JPH10153430A - Angular speed detecting device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely set resonance frequency to a specified value by setting the density of the atmosphere around an oscillator in a certain process substantially equal to the density of an inert gas in the other processes. SOLUTION: A metallized base 100 has a 4-layer structure, and circuit elements 111, 112 for performing excitation, detection of vibration, and angular speed operation are loaded on the reverse side of the first layer 101 which is the bottom layer. The lower end of a metallic lid 110 is fixed to the fourth layer 104 by a sealing resin over the whole circumference. Instead of this, the fixation may be performed by brazing. The space in which an oscillator 10 is housed is thus perfectly shielded from the outside. This internal space is filled with an inert gas having the same density as the atmosphere. As the inert gas, a gas mainly composed of relatively inexpensive nitrogen gas, to which argon gas and helium gas suitable for detecting gas leakage are mixed, is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity detecting device used for an automobile navigation system and attitude control, and more particularly to a vibration type angular velocity detecting device and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a vibration type angular velocity detecting device utilizing the fact that when a vibrating vibrator is rotated, a new vibration corresponding to the rotational angular velocity is generated in a direction perpendicular to the excitation vibration by Coriolis force. Are known. Some of such angular velocity detectors are further sealed in a vacuum atmosphere or an inert gas atmosphere so that the vibrator does not come into contact with the atmosphere. The purpose of sealing the vibrator is to prevent the detection accuracy from being reduced due to the condensation of water vapor in the air on the vibrator and the oxidization and corrosion of the vibrator by oxygen in the air.

On the other hand, the angular velocity detecting device generally adjusts the resonance frequency in a manufacturing process. In particular, in the case where a micro-oscillator such that one side of a prism-shaped vibrating piece end face of the vibrator is smaller than 0.5 mm is mounted, the resonance frequency is precisely adjusted because the sensitivity is lower than that of a large vibrator. There is a need. As an example of a method of adjusting the resonance frequency, there is a “method of adjusting the resonance frequency of the vibrator” described in JP-A-8-146029. This prior art is characterized in that the resonator grinding and the measurement of the resonance frequency by the laser assisted etching processing technique are performed in the same chamber.

[0004]

The resonance frequency is generally adjusted by adjusting the weight of the vibrator. The vibrator itself is ground or a metal film for trimming is previously deposited on the tip of the vibrator. There is a method of grinding this as appropriate. In any case, since these grinding steps are performed in the air, which is extremely effective for simplifying the process equipment and reducing the number of steps, the grinding steps are often actually performed in the air.

However, in the case of the angular velocity detecting device in which the vibrator is sealed in a vacuum atmosphere or an inert gas atmosphere as described above, the atmosphere of the vibrator when adjusting the resonance frequency is different from the sealing atmosphere. For this reason, the resonance frequency at the time of adjustment does not exactly match the resonance frequency after sealing, which hinders improvement in detection accuracy of the device.

[0006]

SUMMARY OF THE INVENTION A method of manufacturing an angular velocity detecting device according to the present invention is made to solve such a problem, and comprises a first step of adjusting a resonance frequency of an angular velocity detecting vibrator. And a second step of sealing the vibrator in an inert gas atmosphere.
The density of the inert gas in the process is substantially the same.

The resonance frequency is correlated with the density of the atmosphere in which the vibrator is placed, and varies by about ± 0.1% according to the density. According to the present invention, since the atmosphere density at the time of adjustment and the atmosphere density at the time of sealing match, the resonance frequency at the time of adjustment matches the resonance frequency after sealing. Therefore, if the resonance frequency is strictly adjusted, the detection accuracy of the angular velocity detecting device can be maximized.

It is desirable that the density of the atmosphere around the vibrator in the first step and the density of the inert gas in the second step be substantially equal to the atmospheric density. Since the resonance frequency adjustment in the first step is performed in the atmosphere, the equipment can be simplified and the operation can be facilitated.

