JPH09292284A - Piezoelectric actuator and pyroelectric infrared sensor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the contact with another member by turning motion in a laminated element type piezoelectric actuator mainly used for an infrared sensor chopper stably driven near resonance. SOLUTION: A flat elastic body is bent to integrally form a shim 11, a displacement extending part 13, a displacing member 18, and a connecting part 19. A piezoelectric body 12 is adhered to the shim 11 to form a unimorph type laminated element. Since the normal of the flat part of the displacing member 18 is set to be orthogonal to both the longitudinal direction of the displacement extending part 13 and the displacing direction, the contact with an infrared detecting part 16 by the rotating motion of a displacement generated according to the increase in displacement can be prevented.

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. Pyroelectric infrared sensor
It utilizes the pyroelectric effect of a pyroelectric material such as a LiTaO ₃ single crystal. The pyroelectric body has spontaneous polarization and surface charges are always generated, but in the steady state in the atmosphere, it is electrically neutral because it is associated with the electric charge in the atmosphere, and infrared rays are incident on this pyroelectric body. Then, the temperature of the pyroelectric body changes, and along with this, the charge state of the surface also changes, breaking the neutral state. A pyroelectric infrared sensor measures the amount of incident infrared rays by detecting the charges generated on the surface.

An 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 it is necessary to change the incident amount of infrared rays when detecting the temperature of an object as a pyroelectric infrared sensor. The means used as this means is called a chopper, and the infrared rays that enter are forcibly interrupted to detect the temperature of the detection object. As a conventional chopper, an electromagnetic motor, a piezoelectric actuator, and the like have been used.

FIG. 5 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. In general, an actuator is constructed by bonding a piezoelectric body to an elastic flat plate such as a metal or the like to form an element, fixing one end of the element, and utilizing the strain of the piezoelectric body to generate a bending motion as a whole. In general, an elastic flat plate with a piezoelectric material bonded to both sides is called a bimorph type, a single-sided elastic plate is called a unimorph type, and an elastic flat plate is called a shim. To call.

FIG. 5 shows a bimorph type element used as a chopper for a pyroelectric infrared sensor, 51 is a shim,
52a and 52b are piezoelectric bodies, 53 is a shielding plate, 54 is a pedestal,
Reference numeral 55 is a fixture, 56 is a wiring for shims, 57a and 57b are wirings for a piezoelectric body, 58 is an infrared detecting section, 59 is a slit, 6
0 is infrared.

Piezoelectric bodies 52a and 52b are provided on both sides of the shim 51.
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 52a and 52b, and polarization treatment is performed in a direction perpendicular to the bonding surface. The polarization directions of the piezoelectric bodies 52a and 52b are the wiring 56 extracted from the shim 51 and the Piezoelectric body 5
Depending on the direction of the electric field applied between the shim 51 and the piezoelectric bodies 52a, 52b by the wirings 57a, 57b taken out from 2a, 52b, the piezoelectric bodies 52a, 52b 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 52a and 52b is distorted in the direction of extension in the polarization direction, the other is contracted in the polarization direction.

The bimorph type element has a base 54 and a fixture 55.
The portion of the shim 51 and the portions of the piezoelectric bodies 52a and 52b are simultaneously sandwiched by and are held. Shim wiring 56 is attached to a portion of the shim 51 where the piezoelectric bodies 52a and 52b are not bonded.
Piezoelectric wires 57a and 57b are attached to the surface of 52b. A shield plate 53 is attached to the free end of the bimorph element, and a slit 59 is provided in the shield plate 53. An infrared detector 58 is arranged near the shield plate 53 so as not to contact the shield plate 53 and the bimorph element.

Shim wiring 56 and piezoelectric wiring 57a,
When an electric field is applied between the shim 51 and the piezoelectric bodies 52a and 52b by 57b, the bimorph type element generates a bending motion with one end fixed, and the shield plate 5 attached to the tip end.
3 and the slit 59 reciprocate according to the change in the direction of application of the electric field. The reciprocating movement of the slit 59 interrupts the infrared rays 60 incident on the infrared detecting section 58.

