JPH06147816A - Angle sensor - Google Patents

Abstract

PURPOSE:To achieve a linear displacement-output characteristic curve over a wide range by disposing magnetoresistive elements of ferromagnetic metal symmetrically to the magnetic axis of a permanent magnet. CONSTITUTION:A rotary section 21 has a circular surface applied with a magnetizing body 23 comprising a permanent magnet having N and S poles extending spirally. A magnetic head 11 comprises a permanent magnet board for forming a bias field, and a magnetoresistive element formed of a ferromagnetic metal film. Direction of the bias field is matched with the longitudinal direction of the board and the magnetic axis extends along the longitudinal direction of the board. The magnetoresistive element has two magneto-sensitive parts crossing perpendicularly each other while making an angle of 45 deg. against the direction of the bias field. When the rotary section 21 rotates with respect to the magnetic head 11, signal field of the magnetic head 11 functioning on the magnetoresistive element varies. Since the relationship between the rotational angular speed of the rotary section 21 and the output voltage from the magnetoresistive element exhibits linearity over a wide range, microrotational angle can be measured highly accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angle sensor for measuring a minute angular displacement with high accuracy.

[0002]

2. Description of the Related Art A displacement sensor using a magnetoresistive element (MR element) is widely used. Such magnetoresistive elements are roughly classified into semiconductor magnetoresistive elements utilizing the Hall effect (semiconductor magnetoresistive effect) and ferromagnetic metal magnetoresistive elements utilizing the magnetoresistive effect of ferromagnetic metals. Ferromagnetic metal magnetoresistive elements are widely used in position sensors because it is easy to obtain linearity in the relationship between the resistance value and the strength and direction of a magnetic field.

The resistance value ρ of the ferromagnetic metal magnetoresistive element is expressed by the following equation 1 as a function of the magnetization direction.

[0004]

[Equation 1]

Where ρ (θ) is the resistance value of the magnetoresistive element, θ is the angle between the current and the saturation magnetization direction, ρ ₁ is the resistance value of the magnetoresistive element when the current and the saturation magnetization direction are orthogonal, ρ ₂ : The resistance value of the magnetoresistive element when the current and the saturation magnetization direction are parallel.

This equation is well known as the Viogt-Thomson equation. Ferromagnetic metals are usually used in a saturation magnetic field because they exhibit a hysteresis action in a magnetic field having a strength equal to or lower than the reversible magnetic field.

As is clear from this equation, the ferromagnetic metal magnetoresistive element has the maximum resistance value ρ ₂ when the current and the magnetization direction (direction of the magnetic field) are parallel, and the current and the magnetization direction (direction of the magnetic field). Has a minimum resistance value ρ ₁ when is orthogonal.

The principle of the ferromagnetic metal magnetoresistive element will be described with reference to FIG. For the details of the principle of the ferromagnetic metal magnetoresistive element and the displacement sensor using the same, see, for example, "Sensor Technology" (November 1981) [Vol.1.N].
O.4] (pp. 47-53), "Displacement detection by ferromagnetic metal thin film element".

As shown in the figure, the two elongated magnetic sensitive portions 31A and 31B of the ferromagnetic metal magnetoresistive element are arranged so as to be orthogonal to each other. Therefore, the directions of the currents I flowing through the magnetic sensitive sections 31A and 31B are orthogonal to each other. First magnetic sensing section 3
The second magnetic sensitive section 3 which has the longitudinal direction of 1A as the Y axis and is perpendicular to the Y axis
The longitudinal direction of 1B is the X axis.

It is assumed that a DC bias magnetic field H _B is applied to the two magnetic sensitive sections 31A and 31B. Therefore, when the signal magnetic field H _S is further applied, the magnetic sensitive portions 31A, 3A
1B is a combined magnetic field H of the bias magnetic field H _B and the signal magnetic field H _S.
Works. The direction of the bias magnetic field H _B is 4 with respect to the Y axis.
5 ° an angle of the direction of the signal magnetic field H _S is if an angle of 90 degrees with respect to Y axis, the direction of the resultant magnetic field H forms an angle of (45 + Δθ) degrees with respect to the Y axis.

