Film capacitor

Abstract

To provide a film capacitor in which voids are unlikely to occur in areas adjacent to a capacitor element.SOLUTION: A film capacitor 1 includes a capacitor element 2 having electrodes 8, a foamed resin portion 3 that entirely covers the capacitor element 2, a non-foamed resin portion 4 that entirely covers the foamed resin portion 3, and a case 5 that houses the capacitor element 2, the foamed resin portion 3, and the non-foamed resin portion 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure generally relates to film capacitors, and more particularly to film capacitors including capacitor elements.

Background Art

[0002] Patent Document 1 discloses a capacitor. This capacitor houses a capacitor element formed by winding or laminating metallized films together or a combination of a metallized film and a non-metallized film in a capacitor case having an opening, and fills the gap between the capacitor element and the capacitor case and the space on the opening side of the capacitor element with resin, and fills the periphery of the capacitor element with resin.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the capacitor of Patent Document 1, there is a risk that the filled resin peels off from the capacitor element. Due to this peeling, voids are likely to occur between the capacitor element and the filled resin. Such voids are often close to a vacuum. In such a case, when a high voltage is applied to the capacitor, discharge occurs in the above voids, and the capacitor may be damaged by this discharge.

[0005] An object of the present disclosure is to provide a film capacitor in which voids are less likely to occur in a location adjacent to a capacitor element.

Means for Solving the Problems

[0006] A film capacitor according to one aspect of the present disclosure includes a capacitor element having electrodes, a foamed resin portion covering the entire capacitor element, a non-foamed resin portion covering the entire foamed resin portion, and a case housing the capacitor element, the foamed resin portion, and the non-foamed resin portion.

Advantages of the Invention

[0007] According to the present disclosure, it is difficult for a gap to occur in a location adjacent to the capacitor element.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] 1. Overview As described above, in the capacitor of Patent Document 1, there is a risk that the filling resin may peel off from the capacitor element. The inventor has presumed at least two reasons for this peeling.

[0010] The first reason is that the surface roughness of the polypropylene film present on the surface of the capacitor element is small. As a result, it is difficult to obtain an anchor effect between the polypropylene film and the filling resin. That is, the adhesion between the polypropylene film and the filling resin is small.

[0011] The second reason is that there is a large difference in the coefficients of thermal expansion between the capacitor element and the filling resin. Therefore, it becomes difficult for the filling resin to follow the thermal expansion of the capacitor element.

[0012] Based on the above reasons, as a result of intensive research, the present inventor has developed the following film capacitor 1.

[0013] That is, as shown in FIG. 1, the film capacitor 1 according to the present embodiment includes a capacitor element 2, a foamed resin portion 3, a non-foamed resin portion 4, and a case 5. The foamed resin portion 3 covers the entire capacitor element 2. The foamed resin portion 3 is softer than the non-foamed resin portion 4 and is excellent in cushioning properties and flexibility. Therefore, the foamed resin portion 3 easily follows the thermal expansion of the capacitor element 2. Also, the foamed resin portion 3 easily follows the thermal expansion of the non-foamed resin portion 4. From this, even if there is a large difference in the coefficients of thermal expansion between the capacitor element 2 and the non-foamed resin portion 4, it is possible to suppress the peeling of the foamed resin portion 3 from the capacitor element 2.

[0014] Therefore, it becomes difficult for a gap to occur at a location adjacent to the capacitor element 2.

[0015] 2. Details (1) First Embodiment <Film Capacitor> Hereinafter, the film capacitor 1 according to the first embodiment will be described with reference to FIG. 1. Note that the drawings are schematic diagrams, and the respective ratios of the sizes and thicknesses of the respective components in the drawings do not necessarily reflect the actual dimensional ratios.

[0016] Arrows indicating directions in the drawings (arrows indicating the vertical and horizontal directions) are not intended to define the direction during the use of the film capacitor 1, but are merely shown for easier understanding of the description and have no physical entity. The direction in which the first electrode 81 and the second electrode 82 are arranged is defined as the vertical direction, the direction in which the first bus bar 71 and the second bus bar 72 are arranged is defined as the horizontal direction, and the direction orthogonal to the vertical and horizontal directions is defined as the front-rear direction (the front side of the paper surface is "front" and the back side of the paper surface is "rear") for the purpose of explanation.

[0017] As shown in FIG. 1, the film capacitor 1 according to the first embodiment includes a capacitor element 2, a foamed resin portion 3, a non-foamed resin portion 4, a case 5, and bus bars 7. Hereinafter, each component will be described in order.

