Magnetic encoder and distance measuring device

Abstract

A magnetic encoder and a distance measuring device are provided. The magnetic encoder includes a magnetic field generator generating an object magnetic field including magnetic field components and a magnetic sensor detecting the object magnetic field. The magnetic sensor includes a plurality of resistors whose resistance values change in response to changes in the intensities of the magnetic field components, respectively. The magnetic field generator is a magnetic scale in which N poles and S poles are alternately arranged in groups. A pole pitch, which is the distance between the centers of two N poles adjacent across one S pole, is different from a design pitch, which is four times the interval between a prescribed position in one of the plurality of resistors and a prescribed position in another of the plurality of resistors.

Description

Technical Field

[0001] The present invention relates to a magnetic encoder including a magnetic field generator and a magnetic sensor, and a ranging device including a magnetic encoder. Background Technology

[0002] A magnetic encoder using a magnetic sensor is used to detect the position of a movable object whose position changes in a specified direction. The specified direction is either a linear direction or a rotational direction. A magnetic encoder for detecting the position of a movable object is configured such that at least one of a magnetic field generator (such as a magnetic scale) and a magnetic sensor operates in response to changes in the position of the movable object.

[0003] When at least one of the magnetic sensor and the magnetic field generator is activated, the intensity of a component of the object's magnetic field generated by the magnetic field generator and applied to the magnetic sensor changes in one direction. The magnetic sensor, for example, detects the intensity of this component of the object's magnetic field in one direction and generates two detection signals that correspond to the intensity of that component but are out of phase. The magnetic encoder generates a detection value corresponding to the position of the movable object based on the two detection signals.

[0004] As a magnetic sensor used in a magnetic encoder, a magnetic sensor employing multiple magnetoresistive elements is used. For example, International Publication No. 2009 / 031558 and International Publication No. 2009 / 119471 disclose magnetic sensors in which multiple GMR (giant magnetoresistive) elements are arranged as magnetoresistive elements in the relative movement direction between the magnet and the magnetic sensor and in a direction orthogonal to the relative movement direction.

[0005] In magnetic sensors used in magnetic encoders, typically, to generate two detection signals with different phases, a first group of magnetoresistive (GMR) elements used to generate one detection signal and a second group of GMR elements used to generate the other detection signal are staggered in one direction. For example, in the magnetic sensor disclosed in International Publication No. 2009 / 119471, multiple GMR elements constitute a bridge circuit for phase A and a bridge circuit for phase B. In this magnetic sensor, when the center-to-center distance (pitch) between the N and S poles of the magnet is λ, the multiple GMR elements are arranged with a center-to-center distance of λ, λ / 2, or λ / 4 in the relative movement direction. An output waveform with a phase shift of λ / 2 can be obtained from the bridge circuit for phase A and the bridge circuit for phase B.

[0006] As with the magnetic sensor disclosed in International Publication No. 2009 / 119471, the offset of the first and second magnetoresistive element groups corresponds to the pole pitch of the magnetic field generator used (e.g., the distance between the centers of two adjacent N poles). When the pole pitch is equal to or approximately equal to four times the aforementioned offset, the higher harmonic components of the second harmonic contained in the detection signal are minimized. Therefore, it is generally not contemplated to change the magnetic field generator of a magnetic encoder to a magnetic field generator with a different pole pitch.

[0007] However, in magnetic encoders used in devices that generate significant vibrations, it is sometimes necessary to increase the distance between the magnetic sensor and the magnetic field generator to prevent collisions. If this distance is increased without changing the pole pitch of the magnetic field generator, there is a concern that the magnetic field applied to the magnetic sensor will weaken, resulting in a smaller detection signal. Therefore, in such cases, a magnetic field generator with a large pole pitch is preferred. However, since the offset, i.e., the pitch of the magnetoresistive element, cannot be easily changed, when a magnetic sensor is used in combination with a magnetic field generator with a large pole pitch while maintaining the pitch of the magnetoresistive element, the error in the detection value of the magnetoresistive element increases. Summary of the Invention

[0008] The object of the present invention is to provide a magnetic encoder capable of reducing errors caused by differences in the magnetic pole pitch of a magnetic field generator, and a ranging device including the magnetic encoder.

[0009] The magnetic encoder of the present invention includes: a magnetic field generator that generates an object magnetic field including a magnetic field component in a first direction; and a magnetic sensor configured to detect the object magnetic field. The magnetic sensor and the magnetic field generator are configured such that when at least one of the magnetic sensor and the magnetic field generator is operational, the intensity of the magnetic field component at a reference position changes. The magnetic field generator is a magnetic scale with multiple sets of alternating N and S poles. The magnetic sensor is configured to include multiple resistive elements, each with a resistance value that changes accordingly to the change in the intensity of the magnetic field component, and to generate a first detection signal and a second detection signal corresponding to the change in the intensity of the magnetic field component.

[0010] The system comprises multiple resistive elements, including two resistive elements. The resistance value of one of the two resistive elements corresponds to a first detection signal. The resistance value of the other resistive element corresponds to a second detection signal. The two resistive elements are positioned at different locations along a first direction such that the phases of the first and second detection signals are different. In the magnetic scale, when the distance between the centers of two adjacent N poles separated by a S pole is defined as the magnetic pole pitch, and the design pitch is defined as four times the distance between a specified position within one resistive element and a specified position within the other resistive element along the first direction, the magnetic pole pitch is larger than the design pitch.

[0011] The first and second detection signals each contain: an ideal component that varies periodically in a manner that depicts an ideal sine curve, and multiple higher harmonic components that are respectively equivalent to higher harmonics of the ideal component. Multiple resistors are configured to reduce the higher harmonic components, at least equivalent to the second harmonic.

[0012] In the magnetic encoder of the present invention, the pole pitch can also be greater than 1.1 times the designed pitch. Alternatively, the pole pitch can be greater than 1.25 times the designed pitch and less than 1.75 times the designed pitch.

[0013] Furthermore, in the magnetic encoder of the present invention, the magnetic sensor may further include: a power supply port, a ground port, a first output port, and a second output port. The plurality of resistors may also include a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor. The first and second resistors may also be arranged sequentially from the power supply port side along a first path connecting the power supply port and the first output port. The third and fourth resistors may also be arranged sequentially from the ground port side along a second path connecting the ground port and the first output port. The fifth and sixth resistors may also be arranged sequentially from the ground port side along a third path connecting the ground port and the second output port. The seventh and eighth resistors may also be arranged sequentially from the power supply port side along a fourth path connecting the power supply port and the second output port.

[0014] The intervals between the first position in the first resistor body and the second position in the second resistor body, the intervals between the third position in the third resistor body and the fourth position in the fourth resistor body, the intervals between the fifth position in the fifth resistor body and the sixth position in the sixth resistor body, and the intervals between the seventh position in the seventh resistor body and the eighth position in the eighth resistor body can each be equal to an odd multiple of 1 / 2 of the design pitch. The intervals between the first and third positions in the first direction, and between the fifth and seventh positions in the first direction, can also be equal to zero or an integer multiple of the design pitch. The interval between the first and fifth positions in the first direction can also be equal to 1 / 4 of the design pitch.

[0015] The magnetic sensor may also include multiple magnetoresistive elements. Each of the multiple magnetoresistive elements may also include a fixed magnetization layer, a free layer, and a spacer layer disposed between the fixed magnetization layer and the free layer. The fixed magnetization layer may also have a first magnetization with a fixed orientation. The free layer may also have a second magnetization with an orientation that can change in a plane parallel to both the first direction and a second direction orthogonal to the first direction. The fixed magnetization layer, the free layer, and the spacer layer may also be stacked in a third direction orthogonal to the first and second directions. The first to eighth resistors may also be constructed using multiple magnetoresistive elements. The first magnetization of the fixed magnetization layer in the first, fourth, sixth, and seventh resistors may also include a component of a first magnetization direction that is parallel to the first direction. The first magnetization of the fixed magnetization layer in the second, third, fifth, and eighth resistors may also include a component of a second magnetization direction that is opposite to the first magnetization direction.

[0016] In the case of multiple resistive elements, including first to eighth resistive elements, the first position can also be the center of gravity of the first resistive element when viewed from a direction parallel to a third party. The second position can also be the center of gravity of the second resistive element when viewed from a direction parallel to a third party. The third position can also be the center of gravity of the third resistive element when viewed from a direction parallel to a third party. The fourth position can also be the center of gravity of the fourth resistive element when viewed from a direction parallel to a third party. The fifth position can also be the center of gravity of the fifth resistive element when viewed from a direction parallel to a third party. The sixth position can also be the center of gravity of the sixth resistive element when viewed from a direction parallel to a third party. The seventh position can also be the center of gravity of the seventh resistive element when viewed from a direction parallel to a third party. The eighth position can also be the center of gravity of the eighth resistive element when viewed from a direction parallel to a third party.

[0017] Furthermore, in the case where multiple resistive elements include first to eighth resistive elements, the first and third resistive elements may also be adjacent to each other in the second direction. The second and fourth resistive elements may also be adjacent to each other in the second direction. The fifth and seventh resistive elements may also be adjacent to each other in the second direction. The sixth and eighth resistive elements may also be adjacent to each other in the second direction.

