JP2000135904A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wet performance without impairing wear resistance. SOLUTION: A tread width TW is 80% or more of a nominal width W of a tire and a sea ratio is 35% or less. A center vertical main groove 3 stretched on a tire equator C and outer vertical main grooves 4 on both sides thereof are arranged on a tread part 2. Lugs 7 not reaching the center vertical main groove 3 from the outer vertical main grooves 4 are provided. The lugs 7 include curvature parts 7a wherein a tilt angle α in regard to the tire circumferential direction at an intersecting part with the outer vertical main grooves 4 is between 30 deg. and 50 deg. and also which curvingly stretches while gradually decreasing the tilt angle, and straight line parts 7b joining the curvature parts 7a. The curvature parts 7a include first curvature parts 7a1 wherein a groove width is 60% to 80% of the vertical main groove, and second curvature parts 7a2 wherein a groove width is 25% or more and not more than 60% of the vertical main groove. A groove width of the straight line parts 7b is 25% or less of the vertical main groove, and also a groove depth is smaller than the groove depth of the first curvature parts 7a1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving wet performance without deteriorating wear resistance.

[0002]

2. Description of the Related Art In a pneumatic tire, improvement of wet performance is one of important issues. Generally, to improve wet performance, it is effective to arrange a so-called vertical main groove extending linearly in the tire circumferential direction on the tread surface. In particular, it is effective to arrange the vertical main groove on the tire equator where the contact pressure is the highest and the contact length is the largest, whereby the water film on the road surface is drained backward in the traveling direction.

In order to further improve the wet performance, a lug groove extending in a direction intersecting with the vertical main groove is arranged in addition to the vertical main groove, and a water film between the road surface and the road surface is directed toward the tread end. It is also necessary to drain.

When the vertical main grooves, lug grooves, etc. are arranged in this manner, the sea ratio, which is the ratio of the total groove area to the total tread area, increases, and although improvement in wet performance can be expected, the tread is generally improved. There is a problem that wear resistance is lowered, for example, causing early wear of the part.

The present invention has been devised in view of the above problems, and is based on limiting the shape of the grooves formed on the tread surface, particularly the shape and depth of the lug grooves.
An object of the present invention is to provide a pneumatic tire capable of improving wet performance without deteriorating wear resistance.

[0006]

According to the first aspect of the present invention, the tread width TW, which is the axial distance between the tread ends, is 80% or more of the nominal width W of the tire, and The sea ratio, which is the ratio of the total groove area to the total tread area between the tires, is 35% or less, and the tread portion has one central vertical main groove extending linearly on the tire equator, and at least on both sides thereof. Each one is provided with an outer vertical main groove extending linearly in the tire circumferential direction, and an inner land portion is formed between the central vertical main groove and the outer vertical main groove,
A lug groove extending in the tire axial direction from the outer vertical main groove to the center vertical main groove without reaching the central vertical main groove is provided on the inner land portion, and the lug groove intersects with the outer vertical main groove. A curved portion that forms an angle of 30 to 50 ° with respect to the tire circumferential direction and gradually extends inward in the tire axial direction while gradually decreasing the angle of inclination, and is linearly connected to the curved portion and along the tire circumferential direction. The curved portion is located on the outer vertical main groove side, the groove width is 60 to 80% of the groove width of the outer vertical main groove, and the groove depth is the outer vertical groove. A first curved portion having substantially the same groove depth as the main groove, and a groove width continuous with the first curved portion and having a groove width of 25% or more and smaller than 60% of the groove width of the outer vertical main groove; And a second curved portion connected to the linear portion by gradually decreasing the groove width of the linear portion. 25% of the groove width of the groove below, and a pneumatic tire comprising a 65% or less of the groove depth of the circumferential main groove depth.

According to a second aspect of the present invention, the lug groove has one end of the linear portion communicating with the curved portion of the lug groove adjacent in the tire circumferential direction. It is a tire containing.

According to a third aspect of the present invention, in the lug groove, the groove depth GD1 of the first curved portion is substantially the same as the groove depth of the outer vertical main groove, and the second curved portion is formed. The groove depth of the portion gradually decreases and continues to the straight portion, and the groove depth of the straight portion is 70% or less of the groove depth of the vertical main groove.
Or the pneumatic tire according to 2.

