JP4319657B2 - Piezoelectric vibrator - Google Patents

Description

  The present invention relates to a piezoelectric vibrator having a structure in which a vibrating arm portion extends from a base portion.

  This type of piezoelectric vibrator, for example, a tuning-fork type quartz vibrator, is generally known as a signal source for engraving the rate of a wristwatch, and has recently been adopted as a synchronization signal source in portable electronic devices. In such a case, there is a demand for a smaller crystal resonator corresponding to the downsizing of electronic equipment.

  The configuration of the tuning fork type crystal resonator is described in Patent Document 1, for example. As shown in FIG. 10, the tuning fork type quartz crystal resonator is provided with tuning fork arms 2a and 2b as a pair of vibrating arms on the base 1, and grooves 3 are formed on both main surfaces of the tuning fork arms 2a and 2b. ing. Excitation electrodes 5 for exciting tuning fork vibrations based on bending vibrations of the tuning fork arms 2a and 2b are provided on both side surfaces of the groove 3 and the tuning fork arms 2a and 2b. When a charge is applied to the tuning fork type vibrator, the side surface of one tuning fork arm 2a and the groove 3 of the other tuning fork arm 2b have the same potential, and the side surface of the other tuning fork arm 2b and the groove 3 of one tuning fork arm 2a. The excitation electrode 5 is connected so that the inside becomes a reverse potential.

  According to such a tuning fork type crystal resonator, the electric field strength in the X-axis direction (tuning fork arm width direction) is increased as compared with the case where the groove 3 is not formed, and between the both side surfaces of the tuning fork arms 2a and 2b. Bending vibration in the Y-axis direction (tuning fork arm length direction) that expands and contracts in opposite directions is strongly excited.

  With this configuration, the vibration loss of the tuning fork arms 2a and 2b is reduced, and a piezoelectric vibrator having a basically good CI (crystal impedance) value can be obtained.

  However, there is a demand for further reduction in the CI value in response to a request for power saving in electronic components using the crystal resonator. Since the tuning fork type crystal resonator described in Patent Document 1 is provided with a groove on the tuning fork arm as described above, the impact resistance is reduced when the crystal resonator is miniaturized, and the impact resistance such as dropping is reduced. There is a risk that problems such as breakage may occur when manufacturing electronic parts and the like because of low properties.

JP 2002-261575 A

  The present invention has been made to solve such a problem, and an object thereof is to reduce the CI value of a piezoelectric vibrator provided with a vibrating arm portion. Another object is to improve impact characteristics of a piezoelectric vibrator having an arm portion.

In the present invention, two vibrating arm portions are extended from the base portion to form a tuning fork type, and at least one of the front surface portion and the back surface portion of the vibrating arm portion is extended along the length direction from the proximal end side of the vibrating arm portion. In a piezoelectric vibrator having a groove formed by
A through-hole provided in a groove located at the base end of the vibrating arm and penetrating between a front surface and a back surface of the vibrating arm;
An electrode that is formed in the through hole and has the same potential as the electrode formed in the groove portion in which the through hole is open ,
When the distal end side and the opposite side of the vibrating arm portion in the piezoelectric vibrator are respectively one end side and the other end side, the other end of the groove portion is more than the tuning fork crotch portion that is the base end portion between the two vibrating arm portions. It is located on the other end side, and one end and the other end of the through hole are located on the one end side and the other end side, respectively, with respect to the tuning fork crotch portion .

Another invention is a piezoelectric vibrator formed in a tuning fork shape by extending two vibrating arms from a base,
A plurality of groove portions formed along the length direction from the base end side of the vibration arm portion and divided along the length direction on at least one of the front surface portion and the back surface portion of the vibration arm portion;
A through-hole provided in a groove located at the base end of the vibrating arm and penetrating between a front surface and a back surface of the vibrating arm;
An electrode that is formed in the through hole and has the same potential as the electrode formed in the groove portion in which the through hole is open ,
When the distal end side and the opposite side of the vibrating arm portion in the piezoelectric vibrator are respectively one end side and the other end side, the other end of the groove portion is more than the tuning fork crotch portion that is the base end portion between the two vibrating arm portions. It is located on the other end side, and one end and the other end of the through hole are located on the one end side and the other end side, respectively, with respect to the tuning fork crotch portion .

In the present invention, a through hole is provided in a groove located at the base end portion of the vibrating arm portion, and an electrode is also provided in the through hole. The force that vibrates the vibrating arm is mainly generated by the electric lines of force between the electrode in the groove and the side electrode of the vibrating arm, but the action of vibrating the vibrating arm by the electric lines of force The root (base end) is large. Therefore, if a through hole is formed in the base end portion of the vibrating arm portion and an electrode is provided here, the electric lines of force at the base end portion are increased and the vibration is efficiently performed. For this reason, the crystal impedance (CI value) of the piezoelectric vibrator is reduced, and power consumption can be suppressed .

