film capacitor

Abstract

A film capacitor with: a capacitor element (1) in which a metallikon electrode (11) is formed at one end; a busbar (2) which is connected to the Metallikon electrode (11); a housing (3) with a container (3A) for receiving the capacitor element (1) and the busbar (2); a lid element (5) that covers an opening of the container (3A); and a heat conducting element (4) arranged between the busbar (2) and the cover element (5), wherein the cover element has a projection (5A1) on a side facing the heat conducting element (4), the projection (5A1) is in contact with the heat conducting element (4) and the heat conducting element (4) is in contact with the busbar (2).

Description

TECHNICAL AREA

[0001] The present invention relates to a film capacitor or plastic capacitor in which capacitor elements are housed in a casing. BACKGROUND

[0002] Until now, it was necessary for a film capacitor installed in an electrical system, an electronic system, an industrial plant, in automobiles or the like, to increase the reliability of the film capacitor by dissipating the heat generated during charging and discharging.

[0003] For example, PTL 1 discloses a film capacitor comprising several capacitor elements and a busbar connected to the capacitor elements. The film capacitor is provided with a heat dissipation device located in an area closest to an external connection point and on the busbar, exhibiting excellent heat dissipation characteristics compared to the other areas. The film capacitor is described in detail below.

[0004] Fig. Figure 6 is a perspective view showing the construction of a conventional film capacitor, and Fig. Figure 7 is a top view of the film capacitor in a state in which one busbar of the positive electrode 92A is omitted on one side of a top surface. The film capacitor houses several capacitor elements 91, the busbar for the positive electrode 92A, and a busbar for the negative electrode 92B in a housing 93. Metallikon electrodes formed at both ends of each capacitor element 91 are connected accordingly to the busbar for the positive electrode 92A and the busbar for the negative electrode 92B.Furthermore, the conventional film capacitor is designed such that no capacitor element 91 is arranged in an area closest to the external terminal for the positive electrode 92A2, which is provided on the busbar for the positive electrode 92A for the external connection, and to an external terminal for the negative electrode 92B2, which is provided on the busbar for the negative electrode 92B for the external connection. The film capacitor is constructed such that only casting resin 96 is present in this area.Even when heat is carried along with current, which is impressed from an input side at the external terminal for the positive electrode 92A2 and the external terminal for the negative electrode 92B2, this heat is first conducted to the casting resin 96 before being carried from the external terminal for the positive electrode 92A2 via the busbar for the positive electrode 92A and the external terminal for the negative electrode 92B2 via the busbar for the negative electrode 92B to the capacitor elements 91. Therefore, the heat can be dissipated from this casting resin 96 to the outside. Thus, in the conventional film capacitor, a large heat transfer that could damage the capacitor elements 91 can be reduced.

[0005] In this way, heat generation in the conventional technology disclosed in PTL 1 can be suppressed to a certain extent. However, a film capacitor with improved heat dissipation characteristics is now required. List of citations from patent literature

[0006] PTL 1: JP 2013 - 26 586 A

[0007] JP 2007 - 150 014 A mentions an electrical storage device capable of sufficiently dissipating heat generated by the capacitor electrodes and busbars during rapid charging with a high current. The electrical storage device comprises a capacitor unit 100 in which the electrodes 11 of several capacitors 10 are connected in series and / or parallel to the busbars 13. A high-temperature conductive insulating material 18 is arranged to encompass at least the capacitor electrode 11 and the busbar 13. The heat from the electrode 11 and the busbar 13 is efficiently dissipated via the high-temperature conductive insulating material 18, thus suppressing the temperature rise in the electrical storage device.

[0008] JP 2012-199350A mentions a technology that enables high heat dissipation performance while simultaneously reducing the size, weight, and cost of a housing capacitor for hybrid vehicles and the like. A capacitor element 1, connected to busbars 3 and 4, is housed in a plastic casing 5, and a molded plastic 7 fills the casing 5. A metal plate 6, with a top surface provided with several protruding parts 6a, is molded onto an outer bottom surface of the casing 5. Furthermore, recesses are formed on an inner bottom surface of the casing 5, allowing the top surfaces of the protruding parts 6a on the metal plate 6 to be exposed to the interior. This structure enables the top surfaces of the protruding parts 6a of the metal plate 6 to come into close contact with the molded resin 7.