[0018] Alternatively, when multiple resistors include first to eighth resistors, the first resistor may be adjacent to the seventh resistor but not adjacent to the eighth resistor. Alternatively, the eighth resistor may be adjacent to the second resistor but not adjacent to the first resistor. Furthermore, the third resistor may be positioned with the first resistor sandwiched between it and the seventh resistor. The fourth resistor may be positioned with the second resistor sandwiched between it and the eighth resistor. The fifth resistor may be positioned with the seventh resistor sandwiched between it and the first resistor. The sixth resistor may be positioned with the eighth resistor sandwiched between it and the second resistor.

[0019] In the case where the magnetic sensor includes multiple magnetoresistive elements, each of the multiple magnetoresistive elements can also be configured to apply a bias magnetic field in a direction intersecting the first direction to the free layer. The spacer layer can also be a tunnel barrier layer.

[0020] Alternatively, in the magnetic encoder of the present invention, the magnetic field generator may be configured to rotate about a rotation axis and have an end face located at an end in a direction parallel to the rotation axis. Multiple sets of N and S poles may also be arranged alternately around the rotation axis and disposed on the end face. The intensity of the magnetic field component at the reference position may also change with the rotation of the magnetic field generator. The magnetic sensor may also be configured to be opposite the end face. The magnetic field generator may also be configured to rotate in conjunction with an optical element used to measure the change in the direction of light travel for measuring the distance to an object.

[0021] Furthermore, in the magnetic encoder of the present invention, the magnetic field generator can also be configured to rotate around a rotation axis and have an outer peripheral surface facing away from the rotation axis. Multiple sets of N and S poles can also be arranged alternately around the rotation axis and disposed on the outer peripheral surface. The intensity of the magnetic field component at the reference position can also change with the rotation of the magnetic field generator. The magnetic sensor can also be configured to face the outer peripheral surface. The magnetic field generator can also be configured to rotate in conjunction with an optical element used to measure the change in the direction of light travel for measuring the distance to an object.

[0022] The ranging device of the present invention measures the distance to an object by detecting the incident light. The ranging device includes: an optical element configured to rotate while changing the direction of light travel; and the magnetic encoder of the present invention. A magnetic field generator is configured to rotate about a rotation axis in conjunction with the optical element. Multiple sets of N and S poles are arranged alternately around the rotation axis. The intensity of the magnetic field component at a reference position changes with the rotation of the magnetic field generator.

[0023] In the ranging device of the present invention, the magnetic field generator may also have an end face located at an end in a direction parallel to the rotation axis. In this case, multiple sets of N poles and S poles may also be provided on the end face. The magnetic sensor may also be configured to face the end face. Alternatively, the magnetic field generator may also have an outer peripheral surface facing away from the rotation axis. In this case, multiple sets of N poles and S poles may also be provided on the outer peripheral surface. The magnetic sensor may also be configured to face the outer peripheral surface.

[0024] In the magnetic encoder and ranging device of the present invention, multiple resistors are configured to reduce higher harmonic components, at least equivalent to the second harmonic, among multiple harmonic components. Therefore, according to the present invention, errors caused by variations in the magnetic pole pitch of the magnetic field generator can be reduced.

[0025] Other objects, features and advantages of the present invention will become fully apparent from the following description. Attached Figure Description

[0026] Figure 1 This is a perspective view of a ranging device according to one embodiment of the present invention.

[0027] Figure 2 This is a perspective view of a magnetic encoder representing one embodiment of the present invention.

[0028] Figure 3 This is a top view showing a magnetic encoder according to one embodiment of the present invention.

[0029] Figure 4 This is a front view of a magnetic encoder representing one embodiment of the present invention.

[0030] Figure 5 This is a top view illustrating a magnetic sensor according to one embodiment of the present invention.

[0031] Figure 6 This is a circuit diagram illustrating the structure of a magnetic sensor according to one embodiment of the present invention.

[0032] Figure 7 This is an explanatory diagram illustrating the configuration of the first to eighth resistors in one embodiment of the present invention.

[0033] Figure 8 This is a top view showing a first resistor element according to one embodiment of the present invention.

[0034] Figure 9 This is a perspective view showing a first example of a magnetoresistive effect element in one embodiment of the present invention.

[0035] Figure 10 This is a perspective view showing a second example of a magnetoresistive effect element in one embodiment of the present invention.

[0036] Figure 11 This is a top view showing the magnetic sensor of the comparative example.

[0037] Figure 12 This is a circuit diagram showing the structure of the magnetic sensor in the comparative example.

[0038] Figure 13 This is a characteristic graph representing the amplitude ratio of the comparative example model obtained through simulation.

[0039] Figure 14 This is a characteristic graph representing the amplitude ratio of the model in the embodiment obtained through simulation.

[0040] Figure 15 This is a characteristic graph representing the error of the detection values ​​of the comparative example model and the embodiment model obtained through simulation.

[0041] Figure 16 This is a perspective view of a magnetic field generator, representing a modified example of a magnetic encoder according to one embodiment of the present invention. Detailed Implementation

[0042] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, referring to... Figure 1 This describes the ranging device of this embodiment. Figure 1 This is a perspective view showing the ranging device 401 of this embodiment.

[0043] Figure 1 The distance measuring device 401 shown is a device that measures the distance to an object by detecting the illuminated light, and is, for example, part of a vehicle-mounted LIDAR (Light Detection and Ranging) system. Figure 1 In the example shown, the ranging device 401 includes a photoelectric unit 411, an optical element 412, and a driving device (not shown).

[0044] The photoelectric unit 411 includes an optical element for illuminating light 411a and a detection element for detecting reflected light 411b from an object. The optical element 412 may be, for example, a mirror supported by a support 413. The optical element 412 is tilted relative to its exit surface to change the respective travel directions of the light 411a and the reflected light 411b. Furthermore, the optical element 412 is configured to rotate about a predetermined rotation axis via a drive device (not shown).

[0045] The magnetic encoder 1 in this embodiment is used as a position detection device for detecting the rotational position of the optical element 412. Hereinafter, reference will be made to... Figures 2-4 The general structure of magnetic encoder 1 is described below. Figure 2 This is a 3D diagram representing magnetic encoder 1. Figure 3This is a top view of magnetic encoder 1. Figure 4 This is the front view of magnetic encoder 1.

[0046] The magnetic encoder 1 in this embodiment includes a magnetic sensor 2 and a magnetic field generator 3. The magnetic field generator 3 is centered on the rotation axis C and... Figure 1 The optical element 412 shown rotates in conjunction with the rotation.

[0047] The magnetic field generator 3 generates the magnetic field (detection target magnetic field) MF, which is the magnetic field to be detected by the magnetic sensor 2 for position detection. The object magnetic field MF includes a magnetic field component in a direction parallel to an imaginary (virtual) straight line. The magnetic sensor 2 and the magnetic field generator 3 are configured such that when at least one of them is activated, the intensity of the magnetic field component at a reference position changes. The reference position can be the location where the magnetic sensor 2 is positioned. The magnetic sensor 2 detects the object magnetic field MF containing the aforementioned magnetic field component and generates first and second detection signals corresponding to the intensity of the magnetic field component, respectively.

[0048] In this embodiment, in particular, the magnetic field generator 3 is a magnetic ruler (rotating ruler) in which multiple sets of N poles and S poles are alternately arranged around a rotation axis C. The magnetic field generator 3 has an end face 3a located at one end in a direction parallel to the rotation axis C. Multiple sets of N poles and S poles are disposed on the end face 3a. Figure 2 and Figure 3 In the diagram, the N pole is shaded for ease of understanding. Figure 4 For ease of understanding, the magnetic field generator 3 is schematically represented by multiple sets of N and S poles. The magnetic sensor 2 is configured to face the end face 3a. The intensity of the magnetic field component MFx at a reference position, such as the position where the magnetic sensor 2 is configured, changes as the magnetic field generator 3 rotates.

[0049] like Figure 4 As shown, the distance between two adjacent N poles in the rotation direction of the magnetic field generator 3, that is, the center-to-center distance between two adjacent N poles separated by one S pole, is called the magnetic pole pitch, and the magnitude of the magnetic pole pitch is represented by the symbol λm. The center-to-center distance between two adjacent S poles separated by one N pole is equal to the magnetic pole pitch λm.

[0050] Here, as Figure 4 As shown, the X, Y, and Z directions are defined. In this embodiment, the two directions orthogonal to the rotation axis C are designated as the X and Y directions, and the direction parallel to the rotation axis C, flowing from the magnetic sensor 2 to the magnetic field generator 3, is designated as the Z direction. Furthermore, the direction flowing from the magnetic sensor 2 to the rotation axis C is designated as the Y direction. Figure 4 In the diagram, the Y direction is represented as from... Figure 4The direction from the front inwards. Additionally, the direction opposite to the X direction is defined as the -X direction, the direction opposite to the Y direction as the -Y direction, and the direction opposite to the Z direction as the -Z direction.

[0051] The magnetic sensor 2 is positioned relative to the magnetic field generator 3 in the -Z direction. The magnetic sensor 2 is configured to detect the intensity of the magnetic field component MFx of the object's magnetic field MF at a predetermined position, in the direction parallel to the X direction. The intensity of the magnetic field component MFx is represented by a positive value when its direction is the X direction and by a negative value when its direction is -X. The intensity of the magnetic field component MFx changes periodically as the magnetic field generator 3 rotates. The direction parallel to the X direction corresponds to the "first direction" in this invention.