The angular velocity detecting device according to the present invention is an angular velocity detecting device which excites a vibrator and detects an angular velocity of rotation from an amplitude of vibration based on Coriolis force generated with rotation of the vibrator. The element is sealed in an inert gas having substantially the same density as the atmospheric density.

According to this angular velocity detecting device, the resonance frequency matches the resonance frequency in the atmosphere before the vibrator is sealed. Therefore, when the resonance frequency adjustment before sealing the vibrator is performed in the easy-to-work atmosphere, high detection accuracy can be provided.

[0011]

FIG. 1A is a plan view showing a vibrator 10 in an embodiment of an angular velocity detecting device according to the present invention. In this figure, the left and right directions are set to the X axis, the right direction is set to the positive direction, the up and down direction is set to the Y axis, the upward direction is set to the positive direction, the direction perpendicular to the paper surface is set to the Z axis, and the front direction is set to the positive direction. The vibrator 10 includes a vibrator base 11 extending in the X-axis direction, first vibrating reeds 12 and 13 extending from the vibrator base 11 in the + Y direction, and a first vibrating reed from the vibrator base 11. A second vibrating piece for detection 14 and 15 extending coaxially with 12 and 13 in the -Y direction, a support rod 16 extending in a -Y direction from the vibrator base 11 between the second vibrating pieces 14 and 15; The fixing plate 17 provided at the end of the support rod 16 is integrally formed with a single crystal substrate of quartz.

Here, the crystal axis of quartz will be briefly described. Natural quartz is generally a columnar crystal, and the longitudinal central axis of the columnar crystal, that is, the <0001> crystal axis is Z
An axis or optical axis is defined, and a line passing through the Z axis and perpendicular to each surface of the columnar crystal is defined as a Y axis or a mechanical axis. A line passing through the Z axis and orthogonal to the vertical ridge line of the columnar crystal is defined as an X axis or an electric axis.

The single crystal substrate used in the vibrator 10 is a substrate called a Z plate, which is a single crystal substrate cut out in a plane perpendicular or substantially perpendicular to the Z axis. Therefore, in the present embodiment, the Z axis of the crystal orientation coincides with the above-described Z axis indicating the arrangement direction of the vibrator 10 in the drawing.
The X axis and the Y axis of the crystal are orthogonal to each other.
There are pairs, and one of the pairs coincides with the X-axis and the Y-axis indicating the arrangement direction of the transducer 10 on the drawing. The quartz used for the vibrator 10 is an artificial quartz, but its structure is the same as a natural quartz.

The first vibrating bars 12 and 13 have the same dimensions as each other, and are both used as vibrating bars for excitation in this embodiment. The second vibrating reeds 14 and 15 also have the same dimensions as each other, and are both used as vibrating reeds for detection.
The second vibrating bars 14 and 15 are connected to the first vibrating bars 12 and 1
3, the first vibrating bar 12,
13, the natural frequency f _{X1 in} the X direction and the second vibrating bars 14 and 15
Are different from each other in the natural frequency f _{X2 in} the X direction. Z
The natural frequencies of the first and second vibrating reeds are also different from each other, but the vibration in the Z direction is coupled because the first and second vibrating vibrates in a coupled manner. Has a natural frequency f _Z of. As for the vibration in the X direction, there is almost no coupled vibration since the transmission rate of the vibration between the first vibrating piece and the second vibrating piece is very low. As described above, the first vibrating piece and the second vibrating piece are not coupled with each other for the vibration in the X direction, and the first vibrating piece and the second vibrating piece are coupled with each other for the vibration in the Z direction. The entire structure 10 is integrally formed of a very thin quartz substrate, and the width of the vibrator base 11 in the Y direction is sufficiently large with respect to the thickness of the quartz substrate.
In the present embodiment, the values of the natural frequency f _{X1 of} the first vibrating bars 12 and 13 in the X direction and the coupled natural frequency f _Z are adjusted to be very close to each other.

