Magnetic grating and position encoder

Abstract

The invention relates to a magnetic scale (5) on which there is a magnetic signal dependent on the position of a reading head (2) on the magnetic scale (5), and to a position encoder (1) comprising such a magnetic scale (5). The magnetic scale (5) comprises a magnetic track comprising first type segments (6) comprising a permanent magnetic material and being magnetized in one magnetization direction and second type segments (7) comprising a permanent magnetic material and being magnetized in another magnetization direction; the first type segments (6) and the second type segments (7) are arranged alternately on the magnetic scale (5). The magnetic signal amplitude over the first type segments (6) assumes one of two distinguishable amplitudes, namely a lower amplitude (A1) or a higher amplitude (A2), and the magnetic signal amplitude over the second type segments (7) also assumes one of the distinguishable amplitudes, namely a lower amplitude (A1') or a higher amplitude (A2'), whereby one data bit is encoded in the respective segments (6, 7).

Description

Technical Field

[0001] This invention relates to a magnetic grating and a position encoder comprising such a magnetic grating and a reading head, the reading head including a sensor with a magnetic sensor element adapted to sense characteristics of a magnetic field above the magnetic grating. By applying a computational method, the sensor output signal is used to determine the position and / or velocity of the reading head relative to the magnetic grating, the reading head being positioned above the grating. Background Technology

[0002] Position encoders are used in a variety of applications, such as determining tool position in machine tools, measuring joint angles in robots, determining rotor position in video surveillance systems, and in electric motors. This allows these devices to be automatically controlled, for example, through software control. The readhead can be attached to the part being measured, while the magnetic grating is attached to a base, and vice versa. The position of the readhead can be expressed as displacement or angle relative to a starting point, and in some applications, the velocity or angular velocity of the readhead or magnetic grating can also be calculated by considering time.

[0003] The sensor in the reading head senses the magnetic field above the magnetic grating. The magnetic field sensed by the sensor above the magnetic grating can be represented as a magnetic signal above the magnetic grating. This magnetic signal depends on the position x or the displacement of the reading head along the magnetic grating, or more precisely, on the magnetic field above the magnetic grating at a specific position along the magnetic grating.

[0004] Prior art discloses magnetic gratings in which information is embedded in the form of magnetic tracks, each track comprising pairs of segments magnetized in different directions; these segments will be terminologically designated as North Pole (N) and South Pole (S). The magnetic grating comprises permanent magnet materials, which are typically magnetized to form magnetic tracks with various segments pointing in different directions after being mechanically shaped into a desired structure. The desired magnetization is achieved by exposing specific regions (segments) of the magnetic grating to a strong magnetic field.

[0005] More specifically, the prior art discloses examples of magnetic gratings comprising magnetic tracks having a repeating pattern of alternating first-type segments and second-type segments, the magnetization of which is paired and points in different directions, wherein all first-type segments are of the same length, all second-type segments are of the same length, and the lengths of the first-type segments and second-type segments are identical. The magnetic signal generated by the magnetic tracks of such a grating is substantially sinusoidal and periodic with a period P, which is determined, for example, by the distance between two peaks of the magnetic signal, or by the distance x by which the reading head travels along the grating from the position where it senses one peak of the magnetic signal to the next position where it senses an adjacent peak.

[0006] In these examples, the period P of the magnetic signal in a linear magnetic grating is essentially equal to the sum of the lengths of the first type segment and the second type segment. The length of the period P of the magnetic signal in a toroidal magnetic grating also depends on the distance at which the magnetic field is measured, i.e., the distance R between the reading head and the grating, particularly in radial gratings, or the distance between the reading head and the center of rotation of the grating, particularly in axial gratings. Ideally, the reading head should be at essentially the same distance R from the grating as it travels along it, but in practice, this varies during operation.

