JP7351179B2 - position detection device - Google Patents

Description

The present invention relates to a magnetic position detection device equipped with a magnetic scale and a magnetic sensor.

A magnetic position detection device including a magnetic scale and a magnetic sensor is used, for example, to detect the position of a movable object whose position changes in a linear direction or a rotational direction. A position detection device used to detect the position of a movable object is configured such that the relative position of the magnetic scale with respect to the magnetic sensor changes within a predetermined range in response to changes in the position of the movable object. .

A magnetic scale includes, for example, a plurality of magnets arranged along a linear direction or a rotational direction. When the relative position of the magnetic scale with respect to the magnetic sensor changes, the direction of the magnetic field to be detected that is generated by the magnetic scale and applied to the magnetic sensor rotates. A magnetic sensor, for example, detects components of a magnetic field to be detected in two different directions, and generates two detection signals corresponding to the intensities of the components in the two directions. Based on the two detection signals, the magnetic sensor generates a detection value that corresponds to the relative position of the magnetic scale with respect to the magnetic sensor.

Patent Document 1 discloses a position detection system that includes a magnetic sensing element and a plurality of magnetic members arranged linearly with magnetic pole faces facing the magnetic sensing element, and detects the position of the magnetic sensing element with respect to the plurality of magnetic members. The equipment is described. Patent Document 2 discloses a magnetic encoder that detects the rotation angle of a magnetic drum, two pieces of which are arranged at opposing positions of about 180 degrees and facing a multipolar magnetized layer formed on the outer peripheral surface of the magnetic drum. A magnetic encoder with a magnetic sensor is described.

Patent Document 3 discloses a magnetic encoder that detects the rotational position of a rotating shaft to be detected, which includes first and second magnetic detection elements and third and fourth magnetic detection elements arranged along the circular outer peripheral surface of a multipolar magnet. A magnetic encoder is described in which magnetic detection elements are arranged at angular positions separated by 180 degrees in mechanical angle along the circumferential direction of a multipolar magnet. In this magnetic encoder, the sum signal or difference signal between the output signal of the first detection signal and the output signal of the third magnetic detection element, the output signal of the second detection signal and the output signal of the fourth magnetic detection element A signal representing the rotational position of the rotating shaft is generated based on the sum signal or difference signal.

Patent Document 4 describes a magnetic detection device that includes two Hall elements arranged side by side on the rotation axis of a detection magnet and a differential output circuit that differentially outputs detection signals from the two Hall elements. ing. This magnetic detection device cancels the offset voltage caused by the disturbance magnetic field by taking the difference between the two Hall voltages, and outputs a voltage with an output waveform that is substantially the same as when no disturbance magnetic field is applied.

Japanese Patent Application Publication No. 2011-137796 Japanese Patent Application Publication No. 2001-12967 International Publication No. 2008/136054 JP2006-250580A

In a magnetic position detection device, in addition to the magnetic field to be detected, a noise magnetic field other than the magnetic field to be detected may be applied to the magnetic sensor. Examples of noise magnetic fields include earth's magnetism and leakage magnetic fields from motors. When a noise magnetic field is applied to the magnetic sensor in this way, the magnetic sensor detects a composite magnetic field of the detection target magnetic field and the noise magnetic field. Therefore, when the direction of the magnetic field to be detected differs from the direction of the noise magnetic field, an error occurs in the detected value.

The position detection device described in Patent Document 1 and the magnetic encoder described in Patent Document 2 do not take noise magnetic fields into consideration. On the other hand, although the magnetic encoder described in Patent Document 3 and the magnetic detection device described in Patent Document 4 can reduce errors caused by noise magnetic fields, the position of the magnetic sensor is restricted.

The present invention has been made in view of such problems, and its purpose is to provide a position detection device that can reduce errors caused by noise magnetic fields without imposing major restrictions on the installation of magnetic sensors. It is in.

The position detection device of the present invention includes a magnetic scale that generates an external magnetic field whose intensity and direction have a spatial distribution, and a magnetic scale that detects a magnetic field to be detected that is a part of the external magnetic field and a noise magnetic field other than the magnetic field to be detected. This is a position detection device equipped with a sensor. The relative position of the magnetic scale to the magnetic sensor can be changed within a predetermined range along a moving direction that is a linear direction or a rotational direction. The direction of the magnetic field to be detected at an arbitrary position rotates around the arbitrary position as the relative position changes. The strength of the magnetic field to be detected changes depending on the distance from the magnetic scale.

The magnetic sensor includes a first detection section and a second detection section arranged to detect a first composite magnetic field that is a composite magnetic field of a detection target magnetic field of a first intensity and a noise magnetic field; The magnetic field includes a third detection section and a fourth detection section arranged to detect a second composite magnetic field that is a composite magnetic field of a detection target magnetic field having a second intensity different from the intensity and a noise magnetic field. . The first detection unit generates a first detection signal corresponding to the intensity of the component in the first direction of the first composite magnetic field. The second detection unit generates a second detection signal corresponding to the intensity of a component of the first composite magnetic field in a second direction different from the first direction. The third detection unit generates a third detection signal corresponding to the intensity of the component of the second composite magnetic field in the third direction. The fourth detection unit generates a fourth detection signal corresponding to the intensity of a component of the second composite magnetic field in a fourth direction different from the third direction.

The magnetic sensor further includes a first calculation circuit that generates a first calculation signal corresponding to the difference between the first detection signal and the third detection signal, and a second detection signal and a fourth detection signal. a second arithmetic circuit that generates a second post-computation signal corresponding to the difference between It includes an arithmetic circuit.

In the position detection device of the present invention, the angle formed by the direction of the magnetic field to be detected detected by the first detection unit with respect to the first direction, which is assumed when the direction of the magnetic field to be detected changes ideally, is 1, and when the angle that the direction of the magnetic field to be detected detected by the third detection section makes with respect to the third direction is the third angle, the first detection section and the third detection section are , the first angle and the third angle may be arranged to be equal to each other. Further, the angle that the direction of the detection target magnetic field detected by the second detection unit makes with respect to the second direction, which is assumed when the direction of the detection target magnetic field changes ideally, is defined as the second angle, and When the angle between the direction of the magnetic field to be detected detected by the fourth detecting section and the fourth direction is the fourth angle, the second detecting section and the fourth detecting section are arranged at the second angle. The fourth angles may be arranged to be equal to each other. The difference between the first angle and the second angle may be 90°, and the difference between the third angle and the fourth angle may be 90°.

Furthermore, in the position detection device of the present invention, the third direction may be the same direction as the first direction, and the fourth direction may be the same direction as the second direction.

Furthermore, in the position detection device of the present invention, the moving direction may be a linear direction. In this case, the first composite magnetic field may be a composite magnetic field of the detection target magnetic field and the noise magnetic field at the first detection position on a virtual straight line that intersects the magnetic scale and is orthogonal to the movement direction. Further, the second composite magnetic field may be a composite magnetic field of the detection target magnetic field and the noise magnetic field at a second detection position different from the first detection position on the virtual straight line.

Furthermore, in the position detection device of the present invention, the movement direction may be a rotation direction about a predetermined central axis. In this case, the first composite magnetic field detected by the first detection unit is a composite magnetic field of the detection target magnetic field and the noise magnetic field at the first detection position on the first imaginary straight line intersecting the central axis. Good too. Further, the first composite magnetic field detected by the second detection unit is the detection target magnetic field at a second detection position on a second imaginary straight line that intersects the central axis and is different from the first imaginary straight line. It may be a composite magnetic field with a noise magnetic field. Further, the second composite magnetic field detected by the third detection unit is a composite magnetic field of the detection target magnetic field and the noise magnetic field at a third detection position different from the first detection position on the first imaginary straight line. There may be. Further, the second composite magnetic field detected by the fourth detection unit is a composite magnetic field of the detection target magnetic field and the noise magnetic field at a fourth detection position different from the second detection position on the second imaginary straight line. There may be.

Further, the position detection device of the present invention may include a plurality of magnets arranged along the movement direction. The external magnetic field is a combination of magnetic fields generated by each of the plurality of magnets. The plurality of magnets may be spaced apart from each other. In this case, the magnetic scale may further include a yoke made of a magnetic material and magnetically connecting the plurality of magnets.

Further, in the position detection device of the present invention, each of the first to fourth detection sections may include at least one magnetoresistive element. Alternatively, each of the first to fourth detection sections may include at least one Hall element.

In the position detection device of the present invention, the first calculated signal corresponds to the difference between the first detection signal and the third detection signal, and the first calculated signal corresponds to the difference between the second detection signal and the fourth detection signal. Based on the second post-computation signal, a detected value having a correspondence relationship with the relative position is generated. In the present invention, there is a requirement that the first and second detection sections be arranged at positions where the magnetic field to be detected can detect the magnetic field whose intensity becomes the first intensity, and a detection whose intensity becomes the second intensity. Although it is necessary to satisfy the requirement that the third and fourth detection sections be placed in positions where they can detect the target magnetic field, these requirements place significant restrictions on the installation of the first to fourth detection sections. It is not something that causes it. Therefore, according to the present invention, it is possible to reduce the error caused by the noise magnetic field without imposing any major restrictions on the installation of the magnetic sensor.

1 is a perspective view showing a schematic configuration of a position detection device according to a first embodiment of the present invention. 1 is a front view showing a schematic configuration of a position detection device according to a first embodiment of the present invention. FIG. 3 is an explanatory diagram showing a reference direction and first to fourth directions in the first embodiment of the present invention. 1 is a block diagram showing the configuration of a magnetic sensor according to a first embodiment of the present invention. FIG. It is a circuit diagram showing an example of the composition of the 1st detection part in the 1st example of the magnetic sensor in the 1st embodiment of the present invention. It is a circuit diagram showing an example of the composition of the 2nd detection part in the 1st example of the magnetic sensor in the 1st embodiment of the present invention. FIG. 7 is a perspective view showing a part of one magnetoresistive element in FIGS. 5 and 6. FIG. It is a perspective view which shows the principal part of the electronic component in the 2nd example of the magnetic sensor in the 1st Embodiment of this invention. It is a circuit diagram showing an example of the composition of the 1st detection part in the 2nd example of the magnetic sensor in the 1st embodiment of the present invention. It is a circuit diagram showing an example of the composition of the 2nd detection part in the 2nd example of the magnetic sensor in the 1st embodiment of the present invention. FIG. 3 is a waveform diagram showing waveforms of first and second detection signals in a first simulation. FIG. 7 is a waveform diagram showing waveforms of third and fourth detection signals in the first simulation. FIG. 7 is a waveform diagram showing waveforms of first and second post-computation signals in the first simulation. FIG. 7 is a characteristic diagram showing detected values of a comparative example in the first simulation. FIG. 7 is a characteristic diagram showing errors in a comparative example in the first simulation. FIG. 3 is a characteristic diagram showing detected values of the example in the first simulation. It is a characteristic diagram showing the error of the example in the first simulation. It is a perspective view which shows the modification of the magnetic scale in the 1st Embodiment of this invention. FIG. 2 is a plan view showing a schematic configuration of a position detection device according to a second embodiment of the present invention. FIG. 7 is a characteristic diagram showing a fluctuation rate obtained by a second simulation. FIG. 7 is a characteristic diagram showing a fluctuation range obtained by a second simulation. FIG. 7 is a characteristic diagram showing the fluctuation rate obtained by a third simulation. It is a top view which shows the modification of the magnetic scale in the 2nd Embodiment of this invention.