Each vibrating piece is provided with an electrode corresponding to its use. That is, the first vibrating bars 12 and 1
3 is provided with an excitation electrode, and the second vibrating bars 14 and 15 are provided with detection electrodes. Regarding the arrangement of the electrodes, FIG.
Are omitted, and are displayed using FIGS. 1B and 1C instead. FIGS. 1B and 1C are a cross-sectional view taken along a line BB and a line CC, respectively, in FIG. As shown, the first resonator element 1
In FIG. 3, electrodes 21 to 24 are provided on four surfaces of an upper surface, a lower surface, and a side surface, respectively.
The vibrating piece extends to a length of about ／ to ／ of the entire length of the resonator element. Similar electrodes 31 to 34 (see FIG. 3) are provided on the first vibrating reed 12. On the other hand, on the second vibrating reed 15, the four electrodes 25 to 28 are connected to the end of the second vibrating reed 15 from the coupling portion with the vibrator base 11 so as to cover the four corners of the rectangular cross section, that is, the ridges. Towards the part, ie-
It extends in the direction of Y to a length of about ／ to ／ of the total length of the resonator element. Note that the same electrode 3 is also provided on the second vibrating reed 14.
5 to 38 (see FIG. 3) are provided.

Each electrode has a two-layer structure of chromium and gold. After depositing these metals on the surface of the vibrator 10, they are appropriately separated by photolithography and patterned into a desired shape. Is obtained by
Each electrode is electrically connected to one of the bonding pads 81 to 84 provided on the fixing plate 17 and further connected to a signal processing circuit described later. The wiring between each electrode on the resonator element and the bonding pad is provided on the surface of the support rod 16 by a film forming technique, though not shown. Further, metal films 142, 143, 144, and 14 for adjusting the resonance frequency are provided on the peripheral surfaces of the first vibrating bars 12 and 13 and the second vibrating bars 14 and 15, respectively, on the distal end side.
5 have been deposited. As described above, the first vibrating reeds 12 and 13 for excitation are formed such that the natural frequency in the X direction is f _X1 . That is, the resonance frequency of the excitation is set to f _X1 . However, since the processing accuracy of the vibrator is limited in practice, it is difficult to accurately set the natural frequency in the X direction of the first vibrating reeds 12 and 13 to f _X1 only by cutting out the crystal Z plate by etching. It is. Therefore, a metal film is provided in advance at the tip of the resonator element, and the natural frequency in a state where the metal film is deposited is formed to be a value slightly lower than f _X1 , and then, while measuring the vibration amplitude, A method is used in which the resonance frequency is adjusted to a desired value f _X1 by grinding the adjustment metal film with laser light or the like. Similarly, the adjustment of the resonance frequency for detection is performed by grinding the metal films 144 and 145. The metal films 142, 1
43, 144, and 145 are used for weight adjustment, and any material may be used as long as grinding is possible. In this embodiment, the same material as the electrodes 21 to 24 is used. 24 and the like to reduce the number of manufacturing steps.

FIG. 2 shows that the vibrator 10 is mounted on a four-layer metallized substrate 100, and a metal lid 11 is provided.
It is a figure which shows the state sealed by 0, FIG. 4A is a plan view, and FIG. 4B is a side view.

The metallized substrate is generally 90% SiO
The _second green sheet (green state), the wiring and the bonding pads by printing with a metal such as tungsten or molybdenum, after pressing stacked this multilayer, a multilayer ceramic made by firing dried It is a wiring board. The wiring in each layer is connected by a connection hole called a via hole. Since the metallized substrate can be easily cut out in a raw state (a state of a green sheet), a substrate having a step on the surface can be easily manufactured. Since each layer is pressed and fired, and the via holes are filled with a metal such as tungsten or molybdenum, the airtightness between the layers is sufficiently maintained. Further, since a high melting point metal such as tungsten or molybdenum is used for the wiring, various mounted components can be brazed at a high temperature without affecting these wirings.