[0009] JP 2011-101 042 A mentions a ready-to-install capacitor for vehicles or similar applications, characterized by excellent heat dissipation properties and heat resistance, thus solving the problem of low heat resistance. In this ready-to-install capacitor, which is formed by connecting several capacitive elements via a busbar at one end, housed in a casing and overmolded with plastic (except for the busbar terminal), the multiple capacitive elements are arranged in parallel. The dielectric strength of one capacitive element located closest to the busbar terminal is enhanced compared to the other capacitive elements, resulting in stable performance, excellent service life, and high reliability for the housing-type capacitor. OVERVIEW

[0010] A film capacitor comprises: a capacitor element in which a metallikon electrode is formed at one end; a busbar connected to the metallikon electrode; a housing with a container for receiving the capacitor element and the busbar; a cover element that covers an opening of the container; and a heat-conducting element arranged between the busbar and the cover element. The cover element has a projection on one side facing the heat-conducting element, the projection being in contact with the heat-conducting element, and the heat-conducting element being in contact with the busbar.

[0011] Therefore, a film capacitor can be provided whose reliability is increased by improving its heat dissipation behavior. BRIEF DESCRIPTION OF DRAWINGS Fig. Figure 1 is a perspective view of a film capacitor in a first illustrative embodiment. Fig. Figure 2 is a perspective elevation view of the film capacitor in the first illustrative embodiment. Fig. Figure 3 is a sectional view of the film capacitor in the first illustrative embodiment. Fig. Figure 4 is a perspective view of a state in which a first cover element and a second cover element are provided separately in the first illustrative embodiment. Fig. Figure 5 is a schematic perspective view illustrating the injection of liquid resin in the first illustrative embodiment. Fig. Figure 6 is a perspective view of a conventional film capacitor. Fig. Figure 7 is a top view of a state in which a busbar for the positive electrode is omitted on the side of the upper surface of the conventional film capacitor. DESCRIPTION OF THE EXECUTION FORM

[0012] In the following, a construction of a film capacitor according to a first illustrative embodiment and a method for manufacturing the film capacitor are described with reference to the drawings.

[0013] Fig. Figure 1 is a perspective view of the film capacitor according to the first illustrative embodiment, and Fig. Figure 2 is a perspective elevation view of a significant part of the film capacitor. Furthermore, Fig. 3 a sectional view, which is drawn along a section line II in Fig. 1 is taken.

[0014] In the present illustrative embodiment, the film capacitor has six capacitor elements 1 for current smoothing. Both ends of each capacitor element 1 are provided with a metallikon electrode 11. The structure of a capacitor element 1 will now be described in detail. The capacitor element 1 has two end faces facing each other and a side face connecting these two end faces. The capacitor element 1 is designed in a flat form (a form with two flat surfaces and two curved surfaces) when viewed from the end face. Furthermore, the capacitor element 1 contains a pair of metallized films. The metallized film is a film in which a vapor-deposited metal layer (a vapor-deposited electrode) is deposited by vapor deposition of aluminum onto at least one of the surfaces of a dielectric film.A layer made of polypropylene (hereinafter referred to as "PP") or the like is formed. This pair of metallized films is then arranged overlapping and wound (around a winding body). Furthermore, the Metallikon electrode 11, made of zinc, is applied to both end faces of the winding body.

[0015] For example, a busbar 2, made of metal, such as copper, is configured as a busbar for the positive electrode 2A and a busbar for the negative electrode 2B. Insulating paper 33 is applied to a surface of the busbar for the negative electrode 2B that faces the busbar for the positive electrode 2A, thus providing insulation with respect to the busbar for the positive electrode 2A. The busbar for the positive electrode 2A is connected to one Metallikon electrode 11 of each capacitor element 1 by soldering or resistance welding. The busbar for the negative electrode 2B is connected to the other Metallikon electrode 11 of each capacitor element 1 by soldering or resistance welding.

