Patent Application
20220307197
The present disclosure relates to a steel cord and a tire.
A metallic cord including a core wire and outer wires arranged so as to surround the core wire is disclosed in Patent Document 1. In the metallic cord disclosed in Patent Document 1, the core wire and the outer wire have the same diameter, the same twist direction, and the same twist pitch. The core wire is not preformed and at least some outer wires are preformed.
[Patent Document 1] U.S. Patent Publication No. 2011/0099967
A steel cord according to the present disclosure includes one or more core filaments, and outer sheath filaments provided so as to surround the one or more core filaments. The one or more core filaments and the outer sheath filaments have an identical wire diameter and an identical twist pitch. At least one of the one or more core filaments is a waved filament having a bent portion and a non-bent portion along a longitudinal direction.
As disclosed in Patent Document 1, a steel cord including a core wire and outer wires arranged so as to surround the core wire and having a configuration in which the twist pitch of the core wire is equal to the twist pitch of the outer wire is conventionally known. The steel cord in which the twist pitch of the core wire is equal to the twist pitch of the outer wire enables good productivity because the core wire and the outer wire can be twisted at the same time.
However, from the viewpoint of increasing the durability of a tire, a steel cord having a high degree of rubber penetration is desired to prevent water from entering a rubber of a tire.
Thus, it is an object of the present disclosure to provide a steel cord having a high degree of rubber penetration.
According to the present disclosure, a steel cord having a high degree of rubber penetration can be provided.
First, embodiments of the present disclosure will be described by listing. In the following description, the same or corresponding elements are referenced by the same reference numerals and the same descriptions will not be repeated for the same or corresponding elements.
(1) A steel cord according to one aspect of the present disclosure includes core filaments and outer sheath filaments arranged so as to surround the core filaments. The one or more core filaments and the outer sheath filaments have an identical wire diameter and an identical twist pitch. At least one of the core filaments is a waved filament having a bent portion and a non-bent portion along a longitudinal direction.
The wire diameter of the core filament is configured equal to the wire diameter of the outer sheath filament, so that the same filaments can be used as the core filament and the outer sheath filament. This can reduce the number of types of filaments prepared, reduce the cost, and increase the productivity, when the steel cord is manufactured.
If the twist pitch of the core filament is equal to the twist pitch of the outer sheath filament, the core filament and the outer sheath filament can be twisted together to manufacture the steel cord. This can increase the productivity of the steel cord.
However, if the core filament and the outer sheath filament have an identical wire diameter and an identical twist pitch, a two-layer twisted steel cord that is obtained has a problem of a low degree of rubber penetration.
Thus, in a steel cord according to one aspect of the present disclosure, at least one of the core filaments is a waved filament. As a result, the steel cord according to one aspect of the present disclosure can increase the distance between the outer sheath filaments and increase the degree of rubber penetration in comparison with a case where the core filaments do not include a waved filament.
(2) The core filaments include two waved filaments arranged adjacent to each other and the two waved filaments may have different wave pitches.
If the wave pitches of the two adjacent core filaments are different, positions of the bent portions of the two adjacent core filaments in the longitudinal direction can be prevented from being matched without adjusting positions of the two adjacent core filaments in the longitudinal direction. As a result, an area of the core can be sufficiently increased and sufficient spaces between the outer sheath filaments can be formed. The degree of rubber penetration in particular can be increased.
(3) The core filaments include two waved filaments arranged adjacent to each other, and the two waved filaments may have different wave heights.
The heights of the two adjacent waved filaments are configured to be different, so that the area of the core can be increased and sufficient spaces between the outer sheath filaments can be formed, even if positions of the bent portions of the adjacent waved filaments in the longitudinal direction are matched. The degree of rubber penetration in particular can be increased.
(4) All the core filaments may be the waved filaments.
All the core filaments included in the steel cord are configured to be the waved filaments, so that the distance between the outer sheath filaments in particular can be increased and the degree of rubber penetration in particular can be increased.
(5) The waved filaments may include portions that form wave shapes in multiple different directions.
As the core filaments of the steel cord, the waved filaments having portions that form wave shapes in multiple different directions are used, so that the distance between the outer sheath filaments can be sufficient and the degree of rubber penetration of the steel cord in particular can be increased, even if the wave height is low. As the core filaments of the steel cord, the waved filaments having portions that form wave shapes in multiple different directions are used, so that the wave height required to achieve a desired degree of rubber penetration can be reduced in comparison with a case in which waved filaments that form wave shapes only in a single direction are used. Thus, the processing amount required when a waved filament is formed can be suppressed and the breaking load of the waved filament can be increased.
