JP5112819B2 - Electrostatic vibrator and oscillator - Google Patents

Description

  The present invention relates to an electrostatic vibrator used for a reference frequency oscillator of various electronic devices.

  A crystal resonator has been used as a small and stable high-frequency signal source in a wireless portable device typified by a cellular phone or the like, or an electronic device such as a personal computer or a watch.

  In recent years, there has been an increasing demand for miniaturization of quartz resonators because they are large compared to other high-frequency electronic components. However, the request cannot be fully satisfied.

  In recent years, electrostatic vibrators manufactured using MEMS (Micro-Electro-Mechanical-System) technology have attracted attention as a means for satisfying such requirements and replacing quartz vibrators. The electrostatic vibrator includes a vibrating body that vibrates mechanically and an electrode that is arranged in parallel with a gap therebetween. A DC voltage is applied between the vibrating body and the electrode. If an alternating voltage is further applied between the vibrating body and the electrode in this state, resonance occurs at a certain frequency. This electrostatic vibrator not only has the same resonance Q value as a quartz crystal resonator, but also has advantages such as miniaturization, integration, and high frequency response compared to a quartz crystal resonator. Expected to be a high-frequency signal source.

  As described above, the electrostatic vibrator has many advantages over the quartz vibrator, but there are also problems to be solved. The electrostatic vibrator has a higher temperature dependency of the resonance frequency than the crystal vibrator, and the stability of the resonance frequency with respect to a temperature change is low. Therefore, it is inferior to a quartz resonator in reliability.

  As one method for solving this problem, Patent Document 1 discloses a method for compensating for a resonance frequency change with respect to a temperature change. This method is a method for compensating for a change in resonance frequency with respect to a temperature change by actively or passively changing the DC voltage applied between the vibrating part and the electrode or the distance of the gap in accordance with the temperature change.

In Patent Document 1, as a method for passively changing the distance between the vibrating body and the electrode with respect to the temperature change, the thermal expansion coefficient differs between the vibrating part constituting the vibrating body, the support body supporting the vibrating body, and the electrode. A method using dissimilar materials is shown. According to this method, by setting design parameters such as dimensions and relative positions of the respective members at the reference temperature, it is possible to design the amount of change in the gap distance with respect to the temperature change. Hereinafter, the design parameters in Patent Document 1 will be described with reference to FIGS. 9 and 10. 9 and 10 are plan views of an electrostatic vibrator according to an embodiment of the invention in Patent Document 1 as seen from the viewpoint of the upper surface of the substrate. 9 and 10, 1 is a vibrating portion, 2 is an electrode, 3 is a substrate, 4 is a lever lever, 5 is a lever lever support, 6 is a lever lever column, and 7 and 8 are vibration body 1 supports. It is. L1, L2, L11, L12, a, b, and d are the design parameters, and the lengths of the support 7 and the support 8 at the reference temperature, the width of the electrode 2, and the length of the support 5 of the lever lever, respectively. The length of the lever lever support 6, the distance from the force point of the lever lever 4 to the fulcrum, the distance from the fulcrum of the lever lever 4 to the electrode 2, and the distance between the vibrating portion 1 and the electrode 2. All of these change linearly with temperature. Further, as a design parameter other than those described above, there is a coefficient of thermal expansion of each member, which can be changed by using a mixed material in which different materials are combined.
US Pat. No. 6,987,432

  According to the design method of the change amount of the gap distance with respect to the temperature change shown in Patent Document 1, since the change in the gap distance is linear with respect to the temperature change, the accuracy of compensation of the resonance frequency is sufficient. It wasn't.

  An object of the present invention is to provide an electrostatic vibrator capable of further improving the accuracy of resonance frequency compensation.

The present invention has been made to solve the above-described problems. The vibrating body, the electrode disposed with a gap with respect to the vibrating body, and the vibrating body are formed of different materials having different thermal expansion coefficients. includes a deformation control member has a, a the electrode and the deformation control member and the electrostatic vibrator fixed to the substrate, the vibrating body, have a bent portion comprising a bent shape on at least a portion The vibrating body is connected to the deformation control body at at least one point, and the bent portion is deformed by a stress generated in the connecting contact due to a temperature change, and the distance of the gap changes nonlinearly due to the deformation. This is an electrostatic vibrator.

  In order to make the change in the gap distance non-linear, a function f is introduced as a new design parameter. The function f represents a function of the curve at arbitrarily determined coordinates when the shape of the vibrating body is approximately represented by a curve.

  The function f can also include non-differentiable points. In this case, the function f is defined piecewise except for the non-differentiable point.

  According to the present invention, the vibrating body is deformed by the stress caused by the temperature change, and the distance of the gap separating the vibrating body and the electrode can be changed by the deformation. This change in the gap distance can be designed nonlinearly. Such a design makes it possible to compensate for changes in the resonance frequency with respect to temperature changes with higher accuracy than in the conventional method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 3 to 8 are plan views of the electrostatic vibrator according to the embodiment of the present invention as seen from the viewpoint of the upper surface of the substrate. FIG. 2 is a diagram in which the shape of the vibrating body 10 in FIG. 1 is approximately expressed by a curve y = f (x).

  FIG. 1 is a plan view showing the structure of an electrostatic vibrator according to Embodiment 1 of the present invention. In FIG. 1, the vibrating body 10 has a long shape and is bent at least partially at a reference temperature. In the present embodiment, the long vibrating body 10 is, for example, substantially in the longitudinal direction. It is in a bent state at the center. In this state, no external force is applied to the vibrating body 10. The vibrating body 10 is connected to the deformation control body 9 at, for example, two points that are both ends, and is joined at at least one point. In all of the following embodiments, when it is said that it is joined at at least one point, a structure that is joined at all the continuous contacts is assumed unless otherwise specified. However, depending on the setting of the reference temperature, there may be a case where a similar effect can be obtained even if the structure is not necessarily joined but is simply in contact, and each embodiment includes such a structure even if not explicitly stated. The electrode 2 is fixed to the substrate 3. For example, the vibrating body 10 is arranged such that a bent portion thereof is separated from the electrode 2 by a gap d. The deformation control body 9 is made of a different material having a smaller thermal expansion coefficient than that of the vibration body 10. Although not shown in the figure, the deformation control body 9 is also fixed to the substrate 3. The shape and arrangement of the vibrating body 10, the electrode 2, and the deformation control body 9 are not limited to this, and different materials having different thermal expansion coefficients can be used for the vibrating body 10 and the electrode 2, respectively.

  When the temperature rises from the reference temperature, the vibrating body 10, the electrode 2, and the deformation control body 9 expand. However, the expansion amount of the deformation control body 9 is smaller than the expansion amount of the vibrating body 10. Therefore, the vibrating body 10 receives the stress 14 and the stress 15 at the continuous contact point with the deformation control body 9. Thereby, the vibrating body 10 is deformed so that the bending angle of the bent portion becomes small, that is, the vibrating body 10 is deformed so as to protrude in the direction of the displacement 23. As a result, the gap d increases.

  When a constant DC voltage is applied between the vibrating body 10 and the electrode 2 by a drive circuit (not shown) and an AC voltage having a frequency in the vibrating body 10 is applied from the electrode 2 in this state, the vibrating body 10 vibrates greatly. The frequency is the resonance frequency of the electrostatic vibrator. Although the resonance frequency changes depending on the temperature change, according to the structure of FIG. 1, the gap d can be changed in a direction to compensate for the change in the resonance frequency. Further, since the vibrating body 10 is bent, a change in the gap d due to a temperature change is a non-linear change.

  As an example in which the gap d changes nonlinearly due to a temperature change, a case where f (x) in FIG. 2 is, for example, a hyperbolic function, a higher-order polynomial function, or a function representing an arc obtained by cutting a part of an ellipse is given. Can do. The functions listed here are merely examples, and f (x) is not limited thereto.

  FIG. 3 is a plan view showing the structure of the electrostatic vibrator according to the second embodiment of the present invention. FIG. 3 is a diagram in which the deformation control body 9 of FIG. 1 is replaced with a deformation control body 16, and there is no difference in other parts. Therefore, the same parts as those in FIG. The deformation control body 16 of FIG. 3 is formed as a rectangular frame surrounding the periphery of the vibrating body 10, and there is no break in the middle of the frame, and the frame is a closed circuit. Although not shown in the figure, the deformation control body 16 is fixed to the substrate 3. The deformation control body 9 in FIG. 1 deforms the vibrating body 10 by the stress 14 and the stress 15, but also deforms itself by the reaction of the stress 14 and the stress 15. By replacing the deformation control body 9 with the deformation control body 16, the deformation control body becomes stronger and the deformation itself due to the reaction between the stress 14 and the stress 15 is suppressed. By suppressing the deformation of the deformation control body, the deformation of the vibrating body 10 increases. Further, the deformation control body 16 has less fatigue of the material due to stress and higher durability than the deformation control body 9. The deformation control body 16 is formed in a rectangular frame shape, but the shape of the deformation control body is not limited to this.

  FIG. 4 is a plan view showing the structure of an electrostatic vibrator according to Embodiment 3 of the present invention. FIG. 4 is a diagram in which the deformation control body 9 of FIG. 1 is replaced with a deformation control body 17, and there is no difference in other parts. Therefore, the same parts as those in FIG. The deformation control body 17 in FIG. 4 is connected at two points, for example, inside the both ends of the vibrating body 10 and joined at at least one point, and is sandwiched between both ends of the vibrating body 10. Although not shown in the figure, the deformation control body 17 is fixed to the substrate 3. This structure has an advantage that the entire electrostatic vibrator can be gathered more compactly than other embodiments.

  FIG. 5 is a plan view showing the structure of an electrostatic vibrator according to Embodiment 4 of the present invention. FIG. 5 is a diagram in which the vibrating body 10 of FIG. 1 is replaced with the vibrating portion 1, the support body 18, and the support body 19, and there is no difference in other portions. Therefore, the same parts as those in FIG. The vibration unit 1 is connected to the support 18 and the support 19. The support 18 and the support 19 are respectively connected to the deformation control body 9 at one point, and are joined at at least one of these two points of connection. The vibration part 1, the support body 18, and the support body 19 serving as a long vibration body are in a state of being bent by the vibration part 1 located at a substantially central part in the longitudinal direction, for example. In addition, materials having different thermal expansion coefficients can be used for the vibration unit 1, the support 18, and the support 19, respectively. If the material for forming the support 18 and the support 19 is changed to a different material having a different thermal expansion coefficient from that of the vibration part 1 while the vibration part 1 is left as it is, the amount of change in the gap d due to temperature change without changing the resonance frequency. Can be changed. That is, only the correction effect of the change in the resonance frequency with respect to the temperature change can be changed without changing the resonance frequency. As a result, the degree of freedom in design increases, and it becomes possible to design the electrostatic vibrator as a whole without changing the resonance frequency.

  FIG. 6 is a plan view showing the structure of an electrostatic vibrator according to Embodiment 5 of the present invention. FIG. 6 is a diagram in which the vibrating body 10 of FIG. 1 is replaced with a vibrating part 11, a fixing part 12, and a fixing part 13, and there is no difference in other parts. Therefore, the same parts as those in FIG. In FIG. 1, the vibrating body 10 is connected to the deformation control body 9 and joined at at least one point. However, in FIG. 6, although not shown in the drawing, the fixing portion 12 and the fixing portion 13 connected to the vibrating portion 11 are fixed to the substrate 3 and connected to the deformation control body 9. The vibration part 11, the fixing part 12, and the fixing part 13, which are long vibrators, are in a state of being bent at, for example, a substantially central part in the longitudinal direction of the long vibration part 11. Further, none of the vibration part 11, the fixing part 12, and the fixing part 13 need be joined to the deformation control body 9. Also in the structure of FIG. 6, as in the other embodiments, an effect that the gap d changes nonlinearly with a temperature change can be obtained. Therefore, in the case where the vibrating body is configured by the vibrating portion and the fixed portion, the vibrating body does not necessarily have to be joined to the deformation control body.

  FIG. 7 is a plan view showing the structure of the electrostatic vibrator according to the sixth embodiment of the present invention. FIG. 7 is a view in which the support 18 in FIG. 5 is replaced with the fixed portion 12 and the support 20, and the support 19 is replaced with the fixed portion 13 and the support 21, and there is no difference in other portions. Therefore, the same parts as those in FIG. In FIG. 5, the support 18 and the support 19 are connected to the deformation control body 9, and at least one of them is joined to the deformation control body 9. However, in FIG. 7, although not shown in the drawing, the fixing portion 12 connected to the support body 20 is fixed to the substrate 3 and connected to the deformation control body 9 and connected to the support body 21. The fixing portion 13 is also fixed to the substrate 3 and connected to the deformation control body 9. The vibrating part 1, the support 20, the support 21, the fixing part 12, and the fixing part 13, which are long vibrating bodies, are in a state of being bent by, for example, the vibrating part 1 located at a substantially central part in the longitudinal direction. In addition, none of the vibration unit 1, the fixed unit 12, the fixed unit 13, the support body 20, and the support body 21 need be joined to the deformation control body 9. Also in the structure of FIG. 7, as in the other embodiments, an effect that the gap d changes nonlinearly with a temperature change can be obtained. Therefore, even when the vibrating body is configured by the vibrating portion, the fixed portion, and the support body, the vibrating body does not necessarily have to be joined to the deformation control body.

  FIG. 8 is a plan view showing the structure of the electrostatic vibrator according to the seventh embodiment of the present invention. 8 replaces the vibrating body 10 of FIG. 1 with the vibrating portion 11 and the fixed portion 12, replaces the deformation control body 9 with the deformation control body 22, and the end point of the vibrating portion 11 that is not connected to the fixed portion is the deformation control body. FIG. In FIG. 8, although not shown in the drawing, the fixing portion 14 connected to the vibrating portion 11 is fixed to the substrate 3, but is not connected to the deformation control body 22. The deformation control body 22 is formed as a rectangular frame that surrounds the vibrating section 11 and the fixed section 12 serving as a vibrating body. There is no break in the middle of the frame, and the frame is a closed circuit. The vibrating portion 11 and the fixing portion 12 that are long vibrating bodies are in a state of being bent at, for example, a substantially central portion in the longitudinal direction of the long vibrating portion 11. Further, the vibrating body constituted by the vibrating portion 11 and the fixed portion 12 is connected to the deformation control body 22 only at the above-described connecting contact. These are the differences between FIG. 1 and FIG. 8, and there is no difference in other parts. Therefore, the same parts as those in FIG. The vibrating body constituted by the vibrating portion 11 and the fixed portion 12 is connected to the deformation control body 22 only at the end point of the vibrating portion 11 that is not connected to the fixed portion. Moreover, although the vibration part 11 and the deformation | transformation control body 22 may be joined in the continuous contact, it is not necessarily required and it may just be in contact. Also in the structure of FIG. 8, as in the other embodiments, an effect that the gap d changes nonlinearly with a temperature change can be obtained. Therefore, when the vibrating body is constituted by the vibrating portion and the fixed portion, the vibrating body does not necessarily have to be connected to the deformation control body at two or more points, and the effect of the present invention can be obtained if there is one point of connection. . Further, although not explicitly shown in the figure, similarly, when the vibrating body is constituted by the vibrating portion, the fixed portion, and the support body, the vibrating body does not necessarily have to be connected to the deformation control body at two or more points. The effect of the present invention can be obtained if there is a single point of contact.

