JPH0782964B2 - Variable capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a variable capacitor, and more particularly to a variable capacitor having a completely sealed structure.

[Prior Art] Since the variable capacitor has a closed structure, for example, the technique described in Japanese Patent Laid-Open No. 60-124910 can be applied. This publication describes a variable capacitor having the following structure.

That is, the variable capacitor includes an insulating case that is molded with the stator terminal and the rotor terminal that forms the central axis inserted therein. A dielectric plate having a hole for receiving the central axis described above is inserted in the insulating case. A stator electrode is formed on the dielectric plate by vapor deposition of silver, for example, so as to make electrical contact with the stator terminal. On the dielectric plate, there is arranged a rotor made of metal, which is provided with a hole for receiving the above-mentioned central axis at the center and is provided with a rotor electrode facing the stator electrode. A spring compounded with a driver plate having a driver groove is arranged above the rotor. An engaging recess is formed on the upper surface of the rotor so that the driver plate, the spring, and the rotor rotate integrally with each other. In this way, after each element is assembled in the insulating case, the upper end portion of the central shaft integrally formed with the rotor terminal is caulked, so that each element is held in the insulating case. Then, a cover sheet having suitable elasticity such as silicone rubber and relatively easily rupturable is formed so as to close the opening of the insulating case,
Thereby, a closed structure is provided.

[Problems to be Solved by the Invention] However, in the variable capacitor having the above-described structure, in relation to the cover sheet for providing the closed structure,
It has the following drawbacks.

First, the cover sheet is merely a thin film stretched while being held by the peripheral portion of the opening of the insulating case. Therefore, it is relatively difficult to properly stretch the cover sheet composed of such a thin film, and the work is troublesome.

Further, when adjusting the electrostatic capacity, a tool such as a screwdriver is inserted into the driver groove while breaking the cover sheet. However, insertion of a tool such as a driver through such a cover sheet is relatively difficult to perform, and the tip of the tool is not easily caught in the driver groove. Also, a relatively large force is required to break the cover sheet.

Therefore, it is an object of the present invention to provide a variable capacitor which can provide a completely sealed structure with relative ease.

Another object of the present invention is to provide a variable capacitor capable of adjusting electrostatic capacitance while maintaining a completely sealed state.

[Means for Solving the Problem] A variable capacitor according to the present invention firstly includes a stator having a stator electrode and a terminal electrically connected to the stator electrode.

A rotor is disposed on the upper surface of the stator. The rotor has a rotor electrode facing the stator electrode via a dielectric.

The rotor is rotatably housed by a cap. The cap has an opening on its lower surface, and an adjustment hole for rotating the rotor is formed on its upper surface. Such a cap is fixed to the stator with the opening closed by the stator.

Further, an inner corner portion formed by the upper surface of the stator and the outer peripheral surface of the rotor is filled with a sealing member made of resin.

In addition, preferably, the above-mentioned seal member is formed so as to fill not only the inner corner portion formed by the upper surface of the stator and the outer peripheral surface of the rotor but also the gap between the cap and the rotor and the gap between the cap and the stator. .

[Operation and Effect of the Invention] According to the present invention, the seal member can advantageously prevent foreign matter from entering the interface between the rotor and the stator, which is most important for the performance of the variable capacitor. Therefore, the flux or cleaning liquid used during soldering is prevented from entering the sliding surface between the rotor and the stator,
Therefore, it is possible to solve the problem that the capacitance changes undesirably and the Q deteriorates.

Further, the seal member used in the present invention can be formed by an extremely simple method in which the variable capacitor is dipped in a liquid resin, then pulled up from the resin, and then dried and cured. Therefore, the variable capacitor can be inexpensively provided with a completely sealed structure.

Embodiments The drawings are for explaining one embodiment of the present invention.

FIG. 1 shows a variable capacitor 1 according to an embodiment of the present invention.
Are shown in cross section. Such a variable capacitor 1
To obtain a semi-finished product 1a as shown in FIGS.
Is prepared first. 2 is a plan view of the semi-finished product 1a, FIG. 3 is a sectional view taken along line III-III of FIG. 2, and FIG. 4 is taken along line IV-IV of FIG. FIG. 5 is a sectional view taken along the line, and FIG. 5 is a bottom view of the semi-finished product 1a.