(6) The core filament may have a brass plating film containing Cu and Zn on a surface thereof.
Cu indicates copper and Zn indicates zinc.
The brass plating film containing Cu and Zn is provided in the core filament, so that when the steel cord is covered with rubber to form a tire, the adhesive strength between the core filament and the rubber can be increased and the durability of the tire in particular can be increased.
(7) The brass plating film may further contain one or more elements selected from Co, Ni, and Fe.
Co indicates cobalt, Ni indicates nickel, and Fe indicates iron.
By configuring the brass plating film to contain one or more elements selected from Co, Ni, and Fe, the adhesive strength between the core filament and the rubber can be further increased and the durability of the tire can be further increased.
(8) The structure may be a 2/7 structure or a 3/8 structure.
The steel cord is formed as the 2/7 structure or the 3/8 structure, so that the breaking load of the steel cord can be increased because the 2/7 or 3/8 structure is a structure in which the number of the outer sheath filaments is close to an acceptable upper limit relative to the number of core filaments. Additionally, in any of the above-described structures, the outer sheath filaments are densely arranged around the core filaments, and thus the degree of rubber penetration conventionally tends to be reduced. However, according to the steel cord of one aspect of the present disclosure, even if any of the above-described structures is used, the degree of rubber penetration can be increased, and a high effect can be particularly obtained.
(9) A tire including the steel cord described in any of (1) to (8).
Since the steel cord according to one aspect of the present disclosure has improved degree of rubber penetration, the steel cord can be filled with rubber, and water or the like can be prevented from entering. Thus, a tire including such a steel cord can be a durable tire.
Additionally, the steel cord according to one aspect of the present disclosure has a flat shape in a cross-section perpendicular to the longitudinal direction. Since the thickness of a belt layer can be selected so that the steel cord arranged in a single row in the rubber can be embedded, the cross-sectional shape of the steel cord can be flat to reduce the thickness of the steel cord, thereby reducing the thickness of the belt layer. Therefore, by using such a steel cord, the amount of rubber contained in the belt layer can be reduced in comparison with, for example, a case where a circular steel cord having the same cross-sectional area is used. As a result, the weight of the belt layer can be reduced, and the weight of the tire including the belt layer can also be reduced.
Specific examples of a steel cord and a tire according to one embodiment of the present disclosure (which is hereinafter referred to as “the present embodiment”) will be described below with reference to the drawings. It should be noted that the present invention is not limited to these examples and is intended to include all modifications in the meaning and within the scope of the claims and equivalents.
[Steel Cord]
In the following, the steel cord according to the present embodiment will be described with reference to
As illustrated in
That is, the steel cord 10 of the present embodiment has a layer twisted structure including a core 111 including the core filaments 11 and an outer sheath 121 including the outer sheath filaments 12 arranged around an outer periphery of the core 111. Here, the layer twisted structure indicates that the filaments are laminated and are arranged in multiple layers in the cross-section perpendicular to the longitudinal direction of the steel cord. The steel cord according to the present embodiment preferably has a two-layer twisted structure in which each of the core 111 and the outer sheath 121 is one layer as illustrated in
Hereinafter, when the core filament 11 and the outer sheath filament 12 are not distinguished and collectively referred, the core filament 11 and the outer sheath filament 12 may be simply described as filaments.
In
Preferably, the steel cord of the present embodiment is, for example, the steel cord 10 having the 2/7 structure illustrated in
The N/M structure described above indicates a two-layer twisted structure in which the number of the core filaments 11 is N, the number of the outer sheath filaments 12 is M, and the core filaments 11 and the outer sheath filaments 12 have an identical twist pitch and an identical twist direction. Thus, the 3/8 structure indicates that the number of the core filament 11 is three and the number of the outer sheath filament 12 is eight, as illustrated in
The steel cord in the present embodiment is formed as the 2/7 structure or the 3/8 structure, so that the breaking load of the steel cord can be increased because the 2/7 structure or the 3/8 structure is a structure in which the number of the outer sheath filaments 12 is close to an acceptable upper limit relative to the number of the core filaments 11. Additionally, in any of the above-described structures, the outer sheath filaments 12 are densely arranged around the core filaments 11, and thus the degree of rubber penetration conventionally tends to be reduced. However, according to the steel cord of the present embodiment, even if any of the above-described structures is used, the degree of rubber penetration can be increased and a high effect in particular can be obtained.
