JP2018185279A - Metal detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal detector with which it is possible to quickly and accurately execute the setting of a set frequency for metal detection.SOLUTION: Provided is a metal detector comprising magnetic field detection means for detecting an alternating magnetic field in an inspection area in a set frequency band, determination means for determining the presence of metal in a workpiece on the basis of the resulting detection signal, and variable setting means for variably setting the operation conditions of the foregoing, the metal detector further including frequency selection/setting means (step S15) which, when the variable setting means is active, selects and sets one of a plurality of frequency bands on the basis of a detection signal of the magnetic field detection means. When one frequency channel having been in use as the set frequency band is deselected by operation of the variable setting means, the frequency selection/setting means stores the one frequency channel as having been used until the number of times the variable setting means is operated reaches a prescribed count after the deselection (step S16) and preferentially sets an other frequency channel not having been used yet as a choice for selecting the set frequency band.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a metal detection apparatus, and more particularly to a metal detection apparatus that detects a metal or a metal component in an inspection object based on a magnetic field fluctuation when the inspection object passes through an alternating magnetic field.

  2. Description of the Related Art Conventionally, metal detectors used for inspection of various items such as food expenses and pharmaceuticals are known.

  In addition, an alternating magnetic field is generated in the inspection area, magnetic field fluctuations due to the influence of the inspection object (work) moving in the inspection area are detected, and metal detection is performed using the output obtained by performing detection processing on the detection signal. The metal detection apparatus made to do so is widely used as one capable of metal detection with high versatility regardless of the type of metal.

  In this type of metal detector, an expert has measured the frequency of external electromagnetic noise at the time of initial setting, and adjusted the detection conditions based on the measurement results. The setting frequency (frequency band with a narrow bandwidth) has been selected, but recently, it is possible to detect the setting frequency of the alternating magnetic field that is not easily affected by noise so that the initial setting can be facilitated. The thing is proposed (for example, refer patent document 1).

JP 2006-64642 A

  The conventional metal detection device described above facilitates the initial setting for selecting the frequency of the alternating magnetic field and enables metal detection with reduced influence of external electromagnetic noise, but has the following unsolved problems. .

  When the external electromagnetic noise changes with time in the environment where the metal detector is installed, the set frequency that temporarily becomes the best SN ratio in a certain time zone is deteriorated in other time zones. Resulting in. Therefore, it may be necessary to frequently reselect the frequency of the alternating magnetic field in an environment where external electromagnetic noise is likely to change with time.

  In such a case, every time there is a concern that the SN ratio deteriorates due to the influence of noise and the detection accuracy of the metal detector decreases, the magnetic field frequency is reset or the frequency measurement of the external electromagnetic noise is performed intermittently. In conventional metal detectors, even if the frequency of setting frequency changes is high, the work is almost the same as in the initial setting. Could not be done.

  On the other hand, for example, it is conceivable to check the operation state by the self-diagnosis function of the metal detection device, but the same problem remains in that the same check is repeated.

  The present invention has been made to solve such an unsolved problem, and an object of the present invention is to provide a metal detection device capable of quickly and accurately setting a set frequency band for metal detection.

  In order to achieve the above object, the present invention provides a magnetic field detecting means for detecting a change in the alternating magnetic field caused by the inspection object passing through the inspection region where the alternating magnetic field is generated in a preset set frequency band, A determination unit configured to execute a determination process for detecting a metal in the inspection object based on a detection signal of the magnetic field detection unit; and a variable setting unit configured to variably set an operation condition related to the detection of the magnetic field detection unit. In the metal detection device, when the variable setting unit operates, based on the detection signal of the magnetic field detection unit, one of a plurality of preset frequency bands is selected to set the set frequency band. The frequency selection setting means further comprises a frequency selection setting means for setting, wherein the frequency selection setting means determines whether the selection state of one frequency band used as the setting frequency band depends on the operation of the variable setting means. When released, until the number of operations of the variable setting means after the release reaches a predetermined number, the one frequency band is stored as a used frequency band, and the frequency band for selecting the set frequency band is stored. As an option, a frequency band other than the used frequency band is set with priority over the one frequency band.

  With this configuration, when the variable setting unit performs an operation of changing the setting of the operation condition related to the detection of the magnetic field detection unit, the set frequency band is changed by the variable setting unit and the frequency selection setting unit, and one used frequency band When the variable setting means is operated next time, the used frequency band has a low priority as a selection target of the set frequency band. Therefore, the next set frequency band is preferentially selected from other frequency bands having a relatively high priority, and the set frequency band can be set quickly and accurately. Moreover, with the repetition of the operation of the variable setting means, for example, the frequency channel in the selection waiting state including the optimal setting frequency band can be narrowed down with respect to the change in the surrounding environment after the initial setting or reset, The optimum setting frequency band can be set easily and accurately.

  In the metal detection device of the present invention, the frequency selection setting unit selects the set frequency band within the range of the other frequency band until the number of operations of the variable setting unit after the release reaches the predetermined number. It can be configured. Therefore, during the period until the number of operations of the variable setting means reaches the predetermined number, the used frequency band is not used, and the frequency band having a high probability including the optimal set frequency band is narrowed down. As a result, the optimum set frequency band can be set easily and accurately.

