JP3762814B2 - Driving method of piezoelectric chopper for pyroelectric infrared sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a driving method and a structure of a piezoelectric chopper for a pyroelectric infrared sensor that detects infrared rays emitted from an object in a non-contact manner.
[0002]
[Prior art]
In recent years, pyroelectric infrared sensors have been used in a wide range of fields such as temperature measurement of food in a microwave oven and detection of the position of a human body in automatic temperature control of an air conditioner. The pyroelectric infrared sensor uses a pyroelectric effect by a pyroelectric material such as a LiTaO3 single crystal.
[0003]
The pyroelectric material described above has spontaneous polarization and always generates a surface charge. However, in a steady state in the atmosphere, the pyroelectric material is electrically neutral in combination with the charge in the atmosphere. When infrared rays are incident on the pyroelectric body, the temperature of the pyroelectric body changes, and the charge state of the surface changes along with the neutral state. A pyroelectric infrared sensor measures the amount of incident infrared rays by detecting a change in the amount of charge generated on the surface electrode.
[0004]
The object emits infrared rays corresponding to its temperature, and the temperature and position of the object can be measured by using this sensor. The pyroelectric effect is caused by a change in the amount of incident infrared rays. When detecting the temperature of an object as a pyroelectric infrared sensor, it is necessary to change the amount of incident infrared rays. A chopper is used as this means, and the incident infrared ray is forcibly interrupted to detect the temperature of the detection object. As a conventional chopper, a chopper using an electromagnetic motor, a piezoelectric actuator or the like has been mainly used.
[0005]
Piezoelectric actuators used as choppers are made by adhering and bonding piezoelectric ceramics to an elastic thin plate such as metal, forming an element (hereinafter referred to as a bimorph type element), holding and fixing one end, and applying a voltage to the piezoelectric ceramic. The bending motion is generated by the strain caused by this.
[0006]
FIG. 23 is a perspective view showing a configuration of a pyroelectric infrared sensor using a bimorph piezoelectric actuator as a chopper. In FIG. 23, 10 is an elastic shim material, 11 is a piezoelectric ceramic, 12 is a shielding plate, 13 is a pedestal, 14 is a fixture, 15 is an infrared detector having a pyroelectric infrared sensor element, and 16 is emitted from an object. Infrared.
[0007]
A piezoelectric ceramic 11 is bonded to one surface of the elastic shim material 10 to form a drive unit 10a made of a bimorph element. An electrode is formed on the surface of the piezoelectric ceramic 11, and polarization treatment is performed in the thickness direction.
[0008]
An amplitude expanding portion 10b as a displacement expanding portion is formed of only the elastic shim material 10 at the tip of the driving portion 10a. The drive unit 10 a is held by the pedestal 13 and the fixture 14 by sandwiching a part of the elastic shim material 10. A shielding plate 12 as a shielding member is attached to the free end of the amplitude expanding portion 10b. In the vicinity of the shielding plate 12, the infrared detection unit 15 is disposed so as not to contact the shielding plate 12.
[0009]
When an electric field is applied between the elastic shim material 10 and the piezoelectric ceramic 11, the drive unit 10a generates a bending motion fixed at one end, and also excites the amplitude expanding unit 10b coupled to the tip. And the shielding board 12 attached to the front-end | tip reciprocates according to the change of the application direction of an electric field. The infrared rays 16 incident on the infrared detector 15 are intermittently caused by the reciprocating motion of the shielding plate 12.
[0010]
As shown in FIG. 24, in the above configuration, the two resonance frequencies of the driving unit 10a and the amplitude expanding unit 10b are made close to each other. Therefore, the resonance characteristic of the drive unit 10a and the resonance characteristic of the amplitude enlargement unit 10b influence each other, so that it is possible to create a stable region of displacement that is insensitive to changes in the drive frequency, and an excellent chopper with stable drive frequency-displacement characteristics. Can be realized.
[0011]
[Problems to be solved by the invention]
However, the piezoelectric chopper for the pyroelectric infrared sensor described above sets a frequency between two fundamental resonance frequencies as a driving frequency. For this reason, when the drive signal is suddenly applied at the time of startup, other frequency components included in the drive frequency also excite vibrations at the respective resonance frequencies.
