JPH06211504A - Production of corona discharger - Google Patents

Abstract

PURPOSE:To mass-produce a corona discharger capable of stably and precisely generating a minute amt. of ozone (e.g. about 0.2ppm in the air current at the flow rate of 100l/min) over a long period and appropriate to deodorization. CONSTITUTION:The intermediabe product of a corona discharger provided with a floating electrode 64 for interconnecting internal electrodes 54 and 56 with reference to capacitance and a protective layer 68 for covering the floating electrode is fabricated. A high-frequency voltage higher than the initial break- down voltage of of the intermediate product is impressed between the internal electrodes 54 and 56 for a short time to run in the intermediate product, and the end product of a corona discharger is obtained. The protective layer is modified by the running-in operation, the initial break-down voltage of the end product is made lower than that of the intermediate product, and the variance in the initial break-down voltage is remarkably reduced in every product.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a corona discharger which can be used as an ozonizer (ozone generator) for deodorization.

[0002]

2. Description of the Related Art An ozonizer is used to deodorize a living space, such as a toilet or a kitchen, which has a bad odor generating source, by ozone to realize a comfortable living environment. The ozonizer artificially generates ozone by corona discharge, and if hydrogen sulfide is taken as an example of a malodorous component, the deodorization reaction by ozone is performed as follows.

The history of H ₂ S + 3O ₃ → SO ₂ + H ₂ O + 3O ₂ ozonizers goes back more than 100 years, and its prototype can be seen in the “Siemens tube” developed in 1857. You can The Siemens tube comprises a double glass tube provided with an air passage, through which dry air is circulated. A rod-shaped inner electrode is arranged in the center of the glass tube, and a casing surrounding the glass tube is used as an outer electrode. When an alternating high voltage is applied between these electrodes, a silent discharge in the form of a corona discharge occurs across the air passage in the double glass tube, converting oxygen to ozone. In the Siemens tube, the corona discharge spreads along the inner surface of the glass tube, and this phenomenon is known as "creeping discharge". It is considered that the creeping discharge is caused by the glass tube acting as an insulating barrier between the electrodes and dispersing a discharge column consisting of an avalanche of electrons along the surface of the glass tube.

Modern ozonizers are often manufactured using solid state device manufacturing techniques and, therefore, electrodes are typically formed flat. However, the operating principle is no different from the Siemens tube described above.

For example, the corona discharger disclosed in FIG. 2 of JP-A-60-157183 and JP-A-61-231573 is
It should be called "opposing electrode type", and as shown in FIG. 1 of the present application, it is provided with a pair of opposed planar electrodes. The internal electrodes 10 are embedded in a substrate 12 made of a dielectric ceramic material, and the external electrodes 1 are formed on the surface of the substrate by a metallizing technique such as tungsten paste printing.
4 is formed. When a high frequency voltage is applied between the electrodes by the power supply 16, an electric field is generated between the electrodes 10 and 14 across the dielectric layer and the air gap, as shown in FIG. It can be considered that the electric field acts along the electric force line 18 (broken line) perpendicular to the equipotential surface 20 (thin solid line). Since the outer electrode 14 is narrower than the inner electrode 10 and as a result the equipotential surface 20 curves upward as shown, part of the electric field will cross the air gap. When the voltage applied to the air gap exceeds the dielectric breakdown voltage of the air gap, dielectric breakdown of air occurs in the air gap, and electric discharge occurs along the lines of electric force as indicated by a thick line 22 in FIG. The corona discharge is observed as a set of a large number of individual discharge columns that are successively generated, and due to the creeping discharge phenomenon described above, the corona discharge exhibits a slight spread along the surface of the dielectric substrate.

The problem with the counter electrode type ozonizer shown in FIG. 1 is that the durability of the electrical connection to the external electrode is not sufficient. That is, in the counter electrode type, one of the lead wires from the power source 16 is arranged above the external electrode, and the end portion of the lead wire is soldered or the like so that the external electrode 14 is formed.
However, since the lead wire and the soldered portion are located in the ozone-rich region above the external electrode, they are easily oxidized and deteriorated by ozone. Furthermore, the external electrode itself is also attacked by ozone.

Japanese Unexamined Patent Publication No. 64-33004 and Japanese Unexamined Patent Publication No. 1-246104 disclose counter electrode type ozonizers in which external electrodes are covered with a protective layer. Although this protective layer made of ceramic has an advantage of protecting the external electrodes from oxidation, it is still the same in that the deterioration of the lead wire and the soldered portion cannot be prevented.