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 in order to obtain a moving distance sufficient to interrupt infrared rays, and a very high driving force is required. Voltage is needed.

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 the 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 is shown below.

FIG. 6 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 the width of the fixing place of the shim portion becomes narrow. In FIG. 6, 61a and 61b are shims, 62a and 62b are piezoelectric bodies, 63a and 63b are weights,
64 is a sensor pedestal, 65a and 65b are unimorph-type element fixing tools, 66a and 66b are shim wiring, and 67a and 67b.
Is a wiring for a piezoelectric body, 68 is an infrared detecting section, 69a, 69b
Is a unimorph type element fixing screw, and 70 is an infrared ray.

FIG. 7 is a perspective view showing the details of the shims 61a and 61b, where 71 is a shield portion, 72 is a piezoelectric body adhesive portion,
73 is a notch part, 74 is a positioning part, and 75a and 75b.
Is a fixing hole. The shielding portion 71 and the piezoelectric body bonding portion 72 are bent at a right angle, and a cutout portion 73 is provided between the piezoelectric body bonding portion 72 and the positioning portion 74 so that the width thereof is smaller than that of the piezoelectric body bonding portion 72. Fixing holes 75a and 75b are provided at both ends of the positioning portion 74.

As shown in FIG. 7, the shims 61a and 61b are provided with a notch 73 having a narrow width, and the notch 73 is sandwiched between the sensor pedestal 64 and the unimorph type element fixtures 65a and 65b as shown in FIG. In addition, the unimorph type element fixing screws 69a and 69b are respectively fixed in the fixing holes 7
5a and 75b are inserted, positioned and fixed at one end, and arranged so as to face each other in parallel. Further, the piezoelectric bodies 62a and 62b are provided on the surfaces of the shims 61a and 61b which face each other, that is, the piezoelectric body bonding portions 72, and the sensor base 6
4, unimorph type element fixtures 65a, 65b and shim 6
Shielding portion 71 at the tip of 1a, 61b, as well as cutout portion 7
The unimorph type piezoelectric actuator is configured by being bonded at a position where it does not come into contact with 3.

The infrared detecting section 68 is arranged near the free end of the unimorph type element on the sensor pedestal 64, and receives the infrared rays 70 or is blocked. The shield portion 71 that connects and disconnects the infrared rays 70 is configured by bending the ends of the shims 61a and 61b on the opposite side to the fixed side.
3a and 63b are adhered respectively. Shim 61a,
The shim wirings 66a and 66b are provided at one place other than the movable portion of the piezoelectric body 62b, that is, at one place of the positioning portion 74.
Piezoelectric wires 67a and 67b are attached to a and 62b at positions close to the fixed portion of the unimorph type element, respectively. The shim wires 66a and 66b and the piezoelectric wire 67 are attached.
a and 67b, the shim 61a, the piezoelectric body 62a, the shim 61
When an electric field is applied between b and the piezoelectric body 62b, the unimorph type element bends and the shield portion 71 at the tip moves. The two unimorph type elements are driven at the same frequency in opposite directions to intermittently block the infrared rays 70.

By providing the notch 73 in the shim portion between the piezoelectric body 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 such as the unimorph type element in the vicinity of resonance, but since it is driven in the vicinity of the resonance frequency, the resonance frequency of the chopper varies between solids. When there is variation, a large difference in displacement occurs, and in order to maintain a constant amount, fine adjustment, and parts machining and assembly that require high precision are required. 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 solve the above problems of resonance driving, the following piezoelectric actuator has been proposed.

FIG. 8 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. 8, reference numeral 81 is a shim, 82 is a piezoelectric body, 83 is a displacement magnifying portion, 84 is a sensor pedestal, 85 is a fixture, 86a and 86b are fixing screws, and 87 is shim wiring.
Reference numeral 88 is a piezoelectric wire, 89 is an infrared detecting section, 90 is infrared, and 91 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 81 and the displacement magnifying portion 83 are integrated, and the shim 81 and the displacement magnifying portion 83 are parallel to each other from the connecting portion. It is configured to have longitudinal dimensions in the same direction. Further, in the displacement enlarging portion 83, a bent portion 91 is formed at a right angle on the tip opposite to the joint portion and on the side opposite to the shim 81. The piezoelectric body 82 is adhered to the surface of the shim 81 to form a piezoelectric body adhesive portion (unimorph type element).

