Capacitor

Abstract

To provide a capacitor capable of realizing a low ESL as well as suppressing a fetching of water into the capacitor.SOLUTION: A first bus bar 3 comprises: a first substrate part 31 that is connected to a first electrode surface 21 in a resin 6; and a first connection part 32 that is extended to the outside of the resin 6 from the first substrate part 31. A second bus bar 4 comprises: a second substrate part 41 that is connected to a second electrode surface 22 in the resin 6, and is closely opposite to the first substrate part 31; and a second connection part 42 that is extended to the outside of the resin 6 from the second substrate part 41. A first insulation member 7 is interposed in the resin 6 between the first substrate part 31 and the second substrate part 41. A second insulation member 8 is interposed from the inner side of the resin 6 to the outer side of the resin 6 between the first connection part 32 and the second connection part 42. The second insulation member 8 is larger in thickness and lower in hygroscopic property than the first insulation member 7, and is overlapped with the first insulation member 7 in the resin 6.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to a capacitor in which an insulating member is provided from inside the resin to outside the resin.

Background Art

[0002] In order to provide insulation between positive and negative busbars or between a busbar and an electrode portion of a capacitor element, for example, insulating paper may be interposed as shown in FIG. 4 of Patent Document 1. Also, an insulating plate made of resin or the like may be used instead of the insulating paper, or both the insulating paper and the insulating plate may be used as in Patent Document 2.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, since no insulating paper is interposed between the external terminals, it is difficult to arrange the external terminals close to each other. If an attempt is made to interpose insulating paper between the external terminals and expose the insulating paper outside the resin, the insulating paper has high hygroscopicity, so there is a possibility that moisture will be taken into the capacitor from there.

[0005] Although it is conceivable to use an insulating plate instead of the insulating paper, since the insulating plate is thicker than the insulating paper, the effect of reducing ESL (equivalent series inductance) generated by bringing the different-pole members closer to each other may be diminished.

[0006] In Patent Document 2, the insulating paper and the insulating plate are provided separately from each other, and the continuity between the insulating paper and the insulating plate is not considered.

[0007] An object of the present invention is to provide a capacitor that can suppress the intake of moisture into the capacitor and achieve a reduction in ESL.

Means for Solving the Problems

[0008] The capacitor of the present invention is a capacitor in which a capacitor element 2 having a first electrode surface 21 and a second electrode surface 22, a first bus bar 3 connected to the first electrode surface 21, and a second bus bar 4 connected to the second electrode surface 22 are housed in a case 5 and filled with a resin 6. The first bus bar 3 includes a first substrate portion 31 connected to the first electrode surface 21 within the resin 6 and a first connection portion 32 extending from the first substrate portion 31 outside the resin 6. The second bus bar 4 includes a second substrate portion 41 connected to the second electrode surface 22 within the resin 6 and facing the first substrate portion 31 in proximity, and a second connection portion 42 extending from the second substrate portion 41 outside the resin 6. A first insulating member 7 is interposed between the first substrate portion 31 and the second substrate portion 41 within the resin 6, and a second insulating member 8 is interposed between the first connection portion 32 and the second connection portion 42 from within the resin 6 to outside the resin 6. The second insulating member 8 is thicker than the first insulating member 7, has a lower hygroscopicity, and overlaps with the first insulating member 7 within the resin 6.

[0009] In the above capacitor, it is preferable that a step 46 for bringing the first substrate portion 31 and the second substrate portion 41 closer is provided at a location where the first insulating member 7 is interposed and the second insulating member 8 is not interposed among the portions where the first substrate portion 31 and the second substrate portion 41 are in proximity and facing each other.

Effects of the Invention

[0010] In the capacitor of the present invention, a second insulating member with low hygroscopicity is interposed between the first connection portion and the second connection portion from inside the resin to outside the resin. Therefore, it is not necessary to expose the first insulating member outside the resin to ensure insulation between the first connection portion and the second connection portion, and it is possible to suppress the intake of moisture into the capacitor through the first insulating member. Further, since the first insulating member is interposed between the first substrate portion and the second substrate portion, it is not necessary to interpose the second insulating member over the entire portion where the first substrate portion and the second substrate portion are close to and face each other. In the portion where only the first insulating member is provided, the first substrate portion and the second substrate portion can be brought close to each other, and the ESL can be reduced. Furthermore, since the second insulating member overlaps the first insulating member within the resin, it is possible to provide insulation without interruption from inside the resin to outside the resin despite using two insulating members.

