JP2009253251A - Film capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely connect outer electrodes with a lead wire by solving a problem of unstable connection of the lead wire with the outer electrodes due to protrusions formed on the surfaces of the outer electrodes under the influence of a core in a film capacitor having an element with the core at the center of a winding body with a metallized film wound round it. <P>SOLUTION: A lengthwise end face of the core 2 is positioned on the same plane as a width-wise end face of the winging body 1 with the metallized film wound round it or is positioned within the winding body 1. Thus, no protrusion is formed on the surfaces of the outer electrodes 3, 4, so that the lead wire can be surely connected with the outer electrodes 3, 4 to increase the reliability of the film capacitor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technology relating to a film capacitor mounted on an electronic or electric circuit of an electronic device or an electric device.

The film capacitor is a metallized film in which a polymer film such as polyethylene terephthalate or polypropylene is used as a dielectric and an electrode of a metal thin film such as aluminum is formed on the surface of the polymer film as described in Patent Document 1 below. The capacitor element is laminated or wound to form a capacitor element, and the capacitor element is packaged with a resin, or is stored in a resin container, and the gap between the capacitor element and the container is filled with resin.
Japanese Patent No. 2877364

  However, in a film capacitor in which the capacitor element 50 has a flat circular shape as described in Japanese Patent No. 2877364 shown in FIG. 6, when an alternating voltage is applied during actual use, the metallized film between the two electrodes The metallized film in the straight line portion (shaded portion in FIG. 6) may vibrate due to the coulomb force generated therebetween, and when the vibration is large, a vibration sound (beat sound) is generated. And when this vibration noise becomes loud, it leaks to the outside of the electrical equipment and electronic equipment, and the quality of the electrical equipment and electronic equipment is impaired.

  The reason why the metallized film of the straight portion of the flat circular capacitor element 50 is likely to vibrate is that such a capacitor element 50 is subjected to pressure from the side surface at a high temperature after being wound into a cylindrical shape. The flattened shape makes it easy to form a gap between the layers of the metallized film in the straight line part. Because.

  In order to suppress the vibration of the metallized film, a capacitor having a structure as shown in FIG. 7 is effective. That is, the capacitor element 60 has a cylindrical shape instead of a flat circular shape. By making the capacitor element 60 cylindrical in this way, the shrinkage force of the metallized film that occurs in the high-temperature treatment after winding is achieved. The entire capacitor element 60 is tightened evenly, and the gap between the metallized film layers is suppressed. As a result, the vibration of the metallized film is suppressed and vibration noise is less likely to be generated.

  However, a capacitor using such a cylindrical capacitor element 60 has a problem to be solved.

  A general method for manufacturing a cylindrical capacitor element is to wind a metallized film on a core with a diameter of several millimeters a predetermined number of times, and then spray metal on both end faces to provide external electrodes. The core used for winding is left as it is in the center of the wound body, or the core once used for winding is removed from the wound body, and then another core is inserted into the center of the wound body. Spray metal.

  This is because when the core is pulled out after winding, a hole having the same diameter as the core remains in the center of the wound body, and when the metal is sprayed to provide an external electrode on the end surface of the wound body, both end faces This is to prevent the metal sprayed from being electrically connected through the holes and to ensure the strength of the capacitor element.

  Thus, if the core at the time of winding is left in the center of the wound body, or a core is inserted later to provide the core at the center of the wound body, the external electrode of the wound body is formed. The end of the lead may protrude from the end face, and when an external electrode is provided on the end face of the wound body with the end of the lead protruding, the portion where the end of the lead protrudes, as shown in FIG. The external electrode 53 formed on the surface becomes a protrusion 57 protruding from the other part. When the lead wire 55 is connected to the external electrode 53 by welding or the like, the connection position of the lead wire 55 is shifted due to a slight difference in the dimensions of the manufacturing process equipment, jig, or wound body, and the protrusion 57. In some cases, a part of the lead wire 55 is hooked and a part of the lead wire 55 is floated or inclined. In particular, this is likely to occur with a small-sized capacitor. As a result, the electrical and mechanical connection strength cannot be obtained, and the current resistance characteristics, dielectric loss tangent, and reliability of the capacitor are deteriorated. There was a problem that the dimensional accuracy between the two lead wires deteriorated.

