JPS58217082A - Magnetic sensor device - Google Patents

Abstract

PURPOSE:To obtain a stable magnetic detecting output, by using a magneto- resistance effect element for a magnetic detecting part. CONSTITUTION:A cylindrical coil bobbin 11 and a printed substrate 12 are supported in a housing 10 consisting of a non-magnetic electric conductor. The outside surface of a bottom wall 15 of the housing 10 forms a sensor face 13, and a guide bank 14 provided on the bobbin 11 is positioned opposingly in the inside of the bottom wall 15. A cylindrical magnetic material pole 18 is stored in the coil bobbin 11 so that its end part is projected a little from a collar part 16b and is retained to the guide bank 14, is retained to the substrate 12, and also is supported so as to be pushed in the direction of the sensor face 13 by a screw 19 grounded electrically and thermally. An electromagnetic coil 20 for magnetizing the magnetic material pole 18 is wound round the bobbin 11. A magneto- resistance effect element 21 stuck onto the end face of the magnetic material pole 18 is placed on the part of the guide bank 13.

Description

[Detailed Description of the Invention] 1. Sensors for reading magnetic patterns of printed matter printed with magnetic ink or written or printed with materials containing magnetic components include an electromagnetic coil type and a magnetoelectric conversion sensor. There is a type. The former type of sensor has the disadvantage that it requires a precise conveyance mechanism for printed matter, as the output characteristics change greatly when the gap between the printing surface and the sensor surface changes or when the conveyance speed changes. The printed side of the paper must always be conveyed toward the sensor surface, and it is also complicated to distinguish between the front and back sides or to specify the conveyance direction.

On the other hand, the latter sensor has a small output fluctuation even when the gap between the printing surface and the sensor surface changes, and the conveyance mechanism is simple, and it is not necessary to distinguish between the front and back of the printed matter or to specify the feeding direction. There is an advantage that speed does not need to be considered.

However, magnetoelectric transducers made from semiconductor materials adapt to high-frequency leakage magnetic flux from motors, etc., causing noise to be mixed into the output, and output characteristics that exhibit low-frequency drift when the temperature of the element changes suddenly. Not only is it not possible to obtain a good SN output, but there is also the drawback that when external pressure or striking force is applied to the element, output pulse noise is superimposed due to the piezo effect, causing the sensor circuit to malfunction.

The present invention provides a magnetic sensor device that fully utilizes the advantages of a magnetoresistive element and significantly improves the above-mentioned drawbacks.

In the device of the present invention, a magnetic resistance element is attached and fixed on the surface of a magnetizing means such as an electromagnet or a permanent magnet, and around the magnetic resistance element, a magnetic film, a magnetic card, or an ink containing a magnetic component is placed. In order to insulate the temperature of objects to be detected that have so-called magnetic information, such as printed matter written or printed with paint, etc., and magnetic pieces that mean the transmission of certain information, the heat of guide banks and shield plates, etc. In order to prevent the magnetoresistive element from being significantly affected by the temperature of the object to be detected, external pressure, magnetic dust or moisture, magnetic signals of It is characterized by being configured to identify patterns with high resolution.

Embodiments of the apparatus of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of the magnetic sensor device of the present invention, in which a box-shaped housing 10 made of a non-magnetic conductor such as brass or nickel silver has a thick A-wall and a thin bottom wall 15. A shaped coil bobbin 11 and a printed circuit board 12 are supported.

The bottom of the housing 10, the outer surface of the wall 15 is the sensor surface 13
The guide embankment 14 provided on the bobbin 11 is located opposite to the inside of the bottom wall 15.

Further, the collar portion 16a of the bobbin 11 is fitted into the housing 10, and the N1. A support portion 17 for regulating fI/ is provided, and a printed circuit board 12 is fixed at right angles to the bobbin 11.

The coil bobbin 11 has a cylindrical magnetic material column 18 attached to the collar portion 16.
b is housed so that its end is latched onto the guide bank 14 and is pushed in the direction of the sensor surface 16 by means of a screw 19 that engages the substrate 12 and is electrically and thermally grounded. It is supported as such. Further, an electromagnetic coil 20 that magnetizes the magnetic column 18 is wound around the bobbin 11 . A magnetoresistive element 21 affixed to the end face of the magnetic column 18 is arranged in the guide embankment 14 .

The housing 10 is made of a non-magnetic material and protects the magnetoresistive element 21 from the temperature of the object to be detected, external shocks, magnetic dust, moisture, water, and salt damage. Furthermore, if the housing 10 is made of, for example, phosphor bronze, beryllium copper, brass, nickel silver, tungsten, molybdenum, etc., and is grounded with a lead wire, electrostatic shielding can be performed at the same time. Furthermore, housing 1
0 prevents magnetic material from adhering to the magnetoresistive element 21 and from coming into contact with moisture, and also prevents the surface concentration of the object to be detected that slides on the sensor surface 13 or passes close to it to have a local temperature difference. Even if the temperature difference between the housing 10 and the element is large, the heat capacity of the housing 10 is large or the heat dissipates quickly, so that the temperature change does not affect the element.

In the above configuration, the housing 1o has the magnetic resistance element 21
The guide bank 14
The flange portion 16b of the coil bobbin 11 secures a certain distance from the inner surface of the bottom wall 15 of the element 21 and blocks heat from the housing 10.

