JPH03120415A - Vibration gyro - Google Patents

Abstract

PURPOSE:To detect torsional moment with high sensitivity by integrally molding two rectangular arm parts and a base part, which couples the arm parts mutually at the lower ends, of a piezoelectric material in a tuning fork shape on the whole. CONSTITUTION:The arm parts 16 and 17 and the base part 15 which are coupled at the lower ends with each other are molded integrally of piezoelectric mate rial. While the arm parts 16 and 17 are directed in the Z-axis direction of a three-dimensional coordinate system at an interval in the Y-axis direction, the base part 15 is polarized in the Y-axis direction and electrodes 24 and 25 are extended in the Y-axis direction on surfaces x1 and x2 at positions close to the top surface z1 of the base. For example, the electrode 24 is grounded and the electrode 25 is connected to a circuit for detection to obtain the vibra tion gyro which senses a component of torsional shearing stress around the Z-axis due to torsional moment when the torsional moment based upon Coroilis forces generated in the arm parts 16 and 17 operates on the base part 15 by rotating the arm parts 16 and 17 around the Z axis while vibrating them symmet rically in the Y-axis direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a vibrating gyro for sensing Coriolis force for the purpose of sensing angular velocity.

[Conventional technology]

As a conventional vibrating gyroscope of this type, for example, there is a piezoelectric type as shown in FIG. Two drive means 5 such as a bimorph vibrator, a unimorph vibrator, etc. made of piezoelectric material are fixed in a tuning fork shape, and each detection device also made of piezoelectric material is attached to the free end of each drive means 5. It is constructed by fixing the means 6 in such a manner that each wide side faces in a direction perpendicular to that of the drive means 5 forming the pair of arm members.

When using such a vibrating gyroscope, first,
An alternating current voltage is applied to the driving means 5 to cause the driving means 5 to vibrate symmetrically in the direction of the solid arrow in the figure (Y-axis direction). In addition to applying an AC voltage to the re-driving means 5, methods for producing such symmetrical vibration include applying an AC voltage to only one driving means 5 and using the other driving means 5 as a vibration monitor. There are methods of controlling the vibration state and thereby stabilizing the vibrations, but in any of these methods, the driving means 5 is vibrated in a resonant state to increase the vibration amplitude in order to strengthen the Coriolis force, which will be described later. It is said that

Next, under the vibration state of the driving means 5, the vibrating gyroscope is moved to Z.
By rotating the detection means 6 around the axis at an angular velocity ω, a Coriolis force Fc acts on the detection means 6 so as to deflect it in the direction of the broken arrow in the figure (X-axis direction) in accordance with the magnitude of the angular velocity ω. As a result, the detection means 6
A voltage is generated between the electrodes provided on the

Here, since this generated voltage is proportional to the magnitude of the Coriolis force Fc, by measuring the generated voltage, a voltage corresponding to the magnitude of the angular velocity ω can be obtained.

Incidentally, in boat fishing, the entire device as described above is supported by the support member 7, thereby increasing the operating efficiency in a resonant state.

[Problem to be solved by the invention]

However, in such conventional technology, the driving means 5
By having a structure in which the detection means 6 is connected to the tip of the
In addition to increasing the size of the device, there is a drawback that the wiring for supplying AC voltage to the drive means 5 and the wiring for extracting the signal voltage from the detection means 6 are complicated.
The wiring for these devices was very difficult due to the difficulty in routing the wires.

That is, the detection means 6 always detects a
The mass and elastic modulus of the wire for extracting the signal voltage, as well as the state of deformation, etc. mainly have a large influence on the vibration of the drive means 5 and reduce the detection sensitivity. Because it is a factor that causes fluctuations, the wire rod,
It is adhered to the side surface 5' of the driving means 5 and extends to the vicinity of the fixing means 4 with low vibration, and is pulled out from there to a predetermined connection terminal, and the predetermined connection terminal is extended to a position near the detection means 6. Therefore, measures have been taken to reduce the influence of the wire by shortening the length of the wire.

However, according to this, a significant reduction in the manufacturing efficiency of the vibrating gyroscope was unavoidable.

