JP2000247112A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of preventing the deterioration of tire performance in a new article. SOLUTION: A plurality of sub-grooves 20 shallower and narrower than a circumferential main groove 14 and a transverse main groove 16 are provided on the tread of a block 18 to form a land part having a negative ratio ranging between 1-40%. Since the sub-grooves 20 take the water interposed between the block 18 and a road surface in traveling on a wet road surface and discharge it to the circumferential main groove 14 and the transverse main groove 16, the same sufficient wet performance as in the worn state can be provided in a new article. Since the tread of the block 18 is roughed when the tread is worn by traveling to some degree, prescribed wet performance can be provided even if the sub-grooves 20 disappear.

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 a pneumatic tire having a land portion defined by a plurality of main grooves in a tread.

[0002]

2. Description of the Related Art In a general pneumatic tire, a plurality of main grooves are formed in a tread in order to secure wet performance.

[0003]

A pneumatic tire is manufactured by loading a green tire into a mold and vulcanizing the green tire.

[0004] Since the inner surface of the mold is extremely smoothed by polishing, the tread surface of the pneumatic tire after vulcanization molding, that is, the land surface, is also extremely smooth.

[0005] When a new pneumatic tire is compared with a pneumatic tire whose running tread surface is worn (rough) to some extent, a new pneumatic tire having an extremely smooth tread surface has slightly inferior wet performance. .

In recent years, with the prohibition of spiked tires, tires without spikes, so-called studless tires, are used for traveling on icy and snowy road surfaces.

[0007] In this studless tire, fine particles are mixed into the tread rubber, and the performance on ice is improved by using the tread rubber as a foamed rubber.

However, even in these studless tires, when they are new, fine particles and bubbles of foamed rubber do not appear on the surface and are extremely smooth, so that their performance on ice is slightly inferior to that of worn tires.

The present invention has been made in view of the above circumstances, and has as its object to provide a pneumatic tire that can solve the problem that the tire performance when new is slightly lower than the tire performance when worn.

[0010]

An invention according to claim 1 is a pneumatic tire having a land portion defined by a plurality of main grooves in a tread, wherein the land portion is provided with a land portion having a plurality of main grooves. A plurality of sub-grooves having a small width and a small depth are provided, and the negative rate Na of the land portion is in a range of 1 to 40%.

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

In the pneumatic tire according to the first aspect, the plurality of narrow and shallow sub-grooves formed in the land portion discharge water interposed between the land portion and the road surface when traveling on a wet road surface.
Sufficient wet performance can be obtained even when new.

If the tread wears after traveling to some extent, the tread surface becomes rough, so that a predetermined wet performance can be obtained even if the sub-groove disappears.

Further, when the pneumatic tire is a studless tire, sufficient performance on ice can be obtained even when the tire is new, due to the edge effect of the sub-groove.

If the tread wears after running to some extent, the tread surface becomes rough, so that a predetermined performance on ice can be obtained even if the sub-groove disappears.

Here, if the negative rate Na of the land portion is less than 1%, the effect of providing the sub-groove cannot be expected. On the other hand, when the negative rate Na of the land portion exceeds 40%, the contact area decreases, so that the steering stability decreases and, in the case of a studless tire, the on-ice performance also decreases.

The negative rate Na of the land is 10 to 10%.
It is preferably within the range of 20%.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the negative rate Na is
Na / Nb, which is the ratio of the negative rate Nb on the ground contact surface of the tread, is in the range of 5 to 150%.

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

In the pneumatic tire according to the second aspect, the ratio of the negative ratio Na on the land portion to the negative ratio Nb on the tread contact surface of the tread, Na / Nb, is in the range of 5 to 150%. It is possible to surely secure the wet performance when new, while maintaining the performance.

When Na / Nb is less than 5%, the number of sub-grooves is reduced, so that sufficient wet performance cannot be obtained. On the other hand, when Na / Nb exceeds 150%, the effect of the decrease in the rigidity of the land portion becomes large, and in particular, the dry performance is reduced and the sub-grooves are easily crushed, so that sufficient wet performance cannot be obtained.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, three or more sub-grooves are provided in the land portion.

Next, the operation of the pneumatic tire according to claim 3 will be described.

In the pneumatic tire according to the third aspect, by providing three or more sub-grooves in the land portion, it is possible to reliably discharge water interposed between the land portion and the road surface, High wet performance can be obtained.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects,
The sub-groove is characterized by being opened in a main groove continuous in a tire circumferential direction among the main grooves.

