JPH03214016A - Angular-velocity sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

2. Description of the Related Art Conventionally, a mechanical rotary gyro has been mainly used as an inertial navigation device using a gyroscope as a means of determining 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 bulky and expensive, and it is difficult to apply it to equipment that requires miniaturization.

On the other hand, there is a vibration-type angular velocity sensor that vibrates an object without using rotational force and detects the "Coriolis force" from the vibrated sensing element. Many of these structures employ piezoelectric and electromagnetic mechanisms.

In these cases, the mass that makes up the gyro does not move at a constant speed, but instead vibrates. Therefore, when an angular velocity is applied, the Coriolis force occurs as a vibration torque with a frequency equal to the frequency of the mass. The principle of a vibration-type angular velocity sensor is to measure angular velocity by detecting vibrations caused by this torque, and in particular, many sensors using piezoelectric bodies have been devised. (Journal of the Japan Society for Aeronautics and Astronautics, Vol. 23, No. 267, pp. 339-360) Based on the above principle, an angular velocity sensor was invented in a prior patent application (Japanese Patent Application No. 126206/1983), and its structure is shown in Figure 2. show. As shown in FIG. 2, the detection piezoelectric element 21 is stacked and connected to the driving piezoelectric element 23 using a joining member 22 so that the vibration direction is perpendicular to the driving piezoelectric element 23, and a driving electrode 26 is formed on the driving piezoelectric element 23. Then, these two sets of assembly members are connected by an elastic connecting member 26. With this structure, lead patterns 24 and 24 are connected to the drive piezoelectric element 23 via lead wires 27 from the support bin 29 installed on the base 30.
It is electrically connected by a signal line formed by 3b, and further connected to the electrode of the detection piezoelectric element 21 by conductive pastes 31aL and 31b.

The related operations of each component of the conventional angular velocity sensor configured as above will be explained. First, an alternating current signal is applied between the driving electrodes 26 on the outer surfaces of a pair of drive piezoelectric elements 23 connected by the elastic coupling member 2e, using the surfaces facing each other as common electrodes. The drive piezoelectric element 23 to which the signal is applied starts to vibrate symmetrically around the elastic coupling member 26, which is what is called a tuning fork vibration.

The detection piezoelectric element 21, which is mechanically joined to the driving piezoelectric element 23 vibrating in this manner by the joining member 22, also vibrates. Therefore, when rotation at an angular velocity ω is applied to the detection piezoelectric element 21 which is vibrating at a speed V, a "Coriolis force" is generated in the detection piezoelectric element 21. This "Coriolis force" is perpendicular to the velocity m and its size is 2 mm where m
represents the equivalent mass of the tip of the sensing piezoelectric element).

Since the tuning fork is vibrating, if one of the detection piezoelectric elements 21 is vibrating at a velocity of ma at a certain point, the other piezoelectric detection element 21 is vibrating at a velocity of The force is -2mm. Coriolis forces acting in opposite directions act on the pair of detection piezoelectric elements 21, causing them to deform in opposite directions, and charges are generated on the surfaces of the elements due to the piezoelectric effect.

The pair of sensor elements are wired so that charges generated by the "Coriolis force" are added to each other.

Therefore, 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 pair of detection piezoelectric elements 21, so that they cancel each other out and no output is produced.

Here, Ma is the speed caused by tuning fork vibration, and the tuning fork vibration speed is Ma=Mao-5inω, 1 Ma0: Tuning fork vibration speed amplitude ω. :If it is the angular period of tuning fork vibration, then "Coriolis force" is F0=2Ill・ma.・ω・Sinω. t, the angular velocity ω and the tuning fork vibration velocity ma. The force is proportional to the force that deforms the detection piezoelectric element 21 in the plane direction. Therefore, the surface charge amount Q0 of the detection piezoelectric element 21 is Qcc+cvo·ω−sinω. 1 Tuning fork vibration velocity amplitude. If is controlled constant, then Qcocω-sinω. 1, and the amount of surface charge Q generated on the detection piezoelectric element 21 is obtained as an output proportional to the angular velocity ω, and this signal is ω.

If synchronous detection is performed at t, a DC signal proportional to the angular velocity ω can be obtained.

Further, charges are generated in a pair of opposing driving electrodes 26 (one electrode is not shown) on the driving piezoelectric element 23 in accordance with the deformation of the driving piezoelectric element 23, but Since the electrodes 26 are symmetrical in shape and have the same area, the generated charges are equal, so by differential input,
The generated charge is canceled by signal processing.

Problems to be Solved by the Invention However, in the past, epoxy-based thermosetting adhesives were used to bond the driving piezoelectric element and the joining member, and the sensing piezoelectric element and the joining member, so the manufacturing process of orthogonal assembly was not possible. This poses a serious problem for angular velocity sensors in that the piezoelectric elements that make up the angular velocity sensor are partially depolarized because they are exposed to high temperatures for thermosetting, which accelerates the deterioration of the element's sensitivity. Ta.

