JP2606785B2 - Method of manufacturing corona discharger - Google Patents

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 for producing a corona discharger usable as an ozonizer (ozone generator) for deodorization.

[0002]

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

[0003] The history of H ₂ S + 3O ₃ → SO ₂ + H ₂ O + 3O ₂ ozonizers goes back more than a hundred years from now, and its prototype can be seen in the “Siemens tube” developed in 1857. Can be. The Siemens tube comprises a double glass tube with an air passage formed therein, through which dry air is circulated. A rod-shaped inner electrode is arranged at 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 is generated across the air passage in the double glass tube, converting oxygen to ozone. In a Siemens tube, the corona discharge occurs by spreading along the inner surface of the glass tube, a phenomenon known as "creeping discharge". Creeping discharges are believed to be due to the glass tube acting as an insulating barrier between the electrodes and dispersing the discharge columns of avalanches along the surface of the glass tube.

[0004] Modern ozonizers are often manufactured using solid-state device manufacturing techniques, and therefore the electrodes are generally formed flat. However, there is no difference in the operation principle from the aforementioned Siemens tube.

For example, the corona discharger described in FIG. 2 of JP-A-60-157183 and JP-A-61-231573 is
It is also referred to as a "counter electrode type", and includes a pair of flat electrodes arranged to face each other as illustrated in FIG. 1 of the present application. The internal electrode 10 is embedded in a substrate 12 made of a dielectric ceramic material, and the external electrode 1 is formed on the surface of the substrate by a metallizing technique such as tungsten paste printing.
4 are 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. The electric field can be considered to act along lines of electric force 18 (dashed lines) perpendicular to the equipotential surface 20 (thin solid lines). Since the outer electrode 14 is narrower than the inner electrode 10 and, consequently, the equipotential surface 20 curves upward as shown, some of the electric field will cross the air gap. When the voltage applied to the air gap exceeds the breakdown voltage of the air gap, air breakdown occurs in the air gap, and discharge occurs along the lines of electric force as indicated by the thick line 22 in FIG. The corona discharge is observed as a set of a large number of individual discharge pillars generated one after another, and exhibits a slight spread along the surface of the dielectric substrate due to the above-described creeping discharge phenomenon.

A problem with the opposing 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 supply 16 is disposed above the external electrode, and the end of the lead wire is soldered or the like to the external electrode 14.
However, since the lead wire and the soldering portion are located in the ozone-rich region above the external electrodes, they are easily oxidized and deteriorated by ozone. Further, the external electrodes themselves are also affected by ozone.

JP-A-64-33004 and JP-A-1-246104 disclose opposing-electrode-type ozonizers in which external electrodes are covered with a protective layer. Although this protective layer made of ceramic has the 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.

[0008] JP-A-58-108559 and US Patent No. 4,783,7
No. 16 describes a corona discharge device in which a pair of internal electrodes are 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 juxtaposition of the internal electrodes allows the leads to be located on the underside of the device, away from the ozone rich region. Therefore, the lead wire is not chemically attacked by ozone. However, this discharger does not appear to be in 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 across the air gap that is strong enough to cause a corona discharge,
It is considered that the ozone generation amount was not sufficient.

In the solid state discharge device disclosed in FIGS. 4 to 8 of Japanese Patent Application Laid-Open No. 60-157183, an intermediate electrode is partially overlapped on a pair of juxtaposed internal electrodes. The voltage is applied between a pair of internal electrodes.
A similar discharge device is shown in FIGS. 3 to 13 of JP-A-62-151463.
FIG. 1 and FIGS. 1 to 4 of JP-A-3-190077. The sectional structure of these discharge devices is shown in FIG.
Post on. As can be seen from FIG. 3, since the intermediate electrode 28 partially overlaps the internal electrodes 30 and 32, when a voltage is applied between the internal electrodes 30 and 32, the intermediate electrode 28 And 32 act as a floating electrode that capacitively couples each other. Thus, the electric field is, as shown, on one hand floating electrode 2
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 upward as in the case of FIG. 1, and the lines of electric force are lifted toward the air gap much higher than in the structure of FIG. A stronger corona discharge occurs in the air gap between electrodes 28 and 32.

