JP3327150B2 - Resonant angular velocity sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an angular velocity sensor for detecting an angular velocity acting on a vehicle such as an automobile or an aircraft and electronic equipment. More specifically, the mass section, which is the inertial mass, is excited, and the angular velocity is determined based on the displacement of the mass section due to the Coriolis force generated in a direction orthogonal to both the excitation direction of the mass section and the rotation axis direction of the angular velocity sensor. The present invention relates to a resonance type angular velocity sensor for detecting

[0002]

2. Description of the Related Art FIG. 16 is a structural view of a resonance type vibration element such as a conventional angular velocity sensor. In this vibrating element 150, a flat plate-shaped mass 152
Are floatingly supported from above and below in the figure by two beams 151 each having one end fixed to the frame 160 of the silicon substrate 520. Mass part 15
2, a comb-shaped electrode 156 is provided on each side in the horizontal direction.
Are formed on the frame 160 so that the comb-shaped electrodes 158 are engaged with and face the comb-shaped electrodes 156, respectively.
Are formed.

[0003] Excitation conductor layers (not shown) are connected to the comb electrodes 156 and 158, respectively. When an AC voltage is applied to the excitation conductor layer, an electrostatic force is generated between the comb-shaped electrodes 156 and 158, and the electrostatic force causes the mass portion 152 to be displaced in the left-right direction in FIG. Vibrates like).

As described above, when the mass 152 is excited in the left-right direction and an angular velocity acting on the left-right direction in the drawing acts as a rotation axis, the mass section 152 moves in a direction perpendicular to both the excitation direction and the rotation axis direction. Coriolis force is generated. When this Coriolis force acts on the mass 152, the mass 152
The direction of action of the Coriolis force
In (a), the mass 152 is displaced in the thickness direction and vibrates.

FIG. 16C is a sectional view taken along the line YY ′ of FIG.
A cross-sectional view along the line is shown. As shown in FIG. 16 (c), displacements for detecting displacement of the mass portion 152 in the thickness direction are provided at positions sandwiching the mass portion 152 from the thickness direction. Detection electrodes 155 and 157 are provided. When the mass portion 152 is displaced in the thickness direction by the Coriolis force as described above, the displacement detection electrodes 155 and 157 detect the displacement by, for example, a capacitance detection method. Then, a signal corresponding to the magnitude of the amplitude of the vibration of the mass section 152 due to the Coriolis force is obtained, and the magnitude of the angular velocity is detected.

[0006]

SUMMARY OF THE INVENTION Conventional angular velocity sensor 1
In 50, the beam 151 supports the mass portion 152 so as to be movable in the excitation direction, and also supports the mass portion 152 so as to be displaceable in the Coriolis force generation direction. Therefore,
The direction of action of the Coriolis force on the mass 152 is structurally
This is in the thickness direction of the substrate. Therefore, in order to detect the displacement of the mass 152 in the thickness direction, as shown in FIG. 16C, the displacement detection electrodes 155 and 1 are disposed above and below the mass 152.
It is necessary to form a three-layer structure (a lower electrode, a mass portion, and an upper electrode). However, the manufacturing process for obtaining such a three-layer structure becomes complicated, and in order to simplify the manufacturing process, a configuration capable of generating a Coriolis force in the plane direction of the substrate and detecting the Coriolis force has been desired.

Further, the angular velocity sensor 150 as described above
Are manufactured using a so-called semiconductor process technology suitable for fine processing. However, even in this semiconductor process technology, variations in the manufacturing process cannot be avoided. For example, due to variations in the etching process, the cross-sectional shape of the beam 151 supporting the mass portion 152 is not an ideal rectangle or square, Of the beam, that is, a trapezoidal shape whose oblique side is the thickness direction of the beam.

When the cross section of the beam 151 becomes trapezoidal, when the mass 152 is vibrated in the excitation direction, the mass 152
When the beam 151 that supports the beam 151 vibrates in the excitation direction, a leak vibration component occurs in the thickness direction of the beam 151.

In the conventional angular velocity sensor 150, as described above, the beam 151 supports the mass portion 152 so as to be movable in the excitation direction and is displaceable in the Coriolis force generation direction (that is, the thickness direction of the beam 151). It is supported, and displacement in the vertical direction in the figure is prohibited. Therefore, most of the leak vibration component of the beam 151 due to the vibration in the excitation direction is generated in the Coriolis force detection direction. Therefore, by exciting the mass portion 152, even if no angular velocity is applied,
The mass 152 is displaced in the detection direction, that is, in the direction perpendicular to the paper surface of FIG. 16A, and an output appears, which may adversely affect the detection accuracy of the angular velocity sensor 150.

In the conventional angular velocity sensor 150, a gap 154 is provided in a base region 159 on one side of the beam 151 in the frame 160. The gap 154 has a width in the Z direction, that is, the beam 151.
Is variably adjusted by a gap width adjusting means (not shown) (not shown). Then, by adjusting the width of the gap 154 by such a gap width adjusting means, the tensile stress of the beam 151 is changed,
As a result, the resonance frequency of the beam 151 is adjusted, and measurement with the best sensitivity is possible.

However, the conventional angular velocity sensor 150
Since the beam 151 is used in both the excitation direction and the detection direction as described above, when the width of the gap 154 is adjusted to apply a tensile stress to the beam 151, the resonance in the excitation direction and the detection direction is thereby reduced. The frequency increases at the same time. However, the resonance frequency of the mass section 152 in the excitation direction and the resonance frequency in the Coriolis force detection direction are different due to the characteristics of the angular velocity sensor.
f is not zero. As described above, the mass 15 is moved in the two directions.
In the configuration for adjusting the tensile stress of the beam 151 supporting the displacement of 2, there is a problem that it is difficult to adjust to obtain the optimum Δf.

Further, the conventional resonance type angular velocity sensor using a vibrator has a large element itself, so that it is possible to perform a trimming process using a laser or the like. However, as shown in FIG. 16, it is extremely difficult to finely adjust the frequency by such a trimming process in recent fine vibration type sensors manufactured by a micromachining technique using a material such as silicon. This is because, while the area to be trimmed of the vibration type sensor is as small as several μm, the spot diameter of a laser beam or the like is as large as 10 to several tens of μm. This is because it is difficult.

As described above, the method of adjusting the resonance frequency of the vibrator to a constant value by the conventional trimming technique is also described.
It is not appropriate as a method of adjusting Δf, and Δf is efficiently adjusted.
There has been a demand for a configuration that is easy to adjust to the optimum value.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a resonance type angular velocity sensor capable of accurately detecting an angular velocity with a simple configuration.

Another object of the present invention is to provide a resonance type angular velocity sensor having a configuration capable of easily and efficiently adjusting a resonance frequency of a mass portion as an inertial mass.

[0016]

In order to achieve the above object, a resonance type angular velocity sensor according to the present invention excites a mass portion serving as an inertial mass, the excitation direction of the mass portion and the rotation axis direction of the angular velocity sensor. A resonance type angular velocity sensor for detecting an angular velocity based on displacement of a mass portion due to Coriolis force generated in a direction orthogonal to both directions, and has the following features.

That is, a pair of mass displacement support bases arranged with the mass portion interposed therebetween in the excitation direction, and each of the mass displacement support bases extending from the mass displacement support base to the mass portion, and generating a Coriolis force of the mass portion when a Coriolis force is generated. And a mass displacement direction support beam supporting the mass displacement support base to allow displacement in the Coriolis force generation direction of the mass displacement support bases, and the mass section through the mass displacement direction support beam. A mass excitation support beam that supports the mass displacement support base so as to allow vibration in an excitation direction, excitation means for exciting the mass portion by exciting the mass displacement support base, Displacement detecting means for detecting displacement. The mass excitation support bee
The folded beam that composes the
At least extending in a direction perpendicular to the vibration direction of the support base
Comprising two parallel-arranged beam bodies of the same length,
The two beam bodies are at one end of each other
The two beam members are connected by a wide connecting portion.
The other end of the beam supports the mass displacement in one beam body
Connected to the base and fixed to the substrate in the other beam body
I have .

