JPS5847364B2 - Radial tires for passenger cars - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to improve the handling performance of a radial tire for a passenger car, maintain ride comfort, and reduce the weight of the tire.

Among radial tires, those with steel cord belts have good C-P (cornering power) characteristics and excellent maneuverability, but they have problems with ride comfort.
On the other hand, it is well known that a vehicle having an organic fiber cord belt has excellent riding comfort, but has a problem in C-P characteristics.

Therefore, various attempts have been made to obtain tires that combine the advantages of both.

For example, a steel cord belt is used to absorb the impact vibrations generated when the belt runs over uneven road surfaces with a buffer layer provided at the bead, and a reinforcing layer made of rubber containing short fibers is used for an organic fiber cord belt. A contact method has been proposed.

However, each of these methods increases the manufacturing process, resulting in higher costs, and increases in tire weight cause fuel consumption to rise, and the drawbacks are that they do not meet the objectives of cost reduction and energy conservation. It was said that

In view of these circumstances, the present invention provides excellent maneuverability and ride comfort while simplifying the manufacturing process.
Tire weight reduction was once invented to provide a new radial tire for passenger cars that could achieve its intended purpose, and in particular, it consisted of one layer of steel cord ply and at least one layer of organic fiber. The belt layer is characterized by the fact that the belt layer is formed by polymerizing cord plies under a specific cord angle relationship.

The contents of the present invention having such characteristics will be explained in detail below with reference to the drawings.

Considering the handling performance characteristics of pneumatic tires, tires with high bending rigidity around the vertical axis within the tire contact patch will prevent the tire from deviating from the traveling trajectory due to centrifugal force when the vehicle turns. It has a large effect on keeping the
Therefore, it is said to have good maneuverability.

The force at this time is quantitatively expressed as CP (cornering power).

On the other hand, in terms of ride comfort, tires with low bending rigidity in the thickness direction that allow the tread surface to easily deform along the uneven shape when the tire runs on a stone or the like have good ride comfort.

Compared to bias tires, radial tires have a belt layer in which steel cords are intersected at a small angle to the circumferential direction. Although it has excellent performance, it is inferior in terms of ride comfort.

On the other hand, a radial tire having a belt layer in which organic fiber cords such as rayon or polyester are arranged has an intermediate performance between the above-mentioned steel radial tire and the above-mentioned bias tire.

This can be easily understood by referring to the tensile modulus in the table of cord characteristics for each belt below.

In order to increase the rigidity of the belt layer used in tires, it is sufficient to increase the tensile rigidity in the circumferential direction of the tire and the shear rigidity against lateral deformation.Tensile rigidity and shear rigidity vary greatly depending on the cord arrangement angle, and the cord arrangement angle The tensile stiffness and shear stiffness tend to be inversely correlated, and taking both into consideration, a practical range of 10 to 300 is considered.

Further, the rigidity of the belt increases as the width increases, and in particular, it is necessary to increase the width of the steel cord belt ply, which has a high elastic modulus, and the width is preferably 80 to 100% of the tread width.

It is known that if the steel cord belt ply width is less than 80%, the cornering power will be small, and if the width is more than 100%, the belt ply reaches near the side of the tread rubber at the end of the belt fly, so cracks are likely to occur on the side of the tread rubber.

Based on this theoretical background, the radial tire according to the present invention is produced by polymerizing one layer of steel cord ply and at least one layer of organic fiber cord ply having an organic fiber cord such as polyester, vinylon, or polyamide. By forming a belt layer using the carcass ply 5, which is fixed to a pair of bead cores 7, as shown in FIGS. An annular belt layer 3 inserted between the central part of the belt and the tread rubber 6 is connected to a one-layer rubber-attached steel cord ply 1 with a cord angle of 300 or less, and the ply 1 has a cord angle of 30 degrees or less where the cords intersect. It is formed by polymerizing with one layer of rubber-coated organic fiber cord ply 2.

Based on this theoretical background, the radial tire according to the present invention is produced by polymerizing one layer of steel cord ply and at least one layer of organic fiber cord ply having an organic fiber cord such as polyester, vinylon, or polyamide to form a belt. By shaping the layer, it is intended to improve both the maneuverability and ride comfort, and as illustrated in FIGS. The annular belt layer 3 inserted between the central part of the belt and the tread rubber 6 is
The shape is formed by polymerization of a layer of rubber-coated steel cord ply 1 and one layer of rubber-coated organic fiber cord ply 2 having a cord angle of 300 or less where the cords intersect.

The Kerr force sply 5 is a normal Kerr force sply 5 having a cord having a cord angle of approximately 90°.

However, the tires shown in both figures have a C
- Although the P properties are further improved, the example shown in Figure 1 shows the rubber-coated organic fiber cord ply 2 which is closer to the Kerr force sply 5.
The belt layer 3 is made of a material that is wider than the rubberized steel cord ply 1, and its both ends are folded to an appropriate length along the corresponding side edges of the rubberized steel cord ply 1, and the belt layer 3 is tightly attached. On the other hand, in the example shown in the second figure, reinforcing rubber 4 made of compound rubber having higher hardness than the rubber of the organic fiber cord ply 2 is brought into contact with both ends of the belt layer 3. , also belt layer 3
It has a reinforced structure at the ends.

