change position is not a single place but a plurality of places, even if the first amplitude change position counted from the tread surface 18A disappears due to wear, there is still an amplitude change position thereunder. Performance degradation can be suppressed.

Further, like the sipe 24 of the present embodiment,
When there are a plurality of the amplitude change positions, the second and subsequent amplitude change positions counted from the tread surface 18A are conditions 1/10 <A in which the water sucked into the sipe described in the first embodiment can be smoothly drained. / B <１ ／, but the adjacent distance λ between the sipe amplitude change positions is preferably at least 0.125B or more. Third Embodiment Next, a third embodiment of the pneumatic tire according to the present invention will be described.
Will be described with reference to FIG. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The sipe 26 of the present embodiment is linear in the tread surface 18 and has a zigzag shape (triangular wave shape) toward the bottom, and its amplitude a gradually increases toward the bottom and increases in the center in the depth direction. , And gradually decreases from the center in the depth direction toward the bottom, and becomes zero at the bottom.

In this embodiment, the relationship between the sipe depth B and the dimension A is set to 1/10 <A / B <2/3.

Also in the sipe 26 of the present embodiment, the contact between the sipe wall surface and the sipe of the conventional shape extending straight in the depth direction (condition of the same depth as the sipe 26) is similar to that of the first embodiment described above. Since the area increases, the function of suppressing the falling of the block-shaped land portion 18 during the braking drive is high.

Also, in the sipe 26, since the amplitude a changes in the depth direction, the sipe cross-sectional shape (perpendicular to the longitudinal direction) is substantially bent in the depth direction, and the block-shaped land portion is formed. Even when the slab 18 is only subjected to compressive deformation, the opposing sipe walls easily come into contact with each other, so that the sipe contact force at the time of block deformation is further increased, and the conventional sipe land portion having a sipe extending straight in the depth direction is formed. In comparison, the block-shaped land portion 18 of the present embodiment is less likely to fall.

Therefore, also in the present embodiment, the increase in the contact area of the sipe wall surface due to having the amplitude a
Due to the increase in sipe contact force when subjected to compressive deformation,
Even when the number of sipes is increased, the falling of the block-shaped land portion 18 during the braking drive can be suppressed as compared with the conventional case, and the wet grip performance, the braking drive performance on ice, the partial wear resistance performance as in the first embodiment. Can be improved.

Since the contact area of the sipe 26 is large, the sipe contact force is further increased.

As a result, the deformation of the block-shaped land portion 18 is suppressed, and the contact property is improved. In particular, uneven wear resistance is improved.

The amplitude a of the sipe of the embodiment described above
Is preferably 1 to 3 mm. When the amplitude a is less than 1 mm, the effect is reduced because the contact area of the sipe wall surface becomes small. On the other hand, if the amplitude a is larger than 3 mm, the sipe interval is widened, so that the number of sipe formed on the block-shaped land portion decreases.

In the above embodiment, a sipe extending in the tire width direction is formed on the block-shaped land portion, but a sipe extending in the tire circumferential direction may be formed on the block-shaped land portion.

By forming the sipe of the present invention extending in the tire circumferential direction on the block-shaped land portion, the cornering performance can be improved as compared with a conventional tire having a straight sipe. [Test Example] In order to confirm the effect of the present invention, a conventional pneumatic tire and a pneumatic tire of an embodiment to which the present invention was applied were prepared, and a test was performed on the braking performance on ice. All tires are 185 / 70R1
Four were used.

The braking performance on ice was measured by measuring the distance from the applied point to the stopping point while the tire was mounted on the vehicle and the vehicle was suddenly braked at a speed of 20 km / h. The conventional example is set to 100) and shown in Table 1. The larger the value, the better the performance. The measurement was performed twice each for a new product and 50% wear.

Example 1 A pneumatic tire provided with a block-shaped land portion shown in FIG. 1 on a tread, wherein the block-shaped land portion has a tire circumferential length L1 of 20 mm and a tire width direction length L2 of 20 mm. The height H is 20 mm and the height H is 10 mm. The sipe has a sipe depth B of 7 mm, a dimension A from the tread surface to an amplitude change position of 3.5 mm, and an amplitude a of 1.5 mm.

Embodiment 2 A pneumatic tire provided with a block-like land portion shown in FIG. 5 on a tread, and the size of the block-like land portion is the same as that of the first embodiment. Sipe 28
The depth B is 7 mm, there are three amplitude change positions between the tread and the bottom, and the adjacent distance λ between the sipe amplitude change positions is 0.
25B (= 1.75 mm), amplitude a (maximum part) is 1.5
mm.

