JP2000028395A - Magnetism detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetism detecting apparatus in which the sensitivity of a magnetism detecting element is high even when an object whose magnetism is to be detected has small uneven parts. SOLUTION: In a magnetism detecting apparatus 1, an IC 104 with a built-in magnetism detecting element is arranged so as to be faced with an object 100 whose magnetism is to be detected, a magnet which applies a bias magnetic field to the magnetism detecting element is provided, and a signal processing circuit by which an analog signal to be output from the magnetism detecting element according to the movement of the object 100 whose magnetism is to be detected is waveform-shaped is provided. A plurality of bias magnets 103a, 103b are arranged in positions which sandwich the magnetism detecting element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic detection device which outputs a pulse signal in accordance with the movement of a magnetic detection object due to a change in a gap (Gap) between the magnetic detection object and the magnetic detection device. More specifically, it is to improve the detection accuracy of the magnetic detection device.

[0002]

2. Description of the Related Art Conventionally, a magnetic detection device for detecting movement of a magnetic object (for example, rotation of a crankshaft of an internal combustion engine) is well known, and a magnetic resistance element (MR element) is used as a magnetic detection element. It is also known to use a giant magnetoresistive element (GMR element) having high detection sensitivity.

In addition, this type of magnetic detection device outputs a magnetic signal in order to output a pulse signal corresponding to the unevenness of the magnetic detection object and a change in the gap (Gap) of the magnetic detection device due to the movement of the magnetic detection object. A signal processing circuit is provided for shaping the waveform of an analog signal output from the detection element into a pulse signal.

[0004]

In the conventional magnetic sensing device, when the unevenness of the magnetic object is small, the change in the magnetic flux linking the magnetic sensing element is small, and the GMR is used as the magnetic sensing element.
There is a problem that the detection output becomes small even when the element is used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is possible to improve the sensitivity of a magnetic detection element even when the unevenness of a magnetic object is small. It is intended to provide a device.

[0006]

According to the first aspect of the present invention,
A magnetic detection element disposed opposite to the magnetic detection object, a magnet for applying a bias magnetic field to the magnetic detection element, and a signal for shaping the waveform of an analog signal output from the magnetic detection element according to the movement of the magnetic detection object A magnetic detection device provided with a processing circuit, wherein a plurality of magnets are arranged at positions sandwiching the magnetic detection element.

The invention according to claim 2 is characterized in that the magnetization directions of the plurality of bias magnets are set to the same direction.
In this case, an in-plane magneto-sensitive type magneto-resistive element is used as the magnetic detecting element, and the magneto-sensitive surface is arranged so as to be substantially parallel to the direction facing the magnetic object, and a plurality of magnets are provided. The sensitivity is further improved by setting the magnetization direction to the direction facing the magnetic object.

According to a third aspect of the present invention, at least one of the bias magnets is disposed behind the magnetic detection element with respect to the magnetic detection object. For example, two biasing magnets are used and a second biasing magnet is located behind the magnetic sensing device.

According to a fourth aspect of the present invention, an in-plane magnetoresistive element is used as the magnetic detecting element, and the magnetosensitive surface is arranged so as to be substantially parallel to the direction facing the magnetic object. It is characterized by having done.

The invention according to claim 5 is characterized in that a plurality of bias magnets are fixed by transfer molding.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side view showing a magnetic detecting device which is a premise of the present invention, for example, a rotation detecting device for detecting rotation of a crankshaft of an internal combustion engine. 2 schematically shows a relative positional relationship between the rotation detection device 100 and the rotation detection device 101.

In FIG. 1, a magnetic detection object 100 to be detected is provided integrally with a rotating shaft of an internal combustion engine, for example, a crankshaft or the like.
And the recess 100b are formed alternately. Further, the rotation detecting device 101 is installed so as to face the magnetic object 100 via a predetermined gap (Gap).

FIG. 2 is a sectional view schematically showing the structure of the rotation detecting device 101 of FIG. In FIG. 2, a rotation detecting device 101 includes one bias magnet 103 and an integrated circuit (I
C) A magnetic circuit is constituted by the magnetic detecting head 104.

The IC 104 has a built-in magnetic detection element and a signal processing circuit, and the magnetic detection element is arranged so that its magnetically sensitive surface is substantially parallel to the direction in which the magnetic detection element faces the magnetic object 100. The signal processing circuit converts an analog signal obtained from the magnetic detection element into a pulse signal and outputs the pulse signal.
The magnet 103 is arranged so that its magnetization direction faces the direction facing the magnetic object 100, and applies a bias magnetic field in the direction facing the magnetic object 100 to the magnetic detecting element in the IC 104. .