As shown in FIGS. 2 to 5, the semi-finished product 1 a generally comprises a stator 2, a rotor 3 and a cap 4.
Hereinafter, these elements will be described with reference to FIGS.
Each of these will be described in more detail with reference to the accompanying drawings.

In FIGS. 6 to 8, the stator 2 is shown alone. FIG. 6 is a plan view of the stator 2, FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 6, and FIG. 8 is a bottom view of the stator 2.

The stator 2 forms a stator electrode on its upper surface, but in this embodiment the stator electrode is divided into first and second stator electrodes 6 and 7, which are separated from each other. The first stator electrode 6 is electrically connected to the first terminal 8, while the second stator electrode 7 is connected to the second terminal 8.
Is electrically connected to the terminal 9. In this example,
First stator electrode 6 and first terminal 8 and second
The stator electrode 7 and the second terminal 9 are integrally formed of a first metal plate 10 and a second metal plate 11, respectively. The stator 2 has these first and second metal plates 10
And 11 are inserted, and the resin is obtained by molding a resin having the above-mentioned insulation property and preferably heat resistance capable of withstanding at least the molten solder temperature. The first and second terminals 8 and 9 have a portion extending along the lower surface of the stator 2 so that they can be directly soldered to a circuit board (not shown).

In FIGS. 9 to 11, the rotor 3 is shown alone. FIG. 9 is a plan view of the rotor 3, and FIG. 10 is
FIG. 11 is a sectional view taken along line XX of FIG. 9, and FIG. 11 is a bottom view of the rotor 3.

The rotor 3 is made of a dielectric material such as ceramic,
A rotor electrode facing the above-described stator electrodes 6 and 7 is formed therein. In this embodiment, as the rotor electrodes, first and second rotor electrodes 13 and 14 separated from each other are formed as shown in FIG. These rotor electrodes 13 and 14 are formed at positions closer to the lower surface of the rotor 3, as shown in FIG.
A driver groove 15 is formed on the upper surface of the rotor 3. The driver groove 15 preferably has a longitudinal dimension smaller than the diameter of the rotor 3 so that the side surface defining the driver groove 15 is not opened at any part. The rotor 3 made of a dielectric material having the rotor electrodes 13 and 14 formed therein can be obtained, for example, by a method similar to that of a laminated ceramic capacitor having internal electrodes.

The cap 4 is shown in FIGS. 12 to 14.
FIG. 12 is a plan view of such a cap 4, and FIG.
FIG. 14 is a sectional view taken along line XIII-XIII in FIG.
The drawing is a sectional view taken along the line XIV-XIV in FIG.

The cap 4 is made of metal, for example, and has a shape that rotatably houses the rotor 3 described above. Further, the lower surface of the cap 4 is an opening 16 closed by the stator 2 described above, and the adjustment hole 17 for exposing the driver groove 15 for the rotation operation of the rotor 3 is formed on the upper surface thereof. In the cap 4, the peripheral portion of the adjustment hole 17 is
The spring portion 18 exerts a spring action of pressing the rotor 3 against the stator 2. The cap 4 is preferably composed of stainless steel. By constructing the cap 4 from such a material, it is possible to exert a sufficient spring action in the spring portion 18, and further, the solder undesirably adheres to the cap 4 when immersed in the molten solder. Can be prevented. The cap 4 has an engaging piece 19 protruding downward.
Is provided. As shown in FIG. 4, the engagement piece 19 is bent later and engaged with the downward-facing surface 20 of the stator 2.
The downwardly facing surface 20 is preferably located above the main lower surface of the stator 2 and thereby prevents the engagement piece 19 from projecting beyond the main lower surface of the stator 2.

The semi-finished product 1a shown in FIGS. 2 to 5 is assembled by using the stator 2, the rotor 3 and the cap 4 which have been described in detail with reference to the drawings shown individually.

First, the rotor 3 is inserted into the inside of the cap 4 through the opening 16 therebelow. Next, the stator 2 is replaced with the cap 4
Is arranged so as to close the opening 16. In order to maintain this state, as shown in FIG. 4, the engaging piece 19 formed on the cap 4 is bent inward to engage the downwardly facing surface 20 of the stator 2.

