JPH0359590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic detector using a magnetoresistive element whose resistance value changes in response to changes in a magnetic field.

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 a front sectional view showing a conventional magnetic detector, and numeral 21 in the figure indicates a housing. The housing 21 is integrally molded from plastic.
The opening 21a formed on the top surface is closed with a protective plate 22 made of a thin film made of copper beryllium.
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 housing 21 with a suitable distance from the protective plate 22. Senki 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 that surrounds the sensor unit 23 is provided on the mount board 28, and the upper surface of the spacer 30 is brought into contact with the periphery of the protection plate 22, thereby increasing the distance between the protection plate 22 and the magnetoresistive elements 26, 27. It is set to a predetermined value. Each magnetoresistive element 26, 2
The leads drawn out from 7 are connected to the terminal 31 provided on the inner wall surface of the housing 21 through the printed wiring on the mount board 28, and then connected to the lead wire 32 led out to the outside 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 casing of such conventional magnetic detectors is made of plastic, which has excellent moldability, and this makes it difficult to assemble the magnetic detector itself and to attach it to the device. This is because it is easy to take measures in terms of shape to improve performance, 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 may occur due to the influence of electrostatic induction on 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 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 present inventors have developed an electrostatic induction system as described above.
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 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 draw a metal casing with locally varying wall thicknesses.

The present invention has been made in view of the above circumstances, and its purpose is to bulge outward the flat wall portion of a metal casing in which the magnetoresistive element is to be placed, in which the magnetoresistive element is to be positioned opposite. The outer surface of the bulging wall portion is polished to a flat surface.
By making this part thinner than other parts, it is possible to easily manufacture a casing with thick and thin parts, which increases the mechanical strength of the entire casing and prevents moisture from coming in from the outside. It is an object of the present invention to provide a method for manufacturing a magnetic detector that can prevent intrusion, and also allows the thin portion to be molded thinner to improve sensitivity.

Hereinafter, the method of the present invention will be specifically explained based on the drawings showing its implementation state. Fig. 2 is a front sectional view of a magnetic detector obtained by the method of manufacturing a magnetic detector according to the method of the present invention, Fig. 3 is a partially fragmented side view of the same, and Fig. 4 A and B are of the casing obtained by the method of the present invention. It is an explanatory diagram showing the manufacturing process, in which 1 is a housing, and 11 is a housing 1.
12 indicates a bottom plate portion.

The main body part 11 is made of brass and has a closed upper end and a rectangular tube shape with slightly rounded corners.The lower end is closed with a bottom plate part 12, and inside there are a mounting board 2 and a sensor. A unit 3, a permanent magnet 4, etc. are arranged, and the space other than the part surrounded by the spacer 5 of the sensor unit 3 is filled with synthetic resin. This main body part 11 is first made of a brass plate which is drawn to have a uniform thickness (approximately 0.5 mm) with its upper end closed, as shown in Figure 4A.
A housing body 10 is formed into a rectangular cylindrical shape, with the center part of the upper wall where the magnetoresistive elements 7 and 8 are to face bulging outward. The outward bulging dimension of the bulging portion 11a on the upper wall of the housing body 10 is made slightly smaller than the wall thickness dimension of the housing body 10, and then, as shown in FIG. The outer wall of the bulged portion 11a is polished to the position shown by the broken line, and the outer surface of the bulged portion 11a is finished to be flat so that it is flush with the surrounding surface. As a result, the outer surface is flat and the inner surface has a recess 11b in the center of the upper wall, and the wall thickness is 0.1 mm.
A main body portion 11 is formed having a thin portion 11c of about 100 mL.

Note that the form of the main body portion 11 is not limited to the above-mentioned form; for example, as shown in FIG. Part 11'a
The size of the bulge from the peripheral edge of the bulge is equal to or larger than the wall thickness, and then the outer surface of the bulge 11'a is polished to a thickness of about 0.1 mm as shown by the broken line, and a recess 11' is formed on the inner surface as shown in FIG. 5B. b, and a main body portion 11' having a thin wall portion 11'c may be formed.

The bottom plate portion 12 is, for example, a plastic molded product, and is fitted and fixed into the lower end opening of the main body portion 11.