The shim 81 is sandwiched between the sensor pedestal 84 and the fixture 85 in the vicinity of the end portion on the opposite side of the joint with the displacement magnifying portion 83, and the sensor pedestal 84 is internally threaded and the fixture 85 is holed. The fixing screw 86
It is fixed by a and 86b. An infrared detecting section 89 is arranged on the sensor base 84, and is located in the vicinity of the bent section 91 at the tip of the displacement enlarging section 83.

A shim wiring 87 is provided near the fixing portion of the shim 81, and a piezoelectric wiring 88 is provided at a position closer to the fixing portion of the shim 81 on the surface opposite to the bonding side of the piezoelectric body 82.
Are attached. Wiring 87 for shim
When an AC signal is applied from the wiring 88 for the piezoelectric body, the shim 81
A potential difference is generated between the piezoelectric body 82 and the piezoelectric body 82, the joint portion of the piezoelectric body adhesive portion with the displacement magnifying portion 83 is displaced, and accordingly, the bent portion 91 at the tip of the displacement magnifying portion is also displaced. The infrared ray 90 entering the infrared ray detector 89 is interrupted to serve as a chopper.

Here, FIG. 9 shows the resonance characteristics of the piezoelectric actuator (chopper) having the above structure.

FIG. 9 shows an example of resonance characteristics of a piezoelectric actuator comprising a shim bent in a U-shape and a displacement magnifying portion. 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 drive frequencies f ₁ and f ₂ , and these are the resonances mainly caused by the vibrations of the piezoelectric bonding portion of the piezoelectric actuator, and those of the displacement magnifying portion. It is one of the resonances caused by the vibration, which corresponds to one of them depending on the configuration of the piezoelectric actuator, and the driving frequencies f ₁ and f ₂ depending on the configuration.
The difference between will also change.

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 driving frequencies f ₁ and f ₂ can be easily manipulated. For example, when the longitudinal dimension of the displacement magnifying portion is constant 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 piezoelectric body is initially In the case where the longitudinal dimension of the adhesive portion is short and the resonance frequency due to the piezoelectric adhesive portion corresponds to f ₂ , that is, when the resonance frequency due to the piezoelectric adhesive portion is higher than the resonance frequency due to the displacement expanding portion, When 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 are overlapped as one resonance, and the longitudinal dimension of the piezoelectric bonded portion is further lengthened. If you do, the relative position of the two will be reversed,
The resonance frequency caused by the displacement magnifying portion has a higher value than the resonance frequency caused by the piezoelectric bonding portion.

FIG. 10 shows the relationship between the drive frequency and the displacement of the tip of the displacement magnifying portion in the case where the drive frequencies f ₁ and f ₂ are arranged close to each other. In FIG. 10, the vertical axis represents the displacement of the tip of the displacement magnifying portion, and the horizontal axis represents the drive frequency.

It can be seen that there is a frequency region in which the displacement is magnified by the influence of both resonances and the displacement amount is relatively stable at the driving frequency between f ₁ and f ₂ . Therefore, by bringing the drive frequencies f ₁ and f ₂ close to each other and driving at a frequency between these frequencies, a displacement magnifying effect due to resonance and a stable displacement can be obtained.

Further, let f _{1 be} the resonance frequency mainly due to the piezoelectric bonding portion and f _{2 be} the resonance frequency mainly due to the displacement magnifying portion, that is, the resonance frequency mainly due to the piezoelectric bonding portion. By having a configuration in which the resonance frequency that is mainly caused by the displacement amplification part is higher, the displacement is expanded and stable, and a wider frequency range is ensured in which the applied AC signal and the time difference between the tip of the displacement expansion part 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 configuration, the shim has a longitudinal dimension of about 16 mm, and the resonance frequency f ₂ caused by the displacement magnifying portion is
Is about 100 Hz, and the resonance frequency f ₁ due to the piezoelectric bonded portion is f _1.
When driven between f ₁ and f ₂ when is about 85 Hz ±
By applying an alternating current of 30 V, it is possible to obtain a displacement of 1.1 ± 0.05 mm at the tip of the displacement magnifying portion in a section of about 6 Hz.

