JPH09209283A - Steel cord for reinforcing rubber and radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord for reinforcing rubber, excellent in rubber permeability and rigidi'ty, suitable for reinforcing a belt part of a radial tire, by twisting plural wires having a very small wave shape in the same direction in the same twisting pitch at one time. SOLUTION: Before wires 1-5 taken out from supply bobbins are introduced into a buncher type twisting machine, the wires are provided with provided with a spiral very small wave shape 100 smaller than the twisting pitch of a cord. The 3 6 wires or the 7-19 wires are twisted in the same direction in the twisting pitch at one time to give the objective steel cord for reinforcing rubber in which both parts in which the wires 1-5 are not mutually crossed and adjoined in parallel to form gaps (s) and parts in which the wires 1-5 are crossed in the frequency of 0.5-4.0 times or 0.5-15 times per pitch P of the cord coexist in the length direction of the cord, which has an elliptical cross-section having the ratio of major axis/minor axis of 0.60-0.90 and the relationship of the very small shape 4p, the wave height (h) and the wire diameter (d) satisfying 1.05<=h/d<=1.50 and 0.25<=hp/P<=0.55.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a steel cord for reinforcing rubber products such as automobile tires and conveyor belts for transportation, and radial tires.

[0002]

Steel cords are used to reinforce the tread portion of radial tires for passenger cars, and to reinforce the tread portion and carcass portion of radial tires for trucks and buses. For the tread reinforcement (belt part) of passenger car tires, steel cords of 1 × n structure in which three to five strands are twisted together have been conventionally used as shown in FIGS. 1 (a) and 1 (b). It was However, in the steel cords of these structures, since there is no gap between each of the strands that make up the cord, rubber does not penetrate to the center of the cord during vulcanization during tire manufacturing, and Leaves voids that are not filled with rubber. For this reason, if the tire steps on a piece of metal during running and receives damage that reaches the steel cord, moisture will penetrate into the cord from this scratch and it will travel through the void in the center of the steel cord that is not filled with rubber. Will end up. As a result, the rust of the steel cord in the tire also spreads, the deterioration of the steel cord and the adhesion with rubber also deteriorate, and a so-called separation phenomenon occurs, which causes a decrease in tire performance as a composite and a remarkable decrease in life. there were.

As a countermeasure against this, as shown in FIG. 2, a steel cord having an open structure in which each element wire is twisted loosely has been used. However, even in this steel cord, if tension is applied to the cord during rubber vulcanization during tire production, there is a problem that the gap between the strands of the cord is narrowed and the penetration of rubber is insufficient. Therefore,
Further, as shown in FIGS. 3 (a) and 3 (b), a steel cord having an open-twisted structure and having a substantially elliptical cross section has been proposed. However, even such a steel cord has the following problems. (1) Compared to the steel cord in Fig. 2, when the tensile force is applied, the gap between the strands is less likely to become narrower, but it is not perfect yet.
A portion having such a cross-sectional shape is likely to occur, and rubber does not penetrate into this portion, so that stability or certainty of rubber permeability is insufficient. (2) Since the center of the steel cord has an elliptical shape with no strands, the major axis tends to be large, and the number of steel cords to be driven in when forming into the reinforcing layer of the tire should be smaller than that of a normal circular-section steel cord. There is a case inevitably, and in this case, there is a drawback that the strength of the reinforcing layer is reduced. (3) Since there is no wire in the center of the steel cord and there is a gap between the wires, there is a drawback that when a metal piece or the like is stepped on, a punch-through occurs and a puncture easily occurs.

On the other hand, to reinforce the carcass of a truck / bus tire, 1 × having a cross-sectional shape as shown in FIG.
Steel cords having a structure of 3 + 9 or 1 × 3 + 9 + 15 as shown in FIG. 4 (b) have been often used, but this structure also has a problem in rubber permeability because there is almost no gap between the wires. In order to improve this, 1 × 3 + 8 as shown in FIG. 5 (a) and 1 × 3 + 8 + 1 as shown in FIG. 5 (b)
Those having the structure of 3 and having a gap between the wires of the second and third layers have begun to be used. However, even in such a structure, there are the following problems. (1) Since the core strand has a 1 × 3 structure, a void portion in which rubber hardly penetrates is formed in the center portion, which is not perfect in terms of corrosion resistance. (2) In the production of the cord, the twisting process is performed twice or three times, which increases the production cost.