[0007] The magnetic signal sensed by the sensor within the readhead, through the response of the sensor element, is converted into one or more electrical signals in various known ways. The position and / or velocity of the readhead within a period can be calculated from these electrical signals in known ways, such as those disclosed in EP0235750A2, EP3907477B1, JP2003075195A, and US8134359B2. However, since the magnetic signal is periodic in this case, it cannot be used to determine which period of all cycles the readhead is located on the magnetic grating. In other words, the absolute position of the readhead relative to the magnetic grating cannot be determined.

[0008] Prior art discloses solutions to the problem of determining the period in which a reading head is located, in addition to determining the position of the reading head within a period. For example, EP2823260 discloses a position encoder with a magnetic grating in which segments of one type (e.g., a first type segment) have a shorter length or a longer length, such that the amplitude of a magnetic signal above the segment is modulated to have one value or another value, for example, a lower value above the shorter length of the first type segment and a higher value above the longer length of the first type segment. In this way, a data bit is encoded into the corresponding period, for example, having logic values ​​0 and 1, where logic value 0 corresponds to the lower value of the magnetic signal above the first type segment and logic value 1 corresponds to the higher value of the magnetic signal above the first type segment.

[0009] In addition to the periodic components of the magnetic signal required to determine the position of the readhead within the first type segment and the adjacent second type segment, the sensor also senses coded data bits. The number of bits sensed by the sensor is equal to the number of first type segments covered by the sensor's extension; therefore, in terms of the number of bits sensed by the sensor, the word length depends on the length of the sensor.

[0010] To ensure the uniformity of the periodic components of the magnetic signal, the centers of adjacent first-type segments encoded with data bits are located at a distance equal to the period P of the periodic components of the magnetic signal. Since the length of a first-type segment is defined by the value of the data bits encoded within that particular first-type segment, and since the distance between the centers of the first-type segments is equal to the length of the magnetic signal period P, the corresponding length of a second-type segment is determined by filling the gap between two adjacent first-type segments. Therefore, this type of modulation does not allow arbitrary modulation of the second-type segment outside of the first-type segments.

[0011] Existing technologies disclose magnetic gratings that either do not encode data bits during the period of a magnetic signal or encode a data bit in a specific manner. Summary of the Invention

[0012] The magnetic grating of this invention allows data bits to be encoded into each segment, i.e., two data bits to be encoded into a magnetic signal period, which greatly improves its performance and application options. This also applies to position encoders including the magnetic grating of this invention and a readhead equipped with a sensor adapted to sense characteristics of the magnetic field above the magnetic grating. The sensor comprises sensor elements arranged substantially on a line segment, as disclosed in the prior art. For example, in a linear magnetic grating, this line segment is substantially parallel to the longitudinal direction of the grating.

[0013] The magnetic tracks in the magnetic grating of this invention comprise first-type segments and second-type segments alternately distributed along the grating. The first-type segments comprise permanent magnet material magnetized in one magnetization direction; the second-type segments comprise permanent magnet material magnetized in the opposite magnetization direction. Therefore, the first-type segments generate a magnetic field with a direction opposite to that of the second-type segments.

[0014] The magnetic tracks in the magnetic grating generate a magnetic signal sensed by a readhead sensor by sensing the characteristics of the magnetic field above the grating. The magnetic signal depends on the position or displacement of the readhead along the grating, or on the magnetic field above the grating at a specific location along the readhead.

[0015] The first type of segment is made in such a way that, depending on its construction, the magnetic signal above it presents one of two distinguishable amplitudes, namely, a lower amplitude or a higher amplitude.

[0016] Similarly, the second type of segment is made in such a way that, depending on its construction, the magnetic signal above it exhibits one of two distinguishable amplitudes, namely, a lower amplitude or a higher amplitude.

[0017] A higher amplitude representation of a magnetic signal, as understood in this patent application, means that the amplitude deviates more significantly from the zero value of the magnetic signal, while a lower amplitude representation means that the amplitude deviates less significantly from the zero value of the magnetic signal.