However, a problem of the corona discharge device shown in 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. In addition, the floating electrode is damaged by sputtering. As a result, the electric resistance of the floating electrode increases with time, and the firing voltage required to induce corona discharge increases. When the corona discharge device is operated at a predetermined normal operating voltage, the corona discharge gradually weakens or partially disappears as the discharge starting voltage rises over time, and finally a necessary amount of ozone is generated. Disappears.

[0011]

The deodorizing technique using an ozonizer is first required to have a large deodorizing power. Therefore, the ozonizer is required to be able to generate a sufficient amount of ozone required for deodorization.

However, ozone has a peculiar odor and, when its concentration is high, adversely affects the respiratory system. Therefore, it is desirable that no ozone remains 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 ozonolysis catalyst is a catalyst in which TiO ₂ , MnO, or the like is carried on a porous carrier having, for example, a honeycomb structure. The ozonolysis catalyst is arranged in an air passage of a deodorization device, and an ozonizer is arranged upstream thereof. Air containing malodor is circulated by a fan to capture odorants on the catalyst surface, and a high-frequency voltage is applied to the ozonizer to generate 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 odorants trapped by the catalyst and convert them to odorless substances. The ozone decomposition catalyst also plays a role of decomposing excess ozone into harmless oxygen as follows.

2O ₃ → 3O ₂ Considering the demand for miniaturization of the deodorizing device as much as possible, it is not always possible to fill a sufficient amount of the ozone decomposing catalyst into the deodorizing device. Usually, it is 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 inventor's findings, the human respiratory system can sense only 0.02 ppm of residual ozone in an air stream 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%, the amount of ozone generated by the ozonizer should be 100 l / liter in order to keep the amount of residual ozone below 0.02 ppm, which can be perceived.
It is desirable that the concentration be 0.2 ppm or less in the air flow per minute.

Therefore, a deodorizing ozonizer used in a living environment firstly generates a very small amount of ozone of only 0.2 ppm in an air flow having a flow rate of 100 l / min, for example, with high precision. Quality that must be able to be performed is required. The reason why a high-precision ozone generation amount is required is that if the ozone generation amount is smaller than a desired amount, the deodorizing power becomes insufficient.

Next, the ozone deodorizing device must have a long lasting deodorizing power. Therefore, secondly, the ozonizer is required to be able to continuously generate a minute amount of ozone with high accuracy for many years. Particularly, in an environment such as a toilet, the ozonizer is eroded by a detergent containing hydrochloric acid or the like, ammonia, or the like. Therefore, it is desirable that the ozonizer has sufficient environmental resistance performance.

An object of the present invention is, in a broad sense, a corona suitable for ozone deodorization, capable of generating a desired very minute controlled amount of ozone stably and with high precision for a long period of time. It is to provide a discharger. It is an object of the present invention, in particular, to provide a manufacturing method suitable for manufacturing a corona discharger having such performance in a mass production system.

[0017]

Configuration of the Invention

In order to achieve the above object, the present inventor has conducted a series of tests on a corona discharger having a floating electrode as 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 while operating the apparatus. The change with time of the starting voltage was observed. In this specification, “discharge starting voltage”
Means the minimum voltage required to generate a corona discharge in the air gap almost instantaneously without an unacceptable delay of the order of a few seconds after voltage application. The “initial discharge starting voltage” means a discharge starting voltage measured when a new unused corona discharger is operated for the first time. 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 increase is defined as the discharge start voltage.

Tests have shown that, as expected, in a discharger where the floating electrode was coated with a ceramic protective layer, FIG.
As shown in the above, compared to the device where the floating electrode is exposed,
The initial firing voltage increased considerably. This may be due to the fact that the presence of the ceramic protective layer impedes the supply of electrons from the floating electrode, so that at a given voltage a considerable delay is required before corona discharge is induced.

However, what was found by the test is that
First, the initial discharge starting voltage varies greatly from product to product. This was completely unexpected, and such large variations in the initial firing voltage are undesirable in mass producing corona dischargers and operating them at a common predetermined normal operating voltage. 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 starting voltage increases with time in the conventional device as described above.

When a high-frequency voltage higher than the initial discharge starting voltage was applied taking this knowledge as a trigger, surprisingly, the product-to-product variation in the initial discharge starting voltage was remarkably reduced and the absolute value of the initial discharge starting voltage was absolutely reduced. The value was found to decrease. Although the reason for this is not necessarily clear, it is considered that the reason is that the protective layer undergoes some aging due to corona discharge and the surface roughness thereof is improved.