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

In the pneumatic tire according to the fourth aspect, water flows along the tire circumferential direction in the main groove continuous in the tire circumferential direction on the ground contact surface when traveling on a wet road surface. Therefore, if the sub-groove is connected to the main groove that is continuous in the tire circumferential direction, water taken in the sub-groove is efficiently transferred to the main groove, and high wet performance can be maintained.

According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects,
When the land portion is a rib-shaped land portion extending along the circumferential direction of the tire, the sub-groove extends outward from the center in the width direction of the rib-shaped land portion in the width direction to partition the rib-shaped land portion. It is characterized by opening in the main groove.

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

Main grooves extending continuously in the tire circumferential direction are arranged on both sides in the tire width direction of the rib-shaped land portions extending in the tire circumferential direction. Water flows along the tire circumferential direction in the main groove continuous in the tire circumferential direction on the ground contact surface when traveling on a wet road surface. Therefore,
If the sub-groove extending from the center in the width direction of the rib-shaped land portion to the outside in the width direction is connected to the main groove continuous in the tire circumferential direction, water taken in the sub-groove is efficiently discharged to the main groove. High wet performance can be maintained.

[0031]

[First Embodiment] A first embodiment of a pneumatic tire according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, the tread 12 of the pneumatic tire 10 of the present embodiment has a tire circumferential direction (arrow S).
A plurality of blocks 18 are defined by a plurality of circumferential main grooves 14 extending along the same direction and a plurality of lateral main grooves 16 extending along the tire axial direction (the direction of the arrow W).

As shown in FIG. 1 and FIG.
A plurality of sub-grooves 20 are formed on the tread surface.

In the block 18 of the present embodiment, four sub-grooves 20 extending along the tire circumferential direction and four sub-grooves 20 extending along the tire axial direction are formed. It is open in the circumferential main groove 14 or the lateral main groove 16.

Incidentally, at least one sub-groove 20 is formed for one block 18, and it is preferable that three or more sub-grooves are formed.

The sub-groove 20 is formed to be narrower and shallower than the circumferential main groove 14 and the lateral main groove 16 which define the block 18.

The width of the sub groove 20 is preferably 0.4 mm to 3 mm. The depth of the sub-groove 20 is preferably 0.5 mm to 3 mm, particularly preferably about 2 mm.

Since the sub-groove 20 of the block 18 has the purpose of discharging water from the contact surface when the block (when new) 18 contacts the wet road surface, the sub-groove 20 is used when the block 18 contacts the road surface. It is important to determine the width, depth, pitch and the like of the sub-groove 20 so that the groove 20 is not crushed and the drainage capacity is not extremely reduced.

The negative rate in the block (the area of the sub-groove / the area of the tread surface of the block) is Na, and the negative rate of the entire tread 12 in the contact surface (the area of the circumferential main groove and the lateral main groove / the contact area). ) Is Nb, the negative rate Na in the block is within 1 to 40%, and the ratio Na / Nb between the negative rate Na and the negative rate Nb is 5 to 15%.
It is preferably set to 0%. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

In the pneumatic tire 10 of the present embodiment, the plurality of narrow and shallow sub-grooves 20 formed in the block 18 take in water interposed between the block 18 and the road surface when the vehicle is running on a wet road surface, and the circumferential direction is different. Main groove 14 and lateral main groove 1
6, the same wet performance as in the case of abrasion can be obtained even when the product is new.

If the tread surface of the block 18 is worn to some extent after running, the tread surface becomes rough, so that a predetermined wet performance can be obtained even if the sub-groove 20 disappears.

Here, if the width of the sub-groove 20 is less than 0.4 mm, the effect of the groove as drainage performance cannot be confirmed much because the groove is too narrow.

On the other hand, if the width of the sub-groove 20 exceeds 3 mm, the area of the surface of the block 18 that contacts the road surface is excessively reduced, and steering stability is deteriorated. Further, the contact pressure on the surface to be grounded is too high, and uneven wear is likely to occur.

When the depth of the sub-groove 20 is less than 0.4 mm,
It is difficult to obtain the drainage effect.

When the depth of the sub-groove 20 is generally 3 mm or more, the block 18 is weakened, and the steering stability is reduced. The depth of the sub-groove 20 is also related to the distance between the sub-groove 20 and the adjacent sub-groove 20.
Ideally, it should be at least 1.5 times the depth of 0.

If the negative rate Na in the block is less than 1%, the ability to drain water between the block 18 and the road surface is too low, and the effect of providing the sub-groove 20 cannot be obtained.

On the other hand, the negative rate Na in the block is 4
If it exceeds 0%, the contact area becomes insufficient, and the dry performance deteriorates.

