Patent Application
20160313284
1. Technical Field
Embodiments described herein relates to a discharge electrode suitable for generation of glow corona discharge and a testing device including the discharge electrode.
2. Description of Related Art
As a conventionally-known phenomenon during operation of airplanes, particles in the air, including water vapor, rain, and snow, are charged by friction therebetween, and when such particles collide with airplane bodies or engines, the bodies and engines are charged with static electricity. Components provided with no grounding path to the atmosphere generate glow corona discharge to the atmosphere due to the charged static electricity. Such a discharge of static electricity sometimes causes failure in radios and flight equipment as noise or the like. This phenomenon is called precipitation static.
Recently, airplanes use many nearly insulating composite materials, and there is a demand for proper evaluation of precipitation static in order to prevent precipitation static even in the airplanes using such composite materials. The evaluation needs to generate stable glow corona discharge so as to replicate the precipitation static. In the process of finally discharging the charged static electricity out of airplanes, it is necessary to provide a proper conducting path for even a metallic component as a conductor to lead the static electricity. Gap in the middle of the conducting path causes unintended discharge.
There is no method established which can stably generate glow corona discharge. Moreover, the glow corona discharge is known to become unstable depending on the conditions, including the electrode shape and the range of voltage, and produce Trichel pulses.
The present embodiments are proposed in the light of the aforementioned circumstances, and an object thereof is to provide a discharge electrode capable of stably generating glow corona discharge and a testing device using the discharge electrode to evaluate a component.
To solve the aforementioned problems, a discharge electrode according to the application is a discharge electrode generating glow corona discharge, including: a tip section including a continuous blade forming a closed curve in a plane vertical to the longitudinal direction of the discharge electrode, the blade including a serrated edge formed in the direction that the blade extends.
The tip section is a cylindrical shape, and the blade is formed by a part of the inner surface of the cylindrical shape and a part of the outer surface thereof inclined inward. The serrated edge may include a plurality of serrations having an identical shape.
A discharge electrode according to the application is a discharge electrode generating glow corona discharge, including: a tip section including a continuous blade forming a closed curve in a plane vertical to the longitudinal direction of the discharge electrode; and a base section supplying voltage to the discharge electrode. The tip section is connected to the base section through a resistor having a predetermined resistance value.
The tip section may have a cylindrical shape, and the blade is formed by a part of the inner surface of the cylindrical shape and a part of the outer surface thereof inclined inward. The tip section and resistor may be joined coaxially by screwing or conducting adhesive.
A testing device according to the application evaluates a component by using any one of the discharge electrodes to supply glow corona discharge to the component through the discharge electrode.
The discharge electrode according to the application is capable of stably generating glow corona discharge with reduced Trichel pulses independently of the conditions including the electrode shape and voltage range.
The discharge electrode according to the application includes the electrode stably generating glow corona discharge and thereby enabling to effectively pursue the test of components over the precipitation static.
Hereinafter, a description is given of embodiments of a discharge electrode and a testing device in detail with reference to the drawings.
The discharge testing device includes an electrode section 10 and an electrode section supporting member 20. On the lower surface of the electrode section supporting member 20, at least one electrode section 10 can be provided. The discharge testing device further includes a grounding plate 30 and an insulator 31. The grounding plate 30 is situated under the electrode section 10 and faces the electrode section 10. The insulator 31 is situated on the grounding plate 30 and has a predetermined thickness. The test piece 100 to be subjected to a discharge test is placed on the grounding plate 30 with the insulator 31 interposed therebetween, and there is a distance D0 between the test piece 100 and electrode section 10.
The grounding plate 30 provides a potential reference to the discharge testing device. The grounding plate 30 can be made of an aluminum or copper plate and have a rectangular or circular shape. The distance D0 between the test piece 100 and electrode section can be 1 inch, or 25.4 mm, for example.
To the electrode section supporting member 20, a predetermined voltage is applied from a power supply 40. The power supply 40 includes a high-voltage DC power supply 41 and a switch 43 and can supply a voltage at a predetermined timing. The high-voltage DC power supply 41 can change the supply voltage in a range from −30 kV to 0 V and can supply 10 μA current at −30 kV.
The test piece 100 is subjected to a test that evaluates performances related to discharge by the discharge testing device. The test piece 100 is an airplane component, for example. The test piece 100 is grounded through a shunt resistance 50. The shunt resistance 50 detects discharge current flown to the test piece 100 from the electrode section 10 as a voltage. The shunt resistance 50 can be 5 kΩ, for example. In this case, discharge current of 10 μA generates a voltage of 50 mV.
The voltage generated across the shunt resistance 50 is measured by an oscilloscope 60 and a personal computer (PC) 70 connected to the oscilloscope 60, The shunt resistance 50 and oscilloscope 60 are connected to each other through a 5 m-long 50 Ω coaxial cable, for example. The shunt resistance 50 is equipped with an overvoltage protection circuit and a filter circuit. The overvoltage protection circuit includes a Zener circuit or the like. The overvoltage protection circuit prevents the oscilloscope 60 from undergoing overvoltage failure due to excess discharge including Trichel pulses. The filter circuit is configured so that the measurement frequency band does not change depending on the length of and bend in the coaxial cable.
