JPS594844B2 - Denkai capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic capacitor whose characteristics can be dramatically improved by improving the separator interposed between the electrodes.

Generally, as shown in Figure 1, an electrolytic capacitor has two valve metal foils 1 made of aluminum tantalum or the like as electrodes, and a separator 2 is sandwiched between the electrodes, which are then wound to form a capacitor element 3. It is constructed by impregnating a liquid and enclosing it in a case 4.

In such electrolytic capacitors, it is known that the separator greatly affects various characteristics such as the impedance value of the capacitor, the reduction in loss value (jan δ), capacitance characteristics at low temperatures, loss characteristics, impedance characteristics, and frequency characteristics. .

Here, taking the impedance of a capacitor as an example, in the above equation Z: Impedance of the capacitor ω: Angular velocity ω-2πf f: Measurement frequency C: Capacitance of the capacitor L: Inductance of the capacitor R: Equivalent series inside the capacitor The equal series resistance R of the resistor capacitor is the resistance R0 between electrodes due to the separator and electrolyte, and the resistance R due to dielectric loss of the dielectric film.
Figure 2 shows the circuit of an electrolytic capacitor.

In FIG. 2, C is the capacitance of the capacitor, and R1 is the interelectrode resistance caused by the separator and electrolyte, and this resistance is not related to the frequency f, but is related to the temperature.

R2 is the resistance due to the dielectric loss of the dielectric film, R2 is inversely proportional to the frequency (R2α了), Ra is the resistance of the dielectric film and is very large (R3>R1, R3>R2)
.

In the high frequency range (10KHz or higher) at low temperatures, R1)>R
2 holes: Reactance caused by the capacitor being constructed by winding foil. In order to further lower the impedance value in the high frequency range at low temperatures of this electrolytic capacitor, R1>R2, and in a capacitor with a small number of foil turns, L should be Since the reactance Lω is very small compared to R1 and can be ignored, it is sufficient to reduce the inter-electrode resistance R1.

In addition, improving the conductivity of the electrolyte in R1 is extremely difficult due to the high-temperature load characteristics of the capacitor, such as preventing gas generation and loss change, and has not been sufficiently studied for current electrolytes. Therefore, it is considered difficult to dramatically improve the characteristics any further.

Therefore, it is necessary to improve the characteristics by studying and improving the separator.

In this way, in the development of separators up to now, the use of manila paper (manila hemp fiber paper), synthetic fiber paper, and mixtures of these papers rather than kraft pulp paper has been considered, and papers made from polypropylene fibers and manila hemp fibers have been developed. .

Synthetic fibers have an ideal fiber shape with a narrow cross-sectional diameter and a circular shape, so capacitors with excellent characteristics have been developed.

However, when synthetic fibers are made into paper, they generate static electricity, and when mixed with kraft paper, manila paper, etc., the characteristics of the fibers are very different, so there are many difficulties.

As a result of various studies on fibers suitable for these purposes, we were able to create a dramatically superior capacitor by using rayon paper made of rayon (regenerated cellulose fiber) and rayon-mixed paper as separators.

Rayon can also be freely mixed with manila paper and kraft paper due to its regenerated cellulose fibers.

FIG. 3 shows fZ characteristics (frequency-impedance characteristics) of an electrolytic capacitor using the separator of the present invention and a conventional electrolytic capacitor.

The product is 50W·■, 33μF, and the difference in interelectrode resistance, that is, the difference in separator, is clearly visible at a low temperature (-40°0).

As described above, the performance of the electrolytic capacitor using the rayon paper of the present invention is dramatically improved.

Table 1 shows the conditions of the separator used in the experiment shown in FIG.

As described above, when comparing the impedance at -40°C and 100 KHz, the impedance is about 1/4 of the current Manila paper, and even compared to Manila P-P mixed paper, it is about 1/2, which is an extremely excellent value.

Furthermore, since rayon paper has low draw strength, it is possible to sufficiently increase the draw strength by mixing it with manila paper.

Furthermore, even when mixed with Manila paper, the properties show sufficiently excellent values.

Table 2 shows the product 50W-V, 33μF, -40℃.

The impedance value of the capacitor at 100 KHz and various conditions for the separator of the present invention are shown.

In this way, the present invention uses rayon paper and rayon-mixed paper to develop capacitors that are significantly superior to conventional Manila paper, and rayon also has the advantage of being cheaper than Manila paper in terms of cost. .

As described above, the higher the rayon mixing ratio, the better the properties, and lowering the mixing ratio and increasing the manila mixing ratio increases the drawing strength, making it possible to wind it even under unreasonable conditions.

Furthermore, the mixed paper ratio of 50% manila and 50% rayon is dramatically superior to the conventional paper.

As described above, the electrolytic capacitor using the rayon paper and rayon mixed paper of the present invention has made an extremely large contribution to industry.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an electrolytic capacitor, FIG. 2 is an equivalent circuit diagram, and FIG. 3 is a comparison diagram of frequency-impedance characteristics of the conventional electrolytic capacitor and the present electrolytic capacitor. 1... Metal foil (electrode), 2... Separator, 3... Capacitor element, 4...
Case.

Claims (1)

[Claims] 1. An electrolytic capacitor characterized by having a capacitor element formed by winding a separator with a rayon-based separator interposed between electrodes and impregnating the separator with an electrolytic solution, and hermetically sealing the capacitor element.