JPH09105676A - Piezoelectric actuator and pyroelectric type infrared sensor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the drive of a laminated element type piezoelectric actuator for the use as a chopper for an infrared sensor to be driven near the resonance. SOLUTION: A shim 11, a displacement expander 13, a bending part 15 and a coupling part 16 are integrally constituted by bending a flat plate-like elastic material. A piezoelectric element 12 is adhered to the shim 11 to constitute a unimorph type laminating element. An angle of 0 degree to 10 degrees is provided between the expander 13 and the piezoelectric element adhered part, and a rubber material 17 is stuck to the vicinity of the part 16. As a result, two resonances are excited in excellent balance, unnecessary resonance can be reduced, and more stably drive can be conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator for converting an electric signal into a mechanical motion and a pyroelectric infrared sensor using the piezoelectric actuator.

[0002]

2. Description of the Related Art In recent years, pyroelectric infrared sensors have been used in a wide range of fields such as temperature measurement of cooked foods in microwave ovens and position detection of human bodies in air conditioners, and it is expected that demand will increase further in the future.

A pyroelectric infrared sensor utilizes the pyroelectric effect of a pyroelectric body such as a LiTaO ₃ single crystal. The pyroelectric body has spontaneous polarization and always generates a surface charge. However, in a steady state in the atmosphere, the pyroelectric body is electrically neutral with the charge in the atmosphere. When infrared light is incident on the pyroelectric body, the temperature of the pyroelectric body changes, and accordingly, the charge state of the surface changes due to the neutral state being broken. The pyroelectric infrared sensor measures the amount of incident infrared rays by detecting the charges generated on the surface. The object emits infrared rays according to its temperature, and the position and temperature of the object can be detected by using this pyroelectric infrared sensor.

The pyroelectric effect is caused by a change in the incident amount of infrared rays, and when detecting the temperature of an object as a pyroelectric infrared sensor, it is necessary to intermittently open or close the infrared incident amount to forcibly change it. is there. A mechanism used as this means is called a chopper, and forcibly interrupts the incident infrared rays to detect the temperature of the detection object. As a conventional chopper, an electromagnetic motor, a piezoelectric actuator, etc. have been used.

FIG. 6 shows a conventional example of a pyroelectric infrared sensor using an actuator in which a piezoelectric material is bonded to an elastic flat plate as a chopper. Generally, an actuator that bonds a piezoelectric body to an elastic flat plate made of metal or the like to form a laminated element, fixes one end, and uses the strain of the piezoelectric body to generate a bending motion in its entirety is generally an elastic body. A piezoelectric material bonded to both sides of a flat plate is called a bimorph type, a flat surface bonded to only one side is called a unimorph type, and an elastic flat plate is called a shim. Each member is called as such.

FIG. 6 shows a bimorph type element used as a chopper for a pyroelectric infrared sensor, 61 is a shim,
62a and 62b are piezoelectric bodies, 63 is a shielding plate, 64 is a pedestal,
Reference numeral 65 is a fixture, 66 is shim wiring, 67a and 67b are piezoelectric wiring, 68 is an infrared detector, 69 is a slit provided in the shield plate 63, and 70 is infrared.

Piezoelectric bodies 62a and 62b are provided on both sides of the shim 61.
Are bonded to each other, and the three are integrated to form a bimorph type element. Electrodes are printed on the surfaces of the piezoelectric bodies 62a and 62b, and polarization processing is performed in a direction perpendicular to the bonding surface. The polarization directions of the piezoelectric bodies 62a and 62b are the same as the wiring 66 taken out from the shim 61. Piezoelectric body 6
Depending on the direction of the electric field applied between the shim 61 and the piezoelectric bodies 62a and 62b by the wirings 67a and 67b taken out from 2a and 62b, the piezoelectric bodies 62a and 62b are different.
It is determined that b always generates strain in directions opposite to each other.

That is, the direction of the applied electric field and the polarization direction are determined such that when one of the piezoelectric bodies 62a and 62b is distorted in the direction of extension in the polarization direction, the other is contracted in the polarization direction.
The bimorph type element is held by the pedestal 64 and the fixture 65 by simultaneously sandwiching the portion of the shim 61 and the portions of the piezoelectric bodies 62a and 62b. The shim wiring 66 is attached to a portion of the shim 61 where the piezoelectric bodies 62a and 62b are not adhered, and the piezoelectric body wirings 67a and 67b are attached to the surfaces of the piezoelectric bodies 62a and 62b.

