Film capacitor and method for manufacturing film capacitor

Abstract

To provide a film capacitor in which the outer periphery of a capacitor element can be fastened more appropriately, and a decrease in electric capacity due to disappearance of a vapor-deposited metal vapor-deposited on a metallized film by discharge is suppressed, and to provide a method of manufacturing the film capacitor.SOLUTION: A film capacitor (1) includes a capacitor element (10) formed by winding a film on which a metal thin film is formed, and an outer cylinder (20) which tightens the outer periphery of the capacitor element and is formed of shape memory plastic. The outer cylinder can appropriately tighten the capacitor element by having the slit (22).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a film capacitor and a method for manufacturing the film capacitor. [Background technology]

[0002] Patent Document 1 discloses a film capacitor using a capacitor element formed by winding a metallized film. The film capacitor is configured such that a heat-shrinkable reinforcing film is wound around the periphery of the capacitor element, and the reinforcing film is thermally shrunk by ambient temperature, and the contraction force tightens the capacitor element, thereby reinforcing the periphery of the capacitor element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 6-23235 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology described above, the reinforcing film and the metallized film may become loose over time. When the reinforcing film and the metallized film become loose, gaps form between the metallized films, causing discharges within the gaps. This discharge causes the vapor-deposited metal on the metallized film to disappear, resulting in a decrease in capacitance.

[0005] One aspect of the present disclosure aims to better tighten the periphery of a capacitor element. [Means for solving the problem]

[0006] In order to solve the above problems, a film capacitor according to one embodiment of the present disclosure comprises a capacitor element having a film on which a thin metal film is formed, and an outer tube formed of shape memory plastic that tightens the outer periphery of the capacitor element. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, the outer periphery of the capacitor element can be tightened more appropriately. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a film capacitor according to an embodiment of the present disclosure. [Figure 2] 1 is a plan view of a film capacitor according to an embodiment of the present disclosure as viewed from an axial direction. [Figure 3] FIG. 1 is a perspective view showing a structure of a capacitor element according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a perspective view of a film capacitor according to an embodiment of the present disclosure before molding. [Figure 5] FIG. 1 is a perspective view of a film capacitor according to another embodiment of the present disclosure. [Figure 6] FIG. 10 is a plan view of a film capacitor according to another embodiment of the present disclosure, viewed from the axial direction. [Figure 7] FIG. 10 is a plan view of a film capacitor according to another embodiment of the present disclosure, viewed from the axial direction of the outer cylinder. [Figure 8] 1 is a flowchart illustrating a method for manufacturing a film capacitor according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Embodiment 1] A film capacitor 1 according to the present disclosure will be described in detail with reference to the drawings. FIG. 1 is a perspective view of the film capacitor 1 according to embodiment 1. FIG. 2 is a plan view of the film capacitor 1 as viewed from the axial direction. Note that the axial direction in the following description refers to the central axis of the capacitor element 10 and the outer cylinder 20. The film capacitor 1 includes the capacitor element 10 and the outer cylinder 20.

[0010] Capacitor element 10 will be described with reference to FIG. 3. FIG. 3 is a perspective view showing the structure of capacitor element 10. Capacitor element 10 has a winding core 12 and a film 13 on which a metal thin film 14 is formed. Capacitor element 10 is a wound-type capacitor in which film 13 is wound around winding core 12, and is formed into a cylindrical shape by being wound. Furthermore, when film 13 is wound around winding core 12, two sheets of film 13 are wound on top of each other. In other words, capacitor element 10 has two sheets of film 13.

[0011] The metal thin film 14 is formed, for example, by vapor-depositing a metal on one side of the film 13. The metal thin film 14 may be made of, for example, zinc (Zn) or aluminum (Al). The material of the film 13 may be an insulating resin, such as polypropylene or polyethylene terephthalate.

[0012] One of the two films 13, film 13A, is vapor-deposited with a metal thin film 14A. The metal thin film 14A is vapor-deposited up to one axial end of film 13A, but not at the other end. Furthermore, the other of the two films 13, film 13B, is vapor-deposited with a metal thin film 14B. Like metal thin film 14A, metal thin film 14B is vapor-deposited up to one axial end of film 13B, but not at the other end. Note that metal thin film 14A and metal thin film 14B are arranged so as to be located at different axial ends of capacitor element 10, and are stacked via film 13.

