JP2000292513A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnetic sensor which will not malfunction even without a special noise-processing circuit. SOLUTION: A magnetic sensor is composed of a magnetoresistance element 12, a magnet for applying a bias magnetic field to the magnetoresistance element 12, and the like. The magnetoresistance element 12 consists of a substrate 22, a magnetism-sensitive part 23 set to an upper face 22a of the substrate 22, and terminal electrodes 24a and 24b set to both of end parts of the substrate 22. The magnetism-sensitive part 23 is formed of a serpentine magnetoresistance pattern 26 to obtain a predetermined magnetic reluctance value, with having a rectangular area as indicated by a chain line. The magnetoresistance element 12 is arranged to make a longitudinal direction of the magnetism-sensitive part 23 parallel to a direction K in which an object to be detected passes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor, and more particularly, to detecting characters, symbols, patterns, etc., printed with magnetic ink, and counting the teeth of a magnetic gear to reduce the rotational speed of a motor. The present invention relates to a magnetic sensor used for detecting or detecting a steel ball.

[0002]

2. Description of the Related Art A magnetic sensor of this type has a magnetoresistive element 1 as shown in FIG. The magnetoresistive element 1 includes a substrate 2 and an upper surface 2a of the substrate 2 (hereinafter, a detection surface 2a).
a) and terminal electrodes 4a and 4b provided at both ends of the substrate 2. The magnetic sensing part 3 is formed of a meandering magnetoresistive pattern 7, and has a rectangular area as shown by a dotted line in FIG. Then, the conventional magnetoresistive element 1 has a detection object passing direction K
In contrast, the magnetic sensing portion 3 is arranged so that the longitudinal direction is orthogonal. This is for the left and right blur of the detection target,
This is to provide more reliable detection capability.

[0003]

By the way, when the passing speed of the detection target increases, the detection target moves to the magnetic sensing unit 3.
The time to pass before is shorter. However, in the conventional magnetoresistive element 1, the width of the output waveform from the magnetic sensor is extremely narrow because the short side direction of the magnetic sensing part 3 coincides with the passing direction K of the detection target, and the waveform based on the passing signal is used. And an instantaneous waveform due to noise (for example, noise due to impact or the like or noise from a power supply) are difficult to distinguish. As a result, the magnetic sensor may malfunction. For this reason, it is necessary to separately provide a noise cut circuit so that noise does not get on the signal line, and the signal processing circuit becomes complicated.

An object of the present invention is to provide a magnetic sensor which does not malfunction even if a special noise processing circuit is not provided.

[0005]

In order to achieve the above object, a magnetic sensor according to the present invention comprises a magnetoresistive element and a magnet for applying a bias magnetic field to the magnetoresistive element. The longitudinal direction of the magnetic sensing part of the element is arranged substantially parallel to the direction in which the detection target passes.

With the above arrangement, the direction of passage of the detection target and the longitudinal direction of the magnetic sensing portion of the magnetoresistive element are substantially the same, and the time for the detection target to pass through the magnetic sensing portion becomes longer. Therefore, the width of the output waveform from the magnetic sensor becomes wider than before, and it becomes easier to distinguish between a waveform based on a passing signal and an instantaneous waveform based on noise.

Further, by making the length of the magnetic sensing portion of the magnetoresistive element in the short side direction shorter than the diameter of the substantially spherical detection object, the short side of the magnetic sensing portion when the detection object passes therethrough. Magnetic flux concentrates throughout the direction. Accordingly, the rate of change in magnetoresistance, that is, the sensitivity, of the entire magnetic sensing portion increases.

Further, in the magnetic sensor according to the present invention, the magnetoresistive element has a magnetic substrate and a magnetic sensing portion provided on the magnetic substrate, and the shape of the magnetic substrate is substantially similar to that of the magnetic sensing portion. It is characterized by being. When a magnetic substrate is used for the magnetoresistive element, the bias magnetic field of the magnet concentrates on the magnetic substrate.
The sensitivity is improved. Further, since the shape of the magnetic substrate and the shape of the magnetically sensitive portion are substantially similar, the intensity of the bias magnetic field applied to the magnetically sensitive portion tends to be uniform.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the magnetic sensor according to the present invention will be described below with reference to the accompanying drawings.

