JPH0633682Y2 - Helical filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a shape of a coupling window that sets a coupling state between helical coils in a helical filter.

[Prior Art] A helical filter is usually constructed by electromagnetically coupling a plurality of helical coils each having one end open and the other end grounded. Specifically, each of the helical coils is wound around a bobbin in a metal case, and the side surfaces of the plurality of cases are fixed by soldering or welding. Also, a plurality of helical coils are provided on a common base. There is a case in which the bobbin is wound around and the whole is covered with a case having a partition wall between the helical coils.

Each helical coil constitutes one resonator, and its resonance frequency is adjusted by changing the distributed capacitance between the helical coil and its surrounding case grounded. The distributed capacitance is changed by disposing a movable body made of a dielectric material between the helical coil and the case or near the open end, or by moving a metal screw electrically connected to the case near the helical coil.

The resonance frequencies of the respective resonators are substantially equal, and the filter resonates with respect to the input signal of this resonance frequency.
The bandwidth of the filter changes depending on the coupling state between the resonators, but is set by designing the side surface of the case between the helical coils and the size of the coupling window of the partition wall during design.

Although there are various configurations of such helical filters, there is a filter configuration in which the helical coils are housed in individual cases, and the sides of the helical coil cases are fixed to each other in a required number according to the required characteristics. Most commonly used.

In such a case, the side surfaces of the case, in which a coupling window of approximately the same size is formed in advance, are fixed, but when trying to obtain strong coupling between the helical coils, the area of the coupling window becomes large and the area around the fixed coupling window is fixed. Area becomes smaller.

FIG. 3 is a diagram showing the shape of the coupling window of the conventional helical filter. As the coupling window 20 becomes larger, the area of the periphery 21 becomes smaller.

When one side of the case becomes about 5 mm, the width W of the periphery 21 becomes as small as about 1 mm, and the adhesion strength between the cases becomes weak.

FIG. 4 is a view showing another shape of the coupling window of the conventional helical filter. However, except for one side below the periphery 23 of the coupling window 22, the periphery 23 is not closed, so that the coupling window is not closed. There is a part that is not fixed around 22 and the characteristics tend to change due to the case being distorted by a slight physical force, which is undesirable from the standpoint of reliability.

〔Task〕

The object of the present invention is to fix the side surface of the case around the entire coupling window even when a strong coupling between the helical coils is obtained.
An object of the present invention is to provide a helical filter that has a strong fixing strength and does not cause distortion of the case.

[Means for Solving the Problems]

According to the present invention, in a helical filter in which a side surface of a metal case covering each of the helical coils is fixed, and a plurality of helical coils are coupled to each other by a coupling window provided on the side surface, the periphery of the coupling window is It is characterized in that it is formed in a ring shape having a cutout portion.

〔Example〕

An embodiment of the helical filter of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a sectional view and FIG. 2 is a perspective view of a case.

The helical filter of this embodiment has an open end on the upper side,
Two helical coils 1 whose lower ends are ground ends are wound around bobbins 3 in different cases 2, respectively. The case 2 is fitted into the lower base portion 4 of the bobbin 3.

A terminal 5 for surface connection is provided on the side surface of the base portion 4,
The ground end of the helical coil 1 is connected to the input and output taps.

A coupling window 6 is provided on the fixed side surface of the case 2, and the coupling state between the helical coils 1 is set by the coupling window 6. A screw of a dielectric is screwed in the vicinity of the open end of the helical coil 1 inside the bobbin 3, and numeral 7 is a hole of the case 2 through which a driver for rotating the screw is passed.

A periphery 8 of the coupling window 6 is provided with a cutout portion 9 on one side of a quadrangle as shown in FIG. 10 is a fixed portion of the periphery 8 by spot welding. Reference numeral 11 denotes a lug of the case 2, which serves to fix the case 2 by bending it to the lower side of the base portion 4. The chain line shows another case 2 which is fixed.

The periphery 8 of the coupling window 6 extends along all four sides, and the cut portion 9
It is formed in a ring shape with a shape and is close to a closed shape.
Therefore, the side surface of the case 2 can be fixed while the entire periphery of the coupling window 6 is fixed along the periphery 8.

Since the periphery of the coupling window of the helical filter of the present invention is almost closed, the area is smaller than that of the conventional coupling window shown in FIG. 4 and the coupling may be weakened. By providing, even if the area is reduced, the bonded state is not weakened. It is considered that this is because the coupling between the helical coils 1 is increased due to the inductance because the induction current does not flow around the coupling window by providing the cutout portion. Therefore, when trying to obtain the same degree of coupling as the conventional one, it is possible to make the area of the coupling window smaller than the conventional one and increase the peripheral area,
It contributes to the effect together with the above-mentioned shape. That is, the area of the coupling window required to obtain the same degree of coupling as the conventional one can be made smaller than the size of the conventional coupling window due to the configuration of the cutout portion, and the width of the peripheral portion is ensured to have sufficient bonding strength. it can.

The shape of the periphery of the coupling window may be a shape other than a quadrangle, for example, a circle.

〔effect〕

As described above, the helical filter of the present invention has a ring shape around the coupling window with the cutout portion. Therefore, in order to obtain the same degree of coupling as in the conventional case, the area of the coupling window can be made smaller than in the conventional case and the area of the periphery of the coupling window can be increased, and the side surface of the case can be firmly fixed around the entire periphery of the coupling window. Further, even if the shape is small, the strength of fixing between the cases is strong and the cases are not distorted, so that it is possible to provide a highly reliable helical filter in which the characteristics are not changed by physical force.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a helical filter of the present invention, FIG. 2 is a perspective view of a case, and FIGS. 3 and 4 are views showing the shape of a coupling window of a conventional helical filter. 2: Case, 6: Combined window, 8: Surrounding

Claims (2)

[Scope of utility model registration request] 1. A helical filter in which a side surface of a metal case covering each helical coil is fixed, and a plurality of helical coils are coupled to each other by a coupling window provided on the side surface, the periphery of the coupling window. Is a helical filter characterized by being formed in a ring shape with a cut portion. 2. The helical filter according to claim 1, wherein a cutout is provided on one side of a quadrangle around the coupling window.