Angle detection device

Abstract

To provide a high-resolution angle detection device based on a principle of a double-row magnetic encoder that has a high degree of freedom in design, can be miniaturized and made light, and can reduce manufacturing costs.SOLUTION: An angle detection device 4 includes: an encoder part 6 having magnetic tracks in which N and S poles are lined up alternately; and a magnetic sensor part 7 facing the magnetic tracks via a gap. In the magnetic tracks, a main track 2 having a magnetic pole width of P and a sub-track 3 having a magnetic pole width of Pn / (n-1) are provided adjacently and in parallel mutually along a longitudinal direction of a sheet-like encoder magnetic body 1 when a reference magnetic width and a reference magnetic pole logarithm are set to P and n, respectively. In the encoder part 6, the sheet-like encoder magnetic body 1 is fixed by winding around an outer peripheral part or an inner peripheral part of a rotor 5 with a length of a reference length of L=2Pn or smaller. The angle detection device 4 includes a correction calculation part 10 for correcting an absolute angle of the rotor by multiplying an absolute angle calculated by an operation part 9 of the magnetic sensor part 7 by a correction coefficient corresponding to the diameter of the encoder part 6.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present invention relates to an angle detection device that detects the rotation angle of a rotary shaft or the like, and in particular to an angle detection device that detects angles in a range of 360° or less with high resolution in order to position a robot joint or the like at a target position. [Background technology]

[0002] Various magnetic encoder devices for detecting a rotation angle have been proposed. The magnetic encoder device disclosed in Patent Document 1 has a cylindrical base made of sintered metal, and the outer circumferential surface, inner circumferential surface, and both end faces of this base are subjected to sizing by pressing.The base is then inserted into a mold, and a resin material mainly composed of thermoplastic resin and magnetic powder is injection molded into the cavity.The molded part then has multiple magnetic poles arranged circumferentially, and two rows of magnetic encoder tracks with different numbers of magnetic pole pairs are formed by multi-pole magnetization.

[0003] The magnetic encoder thus fabricated is fixed to a rotating body, and a magnetic sensor is provided adjacent to and facing the magnetic encoder tracks. The magnetic sensor has two detection elements facing each of the two magnetic encoder tracks, and a calculation unit. Based on the phase difference between the magnetic signals detected by the two detection elements, the absolute angle of the rotating body is calculated with high resolution and output as sensor output.

[0004] The magnetic encoder disclosed in Patent Document 2 consists of a magnetic recording rotor with a tape-shaped magnetic scale member attached to its outer surface, with N and S poles magnetized alternately at an equal pitch, and magnetic information detection means arranged close to the magnetic recording rotor. The magnetic information detection means includes two magnetic information detection elements arranged at a distance along the direction of rotation of the magnetic recording rotor. The magnetic information formed on the magnetic scale member is detected by the two magnetic information detection elements, and A-phase, B-phase, and Z-phase signals are generated from the detection output. This makes it possible to realize a highly accurate, reliable, and versatile magnetic encoder at a relatively low cost. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-75466 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-141259 Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology disclosed in Patent Document 1, a plastic magnet is integrally molded onto a pressed sintered core, and then magnetization is performed so that a predetermined number of magnetized poles are formed per rotation. To realize a high-resolution angle detection device using a multi-track magnetic encoder while satisfying constraints such as available space and cost, it is necessary to use a mass-produced magnetic sensor that packages all the necessary functions into one package.

[0007] For this reason, major specifications such as the pole width and number of pole pairs are predetermined, making it impossible to accommodate individual specifications. For example, once specifications such as the pole width and number of pole pairs are determined, the diameter of the encoder section is also determined by these specifications, making it impossible to manufacture it with an arbitrary diameter, limiting design freedom. Also, since each molded product is individually magnetized, it is difficult to improve productivity. Furthermore, it is difficult to integrate the molded product with the rotating body, and a magnetized part must be attached as a separate part, which increases the size and mass of the rotating body, creating another problem. To manufacture a magnetic encoder device, a core metal mold and a plastic magnet are required. It is necessary to manufacture a mold for injection molding, which increases the manufacturing cost.

[0008] The tape-shaped magnetic scale used in the technology disclosed in Patent Document 2 is lightweight and does not require molding dies, so it can address the above issues, but it does not disclose anything about improving resolution. Furthermore, while both ends of a magnetic scale member attached to a portion of the circumference can be detected by a Z-phase signal, no A-phase or B-phase signal is output when the end of the magnetic scale member is detected. For this reason, there is a problem that, for example, when using angle detection signals to control rotating equipment, a normal control method cannot be used.

