Magnetic encoder

Abstract

The invention provides a magnetic encoder. The magnetic encoder comprises a magnetic code disc and an in-plane orientation magnetoresistive sensor, two in-plane orthogonal magnetic fields generated by the magnetic code disc can saturate the magnetoresistive sensor, and the distance between the sensing center of the magnetoresistive sensor on the opposite plane and the midline of the corresponding magnetic track on the magnetic code disc is not smaller than one fourth of the width of the magnetic track. Wherein the opposite plane is parallel to the magnetic code disc; the sensing center of the magnetoresistive sensor module is the center of a sensing area formed by the plurality of magnetoresistive sensors; the center line of the magnetic track is a line formed by the center points of the magnetic track in the width direction. The precision of the magnetic encoder can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of encoders, and particularly to a magnetic encoder. Background Art

[0002] The magnetic code disk of a magnetic encoder can be composed of multiple pairs of magnetic poles, and the magnetization direction of the magnetic pole pairs can be the horizontal direction along the magnetic track in the plane or the vertical direction perpendicular to the plane. However, whether it is horizontal magnetic poles or vertical magnetic poles, the magnetic field intensity is the strongest at the center of the magnetic track, and there are only two magnetic field components in the two directions at the center of the magnetic track, namely the horizontal direction component and the vertical direction component. Therefore, multiple pairs of magnetic poles cannot provide two orthogonal in-plane horizontal magnetic field components at the center of the magnetic track.

[0003] Thus, in order to match the magnetic field distribution of the magnetic code disk formed by multiple pairs of magnetic poles, one of the sensors needs to adopt a perpendicularly oriented pinned layer. However, out-of-plane (perpendicular orientation) TMR (Tunneling Magnetoresistance) or GMR sensors have shape anisotropy, and there is generally magnetic hysteresis in the magnetic signal, and the linearity is not as good as that of in-plane oriented TMR sensors. It is okay for detecting switching magnetic signals, but due to its low accuracy, it is not suitable for high-precision metrology application scenarios; Therefore, how to improve the accuracy of an encoder by using a magnetic encoder composed of multiple pairs of magnetic poles has become an urgent problem to be solved at present. Summary of the Invention

[0004] To solve the above problems, the magnetic encoder provided by the present invention can improve the accuracy of the magnetic encoder formed by multiple pairs of magnetic poles by defining the distance between the sensing center of the magnetoresistive sensor module and the midline of the corresponding magnetic track on the magnetic code disk in the relative plane, and enabling both groups of in-plane orthogonal magnetoresistive sensors to be in a saturated state.

[0005] In a first aspect, the present invention provides a magnetic encoder, which includes: a magnetic code disk and an in-plane oriented magnetoresistive sensor; The magnetic code disk generates two in-plane orthogonal magnetic fields that can saturate the magnetoresistive sensor, and the distance between the sensing center of the magnetoresistive sensor and the midline of the corresponding magnetic track on the magnetic code disk in the relative plane is not less than one-fourth of the width of the magnetic track; Wherein, the relative plane is parallel to the magnetic code disk; the sensing center of the magnetoresistive sensor module is the center of the sensing area formed by multiple magnetoresistive sensors; the midline of the magnetic track is the line formed by the center point of the magnetic track in the width direction.

[0006] Optionally, the magnetoresistive sensor is used to sense a pair of orthogonal magnetic fields in the direction of the relative plane; The magnetic code disk saturates the magnetoresistive sensor, so that the magnetoresistive sensor only responds to the change in the direction of the magnetic field where it is located, and both the differential sine signal and the differential cosine signal generated by the magnetoresistive sensor are not affected by the change in the magnetic field strength where it is located; When the maximum values of the two in-plane orthogonal magnetic fields generated by the magnetic poles on the magnetic code disk in the two planes where the magnetoresistive sensor is located are different, both the differential sine signal and the differential cosine signal generated by the magnetoresistive sensor are not affected by the change in the magnetic field strength where it is located.

[0007] Optionally, the magnetoresistive sensor is installed on a circuit board, and the circuit board is parallel to the magnetic code disk.

[0008] Optionally, the magnetoresistive sensor includes two sets of Wheatstone bridge circuits; The Wheatstone bridge circuit constructs a differential sine signal and a differential cosine signal for the magnetic encoder.

