JP2003207338A - Vibrator for vibration-type gyroscope and vibration-type gyroscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce variations of zero-point temperature drift in detected values of rotational angular velocity from a vibrator in the case of a vibration-type gyroscope. <P>SOLUTION: The vibrator 33 is equipped with a vibration piece 11 and a fixation part 2 for fixing the vibration piece 11. The vibration piece 11 is formed along a predetermined plane X-Y and equipped with a pair of lateral faces 11a and 11b. The vibrator 33 is equipped with one taper part 13A provided at a root portion 11e of the vibration piece 11 on the side of one lateral face 11a and the other taper part 13B provided at the root portion 11e on the side of the other lateral face 11b. The height B of the other taper part 13B from the fixation part 2 is smaller than the height A of the one taper part 13A from the fixation part 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vibrator for a vibration type gyroscope and a vibration type gyroscope.

[0002]

2. Description of the Related Art Recently, it has been considered to mount a vibration type gyroscope on an automobile and use it for controlling the direction of the body of the automobile. For example, when a vibration type gyroscope is used as a rotation speed sensor used in a vehicle body rotation speed feedback type vehicle control method for an automobile, the direction of the steered wheels is detected by the rotation angle of the steering wheel. At the same time, the rotational speed at which the vehicle body is actually rotating is detected by the vibration gyroscope. Then, the direction of the steered wheels is compared with the actual rotation speed of the vehicle body to obtain a difference, and based on the difference, the wheel torque and the steering angle are corrected to realize stable vehicle body control.

When such vibrators are actually formed by etching or laser processing, variations in the resonance frequency of the pair of flexural vibrating bars occur in each vibrator due to manufacturing errors. Therefore, after forming the vibrator, it is necessary to remove the root portion and the supporting portion of each bending vibration piece by laser processing and adjust the resonance frequency of the pair of bending vibration pieces to a constant value.

However, for use in vehicles, for example, the vibrating gyroscope has a very wide operating temperature range and is required to operate stably in a temperature range of, for example, -40 ° C- + 85 ° C. Even if the resonance frequency of the pair of flexural vibration pieces is adjusted to a constant value at room temperature, when the ambient temperature greatly changes to a high temperature or a low temperature, the resonance frequency may fluctuate or vary greatly. As a result, so-called zero point temperature drift occurs.

The applicant of the present application has disclosed in Japanese Patent Laid-Open No. 2001-12952 that the zero point temperature drift is suppressed by providing tapered portions at the roots of both sides of the bending vibration piece.

[0006]

However, upon further study by the present inventors, it has become clear that there are new problems depending on the material of the vibrator. That is, as described in the above-mentioned publication, the vibration modes of the bending vibration piece are provided by providing tapered portions at the bases of both side surfaces of the bending vibration piece and making the shapes of the tapered portions substantially the same. It is considered that the symmetry of the is increased and the zero point temperature drift is reduced. However, when measuring the zero-point temperature drift for each manufactured oscillator,
There was a case where the value of the zero point temperature drift varied. In this case, the zero-point temperature drift of the oscillator was certainly reduced as a whole. However, due to the large variation in zero-point temperature drift of each oscillator,
As a result, the percentage of defective products increased.

This is because even if the zero-point temperature drift of the oscillator cannot be made zero, if the zero-point temperature drift is a constant value, a temperature drift correction circuit is incorporated in the detection circuit of the vibration gyroscope. , It is possible to cancel the zero point temperature drift. But,
If the variation in the zero-point temperature drift of the manufactured oscillator becomes large, even if the zero-point temperature drift can be canceled by a correction circuit in a certain vibrator, the zero-point temperature drift cannot be canceled in other vibrators, and Type gyroscope is not working properly.

An object of the present invention is to reduce variations in zero-point temperature drift of detected values of rotational angular velocity from a vibrator in a vibration gyroscope.