[0018] The distinguishable amplitude description in this specification means that all lower amplitudes associated with the first type segment fall within a specific amplitude region. This reasonably also applies to all higher amplitudes associated with the first type segment, where the amplitude regions of the lower and higher amplitudes do not overlap and are sufficiently far apart so that the readhead can clearly detect whether the amplitude in question is higher or lower. Similarly, this also applies to both lower and higher amplitudes associated with the second type segment.

[0019] In this way, one data bit is encoded in each segment; that is, two data bits are encoded in a pair consisting of a first type segment and a second type segment. The higher amplitude of the magnetic signal above the first type segment is associated with one logic value of the data bit (e.g., logic 1), while the lower amplitude of the magnetic signal above the first type segment is associated with another logic value of the data bit (e.g., logic 0). Similarly, this also applies to the higher and lower amplitudes of the second type segment, which are associated with one logic value and another logic value of the second data bit.

[0020] The magnetic grating of the present invention preferably comprises segments having the same width W throughout the entire magnetic grating. Attached Figure Description

[0021] The embodiments and operation of the magnetic grating and position encoder of the present invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 A schematic top view of a portion of the linear magnetic grating 5, namely eight pairs consisting of first type segments 6 and second type segments 7, and a sensor 3 comprising thirty-two sensor elements 4.

[0022] Figure 2 The magnetic signal shapes with various amplitudes A1, A2, A1' and A2' are shown above a portion of the magnetic grating 5 (i.e. above the five pairs consisting of the first type segment 6 and the second type segment 7).

[0023] Figure 3 The schematic side view of a portion (six pairs of segments) of the linear magnetic grating 5 is shown, which is an implementation of magnetic signal amplitude modulation by using various permanent magnet materials (i.e., permanent magnet materials with high remanence and permanent magnet materials with low remanence) on segments 6 and 7.

[0024] Figure 4 The schematic diagram shows a side view of a portion (six pairs of segments) of the linear magnetic grating 5, namely an implementation using a permanent magnet material but with magnetic signal amplitude modulation of different magnetization intensities.

[0025] Figure 5The schematic side view of a portion (six pairs of segments) of the linear magnetic grating 5 is shown, namely, an implementation in which magnetic signal amplitude modulation is performed by using sub-segments 8 with opposite magnetization intensities, the sub-segments 8 extending through the entire depth D of segments 6 and 7.

[0026] Figure 6 The schematic side view of a portion (six pairs of segments) of the linear magnetic grating 5 is shown, namely, an implementation in which magnetic signal amplitude modulation is performed by using sub-segments 8 with opposite magnetization intensities, the sub-segments 8 extending only through the upper part of the depth D of segments 6 and 7.

[0027] Figure 7 The schematic side view of a portion (six pairs of segments) of the linear magnetic grating 5 is shown, which is an implementation of magnetic signal amplitude modulation by using sub-segments 8 without magnetization.

[0028] Figure 8 The schematic side view of a portion (six pairs of segments) of the linear magnetic grating 5 is shown, namely, an implementation in which magnetic signal amplitude modulation is performed by using a ferromagnetic layer 10 on the upper surface of some segments 6, 7. Detailed Implementation

[0029] Figure 1 A schematic representation of an embodiment of the linear magnetic grating 5 is shown, i.e., a top view of the linear magnetic grating 5. Eight pairs of segments are shown, each pair comprising a first-type segment 6 and a second-type segment 7. A sensor 3, schematically represented by a reading head 2, is located above the magnetic grating 5 and moves relative to the magnetic grating 5 in the longitudinal direction A to one side or the other during operation. In the illustrated embodiment, the sensor has thirty-two magnetic sensor elements 4 that extend linearly to cover approximately eight segments, i.e., approximately four pairs of adjacent segments with opposite magnetization. The length L1 of the first-type segment 6 in the longitudinal direction and the length L2 of the second-type segment 7 in the longitudinal direction are uniform across the entire magnetic grating 5. Furthermore, the width W of the segments is the same across the entire magnetic grating 5.

