Magnetic encoder

Abstract

The present invention provides a magnetic encoder, which includes a magnetic drum, a magnetic signal detection element and a magnetic signal processing and output element. Wherein, M single-pole magnetic rings are arranged on the outer peripheral wall of the magnetic drum along its axial direction. Along the circumferential direction of each single-pole magnetic ring within the magnetic field range thereof, n magnetic signal detection elements are arranged. On the outer circumferential surface of the single-pole magnetic ring, protrusions and grooves are alternately arranged in sequence along the circumferential direction. The central angle corresponding to the protrusion is α, and the central angle corresponding to the groove is β. The protrusions of two axially adjacent single-pole magnetic rings respectively have a circumferential deflection angle of A along the magnetic drum. The circumferential deflection angle of two axially adjacent magnetic signal detection elements along the magnetic drum is B. A and B are not equal to zero at the same time, where M≥2 and n≥1. According to the present invention, the resolution of the magnetic encoder is ensured by jointly adjusting multiple parameters such as α, β, M, n, A, and B. The relatively large number of adjustable parameters is conducive to designing magnetic encoders with different functions and different control accuracy requirements.

Description

Technical Field

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

[0002] A magnetic encoder is an angle or displacement measuring device mainly composed of a magnetoresistive sensor, a magnetic drum, and a signal processing circuit. Due to its many advantages such as small size, high precision, high resolution, non-contact and non-wearing, high shock resistance, simple installation, long service life, and multiple interface forms, magnetic encoders are widely used in industrial control, machinery manufacturing, ships, textiles, printing, aviation, aerospace, radar, communication, military and other fields.

[0003] The number of magnetic poles on the magnetic drum determines the resolution of the magnetic encoder, the uniformity of the magnetic poles on the magnetic drum determines the quality of the output signal of the magnetic encoder, and the magnetic field strength and action distance of the magnetic poles on the magnetic drum determine the structure and volume of the magnetic encoder. In short, the magnetic drum has an extremely important influence on the various performance parameters of the magnetic encoder, and many performances of the magnetic drum are closely related to the structure of the magnetic signal source on its circumference.

[0004] In the patent of the applicant's prior application, a technical solution of a magnetic ring with a concave-convex structure as the magnetic drum of the magnetic signal is disclosed. The number of magnetic signals that can be generated is the sum of the number of protrusions and grooves. According to this principle, as long as the central angle occupied by the protrusions and grooves is smaller, the number of magnetic signals generated by the magnetic drum is more, which can improve the resolution of the magnetic encoder. However, the minimum central angle of the protrusions or grooves is restricted by four factors: The first factor is the strength and toughness of the magnetic ring material. The minimum central angle of the protrusion part must ensure that the protrusion part has sufficient strength and will not be easily damaged. The second factor is the minimum gap of the processing tool or processing method. For example, the minimum processing gap of a CNC laser machine tool is about 0.1 mm, then the central angle corresponding to the groove part of the magnetic ring cannot be less than the central angle corresponding to the 0.1 mm gap. The third factor is the minimum sensing angle of the magnetic signal detection element. The minimum central angles corresponding to the protrusions and grooves cannot be less than the minimum sensing angle of the magnetic signal detection element, otherwise clear and definite magnetic signals cannot be obtained. The fourth factor is the diameter (outer diameter) of the magnetic ring. The diameter of the magnetic ring on the magnetic drum is not arbitrary, but is determined by the radial space for installing the magnetic encoder. The smaller the radial space, the smaller the magnetic encoder can only be, the smaller the diameter of the magnetic ring can only be, the smaller the number of protrusions or grooves with the same central angle on the magnetic drum, and the fewer the magnetic signals generated by the magnetic drum. Restricted by the above several factors, it is particularly difficult to further improve the detection accuracy and resolution of the magnetic encoder in the prior art. Summary of the Invention

[0005] Therefore, the present invention provides a magnetic encoder to further improve the detection accuracy and resolution of the magnetic encoder.

[0006] To solve the above problems, the present invention provides a magnetic encoder, which includes a magnetic drum, a magnetic signal detection element, and a magnetic signal processing and output element. An outer peripheral wall of the magnetic drum is provided with M single-pole magnetic rings along its axial direction. Along the circumferential direction of each single-pole magnetic ring within the magnetic field range thereof, n magnetic signal detection elements are provided. On an outer circumferential surface of the single-pole magnetic ring, protrusions and grooves are alternately arranged in sequence along the circumferential direction. A central angle formed between two end points of an outer circumferential wall of the protrusion and the center of the single-pole magnetic ring is α, and a central angle formed between two end points of an outer circumferential wall of the groove and the center of the single-pole magnetic ring is β. For two axially adjacent single-pole magnetic rings among the M single-pole magnetic rings, the protrusions respectively have a circumferential deflection angle A along the magnetic drum, and for two axially adjacent magnetic signal detection elements, they have a circumferential deflection angle B along the magnetic drum. A and B are not both equal to zero, where M≥2 and n≥1.