[0009]

The present invention is a resonator element formed along a predetermined plane, the resonator element including a pair of surfaces substantially parallel to the predetermined plane and a pair of side surfaces. The fixing portion for fixing the vibrating piece, one taper portion provided on one side surface side at the base portion of the vibrating piece, and the other taper portion provided on the other side surface side at the base portion of the vibrating piece are provided. The height of the other tapered portion from the fixed portion is smaller than the height of the one tapered portion from the fixed portion.

The present invention also relates to a vibrating gyroscope, which is equipped with the above-mentioned vibrator.

The present invention will be further described below with reference to the drawings. As shown in FIG.
It is assumed that it projects from the surface 2a. The vibrating piece is formed along a predetermined plane (here, the XY plane). Here, at the base portion of the vibrator 1, one taper portion 3A from one side surface 1a toward the surface 2a
Is formed, and the other tapered portion 3B is formed from the other side surface 1b toward the surface 2a.
It is assumed that A and 3B are substantially symmetrical.

In this case, it is considered that when the flexural vibrating element flexurally vibrates in a predetermined plane, the symmetry of the vibration mode is increased and the zero-point temperature drift is reduced. But,
When the zero-point temperature drift is measured for each manufactured oscillator, the zero-point temperature drift value may vary for each oscillator.

On the other hand, in the present invention, as shown in FIG. 2, for example, the fixing portion 2 of the other tapered portion 13B is used.
By making the protrusion height B from the protrusion height A from the fixed portion 2 of the one tapered portion 13A smaller (lower),
We have found that such variations in zero-point temperature drift can be reduced. As described above, it was unexpected that variations in zero-point temperature drift could be reduced by making the shape of the pair of tapered portions at the base of the resonator element asymmetrical with respect to the vibrator.

That is, in the vibrator 33 of FIG. 2, the vibrating piece 11 projects from the fixed portion 2. Vibration piece 11 is XY
It extends along a plane and has an elongated flat plate shape.
Reference numeral 11c is a surface substantially parallel to the predetermined plane XY, and 11a, 1
1b is a side surface. In the base portion 11e of the vibrating piece 11, one tapered portion 13A is formed from one side surface 11a toward the surface 2a, and the other side surface 1a.
The other tapered portion 13B from 1b toward the surface 2a
Are formed. In this example, the surface 14 of the tapered portion
A and 14B are flat.

Here, the height B of the other tapered portion 13B from the fixed portion 2 is defined as the fixed portion 2 of the one tapered portion 13A.
The height is smaller than the height A. As a result, the absolute value of the zero-point temperature drift itself may increase, but the variation or deviation of the zero-point temperature drift among the vibrators can be reduced.

The present inventor has examined the reason for this and found that
The following findings have been reached. That is, for example, after the etching process, a protruding ridge line may be formed on the side surfaces 11a and 11b of the resonator element 11. For example, when a wafer made of quartz is etched to form the resonator element 11, the elongated protrusion 26 remains on one side surface (+ X surface) 11a, as shown in FIG. The height of the protrusion 26 is, for example, 25 to 30 μm.
The width of the protrusion 26 may be about 100 μm. The protrusion 26 is not formed on the −X surface 11b side.

On the other hand, a slender ridge line 29 was formed on the −X plane 11b side, as shown in an enlarged view in FIG. The ridgeline 29 was elongated on the -X plane 11b. On both sides of the ridge line 29, substantially flat inclined surfaces 28A and 28B are formed.
It was extending toward corner 27.

Therefore, the inventor of the present invention has found that the projection 2 on the + X plane side
6 was considered to have caused variations in zero-point temperature drift, but no particular evidence was obtained.

On the other hand, as shown in FIG.
It has been found that the starting points 9A and 9B of 9 are largely changed in the vibrator after the etching treatment. That is, the other tapered portion 3B has a shape shown by a solid line, and the height of the other tapered portion from the fixed portion 2 is A. A is almost the same as the height of the one tapered portion 3A. Here, the above-mentioned ridge line 29 is generated on the side surface 11b, but the lower end of the ridge line 29 may be located on the upper side as in 9A shown in FIG. 5, and in the vicinity of the surface 2a as in 9B. Can be located in. As described above, since the position of the lower end of the ridgeline 29 fluctuated, it was considered that the fluctuation of the zero-point temperature drift among the vibrators was affected.

