JP5934881B2 - Metallized film capacitors - Google Patents

Description

  The present invention relates to a metallized film capacitor that is used in various electronic devices, electrical devices, industrial devices, automobiles, and the like, and is particularly suitable for smoothing, filtering, and snubbing of a motor drive inverter circuit of a hybrid vehicle.

  In recent years, from the viewpoint of environmental protection, all electric devices are controlled by inverter circuits, and energy saving and high efficiency are being promoted. In particular, in the automobile industry, hybrid vehicles (hereinafter referred to as HEVs) that run on electric motors and engines have been introduced into the market, and the development of technologies relating to energy saving and high efficiency has been activated, which is friendly to the global environment.

  Since such an electric motor for HEV has a high operating voltage range of several hundred volts, a metalized film capacitor having high withstand voltage and low loss electric characteristics is attracting attention as a capacitor used in connection with this electric motor. In addition, the trend of adopting a metallized film capacitor having a very long life is conspicuous from the demand for maintenance-free in the market.

  And this metallized film capacitor | condenser is divided roughly into what uses metal foil for an electrode generally, and the thing which uses the vapor deposition metal provided on the dielectric film for an electrode. In particular, a metallized film capacitor using an evaporated metal as an electrode (hereinafter referred to as a metal evaporated electrode) has a smaller volume occupied by the electrode than a metal foil, and can be reduced in size and weight. High reliability against dielectric breakdown due to self-healing function peculiar to metal-deposited electrodes (meaning the ability of the metal-deposited electrodes around the defect to evaporate and scatter and restore the function of the capacitor, generally called self-healing) Therefore, it has been widely used conventionally. The thinner the metal-deposited electrode is, the easier it is to evaporate and scatter, and the better the self-healing property, the higher the withstand voltage.

  FIG. 6 is a cross-sectional view showing the structure of a conventional metallized film capacitor of this type, and FIGS. 7A and 7B are plan views showing a pair of metallized films used in the metallized film capacitor. is there. As shown in FIGS. 6 and 7, the metal vapor deposition electrode 101a and the metal vapor deposition electrode 101b are formed by vapor-depositing aluminum on one surface of dielectric films 102a and 102b such as a polypropylene film except for the insulation margins 103a and 103b at one end. Is formed. The metal vapor-deposited electrodes 101a and 101b are connected to metallicons 104a and 104b formed by spraying zinc at opposite ends of the insulation margins 103a and 103b of the dielectric films 102a and 102b. The electrode is pulled out to the outside.

  Further, the metal vapor-deposited electrodes 101a and 101b are non-vapor-deposited having no metal vapor-deposited electrode formed by oil transfer on the side from the substantially central part of the width W of the effective electrode part forming the capacitance toward the insulation margins 103a and 103b. Are divided into a plurality of divided electrodes 106a and 106b by the slits 105a and 105b, and are positioned on the side opposite to the insulation margins 103a and 103b from the substantially central part of the width W of the effective electrode part and closer to the metallicons 104a and 104b. The dielectric films 102a and 102b are connected in parallel to the metal vapor-deposited electrodes 101a and 101b deposited on one surface of the dielectric films 102a and 102b by fuses 107a and 107b.

  The conventional metallized film capacitor configured as described above has a self-healing property and can realize a metallized film capacitor with less heat generation by the fuses 107a and 107b. In other words, the current passed through the metal vapor-deposited electrodes 101a and 101b increases as it approaches the metallicons 104a and 104b and decreases as it moves away. Therefore, since the fuses 107a and 107b and the divided electrodes 106a and 106b are provided on the side closer to the insulation margins 103a and 103b where the flowing current decreases, the heat generated in the fuses 107a and 107b due to the flowing current can be reduced, and the temperature rises. It was to be able to suppress.

  For example, Patent Documents 1 and 2 are known as prior art document information related to the invention of this application.

JP 2004-134561 A International Publication No. 2011/055517

  As a method of improving the moisture resistance of such a metallized film capacitor, a method of using an alloy for the metal vapor-deposited electrode can be mentioned. That is, it is possible to improve the moisture resistance of the metallized film capacitor by using an alloy formed of a plurality of metals such as aluminum, zinc, and magnesium as an electrode.

  For example, in an alloy electrode mainly composed of aluminum and added with magnesium, moisture in the metallized film or on the surface of the metallized film can be reduced by the reaction shown by the following chemical formula, and moisture resistance is improved. It is possible to improve.