  In the metal detection apparatus of the present invention, the frequency selection setting means, a selection setting unit that variably sets the set frequency band by selecting any one of a predetermined number of frequency channels to be selected from the set frequency band, The currently selected state in which the predetermined number of frequency channels are currently used as the set frequency band, a used state in which the current selected state is canceled and the set frequency band is not selected, and the set frequency band A channel selection condition storage unit that identifiably stores the selection waiting state as a selection target to be selected, and the channel selection setting unit has an upper limit in which the number of frequency channels in the used state is set in advance The frequency channel in the used state is stored until the value is reached, and the frequency channel in the selection waiting state is set to a plurality of channels having a preset lower limit value. When the variable setting means is operated in a state of reaching the frequency channel, the configuration is such that the earliest frequency channel out of the used frequency channels is changed to the frequency channel in the selection waiting state. It can be.

  With this configuration, when the setting of the operation condition related to the detection of the magnetic field detection means is changed by the operation of the variable setting means, one of the predetermined number of frequency channels is selected by the selection setting unit of the variable setting means and the set frequency The band is changed, and the frequency band in the currently selected state is changed. Therefore, the used frequency band that has been released from the current selection state and has not been selected for the set frequency band becomes the used state and is stored so that it can be distinguished from the set frequency band waiting for selection. During the operation of the means, the used frequency band that is not selected at this time is excluded from the set frequency band, and the setting of the set frequency band can be performed quickly and accurately. In addition, as the operation of the variable setting means is repeated, the frequency channel in the waiting state for selection including the optimal setting frequency band is narrowed against changes in the surrounding environment after the initial setting. The frequency band can be easily set.

  In addition, the channel selection setting unit is variable in a state where the number of used frequency channels reaches a preset upper limit value, and frequency channels waiting for selection have reached a plurality of preset lower limit value channels. When the setting means operates, the frequency channel in the selection waiting state is changed back to the earliest frequency channel that has not been selected among the used frequency channels. Therefore, it is possible to always select or approach an appropriate set frequency band with respect to changes in the work environment while using a finite predetermined number of frequency channels to be selected.

  In the metal detection device of the present invention, the frequency selection setting means is one of a plurality of frequency channels waiting for selection, wherein the electromagnetic noise level measured by the magnetic field detection means is a minimum value or a predetermined value or less. You may further have a frequency selection setting part which selects a frequency channel and sets the said setting frequency band. This makes it possible to maintain stable detection accuracy by adopting a frequency channel with a minimum electromagnetic noise level, or to immediately adopt a frequency channel with an electromagnetic noise level of a predetermined value or less to eliminate subsequent measurements. By doing so, it is possible to speed up the variable setting of the set frequency band.

  In the metal detection device of the present invention, the frequency selection setting means sets all the channels of the predetermined number of frequency channels stored in the channel selection condition storage unit to the frequency channels waiting for selection in response to a manual operation input. You may have the reset operation part to change.

  As a result, when the installation environment changes greatly and the history within the predetermined period cannot be used effectively, the reset operation unit is manually operated to change all channels of the predetermined number of frequency channels to the frequency channels waiting for selection. Only effective history information can be held.

  In the metal detection device of the present invention, the frequency selection setting means measures an electromagnetic noise level in the inspection region by the magnetic field detection means while the operating condition is maintained, and based on the measurement result, the frequency selection setting means Information output that prompts a change in operating conditions may be executed.

  In this way, when the electromagnetic noise level in the inspection area deteriorates during normal operation, it is quickly notified to the user, and the operation of the variable setting means by the self-diagnosis function and other functions of the metal detection device is promoted. Is possible.

  ADVANTAGE OF THE INVENTION According to this invention, the metal detection apparatus which can perform the setting of the setting frequency band for metal detection with respect to the influence of external electromagnetic noise and its change rapidly and exactly can be provided.

It is a schematic block block diagram of the metal detection apparatus which concerns on one Embodiment of this invention. It is explanatory drawing of the map for frequency switching in the signal processing part of the metal detection apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the schematic procedure of the setting process of the transmission / reception signal frequency band of the metal detection apparatus which concerns on one Embodiment of this invention. It is explanatory drawing of the state change of the map for frequency switching accompanying the frequency band switching of the transmission / reception signal in the metal detection apparatus which concerns on one Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  1-4 has shown schematic structure of the metal detection apparatus based on one Embodiment of this invention.

  First, the configuration will be described.

  In the metal detection apparatus 10 of the present embodiment, the overall schematic configuration of which is shown in FIG. 1, a workpiece W that is an object to be inspected passes through an inspection region Z in which an alternating magnetic field is generated while being conveyed by a conveyor (not shown). By detecting the magnetic field fluctuation in the inspection area Z accompanying the passage of the workpiece W, the metal in the workpiece W (a foreign material made of metal or a foreign material containing a metal component, not a foreign material in the case of detecting a shortage) As a component). Further, an article detection sensor 11 that detects the entry of the workpiece W into the inspection area Z is installed near the entrance of the inspection area Z.

