JPH0419507Y2 - - 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 accordance with 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 the resistance value changes depending on the state of the magnetic field that acts on it, 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 with an appropriate gap 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 leads are once placed on a terminal plate 30 attached to the inner wall surface of the housing 21, and are connected to lead wires 32 led out of the housing 21 through holes in the bottom plate 31 of the housing 21. The bottom plate 31 is made of synthetic resin and is fitted under the housing 21 after being filled with epoxy resin or the like in the housing 21 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,
This is because it is easy to take measures in terms of shape to improve convenience, and it is inexpensive in terms of cost.

By the way, a magnetic detector is used so that the protection plate 22 faces or comes into sliding contact with the moving area of the test object, but when a high-amplification amplifier is connected to the lead wire 32 to increase detection sensitivity, it is necessary to use magnetic resistance. Element 2
8, 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. Furthermore, when the surface of the protective plate 22 is used to identify banknotes using magnetic ink by sliding the surface of the protective plate 22, static electricity is generated due to friction between the plastic around the protective plate 22 and the paper of the banknote, and the casing is charged. There is a problem in that this discharges into the elements 28, 29 or the electric circuit connected thereto, destroying the elements 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 this application came up with the idea of using a metal casing in order to prevent electrostatic induction and electrostatic discharge as described above, and to increase the strength of the entire casing. There are the following problems when using a manufactured product. 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 from a processing standpoint.

The inventors of the present invention conducted experiments and research on making such a metal casing, and found that by dividing the casing into two specific parts, difficulties in processing could be solved, and assembly would be easy. We found that it is possible to significantly improve quality.

The present invention has been made based on this knowledge, and its purpose is to construct a casing for housing a magnetoresistive element with a metal cylindrical main body portion having an opening at one end, and a metal cylindrical main body portion having an opening at one end. By forming a separate metal cap part on one end that is fixed to close the opening, the overall structure of the casing is significantly strengthened, as well as providing electrostatic shielding and electric shock prevention effects. It is an object of the present invention to provide a magnetic detector that can be easily used and has improved detection sensitivity.

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 product), Fig. 3 is a partially fragmented side view, and Fig. 4 is a plan view.
Figure 5 is a bottom view as well, and in the figure 1 is the housing, 1
Reference numeral 1 designates a main body portion constituting the housing 1, 12 a cap portion, and 13 a 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, with slightly rounded corners, and the upper end of which is a cap fitted here. The lower end is closed by 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. 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 to form a shoulder portion 11a having an arcuate cross section with its peripheral edge facing toward the center line, and a rectangular opening portion 11b is formed in the center. It is mandatory.

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 over 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 spaced below the cap portion 12 via the space 5 at a required distance therefrom. 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 has two magnetoresistive elements 7 on a ferromagnetic substrate 5 such as ferrite fixed to the top surface of the mounting plate 2.
The leads drawn out from the respective magnetoresistive elements 7 and 8 are guided to the lower surface of the mounting plate 2 through holes made in the mounting plate 2, where the lead plates 9a and 9 are fixed.
b, 9c, and the other ends thereof extend downward through a hole bored in the bottom plate portion 13 over a required length. Reference numeral 9d designates a grounding lead plate having one end connected to the inner surface of the main body portion 11 of the casing 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 relative positions on the peripheral edge of the opening 11b, and when the synthetic resin is injected and filled into the housing 1, the main body portion 11 and the cap portion 12 are formed through the notches 11c and 11c. The resin infiltrates the entire circumference between the shoulders 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 cap portion 12 is supported with its shoulder portion 12a 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, housing 1
By making it metal, inconveniences such as electrostatic induction and electric shock are also 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).
The casing can also be easily manufactured using magnetically different materials. In other words, when manufacturing a high-precision detector, by making the main body part magnetic,
This is because it is effective to magnetically shield the internal circuit.

FIG. 6 is a partial sectional view of a housing 1' showing another embodiment of the present invention, in which the main body portion 11' is formed into a uniform rectangular cylindrical shape over the entire length, and the cap portion 12' is a main body portion 11'. At one end of the portion 11' is an opening 1.
It is formed in the shape of a rectangular saucer that is fitted onto the outside in a manner that 1'b is closed. The cap portion 12' is fitted over one end of the main body portion 11', and its peripheral edge is hermetically welded to the main body portion 11'. Although other configurations are not specifically shown,
This is similar to the embodiment shown in FIGS. 2 to 5 above. In the product thus constructed, the main body portion 11' has a simple rectangular cylindrical shape, which has the advantage of being easier to process.

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. At the same time, it is possible to prevent electrostatic induction and electric shock, and by considering the metal material, it is possible to easily provide a magnetic sealing function.Moreover, the shape of the housing components is simplified, making it easy to manufacture and assemble. Furthermore, since there is no step on the surface of the cap like in conventional products, there is no inconvenience such as the test object getting caught on the cap when the test object slides into pressure contact with the cap during use. The present invention has excellent effects.

[Brief explanation of drawings]

Figure 1 is a front sectional view of a conventional magnetic detector;
The figure is a front sectional view of the proposed product, FIG. 3 is a partially fragmented side view of the proposed product, FIG. 4 is a plan view, and FIG.
This figure is also a bottom view, and FIG. 6 is a partial sectional view showing another embodiment of the present invention. 1, 1'... Housing, 2... Mounting plate, 3... Sensor unit, 4... Permanent magnet, 5... Spacer,
6... Substrate, 7, 8... Magnetoresistive element, 9a, 9
b, 9c, 9d...Lead plate, 11, 11'...
Main body part, 11a...Shoulder part, 11b, 11'b...
...opening, 12...cap part, 12a...shoulder part.

Claims (1)

[Scope of utility model registration request] A casing for storing a magnetic resistance element includes a cylindrical main body part made of metal having a substantially uniform wall thickness and having an opening at one end where the magnetic resistance element should be exposed, and the opening at one end side of the main body part. the main body portion, the main body portion being tightly fitted and fixed to the outside to close the main body portion, the portion facing the opening being flat and extending to a side surface of the main body portion that is substantially perpendicular to the portion facing the opening; A magnetic detector characterized by being formed separately from a thin metal cap part.