JP3451135B2 - Detection head of metal detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection head of a metal detection device.

[0002]

2. Description of the Related Art Conventionally, a detection head of this type of metal detection device is usually housed in a metal case made of a metal material, and the main part of the detection head is constructed, for example, as follows.
There is one shown in FIG. In FIG. 9, the detection head 100 includes a transmission coil 101 for generating a magnetic flux,
Two receiving coils 1 arranged so as to interlink with the magnetic flux
02 and 103, and an object to be inspected 104 which is a target of detection of mixed metal, is provided with the sending and receiving coils 101, 102,
A passage 106 passing through the inner space 105 of 103 is passed in the direction of the arrow.

The transmitting coil 101 is excited by a high frequency generator (not shown) to generate high frequency magnetic flux. The two receiving coils 102 and 103 are arranged so that a part of this magnetic flux is linked in an equal amount. Then, one ends of the two receiving coils 102 and 103 have opposite polarities,
That is, they are differentially connected and each output signal V1,
Due to the difference in V2, the transmitting and receiving coils 101, 102,
The metal to be mixed into the object 104 to be inspected passing through the inner space 105 of 103 is detected.

By the way, this detection head 100 is shown in FIG.
As shown in FIG. 0, after the sending and receiving coils 101, 102, 103 are wound around the outer circumference of the coil frame 107 made of an insulator, the coil frame 107 is replaced with the metal case 1 shown in FIG.
It is arranged in 08. Square through holes 108a, 108b (10 provided in the front-back direction of the metal case 108)
As shown in the central cross-sectional view of FIG. 12, a plurality of screw holes 109 penetrating from the outer side to the inner side of the metal case 108 are provided at the edge of (8b is not shown). A fixing screw 110 is screwed onto 109. The fixing screw 110 allows the coil frame 10 to have equal output signals from the two receiving coils 102 and 103 in the front-back direction in which the DUT 104 passes.
7 is positioned, and then a resin-based filler 111 is placed in the space between the metal case 108 and the coil frame 107.
What is filled with is disclosed. (Actual Kaihei No. 5-28984 bulletin)

[0005]

However, the metal case 108 is thus fixed by the fixing screw 110 as described above.
Positioning the coil frame 107 therein not only complicates the process, but also processing the fixing screw 110 and the screw hole 109 causes a cost increase, and
If the coil frame 107 is forcibly positioned by the fixing screw 110, there is a problem in that the metal case 108 and the coil frame 107 are distorted due to the surface irregularities.

Further, in the detection head 100 of the conventional metal detection device, when the filled filling material 111 is cured, a positional displacement occurs in the coil frame 107 due to an action such as heat shrinkage, and thus the reception coil 102. , 103 has a problem that the output signals are out of balance.
For this reason, it has been necessary to add a conventionally known balancing variable resistor, or to attach a metal piece to the coil in the passage space of the inside of the object to be inspected for readjustment. .

Furthermore, when a metal piece is attached to the coil inside the passage space of the object to be inspected, the magnetic flux distribution in the space becomes non-uniform, and the detection sensitivity of the mixed metal is significantly reduced. There was a problem.

The present invention has been made in view of the above points,
An object of the present invention is to solve the above-mentioned problems and provide a detection head of a metal detection device capable of roughly positioning a coil frame in a metal case without using a fixing screw before assembling a detection head before filling with a filler. To do.

Another object of the present invention is to provide a detection head of a metal detection device which is not affected by the hardening of the filling material filled in the coil frame and which can easily balance the signals of the receiving coil by a simple adjusting means. To do.

Still another object of the present invention is to provide a detection head of a metal detection device having extremely good metal detection sensitivity.

[0011]

The structure of the present invention for achieving the above object is such that two receiving units which are housed in a metal case, excite a transmitting coil to generate a magnetic flux, and interlink with the magnetic flux. The detection head of the metal detection device for detecting the metal mixed in the inspected object passing through the inner space of the sending and receiving coils by the difference signal output from the coil is as follows.

[0012] coil frame composed of insulation material, and between the transmission coil, at regular intervals each of the two receiving coils in the front-rear direction along the axis of the coil frame, said feed,
While rotating the receiving coil ,
It is formed on the outer surface of the coil frame and extends along the axis.
Is placed in a recess space having a parallel bottom surface and
Sliding on the bottom surface while holding a part of the transmitting coil
The adjusting coil is provided with the adjusting member,
Move a part of the front and back along the axis of the coil frame
The signals output from the two receiving coils.
A detection head of a metal detection device, which is adjusted so as to be balanced and guides the coil frame to substantially the center of the metal case to roughly position it, thereby forming a guide positioning portion on the inner wall of the metal case. .

