JP2024058883A - Film capacitor - Google Patents

Abstract

[Problem] In a film capacitor, the heat dissipation efficiency is improved by devising a joint base embedded in molded resin in a bus bar. [Solution] A capacitor main part 6 has a capacitor element unit 1 and a bus bar 2 with a joint base 2a joined to an end surface electrode 1a of the unit. The entire unit and the joint base are covered with molded resin 5. An external connection terminal 2c extends from a first edge 2a1 of the joint base 2a in a state exposed to the outside from the molded resin. A heat dissipation promotion part 2e extends from a second edge 2a2 different from the first edge 2a1 of the joint base 2a and is exposed to the outside from the molded resin 5. The heat dissipation promotion part 2e is arranged in a position along the outer surface of the molded resin 5. [Selected Figure] Figure 4

Description

The present invention relates to a film capacitor having a capacitor main part formed by joining a busbar joint base to an end electrode of a capacitor element unit, a molded resin that covers the entire capacitor element unit and the joint base, and an external connection terminal that extends from the joint base and is exposed from the molded resin.

Film capacitors installed in electric vehicles (EVs) are used with their external connection terminals connected to cable terminals (external terminals) from an inverter (DC-AC power conversion device). In recent years, there has been a strong demand for larger currents and smaller size for on-board film capacitors, and as a result, measures to prevent problems caused by capacitor overheating have become an issue.

Generally, film capacitors are resin-molded, so in order to cool them, a heat-conducting sheet or similar must be attached to the surface of the resin. However, there is a problem with heat dissipation when molding resin is in between, in that it is not possible to achieve high heat dissipation efficiency because the thermal conductivity of the resin is very low.

To address these issues, there is a strong demand for ways to improve heat dissipation efficiency without requiring major structural modifications or complexity.

Conventionally, the following measures have been proposed to efficiently release the heat generated between the capacitor element unit, which is covered and protected by the exterior resin or the molded resin inside the exterior case, and the joint base of the bus bar to the outside. For example, the capacitor described in Patent Document 1 has a bus bar including a first portion exposed from the molded resin and having a connection terminal portion connected to an external terminal, a buried portion buried in the molded resin, and an exposed portion located away from the first portion and exposed from the molded resin, and a second portion having a connection portion connected to an electrode of the capacitor element, and a cooler prepared on the inverter device side is attached to the exposed portion, so that the heat generated in the capacitor element and the bus bar when current is applied is released to the outside from the exposed portion (heat is absorbed by the cooler), making it difficult for overheating to occur.

International Publication No. 2020/241145

The electric vehicle industry has been developing remarkably in recent years, and a wide variety of specifications have been developed for the layout of on-board assemblies. In the capacitor described in Patent Document 1, an exposed portion is provided in the second portion where the connection portion connected to the electrode of the capacitor element is provided. In this case, the exposed portion is located at the top surface of the molded resin that covers the capacitor element, and accordingly, the cooler to be attached to the exposed portion is located above the top surface of the resin, facing it.

However, in some cases, it is not possible to position the cooler that should be attached to the exposed portion above the upper surface of the resin, or the conditions are extremely difficult, making this practically impossible.

The present invention aims to enable heat dissipation to the outside, even when there is a prohibited space in a specific area of the space surrounding the outer surface of the molded resin, making it impossible or difficult to place a cooler.

The present invention solves the above problems by taking the following measures:

The film capacitor according to the present invention has:
a capacitor main portion having a capacitor element unit and a bus bar having a joining base joined to an end surface electrode of the capacitor element unit;
a molding resin that covers at least the entire capacitor element unit and the joint base in the capacitor main portion;
an external connection terminal extending from a first edge portion of the joining base in a state exposed from the molding resin and connected to an external terminal,
The heat dissipation promotion portion is disposed so as to extend from a second edge portion of the joint base that is different from the first edge portion, be exposed from the molding resin, and be unconnected to an external terminal.

In this configuration, a capacitor element unit refers to a single capacitor element or an assembly of multiple capacitor elements.

