JPH08278141A - Ceramic piezoelectric complex type angular velocity sensor - Google Patents

Abstract

PURPOSE: To provide a ceramic piezoelectric complex type angular velocity sensor having high sensitivity, a large signal-noise ratio, an excellent temperature drift characteristic, high impact resistance and a low price. CONSTITUTION: A comb type tuning fork is integrally formed to have four parallel vibration arms 11 to 14 of a ceramic piezoelectric material, and tuning fork supports 15 and 16 in common, and only the section of the tuning fork effective for drive and a detected vibration is polarized in an X-direction or a Y-direction. Also, drive electrodes 20 and 21, and detection electrodes 22 and 23 are arranged in a section corresponding to the polarized section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to aircraft, automobiles, ships,
Ceramic-piezoelectric composite used for posture control of moving objects such as vehicles, navigation systems, camera shake prevention for cameras and video cameras, audio; remote control for remote control of video equipment, personal computers, etc., or systems for detecting movements involving rotation The present invention relates to a angular velocity sensor.

[0002]

2. Description of the Related Art There are various conventional angular velocity sensors, but as a prior art, two rectangular arms are disclosed in Japanese Unexamined Patent Publication No. 3-120415 from the viewpoint that the entire tuning fork is formed of a piezoelectric ceramic material. A vibration gyro that has a tuning fork in its overall shape by integrally molding a portion and a base portion interconnecting these arm portions at their lower ends with a piezoelectric material is used. It is disclosed.

The conventional angular velocity sensor will be described below with reference to the drawings. FIG. 15 is a perspective view of a single-shaped tuning fork disclosed in Japanese Patent Laid-Open No. 3-120415.

The polarization direction is an invention in which the base portion is polarized in the Y-axis direction and the driving-side vibrating arm is polarized in the X-axis direction.
The driving electrodes 3 and 4 are partial electrodes of about half of the vibrating arm, and the driving force is 2/8 times when viewed from the use of all four side surfaces.

Further, the vibrating arms 1 and 2 are driven by the Coriolis force.
Causes a bending vibration in the opposite phase in the X direction, so that a torsion moment about the Y axis is generated in the base portion 5. The detection electrodes 6 and 7 detect torsional vibrations of the base portion 5, and have high resonance frequency and low output sensitivity.

Reference numeral 1 is a drive-side vibrating arm, and 2 is a monitor vibrating arm for stable vibration, and although the polarization direction is not explicitly shown, it is considered to be in the X direction due to its function.

[0007]

However, as shown in FIG.
Separates the role and function of the vibrating arms 1 and 2 for driving and the base portion 5 for detection, and there is no disclosure of how to attach or hold the base portion 5, so that no analogy can be made. However, (1) Drive vibration (Bending vibration of opposite phases in the Y direction)
Of the vibration component in the base portion 5 due to (2) the vibration component in the base portion 5 due to the bending vibrations of the opposite phases in the X direction when the Coriolis force is applied, and (3) It is expected that the torsional vibration component around the Y-axis and the disturbance noise component from (4) the holding portion are mixed to form a complicated vibration mode. The separation circuit for each of the four vibration components becomes complicated. Vibration analysis of the base part of a tuning fork has not been clarified even in today's mechanical vibration engineering, and its control seems difficult. Therefore, it is difficult to separate the vibration, which causes a malfunction as a gyro in practical use. In particular, it was vulnerable to the disturbance noise transmitted from the holding portion, and it was difficult to put it into practical use in automobiles and the like.

The torsional vibration has a higher resonance frequency and a smaller vibration amplitude than the bending vibration of the cantilever support rod, and therefore has a low sensitivity. Therefore, if the output sensitivity is lowered, it causes the temperature drift (when the input angular velocity is 0, the detection value changes due to the ambient temperature change).

Further, since the drive electrodes 3 and 4 in FIG. 10 are provided up to the tip in the Y-axis direction of the vibrating arm, according to the vibration theory of the tuning fork, the tip 20 to 30% acts as a stray capacitance and no driving force is applied. However, the electrical noise is not picked up, and electrical noise is picked up, and the ratio between the detection signal and electrical system noise (hereinafter referred to as S / N) is deteriorated.

In order to solve the above-mentioned conventional problems, the present invention does not use a complicated base portion having a vibrating form, that is, a support portion, for detection, and separates the functions of the drive side tuning fork and the detection side tuning fork independently.
In order to eliminate mechanical coupling vibration of the support part, to prevent the drive signal from wrapping around to the detection side, and to improve drift performance, the vibrating arm in the part where the tuning fork vibration is stable is used.