[0016] Several capacitor elements 1, to which the busbar for the positive electrode 2A and the busbar for the negative electrode 2B are connected, are housed in a container 3A, which is provided in a housing 3 made of insulating resin, such as polyphenylene sulfide (hereinafter referred to as "PPS"). The housing 3 is of the type that is open at the top and has a substantially rectangular opening. A rectangular annular end face 3B, which has a substantially rectangular shape, is formed in the housing 3 such that it surrounds the opening of the container 3A.

[0017] Furthermore, each of the two ends of the busbar for the positive electrode 2A and each of the two ends of the busbar for the negative electrode 2B is provided with a holder 2A1 and a holder 2B1, respectively, in one arrangement direction (an X-direction) of the capacitor elements 1. The holder 2A1 and the holder 2B1 are suspended at predetermined positions on the rectangular ring end face 3B of the housing 3. A thermally conductive layer or thermally conductive film 4, made of insulating paper or acrylic resin, is arranged on a surface (a surface for arranging a thermally conductive element) on one side opposite a surface of the busbar for the negative electrode 2B that is connected to the Metallikon electrode 11 (a connection surface for the Metallikon electrode). The thermally conductive layer 4 is in contact with the busbar for the negative electrode 2B.It is preferred that the thickness of the thermally conductive layer 4 be small, provided there is no problem with insulation. For example, the layer can be used with a thickness in the range of 0.5 mm to 1.0 mm. In the present illustrative embodiment, insulating paper in which polyamide paper is bonded to a polyethylene terephthalate (PET) film is used as the thermally conductive layer or thermally conductive film 4. The insulating paper is thin and has excellent handling properties. The thermally conductive layer 4 is an example of a thermally conductive element.

[0018] For example, a cover element 5, made of metal, such as aluminum, is arranged on the rectangular ring end face or circumferential end face 3B of the housing 3 such that it covers the opening of the container 3A of the housing 3. The cover element 5 is fastened to the rectangular ring end face 3B of the housing 3 by screws 8. Furthermore, the external connection for the positive electrode 2A2 of the busbar for the positive electrode 2A is provided at a position that is further away from the housing 3 than the holder 2A1 of the busbar for the positive electrode 2A. Similarly, the external connection for the negative electrode 2B2 of the busbar for the negative electrode 2B is provided at a position that is further away from the housing 3 than the holder 2B1 of the busbar for the negative electrode 2B.

[0019] The cover element 5 is composed of a first cover element 5A and a second cover element 5B. As shown in Fig. As shown in Figure 2, the first lid element 5A is larger than the second lid element 5B. Fig. Figure 4 is a perspective view of the cover element 5 in a state where the first cover element 5A and the second cover element 5B are spaced apart, as viewed from the side of the heat-conducting layer 4. The first cover element 5A has a cutout 5A2. A step 5A5 is provided near three outer edges that form the cutout 5A2 of the first cover element 5A. Furthermore, a step 5B1 is provided near three of the four sides of the rectangular second cover element 5B, as viewed from above. The second cover element 5B is secured by the steps 5B1 of the second cover element 5B fitting into the steps 5A5 of the first cover element 5A. The cover element 5 is formed by the combination of the first cover element 5A and the second cover element 5B.

[0020] As in Fig. As shown in Figure 3, the first cover element 5A has an outer surface 5A3, which forms a surface of the film capacitor, and an inner surface 5A4, which is located on the opposite side to the outer surface 5A3, facing the container 3A of the housing 3. The inner surface 5A4 has a projection 5A1. One end of the projection 5A1 is in contact with the thermal interface material 4. In other words, the thermal interface material 4 is enclosed between the busbar for the negative electrode 2B and the cover element 5 (projection 5A1 of the first cover element 5A). Since the heat generated by the capacitor elements 1 is conducted to the entire cover element 5 via the metallikon electrode 11, the busbar 2, the thermal interface material 4, and the projection 5A1, the heat can be efficiently dissipated from the film capacitor to the outside in this configuration.Furthermore, the thermally conductive layer 4 does not affect the electrical properties of the film capacitor, as it possesses insulating properties. It should be noted that a design in which an insulating resin is poured between the busbar for the negative electrode 2B and the cover element 5 can also be considered a different design than that of the present illustrative embodiment. However, in this case, a sufficient gap must be provided between the busbar for the negative electrode 2B and the cover element 5 to allow the resin to be poured in. If the sufficient gap is provided in this way, heat dissipation is naturally reduced, and excellent heat dissipation as in the present illustrative embodiment cannot be achieved.On the other hand, if the insulating paper in which the polyamide paper is attached to the thin PET film is used, as in the present illustrative embodiment, the distance between the busbar for the negative electrode 2B and the cover element 5 can be sufficiently small. Consequently, excellent heat dissipation can be achieved.

