JP2002107374A - Acceleration sensor, acceleration detecting device, and positioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor, which can be provided in a limited space and can detect rotational acceleration with high sensitivity. SOLUTION: The acceleration sensor 10 comprises 1st and 2nd piezoelectric elements 1 and 2 provided with electrodes 11a and 11b, and 21a and 21b for outputting electric charges generated due to strain deformation, and each of the 1st and 2nd piezoelectric elements is made of at least one piezoelectric body 4 and has a support part 3, which supports the piezoelectric body; and the electrodes are provided on at least the opposite surfaces of the piezoelectric elements, and one surface of the 1st piezoelectric element and one surface of the 2nd piezoelectric element are arranged substantially in parallel to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to detection of angular acceleration (rotational acceleration) and translational acceleration due to an impact applied to various electronic devices.

[0002]

2. Description of the Related Art In recent years, miniaturization of electronic devices has progressed, and portable electronic devices such as notebook computers have become widespread. In order to secure and improve the reliability of these electronic devices against impact, there is an increasing demand for high-performance acceleration (shock) sensors that are small and surface-mountable. For example, if an impact is applied during a write operation to a high-density magnetic recording device, a head displacement will occur. As a result, there is a possibility that a data write error or damage to the head may occur. Therefore, it is necessary to detect the impact applied to the magnetic recording device, stop the writing operation, and retract the head to a safe position.

Further, in magnetic recording devices, the recording density is increasing, and the track width on the disk surface is becoming narrower. For this reason, even a slight vibration tends to cause a head displacement (track displacement). There is a problem that the magnetic head causes a track deviation due to not only shock and vibration applied from outside the magnetic recording apparatus but also small vibration due to rotation of a motor or the like inside the magnetic recording apparatus.

[0004] Vibration applied to a magnetic recording apparatus may include not only translational vibration but also rotational vibration. Therefore, for the control, it is necessary to identify the translational acceleration and the angular acceleration (hereinafter referred to as the rotational acceleration), and a sensor capable of detecting the translational acceleration and the rotational acceleration is required. The translational acceleration can be detected by using one conventional acceleration sensor. In order to detect the rotational acceleration, it is possible to detect the rotational acceleration with the highest sensitivity by arranging the acceleration sensors at two or more positions as far as possible from each other.
At this time, if the two acceleration sensors are arranged at equal distances on both sides of the center of rotation, when a rotational acceleration is applied, the output signals have the opposite signs and the same magnitude. However, the above condition is limited to the case where the position of the rotation center is located between the two acceleration sensors. In addition, when two acceleration sensors having substantially the same characteristics are arranged on the same side with respect to the rotation center, the translational acceleration is the same for each acceleration sensor. Are the same size. On the other hand, when a rotational acceleration is applied, the magnitude of the output signal from each of the acceleration sensors differs because the magnitude of the output signal from the two acceleration sensors varies depending on the distance from the rotation center to each of the acceleration sensors. Therefore, the rotational acceleration can be detected by taking the difference between the two output signals.

As an acceleration sensor, there is known a piezoelectric element made of a piezoelectric material which generates a voltage by being deformed by applying a stress (Japanese Patent Laid-Open No. Hei 10-9674).
No. 2). As a piezoelectric element used for an acceleration sensor, there is a plate-shaped piezoelectric element having a beam portion such as a plate-shaped piezoelectric body. The acceleration can be detected by receiving the distortion deformation due to the acceleration as the vibration of the beam portion of the piezoelectric body and detecting the charge generated thereby.

[0006]

However, when the acceleration sensor is composed of a plurality of piezoelectric elements, there may be a case where the characteristics of each piezoelectric element differ. Further, in an acceleration sensor in which two piezoelectric elements are installed at separate positions, the sensitivity of each piezoelectric element may be affected depending on the state of the installation position. For example, the sensitivity of each piezoelectric element may deviate due to a temperature difference or the like depending on the installation position. In such a case, even when only translational acceleration is applied, a difference occurs in the output signal between the piezoelectric elements, so that the rotational acceleration may be erroneously detected, and the rotational acceleration cannot be accurately recognized. Had a problem. On the other hand, if two piezoelectric elements are housed in a limited space, such as in one package, and the distance between the piezoelectric elements is reduced, the difference between the detection signals becomes smaller and the rotational acceleration cannot be detected with high sensitivity. Had issues.

Therefore, an object of the present invention is to provide an acceleration sensor that can be provided in a limited space and can detect rotational acceleration with high sensitivity.

[0008]

The above object can be attained by the following present invention. That is, the acceleration sensor according to the present invention includes first and second piezoelectric elements provided with electrodes for outputting a potential generated by strain deformation.
And each of the second piezoelectric elements is made of at least one piezoelectric body, and has a support portion for supporting the piezoelectric body, and the electrodes are provided on at least opposing surfaces of the piezoelectric element, respectively. Further, one surface of the first piezoelectric element and one surface of the second piezoelectric element are arranged so as to be substantially parallel to each other.

Here, one surface of the first piezoelectric element and the second surface
Placing one surface of a piezoelectric element substantially parallel to each other means that the vibrating surfaces are parallel to each piezoelectric element so that each piezoelectric element can take the same vibration direction for acceleration in the same direction. It is. Preferably, one surface of the first piezoelectric element and one surface of the second piezoelectric element are in the same plane. Since the piezoelectric element normally vibrates in a direction perpendicular to the surface of the beam, it is preferable to arrange the surfaces of the beam of each piezoelectric element substantially parallel to each other. Further, the piezoelectric body constituting the piezoelectric element may be formed as an integrated body in which the support portion and the beam portion are continuous, or the support portion may be formed as a separate body.

Thus, the first and second piezoelectric elements can be provided in a limited space so that acceleration in the same direction can be detected. Rotational acceleration can be detected with high sensitivity. Further, the rotational acceleration can be detected without being affected by the environment due to the installation position.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein each of the first and second piezoelectric elements includes a support portion for supporting the piezoelectric body and a main surface of the piezoelectric body. A cantilever beam type having a beam portion, wherein the first and second piezoelectric elements have the same longitudinal direction in the same direction, and the support portions are spaced apart in opposite directions with respect to the longitudinal direction and outward. And the inner ends of the beam portions are arranged close to each other, and the end surfaces of the beam portions are arranged to be substantially parallel to each other.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein each of the first and second piezoelectric elements comprises one piezoelectric body, and the polarization directions of the respective piezoelectric bodies are opposite to each other. It is characterized by being.

Still further, the acceleration sensor according to the present invention is the acceleration sensor, wherein each of the first and second piezoelectric elements comprises one piezoelectric body, and the polarization directions of the piezoelectric bodies are the same. Direction.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein each of the first and second piezoelectric elements is formed by joining and laminating a plurality of piezoelectric bodies.

Thus, a larger output signal can be obtained by forming a piezoelectric element by joining a plurality of piezoelectric bodies.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein in each of the first and second piezoelectric elements, the polarization directions of all the piezoelectric bodies constituting each of the piezoelectric elements are the same. It is characterized by being.

Still further, the acceleration sensor according to the present invention is the above-mentioned acceleration sensor, wherein the polarization directions of the respective piezoelectric bodies constituting each of the first and second piezoelectric elements are opposite to each other. And

Further, the acceleration sensor according to the present invention is the above-mentioned acceleration sensor, wherein the polarization directions of the piezoelectric bodies constituting each of the first and second piezoelectric elements are the same as each other. I do.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein each of the first and second piezoelectric elements has at least two piezoelectric bodies whose polarization directions are opposite to each other. It is characterized in that the same surfaces are joined to face each other.

Still further, the acceleration sensor according to the present invention is the acceleration sensor, wherein each of the first and second piezoelectric elements has a direction of polarization of each corresponding piezoelectric body being opposite to each other. And

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein each of the first and second piezoelectric elements is in the same direction as the polarization direction of each corresponding piezoelectric body. I do.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein, in the one piezoelectric element, each piezoelectric body constituting the piezoelectric element is joined via a shim material. And

The shim is not particularly limited as long as it can be bonded to the piezoelectric body. It is preferable that vibration due to acceleration be transmitted to the piezoelectric body. Preferably, it is a silicon substrate.

Still further, the acceleration sensor according to the present invention is the acceleration sensor, wherein the piezoelectric element is formed by joining a plurality of the piezoelectric bodies by direct joining.

Thus, since no adhesive layer is formed at the interface between the piezoelectric bodies, vibration due to acceleration is not absorbed by the adhesive layer, acceleration can be detected with high sensitivity, and a stable element can be realized. it can.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein the piezoelectric element is formed by directly joining a plurality of the piezoelectric members via at least one of an oxygen atom and a hydroxyl group. It is characterized by.

Thus, the piezoelectric bodies can be firmly joined to each other via the hydroxyl group or the oxygen atom.

Further, the acceleration sensor according to the present invention is characterized in that the acceleration sensor has an output terminal corresponding to each electrode of the first and second piezoelectric elements.

Still further, the acceleration sensor according to the present invention is the acceleration sensor, wherein electrodes having different polarities of generated charges are connected between the different piezoelectric elements for each of the first and second piezoelectric elements. It has at least one output terminal.

As described above, in each of the first and second piezoelectric elements, the electrodes having different polarities of the generated charges are connected between the different piezoelectric elements, and this is used as an output terminal. The charge is canceled between the electrodes, and an extra charge is obtained as a difference between the outputs of the respective piezoelectric elements. Here, when rotational acceleration is applied, the amount of charge generated in each piezoelectric element differs depending on the distance from the center of rotation. On the other hand, since the amount of charge generated by the translational acceleration is the same for each piezoelectric element, it is canceled by taking the difference. Therefore, the rotational acceleration can be detected from the difference between the outputs. In other words, an output difference can be obtained by wiring between the piezoelectric elements as described above. Therefore, there is no need to provide an external difference circuit.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein the electrodes having the same polarity of the generated electric charges are connected between different piezoelectric elements for each of the first and second piezoelectric elements. It has an output terminal from an electrode other than the connected electrode.

Also in the above case, in each of the first and second piezoelectric elements, the electrodes having the same polarity of the generated charges are connected in series, so that the charges of the same polarity are canceled out, and each of the piezoelectric elements is applied to each of the piezoelectric elements. The difference between the generated charges can be obtained as an output. As a result, an extra charge is obtained as a difference between the outputs of the respective piezoelectric elements, and the rotational acceleration can be detected from the difference between the outputs. In other words, an output difference can be obtained by wiring between the piezoelectric elements as described above. Therefore, there is no need to provide an external difference circuit.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein the acceleration sensor has at least one set of output terminals for outputting electric charges generated on each electrode of the first and second piezoelectric elements. Features.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein the first piezoelectric element is
The sensitivity is adjusted to be substantially the same as the sensitivity of the second piezoelectric element.

The first and second parts constituting this acceleration sensor
In general, the sensitivity of each piezoelectric element can be made substantially the same by configuring the dimensions of one piezoelectric element to be substantially the same as the dimensions of the other piezoelectric element. Further, in order to improve the accuracy of detecting the acceleration, it is preferable to adjust the sensitivity of one piezoelectric element to be substantially the same as the sensitivity of the other piezoelectric element. The sensitivity adjustment of the piezoelectric element can be performed, for example, by cutting a part of the beam portion or attaching a sensitivity adjuster such as a heavy object to the beam portion.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein the first piezoelectric element has a part of a beam portion cut away.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein the one piezoelectric element has a sensitivity adjuster attached to a part of a beam.

Still further, the acceleration sensor according to the present invention is the acceleration sensor, wherein the first and second piezoelectric elements are fixed in the package by the support so that the beam can vibrate. It is characterized by being.

In this acceleration sensor, the first and second piezoelectric elements are incorporated in the package, and the output from the electrodes provided on each surface of each piezoelectric element can be easily taken out.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein each of the first and second piezoelectric elements is arranged such that the beam portion is inclined with respect to the plane of the package. It is characterized by being implemented in.

By inclining the beam of the piezoelectric element with respect to the plane of the package, the vibration direction of the beam can be inclined with respect to the plane of the package. Therefore, not only acceleration in a direction parallel to the plane of the package but also acceleration in a direction perpendicular to the plane of the package can be detected.

Further, the acceleration sensor according to the present invention is the acceleration sensor, wherein each of the first and second piezoelectric elements has a different inclination angle between the beam and the plane of the package. , And is mounted on the package.

Still further, the acceleration sensor according to the present invention is the acceleration sensor, wherein two sets of piezoelectric elements are mounted on the package, and each of the first set of first and second piezoelectric elements is , The beam portion is mounted in a state perpendicular to the plane of the package, and each of the first and second piezoelectric elements of the second set has the beam portion parallel to the plane of the package. It is characterized by being mounted in a state.

As described above, by providing two sets of piezoelectric elements in which the beam portion of the piezoelectric element is mounted vertically and in parallel to the plane of the package, the acceleration components in the vertical and horizontal directions are independent of the plane of the package. And can be detected. Note that the present invention is not limited to the case where the acceleration in the two-axis direction is detected as described above, and the acceleration component in the three-axis direction may be detected by further mounting a third set of piezoelectric elements.

An acceleration detecting device according to the present invention is characterized by including the acceleration sensor and a signal processing circuit for processing an output signal from the piezoelectric element.

As a result, the acceleration sensor and the signal processing circuit, for example, a semiconductor device can be housed in one package, so that the wiring can be shortened, the influence of noise can be reduced, and the sensitivity can be increased. Acceleration can be detected.

The acceleration detecting device according to the present invention is the acceleration detecting device, wherein each of the first and second piezoelectric elements outputs an output signal having the same polarity with respect to acceleration in the same direction. The output signal is subjected to difference processing in the signal processing circuit.

Further, the acceleration detecting device according to the present invention
In the acceleration detection device, each of the first and second piezoelectric elements is connected to the signal processing circuit so as to output output signals of opposite polarities to acceleration in the same direction, respectively. In the signal processing circuit, the output signal is added.