According to the present invention, as described above, the mass excitation support beam for supporting the mass portion so as to be able to vibrate in the excitation direction,
A mass displacement direction support beam for supporting the mass portion to allow displacement in the Coriolis force generation direction is provided separately. Therefore, when the mass excitation support beam is vibrated in the excitation direction, even if a leakage vibration component in the beam thickness direction is generated in the beam due to a variation in the manufacturing process, the direction of the leakage vibration component is In many cases, the direction of detection of the Coriolis force does not match (specifically, 9
0 °). Therefore, the sensor output of the resonance type angular velocity sensor of the present invention is hardly affected by the beam shape, and a sensor with high detection accuracy can be obtained regardless of the variation in the manufacturing process.

Further, by separating the beams, for example, the tensile stress of each beam is individually adjusted, and the resonance frequency in each of the mass portion excitation direction and the Coriolis force detection direction is set to an appropriate value. It becomes easier. Therefore, adjustment for obtaining the optimum Δf can be easily performed.

Further, by supporting the mass portion with separate beams in two orthogonal directions, it becomes possible in principle to make the excitation direction and the Coriolis force detection direction the same plane direction. For this reason, it becomes possible to simplify the manufacturing process as a resonance type angular velocity sensor.

[Aspects of the Present Invention] The resonance type angular velocity sensor of the present invention can employ, for example, the following aspects.

(I) Aspect 1 First, a folded (folded) beam can be used as a mass excitation support beam that supports a mass displacement support base so that the mass portion can vibrate in the excitation direction.

The folded beam has at least two parallel beam members of the same length extending in a direction perpendicular to the vibration direction of the object to be supported (here, the mass displacement support base). These beam members are connected to each other at one end in a direction orthogonal to the vibration direction. Further, the other ends of the two beam members are fixed to a substrate or the like in one beam member, and connected to a support target in the other beam member.

As the mass excitation support beam, it is possible to use a straight beam composed of one linear beam. However, when this straight beam is used,
When the amplitude of the mass portion with respect to the excitation direction is large, the beam is pulled in the longitudinal direction of the beam, and a tensile stress is generated in the beam. For this reason, the spring constant of the beam increases, and the relationship between the displacement and the restoring force due to the beam becomes non-linear. That is, as the excitation amplitude increases, the resonance frequency in the excitation direction increases, and the sensor characteristics change.

On the other hand, if a folded beam is used, when one of the beam members connected to the support is displaced, the other beam member operates in the same manner, and even if the beam member has a large amplitude, each beam member has a different amplitude. The length does not change. Therefore, the beam is not pulled in the longitudinal direction at the time of large amplitude,
The spring constant is constant, and it is possible to avoid a change in sensor characteristics even with a large amplitude. In particular, in the present invention, two
The connecting part of the parallel arranged beam body is designed wide
In the longitudinal direction of the beam, that is, in the detection direction of the sensor.
The rigidity of the folded-type beam
You. Therefore, vibration leakage in the detection direction of the excitation component is further reduced.
This can contribute to an improvement in the accuracy of the sensor.

(Ii) Aspect 2 As the mass displacement direction support beam for supporting the displacement of the mass portion in the direction in which the Coriolis force is generated, a straight beam (straight beam) extending straight in a direction perpendicular to the displacement allowable direction is used. ) Can be used. This straight beam can be formed without slack in the direction orthogonal to the displacement permissible direction, the support is reliable, and, for example, the stop of vibration at the time of displacement is quick. In addition, since the beam has a straight shape and a simple structure, there is an advantage in improving the yield during manufacturing. Note that if the displacement amount of the straight type beam is large, the above-mentioned disadvantage that a tensile stress is generated on the beam occurs. And the change in the characteristics of the sensor is small.

(Iii) Aspect 3 In the resonance type angular velocity sensor of the present invention, the mass excitation support beam and the mass displacement direction support beam are provided as described above according to the role of the beam. For example, individually adjust the tensile stress,
The resonance frequency in each of the mass portion excitation direction and the Coriolis force detection direction can be set to an appropriate value.

For example, by providing a frequency adjusting mechanism and applying stress to the mass excitation support beams extending from the mass displacement support base, it is possible to adjust only the resonance frequency in the excitation direction of the mass portion. The adjustment to the mass excitation support beam can be realized by applying a tensile stress or a compressive stress to the beam by an electric adjustment method using, for example, an electrostatic force.

As a more specific configuration, for example, when a folded beam is used as the mass excitation support beam, electrodes are formed at the ends of the folded beam which are connected to each other. By controlling the electrostatic force using this electrode, it is possible to apply stress to the beam and adjust the frequency. For example, the end-side connecting portion provided along the mass portion exciting direction of the folded beam may be further extended in the mass portion exciting direction, and a frequency adjusting electrode may be provided at a plurality of portions of the connecting portion. If this is the case, fine adjustment of the resonance frequency in the excitation direction becomes easier.

Further, if detecting means for detecting the excitation state of the mass section is separately provided, the optimum resonance frequency of the mass section can be constantly adjusted based on the excitation state (excitation frequency, amplitude, etc.) obtained by this detection means. It is possible to adjust the stress of the mass excitation support beam so that it can be obtained. In addition, it is preferable that the excitation means for exciting the mass section is feedback-controlled based on the detection result of the detection means so that the vibration frequency in the excitation direction becomes an optimum value.

As a frequency adjustment mechanism, mechanical adjustment such as laser trimming is available as an adjustment means that can be used in place of or in combination with the electrical adjustment means. In this mechanical adjustment method, for example, a trimming pattern formed exclusively for the mass excitation support beam is removed, or a metal material or the like is later attached to the mass excitation support beam, and the mass excitation support beam is removed. Only the resonance frequency can be selectively adjusted. In such a mechanical adjustment method, the adjustment efficiency is high because the frequency adjustment width is large, and it is particularly suitable for rough adjustment of the frequency.

Next, the relationship between the resonance frequency in each direction of the resonance type angular velocity sensor and its frequency adjustment will be described.

Vibration sensors utilizing changes in resonance characteristics have attracted attention because of their excellent characteristics of high sensitivity and high resolution. This is low energy loss,
Since the vibrator is manufactured using a material having a high vibration Q value, in the resonance state where the resonance frequency of the vibrator coincides with the excitation frequency for exciting the vibrator, the characteristic that the amplitude is significantly amplified is utilized. Because it is.

However, on the other hand, when the excitation frequency changes for some reason, the resonance state of the vibration type sensor changes, and the sensitivity of the sensor is significantly reduced. Factors causing such a change in the resonance characteristics include variations in the manufacturing process, temperature changes during use, and changes in the microscopic structure of the vibrating body caused by long-term use (for example, material fatigue). In particular, these effects become problems in a severe environment such as for controlling a vehicle of an automobile, and hinder accurate measurement of angular velocity.

Among the sensor characteristics, with regard to the sensitivity which is the most important, the cause of the fluctuation will be described below.

The sensitivity of the resonance type angular velocity sensor is proportional to the moving speed of the mass when exciting the mass. The moving speed of the mass is proportional to the amplitude of the mass. That is, it is necessary to increase the amplitude of the mass in order to increase the sensitivity. Since this sensor is a resonance type sensor, when the resonance frequency in the excitation direction of the sensor and the frequency of the excitation force are matched, the amplitude is significantly amplified. As a result, a very large excitation amplitude can be obtained with a small excitation voltage. Keeping the excitation voltage low
It is also useful to reduce the noise (crosstalk) that the excitation signal electrically jumps into the detection circuit, which also improves the resolution of the sensor. The same applies to the detection direction. The Coriolis force periodically generated by the angular velocity is an exciting force on the detection side having the same cycle as the excitation frequency. If the generation cycle of this Coriolis force is matched with the resonance frequency in the detection direction, the amplitude generated in the detection direction is also greatly amplified. As a result, high sensitivity can be achieved even in the vibration system in the detection direction.