  The workpiece W is, for example, a product that is mass-produced and packaged individually with a packaging material or in a unit of a predetermined number during transportation. It may be an irregular shape such as a sex bag product. Of course, it is not limited to food.

  The metal detection device 10 generates an alternating magnetic field in the inspection region Z by exciting and driving the transmission coil based on the AC signal from the signal generator 21 that generates an AC signal having a preset set frequency. A magnetic field generation unit 22 (magnetic field generation unit) to be generated, a magnetic field detection unit 23 (magnetic field detection unit) composed of a differential detector or the like that detects a magnetic field variation in the inspection region Z, and a detection signal of the magnetic field detection unit 23 A signal processing unit 30 that captures and executes a plurality of signal processing to be described later, and a metal detection determination unit 40 that determines the presence or absence of a metal foreign object or metal component in the workpiece W based on the detection signal processed by the signal processing unit 30. Determination means).

  Although not shown in detail, the signal generation unit 21 includes a reference signal generation circuit, a signal level adjustment circuit, and an amplification circuit. The article detection sensor 11 detects that at least the workpiece W is about to enter the inspection area Z. When this is done, an alternating current signal that causes the magnetic field generator 22 to generate a magnetic field is output.

  The magnetic field generation unit 22 has a transmission coil and a tuning circuit arranged in the vicinity of the conveyance path of the workpiece W by the conveyor. The transmission coil is excited and driven in accordance with an AC signal from the signal generation unit 21 to perform inspection. A magnetic field in the set frequency band can be generated in the region Z. Note that the alternating magnetic field generated by the magnetic field generation unit 22 may be subjected to frequency diffusion processing so as to suppress the influence of external electromagnetic noise. In this case, the signal generation unit 21 is, for example, a pseudo random noise signal. A PN signal generator that generates a certain PN (Pseudo Noise) signal and a voltage controlled oscillator (hereinafter referred to as a VCO) may be included in the configuration of the diffusion resonator. When the frequency band of the transmission / reception signal between the magnetic field generation unit 22 and the magnetic field detection unit 23 is changed by the frequency spreading process, the set frequency band in the present invention means the frequency band of the transmission / reception signal after the frequency spreading process. To do.

  The magnetic field detection unit 23 is configured to detect a metallic foreign object in the workpiece W in cooperation with the signal generation unit 21 and the magnetic field generation unit 22, and includes a pair of differentially connected reception coils, a tuning capacitor, and the like. It consists of a variable resistor for sensitivity adjustment. The magnetic field detection unit 23 is adjusted so that the induced voltages of the pair of receiving coils with respect to the alternating magnetic field from the magnetic field generation unit 22 are balanced and the differential output of both is zero. When the alternating magnetic field generated by the magnetic field generation unit 22 is subjected to frequency diffusion processing, a signal synthesizer is provided on the subsequent stage side of the above-described sensitivity adjustment variable resistor, and a detection clock signal to the magnetic field detection unit 23 is provided. Can be configured to despread the received signal by inputting the signal to a signal synthesizer by synchronizing the frequency with the above-mentioned PN signal.

  The magnetic metal that passes through the magnetic field attracts more magnetic flux in proportion to the magnitude of the magnetic flux density, and the nonmagnetic metal that passes through the magnetic field swirls in such a direction as to cancel the change in the magnetic flux density due to the movement. An electric current is generated and Joule heat is consumed. Therefore, when the workpiece W on the conveyor passes through the inspection region Z, the balanced state of the output of the receiving coil of the magnetic field detector 23 is lost.

  When the output balanced state between the two receiving coils is lost due to the movement of the workpiece W in the inspection region Z as described above, the magnetic field detection unit 23 outputs a detection signal corresponding to the change in the magnetic field. In this detection signal, a low frequency signal component corresponding to a magnetic field change accompanying the passage of the workpiece W is superimposed on an AC signal component having a set frequency band of the transmission signal corresponding to an alternating magnetic field from the magnetic field generation unit 22 side. It becomes a signal form.

  The signal processing unit 30 incorporates a reception level measurement circuit 25 that constitutes a reception circuit together with the magnetic field detection unit 23. The reception level measurement circuit 25 includes, for example, a pair of synchronous detectors, phase shifters, and bands that perform quadrature detection. A pass filter, an amplifier, an A / D converter, and the like are included.

  A pair of synchronous detectors of the reception level measuring circuit 25 takes in the transmission signal for one side for quadrature detection and a signal adjusted so that the phase is 90 ° different from that for the other, and each of the detection signals corresponds to the transmission signal from the detection signal. A detection output from which high frequency components are removed is generated. Further, the reception level measurement circuit 25 generates a signal obtained by further applying noise removal, A / D conversion, and the like to the detection output described above, and outputs the signal to the metal detection determination unit 40.

  The output of the quadrature detection is, for example, a detection signal in which the influence of a non-magnetic metal causing an external magnetic field change is larger as the magnetic flux density change is larger, or a detection in which the influence of a magnetic metal causing an external magnetic field change is larger as the magnetic flux density is larger. Signal.

