Film capacitor

Abstract

To make suppression of heat damage and improvement of vibration resistance compatible each other, which have been considered to have a trade-off relationship regarding a film capacitor.SOLUTION: A film capacitor comprises: a capacitor element unit 10 in which bus bars 12 and 13 are connected to end face electrodes 11a and 11b at both axial ends of the capacitor element 11, respectively; an exterior case 20 with an opening that houses the main portions of the capacitor element unit 10; and a mold resin 30 that is filled into the exterior case 20 and solidified while covering the main part of the capacitor element unit 10. In at least one bus bar 12 of the pair of bus bars, a heat radiation unit 13c is exposed to the outside of the mold resin 30 and expanded to an external connection terminal unit 13e at the of the bus bar on the outside of the exterior case 20 for heat dissipation. A support leg portion 13 which is introduced and buried in the mold resin 30 and fixed in position, is connected to the heat radiation portion 13c.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a film capacitor including a capacitor element unit in which bus bars are respectively connected to end face electrodes at both axial ends of a capacitor element, an exterior case with an opening for housing a main part of the capacitor element unit, and a molded resin filled and solidified in the exterior case so as to cover the main part of the capacitor element unit.

Background Art

[0002] In a film capacitor configured as described above, in recent years, suppressing thermal damage (improving heat resistance) of a capacitor element and enhancing vibration resistance for preventing mechanical damage such as bus bars have both become major issues.

[0003] A heat dissipation part is formed on a bus bar extending from an end face electrode of a capacitor element. If the area of the heat dissipation part is increased, it becomes possible to effectively avoid thermal damage of the film capacitor. However, on the other hand, the heat dissipation part with an expanded area is likely to resonate with external vibrations, causing problems with the vibration resistance of the film capacitor. On the other hand, if the area of the heat dissipation part is reduced in order to adjust the natural frequency to a higher side for ensuring vibration resistance, the risk of thermal damage to the capacitor element increases. That is, suppression of thermal damage and enhancement of vibration resistance are in a trade-off (antinomy) relationship (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] This invention was created in view of these circumstances, and aims to achieve a balance between "suppression of thermal damage" and "enhanced vibration resistance," which were previously considered to be in a trade-off relationship with film capacitors. [Means for solving the problem]

[0006] The present invention solves the above problems by taking the following measures.

[0007] The film capacitor according to the present invention is A capacitor element unit in which busbars are connected to the end face electrodes at both ends of the axial direction of the capacitor element, An outer case with an opening for housing the main part of the capacitor element unit, The capacitor element unit comprises a molded resin that is filled into the outer case and solidified, covering the main part of the capacitor element unit. At least one of the pair of busbars has a heat dissipation portion that is exposed to the outside of the molded resin and extends to the external connection terminal portion at the tip of the busbar on the outside of the outer casing for heat dissipation. The heat dissipation section is characterized by having support legs connected to it, which are introduced and embedded within the molded resin and fixed in position.

[0008] In the film capacitor of the present invention, at least one busbar is configured as follows.

[0009] By increasing the effective length (area) of the heat dissipation section, the heat conducted from the capacitor element to the heat dissipation section via the embedded busbar is effectively diffused and dissipated to the outside. As a result, the heat dissipation effect is enhanced, preventing the accumulation and increase of heat generated from the capacitor element within the molded resin, and effectively avoiding thermal damage to the capacitor element.

[0010] In addition, by connecting the support legs to the heat dissipation section and introducing and embedding these support legs within the molded resin to fix their position, the length dimension of the portion corresponding to the antinode of the chord in the vibrating member is shortened. As the length is shortened, the natural frequency fn increases, resonance with unspecified external vibrations is suppressed, and as a result, mechanical damage can be suppressed. In other words, the above-mentioned trade-off can be resolved, and thermal damage suppression and vibration resistance can be enhanced.

[0011] The film capacitor of the present invention with the above configuration has several preferred embodiments or modified / deformed embodiments as follows.

[0012] [1] The heat dissipation section extends along the surface of the molded resin at a predetermined distance from the surface of the molded resin. This allows the heat dissipation surface to be expanded while keeping the overall structure compact.