First magnetic sensitive section 31A and second magnetic sensitive section 31B
The resistance values of are assumed to be substantially the same. First magnetic sensitive section 31
Each resistance value of A [rho _A and the resistance value [rho _B of the second sensitive portion 31B using the equation 1 is represented by the formula for a number of 2.

[0012]

[Equation 2]

As shown, the two magnetic sensitive parts 31A, 31
B is connected in series and further connected to a DC power supply 35 (voltage V ₀ ). Therefore, the voltage across the second magnetically sensitive portion 31B is expressed by the following equation (3).

[0014]

[Equation 3]

Substituting the expression of the expression 2 into the expression of the expression 3, the following expression of the expression 4 is obtained.

[0016]

[Equation 4]

The first term on the right side of this equation is the voltage appearing at the output terminal when there is no signal magnetic field, that is, when H _S = 0, and the second term is the voltage portion that changes depending on the magnitude and direction of the signal magnetic field. is there.

When the two equations are added, the following equation 5 is obtained.
Is obtained.

[0019]

[Equation 5]

That is, the sum of the resistance values of the two magnetic sensitive sections 31A and 31B is always constant.

FIG. 4 shows an example of the ferromagnetic metal magnetoresistive element 31. The ferromagnetic metal magnetoresistive element 31 is formed by depositing a ferromagnetic metal thin film on the surface of the substrate 41. A permanent magnet for generating a bias magnetic field H _B is attached to the back surface of the substrate 41. The N and S poles of the permanent magnet are arranged so that the direction of the bias magnetic field H _B is aligned with the longitudinal direction of the substrate as shown. That is, the magnetic axis (the line connecting the N pole and the S pole) is arranged along the longitudinal direction.

The ferromagnetic metal magnetoresistive element 31 includes a magnetic sensing section 43.
A, 43B and lead parts 45A, 45B, 45C. The magnetic sensitive sections are the first magnetic sensitive section 43A and the second magnetic sensitive section 43B.
And each magnetic sensitive portion includes a plurality of parallel thin strip-shaped ferromagnetic metal thin films, which are connected in series. The strip-shaped ferromagnetic metal thin film of the first magnetic sensing portion 43A and the strip-shaped ferromagnetic metal thin film of the second magnetic sensing portion 43B are orthogonal to each other and formed at an angle of 45 degrees with respect to the longitudinal direction of the substrate 41. The substrates 41 are arranged so as to be arranged, and further, are arranged symmetrically with respect to a center line perpendicular to the longitudinal direction of the substrate 41.

The lead portions 45A, 45B, 45C have input terminals 45A, 45C for applying a reference current and output terminals 45B for extracting an output voltage.

Thus, the orientations of the two magnetic sensitive portions 43A and 43B of the ferromagnetic metal magnetoresistive element 31 and the bias magnetic field H _B.
The relationship between the directions of the two magnetic sensitive parts 31A shown in FIG.
The relationship between the orientation of 31B and the direction of the bias magnetic field H _B is the same. The ferromagnetic metal magnetoresistive element is preferably arranged so that the direction of the bias magnetic field H _B is orthogonal to the direction of the signal magnetic field H _S.

FIG. 5 shows an example of a displacement sensor using the ferromagnetic metal magnetoresistive element 31. The displacement sensor is the magnetism generating part 51.
And a detection head 53 which is spaced from the magnetism generator 51 and moves relative to the magnetism generator 51, and the detection head 53 is configured to detect the relative displacement and displacement direction between the two. ing. The magnetic field generator 51 has a signal magnetic field H
_The magnet 55 includes a magnet 55 that generates _S, and the magnet 55 may be, for example, a permanent magnet configured such that north poles and south poles are alternately arranged.

The detection head 53 includes a permanent magnet 47 for generating the bias magnetic field H _B as described with reference to FIG.
1 and a ferromagnetic metal magnetoresistive element 31 formed in
The two magnetic sensitive sections 43A, 4A of the ferromagnetic metal magnetoresistive element 31.
3B are arranged at right angles to each other and at an angle of 45 degrees with respect to the longitudinal direction. In this way, the two magnetic sensitive parts 43A, 4A of the ferromagnetic metal magnetoresistive element 31 of the detection head are
The relationship between the orientation of 3B, the direction of the bias magnetic field H _B generated by the permanent magnet, and the direction of the signal magnetic field H _S generated by the magnet 55 of the magnet unit 51 is shown in FIG.
The relationship between the orientations of the three magnetic sensitive portions 31A and 31B and the direction of the bias magnetic field H _B is the same.