[0012]
As a result, the piezoelectric chopper apparently vibrates at the drive frequency driven by the drive frequency and at the beat frequency that is the difference between the resonance frequencies, and a beat component is superimposed on the drive frequency as shown in FIG. Fall into a state of being runaway (hereinafter referred to as a runaway phenomenon). As a result, the piezoelectric chopper cannot be used as a chopper until it is in a stable state, realizing a high-speed temperature measuring function of the sensor and losing power consumption until it is in a stable state, which greatly hinders low power consumption. .
[0013]
In view of such a conventional problem, the present invention provides a piezoelectric chopper for a pyroelectric infrared sensor capable of improving the startup characteristics of the piezoelectric chopper, improving the high-speed temperature measuring function of the infrared sensor, and reducing power consumption. An object of the present invention is to provide a driving method and a piezoelectric chopper.
[0014]
[Means for Solving the Problems]
A first aspect of the present invention is a bimorph element having a cantilever structure having a drive part made of an elastic body and a piezoelectric body and a displacement enlargement part made only of an elastic body, a holder for holding the bimorph element, and a displacement enlargement part A piezoelectric chopper driving method provided with a shielding member for incident / blocking infrared rays, wherein the voltage level of the driving signal at the time of activation of the piezoelectric chopper This is a method for driving a piezoelectric chopper for a pyroelectric infrared sensor, in which a drive signal is applied while being changed so as to be opposite to fluctuations in movement.
[0015]
The invention according to claim 5 is a bimorph element having a cantilever structure having a drive part made of an elastic body and a piezoelectric body and a displacement enlargement part made only of an elastic body, a holder for holding the bimorph element, and a displacement enlargement part A piezoelectric chopper driving method provided with a shielding member for incident / blocking infrared rays, which is provided at the front end of the driving circuit, wherein when the piezoelectric chopper is activated, the driving frequency of the driving signal is increased with time. This is a method for driving a piezoelectric chopper for a pyroelectric infrared sensor in which a drive signal is applied while moving to a predetermined drive frequency from the vicinity of the resonance frequency or the vicinity of the resonance frequency of the displacement magnifying unit.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof .
FIG. 1 is a block diagram of a piezoelectric chopper drive circuit according to a first configuration example of the invention related to the present invention. In FIG. 1, 21 is an oscillation circuit, 22 is a shaping circuit, 23 is an amplifier, 24 is a bimorph element, and 25 is an arithmetic circuit having a CPU.
[0020]
The small signal of the driving frequency generated by the oscillation circuit 21 is adjusted to a duty ratio of 50:50 by the shaping circuit 22. Then, it is amplified by the amplifier 23 and applied to the bimorph element 24. By the way, an arithmetic unit 25 is added to the amplifier 23 to control the step-up ratio of the amplifier 23.
[0021]
Therefore, the calculation device 25 changes the voltage applied to the element in a linear function and outputs it. An example of the output result at that time is shown in FIG.
[0022]
As a result, the harmonic components at the time of startup are reduced, and the runaway phenomenon at startup (see FIG. 22), which has been a problem in the past, can be improved as shown in FIG.
[0023]
In this configuration example , the case where the applied voltage of the bimorph element 24 is increased linearly from the start is described. However, the method of changing the applied voltage is not limited to this, and for example, a predetermined function As a result, the same effect can be obtained by increasing the number of power functions such as a quadratic function, exponential function, or logarithmic function from the start .
FIG. 4 is a block diagram of a piezoelectric chopper drive circuit according to a second configuration example of the invention related to the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to what makes the same effect | action as the 1st structural example shown in FIG.
[0024]
The second configuration example is different from the first configuration example described above in that the arithmetic unit 25 is removed and a resistor 26 and a capacitive element 27 are connected to the output side of the amplifier 23.
[0025]
Specifically, the harmonic component of the applied signal to the element at the time of activation is removed by a low-pass filter composed of the resistor 26 and the capacitive element 27.
[0026]
With the above configuration, in addition to the same effect as in the first configuration example , the same effect can be obtained by adding two elements in place of the arithmetic unit, so that the cost reduction effect can be obtained at the same time.