A shield plate 63 is attached to the free end of the bimorph element, and a slit 6 is formed in the shield plate 63.
9 are provided. An infrared detector 68 is arranged near the shield plate 63 so as not to contact the shield plate 63 and the bimorph type element. By the shim wiring 66 and the piezoelectric body wirings 67a and 67b, the shim 61 and the piezoelectric body 62a,
When an electric field is applied between 62b, the bimorph element generates a bending motion with one end fixed, and the shield plate 63 and the slit 69 attached to the tip end make a reciprocating motion according to the change in the direction of the electric field application. . The reciprocating movement of the slit 69 interrupts the infrared rays 70 incident on the infrared detecting section 68.

However, in the bimorph type chopper having the above structure, it is necessary to increase the size from the fixed portion to the moving portion at the tip end in order to obtain a sufficient moving distance for interrupting infrared rays, and it is very high. Drive voltage is required.

Therefore, as a conventional improvement method, a load is applied to the tip moving portion of the bimorph type element or the unimorph type element to lower the resonance frequency, and fixing is performed only at the shim portion, whereby the piezoelectric body is brittlely broken. It is possible to obtain a large displacement by driving at a low voltage by preventing the above phenomenon and further lowering the resonance frequency by means such as providing a notch in a shim near the fixed portion as necessary.

An example of the structure of the chopper having the above characteristics will be shown below. FIG. 7 is a perspective view showing an example of a case where a unimorph type element as a chopper for a pyroelectric infrared sensor in a conventional improvement example is formed so that a width of a fixing place of a shim portion becomes narrow. In FIG. 7, 71a and 71b are shims, 72a and 72b are piezoelectric bodies, 73a and 73b are weights, 74 is a sensor pedestal, 75a and 75b are unimorph type element fixtures, 76a and 76b are shim wiring, and 77a and 7b.
Reference numeral 7b is a piezoelectric wire, 78 is an infrared detector, and 79a and 7a.
9b, 79c and 79d are unimorph type element fixing screws, 8
0 is infrared.

FIG. 8 is a perspective view showing the details of the shims 71a and 71b, where 81 is a shielding portion, 82 is a piezoelectric body adhesive portion,
83 is a notch part, 84 is a positioning part, 85a, 85b
Is a fixing hole. The shielding portion 81 and the piezoelectric body bonding portion 82 are bent to form a right angle, and the cutout portion 83 formed such that the width is smaller than that of the piezoelectric body bonding portion 82 from the piezoelectric body bonding portion 82 to the positioning portion 84. And fixing holes 85a and 85b are provided at both ends of the positioning portion 84.

As shown in FIG. 8, the shims 71a and 71b are provided with a notch 83 having a narrow width, and the notch 83 is sandwiched between the sensor pedestal 74 and the unimorph type element fixing members 75a and 75b as shown in FIG. Further, the unimorph type element fixing screws 79a, 79b, 79c, 79d are inserted into the fixing holes 85a, 85b respectively for positioning and one end fixing, and arranged so as to face each other in parallel. In addition, the piezoelectric bodies 72a, 72 are provided on the surfaces of the shims 71a, 71b that face each other, that is, the piezoelectric body bonding portion 82.
b is a sensor pedestal 74 and a unimorph type element fixture 75
The a, 75b and the shims 71a, 71b are bonded at a position where they do not come into contact with the shield portions at the tips and the cutout portions 83 to form a unimorph type piezoelectric actuator.

The infrared detector 78 is arranged on the sensor pedestal 74 near the free end of the unimorph type element, and the infrared ray 80 is provided.
Received or blocked. The shield 81 that connects and disconnects the infrared rays 80 is formed by bending the ends of the shims 71a and 71b on the opposite side to the fixed side, and the weights 73a and 73b are adhered to the plane portions of this portion, respectively. Sim 71
a part other than the movable parts of a and 71b, that is, the positioning part 8
Shim wirings 76a and 76b are provided at one place of the piezoelectric body 7
2a and 72b are provided with piezoelectric wires 77a and 77b, respectively, at positions close to the fixed portion of the unimorph type element. The shim wires 76a and 76b and the piezoelectric wires 77a and 77b are used to connect the shim 71a and the piezoelectric body 72a. When an electric field is applied between the shim 71b and the piezoelectric body 72b, the unimorph type element bends and the shield portion 81 at the tip moves.
The two unimorph type elements are driven in the opposite directions at the same frequency to intermittently block the infrared rays 80.