[First embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, with reference to FIGS. 1 and 2, a schematic configuration of a position detection device according to a first embodiment of the present invention will be described. The position detection device 1 according to this embodiment includes a magnetic scale 2 and a magnetic sensor 3. The magnetic scale 2 generates an external magnetic field MF whose intensity and direction have a spatial distribution. The magnetic sensor 3 detects a detection target magnetic field that is a part of the external magnetic field MF and a noise magnetic field Mex other than the detection target magnetic field.

The relative position of the magnetic scale 2 to the magnetic sensor 3 can be changed within a predetermined range along a moving direction that is a linear direction or a rotational direction. Moreover, the magnetic scale 2 includes a plurality of magnets arranged along the moving direction. The plurality of magnets may be spaced apart from each other. Particularly in this embodiment, the magnetic scale 2 includes three magnets 4, 5, and 6 arranged at intervals from each other as a plurality of magnets. The external magnetic field MF is a combination of magnetic fields generated by each of the three magnets 4, 5, and 6.

Particularly in this embodiment, the magnetic scale 2 is a linear scale. The magnets 4, 5, and 6 are arranged in this order in one direction. The distance between the magnets 4 and 5 and the distance between the magnets 5 and 6 are equal to each other. The magnetic scale 2 further includes a yoke 7 made of a magnetic material such as NiFe. The yoke 7 magnetically connects the magnets 4, 5, and 6, and is used as a substrate that supports the magnets 4, 5, and 6. The yoke 7 has a plate shape that is long in one direction. Further, the yoke 7 has an upper surface 7a and a lower surface 7b. The magnets 4, 5, and 6 are arranged on the upper surface 7a of the yoke 7. The magnetic sensor 3 is arranged to face the upper surface 7a of the yoke 7.

The magnetic scale 2 further includes a protection part 8 made of a non-magnetic material such as resin and covering part of the magnets 4, 5, 6 and the yoke 7. Note that in FIG. 2, the protection part 8 is omitted.

Here, as shown in FIGS. 1 and 2, the X direction, Y direction, and Z direction are defined. In this embodiment, the direction perpendicular to the upper surface 7a of the yoke 7 and going from the lower surface 7b to the upper surface 7a is defined as the Z direction. Further, two directions perpendicular to the Z direction and mutually orthogonal are referred to as an X direction and a Y direction. In FIG. 2, the Y direction is shown as a direction from the front to the back in FIG. Further, the direction opposite to the X direction is defined as the -X direction, the direction opposite to the Y direction is defined as the -Y direction, and the direction opposite to the Z direction is defined as the -Z direction.

The three magnets 4, 5, and 6 are arranged in this order in the X direction. Moreover, each of the three magnets 4, 5, and 6 has an N pole and an S pole. In the magnets 4 and 6, the north pole and the south pole are arranged in this order in the -Z direction. In the magnet 5, the north pole and the south pole are arranged in this order in the Z direction. The yoke 7 magnetically connects the end face of the magnet 4 on the south pole side, the end face of the magnet 5 on the north pole side, and the end face of the magnet 6 on the south pole side. The yoke 7 controls the flow of magnetic flux so that the magnetic flux generated from the N-pole side end face of the magnet 5 efficiently flows into the S-pole side end face of the magnet 4 and the S-pole side end face of the magnet 6. It has the function of

The moving direction is a linear direction and parallel to the X direction. Hereinafter, the moving direction will be represented by the symbol X1. The relative position of the magnetic scale 2 with respect to the magnetic sensor 3 can be changed within a predetermined range along the moving direction X1. Hereinafter, the relative position of the magnetic scale 2 with respect to the magnetic sensor 3 will be simply referred to as a relative position. In this embodiment, one of the magnetic scale 2 and the magnetic sensor 3 moves linearly in the X direction or the -X direction in conjunction with a movable object (not shown). As a result, the relative position changes in the X direction or the -X direction. The direction of the magnetic field to be detected at an arbitrary position rotates around the arbitrary position as the relative position changes.

The position detection device 1 is a device for detecting relative positions. The magnetic sensor 3 generates a detected value that has a correspondence relationship with the relative position. Particularly in this embodiment, the magnetic sensor 3 generates, as a detection value, a value θs representing the angle that the direction of the detection target magnetic field at the reference position makes with respect to the reference direction DR within the reference plane. Hereinafter, the detected value will also be referred to as the detected value θs. The detected value θs has a corresponding relationship with the relative position.

In this embodiment, the range of the detected value θs may be a range in which the relative position can be uniquely specified. Such a range of the detected value θs is a range in which the detected value θs does not have the same value at a plurality of relative positions. This is, for example, a narrower range than 0° to 360°. In order to make the range of the detected value θs narrower than 0° to 360°, set a predetermined range in which the relative position can change (hereinafter referred to as the movable range) to 0° to 360° of the detected value θs. However, the range of the detected value θs actually generated by the magnetic sensor 3 is limited to a range narrower than 0° to 360°, and the relative position corresponding to the limited range of the detected value θs is defined as the corresponding range. Only the range may be a range of detectable relative positions. Alternatively, the movable range may be narrower than the range in which the detected value θs is from 0° to 360°. With these things, the relative position can be uniquely specified by the detected value θs.

The magnetic sensor 3 includes two electronic components 10 and 20. Further, the magnetic sensor 3 includes a first detection section 11 , a second detection section 12 , a third detection section 21 , and a fourth detection section 22 . The first detection section 11 and the second detection section 12 are included in the electronic component 10. The third detection section 21 and the fourth detection section 22 are included in the electronic component 20. The electronic components 10 and 20 are located apart from the magnetic scale 2 in the Z direction.

Here, as shown in FIG. 2, a virtual straight line L that intersects the magnetic scale 2 and is orthogonal to the moving direction X1 is assumed. The electronic components 10 and 20 are arranged at different positions on the imaginary straight line L. The electronic component 20 is placed farther from the magnetic scale 2 than the electronic component 10.

The intensity of the magnetic field to be detected changes depending on the distance from the magnetic scale 2. The first and second detection units 11 and 12 are arranged to detect a first composite magnetic field MF1 that is a composite magnetic field of the detection target magnetic field of the first intensity and the noise magnetic field Mex. The third and fourth detection units 21 and 22 are arranged to detect a second composite magnetic field MF2 that is a composite magnetic field of a detection target magnetic field having a second intensity different from the first intensity and the noise magnetic field Mex. has been done.

Particularly in this embodiment, the first composite magnetic field MF1 is a composite magnetic field of the detection target magnetic field and the noise magnetic field Mex at the first detection position P1 on the imaginary straight line L. The electronic component 10 is placed at the first detection position P1. Thereby, the first and second detection units 11 and 12 can detect the first composite magnetic field MF1. Similarly, the second composite magnetic field MF2 is a composite magnetic field of the detection target magnetic field and the noise magnetic field Mex at a second detection position P2 on the virtual straight line L, which is different from the first detection position P1. The electronic component 20 is placed at the second detection position P2. Thereby, the third and fourth detection sections 21 and 22 can detect the second composite magnetic field MF2.

As shown in FIG. 2, in this embodiment, the second detection position P2 is located farther from the magnetic scale 2 than the first detection position P1.

The direction and intensity of the noise magnetic field Mex at the second detection position P2 are respectively equal to the direction and intensity of the noise magnetic field Mex at the first detection position P1. The noise magnetic field Mex may be a magnetic field whose direction and intensity are constant over time, a magnetic field whose direction and intensity change periodically over time, or a magnetic field whose direction and intensity are constant over time. It may also be a magnetic field that changes randomly.

Hereinafter, the magnetic field to be detected at the first detection position P1 will be referred to as a first partial magnetic field MFa, and the magnetic field to be detected at the second detection position P2 will be referred to as a second partial magnetic field MFb. The intensity of the first partial magnetic field MFa is a first intensity, and the intensity of the second partial magnetic field MFb is a second intensity. The directions of the first and second partial magnetic fields MFa, MFb change according to changes in relative position.

Here, assume that the direction of the magnetic field to be detected changes ideally. A case where the direction of the magnetic field to be detected changes ideally means that the relationship between the change in relative position and the change in the angle that the direction of the magnetic field to be detected at any position makes with respect to a predetermined direction satisfies linearity. This is the case when they are in a relationship. Hereinafter, a case where the direction of the magnetic field to be detected changes ideally will be referred to as an ideal state. The direction of the first partial magnetic field MFa and the direction of the second partial magnetic field MFb, which are assumed in an ideal state, coincide with each other.

The first composite magnetic field MF1 is a composite magnetic field of the first partial magnetic field MFa and the noise magnetic field Mex. The first detection unit 11 detects the first composite magnetic field MF1 and generates a first detection signal S1 corresponding to the intensity of the component in the first direction D1 of the first composite magnetic field MF1. The second detection unit 12 detects the first composite magnetic field MF1 and performs a second detection corresponding to the intensity of a component in a second direction D2 different from the first direction D1 of the first composite magnetic field MF1. Generate signal S2. The first direction D1 is a reference direction in which the first detection unit 11 generates the first detection signal S1. The second direction D2 is a reference direction in which the second detection unit 12 generates the second detection signal S2.

The second composite magnetic field MF2 is a composite magnetic field of the second partial magnetic field MFb and the noise magnetic field Mex. The third detection unit 21 detects the second composite magnetic field MF2 and generates a third detection signal S3 corresponding to the intensity of the component in the third direction D3 of the second composite magnetic field MF2. The fourth detection unit 22 detects the second composite magnetic field MF2 and performs a fourth detection corresponding to the intensity of a component in a fourth direction D4 different from the third direction D3 of the second composite magnetic field MF2. A signal S4 is generated. The third direction D3 is a reference direction in which the third detection section 21 generates the third detection signal S3. The fourth direction D4 is a reference direction in which the fourth detection section 22 generates the fourth detection signal S4.

Here, the angle that the direction of the first partial magnetic field MFa detected by the first detection unit 11 makes with respect to the first direction D1, which is assumed in an ideal state, is called a first angle and is represented by the symbol θ1. . Further, the angle that the direction of the first partial magnetic field MFa detected by the second detection unit 12 makes with respect to the second direction D2, which is assumed in an ideal state, is referred to as a second angle, and is represented by the symbol θ2. Further, the angle that the direction of the second partial magnetic field MFb detected by the third detection unit 21 makes with respect to the third direction D3, which is assumed in an ideal state, is called a third angle and is represented by the symbol θ3. Further, the angle that the direction of the second partial magnetic field MFb detected by the fourth detection unit 22 makes with respect to the fourth direction D4, which is assumed in an ideal state, is called a fourth angle and is represented by the symbol θ4. The first detection section 11 and the third detection section 21 are arranged so that the first angle θ1 and the third angle θ3 are equal to each other. The second detection section 12 and the fourth detection section 22 are arranged so that the second angle θ2 and the fourth angle θ4 are equal to each other.

FIG. 3 is an explanatory diagram showing the reference direction DR and the first to fourth directions D1 to D4 in this embodiment. The reference direction DR is located within the reference plane P. In this embodiment, in particular, the Z direction is set as the reference direction DR. The reference plane P is an XZ plane that intersects the magnetic scale 2. Within this reference plane P, the first partial magnetic field MFa rotates around the first detection position P1, and the second partial magnetic field MFb rotates around the second detection position P2. In the following description, the directions of the first and second partial magnetic fields MFa and MFb refer to directions located within the reference plane P.