According to a fourth aspect of the present invention, in the lug groove, a length La of the first curved portion in the tire circumferential direction is 0.5 to 0. Six times, the length Lb of the second curved portion in the tire circumferential direction is equal to the length L.
The length Lc of the linear portion in the circumferential direction of the tire is 0.2 to 0.3 times the length L.
4. The pneumatic tire according to any one of claims 1 to 3.

According to a fifth aspect of the present invention, the inner land portion extends between the lug grooves adjacent in the tire circumferential direction in the same direction as the curved portion and terminates without reaching the lug groove. 4. A lag groove, and a siping extending in a direction opposite to the curved portion and inclined at an angle of 40 to 50 degrees with respect to a tire circumferential direction, is provided.
A pneumatic tire according to any one of the above.

The definitions used in this specification are as follows. The `` tread end '' is the outermost edge of the tread portion in the tire axial direction of the tread portion, which rims the tire to a regular rim, fills the regular internal pressure, and adds a mass corresponding to the maximum load capacity to a ground surface. Say. Here, when the tire is for a passenger car, the measurement is performed by adding the mass corresponding to the load to 88% of the maximum load capacity determined by the standard in the above measurement conditions.

The "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim for JATMA and a "Design Rim" for TRA Or ETRTO
Then "Measuring Rim".

[0013] The "normal internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. Table "TIRE LOAD LIMITS AT VA"
RIOUS COLD INFLATION PRESSURES "
In the case of TRTO, it is "INFLATION PRESSURE", but when the tire is for a passenger car, it is 180 (kPa).

The "nominal width of the tire" is the "nominal of the cross-sectional width" indicated in the tire designation defined in the standard system, and is, for example, "195 / 60R1485".
H "is 195 mm.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In the pneumatic tire of the present embodiment, the tread width TW, which is the axial distance between the tread ends E, E, is set to 80% or more of the nominal width W of the tire.
Generally, the tread width is 75 times the nominal width W of the tire.
% Or less, and in the present embodiment, the tread width TW is set relatively large according to the tire size to increase the contact area. The definition of the tread width and the like is as described above, and the upper limit is preferably set to, for example, about 95% of the nominal width W.

In this embodiment, the tread ends E,
The sea ratio (Sg / S), which is the ratio of the total groove area Sg to the total tread area S between E, is set to 35% or less. In general, when the sea ratio is increased, the drainage property is increased and the wet performance is improved, but there is a disadvantage that the rigidity of the land portion is reduced and wear is easily promoted. Table 1 shows the relationship between the ratio of the tread width TW to the nominal width W, the sea ratio, and the wear resistance of the pneumatic tire having the standard pattern.

[0017]

[Table 1]

As shown in Table 1, when the ratio of the tread width TW to the nominal width W is increased and the sea ratio is reduced to 35%, the rigidity of the tread portion is increased, and the wear resistance can be greatly improved. As described above, in this example, the wear resistance is improved by a relative increase in the contact area and a reduction in the sea ratio.
If the sea ratio is too small, improvement in wet performance cannot be expected. Therefore, the sea ratio is preferably set to 25 to 35%, more preferably 30 to 35%.

Next, each groove constituting such a sea ratio will be described. In this example, the tread portion 2 includes one central vertical main groove 3 extending linearly on the tire equator C, and two outer vertical main grooves 4 each extending linearly in the tire circumferential direction on both sides thereof. , And 4. Thereby, the central vertical main groove 3
An inner land portion 5 is formed between the outer vertical main groove 4 and the outer vertical main groove 4, and an outer land portion 6 is formed between the outer vertical main groove 4 and the tread end E.

The central vertical main groove 3 and the external vertical main groove 4 (hereinafter sometimes simply referred to as “vertical main groove 3” and “vertical main groove 4”, respectively) are linear in the tire circumferential direction. It is possible to continuously extend and discharge the water film on the road surface during tire running backward in the tire running direction. When the vehicle travels straight, the vertical main groove 3 is located on the tire equator C where the contact pressure is high and the contact length is the longest.
, A more efficient drainage effect can be obtained.

The groove width GW of these vertical main grooves 3 and 4 is
In order to more reliably increase the drainage effect, it is desirable that the width is 2.5% or more, preferably 3% or more, more preferably 4% or more of the tread width TW. Note that the upper limit of the groove width is appropriately determined in consideration of the above-mentioned sea ratio. Further, the vertical main grooves 3 and 4 may have the same groove width or may have different groove widths.