[0009] The object of the present invention is to solve the above-mentioned problems and to provide a high-resolution angle detection device based on the principle of a double-track magnetic encoder, which has a high degree of design freedom, can be made small and lightweight, and can reduce manufacturing costs. [Means for solving the problem]

[0010] The angle detection devices 4, 4A, and 4B of the present invention are angle detection devices including an encoder unit 6, 6A, and 6B having a magnetic track in which N poles and S poles are alternately arranged, and a magnetic sensor unit 7 facing the magnetic track with a gap δ therebetween, The magnetic tracks are arranged in parallel adjacent relation to each other along the longitudinal direction of the sheet-like magnetic body 1 for the encoder, with a main track 2 having a magnetic pole width P and a sub-track 3 having a magnetic pole width Pn / (n-1), where P is a reference magnetic pole width and n is the number of reference magnetic pole pairs. The encoder units 6, 6A, 6B are formed by wrapping the sheet-like magnetic body 1 for the encoder around the outer or inner periphery of the rotors 5, 5A, 5B and fixing it to a length equal to or less than a reference length L=2Pn. the magnetic sensor unit 7 includes two magnetic detection elements 8 facing the main track 2 and the sub-track 3, respectively, and outputting magnetic signals; and a calculation unit 9 calculating absolute angles of the rotating bodies 5, 5A, and 5B based on the magnetic signals of the magnetic detection elements 8; The apparatus includes a correction calculation unit 10 that corrects the absolute angles of the rotating bodies 5, 5A, 5B by multiplying the calculated absolute angles by a correction coefficient according to the diameters of the encoder units 6, 6A, 6B.

[0011] According to this configuration, the sheet-shaped encoder magnetic material 1 is wrapped around and fixed to the outer or inner circumference of the rotating body 5, 5A, 5B and used as the encoder unit 6, 6A, 6B of the angle detection device 4, 4A, 4B. Therefore, even if the diameter of the encoder unit changes, there is no need to manufacture a mold, and the encoder unit 6, 6A, 6B of any diameter can be easily manufactured. The calculation unit 9 can calculate the absolute angle of the rotating body 5, 5A, 5B with high resolution based on the magnetic signals from the two magnetic detection elements 8. The correction calculation unit 10 multiplies the calculated absolute angle by a correction coefficient corresponding to the diameter of the encoder unit 6, 6A, 6B, thereby accurately detecting the absolute angle of the rotating body 5, 5A, 5B having a circumferential length L with high resolution even if the diameter of the encoder unit is not L / π. Furthermore, using existing rotating parts 11A, 11B, 11C as the rotating body eliminates the need for an additional encoder, simplifying the structure of the angle detection device and reducing its size and weight.

[0012] When the magnetic body 1 for the encoder having the reference length L is cut to an arbitrary length and the diameter of the encoder unit 6, 6A, 6B wound around the outer or inner circumference of the rotating body 5, 5A, 5B is S, the correction calculation unit 10 may use the value L / (πS) obtained by dividing the reference length L by the value obtained by multiplying the diameter S by the constant π as the correction coefficient. If the diameter of the encoder units 6, 6A, and 6B is a diameter S that is not equal to L / π, the sensor output from the magnetic sensor unit 7 will differ from the actual angle, but the accurate angle can be obtained by multiplying the sensor output by L / (πS) as a correction coefficient.

[0013] The magnetic body 1 for the encoder, in which the length L1 of the main track 2 and the sub-track 3 is equal to or less than the reference length L, is disposed on the outer periphery of the rotating bodies 5, 5A, 5B, which have a circumferential length longer than the length L1. The encoder unit 6, 6A, 6B is wound around and fixed to the outer periphery or inner periphery of the rotor, The magnetic sensor may further include a limit angle memory unit 12 that stores limit angles corresponding to the output of the magnetic sensor unit 7 at both ends of the magnetic track, and a detection range determination unit 13 that determines whether the absolute angle output from the magnetic sensor unit 7 is within the limit angle range and outputs an identification signal indicating whether the limit angle has been exceeded.

