JP2002075786A - Variable capacitor for printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a variable capacitor by mounting lead wires on a regulating pattern or its vicinity because a variable capacitor, using a conductor projected from a printed board having a complicated cubic structure to disturb flattening of the board and to obtain a planar variable capacitor adjustable in an intrinsic constant (capacity) by changing a contact area of the lead wires with the pattern by a position for mounting the lead wires and a shape of the wire. SOLUTION: The variable capacitor 10 for the printed circuit board constitutes a part of a circuit, by being mounted between two terminal patterns 14 and 16 of a printed board 12. This capacitor 10 comprises a lead wire 18, connected to the one terminal pattern 14 and coated with an insulator, and the regulating pattern 20 continued to another terminal pattern and obliquely formed, so that the distance to the pattern 14 is changed gradually.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable circuit in which a resonance circuit is formed in a printed circuit board together with an inductor (coil) and the resonance frequency or impedance characteristic of the resonance circuit can be changed by changing the capacitance. Related to capacitors.

[0002]

2. Description of the Related Art Heretofore, inductors and capacitors forming a resonance circuit in a printed circuit board circuit have been constituted by electronic components each having a lead wire for wiring. In recent years, the miniaturization of the parts used has been progressing, and electronic parts that do not have wiring leads on individual parts,
Resonant circuits are increasingly formed from so-called surface-mounted components. In addition, since such surface mount components are small and have a planar configuration, a variable inductor (variable induction winding: variable inductor,
No variable inductor coil bobbin or variable capacitor (variable capacitor, trimmer capacitor, etc.) has been developed.

For this reason, in a resonance circuit configured using such surface mount components, when the circuit characteristics are changed to change the resonance frequency or impedance characteristics of the circuit, etc., the individual components of the resonance circuit are changed. Electronic components, inductors and capacitors needed to be replaced. For these replacements, it is necessary to once remove the inductor or capacitor mounted on the printed circuit board by soldering and re-mount a new inductor or the like.

However, in this case, the work of changing the intrinsic constant requires a great deal of time and labor, and the printed circuit board composed of a very fine printed pattern is liable to damage the circuit pattern, resulting in deterioration in quality. There is. Furthermore, there is a possibility that the printed circuit board itself cannot be used due to destruction such as cutting or peeling of the printed pattern.

To solve this problem, a conductor 3 protruding from a printed circuit board 2 is mounted at a position facing the inductor 1 as shown in FIG. 10, and a capacitor 4 is formed between the inductor 1 and the conductor 3. A resonance circuit having such a configuration has been developed (see Japanese Patent No. 2798898). In this resonance circuit, the resonance frequency is changed by adjusting the distance between the inductor 1 and the conductor 3 to change the intrinsic constant of the capacitor 4.

[0006]

However, the above-described variable capacitor is a conductor 3 protruding from the printed circuit board 2.
Is required, the structure becomes complicated and three-dimensional, and the planarization of the printed circuit board 2 is hindered. Also, if the distance changes due to another member touching the conductor 3 or the inductor 1, the capacitor 4 changes. Therefore, unless the space is provided more than necessary on the side surface of the printed circuit board 2 on the side of the capacitor 4, However, it is difficult to reduce the size of the device. In addition, the installation work of the printed circuit board 2 requires attention, so that the work becomes complicated and the workability is deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a variable capacitor for a printed circuit board which has a simple planar structure and can change an intrinsic constant.

[0008]

As a technical means for achieving the above-mentioned object, a variable capacitor for a printed circuit board according to the present invention is mounted between two terminal patterns of a printed circuit board to form one circuit. In the variable capacitor for a printed circuit board constituting a part, a conductor connected to one of the terminal patterns and covered with an insulator, and a distance between the one of the terminal patterns that is continuous with the other one of the terminal patterns and gradually increases. And an adjustment pattern formed obliquely so as to change to a state where the conductive wire is mounted on or near the adjustment pattern, and the intrinsic constant varies depending on the mounting position and shape.

A capacitor is formed by placing the conductor on the adjustment pattern. When the mounting position or shape of the conductor is changed, the contact area between the conductor and the adjustment pattern is changed, so that the intrinsic constant (capacity) of the capacitor can be adjusted.

