JP2018141682A - Metal Detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal detector with which it is possible to improve the accuracy of detecting metal in an inspection object.SOLUTION: The metal detector comprises an exciting coil 21, wound in ring form inside a plane parallel to a conveyance plane on which an inspection object is carried in a prescribed direction of conveyance, for generating a magnetic field; and a detection coil 22, provided facing the exciting coil 21, for detecting metal. The detection coil 22 includes a magnetic core of rectangular tabular shape arranged so that its longitudinal direction runs along the direction of conveyance and its plate thickness direction exists in a direction parallel to the surface of the exciting coil and orthogonal to the direction of conveyance, and at least a pair of coils wound around a magnetic core in mutually opposite directions and connected in series.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a metal detector that detects the presence or absence of a metal in an object to be inspected, such as a food or a medicine.

  Conventionally, a metal detector disclosed in Patent Document 1 is known as this type of metal detector.

  The conventional one described in Patent Document 1 includes an excitation coil 21 that is annularly wound in a plane parallel to a conveyance surface that conveys an object to be inspected in a predetermined conveyance direction, and generates a magnetic field. And a detection coil 22 for detecting metal. The detection coil 22 is arranged such that the longitudinal direction thereof is along the transport direction, a rectangular flat magnetic core 22a having a plate thickness direction in a direction substantially parallel to the surface of the excitation coil 21 and substantially perpendicular to the transport direction. And a pair of coils 22b and 22c that are wound around the magnetic core 22a in opposite directions and connected in series.

  With this configuration, the conventional one can further improve the detection sensitivity of the metal 6 based on the differential output voltage of the pair of coils 22b and 22c.

JP, 2006-217947, A

  However, in recent years, the market demand for higher detection sensitivity has been increasing, and further improvement in detection sensitivity has been desired.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a metal detector capable of improving the detection sensitivity of a metal in an object to be inspected.

  A metal detector according to claim 1 of the present invention is a metal detector for detecting the presence or absence of a metal (6) in an object to be inspected (5) moving in a magnetic field, wherein the object to be inspected moves. An excitation coil (21) that is annularly wound in one of two planes facing each other across the surface and generates the magnetic field, and is provided in the other plane of the two planes to detect the metal A detection coil (22) that is arranged such that a longitudinal direction thereof is along a moving direction of the object to be inspected, a direction parallel to a surface of the exciting coil, and a direction orthogonal to the moving direction. A rectangular flat magnetic core (22a, 23a, 24a) having a plate thickness direction in the direction, and at least a pair of coils (22b and 22c, 62a and 62b) wound in the opposite directions and connected in series to the magnetic core. 63a and 6 And b), using configurations with has.

  With this configuration, the metal detector according to claim 1 of the present invention includes an exciting coil wound in an annular shape in one of two planes facing each other, and in the other of the two planes. Since the detection region provided with the detection coil is provided with a detection coil provided on the inside of one excitation coil, the sensitivity region in which the metal can be detected can be expanded compared to the conventional one, so that in the inspection object. The detection sensitivity of the metal can be improved.

  In the metal detector according to claim 2 of the present invention, the detection coil is wound around the magnetic core in the same direction instead of at least a pair of coils wound around the magnetic core in opposite directions and connected in series. And at least a pair of coils (26b, 26c).

  With this configuration, the metal detector according to claim 2 of the present invention includes an exciting coil wound in an annular shape in one of two planes facing each other, and in the other of the two planes. Since the detection region provided with the detection coil is provided with a detection coil provided on the inside of one excitation coil, the sensitivity region in which the metal can be detected can be expanded compared to the conventional one, so that in the inspection object. The detection sensitivity of the metal can be improved.

  According to a third aspect of the present invention, the metal detector further comprises an angle adjusting means capable of adjusting an angle (θ) between the plane on which the excitation coil is provided and the plane on which the detection coil is provided. doing.

  With this configuration, the metal detector according to claim 3 of the present invention can adjust the angle formed between the excitation coil and the detection coil based on the assumed position of the metal in the inspection object. Since the magnetic field at a predetermined position of the inspection object can be strengthened as compared with the case where the detection coil is parallel, the detection sensitivity of the metal in the inspection object can be improved.