[0014] With this configuration, if rotation is stopped when an identification signal indicating that the limit angle has been exceeded is output, a normal sensor signal indicating the absolute angle will be output, allowing operation to be performed to avoid the undetectable area using normal control methods.

[0015] The rotating bodies 5, 5A, 5B may be rotating parts 11A, 11B, 11C of a robot joint. When detecting the absolute angle of a robot joint, the required angle detection range is often less than 360°. In that case, if the joint of the magnetic substance for encoder 1 is positioned where angle detection is not required, the influence of the joint can be avoided, and an angle detection device can be established. Furthermore, if the rotating parts 11A, 11B, 11C of an existing robot joint are used as rotating bodies and the magnetic substance for encoder 1 is wound and fixed directly around the rotating parts 11A, 11B, 11C, there is no need to attach a separate encoder, and the robot joint can be made smaller and lighter. [Effects of the Invention]

[0016] The angle detection device of the present invention is an angle detection device comprising an encoder unit having a magnetic track on which north and south poles are arranged alternately, and a magnetic sensor unit facing the magnetic track across a gap, wherein the magnetic track comprises a main track having a magnetic pole width of P and a sub-track having a magnetic pole width of Pn / (n-1) arranged adjacent to each other in parallel along the longitudinal direction of a sheet-shaped encoder magnetic material, where P is a reference magnetic pole width and n is the number of reference magnetic pole pairs, and the encoder unit is formed by wrapping the sheet-shaped encoder magnetic material around the outer or inner circumference of a rotating body and fixing it to a length not greater than a reference length L = 2Pn. The magnetic sensor unit comprises two magnetic detection elements facing the main track and the sub-track, respectively, which output magnetic signals, and a calculation unit which calculates the absolute angle of the rotating body based on the magnetic signals of these magnetic detection elements, and a correction calculation unit which corrects the absolute angle of the rotating body by multiplying the calculated absolute angle by a correction coefficient corresponding to the diameter of the encoder unit. This makes it possible to obtain a high-resolution angle detection device based on the principle of a multi-track magnetic encoder, which has a high degree of freedom in design, can be made smaller and lighter, and can reduce manufacturing costs. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating an example of the configuration of an angle detection device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing a structure of a magnetic body for an encoder of the angle detection device. [Figure 3] FIG. [Figure 4A] FIG. 2 is a block diagram of a control system of the angle detection device. [Figure 4B] FIG. 4B is a block diagram in which part of the control system of FIG. 4A is partially modified. [Figure 5] 4A and 4B are diagrams illustrating the phase of a detection signal from a magnetic sensor unit of the angle detection device and a phase difference between the two detection signals. [Figure 6] 10 is a diagram illustrating an example of the configuration of an angle detection device when the diameter of the encoder unit is different from L / π. FIG. [Figure 7] FIG. 2 is a block diagram of a correction calculation unit of the angle detection device. [Figure 8] 10A and 10B are diagrams illustrating an example of the configuration of an angle detection device in which a gap is generated at the joint of the encoder section. [Figure 9] FIG. 2 is a block diagram of a control system of the angle detection device. [Figure 10] 10A and 10B are diagrams illustrating an example in which any of the angle detection devices is applied to a robot joint. DETAILED DESCRIPTION OF THE INVENTION

[0018] [First embodiment] An angle detection device according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 3, the angle detection device 4 includes an encoder unit 6 having a magnetic track and a magnetic sensor unit 7 facing the magnetic track with a gap δ between them. As shown in FIG. 2, the encoder unit 6 has a magnetic track in which N and S poles are arranged alternately. The magnetic track is configured such that, when a reference magnetic pole width is P and the number of reference magnetic pole pairs is n, a main track 2 having a magnetic pole width (circumferential width) of P and a sub-track 3 having a magnetic pole width of Pn / (n-1) are arranged adjacent to each other in parallel along the longitudinal direction of the sheet-like encoder magnetic body 1. As shown in FIG. 1, the encoder unit 6 is configured such that the sheet-like encoder magnetic body 1 is wound around and fixed to the cylindrical outer peripheral portion 5a of the rotor 5 with a length equal to or less than the reference length L.

[0019] The magnetic body 1 for an encoder shown in Figure 2 is produced by, for example, vulcanizing a rubber material kneaded with magnetic powder into a sheet, cutting it to the required length, and then magnetizing the north and south poles alternately in the longitudinal direction at a predetermined magnetic pole width determined by the reference magnetic pole width P and the number of reference magnetic pole pairs n, to form a magnetic track having a main track 2 and a sub-track 3. Alternatively, a sheet that has been magnetized to a length suitable for conditions such as production equipment or material availability can be cut to the required length depending on the application. The reference length is also defined as L = 2Pn.

[0020] For example, if the reference magnetic pole width P is 2 mm and the number of reference magnetic pole pairs n is 32, the magnetized width (magnetized pitch) p2 (= P) of the main track 2 is 2 mm, and the magnetized width p3 (= Pn / (n-1)) of the sub-track 3 is 2.0645 mm. To detect an absolute angle of 360° with the standard accuracy of a magnetic sensor, the number of magnetized pole pairs (number of magnetic pole pairs) n2 (= n) of the main track 2 is 32 pole pairs (64 poles in total, including north and south poles), and the number of magnetized pole pairs n3 (= n-1) of the sub-track 3 is 31 pole pairs (62 poles in total, including north and south poles). The length of the magnetic track in this case is the reference length L, and is L = 2Pn = 128 mm.

[0021] Here, the main track 2 of the encoder magnetic body 1 has a magnetization width of 2 mm and 32 pole pairs, and the sub-track 3 has a magnetization width of 2.0645 mm and 31 pole pairs, but the specifications of the magnetic poles of the encoder magnetic body can be selected appropriately depending on the magnetic sensor to be used.

[0022] The angle detection device 4 shown in Fig. 1 includes an encoder unit 6 in which an encoder magnetic body 1 is fixed to the outer periphery 5a of a rotating body 5 with adhesive or double-sided tape, etc., and a magnetic sensor unit 7. A hole 5b is formed in the center of the rotating body 5, and a rotating shaft (not shown) is inserted into the hole 5b so as to be unable to rotate relative to the rotating body 5. The rotating shaft may be provided integrally with the rotating body 5. "Integrated" means that the rotating shaft and the rotating body 5 are not formed by joining multiple elements, but are formed as part or the whole of a single object from a single material by, for example, forging or machining.

[0023] As shown in Figure 4(A), the magnetic sensor unit 7 includes two magnetic detection elements 8 that face the main track 2 and the sub-track 3 from the radial outside of the rotating body 5, respectively, and output magnetic signals, and a calculation unit 9 that calculates the absolute angle of the rotating body 5 with high resolution based on the phase difference between the magnetic signals detected by these magnetic detection elements 8, and outputs the result as a sensor output.

[0024] As shown in Figure 2, when an encoder magnetic body 1 having a length L and a magnetic track of a reference length L provided along its entire length is wound once around the outer periphery 5a of a rotating body 5 as shown in Figure 1 to produce an encoder unit 6 having a diameter of L / π, as shown in Figures 4(A) and 5, the calculation unit 9 can detect the absolute angle with standard accuracy by taking advantage of the fact that the phase difference (Figure 5(C)) between the signal obtained from the main track 2 (Figure 5(A)) and the signal obtained from the sub-track 3 (Figure 5(B)) is one pole pair per rotation.

[0025] In addition, when the magnetic body 1 for an encoder having a magnetic track of the reference length L shown in FIG. 2 is cut so that the length of the magnetic track is shorter than the reference length L and wound around the rotating body 5 shown in FIG. In this case, even if there is a gap (circumferential gap) at the joint T between one longitudinal end and the other longitudinal end of the encoder unit 6, if the diameter of the encoder unit 6 is L / π, the absolute angle can be detected with the standard accuracy of the magnetic sensor within the range in which the encoder magnetic body 1 is fixed.

[0026] FIG. 5(A) shows the waveform of the detection signal corresponding to the main track 2, and FIG. 5(B) shows the waveform of the detection signal corresponding to the sub-track 3. FIG. 5(C) shows the waveform of the output signal of the phase difference calculated by the calculation unit 9 (FIG. 4A) based on the detection signals of FIGS. 5(A) and 5(B). The calculation unit 9 (FIG. 4A) converts the calculated phase difference into an absolute angle in accordance with preset calculation parameters. The calculation parameters are stored in storage means Mr, such as a nonvolatile memory, provided in the magnetic sensor unit 7 shown in FIG. 4(A). In addition to the calculation parameters, this storage means Mr rewritably stores information necessary for the operation of the device, such as the reference magnetic pole width P of the magnetic track, the number of reference magnetic pole pairs n, the number of magnetized pole pairs for each of the tracks 2 and 3, and the signal output method.