[0018] ≪Capacitor Element≫ The capacitor element 2 is not particularly limited, and examples thereof include a wound capacitor element, a multilayer capacitor element, and the like.

[0019] Specifically, the capacitor element 2 has an element body 20 and electrodes 8.

[0020] The shape of the element body 20 is not particularly limited, and examples thereof include a cylindrical shape, an elliptical cylindrical shape, and a rectangular parallelepiped shape. The element body 20 has a first surface 21 (upper surface), a second surface 22 (lower surface), and an outer peripheral surface 23. The first surface 21 is a surface perpendicular to the vertical direction. The second surface 22 is a surface on the opposite side of the first surface 21 and is parallel to the first surface 21. The outer peripheral surface 23 is a surface connecting the outer peripheral edge of the first surface 21 and the outer peripheral edge of the second surface 22.

[0021] The element body 20 includes a dielectric film, a first internal electrode, and a second internal electrode. Inside the element body 20, the first internal electrode and the second internal electrode face each other with the dielectric film interposed therebetween. In FIG. 1, the illustration of the first internal electrode and the second internal electrode is omitted.

[0022] In the first embodiment, the dielectric film also forms the outer peripheral surface 23 of the element body 20. The material of the dielectric film is not particularly limited, and examples thereof include polypropylene (PP), polyethylene terephthalate (PET), and the like.

[0023] A part of the first internal electrode is exposed on the first surface 21 and not exposed on the second surface 22. A part of the second internal electrode is exposed on the second surface 22 and not exposed on the first surface 21. The materials of the first internal electrode and the second internal electrode are not particularly limited, and examples thereof include aluminum (Al), magnesium (Mg), and alloys thereof.

[0024] The electrode 8 includes a first electrode 81 and a second electrode 82.

[0025] The first electrode 81 is formed by spraying metal on the first surface 21. Thereby, the first electrode 81 is electrically connected to the first internal electrode. The metal to be sprayed is not particularly limited, and examples thereof include zinc (Zn), tin (Sn), and alloys thereof.

[0026] Similarly to the first electrode 81, the second electrode 82 is formed by spraying metal on the second surface 22. Thereby, the second electrode 82 is electrically connected to the second internal electrode.

[0027] ≪Foamed resin part≫ The foamed resin part 3 covers the entire capacitor element 2. Specifically, the foamed resin part 3 covers the outer peripheral surface 23 of the capacitor element 2, the first electrode 81, and the second electrode 82. However, in order to ensure the electrical connection between the capacitor element 2 and the outside, a part of the first electrode 81 (the connection part with the first bus bar 71) and a part of the second electrode 82 (the connection part with the second bus bar 72) are not covered. Note that the foamed resin part 3 has electrical insulation properties.

[0028] The foamed resin part 3 is a porous body. That is, a large number of air bubbles are dispersed and present inside the foamed resin part 3. The air bubbles include open cells and closed cells. Open cells are air bubbles in which a plurality of air bubbles are continuously connected. Closed cells are air bubbles that are not connected to other air bubbles and are independent.

[0029] The foamed resin part 3 is formed of a foamed resin. The material of the foamed resin is not particularly limited, and examples thereof include epoxy resin, polystyrene, polyethylene, polypropylene, and the like.

[0030] The foam molding used when molding the foamed resin part 3 is roughly classified into solid-phase foaming and liquid-phase foaming. The solid-phase foaming is not particularly limited, and examples thereof include bead foaming, batch foaming, press foaming, and normal-pressure secondary foaming. The liquid-phase foaming is not particularly limited, and examples thereof include injection foaming, extrusion foaming, and foam blowing.

[0031] The foaming agent used for foam molding is roughly classified into a chemical foaming agent and a physical foaming agent. The chemical foaming agent is not particularly limited, and examples thereof include organic thermal decomposition type foaming agents, inorganic thermal decomposition type foaming agents, organic reaction type foaming agents, inorganic reaction type foaming agents, and the like. The physical foaming agent is not particularly limited, and examples thereof include nitrogen gas, carbon dioxide gas, and the like.

[0032] There is a rust inhibitor inside the foamed resin part 3. Preferably, the rust inhibitor is present inside the air bubbles. The rust inhibitor is not particularly limited, and examples thereof include vaporizable rust inhibitors. A vaporizable rust inhibitor is a metal corrosion inhibitor that has vaporizability at normal temperature.

[0033] ≪Non-foamed resin part≫ The non-foamed resin part 4 covers the entire foamed resin part 3. However, in order to ensure electrical conduction between the capacitor element 2 and the outside, the portion through which the bus bar 7 passes is not covered. Note that the non-foamed resin part 4 has electrical insulation properties.