  The metal detector according to claim 4 of the present invention further includes a current supply unit that supplies a current having a predetermined frequency for generating the magnetic field in the exciting coil, and a frequency setting unit that sets the frequency of the current. It has a configuration.

  With this configuration, the metal detector according to claim 4 of the present invention can set the frequency of the magnetic field of the exciting coil to a frequency at which metal can be easily detected based on the type of metal in the inspected object. Therefore, the detection sensitivity of the metal in the inspection object can be improved.

  The metal detector according to claim 5 of the present invention further includes transport means (41) having a transport surface (41a) for transporting the object to be inspected in the moving direction, and the excitation coil and the detection coil include the transport coil. It has the structure which is each provided in two mutually opposing planes parallel or perpendicular | vertical to a surface.

  With this configuration, the metal detector according to claim 5 of the present invention is to be inspected even when the exciting coil and the detecting coil are provided in two planes facing each other parallel or perpendicular to the transport surface. The detection sensitivity of the metal in the object can be improved.

  A metal detector according to a sixth aspect of the present invention has a configuration in which the coil intervals of the pair of coils (62a and 62b, 63a and 63b) are different from each other.

  With this configuration, the metal detector according to claim 6 of the present invention can have sensitivity in a wider sensitivity region by the detection coil having coils with different coil intervals.

  The present invention can provide a metal detector having an effect that the detection sensitivity of a metal in an object to be inspected can be improved.

It is a figure which shows typically the structure in 1st Embodiment of the metal detector which concerns on this invention. It is a figure which shows typically the metal detection processing apparatus in 1st Embodiment of the metal detector which concerns on this invention. It is a figure which shows typically the structure of the detection coil in 1st Embodiment of the metal detector which concerns on this invention. It is explanatory drawing of the principle of the metal detection in 1st Embodiment of the metal detector which concerns on this invention. It is a figure which shows an example of the arrangement | sequence of the magnetic core in 1st Embodiment of the metal detector which concerns on this invention. In 1st Embodiment of the metal detector which concerns on this invention, it is a figure which shows typically the metal detection processing apparatus in the modification 1. FIG. In 1st Embodiment of the metal detector which concerns on this invention, it is a figure which shows typically the arrangement | positioning of the excitation coil and detection coil in the modification 2. FIG. In 1st Embodiment of the metal detector which concerns on this invention, it is a figure which shows typically the arrangement | positioning of the excitation coil and detection coil in the modification 2. FIG. In 1st Embodiment of the metal detector which concerns on this invention, it is a figure which shows typically the conveyance means in the modification 3. FIG. In 1st Embodiment of the metal detector which concerns on this invention, it is a figure which shows typically the conveyance means in the modification 3. FIG. In 1st Embodiment of the metal detector which concerns on this invention, it is sectional drawing which shows the structure of the modification 4 typically. In 1st Embodiment of the metal detector which concerns on this invention, it is sectional drawing which shows typically the structure of the detection coil in the modification 5. FIG. It is a figure which shows typically the structure in 2nd Embodiment of the metal detector which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, the structure in 1st Embodiment of the metal detector which concerns on this invention is demonstrated using FIGS. 1-3.

  As shown in FIG. 1, the metal detector 1 in the present embodiment includes a metal detection processing device 10 that performs detection processing of metal that is a foreign object, and a conveyor 40 as a transport unit, The presence or absence of the metal 6 is detected.

  The metal detection processing apparatus 10 includes a metal detection unit 20 and a metal detection circuit 30. The conveyer 40 includes an endless annular conveyer belt 41 as conveying means for conveying the inspection object 5 in the illustrated conveying direction, and conveying rollers 42 and 43. The conveyor belt 41 has a transport surface 41a on which the inspection object 5 is placed and transported in the transport direction.