[0009] Optionally, the magnetoresistive sensor includes at least one of a tunneling magnetoresistive sensor, a giant magnetoresistive sensor, and an anisotropic magnetoresistive sensor.

[0010] Optionally, the shape of the magnetic code disk is an annular shape, a disk shape, or a strip shape.

[0011] Optionally, the magnetic encoder is a rotary encoder or a linear encoder.

[0012] Optionally, the magnetic encoder is an absolute position encoder or an incremental encoder.

[0013] Optionally, the magnetic code disk includes multiple pairs of magnetic poles.

[0014] Optionally, the sensing center of the magnetoresistive sensor is no more than 0.8 times the width of the magnetic track from the midline of the corresponding magnetic track on the magnetic code disk in the relative plane.

[0015] The magnetic encoder provided by the embodiment of the present invention utilizes two principles: 1) At the edge of the magnetic track of the magnetic code disk, two in-plane orthogonal magnetic fields will appear; 2) After the magnetic field on the in-plane magnetoresistive sensor is saturated, the magnetoresistive sensor only responds to the change in the magnetic field direction and has nothing to do with the fluctuation of the magnetic field strength magnitude. In this way, the in-plane magnetoresistive sensor with high linearity can be applied to multiple pairs of magnetic poles, greatly improving the resolution and accuracy of the magnetic encoder. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 A cross-sectional schematic view of an annular magnetic code disk and a sensor according to an embodiment of the present application, where the black dots in the magnetoresistive inductor in the figure represent sensing centers; Figure 2 A perspective view of a magnetic code disk according to an embodiment of the present application; Figure 3 A schematic structural diagram of a partial internal circuit of a magnetoresistive sensor according to an embodiment of the present application; Figure 4 A cross-sectional schematic view of an annular magnetic code disk and a sensor according to an embodiment of the present application, where the black dots A, B, and C in the magnetoresistive inductor in the figure represent that the sensing centers are respectively directly above the midline of the magnetic track, directly above the outer edge of the magnetic track, and above the outside of the magnetic track; Figures 5 to 7 Respectively, the sensing centers are at A, B, and C in the radial direction of the magnetic code disk Figure 4 Schematic diagrams of the changes in the magnetic field strength in two orthogonal planes at the sensing center during the circumferential movement of the magnetic code disk; Figure 8 A schematic diagram of the changes in the maximum values of Hx and Hy, i.e., Hx(max) and Hy(max), during the movement of the sensing center from directly above the midline of the magnetic track to the outside according to an embodiment of the present application; Figure 9 A schematic diagram of the changes in the maximum values of Hx and Hy during the radial movement of the sensing center on an annular magnetic code disk according to an embodiment of the present application.

[0018] Reference numerals: 1. Magnetic code disk; 2. Magnetoresistive sensor; 21. Wheatstone bridge circuit; 3. Circuit board. Detailed implementation manners

[0019] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0021] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. can be used herein to describe the relationship of one element or feature shown in the figures with other elements or features. Meanwhile, for example, "directly above" can be used herein to describe that one element or feature shown in the figures coincides in the vertical line direction, which may be partial coincidence or complete coincidence, specifically determined according to the actual situation or the content shown in the figures. It should be understood that in addition to the orientations shown in the figures, spatial relationship terms also include different orientations of the device during use and operation. For example, if the device in the attached figure is flipped, an element or feature described as "under other elements" or "beneath it" or "under it" will be oriented "above" other elements or features. Therefore, the exemplary terms "under" and "beneath" can include both the upper and lower orientations. In addition, the device may also include other orientations (such as rotating 90 degrees or other orientations), and the spatial descriptive terms used herein are accordingly interpreted.

[0022] It should be noted that when an element is referred to as "fixedly connected" to another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. On the contrary, when an element is referred to as being "directly on" another element, there is no intermediate element. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0023] As used herein, the singular forms of "a", "an" and "the" may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that terms such as "comprises / includes" or "has" etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0024] First of all, it should be noted that the magnetic code disk of the magnetic encoder can be composed of magnetic tracks with multiple pairs of magnetic poles, and the magnetization direction of the magnetic pole pairs can be the in-plane horizontal direction or the out-of-plane vertical direction along the magnetic tracks. However, whether it is a horizontal magnetic pole or a vertical magnetic pole, the magnetic field intensity is the strongest at the center of the magnetic track, and there are only two magnetic field components in the two directions at the center of the magnetic track: the horizontal component along the magnetic track and the vertical component. Therefore, the magnetic code disk formed by multiple pairs of magnetic poles cannot provide two orthogonal in-plane horizontal magnetic field components at the center of the magnetic track. In order to match the magnetic field distribution of the magnetic code disk formed by multiple pairs of magnetic poles, one of the sensors needs to use a vertically oriented pinned layer. However, out-of-plane oriented (vertical) TMR or GMR sensors generally have shape anisotropy, magnetic signals have magnetic hysteresis, and the linearity is not as good as that of in-plane oriented TMR sensors. It is okay for detecting on-off magnetic signals, but it is not suitable for high-precision metrology application scenarios.

