JPH1091249A - Flexural deflection vibrator and its resonance frequency control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the effective excitation of a vibration system by selecting a ratio between the detection voltage and the control voltage for control of the resonance frequency of a drive system when the control voltage proportional to the detection voltage detected by a detection element is applied to a control element. SOLUTION: When the AC voltage of frequency approximately equal to the resonance frequency of a flexural deflection vibrator A is applied to a drive element 1 from an AC power supply 6 via an amplifier 7, a free end of a fixed part held by the holding levers 4 and 4 has the flexural reciprocating motions around the fixed part. Then a mobile lever 5 vibrates with a large amplitude. Then a flexural distortion is caused to a detection element 2 and the AC voltage generated on both sides of the element 2 are inputted to an amplification factor setting means 11. When the control voltage generated by an amplifier 9 and amplified in a prescribed ratio is applied to a control element 3, the element 3 has a flexural motion and its distortion is superposably applied to the vibrator A. Thus, a flexural deflection vibration system is effectively excited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the resonance frequency of a flexural flexural vibration system and a flexural flexural vibrator for implementing the method.

[0002]

2. Description of the Related Art A piezoelectric bimorph (hereinafter referred to as a concept including a piezoelectric monomorph) has an advantage that a large amplitude can be obtained with a simple structure.
It is used as a driving source for various devices such as a vibrating gyroscope and a parts feeder. In order to excite the vibration system driven by the vibrator most efficiently, the resonance frequency of the vibration system and the resonance frequency of the applied voltage may be matched. In particular, in a vibrating gyroscope that has been attracting attention in recent years, it is effective to match the resonance frequency of the detection unit for detecting Coriolis force with the resonance frequency of external excitation as a means of increasing the sensitivity. There is a demand for an easy adjustment method. Furthermore, when driving using a plurality of piezoelectric bimorphs, the resonance frequency of each piezoelectric bimorph needs to match in order to match the drive system.

[0003]

By the way, although the resonance frequency of the piezoelectric bimorph is determined by the shape and the composition ratio of the material at the time of production, a slight difference is caused in the characteristics even when the piezoelectric bimorph having the same specification is produced. In addition, the resonance frequency of the vibration system changes not only due to the piezoelectric bimorph itself as the resonance base, but also due to a change in mechanical conditions such as a variation in the mounting form.

Therefore, even if the frequency of the applied voltage is set so as to coincide with the resonance frequency of the bending flexural vibrator using the piezoelectric bimorph, there actually occurs variation.

[0005] Therefore, it is necessary to adjust the resonance frequency of the piezoelectric bimorph, but this adjustment relies on physical trimming, and it has been difficult to perform precise adjustment after assembly. Further, since the trimming must be performed manually by an operator, there are disadvantages that the cost is high and the yield is low.

Furthermore, it is not possible to cope with a subsequent change in the resonance frequency of the entire vibration system due to the mounting form or the like, only by adjusting the characteristics of the vibration base.

Therefore, in order to efficiently excite the vibration system, there is a need for a resonance frequency adjustment method that can be easily adjusted.
An object of the present invention is to provide a resonance frequency adjusting method capable of responding to such a demand by electrical means, and a flexural vibrator for implementing the method.

[0008]

SUMMARY OF THE INVENTION The present invention provides a drive element to which an alternating voltage of a predetermined frequency is applied, a detection element for generating a detection voltage by vibrating a vibration system that bends and vibrates by the drive element, and a detection element. A control element to which a control voltage proportional to the detection voltage from the control element is applied, and the resonance frequency of the drive system is adjusted by selecting a ratio between the detection voltage and the control voltage. This is a method of adjusting the resonance frequency of the system.

Such a method is established based on the following findings. Vibration of the piezoelectric bimorph can be described by the freedom mass system equations of motion _{·· · mx + λx + κx =} F 1 Formula (1). Here, an attenuation term; λ = mω ₀ / Q, a spring constant; κ = mω ₀ ² . However, ω ₀ can be expressed as the resonance frequency of the spring, and Q can be expressed as the mechanical Q value of the system. Also, F ₁
Is the force generated by the oscillating voltage applied to the bimorph.

