JPH02306110A - Angular velocity sensor - Google Patents

Abstract

PURPOSE:To reduce fluctuation of an offset voltage by sealing a structural body of a tuning fork using a piezoelectric bimorph under an air-tight condition with a gas pressure not higher than 1 atm. CONSTITUTION:A conductive connecting member 7 is inserted between driving piezoelectric bimorphs 3,4, so that the connecting member 7 is electrically and mechanically connected to an inner electrode of each bimorph 3,4. Lead terminals 8,11-16 are electrically connected to bimorphs 1-4, and isolated from a support base 10 through insulating glasses 9,17-20. A relay base plate 23 supports the lead terminals 13-16, and electrically connects the bimorphs 1 with 2. Likewise, the bimorphs 3,4 are connected with each other through soldering. The obtained item is housed in a can 30. A connecting portion between the base 10 and a peripheral edge portion of an opening of the can 30 is air- tightly sealed through electric spot welding. At this time, an air-tight gas 31 is filled inside the can 30. Accordingly, fluctuation of an offset voltage of a sensor can be greatly reduced in this manner.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an angular velocity sensor used in gyroscopes and the like.

BACKGROUND OF THE INVENTION In recent years, with the development of computer technology, products with many functions have been commercialized, and the demand for various types of sensors has increased. Applications of angular velocity sensors include napygear control systems in electrical equipment, direction detection for robots, and stabilizer devices for drive devices, all of which will require small, high-performance devices.

Conventionally, as an inertial navigation device using a gyroscope,
It is mainly used to determine the direction of moving objects such as airplanes and ships. Although this method provides a stable orientation, since it is mechanical, the device is large-scale and costly, and it is difficult to apply it to consumer equipment where miniaturization is desired. On the other hand, a vibrating gyroscope (Japanese Patent Application No. 59-55420) has been proposed that detects angular velocity from the Coriolis force generated when an angular velocity is generated by vibrating an object without using rotational force. This vibration gyroscope can be considered as a vibration sensor having a tuning fork structure. According to this, the driving elastic body (
A rectangular plate (for excitation) and an elastic body for detection are connected linearly and orthogonally, and the Coriolis force acting on the elastic body for detection with a velocity (m/s) is detected.

A conventional angular velocity sensor will be described below with reference to the drawings.

FIG. 6 shows a block diagram including a conventional angular velocity sensor and a drive circuit. There is a sensing piezoelectric bimorph element 101, 102 in which drive piezoelectric bimorph elements 103, 104 and sensing piezoelectric bimorph element 101, 102 are connected parallel to the sensing axis and orthogonally to each other via joining members 105, 108. is a driving piezoelectric bimorph element 103, 104 connected at one end with a support 107 as a vibration element.

Then, the vibration element and the pace 109 are supported and joined by one metal elastic member 108, and the driving piezoelectric bimorph elements 103 and 104 are vibrated to cause tuning fork vibration, and the detection piezoelectric bimorph elements 101 and 102 are made to vibrate. The structure is such that when an angular velocity is added to K, an angular velocity output is obtained.

Next, we will continue to explain the operating circuit. First, the drive piezoelectric bimorph element 104 resonates due to a signal sent from the drive circuit 11 to the drive piezoelectric bimorph element 103, and the drive circuit 110, the GC circuit 111, the drive monitor circuit, and the drive piezoelectric bimorph elements 104, 103 The tuning fork begins to vibrate in a feedback loop. Then, the amplitude signal obtained from the drive piezoelectric bimorph element 104 is fed back to the drive circuit through an automatic gain adjustment circuit (MUGO circuit) 111 to keep the amplitude of the tuning fork vibration constant.

Furthermore, the detection piezoelectric bimorph elements 101 and 102 are connected using the phase signal obtained from the driving piezoelectric bimorph 103.
The angular velocity signal component is extracted from the drive monitor 113, and part of the phase signal information of the detection signal generated in the piezoelectric bimorph for driving 1 is extracted from the drive monitor 113, and the detection circuit 115 and the low-pass filter 116
A DC detection signal corresponding to the angular velocity is detected by

By the way, when such an angular velocity sensor is subjected to a temperature change, the detected information signal (offset output voltage) of the angular velocity sensor fluctuates greatly due to a thermal pyroelectric effect corresponding to the rate of temperature change. That is, even with the same temperature change width, when a temperature change with a slow slope is applied, the fluctuation in the offset voltage of the angular velocity detection signal is small, but when the temperature change is applied in a stepwise manner, the fluctuation in the offset voltage is As shown in the figure, it fluctuates greatly. That is, the pyroelectric effect of the piezoelectric vibrator has a large influence on the temperature drift (change in offset voltage) percentage, which is one of the major performance indexes for an angular velocity sensor.

