JP2000335211A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fatigue resistance at issue specifically and reduce rolling resistance of a pneumatic tire utilizing steel as a reinforcing element for the carcass. SOLUTION: On the crown 6 of the carcass 2 composed of plies retained by a pair of bead cores 4 and connected in a toroid form, belts 7 comprising of at least one sheet of rubber coated steel cord plies 10, 11 and the tread 8 are disposed in sequence. The carcass 2 is composed of a ply burying steel cords and between the carcass 2 and the belts 7 a rubber ply 9 is disposed. The rubber ply 9 has a physical property indicating its 50% modulus in a range of 2/5-6/5 times of 50% modulus of the rubber composing the rubber coated ply of the belts. The width W1 of the rubber ply 9 is 0.2-1.2 times of the width W2 of the lower most rubber coated ply 11 out of the rubber coated plies 10, 11 composing the belts 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire using a steel cord as a reinforcing element for a carcass ply, and more particularly to a pneumatic radial tire for a passenger car, and more specifically, as a reinforcing element for a carcass ply. Compared to conventional tires using organic fiber cord,
It improves the exercise performance and carcass durability (fatigue resistance), and also reduces the rolling resistance.

[0002]

2. Description of the Related Art Generally, steel cord is used as a reinforcing element for a belt and a carcass in a pneumatic tire for heavy loads used for trucks and buses. An organic fiber cord such as polyester, nylon or rayon having excellent fatigue resistance is often used as a reinforcing element.

However, passenger car tires using an organic fiber cord as a carcass have insufficient resistance to trauma, which is likely to occur when the tire side portion comes into contact with a curb, and poor adhesion between the cord and rubber. For,
May lead to cord breakage or separation. Also,
Since the organic fiber cord generally has low flexural rigidity, the rigidity of the side portion of the tire tends to be insufficient, so that sufficient exercise performance may not be obtained depending on a running condition or the like.

[0004] Therefore, even in the case of pneumatic radial tires for passenger cars, attempts have been made to apply steel cords having higher flexural rigidity instead of organic fiber cords as reinforcing elements for carcass, for example. JP-A-64-30803 discloses a radial tire for a passenger car in which a steel cord having a 1 + n structure composed of one core filament and n sheath filaments arranged around the core filament is applied to a carcass. I have.

[0005]

The radial tire for a passenger car described in the above-mentioned publication uses a steel cord having a predetermined twist structure in a carcass, so that the exercise performance can be sufficiently improved. The steel cord used for the carcass has a problem that the cord is easily broken and the fatigue resistance is inferior to the organic fiber cord.

That is, the carcass is subjected to repeated bending and compression deformation for a long period of time with the rolling load of the tire. In particular, the steel cord in the carcass portion adjacent to the belt is compressed when it receives a lateral force during steering of the vehicle. Deformed,
Due to the repetition of the compression deformation, the material fatigue tends to progress. In this case, if the carcass ply receives a large compression input, a buckling phenomenon is likely to occur in the carcass portion also in the tire width direction, and as a result, the cord is broken. Is likely to occur.

[0007] Therefore, in a radial tire for a passenger car using a steel cord for a carcass, it is important to improve the fatigue resistance.

Accordingly, an object of the present invention is to provide a rubber layer having a predetermined physical property value and a predetermined width between a carcass-resistant belt and a carcass-resistant belt by providing excellent exercise performance by using a steel cord. Accordingly, it is an object of the present invention to provide a pneumatic tire, particularly a pneumatic radial tire for a passenger car, which realizes a reduction in rolling resistance in addition to an improvement in fatigue resistance.

[0009]

In order to achieve the above object, a pneumatic tire according to the present invention is provided with at least one steel sheet on a crown portion of a carcass composed of plies which are locked by a pair of bead cores and are connected in a toroidal manner. In a pneumatic tire in which a belt made of a rubberized layer of a cord and a tread are sequentially arranged, the carcass is composed of one ply in which a steel cord is embedded, and a rubber layer is arranged between the carcass and the belt. The 50% tensile stress of the rubber layer is 2/5 of the 50% tensile stress of the rubber constituting the rubberized layer of the belt.
It has physical properties in the range of ６ to ／ and has a width (W ₁ ) of 0.2 to 1.2 times the width (W ₂ ) of the rubberized layer located at the lowermost layer among the rubberized layers constituting the belt. It is characterized by being.

