JPH11133051A - Annular shearing type piezoelectric element and accelerometer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously detect accelerations in multiple directions even in the case of using a single annular shearing type piezoelectric element. SOLUTION: An accelerometer comprises an annular shearing type piezoelectric element 1 having a pair of electrodes 1a, 1b equally provided to have a relation of a symmetry with respect to a plane of an outer periphery, a common electrode 1c provided on an inner periphery to generate a voltage corresponding to a shearing force operated between the inner periphery and the outer periphery between the electrodes 1a, 1b and the electrode 1c, a pendulum 4 engaged with the element 1 to give the shearing force, a piezoelectric element holding member 3 for holding the element 1, and a calculator 6 for calculating a difference or a sum of the voltages generated between the electrodes 1a, 1b and the electrode 1c, thereby detecting an acceleration operating the pendulum 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an annular shear type piezoelectric element for generating a voltage corresponding to a shear force acting between an inner peripheral surface and an outer peripheral surface, and an accelerometer using the same.

[0002]

2. Description of the Related Art Conventionally, a multidirectional accelerometer disclosed in Japanese Utility Model Publication No. 7-938 is known. In this case, three piezoelectric accelerometers having a single sensitive axis are incorporated in one case such that the sensitive axes are orthogonal to each other. However, in the three-directional accelerometer having such a configuration, three sensing parts are required, and in order to assemble them into the case, it is necessary to form a hole in the case. There is a problem that it becomes complicated.

In order to solve this problem, Japanese Patent Laid-Open Publication No. 7-5
A piezoelectric multidirectional accelerometer described in Japanese Patent No. 5832 has been proposed. In this piezoelectric multidirectional accelerometer, six plate-shaped shear-type piezoelectric elements are fixed around a support column, and respective forces generated in four mass bodies by acceleration are received by these shear-type piezoelectric elements. -Simultaneous detection of acceleration in three directions by electrical conversion.

[0004]

However, Japanese Patent Application Laid-Open No. 7-5 / 1995
In the three-directional accelerometer described in Japanese Patent No. 5832, a total of six shear-type piezoelectric elements and four mass bodies are required, and processing to support columns for assembling these to the support columns is required. For example, sufficient simplification has not yet been achieved in terms of the number of parts and the number of assembly steps.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a multi-directional acceleration and acceleration system using a single annular shear type piezoelectric element. An object of the present invention is to provide an annular shear type piezoelectric element capable of simultaneously detecting a force or the like and an accelerometer using the same.

[0006]

According to a first aspect of the present invention, there are provided N pairs of electrodes (N is an integer of 1 or more) so as to have a plane-symmetric relationship with the outer peripheral surface. In addition, a common electrode is provided on the inner peripheral surface, and a voltage corresponding to a shearing force acting between the inner peripheral surface and the outer peripheral surface is generated between the electrode and the common electrode.

According to a second aspect of the present invention, N pairs of electrodes (N is an integer of 1 or more) are equally provided on the inner peripheral surface so as to have a plane-symmetric relationship, and a common electrode is provided on the outer peripheral surface. A voltage corresponding to a shearing force acting between the inner peripheral surface and the outer peripheral surface is generated between the electrode and the common electrode.

According to a third aspect of the present invention, there is provided an annular shearing type piezoelectric element having a pair of electrodes and a common electrode, and a pendulum which is fitted to the annular shearing type piezoelectric element to apply a shearing force. A piezoelectric element holding member for holding the annular shear type piezoelectric element, and a calculation unit for calculating a difference or a sum of respective voltages generated between the pair of electrodes and the common electrode, and acting on the pendulum. This is to detect the acceleration that occurs.