The present invention takes this problem into consideration, and provides a piezoelectric device without deterioration of the piezoelectric element.
The present invention aims to provide an angular velocity sensor using a piezoelectric element.

Means for Solving the Problems In order to achieve the above object, the present invention provides two orthogonal sensor elements in a tuning fork shape, in which a driving pressure and electric element and a detection piezoelectric element are orthogonally connected to each other via a joining member. In the assembled angular velocity sensor, an ultraviolet curing adhesive is used to bond the drive piezoelectric element and the bonding member, and the detection piezoelectric element and the bonding member.

Function: In the angular velocity sensor of the present invention having the above configuration, the driving piezoelectric element and the joining member, and the sensing piezoelectric element and the joining member are hardened and bonded by irradiation with ultraviolet rays, so there is almost no temperature rise, and it is possible to orthogonally assemble. There is no need to expose the piezoelectric element to high temperatures during the manufacturing process, so the polarization state of the piezoelectric element is not destroyed and there is no deterioration in the sensitivity of the element.Furthermore, since a temperature bath is not required, it can be easily bonded when desired.

EXAMPLES Hereinafter, examples of the angular velocity sensor of the present invention will be described with reference to the drawings.

As shown in FIG. 1, a silver electrode 1 is placed on the driving piezoelectric element 6.
, lead patterns 21L and 2b are formed, and the electrical connection with the detection piezoelectric element 3 is made using a conductive silver base) 41L,
This is done in 4b. Mechanical connection is performed by a joining member 6, and an ultraviolet curing adhesive 7 is used for adhesion.

Regarding the angular velocity unit of this embodiment configured as described above, the related operations of the constituent elements will be explained below.

The explanation of the principle of angular velocity detection will be omitted since it is the same as the conventional example. The drive piezoelectric element 6 applies an AC voltage to the electrode 1, causing it to vibrate like a tuning fork, which in turn causes the detection piezoelectric element 3 to vibrate, and when an angular velocity is applied, it receives a force due to the "Coriolis force" and is therefore driven. Strength is required for the bonding between the piezoelectric element 6 and the bonding member 6, and the piezoelectric element 3 for detection and the bonding member 6.

Since the present invention uses an ultraviolet curing type, the bonding is cured with reliable strength by irradiation with ultraviolet rays, and there is almost no temperature rise, and the above bonding can be performed without being exposed to high temperatures during the orthogonal assembly manufacturing process. . Therefore, the polarization state of the piezoelectric element is not destroyed, so there is no deterioration in the sensitivity of the element, and there is no need for a special high temperature bath, so it is possible to provide an innovative angular velocity sensor that can be easily bonded when desired. I can do it. In particular, in the ultraviolet curable adhesive 7, epoxy resins and acrylic resins are nearly transparent and have high hardness and strength, so that workability and reliability are improved.

As an actual ultraviolet curable adhesive, for example, there is an epoxy adhesive XNR-5400 series manufactured by Ciba Geigy Japan.

Effects of the Invention As is clear from the above explanation, the present invention provides an angular velocity sensor in which two sensor orthogonal elements are assembled in a tuning fork shape, in which a drive piezoelectric element and a detection piezoelectric element are orthogonally connected to each other via a joining member. Therefore, the driving piezoelectric element is vibrated by applying an alternating current voltage, and the sensing piezoelectric element is caused to vibrate in its own way by the "Coriolis force." Strength is required for the bonding, but by using an ultraviolet curable adhesive for the adhesive, it is possible to ensure reliable bonding between the drive piezoelectric element and the bonding member, and between the sensing piezoelectric element and the bonding member. In addition to providing strength, since the adhesive is cured by irradiation with ultraviolet rays, there is almost no temperature rise, and there is no exposure to high temperatures during the orthogonal assembly manufacturing process, and the polarization state of the piezoelectric element is not destroyed. There is no deterioration in sensitivity.

Moreover, since a high-temperature bath is not required during curing, it is possible to provide an innovative angular velocity sensor that can be easily bonded when desired.

[Brief explanation of drawings]

FIG. 1 is a partial perspective view of the vicinity of a joining member of an angular velocity sensor according to an embodiment of the present invention, and FIG. 2 is a perspective view of a conventional angular velocity sensor. 3...-Piezoelectric element for detection, 6... Piezoelectric element for drive, 6... Bonding member, 7... Ultraviolet curing adhesive.

Claims (2)

[Claims] (1) A driving piezoelectric element, a sensing piezoelectric element, and a joining member for joining the two piezoelectric elements, the driving piezoelectric element and the sensing piezoelectric element being connected to each other by the joining member. An angular velocity sensor that is stacked and bonded so that the vibration directions are perpendicular to each other, and that an ultraviolet curing adhesive is used for the bonding. (2) The angular velocity sensor according to claim 1, wherein the ultraviolet curable adhesive is an epoxy resin or an acrylic resin.