JP2003312211A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of assuring its rotating performance while keeping its wet performance at the time of its new product state. <P>SOLUTION: Groove bottom lines 40 connecting groove bottom segments to each other in a width direction of a tire are gradually spaced apart from a tire equator plane CL toward outside in a width direction of the tire in respect to a tread surface 30A at least at the time of a new product state of the tire so as to improve its drainage performance and to enable a high wet performance to be attained also at the time of the new product state. It is also possible to assure a rotating performance while keeping a wet performance at the time of a new product state by exposing a central rubber layer 32 constituted by hysterisis loss rubber at a tire equator plane CL side and by exposing both side rubber layers 34 having a high frictional coefficient at both sides at the surface of the tread 30 at the time of new product state. <P>COPYRIGHT: (C)2004,JPO

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 capable of ensuring rolling performance as well as wet performance when it is new.

[0002]

2. Description of the Related Art Conventional wet tires are required to have both wet performance and maneuverability at the time of new product, so as to secure area of groove portion in pattern required for wet performance and rigidity of block which greatly contributes to maneuverability, so-called block area and block. It is a trade-off between height (lower is better), and setting is difficult.

Further, in order to secure the wet performance after abrasion, which is greatly demanded by users, means such as exposing rubber after abrasion is used after abrasion is used, but rolling resistance becomes large by using rubber having wet performance. It was a major concern for rolling performance.

[0004]

The conventional tires are
The tread rubber layer is composed of one layer or two layers, both of which are designed to wear uniformly in the width direction.

Therefore, the rectangle in the grounded state, which largely depends on the wet performance, hardly changes, and the groove volume also decreases, so that the hydroplaning performance deteriorates.

In addition, by using the latter two-layer structure, there is a case where a method of exposing rubber after abrasion is used, etc. is used. However, by using rubber having wet performance, rolling resistance becomes large, There is great concern about rolling performance.

In recent tires, the depth of the groove becomes shallower toward the ground contact end, that is, in FIG. 5 (A).
As shown in FIG. 5 (B), the distance between the groove bottom line 100 connecting the groove bottoms in the tire width direction and the tread surface becomes narrower in the tire width direction. ,
The same is true in the actual ground contact state with the road surface 104.

That is, as shown in FIG. 5, the groove bottom line 10
There is a concern that 0 (groove depth) becomes deeper toward the center of the tread, and water on the ground contact surface may flow toward the center of the tread.

In view of the above facts, it is an object of the present invention to provide a pneumatic tire capable of ensuring rolling performance while ensuring wet performance when it is new.

[0010]

According to a first aspect of the present invention, there is provided a pneumatic tire having a groove for drainage formed in a tread, the tread being provided on a tread surface of a new tire and on an equatorial side of the tire. A central rubber layer, both side rubber layers are exposed on both sides in the tire width direction of the central rubber layer, and when the rubber forming the both side rubber layers is A and the rubber forming the central rubber layer is B, the wet Rubber A has better performance than rubber B,
Rubber B has better rolling performance than rubber A, and the groove bottom line connecting the groove bottoms in the tire width direction is parallel to the tread surface of a new tire or from the tire equatorial side to the tire width direction outside. The feature is that they are gradually separated.

Next, the operation of the pneumatic tire according to claim 1 will be described.

In the pneumatic tire according to claim 1, the groove bottom line connecting the groove bottoms in the tire width direction is at least parallel to the tread surface at the time of new or from the tire equatorial plane side to the tire width direction outside. Gradually separated towards each other, that is,
Since the groove cross-sectional area increases from the tire equatorial side toward the tire width direction outside, the water taken in the groove is efficiently transferred from the tire equatorial side toward the outside of the ground contact end outside the tire width direction when running on a wet road surface. Can be discharged to a high wet performance when new.

On the tread surface of the tread when it is new, a central rubber layer is exposed on the tire equatorial plane side, and both rubber layers are exposed on both sides of the central rubber layer in the tire width direction.

