JP4675738B2 - Steel cord and automotive tire - Google Patents

Description

  The present invention relates to a steel cord used as an embedded reinforcing material for rubber products such as an automobile tire and an automobile tire using the steel cord.

  In order to prevent the entire vehicle from bouncing when the automobile steps on the bumps on the road, the effect of distorting the surface that contacts the road surface of the tire to absorb unevenness (so-called “envelope effect”) It is necessary to increase the torque so that the entire tire is not distorted. For this reason, a steel cord having a high stretchability (that is, a large elongation until breakage) is used as a steel cord embedded in an outer layer portion of a reinforcing layer (breaker or belt) between a carcass and a tread on the outer periphery of the tire. The so-called “high elongation code”) is used. The high elongation cord (H / E cord) used for such purposes has a total elongation to break (elongation to break) of 4% or more, preferably 5% or more (3% or less for ordinary steel cords). It is required to be.

  In addition, the high elongation cord not only has a high total elongation, but also has a primary elongation that is easy to stretch at low loads, and gradually increases its rigidity as the load increases. Thus, it is necessary that the total elongation at break (elongation to break) is 4% or more, preferably 5% or more. Further, since the cord is embedded in the tire, it is indispensable that the entire surface of the cord is covered with rubber and that the rubber enters the cord without any gap.

  However, conventional steel cords have a high elongation of not less than 4%, preferably not less than 5%, and a suitable primary elongation in the low-load region. However, it is not possible to satisfy all the conditions necessary for the high elongation cord to be used by being embedded in the outer layer portion of the reinforcing layer of an automobile tire, which is excellent in rubber penetration.

  Among the conditions for the high elongation cord, the total elongation of 4% or more, preferably 5% or more can be realized by adopting a steel cord having a multi-layer twist (n × m structure). However, in the multi-layer twist (n × m structure), since the strands are in close contact with each other, a closed gap is formed at the center of the strand, rubber penetration is poor, and the gap at the center of the strand remains as it is during tire molding. End up.

  Further, as a single-layer twisted high elongation cord, a cord having a total elongation of 4% or more and 5% or more is known by making the twist pitch smaller than the conventional one (for example, Patent Documents). 1).

  However, the conventional single layer twisted high elongation cord has a very small twist pitch coefficient (twist pitch / cord diameter) of 5 to 10 (the twist pitch coefficient of a general cord is about 20), and the number of twists is high. Therefore, productivity is poor, and therefore, a large number of stranding machines are required, which not only requires equipment costs but also consumes a large amount of energy.

  In addition, since this conventional single-layer twisted high elongation cord is tightly twisted, the gap through which the rubber can enter is small, and the rubber does not easily enter the center of the cord. A so-called 1 × n (n = 3 to 6) steel cord in which 3 to 6 strands (steel filaments) are twisted into a single layer structure has a straw-shaped space in the longitudinal direction of the cord, In the case of the closed twist in which the strands are closely twisted so that the strands are in close contact with each other, the gap in the center portion of the cord is closed. In this case, for example, when the steel cord becomes a composite with rubber in the tire molding process, if the rubber does not penetrate to the gap in the cord central portion and the cord central portion remains as a hollow portion, Moisture that has entered the inside of the cord penetrates into the hollow space in the center of the cord that has become a hollow part, which penetrates the inside of the cord in the longitudinal direction due to capillary action, and as a result, corrosion proceeds from the inside of the cord, resulting in steel. It may deteriorate the fatigue resistance of the cord and shorten the tire life.

  As a cord that is excellent in rubber penetration by single layer twisting, in order to ensure rubber penetration, a steel cord with an open structure in which strands shaped in a circular spiral are loosely twisted so that the strands do not adhere to each other (so-called “ Open code "). Since this cord has an open structure, high extensibility can be obtained without reducing the twist pitch. However, since open cords are stretched greatly with a small load due to loose twisting, handling workability is very poor, and the cords are removed from the reel in the process of sandwiching the cords in the manufacture of tires with rubber sheets (called calendar process) The cord stretches with a small tension when it is unwound, and the gap between the strands disappears. The cord is sandwiched between the rubber sheets in that state, so the cord and rubber are integrated with heat and pressure in the subsequent vulcanization process. When the processing is performed, the gap between the strands is closed, so that the rubber cannot enter the inside of the cord, and a gap that is not filled with rubber remains in the tire.

