JP4638263B2 - Tuning fork type bending vibrator - Google Patents

Description

  The present invention relates to a tuning fork type bending vibrator having a structure for increasing electric field efficiency.

  As shown in FIG. 11, a conventional tuning fork type bending vibrator 1 has a rectangular base portion 2 supported by electrode terminals of a casing (not shown) based on a thin quartz plate and two pieces extending in parallel from the base portion 2. The vibrating arm portions 3 and 4 are formed in a substantially U shape, and the whole has a shape similar to a so-called tuning fork. Such a tuning-fork type bending vibrator 1 has a low vibration frequency and a low current consumption when incorporated in an oscillator, so that it is used as a time reference signal source for a watch.

  The tuning fork-type bending vibrator 1 is formed by cutting at an angle of about + 1 ° X-axis rotation from a rough quartz crystal Z plate. For example, when the bending vibrator 1 uses 32.768 KHz as a reference vibration frequency, the width of each of the vibrating arm portions 3 and 4 with respect to the length L of the vibrating arm portions 3 and 4 is 2.5 mm. W is set to 0.26 mm. Further, excitation electrodes 5 and 6 having different polarities are formed along the longitudinal direction of the vibrating arm portions 3 and 4 from the base end portions of the vibrating arm portions 3 and 4, respectively.

  In such a tuning fork type bending vibrator 1, the resonance motion accompanying the vibration of the vibrating arm portions 3 and 4 is converted into an electric signal by the excitation electrodes 5 and 6, and this is used as a specific vibration frequency.

  As described above, the tuning fork-type bending vibrator 1 has a specific vibration frequency set according to the length and width size of the vibrating arm portions 3 and 4, and the following relational expression (Equation 1) holds.

Where F: vibration frequency (Hz)
L: Length of vibrating arm (m)
W: width of vibrating arm (m)
C ′ ₂₂ : Elastic stiffness constant (N / m ² )
ρ: Crystal density (kg / m ³ )
It is.

  Accordingly, when the tuning fork type bending vibrator 1 shown in FIG. 11 is changed in design based on the required specifications, each parameter is determined under (Equation 1). Therefore, when the vibration frequency 32.768 KHz of the tuning-fork type bending vibrator 1 is fixed and reduced in size, for example, when the length of the vibrating arm portions 3 and 4 is shortened to about 1.9 mm, the vibrating arm The widths of the portions 3 and 4 are as narrow as 0.15 mm.

  However, the width of the vibrating arm portions 3 and 4 is required to be at least 200 μm in order to maintain the mechanical strength and quality as a vibrator. Since the formation width of 6 is also narrowed, the electric field efficiency is lowered. This reduction in electric field efficiency increases the equivalent series resistance value, which has been a factor in deteriorating the quality of the tuning fork type bending vibrator.

  Examples of such a small tuning fork-type bending vibrator for the purpose of improving electric field efficiency are shown in Patent Document 1 and Patent Document 2. For example, as shown in FIGS. 12 and 13, a tuning-fork type bending having a structure in which a groove portion 17 for forming an excitation electrode in the thickness direction t 1 of the vibrating arm portions 13 and 14 is provided in the vibrating arm portions 13 and 14. There is a vibrator 11. The groove portion 17 is set to a depth t2 that does not penetrate from the upper surface and the lower surface of the vibrating arm portions 13 and 14. By providing such a groove portion 17, an excitation electrode opposed to the excitation electrode provided on the side surface of each vibrating arm portion 13, 14 can be formed, thereby increasing the electric field efficiency.

