JPS587310Y2 - Discharge electrode for electromagnetic ultrasonic generation - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement of a discharge electrode for electromagnetic ultrasonic generation that generates high-frequency pulse current to directly send ultrasonic waves to conductive materials through interaction with electricity and magnetism. It is.

Research into the so-called electromagnetic ultrasonic method, which generates and detects ultrasonic waves in conductive materials through interaction with electricity and magnetism, is progressing, and its efficiency is now equal to or higher than that using conventional ultrasonic transducers. It is used for flaw detection, thickness measurement, etc.

Conventionally, discharge electrodes used to generate electromagnetic ultrasonic waves include those with a pair of electrodes placed in the air, and those with a pair of electrodes placed in a ceramic or glass tube and sealed with gas. In the former case, wear and tear on the electrodes due to high temperatures during sparking is unavoidable, and it is often necessary to polish or replace the electrodes.

In addition, there are practical problems such as the humidity of the atmosphere around the discharge electrode and the influence of fine dust making the discharge unstable, and the spark generated during discharge igniting surrounding flammable materials or causing an explosion. ing.

The latter has a high discharge frequency, with a discharge rate of 103 ~ after short-term use.
If the number of times exceeds 105, the gas inside the pipe becomes ionized and becomes unusable, which is a problem as the frequency of replacement is high.

This invention uses a discharge electrode with a structure in which a pair of metal electrodes is placed in a container, a trigger electrode is placed close to one of the metal electrodes, and a nonflammable gas is blown into the container, thereby stabilizing the discharge. It has also been recognized for its remarkable practical usefulness, with a semi-permanent lifespan.

Hereinafter, this will be explained in detail using examples.

FIG. 1 is a schematic diagram showing the principle of electromagnetic ultrasound generation and detection.

When a magnetic field generating coil 2 and an iron core 3 are arranged near the conductive material 1 and a voltage is applied to the magnetic field generating coil 2 from a power source 4, a magnetic field 5 as shown by a dotted arrow is generated within the conductive material 1. .

On the other hand, when a high-frequency pulse current is passed through the ultrasonic excitation coil 6 from a high-frequency pulse power source 7, an eddy current 8 is generated by induction in the conductive material 1, and as a result of the interaction between the eddy current 8 and the magnetic field 5, Fleming The left-hand rule produces a vibrational force 9 shown by the arrow.

This vibration force 9 then travels in the direction shown by arrow 10 as an ultrasonic wave.

When this ultrasonic wave reaches the bottom surface S or an internal defect of the conductive material 1, it is reflected and travels in the direction of the arrow 11, and when it reaches near the material surface, it generates a vibration force 12, which interacts with the magnetic field 5, causing Fleming's An eddy current 13 is generated according to the right-hand rule.

The eddy current is detected by the detection coil 14 and the amplifier 1
5, and the display 16 displays the thickness of the material and internal defects.

Due to its principle, this method can be applied to high-temperature materials and materials with poor surface conditions, and has important industrial value.

FIG. 2 is a schematic diagram showing the structure and operation of the discharge electrode for gas-blown electromagnetic ultrasonic wave generation according to the present invention.

Main electrodes 18 and 19 are arranged facing each other in a container 17,
A trigger electrode 20 is provided close to the main electrode 19, and these electrodes are supported by fixed racks 21, 22, 23 at the bottom of the container 17, and the gaps between each electrode are adjusted by gap adjusting screws 24, 25, 26. can be adjusted and fixed, and the fixing rack 23 of the trigger electrode 20 is mounted so as to be movable in the left and right direction as shown by arrow 27.

The container 17 also has an inlet 28 for inflammable gas G.
It is attached facing the main electrodes 18 and 19, and has a structure in which a gas G' discharge port 29 is opened.

In this operation, first, a nonflammable gas G such as nitrogen or argon is introduced into the container 17 little by little from the gas blowing port 28 and released from the discharge port 29, and the air in the container 17 is filled with nonflammable gas G. Even after the gas is completely replaced, the nonflammable gas is kept continuously flowing in and out in small amounts.

