JP2012099552A - Metalized film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metalized film capacitor with excellent waterproofness and moisture resistance without increasing thickness of a mold resin body.SOLUTION: Metal spray parts 2, 2 are formed on two electrode extraction faces of a metalized film columnar body 1, around which a metalized film is wound or laminated. A hydrophilic film 7 is coated on a periphery other than the electrode extraction face of the metalized film columnar body 1, and an external extraction terminal 3 is jointed to the metal spray part 2. They are housed in a case 5, and embedded in a mold resin body 6 in the case 5, so as to constitute the metalized film capacitor 10.

Description

  The present invention relates to a metallized film capacitor in which a wound or laminated metallized film column is housed in a case and embedded in a mold resin body in the case.

  A conventional metallized film capacitor formed by winding a metallized film or a laminated metallized film capacitor formed by laminating a metallized film, as shown in FIG. Metal sprayed portions m, m (or metallicon, metallicon electrodes) are formed on the two electrode extraction surfaces at both ends of the body f, and the external lead terminals b, b are soldered to the two metal sprayed portions m, m. The thing of the structure where the thing was accommodated in the case c and sealed with the mold resin body j formed in the case c is common. More specifically, a waterproof film is formed by wrapping a waterproof film bf made of polyethylene terephthalate (PET) or the like around the peripheral surface of the metallized film column f several tens of times, and a mold resin body j is formed on the outside. Is formed. For example, Patent Document 1 discloses a metallized film capacitor having this general structure.

  For example, in a wound metallized film capacitor, epoxy resin is generally applied to the material of the mold resin body from the viewpoint of waterproofness and vibration proofing. Moisture permeates into the mold resin, causing oxidation of the metallized film (more specifically, an aluminum film deposited on the surface of the dielectric film) and a decrease in the dielectric breakdown strength of the dielectric film. There is a problem of causing a decrease in electric capacity and a decrease in withstand voltage.

  Therefore, as shown in FIG. 5, the thickness of the mold resin body j that seals the metallized film column f (thickness from the surface of the metallized film column f to the surface of the mold resin body j: t1) is increased. By doing so, the intrusion of moisture is prevented. However, the increase in the amount of mold resin causes the problem of increased material cost and increased capacitor weight.

  In the case of a vehicle-mounted capacitor, the amount of mold resin material used is generally large because the capacitance is as large as several hundred μF and tends to be large. In addition to the above-mentioned problems of increased cost and weight due to an increase in the amount of the mold resin material, the residual stress after the resin material is cured is likely to cause cracks, and the original waterproof function cannot be fully exhibited. It leads to a new problem. As a countermeasure, there is a measure of covering the surface of the mold resin body with a low-elasticity resin material such as urethane resin. However, in addition to an increase in the number of manufacturing steps and the number of capacitor components, there arises a problem of further weight increase.

  Therefore, under a technical idea that is completely different from the conventional technical idea of increasing the thickness of the mold resin body or covering the periphery of the metallized film column with a waterproof film to improve its waterproofness and moisture resistance. Therefore, development of a metalized film capacitor capable of solving all of the above-described various problems is eagerly desired in the art.

JP 2010-16161 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a metallized film capacitor excellent in waterproofness and moisture resistance without increasing the thickness of the molded resin body.

  In order to achieve the above object, the metallized film capacitor according to the present invention has a metal sprayed portion formed on the two electrode extraction surfaces of a metallized film column formed by winding or laminating a metallized film. A hydrophilic film is coated on the peripheral surface of the column body other than the electrode extraction surface, and an external lead terminal is joined to the metal sprayed portion, and these are accommodated in the case and embedded in the mold resin body in the case. Is.

  In the metallized film capacitor of the present invention, the peripheral surface of the metallized film column is covered with a waterproof (water-repellent) film, or the thickness of the mold resin body provided on the peripheral surface of the metallized film column is increased. It is not a technical idea that the permeated water does not permeate the metal vapor deposition film etc., but the permeated water is made into a metal by covering the peripheral surface of the metallized film column with a hydrophilic film and trapping the permeated water with this hydrophilic film. This is based on the technical idea of preventing the film from reaching the fluorinated film column.

  Thus, the thickness of the mold resin body provided on the peripheral surface of the metallized film column is as much as possible because it is based on the technical idea of trapping with a hydrophilic film rather than blocking permeated water. It does not matter if it is thin.

  Here, the metallized film pillar is a laminate of two metallized films in which a metal vapor-deposited film made of aluminum or zinc is formed on the surface of a dielectric film made of polypropylene (PP) or polyphenylene sulfide (PPS). In this way, both metallized films have insulation margins at different ends so that each comes into contact with a unique metal sprayed part (metallicon electrode). Furthermore, of the metal vapor deposition film, the end opposite to the insulation margin and the end contacting the metal sprayed portion is a so-called heavy edge that is thicker than other parts to ensure electrode contact, For example, when the general part of the metal vapor-deposited film is about 30 nm, the heavy edge is adjusted to about double 60 nm.