The metallized substrate 100 has a four-layer structure, and the back surface of the lowermost first layer 101 has excitation,
Circuit element 11 for detecting vibration and calculating angular velocity
1 and 112 are mounted. On the first layer 101, a second layer 102, a third layer 103, and a fourth layer 104 are sequentially stacked. Second layer 102, third layer 103, fourth layer 104
In each case, the center is hollowed out in a rectangular shape, and the length of the opening in the longitudinal direction (the left-right direction in FIG. 2) is sequentially increased, and the left side is stepped by aligning the right side as shown in the figure. ing.

The fixed plate 17 of the vibrator 10 is fixed by welding on the second layer 102 at the step portion of the metallized substrate 100 by soldering, and bonding pads 131 to 134 are formed on the surface of the third layer 103. Is provided. The bonding pads 131 to 134 are respectively connected to the circuit element 11 via wiring and via holes of each layer (not shown).
1 and 112. Since the fixed plate 17 of the vibrator 10 is welded on the second layer 102, the vibrating piece 12
To 15 can be kept floating from the first layer 101. Further, since the bonding pads 131 to 134 on the metallized substrate 100 side are provided on the third layer 103 without being provided on the second layer 102, the height difference between the bonding pads 81 to 84 of the vibrator 10 is reduced, Connection work of the bonding wires 121 to 124 is easy.

The lower end of the metal lid 110 is fixed to the fourth layer 104 with a sealing resin all around. Instead of fixing with a sealing resin, it may be fixed by brazing such as soldering. Thereby, the space in which the vibrator 10 is housed is completely shut off from the outside. In this interior space,
An inert gas having the same density as the atmosphere is filled. Specifically, nitrogen gas N ₂ , argon gas Ar and helium gas H
A mixed gas of e ₂ is sealed at 1 atm in a ratio of N ₂ : Ar: He ₂ = 95: 3.5: 2. The density of this mixed gas is the same as the atmospheric density at 25 ° C., and is 28.96 g / mol.
As described above, since the vibrator 10 is placed in an inert gas atmosphere having the same density as the air, even if the resonance frequency adjustment before sealing is performed in the atmosphere where the work is easy, errors due to sealing may occur. Absent. In other words, the resonance frequency can be adjusted before sealing without taking into account any change in the resonance frequency caused by sealing the inert gas.

As the inert gas, a mixture of an inexpensive nitrogen gas and a mixture of an argon gas and a helium gas suitable for detecting a gas leak is mainly used, but the present invention is not limited to this. If the ease of gas leak detection is not considered, for example, nitrogen gas at 1.033 atm may be used. The density of nitrogen gas at 1.033 atm is 25
It is 28.96 g / mol, which is the same as the atmospheric density at ° C.

The upper surface 140 of the first layer 101 is entirely covered with a metal film, and this metal film and the metal cover 110 are electrically connected via via holes. Therefore, the space in which the vibrator 10 is housed is almost covered with an equipotential metal and is electromagnetically shielded. An operational amplifier is used in a detection circuit and the like described later, and amplification with a high amplification rate is performed. Generally, an amplification circuit having a high amplification rate is vulnerable to electromagnetic noise. Need to be prevented. The electromagnetic shield is effective in preventing such intrusion of noise. The electrodes provided on each vibrating element constitute a capacitor with electrodes facing each other, and the angular velocity is obtained from the change in the amount of charge as described later. The electromagnetic shield surrounding the vibrator 10 is effective for suppressing the influence of noise. When wiring is provided on the surface 140 of the first layer 101,
The metal film for the electromagnetic shield is applied except for the portion so as not to be connected to the wiring.

Next, a processing circuit mounted on the circuit elements 111 and 112 for performing excitation, detection, and angular velocity calculation will be described. FIG. 3 shows an excitation circuit 50, a detection circuit 60, and an angular velocity calculation circuit 70. These circuits and electrodes 21 to 28 and 3 provided on the vibrating bars 12 to 15 are shown.
It is a block diagram which shows the connection relationship with 1-38. Also,
FIG. 4 is a diagram for explaining the inverse piezoelectric effect in the first vibrating bars 12 and 13, and FIG. 5 is a diagram for explaining the piezoelectric effect in the second vibrating bars 14 and 15.

