Multi-core cable

Abstract

To provide a multi-core cable that has self-standing properties and can be kept in an arch shape; and shows improved durability against twisting when used under high-speed movement.SOLUTION: A multi-core cable includes at least one tube, a plurality of wires, and an outer cover that forms the contour of the cable and collectively contains the tube and the wires. The tube has a hardness (Shore D) of 30 or more and the outer cover has a (Asker C) of 60-85.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cable used primarily in industrial robots, and to a multi-core cable that is suitable for use in moving parts that are required to perform complex movements depending on the position and number of joints, such as vertical multi-joint robots, horizontal multi-joint robots, and Cartesian robots. [Background technology]

[0002] In particular, the cables used in horizontal articulated robots connect the tip and base ends of the robot arm. They are arranged in an arch shape and must be maintained in this arch shape at all times, so the cables must be able to stand on their own. Since they will be used for long periods of time in an environment with high-speed movement, they also need to be durable against twisting.

[0003] As an example of a cable for a horizontal articulated robot, the multi-core cable in Patent Document 1 focuses on the relationship between the characteristics of the sheath material, the twisting direction of the wire assembly, and the winding direction of the tape material covering the outer circumference of the wire assembly, and is shown to have improved durability against twisting.

[0004] Patent Document 2 also focuses on the sheath, showing a multi-core cable having an inner sheath made of urethane resin and an outer sheath that protects the inner sheath, and claims the effect of making the cable less susceptible to breakage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-204591 A [Patent Document 2] JP 2020-95790 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a multi-core cable which has excellent self-supporting properties for maintaining an arch shape and which has improved durability against twisting when used under high-speed movement. [Means for solving the problem]

[0007] The gist of the present invention is as follows. (1) A multi-core cable consisting of at least one tube, a plurality of electric wires, and an outer sheath covering these, characterized in that the hardness (Shore D) of the tube is 30 or more, and the hardness (Asker C) of the outer sheath is 60 to 85. (2) It is preferable that the coefficient of dynamic friction of the material of the tube is 0.3 or less. (3) It is preferable that the wall thickness of the tube is 0.50 mm to 3.0 mm, the outside diameter of the tube is 1.0 mm to 10 mm, and the outside diameter of the multi-core cable is 10.0 mm to 30.0 mm. (4) The flatness of the tube (minimum outer diameter / maximum outer diameter) is preferably 0.90 to 1.0. (5) The thickness of the outer jacket is preferably 1.0 mm to 4.0 mm. Effect of the Invention

[0008] According to the present invention, the tube itself contributes to improving the self-supporting property of the multi-core cable, so that when the cable is fixed in an arch shape to a horizontal articulated robot or the like, vibration during high-speed movement is suppressed, thereby reducing the load on the cable. The improved self-supporting property reduces wrinkles in the sheath, which also contributes to reducing the load on the cable. In addition, the improved slipperiness of the tube reduces friction between the tube and the electric wire, preventing breakage of the conductor in the electric wire (signal wire) in particular, improving durability and enabling long-term use. [Brief description of the drawings]

[0009] [Figure 1] 1(a) and (b) show examples of cross-sectional views of a cable of the present invention. [Diagram 2] FIG. 1 shows a schematic diagram illustrating a method for evaluating independence in the present invention. BEST MODE FOR CARRYING OUT THEINVENTION

[0010] Hereinafter, as an example of a cable of the present invention, the basic structure will be described with reference to the drawings.

[0011] The multi-core cable 1 in FIG. 1(a) is composed of at least one tube 2, a plurality of electric wires 3, and an outer sheath 4 that covers the entire cable. 1 (b) further includes a tape wound layer 5 and an interposer 6. From the viewpoint of improving the self-supporting property, the number of the tubes 2 is preferably two or three.

[0012] The durometer hardness type (Shore D) of the tube 2 is 30 or more. This improves the self-supporting property and enables the multi-core cable 1 to be held in an arched shape. The improved self-supporting property makes it possible to suppress the vibration of the multi-core cable 1 during high-speed movement, and as a result, the load on the electric wires (signal wires) in the cable is reduced, which contributes to preventing breakage of the conductor. It is preferably 50 or more. The upper limit is not particularly limited, but from the viewpoint of preventing breakage when bent, it is preferably 60 or less.

[0013] (Hardness measurement method) Durometer hardness D type (Shore D) is measured by a method conforming to JIS K 7215. The measurement sample is a tube shape (inner diameter 4.0 mm, outer diameter 6.0 mm), and the test load is 50 N.