The above-mentioned configuration of the present invention provides the following effects:

There may be restrictions on exposing the heat dissipation promotion part extending from the joint base of the busbar from the molded resin. That is, part of the space surrounding the outer surface of the molded resin may not be suitable for placing the heat dissipation promotion part because it is impossible or difficult to place a cooler there. Such a restricted space is a space where the heat dissipation promotion part cannot be placed.

In order to deal with such a situation, in the present invention, first, for the portion where the heat dissipation promotion portion extends from the joint base, it is exposed from the molded resin at a second edge portion different from the first edge portion of the joint base from which the external connection terminal extends, and the heat dissipation promotion portion that is not connected to the external terminal extends from the joint base. By exposing the heat dissipation promotion portion starting from the second edge portion that is not affected by the external terminal position from the molded resin, it is possible to dissipate heat to the outside (heat absorption by a cooler) while avoiding the prohibited placement space.

The above-mentioned heat dissipation promotion part can be exposed from the molded resin in two main ways:

In the first form (see the first embodiment described later), the surface ("parallel end surface") of the molded resin parallel to the end surface electrode (or the joint base of the bus bar) of the capacitor element unit is taken as a reference, and the space facing the parallel end surface of this molded resin becomes the prohibited placement space. The parallel end surface of the molded resin is perpendicular to the axial direction of the capacitor element. In the first form, the prohibited placement space is located opposite the joint base, but in the structure in which the heat dissipation promotion part extends from the joint base, the heat dissipation promotion part is extended from a second edge portion different from the first edge portion from which the external connection terminal extends, exposing the heat dissipation promotion part to the outside of the molded resin. As a result, the heat dissipation promotion part is positioned along the cylindrical outer peripheral surface of the molded resin corresponding to the cylindrical outer peripheral surface (envelope surface) of the capacitor element unit, and the prohibited placement space is avoided.

The second form of exposure of the heat dissipation promotion portion from the molded resin (see the second embodiment described later) is when the external connection terminal is connected to the joint base of the bus bar joined in surface contact with the end electrode of the capacitor element unit via a connecting portion that satisfies the following arrangement requirement. The connecting portion is arranged along the cylindrical outer circumferential surface (envelope surface) of the capacitor element unit or along the cylindrical outer circumferential surface of the molded resin, and the arrangement requirement is that the tip side of the connecting portion becomes the external connection terminal. In the second form, the first connecting portion on the external connection terminal side of the bus bar is arranged on the cylindrical outer circumferential surface of the molded resin, and the space facing this cylindrical outer circumferential surface becomes the prohibited arrangement space. In this case, the heat dissipation promotion portion is arranged along the parallel end surface of the molded resin that corresponds to the end electrode of the capacitor element unit, and the prohibited arrangement space is avoided.

The film capacitor of the present invention with the above configuration has several preferred aspects and variations/modifications, as follows:

[1] It is preferable to arrange the heat dissipation promotion part in a position that follows the outer surface of the molded resin. With this configuration, it is possible to prevent the volume occupied by the film capacitor from becoming larger than necessary while avoiding prohibited spaces.

[2] This includes cases where the capacitor is configured as a so-called case mold type (see the first embodiment described later). That is, the molding resin is filled inside an open-top case that houses the entire capacitor element unit and the bonding base, and the heat dissipation promotion portion faces closely to the outer surface of the side wall plate of the case.

In the case of a film capacitor in which the molded resin is filled in a top-opening case, the molded resin is in close contact with the inner peripheral surface of the side wall plate of the case. In this embodiment [2], the heat dissipation promotion portion extending from the second edge of the joint base of the busbar faces closely to the outer surface of the side wall plate of the case.

A portion of the heat generated in the capacitor element unit is transmitted from the joint base of the busbar through the second edge portion to the heat dissipation promotion portion, and is dissipated to the outside (heat is absorbed into the cooler).

[3] The molded resin itself is configured as a caseless type that constitutes the protective exterior resin, and the heat dissipation promotion section is arranged on the outer surface of the exterior resin (see the second embodiment described below). In this case, the heat dissipation promotion section is individually connected to both the first and second bus bars that are respectively joined to a pair of end surface electrodes of the capacitor element unit, and arranged on the outer surface of the exterior resin, making it possible to dissipate heat generated from the capacitor element unit to the outside. This is particularly suitable for film capacitors for large currents.