  A metal sprayed portion made of zinc or the like is formed on the electrode extraction surfaces at both ends of the coiled or laminated metallized film column, and a part of the external lead terminal is soldered to the metal sprayed portion. This external lead terminal is made of a bar-like or plate-like bus bar or the like, and copper, aluminum, nickel, stainless steel or the like is applied as the material thereof.

  A hydrophilic film is wound around the peripheral surface of the metallized film column other than the electrode extraction surface. Here, a material having a polar group (hydroxyl group, amide group, etc.) in the molecular structure is preferably applied to the hydrophilic film, and examples of the forming material include polyvinyl alcohol (PVA) and polyamide. . In designing the actual number of windings of the hydrophilic film, etc., after determining the desired water absorption, the hydrophilic film used (specific gravity and water absorption), thickness, area per roll, etc. The number of turns is designed.

  In a posture in which the metallized film column is disposed in a case made of aluminum, resin, or the like, a resin such as epoxy resin, silicone resin, or urethane resin is molded in the case to form a molded resin body. This mold resin body improves both the waterproof and vibration-proof performance of the metallized film capacitor.

  Since the hydrophilic film described above has a large number of polar groups, the adhesion to the mold resin body is also good, and there is no risk of interfacial peeling between the two.

  Further, although the hydrophilic film expands due to water absorption, even when, for example, PVA having a water absorption rate of 30% is applied, the increase in dimensions is at most on the order of micrometers. Therefore, the dimensional stability is good, and problems such as stress concentration do not occur.

  As can be understood from the above description, according to the metallized film capacitor of the present invention, the periphery of the metallized film column is covered with a hydrophilic film, and the permeated water is trapped with this hydrophilic film, thereby metallized film. Since the penetration of permeated water to the column can be eliminated, it is excellent in waterproofness and moisture resistance, and the material cost is reduced by reducing the thickness of the mold resin body formed around the metallized film column as much as possible. Reduction and weight reduction of the capacitor can be achieved.

(A) is a longitudinal cross-sectional view of the metallized film capacitor of this invention, (b) is a bb arrow line view of (a). In designing a hydrophilic film satisfying a desired moisture resistance, it is a diagram simulating a test piece of an example comprising a metallized film column and a hydrophilic film wound around the metallized film column. It is a graph which shows the time-dependent change of the water permeability of a mold resin body in the design of the hydrophilic film which satisfies desired moisture resistance. It is a graph which shows the time-dependent change of the water absorption amount for every usage-amount of a PVA film in design of the hydrophilic film which satisfies desired moisture resistance. It is a longitudinal cross-sectional view which shows the metallized film capacitor of a conventional structure.

  Embodiments of the present invention will be described below with reference to the drawings. 1a is a longitudinal sectional view of the metallized film capacitor of the present invention, and FIG. 1b is a view taken along the line bb of FIG. 1a.

  The metallized film capacitor 10 shown in the figure includes a metallized film column 1 in which a metallized film is wound, and metal sprayed portions 2 and 2 (metallicon electrodes) formed on two electrode extraction surfaces at both ends thereof. An external lead terminal 3 (bus bar) connected to each of the metal sprayed portions 2 and 2 via solder layers 4 and 4, a case 5 for housing them, and a metallized film column formed in the case 5 1 is roughly constituted by a mold resin body 6 in which 1 is embedded.

  A specific configuration of the metallized film column 1 is that a metal vapor deposition film is formed on one side surface of a dielectric film to form a metallized film, and two metallized films are laminated to form a set (two sheets) A pair of metallized films), and a pair of these two metallized films are wound.

  Here, as for the metal vapor deposition film formed in one side of one dielectric film of a set of metallized films, the one end along the longitudinal direction is closely_contact | adhered to one metal spraying part 2, The longitudinal direction A gap region (insulation margin) of about 2 mm, for example, is provided at the other end along the line to be insulated from the other metal sprayed portion 2. In addition, the end of the metal vapor deposition film that is in close contact with the metal sprayed portion 2 has a so-called heavy edge that is thicker than other parts to ensure electrode contact. When the general part is about 30 nm, the heavy edge is adjusted to about double 60 nm.

  Here, the dielectric film can be formed of polypropylene (PP), polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), etc., and the metal vapor deposition film is made of aluminum, zinc, copper or the like as a dielectric. It is formed by vapor deposition on the film surface. Further, the metal sprayed portion 2 is formed by spraying aluminum, zinc, or the like on the electrode extraction surface of the metallized film column 1.

  In the metallized film column 1, a hydrophilic film 7 (PVA film) made of polyvinyl alcohol (PVA) is wound around the area other than the electrode take-out surface a desired number of times.

  Here, if the water absorption rate of the hydrophilic film 7 is low, it will lead to an increase in the size of the film. Therefore, at the design stage, this water absorption rate should be set to at least 5%, preferably 10% or more. When the PVA film is used, a water absorption of 10% or more can be sufficiently satisfied.

