JPH116738A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress offset temperature drift in an angular velocity sensor that has a vibrator in a tuning fork shape consisting of a piezoelectric body or in a shape where a plurality of tuning forks are synthesized. SOLUTION: A sensor is formed in a tuning fork shape by a piezoelectric body and has a vibrator where driving electrodes 12a and 12b and detection electrodes 22a and 22b are provided on an outer wall surface. In this case, a vibrator 2 is formed so that a ratio fd/fs of a driving resonance frequency fd where voltage is applied to the driving electrodes 12a and 12b and the vibrator 2 is excited in Y-axis direction to a resonance frequency fs in X-axis direction where an angular velocity is detected via the detection electrodes 22a and 22b is set to a value that is at least 0.9 and is 0.96 or less or is at least 0.4 and is 1.1 or less, and a ratio G/ts of the distance G between electrodes in Z-axis direction of the driving electrodes 12a and 12b and the detection electrodes 22a and 22b at each of arm parts 4 and 6 to a thickness ts in the X-axis direction of the vibrator 2 is set to a value that is at least 1.4. As a result, the offset temperature drift of the detection signal can be reduced. Also, the fd/fs should be set to the above range in a comb-shaped or H-shaped vibrator where the tuning fork is combined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor used for controlling a vehicle of an automobile, navigation, and preventing camera shake of a video camera, and more particularly to an angular velocity sensor for detecting an angular velocity using a tuning fork vibrator made of a piezoelectric material. Related to sensors.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Unexamined Patent Application Publication No.
As disclosed in Japanese Patent Laid-Open Publication No. 0-205, there is provided a vibrator made of a piezoelectric material formed in a tuning fork shape by a pair of arms and a connecting portion connecting the arms, and the vibrator is arranged in the direction in which the arms are arranged. 2. Description of the Related Art There is known an angular velocity sensor that detects a Coriolis force received by a vibrator when an angular velocity is input while changing the vibration of the vibrator in a direction of a detection axis orthogonal to the drive shaft while constantly vibrating in a drive axis direction.

In this type of angular velocity sensor, a vibrator can be manufactured only by forming an electrode for driving (excitation) or detecting vibration on the outer wall surface of a piezoelectric body formed in a tuning fork shape. Compared to the generally used type of angular velocity sensor in which the vibrator is formed of metal and a piezoelectric body is bonded to the surface, the number of parts is smaller and the structure and the manufacturing process are simpler. There is.

[0004]

However, an angular velocity sensor having a vibrator made of a piezoelectric material has the above advantages as compared with a type in which a piezoelectric material is joined to a metal vibrator, but has a high sensitivity. It is necessary to make the resonance frequency in the drive mode that excites the vibrator in the drive axis direction close to the resonance frequency in the detection axis direction in the detection mode that detects angular velocity. Undesired vibrations are likely to occur due to the influence of vibrations in the modes, and there is a problem that the apparatus is greatly affected by a mechanical noise source generated by the unnecessary vibrations. Further, in an angular velocity sensor in which a vibrator is formed of a piezoelectric body, various electrodes for driving (excitation) or vibration detection are formed on the piezoelectric body. In many cases, there is also a problem that the influence of an electrical noise source is large.

[0005] Such mechanical or electrical noise is superimposed on a detection signal obtained at the time of angular velocity detection.
And since this noise changes with temperature,
A noise component (hereinafter referred to as an offset) of a detection signal obtained when the angular velocity is zero also changes depending on the temperature. In the conventional angular velocity sensor, the angular velocity is stably detected without being affected by the temperature. There was a problem that it was difficult to do.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and is directed to an angular velocity sensor for detecting an angular velocity using a vibrator having a shape of a tuning fork made of a piezoelectric material or a shape obtained by combining a plurality of tuning forks. It is an object of the present invention to suppress a temperature change of an offset (hereinafter, referred to as an offset temperature drift) generated at the time of detecting an angular velocity.

[0007]

In order to achieve the above object, the angular velocity sensor according to the first aspect of the present invention has at least a pair of arms arranged in parallel with each other and a connecting portion connecting one end of each arm. And a drive electrode configured to receive at least an AC voltage from the outside and to excite the arms in a drive axis direction, which is an arrangement direction of the arms, on the outer wall surface, and And a vibrator provided with a pair of detection electrodes for detecting vibration generated in a detection axis direction orthogonal to the drive shaft. In this angular velocity sensor, the vibrator has a ratio fd / fs of the resonance frequency fd in the drive axis direction to the resonance frequency fs in the detection axis direction of 0.9 to 0.96.
Or less, or in the range of 1.04 or more and 1.1 or less.

On the other hand, the angular velocity sensor according to claim 4 is
A vibrator made of a piezoelectric body is formed in a tuning fork shape by a pair of arm portions and a connecting portion connecting one end of each arm portion, and at least a driving electrode and a detecting electrode are formed on an outer wall surface. In this angular velocity sensor, the vibrator has a distance G between the electrodes between the drive electrode and the detection electrode along the longitudinal direction of each arm, and a thickness ts between the front and back surfaces of the vibrator having a concave shape. Are formed so that the ratio G / ts of the first layer is 1.4 or more.

As described above, the shape (numerical value) of the vibrator defined in claim 1 and claim 4 is obtained experimentally based on the following idea, and the present invention (claim 1, claim 4) According to 4), the offset temperature drift can be sufficiently reduced. That is, as described above, the offset temperature drift refers to a temperature change of an output (offset) from the detection electrode when the angular velocity is zero. It has been found that the causes of the offset temperature drift are as follows.