[First Embodiment, see FIGS. 1 to 6] In the first embodiment, a magnetic sensor for detecting characters, symbols, patterns, and the like printed with magnetic ink will be described as an example.

FIG. 1 shows the appearance of the magnetic sensor 11, and FIG.
Indicates the configuration of the magnetic sensor 11. Magnetic sensor 11
Are a magneto-resistive element 12, a magnet 13 for applying a bias magnetic field to the magneto-resistive element 12, a circuit board 14 as a support member for mounting the components 12, 13, and a non-magnetic protective case 1.
6 and the like.

As shown in FIG. 3, the magnetoresistive element 12
It comprises a substrate 22, a magnetic sensing portion 23 provided on an upper surface 22a of the substrate 22 (hereinafter referred to as a detection surface 22a), and terminal electrodes 24a and 24b provided on both ends of the substrate 22. The magnetic sensing portion 23 is formed of a meandering magnetoresistive pattern 26 to obtain a predetermined magnetoresistance value, and has a rectangular area as shown by a dotted line in FIG. The magnetoresistive element 12 is arranged so that the longitudinal direction of the magnetic sensing part 23 is parallel to the passing direction K of the detection target.

The substrate 22 is made of InS on an insulating substrate by vapor deposition or the like.
A substrate formed with a b film or the like, a single crystal semiconductor substrate such as InSb, or a composite substrate in which a separately formed semiconductor thin film or single crystal substrate is attached to an insulating substrate with an adhesive, or the like is used. Here, by using a magnetic substrate as the substrate 22 and providing the magnetic sensing portion 23 on the magnetic substrate 22, the bias magnetic field of the magnet 13 is concentrated on the magnetic substrate 22 and the sensitivity is improved. Further, the shape of the magnetic substrate 22 and the shape of the magnetic sensing part 23 are set to be substantially similar to each other.
3, the intensity of the bias magnetic field applied to
Stable detection becomes possible. The lower surface 22b facing the detection surface 22a is a mounting surface for the magnetoresistive element 12. The resistance value of the magnetoresistive element 12 increases as the magnetic field increases. The magnetoresistive pattern 26 has a high sensitivity by increasing the ratio W / L of the width W to the length L of the segment.

As shown in FIG. 2, the magnetoresistive element 12
It is horizontally fixed on the circuit board 14 by an adhesive or the like. As the circuit board 14, an epoxy or polyimide resin board containing glass fiber, a paper epoxy board, an alumina board, or the like is used. On the other hand, the lead terminals 18 are inserted into through holes 14 a provided in the circuit board 14. Lead terminal 18
And the terminal electrodes 24a and 24b of the magnetoresistive element 12 are electrically connected via a wire 17 (or a lead frame).

A magnet 13 is mounted on the surface of the circuit board 14 opposite to the surface on which the magnetoresistive element 12 is mounted, using an adhesive. This magnet 13 may be a permanent magnet or an electromagnet. The magnet 13 faces the magnetoresistive element 12 with the circuit board 14 interposed therebetween. Parts 12, 13, 18
Is mounted together with the filler 15 in the non-magnetic protective case 16. As the filler 15, an epoxy resin or the like having excellent moisture resistance and relatively high mechanical strength is used. The non-magnetic protective case 16 is made of beryllium copper, phosphor bronze, brass, nickel silver, non-magnetic stainless steel, aluminum,
It is made of a non-magnetic material such as ceramic and resin. In order to increase the detection sensitivity, the magnetoresistive element 12 is mounted on the circuit board 1.
4 may be directly mounted on the magnet 13 without sandwiching it.

Next, the magnetic sensor 11 having the above configuration
The operation and effect of will be described. FIG. 4 shows the magnetic sensor 11.
It is an electric circuit diagram using. The magnetic sensor 11 has a resistance 3
4 in series. Magnetic sensor 11 and resistor 34
Is connected to the base of the amplifying transistor 33, the other end of the magnetic sensor 11 is connected to the emitter of the transistor 33, and the other end of the resistor 34 is connected to the collector of the transistor 33. In this circuit, one end of the resistor 34 and the collector of the transistor 33 are connected to the terminal 35,
One end of the magnetic sensor 11 and the emitter of the transistor 33 are connected to a terminal 36 to form a two-wire output connection circuit.

