JP6263165B2 - Metal detection equipment - Google Patents

Description

  The present invention relates to a method for heating a minute metal material, a method for detecting a metal, and a detection apparatus, and more particularly, a method for heating a minute metal material using induction heating, and a method for detecting a metal in a non-conductive material using induction heating. And a detection apparatus.

  Conventionally, a method of heating a metal material using induction heating has been employed for molding a metal ball (bump ball) for welding a semiconductor element. In this heating method, a metal piece having a particle size of about 700 μm is accommodated in a container or passed through a tube, and the container or tube is induction-heated to heat the metal piece in the container or tube, thereby forming a bump ball. (For example, refer to Patent Document 1).

  However, until now, it has been difficult to directly heat a metal material having a particle diameter of 3 mm or less by induction heating. The reason is that since the heat capacity of the metal material is small, energy absorption (heat storage) and heat dissipation are balanced, and the temperature rise stops. In addition, it is difficult to input magnetic energy into a small metal piece.

Further, in the above conventional heating method, a high frequency of less than 100 kHz is used due to the limitation of the high frequency power generation power source, a large device is required, and there is a limit to increasing the magnetic flux density.
Furthermore, since the heating device is larger than the target heating target, the energy required for heating is dispersed, and the energy cannot be concentrated on the metal material that is the heating target, resulting in a large energy loss. . In addition, the heating device requires a semiconductor device having a high withstand voltage and a high capacity, and the power source has a large capacity, which is contrary to the trend of energy saving.

  On the other hand, fine metal foreign matter may be mixed in magnetic oxides, ceramics, resins (plastics), film-like electrical and electronic materials, and other various industrial materials and products in the manufacturing process. Industrial materials and products contaminated with metallic foreign objects are defective and must be removed before the industrial materials and products themselves must be removed or removed from the industrial materials and products. Need to be inspected.

  As a method for inspecting the presence or absence of metallic foreign matter in such industrial materials and product metals, the object to be inspected arranged between the magnetic poles of the induction coil is induction-heated, and an infrared camera is used to inspect the heated object to be inspected. A method of detecting a metallic foreign object by measuring a temperature distribution is known (for example, see Patent Document 2).

  However, the method described in Patent Document 2 has a problem in that the shape and size of the inspection object are limited because the inspection object is arranged so as to be sandwiched between the magnetic poles. That is, the object to be inspected having a shape or size that does not enter between the magnetic poles could not be inspected. In this case, it is necessary to design a wide space between the magnetic poles. However, since the energy density is small, it is difficult to induction-heat the metal foreign matter contained in the inspected body.

  In addition, since the object to be inspected is placed in the magnetic path existing between the magnetic poles and induction heated, it is necessary to hold the object to be inspected between the magnetic poles, and therefore a holding mechanism must be provided. When it is desired to inspect an arbitrary part of the object to be inspected, the object to be inspected can be moved only within the range of the core size, so that any part of the object to be inspected is linked to the magnetic flux generated between the magnetic poles. It was impossible to move easily to the position.

  Furthermore, although induction heating of a metal foreign object is possible to some extent by the method described in Patent Document 2, it is difficult to specify the type of the metal, and simply detecting the presence or absence of a foreign object in a small object to be inspected. It was only.

JP 2001-181709 A JP 2006-125937 A

An object of the present invention is to provide a method for heating a metal material that makes it possible to heat the metal material in a short time and with a small energy loss.
Another object of the present invention is to provide a metal detection method capable of detecting a metal contained in an object to be inspected having an arbitrary shape and size with high accuracy in a short time.
Still another object of the present invention is to provide a metal detection device capable of detecting a metal contained in an object to be inspected of any shape and size with high accuracy in a short time.

  According to the first aspect of the present invention, a step of arranging a metal material outside the gap of the induction heating means formed by winding a coil around a frame-shaped yoke core having a gap between magnetic poles, and a high frequency is passed through the coil There is provided a method of heating a metal material, comprising: generating a curved magnetic field outside the gap, causing the curved magnetic field to act on the metal material, and heating the metal material by electromagnetic induction generated by the curved magnetic field. .