Japanese Patent Laid-Open No. 58-108559 and US Pat. No. 4,783,7
No. 16 describes a corona discharger having a pair of internal electrodes juxtaposed in a dielectric layer. A cross section of this corona discharger is shown in FIG. 2 of the present application. The advantage of this structure is that the internal electrodes are juxtaposed so that the leads can be placed under the device away from the ozone rich region. Therefore, the lead wire is not chemically corroded by ozone. However, this discharger has not been put to practical use. This is because the electrodes 24 and 26 are laterally separated and most of the electric field generated between the electrodes 24 and 26 is confined in the dielectric layer as shown in FIG.
It is difficult to generate an electric field of sufficient strength across the air gap to generate a corona discharge, which results in
It is thought that this is due to insufficient ozone generation.

In the solid-state discharge device disclosed in FIGS. 4 to 8 of JP-A-60-157183, an intermediate electrode is partially overlapped with a pair of juxtaposed internal electrodes, and an alternating electrode is provided. The voltage is adapted to be applied between the pair of internal electrodes.
A similar discharge device is shown in FIGS. 3 to 13 of JP-A-62-51463.
And FIGS. 1 to 4 of Japanese Patent Laid-Open No. 3-190077. The cross-sectional structure of these discharge devices is shown in FIG.
To publish. As can be seen from FIG. 3, since the intermediate electrode 28 partially overlaps the internal electrodes 30 and 32, respectively, when the voltage is applied between the internal electrodes 30 and 32, the intermediate electrode 28 is And 32 act as floating electrodes that capacitively couple each other. Therefore, the electric field, on the one hand, is shown in FIG.
8 and the internal electrode 30 and, on the other hand, between the floating electrode 28 and the internal electrode 32.
As a result, the equipotential surface curves upwards as in the case of FIG. 1 and the lines of electric force are much higher than in the structure of FIG. A stronger corona discharge is generated between the electrodes and the air gap between the electrodes 28 and 32.

However, a problem with the corona discharge device of FIG. 3 is that the amount of ozone generated decreases with the operation. That is, the floating electrode 28 is not only chemically attacked by the generated ozone, but also electrically attacked by corona discharge, so that the floating electrode 28 is gradually oxidized. Furthermore, the floating electrodes are also damaged by sputtering. As a result, the electric resistance of the floating electrode increases with time, and the discharge starting voltage required to induce corona discharge rises. When operating this corona discharge device at a predetermined normal operating voltage, the corona discharge gradually weakens or partially lacks as the discharge start voltage rises with time, and the required amount of ozone is generated at the end. Disappear.

[0011]

By the way, the deodorizing technique utilizing the ozonizer is required to have a large deodorizing power. Therefore, the ozonizer is required to be able to generate a sufficient amount of ozone necessary for deodorization.

However, ozone has a peculiar odor, and when it is in a high concentration, it adversely affects the respiratory system. Therefore, it is desirable that ozone does not remain in the treated air discharged from the ozone deodorizing device. For this reason,
When operating the ozonizer, it is preferable to use an ozone decomposition catalyst together, as described in Japanese Utility Model Laid-Open No. 1-128822. The ozone decomposition catalyst is, for example, TiO ₂ or MnO supported on a porous carrier having a honeycomb structure. The ozone decomposition catalyst is arranged in the air passage of the deodorizing device, and the ozonizer is arranged upstream thereof. Air containing malodor is circulated by a fan to capture odorous substances on the surface of the catalyst, and high frequency voltage is applied to the ozonizer to cause corona discharge to artificially generate ozone. When the generated ozone comes into contact with the ozone decomposition catalyst, it is decomposed into oxygen molecules and active oxygen atoms, and the active oxygen atoms oxidize the odorant substances captured by the catalyst and convert them into odorless substances. The ozone decomposition catalyst also plays a role of decomposing surplus ozone into harmless oxygen as follows.

2O ₃ → 3O ₂ By the way, considering the demand for miniaturization of the deodorizing device as much as possible, it is not always possible to fill the deodorizing device with a sufficient amount of ozone decomposing device. In reality, it is usually about 90%. In that case, about 10% of the ozone generated by the ozonizer will be released into the surrounding air as residual ozone without being decomposed. According to the knowledge of the present inventor, the human respiratory system can detect only 0.02 ppm of residual ozone in the air flow flowing at a flow rate of 100 l / min. Is preferably suppressed to 0.02 ppm or less. Therefore,
Assuming that the efficiency of the ozone decomposition catalyst is 90%, in order to keep the amount of residual ozone below 0.02 ppm which is perceptible, the ozone generation amount of the ozonizer is 100 l / flow rate.
It is desirable that the air flow rate be 0.2 ppm or less.