In addition, the thickness of the rubber layer is 0.5 to 2.5 m.
It is preferably in the range of m. In addition, "50%
"Tensile stress" means the tensile stress at 50% elongation. The thickness (t) of the rubber layer means a thickness measured on the equatorial plane of the tire as shown in FIG.

Further, the steel cord constituting the carcass ply has a twist structure of 1 × N, 1 + N or 2 + N (N: an integer of 2 to 7), and the wire diameter (d) of the filament is 0.125 to 0.250 mm. And / or the elongation at break is preferably 3.5% or more.

Furthermore, the 50% tensile stress of the rubber layer is 1.
It is preferably in the range of 5 to 3.6 MPa, and in addition, 2/3 to 50% of the 50% tensile stress of the rubber constituting the carcass ply.
More preferably, it is within the range of 5/3.

The belt preferably comprises two rubberized layers.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view in the width direction of a pneumatic tire 1 according to one embodiment of the present invention,
FIG. 2 is an enlarged view of a part of the crown portion.

In the tire 1 having the configuration shown in these figures, the carcass 2 has a substantially radial arrangement of ply cords (specifically, an arrangement at an angle of 70 to 90 ° with respect to the tire equatorial plane 3). The ends of the ply are locked by being wound around a pair of bead cores 4 and bead fillers 5 located immediately above them and tapering outward in the tire radial direction, and are connected in a toroidal shape. And the crown 6 of the carcass 2
In addition, a belt 7 and a tread 8 comprising at least one rubberized layer of steel cord (in FIG. 1, two rubberized layers 10, 11) are sequentially disposed.

In FIG. 1, the belt 7 is connected to the tire equatorial plane 3.
In this case, an intersecting belt is formed by superposing two rubberized layers 10 and 11 in which cords having an inclined arrangement are embedded so that the cords intersect with the tire equatorial plane 3 interposed therebetween. However, the number of rubberized layers constituting the belt, the arrangement angle of the cords, and the like can be appropriately changed as necessary.

The main features of the configuration of the present invention are as follows.
Optimizing the configuration of the carcass 2 and the carcass 2
Rubber layer 9 having predetermined physical property values and width between belt and belt 7
More specifically, the carcass 2 is composed of a single ply in which a steel cord is embedded, and the rubber layer 9 is disposed between the carcass 2 and the belt 7.
The rubber layer 9 has a physical property which is within the range of 2 / 5-6 / 5 times the 50% to 50% of rubber tensile stress constitutes a rubberized layer of the belt tensile stress, the belt width thereof W ₁ Rubberized layer 11 located at the bottom of rubberized layers 10 and 11 constituting 7
It is to in the 0.2 to 1.2 times the width W _2.

That is, the inventor of the present invention has proposed a steel cord having a large flexural rigidity, in place of the organic fiber cord generally used as a reinforcing element of the carcass 2, in order to impart sufficient exercise performance to a tire for a passenger car. Use, and
From the viewpoint of weight reduction, etc., the carcass is configured to be composed of one ply, and deterioration of fatigue resistance due to progress of material fatigue of the ply cord of the carcass 2 which has been regarded as a problem in the tire having such a configuration is considered. As a result of intensive studies on the means for improvement, the provision of a rubber layer 9 having a predetermined physical property value and a width between the carcass 2 and the belt 7 can improve the fatigue resistance. It has been found that the resistance can be reduced.

