JP3203195B2 - Pneumatic tire - Google Patents

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 steering stability without impairing wet performance and noise performance.

[0002]

2. Description of the Related Art In a pneumatic tire, particularly a pneumatic tire for a passenger car, as shown in FIG. 5, a crown groove d extending circumferentially on both sides of a tire equator C on a tread surface t, in order to enhance wet performance, and a crown groove d. A pattern having a total of four circumferential grooves provided with a shoulder groove f extending in the circumferential direction between the groove d and the tread edge E is often adopted.

Further, this pattern includes a tread edge E
Left and right lateral grooves g extending from the crown groove d and extending obliquely with respect to the tire circumferential direction are provided.
The tread surface has a rib in the central region between the crown grooves d and d, and the crown groove d and the shoulder groove f
Between the shoulder groove f and the tread edge E
Is generally formed as a block row in which rhombic blocks h are arranged in the tire circumferential direction.

[0004]

By the way, in such a tread pattern, in order to improve the steering stability, for example, the pitch P of the inclined horizontal groove g is increased and the circumferential length of the diamond-shaped block is increased. It is considered effective to increase the block rigidity, for example, by increasing it.

[0005] However, when the pitch P of the lateral grooves g is large, there is usually a problem that the wet performance is reduced.

Also, during running of the tire, the block h or the lateral groove g repeatedly generates a pitch noise by being grounded and compressed on the road surface, and this noise usually changes the pitch P little by little. The problem is solved by the pitch variation method arranged above.

In this pitch variation method, the noise dispersion effect increases as the total number of pitches in the tire block row increases. However, if the pitch P is set large as described above, the total pitch in the block row decreases. And the noise performance tends to decrease.

The inventor of the present invention has conducted intensive studies on the tread pattern as described above. As a result, the lateral groove is formed by a first lateral groove extending from the tread edge to reach the crown groove, and a circumferential groove extending in the circumferential direction from the first lateral groove. In the intermediate region where the ground pressure is relatively high, a second lateral groove which is arranged alternately and extends from the tread edge to reach the shoulder groove but does not reach the crown groove is used. It is effective to increase the steering length by increasing the circumferential length of the tire, and to increase the pitch variation effect and drainage effect by reducing the length of the block in the shoulder area that discharges the air in the lateral groove to the outside of the tread edge Thus, the present invention has been completed.

As described above, an object of the present invention is to provide a pneumatic tire that can improve the steering stability without impairing the wet performance and the noise performance, particularly, a pneumatic tire for a passenger car.

[0010]

According to the first aspect of the present invention , a crown groove extending circumferentially on both sides of the tire equator and a shoulder groove extending circumferentially between the crown groove and the tread edge are provided on the tread surface. Wherein the tread surface is divided into a central region between the crown grooves, an intermediate region between the crown groove and the shoulder groove, and a shoulder region between the shoulder groove and the tread edge. And before
The crown groove extends linearly in the circumferential direction and
The shoulder groove extends in a zigzag shape in the circumferential direction, and the crown groove has an axial distance L1 from the tire equator C to the center of the groove of 15% or less of the tread width TW, and the shoulder groove extends from the tread edge E to the groove. The distance L2 to the center is 9 to 21% of the tread width TW, and the shoulder region extends from the tread edge to reach the crown groove, and alternately in the circumferential direction with the first lateral groove. A block row arranged in a circumferential direction and arranged by a second lateral groove extending from the tread edge and reaching the shoulder groove but not reaching the crown groove, and the intermediate region is formed by the first region. The blocks divided by the lateral grooves are arranged in a block row arranged in the circumferential direction, and the total number of blocks in the intermediate area is の of the total number of blocks in the shoulder area. It is a pneumatic tire which is characterized.

According to a second aspect of the present invention , the first and second lateral grooves are provided.
However, in the shoulder region, it is 60 to 85 ° with respect to the circumferential direction
And at the same time, the first lateral groove extends
Angle θ of 20 to 40 ° with respect to the circumferential direction in the intermediate region
It is characterized in that it can be extended by two.

According to a third aspect of the present invention, the crown
The groove has a groove width of 2 to 9% of the tread width TW, and the shoulder
The groove 10 has a groove width of 1.8 to 2.6% of the tread width TW.
3. The pneumatic tank according to claim 1, wherein:
No.