[0030] Figure 2 The diagram shows the magnetic signal shapes above five pairs of segments, consisting of a first-type segment 6 and a second-type segment 7, of the magnetic grating 5 of the present invention. Above the first-type segment 6, the magnetic signal exhibits a lower amplitude A1 (e.g., associated with logic value 0) or a higher amplitude A2 (e.g., associated with logic value 1). Similarly, this also applies to the second-type segment 7, above which the magnetic signal can exhibit a lower amplitude A1' (e.g., associated with logic value 0) or a higher amplitude A2' (e.g., associated with logic value 1). Therefore, Figure 2 The diagram shows a magnetic signal encoded with two data bits in each pair of segments. Specifically, viewed from the left, the first pair of segments is encoded with a combination of logic 11, the second pair with a value of 00, the third pair with a value of 01, the fourth pair with a value of 10, and the fifth pair with a value of 01.

[0031] exist Figure 2 In this context, the length of the magnetic signal period P is represented as the distance from one peak of the magnetic signal amplitude to the next peak of the magnetic signal amplitude above the next segment of the same type.

[0032] The longitudinal length of a pair of adjacent segments (including the first type segment 6 and the second type segment 7) is approximately equal to the length of the magnetic signal period P. This is why, in other words, two data bits are encoded in one period P of the magnetic signal.

[0033] The desired length of the magnetic signal period P (e.g., measured from a peak of the magnetic signal at a certain magnetic pole to an adjacent peak of the magnetic signal at the same magnetic pole, such as...). Figure 2 As shown, the readings are substantially the same or as uniform as possible along a specific nominal distance R between the sensor 3 (reading head 2) and the magnetic grating 5, regardless of whether the corresponding peak among these adjacent peaks is equal to the higher or lower amplitude. The uniformity of the length of the magnetic signal period P sensed by the sensor 3 contributes to the accuracy of the calculated position of the reading head 2 relative to the magnetic grating 5.

[0034] exist Figure 3 , 4 In the embodiments shown in 5, 6, 7 and 8, the length L1 of the first type segment 6 is substantially the same across the entire magnetic grating 5; the length L2 of the second type segment 7 is substantially the same across the entire magnetic grating 5; and the length L1 of the first type segment 6 is substantially the same as the length L2 of the second type segment 7.

[0035] In different implementations, the lengths L1 and L2 of the corresponding first or second type segments 6 and 7 can vary, wherein an attempt is made to achieve uniformity in the length of the magnetic signal period P, regardless of whether the corresponding peak in adjacent peaks of the magnetic signal is equal to the higher or lower amplitude. Typically, the difference between lengths L1 and L2 does not exceed 20%, preferably at most 10%.

[0036] The width W of segments 6 and 7 is preferably the same across the entire magnetic grating 5.

[0037] During the production process of magnetic grating 5, sufficient magnetic signal amplitude and uniformity of magnetic signal period P are achieved above the corresponding first or second type segment through various means.

[0038] Figure 3 An implementation of the magnetic grating 5 is shown, wherein two different permanent magnet materials with different remanence are used in the production of segments 6 and 7 to change the magnetic properties of segments 6 and 7, wherein both permanent magnet materials are magnetized to saturation. Figure 3The following figures also show a substrate 9, preferably made of a metallic material, on which segments 6 and 7 are placed, and which in particular provides the mechanical load-bearing capacity for the magnetic grating 5. For example, the first type of segment 6 associated with higher amplitude is made of a permanent magnet material with a higher remanence value, and in... Figure 3 The middle section is represented by a thicker arrow, while the first type segment 6, associated with a lower amplitude, is made of a permanent magnet material with a lower remanence value, and in... Figure 3 The arrow is represented by a thinner arrow. Similarly, this also applies to section 7 of the second type. The arrow points in the direction of magnetization, or more precisely, in the direction of the magnetic field of the magnetic signal. Figure 3 Segments 6 and 7, viewed from left to right, have the following logical values: 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1.

