JPS5960278A - Self-diagnostic metal detector - Google Patents

Abstract

PURPOSE:To enable the discrimination of drop in the sensitivity of a detector with automatization of checking operation in stead of the manual method by providing a circuit for causing a change in the phase in a metal detection receiving coil equivalent to that when ferrous or non-ferrous metal is detected. CONSTITUTION:When a contact piece S1 of a phase adjustor 5 is closed, the phase of an induced voltage advances according to the resistance value of a resistance R1 of a phase changing circuit 11 while when the contact piece S1 is opened and a contact piece S2 is closed, the phase of the induced voltage advances according to the resistance value of a resistor R2 and the same signal is obtained as done when a stainless reference ball Msus run in an inspection line 4. Then, when a contact piece S3 is closed, the amplitude of the induced voltage increases according to the resistance value of a resistor R3 in an amplitude changing circuit 12 and the output gives a voltage in the direction of an induced voltage e1. When the contact piece S3 is opened and a contact piece S4 is closed, on the contrary, an output is obtained in the same direction of the induced voltage e2 and thus, the same signal is obtained as done when an ion reference ball MFe runs in the inspection line 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a self-diagnostic metal detector J4Il that allows confirmation of the operation and sensitivity of a metal detection coil without actually running a test piece.

Traditionally, to check whether a metal detector is working properly or whether metal pieces are being detected with the required sensitivity, a standard iron or stainless steel ball is manually placed on an inspection line as a test piece. I was checking it by running it. However, with this method, the production line must be stopped each time, and confirmation cannot be made without human intervention, resulting in production stoppages and the need for human intervention. Also, if the purpose is to detect foreign matter contamination, but the detection sensitivity is insufficient (・Well, at the same time, defective products are passed on as good products,
This fault is difficult to detect, and the system does not always operate safely.

The above conventional example will be further explained with reference to the drawings.

FIG. 1 is an example of a circuit diagram of a conventional metal detector. In this figure, 1 is a high-frequency power supply, 2 is a sending coil, and the frequency type # is excited and maintained by looking at the voltage from 1. 3a.

3b is the receiving coil, and the connection point between the two is grounded.
It is electromagnetically coupled to the transmitting coil 2, and an inspection line 4 through which the inspected object M passes is formed between the transmitting coil 2,
ing. When the object to be inspected M does not pass, an equal induced voltage e1 r crystal z is generated in the receiving coils 3a and 3bK. 5 is a phase adjuster consisting of a variable resistor, etc., and is grounded to the sliding piece 5. When this is moved upward in FIG. 1, that is, toward the receiving coil 3a side, the parallel resistance on the receiving filter 3a side becomes smaller. , as shown in the vector diagram in Figure 2, the induced voltage 6□0 phase advances and becomes rl,
The difference between the induced voltage and the 'e'H-62=60 is 6
．． The vector 6p is approximately 90 degrees ahead of the vector.

When the sliding piece 5a of the phase rA adjuster 5 is moved in the opposite direction to the above, the phase of the induced voltage 2 advances to become b', and the induced voltage increases. The difference between 1' and 2 is D, resulting in a vector eo that advances approximately 90' with respect to .

6 is an amplitude adjuster consisting of a variable resistor, etc., and 6a is its sliding piece, and by moving this, 'el-
5. =RaD Noru. The ratio of taking out 2 changes. For example, when the sliding piece 6a of the amplitude adjuster 6 is moved upward in FIG. Due to the increase, it appears in phase with 11 as shown in the vector diagram of FIG. 1 is an amplifier, 8a and 8b are synchronous detectors, 9
is a phase shifter.

In the conventional metal detector having such a configuration, the phase adjuster 5 and the amplitude adjuster 6 are adjusted without the inspection object M flowing through the inspection line 4, and the synchronous spacing detectors 13a and 8b are Make sure there is no output.

Next, when a standard iron ball is passed through the inspection line 4, the induced voltage is f when it passes through the receiving coil 3a. Since the induced voltage d2 increases when passing through the receiving coil 3b, an output is obtained from the synchronous detector 8a. Therefore, in this case, it can be determined from the presence or absence of the output of the synchronous detector 8a whether or not the metal detector is operating normally.

Next, when a stainless steel standard ball is passed through the inspection line 4, a vortex flows through the standard ball, causing ps. That is, since the resistance component of the receiving coil 3a or 3b through which the standard bulb passes changes, it becomes equivalent to moving the phase adjuster 5, and thereby the output signal changes. appears. Since this output is a vector advanced by 90 degrees with respect to the induced voltage, the output is obtained from the synchronous detector 8b. Therefore, in this case, it can be determined from the presence or absence of the output of the synchronous detector 8b whether or not the metal detector is operating normally.

The above operations are summarized as shown in FIGS. 4 and 5.