[0007] In some embodiments, for each protrusion on the outer circumference of the single-pole magnetic ring provided on the outer peripheral wall of the magnetic drum along its axial direction, α is not equal, for each groove, β is not equal, and α and β are not equal.

[0008] In some embodiments, for each protrusion on the outer circumference of the single-pole magnetic ring provided on the outer peripheral wall of the magnetic drum along its axial direction, α is equal, for each groove, β is equal, and α and β are equal.

[0009] In some embodiments, for two axially adjacent single-pole magnetic rings among the M single-pole magnetic rings provided on the outer peripheral wall of the magnetic drum along its axial direction, the protrusions respectively have an unequal circumferential deflection angle A along the magnetic drum, and for two axially adjacent magnetic signal detection elements among the M single-pole magnetic rings, they have an unequal circumferential deflection angle B along the magnetic drum.

[0010] In some embodiments, for two axially adjacent single-pole magnetic rings among the M single-pole magnetic rings provided on the outer peripheral wall of the magnetic drum along its axial direction, the protrusions respectively have an equal circumferential deflection angle A along the magnetic drum, and for two axially adjacent magnetic signal detection elements among the M single-pole magnetic rings, they have an equal circumferential deflection angle B along the magnetic drum.

[0011] In some embodiments, the single-pole magnetic ring is an anisotropic magnet, or an isotropic magnet.

[0012] In some embodiments, the single-pole magnetic ring is at least one of a neodymium iron boron magnet, a samarium cobalt magnet, an alnico magnet, a rubber magnet, and a ferrite magnet.

[0013] According to the present invention, the accuracy of the protrusions and grooves of the magnetic encoder drum is ensured by machining, and other characteristics of the magnetic encoder (such as resolution) can be ensured by jointly adjusting multiple parameters such as the magnitudes of the central angles α and β, the number M of single-pole magnetic rings, the number n of magnetic signal detection elements arranged circumferentially within the magnetic field range of each single-pole magnetic ring, the deflection angle A of the protrusions of two axially adjacent single-pole magnetic rings along the circumference of the drum, and the deflection angle B of two axially adjacent magnetic signal detection elements along the circumference of the drum. The relatively large number of adjustable parameters is conducive to designing magnetic encoders with different functions and different accuracy requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 FIG. 6 is a schematic structural diagram (only showing partial segments) of M single-pole magnetic rings of the magnetic encoder according to an embodiment of the invention after being unfolded along the circumference of the drum. The figure shows the deflection angle of the protrusions of two axially adjacent single-pole magnetic rings among the M single-pole magnetic rings along the circumference of the drum, and the state where the M magnetic signal detection elements are arranged in a row along the axis of the drum;

[0015] Figure 2 FIG. 10 is a schematic structural diagram of a single-pole magnetic ring of the magnetic encoder according to an embodiment of the invention;

[0016] Figure 3 FIG. 14 is a schematic structural diagram (only showing partial segments) of M single-pole magnetic rings of the magnetic encoder according to another embodiment of the invention after being unfolded along the circumference of the drum. The figure shows the state where the M single-pole magnetic rings are arranged in a row along the axis of the drum and the deflection angle of two axially adjacent magnetic signal detection elements among the M magnetic signal detection elements along the circumference of the drum.

[0017] The reference signs are as follows:

