JPH0469807B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an explosion-proof structure for an electrolytic capacitor that prevents explosion due to an increase in internal pressure of the electrolytic capacitor. [Prior Art] Due to its structure, electrolytic capacitors generate hydrogen gas in response to operating current, but when a large current (overcurrent) flows, the generation of hydrogen gas becomes noticeable. There is a risk of explosion due to the increase in internal pressure of the outer case due to gas. For this reason, electrolytic capacitors have an explosion-proof structure to prevent explosions caused by a sudden increase in internal pressure. There are things that form. As an example of the former, when the exterior case is made of aluminum or the like, a V-shaped explosion-proof valve that can be opened by a specific pressure is formed on the bottom of the case, and as an example of the latter, as shown in Figure 4. As such, an explosion-proof valve 8 is formed in a sealing body 6 of an exterior case 4 housing an electrolytic capacitor element 2. [Problems to be solved by the invention] By the way, the explosion-proof structure provided in the sealing body 6 is as follows.
Since an elastic material such as rubber is used for the sealing body 6, the elasticity of the material is utilized to form a portion that can be opened by the action of pressure.
As shown in FIG. 5, simultaneously with the molding process of the sealing body 6, an explosion-proof hole 1 is formed in the sealing body 6 using the molds 10 and 12.
4 and a thin wall portion 16 is formed inside thereof to form an explosion-proof valve 8. The accuracy of the dimension d ₁ of the thin wall portion 16 formed by such molds 10 and 12 remains unchanged even if the precision of molding elements such as the interval and molding pressure during molding of the molds 10 and 12 is increased. Since the relief due to the elasticity of the elastic material itself that forms the sealing body 6 has a large effect, it is lower than the dimensional accuracy of the opening diameter _d2 , and the error due to relief cannot be absorbed only by adjusting the mold accuracy. . For example, when the thickness of the thin wall portion 16 forming the explosion-proof valve 8 is set to 0.4 mm, the error reaches as much as ±0.2 mm, which is because the operating pressure of the explosion-proof valve 8 varies from 0.25 to This resulted in fluctuations with a width of 2.25 times, and there was a risk that proper valve opening operation could not be obtained. Since the escape during molding due to the elasticity of the material is also affected by the elastic material and temperature, the operating characteristics of the thin walled portion 16 are not uniform, and as a result, the valve opening operation becomes uneven, and the sealing body side The explosion-proof structure had the drawback of lacking reliability. Therefore, the present invention aims to improve the dimensional accuracy of the valve portion, to make the operating characteristics uniform, and to obtain a highly reliable explosion-proof structure. [Means for Solving the Problems] The explosion-proof structure of the electrolytic capacitor of the present invention has the following features:
As illustrated in A and B of the figure, there is an explosion-proof structure for an electrolytic capacitor using a sealing body 6 made of an elastic material. Projections 34 and 36 formed at different levels toward the front, and these projections 3
A thin wall portion (membrane portion 3
8), and the valve operating portion 32 is provided with the thin wall portion.
It is characterized by the following. [Function] In this way, when the valve operating portion 32 is opposed to the inner wall surface of the explosion-proof hole 28, moldability is improved in that the thin wall portion (membrane portion 38) forming the valve operating portion 32 can be prevented from escaping during molding. As a result, thickness accuracy is improved and operating characteristics are made more uniform. [Embodiment] A and B in FIG. 1 show an embodiment of the explosion-proof structure of an electrolytic capacitor according to the present invention. This example was conducted using a sealing body 6 as a sealing means for sealing an outer case 4 having an oval shape. The exterior case 4 is made of a metal plate made of aluminum or the like, for example, and the electrolytic capacitor element 2 having an elliptical shape is sealed therein. Terminals 18 and 20 on the anode side and the cathode side are drawn out in advance to the electrolytic capacitor element 2,
These terminals 18 and 20 pass through the sealing body 6 and are drawn out of the exterior case 4. The sealing body 6 is made of an airtight elastic material such as rubber and has a shape that matches the opening of the outer case 4. In the embodiment, the sealing body 6 is an elliptical columnar body, and has a step of a similar shape on the upper surface side. A portion 22 is formed. The stepped portion 22 is provided to prevent a difference in level from the top of the curled portion when the opening of the outer case 4 is curled for sealing, and to stabilize installation on a printed circuit board, etc. Because it is a thing,
It is formed at a height that matches the top of the curling portion of the outer case 4. An explosion-proof hole 28 is formed in the stepped portion 22 of the sealing body 6 along with terminal holes 24 and 26 for pulling out the terminals 18 and 20. In order to cope with the case where the surface of the stepped portion 22 of the sealing body 6 is brought into close contact with the surface of the printed circuit board, a groove is provided as an air passage that surrounds the terminal holes 24 and 26 and the explosion-proof hole 28 and reaches the edge of the stepped portion 22. 30 is formed. That is, when soldering to the terminals 18 and 20, this groove 30 allows flux to flow smoothly and prevents unnecessary air from remaining, and also serves as a path for gas injection from the explosion-proof hole 28 when the terminals 18 and 20 are soldered. It is something that accomplishes the following. Inside the explosion-proof hole 28, there is a valve operating part 32 that opens under the action of pressure, facing the inner wall surface.
is installed. For example, as shown in B in FIG. 1, the valve operating portion 32 includes a thick semicircular protrusion 34 that is diametrically different in level so as to close the explosion-proof hole 28 in the middle of the circular explosion-proof hole 28. , 36 are made to protrude, and the part where the respective protrusions 34, 36 meet is placed in the center of the explosion-proof hole 28, and the protrusions 34, 36 are made to protrude at different levels.
36 is constructed with a membrane portion 38 as a thin wall portion extending in a direction perpendicular to the opening surface of the explosion-proof hole 28. Therefore, the thickness of the membrane portion 38 is _D1 .
6 is _D2 , in order to ensure the valve opening operation by the predetermined pressure of the valve operating part 32,
The relationship D ₂ ≧D ₁ is required. As shown in FIG.
It is obtained by pressing molding by pressing 2. That is, the molds 40 and 42 have a circular part 44 of the same shape that forms the opening of the explosion-proof hole 28,
A semi-cylindrical portion 46, which is an extension of a part of the curved surface thereof, is protruded. Each of the molds 40 and 42 has its central axis coincident with each other, and the flat surface 48 of the semi-cylindrical portion 46 is maintained parallel to the thickness D ₁ of the membrane portion 38, and the semi-cylindrical shape during pressure molding is By making the distance between the end faces of the portion 46 constant, each mold 40, 4
For example, a rubber plate is sandwiched between the two as the sealant material, and molding is performed. The membrane portion 38 of the valve operating portion 32 obtained by such molding is obtained by molding the flat surface 48 side of the molds 40, 42 in the shear direction, so that there is less escape due to the elastic force of the material. The dimensional accuracy is determined only by the spacing accuracy of the flat surfaces 48, so that a highly accurate film thickness can be obtained and the operating characteristics can be made uniform. Therefore, according to such an explosion-proof structure, uniform special characteristics can be obtained, and the valve operating section 32
Since it is hidden in the explosion-proof hole 28, it is protected and can be prevented from being damaged by, for example, being poked by a lead, and from changing its operating characteristics. This explosion-proof structure has an explosion-proof hole 28 inside the sealing body 6.
Since the valve actuating portion 32 is provided on the inner wall surface of the valve, other embodiments may include, for example, one in which the opening on the exterior case 4 side is semicircular as shown in FIG. In addition, although the embodiment shows an oval sealing body 6, it can also be applied to a circular sealing body, and even if the explosion-proof valve is fitted into a part of a synthetic resin case, an explosion-proof valve that closes the explosion-proof hole can be used. A similar valve operating portion 32 can be formed in a sealing member equipped with the following. [Experiment results] As a sample, the rated voltage is 200V, the capacitance is 330μF,
An explosion-proof structure according to the present invention was applied to an electrolytic capacitor having a size of 16.3 mm x 25 mm x 40 mm, and the following tests were conducted. (a) Reverse voltage application test In this test, a voltage with the opposite polarity of the standard polarity is applied between the terminals of an electrolytic capacitor.
A current set to 5A or 10A is applied to the valve, and the time (operation time) from when the current is applied until the valve opens is measured. The results are shown in Table 1.

