JP7675330B2 - Capacitor - Google Patents

Description

The present invention relates to a capacitor, and more specifically, to a capacitor with reduced inductance.

In addition to capacitance, capacitors also have resistance and inductance components, and since both resistance and inductance reduce the performance of a capacitor, capacitors are generally designed to have small values.

Patent document 1 describes a capacitor that reduces the equivalent direct current inductance (ESL) by stacking two bus bars and insulating them with an insulating sheet sandwiched between them, thereby reducing the gap between the two bus bars.

The holding body that holds the ends of the two overlapping bus bars prevents misalignment between the bus bars and the insulating sheet and increases the area where the two bus bars overlap, further reducing the ESL.

Patent Publication No. 6575869

However, in the capacitor described in Patent Document 1, the overlapping portion of the two bus bars is not fixed to the case. In an environment where repeated vibrations are input, such as a power supply unit for a vehicle, the overlapping portion of the bus bars vibrates, easily causing the bus bars and the insulating sheet to become misaligned, and the insulation reliability decreases. As a result, it is difficult to increase the area of the overlapping portion of the two bus bars.

The present invention was made in consideration of the problems inherent in the prior art, and its purpose is to provide a capacitor that has high insulation reliability and can reduce inductance even in an environment where repeated vibrations are input.

As a result of extensive research into achieving the above object, the inventors discovered that the above object could be achieved by providing a through hole in the laminated portion in which two bus bars are overlapped with an insulating sheet sandwiched therebetween, and by using an insulating fixing member to fix the laminated portion to a resin case through the through hole, thereby completing the present invention.

That is, the capacitor of the present invention comprises a capacitor element housed in a resin case, and two bus bars connected to the capacitor element.
The laminated portion has an insulating sheet sandwiched between the two bus bars, the laminated portion has a through hole in the stacking direction, and a fixing member passes through the through hole and fixes the laminated portion to the resin case, and at least the portion of the fixing member that comes into contact with the bus bar is insulating.

According to the present invention, a through hole is provided in the laminated portion where two bus bars overlap with an insulating sheet sandwiched between them, and the bus bars are fixed to the resin case through this through hole with an insulating fixing member, thereby providing a capacitor that has high insulation reliability even in an environment where repeated vibrations are input, and can reduce inductance.

FIG. 1 is an exploded perspective view showing an example of a capacitor of the present invention. FIG. 2 is a cross-sectional view showing an example of a capacitor of the present invention taken along the line A-A' in FIG. FIG. 2 is a cross-sectional view showing another example of the capacitor of the present invention taken along the line A-A' in FIG. FIG. 2 is a cross-sectional view showing still another example of the capacitor of the present invention taken along the line A-A' in FIG.

The capacitor of the present invention will now be described in detail.
As shown in FIG. 1, the capacitor of the present invention comprises a capacitor element (1), a resin case (2) that houses the capacitor element, and two bus bars (3a, 3b) connected to the capacitor element.

The capacitor element (1) shown in FIG. 1 has electrodes (11) on the upper and lower surfaces.
One bus bar (3a), for example a P bus bar, is connected to the electrode on the lower surface of the capacitor element, and the other bus bar (3b), for example an N bus bar, is connected to the electrode on the upper surface.

One bus bar (3a) connected to the underside of the capacitor element wraps around the capacitor element (1) and the other bus bar (3b) and extends above the other bus bar (3b) along the inner wall of the resin case (2).

In FIG. 1, for convenience, one bus bar (3a) is shown divided into the lower side of the capacitor element (1) and the upper side of the other bus bar (3b); however, as shown in FIG. 2, it is continuous from the lower side of the capacitor element (1) to the upper side of the other bus bar (3b).
Additionally, the electrodes (11) of the capacitor element (1) may be located on the side surfaces.

The portion of one busbar (3a) that protrudes above the other busbar (3b) overlaps with the other busbar (3b) to form a laminated section (31), and an insulating sheet (4) is provided between the one busbar (3a) and the other busbar (3b) of the laminated section to provide insulation between them.

In this laminated section (31), one bus bar (3a) and the other bus bar (3b) are the same size and overlap perfectly to maintain symmetry, reducing the equivalent DC inductance (ESL).

There are no particular limitations on the insulating sheet (4) as long as it can prevent a short circuit between the two bus bars, but for example, a resin sheet or insulating paper can be used.

In addition, the other bus bar (3b) of the laminated portion (31) abuts against the edge of the resin case (2) and covers at least a portion of the opening of the resin case (2).

In this way, since the laminated portion (31) is disposed on the opening surface of the resin case (2), even if the area of the laminated portion (31) is increased to the same extent as the opening surface of the resin case (2), there is no effect on the overall size of the capacitor, and it is possible to achieve both reduced ESL and miniaturization.

In addition, the laminated portion (31) has a through hole (32) at a location corresponding to the edge of the resin case (2), and a fixing member (5) passes through the through hole (32) to fix the laminated portion (31) to the resin case (2).

In the capacitor of the present invention, the laminated portion (31) covers the opening of the resin case (2) and can be fixed to the edge of the resin case (2), so even if vibration is input, the laminated portion (31) does not vibrate independently.

In addition, since the fixing member (5) passes through the through hole (32) of the laminated portion (31), no misalignment occurs between the two bus bars or between the two bus bars (3a, 3b) and the insulating sheet (4), thereby improving insulation reliability.
In FIG. 1, the laminated portion (31) is fixed at four points, but vibration of the laminated portion (31) can be suppressed if it is fixed at three or more points.