[0025] In a first aspect, the present invention provides a magnetic encoder, which can be a rotary encoder or a linear encoder. In addition, the magnetic encoder can be an absolute position encoder or an incremental encoder, and this embodiment does not make specific limitations on this.

[0026] See Figure 1 and Figure 2 , the magnetic encoder includes: a magnetic code disk 1 and two groups of magnetoresistive sensors 2 with in-plane orthogonal orientations.

[0027] The magnetic code disk 1 generates two in-plane orthogonal magnetic fields in the working area of the magnetoresistive sensor 2, and the two in-plane orthogonal magnetic fields are sufficient to saturate the magnetoresistive sensor 2. The sensing center of the magnetoresistive sensor 2 is not less than one-fourth of the width of the corresponding magnetic track on the magnetic code disk 1 in the relative plane. This embodiment does not limit the specific magnitude of the surrounding magnetic field when the magnetoresistive sensor 2 is in a saturated state.

[0028] Among them, the relative plane is parallel to the magnetic code disk 1; the sensing center of the magnetoresistive sensor 2 module is the center of the sensing area formed by multiple magnetoresistive sensors 2; the midline of the magnetic track is the line formed by the center point in the width direction of the magnetic track.

[0029] Furthermore, the distance between the sensing center of the magnetoresistive sensor 2 and the midline of the corresponding magnetic track on the magnetic code disk 1 in the relative plane is not greater than 0.8 times the width of the magnetic track. Among them, the distance between the sensing center of the magnetoresistive sensor 2 and the midline of the corresponding magnetic track on the magnetic code disk 1 in the relative plane can be 0.3, 0.4, 0.5, 0.6, or 0.7 times the width of the magnetic track, but is not limited thereto.

[0030] In this embodiment, the magnetoresistive sensor 2 is mounted on the circuit board 3, and the circuit board 3 is parallel to the magnetic code disk 1. The magnetoresistive sensor 2 is used to sense a pair of orthogonal magnetic fields in the relative plane direction. By defining the relative positions of the circuit board 3 and the magnetic code disk 1, system integration can be facilitated and the space utilization rate of the encoder can be improved.

[0031] Specifically, the magnetoresistive sensor 2 includes two sets of Wheatstone bridge circuits 21. A plurality of magnetoresistive sensing units are provided in the Wheatstone bridge circuit 21. The Wheatstone bridge circuit 21 constructs differential sine signals and differential cosine signals for the magnetic encoder through the magnetoresistive sensing units.

[0032] It should be noted that the magnetoresistive sensor 2 includes at least one of a tunneling magnetoresistance (TMR) sensor, a giant magnetoresistance (GMR) sensor, and an anisotropic magnetoresistance (AMR) sensor. Among them, one Wheatstone bridge circuit 21 can generate a differential sine signal sin+ and a differential cosine signal cos+, and the other Wheatstone bridge circuit 21 can generate a differential sine signal sin- and a differential cosine signal cos-, but it is not limited thereto.

[0033] Combined Figure 3 , Figure 3 shows how to construct the differential magnetoresistive sensor 2 using in-plane oriented TMR or GMR sensing units. Considering the anti-interference ability, the magnetoresistive sensor 2 generally adopts a Wheatstone bridge circuit 21 to effectively suppress common-mode noise. As Figure 3 shown, the TMR or GMR sensing units construct differential sine signals and differential cosine signals through the in-plane orientation of the pinned layer. At the diagonals of the Wheatstone bridge, the magnetization directions of the pinned layers of the two magnetoresistive sensing units are the same, and the magnetization directions of the pinned layers of the two magnetoresistive sensing units at the other diagonal are 180° opposite to the former. Under the action of the magnetic field of the magnetic code disk 1, the magnetization orientations of the free layers of each sensor unit are the same. Taken together, one set of Wheatstone bridges outputs differential sine signals sin+ and sin-, and the other set of Wheatstone bridges outputs differential cosine signals cos+ and cos-.