[Table] As is clear from Table 1, all of the samples were operating normally, and in the tests conducted on conventional explosion-proof structures for comparison, normal valve opening operation could not be obtained, and the outer case It has been confirmed that the sealing body itself separates from the outer case due to internal pressure, creating an explosion-proof condition. (b) Overvoltage application test This test applies 400V according to the standard polarity, flows a maximum current of 10A, and measures the time (operation time) until the valve opens. The results are shown in Table 2.

[Table] As is clear from Table 2, 4/10 is operating normally, but with the conventional explosion-proof structure, all the sealing bodies protrude, and with the explosion-proof valve formed in the outer case, the electrolytic It has been confirmed that the capacitor element protrudes and causes sparks. (c) AC voltage application test In this test, 100V AC is applied, the added resistance is set to 3.3Ω and 0Ω, and the time from voltage application to valve opening is measured. The results are shown in Table 3.

〔Effect of the invention〕

As explained above, according to the present invention, protrusions are formed on the inner wall of the sealing body made of an elastic material at different levels toward the center thereof, and the protrusions are formed so as to straddle the end surfaces of the respective protrusions. The valve operating part is made by blocking the explosion-proof hole with a thin-walled part, which prevents escape during molding, improves thickness accuracy, equalizes operating characteristics, and improves the reliability of explosion-proof operation. can.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the explosion-proof structure of an electrolytic capacitor according to the present invention, Fig. 2 is a diagram showing a molding process for realizing the explosion-proof structure shown in A in Fig. 1, and Fig. 3 is a diagram showing the invention. Fig. 4 is a cross-sectional view showing the explosion-proof structure of a conventional electrolytic capacitor, and Fig. 5 shows the molding process to realize the explosion-proof structure shown in Fig. 4. FIG. 4... Exterior case, 6... Sealing body, 28... Explosion-proof hole, 32... Valve operating part, 34, 36... Projection part, 38... Membrane part (thin wall part).

Claims (1)

[Scope of Claims] 1. An explosion-proof structure for an electrolytic capacitor using a sealing body made of an elastic material, comprising: an explosion-proof hole formed in the sealing body; An electrolytic electrolyzer, comprising: a protruding part; and a thin wall part that is formed astride between the end faces of these projecting parts and closes the explosion-proof hole together with the projecting part, and the thin wall part is used as a valve operating part. Explosion-proof structure of capacitor.