[0013] [2] The support legs are bent and extended almost perpendicularly from the heat dissipation section and are introduced and embedded in a position almost perpendicular to the surface of the molded resin. When the heat dissipation section is considered as a chord, the node at one end of the chord is the boundary of the embedding, which is bent and extended almost perpendicularly from the heat dissipation section and introduced and embedded in a position almost perpendicular to the surface of the molded resin, while the support legs are the node at the other end of the chord, which is bent and extended almost perpendicularly from the heat dissipation section and introduced and embedded in a position almost perpendicular to the surface of the molded resin. In other words, the heat dissipation section, the boundary of the embedding which is the nodes at both ends, and the support legs form a gate shape as a whole and are fixed with molded resin, which has an advantageous effect on improving vibration resistance. [Effects of the Invention]

[0014] According to the present invention, in a film capacitor, support legs are connected to the heat dissipation portion of the busbar, and these support legs are introduced and embedded in the molded resin to fix their position. This makes it possible to improve vibration resistance while avoiding thermal damage to the capacitor element. [Brief explanation of the drawing]

[0015] [Figure 1] Perspective view of the capacitor element unit in the stage before being housed in the exterior case in an embodiment of the present invention, viewed obliquely from the upper right [Figure 2] Perspective view of the film capacitor in the state where the capacitor element unit in an embodiment of the present invention is housed in the exterior case, viewed obliquely from the upper right [Figure 3] Exploded perspective view of the capacitor element unit in an embodiment of the present invention [Figure 4] Perspective view of the capacitor element unit in the stage before being housed in the exterior case in an embodiment of the present invention, viewed obliquely from the upper left [Figure 5] Perspective view of the film capacitor in the state where the capacitor element unit in an embodiment of the present invention is housed in the exterior case, viewed obliquely from the upper left [Figure 6] Enlarged perspective view of the main part in an embodiment of the present invention (state before resin filling) [Figure 7] Enlarged perspective view of the main part in an embodiment of the present invention (state after resin filling)

Mode for Carrying Out the Invention

[0016] Hereinafter, the film capacitor of the present invention having the above configuration will be described in detail at the level of specific examples with respect to its embodiments.

[0017] In FIGS. 1 to 5, reference numeral 10 denotes a capacitor element unit for a noise filter for an external device such as an inverter. This capacitor element unit 10 has a relatively small capacitance and also a small occupied space volume.

[0018] In the capacitor element unit 10, a first bus bar 12 and a second bus bar 13 are electrically and mechanically connected to upper end face electrodes 11a and lower end face electrodes 11b, respectively, at both axial ends of one capacitor element 11.

[0019] The first busbar 12 consists of an internal connection terminal portion 12a, a first connecting portion 12b, a second connecting portion 12c, and an external connection terminal portion 12d. The internal connection terminal portion 12a is flat and is electrically and mechanically connected in contact with the upper end face electrode 11a of the capacitor element 11. The first connecting portion 12b is a relatively narrow and short rectangular flat plate, bent at almost a right angle upward from the end of the internal connection terminal portion 12a, and extends by a small dimension to a position higher than the upper edge of the side wall upper edge 20a1, which is the upper edge of the outer surface 20a of the outer case 20 in the assembled state. Due to this height relationship, the second connecting portion 12c and the external connection terminal portion 12d of the first busbar 12 are located outside the case, beyond the upper edge of the side wall 20a1 of the outer case 20. The second connecting portion 12c is in an inverted L shape and extends from the upper end of the first connecting portion 12b. The second connecting portion 12c is bent so that the horizontal base portion 12c1 and the hanging portion 12c2 are at approximately a right angle. The base portion 12c1 is bent at approximately a right angle from the upper end of the first connecting portion 12b. The external connection terminal portion 12d is bent so that the base portion 12d1 and the tip portion 12d2 are at approximately a right angle, giving it an inverted L shape. The base portion 12d1 is bent at approximately a right angle from the lower end of the second connecting portion 12c. The base portion 12d1 is in an approximately horizontal position and extends horizontally outward from the side surface of the capacitor element 11. A round mounting hole 12e is formed in the tip portion 12d2 of the external connection terminal portion 12d. In this embodiment, an external connection terminal 12f is connected to an internal connection terminal 12a. The external connection terminal 12f is bent upward at approximately a right angle from a diagonal position of the first connecting portion 12b on the internal connection terminal 12a. A round mounting hole 12g is formed at the tip of the external connection terminal 12f.