[0011]

In order to solve the above-mentioned problems, a ceramic piezoelectric composite angular velocity sensor of the present invention has four parallel vibrating arms made of a flat plate-shaped ceramic piezoelectric material and a tuning fork support portion in common. A comb-shaped tuning fork is integrally formed, and the X-axis of the three-dimensional coordinate system is the width direction of the vibrating arm and the supporting portion, the Y-axis is the longitudinal direction of the vibrating arm, and the Z-axis is the thickness direction of the entire tuning fork. Part of the support along the Y axis is pre-polarized in the X direction by an externally applied voltage, and the outer two sets are the drive side tuning forks, the inner two sets are the detection side tuning forks, or the inner two sets. Is the driving side tuning fork, and the outer two sets are the detecting side tuning forks. The driving side vibrating arm of the comb-shaped tuning fork and the drive electrodes along the Y axis on the front and back surfaces and part of the side surface of the supporting portion are provided on the detecting side vibrating arm. And 2 along the Y-axis on the front and back of part of the support
Divided detection electrodes are arranged corresponding to the partially polarized portions, and an AC signal is applied to the drive electrode of the drive side tuning fork to generate bending vibrations of opposite phases in the X direction (hereinafter referred to as X _D mode). Generated by Coriolis force based on the rotational angular velocity about the Y axis applied from the outside by inducing bending vibrations (hereinafter, referred to as X _S modes) of opposite phases to each other on the detection side tuning fork via mechanical coupling of the supporting portion. The amount of charges generated by bending vibrations in the Z-axis direction opposite to each other (hereinafter referred to as Z _S mode) is detected by the detection electrode of the detection side tuning fork.

[0012]

With the above structure, the vibration transmission efficiency is improved, the detection sensitivity is improved, the sneak of the drive signal is prevented, the electrical / mechanical S / N is improved, the performance is high and stable. Can be one.

[0013]

The ceramic piezoelectric composite angular velocity sensor of the present invention will be described below.

The basis of the present invention is that the base portion having a complicated vibration mode, that is, the support portion is not used for detection, but the functions of the drive side tuning fork and the detection side tuning fork are independently separated, and the machine of the support portion is separated. Of mechanical coupling vibration of drive signal, elimination of mechanical coupling vibration,
In order to prevent the drive signal from wrapping around to the detection side and to improve the drift performance, the vibrating arm of the part where the tuning fork vibration is stable is used.

Next, according to the theory of vibration engineering, the entire vibrating arm is not polarized, and about half to 80% of its length, to be precise, the standard function of mechanical vibrations, and the volume ratio (mechanical ratio of rod) Polarize 62% from the ratio of compliance to electrical capacitance)
By disposing the drive electrode area and the detection electrode area in the portion corresponding to the polarization, the electrode area that maximizes the vibration amplitude and the detection sensitivity due to the driving force can be optimized.

Furthermore, the effective length of the tuning fork vibrating arm that contributes to the resonance frequency is that not only the length of the vibrating arm but also the supporting portion vibrates, and according to classical mechanics, the length from the root of the supporting portion of the vibrating arm. If the length corresponding to the width of the vibrating arm is added to, the resonance frequency can be designed accurately by design unless the tuning fork has a unique shape. Therefore, by polarizing the portion corresponding to the effective length of the vibrating arm and disposing the electrode, the output can be taken out without waste, and unnecessary driving vibration is not generated.

Further, since there is no polarization or electrode in an extra portion that does not contribute to drive vibration or detection vibration, the sneak signal is prevented by the electric coupling due to the wiring of the electrode, and the S due to the stray capacitance.
/ N is a feature that can prevent deterioration, and this effect is also aimed at.

The means of partial polarization and partial electrode in consideration of the standard function of mechanical vibration and the capacitance ratio in the equivalent circuit of the resonant element cannot be applied to the quartz material, and are effective only in the ceramic piezoelectric material. .

Further, stable driving of the tuning fork is very important for eliminating mechanical coupling vibration and improving temperature drift performance. In the present invention, a current amplifier for detecting a current generated in a monitor electrode (hereinafter referred to as a monitor current) at zero voltage, an AC / DC converter for converting an output of the current amplifier into a DC voltage signal proportional to its amplitude, and a current amplifier. The output of is amplified according to the output of the converter and used as the voltage applied to the drive electrode (hereinafter referred to as drive voltage),
That is, a drive level controller having a function of keeping the drive amplitude constant is provided.

The quadrature detection method is used as a means for extracting a signal proportional to the input of the angular velocity from a detection electrode current (hereinafter referred to as detection current) signal, and a timing signal for detection is required. In the present invention, this timing signal is obtained by a zero cross comparator which detects a zero cross of the output signal of the current amplifier.

In order to solve the problem of the conventional angular velocity sensor integrally formed of a ceramic piezoelectric material in which the supporting portion is a detection tuning fork, the polarization direction of the vibrating arm and the supporting portion are made different from each other. A comb-shaped compound tuning fork is integrally formed, and a partial polarization and partial electrode method applicable to the compound tuning fork is used to embody the complex vibration of the support part with the aim of optimizing the output voltage. .

Here, the operation and effect of partial polarization and partial electrodes will be described with reference to FIGS. 13 and 14.

In FIG. 13, assuming that the vibrating arm of the tuning fork and a part of the supporting portion are cantilevered support rods, the rods in the longitudinal direction (that is,
If the vertical axis of the tuning fork is x-axis, the amplitude of vertical vibration perpendicular to the x-axis is ξ, the base of the arm is x = 0, and the tip of the vibrating arm is x = 1, then the amplitude ξ and the vibration occur in the rod. The strain δ is represented by hyperbolic sin and cos from the vibration engineering theory,
It is not represented by a linear function as shown in FIG. However, the vertical axis standardizes the mode function, and ξ = 1 and δ = 1.

As a result, the detected charge proportional to the strain δ of the ceramic piezoelectric rod has a larger output at a position closer to x = 0 and a smaller output at the tip, and becomes zero at x = 1.

