JP2012190969A - Metalized film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metalized film capacitor having excellent humidity resistance and voltage resistance.SOLUTION: A metalized film capacitor comprises: an element in which a first metalized film 1, in which metal vapor deposition electrodes 4a, 4b are formed on polypropylene films 3a, 3b, is made into a pair with a second metalized film 2, the respective metal vapor deposition electrodes 4a, 4b formed on a pair of the metalized films are overlaid opposite to each other via the polypropylene films 3a, 3b and wound or laminated; and a pair of metalized contacts 6a, 6b formed on both ends of the element. An alloy of aluminum and magnesium is used for any one of the metal vapor deposition electrodes 4a, 4b. By this constitution, high humidity resistance of an alloy electrode can be realized while maintaining a self-healing property of the metalized film capacitor, and the metalized film capacitor having both of excellent humidity resistance and voltage resistance can be provided.

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. Among these, metallized film capacitors that use vapor-deposited metal as an electrode (hereinafter referred to as metal vapor-deposited electrode) have a smaller volume occupied by the electrode compared to that of metal foil and can be reduced in size and weight. Widely used in the past because of its high reliability in dielectric breakdown due to the recovery function (meaning the ability of the metal vapor deposition electrode around the defect to evaporate and scatter and the function of the capacitor to recover, generally called self-healing) It is what has been.

  FIG. 5 is a sectional view showing the structure of a conventional metallized film capacitor of this type, and FIGS. 6A and 6B are plan views showing a pair of metallized films used in the metallized film capacitor. As shown in FIGS. 5 and 6, the metal deposition electrode 101a and the metal deposition electrode 101b deposit aluminum on one surface of dielectric films 102a and 102b such as polypropylene film except for the insulation margins 103a and 103b at one end. It is formed by that. 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.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

JP 2004-134561 A

  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 a reaction represented 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 obtained by adding magnesium to aluminum has a reduced self-recovery function and 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 is configured such that an alloy composed of aluminum and magnesium is used only for one of the metal deposition electrodes of the pair of metallized films.

  The metallized film capacitor according to the present invention has a structure in which an alloy composed of aluminum and magnesium is used for either one of a pair of metallized films, while maintaining the self-healing property of the metallized film capacitor. It becomes possible to provide a metallized film capacitor that can exhibit high moisture resistance and can achieve both excellent moisture resistance and voltage resistance.

Sectional drawing which showed the structure of the metallized film capacitor of this invention (A), (b) The top view which showed the structure of the metallized film used for the metallized film capacitor of this invention Graph showing the results of the voltage step-up test Graph showing results of moisture resistance test 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

  Hereinafter, the structure of the metallized film capacitor of the present invention will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a cross-sectional view showing a configuration of a metallized film capacitor of the present invention, and FIGS. 2A and 2B are plan views of a pair of metallized films used in the metallized film capacitor of the present invention. It is.

  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 4 a formed on one surface of a polypropylene film 3 a serving as a dielectric, and is insulated for insulation from the second metallized film 2. The margin 5a is provided. In this embodiment, a polypropylene film is used as the dielectric of each metallized film, but polyethylene terephthalate, polyethylene naphthalate, polyphenyl sulfide, polystyrene, or the like may be used in addition to this.

  This metal vapor deposition electrode 4a is connected to a metallicon 6a formed on the end face so as to draw out the electrode. The metal vapor-deposited electrode 4a has a non-vapor-deposited vertical margin 7a and a horizontal width that do not have the metal vapor-deposited electrode 4a formed by oil transfer on the side from the substantially central portion of the effective electrode portion (width W) forming the capacitance toward the insulating margin 5a. A large electrode portion 9a and a plurality of divided small electrode portions 10a are divided by a margin 8a (shown in FIG. 2).

  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 side of the polypropylene 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 side of the polypropylene 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 insulating margin 5a. However, the present invention is not limited to this, and a plurality of divided small electrode portions 10a may be provided.

  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 (self-healing property). 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 a metal vapor-deposited electrode 4b except for an insulating margin 5b at one end on one surface of a polypropylene film 3b serving as a dielectric, as shown in FIG. 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 of the effective electrode portion (width W) 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.