Conventional Example: As shown in FIG.
This is a pneumatic tire in which a straight sipe 72 is formed on a block-shaped land portion 70 having the same size as that of the tire 2. The sipe depth B of the straight sipe 72 is 7 mm, which is the same as in the embodiment.

[0080]

[Table 1]

From the results shown in Table 1, it was revealed that the tires 1 and 2 of the present invention had better braking performance on ice than the conventional tires.

The reason why the tire of Example 2 is superior to the tire of Example 1 in braking performance on ice at 50% wear is that there are a plurality of amplitude change positions.

[0083]

As described above, the pneumatic tire according to the first aspect has the above-described structure, so that in the case of a sipe extending in the tire width direction, wet grip performance, braking drive performance on ice, and uneven wear resistance performance are achieved. Can be improved,
In the case of a sipe extending in the tire circumferential direction, there is an excellent effect that cornering performance can be improved.

Since the pneumatic tire according to claim 2 has the above-described structure, when the sipe extends along the width direction of the tire, the water sucked into the sipe and the portion where the sipe amplitude becomes zero and the portion where the sipe has zero amplitude are formed. There is an excellent effect that it is possible to smoothly drain water from the block side surface to the main groove through the vicinity, and it is possible to further improve wet grip performance and braking drive performance on ice.

Since the pneumatic tire according to the third aspect has the above-described configuration, the pneumatic tire has an excellent effect that the effect of the second aspect can be surely obtained even during the middle period of wear.

Since the pneumatic tire according to the fourth aspect has the above-described configuration, the deformation suppressing action is greater than that of the sipe according to the second aspect, so that the partial wear resistance is good, and the amplitude of the sipe increases, so that the wear is reduced. It has an excellent effect that the performance on ice at the time is further improved.

The pneumatic tire according to the fifth aspect has the above-described configuration, and thus has an excellent effect that the deformation of the block-shaped land portion can be reliably suppressed from the initial wear to the late wear.

Since the pneumatic tire according to the sixth aspect has the above-described configuration, it is possible to improve mainly the performance when traveling straight, specifically, the wet grip performance, the braking drive performance on ice, and the partial wear resistance performance. , Which is an excellent effect.

[Brief description of the drawings]

FIG. 1 is a perspective view of a block-shaped land portion of a pneumatic tire according to a first embodiment.

FIG. 2 is a plan view showing a part of a tread of the pneumatic tire according to the first embodiment.

FIG. 3 is a perspective view of a block-like land portion of a pneumatic tire according to a second embodiment.

FIG. 4 is a perspective view of a block-like land portion of a pneumatic tire according to a third embodiment.

FIG. 5 is a perspective view of a block-like land portion of a pneumatic tire according to a second embodiment used for a test.

FIG. 6 is a perspective view showing a block-shaped land portion of a pneumatic tire according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Main groove 16 Lug groove 18 Block-shaped land portion 18A Tread surface 20 Sipe 24 Sipe 26 Sipe 28 Sipe

Claims (6)

[Claims] 1. A tread having a plurality of circumferentially extending main grooves and a block-shaped land portion divided by a number of lug grooves intersecting these main grooves, wherein the block-shaped land portion has a plurality of sipes. In the pneumatic tire provided, the sipe has an amplitude in a direction orthogonal to the sipe longitudinal direction at least at any position in the depth direction, and the amplitude is large or small at one or a plurality of positions in the sipe depth direction. A pneumatic tire characterized by changing in size. 2. The pneumatic tire according to claim 1, wherein the sipe has a portion having an amplitude of zero at a position on the bottom side of the tread surface. 3. The relationship between the depth A of a portion where the amplitude becomes zero at a position on the bottom side of the tread surface of the sipe and the depth B of the sipe is 1/10 <A / B <1/2. The pneumatic tire according to claim 2, wherein 4. The pneumatic tire according to claim 1, wherein the sipe has an amplitude of zero on a tread surface. 5. A depth A of a portion where the amplitude is maximum at a position on the bottom side of the tread surface of the sipe, and a depth B of the sipe.
5. The pneumatic tire according to claim 4, wherein the relationship is 1/10 <A / B <2/3. 6. The pneumatic tire according to claim 1, wherein the sipe extends along a tire width direction.