JP3484626B2 - Steel cord and tire radial tire for tire reinforcement - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord used as a reinforcing material for automobile tires and a steel radial tire using the steel cord.

In general, this type of steel cord is used as an automobile tire by covering a plurality of rubber cords in parallel with each other and covering them with a rubber material. The conditions required for the steel cord are, of course, excellent mechanical strength, good chemical and physical adhesion to the rubber material, and steel cord. It has good rubber penetration into the interior. That is, in order for the steel cord to sufficiently fulfill its role as a tire reinforcing material, it is necessary to form a complete composite with a rubber material having excellent mechanical strength.

[0003]

2. Description of the Related Art Conventionally, a typical example of a steel cord of this type is a two-layer twisted (3 + 6) structure steel cord. This (3 + 6) steel cord is formed by twisting three core wires together to form a core, as shown in FIG. 5, and twisting six side wires around the core wire to form a steel cord. Is forming. Since this steel cord requires two twisting steps, the productivity is low and the manufacturing cost is high. Also,
In the (3 + 6) steel cord, rubber hardly penetrates to the center of the three-strand core, and a void is apt to occur in the center of the core. Therefore, internal corrosion and fretting wear easily occur from that portion, and the life of the steel cord is considerably shortened. Further, since the cross section of the steel cord is substantially circular, the rubber sheet becomes thick even in tire design, the weight of the tire becomes heavy, and the riding comfort becomes poor.

Due to such drawbacks, a steel code having a 2/5 structure as described in Japanese Patent Application Laid-Open No. 9-31876 (and a procedure amendment filed thereafter) has recently been proposed. ing. This steel code is shown in FIG.
As shown in (a) and (b), two wires are used as core wires.
A staple made by twisting 5 wires together as a side wire.
A steel cord having a rucored shape in which the molding rate of the core wire is larger than that of the side wire and the cross section thereof is flat. And according to the specification, the following effects are described. Since there are two core wires, it has a structure in which no voids are formed in the core, excellent rubber penetration, and
Since the cross section is flat, it is possible to secure a sufficient spacing between the laying and arranging steps in the calendar processing process, and the rubber sheet
Many books can be lined up on top of each other. Further, in a tire, fretting does not occur, code integrity is improved, and twisting of the wire is less likely to occur. For this reason, the warpage of the rubber sheet does not substantially occur.

However, according to the fact that we made a prototype of this steel code and confirmed the effect, the following problems became clear. Since the type ratio of the core wire is large,
Since the low load elongation when the steel cord is pulled under a low load is too large, the calendar process work in tire production is hindered. For example, when this steel cord is used, it is necessary to pull the steel cord with an extremely low load in the calendar process, and it is difficult to control the tension. In the calendering process in which the tension is excessively high, when the sheet is cut thereafter, the steel cord shrinks, causing a problem that the length of the steel cord becomes shorter than that of the rubber sheet. In addition, since the flatness (minor diameter T / major diameter W) of the steel cord cannot be reduced because the core wire has a large dimensional ratio, the thickness of the rubber sheet cannot be reduced. Since the position of the core wire is not stable, the twisting of the cord is unstable and it is inferior to twisting and buckling.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a steel cord which eliminates various drawbacks of the conventional steel cord as described above, and a tire using the steel cord. The present invention aims to improve the safety, steering stability, riding comfort, cornering performance, economy, etc. of an automobile.

[0007]

In order to achieve the above object, the steel cord for tire reinforcement of the present invention is 0.15.
5 having a wire diameter of 0.34 mm to 0.40 mm with two wires having a wire diameter of mm to 0.25 mm as core wires
A steel cord in which two strands are used as side strands and twisted together in the same direction at a time, and their cross sections are substantially elliptical (long diameter W, short diameter T) with substantially the same orientation in the longitudinal direction. In a tire reinforcing steel cord, two core strands are twisted substantially in contact with each other, and a part of adjacent side strands of five side strands are twisted with a space therebetween. When the books are arranged in a line in the major axis direction of the cross section of the cord, they are present so as to be surrounded by the five side strands, and two core wires are substantially aligned in the major axis direction of the cross section of the cord. One of them when lined up vertically
The one core wire is in contact with the inside of one side wire, and the other core wire is arranged so as to be interrupted between the other two side wires. The flatness (percentage of T / W) is 65% to 88%.