By the adjusting member, one of the transmitting coils is
After the parts are moved and adjusted, the adjusting member is fixed to the bottom surface by the fixing means.
It is a detection head of a metal detection device fixed by.

The shape of the recess space seen from the outer side surface is
A rectangle having sides parallel to the winding direction of the transmitting coil, or
Has a side inclined with respect to the winding direction of the transmission coil
It is a detection head of a metal detection device that is a parallelogram.

[0015]

Since the present invention is configured as described above, the sending and receiving coils are wound by the guide positioning portion formed on the inner wall of the metal case without using a conventional fixing screw. The coil frame can be guided to approximately the center of the metal case and roughly positioned. Then, the space between the metal case and the coil frame is fixed to each other by the filled resin-based filler.

Further, a part of the transmitting coil is moved in the front-back direction along the axial center of the coil frame by the adjusting means to make the amount of magnetic flux interlinking the two receiving coils equal. , The signals output from the two receiving coils are balanced. Therefore, if a part of the transmitting coil is moved by the adjusting means after the filling material filled in the coil frame is cured, the filling material is cured with respect to the balance of the output signals from the two receiving coils. Not affected by.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be exemplarily described in detail below with reference to the drawings. 1 is a perspective view showing an embodiment of a detection head of a metal detection device of the present invention, FIG. 2 is a cross-sectional view in the central portion of FIG. 1, and FIG. 3 is III- of FIG.
A sectional view taken along line III, FIG. 4 is a sectional view taken along line IV-IV in FIG. 2, FIG. 5 is a front view in which a part of FIG. 1 is broken, and FIG. 6 is a perspective view showing a coil frame.

1 to 6, a detection head 1 of a metal detection device has a substantially rectangular parallelepiped shape made of a metal material, and a metal case 2 in which central through-holes 2a and 2b are formed, and The coil case 5 is housed in the metal case 2 and includes a coil frame 5 in which the sending and receiving coils 3 and 4 are wound.

The coil frame 5 is made of an insulating material, for example, a phenol resin material, and has a square shape with a square through passage 5a formed in the central portion thereof. The transmission frame is wound around the outer surface thereof. Since the two receiving coils 4 and 4 are wound at equal intervals in the front-rear direction along the axial center of the coil frame 5 with the coil 3 interposed therebetween, the axial center is provided on the outer surface of the coil frame 5. 3 circumferential grooves 6 at equal intervals in the front-back direction along the
Is provided, and the sending and receiving coils 3, 4, 4 are provided in the circumferential groove 6.
However, it is wound in a so-called coaxial form. The connection terminals of the transmission coil 3 to a high frequency generator (not shown) and the connection terminals of the reception coils 4 and 4 to the external lead wires are omitted.

Then, as shown in FIG. 6 to FIG. 8, the transmitter coil 3 is provided on one outer side surface 5b of the coil frame 5.
In the portion where is wound, a recessed space 7 having a rectangular outer surface shape and having a bottom surface 7a having the same depth as the depth of the circumferential groove 6 is formed parallel to the axial center of the coil frame 5. Has been done. In the space 7, an adjusting member 8 made of the same material as the coil frame 5 and having a U-shaped cross section is used, and while holding a part of the transmitting coil 3 in the groove 8a of the adjusting member 8, The bottom surface 7 is provided along the axis of the coil frame 5 in either direction of the receiving coils 4 and 4 as shown by the arrow.
a Move on and adjust. Although the case where the outer surface shape of the recessed space 7 is rectangular is shown here,
The outer surface shape may be a parallelogram having sides inclined with respect to the winding direction of the transmission coil.

The movement and adjustment by the adjusting member 8 is to balance the output signals from the two receiving coils 4 and 4 so as to be equal to each other. After the adjustment is completed, the adjusting member 8 is moved to the bottom surface 7a. It is fixed to the top with a resin adhesive or fixed by a known fixing means. In this case, it is preferable to use the same material as the coil frame 5 for the fixing means.