More specifically, as described above,
The steel cord in the carcass portion adjacent to the belt 7 usually undergoes compressive deformation when receiving a lateral force during steering of the vehicle, and the repetition of the deformation tends to cause fatigue of the material. In this case, the carcass ply is large. When a compression input is received, a buckling phenomenon easily occurs in the carcass portion also in the tire width direction, and as a result, cord breakage is likely to occur.
0.2 to 1.2 and between the belt 7, the width W ₂ of the rubberized layer 11
By disposing a rubber layer 9 having a width W ₁ is double, the rigidity of the whole is enhanced carcass part which is disposed so as belt 7, with ply cords of the carcass 2 is less likely to buckling Since the ply distortion can be alleviated, the fatigue resistance of the carcass 2 is greatly improved. Further, as the rubber layer 9, high modulus rubber, specifically, 50% tensile stress of the rubber layer is applied to the belt. 2/5 to 6/50 of the 50% tensile stress of the rubber constituting the rubberized layer of
By using a rubber having physical properties within the range of five times, the rolling resistance was successfully reduced.

Here, the 50% tensile stress of the rubber layer 9 is 2/5 to 50% of the 50% tensile stress of the rubber constituting the rubberized layer of the belt.
The reason why the width is set to be within the range of 6/5 is that if it is smaller than the above range, a difference in rigidity between the belt and the rubber constituting the belt becomes too large, which may cause a failure such as separation between the belt and the carcass. Not only that, the effect of the rolling resistance is also lost. On the other hand, if the rolling resistance is larger than the above range, the difference in rigidity between the rubber and the carcass ply becomes too large, and the separation (BLC) between the belt and the carcass, etc. This is because it causes a failure.

If the above-mentioned problem due to the difference in rigidity becomes significant, the 50% tensile stress of the rubber layer 9 is set to 1.5 to 3.6 MP.
More preferably, it is within the range of a.

[0022] In addition, the width W ₁ a rubberized layer 11 of the rubber layer 9
The was limited to 0.2 to 1.2 times the width W ₂ of, if smaller than the range, the effect of improving the fatigue resistance is not remarkable, whereas, even if larger than the above range, further the improvement This is because no further improvement can be expected, but only an increase in weight.

When the rubber layer 9 is composed of a plurality of divided rubber layers juxtaposed in the width direction, the width W ₁ of the rubber layer 9 means the sum of the widths of the divided rubber layers.

In addition, in the present invention, the physical properties of the rubber layer 9 are set to 50% instead of the usual 100% tensile stress.
The reason for expressing the tensile resistance in terms of% tensile stress is that when the strain is represented by 50%, the rolling resistance effect can be more clearly expressed than by the stress at the level of 100%. In other words, 100% tensile stress is used. This is because the rolling resistance cannot be sufficiently expressed with stress.

Various rubbers can be used for the rubber constituting the rubber layer used in the present invention. For example, it is preferable to use natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), etc. Among them, it is more preferable to use natural rubber and butadiene rubber. It is.

In addition, a compounding agent usually used in the rubber industry, for example, a reinforcing material such as carbon black, a vulcanizing agent, a vulcanizing aid, a vulcanization accelerator, an antioxidant, and a softening agent are required as rubber components. It is needless to say that they can be appropriately compounded according to the conditions. By adjusting the type and amount of carbon black, the amount of sulfur, the amount of oil, and the like with respect to the rubber, it is possible to obtain a rubber layer 9 made of rubber having a 50% tensile stress in the above-mentioned appropriate range.

The thickness t of the rubber layer 9 is 0.5 to 2.5 mm.
Is preferably within the range. The thickness t is 0.5 mm
If it is less than 2.5 mm, the effect of relaxing the strain is not sufficient, and if it exceeds 2.5 mm, the rolling resistance increases and disadvantages due to an increase in weight tend to occur.

The thickness t of the rubber layer is, as shown in FIG. 2, the thickness of the rubber covered by the carcass ply and the rubberized layer 11 located at the bottom of the rubberized layers 10 and 11 constituting the belt 7. Means the rubber thickness excluding the thickness of the covering rubber 11b.