Therefore, in the deodorizing ozonizer used in the living environment, firstly, a very small amount of ozone of, for example, only 0.2 ppm in an air flow having a flow rate of 100 l / min is generated with high accuracy. The quality that must be able to be achieved is required. The highly accurate ozone generation amount is required because if the ozone generation amount is less than the desired amount, the deodorizing power becomes insufficient.

Next, the ozone deodorizing device must have a deodorizing power that lasts for a long period of time. Therefore, secondly, the ozonizer is required to be capable of continuously generating a minute amount of ozone with high accuracy for many years. In particular, in an environment such as a toilet, the ozonizer is corroded by a detergent containing hydrochloric acid or the like, ammonia, etc., and therefore it is desirable that the ozonizer has sufficient environmental resistance.

Broadly speaking, the object of the present invention is to provide a corona suitable for ozone deodorization, which can generate a desired very minute controlled amount of ozone stably over a long period of time with high accuracy. It is to provide a discharger. An object of the present invention is to provide a manufacturing method particularly suitable for manufacturing a corona discharger having such performance by a mass production method.

[0017]

[Constitution of the invention]

In order to achieve the above object, the present inventor conducted a series of test studies on a corona discharger of the type having a floating electrode shown in FIG. The present invention is based on the findings obtained by such research.

That is, in order to protect the floating electrode of the corona discharger shown in FIG. 3 from the above-mentioned oxidation and sputtering, the present inventor coated the floating electrode 28 with a ceramic protective film, and discharged it while operating the device. The change in the starting voltage with time was observed. In the present specification, "discharge starting voltage"
Means a minimum voltage required to generate corona discharge in the air gap almost instantaneously without an unacceptable delay of about several seconds after the voltage is applied. The "initial discharge starting voltage" means the discharge starting voltage measured when the unused new corona discharger is first operated. When measuring the discharge start voltage, the voltage of the high frequency current applied to the corona discharger is gradually increased, and the voltage at which discharge is observed almost instantaneously from the voltage rise is defined as the discharge start voltage.

Tests have shown that, as expected, in a discharge vessel in which the floating electrode is coated with a ceramic protective layer, FIG.
Compared to the device with floating electrodes exposed as shown in
The initial discharge firing voltage was considerably higher. It is believed that this is due to the fact that the presence of the ceramic protective layer hinders the supply of electrons from the floating electrode, thus requiring a considerable delay before the corona discharge is induced at a given voltage.

However, the findings of the test are:
First, the initial discharge firing voltage varies greatly from product to product. This is completely unexpected, and in the case of mass-producing corona dischargers and operating them at a common predetermined normal operating voltage, such a large variation in the initial discharge starting voltage is not preferable. This variation is considered to be related to the surface roughness of the ceramic protective layer.

More importantly, it has been found that the firing voltage gradually decreases as the device is operated. This phenomenon is completely contrary to the fact that the discharge start voltage rises with time in the conventional device as described above.

When a high frequency voltage higher than the initial discharge firing voltage was applied on the basis of such knowledge, surprisingly, the variation in the initial discharge firing voltage among products was remarkably reduced and the absolute value of the initial discharge firing voltage was changed. It was found that the value decreased. The reason for this is not necessarily clear, but it is considered that it may be because the protective layer undergoes some aging due to corona discharge and its surface roughness is improved.

The present invention is based on the above findings, and the method of manufacturing a corona discharger of the present invention comprises a step of manufacturing an intermediate product of a corona discharger and a final operation by smoothing the intermediate product at a high voltage. The process consists of obtaining the product. The intermediate product includes first and second planar electrodes embedded in a dielectric substrate and spaced from each other, terminal means for applying a high frequency voltage between the electrodes, and the first and second electrodes. Third electrode (floating electrode) arranged on the substrate for capacitive coupling
And a corrosion-resistant and electrically insulating protective layer for covering the third electrode. In the break-in operation step of obtaining the final product from the intermediate product, a high frequency voltage higher than the initial discharge starting voltage of the intermediate product is applied for a predetermined time between the first electrode and the second electrode.

By applying a high frequency voltage higher than the initial discharge starting voltage of the intermediate product, the protective layer is modified or aged, and a final product having no variation in the initial discharge starting voltage for each product is obtained, and at the same time, the initial product is obtained. A final product with a low discharge start voltage can be obtained.