[0039] Figure 4 An implementation is shown in which the same permanent magnet material is used to produce the entire magnetic grating 5, and different magnetization intensities are used to produce segments 6 and 7 with different magnetic properties to achieve two distinguishable amplitudes. For example, segments 6 and 7 associated with the higher amplitude are magnetized to saturation, and they are in Figure 4 The middle part is represented by a longer arrow; segments 6 and 7, associated with lower amplitudes, are magnetized to values ​​below saturation. Figure 4 The middle arrow represents the direction of magnetization, or more precisely, the direction of the magnetic field of the magnetic signal. Viewed from left to right... Figure 4 The code for segments 6 and 7 has the following logical values: 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1.

[0040] Figure 5 An embodiment of the magnetic grating 5 is shown, which has segments 6 and 7 made of the same permanent magnet material. Various magnetic properties of the respective segments 6 and 7 are achieved by selectively using at least one (preferably one) sub-segment 8 located in certain segments 6 and 7 and magnetized in the opposite direction to the magnetization of these segments 6 and 7. In a certain direction, segments 6 and 7 with higher magnetic signal amplitude are magnetized to saturation and do not include sub-segments 8 with opposite magnetization intensity, while segments 6 and 7 with lower amplitude are initially also magnetized to saturation but include sub-segments 8 with opposite magnetization intensity.

[0041] The lengths L1' and L2' of sub-segment 8, which have opposite magnetization in the longitudinal direction of the magnetic grating, are shorter than the lengths L1 and L2 of segments 6 and 7, to which sub-segment 8 is located. Sub-segment 8 can be magnetized in opposite directions as follows: extending through the entire depth D of the permanent magnet material, so that the depth D' of sub-segment 8 is the same as the depth D of segments 6 and 7 or the permanent magnet material. Figure 5 ).

[0042] exist Figure 6In another embodiment shown, segment 8 is magnetized in the opposite direction and extends only through the upper part of the depth of the permanent magnet material, so the depth D' of segment 8 is less than the depth D of segments 6, 7 or the permanent magnet material.

[0043] The greater the lengths L1' and L2' of sub-segment 8 that are magnetized in opposite directions in the longitudinal direction and / or the deeper the sub-segment 8 is magnetized, the greater the reduction in the magnetic signal amplitude above segments 6 and 7 compared to segments 6 and 7 that do not include sub-segment 8 that are magnetized in opposite directions.

[0044] Looking from left to right, Figure 5 and Figure 6 The code for segments 6 and 7 has the following logical values: 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1.

[0045] Production of magnetic grid 5 having sub-segments 8 magnetized in opposite directions (e.g.) Figure 5 and 6 One possible approach (as shown) essentially involves two steps. In the first step, the first type segment 6 and the second type segment 7 are magnetized, for example, by longitudinally moving a dedicated electric coil above the magnetic grid 5 and changing the direction of the magnetic flux through the coil to achieve alternating magnetization of different types of segments 6 and 7. In the second step, as the coil is moved to the position of the sub-segment 8 on the magnetic grid 5, the direction and intensity of the magnetic flux through the coil are controlled to achieve an appropriate intensity of the opposite magnetic field of the sub-segment 8, thereby correspondingly reducing the amplitude of the common magnetic signal above a certain segment 6 or 7.