The present invention is based on the above findings, and the method for manufacturing a corona discharger according to the present invention comprises the steps of producing an intermediate product of the corona discharger, The process consists of obtaining a product. The intermediate product includes a first and a second planar electrode buried in a dielectric substrate and separated from each other, a terminal means for applying a high-frequency voltage between the electrodes, and the first and second electrodes. Third electrode (floating electrode) disposed on the substrate for capacitive coupling
And a corrosion-resistant and electrically insulating protective layer that covers the third electrode. In the smoothing 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 between the first electrode and the second electrode for a predetermined time.

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

Thus, according to the manufacturing method of the present invention,
Since the initial discharge starting 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 operating voltage slightly higher than the initial discharge starting voltage, a stable corona discharge along the contour where the third electrode overlaps the first and second electrodes is obtained. Is induced. Since the ozone generation amount is proportional to the creeping discharge length of the corona discharge, it is possible to control 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 trace amount of ozone can be stabilized for a long period of time. Can be generated.

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

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 and third electrodes should be 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, as well as other features and advantages of the present invention will become more apparent according to the description of the following embodiments.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure and operation of a corona discharger according to the present invention will be described with reference to FIGS. FIG.
As shown in FIG. 6 to FIG. 6, the corona discharger 50 includes a substrate 52 made of a dielectric material such as alumina ceramic, and has a pair of internal flat electrodes 54 and 56 inside the substrate.
Is arranged. The respective internal electrodes 54 and 56
It comprises, for example, a rectangular inner part 58 involved in the corona discharge and a circular terminal part 60, which are electrically connected by an elongated connection 62. On the upper surface of the dielectric substrate 52, external electrodes 64 having round ends are arranged. The external electrodes 64 are positioned so as to partially overlap the respective inner portions 58 of the internal electrodes 54 and 56, and a dielectric layer 66 is interposed between the external electrodes 64 and the internal electrodes 54 and 56. is there. Although exaggerated in the figures for ease of understanding, the effective thickness D of the dielectric layer 66 is preferably about 25-75 μm, and this thickness depends on the distance between the internal electrodes 54 and 56 (about 1 mm). ). The outer electrode 64 is covered by a protective layer 68 of a corrosion resistant and electrically insulating material such as alumina ceramic or the like, the thickness of which 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, and one end thereof is connected to the terminal portions 60 of the internal electrodes 54 and 56.
Are electrically connected to each other. 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 a high-frequency power source 82 by lead wires 78 and 80, and a high-frequency voltage is applied between the internal electrodes 54 and 56. The outer electrode 64 is connected to the inner electrodes 54 and 5
6 and the dielectric layer 66 is interposed between the external electrode and the internal electrode, so that the electric capacitance is induced between the external electrode 64 and the internal electrode 54 on the one hand, and On the other hand, electric capacitance is induced between the external electrode 64 and the internal electrode 56, and the external electrode 64 is
Acts as a floating electrode that capacitively couples 4 and 56. Accordingly, an alternating electric field is formed between the floating electrode 64 and the respective internal electrodes 54 and 56, and the air gap between the floating electrode and the internal electrode is formed as shown by arc-shaped arrows in FIGS. , A corona discharge is induced.

In the corona discharge, the floating electrode 64 is
Occurs along contours that overlap 4 and 56. The floating electrodes overlap with the inner electrodes 54 and 56, respectively,
In the embodiment shown, both ends of the floating electrode 64 are rounded, as can be seen in FIG. 7, so that the corona discharge occurs along two separate U-shaped regions. Because of the presence of the ceramic protective layer 68, the corona discharge is a creeping discharge that spreads slightly along the surface of the protective layer 68 as shown by hatching in FIG. The amount of ozone generated by the corona discharger 50 is substantially proportional to the surface area of the creeping discharge, and is therefore proportional to the length of the contour where the floating electrode 64 overlaps the internal electrodes 54 and 56 (the creeping discharge length). Therefore, by appropriately setting the length of the floating electrode 64, the amount of ozone generated by 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 flowcharts of FIGS.