Further, the acceleration detecting device according to the present invention is the acceleration detecting device, wherein the signal processing circuit detects an angular acceleration from a difference between outputs of the first and second piezoelectric elements. It is characterized by having.

Here, the first distance different from the center of rotation is different.
And the magnitude of the rotational acceleration applied to the second piezoelectric element is different from each other. On the other hand, the translational acceleration applied to each piezoelectric element is
Is the same. Therefore, by detecting the difference between the outputs of the two piezoelectric elements, the output signal due to the translational acceleration can be canceled out, and the output signal due to the rotational acceleration can be detected.

Still further, the acceleration detecting device according to the present invention is the acceleration detecting device, wherein the signal processing circuit outputs the first and second piezoelectric elements such that the respective sensitivities become substantially equal to each other. It is characterized by adjusting.

The acceleration detecting device according to the present invention is the acceleration detecting device, wherein the signal processing circuit converts an impedance of an output signal from the piezoelectric element.
It is characterized by including one impedance conversion circuit and an amplification circuit for amplifying the converted output signal.

Further, the acceleration detecting device according to the present invention
The acceleration detection device, wherein the signal processing circuit includes two impedance conversion circuits that convert impedances of output signals from the first and second piezoelectric elements, and an addition circuit that adds the converted output signals. It is characterized by including.

Still further, the acceleration detecting device according to the present invention is the acceleration detecting device, wherein the signal processing circuit converts two impedances of output signals from the first and second piezoelectric elements, respectively. It is characterized by including a differential amplifier circuit that detects a difference between the impedance conversion circuit and the converted output signal and amplifies the output signal difference.

Further, the acceleration detecting device according to the present invention is the acceleration detecting device, wherein: a converted output obtained by impedance-converting an output of at least one of the piezoelectric elements; and an amplified output obtained by amplifying the converted output after the impedance conversion. Are simultaneously provided to the outside.

Further, the acceleration detecting device according to the present invention
The acceleration detection device, wherein the first
And the second piezoelectric element is fixed by the support so that the beam can vibrate, and the signal processing circuit is housed therein.

An object positioning apparatus according to the present invention is an object positioning apparatus comprising: the acceleration detecting apparatus for detecting acceleration; moving means for the object; and control means for controlling the moving means. The control means controls the moving means based on an output signal corresponding to the detected acceleration from the acceleration detection device to move and position the object.

Thus, even when disturbance is applied to the positioning device and acceleration is applied, the object can be accurately positioned.

Further, the positioning device according to the present invention is substantially the same as the positioning device, wherein each beam portion of the first and second piezoelectric elements forming the acceleration detecting device supports the object. Are arranged in parallel with each other.

The disk recording / reproducing apparatus according to the present invention comprises:
A disc recording / reproducing apparatus comprising: the acceleration detecting device for detecting acceleration; a head moving unit for moving a head for recording / reproducing to / from a disc; and a control unit for controlling the head moving unit. The means calculates a desired movement amount of the head based on an output signal corresponding to the detected acceleration from the acceleration detection device, and moves the head by the head moving means to position the head. It is characterized by performing.

As a result, the head can be accurately positioned even when a disturbance occurs and acceleration is applied, so that the quake resistance of the disk recording and reproducing apparatus and the density of the disk recording and reproducing apparatus can be increased.

The disk recording / reproducing device according to the present invention is the disk recording / reproducing device, wherein the beam portions of the first and second piezoelectric elements constituting the acceleration detecting device support the head. Are arranged substantially in parallel with each other.

[0063]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Embodiment 1) FIG. 1A shows a perspective view of a piezoelectric element constituting an acceleration sensor according to Embodiment 1 of the present invention, and FIG. 1B shows a plan view thereof. Show. This acceleration sensor includes two piezoelectric elements 1 and 2. Each of the piezoelectric elements 1 and 2 has a cantilever structure in which a bimorph-shaped beam portion in which two piezoelectric bodies are joined so that the polarization directions are opposite to each other is supported at one end by a support portion 3. are doing. Electrodes 11a, 11b, 21a and 21b are formed on two opposing surfaces of the beams of the piezoelectric elements 1 and 2, respectively. Electrode 11 on the surface provided with support 3
Since b and 21b have a step between the beam portion and the support portion 3,
The step surface is also electrically connected to make the beam portion and the support portion 3 electrically conductive. Electrode 11 on the surface opposite to support 3
a and 21a are formed on the entire surface. Since the piezoelectric elements 1 and 2 have a bimorph cantilever structure in which two piezoelectric members 4 are joined, a potential difference generated in the piezoelectric member 4 due to flexural vibration generated in the beam portion due to acceleration transmitted from the support portion 3. Electrodes 11a, 11b, 2 provided on opposite surfaces
It can be taken out from above 1a, 21b. A structure in which one or a plurality of such piezoelectric members are bonded and laminated, and electrodes are provided on each surface is called a piezoelectric element. This acceleration sensor 10
In each of the piezoelectric elements 1, 2, the piezoelectric elements 1 and 2 are arranged such that one surface thereof is parallel to each other, and specifically, are arranged such that the surfaces of the beam portions are substantially in the same plane. Further, in the acceleration sensor 10, the tips of the beam portions of the piezoelectric elements are brought close to each other so that the longitudinal directions are substantially aligned on the same direction, and the respective support portions 3 are arranged in opposite directions in the longitudinal direction. Located away outside.

In the piezoelectric element 1 and the piezoelectric element 2 constituting the acceleration sensor 10, two piezoelectric bodies 4 whose polarization directions are opposite to each other are laminated by joining the surfaces having the same polarization polarity to each other. To constitute one piezoelectric element. The polarization directions of the corresponding piezoelectric bodies of the piezoelectric element 1 and the piezoelectric element 2 are opposite to each other. In other words, the polarities of the polarizations of the opposing surfaces of the bonding surfaces are different between the piezoelectric element 1 and the piezoelectric element 2. In FIG. 1B, the polarization direction of each piezoelectric body is indicated by an arrow. Arrows are shown from the positive polarity side to the negative side. Therefore, the starting point side of the arrow is a plus surface,
The end point pointed by the arrow is the minus plane. In the piezoelectric element 1, two piezoelectric bodies are joined together with negative polar faces, and in the piezoelectric element 2, two piezoelectric bodies are joined together with positive polar faces.

Generally, the resonance frequency of a piezoelectric element is determined by the length and thickness of the piezoelectric element. Since the sensitivity of the piezoelectric element increases with acceleration at a frequency close to the resonance frequency, the shape of the piezoelectric element may be determined so that the resonance frequency is higher than the measurement frequency range. In the first embodiment, the piezoelectric element has a thickness of 100 μm, a length of 2 mm, and a resonance frequency of 20 kHz. The piezoelectric element is formed by joining two piezoelectric bodies having a thickness of 50 μm. As the piezoelectric body, lithium niobate (LiNb) which is a piezoelectric single crystal is used.
O ₃ ) is used.

Next, a method of manufacturing the piezoelectric element constituting the acceleration sensor will be described. First, a piezoelectric material having a thickness of 4
Two 00 μm lithium niobate substrates are joined by direct joining. In the direct bonding step, the surface of the substrate is polished to a uniform mirror surface and then washed to remove dust and contaminants on the surface. This substrate is subjected to a hydrophilic treatment to activate the surface, and after drying, the two substrates are overlaid. here,
FIG. 2 illustrates the principle of joining the base substrate 4 and the piezoelectric substrate 3 by direct joining. FIG. 2 shows Embodiment 1 of the present invention.
3 shows the interface state of the piezoelectric substrate at each stage of the direct bonding in the method of manufacturing the piezoelectric element used for the acceleration sensor in FIG. In FIG. 2, L1, L2, and L3 indicate distances between the piezoelectric substrates. First, both surfaces of two lithium niobate (LiNbO ₃ ) substrates 21a and 21b, which are piezoelectric substrates, are mirror-polished. Then, these lithium niobate substrates 21a and 21b are mixed with a mixed solution of ammonia, hydrogen peroxide and water (ammonia water: hydrogen peroxide solution: water = 1: 1: 6).
(Volume ratio)) and washed with the lithium niobate substrate 21.
a, 21b are subjected to a hydrophilic treatment. As shown in FIG. 2A, the piezoelectric substrates 21a and 21b washed with the mixed solution
Is terminated with a hydroxyl group (-OH group) and becomes hydrophilic (state before bonding).

Next, as shown in FIG.
Treated two piezoelectric substrates (LiNbO₃) 21
a, 21b, the directions of the polarization axes are opposite to each other
(L1> L2). This allows dehydration
Occurs and the piezoelectric substrate (LiNbO ₃) 21a and piezoelectric substrate
(LiNbO₃) 21b is used for polymerization of hydroxyl groups or hydrogen bonding.
It is attracted and joined by any attractive force. Like this, mirror
Surface treatment of polished surfaces to bring them into contact
Surface facing the interface without interposing an adhesive layer such as adhesive
Is called "direct joining". Directly
Since no adhesive is used in joining by joining, the joining interface
No adhesive layer. The adhesive layer absorbs vibration and increases sensitivity
Deterioration, variation, and temperature characteristics
Deterioration or use of direct bonding
No vibration absorption at the joint interface
Bonding can be obtained. Also, in general,
Heat treatment allows sharing from bonding by intermolecular force
Stronger bonds at the atomic level, such as bonds and ionic bonds
Become.

If desired, the piezoelectric substrates (LiNbO ₃ ) 21a and 21b bonded as described above
The heat treatment may be performed at a temperature of 0 ° C. As a result, FIG.
As shown in (c), the piezoelectric substrate (LiNbO ₃ ) 21a
And the constituent atoms of the piezoelectric substrate (LiNbO ₃ ) 21b are covalently bonded via oxygen atoms O (L2> L3), and the piezoelectric substrates 21a and 21b are more directly bonded at the atomic level. You. That is, a bonding state in which no bonding layer such as an adhesive is present at the bonding interface is obtained. As another case, the piezoelectric substrate (LiNbO ₃ ) 21
The constituent atoms of a and the constituent atoms of the piezoelectric substrate (LiNbO ₃ ) 21b are covalently bonded via a hydroxyl group,
In some cases, the piezoelectric substrates 21a and 21b are directly joined firmly at the atomic level. When the piezoelectric substrate is weak to heat, it is not necessary to perform heat treatment. In the case of performing the heat treatment, it is preferable to perform the heat treatment in a temperature range not exceeding the Curie point at which the polarization of the piezoelectric body disappears. Lithium niobate (LiNbO ₃ ) has a Curie point of 1210 ° C., and its properties deteriorate when subjected to a temperature history close to this. As a result, it is possible to perform a stronger direct bonding.

One of the two lithium niobate substrates thus bonded by direct bonding is entirely ground by surface grinding to have a thickness of 50 μm. The other substrate is ground to a thickness of 50 μm except for a portion serving as a support. Thereby, the thickness of the beam portion of the piezoelectric element is 100 μm in total.
m, and the thickness at the support portion is 450 μm. 50 nm thick chromium and 20
An electrode is formed by sequentially depositing 0 nm of gold. At this time, since one surface has a planar shape, the electrode can be formed planarly. The other surface has a support portion, and there is a step between the support portion and the beam portion. In order to electrically conduct between the support and the electrode provided on the beam, vapor deposition was performed using a metal mask on the step surface between the support and the beam.
Thereafter, the beam was cut to a width of 0.5 mm in the longitudinal direction of the beam using a dicing saw.

Using an acceleration sensor composed of two piezoelectric elements
FIG. 3 shows the principle for detecting the rotational acceleration. Less than
The principle of detecting the rotational acceleration will be described below with reference to FIG.
You. Here, the piezoelectric elements 1 and 2 are at a distance r from the rotation center O.
It is installed at the place. The piezoelectric elements 1 and 2
The support parts 3 to be sensed are separated by a distance δr. now,
Rotational acceleration d for the entire system²θ / dt²Occurs when the piezoelectric
Elements 1 and 2 have acceleration a in the tangential direction of rotation._1θ, A_2θ
Is added. If the rotation center does not fluctuate, a_{1 θ}Is r
d²θ / dt², A_2θIs (r + δr) d²θ / dt²
Is proportional to For each piezoelectric element, the magnitude of the acceleration
Has the same proportional coefficient to output a proportional potential difference
Take the output voltage difference V2-V1 between the two piezoelectric elements 1 and 2.
And δr (d ²θ / dt²The size is proportional to
Rolling acceleration (angular acceleration) d²θ / dt²Proportional to the size of
Output signal can be obtained.

Here, when a translational acceleration occurs,
The translational acceleration applied to the piezoelectric elements 1 and 2 has the same magnitude
Therefore, the magnitude of the output signal corresponding to the translational acceleration is almost the same.
The difference is substantially close to zero. On the other hand, the rotational acceleration
If this occurs, the two piezoelectric elements 1 and the pressure
Δd and rotational acceleration d between the element 2²θ / dt ²
There is an output signal difference proportional to the product of So two
By taking the difference between the output signals of the piezoelectric elements 1 and 2, the rotational acceleration
Can be detected. In this case, the resulting rotational acceleration
To increase the accuracy of the degree, the space between the two piezoelectric elements is allowed.
The output signal difference as much as possible.
I just need. In the case of a cantilever type piezoelectric element as shown in FIG.
Since acceleration is applied to the beam from the support part 3, each pressure
Distance of each point where the support part 3 and the beam part of the element contact
Can be regarded as a distance between two piezoelectric elements. Therefore, as shown in FIG.
Sensitivity to angular acceleration in a space where space is limited
You get the highest. In contrast, the output of the two piezoelectric elements
Each force signal shows a constant magnitude, but the difference is almost zero
In the case of, the rotational acceleration is substantially zero and almost
I can ignore it. In this case, one of the piezoelectric elements
The translational acceleration can be detected from the output.