[0046] Figure 7 An embodiment of the magnetic grating 5 is shown, comprising segments 6 and 7 of magnetized permanent magnet material (preferably magnetized to saturation), wherein a reduction in the magnetic signal amplitude above a segment 6 or 7 is achieved by positioning at least one (preferably one) inert sub-segment 8 that is non-magnetized in terms of magnetization within such segments 6 and 7. The larger the size of the inert sub-segment 8, i.e., the larger its length L1' or L2' in the longitudinal direction, its width W' in the transverse direction, and its depth D', the greater the reduction in the magnetic signal amplitude above the segment 6 or 7. The inert sub-segment 8 can be formed in various ways. For example, the region of the inert sub-segment 8 may not contain any permanent magnet material that could be magnetized, for example, the permanent magnet material in the region of the sub-segment 8 may be removed, or the inert sub-segment 8 may include a material that cannot be magnetized. Another way to form the inert sub-segment 8 is that the permanent magnet material is not magnetized in the region of the sub-segment 8.

[0047] therefore, Figure 5 , 6 Figures 6 and 7 show an implementation of the magnetic grating 5, wherein, in order to achieve two distinguishable magnetic signal amplitudes A1, A2 and A1', A2', the corresponding segments 6 and 7 include sub-segments 8 having magnetic properties different from those of the corresponding segments 6 and 7.

[0048] Figure 8 An embodiment of the magnetic grating 5 is shown, comprising segments 6 and 7 of magnetized permanent magnet material (preferably magnetized to saturation). The reduction of the magnetic signal amplitude above a segment 6 or 7 is achieved by coating the upper surface of these segments 6 and 7 with a ferromagnetic material layer 10, which acts as a magnetic shield, thereby reducing the magnetic signal amplitude above these segments 6 and 7 at a distance R where the reading head 2 and its sensor 3 are located. Typically, the ferromagnetic material layer 10 completely or partially covers segments 6 and 7 where the magnetic field amplitude is considered to be relatively low. Figure 8 Twelve segments 6 and 7 are shown, alternately magnetized to saturation. The arrows in segments 6 and 7 indicate the magnetization direction. Segments 6 and 7 with lower amplitudes are covered by the ferromagnetic material layer 10, while segments 6 and 7 with higher amplitudes are not covered by this layer.

[0049] Looking from left to right, Figure 8 The code for segments 6 and 7 has the following logical values: 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1.

[0050] The above-mentioned methods of adjusting the magnetic properties of corresponding segments 6 and 7 can also be combined to achieve two distinguishable amplitudes of the first type segment 6 and the second type segment 7, and to achieve the best possible uniformity of the magnetic signal period P length.

[0051] The magnetic position encoder 1 of the present invention includes the magnetic grating 5 and the reading head 2 described above. The reading head includes a sensor 3 adapted to sense the magnetic field characteristics above the magnetic grating 5. The sensor includes a magnetic sensor element 4.

[0052] One of the key advantages of this invention is that two data bits can be encoded within a single magnetic signal cycle. The data bits encoded in the magnetic signal of the magnetic grating 5 are used as additional data to calculate the absolute position of the reading head 2 relative to the magnetic grating 5. Without this additional data, the magnetic signal above the magnetic grating 5 would repeat periodically, making it impossible to determine the absolute position of the reading head 2 based on the response of the sensor element 4; only its relative position within the cycle could be determined, not its specific period. By encoding the data bits, the sensor 3 senses the encoded data in addition to the periodic portion of the magnetic signal. The number of encoded bits (i.e., the length of the word sensed by the sensor 3) depends on the length of the sensor 3, i.e., the number of magnetic signal cycles covered by the sensor 3. The longer the sensor 3, the longer the word sensed by the sensor 3. As a result, the number of explicit combinations of encoded bits within this word length is higher, meaning that the magnetic grating 5 can be longer, where the combinations of encoded bits in a word sensed by the sensor 3 do not repeat over the entire length of the magnetic grating 5.

