JPH0630325B2 - Feedthrough capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a feedthrough capacitor which is incorporated in an electronic or electric device such as a microwave oven to remove noise.

[Prior Art] Conventionally, as a feedthrough capacitor, one using a cylindrical ceramic dielectric, one using a disk-shaped ceramic dielectric, or a resin film such as polyethylene terephthalate wound in a cylindrical shape. It is well known that such a material is used as a dielectric.

A longitudinal sectional view and a plan view of an example of a conventional feedthrough capacitor using a resin film as a dielectric are shown in FIGS. 6 (a) and 6 (b), respectively.

The feedthrough capacitor 1 includes a cylindrical capacitor unit 2, a feedthrough terminal 3, a grounding terminal plate 4, and a current collector plate 5.
And a cylindrical insulating member S.

As shown in FIG. 7, the capacitor unit 2 has a tape-shaped first dielectric film 7 having a substantially constant width and having a capacitor electrode 6 formed on one main surface, and the first dielectric film 7. The second dielectric film 9 has a width substantially equal to that of the dielectric film 7 and has a tape-shaped second dielectric film 9 having a capacitor electrode 8 formed on one main surface. The capacitor electrode 8 of the second dielectric film 9 is superposed on the other main surface of the first dielectric film 7, and the insulating member S (see FIG. 6 (a)) is wound around the core. Is wound into a cylindrical shape.

Both the capacitor electrode 6 of the first dielectric film 7 and the capacitor electrode 8 of the second dielectric film 9 are formed by vapor deposition or sputtering of aluminum (Al) or zinc (Zn). The capacitor electrode 6 of the first dielectric film 7 reaches the other side from one side of the first dielectric film 7 with a certain margin 11, and is drawn out to one end surface of the capacitor unit 2. The capacitor electrode 8 of the second dielectric film 9 is also
Is a second dielectric film corresponding to the other side of the first dielectric film 7.
The dielectric film 9 reaches the side of the second dielectric film 9 corresponding to the one side of the first dielectric film 7 with a certain margin 12 from the side of the dielectric film 9 and is drawn out to the other end surface of the capacitor unit 2.

On one end surface and the other end surface of the capacitor unit 2,
As shown in FIG. 6 (a), the metallikon electrodes 13 and 14 are formed by spraying molten metal. The metallikon electrode 13 is electrically connected to the capacitor electrode 6 of the first dielectric film 7, and the other metallikon electrode 14 is electrically connected to the capacitor electrode 8 of the second dielectric film 9.

The grounding terminal plate 4 and the current collecting plate 5 are soldered to the metallikon electrodes 13 and 14, respectively. Then, the through terminal 3 inserted into the insulating member S is soldered to the current collector plate 5. An equivalent circuit of the feedthrough capacitor 1 having the above configuration is shown in FIG.

[Problems to be Solved by the Invention] In the feedthrough capacitor 1 described above, the noise current i passes through the feedthrough terminal 3 and then flows through the feedthrough terminal 3 from the collector plate 5, the metallikon electrode 14 to the feedthrough terminal 3. In contrast to this, the metallicone electrode 13 and the grounding terminal plate 4 are bypassed to the ground (see FIGS. 6 (a) and 8). In this case, the higher the frequency of the high-frequency current flowing in the capacitor unit 2, the more the high-frequency current tends to flow near the outer surface of the capacitor unit 2, so that the capacitor with respect to the radius R ₁ of the through terminal 3 becomes larger. The effective radius R _{2 of the} unit 2 is large, and the value of R ₂ / R ₁ is as large as 5 to 10. Therefore, even if the direction of the noise current i flowing through the through terminal 3 and the capacitor unit 2 is opposite, the distance between the noise currents flowing through the two becomes large, and the inductance generated by the noise current i flowing through the through terminal 3 is increased. Therefore, the effect of offsetting the inductance generated by the noise current i flowing through the capacitor unit 2 cannot be expected so much. Therefore, in the conventional feedthrough capacitor 1 of FIGS. 6 (a) and 6 (b), the residual inductance between the feedthrough terminal 3 and the grounding terminal plate 4 against the noise current i is not sufficiently reduced, and this residual There was a problem that the insertion loss in the high frequency range was not sufficient due to the inductance.