The steel radial tire of the present invention is
A steel radial tire reinforced by a steel cord in which a plurality of strands are twisted together, the steel cord comprising:
Are the same, with two strands having a wire diameter of 0.15 mm to 0.25 mm as core strands and five strands having a wire diameter of 0.34 mm to 0.40 mm as side strands. A steel cord for reinforcing a tire, which is a steel cord twisted in one direction at a time, and whose cross-sections have substantially the same direction in the longitudinal direction and a substantially elliptical shape (major axis W, minor axis T). The two core wires are twisted in a substantially contact manner, a part of the adjacent five wires of the side wires are twisted with a space, and the two core wires are twisted in the major axis direction of the cross section of the cord. When the two core wires are lined up substantially vertically in the major axis direction of the cross section of the cord, one of them is surrounded by five side wires. The core wire is in contact with the inside of one side wire, and the other core wire is placed between the other two side wires. And which, moreover aspect ratio of the substantially elliptical shape (percentage of T / W) is characterized in that 65% to 88%.

The twist pitch of the steel cord is preferably about 5 to 20 mm for the reason described below. Moreover, it is preferable to use the core wire and the side wire having the same wire diameter.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 (a) and 1 (b) are schematic views showing an example of the steel code of the present invention and showing a cross section thereof. In this steel cord, two core element wires 1 having a wire diameter of 0.175 mm or 0.20 mm are substantially in contact with each other and twisted together, and five side element wires 2 having a wire diameter of 0.370 mm are adjacent to each other. A part of the wire is twisted with a gap. It is composed of two core wires 1 having a so-called molding rate of about 100% and five side wires 2 having a molding rate of more than 100%. Since the two core strands are twisted in close contact with each other at a shaping rate of about 100%, the low load elongation when the steel cord 3 is pulled under a low load is low. 5 side wires 2
Since there are voids between them, rubber can easily penetrate into the inside of the steel cord.

The core wire 1 has a diameter of 0.15 mm to 0.
It is desirable that the range is 25 mm. This is because if it is thinner than 0.15 mm, sufficient strength cannot be obtained, which is also disadvantageous in terms of cost. If it is thicker than 0.25 mm, the flexibility is poor, and the code diameter becomes large, resulting in a thick rubber sheet. The diameter of the side wire 2 is 0.34 mm
The range of 0.40 mm is desirable. If it is thinner than 0.34 mm, the strength is weak, and it is necessary to increase the number of strands to obtain sufficient strength. If it is thicker than 0.40 mm, the flexibility is poor, the fatigue value is low, the voids between the strands are small, and the rubber penetration is poor.

Further, the core wires 1 are twisted in a manner that they are in close contact with each other, and the cross section of the cord is substantially the same direction in the longitudinal direction and has a substantially elliptical shape. With respect to the major axis direction of the rudder cross section, it may be arranged in the same direction or in a vertical direction. When arranged in the same direction, the two core wires 1 are present so as to be surrounded by the five side wires 2. When aligned in the vertical direction, one core wire is in contact with the inside of one side wire, and the other core wire is arranged so as to be interrupted between two side wires on the opposite side. ing.

Therefore, the twisted shape is stable, and
It is possible to reduce the flatness (minor axis T / major axis W) in the cross section of the groove. Here, when the core wire is cut between the side wires, as shown in FIG. 2, the core wire is crossed over a so-called center line A connecting the centers of the cross sections of the two side wires 2. It means that 1 penetrates in the meantime. When flatness (minor axis T / major axis W) decreases, rubber seal
The tire can be made thinner and the weight of the tire can be reduced.

The flattening ratio (minor axis T / major axis W) of the substantially elliptical shape in the cross section of the steel cord is set to 65% to 88% when it is less than 65%. In the structure, twisting becomes unstable, and at the same time, bending of each wire at the end of the long diameter becomes tight, and the workability of handling is poor and the fatigue resistance is poor. If it exceeds 88%, the cross section approaches a perfect circle, so the effect of the present invention cannot be expected. Also, 65% to 88
In the range of%, when the core wires are aligned in the direction perpendicular to the major axis of the cross section, the core wires are cut between the two side wires, so the core wires do not fall out and the shape is stable. To do.