When the entire tread is made of rubber having a wet performance, rolling resistance is deteriorated. However, in the present invention, a rubber having excellent wet performance is used for the central rubber layer and a rubber having excellent rolling performance is used for both rubber layers. Therefore, rolling performance can be ensured while ensuring wet performance when the product is new.

The rubber having excellent wet performance is, for example,
It is a rubber with a large coefficient of friction (road surface).

The rubber excellent in rolling performance is, for example, rubber having a low hysteresis loss.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the width of the central rubber layer is gradually increased from the tread surface toward the inner side in the tire radial direction. It has a feature.

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

In the pneumatic tire of the second aspect, when the tread wears, the width (area) of the central rubber layer on the tread surface gradually increases and the width (area) of the rubber layers on both sides gradually decreases.

Further, when the tread is worn, the rectangularity is reduced and the hydroplaning performance is improved.

According to a third aspect of the present invention, in the pneumatic tire according to the second aspect, the inner portion of the central rubber layer which is not exposed on the tread surface when the tire is new reaches at least the ground contact end. It is characterized by

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

The rubber layers on both sides, which contribute to the wet performance, need only be exposed on the tread surface from the time of new article to the end of wear, and need not be inside the tread surface at the end of wear.

Further, in consideration of rolling performance, it is preferable to use rubber capable of improving rolling performance in portions other than where wet performance should be exhibited.

By arranging the inner portion of the central rubber layer made of rubber having good rolling performance in the radial direction of the tire to reach at least the ground contact end, the volume of rubber having good rolling performance is increased and rolling performance is improved while ensuring wet performance. It can be maximized.

The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein:
Let Lc be the dimension of the ground contact shape in the tire circumferential direction, and Ls be the length in the tire circumferential direction at the position of 80% of the contact half width from the tire equatorial plane to the tire width direction outer side, (Ls / Lc) × 100
When (%) is defined as a rectangular rate, the rectangular rate is characterized by gradually decreasing as the tread wears.

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

When the rectangular ratio decreases, the shape of the tire on the advancing direction side approaches a rectangular shape from a rectangular shape, and when running on a wet road surface, water on the road surface in the tire advancing direction can be easily removed to the left and right of the tire. As a result, it is difficult for water on the road surface in the tire traveling direction to enter the ground contact surface, and a decrease in wet performance (particularly hydroplaning performance) is suppressed.

According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects,
The degree of decrease in the rectangular ratio during wear is 1-5% in the middle stage of wear,
It is characterized in that it is 2 to 10% at the end of wear.

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

By setting the rate of decrease of the rectangular rate during wear within such a range, it is possible to suppress the deterioration of wet performance until the end of wear.

The middle term of wear is (groove depth-1.6
mm) × 50% when worn.

The term "end of wear" means that the remaining depth of the groove is 1.
It means the time when it became 6 mm.

The invention according to claim 6 is the pneumatic tire according to any one of claims 1 to 5, wherein:
The rubber B is better in wear resistance than the rubber A, and the rubber B is higher in elastic modulus than the rubber A.

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

If the wear resistance of the rubber B is made higher than that of the rubber A, the progress of wear of the rubber B on the tire equator side becomes relatively slower than the progress of wear of the rubber A on both sides of the tread. As the ground contact shape, the speed at which the shape on the tire advancing side changes from a rectangular shape to an arc shape is increased, which is preferable in order to prevent deterioration of wet performance.

If the rubber elastic modulus of the rubber B is made higher than the rubber elastic modulus of the rubber A, the rigidity of the pattern center portion, which has the greatest influence on the response at the time of a small steering angle largely due to the steering performance, is increased. It is possible to improve the steering performance.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION A pneumatic tire according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

First, the overall structure of the pneumatic tire 10 of the present invention will be described.

FIG. 1 shows a cross section of a pneumatic tire 10 (hereinafter, appropriately abbreviated as "tire 10") along the rotational axis.

This tire 10 has a pair of bead cores 12
And a pair of bead cores 12 each having a carcass 14 extending in a toroidal shape.

The carcass ply 16 forming the carcass 14 is folded back around the bead core 12 from the inner side to the outer side in the tire axial direction.