From the above description, it is understood that the relationship between the resonance frequencies on the excitation side and the detection side is important. This relationship is as described below. The vibrator (mass portion) is vibrated in advance by electrostatic force generated by the comb-shaped electrode. The excitation frequency at this time is matched with the resonance frequency in the excitation direction. Here, if an angular velocity is given to the sensor, a Coriolis force Fc proportional to the angular velocity and the vibration velocity of the vibrator is generated in the detection direction. Fc is represented by the following equation (1).

[0038]

Fc = 2 × M × V × Ω (1) where M is the mass of the mass, V is the excitation velocity, and Ω is the angular velocity. The generation cycle of this Coriolis force is the same as the excitation frequency. Due to this Coriolis force, the mass portion starts to vibrate at right angles to the excitation direction, and its cycle becomes the same as the generation cycle of the Coriolis force. At this time, if the frequency of the Coriolis force is made to coincide with the resonance frequency in the detection direction, high sensitivity can be achieved. From the above principle, it is understood that "the highest sensitivity is obtained when the resonance frequency fx in the excitation direction matches the resonance frequency fy in the detection direction". That is, the difference between the frequencies in both directions is Δf
Thus, it can be said that the smaller the Δf is, the higher the sensitivity is. FIG. 17 shows the definition of Δf. It can be seen that the smaller the value of Δf, the greater the degree of overlapping of the resonance frequency curves on the excitation side and the detection side, so that the amplitude A on the detection side at the excitation side resonance frequency fx increases. The greater the amplitude A, the higher the sensor sensitivity. However, Δf is also closely related to the response of the sensor, and the smaller this is, the lower the response to the angular velocity input is. When used as a vehicle sensor, Δf generally requires about several tens to several hundreds Hz. The optimum value of Δf is determined by a trade-off with sensitivity.

However, it is generally said that a manufacturing error in a sensor manufacturing process is about 10%. Therefore, the sensor shape after the manufacturing process varies from the design value. Even if efforts are made to minimize errors in the manufacturing process, there are variations in the mass of each part, the thickness of the beam, and the like, and it is difficult to completely match Δf to the target value. Also, if this Δf changes for some factor, even if the given angular velocity is constant,
The sensitivity, resolution, and zero point output (offset output) all change.

Therefore, in order to solve such a problem, it is necessary to adjust the frequency by a simple and automatic method after the manufacture of the sensor element.

Therefore, by employing a method such as applying a DC voltage between the folded beam and the frequency adjustment electrode adjacent thereto as described above, the resonance frequency in the excitation direction is variably adjusted, and the resonance in the detection direction is adjusted. By approaching the frequency, the sensitivity of the angular velocity sensor can be increased.

In addition, with respect to the manufacturing process of the vibration type sensor, which often poses a problem, and changes in the characteristics of the sensor due to changes over time and temperature, functions are automatically added by contriving the beam shape of the vibrator and the electric circuit. It is possible to automate most of the adjustments after the manufacturing process and maintain high performance for a long period after the manufacturing. Since no special process is used in the manufacturing, the manufacturing cost can be kept low.

(Iv) Aspect 4 In the resonance type angular velocity sensor of the present invention, the following aspects can be further taken.

First, any two of the above-described resonance type angular velocity sensors are used as one set, and the respective mass portions of the one set of sensors are excited so as to have opposite phases in the same excitation direction. That is, an excitation force is applied to each of the two mass portions so as to have a phase difference of 180 degrees. With this configuration, when the mass is displaced by Coriolis force acting in a direction orthogonal to both the excitation direction and the direction of the rotational axis of the angular velocity, the displacement direction of the mass is changed to two mass directions. The opposite is true in the department.

In the case of a single resonance-type angular velocity sensor, when acceleration acts on the mass of the sensor in the same direction as the direction of action of the Coriolis force, the mass acts as if the angular velocity were applied. It will be displaced.

Therefore, if a configuration is adopted in which a pair of resonant angular velocity sensors are used to excite the two mass parts with a phase difference of 180 degrees, when the angular velocity is applied, the two mass parts are respectively applied to the two mass parts as described above. Since the generated Coriolis force is in the opposite direction, it is easy to selectively detect the angular velocity. Therefore, the acceleration effect in the direction of action of the Coriolis force can be easily canceled, and higher reliability is guaranteed.

(V) Mode 5 A configuration in which displacement detecting means for detecting displacement of the mass portion is provided on one side in the displacement direction of the mass portion, and displacement control means is provided on the other side in the displacement direction of the mass portion. Can be adopted. This displacement control means, when the mass portion is displaced by the action of Coriolis force, and when the displacement detection means detects the displacement,
In response to this, the mass section is controlled so as to cancel the displacement of the mass section. Further, the displacement amount of the mass portion is detected based on the control amount required for the displacement detecting means to cancel the displacement. By providing such a displacement control means, it is possible to improve the linearity, sensitivity, frequency characteristics, temperature characteristics and the like of the resonance type angular velocity sensor.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter, referred to as embodiments) will be described with reference to the drawings.

[First Embodiment] (Configuration of Resonant Angular Velocity Sensor) FIG. 1 shows a resonance angular velocity sensor according to the first embodiment (hereinafter referred to as angular velocity sensor).
2 is a sectional view taken along the line AA of FIG. 2, FIG. 3 is an enlarged view of the capacitance detecting electrode, and FIG. 4 shows an example of a manufacturing process of the angular velocity sensor. .

The angular velocity sensor according to the first embodiment is a fine angular velocity sensor manufactured by using a silicon micromachine technology or the like. In the angular velocity sensor 500, the mass portion 1 is floatingly supported on the substrate plane by the mass excitation support beam and the mass displacement support beam.

Specifically, the excitation direction (the vertical direction in FIG. 1)
And a pair of mass displacement support bases 24 and 25 disposed with the mass portion 1 interposed therebetween, and mass displacement support beams 20, 21 and 2.
2 extend from the respective mass displacement support bases 24 and 25 to the mass portion 1 and move the mass portion 1 in the vertical direction of FIG. 1 so as to allow displacement of the mass portion 1 in the direction in which Coriolis force is generated when Coriolis force is generated. From each support.

In the first embodiment, a mass excitation support beam for supporting the mass unit 1 in its excitation direction is
Each beam body 10, 11, 12, 13, 14, 15, 1
A folded-type beam is used, which is composed of 6, 17 and connecting portions 80 and 81 wider than each of the beam members connecting them. In this folded-type beam, the beam members 11, 13, 15, 17 support the respective mass displacement support bases 24, 25 from the left and right directions in FIG. 1, respectively, and the Coriolis force of the mass displacement support bases 24, 25 is provided. Displacement in the generation direction is prohibited, and vibration of the mass portion 1 in the excitation direction is allowed via the mass displacement direction support beams 22 and 23.

In the folded beam, one ends of the beam members 10, 12, 14, 16 are connected to anchor portions 90, 91, 92, 93 fixed to the substrate, respectively. 91, 92, 9
In the angular velocity sensor, the parts (mass part 1 and each support beam, etc.) constituting the vibrating part are floatingly supported on the substrate by 3.

Further, comb-shaped electrodes 50, 61 and 64 are formed on the mass displacement supporting bases 24 and 25 supported by the folded beam, respectively.

Among them, a comb-shaped excitation electrode 51 serving as an excitation means for exciting the mass portion 1 is disposed at a position facing the comb-shaped electrode 50 of the mass displacement support base 24. The base is fixedly supported on a substrate, and an electrode pad 52 is formed on the excitation electrode 51. When an AC voltage is applied between the comb-shaped electrodes 50 and 51 via the electrode pads 52 and 18, an electrostatic attraction is generated, and the mass displacement support base 24 is excited, and the vibration of the mass displacement support base 24 is reduced. The beam is transmitted to the mass unit 1 via the mass displacement supporting beams 22 and 23, and the mass unit 1 vibrates in the excitation direction in the vertical direction in FIG.