FIG. 3 is a perspective view showing a relative positional relationship between the magnetic detection head of the rotation detecting device 101 of FIG. Here, a case where a giant magnetoresistive element (GMR element) is used as a magnetic detection element arranged in the IC 104 will be described. In FIG. 3, the GMR element 20 is composed of two divided line-shaped segments 20a and 20b for improving the magnetic detection sensitivity and detecting the rotation direction of the magnetic detection object 100.

GMR element segments 20a and 20b
Are positioned parallel to the rotation direction (moving direction) of the magnetic detection object 100.

FIG. 4 is a circuit diagram showing a connection state of each of the segments 20a and 20b constituting the GMR element 20. In FIG. 4, each segment 20a, 20b is connected to a power supply Vcc.
Bridge circuit 14 connected in series between
Is composed. The midpoint 14a of the series circuit (segments 20a and 20b) of the bridge circuit 14 outputs an analog signal as the magnetic detection object 100 rotates.

FIG. 5 shows the magnetic field (Oersted:
FIG. 6 is a characteristic diagram showing a change in resistance (ohm: Ω) with respect to a change in Oe). In FIG. 5, the resistance value of the GMR element fluctuates greatly when the applied magnetic field fluctuates as compared with a normal magnetoresistive element (MR element). For example, 21 at zero magnetic field
In the case of a resistance value of about 00Ω, the resistance value decreases by about 400Ω (20% or more) in the saturation magnetic field. In addition, it has hysteresis in the direction in which the magnetic field is applied.

Such a GMR element is described in, for example, "Magnetoresistance effect of artificial lattice" (Journal of the Japan Society of Applied Magnetics, Vol. 15,
No. 51991, pages 813 to 821). According to the above document, the GMR element can be constituted by a laminated body (a so-called artificial lattice film) in which magnetic layers and nonmagnetic layers each having a thickness of several angstroms to several tens angstroms are alternately laminated. The material of the GMR element is (Fe / Cr) n, (Permalloy / Cu
/ Co / Cu) n and (Co / Cu) n.
Here, n indicates the number of layers.

Next, the operation of the rotation detecting device will be described. As shown in FIG. 3, the projections 100 a and the recesses 100 b of the magnetic object 100 alternately face the magnets 103 as the magnetic object 100 rotates. Therefore,
The magnetic field applied to the GMR element 20 is
It increases or decreases with the rotation of 0. That is, the GMR element 20
Is increased when the projection 100a approaches, and decreases when the projection 100a separates.

The change of the magnetic flux linking the GMR element 20 causes the respective segments 20a, 20b of the GMR element 20 to change.
Changes in proportion to the magnitude of the applied magnetic field as shown in FIG. Therefore, the midpoint voltage 14a of the bridge circuit 14 shown in FIG. 4 generates an analog signal as shown in FIG.

FIG. 7 is a block diagram of an electric circuit for converting an analog signal output from the GMR element 20 into a pulse signal.
Shown in The midpoint voltage 14a of the bridge circuit 14 is connected to the differential amplifier 40 via the buffer 30, and the midpoint voltage output is amplified by the differential amplifier 40. Then, for example, through an AC coupling constituted by a capacitor and a resistor,
The DC component of the amplified analog signal is removed. Finally, the pulse signal is binarized by comparing with a predetermined voltage having a hysteresis and outputting a pulse signal.

The reason why AC coupling is performed in the signal processing circuit shown in FIG. 7 is that the DC level of the analog signal changes due to a change in the position at which the magnetic detection element and the magnet are assembled or a change in temperature.
This is because it is necessary to cut off the DC component of the analog signal in order to obtain a pulse signal with high accuracy.

In the above magnetic detecting device, the magnetic detecting object 1
When the irregularities of 00 are reduced, the amount of change of the magnetic flux linking the GMR element 20 is reduced, and the analog output of the bridge circuit 14 is also reduced.

To increase the analog output, it is effective to operate the GMR element 20 near 150 (Oe) where the sensitivity of the GMR element 20 is the highest. However, when the bias magnet 103 is reduced, the combination of the GMR element 20 and the bias magnet 103 is increased. Since the DC level of the analog output of the bridge circuit 14 greatly changes depending on the mounting position accuracy, it is necessary to adjust the mounting position of the magnet 103 or individually change the circuit constant of the amplifier, which causes an increase in cost. For this reason, there has been a problem that a magnetic detection device which is required to be inexpensive is not suitable for detecting a magnetic detection object having small irregularities.

Embodiment 1 8 and 9 are diagrams showing a configuration of a magnetic detection device according to Embodiment 1 of the present invention. FIG. 8A is a plan view showing a relative positional relationship between the magnetic detection device and a magnetic detection object. 8 (b) is a side view of FIG. 8 (a), and FIG. 9 is a detailed view of a main part of FIG. 8 (a).

In the figure, a magnetic detecting device (rotation detecting device) 1 is provided with a predetermined gap (Ga) from a magnetic detection object 100.
p) and two bias magnets 10
3a and 3b, and an integrated circuit device (IC) 104 disposed at a position sandwiched between these magnets.