According to a second aspect of the present invention, in the variable capacitor for a printed circuit board according to the first aspect, an inductor is connected to one of the terminal patterns. And a resonance circuit is formed.

That is, the resonance frequency and impedance characteristics of the resonance circuit are adjusted by changing the intrinsic constant of the capacitor.

Further, a variable capacitor for a printed circuit board according to the invention of claim 3 is the variable capacitor for a printed circuit board according to claim 1 or 2, wherein the resonance circuit is a series resonance circuit. And According to a fourth aspect of the present invention, in the variable capacitor for a printed circuit board according to the first or second aspect, the resonance circuit is a parallel resonance circuit.

Therefore, it is possible to cope with various resonance circuits.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a variable capacitor for a printed circuit board according to the present invention will be described in detail with reference to preferred embodiments shown in the drawings. 1 to 7 show a variable capacitor for a printed circuit board according to an embodiment of the present invention.
Shows 10. This variable capacitor for printed circuit board 10
Is mounted between the two terminal patterns 14 and 16 of the printed circuit board 12 to constitute a part of the circuit, and is connected to the conductor 18 connected to one terminal pattern 14 and the other terminal pattern 16 And an adjustment pattern 20 formed continuously. Then, the variable capacitor 10 is formed by placing the conductor 18 on or near the adjustment pattern 20. Also, the intrinsic constant (capacity) of this variable capacitor 10
Is changed depending on the position where the conductor 18 is placed and the shape of the conductor 18.

The conductor 18 is made of a conductive core material as shown in FIG.
18a and an insulator 18b such as vinyl covering the same. Accordingly, the variable capacitor 10 is formed between the variable capacitor 10 and the adjustment pattern 20, and a short circuit can be prevented. This conductor 18 is soldered to one terminal pattern 14
Connected at 22. The distal end of the conductive wire 18 is free and free. The conductive wire 18 is placed on the adjustment pattern 20 and closely adhered in parallel as shown in FIG. Therefore, the variable capacitor 10 can be configured in a planar manner. The base end of the conductive wire 18, that is, the exposed portion of the core material 18a,
As shown in FIG. 2, the shape is bent downward. Thus, even if the insulator 18b has a thickness as shown in FIG. 3, the core material 18a can be in close contact with the terminal pattern 14, and the insulator 18b can be in close contact with the adjustment pattern 20.

The adjustment pattern 20 includes one terminal pattern 14
Are formed diagonally so that the distance from the と gradually changes. In the present embodiment, it is formed in an oblique linear shape. Thus, by changing the direction of the conductor 18, the overlapping area (length) of the conductor 18 and the adjustment pattern 20 can be changed, so that the capacitance of the variable capacitor 10 can be changed. For example, as shown in FIG.
In the case where the variable capacitor 10 is placed at the nearest part, the contact area becomes large and the capacity of the variable capacitor 10 becomes maximum. In addition, as shown in FIG. 5, when the conductor 18 is placed at an intermediate distance portion of the adjustment pattern 20, the capacitance of the variable capacitor 10 is in the middle. Further, as shown in FIG. 6, when the conductive wire 18 is placed out of the adjustment pattern 20, the contact area is lost and the capacity of the variable capacitor 10 is minimized.

As a method of adjusting the contact area between the conductor 18 and the adjustment pattern 20, the shape of the conductor 18 may be changed, for example, it may be placed in a curved shape. Also in this case, the capacity of the variable capacitor 10 is set according to the contact area with the adjustment pattern 20.

In the present embodiment, the terminal patterns 14,
An inductor 24 is connected to one of the terminals 16, for example, the terminal pattern 14 to which the conductive wire 18 is soldered, and a series resonance circuit 26 is formed by the variable capacitor 10 and the inductor 24. Here, as the inductor 24, a surface mount component is used. The inductor 24 is connected between the terminal pattern 14 and the input terminal 30 of the resonance circuit 26 by solder 28. The other terminal pattern 16 of the variable capacitor 10 is a ground circuit surface.