[0020] The first busbar 12, consisting of the internal connection terminal portion 12a, the first connecting portion 12b, the second connecting portion 12c, and the external connection terminal portions 12d and 12g, is formed by punching out and bending a thin conductive metal sheet such as a copper plate.

[0021] The base 12c1 of the second connecting portion 12c in the first busbar 12 is horizontally extended at a position above the horizontal upper surface 30a of the molded resin 30, and further above the opening surface of the outer case 20.

[0022] The second busbar 13 consists of an internal connection terminal portion 13a, a first connecting portion 13b, a heat dissipation portion 13c, a second connecting portion 13d, and an external connection terminal portion 13e. The internal connection terminal portion 13a is electrically and mechanically connected in contact with the lower end face electrode 11b of the capacitor element 11. The first connecting portion 13b is a relatively narrow and short rectangular flat plate, bent at almost a right angle upward from the end of the internal connection terminal portion 13a, and rises along the side surface of the capacitor element 11, extending to a position higher than the upper end face electrode 11a and the internal connection terminal portion 12a of the first busbar 12.

[0023] The heat dissipation section 13c is bent at almost a right angle from the upper end of the first connecting section 13b and faces the upper end face electrode 11a of the capacitor element 11 and the internal connection terminal section 12a of the first busbar 12 in a horizontal position parallel to their upper surface. To ensure high heat dissipation, the heat dissipation section 13c has a deformed hexagonal shape (a regular hexagon slightly stretched in one direction) and has a width and length larger than the width dimension of the first connecting section 13b. The heat dissipation section 13c extends to the external connection terminal section 13e at the tip of the busbar on the outside of the outer case 20. The second connecting section 13d has a relatively narrow and short rectangular shape and is bent at almost a right angle from one side of the edge of the heat dissipation section 13c and rises down along the side surface of the capacitor element 11. The width dimension of the second connecting section 13d is approximately the same as the width dimension of the first connecting section 13b. The second connecting portion 13d also has a heat dissipation function. The plate surfaces of the first and second connecting portions 13b and 13d are both aligned with the vertical plane, but their plate surfaces are positioned almost perpendicular to each other. The lower end of the second connecting portion 13d is at approximately the same height as the lower end face electrode 11b of the capacitor element 11, and an inverted L-shaped external connection terminal portion 13e is connected to its lower end. The external connection terminal portion 13e is bent so that its base portion 13e1 and tip portion 13e2 are at approximately a right angle, and the base portion 13e1 is bent at approximately a right angle from the lower end of the second connecting portion 13d. The base portion 13e1 is in an almost horizontal position and unfolds in a direction away from the side of the capacitor element 11 in the horizontal direction outward. A round mounting hole 13f is formed in the tip portion 13e2 of the external connection terminal portion 13e. In this embodiment, another external connection terminal portion 13g is connected to the heat dissipation portion 13c. The external connection terminal portion 13g is bent upward at approximately a right angle from one side of the edge of the heat dissipation portion 13c (the side in the deformed hexagonal shape that is opposite to the bent portion for the second connecting portion 13d). A round mounting hole 13h is formed at the tip of the external connection terminal portion 13g.

[0024] Furthermore, in this embodiment, as shown in Figures 6 and 7, a support leg portion 13i is connected to the heat dissipation portion 13c of the second busbar 13, and is introduced and embedded in the molded resin 30 to fix its position. As shown in Figures 4 and 5, this support leg portion 13i is bent downward at approximately a right angle from one side of the edge of the heat dissipation portion 13c at an intermediate position between the second connecting portion 13d that descends from the heat dissipation portion 13c and the external connection terminal portion 13g that rises from the heat dissipation portion 13c, and opposite the first connecting portion 13b that descends from the heat dissipation portion 13c. In other words, it is bent vertically downward from the heat dissipation portion 13c via a partially cylindrical bent portion 13i' (whose axis is horizontal).