FIG. 3 shows the first and second partial magnetic fields MFa, MFb and the first to fourth angles θ1 to θ4 assumed in an ideal state. In FIG. 3, the length of the arrow labeled MFa schematically represents the intensity of the first partial magnetic field MFa, that is, the first intensity. Further, the length of the arrow labeled MFb schematically represents the intensity of the second partial magnetic field MFb, that is, the second intensity. As shown in FIG. 3, the second intensity is smaller than the first intensity.

In an ideal state, the angle that the direction of the first partial magnetic field MFa makes with the reference direction DR and the angle that the direction of the second partial magnetic field MFb makes with the reference direction DR are equal to each other. Hereinafter, these angles will be represented by the symbol θ. The angle θ is expressed as a positive value when viewed clockwise from the reference direction DR, and is expressed as a negative value when viewed counterclockwise from the reference direction DR.

The reference position is located within the reference plane P. In the following description, it is assumed that the directions of the first and second partial magnetic fields MFa and MFb assumed in the ideal state match the direction of the magnetic field to be detected at the reference position assumed in the ideal state. As long as this requirement is met, the reference position may coincide with the first detection position P1, the second detection position P2, or any position different from these positions. There may be. The angle that the direction of the magnetic field to be detected at the reference position assumed in the ideal state makes with respect to the reference direction DR is equal to the angle θ.

In this embodiment, the first direction D1 and the third direction D3 are the X direction, and the second direction D2 and the fourth direction D4 are the Z direction. That is, in this embodiment, the third direction D3 is the same direction as the first direction D1, and the fourth direction D4 is the same direction as the second direction D2.

As described above, the first angle θ1 and the third angle θ3 are equal to each other, and the second angle θ2 and the fourth angle θ4 are equal to each other. Further, the difference between the first angle θ1 and the second angle θ2 is 90°, and the difference between the third angle θ3 and the fourth angle θ4 is 90°. The definitions of positive and negative of the first to fourth angles θ1 to θ4 are the same as the angle θ. As shown in FIG. 3, the second and fourth angles θ2 and θ4 are equal to the angle θ.

Next, the configuration of the magnetic sensor 3 will be described in detail with reference to FIG. 4. FIG. 4 is a block diagram showing the configuration of the magnetic sensor 3. As shown in FIG. As described above, the magnetic sensor 3 includes the first to fourth detection sections 11, 12, 21, and 22. The magnetic sensor 3 further includes analog-to-digital converters (hereinafter referred to as A/D converters) 31, 32, 33, and 34. The A/D converter 31 converts the first detection signal S1 into a digital signal. The A/D converter 32 converts the second detection signal S2 into a digital signal. The A/D converter 33 converts the third detection signal S3 into a digital signal. The A/D converter 34 converts the fourth detection signal S4 into a digital signal.

The magnetic sensor 3 further includes a first arithmetic circuit 35, a second arithmetic circuit 36, and a third arithmetic circuit 37. The first to third arithmetic circuits 35 to 37 can be realized by, for example, an application specific integrated circuit (ASIC) or a microcomputer. The first to third arithmetic circuits 35 to 37 may be functional blocks or may be physically separate circuits.

The first arithmetic circuit 35 outputs a first detection signal S1 converted into a digital signal by the A/D converter 31 and a third detection signal S3 converted into a digital signal by the A/D converter 33. A first post-operation signal Sa corresponding to the difference S1-S3 is generated. The first calculated signal Sa may be the difference S1-S3 itself, or may be the difference S1-S3 plus predetermined corrections such as gain adjustment and offset adjustment.

The second arithmetic circuit 36 outputs a second detection signal S2 converted into a digital signal by the A/D converter 32 and a fourth detection signal S4 converted into a digital signal by the A/D converter 34. A second post-operation signal Sb corresponding to the difference S2-S4 is generated. The second post-computation signal Sb may be the difference S2-S4 itself, or may be the difference S2-S4 plus predetermined corrections such as gain adjustment and offset adjustment.

The third arithmetic circuit 37 generates the detected value θs based on the first and second post-arithmetic signals Sa and Sb. Specifically, the third arithmetic circuit 37 calculates θs using the following equation (1), for example. Note that "atan" represents arctangent.

θs=atan(Sa/Sb)...(1)

Within the range of θs from 0° to less than 360°, the solution of θs in equation (1) has two values that differ by 180°. However, depending on the positive/negative combination of Sa and Sb, it is possible to determine which of the two solutions of θs in equation (1) the true value of θs is. The third arithmetic circuit 37 determines θs within a range of 0° or more and less than 360° by using equation (1) and determining the positive/negative combination of Sa and Sb.

Next, first and second examples of the magnetic sensor 3 will be described. First, a first example of the magnetic sensor 3 will be described. In the first example, each of the first to fourth detection units 11, 12, 21, 22 includes at least one magnetoresistive element. Hereinafter, the magnetoresistive element will be referred to as an MR element.

FIG. 5 shows an example of a specific configuration of the first detection unit 11 in the first example. In this example, the first detection unit 11 includes two MR elements R11 and R12, a power supply port V11, a ground port G11, and an output port E11. One end of the MR element R11 is connected to the power supply port V11. The other end of MR element R11 is connected to one end of MR element R12 and output port E11. The other end of the MR element R12 is connected to the ground port G11. A power supply voltage of a predetermined magnitude is applied to the power supply port V11. Ground port G11 is connected to ground. Output port E11 outputs a signal corresponding to the potential at the connection point of MR elements R11 and R12.

In the first example, the configuration of the third detection section 21 is the same as the configuration of the first detection section 11. Therefore, in the following description, the same reference numerals as the components of the first detection section 11 are used for the components of the third detection section 21.

FIG. 6 shows an example of a specific configuration of the second detection unit 12 in the first example. In this example, the second detection unit 12 includes two MR elements R21 and R22, a power supply port V12, a ground port G12, and an output port E12. One end of the MR element R21 is connected to the power supply port V12. The other end of MR element R21 is connected to one end of MR element R22 and output port E12. The other end of the MR element R22 is connected to the ground port G12. A power supply voltage of a predetermined magnitude is applied to the power supply port V12. Ground port G12 is connected to ground. Output port E12 outputs a signal corresponding to the potential at the connection point of MR elements R21 and R22.

In the first example, the configuration of the fourth detector 22 is the same as the configuration of the second detector 12. Therefore, in the following description, the same reference numerals as the components of the second detection section 12 are used for the components of the fourth detection section 22.

The MR element is, for example, a spin valve type MR element. A spin valve type MR element consists of a magnetization fixed layer whose magnetization direction is fixed, a free layer which is a magnetic layer whose direction of magnetization changes depending on the direction of the magnetic field to be detected, and a structure between the magnetization fixed layer and the free layer. and a non-magnetic layer arranged thereon. The spin valve type MR element may be a TMR element or a GMR element. In a TMR element, the nonmagnetic layer is a tunnel barrier layer. In a GMR element, the nonmagnetic layer is a nonmagnetic conductive layer. In a spin-valve type MR element, the resistance value changes depending on the angle that the direction of magnetization of the free layer makes with the direction of magnetization of the fixed magnetization layer, and when this angle is 0°, the resistance value is the minimum value. , the resistance value reaches its maximum value when the angle is 180°. The arrows drawn on the MR elements R11, R12, R21, and R22 in FIGS. 5 and 6 each represent the direction of magnetization of the magnetization fixed layer included therein.

In the first detection unit 11, the magnetization direction of the magnetization fixed layer of the MR element R11 is the first direction D1 (X direction), and the magnetization direction of the magnetization fixed layer of the MR element R12 is the first direction D1. is in the opposite direction. In this case, the potential at the connection point between the MR elements R11 and R12 changes depending on the intensity of the component of the first composite magnetic field MF1 in the first direction D1. Therefore, the first detection unit 11 detects the component of the first composite magnetic field MF1 in the first direction D1, and outputs a signal corresponding to the intensity as the first detection signal S1.

In the second detection unit 12, the magnetization direction of the magnetization fixed layer of the MR element R21 is the second direction D2 (Z direction), and the magnetization direction of the magnetization fixed layer of the MR element R22 is the second direction D2. is in the opposite direction. In this case, the potential at the connection point between the MR elements R21 and R22 changes depending on the intensity of the component of the first composite magnetic field MF1 in the second direction D2. Therefore, the second detection unit 12 detects the component of the first composite magnetic field MF1 in the second direction D2, and outputs a signal corresponding to the intensity as the second detection signal S2.

In the third detection unit 21, the magnetization direction of the magnetization fixed layer of the MR element R11 is the third direction D3 (X direction), and the magnetization direction of the magnetization fixed layer of the MR element R12 is the third direction D3. is in the opposite direction. In this case, the potential at the connection point between the MR elements R11 and R12 changes depending on the intensity of the component in the third direction D3 of the second composite magnetic field MF2. Therefore, the third detection unit 21 detects the component of the second composite magnetic field MF2 in the third direction D3, and outputs a signal corresponding to the intensity as the third detection signal S3.

In the fourth detection unit 22, the magnetization direction of the magnetization fixed layer of the MR element R21 is the fourth direction D4 (Z direction), and the magnetization direction of the magnetization fixed layer of the MR element R22 is the fourth direction D4. is in the opposite direction. In this case, the potential at the connection point between the MR elements R21 and R22 changes depending on the intensity of the component in the fourth direction D4 of the second composite magnetic field MF2. Therefore, the fourth detection unit 22 detects the component of the second composite magnetic field MF2 in the fourth direction D4, and outputs a signal corresponding to the intensity as the fourth detection signal S4.

The direction of magnetization of the magnetization fixed layer in the plurality of MR elements in the detection units 11, 12, 21, and 22 may be slightly deviated from the above-mentioned direction from the viewpoint of precision in manufacturing the MR elements.

Note that, as described above, in order for the first to fourth detection signals S1 to S4 to represent the strength of the component in one direction of the magnetic field to be detected, the resistance value of the MR element is The magnetic field MF1 and MF2 must not be saturated within the strength range of the combined magnetic fields MF1 and MF2, and the relationship between the change in the strength of the component in one direction of the magnetic field to be detected and the change in the resistance value of the MR element satisfies the relationship of linearity. is necessary. In order to satisfy the above requirements, an MR element of a type that detects the intensity of a component of a magnetic field in one direction may be used as the MR elements R11, R12, R21, and R22. In this type of MR element, for example, by making the planar shape of the MR element approximately rectangular, the direction of magnetization of the free layer of the MR element remains substantially constant in response to changes in the intensity of a component in one direction of the magnetic field. It is configured to change with speed.

Here, an example of the configuration of the MR element will be described with reference to FIG. 7. FIG. 7 is a perspective view showing a part of one MR element in the detection sections 11 and 12 shown in FIGS. 5 and 6. In this example, one magnetic sensing element has a plurality of lower electrodes 62, a plurality of MR films 50, and a plurality of upper electrodes 63. A plurality of lower electrodes 62 are arranged on a substrate (not shown). Each lower electrode 62 has an elongated shape. A gap is formed between two lower electrodes 62 that are adjacent to each other in the longitudinal direction of the lower electrodes 62 . As shown in FIG. 7, MR films 50 are arranged on the upper surface of the lower electrode 62 near both ends in the longitudinal direction. The MR film 50 includes a free layer 51, a nonmagnetic layer 52, a magnetization fixed layer 53, and an antiferromagnetic layer 54, which are laminated in order from the lower electrode 62 side. Free layer 51 is electrically connected to lower electrode 62 . The antiferromagnetic layer 54 is made of an antiferromagnetic material, causes exchange coupling with the magnetization fixed layer 53, and fixes the direction of magnetization of the magnetization fixed layer 53. The plurality of upper electrodes 63 are arranged on the plurality of MR films 50. Each upper electrode 63 has an elongated shape and is disposed on two lower electrodes 62 adjacent to each other in the longitudinal direction of the lower electrode 62 to electrically connect the antiferromagnetic layers 54 of two adjacent MR films 50 to each other. do. With this configuration, the MR element shown in FIG. 7 has a plurality of MR films 50 connected in series by a plurality of lower electrodes 62 and a plurality of upper electrodes 63. Note that the arrangement of the layers 51 to 54 in the MR film 50 may be vertically reversed from the arrangement shown in FIG.