An equivalent circuit of the resonance circuit 26 is as shown in FIG. As shown in the figure, the resonance circuit 26 is a series resonance circuit 26 using the lumped constant variable capacitor 10. In the resonance circuit 26, an inductor 24 (reactance unit) and the variable capacitor 10 are connected in series, and an input terminal
It is composed of a circuit provided between 30 and a ground circuit surface (ground plane) 16. And the variable capacitor 10
, The resonance frequency and impedance characteristics of the resonance circuit 26 can be adjusted.

Here, the resonance frequency f in the resonance circuit 26
And reactance (coil) L and capacitance (variable capacitor 1
0) The relationship with C is approximated by Expression 1, and it is known that the resonance frequency f decreases as the capacitance C increases, and the resonance frequency f increases as the capacitance C decreases. The resonance frequency f can be adjusted by adjusting only the variable capacitor 10 using this characteristic. [Equation 1] f ≒ 1/2 (CL) ^1/2

The operation of the above-described printed circuit board variable capacitor 10 will be described below.

When adjusting the resonance frequency f and the impedance characteristics of the resonance circuit 26, the position and the shape of the conductor 18 are changed in the horizontal direction. At this time, the capacitance of the variable capacitor 10 increases and the resonance frequency f decreases as the conductive wire 18 is placed closer to the adjustment pattern 20 to increase the contact area. Further, as the conductive wire 18 is placed farther from the adjustment pattern 20 or separated from the adjustment pattern 20 and the area of contact with the adjustment pattern 20 is reduced, the capacitance of the variable capacitor 10 is reduced and the resonance frequency f is increased. By adjusting the capacity of the variable capacitor 10 in this manner, the resonance circuit 26
, The resonance frequency f, the impedance characteristics, and the like can be adjusted.

According to the above-described variable capacitor 10 for a printed circuit board, the variable capacitor 10 can be obtained by using the conducting wire 18 without using the variable capacitor 10 of the surface mount component. Can be achieved. Also, the cost of parts can be reduced.
For example, one variable capacitor 10 of surface mount component is about 20
The shape of the conductor 18 is a circle, but if the conductor 18 has a coating used in the present embodiment, it can be reduced to about 2 yen for one conductor.

Further, since the adjustment can be performed without replacing the variable capacitor 10, the damage of the circuit pattern due to the replacement of the components can be prevented, and the reliability of the product can be improved. Furthermore, since there is no need for component replacement, circuit optimization is facilitated, and operability and productivity are dramatically improved. Moreover, even for circuits that require re-adjustment of frequency characteristics, impedance characteristics, etc. due to aging, etc., it is possible to re-adjust to optimal characteristics without the need for component replacement.
Maintainability is also greatly improved.

Further, since the variable capacitor 10 includes the conducting wire 18 and the adjustment pattern 20, the flatness can be improved. For this reason, it is not necessary to provide an unnecessarily large space on the side surface of the printed circuit board 12 on the side of the variable capacitor 10, and the size of the apparatus can be reduced.

The above embodiments are merely examples of preferred embodiments of the present invention, but are not limited thereto, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the variable capacitor 10
Is used in the series resonance circuit 26, but is not limited to this, and may be used in the parallel resonance circuit 32. In this case, as shown in FIGS. 8 and 9, the terminal pattern 14 to which the conductor 18 is soldered is made continuous with the input terminal 30. And the inductor
24 is connected between the terminals 14 and 16 in parallel with the variable capacitor 10. That is, both the variable capacitor 10 and the inductor 24 are connected to the input terminal 30 and the ground circuit surface (the other terminal) 16.
Connected between At this time, the relationship between the resonance frequency f indicating the circuit characteristics, the capacitance C, and the reactance L can be approximated by Expression 1, and shows the same characteristics as the series resonance circuit 26. Also in this parallel resonance circuit 32, the resonance frequency, the impedance characteristic, and the like of the resonance circuit 32 can be adjusted by adjusting the capacitance of the variable capacitor 10.

In the present embodiment, the adjustment pattern 20 is formed in an oblique straight line, but is not limited to this, and may be formed in an oblique curved shape. For example, as shown by a two-dot chain line in FIG. 4, an arc shape protruding toward the conductor 18 or a concave arc shape may be used. In any case, the contact area between the conductor 18 and the adjustment pattern 20 can be changed depending on the mounting position of the conductor 18, so that the capacity of the variable capacitor 10 can be adjusted.