[0011] Also, when a step is provided to bring the first substrate portion and the second substrate portion closer to each other at a location where the first insulating member is interposed and the second insulating member is not interposed among the portions where the first substrate portion and the second substrate portion are close to and face each other, further reduction of the ESL can be achieved.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0013] Next, an embodiment of the capacitor of the present invention will be described in detail with reference to the drawings. As shown in FIGS. 1 and 2, the capacitor 1 of the present invention includes a capacitor element 2, a first bus bar 3, a second bus bar 4, a first insulating member 7, a second insulating member 8, a case 5 that houses these components, and a resin 6 filled in the case 5. Hereinafter, each of the above components will be described. The concept of "up and down" is defined during manufacturing, more specifically during resin filling, and does not necessarily define the up and down during use.

[0014] The capacitor element 2 is, for example, a film capacitor formed by winding a metallized film obtained by vapor-depositing a metal on an insulating film. As shown in FIGS. 1 and 2, a first electrode surface 21 is provided on one end surface in the axial direction, and a second electrode surface 22 is provided on the other end surface. These electrode surfaces are formed, for example, by spraying a metal. When viewed from the axial direction, the capacitor element 2 has a rice-bag shape. Specifically, R (round) is provided at four corner portions, and has a side surface 23 composed of a flat portion 23a and a curved portion 23b between the first electrode surface 21 and the second electrode surface 22 (peripheral surface). A plurality of, specifically four, capacitor elements 2 are arranged in two rows and two columns such that the first electrode surface 21 faces upward, the second electrode surface 22 faces downward, and the flat portions 23a face each other, thereby forming a capacitor element group. Note that the capacitor element 2 is not limited to a film capacitor, and various capacitor elements such as an electrolytic capacitor and a ceramic capacitor may be used. Various shapes such as a cylindrical shape and a prismatic shape may be adopted for the shape. The number can also be appropriately changed.

[0015] The first bus bar 3 is formed by cutting out a conductive metal plate such as aluminum or copper into a predetermined shape and performing appropriate bending processing. The first bus bar 3 includes a first substrate portion 31 that overlaps (contacts) the first electrode surface 21, and a first connection portion 32 that rises from the first substrate portion 31 and is used for connection to an external device (not shown).

[0016] As shown in FIG. 1, the first substrate portion 31 is substantially T-shaped in plan view and overlaps with the first electrode surfaces 21 of all the capacitor elements 2. Specifically, an extension portion 31a corresponding to the first stroke (vertical) of the "T" is located substantially at the center in the longitudinal direction of the capacitor element group in plan view and overlaps with the first electrode surfaces 21 of two capacitor elements 2. A base portion 31b corresponding to the second stroke (horizontal) of the "T" is provided substantially parallel to the longitudinal direction of the capacitor element group and overlaps with the first electrode surfaces 21 of four capacitor elements 2. A tongue-shaped connection portion 33 for connecting to the first electrode surface 21 is provided from the outer edge of the first substrate portion 31.

[0017] The first connection portion 32 extends on the first electrode surface 21. Further, it extends from the outer edge on the extension portion 31a side among the outer edges of the base portion 31b. Therefore, the first bus bar 3 is substantially inverted T-shaped in side view.

[0018] The second bus bar 4 is formed by cutting out a conductive metal plate such as aluminum or copper into a predetermined shape and appropriately bending it, and includes a second substrate portion 41 that overlaps with the second electrode surface 22, and a second connection portion 42 that rises from the second substrate portion 41 and is used for connection to an external device (not shown).

[0019] As shown in FIGS. 1 and 2, the second substrate portion 41 includes a lower horizontal portion 41a that overlaps (contacts) the second electrode surface 22 from below, a vertical portion 41b that extends upward from one side of the lower horizontal portion 41a and is close to and faces the side surface 23 of the capacitor element 2, and an upper horizontal portion 41c that extends laterally from one side of the vertical portion 41b toward the first electrode surface 21 and is close to and faces the first electrode surface 21 and the first substrate portion 31 from above. Therefore, the cross-sectional shape of the second substrate portion 41 is substantially U-shaped and covers the periphery of the capacitor element 2.