First, a slurry of a ceramic-forming dielectric material such as alumina is prepared, and a green sheet is manufactured using this slurry by a doctor blade method or the like. Next, a pair of through holes 8 for piercing the green sheet and arranging the conductors 70 and 72 (FIG. 5) are formed.
Then, a conductive paste 86 containing powdered tungsten or the like is filled in the through holes by a printing technique such as screen printing. After drying the paste, using the same conductive paste, 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. And print on the front and back of the green sheet, respectively.
It is preferable that a terminal pattern 92 for an electric heater described later is simultaneously printed on the back surface of the green sheet.
After the paste is 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, the 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 that for forming the dielectric layer 66 can be used to form the protective layer 68. After drying,
It is fired in a reducing atmosphere to obtain an intermediate product 96 of a corona discharger. Preferably, the terminals 74, 76, 92 are 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 discharge device manufactured as described above to temporarily generate corona discharge. Perform the break-in operation of the product, and
8 is modified. It is desirable that the applied voltage during the running-in operation be as high as possible, but not so high as to cause dielectric breakdown of the dielectric layer 66. However, the applied voltage must be higher than the initial discharge starting 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 internal electrodes 54 and 56. The smoothing operation is performed until the initial discharge starting voltage of the final product substantially decreases and the initial discharge starting voltage of the final product no longer varies. Run-in at least 5
It is preferably performed for 10 seconds, preferably 10-300 seconds.

After the intermediate product has been run-in, an electric heater including a chip resistor 97 and the like is mounted on the substrate 52 and connected to the heater terminal 92. Electric heater 97
Is provided to prevent moisture from condensing on the substrate when the corona discharger is not operating, and to maintain a constant amount of ozone generated by the corona discharger even in a humid environment. Finally, after the lead wires are connected to the respective terminals, the electrical connection portions are sealed with a potting resin to obtain a final product 50 of a corona discharger.

The preferred embodiment of the method of the present invention will now be described with reference to 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. Parts by weight, 12 parts by weight of MgCO ₃ , 7 parts by weight of CaCO ₃ , and 700 parts by weight of water, and the 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 deflocculant, 62 parts by weight of toluene, and 26 parts by weight of isopropyl alcohol were added, About 20 with alumina ball mill
After mixing for hours and degassing by vacuum, the mixture was aged for about 20 hours to obtain a slurry of the ceramic forming material. This slurry was rolled by the doctor blade method to a thickness of about 0.83
A green long body having a thickness of 1 mm was manufactured and punched out with a press to obtain a green sheet. In the press, through holes were simultaneously drilled. One part of the green sheet thus formed was separately stored and used for preparing an alumina paste described later.

Next, the through hole of the green sheet was filled with a tungsten paste by screen printing and dried. After that, a terminal pattern was similarly printed with a tungsten paste on one surface of the green sheet and dried. Further, a printed pattern of the internal electrode 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 covered with an alumina paste by screen printing. In order to equalize the particle size of the dielectric layer and the substrate below it, the alumina paste used for printing the dielectric layer heats a part of the above-described green sheet to evaporate volatile components, which is then used for paste formation. Was adjusted by the addition of a vehicle. After drying the alumina paste for forming the dielectric layer, an electrode pattern for the external floating electrode was screen-printed using a tungsten paste, and the obtained one was dried. Next, in order to form a protective layer, the print pattern for the external floating electrode was coated with the same alumina paste by screen printing, and dried again. The raw material thus obtained was fired in a continuous firing furnace having a temperature gradient of 300 ° C. to 1580 ° C. in a reducing atmosphere in the presence of nitrogen for about 30 hours to obtain a series of intermediate products of a corona discharger.

In each intermediate product, the dielectric layer 66
Has an average thickness D (FIG. 5) of about 50 μm,
Had an average thickness d of 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% (the above, weight%; residual impurities).

Next, the intermediate product manufactured as described above is subjected to a smoothing operation without applying a smoothing operation, or by applying a voltage under various conditions described later, so that the fluctuation of the discharge starting voltage is reduced. Measured.

