JPH0462414A - Angular velocity sensor - Google Patents

Abstract

PURPOSE:To reduce a drift which is caused by unnecessary vibration propagation by using piezoelectric ceramic which is sintered by isotropic hot hydrostatic pressing as an element for detection and driving. CONSTITUTION:The piezoelectric ceramic is formed by performing the isotropic hot hydrostatic pressing for >=1 hour under a condition of up to 300-500atm. within a temperature range from temperature which is 200 deg.C lower than sintering temperature where 85% ideal density is obtained to sintering temperature where 96% ideal density is obtained. This ceramic is used for elements 1 and 2, and 3 and 4 for detection and driving and those elements are joined together alternately and orthogonally into tuning fork structure. Consequently, the low-drift, high-accuracy angular velocity sensor which has superior mechanical shock strength is obtained while the generation of unnecessary vibration is suppressed.

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.

2. Description of the Related Art 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 electrical equipment such as navigation systems, 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. This provides a stable orientation, but
Since it is mechanical, the device is large 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. The original form of this structure is U.S. Patent 25
No. 44646.

According to this, rectangular plates of a driving elastic body (for excitation) and a detection elastic body are linearly and orthogonally joined, and the velocity (V
) to detect the Coriolis force acting on the sensing elastic body. A conventional angular velocity sensor will be explained below with reference to the drawings.

FIG. 3 shows a configuration diagram of a block diagram including a conventional angular velocity sensor and a drive circuit, in which drive piezoelectric bimorph elements 103, 104 and detection piezoelectric bimorph elements 101, 102 are arranged parallel to the detection axis and mutually. There are sensing piezoelectric bimorph elements 101 and 102 orthogonally joined via joining members 105 and 106, and a vibration element that drives this pair and is joined at one end of the driving piezoelectric bimorph elements 108 and 104 with a support 107. shall be. and,
The vibration element and the base 1090 are supported and connected by one metal elastic member 108, and the driving piezoelectric bimorph element 10
3 and 104 causes the tuning fork to vibrate, and when an angular velocity is applied to the detection piezoelectric bimorph elements 101 and 102, an output is obtained.

Next, the operating circuit will be explained. First, by applying a drive signal to the driving piezoelectric bimorph element 103 and causing it to vibrate, the driving piezoelectric bimorph element 104 resonates and starts tuning fork vibration. Then, the amplitude signal obtained from the drive piezoelectric bimorph element 104 is detected by a drive monitor circuit 112, compared with a reference voltage 113, and passed through an automatic gain adjustment circuit (AGC circuit) 114 to a drive circuit 115.
The amplitude of the tuning fork vibration is kept constant by feedback.

Further, the signal obtained from the sensor elements 101 and 102 using the phase signal obtained from the drive piezoelectric bimorph 103 is outputted to the detection circuit 1 by the output signal of the drive monitor circuit 112.
10 performs synchronous detection, and a filter circuit 111 extracts the angular velocity component.

By the way, in these conventional sensors, due to non-uniformity of the members, unnecessary radiant vibrations (spurious) and parasitic vibrations caused by vibration transmission of the driving piezoelectric bimorph elements 103 and 104 and the detection piezoelectric bimorph elements 101 and 102, as well as parasitic vibrations. Higher-order vibrations occur, non-uniform vibrations occur due to imbalance of tuning fork vibrations, and unnecessary vibrations propagate throughout the tuning fork vibration system, resulting in:
When the angular velocity signal component is extracted, a drift over time occurs in the output signal as shown in FIG. Moreover, temperature drift fluctuations are likely to occur in the output due to temperature changes.

That is, as an angular velocity sensor, it greatly influences drift characteristics, which is one of the major performance indicators.

Problems to be Solved by the Invention One of the causes of drift in conventional angular velocity sensors is said to be caused by unnecessary microvibration generation and vibration propagation due to the uniformity of members.

That is, conventional vibration type angular velocity sensors have limitations as high-precision sensors, and it has been difficult to improve them to higher precision.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a low-drift angular velocity sensor in which drift caused by unnecessary vibration propagation is reduced in a small-sized vibrating gyroscope that does not use rotational force.

Means for Solving the Problems Therefore, as a means for solving the problems, the present invention provides a temperature range from a temperature 200° C. lower than a firing temperature at which the theoretical density is 85% to a firing temperature at which the theoretical density is 96%. Piezoelectric ceramics, which are isostatically pressed under conditions of a maximum pressure of 300 to 5,000 atmospheres for more than one hour, are used as sensing and driving elements, and the elements are orthogonally joined to each other to form a tuning fork structure. By doing so, it is possible to obtain a highly reliable angular velocity sensor that suppresses the generation of unnecessary vibrations, has low drift, is highly accurate, and has excellent mechanical impact strength.

