KR100438211B1 - Apparatus for searching pieces of metal and method thereof - Google Patents

Abstract

The present invention relates to an excitation coil for exciting a magnetic field and a metal piece detection device and a method for separating a detection coil for generating a magnetic field by the magnetic field by the excitation coil to detect a metal piece, and a method for generating a magnetic field by receiving power. part; A detection coil part which is physically separated from the excitation coil part and generates an induced voltage according to the change of the magnetic field; It includes a discrimination unit for generating a signal for detecting the metal piece by determining the amount of change in the induced voltage, it is possible to separate and install the excitation coil for applying a magnetic field to the metal piece contained in the conveyed raw material and the detection coil for detecting the change amount of the magnetic field. As a result, the amount of change in the magnetic field according to the presence or absence and the type and size of the metal body can be effectively detected, and the operation stability of the detected signal processing is brought.

Description

Apparatus for searching pieces of metal and method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of detecting metal pieces from a raw material in a liquid state or a powder state, and more particularly, to a metal piece detection device in which an excitation coil for generating a magnetic field and a detection coil for detecting a metal piece are separated.

In general, in the process of processing a large amount of powdery materials with a conveyor, such as a raw material conveying line in the steelmaking process, various metal substances mixed in the raw materials affect the quality of the produced product, and in particular, cause damage to the conveying conveyor. This causes the movement of raw materials to be continuously processed to be interrupted. Indeed, such conveyor belt breakage has very serious consequences when processed in a continuous process. In order to solve this problem, devices have been devised to detect and remove metal substances mixed in the raw materials in various ways. The main metal strip detection device currently used uses one coil and passes the conveyor belt inside the coil. The method of detecting the variation amount of the secondary magnetic field generated in the coil by the metal passing through is used. In the conventional method of detecting a metal piece, the basic principle is to detect the presence or absence of a metal body by measuring a variation of an excitation current for applying a magnetic field to a metal body in a conveyed raw material and a secondary magnetic field generated by the metal body. . In this method, both magnetic field generation and metal body detection are performed by the coil. Due to the characteristics of the coil, it acts as a kind of antenna for external electromagnetic noise components. In the case of electric spark generation, such a noise component is induced in the detection coil, and even when there is no metal body, there is a malfunction of outputting a detection signal. This malfunction has the disadvantage that in the industrial field having a continuous transfer facility, there is a significant operation disruption and productivity deterioration, which inevitably requires the human eye to check the equipment.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a metal piece detecting apparatus and a method for separating an excitation coil and a metal piece detecting coil generating a magnetic field in order to solve the above problems.

Another object of the present invention is to provide a computer-readable recording medium having recorded thereon a program for executing the method on a computer.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the schematic diagram provided in the conveyor belt of the metal piece detection apparatus which concerns on this invention.

2 is a block diagram of a metal piece detection apparatus according to the present invention.

3A and 3B are views illustrating an excitation coil part for generating a magnetic field and a detection coil part for detecting a metal piece by generating an induced voltage in the metal piece detection apparatus according to the present invention.

4 is a diagram showing a distribution table of magnetic fields between the excitation coil portion and the detection coil portion of the metal piece detection apparatus according to the present invention.

5A and 5B show signal waveforms before phase correction and signals after phase correction for two induced voltages detected by the metal piece detecting apparatus according to the present invention.

6 (a) and 6 (b) are diagrams showing the output waveform before the metal piece is introduced and the output waveform after the metal piece is inserted by the metal piece detection apparatus according to the present invention, respectively.

7 is a view showing the flow of a metal piece detection method according to the present invention.

8 is a view showing a signal processing form of the detection window by the metal piece detection method according to the present invention.

According to an aspect of the present invention, there is provided a metal piece detecting apparatus comprising: an excitation coil unit configured to generate a magnetic field by receiving power; And a determination unit configured to determine a change amount of the induced voltage to generate a signal for detecting a metal piece.