[0027]
In this configuration example , a low-pass filter is connected to the output side of the amplifier 23, but the same effect can be obtained by connecting a low-pass filter to the input side of the amplifier 23 instead.
First Embodiment FIG. 5 is a block diagram of a piezoelectric chopper driving circuit of the first embodiment according to the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to what makes the same effect | action as the 1st structural example shown in FIG.
[0028]
The first embodiment is different from the first configuration example in the accuracy of control of the voltage applied to the element.
[0029]
Specifically, the circuit block diagram of FIG. 5 is the same as the first configuration example described above, but in the present embodiment, the applied voltage pattern controlled by the arithmetic unit 25 is checked in advance at the time of startup. This corresponds to the element displacement behavior pattern, which is stored in the arithmetic unit 25 and used.
[0030]
A method for determining a signal to be actually stored in the arithmetic unit 25 will be described.
[0031]
First, the element is driven uncontrolled to obtain the starting characteristics when not controlled. An example of the starting characteristic at that time is shown in FIG.
[0032]
Next, based on this starting characteristic, an applied signal shown in FIG. 7 is created so that the displacement characteristic of the piezoelectric chopper becomes constant at the time of starting.
[0033]
Then, the applied signal (see FIG. 7) is stored in a storage unit (not shown) of the arithmetic device 25, and when the bimorph element 24 is activated, control is performed so as to be the same signal as the pattern storing the signal of the shaping circuit 22. Then, by amplifying and applying the drive signal to the element, excellent starting characteristics can be ensured.
[0034]
In the present embodiment, the case where the element is checked element by element and the displacement behavior pattern at the time of activation is obtained has been described, but not limited to this, for example, for each production lot, for each same type as a group, A displacement behavior pattern of representative elements of the group may be obtained and represented.
Second Embodiment FIG. 8 is a block diagram of a piezoelectric chopper driving circuit of the second embodiment according to the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to what makes the same effect | action as 1st Embodiment shown in FIG.
[0035]
In the first embodiment described above, the vibration behavior of the element is stored in advance in the arithmetic unit, and the applied voltage is controlled based on the behavior. In the second embodiment, the element is driven at the time of driving. The vibration behavior is detected, and the applied voltage is controlled based on the detection result.
[0036]
Specifically, as shown in FIG. 8, a capacitive element 27 having the same electric capacity as that of the bimorph element 24 is connected in parallel, the bimorph element 24 and the capacitive element 27 are connected by a resistor 30, and Both ends are grounded by resistors 28 and 29. In this configuration, the voltage across the resistor 30 or the current flowing through the resistor 30 is detected, and the boosting ratio of the amplifier 23 is controlled by the control circuit 31 based on this.
[0037]
Usually, the vibration behavior of the element and the strain amount of the piezoelectric ceramic maintain a certain relationship. Further, there is a proportional relationship between the strain amount of the piezoelectric ceramic and the amount of electric charge (current flowing through the piezoelectric ceramic) applied to the electrodes of the piezoelectric ceramic. Therefore, there is a certain relationship between the vibration behavior of the element and the current flowing through the piezoelectric ceramic.
[0038]
However, the current that flows through the piezoelectric ceramic is divided into a current that contributes to the distortion of the piezoelectric ceramic called mechanical arm current and a current that flows through the capacitive element portion of the piezoelectric ceramic called electric arm current. Detection of arm current is required.
[0039]
Therefore, in the configuration of the present embodiment, the electric arm current is caused to flow to the capacitive element 27 side by connecting in parallel the capacitive element 27 having the same capacitance as that of the bimorph type element 24. Further, since the mechanical arm current + electrical arm current flows on the bimorph element 24 side, the mechanical arm current flows through the resistor 30. The mechanical arm current change is converted into a voltage change by the resistor 30 and input to the control circuit 31.
[0040]
With the above configuration, it is possible to improve the chopper start-up characteristics by detecting the vibration state of the element and controlling the applied voltage with high accuracy without adding a new sensor for detecting vibration. .
[ Third Embodiment] FIG. 9 is a block diagram showing an example of a piezoelectric chopper drive circuit according to a third embodiment of the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to what makes the same effect | action as 1st Embodiment shown in FIG.