[0014] The dynamic friction coefficient of the material of the tube 2 is not particularly limited, but a material having a dynamic friction coefficient of 0.3 or less is preferable. Examples of materials having a dynamic friction coefficient of 0.3 or less include fluororesin, polyethylene, and nylon 66, and fluororesin is particularly preferable. The dynamic friction coefficient in the present invention is a value measured in accordance with JIS K 7125.

[0015] The thickness of the tube 2 is not particularly limited, but is preferably 0.50 mm to 3.0 mm for the purpose of maintaining the self-supporting property of the multi-core cable 1. It is more preferably 0.50 mm to 2.0 mm, and most preferably 0.50 mm to 1.0 mm.

[0016] For the same purpose, the outer diameter of the tube 2 is preferably 1.0 mm to 10 mm, more preferably 2.0 mm to 10.0 mm, and most preferably 3.0 mm to 8.0 mm.

[0017] The flatness of the tube 2 is not particularly limited, but is preferably 0.90 to 1.0. The flatness here indicates the value when the multi-core cable 1 is in a straight state. Flatness = minimum outside diameter / maximum outside diameter Since the contact portions between the tube 2 and the electric wires 3 are in point contact, friction is reduced and the twist resistance of the multi-core cable 1 is improved. A more preferable range is 0.95 to 1.0.

[0018] The outer diameter of the multi-core cable 1 is not particularly limited, but is preferably 10.0 to 30.0 mm. In addition to the above-mentioned thickness and outer diameter of the tube 2, when the outer diameter of the multi-core cable 1 is 10.0 to 30.0 mm, the improvement in the self-supporting property of the multi-core cable 1 is more remarkable, which is more preferable. It is further preferably 15.0 to 25.0 mm.

[0019] The hardness (Asker C) of the sheath 4 of the multi-core cable 1 is 60 to 85. When the hardness is 60 to 85, the sheath 4 has a suitable flexibility and can ease the load on the electric wires 3 inside the multi-core cable 1 during movement, reducing the occurrence of wrinkles, which contributes to preventing breakage of the conductors 31 and improves durability against twisting. A hardness of 70 to 85 is more preferable.

[0020] When the tube has a hardness (Shore D) of 30 or more and the jacket has a hardness (Asker C) of 60 to 85, the synergistic effect of these two significantly improves durability against twisting.

[0021] The thickness of the outer sheath 4 is not particularly limited, but is preferably 1.0 mm to 4.0 mm. When the outer diameter of the multi-core cable 1 is 10.0 to 30.0 mm and the thickness of the outer sheath 4 is 1.0 mm to 4.0 mm, the occurrence of wrinkles in the outer sheath 4 is suppressed, that is, the load on the inside of the cable is alleviated and the load on the electric wires is reduced, which is more preferable.

[0022] It is more preferable that the hardness (Asker C) of the jacket 4 is 60 to 85 and the thickness is 1.0 mm to 4.0 mm, since this reduces the load on the inside of the cable and the load on the electric wires due to twisting of the multi-core cable.

[0023] The material of the outer cover 4 is not particularly limited, but is preferably polyvinyl chloride or polyurethane.

[0024] There is no particular limitation on the configuration of the electric wire 3. For example, it may be an electric wire in which a single or stranded conductor is covered with an insulating material, a coaxial cable, an optical fiber cable, or a multi-core cable in which these are twisted together with an insert.

[0025] The material of the conductor 31 is not particularly limited, but examples thereof include a metal wire of copper, aluminum, or the like, or an alloy wire of these with tin, iron, zinc, nickel, or the like added thereto. The surface of the metal wire may be plated with silver, tin, or the like.

[0026] Although there are no particular limitations on the configuration of the conductor 31, it is preferable that the conductor 31 has a conjoint stranded structure in which a bunched strand, in which a number of strands are further twisted together, is formed by twisting a number of strands together. This structure has improved bending resistance compared to a single wire structure or a bunched stranded structure.

[0027] The material of the insulator 32 is not particularly limited, but is preferably a fluororesin from the viewpoint of transmission characteristics.

[0028] The inside of the jacket 4 preferably has a tape wound layer 5 made of a material whose static friction coefficient is equal to or less than the dynamic friction coefficient.

[0029] The tape-wound layer 5 is not particularly limited, but is preferably made of a material having a static friction coefficient equal to or less than the dynamic friction coefficient, such as a fluororesin. This reduces friction between the tape-wound layer 5 and the tube 2 or the electric wire 3 that are in contact with the tape-wound layer 5, resulting in improved durability against twisting. PTFE is preferred in terms of versatility, and unsintered PTFE is particularly preferred due to its excellent durability.

[0030] The winding pitch of the tape winding layer 5 is not particularly limited, but is preferably 1 / 6 to 1 / 2 of the tape width. In addition to the effect of holding down the bundled tubes 2 and electric wires 3, this contributes to improving durability by reducing friction as described above. More preferably, it is 1 / 6 to 1 / 3 of the tape width.