Further, Patent Document 2 and Patent Document 3 show examples in which the shape of the groove portion 17 is miniaturized in order to facilitate the processing of the tuning fork type bending vibrator having the groove portion 17. In the tuning fork-type bending vibrator shown in these patent documents, a plurality of small grooves that do not penetrate in the thickness direction are formed along the longitudinal direction of the pair of vibrating arms. Further, according to this tuning fork type bending vibrator processing method, the outer shape of the vibrating arm portion and the processing of the groove portion can be processed by the etching process under the same conditions by finely designing the groove portion made of the small groove. It has become.
JP 2003-60482 Japanese Patent No. 3477618 JP 2004-260593 A

  By the way, in the tuning fork type bending vibrator, it is known that the electric field efficiency increases as the number of excitation electrodes extending substantially in parallel with the excitation electrode provided on the side surface in the thickness direction of the vibration arm portion increases. ing. However, in the groove portion 17 as shown in Patent Document 2 and Patent Document 3, the groove depth t2 is controlled so as not to reach the center of the vibrating arm portions 13 and 14 in the thickness direction. , 14 can not secure an area corresponding to the excitation electrodes 15, 16 provided on the entire side surface.

  Further, when the groove portion 17 is processed by etching, if the anisotropy is not precisely controlled according to the material and thickness of the vibrating arm portions 13 and 14, etching at a shallow angle results in the side surfaces of the vibrating arm portions 13 and 14. As a result, an excitation electrode surface inclined at an angle with respect to the excitation electrodes 15 and 16 provided on the surface is formed. As described above, there is a problem that the electric field efficiency is lowered as the excitation electrode formed on the inner side surface of the groove portion 17 is tilted from the excitation electrode formed on the side surface of the vibrating arm portions 13 and 14.

  Further, as described above, there is a problem in that the etching is controlled so as not to penetrate the thickness direction t1 of the vibrating arm portions 13 and 14 through the groove portion 17 and the shape of the groove portion 17 must be adjusted according to the etching conditions. is there. In particular, in the bending vibrator shown in Patent Document 2, since the processing depths of the groove portion 17 and the vibrating arm portions 13 and 14 are different from each other, the processing of the groove portion 17 and the vibrating arm portions 13 and 14 is different. Must be carried out in a separate process, which requires extra man-hours. Further, since the depth of the groove portion 17 is difficult to control, the variation in the equivalent series resistance value in the final product increases. According to the example shown in Patent Document 3, the groove portion 17 is adjusted in the thickness direction t1 of the vibrating arm portions 13 and 14 in order to adjust the depth processing control of the groove portion 17 by the formation width of the groove portion 17 and the etching time. It is not easy to form it at a predetermined depth so as not to penetrate. Further, since the outer shape of the vibrating arm portions 13 and 14 is processed simultaneously with the processing of the groove portion 17, if the etching conditions are adapted to the groove portion 17, the outer shape processing of the vibrating arm portions 13 and 14 may be affected. As described above, when the accuracy of the outer shape processing deviates from the design condition, there is also a problem that the yield of the final product is lowered because the vibration frequency also fluctuates.

  Accordingly, an object of the present invention is to increase the electric field efficiency and reduce the equivalent series resistance value by forming a plurality of through holes at predetermined positions of the vibrating arm portions constituting the tuning fork type bending vibrator, and to reduce the equivalent series resistance value. An object of the present invention is to provide a tuning fork type bending vibrator that can be easily formed.

  In order to solve the above problems, a tuning fork type bending vibrator of the present invention includes a pair of vibrating arm portions having a predetermined vibration length and vibration width, and a tuning fork type in which excitation electrodes are provided on at least side surfaces of the vibrating arm portions. In the bending vibrator, the vibrating arm portion is positioned along the length direction of the vibrating arm portion at a left and right position sandwiching a neutral line that is the center of vibration on the front surface and the back surface, and at a position close to the outer peripheral side surface. A plurality of through-hole rows in which a plurality of through-holes are arranged are formed in parallel, and the through-holes of the through-hole rows adjacent in the width direction of the vibrating arm portion are shifted in the length direction of the vibrating arm portion.

Further, the through hole of the one adjacent through hole row and the through hole of the other through hole row are arranged so as to be shifted by a half pitch with respect to the length direction of the vibrating arm portion.

