JPH0942970A - Geomagnetic azimuth sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor, which can improve the working accuracy and which can be miniaturized and of which the cost can be reduced and which has a high detecting sensitivity, by providing magneto resistive(MR) elements on a gap so as to nearly cross the magnetic field direction in a magnetic gap of a core made of the ferromagnetic body. SOLUTION: Ferromagnetic body cores K1 , K2 made of ferrite or the like are made to abut on each other in each joining surface S so as to be formed into the square shape. The cores K1 , K2 are formed with gaps G1 , G2 and G3 , G4 made of the glass material, and each RM element M1 -M4 is formed on the gap. Exciting coils C1 , C2 made of Cu are wound around the cores K1 , K2 at a central part thereof, and the bias magnetic field is applied to the MR elements M1 -M4 . The bias magnetic field respectively displaced at 180 degree is applied to the X direction detecting MR elements M1 , M2 and the Y direction detecting MR element M3 , R4 . Resistance value of the MR elements M1 -M4 is changed by the intensity of the magnetic field, and they have the excellent ability for sensing the weak magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a geomagnetic direction sensor that measures a geomagnetic direction by utilizing a bias magnetic field generated by supplying a bias current.

[0002]

2. Description of the Related Art For example, in a color cathode ray tube, the trajectory of an electron beam emitted from an electron gun may be bent by geomagnetism, and the beam arrival position (landing) on the fluorescent screen may change. Especially in high definition cathode ray tubes,
Since the landing margin is small, the landing change (positional shift) causes a problem such as deterioration of color purity.

To correct this, a landing correction coil is usually attached to the cathode ray tube, and an optimum current necessary for landing correction is automatically supplied to the landing correction coil according to the direction of the earth's magnetism.
The trajectory of the electron beam is controlled to prevent mislanding.

Therefore, in the landing correction, it is necessary to accurately detect the azimuth of geomagnetism, and a so-called geomagnetic azimuth sensor is used.

Alternatively, as an alternative to the conventionally used magnet type compass (magnetic compass), a geomagnetic compass sensor is also used as a portable compass.

As described above, the geomagnetic direction sensor is used for various purposes, and its typical structure is known as a so-called fluxgate type or magnetoresistive type (MR type). Has been.

As shown in FIG. 8, the fluxgate type geomagnetic direction sensor comprises a permalloy core 101 around which an electric signal output coil 102 and an excitation coil 103 are wound, and the geomagnetism is focused by the permalloy core. However, the structure is such that this is transmitted to the electric signal output coil 102.

In this geomagnetic direction sensor, an AC bias magnetic field H _B is generated in the permalloy core 101 by supplying an AC bias current to the exciting coil 103, and a pulsed voltage generated when the bias magnetic field is reversed. Is detected as a signal. Since the voltage value of this pulsed voltage changes depending on the direction of the geomagnetism, it can be used as a geomagnetic sensor.

However, this geomagnetic direction sensor is
Since the geomagnetism is converted into an electric signal by the coil, the number of turns of the electric signal output coil 102 is increased in order to increase the sensitivity, and the permalloy core 1 is increased in order to improve the focusing effect.
It is necessary to increase the size of 01. Therefore, it is difficult to reduce the size and price.

On the other hand, the MR type geomagnetic direction sensor is shown in FIG.
As shown in FIG. 3, an MR sensor chip 110 provided with a magnetoresistive effect element (MR element) 111 is attached to an air-core coil 112.
, And the AC bias magnetic field H _{B in the} direction of 45 ° is applied to the MR sensor chips 110 by supplying the AC bias current to the air-core coil 112. An equivalent circuit of this geomagnetic direction sensor is shown in FIG. When used as the geomagnetic direction sensor, one set having the structure shown in FIG. 9 is used so that the winding directions of the air-core coils are orthogonal to each other.

Since this MR type geomagnetic direction sensor uses a magnetoresistive effect element, the MR type geomagnetic direction sensor has higher sensitivity than the fluxgate type geomagnetic direction sensor, but the MR sensor chip 110 alone senses the geomagnetism. Therefore, it is insufficient to detect the orientation of the geomagnetism of about 0.3 Gauss.

[0012]

As described above, the conventionally known geomagnetic direction sensor remains unsatisfactory in terms of sensitivity, and it is difficult to reduce its size and cost.