  The signal processing unit 30 also executes a predetermined control program based on the detection signal of the magnetic field detection unit 23, the user's operation input from the operation input unit 35, and the like, and the signal generation unit 21 and the A signal is output to the metal detection determination unit 40, and a signal is output from the signal generation unit 21 to the magnetic field detection unit 23. This point will be described later.

  On the other hand, the metal detection determination unit 40 has a determination processing program for determining whether or not a metal foreign object is contained in the workpiece W based on a detection signal from the signal processing unit 30, using a known determination method. The determination result by the determination processing program is output to the display output unit 36 via the signal processing unit 30, for example. Further, the metal detection determination unit 40 outputs a sorting command signal for separating defective products from non-defective products to a sorting device provided on the downstream side of the inspection region Z.

  Although the signal processing unit 30 and the metal detection determination unit 40 are not shown in detail in hardware configuration, in addition to the reception level measurement circuit 25 of the signal processing unit 30 described above, for example, a CPU, a RAM, a ROM, and an input / output interface circuit are provided. A control unit having a microcomputer configuration is configured, and the CPU executes various control programs stored in the ROM, so that the metal detection determination unit 40 based on the detection signal taken in via the reception level measurement circuit 25 can be used. In addition to the functions, each function of the signal processing unit 30 as described below can be exhibited.

  That is, the signal processing unit 30 executes various control programs stored in the ROM by the CPU, so that a variable setting unit 31 (variable setting unit) that variably sets an operation condition related to detection by the magnetic field detection unit 23, and a variable When the setting unit 31 operates to variably set the operation condition related to the detection of the magnetic field detection unit 23, a set frequency band set as a frequency band of a transmission / reception signal between the magnetic field generation unit 22 and the magnetic field detection unit 23, Each function with the frequency selection setting unit 32 that selects and sets any one frequency band suitable for the usage environment of the metal detection device 10 among a plurality of different frequency bands can be exhibited. .

  The operating conditions relating to the detection of the magnetic field detecting means here are the set frequency of the alternating magnetic field generated by the magnetic field generating unit 22 and other magnetic field generating conditions, the magnetic field detecting conditions of the magnetic field detecting unit 23, and the reception level measuring circuit 25. This is the processing condition of the magnetic field detection signal.

  The signal processing unit 30 also operates the variable setting unit 31 in response to a user operation input from the operation input unit 35, for example, a maintenance mode execution instruction input for troubleshooting, to generate a magnetic field generated by the magnetic field generation unit 22. The electromagnetic noise level in the inspection area Z is detected by the magnetic field detection unit 23. Then, based on the measurement result, the frequency selection setting unit 32 is operated to select a frequency channel (frequency band) having a minimum or close electromagnetic noise level among the plurality of frequency channels Ch1 to Ch9. Bandwidth is set (details will be described later). Here, when the magnetic field generated by the magnetic field generator 22 is changed, it is set to a predetermined low strength level that is a strength level of the generated magnetic field that does not cause erroneous determination in other metal detection devices.

  As shown in FIG. 2, the signal processing unit 30 includes a storage unit 33 configured by a rewritable memory device, and the frequency selection setting unit 32 stores a map Mf stored and stored in the storage unit 33. On the other hand, the selection process of the frequency channel used as the set frequency band is executed while writing and reading the map value.

  Here, the storage unit 33 stores setting conditions and selection conditions for a plurality of frequency bands corresponding to a predetermined number of frequency channels Ch1 to Ch9, update conditions for the map value of the map Mf according to the usage state, and the like. .

  Further, the map Mf indicates that the use state of the predetermined number of frequency channels Ch1 to Ch9 is “0” for the selection waiting state that can be used as the set frequency band, and the currently selected state that is currently being used as the set frequency band. Is “1”, and the used state where the current selection state is canceled and is not selected as the set frequency band is “2”, “3” depending on the number of operations of the variable setting unit 31 after the selection is canceled. , “4”, “5”, and “6”, respectively, and based on these instruction values “0” to “6”, the use states of a predetermined number of frequency channels Ch1 to Ch9 are stored in an identifiable manner. It is a channel selection condition storage unit.

  That is, in the map Mf, the frequency channel in the currently selected state “1” that is currently in use (corresponding to the frequency channel Ch6 in FIG. 2) and the current selected state are canceled and the set frequency band is not selected. Frequency channels in the used state “2” to “6” (corresponding to the frequency channels Ch3, Ch2, Ch9, Ch5, and Ch7 in FIG. 2) and a selection waiting state “0” that can be a selection target of the next set frequency band Frequency channels (corresponding to frequency channels Ch1, Ch4, and Ch8 in FIG. 2) are stored so that they can be clearly distinguished.

  For this map Mf, the frequency selection setting unit 32 variably sets the operation condition related to detection by the magnetic field detection unit 23 until the number of used frequency channels reaches a preset upper limit value. Each time the operation is performed, the map value of each frequency channel in the used state is incremented, and the number of operations of the variable setting unit 31 after each frequency channel in the used state is released from the current selection state “1” Can be stored in memory.