[4] The heat dissipation promotion portion is provided so as to protrude from each of the joint bases of the pair of bus bars of the positive and negative electrodes in a direction away from the end surface electrodes of the capacitor element unit.

According to the present invention, even if there is a prohibited space in a specific area of the space surrounding the outer surface of the molded resin where it is impossible or difficult to place a cooler, it is possible to dissipate heat to the outside by avoiding the prohibited space.

FIG. 1 is a perspective view showing a configuration of a main part of a film capacitor according to a first embodiment of the present invention before molding resin is filled; FIG. 1 is a perspective view showing a configuration of a main part of a capacitor after being filled with molding resin in a first embodiment of the present invention; FIG. 1 is a perspective view showing the configuration of a main part of a capacitor before being filled with molding resin according to a first embodiment of the present invention, when viewed obliquely from above in an inverted state; FIG. 1 is a front cross-sectional view of a film capacitor with a cooler attached according to a first embodiment of the present invention; FIG. 11 is a perspective view showing the configuration of a main part of a caseless type film capacitor according to a second embodiment of the present invention; FIG. 11 is a front cross-sectional view showing the configuration of a caseless film capacitor according to a second embodiment of the present invention. FIG. 11 is a perspective view of a caseless film capacitor according to a second embodiment of the present invention, taken from the left side; FIG. 11 is a perspective view of a caseless film capacitor according to a second embodiment of the present invention, taken from the right side;

The following describes in detail the film capacitor of the present invention with the above configuration, using specific examples.

[First embodiment]
1 to 4, 1 denotes a capacitor element unit, 1a and 1b denote end surface electrodes at both axial ends of the capacitor element unit 1, 1a denotes an upper end surface electrode, 1b denotes a lower end surface electrode, and 1c denotes a capacitor element. 2 denotes a first bus bar located on the upper side, 2a denotes a joint base which is a base of the first bus bar 2, 2c denotes an external connection terminal which is a free end of the first bus bar 2, 2b denotes a first connection portion which connects the joint base 2a and the external connection terminal 2c, 2e denotes a heat dissipation promotion portion, and 2d denotes a second connection portion which connects the joint base 2a and the heat dissipation promotion portion 2e. 3 denotes a second bus bar located on the lower side, 3a denotes a joint base which is a base of the second bus bar 3, 3c denotes an external connection terminal which is a free end of the second bus bar 3, and 3b denotes a first connection portion which connects the joint base 3a and the external connection terminal 3c. Reference numeral 4 denotes a case (resin case), 5 denotes a molding resin, 5a denotes an upper surface of the molding resin 5, and 6 denotes a main portion of the capacitor.

The capacitor element unit 1 is constructed by arranging multiple capacitor elements 1c in parallel. In other words, they are arranged parallel to each other with their axial direction in the vertical direction, and are closely spaced so that they are in contact with each other on the circumferential surface as a whole. 1d is the cylindrical outer peripheral surface (envelope surface) of the capacitor element unit 1 made up of multiple capacitor elements 1c. The upper end electrode 1a and the lower end electrode 1b, which are parallel to each other, are perpendicular to this cylindrical outer peripheral surface (envelope surface) 1d.

The first busbar 2 has a joint base 2a electrically and mechanically joined to the upper end electrode 1a of the capacitor element unit 1, a first connecting portion 2b extending from the joint base 2a toward the free end, and an external connection terminal 2c connected to the end of the first connecting portion 2b and connected to an external terminal. The first connecting portion 2b is bent at a right angle from the joint base 2a of the capacitor element unit 1 and is composed of a portion that rises in an L-shape along the cylindrical outer peripheral surface (envelope surface) 1d, and three tongue-shaped external connection terminals 2c further protrude horizontally from the free end side of the first connecting portion 2b.

Similarly, the second busbar 3 has a joint base 3a electrically and mechanically joined to the lower end electrode 1b of the capacitor element unit 1, a first connecting portion 3b extending from the joint base 3a toward the free end, and an external connection terminal 3c connected to the end of the first connecting portion 3b and connected to another external terminal. The first connecting portion 3b is bent at a right angle from the joint base 3a of the capacitor element unit 1 and is composed of a portion that rises in an L-shape along the cylindrical outer peripheral surface (envelope surface) 1d, and three tongue-shaped external connection terminals 3c further protrude horizontally from the free end side of the first connecting portion 3b.