Mg + 2H ₂ O → Mg (OH) ₂ + H ₂
Thus, in the electrode using an alloy, the moisture which is a factor of the leakage current can be reduced, and the characteristics of the metallized film capacitor can be improved.

  However, as a result of the inventor's verification, it was confirmed that a metallized film capacitor using an alloy electrode in which magnesium is added to aluminum has a reduced self-healing function and may have a reduced withstand voltage characteristic.

  This is presumed to be caused by the properties of magnesium.

  In other words, the metallized film capacitor has the above-mentioned self-healing property as a feature, but magnesium is found to be less likely to evaporate and scatter. Therefore, a metallized film using an alloy added with magnesium. Capacitors are inferior in self-healing properties compared to conventional metallized film capacitors using electrodes formed of aluminum alone, resulting in deterioration of the withstand voltage characteristics of the metallized film capacitors. Is considered to occur.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a metallized film capacitor capable of solving such problems and achieving both excellent withstand voltage characteristics and moisture resistance.

  In order to solve this problem, the present invention has a configuration in which at least one of the metal-deposited electrodes of a pair of metallized films uses aluminum and magnesium, and the atomic concentration ratio of magnesium is maximized in the large electrode portion. It is.

  The metallized film capacitor according to the present invention can exhibit excellent voltage resistance. The reason is that the withstand voltage of metallized film capacitors is easily affected by the self-healing property of the divided small electrode part, so the decrease in withstand voltage is suppressed by making the magnesium concentration of the divided small electrode part smaller than that of the large electrode part. This is because it can be done.

  As described above, the present invention can improve the voltage resistance.

Sectional drawing which showed the structure of the metallized film capacitor in the Example of this invention (A), (b) The top view which showed the structure of the metallized film used for the metallized film capacitor in the Example of this invention The figure which shows the withstand voltage of the metallized film capacitor in the Example of this invention The figure which shows the moisture resistance of the metallized film capacitor in the Example of this invention The figure which shows the magnesium concentration in a metallized film in an Example of this invention, and a moisture-resistant improvement degree Sectional view showing the structure of a conventional metallized film capacitor (A), (b) The top view which showed the structure of the metallized film used for the conventional metallized film capacitor

  Hereafter, the structure of the metallized film capacitor in the Example of this invention is demonstrated using FIGS. 1-2.

  FIG. 1 is a cross-sectional view showing the configuration of the metallized film capacitor of this example. FIGS. 2 (a) and 2 (b) are plan views of a pair of metallized films used in the metallized film capacitor of the present invention. FIG.

  In FIG. 1, the 1st metallized film 1 is a metallized film for P poles, and the 2nd metallized film 2 is a metallized film for N poles. Then, the first metallized film 1 and the second metallized film 2 are overlapped as a pair, and a metallized film capacitor is formed by using a plurality of turns wound as an element.

  As shown in FIG. 1, the first metallized film 1 has a metal vapor-deposited electrode 4a formed on one surface of a dielectric film 3a made of polypropylene as a dielectric. An insulating margin 5a is provided at the end portion to insulate the second metallized film 2.

  This metal vapor deposition electrode 4a is connected to the metallicon 6a to draw out the electrode. The metallicon 6a can be formed by, for example, zinc spraying, and is formed on the end face of the metal deposition electrode 4a.

  As shown in FIG. 2A, the metal vapor-deposited electrode 4a has a vertical margin 7a and a horizontal margin 8a formed on the side toward the insulating margin 5a from the approximate center in the width W direction of the effective electrode portion forming the capacitance. Yes. The vertical margin 7a and the horizontal margin 8a are formed by oil transfer, and the metal deposition electrode 4a is not deposited. As a result, the metal deposition electrode 4a becomes the large electrode portion 9a on the metallicon 6a side, and becomes the divided small electrode portion 10a divided into a plurality of portions by the vertical margin 7a and the horizontal margin 8a on the insulating margin 5a side.

  As shown in FIG. 2A, the divided small electrode portion 10a is electrically connected in parallel by a large electrode portion 9a and a fuse 11a, and adjacent divided small electrode portions 10a are also connected to the fuse 12a. Are electrically connected in parallel.

  Here, as shown in FIG. 2A, the large electrode portion 9a is formed on one surface of the dielectric film 3a from the substantially central portion of the width W of the effective electrode portion to the metallicon 6a. The width of each divided small electrode portion 10a is about ¼ of the width W of the effective electrode portion, and is formed on one surface of the dielectric film 3a from the substantially central portion of the width W of the effective electrode portion to the insulation margin 5a. The two divided small electrode portions 10a are provided from the substantially central portion of the effective electrode portion (width W) to the insulation margin 5a. However, the present invention is not limited to this, and a configuration in which three or more are provided may be employed.