According to a fourth aspect of the present invention, there is provided an annular shearing type piezoelectric element having two pairs of electrodes and a common electrode, and a pendulum fitted to the annular shearing type piezoelectric element to apply a shearing force. A piezoelectric element holding member that holds the annular shear-type piezoelectric element; and a computing unit that computes a difference or a sum of respective voltages generated between the two pairs of electrodes and the common electrode, wherein the pendulum includes This is to detect the acceleration acting on.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a perspective view of an annular shearing type piezoelectric element according to claim 1 (when N = 1) (a).
FIG. 2 is a cross-sectional view of the sensor unit of the accelerometer according to claim 3, FIG. 3 is a configuration explanatory view of the accelerometer according to claim 3, FIG. A perspective view of an annular shear type piezoelectric element according to claim 1 (when N = 2).
FIG. 6 is a cross-sectional view of the sensor unit of the accelerometer according to claim 4, FIG. 7 is an explanatory diagram of a configuration of the accelerometer according to claim 4, and FIG.

As shown in FIG. 1, in the invention according to the first aspect, the annular shear-type piezoelectric element 1 when N = 1 is provided.
The cross section is formed in a rectangular annular shape and polarized in the height (thickness) direction. The annular shearing type piezoelectric element 1 is provided with a pair of electrodes 1a and 1b that are formed into two equal parts on the outer peripheral surface so as to be in plane symmetry, and a common electrode 1c that is formed over the entire inner peripheral surface. ing.

A two-directional accelerometer using the annular shear type piezoelectric element 1 includes a sensor unit provided with the annular shear type piezoelectric element 1,
It is composed of a calculation unit for calculating the output voltage of the sensor unit. As shown in FIG. 2, the sensor unit 2 includes an annular shear piezoelectric element 1.
A piezoelectric element holding member 3 for holding an outer peripheral surface of the annular shear type piezoelectric element 1 provided with a pair of electrodes 1a and 1b, and a hole for forming an inner peripheral surface of the annular shear type piezoelectric element 1 provided with a common electrode 1c. It comprises a pendulum 4 fitted to the portion 1d, and a case 5 for holding the outer peripheral surface of the piezoelectric element holding member 3 and covering the entire sensor portion 2.

The piezoelectric element holding member 3 is made of an insulating member such as a ceramic and has a rectangular cross section in a rectangular shape. This is for fixing the annular shearing type piezoelectric element 1 to the case 5 in an insulated state by fixing the annular shearing type piezoelectric element 1 to the hole forming the inner peripheral surface with an adhesive or the like. This inner diameter is formed slightly larger than the outer diameter of the annular shear type piezoelectric element 1. The piezoelectric element holding member 3 is bonded and fixed to the bottom of the case 5.

The pendulum 4 is for applying a force generated in accordance with the acceleration acting on the piezoelectric element 1 to the annular shearing type piezoelectric element 1, and is formed in a cylindrical shape from a metal member. In addition, the pendulum 4 has a large-diameter portion 4a and a small-diameter portion 4b because the center of mass of the pendulum 4 is set at a predetermined distance from the annular shear-type piezoelectric element 1.
Consisting of The outer diameter of the small diameter portion 4b is slightly smaller than the inner diameter of the annular shear type piezoelectric element 1. Pendulum 4
The small-diameter portion 4b is fixed with an adhesive or the like in a state where the small-diameter portion 4b is inserted into the hole 1d of the annular shearing type piezoelectric element 4.

The case 5 is fixed to the object to be measured. The case 5 is formed by a metal member into a cylindrical shape with both ends closed.

As shown in FIG. 3, a calculating section 6 for calculating the output voltage of the sensor section 2 includes a difference calculating section 7 and a sum calculating section 8.
Consists of The difference calculator 7 calculates a difference (Va−Vb) between a voltage (Va) generated between the electrode 1a and the common electrode 1c and a voltage (Vb) generated between the electrode 1b and the common electrode 1c. Output. This difference voltage (Va-Vb) becomes a signal corresponding to the acceleration in the X direction.

