JP3775296B2 - Magnetic sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic sensor for reading magnetic information of a paper-like medium such as banknotes used in financial equipment such as an automated teller machine, vending machines, ticket vending machines and the like.
[0002]
[Prior art]
A magnetic sensor for reading magnetic information of banknotes used in an automatic teller machine or the like includes a magnetoresistive element and a permanent magnet housed in a case. In order to read magnetic information such as a pattern drawn with magnetic ink on a banknote, the banknote is sent by rubbing the case surface of the magnetic sensor at high speed. For this reason, the case surface of the magnetic sensor is heavily worn by friction with the bill. In order to prevent malfunction of reading magnetic information due to wear, the case surface was plated with high hardness. For this plating, hard chrome plating was used, and the hardness was 800 Hv and the film thickness was about 7 μm. As a result, the wear life of the plating layer on the case surface of the magnetic sensor with respect to the banknote was ensured up to 10 million passes.
[0003]
[Problems to be solved by the invention]
However, in recent years, banks and the like have been promoting the 24-hour operation of ATM windows in order to cope with the diversification of customers' lives. As a result, the usage time of an automated teller machine has been greatly increased, and a magnetic sensor that has improved the wear life of the plating layer on the case surface with respect to banknotes to 10 million passes or more has become necessary. For this reason, an attempt was made to improve the wear life by setting the thickness of the hard chrome plating formed on the case surface to 7 μm or more. However, when the hard chrome plating was formed with a film thickness of 7 μm or more, the surface of the hard chrome plating gradually became white and could not be formed with a uniform thickness. For this reason, there is a problem in that the wear life of the plated layer on the case surface varies from product to product, and the whitened portion of the hard chrome plating becomes brittle and the wear life cannot be sufficiently improved.
[0004]
The magnetic sensor of the present invention has been made in view of the above-mentioned problems, and aims to provide a magnetic sensor that solves these problems and improves the wear life of the metal layer on the case surface with respect to banknotes. .
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a magnetic sensor of the present invention is a magnetic sensor in which a magnetic detection element and a magnet for applying a magnetic bias to the magnetic detection element are accommodated in a case, and the surface of the case contains ceramic particles. A base metal layer that is covered with a metal layer that includes the ceramic particles and that is the same metal as the metal layer and does not include ceramic particles is formed below the metal layer that includes the ceramic particles .
[0006]
The ceramic particles may be SiC or alumina.
[0007]
Moreover, the metal layer containing the ceramic particles is formed by electroless plating.
[0008]
The surface of the metal layer containing the ceramic particles is electropolished.
[0009]
In addition, the thickness of the metal layer containing the ceramic particles is 6 μm to 40 μm.
[0010]
The metal layer containing the ceramic particles is heat treated.
[0011]
In addition, the thickness of the metal layer containing the ceramic particles is 4 μm to 40 μm.
[0012]
Further, a base metal layer is formed under the metal layer containing the ceramic particles.
[0013]
The metal layer including the ceramic particles has a hardness of 800 Hv or more.
[0014]
The maximum particle size of the ceramic particles is 2 μm.
[0015]
Further, the metal of the metal layer containing the ceramic particles is nickel.
[0016]
The magnetic detection element is a magnetoresistive element.
[0017]
Thereby, since the intensity | strength of the metal layer of the case surface of a magnetic sensor can be improved significantly, the wear life of the metal layer of the case surface with respect to a banknote can be improved.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment, FIGS. 1 to 3]
A magnetic sensor according to a first embodiment of the present invention will be described below with reference to FIGS.
[0019]
FIG. 1 is a schematic sectional view of a magnetic sensor of the present invention. As shown in FIG. 1, the magnetic sensor 10 is configured by housing a magnetoresistive element 1, a permanent magnet 2, and a resin holder 3 in a case 5 having an opening. The case 5 has a flat upper surface 9 on which a nickel plating layer 6 containing ceramic particles is formed.
[0020]
A concave portion is formed on the opening side of the case 5 of the resin holder 3, and the permanent magnet 2 is fixed therein. A convex concave portion is formed on the opposite side of the resin holder 3 from the opening of the case 5, the magnetoresistive element 1 is fixed to the concave portion, and the convex portion is in contact with the inner surface of the case 5. The gap is 0.1 mm. In the permanent magnet 2, the N magnetic pole is directed to the magnetoresistive element 1. An external connection terminal 4 is disposed beside the magnetoresistive element 1 and the permanent magnet 2 and penetrates the resin holder 3. The external connection terminal 4 and the magnetoresistive element 1 are electrically connected by a metal wiring body 11. The case ground terminal 7 is electrically and mechanically attached to the inside of the opening of the case 5. Further, the resin holder 3 and the like are sealed in the case 5 by the casting resin 8.