[0013] Two metallikon electrodes 15 are provided at both axial ends of capacitor element 10. One of the two metallikon electrodes 15, metallikon electrode 15A, is electrically connected to metal thin film 14A, and the other of the two metallikon electrodes 15, metallikon electrode 15B, is electrically connected to metal thin film 14B.

[0014] Next, the outer cylinder 20 will be described with reference to Figures 1, 2, and 4. As shown in Figure 1, the outer cylinder 20 tightens (tightens and fixes) the outer periphery of the capacitor element 10. The outer cylinder 20 is positioned so as to cover the side surface of the wound outer periphery of the capacitor element 10, and tightens so as to compress the capacitor element 10 from the outer periphery side surface.

[0015] Further, outer cylinder 20 has a cylindrical shape. Outer cylinder 20 has an annular shape when viewed from the axial direction, as shown in Fig. 2. Note that this shape is determined arbitrarily in accordance with the shape of capacitor element 10.

[0016] The outer tube 20 is made of a shape-memory plastic, such as polynorbornene, trans-polyisoprene, high-density polyethylene, styrene-butadiene copolymer, polyurethane, or polyester alloy.

[0017] The outer tube 20 made of shape memory plastic has higher rigidity than heat shrink film, and can therefore clamp the capacitor element 10 more firmly and appropriately than a heat shrink film that is wrapped around the capacitor element 10 in multiple layers.

[0018] The outer casing 20 has a slit 22. The slit 22 will now be described with reference to FIG. 4. FIG. 4 is a perspective view of the film capacitor 1 before heat treatment. The film capacitor 1 is formed by clamping the capacitor element 10 to the outer casing 20. The state shown in FIG. 4 is before the capacitor element 10 is clamped to the outer casing 20. The slit 22 shown in FIG. 1 is closed compared to the slit 22 shown in FIG. 4. This is because the slit 22 is closed during the process of clamping the capacitor element 10 to the outer casing 20. Furthermore, the presence of the slit 22 can increase the shrinkage rate of the outer casing 20. In other words, the presence of the slit 22 in the outer casing 20 allows the capacitor element 10 to be clamped more appropriately.

[0019] 1, slit 22 is closed, but does not necessarily have to be closed when capacitor element 10 is tightened. For example, in FIG. 2, outer cylinder 20 has a closed ring shape when viewed from the axial direction, but when slit 22 is open, outer cylinder 20 may have an open ring shape.

[0020] The dimensions of each part of the shape-memory plastic used for outer cylinder 20 are determined taking into consideration that the shape changes depending on the temperature. For example, as shown in Figure 4, the inner diameter of outer cylinder 20 is larger than the outer diameter of capacitor element 10 before tightening. The shape and dimensions of outer cylinder 20 are determined so that the inner diameter of outer cylinder 20 will be smaller than the outer diameter of capacitor element 10 when outer cylinder 20 is heated to or above the glass transition temperature (Tg) of the shape-memory plastic and then cooled without applying external force.

[0021] Compared to when using conventional heat-shrinkable film, the winding tension of the heat-shrinkable film is adjusted only by the winding tension and number of turns of the film, so there is less flexibility in the winding tension. Some winding devices do not allow adjustment of the winding tension of the heat-shrinkable film. However, the shape-memory plastic material, thickness, and inner diameter of the outer tube 20 can be freely changed, allowing the winding tension to be adjusted according to the capacitor element 10.

[0022] [Embodiment 2] Other embodiments of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the first embodiment, and the description thereof will not be repeated.

[0023] 5 is a perspective view of a film capacitor 1A according to embodiment 2. The film capacitor 1A differs from the film capacitor 1 in that it includes multiple capacitor elements 10A, 10B, and 10C and an outer cylinder 20A. The multiple capacitor elements 10A, 10B, and 10C are arranged coaxially. The multiple capacitor elements 10A, 10B, and 10C are electrically connected in series. The outer cylinder 20 fastens the outer periphery of the multiple capacitor elements 10.

[0024] When a heat-shrinkable film is used as in the past, winding multiple capacitor elements can cause misalignment, making the work even more time-consuming. In the second embodiment, outer tube 20 can tighten the outer periphery of capacitor element 10 even when multiple capacitor elements are stacked.

