Variable capacitor

Details Variable capacitor Variable capacitor

1998-09-08

2001-05-01

Dinkins, Athony (Department: 2831)

Electricity: electrical systems and devices

Electrostatic capacitors

Variable

C361S283100, C361S298200

Reexamination Certificate

active

06226168

ABSTRACT:

This application corresponds to Japanese Patent Application No. 9-242305, filed on Sep. 8, 1997, which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The present invention relates to a variable capacitor, and particularly to a variable capacitor in which the effective overlapping area between a stator electrode and a rotor electrode is varied through rotation of the rotor electrode relative to the stator electrode to thereby vary capacitance.
2. Description of the Related Art:
One type of variable capacitor is described in Japanese Patent Application No. 9-126586 filed on May 16, 1997 by the applicant of the present invention.
FIG. 7
shows a variable capacitor
1
proposed in the application for patent.
Referring to
FIG. 7
, the variable capacitor
1
is primarily composed of a stator
2
, a rotor
3
, and a cover
4
. A major portion of the stator
2
is formed of a dielectric, such as ceramic. The rotor
3
is formed of a metal, such as brass. The cover
4
is formed of a metal, such as stainless steel or copper alloy.
The above-mentioned elements of the variable capacitor
1
will next be described in detail.
The stator
2
generally has a symmetrical structure. Stator electrodes
5
and
6
are formed side by side in the stator
2
. Stator terminals
7
and
8
are formed of a conductive film on the outer surfaces of corresponding end portions of the stator
2
so as to establish electric connection with the stator electrodes
5
and
6
, respectively.
A dielectric layer
9
covering the stator electrodes
5
and
6
is formed of a portion of the dielectric that constitutes the stator
2
.
As described above, the two stator electrodes
5
and
6
and the two stator terminals
7
and
8
are formed so as to impart a symmetrical structure to the stator
2
, so that the orientation of the stator
2
need not be a consideration in the assembly of the variable capacitor
1
.
The rotor
3
is placed on the stator
2
so that the rotor
3
comes in contact with the outer surface of the dielectric layer
9
. A substantially semicircular rotor electrode
11
projects from the bottom side (as viewed in
FIG. 7
) of the rotor
3
so as to face the stator electrode
5
(and electrode
6
) with the dielectric layer
9
disposed therebetween.
FIG. 8
shows a bottom view of the rotor
3
.
A protrusion
12
extending out as far as the rotor electrode
11
is also formed on the bottom side of the rotor
3
in a region other than that where the rotor electrode
11
is formed. The protrusion
12
serves to prevent an inclination of the rotor
3
which would otherwise result due to the presence of the rotor electrode
11
.
A driver groove
13
, which assumes a form of, for example, a square through-hole, is formed in the rotor
3
in order to receive a driver or a like tool used for rotating the rotor
3
.
The cover
4
is attached onto the stator
2
while accommodating the rotor
3
. The cover
4
allows the rotor
3
to rotate relative to the stator
2
. The cover
4
has an adjustment hole
14
formed therein that allows the driver groove
13
to be exposed therethrough. Thus, when the rotor
3
is to be rotated, a driver or a like tool can be inserted into the driver groove
13
through the adjustment hole
14
.
The cover
4
has a spring-action portion
15
formed around the adjustment hole
14
. The spring-action portion
15
is partially in contact with the upper surface (as viewed in
FIG. 7
) of the rotor
3
to thereby affect a spring force which presses the rotor
3
against the stator
2
. The spring-action portion
15
is formed in such a manner as to incline downward toward the center of the adjustment hole
14
, thereby applying a spring force by means of a metallic material present around the adjustment hole
14
.
A plurality of protrusions
16
are formed on the spring-action portion
15
at equal intervals along a rotational direction of the rotor
3
. These protrusions
16
substantially come into point contact with the rotor
3
. These protrusions
16
can be formed through, for example, embossing a metallic plate which constitutes the cover
4
.
The cover
4
also has a rotor terminal
17
extending downward (as viewed in FIG.
7
).
The variable capacitor
1
including the above-mentioned stator
2
, rotor
3
, and cover
4
is assembled in the following manner.
The rotor
3
is placed on the stator
2
, and then the cover
4
is placed on the stator
2
in such a manner as to cover the rotor
3
. Next, the cover
4
is attached onto the stator
2
while being pressed toward the stator
2
so as to press the rotor
3
against the stator
2
.
In this case, the rotor terminal
17
integrated with the cover
4
is positioned so as to face the stator terminal
8
provided on the stator
2
. In the structure illustrated in
FIG. 7
, the stator terminal
8
does not function as a stator terminal, and thus no electrical problem will arise.
In the thus-assembled state, the rotor electrode
11
faces the stator electrode
5
with the dielectric layer
9
disposed therebetween to thereby develop capacitance. In order to vary the capacitance through varying the effective overlapping area between the rotor electrode
11
and the stator electrode
5
, the rotor
3
is rotated. The capacitance is externally presented between the stator terminal
7
and the rotor terminal
17
. The stator terminal
7
is electrically connected to the stator electrode
5
. The rotor terminal
17
is integrated with the cover
4
, which is in contact with the rotor
3
on which the rotor electrode
11
is formed.
In the variable capacitor
1
, the protrusions
16
formed on the spring-action portion
15
of the cover
4
are substantially in point contact with the rotor
3
. Accordingly, the positions where the protrusions
16
press against the rotor
3
are reliably fixed. Even when the parallelism of the rotor
3
between the rotor-electrode side and the opposite side is poor or when the flatness of the rotor-electrode side or the opposite side of the rotor
3
or the flatness of a tip portion of the spring-action portion
15
is poor, a contact pressure can be applied in a stable manner to the rotor
3
. That is, the above-described variations in machining are effectively “absorbed” in that they do not have an appreciable impact.
Thus, the rotor
3
is uniformly pressed against the stator
2
over the entire surface of the rotor
3
. Therefore, the capacitance of the variable capacitor
1
is stabilized and varies smoothly with rotation of the rotor
3
. Also, drift in the set position is stabilized, and torque required to rotate the rotor
3
becomes uniform.
When it is desired to make the variable capacitor
1
thinner, this can be effectively accomplished by making the rotor
3
thinner. However, when the rotor
3
is thinned to a thickness of 0.3 mm or less, a pressing force applied to the rotor
3
by the spring-action portion
15
may cause the rotor
3
to deform. Particularly, as in the case of the variable capacitor
1
shown in
FIG. 7
in which the protrusions
16
are formed on the spring-action portion
15
, the pressing force is applied to the rotor
3
in one or more localized regions. Thus, the rotor
3
is known to be susceptible to deformation. Such an undesirable deformation of the rotor
3
hinders smooth capacitance variation affected through rotation of the rotor
3
, typically causing a problem in that the linearity of capacitance variation is impaired, and also rendering the set position (and set capacitance) subject to drift.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a variable capacitor capable of solving at least the above-mentioned problem of undesirable rotor deformation.
The present invention is based in part on the following findings.
In
FIG. 7
, the dot-and-dash line represents the position of a section of the spring-action portion
15
of the cover
4
, which section comes into contact with the rotor
3
. More specifically, this line denotes the position of a contact por

Affiliated with

Also associated with

Rating

Variable capacitor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Variable capacitor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Variable capacitor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2456345