  And, as a steel cord having excellent rubber penetration, it has a 1 × n structure composed of n (n = 3 to 6) strands, and at least one strand is a habit due to shaping for twisting. There has also been proposed a steel cord for reinforcing rubber products that has different small spiral creases and has a substantially oval cross section (see Patent Document 2). However, even in the case of this cord, it is necessary to reduce the twist pitch in order to increase the total elongation, the productivity is poor, a large number of stranding machines are required, the equipment cost is high, and the energy consumption is also large. .

  In addition, by using at least one strand of steel cord consisting of 3 or more strands as a zigzag strand, it is also proposed to form a gap that allows the rubber material to penetrate and improve rubber penetration. (For example, see Patent Document 3). Since this steel cord has many locations where the strands come into contact with each other, unlike the open cord where adjacent strands are separated from each other, the contact portion suppresses the reduction of the gap due to tension, and at the time of low load Elongation is reduced. Moreover, this steel cord can obtain high extensibility by attaching all the strands in a zigzag shape. However, when steel cords (called “zigzag cords”) in which all the strands are attached in a zigzag shape and the total elongation (elongation to break) is to be increased to 5% or more, the zigzag attachment becomes large (pitch and There is a problem that the twist is disturbed and the fatigue resistance is lowered due to the twist disorder. A zigzag wrinkle is a two-dimensional wave type machined with gears and the like, and has a bent portion, but when bending stress is applied (when this cord is used for tire reinforcement, bending stress is always applied due to road surface unevenness. However, there is also a problem that stress is concentrated on the bent portion, thereby reducing fatigue resistance.

JP-A-1-250483 No. 7-30714 JP-A-2-307994

  Therefore, it has high extensibility, has a moderate primary elongation in the low load range, has excellent rubber penetration, and can suppress the equipment cost and production energy consumption, thereby preventing a decrease in productivity. It is an object to provide a steel cord suitable as a high elongation cord to be used by embedding it in an embedded reinforcing material for rubber products, particularly an outer layer of a reinforcing layer of an automobile tire, and an automobile tire using the steel cord.

The steel cord of the present invention is a multi-layered twist formed by twisting m strands (m = 3-7) each consisting of n strands (n = 2-7), each strand being a flat spiral. is shaping the, a steel cord for reinforcing rubber cord cross section a gap is formed by twisted assume a substantially elliptical products between them strands, shaping for all strands twisting In addition to the habit caused by twisting, there is a spiral habit with a smaller wave height and pitch than the habit caused by shaping, and the cross-sectional shape of the spiral habit of each strand is substantially elliptical, and the strand twist rate is 1.01 to 1.46, and the ratio of the major axis to the minor axis of the substantially elliptical cord cross-sectional shape is .1.05 to 1.70 . The lands are not in contact with each other, have a gap of 3/100 mm or more, and have a twist pitch coefficient of 10 or more based on the minor axis of a substantially elliptical cord cross-sectional shape.

This steel cord has an open structure, and since the strand has a spiral shape, the elongation is large, and even if the pitch is not reduced, the total elongation to break is 4% or more, preferably 5% or more. High elongation can be obtained. Therefore, productivity does not decrease, it is not necessary to increase the number of stranding machines, and energy consumption does not increase. Moreover, even if the gap between the strands decreases in the low load region, a spiral habit remains, and rubber penetration is ensured.

In addition, a strand with a spiral wrinkle that is a three-dimensional wave type has a larger elongation than a strand with a zigzag wrinkle that is a two-dimensional wave type. Therefore, it is possible to stabilize the shape and reduce twisting disturbance. Therefore, a decrease in fatigue resistance due to twisting disturbance can be reduced. In addition, the spiral-shaped habit does not have a bent portion where bending stress is concentrated, and there is little deterioration in fatigue due to concentration of bending stress.

