KR970010984B1 - Metal specimen detecting apparatus - Google Patents

Abstract

The metal protrusion detector is capable of detecting whether a metal protrusion exists in accordance with the variation of amplitude and strength of a detection signal. The metal protrusion detector comprises: a counter(11) for counting a clock signal to supply address information to a ROM(12); an H bridge(13) for supplying an alternating current to a generator coil(14); a receiver coil(17) arranged between the generator coil(14) and a conveyor(16), for detecting a magnetic field formed by the generator coil(14); a first differential amplifier(18) for amplifying the induced voltage to the receiver coil(17) to an amplitude variation component; a second differential amplifier(19) for amplifying the induced voltage to the receiver coil(17) to a pulse width variation component; a multiplexer(22) for selecting the outputs of the differential amplifiers(18,19) to supply the outputs to an A/D converter(24); and a microcomputer(10) for processing the data from the A/D converter(24) to display the existence/non-existence of the metal protrusion on a display(26).

Description

Metal piece detection device

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

FIG. 2 is a detailed circuit diagram of the H bridge shown in FIG.

3 is a detailed circuit diagram of the differential and preamplifier shown in FIG.

(A)-(d) are the waveform diagrams of each part of the metal piece detection apparatus by this invention.

FIG. 5A is a graph showing the principle of the amplitude processing method, and FIG. 5B is a graph showing the principle of the decay processing method.

* Explanation of symbols for main parts of the drawings

10: Micom 11: Counter

12: Romans 13: H Bridge

14 generator coil 15 raw material

16: Conveyor 17: Receiver Coil

18,19: differential amplifier 20,21: preamp

22: Multiplexer 23: Sample and Holder

24: A / D converter 25: latch

26: display

The present invention relates to a metal piece detection device for detecting a metal piece contained in the raw material loaded on the conveyor when transferring the raw material transported through a ship or the like to the yard.

In general, the raw material transported by ship or other means of transport is carried in a conveyor to the yard, because the metal pieces contained in the raw material damage the conveyor belt and also when the device is brought into a device such as a crusher. In addition, it should be detected and removed beforehand if metals are included in the raw material.

The metal piece detecting device is provided with a coil on the conveyor to form a magnetic field, and when the material passes through the magnetic field, the metal piece detecting device detects a magnetic field change caused by the metal piece included in the raw material. The change of the signal induced in the receiver coil due to the magnetic field change generated, FIG. 5 (a) is a method of detecting a metal piece according to the change in the size of the detection signal induced in the receiver coil due to the magnetic field change. This graph shows the difference in magnitude of the detection signal between a poorly conductive conductor and a goodly conductive conductor. The amplitude change is small when the material is poorly conductive (i.e. raw material), and the amplitude is changed when the material is very conductive (ie metal piece). Becomes large.

FIG. 5 (b) is a graph which shows the principle of another method using the degree of decay of the detection signal in the conventional metal piece detection device. In the case of a poorly conductive material (i.e., a raw material), the intensity change of the detection signal drops rapidly. Because of the curve, the falling window cannot be read by the measurement window, and in the case of a good conductive material (that is, a piece of metal), since the change in intensity of the detection signal forms a gentle curve, the falling window can be read through the measuring window.

However, the former method using the magnitude difference between the detection signals of the two methods detects only the magnitude of the signal, which is likely to cause malfunction due to frequency disturbance (wireless noise), and the latter method detects by the slope difference of the detection signal intensity curve. There is a problem in that wireless noise is strong but there is a limit in detecting minimum metal pieces.

In addition, a conventional metal piece detection device uses a closed coil, which is difficult to install and maintain when the metal piece detection device is mounted on a conveyor because a metal piece detection coil must be installed after cutting the conveyor valve. There is a problem.

The present invention has been proposed to solve the above-mentioned problems. The object of the present invention is to detect the presence of the metal piece by changing the signal strength as well as the amplitude of the detection signal. To provide.