The twist pitch of the steel cord is 6 mm.
28 mm is preferable. The reason for this is that if the length is less than 6 mm, the amount of bending work becomes extremely large, so that wire breakage is likely to occur, and the number of twists per length of the steel cord increases, resulting in a decrease in productivity. On the other hand, if the twist pitch of the steel cord exceeds 28 mm, the steel cord
Because the flexibility of the cord is lost, the fatigue value becomes low, the twist becomes unstable, and flare easily occurs, which is not practical.

In the steel cord of the present invention, two core wires and five side wires are twisted together at one time, but a preset habit is applied to each of the core wires and the side wires, Manufactured by making the tension of the side strands weaker than the tension of the core strands and twisting them so that they extend a little longer, then passing between rollers with a flat surface, and applying a fairly strong compression process. It is possible.

The steel cord of the present invention can be manufactured by a tuber type twisting machine, but it is more efficient and practical to manufacture it by a buncher type twisting machine. When using a buncher type stranding machine, the strands are twisted, so it is easy to attach it in advance and the finished steel coil
It is necessary to take that into consideration because the behavior of the do is different.

When the tire steel cord having the above structure is used and sandwiched between two rubber sheets to perform pressure vulcanization, the steel cord is applied even if a slightly strong tension is applied to the steel cord. -There is no phenomenon that the cord extends and the gap between the strands disappears, the rubber penetration deteriorates, and the post-calender steel cord shrinks. Then, the rubber completely penetrates into the steel cord to form a stable composite of the steel cord and the rubber. At this time, the steel cords are buried in a horizontal direction with respect to the horizontal direction of the steel cord with respect to the horizontal plane of the sheet, and the steel cords are arranged in a line in the longitudinal direction. The cross section of the steel cord has a stable shape, and since the flatness is small, the thickness of the rubber sheet can be reduced, which contributes to the weight reduction of the tire. Furthermore, the bending rigidity is higher in the left-right direction than in the up-down direction, increasing the rigidity in the width direction of the belt,
Lateral rigidity of the tire is increased, cornering characteristics and steering stability are improved.

[0019]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a schematic view showing a cross section of a steel cord of the present invention. FIG. 1 (a) shows the case where two core wires are arranged substantially vertically in the major axis direction of the cross section of the cord, and FIG. 1 (b) shows the case where they are arranged substantially in a line in the major axis direction.

In order to evaluate the characteristics of the steel cord of the present invention, as shown in Table 1 below, the number of core strands M, the number of side strands N, the twisting pitch P (mm), the molding rate of the core strands,
Examples 1 and 2 of the steel cord in which the shaping ratio of the side wire, the short diameter T (mm) and the long diameter W (mm) of the elliptical cross section of the steel cord are changed within the scope of the present invention, respectively, and FIG.
Conventional example 1 of 3 + 6 steel cord as shown in FIG.
2 / having a cross-sectional shape as shown in FIGS.
A conventional example 2 of steel cord having 5 configurations was manufactured. Then, with respect to each of these steel cords, rubber penetration rate, fatigue resistance, shrinkage margin of the cord, rigidity ratio, workability during tire production, and workability during cord production were evaluated, and as shown in Table 2 below. I got the result. The test conditions and evaluation methods for each item shown in Table 2 are as follows.

Rubber penetration rate: Each steel cord was embedded in rubber in a state where a tensile load of 4 kg was applied and vulcanized, and then the steel cord was taken out from the rubber and the steel
The cord was disassembled and a certain length of the strand was observed, and the ratio of the length with the trace of contact with rubber to the observed length was expressed in%. In the table, the larger the value, the better the rubber penetration rate.

Fatigue resistance: Three-point pulley using a composite sheet in which a plurality of steel cords are embedded in a rubber sheet.
Tested with a bending fatigue tester, the number of repetitions until the embedded steel cord was broken due to fretting wear, buckling, etc., was determined, and the twist structure of Conventional Example 1 was used.
The value of the rucode was set to 100 and displayed as an index. In the table, the larger the value, the better the fatigue resistance.