Thus, according to the manufacturing method of the present invention,
Since the initial discharge start voltage does not vary from product to product,
When the corona discharger mass-produced by the method of the present invention is operated at a desired normal operation voltage slightly higher than the initial discharge start voltage, a stable corona discharge occurs along the contour where the third electrode overlaps the first and second electrodes. Is induced. Since the ozone generation amount is proportional to the creeping discharge length of corona discharge, it is possible to manage the ozone generation amount to a very small amount by appropriately setting the length of the contour where the third electrode overlaps the first and second electrodes. it can.

In the corona discharger manufactured by the method of the present invention, since the third electrode (floating electrode) is protected from oxidation and sputtering by the protective layer, a desired amount of ozone can be stabilized for a long period of time. Can be generated.

It is effective to apply a voltage to the intermediate product at a voltage as high as possible, but in order to avoid dielectric breakdown, it is necessary to apply a voltage higher than the dielectric breakdown voltage of the dielectric layer between the first electrode and the second electrode. Must be done at low voltage. The application of voltage to the intermediate product is preferably for at least about 5 seconds.

In order to operate the corona discharger at a normal operating voltage of about 6 kV _PP or less, the effective thickness of the dielectric layer between the first and second electrodes and the third electrode is about 25-70 μm.
m, and the effective thickness of the protective layer is preferably about 7-20 μm.

The above-mentioned features and effects of the present invention, as well as other features and advantages, will be more apparent according to the description of the following embodiments.

[0030]

First, the outline of the structure and operation of the corona discharger of the present invention will be described with reference to FIGS. Figure 4
6, the corona discharger 50 comprises a substrate 52 made of a dielectric material such as alumina ceramic, inside which a pair of internal planar electrodes 54 and 56 are provided.
Are arranged. The respective inner electrodes 54 and 56 are
It comprises an inner part 58, for example of rectangular shape, which participates in the corona discharge, and a circular terminal part 60, which are electrically connected by an elongated connecting part 62. External electrodes 64 having rounded ends are arranged on the upper surface of the dielectric substrate 52. The outer electrode 64 is positioned so as to partially overlap the inner portions 58 of the inner electrodes 54 and 56, respectively, and the dielectric layer 66 is interposed between the outer electrode 64 and the inner electrodes 54 and 56. is there. Although exaggerated in the drawings for ease of understanding, the effective thickness D of the dielectric layer 66 is preferably about 25-75 μm, which is the distance between the inner electrodes 54 and 56 (about 1 mm. ) Is much smaller than The outer electrode 64 is covered with a protective layer 68 made of a corrosion-resistant and electrically insulating material such as alumina ceramic, and the thickness of this protective layer is preferably about 7-20 μm.

As shown in FIG. 5, a pair of metal conductors 70 and 72 are disposed through the substrate 52, one end of which is the terminal portion 60 of the internal electrodes 54 and 56.
They are electrically connected to each. The other ends of the conductors 70 and 72 are connected to a pair of terminals 74 and 76 provided on the lower surface of the substrate 52, respectively.

In use, as shown in FIG. 5, the corona discharger 50 is connected to the high frequency power supply 82 by the lead wires 78 and 80, and the high frequency voltage is applied between the internal electrodes 54 and 56. The outer electrode 64 is the inner electrodes 54 and 5
6 partially overlaps with each other, and the dielectric layer 66 is interposed between the external electrode and the internal electrode. Therefore, at the same time, an electric capacitance is induced between the external electrode 64 and the internal electrode 54. On the other hand, electric capacitance is induced between the external electrode 64 and the internal electrode 56, and the external electrode 64 is
It acts as a floating electrode that capacitively couples 4 and 56. Therefore, an alternating electric field is formed between the floating electrode 64 and the respective inner electrodes 54 and 56, and the air gap between the floating electrode and the inner electrodes is formed as shown by the arc-shaped arrows in FIGS. 5 and 6. Corona discharge is induced in.