Then, as shown by 13B in FIG. 5, when the height B of the other tapered portion is made smaller than that of A,
The inventors have found that variations in zero-point temperature drift among the oscillators are reduced, and have reached the present invention.

The reason for this is considered as follows. In FIG. 5, the height of the end position 9A of the ridgeline 29 is D, and the height of 9B is C. The height D is close to A, and the ridgeline 29 is short on the other tapered portion 3B. On the other hand, when the end position of the ridgeline 29 is at 9B, the ridgeline 29 becomes longer on the other tapered portion 3B, and it is considered that the zero-point temperature drift is relatively affected. Here, according to the present invention, the other tapered portion 13B
It is considered that the relative lowering of the ridge 29 reduces the deviation or variation in the end position of the ridgeline 29, and as a result, the variation in zero-point temperature drift among the oscillators can be reduced.

However, the height of the ridgeline 29 is very low, for example, about 1 μm. It was unexpected that such a low ridge had a great influence on the variation in zero-point temperature drift.

On the other hand, the protrusion 26 on the + X surface 11a side
Unlike the ridgeline 29, (see FIG. 3) is considerably larger than the thickness of the vibrator. Therefore, if you think about it normally,
It seems to have a great influence on the zero point temperature drift. However, in practice, it was found that the average value of the zero-point temperature drift is greatly affected, but the variation in the zero-point temperature drift among the oscillators is not so affected. This is because the end positions of the protrusions 26 on one taper portion hardly change for each vibrator.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The vibrator of the present invention includes a plate-shaped vibrating piece. Here, the operation mode of the resonator element is not limited, but the bending vibration mode is particularly preferable.
Further, that the vibrating piece is formed along a predetermined plane means that
Manufacturing errors are tolerated rather than geometrically strict. Further, in the vibrator of the present invention, the portion other than the vibrating piece may not be flat. However, in the preferred embodiment, the entire vibrator is flat.

In a preferred embodiment, the resonator element is formed in an elongated shape, and the pair of side surfaces 11a, 1a of the vibrator are provided.
1b extends in the longitudinal direction of the resonator element. In a particularly preferred embodiment, this vibrating element is a vibrating element that flexurally vibrates. In this case, the ridgeline 29 extends in a direction substantially perpendicular to the bending vibration direction. In such a case, the zero-point temperature drift is likely to occur, so that the present invention is particularly effective.

The cause of generation of the ridgeline 29 on the other side surface is not particularly limited. However, in the preferred embodiment,
The vibrating piece is formed by etching, and ridge lines are generated in the process of this etching.

The etchant is not limited, but the following are preferable. The etchant preferably contains hydrofluoric acid, and is preferably a hydrofluoric acid aqueous solution or an aqueous solution in which hydrofluoric acid and ammonium fluoride are mixed at an arbitrary ratio. The concentration of the etchant is preferably 40% by weight or less, and the temperature of the etchant is preferably 40 to 80 ° C.

The material of the vibrator is not particularly limited, but quartz,
It is preferable to use a piezoelectric single crystal made of LiNbO ₃ , LiTaO ₃ , a lithium niobate-lithium tantalate solid solution (Li (Nb, Ta) O ₃ ) single crystal, a lithium borate single crystal, a langasite single crystal, or the like.

Particularly preferably, the vibrator is made of a piezoelectric single crystal having an a-axis which is rotationally symmetric three times in a predetermined plane and a c-axis in a direction perpendicular to the predetermined plane. This is particularly preferably quartz.

In the preferred embodiment, one side 1
1a is

[Equation 3] Surface and the other side is

[Equation 4] The surface.