Therefore, the present invention has been proposed in view of such conventional circumstances, and cracks and warps, glass bubbles,
While eliminating inconvenience during manufacturing such as glass chipping during grinding to improve processing accuracy, it has practical sensitivity.
Moreover, it is an object of the present invention to provide a geomagnetic direction sensor having high detection sensitivity, which can be easily reduced in size and cost.

[0014]

The object of the present invention is to dispose a plurality of ferromagnetic cores for focusing the earth's magnetism in the circumferential direction via a predetermined magnetic gap, and to arrange the magnetic field direction in the magnetic gap. Is a geomagnetic direction sensor in which a magnetoresistive effect element is arranged on a magnetic gap so as to be substantially orthogonal to.

The geomagnetic direction sensor of the present invention is characterized in that the magnetic gap is made of a glass material containing PbO or SiO ₂ as a main component.

As the glass material for the magnetic gap,
In order to prevent the generation of glass bubbles during production and suppress the amount of warpage of the produced substrate to a low value, its melting point is 250 ° C. or higher 6
It is preferable to use a low-melting glass having a temperature of 50 ° C. or lower, and it is preferable to use a glass having an expansion coefficient of 100 or lower.

Here, the magnetoresistive effect element (hereinafter referred to as MR element) is arranged at least at two positions so as to be orthogonal to each other in order to obtain outputs in the X-axis direction and the Y-axis direction which are orthogonal to each other. . Preferably, four MR elements are arranged at equal angular intervals (90 ° intervals).

On the other hand, the ferromagnetic cores have magnetic gaps at equal angular intervals (for example, 90 ° intervals) according to the arrangement of the MR elements, and are arranged in the circumferential direction so as to form a closed magnetic path. From the standpoint of view, it is preferable to have an annular shape or a square shape.

For the ferromagnetic core, a soft magnetic material having high magnetic permeability and high saturation magnetic flux density (so-called soft material) such as permalloy, silicon steel plate, various soft ferrites, etc. is used, and bias magnetic field is applied and geomagnetism is focused. To use.

Therefore, an exciting coil is wound around the ferromagnetic core, and a bias current I _B is caused to flow through the exciting coil to generate a bias magnetic field H _B , so that the MR element has high magnetic field sensitivity and linearity. Use in a good place. The bias magnetic field H _B (bias current I _B ) may be alternating current or direct current.

However, the current value of the bias current I _B is set such that the bias magnetic field H _B is below the saturation magnetic flux density of the ferromagnetic system portion (closed magnetic circuit constituted by the ferromagnetic core) and before and after the magnetic permeability value, and the rotation is performed. While avoiding the magnetization range, allow a margin for the amount of magnetization of the ferromagnetic system part, and use it for focusing the geomagnetism.

As described above, in the geomagnetic direction sensor of the present invention, the ferromagnetic core constitutes the magnetic path of the bias magnetic field and also functions as a so-called focusing horn for focusing the geomagnetism. As a result, the total amount of geomagnetism applied to the MR elements orthogonal to each other is determined according to the angle formed by the geomagnetism and the MR element, respectively, and is perpendicular to the geomagnetic line passing through the center of the closed magnetic circuit formed by the ferromagnetic core from each MR element. It is proportional to the virtual line drawn in.

Further, the magnetic gap is PbO or Si0.
_It is composed of a glass material containing ₂ as a main component, and more preferably has a melting point of 250 ° C. or higher and 650 ° C. or lower, and has a coefficient of expansion of 100 or lower. Various inconveniences that tend to occur in the magnetic gap such as glass bubbles and glass breakage during grinding are suppressed.

Therefore, the reliability of the product is improved, the geomagnetism is efficiently supplied to the MR element as a magnetic signal to obtain a high output, and the azimuth can be detected with high detection sensitivity and high accuracy. Become.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of a geomagnetic direction sensor to which the present invention is applied will be described below in detail with reference to the drawings.

An example of the basic structure of the geomagnetic direction sensor to which the present invention is applied is shown in FIG.