Further, the detecting head 53 has a bias magnetic field H _B.
Is arranged so that the direction of is perpendicular to the direction of the signal magnetic field H _S.

An appropriate signal detection circuit is connected to the detection head as shown in the figure. Such a signal detection circuit includes a differential amplifier circuit 57, and the reference voltage is input from the first terminal 59 and the output voltage V is output from the second terminal 61.
The output voltage V taken out from the terminal 61 has a signal waveform as shown in FIG. 5B. FIG. 5B shows the relationship between the displacement (horizontal axis) and the magnitude of the output voltage V (vertical axis), that is, the displacement-output characteristic.
The relative displacement amount and displacement direction of 3 are detected.

In order to obtain high measurement accuracy with the displacement sensor,
It is preferable that the relationship between the output voltage and the displacement is linear.
However, in the displacement-output characteristic shown in the graph of FIG. 5B, the range in which the output voltage changes linearly, that is, linearly with respect to the displacement is narrow. The wider the range in which the displacement-output characteristic is linear, the higher the accuracy with which the displacement sensor can measure.

Attempts have been made to obtain such linearity of displacement-output characteristics in a wide range.

FIG. 6 shows an example of a displacement sensor configured to improve the linearity of the displacement-output characteristic. In this example, as shown in FIG.
It is configured so as to be inclined with respect to the boundary line between the N pole and the S pole. In such a case, the vector of the bias magnetic field H _B , the vector of the signal magnetic field H _S of the magnet body 55, and the vector of the combined magnetic field H are as shown in FIG. 6B. Thus, the displacement-output characteristic becomes linear over a wide range as shown in FIG. 6C.

Further, as shown in FIG. 7, it is known that the linearity of the displacement-output characteristic can be improved also by arranging the permanent magnets constituting the magnet body 55 apart from the adjacent permanent magnets. There is.

[0033]

As described above, a displacement sensor for detecting linear displacement using the ferromagnetic metal magnetoresistive element 31 in the magnetic head is widely known. Further, in such a displacement sensor, there has been proposed a displacement sensor having a linear displacement-output characteristic over a wide measurement range.

However, in the analog angle sensor for detecting the angular displacement (hereinafter, simply referred to as an angle sensor), the ferromagnetic metal magnetoresistive element 31 is used for the detection head and the displacement-output characteristic is linear over a wide measurement range. Nothing configured to have is known.

Conventionally, an angle sensor using a semiconductor magnetoresistive element for a detection head is known. Although the semiconductor magnetoresistive element has good resistance to noise and vibration and excellent high-speed response, it has a drawback in that it has poor temperature characteristics and requires temperature compensation. On the other hand, the ferromagnetic metal magnetoresistive element has an advantage that it does not require temperature compensation because it has good temperature characteristics. The temperature coefficient of the resistance value of the ferromagnetic metal magnetoresistive element is 3 × 10 ⁻³
Although it is Ω / ° C or less, the temperature coefficient of the resistance value of the semiconductor magnetoresistive element is larger by one digit or more.

In view of the above point, the present invention provides an angle sensor which uses a ferromagnetic metal magnetoresistive element 31 in a detection head and which has a linear displacement-output characteristic over a wide measurement range. To aim.

[0037]

According to the present invention, a magnetoresistive element including a permanent magnet for generating a bias magnetic field and a magnetoresistive element of a ferromagnetic metal is formed in a line perpendicular to the magnetic axis of the permanent magnet. The first magnetic sensitive section and the second magnetic sensitive section, which are symmetrically arranged on both sides of the first magnetic sensitive section, respectively.
Of the magnetic head 11 and the second magnetic sensor, which form an angle of 90 degrees with each other and are arranged at an angle of 45 degrees with respect to the magnetic axis of the permanent magnet. In an angle sensor having a magnetizing body 23 rotatable about a central axis to generate, the magnetizing body 23 has a north pole and a south pole so that a vector of a signal magnetic field changes as a function of a central angle around the central axis. Magnetized to vary as a function of angle, the magnetic head 11 is spaced from the magnet body 23 and is configured so that the output voltage of the magnetic head 11 is represented as a function of the rotation angle of the magnet body 23.