On the other hand, if the wide surface of the driving means 5 and the wide surface of the detecting means 6 are not exactly orthogonal, a vibration component in the Y-axis direction will leak into the detection signal from the detecting means 6. At the same time, the detection accuracy itself decreases. By the way, in a structure in which the end face of the driving means 5 and the end face of the detecting means 6 are directly connected as shown in the figure, it is impossible to achieve high connection accuracy by simply fixing them with adhesive. .

Therefore, a method has been proposed in which the driving means 5 and the detecting means 6 are connected via a connecting member 8 as shown in FIG. Each end portion of the means 6 is formed on the connecting member 8 and faces in mutually orthogonal directions,
By adhering via the electrodes provided thereon, it becomes possible to connect the drive means 5 and the detection means 6 relatively easily and at a high perpendicularity.

However, in this case, since the driving means adhesive surface and the detecting means adhesive surface of the connecting member 8 are oriented in directions perpendicular to each other, the adhesion of the driving means 5 and the detecting means 6 to the connecting member 8 is difficult. To do both at the same time, wait until the adhesive hardens.
Each of the drive means 5 and the detection means 6 is connected to a connecting member 8.
In addition, the structure of the jig required for accurately positioning and holding in a predetermined relative relationship becomes complicated, the jig becomes larger, and workability becomes worse. If the process is divided into steps, the number of man-hours will increase significantly.

[Background technology]

In general, when a force F as shown in FIG. 4 is applied to a piezoelectric bimorph element whose one end is fixed in a cantilever manner to cause it to deflect, approximately, V ” (3gs+-N-F)/(2t-w)g8.: Voltage output coefficient Il: Length t: Thickness W: Width. In addition to polarizing it in the direction shown by the white arrow,
Similarly, when force F is applied to shear deformation of the piezoelectric material 14, which has electrodes (not shown) provided on the upper and lower surfaces and acts as a sliding oscillator, V' = (t'' gta・F)/(
j! '・w') gas! Voltage output coefficient p': Length t': Thickness W': Width A voltage V' is generated.

Taking piezoelectric ceramic materials such as lead zirconate titanate (PZT) as an example, the voltage output coefficient gs+r gta is proportionally g+s/g3t.
~3, and although a sliding vibrator is more advantageous in terms of voltage output coefficient with respect to the applied force, the thickness t, t' width w, w', length f, J of each piezoelectric material As is clear from the above two equations, it cannot be said that a slip oscillator is always advantageous in terms of output voltage.

However, as shown in FIG. 6, the lower end of the driving means 5 is fixed to the fixing means 4, and while an AC voltage is applied to the electrodes of the driving means 5 to vibrate in the Y-axis direction, the fixing means 4 is moved between the two.
When the rotation is made around the axis at an angular velocity ω, the generated Coriolis force Fc is applied to the connecting portion 9 of the fixing means 4 with the driving means 5, in addition to the shear stress in the direction shown by the broken line arrow, as shown by the solid line arrow. A torsion moment l-M shown in FIG. 1 is applied to generate a force in a direction that twists the fixing means 4. Therefore, by actively utilizing this torsional moment M to measure the Coriolis force Fc, it is possible to improve the workability in manufacturing the vibrating gyroscope, and also to realize miniaturization of the vibrating gyroscope. Furthermore, high measurement accuracy can be achieved.

This invention was made with attention to this point,
It is equipped with a new vibration gyroscope that has never existed before.

To explain this in more detail, as shown in FIG.
0 and the arm 12 are connected via an intermediate member 11 having a rectangular profile with a long side length a and a short side length b as shown in FIG. When an axial force F is applied, a shear stress τ=F/
Along with a-b, a torsional moment M=F-L' with the Y-axis as the center of rotation acts, and this torsional moment M causes the intermediate member 11 to twist around the intersection O of the coordinate axes x, y, and z. A shear stress τ′ is generated. This torsional shear stress τ' becomes maximum at the midpoint A of the long side of the intermediate member 11 shown in FIG. 8, and its value is r'max=t"t, '7'α・a-b"α : It is a constant determined by the ratio a/b of the length of the long side and the short side.

This r'max is T'max/r = l for τ
, '/α, l),
Measuring the torsional shear stress τ′ is extremely effective.

