JPH0427891A - Method and device for conductor detection - Google Patents

Abstract

PURPOSE:To detect a conductor existing in a metal enclosure by taking a reference metal enclosure into a magnetic field generated from a reference coil while taking an object enclosure into a magnetic field generated from a detection coil. CONSTITUTION:In case that a reference metal enclosure 26 and a metal enclosure 30 for detection are equivalent, a bridge circuit 16 keeps balanced condition and therefore output voltage from the bridge circuit 16 becomes around 0V. If the bridge circuit 16 loses the balanced condition, however, there must be some difference between the two enclosures. If a foreign object 36 such as a metallic one is in the enclosure 30, a difference in impedance appears between a reference coil 12 and a detection coil 14. As a result, the bridge circuit 16 loses the balanced condition and an a.c. signal is output from the circuit 16, in order to obtain a detection signal 20.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for detecting the difference between two conductors made of metal or the like, and particularly relates to a method and a device for detecting a difference between two conductors made of metal or the like, and particularly to a container, cover, etc. made of a metal plate or metal foil ( The present invention relates to a conductor detection method and apparatus suitable for detecting a conductor existing inside a metal container (hereinafter referred to as a metal container).

[Conventional technology]

FIG. 3 is a block diagram showing an apparatus based on a conventional conductor detection method.

The conductor detection device 50 includes a detection coil 52 and a reference coil 54.
an oscillator 58 that excites the bridge circuit 56; an amplifier circuit 60 that amplifies the difference between the outputs of the two coils 52 and 54; and a detection signal that rectifies the signal amplified by the amplifier circuit 60. A rectifier circuit 62 which outputs an output as 70 is also formed laterally.

Next, the operation of the conductor detection device 50 will be explained.

When a detection conductor 66 made of metal or the like is brought close to the magnetic field 64 generated from the detection coil 52, an eddy current is generated within the detection conductor 66. Then, the impedance of the detection coil 52 changes due to the permeable flux generated by the eddy current 68,
The bridge circuit 56 becomes unbalanced, and a detection signal 70 is outputted via an amplifier circuit 60 and a rectifier circuit 62. Detection signal 7
0 drives a relay (not shown), etc. [Problem to be solved by the invention] By the way, with such conventional conductor detection methods and devices, for example, it is difficult to detect a conductor existing inside a metal envelope. In this case, the conductor inside the metal envelope could not be detected because it would be sensitive to this metal envelope. This is because such conventional conductor detection methods and devices merely detect the presence or absence of a conductor, and do not detect the difference between two conductors.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a conductor detection method and device that can detect a difference between two conductors and detect a conductor existing inside a metal envelope without being sensitive to the metal envelope. I have something to do.

[Means to solve the problem]

A first conductor detection method according to the present invention brings a reference conductor close to a magnetic field generated from a reference coil, and also brings a detection conductor close to a magnetic field generated from a detection coil. The difference between the reference conductor and the detection conductor is detected by measuring the impedance difference between the detection coil and the reference coil.

Further, in the second conductor detection method according to the present invention, the reference metal envelope is brought close to the magnetic field generated from the reference coil, and the detection metal envelope is brought close to the magnetic field generated from the detection coil. Then, by measuring the impedance difference between the detection coil and the reference coil, a conductor existing inside the detection metal envelope is detected.

Furthermore, the conductor detection device according to the present invention includes a bridge circuit having a reference coil and a detection coil, an oscillator that excites this bridge circuit, and an output circuit that outputs an output signal of the bridge circuit as a detection signal. There is. The reference coil is arranged so that a reference conductor can come close to the magnetic field generated from this coil, and the detection coil is arranged so that a detection conductor can come close to the magnetic field generated from this coil.

[Effect]

In the first conductor detection method according to the present invention, first, a reference conductor is brought close to a magnetic field generated from a reference coil, and a detection conductor is brought close to a magnetic field generated from a detection coil. At this time, if an impedance difference occurs between the reference coil and the detection coil, a difference between the reference conductor and the detection conductor is detected.

In the second conductor detection method according to the present invention, first, a reference metal envelope is brought close to the magnetic field generated from the reference coil, and a detection metal envelope is brought close to the magnetic field generated from the detection coil. At this time, although the reference metal envelope and the detection metal envelope are the same,
If an impedance difference occurs between the reference coil and the detection coil, it is detected that there is a difference between the conductor in the reference metal envelope and the conductor in the detection metal envelope.

Further, in the conductor detection device according to the present invention, the bridge circuit is excited by the oscillator to generate a magnetic field from the reference coil and the detection coil. A reference conductor is brought close to the magnetic field generated from the reference coil, and a detection conductor is brought close to the magnetic field generated from the detection coil. At this time, when an impedance difference occurs between the reference coil and the detection coil and an output signal is obtained from the bridge circuit, it is detected that there is a difference between the reference conductor and the detection conductor.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a device based on the conductor detection method according to the present invention.