[0025] Figure 6 shows the state before the mold resin 30 is filled into the outer case 20, and Figure 7 shows the state after the mold resin 30 has been filled. The support leg portion 13i that hangs down from the heat dissipation portion 13c of the second busbar 13 has its lower end portion 13i1 introduced and embedded into the mold resin 30 from the horizontal upper surface 30a of the mold resin 30 and fixed in position. The dashed line L1 drawn at a predetermined height position of the support leg portion 13i in Figure 6 corresponds to the contact boundary line L2 of the support leg portion 13i with respect to the horizontal upper surface 30a of the mold resin 30 in Figure 7.

[0026] The lower end portion 13i1 of the support leg 13i, below the dashed line L1, is embedded in the molded resin 30 to a predetermined thickness and firmly fixed.

[0027] The support leg 13i is provided in close proximity to the outer surface of the capacitor element 11, but spaced apart from it. Because of this spaced-away arrangement, the lower end portion 13i1 of the support leg 13i, including the gap between the outer surface of the capacitor element 11 and the support leg 13i, is embedded in the molded resin 30 and firmly fixed.

[0028] The second busbar 13, which consists of the internal connection terminal portion 13a, the first connecting portion 13b, the heat dissipation portion 13c, the second connecting portion 13d, the external connection terminal portions 13e and 13g, and the support leg portion 13i, is formed by punching out and bending a thin conductive metal sheet such as a copper plate.

[0029] The heat dissipation portion 13c of the second busbar 13 is exposed at a position above the horizontal upper surface 30a of the molded resin 30, and further extends horizontally at a position above the opening surface of the outer case 20. Due to this height relationship, the second connecting portion 12c and the second connecting portion 13d of the second busbar 13 can be positioned outside the case by crossing over the upper edge 20a1 of the side wall of the outer case 20.

[0030] The inverted L-shaped external connection terminal portion 13e of the second busbar 13 is connected to and fixed to a crimp terminal (not shown) at the end of a cable extending from an external device such as an in-vehicle inverter by a screw that is screwed in through a mounting hole 13f.

[0031] We consider the first busbar 12, which extends from the part embedded in the molded resin 30 to the outside of the molded resin 30, as the starting point. The length dimension of the heat dissipation section 13c is the length dimension from the embedding boundary to the external connection terminal section 13e. Increasing the length dimension of the heat dissipation section 13c (area of ​​the heat dissipation surface) to promote heat dissipation will increase the diffusion effect of heat conducted from the capacitor element 11 to the heat dissipation section 13c. As a result, the accumulation and increase of heat generated from the capacitor element 11 within the molded resin 30 will be suppressed, and thermal damage to the capacitor element 11 will be effectively avoided.

[0032] In addition, the support legs 13i are connected to the heat dissipation section 13c, and the support legs 13i are introduced and embedded in the molded resin 30 to fix their position. As a result, the middle portion of the heat dissipation section 13c is fixed and acts as a resistance section against vibration. This ensures that the effect of avoiding thermal damage to the capacitor element 11 is maintained while also enhancing vibration resistance.

[0033] Let's consider the vibrations occurring in the heat dissipation section 13c by replacing them with the vibrations of a string. Now, let's assume that the heat dissipation section 13c is not connected to the support legs 13i (equivalent to the conventional example). The vibrating member is the heat dissipation section 13c without the support legs 13i, and the length L of the string in the vibrating member is the total length of the heat dissipation section 13c. Generally, the relationship between the natural frequency fn and the length L of the string is such that the longer the length L of the string (i.e., the longer the heat dissipation section 13c), the lower the natural frequency fn becomes. When the frequency of unspecified vibrations propagating from the outside to the equipment and devices on which the film capacitor is mounted approaches and synchronizes with the natural frequency fn of the heat dissipation section 13c, the heat dissipation section 13c vibrates significantly (resonance).

[0034] In other words, if the heat dissipation section 13c is widely extended outside the outer case 20 (by increasing the length of the heat dissipation section 13c), the heat dissipation area increases, making it possible to effectively avoid thermal damage to the film capacitor. However, on the other hand, due to the increased length, the heat dissipation section 13c is more susceptible to mechanical damage such as abnormal deformation, cracking, and fracture due to resonance with external vibrations. In other words, this creates a problem with the vibration resistance of the film capacitor. Conversely, if the length of the heat dissipation section 13c is shortened (the area of ​​the heat dissipation section 13c extended outside the outer case 20 is reduced) in an inversely proportional relationship to lowering the probability of resonance with external vibrations and ensuring vibration resistance, the risk of thermal damage to the film capacitor increases.