In the corona discharge, the floating electrode 64 is the inner electrode 5
It occurs along a contour that overlaps 4 and 56. The floating electrodes overlap the inner electrodes 54 and 56 separately,
In the illustrated embodiment, the ends of the floating electrode 64 are rounded, as best seen in FIG. 7, so that corona discharge occurs along two separate U-shaped regions. Due to the presence of the ceramic protective layer 68, the corona discharge becomes a creeping discharge that spreads slightly along the surface of the protective layer 68 as shown by the diagonal lines in FIG. The amount of ozone generated by the corona discharger 50 is approximately proportional to the surface area of the creeping discharge, and thus proportional to the length of the contour where the floating electrode 64 overlaps the internal electrodes 54 and 56 (creeping discharge length). Therefore, by appropriately setting the length of the floating electrode 64, the ozone generation amount of the corona discharger 50 can be managed with extremely high accuracy. Therefore, the corona discharger 50 of the present invention is suitable for generating a minute amount of ozone with high accuracy.

Next, a method of manufacturing the corona discharger 50 of the present invention will be described with reference to the flow charts of FIGS. 8 and 9.

First, a slurry of a ceramic-forming dielectric material such as alumina is prepared, and the slurry is used to prepare a green sheet by a doctor blade method or the like. Next, a pair of through holes 8 for piercing the green sheet and disposing conductors 70 and 72 (FIG. 5).
4, the conductive paste 86 containing powdered tungsten or the like is filled in the through holes by a printing technique such as screen printing. After the paste is dried, the same conductive paste is used so that the electrode patterns 88 for the internal electrodes 54 and 56 and the terminal patterns 90 for the terminals 74 and 76 are brought into contact with the paste 86 filled in the through holes. , Print on the front and back of the green sheet respectively.
It is preferable to simultaneously print a terminal pattern 92 for an electric heater, which will be described later, on the back surface of the green sheet.
Once the paste has dried, the green sheet is pressed with a hot press to smooth the surface.

Next, the dielectric layer 66 is screen-printed using a paste of a ceramic-forming dielectric material having the same composition as the green sheet. After drying, an electrode pattern 94 for the external floating electrode 64 is printed on the dielectric layer 66 with a conductive paste and dried again. Next, the protective layer 68 is formed by screen-printing a paste of a corrosion resistant and electrically insulating material. Since the alumina ceramic has corrosion resistance and electrical insulation, the same paste as the dielectric layer 66 can be used to form the protective layer 68. After drying
The intermediate product 96 of the corona discharger is obtained by firing in a reducing atmosphere. The terminals 74, 76, 92 are preferably plated with nickel to facilitate soldering of the leads.

Next, a high-frequency voltage is applied for a short time between the internal electrodes 54 and 56 of the intermediate product 96 of the corona discharger manufactured in this way to generate a corona discharge provisionally, thereby generating an intermediate discharge. Protective layer 6 after running the product in
Modify 8. The applied voltage during the run-in is preferably as high as possible, but should not be so high as to cause dielectric breakdown of the dielectric layer 66. However, the applied voltage must be higher than the initial firing voltage of the intermediate product. Preferably, the break-in operation is performed at a voltage slightly lower than the breakdown voltage of the dielectric layer 66 between the inner electrodes 54 and 56. The break-in operation is performed until the initial discharge start voltage of the final product is substantially lowered and the variation of the initial discharge start voltage of the final product is eliminated. At least 5 run-in
It is preferable to carry out for 2 seconds, preferably 10-300 seconds.

After the break-in operation of the intermediate product is performed, an electric heater including a chip resistor 97 is mounted on the substrate 52 and connected to the heater terminal 92. Electric heater 97
The purpose is to prevent moisture from condensing on the substrate when the corona discharger is not operating, and to keep the ozone generation amount of the corona discharger constant even in a humid environment. Finally, after connecting the lead wires to the respective terminals, the electrical connection portion is sealed with potting resin to obtain the final product 50 of the corona discharger.

A preferred embodiment of the method of the present invention will now be described. 859 parts by weight of high purity alumina powder containing about 99.5% Al ₂ O ₃ and kaolin 122 containing about 98.6% kaolinite. 1 part by weight, 12 parts by weight of MgCO ₃ , 7 parts by weight of CaCO ₃ and 700 parts by weight of water were mixed, and this mixture was pulverized with an alumina ball mill until the average particle size became about 3 μm. It was dried until the water content was 0.3% or less.
To 225 parts by weight of this material, 18 parts by weight of polyvinyl butyral, 15 parts by weight of dibutyl phthalate, 1 part by weight of a peptizer, 62 parts by weight of toluene, and 26 parts by weight of isopropyl alcohol are added, About 20 with alumina ball mill
After mixing for a period of time and degassing by vacuum, the mixture was aged for about 20 hours to obtain a slurry of a ceramic forming material. This slurry was rolled by the doctor blade method to a thickness of about 0.83.
A long green sheet having a size of mm was produced and punched with a press to obtain a green sheet. The press simultaneously drilled through holes. A part of the green sheet thus formed was separately stored and used for preparing an alumina paste described later.