  In addition, the frequency selection setting unit 32 sets the number of frequency channels in the used state “2” to “6” to the above-described upper limit value, and sets the frequency channel in the selection waiting state “0” to a preset lower limit value. When the variable setting unit 31 operates in a state where the number of channels reaches three, for example, three channels, the used state where the time when the frequency channel of the used state “2” to “6” is not selected is the first. The frequency channel “6” is changed to the frequency channel “0” waiting for selection.

  More specifically, the frequency selection setting unit 32 maps the map when a certain frequency band used as the set frequency band is switched to another frequency band in accordance with the switching operation of the operating condition by the variable setting unit 31. The selection of one frequency channel that was in the current selection state “1” in Mf is cancelled, and an increment value of 1 is added to the map value that has been deselected to change to the used state “2”. Furthermore, when the frequency selection setting unit 32 changes one frequency channel that was in the currently selected state “1” to the used state “2”, at the same time, the map value of each used state is incremented by 1. to add.

  Further, the frequency selection setting unit 32 increases the number of operations of the variable setting unit 31 until the number of operations of the variable setting unit 31 after deselecting each used frequency channel reaches a predetermined number of times, for example, five. Increment 1 is added to the map value to change to the used state “3”, “4”, “5”, “6”, and the passage of the period after the selection is canceled is also stored. Therefore, the map Mf shows the difference in the timing of deselection when the number of used frequency channels out of the predetermined number of frequency channels Ch1 to Ch9 increases to a plurality of upper limit values. It is in an identifiable state.

  In addition, when the frequency selection setting unit 32 changes one frequency channel in the current selection state “1” to the used state “2”, the frequency selection setting unit 32 simultaneously selects a plurality of options to be set in the next set frequency band. The frequency channel in the selection waiting state “0” is selected with priority over the frequency channel that has not been selected and is in the used state.

  Then, the frequency selection setting unit 32 cooperates with the variable setting unit 31, and the above-described electromagnetic noise using each frequency channel in a predetermined order, for example, in the order of channel numbers, with respect to a plurality of selection waiting state “0” frequency channels. Level measurement is executed, and the frequency channel with the minimum noise level of the measurement result is selected and set to the next set frequency band.

  Such a frequency selection setting unit 32 sets all the predetermined number of frequency channels Ch1 to Ch9 that are in the selection waiting state “0” at the time of initial setting of the metal detection device 10 or immediately after a reset operation described later. A frequency channel to be a set frequency band is selected from the channels, and thereafter, the next set frequency band is selected from a plurality of remaining frequency channels in the selection waiting state “0” excluding each frequency channel being used or used. After the frequency channel to be used is selected and the number of used frequency channels reaches the upper limit value, the frequency channel to be set to the next set frequency band from the frequency channel in the waiting state for selection of the lower limit value set in advance to "0" Will be selected.

  Here, for convenience of explanation, the predetermined number of frequency channels is set to 9 channels and the upper limit value of the used frequency channels is set to 5 channels. However, the number of channels may be different from each other. Further, the number of frequency channels waiting for selection may be a plurality of channels.

  The storage unit 33 of the signal processing unit 30 can store and store various setting information related to metal detection, measurement results obtained by the signal processing unit 30 and the like in addition to the map Mf.

  The signal processing unit 30 also performs an operation input (for example, an operation button selection operation on the operation screen) for requesting an operation mode in which the diagnosis function of the metal detection device 10 is exhibited, such as a maintenance mode for troubleshooting, a diagnosis mode, and the like. Etc.), the self-diagnosis function unit 34 for self-diagnosis of the operating state of the metal detection device 10 is provided, and the frequency selection setting unit 32 exhibits the function of the self-diagnosis function unit 34. The setting frequency band, which is the frequency band of the transmission / reception signal between the magnetic field generation unit 22 and the magnetic field detection unit 23, is changed on the condition that the variable setting unit 31 operates based on the above.

  Then, the signal processing unit 30 executes a predetermined control program based on the detection signal of the magnetic field detection unit 23 and the user's operation input from the operation input unit 35, and the frequency selection setting unit 32 performs the map Mf according to the processing result. By operating the variable setting unit 31 while referring to the signal, the signal generation unit 21 outputs a control signal such as a frequency switching command, and the signal generation unit 21 outputs the detection clock signal to the magnetic field generation unit 22. The frequency band of the transmission / reception signal between the magnetic field generation unit 22 and the magnetic field detection unit 23 is set to the frequency channel newly selected as being used (waiting for the current selection) in the map Mf.

  In this way, the signal processing unit 30 first sets the variable setting unit 31 and the frequency selection setting unit 32 in response to a user operation input from the operation input unit 35, for example, a maintenance mode execution instruction input for troubleshooting. While operating, the intensity level of the magnetic field generated by the magnetic field generator 22 is changed, and the electromagnetic noise level in the inspection region Z is measured by the magnetic field detector 23. Then, by sequentially selecting a plurality of frequency channels waiting for selection from the plurality of frequency channels Ch1 to Ch9 and measuring the electromagnetic noise level, it is possible to suppress the number of times of measurement, while waiting for selection as a necessary option. The frequency channel having the minimum electromagnetic noise level among the frequency channels in the state is selected as the next set frequency band, and the map value of the map Mf in the storage unit 33 for this frequency channel is set to the current selection state “1”. Set.