[0025] [Embodiment 3] 6 is a plan view of a film capacitor 1B according to embodiment 3 as viewed from the axial direction. Compared to film capacitor 1, film capacitor 1B includes a capacitor element 10D and an outer cylinder 20B. Capacitor element 10D has an elliptical cylindrical shape, and outer cylinder 20B has an elliptical cylindrical shape.

[0026] [Embodiment 4] 7 is a plan view of a film capacitor 1C according to embodiment 4. Compared to film capacitor 1, film capacitor 1C includes capacitor element 10E and outer cylinder 20C, but does not include core 12.

[0027] Capacitor element 10E is a laminated capacitor in which multiple films 13 are laminated. As in embodiment 1, metal thin films 14 are vapor-deposited on one side of film 13. In capacitor element 10E, films 13 and metal thin films 14 are arranged so as to be alternately laminated. In this way, capacitor element 10E is formed in the shape of a rectangular parallelepiped.

[0028] In contrast, outer cylinder 20C has a rectangular or angular cylindrical shape to match the shape of capacitor element 10E.

[0029] As shown in the third and fourth embodiments, the film capacitor according to the present disclosure may be formed in any shape, and the outer cylinder of a film capacitor of any shape may also be formed in any shape.

[0030] [Manufacturing method of film capacitor 1] 8 is a diagram showing a manufacturing flow of the film capacitor 1 according to embodiment 1. For simplicity of explanation, a manufacturing method of the film capacitor 1 according to embodiment 1 will be described, but this manufacturing method is also effective in the multiple embodiments listed above and other embodiments.

[0031] [Capacitor element formation step] An operator forms a capacitor element 10 using film 13 on which metal thin film 14 is formed (S1). Specifically, two overlapping films 13 are wound around winding core 12. After winding, they may be secured with tape or the like. Metallikon electrodes 15 are formed on both end surfaces of the wound body. This step results in a capacitor element 10 as shown in FIG. 3.

[0032] [Outer cylinder molding step] Next, the worker forms the outer tube 20 using shape-memory plastic (S2). The outer tube 20 may be formed by molding or the like, and the shape of the outer tube 20 formed at this time is the memorized shape with the slit 22 closed.

[0033] [Pre-processing step] The worker increases the diameter of the outer cylinder 20 (S3) to make it easier to fit the outer cylinder 20 onto the capacitor element 10 in a step described later. Specifically, the worker heats the outer cylinder 20 to a temperature equal to or higher than the glass transition temperature (Tg) of the shape-memory plastic used in the outer cylinder 20, applies an external force to open the slit 22 in the outer cylinder 20, and then cools the outer cylinder 20 in this state. This results in the outer cylinder 20 with the slit 22 open.

[0034] [Placement Step] The worker then covers the outer periphery of capacitor element 10 with outer cylinder 20 made of shape-memory plastic (S4), thereby obtaining film capacitor 1 as shown in FIG.

[0035] [Heating step] The worker heats outer cylinder 20 to a temperature above the glass transition temperature of the shape-memory plastic (S5). At this time, outer cylinder 20 is heated together with capacitor element 10 in a reflow furnace or the like. The temperature of capacitor element 10 inside may or may not reach the glass transition temperature or higher. This step causes outer cylinder 20 to return to the shape memorized in S2, closing slit 22.

[0036] [Cooling step] The worker cools the outer tube 20, causing it to tighten around the outer periphery of the capacitor element 10 (S6). This step hardens the outer tube 20 and secures the capacitor element 10. The above steps tighten the outer periphery of the capacitor element 10. The outer tube 20 is not a film, but is a tube whose shape is fixed at room temperature. The outer tube 20 is less likely to deform than heat-shrinkable film, etc. Therefore, even after long-term use, loosening of the wound film 13 can be suppressed. This prevents the occurrence of gaps between the films 13 and the occurrence of discharge.

[0037] In addition, in the case of conventional film capacitors using heat-shrinkable film, the heat-shrinkable film was sandwiched at the end of the winding of film 13 (Figure 3) and then wound. In this case, the capacitor element and the heat-shrinkable film had to be wound consecutively using the same winding device, which tended to lengthen the lead time. This is because the bottleneck of the winding device was occupied until the heat-shrinkable film was completely wound, preventing the next film from being wound. However, as described above, S1, S2, and S3 can be performed independently. This allows the manufacturing of capacitor element 10 and the molding of outer tube 20 to be performed as separate processes, thereby shortening the manufacturing lead time. Furthermore, the task of covering capacitor element 10 with outer tube 20 can be easily performed.