Next, the through holes of the green sheet were filled with a tungsten paste by screen printing and dried, and then a terminal pattern was similarly printed with the tungsten paste on one surface of the green sheet and dried. Further, a printed pattern of the internal electrodes was formed on the other surface of the green sheet and dried. The obtained product was hot pressed at 60 ° C. for about 20 seconds. Next, in order to form a dielectric layer, the internal electrodes were coated with alumina paste by screen printing. In order to make the particle diameters of the dielectric layer and the underlying substrate equal, the alumina paste used for printing the dielectric layer was heated to a portion of the green sheet to evaporate the volatile components, and to form a paste on this. It was adjusted by adding the vehicle. After drying the alumina paste for forming the dielectric layer, an electrode pattern for an external floating electrode was screen-printed using a tungsten paste, and the obtained product was dried. Next, in order to form a protective layer, the print pattern for the external floating electrodes was coated with the same alumina paste by screen printing and dried again. The material thus obtained was fired in a reducing atmosphere in the presence of nitrogen for about 30 hours in a continuous firing furnace having a temperature gradient of 300 ° C to 1580 ° C to obtain a series of intermediate products for corona discharger.

In each intermediate product, the dielectric layer 66
The average thickness D (FIG. 5) of the protective layer 68 is about 50 μm.
The average thickness d of was about 10 μm. The composition of the alumina ceramic forming the dielectric layer 66 and the protective layer 68 is Al
₂ O ₃ about 92.5%, SiO ₂ about 5.7%, CaO about 1.0%, Mg
O was about 0.6% (above, weight%, balance impurities).

Next, the intermediate product manufactured in this manner is subjected to a change in the discharge starting voltage without performing a leveling operation or while performing a leveling operation by applying a voltage under various different conditions described later. Measured.

For comparison, a series of corona dischargers without a protective layer were prototyped and tested. The prototypes for these comparative tests were manufactured in the same manner as the above intermediate product, except that the external floating electrode 64 was not covered with the protective layer 68.

The voltage application to the intermediate product and the prototype for comparative test and the measurement of the discharge start voltage were carried out by using the apparatus shown in FIG. Commercial AC power supply 100 is AC stabilized power supply 10
After being stabilized by 2, the output voltage value was supplied to the high frequency high voltage power source 104 capable of variably adjusting. The output frequency of the high frequency high voltage power supply 104 is fixed (15 kHz). The output of the high frequency high voltage power supply 104 was applied between the inner electrodes 54 and 56 of the individual corona discharger under test via leads. To measure the output voltage of the high frequency high voltage power supply 104,
A high voltage probe (Iwasaki Tsushinki Co., Ltd., HV-P30) was connected between the lead wires, and the output was sent to the first channel of the oscilloscope 108 to read the peak-to-peak voltage. The current flowing through the corona discharger was detected by the current probe 110 arranged on one of the lead wires, its output was amplified by the amplifier 112, and then sent to the second channel of the oscilloscope 108 to read the current value.

In the intermediate product run-in operation, one series of intermediate products is operated at a predetermined voltage for a predetermined time, another series of intermediate products is operated at the same voltage for a different time, and yet another series of intermediate products is operated. This was done by operating at different voltages for different times. Still other series of intermediate products were tested without run-in.

The fluctuation of the discharge starting voltage of each corona discharger was measured as follows. That is, the high frequency high voltage power supply 10
After turning on the power supply to No. 4, the voltage adjusting dial was manually operated, and the voltage was increased until corona discharge occurred within about 10 seconds after the dial operation. The corona discharge is generated by detecting the current flowing through the corona discharger by the current probe 110, and detecting the current through the second channel.
It was displayed on the screen of No. 08 and judged based on the current waveform of the oscilloscope, and the corona discharge was visually confirmed. When the occurrence of corona discharge is confirmed, the
The channel was switched to, the voltage value detected by the high-voltage probe 106 was read, and this was used as the discharge start voltage. As described above, the discharge start voltage measured when the unused corona discharger is first operated is defined as the initial discharge start voltage. Next, use about 5.4 kV for each corona discharger.
Maximum of about 20 at operating voltage of _PP (peak-to-peak voltage)
Operated for 00 seconds. The operation was occasionally interrupted, and the discharge starting voltage at each time point was measured in the same manner as described above.

