JPH0240553Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a magnetic detector using a magnetoresistive element whose resistance value changes in response to changes in a magnetic field, and particularly to the structure of its casing.

Semiconductors with high carrier mobility such as InSb, InSb−NiSb, InAs, or Ni−Co, Ni−Fe, Ni−Fe−
Ferromagnetic materials such as Co have the property that their resistance value changes depending on the state of the magnetic field that acts on them, and this property is used to detect the presence of magnetism, the presence of magnetic material, and the movement of magnetic materials. The detector has been put into practical use.

FIG. 1 is an elevational sectional view showing a conventional magnetic detector, and numeral 21 in the figure indicates a housing. The casing 21 is a plastic molded product, and has a hexagonal shape when viewed in elevation with the upper left and right edges cut off, and the opening 21a formed on the upper surface has a protective plate 22 made of a beryllium-copper thin film. It is closed at. The protection plate 22 is integrally molded with the housing 21, and its outer surface is chrome-plated to improve wear resistance, if necessary. A mounting plate 23 is disposed within the housing 21 at an appropriate distance from the protective plate 22, and a sensor unit 24 is disposed on the upper surface of the mounting plate 23.
Further, one pole end face of a cylindrical permanent magnet 25 is fixed to the lower surface. The mounting plate 23 is provided with a spacer 26 disposed between its peripheral edge and the periphery of the opening 21a of the housing 21 so as to surround the upper surface of the mounting plate 23 on which the sensor unit 24 is disposed, so that the mounting plate 23 is provided with a spacer 26 as required below the protection plate 22. It is arranged approximately parallel to this with an interval of .

The sensor unit 24 is formed by fixing two magnetoresistive elements 28 and 29 to the upper surface of a ferromagnetic substrate 27 such as ferrite disposed on the upper surface of the mounting plate 23. The lead is once placed on a terminal plate 30 attached to the inner wall surface of the casing 21, and is connected to a lead wire 32 led out of the casing 21 through a hole in the bottom plate 31 of the casing 21. The bottom plate 31 is made of synthetic resin, and is fitted under the casing 21 after the casing 21 is filled with epoxy resin or the like after assembly.

By the way, the housing of such conventional magnetic detectors is made of plastic, which has excellent moldability, making it difficult to assemble the magnetic detector itself and attach it to the device. Workability,
It is easy to take measures in terms of shape to improve convenience,
This is because it is inexpensive in terms of cost.

Incidentally, a magnetic detector is used so that the protection plate 22 faces or comes into sliding contact with the area of movement of the object to be inspected. However, when a high-amplification amplifier is connected to the lead wire 32 in order to increase detection sensitivity, a magnetoresistive element is used. 28,
29, or there is a problem in that erroneous detection is caused due to the influence of electrostatic induction applied to the conductor portion within the housing. In addition, when the surface of the protection plate 22 is used to identify banknotes using magnetic ink by sliding the surface of the protection plate 22, the protection plate 22
Friction between the plastic on the periphery and the paper of the banknote generates static electricity, which charges the casing, which charges the elements 28,
There is a problem in that the discharge occurs in the 29 or the electric circuit connected thereto, destroying the device or the amplifier as described above. Discharge may also occur due to reasons other than friction, but the elements are defenseless against electric shock in this case and are exposed to the risk of destruction.
For this reason, the inventors of the present application have proposed the above-mentioned electrostatic induction,
We came up with the idea of using a metal casing in order to prevent electrostatic discharge and increase the strength of the entire casing, but when the casing is made of metal, there are the following problems. That is, in order to improve the detection accuracy, it is desirable to minimize the distance between the magnetoresistive elements 28 and 29 that constitute the sensor unit 24 and the object to be measured. The wall thickness of the part of the casing facing the elements 28 and 29 must be made as thin as possible, while the other parts of the casing must be made to a predetermined thickness in order to maintain practical strength. However, it is extremely difficult to form a casing of metal with locally different wall thicknesses. One possible solution to this problem is to divide the casing into appropriate parts. For example, as shown in FIG. 2, it is divided into a main body part 41 formed into a cylindrical shape so that one end is closed leaving a central opening 41b, and a protection plate 42 that is fitted into the opening 41b to close it. As shown in FIG.
The main body part 4 is divided into a cap part 52 and a cap part 52 that is fitted in a closed manner.
It is difficult to draw one end of the test piece 1, and the object to be inspected is likely to get caught in the step between the opening 41b and the protection plate 42, and the latter is also difficult to draw on the step between the main body part 51 and the cap part 52. The sealing function is not sufficient, the magnetoresistive element tends to deteriorate, and the arc-shaped curved portion of the thin cap portion 52 is easily damaged.