The mass displacement support base 25 shown in FIG.
At positions facing the comb-shaped electrodes 61 and 64, respectively.
A pair of comb-shaped detection electrodes 60 and 63 for detecting the amplitude of excitation of the mass portion 1 are arranged, and at least the bases of these electrodes are fixedly supported on the substrate. Electrode pads 62, 65 are connected to the comb-shaped detection electrodes 60, 63, respectively, and the mass section 1 is excited by the mass displacement support bases 2, via the mass displacement support beams 20, 21.
5, the comb-shaped electrodes 61, 64,
The capacitance between the comb-shaped detection electrodes 60 and 63 changes.
Therefore, the excitation amplitude in the mass section 1 is detected based on the capacitance change. In the first embodiment, in order to reduce the influence of noise, a differential output of a change in capacitance between the electrodes 63 and 64 and a change in capacitance between the electrodes 61 and 60 are obtained. Measurement is possible.

In FIG. 1, parallel plate-shaped extending electrodes 31 and 41 are formed to extend on the left and right side surfaces of the mass portion 1. At the positions facing the extended electrodes 31 and 41, respectively, the mass portion 1 due to the Coriolis force generated by the angular velocity with the rotation axis in the direction perpendicular to the paper of FIG.
Capacitance detecting electrode 3 for detecting the displacement of the right and left in FIG.
0, 32, and a control electrode 40 for controlling the displacement of the mass 1;
42 are arranged and fixed to the substrate, respectively.

Here, when the mass portion 1 is displaced in the left-right direction in FIG. 1 by the Coriolis force based on the angular velocity, the capacitance between the capacitance detection electrodes 30 and 32 and the extension electrode 31 is thereby reduced. Change. On the other hand, between the control electrode 40 and the extension electrode 41, and the control electrode 42,
An AC voltage is applied from the outside to the extension electrode 41 via the electrode pads 43 and 46, and the electrodes 30 and 3 on the capacitance detection side are applied.
Control is performed such that the displacement of the mass portion 1 detected by the first, second, and 31 is zero. Then, the displacement amount of the mass portion 1 is calculated based on the control amount required to make the displacement of the mass portion 1 zero.

In the first embodiment, the capacitance detecting electrodes 30, 3
2 are provided in a pair, between the electrodes 30, 31 and 31,
By measuring the differential output of the capacitance between the 32 and detecting the displacement of the mass unit 1 in the left-right direction, the measurement accuracy is improved. Further, a pair of control electrodes (electrode 4
0, 42), and by controlling them,
The control accuracy has been improved, contributing to further improvement in measurement accuracy.

By the way, if the applied angular velocity is small, the amplitude in the detection direction caused by the Coriolis force is also small. Therefore, the change in the capacitance of the capacitance detection electrodes 30 and 32 provided for measuring such a small change in amplitude is small, and it is not easy to measure such a small change in capacitance.

Therefore, in the first embodiment, in order to increase the change in capacitance at the same amplitude, the number n of plate electrodes, ie, the number of comb teeth, arranged in parallel in a direction that does not hinder the excitation amplitude is increased. I have. FIG. 3 is an enlarged view of the configuration of the comb-shaped capacitance detecting electrodes 30 and 32 of FIG. 1 and the comb-shaped extending electrode 31 opposed thereto.
In the example of 2 and the extension electrode 31 facing each other, the number of comb teeth is 3 respectively. If the number of comb teeth is increased by n times, the amount of change in capacitance is also increased by n times, so that amplitude measurement can be facilitated.

(Manufacturing method) The above angular velocity sensor 500
Can be manufactured by a process as shown in FIG. First, in the angular velocity sensor 500, FIG.
As shown in (a), the material of the substrate 20 is not particularly limited.
0, for example, on a silicon substrate or a substrate such as ceramic or glass, an insulating film such as a thin oxide film 2 (eg, Si
Through O ₂ ), a film 3 made of an elastic material (for example, single crystal or polycrystal) is formed. The elastic material film 3 may be a metal such as nickel or any other elastic material. However, since these films 3 are also used as electrodes for detecting the magnitude of the amplitude of the vibrating body as a change in capacitance, for example, when a silicon material is used, impurities such as phosphorus and boron are doped and diffused. It is preferable to reduce the resistivity.

After the formation of the elastic material film 3, a conductive film 6 for forming an electrode is formed on the elastic material film 3 as shown in FIG. It is patterned into a desired shape by the method described above.

Next, as shown in FIG. 4C, a mask pattern 7 using a resist or the like is formed, and using this mask pattern 7 as a mask, an elastic material is formed by a dry etching technique or an anisotropic wet etching technique. The film 3 is etched and patterned into a desired shape.

Thereafter, each beam and the oxide film 2 under the elastic material film 3 constituting the mass portion 1 are selectively removed by a sacrificial layer etching technique or the like, and FIG. The structure shown in FIG.

Incidentally, in the angular velocity sensor 500,
At the center thereof, a flat plate-shaped mass portion 1 functioning as an inertial mass is formed. And this mass part 1
The oxide film 2 must be selectively removed in the region where the mass portion 1 is formed. As a method for creating such a configuration, the above-described sacrificial layer etching technique is generally used. This sacrifice layer etching utilizes a phenomenon that when the substrate is immersed in a hydrofluoric acid solution, the vibrating portion formed of silicon such as the mass portion 1 remains as it is, and only the silicon oxide portion is eroded by hydrofluoric acid. Therefore, the flat plate-shaped mass portion 1
In (2), a large number of holes are formed in the silicon surface in order to allow hydrofluoric acid to efficiently penetrate into silicon oxide under the silicon (elastic material film 3). Here, there is an optimum value for the size of this hole. If it is too small, hydrofluoric acid will not pass easily,
If it is too large, it will not serve as a mass. Therefore, it is considered appropriate to make the thickness of the mass portion 1 and the diameter of the hole approximately the same.

(Operation) The operation of the angular velocity sensor 500 will be described below. First, the vibration system in the excitation direction will be described.

In the present sensor, the sensor sensitivity to the angular velocity input is proportional to the excitation amplitude. Therefore, in order to obtain high sensitivity, a structure convenient for increasing the excitation amplitude is preferable. For example, if a straight beam such as the beams 20, 21, 22, and 23 in FIG. 1 is used for the excitation amplitude, the beam is stretched in the longitudinal direction at a large amplitude, and a tensile stress is generated in the beam. I do. For this reason, the spring constant of the beam increases, and the relationship between the displacement and the restoring force due to the beam becomes non-linear. That is, as the excitation amplitude increases, the resonance frequency in the excitation direction increases and the sensor characteristics change.

Therefore, in an excitation vibration system having a large amplitude, it is preferable to use not a straight beam but a folded beam as in the first embodiment.
Because, in such a folded type beam, the beam length does not change even at the time of large amplitude unlike the straight type beam due to the difference in the fixing method that supports the beam, and the spring constant is constant even at the time of large amplitude, This is because the sensor characteristics do not change.

The folded beam of the present embodiment has beam members 11, 13, 15 paired with beam members 10, 12, 14, 16 having one ends connected to anchor portions 90, 91, 92, 93, respectively. , 17 have the same length in the left-right direction of FIG. The ends opposite to the ends connected to the respective anchor portions are connected by connecting portions 80 and 81. When an excitation force is applied to the mass displacement support base 24 by the excitation electrode 51, the mass displacement support base 24 vibrates, and at the same time, the beam members 15, 17
Also vibrate in the excitation direction in response to this. This beam body 1
Due to the vibrations of the beam members 5 and 17, the vibrations are also transmitted to the beam members 14 and 16 paired with the beam members 15 and 17 via the connecting portions 80 and 81, and the beam members 15 and 14 and the beam members 17 and 16 Vibrate similarly.

This vibration is transmitted to the beam members 10 and 11 and the beam members 12 and 13 disposed on the excitation detection electrodes 61 and 63 via the connecting portions 80 and 81, and these also vibrate similarly. In this manner, the mass 1 connected to the mass displacement support bases 24 and 25 via the mass displacement support beams 20, 21, 22 and 23 vibrates vertically in FIG. 1.