  In the actual use, when a short circuit occurs in the defective part of the insulation, the metal vapor deposition electrode 4a around the defective part is evaporated and scattered by the short circuit energy, and the insulation is restored. With this self-healing function, the function of the metallized film capacitor is recovered even if a part between the first metallized film 1 and the second metallized film 2 is short-circuited. In addition, when a large amount of current flows through the divided small electrode portion 10a due to a defect in the divided small electrode portion 10a, the fuse 11a or the fuse 12a is scattered and the portion of the divided small electrode portion 10a in which the defect is caused is scattered. The electrical connection is broken and the metalized film capacitor current returns to normal.

  Like the first metallized film 1, the second metallized film 2 is made of metal except for an insulating margin 5b at one end on one side of a dielectric film 3b made of polypropylene as a dielectric, as shown in FIG. A vapor deposition electrode 4b is formed. However, the direction in which the second metallized film 2 and the first metallized film 1 are connected to the metallicon is different, and the second metallized film 2 is a metallicon 6a to which the first metallized film 1 is connected. Are connected to a metallicon 6b arranged opposite to the above. Further, the metal vapor deposition electrode 4b has a large electrode by a non-vapor deposition vertical margin 7b and a horizontal margin 8b which do not have a metal vapor deposition electrode on the side from the substantially central portion in the width W of the effective electrode portion forming the capacitance toward the insulation margin 5b. It is divided into a portion 9b and a plurality of divided small electrode portions 10b.

  As shown in FIG. 2B, the divided small electrode portion 10b has the same configuration as the divided small electrode portion 10a of the first metallized film 1, and is arranged in parallel by the large electrode portion 9b and the fuse 11b. In addition, the divided small electrode portions 10b are connected in parallel by the fuse 12b. The effect obtained by providing the divided small electrode portion 10b and the fuses 11b and 12b is the same as that of the first metallized film 1.

  In this embodiment, the metal vapor-deposited electrodes 4a and 4b are divided into large electrode portions 9a and 9b and divided small electrode portions 10a and 10b, but they function as capacitors even when they are not divided.

  In this embodiment, polypropylene films are used as the dielectric films 3a and 3b. However, polyethylene terephthalate, polyethylene naphthalate, polyphenyl sulfide, polystyrene, and the like may be used.

  In the metallized film capacitor of this example, at least one of the metal vapor deposited electrodes 4a and 4b of the first metallized film 1 or the second metallized film 2 is an alloy electrode film made of aluminum and magnesium. In this metal vapor deposition electrode 4a (4b), the atomic concentration distribution of magnesium becomes maximum at the large electrode portion. The magnesium content in the metal vapor deposition electrodes 4a and 4b per unit area was set to 2.0 wt% to 40 wt%. Moreover, since resistance will become large when there is too much magnesium, it is suitable for the said range.

Example 1
The metalized film capacitor of Example 1 is configured as shown in FIG. 1 above, and aluminum and magnesium are used as electrode materials used for the metal deposition electrode 4a as the P pole and the metal deposition electrode 4b as the N pole. This alloy was used. In addition, the 1st metallized film 1 and the 2nd metallized film 2 of the present Example 1 are formed from the same manufacturing method using the same electrode material and dielectric material (polypropylene dielectric film). Therefore, the characteristics of the metallized film of Example 1 described below are common to the first metallized film 1 and the second metallized film 2.

  Next, as shown in FIGS. 3 and 4, a metallized film on which a conventional metal vapor-deposited electrode consisting only of an aluminum layer was formed as Conventional Example 1.

  As Comparative Example 1, in the metal vapor deposition electrode 4a (4b), a metallized film of the metal vapor deposition electrode having the maximum magnesium atom concentration distribution in the divided subdivision portions was used.

  A short-time withstand voltage test and a moisture resistance test were performed using the metallized film capacitor of Example 1 and the above-described Conventional Example 1 and Comparative Example 1.