[0034] In an alternative embodiment, due to the position differences of the magnetoresistive sensing units, there are slight deviations in the magnetic field intensity and direction of each magnetoresistive sensing unit, and compensation needs to be carried out in the algorithm. This embodiment does not specifically limit the specific compensation algorithm. It should be noted that the sensing center of the magnetoresistive sensor 2 in the present invention refers to the central position where all the magnetoresistive sensor 2 units are combined. Based on this central position, each magnetoresistive sensor 2 unit needs to work in the magnetization saturation region.

[0035] In this embodiment, the magnetoresistive sensor 2 is a tunneling magnetoresistive sensor 2 or a giant magnetoresistive sensor 2, and this embodiment does not make specific limitations in this regard. Combining Figure 3 , the Wheatstone bridge circuit 21 includes four magnetoresistive sensing units.

[0036] It should be noted that taking the magnetic encoder as a rotary encoder as an example, the rotary encoder detects the angular position of the sensor through angle calculation, so as to generate a real-time angular position signal. Each time a TMR or GMR sensor passes through a pair of magnetic poles, a periodic sine or cosine signal will be generated. The angle calculation of the encoder needs to measure two orthogonal signals simultaneously: sin(x) and con(x), so as to calculate the absolute angle value or the angle change value within a 360-degree cycle. Among them, the absolute value encoder measures the absolute angle value, and the incremental encoder measures the angle change value.

[0037] In each group of the Wheatstone bridge circuits 21, two magnetoresistive sensing units are connected in series between the power supply terminal and the ground terminal. The signal output terminals are respectively connected to the positions where the two magnetoresistive sensing units in the two series-connected groups are connected to each other.

[0038] Among them, the magnetoresistive sensor 2 includes a stacked pinned layer and a free layer. In each group of the Wheatstone bridge circuits 21, the magnetization directions of the pinned layers of the two magnetoresistive sensing units connected in series in the same group are opposite, and the magnetization direction of the pinned layer of one of the magnetoresistive sensing units connected in series in a group to the ground terminal is the same as the magnetization direction of the pinned layer of one of the magnetoresistive sensing units connected in series in the other group to the power supply terminal; the magnetization directions of the pinned layers in the two groups of the Wheatstone bridge circuits 21 are perpendicular to each other.

[0039] Specifically, the above two groups of Wheatstone bridge circuits 21 can be a sine Wheatstone bridge circuit 21 and a cosine Wheatstone bridge circuit 21. Among them, the magnetization direction of the pinned layer in the sine Wheatstone bridge circuit 21 is the same as or opposite to the direction of the current flowing through itself on the plane of the circuit board 3; the signal output terminals on the sine Wheatstone bridge circuit 21 are respectively the positive sine signal output terminal sin+ and the negative sine signal output terminal sin-; the magnetization direction of the pinned layer near the ground terminal and connected to the positive sine signal output terminal is consistent with the current direction, and the magnetization direction of the pinned layer near the ground terminal and connected to the negative sine signal output terminal is opposite to the current direction; the signal output terminals on the cosine Wheatstone bridge circuit 21 are respectively the positive cosine signal output terminal cos+ and the negative cosine signal output terminal cos-; the magnetization direction of the pinned layer near the ground terminal and connected to the positive cosine signal output terminal is opposite to the magnetization direction of the pinned layer near the ground terminal and connected to the negative cosine signal output terminal.