The mass excitation support beam is not necessarily limited to a folded beam but may be a straight beam. When a straight beam is used, anchor portions are provided in the left and right directions of the mass displacement support bases 24 and 25 in FIG. 1, and straight beams extending straight from the mass displacement support bases 24 and 25 toward the anchor portions. Is provided. When the straight beam is used, when the amplitude of the mass portion 1 in the excitation direction is large as described above, the beam is supported by the mass portion 1 although the characteristics are slightly inferior to those of the folded beam. The effect of being able to be separated depending on the direction and reliably preventing the leakage vibration of the beam from being generated in the Coriolis force detection direction can be obtained as in the case of the folded type beam.

Next, a description will be given of a vibration system in the direction in which the Coriolis force is detected. In the first embodiment, the detection direction includes:
Unlike the excitation direction, the straight beam (2
0, 21, 22, 23). In a straight beam, the beam is supported at both ends, and the beam is straight. For this reason, the pins are pulled from both sides, so that the manufacture is easy and the support of the mass portion 1 is reliable. If the displacement of the straight beam is large, the above-mentioned disadvantage occurs.However, since the Coriolis force generated by the application of angular velocity on the detection side is small, and the tensile stress generated inside the beam amplitude is negligibly small, the structure is simple and the manufacturing is simple A straight beam having an advantage in improving the yield at the time is suitable as a mass displacement supporting beam.

Next, the operation of the excitation amplitude control mechanism will be described. Since the vibration in the excitation direction is in a resonance state, the amplitude is greatly amplified by the structurally-induced vibration Q (Quality Factor) value. However, it is conceivable that the vibration Q value changes due to a change in the pressure inside the sensor package or a deterioration of the fixed state of the vibrator during a temperature or a long period of time. As a result, the excitation amplitude changes and the sensitivity varies. Therefore, a mechanism for compensating for the change in the Q value is required. In the first embodiment, the excitation amplitude of the mass section 1 is measured by a change in capacitance between the electrodes 61 and 64 detected by the excitation amplitude detection electrodes 60 and 63, and the excitation is measured so that the amplitude becomes constant. The AC voltage applied between the side electrodes 50 and 51 is controlled. As a result, it is possible to obtain a constant sensitivity to the angular velocity regardless of a change in the Q value.

Next, a feedback technique for the vibration of the mass section 1 in the Coriolis force detection direction will be described. As described above, the mass section 1 is excited by the electrodes 50 and 51 on the excitation side. When an angular velocity having a rotation axis in the direction perpendicular to the paper surface of FIG. 1 is given to the mass unit 1 thus excited, a Coriolis force Fc is generated in the left-right direction (detection direction) of FIG. Due to this Coriolis force, the mass section 1 starts to vibrate in a detection direction perpendicular to the excitation direction.

The vibration of the mass 1 in the detection direction causes
The capacitance between the capacitance detection electrodes 30 and 32 and the extension electrode 31 changes. Therefore, information such as the position, velocity, acceleration, and angular velocity of the mass section 1 can be detected from this change. Further, in the first embodiment, the calculated control amount is applied to the control electrodes 40 and 42 as an AC voltage so as to cancel the movement of the mass unit 1. For this reason, a feedback loop is formed, and the movement of the mass unit 1 is restricted near the zero point. In the first embodiment, the control using the so-called null method as described above is performed by using the control electrode, whereby the linearity, the frequency characteristic, the response, the sensitivity, the temperature characteristic, and the like of the sensor are performed. Has been improved.

As described above, in the first embodiment, the mass excitation support beam for supporting the mass portion so as to be able to vibrate in the excitation direction as described above, and the displacement of the mass portion in the Coriolis force generation direction are allowed. And a beam for supporting the mass displacement direction for supporting the beam. Therefore, when the mass excitation support beam is vibrated in the excitation direction, even if a leak vibration component in the beam thickness direction is generated in the beam, the direction of the leak vibration component does not match the direction in which the Coriolis force is detected. ,
The sensor output of the resonance type angular velocity sensor 500 is hardly affected by the beam shape. Therefore, a sensor with high detection accuracy can be obtained irrespective of the variation in the manufacturing process that causes the beam shape to vary.

Also, by separating the beams, it is easy to adjust the tensile stress of each beam individually, for example, and to obtain the optimum Δf.

Further, by supporting the mass portion with separate beams in two orthogonal directions, it is possible to make the excitation direction and the Coriolis force detection direction the same plane direction. Therefore, the manufacturing process as the angular velocity sensor can be simplified.

In the first embodiment, the mass portion 1 is supported by two straight beams 20, 21, 22, and 23 from both sides of the mass portion 1 in the vertical direction. However, the mass portion 1 may be supported by one straight beam from the top and bottom. However, as shown in FIG.
If the mass portion 1 is supported by the mass portions 1, 22, 23, the mass portion 1 is less likely to be distorted in the planar direction, and the support is reliable.

In the first embodiment, the mass 1
The excitation direction and the Coriolis force detection direction are within the plane of the plate-shaped mass portion, but are not necessarily limited to this. As shown in FIG. The direction may be used. In FIG. 5, the mass excitation support beam supports the mass portion through the mass displacement support base from a direction perpendicular to the plane direction of the mass portion (right and left direction in the diagram), and moves the mass portion in the plane direction (vertical direction in the diagram). ). The mass displacement supporting beam supports the mass portion from its excitation direction so as to allow displacement of the mass portion due to Coriolis force. Even in such a case, since the mass excitation support beam and the mass displacement support beam are separated from each other, the leakage vibration due to the vibration of the mass excitation support beam in the mass excitation direction should not appear in the Coriolis force detection direction. Can be.

[Second Embodiment] Next, a second embodiment will be described. In the second embodiment, either the excitation frequency of the mass unit 1 or the vibration frequency in the Coriolis force detection direction can be selectively adjusted, and the frequency difference Δf can be corrected to an appropriate value. FIG. 6 shows the configuration of the angular velocity sensor 501 according to the second embodiment.

In the second embodiment, as in the first embodiment, the mass displacement support beam and the mass excitation support beam are separated. In the second embodiment, the frequency is adjusted by utilizing the characteristics of these beams.

The adjustment may be made in only one of the excitation direction and the detection direction. However, simultaneous changes in the frequencies of both directions must be avoided because the adjustment becomes complicated. In other words, when adjusting the frequency, it is important whether the resonance frequencies in the excitation direction and the detection direction can be changed independently. In order to add a frequency adjustment mechanism to this angular velocity sensor, matching between the adjustment mechanism and the sensor structure is most important.

As a method of adjusting Δf, there are two methods, an electric adjustment method using electrostatic force or the like, and a mechanical adjustment method using laser trimming or the like. In the second embodiment, an electrical adjustment method is used. The principle of the electric adjustment method in the second embodiment is to variably adjust the resonance frequency by changing the spring constant of the beam by pulling or compressing the beam in the longitudinal direction by electrostatic attraction. An advantage of the electrical adjustment is that the adjustment of Δf can be automated. Such Δf
There are three objectives in automating the adjustment of the following.

First, the adjustment process after assembling the sensor is simplified. In other words, the adjustment after the sensor is assembled in the package becomes easy, so that the adjustment cost can be reduced. There is no extra cost if the electric circuit required for the adjustment is made simultaneously with other electric circuits.

Second, it can contribute to long-term stability of the sensor. Generally, a sensor mounted on a vehicle or the like is used for a long period of time. In such a situation, the sensor characteristics may change due to changes in the mechanical characteristics of the vibrator or changes in the pressure inside the package. Therefore, the sensor characteristics are constantly monitored, and the device operates in an optimal state for a longer period of time. It is preferable to automatically adjust the sensor characteristics as described above.

Third is the improvement of the temperature characteristics of the sensor. For vehicle control, the operating temperature of the sensor is -30 degrees to +85
Degree and wide. If used under such severe conditions, the sensor characteristics may change with temperature. By the electric adjustment, this characteristic change can be automatically suppressed, and the temperature characteristic of the sensor can be improved.