Next, a second example of the magnetic sensor 3 will be explained. In the second example, each of the first to fourth detection units 11, 12, 21, 22 includes at least one Hall element.

FIG. 8 is a perspective view showing the main parts of the electronic component 10 in the second example. In the second example, the first detector 11 includes a first Hall element H1 and a third Hall element H3, and the second detector 12 includes a second Hall element H2 and a fourth Hall element H3. and element H4. The electronic component 10 further includes a substrate 41 made of a non-magnetic material and having an upper surface 41a, and a yoke 42 made of a magnetic material. The upper surface 41a is parallel to the XZ plane.

The first to fourth Hall elements H1 to H4 are embedded in the substrate 41 in the vicinity of the upper surface 41a in such a manner that their magnetically sensitive surfaces are parallel to the upper surface 41a. The first and third Hall elements H1 and H3 are arranged so as to be lined up in the X direction. The second and fourth Hall elements H2 and H4 are arranged side by side in the Z direction.

The yoke 42 has a disk shape. The yoke 42 is arranged on the upper surface 41a of the substrate 41 so as to straddle a portion of each of the first to fourth Hall elements H1 to H4. The first Hall element H1 is located near the end of the yoke 42 in the -X direction. The second Hall element H2 is located near the end of the yoke 42 in the −Z direction. The third Hall element H3 is located near the end of the yoke 42 in the X direction. The fourth Hall element H4 is located near the end of the yoke 42 in the Z direction.

FIG. 9 shows an example of a specific configuration of the first detection unit 11 in the second example. FIG. 10 shows an example of a specific configuration of the second detection unit 12 in the second example. As shown in FIG. 9, the first detection unit 11 further includes a power supply port V21, a ground port G21, two output ports E21 and E22, and a difference detector 13. As shown in FIG. 10, the second detection unit 12 further includes a power supply port V22, a ground port G22, two output ports E23 and E24, and a difference detector 23. As shown in FIGS. 9 and 10, each of the first to fourth Hall elements H1 to H4 has a power supply terminal Ha, a ground terminal Hc, and two output terminals Hb and Hd.

In the first detection unit 11, the power terminals Ha of the first and third Hall elements H1 and H3 are connected to the power supply port V21. The ground terminals Hc of the first and third Hall elements H1 and H3 and the output terminals Hd of the first and third Hall elements H1 and H3 are connected to the ground port G21. The output terminal Hb of the first Hall element H1 is connected to the output port E21. The output terminal Hb of the third Hall element H3 is connected to the output port E22. A power supply voltage of a predetermined magnitude is applied to the power supply port V21. Ground port G21 is connected to ground.

In the second detection unit 12, the power terminals Ha of the second and fourth Hall elements H2 and H4 are connected to the power port V22. The ground terminals Hc of the second and fourth Hall elements H2 and H4 and the output terminals Hd of the second and fourth Hall elements H2 and H4 are connected to the ground port G22. The output terminal Hb of the second Hall element H2 is connected to the output port E23. The output terminal Hb of the fourth Hall element H4 is connected to the output port E24. A power supply voltage of a predetermined magnitude is applied to the power supply port V22. Ground port G22 is connected to ground.

In the electronic component 10, the yoke 42 receives the first composite magnetic field MF1 and generates an output magnetic field. The output magnetic field is an output magnetic field component in a direction parallel to the Y direction, and includes an output magnetic field component that changes according to the first composite magnetic field MF1. Specifically, when receiving the X-direction component of the first composite magnetic field MF1, the yoke 42 generates an output magnetic field component in the -Y direction near the first Hall element H1, and generates an output magnetic field component in the -Y direction near the first Hall element H1. An output magnetic field component in the Y direction is generated near the Hall element H3. When the yoke 42 receives the -X direction component of the first composite magnetic field MF1, the direction of the output magnetic field component is opposite to the direction when the yoke 42 receives the X direction component of the first composite magnetic field MF1. become.

In the first detection unit 11, the first and third Hall elements H1 and H3 detect output magnetic field components in the Y direction or -Y direction generated in the vicinity of the first and third Hall elements H1 and H3. By this, the component of the first composite magnetic field MF1 in the X direction or the −X direction is detected. The potential difference between the output ports E21 and E22 changes depending on the intensity of the component of the first composite magnetic field MF1 in the X direction, that is, the first direction D1. The difference detector 13 converts a signal corresponding to the potential difference between the output ports E21 and E22, that is, a signal corresponding to the intensity of the component in the first direction D1 (X direction) of the first composite magnetic field MF1, into a first detection signal. Output as S1.

Furthermore, in the electronic component 10, when the yoke 42 receives the Z-direction component of the first composite magnetic field MF1 , it generates an output magnetic field component in the -Y direction near the second Hall element H2, and An output magnetic field component in the Y direction is generated near Hall element H4 of No. 4. When the yoke 42 receives the -Z direction component of the first composite magnetic field MF1 , the direction of the output magnetic field component is opposite to the direction when the yoke 42 receives the Z direction component of the first composite magnetic field MF1. become.

In the second detection unit 12, the second and fourth Hall elements H2 and H4 detect output magnetic field components in the Y direction or -Y direction generated in the vicinity of the second and fourth Hall elements H2 and H4. As a result, the Z-direction or -Z-direction component of the first composite magnetic field MF1 is detected. The potential difference between the output ports E23 and E24 changes depending on the intensity of the component of the first composite magnetic field MF1 in the Z direction, that is, in the second direction D2. The difference detector 23 converts a signal corresponding to the potential difference between the output ports E23 and E24, that is, a signal corresponding to the intensity of the component in the second direction D2 (Z direction) of the first composite magnetic field MF1, into a second detection signal. Output as S2.

The configurations of the electronic component 20 and the third and fourth detectors 21 and 22 in the second example are the same as the configurations of the electronic component 10 and the first and second detectors 11 and 12 shown in FIGS. 8 to 10. It's the same. Therefore, in the following description, the same reference numerals as those of the electronic component 10 and the first and second detection sections 11 and 12 are used for the components of the electronic component 20 and the third and fourth detection sections 21 and 22. .

In the electronic component 20, the yoke 42 receives the second composite magnetic field MF2 and generates an output magnetic field. The output magnetic field is an output magnetic field component in a direction parallel to the Y direction, and includes an output magnetic field component that changes according to the second composite magnetic field MF2. Specifically, when receiving the X-direction component of the second composite magnetic field MF2, the yoke 42 generates an output magnetic field component in the -Y direction near the first Hall element H1, and generates an output magnetic field component in the -Y direction near the first Hall element H1. An output magnetic field component in the Y direction is generated near the Hall element H3. When the yoke 42 receives the -X direction component of the second composite magnetic field MF2, the direction of the output magnetic field component is opposite to the direction when the yoke 42 receives the X direction component of the second composite magnetic field MF2. become.

In the third detection unit 21, the first and third Hall elements H1 and H3 detect output magnetic field components in the Y direction or -Y direction generated in the vicinity of the first and third Hall elements H1 and H3. By this, the component of the second composite magnetic field MF2 in the X direction or the -X direction is detected. The potential difference between the output ports E21 and E22 changes depending on the intensity of the component of the second composite magnetic field MF2 in the X direction, that is, the third direction D3. The difference detector 13 converts a signal corresponding to the potential difference between the output ports E21 and E22, that is, a signal corresponding to the intensity of the component in the third direction D3 (X direction) of the second composite magnetic field MF2, into a third detection signal. Output as S3.

Further, in the electronic component 20, when the yoke 42 receives the Z-direction component of the second composite magnetic field MF2 , it generates an output magnetic field component in the −Y direction near the second Hall element H2, and An output magnetic field component in the Y direction is generated near Hall element H4 of No. 4. When the yoke 42 receives the -Z direction component of the second composite magnetic field MF2 , the direction of the output magnetic field component is opposite to the direction when the yoke 42 receives the Z direction component of the second composite magnetic field MF2. become.

In the fourth detection unit 22, the second and fourth Hall elements H2 and H4 detect output magnetic field components in the Y direction or -Y direction generated in the vicinity of the second and fourth Hall elements H2 and H4. As a result, the Z-direction or -Z-direction component of the second composite magnetic field MF2 is detected. The potential difference between the output ports E23 and E24 changes depending on the intensity of the component of the second composite magnetic field MF2 in the Z direction, that is, in the fourth direction D4. The difference detector 23 converts a signal corresponding to the potential difference between the output ports E23 and E24, that is, a signal corresponding to the intensity of the component in the fourth direction D4 (Z direction) of the second composite magnetic field MF2, into a second detection signal. Output as S2.

Next, the functions and effects of the position detection device 1 according to this embodiment will be explained. In the present embodiment, the first detection unit 11 generates the first detection signal S1 corresponding to the intensity of the component in the first direction D1, that is, the X direction, of the first composite magnetic field MF1, and The section 12 generates a second detection signal S2 corresponding to the intensity of the component in the second direction D2, that is, the Z direction, of the first composite magnetic field MF1, and the third detection section 21 generates a second detection signal S2 corresponding to the intensity of the component in the second direction D2, that is, the Z direction, of the first composite magnetic field MF1. The fourth detection unit 22 generates a third detection signal S3 corresponding to the intensity of the component in the third direction D3 of the second composite magnetic field MF2, that is, the X direction, and generates the third detection signal S3 corresponding to the intensity of the component in the third direction D3, that is, the A fourth detection signal S4 corresponding to the intensity of the component is generated. Then, a first calculated signal Sa corresponding to the difference between the first detection signal S1 and the third detection signal S3 is generated, and a first calculated signal Sa corresponding to the difference between the second detection signal S2 and the fourth detection signal S4 is generated. A second calculated signal Sb is generated, and a detected value θs is generated based on the first and second calculated signals Sa and Sb.

According to the present embodiment, the first calculated signal Sa corresponding to the difference between the first detection signal S1 and the third detection signal S3 is generated, and the second detection signal S2 and the fourth detection signal By generating the second post-calculation signal Sb corresponding to the difference from S4, it is possible to reduce errors caused by the noise magnetic field Mex. The reason for this will be explained in detail below.

The strength of the first composite magnetic field MF1 is B1, the strength of the second composite magnetic field MF2 is B2, the strength of the first partial magnetic field MFa is Ba, the strength of the second partial magnetic field MFb is Bb, and the noise magnetic field The intensity of Mex is Bex, and the angle that the direction of the noise magnetic field Mex at the first detection position P1 makes with respect to the reference direction DR (the angle that the direction of the noise magnetic field Mex at the second detection position P2 makes with respect to the reference direction DR) ) is denoted by the symbol θex. The intensity B1 of the component in the first direction D1 of the first composite magnetic field MF1 and the intensity B2 of the component in the second direction D2 of the first composite magnetic field MF1, which are assumed in an ideal state, are calculated using the angle θ. , can be expressed by the following equations (2) and (3), respectively.