(First embodiment)
FIG. 1 is a diagram showing an embodiment in which a piezoelectric vibrator of the present invention is applied to a tuning fork type crystal vibrator. A crystal resonator body (crystal piece) in this crystal resonator includes a substantially square base portion 1 having a notch portion 11 in which upper portions of both side portions are cut out in a rectangular shape, and an upper end side of the base portion 1. Two (a pair of) vibrating arm portions 2 (2a, 2b) extending in parallel with an interval are provided, and the entire shape is configured as a tuning fork type crystal piece. Furthermore, a groove portion 3 is formed on the front surface portion and the back surface portion of the vibrating arm portion 2 (2a, 2b) from the proximal end portion to the distal end side of the vibrating arm portion 2 (2a, 2b), respectively. In the groove portion 3 positioned at the base end portion, for example, a rectangular through-hole 4 (which penetrates between both main surfaces 2 (2a, 2b) of the vibrating arm portion, that is, penetrates between the front surface portion and the back surface portion ( 4a, 4b) are formed. In FIG. 1, the through hole 4 is described as being slightly narrower than the groove portion 3, but may be formed in a square shape having a length corresponding to the width of the groove portion 3, for example.

  The planar shape of the base portion 1 between the pair of vibrating arm portions 2a and 2b is curved, and each groove portion 3 has the lowermost portion (the tip side of the vibrating arm portion 2) of the curved portion (tuning fork or fork portion). ) The lower end of the through-hole 4 is positioned at the same height level as the lowermost portion 20.

  Here, the excitation electrode and the extraction electrode will be described with reference to FIG. 2. In this crystal resonator, one electrode and the other electrode forming a pair exist. First, paying attention to the vibrating arm portion 2a, one excitation electrode 51 is formed over the entire inner surface of the groove portion 3 of the vibrating arm portion 2a and the entire inner surface of the through hole 4a in the groove portion 3, and the vibrating arm portion The other excitation electrode 61 is formed in the upper part from the groove part 3 in the both side surfaces 21 and 21 and the main surfaces 22 and 22 (surface part and back surface part) of 2a. In FIG. 2, the excitation electrode 51 is indicated by using a diagonal line and a black dotted area separately for easy viewing of the drawing.

  Focusing on the vibrating arm 2b, the other excitation electrode 61 is formed over the entire inner surface of the groove 3 of the vibrating arm 2b and the entire inner surface of the through hole 4b in the groove 3, and the vibrating arm 2b. One excitation electrode 51 is formed at a position above the groove portion 3 in the both side surfaces 21 and 21 and the main surfaces 22 and 22 (front surface portion and back surface portion). And the pattern which consists of the extraction electrode 52 is formed in the surface of the base 1 so that these one excitation electrodes 51 may be electrically connected, while the other excitation electrodes 61 are electrically connected A pattern made of extraction electrodes 62 is formed on the surface of the base 1.

When the dimensions of each part of the crystal resonator are shown with reference to FIG. 3, the length L1 of the vibrating arm 2 (2a, 2b) is, for example, 1650 μm, and the length L2 of the groove 3 is, for example, 847 μm. A length L3 from the bottom surface of the base portion 1 to the lowermost portion 20 of the tuning fork or portion is, for example, 600 μm. The width W1 of the vibrating arm 2 (2a, 2b) is, for example, 100 μm, the width W2 of the groove 3 is, for example, 65 μm, and the width W3 of the bottom surface of the base 1 is, for example, 500 μm.

  Next, the operation of the above embodiment will be described. Both side surfaces and the main surface of the vibrating arm portion 2a and the groove portion 3 and the through hole 4b of the vibrating arm portion 2b have the same potential, and both the side surface and the main surface of the vibrating arm portion 2b and the groove portion 3 and the through hole of the vibrating arm portion 2a. This is the opposite potential to 4a. FIG. 4A is a diagram schematically showing electric lines of force generated in the vibrating arm portions 2 a and 2 b in a structure in which the through hole 4 is not provided. By forming the groove portion 3, the X-axis direction ( The electric field strength in the width direction of the vibrating arm portion 2 is increased, and bending vibration in the Y-axis direction that expands and contracts in the opposite direction between the vibrating arm portions 2a and 2b is strongly excited. When the through-hole 4 is provided as in the present embodiment, electric lines of force are generated from the inner surface of the through-hole 4 as shown in FIG. 4 (b). Since the electric force line generated here contributes to the vibration of the vibrating arm part 2, the electric force line at the base end part of the vibrating arm part 2 increases. By doing so, the vibration efficiency is increased and the CI value is reduced. When the CI value of the crystal resonator of this embodiment was actually measured, it was about 3 kΩ smaller than that of the crystal resonator having the structure shown in FIG.