A cross-section perpendicular to the longitudinal direction of the steel cord 10 of the present embodiment may be, for example, a flat shape. The length of the long diameter LL in the cross-section perpendicular to the longitudinal direction of the steel cord 10 of the present embodiment is not particularly limited, but is preferably, for example, 1.43 mm or greater and 1.65 mm or less, and is more preferably 1.45 mm or greater and 1.60 mm or less.
The length of the short diameter Ls in the cross-section perpendicular to the longitudinal direction of the steel cord 10 of the present embodiment is not particularly limited, but is preferably, for example, 1.30 mm or greater and 1.50 mm or less, and is more preferably 1.32 mm or greater and 1.45 mm or less.
The lengths of the long diameter and the short diameter of the steel cord of the present embodiment can be adjusted by pressing the steel cord, for example, along the thickness direction that is, specifically, the direction of the short diameter LS.
The wire diameter D11 of the core filament 11 included in the steel cord 10 of the present embodiment is preferably equal to the wire diameter D12 of the outer sheath filament 12. The wire diameter D11 of the core filament 11 is configured equal to the wire diameter D12 of the outer sheath filament 12, so that the same filaments can be used as the core filament 11 and the outer sheath filament 12. This can reduce the number of types of filaments prepared, reduce the cost, and increase the productivity, when manufacturing the steel cord.
The wire diameter D11 of the core filament 11 and the wire diameter D12 of the outer sheath filament 12 are not limited, but are preferably, for example, 0.30 mm or greater and 0.42 mm or less, and are more preferably 0.35 mm or greater and 0.42 mm or less. When the wire diameters D11 and D12 are 0.30 mm or greater, the breaking load of the steel cord can be sufficiently increased. Further, the wire diameters D11 and D12 are configured to be 0.42 mm or less, so that when the steel cord including the filaments is used for the tire, shock can be sufficiently absorbed and the riding comfort during driving can be improved.
The wire diameter D11 of the core filament 11 and the wire diameter D12 of the outer sheath filament 12 each have a certain manufacturing tolerance. Then, the wire diameters of the filaments can be considered as the same if they are within the tolerance.
For example, if the wire diameter D11 of the core filament 11 and the wire diameter D12 of the outer sheath filament are in a relationship of 0.92≤D11/D12≤1.08, the difference can be considered as within the tolerance range. Therefore, when the above-described range is satisfied, the wire diameter D11 of the core filament and the wire diameter D12 of the outer sheath filament may be considered as the same.
In addition, the twist pitch of the core filament 11 is preferably equal to the twist pitch of the outer sheath filament 12.
If the twist pitch of the core filament 11 is equal to the twist pitch of the outer sheath filament 12, the core filament 11 and the outer sheath filament 12 can be twisted together to manufacture the steel cord. This can increase the productivity of the steel cord.
The twist pitch indicates the length in which the filament is twisted once. The length herein indicates the length along the central axis of the steel cord.
Then, as illustrated in
Here, the twist pitch has been described by using a case of the outer sheath filament 12 as an example, but a case of the twist pitch of the core filament 11 is substantially the same.
In the steel cord of the present embodiment, the twist pitch of the outer sheath filament and the twist pitch of the core filament are not particularly limited. However, for example, the twist pitch of the outer sheath filament and the twist pitch of the core filament are preferably 10 mm or greater and 30 mm or less, and more preferably 15 mm or greater and 25 mm or less.
The twist pitch of the core filament 11 and the twist pitch of the outer sheath filament 12 each also has a certain manufacturing tolerance. Thus, the twist pitches of the filaments can be considered as the same if a difference is within the tolerance.
Here, the twist direction of the core filament 11 is preferably the same as the twist direction of the outer sheath filament 12.
In the core filament 11 and the outer sheath filament 12, the wire diameters and the twist pitches are configured to be the same as described above, so that the productivity of the steel cord can be increased. However, if the wire diameters and the twist pitches of the core filament 11 and the outer sheath filament 12 are the same, the two-layer twisted steel cord that is obtained has a problem of reducing the degree of rubber penetration. From the viewpoint of increasing the durability of the tire, a steel cord having an increased degree of rubber penetration is required to prevent water from entering the rubber of the tire.
Therefore, in the steel cord 10 of the present embodiment, at least one of the core filaments 11 is preferably a waved filament having a bent portion and a non-bent portion along the longitudinal direction.
