JP3387382B2 - Variable capacitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable capacitor, and more particularly, to changing the effective facing area between a stator electrode and a rotor electrode by rotating the rotor electrode with respect to the stator electrode, thereby changing the capacitance. The present invention relates to a variable capacitor.

[0002]

2. Description of the Related Art A variable capacitor of interest to the present invention is described in, for example, Japanese Patent Laid-Open No. 6-120079. FIG. 8 shows the variable capacitor described in this publication. Referring to FIG. 8, variable capacitor 1
Comprises a stator 3 made of a ceramic dielectric material, inside of which a stator electrode 2 is formed, and a rotor 5 made of metal, at which a rotor electrode 4 is formed on the lower surface side. Rotor electrode 4
Are opposed to the stator electrode 2 via a part of the ceramic dielectric material forming the stator 3.

Further, in order to change the effective facing area of the rotor electrode 4 with respect to the stator electrode 2, the rotor 5 is held by a cover 6 made of metal so as to be rotatable with respect to the stator 3. The cover 6 has a shape that rotatably accommodates the rotor 5, and is fixed to the stator 3. The cover 6 is formed with an adjusting hole 7 that allows insertion of a tool for rotating the rotor 5. A spring action portion 8 for pressing the rotor 5 toward the stator 3 is provided around the adjustment hole 7 of the cover 6. The spring action portion 8 is provided by the metal material itself around the adjustment hole 7 by being provided with a shape that is inclined downward toward the center around the adjustment hole 7.

In such a variable capacitor 1, in order to extract the electrostatic capacitance formed by the facing of the stator electrode 2 and the rotor electrode 4, the stator electrode 2 is electrically connected to the outer surface of the end of the stator 3. A stator terminal 9 is formed by the conductive film to be connected, while a rotor terminal 10 is provided on a conductive cover 6 that contacts the rotor 5 forming the rotor electrode 4. Therefore, the above-mentioned electrostatic capacity is taken out between the stator terminal 9 and the rotor terminal 10, and by rotating the rotor 5, the effective facing area between the stator electrode 2 and the rotor electrode 4 is changed. And the capacitance can be changed.

[0005]

However, the variable capacitor 1 described above has the following problems to be solved. As a result of the cover 6 having the shape for accommodating the rotor 5 as described above, the end edge 11 of the cover 6 faces the stator 3.

On the other hand, the stator terminal 9 is provided by the conductive film formed on the outer surface of the end portion of the stator 3 as described above. In general, the conductive film is applied to the end portion of the stator 3 by causing the end portion of the stator 3 to project into a layer made of the conductive paste having a predetermined thickness. It is formed by baking.

Since the stator terminal 9 is formed by such a method, as shown in FIG. 9 which is an enlarged view of a part of FIG.
It is usually formed so as to partially extend not only to the end face of the above, but also to the face adjacent to this end face. Where, in particular,
A surface 12 of the stator 3 that the lower surface of the rotor 5 faces.
In particular, the stator terminal 9 has a portion 13 extending onto this surface 12.

From the above, the edge 11 of the cover 6 is
Alternatively, the peripheral surface of the rotor 5 and the portion 13 of the stator terminal 9 directly face each other. Where the cover 6
And the rotor 5 is at the same potential as the rotor electrode 4, while
Since the stator terminal 9 has the same potential as the stator electrode 2,
If a short circuit occurs between the edge 11 of the cover 6 or the peripheral surface of the rotor 5 and the portion 13 of the stator terminal 9, the function of the variable capacitor 1 will stop. In order to prevent such a short circuit and improve the withstand voltage, it is desirable to position the edge 11 of the cover 6 or the peripheral surface of the rotor 5 and the portion 13 of the stator terminal 9 as far as possible from each other.