[0018] 1, single-pole magnetic ring; 11, protrusion; 12, groove; 2, magnetic signal detection element. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Referring jointly to Figures 1 to 3As shown, according to an embodiment of the present invention, a magnetic encoder is provided, which includes a magnetic drum, a magnetic signal detection element, and a magnetic signal processing and output element. Wherein, M single-pole magnetic rings 1 are arranged along the axial direction on the outer peripheral wall of the magnetic drum. Along the circumferential direction of each single-pole magnetic ring 1, n magnetic signal detection elements 2 are arranged. On the outer circumferential surface of the single-pole magnetic ring 1, protrusions 11 and grooves 12 are alternately arranged in sequence along the circumferential direction. The central angle formed between the two end points of the outer circular wall of the protrusion 11 and the center of the single-pole magnetic ring 1 is α, and the central angle formed between the two end points of the outer circular wall of the groove 12 and the center of the single-pole magnetic ring 1 is β. For two axially adjacent single-pole magnetic rings 1 among the M single-pole magnetic rings 1, the protrusions 11 they respectively have are deflected by an angle A along the circumferential direction of the magnetic drum, and for two axially adjacent magnetic signal detection elements 2, they are deflected by an angle B along the circumferential direction of the magnetic drum. A and B are not both equal to zero, where M≥2, n≥1. It should be noted that if A and B are both zero at the same time, the purpose of increasing the magnetic signals generated when the magnetic drum rotates one week cannot be achieved. In this technical solution, it effectively overcomes the deficiencies in the prior art, which are limited by the processing accuracy of the machining dimensions and precision of the concave-convex structure on the outer peripheral wall of a single single-pole magnetic ring 1, material physical properties (such as strength, toughness, etc.), size, and the minimum sensing angle of the magnetic signal detection element. That is, according to the present invention, the accuracy of the protrusions and grooves of the magnetic encoder magnetic drum is ensured through mechanical processing, and other characteristics of the magnetic encoder (such as resolution) are ensured by jointly adjusting multiple parameters, such as the magnitudes of the central angles α and β, the number M of single-pole magnetic rings, the number n of magnetic signal detection elements arranged along the circumferential direction within the magnetic field range of each single-pole magnetic ring, the deflection angle A of the protrusions of two axially adjacent single-pole magnetic rings along the circumferential direction of the magnetic drum, and the deflection angle B of two axially adjacent magnetic signal detection elements along the circumferential direction of the magnetic drum. The relatively large number of adjustable parameters is conducive to designing magnetic encoders with different functions and different control accuracy requirements. It can be understood that since the magnetic field intensity signals obtained by the magnetic signal detection elements in the present invention only have differences in strength and weakness, and the quantity can be large enough, the magnetic signals can be completely processed according to the method of processing digital signals. For example, magnetic signals with high magnetic field intensity are regarded as 1, and magnetic signals with low magnetic field intensity are regarded as 0. Since multiple magnetic signal detection elements can obtain magnetic signals simultaneously in the present invention, the magnetic signals of each group can be arranged and combined for processing to obtain a larger number of magnetic signals.

[0020] The single-pole magnetic ring refers to a magnetic ring whose outer circumferential wall (i.e., the outer circular wall) and / or inner circumferential wall (i.e., the inner circular wall) has only a single magnetic pole (N pole or S pole).

[0021] Specifically, in the present invention, the magnetic signal is generated by the protrusions 11 and grooves 12 alternately arranged along the circumferential direction on the outer circumferential surface of the monopole magnetic ring. As discussed in the technical background section, due to multiple factors, the number of protrusions 11 and depressions 12 of a single magnetic ring cannot increase infinitely. Then, the number of magnetic signals that a single magnetic ring can generate cannot increase without limit. That is to say, there is a limit value for the minimum central angle occupied by a single magnetic signal generated by a single magnetic ring. In order to generate more magnetic signals when the magnetic drum rotates one week, the present invention arranges a plurality of monopole magnetic rings 1 along the axial direction on the outer peripheral wall of the magnetic drum.

[0022] For the convenience of understanding the content of the present invention, the following uses a magnetic encoder drum with the simplest structure of the present invention to illustrate the main technical content of the present invention:

[0023] The central angles of the protrusions 11 and grooves 12 alternately arranged along the circumferential direction on the outer circumferential surface of the monopole magnetic ring 1 are equal, which is α; there are two monopole magnetic rings arranged along the axial direction on the outer peripheral wall of the magnetic drum (that is, M = 2); only one magnetic signal detection element 2 is arranged above each magnetic ring (that is, n = 1), and the two (corresponding to the two monopole magnetic rings 1 respectively) magnetic signal detection elements are located on a straight line parallel to the central axis of the magnetic drum; the protrusions of the two magnetic rings are staggered by an angle of α / 2; after the magnetic drum rotates by an angle of α, each of the 2 magnetic rings generates a magnetic signal, that is, two magnetic signals are generated; in this way, the central angle of the magnetic drum generating a single magnetic signal is reduced from α to α / 2. It can be seen that when there is only one magnetic ring on the surface of the magnetic drum, the magnetic drum can only generate 360 / α magnetic signals when rotating one week, half of which are generated by the protrusions 11 of the magnetic ring and half are generated by the depressions 12 of the magnetic ring. After two magnetic rings are connected in series on the surface of the magnetic drum, the magnetic drum can generate 2×360 / α magnetic signals when rotating one week, and the number of magnetic signals increases by one time.

