JPH0334513A - Film capacitor - Google Patents

Abstract

PURPOSE:To prevent that fire is caught and smoke is emitted by zinc, to design a high potential obliquity and to realize a remarkably small size and a remarkably low cost by a method wherein a part, coming into contact with an electrode extraction part of an electrode film is formed to be thick in a definite width. CONSTITUTION:First insulating groove parts 3, 4 are formed respectively on one face each of two dielectric films 1, 2 at one end part each in a width direction by using an oil masking method. Aluminum and zinc are vapor-deposited in such a way that a thickness at end parts coming into contact with electrode extraction parts 12 faced with the groove parts is made thicker than that in other parts; electrode films 5, 6 are formed. A second insulating groove part 9 is formed intermittently in a length direction at one part in a width direction of, e.g. the electrode film 6 of one film 8 out of obtained metallized films 7, 8. Third insulating groove parts 11 which traverse the groove part 9 and which reach the groove 4 are formed at equal intervals to divide the electrode film 6 to be island-shaped. The metallized films 7, 8 are piled up and wound in such a way that the groove parts 3, 4 are situated at mutually opposite sides and that the electrode films 5, 6 do not come into contact; a capacitor element is formed. The electrode extraction parts 12 are formed at both end parts of this element.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the construction of plastic capacitors.

As the dielectric material of conventional technology film capacitors, polypropylene,
Plastic films such as polyethylene terephthalate and insulating paper (hereinafter collectively referred to as dielectric films)
is used. Then, a metallized film is produced by vacuum-depositing a metal as an electrode material on one or both sides of such a dielectric film. Although various metals are used as electrode materials, aluminum and zinc are generally used.

Among these, aluminum has excellent self-healing properties and weather resistance, but when metallized film capacitors using aluminum are used under AC voltage, the electrode film may have missing parts, protrusions, or When the electric field strength exceeds a certain level (mainly determined by the film thickness, applied voltage, electrode material, and electrode film thickness) in areas where the electric field is concentrated, such as the edge of the electrode film, aluminum changes to oxide or hydroxide. Therefore, a small circular oxide film is formed on the electrode surface, and a transparent band-shaped oxide film is formed along the end face of the electrode. In the case of aluminum, this oxidized part is a highly insulating material, so the electric field concentration moves to the unoxidized part that is in contact with this oxidized part, so the oxidation reaction continues and the small circular or transparent part at the end of the electrode It will continue to grow. Therefore, the effective area as an electrode decreases, resulting in a decrease in capacitance as a capacitor. For this reason, in a film capacitor for AC voltage using aluminum as an electrode material, there is a certain limit to the voltage that can be applied per unit film thickness (hereinafter referred to as potential gradient).

On the other hand, when zinc is used as an electrode material, an oxide film portion is similarly generated. However, since this oxide is a semiconductor, the location where the electric field is concentrated is difficult to move (the critical value of the electric field strength at which the oxidation reaction occurs is high), so the oxidation reaction progresses slowly.

Therefore, the decrease in capacitance of the capacitor can be suppressed to a minimum. Therefore, a film capacitor using zinc as an electrode material can have a higher potential gradient than a film capacitor whose electrodes are made of aluminum. However, although zinc has these characteristics,
Its weather resistance is poor, and it suffers from corrosion and deterioration in a very short period of time due to moisture and oxygen.

In order to solve these problems of aluminum and zinc and take advantage of their respective characteristics, electrode films are being formed with aluminum and zinc.

This provides good handling properties and suppresses capacitance changes due to application of an alternating current voltage, resulting in a certain improvement in potential gradient.

On the other hand, in a metallized film capacitor, in order to improve its characteristic self-healing properties and improve the breakdown voltage of the capacitor, it is desirable to form the electrode film thinly (increase the resistance of the electrode film).

However, even in an electrode film composed of aluminum and zinc, electrochemical oxidation reactions occur at locations where the electric field is concentrated above a certain value. Since the critical electric field strength at which this oxidation reaction proceeds is proportional to the film resistance value, the capacitance reduction due to this oxidation increases as the film resistance becomes higher (the film thickness becomes thinner).

For this reason, it is practically desirable that the film resistance value of the portion of the electrode film that mainly contributes to capacitance formation be 5 to 20 Ω/portion.

On the other hand, as the resistance of this electrode film increases, that is, as the film thickness decreases, the dielectric loss tangent (tan δ) decreases. This is because the contact force between the electrode film and the electrode lead-out portion (metallicon) is reduced. That is,
When the electrode film becomes thinner, the contact resistance of the part in contact with the electrode lead-out part increases, which causes the electrode film to scatter due to the heat generated by the current when energized, and the series resistance bone as a capacitor increases, resulting in a decrease in dielectric loss tangent. It is assumed that this causes a decrease in the amount of water.