However, for example, when trying to reduce the size or height of the variable capacitor 1, the edge 11 of the cover 6 or the peripheral surface of the rotor 5 and the portion 13 of the stator terminal 9 are close to each other. A situation can be brought about. When attempting to downsize the variable capacitor 1, for example, it is effective to reduce the size of the stator 3 in the horizontal direction in FIG. On the other hand, when the diameter of the rotor 5 is shortened, the maximum electrostatic capacity that can be obtained becomes small. Therefore, in order to maintain this maximum electrostatic capacity, the diameter of the rotor 5 cannot be changed so much. Therefore, when it is attempted to downsize the variable capacitor 1 while maintaining the maximum capacitance, the stator 3
8 is reduced only in the left-right dimension, and as a result, between the edge 11 of the cover 6 and the portion 13 of the stator terminal 9, and further between the peripheral surface of the rotor 5 and the portion 13 of the stator terminal 9. Will have to be designed close to each other.

As a result, when there is an error in the alignment of the rotor 5 and the cover 6 with respect to the stator 3 when the variable capacitor 1 is assembled, or when the cover 6 and the rotor 5 are displaced when the rotor 5 rotates, There is a risk of problems such as a short circuit and a withstand voltage failure between the edge 11 of the cover 6 and the portion 13 of the stator terminal 9 or between the peripheral surface of the rotor 5 and the portion 13 of the stator terminal 9.

Therefore, an object of the present invention is to provide a variable capacitor which can solve the above-mentioned problems of short circuit and withstand voltage failure.

[0012]

A variable capacitor according to the present invention is made of a dielectric material and has a stator electrode inside.
A stator having a structure in which a stator terminal formed on the outer surface thereof and electrically connected to the stator electrode is formed; a rotor forming a rotor electrode facing the stator electrode via a dielectric; In order to change the effective facing area of the electrode with respect to the stator electrode, the rotor has a shape to rotatably accommodate with respect to the stator,
In order to solve the above-mentioned technical problem, a conductive cover, which is fixed to the stator and electrically connected to the rotor electrode while having its end facing the stator, is provided.
It is characterized in that the stator terminal is formed so as not to extend to the surface of the stator where the edge of the cover faces.

[0013] In the variable capacitor in the above mentioned, the stator terminals, when given by the conductive film formed on the outer surface of the stator, the conductive film, it preferably that after forming, part of it is removed This ensures that the edges of the cover in the stator do not extend to the opposite surface.

Further, according to the present invention, the cover is formed with an adjusting hole for allowing the insertion of a tool for rotating the rotor, and the rotor is brought into contact with the rotor so that the rotor is pressed against the stator. It is advantageously applied to such a variable capacitor, in which a spring-actuating element is provided around the adjusting hole.

[0015]

1 to 7 are diagrams for explaining a variable capacitor 21 according to an embodiment of the present invention. 1 is a perspective view showing the external appearance of the variable capacitor 21, and FIG. 2 is a variable capacitor 2 shown in FIG.
1 is a perspective view showing the outer appearance of the variable capacitor 1 from the lower surface side, and FIG. 3 is a sectional view of the variable capacitor 21 shown in FIG. In addition, FIG.
It is a perspective view which decomposes | disassembles and shows the element with which the variable capacitor 21 is equipped, and some of each element shown in this FIG. 4 is shown by the perspective view from a respectively different angle in FIG. 5 and FIG. 7 is a cross-sectional view showing a part of FIG. 3 in an enlarged manner.

The variable capacitor 21 is provided with a stator 22, a rotor 23 and a cover 24, when viewed roughly. The main part of the stator 22 is made of a ceramic dielectric. The rotor 23 is made of metal such as brass. The cover 24 is made of a metal such as stainless steel or a copper alloy, and has good solderability.
At least a necessary portion may be surface-treated with solder, tin, silver or the like.

The detailed structure of each element described above will be described below. The stator 22 is shown alone in FIGS. 4 and 6. 1 to 4 and 6, the stator 22 has a symmetrical structure as a whole. Inside the stator 22, stator electrodes 25 and 26 are formed side by side. These stator electrodes 25
Stator terminals 27 and 28 having a conductive film are formed on the outer surface of each end of the stator 22 so as to be electrically connected to the stators 26 and 26, respectively.

As described above, the two stator electrodes 2
5 and 26 and two stator terminals 27 and 2
8 is formed by making the structure of the stator 22 symmetrical,
This is because when assembling the variable capacitor 21 using the stator 22, it is not necessary to consider the direction of the stator 22. Thus, if such advantages are not desired, either one of the stator electrodes 25 and 26 and its associated stator terminals 27 and 28 may be omitted.