[0040] It should be noted that the pinning layer has a very high coercivity. Under normal working conditions, the externally applied magnetic field will not change the magnetization direction of the pinning layer. The free layer is made of a soft magnetic material, and its magnetization direction changes freely with the externally applied magnetic field. There are two possibilities for the magnetization orientation of the pinning layer. One possibility is in-plane orientation, and the other possibility is out-of-plane perpendicular orientation. When the magnetization direction of the free layer is the same as that of the pinning layer, the resistance value of the magnetoresistive sensor 2 is the smallest; when the magnetization direction of the free layer is completely opposite to that of the pinning layer, the resistance value of the magnetoresistive sensor 2 is the largest; when the magnetization direction of the free layer and the pinning layer are at other angles, the resistance value of the magnetoresistive sensor 2 is between the two. The in-plane oriented TMR or GMR sensor has good linearity and can achieve zero hysteresis, which is the basic structure of a high-precision sensor for metrology. After the magnetic field is saturated, the magnetization direction of the free layer is only related to the magnetic field angle and has nothing to do with the magnetic field amplitude, making it suitable for use as an angle sensor. The out-of-plane (perpendicular) oriented TMR or GMR sensor will have hysteresis, and its linearity is also not as good as that of the in-plane oriented TMR or GMR sensor. It is feasible to use it for detecting magnetic signals of switch type, but it is not suitable for use as a magnetic sensor for high-precision metrology.

[0041] In addition, the magnetic code disk 1 of the magnetic encoder can be composed of a single pair of magnetic poles or multiple pairs of magnetic poles. The magnetization direction of the magnetic pole pair can be perpendicular orientation or in-plane orientation. At the center of the magnetic track of the magnetic code disk 1, that is, at the midline of the magnetic track, the magnetic field is the strongest. For the magnetic code disk 1 magnetized either vertically or horizontally, there are only two magnetic field components in the center of the magnetic track: horizontal (x direction) and vertical (z direction). The center of multiple pairs of magnetic code disks 1 cannot provide two orthogonal horizontal magnetic field components. Usually, an orthogonal in-plane double-bridge differential sensor needs to be used in conjunction with a single pair of in-plane oriented magnetic poles to generate high-quality orthogonal sin and cos signals, but using a single pair of magnetic poles limits the accuracy of the encoder.

[0042] See Figure 1 , which shows a cross-sectional view of the magnetic code disk 1 formed by multiple pairs of magnetic poles. The magnetic code disk 1 shown in the figure belongs to out-of-plane (perpendicular) magnetization. The circuit board 3 for the chip magnetoresistive sensor 2 is parallel to the plane of the magnetic code disk 1, and the magnetoresistive sensor 2 is located above the magnetic code disk 1. Due to symmetry, the magnetoresistive sensor 2 and its circuit board 3 can also be located below the magnetic code disk 1.

[0043] Combined with Figures 4 to 7 , when the magnetoresistive sensor 2 is at different radial positions above the magnetic code disk 1, Figures 5 to 7 shows the in-plane magnetic field distribution generated by the magnetic code disk 1 at the magnetoresistive sensor 2. Among them, Figures 5 to 7The abscissas all represent a pair of magnetic poles or a period that the sensing center has traversed along the circumferential direction of the magnetic code disk 1 at a certain position in the radial direction of the magnetic code disk 1. For example, when the sensing center is at the position of "1", it means that the sensing center has traversed one period, i.e., 2π, along the circumferential direction at a certain position in the radial direction of the magnetic code disk 1. The in-plane magnetic field includes two components: Hx in the circumferential x direction of the ring and Hy in the radial y direction of the ring. When the magnetoresistive sensor 2 is located at the center above the magnetic track, i.e., when the magnetic induction center is at point A, only the in-plane magnetic field in one direction, the circumferential magnetic field Hx, can be detected, and the radial magnetic field Hy is zero. When the magnetoresistive sensor 2 is offset to directly above the outer edge of the magnetic track or a certain distance outside the outer edge of the magnetic track, i.e., when the magnetic induction center is at point B or point C, the two orthogonal in-plane magnetic fields Hx and Hy will appear, but their amplitudes may not be the same. Thus, Figures 5 to 7 shows the magnetic field changes of Hx and Hy passing through a pair of magnetic poles. A pair of magnetic poles corresponds to two periods of sine and cosine signals. Among them, Hx generates a sine signal, and Hy generates a cosine signal. The amplitude comparison of the two signals can be characterized by the maximum value of Hx and the maximum value of Hy.