As shown in FIGS. 1 to 5 again, with respect to the metal case 2, when the coil frame 5 is housed in the metal case 2, the adjusting member 8 of the coil frame 5 is arranged. The side surface on the same side as the side surface 5b having the recessed space 7 is opened, and is closed by the outer lid 9. At the same time, in order to guide and roughly position the coil frame 5 at a substantially central position in the metal case 2, the inner wall of the metal case 2 is provided with an edge portion provided with the square through holes 2a and 2b. Along with the "U" shaped guide positioning portion 10
While forming a and 10b, the "U" -shaped opening side is formed toward the outer lid 9 side.

When the coil frame 5 is housed in the metal case 2, the coil frame 5 is placed in the case 2.
The coil frame 5 is inserted through the opening having the outer lid 9 and is guided by the guide positioning portions 10a and 10b formed on the case 2 to approximately the center of the case 2 and is roughly positioned. The front end face 5c and the rear end face 5d in the front-rear direction along the axis of the coil frame 5 are connected to the metal case 2
It is housed so as to be close to the inner wall provided with the through holes 2a and 2b. At this time, the through passage 5a of the coil frame 5
Have the same size and communicate with the through holes 2a and 2b of the metal case 2. In this case, the side surface 5b of the coil frame 5 having the recessed space 7 in which the adjusting member 8 is arranged is arranged on the side of the metal case 2 having the outer lid 9. 1
Reference numeral 1 is a seal member.

After the coil frame 5 is housed in the metal case 2, the detection head 1 has a resin-based filler 1 between the inner wall of the metal case 2 and the outer surface of the coil frame 5.
By the two, they are firmly fixed to each other.

Next, the procedure for assembling the detection head 1 will be described below.

First, the outer lid 9 of the metal case 2 is opened, and the guide positioning portions 10a and 10b formed in the metal case 2 face the case 2 with the opened outer surface facing upward. The coil frame 5 is guided to a substantially central position and is roughly positioned.

Next, the metal case 2 and the seal member 1 in the rectangular through holes 2a, 2b of the metal case 2 are formed.
The gaps between 1 and 11 and the coil frame 5 are closed, and a resin-based filler 12 is injected between the metal case 2 and the coil frame 5. In this case, the filling material 12 to be injected is filled between the coil frame 5 and the metal case 2 excluding the side surface 5b of the coil frame 5 in which the recessed space 7 is provided, and after a predetermined time has elapsed, it is completely filled. Let it harden.

After the filling material 12 is hardened, the adjusting member 8 provided in the concave space 7 on the side surface 5b of the coil frame 5 is used, and the transmitting coil is inserted in the groove 8a of the adjusting member 8. 3, while holding a part of the coil frame 5, along the axial center of the coil frame 5 in one of the directions of the receiving coils 4 and 4, on the bottom surface 7a,
The output signal of No. 4, that is, the voltage induced in the receiving coils 4 and 4 is adjusted to be equal and fixed. Therefore, by moving a part of the transmitting coil 3 in this way,
Since the voltages induced in the receiving coils 4 and 4 are adjusted to be equal to each other, it is not necessary to adjust the position of the coil frame 5 inside the metal case 2 from the outside by a screw or the like as in the related art.

After the adjusting member 8 is fixed, the same resin-based filler 12 is filled between the side surface 5b of the coil frame 5 and the metal case 2 and, after a lapse of a predetermined time, is completely cured.
The filler 1 that occurs during the second curing of the filler 12.
The positional displacement of the coil frame 5 due to the action of heat contraction of 2 is much less than the conventional one due to the curing force of the already cured first filling material 12, and the magnetic force of the reception coils 4 and 4 after curing is reduced. There is almost no deviation in the equilibrium.

In the above embodiment, the guide positioning portion is formed in the shape of a rail on the inner wall of the metal case to guide the coil frame,
Although the example of performing the positioning has been described, various shapes of the metal case and the coil frame form guide positioning portions of different shapes in the metal case, thereby guiding the coil frame and roughly. Can be positioned. For example, by providing a protrusion only on a part of the metal case, the coil frame can be guided and positioned roughly.

Further, in the above-mentioned embodiment, an example in which a part of the transmission coil is moved to balance the induced voltage of the reception coil has been described, but a part of the reception coil is moved by the same adjusting means. The balance can be adjusted.

In the above embodiment, the example in which the present invention is applied to the coaxial type detection head has been described, but two receiving coils and one transmitting coil arranged in parallel on the same plane are used.
The present invention can also be applied to a detection head of a facing type, which faces each other with a passage space of the device under test sandwiched therebetween.