In this embodiment, in order to improve the wet performance, a lug groove 7 extending in the tire axial direction inward from the outer vertical main groove 4 without reaching the central vertical main groove 3 is provided in the inner land portion 5. In addition, an example in which the outer land portion 6 is provided with a shoulder groove 9 that connects the vertical main groove 4 and the tread end E is illustrated.

The lug groove 7 comprises a curved portion 7a and a straight portion 7b in this embodiment. The curved portion 7a has an inclination angle α of 30 to 50 ° with respect to the tire circumferential direction at the intersection with the outer vertical main groove 4 and becomes substantially 0 ° in this example while gradually decreasing the inclination angle α. It is illustrated that it extends to the inside in the tire axial direction and is curved.

The straight portion 7b is formed so as to be continuous with the end of the curved portion 7a and to extend linearly along the tire circumferential direction. In this example, the linear portion 7b is illustrated as communicating with the curved portion 7a of another lug groove 7 adjacent in the tire circumferential direction. Thereby, the lug groove 7
Is preferable in that a groove portion continuous in the tire circumferential direction can be formed on both sides of the tire equator C having a high contact pressure, so that the drainage effect can be further enhanced and the wet performance can be further improved.

The bending portion 7a includes a first bending portion 7a1 and a second bending portion 7a2 in this example.

The first curved portion 7a1 is provided with the outer vertical main groove 4
And the groove width GW1 is the groove width G of the outer vertical main groove 4.
It is formed at 60 to 80% of W. The groove width GW1 is
If the groove width GW of the vertical main groove 4 is less than 60%, a sufficient drainage volume cannot be secured, and if it exceeds 80%, the tread rigidity is reduced and uneven wear is likely to occur. In addition, the first bending portion 7 of the present example
a1 exemplifies a medium bulge in which the groove width gradually increases from the outer vertical main groove 4 and decreases again.

FIG. 2 is a sectional view of the lug groove 7 taken along a groove center line. The groove depth GD1 of the first curved portion 7a1 of the present example is formed to be substantially the same as the groove depth of the outer vertical main groove 4. This can increase drainage volume.

Next, the second curved portion 7a2 is continuous with the first curved portion 7a1 and has a groove width GW2 of at least 25% and less than 60% of the groove width GW of the outer vertical main groove 3. It is formed. In this example, the groove width GW2 gradually decreases toward the linear portion 7b as shown in FIG. This suppresses a decrease in rigidity on the crown side where the contact pressure is high. FIG. 2
As described above, in this example, the groove depth GD2 of the second curved portion 7a2 gradually decreases toward the straight portion 7b and smoothly extends to the groove bottom of the straight portion 7b.

The linear portion 7b has a groove width GW3 of 25% or less of the groove width GW of the outer vertical main groove 4,
In the present example, the one formed with the same width is shown. However, it may be gradually reduced. Further, the groove depth GD3 of the linear portion 7b is smaller than the groove depth GD1 of the first curved portion 7a1, and in this example, is 70% or less of the groove depth GW of the vertical main groove 4, and is preferably 60 or less. To 70%. At this time, the depth may be equal or may be gradually changed.

It is desirable that the center of the groove of the straight portion 7b is located on the inner side in the tire axial direction than the dividing line N which bisects the inner land portion 5 in the width direction. by this,
The water film can be more efficiently discharged from the crown side having a high ground pressure.

The lug groove 7 has a straight portion 7b parallel to the tire circumferential direction and a second curved portion 7 smoothly connected to the straight portion 7b.
a2, and further comprising the first curved portion 7a1 intersecting the vertical main groove 4 at an angle α of 30 to 50 °, it is possible to smoothly guide the water film in the central portion of the tread to the outer vertical main groove 4. Becomes
The wet performance is improved. Here, when such a straight portion 7b is not formed, or when the intersection angle between the outer vertical main groove 4 and the curved portion 7a exceeds 50 °, the change in the inclination angle of the curved portion 7a is smooth. If this is not done, the drainage flowing to the outer vertical main groove 4 will have an energy loss, and the drainage effect will be reduced. The angle α at the intersection of the outer vertical main groove 4 and the curved portion 7a is preferably 40 to 50 °, more preferably 42 to 48 °, and is approximately 45 ° in this example. I have.