  The present invention solves the above-mentioned conventional problems, and in a film capacitor using a cylindrical capacitor element that has a core at the center and hardly generates vibration noise, the lead wire to the external electrode of the capacitor element This ensures electrical and mechanical connections.

  A wound body in which a metallized film having a metal thin film layer is wound on the surface of a dielectric film, external electrodes provided on both end faces of the wound body, and a core provided in the center of the wound body The end surface in the length direction of the core is the same surface as the end surface in the width direction of the wound body or in the wound body.

  According to the film capacitor of the present invention, since no protrusion is formed at the center of the external electrode, the lead wire connected to the external electrode is partially floated, and there is no place where the external electrode is not connected. Connection strength with the wire can be secured, and desired capacitor characteristics and reliability can be secured.

  Hereinafter, a film capacitor according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a view showing a cross section of the film capacitor in Embodiment 1 of the present invention in a state where an exterior resin is removed. In FIG. 1, the core 2 whose length is shorter than the width of the wound body 1 at the center of the wound body 1 constituting the capacitor element 10 does not protrude from both end surfaces 9 of the wound body 1. Further, the end face 8 is provided so as to be positioned in the wound body 1. Further, external electrodes 3, 4 are provided on both end faces 9 of the wound body 1, and lead wires 5, 6 are provided on the surfaces of the external electrodes 3, 4.

  More specifically, as shown in FIG. 2, the wound body 1 is composed of the core 2, one surface of a polypropylene film having a thickness of 3.0 μm as the dielectric film 11, and aluminum having a thickness of 0.02 μm as an electrode. Each of the marginal portions 13 includes a metallized film 14 formed by providing a strip-shaped margin portion 13 without the metal thin film layer 12 in the longitudinal direction of one end in the width direction of the dielectric film 11. Two sheets are overlapped and wound a predetermined number of times so as to be positioned on the opposite side. At this time, the core 2 is made of polyacetal resin, has a diameter of 2.0 mm and a length of 12.9 mm, and the metalized film 14 is wound by rotating the core 2 from both ends with a rotating shaft 15 having a diameter of 1.85 mm. The wound body 1 has a core 2 at the center. The width of the wound body 1 is 13.9 mm.

  Next, as shown in FIG. 3A, a zinc alloy is sprayed on both end faces of the wound body 1 to form external electrodes 3 and 4 having a thickness of 0.35 mm. At this time, a recess 7 having a diameter of 1.7 mm and a depth of 0.5 mm is formed at the center of the external electrodes 3 and 4, but no protrusion is formed.

  Then, lead wires 5 and 6 made of tin-plated copper-coated steel wires having a diameter of 0.8 mm are connected to the external electrodes 3 and 4 by welding, and finally, as shown in FIG. The exterior 40 is applied.

  As described above, according to the present embodiment, since the protrusions cannot be formed on the surfaces of the external electrodes 3 and 4 provided on the wound body 1, in the process of welding the lead wires 5 and 6, Even when the lead wires 5 and 6 are shifted to the vicinity of the center of the wound body 1, the lead wires 5 and 6 do not float and can be reliably connected to the external electrodes 3 and 4, so that desired capacitor characteristics can be obtained. And reliability can be ensured.

  Further, since the lead wires 5 and 6 are not inclined and connected, the dimensional accuracy between the lead wires 5 and 6 is not deteriorated.

  Further, when the external electrodes 3 and 4 have protrusions, contact with the device or the capacitor in the protrusion and conveying process or in the process of removing the burrs of the external electrodes 3 and 4 and adjusting the shape of the capacitor element 10 The protruding portion of the external electrode falls off due to the contact between the elements 10. This is due to the extremely low chemical bond strength between the two materials at the interface between the sprayed metal and the resin. Therefore, moisture easily enters from the drop-off portion and the moisture resistance of the capacitor is impaired. However, according to the present embodiment, this can also be prevented.

(Embodiment 2)
FIG. 4 is a view showing a cross section of the film capacitor according to the present embodiment in a state where an exterior resin is removed. In FIG. 4, a core 22 having the same length as the width of the wound body 21 is provided at the center of the wound body 21, and an end surface 28 of the core 22 so that an end portion thereof does not protrude from both end surfaces 29 of the wound body 21. And the end surface 29 of the wound body 21 is provided so that it may become the same surface. Further, external electrodes 23 and 24 are provided on the end surface 29 of the wound body 21, and lead wires 25 and 26 are connected to the surfaces of the external electrodes 23 and 24. And the several layer of the metallized film 14 of the winding center part 27 is fuse | melted.

