JPH03251718A - Angular velocity sensor - Google Patents

Abstract

PURPOSE:To stabilize characteristic with the prevention of possible undesired electric charge by a method wherein two sheets of piezo-electric body are pasted together through an intermediate electrode with a direction of polarization thereof being the same and an electrode made up of a pressure conducting film with limited change in mass is provided on the external side thereof with the areas of the electrodes being equal so that charge values to be generated from the two sheets of piezo-electric body are the same. CONSTITUTION:Piezo-electric bimorph elements 1-4 composing an angle sensor are built using three components -- PbCMg1/3, Nb2/3O3 and PbTO3 and PbZrO3 -- mainly and elements 1 and 2 are used for detection and those 3 and 4 for driving. Here, the elements 1 and 2 and those 3 and 4 are all polarized in a direction of pasting them and a sound fork is made up of these two construction bodies. The works are integrated with insulating joints 5 and 6 as first joining member and with a conductor 7 as second joining member and the elements 1-4 are provided with four energizing electrodes 1e, 1g, 1h and 1j separately. Thereafter, these construction bodies are housed into a can case 30 and is filled with a gas 31 for airtightness.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention 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 sensors for this purpose has increased. Applications of angular velocity sensors include navigation systems in electrical equipment, direction detection for robots, and stabilizer devices for drive devices, and in the future, small, high-performance sensors will be needed for all of these.

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 object vibrates and generates angular velocity without using rotational force. This vibration gyroscope can be considered as a vibration sensor having a tuning fork structure. According to this, rectangular plates of a driving elastic body (for excitation) and a sensing elastic body are linearly and orthogonally joined, and the Coriolis force acting on the sensing elastic body with a velocity (m/s) This is to detect.

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

FIG. 7 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 driving piezoelectric bimorph elements 103, 104 and sensing piezoelectric bimorph elements 101, 102 are connected parallel to the sensing axis and orthogonally to each other via joining members 105, 106. 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 base 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 an angular velocity output can be obtained when an angular velocity is added to .

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 110 to the drive piezoelectric bimorph element 103, and the drive circuit 110, AGC circuit 111, drive monitor circuit, and drive piezoelectric bimorph elements 104, 103 The tuning fork starts vibrating in a feedback loop. Then, the amplitude signal obtained from the drive piezoelectric bimorph element 104 is fed back to the drive circuit via an automatic gain adjustment circuit (AGC circuit) 111 to keep the amplitude of the tuning fork vibration constant.

Further, by using the phase signal obtained from the driving piezoelectric bimorph 103, the sensing piezoelectric bimorph elements 101, 10
2, and part of the phase signal information of the detection signal generated in the drive piezoelectric bimorph from the drive monitor 113, and the detection circuit 115 and the low-pass filter 11.
6, a DC detection signal corresponding to the angular velocity is detected. By the way, when such an angular velocity sensor is subjected to a temperature change, a self-bias is applied to the piezoelectric bimorph element due to the thermal pyroelectric effect corresponding to the rate of temperature change, and the detected information signal (offset output) of the angular velocity sensor is Voltage)
varies greatly. In other words, even with the same temperature change width, if a slow slope temperature change is applied, the offset voltage of the angular velocity detection signal will fluctuate small, but if the temperature change is applied in steps, the offset voltage will fluctuate significantly. fluctuate. In other words, the pyroelectric effect of the piezoelectric vibrator has a large effect on the temperature drift (offset voltage fluctuation) characteristic, which is one of the major performance indicators 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 due to this temperature softness, and it has been considered difficult to improve them to higher precision.

The present invention takes the above-mentioned problems into consideration and aims to provide an angular velocity sensor with small offset voltage fluctuations with respect to temperature changes.

Means for Solving the Problems In order to achieve the above object, the present invention has a driving piezoelectric bimorph element, a sensing piezoelectric bimorph element, and a driving piezoelectric bimorph element and a sensing piezoelectric bimorph element whose vibration directions are perpendicular to each other. a first joining member that stacks up and joins each other, and a second joining member that joins the pair of joined elements into a tuning fork structure, and includes at least one of a driving piezoelectric bimorph element and a sensing piezoelectric bimorph element. are connected through an intermediate electrode so that the polarization direction of the piezoelectric body is the same.
It is a piezoelectric bimorph element made by laminating two piezoelectric bimorph elements, and the electrodes on both sides of the two piezoelectric bimorph elements are electrically connected. Electrical connections are made using a conductive membrane electrode structure that forms a .