  As described above, the metallized film of the present invention is different from the metallized film described in the section of “Background Art” in its electrode configuration (pattern), but the effects of the points of the present invention described below are as follows. The metallized film described in the background art can also be obtained.

Example 1
In the metallized film capacitor shown in FIG. 1 described above, the electrode materials used for the metal vapor deposition electrode 4a as the P pole and the metal vapor deposition electrode 4b as the N pole are aluminum simple substance and an alloy of aluminum and magnesium, respectively. It was set to 1.

  The N-electrode metal deposition electrode 4b formed of an alloy of aluminum and magnesium is prepared by supplying aluminum and magnesium to a deposition furnace, heating and melting them by resistance heating, and attaching the generated metal fine particles to the polypropylene film 3b. Made by letting.

  The weight ratio of magnesium contained in the N-electrode metal-deposited electrode 4b was measured by fluorescent X-ray analysis (XRF) and found to be about 8%.

(Example 2)
In Example 1, the N-electrode metal deposition electrode 4b was formed of an alloy of aluminum and magnesium. In Example 2, the P-electrode metal deposition electrode 4a was formed of an alloy of aluminum and magnesium. The N-electrode metal deposition electrode 4b was formed of aluminum alone, similarly to the P-electrode metal deposition electrode 4a of Example 1. As described above, the metalized film capacitor of Example 2 has the same configuration as that of Example 1 except for the materials of the respective metal deposition electrodes constituting the P pole and the N pole.

  The P electrode was produced in the same manner as the production method of Example 1.

  As a result of measuring the weight ratio of magnesium contained in the P-electrode metal deposition electrode 4a of Example 2 by XRF, it was about 8% as in Example 1.

(Comparative Example 1)
As Comparative Example 1, a metallized film capacitor in which both the P-electrode metal deposition electrode 4a and the N-electrode metal deposition electrode 4b were formed of aluminum alone was produced. The structure except this point is the same as that of Example 1 and Example 2, that is, the metallized film capacitor of Comparative Example 1 was produced according to the structure shown in FIG.

(Comparative Example 2)
As Comparative Example 2, a metallized film capacitor in which both the P-electrode metal deposition electrode 4a and the N-electrode metal deposition electrode 4b were formed of an alloy of aluminum and magnesium was produced. The configuration other than this point is the same as that of Example 1, Example 2, and Comparative Example 1, that is, a metallized film capacitor of Comparative Example 2 was produced according to the configuration shown in FIG.

  In addition, when the weight ratio of magnesium contained in the P-electrode metal deposition electrode 4a and the N-electrode metal deposition electrode 4b in Comparative Example 2 was measured by XRF, it was about 8%.

  FIG. 3 shows the results of the voltage step-up test of the metallized film capacitors of Examples 1, 2, Comparative Example 1, and Comparative Example 2 described above. The voltage step-up test is a test in which the voltage applied at fixed time intervals is increased by a predetermined amount and the change rate of capacitance is measured. In particular, in this test, the voltage applied to the sample was increased every predetermined time under the condition of an ambient temperature of 100 degrees, and the voltage at the time when the capacitance reached −5% of the initial value was measured.

  Here, in FIG. 3, the curve a shows the change in Example 1, the curve b shows the change in Example 2, the curve c shows the change in Comparative Example 1, and the curve d shows the change in Comparative Example 2.

  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. For this reason, the voltage at the time when the electrostatic capacity of Comparative Example 1 reached -5% of the initial value was approximately 1300 V, whereas Comparative Example 2 was approximately 1240 V, and both metal-deposited electrodes were formed of an alloy. The metallized film capacitor (Comparative Example 2) is inferior in the withstand voltage characteristics compared to the metallized film capacitor (Comparative Example 1) in which both metal vapor-deposited electrodes are formed of aluminum alone.

  On the other hand, in Example 2 in which only the P-electrode metal deposition electrode 4a was formed of an alloy, the voltage when the capacitance reached -5% of the initial value was approximately 1280 V, which was relatively good compared to Comparative Example 2. The withstand voltage characteristics were similar to those of Comparative Example 1.

  Further, in Example 1 in which only the N-pole metal deposition electrode 4b is formed of an alloy, the voltage when the electrostatic capacity becomes -5% of the initial value is approximately 1310 V, which is approximately the same withstand resistance as in Comparative Example 1. The voltage characteristics are shown.