In another embodiment, the steel cord constituting the carcass ply is 1 × N, 1 + N or 2 × N.
It preferably has a single twist or layer twist structure of + N (N: an integer of 2 to 7), and the value of N is more preferably an integer of 3 to 6. When N exceeds 7, the arrangement of the filaments is liable to be lost. As a result, the permeability of the matrix rubber into the inside of the steel cord is reduced, the uniformity as the cord is deteriorated, and a high breaking elongation is obtained. This is because it is not preferable because a problem such as difficulty in forming occurs.

The steel cord constituting the carcass ply has a filament diameter d of 0.125 to 0.250.
mm. The wire diameter d is 0.125
If it is less than mm, it is difficult to draw wire and it is difficult to obtain tensile strength.
This is because the strength of the cord tends to be insufficient and sufficient strength may not be obtained as a tire case member.
If it exceeds 25 mm, the fatigue resistance tends to deteriorate.

Further, the steel cord constituting the carcass ply preferably has an elongation at break of 3.5% or more, more preferably 4.0%, when taken out from the tire and measured. If the elongation at break is less than 3.5%, the steel cord itself is not preferable in terms of fatigue durability. As a means for producing a steel cord having a high elongation at break, for example, the molding amount may be increased with respect to the filament pitch length of the cord.

In addition, the belt 7 has two rubberized layers 10, 1
1 is preferable in order to exhibit the basic performance of the radial tire. In this case, the rubberized layers 10 and 11 are overlapped so that the cords 10a and 11a intersect each other with the tire equatorial plane 3 interposed therebetween. Is more preferable in the same point.

The above description is merely an example of the embodiment of the present invention, and various changes can be made within the scope of the claims.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the tire according to the present invention relating to steering stability, ply cord breakage and rolling resistance will be described. The tires of Examples 1 to 5 are pneumatic radial tires for passenger cars having a tire size of 225 / 60R16, and the structures of the carcass and the rubber layer are shown in Table 1. In each of the embodiments, the belts were constructed by using two rubberized layers as crossed belts, and the cords of each rubberized layer were arranged at an angle of ± 22 ° with respect to the tire equatorial plane and a twisted structure of 1 × 3. × 0.30, the number of shots was 31/5 cm, and the rest of the tire structure was substantially the same as a normal pneumatic radial tire for a passenger car.

For comparison, the number of carcass plies was two, and the tires of Comparative Example 1 using an organic fiber cord (PET cord) as a cord were not provided with a tire and a rubber layer, except that no rubber layer was provided. A tire of Comparative Example 2 having the same configuration as the tire, and a tire of Comparative Example 3 in which the width of the rubber layer and the value of the 50% tensile stress are out of the proper range of the present invention were also produced.

(Test method) For each of the above test tires,
The rim was mounted on a rim having a size of 6.5 JJ × 16, and the following tests were performed.

Driving stability Each of the test tires was placed on a rotary drum having an outer diameter of 3000 mm, and after a load of 400 kgf was applied to the tire, the tire was preliminarily run at a speed of 30 km / h for 30 minutes. After removal and readjustment of the internal pressure to 2 kgf / cm ² , a slip angle was continuously added up to ± 4 ° continuously on the rotating drum under the same speed and the same load. Next, the cornering force (CF) at each of the positive and negative angles was measured, and the following equation was obtained: CP (kgf / degree) = ｛CF (1 °) (kgf) + CF (2
°) (kgf) / 2 + CF (3 °) (kgf) / 3 + CF
The cornering power (CP) was determined at (4 °) (kgf) / 4 ° / 4, and the steering stability was evaluated based on the value of the CP. Table 1 shows the evaluation results. The numerical values of the steering stability in Table 1 are 10
It is shown as an index ratio when it is set to 0, and the larger the value, the better the steering stability.

Cord breakability in carcass ply Each of the above test tires was mounted on a passenger car, and the tire internal pressure was 2.0 kgf.
/ 40 km / cm ^{2 on a} general road
After reducing to kgf / cm ² , the vehicle was driven 30,000 km on a mountain slope. Thereafter, the tire was disassembled, and the presence or absence of a broken cord in the carcass ply at the position below the belt was examined.
Table 1 shows the evaluation results. In addition, in Table 1, when a code break is recognized, "Yes" is described, and when a code break is not recognized, "None" is described.