Further, a part of one of the electrodes on both sides of the piezoelectric bimorph element is divided to provide an electrically independent small electrode, and this small electrode is electrically connected to the intermediate electrode of the piezoelectric bimorph element using the conductive electrode. Therefore, the piezoelectric bimorph element for driving is used as a driving electrode, and the piezoelectric bimorph sensing element is used as an output electrode for a detection signal.

Effect The offset voltage fluctuation, which is a problem with conventional angular velocity sensors, is caused by the pyroelectric effect of the piezoelectric element.The pyroelectric effect is the electric charge generated in the piezoelectric bimorph material in response to thermal changes per unit time. The voltage generated by this charge causes a change in the temperature characteristics of the offset voltage.

Therefore, two pieces of piezoelectric material are bonded together in the same polarization direction via an intermediate electrode, and the two electrodes provided on the outer surface are connected with an electrode made of a conductive film with little mass change. By making the area of each electrode provided on the piezoelectric body approximately equal, the amount of charge generated by the two piezoelectric bodies can be made approximately equal, so the charges cancel out and are neutralized.
As a result, unnecessary charge generation can be prevented. Furthermore, since the vibration during driving can maintain left-right symmetry, the amplitude of the vibration can be stabilized.

Therefore, by preventing this unnecessary charge generation and vibrating with stable amplitude, the output signal of the angular velocity detection information detected by the angular velocity sensor consisting of the tuning fork structure using the piezoelectric bimorph element of this configuration is stable against temperature changes. The properties obtained are very excellent.

In addition, by electrically connecting the small electrode and the intermediate electrode, which are obtained by dividing one of the electrodes on both sides of the piezoelectric bimorph element, with an electrode formed of a conductive film, and using it as an input/output electrode, it is possible to In a piezoelectric bimorph element, it serves as a driving electrode, and in a piezoelectric bimorph detection element, it serves as a signal detection electrode.

Since the driving electrode is connected to the intermediate electrode of the piezoelectric bimorph element, a driving voltage is applied between the intermediate electrode and the electrodes on both sides, and the piezoelectric bimorph element can be driven at a low voltage. By providing the signal detection electrode of the detection piezoelectric bimorph element, the charge due to the pyroelectric effect generated in the intermediate electrode is discharged, thereby reducing the influence.

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

As shown in FIG. 1, piezoelectric bimorph elements 1°2.3.
4 constitutes an angular velocity sensor. In addition, in this embodiment, this piezoelectric bimorph element 1°2.3.4 is made of PbC.
Mg1/3. Nb2/303, PbTiO3, PbZr
0. A piezoelectric ceramic material mainly consisting of three positive components is used.

In this embodiment, the piezoelectric bimorph element 1.2 is a detection piezoelectric bimorph element, and the piezoelectric bimorph element 3.4 is a driving piezoelectric bimorph element.

The detection piezoelectric bimorph element 1.2 is processed to have external dimensions of 9X1.6X0.35+n+n as shown in FIG. The polarization direction of the element is determined by the direction of the immorph element 3.4, which is made by gluing two piezoelectric ceramics 1b for detection.
As shown in Figure 2 1b+, the external dimensions are 9X1.6X
The piezoelectric element is processed to have a thickness of 0.5 mm, and like the detection electrode IC, Ag is used, and the polarization direction of the piezoelectric element is the same along the direction in which the two drive piezoelectric ceramics 1d are glued together. In addition, Fig. 2 181. The direction of the arrow in the figure (b) indicates the direction of polarization. The electrodes 1a and lc have a structure in which only one side of the electrode of the piezoelectric element is partially divided,
It is electrically non-conductive. Next, as shown in FIGS. 3A and 3B, the piezoelectric bimorph element for detection was coated with Ag or Cu conductive paste on the side surface of the piezoelectric bimorph element to form a conductive electrode 1e. As a result, the electrode sandwiched in the center of the piezoelectric bimorph element (hereinafter referred to as an intermediate electrode) and the electrode partially on the side are electrically connected. This is an electrode for detection output. On the other hand, the intermediate electrode at the tip of the bimorph is insulated using epoxy resin 1f, which is an insulator, and a conductive paste of Ag or Cu is applied between both electrodes on the outer surface of the piezoelectric bimorph element through this insulator. A conductive electrode 1g is connected to electrically connect the electrodes on both sides. This completes the detection piezoelectric bimorph element 1.2.