The oscilloscope 60 measures the voltage generated across the shunt resistance 50 and converts the measured voltage into discharge current flowing through the test piece 100 and discharge current flowing without passing through the test piece 100. The PC 70 analyses the measurements obtained by the oscilloscope 60 and provides a voltage-current characteristic (VI characteristic) graph, for example.
The electrode section 10 includes an electrode 10a rotationally axisymmetric in the direction of an axis and a shaft 10b having the same diameter as that of the electrode 10a. The shaft 10b is attached to the electrode 10a so as to extend on the same axis. The base of the electrode 10a, which is opposite to the tip thereof, is screwed to an end of the shaft 10b. The electrode 10a can be fixed by a conductive adhesive instead of screwing. The same goes for the following description.
The electrode section supporting member 20 is made of a circular metallic plate with a predetermined thickness and includes holes 20b at predetermined intervals so as to penetrate the metallic plate. The electrode section 10 is attached to the electrode section supporting member 20 with the other end of the shaft 10b screwed to one of the holes 20b so that the longitudinal direction of the electrode section 10 is vertical to one surface of the electrode section supporting member 20.
The shaft 10b is substantially longer than the electrode 10a in the longitudinal direction so that the electrode 10a is situated at a predetermined distance from the surface of the electrode section supporting member 20. The electrode 10a and shaft 10b of the electrode section 10 and the electrode section supporting member 20 can be made of proper metal such as brass or aluminum, for example.
As illustrated in
These spacers 20a ensure the predetermined distance between the electrode section supporting member 20 and grounding plate 30 so as to maintain the distance D0 between the electrode section 10 and grounding plate 30. Each of the spacers 20a is made of an insulator so as to electrically isolate the electrode section supporting member 20 from the grounding plate 30.
As a first embodiment, a description is given of an electrode 10a having a blade-shaped and serrated tip (hereinafter, just referred to as a blade-shaped/serrated type). The dimensions thereof are just examples of electrodes used in testing, and the actual profile is not limited to the embodiment.
Considering the necessity to equally and continuously arrange the serrations on the circumference and the workability thereof, the number of the serrations may be even but may be odd. At processing of the serration part including an even number of serrations by using a discharge wire, two serrations facing each other across the axis can be simultaneously formed, thus shortening the processing time.
As apparent from
Compared with the first embodiment illustrated in
In the comparative example of
In the first embodiment illustrated in
By setting the apex angles F1 and F2 of each serration in the aforementioned ranges, it is possible to produce an electric field of a predetermined magnitude and ensure the strength and heat radiation performance of the serrations. Accordingly, discharge can be easily generated without causing erosion due to heat or reducing the processing workability.
A line a in
In the first embodiment, it is thought that production of the above-described unequal electric field concentrating at the tip of each serration generates stable discharge as a whole. The discharge voltage is therefore reduced, and there is no Torricelli pulse. As the results of measurement, discharge occurs in a range from 10 to 28 kV and is glow corona discharge stably maintained without producing Trichel pulses. Moreover, as described above, the slope of the change in discharge current with respect to the change in applied voltage is small, and the robust properties are ensured.
In a second embodiment, the electrode 10a has a blade-shaped tip and is combined and paired with a 100 MΩ resistor having the same diameter as that of the electrode 10a.
In the second embodiment, the electrode section 10 includes a pair of the blade-shaped electrode 10a and 100 MΩ resistor 10c which are combined and joined with a screw 10d. The blade-shaped electrode 10a is different from the blade-shaped/serrated electrode 10a of the first embodiment only in including no serrations. The dimensions of the blade-shaped electrode 10a are the same as those of the blade-shaped/serrated electrode 10a of the first embodiment. The resistor 10c has the same dimensions as the shaft 10b of the first embodiment and gives a resistance of 100 MΩ in the longitudinal direction.
The resistor 10c includes a coating which is formed by uniformly applying a resistor to the circumferential surface thereof. The resistor 10c can be a resistor having a cylindrical structure and including a resistive coating on the surface of the composite or glass cylinder, such as a metal glaze resistor or a ceramic resistor.
The resistor 10c includes the resistor coating uniformly formed on the outer circumferential surface and can be considered as metal having a resistivity. Accordingly, the equipotential surfaces are continuous smoothly near the surface across the joint between the electrode 10a and resistor 10c. The electric field is continuous smoothly from the electrode 10a in the longitudinal direction of the resistor 10c.
In this case, the equipotential surfaces are discontinuous at the joint between the electrode 10a and resistor 10c. In this region, the electric field is significantly disturbed from the electrode 10a in the longitudinal direction of the resistor 10c.
In
Comparing the lines b to e of the second embodiment with the lines g to l of the later-described comparative examples, the slope of the change in current with respect to the change in voltage applied to the electrode section 10 is smaller in the second embodiment than in the comparative examples. This shows the robust properties that current is stable under variations in the applied voltage.