The sum calculation unit 8 calculates a voltage (Va) generated between the electrode 1a and the common electrode 1c and a voltage (Va) generated between the electrode 1b and the common electrode 1c.
And the sum (Va + Vb) with the voltage (Vb) generated during the calculation is output. This sum voltage (Va + Vb) becomes a signal corresponding to the acceleration in the Z direction.

The following describes a method using the annular shear type piezoelectric element 1.
The operation of the directional accelerometer will be described with reference to FIGS. 4, illustration of the piezoelectric element holding member 3, the case 5, and the calculation unit 6 is omitted.

As shown in FIG. 4, a pair of electrodes 1a, 1b
It is assumed that acceleration in a direction (hereinafter, referred to as X direction) perpendicular to a plane (hereinafter, referred to as YZ plane) that divides the pendulum into the electrodes 1a and 1b acts on the pendulum 4.

When the acceleration in the X direction acts on the pendulum 4,
Voltage (Va) generated between electrode 1a and common electrode 1c
And a voltage (V) generated between the electrode 1b and the common electrode 1c.
b) have opposite polarities and the same voltage. Therefore, the output voltage of the difference calculation unit 7 is equal to the electrode 1a and the common electrode 1c.
Is twice as high as the voltage (Va) generated during the period.

The output voltage of the sum calculation unit 8 is equal to the voltage of the electrode 1a.
(Va) generated between the electrode 1 and the common electrode 1c.
Since the sum of b and the voltage (Vb) generated between the common electrode 1c is calculated, the sum is 0 [V]. Therefore, the difference calculation unit 7
Outputs a voltage corresponding to the acceleration in the X direction.

Next, it is assumed that the acceleration in the direction of the central axis of the pendulum 4 (hereinafter referred to as the Z direction) acts on the pendulum 4. When acceleration in the Z direction acts on the pendulum 4, the electrode 1a
(Va) generated between the electrode 1 and the common electrode 1c.
The voltage (Vb) generated between b and the common electrode 1c has the same polarity and the same voltage. Therefore, the output voltage of the difference calculation unit 7 is 0 [V].

The output voltage of the sum calculation unit 8 is equal to the voltage of the electrode 1a.
And the voltage (Va) generated between the common electrode 1c and the common electrode 1c. Therefore, the sum calculation unit 8 outputs a voltage corresponding to the acceleration in the Z direction.

Finally, it is assumed that the acceleration in the Y direction orthogonal to both the X direction and the Z direction acts on the pendulum 4. When acceleration in the Y direction acts on the pendulum 4, the electrode 1a
(Va) generated between the first electrode and the common electrode 1c
A and 0 (V) cancel each other out (averaged) in the annular shearing type piezoelectric element 1 sandwiched by the common electrode 1c and a.

Similarly, the voltage (Vb) generated between the electrode 1b and the common electrode 1c also cancels out (averages) in the annular shear type piezoelectric element 1 sandwiched between the electrode 1b and the common electrode 1c. , 0 [V]. Therefore, the output voltage of the difference calculation unit 7 and the output voltage of the sum calculation unit 8 both become 0 [V], and the acceleration in the Y direction is not detected.

As shown in FIG. 5, in the invention according to the first aspect, the annular shearing type piezoelectric element 11 when N = 2 is set.
Has a rectangular cross-sectional shape and is polarized in the height (thickness) direction, similarly to the annular shearing type piezoelectric element 1 shown in FIG. The annular shearing type piezoelectric element 11 is provided with two pairs of electrodes 11a, 11c and electrodes 11b, 11d formed into four equal parts so as to have a plane-symmetric relationship with the outer peripheral surface.
A common electrode 11e formed over the entire inner peripheral surface is provided.

The three-directional accelerometer using the annular shear type piezoelectric element 11 includes a sensor unit provided with the annular shear type piezoelectric element 11, and an arithmetic unit for performing arithmetic processing on the output voltage of the sensor unit. As shown in FIG. 6, the sensor section 12 includes an annular shearing type piezoelectric element 11 and two pairs of electrodes 1a, 1b, 11c, 11d.
Element holding member 13 for holding the outer peripheral surface of annular shear type piezoelectric element 11 provided with a pendulum, and pendulum 14 fitted into hole 11f forming the inner peripheral surface of annular shear type piezoelectric element 11 provided with common electrode 11e. And a case 15 that holds the outer peripheral surface of the piezoelectric element holding member 13 and covers the entire sensor section 12.

The sensor section 12 of the three-way accelerometer has an annular shearing type piezoelectric element provided with two pairs of electrodes 11a, 11b, 11c and 11d formed into four equal parts on the outer peripheral surface so as to have a plane-symmetric relationship. 11 is the same as that of the sensor unit 2 of the two-directional accelerometer, so that the piezoelectric element holding member 13 and the pendulum 14
The description of the case 15 is omitted.

As shown in FIG. 7, an arithmetic unit 16 for calculating the output voltage of the sensor unit 12 includes two difference arithmetic units 17,
18 and a sum operation unit 19. One difference calculation unit 17 is:
The voltage (V) generated between the electrode 11a and the common electrode 11e
a) and the difference (Va−Vc) between the voltage (Vc) generated between the electrode 11c and the common electrode 1e is calculated and output. This difference voltage (Va-Vc) becomes a signal corresponding to the acceleration in the X direction.

The other difference calculating section 18 calculates a voltage (Vb) generated between the electrode 11b and the common electrode 11e,
(Vd) between the voltage (Vd) generated between the common electrode 1e and the common electrode 1e.
b−Vd) is calculated and output. This difference voltage (Vb-V
d) becomes a signal corresponding to the acceleration in the Y direction.

The sum calculation unit 19 includes an electrode 1b and a common electrode 1e.
Between the electrode 1d and the common electrode 1
The sum (Vb + Vd) with the voltage (Vd) generated during e is calculated and output. This sum voltage (Vb + Vd) becomes a signal corresponding to the acceleration in the Z direction.

The operation of the three-directional accelerometer using the annular shear type piezoelectric element 11 will be described below with reference to FIGS. In FIG. 8, the piezoelectric element holding member 1
3, the description of the case 15, and the calculation unit 16 is omitted.

As shown in FIG. 8, a pair of electrodes 11b, 1
It is assumed that acceleration in a direction (hereinafter, referred to as an X direction) perpendicular to a plane (hereinafter, referred to as a YZ plane) that divides 1d into two equally acts on the pendulum 4.

When the acceleration in the X direction acts on the pendulum 14, the voltage (Va) generated between the electrode 11a and the common electrode 11e is the same as the voltage (Vc) generated between the electrode 11c and the common electrode 11e. Polarity and the same voltage. Therefore, the output voltage of the difference calculation unit 17 is
a and twice the voltage (Va) generated between the common electrode 11e.

The voltage (Vb) generated between the electrode 11b and the common electrode 11e is 0 [V]. This is because a shear force acts on the portion sandwiched between the electrode 11b and the common electrode 11e so that the generated voltage becomes 0 [V].

For the same reason, the electrode 11d and the common electrode 11
The voltage (Vd) generated during e also becomes 0 [V]. Therefore, both the output voltage of the difference calculation unit 18 and the output voltage of the sum calculation unit 19 become 0 [V]. Therefore, the output voltage of the difference calculation unit 17 is a signal corresponding to the acceleration in the X direction.

Next, the direction of the center axis of the pendulum 14 (hereinafter, Z
It is assumed that acceleration of the pendulum 14 acts on the pendulum 14. When the acceleration in the Z direction acts on the pendulum 14, the voltage (Va) generated between the electrode 11a and the common electrode 11e
And a voltage (Vc) generated between the electrode 11c and the common electrode 11e have the same polarity and the same voltage. Therefore, the output of the difference calculation unit 17 is 0 [V].

