JP7040698B2 - Anti-twisting cable - Google Patents

Description

The present invention relates to a twist-resistant cable used for, for example, a SCARA robot.

Conventionally, a cable having an aggregate in which a plurality of electric wires are twisted is known (see, for example, Patent Document 1). Such cables are used in a wide variety of applications such as industrial robots, construction equipment, and vehicles.

Japanese Unexamined Patent Publication No. 2017-059319

By the way, in the above-mentioned cable, the aggregate and the tape covering the aggregate are generally wound in opposite directions to each other, which has the advantage of suppressing the bending habit of the cable and stabilizing the bending resistance. be. However, when the winding direction of the aggregate and the tape are opposite to each other, the layer twist of the aggregate and the tightening direction and the loosening direction of the tape are different when the cable is twisted.

When such a cable is used, for example, in a SCARA robot, there is a possibility that a problem may occur in durability. Specifically, first, when the cable is bent and twisted with the operation of the SCARA robot, wrinkles are generated in the stress concentration portion. This wrinkle is generated by creating a space in the cable due to the opposite winding direction of the aggregate and the tape, and as shown in FIG. 6, the sheath falls into the stress concentration portion. If the wrinkles continue to press the inside of the cable, as shown in FIG. 7, there is a problem that the electric wire causes internal fatigue and leads to an early disconnection of the cable.

Further, if the tensile yield stress of the sheath member is low, the stress concentration portion reaches the plastic region, and the sheath member also breaks.
INDUSTRIAL APPLICABILITY According to the present invention, a twist-resistant cable having improved durability that overcomes the above problems is provided.

[1] An aggregate in which a plurality of electric wires are twisted together,
A tape member that covers the outer circumference of the aggregate and
It comprises a sheath member formed of polyvinyl chloride and covering the aggregate covered with the tape member.
The tensile yield stress of the sheath member is 3.5 MPa or more and 10 MPa or less.
Moreover, the twist-resistant cable is characterized in that the twisting direction of the aggregate and the winding direction of the tape member are the same direction.
In this way, by making the twisting direction of the aggregate and the winding direction of the tape member the same direction, it is possible to prevent wrinkles from being generated in the stress concentration portion when the twist-resistant cable is twisted. , It is possible to suppress the internal fatigue of the electric wire caused by twisting. Further, by forming the sheath member with a vinyl chloride resin, the tensile yield stress of the sheath member can be increased. Further, by setting the tensile yield stress of the sheath member to 3.5 MPa or more and 10 MPa or less, it is possible to prevent the sheath member from breaking when the twist-resistant cable is twisted. Therefore, it is possible to provide a twist-resistant cable that is hard to break at the time of twisting and has a high degree of durability.

[2] The twist-resistant cable according to [1], wherein the thickness of the sheath member in the cross-sectional direction is 0.8 mm or more and 3.0 mm or less, and the electric wire is formed by twisting a plurality of cores in a layered manner. ..
With such a sheath thickness, it is possible to provide a sheath member having elasticity that is hard to break and does not hinder the twisting operation.

[ 3 ] The twist-resistant cable according to any one of [1] and [2], wherein the electric wire is formed by twisting a plurality of cores in a layered manner.
In this way, the durability of the electric wire can be improved by forming the electric wire by twisting the plurality of cores in a layered manner.

[ 4 ] A central interposition is provided in the inner center of the twist-resistant cable.
The twist-resistant cable according to any one of [1] to [ 3 ], wherein the plurality of the electric wires are twisted around the central interposition.
This makes it possible to create a twist-resistant cable that is not easily crushed when twisted.

[ 5 ] The twist-resistant cable according to [ 4 ], wherein the central interposition is a resin tube.
Thereby, it is possible to provide an interposition rich in insulation and elasticity.

[ 6 ] The twist-resistant cable according to any one of [1] to [ 5 ], wherein the twist-resistant cable is a robot cable used for a SCARA robot.