[0021] Furthermore, two Y-capacitors 7, which are connected in parallel and adjacent to the capacitor elements 1 on a left side with respect to the plane of the drawing, are shown in Fig. The two Y-capacitors 7 are connected in series with the capacitor elements 1. These two Y-capacitors 7 are intended to reduce noise.

[0022] As further in Fig. As shown in Figure 3, a resin layer 6 is formed for sealing or closing the condenser element 1 in a space bounded by the inner surface of the cover element 5, which faces the container 3A of the housing 3, and by the surface 3A1 of the container 3A of the housing 3, excluding the top of the space. The resin layer 6 completely covers the heat-conducting layer 4, and furthermore, one end of the projection 5A1 is embedded in the resin layer 6 on the side of the heat-conducting layer 4.

[0023] However, according to the present illustrative embodiment, the end region (a lower end region) of the side surfaces of the projection 5A1 of the first cover element 5A is covered (embedded in) the resin layer 6 on the side of the thermal conductivity layer 4. Consequently, the first cover element 5A can be reliably and stably fixed in a state in which the first cover element 5A is in contact with the thermal conductivity layer 4, this being achieved by an anchoring effect of the projection 5A1 in the resin layer 6. As further shown in Fig. 1 and Fig. As shown in the present illustrative embodiment, the first cover element 5A is attached to the rectangular circumferential end face or rectangular annular end face 3B of the housing 3 by the two screws 8, and the screws 8 are located close together and are attached only on one side of the rectangular annular end face 3B. This is due to the requirement for miniaturization of the film capacitor. Therefore, the first cover element 5A is attached on one side instead of on both sides, where the opposing sides are attached to the rectangular annular end face 3B. The first cover element 5A is essentially in a single-point attachment state instead of a two-point attachment state with respect to a Y-direction that is perpendicular to the X-direction.Even if the first cover element 5A and the housing 3 are attached in the manner described above, the stability of the contact between the projection 5A1 and the thermal interface material 4 can still be improved, since the end of the projection 5A1 on the thermal interface material 4 side is embedded in the resin layer 6 in a state where it is in contact with the thermal interface material 4. Consequently, the stability of the contact between the projection 5A1 and the thermal interface material 4 can be improved.

[0024] When the film capacitor is installed in an inverter circuit for controlling a motor (especially in a train, for in-vehicle use), the heat generated by the film capacitor is dissipated more easily because charging and discharging occur with a high current. Therefore, a highly reliable film capacitor can be provided by using the film capacitor of the present illustrated embodiment for such an application. (MANUFACTURING PROCESS)

[0025] The following describes a method for manufacturing the film capacitor of the present illustrative embodiment. (MANUFACTURING PROCESS FOR CAPACITOR ELEMENT)

[0026] The manufacturing process for a capacitor element is described. First, aluminum is deposited by vapor deposition onto a surface of the dielectric film formed from polypropylene (PP), thus producing the metallized film, which is provided with the vapor-deposited metal layer (the vapor-deposited electrode). It should be noted that in this illustrative embodiment, aluminum is used as the vapor-deposited metal. However, a metal other than aluminum, such as zinc or magnesium, or a combination of these metals, can be used.