[0010] Here, if it is possible to apply a force F ₂ = .alpha.x proportional to the displacement x in this system, the above _{formula, ·· · mx + λx + (} κ-α) x = F 1 Formula (2), and the alpha By changing the coefficient, the coefficient of x, that is, the resonance frequency of the vibration system can be changed. FIG.
0 is an operation principle diagram showing such a relationship. The present invention
This α is set to adjust the resonance frequency of the vibration system.

Here, the voltage proportional to the displacement x can be obtained as a detection voltage by a detection bimorph provided so as to directly give a displacement of m. Then generates a control voltage proportional to the detected voltage, by applying a control voltage to the control device, it is possible to generate a force F ₂ which is proportional to the displacement x. This means that it is possible to arbitrarily change α by selecting the ratio α ′ between the detection voltage and the control voltage.

Here, the above relationship is as follows. x = c ₁ V _det (c ₁ ; proportional constant, V _det ; detection voltage) V _cont / V _det = α ′ (V _cont ; control voltage, α ′; proportional constant) F ₂ = c ₂ V _cont (c ₂ F ₂ = c ₂ V _det α ′ α = F ₂ / x = c ₂ V _det α ′ / c ₁ V _det = c α ′ (c; constant) Thus, the detection voltage and the control voltage It can be understood that by selecting the ratio α ′, it is possible to change the coefficient of x (κ−α) including the resonance frequency ω _{0 of the} spring, that is, the resonance frequency of the vibration system, based on Equation 2.

FIG. 6 shows the relationship between the frequency and the amount of displacement when various values of α ′ are selected. It can be seen that the waveform changes when α ′ is changed. Here, the frequency corresponding to the maximum value of the displacement amount of each waveform is the resonance frequency. Therefore, by selecting the waveform α ′ that produces the largest displacement, the flexural vibration system can be efficiently excited. Further, when it is necessary to adjust the resonance frequency of the flexural bending vibration system, α ′ may be selected so that the resonance frequency becomes the target resonance frequency.

Therefore, the detection element is excited by the vibration generated by the drive element to generate a detection voltage, and based on the detection voltage, an AC voltage for control is generated at a required ratio, and this is applied to the control element. Apply. The resonance frequency of the vibration system can be adjusted by driving the control element accordingly.

As a configuration for executing the above-described resonance frequency adjusting method, a drive element to which an AC voltage having a predetermined frequency is applied, a detection element that generates a detection voltage by vibration of a vibration system that bends and vibrates by the drive element, A bending flexural vibrator including a control element to which a control voltage proportional to a detection voltage from the detection element is applied, and amplification ratio setting means including an amplifier or the like that amplifies the detection voltage at a predetermined ratio to generate a control voltage is provided. Suggested. Incidentally, as the amplification ratio setting means, there is a method of adjusting an amplification factor by changing an external feedback resistance or using a variable amplifier. That is, the resonance frequency can be adjusted by changing α ′ by selecting the amplifier or adjusting the amplification factor.

As this piezoelectric bending / flexing vibrator, there is proposed a piezoelectric bending / flexing vibrator in which a drive element, a detection element and a control element are juxtaposed and integrated, one end is fixed, and the open end is used as a drive end.
In this case, manufacturing is facilitated by forming each drive element, detection element and control element with the same material and the same configuration. Furthermore, the drive element, the detection element, and the control element can be easily formed in parallel by attaching one piezoelectric element to a metal plate, and then removing and dividing the element using a dicer or the like. In this case, a small and high Q value can be obtained as compared with the former case where a plurality of elements are integrally assembled.