  According to the second aspect of the present invention, the step of disposing a test object including metal outside the gap of the induction heating means formed by winding a coil around a frame-like yoke core having a gap between magnetic poles, Flowing a high frequency, generating a bending magnetic field outside the gap, causing the bending magnetic field to act on the metal, and heating the metal by electromagnetic induction by the bending magnetic field; and heat generation of the metal contained in the inspected body A method for detecting a metal comprising a detecting step is provided.

In the first and second aspects of the present invention configured as described above, a high frequency of 100 kHz or more can flow through the coil.
A metal material or a metal having a particle diameter of 20 μm to 3 mm can be used.
As the metal material or metal, one selected from the group consisting of iron, steel, stainless steel, brass, copper, aluminum, and an alloy containing one or more of these can be used.
In particular, 100 kHz to 100 MHz can be used as the high frequency.

  According to the third aspect of the present invention, an object to be inspected is formed by winding a coil around a frame-shaped yoke core having a gap between magnetic poles, generating a curved magnetic field in the vicinity of the gap, and including a metal disposed in the vicinity of the gap. Inductive heating means for causing the bending magnetic field to act on, means for relatively moving the object to be inspected and the bending magnetic field generating means, and scanning the inspection target portion of the object to be inspected by the induction heating means, and the bending There is provided a metal detection device including means for detecting heat generation and heat transfer to the surroundings of a metal contained in the body to be inspected heated by electromagnetic induction by a magnetic field.

In the third aspect of the present invention configured as described above, the magnetic flux density can be improved by gently inclining the gap gap on the lower surface of the magnetic pole of the frame-shaped yoke core. A yoke can be provided on the top surface of the magnetic pole of the frame-shaped yoke core.
Furthermore, the means for detecting the heat generation of the metal can be an infrared sensor that detects infrared rays generated from the metal.

In this case, the infrared sensor can be arranged on the downstream side of the object to be inspected that moves relative to the bending magnetic field generating means.
Alternatively, the means for detecting the heat generation of the metal can be a means for detecting discoloration and / or deformation of the object to be inspected in the vicinity of the metal material due to heat generated from the metal. Furthermore, the means for detecting the heat generation of the metal can be a means for detecting a hole formed in the object to be inspected near the metal by heat generated from the metal.

Further, the means for detecting the heat generation of the metal can be a radiation thermometer that detects infrared rays having an emissivity corresponding to the type of the metal.
Furthermore, the induction heating means can be controlled at a high frequency according to a heating frequency appropriate for the type of metal.

According to the first aspect of the present invention, there is provided a method for heating a metal material that can rapidly heat a metal in a short time and can achieve downsizing and energy saving of the apparatus.
According to the second aspect of the present invention, there is provided a metal detection method capable of detecting a metal contained in an object to be inspected having an arbitrary shape and size with high accuracy in a short time.
According to the third aspect of the present invention, there is provided a metal detection apparatus capable of detecting a metal contained in an inspection object having an arbitrary shape and size with high accuracy in a short time.

The schematic diagram and magnetic circuit figure of the induction heating coil used for the heating method of the metal material which concerns on the 1st Embodiment of this invention. The schematic diagram which shows the induction heating apparatus used for the 1st Embodiment of this invention. It is a figure which shows the induction heating coil used for the 2nd and 3rd embodiment of this invention. It is a figure which shows the other example of the induction heating coil used for the 2nd and 3rd embodiment of this invention. It is a figure which shows the metal detection apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the metal detection apparatus which concerns on the 3rd Embodiment of this invention. It is a figure which shows the position of the to-be-heated sample in Example 2 of the 1st Embodiment of this invention. In Example 2 of the 1st Embodiment of this invention, it is a graph which shows the result of having carried out induction heating by moving the position of a to-be-heated sample to a x direction. In Example 2 of the 1st Embodiment of this invention, it is a graph which shows the result of having moved the position of the to-be-heated sample to the y direction, and carrying out induction heating.