A stiffener 2 made of rubber having a relatively high hardness is provided between the main body portion 16A and the folded portion 16B of the carcass ply 16 in order to secure the rigidity of the bead portion 20.
2 are provided.

A side rubber layer 24 is provided on the outer side of the carcass 14 in the axial direction of the tire.

On the outside of the carcass 14 in the radial direction of the tire,
A belt layer 28 including two belt plies 26 is provided.

An inner liner 34 is provided on the inner surface of the carcass 14.

On the outer side of the belt layer 28 in the tire radial direction,
A central rubber layer 32 forming a part of the tread 30 is provided.

The central rubber layer 32 extends from one shoulder portion to the other shoulder portion, and a convex portion 32A is formed at the central portion in the width direction.

The width of the central rubber layer 32 gradually becomes wider toward the inner side in the tire radial direction.

On the outer side of the central rubber layer 32 in the tire radial direction,
Both side rubber layers 34 are provided on both sides of the convex portion 32A.

When the rubber forming the both side rubber layers 34 is A and the rubber forming the central rubber layer 32 is B, the wet performance is better than the rubber B and the rolling performance is the rubber A.
The rubber B is better than the rubber A, the rubber B is better than the rubber A in abrasion resistance, and the rubber B is higher than the rubber A in elastic modulus.

Here, in the present embodiment, the rubber having good wet performance means a rubber having a large grip on the road surface,
That is, it means a rubber having a large friction coefficient with respect to the road surface, and a rubber having a good rolling performance is a rubber having a low hysteresis loss that can reduce the rolling resistance of the tire.

In the tread 30 when it is new, the tread 30
The width W of the central rubber layer 32 exposed on the surface ₁Is the tread width W₀
5 to 15% is preferable.

Here, the "tread width" means that a pneumatic tire is mounted on a standard rim defined in JATMA YEAR BOOK (2001 version, Japan Automobile Tire Manufacturer's Association standard), and the applicable size in JATMA YEAR BOOK. The tire width dimension of the ground contact shape when the maximum load capacity (internal pressure-bold load in the load capacity correspondence table) in ply rating is filled with 100% of the internal pressure (maximum air pressure) and the maximum load capacity is loaded. Is. In addition, TRA standard, E
When the TRTO standard is applied, follow each standard.

The thickness of the rubber layers 34 on both sides is set so as to be exposed on the tread surface until the end of the wear of the tire.

As shown in FIGS. 1 and 2, the tread 30
A plurality of circumferential grooves 36 extending in the tire circumferential direction and lateral grooves 38 extending in the tire width direction are formed in the tire.

As shown in FIG. 1, a groove bottom line connecting the groove bottoms of the circumferential groove 36 and the lateral groove 38 in the tire width direction (2 in FIG. 1).
The dashed line 40 is gradually separated from the tire equatorial plane CL side toward the tire width direction outer side. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

This pneumatic tire 10 is shown in FIGS.
As shown in (A), the groove bottom line 40 that connects the groove bottoms in the tire width direction is gradually separated from the tire equatorial plane CL side toward the tire width direction outer side at least with respect to the tread surface 30A when new. The groove cross-sectional area increases from the tire equatorial plane CL side toward the tire width direction outer side.

As shown in FIG. 4 (B), this state is also the same when touching the wet road surface 42, and the water taken in the groove is used to draw the water taken in from the tire equatorial plane CL side to the outside of the tire width direction. It can be efficiently discharged to the outside. Therefore, high wet performance can be obtained when the product is new.

On the tread surface of the tread 30 when new, a central rubber layer 32 made of rubber having a low hysteresis loss is exposed on the tire equatorial plane CL side, and both side rubber layers 34 having a high friction coefficient are exposed on both sides thereof. Therefore, the rolling performance can be ensured while ensuring the wet performance when the product is new.

When the tread 30 is worn, the width (area) of the central rubber layer 32 gradually increases and the width (area) of the both rubber layers 34 gradually decreases on the tread surface.

