JP5012468B2 - 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 a HEV electric motor has a high operating voltage range of several hundred volts, a metallized film capacitor having high withstand voltage and low loss electric characteristics as a capacitor used in connection with such an electric motor. In addition, there is a tendency to adopt metallized film capacitors that have a very long life due to the demand for maintenance-free in the market, and this kind of metallized film capacitors is high because it is installed in automobiles. Moisture resistance is required, and various developments and proposals for improving moisture resistance have been made.

  5 (a) and 5 (b) are a front sectional view and a side view showing the structure of this type of conventional metallized film capacitor. In FIG. 5, reference numeral 11 denotes a pair of metallized films wound. The formed capacitor element 12 is a film in which a plurality of turns are wound around the outer periphery of the capacitor element 11, and this film 12 has an inorganic oxide layer having a barrier property. Reference numeral 15 denotes an electrode lead portion formed on the winding end face of the capacitor element 11, 16 denotes an external terminal connected to the electrode lead portion 15, 13 denotes an adhesive tape wound around the outer periphery of the film 12, and 14 denotes this adhesive portion. It is a thermosetting insulating resin filled between the tape 13 and the electrode lead portion 15.

  In the conventional metallized film capacitor configured as described above, the film 12 having the inorganic oxide layer is wound around the outer periphery of the capacitor element 11 so that the barrier effect of the inorganic oxide causes the surface of the capacitor element 11 to be removed. Intrusion of moisture and air can be blocked, and capacity reduction due to deterioration of the metallized film constituting the capacitor element 11 can be suppressed, and quality can be stabilized.

  6 is a cross-sectional view showing the configuration of the capacitor element 11 shown in FIG. 5. In FIG. 6, 17 is a dielectric film, and 18 is a metal formed on one side of the dielectric film 17 by vapor deposition. A vapor deposition electrode, 18a is a low resistance portion formed on one end side of the metal vapor deposition electrode 18, and 17a is a margin portion where the metal vapor deposition electrode 18 is not formed. Thereby, a metallized film is formed. The capacitor element 11 is formed by winding a pair so that the metal vapor deposition electrodes 18 face each other with the dielectric film 17 therebetween. Reference numeral 12 denotes a film wound around the outer peripheral surface of the capacitor element 11, and reference numeral 15 denotes electrode lead portions formed on both end faces of the capacitor element 11 including the film 12.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2002-184642 A

  However, in the above conventional metallized film capacitor, the film 12 having the inorganic oxide layer is wound around the outer periphery of the capacitor element 11, so that moisture and air from the surface layer portion of the capacitor element 11 are caused by the barrier effect by the inorganic oxide. The infiltration can be blocked, and the reduction in capacity due to the deterioration of the metallized film constituting the capacitor element 11 can be suppressed to stabilize the quality. When the resin is molded in a case (not shown) and used, the film 12 having the inorganic oxide layer and the molding resin have a low degree of adhesion. Capacitor element 1 is easy even if it is a metallized film capacitor in which air is easy to enter, thereby improving moisture resistance. Internal not it inevitable that moisture and air from entering, there is a problem that can lead to degradation of the performance and quality of the metallized film capacitor.

  Furthermore, after the film 12 having the inorganic oxide layer (the same as a general exterior film having no inorganic oxide layer) is wound around the outer periphery of the capacitor element 11, Since a part of the surface is partially heated at a high temperature of about 300 ° C. to melt the exterior film, the heated and melted part has a reduced film thickness. Therefore, moisture easily enters, and unnecessary vibration occurs due to an applied current in a portion that is not heated and melted, or a surplus portion of the metallicon as an electrode extraction portion 15 formed on both end faces of the capacitor element 11 is formed. In the blasting process at the time of removal, there is a problem that the melted part peels off due to stress, and the problem that the moisture resistance and vibration resistance deteriorate due to these problems It was those that are.

  The present invention solves such a conventional problem and is an inexpensive metalized film capacitor that can exhibit excellent moisture resistance and vibration resistance even when molded in a case using a mold resin. Is intended to provide.