By providing the notch 83 in the shim portion between the piezoelectric member and the fixed portion of the unimorph type element, the resonance frequency can be further reduced as compared with the unimorph type element having the same size and not having the notch portion. Therefore, it is possible to reduce the size of the chopper and increase the amount of displacement during low-frequency driving, as compared with the case where the notch is not provided.

As described above, various advantages can be obtained by driving the bonded type element including the unimorph type element in the vicinity of resonance. However, since it is driven in the vicinity of the resonance frequency, the resonance frequency of the chopper varies between solids. If there is variation, a large difference in displacement occurs, and in order to keep it constant, it is necessary to perform fine adjustment and component processing or assembly that requires high precision. Also, when the resonance frequency changed with time, the displacement changed significantly. Furthermore, when the drive frequency is moved away from the resonance in order to stabilize the displacement, the displacement amount decreases, and a high drive voltage is required to obtain the same displacement. In addition, when the shape is downsized and displacement is obtained, the load on the adhesive layer between the shim and the piezoelectric body increases, causing peeling. Such a problem is not limited to the chopper of the conventional example, and is the same problem when using resonance.

In order to improve the above problems of resonance driving, the following piezoelectric actuator has been proposed. FIG. 9 is a perspective view showing an example of a chopper for a pyroelectric infrared sensor in which a displacement expanding portion is provided on a unimorph type piezoelectric actuator.

In FIG. 9, reference numeral 91 is a shim, 92 is a piezoelectric body, 93 is a displacement magnifying portion, 94 is a sensor pedestal, 95 is a fixture, 96a and 96b are fixing screws, 97 is shim wiring,
Reference numeral 98 is a piezoelectric wire, 99 is an infrared detecting section, 100 is infrared, and 101 is a bent section.

By bending an elastic flat plate made of phosphor bronze, stainless steel alloy or the like into a U-shape, the shim 91 and the displacement enlarging portion 93 are integrally formed, and the shim 91 and the displacement enlarging portion 93 are connected to each other by the joint portion. It is configured to have longitudinal dimensions in parallel and in the same direction. Further, in the displacement enlarging portion 93, a bent portion 101 is formed at the tip opposite to the joint portion at a right angle and on the side opposite to the shim 91. The piezoelectric body 92 is adhered to the surface of the shim 91 to form a piezoelectric body adhesion portion (unimorph type element).

The shim 91 is sandwiched between the sensor pedestal 94 and the fixture 95 in the vicinity of the end portion on the opposite side of the joint with the displacement magnifying portion 93, and the sensor pedestal 94 is internally threaded and the fixture 95 is holed. The fixing screw 96
It is fixed by a and 96b. An infrared detecting section 99 is arranged on the sensor base 94, and is located in the vicinity of the bent section 101 at the tip of the displacement enlarging section 93. Also, sim 9
In the vicinity of the fixed portion 1 of FIG.
The piezoelectric wires 98 are attached at positions on the surface opposite to the bonding side of 2 near the fixing portion of the shim 91.

Here, the shim wiring 97 and the piezoelectric wiring 98 are provided.
When an AC signal is further applied, a potential difference is generated between the shim 91 and the piezoelectric body 92, the joint portion of the piezoelectric body bonding portion with the displacement magnifying portion 93 is displaced, and the tip portion of the displacement magnifying portion 93 is bent accordingly. The bending portion 101 is also displaced, and the infrared ray 100 incident on the infrared ray detecting portion 99 is interrupted by this movement, and plays a role as a chopper.