FIG. 4 shows that when the iron standard ball MF0 is passed through the inspection line 4 as shown in (a) as the object to be inspected, the synchronous detector 8a,
The output of 8b is shown in (b) and (c).

In the case of iron, the output of the synchronous detector 8b is 0, and the output of the synchronous detector 8a has a sine waveform corresponding to the speed of the standard ball My. That is, it continues to pass through the receiving coil 3a. The signal becomes 2, and continues to flow while passing through the receiving coil 3b. <6.
becomes.

In addition, Fig. 5 shows the outputs of the synchronous detectors 8a and 8b as shown in (b) and ←→ when a stainless steel standard ball Msus is passed through the inspection line 4 as shown in (a) as the object to be inspected. It is something. In the case of stainless steel, the output of the synchronous detector 8a is 0, and the output of the synchronous detector 8b is the standard bulb Msus.
It becomes a sine waveform depending on the speed of.

When the standard sphere M8U[l passes through the receiving coil 3a, the phase of the induced voltage advances, and the receiving coil 3b
When the standard sphere Mst+s passes through, the induced voltage a2
The phase of each synchronous detection signal advances, and each synchronous detection signal becomes an output with both positive and negative polarities.

However, in the conventional metal detector described above, iron and stainless steel standard balls Mr* * M are used as test pieces.
As already mentioned, there are drawbacks such as the need to manually flow su8 into the IJ inspection line 4.

This invention was made in order to eliminate the above-mentioned drawbacks, and a circuit is provided in advance to give a phase change equivalent to that when ferrous or non-ferrous metal is detected in the receiving coil of the metal detection coil, and a switch is used to change the phase. By applying phase changes and amplitude changes to the receiving coil by selecting the The purpose of the present invention is to provide a metal detector that can automatically diagnose ferrous or non-ferrous metals at crystal speed without stopping, and with the highest sensitivity.

The present invention will be explained below with reference to the drawings. Figure 6 is a circuit diagram showing one embodiment of the present invention. In this figure, the same reference numerals as in the λ1 figure indicate the same components, and 10a and 10b are bandpass filters provided after the synchronous detectors 8a+8b, respectively. S+ and Sz are the contact pieces of the switch,
When opened, the resistors RI and R2 are connected to the receiving coil 3a, respectively.
Connect in parallel to 3b. Sz and S4 are also contact pieces of the switch, and when opened, resistors Ri and R4 are respectively connected in parallel between the sliding/depressing piece 6a of the amplitude regulator 6 and both ends thereof. Note that 11 represents a phase change circuit, and 12 represents an amplitude change circuit.

Next, the operation of the embodiment shown in FIG. 6 will be explained with reference to FIGS. 7 and 8.

First, when the phase a1.8 rectifier 5 (contact S provided at IQ) is closed, the phase on the side of the induced voltage advances by an amount corresponding to the resistance value of the resistor R1 in the phase change circuit 11, and , contact piece S
, opens and contacts S2 close, the phase of induced 'rJ and pressure i2 advances according to the resistance value of resistor R2, and the second
Output i as the vector shown in the figure. In order to get the result,
The same signal as when a stainless steel standard bulb MsυS is passed through the inspection line 4 is obtained. The waveforms of each part are shown in Figure 7 (A).
).

Next, when the contact piece S3 is closed, the amplitude of the induced voltage crystal increases by an amount corresponding to the resistance value of the resistor R1 in the amplitude change circuit 12, and the output voltage D increases as shown in FIG. 1 pressure. voltage in the direction. Further, when the contact piece S3 opens and the contact piece S4 closes, an output is generated in the same direction as the induced pressure i, contrary to the above. is obtained. Therefore, the same signal as when the iron standard ball M F s is passed through the inspection line 4 can be obtained. The waveforms of each part in this case are shown in FIG.

FIG. 9 shows another embodiment of the present invention, and FIGS. 10 and 11 show waveforms of essential parts for explaining its operation.

The embodiment of FIG. 9 is similar to the embodiment 7A'1. of FIG. In example i, the contact pieces S, , S4 are replaced with one contact piece SsK, and the contact piece S3°S is replaced with one contact piece 36. As the phase change circuit 11, resistors FIB, R6, Rt
are connected in series, respectively t'1. Contacts a+b are provided at the connection points of 1 and 1, and the contacts arbVc and S are connected by switching. Similarly, the amplitude change circuit 12 is connected to resistors R8r and R5r.
A contact point S6 of the switch is provided to the contact point S6.

