Vibration element

Abstract

The present invention provides a resonator element comprising: a resonator substrate having a base part, a bending resonator arm connected to the base part, and a torsional resonator arm connected to the base part; a flexural vibration drive unit that is disposed on the vibration substrate and causes flexural vibration of the flexural vibration arm; and a torsional vibration driving unit that is disposed on the vibration substrate and causes the torsional vibration arm to perform torsional vibration.

Description

Technical Field

[0001] The present invention relates to a vibrating element. Background Art

[0002] For example, in the tuning fork type quartz crystal resonator described in Patent Document 1, the resonant frequency difference between bending vibration and torsional vibration is set within 15%. Thus, the tuning fork type quartz crystal resonator is driven in a mode combining bending vibration and torsional vibration, and the resonant frequency temperature characteristic is improved.

[0003] Patent Document 1: Japanese Patent Publication No. 62-46092 Summary of the invention

[0004] However, in the tuning fork type quartz resonator of Patent Document 1, bending vibration and torsional vibration are excited by a common vibration arm. Therefore, the resonant frequency of torsional vibration and the resonant frequency of bending vibration cannot be adjusted independently, and it is difficult to adjust the difference in their resonant frequencies to a predetermined value.

[0005] The vibration element of the present invention comprises: a vibration substrate having a base, a bending vibration arm connected to the base, and a torsional vibration arm connected to the base; a bending vibration driving unit, which is arranged on the vibration substrate and causes the bending vibration arm to perform bending vibration; and a torsional vibration driving unit, which is arranged on the vibration substrate and causes the torsional vibration arm to perform torsional vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a top view of the MEMS element according to the first embodiment.

[0007] Figure 2 yes Figure 1 AA line section view in.

[0008] Figure 3 yes Figure 1 BB line section view in.

[0009] Figure 4 yes Figure 1 CC line section view in.

[0010] Figure 5 is a top view of the vibrating element.

[0011] Figure 6 is a cross-sectional view of the torsional vibration arm.

[0012] Figure 7 is a cross-sectional view of the torsional vibration arm.

[0013] Figure 8 is a cross-sectional view of the bending vibration arm.

[0014] Fig. 9It is a diagram showing a driving state of a vibration element.

[0015] Fig.10 is a graph showing the resonant frequency temperature characteristics.

[0016] Fig.11 is a graph showing the resonant frequency temperature characteristics.

[0017] Fig.12 It is a perspective view showing a torsional vibration arm included in the vibration element according to the second embodiment.

[0018] Fig.13 It is a perspective view showing a torsional vibration arm included in the vibration element according to the second embodiment.

[0019] Description of symbols

[0020] 1: MEMS element; 10: SOI substrate; 11: silicon layer; 12: BOX layer; 13: surface silicon layer; 131: frame; 14: through electrode; 15: through electrode; 20: vibration element; 21: vibration substrate; 210: base; 211: bending vibration arm; 212: bending vibration arm; 213: bending vibration arm; 221: torsional vibration arm; 221a: arm; 221b: weighting part; 222: torsional vibration arm; 222a: arm; 222b: weighting part; 23: bending vibration driving part; 23A: piezoelectric element; 23B: piezoelectric element; 23 C: piezoelectric element; 231: lower electrode; 232: piezoelectric layer; 233: upper electrode; 24: torsional vibration drive unit; 24A: piezoelectric element; 24B: piezoelectric element; 24C: piezoelectric element; 24D: piezoelectric element; 241: lower electrode; 242: piezoelectric layer; 243: upper electrode; 5: cover; D: thickness; D2a: thickness; F1: end; F2: base end; J: center axis; M1: frequency adjustment membrane; M2: frequency adjustment membrane; PAD1: electrode pad; PAD2: electrode pad; W2a: width; W2b: width; L2b: length. DETAILED DESCRIPTION

[0021] Hereinafter, the vibration element of the present invention will be described in detail based on the embodiments shown in the drawings.