FIG. 10 shows the resonance characteristic of the piezoelectric actuator (chopper) having the above structure. FIG. 10 is an example of resonance characteristics of a piezoelectric actuator including a shim bent in a U shape and a displacement magnifying portion, in which the vertical axis represents admittance and the horizontal axis represents drive frequency. It has been found that there is a resonance phenomenon at each of the resonance frequencies f ₁ and f ₂ , and these are due to the resonance mainly caused by the vibration of the piezoelectric bonding portion of the piezoelectric actuator and the vibration mainly at the displacement magnifying portion. It is one of the resonances that is caused, which corresponds to one of them depending on the configuration of the piezoelectric actuator, and the difference between the resonance frequencies f ₁ and f ₂ also changes depending on the configuration.

As described above, the shim and the displacement magnifying portion have the longitudinal dimension in the same direction from the coupling portion, so that the relative positions of the resonance frequencies f ₁ and f ₂ can be easily manipulated. For example, when the displacement magnifying member has a constant longitudinal dimension and only the length from the fixed portion of the piezoelectric body bonding portion to the piezoelectric body is changed, that is, when only the longitudinal dimension of the piezoelectric body bonding portion is changed, the initial piezoelectric In the case where the longitudinal dimension of the body-bonded portion is short, the resonance frequency caused by the piezoelectric body-bonded portion corresponds to f ₂ , that is, the resonance frequency caused by the piezoelectric body-bonded portion is higher than the resonance frequency caused by the displacement magnifying portion. As the longitudinal dimension of the piezoelectric bonded portion is gradually lengthened, the resonance frequencies of the two become relatively close to each other, and at a certain length, the two become one resonance and overlap, and the longitudinal dimension of the piezoelectric bonded portion is further increased. When is made longer, the relative positions of the two are reversed, and the resonance frequency caused by the displacement magnifying portion has a higher value than the resonance frequency caused by the piezoelectric bonding portion.

FIG. 11 shows the relationship between the displacement of the tip of the displacement magnifying portion and the drive frequency when the resonance frequencies f ₁ and f ₂ are arranged close to each other. In FIG. 11, the vertical axis represents the displacement of the displacement magnifying portion and the horizontal axis represents the drive frequency.
It can be seen that at a driving frequency between the resonance frequencies f ₁ and f _2, the displacement is enlarged due to the influence of both resonances, and there is a frequency region in which the displacement amount is relatively stable. Therefore, by bringing the resonance frequencies f ₁ and f ₂ close to each other and driving them at a frequency between the two frequencies, a displacement magnifying effect due to resonance and a stable displacement can be obtained.

Further, let f _{1 be} a resonance frequency mainly due to the piezoelectric bonding portion and f _{2 be} a resonance frequency mainly due to the displacement magnifying portion, that is, from the resonance frequency mainly due to the piezoelectric bonding portion. Also, by having a configuration in which the resonance frequency, which is mainly caused by the displacement magnifying section, is higher, the displacement is magnified and stable, and a wider frequency range is secured in which the applied AC signal and the time difference between the tip of the displacement magnifying section are constant. it can.

The unimorph type actuator utilizing ordinary resonance shows a large change in displacement depending on the driving frequency.
In order to stabilize this, when driven at a frequency about 5% away from the resonance frequency, a high voltage was required to obtain the same displacement. On the other hand, in the case of the piezoelectric actuator having the above structure, the shim has a longitudinal dimension of about 16 mm, and the resonance frequency f caused by the displacement magnifying portion is f.
₂ is about 100 Hz, and the resonance frequency f ₁ due to the bonded portion of the piezoelectric body
Is about 85 Hz, when driven between resonance frequencies f ₁ and f ₂ , by applying an AC of ± 30 V, a displacement of 1.1 ± 0.05 mm at the tip of the displacement magnifying section can be obtained in a section of about 6 Hz. It is possible.

A similar effect is obtained in the case of a piezoelectric actuator having a structure in which the resonance frequency f ₂ is 120 Hz or less in accordance with the longitudinal dimension of the displacement magnifying portion when the longitudinal dimension of the piezoelectric bonding portion is about 18 mm or less. The difference between ₂ and f ₁ is optimally obtained between approximately 5 and 25% of the resonance frequency f ₂ . Even if it is within 5%, the same effect can be obtained, but in this case, the frequency range in which driving can be performed may be reduced, or one resonance may not be excited.

