JPH03108670A - Supporting method of angular velocity sensor - Google Patents

Abstract

PURPOSE:To enable prevention of the fluctuation of an angular velocity output due to the vibration of or a shock on a piezoelectric bimorph element for detection by fitting a sensor to the fore end of a shock absorber which is fixed at one end to an angular velocity detecting case body and has a cantilever structure. CONSTITUTION:An outer case 11 wherein an angular velocity sensor is held is fitted to the fore end of a shock absorber 13 which is fixed at one end to an angular velocity detecting case body 12 and has a cantilever structure, and the opposite directions of a piezoelectric bimorph element for detection and the direction of deflection of the cantilever are made equal to each other. When a shock is given, according to this constitution, the cantilever of the shock absorber 13 is deflected if the modulus of elasticity thereof is lower than that of the piezoelectric bimorph. Consequently, the whole of the angular velocity sensor fitted to the fore end thereof inclines and no deflection occurs in the piezoelectric bimorph element for detection. When a vibration approximating the resonance frequency of the cantilever is impressed, the cantilever is deflected in a large degree and the angular velocity sensor fitted to the fore end thereof shakes to a large extent. If the resonance frequency of the cantilever is set to be low sufficiently, however, the shaking does not affect an output of the angular velocity sensor. Accordingly, the fluctuation of the angular velocity output due to the vibration can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a tuning fork structure vibration type angular velocity sensor in which a ceramic piezoelectric element is arranged in a tuning fork structure. The present invention relates to a support method in which vibration does not easily affect the operation of a sensor.

Conventional technology A conventional method of supporting an angular velocity sensor is shown in FIG.

In FIG. 8, 1 is an outer case housing a tuning fork structure vibration type angular velocity sensor, 2 is a shock absorber, 3 is a mounting bracket, and 4 is a housing.

Problems to be Solved by the Invention However, such a support method cannot prevent vibrations and shocks from the casing from being transmitted to the sensor body. The tuning fork structure vibration type angular velocity sensor has the disadvantage that its output fluctuates due to external vibrations and shocks, and is particularly vulnerable to vibrations and shocks in the direction of deflection of the piezoelectric bimorph used for detection, and is susceptible to vibrations near the frequency of tuning fork vibrations and tuning fork vibrations. The problem was that it was vulnerable to shocks containing harmonics of frequency components.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention has been developed by attaching it to the tip of a shock absorber having a cantilever structure υ whose one end is fixed to an angular velocity detection casing. and the plane direction of the detection piezoelectric bimorph element.

Also, the first angular velocity detection axis is perpendicular to the angular velocity detection axis. It has a mounting means rotatable about an axis parallel to the plane of the second sensing piezoelectric bimorph element, and the first... The angular velocity sensor is attached to the angular velocity detection housing with a weight distribution such that the mass on the side where the second detection piezoelectric bimorph element is attached is heavier than the other side, and when translational acceleration is applied, the It is equipped with a shock absorber that suppresses rotational force about parallel axes.

Effect When vibration or impact is applied to the above structure, the acceleration generated by the vibration or impact causes the beam supporting the sensor to deflect, tilting the entire tuning fork structure away from the angular velocity detection axis. Although the detection axis may be misaligned, the piezoelectric bimorph for detection does not deflect due to vibration or impact, and the problem of fluctuations in the angular velocity output does not occur.

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

First, a tuning fork structure vibration type angular velocity sensor will be explained using FIGS. 5 to 7.

The angular velocity sensor has a structure as shown in FIG. 6, and is mainly composed of a drive element made of four piezoelectric bimorphs, a monitor element, and first and second detection elements, including a drive element 101 and a first detection element 103. The first
The vibration unit 109 and the second vibration unit 110 in which the monitor element 102 and the second detection element 104 are orthogonally joined at the joint 106 are connected by a connecting plate 107, and this connecting plate 107 is supported at one point by a support rod 108. It has a tuning fork structure.