[0035] In other words, there is a trade-off between suppressing thermal damage and enhancing vibration resistance.

[0036] In contrast, in this embodiment, the support legs 13i are connected to the heat dissipation section 13c, and the support legs 13i are introduced and embedded in the molded resin 30 to fix their position. As a result, the length dimension of the portion corresponding to the antinode of the chord between the embedded boundary corresponding to one node of the chord and the support leg 13i corresponding to the other node is shortened compared to the total length dimension of the heat dissipation section 13c when the support legs 13i are not present. The natural frequency fn changes inversely proportional to this shortened length dimension and increases, so the probability of resonance with unspecified vibrations propagating from the outside is suppressed, and as a result, mechanical damage can be suppressed. In other words, the above-mentioned trade-off can be resolved, and both thermal damage suppression and vibration resistance can be improved.

[0037] The heat dissipation section 13c extends along the surface 30a of the molded resin 30, spaced apart from the surface 30a at a predetermined interval, thereby expanding the heat dissipation surface while making the film capacitor more compact.

[0038] The support legs 13i, which are bent and extended almost vertically from the heat dissipation section 13c, are introduced and embedded in the surface 30a of the molded resin 30 in an almost vertical position. The heat dissipation section 13c, the first connecting section 13b, and the support legs 13i as a whole form a gate shape and are fixed with the molded resin 30, and the support legs 13i and the second connecting section 13d also form a gate shape as a whole and are fixed with the molded resin 30, which is advantageous in improving vibration resistance.

[0039] In the above embodiment, the support leg 13i is embedded in a vertical position relative to the surface 30a of the molded resin 30, but the invention is not limited to this, and may be embedded from an oblique direction relative to the surface 30a of the molded resin 30. Furthermore, in the above embodiment, the support leg 13i is embedded linearly inside the molded resin 30, but the present invention is not limited to this, and the support leg 13i may be bent inside the molded resin 30. For example, the tip of the support leg 13i may be bent horizontally to form an inverted L-shape in cross-section. Also, the direction of bending of the tip of the support leg 13i may be in a direction away from the heat dissipation part 13c or in a direction closer to the heat dissipation part 13c. By bending the support leg 13i inside the molded resin 30, vibration resistance can be further improved. [Industrial applicability]

[0040] The present invention is useful as a technology that can improve vibration resistance while avoiding thermal damage to the capacitor element in film capacitors. [Explanation of symbols]

[0041] 10 Capacitor element unit 11 Capacitor element 11a Upper end electrode 11b Lower end electrode 12 First bus bar 13. Second bus bar 13c Heat dissipation part 13e External connection terminal section 13i Support legs 20 outer cases 20a Outer surface of the outer case 30 mold resin 30a horizontal upper surface

Claims

1. A capacitor element unit in which busbars are connected to the end face electrodes at both ends of the axial direction of the capacitor element, An outer case with an opening for housing the main part of the capacitor element unit, The capacitor element unit comprises a molded resin that is filled into the outer case and solidified, covering the main part of the capacitor element unit. Each of the pair of busbars has a plurality of external connection terminals on the outside of the outer casing, In at least one of the pair of busbars, the portion connecting at least two of the plurality of external connection terminals is exposed to the outside of the molded resin and has a heat dissipation portion that extends to the plurality of external connection terminals for heat dissipation. A film capacitor characterized in that the heat dissipation section is connected to a support leg that is introduced and embedded within the molded resin and fixed in position.

2. The film capacitor according to claim 1, wherein the heat dissipation portion extends along the surface of the molded resin at a predetermined distance from the surface of the molded resin.

3. The film capacitor according to claim 1 or claim 2, wherein the support legs are bent and extended substantially vertically from the heat dissipation portion and are introduced and embedded in a substantially perpendicular position relative to the surface of the molded resin.

Images