The same effect is obtained when the longitudinal dimension of the piezoelectric bonding portion is 1.
8mm in the following state is obtained between 5-25% of the cases, the difference between f ₂ and f ₁ is approximately f ₂ piezoelectric actuator having the configuration f ₂ the following 120Hz depending on the longitudinal dimension of the displacement amplifying section . 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-mentioned 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. Furthermore, 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. In addition, the bent configuration reduces the overall longitudinal size, and by using this configuration as a chopper for a pyroelectric infrared sensor, the pyroelectric infrared sensor can be downsized in its entirety, and it can be mounted on the same pedestal as the infrared detector. By fixing the above, it can be easily integrated with the infrared detecting section, and in addition, since the vicinity of the infrared detecting section can be opened and closed, the opening and 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.

[0033]

However, the conventional W
While the resonance type chopper has been downsized and the amount of displacement increased, the displacement of the tip of the displacement magnifying part becomes closer to a rotary motion from a linear motion due to the shape effect, and the bending part is different from other members during driving. A problem such as contact occurs, and as a result, in the pyroelectric infrared sensor, the infrared detecting portion and the bent portion must be separated from each other, resulting in an increase in the size of the entire sensor unit structure and a displacement amount required for the chopper. There are problems such as a decrease in reliability due to the increase and a decrease in sensor accuracy due to a decrease in the opening / closing area relative to the incident infrared rays.

The present invention solves the above-mentioned problems associated with the miniaturization of the chopper, prevents contact with other members such as the infrared detecting section, and provides a piezoelectric actuator capable of ensuring accuracy as a pyroelectric infrared sensor. The purpose is to

[0035]

In order to achieve the above object, the piezoelectric actuator of the present invention has a shim made of an elastic member, one end of which is fixed to a fixing portion, and the other end of the shim being substantially parallel to the shim through a coupling portion. A displacement magnifying portion is integrally provided, and a polarized plate-shaped piezoelectric body is bonded to the shim, and at least a plane perpendicular to both the longitudinal direction and the displacement direction of the displacement magnifying portion is attached to the free end of the displacement magnifying portion. The displacement member is provided.

With this structure, a highly reliable piezoelectric actuator can be obtained.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is such that a displacement magnifying portion which is substantially parallel to the shim is formed at the other end of a shim made of an elastic member having one end fixed to a fixing part via a coupling part. A displacement member having a flat plate, which is integrally provided and polarized on the shim, is bonded to the free end of the displacement magnifying portion and has a plane perpendicular to both the longitudinal direction and the displacement direction of the displacement magnifying portion. With this configuration, the displacement member moves in parallel with the displacement direction of the displacement magnifying section, so movement in directions other than the displacement direction is suppressed, contact with other members can be prevented, and downsizing can be achieved. Become.

According to the second aspect of the present invention, the displacement member may be formed integrally with the displacement enlarging portion, and thus the displacement member can be formed by simple bending.

According to the third aspect of the present invention, the displacement member is constituted by a member different from the displacement enlarging portion, so that the processing is easy and the material can be effectively utilized.

According to the fourth aspect of the present invention, the displacement magnifying portion is provided with a slit, and the portion separated by the slit is bent to form the displacement member. Therefore, the displacement member can be easily formed.

According to a fifth aspect of the present invention, the displacement member is formed by bending a part of the free end of the displacement enlarging portion so as to be a flat surface portion forming an angle of 10 to 90 degrees with respect to the width direction of the displacement enlarging portion. Since it can be constructed by simple bending, it is excellent in strength.

