JPS5931878B2 - magnetic center device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic sensor device using a semiconductor magnetoelectric conversion element.

Sensors for reading magnetic patterns of printed matter printed with magnetic ink or printed matter written or printed with magnetic components include an electromagnetic coil type and a magnetoelectric conversion type.

The former sensor has the disadvantage that it requires a precise conveyance mechanism for the 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 surface 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. If noise is mixed into the output due to high frequency leakage flux from a motor, etc., or if the temperature of the element changes rapidly, the output characteristics will exhibit low frequency drift, and it will not only be impossible to obtain a good SN output. However, when pressure or striking force is applied to the element from the outside, 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 takes advantage of the advantages of magnetoelectric conversion elements and significantly improves the above-mentioned drawbacks.

In the device of the present invention, a magnetoelectric transducer such as a Hall element or a magnetoresistive element that generates an output in response to a magnetic field is attached and fixed on the surface of a magnetizing means such as an electromagnet or a permanent magnet, and , magnetic films, magnetic cards, printed matter written or printed with ink or paint containing magnetic components, and magnetic pieces that convey certain information, etc., which have so-called magnetic information. In order to insulate the temperature of the object to be detected, a thermal insulation means such as a guide bank or a shield plate is provided to prevent the magnetoelectric transducer from being greatly affected by the temperature of the object to be detected, or being exposed to external pressure, magnetic dust, etc. The device is characterized in that it is configured to identify low-level magnetic signal patterns with high resolution without being affected by moisture.

Embodiments of the apparatus of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a sectional view of the magnetic sensor device of the present invention, in which a cylindrical coil bobbin 11 and a printed circuit board 12 are supported in a box-shaped housing 10. The sensor surface 13 of the housing 10 is provided with a through hole 15 into which the guide bank 14 provided on the bobbin 11 is tightly fitted, and the flange 16a of the bobbin 11 is fitted into the housing 10 to determine the position of the bobbin 11. A support portion 17 is provided for regulating the bobbin 11.
A printed circuit board 12 is fixed so as to form a right angle to the . A cylindrical magnetic material column 18 is attached to the collar portion 1 of the coil bobbin 11.
The direction of the through hole 15 is fixed by a fitting 19 which is housed in such a way that its end protrudes somewhat from the guide bank 14 and is engaged with the substrate 12 and is electrically and thermally grounded. It is supported in such a way that it is pushed towards. Further, an electromagnetic coil 20 that magnetizes the magnetic column 18 is wound around the bobbin 11 . A magnetoelectric transducer 21 (an example of a magnetoresistive element will be described below) attached to the end face of the magnetic column 18 is arranged in the guide embankment 14, and these are connected to the shield cap 2 that covers the through hole 15.
Protected by 2. The shield cap 22 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 shield cap is made of a material with high thermal conductivity, such as ceramic, and a heat escape route is created, the heat shielding effect will be increased. Furthermore, the shield cap can be made of non-magnetic conductive materials such as phosphor bronze, beryllium copper, brass, nickel silver, tungsten,
If it is made of molybdenum or the like and grounded with a lead wire, electrostatic shielding can be performed at the same time. The shield cap 22 is the second
As shown in the figure, it is made into an ashtray-like shape with a flange 22b, that is, a concave cross-sectional shape with a flange, and is buried at the same time as the housing 10 is molded, or after the housing is molded, it is fitted into the through hole 15 and the part of the through hole 15 is formed. This prevents magnetic material from adhering to the magnetoresistive element 21 and from coming into contact with moisture, and also prevents the surface temperature of an object to be detected that slides or approaches the sensor surface 13 from becoming locally heated. Even if there is a difference in temperature, or even if there is a large temperature difference with the element, the shield cap 22 has a large heat capacity or heat escapes quickly, so the temperature change will not affect the element.

In the above configuration, the shield cap 22 is connected to the magnetoresistive element 21
The guide bank 14
The flange portion 16b of the coil bobbin 11 secures a certain distance from the shield cap 22 of the element 21 and blocks heat from the shield cap 22. Further, since the heat capacity of the shield cap 22 can be determined as desired by selecting the size of the brim 22b, sudden temperature changes from the object to be detected are not transmitted to the magnetoresistive element 21. FIG. 3 is an enlarged sectional view of the assembly of the coil bobbin portion, and FIG. 4 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 column 18 is locked by two opposing semicircular guide banks 14a and 14b, and a part of its end surface is exposed between the guide banks 14a and 14b. Two magnetoresistive elements 21a and 21b are attached to the exposed end face of the magnetic material between the guide banks 14a and 14b in parallel with the guide banks 14a and 14b. The guide banks 14a, 14b and the coil bobbin 11 are molded from a material with low thermal conductivity such as resin.
is slightly higher than the thickness of the magnetoresistive elements 21a and 21b.
The element 21a,
21b are always kept at a constant distance without being in direct contact. Further, as the magnetic material 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 oersted 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 when magnetizing. Further, since semi-hard magnetic materials are demagnetized by impact, they can be used without being subjected to impact when they are magnetized, or they may be magnetized after impact is applied. In the above configuration, the detected object 2
3 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 point, 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 23 passes, an alternating current is applied to the electromagnetic coil 20 to demagnetize it. Therefore, the temperature does not rise as compared to when a current is constantly flowing through the coil 20, and magnetic dust does not adhere because the demagnetizing current demagnetizes the body while the object to be detected is not present. A pair of magnetoresistive elements 21a arranged in parallel,
21b is connected to cancel the generated noise. For example, FIG. 5 shows an embodiment of a pair of magnetoresistive elements 21a and 21b used in the device of the present invention, and the electrode 24
, 25, 26, 27 and the conductive parts 28, 29 are shown with diagonal lines, and the magnetically sensitive parts 30, 31 are shown with a pear pattern, but these elements 21a and 21b are made symmetrically,
They also have the same surface area and are made from two chips.
Further, a lead wire 32 connected to the electrode 24 and a lead wire 33 connecting between the electrodes 25 and 26 are arranged almost symmetrically, and a power source is connected between the lead wire 32 and the electrode 27. The lead wire may be a vapor-deposited wire. Therefore, the voltage generated in response to the external magnetic field is applied to the magnetoresistive element 21.
The noise is canceled inside the resistors 21b and 21b according to the division ratio of these resistance values, and the noise appearing at the output terminal 34 becomes extremely low level.