The excitation circuit 50 includes a current-voltage conversion circuit 51, an automatic gain control circuit 52, and a drive circuit 53.
The detection circuit 60 includes current-voltage conversion circuits 61 and 62, an operation amplification circuit 63, and a synchronous detection circuit 64.

The drive circuit 53 outputs a pulse wave having an amplitude corresponding to the output voltage value of the automatic gain control circuit 52 and having a predetermined repetition frequency as an excitation signal, and synchronizes the output signal with a signal having a phase shifted by 90 degrees. The detection circuit 64 outputs a detection signal as a detection signal.
Through the electrodes 22 and 24 on the side surface of the first vibrating reed 13
The electrodes 31 and 33 on the upper and lower surfaces of the resonator element 12 are commonly connected. The remaining electrodes 21 of the first vibrating bars 12 and 13,
23, 32, and 34 are commonly connected to the input terminal of the current-voltage conversion circuit 51 via the terminal 55, thereby being fixed to the intermediate potential of the pulse wave output from the drive circuit 53.

FIG. 4 illustrates the operation of exciting the first resonator element by the excitation circuit 50. FIG.
FIG. 1 is a cross-sectional view of a vibrating reed 13 taken along a ZX plane,
It is a figure equivalent to (b). FIG. 4B is a perspective view showing a bending operation of the first vibrating piece 13. As described above, since the electrodes 21 and 23 are commonly connected to the terminal 55 and the electrodes 22 and 24 are commonly connected to the terminal 56, when the output pulse of the drive circuit 53 is at a low level,
The voltage as shown in FIG.
, A relatively negative voltage is applied to the electrodes 21 and 23, and a positive voltage is applied to the electrodes 21 and 23, respectively. If the output pulse of the drive circuit 53 is at a high level, the opposite polarity is applied.

Considering a state where a voltage as shown in FIG. 4A is applied, an arrow 91 is provided inside the resonator element 13.
To 94 are applied.
On the other hand, since the piezoelectric effect of quartz does not appear in the Z-axis direction, effective electric fields affecting the piezoelectric effect are indicated by arrows 95 and 96. Due to the inverse piezoelectric effect, the crystal of quartz expands in the Y-axis direction when an electric field is applied in the positive direction of the X-axis, and contracts in the Y-axis direction when an electric field is applied in the negative direction of the X-axis. Therefore, FIG.
In the state (a), the vibrating reed 13 contracts on the electrode 24 side and expands on the electrode 22 side, so that the vibrating reed 13 bends with the electrode 24 inside. When the polarity of the voltage applied to the electrodes 21 to 24 is reversed, the resonator element 13
Bend with 2 inside. Therefore, when a pulse signal of a predetermined frequency is applied to the electrodes 21 and 23 from the drive circuit 53 with one end of the resonator element 13 fixed, the resonator element 13
Vibrates in the X direction as shown in FIG.

In this embodiment, the upper and lower electrodes 21 and 23 of the vibrating reed 13 and the left and right electrodes 32 and 34 of the vibrating reed 12 are connected in common as shown in FIG.
Since the left and right electrodes 22 and 24 of the third vibrator and the upper and lower electrodes 31 and 33 of the vibrating reed 12 are connected in common, the vibrating reeds 12 and 13 vibrate in opposite directions in the X direction.

The vibration information of the first vibrating bars 12 and 13 in the X direction is supplied to a current-voltage conversion circuit 51 and an automatic gain control circuit 52.
Is fed back via Current-voltage conversion circuit 51
Is a circuit for converting the amount of change in the electric charges generated in the electrodes 21, 23, 32, and 34 by the piezoelectric effect caused by the bending of the first vibrating bars 12 and 13 into a voltage value.

