Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-10-16
2002-04-16
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S366000
Reexamination Certificate
active
06373169
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric resonator containing electrostatic capacitors, and more particularly, the present invention relates to a capacitor-containing piezoelectric resonance component having an improved arrangement of electrodes arranged to define capacitors and spaces for allowing for free and unhindered vibration of the vibration portion of the piezoelectric resonator.
2. Description of the Related Art
Conventionally, capacitor-containing piezoelectric resonance components have widely been used as piezoelectric vibrators. For example, Japanese Unexamined Patent Application Publication No. 7-94997 discloses a capacitor-containing piezoelectric resonance component
201
, as shown in FIG.
32
. In the capacitor-containing piezoelectric resonance component
201
, dielectric substrates
203
and
204
are, respectively, disposed on upper and lower surfaces of a piezoelectric resonance element
202
. The piezoelectric resonance element
202
uses one of a thickness-vertical vibration mode and a thickness-extensional sliding mode that are energy-trap type vibration modes. Vibration spaces
205
and
206
are arranged to allow for free and unhindered vibration in the vibrating section of the piezoelectric resonance element
202
. In the conventional example, each of the vibration spaces
205
and
206
is defined by a concave section formed in one of the main surfaces of each of the dielectric substrates
203
and
204
, respectively.
In the resonance component
201
, capacitor-forming electrodes
207
to
209
are disposed on outer surfaces of the layered body defined by the stacked dielectric substrates
203
and
204
to define capacitors. The capacitor-forming electrode
208
is connected to a ground potential. The capacitors are positioned individually between the capacitor-forming electrodes
207
(hot side) and
208
and between the capacitor-forming electrodes
209
(hot side) and
208
.
In addition, Japanese Unexamined Patent Application Publication No. 3-240311 discloses a capacitor-containing piezoelectric resonance component
211
, as shown in FIG.
33
. In the capacitor-containing piezoelectric resonance component
211
, dielectric substrates
213
and
214
are disposed on upper and lower surfaces of a piezoelectric resonance element
212
. In this conventional example, the dielectric substrates
213
and
214
are individually adhered to a piezoelectric resonance element
212
via insulating adhesive layers
215
and
216
, respectively. Vibration spaces
217
and
218
are formed of openings in the respective insulating adhesive layers
215
and
216
. Similarly to the capacitor-containing piezoelectric resonance component
201
, capacitor-forming electrodes
219
to
221
are disposed on outer surfaces of the layered body including the stacked dielectric substrates
213
and
214
to define capacitors.
In each of the capacitor-containing piezoelectric resonance components
201
and
211
, capacitors are individually defined between the intermediate capacitor-forming electrodes
208
and
220
(which are connected to the ground potential) and the oppositely arranged capacitor-forming electrodes
207
and
219
, respectively, via a predetermined gap G and between the intermediate capacitor-forming electrodes
208
and
220
and the oppositely arranged capacitor-forming electrodes
209
and
221
, respectively, via the predetermined gap G. In these cases, the electrostatic capacitance of each of the capacitors depends on the relative permittivity of the dielectric substrate, the size of the gap G between the capacitor-forming electrodes, and other such factors.
In the capacitor-containing piezoelectric resonance components
201
and
211
described above, however, a problem arises in that the electrostatic capacitance of the capacitors varies according to variations in the positions of the capacitor-forming electrodes
208
and
220
.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a capacitor-containing piezoelectric resonance component that minimizes and eliminates variation in the electrostatic capacitance.
According to one preferred embodiment of the present invention, a capacitor-containing piezoelectric resonance component includes an energy-trap piezoelectric resonance element having a piezoelectric plate, and a first vibratory electrode and a second vibratory electrode that are individually disposed on portions of two main surfaces of the piezoelectric plate so that a lower surface and an upper surface thereof oppose each other via the piezoelectric plate. A dielectric substrate is disposed on at least one surface of the piezoelectric resonance element with a vibratory space being defined to allow for free and unhindered vibration of a vibrating section. A first capacitor-forming electrode and a second capacitor-forming electrode are arranged on the dielectric substrate so as to oppose each other via a predetermined gap G in a direction that is substantially parallel to the main surface of the dielectric substrate. When G′ represents the distance between an end portion of the second capacitor-forming electrode and an end portion of the vibration space along the direction in which the first capacitor-forming electrode and the second capacitor-forming electrode oppose each other, at least one of the following expressions is satisfied:
G′/G≧
1 and
G′/G≦
−0.4.
As described above, since the ratio G′/G is within the desired range, even in a case where positions of the first and second capacitor-forming electrodes vary, arranging the ratio of G′/G to be within the specific range allows the variation in electrostatic capacitance to be significantly reduced. This is especially effective in a case where the position of the second capacitor-forming electrode varies. Therefore, capacitor-containing piezoelectric resonance components having excellent characteristics are easily obtained with this unique construction. In addition, since manufacturing precision of forming the capacitor-forming electrodes need not be improved, productivity of the capacitor-containing piezoelectric resonance component is greatly improved.
According to another preferred embodiment of the present invention, a capacitor-containing piezoelectric resonance component includes an energy-trap piezoelectric resonance element having a piezoelectric plate, and a first vibratory electrode and a second vibratory electrode that are individually disposed on portions of two main surfaces of the piezoelectric plate so that a lower surface and an upper surface thereof oppose each other via the piezoelectric plate. A dielectric substrate is disposed on at least one surface of the piezoelectric resonance element with a vibration space being secured therein for allowing for free and unhindered vibration of a vibrating section of the resonance element. A dielectric layer is disposed between the piezoelectric resonance element and the dielectric substrate and includes an opening provided for defining at least a portion of the vibration space. When &egr;
1
represents the relative permittivity of the dielectric substrate and &egr;
2
represents the relative permittivity of the dielectric layer, a relationship &egr;
2
/&egr;
1
≦0.063 is satisfied.
As described above, since the &egr;
2
/&egr;
1
ratio is within the desired range, even in a case where positions of the first and second capacitor-forming electrodes vary, arranging the &egr;
2
/&egr;
1
ratio to be within the desired range minimizes the variation in electrostatic capacitance to be significantly reduced. Particularly, this is especially effective in a case where the position of the second capacitor-forming electrode varies. Therefore, capacitor-containing piezoelectric resonance components having excellent characteristics are easily obtained. In addition, since precision of the capacitor-forming electrodes need not be improved, productivity of the capaci
Addison Karen B
Murata Manufacturing Co. Ltd.
Ramirez Nestor
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