JP2001206013A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire simultaneously improving three performances, rolling resistance performance, compartment noise(R/N) performance, and straight running maneuvering stability performance. SOLUTION: Tread rubber has a center region rubber across a tire equator face and different types of both-side region rubbers continued thereto, the both- side region rubber has a composite rubber layer constitution of an outer rubber layer and a different type inner rubber layer, a dynamic storage elasticity EA' of the center region rubber has a larger value than the dynamic storage elasticity EB' of the outer rubber layer, and the inner rubber layer has the physical property tan δ0.1 or less.

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 radial tire for use in relatively small vehicles such as passenger cars and light trucks.
In particular, rolling resistance performance, vehicle interior noise (road noise, hereinafter R
/ N) and a pneumatic tire with improved straight running stability.

[0002]

2. Description of the Related Art Pneumatic tires used in small vehicles described at the outset have excellent performances such as rolling resistance performance, in-vehicle sound (R / N), and straight running stability. Required. Therefore, conventionally, many of these performance improving means have been proposed.

For example, means for applying a so-called cap / base structure to tread rubber is well known as means for improving rolling resistance performance, that is, means for reducing rolling resistance. In this structure, the tread rubber is formed into two layers, and a rubber having a relatively large value of tan δ, which is excellent in wet performance and traction performance, is applied to the cap rubber of the outer layer, and a hysteresis loss is relatively small in the base rubber of the inner layer. A rubber having a small value, for example, a tan δ of 0.1 or less at 60 ° C. is applied.

It is true that a tire provided with the tread rubber having the cap / base structure contributes to low rolling resistance. However, the base rubber for realizing sufficient low rolling resistance performance has low shear rigidity,
As a result, a time delay occurs when transmitting the grip force received on the tread surface of the tread portion to the belt, and the straight running stability performance,
In particular, the steering performance at a small steering angle is disadvantageously reduced.

The above cap / base structure extends over the entire width of the tread portion. In addition, there is also known a means for applying the cap / base structure only to the tread rubber portion on both sides of the tread portion excluding the central region. . This alternative structure has been proposed because the rolling resistance has a high contribution from the shoulder region of the tread portion.

[0006] In addition, means for reducing vehicle interior noise (R / N) include:
For example, it has been proposed to use a rubber having a low hardness or a rubber having a low dynamic storage modulus E ′, for example, a rubber having an E ′ of 11 MPa or less at 30 ° C., for the cap rubber. However, even when the cap rubber is used, the problem of the transmission delay of the force of the base rubber described above still remains. If a high hardness rubber or a high dynamic storage modulus E 'rubber is applied to the cap rubber to solve this problem, there arises a problem that the vibration riding comfort performance and the rolling resistance performance decrease.

As another means for reducing the in-vehicle sound (R / N),
A structure has been proposed in which the outer sides of both side ends of the belt are covered with a pair of separate reinforcing cord layers to reinforce both side ends of the belt.
This structure is known to be effective for reducing the in-vehicle sound (R / N). However, this type of reinforced belt structure involves a problem that the rigidity at the center of the belt is smaller than the stiffness at both sides, so that the straight-ahead steering stability performance is reduced.

[0008]

As described in detail above,
In the prior art, if one of the rolling resistance performance, the in-vehicle sound (R / N), and the straight driving stability performance is to be improved, the remaining performance must be reduced. There is a need for a means to completely solve the problem.

Accordingly, the inventions set forth in claims 1 to 6 of the present invention particularly relate to the pneumatic tire of a relatively small vehicle described at the beginning, which relates to rolling resistance performance, vehicle interior sound (R / N) and straight driving stability. It is an object of the present invention to provide a pneumatic tire capable of simultaneously improving three performances.