[0034] There are no air bubbles in the non-foamed resin part 4. However, air bubbles that unavoidably enter during the molding of the non-foamed resin part 4 may exist inside the non-foamed resin part 4.

[0035] The non-foamed resin part 4 is formed of a non-foamed resin. The material of the non-foamed resin is not particularly limited, and examples thereof include epoxy resins.

[0036] The non-foamed resin part 4 is molded, for example, by a casting molding method.

[0037] ≪Case≫ The case 5 is a container that opens upward. That is, the case 5 has a housing part 50 and an opening part 51. The opening part 51 exists above the case 5 and communicates with the housing part 50.

[0038] The capacitor element 2, the foamed resin part 3, and the non-foamed resin part 4 are housed in the housing part 50. Thus, the case 5 houses the capacitor element 2, the foamed resin part 3, and the non-foamed resin part 4.

[0039] More specifically, the case 5 has a bottom plate 52 and a peripheral wall 53. The peripheral wall 53 projects upward from the outer peripheral edge of the bottom plate 52. The space surrounded by the inner bottom surface (upper surface) of the bottom plate 52 and the inner peripheral surface of the peripheral wall 53 is the housing part 50. The part surrounded by the outer periphery of the upper end of the peripheral wall 53 is the opening part 51. The non-foamed resin part 4 is adhered to the inner bottom surface of the bottom plate 52 and the inner peripheral surface of the peripheral wall 53 without a gap.

[0040] The material of the case 5 is not particularly limited, and examples thereof include polyphenylene sulfide (PPS).

[0041] ≪Bus bar≫ The bus bar 7 is a conductive member. The material of the bus bar 7 is not particularly limited, and examples thereof include copper (Cu), aluminum (Al), and alloys thereof.

[0042] The bus bar 7 is connected to the electrode 8. Specifically, the bus bar 7 includes a first bus bar 71 and a second bus bar 72. The first bus bar 71 is connected to the first electrode 81. The second bus bar 72 is connected to the second electrode 82. However, the first bus bar 71 is not connected to the second electrode 82, and the second bus bar 72 is not connected to the first electrode 81.

[0043] The bus bar 7 penetrates through the foamed resin portion 3 and the non-foamed resin portion 4 and extends to the outside. In the first embodiment, the first bus bar 71 and the second bus bar 72 protrude upward from the surface (upper surface) exposed to the outside of the non-foamed resin portion 4.

[0044] <Method for manufacturing a film capacitor> Next, a method for manufacturing the film capacitor 1 according to the first embodiment will be described with reference to FIGS. 2A to 2C.

[0045] First, as shown in FIG. 2A, a capacitor element 2 is prepared. A bus bar 7 is connected to the electrode 8 of the capacitor element 2.

[0046] Next, a material for the foamed resin is prepared. Hereinafter, a case where an uncured liquid epoxy resin is used as the material for the foamed resin will be described. An appropriate foaming agent and rust inhibitor are added to the uncured liquid epoxy resin. A curing agent or the like may be further added as necessary.

[0047] Then, the capacitor element 2 is lifted by grasping the upper end of the bus bar 7 and immersed in the liquid epoxy resin to which the above foaming agent and rust inhibitor are added, so that the liquid epoxy resin adheres to the entire capacitor element 2. At this time, the liquid epoxy resin is not allowed to adhere to the upper end of the bus bar 7. Then, when the liquid epoxy resin adhering to the capacitor element 2 is heated, as shown in FIG. 2B, the liquid epoxy resin foams and cures to form the foamed resin portion 3.

[0048] Next, as shown in FIG. 2C, the capacitor element 2 covered with the foamed resin portion 3 is housed in the housing portion 50 of the case 5. Then, a non-foamed resin material is injected into the housing portion 50 of the case 5 until the upper surface of the foamed resin portion 3 is hidden. Here, as the non-foamed resin material, for example, the same uncured liquid epoxy resin as described above may be used, or a different uncured liquid epoxy resin from the above may be used. However, at least a foaming agent is not added to the non-foamed resin material.

[0049] Then, when the non-foamed resin material injected into the case 5 is heated, the non-foamed resin material cures to form the non-foamed resin portion 4. As described above, the film capacitor 1 shown in FIG. 1 is manufactured.

[0050] <Operational Effects> In the film capacitor 1 according to the first embodiment, the foamed resin portion 3 covers the entire capacitor element 2. The foamed resin portion 3 is softer than the non-foamed resin portion 4 and is excellent in cushioning property and flexibility. Therefore, the foamed resin portion 3 easily follows the thermal expansion of the capacitor element 2. Also, the foamed resin portion 3 easily follows the thermal expansion of the non-foamed resin portion 4. From this, even if the difference in the coefficient of thermal expansion between the capacitor element 2 and the non-foamed resin portion 4 is large, it is possible to suppress the peeling of the foamed resin portion 3 from the capacitor element 2.