[ 7 ] The twist-resistant cable is connected to a movable portion of the SCARA robot, and the movable range of the movable portion is 120 ° or more and 300 ° or less in a clockwise and counterclockwise direction, respectively [ 6 ]. Anti-twisting cable.

[ 8 ] The twist-resistant cable according to any one of [1] to [ 7 ], wherein the tape member is made of any of non-woven fabric, paper, and resin.

According to the twist-resistant cable of the present invention, durability can be improved.

It is the schematic sectional drawing of the twist-resistant cable which concerns on embodiment. It is an exploded perspective view of the twist-resistant cable which concerns on embodiment. It is a schematic diagram of the SCARA robot using the twist-resistant cable which concerns on embodiment. It is a figure which shows the state of the twisting test performed using the twist-resistant cable which concerns on embodiment. It is a figure which shows the stress-strain curve of the sheath member which concerns on embodiment. It is a photograph showing a state in which a conventional cable is twisted and a wrinkle is generated in the sheath. It is a photograph which shows the state which caused the internal fatigue of the electric wire in the conventional cable.

Hereinafter, the twist-resistant cable according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a twist-resistant cable according to an embodiment. This schematic cross-sectional view shows a cut surface cut in a direction orthogonal to the axial direction in a state where the twist-resistant cable 1 is not twisted and deformed. Here, as shown in FIG. 1, the twist-resistant cable 1 includes an aggregate 2 and a sheath member 8.

The aggregate 2 is composed of a plurality of electric wires 3, an interposition 4, and a twisted string 6 twisted together, and the outer periphery of the aggregate 2 is covered with a tape member 10 made of a non-woven fabric, paper, resin, or the like. ing. The tape member 10 is for reducing the friction between the assembly 2 and the sheath member 8 when the twist-resistant cable 1 is twisted. The electric wire 3 is also made by twisting a plurality of cores 3a in a layered manner, and the outer periphery thereof is covered with a shield 3b having an insulating property. The outer circumference of the shield 3b is further covered with an inner sheath member that reduces friction. The core 3a is an insulating coated wire in which the outer periphery of the conductor is coated with an insulator.

Further, as shown in FIG. 2, the tape member 10 is spirally wound in the same direction as the twisting direction of the electric wires 3 constituting the aggregate 2. As a result, when the twist-resistant cable 1 is twisted, the tape member 10 can be made to follow the twisting direction of the aggregate 2. Therefore, a space is created in the twist-resistant cable 1 to prevent the sheath member 8 from falling into the stress concentration portion, and wrinkles are generated in the stress concentration portion as in the conventional cable shown in FIG. Can be prevented.

The interposition 4 is a flame-retardant resin tube arranged inside the twist-resistant cable 1, and has a cavity 4a inside. As the resin constituting the interposition 4, for example, vinyl chloride, polyurethane, or the like is used. Further, a central interposition 4'is arranged at the center of the twist-resistant cable 1. The plurality of electric wires 3 and the plurality of other interpositions 4 are arranged in a layered manner around the central interposition 4'. This makes it difficult for the twist-resistant cable 1 to be crushed when it is twisted.

The strand 6 is a member that fills the space between the aggregate 2, the interposition 4, and the central interposition 4', and is formed by, for example, twisting a wire rod made of an olefin resin.
The sheath member 8 is a resin tube forming the outer circumference of the twist-resistant cable 1, and is made of vinyl chloride resin. The aggregate 2 covered with the tape member 10 is covered with the sheath member 8. The thickness of the sheath member 8 in the cross-sectional direction is 0.8 mm or more and 3.0 mm or less, and the tensile yield stress of the sheath member 8 is 3.5 MPa or more and 10 MPa or less. In this way, by setting the tensile yield stress of the sheath member 8 to 3.5 MPa or more and 10 MPa or less, the stress concentration portion does not reach the plastic region when the twist-resistant cable 1 is twisted, and the sheath member It is possible to prevent the breakage of 8. Further, by setting the thickness of the sheath member 8 to 0.8 mm or more and 3.0 mm or less, it is possible to have elasticity that is hard to break and does not hinder the twisting operation.