In other words, the present invention provides an effect in which unnecessary vibration components are not generated due to the generation, propagation, reflection, etc. of unnecessary minute vibrations in the tuning fork vibration system.

In other words, by using piezoelectric ceramics for the vibrating element body consisting of a tuning fork structure, which has been improved in density and has fewer micropores, it is possible to absorb this unnecessary vibration.
Or to prevent it.

Furthermore, mechanical strength is improved. Specifically, by using piezoelectric ceramics sintered by isostatic pressing for sensing and driving piezoelectric bimorphs, and by creating a tuning fork structure, unnecessary vibration components are not generated, and unnecessary vibration components are eliminated. It also prevents the propagation of
A low-drift angular velocity sensor will be realized.

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

1 and 2 show the structure of the sensor section. First, let us explain from Fig. 2. 1.2.34 in Figure 2 is a piezoelectric bimorph, Pb (Mgl/3°Nb2/3)03. P
bTio3. A piezoelectric material whose main components are PbZrO3 was used. Here, piezoelectric bimorph 1.2 will be referred to as a sensing piezoelectric bimorph, and piezoelectric bimorph 3.4 will be referred to as a driving piezoelectric bimorph.

First, the raw material powder mainly composed of the three components was
Molded into a columnar shape with an image height of 30m, this molded body was molded into 8011
Preliminary firing was performed at 1150° C. for 2 hours in a fiφ tubular furnace.

The resulting density was 87% of the theoretical density. The pre-fired body thus obtained was heated to a maximum temperature of 110°C using a mixed gas 2 of inert gas and oxygen gas having a volume ratio of argon gas and oxygen gas of 90:10 as a pressure medium.
Piezoelectric ceramics were obtained by performing isostatic press treatment for 2 hours at 0° C. and a maximum pressure of 1000 atm. This piezoelectric ceramic was then processed into a piezoelectric bimorph as follows.

Piezoelectric bimorph 12 for detection has dimensions 9X1.6X0.35
mm, and also piezoelectric bimorph 3 for driving
, 4 have dimensions of 9 x 1.6 x O, and are processed in the same manner in order of 50. The insulator joint 5.6 is made of polyamide plastic and has a recess of φ1.6×2. and,
Piezoelectric bimorphs 1 and 3 are placed in the recess of this insulator joint.
Then, 2 and 4 were made perpendicular to each other and adhesively bonded.

Next, two sets of piezoelectric bimorph orthogonal bodies (1, 5, 3) (2, 6, 4) obtained in this way are placed in a conductor joining member 7, for example, with dimensions of 1.9 x 1.6 x 1.6
Drill a hole of φ0.6 in the center of the brass block marked with the mark, and conductively connect it to form the tuning fork structure shown in Figure 2. That is,
The conductor joining member 7 is inserted between the piezoelectric bimorphs 3.4 for driving, and is electrically conductive and mechanically bonded to the inner surface electrode of the piezoelectric bimorph.

Next, lead terminal parts 8, 11, 12, 13, 14° 15
．． 16 is a lead terminal for electrically connecting the piezoelectric bimorphs 1.2 and 3.4, each of which is made of insulating glass 9.
17.18.19.20 2122, it is attached to the support base 10 mainly made of Fe in an insulated state, and is used as a lead terminal for electrical connection with the outside.

Further, the lead terminal 8 is inserted into the central hole of the conductor joining member 7 and fixed by adhesive.

Next, the relay board 23 is connected to the lead terminals 13, 1415.1.
6 and for electrically connecting the piezoelectric bimorph for detection, the lead terminals 13, 14, 15 .
It is attached to 16. The first section shows the state in which this relay board 23 is installed as a completed product.

Below, FIG. 1 will be explained.

By the way, the relay board 23 described above is made of phenol and has an external dimension of φ7.5. It is processed to a thickness of 0.6 nm, and through holes are provided at four locations through which the lead terminal portions pass, allowing the four lead terminals to pass through and hold.

To hold the relay board 23, copper foil is provided around the upper portions of the four through holes of the relay board 23, and these parts are soldered.
The relay board 23 is held and fixed by soldering.

Next, the detection piezoelectric bimorph 1 and the lead terminal 1316 are connected with lead wires 24 and 25.

For connection, both ends of the lead wires 24 and 25 are joined by soldering. Also, a piezoelectric bimorph for detection 2 and a lead terminal 14.
15 using lead wires 2627 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, the outer electrode part and the tip of the drive piezoelectric bimorph 4 are
The lead wire 2 is connected between the lead terminal 12 bent in a letter shape.
Solder the wires using step 9. In addition, piezoelectric bimorph 3 for driving
Similarly to the above, the outer electrode portion of the piezoelectric bimorph 3 and the lead terminal 11 are connected by soldering using the lead wire 28.