FIG. 11 to FIG. 1 showing changes in the discharge start voltage
Based on the graph of 7, the effect of the protective layer and the effect of the leveling operation will be described. In these graphs, the vertical axis represents the discharge start voltage (kV _PP ) and the horizontal axis represents the operating voltage (about 5.4 V).
Represents the cumulative operating time in kV _PP ). The results plotted with white circles, triangles, and black circles represent the maximum value, minimum value, and average value of the discharge start voltage measured for a series of 5 to 10 corona dischargers, respectively.

First, referring to the graph of FIG. 11, this graph shows how the discharge start voltage changes in accordance with the cumulative operating time in the series of intermediate products of the corona discharger before the run-in operation. It shows how you did it. As can be seen from this graph, in the intermediate product in which the protective layer is not modified, the initial discharge start voltage (that is, the discharge start voltage when the integrated operation time is zero) is about 4.4 kV _{PP for} each product. It shows a large variation in the range up to about 5.1 kV _PP . Such a large variation in the initial discharge inception voltage for each product is probably because the protective layer 68 is formed by firing the ceramic forming material, so that the surface roughness thereof varies for each product. It is considered to be a thing. Also,
As can be seen from the graph of FIG. 11, the variation in the discharge starting voltage sharply decreases and the average value of the discharge starting voltage gradually decreases as the operation is performed at a predetermined operating voltage (about 5.4 kV _PP ). It is considered that this is because the microscopic unevenness existing on the surface of the ceramic protective layer is modified by the energy of the corona discharge.

The graph of FIG. 12 shows the variation of the firing voltage in the corona discharger for the comparative test in which the external floating electrode is not covered with the protective layer. Since there is no protective layer, the initial discharge firing voltage is considerably lower and the product-to-product variations are smaller than the results shown in the graph of FIG.
However, the discharge start voltage gradually increases as the integrated operation time increases. This is apparently due to the increased electrical resistance of the floating electrode due to oxidation and sputtering.

The graphs of FIG. 13 to FIG. 17 show the test results of the corona discharger which was run-in according to the present invention, and the run-in was performed under different conditions.

The graph of FIG. 13 shows the results of a series in which the applied voltage was about 7 kV _PP and the run-in operation was performed for about 3 seconds.
As can be seen from comparison with the graph of FIG. 11, there is no appreciable change in discharge starting voltage. It is considered that the run-in for about 3 seconds was insufficient to improve the properties of the protective layer.

The graph of FIG. 14 shows the results of another series in which a break-in operation was performed for about 30 seconds with an applied voltage of about 7 kV _PP . As can be seen from comparison with the graphs of FIGS. 11 and 13, the variation in the initial discharge firing voltage is significantly reduced. Furthermore, the initial discharge starting voltage itself has dropped significantly. At the time of operating at an operating voltage of about 5.4 kV _PP, the discharge start voltage showed a slight drift at first, but then gradually decreased.

The graph of FIG. 15 shows the results of a further series in which the applied voltage was about 7 kV _PP and a break-in operation was performed for about 300 seconds. Although the average value of the initial discharge start voltage is smaller than the value in FIG. 14, the drift is correspondingly high.

The graphs of FIGS. 16 and 17 show the results of a series of run-in runs for about 30 seconds and about 120 seconds with an applied voltage of about 8 kV _PP , respectively. These graphs show that the break-in operation under such conditions is also effective in lowering the initial discharge starting voltage and reducing variations in the initial discharge starting voltage.

Next, a corona discharger obtained by performing a break-in operation for about 30 seconds with an applied voltage of about 7 kV _PP was 6000.
An accelerated life test corresponding to time was performed. In this test, the amount of ozone generated was measured while operating the corona discharger in a stream of dry air flowing at a flow rate of 10 l / min. The results are shown in the graph of FIG. As you can see from this graph,
The corona discharger, which had been run-in sufficiently for reforming the protective layer, showed about 2 pp over the operating time of 6000 hours.
m (equivalent to 0.2 ppm when the flow rate is 100 l / min)
It was possible to maintain a minute amount of ozone generation. 6
Even after 000 hours of operation, the reduction in ozone generation amount was only about 30%.

[0056]

As described above, according to the method of the present invention, the variation in the initial discharge starting voltage for each product is significantly reduced, and therefore, a very small amount of, for example, 0.2 ppm in the air flow of 100 l / min. It is possible to mass-produce a corona discharger capable of highly accurately generating ozone.