According to a sixth aspect of the present invention, the piezoelectric actuator according to any one of the first to fifth aspects is used, and the displacement member of the piezoelectric actuator is used as a means for connecting and disconnecting infrared rays incident on the infrared detecting section. Since this is an infrared sensor, it can be miniaturized as a whole.

Specific embodiments will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a flat plate-shaped displacement member attached to a displacement magnifying portion in a W resonance type chopper as a piezoelectric actuator according to a first embodiment of the present invention. And a direction parallel to a plane having a normal line perpendicular to two directions of the displacement direction of the free end of the displacement enlargement part and the direction from the coupling part with the piezoelectric body adhesive part to the free end, It is a perspective view showing an example combined with a pyroelectric infrared sensor.

In FIG. 1, 11 is a shim made of an elastic flat plate, 12 is a piezoelectric body adhered to one side of this shim 11, 1
Reference numeral 3 denotes a displacement magnifying portion made of the same elastic flat plate as the shim 11, 1
Reference numeral 4 is a fixing portion for fixing one end of the shim 11, 15 is a piezoelectric wiring, 16 is an infrared detecting portion, 17 is infrared light, 18 is a displacement member provided at the free end of the displacement enlarging portion 13, and 19 is the shim 11
And the displacement magnifying portion 13 are also connected.

The shim 11 is mainly made of copper or iron-based metal flat plate, and is made of an alloy such as 42 alloy or Super Invar such as iron and nickel. Can be reduced, and the temperature dependence of the displacement position can be reduced. Shim 11, displacement magnifying section 1
3. The displacing member 18 and the connecting portion 19 are made of an integral metal member, and are formed by bending each in a flat plate shape. The shim 11 and the displacement magnifying portion 13 are parallel to each other and have a U-shape through the joint portion 19.

A piezoelectric body 12 polarized in the direction perpendicular to the plane is adhered to one side of the shim 11 to form a piezoelectric body adhesion portion. The opposite side of the connecting portion 19 of the shim 11 is fixed to the fixing portion 14 by screwing, bonding, welding or the like. The piezoelectric wiring 1 is provided on the surface of the piezoelectric body 12.
5 is attached, and the material of the fixing portion 14 is a conductive material such as copper. The plane portion of the displacement member 18 is bent substantially at right angles to the plane of the displacement enlarging portion 13.

When an AC signal is applied between the piezoelectric body wiring 15 and the fixed portion 14, an electric field is applied to the piezoelectric body adhesive portion, and the piezoelectric body adhesive portion is bent. The displacement of the free end of is similar to that described in the conventional example. Strictly speaking, the displacement of the free end of the displacement magnifying portion 13 is a rotational movement, but when the displacement amount is small, it can be regarded as a linear reciprocating motion in a direction perpendicular to the plane of the displacement magnifying portion 13.

The displacement amount can be maximized by disposing the displacement member 18 near the free end of the displacement enlarging portion 13. Moreover, the plane of the displacement member 18 is the same as the displacement magnifying portion 13 described above.
Is parallel to the direction of the linear reciprocating motion of the free end of, and is also parallel to the direction connecting the free end of the displacement magnifying part 13 and the coupling part 19, that is, the longitudinal direction of the displacement magnifying part 13. There is. In other words, the displacement member 18 plane is
It has a normal line perpendicular to both the displacement magnifying portion 13 and the displacement direction.
An infrared detector 16 is provided near the displacement member 18
7 is arranged on the opposite side of the incident side, and the plane of the displacement member 18 is perpendicular to the incident direction of the infrared rays 17.

When the overall longitudinal dimension is short and the displacement amount is large, the displacement shifts from the linear reciprocating motion to the rotating motion. In this case, the position of the free end of the displacement magnifying portion 13 varies in the longitudinal direction of the displacement magnifying portion 13, but does not vary in the incident direction of the infrared rays 17. Therefore, the contact between the infrared detection unit 16 and the displacement member 18 can be prevented.

