JP3334450B2 - Piezoelectric actuator and pyroelectric infrared sensor using the same - Google Patents

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 movement and a pyroelectric infrared sensor using the same.

[0002]

2. Description of the Related Art In recent years, pyroelectric infrared sensors have been used in a wide range of fields such as measuring the temperature of foods in a microwave oven and detecting the position of a human body in an air conditioner, and the demand is expected to increase 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. A pyroelectric infrared sensor detects charges generated on the surface and measures the amount of incident infrared light. 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 amount of incident infrared light. When detecting the temperature of an object as a pyroelectric infrared sensor, it is necessary to forcibly change the amount of infrared light intermittently or by opening and closing. 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, and the like have been used.

FIG. 6 shows a conventional example of a pyroelectric infrared sensor using, as a chopper, an actuator obtained by bonding a piezoelectric body to an elastic flat plate. Generally, an actuator that forms a bonding element by bonding a piezoelectric body to an elastic flat plate of metal or the like, fixes one end, and generates a bending motion as a whole by using the distortion caused by the piezoelectric body is generally an elastic body. A plate in which a piezoelectric body is bonded to both sides of a flat plate is called a bimorph type, and a plate in which only one surface is bonded is called a unimorph type, and an elastic flat plate is called a shim. Hereinafter, each member is referred to as such.

FIG. 6 shows a bimorph element used as a chopper for a pyroelectric infrared sensor.
62a and 62b are piezoelectric bodies, 63 is a shielding plate, 64 is a pedestal,
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 shielding plate 63, and 70 is infrared.

On both sides of the shim 61, piezoelectric bodies 62a, 62b
Are bonded to each other to form a bimorph-type element. Electrodes are printed on the surfaces of the piezoelectric bodies 62a and 62b, and a polarization process is performed in a direction perpendicular to the bonding surface. The polarization directions of the piezoelectric bodies 62a and 62b are determined by the wiring 66 taken out from the shim 61 and the wiring 66. Piezoelectric body 6
Depending on the direction of the electric field applied between the shim 61 and the piezoelectric bodies 62a and 62b due to the wirings 67a and 67b taken out from the 2a and 62b, the piezoelectric bodies 62a and 62b are different.
b is determined so as to always generate distortion in directions opposite to each other.

That is, 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, so that the direction of the applied electric field and the polarization direction are determined.
The bimorph-type element is held by the portion of the shim 61 and the portion of the piezoelectric bodies 62a and 62b being sandwiched by the pedestal 64 and the fixture 65 at the same time. A shim wiring 66 is attached to a portion of the shim 61 where the piezoelectric bodies 62a and 62b are not bonded, and piezoelectric wirings 67a and 67b are attached to the surfaces of the piezoelectric bodies 62a and 62b.

A shield plate 63 is attached to the tip of the free end of the bimorph-type element.
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. The shim 61 and the piezoelectric members 62a, 62b are formed by the shim wire 66 and the piezoelectric wires 67a, 67b.
When an electric field is applied during the period 62b, the bimorph-type element generates a bending motion fixed at one end, and the shield plate 63 and the slit 69 attached to the tip reciprocate according to a change in the direction of application of the electric field. . Due to the reciprocating motion of the slit 69, the infrared ray 70 incident on the infrared ray detector 68 is intermittently intermittent.

However, the bimorph-type chopper having the above-described structure requires a large dimension from the fixed portion to the tip moving portion in order to obtain a moving distance sufficient to intermittently transmit infrared rays, and is very high. A drive voltage is required.

Therefore, as a conventional improvement method, a piezoelectric body is brittlely broken by applying a load to the tip moving portion of a bimorph-type element or a unimorph-type element to lower the resonance frequency and fixing only the shim. By further reducing the resonance frequency by, for example, providing a notch in the shim near the fixed portion as necessary, a large displacement can be obtained with low voltage driving.