Further, in the corona discharger manufactured by the method of the present invention, since the external floating electrode 64 is protected from oxidation and sputtering by the protective layer 68, a desired trace amount of ozone is stably generated for a long period of time. Can be made.

In another aspect, the modification of the protective layer lowers the initial discharge onset voltage and allows the corona discharger to operate at a lower normal operating voltage, thus being produced by the method of the present invention. The corona discharger can be driven by a small and inexpensive high frequency power supply.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a conventional counter electrode type corona discharger.

FIG. 2 is a schematic cross-sectional view of a conventional side-by-side electrode type corona discharger.

FIG. 3 is a schematic sectional view of a conventional floating electrode type corona discharger.

FIG. 4 is an enlarged plan view of the corona discharger of the present invention.

5 is a schematic cross-sectional view taken along the line VV of FIG.

6 is a schematic cross-sectional view taken along the line VI-VI of FIG.

FIG. 7 is a partially enlarged plan view of the corona discharger of FIG.

FIG. 8 is a flow chart of a method for manufacturing a corona discharger of the present invention.

FIG. 9 shows a continuation of the flowchart of FIG.

FIG. 10 is a block diagram of an apparatus used for testing a corona discharger and measuring a discharge start voltage.

FIG. 11 is a graph showing changes in the discharge start voltage of the corona discharger that was not subjected to the break-in operation.

FIG. 12 is a graph showing a change in discharge starting voltage of a corona discharger without a protective layer.

FIG. 13 is a graph showing fluctuations in the discharge start voltage of a series that was run-in for about 3 seconds with an applied voltage of about 7 kV _PP .

FIG. 14 is a graph showing fluctuations in the discharge start voltage of a series that was run-in for about 30 seconds with an applied voltage of about 7 kV _PP .

FIG. 15 shows about 300 kV at an applied voltage of about 7 kV _PP .
It is a graph which shows the variation of the discharge start voltage of the series which performed a run-in for a second.

FIG. 16 is a graph showing fluctuations in the discharge start voltage of a series that was run-in for about 30 seconds with an applied voltage of about 8 kV _PP .

Figure 17 is approximately at an applied voltage of about 8kV _PP 120
It is a graph which shows the variation of the discharge start voltage of the series which performed a run-in for a second.

FIG. 18 is a graph showing the results of an accelerated life test.

[Explanation of symbols]

 50: Corona Discharger 52: Substrate 54, 56: Internal Electrode 64: External Electrode (Floating Electrode) 68: Ceramic Protective Layer 70/72/74/76: Terminal Means 96: Intermediate Product of Corona Discharger

Claims (5)

[Claims] 1. A first and a second flat electrode embedded in a dielectric substrate and separated from each other, a terminal means for applying a high frequency voltage between the electrodes, the first electrode and the second electrode. An intermediate product of a corona discharger provided with a third electrode disposed on the substrate to capacitively couple the electrodes and a corrosion-resistant and electrically insulating protective layer that covers the third electrode, The final product of the corona discharger is obtained by applying a high frequency voltage higher than the initial discharge start voltage of the product between the first electrode and the second electrode of the intermediate product for a predetermined time. Manufacturing method. 2. The voltage applied between the first electrode and the second electrode of the intermediate product is slightly lower than the dielectric breakdown voltage between the first electrode and the second electrode. Item 1
Of manufacturing corona discharger based on. 3. The method of manufacturing a corona discharger according to claim 1, wherein the voltage application to the intermediate product is performed for at least about 5 seconds. 4. The effective thickness of the dielectric between the first electrode and the second electrode and the third electrode is about 25-70 μm for operating the final product at an operating voltage of about 6 kV _PP , and the protection is provided. 4. The method of manufacturing a corona discharger according to claim 1, wherein the effective thickness of the layer is about 7-20 [mu] m. 5. A first and a second flat electrode embedded in a dielectric substrate and separated from each other, a terminal means for applying a high frequency voltage between the electrodes, the first electrode and the second electrode. An intermediate product of a corona discharger provided with a third electrode disposed on the substrate to capacitively couple the electrodes and a corrosion-resistant and electrically insulating protective layer that covers the third electrode, An initial discharge start voltage of the intermediate product is modified by applying a high frequency voltage higher than the initial discharge start voltage of the product between the first electrode and the second electrode of the intermediate product for a predetermined time to modify the protective layer. A method of manufacturing a corona discharger, which comprises obtaining a final product of a corona discharger having a lower initial discharge firing voltage.