Hereinafter, embodiments of the present invention will be described.
The method for heating a metal material according to the first embodiment of the present invention includes a step of disposing a metal material outside the gap of induction heating means formed by winding a coil around a frame-shaped yoke core having a gap between magnetic poles. And applying a high frequency to the coil, generating a bending magnetic field outside the gap, applying a bending magnetic field to the metallic material, and heating the metallic material by electromagnetic induction generated by the bending magnetic field. Features.

  The metal material heating method according to the present embodiment can target any size and shape of metal material. It is possible to heat a minute metal material having a particle size of 3 mm or less. In particular, it is possible to heat an extremely minute metal material having a particle diameter of 20 μm to 100 μm. In addition, when the minute metal has an irregular shape, an average particle diameter of 20 μm to 100 μm is considered. In this case, the average particle diameter is a median diameter d50.

Such a fine metal material has been difficult to heat directly by induction heating until now.
In the past, it has been known to directly heat a large-sized metal by induction heating when bending or welding a steel pipe. However, for the first time in the present invention, a metal material having a particle size of 3 mm or less is directly heated by induction heating. It became possible to heat.

  On the other hand, when a metal material that is an object to be heated is placed in the induction heating coil and a high-frequency current is passed through the coil, an eddy current is generated in the metal material due to the action of the magnetic field generated in the coil. It is known to be heated. In addition, there are rare cases where a coil is wound with a gap provided in the core as in this case. However, as described above, in such a method, only a small-sized metal material that can be arranged in the gap or a metal material in a position that can be arranged in the gap can be heated.

  In the present embodiment, when the gap between the magnetic poles of the induction heating coil is narrowed, the phenomenon that a leakage magnetic field having a high magnetic flux density is also generated outside the gap is used. Made it possible to do. As a result, any metal material can be heated regardless of the size, shape, and position of the metal material, and the degree of freedom in heating can be increased.

  The metal material may have any form such as a spherical shape, a cylindrical shape, or a whisker shape. Although the kind of metal material is not particularly limited, iron, steel, stainless steel, brass, copper, aluminum, and alloys containing one or more of these, which are generally used for a wide range of applications, can be used.

  FIG. 1 is a diagram showing an induction heating coil 1 as induction heating means of a metal material heating apparatus used in the heating method according to the present embodiment. In FIG. 1, an induction heating coil 1 includes a yoke core 2 and a coil 3 wound around the yoke core 2. The yoke core 2 has a shape in which a central portion of one side of the frame-like body is removed and a gap 4 between the magnetic poles is provided, and two coils 3 are wound around both sides thereof. The yoke core 2 is made of a soft magnetic material such as pure iron.

  In such an induction heating coil 1, when a high frequency current is passed through the coil 3, a magnetic field is generated in the gap 4 between the magnetic poles, but a curved magnetic field 5 is generated not only in the gap 4 but also outside the gap 4. Therefore, when a metal material is arranged in a region where the bending magnetic field 5 exists outside the gap 4 of the induction heating coil 1, an eddy current flows through the metal material due to the action of the bending magnetic field 5, whereby the metal material generates heat.

  In addition, by devising the shape of the yoke core 2, the magnetic flux density of the curved magnetic field 5 generated outside the gap 4 can be further increased. FIG. 2 shows such an example. In the example shown in FIG. 2A, in the yoke core 2a, the lower surfaces (surfaces inside the core) of both magnetic poles forming the gap 4 are inclined surfaces T, and the yoke core 2a has such a shape. A curved magnetic field 5a having a high magnetic flux density is generated.

  In the example shown in FIG. 2B, the yoke 2b is further added outside the magnetic poles forming the gap 4 of the yoke core 2a having the inclined surface T (the upper surfaces of both magnetic poles in the vicinity of the gap 4). With such a configuration, it is possible to obtain a curved magnetic field 5b having a higher magnetic flux density than the example shown in FIG.

  In the method for heating a metal material according to the present embodiment, it is desirable to use induction heating with a high frequency of 100 kHz or more. By using a high frequency of 100 kHz or more, it is possible to directly heat a minute metal material having a particle size of 3 mm or less, which has been difficult in the past, by induction heating.