In the short-time withstand voltage test, the metallized film of this example and the metallized films of Conventional Example 1 and Comparative Example 1 were boosted by a constant voltage every predetermined time in an atmosphere of 100 ° C., and the capacitance change rate of the capacitor Is a voltage (withstand voltage) at which −5% is obtained, and the withstand voltage is determined from the voltage. The rate of change of withstand voltage indicates (withstand voltage V _{t of} Example 1 or Comparative Example 1−withstand voltage V ₀ of Conventional Example 1) / V ₀ in percentage (%).

The moisture resistance test was 85 ° C / 85% r. h. A voltage of 650 V was continuously applied under the conditions of high temperature and high humidity, and the time (humidity resistance) when the capacitance change rate of the capacitor was −5% was measured. The degree of improvement in moisture resistance is indicated by the moisture resistance h _{t of} Example 1 or Comparative Example 1 / the moisture resistance h ₀ of Conventional Example 1.

  The above (Table 1) shows the withstand voltage change rate (%) and the degree of improvement in moisture resistance of Example 1 and Conventional Example 1 in the short-time withstand voltage test and the moisture resistance test.

  As can be seen from Table 1, Comparative Example 1 shows 1.5 times higher moisture resistance than Conventional Example 1, but the withstand voltage is reduced by 3%. On the other hand, Example 1 shows substantially the same moisture resistance as that of Comparative Example 1 and 1.4 times higher moisture resistance than Conventional Example 1. Further, the withstand voltage is higher than that of Comparative Example 1 and is substantially equivalent to that of Conventional Example 1.

  The reason will be described below. As described above, in a metallized film capacitor using an alloy to which magnesium is added as a metal vapor deposition electrode, the metal vapor deposition electrode is less likely to evaporate and scatter, and the self-healing property is lowered. As a result, the withstand voltage decreases. Further, the withstand voltage of the metallized film capacitor tends to be affected by the self-healing property of the divided small electrode part. Therefore, the self-healing property is maintained and the withstand voltage reduction is suppressed by making the magnesium concentration of the divided small electrode portion smaller than that of the large electrode portion.

  Note that the thickness of the divided small electrode portion may be smaller than the thickness of the large electrode portion. As a result, the divided small electrode portions are easily scattered, and the self-healing property can be further improved. The thickness can be obtained, for example, by observing the cross section of the electrode portion by TEM (Transmission Electron Microscope) and calculating the average value.

  Next, the magnesium concentration and the moisture resistance change in the electrode film using the alloy were confirmed.

  FIG. 5 shows the magnesium concentration in the alloy electrode film of Example 1 and the degree of improvement in moisture resistance. The degree of improvement in moisture resistance indicates the moisture resistance of each sample when the moisture resistance of Conventional Example 1 (aluminum electrode film) is 1. As the amount of magnesium increases to 2.0 wt%, 5.7 wt%, 7.9 wt%, 18.9 wt%, the degree of improvement in moisture resistance is 1.1 times, 1.8 times, 2.0 times 2 Moisture resistance improved by 5 times. From this, it is possible to improve moisture resistance by increasing the amount of magnesium in the alloy electrode film. However, as described above, when the amount of magnesium is too large, the resistance increases. Therefore, it is appropriate that the upper limit is 40 wt%, and 2.0 wt% to 40 wt%.

  The metallized film capacitor according to the present invention has excellent moisture resistance, and can be suitably used as a capacitor used in various electronic equipment, electrical equipment, industrial equipment, automobiles, etc., and particularly has high moisture resistance and high withstand voltage characteristics. This is useful in the field of automobiles that are required.

DESCRIPTION OF SYMBOLS 1 1st metallized film 2 2nd metallized film 3a, 3b Dielectric film 4a, 4b Metal vapor deposition electrode 5a, 5b Insulation margin 6a, 6b Metallicon 7a, 7b Vertical margin 8a, 8b Horizontal margin 9a, 9b Large electrode Part 10a, 10b Divided small electrode part 11a, 11b Fuse 12a, 12b Fuse

Claims (2)

A pair of metallized films on which a metal vapor-deposited electrode is formed on a dielectric film, and the metal vapor-deposited electrodes formed on the pair of metallized films are overlapped so as to face each other through the dielectric film, or wound or With stacked elements,
At least one of the metal vapor deposition electrodes of the pair of metallized films is
It is divided into a large electrode part and a divided small electrode part by a non-evaporation slit without a metal vapor deposition electrode film,
A metallized film capacitor comprising aluminum and magnesium as main components, wherein the atomic concentration distribution of magnesium is maximized at the large electrode portion. The metallized film capacitor according to claim 1, wherein the divided small electrode portion is thinner than the large electrode portion.

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