The automatic gain control circuit 52 receives the voltage signal output from the current-voltage conversion circuit 51, and decreases the output voltage value when the input voltage value increases, and increases the output voltage value when the input voltage value decreases. It works to be.
Therefore, when the vibration amplitude of the first vibrating bars 12 and 13 increases, the charges generated on the electrodes 21, 23, 32, and 34 also increase, and the output voltage of the current-voltage conversion circuit 51 also increases. As a result, the output voltage value of the automatic gain control circuit 52 decreases, and the amplitude of the output pulse of the drive circuit 53 decreases. Thus, the amplitude of the pulse signal output from the drive circuit 53 is feedback-controlled, and the vibration amplitude of the first vibrating bars 12 and 13 is always stable. The frequency at the time of this stabilization coincides with the resonance frequency adjusted in the manufacturing stage.

Next, the Z of the second resonator element as shown in FIG.
The detection circuit 60 that detects the vibration in the direction will be described. The second resonator element 15 vibrates in the Z direction as shown in FIG.
When bending in the + Z direction, the upper half of the resonator element 15
Direction, and the lower half extends in the Y direction. Due to the piezoelectric effect of quartz, dielectric contraction in the X direction occurs when shrinking in the Y direction,
When extending in the Y direction, dielectric polarization in the opposite X direction occurs.
Since the strength of dielectric polarization depends on the magnitude of expansion and contraction, it appears strongly on the upper or lower surface, and becomes weaker toward the middle. Therefore, the dielectric polarization is concentrated on the four corners of the resonator element 15, and positive or negative charges as shown in the figure are collected at the electrodes 25 to 28 provided at the corners due to the dielectric polarization. That is, the electrodes 25 and 27 have the same polarity,
These polarities are opposite to the polarities of the electrodes 26 and 28. When the resonator element 15 swings downward, a polarity completely opposite to that described above appears based on the same principle.

The detection circuit 60 detects the amount of change in the electric charge in each electrode of the vibrating reed 15 thus generated, and outputs a signal corresponding to the vibration amplitude of the second vibrating reed. In this embodiment, the first vibrating reeds 12 and 13 are excited in the X direction in mutually opposite phases, and the first vibrating piece and the second vibrating piece are vibrated in mutually opposite phases in the Z direction. 14 and 1
5 oscillate in opposite phases with respect to the Z direction. The vibrations of the second vibrating bars 14 and 15 in the Z direction are caused by the first vibrating bars 12 and 1.
3 that the X-direction excitation vibration leaked as Z-direction vibration,
The combined vibration is generated with the vibration generated based on the Coriolis force generated when the vibrator 10 rotates, but the phases of the second vibrating reeds 14 and 15 are opposite to each other in any component. Although the details of the mechanism for generating the Z-direction vibration based on the Coriolis force will be described later, anyway, right and left opposite phases of vibration are generated in the Z-direction, and as shown in FIG. The electrodes 36 and 37 of the second vibrating reed 14, which are in plane symmetry with respect to 28, are connected in common and further connected to a terminal 65 of the detection circuit 60. Then, the remaining electrodes 26, 27, 35, 38
Are commonly connected to a terminal 66 of the detection circuit 60.

The current-voltage conversion circuit 61 includes electrodes 25, 28,
The current-voltage conversion circuit 62 amplifies the amount of change in the charges at 36 and 37 and converts it into a voltage value.
This is a circuit that amplifies the amount of change in electric charge at 7, 35, and 38 and converts it into a voltage value. The operation amplification circuit 63 is a circuit that receives the output signals of the current-voltage conversion circuits 61 and 62 and amplifies the potential difference between the two signals. The change in the amplitude of this output signal is caused by the change in the vibration amplitude of the second vibrating reeds 14 and 15. Is proportional to