A DC voltage Vc is applied to the terminal 35 in advance by a sensor power supply, and a DC current is applied to the resistor 34 in advance. When the detection target does not pass in front of the magnetic sensor 11, the bias magnetic field generated by the magnet 13 is
And the resistance of the magnetoresistive element 12 does not change, and its resistance value is low. Therefore, the base-emitter voltage V _BE of the transistor 33 is small,
Operating point is not reached. As shown in FIG. 5, since the transistor 33 is in the cutoff region, the transistor 33 is turned off.
The state remains, and the output current I of this electric circuit is falling.

Next, when the object to be detected comes in the direction of arrow K and passes in front of the magnetic sensor 11, the bias magnetic field generated by the magnet 13 concentrates on the magnetoresistive element 12, so that the resistance value of the magnetoresistive element 12 Will be higher. Therefore, the base-emitter voltage V _BE of the transistor 33 increases,
As shown in FIG. 5, since the transistor 33 reaches the active region, the transistor 33 is turned on. As a result, the collector current Ic of the transistor 33 increases, and the output current I of the electric circuit increases.

When the object to be detected passes in front of the magnetic sensor 11 and separates, the bias magnetic field generated by the magnet 13 does not concentrate on the magnetoresistive element 12, and the resistance value of the magnetoresistive element 12 becomes the original low value. Accordingly, the base-emitter voltage V _BE of the transistor 33 is reduced, the transistor 33 is turned off, and the output current I of the electric circuit decreases. In this way, a pulse-like output current waveform as shown in FIG. 6 is obtained. By counting the number of pulses of this output current waveform, the passage of the detection target can be detected without contact.

Here, since the longitudinal direction of the magnetic sensing portion 23 of the magnetoresistive element 12 is parallel to the passing direction K of the detection target, the time required for the detection target to pass in front of the magnetic sensing portion 23 becomes longer. . Therefore, as compared with the conventional magnetic sensor having the magnetoresistive element 1 whose short side coincides with the passing direction of the detection target as shown in FIG. As a result, the width of the output current waveform of the electric circuit becomes wider, and it becomes easier to distinguish between a waveform due to a passing signal and an instantaneous waveform due to noise.

Specifically, the length of the magnetic sensing portion 23 in the long side direction is D, the length in the short side direction is d, and the width of the output current waveform of the electric circuit using the conventional magnetic sensor is t. Assuming that the width of the output current waveform of the electric circuit using the magnetic sensor 11 of the first embodiment is T, the following relational expression holds. T = t × (D / d)

As a result, it is possible to obtain the magnetic sensor 11 which does not malfunction even if no special noise processing circuit is provided.

[Second Embodiment, see FIGS. 7 to 10]
The embodiment will be described using a steel ball detection sensor such as a pachinko ball as an example.

As shown in FIGS. 7 and 8, the steel ball detection sensor 41 includes a magnetoresistive element 42 and an amplifying transistor 4.
4, a circuit board 45 for mounting the components 42 and 44, a magnet 54 for applying a bias magnetic field to the magnetoresistive element 42, and a non-magnetic protective case 48.

As shown in FIG. 9, the magnetoresistive element 42
It has a substrate 55 and a magnetic sensing portion 56 provided on an upper surface 55a of the substrate 55 (hereinafter, referred to as a detection surface 55a). Further, in the magnetoresistive element 42, a fixed resistor 43 is also provided on the same substrate 55. Thus, the number of components can be reduced, and the mounting cost can be reduced.

The magnetic sensing portion 56 is formed of a meandering magnetoresistive pattern 57 for obtaining a predetermined magnetoresistance value.
It has a rectangular area as shown by the dotted line. The magnetoresistive element 42 is arranged so that the longitudinal direction of the magnetic sensing portion 56 is parallel to the passing direction K of the steel ball 65. The magnetoresistive pattern 57 has a high sensitivity by increasing the ratio W / L of the width W to the length L of the segment.

