JPH0419508Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a magnetic detector using a magnetoresistive element.

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 changes when a magnetic field is applied to them, and magnetic detectors that utilize this property to detect the presence of magnetism, the presence of magnetic materials, and movement. It has been put into practical use.

FIG. 1 is a front sectional view showing a conventional magnetic detector, and numeral 21 in the figure indicates a housing. The housing 21 is a plastic molded product, and an opening 21a formed on the top surface is closed with a protective plate 22 made of a beryllium-copper thin film. The protection plate 22 is integrally molded with the housing 21, and its outer surface is chrome plated as necessary to improve wear resistance.

A sensor unit 23 is disposed within the casing 21 with an appropriate gap between the protective plate 22 and the sensor unit 23 . The sensor unit 23 is a magnetic substrate 2 made of ferrite.
Magnetoresistive element 2 is attached using adhesive resin 25 on 4.
6 and 27 are arranged in parallel, and this magnetic substrate 24 is fitted into a hole drilled in a plastic mount substrate 28, and the magnetic substrate 24 is inserted through a phosphor bronze bottom plate 28' on the lower surface of the mount substrate 28. The lower surface is opposed to a permanent magnet 29 for bias. An annular spacer 30 surrounding the sensor unit 23 is provided on the mount substrate 28, and the annular spacer 30 surrounds the sensor unit 23.
The upper surface of the spacer 30 is brought into contact with the peripheral edge of the spacer 30 so that the distance between the protection plate 22 and the magnetoresistive elements 26 and 27 becomes a predetermined value. Each magnetoresistive element 26,
The leads pulled out from 27 are attached to the mount board 28
The wire is connected to a terminal 31 provided on the inner wall of the casing 21 via the printed wiring above, and then connected to a lead wire 32 led out through the bottom plate.

Note that the space inside the housing 21 is filled with epoxy resin (not shown) or the like.

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.

Normally, 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 measured, but when connecting a high-amplification amplifier to the lead wire 32 to increase detection sensitivity, Magnetoresistive element 2
6, 27, 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 26, 27 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 reduce the distance between the magnetoresistive elements 26, 27 constituting the sensor unit 23 and the test object. The wall thickness of the part of the casing that faces the casing must be as thin as possible, while other parts of the casing must be formed to a predetermined thickness in order to maintain practical strength. However, it is extremely difficult to form a housing made of metal with locally different wall thicknesses.

As a result of experiments and research on making such metal housings, the inventors of the present invention have found that by dividing the housing into two specific parts and electrically connecting them together, electrostatic induction and electric shock can be prevented. can be reliably prevented,
It was also discovered that difficulties in processing could be resolved, assembly would be easy, and product quality could be significantly improved.

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 separately forming a metal cap part on one end side that is fitted to close the opening, and electrically connecting the cap part and the cylindrical main body part while being fitted, To provide a magnetic detector whose entire casing is significantly strengthened in terms of structure, has particularly excellent electrostatic shielding and electric shock prevention effects, is easy to manufacture, and can improve 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 mount board 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 be in surface contact with the shoulder portion 11a. They are tightly fitted onto the upper end of the main body part 11, and are welded to the main body part 11 at a suitable number of spots on the periphery, so that they are electrically connected to each other. Main body part 11
The means for electrically connecting the cap portion 12 with the cap portion 12 is not limited to the above-mentioned spot welding, but may also include other general welding, soldering,
The electrical connections may be made by brazing, conductive adhesive, or by fitting the cap portion 12 into close elastic contact with the main body portion 11. The bottom plate portion 13 is, for example, a plastic molded product, and is similar to the main body portion 1.
It is fitted and fixed to the lower end opening of 1.

The mount board 2 is located in the casing 1 formed by the above-mentioned members, facing the opening 11b of the main body part 11, and is spaced below the cap part 12 by a spacer 5 to maintain a required distance therefrom. A bottom plate 2' made of phosphor bronze is fixed to the bottom surface in such a manner as to close the hole, and the sensor unit 3 is inserted into the hole from the top surface side. is inserted and fixed therein, and one pole end face of a cylindrical permanent magnet 4 is fixed directly below the bottom plate 2' of the lower surface in correspondence with the sensor unit 3. The sensor unit 3 is formed by fixing two magnetic resistance elements 7 and 8 in parallel on a non-magnetic substrate 6 such as silicon fixed in a hole of the mount substrate 2 using a synthetic resin adhesive 6a. The leads pulled out from the elements 7 and 8 are guided to the lower surface of the mount board 2 through holes made in the mount board 2, where they are connected to the lead plates 9a and 9.
b, 9c, and the other end extends downward through a hole bored in the bottom plate portion 13 over a required length. 9d is housing 1
It is a lead plate for grounding with one end connected to the inner surface of the main body part 11, and the other end is also connected to the bottom plate part 1.
It extends downward through the hole drilled in 3.

Therefore, in the case of the present product configured as described above, when a magnetic body as a test object crosses the magnetic field of the permanent magnet 4 formed in front of both the magnetoresistive elements 7 and 8, the magnetic body is located at the position of the magnetic body. Therefore, the movement of the magnetic body is detected by a relative change in the resistance values of both magnetoresistive elements 7 and 8. If the object to be tested moves while sliding on the surface of the cap portion 12, frictional electricity is generated in the cap portion 12, but the cap portion 12 and the main body portion 11 are electrically connected, and the main body portion 11 is lead plate 9d
Since the cap part is grounded by the lead plate 9d, the electricity in the cap part flows through the main body part 11 and the lead plate 9d, and the cap part is charged as it is, so that the magnetoresistive elements 7 and 8 are not affected. It will also be shielded from electrostatic induction and electric shock. Furthermore, if a magnetic material is used for the material of the main body portion 11 and cap portion 12, a magnetic shielding effect can be obtained at the same time.

As mentioned above, in the case of this product, the main body part and the cap part, which are the constituent members of the casing that houses the magnetoresistive element, are made of metal and are electrically connected to each other, so the structure of the entire casing is Not only is it significantly strengthened, but also the frictional electricity generated in the cap part is reliably discharged to the outside through the main body part, and the magnetoresistive element inside the housing is not affected.
Furthermore, by grounding the cap, the magnetoresistive element is protected from electrostatic induction, electric shock, and the like.

Furthermore, when the main body portion and the cap portion are made of magnetic material, a magnetic shielding effect can be obtained, and the detection accuracy is greatly improved, so that the present invention has excellent effects.

[Brief explanation of the drawing]

Figure 1 is a front sectional view of a conventional magnetic detector;
The figure is a front sectional view of the product, FIG. 3 is a partially fragmented side view, FIG. 4 is a plan view, and FIG. 5 is a bottom view. 1... Housing, 2... Mount board, 3... Sensor unit, 4... Permanent magnet, 5... Spacer,
6... Substrate, 6a... Adhesive, 7, 8... Magnetoresistive element, 9a, 9b, 9c, 9d... Lead plate,
11...Body part, 12...Cap part, 13
...Bottom plate 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; It is divided into a thin metal cap part, and the cap part is electrically connected to the cylindrical main body part with the cap part fitted onto the cylindrical main body part, and is mechanically and electrically connected to the main body part. What is claimed is: 1. A magnetic detector comprising: a ground lead plate extending downward along the inner surface of the magnetic detector;