The synchronous detection circuit 64 performs synchronous detection using the AC voltage signal output from the operational amplifier circuit 63 as a detection signal using a pulse signal having a phase shift of 90 degrees with respect to the excitation signal from the drive circuit 53. This is a circuit in which an integration circuit is added to a normal synchronous detection circuit. The vibration in the Z direction due to leakage of the X excitation is in phase with the excitation, and the vibration in the Z direction due to the Coriolis force is
Since the phase is shifted by 0 degrees, the former always becomes a value of zero and the latter becomes an integrated value of full-wave rectification by synchronous detection and integration. That is, the output signal voltage of the synchronous detection circuit 64 is changed by Zio due to the Coriolis force of the second vibrating bars 14 and 15.
The vibration amplitude in the direction is shown.

The angular velocity calculating circuit 70 calculates the rotational angular velocity of the vibrator 10 about an axis parallel to the Y axis based on the output signal of the detection circuit 60 indicating the vibration amplitude of the second vibrating bars 14 and 15 as described later. This is a circuit for calculating based on a relational expression between the angular velocity and the Coriolis force.

Next, the operation of the angular velocity detecting device configured as described above will be described. The excitation circuit 50 includes the first vibrating reed 1
An excitation signal having a frequency corresponding to the natural frequency f _{X1 in} the X direction (referred to as a first natural frequency) in the drive circuit 5
Output from 3. The first natural frequency is set accurately by adjusting the resonance frequency during the manufacturing process. Thereby, the first vibrating reeds 12 and 13 vibrate in the X direction at the natural frequency f _X1 due to the inverse piezoelectric effect. The phases of the resonator element 12 and the resonator element 13 are opposite to each other as described above.

In this state, when the vibrator 10 rotates at an angular velocity ω about an axis parallel to the Y axis (including the Y axis), the first vibrating bars 12 and 13 are expressed by F = 2 mV · ω. Coriolis force F is generated in the Z direction. Here, m is the mass of the resonator element, and V is the vibration speed. Due to the generation of the Coriolis force F, the first vibrating bars 12 and 13 vibrate in the Z direction with a 90 ° phase shift with respect to the vibration in the X direction. That is, the first vibrating reeds 12 and 13 also vibrate in the Z direction at the excitation frequency (first natural frequency) in opposite phases. Since this frequency substantially matches the coupled natural frequency of the first and second vibrating bars in the Z direction, the frequency is efficiently transmitted to the second vibrating bars 14 and 15. The detection circuit 60 detects the vibration in the Z direction based on the Coriolis force, and the angular velocity calculation circuit 70 calculates the angular velocity based on the detection signal from the detection circuit 60.

The resonance frequency of the angular velocity detecting device configured and operated as described above is adjusted before the vibrator sealing step at the time of manufacturing. At this stage, the vibrator 10 includes circuit elements 111 and 1 including an excitation circuit and the like on the metallized substrate 100.
The metal films 142 to 145 for adjusting the resonance frequency are deposited on the tips of the resonator elements 12 to 16 as described above. In the resonance frequency adjustment step, the vibrator 10 is excited by using the excitation circuit 50 shown in FIG. 3, and while observing the output frequency of the drive circuit 53 therein, the metal films 142 and 143 are formed by using a YAG laser device or the like. Trim in air. The vibrator 10 including the electrodes and the metal film is manufactured to have a natural frequency slightly lower than a desired natural frequency. Therefore, when self-excited by the circuit of FIG. In this state, while observing the output frequency of the drive circuit 53, the metal films 142 and 143 are gradually removed to gradually increase the resonance frequency. When the desired value is reached, the removal of the metal film is stopped. When the metal films 142 and 143 receive the laser light emitted from the YAG laser device, only the irradiated portions are removed by heat, so that fine adjustment is easy. This adjustment is what is called mass adjustment, and utilizes the effect that the natural frequency increases when the weight of the tip of the resonator element is reduced.

The metal films 144 and 145 provided on the vibrating bars 14 and 15 are trimmed so that the amplitude of the detected vibration of the vibrating bars 14 and 15 in the Z direction is maximized.

