JPH0627133A - Three dimensional acceleration sensor - Google Patents

Abstract

PURPOSE:To obtain a highly reliable three dimensional acceleration sensor, which can detect the three dimensional accelerations acting on the same mass point and can be manufactured easily. CONSTITUTION:A three dimensional acceleration sensor has three piezoelectric elements 3, which are arranged in the directions of an axis (x), an axis (y) and an axis (z), a spherical body 2, which is inscribed with three piezoelectric elements 3 and bonded to the corresponding piezoelectric element at a contact point, and a charge detection circuit 8, which is connected to each piezoelectric element 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a device using a piezoelectric element.
The present invention relates to a sensor that detects acceleration in three dimensions, and more specifically, to a three-dimensional acceleration sensor that detects the magnitude and direction of a force acting on an object.

[0002]

2. Description of the Related Art In order to accurately obtain gravity and force acting on an object in a three-dimensional space, it is necessary to obtain information on acceleration at the same point in three dimensions at the same point, that is, force acting on the same mass point. is there. A conventionally known three-dimensional acceleration sensor uses three one-dimensional acceleration sensors as disclosed in, for example, Japanese Patent Application Laid-Open No. 63-118667.
In many cases, it constitutes a three-dimensional acceleration sensor.

As shown in FIG. 10, the acceleration sensor disclosed in Japanese Laid-Open Patent Publication No. 63-118667 has three one-dimensional acceleration sensors 22 in which silicon is processed on a block 21, x-axis and y-axis. And arranged in the z-axis direction. In this one-dimensional acceleration sensor 22, the force acting on the weight portion 23 is applied to the bending portion 24 and the resistance portion 2 of the substrate 26 is provided.
At 5, it is detected as a change in the resistance.

However, in such an acceleration sensor, it is difficult to make the weight portion 23, the bending portion 24, and the resistance portion 25 of the three one-dimensional acceleration sensors 22 uniformly, the masses in the respective directions are different, and the sensitivity is also poor. It has the drawback that it tends to be uniform. There is also a problem that the structure and the processing circuit are complicated due to the correction.

In order to solve these problems, a sensor for detecting a three-dimensional acceleration acting on the same mass point is disclosed in Japanese Patent Laid-Open Nos. 63-149568 and 1-220267.
The one proposed in Japanese Patent No. 0 is known.

Here, as an example, Japanese Patent Laid-Open No. 1-20267
The three-dimensional acceleration sensor disclosed in Publication No. 0 will be described with reference to FIG. The acceleration sensor supports the spherical weight 31 via the support medium 33 at three or more fulcrums 32, and detects the magnitude and direction of the force acting on the fulcrum 32 via the support medium 33.

However, in the structure of the sensor according to this method, since the spherical weight 31 is supported by three or more supporting media 33, the occupied space needs to be large to some extent. There are problems that the sensitivity is not uniform and the spherical weight 31 is likely to rotate.

Further, in manufacturing, it is necessary to have an advanced technique in which the fulcrum 32 must be brought into contact with the spherical weight 31 accurately toward the center of the spherical weight 31, and
Since the position of the center of the spherical weight 31 and the position of the center of gravity are strictly different, there is a problem that it is quite difficult to maintain this state stably for a long time. Especially support medium 3
When 3 is an elastic body (a spring in the embodiment),
Even if the center of the spherical weight 31 and the position of the center of gravity are exactly aligned with each other, the shape of the support medium 33 changes due to stress relaxation of the support medium 33, and it is difficult to stably maintain the preferable state for a long time. It is necessary to solve such problems.

[0009]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and works on the same mass point.
An object of the present invention is to provide a three-dimensional acceleration sensor that can detect three-dimensional acceleration, is easy to manufacture, and has high reliability.

[0010]

In order to achieve this object, the three-dimensional acceleration sensor of the present invention has an x-axis which is orthogonal to each other.
Piezoelectric elements each having an axial direction, an y-axis direction, and a z-axis direction as operating axis directions; And a charge detection circuit connected to the element.

It is preferable that the piezoelectric element is supported on a rigid body disposed on the opposite side of the sphere from the piezoelectric element. In addition, the piezoelectric element is preferably thin so that the entire sensor can be made small, and preferably comprises a polymeric piezoelectric film and electrodes provided on both sides of the polymeric piezoelectric film.

[0012]

In such a three-dimensional acceleration sensor, x
Three piezoelectric elements arranged in the three-dimensional directions of the axis, the y axis, and the z axis are directly bonded to one sphere. When acceleration acts on the spherical body, an external force is directly applied from the spherical body to each voltage element by the acceleration, and the piezoelectric element is expanded and contracted by the external force. Due to this expansion and contraction, electric charge is generated in each piezoelectric element, and the electric charge is taken out by the electric charge detection circuit as information representing the external force transmitted from the spherical body to the piezoelectric element, that is, the acceleration. The accelerations acting on one sphere are simultaneously and directly detected by the voltage elements arranged in the three-dimensional direction, that is, the accelerations acting on the same mass point are simultaneously detected in the three-dimensional direction. So 3
Accurate measurement of dimensional acceleration.

Further, since each piezoelectric element is directly bonded to the sphere, the whole sensor can be made compact, and no members are interposed between them, so that the manufacturing is easy and the reliability is high.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show a three-dimensional acceleration sensor according to an embodiment of the present invention. FIG. 1 is a perspective view of a sensor according to the present invention. Here, the three piezoelectric elements 3 are arranged so as to form a box so that their operating axes are the x-axis, the y-axis, and the z-axis direction, and the vinyl chloride sphere 2 is these three piezoelectric elements. It is inscribed in the element 3. In addition, these are arranged in the frame 1 made of vinyl chloride, and the three piezoelectric elements 3
Are respectively joined to the frame 1.

The sphere 2 is an inscribed contact with each piezoelectric element 3,
It is joined to each piezoelectric element 3. The sphere 2 does not have to be made of any material in order to obtain any required mass, and in some cases,
It is also conceivable that the electrodes are made of metal and used as electrodes for extracting charges generated in the piezoelectric element 3.

The three piezoelectric elements 3 are formed of a polymer piezoelectric film 4, specifically P (VDF-TrFE) (vinylidene fluoride-trifluoroethylene copolymer) on both sides of which electrodes A5 are provided.
And an electrode B6. This will be described with reference to the sectional view of the piezoelectric element shown in FIG.

One electrode B6 is formed by evaporating aluminum on the other surface of the polymeric piezoelectric film 4, and the electrode A5 is formed of the polymeric piezoelectric film 4.
4 is bonded to the copper thin film formed on one surface of the rigid plate 7 in FIG. 4 with an epoxy adhesive.

If the polymer piezoelectric film 4 can easily form the electrode B6 and can form the piezoelectric element 3 by adhering it to an electrode formed on another member such as the electrode A5, the other piezoelectric piezoelectric film 4 can be formed. The material may be a piezoelectric film, or may be replaced with an inorganic material.

Further, in general, when the piezoelectric polymer film 4 is flexurally deformed, electrodes A5 and B6 on the front and back of the piezoelectric polymer film 4 are used.
In the well-known signal processing in which the fixed resistor (R1) 12 and the fixed resistor (R1) 12 (FIG. 2) are connected in parallel, an output due to the deformation cannot be obtained. For this reason, when the polymeric piezoelectric film 4 is lined with the rigid plate 7 and subjected to acceleration acting on the sphere 2, the polymeric piezoelectric film 4 does not bend, and expansion and contraction in the thickness direction occurs. , Get the output of the expansion and contraction. Therefore, the rigid plate 7 can be not only a general circuit board material such as glass epoxy but also a thin plate such as silicon, glass or ceramic, which has rigidity and can be easily formed with electrodes.

As is well known, the polymer piezoelectric film 4 has electrodes A5 and B6 on the front and back and a fixed resistance (R1) as described above.
In the circuit configuration in which 12 and 12 are connected in parallel, an output corresponding to the generation of electric charge can be obtained only when the expansion and contraction of the piezoelectric body changes. That is, the piezoelectric element 3 can obtain electric charge only when the sphere 2 is accelerated.

Since the piezoelectric polymer film 4 has a function as a power generator, the current supply from the outside for detecting the acceleration is small and the processing circuit can be easily constructed.

Further, the electrode B6 contacts the sphere 2 at a minute portion, but if the force is increased or decreased in this portion for a long period of time, there is a possibility of damage due to mechanical fatigue. May be added. In the piezoelectric element 3, one electrode A5 is formed on the rigid plate 7 and the polymer piezoelectric film 4 is adhered thereto. However, one in which electrodes are formed on both sides of the polymer piezoelectric film 4 is rigid. It may be attached to the plate 7.

These three piezoelectric elements 3 are arranged in the x-axis, y-axis and z-axis directions in the frame 1 made of vinyl chloride. This frame 1 is made of a rigid material and is used as the electrode A of the piezoelectric element 3.
Although it depends on the arrangement of the electrodes 5, it is preferable to use an insulator so that these electrodes A5 are not short-circuited.

Next, the electric circuit will be described with reference to FIGS. FIG. 2 is a charge detection circuit diagram in the present invention.
The charge detection circuit 8 has a role of converting the charge generated in the polymer piezoelectric film 4 into a voltage, and also a role of impedance conversion for converting a high impedance of the polymer piezoelectric film 4 into a low impedance to facilitate later signal processing. .