In this embodiment, the straight portion 7a has a small-width rib portion 10 formed between the straight portion 7a and the central vertical main groove 3. However, this rib portion 10 tends to be easily deformed during turning of the vehicle. Becomes In the present embodiment, as described above, by forming the groove width GW3 and the groove depth GD3 of the linear portion 7b in the lug groove 7 to be the smallest, it is possible to suppress such a significant decrease in the rigidity of the rib portion 10 and to reduce uneven wear. Can also be suitably prevented. In the curved portion 7a, the groove depth gradually increases, and in the first curved portion 7a1, the groove depth G is substantially the same as the groove depth of the vertical main groove 3.
Since D1 is realized, the total groove volume is sufficiently ensured, and there is no danger of a decrease in wet performance.

In the second curved portion 7a2 of this embodiment, the difference between the groove depth GD3 of the straight portion 7b and the groove depth GD1 of the first curved portion 7a1 is determined by gradually changing the groove depth GD2 of the straight portion 7b1. By joining, it is possible to smoothly change the rigidity based on the difference in the groove depth, and it is possible to maintain good wear resistance performance and the like.

In such a lug groove 7, the length La of the first curved portion 7a1 in the tire circumferential direction is 0.5 to 0.6 times the length L of the lug groove in the tire circumferential direction. Is desirable. Also, the length L of the second curved portion 7a2 in the tire circumferential direction.
b is 0.1 to 0.2 times the length L, and the linear portion 7b
The length Lc of the tire in the circumferential direction is 0.2 to 0.2 of the length L.
It is particularly preferable to set it to 0.3 times.

In this embodiment, the inner land portion 5 is provided between the lug grooves 7 adjacent in the tire circumferential direction.
a second lug groove 11 which is inclined in the same direction as a and extends without reaching the lug groove 7, and the second lug groove 11 is inclined in a direction opposite to the tire circumferential direction at an angle of 40 to 50 ° with respect to the tire circumferential direction. The example provided with the extending siping S is illustrated. In the vicinity of the communicating portion between the straight portion 7b of one lug groove 7 and the curved portion 7a of the other lug groove 7, it extends toward the central vertical main groove 3 and does not reach the vertical main groove 3. An example in which a third lug groove 12 that terminates is provided is illustrated. This third lug groove 1
2 also extends in the opposite direction to the lug groove 7, and is formed, for example, at an inclination of about 40 to 60 ° with respect to the tire circumferential direction.

The second and third lug grooves 11, 1
2. The siping S can eliminate the rigidity directivity of the inner land portion 5 and can improve the wear resistance in a well-balanced manner.

In the present embodiment, the shoulder groove 9 extends from the vertical main groove 4 to the tread end E. In the present embodiment, the shoulder groove 9 is directed to the first shoulder groove 9A having a substantially equal groove width and the tread end E. And a second shoulder groove 9 </ b> B that gradually decreases in the tire circumferential direction. Generally, a large load acts on the tread end E side during turning or the like, but by including the second shoulder groove 9B in which the groove width gradually decreases toward the tread end E side as in this example, A decrease in rigidity in the vicinity of the tread end E can be prevented, and wear resistance at this portion can also be improved. Such a shoulder groove 9 is optional, and the outer land portion 6 may be formed in a rib shape. Also, a siping or the like may be provided on the outer land portion 6 as appropriate.

In the embodiment of the present invention, the illustrated pattern is formed as a point-symmetric pattern, but may be formed as a left-right symmetric pattern centered on the tire equator C. In this case, the present invention can be preferably implemented as a pneumatic tire having a directional pattern in which the rotation direction is determined so that the lug groove 7 comes into contact with the straight portion 7b. In this symmetric pattern, a pattern shift in which each side of the tire equator is shifted in the tire circumferential direction can be adopted, and the present invention can be modified into various modes. In this example, the lug grooves 7 adjacent in the tire circumferential direction are illustrated as communicating with each other, but may be separated from each other without communicating.

[0039]

[Example] Tire size is 205 / 65R15 94H
Pneumatic radial tires for passenger cars (Examples and Comparative Examples) having the basic pattern shown in FIG. 1 were prototyped and tested for wet performance and wear resistance. The test method is as follows.