In this way, the assembly of the semi-finished product 1a is completed. In this assembled state, the rotor 3 is pressed against the stator 2 by the spring action of the spring portion 18 formed in the cap 4,
Adhesion between the rotor 3 and the stator 2 is enhanced. As a result, a stable capacitance is formed. Further, by the spring action exerted on the rotor 3 from the spring portion 18,
Appropriate rotation torque is applied to the rotor 3.

The semi-finished product 1a thus obtained is different from the finished variable capacitor 1 shown in FIG.
The only difference is that 5a, 5b, 5c, 5d are not formed. To obtain the variable capacitor 1 shown in FIG.
The semi-finished product 1a is subjected to the steps shown in FIGS. 15 and 16.

With reference to FIG. 15, a liquid resin 21 is prepared by appropriately diluting a resin to be the seal members 5a to 5d, for example, a silicone resin. On the other hand, the semi-finished product 1a is soaked in the liquid resin 21 as shown by an arrow 22 with the adjusting hole 17 formed in the cap 4 facing downward.

This immersion state is shown in FIG. In FIG. 16, the semi-finished product 1 a is immersed in the liquid resin 21 until the interface between the cap 4 and the stator 2 is located completely below the liquid surface 23 of the liquid resin 21. At this time, the semi-finished product 1a
It may be completely immersed in the liquid resin 21. The immersion time is selected to be, for example, several seconds.

Next, the semi-finished product 1a is pulled up from the liquid resin 21 and heated to dry and cure the liquid resin 21 attached to the semi-finished product 1a.

When such a step is carried out, the liquid resin 21 permeates into the gap formed in the semi-finished product 1a due to a capillary phenomenon or the like, and due to its surface tension, an appropriate amount of the liquid resin 21 exists in the semi-finished product 1a. Stay in the inner corner. The appropriate amount of the liquid resin 21 staying at the inner corners in this manner forms the sealing members 5a to 5d as shown in FIG. 1 when cured as described above.

The seal member 5a fills an inner corner portion formed by the upper surface of the stator 2 and the outer peripheral surface of the rotor 3. Also, the seal member 5b
Fills the gap between the cap 4 and the rotor 3. Further, the seal members 5c and 5d fill the gap between the cap 4 and the stator 2.

The liquid resin 21 may be hardened while remaining in other portions besides forming the seal members 5a to 5d described above. However, such a resin, which may be formed on the surfaces of the terminals 8 and 9 for example, forms only a very thin (for example, several μm) film, so that it is suitable for soldering the terminals 8 and 9. Has no effect.

FIG. 17 shows a state where the above-mentioned first and second stator electrodes 6 and 7 and the first and second rotor electrodes 13 and 14 are opposed to each other. Further, FIG. 18 shows an equivalent circuit obtained by the variable capacitor 1.

As shown in FIG. 17, the first and second stator electrodes 6
When 7 and 7 face the first and second rotor electrodes 13 and 14, four electrostatic capacitances C1, C2, C3, C4 are formed. These capacitances C1, C2, C3, C4 appear as shown in FIG. 18 in the equivalent circuit diagram. As shown in FIG. 18, the electrostatic capacitance C1 is formed between the first stator electrode 6 and the first rotor electrode 13, and the electrostatic capacitance C2 is formed between the second stator electrode 7 and the first stator electrode 7. It is formed between the rotor electrode 13.
Then, these capacitances C1 and C2 are determined by the first rotor electrode 13
The first and second terminals 8 while being connected in series via
And 9 are taken out. On the other hand, the capacitance C3 is formed between the first stator electrode 6 and the second rotor electrode 14, and the capacitance C4 is formed between the second stator electrode 7 and the second rotor electrode 14. Is formed. These capacitances C3, C4
Is connected in series via the second rotor electrode 14,
It is taken out by the first and second terminals 8 and 9.
In the variable capacitor 1 having such a configuration, as shown in FIG. 17, the boundary portion between the first stator electrode 6 and the second stator electrode 7, the first rotor electrode 13 and the second rotor electrode 14 are formed. When the boundary portion of is orthogonal to each other, the total capacitance taken out by the first and second terminals 8 and 9 becomes maximum.