(Embodiment 2) FIG. 4 shows Embodiment 2 of the present invention.
1 shows a perspective view of an acceleration sensor 10 according to the first embodiment. This acceleration sensor 10 is different from the first embodiment in that the acceleration sensor according to the first embodiment is incorporated in a package 6a so that outputs from electrodes provided on each surface of each piezoelectric element can be easily taken out.
The polarization directions and the like of the piezoelectric elements 4 constituting the piezoelectric elements 1 and 2 of the acceleration sensor 10 are the same as those of the acceleration sensor according to the first embodiment. The piezoelectric elements 1 and 2 constituting the acceleration sensor 10 are fixed on the package 6a by the support 3. A groove 7 is dug in the package 6a so that the beam portion of the piezoelectric element does not contact the package 6a to prevent the deflection caused by the transmission of the acceleration. Package 6a
External electrodes 8a and 8b serving as output terminals are formed at both ends of the piezoelectric element 1, and the electrode 11a of the piezoelectric element 1 and the electrode 21a of the piezoelectric element 2 are connected to the external electrode 8a via a conductive layer on the package 6a. . The electrode 11b of the piezoelectric element 1 and the electrode 21b of the piezoelectric element 2 are connected to the external electrode 8b and the package 6.
a through a conductive layer. The conductive layer and the electrode are electrically connected by a conductive paste 9. The package 6a is covered with a package 6b and the acceleration sensor 10
0.

In the piezoelectric elements 1 and 2 shown in FIG. 4, conduction can be established between the conductive layer on the package and the conductive paste on the surface of the support body 3, so that there is no need to conduct electricity at the beam portion of the vibrating portion. The amount of conductive paste applied to the beam does not affect the resonance frequency of the beam. In other words, on one of the plane surfaces 11a and 21a, by connecting the support portion 3 to an external electrode using a conductive paste or the like, variations in characteristics such as the resonance frequency and sensitivity of the piezoelectric element can be reduced. That is, when a conductive paste or the like is applied from the beam portion of the piezoelectric element and taken out, the above characteristics are affected and varied due to a variation in the applied amount or a difference in the amount of the conductive paste protruding from the beam portion. On the other hand, in the case where the piezoelectric element is taken out by the support member 3, the characteristics are substantially determined only by the shape of the piezoelectric element irrespective of the amount of the conductive paste applied since the vibration is not directly affected. In the other surfaces 11b and 21b, there is a step between the support portion and the beam portion, and the electrode portion is separated into two, but is electrically connected. Regarding this surface, since the area of the beam portion is small, the application amount of the conductive paste is limited. Therefore, it is desirable to take out the surface from the electrode on the support body 3 side. In addition, as in the case of the planar surface, when the conductive paste or the like is applied from the beam portion and taken out, the above characteristics are affected by the variation in the application amount and the difference in the amount of the conductive paste protruding to the beam portion, and the above-described characteristics are affected. I will. Therefore, it is desirable to connect the electrodes of the support 3 to the external electrodes. In addition, when using a solder or the like to ensure conduction, if solder is directly connected to the beam, heat will be transmitted to the piezoelectric body that constitutes the piezoelectric element, and the temperature will rise to a high temperature, degrading the characteristics and reducing the sensitivity etc. There is a problem of lowering. On the other hand, by taking out the solder from the support 3 part, the heat to the beam part is hardly transmitted, so that such a problem can be avoided.

Next, a method for detecting acceleration using the acceleration sensor will be described. FIG. 5 shows a block diagram for acceleration detection using the acceleration sensor according to the second embodiment. The electrodes 11a and 21a of the piezoelectric elements 1 and 2 are connected to each other and connected to the signal detecting means 12, while the electrodes 11b and 21b are connected to each other and connected to another terminal of the signal detecting means 12. Further, reference potential generating means 22 for providing a reference potential is provided.

First, the polarization directions of the piezoelectric elements 1 and 2 will be described. In each of the piezoelectric elements 1 and 2, two piezoelectric bodies having opposite polarization directions are joined with their surfaces having the same polarity facing each other. Further, a piezoelectric element 1 and a piezoelectric element 2
In (2) and (3), the polarization directions of the corresponding piezoelectric bodies are set to be opposite to each other so that the joining surfaces for joining the two piezoelectric bodies have different polarities. In FIG. 5, the polarization direction is indicated by an arrow, and the arrow is indicated from the positive polarity surface to the negative polarity surface. Therefore, the starting point side of the arrow becomes a plus surface, and the ending point side indicated by the arrow becomes a minus surface. Since this polarity is due to polarization, it does not always match the polarity of the charge generated when a stress is applied.

Further, what kind of output is obtained from the two piezoelectric elements 1 and 2 when rotational acceleration is applied to the acceleration sensor will be described below with reference to FIG. When the rotation center is on an extension of the beam of the piezoelectric elements 1 and 2,
As shown by the size of the arrow in FIG. 5, the acceleration a1θ applied to the piezoelectric element 1 farther from the rotation center is larger than the acceleration a2θ applied to the piezoelectric element 2. When the accelerations in the directions indicated by the arrows in FIG. 5 are respectively applied, the swing width of the piezoelectric element 1 is larger than that of the piezoelectric element 2 as indicated by the dotted line.

In FIG. 5, in the piezoelectric element 1, the piezoelectric body on the electrode 11b side is expanded and the piezoelectric body on the electrode 11a side is compressed among the two bonded piezoelectric bodies. For this reason, each piezoelectric body generates a charge having the same polarity as the polarization when it is compressed, and on the other hand, when it is expanded, it generates a charge having a polarity opposite to the polarity of the polarization when it is expanded. A potential is generated between them.
As a result, a positive charge having the same polarity as the polarization is generated on the side of the electrode 11a of the compressed piezoelectric body, and a negative charge opposite to the polarity of the polarization is generated on the side of the electrode 11b of the expanded piezoelectric body.

On the other hand, in the piezoelectric element 2, the polarization direction of the opposing piezoelectric bodies at the joint surface of the two piezoelectric bodies is opposite to that of the piezoelectric element 1. Therefore, in the piezoelectric element 2, a negative charge is generated on the side of the compressed electrode 21a of the piezoelectric body, and a positive charge is generated on the side of the expanded electrode 21b of the piezoelectric body.

The electrode 11a, the electrode 21a, and the electrode 11
b and the electrode 21b are connected to each other and output. Therefore, the charges generated at the respective electrodes move, and the difference between the charges generated in the entire piezoelectric element 1 and the piezoelectric element 2 is obtained. In this case, since the charge generated from the piezoelectric element 1 farther from the rotation center is larger than the charge generated from the piezoelectric element 2, the charge generated from the piezoelectric element 2 is eliminated, and the difference in the generated charge amount is reduced. Occurs at the connection. Using this charge as a signal, a rotational acceleration can be obtained from an output signal obtained by detection by the signal detection means 12. In this way, by wiring between the electrodes having different polarities of the charges generated in the respective piezoelectric elements, the generated charges can be canceled each other to obtain a difference in output. Therefore, the output difference can be obtained without providing a difference circuit, and the rotational acceleration can be obtained. It should be noted that the amount of charge generated by the translational acceleration is substantially the same for each piezoelectric element, and thus can be canceled in advance by the wiring. In addition, here, as shown in FIG. 5, the case where the rotation center is on the extension of the beam portion of the piezoelectric elements 1 and 2 has been described, but the magnitude of the rotation acceleration is Since it is proportional to the difference in distance,
The rotational acceleration can be similarly detected for an arbitrary rotation center.

The application of the rotational acceleration is considered to be applied instantaneously. Therefore, the vibration of the piezoelectric body causes a reciprocating vibration from the maximum vibration width due to the application of the rotational acceleration, but the rotational acceleration can be detected by detecting the output accompanying the maximum vibration width.

FIG. 6 is a circuit diagram of a signal detecting means for detecting an acceleration using the acceleration sensor according to the second embodiment.
This signal detecting means includes a field effect transistor (FE)
T) A source follower circuit including a resistor 14 and a resistor, and an operational amplifier 15. Electrodes 1 of piezoelectric elements 1 and 2
1b and 21b are output from a field effect transistor (F
ET) 14 is input to the gate. Electrodes 11a, 2
1a is grounded from the external electrode of the package. A resistor is connected between the gate of the field effect transistor 14 and the ground, and converts an output from the piezoelectric element into a voltage. Further, a resistor is connected to the source of the field effect transistor 14 to form a source follower circuit. This source follower circuit constitutes an impedance conversion circuit. The output of the field effect transistor 14 is input to the operational amplifier 15 via a resistor and amplified. The operational amplifier 15 forms an amplification circuit. The reference potential is obtained by dividing the power supply voltage by resistance. As described above, the difference between the magnitudes of the acceleration applied to the two piezoelectric elements can be detected only by a simple amplifier circuit without using a circuit such as a differential amplifier circuit.

Further, another acceleration detecting method using the acceleration sensor will be described. FIG. 7 shows a second embodiment.
FIG. 2 is a block diagram for detecting acceleration using the acceleration sensor according to FIG. The electrodes 11b and 21a of the piezoelectric elements 1 and 2 are connected to each other, and the electrodes 11a and 21b are
2 input terminals. That is, two piezoelectric elements are connected in series. Further, reference potential generating means 22 for providing a reference potential is provided.

Next, what output is obtained from the two piezoelectric elements 1 and 2 when rotational acceleration is applied to the acceleration sensor will be described below with reference to FIG. When the rotation center is on the extension of the beam portion of the piezoelectric elements 1 and 2, as shown by the size of the arrow in FIG. Greater than. When accelerations in directions indicated by arrows in FIG. 7 are respectively applied, the swing width of the piezoelectric element 1 is larger than that of the piezoelectric element 2 as indicated by a dotted line.

In FIG. 7, in the piezoelectric element 1, the piezoelectric body on the electrode 11b side of the two bonded piezoelectric bodies is expanded, and the piezoelectric body on the electrode 11a side is compressed. For this reason, when each piezoelectric body is compressed, it generates charges of the same polarity as the polarity of the polarization, while when expanded, charges of the opposite polarity to the polarity of the polarization occur on each surface, and the opposite surface A potential is generated between them.
As a result, a positive charge having the same polarity as the polarization is generated on the side of the electrode 11a of the compressed piezoelectric body, and a negative charge opposite to the polarity of the polarization is generated on the side of the electrode 11b of the expanded piezoelectric body.

On the other hand, in the piezoelectric element 2, the polarization direction of the opposing piezoelectric bodies at the joint surface of the two piezoelectric bodies is opposite to that of the piezoelectric element 1. Therefore, in the piezoelectric element 2, a negative charge is generated on the side of the compressed electrode 21a of the piezoelectric body, and a positive charge is generated on the side of the expanded electrode 21b of the piezoelectric body.

Further, since the electrode 11b and the electrode 21a are connected, the respective electric charges move, and the electric charges having the same polarity generated between the electrode 11a of the piezoelectric element 1 and the electrode 21b of the piezoelectric element 2 are generated. Is taken. When rotational acceleration is applied, the charge generated from one of the piezoelectric elements farther from the rotation center is large, and the charge generated from the other piezoelectric element is eliminated, and the difference in the generated charge is signaled. It is input to the processing means 12. Using this charge as a signal, a rotational acceleration can be obtained from an output signal obtained by detection by the signal detection means 12. Since the two piezoelectric elements are connected in series, the capacitance of the acceleration sensor viewed from the input end of the signal detecting means 12 is reduced, and the same electric charge is generated as compared with the case where the connection is made as shown in FIG. The voltage generated also increases. That is, there is an advantage that the sensitivity is increased. FIG. 8 is a circuit diagram of another acceleration detecting signal detecting means using the acceleration sensor according to the second embodiment. The circuit configuration is the same as that of FIG.

Note that the configuration example of the acceleration sensor is not limited to the one shown in the present embodiment.
The two piezoelectric elements are arranged in the same direction as shown in FIG. 12A, the two center-supporting piezoelectric elements are arranged as shown in FIG. As shown in c), two doubly supported piezoelectric elements may be arranged. Further, in the present embodiment, the support portion of the piezoelectric element is of a cantilever type provided on only one surface of the beam portion, but may be provided on both surfaces of the beam portion. Further, in the present embodiment, lithium niobate is used as the piezoelectric body, but the present invention is not limited to this, and lithium tantalate, quartz, or a piezoelectric single crystal may be used. Further, a material using piezoelectric ceramic or a material obtained by laminating piezoelectric ceramics may be used.

Although the bonding of the piezoelectric bodies is performed by direct bonding, the present invention is not limited to this, and the bonding may be performed using an adhesive. Preferably, joining by direct joining is performed.

Although the field effect transistor and the operational amplifier are used as the signal processing circuit, the present invention is not limited to this. The output may be directly input to the operational amplifier without using the field effect transistor. Further, a reference voltage circuit and a filter circuit may be provided. Further, an analog / digital converter may be combined. Furthermore, the conductive paste is used for the connection between the electrodes on the piezoelectric elements 1 and 2 and the conductive layer on the package 6a, but is not limited thereto.
Solder or leadless solder can be used. By using solder or the like, reliability in use under high temperature and high humidity can be improved.