  According to the tuning fork type bending vibrator of the present invention, one or two or more through holes are provided in the vibration length direction of each vibrating arm portion, and an excitation electrode is formed on the inner side surface of the through hole. The effect of improving the electric field efficiency with the excitation electrode provided on the side surface side of the part can be obtained. As a result, it has become possible to reduce the equivalent series resistance value that adversely affects the vibration characteristics. In addition, since a plurality of the through holes are formed at predetermined intervals along the vibration length direction of the vibrating arm portion, the crystal distortion between the excitation electrodes during vibration in the vibrating arm portion increases. As a result, the equivalent series resistance value can be reduced.

  In addition, by providing the through hole at a position that is biased toward the side of the vibration arm having a large vibration amplitude, the electric field efficiency of the excitation electrode provided on the side of the vibration arm is maximized. Can be increased.

  Further, the through holes are provided in parallel with two or more rows with respect to the vibration width direction of the vibrating arm portion, and the through holes extending in one vibration length direction by shifting the positions of the adjacent through holes in the vibration length direction. And the other through-holes can be arranged in an overlapping state between the through-hole formation intervals. Thereby, the influence of the electric field by the excitation electrode formed on the side surface of the vibrating arm portion can be received without leakage by the excitation electrode formed on the inner side surface of the plurality of through holes.

  Moreover, since the said through-hole is formed by the punching process with respect to the thickness direction of each vibration arm part, the process control of the depth direction like the conventional groove part is not required. For this reason, when the groove portion is processed by etching, since it can be performed under substantially the same processing conditions as the outer shape processing conditions of the vibrating arm portion, man-hours are not required and manufacturing is facilitated.

  Hereinafter, embodiments of a tuning fork type bending vibrator of the present invention will be described with reference to the accompanying drawings. Note that the tuning fork type bending vibrator of each embodiment shown below is about + 1 ° from the Z-axis plane in a rectangular crystal orthogonal coordinate system in which the electric axis is the X axis, the mechanical axis is the Y axis, and the optical axis is the Z axis. It is processed into a tuning fork shape from a quartz plate with a cut angle rotated in the X-axis direction. In addition, the vibration frequency is formed with 32.768 KHz as a reference.

  1 to 3 show a tuning fork-type bending vibrator (hereinafter referred to as a bending vibrator) 21 according to the first embodiment. The bending vibrator 21 basically includes a rectangular base portion 22 fixed in a casing (not shown) and a pair of vibrating arm portions 23 and 24 extending in parallel from the base portion 22 as in the conventional example. Yes. In addition, excitation electrodes 31 and 32 having different polarities extending from the base portion 22 are formed in patterns on the vibrating arm portions 23 and 24, respectively. One excitation electrode 32 is formed on the front and back surfaces of the vibrating arm portion 23 and both side surfaces of the vibrating arm portion 24, and the other excitation electrode is formed on the front and rear surfaces of the vibrating arm portion 24 and both side surfaces of the vibrating arm portion 23. 31 is formed. The excitation electrodes 31 and 32 are formed by holding independent regions on the vibrating arm portions 23 and 24.

  The vibrating arm portions 23 and 24 are elongated rectangular pillars extending in parallel from one end of the base portion 22 in the same direction, and have a vibration length (L), a vibration width (W), and a thickness for obtaining a predetermined vibration frequency. (T) is formed. The vibrating arm portions 23 and 24 are provided with through holes 25 to 28 in the thickness (T) direction. These through holes 25 to 28 are provided in order to absorb electric charges generated from the distortion of the vibrating arm portions 23 and 24 at the time of vibration and obtain higher electric field efficiency. High electric field efficiency can be obtained. These through holes 25 to 28 are provided along the vibration length (L) direction of the vibrating arm portions 23 and 24. As shown in the vibration simulation described later, the through holes are smaller than the continuous long through holes. It has been proved that forming a plurality of dots in a broken line shape at a predetermined interval makes the distortion between the excitation electrodes stronger and uniform due to vibration and stabilizes the vibration frequency.