[0051] Therefore, it becomes difficult for voids to occur in the portion adjacent to the capacitor element 2. Thus, since the generation of voids is suppressed, even when a high voltage is applied to the film capacitor 1, it becomes difficult for discharge to occur. Therefore, the possibility of damage to the film capacitor 1 due to discharge is reduced.

[0052] Here, in the foamed resin portion 3, it is preferable that the ratio of continuous bubbles is larger than the ratio of closed cells. Since it is difficult for air to enter and exit closed cells, and it is easy for air to enter and exit continuous bubbles, in the foamed resin portion 3 with a large ratio of continuous bubbles, the heat dissipation property of the film capacitor 1 can also be enhanced.

[0053] In addition, since the film capacitor 1 according to the first embodiment includes the bus bar 7, the film capacitor 1 can be charged or discharged through the bus bar 7.

[0054] In the film capacitor 1 according to the first embodiment, the foamed resin portion 3 covers the electrode 8, and since the rust preventive agent is present inside the foamed resin portion 3, the rust preventive agent can suppress the oxidation of the electrode 8.

[0055] Also in this case, in the foamed resin portion 3, it is preferable that the ratio of the continuous bubbles is larger than the ratio of the closed cells. Since it is difficult for the rust preventive agent to enter and exit the closed cells, and it is easy for the rust preventive agent to enter and exit the continuous bubbles, if the foamed resin portion 3 has a large ratio of continuous bubbles, it becomes easier for the rust preventive agent to contact the electrode 8.

[0056] (2) Second Embodiment <Film Capacitor> Next, the film capacitor 1 according to the second embodiment will be described with reference to FIG. 3. In the second embodiment, the same components as those in the first embodiment may be denoted by the same reference numerals as in the first embodiment, and detailed description thereof may be omitted.

[0057] The second embodiment is different from the first embodiment in that the film capacitor 1 further includes a resin film 6.

[0058] ≪Resin Film≫ As shown in FIG. 3, the resin film 6 is interposed between the capacitor element 2 and the foamed resin portion 3. Specifically, the resin film 6 is interposed between the outer peripheral surface 23 of the element body 20 and the foamed resin portion 3. In this way, the resin film 6 covers the capacitor element 2 except for the electrode 8.

[0059] The material of the resin film 6 is not particularly limited, and examples thereof include polypropylene (PP), polyethylene terephthalate (PET), and the like. Thus, the material of the resin film 6 may be the same as or different from the material of the dielectric film.

[0060] <Effect> The film capacitor 1 according to the second embodiment includes a resin film 6. The resin film 6 is interposed between the capacitor element 2 and the foamed resin portion 3 and covers the capacitor element 2 (excluding the electrode 8). In this way, the capacitor element 2 can be protected by the resin film 6.

[0061] The resin film 6 is common in that it is made of resin and the dielectric film used for the capacitor element 2.

[0062] Therefore, the second embodiment also exhibits the same effects as the first embodiment.

[0063] (3) Third Embodiment <Film Capacitor> Next, the film capacitor 1 according to the third embodiment will be described with reference to FIG. 4. In the third embodiment, the same components as those in the first and second embodiments may be denoted by the same reference numerals as those in the first and second embodiments, and detailed descriptions thereof may be omitted.

[0064] The third embodiment is different from the first and second embodiments in that the foamed resin portion 3 is interposed between the bus bar 7 and the non-foamed resin portion 4.

[0065] ≪Foamed Resin Portion≫ In the third embodiment, the foamed resin portion 3 is interposed between the first bus bar 71 and the non-foamed resin portion 4. Further, the foamed resin portion 3 is interposed between the second bus bar 72 and the non-foamed resin portion 4.

[0066] As shown in FIG. 4, the bus bar 7 is not in contact with the non-foamed resin portion 4. Further, the foamed resin portion 3 interposed between the bus bar 7 and the non-foamed resin portion 4 is exposed to the outside.

[0067] <Effect> The third embodiment also exhibits the same effects as the first embodiment.

[0068] Furthermore, in the film capacitor 1 according to the third embodiment, a foamed resin portion 3 is interposed between the bus bar 7 and the non-foamed resin portion 4. The bus bar 7 is not in direct contact with the non-foamed resin portion 4. As described above, since the foamed resin portion 3 is softer than the non-foamed resin portion 4 and has excellent cushioning properties and flexibility, it is easy to follow the thermal expansion of the bus bar 7. Therefore, even if the difference in the coefficient of thermal expansion between the bus bar 7 and the non-foamed resin portion 4 is large, it is possible to suppress the peeling of the foamed resin portion 3 from the bus bar 7.