For this reason, in order to ensure the contact force between the electrode film and the electrode lead-out part, it is desirable to make the part of the electrode film in contact with the electrode lead-out part so that its resistance value is 1 to 10 Ω/hole. , and it is desirable that the width of this thick portion be 1.0 mm or more.

In view of the above, it is conceivable to form the part of the electrode film in contact with the electrode extension part to be thick with a constant width, and to form the other part thinly. This is made clear in US Pat. No. 4,477,858 and the like.

Problems to be Solved by the Invention By the way, in a film capacitor that uses zinc as one of the electrode materials, when an AC voltage exceeding a certain potential gradient is continuously applied, the insulation resistance decreases and this progresses, causing the capacitor to deteriorate. As a result, a short circuit occurs, resulting in ignition and smoke. This is because when instantaneous destruction (self-healing) occurs in a defective part of a capacitor, zinc, which is an electrode metal, has poor scattering properties, so it remains scattered in the defective part. When an alternating current voltage is further continuously applied in this state, discharge occurs through the scattered zinc parts and heat is generated. This heat generation progresses carbonization of the film, lowers the insulation resistance, and further shortens the film, leading to ignition and smoke.

The inventors formed an electrode film from aluminum and zinc, and in order to make the most of its features and stabilize the capacitor characteristics, the inventors formed the part of the electrode film in contact with the electrode extension part to be thick with a constant width. It also prevents ignition and smoke caused by zinc in metallized film capacitors in which other parts are thin, and enables higher potential gradient designs that were not possible with conventional metallized film capacitors with aluminum-zinc electrodes. The aim is to dramatically reduce the size and cost of the device.

Means for Solving the Problems The film capacitor of the present invention includes a film-like electrode made of at least aluminum and zinc provided on one or both sides of a dielectric material, and a first insulating groove portion provided at one end in the width direction. The thickness of the end in contact with the electrode lead-out part opposite to this is formed to be thicker than the other film-like electrodes, and a second insulating groove part of a certain length is formed in a part of the electrode film in the width direction. A metallized film is formed by continuously forming a metallized film in the direction of the metallization film, and a third insulation groove that crosses the second insulation groove and reaches the first insulation groove, and the metallized film is wound or laminated. However, electrode extension portions are formed on both end faces.

Function: In the film capacitor of the present invention, the electrode film is the third
It has an island shape surrounded by an insulating groove and second insulating grooves formed intermittently in the length direction, and has a structure in which these island-shaped small capacitance capacitors are integrated in parallel. therefore,
A current that flows when a voltage is applied to the capacitor flows from the electrode lead-out portion and flows into the island-shaped electrode film portion through the non-insulated portion between the second insulating groove portions formed intermittently in the length direction. In this case, since the end portion in contact with the electrode lead-out portion is formed to be thick, the contact force of the metallicon portion is strengthened, and stable characteristics are maintained without causing a drop in dielectric loss tangent during energization. If an instantaneous breakdown occurs in a defective part of the dielectric of this capacitor, the abnormal current caused by this instantaneous breakdown will concentrate on the non-insulated part between the second insulating grooves, and the Joule heat caused by this current will cause the The electrode metal in the insulating part vaporizes and loses its conductivity, and the small-capacity capacitor that instantaneously breaks down is separated. The phenomenon in which the electrode metal in the non-insulated portion vaporizes and disappears due to Joule heat is mainly determined by the resistance value of the non-insulated portion. In other words, if the length of this non-insulated part is long and the metal film is thick, it will not evaporate and disappear. Depending on the conditions, even if instantaneous breakdown occurs, the small capacitor will not be separated, and the entire capacitor will ignite and emit smoke. There are cases. On the other hand, if the length of this non-insulating part is short and the metal film is thin, vaporization is more likely to occur, but depending on the conditions, vaporization may occur even under normal current conditions without instantaneous breakdown, resulting in a decrease in capacity. .

In the present invention, in a metallized film capacitor having a structure in which an electrode film is formed of aluminum and zinc and a thick electrode extension part is formed in order to stabilize characteristics and improve self-healing property, a second insulating groove part is formed. This prevents short-circuit accidents of the capacitor, and by limiting the position and dimensions of this second insulating groove, it is possible to stabilize the characteristics of the capacitor and reliably separate the part where instantaneous breakdown has occurred. This is the result.

On the other hand, in a metallized film capacitor that forms such an insulating groove, it has been found that the best way to stabilize the characteristics of the capacitor is to make the electrode film of At and zinc. I found it. That is, for example, A
j? When an An voltage is applied to this capacitor, the non-insulated parts between the second insulating grooves that are formed intermittently change into an insulator through an electrochemical oxidation reaction, and the conductivity is eventually lost. It will become.