  It is effective to provide the through holes 25 to 28 in the vicinity of the side surface having a large strain strength for generating an electric field. For this reason, as shown in FIG. 3, it is desirable that the distance (wall thickness) h from the side surfaces of the vibrating arm portions 23 and 24 be formed at a position where the through-hole processing is possible. FIG. 4 shows the change of the equivalent series resistance value R1 with respect to the wall thickness h verified by simulation. As can be seen from this graph, it can be confirmed that the value of R1 decreases as the wall thickness h is reduced. However, if the wall thickness h is set too thin, it is difficult to form a through hole. Therefore, it is preferable to secure a minimum of 5 μm or more and to make the value of R1 within a range of 20 μm below 60 KΩ. The array length (L1) of the through holes 25 to 28 extending in the vibration length (L) direction is approximately ½ of the length of the vibrating arm portions 23 and 24 from the base portion 22 as shown in FIG. Set to In the present embodiment, the through holes 25 to 28 are equally provided at the left and right positions across the vibration neutral lines X1 and X2 with respect to the vibration length (L) direction of the vibrating arm portions 23 and 24. The through holes 25 to 28 have an electric field efficiency when the opening length is 1/5 or less of the vibration length (L) and the opening width is 1/5 or less of the vibration width (W). The improvement effect is obtained. In particular, each of the through holes 25 to 28 has a rectangular shape with an opening length (L2) of 100 to 400 μm and an opening width (W2) of about 5 to 30 μm, and the vibration length at an interval (S2) of 5 to 100 μm. It is preferable to form an array in the (L) direction.

  Excitation electrodes 31 and 32 formed on the front and back surfaces of the vibrating arm portions 23 and 24 are formed around the inner side surfaces of the through holes 25 to 28. As shown in FIG. 3, when viewed in the cross-section in the width direction of the vibrating arm portions 23, 24, the inner surfaces of the through holes 25, 26 are opposed to the excitation electrodes 31 provided on the side surfaces of the vibrating arm portion 23. Are provided with excitation electrodes 32 facing each other. The excitation electrode 31 is provided in the through holes 27 and 28 so as to face the excitation electrode 32 provided on the side surface of the vibrating arm portion 24. As described above, the excitation electrode surfaces provided on the inner side surfaces of the through holes 25 to 28 are arranged in the same and parallel in the thickness (T) direction with the electrode surfaces provided on the side surfaces of the vibrating arm portions 23 and 24. It will be that. In addition, as shown in FIG. 2, a plurality of the through holes 25 to 28 are provided along the vibration length (L) direction at short intervals (S2). The excitation electrode surfaces formed in the through holes 25 to 28 and the excitation electrode surfaces provided on the side surfaces of the vibrating arm portions 23 and 24 can be opposed to each other with substantially the same area. Thus, by providing the through holes 25 to 28, the electric field efficiency between the inner side surfaces of the through holes 25 to 28 and the outer peripheral surfaces of the vibrating arm portions 23 and 24 is increased, and the equivalent series resistance value is increased. Can be kept small.

  Further, since the through holes 25 to 28 are through holes in which excitation electrodes are formed on the inner surface, the pair of excitation electrodes 31 and 32 extending from the base portion 22 are connected via the upper or lower surfaces of the vibrating arm portions 23 and 24. It can be easily conducted. As a result, the number of electrode patterns routed on the vibrating arm portions 23 and 24 is reduced, so that electrode formation defects are reduced and the product yield is improved.

  In the above-described embodiment, two rows of through holes 25 and 26 are provided for the vibrating arm portion 23, and two rows of through holes 27 and 28 are provided for the vibrating arm portion 24. By providing at least one row of through holes with respect to 23 and 24, an effect of improving electric field efficiency can be obtained. However, in order to balance the left and right vibrations, it is preferable that the positions of the through holes are provided so as to be symmetric with respect to the vibrating arm portions 23 and 24.