The following is an example of the structure of a chopper having the above characteristics. FIG. 7 is a perspective view showing an example in which a unimorph-type element as a chopper for a pyroelectric infrared sensor in a conventional improved example is formed so that the width of a fixing place of a shim portion is reduced. 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 wirings, 77a and 7
7b is a wiring for a piezoelectric body, 78 is an infrared detector, 79a and 7
9b, 79c and 79d are unimorph type element fixing screws, 8
0 is an infrared ray.

FIG. 8 is a perspective view showing details of the shims 71a and 71b, where 81 is a shielding portion, 82 is a piezoelectric bonding portion,
83 is a notch, 84 is a positioning part, 85a and 85b
Is a fixing hole. The shielding portion 81 and the piezoelectric bonding portion 82 form a right angle by bending, and a cutout portion 83 formed so that the width becomes smaller than the piezoelectric bonding portion 82 from the piezoelectric 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 small width, and the notch 83 is sandwiched between the sensor pedestal 74 and the unimorph-type element fixtures 75a and 75b as shown in FIG. Furthermore, unimorph-type element fixing screws 79a, 79b, 79c, 79d are inserted into fixing holes 85a, 85b, respectively, and positioned and fixed at one end, and are arranged so as to face each other in parallel. Also, the piezoelectric bodies 72a, 72b are provided on opposing surfaces of the shims 71a, 71b, that is, on the piezoelectric body bonding portion 82.
b is the sensor pedestal 74 or the unimorph-type element fixture 75
a, 75b and the shielding portions at the tips of the shims 71a, 71b, and in addition, are adhered at positions not in contact with the notch portions 83 to constitute a unimorph type piezoelectric actuator.

An infrared detector 78 is disposed on the sensor pedestal 74 near the free end of the unimorph-type element.
Incident or blocked. The shielding portion 81 for intermitting the infrared light 80 is formed by bending the end of the shim 71a, 71b on the side opposite to the side to which the shim 71a, 71b is fixed, and the weights 73a, 73b are bonded to the plane portion of this portion. Shim 71
a, 71b other than the movable part, namely, the positioning part 8
4 are provided with shim wirings 76a and 76b,
Piezoelectric wires 77a and 77b are attached to the 2a and 72b at positions near the fixed portion of the unimorph type element, respectively. The shim 71a and the piezoelectric material 72a are provided by the shim wires 76a and 76b and the piezoelectric wires 77a and 77b. When an electric field is applied between the shim 71b and the piezoelectric body 72b, the unimorph-type element bends, and the shielding portion 81 at the tip moves.
The two unimorph elements are driven in the opposite direction at the same frequency to intermittently block infrared light 80.

By providing the notch 83 in the shim between the piezoelectric body and the fixed portion of the unimorph element, the resonance frequency can be further reduced as compared with a unimorph element having the same dimensions and having no notch. Since the chopper is not provided, the chopper can be reduced in size and the displacement amount at the time of low-frequency driving can be increased as compared with the case where the notch is not provided.

As described above, various advantages can be obtained by driving a bonded type element such as a unimorph type element in the vicinity of resonance. However, since the driving is performed in the vicinity of the resonance frequency, the resonance frequency of the chopper varies between solids. If there is a variation, a large difference in the amount of displacement occurs, and in order to keep the displacement constant, it is necessary to perform component processing or assembly that requires fine adjustment and high precision. When the resonance frequency changed over time, the displacement changed significantly. Further, when the drive frequency is moved away from resonance to stabilize the displacement, the displacement amount decreases, and a high drive voltage is required to obtain the same displacement. In addition, when the displacement is obtained by reducing the size, the load on the adhesive layer between the shim and the piezoelectric body increases, which causes peeling. Such a problem is not limited to the chopper of the conventional example, but is a problem equivalent to all cases where resonance is used.

The following piezoelectric actuators have been proposed in order to improve the problem of the resonance driving described above. FIG. 9 is a perspective view showing an example of a chopper for a pyroelectric infrared sensor in which a displacement expansion section is provided in a unimorph type piezoelectric actuator.