[0010]

According to a first aspect of the present invention, there is provided a tread portion having a pair of sidewall portions and a pair of bead portions connected to both sides of the tread portion. A radial carcass that reinforces each of these parts between bead cores embedded in a bead part, and a belt that strengthens a tread part on the outer periphery of the radial carcass, and the tread part is a tread rubber composed of a plurality of types of rubber compositions. In the pneumatic tire having, the tread rubber has a center region rubber sandwiching the tire equatorial plane, and another type of both side region rubbers connected to the rubber, and the both side region rubbers have a rubber layer outward in the tire radial direction. It has a composite rubber layer configuration with another inner rubber layer at a temperature of 30 ° C.
° C., under a frequency 50Hz and a dynamic strain of 1% of the test conditions, the dynamic storage modulus of the center region Rubber E _A 'is the dynamic storage modulus E _B of the outer rubber layer of the side regions' relative to The inner rubber layer on both sides has a higher value at a temperature of 60 ° C., a frequency of 50 Hz and a dynamic strain of 1%.
A pneumatic tire having physical properties in which nδ is 0.1 or less.

Here, the dynamic storage elastic modulus E _A ', E
_B ′ and tan δ are values determined according to the method described in the test method of JIS K 7198 (1991). The same applies to the dynamic storage modulus E _C ′ described below.

According to the first aspect of the present invention, there is provided a second aspect.
Under the above-mentioned test conditions for the dynamic storage modulus, the dynamic storage modulus E of the outer rubber layers on both side regions as in the invention described in (1).
_B ′ has a larger value than the dynamic storage modulus E _C ′ of the inner rubber layer.

According to the first and second aspects of the present invention, as in the third aspect of the invention, under the above-mentioned dynamic storage modulus test conditions, the central region rubber has a dynamic storage elasticity of 12 MPa or more. Rate E _A ′, and the outer rubber layers on both sides are 11
MPa with the following dynamic storage modulus E _B '.

According to the first to third aspects of the present invention, as in the fourth aspect of the invention, the outer rubber layer occupies 60 to 90% of the gauge of the tread rubber gauge in both side regions. The inner rubber layer occupies a gauge in the range of 10 to 40%, and in the invention according to claims 1 to 4, as in the invention described in claim 5, the central area rubber is provided with a contact width of the tread portion. Has a tread width in the range of 10 to 20%. Here, the contact width means JATMA YEAR BOOK (1999),
The contact width described in the general information section and the definition of terms shall be followed, provided that the specified air pressure in the description is the maximum air pressure corresponding to the maximum load capacity, and the specified mass is the maximum load capacity. The same applies hereinafter.

Further, according to the invention described in claim 1, as in the invention described in claim 6, the belt has two or more cord cross layers, and both end portions of the cord cross layers are outside the tire radial direction. And at least one pair of tread portions arranged in the circumferential direction and covered with an organic fiber cord layer.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view of the pneumatic tire of the present invention. In FIG. 1, a pneumatic tire (hereinafter, referred to as a tire) 1 has a tread portion 2 and a pair of sidewall portions 3 and a pair of bead portions 4 connected to both sides thereof.

The tire 1 has one or more plies extending between the bead cores 5 embedded in the bead portion 4, in the illustrated example, a one-ply radial carcass 6, and a belt 7 on the outer periphery of the radial carcass 6. The radial carcass 6 reinforces the above parts 2 to 4, and the belt 7 is the tread part 2
To strengthen. The radial carcass 6 is a nylon cord,
It consists of plies in a rubber-coated radial arrangement of organic fiber cords such as polyester cords and rayon cords. The radial carcass 6 shown in FIG. 1 has a turn-up portion 6t that turns around the bead core 5 from the inside of the tire 1 to the outside.

The tread portion 2 has a tread rubber 8 composed of a plurality of types of rubber compositions. The tread rubber 8
It has rubber 8A in a central region Rc sandwiching the tire equatorial plane E, and rubbers 8B and 8C in both side regions Rs. Rubber 8B,
8C is continuous with the rubber 8A along the circumferential direction of the tread portion 2.
The rubbers 8A, 8B, and 8C are made of different types of rubber compositions. The rubbers 8B and 8C in the both side regions Rs have a composite rubber layer configuration of a rubber layer 8B on the outer side in the radial direction (hereinafter referred to as a radial direction) of the tire 1 and a rubber layer 8C on the inner side. The rubber 8A is made of a single rubber composition, and the rubber 8A and the rubber layer 8C are directly bonded to the belt 7.