On the other hand, from the theory of electro-mechanical piezoelectric transducers,
The output voltage is inversely proportional to the capacitance ratio γ of the vibrating arm, and there is a condition that the electrostatic capacitance should be small. If this distortion δ curve and the capacity ratio γ function are calculated, the output can be optimized, and generally x
It becomes the maximum when = 0.62 l. Therefore x = 0.62l
That is, since about 38% of the tip is a non-polarized portion and no electrode is provided, the stray capacitance at the tip is eliminated and the S / N is improved.

Although this is analyzed as an ideal cantilever support rod, it actually differs depending on the tuning fork shape. In the present invention, the lower end of the support portion is held on the nodal line α of vibration, and the support portion is mechanical. Since there is a function of dynamic coupling, it vibrates slightly,
The analysis as a classical cantilever support bar cannot be handled. Therefore, according to the present invention, the range of x = 0.5 to 0.8 l was set by simulation and experiment.

Similarly, in the support portion, it is possible to avoid unnecessary vibration detection and unnecessary driving by avoiding polarization or electrode arrangement in a portion that does not contribute to vibration, and S / N can be greatly improved.

The second feature of the present invention resides in an integrally formed comb-shaped tuning fork made of a ceramic piezoelectric material. That is,
It is characterized in that the outer side having a large volume is the driving side tuning fork and the inner side having a small area or volume is the detecting side tuning fork, and the small inner detecting side tuning fork rides on the large outer driving side tuning fork. Therefore, the driving-side tuning fork vibration can be efficiently transmitted to the detection-side tuning fork. If the driving-side tuning fork is the main turtle and the detection-side tuning fork is the sub-turtle, it is a tuning fork that vibrates as if the sub-turtle was on top of the so-called pro-turtle.

On the contrary, even when the inner two sets are used as the driving side tuning forks and the outer two sets are used as the detection side tuning forks, the operation is the same. It's dressed up as a rider. In this case, it is necessary to increase the driving force by increasing the size of the inner tuning fork or increasing the applied voltage, and it is particularly desirable to consider the shape of the root of the tuning fork.

A third feature of the present invention is that a monitor driving method using a self-excited oscillation circuit is suitable for a compound tuning fork having each function separated from a single tuning fork. The effect is that the amplitude of the monitor current detected at zero voltage is purely proportional to the vibration level (speed) of the tuning fork. According to the above means, the output of the AC / DC converter is proportional to the monitor current, and the controller adjusts the drive voltage so that the output of the AC / DC converter is always constant.

Since the vibration level of the tuning fork changes in proportion to the drive voltage, as a result, the vibration level of the tuning fork is always kept constant. As a result, the tuning fork vibration is stable and the drift performance is improved.

Specific examples of the ceramic piezoelectric composite angular velocity sensor of the present invention will be described below with reference to the drawings.

First, in FIG. 1, four parallel vibrating arms 11, 12, 13, and 14 made of a flat plate-shaped ceramic piezoelectric material are used for driving the vibrating arms 11 and 12, and for vibrating arms 13 and 14 for detecting. In the embodiment in which a comb-shaped tuning fork having the vibrating arms 11 to 14 and the tuning fork supporting portions 15 and 16 in common is integrally formed, the X axis of the three-dimensional coordinate system is set in the width direction of the vibrating arms and the supporting portion. The Y-axis is the longitudinal direction of the comb shape, and the Z-axis is the thickness direction of the entire tuning fork.

[0034] l _D and l _S are each drive-side vibration arms 11,1
2, the length of the detection side vibrating arms 13 and 14,
It is the length from the roots 17 and 17 'of 1 and 12 and the roots 18 of the vibrating arms 13 and 14 to the tip. l _SB represents the length of the support portion 16 of the detection side tuning fork, and is the distance between the roots 17 and 18.

[0035] W _D is the width of the driving side oscillating arms 11, 12, W _S is the width of the detecting side oscillating arms 13, 14, t is the vibrating arms 11 to 14,
The support portions 15 and 16, that is, the thickness of the entire tuning fork, g ₁ represents the slit spacing of the drive-side vibrating arms 11 and 12, and g ₂ represents the slit spacing of the detection-side vibrating arms 13 and 14. 19 is the anti-phase bending vibration in the Z-axis direction when the Coriolis force acts, that is, Z
It is a notch provided on the nodal line α (shown by the dotted line in FIG. 1) of the _S- mode vibration and provided in the lower portion of the supporting portion 15, and serves to hold or mount the angular velocity sensor. Further, the function is the same even if 19 is a small hole instead of a notch.

The white arrow indicates the polarization direction, and the shaded area indicates the polarization direction.
White areas indicate polarized portions and non-polarized portions. That is, outside 2
In the driving side tuning fork of this set, the vibrating arms 11 and 12 are about 0.
7l _DAnd about W on the support 15 side_DThe length of the
About 0.7 l of vibrating arms 13 and 14 on the output side tuning fork_SWhen
L on the support 16 side_SB+ About W_DVolume part made from the length of
By an externally applied voltage with a DC voltage of 3 to 4 KV / mm
Partial polarization is performed in advance so as to penetrate in the X direction.