The conductor detection device 10 includes a reference coil 12 and a detection coil 14.
The bridge circuit 16 generally includes a bridge circuit 16, an oscillator 18 that excites the bridge circuit 16, and an output circuit 22 that outputs an output signal of the bridge circuit 16 as a detection signal 20. The reference coil 12 is the reference coil 1.
A reference metal envelope 26 as a reference conductor is placed so as to be close to the magnetic field 24 generated from the reference conductor. The detection coil 14 also has a magnetic field 28 generated from the detection coil 14.
A detection metal envelope 30 as a detection conductor is arranged so as to be close to the detection conductor. Further, the reference coil 12 and the detection coil 14 are arranged so that the magnetic fields 24 and 28 generated from each do not affect each other.

The bridge circuit 16 includes a reference coil 12 and a detection coil 14.
A series circuit of the resistor 32 and the resistor 34 is connected in parallel to the oscillator 18, respectively. A connection point between the reference coil 12 and the detection coil 14 and a connection point between the resistor 32 and the resistor 34 are connected to the input side of the output circuit 22. Further, the inductance and resistance of the reference coil 12 and the detection coil 14 and the resistance of the resistor 32 and the resistor 34 are respectively set to values that satisfy the equilibrium condition.

The output circuit 22 receives the output signal of the bridge circuit 16, performs processing such as amplification and rectification, and outputs it as a detection signal 20.

In this example, the oscillator 18 has a frequency of 2 kHz, an output voltage of 6 V, a reference coil 12 and a detection coil 14, each having an inductance of 100 mH, a resistance of 100 Ω, and a resistor of 32.34 mH.
is set to Ω for resistor 2.

Next, the operation of the conductor detection device 10 will be explained.

First, the bridge circuit 16 is excited by the oscillator 18, and the magnetic field 24.
Generate 2 days.

Next, the reference metal envelope 26 is brought close to the magnetic field 24 generated from the reference coil 12 within about 10 cm, and the detection metal envelope 30 is brought close to the magnetic field 28 generated from the detection coil 14 within about 10 cm. . Here, if the reference metal envelope 26 and the detection metal envelope 30 are the same, the bridge circuit 16 maintains a balanced state and the output voltage from the bridge circuit 16 becomes approximately O■. In other words, the conductor detection device 10 is not sensitive to the detection metal envelope 30. In addition, a reference metal envelope 26 and a detection metal envelope 30
If the bridge circuit 16 becomes unbalanced even though they are the same, it will be detected that there is a difference in the conductors within the detection metal envelope 30.

For example, if a foreign object 36 made of a conductor such as metal is mixed into the detection metal envelope 30 as shown in the figure, an impedance difference will occur between the reference coil 12 and the detection coil 14, causing the bridge circuit 16 to An unbalanced AC signal is output from the bridge circuit 16 and a detection signal 20 is obtained. At this time, the thicker the difference between the conductors in the detection metal envelope 30, the greater the AC signal output from the bridge circuit 16. In this way, the inclusion of foreign matter 36 is detected.

Further, according to experiments conducted by the present inventor, the frequency of the oscillator 18 that can be detected satisfactorily is approximately 2 to 3 kHz, although it varies depending on the detection conductor.

Furthermore, the shape, size, and magnetic field strength of the reference coil 12 and the detection coil 4 are determined according to the shape, size, and material of the detection conductor.

Note that the bridge circuit 16 is not limited to the above configuration as long as it has the reference coil 12 and the detection coil 14. For example, a series circuit of the reference coil 12 and the resistor 32 and a series circuit of the detection coil 14 and the resistor 34 are connected in parallel to the oscillator 18, and the connection point of the reference coil 12 and the resistor 32 and the detection coil 14
A configuration may also be adopted in which the connection point between the resistor 34 and the resistor 34 is connected to the input side of the output circuit 22. Also, bridge circuit 1
6, a resistor, capacitor, coil, etc. for adjustment may be added.

Further, in this embodiment, the conductor detection device 10 is used to detect the inclusion of foreign matter 36, but as in the next embodiment, the conductor present in the reference metal envelope 26 is detected by the detection metal envelope 26. 30 may be detected.

FIG. 2 is a block diagram showing another embodiment of the conductor detection method and apparatus according to the present invention. In this embodiment, the conductor detection device 10 shown in FIG. 1 is used to inspect missing items of cup noodles.

The conductor detection device 10 includes a reference part 82 in which a reference coil I2 is housed in a housing 80, a detection part 84 in which a detection coil 14 is housed in a housing 80, and a main body part 86 in which other components are housed. It is divided into

The housing 80 is formed with an opening 88 for holding the reference coil 12 or the detection coil 14 in an exposed state.