The mount board 2 has a thin part 11 of the main body part 11 inside the casing 1 formed by the above-mentioned members.
c, 11'c, and the thin portion 11c,
Spacer 5 whose upper end is in contact with the lower surface of 11'c
Therefore, the sensor unit 3 is arranged at a required distance from this, and the sensor unit 3 is fixed to the upper surface of the magnet located in the recesses 11b and 11'b, and the end face of one pole of a cylindrical permanent magnet 4 is fixed to the lower surface. There is. Sensor unit 3
is formed by fixing two magnetoresistive elements 7 and 8 in parallel on the magnetic substrate 6 on the upper surface of the mount board 2 using adhesive resin 6a, and the leads drawn out from each magnetoresistive element 7 and 8 are attached to the mount board 2. 2 through the holes drilled in the lead plates 9a,
9b and 9c, and the other ends thereof extend downwardly through a hole bored in the bottom plate portion 12 over a required length. Reference numeral 9d denotes 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 12.

In the present invention, the casing 1 is made of metal, and the casing bodies 10 and 10' are made such that the wall portions of the portions where the magnetoresistive elements 7 and 8 are to face each other are bulged outward. Swelling parts 11a and 11'a at 10 and 10'
Since it is manufactured by polishing and thinning the surface, the surface is smooth and there is no difference in level between the casing and the protective plate as in the conventional case, which causes problems such as the object to be inspected getting stuck. There is no thinning part 1.
1c and 11'c have peripheral edges that are integrally connected to the thick portion, so they have great strength, can be made thinner, and can greatly improve detection sensitivity. Further, even if frictional electricity is generated due to friction with the test object, it will be discharged through the grounding lead plate 9d, and the magnetoresistive elements 7 and 8 can be protected from electrostatic induction, electric shock, etc. Moreover, since the housing 1 is integrally formed except for the bottom plate portion 12,
The airtightness is high, and the characteristics of the magnetoresistive elements 7 and 8 do not deteriorate due to moisture intrusion.

As described above, in the method of the present invention, after the flat wall portion of the metal casing facing the magnetoresistive element is bulged outward, the outer surface of the bulged portion is polished flat to reduce its thickness. Because it involves a manufacturing process, the magnetoresistive element can be faced parallel to the wall and even the object to be tested with uniform spacing, resulting in less variation in detection values and high accuracy.Also, the housing can be integrally molded, making it possible to It has high mechanical strength as a whole, can protect the magnetoresistive element from electrostatic induction and electric shock, and has high airtightness inside the casing to reliably prevent moisture from entering, and is also thinner. The present invention has excellent effects such as being able to make the portion thinner, thereby shortening the distance between the object to be inspected and the magnetoresistive element, and greatly improving detection accuracy.

[Brief explanation of drawings]

Figure 1 is a front sectional view of a conventional magnetic detector;
The figure is a front sectional view of a magnetic detector manufactured by the method of the present invention, FIG. 3 is a partially fragmented side view, FIG. A and B are explanatory diagrams similarly showing other manufacturing modes of the casing. 1... Housing, 2... Mount board, 3... Sensor unit, 4... Permanent magnet, 5... Spacer,
6... Magnetic substrate, 6a... Adhesive, 7, 8...
Magnetoresistive element, 9a, 9b, 9c, 9d... Lead plate, 10, 10'... Housing body, 11, 11'...
Main body portion, 11a, 11'a...bulging portion, 11b,
11'b... recess, 11c, 11'c... thin wall portion, 12... bottom plate portion.

Claims (1)

[Claims] 1. A metal casing with a closed upper end that houses a magnetic resistance element by drawing a metal plate, and a flat upper wall of the metal casing that is to face the magnetic resistance element and bulges outward. Step 1, a second step of flattening the bulging part of the upper wall to make it thinner than other parts, and adding at least a spacer and a lead to the dent formed on the inner surface of the casing when the bulging part was bulged. a third step of storing the provided magnetoresistive element;
A method for manufacturing a magnetic detector, comprising a fourth step of injecting a resin into the metal casing, and a step of connecting a grounding lead to the inner surface of the casing after the second step.