Although the details of the waved filament will be described below, as illustrated in
The same applies to the steel cord 30 having the 3/8 structure, illustrated in
For comparison,
As described above, at least one of the core filaments 11 is configured to be a waved filament, so that the distance between the outer sheath filaments 12A and 12B can be increased, and the degree of rubber penetration can be increased in comparison with the case where the core filaments 11 do not include a waved filament.
The number of the waved filaments included in the steel cord of the present embodiment is not particularly limited. At least one of the core filaments 11 may be a waved filament as described above. All the core filaments 11 included in the steel cord of the present embodiment may be waved filaments. The waved filaments are used for all the core filaments 11 included in the steel cord of the present embodiment, so that the distance between the outer sheath filaments 12 in particular can be expanded, and the degree of rubber penetration in particular can be increased.
If the core filaments 11 include two waved filaments arranged adjacent to each other, the two waved filaments preferably differ in a wave pitch P described below. That is, in a case where multiple filaments of the core filaments 11 are waved filaments and at least some of the waved filaments are arranged adjacent to each other, the wave pitches P preferably differ between the adjacent waved filaments.
If the wave pitches P of the two adjacent waved filaments are the same, positions of the bent portions of the adjacent waved filaments in the longitudinal direction may be matched unless the positions of the adjacent waved filaments in the longitudinal direction are adjusted. If the positions of the bent portions of the adjacent waved filaments in the longitudinal direction are matched, the effect of increasing the area of the core 111 is reduced and the effect of increasing the degree of rubber penetration might be inhibited.
With respect to the above, if the wave pitches P of the two adjacent waved filaments are different, the positions of the bent portions of the two adjacent waved filaments in the longitudinal direction are prevented from being matched without adjusting the positions of the two adjacent waved filaments in the longitudinal direction. As a result, the area of the core 111 can be sufficiently increased to form sufficient spaces between the outer sheath filaments 12. The degree of rubber penetration in particular can be increased.
The difference between the wave pitches P of the two adjacent waved filaments is not particularly limited, but is preferably 1.5 mm or greater, and is more preferably 1.7 mm or greater. By configuring the difference between the wave pitches P of the adjacent waved filaments to be 1.5 mm or greater, the positions of the bent portions of the adjacent waved filaments in the longitudinal direction can be prevented from being matched without adjusting the positions of the waved filaments in the longitudinal direction while manufacturing the steel cord. Thus, the area of the core 111 in particular can be increased, and the degree of rubber penetration in particular can be increased.
However, since it may be difficult to increase the difference between the wave pitches P of the adjacent waved filaments to be 5 mm or greater, the difference between the wave pitches P of the adjacent waved filaments is preferably 5 mm or less, and is more preferably 4 mm or less.
If the waved filaments include two waved filaments arranged adjacent, the two waved filaments preferably have different wave heights H described below. That is, if the waved filaments are used for multiple core filaments among the core filaments 11 and at least some of the waved filaments are arranged adjacent, the wave heights H preferably differ between the adjacent waved filaments.
A configuration in which the wave heights H of the two adjacent waved filaments are different is used, so that the area of the core 111 can be increased and sufficient spaces can also be formed between the outer sheath filaments, even if the positions of the bent portions of the adjacent waved filaments in the longitudinal direction are matched. The degree of rubber penetration in particular is increased.
The difference between the wave heights H of the adjacent waved filaments is not particularly limited, but is preferably 20% or greater relative to the wire diameter of the waved filament and is more preferably 25% or greater relative to the wire diameter of the waved filament. The difference between the wave heights H of the adjacent waved filaments is configured to be 20% or greater relative to the wire diameter, the area of the core 111 can be increased and the degree of rubber penetration can be increased even if the portions of the bent portions of the adjacent waved filaments in the longitudinal direction are matched.
Additionally, the upper limit of the difference between the wave heights H of the adjacent waved filaments is not particularly limited, but the difference between the wave heights H of the adjacent waved filaments is preferably 150% or less relative to the wire diameter of the waved filament and more preferably 100% or less. If the difference between the wave heights H of the adjacent waved filaments is configured to be 150% or less relative to the wire diameter of the waved filament, the outer diameter of the steel cord can be prevented from being excessively large.
Here, in the steel cord of the present embodiment, a straight filament having no bent portion may be used for the outer sheath filament 12, instead of a waved filament. That is, just one or more core filaments selected from the core filaments 11 may be waved filaments, and the other filaments including the outer sheath filament 12 may be straight filaments.