  In forming the through-hole 4, it is necessary to have a size that does not generate a vibration mode other than the original vibration mode. In other words, from the viewpoint of increasing the lines of electric force, the larger the through hole 4 is, the better. However, if it is made too large, the vibration mode between the mutually facing surfaces in the through hole 4 increases, and a planned oscillation frequency, for example, 32 kHz is obtained. I can't do that.

  FIG. 5 shows a modification of the first embodiment. In this example, the vertical center point of the through-hole 4 is located at the same height level as the lowermost part 20.

(Second Embodiment)
As a second embodiment, a substantially square base 1 provided with a notch 11 in which the upper sides of both sides are cut out in a rectangular shape, and the base 1 extend from the upper end side in parallel with each other at an interval. 2 (a pair of) vibrating arm portions 2 (2a, 2b), and further, a groove portion 3 is formed along the length direction from the upper end side of the base portion of each vibrating arm portion 2, and the groove portion 3 is The crystal resonator divided in the length direction will be described.

  For example, as shown in FIG. 6, such a crystal resonator has grooves 31 and 32 that are bisected in the length direction on the front surface and / or the back surface of the vibrating arms 2 a and 2 b from the base end side. It is comprised so that it may form along a length direction.

  As another example, in the crystal resonator, as shown in FIGS. 7 and 8, two groove portions 31 and 32 having different lengths in the length direction from the base end portion on the front surface portion and / or the back surface portion of the tuning fork arm. Are formed respectively.

As yet another example, as shown in FIG. 9, the crystal resonator has grooves 31, 32, and 33 that are divided into three equal parts in the length direction on the front surface and / or back surface of the tuning fork arm. It is comprised so that it may form along a length direction from the side. In addition, the crystal resonator may be configured by combining the first embodiment and the second embodiment. For example, in FIG. 6, the through hole 6 may be formed in the groove 32 on the base end side as in the first embodiment .

1 is a schematic plan view showing a tuning fork type crystal resonator according to a first embodiment of the present invention. 1 is a perspective view showing a tuning fork type crystal resonator according to a first embodiment of the present invention. It is explanatory drawing which shows the dimension of the said tuning fork type crystal resonator. It is the FF 'sectional view taken on the line of FIG. It is a schematic plan view which shows the other example of the tuning fork type crystal resonator based on the 1st Embodiment of this invention. FIG. 6 is a schematic plan view showing a tuning fork type crystal resonator according to a second embodiment of the present invention. It is a schematic plan view which shows the other example of the tuning fork type | mold crystal resonator based on the 2nd Embodiment of this invention. It is a schematic plan view which shows the other example of the tuning fork type | mold crystal resonator based on the 2nd Embodiment of this invention. It is a schematic plan view which shows the other example of the tuning fork type | mold crystal resonator based on the 2nd Embodiment of this invention. It is a schematic plan view showing a conventional tuning fork type crystal resonator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base part 11 Notch part 2 Vibrating arm part 20 Lowermost part 3 Groove part 4 Through-hole 51 One excitation electrode 61 The other excitation electrode

Claims (2)

Two vibrating arm portions extend from the base portion to form a tuning fork shape, and are formed on at least one of the front surface portion and the back surface portion of the vibrating arm portion along the length direction from the proximal end side of the vibrating arm portion. In a piezoelectric vibrator having a groove,
A through-hole provided in a groove located at the base end of the vibrating arm and penetrating between a front surface and a back surface of the vibrating arm;
An electrode that is formed in the through hole and has the same potential as the electrode formed in the groove portion in which the through hole is open ,
When the distal end side and the opposite side of the vibrating arm portion in the piezoelectric vibrator are respectively one end side and the other end side, the other end of the groove portion is more than the tuning fork crotch portion that is the base end portion between the two vibrating arm portions. A piezoelectric vibrator, wherein the piezoelectric vibrator is located on the other end side, and one end and the other end of the through hole are located on the one end side and the other end side of the tuning fork crotch portion , respectively. In the piezoelectric vibrator formed in a tuning fork shape by extending two vibrating arms from the base,
A plurality of groove portions formed along the length direction from the base end side of the vibration arm portion and divided along the length direction on at least one of the front surface portion and the back surface portion of the vibration arm portion;
A through-hole provided in a groove located at the base end of the vibrating arm and penetrating between a front surface and a back surface of the vibrating arm;
An electrode that is formed in the through hole and has the same potential as the electrode formed in the groove portion in which the through hole is open ,
When the distal end side and the opposite side of the vibrating arm portion in the piezoelectric vibrator are respectively one end side and the other end side, the other end of the groove portion is more than the tuning fork crotch portion that is the base end portion between the two vibrating arm portions. A piezoelectric vibrator, wherein the piezoelectric vibrator is located on the other end side, and one end and the other end of the through hole are located on the one end side and the other end side of the tuning fork crotch portion , respectively.

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