The geomagnetic direction sensor is formed by forming a pair of substantially U-shaped ferromagnetic cores K ₁ and K ₂ made of ferrite or the like into a square shape by abutting each other at their joint surfaces S. Here, each ferromagnetic core K _1, K _2, respectively made of glass material in G _1, G ₂ and G _3, and G ₄ is formed, the magnetic cores K _1, K ₂ are square The magnetic gaps G ₁ , G ₂ , G ₃ , G ₄
Will be placed at four corners at 90 ° intervals. And, on each of the magnetic gaps G ₁ , G ₂ , G ₃ and G ₄ , there is M respectively.
R elements M ₁ , M ₂ , M ₃ and M ₄ are formed.

Excitation coils C ₁ and C ₂ made of Cu are wound around the central portions of the respective ferromagnetic cores K ₁ and K ₂ to form magnetic gaps G ₁ , G ₂ , G ₃ and G. _A bias magnetic field H _B is applied to each of the MR elements M ₁ , M ₂ , M ₃ and M ₄ arranged on the upper part ₄ .

Here, the magnetic gaps G ₁ , G ₂ , G ₃ ,
G ₄ is composed of PbO or SiO ₂ as a main component, and further comprises a low melting point glass having a melting point of 250 ° C. or higher and 650 ° C. or lower and an expansion coefficient of 100 or lower.

The MR elements M ₁ , M ₂ , M ₃ and M
₄ is, for example, two MR elements M ₁ and M for detecting the X-axis direction.
₃ and two MR elements M ₂ and M ₄ for detecting the Y-axis direction which is orthogonal to this, are classified into two types.

Further, on the surface of each of the ferromagnetic cores K ₁ and K ₂ , a lead wire pad 11 serving as an output terminal of the MR elements M ₁ , M ₂ , M ₃ and M ₄ and an exciting coil C _{1 are formed.} , C ₂ and a constant potential terminal pad 14 for supplying a sense current to the MR elements M ₁ , M ₂ , M ₃ and M ₄ , respectively. ing.

The MR elements M ₁ , M ₂ , M ₃ , M
₄ and lead wire pad 11, and near the tip portion 2 of the wire rod constituting the coil pad 12 for excitation coil C _1, C ₂
2 are electrically connected to each other, and the other end of the wire is connected to the coil pad 12 on the opposite side.

Then, the lead wire pad 11, the coil pad 12, the constant potential terminal pad 14 and the terminal pins (not shown) provided in the accommodating means of the geomagnetic direction sensor are made of Au as an external wiring (not shown).・ Electrically connected by wire.

An equivalent circuit of the geomagnetic direction sensor having the above structure is shown in FIG. That is, the outputs from the two MR elements M ₁ and M ₃ for detecting the geomagnetism in the X axis direction are output by the differential amplifier A _{1 in the} X axis direction (X output). Similarly, that is, the outputs from the _two MR elements M ₂ and M ₄ for detecting the geomagnetism in the Y-axis direction are output by the differential amplifier A _{2 in the} Y-axis direction (Y output).

MR elements M ₁ , M ₂ , for geomagnetic detection,
A constant potential terminal pad 14 is provided on one end 13 of each of M ₃ and M _4.
The MR elements M ₁ and M ₃ and the MR elements M ₂ and M ₄ are connected as a set to the constant-potential power supply V _CC , and a sense current is supplied.

MR elements M ₁ and M for detecting the X-axis direction are also used.
Bias magnetic fields (H _B and −H _B ) having different 180 ° azimuths are applied to the R element M ₃ , and similarly, MR elements M ₂ and MR element ₄ for detecting the Y-axis direction also have different 180 ° azimuths. Bias magnetic fields (H _B and −H _B ) are applied.

In the geomagnetic direction sensor having the above structure, M
The R elements M ₁ , M ₂ , M ₃ and M ₄ have the following features.

(1) The resistance value changes depending on the strength of the magnetic field. (Magnetic resistance effect) (2) It has excellent ability to detect a weak magnetic field. (3) The change in resistance value can be taken out as an electric signal.

The above geomagnetic direction sensor utilizes this feature to convert a magnetic signal due to geomagnetism into an electric signal.