The length of the first connecting portion 3b of the second busbar 3 is longer than the length of the first connecting portion 2b of the first busbar 2 by the axial dimension of the capacitor element unit 1 (capacitor element 1c). The upper end portion (lower end portion in FIG. 3) of the first connecting portion 3b of the second busbar 3 faces closely to the first connecting portion 2b of the first busbar 2, with an insulating plate (not shown) interposed between them. Note that the second busbar 3 is not connected to a heat dissipation promotion portion or a connecting portion to the heat dissipation promotion portion.

The joint base 2a of the first busbar 2 is joined to the upper end electrode 1a of the capacitor element unit 1, and the joint base 3a of the second busbar 3 is joined to the lower end electrode 1b to form the capacitor main part 6. The capacitor main part 6 does not include the case 4 or molded resin 5.

The first connecting portion 2b to the external connection terminal 2c extends from the first edge portion _2a1 of the joint base portion 2a, which is horizontally extended. A second connecting portion 2d extends from a second edge portion _2a2 (FIG. 4) different from the first edge portion _2a1 , and the heat dissipation promotion portion 2e is connected to the second connecting portion 2d. The second connecting portion 2d to the heat dissipation promotion portion 2e rises slightly once and then bends to a horizontal position. The heat dissipation promotion portion 2e connected to the end of the horizontal bend hangs down almost straight down. The main surface of the heat dissipation promotion portion 2e is in a position almost perpendicular to the main surface of the joint base portion 2a, and is not connected to the external terminal. The portion from the second connecting portion 2d to the heat dissipation promotion portion 2e is bent into a small inverted U-shape.

The capacitor element unit 1 (the entirety of the multiple capacitor elements 1c) and the upper and lower joint bases 2a, 3a are housed in a resin case 4 with an open top, and the molded resin 5 injected into the inside of the case 4 is filled up to a position slightly above the joint base 2a. The upper surface 5a of the molded resin 5 is extended on a horizontal plane at a position slightly lower than the upper opening edge of the vertical side wall plate 4a of the case 4, and the middle part of the first connecting part 2b to the external connection terminal 2c and the middle part of the second connecting part 2d to the heat dissipation promotion part 2e are exposed to the external space from the upper surface 5a of the molded resin 5.

Although some of the description is repeated, the joint base 2a of the first busbar 2 has a substantially rectangular shape. A first connecting portion 2b to the external connection terminal 2c is connected to a first edge portion _2a1 corresponding to a long side of the rectangular joint base 2a (see Figs. 1 and 4), and a second connecting portion 2d to the heat dissipation promotion portion 2e is connected to a second edge portion _2a2 corresponding to a short side of the rectangular joint base 2a (see Fig. 4).

The plate-shaped heat dissipation promotion portion 2e hangs down in a position that is almost parallel to the outer surface of one of the vertical side wall plates 4a of the case 4. The heat dissipation promotion portion 2e and the side wall plate 4a face each other with a small gap between them. The area of the heat dissipation promotion portion 2e can be made close to the area of the one of the vertical side wall plates 4a (approximately 3/5 of the area in the illustrated example).

The plate-shaped heat dissipation promotion portion 2e and the second connecting portion 2d to the heat dissipation promotion portion 2e are provided with a slit-shaped notch _2d1 . This reduces the bending resistance when bending from the second connecting portion 2d to the heat dissipation promotion portion 2e into an inverted U-shape when manufacturing the first busbar 2 from a sheet metal material, and enables the heat dissipation promotion portion 2e to be positioned in a desired direction and attitude.

The film capacitor of this embodiment is mounted on an electric vehicle as an on-board device, for example, and is fixed to the frame. In the process of connecting cables from the external connection terminals 2c, 3c to the inverter, a thermally conductive sheet 7 is attached to the flat plate surface of the heat dissipation promotion portion 2e that is exposed to the outside, and a cooler 8 is placed on the surface of the thermally conductive sheet 7. The inside of the cooler 8 is a relatively large space that stores and flows the cooling medium, and inlet and outlet pipes 9 that communicate with this space are connected to the cooler 8.