In FIG. 9, 91 is a shim, 92 is a piezoelectric body, 93 is a displacement expanding portion, 94 is a sensor base, 95 is a fixture, 96a and 96b are fixing screws, 97 is a shim wiring,
Reference numeral 98 denotes a piezoelectric wiring, 99 denotes an infrared detection unit, 100 denotes an infrared ray, and 101 denotes a bent portion.

By bending an elastic plate made of phosphor bronze or stainless steel alloy 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 mutually joined 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 a right angle at a tip opposite to the joint portion and at a side opposite to the shim 91. A piezoelectric body 92 is bonded on the surface of the shim 91 to form a piezoelectric bonded portion (unimorph element).

The shim 91 is sandwiched between the sensor pedestal 94 and the fixture 95 near the end opposite to the joint with the displacement enlarging portion 93. The fixing screws 96
a, 96b. An infrared detecting section 99 is arranged on the sensor base 94 and is located near the bent section 101 at the tip of the displacement enlarging section 93. Sim 9
In the vicinity of the fixing portion of the first member 1, a shim wiring 97 is further provided.
At a position near the fixing portion of the shim 91 on the surface opposite to the bonding side of No. 2, piezoelectric wiring 98 is attached.

Here, the shim wiring 97 and the piezoelectric wiring 98
When an AC signal is further applied, a potential difference is generated between the shim 91 and the piezoelectric member 92, and the joint between the shim 91 and the displacement expanding portion 93 is displaced. Accordingly, the tip of the displacement expanding portion 93 is bent. The bent portion 101 is also displaced, and the movement intermittently interrupts the infrared light 100 incident on the infrared detection portion 99, thereby serving as a chopper.

FIG. 10 shows the resonance characteristics of the piezoelectric actuator (chopper) having the above configuration. FIG. 10 shows an example of the resonance characteristics of a piezoelectric actuator composed of a shim bent in a U-shape and a displacement enlarging portion. The vertical axis indicates admittance, and the horizontal axis indicates drive frequency. It can be seen that there are resonance phenomena at each of the resonance frequencies f ₁ and f ₂ , which are caused by the resonance mainly caused by the vibration of the piezoelectric bonding portion of the piezoelectric actuator and the vibration mainly by the displacement expanding portion. are either resonance caused by, and corresponds to either the configuration of the piezoelectric actuator, and also changes the difference between the resonance frequencies f ₁ and f ₂ by the configuration.

[0024] With the structure having a longitudinal dimension in the same direction from the coupling portion and the shim and displacement amplifying section as described above, the operation of the relative positions of the resonance frequencies f ₁ and f ₂ becomes easy. For example, when the longitudinal dimension of the displacement enlarging member is constant and only the length from the fixed portion of the piezoelectric body bonding portion to the piezoelectric body is changed, that is, only the longitudinal dimension of the piezoelectric body bonding portion is changed, When the resonance frequency due to the piezoelectric bonding portion is equivalent to f ₂ in a state where the longitudinal dimension of the body bonding portion is short, that is, when the resonance frequency due to the piezoelectric bonding portion is higher than the resonance frequency due to the displacement expanding portion As the longitudinal dimension of the piezoelectric bonding part is gradually increased, the resonance frequencies of the two become relatively closer, and at a certain length, the two are overlapped as one resonance, and the longitudinal dimension of the piezoelectric bonding part is further increased. When the length is increased, the relative positions of the two are reversed, and the resonance frequency caused by the displacement expanding portion has a higher value than the resonance frequency caused by the piezoelectric body bonding portion.

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

Further, let f _{1 be} a resonance frequency mainly attributable to the piezoelectric bonding portion, and f _{2 be} a resonance frequency mainly attributable to the displacement magnifying portion, that is, from the resonance frequency mainly attributable to the piezoelectric bonding portion. Also has a configuration in which the resonance frequency mainly due to the displacement enlargement section is higher, so that the displacement is enlarged and stable, and the frequency range where the time difference between the applied AC signal and the tip of the displacement enlargement section is constant is wider. it can.