An object of the first invention of the present application is to provide a feedthrough capacitor having a small residual inductance and a large insertion loss in a high frequency range.

It is an object of a second invention of the present application to provide a feedthrough capacitor that has a smaller residual inductance than that of the first invention of the present application and has a larger insertion loss in a high frequency range.

[Means for Solving the Problem] Therefore, according to the first invention of the present application, one capacitor electrode is drawn out to the terminal electrode formed on one end surface and another capacitor electrode is formed on the other end surface. A cylindrical capacitor unit in which another capacitor electrode forming an electrostatic capacity with the above-mentioned one capacitor electrode is drawn out, and a through terminal inserted into the axial center of this cylindrical capacitor unit. And a current collecting member that electrically connects the terminal electrode and the through terminal of the capacitor unit,
The capacitor unit is formed of a metal case with one end opening that fits over substantially the entire length of the capacitor unit, has a grounding terminal portion for grounding on the outer periphery of the one end opening side, and penetrates the central portion of the other end facing the one end opening. There is a hole in which the terminal is loosely fitted, and a grounding case member electrically connected to the other terminal electrode of the capacitor unit at the outer peripheral portion of the hole, and an interposing between the capacitor unit and the through terminal. A first insulating member that is mounted to electrically insulate the both; and a sheet-shaped second insulating member that is interposed between the capacitor unit and the grounding case member to insulate the two, the through terminal High-frequency current flowing from the grounding case member to the grounding terminal portion of the capacitor unit flows back from the vicinity of the grounding case member of the capacitor unit through the grounding case member. It is characterized in that it has to so that.

The second invention of the present application is such that a capacitor electrode is drawn out to a terminal electrode formed on each one end surface, and another terminal electrode formed on each other end surface has a capacitance between the capacitor electrode and the other terminal electrode. The other capacitor electrode forming the is drawn out, and the one located outside is shorter than the one located inside and is coaxially arranged so that the above-mentioned one end faces coincide with each other. A plurality of cylindrical capacitor units, a through terminal inserted through the axial center of these cylindrical capacitor units, and a current collector for electrically connecting the above-mentioned one terminal electrode and through terminal of each capacitor unit. And a metal case having an opening at one end that is fitted over the outer surface of the outermost capacitor unit from each of the other terminal electrodes of the capacitor unit. In addition to having a grounding terminal portion for grounding on the outer periphery, a hole into which the through terminal is loosely fitted is provided at the center of the other end opposite to the one end opening. A grounding case member electrically connected to one terminal electrode, a first insulating member interposed between the innermost capacitor unit and the through terminal to electrically insulate the two, and an outermost capacitor A sheet-shaped second insulating member interposed between the unit and the grounding case member to insulate the unit and the grounding case member, and the high frequency current flowing from the through terminal to the grounding terminal portion of the grounding case member is the outermost The capacitor unit is characterized in that the capacitor unit is folded back from the vicinity of the grounding case member and flows through the grounding case member.

[Operation] In the first and second inventions of the present application, the higher the frequency of the high frequency current flowing through the capacitor unit, the more it tends to flow near the outer peripheral portion of the capacitor unit due to the so-called skin effect. That is, the high frequency current flowing through the capacitor unit is concentrated and flows near the outer peripheral portion of the capacitor unit when the frequency becomes high. On the other hand, the grounding case member is in contact with the outer surface of the capacitor unit via the sheet-shaped second insulating member, and the grounding terminal portion is located at one end opening side of the grounding outer case, so that the grounding case member is provided. The high-frequency current flowing through the capacitor unit flows near the outer peripheral surface of the capacitor unit, and flows in the direction opposite to the inside of the capacitor unit. As a result, the magnetic field generated by the high frequency current flowing through the capacitor unit and the magnetic field generated by the high frequency current flowing through the grounding case member cancel each other out, and the residual inductance is reduced.