[0010] Temperature change of unnecessary vibration at the same resonance frequency as the detection resonance mode generated by the interaction between the driving resonance mode and the detection resonance mode. Electric noise generated because the area where the drive electrode is formed and the area where the detection electrode is formed in the piezoelectric body are electrically coupled by capacitance.

[0011] Mechanical background noise temperature change due to other resonance modes of the vibrator other than the detection resonance mode. Regarding the above factors, the resonance frequency fd in the drive axis direction of the vibrator (hereinafter, referred to as drive resonance frequency) fd and the resonance frequency fs in the detection axis direction (hereinafter, referred to as detection resonance frequency) fs are brought close to each other. It can be reduced by mechanically amplifying the sensitivity. That is, the noise component is relatively reduced with respect to the signal component corresponding to the angular velocity. However, the driving resonance frequency fd and the detection resonance frequency f
If s is too close, the above causes (unnecessary vibration)
It was found that the offset temperature drift deteriorated. As a result, when the relationship (ratio fd / fs) between the drive resonance frequency fd and the detection resonance frequency fs is defined, the factors (i.e., mechanical factors and electrical factors) described above are reduced, and the offset temperature is reduced. It was found that drift could be suppressed.

On the other hand, it has been found that the above factors are related to the separation distance (inter-electrode distance G) in each arm between the drive electrode and the detection electrode. Therefore, it has been found that when the inter-electrode distance G between the drive electrode and the detection electrode is defined, the above-mentioned generation factor (electric factor) can be reduced and the offset temperature drift can be suppressed.

In view of these findings, the present inventor has determined that the ratio f of the drive resonance frequency fd to the detected resonance frequency fs is f.
d / fs, and the distance G between the drive electrode and the detection electrode
Various experiments were carried out in order to set the optimum values for reducing the offset temperature drift, and the inventions of claims 1 and 4 were completed.

The effect of reducing the offset temperature drift according to the first and fourth aspects of the present invention will be described in the following embodiments using various experimental results. here,
A vibrator provided in the angular velocity sensor according to claim 1,
The invention is defined by at least one pair of arms arranged in parallel with each other and a connecting portion connecting the arms, and the invention according to claim 1 is, for example, a tuning fork shape as described in claim 2 Or a comb-shaped or H-shaped vibrator as described in claim 3.

That is, when an angular velocity is detected using a tuning fork, the vibrator is generally formed in a tuning fork shape by a pair of arms and a connecting portion as described in claim 2. As described in claim 3, two sets of tuning forks each including a pair of arms and a connecting portion are formed in a comb shape or an H shape by integrating the tuning fork portions with a common connecting portion. The angular velocity can be detected by using a vibrator.

When detecting the angular velocity by using such a comb-shaped or H-shaped vibrator, a drive electrode is provided on one arm constituting one tuning fork, and an arm constituting the other tuning fork. A detection electrode is formed respectively, and each arm part constituting one tuning fork part is excited in a drive axis direction orthogonal to a central axis in a longitudinal direction of each arm part, and each of the arm parts constituting the other tuning fork part is excited. By detecting the generated vibration in the detection axis direction orthogonal to the drive shaft, it is possible to detect the angular velocity around the central axis of the vibrator along the axial direction of each arm.

On the other hand, the vibrator provided in the angular velocity sensor according to the fourth aspect is a tuning fork-shaped vibrator.
The invention described in (1) cannot be applied to an angular velocity sensor provided with a vibrator having a shape obtained by combining a plurality of tuning forks, such as a comb shape or an H shape. This is because the invention according to claim 4 is an invention for suppressing an offset temperature drift caused by a distance G between the electrodes when a drive electrode and a detection electrode are provided in one arm. This is because, in a vibrator having a shape in which a plurality of tuning forks are combined, it is not necessary to form a drive electrode and a detection electrode on one arm.

As a specific example of the vibrator formed in a tuning fork shape according to claim 2 or claim 4, for example, as described in claim 5, a drive electrode is provided on the inner surface of the outer wall surface. A vibrator having a polarization electrode on the front surface of each arm, a detection electrode at a position corresponding to each polarization electrode on the side surface of each arm, and a common electrode corresponding to each electrode on the back surface can be cited. .

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view illustrating the entire configuration of the angular velocity sensor according to the embodiment, and FIG. 2 is an explanatory diagram illustrating the vibrator according to the embodiment as viewed from front, rear, left and right.

As shown in FIG. 1, the angular velocity sensor of the present embodiment has a vibrator formed in a tuning fork shape by a pair of left and right arms 4 and 6 and a connecting portion 8 connecting one end of each arm 4 and 6. 2 is provided. The arm portions 4 and 6 and the connecting portion 8 of the vibrator 2 are each in the shape of a quadrangular prism, and the vibrator 2 is manufactured by integrally forming these components with a piezoelectric body.
The piezoelectric body constituting the vibrator 2 can be a ceramic piezoelectric body such as PZT, quartz, or the like. However, the vibrator 2 of this embodiment can be set to any polarization direction and is easy to manufacture. PZT is used.

Next, as shown in FIG. 2A, one surface (surface; hereinafter referred to as X1 surface) of the vibrator 2 having a concave shape extends from the connecting portion 8 to each of the arm portions 4 and 6. A pair of drive electrodes 12a and 12b are formed, and monitor electrodes 14a and 14b, temporary GND electrodes 16a and 16b, and electrodes for polarization are provided at a portion from each of the drive electrodes 12a and 12b to the tip of each of the arms 4 and 6. 18a and 18b are formed in order, and pad electrodes 20a and 20b for extracting detection signals are formed at the tips of the arms 4 and 6, respectively.