Shrinkage margin of code: About 100 steel cords are arranged in parallel at intervals of 2 mm and embedded in a rubber sheet to prepare a composite sheet having a width of 20 cm and a length of 2 m. Cut the steel cord at both ends. If the steel cord is greatly extended, the length of the steel cord will be greatly reduced after cutting. In that case, the percentage of the contracted length of the steel cord and the length of the rubber sheet was used as the contraction allowance of the cord.

Stiffness ratio: As shown in FIG. 3A, "5 steel cords have a 100% modulus of 35 kg /
The rubber sheet 11 having a size of cm ² was embedded in a line so that the major axis of the steel cord cross section was in a horizontal direction. "Test piece 12 and" 5 pieces "as shown in FIG. 3 (b). 4 was embedded in parallel with the rubber sheet 11 so that the major axis of the cross section of the steel cord was vertical. "A test piece 13 was manufactured and shown in FIG. As described above, the test pieces 12 or 13 are mounted on a three-point bending tester with a span Sp = 20 mm, and "weight G when the test piece 12 is pressed down by 5 mm" / "test piece 1".
The weight ratio G when 3 was pressed down by 5 mm was defined as the rigidity ratio.

That is, the rigidity ratio of "the bending rigidity of the steel cord in the minor axis direction" / "the bending rigidity of the steel cord in the major axis direction" was defined as the rigidity ratio. In the table, the smaller the value, the difference in bending rigidity. The conventional example 1
Since there is no major axis or minor axis in the rucode, the rigidity ratio is 1.00. The test piece 12 or 13 has a thickness of 4 mm, a width of 15 mm and a length of 100 mm.

Workability during cord production: Good workability and productivity in the wire feeding, twisting and winding operations in the twisting process of the steel cord production, and ◯ are bad. The ones were marked with x, and those in the middle were marked with Δ. Handling workability at the time of tire manufacturing: In the handling work of the tire manufacturing process, those with good workability and productivity in each work such as feeding of steel cord, calendar, calendar cut, tire molding, and vulcanization ◯, defective ones were marked x, and intermediate ones were marked.

[0027]

[Table 1]

[0028]

[Table 2]

The following points are apparent from Tables 1 and 2. In Conventional Example 1, three core wires having a wire diameter of 0.20 mm are twisted into a Z-twist at a twist pitch of 10.0 mm, and six side wires having a wire diameter of 0.35 mm are twisted around the core wire with a twist pitch of 18. 0m
It is a steel cord twisted into an S twist at m. Z /
It is a steel cord with a perfect circular cross section that is twisted into S twist and closed twist. It has excellent shrinkage of the code and handling workability during tire manufacturing, but rubber infiltration. Is poor in fatigue resistance and rigidity ratio.
Two-step work of twisting and S twisting, resulting in poor productivity.

In the conventional example 2, two core element wires having a wire diameter of 0.175 mm and five side element wires having a wire diameter of 0.35 mm are twisted at a twist pitch of 18.0 mm at a time in an S twist to form a core element. The wire patterning rate is 133%, the side wire patterning rate is 115%,
The flatness is 80%. This steel cord is excellent in rubber penetration, fatigue resistance and rigidity ratio,
The code has a large shrinkage margin and is inferior in handling workability during tire production and code production.

The steel cords of Examples 1 and 2 do not have the above-mentioned drawbacks and are excellent in any of the characteristics. When used in tires, the steel cords are deformed in response to the force from the road surface. It's comfortable and has good cornering characteristics.
Tires are not easily deformed when cornering.