Problems to be Solved by the Invention In a conventional tuning fork type angular velocity sensor using a piezoelectric vibrator, one of the causes of temperature drift is a pyroelectric effect phenomenon unique to the piezoelectric vibrator. That is, when a piezoelectric vibrator is irradiated with far infrared rays, an electromotive force is generated. In other words, conventional vibration-type angular velocity sensors have limitations as high-precision sensors.
It was considered difficult to improve the accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an angular velocity sensor with small offset voltage fluctuations due to temperature changes.

Means for Solving the Problems As a means for solving the problems, the present invention provides a tuning fork constructed by orthogonally joining a piezoelectric bimorph element for driving and a piezoelectric bimorph element for detection to form a tuning fork structure. This tuning fork structure is hermetically sealed at a pressure of less than 1 atmosphere.

By the way, the pyroelectric effect is an electric charge generated in the piezoelectric bimorph material in response to thermal changes per unit time, and this is the main cause of changes in temperature characteristics. This pyroelectric effect causes the tuning fork structure, including the piezoelectric bimorph, to move under normal pressure (1 atm).
By performing hermetic sealing at a pressure of less than 1,000 yen, the lower the pressure of the hermetic filling gas, the lower the molecular density of the filling gas, so thermal conduction from the outside can be suppressed. As a result, unnecessary charge generation in the piezoelectric piezoelectric material can be prevented. .

Therefore, by preventing this unnecessary charge generation,
The output signal of angular velocity detection information detected by an angular velocity sensor having a tuning fork structure using a piezoelectric bimorph has very excellent dependence characteristics on temperature changes.

EXAMPLE Hereinafter, an example of the angular velocity sensor of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 show the structure of an angular velocity sensor according to an embodiment of the present invention. First, we will explain from FIG. 2. In Fig. 2, 1, 2, 3.4 are piezoelectric pimo IL/7,
In this example, Pb(MgXA.

A piezoelectric material mainly composed of three components: Nb%)05, PbTiO3, and PbZrO3 was used.

In this embodiment, the piezoelectric bimorph 1.2 will be referred to as a sensing piezoelectric bimorph, and the piezoelectric bimorph 3.4 will be referred to as a driving piezoelectric bimorph.

Piezoelectric bimorph 1.2 for detection has mug electrodes attached to both sides and is processed to dimensions 9X1, 6X0, 35ffff, and piezoelectric bimorphs 3 and 4 for drive have dimensions 9X1.
, 6X0, 5ff. Insulator joint 6
．． 6 is made of polyamide plastic and has a concave groove in the center. And this insulator dicho intro, piezoelectric bimorphs 1 and 3, and 2 and 4 in the recess of 6.
are perpendicular to each other and adhesively bonded.

Next, the orthogonal body of the piezoelectric bimorph obtained in this way (
1, e5, 3) and (2, 6, 4) are made into a conductor bonding member 7, for example, by drilling a hole in the center of a brass block and connecting them to form a tuning fork structure as shown in Figure 2. They are joined to form a tuning fork structure.

That is, the conductor bonding member 7 connects the driving piezoelectric bimorph 3
, 4, and is electrically conductive and mechanically bonded to the inner surface electrode of each piezoelectric bimorph 3.4.

Next, lead terminals 8, 11, 12, 13, 14°15.
16 is a piezoelectric piemo/l'71. 2.3.4 is a lead terminal for electrically connecting F
It is attached to the support base 1o so as to be insulated from the support base 1°, which is mainly composed of e, and to penetrate through the support base 1o, and serves as a lead terminal for electrical connection with the outside. or,
One end of the lead terminal 8 is inserted into a hole in the center of the conductor joining member 7 and fixed with adhesive.

Next, the relay board 23 connects the lead terminals 13, 14, 15.
16, a relay board for electrically connecting the piezoelectric bimorph for detection, and lead terminals 13, 14, 1.
It is attached to 5.16. FIG. 1 shows a state in which this relay board 23 is attached.

By the way, the relay board 23 described above is made of phenol and has an external dimension of φ6. Processed to have a thickness Q (3ff), through holes are provided at four locations through which the lead terminal portions pass, and the lead terminals 13, 14, 15° 16 are held in the through holes.

To hold the relay board 23, copper foil is provided around the upper part of the through hole of the relay board 23, and the lead terminals 13, 14 are attached to this part.
, 15 and 16 are soldered to hold and fix the relay board 23.