  If a high frequency of less than 100 kHz is used, for example, it may be difficult to heat a minute metal material having a particle diameter of 3 mm or less in a short time. For example, since a metal material having a particle size of 3 mm or less has a small heat capacity, induction heating with a high frequency of less than 100 kHz cannot efficiently supply energy per unit time, and the rate of temperature rise decreases. Absorption (heat storage) and heat dissipation balance, and temperature rise stops.

  The frequency of the high frequency is preferably 100 kHz or more, but more preferably 100 kHz to 100 MHz, still more preferably 100 kHz to 10 MHz, and most preferably 500 kHz to 2 MHz from the viewpoint of further effective heating.

The heating temperature is not particularly limited, and heating from room temperature to 1500 ° C. is possible depending on the application of heating.
As described above, in the method for heating a metal material according to the present embodiment, when induction heating using a high frequency of 100 kHz or more and not conventionally used is used, a metal material having a particle size of 3 mm or less is rapidly heated in a short time. Is possible.

Normally, the skin effect of magnetic flux cannot be expected with a metal material having a particle size of 3 mm or less, but the skin effect of magnetic flux can be expected due to the alternating magnetic flux of ultrahigh frequency of 100 kHz or more, and the use of this makes a rapid rise. Temperature becomes possible.
Further, by using a high frequency of 100 kHz or more, it is possible to make the induction heating device much smaller than those conventionally used. As a result, the magnetic flux density can be increased, and highly efficient heating without energy loss is possible.

In other words, when the induction heating device can be reduced in size, the ratio of the heating part of the device to the minute metal material that is the heating object approaches, and the magnetic flux density can be consolidated with respect to the heating object, thereby reducing energy loss. It can be done.
Hereinafter, the reason why the apparatus can be miniaturized by using a high frequency of 100 kHz or more will be described.

  FIG. 3A shows a schematic diagram of an induction heating coil used in the method for heating a metal material according to this embodiment, and FIG. 3B shows an equivalent circuit diagram of the magnetism. The induction heating coil 11 shown in FIG. 3A is formed by winding a coil 13 having a winding number N around a core 12, and the core 12 is, for example, a gap 14 having a gap length Lg on one side of a frame-like body having the dimensions shown in the figure. Is provided.

FIG. 3B is a magnetic circuit diagram of the induction heating coil 11. In the magnetic circuit diagram of FIG. 3B, φ indicates magnetic flux, and Rm and R′m indicate magnetic resistance.
In such an induction heating apparatus, a current of I (A) is passed through the coil 13 to generate high frequencies of 1 MHz and 75 kHz, and a stainless steel (SUS304) metal material (not shown) disposed between the gaps 14 is heated. Consider the case.

(1) Calculation of magnetic flux density When the magnetic flux density required for heating a metal material of stainless steel (SUS304) having a particle diameter of 1 mm at 200 ° C. in 5 seconds is calculated by the formula of magnetic flux density, it is as follows. .
In case of high frequency of 1MHz 4.6mT
For high frequency of 75 kHz 60.96 mT

(2) Calculation of the number of turns N of the coil The number N of turns of the coil is expressed by the following formula.
N = BLg / μ ₀ I
Here, B is the magnetic flux density obtained above, where the gap length Lg is 5 mm, the vacuum permeability μ ₀ is 4π · 10 ⁻⁷ , and the current effective value I is 8 A, the number of turns N of the coil is as follows: become.
For high frequency of 1MHz N = 2.4
In the case of high frequency of 75 kHz, N = 30.3

(3) Calculation of the size of the core 1 The window area Q (mm ² ) of the core 1 is represented by the following equation.
Q = IN / pq (p is current density, q is space factor)
The volume V of the core 1 is represented by the following formula.
V = a ・ b ・ c
= (Q ^1/2 + 2Ae ^1/2 ) ² · Ae ^1/2 (Ae is the core cross-sectional area)

When the current density p is 3 A / mm ² , the space factor q is 0.1, and the core cross-sectional area Ae is 100 mm ² , V is as follows.
In case of high frequency of 1MHz V = 7734mm ³
In the case of high frequency of 75 kHz V = 23445 mm ³

As described above, it can be seen that the volume of the core 1 required when a high frequency of 1 MHz is used may be about one third of the volume of the core 1 required when a high frequency of 75 kHz is used.
Thus, when a high frequency exceeding 100 kHz is used, the induction heating device can be made much smaller than that conventionally used. Therefore, highly efficient heating without energy loss is possible.