With the above-described structure, the drive utilizing the resonance can be stably performed at a lower voltage, and the drive, the assembly, and the processing of the members can be facilitated. Further, since the amount of vibration of the portion bonded to the piezoelectric body can be reduced, peeling between the piezoelectric body and the shim is less likely to occur. Also, due to the bent configuration, the overall longitudinal size is reduced, and by using this configuration as a chopper for a pyroelectric infrared sensor, the overall size of the sensor can be reduced, and the infrared detector can be fixed to the same pedestal. As a result, the infrared detector can be easily integrated with the infrared detector, and the vicinity of the infrared detector can be opened / closed. Therefore, the opening / closing area can be reduced and the load on the chopper can be reduced. Further, by driving at a low voltage, it is possible to reduce the influence of noise from the piezoelectric body on the infrared detecting section.

The chopper having the above characteristics is hereinafter referred to as a W resonance type chopper or actuator for simplicity.

[0031]

When driving is performed using the above W resonance type actuator, it is necessary to efficiently excite two resonances, and one resonance may be influenced by the other resonance in some cases. Since it was hardly excited and a sufficient displacement was not obtained, it was necessary to optimize each configuration for this.

Further, in the conventional W resonance type chopper, unnecessary vibrations other than the vibration mode used for driving are also excited, so that the chopper becomes uncontrollable, and when it is used as a chopper of a pyroelectric infrared sensor, temperature measurement is completely possible. There was a case where it disappeared. Moreover, the destabilization of the displacement due to unnecessary resonance significantly impairs the accuracy of the sensor.

It is an object of the present invention to provide a W resonance type actuator in which driving can be more stabilized and a sufficient displacement can be secured.

[0034]

In order to achieve the above-mentioned object, the W resonance type actuator of the present invention is configured such that the piezoelectric bonding portion and the displacement magnifying portion have an angle of 0 to 10 degrees, and the resonance on the lower side is achieved. It is possible to increase the resonance level of a certain resonance frequency f ₁ and efficiently excite both resonances.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention.
Is a flat plate-shaped piezoelectric body that has been polarized
Adhere to one side or both sides of the member and fix one end with a fixing member
The fixed piezoelectric adhesive part and the piezoelectric adhesive part
The free end has a fixed portion of the piezoelectric bonding portion rather than the coupling portion.
Has a displacement magnifying portion located at a distance close to
An electric field is applied to the adhesion part to bend the piezoelectric adhesion part.
The free end of the piezoelectric bonded portion and the displacement magnifying portion.
A piezoelectric actuator in which the free end of the
Resonance frequency f caused by vibration of the adhesive part₁And before
Resonance frequency f caused by the vibration of the displacement magnifying section f_Two
Of the resonance frequency f_TwoIs the resonance frequency
f₁Has a structure with a high frequency within 30% of
The resonance frequency f₁And f _TwoAC voltage at frequencies between
In a piezoelectric actuator that drives by applying
Longitudinal direction of the piezoelectric bonded part and longitudinal direction of the displacement magnifying part
Is between 0 and 10 degrees and the displacement is
The free end of the enlarged portion is closer to the piezoelectric bonding portion than the vicinity of the coupling portion.
Of the lower side,
Resonance frequency f₁Increase the resonance level of
Vibrations can be excited efficiently and drive can be stabilized.
It has the effect of ensuring a sufficient amount of displacement.
You.

According to the second aspect of the present invention, at least a part of the rubber material and another member having mechanical properties similar to the rubber material are arranged on the elastic member, whereby unnecessary at a certain higher frequency. This has the effect of reducing the resonance level and stabilizing the drive.

According to a third aspect of the present invention, the elastic plate is bent to integrally form the piezoelectric bonding portion, the coupling portion, and the displacement magnifying portion, and the distance between the piezoelectric body and the coupling portion is set. In addition, the piezoelectric member has an unbonded portion, and a rubber material or another member having mechanical properties similar to this is attached to the unbonded portion, thereby reducing the level of unnecessary resonance. Is obtained.

According to a fourth aspect of the present invention, a rubber material or another member having a mechanical property similar to this is attached near the fixing portion of the elastic flat plate to further reduce the level of unwanted resonance.

The invention according to claim 5 is a pyroelectric infrared sensor using the piezoelectric actuator according to any one of claims 1 to 4 as a means for connecting and disconnecting incident infrared rays, and can have high measurement accuracy.