  As shown in FIG. 2, the metal detection circuit 30 includes an oscillator 31, amplifiers 32 (32 a to 32 d) as amplification means, a detection unit 33 (33 a to 33 d), and an ADC (analog / digital converter) 34 (34 a to 34 d). , A determination unit 35 (35a to 35d) as a determination unit, a result display unit 36, and a frequency setting unit 37 are provided.

  The metal detection unit 20 includes an excitation coil 21 that generates a magnetic field and a detection coil 22 that detects the metal 6 in the inspection object 5. The detection coils 22 are arranged in four rows in a direction substantially parallel to the surface on which the excitation coil 21 is formed and in a direction substantially perpendicular to the transport direction (sometimes referred to as the “width direction of the transport surface 41a”). . In the present embodiment, an example in which the detection coils 22 are arranged in four rows is given, but the present invention is not limited to this, and may be one row, for example. In the drawing, the width direction of the transport surface 41 a is simply indicated as “width direction”.

  The exciting coil 21 has a rectangular shape. The exciting coil 21 is annularly wound in a plane that is substantially parallel to the conveyance surface 41a in the vicinity of the conveyance surface 41a (see FIG. 1). The detection coil 22 is provided in a plane facing the excitation coil 21 at a predetermined distance from the excitation coil 21. Each formation surface on which the exciting coil 21 and the detection coil 22 facing each other sandwich the conveyance surface 41a on which the inspection object 5 is conveyed and moved. That is, the exciting coil 21 is wound in an annular shape in one of two planes facing each other across the region in which the inspection object 5 moves. The detection coil 22 is provided in one of the two planes.

  The number of turns of the exciting coil 21 is, for example, about 1 to 5 turns. The exciting coil 21 is connected to an oscillator 31 and generates a magnetic field in a region through which the inspection object 5 passes. The shape of the exciting coil 21 is not limited to a rectangular shape, and may be a circular shape, an elliptical shape, or the like.

  As shown in FIG. 3, the detection coil 22 includes a plurality of elongated rectangular flat magnetic cores 22a and a pair of coils 22b and 22c wound around the magnetic core 22a.

  The magnetic core 22a is formed of a flat-shaped magnetic body, for example, an amorphous magnetic body, and is arranged so that the longitudinal direction is along the transport direction. The magnetic core 22a has a plate thickness direction in the width direction of the transport surface 41a, and a plurality of magnetic cores 22a are stacked in the plate thickness direction. The magnetic core 22a may have a single configuration.

  Each of the coils 22b and 22c is wound around the stacked magnetic cores 22a in opposite directions and connected in series, and has a configuration of a pair of anti-series connection coils. One end of the coil 22b is connected to the input terminal of the amplifier 32 (see FIG. 2). The other end of the coil 22b is connected to one end of the coil 22c. The other end of the coil 22c is connected to the ground.

  Returning to FIG. 2, the oscillator 31 generates a current having a frequency of several kHz to 10 MHz, for example, and supplies the current to the excitation coil 21 and the detection unit 33 of the metal detection unit 20. The oscillator 31 is an example of a current supply unit.

  The amplifier 32 includes amplifiers 32a to 32d, each having one input terminal and one output terminal.

  Each of the amplifiers 32a to 32d has an input terminal connected to one end of the coil 22b, and amplifies the signal voltage difference from the two coils 22b and 22c forming a pair.

  The detection unit 33 includes detection units 33a to 33d. The detectors 33a to 33d are connected to the oscillator 31 and the output terminals of the amplifiers 32a to 32d, respectively, and synchronously detect the output signals of the amplifiers 32a to 32d in synchronization with the output of the oscillator 31. .

  The ADC 34 includes ADCs 34a to 34d. The ADCs 34a to 34d convert the output signals of the detectors 33a to 33d from analog signals to digital signals, respectively.

  The determination unit 35 includes determination units 35a to 35d. The determination units 35a to 35d are connected to the output terminals of the ADCs 34a to 34d, respectively, and based on these output signals, determine the presence or absence of the metal 6 in the inspection object 5 with reference to a predetermined determination threshold value. It is supposed to be.

  The result display unit 36 displays the determination result of the presence or absence of the metal 6 by the determination units 35a to 35d, for example, on a liquid crystal screen.