The inventors of the present invention have conducted various experiments and research on the method of dividing the metal casing.
It has been found that the above-mentioned inconveniences can be solved by forming each part separately, and that manufacturing and assembly are easy, and at the same time, the detection accuracy can be greatly improved.

The present invention has been made based on this knowledge, and its purpose is to provide a casing for housing a magnetoresistive element, with an opening on one end of which the magnetoresistive element is to be exposed, and a periphery of the casing to accommodate the magnetoresistive element. A cylindrical main body portion drawn to form an arcuate shoulder toward the center, and a portion of the main body portion facing the opening is flat, and a portion facing the shoulder portion is in surface contact with the main body portion. The entire housing is significantly strengthened structurally by forming it into two parts: a cap part that is curved into an arc shape and is tightly fitted onto one end of the main body part to close the opening of the main body part; It is an object of the present invention to provide a magnetic detector which can obtain electrostatic induction and electric shock prevention effects, is easy to manufacture, and can improve detection accuracy.

Hereinafter, the present invention will be specifically explained based on drawings showing embodiments thereof.

FIG. 2 is a front sectional view of the magnetic detector according to the present invention (hereinafter referred to as the present product), FIG. 3 is a partially fragmented side view, FIG. 4 is a plan view, and FIG. 5 is a bottom view. In the figure, 1 is a housing, 11 is a main body part that constitutes the housing 1, 12 is a cap part, 1
3 indicates the bottom plate portion. The main body part 11 is formed by drawing a brass plate, and is formed into a rectangular cylinder shape with a wall thickness of 0.5 mm and rounded corners, and its upper end is fitted here. The lower end is closed by the cap part 12 and the bottom plate part 13 which is also fitted here, and the mounting plate 2, sensor unit 3, permanent magnet 4, etc. are arranged inside, and the other space is closed. The portion 14 is filled with synthetic resin.

The main body part 11 has a rectangular shape with a uniform cross-section in the lower half, and the upper end into which the cap part 12 is fitted has the same wall thickness and the cross-sectional shape is the same as that of the cap part 12. The upper end is narrowed down to form a shoulder portion 11a having an arcuate cross section with its peripheral edge facing toward the center line, and a rectangular opening 1 is reduced in the center.
1b is formed.

The cap portion 12 is formed by drawing a phosphor bronze plate into a rectangular saucer shape with a wall thickness of 0.1 mm.
The portion of the main body portion 11 facing the opening 11b is formed into a flat surface, and the portion facing the shoulder portion 11a is formed with an arcuate shoulder portion 12a having a similar curvature so as to make surface contact therewith. It is tightly fitted onto the upper end of the portion 11 and welded to the main body portion 11 either around the entire circumference or at a suitable number of spots. The bottom plate portion 13 is, for example, a plastic molded product, and is fitted and fixed into the lower end opening of the main body portion 11.

