JPS605585Y2 - Plastic case for capacitor - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a plastic case for a capacitor.

Generally, the internal pressure of a capacitor increases during use, and at the end of its life, this increase in internal pressure increases the risk of explosion.

If a capacitor explodes, it will not lose its function as a capacitor; a large current will flow through the circuit in which such a capacitor is installed, or the contents of the capacitor will be scattered, damaging other electrical components and destroying the entire circuit. This is not desirable as it may cause malfunction.

For this reason, capacitors with a high risk of explosion, such as aluminum electrolytic capacitors in particular, are usually provided with an explosion-proof valve on their lids.

This explosion-proof valve operates when the internal pressure of the capacitor exceeds a predetermined value, and releases the gas filled inside the capacitor to the outside, thereby preventing the capacitor from exploding.

However, if the case body containing the capacitor element is a metal case, the mechanical strength (
In particular, tensile stress) does not decrease significantly, but in the case of plastics, the effects of heat etc. are significant.

For example, when both are placed in an atmosphere of 85° C. for 1000 hours, the mechanical strength of the former hardly changes, while that of the latter decreases to 1 n or less compared to the initial state.

Therefore, if a plastic case with a normal explosion-proof valve installed in the lid is used, the plastic case will be destroyed before the explosion-proof valve operates due to the reduction in mechanical strength, and the explosion-proof valve will be damaged. It often happens that they are unable to perform their functions.

That is, the conventional plastic case has an incomplete explosion-proof structure and has the drawback of reducing the safety of the circuit.

The object of the present invention is to provide a plastic case for a capacitor that improves the above-mentioned drawbacks.

The gist of the present invention is to achieve the above-mentioned purpose in a plastic case for a capacitor in which the welded parts provided on the case body and the lid are melted and welded to each other. The object of the present invention is to provide a plastic case for a capacitor, which is characterized by having an incompletely welded portion formed by welding with a low degree of melting.

Hereinafter, embodiments of the present invention will be described based on the drawings.

In FIG. 1, reference numeral 1 denotes a cylindrical case body made of plastic such as polypropylene or polyester, and a first welded portion 2 is provided at the open end.

3 is a lid made of plastic like the case body 1, and a second welded portion 4 is provided so as to correspond to the first welded portion 2 of the case body 1.

This lid 3 has an external lead terminal 5 for connecting a lead wire of a built-in capacitor and for drawing out an electrode to the outside of the case.

6 and 7 are the first welded part 2 of the case body 1 and the second welded part of the lid 3.
This is a hot plate for welding the welding part 4.

In particular, a convex portion 8 is provided on the end surface of the hot plate 6 so that the end surfaces of the hot plates 6 and 7 do not come into close contact with each other and maintain a predetermined distance l from each other.

When the first welded part 2 and the second welded part 4 come into contact with the hot plates 6 and 7 and are pressed, as shown in FIG. Since less heat is applied compared to the above, protrusions 9 and 10 having a low degree of melting are formed in the first welding part 2 and the second welding part 4, respectively.

Then, the first welded part 2 and the second welded part 4 are brought into contact and welded together.

"-When the base body 1 and the lid 3 are integrated, the protrusions 9 and 10
Since welding is less in the welded portion 11, one or more incomplete welded portions 12 are formed in the welded portion 11, as shown in the third figure.

That is, when the internal pressure of the plastic case increases to the extent that it is likely to explode, the gas inside is released from the incompletely welded portion 12, thereby preventing an explosion.

Moreover, the material of the incompletely welded part 12 is the case body 1 and the lid 3.
Even if the mechanical strength of the plastic case 1 deteriorates, the mechanical strength of the incompletely welded part 12 will also deteriorate in the same way. shall not be prevented from performing its functions.

For example, if a case made of polypropylene with a wall thickness of 5 mm is used, the case body with a wall thickness of 3rIan at the first weld and the second
The welded part was formed by thermal welding with the 3TrrIrL lid by varying the spacing l between the hot plates at 85°C.
After being left in the air for 1000 hours, the function of the incompletely welded part was investigated, and the results shown in the table were obtained.

In other words, there are 11 cases that do not have conventional incompletely welded parts.
．． While the explosion occurs at an internal pressure of 0 kg/cIf, the cases according to the present invention all release gas at a lower internal pressure due to the function of the incompletely welded portion.

Moreover, increasing the interval between the hot plates and widening the width of the incompletely welded part can more reliably achieve its function, but there is a risk that the airtightness will deteriorate.

In addition, as shown in FIG. 4, a hot plate 13 having a stepped end face is used, and the first welded part of the case body and the second welded part of the lid are formed at asymmetrical positions to provide an incompletely welded part. You can do it like this.

Further, in the above embodiments, the incompletely welded portion was provided by a thermal welding method using a hot plate, but an ultrasonic method may also be used.

In the ultrasonic method, a lid is brought into contact with the case body, a bell-shaped joint made of metal such as aluminum is brought into contact with the lid, and this joint is vibrated at an appropriate frequency and pressurized. and the lid.

In this case, use a joint with a notch in the part of the edge that contacts the lid, or apply a thin layer of paraffin or wax to the part of the contact area between the case body and the lid. By doing so, it is possible to form an incompletely welded part in a part of the welded part where the degree of melting is lower than in other parts.

Furthermore, no protrusions as shown in Figure 2 are formed in the welded part, and the low melting degree and other parts are almost the same height, and the case body and lid are welded together in this state. Ru.

In addition, for example, made of synthetic resin such as polypropylene,
To weld the case body and lid with an outer diameter of 35 TI@ and a wall thickness of 1 wn, apply ultrasonic waves of about 10 W/ct at a frequency of 16 KHz for several seconds and pressurize the joint with a pressure of 3 to 4 ko/Clft. do it.

As described above, according to the present invention, an explosion can be prevented even if the plastic case deteriorates, and a highly reliable product can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the embodiment of the present invention when it is formed using a hot plate;
Figure 2 is a partial front view of the embodiment of the present invention after the hot plate has been removed;
FIG. 3 shows a part of the front view of the embodiment of the present invention, and FIG. 4 shows a front view of the hot plate. DESCRIPTION OF SYMBOLS 1... Case body, 2... First welding part, 3... Lid, 4... Second welding part, 5...
...External lead-out terminal, 6.7, 13... Heat plate, 8... Protrusion, 9, 10... Protrusion,
11... Welded part, 12... Incompletely welded part.

Claims (1)

[Scope of utility model registration request] In a plastic case for a capacitor, which is made by melting and welding the welded parts on the case body and the lid, welding is done by welding a part of the welded part to a lower degree of melting than other parts. A plastic case for a capacitor characterized by having an incompletely welded part.