Further, in the second invention of the present application, the outermost capacitor unit on which the high frequency current is concentrated has a short length and can have a small electrostatic capacitance, the residual inductance becomes smaller accordingly, and the usable frequency is further increased. Get higher

EFFECTS OF THE INVENTION According to the present invention, the high-frequency current flowing through the capacitor unit concentrates near the outer peripheral portion of the capacitor unit closer to the grounding case member as the frequency increases, and moreover, the grounding case member The grounding terminal is located at one end opening side of the grounding case member.In the grounding case member, high-frequency currents flow in the opposite direction to the high-frequency currents of the capacitor unit and are close to each other. The effect of canceling the magnetic field due to the magnetic field and the magnetic field due to the high-frequency current flowing through the grounding case member is increased, and a feedthrough capacitor having a small residual inductance in the high frequency band can be obtained.

In addition, when the frequency of the high frequency current flowing through the capacitor unit becomes high, the high frequency current concentrates near the outer periphery of the capacitor unit, so the length of the outermost capacitor unit among the coaxially arranged capacitor units By shortening, the path through which the high-frequency current flows becomes shorter, and the residual inductance can be further reduced.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings.

A longitudinal sectional view and a plan view of one embodiment of one feedthrough capacitor are shown in FIGS. 1 (a) and 1 (b), respectively.

The feedthrough capacitor includes a tubular capacitor unit 21 that uses a resin film as a dielectric, a feedthrough terminal 22 that is inserted into an axial center portion of the capacitor unit 21, and
A current collecting member 24 that electrically connects the through terminal 22 and the terminal electrode 23 of the capacitor unit 21, and a grounding case member 25 that is externally fitted to the capacitor unit 21.
A first insulating member 26 that electrically insulates the capacitor unit 21 and the through terminal 22 from each other, and a second insulating member 27 that electrically insulates the capacitor unit 21 and the grounding case member 25 from each other.

The capacitor unit 21 has the same structure as that described in FIG. Therefore, detailed description thereof will be omitted.

The capacitor electrode of the capacitor unit 21 (corresponding to the capacitor electrode 6 in FIG. 7) is drawn out to the terminal electrode 23 formed on one end surface of the capacitor unit 21. Further, another capacitor electrode (corresponding to the capacitor electrode 8 in FIG. 7) forming an electrostatic capacitance with the capacitor electrode is connected to the terminal electrode 28 formed on the other end surface of the capacitor unit 21. Be withdrawn.

The penetrating terminal 22 is partially covered with a tube-shaped first insulating member 26 made of an insulating resin,
The capacitor unit 21 is inserted into the axial center portion. Further, a current collecting member 2 formed by punching a metal plate into a disc shape.
The through terminal 22 is inserted into a hole 24a formed at the center of the No. 4 connector. Further, the current collecting member 24 has the through terminal 2
2 and the terminal electrodes 23 of the capacitor unit 21 are conductively adhered by solder or the like.

On the other hand, the grounding case member 25 is made of a metal case having an opening at one end and having a tubular portion 25a fitted over substantially the entire length of the capacitor unit 21. The flat plate portion 25 facing the one end opening of the grounding case member 25.
The center portion of b has a hole 29 into which the through terminal 22 is loosely fitted. The flat plate portion 25b of the grounding case member 25 is
Solder or the like supplied through this hole 29 and another hole 30 which is formed if necessary is conductively bonded to the other terminal electrode 28 of the capacitor unit 21.

The second insulating member 27 is made of an insulating resin sheet. The second insulating member 27 is wound around the outer circumference of the capacitor unit 21, and the grounding case member 25 is provided thereon.
Are fitted. Further, the second insulating member 27 has a size that partially projects from the one end opening side of the grounding case member 25.

The grounding case member 25 has a flange portion 31 on one end opening side thereof, and the feedthrough capacitor is fixed to a chassis, a case, or the like of an electronic device by a mounting hole 32 formed in the flange portion 31. Although not shown, a screw may be cut around the grounding case and screwed into a chassis, a case or the like to be fixed.