[0052] Next, refer to Figure 5 and Figure 6 The magnetic sensor 2 will be described in detail. Figure 5 This is a top view showing magnetic sensor 2. Figure 6 This is a circuit diagram showing the structure of magnetic sensor 2. (For example...) Figure 6 As shown, the magnetic encoder 1 also includes a detection value generation circuit 4. The detection value generation circuit 4 generates a detection value Vs that corresponds to the rotational position of the magnetic field generator 3, i.e., the rotational position of the optical element 412, based on a first detection signal S1 and a second detection signal S2 generated by the magnetic sensor 2 that correspond to the strength of the magnetic field component MFx. The detection value generation circuit 4 can be implemented, for example, by an application-specific integrated circuit (ASIC) or a microcomputer.

[0053] The magnetic sensor 2 includes a first resistive element R11, a second resistive element R12, a third resistive element R13, a fourth resistive element R14, a fifth resistive element R21, a sixth resistive element R22, a seventh resistive element R23, and an eighth resistive element R24, each configured such that its resistance value changes in response to the intensity of the magnetic field component MFx. Furthermore, the magnetic sensor 2 includes multiple magnetoresistive elements (hereinafter referred to as MR elements) 50. The first to eighth resistive elements R11–R14 and R21–R24 are each constructed using multiple MR elements 50.

[0054] The magnetic sensor 2 also includes a power supply port V1, a ground port G1, a first output port E1, and a second output port E2. The ground port G1 is grounded. The first and second output ports E1 and E2 are connected to the detection value generation circuit 4. The magnetic sensor 2 can be driven by either a constant voltage or a constant current. When the magnetic sensor 2 is driven by a constant voltage, a predetermined voltage is applied to the power supply port V1. When the magnetic sensor 2 is driven by a constant current, a predetermined current is supplied to the power supply port V1.

[0055] The magnetic sensor 2 generates a signal corresponding to the potential of the first output port E1 as a first detection signal S1, and generates a signal corresponding to the potential of the second output port E2 as a second detection signal S2. The detection value generation circuit 4 generates a detection value Vs based on the first and second detection signals S1 and S2. Furthermore, at least one of the magnetic sensor 2 and the detection value generation circuit 4 can be configured to correct the amplitude, phase, and offset of the first and second detection signals S1 and S2 respectively.

[0056] The first to eighth resistors R11-R14 and R21-R24 satisfy the following requirements regarding the circuit structure configuration. The first resistor R11 and the second resistor R12 are sequentially arranged from the power supply port V1 side in the first path 5, connecting the power supply port V1 and the first output port E1. The third resistor R13 and the fourth resistor R14 are sequentially arranged from the ground port G1 side in the second path 6, connecting the ground port G1 and the first output port E1. The fifth resistor R21 and the sixth resistor R22 are sequentially arranged from the ground port G1 side in the third path 7, connecting the ground port G1 and the second output port E2. The seventh resistor R23 and the eighth resistor R24 ​​are sequentially arranged from the power supply port V1 side in the fourth path 8, connecting the power supply port V1 and the second output port E2.

[0057] like Figure 5 As shown, the magnetic sensor 2 also includes a substrate 10, a power terminal 11, a ground terminal 12, a first output terminal 13, and a second output terminal 14 disposed on the substrate 10. The power terminal 11 constitutes a power port V1. The ground terminal 12 constitutes a ground port G1. The first and second output terminals 13 and 14 constitute the first and second output ports E1 and E2, respectively.

[0058] Next, refer to Figure 7 The configuration of the first to eighth resistors R11 to R14 and R21 to R24 is explained. Figure 7 This is an explanatory diagram illustrating the configuration of the first to eighth resistors R11-R14 and R21-R24. The resistance values ​​of each of the first to fourth resistors R11-R14 correspond to the first detection signal S1. The resistance values ​​of each of the fifth to eighth resistors R21-R24 correspond to the second detection signal S2. The groups of the first to fourth resistors R11-R14 and the groups of the fifth to eighth resistors R21-R24 are arranged at different positions in a direction parallel to the X-direction, such that the phases of the first detection signal S1 and the second detection signal S2 are different from each other.

[0059] exist Figure 7In the attached figures, reference numeral C11 indicates the first position within the first resistor R11, reference numeral C12 indicates the second position within the second resistor R12, reference numeral C13 indicates the third position within the third resistor R13, and reference numeral C14 indicates the fourth position within the fourth resistor R14. The first to fourth positions C11 to C14 are used to determine the physical positions of the first to fourth resistors R11 to R14. In this embodiment, the first position C11 is specifically the center of gravity of the first resistor R11 when viewed from the Z-direction, i.e., when the magnetic sensor 2 is viewed from a position in front of it in the Z-direction. Furthermore, the second position C12 is the center of gravity of the second resistor R12 when viewed from the Z-direction, the third position C13 is the center of gravity of the third resistor R13 when viewed from the Z-direction, and the fourth position C14 is the center of gravity of the fourth resistor R14 when viewed from the Z-direction.

[0060] In addition, Figure 7 In the attached figures, reference numeral C21 indicates the fifth position within the fifth resistor R21, reference numeral C22 indicates the sixth position within the sixth resistor R22, reference numeral C23 indicates the seventh position within the seventh resistor R23, and reference numeral C24 indicates the eighth position within the eighth resistor R24. The fifth to eighth positions C21 to C24 are used to determine the physical positions of the fifth to eighth resistors R21 to R24. In this embodiment, specifically, the fifth position C21 is the center of gravity of the fifth resistor R21 when viewed from the Z direction, the sixth position C22 is the center of gravity of the sixth resistor R22 when viewed from the Z direction, the seventh position C23 is the center of gravity of the seventh resistor R23 when viewed from the Z direction, and the eighth position C24 is the center of gravity of the eighth resistor R24 ​​when viewed from the Z direction.

[0061] Here, the design pitch λs is defined as follows. The design pitch λs is four times the distance between a predetermined position within the first resistor R11 and a predetermined position within the fifth resistor R21 in a direction parallel to the X direction. In this embodiment, the predetermined position within the first resistor R11 is specifically the first position C11, and the predetermined position within the fifth resistor R21 is the fifth position C21.

[0062] Furthermore, in this embodiment, the intervals between the first position C11 and the fifth position C21 in the direction parallel to the X direction, the interval between the second position C12 and the sixth position C22 in the direction parallel to the X direction, the interval between the third position C13 and the seventh position C23 in the direction parallel to the X direction, and the interval between the fourth position C14 and the eighth position C24 in the direction parallel to the X direction are all equal. Therefore, it is also possible to use the group of the second and sixth resistors R12, R22, the group of the third and seventh resistors R13, R23, or the group of the fourth and eighth resistors R14, R24 instead of the group of the first and fifth resistors R11, R21 to define λs.

[0063] Figure 4 The magnetic pole pitch λm shown is larger than the design pitch λs. The magnetic pole pitch λm is preferably 1.1 times larger than the design pitch λs, more preferably 1.25 times larger than the design pitch λs, and smaller than 1.75 times the design pitch λs.

[0064] Here, we envision a hypothetical magnetic field generator that differs from the magnetic field generator 3 in this embodiment. The hypothetical magnetic field generator has the same structure as the magnetic field generator 3, except that its pole pitch λm differs from that of the magnetic field generator 3. The pole pitch of the hypothetical magnetic field generator is equal to the designed pole pitch λs. Therefore, the pole pitch λm is greater than that of the hypothetical magnetic field generator. When the magnetic field generator 3 is replaced by the hypothetical magnetic field generator, the phase difference between the first detection signal S1 and the second detection signal S2 is 90°. The groups of first to fourth resistors R11 to R14 and the groups of fifth to eighth resistors R21 to R24 are arranged at different positions in a direction parallel to the X direction, such that when the magnetic field generator 3 is replaced by the hypothetical magnetic field generator, the phase difference between the first detection signal S1 and the second detection signal S2 is 90°.

[0065] The first to eighth resistors R11-R14 and R21-R24 satisfy the following physical configuration requirements: The intervals between the first position C11 and the second position C12 in the direction parallel to the X-direction, the intervals between the third position C13 and the fourth position C14 in the direction parallel to the X-direction, the intervals between the fifth position C21 and the sixth position C22 in the direction parallel to the X-direction, and the intervals between the seventh position C23 and the eighth position C24 in the direction parallel to the X-direction are all odd multiples of half the design pitch λs. The intervals between the first position C11 and the third position C13 in the direction parallel to the X-direction, and the intervals between the fifth position C21 and the seventh position C23 in the direction parallel to the X-direction are all equal to zero or integer multiples of the design pitch λs. The interval between the first position C11 and the fifth position C21 in the direction parallel to the X-direction is equal to one-quarter of the design pitch λs.

[0066] In this embodiment, the second position C12 is a position spaced λs / 2 apart in the X direction relative to the first position C11, and the fourth position C14 is a position spaced λs / 2 apart in the X direction relative to the third position C13. Furthermore, the interval between the first position C11 and the third position C13 in a direction parallel to the X direction is zero. That is, the third position C13 in a direction parallel to the X direction is the same as the first position C11 in the same direction. The third position C13 is located in front of the first position C11 in the -Y direction. Similarly, the fourth position C14 in a direction parallel to the X direction is the same as the second position C12 in the same direction. The fourth position C14 is located in front of the second position C12 in the -Y direction.