Further, when the tread 30 is worn, the rectangular ratio is reduced and the hydroplaning performance is improved.

In the tread 30, the rubber A having a high coefficient of friction is arranged only in the necessary places, and the other is the rubber B having a low hysteresis loss, so that the rolling performance is maximized while ensuring the wet performance. be able to.

Further, since the rubber B constituting the central rubber layer 32 has better wear resistance than the rubber A constituting the rubber layers 34 on both sides, the progress of wear of the central rubber layer 32 on the rubber layers 34 on both sides progresses. Relatively slower than the progress of wear, the rectangular ratio decreases, for example, the speed at which the shape of FIG. 3 (A) changes to the shape of FIG. 3 (B) becomes faster, and the tire traveling direction during running on a wet road surface is increased. The water on the road surface can be easily removed to the left and right of the tire, and as a result, it is difficult for water on the road surface in the tire traveling direction to enter the ground contact surface, and deterioration of wet performance (hydroplaning performance) is suppressed.

In order to suppress the deterioration of the wet performance, the degree of decrease of the rectangular ratio at the time of wear is set to 1 to 5 in the middle period of wear.
%, And 2 to 10% at the end of wear.

Further, the rubber B constituting the central rubber layer 32
Has a higher elastic modulus of rubber than the rubber A forming the rubber layers 34 on both sides, so that the rigidity of the pattern center portion, which is most affected by the response at the time of a small steering angle due to the steering performance, can be increased. It is possible to improve the steering performance.

By setting the degree of decrease in the rectangular ratio at the time of wear to 1 to 5% at the middle stage of wear and 2 to 10% at the final stage of wear, it is possible to suppress the deterioration of wet performance until the final stage of wear.

In the tread 30 when new, if the width W ₁ of the central rubber layer 32 exposed on the tread surface 30A is less than 5% of the tread width W ₀ , the steering performance when new is insufficient.

In the tread 30 when new, if the width W ₁ of the central rubber layer 32 exposed on the tread surface 30A exceeds 25% of the tread width W ₀ , the wet performance when new is insufficient.

The pneumatic tire 10 of the above embodiment is used.
The groove bottom line 40 was gradually separated from the tread surface 30A toward the tire width direction outer side from the tire equatorial plane CL side,
It may be partially parallel or entirely parallel.

At least the tread surface 30A and the groove bottom line 40
The distance between and should not be narrowed toward the tire equatorial plane CL side.

Further, the pneumatic tire 10 of the above embodiment
The tread 30 has a plurality of circumferential grooves 36 extending along the tire circumferential direction and a plurality of lateral grooves 38 extending along the tire width direction, but the present invention is not limited to this, and is formed on the tread 30. The shape of the groove is not limited to the block pattern as shown in FIG. 2, but may be another known pattern such as a directional pattern. (Test Example) In order to confirm the effect of the present invention, a tire of a conventional example and a tire of an example to which the present invention is applied are prepared, and dry handling property, wet handling property, wear mode, acceleration H
P, CHP (55-80 km / h average) G, wet brake, rectangular ratio, and rolling resistance were compared.

The construction of the tire, the test method, and the test method of the rubber used in the tire will be described below.

Tire of Example: A tire whose tread is composed of a central rubber layer and rubber layers on both sides as shown in FIG. The width of the central rubber layer that appears on the tread when new is 20% of the tread width (when mounted on an actual vehicle).

The compounding contents and characteristics of the rubber used for the tread are as shown in Table 1 below.

Conventional tire: As shown in FIG. 6, the boundary between the central rubber layer 32 and the both side rubber layers 34 is located outside the groove bottom line (two-dot chain line in FIG. 6) 40 in the tire radial direction. The thickness of the rubber layers 34 on both sides is set so that the rubber layers 34 are worn away during the middle period of wear of the tire.

The compounding contents and characteristics of the rubber used for the tread are the same as those in the examples.

Abrasion resistance: Using a Lambourn type abrasion tester, a test was conducted indoors under the condition of a slip ratio of 25%, and the evaluation was expressed by an index with the reciprocal of the abrasion amount of the conventional example being 100.