  Next, based on FIGS. 5 to 7, the vibration model of the bending vibrator 21 having a plurality of through-holes shown in the first embodiment and the bending vibrator having a long hole of an unspecified size are formed. A description will be given in comparison with 51 vibration models. This comparison was performed by simulation using a finite element method (ANSY 8.0). FIG. 5A shows the entire vibration model of the bending vibrator 51 in which one through long hole 52 is formed, and FIG. 5B shows a plurality of through holes 25 formed in broken lines. The whole vibration model of the bending vibrator 21 is shown. The bending vibrators 21 and 51 are set such that the vibration width W of the vibrating arm portion is 125 μm, the vibration length L is 1800 μm, and the base portion length D is 400 μm. Further, as shown in FIG. 6A, the through long hole 52 is set to have an opening width W2 = 50 μm and an opening length L2 = 800 μm that are out of the above-defined range. On the other hand, the bending vibrator 21 shown in FIG. 6B is set to have an opening width W2 = 20 μm and an opening length L2 = 200 μm. In addition, the wall thickness h from the vibrating arm portion to the through long hole 52 or the through hole 25 is common to 20 μm. FIGS. 7A and 7B are partially enlarged views at the base end portion of the vibrating arm portion, and show the strain intensity for generating an electric field by gray scale. The black and white density represented by this gray scale indicates that the distortion intensity is so large that white or black appears clearly. Note that the polarity of the electric field is different between white and black.

  In the vibration model shown in FIG. 5 (b), it can be seen that the respective vibrating arm portions are bent inward in the entire vibration length (L) direction without bending at the intermediate portion. Further, as shown in FIG. 7 (b), since the shade representing the strain intensity is uniform with respect to the arrangement of the through holes 25 extending in the vibration length (L) direction, a stable vibration frequency is generated. Can be made. On the other hand, in the vibration model shown in FIG. 7A, shading representing distortion appears irregularly in the direction in which the through long hole 52 extends. When such shading appears irregularly, the vibration is often unstable. Further, as shown in FIG. 6A, the opening width W2 of the pair of through-holes 52 formed in the respective vibrating arm portions is large and formed closer to the inner side of each vibrating arm portion. The effective width E of the vibrating arm portion is narrowed. As described above, when the effective width E of the vibrating arm portion is narrowed, the strain intensity becomes irregular as in the vibration model shown in FIG. 7A, and it is difficult to obtain a stable vibration frequency. There are many. From the above simulation results, even if the same through-hole is not formed continuously long, a plurality of short through-holes are arranged in a broken line shape, and the vibration mode becomes more proximate to the side of the vibrating arm portion. It proved to be good.

  Next, a bending vibrator 41 according to a second embodiment of the present invention is shown in FIGS. 8 is a plan view of the bending vibrator 41, FIG. 9 is a sectional view taken along the line BB of the bending vibrator 41, and FIG. 10 is a sectional view taken along the line CC of the bending vibrator 41. As shown in FIG. 8, the bending vibrator 41 includes two through-hole rows in which a plurality of through-holes are arranged along the vibration length (L) direction at positions close to both side surfaces of the vibrating arm portions 43 and 44. It is provided so as to be adjacent to each other in parallel. The through holes constituting the through hole rows 45a, 46a, 47a, and 48a and the through holes constituting the through hole rows 45b, 46b, 47b, and 48b have the same size, shape, and arrangement interval. The hole rows 45a, 46a, 47a, 48a and the through-hole rows 45b, 46b, 47b, 48b are provided so as to be shifted by a half pitch with respect to the vibration length (L) direction. In this way, each through hole of the adjacent through hole row is formed so as not to overlap in the vibration length (L) direction, so that it is formed on the side surfaces of the vibrating arm portions 43 and 44. And the excitation electrode formed on the inner surface of the pair of adjacent through-hole rows can be opposed to each other without a gap. Thereby, the electric field efficiency can be further improved. In the present embodiment, the through-hole rows 45a, 46a, 47a, 48a and the through-hole rows 45b, 46b, 47b, 48b are separated by a half pitch. However, the excitation electrode on the through-hole side is the vibrating arm 43. , 44 as long as the excitation electrodes can be formed without breaks in the vibration length direction.