[0021]
Here, the magnetoresistive element 1 is made of an InSb semiconductor material, and two magnetoresistive elements 1 are formed in a meander line shape on a silicon substrate. The two magnetoresistive elements 1 are provided with three terminals including one common terminal. The resin holder 3 is made of PPS resin, the permanent magnet 2 is made of SmCo, and the case 5 is made of brass. Since FIG. 1 is a cross-sectional view, only one of the three external connection terminals 4 is shown.
[0022]
In the magnetic sensor 10, the bill is fed at a high speed of 1 to 4 m / sec so as to rub the plated portion of the upper surface 9 of the case 5. At this time, the two magnetoresistive elements 1 detect specific magnetic signals from the density, line width, and line interval of the pattern ink drawn with the magnetic ink of the banknote, and thereby the authenticity determination of the banknote is performed. Yes.
[0023]
Next, the nickel plating layer 6 containing ceramic particles formed on the surface of the case 5 will be described with reference to FIG. 2 shows an enlarged cross-sectional view of the upper surface 9 portion of the case 5 of the magnetic sensor 10 shown in FIG. As shown in FIG. 2, a nickel plating layer 6 including ceramic particles 21 is formed on the surface of the case 5. Case 5 is formed of brass having a thickness of 200 μm.
[0024]
Hereinafter, the manufacturing method and effects of the nickel plating layer 6 will be described.
[0025]
The ceramic particles 21 are SiC particles having a maximum particle diameter of 2 μm and a hardness of 1400 Hv. This particle size is preferably 2 μm or less in consideration of mixing the ceramic particles 21 uniformly in the nickel plating layer 6. The ceramic particles 21 are contained in an electroless nickel plating solution. Then, the nickel plating layer 6 containing the ceramic particles 21 is formed on the surface of the case 5 by 40 μm by electroless plating. Here, although the hardness of the normal nickel plating layer is 400 Hv, since the hardness of the SiC particles is 1400 Hv, the hardness of the nickel plating layer 6 including the ceramic particles 21 is about 800 Hv. As a result, the wear life of the nickel plating layer 6 was improved to about 55 million passes. Thus, the wear life of the magnetic sensor is improved and it can be used for a long time.
[0026]
Furthermore, the magnetic sensor can be improved by performing electropolishing. The surface of the nickel plating layer 6 containing the ceramic particles 21 had small irregularities, and the surface roughness was about 3.9 μm. Therefore, the surface of the nickel plating layer 6 containing ceramic particles is electropolished to be flat. As a result, the surface roughness was about 0.8 μm and could be reduced to 1/5. As a result, the coefficient of friction in contact with the banknote is reduced, and the amount of wear on the banknote can be reduced. At this time, the wear life of the nickel plating layer 6 is about 55 million passes, and it can sufficiently cope with ATM's 24-hour response.
[0027]
In addition, the wear life can be further improved by heat treatment. The nickel plating layer 6 including the ceramic particles 21 is heat-treated at a temperature of 300 ° C. to 400 ° C. for 2 hours to 4 hours. By performing this heat treatment, since the Ni—Ni ₃ P eutectic is formed in the nickel plating layer 6 containing the ceramic particles 21, the hardness of the nickel plating layer 6 can be increased. In this example, heat treatment was performed at 300 ° C. for 2 hours, and the hardness of the nickel plating layer 6 including the ceramic particles 21 could be improved to 1400 Hv. Thereby, the nickel plating layer 6 containing the ceramic particles 21 was able to obtain a hardness of about 1.7 times the hardness 800Hv of the conventional hard chrome plating layer. As a result, the wear life of the nickel plating layer 6 was improved to about 11 million passes. As a result, it is possible not only to support ATM for 24 hours, but also to support higher speed processing of 4 m / second or more.
[0028]
Next, the relationship between the thickness of the nickel plating layer containing ceramic particles, the output ratio, and the wear life will be described with reference to the characteristic diagram of FIG.