[0005]

SUMMARY OF THE INVENTION The present invention was devised to solve the above-mentioned problems, and its purpose is to achieve stable rubber permeability and high durability even though the section is compact. The present invention provides a practical steel cord having high flexibility and high bending rigidity on the long diameter side, which can be used for both reinforcement of the belt portion and the carcass portion and can be manufactured at low cost. Another object of the present invention is to provide a high performance and lightweight radial tire.

[0006]

In order to achieve the above object, the present invention provides a steel cord having a 1 × n structure in which three or more strands are twisted at once in the same direction and at the same pitch. A structure that has a small wavy pattern smaller than the twist pitch of the cord, and the portions where the wires do not intersect and the portions where they intersect are mixed in the longitudinal direction of the cord, and the cross section of the cord is approximately elliptical in the same direction. It is what
In this case, preferably, when the number of strands is 3 to 6, the frequency at which the strands intersect with each other is 0.5 to 4.0 times per twist pitch of the cord, and the short diameter D1 and the long diameter of the cord cross section. The ratio D1 / D2 of D2 is set in the range of 0.60 to 0.90. Further, preferably, when the number of strands is 7 to 19,
The frequency at which the wires cross each other is 0.5 to 15.0 times per twist pitch of the cord, and the minor diameter D1 of the cord cross section
And the ratio D1 / D2 of the major axis D2 to the range of 0.60 to 0.90. Further, in any case, it is preferable that the wave pitch p and the wave height h of the minute wave habits satisfy the following equation in relation to the wire diameter d and the cord twist pitch length P. 1.05 ≦ h / d ≦ 1.50 0.25 ≦ p / P ≦ 0.55 The present invention is also characterized in that any one of the above cords is used as a reinforcing material in a part of a belt or carcass of a radial tire. I am trying.

[0007]

Function: This is a flat type steel cord in which three or more strands are twisted at a time in the same direction and the same twist pitch. However, in the present invention, a normal twist (parallel twist) is simply changed to a flat twist. Instead, mix the parts where the wires intersect and the parts that do not intersect in the longitudinal direction of the cord,
In that state, the cord is flat. In this way, when the wires are appropriately switched and intersected in the longitudinal direction of the cord, the following characteristics are obtained. First, the twisted lengths between the individual wires are made uniform, and the individual wires can be evenly added. Secondly, when the wires are crossed with each other, the wires are entangled with each other and restrained at the intersecting parts. Therefore, even when a compressive force is applied in the cord axial direction, the wires are unlikely to bulge like a cage, and deformation resistance is reduced. Can be improved. Thirdly, a gap is formed between the strands due to the intersection, and the restraint action as described above can fix the gap between the strands against external force such as tension at the time of tire manufacturing. Can be realized. Fourthly, the strands are moved to the center of the cord due to crossing and non-crossing, so the strands become entangled at the intersection, making it difficult for the strands to move, and improving the filling degree of the strand in the cord cross section. (However, even in this case, the gap between the wires is secured),
As a result, the rigidity can be increased, so that it is possible to secure a certain degree of rigidity even when the major axis of the cord is not parallel to the tread surface, and it is also difficult for the metal piece to pierce, so it is possible to prevent the occurrence of puncture.

In particular, the crossing frequency of the strands is 0.5 to 4.0 times (the number of strands is 3 to 6) or 0.5 to 15 depending on the cord twist pitch P according to the number of strands. .0 times (7 to 19 strands)
In this case, it is possible to form an appropriate size gap between the strands, and to obtain compression resistance, as well as imbalance in strand length and good durability. Can be Moreover, when the elliptical shape has a minor axis D1 / major axis D2 of the cord cross section of 0.60 to 0.90, the cord can have good durability and rigidity. In addition to this, since each wire is continuously provided with a minute wave pattern with a pitch smaller than the twist pitch of the cord, there is a gap even in the part where the wires outside the intersection are parallel and adjacent to each other. A gap between the strands is ensured even if the strands are formed and compressed in the radial direction by the tension applied to the cord during vulcanization. Therefore, stable rubber permeability can be secured even with an open cord structure that is more compact. Especially, the pitch length p (mm) of the small wave is set to p / P = 0.25 to 0.55 in relation to the twist pitch (mm) of the cord, that is, the pitch length P of the wave by twisting the cord, The height h (mm) of the small wave is related to the wire diameter d (mm) by h
When / d = 1.05 to 1.50, shape stability and low load elongation can be achieved in a well-balanced manner, and the wire length due to the movement of the wire to the central part and the outer layer accompanying the intersection It is possible to alleviate local unbalance of stress and local stress concentration when a load is applied.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the accompanying drawings. FIG. 6 schematically shows a cross section of each part of a 1 × 5 structure steel cord to which the present invention is applied, which is cut at five places for the length of one twist pitch. Is in the range of about 0.10 to 0.45 mm. The strands 1 to 5 are brass-plated in order to vulcanize and adhere to the surface of the rubber, and are twisted at the same twist pitch in the same direction at a time. As described above, not a parallel twist in which the phase is shifted in the circumferential direction while the arrangement is specified, but a portion where all or a part of the strands 1 to 5 intersect is always formed in the cord longitudinal direction. That is, the parallel twist portion and the cross twist portion are mixed.