According to a study of inventors of the present invention, in a case where the waved filaments are used as the core filaments 11, the number of the waved filaments required to achieve a desired degree of rubber penetration can be reduced, in comparison with a case where the waved filaments are used as the outer sheath filaments 12. Thus, the number of the waved filaments required in manufacturing the steel cord can be reduced and the productivity of the steel cord can be increased.
In a case where the waved filaments are used as the core filaments 11, the long diameter LL and the short diameter LS of the steel cord when the desired degree of rubber penetration is achieved can be reduced in comparison with a case where the waved filaments are used as the outer sheath filaments 12. The steel cord can be applied to, for example, the belt layer of the tire described below, but the thickness of the belt layer can be selected so as to embed the steel cord in the rubber of the belt layer. Specifically, for example, the thickness of the belt layer may be defined as a value obtained by adding a predetermined value to the thickness of the steel cord to embed the steel cord. Thus, by reducing the long diameter LL and the short diameter LS of the steel cord, the thickness of the belt layer can be reduced, thereby reducing the amount of rubber contained in the belt layer. As a result, the weight of the tire including the belt layer can be reduced, and the fuel economy of the vehicle to which the tire is attached can be improved.
Details of the waved filament will be described with reference to
The waved filament can be formed by placing multiple preforms 51 and passing a straight filament 52, which is formed to be the waved filament, between the multiple preforms 51 along the direction of the block arrow in the drawing, for example, as illustrated in
The specific wave shape of the waved filaments is not particularly limited. However, the wave height H of the waved filament is preferably 200% or greater and 350% or less relative to the wire diameter of the waved filament, and is more preferably 220% or greater and 320% or less.
As illustrated in
The wave height H is configured to be 200% or greater relative to the wire diameter of the waved filament, so that sufficient spaces can be formed between the outer sheath filaments and the degree of rubber penetration of the steel cord in particular can be increased when the waved filament is used as the core filament of the steel cord.
The wave height H is configured to be 350% or less relative to the wire diameter of the waved filament, so that the outer diameter of the steel cord can be prevented from being excessively large. Additionally, the wave height H is preferably configured to be 350% or less relative to the wire diameter of the waved filament because the generation of flare that is a state in which a twisted filament is unwound and expanded when the steel cord is cut can be prevented.
In the waved filament, a wave pitch P that is a pitch of repeating the bent portion and the non-bent portion is not particularly limited, but, for example, is preferably 2.0 mm or greater and 30.0 mm or less, and is more preferably 3.0 mm or greater and 15.0 mm or less.
The wave pitch indicates the distance between bent portions having the same shape and indicates the length of the steel cord from a reference bent portion to a bent portion next to a next bent portion of the reference bent portion in the longitudinal direction. Thus, in the example illustrated in
The wave pitch P is configured to be 2.0 mm or greater, so that it is easy to form the bent portion and the non-bent portion of the filament, and to control the filament accurately. Additionally, the wave pitch is configured to be 30.0 mm or less, so that the bent portion and the non-bent portion can be manufactured with a relatively simple device, thereby reducing the manufacturing cost.
The waved filament including portions that form wave shapes in multiple different directions is used as the core filament of the steel cord, so that a sufficient distance between the outer sheath filaments 12 can be obtained, thereby particularly increasing the degree of rubber penetration of the steel cord, even if the wave height H is low. Additionally, the waved filament including portions that form wave shapes in multiple different directions are used as the core filament of the steel cord, so that the wave height required to achieve desired degree of rubber penetration can be reduced in comparison with a case of using a waved filament that forms wave shapes only in one direction. Therefore, the processing amount required to form the waved filament can be reduced, thereby increasing the breaking load of the waved filament.
Materials of the core filament included in the steel cord of the present embodiment is not particularly limited, but may be, for example, a steel wire. The core filament included in the steel cord of the present embodiment may also have a steel wire 13 and a plating film 14 disposed on the surface of the steel wire 13, for example, as illustrated as the core filament 11B in
A high carbon steel wire may be preferably used as the steel wire 13.
The plating film 14 is preferably a brass plating film having, for example, copper (Cu) and zinc (Zn) as metal components. The brass plating film may consist of only Cu and Zn, but may also contain a metal component other than Cu and Zn. The brass plating film may further contain, for example, one or more elements selected from cobalt (Co), nickel (Ni), and iron (Fe) as metal components.