Then, the drive electrodes 12a and 12b pass through the connecting portion 8 and the opposing surfaces of the arms 4, 6 facing each other, and the left and right outer surfaces (Y1, Y
2) and the monitor electrodes 14a and 14
b is formed on each of the facing surfaces of the arms 4 and 6, respectively, and the provisional GND electrodes 16a and 16b are
The polarization electrodes 18a and 18 are formed on the Y1 and Y2 surfaces, respectively.
b is formed in the entire width direction from the Y1, Y2 surface side of each arm portion 4, 6 to the opposing surface side, and the pad electrodes 20a and 20b are respectively formed on the Y1, Y2 surface side of each arm portion 4, 6 respectively. Is formed. In addition, each of the polarization electrodes 18a and 18b is
The temporary GND electrode 16 is connected via the short-circuit electrodes 26a and 26b.
a, 16b are respectively connected (short-circuited).

On the other hand, as shown in FIGS. 2B and 2C, the Y1 and Y2 surfaces of the arms 4 and 6 correspond to the polarization electrodes 18a and 18b, respectively. The detecting electrode 2 is located at a position deviated from the center along the longitudinal direction to the X2 plane.
2a and 22b are formed. On the other surface (rear surface; hereinafter, referred to as X2 surface) of the vibrator 2 having a concave shape, as shown in FIG.
2b, monitor electrodes 14a, 14b and detection electrodes 18a,
A temporary GND electrode 24 serving as a common electrode 18b is formed.

The provisional GND electrodes 24 formed on the X2 plane and the provisional GND electrodes 16a and 16b formed on the X1 plane.
Are connected (short-circuited) to each other via short-circuiting electrodes 28a and 28b formed on the Y1 and Y2 surfaces of the arm portions 4 and 6, respectively, and the pad electrode 2 formed on the X1 surface.
0a, 20b and detection electrodes 22 formed on the Y1, Y2 planes
a and 22b are connected (short-circuited) to each other via detection signal extraction electrodes (extraction electrodes) 30a and 30b formed on the Y1 and Y2 planes, respectively.

The vibrator 2 of this embodiment has the above-mentioned electrodes formed on the X1 and X2 surfaces of a piezoelectric body formed in a tuning fork shape.
By applying a voltage between the electrodes, the piezoelectric body is polarized in the direction from the X1 plane to the X2 plane (the direction indicated by the arrow in FIG. 1), and then the electrodes are formed on the Y1 and Y2 planes. It is produced by such a procedure.

Next, in the vibrator 2 thus manufactured, an end face on the connecting portion 8 side is attached to the pedestal portion 32b of the supporter 32 having a U-shaped cross section by an adhesive (for example, an epoxy-based adhesive). By fixing the main body side of the supporter 32 to the surface of the plate-like base 36 by welding or bonding via a spacer 34, the X2 surface is in contact with the surface of the base 22 with respect to the base 36. It is fixed so as to face each other.

The supporter 32 has a pedestal portion 32 for joining the vibrator 2 to a main body fixed to a base 36 via a spacer 34 via a neck portion 32a for absorbing vibration.
b, and is integrally formed in a D-shaped cross section with a metal such as 42N, for example. Further, the base 36 is for fixing the vibrator 2 directly or via a vibration-proof rubber to a housing of the angular velocity sensor or a vehicle body or the like for which an angular velocity is to be detected. The base 36 has eight terminals T1 to T8 corresponding to the drive electrodes 12a and 12b, the monitor electrodes 14a and 14b, the temporary GND electrodes 16a and 16b, and the pad electrodes 20a and 20b formed on the vibrator 2. It is erected. Each terminal T1-T8
Is for relaying each electrode to a detection circuit (not shown), and each electrode and terminals T1 to T8 are
They are connected by wire bonding via wires W1 to W8, respectively. Note that the base 36 and the terminals T1 to T8 are electrically insulated.

When the angular velocity is detected using the angular velocity sensor of the present embodiment configured as described above, the provisional GND electrodes 16a, 16a are connected via the terminals T5, T6 connected to the temporary GND electrodes 16a, 16b. 16b, polarization electrode 18
a, 18b and the temporary GND electrode 24 are grounded to a reference potential, and the terminal T connected to the drive electrodes 12a, 12b
An AC drive signal having a phase difference of 180 degrees is input to each of the drive electrodes 12a and 12b via the drive electrodes 1 and T2. This drive signal is an alternating current signal that changes positively and negatively around a reference potential, and its frequency varies in the direction of the drive axis (Y axis shown in FIG. 1), which is the direction in which the left and right arms 4 and 6 are arranged. This is the resonance frequency (drive resonance frequency) of the child 2.

As a result, the drive electrodes 12a, 1a on the X1 plane
An AC voltage whose phase is inverted is applied between the temporary ground electrode 2b and the provisional GND electrode 24 on the X2 plane, and the arms 4 and 6 resonate in the Y-axis direction. At the time of this driving, the monitor electrodes 14 are connected via the terminals T3 and T4.
a, 14b (specifically, the monitor electrode 14
a), and the drive signal is controlled so that the amplitude of each of the arms 4 and 6 in the Y-axis direction becomes constant even when the temperature changes (see FIG. 4). Self-excited control oscillation).