In a unimorph type actuator using ordinary resonance, the displacement shows a large change depending on the driving frequency.
When driving at a frequency about 5% apart from the resonance frequency to stabilize this, 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 is about 100 Hz, and the resonance frequency f ₁ caused by the piezoelectric bonding portion
Is about 85 Hz, when driving between the resonance frequencies f ₁ and f ₂ , it is possible to obtain a displacement of 1.1 ± 0.05 mm in the section of about 6 Hz at the tip of the displacement enlarging portion by applying an alternating current of ± 30 V. It is possible.

A similar effect is obtained when the piezoelectric actuator has a configuration in which the resonance frequency f ₂ is 120 Hz or less in accordance with the longitudinal dimension of the displacement enlarging portion when the longitudinal dimension of the piezoelectric body bonding portion is about 18 mm or less. the difference between the ₂ and f ₁ is best obtained between approximately 5-25% of the resonance frequency f _2. The same effect can be obtained even if it is within 5%, but in this case, the frequency range in which driving can be performed may be reduced, or one of the resonances may not be excited.

With the above-described configuration, the drive utilizing resonance can be stably performed at a lower voltage, and the drive, assembly, and machining of members are facilitated. Further, since the vibration amount of the portion bonded to the piezoelectric body can be reduced, peeling of the shim from the piezoelectric body hardly occurs. In addition, the bent configuration reduces the overall longitudinal dimension, and by using this configuration as a chopper of a pyroelectric infrared sensor, the entire sensor can be reduced in size and fixed to the same pedestal as the infrared detector. This facilitates integration with the infrared detection unit, and furthermore, the vicinity of the infrared detection unit can be opened and closed, so that the opening and closing area can be reduced and the load on the chopper can be reduced. Further, by driving at a low voltage, the influence of noise from the piezoelectric body on the infrared detection unit can be reduced.

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

[0031]

In the case of driving using the above-described W resonance type actuator, it is necessary to efficiently excite two resonances, and in some cases, one resonance is affected by the other resonance. As a result, a sufficient amount of displacement could not be obtained because of little excitation, and each component had to be optimized for this purpose.

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 the temperature can not be measured when used as a chopper of a pyroelectric infrared sensor. Some cases have disappeared. In addition, the instability of displacement due to unnecessary resonance significantly impairs the accuracy of the sensor.

An object of the present invention is to provide a W-resonant type actuator which can achieve a more stable drive and a sufficient displacement.

[0034]

In order to achieve the above object, a W resonance type actuator according to the present invention is characterized in that a piezoelectric bonding portion and a displacement enlarging portion have an angle of 0 to 10 degrees , and at least,
Also have some rubber materials and similar mechanical properties
A structure for distributing a separate member to the elastic member, increasing the resonance level of the resonance frequency f ₁ which is lower sides of the resonance, it is possible to excite both resonant efficiently, the unnecessary resonance level
Can be reduced.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a plate-shaped piezoelectric body subjected to polarization treatment is adhered to one or both sides of a plate-shaped elastic member, and one end is fixed by a fixture . Piezoelectric bonding part, and bonded to the piezoelectric bonding part
Is connected via a coupling portion and than its free end the coupling part has a displacement amplifying section which is located at a distance closer to the fixture of the piezoelectric adhering part, said applying an electric field to said piezoelectric body adhesive portion A piezoelectric actuator in which a free end of the piezoelectric bonding portion and a free end of the displacement enlarging portion are displaced by bending the piezoelectric bonding portion, and a resonance frequency f ₁ generated due to vibration of the piezoelectric bonding portion. When the is close to the difference between the resonance frequency f ₂ generated due to vibration of the displacement amplifying section has a structure in which the resonance frequency f ₂ is higher frequency within 30% over the resonance frequency f _1, in the piezoelectric actuator is driven by applying an AC voltage at a frequency between the resonance frequencies f ₁ and f _2, the longitudinal direction of the piezoelectric adhering part, the angle is 0 degrees formed by the longitudinal direction of the displacement amplifying section 1
It is between 0 ° and the free end of the displacement amplifying section is to increase the distance between the piezoelectric bonded portion than near the coupling portion, small
At least a part of rubber material and similar mechanical properties
Another member is a piezoelectric actuator arranged on the elastic member, thereby a lower side of the resonance increases the resonance level of the resonance frequency f _1, stability in operation can be excited both resonant efficiently is Hakare to , While ensuring sufficient displacement, and reducing unnecessary resonance levels at specific higher frequencies.
And has the effect of stabilizing the drive .