Thus, as in the core filament 11B illustrated in
The core filament has the brass plating film containing Cu and Zn, so that when the steel cord is covered with rubber to form a tire, the adhesive strength between the core filament and the rubber can be increased, thereby increasing the durability of the tire. Additionally, the brass plating film further contains one or more elements selected from Co, Ni, and Fe, so that the adhesive strength between the core filament and the rubber can be further increased, thereby further increasing the durability of the tire.
<Tire>
The tire of the present embodiment will be described with reference to
The tire of the present embodiment may include the steel cord described above.
As illustrated in
The tread 61 is a portion that is in contact with a road surface. The bead 63 is provided toward the inside of the tire 60 from the tread 61. The bead 63 is a portion that is in contact with a rim of a wheel of a vehicle. The sidewall 62 connects the tread 61 to the bead 63. When the tread 61 is impacted through the road surface, the sidewall 62 is elastically deformed to absorb the impact.
The tire 60 includes an inner liner 64, a carcass 65, a belt layer 66, and a bead wire 67.
The inner liner 64 is formed of rubber and seals a space between the tire 60 and the wheel.
The carcass 65 forms a backbone of the tire 60. The carcass 65 is formed of an organic fiber, such as polyester, nylon, and rayon, or a steel cord; and rubber.
The bead wire 67 is provided in the bead 63. The bead wire 67 receives a tensile force acting on the carcass.
The belt layers 66 tighten the carcass 65 to increase the rigidity of the tread 61. In the example illustrated in
As illustrated in
Since the above-described steel cord has an improved degree of the rubber penetration, the steel cord can be filled with the rubber to prevent water or the like from entering the steel cord. Therefore, according to the tire of the present embodiment including the steel cord described above, the durability of the tire can be increased.
Additionally, the steel cord described above has a flat shape in a cross-section perpendicular to the longitudinal direction. Since the thickness of the belt layer can be selected so that the steel cords arranged in a single row can be embedded in the rubber, a shape of the cross-section of the steel cord is configured to be flat and the thickness is reduced, thereby reducing the thickness of the belt layer. Therefore, by using the steel cord described above, the amount of rubber included in the belt layer can be reduced in comparison with, for example, a case where a circular steel cord having the same cross-sectional area is used. As a result, the weight of the belt layer can be reduced, and the weight of the tire including the belt layer can also be reduced.
The embodiments have been described in detail above, but are not limited to any specific embodiment. Various modifications and alterations can be made within the scope of the claims.
Specific examples will be described below. However, the present invention is not limited to these examples.
A method of evaluating the steel cords produced in the following experimental examples will be described.
The wire diameter of the filament was measured using a micrometer.
The steel cord to be evaluated was embedded in a transparent resin and a sample was cut so as to expose a plane (i.e., a cross section) perpendicular to the longitudinal direction of the steel cord.
Then, a projector was used to measure a short diameter Ls of the steel cord and the long diameter LL in the cross section.
The measurement was performed by the tracing method of JIS G 3510 (1992). Specifically, a thin paper that is traceable was placed on the outer periphery of the produced steel cord, and was rubbed with a pencil over the paper to copy a trace of the twist of the outer sheath filament. Then, five twist pitches of the outer sheath filament along the central axis of the steel cord was measured by a ruler from the obtained trace of the twist of the outer sheath filament, and a value obtained by dividing the measured value by 5 was used as the twist pitch of the outer sheath filament.
After untwisting the outer sheath filament and exposing the core filament, the twist pitch of the core filament was also measured in a similar manner. However, since the twist pitch of the outer sheath filament was the same as the twist pitch of the core filament in each of the following examples, only one value is shown as the evaluation result.
First, the produced steel cords were arranged on a tire rubber sheet such that the spaces between the steel cords are equal, that is the distance between the steel cords is twice as long as the long diameter of the steel cord, and the rubber sheet was placed over the steel cords. Thus, a laminate of a rubber sheet having a cuboid shape and a steel cord with a thickness being five times as long as the shorter diameter of the steel cord in total, was prepared. The laminate of the rubber sheet and the steel cord was vulcanized at 160° C. for 18 minutes.
After natural cooling, the steel cord was retrieved with a cutter knife from the obtained steel cord and rubber complex.
Then, two adjacent outer sheath filaments were removed from the retrieved steel cord. The degree of rubber penetration was determined as a percentage obtained by calculating a rate of the length of a portion being covered with the rubber in the observation length of 100 mm along the central line of a region exposed by removing the two adjacent outer sheath filaments in the width direction.