The feedthrough capacitors shown in FIGS. 1 (a) and 1 (b) having the above-described configuration have an equivalent circuit as shown in FIG. 3 in terms of a distributed constant circuit. That is, in this equivalent circuit, the distance dk (k = 1, 2, ..., From the through terminal 22 in the radial direction of the through terminal 22 is provided between the current collecting member 24 and the flat plate portion 25b of the grounding case member 25. n), the capacitance Ck (k = 1,2,
, N) and the inductance Lk (k = 1, 2, ..., N) are connected in series.

It is known that the inductance Lk is proportional to log nd / dk (1), where d is the distance from the through terminal 22 to the tubular portion 25a of the grounding case member 25. From this equation (1), it can be seen that the inductance Lk decreases as the number k increases, that is, the inductance Lk becomes closer to the tubular portion 25a of the grounding case member 25.

By the way, from the through terminal 22 to the grounding case member 25.
The higher-frequency current bypassed to the flange portion 31 of FIG. 2 tends to flow through the series circuit of the inductance and the capacitor, which is farther from the through terminal 22 as the frequency becomes higher. That is, as the frequency becomes higher, the high frequency current i _{1 in} the series circuit of the capacitance C ₁ and the inductance L ₁ becomes smaller in FIG. 3, and the high frequency current in flowing in the series circuit of the capacitance Cn and the inductance Ln Grows larger. Therefore, when the frequency becomes high, the high frequency current becomes a capacitance Cn.
And the inductance Ln flow in a concentrated manner in the series circuit. In this case, at d / dk, k = n and d / d
Since dk becomes the minimum (1.2 to 1.05), from equation (1),
It can be seen that the inductance Ln (residual inductance of feedthrough capacitor) is minimized. This means that the high frequency current flowing through the series circuit of the capacitance Cn and the inductance Ln is closest to the grounding case member 25, so that the high frequency current flowing through the grounding case member 25 in the opposite direction to the above case. It is also clear from the fact that the generated magnetic field and the magnetic field generated by the high frequency current flowing through the series circuit cancel each other efficiently.

When the frequency and insertion loss characteristics of the feedthrough capacitor shown in FIG. 1 were measured, the result shown by the dotted line h ₁ in FIG. 5 was obtained. Further, the frequency-insertion loss characteristic of the conventional feedthrough capacitor described in FIGS. 6 (a) and 6 (b) is shown by a solid line h ₃ in FIG. From FIG. 5, it can be seen that the feedthrough capacitors of FIGS. 1 (a) and 1 (b) have a larger insertion loss of about 20 dB at 1000 MHz than the conventional feedthrough capacitors described above.

Next, a vertical sectional view and a plan view of another embodiment of the feedthrough capacitor are shown in FIGS. 2 (a) and 2 (b), respectively, and
This equivalent circuit is shown in FIG.

The feedthrough capacitor is the feedthrough capacitor described in FIGS. 1 (a) and 1 (b), in which the capacitor unit 21 is divided into two (or more) capacitor units 21a and 21b in the radial direction, Capacitor unit 21a
The length l ₂ of the outer capacitor unit 21b is shorter than the length l ₁ of the capacitor unit 21a.

In this way, if the length l ₂ of the outer capacitor unit 21b close to the grounding case member 25 is reduced, as can be seen from FIG. 4, the path through which the high-frequency current flows becomes shorter, and the residual inductance becomes smaller accordingly. Become.

2 (a) and 2 (b), FIG. 1 (a)
The parts corresponding to those in FIG. 1 (b) are designated by the corresponding reference numerals, and the duplicated description will be omitted.

The insertion loss-frequency characteristics of the feedthrough capacitor shown in FIGS. 2 (a) and 2 (b) are shown by a chain double-dashed line h ₂ in FIG.
From FIG. 5, in the feedthrough capacitor shown in FIGS. 2 (a) and 2 (b), as compared with the feedthrough capacitor shown in FIGS. 1 (a) and 1 (b), about 10 dB at 1000 MHz, It can be seen that the insertion loss is large.