The metal piece detection method according to the present invention for achieving the above object, (a) generating a magnetic field by applying a pulse voltage and detecting the induced voltage generated by the magnetic field; (b) a trigger for generating the pulse voltage Reading only the induced voltage in the time domain corresponding to the pulse width of the voltage; (c) comparing the magnitude of the induced voltage read in step (b) with a reference value to determine whether a metal piece is present.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

In the present invention, in order to solve various problems in the metal piece detection apparatus using a conventional single coil, the magnetic field according to the presence and type and size of the excitation coil and the metal body for applying the magnetic field to the metal pieces contained in the raw material to be transported It has two detection coils connected in parallel with three coils to effectively detect the change amount, and measures the change in the magnetic field attenuation rate that replaces the detection method by the peak voltage of the conventional magnetic field variation. Disclosed is a metal piece detection device that secures detection efficiency and operational stability.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the schematic diagram which installed the metal piece detection apparatus which concerns on this invention in a conveyor belt.

The coil unit 120 is a detection coil for generating an induced voltage by an amount of change in the magnetic field caused by metal pieces included in the powder material or raw material conveyed from the excitation coil unit and the Kenvey belt 150 that generate a magnetic field by receiving power. When the induction voltage detected by the detection coil part is compared with the reference value in the control box 130 and the metal value is determined to be present when it is not the same as the reference value, and generates and outputs a metal piece detection signal, the alarm sound generating unit ( In 140, an alarm sound is generated or an alarm lamp is displayed to confirm the presence of the metal piece. In addition, the conveyor belt is stopped by the motor control by the presence signal of the metal piece. Here, the reference value compared with the induction low pressure indicates an induction voltage value experimentally obtained when the metal piece is not included in the material or the raw material moved to the conveyor belt.

2 is a block diagram of the metal piece detecting apparatus according to the present invention, and includes a power supply unit 210, a coil unit 220, a control box 230, an alarm signal unit 241, and a motor control unit 243. do.

3A and 3B illustrate an embodiment of an excitation coil portion 221 for generating a magnetic field and a detection coil portion 223 for generating a induced voltage to detect a metal piece in the metal piece detection apparatus according to the present invention. It is a figure which shows.

4 is a diagram showing a distribution table of magnetic fields between the excitation coil portion and the detection coil portion of the metal piece detection apparatus according to the present invention.

5A and 5B show signal waveforms before phase correction and signals after phase correction for two induced voltages detected by the metal piece detecting apparatus according to the present invention.

6 (a) and 6 (b) are diagrams showing the output waveform before the metal piece is introduced and the output waveform after the metal piece is inserted by the metal piece detection apparatus according to the present invention, respectively.

2 to 6 together will be described below.

The power supply unit 210 includes a power supply 211, a pulse voltage generator 215, and a trigger voltage generator 213. The power supply 211 outputs a rectified DC component by receiving an AC voltage and maintains the constant voltage by the constant voltage circuit. The pulse voltage generator 215 is configured using a field effect transistor (FET) and receives a DC component maintained at a constant voltage and a trigger voltage output from the trigger voltage generator 213 to generate a pulse voltage. do. The reason for generating the pulse voltage is to generate a periodic magnetic field by generating a periodic magnetic field and synchronizing with the conveying speed of the Kenvey belt in order to measure the magnetic field fluctuation caused by the metal piece. In the present invention, the frequency of the pulse voltage generator 215 has a frequency of about 500 Hz and the duty ratio of the pulse voltage is about 23 [%]. The pulse voltage generated in this way is supplied to the pulse voltage of about 200V through the power amplification in order to supply to the excitation coil unit 221. Here, the trigger voltage turns on the FET so as to generate a pulse voltage only for a predetermined period t within a predetermined period T.