[0022] <First Embodiment>

[0023] Figure 1 It is a top view of the MEMS element according to the first embodiment. Figure 2 yes Figure 1 AA line section view in. Figure 3 yes Figure 1 BB line section view in. Figure 4 yes Figure 1 CC line section view in. Figure 5 is a top view of the vibrating element. Figure 6 as well as Figure 7 They are cross-sectional views of the torsional vibration arms respectively. Figure 8 A cross-sectional view of a bending vibration arm. Fig. 9 It is a diagram showing a driving state of a vibration element. Fig.10 and Fig.11 These are graphs showing the resonant frequency-temperature characteristics.

[0024] In addition, for the sake of convenience, Figures 1 to 9 In each figure, the X-axis, Y-axis, and Z-axis that are perpendicular to each other are shown. In addition, the arrow side of each axis is also called the "positive side", and the opposite side is called the "negative side". In addition, the positive side of the Z-axis direction is also called the "upper", and the negative side is called the "lower".

[0025] like Figure 1 As shown, the MEMS element 1 has an SOI (Silicon on Insulator) substrate 10 on which a vibration element 20 is formed and a cover 5 for airtightly sealing the vibration element 20. The cover 5 is made of single crystal silicon or the like and has a recessed portion opened toward the lower surface. Moreover, the lower surface of the cover 5 is bonded to the upper surface of the SOI substrate 10.

[0026] like Figure 2 and Figure 3 As shown, the SOI substrate 10 is a substrate formed by sequentially stacking a silicon layer 11, a BOX (Buried Oxide) layer 12 and a surface silicon layer 13. For example, the silicon layer 11 and the surface silicon layer 13 are composed of single crystal silicon, and the BOX layer 12 is composed of a silicon oxide layer (SiO2, etc.).

[0027] Furthermore, the surface silicon layer 13 includes a vibration substrate 21 and a frame portion 131 surrounding the vibration substrate 21. Figure 2 As shown, a pair of electrode pads PAD1 and PAD2 are arranged on the upper surface of the frame portion 131. In addition, through electrodes 14 and 15 are formed at positions overlapping with the electrode pads PAD1 and PAD2, penetrating the SOI substrate 10 in the thickness direction. Moreover, the through electrode 14 is electrically connected to the electrode pad PAD1, and the through electrode 15 is electrically connected to the electrode pad PAD2. Thus, the electrode pads PAD1 and PAD2 are led out to the outside of the MEMS element 1.

[0028] The vibration element 20 has a vibration substrate 21 formed on the surface silicon layer 13. That is, the vibration substrate 21 is formed of a silicon substrate. Thus, the vibration substrate 21 can be formed by a silicon wafer process, so the processing of the vibration substrate 21 becomes easy, and the vibration substrate 21 can be formed with high processing accuracy. Figures 1 to 4As shown, the vibration substrate 21 has: a base 210 supported by the silicon layer 11 and the BOX layer 12; three bending vibration arms 211, 212, 213 separated from the BOX layer 12; and two torsional vibration arms 221, 222 separated from the BOX layer 12. The vibration substrate 21 is formed to have the same thickness as the surface silicon layer 13 as a whole.

[0029] like Figure 5 As shown, the bending vibration arms 211, 212, and 213 extend from the end portion of the base 210 on the positive side in the Y-axis direction, i.e., the terminal portion, toward the positive side in the Y-axis direction, and are arranged at equal intervals in the X-axis direction. In addition, the bending vibration arms 211, 212, and 213 are aligned in the same shape as each other. These bending vibration arms 211, 212, and 213 perform bending vibration in the Z-axis direction.

[0030] In addition, a frequency adjustment film M1 for adjusting the resonance frequency fr1 of the bending vibration is arranged on the upper surface of the distal end of the bending vibration arms 211, 212, and 213. The resonance frequency fr1 can be adjusted by removing a portion of the frequency adjustment film M1 by laser irradiation or the like as needed. However, the structure of the bending vibration arms 211, 212, and 213 is not particularly limited, and the frequency adjustment film M1 may be omitted.