Further, in addition to the above-mentioned alternating magnetic field, a detection head which uses a unidirectional magnetic field by a DC power source or a permanent magnet or a pulsating magnetic field obtained by modulating the strength of the unidirectional magnetic field at a predetermined frequency as an inspection magnetic field Also, the present invention can be similarly applied.

Note that the technique of the present invention is not limited to the technique in the above-described embodiment, and may be implemented by means of another mode that achieves the same function, and the technique of the present invention can be variously modified within the scope of the above configuration. Can be changed or added.

[0036]

According to the detection head of the metal detector obvious to the present invention from the above description, the coil frame composed of insulation material, and between the transmission coil, the two receiver coils at equal intervals in the longitudinal direction along the axis of the coil frame, respectively, the feed, convolutions Then together the receiver coil
The adjusting means is formed on the outer surface of the coil frame.
And a recess having a bottom surface parallel to the axis.
Is arranged in space and holds a part of the transmitter coil
While providing a slidable adjusting member on the bottom surface,
Depending on the material, part of the transmission coil is
Move it back and forth along your heart to move the two receiving coils.
The signal output from the coil is adjusted so as to be balanced, and the coil frame is guided to approximately the center of the metal case.
Te, in order to roughly positioned, so to form a guide positioning part on the inner wall of the metal case, the transmit coil
The movement of a part of the
Afterwards, to cure the filler that fills the coil frame.
It is unaffected and can be easily received by simple adjustment means.
Signals can be balanced.

Further, the magnetic flux component of the magnetic flux from the transmitter coil
When the cloth becomes uniform and the metal detection sensitivity becomes extremely good,
Mostly, a metal piece is attached to the space through which the inspection object passes, as in the past.
The temperature characteristics are also much better than when mounted.
It Moreover, the screwing work before filling the filling material like the conventional
Since it becomes unnecessary, the metal case and coil frame
Distortion is significantly reduced and manufacturing cost is reduced.

[0038]

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a detection head of a metal detection device of the present invention.

FIG. 2 is a cross-sectional view of the central portion of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a front view in which a part of FIG. 1 is cut away.

FIG. 6 is a perspective view showing a coil frame.

7 is a front view showing a structure of a balance adjusting unit of the coil frame in FIG.

8 is a sectional view taken along line VIII-VIII of FIG.

FIG. 9 is a diagram for explaining the detection principle of the coaxial type detection head of the detection head of the conventional metal detection device.

10 is a diagram showing a main configuration of the detection head of FIG.

FIG. 11 is a perspective view showing a detection head of a conventional metal detection device.

12 is a cross-sectional view of the central portion of FIG.

[Explanation of symbols]

1 Detection head 2 metal cases 2a, 2b through hole 3 transmitter coils 4 receiver coil 5 coil frame 5a through passage 5b side 6 circumferential groove 7 Recessed space 7a bottom 8 adjustment members 8a groove 10a, 10b Guide positioning part 12 Filling material 104 Inspection object

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Claims (3)

(57) [Claims] 1. An inner space of the transmitting and receiving coils is housed in a metal case to excite a transmitting coil to generate a magnetic flux, and a difference signal output from two receiving coils interlinking with the magnetic flux. In a detection head of a metal detection device for detecting a metal mixed in an object to be inspected that passes through, a coil frame made of an insulator is provided between the transmission coil and each of the two reception coils. The transmitting and receiving coils are wound at equal intervals in the front-rear direction along the axis , and the coil frame of the coil frame is used as an adjusting means.
It is formed on the outer surface and parallel to the axis.
The transmission coil is disposed in a recessed space having a bottom surface.
Adjustment member that can slide on the bottom surface while holding a part of
And a part of the transmitting coil is provided by the adjusting member,
Move in the front-back direction along the axis of the coil frame,
Note: Balance the signals output from the two receiving coils.
And sea urchin adjustment, and to guide the coil frame in a substantially central within the metal case, in order to roughly position, the detection head of the metal detector, characterized in that to form the guide positioning part on the inner wall of the metal casing . 2. The adjusting coil adjusts the transmission coil
After moving or adjusting a part, fix the adjustment member on the bottom surface.
The detection head of the metal detection apparatus according to claim 1, wherein the detection head is fixed in stages . 3. The shape of the recess space seen from the outer side surface is
A rectangle having sides parallel to the winding direction of the transmission coil, or
Or has a side inclined with respect to the winding direction of the transmitter coil.
The parallelogram according to claim 1, wherein the parallelogram is formed.
Detection head of metal detection device.