Here, the MR elements M ₁ , M ₂ , M ₃ and M ₄
The function of will be described. These MR elements M ₁ , M ₂ ,
The electric resistance R of M ₃ and M ₄ is the same as that of the MR elements M ₁ , M ₂ and
It changes according to the magnetic flux intensity (magnetic flux amount) input to M ₃ and M ₄ . That is, the external magnetic field dependence of the electric resistance R of the MR element is represented by the MR curve shown in FIG. 3 as the MR characteristic.
In FIG. 3, the horizontal axis represents MR elements M ₁ , M ₂ , M ₃ ,
The strength of the magnetic field applied perpendicularly to M ₄ , the vertical axis represents the MR element M ₁ ,
This is a change in the resistance value of M ₂ , M ₃ , M ₄ or a change in the output voltage (when a DC current is passed through the MR elements M ₁ , M ₂ , M ₃ , M ₄ ).

The resistance values of the MR elements M ₁ , M ₂ , M ₃ and M ₄ are maximum when the magnetic field is zero, and are large magnetic fields (MR element M ₁ ,
Depending on the pattern shape of M ₂ , M ₃ , M ₄ , etc.
It becomes about 3% smaller when a voltage of about 200 gauss is applied.

In order to improve the S / N (output voltage amplitude) and the distortion factor of the outputs of the MR elements M ₁ , M ₂ , M ₃ and M ₄ ,
A bias magnetic field H _B is required. This bias magnetic field H _B
Is given by winding the exciting coils C ₁ and C ₂ around the ferromagnetic cores K ₁ and K ₂ , respectively, and supplying the AC bias current I _B to the coils as described above.

At this time, the MR element M ₁ for detecting the X-axis direction
The direction of the bias magnetic field applied to the MR element M ₃ and the direction of the bias magnetic field applied to the MR element M ₃ are reversed by 180 °. Similarly, the direction of the bias magnetic field applied to the MR element M ₂ for Y-axis direction detection and the direction of the bias magnetic field applied to the MR element M ₄ are also inverted by 180 °.

Here, when the geomagnetic signal H _E comes in,
For example, the strength of the magnetic field applied to the MR elements M ₁ and M ₃ for detecting the X-axis direction is as follows.

The MR element _{M 1: H B + H E} MR element _M 3: When -H _B + H _E example applying an alternating bias magnetic field, MR element M ₁
The magnetic field applied to is changed as shown by a line A in FIG. 3, and the change of this magnetic field is output as a voltage change as shown by a line B in FIG. On the other hand, the magnetic field applied to the MR element M ₃ changes as shown by the line C in FIG. 3, and this change in the magnetic field is output as a voltage change as shown by the line D in FIG.

The output from this MR element M ₁ (line B) and M
The output difference L of the output (line D) from the R element M ₃ is taken out as a differential signal (X output) amplified by the differential amplifier A ₁ . The same applies to the MR elements M ₂ and M ₄ for detecting the Y-axis direction, and the differential signal (Y output) amplified by the differential amplifier A ₂ is taken out.

These differential signals change depending on the direction of the geomagnetism H _E and are proportional to H _E sin θ and H _E cos θ, respectively. Therefore, when the output potential is plotted by taking the azimuth θ on the horizontal axis, the X output and the Y output are as shown in FIG.

Therefore, the azimuth θ with respect to the geomagnetism can be calculated from these X output and Y output.

That is, the ratio X / Y of the X output and the Y output is
Since these output is proportional H _E sin [theta, the H _E cos [theta], can be expressed by sin [theta / cos [theta].

X / Y = sin θ / cos θ = tan θ Therefore, θ = tan ⁻¹ (X / Y) (where 0 ≧ θ ≦ 180 °, X ≧ 0, 180 ° <
When θ <360 °, X <0. ) From the above, the direction θ of the geomagnetism H _E can be known.

Next, the principle of geomagnetic focusing by the ferromagnetic cores K ₁ and K ₂ will be described.

First, FIG. 5 schematically shows how the ferromagnetic core K made of ferrite, permalloy or the like affects the earth's magnetism.

Since the ferromagnetic material has a smaller magnetic resistance than that in the air, it is bent so as to attract the earth's magnetism, and passes through the ferromagnetic material core K to come out again.

Therefore, the ferromagnetic core K focuses the geomagnetism and converts it into a large magnetic flux density (actually, the magnetism magnetizes the ferromagnetic core K to generate a large magnetic field in the magnetic gap).

