JPS62188975A - Piezoelectric angular velocity sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor having a stable performance suitable for mass production with a simple construction, by arranging a drive section vibrating vertically or laterally along the length thereof and a sensor section extended vertically thereto, both made up of a uniform one piece piezoelectric body. CONSTITUTION:When a voltage is applied from an AC power source 6, a drive section 1 vibrates laterally in the direction X being parallel with electrodes 3a and 3b with a resonance frequency according to the length and a sensor section 2 integral with this portion does so in the direction of X accordingly. Under such a condition, as an angular velocity OMEGA of rotation is applied about an axis in the direction of the sensor section 2 extends, namely, in the direction Z, a force works in the direction Y vertical to both directions X and Z to cause the sensor section 2 to perform a bending vibration in the direction Y starting from the joint with the drive section 1. With the bending vibration of the sensor section 2, voltages, with the size almost equal, proportional to forces working on respective electrode faces are generated by a piezoelectric property, but opposite in the porality to each other. The voltages opposite in the porality are added up respectively by conducting connections properly to obtain a large voltage. So to speak, it possible to detect a voltage with a size proportional to an angular velocity OMEGA of rotation about the Z axis.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a vibrating piezoelectric angular velocity sensor.

2. Description of the Related Art Conventionally, an angular velocity sensor configured as shown in FIG. 7 has been commercially available. In the figure, numeral 2 is a drive section made of bimorph, and 2' is a sensor section also made of bimorph, which are abutted at right angles at their ends and joined with adhesive.

The bimorph has electrodes 3' a and 3' on both sides, respectively.
b (or 3'0.3'd) attached to the central metal plate 3 (the electrode on the adhesive surface is not shown).
It has a structure in which both sides of 'e are bonded with adhesive, and between electrodes 3'a and 3'b on both surfaces, or between electrodes 3'a and 3'b,
When a voltage is applied between 'a (or 3'b) and the central metal plate 3'e, one piezoelectric plate expands in the length direction and the other piezoelectric plate contracts. It is possible to cause bending displacement. Conversely, if force is applied to the bimorph to cause bending displacement, what happens to both surfaces? Il&3'c
, 3'd, or between electrodes 3'C (or 3'd
) and the central metal plate 3'e.

4' is a support for fixing one end of the drive section, 5' is a lead wire for applying voltage to the drive section, and 6' is a power source. Further, 7'a and 7'b are lead wires for detecting the voltage generated in the sensor section 2'.

Now, when an AC voltage is applied to the electrodes 3'a and 3'b under the drive part from the electric current [6', the drive part causes bending vibration, and the tip of the sensor part 2' moves in the bending direction of the drive part, that is, in the X direction. It vibrates. In this state, when an angular velocity Ω is applied around the Z axis, a Coriolis force is generated in the Y direction.
ce), the sensor part 2', whose lower end is fixed under the drive, generates bending vibration in its bending displacement direction (Y direction), and a voltage proportional to the displacement, that is, the Coriolis force, is applied to the lead wire 7. 'a.

7'b, and a voltage ■ proportional to the angular velocity Ω can be detected. (V ac vΩ when the perturbation velocity is V) Problems to be Solved by the Invention This type of angular velocity sensor is small, has a large eaves, has a simple structure, and can be a highly sensitive sensor.

However, various problems occur when using a bimorph-structured vibrator. For example, the two piezoelectric plates attached to both sides of the central metal plate 3'e are required to have exactly the same shape and the same performance. If the performance of the two piezoelectric plates is different, the bimorph will bend or twist as the temperature changes, resulting in a decrease in accuracy and temperature drift. Furthermore, a similar phenomenon occurs when the state of adhesion to the central metal plate is different. These are in a range that cannot be controlled under normal manufacturing conditions. In addition, the adhesive is plastic, and its thermal and mechanical properties cannot be said to be stable, and it does not necessarily return to its original position after force is applied to the angular velocity sensor or after the infection changes, and it does not return to zero point. This causes a drift.

Furthermore, these phenomena are also related to the difference in thermal expansion between the central metal plate and the piezoelectric plate. The same is true for bimorphs that do not use adhesive, in which a metal layer is embedded in place of the central metal plate and sintered together.

Most of the above problems are caused by the use of two piezoelectric plates in the vibrator, which results in uneven performance of the piezoelectric bodies on both sides.

Means for Solving the Problems In the present invention, a drive section that vibrates vertically or transversely in the length direction and a sensor section that extends perpendicularly to the drive section are made of a homogeneous integral piezoelectric material, and the drive section vibrates vertically or horizontally in the direction of the sensor. The sensor part is configured to bend due to a force acting perpendicularly to both directions, and the angular velocity of rotation is measured by detecting the voltage generated by the bending. By using a piezoelectric body that is homogeneous and integrated as a whole, problems caused by the presence of bonded parts and layers are eliminated, and stable vibration in one direction is easier to obtain for driving than the bending vibration of bimorphs. To obtain an angular velocity sensor that uses vertical or transverse vibration of a piezoelectric body and easy-to-detect bending vibration in the sensor part, is suitable for mass production, and has stable performance.