The lower surface of the stator 22 is provided with recesses 29 and 30 which extend inwardly from opposite ends thereof. With the rotor 23 alone, FIG.
And shown in FIG. 1 and 3 to 5
Referring to, the rotor 23 is arranged on the upper surface of the stator 22 described above, and a substantially semi-circular rotor electrode 31 having a protruding step portion is formed on the lower surface thereof. In addition, a convex portion 32 having a height equal to that of the rotor electrode 31 is formed on the lower surface of the rotor 23, and the rotor 23 is prevented from tilting due to the presence of the rotor electrode 31.

The rotor 23 is provided with a driver groove 33 for receiving a tool such as a driver for rotating the rotor 23. The driver groove 33 is provided in this embodiment by a through hole of square cross section. The cover 24 is shown alone in FIG. Referring to FIGS. 1 to 4,
The cover 24 accommodates the rotor 23, while the stator 2
The rotor 23 is held by the cover 24 so as to be rotatable with respect to the stator 22. The cover 24 has a driver groove 33 of the rotor 23.
The adjustment hole 34 for exposing the
Insertion of a tool such as a driver for rotating the rotor 23 is allowed.

Around the adjustment hole 34, a spring action portion 35 for contacting the rotor 23 and pressing the rotor 23 toward the stator 22 is provided. The spring action portion 35 is provided around the adjustment hole 34 by the metal material itself around the adjustment hole 34 by being inclined downward toward the center.

The spring action portion 35 is preferably provided with a protrusion 36 which makes a substantially point contact with the rotor 23,
As a result, the spring action portion 35 is brought into contact with the rotor 23 at a plurality of points independent of each other. In this embodiment, three protrusions 36 are provided so as to be distributed at equal intervals along the rotation direction of the rotor 23. These protrusions 36 can be formed, for example, by performing a molding process on a metal plate that forms the cover 24.

The cover 24 is also provided with engagement pieces 37 and 38 extending downward so as to face each other.
Since the engagement pieces 37 and 38 engage with the recesses 29 and 30 formed in the lower surface of the stator 22, respectively,
To be bent later, the engaging pieces 37 and 38 are provided with holes respectively to facilitate this bending.

Further, the cover 24 is provided with a rotor terminal 39 so as to extend downward from a position different from the position where the engaging pieces 37 and 38 are provided. The variable capacitor 21 is assembled as follows using the stator 22, the rotor 23, and the cover 24 as described above.
A rotor 23 is arranged on the stator 22, and a cover 24 is arranged so as to cover the rotor 23. Then the rotor 2
While pressing the cover 24 toward the stator 22 so that 3 is pressed against the stator 22, the respective ends of the engaging pieces 37 and 38 provided on the cover 24 are bent inward. Thereby, the engagement pieces 37 and 38
Are the recesses 2 formed on the lower surface of the stator 22, respectively.
9 and 30 are engaged.

At this time, the rotor terminal 39 provided on the cover 24 is the stator terminal 2 provided on the stator 22.
8 (in the illustrated embodiment, it does not function as a stator terminal). Therefore, solder (not shown) or the like is applied between the rotor terminal 39 and the stator terminal 28 to make the fixing state of the cover 24 with respect to the stator 22 stronger, and also to fix the stator terminal 28 to the rotor terminal 28. You may make it function as.

In this way, the assembly of the variable capacitor 21 is completed. In this assembled state, as well shown in FIG.
In contrast, they face each other via a part of the ceramic dielectric material forming the stator 22 to form an electrostatic capacitance. In order to change the electrostatic capacitance, the effective facing area of the rotor electrode 31 with respect to the stator electrode 25 is changed, so that the rotor 23 is rotated. This electrostatic capacitance is applied to the stator terminal 27 that is electrically connected to the stator electrode 25 and the cover 24 that contacts the rotor 23 that forms the rotor electrode 31.
It is taken out between the rotor terminal 39 and the rotor terminal 39.