As shown in FIG. 3, the twist-resistant cable 1 configured as described above is mainly used for the SCARA robot 20 as a robot cable. The SCARA robot 20 includes a base 22, a first arm 24, and a second arm 26. One end of the twist-resistant cable 1 is fixed to the base 22, and the other end is fixed to the second arm 26 (movable part). Further, the first arm 24 is fixed to the base 22 so as to be rotatable around the first axis J1, and the second arm 26 is attached to the first arm 24 so as to be rotatable around the second axis J2. It is fixed.

Here, the rotation angle of the first arm 24 with respect to the base 22 on the first axis J1 is ± 120 °. Here, + 120 ° means a state in which the first arm 24 is rotated 120 ° clockwise when the reference position of the first arm 24 with respect to the base 22 is 0 °, and −120 ° means a counterclockwise direction. It means a state of being rotated by 120 °. Further, the rotation angle of the second arm 26 with respect to the first arm 24 on the second axis J2 is ± 180 °. Even in this case, + 180 ° means a state in which the second arm 26 is rotated 180 ° clockwise when the reference position of the second arm 26 with respect to the first arm 24 is 0 °, and −180 ° means. It means a state of being rotated 180 ° counterclockwise. Therefore, the rotation angle of the second arm 26 with respect to the base 22 is 300 ° or less (± 300 ° or less) in the clockwise and counterclockwise directions, respectively.

According to the twist-resistant cable 1 according to this embodiment, the twisting direction of the aggregate 2 and the winding direction of the tape member 10 are set to be the same direction, so that the stress is stressed when the twist-resistant cable 1 is twisted. It is possible to prevent wrinkles from being generated in the concentrated portion, and it is possible to suppress internal fatigue of the electric wire caused by twisting. Further, by setting the tensile yield stress of the sheath member 8 to 3.5 MPa or more and 10 MPa or less, it is possible to prevent the sheath member 8 from breaking when the twist-resistant cable 1 is twisted. Therefore, it is possible to provide a twist-resistant cable 1 that is hard to break at the time of twisting and has a high degree of durability.

Further, the present invention is not limited to the above-described embodiment, and for example, the core 3a constituting the electric wire 3 may be formed of a coaxial wire, a twisted wire, or a shielded twisted wire. .. Alternatively, the core 3a may be formed by combining two or more types of an insulating coated wire, a coaxial wire, a pair of twisted wires, and a shielded pair of twisted wires.

<Example 1>
Next, an experiment on the winding direction of the tape member performed using the twist-resistant cable 1 and another cable (conventional product) according to the present embodiment will be described. Here, the twist-resistant cable 1 has the twisting direction of the aggregate 2 and the winding of the tape member 10 in the same direction, whereas the other cables have the twisting direction of the aggregate and the winding of the tape member. Is the opposite direction. In the experiment in Example 1, the winding direction of the tape member and the relationship between the twist angle and the space generated in the cable were observed.

First, in the experiment, the tester prepared a twisting tester 30 and set each sample as shown in FIG. Here, the fixing distance L between the fixing portion to the fixing arm 32 and the fixing portion to the rotating portion 34 is 0.5 m. In the experiment, as shown in Table 1, the rotating portion was rotated in the + direction and the − direction with the sample set in the twisting tester 30.

As a result of the experiment, with other cables, no space was found in the cable until it was rotated by 90 ° in both directions (clockwise and counterclockwise), but when it was rotated by an angle exceeding 90 °, it was inside the cable. Space was generated in. On the other hand, in the twist-resistant cable 1 according to the present embodiment, no space was observed in the twist-resistant cable 1 until it was rotated by 400 ° in both directions. That is, it was found that the durability of the twist-resistant cable 1 is improved by setting the twisting direction of the aggregate 2 and the winding of the tape member 10 in the same direction.