  The variable setting unit 31 is also inspected by the magnetic field detection unit 23 while the operating condition of the metal detection device 10 specified by the map value of the map Mf in the storage unit 33 is maintained constant, for example, at the start of operation. Screen output that prompts to measure the electromagnetic noise level in the region Z and to exercise the diagnostic function by the self-diagnostic function unit 34 based on the measurement result (accordingly, the operation condition is changed by the operation of the variable setting unit 31) In addition, information output to other display devices, for example, information output for notifying an increase of the external electromagnetic noise level to the upper limit range is executed.

  Further, the operation input unit 35 connected to the signal processing unit 30 is a reset that changes all channels of the predetermined number of frequency channels Ch1 to Ch9 corresponding to the plurality of frequency channels Ch1 to Ch9 to the frequency channels in the selection waiting state “0”. An operation unit 35a is provided.

  Next, the operation will be described.

  In the metal detection device of the present embodiment configured as described above, immediately after the maintenance mode for troubleshooting of the metal detection device is selected or immediately after the reset operation unit 35a is operated, The set frequency band selection and setting process as described below is executed as an interrupt process, and the set frequency band of the transmission / reception signal between the magnetic field generator 22 and the magnetic field detector 23 is automatically set or reset.

  FIG. 3 is a flowchart showing a schematic procedure of the setting and setting process of the set frequency band.

  First, the frequency selection setting unit 32 of the signal processing unit 30 refers to the map Mf, and the frequency channel having the smallest channel number among the plurality of selection waiting state “0” frequency channels in the map Mf is set as the frequency band to be measured. Selected (step S11). In FIG. 3, there is a portion that is simply described as frequency in the sense of the center frequency of a frequency band having a predetermined bandwidth, and Ch in terms of a channel.

  Next, the operation of the variable setting unit 31 outputs a control signal such as a frequency switching command to the signal generation unit 21 so that the frequency channel selected as the frequency band to be measured is obtained, and the signal generation unit 21 outputs a magnetic field generation unit. The detection clock signal is output to 22, and the frequency band of the transmission / reception signal between the magnetic field generation unit 22 and the magnetic field detection unit 23 is set to the set frequency band corresponding to the frequency channel to be measured. In addition, the transmission signal level from the magnetic field generation unit 22 can be suppressed to about one fifth or less of the normal metal detection operation due to the amplitude limitation of the reference signal in the signal generation unit 21. In this state, the magnetic field detector 23 measures the influence of the external electromagnetic noise on the alternating magnetic field in the inspection area Z, and the measurement result is temporarily stored and saved (steps S12 and S13).

  Next, it is checked whether or not other frequency channels not selected for measurement remain among the plurality of frequency channels waiting for selection “0” (step S14). In the case), selection of the frequency channel to be measured next, measurement using the frequency channel, and storage of the result are performed.

  Furthermore, when there is no remaining frequency channel that is not selected for measurement among the plurality of frequency channels in the selection waiting state “0” in the map Mf (No in step S14), based on the stored measurement result, The frequency channel with the least influence of the external electromagnetic noise level, that is, the frequency channel with the minimum value of the external electromagnetic noise level is automatically selected as the frequency band that can be used as it is. Step S15).

  At the same time as this automatic selection, the use state of one frequency channel suitable for the use environment automatically selected is changed from the selection waiting state “0” to the current selection state “1” for the map Mf. The map value is changed and stored so that the used state of the frequency channel in the selected state “1” is changed to the used state “2” and the incremented value is added to each other used frequency band. This is written in the unit 33 (step S16), and a series of setting frequency band selection setting processing is completed.

  FIG. 4 shows an example of a procedure for rewriting the map Mf when it is assumed that the external electromagnetic noise fluctuates randomly for convenience of explanation.

  First, measurement of the external magnetic field noise level is started after all channels are rewritten to the selection waiting state “0” at the time of initial setting or immediately after the operation of the reset operation unit 35a. For one frequency channel with the least level influence, the set frequency band is automatically set. As shown in FIG. 4A, for example, the frequency channel Ch4 among all the channels Ch1 to Ch9 is in the currently selected state "1". Is set.

  After this setting, the metal detector 10 is operated using the set frequency corresponding to the frequency channel Ch4.

  Then, for example, a maintenance mode for troubleshooting or the like or an operation mode in which the diagnostic function of the self-diagnosis function unit 34 is exhibited is selected according to the result of inspection of the article by the metal detection device 10, and according to the diagnosis result. In order for the variable setting unit 31 to variably set the operation condition related to the detection of the magnetic field detection unit 23, any of the operation conditions of the signal generation unit 21, the magnetic field generation unit 22, the magnetic field detection unit 23, and the reception level measurement circuit 25 is variable. When the setting operation is executed, the set frequency band selection setting process is executed again.

  At this time, the external magnetic field noise level is measured for a plurality of frequency channels in the selection waiting state “0” in the map Mf, and the set frequency band is automatically set for one frequency channel having the least influence of the external electromagnetic noise level. As shown in FIG. 4B, the frequency channel Ch4 that has been in the currently selected state “1” among all the channels Ch1 to Ch9 is reset to the used state “2” and the external electromagnetic One frequency channel Ch7 having the least influence of the noise level is reset from the selection waiting state “0” to the current selection state “1”.