Here, the “tread width” is defined as follows: a pneumatic tire is assembled to a measurement rim (a rim specified in JATMA) by a rim and filled with a specified internal pressure, and the air pressure-load capacity corresponding to the JATMA is satisfied. It is defined as the axial distance between the ground contact ends of the tire when a vertical load of 80% of the load capacity at the specified internal pressure in the table is applied. A position on the outer surface of the tread corresponding to the distance of the tread width is defined as a tread edge E.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire 1
In this example, the carcass 6 has a radial structure which is folded back around the bead core 5 of the bead portion 4 from the tread portion 2 to the side wall portion 3 and is locked, and a radially outer side of the carcass 6 and the tread portion 2 A radial tire for a passenger car having a belt layer 7 disposed inside is illustrated.

In the present embodiment, the carcass 6 comprises one or more plies in which organic fiber cords are arranged at an angle of 75 ° to 90 ° with respect to the tire equator C.
In this example, the steel cord is
A belt ply 7A and a belt ply 7B, which are arranged at an angle of up to 35 °, are illustrated.

The tread surface 2A of the tread portion 2
1 and 2, a crown groove 9 extending circumferentially on both sides of the tire equator C and a shoulder groove 10 extending circumferentially between the crown groove 9 and the tread edge E are provided. ing. In addition, each crown groove 9, shoulder groove 10
Are provided at substantially symmetric positions about the tire equator C, respectively.

By the crown groove 9 and the shoulder groove 10, the tread surface 2A forms a central region Cr between the crown grooves 9, 9, an intermediate region Md between the crown groove 9 and the shoulder groove 10, and It is divided into a shoulder region Sh between the shoulder groove 10 and the tread edge E.

The crown groove 9 is linearly connected in the circumferential direction.
It is formed by a straight groove extending continuously. Since the crown groove 9 is located on both sides of the tire equator C having a high contact pressure , the crown groove 9 is formed as a straight groove to further promote drainage.

In the crown groove 9, the distance L1 from the tire equator C to the center of the groove is 15% or less of the tread width TW;
Preferably, it is set to 10 to 15%. If the distance L1 exceeds 15%, the crown groove 9 tends to be too far from the tire equator C, which has an effect on noise performance but lowers drainage of the crown region Cr.

If the crown groove 9 is too close to the tire equator C, the rigidity of the crown region Cr is reduced, and there is a tendency that steering stability on a dry road surface and noise performance are reduced. From this viewpoint, the lower limit of the distance L1 is the tread width TW.
Is preferably 10%.

The definition of the "tread width" is as described above. In this embodiment, the pneumatic tire is measured with a measuring rim (JAT).
The rim is assembled to the specified rim described in MA).
0 kPa, 80% of the load capacity at 200 kPa in the pneumatic-load capacity correspondence table specified by JATMA.
The axial distance between the contact ends of the tire when the vertical load is applied.

If the width of the crown groove 9 is too small, the drainage property tends to decrease, and if the groove width is too large, the noise performance tends to decrease. From this viewpoint, the groove width of the crown groove 9 is, for example, 2 to 9%, preferably 3 to 7%, more preferably 5 to 7% of the tread width TW, and in this example, 5.3%. And

Since the crown grooves 9, 9 are formed by linear grooves, in the present embodiment, the crown region Cr is formed.
Are formed as straight ribs extending linearly in the tire circumferential direction. This straight rib is not provided with a lateral groove or the like in the present embodiment, but is provided with a siping or the like having substantially no groove width.
It is not a problem to extend 1a without interruption.

The shoulder groove 10 has an axial distance L2 from the tread edge E to the center of the groove that is 9 to 9 times the tread width TW.
It is necessary to set it to 21%. The distance L2 is
If the width exceeds 21% of the tread width TW, the shoulder groove 10 tends to be too far from the tread edge E, and the noise performance deteriorates. Conversely, if the distance L2 is less than 9% of the tread width TW, the shoulder groove 10 tends to be too close to the tread edge E, and the noise performance is improved, but the rigidity of the shoulder region Sh is weakened and the steering stability is reduced.