FIG. 2 shows the structure of the drive electrodes and the detection electrodes after the partial polarization. Basically, the electrodes are provided corresponding to the polarized parts in FIG. Regarding the drive electrodes, the polarization electrodes can be used as they are, but the polarization electrodes are provided on the side surfaces of the vibrating arms 13 and 14 of the inner detection side tuning fork, and are removed after polarization. The figure shows the state after removal. Further, it is desirable that the length of the drive electrode on the supporting portion side is about 0.5 to 1 times the width W _D of the vibrating arm.

In FIG. 2, + -side and-side drive electrodes 20 and 21 are formed on the four surfaces of the drive-side vibrating arms 11 and 12, respectively.
On the front and back surfaces of the detection-side vibrating arms 13 and 14, + -side and-side detection electrodes 22 and 23 are formed side by side.

FIG. 3 shows an embodiment in which the polarization directions are all in the Z direction, that is, the thickness direction of the tuning fork, and the polarization portion is the same as in FIG. When the polarization direction is the Z-axis direction, the configurations of the drive and detection electrodes are reversed, and the drive electrodes 20 and 21 are divided into two electrodes in the Y-axis direction of the vibrating arms 11 and 12, and the detection electrode 22 as shown in FIG. , 23 are front and back surfaces of the vibrating arms 13 and 14,
It is necessary to provide electrodes on both sides.

FIGS. 5 and 6 show electrode configurations and connection diagrams corresponding to FIGS. 1 and 3. This will be described.

As shown in FIG. 5, the front and back surfaces of the drive-side vibrating arm 12 are positive side drive electrodes 20, and the side surfaces are negative side drive electrodes 21.
The drive-side vibrating arm 11 is reversely connected, and the front and back sides are commonly connected so that the drive electrode 21 on the − side and the side face are the drive electrodes 20 on the + side, and the input terminal 24 of the sensor is connected to the positive electrode of the drive signal and input. The terminal 25 is the negative electrode. If the AC signal is continuously applied between the input terminals 24 and 25, the driving-side vibrating arms 11 and 12 have bending vibrations in opposite phases in the X-axis i and j directions (X _D mode).
To last. This X _D mode vibration is generated by the support portions 15 and 16
Bending vibrations (X _S mode) of opposite phases are induced in the q- and r-directions of the X-axis of the detection-side vibrating arms 12 and 13 through the mechanical coupling of.

When the detection electrodes 22 and 23 are divided into two parts only on the front and back surfaces of the vibrating arms 13 and 14 of the detection side tuning fork, and when a rotational angular velocity (ω) is applied from the outside around the Y axis, the vibrating arms are generated by the Coriolis force. If 13 moves in the direction of arrow k, the vibrating arm 14 moves in the direction of arrow p (Z _S mode), so that the detection electrodes 22, 23 on the surface of the vibrating arm 13 are (-, +) as shown in FIG.
, The opposite electric charges of (+,-) are generated on the detection electrodes 22 and 23 on the back surface thereof.

On the other hand, the detection electrodes 22 on the surface of the vibrating arm 14,
In contrast to the above, (+, −) is generated in 23, and (−, +) charges are generated in the detection electrodes 22, 23 on the back surface thereof. Connect the same polarity of these charges to each other, and connect the positive side to the detection terminal 26.
If the negative side is connected to the detection terminal 27,
It can be detected as a potential difference between 27.

The drive electrodes 20 and 21 shown in FIG. 6 are two-divided electrodes, and the diagonal sides of the front and back surfaces of the vibrating arm 12 are used as the + side drive electrode 20 and the-side drive electrode 21, and the vibrating arm 11 is symmetrical thereto. In addition, common connection is made so as to be the + side drive electrode 20 and the-side drive electrode 21, and the input terminal 24 of the sensor is the positive electrode of the drive signal and the input terminal 25 is the negative electrode. Input terminals 24, 2
If the AC signal is continuously applied for 5 seconds, the vibrating arms 11, 12,
Similar to FIG. 5, 13 and 14 induce vibrations in the q and r directions (X _S mode) by vibrations in the i and j directions (X _D mode).

The front and back surfaces of the vibrating arms 13 and 14 of the detection side tuning fork,
When the detection electrodes 22 and 23 are provided on the side surfaces and a rotational angular velocity (ω) is applied from the outside about the Y axis, the Coriolis force causes the vibrating arms 13 and 14 to vibrate in opposite phases in the k and p directions (Z _S mode). As a result, (+) charges are generated on the front and back surfaces of the vibrating arm 13, and (-) charges are generated on both side surfaces, and quite the opposite charges are generated on the vibrating arm 14. Connect the same polarity of these charges,
If the + side is connected to the detection terminal 26 and the − side is connected to the detection terminal 27, it can be detected as a potential difference between the detection terminals 26 and 27.

One example of specific design dimensions for the embodiment of FIG. 3 is shown below, and the holding or mounting position is the small hole 1
9 (see FIG. 7).

* Length of drive-side vibrating arms 11 and 12 ………………_D = 20mm, * Tuning fork thickness …………………………………… t = 1.5mm, * Width of the vibrating arms 11 and 12 on the drive side ……………… W_D = 2.9 mm, * width of the vibrating arms 13 and 14 on the detection side …………………… W_S = 2.0 mm, * Length of the vibrating arms 13 and 14 on the detection side ……………… l_S = 17mm, * Length of the support part 16 of the detection side tuning fork ……………… l_SB= 3.1 mm, * Slit spacing between the vibrating arms 11 and 12 on the driving side ... s₁ = 3.0 mm, * Slit spacing between the vibrating arms 13 and 14 on the detection side ... s₂ = 4.0mm, and adjust the resonance frequency by trimming.
Then X_DMode resonance frequency f_DX= 9830 Hz, f_SZ
= 5335 Hz. This example shows the drive resonance frequency
Number f_DXAnd the detected resonance frequency f_SZWhen is different from. This
Ceramic material is Pb (Mg_1/3Nb_2/3) O₃-Pb
TiO₃-PbZrO₃The composition of the three main components of
The lower PCM system) and obtained by sintering.
It This PCM system Young's modulus E in the X direction_X= 7.945 ×
10¹¹(N / m²), Young's modulus in the Z direction E _Z= 7.862 ×
10¹¹(N / m²), Density ρ = 7.645 × 10³(Kg
/ M³)It was used.

In addition to the compositions used in the above examples, PbTiO ₃ and Pb (Zr- having a perovskite type crystal structure are used.
_{Ti) O 3, LiNbO 3,} LiTaO 3 or the composition as a main component such as PbNb ₂ O ₆ tungsten bronze type crystal structure, further, these complex metal oxide can be used as well, to obtain the same effect You can

As a second concrete design example, f _DX ≠ f
_{In the case of SX} and f _DX ≈f _SZ , in the above example, if the length of the vibrating arm is not changed and adjustment is made by W _D for convenience, then * width of the driving side vibrating arms 11 and 12 ...... ………… W _D = 1.66 mm, * Other specifications ………………………………………… All the same as above, resonance frequency f _DX = 5345 Hz, f _SZ = 533
5 Hz, which is slightly different is the width of the vibrating arm W _D , W _S ,
And the effective length of the vibrating arm varies depending on the thickness t,
Resonance frequency f _DX ≈ f _SZ ≈ 5342Hz by trimming
Set to.

The degree of approximation of f _DX ≈f _SZ in the resonance type design should be set according to the frequency characteristics of the sensor output with respect to the input angular velocity ω applied from the outside.

Trimming is performed by cutting the corners of the vibrating arm diagonally, cutting the root of the vibrating arm by V-grooves, cutting the bottom of the support portion, or cutting the tip of the vibrating arm according to a known method already announced. It was carried out by a method of adhesively adding a small mass.

Next, the position where the tuning fork is held or attached will be described with reference to FIG. FIG. 7 is a diagram for explaining the vibration mode, where the + and-signs indicate when Coriolis force is applied.
The amplitude phase of the detection side tuning fork in the Z _S mode is shown.

When the drive-side vibrating arms 11 and 12 are in the X-direction drive mode, that is, in the X _D mode, the vibrating arm 13 of the detection-side tuning fork is
In 14, vibration modes of q and r narrowing inward, that is, an X _S mode is induced. At this time, when an angular velocity ω is applied from the outside about the Y axis, the vibrating arm 13 moves in the front k direction to the vibrating arm 1.
4 vibrates in the p direction countercurrent side, when this is defined as Z _S mode, Z _S mode in the thickness direction of the tuning fork is the centerline of the tuning fork is Y
It becomes a nodal line α (indicated by a dotted line) of the vibration in the axial direction, and the support part 16 of the detection side tuning fork becomes +, − as shown in the figure with the α line as a boundary, and the vibrating arms 13, 14 Is the opposite phase. It can be said that supporting on the α line does not dampen the vibration of the detected tuning fork, and is strong against external noise. Further, the place where the influence on the mechanical impedance on the drive side is small is preferably as low as possible on the α line.

Since the tuning-fork type crystal resonator currently used in a clock or the like has resonance only in the X direction, that is, in the width direction of the tuning fork, even if the bottom surface of the tuning fork support portion is fixed, there is no influence on the resonance. Although almost negligible, in the Z-direction, that is, the anti-phase vibration in the thickness direction of the tuning fork, fixing or supporting the bottom surface of the supporting portion greatly affects resonance, so that the supporting method of the present invention is a reasonable method. I can say.

Next, for reference, a method of designing the resonance frequency will be described with reference to FIG. 1 of the embodiment. The tuning fork vibrating arm shown in FIG. 1 can be handled as a cantilever support rod based on the theory of "electroacoustic vibration engineering", but the effective length of the tuning fork vibrating arm is longer than l _D , and if h _D , the X _D mode Resonance frequency f
_DX becomes as shown in (Equation 1).

[0056]

[Equation 1]

The resonance frequency f _SX of the detection tuning fork side X _S mode induced by the X _D mode is similarly (Equation 2) when the effective length of the detection side vibrating arm is h _S.

[0058]

[Equation 2]

The design condition of the mechanical coupling of the tuning fork supporting portion for inducing the X _S mode may be (Equation 1) = (Equation 2), and therefore the following (Equation 3) is obtained.

[0060]

(Equation 3)

Therefore, it can be seen that the design guide for the shape and size of the tuning fork may be designed so as to satisfy (Equation 3).

Further, by selecting three resonance frequencies, W _D ,
Depending on the design of W _S and I _D , there may be a case where I _S ≧ I _D.