(Embodiment 3) FIG. 9 is a perspective view of an acceleration detecting apparatus 100 according to Embodiment 3 of the present invention. This acceleration detection device 100 incorporates the acceleration sensor 10 according to the first embodiment into packages 6a and 6b,
The acceleration sensor according to the first embodiment and the acceleration sensor according to the second embodiment in that the semiconductor element 16 connected to the external electrodes 8a, 8b, 8c, and 8d and processing the output is also incorporated in the package. Is different from This acceleration detecting device 100 includes piezoelectric elements 1 and 2, semiconductor element 16, packages 6a and 6b, and external electrodes 8a, 8b and 8
c, 8d. The piezoelectric elements 1 and 2 are the same as the piezoelectric elements constituting the acceleration sensor according to the first embodiment. The semiconductor element 16 is used as a bare chip. The size can be reduced by using a bare chip. The electrode on the upper surface of the semiconductor element 16 and the conductive layer on the package 6a were connected by wire bonding, and the electrode on the back surface was die-bonded. The electrode of the piezoelectric element and the conductive layer were connected with a conductive paste. The external electrodes 8a, 8b, 8c, 8d are used as power terminals, ground terminals, output terminals, and the like. Semiconductor element 16
Is an integrated circuit of the block diagram shown in FIG. 5 in the acceleration sensor according to the second embodiment. Specifically, a signal processing circuit in a semiconductor device includes a source follower circuit including a field effect transistor (FET) and a resistor, and an operational amplifier. This source follower circuit constitutes an impedance conversion circuit.
The output of the field-effect transistor is input to the operational amplifier 15 via a resistor and amplified. The operational amplifier constitutes an amplifier circuit. Therefore, in this case, the signal processing circuit includes one impedance circuit and an amplifier circuit. The operation of each circuit is as described in the second embodiment. The circuit configuration of the semiconductor element 16 using a field-effect transistor is as shown in FIG. 6, and its operation has been described in Embodiment 2 and will not be described.

A detection circuit can be formed even if each element is arranged on a printed circuit board. However, if the wiring length is long, the influence of noise increases, and the S / N ratio deteriorates. By housing the semiconductor element and the resistor close to each other in the same package as the piezoelectric element, noise can be reduced and high S / N can be maintained. Since the detection resolution of the sensor is determined by the S / N, high resolution can be obtained by enclosing a semiconductor element or the like in a package. In particular, in the case of a piezoelectric element using a piezoelectric single crystal such as lithium niobate, noise is easily picked up because the capacitance is small and the impedance is high. Further, when the cutoff frequency on the low frequency side is reduced, the resistance value of the resistor for current-voltage conversion must be increased, so that the resistance to noise is easily increased. In such a case, the configuration of the present embodiment is extremely effective. In addition, since not only the piezoelectric element but also the semiconductor element can be housed in the same package, a difference in amplification factor or the like due to a difference in environment such as temperature can be almost neglected, so that the rotational acceleration can be detected very accurately.

The circuit configuration of the semiconductor element is not limited to the circuit shown in the present embodiment, but can be directly input to an amplifier circuit or take a gain at a subsequent stage without using a buffer amplifier or an impedance conversion circuit. May be provided. Further, an amplifier circuit or an analog-digital conversion circuit for obtaining a gain may be provided at a subsequent stage. In addition, all the circuit components are not housed in the package, and only some of the elements are packaged in the packages 6a and 6b.
And the remaining elements may be provided on a printed circuit board or the like. Further, the configuration example of the acceleration sensor is not limited to the one shown in the first embodiment, but is a configuration in which two piezoelectric elements are arranged in parallel in the same direction as shown in FIG. As shown in FIG. 12, it is possible to use piezoelectric elements of various shapes, such as one in which two center-supporting piezoelectric elements are arranged, and one in which a doubly supported piezoelectric element is used as shown in FIG. it can. As described above, a small acceleration sensor that can detect the rotational acceleration with a single sensor with high sensitivity, has excellent S / N, and has high resolution can be realized.

(Embodiment 4) The external appearance of the acceleration detecting device according to the fourth embodiment is substantially the same as that shown in FIG. 9 when compared with the acceleration detecting device according to the third embodiment. The difference is that the circuit configuration of the semiconductor element 16 housed in the packages 6a and 6b is different. FIG. 10 shows a block diagram of the acceleration detection device 100. The acceleration sensor 10 constituting the acceleration detection device is the same as the acceleration sensor according to the first embodiment. The piezoelectric elements 1 and 2 are connected to the signal detecting means 12 and the reference potential generating means 22, respectively. Electrodes on the same side on the left and right sides of the piezoelectric elements 1 and 2 are connected to terminals of the same function of the signal detection means 12, respectively. The output signal from each piezoelectric element is input to the adding circuit 23. Since the two piezoelectric elements have opposite polarities at the joining surface of the two piezoelectric elements constituting the piezoelectric elements 1 and 2, the output from the signal detecting means 12 is not affected by the acceleration in the same direction. The signal has the opposite polarity. When these output signals are input to the addition circuit 23, a signal proportional to the difference between the accelerations applied to the two piezoelectric elements is output from the addition circuit 23, and the rotational acceleration can be detected.

FIG. 11 is a circuit diagram of an acceleration detecting device according to the fourth embodiment. This circuit diagram embodies the circuit configuration of the block diagram of FIG. The signal detecting means 12 has buffer amplifiers 24a and 24b and a resistor, and the adding circuit 23 has a differential circuit 26 and a resistor provided at a subsequent stage, and outputs a signal of the rotational acceleration from the adding circuit 23. Output. The reference potential generation circuit 22 is configured by a resistor voltage divider. Since the buffer amplifier and the differential circuit can be constituted by operational amplifiers, operational amplifiers can be used as semiconductor elements, which is simple. In this circuit, the signal processing circuit includes two signal detecting means 12 each including a buffer amplifier and a resistor, and an adding circuit 23 including a differential circuit and a resistor. More specifically, it comprises two impedance conversion circuits and an addition circuit. With this circuit, a signal proportional to the rotational acceleration is obtained from the output terminal of the adding circuit. In the drawings, some wirings such as a power supply and a ground are omitted.
In addition, when the output signals from the two piezoelectric elements are added, they have substantially the same magnitude and opposite polarities. Therefore, when the difference is substantially zero, the rotational acceleration is substantially ignored. Can be. In this case, the output signal of one of the signal detection means is considered to represent the translational acceleration. When detecting the translational acceleration, for example, the output of the buffer amplifier 24a in FIG. 9 may be connected to an external electrode. Therefore, it is possible to detect the rotational acceleration by this acceleration detecting device, and to detect the translational acceleration by the same acceleration detecting device when the rotational acceleration is substantially zero and only the translational acceleration is received. Can be.

With this acceleration detecting device 100, the acceleration sensor 10 and the semiconductor element 16 can be housed in one package as in the acceleration detecting device of the third embodiment shown in FIG. Therefore, it is easy to connect the electrodes on the same side of the piezoelectric element to the terminals of the same function of the semiconductor element, and the wiring can be simplified. In addition, since the outputs of the piezoelectric elements 1 and 2 have opposite polarities, an adder circuit can be used, and there is no need to use an operational amplifier having high common-mode rejection when using a differential circuit. Can be made easier. Further, the detection circuit can be configured even if each element is arranged on a printed circuit board. However, if the wiring length is long, the influence of noise increases, and the S / N deteriorates. By housing the semiconductor element and the resistor close to each other in the same package as the piezoelectric element, noise can be reduced and high S / N can be maintained. Since the detection resolution of the sensor is determined by the S / N, high resolution can be obtained by enclosing a semiconductor element or the like in a package. In particular, in the case of a piezoelectric element using a piezoelectric single crystal such as lithium niobate, noise is easily picked up because the capacitance is small and the impedance is high. Further, when the cutoff frequency on the low frequency side is reduced, the resistance value of the resistor for current-voltage conversion must be increased, so that the resistance to noise is easily increased. In such a case, the present embodiment is extremely effective. Also, since not only the piezoelectric element but also the semiconductor element can be housed in the same package, the difference in amplification factor due to the difference in environment such as temperature can be almost ignored, so that the rotational acceleration can be detected very accurately. it can.

The circuit configuration of the semiconductor element is not limited to the circuit of the present embodiment. The output from the piezoelectric element can be directly input to the amplifier circuit without using a buffer amplifier or an impedance conversion circuit. An amplifier circuit for obtaining a gain may be provided at a subsequent stage. Further, an amplifier circuit for obtaining a gain or an analog-digital conversion circuit may be provided at a stage subsequent to the addition circuit. Note that all of the circuit components may not be housed in the package, but may be only a part, and the rest may be provided on a printed circuit board or the like. Also,
The acceleration sensor 1 according to the first embodiment is used as a piezoelectric element.
0, two piezoelectric elements are arranged in the same direction as shown in FIG. 12A, and a center-supporting type piezoelectric element shown in FIG. 12B is arranged. Alternatively, a double-supported piezoelectric element shown in FIG. 12C may be provided. As described above, a small acceleration sensor that can detect the rotational acceleration with a single sensor with high sensitivity, has excellent S / N, and has high resolution can be realized.

(Embodiment 5) FIG. 13A is a perspective view of an acceleration sensor according to Embodiment 5 of the present invention.
FIG. 13B shows a plan view thereof. Compared to the acceleration sensor according to the first embodiment, the acceleration sensor 10 is configured by joining two piezoelectric bodies having the same polarization direction with respect to one piezoelectric element with the polarization directions opposite to each other. In that they are common. However, the acceleration sensor 10 is different from the acceleration sensor according to the first embodiment in that
The difference is that the polarization directions of the corresponding piezoelectric bodies in the piezoelectric element 1 and the piezoelectric element 2 are the same. More specifically, the polarity of the polarization of the opposing surface of the bonding surface
The piezoelectric elements 2 and 3 are joined in the same direction so that the polarization directions of the piezoelectric bodies are the same. In other words, the polarization directions of the two piezoelectric bodies constituting one piezoelectric body are opposite to each other symmetrically with respect to the bonding surface, and the two piezoelectric elements 1 and 2 have the same piezoelectric body 4 on the same side. Are in the same direction.

This acceleration sensor 10 is composed of two piezoelectric elements 1 and 2. Each piezoelectric element has a bimorph-shaped beam portion formed by joining two piezoelectric members so that their polarization directions are opposite to each other, at one end. And has a cantilever structure supported by the support portion 3. Electrodes 11a are provided on two opposing surfaces of the beam,
11b, 21a and 21b are respectively formed. Since there is a step between the beam portion and the support portion, the electrode on a surface of the support portion 3 is also formed continuously on the surface of the step surface so as to be electrically connected. The electrodes 11a and 21a on the surface opposite to the surface of the support portion 3 are formed on the entire surface. Since the cantilever is a bimorph type in which two piezoelectric members are joined, it can convert bending vibration due to acceleration into an electric signal and take it out from the electrode. In order to detect acceleration in the same direction with two piezoelectric elements, the piezoelectric elements 1,
The two cantilever beams are arranged such that the surfaces of the beam portions thereof are substantially aligned on the same surface. At this time, in order to improve the accuracy of detecting the rotational acceleration in the limited space as much as possible, the support portions 3 to which the acceleration is transmitted for the two piezoelectric elements are separated from each other and the tips of the cantilever beams are close to each other. It is preferable to arrange them. Specifically, the longitudinal directions of the piezoelectric elements are set to be the same direction, the respective support portions are arranged outside in a direction opposite to each other in the longitudinal direction, and the end surfaces of the beam portions are arranged close to each other and inside. The acceleration sensor 1
The piezoelectric elements 1 and 2 constituting the acceleration sensor 0 are manufactured by directly joining two piezoelectric bodies similarly to the piezoelectric elements constituting the acceleration sensor according to the first embodiment.

(Embodiment 6) FIG. 14 is a perspective view of an acceleration sensor according to Embodiment 6 of the present invention. Comparing this acceleration sensor 10 with the acceleration sensor according to the fifth embodiment,
The acceleration sensor according to the fifth embodiment is connected to packages 6a and 6
b, so that the output from each piezoelectric element can be easily taken out to an external electrode. In this acceleration sensor 10, the piezoelectric elements 1 and 2 are fixed on the package 6a by the support 3. Package 6a includes:
The groove 7 is dug so that the beam portion of the piezoelectric element does not hinder the deflection by contacting the package. External electrodes 8a, 8b, 8c serving as output terminals are provided at both ends and the center of the package 6a.
Are formed, and the electrodes 11a and 11b of the piezoelectric element 1 are connected to the external electrodes 8c and 8b via conductive layers on the package 6a, respectively. The electrode 2 of the piezoelectric element 2
1a and 21b are connected to external electrodes 8c and 8a via conductive layers on the package 6a, respectively. The conductive layer and the electrode are electrically connected by a conductive paste 9. The package 6a is covered with the package 6b to form the acceleration sensor 10.

In this acceleration sensor 10, conduction can be established between the conductive layer on the package and the conductive paste on the surface of the support portion 3, and the resonance frequency of the beam is not affected by the amount of the conductive paste applied. . That is, by connecting to the electrodes from the support portion 3 with a conductive paste or the like, it is possible to reduce variations in characteristics such as the resonance frequency and sensitivity of the piezoelectric elements 1 and 2. That is, when a conductive paste or the like is applied from the beam portion of the piezoelectric element and taken out, the above characteristics are affected and varied due to a variation in the application amount or a difference in the amount of protrusion to the beam portion. By taking out the output from the support portion, the characteristics can be substantially determined only by the shape of the piezoelectric element regardless of the application amount of the conductive paste and the like, so that the variation can be reduced. On the surface where the electrode is separated into two parts, the area of the connection part is small, so that the amount of the conductive paste applied is limited. Therefore, it is preferable to take out the electrode from the support part. Further, in the case where conduction is ensured by using solder or the like, there is a problem that the temperature of the piezoelectric body constituting the piezoelectric element becomes high, the characteristics are deteriorated, and the sensitivity of the piezoelectric element is reduced. However, such a problem can be avoided by taking out from the support body 3 by soldering.

Next, a method for detecting acceleration using the acceleration sensor 10 will be described. FIG. 15 shows a block diagram of acceleration detection using the acceleration sensor 10. Outputs from the piezoelectric elements 1 and 2 of the acceleration sensor 10 are connected to signal detection means 12 respectively.
Are connected to the differential amplifying means 13. Further, reference potential generating means 22 for providing a reference potential is provided. The electrodes (11a and 21a and 11b and 21b) on the same side of the beam portions of the piezoelectric elements 1 and 2 are connected to terminals of the same function of the signal detection means 12, respectively. Further, the electrode 11a and the electrode 21b are connected to the reference potential generating means 22. As a result, when acceleration is applied in the direction shown in the drawing, both positive signals are output from the signal detecting means 12.