For a comparative test, 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 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 the comparative test and the measurement of the discharge starting voltage were performed using the apparatus shown in FIG. The commercial AC power supply 100 is replaced with the AC stabilized power supply 10
After the stabilization, the output voltage was supplied to a high-frequency high-voltage power supply 104 capable of variably adjusting the output voltage. 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 internal electrodes 54 and 56 of each corona discharge device under test via a lead wire. In order to measure the output voltage of the high-frequency high-voltage power supply 104,
A high voltage probe (Iwasaki Communication Equipment, HV-P30) was connected between the leads, 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 a current probe 110 arranged on one lead wire, and its output was amplified by an amplifier 112, and then sent to the second channel of the oscilloscope 108 to read the current value.

In the running-in operation of the intermediate product, 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 further another series of intermediate products is operated. It was run at different voltages and for different times. Still other series of intermediate products were tested without running-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 to No. 4, the voltage adjustment 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 with the current probe 110 and using the oscilloscope 1 via the second channel.
08 was displayed on the screen of FIG. 8, and a judgment was made based on the current waveform of the oscilloscope, and corona discharge was visually confirmed. When the occurrence of corona discharge is confirmed, the oscilloscope
After switching to the channel, the voltage value detected by the high voltage probe 106 was read, and this was used as the discharge starting voltage. As described above, the discharge start voltage measured when an unused corona discharger is operated for the first time is defined as the initial discharge start voltage. Next, each corona discharger was set to about 5.4 kV
Up to approx. 20 at _PP (peak-to-peak voltage) operating voltage
Operated for 00 seconds. The operation was interrupted from time to time, and the discharge starting voltage at each time was measured in the same manner as described above.

FIGS. 11 to 1 showing the variation of the discharge starting voltage.
The effect of the protective layer and the effect of the smoothing operation will be described based on the graph of FIG. In these graphs, the vertical axis indicates the discharge starting voltage (kV _PP ), and the horizontal axis indicates the operating voltage (about 5.4 V).
kV _PP ). The results plotted with white circles, triangles, and black circles represent the maximum, minimum, and average values of the discharge starting voltage measured for a series of five to ten corona dischargers, respectively.

First, referring to the graph of FIG. 11, the graph shows how the discharge starting voltage varies depending on the integrated operation time in a series of intermediate products of the corona discharger before the break-in operation. Is shown. As can be seen from this graph, in the intermediate product in which the protective layer is not modified, the initial firing voltage (ie, the firing voltage when the integrated operation time is zero) is about 4.4 kV _PP per product. It shows a large variation in the range up to about 5.1 kV _PP . Such a large variation in the initial discharge starting voltage for each product is probably due to the fact that the surface roughness varies from product to product because the protective layer 68 is formed by firing the ceramic forming material. It is considered something. Also,
As can be clearly understood from the graph of FIG. 11, as the device is operated at a predetermined operating voltage (approximately 5.4 kV _PP ), the variation in the discharge starting voltage sharply decreases, and the average value of the discharge starting voltage gradually decreases. This is considered to be due to the fact that 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 discharge device for the comparative test in which the external floating electrode is not covered with the protective layer. Since there is no protective layer, compared to the results shown in the graph of FIG. 11, the initial firing voltage is much lower and the variation among products is small.
However, as the integrated operation time increases, the discharge starting voltage gradually 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 operated in accordance with the present invention, and the operation was performed under different conditions.

The graph of FIG. 13 shows the results of a series in which a running-in operation was performed at an applied voltage of about 7 kV _PP for about 3 seconds.
As can be seen from the comparison with the graph of FIG. 11, there is no appreciable change in the discharge starting voltage. It is believed 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 running-in operation was performed at an applied voltage of about 7 kV _PP for about 30 seconds. As can be seen from the comparison between the graphs of FIGS. 11 and 13, the variation of the initial firing voltage is significantly reduced. Furthermore, the initial discharge starting voltage itself has been significantly reduced. As operated at an operating voltage of about 5.4 kV _PP, the firing voltage initially showed some drift, but then gradually decreased.

The graph of FIG. 15 shows the results of still another series in which the running-in operation was performed at an applied voltage of about 7 kV _PP for about 300 seconds. Although the average value of the initial discharge starting voltage is smaller than the value in FIG. 14, the drift is correspondingly increased.

The graphs of FIG. 16 and FIG. 17 show the results of a series in which a running-in operation was performed at an applied voltage of about 8 kV _PP for about 30 seconds and about 120 seconds, respectively. These graphs show that the running-in operation under such conditions is also effective in reducing the initial firing voltage and reducing the variation in the initial firing voltage.