The metal films 142 to 145 by the laser light
After the trimming is completed, the vibrator 10 while being mounted on the metallized substrate 100 is sent into a chamber for performing a sealing process. The inside of the chamber is once evacuated, and then an inert gas for sealing is introduced. As described above, the inert gas is a mixture of nitrogen gas N ₂ , argon gas Ar, and helium gas He ₂ to have a density at 1 atmosphere of 28.96 which is the same as the atmospheric density at 25 ° C. When the lid 110 is welded and fixed to the metallized substrate 100 in the inert gas atmosphere as shown in FIG. 2 and taken out of the chamber, the vibrator 10 is sealed in an inert gas atmosphere having the same density as the atmosphere, and the angular velocity detection is performed. A device is obtained.

In this embodiment, the vibrator is mounted on the metallized substrate, but is not limited to this. For example, the vibrator may be mounted on a metal substrate. In that case, the lid can be bonded to the substrate by a technique such as projection welding.

The vibrator according to the present embodiment is a very small crystal vibrator having a vibrating reed having a cross section of about 0.5 mm or less, but is not limited thereto. May be a metal vibrator of about 10 to 25 mm.

[0044]

As described above, according to the method of manufacturing the angular velocity detecting device of the present invention, the resonance frequency at the time of adjustment exactly matches the resonance frequency after sealing, so that even the resonance frequency adjustment is strictly performed. If it is performed, the resonance frequency of the completed angular velocity detection device can be set to a desired value without error, and the detection accuracy can be maximized.

If the density of the inert gas is made substantially equal to the density of the atmosphere, the resonance frequency can be adjusted in the atmosphere, and the equipment can be simplified and the work can be simplified.

According to the angular velocity detecting device of the present invention,
The resonance frequency matches the resonance frequency in the atmosphere before sealing the vibrator. Therefore, when the resonance frequency adjustment before sealing the vibrator was performed in the easy-to-work atmosphere,
High detection accuracy can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a vibrator of an angular velocity detecting device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a state in which the vibrator of FIG. 1 is mounted on a metallized substrate and packaged.

FIG. 3 shows an excitation circuit 50, a detection circuit 60, and an angular velocity calculation circuit 70 used in the angular velocity detection device of the first embodiment, and shows these circuits and electrodes 21 to 28 and 31 provided on the vibrating bars 12 to 15; The block diagram which shows the connection relationship with -38.

FIG. 4 is a view for explaining an inverse piezoelectric effect in the first vibrating bars 12 and 13;

FIG. 5 is a view for explaining a piezoelectric effect in the second vibrating bars 14 and 15.

[Explanation of symbols]

10, 200: vibrator, 11: vibrator base, 12, 13
.., First vibrating reed, 14, 15 ... second vibrating reed, 16 ... support rod, 17 ... fixed plate, 21-28, 31-38 ... electrode, 5
0: excitation circuit, 60: detection circuit, 70: angular velocity calculation circuit, 100: metallized substrate, 142 to 145: metal film.

Claims (3)

[Claims] 1. A method for manufacturing an angular velocity detecting device, comprising: a first step of adjusting a resonance frequency of an angular velocity detecting vibrator; and a second step of sealing the vibrator in an inert gas atmosphere. A method of manufacturing an angular velocity detecting device, wherein an atmosphere density around the vibrator in the first step and a density of an inert gas in the second step are substantially the same. 2. The method according to claim 1, wherein the resonance frequency of the vibrator in the first step is adjusted in the atmosphere, and the density of the inert gas in the second step is made substantially equal to the air density. A manufacturing method of the angular velocity detecting device according to the above. 3. An angular velocity detecting device for exciting a vibrator and detecting an angular velocity of the rotation from an amplitude of vibration based on Coriolis force generated with the rotation of the vibrator, wherein the vibrator is substantially equivalent to an atmospheric density. An angular velocity detecting device characterized by being sealed in an inert gas of the same density.