Then, the steel cord, by percentage narrowing twisting of the strands is from 1.01 to 1.46, 1 TsugiShindo can be prevented from becoming too unnecessarily large, moderate primary to low load region It has an elongated portion and can gradually increase the rigidity as the load increases, so that the total elongation at break (elongation until break) is 4% or more, preferably 5% or more. .

As is well known, the twist rate is defined by the length (ratio) of strands or strands necessary for making a steel cord of unit length, and the strands or strands have a substantially elliptical cross-sectional shape. In a steel cord that is shaped into a flat spiral with a spiral shape and twisted into a cord having a substantially elliptical cross section, if the twist rate is less than 1.01, the strand or strand has a substantially elliptical cross section. The effect of the spiral bevel on the extensibility is small, and the extensibility required for high elongation with a total elongation of 4% or more, preferably 5% or more cannot be obtained. Also, if the twist rate exceeds 1.46, the wave length of the long diameter part becomes excessively large and not only is the twisted wire processing difficult, but the elongation becomes too large and the reinforcing function of the original tire as a steel cord is impaired. It is.

In addition, this steel cord has a substantially cross-sectional shape of the cord and a substantially elliptical cross-sectional shape of the strand of the strand. By arranging the side in the thickness direction of the tire rubber, the thickness of the tire can be reduced. Moreover, the rigidity in the tire radial direction is thereby reduced, and the effect of absorbing irregularities when the projection is stepped on during traveling is increased.

In addition, this steel cord has a substantially elliptical cross section, which increases the frequency of contact between at least two adjacent strands at least at one end on the long side of the cord and restricts the free movement of the strands. Therefore, it is possible to prevent the gap between the strands from being reduced by the external pressure due to the rubber flow generated when the steel cord is embedded in the rubber and vulcanized, and to ensure the invasion of the rubber. Fatigue resistance is improved.

Moreover, this steel cord makes the cross-sectional shape of the cord substantially elliptical and the cross-sectional shape of the spiral-like strand of the strand is substantially elliptical, so that the twisted wire effect is sufficiently exhibited and the fatigue resistance is improved. The elongation of the cord, that is, the total elongation before breaking, can be increased by increasing the wave height of each strand spiral spiral, but simply increasing the strand spiral wave height will twist the strands. The combined cord is an aggregate of spiral strands , and the twisted wire effect is not sufficiently exhibited, and sufficient fatigue resistance cannot be obtained.

Further, the steel cord, in particular, in long diameter ratio to the minor diameter of the substantially elliptical code cross section 1.05 to 1.70, the strands each other definitive twisted monolayer in the major axis direction of the code section of substantially elliptical By not having contact and having a gap of 3/100 mm or more, the rubber for covering both sides can be made thin when molding the tire, the rubber penetration is increased and the fatigue life of the cord is increased. At the time of molding, the rubber for covering both sides can be made thin, improving the economy. If the ratio of the major axis to the minor axis (major axis / minor axis) is less than 1.05, this effect cannot be obtained. On the other hand, if the major axis / minor axis exceeds 1.7, the solstice becomes too large, the stranded wire effect is reduced, and the fatigue life is reduced.

Further, this steel cord has the above characteristics as a high elongation cord even when the twist pitch coefficient (twist pitch / cord minor axis) is 10 or more based on the minor axis of the substantially elliptical cord cross-sectional shape. Can be.

  The automobile tire according to the present invention is characterized in that the steel cord having the above configuration is embedded in rubber as a reinforcing material. This tire has a great effect of absorbing irregularities at the outer periphery of the tire when the automobile steps on the protrusion on the traveling road so that the entire automobile does not bounce. Moreover, the fatigue resistance of the steel cord is high and the tire life is long.