[0041]
In the first embodiment, the vibration behavior of the element is stored in advance in the arithmetic device, and the applied voltage is controlled based on the behavior. In the third embodiment, the vibration of the element is driven during driving. The behavior is detected and the applied voltage is controlled.
[0042]
Specifically, a sensor electrode 40 is provided on a part of the surface electrode of the bimorph element 24, and the voltage applied to the element is controlled based on the electric charge generated at the sensor electrode 40.
[0043]
Usually, the vibration behavior of the element and the strain amount of the piezoelectric ceramic maintain a certain relationship. In addition, the amount of strain of the piezoelectric ceramic and the charge generated on the piezoelectric ceramic surface electrode (sensor electrode) have a proportional relationship. Therefore, a constant relationship is maintained between the vibration behavior of the element and the charge generated in the piezoelectric ceramic sensor electrode 40.
[0044]
Therefore, in the configuration of the present embodiment, the sensor electrode 40 is formed on a part of the surface electrode of the bimorph element 24, the electric charge (voltage) generated at the electrode is input to the control circuit 31, and the amplifier is based on the input. With the above configuration controlling the step-up ratio of 23, the chopper can be started up by detecting the vibration state of the element and controlling the applied voltage with high accuracy without adding a new sensor for detecting vibration. It is possible to improve the characteristics.
[0045]
FIG. 10 is a diagram showing a first example of sensor electrodes of the piezoelectric chopper.
[0046]
Specifically, the electrode on the surface side of the piezoelectric ceramic 11 attached to the driving unit is divided into three parts in the width direction (the central part is equal to or less than 1/3 of the whole and the two ends are equal in area). The center electrode is referred to as a sensor electrode 40, and the electrodes at both ends are referred to as drive electrodes 41.
[0047]
Piezoelectric ceramics generate strain when a charge is applied. It is the drive electrode 41 that uses this effect to drive the chopper. However, the opposite effect occurs at the same time. That is, if the strain is applied to the piezoelectric ceramic, a charge is generated in the surface electrode. The sensor electrode 40 utilizes this phenomenon, and can detect the state of vibration.
[0048]
By arranging the sensor electrode 40 in a well-balanced manner with a necessary minimum area, the sensor electrode 40 is prevented from becoming more than necessary for a driving load, and torsional vibration is prevented from being excited in the element.
[0049]
Similarly, FIG. 11 is a diagram illustrating a second example of the sensor electrode of the piezoelectric chopper. The positions of the sensor electrode 40 and the drive electrode 41 are different from those in FIG.
[0050]
Specifically, the electrode on the surface side of the piezoelectric ceramic 11 attached to the driving unit is divided into three parts in the width direction (the central part is 1/2 or more of the whole and the two end parts are equal in area). The central electrode is referred to as a driving electrode 41, and the electrodes at both ends are referred to as a sensor electrode 40.
[0051]
In addition to the same effects as in FIG. 10, the sensor electrode 40 can be used instead of the piezoelectric ceramic electrode that is usually required to improve moisture resistance by providing the sensor electrode 40 on both sides of the drive electrode 41. The driving area can be increased.
[0052]
It should be noted that there is no problem even if the sensor electrode 40 is divided in the length direction, and the number of divisions need not be limited to three.
[ Fourth Embodiment] FIG. 12 is a block diagram showing an example of a piezoelectric chopper drive circuit according to a fourth embodiment of the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to what makes the same effect | action as the 1st structural example shown in FIG.
[0053]
In the first configuration example , the level of the voltage applied to the element is controlled. However, the fourth embodiment is different in that the frequency of the signal applied to the element is controlled.
[0054]
More specifically, an oscillator group 32 including an arithmetic device 25 and two or more oscillators (here, three) is added to the oscillation circuit 21, and the oscillator is switched by the arithmetic device 25, so that the frequency of the drive signal is set at the time of startup. It changes with time.
[0055]
Further, as shown in FIG. 13, the driving frequency at the time of start-up is set to a frequency slightly closer to the driving frequency side than the resonance of the amplitude enlargement unit, and the arithmetic unit 25 gradually shifts to the original driving point frequency. To work. Thereby, only the resonance vibration of the amplitude expanding portion is excited at the time of startup, and gradually shifts to the vibration of the target frequency, so that the runaway phenomenon at the time of startup can be suppressed. FIG. 14 shows an example of the element displacement behavior result at the start-up according to this embodiment.
[0056]
With the above configuration, it is possible to remarkably improve the starting characteristics of the piezoelectric chopper as compared with the prior art.
[0057]
In this embodiment, the drive frequency is shifted from a frequency slightly closer to the drive frequency than the resonance of the amplitude expansion unit, but is shifted from a frequency slightly closer to the drive frequency than the resonance of the drive unit. However, the same effect can be obtained.
[ Fifth Embodiment] FIG. 15 is a block diagram showing an example of a piezoelectric chopper drive circuit according to a fifth embodiment of the present invention. In the following description, the same reference numerals are used for the same functions as those in the fourth embodiment shown in FIG.
[0058]
The fifth embodiment differs from the fourth embodiment in that a variable frequency oscillator 33 is provided in place of the arithmetic unit and the oscillator group.
[0059]
Specifically, a frequency variable oscillator 33 such as a VCO is used as the oscillator of the oscillation circuit 21. Thus variable frequency oscillator 33 is capable of controlling the frequency of the external from the output signal, it is possible to realize the same operation as the fourth embodiment, therefore, the same effect as the fourth embodiment can be obtained.
FIG. 16 is a diagram showing a first example of the configuration of the piezoelectric chopper in the third configuration example of the invention related to the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to what performs the same effect as the prior art example shown in FIG. Here, the bimorph element has a cantilever structure having a drive unit 10a having a piezoelectric ceramic 11 and an amplitude expansion unit 10b which is a displacement expansion unit, and the pedestal 13 and the fixture 14 constitute a holder. . This third configuration example is different in resonance characteristics from the conventional example.
[0060]
Specifically, in the chopper configuration of FIG. 16, the element size is determined so that the resonance resistance of the drive unit 10a is at least twice as large as the resonance resistance of the amplitude enlargement unit 10b, thereby increasing the amplitude of the drive unit 10a. In the drive with the predetermined drive frequency with the unit 10b, the resonance vibrations of the drive unit and the amplitude expansion unit that have been excited as unnecessary vibrations in the past are generated by the resonance vibration of the drive unit and the amplitude expansion unit with a very small amplitude. Resonant vibration. As a result, the influence of the resonance vibration of the amplitude expanding portion is almost eliminated, and the vibration of the drive frequency and the vibration of the resonance vibration of the drive portion are almost the same as when excited at startup.
[0061]
As a result, without adding a new control circuit, as shown in FIG. 19, a more stable start-up characteristic is exhibited as compared with the conventional start-up characteristic. FIG. 18 shows an example of the resonance characteristics of the configuration of this configuration example .
[0062]
FIG. 17 shows an example of another configuration for realizing this resonance characteristic. The difference from FIG. 16 is the coupling part of the driving part 10a and the amplitude enlarging part 10b.
[0063]
Specifically, the resonance resistance of the amplitude expanding portion 10b is increased by reducing the width of the connecting portion, weakening the bending rigidity of the connecting portion, and making the fundamental mode vibration of the amplitude expanding portion 10b less likely to occur. .
[0064]
In addition, the bending rigidity is reduced by forming a slit or reducing the plate thickness without reducing the width of the coupling portion, and the same effect can be obtained.
[0065]
Further, the same effect can be obtained by increasing the mass of the shielding plate 12 attached to the free end of the amplitude expanding portion 10b so that the fundamental mode vibration of the amplitude expanding portion 10b is less likely to occur .
FIG. 20 is a diagram showing a first example of the piezoelectric chopper configuration in the fourth configuration example of the invention related to the present invention. In the following description, the same reference numerals are given to the same components as those in the third configuration example shown in FIG.
[0066]
The fourth configuration example is different in resonance characteristics from the third configuration example .