As a value of the degree of rubber penetration increases, the degree of rubber penetration indicates improved rubber penetration. The degree of rubber penetration that is 50% or greater indicates being sufficient for practical use.
In the following, a producing condition of the steel cord in each experimental example will be described. Experimental examples 1 to 19 are the embodiments and Experimental examples 20 to 22 are comparative examples.
The steel cord was produced by the following procedure.
A copper layer and a zinc layer were formed on the surface of a steel filament matrix by plating. The copper layer was formed using copper pyrophosphate as a plating solution with a current density of 22 A/dm2 and a processing time of 14 seconds. The zinc layer was formed using zinc sulfate as a plating solution with a current density of 20 A/dm2 and a processing time of 7 seconds.
After plating, heat treatment was performed by heating at 600° C. for 9 seconds under the atmosphere, and metal components were diffused to form the plating films.
By performing wire stretching processing on the filament matrix on which the obtained plating films were formed, a filament having a wire diameter of 0.38 mm and having a brass plating film on the surface of the steel wire was obtained.
Then, the obtained filaments having the plating films were twisted by a twisting machine so that the steel cord according to Experimental example 1 having the 2/7 structure illustrated in
When the steel cord of Experimental example 1 described above was produced, one filament among the two core filaments 11 was a waved filament. The waved filament was a filament in which the bent portion and the non-bent portion are repeatedly formed along the longitudinal direction such that the wave height H is 0.95 mm (i.e., 250% of the wire diameter) and the wave pitch P between the bent portion and the non-bent portion is 4.3 mm. The remaining one filament was a straight filament in which the bent portions were not formed. In the following other experimental examples, among the core filaments 11, the filaments that are not the waved filaments are straight filaments in which the bent portions are not formed. Additionally, for all the outer sheath filaments 12, straight filaments in which the bent portions were not formed were used.
In the waved filament used in the present experimental example, wave shapes are formed along one direction, as in the waved filament 40 illustrated in
The degree of rubber penetration in the steel cord of Experimental example 1 was evaluated. The result is shown in Table 1.
The steel cords were produced and evaluated in a manner similar to Experimental example 1 except that the wave pitch P and the wave height H of each of the Waved filaments were values shown in Table 1.
In each of the experimental examples, a steel cord having the 2/7 structure was produced, and one of the core filaments 11 was a waved filament.
The evaluation results are shown in Table 1.
The steel cord was produced and evaluated in a manner similar to Experimental example 1 except that both of the two core filaments were waved filaments and the wave pitch P and the wave height H of each of the waved filaments were values shown in Table 1.
Here, also in these experimental examples, the steel cord having the 2/7 structure was produced.
In Experimental example 9, the wave height H of each of the two waved filaments was 0.95 mm, and the wave pitches were respectively 4.3 mm and 6.2 mm.
In Experimental example 10, the wave height H of each of the two waved filaments was 0.95 mm, and the wave pitches were respectively 4.3 mm and 8.3 mm.
The evaluation results are shown in Table 1.
The steel cord was produced and evaluated in a manner similar to Experimental example 1 except that both of the two core filaments were waved filaments and the wave pitch P and the wave height H of each of the waved filaments were values shown in Table 1.
When the filaments were twisted, the filaments were adjusted to produce the steel cord, so that bent positions of the two core filaments are shifted in the longitudinal direction.
The steel cord having the 2/7 structure was produced also in the present experimental example.
The wave height H of each of the two waved filaments was 0.95 mm, and the wave pitch was each 4.3 mm.
The steel cord was produced and evaluated in a manner similar to Experimental example 1 except that both of the two core filaments were waved filaments and the wave pitch P and the wave height H of each of the waved filaments were values shown in Table 1.
Here, also in these experimental examples, the steel cord having the 2/7 structure was produced.
The wave heights H of the two waved filaments were respectively 0.95 mm and 1.06 mm, and the wave pitch was each 4.3 mm.
The evaluation results are shown in Table 1.
The waved filament having portions that form wave shapes along multiple different directions was used as the waved filament, and the wave pitch P and the wave height H were the values shown in Table 1. Except the above points, the steel cord was produced and evaluated in a manner similar to Experimental example 1.
The steel cord having the 2/7 structure was produced and one of the core filaments 11 was a waved filament.
The evaluation results are shown in Table 1.