A radial tire with such a structure has approximately the same ride comfort as a tire whose belt layer is made up of only organic fiber cord, but its handling performance is approximately the same as that of a tire whose belt layer is made up of only steel cord → 1. As a result of the comparative measurements described later, it became clear that the two were equivalent.

In addition, a normal belt using organic fiber cord for the belt layer is composed of four ply layers, and a belt using steel cord is composed of two ply layers, but the tires of both examples mentioned above are Since it is composed of 11 layers of steel cord ply and 21 layers of organic fiber cord ply, the weight of the belt is significantly reduced, and it goes without saying that this contributes to a reduction in the weight of the tire.

By the way, when considering the strength of a tire, the carcass ply bears the burden in the radial direction, and the belt layer 3 bears the burden in the circumferential direction. Since there is no big difference in the physical properties of the belt ply, there is no need to perform strict calculations regarding the strength. If
If the arrangement angle of the cord is not calculated precisely, stress may concentrate on one side and the cord may break.

In order to share the strength between the two crossed cord ply layers, consider the belt as a laminate of unidirectional reinforced sheets, make the composite tensile modulus of elasticity in the circumferential direction of the tire approximately the same, and apply tension equally to both layers. It is desirable to do so.

Various theoretical formulas have been proposed for the relationship between the cord angle and the composite modulus of unidirectionally reinforced sheets, but all of them are complex formulas that require the help of an electronic computer, and are difficult to understand unless you have specialized knowledge. There are difficulties in handling it freely, and complete agreement with actual measured values has not been obtained.

After carefully examining these conventionally known formulas, we found that
The inventors of the present invention have found that the following approximate formula is relatively consistent with the actual measured values. Using this approximate formula, the composite modulus of elasticity of the ply in the belt layer 3 can be easily calculated, and the desired purpose can be achieved. Radial tires can now be easily determined at the design stage.

In order to prove that the value calculated using the above calculation formula is appropriate, a steel cord with a structure of 1 x 4 pieces x 0.22% was made into 2 2 pieces/2 5.4 mm ends, and the tensile elasticity Rate l. Composite elastic modulus Es of a rubberized steel cord ply with a thickness of 1.1 embedded in 5 kg//nfL rubber and a 1500 denier/3-strand polyester cord with an end count of 17/25.4 Elastic modulus lv! The relationship between the composite elastic modulus Et and the angle of the organic fiber cord ply with rubber embedded in the rubber of A and having a thickness of 1.3 was compared between the calculated value using the above formula and the actual measured value, as shown in Figure 3. The results shown are obtained, and it is clear that the calculation formula is suitable for obtaining approximate values.

However, when we investigated the characteristics of a belt layer in which each ply of steel cord and organic fiber cord was cross-arranged, we found that by making logEs and logEt approximately the same size, we could increase the strength to resist tension in the circumferential direction. It has been found that a belt with high strength can be obtained by appropriately dividing the parts and making effective use of a small amount of material.

In this case, the ratio of logEt to logEs is 0,
It has become clear that a range of 85 to 1.15 is desirable.

At both ends of the belt, the net structure formed by the crossing of the cords does not work effectively, and there is a so-called drop in rigidity at the ends of the belt, and the effective width of the belt is narrower than the actual width of the belt. Become.

Therefore, as shown in Figs. 1 and 2, by folding back the organic fiber cord ply to reinforce the belt end or by reinforcing the belt end with hard rubber, the effective belt width can be increased and the handling performance can be improved. Cornering power characteristics are improved.

If we consider a normally used belt ply with a width of 120 mm as a unidirectional reinforcing sheet and calculate the width that does not work effectively, there is a portion of about 15% of the total width at each end, and therefore about 2 It is preferable to overlap by double the amount, 20 to 30%, by folding.

On the other hand, a preferable result was obtained in which the reinforcing rubber at the end of the belt has a JIS hardness of 5 degrees or more greater than the rubber embedded in the organic fiber cord.

Next, as examples of tires of the present invention, we will list several types of radial tires using a belt layer consisting of one layer of steel cord ply and one layer of organic fiber cord ply, and compare the performance with comparative tires. It is as follows.

If the steel cord ply and the adjacent organic fiber coated ply have approximately the same composite modulus in the circumferential direction, one additional layer of organic fiber cord ply may be added in the same direction as the organic fiber cord. The above additions are naturally included within the scope of the present invention.