[0032]

Since the steel cord for tire reinforcement and the steel radial tire of the present invention are constructed as described above, they have the following effects. 1) Since the molding rate of the core wire is set to be smaller than that of the side wire, the elongation of the steel cord under a low load is small, and the deformation or damage of the take-up reel wound with the steel cord is prevented. There are few, and workability is good. 2) In the calendering process in tire manufacturing, even if a little tension is applied to the steel cord to pull it, the steel cord does not grow much, and the steel cord does not deform or shrink, resulting in excellent tire quality and workability in manufacturing. . 3) The flatness of the cross section of the cord (minor diameter T / major diameter W) can be made smaller than that of the conventional steel cord, and the rubber sheet thickness when embedding in rubber to form a sheet further reduces the tire. It is possible to reduce the weight, reduce tire costs, and improve automobile fuel efficiency. 4) Since the core wire has a structure in which it is cut between the side wires at a 1/2 pitch interval, the core wire does not fall out. 5) By reducing the flatness and lowering the rigidity in the tire rotation direction, the riding comfort is improved, while the rigidity in the direction orthogonal to the tire rotation direction can be increased, so the cornering performance can be improved. 6) The arrangement of the two core wires and the five side wires is very stable, and the rubber penetration into the inside is very good and the fatigue resistance is also good. 7) It can be manufactured with both conventional tubular type and buncher type stranding machines, and troubles such as twisting defects are reduced and handling workability is excellent.

[Brief description of drawings]

FIG. 1 shows an example of a steel cord for reinforcing a tire of the present invention. It is the schematic which shows the cross section of 2/5 structure.
(A) is when two core wires are arranged substantially vertically in the major axis direction of the cross section of the cord, and (b) is when the core wires are aligned substantially in the major axis direction.

FIG. 2 is an explanatory diagram illustrating a case where a core wire 1 is cut between side wires 2.

FIG. 3 is a view showing a test piece used for a three-point bending test, (a) is a schematic view of a test piece for measuring bending rigidity in a minor axis direction, and (b) is a measuring piece for bending rigidity in a major axis direction. It is a schematic diagram of a test piece of.

FIG. 4 is an explanatory diagram showing a three-point bending test method.

FIG. 5 is a cross-sectional view of a conventional steel cord having a close twisted 3 + 6 structure.

FIG. 6 is a sectional view of a conventional steel cord having a 2/5 structure.

[Explanation of symbols] 1 ... Core wire 2 ... Side wires 3 ... Steel code 11 ... Rubber sheet 12, 13 ... Test piece W: major axis of steel cord cross section T ... Short diameter of steel cord cross section A: Center line

Claims (2)

(57) [Claims] 1. A core wire comprising two wires having a wire diameter of 0.15 mm to 0.25 mm, and 0.34 mm to 0.40.
Five strands having a wire diameter of mm are used as side strands, and these strands are twisted together in the same direction at a time, and their cross sections have substantially the same direction in the longitudinal direction and a substantially elliptical shape (long diameter W, short diameter T). In the steel cord for tire reinforcement configured as described above, the molding ratio of the core wire is set to be smaller than the molding ratio of the side wire, and the two core wires are twisted so as to be substantially in contact with each other. Part of adjacent strands are twisted together with a space, and when two core strands are aligned in a line in the major axis direction of the cross section of the cord, they are internally surrounded by five side strands. However, when two core strands are arranged substantially vertically in the major axis direction of the cross section of the cord, one of the core strands contacts the inside of one side strand and the other core strand. Is arranged so as to be interrupted between the other two side strands, and has the substantially elliptical flat shape. (Percentage of T / W) 65% to 88
% Steel cord for reinforcing tires. 2. A steel radial tire reinforced by a steel cord in which a plurality of strands are twisted together, the steel cord comprising two strands having a diameter of 0.15 mm to 0.25 mm. As a core wire, 0.34 mm ~
It is a steel cord in which five strands having a wire diameter of 0.40 mm are twisted at once in the same direction as side strands, and their cross sections have substantially the same direction in the longitudinal direction and a substantially elliptical shape (major axis W , A steel cord for tire reinforcement having a short diameter T), two core strands are twisted substantially in contact with each other, and a part of adjacent side strands of five side strands are twisted with a space. When two strands are arranged in a line in the major axis direction of the cross section of the cord, they are present so as to be surrounded by five side strands, and two core strands are substantially perpendicular to the major axis of the cross section of the cord. When they are lined up in a line, one of the core wires is in contact with the inside of one side wire, and the other core wire is placed between the other two side wires. And the flatness (percentage of T / W) of the above-mentioned substantially elliptical shape is 65% to 8
Steel radial tire characterized by 8%.