  Then, as shown in FIG. 4C to FIG. 4F, the influence of the external electromagnetic noise level is the smallest every time the variable setting unit 31 performs a predetermined operation in the maintenance mode or the like in the same manner. At the same time that one frequency channel is reset from the selection waiting state “0” to the current selection state “1”, the selection of the one frequency channel that was in the current selection state “1” is released and used. The process is changed to 2 ″, and the process of adding 1 which is an increment value to the map value for each of the other used frequency channels is repeated.

  Accordingly, as shown in FIG. 4 (f), when the number of operations of the variable setting unit 31 after deselecting the used frequency channel Ch4 that has been deselected first reaches five, The number of frequency channels reaches 5 channels indicated by the indication values “2” to “6”, that is, reaches the preset upper limit value, and the number of frequency channels in the selection waiting state “0” is the lower limit value of 3 channels. To reach.

  Then, when the variable setting unit 31 operates next time, the number of operations of the variable setting unit 31 after deselecting the used frequency channel Ch4 that has been deselected first exceeds five times. In addition, as shown in FIG. 4G, the instruction value of the used frequency channel Ch4 is cleared and returned from "6" to "0", and the frequency channel Ch4 is returned to the selection waiting state again.

  As described above, in the present embodiment, when the setting of the operation condition related to the detection of the magnetic field detection unit 23 is changed by the operation of the variable setting unit 31 for troubleshooting or the like according to the manual operation input of the user, The setting frequency band is automatically changed by the setting unit 31 and the frequency selection setting unit 32, and the used frequency band is stored, so that when the variable setting unit 31 is operated next time, the used frequency channel is the next. As a selection target of the set frequency band, the one with a low priority (in this case, the selection target is excluded). Therefore, the next set frequency band is preferentially selected from other selection waiting frequency channels having a relatively high priority, and the set frequency band can be set quickly and accurately.

  Moreover, in response to repeated operations of the variable setting unit 31, changes in the surrounding environment after initial setting and resetting operations (addition of other metal detection devices, installation of inverter-equipped devices, presence / absence of operation, removal, etc.) Thus, it is possible to narrow down the frequency channels waiting for selection while excluding inappropriate setting frequency bands, so that the optimum setting frequency band can be set easily and accurately.

  Further, in the present embodiment, while the number of operations of the variable setting unit 31 reaches a predetermined number of times, for example, 5 times, the frequency channels that have been used increase without being used, while an optimum set frequency band is set. Since the frequency band having a high probability of inclusion is narrowed down, the optimum set frequency band can be set easily and accurately.

  Further, in the present embodiment, the frequency selection setting unit 32 is configured so that the number of used frequency channels reaches the upper limit value and the frequency channels in the selection waiting state have reached a plurality of lower limit value channels. Is operated, the earliest frequency channel (Ch4 in FIG. 4) is changed to a frequency channel waiting for selection, so that the variable range of the set frequency can be changed for all frequency channels Ch1 to Ch9. When selecting a frequency channel suitable for avoiding the influence of external electromagnetic noise while ensuring a wide range, it is possible to suppress the number of processings required for it.

  In addition, a frequency channel that minimizes the electromagnetic noise level is selected while speeding up the setting frequency by suppressing the required number of measurements, so that a constant number of frequency channels Ch1 to Ch9 are always used. It is possible to stably maintain the detection accuracy of the metal detection device 10 by selecting an appropriate set frequency with respect to environmental fluctuations or approaching the optimum set frequency.

  As described above, according to this embodiment, it is possible to provide the metal detection device 10 that can quickly and accurately set the setting frequency for metal detection with respect to the influence or change of the external electromagnetic noise.

  In the above-described embodiment, the frequency selection setting unit 32 has the least influence of the external electromagnetic noise level (the external electromagnetic noise level is the minimum value) among the plurality of frequency channels in the selection waiting state “0”. Although the frequency channel is selected as the set frequency band, there is often no substantial difference as long as it is below a predetermined electromagnetic noise level that is a threshold for determining the allowable noise level. Therefore, when the measurement result falls below a predetermined electromagnetic noise level, the frequency band can be used and the set frequency band can be automatically set without selecting another frequency channel for measurement. Good. By doing so, it is not necessary to measure the influence of the external magnetic field noise level for all frequency channels immediately after the reset operation, and the speed can be further increased. If the metal detection performance is not sufficient, a more preferable setting frequency band can be selected when the mode selection for automatically setting the setting frequency band is performed again.

  In the present embodiment, when the installation environment changes greatly and the history within a predetermined period cannot be used effectively, the reset operation unit 35a is manually operated to select all the predetermined number of frequency channels that are in a selection waiting state. It is possible to change to a channel and keep only valid history information.