Furthermore, if zinc is a metal, it will corrode in a very short time due to moisture and oxygen, and the conductivity of this non-insulated part will be inhibited.

In order to compensate for these drawbacks and achieve stable characteristics, we have discovered that it is best to form metalized electrodes with both aluminum and zinc.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view for explaining the structure of this embodiment and its manufacturing method.

First, a first insulating groove 3.4 is provided on one side of each of the two dielectric films 1.2 at one end in the width direction by oil masking, and a first insulating groove 3.4 is provided on one side of the two dielectric films 1.2 at one end in the width direction. The electrode films 5 and 6 are formed by depositing aluminum and zinc in a mixed or alloyed state so that the thickness of the electrode films 5 and 6 is thicker than other parts. Second insulating grooves 9 are intermittently formed in the length direction in one of the thus obtained metallized films 7, 8, for example, in a part of the electrode film 6 of the film 8 in one width direction. 10 indicates a non-insulating part), and a third insulating groove part 1 that crosses this second insulating groove part and extends from the electrode lead-out end to the first insulating groove part 4.
1 are formed at equal intervals, and this electrode film 6 is divided into island shapes. Then, the metallized films 7.8 are wound one on top of the other so that the insulating grooves 3.4 at the ends are located on opposite sides and the electrode films 5.6 do not touch, forming a capacitor element. After winding is completed, electrode extension portions 12 (the opposite side is not shown) are formed at both ends of the capacitor element, and lead wires 13 and 14 are connected to each end.

This capacitor, as shown in the equal-sized circuit diagram in Figure 2,
It has a structure in which a plurality of small capacitance capacitors are connected in parallel between lead wires 13 and 14 as terminal electrodes. Current flows through each small-capacity capacitor through a non-insulated portion 10, but when discussed in terms of an equivalent circuit, this non-insulated portion 10 can be expressed as a resistor (determined by the length and film thickness of the non-insulated portion) or a fuse. . Therefore, the structure is such that a resistor or fuse is connected in series with each small capacitor.

When voltage is applied to a capacitor, if there is a defective part and instantaneous destruction occurs, the small capacity capacitor with this damaged part will be disconnected at the fuse part, so no voltage will be applied to the part where this instantaneous destruction occurred. is no longer applied. Therefore, it is possible to prevent short-circuit accidents in the capacitor that would otherwise occur when the electrode film is made of a metal containing zinc.

Figure 4 shows the change in insulation resistance when a continuous high-temperature durability test was conducted under the application of AC voltage for the film capacitor of this example and a film capacitor with a conventional structure in which the electrode film is not separated into islands. Show a comparison. As is clear from this result, in the case of a capacitor with a conventional structure, the insulation resistance decreases over time, but in the capacitor of this example, no decrease in insulation resistance was observed, and instantaneous breakdown occurred. It was confirmed that the small capacitance capacitor was disconnected.

FIG. 5 shows the relationship between the applied voltage and the survival rate of the capacitor when this AC voltage was applied for 2000 hours. As is clear from this result, when an AC voltage of a certain value or more is continuously applied to a capacitor having a conventional structure, the survival rate of the capacitor decreases significantly. on the other hand,
In the film capacitor of the present invention, short-circuit damage did not occur, and the occurrence of short-circuit damage and resulting accidents such as ignition and smoke generation was not observed as in conventional products.

As described above, according to the present invention, since the electrode film on the dielectric film is formed of aluminum and zinc, the handling property in manufacturing the film capacitor is improved, and the electrode film on the metal contact portion is made of aluminum and zinc. Because it is thick and other parts are thin, it has good metallization contact and excellent self-healing properties.Furthermore, there is extremely little risk of short circuit accidents due to the application of AC voltage, and the design has a high potential gradient. It becomes possible.

Now, a metal film is formed using aluminum and zinc of the present invention,
1st. Second. When forming the third insulating groove, the interval between the third insulating grooves can be formed to any size, and is generally formed by heat treatment such as electrical discharge or laser processing, or by vapor deposition, etc. When forming a metal film with
A metal film having insulating grooves can be formed by masking or by processing the film in advance. In any of these methods, in order to ensure stable dimensional accuracy, the interval between the third insulating grooves must be 5.
It is necessary to be more than concerned.

On the other hand, it is possible to increase this spacing based on the construction method, but as the spacing increases, the capacity decreases in the event of instantaneous breakdown in some parts (capacity due to island-like electrodes being separated when instantaneous breakdown occurs). (decrease) increases. Therefore, the maximum value should be 150ffI11.

FIG. 6 shows that the interval between the third insulating grooves is constant at 50 mm, the thickness of the electrode film structure on the external electrode extension side is constant at 2 to 5 Ω/2 in resistance value, and the other parts (
The part that forms the capacitance of the capacitor) is 5 to 10Ω/port,
10-20Ω/mouth.