The coil unit 220 includes an excitation coil unit 221 for generating a magnetic field and a detection coil unit 223 for generating an induced voltage. The pulse voltage output from the pulse voltage generator 215 is input to the excitation coil unit 215 to form a constant alternating magnetic field between the excitation coil unit 221 and the detection coil unit 223. At this time, if the distance between the excitation coil unit 221 and the detection coil unit 223 is fixed constantly, the three detection coils of the excitation coil unit 221 and the first detection coil unit 323 of the detection coil unit 223 are separated. A magnetic field with a certain decay rate is produced. In addition, a constant magnetic field is generated between the excitation coil portion 221 and the second detection coil portion 325 of the detection coil portion 223. In fact, the magnetic field distribution in the case of maintaining the coil spacing (interval between the excitation coil part and the detection coil part) of 1400 mm is shown in FIG. 4 so that an equal magnetic field is formed between the excitation coil part 221 and the detection coil part 223. The better the uniformity, the more equal the detection sensitivity can be realized for the whole width of the conveyor belt. When the magnetic field is formed as described above, when the metal body passes through the magnetic field, an even magnetic field is shaken, and the metal body is detected through the amount of change in the magnetic field.

The control box 230 includes an amplifier 231, a switching unit 233, and a determination unit 235. The amplifier 231 is configured as a differential amplifier that differentially amplifies the two induced voltages output from the detection coil unit 221. The switching unit 233 switches and outputs the signal output from the amplifier 231 according to the trigger voltage of the trigger voltage generator 213. It is necessary to minimize the loss of a signal in the switching process of the switching unit 233, and in particular, to match the phase between the trigger voltage and the signal output from the detection coil unit 223 to prevent distortion of the signal. Impedance matching of each of the three detection coils 323 and the second detection coil unit 324 is necessary, and through this process, an environment in which a signal can be obtained completely must be set. FIG. 5A shows waveforms when the detected two induced voltages do not coincide with each other, and FIG. 5B shows output waveforms when the phases coincide with each other. In this way, the distortion and loss of the detection waveform obtained by the generated magnetic field of the excitation coil part 221 can be minimized through the coincidence of the phases.

Next, the detection waveform when the metal piece is present or not is shown in FIG. 6. First, FIG. 6 (a) shows a case where there is no metal piece and FIG. 6 (b) shows a case where the metal piece passes through the conveyor belt. The output when the metal piece passes when comparing the voltages obtained from the output waveforms of the two cases. It can be seen that the voltage of the waveform has increased. As such, it is possible to know whether the metal body passes through the increase in the output voltage. Here, reference numerals 611 and 613 correspond to waveforms of pulse voltages, and 631 and 633 denote signals output from the switching unit 233.

The determination unit 235 compares the signal output from the switching unit 233 with a reference value, and generates and outputs a signal detecting the metal piece if the signal output from the switching unit 233 is not equal to the reference value. Upon receiving the metal piece detection signal, the alarm signal unit 241 displays an alarm sound or an alarm lamp, and the motor control unit 243 stops the conveyor belt.

7 is a view showing the flow of a metal piece detection method according to the present invention.

When a pulse voltage is applied to the excitation coil part 221 (step 710) to generate a uniform magnetic field (step 721), the detection coil part 223 generates two induced voltages due to an induction magnetic field (step 723). When the induced voltage is detected (step 725) and the amplification unit 231 receives two induced voltages and differentially amplifies and outputs it (step 731), the determination unit 235 triggers the pulse voltage among the differentially amplified signals. When only the time portion corresponding to the pulse width of the signal is read (step 733), the read signal is compared with the reference value and determined to be not the same value (step 735). Then, the motor stop signal and the alarm signal sound generation signal are generated (step 737). The alarm signal unit 241 sounds an alarm sound or displays an alarm light to inform the user of the presence or absence of a metal piece, and the motor stop unit 243 stops the conveyor belt.

Problems in this detection process are changes in the permeability of raw materials passing through and noise from the outside. Changes in the permeability of the raw material will eventually affect the detection waveform obtained to reduce the detection resolution, especially when the raw material is iron ore, can cause a very serious detection obstacle. In addition, when noise is input from an external device such as a wireless device, such a component may affect the output voltage and cause a malfunction regardless of the presence or absence of a metal piece. In order to solve this problem, the present invention uses a detection method to obtain only a matched portion of an induced voltage waveform detected by using a trigger signal of a pulse voltage generating a magnetic field.