[0029]
In FIG. 3, the output ratio represents the degree of change in output when plating is applied, compared to when the output of the magnetic sensor without plating is 100%. FIG. 3 shows that as the thickness of the nickel plating layer containing ceramic particles increases, the wear life becomes longer, but the output of the magnetic sensor decreases. Here, if the thickness of the nickel plating layer is 40 μm or less, the change in the magnetic signal output of the magnetic sensor can be suppressed to within 10%. Within this range, since the input signal allowable range of the amplifier circuit of the magnetic sensor is not exceeded, the authenticity can be determined stably. For this reason, the thickness of the nickel plating layer needs to be 40 μm or less. Further, according to FIG. 3, in order to secure a wear life of 10 million passes for the banknote, the thickness of the nickel plating layer needs to be about 6 μm when not heat-treated and about 4 μm when heat-treated. . As described above, the thickness of the nickel plating layer needs to be set to 6 μm to 40 μm when not heat-treated, and 4 μm to 40 μm when heat-treated.
[0030]
[Second Example, FIG. 4]
Hereinafter, a magnetic sensor according to a second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 4, a nickel plating layer 22 having a thickness of 5 μm is formed on the case 5 by electroless plating. Furthermore, a nickel plating layer 6 containing ceramic particles 21 is formed thereon with a thickness of 40 μm. Here, the method of forming the nickel plating layer 6 including the ceramic particles 21 is the same as that in the first embodiment. Even in such a configuration, the same effect as in the first embodiment can be obtained. Particularly in this case, the underlying nickel plating layer 22 acts as a buffer, and the unevenness of the surface of the nickel plating layer 6 including the ceramic particles 21 can be suppressed. In this embodiment, the nickel plating layer 6 containing the same ceramic particles 21 as in the first embodiment is laminated on the nickel plating layer 22 which is easily worn but has a smooth surface. As a result, a magnetic sensor having the characteristics that the surface roughness was as small as about 1.6 μm and the wear life was long was obtained.
In this embodiment, only the case where SiC particles are used as the ceramic particles has been described. However, the ceramic particles may have a hardness of 800 Hv or more, and alumina or the like may be used. Moreover, although only the case where nickel was used for the plating metal of a metal layer was demonstrated, you may use a nickel alloy. Moreover, you may use metals, such as a copper type and an aluminum type.
[0031]
【The invention's effect】
As described above, according to the present invention, by forming the metal layer containing ceramic particles on the surface of the case of the magnetic sensor, it is possible to ensure a wear life of 10 million passes or more for bills and the like. As a result, it can be used for a 24-hour automatic teller machine.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a magnetic sensor according to a first embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a case upper surface portion of the magnetic sensor.
FIG. 3 is a characteristic diagram showing the relationship between the thickness of a nickel plating layer containing ceramic particles, the output ratio of a magnetic sensor, and the wear life.
FIG. 4 is an enlarged cross-sectional view of a case upper surface portion of a magnetic sensor according to a second embodiment of the present invention.
[Explanation of symbols]
1 ----- Magnetoresistance element 2 ----- Permanent magnet 3 ----- Resin holder 4 ----- External connection terminal 5 ----- Case 6 ----- Ceramic particles Nickel plating layer 7 containing ----- Case ground terminal 8 ----- Injection resin 9 ----- Case upper surface 10 ----- Magnetic sensor 11 ----- Metal wiring body 21- ---- Ceramic particle 22 ----- Underlying nickel plating layer

Claims (11)

A magnetic sensor in which a magnetic detection element and a magnet for applying a magnetic bias to the magnetic detection element are housed in a case,
The surface of the case is covered with a metal layer containing ceramic particles, and a base metal layer that is the same metal as the metal layer and does not contain ceramic particles is formed under the metal layer containing ceramic particles. a magnetic sensor, characterized in that are.  The magnetic sensor according to claim 1, wherein the ceramic particles are SiC or alumina.  The magnetic sensor according to claim 1 or 2, wherein the metal layer containing the ceramic particles is formed by electroless plating.  The magnetic sensor according to any one of claims 1 to 3, wherein a surface of the metal layer containing the ceramic particles is electropolished.  5. The magnetic sensor according to claim 1, wherein a thickness of the metal layer including the ceramic particles is 6 μm to 40 μm.  The magnetic sensor according to claim 1, wherein the metal layer including the ceramic particles is heat-treated. The magnetic sensor according to claim 6 , wherein a thickness of the metal layer including the ceramic particles is 4 μm to 40 μm. The magnetic sensor according to any one of claims 1 to 7 , wherein the metal layer containing the ceramic particles has a hardness of 800 Hv or more. Wherein the maximum particle size of the ceramic particles is 2 [mu] m, the magnetic sensor according to claims 1 to 8. Metal of the metal layer containing ceramic particles, characterized in that it is a nickel, a magnetic sensor according to any of claims 1 to 9. Wherein the magnetic detecting element is a magneto-resistive element, the magnetic sensor according to any of claims 1 to 10.

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