Next, the resonance frequency f _SZ of the Z mode is experimentally known to be longer than h _S as the effective length of the vibrating arm of the Z mode. Therefore, if this is h _Z (Equation 4) Becomes

[0064]

[Equation 4]

If the resonance type tuning fork design is a condition, (Equation 2) = (Equation 4) or (Equation 1) = (Equation 4)
Should be satisfied, that is, (Equation 5) or (Equation 6).

[0066]

(Equation 5)

[0067]

(Equation 6)

Therefore, the thickness (t) of the vibrating arm of the detection-side tuning fork
The ratio of the width (W _S ) and the width (W _D ) is measured by measuring the Young's modulus E _Z , E _X, and the effective length of the vibrating arm (h _Z / h _S ) ² and (h _Z /
It can be obtained from h _D ) ² .

High sensitivity can be expected if the design conditions satisfying both (Equation 3) and (Equation 5), that is, the three frequencies of f _DX , f _SX , and f _SZ are made equal, but frequency adjustment in manufacturing is possible. However, f _DX = f _SX ≠ f
_It is desirable that _SZ and f _SZ = f _DX ≠ f _SX . Also, the Q value of the resonance of the ceramic material is lower than that of quartz, and the P value used here
For CM-based materials, Q _{DX is about} 800 to 1000, f _DX = f _SX
This is easier to manufacture than quartz. Further, by utilizing the degeneracy phenomenon, it is possible to approximate f _DX ≈f _SX .

Finally, an embodiment of the angular velocity sensor element made of the ceramic piezoelectric material of the above embodiment and a circuit system for driving and detecting it will be described with reference to the drawings. 8 and 9 are connection diagrams of a monitor method corresponding to FIGS. 5 and 6. 8 and 9 are block diagrams of drive and detection circuits, and FIG.
0 indicates a qualitative operation waveform of each part.

In FIGS. 8 and 9, 28 is a GND electrode serving as a reference potential of a signal, 29 is a drive electrode, 30 is a detection electrode,
Reference numeral 31 is a monitor electrode. In FIG. 10, 32 is a current amplifier of a monitor circuit, 33 is a charge amplifier of a detection circuit, 3
4, 35 are AC voltage amplifiers, 36 is a drive voltage controller, 37 is an AC / DC converter, 38 is a zero cross comparator,
Reference numeral 39 is a quadrature detector, and 40 is an integrating DC amplifier.

FIG. 8, FIG. 9 and FIG. 10 are known monitor methods for stabilizing self-excited oscillation, but it is also a feature of the present invention that they are applied to a composite type ceramic piezoelectric tuning fork to obtain a new effect. When an alternating voltage shown in FIG. 11A is applied to the drive electrode 29 from the drive voltage controller 36, the vibrating arm of the comb-shaped tuning fork produces vibrations in the X _D mode and the X _S mode, and the monitor electrode 3
An electric charge is generated in AC in 1 (current flowing by generation is
(Hereinafter referred to as monitor current), the current is detected by the current amplifier 32 while the voltage is zero, and the AC voltage amplifiers 34, 35,
Positive feedback is provided to the drive electrode 29 through the action of the drive voltage controller 36. Since the tuning fork is a kind of mechanical filter that amplifies only the resonance frequency, the positive feedback loop from the vibrating arm 11 to the vibrating arm 12 is a resonance frequency self-excited oscillation circuit having a very large sharpness (Q value). In a single tuning fork, one vibrating arm must be provided with the monitor electrode and the detection electrode, and f
_{The DX} = f _SZ method (resonance type tuning fork design) has a drawback in that the signal processing circuit becomes complicated, the S / N is poor, and the cost is high.

Next, description will be made with reference to FIG. X direction and 9
Figure 11 shows the Z _S mode Coriolis vibration with 0 ° phase shift.
FIG. 11 shows a 90 ° phase shift from the monitor current shown in (c).
The detection current (current of zero voltage) shown in (d) is detected by the detection electrode 30.

On the other hand, from the detection electrode 30, the coupled detection current shown in FIG. 11 (d) at a voltage zero in phase with the monitor current due to the X _S mode coupling vibration (hereinafter referred to as Z _MS ) mechanically coupled to the X _D mode vibration. a'is also detected. This combined detection current a'is usually much larger than the detection current a due to the Coriolis force and is detected in a superimposed manner, so it is necessary to separate the two. Therefore, both currents are integrated by the charge amplifier 33 into the charge signal shown in FIG. 11E, and then the zero-cross comparator 38 is used from the in-phase proportional signal of the monitor current shown in FIG. The quadrature detection timing signal shown in FIG. When the charge signal of FIG. 11E is quadrature-detected by the quadrature detector 39 using this as a detection signal,
FIG. 11 shows the zero cross point of the monitor current in (c).
The charge signal b in (e) is inverted, and the quadrature detection output c in FIG. 11 (f) is obtained. When this is passed through the integrating DC amplifier 40, the waveform derived from the detection current due to the Coriolis force shown in the quadrature detection output c in FIG. 11 (f) is output as an effective DC value, and the waveform c ′ derived from the coupling current is the result of integration. It becomes zero and the two are separated.

FIG. 12 shows a third embodiment of the present invention, in which the inner two vibrating arms are drive side vibrating arms 11 and 12 used as drive side tuning forks, and the outer two vibrating arms are used as detection side vibrating arms 13 and 14. This is a case where the tuning fork is used as the detection side and partially polarized in the thickness direction of the tuning fork (Z-axis direction). The electrode numbers correspond to those in FIG.