8 shows a window for the detection method according to the present invention, which first generates a pulse voltage 810 for the magnetic field generated by the excitation coil part 221 and then corresponds to a rising time of the pulse, that is, a time domain corresponding to the pulse width. The signal 730 obtained by differentially amplifying the induced voltage waveform 720 and the two induced voltage waveforms is read. Through this process, even if the change of external noise and permeability appears, only the signal in the region that is completely coincident with the point of excitation of the magnetic field is read. Therefore, the influence of the malfunction due to the external environmental change is remarkably reduced. Since it is possible to increase the detection efficiency and improve the resolution, it is possible to derive very excellent characteristics compared to the existing detection apparatus. Therefore, it has the capability to detect a small metal piece.

Meanwhile, the above-described embodiments of the present invention can be written as a program that can be executed on a computer. And, it can be implemented in a general-purpose digital computer for operating the program using a medium used in the computer. The media may be stored such as magnetic storage media (e.g., ROM, floppy disk, hard disk, etc.), optical reading media (e.g., CD-ROM, DVD, etc.) and carrier waves (e.g., transmission over the Internet). Media.

As described above, according to the present invention, it is possible to solve the problem of malfunction caused when the minimum detection limit is set low, and to detect a metal piece mixed with a material having magnetic permeability such as iron ore. Applicable The minimum detection limit obtained in the existing apparatus is 250x250x10 [mm] in the case of steel sheet, while the apparatus according to the present invention shows an improved feature of 120x120x5 [mm], and in particular, it is possible to detect various raw material conditions. As such, when using the metal piece detection apparatus according to the present invention, various metal substances mixed in the raw material transfer line can be more effectively removed, and a stable operation can be secured compared to the existing apparatus.

Claims (12)

An excitation coil part receiving power and generating a magnetic field in a predetermined detection area; A moving unit for moving a raw material in a liquid or powder state to pass through the detection area; A detection coil part which is physically separated from the excitation coil part and generates an induced voltage according to a change of a magnetic field generated by a metal piece included in the raw material entering the detection area; And And a discrimination unit for outputting a detection signal indicating whether a metal piece is included in the raw material based on the magnitude of the induced voltage. The method of claim 1, A trigger voltage generator for generating a trigger voltage having a predetermined period and pulse width; And And a pulse voltage generator for generating a pulse voltage for a time corresponding to the pulse width of the trigger voltage and supplying the pulse voltage to the excitation coil part. The method of claim 1, wherein the excitation coil portion And a magnetic field generating device on a conveyor belt for carrying the raw material. The method of claim 1, wherein the detection coil portion And connecting the same coils three by three to form one detection coil, and the detection coils are configured in two pairs to generate two induced voltages. The method of claim 4, wherein An amplifier for differentially amplifying the two induced voltages output from the detection coil unit as inputs; And And a switching unit configured to switch the differentially amplified and output induced voltage based on a magnetic field change period of the excitation coil unit. The method of claim 1, wherein the determining unit Metal piece detection device for generating a metal piece detection signal by comparing the magnitude of the induced voltage generated in the detection coil portion and the reference voltage set according to the raw material The method of claim 3, And a motor control unit for controlling the operation of the conveyor belt in response to the detection signal of the metal piece. (a) applying a pulse voltage to generate a magnetic field in a predetermined detection area; (b) moving the raw material in liquid or powder state through the detection zone; (c) detecting an induced voltage according to a change in a magnetic field generated by a metal piece included in the raw material entering the detection region; (d) reading the induced voltage of the time domain corresponding to the pulse width of the pulse voltage from the detected induced voltage; And (e) comparing the magnitude of the read induced voltage with a magnitude of a reference voltage set according to the raw material to determine whether a metal piece is present in the raw material. The method of claim 8, And setting a time domain corresponding to the pulse width of the pulse voltage before step (c). The method of claim 8, (f) if it is determined that the metal piece is present, generating a signal for controlling the conveyor belt for conveying the raw material. The method of claim 8, If it is determined that the metal piece is present, further comprising the step of generating an alarm signal indicating the presence of the metal piece. A computer-readable recording medium having recorded thereon a program for executing the method of claim 8 on a computer.