The larger the numerical value of the index, the better the abrasion resistance.

Rubber elastic modulus: Dynamic storage elastic modulus E is JIS
The value is determined according to the method described in the test method of K 7198 (under the test conditions of temperature 30 ° C., frequency 50 Hz, and dynamic strain 1%).

Dry controllability (feeling): test tires were attached to all wheels of a 2.0-liter passenger car,
Evaluated by the feeling of the test driver when traveling at 60-80 km / h on the road.

The evaluation was a 10-point evaluation (feeling) by a test driver. The larger the value, the better the dry maneuverability.

Wet controllability (feeling): Water was sprinkled on the test course to obtain a wet road surface, which was evaluated in the same manner as dry controllability.

The evaluation was a 10-point perfect evaluation (feeling) by a test driver. The larger the value, the better the wet controllability.

Wear mode: Acceleration / deceleration of about 0.8 G is 4 km
The running mode repeated twice is repeated. Calculate the ratio of the center wear rate near the center of the tread to the shoulder block wear rate near the shoulder.

Acceleration HP (Hydroplaning) (Instrument): Accelerates on a wet road surface, measures the vehicle traveling speed and the number of rotations of the tire, and the speed at which the number of rotations of the tire rises (the tire on the driving side slips to the tire). When the peripheral speed of is higher than the traveling speed of the vehicle) is the hydroplaning generation speed.

The evaluation is expressed by an index with the hydroplaning generation rate of a conventional product as 100, and the larger the value, the less hydroplaning occurs.

CHP (Cornering Hydroplaning: 55-85 km / h average) G (instrument): Running along a test turning radius (100 m in this case) and maintaining a constant lateral acceleration in the measurement section (wet road surface) . At this time, the vehicle speed and the lateral acceleration are measured. Each time the vehicle travels in the measurement section, the speed is increased and the measurement is performed. Measure the vehicle speed when the lateral acceleration decreases due to hydroplaning. The evaluation is the same as the acceleration HP.

Wet brake (instrument): Test tires were mounted on all wheels of a passenger car, and sprinkled with water to brake on a test course with a wet road surface at 60 km / h. The distance (braking distance) was measured.

For the evaluation, the braking distance at the time of new article of the conventional example is 10
It is represented by an index of 0, and the smaller the value, the better the wet braking performance.

Rolling resistance (instrument): The tire was pressed against a drum having a diameter of 1.7 m, which was filled with an internal pressure of 200 kPa and rotated at 60 km / h under the load of 4.9 N, and the rolling resistance was measured. Is displayed as an index with the conventional (new) as 100. The higher the value, the smaller the rolling resistance,
It shows that it has excellent rolling performance. Indoor test conditions Tire size: PSR205 / 65R15 Rim width: 6.5J × 15 Internal pressure: 210kPa Load: 4.81kN Actual vehicle test conditions Tire size: PSR205 / 65R15 Rim width: 6.5J × 15 Internal pressure: 210kPa Vehicle: Toyota Motor Corporation Company Camry (displacement 2000
cc) Load: Vehicle weight + driver + passenger seat 60kgf

[0092]

[Table 1] Carbon: Tokai Carbon Co., Ltd., Seast KH (product name) Silica: Nippon Silica Industry Co., Ltd., Nipseal AQ (product name) Oil: Aroma oil vulcanization accelerator: Diphenylguanidine

[0093]

[Table 2] Test Results With regard to dry handleability and wet handleability, the tires of the examples have a feeling equal to or better than that of the tires of the conventional example when new and worn, and superiority can be confirmed.

It can be confirmed that there is no early wear sensation, since the wear patterns after running show almost the same amount of change.

Hydroplaning (acceleration HP, CH
In P (G)), the tire of the example has a result equal to or higher than that of the tire of the conventional example when it is new, and the superiority can be confirmed, and the performance deterioration from new to wear You can confirm that there are few things.

Regarding the rectangular ratio, it can be confirmed that the contact shape change after abrasion hardly changes in the tire of the conventional example, while the tire of the example shifts to the rounding direction.