[0017] Alternatively, one of two elements, a driving element, a detecting element and a control element, is juxtaposed on one side of a metal plate, the other element is arranged on the other side, one end is fixed, and the open end is fixed. It may be a driving end. In this configuration, the area can be freely set by, for example, disposing the detection element widely so as to cover the entire other surface of the metal plate, and the degree of design freedom is improved. Furthermore, as another method of making a drive element, a detection element, and a control element, at least three independent partial electrodes are formed on the main surface of at least one piezoelectric element, and each electrode is used for drive, detection, and control. Function can be provided. In such a configuration, the productivity is greatly improved because only the screen mask corresponding to the partial electrode is used at the time of printing the electrode without assembling the three elements integrally or dividing the element by a dicer or the like.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a bending flexure vibrator A according to the present invention.
It shows. Here, this bending flexural vibrator A
A detection element 2 and a control element 3 are arranged side by side on both sides of a driving element 1. The base ends of the elements 1, 2, 3 are fixed by holding rods 4, 4 which are crossed over from front to back. The movable rod 5 is extended to one side of the end to connect each free end. The drive element 1 and the control element 3 are each composed of a piezoelectric bimorph having a known structure in which two piezoelectric elements each having electrodes formed on the front and back of a piezoelectric ceramic are joined via a metal plate. On the other hand, by employing the same piezoelectric bimorph as the detection element 2, it is only necessary to make each piezoelectric element correspond to each piezoelectric element of the control element 3, so that voltage application control becomes easy. Note that the control element 2 may be constituted by a single piezoelectric element.

An AC power supply 6 is connected to the front and back electrodes of the drive element 1 via an amplifier 7, and the detection voltage is reduced to 1/10 in the detection element 2. , The ratio α ′ of the power amplifier 10
Is set, and the output side thereof is connected to the electrode of the control element 3.

When such a structure is mounted on a vibrating gyroscope, a parts feeder, or the like, the holding rods 4, 4 may be attached to a fixed base, and the movable rod 5 may be fixed to the movable part.

In this configuration, when an AC voltage having a frequency substantially matching the resonance frequency of the flexural vibrator A is applied from the AC power source 6 via the amplifier 7 in advance, the holding rods 4 and 4 hold the AC voltage. The free end reciprocates around the fixed portion, and the movable rod 5 swings with a large amplitude.

Then, a bending distortion occurs in the detecting element 2 due to the driving, and AC voltages generated on the front and back sides are input to the amplification ratio setting means 11, and the AC electrode amplified by the amplifier 8 is applied to the control element 3. Then, the control element 3 moves.
Then, this strain is applied to the vibrator flexure vibrator A in a superimposed manner.

That is, the AC voltage applied from the AC power supply 6 to the drive element 1 and the resonance frequency of the flexural vibrator A are set in advance so as to substantially match, but the formation of the drive element 1 varies. Due to such factors,
The resonance frequency of the bending flexure vibrator A is not always an accurate value in accordance with the specifications, but may vary depending on the mode and dimensions of various mounting members, the mass of the driven part itself, and the mounting form. It is not constant as a whole.

Therefore, the vibration caused by the drive element 1 is detected as a voltage value by the detection element 2, and the control voltage generated by amplifying the detected voltage by the amplification ratio setting means 11 at a predetermined ratio α ′ is controlled. The adjustment is performed by applying the voltage to the element 3. This theoretical basis is based on the finding that, as described above, it is possible to change the resonance frequency of the vibration system by changing the ratio α ′ based on Equation (2).

The amplification ratio α 'can be changed by changing the value of an external feedback resistor (not shown) of the amplifier. Here, the elements 1, 2, and 3 are set to have a width (a) of 2 m.
m, length (b) 15 mm, thickness (c) 0.53 mm and the same structure. The flexural flexural vibrator A is manufactured, α ′ is changed, and the frequency and displacement amount are changed. When the relationship was examined, the result was as shown in FIG. From this result, it is understood that changing α ′ changes the waveform. Here, the frequency corresponding to the maximum value of the displacement amount of each waveform is the resonance frequency. Therefore, by selecting the waveform α ′ that produces the largest displacement, the flexural vibration system can be efficiently excited. Further, the resonance frequency can be adjusted to an arbitrary value as needed.

Further, an embodiment of the bending flexure vibrator according to the present invention will be described with reference to FIGS. Here, FIG.
7 shows a bending flexure vibrator B of a second embodiment. The flexural flexural vibrator B has strip-shaped piezoelectric elements formed by forming electrodes on the front and back sides of a strip-shaped piezoelectric ceramic on the front and back surfaces of the metal plate 20, respectively. Thus, a drive element 21, a detection element 22, and a control element 23 having a bimorph structure are provided. That is, the metal plate 20
A drive element 21 is provided at the center of the sensor, a detection element 22 is provided at an interval on the left side in the figure, and a control element 23 is similarly provided on the right side. As an example of the dimensions, it is proposed that the length in the vertical direction is 15 mm, the width of the metal plate 20 is 2 mm, and the thickness of a portion where each element is joined is 0.5 mm.