  The frequency setting unit 37 can set the oscillation frequency of the oscillator 31 based on the assumed type of the metal 6 in the inspection object 5. The frequency setting unit 37 is an example of a frequency setting unit.

  Specifically, when the metal 6 in the inspected object 5 is a magnetic metal (for example, iron), the frequency setting unit 37 sets the frequency of the oscillator 31 to a predetermined low frequency. On the other hand, when the assumed metal 6 in the inspected object 5 is a non-magnetic metal (for example, SUS304), the frequency setting unit 37 sets the frequency of the oscillator 31 to a predetermined high frequency. It should be noted that the relationship between the type of the metal 6 in the inspected object 5 and the frequency at which they are easy to detect is determined in advance by experiment, for example, five frequencies are determined, and the frequency is appropriately determined based on the type of the metal 6. If the frequency is changed, the detection sensitivity and workability can be improved.

  Next, the principle of metal detection of the metal detection unit 20 will be described with reference to FIG. FIG. 4A is a plan view of the metal detection unit 20, in which the detection coil 22 is viewed from above the excitation coil 21. FIG. 4B is a cross-sectional view in the transport direction in FIG. FIG. 4C is a cross-sectional view in the transport direction when the inspection object 5 includes the metal 6. For the sake of simplicity, it is assumed that there is one detection coil 22 having one magnetic core 22 a inside the excitation coil 21. Here, the inside of the excitation coil 21 refers to a region surrounded by the projected excitation coil 21 when the excitation coil 21 is projected onto the surface on which the detection coil 22 is provided.

  As shown in FIGS. 4A and 4B, the longitudinal direction of the magnetic core 22a having the plate thickness direction in the width direction of the transport surface 41a is along the transport direction in the detection coil 22 inside the excitation coil 21. Has been placed. The coils 22b and 22c are wound in opposite directions and connected in series.

  That is, the direction of the magnetic field generated by the excitation coil 21 and the sensitivity axis of the detection coil 22 are orthogonal. The arrangement position of the detection coil 22 is adjusted so that no induced voltage is generated even when an alternating current is passed through the excitation coil 21. Normally, if the detection coil 22 is arranged at the center between the left coil 21a and the right coil 21b of the exciting coil 21, no induced voltage is generated. Here, that the induced voltage does not occur does not only mean that the induced voltage is zero volts, but means that the induced voltage is low enough to detect the metal 6.

  Further, in addition to the above arrangement, the metal detector 1 has a detection coil 22 connected in a differential configuration, so that high balance can be realized and highly sensitive detection is possible.

  Furthermore, since the metal detector 1 uses the thickness direction of the magnetic core 22a as the width direction of the transport surface 41a, the cross-sectional area through which the magnetic flux generated by the exciting coil 21 can pass is extremely narrow, and the magnetic core 22a is swirled. It is a structure that does not easily generate current. As a result, compared to the case where the plate thickness direction of the magnetic core 22a is orthogonal to the transport surface 41a, the metal detector 1 (1) makes it difficult for the power of the exciting coil 21 to be consumed by eddy currents, and thus achieves low power consumption. (2) Since eddy currents are less likely to occur in the magnetic core 22a, the output signals of the detection coils 22 can be easily balanced, and the output signals can be stabilized.

  Furthermore, since the metal detector 1 can increase the volume of the magnetic material by laminating the magnetic cores 22a in the plate thickness direction, the metal detection sensitivity can be further improved.

  The coil wire used between the coil 22b and the coil 22c or at the connection portion from the detection coil 22 to the outside is preferably a twisted pair wire in order to avoid the influence of the magnetic field.