Regarding the rolling performance, it can be confirmed that the rolling resistance is improved when it is new and when it is worn.

[0098]

As described above, since the pneumatic tire according to claim 1 has the above-mentioned structure, it has an excellent effect that the rolling performance can be secured while the wet performance is secured when the pneumatic tire is new. Have.

Since the pneumatic tire according to claim 2 has the above-mentioned constitution, it has an excellent effect that the hydroplaning performance is improved.

Since the pneumatic tire according to claim 3 has the above-mentioned constitution, it has an excellent effect that rolling performance can be maximized while ensuring wet performance.

Since the pneumatic tire according to claim 4 has the above-mentioned constitution, it has an excellent effect that the deterioration of wet performance due to the progress of wear can be suppressed.

Since the pneumatic tire according to claim 5 has the above-mentioned constitution, it has an excellent effect that the deterioration of wet performance can be suppressed until the end of wear.

Since the pneumatic tire according to claim 6 has the above-mentioned constitution, it has an excellent effect that the deterioration of wet performance can be further suppressed and the steering performance can be improved. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view taken along a rotation axis of a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is a plan view of the tread of the pneumatic tire according to the embodiment of the present invention.

FIG. 3A is a ground contact shape of a pneumatic tire according to one embodiment when new, and FIG. 3B is a ground contact shape when the pneumatic tire according to one embodiment is worn.

FIG. 4A is a cross-sectional view of the pneumatic tire according to one embodiment when the tread is not grounded, and FIG. 4B is a cross-sectional view of the tread when the pneumatic tire is grounded according to one embodiment. .

FIG. 5A is a cross-sectional view of a pneumatic tire according to a conventional example when the tread is not grounded, and FIG. 5B is a cross-sectional view of a tread of a pneumatic tire according to the conventional example that is grounded.

FIG. 6 is a cross-sectional view taken along a rotation axis of a pneumatic tire according to a conventional example.

[Explanation of symbols]

10 pneumatic tires 32 Central rubber layer 34 Rubber layers on both sides 36 circumferential groove 38 lug groove

Claims (6)

[Claims] 1. A pneumatic tire having a groove for drainage formed in a tread, wherein the tread has a central rubber layer on the tire equatorial side on the tread surface of a new tire, and both sides of the central rubber layer in the tire width direction. When both side rubber layers are exposed at A, the rubber forming the both side rubber layers is A and the rubber forming the central rubber layer is B, the wet performance is rubber B.
Rubber A is better than rubber A, and rolling performance is better than rubber A
Good, the groove bottom line connecting the groove bottom of the groove in the tire width direction is parallel to the tread surface at the time of new or gradually separated from the tire equatorial plane side toward the tire width direction outer side, A characteristic pneumatic tire. 2. The width of the central rubber layer is gradually increased from the tread surface toward the inner side in the tire radial direction,
The pneumatic tire according to claim 1, wherein: 3. The pneumatic tire according to claim 2, wherein in the central rubber layer, a tire radial direction inner portion which is not exposed to the tread surface when it is new reaches at least the ground contact end portion. . 4. The dimension of the ground contact shape in the tire circumferential direction is Lc,
80% of contact half width from the tire equatorial plane to the outside in the tire width direction
Let Ls be the tire circumferential length at the position, and (Ls / L
The c) × 100 (%) is defined as a rectangular rate, and the rectangular rate is gradually reduced as the tread is worn, and the rectangular rate according to any one of claims 1 to 3. Pneumatic tires. 5. The degree of decrease in rectangularity ratio during wear is 1 to 5% in the middle stage of wear and 2 to 10% in the final stage of wear, according to any one of claims 1 to 4. Pneumatic tire described in. 6. When the rubber forming the rubber layers on both sides is A and the rubber forming the central rubber layer is B, the abrasion resistance is better than that of the rubber A, and the rubber elastic modulus is rubber. The pneumatic tire according to any one of claims 1 to 5, wherein the rubber B is higher than the rubber A.