JPS5944672A - Magnetism detector - Google Patents

Abstract

PURPOSE:To prevent an erroneous detection due to electrostatic induction and a breakdown due to electric discharge, and to obtain a magnetism detector having a high S/N ratio, by containing a magneto-resistance element in a housing whose part or whole consists of a non-magnetic metal. CONSTITUTION:A flat housing 36 which cuts a corner of the left and right upper end part and has a hexagonal shape in elevation view is obtained by forming a non-magnetic metallic plate, for instance, of brass, etc. by a press, and an opening part 36a is closed by a protecting plate 37 consisting of a thin film made of a non-magnetic metal such as phosphor bronze, etc. Magneto-resistance elements 32, 33 are provided in parallel on the left and right so as to have a suitable interval to the protecting plate 37. A sensor unit 30 obtained by forming two elements 32, 33 on a ferromagnetic material 39 such as ferrite, etc. is fixed onto a substrate 38 consisting of an insulating material. In this way, since the housing 36 is constituted of a nonmagnetic metallic body, such influence as disorders an external magnetic field is not exerted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic detector, and more particularly to a magnetic detector using a magnetoresistive element whose resistance value changes in response to changes in a magnetic field.

Engineering nsb, ■nsb -NiSb, Engineering nAs
Semiconductors with high carrier mobility such as uNi-Co
, Ni-Fe, N1-Fe-G.

Ferromagnetic materials such as ferromagnetic materials have the property that their resistance value increases when a magnetic field is applied to them.Using this property, magnetic detectors that detect the presence of magnetism, the presence of magnetic materials, and the transition (Iυ1) have been put into practical use. There are 5 people.

FIG. 1 is a schematic diagram illustrating the principle of detecting the approach and movement of a magnetic body. An identical magnetoresistive element 12 and 13 made of aluminum Sb is placed facing one magnetic end m of a permanent magnet (an electromagnet may also be used) 11, and a pixel element is formed on the magnet 11. Equal magnetic force is determined by the degree of each force.

The elements 12 and 13 are connected in series, and a voltage is applied between both terminals of this series circuit, with the connection point of the pixel elements serving as the output terminal 14.

When the subject 15, which is a magnetic material facing toward the object, approaches the force/inclination detector on the side of the probe 13 and moves toward the side 12, the element 13 of the subject 5
By approaching the side, the magnetic flux concentrates on the cord 13 side, and the resistance value of the element 13 increases, while the resistance value 1 of the element 12 increases.
As the voltage decreases, the potential VI4 of the output terminal 14 becomes higher than the voltage V/2 before the subject 15 approaches. Then, when the object 15 approaches the probe 12, the resistance value is reversed, and ■□4 becomes V
/2 The L value also becomes lower. In this way, by monitoring the potential of KV, it is possible to detect the approach and movement of a magnetic body. 2.1 is a vertical plan view showing the structure of a conventional magnetic detector. The flat casing 26, which has a hexagonal shape when seen in elevation with the left and right upper edges cut off, is a plastic molded product, and the opening 26a provided on the top surface is a protective plate 2' made of copper pleura. The tail was closed at 7. The protection plate 27 is partially molded into the housing 26, and its outer surface is chrome plated to improve wear resistance. Magnetoresistive element 22.2 is placed so as to have an appropriate gap with this protection plate 27.
3 are placed side by side on the left and right. That is, the sensor unit 2o formed by forming two elements 22 and 23 on a ferromagnetic material 29 such as ferrite is fixed to the upper surface of the second substrate, and the sensor unit 2o is attached to the upper surface of the periphery of the second substrate. The lower surface of the annular spacer 25 is fixed, and the upper surface of the spacer 25 is fixed to the periphery of the opening 25a inside the casing 26 or the periphery of the protective plate 27. Furthermore, a cylindrical magnet 21 is placed on the bottom surface of the substrate 2.
One pole end face is fixed. The leads drawn out from the elements 221 and 23 are conductors formed on the substrate 28 or the substrate 28.
Using the entire conductor passed through the terminal board, the lead wire 24 is inserted into the terminal board attached to the inner wall surface of the housing 26, and is connected to the lead wire 24 that completely penetrates the bottom plate 26b of the housing 26. The bottom plate 26b is the housing 26
It is molded separately from the other parts of υ2 and is sealed after assembly. Although other special VCs are not shown, the casing 26 yen is filled with resin such as epoxy.

Now, such a conventional magnetic detector is used so that the protective plate 27 faces or slides into the area in which the subject is moving, but when an amplifier with high amplification is connected to the lead wire 24 in order to increase the detection sensitivity, However, there is a problem in that the influence of electrostatic induction on the magnetoresistive elements 22, 23 or the conductor portion inside the housing causes false detection. When the surface of the folded protection plate 27 is used to identify banknotes using magnetic ink by sliding the surface of the protection plate 27, static electricity is generated due to friction between the plastic around the edge of the protection plate 27 and the paper of the banknote, and the casing is charged. And this is element 22.23
Alternatively, there is a problem that the discharge occurs in the electric circuit connected to fL, destroying the device or the amplifier as described above. Mafc
Electric discharge can occur due to reasons other than friction, but
In this case, the elements are defenseless against electric shock and are at risk of destruction. It has excellent formability, so it is easy to assemble the magnetic detector itself and attach the magnetic detector to the equipment, etc., and it is easy to take all the measures in terms of shape to improve workability and convenience.It is also inexpensive in terms of cost. The present invention was completed in order to eliminate the casing made of plastic snacks that had been used for some time.

