JPH0376005B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a case for a film capacitor. (Prior art) As shown in FIG. 2, a conventional film capacitor consists of a film-like dielectric 22 and a metal foil 2 such as copper foil.
4 are stacked alternately, the lead wire 16 for wiring is connected to the metal foil 24, the dielectric material 22 is sandwiched between the tip of the winding core 26 whose tip 28 is shaped like a split pin, and the winding core 26 is rotated. Then, the dielectric material 22 and the like are wound and formed. Its shape is as shown in FIG. Next, when heat treatment is performed, the dielectric material 22 made of styrene or polypropylene thermally shrinks and hardens, closing the winding core removal hole 30 and causing the lead wire 1
Fix 6. The film capacitor 11 thus formed is coated with printing, coloring, or the like. When forming the circuit, the lead wire 16 is used while being fixed to the printed circuit board by soldering. However, since modern electronic devices handle minute signals, the film capacitor 11 is often induced by electromagnetic waves from the device itself or from outside, which often degrades the performance of the device. In order to prevent this electromagnetic induction, a method is used in which the film capacitor 11 and the like are covered with a box made of aluminum, iron, copper, etc., and the box is connected to ground or a low potential side. (Problems to be Solved by the Invention) However, the above film capacitors have the following problems. The method of covering a film capacitor with an aluminum box to prevent induction requires installation work to secure the aluminum box and work to connect the aluminum box to ground or the low potential side. Furthermore, since an aluminum box is used, the area occupied on the board becomes large, which is a problem in that it becomes a problem in miniaturization. Therefore, the inventor devised a method of covering the film capacitor with a metal cylindrical casing to prevent induction, but if the lead wire is thin, it cannot withstand the weight of the casing, and the lead wire may be broken due to vibration etc. However, there was a problem in that the lead wires were bent and short-circuited. The problem may be solved by making the lead wire thicker, but if the lead wire is too thick, a large amount of the heat required for soldering during product mounting will be conducted through the lead wire and enter the film capacitor, causing the film to become damaged. This results in frequent short-circuit failures. Furthermore, when a film capacitor is sealed inside a casing with resin, if the film capacitor is not positioned in the center of the casing, the temperature characteristics of the film capacitor may vary due to the uneven thickness of the resin when the film capacitor is sealed with resin. There is a problem that it may cause a short circuit between the lead wire and the casing. (Means for Solving the Problems) In order to solve the above problems, the present invention has the following configuration. That is, in order to prevent electromagnetic induction of the film capacitor, there is a cylindrical casing capable of accommodating the film capacitor, with one end face closed and the other end face open, and an inner surface of the closed end face of the casing. an earth wire that protrudes from the casing toward the open end face, is inserted into the winding core removal hole of the film capacitor, and protrudes from the open end face of the casing to a length that allows connection to ground or to a low potential side; It is characterized by comprising the following. (Function) Next, the function will be explained with reference to FIG. In the core removal hole 30 of the film capacitor 11,
An earth wire 14 whose end is electrically and mechanically connected is inserted inside the closed end surface 18 of the casing 12 and sealed with a thermosetting resin 32. At this time, since the ground wire 14 is provided protruding from the center of the closed end face 18, uneven thickness of the sealed resin does not occur. Furthermore, electrically, the conductive casing 12 is connected to the ground or to the low potential side by the ground wire 14, so that charges generated by electromagnetic induction are grounded from the ground wire 14, thereby suppressing the generation of noise. (Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, the configuration will be explained. FIG. 1 shows a state in which a film capacitor according to the present invention is housed inside a metal case. 12 is a casing made of copper. In the figure, the upper surface of the casing 12 is a closed end surface 18, and the other end is an open end surface, which is open. Reference numeral 14 denotes an earth wire, which is a metal wire projecting downward from the center of the inner side of the closed end surface 18, and has a diameter of 0.8 mm. 16 is a lead wire of a film capacitor (not shown) housed inside the casing. The lead wire 16 is a solder-plated copper wire with a thickness of 0.4 mm. The method for manufacturing a film capacitor has been described in the prior art section, so a description thereof will be omitted. Next, a method for sealing the film capacitor 11 into the case will be described with reference to FIG. In the core removal hole 30 of the film capacitor 11,
An earth wire 1 protrudes from the inner center of the closed end surface 18 of the casing 12 toward the open end surface 20.
4, the film capacitor 11 is pushed into the casing 12 from the direction of the open end surface 12 of the casing 12. After positioning the film capacitor 11, heat treatment is performed to harden the dielectric 22 of the film capacitor 11.
When the dielectric 22 is hardened by heat treatment, the diameter of the winding core removal hole 30 is reduced and the film capacitor 11 is fixed to the ground wire 14. If the dielectric material 22 is made of styrene, it has a high thermosetting property and therefore has sufficient functionality at this stage.
In order to increase the moisture resistance, the gaps in the casing 12 may be filled with thermosetting epoxy resin 32 and heat treated. Connect the film capacitor 1 to the ground wire 14 in advance.
1 has been fixed by heat treatment, so the casing 12
It is also possible to prevent the film capacitor 11 from floating up when the inside is filled with the thermosetting epoxy resin 32. This bulge is film capacitor 11
This phenomenon occurred because the specific gravity of the thermosetting epoxy resin 32 was greater, and it was also a problem in terms of work. Further, since the ground wire 14 substantially coincides with the central axis of the casing 12, it is possible to prevent uneven thickness of the encapsulated resin after resin filling. To attach the film capacitor 11 covered with the case thus formed to a printed circuit board (not shown), a lead wire 16 and a ground wire 1 are used.
4 can be soldered. Of course ground wire 1
4 is connected to ground or a low potential point by a printed circuit. Since the film capacitor 11 is supported on the printed circuit board by the lead wire 16 and the ground wire 14, which is twice the thickness of the lead wire 16, the mechanical strength can be improved far more than that of conventional film capacitors, and the film capacitor 11 can be bent easily. It is strong against stress and tension, and prevents problems such as disconnection or short circuits due to disconnection or bending. As for the electrical function, it is possible to drop the charge due to electromagnetic induction generated in the film capacitor 11 from inside and outside the device from the casing 12 via the earth wire 14 directly to the ground or to the low potential side, so noise etc. can be cut. can. In addition, as shown in Table 1, the temperature characteristics of the film capacitor according to this example and the case without a ground wire are shown, but it is clear that it is better to use a metal case with a ground wire. There is little variation. The specifications of the metal case in this case are as follows. First of all, the casing is made of copper, outer diameter: 8.0mm, and thickness:
0.2mm, length: 12mm, earth wire material: solder-plated copper wire, outer diameter: 0.8mm, length: 15mm
The film capacitor is a styrene film dielectric with a thickness of 30μ and a width of 10mm, a copper foil with a thickness of 7μ and a width of 6mm, and the lead wire has an outer diameter of 0.4mm and a length of 30mm. Using solder-plated copper wire,
It is wound using a 2.0 mm core and has a capacitance of 1000 pF, and the resin charged in the casing is thermosetting epoxy resin that has been heat-treated at 100°C for 30 minutes.