  As shown in FIG. 4C, when the metal 6 passes through the upper part of the metal detection unit 20, a new magnetic field is generated in the metal 6 by the magnetic field generated by the excitation coil 21. In this case, the mechanism differs depending on whether the metal 6 is a conductor or a magnetic material. In the case of a magnetic material, the metal 6 is magnetized to generate a new magnetic field, and in the case of a conductor, an eddy current is generated in the metal 6 to generate a new magnetic field. When the metal 6 passes near the center of the coils 22b and 22c, in the state shown in FIG. 4C, the newly generated magnetic field is in the direction opposite to the conveying direction in the coil 22b and in the conveying direction in the coil 22c. Flowing into. As a result, an induced voltage generated by a new magnetic field is generated in the detection coil 22, and the induced voltage of the detection coil 22 is added by the amplifier 32 and synchronously detected by the detection unit 33, whereby a spike-like voltage signal (FIG. 2) is obtained. Reference) will occur.

  Next, a modification of the detection coil 22 will be described with reference to FIG. In the above description, the detection coil 22 has a configuration in which the coils 22b and 22c are wound around one magnetic core 22a. This invention is not limited to this, It can also be set as the structure which has arrange | positioned the several magnetic core side by side in the conveyance direction. Hereinafter, an example in which two magnetic cores are arranged in the transport direction will be described.

  FIG. 5A shows an example in which the detection coils 23 and 24 are arranged in a line substantially along the transport direction. The detection coils 23 and 24 have magnetic cores 23a and 24a, respectively. The magnetic cores 23a and 24a have coils 23b and 24b wound individually. The coils 23b and 24b are wound in opposite directions and connected in series. FIG. 5B shows a configuration in which the detection coils 23 and 24 are arranged substantially along the conveyance direction, and the detection coil 24 is arranged inclined at a predetermined angle with respect to the conveyance direction. FIG. 5C shows a configuration in which the detection coils 23 and 24 are both arranged in a line inclined at substantially the same angle with respect to the transport direction. FIG. 5D shows a configuration in which the detection coils 23 and 24 are arranged at different angles with respect to the transport direction.

  The metal 6 (see FIG. 1) is actually assumed to have various shapes (for example, a needle shape). When the metal 6 is not a perfect sphere, directivity is generated in the magnetic field generated by the magnetized metal 6. In that case, by configuring the detection coil as shown in FIG. 5, the metal detector 1 in the present embodiment can improve the detection sensitivity.

  Next, operation | movement of the metal detector 1 in this embodiment is demonstrated using FIG.1 and FIG.2.

  The oscillator 31 generates a current having a frequency set by the frequency setting unit 37, for example, a frequency of 100 kHz, and supplies the current to the excitation coil 21 and the detection unit 33 of the metal detection unit 20. As a result, the exciting coil 21 generates a magnetic field in a region through which the inspection object 5 passes.

  When the inspection object 5 including the metal 6 passes near the upper part of the detection coil 22 in a state where the excitation coil 21 generates a magnetic field, a new magnetic field is generated by the metal 6. An induced voltage generated by the new magnetic field is generated in the detection coil 22.

  The amplifier 32 adds and amplifies each induced voltage generated by the two coils 22 b and 22 c forming a pair, and outputs the amplified voltage to the detector 33.

  The detection unit 33 outputs a spike-shaped voltage signal to the ADC 34 by synchronously detecting the signal amplified by the amplifier 32 based on the transmission signal from the oscillator 31.

  The ADC 34 converts the voltage signal from the detection unit 33 from an analog value to a digital value signal and outputs the signal to the determination unit 35.

  The determination unit 35 determines the presence / absence of the metal 6 in the inspection object 5 based on the output signal of the ADC 34 and a predetermined threshold for determination, and outputs data of the determination result to the result display unit 36.

  The result display unit 36 displays the determination result by the determination unit 35 on, for example, a liquid crystal screen. Here, the result display unit 36 has a configuration for displaying the determination result for each detection coil 22, and preferably displays the position where the metal 6 in the inspection object 5 is detected.

  Next, a modified example of the metal detector 1 in the present embodiment will be described. In addition, the same code | symbol is attached | subjected to the structure similar to the above-mentioned metal detector 1, and the description is abbreviate | omitted.