[0044] Furthermore, combined with Figure 8 , where Figure 8 the abscissa is the position change of the sensing center along the radial direction of the magnetic code disk 1, marked as the normalized position. The center of the magnetic track is defined as the normalized position 0, and the position of the outer diameter of the magnetic track, i.e., the position of the outer sidewall of the magnetic code disk 1, is defined as the normalized position 1. Figure 8 shows the changes of the maximum value of Hx and the maximum value of Hy from the center of the magnetic track to the outside of the outer diameter of the magnetic track. At the outer diameter of the magnetic track, the circumferential in-plane magnetic field intensity Hx along the magnetic code disk 1 decreases significantly compared with that at the center of the magnetic track, but the in-plane radial magnetic field Hy reaches the maximum. Outside the outer diameter of the magnetic track, the maximum values of Hx and Hy may be the same. When the maximum values of the two in-plane orthogonal magnetic fields generated by the magnetic poles on the magnetic code disk 1 in the magnetoresistive sensor 2 are different, the differential sine signal and the differential cosine signal generated by the magnetoresistive sensor 2 are not affected by the change in the magnetic field intensity where the magnetoresistive sensor 2 is located.

[0045] Combined with Figure 9 , Figure 9 shows the changes of the maximum values of the two in-plane magnetic field components Hx and Hy generated by the magnetic track on the circular magnetic code disk 1 along the radial direction of the magnetic ring across different positions of the magnetic track. Among them, the circumferential in-plane magnetic field component Hx is the largest at the center of the magnetic track and gradually becomes smaller as it deviates from the center of the magnetic track; the radial in-plane magnetic field component Hy is 0 at the center of the magnetic track and reaches the maximum at the outer diameter and inner diameter of the magnetic track.

[0046] Place the magnetic sensor on the outer edge of the magnetic track of the magnetic code disk 1. The placement position of the magnetoresistive sensor 2 in the encoder mainly considers the intensity of the in-plane radial magnetic field and needs to ensure Figure 3All magnetoresistive sensing units in the middle magnetoresistive sensor 2 reach saturation magnetization. The optimal position is at the normalized position of 1. For the magnetic code disk 1 with a strong magnetic moment, the center of the magnetoresistive sensor 2 can be in the saturation working area when it is within the range of the normalized position from 0.5 to 1.6. Due to the relatively wide working area, the specific encoder design can be selected according to requirements such as size limitations.

[0047] Similarly, place the magnetic sensor at the inner edge of the magnetic track of the magnetic code disk 1. The placement position of the magnetoresistive sensor 2 in the encoder mainly considers the strength of the in-plane radial magnetic field. The optimal position is at the normalized position of -1. For the magnetic code disk 1 with a strong magnetic moment, the center of the magnetoresistive sensor 2 can be in the saturation working area when it is within the range of the normalized position from -0.5 to -1.6. Due to the relatively wide working area, the specific encoder design can be selected according to requirements such as size limitations.

[0048] In this embodiment, the magnetic code disk 1 includes multiple pairs of magnetic poles. The overall shape of the magnetic code disk 1 is circular ring-shaped, disk-shaped, or strip-shaped. It can be understood that when the magnetic code disk 1 is circular ring-shaped or strip-shaped, the area occupied by the magnetic code disk 1 in the horizontal direction is the area occupied by the magnetic track in the horizontal direction; when the magnetic code disk 1 is disk-shaped, the area occupied by the magnetic code disk 1 in the horizontal direction except for the central area is the area occupied by the magnetic track in the horizontal direction. This embodiment does not elaborate on this too much. The magnetic encoder of this embodiment can improve the resolution and accuracy of the magnetic encoder without increasing the diameter of the magnetic encoder.

[0049] Among them, when the distance from the sensing center to the midline of the corresponding magnetic track on the magnetic code disk 1 on the relative plane can be 0.5 times the width of the magnetic track, when the magnetic code disk 1 is circular ring-shaped, the sensing center is directly above or below the inner or outer sidewall of the magnetic code disk 1; when the magnetic code disk 1 is disk-shaped, the sensing center is directly above or below the outer sidewall of the magnetic code disk 1, but it is not limited to this; when the magnetic code disk 1 is a strip-shaped extending in the left-right direction, the sensing center is directly above or below the front or rear sidewall of the magnetic code disk 1; In this embodiment, the shape of the magnetic code disk 1 is taken as an example of a circular ring shape, and the sensing center is directly above the outer sidewall of the magnetic code disk 1.

[0050] In an alternative embodiment, the magnetic encoder further includes a housing, and the magnetic code disk 1, the magnetoresistive sensor 2, and the circuit board 3 are all fixedly arranged inside the housing. The material of this housing is a magnetic material, which is used to shield the external magnetic field of the magnetic encoder. This embodiment does not limit the specific material of the housing.