The S / N of the output sensitivity due to the Coriolis force of the ceramic piezoelectric composite angular velocity sensor implemented by the above method
It has been confirmed that the ceramic piezoelectric composite type angular velocity sensor, which is improved by about 15 to 18 dB as compared with the conventional one shown in FIG. 15, and has a temperature drift (because of S / N) is remarkably small, can be provided at low cost.

[0077]

As described above, the ceramic piezoelectric composite angular velocity sensor of the present invention is a comb-shaped tuning fork, has a plurality of parallel tuning fork vibrating arms with a common support portion, and vibrates in the longitudinal direction of the tuning fork. It is possible to improve the vibration transmission efficiency and improve the detection sensitivity by maintaining the vicinity of the end surface of the support portion on the nodal line α, and leave two of the four comb-shaped vibrating arms for driving.
The function of the book is separated for detection, the drive signal is prevented from sneaking into the detection side, the characteristics of the ceramic piezoelectric material are utilized, and the stray capacitance is removed and supported by partial polarization and partial electrode method. By eliminating unnecessary vibration of the part, the electrical and mechanical S / N can be dramatically improved, and since it is a comb-shaped tuning fork integrally formed with ceramic, the number of tuning forks is twice that of the conventional example, and bending is also possible. Since the shape of the tuning fork is set to vibrate and f _DX = f _SX and f _DX = f _SZ , the temperature drift due to the improved sensitivity is extremely small, and the drive signal leaks to the detection side. It is possible to provide a ceramic piezoelectric composite type angular velocity sensor which has high performance such as suppression of current and is stable.

Further, practical effects such as stable self-excited oscillation by the monitor driving method suitable for the composite tuning fork and improvement of S / N by separating the monitor current due to Z _MS can be expected, and Z _{S of the} detection side tuning fork can be expected. Since the lower part or both ends of the supporting part are held on the nodal line α of the mode vibration, it is 50 in the impact test.
Since it withstood 00G and also withstood a drop test of 3 m, it can be used for automobiles, can be expected in quantity, can be manufactured at low cost, and is of great industrial value.

[Brief description of drawings]

FIG. 1 is a perspective view showing partial polarization in a X direction of a comb-shaped tuning fork used in a ceramic piezoelectric composite angular velocity sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view of the same comb-shaped tuning fork provided with electrodes.

FIG. 3 is a perspective view showing partial polarization in the Z direction of the comb-shaped tuning fork.

FIG. 4 is a perspective view of the same comb-shaped tuning fork provided with electrodes.

FIG. 5 is a wiring diagram of an electrode configuration of the same X-direction polarization and a driving / detecting circuit.

FIG. 6 is a wiring diagram of an electrode configuration and a drive / detection circuit of the same Z-direction polarization.

FIG. 7 is a diagram illustrating a vibration mode and a holding position of the tuning fork.

FIG. 8 is a connection diagram of a monitor drive and detection method of a tuning fork in the case of the same X-direction polarization.

FIG. 9 is a connection diagram of a monitor drive and detection method of a tuning fork in the case of the same Z-direction polarization.

FIG. 10 is a block diagram of a drive and detection circuit of the same comb-shaped tuning fork.

FIG. 11 is an operation waveform diagram of each part of the circuit block.

FIG. 12 is a perspective view of an inner tuning fork according to another embodiment of the present invention, which is used for driving and is polarized in the thickness direction.

FIG. 13 is a diagram illustrating the theory of partial polarization and partial electrodes.

FIG. 14 is an explanatory diagram showing the same characteristics.

FIG. 15 is a perspective view of a conventional tuning fork in which a torsional vibration of a support portion is detected.

[Explanation of symbols]

11,12 Drive side vibrating arm 13,14 Detection side vibrating arm 15 Drive side tuning fork support 16 Detection side tuning fork support 17,17 'Drive vibrating arm base 18 18 Detection vibrating arm base 19 Lower part of support Notch, small hole for holding or attaching of electrodes 20,21 Drive electrode 22,23 Detection electrode 24,25 Drive electrode input terminal 26,27 Detection electrode output terminal 28 GND electrode 29 Drive electrode (D) 30 Detection electrode (S) 31 Monitor electrodes 32, 33 Current amplifier of monitor circuit 34, 35 AC voltage amplifier 36 Drive voltage controller 37 AC / DC converter 38 Zero cross comparator 39 Quadrature detector 40 Integral DC amplifier

Front page continuation (72) Inventor Jiro Terada 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masami Tamura, 1006 Kadoma, Kadoma City Osaka Prefecture

Claims (9)