Here, in order to simplify the explanation, the intermediate member 11 has a rectangular contour shape with a>b, but if a<b in FIG. 8, the maximum torsional shear stress acts on the midpoint B. Therefore, if a=b, the maximum torsional shear stress will act on both midpoints A and H. Incidentally, the torsional shear stress τ' exhibits a distribution in which it becomes zero at the center O and the four corners of the intermediate member 11, and has a high value at the midpoint of the sides.

As described above, as a result of the torsional shear stress τ' acting on the intermediate member 11 in addition to the shear stress τ, the intermediate member 11 undergoes a shear strain T due to the shear stress τ, as shown in FIG. and shear strain γ' due to torsional shear stress τ'.

Here, looking at the relationship between tensile and shear stress and electric displacement, the electric displacement generated when stress T and electric field E are applied to a piezoelectric material is expressed by the formula, and the piezoelectric material is lead zirconate titanate. For example, it is expressed as the electrical change when only stress T is applied. Here, it is assumed that the applied stresses T, ~T6 are acting in the directions shown in FIGS. 10 and 11, and the piezoelectric material is polarized in the third axis direction, as shown by the white arrow. It is assumed that

From the above, when the electrode is provided on a plane perpendicular to the first axis, the electrical displacement in the first axis direction due to stress is D+=d+5−Ts, which is equivalent to the shear around the second axis. It becomes a slip oscillator that generates electrical displacement in response to stress Ts.

Next, as shown in FIG. 12, a plane Xl perpendicular to the X-axis
+X2, a plane y++ yz perpendicular to the Y axis, and a plane ZI+22 perpendicular to the two axes. Torsional shear stress τ in orthogonal planes
Consider the electrical displacement caused by the action of ′.

First, the piezoelectric material 14 is polarized in the X-axis direction, and a torsional shear stress τ'ρ acts on a point P+ on the plane y1.

If the direction of makes an angle α with the X axis, then the plane y,
A torsional shearing stress τIpI, which is equal in magnitude and opposite in direction to the torsional shearing stress τ′ρ1 acting on the point P1, acts on the upper point P2, which is opposite to the point P, and both points Pl.

In the region connecting Pt, the electrical displacement from point P toward point P2 is pp+=d,, τ'PI CO5α, so this electrical displacement is in the range of −π/2≦α<π/2, The polarity is different in the range of π/2≦α<3π/2.

Therefore, the present invention achieves a torsion moment M by appropriately combining the polarization direction of the piezoelectric material and the electrode arrangement.
To provide a small and highly accurate vibration gyroscope that can detect with high sensitivity.

[Means to solve the problem]

The vibrating gyroscope of the present invention has two rectangular arm portions (with adjacent surfaces facing perpendicular to each other) and a base portion interconnecting these arm portions at their lower ends using a piezoelectric material. The entire shape is shaped like a tuning fork, and both arms are oriented in the Z-axis direction of the three-dimensional coordinate system, and the base part is positioned at intervals in the Y-axis direction.
Polarized in the axial direction, located on each surface of the base portion perpendicular to the X axis, located close to the top surface, bottom surface, or both sides of the top and bottom surfaces of the base portion, and extending in the Y-axis direction. It is equipped with a detection electrode.

[For production]

Here, when both arm parts are vibrated symmetrically in the Y-axis direction and rotated around the Z-axis to generate a Coriolis force in each arm part, the base part will have the same effect as described above. , a torsional moment due to the Coriolis force acts, and a torsional shear stress is generated due to this screw moment. Therefore, in the vibrating gyroscope of the present invention, the vibration around the Z axis generated in the base portion by both arm portions is By detecting the torsional shear stress component, the torsional moment and thus the Coriolis force can be detected with excellent sensitivity.

Moreover, in this vibrating gyroscope, by making the fixed part that is integrated with the arm part function as a sliding oscillator, the detection means 6 mentioned in the prior art can be made unnecessary, and the device can be sufficiently miniaturized. By making it possible to arrange the wire in the fixed part and its vicinity, it is possible to advantageously eliminate the trouble associated with routing the wire.

In addition, since there is no need to connect the arm portion to the fixed portion, it is possible to manufacture a vibrating gyroscope with high dimensional accuracy and uniform performance.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIGS. 1(a) to 1(e) are perspective views showing embodiments of the present invention.

