JPH0113763B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a so-called π-type LC noise removal filter that combines a ferrite and a capacitor.

(Prior art) Conventionally, this type of noise removal filter was
For example, as shown in FIG. 1, capacitors 2 and 3 are arranged coaxially on both sides of a ferrite bead 1, and a through terminal 4 is passed through the ferrite bead 1 and capacitors 2 and 3.
The electrodes 2a and 3a of capacitors 2 and 3 are soldered to
electrodes 2 of the capacitors 2 and 3.
It is generally known that parts b and 3b are soldered to a metal case 5, and the metal case 5 is filled with resin 6.

Further, as shown in FIG. 2, one leg 11a of the U-shaped through terminal 11 is inserted through the ferrite beads 13 and the capacitor 14 housed in the resin case 12, while the other leg 11b is inserted into the resin case 12. It is inserted into the case 12 and another capacitor 15, and the electrodes 14a and 14b of the capacitor 14 are soldered to the leg 11a and the ground plate 16, respectively.
It is also generally known that the electrodes 15a and 15b of another capacitor 15 are soldered to the leg portion 11b and the ground plate 16, respectively.

In both of the noise removal filters shown in FIGS. ₁ and 2, as shown in FIG. It has a π-type LC type circuit configuration bypassed to ground with capacitors C ₁ and C ₂ .

By the way, the noise removal filters shown in FIGS. 1 and 2 require the metal case 5, the ground plate 16, or the resin case 12, which increases the number of parts. It was necessary to make a hole and fill the metal case 5 with resin 6, making assembly difficult.

(Object of the Invention) The present invention has been made to solve the above problem, and its purpose is to eliminate both legs of a U-shaped through terminal in a π-type LC noise removal filter that utilizes ferrite inductance. By incorporating a capacitor inside the block-shaped ferrite, the ferrite has the function of a case, creating an easy-to-manufacture, low-cost, circuit board-mounted noise removal filter that does not require a special case or resin filling. It's about getting.

(Structure of the Invention) Therefore, in the present invention, both legs of a through terminal curved into a roughly U-shape are inserted into through holes passing through a pair of opposing surfaces of a block-shaped ferrite from one side to the other. One electrode of each of the two capacitors housed in a capacitor housing hole provided between these through holes and having an end opening into the through hole, and each of the two leg portions of the through terminal, respectively. The end of the capacitor housing hole is electrically connected, and the other electrode of the capacitor and the ground terminal are electrically connected, and the ground terminal is drawn out of the ferrite together with both legs of the through terminal. It is characterized by

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

In FIG. 4, 21 is a ferrite, 22 is a through terminal formed by bending a lead wire with a circular cross section into a roughly U-shape made of a metal with good electrical conductivity;
3 and 24 are chip-shaped ceramic capacitors, 2
Reference numeral 5 designates a ground terminal; 26 and 27 designate planar electrodes that are electrically connected to the through terminal 22; and 28, a planar ground electrode that is electrically connected to the ground terminal 25.

The ferrite 21 is block-shaped and has an approximately rectangular parallelepiped shape, and a top view of the ferrite 21 is shown in FIG. 5a.
FIG. 5b shows a sectional view taken along the line - in FIG. 5a, and
A bottom view is shown in FIG. 5c.

The ferrite 21 is formed with through holes 21a and 21b through which the legs 22a and 22b of the through terminal 22 are inserted, respectively. The through holes 21a and 21b penetrate from one side to the other of a pair of opposing surfaces _S1 and _S2 of the ferrite 11, and the through holes 21a _and 21b are connected to one surface S1 of the ferrite 21. A groove 21c is formed into which a connecting portion 22c that connects both legs 22a and 22b of the through terminal 22 is inserted.