[0027] Next, the metallized foil for one polarity and the metallized foil for the other polarity are arranged overlapping and wound in a state where the ends are slightly displaced in the lateral direction. This produces the cylindrical winding body. Subsequently, a curved outer circumferential surface of this winding body is compressed radially from both sides to flatten the winding body (the shape having two flat surfaces and two curved surfaces). The metallikon electrode 11 is then produced by spraying zinc onto the two facing end surfaces of the flattened winding body. Thus, the assembly of the capacitor element 1 is completed, in which the vapor-deposited metal layers, facing each other via the dielectric foil, are connected to the metallikon electrode 11. (PROCESS FOR CONNECTING THE POWER LINE)

[0028] First, the busbar for the negative electrode 2B, the busbar for the positive electrode 2A, the Y-capacitor 7, and a GND connection (ground connection) 7A are prepared. The insulating paper 33 is applied to the surface of the busbar for the negative electrode 2B opposite the busbar for the positive electrode 2A to provide insulation from the busbar for the positive electrode 2A. Next, the busbar for the positive electrode 2A is connected to a Metallikon electrode 11 of each of the six capacitor elements 1 by soldering or resistance welding, and the busbar for the negative electrode 2B is connected to the other Metallikon electrode 11 of the capacitor element by soldering or resistance welding.Furthermore, one Metallikon electrode 11 of the Y-capacitor 7 and one end of the GND terminal 7A are connected by soldering or resistance welding, and the other Metallikon electrode of the Y-capacitor 7 and the busbar for the positive electrode 2A are connected by soldering or resistance welding. (SEALING PROCESS)

[0029] First, the housing 3, made of PPS, is of the type which is open at the top and contains the container 3A. The housing 3 has the rectangular annular end surface 3B, which is formed in an essentially rectangular shape such that it encloses the opening of the container 3A.

[0030] The holders 2A1 are positioned at the ends of the busbar for the positive electrode 2A in the direction (the X-direction) of the capacitor elements. The holders 2B1 are positioned at the ends of the busbar for the negative electrode 2B in the direction of the capacitor elements. The holders 2A1 and 2B1 are mounted so that they are suspended from the predetermined positions of the rectangular ring end face 3B of the housing 3. The six capacitor elements 1 and the two Y-capacitors 7, which connect the busbar for the positive electrode 2A and the busbar for the negative electrode 2B, are housed in the container 3A of the housing 3.At this point, another end of the GND terminal 7A, which is connected to one of the metalicon electrodes of the Y capacitor 7, is also in contact with the rectangular ring end face 3B, so that a through hole of the GND terminal overlaps with a screw hole provided in the rectangular ring end face 3B.

[0031] Next, the thermally conductive layer 4, made of insulating paper or acrylic resin, is positioned on the mounting surface for the thermal element, which is located on the side opposite the terminal surface for the Metallikon electrode of the busbar for the negative electrode 2B. Next, the first cover element 5A, made of metal, for example aluminum, is positioned on the rectangular annular end face 3B of the housing 3 such that it covers the opening of the container 3A of the housing 3. Furthermore, the projection 5A1, which is provided in the first cover element 5A on one side opposite the thermally conductive layer 4, is brought into contact with the thermally conductive layer 4. Finally, the first cover element 5A and the GND terminal 7A are fastened to the housing 3 using nuts embedded in the housing 3 and screws 8.It should be noted that the external connection for the positive electrode 2A2 of the busbar for the positive electrode 2A and the external connection for the negative electrode 2B2 of the busbar for the negative electrode 2B are exposed to the outside in relation to the housing 3 and the first cover element 5A.

[0032] Fig. Figure 5 is a schematic perspective view illustrating the injection of liquid resin to produce the resin layer 6 for sealing the capacitor elements. To facilitate understanding, components such as the capacitor elements 1, which are contained in the container 3A of the housing 3, have been omitted. As shown in Fig. As shown in Figure 5, the liquid resin is injected at high temperature into the container 3A from the opening (an opening for injecting liquid resin) 6A, which is formed from part of the rectangular ring end surface 3B of the housing 3 and the cut-out part 5A2 of the first lid element 5A. As shown in Fig. As shown in Figure 3, the gap between the surface 3A1 of the container 3A of the housing 3 and the capacitor element 1, the busbar 2, or the like is filled with the liquid resin. The liquid resin cools, forming the resin layer 6. The resin layer 6 completely covers the heat-conducting layer 4 and at least covers the end of the projection 5A1 on the side of the heat-conducting layer. In other words, the projection 5A1 of the first cover element 5A has a region that is embedded in the resin layer 6.