Embodiment FIG. 1 shows an embodiment of the angular velocity sensor of the present invention, which comprises a vibrator, a power source, a fixing base, etc.

In the figure, 20 is a piezoelectric vibrator that constitutes the main part of the angular velocity sensor, and 1 is a drive unit installed at the bottom of the drawing, and both sides are made of silver, platinum, etc. as indicated by diagonal lines. Electrodes 3a and 3b are provided, and this electrode [!
For example, the electrodes are polarized perpendicularly to the electrode plane. Reference numeral 2 denotes a sensor section extending perpendicularly from the drive section, and on both sides of the sensor section are interdigitated electrodes 3c made of an electrically conductive metal such as silver or platinum.

3d is installed, and the interdigital electrodes 30.3dlO are polarized on both sides in the direction perpendicular to the electrodes. Reference numeral 9 denotes a support section that is on the same plane as the sensor section and extends perpendicularly from the drive section 1, and this section does not need to be polarized.

4 is a fixing base for fixing the support part 9. , 5 is the electrode 3a
, 3b are connected to lead wires, and 6 is an AC power source. 7
a, 7b are interdigital electrodes 3c.

3d, so that the detection signals of the electrodes 3c and 3d on both sides, which are provided plane symmetrically, are added.
Lead a7''a (not shown) on the back side is lead 1 on the front side.
I7b and the lead wire 7''b (not shown) on the back side are connected to the glue dot t/jA7a on the front side. 10 is a slit for separating the sensor part 2 and the support part 9.

In this device, when a voltage is applied to the drive section 1 from the AC power source 6, the drive section moves to the electrode 3a at a resonant frequency depending on the length.
, 3b, that is, in the X direction, the sensor portion 2, which is integrated with this portion, also vibrates in its width direction (X direction). In this case, depending on the length of the sensor section extending from the drive section, the sensor section also causes bending vibration in the X direction. Under these conditions, when an angular velocity Ω of rotation is applied in the direction in which the sensor section extends, that is, around the axis in the Z direction, a force acts in a direction perpendicular to both the X and two directions (Y direction), and the sensor section 2 performs bending vibration in the Y direction starting from the joint with the drive section. When the sensor section undergoes bending vibration, the length of one rrL pole surface in the sensor extension direction contracts, and the distance between the electrodes expands. In addition, opposite dimensional changes occur on other electrode surfaces. When such a dimensional change occurs, due to piezoelectricity, approximately equal voltages are generated on the six electrode surfaces in proportion to the applied force, but with opposite signs. Voltages of opposite sign can be added by making suitable connections to obtain larger voltages. That is, a voltage proportional to the angular velocity Ω of rotation around the Z-axis can be detected.

The homogeneous, integral vibrator 20 of the present invention can be easily manufactured by providing slits 10 in a piezoelectric plate by cutting or other methods. That is, slits 10 are formed in a piezoelectric plate made of sintered material such as lead zirconate titanate using a cutter or the like. Next, the electrode 3 is formed by a method such as screen printing or vapor deposition.
8-3d [pull]. A DC high voltage is applied in a conventional manner between the electrodes g+3a and 3b and between the electrodes 3C and 3d on both sides of the sensor section to polarize them. By making the electrodes 30 and 3d on both sides of the sensor section plane symmetrical not only in their arrangement but also in their polarization as described above, it is effective to prevent bending or twisting of the sensor section due to stress generated during manufacturing. Incidentally, the slit 10 can also be provided after the polarization is completed.

Fig. 2 shows another embodiment of the present invention, which has two sensor parts extending from the drive part in a pair and a support part 9 for fixing it in the center of the drive part. This embodiment is different from the embodiment shown in FIG. 1, but the functions of the drive section and sensor section are the same as in FIG. In this embodiment, when the drive section vibrates in a direction parallel to the electrodes 3a and 3b, that is, in the X direction, each pair of sensors vibrates in opposite directions in the width direction, that is, in the X direction. Therefore, when an angular velocity Ω is applied in the direction in which the sensor extends, that is, around the axis in the Z direction, the directions of vibration of each sensor caused by the force in the Y direction also become opposite to each other, and the single sensor section described in Fig. 1. The voltages added on the front and back sides are almost the same in magnitude for a pair of sensor sections, but have opposite polarities.

It has been disclosed in Japanese Patent Application Publication No. 2003-11111 that when the signals of a pair of vibrators vibrating in opposite directions are connected in a cylinder manner, the signal itself becomes larger, and also has the effect of canceling out various acoustic noises added from the outside. This is also described in Publication No. 174854/1982.

Similarly to FIG. 1, the angular velocity sensor of this embodiment can also be manufactured as an integral piece by cutting or slitting a homogeneous piezoelectric plate.

Fig. 3 shows a vibrator 20, which is the main part of an angular velocity sensor, in which two slits 10 are provided in a homogeneous piezoelectric plate, both ends of which are used as sensor sections, and a support section 9 is provided between the two slits.
This shows another embodiment, and its operation and functions are exactly the same as the embodiment shown in FIG. This embodiment has the advantage that the support section is formed by the slit section 10, and that there is a margin in design for the length of the drive section and the width dimension of the sensor section.