[0025] Then, formed by the shoulder groove 10 is zigzag groove extending continuously in a zigzag form in the circumferential direction.
As described above, when the shoulder groove 10 is a zigzag groove, the groove capacity is increased and the wet performance is improved as compared with the case where the shoulder groove 10 is a straight groove. In this case, the distance L2 is specified by the center of the zigzag amplitude of the groove center line of the shoulder groove 10.

If the shoulder groove 10 has a too small groove width, the drainage performance is reduced.
In particular, the noise outside the vehicle tends to deteriorate. From this perspective,
The groove width of the shoulder groove 10 is, for example, 1.1 of the tread width TW.
It is desirable that the content be 8 to 2.6%, more preferably 2.0 to 2.4%.

The crown groove 9 and the shoulder groove 10
The groove depth is preferably 5 mm or more, more preferably 7 mm or more.

Next, the shoulder region Sh extends from the tread edge E to reach the crown groove 9.
1a and a second lateral groove 11b alternately arranged in the circumferential direction with the first lateral groove 11a and extending from the tread edge E to reach the shoulder groove 10 but not to the crown groove 9.
Are formed as a row of blocks arranged in the circumferential direction.

The intermediate region Md is formed as a block row in which blocks 13 separated by only the first lateral grooves 11a are arranged in the circumferential direction, and the total number of blocks in the intermediate region Md is equal to the total number of blocks in the shoulder region Sh. Of 1
/ 2.

Thus, by increasing the number of blocks in the shoulder region Sh which greatly affects the noise performance and the wet performance of discharging the water or air in the lateral groove from the tread edge E, the pitch noise and the noise can be reduced without impairing the wet performance. The muffled sound during traveling at low speeds is advantageously improved, and the number of blocks in the intermediate region Md, which has a strong influence on steering stability, is reduced, so that the block circumferential length can be increased and the block rigidity can be increased. Driving stability can be improved. In the present embodiment, the first lateral groove 11a is
An example is shown that extends from the tread edge E and reaches the crown groove 9 via one side 10a of the shoulder groove 10 in a zigzag manner.

Here, the first and second lateral grooves 11a, 1a
In the case of 1b, when the groove width is too small, the wet performance tends to decrease, and when too large, the outside noise tends to increase. From this viewpoint, the first and second lateral grooves 11a,
11b is, for example, 2 to 4% of the tread width TW, preferably 2.4 to 3.4%, more preferably 2.6 to 3.3%.
It is desirable to set it to 2%, and it is also desirable that both of the groove depths be 5 mm or more.

The ratio of the total groove area to the total tread area between the tread edges E, E, the so-called sea ratio, is more preferably 28% or less. Thereby, steering stability and abrasion resistance performance are further improved.

When the total number of blocks in the intermediate area Md is less than 1/2 of the total number of blocks in the shoulder area Sh, the wet performance is remarkably reduced and the noise outside the vehicle is increased. The improvement of the property cannot be expected.

Further, in the intermediate region Md, it is preferable that another groove having a groove width of 2 mm or more and a depth of 3 mm or more and intersecting with the first lateral groove is not formed. When such another groove is provided, it tends to hinder the improvement of the block rigidity of the intermediate region Md. Conversely, a siping having a groove width of less than 1.0 mm and having substantially no groove width may be provided as appropriate.
It is preferable to be provided in parallel with a in that the low-speed muffled sound can be further reduced.

In the present embodiment, the intermediate region Md and the shoulder region Sh employ a pitch variation method in which the arrangement pitches of the lateral grooves 11a and 11b are non-uniform, and the zigzag pitch PG of the shoulder groove 10 is used.
Exemplifies one provided at a pitch equal to the arrangement pitch of the first and second lateral grooves 11a and 11b. Therefore,
A pitch variation is also adopted for the pitch PG of the shoulder groove 10, and the total number of zigzag pitches of the shoulder groove 10 can be equal to the number of blocks of the shoulder region Sh and twice the number of blocks of the intermediate region Md. As a result, the pitch noise based on the shoulder grooves 10 is effectively dispersed, which helps to improve the noise performance.

The first and second lateral grooves 11a, 11a
1b preferably extends at an angle θ1 of 60 to 85 ° with respect to the tire circumferential direction in the shoulder region Sh. When the angle θ1 is in the range of 60 to 85 °, wet performance and noise performance are maintained at a high level.
When the angle θ1 is less than 60 °, the steering stability performance tends to relatively decrease. Further, when the angle θ1 exceeds 85 °, the wet performance tends to relatively decrease.