[0020] The planar shape of the lower horizontal portion 41a is substantially rectangular and overlaps with the second electrode surfaces 22 of all the capacitor elements 2. This lower horizontal portion 41a faces the bottom portion 51 of the case 5 described later. Further, a tongue-shaped connecting portion 43 for connecting to the second electrode surface 22 is provided on the lower horizontal portion 41a. As shown in FIG. 2, the vertical portion 41b also faces the side wall portion 52 of the case 5 described later in a closely opposed manner. The upper horizontal portion 41c faces the first electrode surfaces 21 of all the capacitor elements 2 in a closely opposed manner. Note that a first substrate portion 31 is interposed between the upper horizontal portion 41c and the first electrode surface 21. Accordingly, the upper horizontal portion 41c also faces the first substrate portion 31 in a closely opposed manner. Further, a step 46 is provided on the upper horizontal portion 41c to be closer to the first substrate portion 31, and the upper horizontal portion 41c is partitioned into an upper stage portion 46a and a lower stage portion 46b with the step 46 as a boundary. Note that the upper stage portion 46a is located on the side of the second connecting portion 42, and the lower stage portion 46b is located on the side of the vertical portion 41b. Further, a hole 44 or a notch 45 for exposing the connecting portion 33 of the first substrate portion 31 upward is provided in a portion of the upper horizontal portion 41c that faces the connecting portion 33 of the first substrate portion 31 in a closely opposed manner.

[0021] The second connecting portion 42 extends from a portion where the extending portion 31a of the first substrate portion 31 and the upper stage portion 46a of the upper horizontal portion 41c of the second substrate portion 41 face each other closely on the first electrode surface 21. Further, it rises in the same direction as the first connecting portion 32. This second connecting portion 42 does not face the first connecting portion 32 and is arranged in a direction orthogonal to the plate thickness direction with the first connecting portion 32. A rising portion 47 extending substantially parallel to the first connecting portion 32 is provided at a portion of the outer edge of the upper stage portion 46a that faces the first connecting portion 32. This rising portion does not protrude from the resin 6 and is embedded in the resin 6.

[0022] The first insulating member 7 is insulating paper or insulating cloth, is fibrous, and has flexibility. Specifically, it is made of plant or resin fibers, or is impregnated with oil or resin in the fibers, and has higher hygroscopicity than a liquid resin formed into a sheet or plate shape. Further, it may have continuous voids between the fibers and have higher air permeability than a liquid resin formed into a sheet or plate shape. The thickness is, for example, 0.1 to 1 mm.

[0023] This first insulating member 7 is interposed between the side surface 23 of the capacitor element 2 and the vertical portion 41b of the second bus bar 4, and between the first electrode surface 21 and the upper horizontal portion 41c in order to insulate the first electrode surface 21 of the capacitor element 2 from the second bus bar 4, as shown in FIG. 2. Preferably, its size is larger than that of the upper horizontal portion 41c in plan view. Holes 71 and notches 72 are also provided at positions facing the holes 44 and notches 45 of the first bus bar (see FIG. 1). Further, in a portion where the upper horizontal portion 41c and the first substrate portion 31 of the first bus bar 3 are in close proximity and opposed to each other, it is interposed therebetween in order to insulate the two. Note that it is not interposed between the first substrate portion 31 and the first electrode surface 21. Further, the first insulating member 7 does not face the second connection portion 42 or the rising portion 47 and is not exposed outside the resin 6.

[0024] The second insulating member 8 is an insulating plate. The insulating plate is, for example, formed by molding a liquid resin into a plate shape and has a hardness such that it does not deform under its own weight. Further, it has no continuous voids inside and does not have water permeability. Its hygroscopicity is lower than that of the first insulating member 7. The type of the resin is a thermoplastic resin, for example, polyphenylene sulfide (PPS). Its thickness is thicker than that of the first insulating member 7 and is, for example, 0.5 to 2 mm.

