JPH0136641B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a spiral wire-wound low-noise electric wire.

As shown in FIG. 1, a low-noise electric wire is known in which a wire 2 having a circular cross section is wound around the outer periphery of an electric wire 1. However, when the configuration in this case is viewed in cross section, as shown in FIG. 2, recesses 2a are formed on both sides where the electric wire 1 and the strand 2, each having a circular cross section, are in contact with each other. This recessed part 2a is considered to be rather effective in preventing noise, but from the perspective of wind pressure, the flow of air fluid on the surface of the wire changes greatly at part 2a, so the wake becomes large, and the apparent wind pressure The value will increase.

Also, from the standpoint of snow accretion, the spiral wire 2
Although this has the effect of preventing snow from rotating around the electric wire, snow is trapped in the recessed portion 2a,
This may cause the snow to be less effective at cutting snow, making it difficult for the snow to fall. Furthermore, if the wire 2 protrudes as shown in FIG. 2, when a water droplet adheres to the surface of the wire 2, the electric field strength at the tip of the water droplet increases, which may cause an increase in audible noise due to corona. There are still many problems that I would like to solve.

The present invention aims to provide a low-noise electric wire that can solve the above-mentioned problems associated with low-noise electric wires using the strand winding method. In a low-noise electric wire formed by winding a filament formed on a cut surface and having a substantially flat semicylindrical cross section, the maximum height H of the semicylindrical shape, the height h of the cut surface, the radius of curvature R of the semicylindrical upper surface, and the wire When the outer diameter is D, the structure is such that 0.1≦H/D≦0.3, 0.3≦h/H≦0.8, and 0.2≦R/D, respectively.

The following is a sequential explanation based on examples.

FIG. 3 is a schematic diagram showing a cross section of a low-noise electric wire according to the present invention, where 1 is the electric wire and 3 is a wound wire according to the present invention. As shown in the figure, the upper surface 3a of the wound wire 3 is formed into a substantially flat semicylindrical shape.
The side surface portion 3b is formed into a cut-off surface as shown in the figure.

The technical idea of configuring the wound wire 3 as described above as a prerequisite for the present invention is to configure it in a shape that completely eliminates the existence of the recessed portion 2a in FIG. This means that the noise effect can be maintained as before.

Even if the wound wire 3 is configured in a flat semicylindrical shape as shown in FIG. 3, if the maximum height H is within a certain range, the noise reduction effect can be sufficiently exhibited.

That is, FIG. 5 shows that the outer diameter D of the electric wire 1 was determined by a wind tunnel experiment.
This figure shows the relationship between the ratio H/D of H to the maximum height H of the wound strand 3, the wind noise level, and the resistance coefficient under wind pressure. When H/D is smaller than 0.1, the effect of winding the wound wire 3 does not appear, but when it is larger than 0.1, the wind noise level is clearly reduced. This reduced value is almost the same numerically as when the circular wire 2 shown in FIG. 2 is used.

However, as a matter of course, H/D
As the value of increases, the drag coefficient under wind pressure increases.

Here, the resistance coefficient C _G is a value expressed by equation (1).

C _G = G / (1/2) ρ・A・V ² ...(1) G: Wind pressure resistance (Kg) ρ: Density (Kg・S ² /m ⁴ ) A: Projected area (m ² ) V: Wind speed (m/S) If we transform equation (1) and find the wind pressure resistance G using equation (2), we get G=C _G・{(1/2)ρ・A・V ² ……(2) That is, the same In terms of wind speed and projected area, the smaller C _G is, the smaller the wind pressure resistance G is, and if C _G is the same, then A
The smaller is, the smaller G is.

From the perspective of wind noise level alone, there is no problem even if H/D exceeds 0.3, but as shown in Figure 5, the drag coefficient suddenly increases. Therefore, considering the H/D relationship, it is desirable to configure H/D to be between 0.1 and 0.3.

FIG. 6 also shows the relationship between the ratio R/D of the radius of curvature R of the outer surface of the wire 3 to the outer diameter D of the wire and the resistance coefficient, based on the results of the wind tunnel experiment. It can be seen that the resistance coefficient increases both when R/D becomes smaller than 0.2 and when it becomes larger than 1.0. This is thought to be because when it is smaller than 0.2, the turbulence of the fluid on the wire increases, and when it is larger than 1.0, the influence of the cut-off surface becomes apparent.

Furthermore, FIG. 7 shows the relationship between the ratio h/H of the maximum height H of the strand to the height h of the cut-off surface, the resistance coefficient, and the snow load. The snow accretion load was measured by an artificial snow accretion experiment using a freezer.

When h/H becomes larger than 0.8, the resistance coefficient suddenly increases. This is thought to be because the effect of the cut-off surface, similar to the case of R/D, becomes strong. However, when h/H becomes smaller than 0.3, the effectiveness of cutting snow during snowfall decreases, and it becomes difficult for snow to fall. Therefore, if both conditions are within a satisfactory range, h/H is preferably 0.3 to 0.8.

If you want to further reduce this snow load, the 8th
As shown in the figure, when tetrafluoroethylene resin (PTFE), which has an extremely low coefficient of friction, is attached to the cut-off surface, the snow falling effect becomes greater, and as shown in Figure 7, a significant reduction in snowfall load is seen. .

Furthermore, in order to prevent audible noise caused by corona, it is preferable to form a groove 5 on the upper surface of the wire 3, as shown in FIG. Due to the capillary phenomenon caused by the grooves 5, the water droplets adhering to the strands 3 are flattened, thereby preventing the generation of corona.

As detailed above, if the low-noise electric wire according to the present invention is used, the low-noise effect is the same as that of the conventional example, and the wind pressure resistance is greatly reduced, and it is also highly effective in preventing snow accumulation and corona noise. The significance of saying "don't get it" is huge.

[Brief explanation of drawings]

Fig. 1 is a sketch of a conventional low-noise electric wire, Fig. 2 is a schematic sectional view thereof, Fig. 3 is an explanatory sectional view of an embodiment according to the present invention, and Fig. 4 is another embodiment according to the present invention. 5 to 7 are diagrams showing various characteristics of the low-noise electric wire according to the present invention, and FIG. 8 is an explanatory sectional view showing still another embodiment according to the present invention. 1: electric wire, 2, 3: filament (strand), 4: tetrafluoroethylene resin, 5: groove.

Claims (1)

[Scope of Claims] 1. A low-noise electric wire formed by winding around the outer periphery of a wire having a substantially flat semi-cylindrical cross section with the side portions formed as cut-off surfaces, the maximum height H of the semi-cylindrical shape and the cut-off surface. When the height h, the radius of curvature R of the semicylindrical upper surface, and the outer diameter D of the electric wire, it is configured so that 0.1≦H/D≦0.3, 0.3≦h/H≦0.8, and 0.2≦R/D, respectively. Low noise electric wire. 2. The low-noise electric wire according to claim 1, wherein a tetrafluoroethylene resin is attached to the cut-off surface portion.