Of the above adjustments, it is impossible to adjust the angular velocity sensor before shipment in order to achieve the second and third objects. This is because the environment that causes these changes in sensor characteristics depends on the sensor being shipped. Therefore, in order to adjust the resonance frequency in the excitation or detection direction independently, it is one of preferable solutions to separate and excite the respective vibration systems for excitation and detection. This means that the beam supporting the vibrating mass 1 is separated and independent for excitation and detection. Furthermore, it is necessary that the mass unit 1 can freely move to both excitation and detection. This is because the mass unit 1 must always be excited, but when an angular velocity is applied, it must start to vibrate at right angles to the exciting direction.
In the second embodiment, similarly to the first embodiment, a structure with good adjustment efficiency is obtained by skillfully separating and independent the beam used in the excitation direction and the beam used in the detection direction.

The angular velocity sensor 501 shown in FIG. 6 adjusts the excitation frequency of the two frequencies by applying a tensile stress or a compressive stress to the mass excitation support beam.

More specifically, in FIG. 6, the mass excitation support beam is composed of a folded beam, and the beam members 10, 11,
Comb-shaped frequency adjusting extension electrodes 71, 73, 75, 77 are formed on side surfaces of connecting portions 80, 81 connecting one ends of 12, 13, 14, 15, 16, 17. Comb-shaped frequency adjusting electrodes 70, 72, 7 are provided at positions facing the respective comb-shaped extending electrodes 71, 73, 75, 77 so as to mesh with these extending electrodes 71, 73, 75, 77.
4, 76 are arranged respectively. Note that electrode pads 100, 101, 102, and 103 made of a conductive material are respectively formed on the adjustment electrodes 70, 72, 74, and 76.

Here, these frequency adjusting electrodes 70, 7
2, 74, 76, 77 and the corresponding extension electrodes 71, 7
When a DC voltage is applied between the beam members 3, 75, and 77, and an electrostatic attraction is applied between them, the beam members 10 and 11, 12, and 13, 14, 15, 16, and 17 move in the direction of the frequency adjustment electrode. Pulled by. Therefore, each beam body 10, 1
Tensile stresses are generated at 1, 12, 13, 14, 15, 16, and 17, respectively, and the resonance frequency of the beam body in the excitation direction, that is, the resonance frequency of the mass section 1 in the excitation direction increases. If an electrostatic repulsive force is applied between them, each of the beam members 10, 11, 12, 13, 14, 15, 1, 1
Compressive stress is generated in 6, 17 and the resonance frequency (excitation frequency of the mass section 1) of the beam body is lowered.

Generally, when a DC voltage is applied between the frequency adjusting electrode and the electrode facing the frequency adjusting electrode, an electrostatic attractive force acts between the electrodes and a tensile stress is generated in each beam member. 70, 71, 72, 73, 74, 75, 7
By changing the positions of the arrangements 6 and 77, it is also possible to apply an electrostatic attraction between them to generate a compressive stress in the beam body. This is because, for example, in the configuration shown in FIG. 6, the extension electrodes 71, 73
By forming a comb-shaped extending electrode similar to that described above, a frequency adjusting electrode is disposed in opposition to the electrode, and the center portion is pulled outward in the left and right directions in the drawing to form beam members 10, 11, 12, 13,.
It can be achieved by generating a compressive stress at 14, 15, 16, and 17. The excitation resonance frequency can be reduced by such a compressive stress.

In the frequency adjusting mechanism using a comb-shaped electrode as shown in FIG. 6, the frequency adjusting electrodes 70, 72, 74, 76 are arranged with a large number of comb teeth in a small area so as to face the comb-shaped electrode. And the beam members 10, 11, 1
2, 13, 14, 15, 16, and 17 make it possible to efficiently apply a tensile stress or a compressive stress.
In the configuration of FIG. 6, the electrodes 70, 71, 72, 73,
74, 75, 76, 77 are beam members 10, 11, 1
It is located near the extension of 2, 13, 14, 15, 16 and 17. This is to ensure that a tensile stress is generated in the beam.

By providing such a frequency adjusting mechanism, in the second embodiment, the beam members 10, 11,
12, 13, 14, 15, 16, 17 can be subjected to a desired tensile or compressive stress. The tensile or compressive stress on the beam does not affect the beams 20, 21, 22, and 23, which are the mass displacement support beams. Therefore, as a result, only the resonance frequency in the excitation direction can be freely adjusted.

(Circuit Configuration and Operation) The driving of the angular velocity sensor 501 of the second embodiment and the adjustment of the resonance frequency in each direction are performed using, for example, a circuit configuration as shown in FIG.

[Driving of Angular Velocity Sensor 501] When driving the angular velocity sensor, the control unit 191 sets SW1 to the displacement control circuit 182 and SW2 to the self-excitation circuit 176.

An AC voltage supplied from the self-exciting circuit 176 through the amplitude control circuit 177 and the AC amplifier 179 is applied to the excitation electrode 51, whereby the mass section 1 vibrates in the excitation direction, and the vibration is excited. The capacitance is detected by the capacitance detection circuit 170 via the amplitude detection electrodes 60 and 63. The detection output from the capacitance detection circuit 170 is supplied to the self-exciting circuit 176,
The self-exciting circuit 176 generates a self-exciting signal based on the detected output, and the amplitude control circuit 177 controls the amplitude of the vibration to be constant based on the exciting control signal. With these configurations, a feedback loop is formed such that the mass unit 1 always vibrates in the excitation direction at an appropriate frequency and with an appropriate amplitude.

When the mass 1 is displaced and vibrated in the detection direction by Coriolis force due to angular velocity while the mass 1 is vibrating in the excitation direction, the vibration of the mass 1 in the detection direction is The change is transmitted to the capacitance detection circuit 173 as a capacitance change via the detection electrodes 30 and 32, and the change is detected.

The detection output from the capacitance detection circuit 173 is supplied to a displacement control circuit 182.
Based on this detection output, the AC power supply 181 is controlled so that the displacement of the mass section 1 becomes zero, and a corresponding control voltage is applied to the control electrodes 40 and 42 via the AC amplifier 180.

The displacement control circuit 182 determines the Coriolis force acting on the mass 1 based on a control signal required to make the displacement of the mass 1 zero, and calculates a corresponding angular velocity. Then, the calculated angular velocity is displayed on the angular velocity display unit 19.
0, and a desired display is performed.

"Adjustment of Frequency" First, the control unit 191 switches SW1 to the self-exciting circuit 192 and
W2 is set on the self-exciting circuit 176 side.

Next, the control electrodes 40 and 42 and the extension electrode 41
, An AC voltage is applied from the self-exciting circuit 192 via the AC amplifier 180. The vibration of the mass section 1 in the detection direction is transmitted to the capacitance detection circuit 173 via the capacitance detection electrodes 33 and 36 as a capacitance change. The capacitance detection circuit 173 generates a detection output corresponding to the change in the capacitance, and the detection output is supplied to the frequency control circuit 174.

Next, an excitation frequency in the excitation direction separated by Δf from the resonance frequency in the detection direction of the mass unit 1 obtained by the above driving is obtained and set. On the other hand, the self-excited oscillation circuit 1 oscillates, and this is supplied to the excitation electrode 50 via the AC amplifier 179, and the mass section 1 oscillates in the excitation direction. The vibration of the mass section 1 in the excitation direction is detected by the capacitance detection circuit 170, and the mass 1 oscillates in the excitation direction with its resonance frequency. The detection output is output from the frequency control circuit 174.
Supplied to

The frequency control circuit 174 determines the difference between the optimum frequency difference Δf and the actual frequency difference Δf based on each detection output from the capacitance detection circuit 173 in the detection direction and the capacitance detection circuit 170 in the excitation direction. The DC power supply 175 is controlled according to the deviation. The DC voltage from the DC power supply 175 is applied to each of the frequency adjusting electrodes 70, 72, 74, 76.
When applied to the beam body, a predetermined stress acts on the beam members 10 to 17, thereby changing the vibration frequency in the excitation direction.
The frequency difference Δf between the vibration frequency in the detection direction and the vibration frequency in the excitation direction changes.