The charges generated on the electrodes A5 and B6 of the polymer piezoelectric film 4 are fixed resistance (R1) connected to the electrode A5.
The voltage flows to 12 and becomes a voltage according to the amount of charge, and is impedance converted into the resistance value of the resistor (R2) 14 through the field effect transistor (Tr) 13. Although not shown, the electrode B6 is connected to the minus power supply terminal 11 of the charge detection circuit 8 by a lead wire or the like. In FIG. 2, the arrow in the piezoelectric polymer film 4 indicates the polarization direction.

The back side of a rigid plate incorporating this circuit is shown in FIG. This is the above-mentioned field effect transistor (Tr) 1
3, the specific mounting of the resistor (R1) 12 and the resistor (R2) 14 is illustrated. Note that the charge detection circuit 8 does not necessarily have to be provided on the back surface of the rigid plate 7, and may be provided at a place where electrical noise from a commercial power source or other electrical equipment can be shielded.

By the way, as one method of removing noise due to environment such as temperature and other vibrations and pressure changes to improve accuracy, as shown in FIG. 7, one piezoelectric element 3a used for measurement has the same environment. The other piezoelectric element 3b is provided in a position close to that so that the detection value of only the noise component of the other piezoelectric element 3b is subtracted from the detection value including the noise component of the one piezoelectric element 3a used for measurement. There is a method of removing noise.

For example, as shown in the surface of a rigid plate according to another embodiment in FIG. 6, two electrodes C5 having the same area are formed on the rigid plate 7.
a, an electrode D5b is provided, and one of the two piezoelectric elements is electrically opposed to the other piezoelectric element 3b as shown in FIG. They are connected in series, one piezoelectric element 3a detects the acceleration (force) from the sphere 2, and the other piezoelectric element 3a.
For b, only the noise component is detected. According to this structure, since the polarization directions of the piezoelectric elements 3a and 3b are opposed to each other, the noise component is automatically erased in the two piezoelectric elements 3.

As still another method, another piezoelectric element 3 is provided so that an output with a sign opposite to that of the piezoelectric element 3 used for measurement is obtained, and the piezoelectric element 3 common to the pair of two piezoelectric elements 3 is provided. It is also possible to obtain a doubled output signal as a sum by subtracting and removing the noise component and subtracting the signal component.

For example, as shown in FIG. 8 as a three-dimensional acceleration sensor according to another embodiment, two piezoelectric element assemblies shown in FIG. 1 are made and their directions are changed to each other to form a box. To configure. There is only one sphere 2 and this sphere 2
Are inscribed in two piezoelectric elements 3 arranged in the x-axis, y-axis and z-axis directions, that is, a total of six piezoelectric elements 3 of two pairs, and are bonded to the corresponding piezoelectric elements 3 at the contact points. To do. As a result, the two piezoelectric elements 3 in the x-axis, y-axis, and z-axis directions are provided with signal outputs having polarities opposite to each other, and a substantially common noise component is superimposed.

As described above, the pair of piezoelectric elements 3 are connected in series with the polarization directions of the piezoelectric elements 3 facing each other, or in FIG. 9, the piezoelectric element 3 is connected in parallel. As shown in FIG. 3, the noise component is automatically erased in the two piezoelectric elements 3 by any of the methods in which the polarization directions are opposite to each other and are connected in parallel. In the two piezoelectric elements 3, the signal component is doubled in the above series connection,
It does not change in parallel connection. By adopting these methods, a three-dimensional acceleration sensor with a high SN ratio can be obtained.

Incorporating the present invention into any device, for example:
When the toy (car) is fixed and the toy is actuated, a force obtained by multiplying the mass by acceleration is applied to the sphere in each axial direction (x axis, y axis, and z axis) of the sphere, and the x axis, y axis, and Each of the three piezoelectric elements detects the component force in the z-axis direction. In fact, a reaction force, which is equivalent to the force acting on the mass of the sphere with respect to the inertial force of the sphere (mass point) and the sign of the direction is opposite, is applied to the three piezoelectric elements as a component force in each direction.

Specifically, each piezoelectric element is supported on a rigid body, and the component forces acting on the sphere in the x-axis, y-axis and z-axis directions are applied in the thickness direction of the polymer piezoelectric film, respectively. The polymeric piezoelectric film does not bend, and expands and contracts in the thickness direction. (In the case of deflection, almost no output of the charge detection circuit is obtained.) Since this expansion and contraction is proportional to the force, the x-axis, y-axis, and z-axis of each charge detection circuit connected to each piezoelectric element are An output proportional to the component force can be obtained. From the obtained output, the component forces of the acceleration acting on the sphere (that is, the same mass point) in the x-axis, y-axis, and z-axis directions can be calculated, and the direction of the vector-combined acceleration can be known.