When a sine wave voltage signal is applied to the drive element 101.

The first vibration unit 109 starts to vibrate due to the inverse piezoelectric effect, and the second vibration unit 11o also starts to vibrate due to the tuning fork vibration. Therefore, the charge generated on the surface of the monitor element 102 due to the piezoelectric effect is proportional to the sinusoidal voltage signal applied to the drive element 101. This monitor element 10
Stable tuning fork vibration can be obtained by detecting the electric charge generated in the tuning fork 2 and controlling the sinusoidal voltage signal applied to the drive element 101 so that the electric charge has a constant amplitude.

The mechanism by which this sensor generates an output proportional to the angular velocity will be explained using FIGS. 6 and 7. Figure 6 shows the angular velocity sensor shown in Figure 6 viewed from above, and shows the speed υ
When rotation at an angular velocity ω is applied to the sensing element 103 which is vibrating at , a "Coriolis force" is generated in the sensing element 103.

This "Coriolis force" is perpendicular to the speed υ and has a magnitude of 2 mυ
It is ω. Since the detection element 103 is vibrating like a tuning fork,
If the sensing element 103 is vibrating at a speed υ at a certain point, the sensing element 104 is vibrating at a speed -0, and the "Coriolis force" is -2 mυω.

Therefore, the sensing elements 103 and 104 are connected to each other as shown in FIG.
The device is deformed in the direction of the Coriolis force, and a charge is generated on the surface of the device due to the piezoelectric effect. Here, υ is the motion caused by the vibration of the tuning fork, and if the vibration of the tuning fork is (j = ll @sin ωot Good: amplitude of tuning fork vibration ω.: the period of tuning fork vibration, then the "Coriolis force" is F = a -ω*sinωot, which is proportional to the angular velocity ω and the tuning fork amplitude a.

This becomes a force that deforms the sensing elements 103 and 104 in the plane direction. Therefore, the amount of surface charge Q of the sensing elements 103 and 104 is.

Qoc a −ω−sinω. t, and assuming that the tuning fork amplitude a is controlled to be constant.

Qocω-sinω. 1, and the amount of surface charge Q generated on the sensing elements 103 and 104 is obtained as an output proportional to the angular velocity ω, and this signal is ω. If the waveform is detected at t, a DC signal proportional to the angular velocity ω can be obtained.

Note that even if a translational motion other than angular velocity is applied to this sensor, charges of the same polarity are generated on the surfaces of the two sensing elements 1o3 and 104, so when converted to a DC signal, they cancel each other out and the output is output. It looks like there isn't.

However, in reality, there are variations in sensitivity of piezoelectric bimorph elements and variations in sensor assembly, so when vibrations or shocks are applied, the angular velocity output fluctuates. In particular, near the resonant frequency of the tuning fork, resonance causes a large deflection of the sensing piezoelectric bimorph element, resulting in a large fluctuation in the angular velocity output.

FIG. 1 shows one embodiment of the present invention, in which an outer case 11 containing a tuning fork structure vibration type angular velocity sensor has a shock absorber 1 having a cantilevered structure with one end fixed to an angular velocity detection housing 12.
3, and both directions of the detection piezoelectric bimorph element and the direction of deflection of the beam are the same.

When an impact is applied using the conventional method of supporting an angular velocity sensor, the piezoelectric bimorph sensing element is deflected as shown in FIG. 2, and an electric charge is generated on its surface. According to the method for supporting an angular velocity sensor of the present invention, when an impact is applied, if the beam of the impact absorber 13 has an elastic modulus lower than that of the piezoelectric bimorph, as shown in FIG. The entire angular velocity sensor at the tip is tilted (piezoelectric for detection)
(No deflection occurs in the immolor element. When vibration near the beam's resonant frequency is applied, the beam deflects greatly and the angular velocity sensor at its tip sways greatly, but the beam υ
If the resonance frequency is set sufficiently low, even large fluctuations will not affect the output of the angular velocity sensor.