As described above, the actual frequency difference Δf is detected, and a desired voltage is applied to the frequency adjusting electrodes 70, 72, 74, and 76 so that the actual frequency difference Δf matches the optimum frequency difference Δf. Adjust the vibration frequency selectively.
These circuits automatically perform this adjustment operation, so that the angular velocity sensor 501 always has the optimum Δf.
, And high reliability can be maintained for a long period of time.

The following method may be used as the frequency adjustment method. When the mass is vibrated in the excitation direction, mechanical coupling occurs between the vibration in the excitation direction and the vibration in the detection direction due to manufacturing errors such as the beam cross-sectional shape, even if the angular velocity is not given, and the excitation vibration is generated. In some cases, it leaks to the detection side. Therefore, in such a case, the leaked vibration component is positively used to adjust Δf. There are two approaches for this.

As a first method, first, the control unit 192 sets SW2 on the self-exciting circuit 176 side. The AC voltage generated by the self-excitation circuit 176 is supplied to the excitation electrode 52 via an amplitude control circuit 177 and an AC amplifier 179.
To excite the mass unit 1 in the excitation direction. The frequency at this time is the natural frequency in the excitation direction. Further, the vibration in the detection direction caused by the coupling is monitored by the capacitance detection electrodes 30, 31, 32 while the frequency adjustment electrode 7 is being monitored.
By sweeping the voltage applied to 0, 72, 74, 76, the resonance characteristics in the detection direction can be known. The resonance frequency in the detection direction is obtained from the peak value of the amplitude obtained here. Therefore, the frequency adjusting electrodes 70 and 7 are set so that the desired Δf is obtained.
The voltage applied to 2, 74, 76 is determined.

As a second method, the control unit 192 sets SW2 to the oscillator 178 side. The AC voltage generated by the oscillator 178 is applied to the excitation electrode 52 via the AC amplifier 179, and excites the mass unit 1 in the excitation direction. The excitation frequency at this time is not necessarily the natural frequency in the excitation direction. Therefore, the resonance characteristic in the detection direction can be known by sweeping the oscillation frequency of the oscillator 178 while monitoring the vibration in the detection direction by the capacitance detection circuit 173. Also, the resonance frequency in the excitation direction can be known from the output of the capacitance detection circuit 170. So the desired Δ
f, the frequency adjustment electrodes 70, 72, 74, 76
Is determined.

[Embodiment 3] FIG. 8 shows an angular velocity sensor 5 having an electrical frequency adjustment mechanism different from the mechanism shown in FIG.
02 is shown. In the configuration shown in FIG. 8, the connecting portions 81 and 80 in FIG. 6 extend in the vertical direction in the figure, in this case, extend in the excitation direction of the mass portion 1 to form the frame portions 82 and 83. Then, opposed electrodes 84 and 85 for frequency adjustment are provided at a small distance from the frame portions 82 and 83. Counter electrode 8
An electrode pad 1 is provided at the center of each of the excitation directions 4 and 85.
04 and 105 are formed.
By applying a DC voltage between both the beam 85 and the frame portions 82 and 83, the beam members 10, 11, 12, 13, 1
4, 15, 16 and 17 are stressed. FIG. 9 shows the configuration shown in FIG.
The state of each part when the center part in the excitation direction of the frame parts 82 and 83 is pulled outward is shown. FIG. 9A shows a state where no voltage is applied between the counter electrodes 84 and 85 and the frame portions 82 and 83, and FIG.
Indicates a state in which a tensile force due to electrostatic attraction is acting between the two. When an outward pulling force is applied to the central portions of the frame portions 82 and 83, as shown in FIG. 9B, the beam members 10, 11, 12, 13, 14, 15, and
Compressive stress is generated in the sections 16 and 17, and the resonance frequency of the mass section 1 in the excitation direction changes (in this case, the resonance frequency decreases) due to such a configuration. In the configuration shown in FIG. 8, a comb-shaped electrode as shown in FIG.
The configuration provided in the center region in the excitation direction of 81 can also be used.

[Embodiment 4] Next, an angular velocity sensor 503 provided with an electric frequency adjusting mechanism different from those of the above-described Embodiments 2 and 3 will be described with reference to FIG. In FIG. 10, a frame portion 82 extended in the excitation direction of the mass portion 1,
The three frequency-adjusting opposing electrodes 120, 121, 122, 1
23, 124 and 125 are provided. Here electrode 12
When a DC voltage is applied between the frame members 82, 83 and the frame portions 82, 83 to give electrostatic attraction, the beam members 10, 11, 12, 13, 14, 15, 1, 1
Since a tensile stress is generated in each of 6, 6 and 17, the resonance frequency in the excitation direction increases. Conversely, when a DC voltage is applied between the electrodes 121 and 124 and the frame portions 82 and 83 to apply electrostatic attraction, the beam 1
Compressive stress is generated at 0, 11, 12, 13, 14, 15, 16, 17 and the resonance frequency in the excitation direction decreases.

The configuration using the frame portions 82 and 83 and the counter electrode for frequency adjustment as shown in FIG. 8 of the third embodiment and FIG. 10 of the fourth embodiment has a simple configuration and a high yield in the manufacturing process. There is a merit that can be improved. In the configuration of the fourth embodiment, the excitation resonance frequency can be further increased or decreased depending on the combination of the electrodes used.

FIG. 11 shows a case where the comb electrode system shown in FIG. 6 according to the second embodiment and the projecting electrode system shown in FIG. 10 according to the fourth embodiment are used (for example, the counter electrode 12 shown in FIG. 10).
5 shows changes in the applied voltage between the electrodes and the resonance frequency when only 0, 122, 123, and 125 are used.
In either method, as the voltage applied between the electrodes is increased, the resonance frequency in the drive side, that is, the excitation direction of the mass portion can be increased. And
According to these electrical adjustment methods, fine adjustment of the resonance frequency can be performed.

[Fifth Embodiment] The fifth embodiment differs from the second to fourth embodiments in that a mechanism for adjusting the frequency by a mechanical adjustment method is provided.

In such a mechanical adjustment method, although the adjustment efficiency is high, the mechanical adjustment is possible only in the factory.
Further, since fine adjustment is difficult, it is particularly effective as a rough adjustment up to a range where an electrical adjustment method can be performed.

In the fifth embodiment, a method of changing the rigidity of the beam among the mechanical adjustments is employed. More specifically, as shown in FIGS. 12A and 12B, a ladder-like pattern 140 is formed near a portion where the stress due to deformation is large, for example, near the fixing portion of the beam body 16 of the folded beam, which is a mass excitation support beam. Are added to constitute the angular velocity sensor 504. In addition, this ladder-like pattern 140
The other end of the beam body 16 and the beam bodies 11, 12, 13, 1
It may be provided at any one of 4, 15, and 17 ends. Then, the patterns are burned off one by one by a laser trimming device according to a desired frequency change width. The change width of the resonance frequency can be calculated in advance, and a desired change width can be obtained by laser trimming.

FIG. 13 shows the relationship between the ladder pattern removal ratio and the change in the resonance frequency. FIG.
As is clear from FIG. 7, as the removal ratio of the ladder pattern increases, the resonance frequency on the driving side indicated by ●, that is, the resonance direction in the mass part excitation direction decreases, and the change is relatively large. On the other hand, even if the ladder pattern is removed, the resonance frequency on the detection side indicated by 、, that is, the direction of detection of the Coriolis force does not change.

From the above, it is apparent that the fifth embodiment makes it possible to selectively adjust only one resonance frequency (here, the resonance frequency in the excitation direction). Further, in the configuration shown in FIG. 12, since the ladder pattern to be cut is away from the main body of the beam body, the risk of erroneously cutting the beam is reduced.