In addition to the above configuration, by using the resonance characteristics and the driving method of the W resonance type chopper described in the conventional example, the displacement amount of the displacement member 18 can be made stable and large, and the pyroelectric infrared sensor Contributes to downsizing and stabilization of characteristics. Further, by adopting the configuration of the present embodiment, it is possible to prevent the contact between the infrared detecting unit 16 and the displacement member 18, so that the distance between the two can be reduced, and the pyroelectric infrared sensor as a whole can be miniaturized.

Further, the pyroelectric infrared sensor usually has a condensing means such as a lens, so that the range through which the infrared rays 17 pass is narrower as it is closer to the infrared detecting section 16. Therefore, the closer the infrared detector 16 and the infrared opening / closing point by the chopper are, the smaller the opening / closing area can be made, but this can be easily realized by using the chopper of this configuration, and the reduction in the displacement amount due to the decrease in the opening / closing area can be reduced to It is possible to reduce the load on the device, further reduce the size, and improve the reliability. In addition, in the configuration described in the conventional example, the pyroelectric infrared sensor as a whole is elongated in the infrared ray incident direction, but in this configuration, the dimension in the same direction can be shortened.

Needless to say, the bending angle at each bending portion does not necessarily have to be a right angle as long as the characteristics allow, and an appropriate R can be provided. In particular, with respect to the displacement member 18, even if the flat surface portion and the flat surface portion of the displacement magnifying portion 13 are not at right angles, there is no problem as long as the opening / closing area can achieve the purpose of interrupting the incident infrared rays. Needless to say, the same effect can be obtained even when the flat portion is replaced by a substantially flat portion having an arbitrary curve or refraction.

(Embodiment 2) FIG. 2 is a perspective view showing an example in which a W resonance type chopper in which the displacement member in the second embodiment of the present invention is constituted by another member is combined with a pyroelectric infrared sensor. .

In FIG. 2, 21 is a shim, 22 is a piezoelectric body, 23 is a displacement magnifying section, 24 is a fixed section, 25 is a piezoelectric body wiring, 26 is an infrared detecting section, 27 is infrared, 28 is a displacing member, 29 Is the joint.

The displacement member 28 and the displacement enlarging portion 23 are constituted by separate members, and the displacement member 28 has a structure in which two planes form a right angle, and one of the plane portions is separated from the displacement enlarging portion 23 by a method such as bonding. Are connected.

Other configurations, driving methods, and effects are the same as those of the first embodiment. In addition, the displacement member 28 has a bending direction different from that of the other bending portions, but the displacement member 28 is a separate member. By this, this bending can be omitted, the bending process can be simplified, and the convex portion of the outer shape of the member that integrally configures the shim 21 and the displacement enlarging portion 23 can be omitted to form a rectangle, which improves the workability of the member and improves the material. Can be used more effectively.

It should be noted that it is not only the displacement member 28 that uses adhesive instead of bending, but the shim 21 and the displacement enlarging portion 23 are also used.
It goes without saying that it can also be applied to the combination with. Needless to say, even if the member to be bonded as the displacing member 28 has a block shape having a large dimension in the direction perpendicular to the displacing direction, the above effect can be obtained in the same manner.

(Embodiment 3) FIG. 3 shows a W resonance chopper having a displacement member according to a third embodiment of the present invention, which is formed by bending a member adjacent to a slit portion provided in a displacement enlargement portion. It is a perspective view showing an example combined with an electric infrared sensor.

In FIG. 3, 31 is a shim, 32 is a piezoelectric body, 33 is a displacement magnifying portion, 34 is a fixed portion, 35 is a piezoelectric wiring, 36 is an infrared detecting portion, 37 is infrared ray, 38 is a displacing member, 39 Is a coupling part, and 40 is a slit part.

A slit portion 40 is provided in the width direction in the vicinity of the free end of the displacement enlarging portion 33, whereby the displacement member 38 is formed by bending the portion on the free end side.

Other configurations, driving methods, effects, etc. are the same as those of the first embodiment, but in addition, in the case of bending the displacement member of the first embodiment, the shim before the bending, the displacement enlarging portion, and the coupling are formed. Since it is necessary to provide the convex portion on the member integrated with the member, the member is complicated to process, and it is difficult to use the material efficiently. However, the configuration of the present embodiment causes the above problems. Points are eliminated, productivity is increased, and effective use of materials becomes easier.