Further, in the second embodiment, the magnetic sensing unit 56
Are set shorter than the diameter of the steel ball 65. Thereby, when the steel ball 65 passes in front of the magnetic sensing part 56, the magnet 54 extends over the entire short side direction of the magnetic sensing part 56.
Bias magnetic field is efficiently concentrated. Therefore, the magnetic sensing part 5
6 can increase the rate of change in magnetoresistance, that is, the sensitivity. Further, the size of the magnetoresistive element 42 can be reduced. If the length of the magnetic sensing portion 56 in the short side direction is longer than the diameter of the steel ball 65, the bias magnetic field becomes considerably weak at the edge of the magnetic sensing portion 56 in the short side direction, and the magnetic sensing portion 56 as a whole The sensitivity is relatively small.

The magnetoresistive element 42 is made of, for example, InSb,
After a compound semiconductor such as InAs or GaAs is provided in a thin film on the substrate 55 by an evaporation method or a sputtering method, a metal film such as Al is formed on the surface of the compound semiconductor thin film by a method such as an evaporation method or a sputtering method. It is formed at a pitch. Alternatively, the magnetoresistive pattern 57 is made of InS
A metal film such as Al may be formed at a predetermined pitch on the surface of the single crystal semiconductor substrate 55 such as b. Also,
The semiconductor thin film may be formed directly on the substrate 55 as described above, or a single crystal semiconductor substrate may be used as it is, or a separately formed semiconductor thin film or single crystal semiconductor substrate may be formed of a substrate 55 made of glass, alumina, ferrite, or the like. It may be a composite substrate that is pasted on with an adhesive.

Here, by using a magnetic substrate as the substrate 55 and providing the magnetic sensing portion 56 on the magnetic substrate 55, the bias magnetic field of the magnet 54 is concentrated on the magnetic substrate 55 to improve the sensitivity. . Further, the shape of the magnetic substrate 55 and the shape of the magnetic sensing portion 56 are set to be substantially similar to each other.
6, it is easy for the intensity of the bias magnetic field applied to be uniform,
Stable detection becomes possible.

The fixed resistor 43 is formed by forming a semiconductor thin film of InSb or the like, a single crystal semiconductor substrate of InSb or the like, a metal thin film of Al or Nichrome, or a thick film of metal glaze or the like on the substrate 55 in a meandering line. It was done. One end of the magnetoresistive pattern 57 is connected to the output electrode 62,
The other end is connected to the relay electrode 64. One end of the fixed resistor 43 is connected to the output electrode 63, and the other end is connected to the relay electrode 64.

When the substrate 55 is made of a magnetic material such as ferrite, the bias magnetic field of the magnet 54 increases at the edge of the substrate 55 (see the magnetic flux density distribution diagram shown in FIG. 9). Therefore, as shown in FIG.
5, the sensitivity is further improved. When the magneto-sensitive portion 56 is disposed at the center of the substrate 55 as in the magnetoresistive element 42A shown in FIG. 10, the bias magnetic field of the magnet 54 is slightly low but stable. (See distribution diagram), and stable sensitivity is obtained.

The magnetoresistive element 42 has the detection surface 55a as a mounting surface, and directly solders the output electrodes 62 and 63 and a circuit pattern (not shown) of the circuit board 45 or joins the conductive pattern with a conductive adhesive or the like. By doing so, it is mounted on the circuit board 45.

The non-magnetic protective case 48 has a detection hole 49 having a diameter slightly larger than the diameter of the steel ball 65 and a circuit board 45.
And a component accommodating portion 51 for accommodating the like. The detection hole 49 is not limited to a polygon but may be a circle, an ellipse, or the like.
The detection hole 49 is provided on the side of the detection hole 49 where the magnetoresistive element 42 is disposed.
An opening 49a extending in the axial direction is provided. The circuit board 4 is located at the boundary between the detection hole 49 and the component housing 51.
5 is provided with a guide recess 52. A step 53 is formed on the side opposite to the detection hole 49 side of the component accommodating section 51, and a recess 53 provided in the step 53 is provided.
The magnet 54 is fitted in a.