[0067]
Specifically, in the chopper configuration of FIG. 20, as shown in FIG. 22, by determining the element dimensions so that the resonance resistance of the drive unit 10a is at least twice as large as the resonance resistance of the amplitude expansion unit 10b. Even in the drive at a predetermined drive frequency between the drive unit 10a and the amplitude expansion unit 10b, the resonance vibration of the drive unit and the amplitude expansion unit that has been conventionally excited as unnecessary vibration is significantly different from the resonance vibration of the amplitude expansion unit. Resonant vibration of the drive unit having a small amplitude.
[0068]
As a result, the influence of the resonance vibration of the drive unit is almost eliminated, and the vibration of the drive frequency and the vibration of the resonance vibration of the amplitude expansion unit are almost the same as when excited at startup.
[0069]
With the above configuration, the same effect as the third configuration example can be obtained, and at the same time, the resonance resistance of the drive unit 10a is increased, so that the vibration of the drive unit 10a during driving can be suppressed to a small level. The strain applied to the adhesive layer can be reduced, and the reliability of the element can be improved.
[0070]
FIG. 21 shows an example of another configuration for realizing this resonance characteristic. The difference from FIG. 16 is that the distance from the end of the piezoelectric ceramic 11 of the drive unit 10a to the fixture 14 is increased. Thereby, the fundamental mode vibration of the drive unit 10a is less likely to occur, and the resonance resistance of the drive unit 10a is increased.
[0071]
Note that a slit is formed on the elastic shim material 10 between the end of the piezoelectric ceramic 11 and the fixture 14 without increasing the distance from the end of the piezoelectric ceramic 11 to the fixture 14, or the end of the piezoelectric ceramic 11. Or a portion between the fixture 14 and the pedestal 13 that sandwiches at least the elastic shim material 10 is made of a material having a small Young's modulus such as silicon or natural rubber. This makes it difficult for fundamental mode vibration to occur, and the same effect can be obtained.
[0072]
Further, the same effect can be obtained by increasing the mass of the amplitude expanding portion 10b and the shielding plate 12 so that the fundamental mode vibration of the driving portion 10a is less likely to occur.
[0073]
With the above configuration, the starting characteristics of the piezoelectric chopper can be improved, and the high-speed temperature measurement function of the pyroelectric infrared sensor can be improved. Furthermore, since the piezoelectric chopper is immediately stabilized after the activation, there is almost no power consumption loss at the time of activation as in the prior art, and the battery life can be extended by reducing the power consumption.
[0074]
【The invention's effect】
As is clear from the above description, the present invention applies the drive signal while changing the voltage level of the drive signal to a predetermined level with the passage of time when the piezoelectric chopper is started. It has the advantage that improvement in power consumption and reduction in power consumption are possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of a piezoelectric chopper drive circuit in a first configuration example of the present invention.
FIG. 2 is a diagram showing an example of an output voltage obtained by changing a device applied voltage in a linear function by the piezoelectric chopper drive circuit in the first configuration example of the present invention.
FIG. 3 is a diagram illustrating an example of a result of driving a piezoelectric chopper by the piezoelectric chopper driving circuit according to the first configuration example of the present invention.
FIG. 4 is a block diagram showing an example of a piezoelectric chopper drive circuit in a second configuration example of the present invention.
5 is a block diagram showing an example of the piezoelectric chopper drive circuit in the first embodiment of the present invention.
6 is a diagram showing a driving result when the piezoelectric chopper is not controlled in the first embodiment; FIG.
7 is a diagram showing an example of the applied signal of the piezoelectric chopper in the first embodiment.
FIG. 8 is a block diagram illustrating an example of a piezoelectric chopper drive circuit according to a second embodiment of the present invention.
FIG. 9 is a block diagram illustrating an example of a piezoelectric chopper drive circuit according to a third embodiment of the present invention.
FIG. 10 is a diagram illustrating a first example of sensor electrodes of the piezoelectric chopper according to the third embodiment.
FIG. 11 is a diagram showing a second example of the sensor electrode of the piezoelectric chopper according to the third embodiment.
FIG. 12 is a block diagram illustrating an example of a piezoelectric chopper drive circuit according to a fourth embodiment of the present invention.
FIG. 13 is an operation explanatory diagram of the piezoelectric chopper drive circuit according to the fourth embodiment.