Next, the piezoelectric bimorph 1 for detection and the lead terminal 13.16
and are connected with lead wires 24 and 25. For connection, both ends of the lead wires 24 and 25 are joined by soldering. or,
The detection piezoelectric bimorph 2 and the lead terminals 14.15 are connected with the lead wires 26.27 in the same manner as described above. For connection, both ends of the lead wires 26 and 27 are joined by soldering in the same manner as described above. Next, a lead wire 29 is soldered to connect the outer electrode portion of the driving piezoelectric bimorph 4 to the lead terminal 12 whose tip is bent into an L-shape. Further, the driving piezoelectric bimorph μ) 3 has a lead wire 28 between the outer electrode portion of the piezoelectric bimorph 3 and the lead terminal 11 in the same manner as described above.
Connect by soldering. Then, the product created in this way is stored in a bottomed cylindrical can case 3o made of Fe,
Then, the contact portion between the support base 10 and the opening peripheral portion of the can case 30 is hermetically sealed and joined by spot electric welding.

When the can case 30 is hermetically sealed, the inside of the can case 30 is filled with an airtight filling gas 31.

Here, as the airtight filling gas 31, the airtight filling gas pressure is 0.1 HHg to 76
Fourteen types of material samples were created by changing the temperature up to 0flHg. The contents of this material sample/1/14 are shown in Table 1.

(Leaving space below) Table 1 14 types of samples of this material were used, and using the operating circuit shown in Fig. 6, the sensor part in Fig. 5 was created using the above material sample) v1
The fluctuations in the offset voltage of the sensor were investigated by replacing each of the four types (material numbers 1 to 14). In addition, for the material sample/l/14 types, use a constant temperature bath, for example -
As an example, the ambient temperature around the sensor was changed from 20'C to 3o''C.
Figure 3 shows the results of investigating the offset voltage of the operating circuit shown in the figure.
It is shown in Figure 4.

FIG. 3 shows the pressure of material samples 1 to 7, and FIG. 4 shows the pressure of material samples I to 8 to 14.

According to the results shown in Figures 3 and 4, material sample 1.8 is a tuning fork structure using piezoelectric Vimo/I/7 sealed with 1 atm air or nitrogen. L'2.
It can be seen that as the sealing gas pressure decreases sequentially from 3...7 or 8, 9...14, the change value of the offset output voltage of the sensor becomes smaller. That is,
When a temperature change is applied to the outer periphery of the sensor, the lower the gas pressure sealing the tuning fork structure is than normal pressure (1 atm), the smaller the fluctuation voltage of the offset voltage. Moreover, from the results shown in FIGS. 3 and 4, similar effects were obtained even when air or nitrogen gas was used as the filling gas. Furthermore, the gas pressure is 0 in the example.
．． Although no examples are given below lffHg, results similar to those described above can be obtained.

Effects of the Invention As described above, according to the present invention, a tuning fork structure using a piezoelectric bimorph is hermetically sealed with a gas pressure of 1 atm or less, so that when a temperature change is applied to the outer circumference of the sensor, the piezoelectric bimorph is The included tuning fork structure has a low gas density, which suppresses heat conduction from the outer periphery of the sensor, and has the effect of greatly reducing offset voltage fluctuations of the sensor caused by the pyroelectric effect unique to piezoelectric materials. can get. Furthermore, by reducing the pressure of the hermetic sealing gas from 1 atm for sealing, the present invention has the effect of eliminating offset voltage drift fluctuations due to unnecessary signal components to the sensor due to vibration propagation due to external sound waves, etc. You can also get

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of an angular velocity sensor according to an embodiment of the present invention, FIG. 2 is a perspective view showing an assembled structure of the sensor, and FIGS. 3 and 4 are sensors of the present invention. FIG. 6 is a block diagram for explaining the configuration and operation of the angular velocity sensor. FIG. 6 is a characteristic diagram showing the offset voltage versus temperature change of a conventional angular velocity sensor. be. 1.2...Piezoelectric bimorph for detection, 3,4...
... Drive piezoelectric bimorph, 5.6 ... Insulator joint, 7 ... Conductor joining member, 1o
...support pace, 30 ...can case,
31...Hermetic filling gas. Name of agent: Patent attorney Shigetaka Awano and 1 other person11
15! J Figure 2 Figure 3 Copy JIM (coffin) Figure 4 Route i Hakubun (minute Q

Claims (1)

[Claims] It has a tuning fork structure formed by orthogonally joining a piezoelectric bimorph element for driving and a piezoelectric bimorph element for detection to form a tuning fork structure, and this tuning fork structure is hermetically sealed at a pressure of less than 1 atmosphere. An angular velocity sensor characterized by: