JP2003168832A - Method for inspecting piezoelectric transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that 100% inspection process of temperature rise measurement of a piezoelectric transformer having possibility of abnormal temperature rise is impossible in a mass production line because a long inspection time is required, and to provide an inspection method being carried out conveniently in a short time in the inspection process thus ensuring high degree quality control economically. <P>SOLUTION: In the inspection system for measuring the conductance of a piezoelectric transformer performing voltage conversion through means for holding the piezoelectric transformer, conductance of the piezoelectric transformer is measured at the resonance frequency thereof and saturation temperature rise of the piezoelectric transformer is estimated after continuous driving thereof thus performing efficient inspection in a short period of time. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a piezoelectric transformer inspection method.

[0002]

2. Description of the Related Art A conventional power conversion device using a piezoelectric transformer is disclosed in, for example, Japanese Patent Laid-Open No. 2000-216450.

In Japanese Patent Laid-Open No. 2000-216450, since the drive frequency at which the maximum conversion efficiency of the piezoelectric transformer is maximized substantially coincides with the frequency at which the phase of admittance is minimized, the piezoelectric transformer driving device described above The drive frequency of the transformer is set so as to track the lowest phase frequency, and the piezoelectric transformer is driven with the maximum conversion efficiency even if the frequency changes during driving.

[0004]

However, the conventional Japanese Unexamined Patent Publication No. 2000-216450 discloses a piezoelectric transformer driving circuit which is driven at a driving frequency which maximizes the conversion efficiency of the input-output characteristics of the piezoelectric transformer. However, even if the piezoelectric transformer is driven at a driving frequency that maximizes the conversion efficiency of the input-output characteristics, the individual input-
Since there is a large variation in the conversion efficiency of the output characteristics, a piezoelectric transformer with poor conversion efficiency of the input-output characteristics is mounted in the drive circuit to drive at a drive frequency that maximizes the conversion efficiency, but a high set output voltage is required. In that case, a high input voltage is required.

If the conversion efficiency of the input-output characteristics of the piezoelectric transformer is poor, the piezoelectric transformer will have an abnormal temperature rise. Therefore, there is a problem in that it is not possible to prevent an abnormal temperature rise, which is one of the factors that damage the piezoelectric transformer, by simply driving the piezoelectric transformer at a driving frequency that maximizes conversion efficiency. .

Further, in order to select all defective products which have an abnormal temperature rise by a single piezoelectric transformer, it is necessary to measure the temperature rise individually, which requires a long measurement time and cannot be selected in a mass production inspection process. Until now, it has not been technically or economically feasible.

The present invention solves the above-mentioned conventional problems, and the temperature of the piezoelectric transformer is measured by the conductance value at the resonance frequency of the piezoelectric transformer without measuring the temperature rise of the piezoelectric transformer. By making it possible to estimate the rise, it is possible to easily remove a defective product that causes an abnormal rise in the temperature of the piezoelectric transformer in a short time in the mass production inspection process, and to provide an inspection method that is economically efficient and enables advanced quality control of all products. Is intended.

[0008]

In order to solve the above-mentioned problems, the first aspect of the present invention is to provide a piezoelectric transformer for performing voltage conversion, through a piezoelectric transformer holding means for measuring and holding the piezoelectric transformer, and a conductance value of the piezoelectric transformer. In the inspection device for measuring, the conductance value of the piezoelectric transformer at the resonance frequency of the piezoelectric transformer is measured, and the saturation temperature rise value of the continuously driven piezoelectric transformer is estimated.

As described above, in the mass production inspection process of the piezoelectric transformer, it is not possible to take a lot of time to perform a 100% measurement inspection of temperature rise, and a saturation temperature rise is performed from the conductance value of the piezoelectric transformer at the resonance frequency of the piezoelectric transformer. By estimating the value, it is possible to easily perform 100% measurement inspection in a short time.

According to a second aspect of the present invention, the means for holding the piezoelectric transformer allows the lead terminal on the primary side, which is attached at a position serving as a node of vibration when the piezoelectric transformer vibrates, to be inserted / removed vertically downward. If it has a socket and a part that supports the secondary side that serves as a node of vibration, since it supports the no-displacement node part of the vibrating piezoelectric transformer, the vibration of the part that is supported is There is no influence, and the conductance value of the piezoelectric transformer can be measured with high accuracy at the resonance frequency of the piezoelectric transformer.

Further, because of the socket structure, the piezoelectric transformer can be easily inserted and removed in a short time.

According to a third aspect of the present invention, if the means for holding the piezoelectric transformer is made of a material having a low relative dielectric constant, the holding means does not affect the resonance frequency of the piezoelectric transformer. The conductance value of the piezoelectric transformer can be measured with high accuracy.

According to a fourth aspect of the present invention, the threshold value for determining the temperature rise failure of the piezoelectric transformer is a temperature at which the saturation temperature rise value of the piezoelectric transformer rapidly rises, and the conductance value of the piezoelectric transformer at the temperature is set. By setting the threshold value, it is possible to determine the piezoelectric transformer in which the conversion efficiency of the piezoelectric transformer is poor and the loss is large.

According to a fifth aspect of the present invention, since the measurement point of the saturation temperature rise of the piezoelectric transformer is a node of vibration of the piezoelectric transformer, the stress of vibration concentrates on the node, so that the maximum saturation temperature is reached. The rise value can be measured, a wide measurement range can be obtained, and inspection can be performed with high accuracy.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a structural diagram of the piezoelectric transformer, FIG. 2 is a piezoelectric transformer inspection device, FIG. 3 is a measurement variation due to a material difference of the piezoelectric transformer holding means, and FIG. 4 is a primary-side maximum conductance characteristic at the resonance frequency of the piezoelectric transformer. Fig. 5 is a characteristic diagram of the maximum conductance-saturation temperature rise value of the piezoelectric transformer,
FIG. 6 is an inspection flowchart of the piezoelectric transformer.

FIG. 1 shows the structure of a Rosen type piezoelectric transformer. The piezoelectric transformer 1 is composed of a thin plate-shaped piezoelectric vibrator, and on the surface thereof, a primary side lead 2 connected to an input electrode and a secondary side output lead 3 connected to an output electrode are provided. For the voltage conversion of the piezoelectric transformer 1, when an input voltage 14 matching the resonance frequency of the secondary side mechanical vibration is applied to the primary side 4 of the piezoelectric transformer 1 as an electric energy, ten dozen volts is applied between the primary side leads 2. , The piezoelectric energy is applied to the applied electric energy, that is, the polarization direction 8 on the primary side of the applied electric field and the displacement direction 9 on the primary side are displaced in a direction perpendicular to each other, so that the stretching vibration in the longitudinal direction is generated. Converted to energy. At the same time, the elastic energy of this stretching vibration propagates in the longitudinal direction through the entire piezoelectric transformer, and on the output side of the secondary side 5 of the piezoelectric transformer 1, the piezoelectric longitudinal effect, that is, the secondary direction parallel to the displacement direction 11 on the secondary side. By generating an electric flux in the polarization direction 10 on the side, the secondary side output 3 is converted into electric energy and a high voltage output of several thousand hundreds of volts is obtained on the secondary side 5 of the piezoelectric transformer without load.

FIG. 2 shows a piezoelectric transformer inspection apparatus according to the present invention. The structure for holding the piezoelectric transformer 1 in the inspection apparatus is to hold the piezoelectric transformer 1 in a vertically downward direction with a socket 15 provided on the piezoelectric transformer holding means 18 into which the piezoelectric transformer 1 can be inserted and removed. The position of the socket 15 where the piezoelectric transformer 1 is fixed is determined by the vibration node 6 on the primary side 4 of the piezoelectric transformer 1 when vibrating.
The size is the same as the dimension between the primary-side leads 2 attached at the positions such that the shape of the leads does not change, and there is no play in fitting, and the dimension is maintained in the vertical downward direction.
The piezoelectric transformer 1 has a portion 17 for supporting the vibration node 7 on the piezoelectric transformer secondary side 5, and the piezoelectric transformer 1 includes two primary side leads 2 of the socket 15 and the piezoelectric transformer secondary side 5. As the three-point support of the portion 17 supporting the vibration node 7, the piezoelectric transformer 1 is made to have a uniform residual stress without being tilted, and the measurement accuracy of the inspection device is improved to be stably held.

Next, the electrical connection between the piezoelectric transformer 1 and the primary side maximum conductance measuring device 20 at the resonance frequency is provided with the primary side lead portion 2 of the piezoelectric transformer 1 on the piezoelectric transformer holding means 18. By being inserted into the socket 15, it is electrically connected to the socket terminal 16. The test pin 19 of the primary side maximum conductance measuring device 20 at the resonance frequency is brought into contact with the socket terminal 16 under the piezoelectric transformer holding means 18 to electrically connect to the primary side maximum conductance measuring device 20 at the resonance frequency. It is connected. In the structure for holding the piezoelectric transformer 1, the socket 15 electrically connected to the test pin 19 of the maximum conductance inspection device 20 has a relative permittivity because the outer shell minimizes the stray capacitance between the sockets 15. It is composed of an insulator such as hard ENVI, which has a low level of 2.3 to 3.6. Then, the inner surface of the socket 15 becomes a hollow socket terminal covered with a conductor such as copper, and the primary side lead 2 and the test pin 19 of the maximum conductance inspection device 20.
Electrically connected to. Further, the portion 17 supporting the vibration node 7 on the secondary side 5 of the piezoelectric transformer 1 does not hinder the vibration, and the vibration node 7 on the secondary side 5 of the piezoelectric transformer 1 does not interfere.
The contact with is configured to be a point contact.

Explaining the piezoelectric transformer of the present invention, the material is lead zirconate titanate, and the outer shape is 50 mm (length).
* 13mm (height) * 2mm (thickness), 5 secondary side
The secondary output 3 has a voltage of about 7KV and a frequency of about 72k.
A high voltage of Hz can be obtained.

As described above, since a high voltage is generated on the secondary side 5 of the piezoelectric transformer 1, the material of the portion 17 supporting the lower portion of the vibration node 7 on the secondary side 5 has a dielectric strength of 17 to Fifty
It is composed of an insulator such as hard ENVI having a high kV / mm and a low relative dielectric constant of 2.3 to 3.6. The table on which the piezoelectric transformer holding means 18 is placed has an outer shape of 60 mm (length)
* 30 mm (width) * 3 mm (height), the material is highly insulating, is not easily affected by stray capacitance, and has a dielectric strength of 17-
It is composed of an insulator such as hard ENVI, which has a high relative dielectric constant of 2.3 to 3.6 and is as high as 50 kV / mm.

FIG. 3 shows the measurement variation due to the material difference of the piezoelectric transformer holding means of the embodiment according to the present invention. When the material of the holding means is hard ENVI and urea resin, the maximum conductance of the same piezoelectric transformer is repeatedly measured by the inspection device. The 3σ _n-1 representing the variation is 0.28 mS for hard ENVI. On the other hand, the dielectric strength is 7.2 to 10.5 kV / mm and the relative permittivity is 5 to 7 for urea resin, which is 0.69 mS. By configuring the piezoelectric transformer holding means 18 with an insulator such as hard ENVI, when the piezoelectric transformer 1 is driven at a frequency of 72 kHz and a high output voltage of about 7 kV is generated, measurement by the frequency component is performed. A highly reliable inspection device is constructed so that it is less susceptible to the coupling of stray capacitance of the system and the inspection device is less affected by the installation environment.

FIG. 4 shows the primary side maximum conductance characteristic at the resonance frequency of the piezoelectric transformer primary side.

In obtaining the primary side maximum conductance value 21 at the resonance frequency of the primary side 4 of the piezoelectric transformer 1, an impedance analyzer is used for the primary side maximum conductance measuring device 20 at the resonance frequency, and the primary side of the piezoelectric transformer 1 is used. The measurement terminal of the impedance analyzer is connected to the side 4, and the primary resonance section 2 of the piezoelectric transformer 1 has a characteristic resonance frequency of 72 kHz of the piezoelectric transformer 1.
Conductance of FIG. 4 obtained by applying a voltage whose frequency is swept from 67 kHz to 77 kHz around z.
Regarding the frequency characteristic, the primary-side maximum conductance value 21 at the resonance frequency is obtained from the resonance characteristic of FIG.

Since the primary-side maximum conductance value 21 at the resonance frequency is a condition for impedance matching when the piezoelectric transformer resonates, the impedance has a minimum value at the resonance frequency. That is, the conductance of the admittance component becomes the maximum value.

FIG. 5 shows a characteristic diagram of the maximum conductance-saturation temperature rise value on the primary side of the piezoelectric transformer.