The ferrite 21 also has capacitor housing holes 29a and 29b for housing the chip-shaped ceramic capacitors 23 and 24, respectively.
is formed between the through holes 21a and 21b. These capacitor housing holes 29a and 29
b are both open to the surface _S2 of the ferrite 21, both ends of the capacitor accommodation hole 29a are opened to the through hole 21a and the ground terminal insertion hole 31, respectively, and both ends of the other capacitor accommodation hole 29b are opened to the through hole 21a and the ground terminal insertion hole 31, respectively. It opens into the through hole 21b and the ground terminal insertion hole 31.

The ground terminal insertion hole 31 is formed at a position approximately equidistant from the through holes 21a and 21b of the ferrite 21.

A slit 32 is provided between the through hole 21a of the ferrite 21 and the ground terminal insertion hole 31, and
A slit 33 is formed between the other through hole 21b and the ground terminal insertion hole 31, respectively. These slits 32 and 33 are formed from the surface _S2 side of the ferrite 11 toward the surface _S1 so as to be substantially orthogonal to the capacitor housing holes 29a and 29b, respectively.

The capacitor housing holes 29a and 29b of the ferrite 21 having the above-described configuration have a
As shown in the figure, ceramic capacitors 23 and 24 are housed, and a ferrite 21
The legs 22a, 22b of the through terminal 22 are inserted into the through holes 21a, 21b and the ground terminal insertion hole 31, respectively.
and ground terminal 25, and both electrodes 23a and 23 of ceramic capacitor 23 are inserted and fitted.
b are soldered to the leg portion 22a and the ground terminal 25, respectively, with solders 34, 34, and both electrodes 24a, 24b of the ceramic capacitor 24 are soldered to the leg portion 22b and the ground terminal 25, respectively, with solders 34, 34. are doing.

As shown in FIG. 6, flat electrodes 26, 27 having springs 35, 35 in pressure contact with the side walls of the ferrite 21 are provided on the tip surfaces of both legs 22a, 22b of the through terminal 22 and the tip surface of the ground terminal 25, as shown in FIG. And a flat ground electrode 28 is soldered.

With the above arrangement, the ferrite 21 acts as an inductance on both legs 22a and 22b of the through terminal ₂₂ , and as shown in FIG. Capacitance C ₂₃ , C ₂₄
It is possible to obtain a π-type LC noise removal filter in which . In addition, in the above noise removal filter, the ferrite 21 is the ceramic capacitor 2.
It also functions as a case for 3 and 24, and does not require a special case or resin filling.

Incidentally, the ceramic capacitors 23 and 24 may be filled with resin for external insulation, if necessary.

In the above embodiment, the slits 32 and 33 allow the magnetic flux running along the side surface connecting the surfaces S ₁ and S ₂ of the ferrite 21 to the respective legs 22 a and 2 of the through terminal 22 .
It has a function of converting into magnetic flux running around the legs 2b and increasing the inductance acting on the legs 22a and 22b.

That is, if the slits 32 and 33 are not present, as shown in FIG. Legs 22a and 22 of the through terminal 22 along the side surface
Run around b. Furthermore, of the magnetic flux 42 running around the leg portion 22b of the through terminal 22, the magnetic flux 42a running near the side surface of the ferrite 21 is
It runs along the side surface so as to surround the legs 22a and 22b of the through terminal 22.

The magnetic fluxes 41a and 42a interfere with each other and weaken each other at substantially equal positions from the leg portions 22a and 22b of the through terminal 22, thereby reducing the inductance.

On the other hand, ferrite 11 has slit 3
2, 33, the magnetic flux 41a running along the side surface of the ferrite 21 as shown in FIG.
and 42a reach between the leg portions 22a and 22b of the through terminal 22 along the slits 32 and 33, and wrap around the leg portions 22a and 22b, respectively, at this portion.

Even when the directions of the magnetic fluxes 41 and 42 are reversed to the above, the same relationship as above can be obtained.

Therefore, magnetic fluxes 41a and 42a are different from other magnetic fluxes 4
The inductance can be increased by acting on the legs 22a and 22b of the through terminal 22, respectively, without being weakened by interference with the through terminals 1 and 42.

Next, another embodiment of the noise removal filter according to the present invention is shown in FIG.