Further, in the assembled state of the variable capacitor 21, the protrusion 3 provided on the spring action portion 35 of the cover 24.
6, the spring action portion 35 can exert a stable spring action on the rotor 23, and thus a stable contact state between the rotor 23 and the stator 22 is obtained. Therefore, the rotor 23 is pressed uniformly against the stator 22 over its entire surface, and therefore,
The electrostatic capacitance is stabilized, the electrostatic capacitance changes smoothly due to the rotation of the rotor 23, the setting drift is stabilized, and the torque for the rotation of the rotor 23 is prevented from becoming uneven.

In such a variable capacitor 1, the cover 24 has a shape for accommodating the rotor 23 as described above, and as a result, as shown in FIG. It faces to 22. On the other hand, the stator terminals 27 and 28 are, as described above,
It is provided by a conductive film formed on the outer surface of the end of the stator 22. As in the conventional case described above, this conductive film is generally formed by piercing each end portion of the stator 22 into a layer made of a conductive paste having a predetermined thickness to thereby form each end portion of the stator 22. It is formed by applying a conductive paste to and baking it.

Therefore, the stator terminals 27 and 28
Is usually formed so as to partially extend not only to the end faces of the stator 22 but also to the faces adjacent to these end faces.
Will be formed so that the lower surface of the same extends to the surface 41 facing it. However, in this embodiment, the stator terminals 27 and 28 are formed so as not to extend onto the surface 41 of the stator 22. That is, a part of the stator terminals 27 and 28, which is the surface 41 of the stator 22.
The upper portion is removed by polishing or lapping after the formation of the stator terminals 27 and 28.

FIG. 7 shows one of the stator terminals 27 thus partially removed. As a result of this removal, as shown in FIG. 7, the upper end portion of the stator terminal 27 is
It can be located at a relatively long distance from the edge 40 of the cover 24 or the peripheral surface of the rotor 23.
Therefore, even if an error occurs in the alignment of the rotor 23 and the cover 24 with respect to the stator 22 when the variable capacitor 21 is assembled, or the position of the cover 24 and the rotor 23 shifts when the rotor 23 rotates, the cover 24 does not move. It is possible to reduce the risk of causing a problem of short circuit or defective withstand voltage between the edge 40 and the upper end of the stator terminal 27, or between the peripheral surface of the rotor 23 and the upper end of the stator terminal 27. .

In this embodiment, the stator terminal 27 is used for efficiency in applying polishing, lapping or the like.
Although the portion on the surface 41 of the stator 22 has been removed for both Nos. 28 and 28, the portion on the surface 41 may be removed only for one stator terminal 27 that is effective as a stator terminal. Further, when the stator terminals 27 and 28 are made of a conductive film, they may not be formed on the surface 41 of the stator 22 from the beginning. This is possible, for example, by applying a mask when applying the conductive paste or by applying the printing only to selective areas.

The conductive film for the stator terminals 27 and 28 may be formed by using a conductive paste, wet plating, dry plating, or a combination of these methods. Also, the stator terminals 27 and 2
8 is not formed of a conductive film, but is, for example,
You may form using members, such as a metal foil or a metal plate.

Further, in the above-described embodiment, the cover 24 is made of metal and the rotor 23 is made of metal so that a conductive path for drawing out the rotor electrode 31 is formed by the rotor 23 itself and the cover 24 itself. However, although the rotor terminal 39 is provided on the cover 24, it is not limited to such a configuration. For example, with respect to the rotor, the rotor may be replaced with a rotor which is not made of metal as a whole but is made of an electrical insulator such as alumina and a conductor is formed in a necessary portion. Further, the cover may not be made of metal as a whole, but may be made of an electric insulator such as resin and replaced with, for example, a conductor formed only on the surface.

[0034]

As described above, according to the present invention, the stator terminal formed on the stator is
Since the end edges of the cover do not extend to the opposite surfaces, it is possible to relatively separate the end edges of the cover and the stator terminals and the peripheral surface of the rotor and the stator terminals. Therefore, even if an error occurs in the alignment of the rotor and the cover with respect to the stator when the variable capacitor is assembled, or if the cover and the rotor are misaligned when the rotor rotates, the edges of these covers and the stator terminals are It is possible to reduce the possibility that a short circuit or defective withstand voltage may occur between the rotor and the peripheral surface of the rotor and the stator terminal.
Therefore, it is possible to reduce the size and height of the variable capacitor without encountering the problems of short circuit and withstand voltage failure.