The detected object 23 moves in a direction perpendicular to the magnetoresistive elements 21a and 21b arranged in parallel, but the magnetic material pattern of the detected object 23, for example, a linear pattern 35 as shown in FIG. The spacing between the magnetically sensitive parts 30 and 31 and the magnetically sensitive parts 30, 31 are such that
The width is determined.

With this configuration, an output with a high peak value can be obtained from the output terminal 34. When using the magnetic sensor device described above,
As shown in FIG. 7, the electromagnetic coil 20 is connected to a pulse power source 36
and a pair of serially connected magnetoresistive elements 21
The electrodes 24 and 27 of a and 21b are connected to a DC power source 37.

A current flows through the power source 37 when the object 23 to be detected approaches the elements 21a and 21b, and the current is cut off after the object 23 has passed. Therefore, when the object to be detected 23 is transported, current flows through the magnetoresistive elements 21a and 21b, and a magnetic field is applied.

Then, as the magnetic material pattern 35 passes, the elements 21a,
The magnetic field acting on the magnetic field 21b is changed, and the amount of this change is taken out from the terminal 34 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.

Further, instead of the above-mentioned housing, a cylindrical body made of a non-magnetic conductor such as brass or nickel silver can be used.

Furthermore, when using a Hall element as a magnetoelectric conversion element, two Hall elements are arranged at the position of the magnetoresistive element.

Hall elements have good linear output characteristics, so
The applied magnetic flux density may be smaller than that of a magnetoresistive element. The two Hall elements 38, 39 are connected in parallel to a constant voltage DC power supply 40, as shown in FIG. 8, and the output voltages are processed by operational amplifiers 41, 42, 43.

Since the present invention has the above-described configuration, it has the following advantages.

(1) Since a magneto-electric transducer 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 is not affected by 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 burden on the user.

(2) Since the magnetoelectric transducer is protected by a shield cap, even if the object to be detected is uneven or wrinkled, it will not come into direct contact with the magnetoelectric transducer, and the roller that sends the object to be detected will bounce and the shield cap will protect the sensor. Even if you hit the device, the impact is not directly transmitted to the element, so no pulse-like nozzle is generated.

(3) Since the guide bank is made of a material with low thermal conductivity and the magnetoelectric transducer is attached directly to the magnetic column or magnet, the temperature of the detected object differs locally. Even if a difference is applied to the element, the temperature of the element is affected by the temperature of the magnetic column or magnet, which has a large heat capacity.
No sudden changes in temperature 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 magnetoelectric conversion elements are attached to the same magnetic material, there is no temperature difference between the two elements, and the output level is not biased.

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

(6) - Since the through hole of the housing is sealed with a shield cap, it is possible to completely block out the intrusion of magnetic dust, moisture, etc. from the outside.

Therefore, the performance of the magnetoelectric conversion element is prevented from deteriorating, so that the magnetic sensor device can be used for a long period of time.

[Brief explanation of the drawing]

1 is a sectional view of the device of the present invention, FIG. 2 is an enlarged sectional view of the shield cap portion in FIG. 1, FIG. 3 is a sectional view of the coil bobbin portion of the device of the present invention, and FIG. FIG. 5 is a plan view of the sensor surface of the bobbin of the present invention, FIG. 5 is an example of a magnetoresistive element used in the device of the present invention, FIG. 6 is a plan view showing an example of a magnetic pattern, and FIG. 7 is a diagram of the sensor surface of the device of the present invention FIG. 8 is a configuration diagram showing a usage mode, and is a wiring diagram when a Hall element is used in the device of the present invention. 10: Housing, 11: Coil boppin, 14, 14a
, 14b: Guide bank, 18: Magnetic column, 20: Electromagnetic coil, 21, 21a, 21b: Magnetoresistive element, 22: Shield cap.

Claims (1)

[Scope of Claims] 1. A housing, a through hole provided in the housing, a concave thermal insulating means made of a non-magnetic material that seals the through hole, and a thermal insulating means housed in the housing to prevent a magnetic field. comprising a magnetizing means for generating magnetism, and a magnetoelectric conversion element attached to the magnetic pole surface of the magnetizing means with a certain gap from the insulating means,
The magnetic sensor device is characterized in that the insulating means insulates the magnetoelectric transducer from the temperature of the object to be detected, and also eliminates impact to the magnetoelectric transducer from outside the housing. 2. The magnetic sensor device according to claim 1, wherein the thermal insulation means is formed of a non-magnetic conductor and has a concave cross-section that matches the shape of the through hole. 3. The magnetic sensor according to claim 2, wherein the thermal insulation means includes a flange wider than the through hole, and the flange is embedded in the housing to seal the through hole. Device. 4. The magnetic sensor device according to claim 2, wherein the thermal insulation means is configured to seal the through hole by fitting into the through hole of the housing. 5. Claims 2, 3, or 4 characterized in that the magnetic pole surface to which the magnetoelectric conversion element of the magnetizing means is attached is positioned within the space formed by the thermal insulation means.
The magnetic sensor device described in Section 1. 6. Claims 1 or 2 or 3 or 4 or 6. The magnetic sensor device according to item 5.