Circuit board 45 on which components 42 and 44 are mounted
Are placed in contact with the detection hole 49 so that they are parallel to the axial direction of the detection hole 49 (in other words, the passing direction K of the steel ball 65) by inserting both ends thereof into the guide concave portion 52. Is done. The surface of the circuit board 45 opposite to the surface on which the magnetoresistive element 42 is mounted is exposed to the opening 49 a of the detection hole 49 and is also used as a part of the inner wall of the detection hole 49.
The magnetoresistive element 42 is arranged between the circuit board 45 and the magnet 54, and the longitudinal direction of the magnetic sensing portion 56 of the magnetoresistive element 42 is parallel to the axial direction of the detection hole 49. The magnet 54 faces the magnetoresistive element 42. Further, the circuit board 45
The circuit pattern of FIG.
a and 46b are electrically connected.

The steel ball detection sensor 41 having the above configuration
Can achieve the same operation and effect as the magnetic sensor 11 of the first embodiment. Further, the steel ball sensor 41
Incorporates a fixed resistor 43 and an amplifying transistor 44,
Since the electric circuit shown in FIG. 4 is provided, the size of the steel ball detection sensor device can be reduced as a whole.

[Third Embodiment, See FIGS. 11 to 14] A magnetic sensor according to a third embodiment will be described in which two magnetic resistance elements are provided. This magnetic sensor can reduce the temperature change of the output signal by using two magnetoresistive elements having substantially the same temperature characteristics.

As shown in FIG. 11, the magnetic sensor 71
Two magneto-resistive elements 12A, 12B, 12
A magnet 73 for applying a bias magnetic field to A and 12B, component 1
It comprises a circuit board 74 for mounting 2A, 12B, 73, a non-magnetic protective case 76, and the like. The magnetoresistive elements 12A and 12B correspond to the magnetoresistive elements 12 shown in FIG.
And the detailed description is omitted. In FIG. 11, the lead terminals are omitted.

As shown in FIG.
A and 12B are arranged at a predetermined interval, and are arranged such that the longitudinal direction of the magnetic sensing part 23 is parallel to the passing direction K of the detection target. FIG. 13 shows a magnetic sensor 71.
FIG. In this circuit, assuming that the resistance values of the magnetoresistive elements 12A and 12B are R ₁ and R ₂ , respectively, and the voltage input to the power supply lead terminal 85 is Vd, the resistance between the output lead terminal 86 and the ground lead terminal 87 is Is generated by the following equation (1). Vo = {R ₁ / (R ₁ + R ₂ )} × Vd (1)

When the object to be detected is the magnetoresistive element 12A, 12A,
B, the two elements 12A, 12B
Are equal in the magnetic field of the magnet 73 biased to. Therefore, the resistance values of both elements 12A and 12B are R ₁ = R ₂ = R ₀ , and the output voltage Vo ₁ is expressed by the following equation (2) from the equation (1). Vo ₁ = [(1 + P) R ₀ / {(1 + P) R ₀ + (1 + P) R ₀ }] × Vd = Vd / 2 (2) (where P is sensitivity)

When the object to be detected approaches the magnetoresistive elements 12A and 12B from the direction of arrow K, first, a magnetic field concentrates on the magnetoresistive element 12A facing the object to be detected. Becomes larger, and the element 12B
Becomes smaller. As the detection target moves, the magnetoresistive element to which the detection target faces is the element 12A.
, The output signal of the output lead terminal 86 has a continuous signal waveform of one valley and one peak, as shown in FIG.

The magnetic sensor 71 having the above configuration can provide the same operation and effect as the magnetic sensor 11 of the first embodiment.

[Other Embodiments] The magnetic sensor according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the gist. For example, the magnetoresistive element may be configured using a semiconductor magnetoresistive element or a ferromagnetic thin film.