Further , in the present invention , the stator has a structure in which the stator is made of a dielectric material, the stator electrode is formed in the inside thereof, and the stator terminal is formed on the outer surface thereof .
In, in order to increase the short to obtain the maximum capacitance of the opposing distance between the stator electrode and the rotor electrode, the stator electrode in the stator must be positioned close to the rotor or the cover, as a result The stator terminal electrically connected to the stator electrode also comes to be located close to the rotor or the cover. Therefore, the stator terminal tends to be easily designed so that the edge of the cover extends to the opposite surface of the stator, and as a result, problems such as short circuit and defective withstand voltage are likely to be encountered. Will end up. Therefore, in the variable capacitor having the stator having such a structure, as described above, positive design of the stator terminals so that the edges of the cover do not extend to the opposite surface of the stator is short-circuited. It is extremely meaningful for solving the problem of avoiding the problem of poor withstand voltage and withstand voltage.

Further, in the variable capacitor having the stator having the above-described specific structure, when the stator terminal is provided by the conductive film formed on the outer surface of the stator, after the conductive film is formed, one of them is provided. By removing the portion so that the stator terminal does not extend to the surface of the stator facing the edge of the cover, the conductive film can be formed efficiently.

Further, the cover is provided with an adjusting hole for allowing the insertion of a tool for rotating the rotor, and a spring action for contacting the rotor to press the rotor toward the stator. Since such a variable capacitor in which the portion is provided around the adjustment hole is advantageous for downsizing and height reduction, the present invention is applied to such a variable capacitor. At this time, the effect of being able to reduce the possibility of the above-mentioned problems of short circuit and defective withstand voltage becomes more significant.

[Brief description of drawings]

FIG. 1 is a variable capacitor 2 according to an embodiment of the present invention.
It is a perspective view which shows the external appearance of 1 from the upper surface side.

FIG. 2 is a perspective view showing the outer appearance of the variable capacitor 21 shown in FIG. 1 from the lower surface side.

FIG. 3 is a cross-sectional view of the variable capacitor 21 shown in FIG.

4 is an exploded perspective view showing elements included in the variable capacitor 21 shown in FIG. 1. FIG.

5 is a perspective view showing the rotor 23 shown in FIG. 4 from the lower surface side.

FIG. 6 is a perspective view showing the stator 22 shown in FIG. 4 from the lower surface side.

FIG. 7 is a cross-sectional view showing a part of FIG. 3 in an enlarged manner.

8A and 8B show a conventional variable capacitor 1 which is of interest to the present invention, in which FIG. 8A is a plan view and FIG. 8B is a sectional view taken along line BB in FIG. 8A.

FIG. 9 is a cross-sectional view showing an enlarged part of FIG.

[Explanation of symbols]

21 Variable capacitor 22 Stator 23 rotor 24 cover 25 Stator electrode 31 rotor electrode 34 Adjustment hole 35 Spring action part 37, 38 Engaging piece 40 Edge of cover 41 Surface of the stator where the edges of the cover face each other

Claims (3)

(57) [Claims] 1. A stator made of a dielectric material having a stator electrode inside.
A stator having a structure in which a pole is formed and a stator terminal electrically connected to the stator electrode is formed on an outer surface thereof, and a rotor facing the stator electrode via a dielectric. A rotor forming an electrode, and a shape in which the rotor electrode is rotatably housed with respect to the stator in order to change an effective facing area of the rotor electrode with respect to the stator electrode. A conductive cover fixed to the stator and electrically connected to the rotor electrode while facing each other, and the stator terminal is on a surface of the stator facing an edge of the cover. A variable capacitor, characterized in that it is formed so as not to extend to . 2. The stator terminal is provided by a conductive film formed on an outer surface of the stator, and after the conductive film is formed, a part of the conductive film is removed so that The variable capacitor according to claim 1 , wherein the edges of the cover are configured not to extend to the opposite surface. 3. The cover is formed with an adjusting hole for allowing insertion of a tool for rotating the rotor, and is brought into contact with the rotor to press the rotor toward the stator. spring action portion for is provided around the adjustment hole, according to claim 1 or 2
Variable capacitor described in.