If the maximum capacitance obtained by the variable capacitor 1 may be smaller, one of the first and second rotor electrodes 13 and 14 may not be formed.

Further, according to the present invention, the stator electrode is not divided like the first and second stator electrodes 6 and 7, and for example, one semicircular stator electrode and one semicircular rotor electrode are used. It can also be applied to a variable capacitor formed such that and are opposed to each other. In this case, the stator electrode is electrically connected to one terminal in the stator as it is, but the rotor electrode is electrically connected to the other terminal held by the stator through an appropriate electric connection means. Will be connected.

The present invention can also be applied to a variable capacitor using a spring and a driver plate prepared as separate parts, as in the above-mentioned conventional technique.

Further, in the above-described embodiment, the rotor 3 is made of a dielectric material, but the present invention can be applied to a variable capacitor having such a dielectric material formed on the stator side.

Further, in the above-described embodiment, in order to fix the cap 4 to the stator 2, the engaging piece 19 formed on the cap 4 is bent after assembly to engage with the downwardly facing surface 20 of the stator 2. However, for a member corresponding to the engaging piece 19, a shape capable of engaging with the stator is provided in advance,
By pressing the stator into the cap, a member corresponding to the engaging piece may be engaged with the stator to fix the cap to the stator. Further, the cap and the stator may be fixed by adhesion.

The cap may be made of resin instead of metal.

Further, in the illustrated embodiment, the seal members 5a to 5d are formed at some places in the variable capacitor 1, but among these seal members 5a to 5d, the essential one is the stator 2
It should be pointed out that there is only the seal member 5a formed so as to fill the inner corner portion formed by the upper surface of the above and the outer peripheral surface of the rotor 3.

[Brief description of drawings]

FIG. 1 shows a variable capacitor 1 according to an embodiment of the present invention.
FIG. FIG. 2 is a plan view showing a semi-finished product 1a prepared to obtain the variable capacitor 1 shown in FIG. Figure 3 shows
FIG. 3 is a sectional view taken along the line III-III in FIG. 2. FIG. 4 is a sectional view taken along the line IV-IV in FIG. FIG. 5 is a bottom view of the semi-finished product 1a shown in FIG. FIG. 6 is a plan view of the stator 2. FIG. 7 shows the sixth
FIG. 7 is a sectional view taken along the line VII-VII in the figure. FIG. 8 is a bottom view of the stator 2 shown in FIG. FIG. 9 is a plan view of the rotor 3. FIG. 10 is a sectional view taken along the line XX of FIG. FIG. 11 is a bottom view of the rotor 3 shown in FIG. FIG. 12 is a plan view showing the cap 4. Figure 13 shows
FIG. 13 is a sectional view taken along the line XIII-XIII in FIG. 12. Figure 14 shows
FIG. 13 is a sectional view taken along the line XIV-XIV in FIG. 12. 15 and 16 show a seal member 5a to be implemented to obtain the variable capacitor 1 shown in FIG. 1 from the semifinished product 1a.
It is an illustration figure which shows an example of the formation method of 5d. FIG. 17 is a plan view showing a state where the first and second stator electrodes 6 and 7 and the first and second rotor electrodes 13 and 14 face each other. FIG. 18 is an equivalent circuit diagram of the variable capacitor 1. In the figure, 1 is a variable capacitor, 1a is a semi-finished product, 2 is a stator, 3 is a rotor, 4 is a cap, 5a, 5b, 5c and 5d are seal members, 6 and 7 are stator electrodes, 8 and 9 are terminals, 13 , 14 are rotor electrodes, 16 are openings, 17 are adjusting holes, 19 are engaging pieces, and 21 is liquid resin.

Claims (1)

[Claims] 1. A stator having a stator electrode and a terminal electrically connected to the stator electrode, and a rotor electrode disposed on an upper surface of the stator and facing the stator electrode via a dielectric. A rotor, the rotor being rotatably housed, the lower surface being an opening, and an adjustment hole for rotating the rotor being formed in the upper surface, and the stator being closed in the opening. A variable capacitor, comprising: a cap fixed to the inner surface of the stator; and a sealing member made of resin that fills an inner corner portion formed by an upper surface of the stator and an outer peripheral surface of the rotor.