In this example, the wires 1 to 5 are arranged counterclockwise in that order at the sectional position of (a).
At the subsequent cross-section position (b), the wire 5 has begun to move toward the center of the cord. At the subsequent cross-section position (c), the wire 5 is the wire 1.
Interruption is starting between 2 and 2. At the subsequent cross-section position (d), the strand 5 is cut between the strands 1 and 2 and returns in the outer layer direction so as to line up next to the strand 2, and at the subsequent cross-section position (e), the strand 1 is located at the center of the cord. It moved in a depressed manner, and the formation of intersections began. The circumscribed circular shape of the cord is substantially elliptical, and its cross-sectional shape is substantially the same in the cord longitudinal direction, that is, the major axis direction is lateral in this example, as is clear from (a) to (e). FIG. 7 shows 1 × to which the present invention is applied.
11 shows two cross sections of a cord having 11 structures, in which the wires 1 to 11 in the arrangement shown in (a) are replaced as shown in (b) due to intersections at different cross sectional positions, and the circumscribed circular shape is the same as in the above embodiment. Has a substantially elliptical shape, and its cross-sectional shape is substantially the same in the cord longitudinal direction, that is, the major axis direction is laterally oriented in this example.

In any of the embodiments, the crossing of the strands includes the crossing of the cord outer diameter side strands and the crossing of the cord outer diameter side strands and the cord center side strands. This includes a case where two or more strands to be crossed are crossed with one or more other strands while remaining parallel to each other. Moreover, each of the strands 1 to 5 and 1 to 11 constituting the cord is not simply straight, and has the micro wave habit 100 having a pitch p shorter than the cord twist pitch P. A gap s is formed between parallel strands that do not intersect each other due to the habit 100 and that are parallel to each other.

The micro wave habit 100 is applied in advance to each of the strands 1 to 5, 1 to 11 before twisting. The micro wave habit 100 is, as shown in FIG. 8, a cord twist pitch. Length (wave pitch length due to twisting) P
(mm) and the wire diameter d (mm), it is preferable to have a predetermined pitch p (mm) and a predetermined height h (mm). In this figure, the wire is shown as W. In particular,
p / P is about 0.25 to 0.55, h / d is 1.05
About 1.50 is preferable. The reason is as follows. That is, if p / P is smaller than 0.25, it is difficult to process, so that the wire is scratched and the strength is reduced, or the durability is reduced. In addition, the shape of the cord tends to be unstable. However, if p / P is larger than 0.55, the strands become close to the undulations of the cord and the strands are more likely to move due to external force. Substantially disappears or the strand arrangement is offset, resulting in poor rubber permeability. Further, if h / d is smaller than 1.05, the effect of forming a gap by imparting a slight wave pattern becomes poor. However, if it is larger than 1.50, the shape of the cord is not stable, the load is not evenly applied to each strand, the elongation of the cord at a low load increases, and the breaking load of the cord decreases.

The micro wave habit 100 normally has a spiral shape. In order to obtain the former mode, each strand drawn from the supply bobbin may be applied in front of the stranding machine main body.
For example, a corrugating device having three or five pins in a parallel or zigzag pattern is arranged on a path line between a supply bobbin and a buncher-type stranding machine main body, and a wire is arranged along the pin. In this state, the corrugating device may be revolved around the strand in the direction opposite to the rotating direction of the twisting machine. Or instead of this, the corrugating device is fixed in position,
Before and after this device, there is a method of rotating the strands in the same direction as the rotation direction of the twisting machine. In the case of the latter method, a wire twister is provided immediately downstream of the corrugating device, and each wire with a slight wave curl is guided to the wire twister, and these wire twisters are rotated relative to the wire in the direction of rotation of the twisting machine body. Revolve in the same direction as (the corrugating device is fixed) and twist the strand. However, the micro wave habit 100 may be two-dimensional in some cases. In this case, a pair of gears that mesh with each other may be used, and the wire may be passed between them.