[0034]

As described above, the three-dimensional acceleration sensor of the present invention has three piezoelectric elements supported by a rigid plate.
It is arranged in the axial, y-axis and z-axis directions, and a sphere is inscribed in and bonded to these three piezoelectric elements. Therefore, the problems of the conventional three-dimensional acceleration sensor are solved as follows.

1) Three piezoelectric elements arranged in the x-axis, y-axis and z-axis directions so as to form a box, and these three
Since a sphere that is inscribed in each piezoelectric element and is joined to the corresponding piezoelectric element at the contact point and a charge detection circuit connected to each of the piezoelectric elements are provided, three-dimensional corresponding to the same mass point Can be detected by three piezoelectric elements as the force acting on one sphere and the direction of the force.

2) A piezoelectric element is supported on a rigid plate, and
Since the sphere is bonded to the piezoelectric element, the structure is stable and can withstand long-term use.

3) The piezoelectric element comprises a polymer piezoelectric film and electrodes contacting one surface and the other surface of the polymer piezoelectric film,
An electrode on one surface is formed on a rigid body, and a piezoelectric polymer film is bonded to the electrode. As described above, the piezoelectric element is an electrode in contact with the piezoelectric polymer film and one surface and the other surface of the piezoelectric polymer film. Since the one surface electrode is formed on the rigid body, the polymer piezoelectric film and the rigid plate can be separately manufactured. Therefore, the structure is simple, and it can be easily manufactured.

In addition to this, it has been found that there is an effect that a highly sensitive and thermally stable output can be obtained. As described above, since it is possible to provide a three-dimensional acceleration sensor that is easy to manufacture and highly reliable and that can detect three-dimensional acceleration acting on the same mass point, it has sufficient performance as a mere acceleration measurement or vibration measurement device. Since it is possible to detect three-dimensional acceleration with high accuracy, it can be used for acceleration measurement that requires high accuracy not only in distance and speed but also in direction, such as in a navigation system.

[Brief description of drawings]

FIG. 1 is a perspective view of a three-dimensional acceleration sensor according to an embodiment of the present invention.

FIG. 2 is a charge detection circuit diagram in the three-dimensional acceleration sensor of FIG.

3 is a sectional view of a piezoelectric element in the three-dimensional acceleration sensor of FIG.

FIG. 4 is a plan view of a surface of a rigid plate in the three-dimensional acceleration sensor of FIG.

5 is a plan view of the back surface of the rigid plate in the three-dimensional acceleration sensor of FIG. 1. FIG.

FIG. 6 is a plan view of a surface of a rigid plate in a three-dimensional acceleration sensor according to another embodiment of the present invention.

7 is a set of charge detection circuit diagrams in the three-dimensional acceleration sensor of FIG.

FIG. 8 is a perspective view of a three-dimensional acceleration sensor according to another embodiment of the present invention.

9 is a set of charge detection circuit diagrams in which piezoelectric elements in the three-dimensional acceleration sensor of FIG. 8 are connected in parallel.

FIG. 10 is a schematic diagram of a three-dimensional acceleration sensor using a conventional one-dimensional acceleration sensor.

FIG. 11 is a schematic diagram of a conventional sensor that detects three-dimensional acceleration with respect to the same mass point.

[Explanation of symbols]

 1 Frame 2 Sphere 3 Piezoelectric Element 3a One Piezoelectric Element 3b Other Piezoelectric Element 4 Polymer Piezoelectric Film 5 Electrode A 5a Electrode C 5b Electrode D 6 Electrode B 7 Rigid Plate 8 Charge Detection Circuit 9 Output Terminal of Charge Detection Circuit 10 Charge Positive power supply terminal of detection circuit 11 Negative power supply terminal of charge detection circuit 12 Fixed resistor (R1) 13 Field effect transistor (Tr) 14 Fixed resistor (R2)

Claims (4)

[Claims] 1. Piezoelectric elements that have x-axis, y-axis, and z-axis directions orthogonal to each other as their operating axis directions, and inscribed on one surface of each of the three piezoelectric elements and corresponding piezoelectric elements at the contact points. A three-dimensional acceleration sensor comprising a bonded sphere and a charge detection circuit connected to each piezoelectric element. 2. The three-dimensional acceleration sensor according to claim 1, wherein the piezoelectric element is supported on a rigid body disposed on the opposite side of the sphere from the piezoelectric element. 3. The three-dimensional acceleration sensor according to claim 1, wherein the piezoelectric element includes a polymer piezoelectric film and electrodes contacting one surface and the other surface of the polymer piezoelectric film. 4. The three-dimensional acceleration sensor according to claim 3, wherein an electrode on one surface of the piezoelectric element is formed on a rigid body, and a polymer piezoelectric film is bonded to the electrode.