The above characteristic diagram is a characteristic diagram in which the saturation temperature rise value corresponding to the primary side maximum conductance 21 at the resonance frequency of each piezoelectric transformer 1 is obtained. In determining the saturation temperature rise value, the measurement point of the saturation temperature rise of the Rosen type piezoelectric transformer 1 is the vibration in which the vibration of the piezoelectric transformer is one wavelength in the piezoelectric transformer length 12 in the mechanical displacement direction 12 of the piezoelectric transformer 1. In the piezoelectric transformer 1 that is vibrating in the λ mode (secondary resonance mode), since there is no vibration displacement and the stress becomes maximum, the saturation temperature rises at the nodes 6 and 7 of the vibration on the primary side and the secondary side. Is a large measurement point.

The electric energy applied to the primary side of the piezoelectric transformer 1 causes a piezoelectric transverse effect, that is, a displacement in the direction perpendicular to the applied electric field, to cause extensional vibration in the longitudinal direction. Converted to energy.

The elastic energy of the stretching vibration propagates in the longitudinal direction through the entire piezoelectric transformer, and the vibration 11 on the secondary side is converted into electric energy by the generation of an electric flux parallel to the piezoelectric longitudinal effect, that is, the displacement on the output side. It Considering the energy conversion loss of the primary side and the secondary side, the primary side where the electric field and displacement are perpendicular becomes larger. As a result, the measurement point of the saturation temperature rise of the piezoelectric transformer 1 is the node 6 of the primary side vibration. Next, in measuring the temperature, in order to eliminate the influence of vibration of the piezoelectric transformer 1 of the measuring device,
The measurement is performed with a non-contact type thermal imager. The measurement is performed until the temperature rise of the piezoelectric transformer 1 becomes saturated. At that time, as a temperature measurement condition, the input voltage 14 of the piezoelectric transformer primary side 4 and the output voltage of the piezoelectric transformer secondary side 5 of each piezoelectric transformer 1 are the same. By performing the temperature measurement as described above, the amount of temperature rise can be made large, the variation due to the temperature measurement can be reduced, and the accuracy of the temperature measurement can be improved.

The primary-side maximum conductance measuring device 20 at the resonance frequency measures the primary-side maximum conductance value 21 at the resonance frequency of the piezoelectric transformer 1, and the saturation temperature rise value of the continuously driven piezoelectric transformer 1 is shown in FIG. It is estimated from the characteristic diagram of the maximum conductance-saturation temperature rise value on the primary side of the piezoelectric transformer shown in FIG. 1, and the characteristic diagram shows the maximum conductance value 21 on the primary side at each resonance frequency of the piezoelectric transformers 1 and their respective saturation values. The data of the temperature rise value is obtained and is shown in the characteristic table and the regression curve.

As a result of the above, those having a low conductance are
It can be seen that the conversion efficiency of the piezoelectric transformer 1 is poor, and although the loss is large and the current increases, it becomes heat and the saturation temperature rises rapidly. G (conductance) that has the strongest correlation with the maximum saturation temperature rise value of the piezoelectric transformer 1 is adopted.

In addition to the primary-side maximum conductance 21 at the resonance frequency of the primary side 4 of the piezoelectric transformer 1, the mechanical-electrical coupling coefficient of the primary side 4 of the piezoelectric transformer 1 is obtained as a correlation with temperature rise. Capacitor capacitance value, susceptance value, or machine on the secondary side 5 of the piezoelectric transformer 1.
-It was verified by assuming the relationship between the electrical coupling coefficient, the capacitance value of the capacitor, the conductance value, the susceptance value and the temperature rise, but the correlation was weaker than the conductance value of the primary side 4 of the piezoelectric transformer 1.

In FIG. 5, the threshold value for judging the temperature rise failure in the piezoelectric transformer 1 is the temperature 22 at which the temperature rise at the resonance frequency of the piezoelectric transformer 1 sharply rises.
The primary side conductance value 23 at which the temperature rise at the resonance frequency of the piezoelectric transformer of the piezoelectric transformer 1 rapidly rises.
Is the threshold.

That is, the electric characteristics of the piezoelectric transformer, which has an abnormal temperature rise due to the poor energy conversion efficiency, are measured without measuring the saturation temperature rise in which the temperature rise is constant at the resonance frequency of each piezoelectric transformer 1. The primary side maximum conductance 21 at the resonance frequency of the piezoelectric transformer 1 may be measured by paying attention to the conductance, which is one of the above, as the original data for discriminating the piezoelectric transformer having an abnormal temperature rise. it can.