[0067] The fifth to eighth resistors R21 to R24 are positioned in front of the first to fourth resistors R11 to R14 in the Y direction. The physical configuration of the fifth to eighth resistors R21 to R24 is the same as that of the first to fourth resistors R11 to R14. If the first to fourth resistors R11 to R14 and the first to fourth positions C11 to C14 in the description of the physical configuration of the first to fourth resistors R11 to R14 are replaced with the fifth to eighth resistors R21 to R24 and the fifth to eighth positions C21 to C24, respectively, then this becomes a description of the physical configuration of the fifth to eighth resistors R21 to R24.

[0068] Furthermore, in this embodiment, the fifth position C21 (seventh position C23) is located λs / 4 ahead of the first position C11 (third position C13) in the X direction. The sixth position C22 (eighth position C24) is located λs / 4 ahead of the second position C12 (fourth position C14) in the X direction.

[0069] The first resistor R11 is adjacent to the seventh resistor R23, but not adjacent to the eighth resistor R24. The eighth resistor R24 ​​is adjacent to the second resistor R12, but not adjacent to the first resistor R11.

[0070] The third resistor R13 is positioned between itself and the seventh resistor R23, sandwiching the first resistor R11. The fourth resistor R14 is positioned between itself and the eighth resistor R24, sandwiching the second resistor R12. The fifth resistor R21 is positioned between itself and the first resistor R11, sandwiching the seventh resistor R23. The sixth resistor R22 is positioned between itself and the second resistor R12, sandwiching the eighth resistor R24.

[0071] Next, the structure of the first to eighth resistors R11-R14 and R21-R24 will be described. The first and second detection signals S1 and S2 each include an ideal component that changes periodically with a predetermined signal period, in a manner that depicts an ideal sine curve (including sine and cosine waveforms). In this embodiment, the first to eighth resistors R11-R14 and R21-R24 are configured such that the phase of the ideal component of the first detection signal S1 and the phase of the ideal component of the second detection signal S2 are different from each other. Figure 7 The design pitch λs shown corresponds to one cycle of the ideal component, i.e., 360° of the electrical angle, when the hypothetical magnetic field generator described above is used. In the magnetic encoder 1 of this embodiment, a magnetic field generator 3 with a pole pitch of λm is used. When this magnetic field generator 3 is used, the pole pitch λm corresponds to one cycle of the ideal component (360° of the electrical angle). That is, the period of the ideal component is λm.

[0072] In addition, the first and second detection signals S1 and S2 each contain not only the ideal component but also multiple higher harmonic components that are equivalent to the higher harmonics of the ideal component. In this embodiment, the first to eighth resistors R11 to R14 and R21 to R24 are configured to reduce the multiple higher harmonic components.

[0073] The structures of the first to eighth resistors R11-R14 and R21-R24 will now be described in detail. First, the structure of the MR element 50 will be described. In this embodiment, the MR element 50 is a spin-valve type MR element. This spin-valve type MR element includes a magnetized fixed layer, a free layer, and a spacer layer disposed between the magnetized fixed layer and the free layer. The magnetized fixed layer has a first magnetization whose direction is fixed. The free layer has a second magnetization whose direction can change in a plane parallel to both the X-direction and the Y-direction (in the XY plane). The magnetized fixed layer, the free layer, and the spacer layer are stacked in a direction parallel to the Z-direction. The direction parallel to the Y-direction corresponds to the "second direction" in this invention. The direction parallel to the Z-direction corresponds to the "third direction" in this invention.

[0074] The spin-valve type MR element can be either a TMR (tunnel magnetoresistive) element or a GMR (giant magnetoresistive) element. In this embodiment, to reduce the size of the magnetic sensor 2, the MR element 50 is preferably a TMR element. In a TMR element, the spacer layer is a tunnel barrier layer. In a GMR element, the spacer layer is a non-magnetic conductive layer. In the spin-valve type MR element, the resistance value varies accordingly with the angle between the magnetization direction of the free layer and the magnetization direction of the magnetized fixed layer; the resistance value is minimum when the angle is 0° and maximum when the angle is 180°.

[0075] exist Figure 5 and Figure 6 In the diagram, the arrows drawn within the first to eighth resistors R11~R14 and R21~R24 indicate the first magnetization direction of the magnetization fixation layer of each of the plurality of MR elements 50 included in the resistor.

[0076] The first to eighth resistors R11-R14 and R21-R24 satisfy the following requirements regarding the magnetization of the magnetization fixing layer. The first magnetization of the magnetization fixing layer in the first and fourth resistors R11 and R14 includes a component of a first magnetization direction, which is parallel to the aforementioned first direction (a direction parallel to the X direction). The first magnetization of the magnetization fixing layer in the second and third resistors R12 and R13 includes a component of a second magnetization direction opposite to the first magnetization direction. The first magnetization of the magnetization fixing layer in the fifth and eighth resistors R21 and R24 includes a component of the second magnetization direction. The first magnetization of the magnetization fixing layer in the sixth and seventh resistors R22 and R23 includes a component of the first magnetization direction. In this embodiment, in particular, the first magnetization direction is the -X direction, and the second magnetization direction is the X direction.

[0077] Furthermore, when the first magnetization includes a component with a specific magnetization direction, that component with the specific magnetization direction may also be the principal component of the first magnetization. Alternatively, the first magnetization may not include a component with a direction orthogonal to the specific magnetization direction. In this embodiment, when the first magnetization includes a component with a specific magnetization direction, the first magnetization direction is either a specific magnetization direction or a substantially specific magnetization direction.

[0078] The second magnetization direction of the free layer of each of the multiple MR elements 50 varies in the XY plane correspondingly with the intensity of the magnetic field component MFx. Consequently, the potentials of the first and second output ports E1 and E2 vary correspondingly with the intensity of the magnetic field component MFx.

[0079] Next, the arrangement of the multiple MR elements 50 in each of the first to eighth resistors R11-R14 and R21-R24 will be described. Here, a collection of more than one MR element 50 is referred to as an element group. Each of the first to eighth resistors R11-R14 and R21-R24 includes multiple element groups. The multiple element groups are arranged at predetermined intervals based on the design pitch λs to reduce error components. Furthermore, in the following description, when describing the arrangement of multiple element groups, the description is based on a predetermined position of the element group. The predetermined position is, for example, the center of gravity of the element group when viewed from the Z direction.

[0080] Figure 8 This is a top view showing the first resistor R11. (Example) Figure 8 As shown, the first resistor R11 includes eight element groups 31, 32, 33, 34, 35, 36, 37, and 38. Element groups 31 to 38 are each divided into four sections. One or more MR elements 50 are disposed in each section. Therefore, each element group includes four or more MR elements 50. Multiple MR elements 50 can also be connected in series within each element group. In this case, multiple element groups can also be connected in series. Alternatively, multiple MR elements 50 can be connected in series independently of element groups.

[0081] exist Figure 8 In the case of using the hypothetical magnetic field generator described above, the component groups 31 to 38 are configured to reduce the higher harmonic components corresponding to the ideal components of the third higher harmonic (third harmonic), the fifth higher harmonic (fifth harmonic), and the seventh higher harmonic (seventh harmonic). Figure 8 As shown, component groups 31 to 34 are arranged along the X direction. Component group 32 is arranged relative to component group 31 at a position away from λs / 10 in the X direction. Component group 33 is arranged relative to component group 31 at a position away from λs / 6 in the X direction. Component group 34 is arranged relative to component group 31 at a position away from λs / 10 + λs / 6 in the X direction (at a position λs / 6 away from component group 32 in the X direction).

[0082] In addition, such as Figure 8As shown, component groups 35-38 are arranged in front of component groups 31-34 in the -Y direction along the X direction. Component group 35 is positioned relative to component group 31 at a distance of λs / 14 in the X direction. Component group 36 is positioned relative to component group 31 at a distance of λs / 14+λs / 10 in the X direction (relative to component group 32 at a distance of λs / 14 in the X direction). Component group 37 is positioned relative to component group 31 at a distance of λs / 14+λs / 6 in the X direction (relative to component group 33 at a distance of λs / 14 in the X direction). Component group 38 is positioned relative to component group 31 at a distance of λs / 14+λs / 10+λs / 6 in the X direction (relative to component group 34 at a distance of λs / 14 in the X direction).

[0083] The configuration of multiple groups of components for reducing multiple higher harmonic components is not limited to Figure 8 The example shown is illustrated here. Let k and m be distinct integers greater than or equal to 1. For instance, when reducing a higher harmonic component corresponding to the 2k+1th harmonic, the first element group is positioned at a distance of λs / (4k+2) in the X direction relative to the second element group. Furthermore, when reducing an error component corresponding to the 2m+1st harmonic, the third element group is positioned at a distance of λs / (4m+2) in the X direction relative to the first element group, and the fourth element group is positioned at a distance of λs / (4m+2) in the X direction relative to the second element group. Thus, when reducing harmonic components corresponding to multiple higher harmonics, each of the multiple element groups used to reduce an error component corresponding to one higher harmonic is positioned at a predetermined interval in the X direction relative to the corresponding element group among the multiple element groups used to reduce error components corresponding to other higher harmonics, based on the design pitch λs.