FIG. 6 shows how the geomagnetism of each of the MR elements M ₁ , M ₂ , M ₃ , when a circular ferromagnetic core K is used.
It is shown whether or not it is transmitted to M ₄ , and the total amount of geomagnetism applied as a magnetic signal to each MR element M ₁ , M ₂ , M ₃ , M ₄ is the MR element M ₁ , M ₂ , M ₃ , It corresponds to the length of a line perpendicular to the geomagnetic line H _EO passing through the center of the ferromagnetic core K from M ₄ .

The total amount of geomagnetism applied to the X-axis direction detecting MR elements M ₁ and M ₃ : rsinθ The total amount of geomagnetism applied to the Y-axis direction detecting MR elements M ₂ and M ₄ : rcos θ Therefore, From the geomagnetic orientation sensor output (X output, Y output) output based on the total amount, the azimuth θ of the geomagnetism H _E is calculated according to the above calculation formula.

The same applies to the case where the ferromagnetic core K has a square shape as shown in FIG. 7, as long as it has a symmetrical shape when the ferromagnetic core K is rotated 90 ° about the center point of the ferromagnetic core K. In any case, the same output can be obtained.

As described above, in the present embodiment, the pair of ferromagnetic material cores K ₁ and K ₂ are joined and integrated to form a closed magnetic circuit for the bias magnetic field, and as a so-called focusing horn that focuses the earth magnetism. Function. As a result, the total amount of geomagnetism applied to the MR elements M ₁ , M ₂ , M ₃ , and M ₄ orthogonal to each other is the same as the geomagnetism and the MR elements M ₁ , M ₂ , and M ₄ , respectively.
It depends on the angle between M _3, M _4, a geomagnetic line passing through the center of the formed closed magnetic path by the magnetic cores K _1, K ₂ from each MR element _{M 1, M 2, M 3} , M 4 Proportional to the line drawn at right angles.

Further, the magnetic gaps G ₁ , G ₂ , G ₃ ,
G ₄ is composed of a glass material containing PbO and SiO ₂ as main components, more preferably a glass material having a melting point of 650 ° C. or less and an expansion coefficient of 90 or less is used to prevent cracking, warpage, and melting. Various inconveniences that tend to occur in the magnetic gaps G ₁ , G ₂ , G ₃ , G ₄ such as glass bubbles during wearing and glass breakage during grinding are suppressed.

Therefore, the reliability as a product is improved, and the geomagnetism is efficiently generated by the MR elements M ₁ , M ₂ , M.
₃ is supplied a high output as the magnetic signal to the M ₄ is obtained,
The azimuth can be detected with high accuracy with high detection sensitivity.

Next, a method of manufacturing the geomagnetic direction sensor will be described.

First, a first groove is formed in a substrate made of ferrite, and a glass material made of the above-mentioned components is poured as a predetermined fused glass into the first groove to form the gaps G ₁ , G ₂ , and G. ₃ and G ₄ are formed, and the surface on the side of the gaps G ₁ , G ₂ , G ₃ , and G _{4 of} the above substrate is subjected to a super-mirror surface treatment so that the surface roughness is 10 nm or less.

Next, the magnetic gaps G ₁ , G ₂ , G ₃ , and G ₄ (herein, simply referred to as the magnetic gaps) subjected to the super-mirror surface treatment by the sputtering method and the photolithography technique are used. MR elements M ₁ , M ₂ ,
While forming M ₃ and M ₄ (hereinbelow, simply referred to as MR element), the lead wire pad 11 and the coil pad 12 are formed.

Then, as described above, the MR elements M ₁ , M ₂ ,
After forming M ₃ , M ₄ , the lead wire pad 11 and the coil pad 12, the MR elements M ₁ , M ₂ ,
The thickness of the substrate is adjusted by polishing the entire surface (back surface) on which M ₃ , M ₄ etc. are not formed.

Then, the gap G ₁ on the back surface of the substrate,
A _second gap is formed at a position corresponding to G ₂ , G ₃ , and G ₄ to form a back gap for geomagnetic focusing.
In this case, the substrate is separated by a gap _{G 1, G 2, G 3} , G 4 , the substrate separated is joined by fusion glass forming the gap _{G 1, G 2, G 3} , G 4 Formed. Subsequently, after forming grooves for winding the exciting coils C ₁ and C ₂ by machining, the substrate is cut and cut into core chips.