FIG. 16 shows a circuit diagram of the signal detecting means in the present embodiment. Electrodes 11b and 21 of piezoelectric elements 1 and 2
The output from b is a field effect transistor (FET) 14
a and 14b are input to the gates. Electrodes 11a, 2
1a is grounded from the external electrode of the package. A resistor is connected in parallel with the piezoelectric elements 1 and 2 to convert the output to a voltage. Further, the field effect transistor 14a,
A resistor is connected to the source 14b to form a source follower circuit. This source follower circuit constitutes an impedance conversion circuit. The reference potential is a ground potential. When acceleration occurs in the direction of the arrow in the figure, both output positive signals. Field effect transistors 14a, 1
The output of 4b is input to the operational amplifier 15 via a resistor and amplified. The operational amplifier 15 forms a differential amplifier circuit, and has an output terminal connected to a field effect transistor 14a,
The difference in the magnitude of the output signal from 14b is output. Therefore, the difference between the output signals of the two piezoelectric elements 1 and 2 is detected. As described above, the difference between the magnitudes of the acceleration applied to the two piezoelectric elements can be detected.

As described above, the rotational acceleration can be detected from the differential output. The detection sensitivity of the rotational acceleration is shown in FIG.
As shown in the figure, the distance is proportional to the distance δr between the support portions 3 of the two piezoelectric elements 1 and 2. Therefore, in order to increase the detection sensitivity of the rotational acceleration, it is necessary to increase δr as much as possible. In the case of a cantilever-type acceleration sensor, it operates in a fixed-end drive mode in which acceleration is applied from the support. Therefore, it is desirable to increase the distance between the support portions 3 of the two piezoelectric elements. In the sixth embodiment, the support 3 is disposed at both ends in the packages 6a and 6b, so that the difference in the distance can be maximized. In addition,
As the signal detecting means 12, a field effect transistor and an operational amplifier are used, but the present invention is not limited to this. The output from the piezoelectric element may be directly input to the operational amplifier without using the field effect transistor. Further, a reference voltage circuit and a filter circuit may be provided. Further, an analog / digital converter may be combined.

(Embodiment 7) When the acceleration sensor according to Embodiment 7 is compared with the acceleration sensor according to Embodiment 6, the acceleration sensor according to Embodiment 5 is
Although they are the same in that they are incorporated in a and 6b, they differ in the external electrodes that are provided as output terminals. That is,
This acceleration sensor includes a pair of external electrodes that connect electrodes having different polarities of generated charges between piezoelectric elements. Specifically, the electrode 11a of the piezoelectric element 1 is connected to the electrode 21b of the piezoelectric element 2, and the electrode 11a of the piezoelectric element 1 is connected.
b and the electrode 21a of the piezoelectric element 2 are connected to each other to form an external electrode serving as a set of output terminals. The electrodes are connected via a conductive layer on the package.

FIG. 17 is a block diagram showing a method for detecting an acceleration using the acceleration sensor 10.
The output from the piezoelectric elements 1 and 2 of the acceleration sensor 10 is such that the electrodes having different polarities of the generated charges are connected between the piezoelectric elements and connected to the signal detecting means 12. Specifically, it is connected between the electrodes (11a and 21b, and 11b and 21a) on the different sides of the beam portions of the piezoelectric elements 1 and 2, and then connected to the terminal of the signal detection means 12. As a result, when acceleration is applied in the direction shown in the figure, rotational acceleration can be obtained from the signal detection means 12 based on an output signal corresponding to the difference in electric charge generated between the two piezoelectric elements 1 and 2.

Next, FIG. 18 shows a circuit diagram of an example which embodies the block diagram of FIG. This signal detecting means comprises a source follower circuit comprising a field effect transistor (FET) 14 and a resistor, and an operational amplifier 15. Outputs from the electrodes 11b and 21a of the piezoelectric elements 1 and 2 are input to the gate of a field effect transistor (FET) 14. The electrodes 11a and 21b are grounded from the external electrodes of the package. A resistor is connected between the gate of the field effect transistor 14 and the ground, and converts an output from the piezoelectric element into a voltage. Further, a resistor is connected to the source of the field effect transistor 14 to form a source follower circuit. This source follower circuit constitutes an impedance conversion circuit. The output of the field effect transistor 14 is input to the operational amplifier 15 via a resistor and amplified. The operational amplifier 15 forms an amplification circuit. The reference potential is obtained by dividing the power supply voltage by resistance. As described above, the difference between the magnitudes of the acceleration applied to the two piezoelectric elements can be detected only by a simple amplifier circuit without using a circuit such as a differential amplifier circuit.

FIG. 19 shows another circuit diagram that embodies the block diagram of FIG. This signal detecting means directly inputs the output from the piezoelectric element to the operational amplifier without using the field effect transistor (FET) 14, and is composed of two operational amplifiers and a resistor. Piezoelectric elements 1, 2
The outputs from the electrodes 11b and 21a are input to the operational amplifier 15a. The electrodes 11a and 21b are grounded from the external electrodes of the package. The output of the operational amplifier 15a is input to the operational amplifier 15 via a resistor and amplified. The operational amplifier 15 forms an amplification circuit. The reference potential is obtained by dividing the power supply voltage by resistance. As described above, the difference between the magnitudes of the acceleration applied to the two piezoelectric elements can be detected by the simple amplifier circuit composed of the operational amplifier.

FIG. 20 shows another block diagram of a method of detecting acceleration using the acceleration sensor 10. Outputs from the piezoelectric elements 1 and 2 of the acceleration sensor 10 are connected between electrodes having the same polarity of generated charges between the piezoelectric elements, and the remaining electrodes are connected to the signal detecting means 12. Specifically, the electrodes (11a and 21a) on the same side of the beam portions of the piezoelectric elements 1 and 2 are connected to each other, and the electrodes (11
b and 21b) are connected to the terminals of the signal detection means 12. That is, two piezoelectric elements are connected in series. As a result, when acceleration is applied in the direction shown in the drawing, two piezoelectric elements 1
The rotational acceleration can be obtained from the output signal corresponding to the difference between the charges generated between the two. Since the two piezoelectric elements are connected in series, there is an advantage that the capacitance of the acceleration sensor as viewed from the input end of the signal detection means 12 is reduced and the sensitivity is increased. Next, FIG. 21 shows an example of a circuit diagram which embodies the block diagram of FIG. The configuration of the circuit is the same as that of FIG. Note that the same circuit as in FIG. 20 may be used.

(Eighth Embodiment) FIG. 22 shows a perspective view of an acceleration detecting apparatus 100 according to an eighth embodiment of the present invention. The acceleration detecting device 100 is different from the acceleration sensor according to the sixth embodiment in that a semiconductor element 16 for processing the output of a piezoelectric element is provided in the packages 6a and 6b. The acceleration detecting device 100 includes a piezoelectric element 1,
2, the semiconductor device 16, the packages 6a and 6b, and the external electrodes 8a, 8b, 8c and 8d. The piezoelectric elements 1 and 2
This is the same as that of the acceleration sensor according to the fifth embodiment. The semiconductor element 16 is used as a bare chip. The size can be reduced by using a bare chip. This semiconductor element 16
Constitutes a signal processing circuit, and comprises two impedance conversion circuits and a differential amplifier circuit. The electrode on the upper surface of the semiconductor element 16 and the conductive layer on the package 6a are connected by wire bonding, and the electrode on the back surface is die-bonded. The electrode of the piezoelectric element and the conductive layer are connected by a conductive paste. The external electrodes 8a, 8b, 8c, 8d
It is used as a power terminal, ground terminal, output terminal, and the like.
The semiconductor element 16 is obtained by integrating the circuit shown in the block diagram of FIG. The operation is as described in the fifth embodiment. The semiconductor element 16 using a field-effect transistor is a specific example of the circuit configuration shown in FIG. 16, and its operation has been described in Embodiment 5 and will not be described.

(Embodiment 9) The external appearance of the acceleration detecting apparatus according to Embodiment 9 is substantially the same as that shown in FIG. 22 when compared with the acceleration detecting apparatus according to Embodiment 8, The difference is that the circuit configuration of the semiconductor element 16 housed in the packages 6a and 6b is different. FIG. 23 shows a circuit diagram of the acceleration detection device 100. This is shown in FIG.
Is a configuration different from the circuit diagram shown in FIG. Here, the signal detection means 12 includes buffer amplifiers 24a and 24b, and a differential circuit 25 is provided at a subsequent stage. The reference potential generation circuit 22 is configured by a resistance voltage division. Since the buffer amplifier and the differential circuit can be constituted by operational amplifiers, operational amplifiers can be used as semiconductor elements, which is simple. In the drawings, wires such as a power supply and a ground are omitted.

(Embodiment 10) The external appearance of the acceleration detecting device according to the tenth embodiment is substantially the same as that shown in FIG. 22 when compared with the acceleration detecting device according to the eighth embodiment. The difference is that the circuit configuration of the semiconductor element 16 housed in the packages 6a and 6b is different. FIG. 24 shows a circuit diagram of the acceleration detection device 100. This is different from the block diagram of FIG. 15 in that the electrodes (11a and 21a, 11b and 21b) on the same side with respect to the beam portions of the piezoelectric elements 1 and 2 are provided.
And the signal detecting means 12 and the reference potential generating means 22 are connected. That is, the electrode 11a and the electrode 21b are connected to the reference potential generating means 22, and the electrode 11b and the electrode 21a are directly connected to the signal detecting means 12. Therefore, when acceleration is applied in the direction of the arrow in the figure, the polarities of the signals output from the piezoelectric elements 1 and 2 via the signal detecting means 12 are reversed. This output signal is input to the addition circuit 23. Since the outputs from the piezoelectric elements 1 and 2 have opposite polarities, a signal proportional to the difference between the accelerations applied to the two piezoelectric elements is output from the addition circuit 23, and the rotational acceleration can be detected.

An example of a circuit diagram showing the circuit configuration of the block diagram of FIG. 24 is shown in FIG. The circuit of the acceleration detection device 100 can be configured using an operational amplifier as in FIG. Since the positions of the non-inverting input terminal of the buffer amplifier 24 and the electrodes connected to the reference potential generating means 22 are different between the piezoelectric elements 1 and 2, the polarities of the outputs of the buffer amplifiers 24a and 24b are reversed. The adding circuit 26 is similarly configured by an operational amplifier. With this circuit, a signal proportional to the rotational acceleration is obtained from the output terminal of the adding circuit. In the drawings, wires such as a power supply and a ground are omitted. Even if each element is arranged on a printed circuit board separated from the piezoelectric element, the detection circuit can be formed. However, if the wiring length is long, the influence of noise increases, and the S / N is deteriorated. By housing the semiconductor element, the resistor, and the like close to the same package as the piezoelectric element, noise can be reduced and a high S / N can be maintained.
Since the detection resolution of the acceleration sensor is determined by the S / N, high resolution can be obtained by enclosing a semiconductor element or the like in a package. In particular, in the case of a piezoelectric element using a piezoelectric single crystal such as lithium niobate, noise is easily picked up because the capacitance is small and the impedance is high. Further, when the cutoff frequency on the low frequency side is reduced, the resistance value of the resistor for current-voltage conversion must be increased, so that the resistance to noise is easily increased.
In such a case, the present embodiment is extremely effective. In addition, since not only the piezoelectric element but also two semiconductor elements can be housed in the same package, the difference in amplification factor due to the difference in environment such as temperature can be almost ignored. it can.

The circuit configuration of the semiconductor element is not limited to the circuit configuration shown in the present embodiment, but may be directly input to an amplifier circuit without using a buffer amplifier or an impedance conversion circuit, or may be provided with a gain at a subsequent stage. May be provided. Further, an amplifier circuit or an analog-digital conversion circuit for obtaining a gain may be provided at a stage subsequent to the addition circuit or the differential circuit. Note that all of the circuit components may not be housed in the package, but may be only a part, and the rest may be provided on a printed circuit board or the like. Further, the piezoelectric element is not limited to that of the present embodiment, but may be one in which two piezoelectric elements are arranged in the same direction as shown in FIG. The same type of piezoelectric element is arranged, and (c)
As shown in the figure, a double-supported beam type piezoelectric element may be arranged. As described above, a small acceleration sensor that can detect the rotational acceleration with one sensor with high sensitivity, has excellent S / N, and has high resolution can be realized.

(Eleventh Embodiment) FIG. 27 is a plan view of an acceleration sensor according to an eleventh embodiment of the present invention. Compared to the acceleration sensor according to the first embodiment, the acceleration sensor 10 is a unimorph type in which each piezoelectric element is formed of one piezoelectric body, and is configured by being joined to a silicon substrate serving as a support. Is different. This acceleration sensor 1
Reference numeral 0 denotes two piezoelectric elements 1 and 2, each of which supports a unimorph-type beam using one piezoelectric body bonded to a silicon substrate 30 at one end by a support portion 3. It has a cantilever structure. In the piezoelectric element 1 and the piezoelectric element 2, the polarization directions of the respective piezoelectric bodies are opposite to each other. The electrodes 11a, 11b, 21a, 21a are provided on two opposing surfaces of the beam portions of the piezoelectric elements 1, 2.
b are formed respectively. The outputs of the electrodes 11b and 21b on the surface to which the silicon substrate 30 is joined are taken out from the ends. An electrode 11a on a surface opposite to the support portion 3;
21a is formed on the entire surface. This piezoelectric element 1,
2 has a cantilever structure, and the piezoelectric body 4 is formed by bending vibration generated in the beam due to acceleration transmitted from the support 3.
Electrodes 11a, 1
1b, 21a and 21b. In this acceleration sensor 10, each of the piezoelectric elements 1 and 2 is arranged such that one surface thereof is parallel to each other, and is arranged such that the surfaces of the beam portions are on the same plane. Specifically, the longitudinal directions of the piezoelectric elements are set to be the same direction, and the support members 3 are arranged outside in the longitudinal direction so as to be substantially aligned with each other, and the ends of the beam portions are close to each other. It is located inside. Note that the bonding between the silicon substrate serving as the support portion and the piezoelectric body 4 may be bonding using an adhesive or bonding using direct bonding. Preferably, the joining is performed by direct joining.