As in the previous embodiment, it can be manufactured by slitting a homogeneous piezoelectric plate.

FIG. 4 shows another embodiment of the vibrator. In the embodiment of FIG. 3, the vibrator 20 has a slit 10' in the center of the sensor section parallel to the electrode surface, and The thin comb makes it easier to cause bending vibration, and this thickness also makes interdigitation 1! The purpose is to provide a design margin in the relationship between I#I3c and 3dll& to obtain an optimal state for voltage detection.

In this embodiment, each sensor section is provided with electrodes 3c and 3d on only one side, and the electrodes are polarized. Therefore, the two sensors on the front and back sides can be used as one sensor in the same way as shown in FIG. 3, or the sensors on the diagonals can be used as a pair of sensors, and various other methods can be used.

FIG. 5 shows another embodiment of the vibrator 20 formed in the shape of a single rail, in which numeral 1 denotes a driving section, and electrodes 3a and 3 are provided on both sides of the vibrator 20.
b is provided, and the electrodes are polarized. Two slits 10 extending perpendicularly to the electrode surface of the driving section provide a sensor section 2 having interdigital electrodes 3c and 3d at both ends, respectively, and has a configuration similar to that shown in FIG. 3. That is, an AC voltage is applied between the electrodes 3a and 3b of the drive section,
When vibrated horizontally in the X direction, the sensor sections 2 at both ends vibrate in opposite directions in the width direction, and function similarly to the embodiment shown in FIG. 3.

This vibrator can be obtained as a homogeneous integral body by cutting the piezoelectric block shown by the dashed line.

Figure ff16 shows an embodiment of the vibrator 20 that can detect rotational angular velocities in two directions that are perpendicular to each other.

It is integrally composed of four plate-shaped stomachs that are orthogonal to each other, and the two adjacent wings are sensor parts 2-1 and 2-2 (
The device has interdigital electrodes (not shown) for detecting voltage on the surface, and drive portions 1-1 and 1-2 at the bottom, respectively, and has a structure similar to that of the embodiment shown in FIG. The other two plates 11-3, 1-4 form part of the driving section, and electrodes 3a are provided on the surface of the flat plate.

3b, and the space between them is polarized in the thickness direction.

That is, when an AC voltage is applied between the electrodes 3a and 3b with the support part 9 fixed, the drive part 1 vibrates the sensor part 2 in the width direction by transverse vibration, and the sensor part 2-1 at both ends
and 2-2 both vibrate in opposite directions as in the target embodiment. In this state, when an angular velocity Ω of rotation is applied in the Z-axis direction, the sensor section 2-1 bends in the Y direction and generates a signal, and the angular velocity Ω of rotation in the Z-axis direction is applied.
When ' is applied, the sensor section 2-2 bends in the Y-(Z) direction and generates a signal. In this embodiment, the plate-shaped drive portion 1-3.1-4 is effective in increasing the excitation force and at the same time maintaining balance.

As can be inferred from FIG. 5, this embodiment can also be manufactured as an integral piece by cutting or other methods from a block made of a homogeneous piezoelectric material.

Effects of the Invention Since the vibrator of the present invention can be manufactured from a single plate-shaped or block-shaped material, the entire vibrator is homogeneous. In addition, the structure is simple and can be manufactured as a single piece with minimal processing such as cutting, which improves the performance that would otherwise occur when using multiple materials or using a composite material that has undergone processing such as adhesion or bonding. It is excellent for this type of sensor that can prevent bias and requires high accuracy and reproducibility.

As is clear from each of the embodiments, the structure is extremely simple and the manufacturing process is easy, so another major feature of the present invention is that it can be easily produced and manufactured at low cost while maintaining high precision.

By combining the vertical or transverse vibration drive of a piezoelectric material with excellent directionality compared to the bending vibration of a bimorph, and the bending vibration that allows easy signal detection, a vibrating piezoelectric angular velocity sensor with the above-mentioned characteristics can be obtained. It will be done.

In addition, in the embodiment, the vibration of the drive unit is transverse vibration in the direction perpendicular to the electric field, but for example, in the embodiment shown in FIG. 3, electrodes are provided at both ends of the drive unit 1 in the death,
When applying an alternating current voltage between the same electrodes, it is also possible to vibrate in the X direction as longitudinal vibration.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing one embodiment of the angular velocity sensor of the present invention, Fig. 2 is a perspective view showing another embodiment of the invention, and Figs. FIG. 7 is a perspective view showing a conventional example of an angular velocity sensor.

Claims (1)

[Claims] A driving part that vibrates vertically or horizontally in the length direction and a sensor part that extends perpendicularly to the drive part are made of a homogeneous and integrated piezoelectric material, and the sensor part is bent by the force acting perpendicularly to both directions, and the sensor part is bent by the bending. A piezoelectric angular velocity sensor configured to detect voltage.