[0031] The torsional vibration arm 221 extends from the end of the base 210 on the positive side in the X-axis direction toward the positive side in the X-axis direction, and the torsional vibration arm 222 extends from the end of the base 210 on the negative side in the X-axis direction toward the negative side in the X-axis direction. That is, the torsional vibration arms 221 and 222 are located on opposite sides of each other across the base 210. Thus, the torsional vibration arms 221 and 222 can be evenly arranged in the vibration element 20. In addition, the torsional vibration arms 221 and 222 are aligned in the same shape as each other. These torsional vibration arms 221 and 222 respectively vibrate torsionally around their center axes J. That is, the torsional vibration arms 221 and 222 vibrate torsionally around the X-axis.

[0032] However, the configuration of the torsion vibration arms 221 and 222 is not particularly limited, and the torsion vibration arms 221 and 222 may both extend from the end of the base 210 on the positive side in the X-axis direction toward the positive side in the X-axis direction, or may both extend from the end of the base 210 on the negative side in the X-axis direction toward the negative side in the X-axis direction. In addition, the torsion vibration arms 221 and 222 may also extend from the end of the base 210 on the positive side in the Y-axis direction toward the positive side in the Y-axis direction in parallel with the bending vibration arms 211, 212, and 213.

[0033] Furthermore, the torsional vibration arm 221 includes an arm portion 221a extending from the base portion 210 toward the positive side in the X-axis direction, and a weight portion 221b disposed at the distal end of the arm portion 221a. Similarly, the torsional vibration arm 222 includes an arm portion 222a extending from the base portion 210 toward the negative side in the X-axis direction, and a weight portion 222b disposed at the distal end of the arm portion 222a.

[0034] In addition, if Figure 6 and Figure 7 As shown, the width W2a of the arm portions 221a and 222a, i.e., the length in the Y-axis direction, is smaller than the thickness D2a of the arm portions 221a and 222a, i.e., the length in the Z-axis direction. That is, W2a<D2a. As a result, the cross-sectional shape of the arm portions 221a and 222a becomes a rectangle extending in the Z-axis direction, so the torsional vibration arms 221 and 222 are easy to torsionally vibrate around the X-axis. However, the shape of the arm portions 221a and 222a is not particularly limited, for example, it can be W2a>D2a as in the second embodiment described later, or it can be W2a=D2a.

[0035] In addition, if Figure 5 As shown, the width W2b of the weight portions 221b and 222b, i.e., the length in the Y-axis direction, is greater than the width W2a of the arm portions 221a and 222a. That is, W2b>W2a. According to this structure, due to the mass effect of the weight portions 221b and 222b, the total length of the torsional vibration arms 221 and 222 can be shortened compared to the case where there are no weight portions 221b and 222b, even if the resonance frequency fr2 described later is the same. Therefore, the miniaturization of the vibration element 20 can be achieved. However, the structure of the torsional vibration arms 221 and 222 is not particularly limited, and the weight portions 221b and 222b can also be omitted.

[0036] In particular, the weighting portions 221b and 222b extend along the Y-axis direction, i.e., the extension direction of the bending vibration arms 211, 212, and 213, respectively. Furthermore, the width W2b of the weighting portions 221b and 222b is greater than the length L2b, i.e., the length in the X-axis direction. That is, W2b>L2b. According to this structure, the weighting portions 221b and 222b can be formed larger while suppressing the total length of the vibration element 20 in the Y-axis direction. Therefore, the miniaturization of the vibration element 20 can be achieved. However, the structure of the weighting portions 221b and 222b is not particularly limited, for example, W2b≤L2b may also be used.

[0037] In addition, if Figure 5As shown, the ends of the weight portions 221b and 222b on the positive side in the Y-axis direction are closer to the negative side in the Y-axis direction than the ends F1 of the bending vibration arms 211, 212, and 213, and the ends of the weight portions 221b and 222b on the negative side in the Y-axis direction are closer to the positive side in the Y-axis direction than the base end F2 of the base 210. According to this structure, it is possible to suppress the total length of the vibration element 20 in the Y-axis direction while preventing the increase in the total length of the vibration element 20 in the X-axis direction due to the addition of the torsional vibration arms 221 and 222. Therefore, it is possible to achieve miniaturization of the vibration element 20. However, the structure of the weight parts 221b and 222b is not particularly limited. For example, the ends of the weight parts 221b and 222b on the positive side in the Y-axis direction can be closer to the positive side in the Y-axis direction than the ends of the bending vibration arms 211, 212, and 213, or the ends of the weight parts 221b and 222b on the negative side in the Y-axis direction can be closer to the negative side in the Y-axis direction than the base end of the base 210.