B1=Ba・sinθ+Bex・sinθex…(2)
B2=Ba・cosθ+Bex・cosθex…(3)

In equation (2), Bex·sinθex represents the intensity of the component of the noise magnetic field Mex in the X direction. Furthermore, in equation (3), Bex·cosθex represents the strength of the Z-direction component of the noise magnetic field Mex.

Similarly, the intensity B3 of the component in the third direction D3 of the second composite magnetic field MF2 and the intensity B4 of the component in the fourth direction D4 of the second composite magnetic field MF2, which are assumed in an ideal state, are at an angle θ can be expressed by the following equations (4) and (5), respectively.

B3=Bb・sinθ+Bex・sinθex…(4)
B4=Bb・cosθ+Bex・cosθex…(5)

Hereinafter, the first detection signal S1 is defined as the product A·B1 of the intensity B1 and an arbitrary constant A, the second detection signal S2 is defined as the product A·B2 of the intensity B2 and the constant A, and the third detection signal S3 is the product A·B3 of the intensity B3 and the constant A, and the fourth detection signal S4 is the product A·B4 of the intensity B4 and the constant A. If the first calculated signal Sa is the difference S1-S3 between the first detection signal S1 and the third detection signal S3, then the first calculated signal Sa is expressed by the following equation (6). Ru.

Sa=A・B1−A・B3
=A(Ba・sinθ+Bex・sinθex)
-A (Bb・sinθ+Bex・sinθex)
=A(Ba-Bb)sinθ...(6)

Further, if the second calculated signal Sb is the difference S2-S4 between the second detection signal S2 and the fourth detection signal S4, then the second calculated signal Sb is calculated by the following equation (7). expressed.

Sb=A・B2−A・B4
=A(Ba・cosθ+Bex・cosθex)
-A (Bb・cosθ+Bex・cosθex)
=A(Ba-Bb)cosθ...(7)

As shown in equation (6), when the difference between the first detection signal S1 and the third detection signal S3 is calculated, Bex·sin θex is canceled out, and a signal that does not depend on the noise magnetic field Mex is obtained. Furthermore, as shown in equation (7), when the difference between the second detection signal S2 and the fourth detection signal S4 is calculated, Bex・cosθex are canceled out, and a signal that does not depend on the noise magnetic field Mex is obtained. . By substituting equations (6) and (7) into equation (1), the following equation (8) is obtained.

θs=atan(Sa/Sb)
= atan ((A(Ba-Bb) sin θ)/(A(Ba-Bb) cos θ))
=atan(sinθ/cosθ)
=θ...(8)

As shown in equation (8), the detected value θs is theoretically equal to the angle θ, that is, the angle that the direction of the detection target magnetic field at the reference position makes with respect to the reference direction DR, which is assumed in an ideal state. As understood from equations (6) to (8), according to the present embodiment, the first calculated signal Sa corresponding to the difference between the first detection signal S1 and the third detection signal S3 is and reduce the error caused by the noise magnetic field Mex of the detected value θs by generating a second calculated signal Sb corresponding to the difference between the second detection signal S2 and the fourth detection signal S4. I can do it.

In addition, in order to reduce the error caused by the noise magnetic field Mex as described above, a magnetic field to be detected at a position where the intensity becomes the first intensity, that is, a position where the first partial magnetic field MFa can be detected, The first requirement is to arrange the first and second detection units 11 and 12, and the magnetic field to be detected at the position where the intensity becomes the second intensity, that is, the second partial magnetic field MFb can be detected. , it is necessary to satisfy the second requirement of arranging the third and fourth detection sections 21 and 22. In other words, the first to fourth detection units 11, 12, 21, 22 can be placed at any position as long as the first and second requirements are met. For example, in the present embodiment, the electronic component 20 that includes the third and fourth detection sections 21 and 22 is placed on the magnetic scale 2 from the electronic component 10 that includes the first and second detection sections 11 and 12. It is located further away. As long as the first and second requirements are satisfied, the electronic component 10 and the electronic component 20 may be placed at the same position in the Y direction, or may be placed at different positions in the Y direction.

Further, as long as the first and second requirements are satisfied, the electronic component 10 and the electronic component 20 may be arranged at the same position in the X direction, or may be arranged at different positions in the X direction. In the latter case, at least one of the first detection signal S1 and the third detection signal S3 may be corrected so that the phase difference between the first detection signal S1 and the third detection signal S3 becomes 0, At least one of the second detection signal S2 and the fourth detection signal S4 may be corrected so that the phase difference between the second detection signal S2 and the fourth detection signal S4 becomes zero. In the latter case, especially when each of the first to fourth detection units 11, 12, 21, 22 includes at least one MR element, the first detection signal S1 and the third The direction of magnetization of the magnetization fixed layer of the MR element included in the first detection section 11 and the magnetization direction of the magnetization fixed layer of the MR element included in the third detection section 21 are adjusted so that the phase difference of the detection signal S3 becomes 0. At least one of the directions may be shifted from the direction shown in FIG. At least one of the direction of magnetization of the fixed magnetization layer of the MR element included in the fourth detecting section 22 and the direction of magnetization of the fixed magnetization layer of the MR element included in the fourth detection section 22 may be shifted from the direction shown in FIG.

Further, the first detection section 11 and the second detection section 12 may be included in two different physically separated electronic components instead of the electronic component 10. In this case, the electronic component including the first detection section 11 and the electronic component including the second detection section 12 may be placed at the same position in the X direction, or may be placed at different positions in the X direction. You can leave it there. In the latter case, at least one of the first detection signal S1 and the second detection signal S2 may be corrected so that the phase difference between the first detection signal S1 and the second detection signal S2 is 90°. . In the latter case, especially when each of the first and second detection units 11 and 12 includes at least one MR element, the difference between the first detection signal S1 and the second detection signal S2 The direction of magnetization of the fixed magnetization layer of the MR element included in the first detection section 11 and the direction of magnetization of the fixed magnetization layer of the MR element included in the second detection section 12 are adjusted so that the phase difference is 90°. At least one of them may be shifted from the direction shown in FIGS. 5 and 6.

Similarly, the third detection section 21 and the fourth detection section 22 may be included in two different physically separated electronic components instead of the electronic component 20. In this case, the electronic component including the third detection section 21 and the electronic component including the fourth detection section 22 may be placed at the same position in the X direction, or may be placed at different positions in the X direction. You can leave it there. In the latter case, at least one of the third detection signal S3 and the fourth detection signal S4 may be corrected so that the phase difference between the third detection signal S3 and the fourth detection signal S4 is 90°. . In the latter case, especially when each of the third and fourth detection units 21 and 22 includes at least one MR element, the difference between the third detection signal S3 and the fourth detection signal S4 The direction of magnetization of the fixed magnetization layer of the MR element included in the third detection section 21 and the direction of magnetization of the fixed magnetization layer of the MR element included in the fourth detection section 22 are adjusted so that the phase difference is 90°. At least one of them may be shifted from the direction shown in FIGS. 5 and 6.

As explained above, in this embodiment, the first to fourth detection units 11, 12, 21, and 22 can be placed at any position as long as the first and second requirements are satisfied. Therefore, according to the present embodiment, it is possible to reduce errors caused by the noise magnetic field Mex without imposing any major restrictions on the installation of the first to fourth detection units 11, 12, 21, and 22.

Note that so far, the effects of this embodiment have been described assuming an ideal state. In reality, at relative positions other than those where the angle θ is 0°, 90°, 180°, and 270°, when the distance from the magnetic scale 2 changes, the direction of the magnetic field to be detected at any position changes from the ideal It deviates from the direction in the state. As a result, an error caused by the magnetic scale 2 may occur in the detected value θs. Therefore, conventionally, it has been necessary to arrange the detection section of the magnetic sensor so that there is no deviation in the direction of the magnetic field to be detected. On the other hand, in this embodiment, a deviation in the direction of the magnetic field to be detected is allowed. Instead, in this embodiment, the first to fourth detection units 11, 12, 21, and 22 are arranged so as to satisfy the first and second requirements to reduce the error caused by the noise magnetic field Mex. are doing. Note that the error caused by the magnetic scale 2 can be corrected by, for example, gain adjustment and offset adjustment so that the waveforms of changes in the first and second calculated signals Sa and Sb due to changes in relative position approach sine waves. can be reduced by correcting the first and second post-computation signals Sa and Sb.

The effects of this embodiment will be described below with reference to the results of the first simulation. In the first simulation, the error in the detected value θs was determined when the detected value θs was generated under the presence of a noise magnetic field Mex having a constant direction and intensity. In the first simulation, the magnitude of the strength Bex of the noise magnetic field Mex is determined by 30% of the strength Ba of the first partial magnetic field MFa detected by the first and second detection units 11 and 12, that is, the magnitude of the first strength. %, and the angle θex that the direction of the noise magnetic field Mex at the first detection position P1 makes with respect to the reference direction DR was set to 60°.

In the first simulation, a model corresponding to the position detection device 1 was used. Here, the positions of the magnets 4, 5, and 6 in the X direction are defined as follows. First, a straight line located on the upper surface 7a of the yoke 7 and extending in the X direction and in contact with the magnets 4, 5, and 6 is defined as a position reference line. Then, the position of the midpoint of the line segment of the position reference line that overlaps with each of the magnets 4, 5, and 6 is defined as the position of each of the magnets 4, 5, and 6 in the X direction. In the model used in the first simulation, the distance between the position of magnet 4 in the X direction and the position of magnet 5 in the X direction, and the distance between the position of magnet 5 in the X direction and the position of magnet 6 in the Both were 12 mm.

Further, in the model used in the first simulation, the relative position was defined with the state where the magnet 5 and the electronic components 10 and 20 are at the same position in the X direction as the origin. That is, in the model of the example, the relative position when the magnet 5 and the electronic components 10, 20 are at the same position in the X direction is 0 mm, and the relative position when the magnet 4 and the electronic components 10, 20 are at the same position in the X direction is 0 mm. The relative position was set to -12 mm, and the relative position when the magnet 6 and the electronic components 10 and 20 were at the same position in the X direction was set to 12 mm.

In addition, in the model used in the first simulation, the intensity Bb of the second partial magnetic field MFb detected by the third and fourth detection units 21 and 22, that is, the magnitude of the second intensity, is the same as that of the first and second magnetic fields. The first to fourth detecting sections 11, 12, 21, 22 are set so that the intensity Ba of the first partial magnetic field MFa detected by the detecting sections 11, 12 is 20% of the first intensity. Placed.

In the first simulation, the difference S1-S3 between the first detection signal S1 and the third detection signal S3 is used as the first calculated signal Sa, and the difference between the second detection signal S2 and the fourth detection signal S4 is The difference S2-S4 was defined as the second post-computation signal Sb. Then, the detected value θs was obtained by substituting each value of the first and second post-computation signals Sa and Sb into equation (1). Hereinafter, this detected value θs will be referred to as the detected value θs of the embodiment.

In addition, in the first simulation, by substituting the value of the first detection signal S1 for Sa in equation (1) and substituting the value of the second detection signal S2 for Sb in equation (1), the comparative example The detected value θs was determined.

In addition, in the first simulation, the error in the detected value θs of the example (hereinafter referred to as the error E1 of the example) and the error of the detected value θs of the comparative example (hereinafter referred to as the error E2 of the comparative example) were calculated. I asked for it. In the first simulation, the difference between the detected value θs of the example and the angle θ was defined as the error E1 of the embodiment, and the difference between the detected value θs of the comparative example and the angle θ was defined as the error E2 of the comparative example.