FIG. 14 is a diagram showing an example of a result of driving a piezoelectric chopper by the piezoelectric chopper drive circuit according to the fourth embodiment.
FIG. 15 is a block diagram illustrating an example of a piezoelectric chopper drive circuit according to a fifth embodiment of the present invention.
FIG. 16 is a diagram showing a first example of a configuration of a piezoelectric chopper in a third configuration example of the present invention.
FIG. 17 is a diagram showing a second example of the piezoelectric chopper configuration in the third configuration example .
FIG. 18 is a diagram showing an example of resonance characteristics of the piezoelectric chopper in the third configuration example .
FIG. 19 is a diagram showing an example of a result of driving the piezoelectric chopper in the third configuration example .
FIG. 20 is a diagram showing a first example of a piezoelectric chopper configuration in a fourth configuration example of the present invention.
FIG. 21 is a diagram showing a second example of the piezoelectric chopper configuration in the fourth configuration example .
FIG. 22 is a diagram showing an example of resonance characteristics of the piezoelectric chopper in the fourth configuration example .
FIG. 23 is a diagram illustrating an example of a configuration of a conventional piezoelectric chopper.
FIG. 24 is a diagram illustrating an example of a relationship between a driving frequency and a displacement amount of a conventional piezoelectric chopper.
FIG. 25 is a diagram illustrating an example of a result of driving a conventional piezoelectric chopper.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Elastic shim material 10a Drive part 10b Amplitude expansion part 11 Piezoelectric ceramic 12 Shield plate 13 Base 14 Fixture 15 Infrared detection part 16 Infrared ray 21 Oscillation circuit 22 Shaping circuit 23 Amplifier 24 Bimorph type element 25 Arithmetic devices 26, 28, 29, 30 Resistor 27 Capacitor 31 Control circuit 32 Oscillator group 33 Frequency variable oscillator

Claims (7)

A bimorph element having a cantilever structure having a drive part made of an elastic body and a piezoelectric body and a displacement enlargement part made only of an elastic body, a holder for holding the bimorph element, and a tip of the displacement enlargement part, A method of driving a piezoelectric chopper comprising a shielding member for incident / blocking infrared rays, wherein the voltage level of the driving signal is reversed from the fluctuation of the movement of the tip of the displacement expanding portion when the piezoelectric chopper is activated. The method of driving a piezoelectric chopper for a pyroelectric infrared sensor, wherein the driving signal is applied in such a manner as to change. 2. The method of driving a piezoelectric chopper for a pyroelectric infrared sensor according to claim 1 , wherein the voltage level change of the drive signal applied at startup is performed based on a previously determined change pattern at startup. The voltage level change of the driving signal to be applied on startup, said detects a change in current flowing to the bimorph element, pyroelectric infrared sensor piezoelectric chopper of claim 1, characterized in that depending on the detected current change Driving method. The piezoelectric body has a sensor electrode for detecting a voltage change, and the voltage level change of the drive signal applied at the time of starting is performed based on the voltage change detected by the sensor electrode. The method of driving a piezoelectric chopper for a pyroelectric infrared sensor according to claim 1 . A bimorph element having a cantilever structure having a drive part made of an elastic body and a piezoelectric body and a displacement enlargement part made only of an elastic body, a holder for holding the bimorph element, and a tip of the displacement enlargement part, A method for driving a piezoelectric chopper comprising a shielding member for incident / blocking infrared rays, wherein when the piezoelectric chopper is activated, the driving frequency of the driving signal is increased with time, in the vicinity of the resonance frequency of the driving unit, or A method of driving a piezoelectric chopper for a pyroelectric infrared sensor, wherein the driving signal is applied while moving from a vicinity of a resonance frequency of the displacement enlarging unit to a predetermined driving frequency. 6. The method of driving a piezoelectric chopper for a pyroelectric infrared sensor according to claim 5 , wherein movement of the drive frequency of the drive signal applied at startup is performed based on a predetermined function. 6. The method of driving a piezoelectric chopper for a pyroelectric infrared sensor according to claim 5 , wherein movement of the drive frequency of the drive signal applied at startup is performed using a variable frequency oscillator.

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