  Further, although the hydrophilic film 7 expands due to water absorption, for example, even when a PVA film having a water absorption rate of 30% is used, the dimensional change remains on the order of micrometers, and is further restrained from the outer periphery by the mold resin body 6 having a high elastic modulus. Therefore, the dimensional stability is good and the problem of stress concentration does not occur.

  The required water absorption amount of the hydrophilic film at this design stage (the water permeability of the capacitor) is the product of the area of the peripheral surface of the metallized film column 1 and the thickness of the film (the volume per turn of the hydrophilic film). On the other hand, the weight per one turn of the hydrophilic film is obtained by multiplying the specific gravity, and the water-absorbable weight per turn of the hydrophilic film is obtained by multiplying the water absorption rate of the hydrophilic film. Furthermore, by multiplying this by the number of turns of the hydrophilic film, it is possible to design a hydrophilic film having a quantity (area, number of turns, etc.) corresponding to the desired water absorption.

  According to the metallized film capacitor 10 shown in FIG. 1, the thickness of the mold resin body provided on the peripheral surface of the metallized film column is not increased to improve its moisture resistance. The peripheral surface is covered with a hydrophilic film 7 and trapped in the permeated water with this hydrophilic film 7 so as not to reach the metal vapor deposition film or the like constituting the metallized film column 1. The thickness t2 of the mold resin body 6 may be as thin as possible (if compared with the thickness t1 of the mold resin body j having the conventional structure in FIG. 5). The difference is clear).

  Therefore, while having excellent waterproof and moisture resistance, the amount of mold resin body used can be significantly reduced compared to conventional metallized film capacitors, thereby reducing the overall size and weight of the metallized film capacitor. Reduction and cost reduction of the molding resin material can be achieved.

[Design of hydrophilic film satisfying desired moisture resistance]
The inventors made a test piece of the example consisting of the metallized film column simulated in FIG. 2 and the PVA film around it, and trapped the water permeability in the case of a thin resin layer as much as possible. The design of the hydrophilic film which can do was performed.

  Here, FIG. 3 shows a change with time of the water permeability of the molded resin body specified by the present inventors. Regarding the amount of water permeation, the thickness of the metallized film column and the surface of the molded resin body (thickness t2 in FIG. 1) is 0.5 mm, 1 mm, 3 mm, and 6 mm under an indoor condition of 85% RH at 85 ° C. The change in water permeability with time was measured with four test pieces.

  From FIG. 3, the water permeability of each test piece after 1000 hours is 400 mg for the 0.5 mm thick, 200 mg for the 1 mm thick, 50 mg for the 3 mm thick, and 20 mg for the 6 mm thick. It has been specified.

  For example, in the case of a test piece having a thickness of 6 mm, 20 mg may enter the metal vapor deposition film constituting the metallized film column under the test conditions of 85 ° C., 85% RH, and 1000 hours.

  On the other hand, FIG. 4 shows the change over time in the water absorption amount for each usage amount of the PVA film specified by the present inventors.

One design example of the PVA film using the various data described above is described below.
From the dimensions of the example shown in FIG. 2, the outer peripheral length is 20 mm × 2 + 2π × 10 mm = 102.8 mm, and the required area per roll of PVA film is 102.8 mm × 100 mm≈10000 mm ² .

Here, when using a PVA film with a film thickness of 20 μm, the required volume per roll of PVA film is 10,000 mm ² × 0.02 mm = 200 mm ³ , and the required weight per roll of PVA film is 200 mm ³ × 1.2 mg / mm ³ (PVA specific gravity) = 240 mg, and the weight of water that can be absorbed per roll of PVA film is 240 mg × 0.3 (PVA water absorption) = 72 mg.

  Therefore, the water-absorbable amount of this PVA film can be calculated by 72 (mg / turn) × number of turns.

  From FIG. 3, since the water permeability after 1000 hours when the thickness of the molded resin body is 0.5 mm is 400 mg, 400 mg ÷ 72 (mg / one roll) = 5.56 (wind), and PVA By winding the film 6 times, sufficient moisture resistance can be satisfied even with a mold resin body having a thickness of 0.5 mm.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Metallized film pillar, 2 ... Metal sprayed part (metallicon electrode), 3 ... External lead-out terminal (bus bar), 4 ... Solder layer, 5 ... Case, 6 ... Mold resin body, 7 ... Hydrophilic film (PVA film) 10 ... Metalized film capacitor

Claims (2)

  A metal sprayed portion is formed on two electrode extraction surfaces of a metallized film column formed by winding or laminating a metallized film, and a hydrophilic film is formed on a peripheral surface other than the electrode extraction surface of the metallized film column A metallized film capacitor which is coated and external lead terminals are joined to a metal sprayed portion, which are housed in a case and embedded in a molded resin body in the case.   The metallized film capacitor according to claim 1, wherein the hydrophilic film is made of polyvinyl alcohol.

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