The piezoelectric elements 1 and 2 constituting the acceleration sensor 10 are arranged so that the polarization directions of the piezoelectric bodies 4 are different. In FIG. 27, the polarization direction of each piezoelectric body is indicated by an arrow. The start point side of the arrow is a plus plane, and the end point side is a minus plane. In the piezoelectric element 1, the electrode 11a has a plus surface, and the electrode 11b has a minus surface. In the piezoelectric element 2, the electrode 21a has a minus surface, and the electrode 21b has a plus surface.

Next, a method for detecting acceleration using the acceleration sensor will be described. FIG. 28 is a block diagram of acceleration detection. The electrodes 11a and 21a of the piezoelectric elements 1 and 2 are connected to each other and connected to the signal detecting means 12,
On the other hand, the electrodes 11b and 21b are connected to each other and to another terminal of the signal detecting means 12. Further, reference potential generating means 22 for providing a reference potential is provided. FIG.
When acceleration in the direction indicated by the arrow in FIG. 8 is applied, in the piezoelectric element 1, a positive charge is generated on the electrode 11a side and a negative charge is generated on the electrode 11b side. At this time, in the two piezoelectric elements, the polarization directions of the constituent piezoelectric materials are opposite to each other, so that a negative charge is generated on the electrode 21a side and a positive charge is generated on the electrode 21b side of the piezoelectric element 2. Electrode 11a
Since the electrode 21a and the electrode 11b are connected to the electrode 21b, the respective charges move, and the generated charges are balanced in the piezoelectric element 1 and the piezoelectric element 2 as a whole. When a rotational acceleration is applied, the generated charge from one of the piezoelectric elements farther away from the center of rotation is large, so the generated charge from the other piezoelectric element is eliminated, and the difference in the generated charge amount is reduced. Occurs at the connection. Using this charge as a signal,
The rotational acceleration can be represented by an output signal detected by the signal detecting means 12.

(Embodiment 12) FIG. 29 is a plan view of an acceleration sensor according to Embodiment 12 of the present invention. This acceleration sensor 10 is different from the acceleration sensor according to the eleventh embodiment in that the polarization directions of the piezoelectric bodies are the same. The acceleration sensor 10 includes two piezoelectric elements 1 and 2, each of which is a unimorph-type beam using one piezoelectric body in which one piezoelectric body is bonded to a silicon substrate 30. Has a cantilever structure supported by the support portion 3 at one end. And the piezoelectric element 1
In the piezoelectric element 2 and the piezoelectric element 2, the polarization direction of each piezoelectric body is the same.

(Thirteenth Embodiment) FIG. 30 is a plan view of an acceleration sensor according to a thirteenth embodiment of the present invention. The acceleration sensor 10 is different from the acceleration sensor according to the first embodiment in that each piezoelectric element is configured by joining two piezoelectric bodies having the same polarization direction. In other words, the polarization directions of all the piezoelectric bodies constituting one piezoelectric element are the same. In addition, since the opposite surfaces of the two piezoelectric bodies have different polarities, it is necessary to use the potential at the bonding surface as an output, and therefore, there is a difference in that an electrode is provided on the bonding surface. The acceleration sensor 10 includes two piezoelectric elements 1 and 2, and each of the piezoelectric elements 1 and 2 is formed by joining two piezoelectric bodies having the same polarization direction. Also,
In the piezoelectric element 1 and the piezoelectric element 2, the polarization directions of the respective piezoelectric bodies constituting the respective piezoelectric elements are opposite to each other.

Each piezoelectric element has a cantilever structure in which a bimorph-shaped beam portion in which two piezoelectric bodies are joined is supported by a support portion 3 at one end. Electrodes 11a, 11b, 21a,
21b are formed, and electrodes 11c and 21c are provided on the joint surface between the two piezoelectric bodies. The electrodes 11b and 21b on the surface on which the support portion 3 is provided electrically connect the step surfaces since there is a step between the beam portion and the support portion. The electrodes 11a and 21a on the surface opposite to the support 3 are formed on the entire surface. Electrodes 11c and 21 on the joint surface
It is preferable that c be provided before joining the two piezoelectric members. Since the piezoelectric elements 1 and 2 have a cantilever structure, the potential difference generated in the piezoelectric body 4 due to the flexural vibration generated in the beam due to the acceleration transmitted from the support 3 is provided on the opposing surfaces. 21a, 2
1b and the electrodes 11c and 21c provided on the joint surface. In this acceleration sensor 10, each of the piezoelectric elements 1 and 2 is arranged such that one surface thereof is parallel to each other, and is arranged such that the surfaces of the beam portions are on the same plane. More specifically, the longitudinal directions of the piezoelectric elements are set to be the same direction, and are arranged substantially in a straight line. Are located close and inside.

The acceleration sensor 10 includes a piezoelectric element 1 and a piezoelectric element 2. Each piezoelectric element is formed by joining two piezoelectric bodies 4 having the same polarization direction. The adjacent piezoelectric elements 1 and 2 are arranged such that the polarization directions of the piezoelectric bodies 4 are opposite to each other. In FIG. 30, the direction of polarization of each piezoelectric body is indicated by an arrow.
The start point side of the arrow is a plus plane, and the end point side is a minus plane.
In the piezoelectric element 1, the electrode 11a is a plus surface, the electrode 11b is a minus surface, and the electrode 11c is an interface between the plus and minus surfaces. In the piezoelectric element 2, the electrode 21a is a minus surface, the electrode 21b is a plus surface, and the electrode 21c is an interface between the plus and minus surfaces.

Next, a method for detecting acceleration using the acceleration sensor will be described. FIG. 31 is a block diagram of acceleration detection. The electrodes 11a and 21a of the piezoelectric elements 1 and 2 are connected to each other and connected to the signal detecting means 12,
On the other hand, the electrodes 11b and 21b are connected to each other and to another terminal of the signal detecting means 12. Further, reference potential generating means 22 for providing a reference potential is provided. FIG.
When acceleration in the direction indicated by the arrow in FIG. 1 is applied, in the piezoelectric element 1, a positive charge is generated on the electrode 11a side, a positive charge is generated on the electrode 11b side, and a negative charge is generated on the electrode 11c side. At this time, in the two piezoelectric elements, the polarization directions of the piezoelectric bodies constituting the two piezoelectric elements are opposite to each other. appear. Electrode 11a, electrode 11b, electrode 21a, and electrode 21b
Are connected, and since the electrode 11c and the electrode 21c are connected, the respective electric charges move, and the generated electric charges are balanced in the piezoelectric element 1 and the piezoelectric element 2 as a whole. When a rotational acceleration is applied, the generated electric charge from one of the piezoelectric elements farther from the rotation center is larger, so that the generated electric charge from the other piezoelectric element is erased,
A difference in the generated charge amount occurs at the connection. This charge is detected as a signal by the signal detection means 12, and the output signal can indicate the rotational acceleration.

(Embodiment 14) FIG. 32 is a plan view of an acceleration sensor according to Embodiment 14 of the present invention. The acceleration sensor 10 is different from the acceleration sensor according to the thirteenth embodiment in that the polarization directions of the piezoelectric elements constituting each piezoelectric element are the same in the piezoelectric element 1 and the piezoelectric element 2. This acceleration sensor 10 is composed of two piezoelectric elements 1 and 2, and each piezoelectric element 1 and 2 has a bimorph-shaped beam joined at one end so that the polarization directions of two piezoelectric bodies are in the same direction. Has a cantilever structure supported by the support portion 3.

(Embodiment 15) FIG. 33 is a plan view of an acceleration sensor according to Embodiment 15 of the present invention. The acceleration sensor 10 is different from the acceleration sensor according to the first embodiment in that the two piezoelectric bodies constituting the piezoelectric element are not bonded to each other as they are but are bonded via a shim material. Specifically, the acceleration sensor 10
Is composed of two piezoelectric elements 1 and 2, and each piezoelectric element 1
No. 2 joins two piezoelectric bodies having opposite polarization directions via a shim material. In addition, the polarization directions of the corresponding piezoelectric bodies of the piezoelectric elements 1 and 2 are opposite to each other. In other words, the polarization directions of the corresponding piezoelectric bodies in the adjacent piezoelectric elements are opposite to each other so that the polarities of the polarizations at the joint surface between the piezoelectric body and the shim material are different for the adjacent piezoelectric elements.

Each piezoelectric element has a cantilever structure in which a bimorph-type beam portion in which two piezoelectric members are joined via a shim material is supported by a support portion 3 at one end. Electrodes 11a, 1
1b, 21a and 21b are formed respectively. The electrodes 11b and 21b on the surface on which the support portion 3 is provided electrically connect the step surfaces since there is a step between the beam portion and the support portion. Electrodes 11a and 21 on the surface opposite to support 3
a is formed on the entire surface. The piezoelectric elements 1, 2
Have electrodes 11a, 11a provided on opposite surfaces with a potential difference generated in the piezoelectric body 4 due to flexural vibration generated in the beam section due to acceleration transmitted from the support section 3 because of the cantilever structure.
b, 21a and 21b. In the acceleration sensor 10, each of the piezoelectric elements 1 and 2 is arranged such that one surface thereof is parallel to each other.
The beams are arranged so that the surfaces thereof are flush with each other. Further, the longitudinal direction of each piezoelectric element is set to be the same direction, and the support portions 3 are arranged outside in the opposite directions in the longitudinal direction so as to be substantially aligned with each other, and the ends of the beam portions are brought close to each other. It is located inside.

In FIG. 33, the polarization direction of each piezoelectric body is indicated by an arrow. The start point side of the arrow is a plus plane, and the end point side is a minus plane. In the piezoelectric element 1, the positive surface is connected to the electrode 11a, and the positive surface is connected to the electrode 11b. In the piezoelectric element 2, the negative surface is connected to the electrode 21a, and the negative surface is connected to the electrode 21b.

Next, a method of detecting acceleration using the acceleration sensor will be described. FIG. 34 is a block diagram of acceleration detection. The electrodes 11a and 21a of the piezoelectric elements 1 and 2 are connected to each other and connected to the signal detecting means 12,
On the other hand, the electrodes 11b and 21b are connected to each other and to another terminal of the signal detecting means 12. Further, reference potential generating means 22 for providing a reference potential is provided. FIG.
When acceleration in the direction indicated by the arrow in FIG. 4 is applied, in the piezoelectric element 1, a positive charge is generated on the electrode 11a side, and a negative charge is generated on the electrode 11b side. At this time, in the two piezoelectric elements, the polarization directions of the constituent piezoelectric materials are opposite to each other, so that a negative charge is generated on the electrode 21a side and a positive charge is generated on the electrode 21b side of the piezoelectric element 2. Electrode 11a
Since the electrode 21a and the electrode 11b are connected to the electrode 21b, the respective charges move, and the charges generated in the entire piezoelectric element 1 and the piezoelectric element 2 are balanced. When rotational acceleration is applied, the charge generated from one of the piezoelectric elements farther from the rotation center is larger, so the charge generated from the other piezoelectric element is eliminated, and the difference in the generated charge Occurs at the connection. This charge is detected as a signal by the signal detection means 12, and the output signal can indicate the rotational acceleration.

(Embodiment 16) FIG. 35 is a plan view of an acceleration sensor according to Embodiment 16 of the present invention. This acceleration sensor 10 is different from the acceleration sensor according to the fifteenth embodiment in that the polarization directions of the piezoelectric elements corresponding to the piezoelectric element 1 and the piezoelectric element 2 are the same. In other words, the piezoelectric element 1 and the piezoelectric element 2 are different from each other in that the polarity of the polarization at the joint surface of each piezoelectric body constituting the piezoelectric element with the shim material is the same. This acceleration sensor 10 is composed of two piezoelectric elements 1 and 2, and each of the piezoelectric elements 1 and 2 is a bimorph-type beam in which two piezoelectric bodies having polarization directions opposite to each other are joined via a shim material. It has a cantilever structure supported at one end by a support 3.

(Embodiment 17) FIG. 36 is a plan view of an acceleration sensor according to Embodiment 17 of the present invention. The acceleration sensor 10 is different from the acceleration sensor according to the first embodiment in that four piezoelectric bodies are joined to form one piezoelectric element. This acceleration sensor 10
Is composed of two piezoelectric elements 1 and 2, and each piezoelectric element 1
Reference numeral 2 denotes a combination of two piezoelectric bodies having opposite polarization directions joined and laminated. In the piezoelectric element 1 and the piezoelectric element 2, the polarization directions of the corresponding piezoelectric bodies are opposite to each other. In other words, the polarity of the bonding surface of the piezoelectric body is made different between the piezoelectric element 1 and the piezoelectric element 2.

Each piezoelectric element is a combination of two piezoelectric elements joined and laminated, and has a cantilever structure in which a beam part is supported by a support part 3 at one end. .
Electrodes 1 are provided on two opposing surfaces of the beam portion of each of the piezoelectric elements 1 and 2.
1a, 11b, 21a and 21b are respectively formed. As shown in FIG. 36, the electrode 11a is electrically connected to a surface on which charges of the same polarity are generated when acceleration is applied. Similarly, the electrode 11b is electrically connected to a surface on which charges of the same polarity are generated. Connected. The same applies to the electrodes 21a and 21b. Since the piezoelectric elements 1 and 2 have a cantilever structure, the potential difference generated in the piezoelectric body 4 due to the flexural vibration generated in the beam due to the acceleration transmitted from the support 3 is provided on the opposing surfaces. 21a, 21
b. This acceleration sensor 10
In each of the piezoelectric elements 1 and 2, the piezoelectric elements 1 and 2 are arranged such that one surface thereof is parallel to the other, and the piezoelectric elements 1 and 2 are arranged such that the surfaces of the beam portions are on the same plane. In addition, the longitudinal directions of the piezoelectric elements are set to be the same direction, and are arranged substantially in a straight line, and the respective support portions 3 are disposed apart from each other in the longitudinal direction. Has been placed.