  In order to solve the above problems, the present invention uses a multilayer polypropylene film having two or more layers of polypropylene films having different melting points as an exterior film wound around the outer periphery of the element, and has a layer having the lowest melting point. The polypropylene film is wound on the inner surface side.

  As described above, the metallized film capacitor according to the present invention uses a multi-layered polypropylene film having the same material and different only in melting point as an exterior film, and has a structure in which a low-melting polypropylene film is in contact with the element, so that the exterior is used in the aging process. The low melting point polypropylene film that composes the film melts and adheres to the outer peripheral surface of the element, and the outer film shrinks uniformly, so that the tightening of the element becomes uniform and the occurrence of looseness is eliminated. The effect that lifetime, moisture resistance, and vibration resistance are improved is obtained.

In order to solve the above problems, the metallized film capacitor of the present invention uses a multilayered polypropylene film having two or more layers of polypropylene films having different melting points as the exterior film wound around the outer periphery of the element, and most A polypropylene film having a low melting point is wound on the inner surface side, and heat-sealed to shrink the multilayered polypropylene film.

(Embodiment)
Hereinafter, the invention described in the entire claims of the present invention will be described by using embodiments.

  FIG. 1 is a sectional view showing the structure of a metallized film capacitor according to an embodiment of the present invention, FIG. 2 is a developed perspective view showing elements of the metallized film capacitor, and FIG. 3 is used for the metallized film capacitor. FIG. 1 is a cross-sectional view showing the configuration of an exterior film. In FIGS. 1 to 3, 1 is a metallized film capacitor, 2 is an element, and 3 is a metallicon electrode.

  4 is a dielectric film made of polypropylene, 5 is a metal vapor-deposited electrode formed by vapor deposition on one side of the dielectric film 4, 5a is a low resistance portion formed on one end side of the metal vapor-deposited electrode 5, and 4a is the above metal It is a margin part where the vapor deposition electrode 5 is not formed, and a metallized film is formed thereby, and the metallized film is paired and wound so that the metal vapor deposition electrode 5 faces the dielectric film 4. Thus, the element 2 is formed.

  6 is an exterior film wound around the outer periphery of the element 2, 7 is a corona-treated surface provided on one side which is the outer surface side of the exterior film 6, and the exterior film 6 is shown in detail in FIG. As described above, polypropylene films having different melting points (hereinafter referred to as PP films) have a plurality of layers (in this embodiment, a two-layer structure is taken as an example, but the present invention is not limited to this). The PP film 6a having the lowest melting point is wound on the inner surface side so as to come into contact with the element 2.

  Further, as the exterior film 6 used in the present embodiment, the PP film 6a forming the low melting point layer disposed on the inner surface side has a melting point of 90 ° C. (needs a melting point of 120 ° C. or less) The PP film 6b for forming a high melting point layer disposed on the outer surface side is a film having a melting point of 150 ° C., and this two-layer exterior film 6 is wound around the outer periphery of the element 2 After that, heat sealing was performed by heating at 100 ° C. for 1 second at 0.1 MPa so that the heat seal strength according to JIS-Z-0238 exhibited 3 N / 15 mm or more. The starting temperature of the seal is configured to be 120 ° C. or less, which is a temperature at which the heat seal strength reaches 3N.

  A conventional product as a comparative example (multi-layer structure) was obtained by producing a case mold type capacitor in which the metallized film capacitor according to the present embodiment thus configured was molded in a case using a mold resin and performing a moisture resistance test. FIG. 4 shows a comparison with a non-PP film used as an exterior film. As test conditions, DC 600V was applied, and the capacity reduction rate at an ambient temperature of 85 ° C. and humidity of 85% was measured.

  In FIG. 4, the embodiment (1) is a multi-layer PP film, the (2) is (1) + corona treatment on the outer surface, and the (3) is (1) + gas barrier treatment on the outer surface. Shows what

  As is clear from FIG. 4, while the conventional product has a sudden capacity decrease after 1000 hours, the one using the metallized film capacitor according to the present embodiment has a moderate capacity even after 1000 hours. It can be understood that stable capacitor characteristics can be obtained over a long period.