[Modification 1]
FIG. 6 shows a metal detection processing apparatus according to the first modification. The metal detection unit 20 of this metal detection processing apparatus includes one detection coil 25. In the detection coil 25, a plurality of cores 22a are stacked to the same extent as the length in the width direction of the transport surface 41a (see FIG. 1). Coils 22b and 22c are wound in opposite directions and connected in series to the laminated magnetic core 22a. One amplifier 32 is connected to the coils 22b and 22c. With this configuration, the metal detection processing device according to the first modification can be configured with one each from the amplifier 32 to the determination unit 35, and thus the circuit configuration can be simplified.

[Modification 2]
Next, Modification 2 will be described with reference to FIGS. Modification 2 relates to the arrangement of the excitation coil 21 and the detection coil 22 in the present embodiment. In addition, the side where the above-mentioned conveyance surface 41a exists is called the upper side belt 41b, and the belt under it is called the lower side belt 41c.

  FIG. 7 schematically illustrates a configuration example in which the excitation coil 21 and the detection coil 22 are provided in two planes facing each other parallel to the transport surface 41a.

  As shown in FIG. 7A, the excitation coil 21 may be disposed above the upper belt 41b and the detection coil 22 may be disposed below the lower belt 41c.

  Further, as shown in FIG. 7B, the detection coil 22 is arranged on the upper side of the upper belt 41b, and the excitation coil 21 is arranged in the vicinity of the lower surface of the upper belt 41b (the surface opposite to the conveying surface 41a). You can also.

  Further, as shown in FIG. 7C, the detection coil 22 may be disposed on the upper side of the upper belt 41b and the excitation coil 21 may be disposed in the vicinity of the lower surface of the lower belt 41c.

  FIG. 8 schematically shows a configuration example in which the excitation coil 21 and the detection coil 22 are provided in two planes facing each other perpendicular to the conveyance surface 41a.

  As illustrated in FIG. 8, the excitation coil 21 may be disposed on the left side of the conveyor belt 41 and the detection coil 22 may be disposed on the right side of the conveyor belt 41 in the transport direction.

  In FIG. 8, the detection coil 22 may be disposed on the left side of the conveyor belt 41 and the excitation coil 21 may be disposed on the right side of the conveyor belt 41 in the transport direction.

[Modification 3]
Next, Modification 3 will be described with reference to FIGS. This modified example 3 replaces the conveyor 40 as the conveying means in the present embodiment.

  FIG. 9 shows a main part of a metal detector provided with a slide-like transport unit 45 as a transport means. The transport unit 45 is formed of a non-metallic material, for example, a resin. The inspection object 5 slides down the transport unit 45 while being accelerated by gravity.

  As shown in FIG. 9, for example, the detection coil 22 is arranged on the conveyance unit 45 side and the excitation coil 21 is arranged on the opposite side of the conveyance unit 45, so that even if the conveyance unit has a slide shape. As in the embodiment shown in FIG. 1, the metal 6 in the inspection object 5 can be detected.

  FIG. 10 shows a main part of a metal detector provided with, for example, a cylindrical passage 46 as a conveying means. The passage part 46 is made of a non-metallic material, for example, a resin. The inspection object 5 naturally falls inside the passage portion 46 while being accelerated by gravity.

  As shown in FIG. 10, the embodiment shown in FIG. 1 can be used even when the object to be inspected 5 is naturally dropped by disposing the exciting coil 21 and the detection coil 22 so as to sandwich the passage portion 46. Similarly to the above, the metal 6 in the inspection object 5 can be detected.

[Modification 4]
Next, Modification 4 will be described with reference to FIG. FIG. 11 is a diagram schematically showing a cross section in the width direction of the present embodiment shown in FIG.

  The metal detector in Modification 4 includes an exciting coil holding unit 47 and a rotating shaft 48.

  The exciting coil holding unit 47 holds the exciting coil 21.

  The rotating shaft 48 is provided in the excitation coil holding part 47, and can adjust the angle θ between the plane on which the excitation coil 21 is provided and the plane on which the detection coil 22 is provided. In the illustrated example, the interval between the excitation coil 21 and the detection coil 22 is adjusted so that the left side is narrower than the right side in the drawing.