In addition, the drive piezoelectric bimorph is made by applying a conductive paste of Ag or Cu to the end side of the piezoelectric bimorph element as shown in Fig. 3 (1al) and (bl) to form a conductive electrode 1h. This electrode is a driving electrode.The tip of the one-pressure bimorph element and the side surface near the center are insulated using an insulator, epoxy resin 11, and this insulator is Ag or C between the outer electrodes of the piezoelectric bimorph through
U conductive paste is applied to form a conductive electrode 1j that electrically connects the outer electrodes on both sides. This completes the sensing piezoelectric bimorph element 3.4.

Next, piezoelectric bimorph element 1.2 obtained in this way
, 3.4 are constructed as shown in FIG.

The insulator joint 5.6, which is the first joining member, is made of polyamide plastic and has a concave groove in the center. The piezoelectric bimorph 1, the piezoelectric bimorph 3, and the piezoelectric bimorph 2 and the piezoelectric bimorph 4 are respectively perpendicular to each other and adhesively bonded to the recessed portion of the insulator joint 5.6.

Next, the two sets of orthogonal piezoelectric bimorph elements obtained in this way are attached to a conductor bonding member 7, which is a second bonding member.
(For example, a member made of a brass block with a hole drilled in the center) and conductively joined to form a tuning fork structure as shown in FIG. 5 to form a tuning fork structure. That is, the conductor bonding member 7 is inserted between the driving piezoelectric bimorph elements 3.4, electrically conductive with the inner surface electrode of each piezoelectric bimorph element 3.4, and mechanically bonded to the piezoelectric bimorph elements 3.4.

Next, lead terminals 8.11, 12, 13, 14°15
．． 16 is a lead terminal for electrically connecting the piezoelectric bimorph elements 1, 2, 3, and 4 degrees, through insulating glasses 9, 17, 18, 19, 20 degrees, and 21, 22, respectively.
It is insulated from the support base 10, which is mainly made of Fe, and is attached to the support base 10 so as to penetrate through the support base 10, and serves as a lead terminal for electrical connection with the outside.

Further, one end of the lead terminal 8 is inserted into a hole in the center of the conductor joining member 7 and fixed by adhesive.

Next, the relay board 23 has lead terminals 13.14°15.
．． This is a relay board 23 for supporting the detection piezoelectric bimorph element 1.2 and electrically connecting the detection piezoelectric bimorph element 1.2, and is attached to the lead terminals 13, 14, 15, and 16. FIG. 1 shows a state in which this relay board 23 is attached.

The relay board 23 is made of phenol and has an external dimension of φ7.0.
Processed to a thickness of 0.6nun, the part 4 through which the lead terminal part passes
Through-holes are provided at these locations, and the lead terminals 13, 1 are inserted into the through-holes.
4. Penetrate and hold 15.16.

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.
．． The relay board 23 is held and fixed by soldering the tips of 15 and 16.

Next, the detection piezoelectric bimorph element 1 and the lead terminal 13
．． 16 with lead wires 24 and 25. For connection, both ends of the lead wires 24 and 25 are joined by soldering. Note that the lead wire 24 is connected to the conductive electrode 1e provided on the detection piezoelectric bimorph element 1 to obtain a detection signal output. Furthermore, the detection piezoelectric bimorph element 2 and the lead terminals 14 and 15 are connected to the lead wires 26 and 2 in the same manner as described above.
Connect at 7. The connection is made using lead wire 2 in the same way as above.
6. Join both ends of 27 with solder. Note that the lead wire 26 is connected to the conductive electrode 1e provided on the piezoelectric bimorph element 2 for detection, similarly to the piezoelectric bimorph element 1 for detection. Next, a lead wire 29 is soldered to connect the outer electrode portion of the drive piezoelectric bimorph element 4 and the lead terminal 12 whose tip is bent into an L-shape. This lead wire 29 is connected to a conductive electrode 1h provided on the driving piezoelectric bimorph element 4, and a driving voltage is applied thereto. Since this conductive electrode 1h is connected to the intermediate electrode of the driving piezoelectric bimorph element 4, the driving voltage is applied to the intermediate electrode and the amphoteric electrode, so that driving can be performed with a low voltage. Further, the driving piezoelectric bimorph element 3 is connected by soldering between the outer electrode portion of the piezoelectric bimorph element 3 and the lead terminal 11 using the lead wire 28 in the same manner as described above. The product thus created is then stored in a bottomed cylindrical can case 30 made of Fe, and the contact area between the support base 10 and the opening periphery of the can case 30 is hermetically sealed by spot electric welding. Make a fixed connection.

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

Next, the characteristics of the angular velocity sensor using the piezoelectric bimorph elements 1, 2, 3.4 of the embodiment configured as described above will be explained below.

Four types of material samples were prepared to check the characteristics of this example. Table 1 shows the contents of these four sample materials.

