JP3294039B2 - 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 having a directional tread pattern, and more particularly, to a pneumatic tire for a passenger car, particularly for improving dry performance while maintaining wet performance.

[0002]

2. Description of the Related Art In a pneumatic tire for a passenger car, there is a method of increasing a groove area and a pitch number in order to improve drainage on a wet road surface. However, simply increasing the groove area and the number of pitches causes a decrease in dry performance due to a decrease in block rigidity and a decrease in ground contact area.

[0003] As a countermeasure, there is a proposal to adopt a directional tread pattern in which a tire rotation direction is specified. For example, as shown in FIG. 2, the three directional tread patterns include three main tread patterns extending in the tire circumferential direction T in the tire contact center region of the tread surface 11 in which the tire rotation direction R is specified in one direction. A plurality of lateral grooves 13 are provided at a predetermined pitch, provided with the grooves 12, and communicated with the main grooves 12 from the outer main grooves 12 and respectively inclined in the opposite directions outward in the tire width direction and extending to the tire grounding end E, Main groove 12 and lateral groove 1
3 to form a block B which is divided. In this way, by forming the directional tread pattern in which the lateral groove 13 communicating with the main groove 12 is inclined in the tire width direction and extends to the tire contact end E, drainage is greatly promoted in the tire width direction. ing.

[0004] However, a pneumatic tire using the directional tread pattern is preferable in terms of enhancing the drainage improvement effect, but on the other hand, the rigidity of the block B cannot be reduced, and the dry performance cannot be avoided. And it is difficult to achieve both wet performance and dry performance.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to improve dry performance of a pneumatic tire having a directional tread pattern while maintaining wet performance at least equal to that of a conventional directional tread pattern. It is to provide a pneumatic tire that can be used.

[0006]

According to the present invention, which achieves the above objects,
On the tread surface where the tire rotation direction is specified in one direction, at least one main groove provided only in the tire contact center region and extending in the tire circumferential direction is provided, and the main groove is communicated from both sides of the main groove. A large number of lateral grooves which are inclined in the opposite direction to the outer side in the tire width direction and extend to the tire grounding end, and intersect with one of the lateral grooves adjacent to the tire rotation direction side from both sides of the main groove without communicating with the main groove. A plurality of bent sub-grooves extending to the tire ground contact end are arranged alternately at a predetermined pitch on the outer side in the tire width direction to form a directional tread pattern. In addition, the present invention
Akira is a tread surface where the tire rotation direction is specified in one direction
In the tire circumferential direction only
Provide multiple main grooves extending in the direction and form ribs between the main grooves
While communicating with the main groove from both sides of the main groove.
To the tire contact point
A number of lateral grooves extending therefrom and communicating with the main groove from both sides of the main groove
Without one of the lateral grooves adjacent to the tire rotation direction side
Cross each other and extend outward in the tire width direction to the tire contact edge.
A large number of sub-grooves are arranged alternately at a specified pitch
And a directional tread pattern is formed.
You. In the pneumatic tire provided with the directional tread pattern as described above, from both sides of the tire circumferential main groove provided in the tire grounding central region of the tread surface, the tire communicates with the main groove and in the opposite direction outward in the tire width direction. By alternately arranging a lateral groove that extends to the tire grounding end and an auxiliary groove that intersects one of the lateral grooves and extends to the tire grounding end outside in the tire width direction, the lateral groove and the auxiliary groove are interposed. As a result, a high drainage property in the tire width direction can be obtained, so that the wet performance can be kept equal to or higher than that of the conventional directional tread pattern.

[0007] Further, since the sub-groove is formed in a bent shape and does not communicate with the main groove but intersects with one of the lateral grooves and extends to the tire contact end, the groove area can be reduced in the same manner as in the conventional directional tread pattern. Even if the lateral groove and the sub-groove are arranged so that the main groove,
Since the block shape divided by the lateral groove and the bent sub-groove can be made larger than before to increase the block rigidity, dry performance such as turning performance on dry road surface, traction performance, marginal performance, etc. is also improved. can do.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an example of the tread pattern of the pneumatic tire of the present invention, and the tire is instructed to rotate in the direction of arrow R. Thus, three main grooves 2 extending straight in the tire circumferential direction T are provided in the tire contact center region of the tread surface 1 in which the tire rotation direction R is specified in one direction. These main grooves 2 are arranged only in the central region of the tire ground, and are not provided in other regions, and ribs 7 are formed between the main grooves 2.

In the tire contact areas on both sides of the main groove 2, both sides of each of the outer main grooves 2 communicate with the main grooves 2, and are inclined in the opposite directions to the outside in the tire width direction and in the anti-tire rotation direction, respectively.
A large number of lateral grooves 3 extending to the tire ground contact end E are separated from both sides of each of the outer main grooves 2 without communicating with the main grooves 2 and intersect with only one of the lateral grooves 3 adjacent to the tire rotation direction side. A plurality of bent sub-grooves 4 extending to the tire grounding end E are arranged alternately at a predetermined pitch on the outer side in the tire width direction, and the outer main groove 2, the lateral groove 3 and the sub-groove 4 are formed on the tread surface 1.
And a directional tread pattern in which a block B2 divided by the lateral groove 3 and the sub-groove 4 is formed.

The sub-groove 4 has a first sub-groove 4A intersecting with the lateral groove 3 and a second sub-groove communicating with the first sub-lateral groove 4A through the bent portion 4B and extending beyond the tire contact end E. is composed of a 4C, the first sub-groove portion 4A, the tip end 4A ₁ is the main groove 2 is adapted to position the central portion between the lateral grooves 3 in the block B1 to the not connected. Also, the first sub-groove 4A
Are arranged so as to be inclined within 90 ° with respect to the tire width direction, and the second sub-groove portion 4C
It extends toward the tire grounding end E side at an inclination angle of not less than °.

As described above, the present invention relates to a pneumatic tire provided with a directional tread pattern. Lateral grooves 3 communicating with the main grooves 2 and extending in the opposite direction to the tire width direction and extending to the tire grounding end E are provided at a predetermined pitch, and intersect with one of the lateral grooves 3 from both sides of the both main grooves 2. Since the sub-grooves 4 extending to the tire grounding end E are arranged alternately with the lateral grooves 3 on the outer side in the tire width direction, the lateral grooves 3 and the sub-grooves 4 can promote the drainage effect in the tire width direction. The wet performance can be equal to or higher than the conventional directional tread pattern.

In addition, since the sub groove 4 formed in a bent shape crosses one of the lateral grooves 3 and extends to the tire grounding end E without communicating with both main grooves 2, the same groove as the conventional directional tread pattern is formed. Even if the grooves are arranged so as to secure an area, the block B1 defined by the main groove 2 and the lateral grooves 3 and the bent sub-grooves 4 can be made larger than before and the block rigidity can be increased, thereby. In addition, dry performance such as turning performance on a dry road surface, traction, and marginal performance can be improved.

In the present invention, in the sub-groove 4, the intersection angle a of the first sub-groove portion 4A with the lateral groove 3 is set at 30 ° ≦ a ≦ 7.
0 ° and the second sub-groove 4 with respect to the first sub-groove 4A.
It is preferable that the bending angle b of C is set to 110 ° ≦ b ≦ 150 °. Further, the lateral groove 3 preferably has an inclination angle c with respect to the tire width direction of 10 ° ≦ c ≦ 60 °. The sum a + c of the intersection angle a and the inclination angle c is set in a range of a + c ≦ 90 °.

If the intersection angle a of the first sub-groove portion 4A is smaller than 30 °, the corners of the blocks B1 and B2 become too acute, causing a reduction in rigidity, causing problems such as uneven wear and the like. If the intersection angle a is greater than 70 °, the drainage effect will be reduced. If the bending angle b of the second sub-groove 4C is less than 110 °, it becomes difficult to maintain wet performance, and if the bending angle b exceeds 150 °, it becomes impossible to form a large block. Dry performance cannot be improved. When the inclination angle c of the lateral groove 3 is smaller than 10 °, the wet performance and the noise performance are reduced, and
If the inclination angle c is larger than 60 °, the blocks B1, B
2 has an adverse effect such as uneven wear.

More preferably, the sub-grooves 4 are arranged so as to expand toward the outside of the tire while being inclined with respect to the tire width direction from the tire rotation direction R toward the rear side (anti-tire rotation direction side). Good. The sub groove 4 has a bent portion 4B.
Consisting of the distance w between the bending point 4B ₁ and the tire ground contact end E, the outer main grooves 2 and 0.2 ≦ w / W ≦ 0.8 the relationship w / W of the distance W between the tire ground contact end E It is good to arrange as follows. If w / W is smaller than 0.2, the bent portion 4 of the sub-groove 4
B becomes too much on the shoulder side, so that the steering stability and uneven wear resistance on dry road surfaces decrease, and if w / W is larger than 0.8, the bent portion 4B is too located on the center side of the tread surface 1. In addition, it is difficult to form a large block having increased rigidity.

In the above-described embodiment, three main grooves 2 are arranged. However, at least one straight main groove 2 extending in the circumferential direction of the tire is provided in the central region of the tire contact with the ground. Often, when one main groove 2 is arranged, the lateral grooves 3 on both sides extending inclining in the opposite direction to the tire width direction,
Each of the main grooves 2 communicates with each other. The upper limit of the main groove 2 arranged in the tire contact center region is 3
Books are preferred.

The first sub-groove portion 4A and the second sub-main groove 4C constituting the sub-groove 4 can be formed in a straight line or a curved line having a large curvature, respectively. , Can be arranged so that the tire rotation direction R side is depressed. Further, it is preferable that the width of the sub-groove 4 is increased toward the tire ground contact end E side. Further, the lateral grooves 3 and the sub-grooves 4 are preferably arranged at the same pitch, and the sub-grooves 4 are preferably arranged so that the second sub-groove 4C is located at the center between the adjacent lateral grooves 3.

[0018] Note that the tire contact center region in the present invention refers to 50% of the tire contact width L on the left and right sides from the tire center line CL of the tread surface 1. Also,
The above-mentioned main groove 2 refers to the tire circumferential direction T regardless of the groove width.
Means the circumferential grooves arranged along. Also,
The aforementioned bending point 4B _1, first auxiliary groove portion 4A and the second auxiliary groove portions 4
The intersection of the groove center line of C is shown.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The tire of the present invention having the directional tread pattern shown in FIG. 1 and the conventional tire having the directional tread pattern shown in FIG. Each was manufactured in substantially the same manner. In the tire of the present invention, the intersection angle a of the auxiliary groove is 40 °, the bending angle b is 135 °, and the inclination angle c of the lateral groove is 20 ° for both the tire of the present invention and the conventional tire.

Each of these test tires was rim size 8JJ ×
Attach to 16 rims and adjust the air pressure to 2.2 kgf / cm ² for 25
It was attached to a 00 cc passenger car and subjected to an evaluation test of dry performance and wet performance under the following measurement conditions. The results shown in Table 1 were obtained.

Dry performance Turning performance Evaluation was made by a feeling test by a panelist (test driver) when the vehicle traveled on a circuit course on a dry road surface of 2 km per lap in a fixed traveling pattern, and the result was shown as an index value with the conventional tire being 100. The larger the value, the better the turning performance. 2. Traction Performance A traction performance was evaluated by a feeling test by a panelist (test driver) when the vehicle ran on a fixed circuit pattern on a dry road surface of 2 km per lap, and the result was shown as an index value with the conventional tire being 100. The larger the value, the better the traction performance. 3. Braking performance Measure the braking distance when sudden braking is performed from a speed of 150 km / h on a straight course and evaluate it by a feeling test by a panelist (test driver). Indicated. The larger this value, the better the braking performance. 4. Marginal performance The best time of one lap and the feeling test (sensory evaluation) by a panelist (test driver) when driving around the circuit course on a dry road of 2km per lap, and the result is set to 100 for the conventional tire. Indicated by exponential value. The larger the value, the better the marginal performance.

Wet performance Driving Stability On a test course on a wet road surface, the maximum lateral acceleration G when the speed was increased while traveling in a steady circular turning on a flat ground having a water depth of about 1 mm was measured, and evaluated by an index value with the conventional tire being 100. The larger the index value, the better the steering stability. 2. Slalom test On a wet road surface test course with a water depth of about 4 mm, the vehicle was run on a slalom test road on which pylons were erected at regular intervals, and the average speed was evaluated. The results are shown as index values with the conventional tire being 100. The larger this value, the better the steering stability. 3. Drainage performance On a wet road test course, water depth average 10mm
The speed was increased while drawing an arc with a radius of 100 m on the flat ground, and the limit speed until the hydroplaning phenomenon occurred was measured. The larger the index value, the better the drainage performance.

[0023]

[Table 1]

As is clear from Table 1, the tire of the present invention improves the dry performance of a pneumatic tire having a directional tread pattern while maintaining the wet performance at least equal to that of the conventional directional tread pattern. You can see that it can be done. Further, test tires 1 to 3 having the same tire size as described above and changing the intersection angle a of the sub-groove as shown in Table 2 in the directional tread pattern of FIG.
5, test tires 6 to 10 in which the bending angle b of the sub groove was changed as shown in Table 3, test tires 11 to 15 in which the inclination angle c of the lateral groove was changed as shown in Table 4, and sub tires as shown in Table 5. Test tires 16 to 20 in which the relationship w / W between the bending point of the groove and the distance w between the tire grounding end and the distance W between the main groove and the tire grounding end was changed.
Was produced respectively.