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIGS. 1 (a) and 1 (b) show that an angle is provided between the piezoelectric bonding portion and the displacement magnifying portion in the first embodiment of the present invention, and a rubber-like member is partially formed. It is a perspective view and a top view showing an example pasted on.

In FIG. 1, 11 is a shim, 12 is a piezoelectric body, 13 is a displacement magnifying portion, 14a and 14b are fixtures, and 15
Is a bent portion, 16 is a coupling portion, 17 is a rubber material, 18 is an infrared detection portion, and 19 is infrared light. The shim 11, the displacement magnifying portion 13, the bent portion 15, and the joint portion 16 are integrally configured by bending a single plate-shaped conductive metal body. On one surface of the shim 11, there is formed a piezoelectric material bonding portion to which the piezoelectric material 12 that is polarized in the thickness direction and has electrodes on both surfaces is bonded. A W resonance type actuator is formed by being sandwiched by fixtures 14a and 14b and fixed at one end in the vicinity of the end portion of the shim 11 opposite to the coupling portion 16.

The fixtures 14a and 14b are also made of a conductive material similarly to the shim 11, and the fixtures 14a and the piezoelectric body 1 are formed.
An alternating electric field is applied between the two unbonded surface electrode portions. The piezoelectric body 12 is adhered to the joint portion 16 with a certain distance, which enables bending after the piezoelectric body is adhered. A sheet-shaped rubber material 17 is attached to the unbonded portion of the piezoelectric body 12, and the rubber material 17 is called a damper material or the like.

As shown in FIG. 1 (b), the piezoelectric bonding portion and the displacement magnifying portion 13 form a longitudinal angle of θ with each other, that is, the bending portion at the base of the displacement magnifying portion 13 forms an obtuse angle, and at the same time, is bent. The bent portion 15 has a larger distance to the piezoelectric bonding portion than when the bent portion has a right angle. By applying an AC electric field to the piezoelectric body 12 and the fixtures 14a and 14b, the bent portion 15 reciprocates in the vicinity of the infrared detecting portion 18, and the infrared ray 19 is intermittently incident to function as a chopper.

By configuring the displacement magnifying portion 13 with an angle of θ, it is possible to increase the resonance level on the lower side of the two resonances used for driving the W resonance type actuator.

FIGS. 2 (a) and 2 (b) are examples of resonance characteristic diagrams when the displacement magnifying portion and the piezoelectric bonding portion are parallel to each other and when the angle θ is provided. In the resonance characteristic diagram, the vertical axis represents the admittance of the W resonance type actuator, and the horizontal axis represents the drive frequency. FIG. 2A shows a case where the displacement magnifying portion and the piezoelectric body bonding portion are substantially parallel to each other, f ₁ is a resonance frequency caused by the vibration of the piezoelectric material bonding portion, and f ₂ is a resonance caused by the vibration of the displacement magnification portion. Indicates the frequency.

Similarly, FIG. 2B shows the displacement magnifying section and the piezoelectric body.
This is the case where the bonded portion has an angle of θ. Have an angle θ
The resonance frequency f₁The resonance level at
Resonance frequency f increases_TwoResonance level at
I do. That is, by giving an angle θ,
Vibration frequency f₁To excite the resonance of the
It is possible to secure the resonance level due to variations in assembly and changes over time.
It is possible to have a sufficient margin even when the bell is lowered.
On the contrary, the resonance frequency f_TwoThe resonance level of the
Bell has resonance frequency f₁Larger than most
The resonance frequency f is the optimum driving range where stable displacement can be obtained.₁
The impact is small. However, if θ is too large, the sensor unit
When used as a knit, the volume increases and resonance
Frequency f _TwoDo not reduce the displacement level because the level of
Which problem occurs, the optimum range of θ is almost 0 degrees.
Larger than 10 degrees.

Bending is also easier when 90 ° + θ is set, rather than bending at 90 °. 3 (a) and FIG.
(B) is an example of a resonance characteristic diagram when a rubber material is pasted and not pasted between the coupling portion and the piezoelectric body. In the resonance characteristic diagram, the vertical axis represents the admittance of the W resonance type actuator, and the horizontal axis represents the drive frequency. The W resonance type actuator has unnecessary resonance having a higher level at frequencies higher than the resonance frequencies f ₁ and f ₂ used for driving. The level and frequency of unnecessary resonance differ depending on the configuration, but as an example, the total length is about 16 mm and the resonance frequency f
_In the case of the W resonance type actuator having the configuration of FIG. 1A in which ₁ is 80 Hz and the resonance frequency f ₂ is 95 Hz, the unnecessary resonance frequency f ₃ is about 800 Hz and the unnecessary resonance frequency f ₄ is about 1200 Hz.
Thus, both have resonance levels much higher than the resonance frequencies f ₁ and f ₂ .