<Example 2>
In Example 2, an experiment on the tensile yield stress of the sheath member was performed. In the experiment, as shown in Table 2, in addition to the sheath member 8 according to the present embodiment, the sheath member A, the sheath member B, and the sheath member C were used. Here, the sheath member 8 according to the present embodiment is made of polyvinyl chloride having higher slidability than the sheath member A according to the comparative example. Further, the sheath member C according to the comparative example is made of polyurethane, which is more slippery than the sheath member B.

In the experiment, a Tensilon universal tester (Model: RTE-1210 manufactured by Orientec Co., Ltd.) was used as the measurement tester. The applicable standard of the experiment is based on JIS K 7161-1. The tensile speed of each sheath member was 500 mm / min, and the test piece used was a dumbbell-shaped punched piece having a width of 3 mm. The distance between the chucks, which are both tension portions of the measuring tester, is 40 mm.

The graph shown in FIG. 5 shows the stress-strain curve of each sheath member in the above-mentioned tensile yield stress. The four straight lines shown in this graph are tangents to the stress-strain curve of each sheath member. The range in which this tangent line is in contact with the stress-strain curve is the elastic range of each sheath member. Further, the point where the tangent line is separated from the stress-strain curve is the yield point, which is the boundary between the elastic range and the plastic range of each sheath member.

Here, the tensile yield stress at the yield point of the sheath member 8 according to the present embodiment is 7.1 MPa, as shown in Table 2. The tensile yield stress at the yield point of the sheath member A is 4.4 MPa. The tensile yield stress at the yield point of the sheath member B is 3.4 MPa. The tensile yield stress at the yield point of the sheath member C is 2.9 MPa.

According to this experiment, the vinyl chloride-based sample such as the sheath member 8 and the sheath member A according to the present embodiment has a higher tensile yield stress than the urethane-based sample such as the sheath member B and the sheath member C. It can be seen that it is difficult to reach the plastic region even when stress is applied. Therefore, the durability of the cable can be improved by using the sheath member made of a vinyl chloride material. Further, the sheath member 8 according to the present embodiment, which uses polyvinyl chloride having a higher slidability than the sheath member A, can have a higher tensile yield stress at the yield point, and the sheath is rich in elasticity. Members can be provided.

1 Twist resistant cable 2 Aggregate 3 Wire 3a Core 3b Shield 4 Intervention 4'Center intervening 4a Cavity 6 Twist 8 Sheath member 10 Tape member 20 SCARA robot 22 Base 24 1st arm 26 2nd arm 30 Twist test Machine 32 Fixed arm 34 Rotating part J1 1st axis J2 2nd axis L Fixed distance

Claims (8)

An aggregate of multiple wires twisted together,
A tape member that covers the outer circumference of the aggregate and
It comprises a sheath member formed of polyvinyl chloride and covering the aggregate covered with the tape member.
The tensile yield stress of the sheath member is 3.5 MPa or more and 10 MPa or less.
Moreover, the twist-resistant cable is characterized in that the twisting direction of the aggregate and the winding direction of the tape member are the same direction. The twist-resistant cable according to claim 1, wherein the thickness of the sheath member in the cross-sectional direction is 0.8 mm or more and 3.0 mm or less. The twist-resistant cable according to claim 1 or 2 , wherein the electric wire is formed by twisting a plurality of cores in a layered manner. A central interposition is provided in the inner center of the twist-resistant cable.
The twist-resistant cable according to any one of claims 1 to 3 , wherein the plurality of electric wires are twisted around the central interposition. The twist-resistant cable according to claim 4 , wherein the central interposition is a resin tube. The twist-resistant cable according to any one of claims 1 to 5 , wherein the twist-resistant cable is a robot cable used for a SCARA robot. The sixth aspect of claim 6 , wherein the twist-resistant cable is connected to a movable portion of the SCARA robot, and the movable range of the movable portion is 120 ° or more and 300 ° or less in a clockwise direction and a counterclockwise direction, respectively. Anti-twist cable. The twist-resistant cable according to any one of claims 1 to 7 , wherein the tape member is made of any of non-woven fabric, paper, and resin.

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