[Claims] 1. A flat piezoelectric ceramic material 4
A comb-shaped tuning fork with a common parallel vibrating arm and tuning fork support is integrally formed, and the X axis of the three-dimensional coordinate system is the width direction of the vibrating arm and the supporting section, and the Y axis is the longitudinal direction of the vibrating arm. , Z-axis is the thickness direction of the entire tuning fork, and a part of the vibrating arm and the supporting portion along the Y-axis is pre-polarized in the X direction by an externally applied voltage, and the outer two sets are set to the drive side tuning fork and the inner two. This set is used as the detection side tuning fork, or the inner two sets are used as the drive side tuning fork, and the outer two sets are used as the detection side tuning fork. Is a drive electrode along the Y-axis, and two-divided detection electrodes along the Y-axis are disposed on the front and back surfaces of a part of the detection-side vibrating arm and the support portion so as to correspond to the partially polarized portion. by applying an AC signal to the drive electrodes of opposite phases of the bending vibration in the X-direction (hereinafter referred to as X _D mode) generated Allowed the to induce opposite phases of the bending vibration through the mechanical coupling of the support portion to the detection side tuning fork (hereinafter called X _S mode), the Coriolis force based on Y-axis of the rotational angular velocity applied from the outside A ceramic-piezoelectric composite angular velocity sensor that detects the amount of electric charge generated by bending vibrations of opposite phases in the Z-axis direction (hereinafter referred to as Z _S mode) that are generated by the detection electrodes of the detection side tuning fork. 2. A flat piezoelectric ceramic material 4
A comb-shaped tuning fork with a common parallel vibrating arm and tuning fork support is integrally formed, and the X axis of the three-dimensional coordinate system is the width direction of the vibrating arm and the supporting section, and the Y axis is the longitudinal direction of the vibrating arm. , Z-axis is the thickness direction of the entire tuning fork, a part of the vibrating arm and the supporting portion along the Y-axis is pre-polarized in the Z direction by an externally applied voltage, and the outer two sets are set to the driving side tuning fork and the inner two. This set is used as the detection side tuning fork, or the inner two sets are used as the driving side tuning fork, and the outer two sets are used as the detection side tuning fork. Drive electrodes divided into two along the axis are arranged on the front and back surfaces of the detection side vibrating arm, and the detection electrodes along the Y axis are arranged on the front and back surfaces of the side surface and part of the support portion in correspondence with the partially polarized portion, An AC signal is applied to the drive electrode of the drive side tuning fork to cause bending vibrations of opposite phases in the X direction (hereinafter referred to as X _D
Mode), and bending vibrations of opposite phases (hereinafter referred to as X _S modes) are induced in the detection side tuning fork through mechanical coupling of the supporting portion, and the rotational angular velocity around the Y axis is applied from the outside. Generated by the Coriolis force based on Z
A ceramic-piezoelectric composite angular velocity sensor that detects the amount of electric charge generated by bending vibrations of opposite phases in the axial direction (hereinafter referred to as Z _S mode) by a detection electrode of a detection side tuning fork. 3. The drive-side vibrating arm extends from the root of the support portion of the drive-side vibrating arm in the Y-axis direction to about half the length of the supporting arm.
About 0% and the approximate length corresponding to the width of the driving side vibrating arm from the base along the Y axis in the direction of the supporting portion, and for the detecting side vibrating arm, the same from the supporting portion root of the detecting side vibrating arm in the Y axis direction. , About half to 80% of the length, and a volume part made up of a dimension obtained by adding the approximate length corresponding to the width of the driving side vibrating arm to the entire length of the support portion along the Y axis from the root of the detection side tuning fork X 3. The ceramic-piezoelectric composite type angular velocity sensor according to claim 1 or 2, which is partially polarized so as to penetrate in the Z direction or the Z direction. 4. The resonance frequency of the drive-side tuning fork in the X _D mode and the resonance frequency of the detection-side tuning fork in the X _S mode are the same, and the resonance frequency of the Z _S mode generated by the Coriolis force is close to a value. 4. The ceramic-piezoelectric composite angular velocity sensor according to claim 1, 2 or 3, wherein the four vibrating arms and the supporting portion of the comb-shaped tuning fork are set to the shape. 5. The resonance frequency of the X _D mode of the drive side tuning fork and the resonance frequency of the X _S mode of the detection side tuning fork are made the same, and the resonance frequency of the Z _S mode generated by the Coriolis force is made different. 4. The shape dimensions of the four vibrating arms and the supporting portion of the comb-shaped tuning fork are set.
A ceramic piezoelectric composite angular velocity sensor as described. 6. The resonance frequency of the drive-side tuning fork in the X _D mode is made different from the resonance frequency of the detection-side tuning fork in the X _S mode, and is close to the Z _S mode resonant frequency generated by the Coriolis force. 4. The ceramic-piezoelectric composite angular velocity sensor according to claim 1, 2 or 3, wherein the four vibrating arms and the supporting portion of the comb-shaped tuning fork are set to the shape. 7. A cutout portion or a small hole is provided in a lower portion of a support portion of the drive side tuning fork on a nodal line of vibration of the detection side tuning fork in the Y-axis direction, and the cutout portion or the small hole is held or attached. Claims 1, 2, 3, 4, 5 provided for
Alternatively, the ceramic piezoelectric composite type angular velocity sensor described in 6 above. 8. applying an AC signal to one driving electrode of one oscillating arm of the driving side tuning fork, AC amplitude X _D mode of the current induced in the other monitor electrode of other oscillating arm of the driving side tuning fork 8. The ceramic piezoelectric composite angular velocity sensor according to claim 1, further comprising a constant AC current control circuit for holding the temperature constant. 9. A timing signal for detecting and extracting an induced current due to an angular velocity about the Y-axis applied from the outside is generated from a zero-cross signal of the current induced in the monitor electrode. 5. A ceramic piezoelectric composite angular velocity sensor according to 5, 6, 7 or 8.