Next, when the vibrator 2 is self-excited and oscillated in this manner, a Z-axis centered on the Z-axis parallel to the arms 4 and 6 is provided at the center position of the arms 4 and 6. When the angular velocity Ω around the axis is input, each of the arm portions 4 and 6 vibrates in the X-axis direction (detection axis direction) penetrating the X1 and X2 planes by Coriolis force. Since the vibration component in the X-axis direction is proportional to the current flowing between the detection electrodes 22a and 22b and the temporary GND electrode 24, the current between these electrodes is applied to the detection electrodes 22a and 22b, respectively. Extraction electrodes 30a, 30b
Then, the signals are taken in via terminals T7, T8 connected via pad electrodes 20a, 20b, converted into voltage signals by a current-voltage conversion circuit, and further, each voltage signal is differentially amplified via a differential amplifier. As a result, a detection signal representing the angular velocity Ω around the Z axis is generated.

Incidentally, the detection signal thus generated includes an offset component due to the above-mentioned mechanical and electrical factors, and the offset component changes with temperature. Therefore, in order to suppress such a temperature change of the offset (offset temperature drift), the relationship between the drive resonance frequency fd of the vibrator 2 and the detection resonance frequency fs, and
The optimal region of the distance between the drive electrodes 12a, 12b and the detection electrodes 22a, 22b was investigated.

Hereinafter, the results of an experiment performed for this investigation will be described. First, an experiment performed for defining the relationship between the drive resonance frequency fd and the detection resonance frequency fs will be described. In performing this experiment, FIG.
As shown in (a), the length (height) of the pedestal portion 32b and the neck portion 32a of the supporter 32 supporting the vibrator 2 in the Z-axis direction is set to 1 mm, and the connecting portion 8 is set.
Longitudinal direction (Z-axis direction) of each arm part 4, 6 protruding from
Is L, the width of each of the arms 4 and 6 in the Y-axis direction is tD,
Assuming that a gap (gap) between the arms 4 and 6 in the Y-axis direction is w, a height of the connecting portion 8 in the Z-axis direction is d, and a width of the neck portion 32a of the supporter 32 in the Y-axis direction is v, these values are set. L, t
D, w, d, and v are defined as 1 to 3 according to the level table shown in FIG.
3 is set to each level, and further, the X1 plane of the vibrator 2−X
By adjusting the thickness ts between the two surfaces (in other words, the thickness in the Y-axis direction) ts, the ratio fd / fs of the drive resonance frequency fd to the detection resonance frequency fs can be varied within a range of 0.8 to 0.99. A large number of vibrators 2 with supporters 32, which were set appropriately, were produced. However, in each of these transducers 2, the drive electrodes 12a and 12b and the detection
The ratio G / ts of the distance G between the electrodes a and 22b in the Z-axis direction and the thickness ts of the vibrator 2 is in the range of 1.4 or more and 1.8 or less.

First, FIG. 4 shows that the width tD of each of the arms 4 and 6 is 2.0 mm and the gap w between each of the arms 4 and 6 is 0.6.
mm, the height d of the connecting portion 8 is 3.0 mm, the width v of the neck portion 32a of the supporter 32 is 1.0 mm, and each arm portion 4, 6
Is set to 10 mm, 17 mm, and 27 mm, and the resonance frequency ratio fd / fs is adjusted stepwise by adjusting the thickness ts of the resonator 2 to obtain a resonance frequency 9 shows the results of Experiment 1 in which the relationship between the ratio fd / fs and the offset temperature drift was measured. And
From the result of Experiment 1, the offset temperature drift has the same tendency regardless of the length L of the arm portions 4 and 6, and becomes large when the resonance frequency ratio fd / fs is 0.98 or more and 0.88 or less. It was found that the optimum range of the resonance frequency ratio fd / fs should be set to 0.9 or more and 0.96 or less.

The length L of each of the arms 4 and 6 shown in FIG.
The measured value of the offset temperature drift with respect to the resonance frequency ratio fd / fs represents the average of the measured values of 10 vibrators, and the same applies to the measured values in FIGS. 5 to 9 described below. . Next, FIG. 5 shows that the length L of each of the arms 4 and 6 is 17 mm, the gap w between the arms 4 and 6 is 0.6 mm, the height d of the connecting portion 8 is 3.0 mm,
The width v of the neck 32a of the supporter 32 is set to 1.0 mm, and the width tD of each of the arms 4 and 6 is set to 1.5 mm, 2.0 mm,
2.5 mm, the resonance frequency ratio fd / fs is set stepwise by adjusting the thickness ts of the resonator 2, and the resonance frequency ratio fd / fs and the offset temperature drift are used. 4 shows the result of Experiment 2 in which the relationship was measured. From the result of Experiment 2, the offset temperature drift has the same tendency regardless of the width tD of the arm portions 4 and 6, and becomes large when the resonance frequency ratio fd / fs is 0.98 or more and 0.88 or less. Therefore, it was found that the optimum range of the resonance frequency ratio fd / fs should be set to 0.9 or more and 0.96 or less.

FIG. 6 shows the length L of each of the arms 4 and 6.
17 mm, the width tD of each of the arms 4 and 6 is 2.0 mm,
The height d of the connecting portion 8 is 3.0 mm, and the neck 3 of the supporter 32 is
The width v of the arm 2a is set to 1.0 mm, the gap w between the arms 4 and 6 is set to 0.2 mm, 0.6 mm, and 1.0 mm, and the resonance frequency is adjusted by adjusting the thickness ts of the vibrator 2. 4 shows the results of Experiment 3 in which the relationship between the resonance frequency ratio fd / fs and the offset temperature drift was measured using a number of transducers in which the ratio fd / fs of the above was set stepwise. From the result of Experiment 3, the offset temperature drift has the same tendency regardless of the gap w between the arm portions 4 and 6, and the resonance frequency ratio fd / fs is 0.98 or more,
Since it becomes large below 0.88, the resonance frequency ratio fd
It has been found that the optimum range of / fs should be set to 0.9 or more and 0.96 or less.