In FIG. 1(a), 15 in the figure indicates the base part, and
16 and 17 indicate the first and second arm portions, respectively;
These arm parts 16,17 are integrally formed of piezoelectric material with the base part 15 interconnecting their lower ends.

Here, this molded body having a tuning fork shape as a whole with adjacent surfaces facing each other at right angles is attached to the arm portion 1.
6.17 is oriented in the Z-axis direction of the three-dimensional coordinate system, and
In the state where the first arm portion 16 is positioned at intervals in the Y-axis direction, the first arm portion 16 is polarized in the X-axis direction as shown by the white arrow in the figure, and this first arm portion 16 is 16, X
The first surface (the surface on the near side in the figure) perpendicular to the axis XI and the second surface first and second electrodes 18,19 are provided.

Here, among these electrodes, if the first electrode 18 is grounded and a driving AC voltage is applied to the second electrode 19,
The first arm portion 16 vibrates in the Y-axis direction.

By the way, if the frequency of the applied alternating current voltage is the resonant frequency of the molded body, then the first arm portion 16 and the second arm portion 17
vibrate symmetrically in the Y-axis direction, resulting in a large vibration amplitude.

Note that here, if the second arm portion 17 is polarized in an appropriate direction and an electrode is also formed there,
The second arm portion 17 can function as a vibration monitor for controlling the vibration state.

Further, in the base portion 15 of the molded body in the above-mentioned posture, it is polarized in the Y-axis direction, and electrodes 24, 25 are placed at positions close to the top surface z1 of the base on each surface Xl, x. Each of these is provided to extend in the Y-axis direction.

Note that the one shown in FIG.
25' is provided close to the bottom surface z2 of the base portion 15, and in the example shown in FIG. An example is shown in which a pair of detection electrodes 24.24' and 25.25' are provided, and these also provide the same functions and effects as the above embodiment (FIG. 1a).

According to such a configuration, for example, by grounding the electrode 24 and connecting the electrode 25 to a detection circuit, the first arm portion 16 and the second arm portion 17 can be vibrated symmetrically in the Y-axis direction. At the same time, when a torsional moment based on the Coriolis force generated in each arm portion 16, 17 is applied to the base portion 15 by rotating it around the Z-axis, the torsional shear stress due to the torsional moment is A vibrating gyro that senses the components of is introduced.

Although the present invention has been described above based on the illustrated examples, it goes without saying that various materials such as lead zirconate titanate, lead titanate, barium titanate, etc. can be used as the piezoelectric material 14.

〔Effect of the invention〕

Thus, according to the present invention, by detecting the Coriolis force at the base portion, the vibrating gyroscope can be made smaller and lighter, and the electrodes can be concentrated on the base portion and its vicinity. This makes it extremely easy to route the wire.

Moreover, by integrally molding the base portion and the first and second arm portions using piezoelectric material, there is no need to connect them at all, and vibrations with high dimensional accuracy and stable performance can be achieved. Can bring gyro.

In addition, two planes X whose electrode formation planes are perpendicular to the X axis.

Since it is limited to x2, it is possible to reduce the number of electrode printing steps and reduce production costs.

[Brief explanation of the drawing]

Figures 1(a) to (C) are perspective views showing embodiments of the present invention, Figure 2 is a perspective view showing a conventional example, and Figure 3 is a perspective view illustrating a conventional connecting member. , 4th to 1st
2 are reference views for explaining the present invention. 14... Piezoelectric material, 15... Base portion, 16, 1
7...Arm part, 18.19...Electrode, 20-27
···electrode. Figure 1 (a) Figure 9! ! Figure 0 @ 11 Figure 31 Arc stress/Force force - To r/Ka

Claims (1)

[Claims] 1. Two rectangular arm portions and a base portion that interconnects these arm portions at their lower ends are integrally molded from a piezoelectric material to have a tuning fork shape as a whole, and the both arm portions are made of The base part is polarized in the Y-axis direction, with the base part facing in the Z-axis direction of the three-dimensional coordinate system and spaced apart in the Y-axis direction, and the base part is perpendicular to the X-axis. A vibrating gyroscope in which each surface is provided with a detection electrode located close to the top surface, bottom surface, or both sides of the top and bottom surfaces of a base part.