The IC 104 has a built-in magnetic detecting element and a signal processing circuit, and is arranged so that the magneto-sensitive surface of the magneto-resistive element is substantially parallel to the direction in which the magnetic object 100 is opposed. As the magnetic detecting element, a magnetoresistive element (MR
Element) or a giant magnetoresistive element (GMR element). In the first embodiment, an example in which a GMR element having higher detection sensitivity is used will be described.

As shown in FIG. 9, the GMR element 20 is constituted by two linear segments 20a and 20b divided into two, and each of the segments 20a and 20b is a magnetic object 1
It is located in parallel to the rotation direction (moving direction) of 00. A circuit diagram showing the connection state of each segment 20a, 20b is as shown in FIG. 4, and a block diagram of an electric circuit for converting an analog signal output from the GMR element 20 into a pulse signal is also the same as FIG.

Here, an experiment of magnetic detection is performed under the following setting conditions. That is, the size of each segment of the GMR element 20 is defined as width 0.2 (mm) × length 0.66 (mm).
A GMR film having a line width of 10 (μm) is meandered therein. Then, the segment of the GMR element is set at the pitch P
Two are arranged at an interval of = 1.6 (mm) to form the bridge circuit 14 of FIG.

The first bias magnet 103a is 8 ×
As a rare earth magnet of 3 × 10 T (mm), its magnetization direction is the direction facing the magnetic object 100. The second bias magnet 103b is a rare earth magnet of 5 × 3 × 2T (mm), and its magnetization direction is set to the rotation axis direction of the magnetic detection object 100.

Further, as shown in FIG. 10, a magnetic detection object 100 is formed of SPCC material, and its shape is 100 mm in diameter.
(Mm), thickness 2 (mm), 60 convex portions 100a and concave portions 100b are formed at equal pitches on the circumference.

FIG. 11 shows the GMR element 2 under the above set conditions.
The output when the midpoint voltage of 0 is amplified 27 times by an amplifier is shown. Here, when the second bias magnet 103b is removed, the output of the amplifier similarly amplified 27 times is as shown in FIG. From the output results of FIGS. 11 and 12, the output is increased by a factor of 5 by adding the second bias magnet 103b.

That is, by adding the second bias magnet 103b, the operating magnetic field of the GMR element becomes 300 (O
It changes from around e) to around 150 (Oe).

According to the first embodiment, the magnet 103
Since a and 103b are arranged so as to sandwich the IC 104, there is an advantage that the connection terminals can be configured flat as in FIG. If the connection terminals are flat, it is possible to seal the IC 104 including the chip component with transfer mold having high reliability as a sealing technology for general integrated circuits, and it is possible to improve the reliability of the product.

Further, if the bonding pedestal for the magnets 103a and 103b is formed by the transfer molding technique, the positional accuracy of the magnetic detecting element and the magnet can be improved, and the signal detecting accuracy can be improved.

Embodiment 2 In the second embodiment, the size, arrangement, and the like of the second bias magnet 103b are the same as those in the first embodiment, but the magnetization direction is the first bias magnet 103a.
In the same direction as the magnetization direction.

FIG. 13 is a diagram showing an arrangement of a magnetic detection device according to the second embodiment.
The magnetizing direction of 3b is the facing direction of the magnetic detection object 100, similarly to the magnetizing direction of the first bias magnet 103a. As described above, even when the magnetization direction of the second bias magnet 103b is changed as shown in FIG. 13, the same effect as in the first embodiment can be obtained.

In the first embodiment, since the magnetization directions of the two bias magnets are different from each other by 90 degrees, the magnetization cannot be performed after the two magnets are assembled. On the other hand, in the second embodiment, the magnets can be magnetized after the two magnets are assembled, so that the output of the magnetism detection device and the productivity can both be improved.

Embodiment 3 In Embodiments 1 and 2,
The position of the second bias magnet 103b is set at a position where the GMR element 20, which is a magnetic detection element, is sandwiched by the first bias magnet 103a. In this case, if the second bias magnet 103b is disposed behind (in the direction away from the magnetic detection object) the rear end line (AA line in FIGS. 9 and 13) of the GMR element 20, the output can be improved particularly efficiently. .

[0041]

As described above, according to the first aspect of the present invention,
A magnetic detection element disposed opposite to the magnetic detection object, a magnet for applying a bias magnetic field to the magnetic detection element, and a signal for shaping the waveform of an analog signal output from the magnetic detection element according to the movement of the magnetic detection object In a magnetic detection device provided with a processing circuit, the sensitivity of the magnetic detection element can be improved by arranging a plurality of magnets at positions sandwiching the magnetic detection element.