As described above, the cords of the above-described embodiments are subjected to fine corrugation of strands by means of a corrugating device and a wire twister as described above, followed by passing through a molding device to impart excessive twisting, and subsequently. It is made by twisting these strands at the entrance of the twisting machine while interchanging the strands at the same time and at the same pitch, and finally compressing them in two directions using a straightening roller or the like. As described above, according to the present invention, the strands have a small wave pattern 1
00 is attached, the cross-sectional shape is broken by the exchange between the strands, and a plurality of gaps s are created between the strands due to the elliptical shape. It is firmly fixed by the entanglement restraint phenomenon of.

The number of strands constituting the steel cord of the present invention may be 20 or more, for example 27 or 36. However, if the number of strands is too large, it becomes difficult for the rubber to reach from the outside of the cord to the center of the cord, so 19 or less is desirable. The frequency of wire crossing is
At least 0.5 times is preferable per twist pitch of the cord. The reason for this is that if the crossing frequency is lower than this, the degree of restraint of the gap is insufficient even if the flatness of the cord is appropriate, and the rubber permeability decreases. Moreover, since the binding force between the wires is insufficient, the wires are likely to swell when a compressive force acts in the cord axial direction, and the compression resistance decreases. However, if the crossover frequency is too high and the number of strands exceeds 4.0 for 3 to 6 strands or exceeds 15.0 for 7 to 19 strands, the strands will be replaced. Since it becomes complicated, imbalance occurs in the twisted length of the wire, and the durability is reduced. Further, the flatness ratio is 0.60 to 090 in the minor axis D1 / major axis D2 in the cord cross section.
It is preferable to be within the range. The reason is that if the minor axis D1 / major axis D2 is less than 0.60, the flattening degree becomes large and the durability becomes insufficient, and if it exceeds 0.90, the rubber permeability decreases. It is preferable that all the wires have the same diameter, but in some cases, wires having different diameters may be used.

[0016]

Next, specific examples of the present invention will be described. [Specific Example 1] On the path line in front of the twisting opening of the buncher type twisting machine body, a device for changing the tension of the wires by a guide roller rotating eccentrically and in a crank shape to replace the wires is arranged. At the same time, a fixed type corrugating device, in which 3 pins are arranged in a zigzag pattern, is provided on the path line of each strand on the upstream side of this, and a wire twister is provided after that, to perform over-molding on the downstream side. A shaping device having a pin is provided, and the wire twister is revolved in the same direction as the rotation direction of the stranding machine main body with respect to the strand to twist the strand. Further, after the twisted wire, a compression device composed of a straightening roller was provided on the pass line before winding.
After passing 5 strands of wire with a diameter of 0.25 mm through these devices and a stranding machine, they were twisted in the S direction at a twist pitch of 10 mm at a time, and the flatness and the crossing frequency of strands were set to 1 × 5. Structural steel cords (Examples 1 to 6) were produced. A flat structure using the same strands as the characteristics of these steel cords
Table 1 shows the conventional example (twisting direction: S, twisting pitch 10 mm).

Specific Example 2 In the same manner as in Specific Example 1, 0.
Eleven wires having a diameter of 22 mm were simultaneously twisted in the S direction at a twist pitch of 14.0 mm to manufacture steel cords (Examples 7 to 11) having different flatness and crossing frequency.
The characteristics of these steel cords are
It is shown in Table 2 together with a conventional example of × 3 + 8 structure (core: 6.0 mmS, side 12.0 mmS). In Tables 1 and 2, “rubber permeability” means that a linear cord is vulcanized in the rubber under a tension of 100 gr to prepare a sample, and then the cord is divided in the longitudinal direction so that the rubber inside the cord is divided. The degree of penetration was visually observed, and it was judged that 100% of the cord was completely covered with rubber. “Durability” is that band-shaped samples obtained by vulcanizing cords in rubber are stretched over three rolls with a constant diameter arranged under a load of 10% of the cord breaking load, and the rolls are repeated left and right. It is the result of reciprocating the sample to repeatedly bend the sample and measuring the number of repetitions until the cord breaks. "Bending rigidity" is a value obtained by measuring the load that reaches a certain amount of deflection using a compression tester on a plate-shaped sample obtained by vulcanizing a cord in rubber. expressed.