Further, when the ratio Na / Nb of the negative rate Na and the negative rate Nb is less than 5%, the sub-groove 20 is reduced, so that sufficient wet performance cannot be obtained.

On the other hand, when Na / Nb exceeds 150%,
The effect of the decrease in the rigidity near the tread surface of the block 18 becomes large, and in particular, the dry performance is reduced, and the sub-groove 20 is easily crushed, so that sufficient wet performance cannot be obtained.

The present invention can be applied to various pneumatic tires, and is not limited to all-seam type tires, but can be applied to, for example, studless tires.

Further, when the present invention is applied to a studless tire, sufficient on-ice performance can be obtained even when new, due to the edge effect of the sub-groove. In addition, when the tread is worn after traveling to some extent, the tread surface is roughened, so that a predetermined performance on ice can be obtained even if the sub-groove disappears. [Second Embodiment] A second embodiment of the pneumatic tire according to the present invention will be described with reference to FIGS.

As shown in FIG. 3, a plurality of circumferential main grooves 34 extending along the tire circumferential direction are formed in the tread 32 of the pneumatic tire 30 of the present embodiment, and the tread pattern is a so-called rib pattern. It has become.

As shown in FIG. 4, the rib 36 extending along the circumferential direction defined by the circumferential main groove 34 has
8 are formed.

The sub-groove 38 extends from the center in the width direction of the rib 36 to the outside in the width direction so as to be inclined with respect to the tire circumferential direction, and terminates near the rib end.

The sub-grooves 38 are formed between one side and the other side in the tire axial direction with the center in the width direction of the rib 36 interposed therebetween.
The inclination directions are opposite and the phases are shifted.

The sub-groove 38 is formed to be narrower and shallower than the circumferential main groove 34 that defines the rib 36.

The width of the sub groove 38 is preferably 0.4 mm to 3 mm.

The depth of the sub-groove 38 depends on the sub-groove 38 and the adjacent sub-groove 3
Although it is related to the distance between the sub-grooves 8, it is preferable that the distance be at least 2/3 times the distance between the sub-grooves 38. When the depth is further increased, the rib 36 is easily bent, and the steering stability is significantly reduced. In the case of a general passenger car tire, it is preferably about 0.5 mm to 3 mm.

When the rib 36 is grounded, the sub groove 38
In order to prevent the drainage capacity from being extremely collapsed due to the collapse of
It is important to determine the width, depth, pitch, etc.

Further, the negative ratio in the rib (the area of the sub-groove / the area of the tread surface of the block) is Na, and the negative ratio of the whole in the contact surface of the tread 32 (the area of the circumferential main groove and the lateral main groove / the contact area). ) Is Nb, the negative rate Na in the rib is preferably within 1 to 40%, and the ratio Na / Nb between the negative rate Na and the negative rate Nb is preferably 5 to 150%.

Next, the operation of the pneumatic tire 30 of this embodiment will be described.

In the pneumatic tire 30 of the present embodiment, the plurality of narrow and shallow sub-grooves 38 formed in the ribs 36 take in water interposed between the ribs 36 and the road surface when the vehicle is running on a wet road surface. , Sufficient wet performance similar to that at the time of wear can be obtained.

When the tread surface of the rib 36 is worn to some extent after running, the tread surface becomes rough, so that a predetermined wet performance can be obtained even if the sub-groove 38 disappears.

As shown in FIG. 5, the sub-groove 38 may be connected to the opening on the side surface of the rib, that is, to the circumferential main groove 34 (not shown in FIG. 5).

In the circumferential main groove 34 extending in the tire circumferential direction, water flows along the tire circumferential direction (the direction of arrow A in FIG. 5). Therefore, if the sub-groove 38 extending from the center in the width direction of the rib 36 to the outside in the width direction is connected to the circumferential main groove 34, water taken in the sub-groove 38 is efficiently discharged to the circumferential main groove 34. The auxiliary groove 38 can be
Higher wet performance can be obtained compared to a tire that is not connected to a tire.

The present invention can be applied to all pneumatic tires having a land portion defined by a main groove in a tread, and the shape of the land portion is not limited to the above example.

The sub-grooves may be linear, curved or zigzag, and may be arranged in a certain direction (for example, in the tire circumferential direction, the tire axial direction, etc.). They may be arranged in different directions. (Test Example 1) In order to confirm the effect of the present invention, a plurality of tires each having a different land area negative rate were trial-produced, mounted on an actual vehicle, and compared.

The test was conducted on a test course, and a vehicle equipped with test tires was run on a dry road surface, a wet road surface, and an ice floe, and the test driver evaluated the feeling.