According to the present invention, as shown in FIG. 1, for example, in the angle sensor, the magnet body 23 has a circular surface perpendicular to the central axis, and the circular surface is centered in the radial dimension of the N pole and the S pole. The magnetic head is magnetized so that it changes as a function of the central angle around the axis and the direction of the signal magnetic field is parallel to the central axis, the magnetic head is spaced from the circular surface of the magnetizer 23, and the direction of the bias magnetic field is the direction of the signal magnetic field. Are arranged so as to be orthogonal to the central axis.

According to the present invention, for example, as shown in FIG. 2, in the angle sensor, the magnetizing body 23 has a circumferential surface parallel to the central axis, and the circumferential surface is the axis line of N pole and S pole. The direction dimension changes as a function of the central angle about the central axis and the direction of the signal magnetic field is magnetized so as to be orthogonal to the central axis, the magnetic head is spaced from the circumferential surface of the magnet and The bias magnetic field is arranged so as to be parallel to the central axis so that the direction of the bias magnetic field is orthogonal to the direction of the signal magnetic field.

[0040]

In the magnetic sensor of the present invention, the magnetizing body 23 mounted on the rotating portion 21 has a permanent magnet that changes as a function of the central angle, and when the rotating portion 21 rotates with respect to the magnetic head 11, the magnetic field of the magnetic head is changed. The signal magnetic field acting on the resistance element changes. Since the relationship between the rotation angular velocity of the rotating unit 21 and the output voltage of the magnetoresistive element, that is, the displacement-output characteristic has linearity in a wide range, it is possible to measure a minute rotation angle with high accuracy.

[0041]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows a first example of the angle sensor of the present invention, which has a magnetic head 11 and a rotating portion 21.

The rotating portion 21 has a substantially disk shape rotatable about the central axis O--O, and a magnetizing body 23 made of a permanent magnet is mounted on its circular surface. The magnetizer 23 of this example is arranged so that the N and S poles of the permanent magnet extend in a spiral shape as shown in the figure. That is, on the circular surface of the magnet body 23, the widths of the N pole and the S pole of the permanent magnet in the radial direction continuously change with the central angle. When polar coordinates (r, θ) having a point passing through the central axis O-O on the circular surface as a pole are set, the boundary line between the N pole and the S pole is, for example, a function r = f ( θ).

In this way, the direction of the signal magnetic field H _S generated by the magnetic generator 23 on the circular surface is parallel to the central axis O--O of the rotating portion 21 as shown by the arrow in the figure.

The magnetic head 11 may have the same form as the conventional magnetic head 11 as shown in FIGS. 5 to 7, for example, and a substrate made of a permanent magnet for generating the bias magnetic field H _B and the magnetic head 11. A ferromagnetic metal magnetoresistive element (hereinafter simply referred to as a magnetoresistive element) including a ferromagnetic metal film mounted on such a substrate is included. The direction of the bias magnetic field H _B is configured to match the longitudinal direction of the substrate, and the magnetic axis (the line connecting the N pole and the S pole) is along the longitudinal direction of the substrate.

The two magnetic sensitive parts of the magnetoresistive element are arranged so as to be orthogonal to each other and form an angle of 45 degrees with respect to the direction of the bias magnetic field H _B , and further, with respect to the center line perpendicular to the longitudinal direction of the substrate. Are arranged symmetrically.

The magnetic head 11 is arranged on the circular surface of the magnetic body 23 and is spaced apart from the circular surface, and the longitudinal direction of the substrate 41 is arranged along the radial direction of the circular surface of the magnetic body 23. Further, the magnetic head 11 is arranged so that the direction of the bias magnetic field H _B is orthogonal to the direction of the signal magnetic field H _S. Thus, the relationship between the orientations of the two magnetically sensitive portions of the magnetoresistive element of the magnetic head 11 and the direction of the bias magnetic field H _B generated by the permanent magnet is the same as that of the two ferromagnetic metal magnetoresistive elements shown in FIGS. It is the same as the relationship between the orientation and the direction of the bias magnetic field H _B.

Further, two of the magnetoresistive elements of the magnetic head 11 are used.
The relationship between the orientation of the two magnetic sensitive parts and the direction of the bias magnetic field H _B generated by the permanent magnet and the direction of the signal magnetic field H _S generated by the magnetizer 23 of the rotating part 21 is shown in FIGS.
The relationship between the orientations of the two ferromagnetic metal magnetoresistive elements and the direction of the bias magnetic field H _{B and} the direction of the signal magnetic field H _{S shown} in FIG.

The magnetic head 11 may be connected to a signal detection circuit as shown in FIG. 5, for example. Thus, according to the present example, when the rotating portion 21 rotates about the central axis O--O by a small angle, the strength and the direction of the signal magnetic field H _S detected by the magnetic head 11 change, so that the magnetic head 11 is connected. The output voltage is detected at the output terminal of the signal detection circuit.

FIG. 1B shows the relationship between the rotation angle of the rotating portion 21 and the output voltage of the magnetoresistive element. It can be seen that the linearity can be obtained in a wide angle range in the angle displacement-output voltage characteristics as shown in the figure.

FIG. 2 shows a second example of the angle sensor of the present invention. In FIG. 2A, the angle sensor is the magnetic head 1 as in FIG.
1 and the rotating part 21 are shown.

The rotating part 21 has a substantially cylindrical shape rotatable about the central axis O--O, and a magnetizing body 23 made of a permanent magnet is mounted on its circumferential surface. The magnetizer 23 of this example is arranged so that the N poles and S poles of the permanent magnets extend spirally as shown in the figure. That is, the widths of the N pole and the S pole of the permanent magnet in the axial direction on the circumferential surface of the magnetizing body 23 are continuously changed with the central angle around the central axis OO. If the z axis is parallel to the central axis OO on the developed circumferential surface and the θ axis is perpendicular to it, the N pole and S
The boundary line of the pole is, for example, a function z = f of the variable z and the argument θ.
It can be expressed as (θ).

In this way, the direction of the signal magnetic field H _S generated by the circumferential surface of the magnetizing body 23 is perpendicular to the central axis O--O of the rotating portion 21 as indicated by the arrow.

Similar to the first example, the magnetic head 11 may have the same form as the conventional magnetic head 11 as shown in FIGS. 5 to 7, for generating the bias magnetic field H _B. And a magnetoresistive element mounted on the substrate. The direction of the bias magnetic field H _B is configured to match the longitudinal direction of the substrate, and the magnetic axis (the line connecting the N pole and the S pole) is along the longitudinal direction of the substrate.

The two magnetic sensitive parts of the magnetoresistive element are arranged so as to be orthogonal to each other and form an angle of 45 degrees with respect to the direction of the bias magnetic field H _B , and further, with respect to the center line perpendicular to the longitudinal direction of the substrate. Are arranged symmetrically.

The magnetic head 11 is arranged on the circumferential surface of the magnetizing body 23 and spaced apart from it, and is arranged such that the longitudinal direction of the substrate is along the axial direction. Furthermore, the magnetic head 1
1 is arranged so that the direction of the bias magnetic field H _B is orthogonal to the direction of the signal magnetic field H _S , that is, along the axial direction. Thus, the orientation of the two magnetic sensitive parts of the ferromagnetic metal magnetoresistive element of the magnetic head 11, the direction of the bias magnetic field H _B generated by the permanent magnet, and the signal magnetic field H _S generated by the magnetizer 23 of the rotating part 21 are controlled. The relationship between the directions is shown in FIG.
Orientation of two ferromagnetic metal magnetoresistive elements and bias magnetic field H _B
And the direction of the signal magnetic field H _S are the same.

The magnetic head 11 may be connected to a signal detection circuit as shown in FIG. 5, for example. Thus, according to this example, when the rotating portion 21 rotates about the central axis O--O by a small angle, the strength of the signal magnetic field H _S detected by the magnetic head 11 changes, so that the signal detection connected to the magnetic head 11 is detected. The output voltage is detected at the output terminal of the circuit.

FIG. 2B shows the angle sensor of the second example,
The relationship between the rotation angle of the rotating unit 21 and the output voltage of the magnetoresistive element is shown. As with FIG. 1B, it can be seen that in the angular displacement-output voltage characteristic, linearity can be obtained in a wide angle range.

The first example shown in FIG. 1 and the second example shown in FIG.
In the above example, the magnetizing body 23 of the rotating portion 21 is made of a permanent magnet of ferromagnetic metal, but may be made of a permanent magnet made of rubber containing ferromagnetic metal powder, for example. Further, the magnetizing body 23 of the rotating portion 21 may be manufactured by bonding two spiral or spiral permanent magnets.

Although the embodiments of the present invention have been described in detail above, those skilled in the art will understand that the present invention is not limited to the above-mentioned embodiments and various other configurations can be adopted without departing from the gist of the present invention. Easy to understand.

[0060]

According to the present invention, since a ferromagnetic metal magnetoresistive element is used in the detection head, there is an advantage that an angle sensor having excellent temperature characteristics can be provided.

According to the present invention, in the angle sensor using the ferromagnetic metal magnetoresistive element, there is an advantage that the linearity of the angular displacement-output voltage characteristic can be improved.

According to the present invention, since the linearity of the angular displacement-output voltage characteristic of the angle sensor using the ferromagnetic metal magnetoresistive element becomes good, it is possible to measure the minute angular displacement with high accuracy. There is.

[Brief description of drawings]

FIG. 1 is a diagram showing a first example of an angle sensor of the present invention.

FIG. 2 is a diagram showing a second example of the angle sensor of the present invention.

FIG. 3 is an explanatory diagram illustrating a principle of detecting a displacement by a ferromagnetic metal magnetoresistive element.

FIG. 4 is a diagram showing a configuration example of a ferromagnetic metal magnetoresistive element.

FIG. 5 is a diagram showing a configuration of a conventional example of a displacement sensor using a ferromagnetic metal magnetoresistive element.

FIG. 6 is a diagram showing a conventional example for improving displacement-output voltage characteristics of a displacement sensor.

FIG. 7 is a diagram showing another conventional example for improving the displacement-output voltage characteristic of the displacement sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 magnetic head 21 rotating part 23 magnetic generator 31 ferromagnetic metal magnetic resistance element 31A, 31B magnetic sensitive part 35 DC power supply 37 output terminal 41 substrate 43A, 43B magnetic sensitive part 45A, 45B, 45C lead part 47 permanent magnet 51 magnetic generator part 53 Detection Head 55 Magnetizer 57 Differential Amplifier Circuit 59, 61 Terminal

Claims (3)

[Claims] 1. A permanent magnet for generating a bias magnetic field and a magnetoresistive element made of a ferromagnetic metal, the magnetoresistive element being symmetrical with respect to a line orthogonal to the magnetic axis of the permanent magnet and on both sides thereof. A first magnetism sensitive portion and a second magnetism sensitive portion which are arranged respectively, and the first magnetism sensitive portion and the second magnetism sensitive portion form an angle of 90 degrees with each other and the magnetism of the permanent magnet. In an angle sensor having a magnetic head configured to be arranged at an angle of 45 degrees with respect to an axis and a magnetizing body rotatable about a central axis to generate a signal magnetic field, the magnetizing body is the signal The magnetic pole is magnetized so that the N pole and the S pole change as a function of the central angle so that the vector of the magnetic field changes as a function of the central angle around the central axis, and the magnetic head is spaced apart from the magnet body. The output voltage of the head depends on the rotation angle of the magnet. An angle sensor, characterized in that it is configured to be expressed as a number. 2. The angle sensor according to claim 1, wherein the magnetizing body has a circular surface perpendicular to the central axis, and the circular surface has N and S poles in radial directions around the central axis. The direction of the signal magnetic field changes as a function of the central angle and is magnetized so that the direction of the signal magnetic field is parallel to the central axis, the magnetic head is spaced from the circular surface of the magnetizer, and the direction of the bias magnetic field is the direction of the signal magnetic field. An angle sensor, wherein the angle sensor is arranged so as to be orthogonal to the direction and orthogonal to the central axis. 3. The angle sensor according to claim 1, wherein the magnetizing body has a circumferential surface parallel to the central axis, and the circumferential surface has N and S poles in the axial direction. The direction of the signal magnetic field changes as a function of the surrounding central angle and is magnetized so that the direction of the signal magnetic field is orthogonal to the central axis, the magnetic head is spaced from the circumferential surface of the magnet body, and the direction of the bias magnetic field is the signal. An angle sensor, which is arranged so as to be orthogonal to the direction of the magnetic field and parallel to the central axis.