Here, it is assumed that the following dynamic storage modulus relationship is established between the rubber 8A in the central region Rc and the outer rubber layer 8B in both side regions Rs. That is, temperature 3
Under the test conditions of 0 ° C., a frequency of 50 Hz, and a dynamic strain of 1%, the dynamic storage modulus E _A ′ of the rubber A in the central region Rc is:
Dynamic storage elastic modulus E _B ′ of outer rubber layer 8B in both side regions Rs
Has a larger value than.

The inner rubber layers 8C in the both side regions Rs are
It has physical properties such that tan δ is 0.1 or less under test conditions of a temperature of 60 ° C., a frequency of 50 Hz, and a dynamic strain of 1%. In this respect, the inner rubber layer 8C corresponds to the conventional base rubber, and therefore, the outer rubber layer 8B on both side regions Rs.
Dynamic storage modulus E _B 'of the dynamic storage modulus E _C of the inner rubber layer 8C' shall have a value greater than than the.

Now, when a slip angle of 1 ° is applied to a slick tire that rolls under a load, the relationship between the contact width position of the tread surface of the tread portion 2 and the generated lateral force (side force) will be described. As is clear from FIG. 2, which is clarified by measurement and the result is plotted, it is clear that the lateral force generated in the center contact region is significantly larger than the lateral force generated in both end regions. The lateral force generated as a whole tire is represented by an area (N) surrounded by a plot diagram. The symbol e is a straight line on the tire equatorial plane.

The tire 1 provided with the tread rubber 8 described above first has a dynamic storage modulus E of the rubber 8A in the central region Rc of the tread rubber 8 based on the plot diagram shown in FIG.
_{Since A} 'is the largest in the tread rubber 8, the tire 1
Indicates that a large lateral force can be generated at a small steering angle, and that the steering stability is excellent.

Next, the in-vehicle sound (R / N) is dominated by the input from the portion of the tread 2 where the tread surface contact pressure is high under the load of the tire 1, and the radial ply tire In this case, it has been found that the ground pressure in both side regions Rs is higher than that in the central region Rc.

Therefore, a high dynamic storage elastic modulus E _A ′ is provided in the central region Rc where the degree of influence on the in-vehicle sound (R / N) is small.
Of the outer rubber layer 8B in both side regions Rs
Dynamic storage modulus E _B in 'and the dynamic storage modulus E _C of the inner rubber layer 8C' is, if it is a smaller value than the dynamic storage modulus E _A 'of the rubber A central region Rc By the tire 1
Reduces the in-vehicle sound (R / N) level.

Finally, even if the rubber 8A having a high dynamic storage elastic modulus E _A ′ is arranged in the central region Rc, the increased amount of rolling resistance is absorbed by the outer rubber layer 8B. The dynamic storage elastic modulus E _C ′ of the rubber layer 8 _C is
s is smaller than the dynamic storage modulus E _B ′ of the outer rubber layer 8B and the tan δ of the inner rubber layer 8C is 0.1 or less, so that the tire 1 has low rolling resistance. Performance is improved.

As described above, the tire 1 provided with the tread rubber 8 has the three performances without sacrificing any of the three performances of the rolling resistance performance, the in-vehicle sound (R / N) and the straight running stability. Can be improved at the same time.

The actual value of each dynamic storage elastic modulus is such that the rubber 8A in the central region Rc is 12 MPa under the test conditions described above.
More dynamic storage modulus E _A 'has a dynamic storage modulus outer rubber layer 8B following 11MPa in both the side regions Rs E _B'
Is suitable for simultaneously improving the three performances. In particular, the application of the rubber 8A in the central region Rc having a dynamic storage modulus E _A ′ of 12 MPa or more exhibits straight running stability that can be detected by a general driver.

Here, if the dynamic storage elastic modulus E _A ′ of the rubber 8A in the central region Rc is less than 12 MPa, the straight running stability performance, particularly the straight running stability performance at a small steering angle, cannot be reduced. In addition, the outer rubber layers 8 on both side regions Rs
If the dynamic storage elastic modulus E _B ′ of _B exceeds 11 MPa, the rolling resistance increases, and the in-vehicle sound (R / N) level increases, which is not possible.