  In the initial stage of energization, moisture permeation from the opening surface of the mold resin is dominant, but after long-term energization, the interface between the exterior film 6 and the mold resin, the interface between the exterior film 6 and the element 2, and the exterior film 6 Since moisture permeation from the heat-melted portion (heat seal portion) becomes dominant, the case mold type capacitor using the metallized film capacitor according to the present embodiment in which the degree of adhesion between the exterior film 6 and the element 2 is improved. However, it is considered that stable performance can be exhibited over a long period of time.

  As described above, the metallized film capacitor according to the present embodiment uses a multi-layer PP film having the same material and only different melting points as the exterior film 6, and the low melting PP film 6 a is in contact with the element 2. In the aging process, the low-melting PP film constituting the exterior film 6 melts and adheres closely to the outer peripheral surface of the element 2, and the exterior film 6 contracts uniformly, so that the tightening of the element 2 becomes uniform and looseness occurs. As a result, the moisture resistance and vibration resistance of the element 2 can be improved, and furthermore, since the heat seal temperature is low, the thermal damage to the element 2 can be greatly reduced. There is an effect.

  In addition, since the PP film having a multilayer structure used as the exterior film 6 can be a PP film that is generally used for packaging, unlike an electrical film that is generally used conventionally, However, it is possible to use a product that is cheaper by one digit or more, so that the cost can be reduced.

  Furthermore, many PP films for packaging have a heat seal layer on one side (inner surface) and a barrier layer against oxygen, nitrogen, water, etc. on the other side (outer surface), and these are used. Therefore, it is possible to further improve the moisture resistance.

  Furthermore, by corona-treating the surface of the polypropylene film 6b that forms a layer having a high melting point disposed on the outer surface side of the exterior film 6, such a metallized film capacitor is molded using a mold resin. When using it molded inside, the adhesion between the mold resin is improved and the gap between the exterior film 6 and the mold resin can be greatly reduced, so that further improvement of moisture resistance is achieved. There is also an extraordinary effect of being able to.

  The metallized film capacitor according to the present invention is excellent in moisture resistance and vibration resistance and has an effect that it can be provided at low cost, and is particularly useful as a resin mold type automobile capacitor.

Sectional drawing which showed the structure of the metallized film capacitor by one embodiment of this invention An exploded perspective view showing the element of the metallized film capacitor Sectional view showing the structure of the exterior film used in the metallized film capacitor Characteristic diagram showing the results of a moisture resistance test of a case mold type capacitor using the same metallized film capacitor (A) Front sectional view showing the structure of a conventional metallized film capacitor, (b) Side view Sectional view showing the configuration of a capacitor element of a conventional metallized film capacitor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metallized film capacitor 2 Element 3 Metallicon electrode 4 Dielectric film 4a Margin part 5 Metal vapor deposition electrode 5a Low resistance part 6 Exterior film 6a Low melting point side polypropylene film 6b High melting point side polypropylene film 7 Corona treatment surface

Claims (5)

An element in which a pair of metallized films having a metal vapor-deposited electrode formed on a dielectric film are wound so that the metal vapor-deposited electrode faces through the dielectric film, and an exterior film wound around the outer periphery of the element; In a metallized film capacitor comprising metallicon electrodes formed by metal spraying on both end faces of an element including the exterior film, the exterior film wound around the outer periphery of the element has two or more layers of polypropylene films having different melting points. A metallized film capacitor using the multilayered polypropylene film having the lowest melting point, wound on the inner surface side, and heat-sealed to shrink the multilayered polypropylene film . 2. The metallized film capacitor according to claim 1, wherein the polypropylene film having the lowest melting point of the multilayer structure polypropylene film used as the exterior film has a melting point of 120 ° C. or lower. 2. The metallized film capacitor according to claim 1, wherein the heat seal strength according to JIS-Z-0238 between the outer periphery of the element and a polypropylene film having a multilayer structure used as an exterior film is 3 N / 15 mm or more. 2. The metallized film capacitor according to claim 1, wherein the heat seal start temperature between the outer periphery of the element and the multilayered polypropylene film used as an exterior film is 120 ° C. or less. The metallized film capacitor according to claim 1, wherein the surface of the polypropylene film disposed on the outer surface side of the polypropylene film having a multilayer structure used as the exterior film is subjected to corona treatment.

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