FIG. 4 is a diagram showing another embodiment of the method for supporting an angular velocity sensor according to the present invention. The sensor is constructed so that the entire sensor rotates when a 1gf1 impact is applied, and the detection axis is rotated as explained in FIG. 3. The piezoelectric bimorph element for detection does not bend due to misalignment.

In FIG. 4, reference numeral 14 denotes a holding member provided on the outer periphery of the outer case 11, and a bearing plate 1 attached to the angular velocity detection housing 12.
6 is rotatably supported.

16 is a shock absorber attached to the lower surface of the holding member 14.

That is, a mounting means is provided that is rotatable about an axis perpendicular to the angular velocity detection axis and parallel to the surface of the piezoelectric bimorph element for detection, and the piezoelectric bimorph element for detection is attached to this parallel axis. The angular velocity sensor is attached to the angular velocity detection casing 12 in such a manner that the mass of one side is heavier than the other, and a shock absorber suppresses the rotational force with respect to the parallel axis when translational acceleration is applied. 16.

Note that it is preferable for the shock absorber 1e to be made of a material with a spring elastic modulus as small as possible.

Effects of the Invention According to the present invention, it is possible to prevent fluctuations in the angular velocity output due to in-plane vibrations and impacts of the detection piezoelectric bimorph element, which are the most serious problem of the tuning fork structure vibrating angular velocity sensor.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a method for supporting an angular velocity sensor according to an embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams for explaining the effects thereof, and FIG. 4 is another embodiment of the present invention. FIG. 6 is a perspective view of a tuning fork structure vibration type angular velocity sensor, FIGS. 6 and 7 are explanatory diagrams of operation, and FIG. 8 is a perspective view showing a conventional method of supporting an angular velocity sensor. 11... Outer case, 12... Angular velocity detection housing. 13.16... Shock absorber, 14...
Holding member. 16... Bearing is plate, 101... Drive element, 1o2... Monitor element, 103...
...First sensing element, 104... Second sensing element, 106, 106... Joint part, 107...
...Connecting plate, 109...First vibration unit, 110...Second vibration unit.

Claims (2)

[Claims] (1) A first vibration unit in which a driving piezoelectric bimorph element and a first sensing piezoelectric bimorph element are mutually orthogonally joined, and a monitoring piezoelectric bimorph element and a second sensing piezoelectric bimorph element are mutually connected. The driving piezoelectric bimorph element and the monitoring piezoelectric bimorph element are arranged so that the first and second vibration units are parallel to each other along the detection axis. When installing an angular velocity sensor with a tuning fork structure in which the free ends are connected by a connecting plate to an angular velocity detection housing, one end is attached to the tip of a shock absorber with a cantilevered structure fixed to the angular velocity detection housing. , and the deflection direction of the beam and the first,
A method for supporting an angular velocity sensor in which both directions of a second piezoelectric bimorph element for detection are aligned. (2) A first vibration unit in which a driving piezoelectric bimorph element and a first sensing piezoelectric bimorph element are mutually orthogonally joined, and a monitoring piezoelectric bimorph element and a second sensing piezoelectric bimorph element are mutually connected. The driving piezoelectric bimorph element and the monitoring piezoelectric bimorph element are arranged so that the first and second vibration units are parallel to each other along the detection axis. When installing an angular velocity sensor with a tuning fork structure in which the free ends are connected by a connecting plate to an angular velocity detection housing, a It has a mounting means that is rotatable about the shaft, and the mass of the side on which the first and second sensing piezoelectric bimorph elements are mounted is heavier than the other side with respect to the parallel shaft. A method for supporting an angular velocity sensor, which includes: mounting an angular velocity sensor on an angular velocity detection casing with a different weight ratio; and providing a shock absorber that suppresses rotational force with respect to the parallel axis when translational acceleration is applied.