Examples of the present embodiment will be described.
Example 1
FIG. 4 is a schematic diagram of the induction heating device 21 used for heating the metal material in the present embodiment. The induction heating device 21 shown in FIG. 4 has the same configuration as that of the induction heating coil 11 shown in FIG. 3A, and is formed by winding a coil 23 having N turns around a core 22. The core 22 has, for example, a shape in which a gap 24 having a gap length Lg (5 mm) is provided on one side of a frame-like body having the illustrated dimensions.
The coil 23 is connected to a full-bridge high-frequency power source (not shown) having a voltage of 50 V and a frequency of 1 MHz.
Instead of the induction heating coil 11 shown in FIG. 3A, an induction heating coil 1 in which two coils shown in FIG. 1A are wound may be used.

A heated sample 25 is arranged outside the gap 24 in a region where a curved magnetic field exists, and a thermography 26 for measuring the temperature distribution of the heated sample 25 is provided above the heated sample 25. ing.
A high frequency having a frequency of 1 MHz and a current of 8 A was passed through the coil 23 for 5 seconds to perform induction heating of the sample 25 to be heated. As the sample 25 to be heated, iron particles having an average particle diameter of about 1 mm were used.
When the temperature of the iron particles as the heated sample 25 was measured by the thermography 26 arranged above the heated sample 25, the iron particles increased from room temperature 18 ° C. to 193.7 ° C.

Comparative example
When the coil 23 is given a circuit constant that resonates at a frequency of 75 kHz, the energy input conditions are made equal, and a high frequency current of 8A is flowed for 5 seconds and heated, the iron particles are only at room temperature from 17.8 ° C to 6.9 ° C. It did not rise. Moreover, even if it heated for 3 second, only 16.0 degreeC rose, and even if heated for 5 minutes, only 16.8 degreeC rose.

Reference Example A coil 23 is wound 10 times around the core 22 of the induction heating device 21 shown in FIG. 4, a high frequency of 1 MHz and a current 7A is passed for 5 seconds, and the sample 25 to be heated is placed in the center of the gap 24 for induction heating. went. As the sample 25 to be heated, a 300 μm steel ball (SUS304) fixed to a wooden support rod was used. When the temperature of the steel ball as the sample 25 to be heated was measured by thermography (not shown) arranged in front of the core 22, the steel ball rose from room temperature 17.3 ° C to 9.8 ° C. Furthermore, heat conduction was performed from the steel ball to the indicator rod, and the heated steel ball was observed to be enlarged 5 to 30 times on the thermography.

Example 2
A coil 23 is wound 8 times around the core 22 of the induction heating device 21 shown in FIG. 4, a high frequency of 1 MHz and current 8A is supplied for 5 seconds, and the sample 25 to be heated is placed 8.0 mm above the center of the gap 24 to induce. Heating was performed. The heated sample 25 was a 1.0 mm steel ball (SUJ-2) fixed to a wooden support rod. The temperature of the steel ball that is the sample to be heated 25 was measured by thermography (not shown) arranged in front of the core 22.

  As shown in FIG. 7, the same experiment is conducted by induction heating by moving the position of the sample 25 to be heated from the origin by 1.0 mm in the side direction (x direction) from the center of the gap 24 by 8.0 mm. FIG. 8 shows the results of the induction heating performed by moving 1.0 mm each in the front direction (referred to as the y direction). 8 and 9, the horizontal axis represents x (distance from the origin to the side surface direction) and y (distance from the origin to the front direction), respectively, and the vertical axis represents the temperature increased from room temperature 21.1 ° C. .