[0084] In this embodiment, the structure and arrangement of the multiple element groups in each of the second to eighth resistors R12-R14 and R21-R24 are the same as the structure and arrangement of the multiple element groups in the first resistor R11. That is, each of the second to eighth resistors R12-R14 and R21-R24 also includes Figure 8 The structure and positional relationship of the eight component groups 31 to 38 are shown. Furthermore, component group 31 of the third resistor R13 is positioned in the X direction at the same position as component group 31 of the first resistor R11. Component group 31 of the fourth resistor R14 is positioned in the X direction at the same position as component group 31 of the second resistor R12. Component group 31 of the second resistor R12 is positioned relative to component group 31 of the first resistor R11 at a position λs / 2 away in the X direction. Component group 31 of the fourth resistor R14 is positioned relative to component group 31 of the third resistor R13 at a position λs / 2 away in the X direction.

[0085] The element group 31 of the seventh resistor R23 is positioned in the X direction at the same location as the element group 31 of the fifth resistor R21. The element group 31 of the eighth resistor R24 ​​is positioned in the X direction at the same location as the element group 31 of the sixth resistor R22. The element group 31 of the fifth resistor R21 is positioned relative to the element group 31 of the first resistor R11 at a position λs / 4 away in the X direction. The element group 31 of the sixth resistor R22 is positioned relative to the element group 31 of the fifth resistor R21 at a position λs / 2 away in the X direction. The element group 31 of the eighth resistor R24 ​​is positioned relative to the element group 31 of the seventh resistor R23 at a position λs / 2 away in the X direction.

[0086] With the structure of the first to eighth resistors R11 to R14 and R21 to R24 described above, the phase difference between the ideal component of the second detection signal S2 and the ideal component of the first detection signal S1 is an odd multiple of 1 / 4 of the specified signal period (the signal period of the ideal component), and multiple higher harmonic components of the first and second detection signals S1 and S2 can be reduced.

[0087] Furthermore, from the perspective of manufacturing precision of MR element 50, the positions of the first to eighth resistors R11 to R14, R21 to R24 and the positions of element groups 31 to 38 can be slightly deviated from the above positions.

[0088] Next, refer to Figure 9 and Figure 10 The first and second examples of MR element 50 will be described. Figure 9 This is a perspective view showing a first example of an MR element 50. In this first example, the MR element 50 includes a laminated film 50A, which comprises a magnetized fixing layer 51, a spacer layer 52, and a free layer 53 sequentially stacked in the Z direction. The planar shape of the laminated film 50A when viewed from the Z direction can be circular or... Figure 9 The image shown is a square or approximately a square.

[0089] The lower surface of the laminated film 50A of the MR element 50 is electrically connected to the lower surfaces of the laminated films 50A of other MR elements 50 via a lower electrode (not shown). The upper surface of the laminated film 50A of the MR element 50 is further electrically connected to the upper surfaces of the laminated films 50A of other MR elements 50 via an upper electrode (not shown). Thus, multiple MR elements 50 are connected in series. Furthermore, the arrangement of layers 51 to 53 in the laminated film 50A can also be... Figure 9 The configuration shown is reversed from top to bottom.

[0090] The MR element 50 also includes a bias magnetic field generator 50B that generates a bias magnetic field applied to the free layer 53. The direction of the bias magnetic field is intersecting a direction parallel to the X-direction. In the first example, the bias magnetic field generator 50B includes two magnets 54 and 55. Magnet 54 is positioned in front of the laminated film 50A in the -Y direction. Magnet 55 is positioned in front of the laminated film 50A in the Y direction. In the first example, specifically, the laminated film 50A and magnets 54 and 55 are positioned at an intersection with an imaginary plane parallel to the XY plane. Furthermore, in Figure 9 In the diagram, the arrows inside magnets 54 and 55 indicate the magnetization directions of magnets 54 and 55. In the first example, the direction of the bias magnetic field is the Y direction.

[0091] Figure 10 This is a perspective view showing a second example of the MR element 50. Except for the planar shape of the laminated film 50A and the positions of the magnets 54 and 55, the structure of the second example of the MR element 50 is the same as that of the first example. In the second example, the magnets 54 and 55 are positioned differently in the Z-direction from those of the laminated film 50A. Figure 10 In the example shown, magnets 54 and 55 are specifically positioned in front of the laminated film 50A in the Z direction. Furthermore, when viewed from the Z direction, the planar shape of the laminated film 50A is a rectangle that extends in the Y direction. When viewed from the Z direction, magnets 54 and 55 are positioned at a point overlapping with the laminated film 50A.

[0092] Furthermore, the direction of the bias magnetic field and the configuration of magnets 54 and 55 are not limited to... Figure 9 and Figure 10 The example shown illustrates this. For instance, the direction of the bias magnetic field can be any direction that intersects the directions parallel to the X and Z directions, or it can be a direction tilted relative to the Y direction. Additionally, magnets 54 and 55 can be offset from each other in a direction parallel to the X direction.

[0093] Alternatively, a bias magnetic field can be applied to the free layer 53 by means of uniaxial magnetic anisotropy, such as shape magnetic anisotropy or crystal magnetic anisotropy, instead of the bias magnetic field generator 50B.

[0094] Next, the method for generating the detection value Vs in this embodiment will be described. The detection value generation circuit 4 generates the detection value Vs, for example, as described below. The detection value generation circuit 4 first performs a predetermined correction process on the first and second detection signals S1 and S2 respectively. The correction process includes at least a process that makes the phase difference between the first detection signal S1 and the second detection signal S2 90°. The correction process may also include at least one of a process that corrects the amplitude of each of the first and second detection signals S1 and S2, and a process that corrects the offset of each of the first and second detection signals S1 and S2. Next, the detection value generation circuit 4 obtains an initial detection value within a range of 0° to less than 360° by calculating the arctangent of the ratio of the second detection signal S2 to the first detection signal S1, i.e., atan(S2 / S1). The initial detection value may be the arctangent value itself, or it may be a value obtained by adding a predetermined angle to the arctangent value.

[0095] When the arctangent value is 0°, when viewed from the Z direction, the position of the S pole of the magnetic field generator 3 coincides with the position of the element group 31 of the first and third resistors R11 and R13, respectively. Furthermore, when the arctangent value is 180°, when viewed from the Z direction, the position of the N pole of the magnetic field generator 3 coincides with the position of the element group 31 of the first and third resistors R11 and R13, respectively. Therefore, the initial detection value corresponds to the rotational position of the magnetic field generator 3 within the range from one S pole to another S pole adjacent to an N pole.

[0096] Furthermore, the detection value generation circuit 4 sets the initial detection value's cycle to 360° of the electrical angle and counts the rotational speed of the electrical angle from the reference position. The electrical angle corresponds to the rotational position of the magnetic field generator 3; one rotation of the electrical angle corresponds to the movement from one S pole to another S pole adjacent to it, separated by an N pole. Based on the initial detection value and the rotational speed of the electrical angle, the detection value generation circuit 4 generates a detection value Vs that corresponds to the rotational position of the magnetic field generator 3.

[0097] Next, a brief description of the manufacturing method of the magnetic sensor 2 according to this embodiment will be given. The manufacturing method of the magnetic sensor 2 includes: a process of forming a plurality of MR elements 50 on a substrate 10; a process of forming terminals 11 to 14 on the substrate 10; and a process of forming a plurality of wirings that are connected to the plurality of MR elements 50 and terminals 11 to 14.

[0098] In the process of forming multiple MR elements 50, multiple initial MR elements that will later become multiple MR elements 50 are first formed. Each of the multiple initial MR elements includes an initial magnetization fixation layer that will later become a magnetization fixation layer 51, a free layer 53, and a spacer layer 52.

[0099] Next, the magnetization direction of the initial magnetization fixing layer is fixed to the aforementioned predetermined direction using a laser and an external magnetic field in a predetermined direction. For example, among the multiple initial MR elements that subsequently become multiple MR elements 50 constituting the first, fourth, sixth, and seventh resistive elements R11, R14, R22, and R23, a laser is applied to the multiple initial MR elements while an external magnetic field in the first magnetization direction (-X direction) is applied. When the laser irradiation ends, the magnetization direction of the initial magnetization fixing layer is fixed in the first magnetization direction. Thus, the initial magnetization fixing layer becomes a magnetization fixing layer 51, and the multiple initial MR elements become multiple MR elements 50 constituting the first, fourth, sixth, and seventh resistive elements R11, R14, R22, and R23.

[0100] Furthermore, in the other initial MR elements that subsequently constitute the second, third, fifth, and eighth resistive elements R12, R13, R21, and R24, the magnetization direction of the initial magnetization fixing layer of each of the other initial MR elements can be fixed in the second magnetization direction by making the direction of the external magnetic field the second magnetization direction (X direction). In this way, multiple MR elements 50 can be formed.

[0101] Next, the function and effect of the magnetic encoder 1 in this embodiment will be explained. In this embodiment, the first to eighth resistors R11-R14 and R21-R24 are configured to reduce at least the second harmonic component among the plurality of higher harmonic components. Specifically, as described above, the first to eighth resistors R11-R14 and R21-R24 are configured to satisfy requirements regarding the circuit structure, the physical configuration, and the magnetization of the magnetization fixing layer. Therefore, according to this embodiment, the error caused by the difference between the magnetic pole pitch λm of the magnetic field generator 3 and the design pitch λs of the magnetic sensor 2 can be reduced.