In addition, since the fixing member (5) has insulating properties at least in the area in contact with the bus bars (3a, 3b), the two bus bars (3a, 3b) are prevented from being short-circuited via the fixing member (5).

It is preferable that the inner peripheral surface of the through hole (32) is flush with the two bus bars (3a, 3b).
Since the inner circumferential surface is flush and the two bus bars (3a, 3b) are not misaligned, the projected areas of the two bus bars (3a, 3b) are the same at the fixed portion, thereby reducing the equivalent DC inductance (ESL).

Next, we will explain how to fix the laminated portion (31) to the resin case (2) using the fixing member (5).

The fixing member (5) may be, for example, a screw, a rivet, or an adhesive. However, metal screws and rivets are preferably used because they provide a large fastening force and can firmly fix the laminated portion (31) to the resin case (2).

When the fixing member (5) is made of an insulating material such as resin, as shown in FIG. 2, even if the fixing member (5) is passed directly through the through hole (32), a short circuit does not occur through the fixing member (5). Therefore, for example, a resin screw can be screwed into the resin case to fix the fixing member (5).

When fixing with adhesive, the adhesive can be poured into the through hole (32) to fix it to the resin case (2).

If the fixing member (5) is a metal screw or rivet, the two bus bars (3a, 3b) will be short-circuited via the fixing member (5), so an insulating fixing plate (51) is used to prevent the screws or rivets from coming into direct contact with the bus bars.

The insulating fixing plate (51) may be a flat or hat-shaped fixing plate having a through hole (52), and the insulating fixing plate (51) may be made of, for example, resin or ceramic.

When using a flat fixing plate, as shown in FIG. 3, the through hole (52) of the insulating fixing plate (51) is aligned with the through hole (32) of the laminated section (31) and the insulating fixing plate (51) is abutted against the surface of the laminated section (31), the shafts of screws or rivets are passed through these through holes (32, 52), and the seat of the screw or rivet is pressed against the laminated section (31) via the insulating fixing plate (51) to fix it to the eaves (21) provided on the edge of the resin case (2).

At this time, if there is a gap between the axis of the screw or rivet and the inner surface of the through hole (32) of the laminated portion (31) and the axis and the inner surface of the through hole (32) are not in contact with each other, a short circuit between the two bus bars (3a, 3b) can be prevented, but it is preferable to provide a guide portion (22) on the eaves (21) of the resin case (2) that protrudes toward the laminated portion (31).

By fitting the through hole (32) of the laminated portion (31) into the guide portion (22), not only can a short circuit between the two bus bars (3a, 3b) be prevented, but also the bus bars (3a, 3b) of the laminated portion (31) and the insulating sheet (4) can be prevented from shifting.

When using a fixing plate with a hat-shaped cross section, as shown in FIG. 4, the hat-shaped crown portion (53), i.e., the portion forming the recess in FIG. 4, is inserted into the through hole (32) of the laminated portion (31), and the hat-shaped brim portion (54) is brought into contact with the surface of the laminated portion (31).

Then, the shaft of a screw or rivet is passed through the through hole (52) in the crown portion, and the seat is brought into contact with the crown portion (53) to fix the laminated portion (31) to the eaves (21) attached to the edge of the resin case (2).

The guide portion (22) is not necessarily required for the fixing plate with a hat-shaped cross section because the crown portion (53) fits into the through hole (32) of the laminated portion (31) and can prevent a short circuit between the axis of the screw or rivet and the bus bar (3a, 3b). However, providing the guide portion (22) as in Figure 3 makes positioning easier.

In addition, by using a fixing plate with a hat-shaped cross section, the heads of the screws and rivets fit inside the crown portion (53), making it possible to reduce the overall height of the capacitor and thus make it more compact.

The capacitor of the present invention can be suitably used as a smoothing capacitor for a power conversion device by connecting one end of the laminated portion, for example, the front side of the paper in Figures 2 to 4, to a battery, and connecting the other end of the laminated portion, for example, the rear side of the paper in Figures 2 to 4, to a power module.

REFERENCE SIGNS LIST 1 capacitor element 11 electrode 2 resin case 21 eaves 22 guide portion 3 bus bar 31 laminated portion 32 through hole 4 insulating sheet 5 fixing member 51 insulating fixing plate 52 through hole 53 crown portion 54 flange portion

Claims (4)

A capacitor element accommodated in a resin case;
and two bus bars connected to the capacitor element,
a laminated portion in which the two bus bars are overlapped with an insulating sheet sandwiched therebetween;
The laminated portion has a through hole in the lamination direction,
a fixing member that passes through the through hole and fixes the laminated portion to the resin case,
A capacitor, wherein at least a portion of the fixing member that comes into contact with the bus bar has insulating properties. The capacitor according to claim 1, characterized in that the inner circumferential surface of the through hole formed in the laminated portion is flush. The fixing member includes a screw and/or a rivet and an insulating fixing plate,
the screws and/or rivets are electrically conductive;
3. The capacitor according to claim 1, wherein the seating surface of the screw and/or rivet abuts against the surface of the laminated portion via the insulating fixing plate, and the axis of the screw and/or rivet is not in contact with the inner surface of the through hole. The insulating fixing plate has a hat-shaped cross section,
The flange portion of the insulating fixing plate abuts against the surface of the laminated portion,
The crown portion of the insulating fixing plate is inserted into the through hole,
4. The capacitor according to claim 3, wherein the seat of the screw and/or rivet abuts a crown portion in the through hole.

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