[0031] When the tape-wound layer 5 is applied, it is preferable to provide a gap (not shown) between the tape-wound layer 5 and the jacket 4. The gap can reduce the load on the electric wire 3 (conductor 31) caused by twisting.

[0032] It is preferable that a filler 6 is used between the electric wires 2 and the tubes 3. The material of the filler is not particularly limited, but examples include plastic materials such as polyester and nylon, and thread-like, string-like, and rod-like materials made of cotton. From the viewpoint of low friction, it is preferable that the filler is made of a material whose static friction coefficient is equal to or less than the kinetic friction coefficient, like the material of the tube. EXAMPLES

[0033] The multi-core cable 1 of the present invention will be specifically described below by giving examples, but the scope of the present invention is not limited to these.

[0034] Example 1 is a multi-core cable 1 shown in Fig. 1(a), which is made by bundling three tubes 2 each having an inner diameter of 2.0 mm and an outer diameter of 4.0 mm, a plurality of electric wires 3 each consisting of a four-core multi-core cable or twisted wires, and applying a 2.0 mm thick PVC jacket 4 to the outer periphery. The hardness (Asker C) of the PVC is about 80.

[0035] In Comparative Example 1, in Example 1, the material of the tube 2 is polyurethane.

[0036] The cables of the above examples and comparative examples were subjected to an evaluation of their self-supporting ability, the presence or absence of wrinkles when bent, and a twisting resistance test. The results are shown in Table 1.

[0037] (Method of measurement for the Independence Assessment Test) As shown in Figure 2, Both ends of a 700 mm long multi-core cable 1 are fixed to a 400 mm wide stand, and the rest are hung outside the stand. A 300 gf weight is hung from the middle of the cable, and the amount of deflection from the stand is measured.

[0038] (Twist resistance test method) The measurement conditions are: sample length 500mm, fixation distance 200mm. One cycle is defined as twisting both ends of the sample simultaneously by approximately 140 degrees to the left and right, at a speed of approximately 150 cycles / min. The increase rate (%) from the conductor resistance value before the test is confirmed, and the number of twists at which the resistance reaches 10% or more is counted.

[0039] [Table 1]

[0040] Example 1 has excellent self-supporting properties because the tube material is FEP and the tube hardness is 30 or more. It is understood that the load on the inside of the cable is mitigated, that is, the load on the electric wire is reduced, because the occurrence of wrinkles in the outer jacket is small. As a result, the results of the twist resistance test are also superior to those of Comparative Example 1.

[0041] As for the material of the tube, in Example 1, the tube is made of a material having a dynamic friction coefficient of 0.3 or less, which reduces friction between the tube and the electric wire and improves durability against twisting. [Industrial Applicability]

[0042] INDUSTRIAL APPLICABILITY The multi-core cable of the present invention has excellent durability in terms of self-support and twistability, and is therefore useful in industrial robots, particularly horizontal articulated robots, but is not limited thereto. [Explanation of symbols]

[0043] 1 Multi-core cable 2 Tubes 3 electric wire 31 Conductor 32 Insulators 4 Outer cover 5 Tape winding layer 6 intervention

Claims

1. A multi-core cable including at least one tube, a plurality of electric wire units, and an outer sheath that covers the entire cable, The electric wire unit is composed of a plurality of electric wires, the tube and the electric wire unit are disposed circumferentially along an inner circumference of the jacket, A filler is used between the tube and the wire unit arranged in a circumferential manner, The tube has a hardness (Shore D) of 30 or more, The hardness (Asker C) of the outer covering is 60 to 85, A multi-core cable characterized in that the dynamic friction coefficient of the material of said tube is 0.3 or less.

2. The material of the tube is a fluororesin.

2. The multi-core cable according to claim 1.

3. The wall thickness of the tube is 0.50 mm to 3.0 mm, The outer diameter of the tube is 1.0 mm to 10 mm, The outer diameter of the multi-core cable is 10.0 mm to 30.0 mm.

3. A multi-core cable according to claim 1 or 2.

4. The flatness of the tube (minimum outer diameter / maximum outer diameter) is 0.90 to 1.

0. A multi-core cable according to any one of claims 1 to 3.

5. The thickness of the outer jacket is 1.0 mm to 4.0 mm. A multi-core cable according to any one of claims 1 to 4.

6. The present invention is characterized in that the inner surface of the outer cover has a tape-wound layer made of a material having a static friction coefficient equal to or lower than a dynamic friction coefficient. A multi-core cable according to any one of claims 1 to 5.

7. The winding pitch of the tape is 1 / 6 to 1 / 2 of the width of the tape. The multi-core cable according to claim 6.

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