In the case of the conventional example, the cooler 8 could not be placed in the space facing the upper surface 5a of the molded resin 5, and if this space was a prohibited placement space, the cooler could not dissipate (absorb) heat from the exposed part, which was a bottleneck in the cooling function. In contrast, in the case of this embodiment, in such an environment, the space facing the upper surface 5a of the molded resin 5 is avoided as the placement space for the cooler 8, and the cooler 8 is connected to the heat dissipation promotion part 2e that faces closely to the outer surface of the side wall plate 4a of the case 4. This increases the degree of freedom in the placement relationship between the film capacitor and the cooler 8.

In the first embodiment shown in the figures, the second connecting portion 2d extending from the heat dissipation promotion portion 2e is connected to the short side portion of the second edge portion 2a2 of the joint base portion _2a , but in the present invention, the manner of connection is not limited to that shown in the figures. That is, it may extend from not only one short side but another opposing short side, or may extend from a long side instead of a short side, or may extend from one short side and one long side, or may extend from two short sides and one long side.

In addition, while the heat dissipation promotion section in the illustrated example is connected to the first bus bar 2, the heat dissipation promotion section may be connected to the second bus bar 3 instead of the first bus bar 2, or the heat dissipation promotion section may be connected independently to each of the first bus bar 2 and the second bus bar 3.

In addition, the capacitor element unit 1 may consist of any number of capacitor elements 1c, either multiple or single.

Second Example
Next, an embodiment of a caseless type film capacitor in which the molding resin itself constitutes the exterior resin for covering and protecting the capacitor will be described.

The film capacitor shown in Figures 5 to 8 is configured as a caseless type. That is, the molded resin 5 that covers and protects the capacitor element unit 1 and the joint bases 2a, 3a of the first and second bus bars 2, 3 serves as an exterior resin for protecting the product. The case (resin case) 4 used in the first embodiment is not used.

In this embodiment, the capacitor element unit 1 is composed of one capacitor element 1c. However, it may be composed of a set of multiple capacitor elements 1c.

In this embodiment, both the joint base 2a of the first busbar 2 and the joint base 3a of the second busbar 3 have heat dissipation promotion portions 2e, 3e.

The first bus bar 2 is configured as follows: It has a joining base 2a electrically and mechanically joined to the left end electrode 1a of the capacitor element unit 1 (single capacitor element 1c), a first connecting portion 2b extending from a first edge portion _2a1 of the joining base 2a toward the free end, and an external connection terminal 2c connected to an end of the first connecting portion 2b.

The main parts of the capacitor element unit 1 and the first and second bus bars 2 and 3 are covered and protected by molded resin 5. The first connecting part 2b is bent at a right angle from the joining base 2a so that it fits along the flat part of the cylindrical outer circumferential surface (envelope surface) 1d of the capacitor element unit 1, and is then further extended in the same plane to be exposed outside the molded resin 5 and form the external connection terminal 2c.

The tip of the second connecting portion 2d, which protrudes from the second edge portion 2a ₂ of the joining base 2a joined to the left end electrode 1a inside the molded resin 5 in a direction away from the end electrode 1a and is bent vertically, is exposed from the left outer surface 5b of the molded resin 5, which is the exterior resin, and is further bent at a right angle from the exposed tip to form the heat dissipation promotion portion 2e, which is disposed in a position along the left outer surface 5b of the molded resin 5. The heat dissipation promotion portion 2e is not connected to the external terminal and is exposed in a state of being flush with the left outer surface 5b of the molded resin 5. The first bus bar 2, which is composed of the joining base 2a, the first connecting portion 2b, the external connection terminal 2c, the second connecting portion 2d and the heat dissipation promotion portion 2e, is produced by cutting and bending a single conductive plate.

The second bus bar 3 has a structure that is a mirror image of the first bus bar 2. That is, the second bus bar 3 has a joint base 3a electrically and mechanically joined to the right end electrode 1b of the capacitor element unit 1 (single capacitor element 1c), a first connecting portion 3b extending from a first edge portion _3a1 of the joint base 3a toward a free end, and an external connection terminal 3c connected to an end of the first connecting portion 3b. The extension portion of the first connecting portion 3b from the joint base 3a is bent at a substantially right angle to be aligned with a flat portion of the cylindrical outer circumferential surface (envelope surface) 1d of the capacitor element unit 1, and is further extended in the same plane to be exposed outside the molded resin 5 and extend to form the external connection terminal 3c.