The outer rubber layer 8B occupies a gauge in the range of 60 to 90%, and the inner rubber layer 8C occupies a gauge in the range of 10 to 40% of the gauge of the tread rubber 8 in both side regions Rs. Is suitable for the simultaneous improvement of the three performances.

Here, regarding the gauge of the outer rubber layer 8B,
When the ratio of the tread rubber 8 to the gauge is less than 60%, the straight running stability is deteriorated, and when the ratio is more than 90%, the rolling resistance is increased, so that neither is possible. Regarding the gauge of the inner rubber layer 8C, when the ratio of the tread rubber 8 to the gauge is less than 10%, the rolling resistance increases, and when the ratio exceeds 40%, the straight running stability is deteriorated. .

The rubber 8A in the central region Rc has a tread portion 2 width within a range of 10 to 20% of the contact width (as described above) of the tread portion 2. This width is the width of the central region Rc shown in FIG. 1, and each width end is located on a plane parallel to the tire equatorial plane E. This allows
The simultaneous improvement of the three performances is further ensured.

Here, if the rubber 8A in the central region Rc is less than 10% of the contact width of the tread portion 2, the improvement of the straight running stability becomes insufficient, and if it exceeds 20%, the rolling resistance performance and the inside sound (R / N) is an undesired performance, so neither is possible.

Here, in order to further reduce the in-vehicle sound (R / N), as shown in FIG. 1, the belt 7 has two or more (two in the example shown) cord crossing layers 7-1. , 7-2 and at least one pair (two in the illustrated example) of tread portions arranged circumferentially outward from both sides of the cord crossing layers 7-1, 7-2 from outside in the tire radial direction. It is suitable to have

The code crossing layers 7-1 and 7-2 indicate a laminated structure in which the rubber-coated cords of the respective layers intersect each other across the tire equatorial plane E, and a steel cord is suitable for this cord. The circumferentially arranged organic fiber cord layer 9 is formed by spirally winding one or more, preferably two or more organic fiber cords, for example, a strip having a width of 4 to 15 mm, such as a nylon cord, a polyester cord, a rayon cord, or the like. It can be either a layer or a layer in which a predetermined width of the code layer 9 is wound and overlapped. Even if this cord layer 9 is used, the central region R of the tread rubber 8
By applying the rubber 8A to c, the straight running stability is not reduced.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A radial ply tire for a passenger car, having a size of 205 / 65R15, has the same structure as shown in FIG. The radial carcass 6 has a rubber coating of 1500 D /
The tire 1 has one ply in which the polyester cords are arranged at about 90 ° with respect to the equatorial plane E of the tire 1. The belt 7 has two cord cross layers 7-1 and 7-2 and a pair of narrow circumferentially arranged organic fiber cord layers 9.

The codes of the code cross layers 7-1 and 7-2 are 1 ×
Steel cords having a 3 × 0.23 structure were applied, and each steel cord was arranged at an inclination of 22 ° with respect to the tire equatorial plane E. The code layer 9 is a two-layer structure in which a strip of five 1260D / 2 nylon cords is spirally wound.

The tread rubber 8 has the following configuration. (1) The width of the central region Rc: 15% of the ground width, the both side regions R
s width: 42.5% of the contact width, (2) dynamic storage modulus E _A rubber A ': 20 MPa, (3) dynamic storage modulus of the rubber layer _{8B E B': 9MPa, (} 4) Dynamic storage elastic modulus E _C ′ of rubber layer 8C: 3 MPa (5) Tan δ of rubber layer 8C: 0.1, (6) Gauge ratio of rubber layer 8B to tread rubber 8 gauge: 75%, rubber layer 8C Gauge ratio: 25%. However, the dynamic storage modulus _{E A ', E B',} E C ' and tanδ were measured using a Toyo Precision Machine spectrometer.

In order to evaluate the effect of the example tire, a conventional example tire was prepared in accordance with the example tire except for the tread rubber. The tread rubber of the conventional tire had a cap / base structure, the same rubber as the rubber layer 8B of the example tire was applied to the cap, and the same rubber as the rubber layer 8C of the example tire was applied to the base.