The heights of one tapered portion and the other tapered portion from the fixed portion mean the heights A and B from the surface 2a of the fixed portion 2 in the embodiment shown in FIG. In this way, when the tapered portion rises directly from the surface of the fixed portion, the height of the tapered portion can be determined as the height from the surface of the fixed portion. However, one taper portion or the other taper portion may not rise directly from the surface of the fixed portion. For example, in the case shown in FIG.
The other tapered portion 20B is a surface 17b of the fixed portion 17,
It has risen from 17c. Therefore, the tapered portion 20
The height of B from the fixed portion 17 is the height B from the surfaces 17b and 17c. However, one taper portion 20A is
It does not rise directly from the height-referenced surfaces 17b, 17c. However, also in this case, since the taper portion 20A rises from the end portion 17a of the fixed portion 17, the height of the taper portion 20A is defined as the height A from the extended surface F of the surfaces 17b and 17c.

The ratio B / A of the height B of the other taper portion to the height A of one taper portion is preferably 0.97 or less from the viewpoint of achieving the effects of the present invention, It is more preferably 95 or less. However, if B becomes too small, the amplitude of vibration modes other than the desired vibration mode tends to increase, which causes an increase in the zero-point temperature drift itself. Therefore, from this viewpoint, B / A is preferably 0.7 or more,
More preferably, it is 0.8 or more.

The lower limit of the ratio A / L of the height A of the one taper portion to the length L (see FIG. 2) of the resonator element 11 is not limited, but is often 3% or more. From the viewpoint of reducing the zero point temperature drift, A / L is preferably 10% or less.

The ratio B / L of the height B of the other tapered portion to the length L of the vibrating piece 11 is preferably 10% or less from the viewpoint of achieving the effects of the present invention, and is 9.5. % Or less is more preferable. Although the lower limit of B / L is not particularly limited, it is often 3% or more.

The surface 14A of one taper portion 13A is
The angle θA formed with respect to the center plane S of the vibrating piece 11 is often 20 ° or more. However, from the viewpoint of suppressing an increase in zero-point temperature drift, it is preferably 40 ° or less.

The surface 14B of the other tapered portion 13B is
The angle θB formed with respect to the center plane S of the vibrating piece 11 is often 20 ° or more. However, from the viewpoint of suppressing an increase in zero-point temperature drift, it is preferably 40 ° or less.

The vibrating gyroscope of the present invention includes the above-mentioned vibrator. This vibrating gyroscope further includes a driving unit and a detecting unit. Drive means,
The detection means are generally in the form of electrodes formed on the oscillator.

In a preferred embodiment, the vibrating gyroscope of the present invention has a predetermined plane X on which a vibrating piece is provided.
The rotational angular velocity about a rotation axis Z that is substantially perpendicular to Y is measured. Particularly preferably, each vibrating element flexurally vibrates along a predetermined plane XY. 6 and 7 show a vibrator according to this embodiment.

The vibrator 15 can measure the rotational angular velocity about the Z axis which is substantially perpendicular to the predetermined plane (XY plane). The base 16 of the vibrator 15 has a center of gravity G of the vibrator.
It is a square with four-fold symmetry around O. Base 16
From the peripheral edge of the four radial directions toward the four driving vibration systems 30A and 30B and two detection vibration systems 31A and 31B.
And are protruding, and the respective vibration systems are separated from each other.

The drive vibration systems 30A and 30B are respectively
The elongated fixing portion 17 protruding from the peripheral portion of the base portion 16 and the bending vibration pieces 18A, 18B, 18C, 18 extending in the direction orthogonal to the fixing portion 17 from the tip portion 17a side of the fixing portion 17.
And D. A drive electrode 32 is provided on each bending vibration piece. Detection vibration system 31A, 31B
Is composed of elongated circumferential bending vibration pieces 19A and 19B,
A detection electrode 33 is provided on each vibrating piece.