[0024] Similarly, if the outer wall of the magnetic drum is composed of M magnetic rings connected in series, if the protrusions of the M magnetic rings are staggered by an angle of α / M, then M magnetic signals can be generated after the magnetic drum rotates by an angle of α, and 360M / α magnetic signals can be generated when the magnetic drum rotates 360°. The purpose of generating a magnetic signal when the magnetic drum rotates a very small central angle can be achieved, and finally the resolution of the magnetic encoder can be improved. If more magnetic signals are desired from a single magnetic ring, a plurality of magnetic signal detection elements 2 can be arranged along the circumferential direction within the magnetic field range of each monopole magnetic ring.

[0025] Because the uses of magnetic encoders are very extensive, magnetic encoders for different uses must meet different control signal requirements. Therefore, in the present invention, the α of each protrusion 11 on the outer circumference of the monopole magnetic ring 1 arranged along the axial direction on the outer peripheral wall of the magnetic drum can be unequal, the β of each groove 12 can be unequal, and α and β can be unequal. Usually, however, the α of each protrusion 11 is designed to be equal, the β of each groove 12 is designed to be equal, and α and β are also equal.

[0026] To achieve the purpose that each magnetic ring on the surface of the drum can generate a magnetic signal after the drum rotates by a certain angle, the protrusions 11 of two adjacent single-pole magnetic rings need to be circumferentially deflected by an angle A along the drum, or two adjacent magnetic signal detection elements 2 need to be circumferentially deflected by an angle B along the drum, and A and B cannot be zero at the same time. For example, A = 0 and B ≠ 0 means that the protrusions 11 of two adjacent single-pole magnetic rings on the drum surface are axially aligned with each other along the drum, but two adjacent magnetic signal detection elements 2 on the drum surface are circumferentially deflected by an angle B; A ≠ 0 and B = 0 means that the protrusions 11 of two adjacent single-pole magnetic rings 1 on the drum surface are circumferentially deflected by an angle A with respect to each other, but two adjacent magnetic signal detection elements 2 on the drum surface are axially aligned with each other. Specifically, see Figure 1 As shown, all the magnetic signal detection elements 2 for detecting the magnetic signals of the magnetic rings are located on a straight line parallel to the central axis of the drum (the vertically extending dotted line in the figure), that is, B = 0, and the protrusions or grooves of all the magnetic rings are staggered from each other by an angle A; in another embodiment, see Figure 3 As shown, the protrusions of all the magnetic rings are aligned with the protrusions and the grooves are aligned with the grooves (that is, the circumferential magnetic rings are not deflected axially), that is, A = 0, but the magnetic signal detection elements for detecting the magnetic signals of the magnetic rings are staggered from each other by an angle B; in another embodiment, the alignment mode of the protrusions or grooves of the magnetic rings and the installation positions of the magnetic signal detection elements 2 are arranged as required, that is, A ≠ 0 and B ≠ 0, to meet the signal requirements of the magnetic encoder for different control types, that is, the mixed arrangement mode of the deflection angles.

[0027] Two axially adjacent single-pole magnetic rings 1 have the same magnetism, or two axially adjacent single-pole magnetic rings 1 have opposite magnetism, that is, the polarities of two axially adjacent single-pole magnetic rings 1 can be N poles or S poles at the same time, or one can be an N pole and the other can be an S pole. The specific polarity combination method can be determined according to the processing program of the magnetic encoder chip for the magnetic signals of the drum.

[0028] In some embodiments, the protrusions 11 and the grooves 12 are formed by machining, specifically, for example, by laser processing, so as to ensure the dimensional accuracy of each protrusion and groove, ensure the uniform distribution of the magnetic signal source in 360°, and effectively overcome the defects of the magnetic-free zone between the N pole and the S pole being blurred, deformed and inconsistent in width during the magnetization process of the magnetic ring, greatly improve the quality of the magnetic signal source of the drum, and ensure the accuracy of the magnetic encoder.

[0029] The single-pole magnetic ring 1 in the present invention can be an anisotropic magnet or an isotropic magnet. The single-pole magnetic ring 1 in the present invention can be a neodymium iron boron magnet, a samarium cobalt magnet, an alnico magnet, a rubber magnet, a ferrite magnet or other types of permanent magnets, or a combination thereof.

[0030] The following uses α = β = 1°, A = 0.25°, B = 0, and M = 4 as specific embodiments to further elaborate on the technical solution of the present invention.