  The bending vibrators 21 and 41 shown in the above embodiment include an outer shape portion including a base portion 22 and vibration arm portions 23 and 24 by etching or punching from a quartz substrate that cuts out a quartz substrate having a predetermined cut angle from a quartz raw stone, A through hole is formed. The etching process uses a chemical wet etching method, but can also be performed using physical dry etching or a powder beam. After this shape processing, excitation electrodes are formed on the outer peripheral surfaces of the vibrating arm portions 23 and 24 and the inner side surfaces of the through holes. The excitation electrode is patterned in a predetermined shape by a heating vapor deposition method, a sputtering method, or the like.

It is a perspective view of the tuning fork type bending vibrator of a 1st embodiment concerning the present invention. It is a top view of the tuning fork type bending vibrator of the first embodiment. It is AA sectional drawing of the tuning fork type bending vibrator shown in FIG. It is a graph which shows the relationship between the wall thickness of a vibrating arm part, and an equivalent series resistance value. It is a figure which shows the vibration model of each tuning fork type bending vibrator provided with the through-hole inside and outside regulation. It is an enlarged view of the through-hole shown in the said FIG. It is a figure which shows the distortion strength of each tuning fork type bending vibrator shown in the said FIG. It is a top view of the bending vibrator of 2nd Embodiment concerning this invention. It is BB sectional drawing of the bending vibrator of the said 2nd Embodiment. It is CC sectional drawing of the bending vibrator of the said 2nd Embodiment. It is a perspective view of the conventional general tuning fork type bending vibrator. It is a perspective view of the conventional tuning fork type bending vibrator provided with the groove part. It is sectional drawing of the conventional tuning fork type bending vibrator provided with the said groove part.

Explanation of symbols

21, 41 Tuning fork type bending vibrator 22, 42 Base 23, 24 Vibrating arm 25, 26, 27, 28 Through hole 31, 32 Excitation electrode 43, 44 Vibrating arm 45a, 46a, 47a, 48a Through hole row 45b, 46b, 47b, 48b through-hole row

Claims (5)

In a tuning-fork type bending vibrator comprising a pair of vibrating arm portions having a predetermined vibration length and vibration width and provided with excitation electrodes on at least side surfaces of the vibrating arm portions,
In the vibrating arm part, at the left and right positions sandwiching the neutral line that is the center of vibration on the front and back surfaces, and at the position close to the outer peripheral side surface
A plurality of through-hole rows in which a plurality of through-holes are arranged along the length direction of the vibrating arm portion are formed in parallel, and the through-holes of the through-hole rows adjacent to the width direction of the vibrating arm portion are the length direction of the vibrating arm portion. A tuning-fork type bending vibrator characterized by 2. The tuning fork type bending according to claim 1, wherein the through-holes of the one adjacent through-hole row and the through-holes of the other through-hole row are arranged so as to be shifted by a half pitch with respect to the length direction of the vibrating arm portion. Vibrator. The opening length of the through hole is 1/5 or less of the length of the vibrating arm portion, and the opening width is 1/5 or less of the width of the vibrating arm portion. The tuning fork type bending vibrator according to 1 or 2 . Wherein the pair of excitation electrodes disposed on the inner surface of the through hole, the excitation electrode closer to the side surface of the vibrating arm portion, the vibration claims from the side of the arm portion is formed within a distance of 5 to 20 [mu] m 1 or 2. A tuning-fork type bending vibrator according to 2. The through hole, the aperture length is 100-400, the opening width is formed in 5 to 30 [mu] m, the tuning-fork flexural vibrator according to claim 1 or 2 are arranged and formed at intervals of 5 to 100 [mu] m.