(Embodiment 4) FIG. 4 shows a W resonance having a bent portion which forms an angle of 10 degrees or more with the width direction in a part of the flat plate-shaped displacement magnifying portion in the fourth embodiment of the present invention. It is a perspective view showing an example which combined a model chopper with a pyroelectric infrared sensor.

In FIG. 4, reference numeral 41 is a shim, 42 is a piezoelectric body, 43 is a displacement enlargement portion, 44 is a fixed portion, 45 is a piezoelectric body wiring, 46 is an infrared detection portion, 47 is infrared rays, 48 is a displacement member, and 49. Is the joint.

The displacement magnifying portion 43 has a flat plate shape, and the displacement member 48 is integrally formed with the displacement magnifying portion 43 by bending at the tip thereof. In addition, the bent portion of the displacement member 48 is linear and forms an angle of approximately 45 degrees with respect to the width direction of the displacement magnifying portion 43. A part of the tip of the displacement member 48 is removed in a direction parallel to the displacement enlargement portion 43. The plane portion of the displacement magnifying portion 43 is arranged so as to be parallel to the traveling direction of the infrared rays 47.

Other configurations, driving methods, effects, etc. are the same as those of the first embodiment, but in addition, the configuration of the displacement member 48 is due to bending. In the above configuration, the bent portion forming the displacement member 48 is displaced. Since it is not necessary to newly provide it on the enlarged portion 43 and it can be formed in a flat plate shape, the member for constituting the displacement enlarged portion 43 and the like can be easily processed, and the productivity is improved and the material efficiency is improved.

In the case where the W resonance type actuator having the above-mentioned structure is used as a chopper of a pyroelectric infrared sensor, the displacement member 48 has an area that sufficiently fulfills the opening / closing function in the incident direction of the infrared rays 47, that is, the shielding portion area. By setting the width of the displacement magnifying portion 43 and the angle between the bending line and the width direction, the function as a chopper is achieved.

The angle between the bending line and the width direction is 0.
Since the shielding member has an opening / closing function only for the thickness of the displacement member 48 when the infrared ray 47 is incident, it does not have an opening / closing function. Therefore, it is possible to increase the shielding member area by giving a certain angle. It can have various opening and closing functions. When the angle is small, the area of the shielding portion is small, and when the angle is 90 degrees, the area of the shielding portion can be maximized. However, the larger the angle, the longer the bending line becomes, and the larger the dimension of the displacement magnifying portion 43 in the longitudinal direction becomes. Leads to larger overall shape. Therefore, it seems that about 45 degrees is relatively suitable, but the function as a chopper can be fulfilled at other angles.

Since the displacement member 48 is constructed by simple bending, the displacement member 48 is superior in strength as compared with bonding and the like, and the configuration is easy as compared with twisting or the like. Further, since the displacement member 48 appropriately adjusts the incident amounts of the infrared ray detecting portion 46 and the infrared ray 47, it is possible to perform processing such as removing the tip portion.

[0069]

As described above, according to the present invention, by bending an elastic flat plate called a shim or attaching another member by a method such as bonding, a displacement magnifying portion having a simple shape and good productivity is attached to the piezoelectric actuator. Can be easily provided. Further, the resonance frequencies of the displacement magnifying section and the piezoelectric body bonding section are the thickness, length, width, and material of the piezoelectric body and the elastic body,
The setting can be easily changed by operating the bonding position of the piezoelectric body, the bending position, the mounting position of the displacement magnifying section, the fixing position of the actuator, and the like. Further, by mounting the displacement magnifying portion near the tip of the piezoelectric body bonding portion, and further disposing the displacement magnifying portion toward the piezoelectric body bonding portion,
The resonant frequencies of the piezoelectric bonding portion and the displacement magnifying portion are less affected by the shapes of the mating members, which makes it easier to operate the resonant frequencies. In addition, by making the resonance frequencies close to each other by the above-mentioned operation and driving at the frequencies in between, the displacement is efficiently expanded by both resonances, and the actuator can be miniaturized. In addition, the sensitivity gradients of both resonance displacements are opposite between both resonance frequencies,
Therefore, the frequency dependence of the displacement is reduced by the offsetting effect of the gradient, and the displacement is stabilized. Furthermore, since both resonances are driven with a constant distance and driven in the region where the displacement sensitivity is reduced, stable displacement can be secured against fluctuations in the resonance frequency due to disturbances such as temperature changes, Further, for the same reason, the variation of the displacement characteristic due to the assembly variation can be suppressed to be small.