A metallized film formed by a vapor deposition method so as to have a resistance of 20 to 30 Ω/hole, and a second insulating groove formed in a thick part of the electrode film and a thin part of the electrode film of each resistance value. In capacitors, J I 5-C490
8-8, 15+21 in the case of carrying out the safety test, the total length of the non-insulated part between the second insulating grooves (the non-insulating part existing between the adjoining third insulating grooves at an interval of 50 m1) This shows the results of the exam pass rate by numerical value.

This result shows that when the third insulating groove is formed in the thick part of the 2 to 5 Ω/gate electrode film, the range of conditions for passing the test is narrow and the variation is large. On the other hand, for thin parts, the range of conditions for passing the test gradually expands.

From this, it can be said that it is better to form the second insulating groove in a thin part of the electrode film in the range of 5 to 30 Ω/hole in order to stabilize the test pass rate and characteristics.

On the other hand, as mentioned above, when an AC voltage is applied to an electrode film composed of aluminum and zinc, a capacitance change occurs due to an electrochemical oxidation reaction, but this capacitance change is proportional to the electrode film thickness (membrane resistance value). Because of this relationship, it is practically desirable that the membrane resistance value be 20 Ω/mouth or less.

, when the membrane resistance value is 20 Ω/hole or less, the total length of the non-insulating portion between the second insulating grooves existing between the adjacent third insulating grooves is 0, .5~10+n
It is desirable to set the range to m.

FIG. 3 is a diagram showing the structure of a metallized film according to another embodiment of the present invention. That is, the third insulating groove is formed so as to reach the end in contact with the electrode extension part.

By adopting this structure, the fuse mechanism is doubled in case instantaneous breakdown occurs in a partially defective part of the capacitor (the non-insulated part between the adjacent second insulating groove part and the electrode lead-out part). The connecting part... due to the contact resistance, the connecting part generates heat due to the abnormal current during instantaneous breakdown, and the electrode metal at the connecting part vaporizes and disappears, causing the contact to be lost.) Therefore, capacitor ignition 9 smoke This makes it possible to extremely minimize the risk. In the case of this structure, it is desirable that at least one out of every two third insulating grooves reaches the electrode lead-out point.

In this example, the second. Although the third insulating groove is formed in only one of the two metallized films, it may be formed in both. Alternatively, a double-sided metallized film may be used with insulating grooves formed on one or both sides.

Effects of the Invention As described above, the film capacitor of the present invention has the advantages of the conventional film capacitor with electrodes formed using aluminum and zinc, such as good hunt linkability and little change in capacitance due to the application of AC voltage. However, the problem was the decrease in insulation resistance and the ignition due to short circuit breakdown 2
Fuming can be solved. Therefore, it is possible to design an even higher potential gradient, and it is possible to achieve not only significant miniaturization, but also excellent effects such as lower cost and stable characteristics.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the main parts of one embodiment of the film capacitor of the present invention, FIG. 2 is an equivalent circuit diagram thereof, and FIG. 3 is a perspective view showing the main parts of another embodiment of the film capacitor of the present invention. Figure 4 shows a comparison of changes in insulation resistance when the film capacitor of the present invention and a conventional product are subjected to AC high temperature continuous durability tests. FIG. 6 is a diagram showing the test pass rate in the safety test for each film resistance of the electrode film in the portion where the third insulating groove is formed. 1.2...Dielectric film, 3.4...
・First insulating groove portion, 5.6... Electrode film, 7.8
...Metalized film, 9...Second insulating groove, 10...Non-insulating part, 11...
Third insulating groove portion, 12... Electrode extraction portion, 13
．． 14...Lead wire.

Claims (4)

[Claims] (1) A film-like electrode made of at least aluminum and zinc is provided on one or both sides of a dielectric, a first insulating groove is provided at one end in the width direction, and the opposite end is in contact with the electrode lead-out part. A second insulating groove portion of a certain length is formed intermittently in a part of the width direction of this electrode film in the length direction. A metallized film is formed by providing a third insulating groove that crosses the first insulating groove and reaches the first insulating groove, and the metalized film is wound or laminated to form electrode extension parts on both end faces. A film capacitor characterized by: (2) The film capacitor according to claim 1, wherein the second insulating groove is provided in a thin portion of the electrode film. (3) The interval between adjacent third insulation grooves is 5 to 150 mm.
and the second insulating groove portions formed intermittently in the length direction are formed so that the total length of the non-insulating portions existing between the adjacent third insulating groove portions is 0.5 to 10 mm. The film capacitor according to claim 1 or 2, characterized in that: (4) The film capacitor according to any one of claims 1 to 3, wherein the third insulating groove crossing the second insulating groove is formed so as to reach an end in contact with the electrode extension part.