  With this configuration, the metal detector in the modified example 4 includes the exciting coil 21 and the detection coil 22 for the object to be inspected where the metal position in the object to be inspected is assumed to be the left side in the figure. The magnetic field on the left side in the figure can be strengthened compared to the case of being parallel. As a result, the metal detector in the modified example 4 can improve the detection sensitivity of the metal in the inspected object that is assumed to exist on the left side in the drawing.

  Also, with this configuration, the metal detector in the fourth modification can tilt the excitation coil 21 according to the shape of the inspection object conveyed on the conveyance surface 41a. In the example shown in the figure, it is preferable that the inspection object is applied to the object whose left side is lower than the right side in the drawing.

[Modification 5]
In the above-described embodiment, the coils 22b and 22c wound in opposite directions and connected in series have been described as an example (see FIGS. 2 and 3). FIG. 12 shows a configuration of Modification 5 instead of this.

  As shown in FIG. 12, the detection coil 26 according to Modification 5 includes a plurality of elongated rectangular flat magnetic cores 26 a and a pair of coils 26 b and 26 c wound around the magnetic core 26 a.

  The coils 26b and 26c are wound around the laminated magnetic core 26a in the same direction. One end of the coil 26 b is connected to one input terminal of the differential amplifier 38. The other end of the coil 26b is connected to the ground. One end of the coil 26 c is connected to the other input terminal of the differential amplifier 38. The other end of the coil 26c is connected to the ground.

  The output terminal of the differential amplifier 38 is connected to the detection unit 33. The configuration after the detection unit 33 is the same as the configuration shown in FIGS.

  With the above-described configuration, the detection coil 26 in the modified example 5 has a function equivalent to the coils 22b and 22c that are wound in opposite directions and connected in series.

  As described above, the metal detector 1 according to this embodiment includes the excitation coil 21 that is annularly wound in one of the two planes facing each other and the other plane of the two planes. Since the detection coil 22 provided is provided, the sensitivity region in which metal can be detected can be expanded compared to the conventional one in which the detection coil is provided inside one excitation coil. The detection sensitivity of the metal can be improved.

(Second Embodiment)
The structure of the metal detector in this embodiment is demonstrated using FIG.

  As shown in FIG. 13, the metal detector in this embodiment is different in that a metal detection processing device 50 is provided instead of the metal detection processing device 10 (see FIG. 2) in the first embodiment. Therefore, the description of the same structure as the first embodiment is omitted.

  The metal detection processing device 50 includes a metal detection unit 60 and a metal detection circuit 70. The metal detection unit 60 includes an excitation coil 21 and a detection coil 61. The metal detection circuit 70 includes an oscillator 31, an amplifier 32 (32a to 32b) as an amplification unit, a detection unit 33 (33a to 33b), an ADC 34 (34a to 34b), a determination unit 35 (35a to 35b) as a determination unit, A result display unit 36 is provided.

  The detection coil 61 is arranged in a direction substantially coinciding with the transport direction. In the present embodiment, an example is described in which one detection coil 61 is arranged in a direction substantially orthogonal to the conveyance direction. However, the present invention is not limited to this, and a plurality of detection coils may be arranged. .

  The detection coil 61 includes a core 22a laminated in the same manner as in the first modification of the first embodiment (see FIG. 6), two pairs of coils 62a and 62b wound around the laminated magnetic core 22a, and coils 63a and 63b. And having.

  In the coils 62a and 62b, which are a pair of coils, one end of the coil 62a is connected to the input terminal of the amplifier 32b, the other end of the coil 62a is connected to one end of the coil 62b, and the other end of the coil 62b is connected to the ground. Has been.

  In the coils 63a and 63b, which are the other pair of coils, one end of the coil 63a is connected to the input terminal of the amplifier 32a, the other end of the coil 63a is connected to one end of the coil 63b, and the other end of the coil 63b is connected to the ground. Has been.