FIG. 11 is a waveform diagram showing the waveforms of the first and second detection signals S1 and S2 in the first simulation. FIG. 12 is a waveform diagram showing the waveforms of the third and fourth detection signals S3 and S4 in the first simulation. FIG. 13 is a waveform diagram showing the waveforms of the first and second post-operation signals Sa and Sb in the first simulation. The horizontal axis in FIGS. 11 to 13 indicates relative position. The vertical axis in FIG. 11 indicates the magnitude of the first and second detection signals S1 and S2. The vertical axis in FIG. 12 indicates the magnitude of the third and fourth detection signals S3 and S4. The vertical axis in FIG. 13 indicates the magnitude of the first and second post-operation signals Sa and Sb. In FIG. 11, a curve labeled 71 shows the waveform of the first detection signal S1, and a curve labeled 72 shows the waveform of the second detection signal S2. In FIG. 12, the curve labeled 73 shows the waveform of the third detection signal S3, and the curve labeled 74 shows the waveform of the fourth detection signal S4. In FIG. 13, the curve labeled 75 shows the waveform of the first post-computation signal Sa, and the curve labeled 76 shows the waveform of the second post-computation signal Sb. Note that in the first simulation, the first to fourth detection signals S1 to S4 are normalized so that the amplitudes of the first and second detection signals S1 and S2 in the absence of the noise magnetic field Mex are 1. ing.

FIG. 14 is a characteristic diagram showing the detected value θs of the comparative example. FIG. 15 is a characteristic diagram showing the error E2 of the comparative example. FIG. 16 is a characteristic diagram showing the detected value θs of the example. FIG. 17 is a characteristic diagram showing the error E1 of the example. The horizontal axis in FIGS. 14 to 17 indicates relative position. The vertical axis in FIG. 14 indicates the magnitude of the detected value θs of the comparative example. The vertical axis in FIG. 15 indicates the magnitude of the error E2 in the comparative example. The vertical axis in FIG. 16 indicates the magnitude of the detected value θs in the example. The vertical axis in FIG. 17 indicates the magnitude of the error E1 in the example. As shown in FIGS. 15 and 17, the error E1 of the example is smaller than the error E2 of the comparative example, and theoretically becomes 0. The error E2 in the comparative example is an error when the detected value θs is generated based only on the first and second detection signals S1 and S2. Therefore, according to the present embodiment, the error in the detected value θs can be made smaller than when the detected value θs is generated based only on the first and second detection signals S1 and S2.

[Modified example]
Next, a modification of the magnetic scale 2 will be described with reference to FIG. 18. FIG. 18 is a perspective view showing a modification of the magnetic scale 2. The configuration of the modified example of the magnetic scale 2 differs from the configuration of the magnetic scale 2 shown in FIGS. 1 and 2 in the following points. In the modified example, the magnet 6 is not provided. That is, in the modified example, the magnetic scale 2 includes two magnets 4 and 5 as the plurality of magnets. Note that in the modified example, the range of the detected value θs is limited to a range somewhat wider than 0° to 180°.

[Second embodiment]
Next, referring to FIG. 19, a second embodiment of the present invention will be described. FIG. 19 is a plan view showing a schematic configuration of a position detection device according to this embodiment. The position detection device 1 according to this embodiment includes a magnetic scale 102 that generates an external magnetic field whose intensity and direction have a spatial distribution, instead of the magnetic scale 2 in the first embodiment. Magnetic scale 102 includes a plurality of magnets 104. The plurality of magnets 104 are spaced apart from each other. The external magnetic field generated by the magnetic scale 102 is a combination of magnetic fields generated by each of the plurality of magnets 104.

The magnetic scale 102 further includes a substrate 105 made of a non-magnetic material such as resin or aluminum and supporting a plurality of magnets 104. The substrate 105 has a disk shape with its center located on a predetermined central axis C. Further, the substrate 105 has an upper surface 105a and a lower surface. The plurality of magnets 104 are arranged on the upper surface 105a of the substrate 105.

The magnetic scale 102 rotates in a rotation direction R about a central axis C in conjunction with a movable object (not shown) that rotates. Thereby, the relative position of the magnetic scale 102 with respect to the magnetic sensor 3 changes within a predetermined range along the rotation direction R. Hereinafter, the relative position of the magnetic scale 102 with respect to the magnetic sensor 3 will be simply referred to as a relative position. Note that the rotation direction R includes a clockwise direction in FIG. 19 and a counterclockwise direction in FIG. 19. The rotation direction R corresponds to the movement direction in the present invention.

The plurality of magnets 104 are arranged along the rotation direction R (movement direction). Each of the plurality of magnets 104 has a first end face closest to the central axis C and a second end face furthest from the center of rotation. The distances from the central axis C to the first end surfaces of each of the plurality of magnets 104 are mutually equal, and the distances from the central axis C to the second end surfaces of each of the plurality of main magnets are equal to each other.

Further, each of the plurality of magnets 104 has an N pole and an S pole. Here, attention is paid to arbitrary two magnets 104 adjacent to each other in the rotation direction R among the plurality of magnets 104. On one of the two magnets 104, the north pole and the south pole are arranged in this order in a direction moving away from the central axis C. On the other of the two magnets 104, the north pole and the south pole are arranged in this order in the direction approaching the central axis C.

Although not shown, in this embodiment, the magnetic sensor 3 detects a detection target magnetic field that is part of the external magnetic field generated by the magnetic scale 102 and a noise magnetic field Mex other than the detection target magnetic field. The first to fourth detection parts 11, 12, 21, and 22 of the magnetic sensor 3 are arranged on the outside of the substrate 105 in the radial direction so as to face the outer circumference of the substrate 105. The direction of the magnetic field to be detected at an arbitrary position rotates around the arbitrary position as the relative position changes. Particularly in the example shown in FIG. 19, when the magnetic scale 102 rotates once, the direction of the magnetic field to be detected at an arbitrary position rotates four times.

Here, as shown in FIG. 19, a first imaginary straight line L1 intersects with the central axis C, and a second imaginary straight line L2 intersects with the central axis C and is different from the first imaginary straight line L1. Assume that Particularly in this embodiment, the first and second imaginary straight lines L1 and L2 are both perpendicular to the central axis C. Further, the first and second imaginary straight lines L1 and L2 are both on an imaginary plane that intersects the magnetic scale 102 and is perpendicular to the central axis C. Hereinafter, this virtual plane will be referred to as a reference plane. Furthermore, an arbitrary position where the magnetic field to be detected has the first intensity on the reference plane is defined as a first detection position P11. The first imaginary straight line L1 passes through the first detection position P11. Further, a position where the magnetic field to be detected has the first strength on the reference plane and which is shifted in the rotational direction R by an angle corresponding to 90 degrees of electrical angle from the first detection position P11 is set as a second position. It is assumed that the detection position is P12. The second virtual straight line L2 passes through the second detection position P12. Particularly in the example shown in FIG. 19, the second detection position P12 is located at a position shifted by 22.5 degrees in the rotational direction R from the first detection position P11.

As described in the first embodiment, the first and second detection units 11 and 12 detect the first composite magnetic field that is a composite magnetic field of the detection target magnetic field of the first intensity and the noise magnetic field Mex. It is arranged so that In the present embodiment, the first detection unit 11 is arranged at the first detection position P11, and generates a composite magnetic field of the detection target magnetic field and the noise magnetic field Mex at the first detection position P11 as the first composite magnetic field. To detect. The second detection unit 12 is arranged at the second detection position P12, and detects, as the first composite magnetic field, a composite magnetic field of the detection target magnetic field and the noise magnetic field Mex at the second detection position P12.

Further, a third detection position is a position on the first imaginary straight line L1, which is a position different from the first detection position P11 on the first imaginary straight line L1, and where the magnetic field to be detected has a second intensity. It is assumed that the position is P21. Further, a fourth detection position is a position on the second imaginary straight line L2, which is a position different from the second detection position P12 on the second imaginary straight line L2, and where the magnetic field to be detected has the second intensity. It is assumed that the position is P22. In the example shown in FIG. 19, the third detection position P21 is a predetermined distance away from the first detection position P11 in the direction away from the central axis C, and the fourth detection position P22 is a This is a position that is a predetermined distance away from the detection position P12 in the direction away from the central axis C.

As described in the first embodiment, the third and fourth detection units 21 and 22 detect a second composite magnetic field that is a composite magnetic field of the detection target magnetic field of the second intensity and the noise magnetic field Mex. It is arranged so that In this embodiment, the third detection unit 21 is arranged at the third detection position P21, and generates a composite magnetic field of the detection target magnetic field and the noise magnetic field Mex at the third detection position P21 as the second composite magnetic field. To detect. The fourth detection unit 22 is arranged at the fourth detection position P22, and detects, as the second composite magnetic field, a composite magnetic field of the detection target magnetic field and the noise magnetic field Mex at the fourth detection position P22.

In the present embodiment, the first direction D1, which is the reference for the first detection unit 11 to generate the first detection signal S1, is one direction perpendicular to the first imaginary straight line L1 (to the right in FIG. 19). direction). Further, the second direction D2, which is the reference for the second detection unit 12 to generate the second detection signal S2, is one direction perpendicular to the second imaginary straight line L2 (direction toward the upper right side in FIG. 19). It is. The third direction D3, which serves as a reference for the third detection unit 21 to generate the third detection signal S3, is the same direction as the first direction D1. The fourth direction D4, which serves as a reference for the fourth detection unit 22 to generate the fourth detection signal S4, is the same direction as the second direction D2.

The first angle θ1 that the direction of the detection target magnetic field detected by the first detection unit 11 makes with respect to the first direction D1, which is assumed in an ideal state, and the detection target magnetic field detected by the third detection unit 21 The third angles θ3 that the directions make with respect to the third direction D3 are equal to each other. Furthermore, the second angle θ2 that the direction of the detection target magnetic field detected by the second detection unit 12 makes with respect to the second direction D2, which is assumed in an ideal state, and the detection detected by the fourth detection unit 22 The fourth angle θ4 that the direction of the target magnetic field makes with respect to the fourth direction D4 is equal to each other. Further, the difference between the first angle θ1 and the second angle θ2 is 90°, and the difference between the third angle θ3 and the fourth angle θ4 is 90°.

Although not shown, the reference direction DR is located within the aforementioned reference plane. The reference position may be the same position as any of the first to fourth detection positions P11, P12, P21, P22, or a position different from the first to fourth detection positions P11, P12, P21, P22. It may be. In one example, the reference position is the same position as the first detection position P11, and the reference direction DR is a direction from the first detection position P11 toward the central axis C.

Similarly to the first example of the magnetic sensor 3 in the first embodiment, each of the first to fourth detection sections 11, 12, 21, 22 may include at least one MR element. The relationship between the magnetization direction of the magnetization fixed layer of the MR element included in the first detection unit 11 and the first direction D1 is the same as in the first embodiment. Similarly, the relationship between the magnetization direction of the magnetization fixed layer of the MR element included in the second detection unit 12 and the second direction D2 is the same as in the first embodiment. Similarly, the relationship between the magnetization direction of the magnetization fixed layer of the MR element included in the third detection unit 21 and the third direction D3 is the same as in the first embodiment. Similarly, the relationship between the magnetization direction of the magnetization fixed layer of the MR element included in the fourth detection unit 22 and the fourth direction D4 is the same as in the first embodiment.