[0102] The effects of the magnetic encoder 1 of this embodiment will be explained below compared with the magnetic encoder of the comparative example. First, the structure of the magnetic encoder of the comparative example will be described. The difference between the structure of the magnetic encoder of the comparative example and the structure of the magnetic encoder 1 of this embodiment is that the magnetic sensor 102 of the comparative example is included instead of the magnetic sensor 2 of this embodiment.

[0103] Figure 11 This is a top view of the magnetic sensor 102, which is a comparative example. Figure 12 This is a circuit diagram showing the structure of the comparative example magnetic sensor 102. The magnetic sensor 102 includes a first resistive element R1, a second resistive element R2, a third resistive element R3, and a fourth resistive element R4, each configured such that their resistance values ​​change in accordance with the intensity of the magnetic field component MFx. Furthermore, the magnetic sensor 102 includes multiple MR elements 50. The first to fourth resistive elements R1 to R4 are each constructed using multiple MR elements 50.

[0104] The magnetic sensor 102 also includes a power supply port V101, a ground port G101, a first output port E101, and a second output port E102. The ground port G101 is grounded. The first and second output ports E101 and E102 are connected to the detection value generation circuit 4.

[0105] The magnetic sensor 102 generates a signal corresponding to the potential of the first output port E101 as a first detection signal S101, and generates a signal corresponding to the potential of the second output port E102 as a second detection signal S102. The detection value generation circuit 4 connected to the magnetic sensor 102 generates a detection value Vs based on the first and second detection signals S101 and S102.

[0106] The first resistor R1 is located in the path connecting the power supply port V101 and the first output port E101. The second resistor R2 is located in the path connecting the ground port G101 and the first output port E101. The third resistor R3 is located in the path connecting the ground port G101 and the second output port E102. The fourth resistor R4 is located in the path connecting the power supply port V101 and the second output port E102.

[0107] The center of gravity of the second resistor R2, viewed from the Z direction, is positioned relative to the center of gravity of the first resistor R1, located at a position away from λs / 2 in the X direction. The center of gravity of the third resistor R3, viewed from the Z direction, is positioned relative to the center of gravity of the fourth resistor R4, located at a position away from λs / 2 in the X direction. The center of gravity of the fourth resistor R4, viewed from the Z direction, is positioned relative to the center of gravity of the first resistor R1, located at a position away from λs / 4 in the X direction.

[0108] exist Figure 11 and Figure 12 In the diagram, the arrows drawn within the first to fourth resistors R1 to R4 indicate the first magnetization direction of the magnetization fixing layer of each of the plurality of MR elements 50 included in the resistor. In the comparative example, the first magnetization direction is the -X direction in all the first to fourth resistors R1 to R4.

[0109] The first to fourth resistors R1 to R4 each include multiple element groups. The structure and arrangement of the multiple element groups in each of the first to fourth resistors R1 to R4 are the same as the structure and arrangement of the multiple element groups in the first resistor R11 of the magnetic sensor 2 in this embodiment.

[0110] Next, the first detection signal S101 in the comparative example will be explained. In the comparative example, the resistance value R1 of the first resistor R1 and the resistance value R2 of the second resistor R2 are represented by the following equations (1) and (2), respectively. Furthermore, in equations (1) and (2), R0 and ΔR are defined constants, and θ represents the electrical angle.

[0111] R1=R0+ΔRcos(θ)……(1)

[0112] R2=R0+ΔRcos(θ+λs / λm×π)……(2)

[0113] In addition, the first detection signal S101 is represented by the following formula (3).

[0114] S101=R2 / (R1+R2)……(3)

[0115] When the magnetic pole pitch λm is equal to the design pitch λs, according to equations (1) to (3), the first detection signal S101 is represented by the following equation (4).

[0116] S101=R2 / (2R0+ΔRcos(θ)-ΔRcos(θ))

[0117] =R2 / 2R0……(4)

[0118] When the magnetic pole pitch λm is different from the design pitch λs, according to equations (1) to (3), the first detection signal S101 is represented by the following equation (5).

[0119] S101

[0120] =R2 / (2R0+ΔRcos(θ)+ΔRcos(θ+λs / λm×π))……(5)

[0121] As understood from equation (4), when the magnetic pole pitch λm is equal to the design pitch λs, the first detection signal S101 is equal to a constant multiple of R2. In this case, ideally, the first detection signal S101 varies periodically in a manner that depicts an ideal sine curve according to the electrical angle θ (refer to equation (2)). On the other hand, as understood from equation (5), when the magnetic pole pitch λm is different from the design pitch λs, the denominator of equation (5) contains a component that varies according to the electrical angle θ. This component causes the first detection signal S101 to generate a higher harmonic component equivalent to the second harmonic.

[0122] The explanation of the first detection signal S101 also applies to the second detection signal S102. The resistance values ​​R3 of the third resistor R3, R4 of the fourth resistor R4, and the second detection signal S102 can each be represented using a sin function that varies according to the electrical angle θ. When the magnetic pole pitch λm differs from the designed pitch λs, the second detection signal S102 also generates higher harmonic components equivalent to the second harmonic. The higher harmonic components of the first and second detection signals S101 and S102 respectively cause errors in the detected value Vs.

[0123] Next, the first detection signal S1 in this embodiment will be described. In this embodiment, the resistance value R of the first resistor R11 is... 11 The resistance value R of the second resistor R12 12 The resistance value R of the third resistor R13 13 The resistance value R of the fourth resistor R14 14 They are represented by the following formulas (6) to (9).

[0124] R 11 =R0+ΔRcos(θ)……(6)

[0125] R 12 =R0+ΔRcos(θ+λs / λm×π+π)

[0126] =R0-ΔRcos(θ+λs / λm×π)……(7)

[0127] R 13 =R0 + ΔRcos(θ + π)

[0128] =R0-ΔRcos(θ+π)……(8)

[0129] R 14 =R0+ΔRcos(θ+λs / λm×π)……(9)

[0130] The first detection signal S1 is represented by the following formula (10).

[0131] S1=(R 13 +R 14 ) / (R 11 +R 12 +R 13 +R 14 )

[0132] =(R 13 +R 14 ) / 4R0……(10)

[0133] As understood from equation (10), in this embodiment, regardless of whether the magnetic pole pitch λm is equal to the design pitch λs, the denominator of equation (10) is a constant, and the first detection signal S1 is equal to the resistance value R. 13 and resistance value R 14 The sum is a constant multiple. Therefore, in this embodiment, regardless of whether the magnetic pole pitch λm is equal to the design pitch λs, ideally, the first detection signal S1 changes periodically in a manner that depicts an ideal sine curve according to the electric angle θ (refer to equations (8) and (9)).

[0134] The description of the first detection signal S1 also applies to the second detection signal S2. The second detection signal S2 can be represented by the resistance value R of the fifth resistor R21. 21 The resistance value R of the sixth resistor R22 22 The resistance value R of the seventh resistor R23 23 The resistance value R of the eighth resistor R24 24 R in substitution (10) 11 R 12 R 13 R 14 The resulting formula is used to represent this. Similar to the first detection signal S1, regardless of whether the magnetic pole pitch λm is equal to the design pitch λs, ideally, the second detection signal S2 changes periodically in a manner that depicts an ideal sine curve based on the electric angle θ.

[0135] As explained above, in this embodiment, the configuration is designed to reduce the second harmonic component among multiple higher harmonic components. Therefore, according to this embodiment, errors in the detected value Vs can be prevented. This effect will now be explained with reference to simulation results.

[0136] In the simulation, models of the comparative examples and the embodiments were used. The model of the comparative examples was a model of the magnetic encoder of the comparative examples. The model of the embodiments was a model of the magnetic encoder 1 of this embodiment.

[0137] In the simulation, the design pitch λs is set to 800 μm. In the comparative example model, the first to fourth resistors R1 to R4 are configured as follows: the center of gravity of the second resistor R2 is positioned 400 μm away from the center of gravity of the first resistor R1 in the X direction; the center of gravity of the third resistor R3 is positioned 400 μm away from the center of gravity of the fourth resistor R4 in the X direction; and the center of gravity of the fourth resistor R4 is positioned 200 μm away from the center of gravity of the first resistor R1 in the X direction.

[0138] In the model of the embodiment, the first to eighth resistors R11 to R14 and R21 to R24 are configured as follows: the second position C12 is located 400 μm away from the first position C11 in the X direction; the fourth position C14 is located 400 μm away from the third position C13 in the X direction; the sixth position C22 is located 400 μm away from the fifth position C21 in the X direction; the eighth position C24 is located 400 μm away from the seventh position C23 in the X direction; and the fifth position C21 is located 200 μm away from the first position C11 in the X direction.

[0139] In addition, in the simulation, the spacing between the magnetic sensor 2 and the magnetic field generator 3 in the direction parallel to the Z direction, and the spacing between the magnetic sensor 102 and the magnetic field generator 3 in the direction parallel to the Z direction, are both set to 0.4 mm. Furthermore, the voltage applied to power port V1 and the voltage applied to power port V101 are both set to 1 V.