In this state, when DC voltage is supplied from the DC voltage generator 30 to the capacitor 32 via the resistor 31, the capacitor 32 is charged with electric charge for discharging.

On the other hand, the main electrode 19 is connected to the ultrasonic excitation coil 6, and when a trigger pulse voltage is applied to the trigger electrode 20 from the trigger power source 33 in this state, the difference between the trigger electrode 20 and the main electrode 19 is A micro discharge occurs, which induces a main discharge between the main electrodes 18 and 19, and a high-frequency pulse current flows through the ultrasonic excitation coil 6.
As described above, ultrasonic waves are transmitted to the conductive material.

Inject nitrogen gas into the container 17 at a flow rate of 0.27117 m in
, a pressure of 1.5 kg and 7 crlL was blown from the gas inlet 27, 5 mm diameter tungsten rods were used for the main electrodes 18 and 19, and 1.0 mm diameter tungsten rods were used as the trigger electrode 20, and the DC voltage was set to 20 mm. , resistance 2MΩ, capacitor capacity 0.1μF, discharge gap 10 between the main electrodes, and when a trigger pulse voltage of 10KV was applied, the main electrode 1
A stable discharge could be generated between 8 and 19, and a high frequency pulse current with sufficient output was obtained.

This stabilization of the discharge is achieved by maintaining a constant atmospheric condition between the main electrodes 18 and 19 by the nitrogen gas blown into the container 17. I almost no longer receive it.

In addition, wear and tear on the main electrodes 18 and 19 due to high temperatures during sparking is practically negligible, making semi-permanent use possible.

Furthermore, since the spark during discharge is surrounded by nitrogen gas, there is no need to take precautions against igniting surrounding flammable substances or causing explosions, which has been recognized as being of great practical utility.

As described above, according to the present invention, it is possible to provide a discharge electrode for generating electromagnetic ultrasonic waves that is capable of generating stable discharge and has a long life.

In addition, in the example, explanation was given using a discharge electrode provided with a trigger electrode, but a discharge method using a pair of counter electrodes with both electrodes fixed, or a method in which discharge is performed by swinging one of the electrodes is also possible. Application to electrodes is also effective.

Although a tungsten rod is used as the electrode, other conductive metals such as stainless steel may be used.

Further, the gas blown into the container 17 is not particularly limited as long as it is a nonflammable gas.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram illustrating the principle of electrode ultrasound generation and detection. FIG. 2 shows a schematic diagram of a discharge electrode for gas-blown electromagnetic ultrasonic wave generation according to the present invention. 1... Conductive material, 2... Coil for magnetic field generation, 3... Iron core, 4... Power supply, 5
...Magnetic field, 6 ... Ultrasonic excitation coil, 7 ... High frequency pulse power supply, 8 ... Eddy current, 9 ... Vibration Power, 10...Arrow,
11...Arrow, 12...Vibration force, 13
...Eddy current, 14...Detection coil, 1
5...Amplifier, 16...Display device, 17
...Container, 18...Main electrode, 19...
...Main electrode, 20...Trigger electrode, 2
1...Fixed rack, 22...Fixed rack, 23
... Fixed rack, 24 ... Gap adjustment screw, 25 ... Gap adjustment screw, 26 ...
Gap adjustment screw, 27...arrow, 28...
...Gas inlet, 29...Discharge port, 30.
...DC voltage generator, 31...Resistor,
32... Capacitor 33... Power supply for trigger.

Claims (1)

[Scope of utility model registration request] An ultrasonic excitation coil is used to flow a high-frequency pulse current near the surface of a conductive material, and the high-frequency current flowing through the ultrasonic excitation coil alone or mutually with a magnetic field from a magnetic field generator provided separately is used. In a high-frequency pulse power source that flows a high-frequency pulse current to an ultrasonic excitation coil of an electromagnetic ultrasonic generator that generates ultrasonic waves in a conductive material by action, it houses a discharge electrode and has a nonflammable gas blowing hole. A discharge electrode for generating electromagnetic ultrasonic waves characterized by being provided with a storage container.