[0038] In addition, a frequency adjustment film M2 for adjusting the resonant frequency fr2 of the torsional vibration is arranged on the weighting portion 221b, 222b. The resonant frequency fr2 can be adjusted by removing a portion of the frequency adjustment film M2 by laser irradiation or the like as needed. In particular, the frequency adjustment film M2 is arranged asymmetrically with respect to the center axis J when viewed from above in the Z-axis direction. In the present embodiment, it is arranged separated from the center axis J in the positive side in the Y-axis direction. According to such a structure, when viewed from above in the Z-axis direction, the center of gravity of the torsional vibration arms 221, 222 deviates from the center axis J, and therefore, it is easy to excite the torsional vibration arms 221, 222 to perform torsional vibration. However, the configuration of the frequency adjustment film M2 is not particularly limited.

[0039] like Figure 5 As shown, the vibration element 20 further includes a bending vibration driving unit 23 that causes the bending vibration arms 211 , 212 , 213 to perform bending vibration in the Z-axis direction, and a torsional vibration driving unit 24 that causes the torsional vibration arms 221 , 222 to perform torsional vibration about the X-axis.

[0040] In addition, if Figure 8 As shown, the bending vibration driving unit 23 is arranged on the upper surface of the vibration substrate 21. Specifically, the bending vibration driving unit 23 has: a piezoelectric element 23A, which is arranged on the upper surface of the bending vibration arm 211; a piezoelectric element 23B, which is arranged on the upper surface of the bending vibration arm 212; and a piezoelectric element 23C, which is arranged on the upper surface of the bending vibration arm 213. These piezoelectric elements 23A, 23B, and 23C have the same structure as each other. The piezoelectric elements 23A, 23B, and 23C respectively have: a lower electrode 231 arranged on the upper surface of the bending vibration arms 211, 212, and 213; a piezoelectric layer 232 arranged on the upper surface of the lower electrode 231; and an upper electrode 233 arranged on the upper surface of the piezoelectric layer 232.

[0041] In addition, if Fig. 9 As shown, the piezoelectric elements 23A, 23B, and 23C are wired so that the adjacent bending vibration arms 211, 212, and 213 perform bending vibrations in opposite phases to each other. That is, the piezoelectric elements 23A, 23B, and 23C are wired in a manner of alternately repeating a first state and a second state, wherein the first state is that the bending vibration arms 211 and 213 are bent and deformed upward and the bending vibration arm 212 is bent and deformed downward, and the second state is that the bending vibration arms 211 and 213 are bent and deformed downward and the bending vibration arm 212 is bent and deformed upward. Specifically, the lower electrodes 231 of the piezoelectric elements 23A and 23C and the upper electrodes 233 of the piezoelectric element 23B are electrically connected to the electrode pad PAD1 via wiring not shown in the figure, and the upper electrodes 233 of the piezoelectric elements 23A and 23C and the lower electrodes 231 of the piezoelectric element 23B are electrically connected to the electrode pad PAD2 via wiring not shown in the figure. In this way, by making the adjacent flexural vibration arms 211 , 212 , and 213 flexurally vibrate in opposite phases to each other, the vibrations of the flexural vibration arms 211 , 212 , and 213 can be canceled out, and vibration leakage of the vibration element 20 can be effectively suppressed.