In the second embodiment, it is thought that addition of the 100 MΩ resistor 10c increases the intensity of the electric field at the tip of the blade-shaped electrode 10a and therefore reduces the discharge voltage. As the result of measurement, discharge occurs in a range from 10 to 28 kV, and the discharge is glow corona discharge stably maintained without producing Trichel pulses.
In a third embodiment, the electrode 10a has a blade-shaped/serrated tip and is combined and paired with a 100 MΩ resistor 10c having the same diameter as that of the electrode 10a. The third embodiment is the same as the second embodiment except that the blade-shaped electrode 10a in the second embodiment illustrated in
In
As for the line f of the third embodiment, the slope of the change in current with respect to the change in voltage is smaller than the slope of not only lines g to l of the comparative examples described later but also the slope of the line a of the first embodiment and the lines b to e of the second embodiment. This shows that the third embodiment provides better robust properties that current is more stable under variations in the applied voltage.
In the third embodiment, it is thought that the serrated tip generates a non-uniform electric field while the addition of the 100 MΩ resistor 10c increases the intensity of the electric field at the tip of the electrode 10a. The discharge voltage is therefore further reduced. The discharge is glow corona discharge stably maintained without producing Trichel pulses. Moreover, in the third embodiment, the robust properties are excellent as described above.
The fourth embodiment is a comb-shaped electrode in which the electrode section 10 includes metallic pins arranged on the surface of the electrode section supporting member 20 in a comb fashion.
The electrode section 10 includes plural metallic pointed pins on the surface of the electrode section supporting member 20. The plural pins are arranged at predetermined intervals in a tetragonal arrangement so that the longitudinal direction of each pin extends vertically to the surface of the electrode section supporting member 20. The electrode section 10 can be formed by sticking the pins into the electrode section supporting member 20, which is made of a thin metallic plate, from the back side, for example.
A line e illustrates the result when the area of the electrode section 10 or electrode section supporting member 20 facing the grounding plate 30 is reduced to one third while the distance D0 between the electrode section 10 and grounding plate 30 is maintained at 25.4 mm and the intervals of the pins are maintained at 10 mm. A line f illustrates the result when the distance D0 is maintained at 25.4 mm and the intervals of the pins are increased to 20 mm.
As apparent from the results, as the distance D0 between the electrode section 10 and grounding plate 30 is increased to 25.4, 34, 52, and 64 mm with the intervals of the pins fixed to 110 mm, as illustrated by the lines a to d, the discharge current lowers, and the discharge inception voltage increases. As illustrated by the line e, the discharge current is reduced when the areas of the electrode section 10 and electrode section supporting member 20 are reduced to one third.
On the other hand, as illustrated by the line f, the discharge current increases when the intervals of the pins are increased from 10 mm to 20 mm. This is considered to be because uniform electric fields at the tips of the pins are more likely to be cancelled each other when the intervals of the pins are smaller as 10 mm.
According to the fourth embodiment, stable glow corona discharge is obtained without including Trichel pulses. The discharge occurs in a range from 7 to 11 kV when the pitch is 10 mm and occurs in a range from 5 to 10 kV when the pitch is 20 mm. The robust properties are ensured. Moreover, the discharge occurs uniformly across the electrodes,
In Comparative example 1, the electrode 10a has a blade-shaped tip.
In
As apparent from the lines g to l, as the number of electrodes 10a is increased from one to nine, the discharge current increases and becomes more stable under variations in voltage. However, in every case of Comparative example 1, discharge includes Trichel pulses and is unstable.
Comparative example 2 includes linear electrodes of metallic wires with a predetermined diameter. The metallic wires are linearly extended on the front side of the electrode section supporting member 20 and are arranged at a predetermined distance from the surface of the electrode section supporting member 20 with predetermined intervals.
In Comparative example 2, the metallic wires as the electrodes can be 0.2 diameter wires for use in discharge processing, for example. In Comparative example 2, Trichel pulses sometimes occur, and spark discharge sometimes appears. To generate a non-uniform electric field, the diameter of each metallic wire is preferably smaller. It can be thought that discharge is stabilized with thinner wires.
The embodiments show the electrodes 10a having a tip rotationally axisymmetric by way of example. However, the present embodiments are not limited thereto. The tip of the electrode does not need to be rotationally symmetric and needs to be continuous in a plane. For example, the tip may be a continuous blade forming a closed curve in a plane vertical to the longitudinal direction of the discharge electrode. For example, the electrode may have a tip formed by diagonally cutting the top or may have a polygonal cross section.
In the embodiments, the dimensions of the electrodes and various specifications of the testing device are described by way of example, but the present embodiments are not limited thereto. It can be understood by those skilled in the art that the present embodiments can be also implemented by properly changing the numerical values of the dimensions and specifications.
While embodiments have been exemplified with the help of the drawings, many modifications and changes are apparent to those skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-094461 | May 2014 | JP | national |
This application is a continuation application of international application No. PCT/JP2014/078784 filed Oct. 29, 2014, which claims priority to Japanese Patent Application No. 2014-94461 filed May 1, 2014, each of which is hereby incorporated by reference in their entity.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2014/078784 | Oct 2014 | US |
| Child | 15200545 | US |