Alternatively, similarly to the second example of the magnetic sensor 3 in the first embodiment, each of the first to fourth detection units 11, 12, 21, 22 may include at least one Hall element. good. Particularly in this embodiment, each of the first to fourth detection units 11, 12, 21, and 22 may be included in separate electronic components. Similar to the electronic components 10 and 20 of the second example of the magnetic sensor 3 in the first embodiment, this electronic component includes a substrate made of a non-magnetic material and a yoke made of a magnetic material. The substrate has an upper surface parallel to the aforementioned reference plane. At least one Hall element is embedded in the substrate.

The electronic component including the first detection unit 11 includes a Hall element and a yoke so that the Hall element included in the first detection unit 11 can detect the component of the first composite magnetic field in the first direction D1. is configured. The electronic component including the second detection section 12 includes a Hall element and a yoke so that the Hall element included in the second detection section 12 can detect a component in the second direction D2 of the first composite magnetic field. is configured. The electronic component including the third detection unit 21 includes a Hall element and a yoke so that the Hall element included in the third detection unit 21 can detect a component in the third direction D3 of the second composite magnetic field. is configured. The electronic component including the fourth detector 22 includes a Hall element and a yoke so that the Hall element included in the fourth detector 22 can detect a component in the fourth direction D4 of the second composite magnetic field. is configured.

Note that up to this point, there are the first detection position P11 and the third detection position P21 on the first imaginary straight line L1, and the second detection position P12 and the third detection position P21 are on the second imaginary straight line L2. An example in which there are four detection positions P22 has been described. However, the positions of the first to fourth detection positions P11, P12, P21, and P22 in this embodiment are not limited to the example shown in FIG. 19. For example, the third detection position P21 may be a position shifted in the rotational direction R from the third detection position P21 shown in FIG. 19 by an angle corresponding to 360 degrees of electrical angle, that is, 90 degrees. Similarly, the fourth detection position P22 may be a position shifted in the rotation direction R by an angle corresponding to 360 degrees of electrical angle, that is, 90 degrees, from the fourth detection position P22 shown in FIG. .

Next, the results of second and third simulations in which the shape and arrangement of the plurality of magnets 104 of the magnetic scale 102 were investigated will be explained. Ideally, the intensity of the magnetic field to be detected at any detection position is constant regardless of changes in the relative position of the magnetic scale 102 with respect to the magnetic sensor 3. However, in reality, the strength of the magnetic field to be detected at any detection position is determined by a change in the relative position of the magnetic scale 102 with respect to the magnetic sensor 3, specifically, a change in the relative position of the plurality of magnets 104 with respect to any detection position. may vary depending on the

By the way, in order to reduce the influence of the noise magnetic field Mex, it is conceivable to move the detection position closer to the magnetic scale 102 and make the intensity of the noise magnetic field Mex smaller relative to the intensity of the magnetic field to be detected. This makes it possible to reduce the influence of the noise magnetic field Mex, increase the strength of the magnetic field to be detected, and improve the quality of the first to fourth detection signals S1 to S4. However, if the detection position is placed too close to the plurality of magnets 104, variations in the strength of the magnetic field to be detected will become noticeable as the relative position changes. Particularly in this embodiment, the second detection position P12 is located at a position shifted from the first detection position P11 in the rotational direction R, and the fourth detection position P22 is located at a position shifted from the third detection position P21 in the rotational direction R. It is located at a different position. Therefore, when the strength of the magnetic field to be detected changes, the first detecting section 11 and the second detecting section 12 will not be able to detect the magnetic field of the same intensity at the same timing, and the third detecting section 21 and The fourth detection unit 22 will no longer be able to detect magnetic fields to be detected with the same intensity at the same timing. As a result, the detected value θs cannot be generated with high accuracy. Therefore, it is preferable that the first to fourth detection positions P11, P12, P21, and P22 are located at such positions that fluctuations in the strength of the magnetic field to be detected due to changes in relative positions are reduced.

In the second simulation, positions were investigated where variations in the intensity of the magnetic field to be detected due to changes in relative position would be small. Specifically, a plurality of points having different distances from the magnetic scale 102 were assumed. Then, the strength of the magnetic field to be detected at these multiple points was determined.

In the second simulation, a model of the magnetic scale 102 shown in FIG. 19 was used. However, in the second simulation, the interval between two adjacent magnets 104 in the rotation direction R was set to 0. Further, the maximum dimension of the magnet 104 in the rotation direction R when viewed from one direction parallel to the central axis C is 6 mm, and the magnet 104 in the radial direction of the substrate 105 when viewed from one direction parallel to the central axis C. The dimension was set to 3 mm.

Here, among the plurality of magnets 104, three magnets 104 arranged in the rotation direction R are referred to as a first magnet, a second magnet, and a third magnet. Also, a point on an imaginary straight line passing through the boundary between the first magnet and the second magnet and the central axis C in the reference plane, located at a position away from the magnetic scale 102 by a predetermined distance, and The point closest to the magnet is the first point. Also, a point on an imaginary straight line passing through the center of the third magnet in the rotational direction R and the central axis C in the reference plane, located at a position away from the magnetic scale 102 by the predetermined distance, and the third magnet. Let the point closest to the magnet be the 10th point.

Also, a virtual curve that passes through the first point and the tenth point in the reference plane and is located at a position separated from the magnetic scale 102 by the predetermined distance, and the first point and the tenth point on this virtual curve. Assume eight points in between. These eight points are defined as second to ninth points in order of proximity to the first point. The first to tenth points are arranged at equal intervals. The first to tenth points have different positional relationships with the first to third magnets. The fourth point is a point on an imaginary straight line passing through the center of the second magnet in the rotational direction R and the central axis C within the reference plane, and is located at a position away from the magnetic scale 102 by the predetermined distance. This is the point closest to the second magnet. Further, the seventh point is a point on an imaginary straight line passing through the boundary between the second magnet and the third magnet and the central axis C in the reference plane, and is a position separated from the magnetic scale 102 by the predetermined distance. This is the point located at the second magnet and closest to the second magnet.

Hereinafter, the distance between the virtual curve and the magnetic scale 102 will be represented by the symbol WD. In the second simulation, the distance WD was changed in increments of 0.5 mm within the range of 1 mm to 3.5 mm, and for each of a plurality of virtual curves with different distances WD, the distance between the first point on the virtual curve and the The strength of the magnetic field to be detected at each of the tenth points and the average value of the strength of the magnetic field to be detected at all points on the virtual curve were determined. Then, for each point, find the difference between the strength of the magnetic field to be detected at that point and the average value of the strength of the magnetic field to be detected at all points on the virtual curve passing through that point, and calculate the average value of this difference. The ratio was calculated. Hereinafter, this ratio will be referred to as the fluctuation rate.

The variation in the strength of the magnetic field to be detected at each of the first to tenth points on any one virtual curve is on the virtual curve as the relative position of the magnetic scale 102 with respect to the magnetic sensor 3 changes. It represents the variation in the intensity of the magnetic field to be detected at an arbitrary detection position. The difference between the maximum value and the minimum value of the rate of variation of all points on any one virtual curve represents the range of variation in the intensity of the magnetic field to be detected at any detection position on the virtual curve. In the second simulation, the difference between the maximum and minimum fluctuation rates was determined for each of a plurality of virtual curves. Hereinafter, this difference will be referred to as the fluctuation range.

FIG. 20 is a characteristic diagram showing the fluctuation rate determined by the second simulation. In FIG. 20, the horizontal axis indicates the position on the virtual curve. In FIG. 20, the first to tenth points are shown as positions on the virtual curve. Note that in FIG. 20, the first to tenth points are each represented by a number from 1 to 10. Furthermore, in FIG. 20, the vertical axis indicates the rate of change. Moreover, in FIG. 20, a curve with reference numeral 81 indicates the fluctuation rate of each point on a hypothetical curve with an interval WD of 1 mm. The curve labeled 82 shows the rate of variation of each point on a virtual curve with a distance WD of 1.5 mm. The curve labeled 83 shows the rate of variation of each point on the virtual curve with the distance WD of 2.0 mm. The curve labeled 84 shows the rate of variation of each point on the virtual curve with the distance WD of 2.5 mm. The curve labeled 85 shows the fluctuation rate of each point on the virtual curve with the distance WD of 3.0 mm. The curve labeled 86 shows the rate of variation of each point on the virtual curve with the distance WD of 3.5 mm. From FIG. 20, it can be seen that the fluctuation rate of any point on the virtual curve changes depending on the positional relationship with the first to third magnets. This result shows that the intensity of the magnetic field to be detected at any detection position varies as the relative position changes.

FIG. 21 is a characteristic diagram showing the fluctuation range obtained by the second simulation. In FIG. 21, the horizontal axis shows the interval WD, and the vertical axis shows the variation width. From FIG. 21, it can be seen that the fluctuation rate of the hypothetical curve where the distance WD is 2.5 mm is the minimum. From this result, it can be seen that when the distance between the detection position and the magnetic scale 102 is 2.5 mm, the range of variation in the strength of the magnetic field to be detected due to a change in relative position is minimized.

As described above, in order to improve the quality of the first to fourth detection signals S1 to S4, it is preferable to move the detection position closer to the magnetic scale 102, that is, to reduce the distance WD. From FIG. 21, it can be seen that when the distance WD is smaller than 2.5 mm, the variation range increases as the distance WD becomes smaller. From this result, when the distance between the detection position and the magnetic scale 102 is smaller than 2.5 mm, as the distance between the detection position and the magnetic scale 102 becomes smaller, the range of variation in the strength of the magnetic field to be detected increases due to changes in the relative position. I know it will happen.

Incidentally, the rate of variation can also change depending on the interval between two adjacent magnets 104 in the rotation direction R. The intensity of the magnetic field to be detected at each of the first to tenth points on one virtual curve was determined by changing the distance between the two magnets 104. Then, as in the second simulation, the rate of variation was determined for each point.

In the third simulation, similarly to the second simulation, the model of the magnetic scale 102 shown in FIG. 19 was used. However, in the third simulation, the maximum dimension of the magnet 104 in the rotation direction R when viewed from one direction parallel to the central axis C is changed to 6 mm, 5 mm, 4.35 mm, and 4 mm. The distance between two adjacent magnets 104 was changed to 0 mm, 1 mm, 1.65 mm, and 2 mm. In addition, in the third simulation, the distance WD between the virtual curve and the magnetic scale 102 is set on the assumption that the detection position is brought closer to the magnetic scale 102 in order to improve the quality of the first to fourth detection signals S1 to S4. , the width of variation was set to 1.5 mm, which is smaller than the minimum 2.5 mm.

FIG. 22 is a characteristic diagram showing the fluctuation rate obtained by the third simulation. In FIG. 22, the horizontal axis shows the position on the virtual curve, and the vertical axis shows the fluctuation rate. The way the positions on the virtual curve are represented in FIG. 22 is the same as in FIG. 20. Furthermore, in FIG. 22, a curve labeled 91 shows the rate of variation at each point when the distance between the two magnets 104 is 0 mm. A curve labeled 92 shows the rate of variation at each point when the distance between the two magnets 104 is 1 mm. The curve labeled 93 shows the rate of variation at each point when the distance between the two magnets 104 is 1.65 mm. The curve labeled 94 shows the rate of variation at each point when the distance between the two magnets 104 is 2 mm. From FIG. 22, it can be seen that when the interval between the two magnets 104 is 0 mm (symbol 91), the difference between the maximum value and the minimum value of the fluctuation rate, that is, the fluctuation width is maximum, and when the interval between the two magnets 104 is other than 0 mm, Sometimes, the fluctuation width becomes smaller than when the interval between the two magnets 104 is 0 mm, and sometimes the fluctuation width becomes the minimum when the interval between the two magnets 104 is 1.65 mm (symbol 93). I understand. The results of the third simulation show that by providing an unmagnetized portion between the two magnets 104, it is possible to reduce the range of variation in the strength of the magnetic field to be detected due to changes in relative position.