From FIG. 8 and FIG. 9, the temperature rise of the steel ball is observed not only immediately above the gap 24 but also at a position moved in the horizontal direction from right above the gap 24 in the front-rear and left-right directions. It was confirmed that it was wide-ranging.
As described above, by performing induction heating using a high frequency of 1 MHz, it is possible to rapidly heat minute iron particles having an average particle diameter of 1 mm to a temperature of about 200 ° C. in a short period of 5 seconds. It can be seen that it is.
The first embodiment of the present invention described above can be applied to various heating of metal materials. For example, melting of metal materials, semi-melting, joining of metal materials and other materials, welding, and heating of metal material properties, and utilizing the heat generated by the metal, non-magnetic and fine processing of insulator materials Application to is considered.

Next, a second embodiment of the present invention will be described.
It is well known that when a metal is placed in an induction heating coil and a high-frequency current is passed through the coil, an eddy current is generated in the metal by the action of a magnetic field generated in the coil, thereby heating the metal. Furthermore, as this applied technology, by inserting a core and providing a gap, it is possible to use this phenomenon to place an object to be inspected in the gap and detect a metal contained in the object to be inspected.
However, as described above, in such a method, only a small-sized object that can be arranged in the gap can be used as an object to be inspected.

In this embodiment, attention is paid to the phenomenon that a leakage magnetic field (curved magnetic field) having a high magnetic flux density is generated not only in the gap between the magnetic poles but also outside the gap. It was possible to detect the metal contained in. Such a curved magnetic field is generated particularly when the gap between the magnetic poles of the induction heating coil is narrowed.
As a result, it is possible to inspect the inspected object while continuously moving the long inspected object and the induction heating coil in the longitudinal direction of the inspected object, and continuously detect the metal contained therein. It has become possible.

Although it does not specifically limit as a to-be-inspected object, For example, it can apply to the resin sheet and resin pellet for test | inspecting mixing of the metal which is a foreign material.
The present embodiment has been made based on such knowledge.

  FIG. 5 is a diagram showing an outline of the metal detection device according to the present embodiment. In the metal detection device shown in FIG. 5, for example, a resin sheet 36 as an object to be inspected is disposed in proximity to the induction heating coil 1 shown in FIG. 1. An infrared detector 39 is arranged on the upper right side of the resin sheet 36.

  First, a high frequency current is supplied from a high frequency power source (not shown) to the induction heating coil 31 and the induction heating coil 31 is scanned with respect to the upper surface of the resin sheet 36. When a high frequency current flows through the coil 33, a bending magnetic field 35 is generated in the vicinity of the gap 34. When the metal 37 is present in the resin sheet 36 in the bending magnetic field, an eddy current is generated in the metal 37 and heated. When the metal 37 is heated, the peripheral portion 38 of the metal 37 of the resin sheet 36 is also heated. By detecting the infrared rays 40 emitted from the metal 37 and the peripheral portion 38 by the infrared detector 39, the presence of the metal 37 contained in the resin sheet 36 can be easily detected. Thermal expansion due to heat transfer of metal to the surrounding non-metal also aids detection.

In this case, by scanning the induction heating coil 31 over the entire surface of the resin sheet 36, it is possible to inspect the presence or absence of metal in the entire resin sheet 36. Alternatively, it is possible to scan and inspect an arbitrary region of the resin sheet 36.
In the metal detector according to the present embodiment, the high frequency passed through the induction heating coil 31 is preferably a high frequency as described above, and preferably 100 kHz to 100 MHz. Thus, by using a high frequency of 100 kHz or more, it is possible to detect a minute metal having a particle diameter of 3 mm or less in a short time.

  In order to accurately detect the infrared rays 40 emitted from the metal 37 and the peripheral portion 38 contained in the resin sheet 36 that is the object to be inspected by the infrared detector 39, the metal needs to have a predetermined calorific value. In this case, the amount of heat generation depends on the amount of eddy current generated in the metal 37, and the amount of eddy current depends on the magnetic flux density. Since the magnetic flux density depends on the number of turns N of the coil 33 and the high-frequency current I, by controlling the number of turns N of the coil 33 and the high-frequency current I, the heat generation amount of the metal 37 that can be accurately detected by the infrared detector 39 Is possible.