That is, the magnetic detector according to the present invention is characterized in that part or all of the housing is made of non-magnetic metal. The metal casing prevents electrostatic induction, charging, and discharge, making it possible to prevent false detection and completely avoid destruction of the magnetoresistive element and associated amplifier. become. What is more important is that non-magnetic metal is used, so that the L-shape does not have any influence on the disturbance magnetic field, and the original detection ability is not impaired.

As is clear from the above, a magnetic detector detects the presence of magnetic material due to magnetic field fluctuations.

Therefore, it is easily affected by disturbance magnetic fields, and if there is a transformer with large leakage magnetic flux nearby, this leakage magnetic flux will be erroneously detected as a signal, making it impossible to detect the presence of weaker magnetism than originally required. For this reason, the shape of the magnetoresistive element, even in the conventional type as described above, is ? Special measures have been taken to apply the a-air bias, etc., in order to avoid the influence of the disturbance magnetic field. A similar device is also used in the present invention.
KM is necessary, but if all 41 metal bodies are used in the housing, the disturbance magnetic field will be concentrated on the housing, and the disturbance magnetic flux density in the magnetoresistive element portion will increase. In this sense, it is important to construct the casing using non-magnetic gold that does not have any influence on the disturbance magnetic field.

FIG. 3 is a vertical plan view showing the structure of the magnetic detector according to the present invention. The flat casing 36, which has a hexagonal shape when seen in elevation with the left and right upper edges cut off, is formed by press-molding a non-magnetic metal plate such as brass, and the opening 36a provided on the top surface is made of phosphor bronze or the like. Non-magnetic metal thin film (about 0.1 inch thick), I
l: Closed with a protective plate 37. Protective plate 37
and the housing 36 are soldered for fixation and electrical continuity. The material of the housing 36 may be any non-magnetic metal and is not limited to brass, but if brass is used, sufficient mechanical strength can be obtained with a thickness of about 0.5 mm. . The surface of the maintenance plate 37 is coated with Yt to improve its resistance to abrasion.
The surface may be chrome plated.

Magnetoresistive elements 32 and 33 are arranged side by side on the left and right so as to have an appropriate gap from the protective plate 37 f'L. On the upper surface of the substrate 38 made of insulation, a ferromagnetic material 39 such as ferrite [
Sensor unit 3 formed entirely of two elements 32 and 33
0 is fixed, and the lower surface of an annular smoother 35 surrounding the sensor unit 30 is fixed to the upper surface of the periphery of the substrate 3.
The upper surface of the spacer 35 is fixed to the periphery of the opening 36a in the entire housing 36 or to the periphery of the protection plate 370. Further, on the lower surface of the substrate 38, one pole end face of a cylindrical permanent magnet (an electromagnet may be used) 31 for biasing is stacked.

The elements 32 and 33 are connected in series as shown in FIG. The lead wire 3 is placed on the terminal board attached to the inner wall of the housing 36 using a conductor, and then passes through the bottom plate 36b of the housing 36.
4vc are connected.

Needless to say, these lead wires 34 are connected in the same manner as in the conventional wires. Further, the housing 36 is preferably grounded in order to completely prevent the above-mentioned discharge and the like. The bottom plate 36b is formed separately from the other parts of the housing 36 and is made of non-magnetic metal, but is sealed after all of the internal parts described above are assembled.

Since the bottom plate 36b is far from the magnetoresistive elements 32 and 33, it may be made of plastic like the conventional one. The housing 36 is filled with a resin such as epoxy (not shown). false detection due to electrostatic induction,
Problems such as destruction due to electrostatic discharge are solved, and furthermore, a magnetic detector with a high 8/N ratio can be realized without affecting the external magnetic field to disturb the magnetic field. Incidentally, the S/N ratio was improved by 3 to 4 times compared to the conventional glass one. In addition, when comparing the product of the present invention with a case constructed using a magnetic metal body, for example, permalloy with a thickness of 0.5 mm, the former generates more disturbance magnetic field signals (magnetic noise) than the latter.
was about 50% higher, and the effects of the present invention became clear by modifying these factors.

As described above, the magnetic detector of the present invention is characterized in that a magnetoresistive element is housed in a housing partially or entirely made of non-I
There is no erroneous detection due to induction or destruction due to discharge, and a magnetic drive with a high S/N ratio can be realized. In particular, in order to completely avoid the influence of magnetic noise, a sensor unit that is not easily sensitive to magnetic fields (low sensitivity) is used. C for threatening
; [According to the present invention, it is possible to detect magnetic substances and magnetism that should be detected without unnecessarily drawing in an external magnetic field.
It can be done with N ratio. It goes without saying that the present invention can also be applied to a single device using a strong magnetic resistance element such as Ni--Co.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the detection principle of the ll-1JjF1 air detector, FIG. 2 is an erect view of a conventional magnetic detector, and FIG. 3 is an erect view of the magnetic detector of the present invention. 30...Sensor unit 31...Permanent magnet 32.3
3... Magnetoresistive element 3°6... Housing 37... Protective plate 38... Board #31 diagram review bird 3 Figure

Claims (1)

[Claims] 1. A magnetic detector characterized in that an EB magnetoresistive element is housed in a housing partially or entirely made of non-magnetic metal.