[Embodiment 6] In Embodiment 6, the mechanical adjustment is performed as in Embodiment 5 described above. The difference from Embodiment 5 is that the connecting portions 80 and 81 shown in FIG. Adjusting the mass. The thing to note here is that
Since the mass 1 at the center is involved in the resonance frequency in both the excitation direction and the excitation direction, the mass 1 itself cannot be used as an adjustment point.

Therefore, in the sixth embodiment, a metal material such as gold is previously added to the connecting portions 80 and 81 by vapor deposition or the like. This is because the mass of the connecting portions 80 and 81 is related only to the resonance frequency in the excitation direction, and can change only the excitation frequency. At this time, the resonance frequency in the detection direction hardly changes. FIG. 14 shows the state of the change in the resonance frequency with respect to the removal ratio of gold, in which gold (Au) is deposited as a metal material on the connecting portions 20 and 81 in advance.
Techniques such as laser irradiation and etching are conceivable for gold removal. For frequency adjustment, the addition ratio of the metal material may be adjusted. As is clear from FIG. 14, according to the configuration of the present embodiment, it is possible to change only the resonance frequency in the excitation direction without changing the resonance frequency on the Coriolis force detection side.

By the way, in the sensor which has completed the manufacturing process similar to that of FIG. 4 of the first embodiment, the resonance frequency is measured in each of the excitation direction and the detection direction. If the frequency difference Δf is not appropriate based on the measurement result of this value, it is preferable to perform a mechanical rough adjustment as described in the fifth and sixth embodiments. If Δf approaches the target value due to the mechanical coarse adjustment, the sensor is packaged (for example, vacuum packaging). However, if Δf is originally close to the target value, the mechanical coarse adjustment is unnecessary. After that, the electrical frequency adjustment mechanism described in the second to fourth embodiments and the like further causes the circuit configuration (FIG. 7) shown in the second embodiment to further reduce Δ 共振 due to a shift in the resonance frequency that occurs later.
f is always adjusted to an appropriate value.

[Embodiment 7] In the angular velocity sensor as described above, when a horizontal acceleration is applied to the substrate, if the frequency component of the acceleration is close to the frequency component of the angular velocity, it is difficult to distinguish between the angular velocity and the acceleration. May be gone. In order to solve this problem, in the seventh embodiment, for example, two angular velocity sensors 501 as shown in the second embodiment are used via the connecting portion 116 as shown in FIG. Installed in Further, the respective mass portions 1 are excited with their excitation vibrations shifted by 180 ° from each other. The connecting portion 116 may be fixed or not fixed to the substrate.

When the phase of the excitation vibration is shifted by 180 ° as described above, as a result, the Coriolis force generated by the angular velocity acts on the two mass portions 1 in opposite directions.
Therefore, the sensor output for the applied angular velocity is also 180
°. On the other hand, when acceleration is applied, the two mass portions 1 are displaced in the same direction by the acceleration. Therefore, by taking the difference between the outputs of these two angular velocity sensors 501, it becomes possible to separate angular velocity and acceleration very easily.

Also, since the two are vibrated in opposite phases, the center of gravity of the two sensors is always immobile like a tuning fork, so that the energy of the vibration hardly leaks to the outside. As a result, the vibration Q value as a vibrator is improved, and a highly sensitive sensor can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view showing an angular velocity sensor according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional view of the angular velocity sensor 500 of FIG. 1 taken along line AA.

FIG. 3 is a diagram illustrating a configuration near a capacitance detection electrode in FIG. 1;

FIG. 4 is a diagram showing a manufacturing process of the angular velocity sensor 500 of FIG.

FIG. 5 is a diagram showing another configuration of the angular velocity sensor according to the first embodiment.

FIG. 6 is a plan view showing an angular velocity sensor according to Embodiment 2 of the present invention.

7 is a diagram showing a circuit configuration for controlling the angular velocity sensor 501 of FIG.

FIG. 8 is a plan view showing an angular velocity sensor according to Embodiment 3 of the present invention.

FIG. 9 is a conceptual diagram showing the operation of the angular velocity sensor 502 in FIG.

FIG. 10 is a plan view showing an angular velocity sensor according to Embodiment 4 of the present invention.

FIG. 11 is a diagram showing frequency adjustment characteristics of angular velocity sensors 501 and 503.

FIG. 12 is a diagram showing an angular velocity sensor having a ladder pattern according to Embodiment 5 of the present invention.

FIG. 13 is a diagram illustrating frequency adjustment characteristics of the angular velocity sensor 504 of FIG.

FIG. 14 is a diagram illustrating frequency adjustment characteristics of an angular velocity sensor according to Embodiment 6 of the present invention.

FIG. 15 is a plan view showing an angular velocity sensor according to a seventh embodiment of the present invention.

FIG. 16 is a diagram showing a conventional angular velocity sensor.

FIG. 17 is a diagram illustrating a difference Δf between two resonance frequencies.

[Explanation of symbols]

1 Mass section, 10, 11, 12, 13, 14, 15, 1
6,17 beam body, 20,21,22,23 mass displacement direction support beam, 24,25 mass displacement support base, 3
0,32 capacitance detection electrode, 31,41 extension electrode 3
3,36,43,46,52,62,65,100,1
01, 102, 103 electrode pad, 40, 42 control electrode, 51 excitation electrode, 60, 63 excitation amplitude detection electrode, 70, 72, 74, 76 frequency adjustment electrode, 71,
73, 75, 77 Extension electrodes for frequency adjustment, 80, 81
Connecting part, 82, 83 Frame part, 84, 85, 120, 1
21, 122, 123, 124, 125 Counter electrodes for frequency adjustment, 90, 91, 92, 93 Anchor part, 14
0 Ladder pattern.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tokuo Fujitsuka 41-1, Oku-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. (56) References JP-A-8-159776 (JP, A) JP-A-5-312576 (JP, A) JP-A-6-123631 (JP, A) JP-A-6-281665 (JP, A) JP-A-7-120266 (JP, A) JP-A-6-249667 (JP, A) JP-A-5-333038 (JP, A) JP-A-4-242114 (JP, A) JP-A-8-54242 (JP, A) JP-A-7-218268 (JP, A) Japanese Unexamined Patent Publication No. Hei 8-2219795 (JP, A) Japanese Unexamined Patent Publication No. Hei 7-301535 (JP, A) Japanese Unexamined Patent Publication No. Hei 7-43166 (JP, A) JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01C 19/56 G01P 9/04

Claims (2)

(57) [Claims] 1. A mass section serving as an inertial mass is excited, and an angular velocity is detected based on a displacement of the mass section due to a Coriolis force generated in a direction orthogonal to both an exciting direction of the mass section and a rotation axis direction of an angular velocity sensor. A pair of mass displacement support bases arranged with the mass portion interposed therebetween in the excitation direction, and extending from the mass displacement support bases to the mass portions, respectively, and the mass is provided when Coriolis force is generated. A mass displacement direction support beam for supporting the portion to allow displacement in the Coriolis force generation direction, and prohibiting displacement of each of the mass displacement support bases in the Coriolis force generation direction, and via the mass displacement direction support beam. A beam that supports the mass displacement support base so as to allow the mass portion to vibrate in the excitation direction,
A mass excitation made of a folded beam that is folded back from the support position at an end extending in a direction perpendicular to the vibration direction of the mass displacement support base, extends from the folded portion toward the vicinity of the support position, and is fixed near the support position A support beam; excitation means for exciting the mass displacement support base; and displacement detection means for detecting displacement of the mass part.
And the folded excitation type beam constituting the mass excitation support beam
The beam extends in a direction perpendicular to the vibration direction of the mass displacement support base
At least two parallel beams of the same length
The two beam bodies are at one end thereof
The two beads are connected by a connecting part wider than the body.
The other end of the beam body is the mass displacement in one beam body.
Connected to the support base, the other beam body is fixed to the substrate
A resonance type angular velocity sensor characterized in that: 2. The resonance type angular velocity sensor according to claim 1,
Oite further resonant angular velocity sensor, characterized in that to adjust the stress applied to the mass excitation support beam comprises a frequency adjustment mechanism for adjusting the resonance frequency of the excitation direction of the mass portion.