JPH0240554Y2 - - 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 their 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 space 30 surrounding the sensor unit 23 is provided on the mount substrate 28, and the space between the protection plate 22 and the magnetoresistive elements 26 and 27 is adjusted by bringing the upper surface of the spacer 30 into contact with the periphery of the protection plate 22. It is set to a predetermined value. Each magnetoresistive element 26, 2
The leads pulled out from 7 pass through the printed wiring on the mount board 28, are once placed on the terminal board 31 provided on the inner wall surface of the housing 21, and are then connected to the lead wires 32 led out to the outside through the bottom plate. There is.

It should be noted that the space inside the housing 21 is designed to prevent moisture from entering the housing, changing the characteristics of the magnetoresistive elements 26 and 27, and promoting deterioration of the characteristics over time.
Furthermore, in order to increase the strength against mechanical shock, the casing is filled with epoxy resin (not shown) 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,
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 protective 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. However, there is a problem in that erroneous detection occurs due to the influence of electrostatic induction on the magnetoresistive elements 26, 27 or the conductor portion inside 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 circuits 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.

The present invention was developed in view of the above circumstances, and its purpose is to divide the casing into two metal parts that can be fitted and connected to each other, and to connect both parts with electricity. In addition, by interposing a filler such as synthetic resin in the gap between the mating parts of both parts, the entire housing is strengthened and the sensor unit inside the housing is protected against electrostatic induction and electric shock. It is an object of the present invention to provide a magnetic detector which can protect the magnetoresistive element from moisture and prevent characteristic change and characteristic deterioration of the magnetic resistance element due to the intrusion of moisture into the housing.

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 proposed product), Fig. 3 is also a partially fragmented side view, Fig. 4 is a partially cutaway front view of the main body of the proposed product, and Fig. 5 1 is also a plan view, in which reference numeral 1 indicates a housing, 11 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 and rounded corners, and its upper end is fitted here. The cap part 12 closes the lower end, and the bottom part 13 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. 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. It is reduced in size by a considerable amount, and 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. This narrowing width dimension is large in the long side direction and small in the short side direction in a rectangular cross section, and the square opening 1 is reduced in the center.
1b is formed. The four peripheries of the opening 11b are provided with two opposing sides on the side with the larger narrowing width dimension as introduction portions for introducing the filler into the gap formed at the overlapping portion of the main body portion 11 and the cap portion 12. In the center, notches 11c, 11c are V-shaped in plan view so as to be sharp outward from the periphery of the opening 11b, and in the center of the other two sides perpendicular to this, the cutouts 11c, 11c are V-shaped in cross section. Groove 1
1d and 11d are formed at opposing positions, respectively. The cutting angle of the V-shaped notches 11c, 11c and the groove bottom angle of the grooves 11d, 11d are both set to 90 degrees, but these angles are not particularly limited. Any angle that can be used will suffice. In addition, the shape, the number of formed notches 11c, 11c that constitute the introduction part, and the groove 1
The shape of 1d and 11d and the number of formed pieces are not particularly limited, and they may be formed in an appropriate combination.

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 therewith. It is tightly fitted onto the upper end of the main body portion 11 and welded to the main body portion 11 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 to the lower end opening of the main body portion 11.

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 at a required distance. arranged,
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 attached to the board 6 on the top surface of the mount board 2.
Two magnetoresistive elements 7, 8 are fixed on top using adhesive resin 6a, and each magnetoresistive element 7,
The leads pulled out from the mount board 2 are guided to the bottom surface thereof through holes made in the mount board 2, and are connected to one end of each of the lead plates 9a, 9b, and 9c here. They each extend for the required length through and below. 9
Reference numeral d 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.

In the present product configured as described above, when a magnetic body crosses the magnetic field formed in front of both magnetoresistive elements 7 and 8 by the permanent magnet 4, for example, the magnetic flux density changes due to the magnetic field. As a result, the resistance value of each magnetoresistive element 7, 8 changes, and the presence or absence of a magnetic substance can be detected from the resulting change in voltage value.

In addition, in the case of this product, in the process of filling the synthetic resin material into the housing 1 after assembling the housing 1, the sensor unit 3, etc., the synthetic resin is injected from the bottom plate portion 13 side of the housing 1. , the synthetic resin reaches the inner wall of the cap portion 12, and from there, a portion thereof is formed into the notches 11c, 11c and the grooves 11d, 11, respectively.
d, and is introduced from each tip into the gap between the opening 11b of the main body portion 11, the periphery, and the inner circumferential surface of the cap portion 12, spreads around the periphery, fills this gap, and is cured. Therefore, moisture enters into the housing 1 through the gap, and the characteristics of the magnetoresistive elements 7 and 8 change.
This prevents the characteristics from deteriorating and significantly extends its life.

As described above, in the case of this product, the casing that houses the magnetic resistance element is divided into a metal main body part and a metal cap part that is fitted and fixed to one end of this main body part. Not only does it strengthen the structure of the entire housing, but it also protects the magnetoresistive element from electrostatic induction and electric shock.In addition, the gap between the main body and the cap is formed around the opening of the main body. The filler can penetrate smoothly all around the circumference through the introduced part of the filler, sealing the gap, preventing moisture from entering through the gap, and preventing changes in the characteristics of the magnetoresistive element due to moisture intrusion. It is possible to effectively reduce the
The present invention has excellent effects.

[Brief explanation of the drawing]

Figure 1 is a front sectional view of the conventional product, Figure 2 is a front sectional view of the proposed product, and Figure 3 is a partially cutaway side view.
FIG. 4 is a partially cutaway front view of the main body portion of the casing constituting the product, and FIG. 5 is a plan view of the same. 1... Housing, 2... Mount board, 3... Sensor unit, 4... Permanent magnet, 5... Spacer,
6... Substrate, 7, 8... Magnetoresistive element, 9a, 9
b, 9c, 9d...Lead plate, 11...Body portion, 11c...Notch, 11d...Groove, 12...
...cap part, 13...bottom plate part.

Claims (1)

[Scope of utility model registration request] A housing for housing a magnetic resistance element is a metal tube that has an opening on one end where the magnetic resistance element should be exposed, and is drawn so that the peripheral edge faces toward the center to form an arcuate shoulder. a metal body which is curved in an arc shape so as to be in surface contact with a portion facing the body, and is fitted and fixed to one end of the body in close contact with the outside to close the opening of the body; a cap portion, and an introduction portion is provided at the periphery of the opening of the main body portion to allow the filler to enter the gap between the main body portion and the cap portion fitted onto the main body portion, and fills the inside of the casing. A magnetic detector characterized by being filled with a material.