[0031] Each convex and concave part of the magnetic ring has an equal central angle, which is 1° (i.e., α = β = 1°). In this structure, the magnetic drum generates a magnetic signal every time it rotates 1°, and it can generate 360 magnetic signals in one rotation, including 180 convex magnetic signals (with a high magnetic field strength value) and 180 concave magnetic signals (with a low magnetic field strength value). Further, 4 such magnetic rings are serially connected axially on the magnetic drum (i.e., arranged in sequence along the axis of the magnetic drum), with the convex or concave parts of each magnetic ring differing by 0.25° (A = 1° / 4). A magnetic signal detection element is placed above each magnetic ring, and all magnetic signal detection elements are located on a straight line parallel to the central axis of the magnetic drum (B = 0, as shown in Figure 1 the figure). In this way, the magnetic drum can generate a magnetic signal every time it rotates 0.25°, and it can generate 1440 magnetic signals in one rotation. Similarly, if 10 magnetic rings are serially connected, the magnetic drum can generate 3600 magnetic signals in one rotation. If the current common method is used, that is, 4 magnetic signal detection elements 2 are arranged circumferentially within the magnetic field range of each single-pole magnetic ring 1, then the magnetic drum can generate 4 × 3600 magnetic signals, that is, 14400 magnetic signals in one rotation.

[0032] It can be understood that the magnetic signal processing and output element is used to obtain the magnetic signals detected by the magnetic signal detection element and process the magnetic signals according to a preset rule to form corresponding output signals and output them to the corresponding control system. This part is a conventional technology of the magnetic encoder and will not be elaborated here.

[0033] Those skilled in the art can easily understand that, on the premise of no conflict, the above advantageous ways can be freely combined and superimposed.

[0034] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and variations can be made without departing from the technical principle of the present invention, and these improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. A magnetic encoder, characterized in that, It includes a magnetic drum, a magnetic signal detection element, and a magnetic signal processing and output element. On the outer peripheral wall of the magnetic drum, M single-pole magnetic rings (1) are provided along its axial direction. Within the magnetic field range of each single-pole magnetic ring (1), n magnetic signal detection elements (2) are provided along its circumferential direction. On the outer circumferential surface of the single-pole magnetic ring (1), protrusions (11) and grooves (12) are alternately arranged in sequence along its circumferential direction. The central angle formed between the two end points of the outer circular wall of the protrusion (11) and the center of the single-pole magnetic ring (1) is α, and the central angle formed between the two end points of the outer circular wall of the groove (12) and the center of the single-pole magnetic ring (1) is β. For two axially adjacent single-pole magnetic rings (1) among the M single-pole magnetic rings (1), the protrusions (11) respectively have a circumferential deflection angle A along the magnetic drum, and for two axially adjacent magnetic signal detection elements (2), the circumferential deflection angle B along the magnetic drum. A and B are not both equal to zero, where M≥2 and n≥1; two axially adjacent single-pole magnetic rings (1) have the same magnetism; for each protrusion (11) on the outer circumference of the single-pole magnetic rings (1) provided along the axial direction on the outer peripheral wall of the magnetic drum, α is not equal, for each groove (12), β is not equal, and α and β are not equal.

2. The magnetic encoder according to claim 1, characterized in that, For two axially adjacent single-pole magnetic rings (1) among the M single-pole magnetic rings (1) provided along the axial direction on the outer peripheral wall of the magnetic drum, the circumferential deflection angle A of the protrusions (11) respectively is not equal, and for two axially adjacent magnetic signal detection elements (2) among the M single-pole magnetic rings (1), the circumferential deflection angle B along the magnetic drum is not equal.

3. The magnetic encoder according to claim 1, wherein, For two axially adjacent single-pole magnetic rings (1) among the M single-pole magnetic rings (1) provided along the axial direction on the outer peripheral wall of the magnetic drum, the circumferential deflection angle A of the protrusions (11) respectively is equal, and for two axially adjacent magnetic signal detection elements (2) among the M single-pole magnetic rings (1), the circumferential deflection angle B along the magnetic drum is equal.

4. The magnetic encoder according to any one of claims 1 to 3, characterized in that The single-pole magnetic ring (1) is an anisotropic magnet, or an isotropic magnet.

5. The magnetic encoder according to any one of claims 1 to 3, characterized in that The single-pole magnetic ring (1) is at least one of a neodymium iron boron magnet, a samarium cobalt magnet, an alnico magnet, a rubber magnet, and a ferrite magnet.

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