In FIG. 36, the polarization directions of the respective piezoelectric bodies are indicated by arrows. The start point side of the arrow is a plus plane, and the end point side is a minus plane. In the piezoelectric element 1, the minus surfaces of the piezoelectric bodies 4 are joined together, and in the piezoelectric element 2, the plus surfaces of the piezoelectric bodies 4 are joined.

Next, a method for detecting acceleration using the acceleration sensor will be described. FIG. 37 is a block diagram of acceleration detection. The electrodes 11a and 21a of the piezoelectric elements 1 and 2 are connected to each other and connected to the signal detecting means 12,
On the other hand, the electrodes 11b and 21b are connected to each other and to another terminal of the signal detecting means 12. Further, reference potential generating means 22 for providing a reference potential is provided.

When acceleration is applied in the direction indicated by the arrow in FIG. 37, in the piezoelectric element 1, a positive charge is generated on the electrode 11a side and a negative charge is generated on the electrode 11b side. At this time, in the two piezoelectric elements, the polarization directions of the piezoelectric bodies constituting the two piezoelectric elements are opposite to each other.
A negative charge is generated on the a side and a positive charge is generated on the electrode 21b side. Electrode 11a and electrode 21a, electrode 11b and electrode 21
Since b is connected, each electric charge moves, and the generated electric charges are balanced in the piezoelectric element 1 and the piezoelectric element 2 as a whole. When rotational acceleration is applied, the charge generated from one of the piezoelectric elements farther from the rotation center is larger, so the charge generated from the other piezoelectric element is eliminated, and the difference in the generated charge Occurs at the connection. This charge is detected as a signal by the signal detection means 12, and the output signal can indicate the rotational acceleration.

(Embodiment 18) FIG. 38 is a plan view of an acceleration sensor according to Embodiment 18 of the present invention. The acceleration sensor 10 is different from the acceleration sensor according to the seventeenth embodiment in that the polarization directions of the corresponding piezoelectric bodies of the piezoelectric element 1 and the piezoelectric element 2 are the same. In other words, the difference is that the polarity at the bonding surface of the piezoelectric body is the same between the piezoelectric element 1 and the piezoelectric element 2.
The acceleration sensor 10 includes two piezoelectric elements 1 and 2, and each of the piezoelectric elements 1 and 2 is configured by combining two piezoelectric elements having two polarization members whose polarization directions are opposite to each other. Has a cantilever structure in which the beam is supported at one end by the support 3.

(Embodiment 19) FIG. 39 is an exploded perspective view of an acceleration sensor according to Embodiment 19 of the present invention.
The acceleration sensor according to the present embodiment can detect rotational accelerations in two axial directions. That is, it can be detected for each component of the rotational acceleration in two directions, that is, the rotational acceleration component in the direction parallel to the mounting surface of the package 6a and the rotational acceleration component in the direction perpendicular to the package 6a. The rotation acceleration component in the horizontal direction can be detected by a set of the piezoelectric elements 1a and 2a. This is the same as the case shown in FIG. In addition, the rotational acceleration component in the vertical direction can be detected by a set of the piezoelectric elements 1b and 2b. Two piezoelectric elements 1
In b and 2b, the surfaces of the beam portions are made horizontal, and the ends of the beam portions are arranged substantially linearly close to each other and fixed by a support portion. In this case, since the beam portion is located above the plane of the package and can vibrate, there is no need to provide a groove for the beam portion to vibrate in the plane of the package 6a. Further, the bottom portion of the support was fixed with a conductive paste, and the electrodes electrically connected to the support were electrically connected to the external electrodes 8d of the package 6a. The electrode on the upper side of the beam portion was connected to the external electrode 8d by wire bonding. With such an arrangement, the rotational acceleration components in the two axial directions can be independently detected by one package.

Note that the piezoelectric element used here may have any of the structures of Embodiments 1 to 18. Also,
Either the connection of the electrodes between the piezoelectric elements or the circuit configuration may be used. Further, as shown in FIG. 9, a semiconductor circuit for two axes may be incorporated. Furthermore, a third set of piezoelectric elements may be provided so as to independently detect acceleration components in three axial directions.

Twentieth Embodiment An acceleration sensor according to a twentieth embodiment is mounted in a state where the surface of the beam portion of the piezoelectric element is inclined with respect to the mounting surface. FIG. 40A is a perspective view of a piezoelectric element included in an acceleration sensor according to Embodiment 20 of the present invention. FIG. 40 (b) shows a side view of the acceleration sensor as viewed from the direction of the arrow in FIG. 40 (a). In this side view, for convenience, the side views of the piezoelectric elements 1 and 2 are shown side by side. The components of the piezoelectric elements 1 and 2 are the same as those of the acceleration sensor according to the fifth embodiment, and the polarization directions of the piezoelectric bodies of one piezoelectric element are opposite to each other. However, as compared with the case of the acceleration sensor according to the fifth embodiment, the difference is that the main surface of the beam portion is inclined by 25 ° with respect to the perpendicular to the surface to be mounted. Since the beam part is inclined and the vibration direction is inclined with respect to the mounting surface, the piezoelectric element 1,
2 has sensitivity to acceleration in both the horizontal and vertical directions. By using this acceleration sensor,
Although the horizontal and vertical rotational acceleration components cannot be separated by the same method as the signal processing method using the piezoelectric element according to the fifth embodiment, the rotational acceleration including the rotational acceleration components in two directions can be separated into one package. Of the device.

FIGS. 41A to 41C are side views of a set of piezoelectric elements in which the surface of the beam portion of the piezoelectric element is inclined with respect to the plane of the package, and is shown in FIG. 40B. 9 shows another aspect of the combination of the inclinations of the beam portions of the piezoelectric element. For convenience, side views of the two piezoelectric elements 1 and 2 are shown side by side. FIG. 41 (a) has the same combination of polarization directions as FIG. 40 (b), but the inclination directions of the beam portions are different from each other. The piezoelectric element 1 shown in FIG.
15, 2, and 7, the rotational acceleration is detected as a horizontal component, and the translational acceleration is detected as a vertical component. On the other hand, FIG. 5, FIG.
When the connection is made like 0, the translational acceleration is detected for the horizontal component, and the rotational acceleration is detected for the vertical component. Also,
FIG. 41B shows a case where the directions of the piezoelectric bodies of the piezoelectric elements 1 and 2 are opposite to each other, but the directions of the inclinations are the same. On the other hand, when the connection is made as shown in FIGS. 5 and 7, the rotational acceleration can be detected both in the horizontal and vertical directions. When the piezoelectric elements 1 and 2 in FIG. 41C are connected as shown in FIGS. 15, 17, and 20, the translational acceleration is detected for the horizontal component, and the rotational acceleration is detected for the vertical component. On the other hand, when the connection is made as shown in FIG. 5, FIG. 7, and FIG. 10, the rotational acceleration is detected for the horizontal component, and the translational acceleration is detected for the vertical component. By inclining the main sensitivity axis as described above, it is possible to detect both horizontal and vertical rotational accelerations. Further, the translational acceleration can be detected by changing the tilt direction.

(Embodiment 21) FIGS. 42 (a) and (b)
33 is a conceptual diagram showing a method for adjusting the sensitivity of the piezoelectric element in the acceleration sensor according to Embodiment 21. FIG. When rotational acceleration is detected using two piezoelectric elements, if there is a sensitivity difference between the two piezoelectric elements, a component due to translational acceleration cannot be sufficiently removed from the outputs of the two piezoelectric elements, and measurement accuracy decreases. Therefore, it is desirable that the sensitivity difference between the two piezoelectric elements is as small as possible. When detecting the angular acceleration by mounting two acceleration sensors separately, there is no other way than to make adjustments after the user mounts them, but usually, the acceleration sensor is already housed in the package, so the piezoelectric element itself must be adjusted. Can not. However, as shown in this embodiment, when an acceleration sensor is mounted on one package and provided, the manufacturer can adjust the sensitivity of the piezoelectric element before shipping.

Next, a method of adjusting the sensitivity of one of the two piezoelectric elements in the acceleration sensor to be substantially the same as the sensitivity of the other piezoelectric element will be described. FIG. 42A is a diagram for explaining a method of cutting a part of a beam portion as one of the sensitivity adjustment methods of the piezoelectric element.
By cutting a part of the beam portion of one piezoelectric element 1 (grinding section 25), the sensitivity can be changed to be substantially equal to the sensitivity of the piezoelectric element 2. As a method of shaving the beam, there are a method using a grindstone, a method using laser irradiation, and the like.

FIG. 42 (b) shows one method of adjusting the sensitivity of the piezoelectric element.
FIG. 4 is a diagram for explaining a method of attaching a substrate. A method of increasing the sensitivity by attaching a substance 26 serving as a weight on the beam portion of one piezoelectric element 1 to make the sensitivity equal to the sensitivity of the piezoelectric element 2 is shown. Sensitivity can be increased by attaching a substance on the beam. As the substance to be attached as the sensitivity adjuster 26, resin, metal, or the like can be used. Examples of a method for attaching the sensitivity adjuster 26 include coating and bonding. Further, a method such as an ink jet method or vapor deposition may be used.

As described above, the translational acceleration component can be made extremely small before shipping by directly adjusting the sensitivity of the piezoelectric element. In addition, the method of adjusting the sensitivity is not limited to the method of adjusting the piezoelectric element, but may be the method of FIG. 10, FIG. 11, FIG.
3, When an amplifier is provided for each output signal of the piezoelectric element as shown in FIGS. 24 and 25, the sensitivity may be adjusted by adjusting the amplification factor of the amplifier.

(Embodiment 22) Embodiment 2 of the present invention
FIG. 43A shows a schematic configuration diagram of a disk recording / reproducing apparatus 200 according to the second embodiment. Disc recording / playback device 20
0, the disk 31 for recording data, the disk 31
Head 32 for recording / reproducing to / from head, head moving means 40 for moving head 32, position detecting means 50 for detecting the position of head 32, control means 60 for controlling head moving means 40, determining the presence or absence of rotational acceleration There is an acceleration discriminating means 70 that performs the operation. The head 32 is moved by the head moving means 40 in the radial direction of the disk 31 and is positioned at a designated position on the disk 31. When acceleration is applied as a disturbance to the disk recording / reproducing apparatus 200,
The position of the head 32 is shifted from the specified position due to the acceleration. To prevent this, an acceleration sensor 10 is installed to detect the rotational acceleration and the translational acceleration applied to the disk recording / reproducing apparatus 200 and control the position of the head 32 against disturbance.

In general, the position of the center of rotation of rotational vibration applied as a disturbance to a disk recording / reproducing apparatus is not constant. When the head is moved at high speed by the head moving means 40, a rotational vibration is often generated by the reaction. In this case, the vicinity of the pivot 41 supporting the head is likely to be the center of rotation. Arm 4 for supporting the head
Rotational motion such that 2 is the radial direction is likely to occur. From such a viewpoint, if the arm 42 is installed so as to be substantially parallel to the longitudinal direction of the beam portion of the piezoelectric element constituting the acceleration sensor 10, the rotational acceleration can be detected with high sensitivity. Therefore, it is desirable that the acceleration sensor 10 be installed such that the longitudinal direction of the beam portion of the piezoelectric element is parallel to the arm 42.

FIG. 43B shows a block diagram of control in the disk recording / reproducing apparatus 200. When there is no disturbance vibration, the position of the head 32 is recognized by the position detecting means 50 based on the position information recorded on the disk 31, the moving amount of the head 32 is determined by the control means 60, and the head moving means 40 moves the head. Move and position. When disturbance vibration or the like occurs, the output detected by the acceleration detection device 100 is determined by the acceleration determination means 70 as to whether or not there is a rotational acceleration and its magnitude. If the rotational acceleration is substantially negligible, a translational acceleration is detected. Acceleration determination means 7
The control means 60 calculates a moving amount for moving the head 32 to a predetermined position based on the determination result based on 0, and gives an instruction to the head moving means 40 to move the head 32 by the head moving means 40. When only the rotational acceleration is output from the output of the acceleration detection device 100, the acceleration determining means 70 may not be provided. Further, the control unit 60 may perform the same processing regarding the determination of the acceleration. In that case, the acceleration determination unit 70 does not necessarily need to be provided separately. Further, when the control unit 60 is provided with a function of detecting the position of the head 32, the position detection unit may not be provided. By such control, the head 32 can be positioned at a predetermined position even when rotational acceleration or the like is applied as disturbance vibration. Therefore, the head 32 can be precisely positioned, and the density of the disk 31 can be increased.

[0146]

As described above in detail, according to the acceleration sensor according to the present invention, by disposing at least two piezoelectric elements in a limited space with a distance between the support portions, the same direction can be obtained. The acceleration can be detected, and the rotational acceleration can be detected from the output difference between the piezoelectric elements. This allows one acceleration sensor to detect rotational acceleration (angular acceleration) with high sensitivity and high resolution regardless of environmental conditions such as temperature, and also identifies translational acceleration when rotational acceleration can be almost ignored. Thus, an acceleration sensor that can be detected as a result can be provided. Further, it is possible to provide an acceleration detection device and an acceleration detection method using the acceleration sensor, and a positioning device using the acceleration detection device.

[Brief description of the drawings]

1A is a perspective view of an acceleration sensor according to a first embodiment, and FIG. 1B is a plan view thereof.

2A is a cross-sectional view of a stage in which a surface subjected to a hydrophilization treatment is brought close to the first embodiment in order to perform bonding by direct bonding, and FIG. 2B shows that bonding is caused by direct bonding such as hydrogen bonding at an interface. And (c) a cross-sectional view showing a state in which the interface is directly bonded via an oxygen atom.

FIG. 3 is a detection principle diagram illustrating a method of detecting rotational acceleration by the acceleration sensor according to the first embodiment.

FIG. 4 is a perspective view of an acceleration sensor according to a second embodiment.