The mounting plate 2 is located within the casing 1 formed by the above-mentioned members, facing the opening 11b of the main body portion 11, and is placed below the cap portion 12 via a spacer 5 at a required distance from the cap portion 12. A sensor unit 3 is fixed to the upper surface, and one pole end face of a cylindrical permanent magnet 4 is fixed to the lower surface. The sensor unit 3 is formed by fixing two magnetoresistive elements 7, 8 on a ferromagnetic substrate 5, such as ferrite, which is fixed on the upper surface of the mounting plate 2.
The leads pulled out from the mounting plate 2 are guided to the lower surface of the mounting plate 2 through holes made therein, where they are connected to the lead plates 9a and 9a.
9b and 9c, and the other ends thereof extend downward through a hole bored in the bottom plate portion 13 over a required length, respectively. Reference numeral 9d designates a grounding lead plate having one end connected to the inner surface of the main body portion 11 of the housing 1, and the other end extending downward through a hole made in the bottom plate portion 13.

Note that 11c and 11c in the figure are triangular notches formed at opposing positions on the peripheral edge of the opening 11b, and when the synthetic resin is injected into the housing 1, the main body portion 11 and the cap portion are formed through the notches 11c and 11c. The resin infiltrates the entire circumference between the shoulder and the shoulder 12 to fill the gap between the two and enhance the sealing effect.

In the case of the present product configured as described above, the casing 1 has a thick wall, the distance between the main body portion 11, the magnetoresistive elements 7 and 8, and the test object is set so as to obtain practical strength. Since it is divided into a thin cap part 12 so that it can be shortened, and is assembled by fitting and fixing the cap part 12 to the main body part 11, the entire casing 1 is made of metal, which greatly improves the structure. It can be strengthened. Furthermore, in the above embodiment,
Since the thin-walled cap portion has its shoulder portion 12a supported in surface contact with the shoulder portion 11a of the main body portion 11, damage to the cap portion 12 is avoided even when the cap portion 12 is strongly pressed against the test object. Prevented. Further, both the main body portion 11 and the cap portion 12 have uniform wall thicknesses, and drawing processing can be easily applied, resulting in good manufacturing efficiency. Furthermore, by making the casing 1 made of metal, inconveniences such as electrostatic induction and electric shock can be prevented.

Unlike the above embodiment, the cap part is made of non-magnetic material and the main part is made of magnetic material (e.g. permalloy).
In this way, the casing can be easily manufactured using magnetically different materials. That is, when manufacturing a highly accurate detector, it is effective to magnetically shield the internal circuit by making the main body part a magnetic material.

As mentioned above, in the case of this product, the casing is made of metal and is divided into a cylindrical main body part and a cap part that is fitted into the main body part, which strengthens the overall structure of the cylindrical body. It also has an excellent sealing function, can prevent electrostatic induction and electric shock, and can easily be provided with a magnetic sealing function by considering the metal material. It is simple and easy to manufacture and assemble.Furthermore, since the cap part is a single piece and its surface is smooth, the test object will not get caught even if the test object slides while in pressure contact with it. The present invention has excellent effects, such as eliminating inconveniences.

[Brief explanation of the drawing]

Figure 1 is a front sectional view of a conventional magnetic detector, Figures 2 and 3 are partial sectional views of the casing that the inventors considered during the process of creating the invention, and Figure 4 is a front sectional view of the proposed product. FIG. 5 is a partially fragmented side view of the product, FIG. 6 is a plan view, and FIG. 7 is a bottom view. 1... Housing, 2... Mounting plate, 3... Sensor unit, 4... Permanent magnet, 5... Spacer, 6...
Substrate, 7, 8... Magnetoresistive element, 9a, 9b, 9
c, 9d... Lead plate, 11... Main body part, 11
a...shoulder part, 11b...opening part, 12...cap part, 12a...shoulder part.

Claims (1)

[Scope of utility model registration request] A metal casing that houses a magnetoresistive element has an opening on one end that exposes the magnetoresistive element,
A cylindrical main body part drawn with the peripheral edge facing toward the center to form an arc-shaped shoulder part, and a part facing the opening of the main body part is flat, and a part facing the shoulder part has a flat shape. The cap is formed into a curved arc shape so as to make surface contact, and is fitted and fixed to one end of the main body in close contact with the outside to close the opening, and is divided into a cap part that is thinner than the main body. Features a magnetic detector.