[0140] Here, the component whose signal period coincides with that of the ideal component is called the first component; the higher harmonic component corresponding to the second higher harmonic is called the second component; the higher harmonic component corresponding to the third higher harmonic is called the third component; the higher harmonic component corresponding to the fourth higher harmonic is called the fourth component; the higher harmonic component corresponding to the fifth higher harmonic is called the fifth component; and the higher harmonic component corresponding to the sixth higher harmonic is called the sixth component. Furthermore, the ratio of the amplitude of a higher harmonic component to the amplitude of the first component is called the amplitude ratio of that higher harmonic component. Additionally, the difference between the assumed initial detection value when the detection signals S1, S2, S101, and S102 each contain only the ideal component and the initial detection value obtained through simulation is called the error of the detection value Vs. Moreover, the initial detection value is a value equivalent to the electrical angle obtained through calculation, expressed as a value greater than 0° and less than 360°. Therefore, the error unit of the detection value Vs is expressed in degrees.

[0141] In the simulation, the magnetic pole pitch λm was varied by 200 μm each time within the range of 600 μm to 2600 μm. In the comparative example model, the first and second detection signals S101 and S102 and the detection value Vs were obtained for each magnetic pole pitch λm when the magnetic field generator 3 was rotated. Furthermore, by performing a Fourier transform on the first detection signal S101, the first to sixth components of the first detection signal S101 were obtained, and the amplitude ratios of the second to sixth components of the first detection signal S101 were calculated. Additionally, the error of the detection value Vs was determined.

[0142] Similarly, in the model of the embodiment, the first and second detection signals S1, S2 and the detection value Vs when the magnetic field generator 3 is rotated are obtained according to each magnetic pole pitch λm. Furthermore, by performing a Fourier transform on the first detection signal S1, the first to sixth components of the first detection signal S1 are obtained, and the amplitude ratios of the second to sixth components of the first detection signal S1 are determined. Additionally, the error of the detection value Vs is calculated.

[0143] Figure 13 This is a characteristic graph representing the amplitude ratio of the comparative model obtained through simulation. Figure 14 This is a characteristic graph representing the amplitude ratio of the model in the embodiment obtained through simulation. Figure 13 and Figure 14 In the diagram, the horizontal axis represents the magnetic pole pitch λm, and the vertical axis represents the amplitude ratio. Additionally, in... Figure 13 In the figures, reference numeral 71 indicates the amplitude ratio of the second-order component, reference numeral 72 indicates the amplitude ratio of the third-order component, reference numeral 73 indicates the amplitude ratio of the fourth-order component, reference numeral 74 indicates the amplitude ratio of the fifth-order component, and reference numeral 75 indicates the amplitude ratio of the sixth-order component. Additionally, in... Figure 14 In the figure, reference numeral 81 indicates the amplitude ratio of the second-order component, reference numeral 82 indicates the amplitude ratio of the third-order component, reference numeral 83 indicates the amplitude ratio of the fourth-order component, reference numeral 84 indicates the amplitude ratio of the fifth-order component, and reference numeral 85 indicates the amplitude ratio of the sixth-order component.

[0144] like Figure 13 As shown, in the comparative example model, the amplitude ratios of the fourth, fifth, and sixth components (reference numerals 73, 74, and 75) are zero or approximately zero. Furthermore, in the comparative example model, it is evident that the amplitude ratio of the second component (reference numeral 71) is the largest, except when the pole pitch λm is 800 μm. It is also evident that the amplitude ratio of the second component (reference numeral 71) is the smallest when the pole pitch λm is 800 μm, and increases as the pole pitch λm increases from 800 μm. The case where the pole pitch λm is 800 μm refers to the case where the pole pitch λm equals the design pitch λs.

[0145] like Figure 14 As shown, in the model of the embodiment, the amplitude ratios of the fourth component (reference numeral 83), fifth component (reference numeral 84), and sixth component (reference numeral 85) are zero or approximately zero, similar to the model of the comparative example. Furthermore, in the model of the embodiment, the amplitude ratio of the second component (reference numeral 81) is zero.

[0146] Figure 13 and 14The results shown also apply to the second detection signals S2 and S102. According to the simulation results, in this embodiment, the configuration is capable of reducing the second harmonic component (second harmonic component) among multiple higher harmonic components.

[0147] Figure 15 This is a characteristic graph representing the error of the detection value Vs of the comparative example model and the embodiment model, respectively, obtained through simulation. Figure 15 In the diagram, the horizontal axis represents the magnetic pole pitch λm, and the vertical axis represents the error of the detected value Vs. Additionally, in... Figure 15 In the figures, reference numeral 91 indicates the error of the comparative example model, and reference numeral 92 indicates the error of the embodiment model.

[0148] As described above, in the simulation, the error of the detected value Vs is calculated using the initial detected value, and the initial detected value is calculated using the detected signals S1, S2, S101, and S102. The waveforms of the detected signals S1, S2, S101, and S102 are distorted from a sine curve depending on the amplitude ratio of the higher harmonic components. Therefore, the error of the detected value Vs depends on the amplitude ratio of the higher harmonic components. (The last sentence appears to be incomplete and possibly refers to a different topic.) Figure 13 and Figure 15 It is understood that in the comparative example model, the error of the detected value Vs ( Figure 15 The reference numeral 91 in the figure depends significantly on the amplitude ratio of the second component. Figure 13 (See figure 71). The ratio of the error of the detected value Vs to the amplitude of the secondary component is also minimized when the magnetic pole pitch λm is equal to the design pitch λs (800 μm), and increases as the magnetic pole pitch λm increases from 800 μm, that is, as the magnetic pole pitch λm deviates more from the design pitch λs.

[0149] Additionally, as from Figure 14 and Figure 15 It is understood that in the model of the embodiment, because the amplitude ratio of the second component ( Figure 14 The figure in Figure 81) is zero, so the error of the detected value Vs is ( Figure 15 The reference numeral 92 in the figure depends significantly on the amplitude ratio of the third component. Figure 14 (Ref. 82 in the attached figures). However, the amplitude ratio of the third component of the model in the embodiment ( Figure 14 The amplitude ratio of the second component of the model in Figure 82 to that of the comparative example model (see figure 82) Figure 13 The reference numeral 71 in the attached figure is sufficiently small compared to this. Therefore, as shown in the figure... Figure 15 As shown, the error of the model in the embodiment (reference numeral 92) is sufficiently small compared to the error of the model in the comparative example (reference numeral 91).

[0150] As can be understood from the simulation results, according to this embodiment, by configuring it in a way that can reduce the second harmonic component (second harmonic component) among multiple higher harmonic components, the error in the detection value Vs caused by the difference between the magnetic pole pitch λm and the design pitch λs can be prevented.

[0151] Furthermore, as described above, in this embodiment, the element groups 31 to 38 are configured to reduce higher harmonic components corresponding to the third harmonic, the fifth harmonic, and the seventh harmonic. That is, in this embodiment, the first to eighth resistors R11 to R14 and R21 to R24 are configured to reduce not only the higher harmonic components corresponding to the second harmonic, but also the higher harmonic components corresponding to the third, fifth, and seventh harmonics. Therefore, according to this embodiment, the error of the detected value Vs can be further reduced.

[0152] However, when the magnetic encoder 1 is applied to a device that generates significant vibration, it is sometimes necessary to increase the distance between the magnetic sensor 2 and the magnetic field generator 3 to prevent collision between them. In this case, to ensure the magnetic field component MFx at the location where the magnetic sensor 2 is positioned (refer to...) Figure 4 The strength of the magnetic poles is preferably larger than the designed pitch λs, to achieve the desired strength. Specifically, the magnetic pole pitch λm is preferably greater than 1.1 times the designed pitch λs, and more preferably greater than 1.25 times the designed pitch λs. On the other hand, as from... Figure 15 It is understood that when the magnetic pole pitch λm is 1400 μm or more, that is, when the magnetic pole pitch λm is more than 1.75 times the design pitch λs, the error of the detected value Vs increases as the magnetic pole pitch λm increases. Therefore, it is preferable that the magnetic pole pitch λm is less than 1.75 times the design pitch λs.

[0153] [Variation Example]

[0154] Next, refer to Figure 16 A variation of the magnetic encoder 1 of this embodiment will be described. Figure 16 This is a perspective view showing a modified example of the magnetic encoder 1. In the modified example, the magnetic encoder 1 includes a magnetic field generator 103 instead of... Figure 2 and Figure 3 The magnetic field generator 3 is shown. The magnetic field generator 103 has outer peripheral surfaces 103a and 103b, respectively, facing away from the rotation axis C. The outer peripheral surfaces 103a and 103b are arranged at different positions in a direction parallel to the rotation axis C. The outer peripheral surface 103a is arranged at a position farther away from the rotation axis C than the outer peripheral surface 103b.

[0155] Multiple sets of N-pole and S-pole are disposed on the outer peripheral surface 103a. Figure 16In the diagram, the N pole is shaded for ease of understanding. Magnetic sensor 2 is configured opposite the outer peripheral surface 103a. The magnetic field component MFx at the reference position, such as the position where magnetic sensor 2 is configured (see reference). Figure 4 The intensity of the magnetic field changes as the magnetic field generator 103 rotates.

[0156] In a modified example, the direction parallel to the rotation axis C can be set as the Y direction, and the direction orthogonal to the rotation axis C and moving from the magnetic sensor 2 to the rotation axis C can be set as the Z direction.

[0157] Furthermore, the present invention is not limited to the embodiments described above, and various modifications can be made. For example, as long as the requirements of the invention are met, the number and arrangement of the MR elements 50 are not limited to the examples shown in each embodiment, and are arbitrary.