Test tire: The block shape is a square similar to that shown in FIG. 2, a large number of blocks having a tire circumferential dimension of 20 mm, a tire axial dimension of 20 mm, and a height of 8 mm are provided on the tread, and the block tread surface has a grid-like depth. A tire having a sub-groove of 2 mm and a tire having no sub-groove were prototyped. In the block where the sub-groove is formed, four sub-grooves extending along the tire circumferential direction and four sub-grooves extending along the tire axial direction are formed. The negative rate of the land was determined by changing the width of the sub-groove.

[0070]

[Table 1]

As a result of the test, the negative rate was 1% to 40%.
As a result, the wet steering stability and the on-ice steering stability can be improved with respect to a tire having no sub-groove (negative rate: 0%) while minimizing a decrease in dry steering stability. It has been found that the wet steering stability and the on-ice steering stability can be particularly improved by setting the content to ２０20%. (Test Example 2) In order to confirm the effects of the present invention, a plurality of tires having different ratios Na / Nb between the negative rate Na of the block and the negative rate Nb of the entire contact surface were trial-produced, mounted on an actual vehicle, and compared. .

The test was conducted on a test course, and a vehicle equipped with test tires was run on a dry road surface and a wet road surface, and a test driver evaluated feeling.

Test tires: a tire having a large number of blocks in the tread having a tire circumferential dimension of 40 mm, a tire axial dimension of 40 mm, and a height of 14 mm, and a sub-groove having a depth of 2 mm on the block tread surface, and a tire having no sub-groove. And prototyped.

FIGS. 6 (A) to 6 (I) show the sub-grooved blocks used in the test. Note that reference numeral 20 in FIG. 6 is a sub groove.

[0075]

[Table 2]

The results of the test are as shown in the graph of FIG. 7, in which the Na / Nb content is set to 0.5% to 150% to minimize the decrease in dry steering stability, and to eliminate the minor groove. (Negative rate: 0%) It was found that the wet steering stability could be improved with respect to the tire, and in particular, the wet steering stability could be particularly improved by setting it to around 50%. (Test Example 3) In order to confirm the effects of the present invention, in order to confirm the effect of the present invention, a tire having a rib pattern without a sub-groove, a tire having a rib pattern with a sub-groove having an open main groove, and a tire having a sub-groove having no main groove open Three types of tires were prototyped and mounted on an actual vehicle for comparison.

The test was conducted on a test course, and a vehicle equipped with test tires was run on a dry road surface, a wet road surface, and on an ice floe, and a test driver evaluated feeling.

[0078]

[Table 3]

As a result of the test, by providing the sub-groove in the rib-shaped land portion, the wet steering stability and the on-ice steering stability were improved for the tire having no sub-groove, and the sub-groove was opened in the main groove. It has been found that the wet steering and the on-ice steering stability can be particularly improved by doing so.

[0080]

As described above, the pneumatic tire of the present invention has the above-mentioned structure, and therefore, the problem that the tire performance when new is slightly lower than the tire performance when worn can be solved. , Which is an excellent effect.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread of a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a block shown in FIG.

FIG. 3 is a front view of a pneumatic tire according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a rib shown in FIG. 3;

FIG. 5 is a perspective view of a rib of a pneumatic tire according to another embodiment.

FIGS. 6A to 6I are plan views of blocks used in Test Example 2. FIGS.

FIG. 7 is a graph showing test results of Test Example 2.

[Explanation of symbols]

 Reference Signs List 10 Pneumatic tire 14 Circumferential main groove (main groove) 16 Lateral main groove (main groove) 18 Block (land portion) 34 Circumferential main groove (main groove) 36 Rib (rib-shaped land portion) 38 Sub groove (sub) groove)

Claims (5)

[Claims] 1. A pneumatic tire having a land portion defined on a tread by a plurality of main grooves, wherein the land portion has a plurality of sub-grooves having a width smaller than the main groove and a depth smaller than the main groove. A pneumatic tire provided with a groove, wherein a negative rate Na of the land portion is in a range of 1 to 40%. 2. The ratio of the negative rate Na to the negative rate Nb on the tread surface of the tread, Na / N.
The pneumatic tire according to claim 1, wherein b is in the range of 5 to 150%. 3. The pneumatic tire according to claim 1, wherein three or more sub-grooves are provided in the land portion. 4. The pneumatic pump according to claim 1, wherein the sub-groove is opened in a main groove that is continuous in a tire circumferential direction among the main grooves. tire. 5. When the land portion is a rib-shaped land portion extending along the circumferential direction of the tire, the sub-groove extends from the center in the width direction of the rib-shaped land portion to the outside in the width direction. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is opened in a main groove defining a land portion.