Grooves are formed on the core chip to form substantially U-shaped ferromagnetic cores K ₁ and K _2, and Cu is respectively filled in the winding grooves of the ferromagnetic cores K ₁ and K ₂ . After the winding of 500 turns or more is performed by using the wire material as the material to form the exciting coils C ₁ and C ₂ , the ferromagnetic cores K ₁ and K ₂ are formed.
Are joined together at their respective joint surfaces S to form a square closed magnetic circuit.

At this time, each exciting coil C is attached to the barrier-like hooking portion 21 provided in the vicinity of the MR element M ₁ and the MR element M ₄ formed on the surfaces of the ferromagnetic cores K ₁ and K _{2. 1} ,
The tip-end portions 22 of the wire rods forming C ₂ are hooked and fixed.

Next, the ferromagnetic cores K ₁ and K ₂ are housed in the housing means, and the lead wire pad 11, the coil pad 12, the constant potential terminal pad 14 and the mold package 2 are not shown. Each terminal pin is connected using a bonding wire.

Then, in order to improve the adhesive force, a predetermined binder is applied to the above-mentioned bonding site, and then a predetermined resin is filled in the accommodating means and sealed.

Although the embodiment to which the present invention is applied has been described above, the present invention is not limited to this embodiment, and the shape, the material, the dimension, etc. can be set without departing from the gist of the present invention. It can be changed arbitrarily.

[0071]

EFFECTS OF THE INVENTION According to the present invention, inconveniences in manufacturing such as cracks and warps, glass bubbles, and glass breakage during grinding are eliminated to improve processing accuracy, and practical sensitivity is provided. It becomes possible to realize a geomagnetic direction sensor having high detection sensitivity, which can be easily reduced in size and cost.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a configuration example of a geomagnetic direction sensor to which the present invention is applied.

FIG. 2 is a circuit diagram showing an example of an equivalent circuit of the geomagnetic direction sensor shown in FIG.

FIG. 3 is a characteristic diagram showing a magnetoresistive effect characteristic of an MR element.

FIG. 4 is a characteristic diagram showing a relationship between an output voltage and an azimuth.

FIG. 5 is a schematic diagram showing a focused state of geomagnetism by a ferromagnetic core.

FIG. 6 is a schematic diagram showing the total amount of geomagnetism applied to each MR element when a circular core is used.

FIG. 7 is a schematic diagram showing the total amount of geomagnetism applied to each MR element when a square core is used.

FIG. 8 is a schematic plan view showing an example of a conventional fluxgate type geomagnetic direction sensor.

FIG. 9 is a schematic plan view showing an example of a conventional MR type geomagnetic direction sensor.

FIG. 10 is an equivalent circuit diagram of the geomagnetic direction sensor shown in FIG.

[Explanation of symbols]

M ₁ , M ₂ , M ₃ , M ₄ MR element K ₁ , K ₂ Ferromagnetic core G ₁ , G ₂ , G ₃ , G ₄ Magnetic gap C ₁ , C ₂ Excitation coil 11 Lead wire pad 12 Coil Pad

Claims (5)

[Claims] 1. A plurality of ferromagnetic cores for focusing geomagnetism are arranged in a circumferential direction through a predetermined magnetic gap, and a magnetoresistive effect element is arranged so as to be substantially orthogonal to a magnetic field direction in the magnetic gap. a geomagnetic direction sensor comprising disposed on a magnetic gap, a geomagnetic direction sensor, characterized in that the magnetic gap is made of a glass material mainly composed of PbO or Si0 _2. 2. The melting point of the glass material of the magnetic gap is 250.
The geomagnetic direction sensor according to claim 1, wherein the temperature is not less than ℃ and not more than 650 ° C. 3. The expansion coefficient of the glass material of the magnetic gap is 1
The geomagnetic direction sensor according to claim 1, wherein the geomagnetic direction sensor is 00 or less. 4. The geomagnetic direction sensor according to claim 1, further comprising at least a pair of magnetoresistive effect elements that are substantially orthogonal to each other. 5. An exciting coil is wound around a ferromagnetic core, and a bias magnetic field is applied to the magnetoresistive effect element in the magnetic gap by supplying a current to the exciting coil. The geomagnetic direction sensor according to Item 1.