When the W resonance type actuator is mainly driven by a rectangular wave, these unnecessary resonances are excited at the same time, and the displacement waveform is disturbed, which makes control impossible. FIG.
FIG. 3A is a resonance characteristic diagram when a rubber material is not attached, and FIG. 3B is a resonance characteristic diagram when a rubber material is attached between the coupling portion and the piezoelectric body. By attaching the rubber material and other damper material, the energy of vibration is lost and the resonance level is lowered as a whole. However, the resonance level due to the vibration of the adhered part is particularly large like the unnecessary resonance frequency f _3. Greatly reduced.

By attaching the damper material in this way, the resonance level of unnecessary resonance can be lowered and the influence on driving can be suppressed. Further, by selecting the damper material and the attachment place, a particularly great effect can be obtained with respect to resonance at a specific frequency. By in W resonant actuator arrangement of FIGS. 1 (a) of affixing a damper member between the coupling portion and the piezoelectric body, reduce the large unwanted levels of the resonance frequency f ₃ of the nearest impact on higher driving frequency level Therefore, the driving can be easily stabilized.

In detecting the temperature of the pyroelectric infrared sensor, the displacement amount and displacement waveform of the chopper have a great influence on the detection accuracy, and by using the above W resonance type actuator as the chopper, the sensor unit can be made compact and highly accurate. Can be realized.

(Embodiment 2) FIG. 4 shows an example in which an angle is provided between the piezoelectric bonding portion and the displacement magnifying portion in the second embodiment of the present invention, and a rubber member is attached near the fixing portion. It is a perspective view.

In FIG. 4, reference numeral 41 is a shim, 42 is a piezoelectric body, 43 is a displacement magnifying portion, 44a and 44b are fixtures, and 45
Is a bent portion, 46 is a connecting portion, 47a and 47b are rubber materials,
Reference numeral 48 is an infrared detecting section, and 49 is infrared. In the vicinity of the fixed portion of the shim 41, rubber materials 47a and 47b are attached on both sides. Other configurations are the same as those of the first embodiment.

By attaching a damper material such as a rubber material on both sides, the effect of further reducing the level of unwanted resonance is increased. Unlike the first embodiment, the unnecessary resonance that is mainly reduced by attaching the damper material near the fixed portion is different from the first embodiment.

FIGS. 5 (a) and 5 (b) are examples of resonance characteristic diagrams with and without a damper material attached in the vicinity of the fixed portion. In the resonance characteristic diagram, the vertical axis represents the admittance of the W resonance type actuator, and the horizontal axis represents the drive frequency. FIG. 5 (a) is the case where it is not attached, and FIG. 5 (b) is the case where it is attached. In this case, the level reduction effect is particularly great for the resonance of the unnecessary resonance frequency f ₄ . The undesired resonance frequency f ₄ has a great influence on driving similarly to f _3, and therefore, from the relationship between the frequency used for driving and the undesired resonance to be excited,
About resonance that affects driving, the drive location is roughly specified, and a damper material is attached to that portion, whereby unnecessary resonance can be easily reduced.

[0055]

As described above, according to the present invention, the resonance level used for driving is adjusted by allowing the piezoelectric bonding portion and the displacement magnifying portion of the W resonance type actuator to have an angle of 0 to 10 degrees. it can. By amplifying the resonance of a small level, the resonance of a large level is less likely to be affected, so that the drive frequency can be set and adjusted in a wider range, and various drive frequencies can be dealt with. By exciting both resonances in a balanced manner, the amount of displacement in the stable region can be increased, and more efficient driving can be performed.