[0038] 〔summary〕 A film capacitor according to a first aspect of the present disclosure includes a capacitor element having a film on which a metal thin film is formed, and an outer cylinder made of shape-memory plastic that fastens the outer periphery of the capacitor element.

[0039] A film capacitor according to a second aspect of the present disclosure is the film capacitor of the first aspect, wherein the outer cylinder has a slit.

[0040] A film capacitor according to a third aspect of the present disclosure is the film capacitor of the first or second aspect, wherein the outer cylinder has a cylindrical shape or an elliptical cylindrical shape.

[0041] A film capacitor according to a fourth aspect of the present disclosure is any one of the first to third aspects, wherein the capacitor element is a wound type capacitor in which the film is wound.

[0042] The film capacitor of aspect 5 of the present disclosure is any one of aspects 1 to 4, wherein when the outer tube is heated to a temperature equal to or higher than the glass transition temperature of the shape memory plastic and then cooled without applying an external force, the inner diameter of the outer tube is smaller than the outer diameter of the capacitor element.

[0043] A sixth aspect of the present disclosure is a film capacitor according to any one of the first to fifth aspects, which includes a plurality of the capacitor elements, and the outer cylinder tightens the outer periphery of the plurality of capacitor elements.

[0044] A seventh aspect of the present disclosure provides a film capacitor according to the first or second aspect, wherein the capacitor element is a laminated capacitor in which a plurality of films are laminated.

[0045] The manufacturing method of a film capacitor of aspect 8 according to the present disclosure includes a forming step of forming a capacitor element using a film having a metal thin film formed thereon, an arrangement step of covering the outer periphery of the capacitor element with an outer tube formed of shape memory plastic, a heating step of heating the outer tube to a temperature equal to or higher than the glass transition temperature of the shape memory plastic, and a cooling step of cooling the outer tube to tighten the outer periphery of the capacitor element with the outer tube.

[0046] The manufacturing method of a film capacitor of aspect 9 according to the present disclosure includes, in aspect 8, a pretreatment step of heating the outer tube to a temperature above the glass transition temperature of the shape memory plastic prior to the placement step, and cooling the outer tube while the outer tube is in an open state.

[0047] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0048] 1, 1A, 1B, 1C film capacitors 10, 10A, 10B, 10C, 10D, 10E capacitor elements 12 Core 13, 13A, 13B Film 14, 14A, 14B Metal thin film 15, 15A, 15B Metallicon electrodes 20, 20A, 20B, 20C outer cylinder 22 Slit

Claims

1. a capacitor element having a film on which a metal thin film is formed; A film capacitor comprising an outer cylinder formed of shape-memory plastic and fastening the outer periphery of the capacitor element.

2. The film capacitor according to claim 1 , wherein the outer cylinder has a slit.

3. The film capacitor according to claim 1 , wherein the outer cylinder has a cylindrical shape or an elliptical cylindrical shape.

4. The film capacitor according to claim 3 , wherein the capacitor element is a wound type capacitor in which the film is wound.

5. 3. The film capacitor according to claim 1, wherein the inner diameter of the outer tube is smaller than the outer diameter of the capacitor element when the outer tube is heated to a temperature equal to or higher than the glass transition temperature of the shape memory plastic and then cooled without applying an external force.

6. A plurality of the capacitor elements is provided, The film capacitor according to claim 1 , wherein the outer cylinder clamps the outer periphery of the plurality of capacitor elements.

7. 3. The film capacitor according to claim 1, wherein the capacitor element is a laminated capacitor in which a plurality of films are laminated.

8. A method for manufacturing a film capacitor, a forming step of forming a capacitor element using a film on which a metal thin film is formed; a placement step of covering the outer periphery of the capacitor element with an outer cylinder made of shape memory plastic; a heating step of heating the outer cylinder to a temperature equal to or higher than the glass transition temperature of the shape memory plastic; a cooling step in which the outer cylinder is cooled to tighten the outer periphery of the capacitor element with the outer cylinder.

9. 9. The method for manufacturing a film capacitor according to claim 8, further comprising a pretreatment step of heating the outer tube to a temperature equal to or higher than the glass transition temperature of the shape memory plastic before the placing step, and cooling the outer tube while the outer tube is in an open state.

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