[0018]

[Table 1]

[0019]

[Table 2]

According to Examples 1 to 11, since the crossing frequency and the flatness of the strands are proper and the fine wave has a proper range, rubber penetration and durability are good, and bending is good. The rigidity also increases the surface rigidity in the width direction, that is, the major axis direction, due to the filling of the wires in the center of the cord due to the intersection.

[0021]

According to the first aspect of the present invention described above, since the strands have a slight wave pattern, a gap is formed even in a portion where the strands are parallel and adjacent to each other due to the peaks and valleys of the strands. In addition, the gap is formed by the crossing of the wires, and the gap is fixed by the restraining action due to the entanglement.
Also, since the strands are arranged in the center of the cord due to the intersection, the filling degree of the strands in the cord cross section increases
Even if the cord has the same number of strands as the conventional one, the cord becomes compact, but there is a gap due to the slight wave pattern.
Therefore, it has stable rubber permeability, high durability and high bending rigidity on the long diameter side despite its compact cross section, and can be used for both reinforcement of the belt part and the carcass part, and also has good punch-through resistance. In addition, it is possible to obtain a sufficient number of shots, and yet it is possible to realize the excellent effect that the cost can be reduced because it is manufactured by collective twisting.

According to the second and third aspects, since the range of the frequency of crossing the strands and the range of the flatness ratio are made appropriate,
The excellent effect that the rubber permeability, compression resistance, fatigue resistance and surface rigidity can be improved is obtained. According to claim 4, since the pitch and height of the micro wave can be made appropriate, durability, rubber permeability,
An excellent effect that the breaking load becomes favorable and the feature of claim 1 can be exerted to the maximum extent can be obtained. According to the fifth aspect, an excellent effect that a lightweight tire having high durability, less puncture resistance and good steering stability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a conventional steel cord having a 1 × n structure.

FIG. 2 is a cross-sectional view showing a conventional open type steel cord having a 1 × n structure.

FIG. 3 is a cross-sectional view showing a conventional flat open type steel cord having a 1 × n structure.

FIG. 4 is a cross-sectional view showing a conventional multilayer twisted steel cord.

FIG. 5 is a cross-sectional view showing a conventional multilayer twist tight open type steel cord.

FIG. 6 is an explanatory view schematically showing an example of a rubber-reinforcing steel cord according to the present invention with different cross sections perpendicular to the longitudinal direction.

FIG. 7 is an explanatory view schematically showing another example of the rubber-reinforcing steel cord according to the present invention, with different cross sections perpendicular to the longitudinal direction.

FIG. 8 is an explanatory diagram showing a relationship between a cord twist pitch of a strand of wire taken out by disassembling a cord, a pitch of a slight wave, and a wave height in the present invention.

[Explanation of symbols]

 1 to 11 Elementary wire 100 Micro wave s s Gap D1 Minor diameter D2 Long diameter H Wave height of element wire h Wave height of minute wave P Wave pitch of cord P Pitch pitch of minute wave d Element wire diameter

Claims (5)

[Claims] 1. A steel cord having a 1 × n structure in which three or more strands are twisted at once in the same direction and at the same pitch, and each strand has a minute wavy pattern smaller than the twist pitch of the cord. A rubber-reinforcing steel cord, characterized in that a portion where strands do not intersect and a portion where strands intersect are mixed in the cord longitudinal direction, and the cross-sections of the cord are substantially elliptical in substantially the same direction. 2. The number of strands is 3 or more and 6 or less, the frequency at which the strands intersect with each other is 0.5 to 4.0 times per twist pitch of the cord, and the minor diameter D1 of the cord cross section. The steel cord for rubber reinforcement according to claim 1, wherein a ratio D1 / D2 of the long diameter D2 and the long diameter D2 is in the range of 0.60 to 0.90. 3. The number of strands is 7 or more and 19 or less,
The frequency at which the wires cross each other is 0.5 to 15.0 times per twist pitch of the cord, and the ratio D1 / D2 of the minor diameter D1 and the major diameter D2 of the cord cross section is in the range of 0.60 to 0.90. The steel cord for rubber reinforcement according to claim 1, wherein 4. A minute wave habit of a wire, wherein a wave pitch p and a wave height h satisfy the following expressions in relation to a wire diameter d and a cord twist pitch length P. The steel cord for rubber reinforcement according to any one of 1. 1.05 ≦ h / d ≦ 1.50 0.25 ≦ p / P ≦ 0.55 5. A radial tire, wherein the steel cord according to claim 1 is used in at least a part of a belt portion or a carcass portion.