Next, a corona discharger obtained by performing a running-in operation for about 30 seconds at an applied voltage of about 7 kV _PP was 6000
An accelerated life test equivalent to hours was performed. In this test, the amount of ozone generated was measured while operating the corona discharger in a flow 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 has been sufficiently operated for the reforming of the protective layer, has a running time of about 2 pp for a working time equivalent to 6000 hours.
m (equivalent to 0.2 ppm when the flow rate is 100 l / min)
That is, a very small amount of ozone generated. 6
Even after 2,000 hours of operation, the decrease in ozone generation remains at about 30%.

[0056]

As described above, according to the method of the present invention, the variation of the initial discharge starting voltage for each product is greatly reduced, so that a very small amount of, for example, 0.2 ppm in an air flow of 100 l / min. The mass production of corona dischargers capable of generating ozone with high accuracy can be achieved.

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 minute amount of ozone is stably generated for a long period of time. Can be done.

In another aspect, modification of the protective layer lowers the initial firing voltage and allows the corona discharger to operate at a lower normal operating voltage, and thus is manufactured 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 the drawings]

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

FIG. 2 is a schematic sectional view of a conventional juxtaposed electrode type corona discharger.

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

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

FIG. 5 is a schematic sectional view taken along line VV of FIG. 4;

FIG. 6 is a schematic sectional view taken along the line VI-VI of FIG. 4;

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

FIG. 8 is a flowchart of a method for manufacturing a corona discharger according to the present invention.

FIG. 9 shows a continuation of the flowchart of FIG. 8;

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

FIG. 11 is a graph showing a change in a discharge starting voltage of a corona discharger that did not perform a break-in operation.

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

FIG. 13 is a graph showing a change in a discharge starting voltage of a series in which a running operation was performed for about 3 seconds at an applied voltage of about 7 kV _PP .

FIG. 14 is a graph showing a change in a discharge starting voltage of a series in which a running-in operation was performed for about 30 seconds at an applied voltage of about 7 kV _PP .

FIG. 15 shows about 300 kV _{PP at} an applied voltage of about 7 kV _PP .
It is a graph which shows the fluctuation | variation of the discharge starting voltage of the series which performed the running-in for seconds.

FIG. 16 is a graph showing a change in a discharge starting voltage of a series in which a normalizing operation was performed for about 30 seconds at an applied voltage of about 8 kV _PP .

FIG. 17 shows an applied voltage of about 8 kV _PP for about 120
It is a graph which shows the fluctuation | variation of the discharge starting voltage of the series which performed the running-in for seconds.

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)

(57) [Claims] A first and a second planar electrode buried in a dielectric substrate and separated from each other; a terminal means for applying a high-frequency voltage between the electrodes; a first electrode and a second electrode; Producing an intermediate product of a corona discharger comprising: a third electrode disposed on the substrate to capacitively couple the corona discharger; and a corrosion-resistant and electrically insulating protective layer covering the third electrode. A corona discharge device which is obtained by applying a high-frequency voltage having a voltage higher than an 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. A voltage applied between a first electrode and a second electrode of the intermediate product is slightly lower than a dielectric breakdown voltage between the first electrode and the second electrode. Item 1
Of manufacturing a corona discharger based on the method. 3. The method according to claim 1, wherein applying the voltage to the intermediate product is performed for at least about 5 seconds. 4. The effective thickness of the dielectric between the first and second electrodes and the third electrode is about 25-70 μm for operating the final product at an operating voltage of about 6 kV _PP , 4. The method according to claim 1, wherein the effective thickness of the layer is about 7-20 [mu] m. 5. A first and second planar electrode buried in a dielectric substrate and separated from each other, a terminal means for applying a high-frequency voltage between the electrodes, and the first and second electrodes. Producing an intermediate product of a corona discharger comprising: a third electrode disposed on the substrate to capacitively couple the corona discharger; and a corrosion-resistant and electrically insulating protective layer covering the third electrode. The protective layer is modified by applying a high-frequency voltage higher than the initial discharge starting voltage of the product between the first electrode and the second electrode of the intermediate product for a predetermined time, and the initial firing voltage of the intermediate product is modified. A method for manufacturing a corona discharger, comprising obtaining a final product of a corona discharger having a lower initial firing voltage.