The product thus produced was sealed with an Fe can case 30 (dimensions: φ8.2×28 m+n), and the contact portion between the base 10 and the can case 30 was joined by spot electric welding. For comparison, we also prototyped an angular velocity sensor with a tuning fork structure using a piezoelectric bimorph obtained by conventional heating treatment in air.

Two kinds of material samples obtained as above (material numbers 1 to 2)
2) and the temporal and temperature drift characteristics of the output signal of the sensor are shown in Table 1.

The temporal drift characteristics were evaluated by replacing the part of the conventional angular velocity sensor shown in FIG. 3 with the aforementioned material sample numbers 1 and 2. By the way, the temporal drift characteristic values in Table 1 shown in the present invention are as follows:
It was expressed as a voltage signal level ratio of 0.1 to 101 (z) in the angular velocity detection signal component. Example: The drift value over time of sample number 2 is expressed as Odb.The temperature drift indicates the offset fluctuation rate of the sensor when the temperature is -35℃ to 85℃, compared with conventional Example standard 0%
That is.

Table 1 As is clear from Table 1, the angular velocity sensor of the present invention has a drift variation value over time of -3 compared to that of the conventional example.
Very low at 0db. In addition, since the sensor of the present invention has a lower level of unnecessary vibration, it has a higher temperature drift (change in output offset voltage with respect to temperature fluctuations of -35 to 85°C) than a sensor obtained with a conventional configuration. Fluctuations are improved by 40% compared to the conventional method. moreover,
A 30% increase in strength against mechanical impact can also be obtained.

In other words, by using piezoelectric ceramics obtained through isostatic pressing, it is possible to improve temporal drift fluctuations, temperature drift fluctuations, and mechanical impact strength, thereby improving reliability. An angular velocity sensor with excellent characteristics can be obtained.

By the way, the reason why the piezoelectric ceramic of the piezoelectric bimorph is subjected to isostatic pressing is based on the following three reasons.

(1) The first reason is that dense piezoelectric ceramics cannot be obtained at a firing temperature of 200°C or lower than the firing electric potential at which the theoretical density is 85%, or at pressure conditions of 300 atm or lower, and it is difficult to reduce temperature drift. does not have a large effect.

(2) The second reason is that when hot isostatic pressing is performed at a firing temperature of 96% or higher of theoretical density, the composition of piezoelectric ceramics becomes partially unstable, and the tuning fork vibration function as a sensor deteriorates. do.

(3) The third reason is that if the pressure of the isostatic press is 5,000 atmospheres or more, the effect of densification cannot be improved as a ceramic, and the effect in terms of sensor characteristics is saturated. It is.

Effects of the Invention As described above, the angular velocity sensor of the present invention has a lower drift fluctuation value over time than the conventional one, and the sensor of the present invention has a low unnecessary vibration level, so it is less susceptible to temperature changes. Compared to sensors obtained with conventional configurations, temperature drift (change in output offset voltage in response to temperature fluctuations of -35 to 85°C) has been improved, and the strength against mechanical shock has also been improved. can be done.

In other words, by using piezoelectric ceramics obtained through isostatic pressing, it is possible to improve temporal drift fluctuations, temperature drift fluctuations, and mechanical impact strength, thereby improving reliability. An angular velocity sensor with excellent characteristics can be obtained.

[Brief explanation of drawings]

1 and 2 are a partially cutaway perspective view and an exploded perspective view showing the structure of an angular velocity sensor according to an embodiment of the present invention, respectively, FIG. 3 is a block diagram showing a conventional angular velocity sensor and a drive circuit, and FIG. The figure is a diagram showing the temporal drift characteristics of a conventional angular velocity sensor. 1.2...Piezoelectric bimorph for detection, 34...
... Drive piezoelectric bimorph, 5.6 ... Insulator joint, 7 ... Conductor joining member, 8, 1
1,1213.14.15.16...Lead terminal section, 917.18,19,20,21.22...
...Insulating glass, 10...Support base, 23.
...Relay board, 24, 25. 26.
27. 28. 29 ・・・ ・ ri −
Dwyer, 30...can case. Name of agent: Patent attorney Shigetaka Awano Haka 1 person! , //
, //, 〃, ま, /j, It Lead Sabako EP! , /7. //, ! l //, //, //S stand, Suino 1 lath // Support J (base〃 Medium super grave removal 14,,', r, //, /ri, //,, PP lead wire J/ Den case

Claims (1)

[Claims] Isostatic hot isostatic pressing for 1 hour or more under conditions of a maximum of 300 to 5000 atm in a temperature range from 200°C lower than the firing temperature at which the theoretical density is 85% to the firing temperature at which the theoretical density is 96%. An angular velocity sensor characterized in that piezoelectric ceramics are used as sensing and driving elements, and the elements are orthogonally joined to each other to form a tuning fork structure.