The following three tests were carried out using the above two examples as test tires. (1) Rolling resistance test: Each tire is pressed against a 1.7 m-diameter drum rotating at 60 km / h under a load of 4.9 kN under an internal pressure of 200 kPa, and the rolling resistance is measured. The measurement results are represented by an index with the conventional tire being 100, and the smaller the value, the better. (2) Vehicle interior sound (R / N) test: Vehicle interior sound at the front seat when mounted on all wheels of a 2.5-liter passenger car and running at 40 km / h on a cobblestone asphalt surface of a test course ( R / N) was measured. The measurement result is 10 for the conventional tire.
It is represented by an index of 0, and the smaller the value, the better. (3) Straight-running steering stability test: The tires of the conventional example were mounted on all the wheels of a 2.5-liter passenger car, and the tires of the conventional example were reduced by 10 to 100 km / h on a highway.
Scoring was evaluated using an index of 0. The larger the value, the better.

The index values of the example tires based on the above test results are as follows: the rolling resistance is 85, the in-vehicle sound (R / N) is 90,
The straight running stability performance is 105. From these results, it can be seen that the tires of the example simultaneously improved all of the three performances of the rolling resistance performance, the in-vehicle sound (R / N) performance, and the straight driving stability performance.

[0041]

According to the first to sixth aspects of the present invention, it is possible to simultaneously improve all three performances of rolling resistance performance, in-vehicle sound (R / N) performance, and straight driving stability performance. A pneumatic tire can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a pneumatic tire according to the present invention.

FIG. 2 is an explanatory diagram showing a degree of occurrence of a lateral force at a contact position of a tread portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Radial carcass 6t Folding part 7 Belt 7-1, 7-2 Cord cross layer 8 Tread rubber 8A Central area rubber 8B Outer rubber layer of both side areas Rs 8C Inner rubber layer of both side regions Rs 9 Circumferentially arranged organic fiber cord layer E Tire equatorial plane Rc Central region Rs Both side regions

Claims (6)

[Claims] 1. A radial carcass having a tread portion, a pair of side wall portions and a pair of bead portions connected to both sides thereof, and reinforcing each of these portions between bead cores embedded in the bead portion. With a belt that strengthens the tread portion at the outer periphery, the tread portion is a pneumatic tire having tread rubber composed of a plurality of types of rubber compositions, the tread rubber is a central region rubber sandwiching the tire equatorial plane,
A rubber layer on the outer side in the tire radial direction and a rubber layer on the inner side of the rubber layer, and the rubber on both sides has a composite rubber layer configuration, and a temperature of 30 ° C. under frequency 50Hz and a dynamic strain of 1% of the test conditions, the dynamic storage modulus of the central region rubber (E _a ')
Is the dynamic storage modulus (E _B ') of the outer rubber layers on both sides.
The inner rubber layers on both sides have a temperature of 60 ° C. and a frequency of 50 Hz.
And tan δ under the test condition of 1% dynamic strain is 0.
A pneumatic tire having physical properties of 1 or less. 2. The dynamic storage modulus (E _B ′) of the outer rubber layers on both sides under the test conditions for the dynamic storage modulus described above.
The tire of claim 1 having a value greater than than the dynamic storage modulus of the inner rubber layer (E _C '). 3. Under the above-mentioned dynamic storage modulus test conditions, the central region rubber has a dynamic storage modulus (12 MPa or more).
E _A ') having, outer rubber layer on both sides regions 11MPa following dynamic storage modulus (E _B' claim 1 or 2 having a)
Tire described in. 4. The tread rubber gauge on both sides of the region,
The tire according to any one of claims 1 to 3, wherein the outer rubber layer occupies a gauge in a range of 60 to 90%, and the inner rubber layer occupies a gauge in a range of 10 to 40%. 5. The tread portion width of the central region rubber is in a range of 10 to 20% of a tread portion contact width.
The tire according to any one of claims 1 to 4. 6. The belt comprises two or more cord crossing layers,
2. The tire according to claim 1, further comprising a pair of or more tread circumferentially arranged organic fiber cord layers that cover both end portions of the cord crossing layer from outside in the tire radial direction. 3.