[0025] As shown in FIGS. 1 and 2, this second insulating member 8 has a substantially L-shaped side view composed of a vertical portion 81 and a horizontal portion 82 extending laterally from the lower end of the vertical portion 81. The vertical portion 81 is interposed between the first connection portion 32 and the second connection portion 42 from within the resin 6 to outside the resin 6. Specifically, the vertical portion 81 is bent in a substantially Z shape in plan view, and a bent portion 81a is located between the first connection portion 32 and the second connection portion 42 arranged in a direction orthogonal to the plate thickness direction (see FIG. 3). Among the vertical portion 81, the portion facing the first connection portion 32 is located between the first connection portion 32 and the rising portion 47. The portion facing the second connection portion 42 ensures insulation between the second connection portion 42 and the first electrode surface 21, and between the second connection portion 42 and the extending portion 31a. The horizontal portion 82 is smaller than the first substrate portion 31 and the upper horizontal portion 41c of the first bus bar 3 in plan view, and is mainly interposed between the base portion 31b of the first substrate portion 31 and the upper stage portion 46a of the upper horizontal portion 41c, and overlaps a part of the first insulating member 7. The overlapping margin is, for example, 3 to 6 mm. It is preferably larger than the thickness of the second insulating member 8. Also, in plan view, the overlapping width in the direction orthogonal to the overlapping margin is larger than the widths of the first substrate portion 31 and the upper stage portion 46a. Note that the second insulating member 8 is not interposed between the extending portion 31b and the lower stage portion 46b. The step 46 of the second bus bar 4 is provided at a location where the first insulating member 7 is interposed and the second insulating member 8 is not interposed. Note that in the lower stage portion 46b, the first insulating member 7 ensures insulation from the first bus bar 3 and the first electrode surface 21.

[0026] As shown in FIG. 1, the case 5 includes a bottom portion 51 having a substantially rectangular shape in plan view and side wall portions 52 rising upward from the four sides of the bottom portion 51. An opening 53 is provided above the case 5, and the capacitor element 2, the first bus bar 3, and the second bus bar 4 are accommodated in the case 5 through this opening 53. Also, the first connection portion 32 and the second connection portion 42 extend out of the case 5 from this opening 53. This case 5 is made of a non-conductive material such as synthetic resin, for example. However, a metal case may also be used.

[0027] The resin 6 filled in the case 5 is, for example, an epoxy resin. However, it is not limited to this, and various known resins such as urethane resins can be used, but it is preferable to employ a resin with excellent moisture resistance or a resin with high thermal conductivity. The resin 6 is filled so as to cover the first substrate portion 31 and the second substrate portion 41 in addition to the capacitor element 2. Note that the upper portions of the first connection portion 32 and the second connection portion 42 protrude outside the resin 6. The resin thickness (the distance from the resin surface to the capacitor element 2) is appropriately changed according to the type and characteristics of the resin used.

[0028] Next, the assembly of the capacitor 1 will be described. First, the first substrate portion 31 of the first bus bar 3 is overlapped with the first electrode surface 21 of the capacitor element 2 and connected by soldering or the like. Subsequently, the vertical portion 81 and the horizontal portion 82 of the second insulating member 8 are respectively overlapped with the upper stage portion 46a of the first bus bar 3 and the first connection portion 32. Also, the first insulating member 7 is overlapped with the horizontal portion 82 of the second insulating member 8, the first electrode surface 21, and the side surface 23 of the capacitor element 2.

[0029] Then, the capacitor element 2 and the first substrate portion 31 are placed inside the second bus bar 4 having a substantially U-shaped cross section, and the lower horizontal portion 41a of the second substrate portion 41 is overlapped with the second electrode surface 22 of the capacitor element 2 and connected by soldering or the like to form a capacitor module. In this state, the upper horizontal portion 41c of the second substrate portion 41 is close to and faces the first electrode surface 21 via the first substrate portion 31. Also, the first connection portion 32 and the second connection portion 42 protrude in the same direction.

[0030] Subsequently, the capacitor module is accommodated in the case 5 from the upper opening 53. At this time, the first connection portion 32 and the second connection portion 42 are placed upward so that the first connection portion and the second connection portion extend outside the case 5 from the opening 53 (see FIG. 3). Also, the vertical portion 41b of the second bus bar 4 is close to and faces the side wall portion 52 of the case 5. Then, the case 5 is filled with the resin 6 to seal the capacitor element 2, thereby completing the manufacture of the capacitor. Note that in a state where the filling of the resin 6 is completed, the vicinity of the upper end portion of the vertical portion 81 of the second insulating member 8 is exposed outside the resin 6, but the first insulating member 7 is not exposed outside the resin 6.