The voltage (Vb) generated between the electrode 11b and the common electrode 11e, and the voltage (Vb) between the electrode 11d and the common electrode 11e
Are generated with the same polarity and the same voltage. Therefore, the output voltage of the difference calculation unit 18 is 0 [V], and the output voltage of the sum calculation unit 19 is twice the voltage (Vb) generated between the electrode 11b and the common electrode 11e. Therefore, the output voltage of the sum calculation unit 19 is a signal corresponding to the acceleration in the Z direction.

Finally, it is assumed that the acceleration in the Y direction orthogonal to both the X direction and the Z direction acts on the pendulum 14. When acceleration in the Y direction acts on the pendulum 14, the electrode 1
1b and the voltage (Vb) generated between the common electrode 11e;
The voltage (V) generated between the electrode 11d and the common electrode 11e
d) have opposite polarities and the same voltage. Accordingly, the output voltage of the difference calculation unit 18 is twice the voltage (Vb) generated between the electrode 11b and the common electrode 11e, and the output voltage of the sum calculation unit 19 is 0 [V].

The voltage (Va) generated between the electrode 11a and the common electrode 11e is 0 [V]. This is because a shearing force acts on the portion between the electrode 11a and the common electrode 11e so that the generated voltage becomes 0 [V].

For the same reason, the electrode 11c and the common electrode 11
The voltage (Vc) generated during e also becomes 0 [V]. Therefore, the output voltage of the difference calculation unit 17 is 0 [V]. Therefore, the output voltage of the difference calculation unit 18 is a signal corresponding to the acceleration in the Y direction.

In the embodiment of the present invention described above, the pair of electrodes 1a, 1b or the two pairs of electrodes 11a, 1b are arranged so that the outer peripheral surfaces of the annular shear type piezoelectric elements 1, 11 have a plane-symmetric relationship.
1b, 11c, and 11d are provided equally, and common electrodes 1c and 11e are provided on the inner peripheral surface. A voltage corresponding to the shearing force acting between the inner peripheral surface and the outer peripheral surface is generated between the electrodes and the common electrode. The case where it does is explained.

However, as in the invention according to claim 2, a pair of electrodes or two pairs of electrodes are equally provided on the inner peripheral surface so as to have a plane-symmetric relationship, and a common electrode is provided on the outer peripheral surface.
An annular shear-type piezoelectric element in which a voltage corresponding to a shear force acting between the inner peripheral surface and the outer peripheral surface is generated between the electrode and the common electrode may be used.

In the embodiment of the invention described above, the outer peripheral side of the annular shear type piezoelectric elements 1 and 11 is
15 has been described, and the pendulums 4 and 14 have been fixed to the inner peripheral side.

However, when acceleration is applied to the cases 5 and 15, a shearing force parallel to the inner peripheral surface and the outer peripheral surface of the annular shear type piezoelectric elements 1 and 11 only has to act on these surfaces. Therefore, the inner peripheral side of the annular shear type piezoelectric elements 1 and 11 may be fixed to the case, and the pendulums 4 and 14 may be fixed to the outer peripheral side.

Further, in the embodiment of the invention relating to the accelerometer according to the fourth aspect, the sum calculating section 19 includes the electrode 11
The configuration for calculating and outputting the sum (Vb + Vd) of the voltage (Vb) generated between b and the common electrode 11e and the voltage (Vd) generated between the electrode 11d and the common electrode 11e has been described.

However, regarding the sum operation unit 19, the electrode 1
Voltage (Va) generated between 1a and common electrode 11e and voltage (Vc) generated between electrode 11c and common electrode 11e.
The sum (Va + Vc) may be calculated and output.

The voltage (Va) generated between the electrode 11a and the common electrode 11e, and the voltage (Va) generated between the electrode 11b and the common electrode 11e.
, A voltage (Vc) generated between the electrode 11c and the common electrode 11e, and a sum (Va) of a voltage (Vd) generated between the electrode 11d and the common electrode 11e.
+ Vb + Vc + Vd) may be calculated and output.