By attaching a damper material such as a rubber material to the W resonance type actuator, the level of unnecessary resonance can be lowered. In addition, by selecting the attachment location of the damper material according to the configuration, it is possible to reduce the level of particular unnecessary resonance that particularly affects driving, and minimize the effect on resonance necessary for driving. Moreover, since the attachment member can be minimized, the load on the drive is minimized and the drive efficiency is not impaired. In addition, since unnecessary vibration due to unnecessary resonance is eliminated, deterioration of mechanical strength due to driving can be prevented, and long-term reliability is improved.

Since the W resonance type actuator is small and can obtain a large displacement, it contributes to the miniaturization of the entire unit such as a sensor, and especially for the pyroelectric infrared sensor which requires a chopper for temperature detection, Contributes to higher precision and increases versatility. By adjusting the resonance used for driving and reducing the unnecessary resonance, a chopper capable of stable opening and closing with a larger displacement can be realized, and the detection accuracy of the sensor can be stabilized and the reliability can be improved.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a first embodiment of a piezoelectric actuator of the present invention, and FIG.

FIG. 2A is a conventional resonance characteristic diagram for comparison with the first embodiment. FIG. 2B is a resonance characteristic diagram of the first embodiment.

FIG. 3A is a conventional resonance characteristic diagram for comparison with the first embodiment. FIG. 3B is a resonance characteristic diagram of the first embodiment.

FIG. 4 is a perspective view showing a second embodiment of the present invention.

FIG. 5A is a conventional resonance characteristic diagram for comparison with the second embodiment. FIG. 5B is a resonance characteristic diagram of the second embodiment.

FIG. 6 is a perspective view showing the configuration of a conventional piezoelectric bimorph type chopper.

FIG. 7 is a perspective view showing the configuration of a conventional resonance type chopper.

FIG. 8 is a perspective view showing details of the structure of a conventional resonance type chopper.

FIG. 9 is a perspective view showing a configuration of a conventional W resonance type actuator.

FIG. 10 is a admittance characteristic diagram of a conventional W resonance type actuator.

FIG. 11 is a displacement characteristic diagram of a conventional W resonance type actuator.

[Explanation of symbols]

 11,41 Shim 12,42 Piezoelectric body 13,43 Displacement expanding part 15,45 Bending part 16,46 Coupling part

Claims (5)

[Claims] 1. A plate-shaped piezoelectric body that has been polarized is adhered to one or both sides of a plate-shaped elastic member, and one end of the plate-shaped elastic member is fixed by a fixing member. And a free end having a displacement magnifying portion located closer to the fixing portion of the piezoelectric body bonding portion than the coupling portion, and applying an electric field to the piezoelectric body bonding portion to cause the piezoelectric body bonding portion to make a bending motion. With this, a piezoelectric actuator in which the free end of the piezoelectric bonding portion and the free end of the displacement magnifying portion are displaced,
The difference between the resonance frequency f ₁ generated due to the vibration of the piezoelectric bonding portion and the resonance frequency f ₂ caused due to the vibration of the displacement magnifying portion is brought close to each other, and the resonance frequency f ₂ is the resonance frequency. A piezoelectric actuator having a structure with a frequency higher than f ₁ by 30% or less and driving by applying an AC voltage at a frequency between the resonance frequencies f ₁ and f ₂ , in the longitudinal direction of the piezoelectric body bonding portion. And the angle formed by the longitudinal direction of the displacement magnifying portion between 0 degrees and 10 degrees, and the free end of the displacement magnifying portion has a larger distance to the piezoelectric bonding portion than in the vicinity of the coupling portion. . 2. The piezoelectric actuator according to claim 1, wherein at least a part of the rubber member and another member having a mechanical property similar to the rubber member are arranged on the elastic member. 3. A piezoelectric body adhesive portion, a joint portion, and a displacement magnifying portion are integrally formed by bending an elastic plate, and a piezoelectric body is not provided at a distance between the piezoelectric body and the joint portion. The piezoelectric actuator according to claim 1, further comprising an adhesive portion, and a rubber member or another member having mechanical properties similar to this is attached to the non-adhesive portion. 4. The piezoelectric bonding portion, the coupling portion and the displacement magnifying portion are integrally formed by bending the elastic flat plate,
The piezoelectric actuator according to claim 1, wherein a rubber material or another member having mechanical properties similar to this is attached in the vicinity of the fixing portion. 5. A pyroelectric infrared sensor using the piezoelectric actuator according to any one of claims 1 to 4 as a means for interrupting incident infrared light.