  Here, the metallized film capacitor of Example 1 thus exhibited substantially the same withstand voltage characteristics as the metallized film capacitor of Comparative Example 1, and was slightly different from that of Example 2 in the withstand voltage characteristics. Briefly explain the reason for the reason why the error occurred.

  This reason is probably due to the difference in self-healing properties between the P pole and the N pole. In other words, the metallized film capacitor frequently undergoes self-healing at the P pole rather than the N pole when voltage is applied, and the withstand voltage characteristic of the metallized film capacitor is higher or lower than the N pole. High dependence on Therefore, since Example 1 uses an alloy for the N-pole metal vapor deposition electrode 4b instead of the P-pole metal vapor deposition electrode 4a, the P-pole metal vapor deposition electrode 4b has a P-pole rather than the Example 2 using an alloy. It is considered that the self-healing property is increased and a difference occurs in the withstand voltage characteristics between the first embodiment and the second embodiment. Further, since the self-healing property of the N pole hardly affects the withstand voltage characteristic of the metallized film capacitor, it is considered that Example 1 exhibited a withstand voltage characteristic substantially equivalent to that of Comparative Example 1.

  Furthermore, the inventor of the present invention manufactured a plurality of metallized film capacitors corresponding to Example 1, Example 2, Comparative Example 1, and Comparative Example 2, and conducted each voltage step-up test a plurality of times, thereby making each metal The tendency of withstand voltage characteristics of reinforced film capacitors was investigated. As a result, with respect to the voltage at the time when the electrostatic capacity became −5% of the initial value, although there was variation for each test, Example 2 exceeded Comparative Example 2 in all tests, and Example 1 was further an Example. It was confirmed that there was a tendency to show a value substantially higher than 2 and comparable to that of Comparative Example 1.

  Next, FIG. 4 shows the results of a moisture resistance test performed on the metallized film capacitors of Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

  This moisture resistance test was conducted at 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 change of the capacity was measured.

  Here, in FIG. 4, the curve A shows the change in Example 1, the curve B shows the change in Example 2, the curve C shows the change in Comparative Example 1, and the curve D shows the change in Comparative Example 2.

  As can be seen from FIG. 4, in Comparative Example 2 in which an alloy is used for both metal vapor deposition electrodes, the moisture resistance is dramatically improved compared to Comparative Example 1 in which both metal vapor deposition electrodes are made of aluminum alone. Specifically, according to the present moisture resistance test, the capacity reduction of Comparative Example 2 was only 1% during the time when the capacity of Comparative Example 1 was reduced by 5%.

  On the other hand, it can be seen that Example 1 in which the alloy is used only for the N-electrode metal deposition electrode 4b has superior moisture resistance as compared with Comparative Example 1. Further, in Example 2 in which an alloy is used only for the P electrode, although it is slightly less than Comparative Example 2, it can be seen that the moisture resistance is dramatically improved as compared with Comparative Example 1. In addition, the capacity | capacitance fall of these Examples 1 and 2 in the time when the capacity | capacitance of the comparative example 1 fell 5% was 1% similarly to the comparative example 2 mentioned above.

  As described above, although Example 2 does not reach Comparative Example 2, the moisture resistance is remarkably improved as compared with Comparative Example 1, and the reason why the difference between Example 2 and Example 1 occurs is briefly described below. State.

That is, when moisture enters the metallized film capacitor, a phenomenon represented by the following chemical formula occurs on the P electrode side, and the metal vapor deposition electrode made of aluminum becomes aluminum oxide (Al ₂ O ₃ ) which is an aluminum insulator. Therefore, it becomes difficult to function as a metal vapor deposition electrode.
(P pole side)
Al + 3H ₂ O → Al (OH) ₃ + 3H ⁺ + 3e ⁻
2Al (OH) ₃ → Al ₂ O ₃ + 3H ₂ O
(N pole side)
^{3H + + 3e - → 3 /} 2H 2
Here, in Example 2 in which the metal deposition electrode 4a of the P electrode is an alloy, magnesium absorbs moisture, and generation of aluminum oxide, which is a cause of capacity reduction, can be effectively suppressed. As a result, Example 2 has drastically improved moisture resistance as compared with Comparative Example 1 in which aluminum alone is used for both metal deposition electrodes. On the other hand, a chemical reaction that leads to a decrease in capacity does not occur on the N pole side as compared with the P pole side, and the metallized film capacitor having the N pole metal vapor deposition electrode 4b as an alloy is the P metal deposition electrode 4a. The effect of improving moisture resistance is low compared to a metallized film capacitor made of alloy. Therefore, it is considered that there was a difference between Example 2 and Example 1 in which the N pole side was an alloy.