According to the second aspect of the present invention, by setting the magnetization directions of the plurality of bias magnets to the same direction, the magnets can be magnetized after assembling the plurality of magnets, and the output of the magnetism detecting device can be increased. Improvement and productivity improvement can both be achieved. Also, in this case, an in-plane magneto-sensitive type magneto-resistive element is used as the magnetic detecting element, and the magneto-sensitive surface is arranged so as to be substantially parallel to the direction facing the magnetic object,
The sensitivity is further improved by setting the magnetization directions of the plurality of magnets to the direction facing the magnetic detection object.

According to the third aspect of the present invention, since at least one of the bias magnets is disposed behind the magnetic detection element with respect to the magnetic detection object, the output of the magnetic detection element can be particularly efficiently improved.

According to the fourth aspect of the present invention, an in-plane magneto-sensitive type magnetoresistive element is used as the magnetic detecting element, and the magneto-sensitive surface is formed so as to be substantially parallel to the direction facing the magnetic object. By arranging, the sensitivity can be improved, and the position of the magnet is sandwiched by the integrated circuit device having the built-in magnetic detection element, so that the connection terminal can be configured in a planar shape.

According to the fifth aspect of the present invention, by fixing a plurality of bias magnets by transfer molding, the positioning of the magnets can be integrally and accurately performed, and the signal accuracy of the magnetic detector can be improved. Can be planned.

[Brief description of the drawings]

FIG. 1 is a side view showing a rotation detecting device as a magnetic detecting device on which the present invention is based.

FIG. 2 is a cross-sectional view showing an internal configuration of a magnetic detection head of the magnetic detection device on which the present invention is based.

FIG. 3 is a perspective view showing a relative positional relationship between a magnetic detection head of a magnetic detection device and a magnetic magnetic detection object, which is a premise of the present invention.

FIG. 4 is a circuit diagram showing a connection state of each segment constituting a magnetic detection element of the magnetic detection device.

FIG. 5 is a diagram showing a change in resistance value of a general giant magnetoresistive element with respect to a magnetic field.

FIG. 6 is a diagram illustrating a shape of a magnetic detection object and a voltage output waveform of a midpoint voltage of a bridge circuit of the magnetic detection device.

FIG. 7 is a block diagram illustrating a signal processing circuit of the magnetic detection device.

FIG. 8 is a plan view and a side view showing the configuration of the magnetic detection device according to the first embodiment of the present invention.

FIG. 9 is a main part detailed view showing the configuration of the magnetic detection device according to the first embodiment of the present invention.

FIG. 10 is a partial plan view showing the shape of a magnetic detection object for generating multiple pulses.

FIG. 11 is a signal waveform diagram after amplification when a second bias magnet is provided according to the first embodiment of the present invention.

FIG. 12 is a signal waveform diagram after amplification in the case where there is no second bias magnet according to the first embodiment of the present invention.

FIG. 13 is a side view showing a configuration of a magnetic detection device according to a second embodiment of the present invention.

[Explanation of symbols]

1 Magnetic detection device (rotation detection device), 10 resin, 14
Bridge circuit, 14a Midpoint voltage of bridge circuit, 2
0, 20a, 20b Magnetic sensing element (GMR element), 3
0 buffer, 40 differential amplifier, 50 comparator, 100 magnetic object, 100a convex part of magnetic object, 100b concave part of magnetic object, 101 magnetic detector, 103, 103a, 103b bias magnet,
104 Integrated Circuit Device (IC).

Continuation of front page (72) Inventor Izumi Shinjo 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 2F063 AA35 BA07 BB05 BC03 BD16 CA04 CA09 DA01 DA04 DB07 DC08 DD03 GA52 GA69 LA11 LA27 2F077 NN02 NN21 PP11 TT13 TT35 UU11 2G017 AB05 AC04 AC06 AC09 AD55 AD63 AD65 BA09

Claims (5)

[Claims] 1. A magnetic sensing element disposed opposite to a magnetic detection object, a magnet for applying a bias magnetic field to the magnetic detection element, and an output from the magnetic detection element in response to movement of the magnetic detection object A magnetic detection device comprising a signal processing circuit for shaping a waveform of an analog signal, wherein a plurality of the magnets are arranged at positions sandwiching the magnetic detection element. 2. The magnetic detecting device according to claim 1, wherein the magnetization directions of the plurality of bias magnets are the same. 3. The magnetic detection apparatus according to claim 1, wherein at least one of the bias magnets is disposed behind the magnetic detection element with respect to the magnetic detection object. 4. An in-plane magneto-sensitive type magneto-resistive element is used as the magnetic detecting element, and the magneto-sensitive surface is arranged so as to be substantially parallel to a direction facing the magnetic detection object. The magnetic detection device according to claim 1, wherein: 5. The magnetic detecting device according to claim 1, wherein the plurality of bias magnets are fixed by transfer molding.