[0053] Since two data bits are encoded in each magnetic signal cycle of the magnetic grating 5 of the present invention (instead of one as disclosed in the prior art), the number of cycles on the magnetic grating 5 can be reduced by a factor of two to one for a given length of the magnetic grating 5 and the sensor 3, while the sensor 3 still senses enough encoded bits in a word to determine the absolute position of the reading head 2. Reducing the number of cycles for the same length of the magnetic grating 5 naturally means increasing the length of the cycle P. Since the range of distances between the reading head 2 and the magnetic grating 5 (which still produces acceptable results in terms of the accuracy of the calculated position of the reading head 2) depends on the length of the cycle P, increasing the length of the cycle P results in a wider acceptable distance range. This positively impacts the ease of installation by increasing the mounting tolerance of the encoder, while the accuracy of the calculated position of the reading head 2 is substantially unaffected within the mounting tolerance range. Therefore, the negative impact of potentially uneven distances between the reading head 2 and the magnetic grating 5 during operation of the position encoder 1 is relatively reduced.

[0054] This invention applies to a position encoder 1 comprising a linear, radial, or axial magnetic grating 5. In the axial magnetic grating 5, this invention facilitates more accurate position calculation compared to the radial magnetic grating 5. This is because the non-uniformity of the period P length in the radial magnetic grating 5 poses a greater problem and produces a larger error than in the axial magnetic grating 5. Since the magnetic sensor elements 4 are typically arranged linearly within the sensor 3, the distance between each sensor element 4 and the upper surface of the magnetic grating 5 varies due to the curvature of the grating 5, resulting in a more severe distortion of the period P length sensed by the sensor 3 in the radial magnetic grating 5.

[0055] In some embodiments, the magnetic track of the magnetic grating 5 of the present invention can be used as a stand-alone unit in the magnetic position encoder 1, while in other embodiments, it can be used in combination with additional magnetic tracks and associated additional sensor elements as disclosed in WO2023 / 075711.

Claims

1. A magnetic grating (5) for a position encoder (1), the position encoder including a reading head (2) in addition to the magnetic grating (5), the reading head including a sensor (3) with a sensor element (4) and adapted to sense the characteristics of a magnetic field above the magnetic grating (5), the magnetic grating (5) including magnetic rails, the magnetic rails including a first type segment (6) and a second type segment (7), the first type segment including a permanent magnet material and magnetized along one magnetization direction, the second type segment including a permanent magnet material and magnetized along another magnetization direction, the first type segment (6) and the second type segment (7) being arranged alternately on the magnetic grating (5), wherein the magnetic rails generate a magnetic signal sensed by the reading head (2) by sensing the characteristics of the magnetic field above the magnetic grating (5), and the magnetic signal depends on the position of the reading head (2) relative to the magnetic grating (5). Its features are, The magnetic signal amplitude above the first type segment (6) presents one of two distinguishable amplitudes, namely a lower amplitude (A1) or a higher amplitude (A2), and the magnetic signal amplitude above the second type segment (7) presents one of two distinguishable amplitudes, namely a lower amplitude (A1') or a higher amplitude (A2'), thereby encoding a data bit in the corresponding segment (6, 7).

2. The magnetic grating (5) according to claim 1, characterized in that, The first type segment (6) and the second type segment (7) are made of the same permanent magnet material.

3. The magnetic grating (5) according to any one of claims 1 to 2, characterized in that, In order to achieve two distinguishable magnetic signal amplitudes (A1, A2) above the first type segment (6) and two distinguishable magnetic signal amplitudes (A1', A2') above the second type segment (7), the corresponding segments (6, 7) are magnetized with different intensities. Preferably, the segments (6, 7) are magnetized to saturation to achieve higher amplitudes (A2) and (A2'), and the segments (6, 7) are magnetized to values ​​below saturation to achieve lower amplitudes (A1) and (A1').

4. The magnetic grating (5) according to any one of claims 1 to 2, characterized in that, In order to achieve two distinguishable magnetic signal amplitudes (A1, A2) and (A1', A2'), the corresponding segments (6, 7) include sub-segments (8) with different magnetic properties from these corresponding segments (6, 7).