[0069] Therefore, it is less likely that voids will occur in the portion adjacent to the bus bar 7 (especially the portion that does not extend to the outside). In this way, since the generation of voids is suppressed, even when a high voltage is applied to the film capacitor 1, it is less likely that discharge will occur. Therefore, the possibility of damage to the film capacitor 1 due to discharge is reduced.

[0070] Here, as shown in FIG. 4, it is preferable that the foamed resin portion 3 is divided into and integrated with a closed-cell portion 32 and an open-cell portion 31.

[0071] The closed-cell portion 32 is a portion having a surface facing the outside, and is a portion where the ratio of closed cells is larger than the ratio of open cells. Since it is difficult for air to enter and exit the closed cells, it is possible to suppress moisture from entering the capacitor element 2 from the outside.

[0072] On the other hand, the open-cell portion 31 is the portion of the foamed resin portion 3 other than the closed-cell portion 32, and is a portion where the ratio of open cells is larger than the ratio of closed cells. Since air can easily enter and exit the open cells, the heat dissipation property of the film capacitor 1 can also be enhanced.

[0073] 3. Modification In the first to third embodiments, the film capacitor 1 includes the bus bar 7, but the film capacitor 1 may not include the bus bar 7.

[0074] In the first to third embodiments, a rust preventive agent is present inside the foamed resin portion 3, but the rust preventive agent may not be present.

[0075] 4. Aspects As is clear from the above-described embodiments and modifications, the present disclosure includes the following aspects. Hereinafter, for the sole purpose of clarifying the correspondence with the embodiments, reference numerals are attached in parentheses.

[0076] A first aspect is a film capacitor (1), comprising: a capacitor element (2) having electrodes (8); a foamed resin part (3) covering the entire capacitor element (2); a non-foamed resin part (4) covering the entire foamed resin part (3); and a case (5) housing the capacitor element (2), the foamed resin part (3), and the non-foamed resin part (4).

[0077] According to this aspect, it is less likely that voids are generated in locations adjacent to the capacitor element (2).

[0078] A second aspect is a film capacitor (1) based on the first aspect. In the second aspect, a resin film (6) interposed between the capacitor element (2) and the foamed resin part (3) is further provided. The resin film (6) covers the capacitor element (2) except for the electrodes (8).

[0079] According to this aspect, it is less likely that voids are generated in locations adjacent to the capacitor element (2). The capacitor element (2) can also be protected by the resin film (6).

[0080] A third aspect is a film capacitor (1) based on the first or second aspect. In the third aspect, a bus bar (7) connected to the electrodes (8) is further provided. The bus bar (7) penetrates the foamed resin part (3) and the non-foamed resin part (4) and extends to the outside.

[0081] According to this aspect, the film capacitor (1) can be charged or discharged through the bus bar (7).

[0082] The fourth aspect is a film capacitor (1) based on the third aspect. In the fourth aspect, the foamed resin portion (3) is interposed between the bus bar (7) and the non-foamed resin portion (4).

[0083] According to this aspect, it becomes difficult for voids to occur at locations adjacent to the bus bar (7) (especially the portion that does not extend externally).

[0084] The fifth aspect is a film capacitor (1) based on any one of the first to fourth aspects. In the fifth aspect, an anti-rust agent is present inside the foamed resin portion (3).

[0085] According to this aspect, oxidation of the electrode (8) can be suppressed.

Explanation of Reference Numerals

[0086] 1 Film capacitor 2 Capacitor element 3 Foamed resin portion 4 Non-foamed resin portion 5 Case 6 Resin film 7 Bus bar 8 Electrode

Claims

1. A capacitor element having electrodes, A foamed resin part covering the entire capacitor element, A non-foamed resin part covering the entire foamed resin part, And a case for housing the capacitor element, the foamed resin part, and the non-foamed resin part. A film capacitor.

2. Further comprising a resin film interposed between the capacitor element and the foamed resin part, The resin film covering the capacitor element except for the electrodes. The film capacitor according to claim 1.

3. Further comprising a bus bar connected to the electrodes, The bus bar penetrating through the foamed resin part and the non-foamed resin part and extending to the outside. The film capacitor according to claim 1.

4. The foamed resin part intervening between the bus bar and the non-foamed resin part. The film capacitor according to claim 3.

5. There is a rust inhibitor inside the foamed resin part. The film capacitor according to claim 1.

Images