FIG. 6 shows a flow chart for inspecting the temperature rise defect of the piezoelectric transformer 1. In FIG. 6, first, S1
At 01, the primary side maximum conductance measuring device 20 at the resonance frequency measures the primary side maximum conductance value 21 at the resonance frequency of the piezoelectric transformer 1. Next, in S102, it is determined whether the measured value 21 is 15 mS or less, which is a conductance threshold value of 23 or less on the primary side conductance value at which the temperature rise at the resonance frequency of the piezoelectric transformer rapidly increases. If the result in S102 is affirmative, the process proceeds to S104, in which a defective temperature rise product is output. If the result in S102 is negative, the process proceeds to S103, in which a temperature rise normal product is output. As described above, by using the present inspection device, the piezoelectric transformer having an abnormal temperature rise does not require the measurement inspection of the temperature rise, which takes a lot of time in the 100% inspection process of the piezoelectric transformer and is impossible in the mass production process, By performing 100% measurement and inspection only on the conductance value at the resonance frequency of the piezoelectric transformer, it is possible to easily detect a defective product that causes an abnormal temperature rise of the piezoelectric transformer in a short time.

[0036]

Since the present invention is constructed as described above,
For all the piezoelectric transformers that cause abnormal temperature rise, it takes a lot of time in the inspection process of all the piezoelectric transformers, and the conductance value at the resonance frequency of the piezoelectric transformer is all Providing an unprecedented inspection method that can easily remove defective products that cause abnormal temperature rise of the piezoelectric transformer in a short time by measuring and inspecting, which is extremely economical and enables high quality control. can do.

[Brief description of drawings]

FIG. 1 is a structural diagram of a piezoelectric transformer according to an embodiment of the present invention.

FIG. 2 is a piezoelectric transformer inspection device according to an embodiment of the present invention.

FIG. 3 is a measurement variation due to a material difference of a piezoelectric transformer holding means of an embodiment according to the present invention.

[Fig. 4] Primary-side maximum conductance characteristic diagram at the resonance frequency of the piezoelectric transformer

FIG. 5: Primary-side maximum conductance-saturation temperature rise value characteristic diagram of the piezoelectric transformer

FIG. 6 is an inspection flowchart of a piezoelectric transformer according to an embodiment of the present invention.

[Explanation of symbols]

1: Piezoelectric transformer 2: Primary side lead 3: Secondary side output 4: Piezoelectric transformer primary side 5: Piezoelectric transformer secondary side 6: Primary side vibration node 7: Secondary side vibration node 8: Primary side Polarization direction 9: Primary side displacement direction 10: Secondary side polarization direction 11: Secondary side vibration direction 12: Mechanical displacement direction 13: Stress 14: Input voltage 15: Socket 16: Socket terminal 17: Secondary Side supporting portion 18: Piezoelectric transformer holding means 19: Test pin 20: Primary side maximum conductance measuring device at resonance frequency 21: Primary side maximum conductance at piezoelectric transformer resonance frequency 22: Temperature at piezoelectric transformer resonance frequency Temperature 23 at which the temperature rises rapidly: Primary-side conductance value at which the temperature rises sharply at the resonance frequency of the piezoelectric transformer

Claims (5)

[Claims] 1. An inspection apparatus for measuring a conductance value of a piezoelectric transformer for performing voltage conversion through a piezoelectric transformer holding unit for measuring and holding the piezoelectric transformer, wherein the piezoelectric transformer has a resonance frequency of the piezoelectric transformer. A method for inspecting a piezoelectric transformer, which comprises measuring a conductance value of the transformer and estimating a saturation temperature rise value of the continuously driven piezoelectric transformer. 2. The inspection method according to claim 1, wherein the holding means is capable of vertically inserting / removing a primary side lead terminal attached at a position serving as a node of vibration when the piezoelectric transformer vibrates. A method for inspecting a piezoelectric transformer, characterized by having a socket for supporting the secondary side, which serves as a vibration node. 3. The inspection method for a piezoelectric transformer according to claim 1, wherein the holding unit is made of a material having a low relative dielectric constant. 4. The threshold value for determining the temperature rise failure in the piezoelectric transformer is a temperature at which the saturation temperature rise value of the piezoelectric transformer rapidly rises, and the conductance value of the piezoelectric transformer at the temperature is set as the threshold value. The method for inspecting a piezoelectric transformer according to claim 1, which is characterized in that. 5. The method for inspecting a piezoelectric transformer according to claim 1, wherein the measurement point of the saturation temperature rise of the piezoelectric transformer is a node of vibration of the piezoelectric transformer.