5. The magnetic grating (5) according to claim 4, characterized in that, In the segment (6, 7) with a lower magnetic signal amplitude (A1, A1') above, at least one, preferably one, sub-segment (8) is positioned, which has a length (L1', L2') in the longitudinal direction of the magnetic grating and is magnetized in the opposite direction to the magnetization direction of the segment (6, 7) in which the sub-segment (8) is located. The length (L1', L2') of the sub-segment (8) is less than the length (L1, L2) of the segment (6, 7) in which it is located.

6. The magnetic grating (5) according to claim 5, characterized in that, The sub-segments (8) are magnetized such that the depth (D') of the sub-segments (8) is the same as the depth (D) of the segments (6, 7) in which these sub-segments (8) are located.

7. The magnetic grating (5) according to claim 5, characterized in that, The sub-segments (8) are magnetized such that they extend only through the upper part of the permanent magnet material depth of the segments (6, 7), that is, the depth (D') of the sub-segments (8) is less than the depth (D) of the segments (6, 7).

8. The magnetic grating (5) according to claim 4, characterized in that, In the segment (6, 7) with a lower magnetic signal amplitude (A1, A1') above, at least one, preferably one, sub-segment (8) is positioned, which has a length (L1', L2'), width (W') and depth (D') in the longitudinal direction of the magnetic grating (5) and is not magnetized. The length (L1', L2') of the sub-segment (8) is less than the length (L1, L2) of the segment (6, 7), the width (W') of the sub-segment (8) is less than or equal to the width (W) of the segment (6, 7), and the depth (D') of the sub-segment (8) is less than or equal to the depth (D) of the segment (6, 7).

9. The magnetic grating (5) according to any one of claims 1 to 2, characterized in that, The upper surface of the segments (6, 7) with lower magnetic signal amplitudes (A1, A1') is partially or completely coated with a ferromagnetic material layer (10).

10. The magnetic grating (5) according to claim 1, characterized in that, The first type segment (6) and the second type segment (7) with higher magnetic signal amplitude (A2, A2') are made of permanent magnet materials with a certain magnetic remanence density and magnetized to saturation, and the first type segment (6) and the second type segment (7) with lower magnetic signal amplitude (A1, A1') are made of different permanent magnet materials with lower magnetic remanence density and magnetized to saturation.

11. The magnetic grating (5) according to any one of claims 1 to 10, characterized in that, The length of the period (P) of the magnetic signal is substantially the same across the entire magnetic grating (5) and at a specific nominal distance (R) between the sensor (3) of the reading head (2) and the magnetic grating (5).

12. The magnetic grating (5) according to any one of claims 1 to 11, characterized in that, The width (W) of all segments (6, 7) is the same across the entire magnetic grid (5).

13. The magnetic grating (5) according to any one of claims 1 to 12, characterized in that, The length (L1) of the first type segment (6) in the longitudinal direction (A) and the length (L2) of the second type segment (7) in the longitudinal direction (A) are the same and uniform across the entire magnetic grid (5).

14. The magnetic grating (5) according to any one of claims 1 to 12, characterized in that, The corresponding length (L1) of the first type segment (6) is different from the corresponding length (L2) of the second type segment (7).

15. The magnetic grating (5) according to any one of claims 1 to 14, characterized in that, The magnetic grating (5) is linear.

16. The magnetic grating (5) according to any one of claims 1 to 14, characterized in that, The magnetic grating (5) is radial.

17. The magnetic grating (5) according to any one of claims 1 to 14, characterized in that, The magnetic grating (5) is axial.

18. The magnetic grating (5) according to any one of claims 1 to 17, characterized in that, It includes a magnetic track.

19. A position encoder (1) comprising a magnetic grating (5) according to any one of claims 1 to 18 and a reading head (2), the reading head comprising a sensor (3) with a sensor element (4) and the reading head (2) being adapted to sense the characteristics of a magnetic field above the magnetic grating (5).

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