  As described above, according to the present invention, it has a high elongation property, has an appropriate primary elongation portion in a low load region, has excellent rubber penetration, and suppresses equipment costs and production energy consumption. It is possible to provide a steel cord that can prevent a decrease in productivity, and an automobile tire using the steel cord.

FIG. 1 is a cross-sectional view of a steel cord having a 1 × 5 structure according to a reference example of an embodiment of the present invention. In this steel cord, n strands (n = 3 to 6) having a strand diameter of 0.20 to 0.45 mm are each formed into a flat spiral shape so that a gap is formed between the strands in a single layer. Twisted 1xn open twist structure, cord cross-sectional shape is almost elliptical, and all strands are shaped by twisting to form a twist. A steel cord having the same spiral shape with a smaller wave height and smaller pitch, and a cross-sectional shape of the spiral shape of each of the strands is a substantially elliptical steel cord.

  This steel cord is embedded in an outer layer portion of a reinforcing layer (breaker or belt) between a carcass and a tread as a reinforcing material for an automobile tire, for example.

FIG. 1 shows an example of a steel cord of this reference example, a steel having a 1 × 5 structure in which five strands 1, 2, 3, 4, and 5 having strand diameters of 0.20 to 0.45 mm are twisted together. The code is shown schematically.

  The spiral shape of the strands 1, 2, 3, 4 and 5 has a ratio of the major axis to the minor axis (major axis / minor axis) of the cross-sectional shapes 11, 12, 13, 14, and 15 that are substantially elliptical. To 4.0 and the twisting rate to 1.01 to 1.46.

  Further, the ratio of the major axis to the minor axis (major axis / minor axis) of the substantially elliptical cross-sectional shape 10 of the cord is 1.05 to 1.70, and the strands are in contact with each other in the major axis direction of the substantially elliptical cord section. It shall have a gap of 3/100 mm or more.

  This steel cord has an open structure, and each of the strands 1, 2, 3, 4 and 5 has a spiral crease. Therefore, the steel cord has a large elongation, and even if the pitch is not reduced, the total elongation until breakage is achieved. High extensibility with a degree of 4% or more, preferably 5% or more can be obtained. Therefore, productivity does not decrease, it is not necessary to increase the number of stranding machines, and energy consumption does not increase. Further, even if the gap between the strands is reduced in the low load region, a spiral habit remains, and rubber penetration is ensured.

  In addition, the strands 1, 2, 3, 4 and 5 with a spiral-like shape that is a three-dimensional wave type can stabilize the shape while ensuring high elongation, and can reduce twist disturbance. It is possible to reduce the decrease in fatigue resistance due to the disturbance of the stress, and there is little decrease in fatigue due to the concentration of bending stress.

  And this steel cord can suppress that the primary elongation becomes excessively large because the twist rate of the strands 1, 2, 3, 4, and 5 is 1.01 to 1.46. It has a moderate primary elongation in the low-load region, and gradually increases its rigidity with increasing load. The total elongation at break (elongation to break) is 4% or more, preferably 5 % Or more.

  Further, this steel cord has a short cross-sectional shape 10 because the cross-sectional shape 10 of the cord is substantially elliptical and the cross-sectional shapes 11, 12, 13, 14, and 15 of the strands of the strands are substantially elliptical. A diameter side dimension can be made small and the thickness of a tire can be made thin by arrange | positioning a breadth side in the thickness direction of the rubber | gum of a tire. Moreover, the rigidity in the tire radial direction is thereby reduced, and the effect of absorbing irregularities when the projection is stepped on during traveling is increased.

  In addition, since the cross-sectional shape 10 of the cord is substantially elliptical, the steel cord has an increased frequency of contacting at least two adjacent strands at least at one end on the major axis side of the cord. The movement is restricted, so it is possible to prevent the gap between the strands from decreasing due to the external pressure caused by the rubber flow generated when the steel cord is embedded in rubber and vulcanized, and the rubber can be surely intruded. , Thereby improving fatigue resistance.