(Left below) To check the characteristics of the four types of angular velocity sensors sampled in this document, the operating circuit shown in Figure 7 was used. Four types of material samples (material symbols A-D) show the sensor parts in Figure 7 in Table 1.
The fluctuations in the offset voltage of the sensor were investigated by replacing each of the two. In addition, for four types of data samples, the offset voltage was measured by changing the ambient temperature around the sensor from 20° C. to 30° C. using a constant temperature bath. FIG. 6 shows the results of examining the change in offset voltage in relation to temperature elapsed time.

According to the results shown in Figure 6, sample A is a conventional type of piezoelectric ceramic made by bonding two pieces of piezoelectric ceramic in series with opposite polarization axes for detection and drive. belongs to.

Material sample B is an angular velocity sensor with a tuning fork structure using piezoelectric bimorph elements 1.2 for detection, and material sample C is an angular velocity sensor using piezoelectric bimorph elements 3.4 for driving. Sample D is piezoelectric bimorph 1 for detection.
, 2 and a driving piezoelectric bimorph element 3.4 at the same time. In other words, by using either a sensing or driving piezoelectric bimorph element,
It can be seen from FIG. 6 that the change value of the offset output voltage of the angular velocity sensor has become smaller. In other words, it is possible to realize an angular velocity sensor whose major feature is that the variation in offset voltage is small when a temperature change is applied to the outer circumference of the sensor.

Effects of the Invention As is clear from the above explanation, according to the present invention, when a temperature change is applied to the outer circumferential portion of the sensor, the tuning fork structure including the piezoelectric bimorph element generates piezoelectricity due to heat conduction from the outer circumferential portion of the sensor. The effect was that offset voltage fluctuations in the sensor caused by the pyroelectric effect unique to the material were significantly reduced. In addition, in the same way as the electrical connection using a conductive electrode for canceling the pyroelectric effect according to the present invention, a small electrode and an electrical connection are made by dividing one part of the intermediate electrode and the outer picture electrode of the bimorph element on the cantilever support side. Since the connected terminal can be taken out as a lead electrode terminal and used as the drive electrode of the piezoelectric bimorph element for driving, it is possible to obtain stable vibration without imbalance of vibration amplitude with respect to the center of the piezoelectric bimorph element. Since the piezoelectric bimorph element can be driven with a low voltage, it is possible to eliminate drift fluctuations in the offset voltage caused by unnecessary vibrations of the piezoelectric bimorph element.

[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, and FIG. A graph showing changes in the offset voltage of the angular velocity sensor over time when the angular velocity sensor is changed. Fig. 7 is a block diagram of the conventional angular velocity sensor drive circuit. 1.2...・Piezoelectric bimorph element for detection, 3.4
...Piezoelectric bimorph element for driving, 5.6...
...Insulator joint (first joining member), 7...
... Conductor bonding member (second bonding member), 1a, 1c
... Electrode, le, Ig, lh, lj...
・Conducting electrode.

Claims (3)

[Claims] (1) A driving piezoelectric bimorph element, a sensing piezoelectric bimorph element, a first joining member for stacking and joining the driving piezoelectric bimorph element and the sensing piezoelectric bimorph element so that their vibration directions are orthogonal; a second joining member that joins the pair of elements to the tuning fork structure, and at least one of the driving piezoelectric bimorph element and the sensing piezoelectric bimorph element connects the piezoelectric body in the same polarization direction through an intermediate electrode. An angular velocity sensor which is a piezoelectric bimorph element made by bonding two piezoelectric bimorph elements together, and in which electrodes on both sides of the two piezoelectric bimorph elements are electrically connected. (2) The angular velocity sensor according to claim 1, wherein the electrodes on both sides of the drive piezoelectric bimorph element and the detection piezoelectric bimorph element are electrically connected by a conductive membrane electrode. (3) a driving piezoelectric bimorph element, a sensing piezoelectric bimorph element, a first joining member for stacking and joining the driving piezoelectric bimorph element and the sensing piezoelectric bimorph element so that their vibration directions are perpendicular; a second joining member that joins the pair of the piezoelectric bimorph elements to the tuning fork structure, and at least one of the driving piezoelectric bimorph element and the sensing piezoelectric bimorph element is connected to one of the electrodes on both sides of the piezoelectric bimorph element. a small electrode electrically separated from a part of the electrode, and the small electrode and the intermediate electrode of the piezoelectric bimorph element are electrically connected by a conductive membrane electrode, and the conductive membrane electrode is connected to the piezoelectric bimorph element. Angular velocity sensor used as input and output electrodes of the element.