The bending and bending vibrator B is a metal plate 20
By bonding one element so as to cover the entire surface of the front and back, by dicing the two elements with a dicer on the front and back, respectively, dividing and forming a piezoelectric element plate separately on each surface,
It can be manufactured by arranging the drive element 21, the detection element 22, and the control element 23. The circuit configuration is the same as in FIG.
Omitted. As described above, in the structure in which the driving element and the detecting element are integrally arranged on one metal plate, the size is smaller than that of the piezoelectric flexural vibrator A of the first embodiment in which a plurality of elements are separately assembled. And a high Q value can be obtained, so that a large displacement can be obtained.

FIG. 3 shows a bending flexure vibrator C according to a third embodiment. Here, a strip-shaped piezoelectric element constituting the control element 33 is disposed at the center on one side of the metal plate 30, and a strip-shaped piezoelectric element similarly constituting the drive element 31 is disposed on the left and right sides thereof. So that the other surface of the plate 30 covers the entire surface,
The detection element 32 is formed by joining a piezoelectric element. In this configuration, the driving element 31 and the control element 3
Reference numeral 3 denotes a monomorph structure including one strip-shaped piezoelectric element and a metal plate 30.

In this configuration, since the detecting element 32 can use the entire surface of the metal plate 30, the degree of freedom of design increases and a large area can be secured, so that a large detecting voltage can be obtained. In this configuration, the flexural vibrator B
In contrast to this, it can be manufactured by cutting only the element on one surface side in the vertical direction and forming the driving element 31 and the control element 33. The combination of the arrangement of the drive element, the detection element, and the control element is not limited to this example, and can be arbitrarily selected.

FIG. 4 shows the configuration of the bending / flexing vibrator C. The dimensions of each part are 2 mm in width (a ') and 15 mm in length (b').
mm, thickness (c)) of 0.5 mm, and the ratio α ′ was changed in the same manner as in the first embodiment of FIG. 1 to examine the relationship between the frequency and the displacement amount. Was. From this result, it is understood that the waveform changes by changing the ratio α ′. Further, when the change rate of the resonance frequency with respect to the ratio α ′ was obtained, the result was as shown in FIG. From this result, it is understood that the resonance frequency can be linearly controlled with respect to the change in the ratio α ′.

FIG. 5 shows a flexural vibrator D according to a fourth embodiment. In such a configuration, two identical piezoelectric elements 3
In a bimorph structure in which 5, 35 are attached via or without a metal plate, or in a monomorph structure in which one piezoelectric element 35 is attached instead of a non-piezoelectric element such as a metal plate,
At least the outer electrode of one piezoelectric element 35 is divided into three partial electrodes, the part corresponding to the central electrode is used as the driving element 36, and the parts corresponding to the electrodes on both sides are used as the detecting element 37 and the control element 38, respectively. It is configured to work.

In such a configuration, the piezoelectric flexural vibrator A of the first embodiment in which three independent elements are integrally assembled and the piezoelectric flexural vibrator of the second and third embodiments in which the three elements are divided by a dicer. Compared with B and C, it is only necessary to use a screen mask corresponding to the partial electrode at the time of electrode printing, so that there is an advantage that productivity can be remarkably improved.

Next, an application example of the bending / flexing vibrator will be described. FIG. 9 shows an example in which the present invention is applied to a vibrating gyroscope 40. The vibrating gyroscope 40 includes a plurality of flexural vibrators A to A according to the present invention for applying rotational vibration to a detection device 46 described below between a movable base plate 41 and a fixed base plate 42.
D is provided. With the function of adjusting the resonance frequencies of the bending bending vibrators A to D, the resonance frequency of the detection device 46 and the resonance frequency of the external excitation can be matched, and the matching of the frequencies of the bending bending vibrators A to D is maintained. Therefore, the sensitivity of the vibrating gyroscope can be greatly improved.