Further, when the displacement member is arranged at the tip of the actuator, the displacement member surface is arranged by arranging so that the normal line of the plane portion of the displacement member is perpendicular to both the longitudinal direction of the displacement magnifying portion and the displacement direction. Can be moved in parallel with the displacement direction, and when the displacement amount of the tip of the displacement enlarging part becomes large, the movement of the displacement member in the direction other than the displacement direction due to the rotational movement is suppressed, and contact with other members Can be prevented.
By using the W resonance type actuator having the above configuration as the chopper for the pyroelectric infrared sensor, the distance between the infrared detecting section and the shielding section of the chopper, that is, the displacement member can be reduced,
Therefore, especially when infrared rays are condensed by a lens or the like, the opening / closing area of the chopper can be reduced, and the displacement amount required for the chopper can be reduced. As a result, the shape of the chopper can be reduced, contributing to downsizing of the pyroelectric infrared sensor as a whole.
Further, the mechanical load on the chopper can be reduced, the reliability is improved, and the power required for driving the chopper can be reduced.

Further, in the displacement magnifying portion, the displacement member is formed by bending with an angle other than 0 degree such as 45 degrees with respect to the width direction, whereby the processing is easy and the displacement is similar to the above. It can be used as a chopper for a pyroelectric infrared sensor by preventing contact of other members with other members.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a piezoelectric actuator according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a piezoelectric actuator according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing a configuration of a piezoelectric actuator according to a third embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of a piezoelectric actuator according to a fourth embodiment of the present invention.

FIG. 5 is a perspective view showing a configuration of a chopper using a conventional piezoelectric actuator.

FIG. 6 is a perspective view showing the configurations of a conventional chopper and a pyroelectric infrared sensor using resonance.

FIG. 7 is a perspective view showing a shim used in a conventional chopper using resonance.

FIG. 8 is a perspective view showing a configuration of a conventional W resonance type chopper.

FIG. 9 is an admittance characteristic diagram of a conventional W resonance type actuator.

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

[Explanation of symbols]

 11,21,31,41 Shim 12,22,32,42 Piezoelectric body 13,23,33,43 Displacement expansion part 18,28,38,48 Displacement member 19,29,39,49 Coupling part

Claims (6)

[Claims] 1. A displacement magnifying portion, which is substantially parallel to the shim, is integrally provided at the other end of a shim made of an elastic member having one end fixed to a fixing portion via a coupling portion, and the shim has a flat plate shape. A piezoelectric actuator in which a piezoelectric body is bonded, and a displacement member having a flat surface perpendicular to both the longitudinal direction and the displacement direction of the displacement magnifying portion is provided at the free end of the displacement magnifying portion. 2. The piezoelectric actuator according to claim 1, wherein the displacement member is formed integrally with the displacement enlarging portion. 3. The piezoelectric actuator according to claim 1, wherein the displacement member is composed of a member different from the displacement enlarging portion. 4. The piezoelectric actuator according to claim 1, wherein a slit is provided in the displacement magnifying portion, and a portion separated by the slit is bent to form a displacement member. 5. The displacement member according to claim 1, wherein a part of the free end of the displacement enlarging portion is bent so as to be a flat surface portion forming an angle of 10 to 90 degrees with respect to the width direction of the displacement enlarging portion. Piezoelectric actuator. 6. A pyroelectric infrared sensor using the piezoelectric actuator according to claim 1, wherein a displacement member of the piezoelectric actuator serves as a means for connecting and disconnecting infrared rays incident on an infrared detecting section.