  More specifically, the wound body 21 has a thickness as an electrode on one surface of a polypropylene film having a thickness of 3 μm as the dielectric film 11 as shown in FIG. A metallized film in which a metal thin film layer 12 made of 0.02 μm aluminum is provided in the longitudinal direction of one end in the width direction of the dielectric film 11 by providing a strip-shaped margin portion 13 in which the metal thin film layer 12 is not provided. No. 14 is wound two times so that the margin portions 13 are positioned on opposite sides.

  The difference from the first embodiment is that when the metallized film 14 is wound, the winding center portion 27 from the start of winding to the winding core to the 15th turn is formed on the surface of the metallized film 14. An electrode for applying voltage is brought into contact with the thin metal film layer 12 and is removed by applying a voltage to the electrode to sublimate the thin metal film layer 12, and on the surface of the wound metallized film 14, An electric heater heated to 275 ° C. is contacted to fuse the metallized films 14 together, and after winding, the winding core is once extracted, and the cylindrical shape at the center of the wound body 21 after being extracted. The core 22 is inserted into the hole.

  Here, the width of the wound body 21 is 13.9 mm. And the diameter of the winding core used for winding is 2 mm, the core 22 to be inserted is made of polyacetal resin and has a diameter of 1.95 mm, and has the same length as the width 13.9 mm of the wound body 21 in advance. is there.

  Next, as shown in FIG. 5, zinc alloy is sprayed on both end faces of the wound body 21 to form external electrodes 23 and 24 having a thickness of 0.35 mm. At this time, no protrusion is formed at the center of the external electrodes 23 and 24.

  Next, lead wires 25 and 26 made of tin-plated copper-clad steel wires having a diameter of 0.8 mm are connected to the external electrodes 23 and 24 by welding, and finally the exterior is coated with an epoxy-based powder resin.

  As described above, according to the present embodiment, since the projections cannot be formed on the surfaces of the external electrodes 23 and 24 provided on the wound body 21, the same effect as in the first embodiment can be obtained.

  And as shown in FIG. 4, since the several layer of the said metallized film 14 of the winding center part 27 of the wound body 21 is melt | fused, the wound body 21 compared with the case where it is not melt | fused. The rigidity of the center is obtained, and the winding start portion of the film is fixed. Therefore, even if the winding core is pulled out after winding the metallized film 14, the shape of the wound body 21 is disturbed in the width direction, that is, the metallized film 14 protrudes spirally from the end face of the wound body 21. Thus, the cylindrical shape at the center of the wound body 21 can be reliably maintained. As a result, even when the core 22 is inserted into the central portion of the wound body 21, there is an effect that the shape of the wound body 21 is not destroyed by the insertion force.

  In this embodiment, a plurality of layers of the metallized film 14 at the winding center portion 27 of the wound body 21 are fused by heat, but an adhesive is applied between the layers of the metallized film 14 for adhesion. May be.

  As described above, the present invention can stabilize the initial characteristics and improve the reliability of the film capacitor, and thus can be used for a wide range of electronic devices and electrical devices.

Sectional drawing which shows the structure of the film capacitor by one embodiment of this invention The perspective view which shows the structure of the film capacitor by one embodiment of this invention (a), (b) The perspective view which shows the structure of the film capacitor by one embodiment of this invention Sectional drawing which shows the structure of the film capacitor by one embodiment of this invention The perspective view which shows the structure of the film capacitor by one embodiment of this invention The perspective view which shows the structure of the conventional film capacitor The perspective view which shows the structure of the conventional film capacitor

Explanation of symbols

1, 21 Winding body 2, 22 cores 3, 4, 23, 24 External electrode 5, 6, 25, 26 Lead wire 10, 30 Capacitor element

Claims (2)

A wound body in which a metallized film having a metal thin film layer is wound on the surface of a dielectric film, external electrodes provided on both end faces of the wound body, and a core provided in the center of the wound body And the end face in the length direction of the core is on the same plane as the end face in the width direction of the wound body or in the wound body. The film capacitor according to claim 1, wherein the plurality of metallized film layers at the winding center of the wound body are bonded or fused.