Both of the two core filaments were waved filaments. The waved filaments having portions that form wave shapes along multiple different directions were used as the two waved filaments, and the wave pitch P and the wave height H were the values shown in Table 1. Except the above points, the steel cords were produced and evaluated in a manner similar to Experimental example 1.
Here, also in these experimental examples, the steel cord having the 2/7 structure was produced.
In Example 14, for each of the two waved filaments, the wave height H was 1.06 mm and the wave pitch P was 4.3 mm.
In Experimental example 15, for each of the two waved filaments, the wave height H was 0.85 mm and the wave pitch P was 4.3 mm.
The evaluation results are shown in Table 1.
The steel cord having the 3/8 structure illustrated in
In producing the steel cord, one of the three filaments of the core filaments 11 was a waved filament. The waved filament was a filament in which a bent portion and a non-bent portion were repeatedly formed along the longitudinal direction, such that the wave height H is 0.95 mm (i.e., 250% of the wire diameter) and the wave pitch P between the bent portion and the non-bent portion is 4.3 mm. Straight filaments in which bent portions were not formed were used as the remaining two filaments. Also, the outer sheath filaments 12 were straight filaments in which bent portions were not formed.
The degree of rubber penetration of the produced steel cord was evaluated. The result is shown in Table 1.
In Experimental example 17, two filaments of the three core filaments 11 were waved filaments.
In Experimental example 18, all of the three core filaments 11 were waved filaments, that is, the three filaments were waved filaments.
In Experimental example 17, for each of the two waved filaments, the wave height H was 0.95 mm, and the wave pitches were respectively 4.3 mm and 6.2 mm.
In Experimental example 18, for each of the three waved filaments, the wave height H was 0.95 mm, and the wave pitches were respectively 4.3 mm, 6.2 mm, and 8.1 mm.
Except the above points, the steel cord was produced and evaluated in a manner similar to Experimental example 16.
Here, in each of these experimental examples, a steel cord having the 3/8 structure was produced.
The evaluation results are shown in Table 1.
One core filament among the three core filaments 11 was a waved filament. As such a waved filament, a waved filament including portions that form wave shapes along multiple different directions was used, and the wave pitch P and the wave height H were the values shown in Table 1. Specifically, the wave height H was 0.95 mm and the wave pitch P was 4.3 mm.
Except the above points, the steel cord was produced and evaluated in a manner similar to Experimental example 16.
Here, also in this experimental example, the steel cord having the 3/8 structure was produced.
The evaluation result is shown in Table 1.
Four outer sheath filaments were waved filaments, and the wave pitch P and wave height H of the waved filaments were set as the values shown in Table 1. The waved filaments and the straight filaments in which the bent portions were not formed are alternately disposed along the circumferential direction of the core 111. Additionally, the core filaments 11 were each a straight filament in which the bent portions were not formed. Except the above points, the steel cord was produced and evaluated in a manner similar to Experimental example 1.
Here, in this experimental example, the steel cord having the 2/7 structure was produced.
The evaluation result is shown in Table 1.
As the outer sheath filaments and the core filaments, the straight filaments in which the bent portions were not formed were used. That is, the steel cord 20 having the structure illustrated in
Here, also in this experimental example, the steel cord having the 2/7 structure was produced.
As the outer sheath filaments and the core filaments, straight filaments in which the bent portions were not formed were used. Except the above points, the steel cord was produced and evaluated in a manner similar to Experimental example 16.
Here, in this experimental example, the steel cord having the 3/8 structure was produced.
The evaluation result is shown in Table 1.
According to the results shown in Table 1, in Experimental example 1 to Experimental example 19 in which at least one of the core filaments was the waved filament, the rubber penetration was 50% or greater, and it was found that a steel cord having an improved degree of rubber penetration was obtained.
In the steel cord of Experimental example 20, since the four outer filaments are configured as the waved filaments, the degree of rubber penetration can be 50% or greater. However, comparing Experimental example 20 with Experimental example 4, although the degrees of rubber penetration are the same, it is necessary to increase the number of waved filaments to four in Experimental example 20, and it can be found that the productivity is inferior to the productivity of Experimental example 4.
It is also found that the steel cord of Experimental example 20 has a larger outer diameter than the steel cords of the other experimental examples.
It is found that since the steel cords of Experimental example 21 and Experimental example 22 do not include the waved filaments, the degrees of rubber penetration rate are respectively 40% and 45%, which are remarkably low.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/032249 | 8/26/2020 | WO |