In the vibrating gyroscope 40, at least four vibrating plates 44 are provided on a substrate 43 made of a semiconductor such as silicon as the detecting device 46 on the movable base plate 41. Each of the vibration plates 44 is also made of a semiconductor such as silicon and has a cantilever shape having one end fixed to the substrate 43 via an insulating layer 45. When a rotational motion about the z-axis is given to the center of the detection device 41 by the bending / flexing vibrators A to C, a rotational angular velocity about the y-axis is applied, and a force in the z-axis direction is generated by Coriolis force. Thus, the capacitance between the diaphragm 44 and the semiconductor facing the diaphragm 44 changes. At this time, since the capacitance changes according to the magnitude of the rotational angular velocity, the angular velocity can be obtained from the amount of change.

In addition, the bending / flexing vibrators A to C are used as a vibration source of a parts feeder and a driving source of various transporting devices. At this time, a plurality of flexural vibrators A to C
Is used, it is necessary to match the resonance frequency, or by matching the resonance frequency of the vibration system to the frequency of the drive voltage, it is possible to drive efficiently, so that the above α ′ Is adjusted to adjust the resonance frequency.

[0036]

According to the present invention, the resonance frequency of the drive system is adjusted by selecting the ratio between the detection voltage and the control voltage. Therefore, the resonance frequency can be adjusted by electric means. Adjustment becomes easy. Therefore, by adjusting the resonance frequency of the vibration system in the mounted state, it is possible to adjust the resonance frequency to be the maximum displacement amount. Further, even when applying a plurality of bending flexure vibrators, the resonance frequencies can be easily matched. There are excellent effects such as being able to do. In particular, when the present invention is applied to the vibrating gyroscope shown in FIG. 9, the sensitivity can be greatly improved by arbitrarily changing the resonance frequency of the drive system so as to match the resonance frequency of the detection device. There is an effect that it can be.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a bending flexure vibrator A according to a first embodiment together with a drive circuit thereof.

FIG. 2 is a perspective view of a flexural vibrator B according to a second embodiment.

FIG. 3 is a perspective view of a flexural vibrator C according to a third embodiment.

FIG. 4 is a perspective view showing the bending flexure vibrator C together with its drive circuit.

FIG. 5 is a perspective view of a flexural vibrator D according to a fourth embodiment.

FIG. 6 shows a bending ratio α ′ when the bending flexure vibrator A is used.
6 is a graph showing a relationship between the frequency and the resonance frequency.

FIG. 7 is a graph showing resonance characteristics when a bending flexure vibrator C is used.

FIG. 8 is a graph showing a resonance frequency change rate when the bending flexure vibrator C is used.

FIG. 9 is a perspective view showing an example of application to a vibration gyro.

FIG. 10 is an operation principle diagram.

[Explanation of symbols]

 AC flexural flexural vibrator 1,21,31,36 Driving element 2,22,32,37 Detection element 3,23,33,38 Control element 6 AC power supply 9 Amplifier 11 Amplification ratio setting means 20,30 Metal plate

Claims (5)

[Claims] 1. A drive element to which an AC voltage having a predetermined frequency is applied, a detection element that generates a detection voltage by vibration of a vibration system that bends and vibrates by the drive element, and a control that is proportional to the detection voltage from the detection element. A resonance frequency adjustment method for a flexural vibration system, comprising: a control element to which a voltage is applied; and adjusting a resonance frequency of the drive system by selecting a ratio between the detection voltage and the control voltage. 2. A drive element to which an AC voltage having a predetermined frequency is applied, a detection element that generates a detection voltage by vibration of a vibration system that bends and vibrates by the drive element, and a control that is proportional to the detection voltage from the detection element. A flexural vibrator comprising: a control element to which a voltage is applied; and amplification ratio setting means for amplifying a detection voltage at a predetermined ratio to generate a control voltage. 3. The piezoelectric bending vibration device according to claim 2, wherein the drive element, the detection element and the control element are juxtaposed and integrated, one end is fixed, and the open end is the drive end. 4. A metal plate, on which one of two elements of a drive element, a detection element and a control element is juxtaposed, and the other element is arranged on the other surface, one end of which is fixed, and the open end thereof. The piezoelectric bending / flexing vibrator according to claim 2, wherein a is a drive end. 5. The piezoelectric bending deflection according to claim 2, wherein a drive element, a detection element, and a control element are formed by three divided electrodes independently formed on a main surface of at least one piezoelectric element. Vibrator.