As a technical means for achieving the object of the present invention described above, the present invention is a metal piece detection device for detecting whether a metal piece is included in the raw material to be conveyed to the Ken Bear belt, the counter for counting the clock pulse output from the microcomputer, A ROM for storing the control signal of the H bridge, receiving the output value of the counter as an address signal, and outputting a control signal stored at the corresponding address; and an H bridge for applying an alternating current to the generator coil according to the control signal output from the ROM. By shaping the magnetic field forming means consisting of a generator coil installed on the upper side of the kenber belt, a receiver coil provided on the lower part of the conveyor belt opposite to the generator coil, and amplitude components of the voltage induced at both ends of the receiver coil. Amplified differential amplifier 1 and the both ends of the receiver coil A differential amplifier 2 for shaping and amplifying the slope component of the pressure, a multiplexer for selectively outputting the output signals of the differential amplifier 1 and the differential amplifier 2 under the control of the microcomputer, and a sample for holding the output signal from the multiplexer A detection means comprising an and hold, an A / D converter for converting a value output from the sample and hold into a digital signal, and outputting the digital signal to a microcomputer; and a digital signal input from the detection means after operating the magnetic field forming means. Check to determine the peak value of the voltage induced in the receiver coil and the slope indicating the intensity change, and when the calculated peak value and the slope value both indicate the presence of the metal piece, the metal piece is present in the raw material to be transferred onto the conveyor. A microcomputer for judging, a latch for temporarily storing a determination result output from the microcomputer and the And a display unit configured to display a determination result stored in the latch.

Hereinafter, the configuration and operation of the present invention in detail based on the accompanying drawings.

1 is a block diagram of a metal piece detection apparatus according to the present invention, which outputs a reference clock pulse and checks a digital signal input from the A / D converter 24 to determine the peak value and slope of the voltage induced in the receiver coil. A microcomputer 10 for determining that the metal piece is present when the calculated peak value and the slope both show a magnetic field change due to the metal piece, a counter 11 for counting the clock pulses output from the microcom 10; An alternating magnetic field is formed in the ROM 12 that receives a counter value output from the counter 11 as an address value and outputs a value stored at the address, and the generator coil 14 according to the output value from the ROM 12. An H bridge 13 for supplying a current to be supplied, a generator coil 14 provided on a conveyor to which raw materials are conveyed, and the generator coil 14 facing each other with the conveyor interposed therebetween. Receiver coil 17, differential amplifiers 1, 2 (18, 19) for amplifying the amount of electricity induced in the receiver coil 17, preamps 1, 2 (20, 21), and the microcomputer 10 Sampling and outputting the multiplexer 22 for selectively outputting the output signal of the preamplifier 1 (20) and the output signal of the preamplifier 2 (21) according to the control signal from the multiplexer (22); A sample end holder 23 for holding and outputting to the A / D converter 24, an A / D converter 24 for converting the value output from the sample end holder 23 into a digital signal, and the microcomputer A latch 25 for temporarily storing a determination result indicating whether or not a metal piece is present in the raw material outputted from (10) and then applying it to the display unit 26, and under the control of the microcomputer 10, the latch ( And a display unit 26 for displaying the result stored in 25.

FIG. 2 is a circuit diagram showing the internal structure of the H bridge 13 in FIG. 1, and is provided at both ends of the generator coil 14 by drive transistors Q7 and Q8 respectively driven to the A and B outputs of the ROM 12. FIG. The power transistors Q3 and Q4 for selectively grounding are controlled and connected to both ends of the generator coil 14 by drive transistors Q5 and Q6 driving the C and D outputs of the ROM 12, respectively. Optionally, the power transistors Q1 and Q2 supplying the V + voltage are connected to be controlled.

3 is a circuit diagram showing differential amplifiers 1, 2 (18, 19) and preamps 1, 2 (20, 21) in FIG. 1, where differential amplifiers 1, 2 (18, 19) are receiver coils. The voltages shaped by the clip diodes D1 and D2 and D3 and D4 for limiting the generated voltage level between both ends of 17 and the clip diodes D1 and D2 and D3 and D4 Transistors Q9 and Q10 and Q11 and Q12 that are transmitted to the inverting input terminal (-) and the non-inverting input terminal (+) of the operational amplifiers OP1 and OP2, respectively, and the transistors Q9 and Q10 and Q11. And operational amplifiers OP1 and IP3 for differentially amplifying the voltage input through Q12. The differential amplifiers 1 and 2 (18 and 19) are configured in the same manner as above, but the operating points thereof are set differently. .

The preamplifiers 1 and 2 (20 and 21) may include resistors R1, R2, and capacitor C1 configured as a high pass filter to filter the output signals of the differential amplifiers 1 and 2 (18, 19), respectively. (C2) and the operational amplifier (OP2), (OP4) for amplifying the signal passing through the resistor (R1), (R2) and capacitor (C1), (C2), and preamplifier 1 (20) and The preamplifier 2 21 has a different amplification degree.

Referring to the operation of the present invention configured as described above are as follows.

In the metal piece detection apparatus configured as shown in FIGS. 1 to 3, the microcomputer 10 inputs a clock pulse as shown in FIG. 4 (a) to the counter 11, and the counter 11 inputs a clock. The pulse is counted and output to the address terminal of the ROM 12. The ROM 12 outputs the data stored at the address input from the counter 11 to the H bridge 13, and the ROM 12 is shown in FIG. It has four output terminals B, C and D. The ROM 12 outputs a high level signal to the A and C terminals and a low level signal to the B and D terminals according to the input from the counter 11 as described above. Or a low level signal to the A and C terminals and a high level signal to the B and D terminals.

When the A and C outputs of the ROM 12 become high level and the B and D outputs become low level, the power transistor Q2 is turned on by the turn-on of the drive transistor Q6 in the H bridge 13 and the drive is turned on. The power transistor Q3 is turned on by turning on the transistor Q7 so that a current flows in the generator coil 14.

Next, when the A and C outputs of the ROM 12 are low level and the B and D outputs are high level, the power transistors Q1 and Q1 are turned on by turning on the drive transistors Q5 and Q8 in the H bridge 13. Q4) is turned on so that a current flows in the generator coil 14, and a current in the opposite direction to the generator coil 14 flows in the opposite direction to the case where the A and C outputs are high level and the B and D outputs are low level. do.

The H bridge 13 applies a current to the generator coil 14 every time the clock pulse shown in FIG. 4 (a) is turned on under the control of the counter 11 and the ROM 12. As shown in Fig. 4 (b), alternating currents with alternating + and − currents are applied.

A magnetic field is formed around the generator coil 14 by applying the current as shown in FIG. 4 (b), and a predetermined voltage is induced in the receiver coil 17 by the formed magnetic field.

The voltage induced in the receiver coil 17 is input to the differential amplifiers 1, 2 (17, 19) having different circuit constant values and amplification degrees, and is shaped and amplified. The differential amplifier 1 configured as shown in FIG. The output waveform of (17) is the measurable range of the waveform shown in FIG. 4C, that is, the amplitude component of the voltage is standardized, and the differential amplifier 2 19 is the receiver coil 17 as shown in FIG. 4D. The gradient component indicated in the measurable range among the induced voltages is shaped and amplified. The output signals of the differential amplifiers 1 and 2 (17 and 19) are respectively amplified by the preamplifiers 1 and 2 (20 and 21) and input to the multiplexer 22.

The multiplexer 22 selectively outputs any one of the preamplifier 1 (20) and the preamplifier 2 (21) according to the control signal of the microcomputer 10, the preamplifier 1 (20) and preamplifier 1 (21) alternates.

As described above, the output signals of the preamplifier 1 (20) and the preamplifier 2 (21) output from the multiplexer 22 are sampled and held at regular intervals by the sample and hold 23, and output to the A / D converter 24. do.

The sample hold value of the output signal of the preamplifier 1 (20) output from the sample and hold 23 and the sample hold value of the output signal of the preamplifier 2 (21) are converted into digital signals by the A / D converter 24. It is converted and input to the microcomputer 10.

The microcomputer 10 calculates the peak value of the voltage induced in the receiver coil 17 and the intensity variation of the voltage, that is, the slope, from the digital data input from the A / D converter 24. The digital data input from the converter 24 is obtained by sampling the output signal of the preamplifier 1 (20) and the output signal of the preamplifier 2 (20), from two values obtained by sampling the output signal of the preamplifier 1 (20). The peak value of the voltage induced in the receiver coil 17 is calculated, and the degree of change (ie, the slope of the voltage signal induced in the receiver coil) is compared by comparing three digital corals obtained by sampling the output signal of the preamplifier 2 (20). ) Can be calculated.

In addition, the voltage induced in the receiver coil 17 has a low conductivity (a raw material in the present invention) in the magnetic field formed by the generator coil 14 and a good conductor (which is a metal piece in the present invention). If present, the peak difference is as shown in the graph shown in FIG. That is, when the metal piece is in the magnetic field, the peak value of the voltage induced in the receiver coil 17 becomes higher than in the case of the raw material.

In addition, the intensity change of the voltage induced in the receiver coil 17 is also a case of a good conductor (i.e., a metal piece) and a poor conductor (i.e., a raw material) in the case of a metal piece as shown in FIG. 5 (b). The change is smooth (i.e., the slope is smaller), and in the case of raw materials, the change in strength is rapid (i.e., the slope is larger).

Therefore, in the microcomputer 10, the peak value of the voltage induced in the receiver coil 17 calculated as described above is higher than the set value (set to the middle value between the peak value in the conductor with good conductivity and the peak value in the conductor with poor conductivity), When the degree of change in strength (i.e., the slope) is gentler than the set value (set to a middle value between the change in strength of a poorly conductive conductor and the strength change of a conductor having good conductivity), the metal piece may be transferred to the raw material 15 passing through the magnetic field. I judge it exists. In the above, when only the peak value is higher than the set value, or only the degree of change in intensity is gentler than the set value, that is, the presence of the metal piece only at the peak value or the presence of the metal piece only at the intensity change is regarded as malfunction due to external noise.

In the above, the measurement sensitivity can be further increased by adjusting the peak value, which is the determination standard of the microcomputer 10, to the lowest as possible, or by adjusting the setting value of the intensity change degree to be slightly higher than the inclination value when the raw material is a raw material.

The microcomputer 10 outputs the result determined as described above to the latch 25 and controls the display 26 to display a determination result indicating whether the metal piece is included in the material to be conveyed.

As described above, the present invention superimposes the peak value of the voltage induced in the receiver coil and the degree of change in strength thereof in determining whether the metal piece is present in the raw material passing through a certain magnetic field from the voltage induced in the receiver coil. By applying, analyzing and judging, it is possible to eliminate the misjudgment by wireless noise and to detect the fine metal pieces, thereby improving the detection reliability, and to separate the coils for generating the magnetic field and detecting the magnetic field into generator coils and receiver coils. By constructing it can be installed without cutting the conveyor belt, there is an excellent effect to save time and money by convenient facility construction and maintenance.

Claims (1)

A metal piece detection device for detecting whether a metal piece is included in a raw material conveyed by a conveyor belt, wherein a counter for counting a clock pulse output from a microcomputer and a control signal of an H bridge are stored to receive an output value of the counter as an address signal. Magnetic field forming means comprising: a ROM for outputting a control signal stored at the address; an H-bridge for applying an alternating current to the generator coil in accordance with the control signal output from the ROM; and a generator coil provided above the conveyor belt; Only the receiver coil installed at the lower part of the conveyor belt opposite to the generator coil, the differential amplifier 1 for shaping and amplifying the amplitude component of the voltage induced at both ends of the receiver coil and the gradient component of the induced voltage at both ends of the receiver coil Differential amplifier 2 for shaping and amplifying A multiplexer for alternately selecting and outputting the output signals of the differential amplifier 1 and the differential amplifier 2, a sample and hold for sample-holding the output signal from the multiplexer, and a value output from the sample and hold into digital signals. The detection means comprising an A / D converter for outputting to the microcomputer and the magnetic field forming means, and then checking the digital signal input from the detection means to determine the peak value of the voltage induced in the receiver coil and the degree of change of the intensity thereof. And a latch for temporarily storing a determination result outputted from the micom, and a latch for determining that the metal piece exists in the raw material conveyed on the conveyor when both the calculated peak value and the slope value indicate the presence of the metal piece. It is provided with a display unit consisting of a display for displaying the determination results stored in Metal piece detection device characterized in that.