Rolling Resistance Each test tire adjusted to an internal pressure of 1.70 kgf / cm ² was placed on a rotating drum having an outer diameter of 1708 mm, and after applying a load specified by JIS standard D4202 based on the tire size and the internal pressure. , 80
Drive for 30 minutes at km / h and readjust the air pressure to 200km / h.
After the drum rotation speed is increased to the speed of h, the drum is coasted, and the moments of inertia of the drum and the tire until the drum rotation speed decreases from 185 km / h to 20 km / h are obtained, and the rolling resistance is calculated from the following equation. Was calculated. Rolling resistance _{= ds / dt (I D /} R D 2 + I t / R t 2) -
Drum single resistor, however, the I _D in the formula is the moment of inertia, I _t of the drum the moment of inertia of the tire, R _D is the drum radius, and R _t is the tire radius. In this test, the rolling resistance at 50 km / h was determined as a representative value. The measurement was performed in a room controlled at 24 ± 2 ° C. Table 1 shows the evaluation results. The numerical values in Table 1 are shown as exponential ratios from the following formula, and the larger the value is, the smaller the rolling resistance is, and thus the better the fuel economy performance is. Test tire index = 100 + 100 × {(representative value of tire of comparative example 1−representative value of test tire) / representative value of tire of comparative example 1}

[0040]

[Table 1]

From the evaluation results shown in Table 1, the tires of Examples 1 to 5 are all superior in steering stability and rolling resistance as compared with the tire of Comparative Example 1, and have the same ply as in Comparative Example 1. No code break was found. On the other hand, in Comparative Examples 2 and 3, the ply cord was broken, and the fatigue resistance was poor.

[0042]

According to the present invention, it has become possible to provide a pneumatic tire excellent in exercise performance and fatigue resistance and low in rolling resistance, particularly a pneumatic radial tire for a passenger car.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in the width direction of a pneumatic tire according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

[Explanation of symbols]

 Reference Signs List 1 pneumatic tire 2 carcass 3 tire equatorial plane 4 bead core 5 bead filler 6 carcass crown 7 belt 8 tread 9 rubber layer 10, 11 rubberized layer

Claims (8)

[Claims] 1. An air in which at least one belt made of a rubberized layer of a steel cord and a tread are sequentially arranged on a crown portion of a carcass made of plies which are locked by a pair of bead cores and are connected in a toroidal shape. In a tire with a car, the carcass consists of a single ply with a steel cord embedded, and a rubber layer is placed between the carcass and the belt.
Tensile stress is 50% of the rubber constituting the rubberized layer of the belt.
It has physical properties within the range of 2/5 to 6/5 times the tensile stress, and has a width (W ₁ ) of the rubberized layer located at the lowermost layer (W ₂ ) of the rubberized layer constituting the belt. ) 0.2-1.2
A pneumatic tire characterized by a factor of two. 2. The thickness (t) of the rubber layer is 0.5 to 2.5.
The pneumatic tire according to claim 1, which is in a range of mm. 3. The steel cord constituting the carcass ply is 1 × N, 1 + N or 2 + N (N: an integer of 2 to 7).
The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire has a twisted structure. 4. The steel cord constituting the carcass ply has a filament diameter (d) of 0.125 to 0.250.
The pneumatic tire according to claim 1, 2 or 3, which is in the range of mm. 5. The pneumatic tire according to claim 1, wherein the steel cord constituting the carcass ply has a breaking elongation of 3.5% or more. 6. The rubber layer according to claim 1, wherein the 50% tensile stress of the rubber layer is in the range of 2/3 to 5/3 times the 50% tensile stress of the rubber constituting the carcass ply. A pneumatic tire according to claim 1. 7. The rubber layer has a 50% tensile stress of 1.5 to 3.6 MP.
The pneumatic tire according to any one of claims 1 to 6, which is in the range of a. 8. The pneumatic tire according to claim 1, wherein the belt comprises two rubberized layers.