FIG. 7 shows the length L of each of the arms 4 and 6.
17 mm, the width tD of each of the arms 4 and 6 is 2.0 mm,
The gap w between the arms 4 and 6 is 0.6 mm, the width v of the neck 32a of the supporter 32 is 1.0 mm,
Are set to 2.0 mm and 3.0 mm, and the thickness ts of the vibrator 2 is adjusted to obtain the resonance frequency ratio f.
The result of Experiment 4 in which the relationship between the resonance frequency ratio fd / fs and the offset temperature drift was measured using a number of transducers in which d / fs was set stepwise is shown. From the result of Experiment 4, the offset temperature drift has the same tendency irrespective of the height d of the connection portion 8, and the resonance frequency ratio fd
Since / fs becomes 0.98 or more and 0.88 or less, the optimum range of the resonance frequency ratio fd / fs is as follows.
It was found that the value should be set to 0.9 or more and 0.96 or less.

FIG. 8 shows the length L of each of the arms 4 and 6.
17 mm, the width tD of each of the arms 4 and 6 is 2.0 mm,
The gap w between the arms 4 and 6 is 0.6 mm, the height d of the connecting portion 8 is 3.0 mm, and the neck 32 of the supporter 32 is formed.
The width v of a is set to 0.5 mm, 1.0 mm, and 1.5 mm, and furthermore, by adjusting the thickness ts of the vibrator 2, a number of vibrators in which the resonance frequency ratio fd / fs is set stepwise can be obtained. 5 shows the results of Experiment 5 in which the relationship between the resonance frequency ratio fd / fs and the offset temperature drift was measured. From the result of Experiment 5, the offset temperature drift has the same tendency regardless of the width v of the neck 32a of the supporter 32, and the resonance frequency ratio fd / fs is 0.98 or more,
Since it becomes large below 0.88, the resonance frequency ratio fd
It has been found that the optimum range of / fs should be set to 0.9 or more and 0.96 or less.

In the above experiment, the drive resonance frequency fd was set to be lower than the detection resonance frequency fs.
Since the frequency may be set to be higher than s, the inventor of the present application has performed experiments similar to the above experiments even in a region where the resonance frequency ratio fd / fs is larger than 1. As a result, the above-described resonance frequency ratio fd / fs represents the relative relationship between the driving resonance frequency fd and the detection resonance frequency fs, and the value in the above-described optimum range is such that the ratio is reversed to fs / fd. It was also found that similar characteristics could be obtained. That is, as the optimum range of the resonance frequency ratio fd / fs,
It was found that the value may be set in the range of 1.04 or more and 1.1 or less.

Therefore, the optimum drive resonance frequency fd and the detected resonance frequency fs for reducing the offset temperature drift
Is in the range of 0.9 or more and 0.96 or less, or 1.04 or more and 1.1 or less, and the vibrator is set so that the resonance frequency ratio fd / fs is in this range. It can be seen that setting the dimensions of the respective parts 2 reduces both mechanical and electrical factors of the offset temperature drift and realizes an angular velocity sensor with a small offset temperature drift.

Next, a description will be given of Experiment 6, which was performed to define the distance G between the drive electrodes 12a and 12b and the detection electrodes 22a and 22b in the Z-axis direction in each of the arm portions 4 and 6. In this experiment 6, as shown in FIG. 9, the length L of each of the arms 4 and 6 was 17 mm, and the width t of each of the arms 4 and 6 was t.
D is 2.0, and the gap w between the arms 4 and 6 is 0.6.
mm, the height d of the connecting portion 8 is 3.0 mm, the width v of the neck portion 32a of the supporter 32 is 1.0 mm, and the thickness t of the vibrator 2 is
By adjusting s, the driving resonance frequency f of the vibrator 2 is adjusted.
The ratio fd / fs between d and the detected resonance frequency fs is represented by
Using a number of angular velocity sensors which are set to 0.88 and 0.92 and the distance G between the electrodes is appropriately changed, the distance G between the electrodes is obtained.
The relationship between the ratio G / ts between the temperature and the thickness ts of the vibrator 2 and the offset temperature drift was measured.

From the result of the experiment 6, the offset temperature drift shows that the ratio G / ts of the distance G between the electrodes and the thickness ts of the vibrator 2 is independent of the resonance frequency ratio fd / fs.
It can be seen that when the ratio G / ts is set to 1.4 or more, the offset temperature drift becomes substantially flat, and the offset temperature drift is small and stable. Therefore, the optimum distance G between the electrodes for reducing the offset temperature drift may be set so that the ratio G / ts to the thickness ts of the vibrator 2 is 1.4 or more. It can be understood that the electrical factor of (1) can be reduced to realize an angular velocity sensor with small offset temperature drift.

FIGS. 1 and 2 show the embodiment of the present invention.
The ratio fd / fs between the driving resonance frequency fd and the detection resonance frequency fs, which is optimal for suppressing the offset temperature drift, and the ratio between the distance G between the electrodes and the thickness ts of the vibrator 2 using the angular velocity sensor shown in FIG. Although the experimental results of measuring G / ts have been described, the present invention is not limited to the angular velocity sensor having the configuration shown in FIGS. 1 and 2, and is formed in a tuning fork shape made of a piezoelectric material, and its outer wall surface is formed. Any angular velocity sensor using a vibrator in which a drive electrode and a detection electrode are formed can be applied.

