JPH0721843A - Bending-resistant cable - Google Patents

Abstract

PURPOSE:To provide an economical bending-resistant cable by using pure copper wire for which crystal particle size is adjusted merely by annealing. CONSTITUTION:The crystal particle size of a pure copper wire is adjusted to be 8mum or smaller by annealing and a cable 3 is manufacture by twisting pure copper wires adjusted in this way and coated with an insulating coating. For the pure copper wire, copper with little oxide particles of Cu2O such as oxygen-free copper (OFC) is preferable. When the wire diameter of the pure copper wire becomes as thin as phi0.1mm, the size of the crystalline particles of the pure copper wire affects on the mechanical properties and in the case the crystal particle size is made to be 8mum or small, the bending resistant is greatly improved. That is proved by bending life evaluation of the cable 3 by setting the cable 3 between the upper and the lower clamps 1, 2 of a bending test apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bending resistant cable suitable for robot cables and vehicle cables.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for smaller diameters for cables for robots and cables for vehicles, and there has been a demand for flex-resistant cables that can sufficiently withstand repeated bending and vibration even if the diameter is reduced. There is.

Therefore, conventionally, Cu-F has been used as a flexible cable conductor in order to improve the flexible cable.
An eP precipitation-type high-strength alloy has been reported (Fujio et al. 9
Name: Tatsuta Electric Wire Technical Report, July 1992, P1).

When ordinary pure copper is used as a conductor, the conductor is densely wound around the stranded wire structure,
A horizontally wound conductor having a horizontally wound structure with improved bending characteristics is known.

[0005]

If a special copper alloy such as the above-mentioned Cu--Fe--P type precipitation-type high strength alloy is used to improve the flex resistance of the cable, the flex fatigue resistance of the cable is surely achieved. Although the strength is increased, the manufacturing cost is high and there is a problem in economic efficiency. Further, a cable using a pure copper wire having a horizontal winding structure requires a complicated process for horizontal winding, resulting in an increase in cable cost.

From this, it is desired to develop a cable having excellent bending resistance without using a pure copper wire and having a complicated structure such as a horizontal winding structure.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide an inexpensive bending resistant cable which can improve bending characteristics with pure copper.

[0008]

The flex resistant cable according to the present invention uses a pure copper wire whose grain size is adjusted to 8 μm or less by annealing. Due to its characteristics, this flex-resistant cable is preferably used for robots or vehicles.

A pure copper wire having a crystal grain size of 8 μm or less is coated with an insulator and twisted together to form a cable. Alternatively, a pure copper wire is twisted and then covered with an insulator to form a twisted cable. Also, rather than a stranded structure,
A cable having a horizontally-wound structure conductor in which the pure copper wire is tightly horizontally wound may be used.

As for the material of the pure copper wire, the tough pitch copper and the oxygen-free copper (OFC) can improve the bending life, but since the oxide particles (Cu ₂ O) play a role of a kind of defect, the OFC It is preferable to use. But OF
Not be a C, (in the tough pitch copper about 350wtppmO ₂₎ copper wire, including the following O ₂ 100 ppm improving effect even bending life is great.

[0011]

[Function] The diameter of the pure copper wire, which is the strand of the cable conductor, is 0.
It was found that the size of the crystal grain size of pure copper greatly affects the mechanical properties when it becomes about 1 mm.
It was found that a cable having excellent bending resistance can be obtained by adjusting the thickness to less than or equal to μm. On the other hand, in the case of a pure copper wire having a crystal grain size of 8 μm or more, the bending resistance is not improved so much, the crystal grain size varies greatly, and the mechanical specific stability is poor.

[0012]

EXAMPLES Examples of the present invention will be described below.

First, φ 0. made of oxygen-free copper (OFC).
Using a pure copper wire of 12 mm, the pure copper wire was annealed to adjust the crystal grain size, and as shown in Table 1 below, the crystal grain size was 2 μm.
m or less strands (Example 1), 2 to 4 μm strands (Example 2), 4 to 6 μm strands (Example 3), and 5 to 8 μm strands (Example 4) were produced. The comparative example in Table 1 is an ordinary pure copper wire having a crystal grain size of 40 μm or less and a large crystal grain size of about 30 μm. Next, after 112 wires of the above-mentioned strands (pure copper wires) were twisted, a cable for a robot was produced by covering the wires with an insulator and twisting them together.

The bending life of the cable thus manufactured was evaluated by the bending test apparatus shown in FIG. This test conforms to what is legally called a seismic test, and the test method is as follows. As a sample, take a cable 3 of an appropriate length, bend the cable 3 into a U shape, fix both ends of the cable 3 with the upper clamp 1 of the bending test apparatus of FIG. 1, and lower the cable 3 to the lower end side. Install the clamp 1. Between the upper clamp 1 and the lower clamp 2, a bending guide support 4 is installed so as to sandwich the cable 3. The curvature radius r of the surface of the bending guide support 4 facing the cable 3 is 3 mm, the vertical thickness d is about 6 mm, and the distance h between the lower clamp 2 and the bending guide support 4 is about 30 mm ( FIG. 1A). In the test, the lower clamp 2 is bent to the left and right with the bending guide support 4 as a fulcrum.
° The operation of vibrating and bending is continuously performed at a speed of about 200 times per minute. The results of the flex life of each cable are shown in Table 1.

[0015]

[Table 1]

As can be seen in Table 1, the crystal grain size is 40 μm.
In the cables of Examples 1 to 4 having a crystal grain size of 8 μm or less, the bending life is extended to about twice as long as that of the cable of the comparative example using the normal copper wire having a large crystal grain size of about 30 μm. The effect of improving the flex life is recognized.

[0017]

As is apparent from the above description, the present invention has the following effects. (1) In order to improve the bending property, since an expensive alloy wire is not used and a pure copper wire whose crystal grain size is simply adjusted by annealing is used, it is excellent in economic efficiency.

(2) Since the crystal grain size is 8 μm or less,
A cable composed of pure copper wire having a substantially uniform crystal grain size is obtained, and mechanical properties such as proof strength are stable.

(3) It is not necessary to intentionally perform horizontal winding, which is a complicated process for improving the bending characteristics, and the bending life can be extended to about twice that of the conventional product even with the stranded wire structure. In this case, there is almost no increase in cable cost as compared with the conventional ordinary cable, and it is possible to provide a high-performance flex-resistant cable with good economical efficiency.

(4) In particular, even when it is used as a cable for a robot or a cable for a vehicle, which is strongly required to have a small diameter, it can sufficiently withstand repeated bending and vibration.

[Brief description of drawings]

FIG. 1 shows an outline of a cable bending test apparatus.
The figure (A) is a side sectional view and the figure (B) is a front view.

[Explanation of symbols]

 1 Upper clamp 2 Lower clamp 3 Cable 4 Bending guide support d Thickness r Curvature radius h Distance

Front Page Continuation (72) Inventor Shiro Sakata 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki Hitachi Cable Co., Ltd. Hidaka Plant

Claims (2)

[Claims] 1. A flex-resistant cable characterized by using a pure copper wire having a crystal grain size of 8 μm or less by annealing. 2. A bend-resistant cable, characterized in that the bend-resistant cable is used for a robot or a vehicle.