JPS6270715A - Angular velocity sensor - Google Patents

Abstract

PURPOSE:To obtain the title sensor having a simple structure, enhanced in strength to impact and having high reliability, by coating the free end of a detecting piezoelectric element with an elastic member for absorbing impact. CONSTITUTION:A sensor element has such a structure that a driving piezoelec tric vibrator 2 and a detecting piezoelectric bimorph element 1 are arranged in parallel to a detection axis and orthogonally connected to each other. The free end of the element 1 is covered with an impact absorbing elastic member 7. The member 7 is formed, for example, from butyl rubber and the covering distance is limited only to the vicinity of the free end in order not to lower sensitivity detecting Coriolis force. By this method, the member 1 impinges against a sensor case 8 in the deflection quantity within the elastic limit of the vibrator 2 and the element 1 to prevent the deflection equal to or more than said elastic limit and the destruction of the leading end part of the element 1 by the collision of the vibrator 2 with the wall surface of the case 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a gyroscope, particularly to the structure of an angular velocity sensor using a piezoelectric vibrator.

BACKGROUND OF THE INVENTION Conventionally, a mechanical rotary gyro has been mainly used as an inertial navigation device using a gyroscope to determine the direction of a moving object such as an airplane or a ship.

Although this method can provide 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, there is a vibration-type angular velocity sensor that detects Coriolis force from a detection element excited by vibrating an object without using rotational force. Many have structures that employ piezoelectric and electromagnetic mechanisms.

In these, the motion of the mass that makes up the gyro is vibration rather than rotational motion at a constant angular velocity. Therefore, when an angular velocity of Ω is applied, the Coriolis force is generated as a vibration torque with a frequency equal to the frequency of the mass. The principle of the tJ+ type angular velocity sensor is to measure angular velocity by detecting vibrations caused by this torque, and in particular, many sensors using piezoelectric materials have been devised. (Journal of the Japan Society for Aeronautics and Astronautics, Vol. 23, No. 257, pages 339-350) Problems to be solved by the invention Based on the above principles, the prior patent application (Japanese Patent Application No. 1983-
185,825), but in order to achieve the compact and lightweight design that is characteristic of the vibrating type, a case to protect the vibrator is required, and a design with minimum dimensions is required. This is particularly an important factor for angular velocity sensors used in consumer equipment and electrical equipment.

On the other hand, the usage conditions in this field are strict, and the reliability of the sensor is also highly dependent. In particular, in the invention of the prior application which utilizes deflection vibration due to fixation of one end of the piezoelectric vibrator, the limit of deflection due to impact becomes a problem. The structure of a piezoelectric vibrator is that a thin ceramic plate is attached to a metal plate, and it vibrates elastically within a certain range, but when a large amount of deflection is applied, the ceramic plate cracks and loses its characteristics as a piezoelectric vibrator. destroy. As seen in the structure of the prior invention, the sensing piezoelectric element is orthogonally joined to the driving piezoelectric element, and the stress applied to the driving piezoelectric element increases, and the force received from impact increases, which may result in a fatal defect. was there. (There is no vibration at all.) The present invention has been made in view of the above points, and an object of the present invention is to obtain a highly reliable angular velocity sensor that has a simple structure, has increased strength against impact, and has high reliability.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention covers the free end of the detection piezoelectric element with a shock-absorbing elastic member, or provides a shock-absorbing elastic member inside the container housing the sensor. It is a covered structure.

action The effect of this technical means is as follows.

By covering the free end of the detection piezoelectric element with a shock absorbing elastic member, vibration resistance and shock resistance can be achieved. Up to a certain impact value, the shock is absorbed as a deflection of the support rod and within the elastic limit of the driving piezoelectric element, but if a greater deflection is applied, the sensor will be destroyed. In order to overcome the shock at this time, a shock absorbing elastic member is arranged, and when the drive piezoelectric vibrator, the detection piezoelectric vibrator, and the piezoelectric vibrator are deflected within the elastic limit, the shock absorbing elastic member hits the sensor case. By preventing the tip from bending further, it is possible to prevent the tip of the detection piezoelectric element from being destroyed due to a collision between the vibrator and the case wall.

The embodiment diagram is a structural diagram showing an embodiment of the angular velocity sensor of the present invention. In the figure, l is a detection piezoelectric element, 2 is a drive piezoelectric element, 3 is an electrode block, 4 is a support rod, 5 is a base, and 6
7 represents a joint member, 7 represents a shock absorbing elastic member, and 8 represents a case.

The operation of the angular velocity sensor of this embodiment configured as described above will be explained below.

First, to drive the driving piezoelectric element, an alternating current signal is applied between the opposing surfaces as common electrodes and the respective outer surfaces. The driving piezoelectric element 2 to which the signal is applied starts to vibrate with a phase difference of 18° based on the electrode block 3.
This is what is called tuning fork vibration.

Generally, a piezoelectric element having a cantilevered structure is determined by the piezoelectric constant of the material, dimensions and shape, but in this case, the piezoelectric element for detection 1, the piezoelectric element for drive 2, the joining member 6, the adhesive used for joining, etc. It is determined by the overall performance of

The resonance frequency of the tuning fork vibrator in this example is 260 to 300.
11z, and the amplitude at the free end of the detection piezoelectric element 1 is made to vibrate to about 100 μm.

At this time, butyl rubber was applied as a shock-absorbing elastic member to the free end of the detection piezoelectric element 1 to a thickness of 1 ml by dipping. Although butyl rubber was used in the example, it is generally a material that absorbs shock (rubber, plastic, fiber).
It is clear that the same effect can be obtained. It is best to limit the gap distance to only the vicinity of the free end. This is in order not to reduce the sensitivity for detecting Coriolika. or,
By adding mass to the tip, Coriolika works more, increasing the sensitivity of the sensor. However, if it becomes heavier, the Qm of the vibration system becomes smaller, so it is not preferable to make it too large.

In this example, the distance between the tuning fork vibrator and the inner wall of the case is approximately I.
It is designed to be about +1-.

Effects of the Invention As described above, according to the method of the present invention, a highly practical angular velocity sensor can be realized by increasing the impact resistance of the angular velocity sensor and without changing the function of the sensor.

[Brief explanation of drawings]

The figure is a schematic diagram showing one embodiment of the angular velocity sensor 11 of the present invention. 1... piezoelectric element for detection, 2... piezoelectric element for drive, 380010. Electrode pull 0.7, 41080
3. Support I Bong, 501.10. Base, 6...
Bonding member, 7... Elastic 915 material for shock absorption, 8
······Case. Name of agent: Patent attorney Toshio Nakahori Muyori・1 person/-&
For Clere/Lt, wood or 2--1 dynamic pressure" Hieko J--Electric collar 4-L line 5-Base 61--Torture (p morning 7-frrt! East expropriation Tanze Haoyu δ−−− Case

Claims (1)

[Claims] There is a sensor element in which a drive piezoelectric vibrator and a detection piezoelectric bimorph element are connected parallel to the detection axis and orthogonally to each other.
An angular velocity sensor characterized in that a free end of the piezoelectric bimorph element for detection is covered with an elastic member for shock absorption.