[Table] Next, other examples will be described. First, when polypropylene is used as the dielectric material of a film capacitor, the heat shrinkability of polypropylene is inferior to that of styrene, so it is necessary to fill the casing with resin to prevent it from falling out. When the casing and the ground wire are separated, the ground wire is inserted through the winding core removal hole of the film capacitor, the dielectric is shrunk by heat treatment, and the ground wire with the film capacitor fixed is inserted into the center of the inside of the closed end face of the casing. spot welding,
It is also possible to connect mechanically and electrically by an appropriate method such as soldering. Even if the casing is made of aluminum, there is no problem in practical use, although the linearity is somewhat inferior. Further, the casing and/or the ground wire may be formed of a conductive resin as long as the electrical properties are acceptable. Various preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-mentioned embodiments. For example, the casing is not cylindrical,
It goes without saying that many modifications can be made without departing from the spirit of the invention, such as a cylindrical shape. (Effects of the Invention) When the film capacitor case according to the present invention is used, it is possible to prevent electromagnetic induction interference of the film capacitor, improve the mechanical attachment strength, etc., make the temperature characteristics uniform, downsize the device, and use resin at the manufacturing stage. Due to the buoyancy, the cumbersome resin filling work can be simplified, and other remarkable effects can be achieved.

[Brief explanation of drawings]

FIG. 1 is an external perspective view of the film capacitor fixed inside the case of the film capacitor according to the present invention, FIG. 2 is a perspective view illustrating how to make the film capacitor, and FIG.
FIG. 4 is an external perspective view of a film capacitor formed by the method shown in the figure, and FIG. 4 is a cross-section of a case of the film capacitor in which the film capacitor is fixed. 11...Film capacitor, 12...Casing, 14...Earth wire, 16...Lead wire.

Claims (1)

[Claims] 1. In order to prevent electromagnetic induction in the film capacitor, there is provided a cylindrical casing capable of accommodating the film capacitor, with one end face closed and the other end face open; A length that protrudes from the inner surface of the closed side end face toward the open side end face, is inserted into the winding core removal hole of the film capacitor, and can be connected to ground or a low potential side from the open side end face of the casing. A film capacitor case characterized by comprising a ground wire protruding from the top. 2. The film capacitor case according to claim 1, wherein the ground wire is provided protruding from the center inside the closed end surface of the casing. 3. The film capacitor case according to claim 1 or 2, wherein the casing and the ground wire are integrally formed. 4. The film capacitor case according to claim 1 or 2, wherein the ground wire is connected to the casing by spot welding. 5. The film capacitor case according to claim 1 or 2, wherein the ground wire is connected to the casing by soldering. 6. Claims 1, 2, and 3, characterized in that the casing is made of copper.
A case of a film capacitor according to item 4, item 5, or item 5. 7. The film capacitor according to claim 1, 2, 3, 4, 5, or 6, characterized in that the casing is sealed with a resin. Film capacitor case. 8. The film capacitor case according to claim 7, wherein the resin is a thermosetting resin.