For example, in the above embodiment, the drive electrodes 12a and 12a for exciting the vibrator 2 in the drive axis (Y axis) direction are used.
b has been described for an angular velocity sensor formed continuously from the connecting portion 8 of the vibrator 2 to the left and right connecting portions 4 and 6, but the drive electrodes 12a and 12b are cut off at the connecting portion 8 as shown in FIG. The offset temperature drift can be reduced by applying the present invention even to an angular velocity sensor using a vibrator formed only on the left and right arms 4 and 6. Further, in the above embodiment, the detection electrodes 22a, 22
Although the angular velocity sensor provided with the vibrator 2 formed on the outer side surface (Y1, Y2 surface) of the left and right arm portions 4, 6 has been described, for example, the detection electrodes 22a, 22b are connected to the X1 of each arm portion 4, 6 by X1. A temporary GND electrode corresponding to each of the detection electrodes 22a and 22b is formed on the Y1, Y2
Even if the angular velocity sensor is formed on a surface so that a detection signal can be directly extracted from a detection electrode provided on the surface (X1 plane) of the vibrator 2, the offset temperature can be obtained by applying the present invention. Drift can be reduced.

According to the first aspect of the present invention, in addition to the angular velocity sensor having the tuning fork-shaped vibrator 2 as in the above embodiment, the angular velocity sensor having the vibrator according to the third aspect is provided. Specifically, as shown in FIGS. 11 and 12,
Two sets of two arm portions constituting a tuning fork are provided, and these arm portions 103, 104, 105, and 106 are arranged in parallel, and one end thereof is connected by a common connecting portion 102, thereby forming a comb shape. An angular velocity sensor provided with the vibrator 100 formed as described above, or as shown in FIG. 13, two sets of two arms forming a tuning fork are provided.
The angular velocity sensor having the vibrator 200 formed in an H-shape can be applied by arranging and connecting the elements 204, 205, and 206 on both sides of the connecting part 202, respectively.

Hereinafter, the vibrator 10 shown in FIGS.
An angular velocity sensor having 0,200 will be described. Vibrator 100 of angular velocity sensor shown in FIGS. 11 and 12
Is a so-called four-leg tuning fork in which two sets of tuning forks with different intervals between the arms 103, 104 and 105, 106 are combined. Are arranged in a narrow interval, and the connecting portions of the tuning forks are connected (comb shape). As in the case of the vibrator 2 shown in FIG. 1, a supporter 107 having a torsion beam 108 in the center is formed of an adhesive material or the like for the connecting portion 102 of the vibrator 100 in the same manner as the vibrator 2 shown in FIG. The supporter 107 further connects the arm portions 103 to 106 to each other.
In order to dispose the base 111 in parallel at a predetermined distance from the base 111, the base 111
The upper part is fixed by welding or the like.

FIG. 11 is a perspective view showing the entire structure of the angular velocity sensor having the comb-shaped vibrator 100, and FIG.
FIG. 4 is an explanatory diagram showing a state in which the vibrator 100 is viewed from front and rear (X1 plane, X2 plane) and left and right (Y1 plane, Y2 plane).
The vibrator 100 is formed in a comb shape by, for example, machining PZT by dicing or the like. The four arms 103 to 10 constituting the vibrator 100
6, a pair of arm portions 10 constituting a central tuning fork portion.
The vibrator 100 is attached to each of the arm portions 103-1 to 3-4.
The electrodes for vibrating in the arrangement direction (Y-axis direction) of the pair 06 are formed, and a pair of arm portions 10 constituting an outer tuning fork portion are formed.
5 and 106, each arm portion 1 added to the vibrator 100 is provided.
Electrodes for detecting the angular velocity Ω around the Z-axis parallel to the central axes of 03 to 106 are formed.

That is, as shown in FIG.
The drive electrodes 112 and the monitor electrodes 113 are respectively formed on the X1 surface (the surface opposite to the base 111) of the X-rays 3 and 104, and the X2 surface (the back surface facing the base 111) is formed on the X3 surface. Temporary GND electrode 12 for grounding to a reference potential
0 is formed. And each of the arm portions 103, 10
4 drive electrode 112 and monitor electrode 113
Are connected to each other on the X1 plane of the connecting part 102, and are formed on the X2 plane of the arm parts 103 and 104, respectively.
The electrodes 120 are connected to each other on the X2 plane of the connection part 102.

On the other hand, a detection electrode 114 is formed on the X1 surface of the arm portion 105, a detection electrode 122 is formed on the X2 surface, and a Y1 surface, which is the outer side surface of the vibrator 100, is formed on the X1 surface.
A temporary GND electrode 125 is formed, and a short-circuit electrode 129 that connects (short-circuits) the detection electrodes 114 and 122 on the X1 and X2 planes is formed. The arm 10
6, a temporary GND electrode 115 is formed on the X1 plane,
A temporary GND electrode 121 is formed on the surface, and the vibrator 100
The detection electrode 124 is formed on the Y2 surface, which is the outer side surface of the X-ray, and the provisional GND electrodes 115 and 12 on the X1 and X2 surfaces.
1 are connected to each other (short-circuit).

Next, a pad electrode 116 for extracting a detection signal is formed on the X1 surface of the connecting portion 102. The pad electrode 116 is connected to the X1 surface of the arm portion 105 via an extraction electrode 118. The arm portion 106 is connected to the formed detection electrode 114 and is connected to the arm portion 106 via the extraction electrode 126.
Is connected to the detection electrode 124 formed on the Y2 plane. A pad electrode 117 for grounding a temporary GND electrode is also formed on the X1 plane of the connecting portion 102. The pad electrode 117 is connected to the arm portion 1 via an extraction electrode 119.
The temporary GND electrode 115 formed on the X1 plane of No. 06 is connected. The temporary GND electrode 121 of the arm 106 connected to the temporary GND electrode 115 is connected to the connecting portion 1.
02 through the extraction electrode 123 formed on the X2 plane and the extraction electrode 127 formed on the Y1 plane of the arm 105.
Temporary GND electrode 12 formed on Y1 surface of arm 105
5 and the provisional GND electrodes 120 formed on the X2 plane of the arm portions 103 and 104 are connected to each other.