[0158] In addition, the first to eighth positions C11~C14 and C21~C24 can also be positions other than the center of gravity, such as the ends of the corresponding resistors in the -X direction.

[0159] Alternatively, the third, fourth, seventh, and eighth resistors R13, R14, R23, and R24 may be positioned relative to the first, second, fifth, and sixth resistors R11, R12, R21, and R22 at positions that are integer multiples of the design pitch λs in the X direction or -X direction.

[0160] Alternatively, the magnetic field generator of the present invention can also be a linear scale with multiple sets of N and S poles magnetized in a straight direction. In this case, the magnetic encoder of the present invention can also be applied to a position detection device for detecting the position of an object whose position can change. The magnetic sensor and the magnetic field generator can also be configured such that the intensity of the magnetic field component changes when the position of the object changes.

[0161] Alternatively, the magnetic sensor of the present invention may also include a first full-bridge circuit configured to output a first detection signal and a second full-bridge circuit configured to output a second detection signal. Each of the first and second full-bridge circuits may also be composed of multiple resistors.

[0162] Based on the above description, it is evident that various methods and variations of the present invention can be implemented. Therefore, within the equivalent scope of the invention, methods other than the preferred methods described above can also be used to implement the present invention.

Claims

1. A magnetic encoder, characterized in that, include: A magnetic field generator that produces an object magnetic field containing a magnetic field component in a first direction; and A magnetic sensor, configured to detect the magnetic field of the object, The magnetic sensor and the magnetic field generator are configured such that when at least one of the magnetic sensor and the magnetic field generator is operational, the intensity of the magnetic field component at the reference position changes. The magnetic field generator is a magnetic ruler with multiple sets of alternating N and S poles. The magnetic sensor is configured to include multiple resistive elements, each with a resistance value that changes in response to a change in the intensity of the magnetic field component, and to generate a first detection signal and a second detection signal corresponding to the change in the intensity of the magnetic field component. The plurality of resistors includes two resistors. The resistance value of one of the two resistors corresponds to the first detection signal. The resistance value of the other of the two resistors corresponds to the second detection signal. The one resistor and the other resistor are positioned at different locations in the first direction such that the phase of the first detection signal is different from the phase of the second detection signal. In the magnetic scale, when the distance between the centers of two adjacent N poles separated by an S pole is defined as the magnetic pole pitch, and the design pitch is defined as four times the distance between a specified position within one resistor and a specified position within the other resistor in the first direction, the magnetic pole pitch is larger than the design pitch. The first detection signal and the second detection signal each include: an ideal component that varies periodically in a manner that depicts an ideal sine curve; and a plurality of higher harmonic components, each corresponding to a higher harmonic of the ideal component. The plurality of resistors are configured to reduce at least the second harmonic component among the plurality of higher harmonic components. The magnetic sensor also includes: a power supply port, a grounding port, a first output port, and a second output port. The plurality of resistors includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor. The first resistor and the second resistor are sequentially arranged starting from the power port side in the first path connecting the power port and the first output port. The third resistor and the fourth resistor are sequentially arranged starting from the ground port side in the second path connecting the ground port and the first output port. The fifth resistor and the sixth resistor are sequentially arranged starting from the ground port side in the third path connecting the ground port and the second output port. The seventh resistor and the eighth resistor are sequentially arranged starting from the power port side in the fourth path connecting the power port and the second output port. The intervals between the first position in the first resistor and the second position in the second resistor, the intervals between the third position in the third resistor and the fourth position in the fourth resistor, the intervals between the fifth position in the fifth resistor and the sixth position in the sixth resistor, and the intervals between the seventh position in the seventh resistor and the eighth position in the eighth resistor, in the first direction, are each equal to an odd multiple of half the design pitch. The interval between the first position and the third position in the first direction, and the interval between the fifth position and the seventh position in the first direction, are respectively equal to zero or an integer multiple of the design pitch. The interval between the first position and the fifth position in the first direction is equal to 1 / 4 of the design pitch. The magnetic sensor also includes multiple magnetoresistive elements. Each of the plurality of magnetoresistive effect elements includes a magnetized fixed layer, a free layer, and a spacer layer disposed between the magnetized fixed layer and the free layer. The magnetization fixing layer has a first magnetization with a fixed orientation. The free layer has a second magnetization whose direction can change in a plane parallel to both the first direction and a second direction orthogonal to the first direction. The magnetized fixed layer, the free layer, and the spacer layer are stacked in a third direction orthogonal to the first and second directions. The first resistor, the second resistor, the third resistor, the fourth resistor, the fifth resistor, the sixth resistor, the seventh resistor, and the eighth resistor are constructed using the plurality of magnetoresistive effect elements. The first magnetization of the magnetization fixing layer in the first resistive element, the fourth resistive element, the sixth resistive element, and the seventh resistive element includes a component of a first magnetization direction that is parallel to the first direction. The first magnetization of the magnetization fixing layer in the second, third, fifth, and eighth resistive elements includes a component of a second magnetization direction opposite to the first magnetization direction.

2. The magnetic encoder according to claim 1, characterized in that: The magnetic pole pitch is greater than 1.1 times the designed pitch.

3. The magnetic encoder according to claim 2, characterized in that: The magnetic pole pitch is greater than 1.25 times the designed pitch and less than 1.75 times the designed pitch.

4. The magnetic encoder according to claim 1, characterized in that: The first position is the center of gravity of the first resistive element when viewed from a direction parallel to the third party. The second position is the center of gravity of the second resistive element when viewed from a direction parallel to the third party. The third position is the center of gravity of the third resistive element when viewed from a direction parallel to the third party. The fourth position is the center of gravity of the fourth resistive element when viewed from a direction parallel to the third party. The fifth position is the center of gravity of the fifth resistive element when viewed from a direction parallel to the third party. The sixth position is the center of gravity of the sixth resistor when viewed from a direction parallel to the third party. The seventh position is the center of gravity of the seventh resistive element when viewed from a direction parallel to the third party. The eighth position is the center of gravity of the eighth resistor when viewed from a direction parallel to the third party.

5. The magnetic encoder according to claim 1, characterized in that: The first resistor and the third resistor are adjacent in the second direction. The second resistor and the fourth resistor are adjacent in the second direction. The fifth resistor and the seventh resistor are adjacent in the second direction. The sixth resistor and the eighth resistor are adjacent in the second direction.

6. The magnetic encoder according to claim 1, characterized in that: The first resistor is adjacent to the seventh resistor, but not adjacent to the eighth resistor. The eighth resistor is adjacent to the second resistor, but not adjacent to the first resistor.

7. The magnetic encoder according to claim 6, characterized in that: The third resistor is positioned such that the first resistor is sandwiched between it and the seventh resistor. The fourth resistor is positioned such that the second resistor is sandwiched between it and the eighth resistor. The fifth resistor is positioned such that the seventh resistor is sandwiched between it and the first resistor. The sixth resistor is positioned such that the eighth resistor is sandwiched between it and the second resistor.

8. The magnetic encoder according to claim 1, characterized in that: Each of the plurality of magnetoresistive effect elements is configured to apply a bias magnetic field in a direction intersecting the first direction to the free layer.

9. The magnetic encoder according to claim 1, characterized in that: The spacer layer is a tunnel barrier layer.

10. The magnetic encoder according to claim 1, characterized in that: The magnetic field generator is configured to rotate about a rotation axis and has an end face located at an end in a direction parallel to the rotation axis. The multiple sets of N and S poles are arranged alternately around the rotation axis and disposed on the end face. The intensity of the magnetic field component at the reference position changes as the magnetic field generator rotates. The magnetic sensor is configured to face the end face.

11. The magnetic encoder according to claim 10, characterized in that: The magnetic field generator is configured to rotate in conjunction with an optical element, which is used to measure the change in the direction of light travel to an object.

12. The magnetic encoder according to claim 1, characterized in that: The magnetic field generator is configured to rotate about a rotation axis and has an outer peripheral surface facing away from the rotation axis. The multiple sets of N and S poles are arranged alternately around the rotation axis and disposed on the outer peripheral surface. The intensity of the magnetic field component at the reference position changes as the magnetic field generator rotates. The magnetic sensor is configured to face the outer peripheral surface.

13. The magnetic encoder according to claim 12, characterized in that: The magnetic field generator is configured to rotate in conjunction with an optical element, which is used to measure the change in the direction of light travel to an object.

14. A ranging device that measures the distance to an object by detecting illuminated light, the ranging device being characterized by comprising: An optical element configured to rotate while changing the direction of light travel; and The magnetic encoder of claim 1, The magnetic field generator is configured to rotate about a rotation axis in conjunction with the optical element. The multiple sets of N and S poles are arranged alternately around the rotation axis. The intensity of the magnetic field component at the reference position changes as the magnetic field generator rotates.

15. The ranging device according to claim 14, characterized in that: The magnetic field generator has an end face located at one end in a direction parallel to the rotation axis. The multiple sets of N and S electrodes are disposed on the end face. The magnetic sensor is configured to face the end face.

16. The ranging device according to claim 14, characterized in that: The magnetic field generator has an outer peripheral surface facing away from the rotation axis. The multiple sets of N and S electrodes are disposed on the outer peripheral surface. The magnetic sensor is configured to face the outer peripheral surface.

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