Further, in the embodiment of the present invention described above, the case where the annular shear type piezoelectric elements 1 and 11 are applied to a multidirectional accelerometer has been described. However, when a shearing force is applied between the inner peripheral surface and the outer peripheral surface, a voltage corresponding to this is generated between each electrode and the common electrode in the annular shearing type piezoelectric elements 1 and 11. , For example, a piezoelectric multi-directional force detector. Further, the number of pairs of electrodes may be increased according to the purpose.

[0050]

As described above, according to the first aspect of the present invention, it is possible to realize an annular shear type piezoelectric element capable of detecting acceleration or force in multiple directions with a simple structure.

According to the second aspect of the present invention, it is possible to realize an annular shear type piezoelectric element capable of detecting accelerations or forces in multiple directions with a simple structure.

According to the third aspect of the present invention, accelerations in two directions orthogonal to each other can be simultaneously detected without using many piezoelectric elements.

According to the invention of claim 4, accelerations in three directions orthogonal to each other can be detected simultaneously without using many piezoelectric elements.

[Brief description of the drawings]

FIG. 1 is a perspective view (a) and a plan view (b) of an annular shearing type piezoelectric element (when N = 1) according to claim 1;

FIG. 2 is a sectional view of a sensor section of the accelerometer according to claim 3;

FIG. 3 is a configuration explanatory view of an accelerometer according to claim 3;

FIG. 4 is a diagram illustrating the operation of the accelerometer according to claim 3;

5A and 5B are a perspective view and a plan view, respectively, of an annular shearing type piezoelectric element according to claim 1 (when N = 2).

FIG. 6 is a sectional view of a sensor section of the accelerometer according to claim 4.

FIG. 7 is an explanatory diagram of a configuration of an accelerometer according to claim 4.

FIG. 8 is a diagram illustrating the operation of the accelerometer according to claim 4.

[Explanation of symbols]

1,11 ... annular shear type piezoelectric element, 1a, 1b, 11a,
11b, 11c, 11d: electrodes, 1c, 11e: common electrodes, 2, 12: sensor unit, 3, 13: piezoelectric element holding member, 4, 14: pendulum, 5, 15: case, 6, 16 ...
Arithmetic units, 7, 17, 18 ... difference arithmetic units, 8, 19 ... sum arithmetic units.

Claims (4)

[Claims] 1. An N-number of electrodes (N is an integer of 1 or more) are equally provided so as to have a plane-symmetric relationship with an outer peripheral surface, and a common electrode is provided on an inner peripheral surface. An annular shear-type piezoelectric element, wherein a voltage corresponding to a shear force acting between surfaces is generated between the electrode and the common electrode. 2. An N-number of electrodes (N is an integer of 1 or more) are equally provided on the inner peripheral surface so as to have a plane-symmetric relationship with the inner peripheral surface, and a common electrode is provided on the outer peripheral surface. An annular shear-type piezoelectric element, wherein a voltage corresponding to a shear force acting between surfaces is generated between the electrode and the common electrode. 3. The semiconductor device according to claim 1, further comprising a pair of electrodes and a common electrode.
Or the annular shear-type piezoelectric element according to 2, a pendulum fitted to the annular shear-type piezoelectric element to apply a shearing force, a piezoelectric element holding member for holding the annular shear-type piezoelectric element, the pair of electrodes, and An accelerometer, comprising: a calculation unit for calculating a difference or a sum of respective voltages generated between the common electrode and the common electrode, and detecting an acceleration acting on the pendulum. 4. The method according to claim 1, further comprising two pairs of electrodes and a common electrode.
Or the annular shear-type piezoelectric element according to 2, a pendulum that fits the annular shear-type piezoelectric element to apply a shearing force, a piezoelectric element holding member that holds the annular shear-type piezoelectric element, and the two pairs of electrodes. An accelerometer, comprising: a calculation unit for calculating a difference or a sum of respective voltages generated between the common electrode and the common electrode, and detecting an acceleration acting on the pendulum.