  Further, this steel cord has a twisted wire effect because the cross-sectional shape 10 of the cord is substantially elliptical and the cross-sectional shapes 11, 12, 13, 14, and 15 of the strands of the strands are substantially elliptical. It is fully demonstrated and fatigue resistance is improved.

  The steel cord has a ratio of the major axis to the minor axis of the substantially elliptical cross-sectional shape 10 of 1.05 to 1.70, and the strands do not contact each other in the major axis direction of the substantially elliptical cord cross section, By having a gap of 3/100 mm or more, the rubber for covering both sides can be made thin when the tire is molded, which is economical, the rubber penetration increases, the fatigue life of the cord increases, and the tire During molding, the rubber for covering both sides can be made thin, which improves the economy.

  The steel cord may have a twist pitch coefficient (twist pitch / cord minor axis) of 10 or more based on the minor axis of the substantially elliptical cord cross-sectional shape. Even if the twist pitch coefficient is 10 or more, it can have the above characteristics as a high elongation cord.

  This steel cord is embedded in the outer layer of the reinforcing layer (breaker or belt) between the carcass and tread of an automobile tire as a reinforcing material. Absorb and function so that the entire car does not bounce. Moreover, the fatigue resistance of the steel cord is high, and the tire life is improved.

In the above reference example , an example of a steel cord having a 1 × 5 structure has been described. However, this technique can be applied to other single layer twisted steel cords formed by twisting n (n = 3 to 6) strands. It can also be applied to. Moreover, this technique is a multi-layered steel cord formed by twisting m strands (m = 3-7) each consisting of n strands (n = 2-7), such as a 4 × 2 structure. It can also be applied to.

The steel cord of the present invention is a multi-layered steel cord formed by twisting m strands (m = 3 to 7) each consisting of n strands (n = 2 to 7). In the case of multi-layer twisting, all the strands have the same spiral shape with a smaller wave height and pitch than the shape caused by twisting, apart from the shape caused by twisting. The steel cord is configured so that the cross-sectional shape of the spiral-like habit is substantially elliptical. And the spiral form of the strand makes the ratio (major axis / minor axis) of the major axis to the minor axis of the substantially elliptical cross-sectional shape 1.3-4.0, and the twist rate is 1.01-1. 46. The ratio of the major axis to the minor axis of the substantially elliptical cross-sectional shape of the cord (major axis / minor axis) is 1.05 to 1.70, and the strands do not contact each other in the major axis direction of the substantially elliptical cord section, It shall have a gap of 3/100 mm or more.

  The steel cord of the present invention can also be applied as an embedded reinforcing material for rubber products other than automobile tires.

Table 1, using the wire of the same material, steel cord two ( "Example 1" (Reference Example) "Example 2") according to the present invention the cross-sectional shape of the spiral habit of wire Samples of Comparative Example 1 ("Comparative Example") and 2 Conventional Examples ("Conventional Example 1", "Conventional Example 2") were prepared and vulcanized after rubber coating, and stretched. The results of a comparative test of each of the properties of fatigue, fatigue resistance, rubber penetration, productivity, and consumption of processing energy are shown.

“Example 1” is a 1 × 5 single layer twisted steel cord of a reference example using a strand having a diameter of 0.30 mm, and the spiral height of the strand of the strand (long diameter / single diameter) is 1. 04 mm / 0.93 mm, the twist pitch is 15 mm, the cord diameter (major axis / minor axis) is 1.05 mm / 0.94 mm, and the twist pitch coefficient (twist pitch / cord diameter) is 15.1.

  “Example 2” is a steel cord of a multi-layered twisted 4 × 4 structure according to the present invention using a strand having a diameter of 0.20 mm, and the wave height (long diameter / single diameter) of the spiral spiral of the strand is 1.81 mm. /1.09 mm, twist pitch (strand twist pitch / cord twist pitch) is 8 mm / 15 mm, cord diameter (major axis / minor axis) is 1.84 mm / 1.11 mm, and twist pitch coefficient (twist pitch / cord diameter) is 10. .1.