Example 1 Tensile modulus 1 6. 6 8 0 '9/,, i steel cord with a tensile modulus of elasticity of 1.22 ends/25.4 mm. A rubber-coated steel cord ply 1 with a width of 120 mm, which is buried in rubber of 5 kg/n, 4 so that the cord volume ratio is 0.18 and arranged so that the cord angle is 200, has an elastic modulus of 800. kg/n,j polyester cord with a ratio of 17 ends and 725.4 mm to rubber with an elastic modulus of 0.8 and a hardness of 65 (JIS).
The volume ratio of the cord is 0. Rubber-attached polyester cord ply 20 was buried so that the angle was 2 5 9 and the cord angle was 13° in the opposite direction to the steel cord. Both ends were folded back by 30 mm, and the belt was brought into contact with the steel cord ply 1 so as to wrap around both ends. A radial tire in which layer 3 is arranged between carcass ply 5 and tread rubber 6 (
Size 165SR13, tread width 130mm).

(Same size for each example below) Example 2 The same belt ply as used in Example 1 was used as the material, but the cord angle of the polyester cord was 17°,
A radial tire that differs from Example 1 in that the folded width is 25 mm.

Example 3 Using the same belt ply as used in Example 1, a steel cord ply 1 with rubber was arranged at a cord angle of 15°, and a polyester cord ply 2 was placed on top of it at a cord angle of 15°. A radial tire with a belt structure in which reinforcing rubber 4 with a JIS hardness of 75 degrees is brought into contact so as to cover both ends of the belt layer 30 arranged, Comparative Example 1 Rubber using the same belt ply material as used in Example 1 A tire having the same structure as Example 2, except that the attached steel cord layer was placed on the steel cord layer with a cord angle of 25 degrees, and the rubber attached polyester cord layer was placed on the steel cord layer with a cord angle of 15 degrees.

Comparative Example 2 The rubberized polyester cord layer used in Example 1 was
A conventional tire has belt layers formed by laminating alternate layers so as to intersect with each other at a cord angle of 20°.

Comparative Example 3 Conventional tire with a belt layer in which the two rubber-attached steel cord layers used in Example 1 were laminated so that the cord angles were 20 degrees in opposite directions, test method Maneuverability: US automobile technology Society standards (Socie
-ty of Automotive Engine-
neers) SA. According to the method described in E-J 1 1 0 6, internal pressure 1.9 kg / 611 yen load 42
The cornering power (C-P) was measured at 0 kg and a slip angle of 2°, and the conventional tire (comparative example 2) was expressed as an index with the conventional tire (comparative example 2) set as 100. Ride comfort. The road surface with a triangular prism attached perpendicular to the direction of travel of the vehicle was 50"/ Measure the amplitude of vertical vibration when passing at a speed of After testing, the tire is disassembled and inspected for cord breakage.

○ for cords with no cord cutting; ○ for cords with cord cutting. is displayed as ×.

As a result of these experiments, when the cord angles of the steel cord and organic fiber cord were set so that the value of logEt/1ogEs was approximately in the range of 1.0±0.15, the maneuverability increased by 1logEt/logEs. However, ride comfort slightly decreases.

However, the ride comfort was found to be as good as the best conventional tires.

As is clear from the detailed description above, the present invention has two layers of steel cord ply that contribute to improving cornering characteristics, and at least one layer of organic fiber cord ply that contributes to maintaining ride comfort. It is possible to provide an excellent radial tire for passenger cars that can fully demonstrate the following.

Moreover, since the steel cord ply is only in the L layer,
Significantly reducing the weight of the belt and the overall weight of the tire has played a significant role in improving fuel efficiency.

On the other hand, in terms of tire manufacturing, the tire product cost can be reduced because it can be easily and efficiently mass-produced without modifying the general radial tire manufacturing process.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views showing the left half of each example of the tire of the present invention, and Figure 3 is a comparison between actually measured values and calculated values of the relationship between the cord angle and composite modulus of the belt layer used in the tire. It is a line diagram shown in . 1... Steel cord ply with rubber, 2...
...Organic fiber cord ply with rubber, 3...Belt layer, 4...Reinforcement rubber, 5...Ker force sply, 6...Tread rubber ,7...
...Bead core.

Claims (1)

[Scope of Claims] 1. A carcass ply having a cord angle of approximately 900 and having both ends fixed to a pair of bead cores, and a belt layer between the tread rubber and the belt layer. One layer of rubberized steel cord ply with a cord angle of 300 or less,
This steel cord ply is formed by polymerization with at least one rubber-coated organic fiber cord ply having an intersecting cord angle of 30 degrees or less, and has a composite modulus of elasticity in the tire circumferential direction for each cord ply of the belt layer.
is determined by the following formula, and the rubber A radial tire for a passenger car characterized by having a set cord angle of an attached organic fiber cord ply. 2. The radial tire for a passenger car according to claim 1, wherein the belt layer has both ends of the rubberized organic fiber cord ply folded back to reinforce both ends of the belt layer. 3. The radial tire for a passenger car according to claim 2, wherein the folded portion of the rubber-attached organic fiber cord ply has a width of 20 to 30% of the width of the belt layer. 4. Claim 1, wherein the belt layer has reinforcing bodies made of compound rubber that is at least 5 degrees higher in JIS hardness than the rubber of the rubber-attached organic fiber cord ply, in contact with both end portions of the belt layer. Radial tires for passenger cars as described in section.