According to a second aspect of the present invention, the elastic flat plate is folded.
The bending, bending and displacement of the piezoelectric body
Most are integrally configured, between the piezoelectric body and the joint
Having an unbonded portion having no piezoelectric body at a certain distance, and
Rubber material or similar mechanical properties at unbonded parts
2. The piezoelectric actuator according to claim 1, wherein another member having quality is attached.
Tutor, which reduces unwanted resonance levels
The effect of making it work is obtained.

According to a third aspect of the present invention, the elastic flat plate is folded.
The bending, bending, and expansion of the piezoelectric
A large part is integrally formed, and rubber is
Material or another member with similar mechanical properties
2. The piezoelectric actuator according to claim 1, wherein
This is to further reduce the level of resonance required.

The invention according to claim 4 is the invention according to claims 1 to 3
The piezoelectric actuator described in the above with intermittent means of incident infrared
Pyroelectric infrared sensor with high measurement accuracy
Things.

According to a fifth aspect of the present invention, there is provided a pyroelectric infrared sensor using the piezoelectric actuator according to the first to fourth aspects as a means for interrupting incident infrared rays.

In FIG. 1, 11 is a shim made of an elastic member , 12 is a piezoelectric body, 13 is a displacement enlarging portion, and 14a and 14b.
Is a fixture, 15 is a bent portion, 16 is a coupling portion, 17 is a rubber material, 18 is an infrared detecting portion, and 19 is an infrared ray. Sim 1
1. The displacement enlarging portion 13, the bent portion 15, and the connecting portion 16 are integrally formed by bending a single plate-shaped conductive metal body. One surface of the shim 11 is provided with a piezoelectric body bonding portion to which a piezoelectric body 12 that is polarized in the thickness direction and has electrodes formed on both surfaces is bonded. Joint 1 of shim 11
In the vicinity of the end opposite to 6, the W resonance type actuator is formed by being sandwiched by fixtures 14a and 14b and fixed at one end.

In FIG. 1, 11 is a shim, 12 is a piezoelectric body, 13 is a displacement enlarging portion, 14a and 14b are fixtures, 15
Is a bent portion, 16 is a coupling portion, 17 is a rubber material, 18 is an infrared detecting portion, and 19 is an infrared ray. The shim 11, the displacement enlarging portion 13, the bent portion 15, and the connecting portion 16 are integrally formed by bending a single plate-shaped conductive metal body. One surface of the shim 11 is provided with a piezoelectric body bonding portion to which a piezoelectric body 12 that is polarized in the thickness direction and has electrodes formed on both surfaces is bonded. In the vicinity of the end opposite to the joint 16 of the shim 11, the W-resonant actuator is formed by being sandwiched between the fixtures 14a and 14b and fixed at one end.

The fixtures 14a and 14b are also formed of a conductive material similarly to the shim 11, and the fixture 14a and the piezoelectric element 1
An alternating electric field is applied between the two non-bonded surface electrodes. The piezoelectric body 12 is bonded to the coupling portion 16 at a certain distance to enable bending after bonding the piezoelectric body. A sheet-like rubber material 17 is attached to a portion of the piezoelectric body 12 to which the piezoelectric material 12 is not bonded, and the rubber material 17 is called a damper material or the like.

As shown in FIG. 1B, the longitudinal directions of the piezoelectric body bonding portion and the displacement enlarging portion 13 form an angle θ with each other, that is, the bent portion at the base of the displacement enlarging portion 13 forms an obtuse angle, and The bent portion 15 is configured to have a larger distance from the piezoelectric body bonding portion than when the bent portion is 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 to interrupt the incidence of the infrared light 19 to function as a chopper.