Then, as shown in FIG.
Reference numeral 1 denotes a drive electrode 1 formed on the X1 plane of the connecting portion 102.
12, four terminals T31 to T3 corresponding to the monitor electrode 113, the pad electrode 116, and the pad electrode 117.
4 and each of these electrodes and each terminal T3.
1 to T34 are connected by bonding wires W31 to W34, respectively. The vibrator 1
The procedure for forming the electrodes on each surface of 00 is exactly the same as that of the vibrator 2 shown in FIG.

When detecting the angular velocity by using the angular velocity sensor thus configured, the driving arm 10 is used.
By applying a drive signal (AC voltage) between the drive electrode 112 formed on the third and fourth electrodes 104 and the provisional GND electrode 120, the inner tuning fork formed by the arms 103 and 104 is driven left and right. By controlling the drive signal using a control circuit (not shown) so as to resonate in the axial direction (Y-axis direction shown in the drawing) and to keep the output from the monitor electrode 113 constant, the tuning fork inside the vibrator 100 is formed. The part is self-oscillated. When the vibrator 100 is self-excited and oscillated in this manner, when an angular velocity Ω about the longitudinal central axis (Z axis) of the vibrator 100 is input,
The arms 103 and 104 also vibrate in the X-axis direction (detection axis direction) penetrating the X1 and X2 planes by Coriolis force. Then, each arm part 1 constituting the outer tuning fork part
05, 106 also vibrate in the X-axis direction, and the detection electrodes 114, 1
22 and the provisional GND electrode 125 and the detection electrode 12
4 and the provisional GND electrodes 115 and 12170, a current proportional to the vibration in the X-axis direction flows. By converting the current between these electrodes into a voltage value, the angular velocity Ω around the Z-axis is changed. To detect.

Then, as described above, the comb-shaped vibrator 100
Drive frequency fd
It is found that if the ratio fd / fs between the detection frequency fs and the detection resonance frequency fs is set within the above-mentioned optimum range, the same effect as the angular velocity sensor having the tuning-fork-shaped vibrator 2 can be obtained.

Next, the vibrator 200 of the angular velocity sensor shown in FIG.
Each of the tuning forks has an H-shape connected at a connecting portion 202 such that the reference numerals 3, 204 and 205, 206 face in opposite directions. The vibrator 200 is formed in an H-shape by machining PZT by dicing or the like, and the vibrator 200 is attached to the pair of arms 203 and 204 forming one tuning fork. An electrode for vibrating in the arrangement direction (Y-axis direction) is formed, and a pair of arms 205 and 206 constituting the other tuning fork are provided with the arms 203 to 206 applied to the vibrator 200.
An electrode for detecting the angular velocity around the z-axis parallel to the central axis of is formed.

That is, the drive electrode 207 and the monitor electrode 208 are formed on the X1 plane (one of the vibrators 200 of the H-shape) of the arms 203 and 204. Then, the drive electrode 20 of each arm 203, 204
7 and the monitor electrode 208 are connected to each other at the connection portion 202. Further, temporary GND electrodes 210 and 211 are formed on the X1 surface of the arm portions 205 and 206, respectively.
The detection electrodes 212 and 21 are provided on the Y1 and Y2 planes (outer side surfaces of the vibrator 200 in the respective arm portions 205 and 206).
3 are formed.

The X2 plane of the vibrator 200 (vibrator 20
0), an arm 2
03 and 204 through the connecting portion 202 and the arm portion 20
Temporary GND electrodes 209 are formed over substantially the entire area extending to the arm portions 205 and 206. The temporary GND electrodes 210 and 211 formed on the X1 plane of the arm portions 205 and 206
Short-circuit electrodes 21 formed on the Y1 and Y2 planes 206
8, 219 are connected to the temporary GND electrode 209 on the X1 plane. Further, pad electrodes 214 and 215 for extracting a detection signal are formed on the X1 surface of the connection portion 202, and the detection electrodes 212 and 213 formed on the Y1 and Y2 surfaces of the arm portions 205 and 206 are connected to the extraction electrode 216. , 217 are connected to the pad electrodes 214, 215, respectively.

When the angular velocity is detected by using the vibrator 200 having the above-described configuration, for example, the X
At the same time as fixing the two surfaces on the base via the supporter,
The temporary GND electrode 209 on the X2 plane is grounded to the reference potential. Then, the drive electrodes 2 formed on the arm portions 203 and 204 are formed.
07 and the provisional GND electrode 209, a drive signal (AC voltage) is applied between these arm portions 103, 1
The drive signal is generated by using a control circuit (not shown) so that the tuning fork formed by the drive circuit 04 resonates in the left and right drive axis directions (Y axis direction shown in the figure) and the output from the monitor electrode 208 becomes constant. By performing the control, the tuning fork inside the vibrator 200 is caused to self-oscillate.