[0042] like Figure 5 As shown, the torsional vibration driving unit 24 is arranged on the upper surface of the vibration substrate 21. Specifically, the torsional vibration driving unit 24 has a pair of piezoelectric elements 24A and 24B arranged on the upper surface of the arm portion 221a of the torsional vibration arm 221, and a pair of piezoelectric elements 24C and 24D arranged on the upper surface of the arm portion 222a of the torsional vibration arm 222. When viewed from the Z-axis direction, the pair of piezoelectric elements 24A and 24B are arranged in a manner that sandwiches the central axis J of the arm portion 221a. That is, the piezoelectric element 24A is arranged on the positive side of the central axis J in the Y-axis direction, and the piezoelectric element 24B is arranged on the negative side of the central axis J in the Y-axis direction. According to this arrangement, the torsional vibration arm 221 can be easily torsionally vibrated. Similarly, when viewed from the Z-axis direction, the pair of piezoelectric elements 24C and 24D are arranged in a manner that sandwiches the central axis J of the arm portion 222a. That is, the piezoelectric element 24C is arranged on the positive side of the central axis J in the Y-axis direction, and the piezoelectric element 24D is arranged on the negative side of the central axis J in the Y-axis direction. With such an arrangement, the torsional vibration arm 222 can be easily torsionally vibrated.

[0043] like Figure 6 as well as Figure 7 As shown, these piezoelectric elements 24A, 24B, 24C, and 24D have the same structure as each other, and have a lower electrode 241 arranged on the upper surface of the arm portions 221a and 222a, a piezoelectric layer 242 arranged on the upper surface of the lower electrode 241, and an upper electrode 243 arranged on the upper surface of the piezoelectric layer 242.

[0044] In addition, if Fig. 9 As shown, the piezoelectric elements 24A, 24B, 24C, and 24D are wired in such a way that the torsional vibration arms 221 and 222 vibrate in opposite phases. That is, the piezoelectric elements 24A, 24B, 24C, and 24D are wired so that, when viewed from the positive side in the X-axis direction, the first state and the second state are repeated alternately, wherein the first state is that the torsional vibration arm 221 is torsionally deformed in the clockwise direction and the torsional vibration arm 222 is torsionally deformed in the counterclockwise direction, and the second state is that the torsional vibration arm 221 is torsionally deformed in the counterclockwise direction and the torsional vibration arm 222 is torsionally deformed in the clockwise direction. Specifically, the upper electrodes 243 of the piezoelectric elements 24A and 24D and the lower electrodes 241 of the piezoelectric elements 24B and 24C are electrically connected to the electrode pad PAD1 via wiring not shown, and the lower electrodes 241 of the piezoelectric elements 24A and 24D and the upper electrodes 243 of the piezoelectric elements 24B and 24C are electrically connected to the electrode pad PAD2 via wiring not shown. In this way, by making the torsional vibration arms 221 and 222 torsionally vibrate in opposite phases to each other, the vibrations of the torsional vibration arms 221 and 222 are canceled, thereby effectively suppressing the vibration leakage of the vibration element 20.

[0045] In this way, the piezoelectric elements 23A, 23B, 23C of the bending vibration driving unit 23 and the piezoelectric elements 24A, 24B, 24C, 24D of the torsional vibration driving unit 24 are electrically connected to the electrode pads PAD1 and PAD2, so that the bending vibration driving unit 23 and the torsional vibration driving unit 24 are electrically coupled. In addition, the constituent materials of each part of the piezoelectric elements 23A, 23B, 23C, 24A, 24B, 24C, 24D are not particularly limited. For example, the piezoelectric body layers 232 and 242 are made of aluminum nitride (AlN) or the like, and the lower electrodes 231 and 241 and the upper electrodes 233 and 243 are made of titanium nitride (TiN) or the like.

[0046] Here, when the resonant frequency of the bending vibration of the bending vibration arms 211, 212, and 213 is fr1, and the resonant frequency of the torsional vibration of the torsional vibration arms 221 and 222 is fr2, the resonant frequencies fr1 and fr2 are adjusted so that the difference Δfr (=|fr1-fr2|) between the resonant frequency fr1 and the resonant frequency fr2 becomes less than 1% of the resonant frequency fr1. Specifically, the resonant frequency fr1 is adjusted to a desired frequency, for example, 32kHz, and the resonant frequency fr2 is further combined in a manner that becomes a frequency within 1% of the resonant frequency fr1. In this way, the bending vibration of the bending vibration arms 211, 212, and 213 and the torsional vibration of the torsional vibration arms 221 and 222 can be excited at the same time, and the torsional vibration and the bending vibration can be combined.