The distance WD between the virtual curve and the magnetic scale 102 is a reference for determining the positions of the first to fourth detection positions P11, P12, P21, and P22. From the results of the third simulation, when the distance WD is 1.5 mm, the maximum dimension of the magnet 104 in the rotation direction R when viewed from one direction parallel to the central axis C is 4.35 mm, and the rotation direction R The distance between the two adjacent magnets 104 is 1.65 mm, the distance between the first and second detection positions P11, P12 and the magnetic scale 102 is slightly smaller than 1.5 mm, and the distance between the third and fourth detection positions P11 and P12 is slightly smaller than 1.5 mm. By making the distance between the detection positions P21, P22 and the magnetic scale 102 slightly larger than 1.5 mm, the intensity of the magnetic field to be detected can be changed at all of the first to fourth detection positions P11, P12, P21, P22. The width can be reduced.

As understood from the results of the second and third simulations, the distance between the first to fourth detection positions P11, P12, P21, P22 and the magnetic scale 102 is adjusted, and the distance between the two magnets 104 is adjusted. By adjusting, it is possible to reduce the range of variation in the strength of the magnetic field to be detected at each of the first to fourth detection positions P11, P12, P21, and P22. Therefore, in order to reduce the range of variation in the strength of the magnetic field to be detected, it is possible to determine the first to fourth detection positions P11, P12, P21, and P22 after considering adjusting these intervals. preferable.

The results of the second and third simulations also apply to the position detection device 1 according to the first embodiment. That is, by adjusting the distance between the first and second detection positions P1, P2 and the magnetic scale 2, and adjusting the distance between the magnets 4, 5 and the distance between the magnets 5, 6, the first and second detection positions P1, P2 can be adjusted. It is possible to reduce the range of variation in the strength of each of the partial magnetic fields MFa and MFb. Therefore, it is preferable to determine the first and second detection positions P1 and P2 after considering adjusting these intervals in order to reduce the range of variation in the strength of the magnetic field to be detected.

[Modified example]
Next, a modification of the magnetic scale 102 will be described with reference to FIG. 23. FIG. 23 is a plan view showing a modification of the magnetic scale 102. In a modified example, the magnetic scale 102 includes, in addition to a plurality of magnets 104 and a substrate 105, a plurality of nonmagnetic bodies 106 made of a nonmagnetic material such as resin or aluminum, and a yoke 107 made of a magnetic material such as NiFe. I'm here. A plurality of nonmagnetic materials 106 and a yoke 107 are arranged on the upper surface 105a of the substrate 105. Each of the plurality of nonmagnetic bodies 106 is arranged between two adjacent magnets 104.

Yoke 107 magnetically connects the plurality of magnets 104. In the example shown in FIG. 23, the yoke 107 has an annular shape with its center located on the central axis C. The yoke 107 magnetically connects the first end surface of each of the plurality of magnets 104 closest to the central axis C. Here, attention is paid to arbitrary two magnets 104 adjacent to each other in the rotation direction R among the plurality of magnets 104. Of these two magnets 104, the magnet 104 whose first end face is on the north pole side is called the first magnet 104, and the magnet 104 whose first end face is on the south pole side is called the second magnet. Say 104. The yoke 107 has a function of controlling the flow of magnetic flux so that the magnetic flux generated from the first end surface of the first magnet 104 efficiently flows into the first end surface of the second magnet 104. ing.

The other configurations, operations, and effects of this embodiment are the same as those of the first embodiment.

Note that the present invention is not limited to the above embodiments, and various modifications are possible. For example, the arrangement of the first to fourth detection sections 11, 12, 21, and 22 is not limited to the examples shown in each embodiment, but is arbitrary as long as the requirements of the claims are met.

Further, the number and shape of the plurality of magnets of the magnetic scale 2 or 102, and the positions of the N and S poles are not limited to the examples shown in each embodiment, but are arbitrary. Further, in the first embodiment, the magnetic scale 2 may include a linear multipolar magnetized magnet instead of the magnets 4, 5, and 6. Further, in the second embodiment, the magnetic scale 102 may include an annular multipolar magnetized magnet instead of the plurality of magnets 104.

DESCRIPTION OF SYMBOLS 1... Position detection device, 2... Magnetic scale, 3... Magnetic sensor, 4-6... Magnet, 7... Yoke, 8... Protective part, 10, 20... Electronic component, 11... First detection part, 12... Second Detection unit, 21...Third detection unit, 22...Fourth detection unit, 31-34...A/D converter, 35...First arithmetic circuit, 36...Second arithmetic circuit, 37...Third arithmetic circuit arithmetic circuit, 41... substrate, 42... yoke , H1 to H4... Hall elements, R11, R12, R21, R22... MR element.

Claims (11)

A position including a magnetic scale that generates an external magnetic field whose intensity and direction have a spatial distribution, and a magnetic sensor that detects a magnetic field to be detected that is part of the external magnetic field and a noise magnetic field other than the magnetic field to be detected. A detection device,
The relative position of the magnetic scale to the magnetic sensor can be changed within a predetermined range along a moving direction that is a linear direction or a rotational direction,
The direction of the magnetic field to be detected at an arbitrary position within the reference plane rotates around the arbitrary position as the relative position changes,
The strength of the magnetic field to be detected changes depending on the distance from the magnetic scale,
The magnetic sensor is
The magnetic field to be detected is the magnetic field to be detected at a position within the reference plane whose intensity is a first intensity , and whose direction is a composite magnetic field of the magnetic field to be detected and the noise magnetic field rotating within the reference plane. a first detection section and a second detection section arranged to detect the composite magnetic field;
The magnetic field to be detected at a position within the reference plane whose intensity is a second intensity different from the first intensity, the magnetic field to be detected whose direction rotates within the reference plane, and the noise magnetic field. a third detection unit and a fourth detection unit arranged to detect a second composite magnetic field that is a composite magnetic field of
The first detection unit generates a first detection signal corresponding to the intensity of a component in a first direction of the first composite magnetic field,
The second detection unit generates a second detection signal corresponding to the intensity of a component of the first composite magnetic field in a second direction different from the first direction,
The third detection unit generates a third detection signal corresponding to the intensity of a component in a third direction of the second composite magnetic field,
The fourth detection unit generates a fourth detection signal corresponding to the intensity of a component of the second composite magnetic field in a fourth direction different from the third direction,
The magnetic sensor further includes:
a first arithmetic circuit that generates a first arithmetic signal corresponding to a difference between the first detection signal and the third detection signal;
a second calculation circuit that generates a second calculated signal corresponding to the difference between the second detection signal and the fourth detection signal;
A position detection device comprising: a third arithmetic circuit that generates a detected value having a correspondence relationship with the relative position based on the first and second post-arithmetic signals. The first angle is an angle that the direction of the detection target magnetic field detected by the first detection unit makes with the first direction, which is assumed when the direction of the detection target magnetic field changes ideally. , when the angle formed by the direction of the magnetic field to be detected detected by the third detection unit with respect to the third direction is a third angle, the first detection unit and the third detection unit are arranged such that the first angle and the third angle are equal to each other,
A second angle is an angle that the direction of the detection target magnetic field detected by the second detection unit makes with the second direction, which is assumed when the direction of the detection target magnetic field changes ideally. , when the angle between the direction of the magnetic field to be detected detected by the fourth detection unit and the fourth direction is defined as a fourth angle, the second detection unit and the fourth detection unit 2. The position detection device according to claim 1, wherein the angles are arranged such that the second angle and the fourth angle are equal to each other. The difference between the first angle and the second angle is 90°,
3. The position detection device according to claim 2, wherein a difference between the third angle and the fourth angle is 90°. The third direction is the same direction as the first direction,
4. The position detection device according to claim 1, wherein the fourth direction is the same direction as the second direction. The moving direction is a linear direction,
The first composite magnetic field is a composite magnetic field of the detection target magnetic field and the noise magnetic field at a first detection position on a virtual straight line that intersects the magnetic scale and is orthogonal to the movement direction,
The second composite magnetic field is a composite magnetic field of the detection target magnetic field and the noise magnetic field at a second detection position different from the first detection position on the imaginary straight line. 5. The position detection device according to any one of 1 to 4. A position including a magnetic scale that generates an external magnetic field whose intensity and direction have a spatial distribution, and a magnetic sensor that detects a magnetic field to be detected that is part of the external magnetic field and a noise magnetic field other than the magnetic field to be detected. A detection device,
The relative position of the magnetic scale with respect to the magnetic sensor can be changed within a predetermined range along a movement direction that is a rotation direction around a predetermined central axis,
The direction of the magnetic field to be detected at an arbitrary position rotates around the arbitrary position as the relative position changes,
The strength of the magnetic field to be detected changes depending on the distance from the magnetic scale,
The magnetic sensor is
a first detection unit and a second detection unit arranged to detect a first composite magnetic field that is a composite magnetic field of the detection target magnetic field and the noise magnetic field having a first intensity;
a third detection unit and a fourth detection unit arranged to detect a second composite magnetic field that is a composite magnetic field of the detection target magnetic field and the noise magnetic field having a second strength different from the first strength; including the
The first detection unit generates a first detection signal corresponding to the intensity of a component in a first direction of the first composite magnetic field,
The second detection unit generates a second detection signal corresponding to the intensity of a component of the first composite magnetic field in a second direction different from the first direction,
The third detection unit generates a third detection signal corresponding to the intensity of a component in a third direction of the second composite magnetic field,
The fourth detection unit generates a fourth detection signal corresponding to the intensity of a component of the second composite magnetic field in a fourth direction different from the third direction,
The magnetic sensor further includes:
a first arithmetic circuit that generates a first arithmetic signal corresponding to a difference between the first detection signal and the third detection signal;
a second calculation circuit that generates a second calculated signal corresponding to the difference between the second detection signal and the fourth detection signal;
a third arithmetic circuit that generates a detected value having a correspondence relationship with the relative position based on the first and second post-arithmetic signals;
The first composite magnetic field detected by the first detection unit is a composite magnetic field of the detection target magnetic field and the noise magnetic field at a first detection position on a first imaginary straight line intersecting the central axis. can be,
The first composite magnetic field detected by the second detection unit intersects the central axis and is detected at a second detection position on a second imaginary straight line that is different from the first imaginary straight line. is a composite magnetic field of the target magnetic field and the noise magnetic field,
The second composite magnetic field detected by the third detection unit is a combination of the detection target magnetic field and the noise magnetic field at a third detection position different from the first detection position on the first imaginary straight line. is the composite magnetic field of
The second composite magnetic field detected by the fourth detection unit is composed of the detection target magnetic field and the noise magnetic field at a fourth detection position different from the second detection position on the second imaginary straight line. A position detection device characterized by a composite magnetic field of. The magnetic scale includes a plurality of magnets arranged along the moving direction,
7. The position detection device according to claim 1, wherein the external magnetic field is a combination of magnetic fields generated by each of the plurality of magnets. 8. The position detection device according to claim 7, wherein the plurality of magnets are arranged at intervals from each other. 9. The position detection device according to claim 8, wherein the magnetic scale further includes a yoke made of a magnetic material and magnetically connecting the plurality of magnets. 9. The position detection device according to claim 1, wherein each of the first to fourth detection units includes at least one magnetoresistive element. 9. The position detection device according to claim 1, wherein each of the first to fourth detection units includes at least one Hall element.

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