  The results of evaluating the moisture resistance and the results of the voltage step-up test described above are summarized in Table 1. In this (Table 1), the withstand voltage characteristic item is the voltage at the time when the above-mentioned capacitance becomes -5% of the initial value, and the moisture resistance item is the time when the capacity of the above-described Comparative Example 1 is reduced by 5%. The capacity reduction rate of each metallized film capacitor is described.

  As can be seen from (Table 1), it can be seen that Comparative Example 1 in which both metal vapor-deposited electrodes are made of aluminum alone is inferior to Examples 1, 2 and 2 in terms of moisture resistance. Moreover, it turns out that the comparative example 2 which made the both metal vapor deposition electrode an alloy is inferior compared with Example 1, Example 2, and the comparative example 1 in the withstand voltage characteristic.

  That is, Comparative Example 1 and Comparative Example 2 are extremely bad in either the withstand voltage characteristic or the moisture resistance characteristic.

  On the other hand, Example 1 in which the metal deposition electrode 4b of the N pole is made of an alloy has a withstand voltage characteristic substantially equivalent to that of Comparative Example 1 in which both metal deposition electrodes are made of aluminum alone. It turns out that it is excellent.

  Further, Example 2 in which the P-electrode metal deposition electrode 4a was made of an alloy had a withstand voltage characteristic similar to that of Comparative Example 1 in which both metal deposition electrodes were made of aluminum alone. Further, as can be seen from FIG. It can be seen that the film has moisture resistance close to that of Comparative Example 2 in which is used as an alloy.

  That is, a metallized film capacitor using an alloy composed of aluminum and magnesium for either one of the metal vapor-deposited electrodes is a metallized film capacitor having both metal vapor-deposited electrodes as a single element of aluminum or an alloy of aluminum and magnesium. It can be seen that it has both excellent moisture resistance and excellent withstand voltage characteristics compared to the metallized film capacitor.

  Here, when Example 1 and Example 2 are compared, Example 1 is slightly superior in withstand voltage characteristics, and Example 2 is slightly superior in moisture resistance.

  In other words, in the actual usage, when specifications with an emphasis on withstand voltage are required, it is preferable to use an alloy only for the metal deposition electrode 4b of the N pole of the P pole and the N pole. As a result, it is possible to realize a metallized film capacitor having both excellent withstand voltage characteristics and moisture resistance and particularly excellent withstand voltage characteristics.

  Similarly, in the actual use aspect, when specifications with an emphasis on moisture resistance are required, it is preferable to use an alloy only for the metal deposition electrode 4a of the P pole of the P pole and the N pole. As a result, it is possible to realize a metallized film capacitor having both excellent voltage resistance characteristics and moisture resistance and particularly excellent moisture resistance.

  As described above, the metallized film capacitor according to the present invention can achieve both excellent withstand voltage characteristics and moisture resistance.

  Although the winding type metalized film capacitor has been described as an example in the present invention, the present invention is not limited to this, and the present invention can also be applied to a laminated type metalized film capacitor. .

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

DESCRIPTION OF SYMBOLS 1 1st metallized film 2 2nd metallized film 3a, 3b Polypropylene 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 (3)

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 Stacked elements,
It consists of a pair of metallicon electrodes formed on both end faces of this element,
A metallized film capacitor using an alloy of aluminum and magnesium for any one of the metallized films of the pair of metallized films. The metallized film capacitor according to claim 1, wherein the metal deposition electrode using an alloy of aluminum and magnesium is an N pole. The metallized film capacitor according to claim 1, wherein the metal vapor deposition electrode using the alloy of aluminum and magnesium is a P electrode.

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