[0051] The magnetic encoder provided by the embodiment of the present invention utilizes two principles: 1) At the edge of the magnetic track of the magnetic code disk 1, two in-plane orthogonal magnetic fields will appear; 2) After the magnetic field on the magnetoresistive sensor 2 reaches saturation, the magnetoresistive sensor 2 only responds to the change in the direction of the magnetic field where it is located and is independent of the fluctuation of the magnetic field intensity where it is located. In this way, the in-plane magnetoresistive sensor 2 with high linearity can be applied to the magnetic code disk 1 formed by multiple pairs of magnetic poles, greatly improving the resolution and accuracy of the magnetic encoder.

[0052] Among them, for principle 2), although the amplitudes of the in-plane circumferential magnetic field and the radial magnetic field at the edge of the magnetic code disk 1 are different, after ensuring that both groups of magnetoresistive sensors 2 reach saturation, orthogonal sin and cos signals with equal amplitudes can be obtained. Using this pair of orthogonal signals for angle calculation, the magnetic encoder in this embodiment is constructed.

[0053] See Figure 8 , although at most positions in the radial direction of the magnetic code disk 1, the amplitudes of the two orthogonal horizontal components Hx and Hy generated by the magnetic code disk 1 are different, when the magnetic field intensity of the magnetic code disk 1 is sufficient to saturate the TMR or GMR sensor, the sensor only changes with the direction and is independent of the magnetic field amplitude. Therefore, two sinusoidal and cosine signals with constant amplitudes can be obtained within a wide range.

[0054] In the description of this specification, the description with reference to terms such as "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or features described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0055] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0056] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A magnetic encoder, characterized in that: The magnetic encoder comprises: a magnetic code disk and an in-plane oriented magnetoresistive sensor; The two in-plane orthogonal magnetic fields generated by the magnetic code disk can saturate the magnetoresistive sensor, and the distance between the sensing center of the magnetoresistive sensor and the center line of the corresponding magnetic track on the magnetic code disk on the relative plane is not less than one quarter of the width of the magnetic track; The relative plane is parallel to the magnetic code disk; the sensing center of the magnetoresistive sensor module is the center of the sensing area formed by the multiple magnetoresistive sensors; and the center line of the magnetic track is the line formed by the center points of the magnetic track in the width direction.

2. The magnetic encoder according to claim 1, characterized in that The magnetoresistive sensor is used to sense a pair of orthogonal magnetic fields in the direction of the relative plane; The magnetic code disk saturates the magnetoresistive sensor so that the magnetoresistive sensor only responds to the change in the direction of the magnetic field, and the differential sine signal and the differential cosine signal generated by the magnetoresistive sensor are not affected by the change in the strength of the magnetic field; When the maximum values ​​of the two in-plane orthogonal magnetic fields generated by the magnetoresistive sensor are different for the magnetic poles on the magnetic code disk, the differential sine signal and the differential cosine signal generated by the magnetoresistive sensor are not affected by the change of the strength of the magnetic field.

3. The magnetic encoder according to claim 1, characterized in that: The magnetoresistive sensor is mounted on a circuit board, and the circuit board is parallel to the magnetic code disk.

4. The magnetic encoder according to claim 1, characterized in that: The magnetoresistive sensor includes two groups of Wheatstone bridge circuits; The Wheatstone bridge circuit constructs a differential sine signal and a differential cosine signal for the magnetic encoder.

5. The magnetic encoder according to claim 1, characterized in that: The magnetoresistive sensor includes at least one of a tunnel magnetoresistive sensor, a giant magnetoresistive sensor and an anisotropic magnetoresistive sensor.

6. The magnetic encoder according to claim 1, characterized in that: The shape of the magnetic code disk is annular, disc-shaped or long strip.

7. The magnetic encoder according to claim 1, characterized in that: The magnetic encoder is a rotary encoder or a linear encoder.

8. The magnetic encoder according to claim 1, characterized in that: The magnetic encoder is an absolute position encoder or an incremental encoder.

9. The magnetic encoder according to claim 1, characterized in that: The magnetic code disk includes a plurality of pairs of magnetic poles.

10. The magnetic encoder according to any one of claims 1 to 9, characterized in that: The distance between the sensing center of the magnetoresistive sensor on the relative plane and the center dividing line of the corresponding magnetic track on the magnetic code disk is no more than 0.8 times the width of the magnetic track.

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