[0031] In the capacitor 1 configured as described above, since the second insulating member 8 with low hygroscopicity is used as the insulating member extending outside the resin 6, the ingress of moisture into the capacitor 1 can be suppressed compared to the case where insulating paper with high hygroscopicity is used, and the degradation of the insulation performance and breakdown voltage performance of the capacitor element 2 can be suppressed. The above configuration is particularly effective when the electrode surface of the film capacitor, which generally has a property of being easily hygroscopic, is directed toward the opening 53 (resin surface) of the case 5 as shown in FIG. 2 and the distance from the outside air is short.

[0032] FIG. 4 is a graph showing the difference in leakage current when an insulating plate and insulating paper are used as the insulating member extending outside the resin. The number of tests is 3 for each of the insulating plate and insulating paper, and the graph represents the average value. The test conditions were a temperature and humidity of 85°C / 85% and a voltage of 420 VDC. As shown in the graph, it can be seen that the leakage current after a predetermined time is smaller for the one using the insulating board (dashed line) than for the one using the insulating paper (solid line).

[0033] Also, inside the resin 6, the first insulating member 7, which is mainly thinner than the second insulating member 8, is used. In addition, since a step 46 for bringing the first bus bar 3 and the second bus bar 4 closer is provided, the base portion 31b of the first bus bar 3 and the lower portion 46b of the second bus bar 4 can be brought closer, and the capacitor 1 can be miniaturized and its ESL can be reduced. Also, since the first insulating member 7 and the second insulating member 8 are partially overlapped, the continuity of insulation can be maintained. Also, if the first insulating member 7 is fixed to the second insulating member 8 using the overlapping margin, the effect of preventing the displacement of the first insulating member 7 can also be obtained. As the fixing method, various methods such as double-sided tape, adhesive, and crimping can be adopted. Regarding the second insulating member 8, it is fixed by the bent portion 81a being sandwiched between the first connection portion 32 and the second connection portion 42, or the horizontal portion 82 being sandwiched between the first substrate portion 31 and the upper horizontal portion 41c.

[0034] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made and implemented within the scope of the present invention. For example, in the above embodiment, the step 46 is provided on the second bus bar 4, but it may be provided on the first bus bar 3, or may be provided on both the first bus bar 3 and the second bus bar 4. Further, although the first insulating member 7 is overlapped on the horizontal portion 82 of the second insulating member 8, it may be overlapped below. Further, although the first electrode surface 21 of the capacitor element 2 is directed upward, it may be directed sideways.

Explanation of Signs

[0035] 1 Capacitor 2 Capacitor element 21 First electrode surface 22 Second electrode surface 23 Side surface 23a Flat portion 23b Curved portion 3 First bus bar 31 First substrate portion 31a Extension portion 31b Base portion 32 First connection portion 33 Connection portion 4 Second bus bar 41 Second substrate portion 41a Lower horizontal portion 41b Vertical portion 41c Upper horizontal portion 42 Second connection portion 43 Connection portion 44 Hole 45 Notch 46 Step 46a Upper stage portion 46b Lower stage portion 47 Rising portion 5 Case 51 Bottom portion 52 Side wall portion 53 Opening 6 Resin 7 First insulating member 71 Hole 72 Notch 8 Second insulating member 81 Vertical portion 81a Bent portion 82 Horizontal portion

Claims

1. A capacitor comprising a capacitor element having a first electrode surface and a second electrode surface, a first bus bar connected to the first electrode surface, and a second bus bar connected to the second electrode surface, which are housed in a case and filled with resin, The first bus bar includes a first substrate portion connected to the first electrode surface within the resin and a first connection portion extending from the first substrate portion outside the resin, The second bus bar includes a second substrate portion connected to the second electrode surface within the resin and facing the first substrate portion in proximity, and a second connection portion extending from the second substrate portion outside the resin, A first insulating member is interposed between the first substrate portion and the second substrate portion within the resin, A second insulating member is interposed between the first connection portion and the second connection portion from within the resin to outside the resin, The second insulating member is thicker than the first insulating member, has low hygroscopicity, and overlaps with the first insulating member within the resin. A capacitor characterized by this.

2. The capacitor according to claim 1, wherein a step for bringing the first substrate portion and the second substrate portion closer together is provided at a location where the first insulating member is interposed and the second insulating member is not interposed among the portions where the first substrate portion and the second substrate portion face each other in proximity.

Images