The belt conveyor 90 loops a belt 96 around two belt pulleys 92 and a mounting table 94, and moves the belt pulley 9 in the direction of an arrow 97.
By rotating the belt 96, the cup noodles 98a, 98b, and 98C are carried on the belt 96.

A detection hole 100 is bored in the mounting table 94, and the detection part 8 is inserted so that the detection coil 14 is exposed through the detection hole 100.
4 will be installed.

Cup ramen 98a... has a maximum diameter of 159mm
The soup bag 102 is shaped like a bowl with a height of 65 mm.
Powdered soup is sealed in a styrofoam container 106 together with dried noodles 104, and the container 106 is sealed with a lid 108. The soup bag 102 and the lid 108 are made of a laminated sheet of synthetic resin and aluminum foil, and the thickness of this aluminum foil is 15 μm. The soup bag 102 has a rectangular shape, and has a length of 80 mm, a width of 65 mm, and a thickness of 5 mm when filled with powdered soup. The lid 108 is a disk-shaped metal envelope and has a diameter of 150 mm.

Next, the operation of the conductor detection device 10 will be explained.

First, a reference cup ramen 98s is placed on the reference coil 12 of the reference part 82. On the other hand, on the belt conveyor 90, detection cup noodles 98a, 98b, and 98C to be inspected for missing items are sequentially conveyed onto the detection coil 14 of the detection unit 84. And cup ramen 9
8a contains a soup bag 102 like the cup ramen 98s, so the bridge circuit 16 shown in FIG. 1 is balanced and its output voltage becomes about OmV. That is, the cup ramen 98a is determined to be a good product.

Also, unlike the cup ramen 98s, the cup ramen 98b does not contain the soup bag 102, so the bridge circuit 16 shown in FIG. 1 becomes unbalanced and its output voltage is approximately 1.
mV. In other words, the cup ramen 98b is determined to be defective because the soup bag 102 is missing.

At this time, a detection signal 20 shown in FIG. 1 is output from the conductor detection device 10. Although not particularly shown, this detection signal 20 is used to drive an indicator lamp, a buzzer, etc., stop the rotation of the belt wheel 92, or remove defective products to distinguish between good products and defective products. .

Note that even if the type of cup ramen noodles changes, it is sufficient to simply place the reference cup ramen noodles on the reference coil 12 of the reference part 82, and complicated operations such as adjustment are not necessary.

Furthermore, when nothing is placed on the reference coil 12 of the reference section 82, the presence or absence of the detection conductor is detected in the same way as in the conventional case.

〔Effect of the invention〕

According to the conductor detection method and device according to the present invention, the difference between two conductors is detected by bringing the reference conductor close to the magnetic field generated from the reference coil and also bringing the detection conductor close to the magnetic field generated from the detection coil. It is also possible to detect conductors present within the metal envelope.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of a device based on the conductor detection method according to the present invention, FIG. 2 is a block diagram showing another embodiment of the device based on the conductor detection method according to the present invention, and FIG. 1 is a configuration diagram showing an apparatus based on a conventional conductor detection method. 10...Conductor detection bag! 12... Reference coil 14... Detection coil 16... Bridge circuit 18... Oscillator 20... Detection signal 22... Output circuit 24... Magnetic field generated from the reference coil 26... Reference Metal envelope for detection (reference conductor) 28...Magnetic field generated from the detection coil 30...Metal envelope for detection (conductor for detection) Patent applicant Kaisei Engineer Co., Ltd. Same as above
Yoshiharu Tomoyo Co., Ltd. Patent Attorney Yoshi 1) Yoshiharu

Claims (3)

[Claims] (1) By bringing a reference conductor close to the magnetic field generated from the reference coil and bringing the detection conductor close to the magnetic field generated from the detection coil, and measuring the impedance difference between the detection coil and the reference coil, A conductor detection method for detecting a difference between a reference conductor and the detection conductor. (2) Bring the reference metal envelope close to the magnetic field generated from the reference coil, and also bring the detection metal envelope close to the magnetic field generated from the detection coil to reduce the impedance difference between the detection coil and the reference coil. By measuring,
A conductor detection method for detecting a conductor present inside the detection metal envelope. (3) A bridge circuit having a reference coil and a detection coil, an oscillator that excites this bridge circuit, and an output circuit that outputs an output signal of the bridge circuit as a detection signal, and the reference coil is generated from this coil. A conductor detection device, wherein a reference conductor is arranged so as to be close to the magnetic field generated by the coil, and the detection coil is arranged so that the detection conductor can be brought close to the magnetic field generated from the coil.