The present invention relates to a feedthrough capacitor for a power filter of a microwave oven, an electromagnetic interference filter (EMI) filter capacitor,
Alternatively, it can be widely applied to various bypass capacitors and the like.

[Brief description of drawings]

1 (a) and 1 (b) are respectively a longitudinal sectional view and a plan view of one embodiment of a feedthrough capacitor according to the present invention, and FIGS. 2 (a) and 2 (b) are respectively shown. FIG. 3 is a vertical sectional view and a plan view of another embodiment of a feedthrough capacitor according to the present invention. FIG. 3 is an equivalent circuit diagram of the feedthrough capacitor shown in FIGS. 1 (a) and 1 (b), and FIG. 2 (a) and 2 (b) are equivalent circuit diagrams of the feedthrough capacitor, FIG. 5 is a frequency-insertion loss characteristic diagram of the feedthrough capacitor of the present invention and a conventional feedthrough capacitor, FIG. 6 (a) and FIG. FIG. 6 (b) is a longitudinal sectional view and a plan view of a conventional feedthrough capacitor, FIG. 7 is a structural explanatory view of a capacitor unit, and FIG. 8 is a feedthrough capacitor of FIGS. 6 (a) and 6 (b). 2 is an equivalent circuit diagram of FIG. 21, 21a, 21b ... Capacitor unit, 22 ... Penetration terminal, 23 ... Terminal, 24 ... Current collecting member, 25 ... Grounding case member, 26 ... First insulating member, 27 ... Second insulating Member, 28 ... Terminal electrode, 29 ... Hole.

Claims (2)

[Claims] 1. A capacitor electrode is drawn out to a terminal electrode formed on one end face, and a capacitance is formed between the other capacitor electrode and another terminal electrode formed on the other end face. Another cylindrical capacitor unit with one capacitor electrode pulled out, a through terminal inserted into the axial center of this cylindrical capacitor unit, and the above-mentioned terminal electrode and through terminal of the capacitor unit are electrically connected. And a current-collecting member connected to the one end of the capacitor unit, and a one-end opening-shaped metal case that fits over the entire length of the capacitor unit. At the center of the other end, there is a hole into which the through terminal is loosely fitted, and the outer peripheral part of this hole is electrically connected to the other terminal electrode of the capacitor unit. A grounding case member, a first insulating member interposed between the capacitor unit and the through terminal to electrically insulate the two, and a grounding case member interposed between the capacitor unit and the grounding case member. A sheet-shaped second insulating member that insulates the two from each other, and a high-frequency current flowing from the through terminal to the grounding terminal portion of the grounding case member is connected to the grounding case from a portion near the grounding case member of the capacitor unit. A feedthrough capacitor characterized by being folded back through a member so as to flow. 2. A capacitor electrode is drawn out to a terminal electrode formed on each one end surface, and a capacitance is formed between another capacitor terminal and another terminal electrode formed on each other end surface. One more capacitor electrode is drawn out, the one located outside is shorter than the one located inside it, and a plurality of cylinders are arranged coaxially so that the above-mentioned one end faces coincide. Capacitor unit, a through terminal that is inserted into the axial center of these cylindrical capacitor units, a current collecting member that electrically connects the one terminal electrode and the through terminal of each capacitor unit, and It consists of a metal case with an open end that covers the outer surface of the outermost capacitor unit from each of the other terminal electrodes of the capacitor unit. In addition to having a ground terminal portion, a hole into which the through terminal is loosely fitted is provided in the center portion of the other end opposite to the one end opening, and at the outer peripheral portion of this hole, to each of the other terminal electrodes of each capacitor unit. A grounding case member electrically connected, a first insulating member interposed between the innermost capacitor unit and the through terminal to electrically insulate the two, an outermost capacitor unit and a grounding case A sheet-shaped second insulating member interposed between the grounding member and the member to insulate them from each other, and the high-frequency current flowing from the penetrating terminal to the grounding terminal portion of the grounding case member is the grounding of the outermost capacitor unit. A feedthrough capacitor, characterized in that the feedthrough capacitor is configured so as to flow back from the vicinity of the case member through the case member for grounding.