JPH0436007Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to improvements in insulating molded products, such as bushings.

<Prior Art and Problems> In bushings in which a resin, for example, a thermosetting resin insulator is cast onto a conductor rod, it is necessary to ensure long-term airtightness at the interface between the conductor rod and the insulator. Therefore, it is necessary to provide a strong connection between the conductor rod and the insulator against torsional torque and axial force.For this purpose, the conductor rod is knurled.
It is known to bite insulating resin into the knurled grooves.

However, the electric field concentrates on the edge of the knurled groove, increasing the electrical stress at that point.
There is a problem that the dielectric breakdown strength decreases,
In particular, at the knurled edge, the effect of increasing electrical stress due to the edge effect is even greater.
There's a problem.

<Purpose of the invention> The purpose of the invention is to sufficiently alleviate the increase in electrical stress caused by the knurled grooves and to strengthen the bond between the metal conductor and the resin insulator.

<Structure of the invention> The insulating molded product according to the invention is characterized in that a resin insulator is cast onto a metal conductor whose outer surface is partially knurled and the knurled surface is sandblasted. It is.

<Explanation of Examples> The present invention will be explained below with reference to the drawings.

FIG. 1 shows a through bushing according to the present invention.

In Fig. 1, 1 is a conductor rod (made of copper);
A knurling process 2 is applied to the central part, and a sandblasting process 3 is applied to this knurling surface. The range l ₃ of this sandblasting process 3 is made wider than the range l ₂ of the knurling process in order to reliably sandblast the knurled edges. Reference numeral 4 denotes a resin insulator, which is cast on the conductor rod 1, with a groove for clamping provided in the center of the outer surface, and conductive paint 5 is applied to the groove surface for earth shielding. .

FIG. 2 shows a support bushing according to the invention.

In Fig. 2, 1 is an electrode rod (made of copper);
A knurling process 2 is applied to the area excluding both ends, and a sandblasting process ₃ is applied to this knurling surface in an area _l3 wider than the area l2. 4 is a resin insulator in which the electrode rod 1 described above is embedded.

In the above, since the resin of the insulator bites into the knurled grooves of the metal conductor, the bond between the metal conductor and the resin insulator is strong. Strong coupling can be ensured even against torsional moments. Furthermore, since the knurled surface is sandblasted, the edges of the knurled grooves can be well relaxed, and an increase in electrical stress caused by the edges can be effectively eliminated. In particular, since the sandblasting range is wider than the knurling range, the edge of the groove at the knurled end can be reliably relaxed, and the so-called edge effect of the edge at the knurled end can also be reduced. Therefore,
Electric field concentration and increase in electrical stress caused by the edges can be effectively reduced, and voltage resistance can be ensured well.

The pitch of the above knurling process is usually 0.5~
It is 1.5mm. Sandblasting has a surface roughness of 20μm
The above is preferably 40 μm to 60 μm, and emery sand #20 to #70, preferably #30 to #60 is used at a pressure of 5 to 8
Just spray at Kg/cm ² G.

The resin of the above-mentioned insulator includes a thermosetting resin, in particular,
Preferably, a bisphenol epoxy resin is used.

<Effects of the invention> The insulating molded product according to the invention has the structure as described above, and the knurled surface of the metal conductor is sandblasted, so the edges of the knurled grooves can be well softened. It can effectively reduce the concentration of electric field caused by the electric field, and has excellent voltage resistance.

Actually, in the bushing shown in Fig. 1, d ₁ =
20mm, d ₂ = 50mm, t = 3mm, curvature R = 10mm, l ₁
= 200 mm, bisphenol-based epoxy resin containing silica powder was used as the insulator, knurling was performed with a range l ₂ : 10 mm and a pitch 1.0 mm, and sandblasting was performed with a range l ₃ : 12 mm and a surface roughness equivalent to 60 μm. However, the pressure resistance was as high as 35 to 45 KV/mm. In contrast, it was 25 to 30 KV/mm without sandblasting.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are explanatory diagrams each showing an embodiment of the present invention. In the figure, 1 is a conductor, 2 is a knurled part, 3 is a sandblasted part, and 4 is a resin insulator.

Claims (1)

[Scope of utility model registration request] 1. An insulating molded article, characterized in that a resin insulator is cast onto a metal conductor whose outer surface is partially knurled and the knurled surface is sandblasted.