By forming the displacement enlarging unit 13 with an angle of θ, the resonance level on the lower side of the two resonances used for driving the W resonance type actuator can be increased.

FIGS. 2 (a) and 2 (b) are examples of resonance characteristics when the displacement enlarging portion and the piezoelectric body bonding portion are parallel to each other and when they have an angle θ. In the resonance characteristic diagram, the vertical axis indicates the admittance of the W resonance type actuator, and the horizontal axis indicates 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 vibration of the piezoelectric body bonding portion, and f ₂ is a resonance frequency caused by vibration of the displacement magnifying portion. Indicates the frequency.

FIG. 2B similarly shows a displacement enlarging portion and a piezoelectric body.
This is the case where the angle with the bonding portion is θ. Angle θ
The resonance frequency f₁The resonance level at
Increase, and conversely, the resonance frequency f_TwoResonance level at
I do. That is, by giving the angle θ,
Vibration frequency f₁Enhance the resonance excitation of
Resonance resonance due to assembly variations and aging.
It is possible to have a sufficient margin for the bell drop.
Conversely, the resonance frequency f_TwoThe resonance level of the
Bell has resonance frequency f₁Larger than the
The optimum driving region where stable displacement can be obtained is the resonance frequency f₁
The effect is small. However, if θ is too large,
When used as a knit, the volume increases and resonance occurs.
Frequency f _TwoThe displacement level is too low
The optimal range of θ is almost 0 degrees because any problem occurs.
Between 10 degrees and larger.

Bending is easier when the angle is set to 90 ° + θ than when it is bent at 90 °. FIG. 3 (a), FIG.
(B) is an example of a resonance characteristic diagram in a case where a rubber material is stuck between the coupling portion and the piezoelectric body and in a case where a rubber material is not stuck. In the resonance characteristic diagram, the vertical axis indicates the admittance of the W resonance type actuator, and the horizontal axis indicates the drive frequency. The W resonance type actuator has an unnecessary resonance having a higher level at a frequency higher than the resonance frequencies f ₁ and f ₂ used for driving. The level and frequency of the unnecessary resonance vary depending on the configuration. For example, when 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 where 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.
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 simultaneously excited, and the displacement waveform is disturbed, and in some cases, it becomes impossible to control. 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 a coupling portion and a piezoelectric body. It is loss energy of the vibration by attaching a rubber material and other damper material, but overall the resonance level decreases, the level of the resonance caused by vibration of the patch portion particularly as unwanted resonance frequency f ₃ Greatly reduced.

By attaching the damper material in this manner, the resonance level of unnecessary resonance can be reduced, and the influence on driving can be suppressed. In addition, by selecting a damper material and a sticking place, a particularly large effect can be obtained for 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 The driving can be easily stabilized.

In detecting the temperature of the pyroelectric infrared sensor, the displacement amount and the displacement waveform of the chopper greatly affect the detection accuracy. By using the above-described W resonance type actuator as a chopper, the sensor unit can be reduced in size and highly accurate. Can be achieved.

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

In FIG. 4, reference numeral 41 denotes a shim; 42, a piezoelectric body; 43, a displacement enlarging portion;
Is a bent portion, 46 is a joint portion, 47a and 47b are rubber materials,
48 is an infrared detector, and 49 is an infrared ray. In the vicinity of the fixing portion of the shim 41, rubber members 47a and 47b are attached to both surfaces. Other configurations are the same as those of the first embodiment.

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

FIGS. 5 (a) and 5 (b) are examples of resonance characteristics when a damper material is adhered near the fixed portion and when it is not attached. In the resonance characteristic diagram, the vertical axis indicates the admittance of the W resonance type actuator, and the horizontal axis indicates the drive frequency. If Figure 5 (a) is not attached, although FIG. 5 (b) is obtained by sticking, the effect in this case is particularly reduced levels the resonance of the unwanted resonance frequency f ₄ is large. Unwanted resonance frequency f ₄ is also greatly affected by the same drive as f _3, thus the relationship between the unwanted resonance to be excited with a frequency used in the driver,
Unnecessary resonance can be easily reduced by roughly specifying the driving location of the resonance affecting driving and attaching a damper material to that portion.