[0047] In addition, the difference Δfr can be less than 1% of the resonant frequency fr1, but is preferably less than 0.1%, more preferably less than 0.01%, and further preferably zero. As a result, the bending vibration of the bending vibration arms 211, 212, and 213 and the torsional vibration of the torsional vibration arms 221 and 222 can be excited more reliably at the same time. In addition, in the present embodiment, the "bending vibration" refers to the fundamental wave (fundamental mode), not the harmonic (higher-order mode). Similarly, the "torsional vibration" refers to the fundamental wave (fundamental mode), not the harmonic (higher-order mode).

[0048] In this way, by combining torsional vibration with bending vibration, the resonant frequency temperature characteristic of the vibration element 20 can be improved. Fig.10 As shown, compared with the resonant frequency-temperature characteristic of the vibration element 20 that only performs bending vibration, the resonant frequency-temperature characteristic of the vibration element 20 that combines torsional vibration and bending vibration has a smaller frequency change relative to temperature, thereby having an excellent resonant frequency-temperature characteristic. Fig.10 In the case where the vibration substrate 21 is formed by the ion-doped surface silicon layer 13, the resonance frequency temperature characteristic is the first order. Fig.11 As shown, it becomes a secondary resonant frequency temperature characteristic. In this case, compared with the resonant frequency temperature characteristic of the vibration element 20 that only performs bending vibration, the resonant frequency temperature characteristic of the vibration element 20 that combines torsional vibration and bending vibration has a smaller frequency change relative to temperature, thereby having an excellent resonant frequency temperature characteristic.

[0049] Since the vibration element 20 includes the bending vibration arms 211, 212, 213 and the torsional vibration arms 221, 222, the resonance frequencies fr1 and fr2 can be adjusted independently. Therefore, the resonance frequency fr1 can be easily adjusted to a desired frequency and the difference Δfr can be easily adjusted to fall within a predetermined value.

[0050] In addition, the resonant frequency fr2 tends to become higher relative to the resonant frequency fr1. For example, in the case of a quartz resonator, due to the limit of the processing accuracy of wet etching, when the resonant frequency fr1 = 32kHz, the resonant frequency fr2 can only be reduced to about 100kHz. In contrast, if the vibration element 20 is formed by a silicon substrate (surface silicon layer 13) as in the present embodiment, high-precision fine processing can be performed using a silicon wafer process, i.e., dry etching, and the width W2a of the arm portions 221a and 222a of the torsional vibration arms 221 and 222 can be formed thinner. Therefore, the resonant frequency fr2 can be easily reduced to the level of the resonant frequency fr1.

[0051] In the vibration element 20 of such a structure, by applying a driving voltage between the electrode pads PAD1 and PAD2, as shown in FIG. Fig. 9As shown, the piezoelectric elements 23A and 23C expand and contract in anti-phase with the piezoelectric element 23B, and the adjacent bending vibration arms 211, 212, and 213 perform bending vibration in anti-phase in the Z-axis direction, and the piezoelectric elements 24A and 24D expand and contract in anti-phase with the piezoelectric elements 24B and 24C, and the torsional vibration arms 221 and 222 perform torsional vibration around the X-axis in opposite phases. As a result, the torsional vibration of the torsional vibration arms 221 and 222 is combined with the bending vibration of the bending vibration arms 211, 212, and 213, thereby exerting the above-mentioned effect. The bending vibration of the bending vibration arms 211, 212, and 213 is greatly excited at the resonance frequency fr1, so that the impedance becomes minimum. As a result, by connecting the MEMS element 1 to the oscillation circuit, it oscillates at an oscillation frequency determined by the resonance frequency fr1.