  “Comparative example” is a 1 × 5 single-strand steel cord using a 0.30 mm diameter strand, the spiral cross section of the strand is circular, the wave height is 0.99 mm, and the twist pitch is 15 mm, cord diameter (major axis / minor axis) is 1.00 mm / 0.99 mm, and twist pitch coefficient (twist pitch / cord diameter) is 15.1.

  “Conventional example 1” is a conventional single unit having a 1 × 5 structure in which a twist pitch coefficient (twist pitch / cord diameter) is extremely small (twist pitch / cord diameter = 6.4) using a 0.30 mm diameter strand. A layered high elongation cord (see Patent Document 1), the twist pitch is 5.5 mm, the cord diameter is 0.85 mm, and the twist pitch coefficient (twist pitch / cord diameter) is 6.4.

  “Conventional Example 2” is a 4 × 4 multi-layer steel cord using a 0.20 mm diameter strand, the twist pitch (strand twist pitch / cord twist pitch) is 3.5 mm / 7 mm, and the cord diameter Is 1.46 mm and the twist pitch coefficient (twist pitch / cord diameter) is 4.8.

In Table 1,
“Primary elongation” is the elongation until the gap between the strands and strands disappears when the tensile test is performed. “Secondary elongation” is after the gap between the strands and strands disappears. The “rubber coverage” is an elongation of 50N, where the cord is embedded in rubber under a tensile load of 50N, vulcanized, and then the cord is taken out and the cord is disassembled. The ratio of the length of the traced contact with the rubber material to the observed length is displayed as a percentage, and the `` Rotating Bending Life Index '' is an abbreviation for cords in Hunter type fatigue tests. Connected and rotated while bent into a U-shape (the bending shape is set so that a stress of 150 kg / mm ² is applied to the maximum curvature point of the cord), and the total number of rotations until the vicinity of the maximum curvature point breaks The unit "Production index between" is indexed with the production efficiency per unit time as "conventional example 1" as 100. "Strength wire energy consumption index" is the ratio of energy consumed per unit production. Is expressed as an index with “Conventional Example 1” being 100.

From the results of this comparative test (Table 1), the steel cords of Example 1 (reference example) and Example 2 are characterized by elongation characteristics (primary elongation, secondary elongation), fatigue resistance (rotational bending life index), It can be seen that productivity (production index per unit time per twister) can be improved and processing energy consumption (energy consumption index for stranded wire processing) can be reduced without impairing rubber penetration (rubber coverage). .

It is sectional drawing of the steel cord of 1 * 5 structure of embodiment of this invention. It is a graph which shows the influence on the fatigue life of the cord cross-sectional shape of the steel cord of 1 * 5 structure of embodiment of this invention compared with the comparative example whose cross-sectional shape of the spiral form of a strand is circular.

Explanation of symbols

1, 2, 3, 4, 5 Strand 10 Cross section of cord 11, 12, 13, 14, 15 Cross section of spiral spiral of strand

Claims (2)

Each of the strands is formed in a flat spiral shape by a multi-layer twist formed by twisting m strands (m = 3-7) each consisting of n strands (n = 2-7). It is a steel cord for reinforcing rubber products that is twisted so that a gap is formed between the strands and the cross-sectional shape of the cord exhibits a substantially elliptic shape,
Has a smaller spiral habit crest and pitch than habit by shaping for separately該撚Ri alignment the habit by shaping for all intertwining of the strands, the cross-sectional shape thereof spiral habit of each strand Is approximately oval, and the strand twist rate is 1.01-1.46,
The ratio of the major axis to the minor axis of the substantially elliptical cord cross-sectional shape is .1.05 to 1.70, and the strands do not contact with each other in the major axis direction of the substantially elliptical cord cross-section and are 3/100 mm or more. With a gap,
A steel cord having a twist pitch coefficient of 10 or more based on the minor axis of the substantially elliptical cord cross-sectional shape. An automotive tire comprising the steel cord according to claim 1 embedded in rubber as a reinforcing material.

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