In the above description, the induction heating coil 31 is moved and the entire surface of the resin sheet 36 is scanned. However, the induction heating coil 31 can be fixed and the resin sheet 36 can be moved.
In addition, when the infrared detector 39 is disposed immediately above the gap of the induction heating coil 31 and the heat generating portion is detected from a vertical position, the entire vicinity of the gap is detected as heat generation, and the heat generation of the metal 37 is accurately detected. It may be difficult to detect. In such a case, as shown in FIG. 5, it is desirable to arrange the infrared detector 39 on the downstream side in the moving direction of the resin sheet 36 and detect infrared rays from an oblique direction.
According to the metal material detection apparatus according to the second embodiment of the present invention described above, the metal contained in the object to be inspected is heated in a short time by induction heating using a high frequency, and the heat generation is performed by the infrared sensor. It is possible to detect with high accuracy. Moreover, since it can detect including the heat | fever which conducted to the metal and to-be-inspected object, it can detect still more easily and simply.

FIG. 6 is a diagram showing a metal detection device according to the third embodiment of the present invention. In the metal detector shown in FIG. 5, the infrared ray 40 emitted from the metal 37 and the peripheral portion 38 is detected by the infrared detector 39. In the metal detector shown in FIG. 6, the object to be inspected is the non-heat resistant resin sheet 42. In this case, the surrounding non-heat-resistant resin is melted by the heat generated by the metal 43 contained therein to form holes, and the holes 46 are detected.
That is, in FIG. 6, an induction heating device 41 having the same configuration as the induction heating coil 31 shown in FIG. 5 is arranged, and a light source 45 is arranged adjacent to the induction heating device 41, and the CCD is located above the light source 45. A camera 48 is installed.

When the metal 43 contained in the non-heat resistant resin sheet 42 traveling in the right direction is heated by the induction heating device 41, heat is generated and the surrounding non-heat resistant resin 44 is melted. The melted portion of the non-heat resistant resin 44 becomes a finer hole 46, passes through the light 47 from the light source 45, expands due to light diffusion, and is imaged by the CCD camera 48. The captured image is displayed as an image 50 on the monitor 49.
In the example shown in FIG. 6, the non-heat-resistant resin sheet 42 is run and scanned with respect to the induction heating device 41. However, the non-heat-resistant resin sheet 42 is fixed and the induction heating device 41, the light source 45, and the CCD camera are scanned. 48 may be moved.

Further, in the example shown in FIG. 6, the CCD camera 48 picks up the light that is diffused and expanded through the hole 46 and detects the presence of the metal 43. It is also possible to measure the change in capacitance and thereby detect the presence of the metal 43.
According to the above-described metal detection device according to the third embodiment of the present invention, the metal contained in the object to be inspected is heated in a short time, and its surroundings are melted and evacuated, thereby forming the fine voids. The hole can be detected with high accuracy by a CCD camera.

  In the above third embodiment of the present invention, the non-heat-resistant resin sheet is used as the object to be inspected, and the periphery of the metal is melted and vacated, but does not lead to vacancy, discoloration, deformation, visual It may be detectable. That is, the surface layer portion around the metal may be burned to be browned or blackened, or the surface layer portion around the metal may be raised or depressed. Such discoloration and deformation around the metal can exaggerate the presence of the metal and facilitate detection.

Next, a fourth embodiment of the present invention will be described. In the second and third embodiments, the presence or absence of the metal contained in the object to be inspected is inspected, but in this embodiment, the type of metal contained in the object to be inspected is detected.
That is, in the second embodiment described above, the infrared rays emitted from the metal 37 and the peripheral portion 38 included in the resin sheet 36 are detected by the infrared detector 39, but the emissivity of infrared rays from the heated metal 37 is as follows. It depends on the type of metal. Therefore, if the infrared emissivity from the metal 37 is detected, the type of the metal 37 can be specified.