Furthermore, in each of the above-described embodiments, the other terminal 16 to which the adjustment pattern 20 is connected is used as a ground circuit surface. However, the present invention is not limited to this, and it may be connected to other circuit elements. In each of the embodiments described above, the resonance circuit 26, 32
However, the present invention is not limited to this, and may be used as a single component.

[0029]

As described above, according to the variable capacitor for a printed circuit board according to the first aspect of the present invention, the conductor covered with the insulator is placed on the adjustment pattern or in the vicinity thereof. Since the intrinsic constant (capacity) differs depending on the position and shape of the conductor, the capacitance can be adjusted by changing the position and shape of the conductor. For this reason, the circuit and device configuration can be simplified, and the component cost can be reduced as compared with the case where a capacitor which is a single component is used.

Further, since the adjustment can be performed without replacing the variable capacitor, it is possible to prevent the circuit pattern from being damaged due to the replacement of components, and to improve the reliability of the product.
Furthermore, since component replacement is not required, circuit optimization is facilitated, and operability and productivity can be dramatically improved. Moreover, even for circuits that require re-adjustment of frequency characteristics, impedance characteristics, etc. due to aging, etc., it is possible to re-adjust to the optimum characteristics without replacing parts, greatly improving maintainability. can do.

Further, since the variable capacitor includes the conducting wire and the adjustment pattern, the flatness can be improved. For this reason, it is not necessary to provide an unnecessary space on the side surface of the printed circuit board on the side of the variable capacitor, and the apparatus can be downsized.

According to the variable capacitor for a printed circuit board according to the second aspect of the present invention, since the resonance circuit is formed together with the inductor, the resonance frequency and the impedance characteristics of the resonance circuit can be changed by changing the intrinsic constant of the capacitor. Can be adjusted.

According to the third aspect of the present invention, the resonant circuit is a series resonant circuit. Alternatively, according to the fourth aspect of the present invention, the resonant circuit is a series resonant circuit. It is designed to be a parallel resonance circuit. Therefore, it is possible to cope with various resonance circuits.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment in which a variable capacitor for a printed circuit board of the present invention is used in a series resonance circuit.

FIG. 2 is a perspective view showing a conductive wire.

FIG. 3 is a side view of an embodiment in which a variable capacitor for a printed circuit board is used in a series resonance circuit.

FIG. 4 is a plan view showing when the capacitance of the variable capacitor for a printed circuit board is at a maximum.

FIG. 5 is a plan view showing when the capacitance of the variable capacitor for printed circuit board is medium.

FIG. 6 is a plan view showing when the capacitance of the variable capacitor for a printed circuit board is at a minimum.

FIG. 7 is an equivalent circuit diagram of an embodiment in which a variable capacitor for a printed circuit board is used in a series resonance circuit.

FIG. 8 is a perspective view of an embodiment in which a variable capacitor for a printed circuit board is used in a parallel resonance circuit.

FIG. 9 is an equivalent circuit diagram of an embodiment in which a variable capacitor for a printed circuit board is used in a parallel resonance circuit.

FIG. 10 is a side view of a conventional series resonance circuit using a variable capacitor.

[Explanation of symbols]

 10 Variable capacitor 12 Printed circuit board 14 One terminal 16 The other terminal 18 Conductor 20 Adjustment pattern 24 Inductor 26 Series resonance circuit 32 Parallel resonance circuit

Claims (4)

[Claims] 1. A variable capacitor for a printed circuit board mounted between two terminal patterns of a printed circuit board and constituting a part of a circuit, wherein a conductive wire connected to one of the terminal patterns and covered with an insulator. And an adjustment pattern that is continuous with the other terminal pattern and that is formed obliquely so that the distance from the one terminal pattern gradually changes, wherein the conductive wire is placed on or near the adjustment pattern. A variable capacitor for a printed circuit board characterized in that its intrinsic constant varies depending on the mounting position and shape. 2. The variable capacitor according to claim 1, wherein an inductor is connected to one of the terminal patterns to form a resonance circuit together with the inductor. 3. The variable capacitor according to claim 1, wherein the resonance circuit is a series resonance circuit. 4. The variable capacitor according to claim 1, wherein the resonance circuit is a parallel resonance circuit.