In the drive mode, each bending vibration piece 18
A, 18B, 18C and 18D flexurally vibrate as indicated by an arrow A around the tip portion 17a of the fixed portion 17. In the detection mode, each fixed portion 17 flexurally vibrates in the circumferential direction as indicated by an arrow C around the base of the fixed portion 17 as a center. Corresponding to this, each bending vibration piece 19A, 19B
However, bending vibration occurs as indicated by arrow B. Each bending vibration piece 19
The angular velocity of rotation about the vertical axis Z is measured by measuring each detected vibration excited in A, 19B.

Each of the detection vibrating pieces 19A and 19B has a side surface 19a on the + X plane side and a side surface 19b on the -X plane side. Then, at the base portion 19c, +
One taper portion 13A is provided on the X surface 19a side, and the other taper portion 13B is provided on the -X surface 19b side.

Further, each drive vibrating piece 18A, 18B, 18
C and 18D are a side surface 18a on the + X side and a −, respectively.
And a side surface 18b on the X surface side. Then, as shown in an enlarged manner in FIG. 7, in the root portion 18c, one taper portion 20A is provided on the + X surface 18a side, and the other taper portion 20B is provided on the −X surface 18b side. There is. 21A and 21B are tapered portions 20A and 2A,
0B surface.

Further, in a preferred embodiment, the vibrating gyroscope of the present invention measures a rotational angular velocity about a rotational axis Y substantially parallel to a predetermined plane XY on which a vibrating piece is provided. FIG. 8 shows a vibrator 25 according to this embodiment.

The vibrator 25 includes a fixed portion 22, a drive vibration system 30C including a pair of tuning fork type vibrating pieces 23A and 23, and a detection vibrating system 3 including a pair of tuning fork type vibrating pieces 24A and 24B.
1C and. Each bending vibration piece 23A, 23B, 2
4A and 24B extend in the Y-axis direction. Each drive vibrating piece 2
3A and 23B are vibrated in the X-axis direction in the XY plane as indicated by arrow A. When the mounting board is rotated about the Y axis, the detection vibrating pieces 24A and 24B vibrate in the direction of the vertical axis Z as indicated by arrow C. By detecting this vibration, the rotational angular velocity about the Y axis is measured.

In this embodiment, the entire vibrator is formed along the XY plane (predetermined plane). The bending vibration pieces 23A and 23B respectively extend in the Y-axis direction. The base portion 23 of the vibrating pieces 23A and 23B
In c, one taper portion 13 is provided on the + X surface 23a side.
A is provided, and the other tapered portion 13B is provided on the −X surface 23b side. In addition, each bending vibration piece 24
A and 24B respectively extend in the Y-axis direction. In the root portions 24c of the vibrating pieces 24A and 24B, one taper portion 13A is provided on the + X surface 24a side, and the other taper portion 13 on the -X surface 24b side.
B is provided. 22 a and 22 b are the surfaces of the fixed portion 23.

[0047]

EXAMPLE A vibrating gyroscope shown in FIGS. 6 and 7 was produced. Specifically, a chromium film having a thickness of 200 angstroms and a gold film having a thickness of 5000 angstroms were formed on a wafer of a quartz Z plate having a thickness of 0.3 mm by a sputtering method. Both sides of the wafer were coated with resist.

This wafer was dipped in an aqueous solution of iodine and potassium iodide to remove the excess gold film by etching, and then the wafer was dipped in an aqueous solution of cerium ammonium nitrate and perchloric acid to obtain an excess chromium film. Was removed by etching. Immerse the wafer in ammonium bifluoride at a temperature of 80 ° C. for 20 hours to etch the wafer,
The outer shape of the vibrator 15 was formed. Using a metal mask, an aluminum film having a thickness of 2000 Å was formed as an electrode film.

The dimensions of the base portion 16 of the obtained vibrator 15 are 6.0 mm × 6.0 mm. Each drive vibrating piece 18A ~
The dimensions of 18D are 1.0 mm width x 6.0 mm length. The size of each drive electrode 32 is 0.6 mm in width × 2.
It is 8 mm. The size of each detection vibrating piece 19A, 19B is
The width is 1.0 mm and the length is 6.0 mm. Each detection electrode 33
Has a width of 0.6 mm and a length of 2.8 mm.