  Further, as described above, in addition to the setting frequency being automatically set (reset) during the maintenance mode for troubleshooting and the like during reset operation, while the operating condition of the metal detection device 10 is maintained, For example, when the metal detector 10 is started, the electromagnetic noise level in the inspection region is measured by the magnetic field detector 23, and information output for prompting the change of the operating condition is executed based on the measurement result. Therefore, when an environmental change that deteriorates the electromagnetic noise level occurs, it is possible to promptly notify the user and prompt the operation of the variable setting unit 31 by the self-diagnosis function and other functions of the metal detection device 10. It becomes.

  In the above-described embodiment, the setting frequency band is described as the setting frequency of the alternating magnetic field generated exclusively by the magnetic field generator 22, but in this case, a specific frequency channel among the frequency channels Ch1 to Ch9 is described. The other frequency channels may be set relative to each other with reference to the center frequency, and the frequency channels Ch1 to Ch9 may be set at predetermined intervals (may be unequal frequency intervals) with independent center frequencies. . Of course, the number of all frequency channels, the upper limit value of the number of used frequency channels, and the lower limit value of the number of frequency channels waiting for selection can be increased or decreased. It goes without saying that the channel selection condition storage unit that can be replaced by the map Mf is configured by a shift register or buffer having a first-in first-out function.

  Further, when generating an alternating magnetic field corresponding to a transmission signal frequency-spread by the magnetic field generation unit 22, a spreading condition suitable for the use environment is selected among a plurality of spreading codes by the same procedure as the setting frequency selection setting procedure described above. It is also possible to make a selection by selecting one or the like.

  As described above, the present invention can provide a metal detection device capable of quickly and accurately performing setting of a set frequency for metal detection against the influence of external electromagnetic noise and changes thereof. The present invention is useful for all metal detection devices that detect a metal or a metal component in an object to be inspected based on a magnetic field fluctuation when the object passes through an alternating magnetic field.

DESCRIPTION OF SYMBOLS 10 Metal detection apparatus 11 Article detection sensor 21 Signal generation part 22 Magnetic field generation part (magnetic field generation means)
23 Magnetic field detection part (magnetic field detection means)
25 Receive Level Measurement Circuit 30 Signal Processing Unit (Control Unit)
31 Variable setting part (variable setting means)
32 Frequency selection setting section (frequency selection setting means, channel selection setting section)
33 storage unit (frequency selection setting means, channel selection condition storage unit)
34 Self-diagnosis function part 35 Operation input part 35a Reset operation part 36 Display output part 40 Metal detection determination part (determination means)
Ch1, Ch2, Ch3, Ch4, Ch5, Ch6, Ch7, Ch8, Ch9 Frequency channel Mf map (channel selection condition storage unit)
W Workpiece (inspected object)
Z inspection area

Claims (6)

Based on the detection signal of the magnetic field detection means, the magnetic field detection means for detecting the change of the alternating magnetic field due to the inspection object passing through the inspection area where the alternating magnetic field is generated in a preset frequency band set. A metal detection apparatus comprising: determination means for performing determination processing for metal detection in the object to be inspected; and variable setting means for variably setting an operation condition related to detection by the magnetic field detection means,
Frequency selection setting means for selecting one of a plurality of preset frequency bands and setting the set frequency band based on a detection signal of the magnetic field detection means when the variable setting means operates. In addition,
When the selection state of one frequency band used as the set frequency band is released by the operation of the variable setting means, the frequency selection setting means sets the number of operations of the variable setting means after the release to a predetermined number. The one frequency band is stored as a used frequency band until reaching, and as a frequency band option for selecting the set frequency band, other frequency bands other than the used frequency band are selected as the one frequency. A metal detection device characterized in that it is set with priority over a band.   The frequency selection setting means selects the set frequency band within the range of the other frequency band until the number of operations of the variable setting means after the release reaches the predetermined number. Metal detection apparatus as described in. The frequency selection setting means selects one of a predetermined number of frequency channels to be selected for the set frequency band and variably sets the set frequency band; and the predetermined number of frequency channels, The currently selected state currently being used as the set frequency band, the used state in which the current selected state is canceled and the set frequency band is not selected, and the selection waiting state to be selected from the set frequency band And a channel selection condition storage unit that stores the information in an identifiable manner,
The channel selection setting unit stores the used frequency channels until the number of used frequency channels reaches a preset upper limit value, and the selection-waiting frequency channels are preset. When the variable setting means operates in a state where a plurality of lower limit channels have been reached, the frequency channel in the used state that is not selected is the earliest frequency channel that is in the selection waiting state. The metal detection device according to claim 1, wherein the metal detection device is changed to a channel.   The frequency selection setting means selects and sets one of the plurality of selection wait state frequency channels whose electromagnetic noise level measured by the magnetic field detection means is a minimum value or a predetermined value or less. The metal detection apparatus according to claim 1, further comprising a frequency selection setting unit that sets a frequency band.   The frequency selection setting unit has a reset operation unit that changes all channels of the predetermined number of frequency channels stored in the channel selection condition storage unit to the frequency channels in the selection waiting state in response to a manual operation input. The metal detection device according to claim 1, wherein the metal detection device is provided.   The frequency selection setting means measures the electromagnetic noise level in the inspection area by the magnetic field detection means while the operation condition is maintained, and outputs information for prompting the change of the operation condition based on the measurement result The metal detection device according to claim 1, wherein:

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