[0055]

As described above, according to the present invention, the level of resonance used for driving is adjusted by giving an angle between 0 ° and 10 ° to the piezoelectric bonding portion and the displacement enlarging portion of the W resonance type actuator. it can. Amplifying the low-level resonance makes it less likely to be affected by the high-level resonance, so that the drive frequency can be set and adjusted over a wider range, and various drive frequencies can be handled. By exciting both resonances in a well-balanced manner, the amount of displacement in the stable region can be increased, and more efficient driving can be performed.

Further, by sticking a damper material such as a rubber material to the W resonance type actuator, the level of unnecessary resonance can be reduced. In addition, by selecting a place where the damper material is to be attached according to the configuration, the level can be reduced particularly for specific unnecessary resonance that has an effect on driving, and the effect on resonance required for driving can be minimized. In addition, since the number of sticking members 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 increases.

Since the W resonance type actuator is small in size and can obtain a large displacement, it contributes to the miniaturization of the whole unit such as a sensor. In particular, it is possible to reduce the size of the pyroelectric infrared sensor which requires a chopper for temperature detection. Contributes to higher accuracy and increases versatility. By adjusting the resonance used for driving and reducing unnecessary resonance, a chopper that can perform 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 according to the present invention. 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 a configuration of a conventional piezoelectric bimorph chopper.

FIG. 7 is a perspective view showing a 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 an 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 enlargement part 15, 45 Bend part 16, 46 Joining part

Continuation of the front page (56) References WO 96/14687 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02N 2/00 G01J 1/02 G01J 5/62 H01L 37 / 02 H01L 41/09

Claims (4)

(57) [Claims] 1. A plate-shaped piezoelectric body subjected to a polarization treatment is adhered to one or both sides of a plate-shaped elastic member and one end is fixed.
A piezoelectric adhesive portion fixed by immediately, the coupled via a coupling portion coupled to the piezoelectric member bonded portion and its free end is located at a distance closer to the fixture of the piezoelectric adhering part than the coupling portion A piezoelectric actuator having a displacement enlargement portion, wherein a free end of the piezoelectric adhesion portion and a free end of the displacement enlargement portion are displaced by applying an electric field to the piezoelectric adhesion portion to cause the piezoelectric adhesion portion to bend; in the resonance frequency f ₁ caused by the vibration of the piezoelectric element adhering part, the due to the vibration of the displacement amplifying section is brought close to the difference between the resonance frequency f ₂ generated, the resonance frequency f ₂ is the 30 than the resonance frequency f ₁
Has a high frequency and comprising structure within%, in the piezoelectric actuator to drive an AC voltage is applied at a frequency between the resonance frequencies f ₁ and f _2, the longitudinal direction of the piezoelectric adhering part, the displacement enlargement The angle formed in the longitudinal direction of the part is 0
Between 10 degrees and 10 degrees, and the free end of the displacement enlarging portion has a greater distance from the piezoelectric bonding portion than near the coupling portion.
And at least in part, rubber and similar mechanical
A piezoelectric actuator in which another member having properties is arranged on an elastic member . 2. A piezoelectric device by bending an elastic flat plate.
The body bonding part, joining part and displacement enlargement part are integrally configured.
The piezoelectric body at a distance between the piezoelectric body and the coupling portion.
Not having an unbonded portion, and rubber at the unbonded portion
Material or another member with similar mechanical properties
The piezoelectric actuator according to claim 1 attached. 3. A piezoelectric device by bending an elastic flat plate.
The body bonding part, joint part and displacement enlargement part are integrally configured.
And a rubber material or the like near the fixing portion.
2. A separate member having a mechanical property which is attached to the substrate.
Piezoelectric actuator. 4. A piezoelectric actuator according to claim 1, wherein
Pyroelectric Infrared using the data as intermittent means of incident infrared
Sensor.