Next, the operation will be explained. First, when contact piece S6 is in contact with 5VC contact bK as shown in FIG.
In other words, assuming that the induction 1 is a pressure 61, both the phase and amplitude will be the same, so that -! In addition, when the contact piece S is switched to the contact point a, the values of the resistors R5 to R7 are changed so that the phase of the induction 111 and the pressure resistance advance.
do. During the time that the contact piece S is in contact with the contact point aK, the standard ball M F s or M 8U8 is in contact with the contact point aK.
: or i6 < to a value approximately equal to passing one of 3b. The output from the synchronous detector 8b at this time is the 141st
As shown in the figure, it becomes a square wave, but the 1α flow is cut off by passing it through the bandpass filter 10b.
An AC waveform with approximately half the amplitude of a square wave is
be talented. Therefore, resistors R6~
By selecting fMf of R7, the contact pieces S+ and Sz of the embodiment shown in FIG. 6 can be made to have the same effect with one contact piece SsK.

Next, Fig. 1A11 shows the output waveform of the mounting section in case 8b when the contact piece S6 is switched to the contact point a. That is, in this case,
It is possible to carry out the same diagnosis as in the case where a standard iron ball MFe is passed through the inspection line 4.

Note that the adjusting means in the phase change circuit 11 and amplitude change circuit 12 in each of the embodiments described above is not limited to resistors, and a musical impedance element may also be used.

In addition, if the operation for self-diagnosis is performed after the test food M passes through the inspection line 4 and before the next test object M arrives, it is possible to constantly perform self-diagnosis. This can be done without stopping the line. At this time 2 Self-examination 1
1noi 11. 7th. ni raw 1', should be sigma for te out i, 1
If no code is detected, check line 4 'R' II
Zof'ro judges the Naru test material M to be defective') &U
1-11, it is also possible to prevent defective products from being distributed due to failure of the bow detection device BRT.

As explained above in iiY'#llI, this invention is money from υC! 11, the induction of at least one of the two receiving coils 'i11. A phase change circuit that changes the phase of the pressure and a switch that opens and closes the kneading are installed, so when the phase change circuit is operated, a standard ball made of non-ferrous metal is placed on the inspection line to produce a phase change equivalent to that of a master ball. Upper S
, [: can be given to the induced mixed pressure in the receiving coil.

Similarly, we have provided an amplitude change circuit that changes the amplitude of the induced '+tj pressure in at least one of the two receiving coils and a switch that closes this (ii1), so when the amplitude change circuit is operated, it is necessary to check The amplitude change induced in the receiving coil 1 (L pressure 11
CJ5 can be drawn - pulled. For this reason, it is not only possible to automate operation checks that were conventionally performed manually (it is also possible to detect a decrease in the sensitivity of the metal detector itself; it is also possible to automatically perform self-diagnosis). This has excellent effects such as being able to perform diagnosis at high speed with only switching by utilizing one gap between the objects to be inspected.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a conventional metal detector, Figures 2 and 3 are vector diagrams to explain the operation of the circuit in Figure 1, and Figures 4 and 5 are the same. (Figure 1 is a diagram showing the arrangement of the transmitting coil and receiving coil and the output waveform to explain the operation of the circuit. Figure 6 is a circuit diagram showing an embodiment of the present invention. Figures 7 and 8 are FIG. 6 is a waveform diagram of the main part for explaining the operation of the embodiment, FIG. 9 is a circuit diagram showing another practical example of the present invention, and FIGS. 10 and 11 are the embodiment of FIG. 9. 1 is a waveform diagram of the equipment for explaining the operation of the equipment. In the figure, 1 is a high frequency power supply, 2 is a transmitting coil, 3a+3b is a receiving coil, 4 is an inspection line, 5 is a phase adjuster, and 5a is a sliding piece. , 6 is an amplitude adjuster, I is an amplifier, 8a + 8b is a synchronous detector, 9 is a phase shifter, 10a. 10b is a band pass filter, 11 digit a change circuit h11
．． 12 +t nrt 'I'ij change circuit, s1~s
6 is a contact piece, a. bf is a point, R1 to R0 are resistors, My is an iron standard ball, and M811111 is a stainless steel stopper ball. 386 Fig. 1 9 Fig. 2 Fig. 4 (a) 22224: Concave MFe o-~4 2° (a). Eeeee uni. Msus' -~4 a (b)

Claims (1)

[Claims] Cross 1. (The difference between the transmitting coil driven by No. U and the two receiving coils installed across the inspection line where the inspected object flows within the electromagnetic field of this transmitting coil, and the rainfall force signal of these two receiving coils. In a metal detector consisting of a synchronous inverse wave detector that synchronously detects the output signal of a signal synchronized with the alternating current signal, the phase of the induced voltage of at least one of the receiving filters is set to the non-ferrous metal J, i mark by 11 balls. a phase change circuit that changes the phase by an amount equivalent to the phase i that occurs when passing through the inspection line; a switch that opens and closes this phase change circuit; A self-diagnosis type metal detector characterized in that it is provided with an amplitude changing circuit that changes the amplitude by an amount equal to the amplitude difference that occurs when passing through the liquefaction line; and a switch that opens and closes the amplitude liquefaction circuit.