  In the present embodiment, the detection coil 61 has two pairs of coils 62a and 62b and coils 63a and 63b, the coil interval between one pair of coils 62a and 62b, and the coil between the other pair of coils 63a and 63b. The intervals are different from each other. That is, the coil interval between one pair of coils 62a and 62b is wider than the coil interval between the other pair of coils 63a and 63b.

  With this configuration, the metal detection processing device 50 according to the present embodiment has sensitivity in a wider sensitivity region by the two pairs of coils 62a and 62b and coils 63a and 63b having different coil intervals. Specifically, the metal detection processing device 50 has a metal detection sensitivity at a relatively distant position by one pair of coils 62a and 62b, and a metal detection sensitivity at a relatively close position by the other pair of coils 63a and 63b. Have

  Therefore, in addition to the effects of the first embodiment, the metal detector in the present embodiment can improve the detection sensitivity of the metal 6 in the inspection object 5 and save space, and can reduce the cost. Furthermore, it has sensitivity in a wider sensitivity range.

  In the second embodiment, two pairs of coils have been described as examples. However, the present invention is not limited to this, and a configuration in which three or more pairs of coils are provided in the magnetic core 22a is also possible. Good. The metal detector having this configuration has a sensitivity in a wider sensitivity region than that using two pairs of coils.

  Further, the two pairs of coils described in the second embodiment are two pairs of coils wound in the same direction as described in the fifth modification of the first embodiment, and the outputs of these coils are differentially set. The same effect can be obtained by a configuration in which amplification is performed by an amplifier.

  As described above, the metal detector according to the present invention has an effect that the detection sensitivity of the metal in the inspection object can be improved, and the presence / absence of the metal in the inspection object such as food or medicine is detected. It is useful as a metal detector to detect.

DESCRIPTION OF SYMBOLS 1 Metal detector 5 Inspected object 6 Metal 10, 50 Metal detection processing apparatus 20, 60 Metal detection part 21 Excitation coil 22, 23, 24, 25, 61 Detection coil 22a, 23a, 24a Magnetic core 22b, 22c, 23b, 24b, 62a, 62b, 63a, 63b Coil 30, 70 Metal detection circuit 31 Oscillator (current supply means)
32 (32a to 32d) amplifier (amplifying means)
35 (35a-35d) determination part (determination means)
37 Frequency setting part (frequency setting means)
38 Differential amplifier 41 Conveyor belt (conveying means)
41a Conveying surface 45 Conveying section (conveying means)
46 Passing part (conveying means)

Claims (6)

A metal detector for detecting the presence or absence of a metal (6) in an inspection object (5) moving in a magnetic field,
An exciting coil (21) that is annularly wound in one of two planes facing each other across an area in which the object to be inspected moves and generates the magnetic field;
A detection coil (22) that is provided in one of the two planes and detects the metal;
With
The detection coil is
A rectangular flat magnetic core (22a, 22a, having a plate thickness direction in a direction parallel to the surface of the exciting coil and perpendicular to the moving direction, the longitudinal direction of which is arranged along the moving direction of the inspection object 23a, 24a),
At least a pair of coils (22b and 22c, 62a and 62b, 63a and 63b) wound in opposite directions around the magnetic core and connected in series;
A metal detector characterized by comprising:   The detection coil includes at least a pair of coils (26b, 26c) wound around the magnetic core in the same direction instead of at least a pair of coils wound around the magnetic core in opposite directions and connected in series. The metal detector according to claim 1.   The metal according to claim 1 or 2, further comprising angle adjusting means capable of adjusting an angle (θ) between a plane on which the excitation coil is provided and a plane on which the detection coil is provided. Detector. Current supply means for supplying a current of a predetermined frequency for generating the magnetic field in the excitation coil;
Frequency setting means for setting the frequency of the current;
The metal detector according to any one of claims 1 to 3, further comprising: A transport means (41) having a transport surface (41a) for transporting the inspection object in the moving direction;
The excitation coil and the detection coil are provided in two planes facing each other in parallel or perpendicular to the transport surface, respectively. Metal detector according to item.   The metal detector according to any one of claims 1 to 5, wherein a coil interval of each of the pair of coils (62a and 62b, 63a and 63b) is different from each other.

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