It is preferable that the first lateral groove 11a extends at an angle θ2 of 20 to 40 ° with respect to the tire circumferential direction in the intermediate region Md. This angle θ2 is 2
It is preferable that the angle is in the range of 0 to 40 ° because wet performance and noise performance are maintained at the highest dimension. Note that the angle θ
In the case of No. 2, when the angle falls below 60 °, the relative steering stability tends to decrease. If the angle θ1 exceeds 85 °, the relative wet performance tends to decrease.

When the angle θ1 is 60 to 85 ° and the angle θ2 is 20 to 40 °, the wet performance and the noise performance are preferably maintained at the highest dimension.

It is also preferable that the first lateral groove 11a forms a changing portion in which the inclination angle changes from θ2a to θ2b in the middle region Md from the outside to the inside in the tire axial direction. By setting θ2a> θ2b, the first lateral groove 11a is preferable in that the inclination angle decreases toward the tire equator C, and drainage on the tire equator having a high contact pressure can be further improved. .

The first and second lateral grooves 11a, 1
1b is arranged at a substantially point symmetric position about a point on the tire equator C, and in this example, forms a non-directional flow pattern flowing from the upper left side to the lower right side in the figure. Therefore, the pneumatic tire of the present example can exhibit excellent wet performance, noise performance, and steering stability performance without specifying the rotation direction when the vehicle is mounted.

It should be noted that the pneumatic tire of the present invention can be preferably employed for a pneumatic tire for passenger cars having an aspect ratio of 60 to 70%.

As described in detail above, FIG.
FIG. 4 merely discloses a case where the zigzag groove is formed, and FIG. 4 shows a case where both the crown groove 9 and the shoulder groove 10 are linear grooves.

[0043]

[Example] The tire size is 195 / 65R15 91
H, a radial tire for passenger cars having the structure shown in FIG. 1 and the tread pattern shown in FIG. 2 was prototyped (Examples 1 to 13 ), and the performance was tested. In addition, tires other than the present invention (conventional examples 1 and 2 and comparative examples 1 to 5 (shown in FIGS. 3 and 4)
) ) Was also prototyped and tested. The test method is as follows.

B) Pitch noise and low-speed muffled sound Pitch noise was evaluated on a smooth road surface at a speed of 60 km / H with a domestically produced 2500 cc car at a speed of 60 km / H and evaluated by a 10-point method based on the driver's feeling. The low-speed muffled sound was evaluated on a 10-point scale based on the driver's feeling while traveling on the smooth road at a speed of 40 km / H.

B) Wet performance (hydroplaning resistance) On an asphalt road surface with a radius of 100 m, a water depth of 5 mm and a length of 2
On a course provided with a puddle of 0 m, a vehicle equipped with test tires enters while increasing the speed stepwise,
The lateral acceleration (lateral G) was measured, and the maximum lateral G of the front wheels at a speed of 50 to 80 km / h was calculated. The results are represented by an index with Conventional Example 1 being 100, and the larger the value, the better.

C) Out-of-vehicle noise test The test course (I) was conducted in accordance with JASO / Z101-83.
(SO road surface) at a passing speed of 60 km / h for a distance of 50 m while passing by a fixed microphone installed at a position 7.5 m laterally from the running center line and 1.2 m from the road surface at the middle point of the course. The noise level was measured and the maximum sound pressure level dB (A) was compared.

D) Steering stability The test tires were applied to a 15 × 6-JJ wheel rim with an internal pressure of 20
After assembling the rim at 0 kpa (same fore and aft), the vehicle was mounted on four wheels of a 2500 cc test vehicle, and was run on a tire test course with only one driver riding alone. The higher the value, the better.

The 10-point evaluation was 10: excellent, 9: very good, 8: fairly good, 7: good, 6:
Acceptable, 5: Allowable lower limit, when the difference is 1, it is a level that can be understood if one is riding at the same time and pays attention, and the difference is 2
At the time of, the level which can be recognized without paying much attention on the same day, and when the difference is 3, the level can be recognized without paying much attention on another day, and when the difference is 4, it can be understood by anyone Level. Table 1 shows the test results.