The type of metal and the emissivity of infrared are, for example, as emissivity for a wavelength of 1 μm as follows.
For iron: non-oxidized surface 0.35, oxidized surface 0.85
For brass: Oxidized surface 0.7
For copper: 0.06
In the case of aluminum: non-oxidized surface 0.13, oxidized surface 0.4
For example, if iron is to be detected, a radiation thermometer is installed instead of the infrared sensor 39, and the emissivity of the radiation thermometer is set to 0.85. If the emissivity of the metal other than iron is 0.85, Because it is not possible to detect, iron can be detected.

If a plurality of radiation thermometers set to different emissivities are installed, it is possible to specify a plurality of types of metals.
Further, the type of metal can be specified by controlling the frequency of the high frequency. That is, when a metal is induction-heated with a high frequency, an appropriate heating frequency exists depending on the type of metal. Therefore, if the metal contained in the inspection object is induction-heated by the appropriate heating frequency of the metal to be detected, the target metal can be heated without heating the other metal, so the target metal is detected. It is possible.

In this case, the appropriate heating frequency of a large metal (several centimeters or more) varies depending on the shape, size, heating rate, power source, etc., but is as follows, for example.
Steel (1200 ° C.): 500 Hz to 1 kHz
Stainless steel / 18-8 (1200 ° C): 1 kHz
Brass (1800 ° C): 500 Hz to 3 kHz
Copper (850 ° C.): 50 Hz to 10 kHz
Aluminum (500 ° C.): 50 Hz to 10 kHz
However, even when the minute metal is heated at a high frequency of 100 kHz or more as in this case, according to the fourth embodiment of the present invention, the metal contained in the object to be inspected from the appropriate frequency and the temperature increase rate at 100 kHz or more. It is possible not only to detect the presence or absence of metal, but also to specify the type of metal.

  In this way, the minute metal heating technology is a pin-point heating of a part of the metal in a short time, so that it can be used for fine metal processing, welding of fine metals, resin heat processing machine with metal micro head. Furthermore, the application field can be expanded to a heating head that inserts metal pieces into cancer cells and burns them.

DESCRIPTION OF SYMBOLS 1, 11, 31 ... Induction heating coil 2, 2a, 12, 22, 32 ... Yoke core 2b ... Yoke 3, 13, 23, 33 ... Coil 4, 14, 24, 34 ... Gap 5, 5a, 5b, 35 ... Curve Magnetic field 21, 41 ... Induction heating device 25 ... Sample to be heated 26 ... Thermography 36 ... Resin sheet 37, 43 ... Metal 38 ... Metal material peripheral part 39 ... Infrared detector 40 ... Infrared 42 ... Non heat resistant resin sheet 44 ... Molten resin 45 ... Light source 46 ... Hole 47 ... Light 48 ... CCD camera 49 ... Monitor 50 ... Image

Claims (4)

An induction heating means that is formed by winding a coil around a frame-shaped yoke core having a gap between magnetic poles, generates a bending magnetic field in the vicinity of the gap, and causes the bending magnetic field to act on an object to be inspected disposed in the vicinity of the gap;
Wherein by relatively moving the said induction heating means and the object to be inspected, said means for scanning by said induction heating means to be inspected portion of the object to be inspected, and the test subject that is heated by electromagnetic induction caused by the bending magnetic field Equipped with an infrared sensor that detects the heat generated by the metal contained in and the heat transfer to the surroundings using infrared rays ,
The metal detection apparatus , wherein the infrared sensor is disposed on the downstream side of the inspection object that moves relative to the induction heating unit . 2. The metal detection device according to claim 1 , wherein the gap gap on the lower surface of the magnetic pole of the frame-shaped yoke core is gently inclined. The top surface of the pole of the frame-like yoke core, the metal detection device according to claim 1 or 2, characterized in that the yoke is provided. It said induction heating means, a metal detection device according to claim 1 to 3 any one of claims, characterized in that the high frequency is controlled in accordance with the appropriate heating frequency to the type of the metal.

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