It is a top view which shows the structure of the electrostatic vibrator by Embodiment 1 of this invention. It is the figure which expressed the shape of the vibrating body 10 of FIG. 1 approximately by curve y = f (x). It is a top view which shows the structure of the electrostatic vibrator by Embodiment 2 of this invention. It is a top view which shows the structure of the electrostatic vibrator by Embodiment 3 of this invention. It is a top view which shows the structure of the electrostatic vibrator by Embodiment 4 of this invention. It is a top view which shows the structure of the electrostatic vibrator by Embodiment 5 of this invention. It is a top view which shows the structure of the electrostatic vibrator by Embodiment 6 of this invention. It is a top view which shows the structure of the electrostatic vibrator by Embodiment 7 of this invention. 10 is a plan view showing a structure of an electrostatic vibrator according to an embodiment of the invention described in Patent Document 1. FIG. 10 is a plan view showing a structure of an electrostatic vibrator according to an embodiment of the invention described in Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 ... Vibration part, 2 ... Electrode, 3 ... Board | substrate, 4 ... Lever lever, 5 ... Lever lever support body, 6 ... Lever lever support | pillar, 7, 8, 18, 19, 20, 21 ... Support body, 9, 16, 17, 22 ... deformation control body, 10 ... vibrating body, 12, 13 ... fixed part, 14,15 ... stress, 23 ... displacement, d ... gap between vibrating body and electrode, f ... function representing shape of vibrating body

Claims (10)

A vibrating body, an electrode disposed with a gap to the vibrating body, and a deformation control body formed of a different material having a different thermal expansion coefficient from the vibrating body, the electrode and the deformation control body, Is an electrostatic vibrator fixed to the substrate,
The vibrator has a bent portion comprising a bent shape at least in part,
The vibrating body is connected to the deformation control body at at least one point;
The bent portion is deformed by stress generated in the continuous contact due to a temperature change,
The electrostatic vibrator according to claim 1, wherein the distance of the gap changes nonlinearly with respect to the temperature change by the deformation.   The electrostatic vibrator according to claim 1, wherein the vibrating body and the deformation control body are joined by at least one of the connection contacts. The electrostatic vibration according to claim 1, wherein the vibrating body includes a vibrating portion that vibrates due to an alternating voltage from the electrode, and at least one support that forms the bent portion and supports the vibrating portion. Child. The said vibrating body consists of the vibration part which comprises the said bending part, and vibrates with the alternating voltage from the said electrode, and at least 1 fixing | fixed part which fixes the said vibration part to the said board | substrate. Electrostatic vibrator. The vibrating body vibrates with an alternating voltage from the electrode, at least one support that forms the bent portion and supports the vibrating portion, and a fixing portion that fixes the support to the substrate, The electrostatic vibrator according to claim 1, comprising:   The electrostatic vibrator according to claim 1, wherein the vibrator and the electrode are formed of different materials having different coefficients of thermal expansion.   The electrostatic vibrator according to claim 3, wherein one of the vibrating portion and the support is formed of a different material having a different thermal expansion coefficient from the other.   The electrostatic vibrator according to claim 4, wherein one of the vibrating portion and the fixed portion is formed of a different material having a different thermal expansion coefficient from the other.   The electrostatic vibrator according to claim 5, wherein at least one of the vibrating portion, the support body, and the fixing portion is formed of a different material having a different thermal expansion coefficient from the rest. The electrostatic vibrator according to any one of claims 1 to 9,
An oscillator comprising: a drive circuit that applies a drive voltage to the electrode;

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