The noise removal filter shown in FIG. 9 uses a flat plate-shaped through terminal 52 having a constant width in place of the through terminal 22 using a lead wire with a circular cross section in the noise removal filter shown in FIG. Both ends of the ferrite 21 are bent inward at right angles on the surface _S2 side, and a ground terminal 2 is inserted between the ceramic capacitors 23 and 24 housed in the capacitor housing holes 29a and 29b of the ferrite 21, respectively.
5, a spring terminal 55 is press-fitted therein.

If it is done as shown in FIG. 9, the flat electrode 2 in FIG.
6, 27 and the flat ground electrode 28 are no longer necessary, making the noise removal filter easier to assemble.

In the embodiment shown in FIG. 9, in place of the through terminal 52 and the spring terminal 55, as shown in FIG. 10, a through terminal 62 is formed by punching out a U-shaped plate material (not shown). As shown in FIG. 11a, a spring terminal 65 having a spring portion 65a formed at one end is used, and both leg portions 6 of the through terminal 62 are
Ceramic capacitors 23 and 24 are connected to 2a and 62b.
The electrodes 23a, 24a may be soldered, respectively, and the spring portion 65a of the spring terminal 65 may be brought into pressure contact with the electrodes 23b, 24b of the ceramic capacitors 23, 24. In addition, instead of the spring terminal 65, a spring terminal 75 as shown in FIG. 75a may be brought into pressure contact with the side wall of the ferrite 21.

(Effects of the Invention) As is clear from the above detailed description, the present invention provides a π-type LC noise removal filter that combines a ferrite and a capacitor. L.C.
Since we configured a type filter circuit,
The ferrite functions as the inductance and case of the noise removal filter, and a small chip-type noise removal filter that does not require a special case like conventional noise removal filters and is easy to assemble can be obtained.

Furthermore, according to the present invention, by forming the slit in the ferrite, the magnetic flux running along the side surface of the ferrite is converted into the magnetic flux running around both legs of the through terminal, and the inductance acting on these legs is reduced. It is possible to obtain a noise removal filter that is large in size and has good characteristics.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional views of conventional noise removal filters, FIG. 3 is an equivalent circuit diagram of the noise removal filters of FIGS. 1 and 2, and FIG. 4 is a noise removal filter according to the present invention. FIG. 5a is a top view of the ferrite used in the noise removal filter of FIG. 4, and FIG. 5b is a cross-sectional view of one embodiment.
Figure 5c is a bottom view of the ferrite shown in Figure 5a, Figure 6 is a side view of the flat electrode and flat ground electrode, and Figure 7 is the noise removal filter shown in Figure 4. FIG. 8a and FIG. 8b are respectively explanatory diagrams of the action of the ferrite slits. FIG. 9 is a longitudinal sectional view of another embodiment of the noise removal filter of FIG. 4, and FIG. 10. is an explanatory diagram of a modification of the noise removal filter shown in FIG. 9, and FIGS. 11a and 11b are side views of modifications of the ground terminal used in the noise removal filter of FIG. 21... Ferrite, 22... Penetration terminal, 22a,
22b... Leg portion, 23, 24... Ceramic capacitor, 25... Earth terminal, 29a, 29b... Capacitor accommodation hole, 32, 33... Slit, 52... Penetration terminal, 55... Spring terminal, 62... Penetration terminal, 65,
75...Spring terminal.

Claims (1)

[Claims] 1. Both legs of a through terminal curved into a roughly U-shape are inserted into through holes that penetrate from one side to the other of a pair of opposing surfaces of a block-shaped ferrite, and a through hole is provided between these through holes. one electrode of each of the two capacitors housed in the capacitor housing hole whose ends are respectively open to the through hole, and each of the legs of the through terminal are electrically conductive at the end of the capacitor housing hole. Along with being connected,
A noise removal filter characterized in that the other electrode of the capacitor and the ground terminal are electrically conductively connected, and the ground terminal is drawn out to the outside of the ferrite together with both legs of the through terminal.