[0049]

[Table 1]

As a result of the test, it was confirmed that all the examples had excellent steering stability without impairing the wet performance and the noise performance. From the test results, FIGS.
In the tread pattern (1), it was confirmed that the one in which the crown groove was a straight groove was excellent in steering stability. When the crown groove was a straight groove, it was confirmed that the noise performance was improved when the shoulder groove was a zigzag groove, and that the wet performance was enhanced by the straight groove.

[0051]

As described above, in the pneumatic tire according to the first aspect of the present invention, the lateral groove extends from the tread edge to reach the crown groove, and the first lateral groove and the first lateral groove extend in the circumferential direction. And the second lateral groove extending from the tread edge to reach the shoulder groove and not reaching the crown groove, so that the number of blocks is reduced in the intermediate region where the ground pressure is relatively high. 1/2 of shoulder area
In the shoulder area where the water or air in the lateral groove is discharged to the outside of the tread edge, the number of blocks should be twice as long as the middle area. Thereby, wet performance and noise performance can be improved.

According to the second aspect of the present invention, since the location and the shape of the crown groove and the shoulder groove are specified, the wet performance, the noise performance and the steering stability can be further improved.

According to the third aspect of the present invention, the first and second lateral grooves extend at a large angle θ1 of 60 to 85 ° with respect to the circumferential direction in the shoulder region.
An increase in pitch sound can be prevented while suppressing a decrease in steering stability, and the first lateral groove extends at a small angle θ2 of 20 to 40 ° with respect to a circumferential direction in the intermediate region, thereby making contact with the ground. Driving performance in the high pressure middle area is improved, and steering stability is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a pneumatic tire showing an embodiment of the present invention.

FIG. 2 is a developed view of the tread pattern.

FIG. 3 is a plan view simply disclosing another pattern configuration.

FIG. 4 is a plan view simply disclosing another pattern configuration.
You.

FIG. 5 is a development view of a tread pattern for explaining a conventional technique.

FIG. 6 is a development view of tread patterns of Conventional Examples 1 and 2.

[Explanation of symbols]

 2 Tread portion 2A Tread surface 9 Crown groove 10 Shoulder groove 11a First lateral groove 11b Second lateral groove 12, 13 Block E Tread edge C Tire equator TW Tread width θ1 Angle of first and second lateral grooves θ2 in shoulder region Angle of the first lateral groove in the middle area

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 11/00-11/24 B60C 9/00-9/30

Claims (3)

(57) [Claims] A tread surface is provided with a crown groove extending circumferentially on both sides of a tire equator, and a shoulder groove extending circumferentially between the crown groove and a tread edge, and the tread surface is defined by the crown groove. A pneumatic tire divided into a middle region between the crown groove and the shoulder groove, and a shoulder region between the shoulder groove and the tread edge, wherein the crown groove has a circumferential direction. Along a straight line
The shoulder groove extends in a zigzag shape in the circumferential direction, and the crown groove has an axial distance L1 from the tire equator C to the groove center of 15% or less of the tread width TW, and the shoulder groove has a groove extending from the tread edge E to the groove. Distance L to center
2 is 9 to 21% of the tread width TW, and the shoulder region extends from the tread edge to reach the crown groove, and the first tread is alternately arranged in the circumferential direction with the first tread, and the tread is arranged. Blocks separated by a second lateral groove extending from an edge and reaching the shoulder groove but not reaching the crown groove form a block row arranged in a circumferential direction, and the intermediate region is partitioned by the first lateral groove. The pneumatic tire is characterized in that the blocks are arranged in a block row arranged in the circumferential direction, and the total number of blocks in the intermediate region is の of the total number of blocks in the shoulder region. 2. The first and second lateral grooves extend at an angle θ1 of 60 to 85 ° with respect to the circumferential direction in the shoulder region, and the first lateral groove extends with respect to the circumferential direction in the intermediate region. The pneumatic tire according to claim 1 or 2, wherein the tire extends at an angle θ2 of 20 to 40 °. 3. The crown groove has a groove width TW.
2 to 9% of the shoulder groove 10, the groove width is the tread width
The TW is 1.8 to 2.6% of the TW.
3. The pneumatic tire according to 1 or 2.