[0043]

As is apparent from the above description, according to the present invention, the longitudinal direction of the magneto-sensitive portion of the magnetoresistive element is arranged substantially parallel to the direction in which the detection object passes, so that the magnetic sensor can be used. , The magnetic detection distance becomes longer. Therefore, the width of the output waveform from the magnetic sensor becomes wider than before, and it becomes easier to distinguish between a waveform based on a passing signal and an instantaneous waveform based on noise. As a result, it is possible to accurately perform the processing of the waveform by the passing signal, and it is possible to obtain a magnetic sensor that does not malfunction without providing a special noise processing circuit.

Further, by making the length of the magnetic sensing portion of the magnetoresistive element in the short side direction shorter than the diameter of the substantially spherical detection object, the short side of the magnetic sensing portion when the detection object passes therethrough. The magnetic flux can be concentrated over the entire direction, and the sensitivity of the entire magnetic sensing unit can be increased. Further, the size of the magnetoresistive element can be reduced.

Further, by using a magnetic substrate for the magnetoresistive element, the bias magnetic field of the magnet concentrates on the magnetic substrate, and the sensitivity of the magnetoresistive element can be improved. Further, by setting the shape of the magnetic substrate and the shape of the magnetic sensing portion to be substantially similar, it becomes easy to make the intensity of the bias magnetic field applied to the magnetic sensing portion uniform, and stable detection becomes possible.

[Brief description of the drawings]

FIG. 1 is an external perspective view showing a first embodiment of a magnetic sensor according to the present invention.

FIG. 2 is a sectional view of the magnetic sensor shown in FIG. 1;

FIG. 3 is a perspective view showing the relationship between the arrangement of the magnetoresistive elements shown in FIG. 2 and the passing direction of a detection target.

FIG. 4 is an electric circuit diagram using the magnetic sensor shown in FIG. 1;

FIG. 5 is a graph showing current-voltage characteristics of an amplification transistor.

6 is a graph showing an output signal waveform of the electric circuit shown in FIG.

FIG. 7 is a plan view showing a second embodiment of the magnetic sensor according to the present invention.

8 is a sectional view taken along the line VIII-VIII in FIG. 7;

FIG. 9 is a perspective view showing the relationship between the arrangement of the magnetoresistive elements shown in FIG. 7 and the direction in which the detection target passes.

FIG. 10 is an exemplary perspective view showing a modification of the magnetoresistance element shown in FIG. 9;

FIG. 11 is a sectional view showing a third embodiment of the magnetic sensor according to the present invention.

FIG. 12 is an explanatory diagram showing the relationship between the arrangement of the magnetoresistive elements shown in FIG. 11 and the direction in which the detection target passes.

FIG. 13 is an electric circuit diagram of the magnetic sensor shown in FIG. 11;

FIG. 14 is a graph showing an output signal waveform of the magnetic sensor shown in FIG. 11;

FIG. 15 is a perspective view showing a relationship between a conventional arrangement of magnetoresistive elements and a passing direction of a detection target.

[Explanation of symbols]

 11, 71: Magnetic sensor 12, 12A, 12B: Magnetic resistance element 13, 73: Magnet 23: Magnetic sensing part 41: Steel ball sensor 42, 42A: Magnetic resistance element 54: Magnet 56: Magnetic sensing part

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tomoharu Sato 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. (reference) 2F063 AA02 AA35 CA08 DA05 EA02 EA03 GA52 2G017 AA00 AB07 AC09 AD55 AD59 AD61 AD65 BA05

Claims (3)

[Claims] 1. A magnetoresistive element, and a magnet for applying a bias magnetic field to the magnetoresistive element, wherein a longitudinal direction of a magneto-sensitive portion of the magnetoresistive element is substantially parallel to a passing direction of an object to be detected. A magnetic sensor, comprising: 2. The magnetic sensor according to claim 1, wherein a length of the magnetic sensing portion of the magnetoresistive element in a short side direction is shorter than a diameter of the substantially spherical detection target. 3. The method according to claim 2, wherein the magnetoresistive element has a magnetic substrate and the magnetic sensing portion provided on the magnetic substrate, and the shape of the magnetic substrate is substantially similar to the magnetic sensing portion. The magnetic sensor according to claim 1, wherein: