JP2023136569A - position sensor - Google Patents

Abstract

To detect a position of a movable part with a resolution finer than before.SOLUTION: A position sensor includes: a bridge circuit 1 that is a sensor circuit including a magneto resistance effect element; a magnet 11 that linearly moves on a plane 9 crossing a sensor plane 6 on which a thin film resistor pattern of the magneto resistance effect element is formed; a sensor output detection unit 21 that detects output of the bridge circuit 1; an angle calculation unit 22 that calculates an angle of a magnetic field generated by the magnet 11 on the basis of the output of the bridge circuit 1; and a position calculation unit 23 that calculates coordinates of the magnet 11 on the basis of the angle of the magnetic field.SELECTED DRAWING: Figure 6

Description

The present invention relates to a position sensor that detects the position of a movable part that moves linearly.

BACKGROUND ART Conventionally, linear encoders and the like have been commonly used as position sensors that detect positions with high precision in a non-contact manner (see Patent Document 1). There are two types of linear encoders: magnetic and optical. The optical linear encoder consists of a scale 200 in which a slit is formed and a detector 201 that detects position information, as shown in FIG. 15, and the detector 201 detects light transmitted or reflected by the scale 200. Detects the position. A magnetic linear encoder detects a position by using a magnetic sensor to detect changes in the magnetic field distribution created by a magnetic scale in which S poles and N poles are arranged finely and alternately.

In the conventional technology, since a scale is used in both magnetic and optical linear encoders, there is a problem in that it is not possible to detect a position with a resolution finer than the interval between graduations of the scale.

Japanese Patent Application Publication No. 2007-121277

The present invention has been made to solve the above problems, and an object of the present invention is to provide a position sensor that can detect the position of a movable part with finer resolution than conventional ones.

The position sensor of the present invention includes a sensor circuit including a magnetoresistive element, a magnet configured to move linearly on a plane intersecting a sensor surface on which a thin film resistance pattern of the magnetoresistive element is formed, and the magnetoresistive element. a sensor output detection section configured to detect the output of the sensor circuit; an angle calculation section configured to calculate the angle of the magnetic field generated by the magnet based on the output of the sensor circuit; and the magnetic field. and a position calculation unit configured to calculate the coordinates of the magnet based on the angle.

Further, in one configuration example of the position sensor of the present invention, a reference position at which the output voltage of the sensor circuit becomes zero coincides with an intersection line between the plane and the sensor surface, and the magnet moves on the plane. The magnet moves linearly in the direction of the intersection line, and the position calculation unit calculates the coordinates of the magnet in the direction of the intersection line based on the angle of the magnetic field.
Further, in one configuration example of the position sensor of the present invention, the reference position at which the output voltage of the sensor circuit becomes zero is not on the intersection line between the plane and the sensor surface, and the magnet moves on the plane at the intersection. The position calculation unit calculates the coordinates of the magnet in the direction of the line of intersection based on the angle of the magnetic field and the angle between the reference position on the sensor surface and the line of intersection. This method is characterized by calculating .

Further, the position sensor of the present invention is configured to linearly move along a trajectory on a plane parallel to a sensor surface on which a sensor circuit including a magnetoresistive element and a thin film resistance pattern of the magnetoresistive element are formed. a first magnet; a second magnet disposed at a fixed position on the plane so as to face the first magnet with the sensor circuit therebetween; and a second magnet configured to detect the output of the sensor circuit. a sensor output detection section configured to, an angle calculation section configured to calculate an angle of a magnetic field generated by the first and second magnets based on the output of the sensor circuit, and an angle of the magnetic field. and a position calculation unit configured to calculate the coordinates of the first magnet based on the coordinates of the first magnet.

Further, in one configuration example of the position sensor of the present invention, the first magnet moves linearly in the direction of the trajectory that intersects the direction of the reference position where the output voltage of the sensor circuit becomes zero, and the position calculation unit is based on the distance from the sensor circuit to the intersection of the direction of the reference position and the trajectory, the distance from the sensor circuit to the second magnet, and the angle of the magnetic field. The present invention is characterized in that coordinates on the orbit of are calculated.
Further, in one configuration example of the position sensor of the present invention, both magnetic poles of the first and second columnar magnets are magnetized so as to face each other in the radial direction, and free rotation around the axis is allowed. The first magnet is housed in a housing cylinder in a state in which the first magnet is placed in the housing cylinder, and is arranged such that the axial direction thereof is perpendicular to the direction of the orbit of the first magnet.
Further, in one configuration example of the position sensor of the present invention, the sensor circuit is a bridge circuit in which four of the magnetoresistive elements are connected, and the output of the sensor circuit detected by the sensor output detection section is It is the midpoint potential difference of the circuit.

According to the present invention, a sensor circuit including a magnetoresistive element, a magnet that moves linearly on a plane intersecting a sensor surface on which a thin film resistance pattern of the magnetoresistive element is formed, and a sensor that detects the output of the sensor circuit. By providing an output detection section, an angle calculation section that calculates the angle of the magnetic field generated by the magnet based on the output of the sensor circuit, and a position calculation section that calculates the coordinates of the magnet based on the angle of the magnetic field, The position of the magnet, which is a movable part, can be detected with a finer resolution.

Further, in the present invention, a sensor circuit including a magnetoresistive element, a first magnet that linearly moves on a trajectory on a plane parallel to a sensor surface on which a thin film resistance pattern of the magnetoresistive element is formed, and a sensor circuit are provided. a second magnet disposed at a fixed position on a plane so as to face the first magnet; a sensor output detection section that detects the output of the sensor circuit; By providing an angle calculation section that calculates the angle of the magnetic field generated by the first and second magnets, and a position calculation section that calculates the coordinates of the first magnet based on the angle of the magnetic field, finer resolution than before can be achieved. The position of the first magnet, which is the movable part, can be detected.

FIG. 1 is a diagram showing the configuration of a conventional angle sensor. FIG. 2 is a circuit diagram of a bridge circuit made up of AMR elements. FIG. 3 is a diagram explaining the principle of the angle sensor used in the present invention. FIG. 4 is a diagram showing the trajectory of the magnet as the rotating body rotates in the angle sensor shown in FIG. FIG. 5 is a diagram showing the trajectory of the magnet as the rotating body rotates in the angle sensor shown in FIG. FIG. 6 is a diagram showing the configuration of a position sensor according to the first embodiment of the present invention. FIG. 7 is a diagram in which the locus of the magnet according to the first embodiment of the present invention is projected onto the sensor surface. FIG. 8 is a diagram showing the configuration of a position sensor according to a second embodiment of the present invention. FIG. 9 is a diagram in which the locus of a magnet according to the second embodiment of the present invention is projected onto a sensor surface. FIG. 10 is a diagram illustrating the effect of the position sensor according to the second embodiment of the present invention. FIG. 11 is a diagram showing the configuration of a position sensor according to a third embodiment of the present invention. FIG. 12 is a diagram in which the trajectory of the first magnet according to the third embodiment of the present invention is projected onto the sensor surface. FIG. 13 is a cross-sectional view of the first and second magnets according to the third embodiment of the present invention. FIG. 14 is a block diagram showing an example of the configuration of a computer that implements the position sensor according to the first to third embodiments of the present invention. FIG. 15 is a diagram showing the configuration of a conventional linear encoder.

[Principle of the invention]
In the present invention, a position is detected using an angle sensor using an anisotropic magnetoresistive effect (AMR) element. In an angle sensor using an AMR element, as long as the orbit of the magnet that generates the magnetic field is known, the position of the magnet can be measured from the angle of the magnetic field even when the magnet moves not in rotation but in a linear motion.

An angle sensor using an AMR element, a Hall element, or the like generally measures the angle of a magnetic field by rotating a magnet around the outer periphery of a sensor circuit. On the other hand, as in the present invention, if the magnet is moved across the surface of the sensor circuit rather than the outer periphery of the sensor circuit, by detecting the angle of the magnetic field, the position can be measured with finer resolution and accuracy than before. Is possible.

[Conventional example]
First, before describing embodiments of the present invention, a conventional angle sensor will be described in detail. FIG. 1 is a diagram showing the configuration of an angle sensor. The angle sensor measures the rotation angle of the magnetic field generated by the magnets 3 and 4 attached to the rotating body 2. A bridge circuit 1, which is a sensor circuit using an AMR element, is used for angle measurement. 1 indicates the direction of the magnetic field generated by the magnets 3 and 4, and 6 indicates the sensor surface of the bridge circuit 1. In FIG. A conventional angle sensor is installed so that the sensor surface 6 and the rotating surface of the magnetic field are parallel to each other, as shown in FIG.

FIG. 2 shows a bridge circuit 1 composed of an AMR element whose electrical resistance changes depending on a magnetic field. The bridge circuit 1 includes a first series circuit 10-5 in which a first AMR element 10-1 and a second AMR element 10-2 are connected in series, a third AMR element 10-3, and a fourth AMR element 10-2. A second series circuit 10-6 in which an AMR element 10-4 is connected in series is connected in parallel.

As shown by the double-headed arrow in FIG. 2, the magnetic sensing direction (the direction of the magnetic field where the resistance value is minimum) of the facing AMR elements 10-1 and 10-4 is the same, and the facing AMR elements 10-2 and 10- 3 have the same magnetic sensing direction. Further, the magnetic sensing directions of adjacent AMR elements are orthogonal to each other.

The rotating surface of the magnetic field generated by the magnets 3 and 4 of the angle sensor, and the sensor surface 6 on which the thin film resistance patterns of the four AMR elements 10-1 to 10-4 are formed (the magnetic sensing direction of the AMR elements 10-1 to 10-4) When a constant current I is passed through the bridge circuit 1 from a power supply (not shown), the midpoint potential difference (the first series circuit 10-5 The potential difference (V(θ)) between the midpoint and the midpoint of the second series circuit 10-6 is expressed by equation (1) depending on the rotation angle θ of the magnetic field.

From equation (1), the midpoint potential difference V(θ) is a periodic function with an amplitude of V ₀ and two periods during one rotation of the magnetic field. The rotation angle θ of the magnetic field is determined from the midpoint potential difference V(θ) as shown in equation (2).

If the half period is exceeded, the rotation angle θ cannot be uniquely determined with respect to the midpoint potential difference V(θ), so the angle measurement range of the conventional angle sensor is within 90 degrees.

[I. When the rotating surface of the magnetic field and the sensor surface are not parallel]
Next, in the first and second embodiments of the present invention, the magnet that generates the magnetic field is configured to pass along a trajectory on a plane that intersects the sensor surface of the angle sensor at an angle α. Before explaining, the operation of the angle sensor when the rotational surface intersects the sensor surface will be explained.

FIG. 3 is a diagram explaining the principle of the angle sensor used in the present invention. In the configuration of FIG. 3, the bridge circuit 1, the rotating body 2, and the magnets 3, 4 are arranged so that the rotating surface 7 of the magnetic field intersects the sensor surface 6. The magnets 3 and 4 are attached to the rotating body 2 and rotate about the rotation axis A as the rotating body 2 rotates. An extension of the rotation axis A passes through the center of the rhombic (square) bridge circuit 1 shown in FIG.

In a magnetically saturated state, the outputs of the AMR elements 10-1 to 10-4 remain unchanged regardless of the distance from the magnets 3 and 4, and depend only on the angle of the magnetic field. Therefore, when the rotating surface 7 of the magnetic field is tilted with respect to the sensor surface 6 as shown in FIG. ~10-4 maintains a magnetic field strength sufficient to reach a magnetic saturation state, there is no need to consider changes in distance due to the rotational orbits of the magnets 3 and 4.

As the rotating body 2 rotates, the magnets 3 and 4 draw perfect circular orbits in the plane of the rotating surface 7 of the magnetic field. Here, if the rotation angle of the magnetic field is φ, the angle between the rotation surface 7 of the magnetic field and the sensor surface 6 is α, and the rotation angle of the magnetic field on the sensor surface 6 is θ, then as described above, the angle between the magnets 3 and 4 is Since there is no need to consider distance, the rotation of the magnets 3 and 4 can be considered as an elliptical orbit rather than a perfect circle. Specifically, the orbits of the magnets 3 and 4 can be considered as the orbits of an ellipse 8 in FIG. 4, where the radius of rotation of the magnets 3 and 4 is R, and the minor axis is R and the major axis is R/cosα.

From FIG. 4, equations (3) to (6) are obtained.
cosφ=cosθ...(3)
sinφ=sinθ/cosα...(4)
tanφ=sinφ/cosφ=(sinθ/cosα)/cosθ
=tanθ/cosα...(5)
φ=tan ^-1 (tanθ/cosα) ...(6)

Here, equation (8) is obtained from equation (7).

Furthermore, since sin2θ=V(θ)/V ₀ , by setting V(θ)/V ₀ =v, equation (9) is obtained.

Therefore, the rotation angle φ of the magnetic field can be determined from the output of the bridge circuit 1. Here, consider how the range of the rotation angle φ of the magnetic field corresponding to the 90° range of -45°≦θ≦45° changes depending on the inclination angle α of the rotating surface 7 of the magnetic field with respect to the sensor surface 6. . In this range of θ, -1≦sin2θ≦1, and the rotation angle φ of the magnetic field takes a maximum value φ _max when θ is 45°, and a minimum value φ _min when θ is −45°.

The difference between the maximum value φ _max and the minimum value φ _min , that is, the range Δφ of the measurable rotation angle φ of the magnetic field, is expressed by equation (12).

When the inclination angle α=0°, since φ=θ, the measurable range of the rotation angle φ of the magnetic field is Δφ=90°. On the other hand, when the tilt angle α=±90°, the rotation angle φ does not depend on the value of θ and cannot be measured.

[II. When the rotating surface of the magnetic field and the sensor surface are not parallel and there is no reference position on the intersection line of the planes]
In the example of FIG. 4, the direction (reference position) in which the midpoint potential difference V(θ) of the bridge circuit 1 is zero is the intersection line ( The bridge circuit 1, the rotating body 2, and the magnets 3 and 4 were arranged so as to correspond to L in FIG. 4. In FIGS. 2 and 4, the reference position is indicated by θ ₀ . In the example of FIG. 2, the reference position θ ₀ is parallel to the magnetic sensing direction of the AMR elements 10-2 and 10-3 and perpendicular to the magnetic sensing direction of the AMR elements 10-1 and 10-4.

On the other hand, in the example of FIG. 5, the rotation surface of the magnetic field (the surface of the orbit 8 in FIG. 5) is not parallel to the sensor surface 6, and the reference position θ ₀ of the bridge circuit 1 is between the rotation surface of the magnetic field and the sensor surface. 6 will be explained below. Here, as shown in FIG. 5, the reference position θ ₀ of the bridge circuit 1 is shifted by an angle β with respect to the intersection line L on the sensor surface 6, and by an angle ψ with respect to the intersection line L on the rotating surface of the magnetic field. Consider the case where there is a deviation.

By replacing φ→φ−ψ and θ→θ−β in equation (6), equation (13) is obtained.

Furthermore, the relationship shown in equation (14) also holds between angles ψ and β.

By substituting equation (14) into equation (13), the rotation angle φ of the magnetic field becomes as shown in equation (15).

When the right side of equation (15) is rearranged and expressed using v, it becomes equation (16).

The range Δφ of the rotation angle φ of the magnetic field that can be measured in the range of −45°≦θ≦45° is the inclination angle α of the rotational surface of the magnetic field with respect to the sensor surface 6, and the intersection line between the rotational surface of the magnetic field and the sensor surface 6. It changes depending on the angle β of the reference position θ ₀ on the sensor surface 6 with respect to L.
In the present invention, the position of the magnet is detected using the operating principle of the angle sensor explained in FIGS. 2 to 5.

[First example]
FIG. 6 is a diagram showing the configuration of a position sensor according to the first embodiment of the present invention. The position sensor of this embodiment includes a bridge circuit 1 (sensor circuit), a magnet 11 that is a movable part that moves linearly on a plane 9 that intersects a sensor surface 6 on which a thin film resistance pattern of an AMR element is formed, and a bridge circuit. 1, a sensor output detection unit 21 that detects the output of the bridge circuit 1, and an angle calculation unit 22 that calculates the angle of the magnetic field generated by the magnet 11 based on the output of the bridge circuit 1. , and a position calculation unit 23 that calculates the coordinates of the magnet 11 based on the angle of the magnetic field.

In this embodiment, the magnet 11, which is a movable part, moves linearly on a plane 9 that intersects the sensor surface 6 of the bridge circuit 1 at an angle α, as shown by the trajectory p in FIG. The intersection line between the plane 9 and the sensor surface 6 passes through the center of the bridge circuit 1. However, the trajectory p does not pass through the center of the bridge circuit 1.

The magnet 11 is mounted, for example, on a carriage of a linear guide mechanism (not shown), and can move linearly on the plane 9 by moving the carriage along the rails of the linear guide mechanism. In addition, when using a linear guide mechanism, it is desirable that the carriage and the rail be made of a non-magnetic material that is not attracted to the magnet 11 and a magnetically permeable material that allows the lines of magnetic force of the magnet 11 to pass through.

The direction of the intersection between the plane 9 and the sensor surface 6 is x, the direction perpendicular to the x direction on the sensor surface 6 is y, the normal direction of the sensor surface 6 is z, and the direction of the bridge circuit 1 on the sensor surface 6 is Let the direction of the reference position be θ ₀ and the angle of the magnetic field from the reference position θ ₀ on the sensor surface 6 be θ. This embodiment is an example in which the reference position θ ₀ and the x direction coincide. FIG. 7 is a diagram in which the trajectory p of the magnet 11 in FIG. 6 is projected onto the sensor surface 6.

In this embodiment, v is defined as in equation (17) from the midpoint potential difference V(θ)=V ₀ ·sin2θ of the bridge circuit 1, which is the output of the angle sensor.
v=V(θ)/V ₀ =sin2θ...(17)

Let the coordinates of the magnet 11 be f(θ) = (x, y, z), and as shown in FIGS. 6 and 7, the straight line from the center of the bridge circuit 1 to the magnet 11 is projected onto the sensor surface 6. When the length is L(θ), the x-coordinate, y-coordinate, and z-coordinate of the magnet are as shown in equations (18) to (20), respectively.
x=L(θ)・cos(θ)...(18)
y=L(θ)・sin(θ)...(19)
z=y・tanα=L(θ)・sin(θ)・tanα...(20)

For example, if the magnet 11 is predetermined to move linearly in the x direction, the position of the magnet 11 can be expressed by equation (21).
y=c...(21)

c in equation (21) is a constant. Therefore, the length L(θ) is determined as shown in equation (22).
L(θ)=c/sin(θ)...(22)

From equations (17) to (22), the x-coordinate and z-coordinate of the magnet 11 can be determined as shown in equations (23) and (24), respectively.

z=c・tanα...(24)
At this time, since z does not appear in the x term, variations in z do not affect the measurement of x.

The power supply 20 of this embodiment shown in FIG. 6 supplies a constant current I to the bridge circuit 1. The sensor output detection unit 21 detects the midpoint potential difference V(θ) of the bridge circuit 1 as a sensor output.

The angle calculation unit 22 calculates the angle θ of the magnetic field on the sensor surface 6 based on the midpoint potential difference V(θ). At this time, the angle calculation unit 22 calculates the angle θ of the magnetic field from the midpoint potential difference V(θ) using a preregistered approximation function that indicates the relationship between the midpoint potential difference V(θ) and the magnetic field angle θ. All you have to do is calculate.

The position calculation unit 23 calculates the x-coordinate of the magnet 11 using equation (23) based on the angle θ of the magnetic field and the known constant c. In this way, in this embodiment, the position of the magnet 11 can be calculated.

In this embodiment, the angle θ of the magnetic field is detected using the principle of an angle sensor using a bridge circuit 1 made up of AMR elements 10-1 to 10-4. Since the angle sensor can continuously detect the angle θ of the magnetic field, there is no restriction on resolution as with conventional linear encoders. Therefore, in this embodiment, the position of the magnet 11 can be detected with finer resolution than the conventional method.

[Second example]
Next, a second embodiment of the present invention will be described. FIG. 8 is a diagram showing the configuration of a position sensor according to a second embodiment of the present invention. In the first embodiment, the plane 9 through which the magnet 11 passes is not parallel to the sensor surface 6, and the reference position θ ₀ , which is the direction in which the midpoint potential difference V(θ) of the bridge circuit 1 is zero, is parallel to the plane 9. The plane 9 was determined to coincide with the line of intersection with the sensor surface 6.

In contrast, in this embodiment, a case will be described in which the plane 9 is not parallel to the sensor surface 6 and the reference position θ ₀ of the bridge circuit 1 is not on the intersection line between the plane 9 and the sensor surface 6. As in the first embodiment, the line of intersection between the plane 9 and the sensor surface 6 passes through the center of the bridge circuit 1.

The direction of the intersection between the plane 9 and the sensor surface 6 is x, the direction perpendicular to the x direction on the sensor surface 6 is y, the normal direction of the sensor surface 6 is z, and the direction of the bridge circuit 1 on the sensor surface 6 is The direction of the reference position is θ ₀ , the angle of the magnetic field from the reference position θ ₀ on the sensor surface 6 is θ, and the angle between the reference position θ ₀ and the intersection line (x-axis) on the sensor surface 6 is β . FIG. 9 is a diagram in which the trajectory p of the magnet 11 in FIG. 8 is projected onto the sensor surface 6.

As in the first embodiment, let the coordinates of the magnet 11 be f(θ) = (x, y, z), and draw a straight line from the center of the bridge circuit 1 to the magnet 11 as shown in FIGS. 8 and 9. When the length of the straight line projected onto the sensor surface 6 is L(θ), the x-coordinate, y-coordinate, and z-coordinate of the magnet are as shown in equations (25) to (27), respectively.
x=L(θ)・cos(θ-β)...(25)
y=L(θ)・sin(θ−β) (26)
z=y・tanα=L(θ)・sin(θ−β)・tanα...(27)

Similar to the first embodiment, when the magnet 11 is predetermined to move linearly in the x direction, the position of the magnet 11 can be expressed by equation (21). Therefore, the length L(θ) is determined as shown in equation (28).
L(θ)=c/sin(θ-β)...(28)

From Equations (17) and Equations (25) to (28), the x-coordinate and z-coordinate of the magnet 11 can be determined as shown in Equations (29) and Equations (24), respectively.

Note that in equation (29), tanθ is transformed as in equation (30).

Similar to the first example, variations in z do not affect the measurement of x. Since the angle sensor has a track record of measuring with a resolution of 1/100° or less, when c=1 mm, it is possible to detect the x-coordinate of the magnet 11 with a calculated resolution of about 10 μm in the vicinity of v=0.

The closer c is to 0 (the closer the orbit of the magnet 11 is to the center of the bridge circuit 1), the more accurately the movement of the magnet 11 over a short distance can be detected. FIG. 10 shows the relationship between v and x/c. According to FIG. 10, it can be seen that the slope becomes gentle near x/c=0, and the output change v becomes large for a small movement amount of the magnet 11.

The operations of the power supply 20, sensor output detection section 21, and angle calculation section 22 are as described in the first embodiment.
The position calculation unit 23a of this embodiment calculates the x-coordinate of the magnet 11 using equation (29) based on the angle θ of the magnetic field calculated by the angle calculation unit 22, the known constant c, and the known angle β. .

[Third example]
In the first and second embodiments, only one magnet was used. In order to arrange the magnetic field, it is desirable to use two magnets. When two magnets are used, it becomes difficult to move the two magnets in a pair symmetrically with respect to the center of the bridge circuit. Therefore, in this embodiment, the position of the other second magnet is fixed with respect to the first magnet serving as the movable part. It is desirable that the magnetic fields generated by the first and second magnets pass through the center of the bridge circuit, but it is difficult to place the magnets in the center of the bridge circuit, so the second magnet is placed outside the bridge circuit. .

FIG. 11 is a diagram showing the configuration of the position sensor according to this embodiment. The position sensor of this embodiment has a bridge circuit 1, a first magnet 11-1 which is a movable part that moves linearly on a trajectory on a plane parallel to the sensor surface 6 of the bridge circuit 1, and a bridge circuit 1 between which a second magnet 11-2 placed at a fixed position on the plane so as to face the first magnet 11-1; a power source 20 for supplying current to the bridge circuit 1; A sensor output detection unit 21b that detects the output; an angle calculation unit 22b that calculates the angle of the magnetic field generated by the first and second magnets 11-1 and 11-2 based on the output of the bridge circuit 1; , and a position calculation unit 23b that calculates the coordinates of the first magnet 11-1 based on the angle of the first magnet 11-1.

12 in FIG. 11 indicates the direction of the magnetic field generated by the magnets 11-1 and 11-2. In this embodiment, the plane on which the magnets 11-1 and 11-2 are arranged and the sensor surface of the bridge circuit 1 are parallel. As in the first and second embodiments, the magnet 11-1 is mounted, for example, on a carriage of a linear guide mechanism (not shown), and as the carriage moves along the rails of the linear guide mechanism, the magnet 11-1 is moved to the reference position of the bridge circuit 1. Move linearly in the direction perpendicular to θ ₀ . In this embodiment, the direction perpendicular to this reference position θ ₀ is defined as x.

FIG. 12 is a diagram in which the trajectory p of the magnet 11-1 in FIG. 11 is projected onto the sensor surface 6. As shown in FIG. 12, the distance from the center of the bridge circuit 1 to the intersection of the reference position θ ₀ of the bridge circuit 1 and the orbit p of the magnet 11-1 is L _A , and the distance from the center of the bridge circuit 1 to the intersection of the orbit p of the magnet 11-2 is L A Let L _B be the distance to the sensor surface 6, ω be the angle of the magnetic field from the reference position θ ₀ of the bridge circuit 1 on the sensor surface 6, and λ be the angle between the center of the bridge circuit 1 and the magnet 11-1. From the midpoint potential difference V(ω)=V ₀ ·sin2ω of the bridge circuit 1, v is defined as in equation (31).
v=V(ω)/V ₀ =sin2ω...(31)

The relationship between the distances L _A and L _B and the angles λ and ω is as shown in equations (32) and (33).
L _A・tanλ=(L _A +L _B )・tanω (32)

Therefore, the x-coordinate of the magnet 11-1 is as shown in equation (34).

The power supply 20 of this embodiment supplies a constant current I to the bridge circuit 1. The sensor output detection unit 21b detects the midpoint potential difference V(ω) of the bridge circuit 1 as a sensor output.

The angle calculation unit 22b calculates the angle ω of the magnetic field on the sensor surface 6 based on the midpoint potential difference V(ω). At this time, the angle calculation unit 22b calculates the angle ω of the magnetic field from the midpoint potential difference V(ω) using a preregistered approximation function that indicates the relationship between the midpoint potential difference V(ω) and the angle ω of the magnetic field. All you have to do is calculate.

The position calculation unit 23b calculates v using equation (31) based on the angle ω of the magnetic field, and calculates the position of the magnet 11-1 using equation (34) based on the calculated v and the known distances L _A and L _B. Calculate the x coordinate.

It is necessary for the magnets 11-1 and 11-2 to attract each other, but while the position of the magnet 11-2 is fixed, the position of the magnet 11-1 changes. There is a possibility that the magnet 11-2 will repel the magnet 11-2. Therefore, even if the position of the magnet 11-1 changes, the position of the magnetic poles is automatically changed so that the magnets 11-1 and 11-2 attract each other.

FIG. 13 shows a cross section of the magnets 11-1 and 11-2. Each of the magnets 11-1 and 11-2 is formed into a cylindrical shape, and two poles, an N pole and an S pole, are magnetized to face each other in the radial direction of the cylinder.
The housing cylinders 13-1 and 13-2 are made of a non-magnetic material that is not attracted to the magnets 11-1 and 11-2, and a magnetically permeable material that allows the lines of magnetic force of the magnets 11-1 and 11-2 to pass through (for example, synthetic resin). It is formed into a cylindrical shape with both ends closed. Magnets 11-1 and 11-2 are housed in the cylindrical internal spaces of the housing cylinders 13-1 and 13-2, respectively.

The inner diameters of the housing cylinders 13-1 and 13-2 are slightly larger than the outer diameters of the magnets 11-1 and 11-2. Further, the length of the internal space of the housing tubes 13-1 and 13-2 is slightly longer than the length of the magnets 11-1 and 11-2. With such a structure, the magnets 11-1 and 11-2 are allowed to freely rotate around their axes inside the housing tubes 13-1 and 13-2. The inner wall surfaces of the housing cylinders 13-1 and 13-2 may be subjected to surface treatment so as to exhibit smoothness between them and the magnets 11-1 and 11-2.

The magnets 11-1, 11-2 and the housing tubes 13-1, 13-2 are arranged so that the axial direction of the magnets 11-1, 11-2 is perpendicular to the direction of the orbit p of the magnet 11-1 (at the reference position). (parallel to the direction of θ ₀ ).

Even if the magnets 11-1 and 11-2 were to repel when the magnet 11-1 moved in a straight line, the magnets 11-1 and 11-2 would move in the housing tubes 13-1 and 13-, respectively. The different polarities of the magnets 11-1 and 11-2 attract each other. That is, the positions of the magnetic poles of the magnets 11-1 and 11-2 are automatically changed. Therefore, even if the position of the magnet 11-1 changes, the magnets 11-1 and 11-2 will not repel each other. The structure of the magnets 11-1 and 11-2 as described above is disclosed in Japanese Patent No. 3822062. Note that the magnets 11-1 and 11-2 do not need to have the same shape.

The angle calculation units 22, 22b and the position calculation units 23, 23a, 23b described in the first to third embodiments are composed of a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface with the outside. This can be realized by a program that controls hardware resources. An example of the configuration of this computer is shown in FIG. The computer includes a CPU 300, a storage device 301, and an interface device (I/F) 302. The hardware of the sensor output detection units 21 and 21b, etc. are connected to the I/F 302. The CPU 300 executes the processes described in the first to third embodiments according to the program stored in the storage device 301.

INDUSTRIAL APPLICATION This invention can be applied to the technique of detecting the position of the movable part which moves linearly.

1... Bridge circuit, 10-1 to 10-4... AMR element, 11, 11-1, 11-2... Magnet, 13-1, 13-2... Housing tube, 20... Power supply, 21, 21b... Sensor output detection 22, 22b... Angle calculation part, 23, 23a, 23b... Position calculation part.

Claims (7)

a sensor circuit including a magnetoresistive element;
a magnet configured to move linearly on a plane intersecting a sensor surface on which a thin film resistance pattern of the magnetoresistive element is formed;
a sensor output detection section configured to detect the output of the sensor circuit;
an angle calculation unit configured to calculate the angle of the magnetic field generated by the magnet based on the output of the sensor circuit;
A position sensor comprising: a position calculation unit configured to calculate coordinates of the magnet based on the angle of the magnetic field. The position sensor according to claim 1,
a reference position at which the output voltage of the sensor circuit is zero coincides with an intersection line between the plane and the sensor surface;
The magnet moves linearly on the plane in the direction of the intersection line,
The position sensor is characterized in that the position calculation unit calculates coordinates of the magnets in the intersecting direction based on the angle of the magnetic field. The position sensor according to claim 1,
A reference position at which the output voltage of the sensor circuit becomes zero is not on an intersection line between the plane and the sensor surface,
The magnet moves linearly on the plane in the direction of the intersection line,
The position calculation unit calculates coordinates of the magnet in the intersection line direction based on the angle of the magnetic field and the angle between the reference position on the sensor surface and the intersection line. position sensor. a sensor circuit including a magnetoresistive element;
a first magnet configured to move linearly on a trajectory on a plane parallel to a sensor surface on which a thin film resistance pattern of the magnetoresistive element is formed;
a second magnet disposed at a fixed position on the plane so as to face the first magnet with the sensor circuit in between;
a sensor output detection section configured to detect the output of the sensor circuit;
an angle calculation unit configured to calculate the angle of the magnetic field generated by the first and second magnets based on the output of the sensor circuit;
and a position calculation unit configured to calculate coordinates of the first magnet based on the angle of the magnetic field. The position sensor according to claim 4,
The first magnet moves linearly in a direction of the trajectory that intersects with a direction of a reference position where the output voltage of the sensor circuit is zero,
The position calculating unit calculates the position based on the distance from the sensor circuit to the intersection of the direction of the reference position and the trajectory, the distance from the sensor circuit to the second magnet, and the angle of the magnetic field. A position sensor that calculates the coordinates of the first magnet on the orbit. The position sensor according to claim 4 or 5,
The first and second columnar magnets have both magnetic poles magnetized so as to face each other in the radial direction, and are housed inside the housing tube in a state where free rotation around the axis is allowed. is arranged so as to be perpendicular to the direction of the orbit of the first magnet. The position sensor according to any one of claims 1 to 6,
The sensor circuit is a bridge circuit connecting the four magnetoresistive elements,
The position sensor, wherein the output of the sensor circuit detected by the sensor output detection section is a midpoint potential difference of the bridge circuit.

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