JP4298322B2 - Tuning fork crystal unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tuning fork type crystal resonator (hereinafter referred to as a tuning fork type resonator) as an industrial technical field, and more particularly to a tuning fork type resonator that promotes downsizing while maintaining a small crystal impedance (CI).
[0002]
[Prior art]
(Background of the Invention) A tuning fork type vibrator is known as a signal source for engraving a rate for a watch in particular, and has recently been applied to a gyroscope sensor element or the like. Even in such a case, downsizing is required in the same manner as other electronic components.
[0003]
(Example of Prior Art) FIG. 3 is a diagram of a tuning fork vibrator for explaining one conventional example. FIG. 3 (a) is an external view, FIG. 3 (b) is a top view, and FIG. 3 (c) is a front view. It is.
The tuning fork vibrator is made of, for example, a Z-cut (commonly known as +5 degree X cut) tuning fork crystal piece, and has a tuning fork base 1 and a pair of tuning fork arms 2 (ab). Usually, the X axis of the crystal axis (XYZ) is the width, the Y axis is the length, and the Z axis is the thickness. Then, the excitation electrode 3 is formed on the four surfaces of each tuning fork arm 2 (ab) (FIG. 3A).
[0004]
In the excitation electrode 3, in one tuning fork arm 2 a, each set of opposed surfaces (both main surfaces and both side surfaces) has the same potential, and one set and the other set of opposed surfaces have opposite potentials. In the other tuning fork arm 2b, the same potential of one tuning fork arm 2 (ab) is connected in common with the other tuning fork arm 2a as a reverse potential with respect to one tuning fork arm 2a.
[0005]
In such a case, for example, if both main surfaces of one tuning fork arm 2a are set to a positive potential and both side surfaces are set to a negative potential, the electric fields indicated by the arrows cause the main surface of the tuning fork arm 2 (ab) to be connected to the outer surface and the inner surface. “FIG. 3B” where electric field synthesis vectors P and Q directed to the side face are generated.
[0006]
Then, due to the piezoelectric inverse effect caused by the electric field synthesis vectors P and Q, the outer surface of one tuning fork arm 2a is reduced and the inner surface is expanded. Therefore, the tuning fork arm 2a bends outward as indicated by the arrow A. Then, the other tuning fork arm 2b having the potential opposite to that of the one tuning fork arm 2a is bent outward in the opposite direction as shown by an arrow B (FIG. 3 (c)).
[0007]
Contrary to the above, if both main surfaces of one tuning fork arm 2a are set to -potential (not shown) and both side surfaces are set to + potential, the outer surface and the inner surface of one tuning fork arm 2a are directed to both main surfaces. An electric field vector is generated. The outer surface expands and the inner surface contracts. Therefore, one tuning fork arm 2a bends inward. The other tuning fork bay 2b bends inward in the opposite direction.
[0008]
Thus, when an alternating voltage having a ± potential is applied to both main surfaces and both side surfaces, the pair of tuning fork arms 2 (ab) excite horizontal vibration, that is, tuning fork vibration in opposite directions. In these, the resonance frequency is determined by the length L and the width W of the tuning fork arm 2 (ab), and is approximately proportional to W / L2. Then, it is incorporated into an oscillation circuit and functions as an inductor element having a high Q here as an oscillator.
[0009]
[Problems to be solved by the invention]
(Problems of the prior art) However, the tuning fork vibrator having the above-described configuration has a problem that the CI increases as the size of the tuning fork vibrator decreases. That is, when the width of the tuning fork arm 2 (ab) is reduced, the width of the main surface electrode of the excitation electrode 3 is also reduced, and a sufficient electric field cannot be supplied, resulting in an increase in CI.
[0010]
When a tuning fork type vibrator is applied to a tuning fork type angular velocity sensor, for example, an excitation electrode for exciting tuning fork vibration is formed on one tuning fork arm 2a, and a sensor electrode (not shown) for detecting angular velocity is formed on the other tuning fork arm 2b. To do. Therefore, since tuning fork vibration is excited only by one tuning fork arm 2a, there is a problem that CI becomes large.
[0011]
(Object of the Invention) An object of the present invention is to provide a tuning fork type vibrator that keeps CI small and promotes miniaturization.
[0012]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-204141
[Means for Solving the Problems]
(Points of interest) The present invention has focused on the relationship between the main surface electrode width and CI described above, that is, the CI decreases as the main surface electrode area increases. In Patent Document 1, a concave portion 4 is provided to obtain a linear electric field in the X-axis direction, and the idea is basically different.
[0014]
[Means for Solving the Problems]
The present invention provides a tuning-fork crystal consisting of a pair of tuning fork arms and fork base having an excitation electrode for exciting the tuning fork to the main surface and the side surface, in either direction of the two-dimensional direction to the main surface of the tuning fork arms Each of the plurality of concave and convex portions is provided to form the excitation electrode. As a result, the area of the excitation electrode is increased, the electric field strength is increased, and the CI is reduced. An embodiment of the present invention will be described below.