[0052] The MEMS element 1 has been described above. As described above, the vibration element 20 of such a MEMS element 1 includes: a vibration substrate 21 having a base 210, bending vibration arms 211, 212, 213 connected to the base 210, and torsional vibration arms 221, 222 connected to the base 210; a bending vibration driving unit 23, which is arranged on the vibration substrate 21 and causes the bending vibration arms 211, 212, 213 to perform bending vibration; and a torsional vibration driving unit 24, which is arranged on the vibration substrate 21 and causes the torsional vibration arms 221, 222 to perform torsional vibration. In this way, by respectively providing the bending vibration arms 211, 212, 213 that perform bending vibration and the torsional vibration arms 221, 222 that perform torsional vibration, the resonant frequency fr1 of the bending vibration and the resonant frequency fr2 of the torsional vibration can be adjusted independently. Therefore, while the resonant frequency fr1 is set to a desired frequency band, the difference Δfr between the resonant frequencies fr1 and fr2 can be easily made to fall within a specified value.

[0053] As described above, the torsional vibration arms 221 and 222 have arm portions 221a and 222a extending from the base portion 210. The width W2a of the arm portions 221a and 222a is smaller than the thickness D2a of the arm portions 221a and 222a. Thus, the torsional vibration arms 221 and 222 have a shape that facilitates torsional vibration.

[0054] In addition, as described above, the torsional vibration arms 221 and 222 have weight portions 221b and 222b disposed at the distal ends of the arm portions 221a and 222a, and the width W2b of the weight portions 221b and 222b is greater than the width W2a of the arm portions 221a and 222a. According to this structure, the mass effect of the weight portions 221b and 222b can shorten the total length of the torsional vibration arms 221 and 222 compared to the case where there are no weight portions 221b and 222b, even if the resonance frequency fr2 described later is the same. Therefore, the miniaturization of the vibration element 20 can be achieved.

[0055] As described above, the weight portions 221b and 222b extend along the extending direction of the flexural vibration arms 211, 212, and 213. This can make the weight portions 221b and 222b larger while suppressing the length of the vibration element 20 in the Y-axis direction. Therefore, the vibration element 20 can be miniaturized.

[0056] In addition, as described above, the vibration substrate 21 has a pair of torsion vibration arms 221 and 222 located on opposite sides of each other across the base 210. Furthermore, the torsion vibration driving unit 24 causes the pair of torsion vibration arms 221 and 222 to torsionally vibrate in opposite phases to each other. Thus, the vibrations of the torsion vibration arms 221 and 222 are offset, thereby effectively suppressing vibration leakage from the vibration element 20.

[0057] In addition, as described above, the vibration substrate 21 has three bending vibration arms 211, 212, and 213 arranged in a direction perpendicular to the extension direction, that is, in the X-axis direction. Moreover, the bending vibration driving unit 23 causes the pair of bending vibration arms 211 and 213 located on both sides to perform bending vibration in opposite phases to the bending vibration arm 212 located in the center. As a result, the vibrations of the bending vibration arms 211, 212, and 213 are offset, thereby effectively suppressing the vibration leakage from the vibration element 20.

[0058] As described above, the vibration substrate 21 is formed of the surface silicon layer 13 as a silicon substrate. Thus, the vibration substrate 21 can be formed by a silicon wafer process, so that the vibration substrate 21 can be easily processed and formed with high processing accuracy.

[0059] <Second Embodiment>

[0060] Fig.12 and Fig.13 Each of them is a perspective view showing a torsional vibration arm included in the vibration element according to the second embodiment.

[0061] This embodiment is the same as the first embodiment described above, except that the shapes of the torsional vibration arms 221 and 222 are different. In addition, in the following description, the present embodiment is described mainly with the differences from the first embodiment described above, and the description of the same matters is omitted. In addition, in each figure of the present embodiment, the same reference numerals are used for the same structures as those in the above embodiment.

