JPS596521A - Metallized film condenser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metallized film capacitor constructed by winding a metalized film in which metal electrodes are formed on the surface of a dielectric film by vapor deposition or the like.

Conventionally, in metallized film capacitors, Fig. 1a
, b, a metal electrode 2 is attached to one or both sides of a dielectric film 1 such as a polypropylene film, a polyester film, or a polycarbonate film at the widthwise end portion of the dielectric film 1 by vapor deposition, sputtering, or the like. The metallized film 4 is obtained by forming an insulating groove part (usually called a margin part, hereinafter referred to as a margin part) 3 of about 0.5 to 6 words.

When obtaining a capacitor using such a metallized film 4, two metallized films 4 are overlapped and wound as shown in FIG. 2, and both end surfaces of the wound metallized film 4 are Zn, Sn, Cu.

The electrode lead portion 5 is formed by thermal spraying a metal material such as PB,
Either connect the lead wire e to the electrode extension part 6 by welding or the like to form a capacitor element, or stack the metallized films 4 one by one so that the margin part 3 is on the opposite side as shown in FIG. , and the electrodes are drawn out to form a capacitor element, similar to the above-mentioned wound type capacitor.

By the way, if we analyze and evaluate such wound type and laminated type capacitors in detail from the viewpoint of productivity, capacitor characteristics, etc., each type has its advantages and disadvantages.

In particular, the major difference in characteristics is that multilayer capacitors have a structure in which multiple small capacitance capacitors are connected in parallel, so even if a part of the metallized film breaks down due to some abnormality during use, Only one capacitor element loses its function, with little effect on other capacitor elements, resulting in only a slight reduction in capacitance. This means that it is a very safe capacitor with a safety function.

On the other hand, wound-type capacitors are currently mainstream because they can be easily manufactured with conventional general equipment, but some abnormalities in the metallized film may occur during use. When a breakdown occurs in the capacitance, the capacitance change due to the breakdown is negligible at the initial stage because the change in capacitance due to the breakdown is only proportional to the reduced area of the metallized film electrode. Since a circular type capacitor is a single capacitor as a whole, the destruction progresses gradually without stopping, with one part of the capacitor becoming a core. Safety cannot be ensured.

In view of the current situation, the present inventors have proceeded with the development of a capacitor that combines the high productivity of a wound type capacitor with the high safety of a laminated type capacitor. As a result, as shown in FIG. 4, the electrode 2 is separated into a plurality of rectangular islands in the length direction of the metallized film 4, separate from the margin section 3 provided at the end in the width direction. A margin portion 7 connected to the margin portion 3 is provided in the capacitor element, and two such metallized films 4 are overlapped and wound to form a capacitor element. In addition, since the electrode structure is similar to that of the laminated type, even if a breakdown occurs in a part of the electrode 2, it will not spread to the whole, and accidents such as smoke and ignition can be prevented. In other words, they discovered that it is possible to add a safety function.

However, even when metallized films with this structure are used, flat capacitors and round capacitors made by pressing common capacitor elements break down at high ambient temperatures of 100°C or higher. In some cases, safety is not always fully satisfied. This phenomenon occurs because the withstand voltage level of the plastic film itself used as a dielectric decreases as the temperature increases, and even if a part of the film breaks down, the adjacent film will break before the safety function operates. This is because the damage instantly develops into destruction of the entire capacitor element.

The present invention is the result of further development of the capacitor having the above-mentioned structure, and provides a metallized film capacitor whose safety function can be operated reliably even at high ambient temperatures of 100°C or higher. Hereinafter, the contents of the present invention will be explained in detail.

In the present invention, as a result of various experiments and studies to ensure that the safety function operates reliably even at ambient temperatures of 100°C or higher, we have developed a plate-shaped insulator made of film or insulating paper as shown in Figure 6. They found that it is sufficient to position 8 at the center of the capacitor element and make it a flat capacitor element.

Figure 6 is a diagram showing the results of a safety operation test. is the capacitor element of the present invention, and θ is the capacitor element of the present invention.

The safety factor in Figure 6 is (the number of capacitors in which the capacitors are completely open without any abnormalities such as smoke or ignition) ÷ ( The total number of capacitors tested) x 100.

As is clear from Fig. 6, the conventional products ■ and @ are 100
A safety factor of 100% cannot be obtained at an ambient temperature of 1: or more, whereas a safety factor of 100% is ensured in the product O of the present invention even at a high temperature of 160°C. This phenomenon is caused by the fact that in conventional flat capacitor elements, all adjacent films are made of dielectric material, so when breakdown occurs at high temperatures, the breakdown rapidly spreads to the entire capacitor element, causing the safety function to malfunction. This occurs due to a delay in In addition, because conventional round capacitor elements have insulating material in the center of the element, the safety factor is slightly lower than that of conventional products.
As with conventional product ■, 100% safety cannot be ensured at temperatures above 100'C. This phenomenon occurs because the gas generated by the dielectric breakdown of the metallized film causes the internal pressure of the capacitor to rise rapidly, leading to an explosion, smoke, and ignition.

On the other hand, the second invention product θ ensures safe operation due to the following two effects.

(1) By providing a plate-shaped insulator made of insulating paper or film as an insulating material in the center of the capacitor element, the spread of destruction is stopped at the center of the element, and the operation of the safety function is ensured.

(2) Since it is a flat capacitor element, the heat generated when the edge breaks causes the capacitor element itself to deform due to film shrinkage, causing damage to the outer case.

According to the metallized film capacitor of the present invention, a crack occurs mechanically between the exterior resin or the exterior case and the resin, and the gas generated at the time of breakdown is led out to the outside of the capacitor. It is possible to add a safety function that ensures 100 degrees of safety even at high temperatures of 100 degrees Celsius or higher.

[Brief explanation of the drawing]

Figures 1a and b are perspective views showing examples of general metallized film, Figure 2 is a perspective view showing the main parts of a general rolled metallized film capacitor, and Figure 3 is a perspective view of a general laminated film capacitor. Fig. 4 is a perspective view showing the main parts of a metallized film capacitor; Fig. 4 is a perspective view showing the main parts of a metallized film equipped with a safety function;
The figure is a perspective view showing the main parts of a metallized film capacitor according to an embodiment of the present invention, and FIG. 6 is a characteristic diagram for explaining the effects of the metallized film capacitor of the present invention. 1... Dielectric film, 2... Electrode,
3゜7...Margin part, 4...Metalized film, 8...Plate insulator. Figure 1 Figure 2

Claims (1)

[Claims] An insulating groove is provided at the end of the width direction on one or both sides of the dielectric film to form an electrode, and a plurality of insulating grooves are provided to separate the electrode into a plurality of islands in the length direction of the film. 1. A metallized film capacitor characterized in that a plate-shaped insulator is positioned at the center of a capacitor element formed by winding the metallized film and forming a flat structure.