[0015]
【Example】
FIG. 1 is a partial external view of a tuning fork vibrator for explaining an embodiment of the present invention. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.
[0016]
As described above, the tuning fork vibrator is composed of a Z-cut tuning fork crystal piece having a tuning fork base 1 and a pair of tuning fork arms 2 (ab), and an excitation electrode 3 for exciting tuning fork vibration is provided on each tuning fork arm 2 (ab). It is provided. However, the X axis is the width, the Y axis is the length, and the Z axis is the thickness.
[0017]
Then, on both main surfaces of each tuning fork arm 2 (ab), recesses 4 are formed at regular intervals by etching using, for example, a printing technique in a two-dimensional direction of length (Y axis of crystal axis) and width (X axis of the crystal axis). Is provided. In short, two-dimensional concavo-convex portions 4 and 5 are provided on both main surfaces of each tuning fork arm 2 (ab). Here, the concave and convex portions 4 and 5 are the same square, and each side is parallel to the length and width direction, and five in the width direction and eight in the length direction are formed. The depth of the recess 4 is the length of one side of the square, that is, the recess 4 is a cube. And it is set as the structure which formed the excitation electrode 3 on the uneven | corrugated | grooved parts 4 and 5 containing the side surface in the recessed part of both main surfaces.
[0018]
In such a case, the surface area of the tuning fork main surface on which the excitation electrode 3 according to the present embodiment is formed is three times that of the conventional example in which the tuning fork main surface is a flat surface. For example, if the length of one side of the concavo-convex portions 4 and 5 is 10 μm, for example, it is 4000 μm ^{2 in the} conventional example, and 12000 μm ^{2 in} this embodiment. Therefore, since the electric field density between both main surfaces and both side surfaces increases, CI decreases.
[0019]
[Other matters]
In the above-described embodiment, each side of the square having the concavo-convex portions 4 and 5 is parallel to the width and length direction of the tuning fork arm, but may be as shown in FIG. 2 (plan view), for example. That is, the uneven portions 4 and 5 may be formed along the X′Y ′ coordinates by rotating a two-dimensional geometric coordinate axis XY (not shown) by 45 degrees. Note that the black coating portion is the recess 4. In this case, compared with the case where each side of the square forming the recess 4 is parallel to the width and the length direction, the electric field density from the side surface of the recess to the side surface of the tuning fork increases, so that the CI can be further reduced.
[0020]
Moreover, although the uneven | corrugated | grooved parts 4 and 5 were each square, for example, the recessed part 4 may be arranged in a two-dimensional direction as a circle, and the shape of the uneven | corrugated | grooved parts 4 and 5 can be selected arbitrarily. However, the surface area can be maximized when it is square. Moreover, although the recessed part 4 was made into the cube, the depth direction can be set arbitrarily. However, it goes without saying that the surface area increases in proportion to the depth.
[0021]
Further, in practice, the concave portion 4 is formed by etching, so that it does not necessarily become a geometrical cube. And although the excitation electrode 3 was formed only on the uneven surface for convenience, it is actually formed over the outer periphery of the uneven surface. Although described as a tuning fork vibrator, it is needless to say that the present invention can also be applied to a drive electrode that excites the tuning fork vibration in the angular velocity sensor described above.
[0022]
【The invention's effect】
The present invention provides a tuning-fork crystal consisting of a pair of tuning fork arms and fork base having an excitation electrode for exciting the tuning fork to the main surface and the side surface, in either direction of the two-dimensional direction to the main surface of the tuning fork arms Each of the plurality of concave and convex portions is provided to form the excitation electrode. Therefore, it is possible to provide a tuning fork vibrator that increases the area of the excitation electrode to increase the electric field strength and promotes downsizing while maintaining the CI small.
[Brief description of the drawings]
FIG. 1 is a partial external view of a tuning fork vibrator for explaining an embodiment of the present embodiment.
FIG. 2 is a partial plan view of a tuning fork vibrator for explaining another example of the present embodiment.
3A and 3B are diagrams of a tuning fork type vibrator for explaining a conventional example. FIG. 3A is an external view, FIG. 3B is a top view, and FIG. 3C is a front view.
[Explanation of symbols]
1 tuning fork base, 2 tuning fork arm, 3 excitation electrode, 4 concave, 5 convex.

Claims (1)

In the tuning fork type quartz resonator consisting of a pair of tuning fork arms and fork base having an excitation electrode for exciting the tuning fork to the main surface and side surfaces, respectively in either direction of the two-dimensional direction to the main surface of the tuning fork arms and a plurality tuning fork crystal resonator, characterized in that the formation of the excitation electrodes an uneven portion formed by providing.

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