[0062] like Fig.12 as well as Fig.13 As shown, in the vibration element 20 of the present embodiment, the width W2a of the arm portions 221a and 222a is greater than the thickness D2a of the arm portions 221a and 222a. That is, W2a>D2a. As a result, the cross-sectional shape of the arm portions 221a and 222a becomes a rectangle extending in the Y-axis direction, so the torsional vibration arms 221 and 222 are prone to torsional vibration.

[0063] In particular, in the present embodiment, the thickness D2a of the arm portions 221a and 222a is thinner than the thickness D of the vibration substrate 21, that is, the thickness of the surface silicon layer 13. As a result, the rigidity of the arm portions 221a and 222a is reduced, and the resonance frequency fr2 can be easily reduced to the level of the resonance frequency fr1. Such arm portions 221a and 222a are formed by thinning the vibration substrate 21 from the upper surface side. As a result, the arm portions 221a and 222a can be easily formed. However, this is not limited to this, and for example, the arm portions 221a and 222a can also be formed by thinning the vibration substrate 21 from the lower surface side.

[0064] In the vibration element 20 described above, the torsional vibration arms 221 and 222 have arm portions 221a and 222a extending from the base portion 210. The width W2a of the arm portions 221a and 222a is greater than the thickness D2a of the arm portions 221a and 222a. Thus, the torsional vibration arms 221 and 222 have a shape that facilitates torsional vibration.

[0065] According to the second embodiment as described above, it is also possible to produce the same effects as those of the first embodiment described above.

[0066] The vibration element of the present invention is described above based on the illustrated embodiments, but the present invention is not limited thereto. The structure of each part can be replaced with any structure having the same function. In addition, other arbitrary structures can also be added to the present invention. In addition, the present invention can also combine any two or more structures in the above-mentioned embodiments.

Claims

1. A vibration element, characterized in that: have: a vibration substrate having a base, a bending vibration arm connected to the base, and a torsional vibration arm connected to the base; a bending vibration driving unit, which is disposed on the vibration substrate and causes the bending vibration arm to perform bending vibration; as well as The torsional vibration driving unit is disposed on the vibration substrate and causes the torsional vibration arm to torsionally vibrate.

2. The vibration element according to claim 1, wherein The torsional vibration arm has an arm portion extending from the base portion, The width of the arm portion is smaller than the thickness of the arm portion.

3. The vibration element according to claim 1, wherein The torsional vibration arm has an arm portion extending from the base portion, The width of the arm portion is greater than the thickness of the arm portion.

4. The vibration element according to claim 2 or 3, wherein: The torsional vibration arm includes a weight portion disposed on a distal end side of the arm portion, The width of the weight-applying portion is greater than the width of the arm portion.

5. The vibration element according to claim 4, wherein: The weight portion extends along an extending direction of the bending vibration arm.

6. The vibration element according to claim 1, wherein The vibration substrate includes a pair of torsional vibration arms located on opposite sides of the base portion. The torsional vibration driving unit causes the pair of torsional vibration arms to torsionally vibrate in opposite phases to each other.

7. The vibration element according to claim 1, wherein The vibration substrate has three bending vibration arms arranged in a direction perpendicular to the extending direction. The flexural-vibration driving section flexurally vibrates the pair of flexural-vibration arms located at both sides and the flexural-vibration arm located at the center in opposite phases to each other.

8. The vibration element according to claim 1, wherein The vibration substrate is formed of a silicon substrate.

9. A vibration element, characterized in that: have: a vibration substrate having a base, a bending vibration arm connected to the base, and a pair of torsional vibration arms located on opposite sides of each other across the base; a bending vibration driving unit, which is disposed on the vibration substrate and causes the bending vibration arm to perform bending vibration; as well as The torsional vibration driving unit is disposed on the vibration substrate and causes the torsional vibration arm to torsionally vibrate.

10. The vibration element according to claim 9, wherein The vibration substrate has three bending vibration arms arranged in a direction perpendicular to the extending direction. The flexural-vibration driving section flexurally vibrates the pair of flexural-vibration arms located at both sides and the flexural-vibration arm located at the center in opposite phases to each other.

11. The vibration element according to claim 9, wherein The vibration substrate is formed of a silicon substrate.

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