FIG. 5 is a block diagram for detecting acceleration using the acceleration sensor according to the second embodiment.

FIG. 6 is a circuit diagram for detecting acceleration using the acceleration sensor according to the second embodiment.

FIG. 7 is a block diagram for detecting acceleration in another mode using the acceleration sensor according to the second embodiment.

FIG. 8 is a circuit diagram for detecting acceleration in another mode using the acceleration sensor according to the second embodiment.

FIG. 9 is a perspective view of an acceleration sensor according to a third embodiment.

FIG. 10 is a block diagram of an acceleration detection device according to a fourth embodiment.

FIG. 11 is a circuit diagram of an acceleration detection device according to a fourth embodiment.

FIGS. 12A and 12B are plan views showing another arrangement of the acceleration sensor according to the present invention, wherein FIG. 12A shows a case where two piezoelectric elements are arranged in the same direction, and FIG. In the case of arranging the elements, (c) shows the case of arranging the doubly supported piezoelectric element.

13A is a perspective view of an acceleration sensor according to Embodiment 5, and FIG. 13B is a plan view thereof.

FIG. 14 is a perspective view of an acceleration sensor according to a sixth embodiment.

FIG. 15 is a block diagram for detecting acceleration using the acceleration sensor according to the sixth embodiment.

FIG. 16 is a circuit diagram for acceleration detection using the acceleration sensor according to the sixth embodiment.

FIG. 17 is a block diagram for acceleration detection using the acceleration sensor according to the seventh embodiment.

FIG. 18 is a circuit diagram for acceleration detection using the acceleration sensor according to the seventh embodiment.

FIG. 19 is a circuit diagram for detecting acceleration using the acceleration sensor according to the seventh embodiment.

FIG. 20 is a block diagram for another type of acceleration detection using the acceleration sensor according to the seventh embodiment.

FIG. 21 is a circuit diagram for acceleration detection in another mode using the acceleration sensor according to the seventh embodiment.

FIG. 22 is a perspective view of the acceleration detection device according to the eighth embodiment.

FIG. 23 is a circuit diagram of the acceleration detection device according to the ninth embodiment.

FIG. 24 is a block diagram of an acceleration detection device according to a tenth embodiment.

FIG. 25 is a circuit diagram of the acceleration detection device according to the tenth embodiment.

26A and 26B are plan views showing another arrangement of the acceleration sensor according to the present invention, wherein FIG. 26A shows a case where two piezoelectric elements are both arranged in the same direction, and FIG. FIG. 4C is a plan view of a case where a doubly-supported piezoelectric element is arranged when an element is arranged.

FIG. 27 is a plan view of the acceleration sensor according to the eleventh embodiment.

FIG. 28 is a block diagram for detecting acceleration using the acceleration sensor according to the eleventh embodiment.

FIG. 29 is a plan view of the acceleration sensor according to the twelfth embodiment.

FIG. 30 is a plan view of the acceleration sensor according to the thirteenth embodiment.

FIG. 31 is a block diagram for acceleration detection using the acceleration sensor according to the thirteenth embodiment.

FIG. 32 is a plan view of the acceleration sensor according to the fourteenth embodiment.

FIG. 33 is a plan view of the acceleration sensor according to the fifteenth embodiment.

FIG. 34 is a block diagram for detecting acceleration using the acceleration sensor according to the fifteenth embodiment.

FIG. 35 is a plan view of the acceleration sensor according to the sixteenth embodiment.

FIG. 36 is a plan view of the acceleration sensor according to the seventeenth embodiment.

FIG. 37 is a block diagram for acceleration detection using the acceleration sensor according to the seventeenth embodiment.

FIG. 38 is a plan view of the acceleration sensor according to the eighteenth embodiment.

FIG. 39 is an exploded perspective view of the acceleration sensor according to the nineteenth embodiment.

FIG. 40 (a) is a perspective view of an acceleration sensor according to Embodiment 20, and FIG. 40 (b) is a side view thereof.

41A and 41B are side views showing another arrangement of the acceleration sensor according to the twentieth embodiment. FIG. 41A shows a case where the polarization direction is the same and the inclination of the beam is plane-symmetric with respect to the vertical plane. , (B) shows the case where the polarization direction is opposite and the inclination of the beam part is the same, and (c) shows the case where the polarization direction is opposite and the inclination of the beam part is plane symmetric with respect to the vertical plane. is there.

FIG. 42 is a diagram illustrating a sensitivity adjustment method of the piezoelectric element in the acceleration sensor according to the twenty-first embodiment.

FIG. 43 (a) is a schematic configuration diagram of a disk recording / reproducing apparatus according to Embodiment 22, and FIG. 43 (b) is a control block diagram thereof.

[Explanation of symbols]

1, 2 Piezoelectric element 3 Support 4 Piezoelectric 6a, 6b Package 7 Groove 8a, 8b, 8c,
8d External electrode 9 Conductive paste 10 Acceleration sensor 11a, 11b, 21a, 21b Electrode 12 Signal detection means 13 Differential amplification means 14a, 14b Field effect transistor 15, 15a, 25, 26 Operational amplifier 16 Semiconductor element 22 Reference potential generation means 23 Adder circuits 24a, 24b Buffer amplifier 25 Grinding unit 26 Sensitivity adjuster 30 Silicon substrate 31 Disk 32 Head 40 Head moving unit 41 Bibot 42 Arm 50 Position detecting unit 60 Control unit 70 Signal detecting unit 100 Acceleration detecting device 200 Disk recording / reproducing device

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Fumihiko Taniguchi 55-12 Osumihama, Kyotanabe-shi, Kyoto Matsushita Nitto Electric Co., Ltd. F-term (reference) 5D088 PP01 TT10 UU07 5D096 VV03

Claims (39)

[Claims] The first and second piezoelectric elements are provided with electrodes for outputting electric charges generated by the strain deformation, and each of the first and second piezoelectric elements has at least one electrode.
One of the first piezoelectric element, comprising a support portion for supporting the piezoelectric body, the electrodes being provided at least on opposing surfaces of the piezoelectric element, respectively. And one surface of the second piezoelectric element are arranged so as to be substantially parallel to each other. 2. The first and second piezoelectric elements are of a cantilever type having a support portion for supporting the piezoelectric body and a beam portion including a main surface of the piezoelectric body. The respective longitudinal directions of the second piezoelectric element are set to the same direction, the respective support portions are arranged outside in a direction opposite to each other in the longitudinal direction, and the distal ends of the beam portions are arranged close to each other and inward, The acceleration sensor according to claim 1, wherein end faces of the beam portions are arranged so as to be substantially parallel to each other. 3. The device according to claim 1, wherein each of the first and second piezoelectric elements is formed of one piezoelectric body, and the polarization directions of the piezoelectric bodies are opposite to each other.
2. The acceleration sensor according to 1. 4. The method according to claim 1, wherein each of the first and second piezoelectric elements is formed of one piezoelectric body, and the polarization directions of the piezoelectric bodies are the same.
2. The acceleration sensor according to 1. 5. The acceleration sensor according to claim 1, wherein each of the first and second piezoelectric elements is formed by joining and laminating a plurality of piezoelectric bodies. 6. In each of the first and second piezoelectric elements, the polarization direction of all the piezoelectric bodies constituting each of the piezoelectric elements is:
The acceleration sensor according to claim 5, wherein the directions are the same. 7. The acceleration sensor according to claim 6, wherein the polarization directions of the respective piezoelectric bodies constituting each of the first and second piezoelectric elements are opposite to each other. 8. The acceleration sensor according to claim 6, wherein the polarization directions of the respective piezoelectric bodies constituting each of the first and second piezoelectric elements are the same. 9. Each of the first and second piezoelectric elements is formed by joining at least two piezoelectric bodies whose polarization directions are opposite to each other, with surfaces having the same polarization polarity facing each other. The acceleration sensor according to claim 5, wherein 10. The acceleration sensor according to claim 9, wherein each of the first and second piezoelectric elements has a polarization direction of a corresponding one of the piezoelectric bodies opposite to each other. 11. The acceleration sensor according to claim 9, wherein each of the first and second piezoelectric elements has the same polarization direction of each corresponding piezoelectric body. 12. The one piezoelectric element according to claim 5, wherein each of the piezoelectric elements constituting the piezoelectric element is joined via a shim material. Acceleration sensor. 13. The acceleration sensor according to claim 5, wherein the piezoelectric element is formed by joining a plurality of the piezoelectric bodies by direct joining. 14. The acceleration sensor according to claim 13, wherein the piezoelectric element is formed by joining a plurality of the piezoelectric bodies through at least one of an oxygen atom and a hydroxyl group by direct joining. 15. The acceleration sensor according to claim 1, further comprising an output terminal corresponding to each electrode of the first and second piezoelectric elements. 16. The apparatus according to claim 1, wherein each of said first and second piezoelectric elements has at least one output terminal in which electrodes having different polarities of generated charges are connected between different piezoelectric elements. 16. The acceleration sensor according to any one of items 15 to 15. 17. Each of the first and second piezoelectric elements may be configured such that electrodes having the same polarity of generated electric charges are connected between different piezoelectric elements, and output terminals from electrodes other than the connected electrodes are provided. 16. The method according to claim 1, wherein:
The acceleration sensor according to claim 1. 18. The device according to claim 1, further comprising at least one pair of output terminals for outputting electric charges generated at each of the first and second piezoelectric elements. Acceleration sensor. 19. The acceleration sensor according to claim 1, wherein the first piezoelectric element is adjusted to have substantially the same sensitivity as that of the second piezoelectric element. 20. The acceleration sensor according to claim 19, wherein a part of a beam portion of the first piezoelectric element is cut. 21. The first piezoelectric element according to claim 19, wherein a sensitivity adjuster is attached to a part of a beam portion.
2. The acceleration sensor according to 1. 22. The apparatus according to claim 1, wherein each of the first and second piezoelectric elements is fixed in the package by the support so that the beam can vibrate.
The acceleration sensor according to claim 1. 23. The package according to claim 22, wherein each of the first and second piezoelectric elements is mounted on the package with the beam portion inclined with respect to the plane of the package. Acceleration sensor. 24. The package according to claim 23, wherein each of the first and second piezoelectric elements is mounted on the package with different inclination angles between the beam and the plane of the package. 2. The acceleration sensor according to 1. 25. Two sets of piezoelectric elements are mounted on the package, and each of the first set of the first and second piezoelectric elements has a state in which the beam is perpendicular to the plane of the package. 25. The method according to claim 22, wherein each of the first and second piezoelectric elements of the second set is mounted in a state where the beam portion is parallel to a plane of the package. The acceleration sensor according to claim 1. 26. An acceleration detection device comprising: the acceleration sensor according to claim 1; and a signal processing circuit that processes an output signal from the piezoelectric element. 27. Each of the first and second piezoelectric elements is connected to the signal processing circuit so as to output an output signal having the same polarity with respect to acceleration in the same direction. The acceleration detection device according to claim 26, wherein the output signal is subjected to a difference process. 28. The first and second piezoelectric elements are connected to the signal processing circuit so as to output output signals of opposite polarities to acceleration in the same direction, respectively. The acceleration detection device according to claim 26, wherein the output signal is subjected to an addition process. 29. The signal processing circuit according to claim 26, wherein the signal processing circuit includes a circuit for detecting an angular acceleration from a difference between outputs of the first and second piezoelectric elements. The acceleration detection device according to any one of the preceding claims. 30. The signal processing circuit according to claim 26, wherein the signal processing circuit adjusts the output so that the sensitivities of the first and second piezoelectric elements become substantially equal to each other.
10. The acceleration detection device according to 9. 31. The signal processing circuit includes one impedance conversion circuit for converting the impedance of an output signal from the piezoelectric element and an amplification circuit for amplifying the converted output signal. 26 to 30
The acceleration detection device according to any one of the above. 32. The signal processing circuit includes two impedance conversion circuits for converting impedances of output signals from the first and second piezoelectric elements, and an addition circuit for adding the converted output signals. Claim 2
31. The acceleration detection device according to any one of 6 to 30. 33. The signal processing circuit, comprising: two impedance conversion circuits for converting impedances of output signals from the first and second piezoelectric elements; and detecting a difference between the converted output signals and detecting a difference between the output signals. 31. The acceleration detection device according to claim 26, further comprising a differential amplifier circuit that amplifies the acceleration. 34. A system according to claim 26, further comprising a plurality of output terminals for simultaneously outputting externally a converted output obtained by impedance-converting the output of said piezoelectric element and an amplified output obtained by amplifying said converted output after impedance conversion. From 3
4. The acceleration detection device according to claim 3. 35. A package, wherein each of said first and second piezoelectric elements is fixed by said support portion so that said beam portion can vibrate, and said signal processing circuit is housed therein. The acceleration detection device according to any one of claims 26 to 34. 36. The method according to claim 26, wherein the acceleration is detected.
An acceleration detection device according to any one of the preceding claims, an object movement device, and a target positioning device including a control device that controls the movement device, wherein the control device is configured to control the acceleration detection device from the acceleration detection device. A positioning device that controls the moving means based on an output signal corresponding to the detected acceleration to move and position the object. 37. The apparatus according to claim 37, wherein each of the beam portions of the first and second piezoelectric elements constituting the acceleration detecting device is arranged substantially in parallel with the means for supporting the object. 36. The positioning device according to claim 36. 38. The method according to claim 26, wherein the acceleration is detected.
A disk recording / reproducing apparatus comprising: an acceleration detecting device according to any one of claims 1 to 3, head moving means for moving a head for performing recording / reproducing on a disk, and control means for controlling the head moving means. The control means calculates a desired movement amount of the head based on an output signal corresponding to the detected acceleration from the acceleration detection device, and moves the head by the head movement means, A disc recording / reproducing apparatus for performing positioning of a disc. 39. The beam detecting device according to claim 37, wherein the beam portions of the first and second piezoelectric elements constituting the acceleration detecting device are arranged substantially in parallel with an arm supporting the head. The recording / reproducing apparatus according to claim 1.