The tip of the second connecting portion 3d, which protrudes from the second edge portion 3a2 of the joining base 3a joined to the right end electrode _1b inside the molded resin 5 in a direction away from the end electrode 1b and is bent vertically, is exposed from the right outer surface 5c of the molded resin 5, which is the exterior resin, and is further bent at a right angle from the exposed tip to form a heat dissipation promotion portion 3e, which is disposed in a position along the right outer surface 5c of the molded resin 5. The heat dissipation promotion portion 3e is not connected to the external terminal and is exposed in a state of being flush with the right outer surface 5c of the molded resin 5. The second bus bar 3, which is composed of the joining base 3a, the first connecting portion 3b, the external connection terminal 3c, the second connecting portion 3d, and the heat dissipation promotion portion 3e, is produced by cutting and bending a single conductive plate.

The film capacitor of this embodiment is fixed to the frame of the electric vehicle, and in the process of connecting cables from the external connection terminals 2c, 3c to the inverter, a heat conductive sheet (not shown) is attached to the flat plate surfaces of the heat dissipation promotion parts 2e, 3e that are exposed to the outside, and a cooler (not shown) is placed on the surface of the heat conductive sheet. Even in an environment where a cooler cannot be placed in the space outside the cylindrical outer circumferential surface (envelope surface) 5d of the molded resin 5, the degree of freedom in the relative placement of the film capacitor and the cooler can be increased.

In the second embodiment, the heat dissipation promotion parts 2e and 3e are exposed and arranged on the left and right flat surfaces of the molded resin 5, respectively, but either one of the heat dissipation promotion parts 2e and 3e may be omitted.

The present invention is useful as a technology that allows heat to be dissipated to the outside by avoiding a prohibited space in which it is impossible or difficult to place a cooler that is to be connected to a heat dissipation promotion part, even if such a prohibited space exists in part of the space surrounding the outer surface of the molded resin.

REFERENCE SIGNS LIST 1 Capacitor element unit 1a Upper end surface electrode 1b Lower end surface electrode 1c Capacitor element 2 First bus bar 2a Joining base 2a ₁ First edge portion 2a ₂ Second edge portion 2b First connecting portion 2c External connection terminal 2d Second connecting portion 2e Heat dissipation promotion portion 3 Second bus bar 3a Joining base 3a ₁ First edge portion 3a ₂ Second edge portion 3b First connecting portion 3c External connection terminal 3d Second connecting portion 3e Heat dissipation promotion portion 4 Case (resin case)
4a: Side wall plate of case 5: Molding resin 5a, 5b: Outer surface of molding resin 6: Main part of capacitor

Claims (5)

a capacitor main portion having a capacitor element unit and a bus bar having a joining base joined to an end surface electrode of the capacitor element unit;
a molding resin that covers at least the entire capacitor element unit and the joint base in the capacitor main portion;
an external connection terminal extending from a first edge portion of the joining base in a state exposed from the molding resin and connected to an external terminal,
A film capacitor characterized in that a heat dissipation promotion portion is arranged extending from a second edge portion of the joining base that is different from the first edge portion, exposed from the molding resin, and not connected to an external terminal. The film capacitor according to claim 1, characterized in that the heat dissipation promotion part is arranged in a position along the outer surface of the molded resin. the molding resin is filled inside an open-top case that houses the entire capacitor element unit and the bonding base,
3. The film capacitor according to claim 1, wherein the heat dissipation promotion portion faces an outer surface of a side wall plate of the case in close proximity to the outer surface. The mold resin itself constitutes a caseless type exterior resin for covering and protecting the case.
3. The film capacitor according to claim 1, wherein the heat dissipation promotion portion is disposed on an outer surface of the exterior resin. The film capacitor according to claim 4, wherein the heat dissipation promotion portion is provided so as to protrude from the respective joint bases of the pair of bus bars of the cathode and anode electrodes in a direction away from the end surface electrodes of the capacitor element unit.

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