Here, the height A of one tapered portion and the heights B, θA and θB of the other tapered portion were changed as shown in Table 1.

Next, a square support hole of 0.75 mm × 0.75 mm is formed in the center of the base portion 16 of each vibrator 15, and a metal pin having a diameter of 0.6 mm is passed through this support hole to the metal pin. The vibrator 15 was adhered with a silicone resin adhesive. About each vibration type gyroscope using each obtained vibrator, the measured value of the detection signal is -40 ° C.
The temperature fluctuation of the zero-point signal in the temperature range of + 85 ° C was measured. The results are shown in Table 1.

[0052]

[Table 1]

[0053]

As described above, according to the vibrating gyroscope of the present invention, it is possible to reduce the variation in zero-point temperature drift of the detected value of the rotational angular velocity from the vibrator.

[Brief description of drawings]

FIG. 1 is a plan view showing a state where a resonator element 1 is protruding from a fixed portion 2.

FIG. 2 is a plan view showing a state where a vibrating piece 11 of the present invention projects from a fixed portion 2.

FIG. 3 shows a cross-sectional shape of the resonator element 11.

FIG. 4 is a cross-sectional view showing a shape of the other side surface 11b of the vibrating piece 11.

5 is a diagram showing the relationship between the form of the root portion of the vibrating piece 11 and the position of the ridge line 29. FIG.

FIG. 6 is a plan view showing a vibrator 15 according to an embodiment of the present invention.

7 is an enlarged view showing the vicinity of a fixed portion 17 of the vibrator 15. FIG.

FIG. 8 is a plan view showing a vibrator 25 according to an embodiment of the present invention.

[Explanation of symbols]

1, 11, 18A, 18B, 18C, 18D, 19A,
19B, 23A, 23B, 24A, 24B Vibrating piece
1a, 11a, 18a, 19a, 23a, 24a
One side surface of the vibrating piece 1b, 11b, 18
b, 19b, 23b, 24b The other side surface of the resonator element
2, 16, 17, 22 Fixed part 2a, 16
a, 17b, 17c, 22a, 22b Surface of fixed part
9A, 9B Terminal position of ridgeline 29 11
c, 11d A pair of surfaces that are substantially parallel to the predetermined plane 11
e, 18c, 19c, 23c, 24c Base portion of the vibrating piece 13A, 20A One taper portion
13B, 20B The other taper portion 14A,
21A One taper surface 14B, 21B The other taper surface 1
5, 25, 33 Transducer 26 Projection on one side surface 29 Ridge line A on the other side surface Height of one taper portion from the fixed portion B
Height of the other tapered part from the fixed part F Extension surface of the fixed part L Length of the vibrating piece S Center plane of the vibrating piece XY Predetermined plane θ
A Angle formed by the surface of one tapered portion with respect to the center plane S of the vibrating piece θB Angle formed by the surface of the other tapered portion with respect to the center plane S of the vibrating piece

Claims (5)

[Claims] 1. A vibrating piece formed along a predetermined plane, the vibrating piece having a pair of surfaces substantially parallel to the predetermined plane and a pair of side surfaces, and a fixing member for fixing the vibrating piece. Section, one taper portion provided on the one side surface side at the base portion of the vibrating piece, and the other taper portion provided on the other side surface side at the base portion of the vibrating piece. The height of the other tapered portion from the fixed portion is smaller than the height of the one tapered portion from the fixed portion,
Vibratory gyroscope oscillator. 2. The vibrator according to claim 1, wherein the vibrating piece is formed by etching. 3. The vibrator according to claim 1, wherein the vibrating element flexurally vibrates in the predetermined plane. 4. The one side surface is expressed by Surface, and the other side surface is A vibrator according to any one of claims 1 to 3, which is a surface. 5. A vibrating gyroscope, comprising the vibrator according to any one of claims 1 to 4.