When the angular velocity Ω around the Z-axis is input during the self-excited oscillation of the vibrator 200, the arms 203 and 204 are moved to the X1 and X2 planes by Coriolis force. Vibrates also in the X-axis direction (not shown) penetrating through. Then, each of the arm portions 2 constituting the other tuning fork portion
05 and 206 also vibrate in the X-axis direction.
2 and the provisional GND electrodes 209 and 210, and between the detection electrode 213 and the provisional GND electrodes 209 and 211, X
A current proportional to the axial vibration flows. Then, this current is taken out through the pad electrodes 214 and 215 and converted into a voltage value, thereby detecting the angular velocity Ω around the Z axis. In the angular velocity sensor including the H-shaped vibrator 200 as described above, if the ratio fd / fs between the driving resonance frequency fd and the detection resonance frequency fs is set within the above-described optimum range, the tuning fork shape is obtained. It turned out that the same effect as the angular velocity sensor provided with the vibrator 2 was obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of an angular velocity sensor according to an embodiment.

FIG. 2 is an explanatory diagram showing electrodes formed on the vibrator shown in FIG.

FIG. 3 is an explanatory diagram illustrating shapes of a vibrator and a supporter manufactured for measuring a relationship between a resonance frequency ratio fd / fs and an offset temperature drift.

FIG. 4 is a graph showing a measurement result of an experiment 1 in which a relationship between a resonance frequency ratio fd / fs and an offset temperature drift was measured.

FIG. 5 is a graph showing a measurement result of Experiment 2 in which a relationship between a resonance frequency ratio fd / fs and an offset temperature drift was measured.

FIG. 6 is a graph showing a measurement result of Experiment 3 in which a relationship between a resonance frequency ratio fd / fs and an offset temperature drift was measured.

FIG. 7 is a graph showing a measurement result of Experiment 4 in which a relationship between a resonance frequency ratio fd / fs and an offset temperature drift was measured.

FIG. 8 is a graph showing a measurement result of Experiment 5 in which a relationship between a resonance frequency ratio fd / fs and an offset temperature drift was measured.

FIG. 9 shows a ratio G between the inter-electrode distance G and the thickness ts of the vibrator 2.
13 is a graph showing measurement results of Experiment 6 in which the relationship between / ts and offset temperature drift was measured.

FIG. 10 is an explanatory diagram illustrating another configuration example of the tuning-fork vibrator.

FIG. 11 is an explanatory diagram illustrating a configuration of an angular velocity sensor including a comb-shaped vibrator having two sets of tuning forks.

FIG. 12 is an explanatory view showing electrodes formed on the comb-shaped vibrator shown in FIG.

FIG. 13 is an explanatory diagram illustrating a configuration of an H-shaped vibrator having two sets of tuning forks.

[Explanation of symbols]

2,100,200 ... vibrator, 4,6,103-10
6, 203-206 ... arm part, 8, 102, 202 ...
Connecting parts, 12a, 12b, 112, 207 ... drive electrodes,
14a, 14b, 113, 208 ... monitor electrode, 16
a, 16b, 24, 115, 120, 121, 125,
209, 210, 211 ... temporary GND electrode, 18a, 18
b ... polarizing electrode, 20a, 20b, 116, 117, 2
14, 215: pad electrode, 22a, 22b, 114,
122, 124, 212, 213 detection electrodes, 26a,
26b, 28a, 28b, 128, 129, 218, 2
19 ... Short-circuiting electrodes 30a, 30b, 118, 11
9, 123, 126, 127, 216, 217 extraction electrode, 32, 107 supporter 34, 110 spacer, 36, 111 base, T1 to T8, T31 to 34
... Terminal, 40... Current-voltage conversion circuit.

Claims (5)

[Claims] 1. A piezoelectric body formed by at least a pair of arms arranged in parallel with each other and a connecting part connecting one end of each arm, and at least one of:
A drive electrode that receives an AC voltage from the outside and excites each arm in a drive axis direction that is an arrangement direction of each arm, and detects a vibration that occurs in a detection axis direction orthogonal to the drive shaft in each arm. An angular velocity sensor provided with a vibrator having a pair of detection electrodes formed thereon, wherein the vibrator has a resonance frequency fd in the drive axis direction,
The ratio fd / fs to the resonance frequency fs in the detection axis direction
Is 0.9 or more and 0.96 or less, or 1.04 or more.
An angular velocity sensor formed to be within a range of 1 or less. 2. The angular velocity sensor according to claim 1, wherein the vibrator is formed in a tuning fork shape by a pair of arms and a connecting portion connecting one end of each of the arms. 3. The vibrator is configured such that two sets of tuning forks each including a pair of arms and a connecting portion for connecting one end of each of the arms to each other are integrated with a common connecting portion between the tuning forks. And a drive electrode is formed on an arm portion forming one tuning fork portion, and the detection electrode is formed on an arm portion forming the other tuning fork portion. The angular velocity sensor according to claim 1, wherein 4. A piezoelectric body formed in a tuning fork shape by a pair of arm portions and a connecting portion connecting one end of each arm portion, and each of said arm portions receives at least an AC voltage from the outside on an outer wall surface. And a pair of detection electrodes for detecting a vibration generated in a detection axis direction orthogonal to the drive shaft in each arm portion. In the angular velocity sensor provided with the vibrator, the vibrator may be a table having an inter-electrode distance G between the drive electrode and the detection electrode along a longitudinal direction of each of the arms, and a concave shape in the vibrator. An angular velocity sensor formed so that a ratio G / ts to a thickness ts between the back surfaces is 1.4 or more. 5. The vibrator includes: a drive electrode on a surface side of the outer wall surface; a polarization electrode on a surface side of each arm; and a polarization electrode on a side surface of each arm. 5. The angular velocity sensor according to claim 2, wherein the detection electrode is provided at a corresponding position, and a common electrode corresponding to each of the electrodes is provided on a back surface side. 6.