[0033] Next, as indicated by arrow E in Fig.As shown in Figure 5, the steps 5B1 of the second cover element 5B are fitted into the steps 5A5 provided on the cut-out part 5A2 of the first cover element 5A, such that the opening for injecting liquid resin 6A is closed by the second cover element 5B. The second cover element 5B is then attached, thus completing the film capacitor of the present illustrative embodiment.

[0034] According to the present illustrative embodiment, the cover element 5 is formed by dividing it into the first cover element 5A and the second cover element 5B. Therefore, when the resin layer 6 is produced, the opening for injecting liquid resin 6A can be provided by the opening formed by a portion of the rectangular annular end face 3B of the housing 3 and the cut-out portion 5A2 of the first cover element 5A, thus ensuring efficient injection of the liquid resin. Furthermore, since the opening for injecting liquid resin 6A can be closed by attaching the second cover element 5B to the housing 3, moisture protection can be improved. Additionally, since the second cover element 5B acts as a heat dissipation element, the heat conducted by the condenser elements can be efficiently dissipated through it.

[0035] Furthermore, in the present illustrative embodiment, the second cover element 5B has the projection 5B2, which protrudes on the side of the capacitor elements 1, and the projection 5B2 of the second cover element 5B is arranged closer to the resin layer 6 than the steps 5B1 of the second cover element 5B. With this design, in the present illustrative embodiment, the heat conducted by the capacitor elements 1 can be dissipated more efficiently through the projection 5B2 of the second cover element 5B.

[0036] It should be noted that the gap formed between the surface 3A1 of the container 3A of the housing 3 and the capacitor element 1 or the busbar 2 can be efficiently and reliably filled with the injected liquid resin, since the second cover element 5B is located at a central area in a longitudinal direction of the opening of the container 3A.

[0037] In the present illustrative embodiment, the heat-conducting element is formed by a single heat-conducting layer. However, the present invention is not limited to this. For example, an element produced by stacking two heat-conducting layers of the same material can be used. Furthermore, components with different materials / shapes, for example, an element produced by stacking insulating paper and a metal plate, or an element formed by stacking insulating paper and a single acrylic resin sheet, also fall within the technical scope of the heat-conducting element of the present invention. INDUSTRIAL APPLICABILITY

[0038] A film capacitor can be provided which has been further improved in its heat dissipation behavior.

[0039] The film capacitor according to the present invention can improve heat dissipation. Therefore, the film capacitor can be used in a suitable manner as a film capacitor suitable for a hybrid vehicle used under demanding external conditions. REFERENCE MARKS IN THE DRAWINGS 1 capacitor element 11 Metallikon electrode 2 busbar 2A busbar for the positive electrode 2B busbar for the negative electrode 3 cases 3A Container 3A1 Surface of the container 3B rectangular ring end face 4. Thermal conducting layer (thermal conducting material), thermal conducting element 5 lid element 5A first cover element 5A1 advantage 5A2 cut-out part 5A3 Exterior area 5A4 inner surface 5A5 Stage 5B second lid element 5B1 Level 6. Resin layer 6A Opening for injecting casting resin 7 Y-capacitor 7A GND connection 8 screws

Claims

[1] A film capacitor with: a capacitor element (1) in which a metallikon electrode (11) is formed at one end; a busbar (2) which is connected to the Metallikon electrode (11); a housing (3) with a container (3A) for receiving the capacitor element (1) and the busbar (2); a lid element (5) that covers an opening of the container (3A); and a heat conducting element (4) arranged between the busbar (2) and the cover element (5), wherein the cover element has a projection (5A1) on a side facing the heat conducting element (4), the projection (5A1) is in contact with the heat conducting element (4) and the heat conducting element (4) is in contact with the busbar (2). [2] The film capacitor according to claim 1, wherein a resin layer (6) for sealing the capacitor element (1), to which the busbar (2) is connected, is formed inside the container (3A), and the lid element (5) is formed from a first lid element (5A) having the projection (5A1) and a second lid element (5B), and the first lid element (5A) and the second lid element (5B) cover the opening of the container (3A). [3] The film capacitor according to claim 2, wherein the projection (5A1) has a region which is embedded in the resin layer (6). [4] The film capacitor according to claim 2 or 3, wherein the second cover element (5B) is provided at a central area in a longitudinal direction of the opening.

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