(1) Wet performance (hydroplaning test) On an asphalt road surface with a radius of 100 m, a water depth of 5 mm and a length of 2
The vehicle was entered on a course provided with puddles of 0 m while gradually increasing the speed, the lateral acceleration (lateral G) was measured, and the average lateral G of the front wheels at a speed of 50 to 80 km / h was calculated. . The results are indicated by an index with the comparative example being 100, and the larger the numerical value, the better.

(2) Wear resistance The test tire was assembled on a 6JJ rim and the internal pressure was 200
kPa and a displacement of 3000cc
Test course (50% for highway type, 35% for general road type, 15% for mountain road type)
%) After traveling 8000 km, the depth of the central vertical main groove was measured, and the result was indicated by an index with Comparative Example 1 being 100. The higher the numerical value, the higher and better the abrasion resistance. Table 2 shows the test results and the like.

[0042]

[Table 2]

As a result of the test, it can be seen that the example of the present invention has a better balance of wet performance and abrasion resistance than the comparative example.

[0044]

As described above, the pneumatic tire of the present invention can improve the wet performance without deteriorating the wear resistance.

[Brief description of the drawings]

FIG. 1 is a development view of a tread portion showing one embodiment of the present invention.

FIG. 2 is a partial cross-sectional view taken along a groove center line of a lug groove.

[Explanation of symbols]

 2 Tread part 3 Central vertical main groove 4 Outer vertical main groove 5 Land part inside 6 Land part outside 7 Lug groove 7a Curved part 7a1 First curved part 7a2 Second curved part 7b Linear part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B60C 11/08 A

Claims (5)

[Claims] 1. A seat ratio in which a tread width TW, which is a distance in the tire axial direction between tread ends, is 80% or more of a nominal width W of a tire and a ratio of a total groove area to a total tread area between the tread ends. Is not more than 35%, and at the tread portion, one central vertical groove extending linearly on the tire equator, and at least one of the outer vertical grooves extending linearly in the tire circumferential direction on both sides thereof. And arranging a groove to form an inner land portion between the central vertical main groove and the outer vertical main groove, and, on the inner land portion, from the outer vertical main groove to the central land portion. A lug groove extending in the tire axial direction without reaching the vertical main groove is provided, and the lug groove has an inclination angle of 30 to 50 ° with respect to the tire circumferential direction at an intersection with the outer vertical main groove, and A curved section that gradually extends inward in the tire axial direction and curves while gradually decreasing the inclination angle A linear portion that is continuous with the curved portion and extends linearly along the tire circumferential direction, and the curved portion is located on the outer vertical main groove side and has a groove width of the outer vertical main groove. A first curved portion having a width of 60 to 80%, and a second curved portion connected to the first curved portion and having a groove width of 25% or more and smaller than 60% of the groove width of the outer vertical main groove. And a groove width of the linear portion is 25% or less of a groove width of the outer vertical main groove, and a groove depth is smaller than that of the first curved portion. 2. The pneumatic tire according to claim 1, wherein one end of the linear portion of the lug groove communicates with the curved portion of the lug groove adjacent in the tire circumferential direction. 3. The lug groove, wherein a groove depth GD1 of the first curved portion is substantially equal to a groove depth of the outer vertical main groove, and a groove depth of the second curved portion is gradually reduced. To the straight part, and the groove depth of the straight part is 7 times the groove depth of the vertical main groove.
The pneumatic tire according to claim 1, wherein the content is 0% or less. 4. The lug groove, wherein the length La of the first curved portion in the circumferential direction of the tire is 0.5 to 0.6 times the length L of the lug groove in the circumferential direction of the tire, and The length Lb of the curved portion in the tire circumferential direction is 0.1 to 0.2 times the length L, and the length Lc of the straight portion in the tire circumferential direction is 0.2 to 0.2 times the length L.
The pneumatic tire according to any one of claims 1 to 3, wherein the ratio is 0.3 times. 5. The lug groove according to claim 1, wherein the inner land portion extends between the lug grooves adjacent to each other in the tire circumferential direction, extends in the same direction as the curved portion, and terminates without reaching the lug groove. The pneumatic tire according to any one of claims 1 to 4, further comprising a siping that is opposite to the curved portion and that extends at an angle of 40 to 50 with respect to the tire circumferential direction.