FIG. 2 is an enlarged sectional view of the assembly of the coil bobbin portion, and FIG. 3 is a plan view of the assembly, in which the same parts as in FIG. 1 are given the same reference numerals. The cylindrical magnetic material column 18 is locked by two opposing semicircular guide banks 14a and 14b, and a portion of its end surface is exposed between the guide banks 14a and 14b. And guide embankment '14a and 14b
Two magnetoresistive elements 21a and 21b are attached to the exposed end faces of the magnetic material between the guide walls 14a and 14h in parallel with each other. The guides 514a, 14b and the coil bobbin 11 are molded from a material with low thermal conductivity such as resin, and the guide banks 14a,
The height of the magnetoresistive elements 21a and 21b is slightly higher than the thickness of the magnetoresistive elements 21a and 21b, and the elements 21a and 21b do not come into direct contact with the detected object 22, which is conveyed against the sensor surface 13, and always maintain a constant distance. It looks like this.
However, for the magnetic column 18, an anisotropic magnetic material, that is, a hard or semi-hard magnetic material is used. As the hard magnetic material, a material with a coercive force of about 300 to 800 degrees is used in order to keep the heat generation of the magneto-electric coil as small as possible since an ampere turn of about 5 times the coercive force is required during magnetization.

Furthermore, since semi-hard magnetic materials are demagnetized by impact, they may be used without being subjected to impact when magnetized, or they may be magnetized after impact occurs.

In the above configuration, when the detected object 22 passes over the magnetoresistive elements 21a and 21b, a pulse current is applied to the electromagnetic coil 20 to magnetize the magnetic column 18.

Thus, after this, even if the electromagnetic coil 20 is deenergized, the magnetic field continues to act on the magnetoresistive elements 21a and 21b. When the detected object 22 passes, an alternating current is applied to the electromagnetic coil 20 to demagnetize it. Therefore, compared to when a current is constantly flowing through the coil 20, the humidity does not increase, and magnetic dust does not adhere because the demagnetizing current demagnetizes the sensor while the object to be detected is not present.

The detected object 22 moves in a direction perpendicular to the magnetoresistive elements 218.21b arranged in parallel. The spacing and width of the magnetoresistive elements 21a and 21b are determined such that the magnetoresistive elements 21a and 21b act alternately on the magnetoresistive elements 21a and 21b. With this configuration, the output terminal 26
A high peak value output can be obtained.

When using the magnetic sensor device described above, as shown in FIG. 5, connect the electromagnetic coil 20 to the pulse power source 24,
Also, a pair of series-connected magnetoresistive elements 21a, 21b
is connected to the night current power supply 25. A current flows through the power source 25 when the object 22 to be detected approaches the elements 21a and 21b, and the current is cut off after the object 22 has passed.

Therefore, when the object to be detected 22 is transported, current flows through the magnetoresistive elements 21a and 21b, and a magnetic field is applied. Then, as the magnetic material pattern 23 passes, the element 21a
, 21b is changed, and the amount of this change is taken from the terminal 26 as an output voltage.

Incidentally, when it is easy to remove the dust of the magnetic powder, a permanent magnet may be used instead of the magnetic column 18, and in this case, the electromagnetic coil 20 is unnecessary.

Since the present invention has the structure as described above, it has the following effects.

(1) Since a magnetoresistive element is used in the magnetic detection part, the output does not decay exponentially with the distance to the detected object unlike a coil type sensor, and it also affects the frequency of the detected signal. Therefore, the conveyance speed of the object to be detected may be random, and there is no need to identify the front or back of the object to be detected or to specify the feeding direction, which reduces complexity and negative aspects for the user.

(2) Since the magnetoresistive element and the magnetizing means are housed and protected in the housing, even if the object to be detected has irregularities or chicks, it will not come into direct contact with the magnetoresistive element, and the object to be detected will not come into direct contact with the object. Even if the feeding roller bounces and hits the housing, the impact is not transmitted to the interview element, so no pulse-like noise is generated.

(3) Since the housing is made of metal with good thermal conductivity and the magnetic resistance element is directly attached to the magnetic column or magnet, even if the temperature of the object to be detected differs locally, there will be no sudden change in temperature. No significant changes will occur. Therefore, no low-frequency drift occurs in the output, and no pulse-like noise occurs. Therefore, stable output characteristics can be achieved, and noise can be easily removed.

(4) Since the two magnetoresistive elements are attached to the same magnetic material, there will be no temperature difference between the two elements, and the output level will not be biased.

(5) Low-level magnetic signal patterns can be identified with high resolution.

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[Brief explanation of the drawing]

FIG. 1 is a sectional view of the magnetic sensor device of the present invention, FIG. 2 is an enlarged sectional view of the magnetizing means according to the device of the present invention, FIG. 3 is a plan view of FIG. 2, and FIG. 4 is an example of a magnetic material pattern. 10: Housing, 11: Coil bobbin, 14° 14a
, 14b guide bank, 18: magnetic column, 20: electromagnetic coil, 21, 21a, 21b: magnetoresistive element. Patent Applicant Denki Onkyo Co., Ltd. 10- Figure 1] O Figure 2 Procedural Amendment Form Ch Formula) % Formula % l Indication of the Case Japanese Patent Application No. 58 No. 20414 2 Title of the Invention Magnetic Sensor Device 3 Case of Person Who Amends Relationship with Patent Applicant Representative Director Seki Tian f Introduction 4, Date of amendment order June 28, 1980 Figure 1

Claims (1)

[Claims] (1) A magnetizing means for generating a magnetic field is inserted into a bottomed cylindrical housing made of a non-magnetic conductor with one magnetic pole facing the bottom, and a pair of magnetoresistive elements are attached to the magnetic pole surface of the magnetic pole. A magnetic sensor device featuring an attached configuration.