Each of these test tires was subjected to the same conditions as described above.
Reputation for dry performance and wet performance (steering stability)
Value test, and under the measurement conditions shown below,
Performance and uneven wear resistance evaluation tests were performed.
The results shown in Tables 2 to 5 were obtained. Noise performance In-car noise when driving on a dry circuit track
Is measured and evaluated by an index value with the conventional tire being 100.
Was. The larger the value, the better the noise performance. Partial wear resistance After traveling 10,000 km on the test road consisting of paved surfaces,
Measure the amount of uneven wear that occurred and set the conventional tire to 100
It was evaluated by an index value. The larger the value, the better the uneven wear resistance
Have been.

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

From Tables 2 to 4, the intersection angle a of the first sub-groove portion with respect to the lateral groove is 30 ° ≦ a ≦ 70 °, the bending angle b of the second sub-groove portion with respect to the first sub-groove portion is 110 ° ≦ b ≦ 150 °, The inclination angle c of the lateral groove with respect to the tire width direction is 10 ° ≦ c ≦ 6.
It can be seen that it is better to set the range to 0 °. Table 5
From the relation w / W between the distance w between the bending point of the sub-groove and the tire contact end and the distance W between the main groove and the tire contact end is 0.2 ≦ w /
It can be seen that W ≦ 0.8 should be satisfied.

[0031]

As described above, according to the present invention, at least one main groove extending in the tire circumferential direction is provided in the tire contact center region on the tread surface in which the tire rotation direction is specified in one direction. Numerous lateral grooves communicating with the main groove from both sides and extending in the opposite direction to the tire width direction and extending to the tire ground end, respectively, and from both sides of the main groove to the side opposite to the tire rotation direction without communicating with the main groove. Since a plurality of bent sub-grooves that intersect with one of the adjacent lateral grooves and extend to the tire ground end on the outer side in the tire width direction are alternately arranged at a predetermined pitch to form a directional tread pattern, the wet performance is improved. Can be improved while maintaining the same as or higher than the conventional directional tread pattern.

[Brief description of the drawings]

FIG. 1 is a development view of an essential part showing an example of a directional tread pattern in a pneumatic tire of the present invention.

FIG. 2 is an essential part developed view showing a directional tread pattern in a conventional pneumatic tire.

[Explanation of symbols]

Reference Signs List 1 tread surface 2 main groove 3 lateral groove 4 sub-groove 4A first sub-groove portion 4B bent portion 4B ₁ bending point 4C second sub-groove portion E Tire grounding end R Tire rotation direction T Tire circumferential direction CL Tire center line

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-43105 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 11/04

Claims (4)

(57) [Claims] At least one main groove which is disposed only in a tire contact center region and extends in a tire circumferential direction is provided on a tread surface in which a tire rotation direction is specified in one direction, and said main groove is provided. A large number of lateral grooves communicating with the main groove from both sides thereof and extending in the opposite direction to the tire width direction and extending to the tire grounding end, and a side opposite to the tire rotation direction without communicating with the main groove from both sides of the main groove. A pneumatic tire having a directional tread pattern in which a plurality of bent sub-grooves intersecting with one of the lateral grooves adjacent to the tire and extending to the tire ground end on the outer side in the tire width direction are alternately arranged at a predetermined pitch. . 2. A tire having a tire rotation direction designated as one direction.
On the red surface, only the tire
A plurality of main grooves extending in the circumferential direction are provided, and
And a communication with the main groove from both sides of the main groove.
To the outside of the tire in the width direction,
A large number of lateral grooves extending to the ground edge;
The lateral groove adjacent to the tire rotation direction side without communicating with the groove
Crosses with one of the tires and touches the tire on the outside in the tire width direction
A large number of bent sub-grooves extending to the end
Pneumatic inlets placed side by side to form a directional tread pattern
Tires. 3. The sub-groove comprises: a first sub-groove crossing the lateral groove; and a second sub-groove communicating with the first sub-groove through a bent portion and extending to a tire contact end. The intersection angle a of the first sub-groove portion with respect to the lateral groove is 30 ° ≦ a ≦ 70.
°, the bending angle b of the second sub-groove portion with respect to the first sub-groove portion is set to 110 ° ≦ b ≦ 150 °, and the inclination angle c of the lateral groove with respect to the tire width direction is set to 10 ° ≦ c ≦ 60 °, and The sum a + c of the intersection angle a and the inclination angle c is a + c
The pneumatic tire according to claim 1 or 2 , wherein ≤ 90 °. 4. A relationship w / W between a distance w between a bending point of the sub groove bending portion and a tire grounding end and a distance W between the main groove and the tire grounding end is 0.2 ≦ w / W ≦. Claim 1 set to 0.8
A pneumatic tire according to any one of claims 1 to 3 .