[0027] This angle detection device 4 is equipped with a correction calculation unit 10 after the calculation unit 9. The correction calculation unit 10 multiplies the absolute angle output from the calculation unit 9 by a correction coefficient according to the diameter of the encoder unit 6 to correct the absolute angle of the rotating body 5. When an encoder magnetic body 1 having a reference length L is cut to an arbitrary length and the diameter of the encoder part 6 wound around the outer circumferential part 5a (Figure 1) of the rotating body 5 is S, the correction calculation part 10 divides the reference length L by the value obtained by multiplying the diameter S by the circular constant π, and determines the value L / (πS) as the correction coefficient.

[0028] If the diameter of the encoder unit 6 is not equal to L / π, the sensor output from the magnetic sensor will differ from the actual angle. However, the correct angle can be obtained by multiplying the sensor output by a correction coefficient. As mentioned above, if the diameter of the encoder unit 6 is S, the absolute angle output from the calculation unit 9 can be multiplied by the correction coefficient L / (πS). This correction calculation unit 10 includes a storage function for storing the correction coefficient and a calculation function, and performs correction calculations using the stored correction coefficient according to the calculation function. In this example, the correction calculation unit 10 is located after the calculation unit 9 within the magnetic sensor unit 7. However, the correction calculation unit 10 may also be located within the calculation unit 9. Alternatively, as shown in Figure 4(B), the correction calculation unit 10 may be located as a dedicated circuit near the magnetic sensor unit 7, or the correction calculation unit may be included in a higher-level control unit (not shown).

[0029] <Action and effect> According to the angle detection device 4 described above, the sheet-like encoder magnetic material 1 shown in FIG. 1 is wrapped around and fixed to the outer periphery 5a of the rotating body 5 and used as the encoder unit 6 of the angle detection device 4. Therefore, even if the diameter of the encoder unit 6 changes, there is no need to manufacture a mold, and the encoder unit 6 can be easily manufactured with any diameter. The calculation unit 9 can calculate the absolute angle of the rotating body 5 with high resolution based on the magnetic signals from the two magnetic detection elements 8. The correction calculation unit 10 multiplies the calculated absolute angle by a correction coefficient corresponding to the diameter of the encoder unit 6, thereby accurately detecting the absolute angle of the rotating body 5 with high resolution even if the diameter of the encoder unit 6 is not L / π. Furthermore, using an existing rotating part as the rotating body 5 eliminates the need to add a separate encoder, thereby simplifying the structure of the angle detection device 4 and making it smaller and lighter.

[0030] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description will be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as the previously described embodiment unless otherwise specified. The same functions and effects are achieved from the same configuration. It is not limited to combinations of parts specifically described in each embodiment, but it is also possible to partially combine embodiments together as long as there is no particular problem with the combination.

[0031] [Second embodiment] Fig. 6 is a diagram showing an example of the configuration of an angle detection device 4A when the diameter of the encoder unit is different from L / π. Fig. 7 is a block diagram of a correction calculation unit 10 of the angle detection device. If the diameter of the encoder, which is made by winding an encoder magnetic material of reference length L around a rotating body, is different from L / π, the sensor output from the magnetic sensor unit will differ from the actual angle. In this case, if a correction calculation unit 10 is provided in the angle detection device 4A and the sensor output is multiplied by a correction coefficient, an accurate absolute angle can be obtained.

[0032] FIG. 6 shows an angle detection device 4A in which an encoder magnetic body 1 having a length L and a magnetic track of a reference length L provided along its entire length is cut to a length L / 2 and wound once around the outer periphery 5Aa of a rotating body 5A in the circumferential direction to form an encoder unit 6A having a diameter of L / (2π) and capable of detecting an absolute angle of 360°. Since the outer periphery length of the encoder unit 6A is half the reference length L, the detected output of the absolute angle output from the magnetic sensor unit 7 is half the actual angle. Therefore, by providing a correction calculation unit 10 shown in Fig. 7 and multiplying the sensor output by a correction coefficient "2", the actual absolute angle can be obtained.

[0033] [Third embodiment] 8 shows an angle detection device 4B in which the encoder magnetic body 1 is wound around part of the outer circumferential portion 5Ba of the rotor 5B, and a large gap exists between one longitudinal end and the other longitudinal end of the encoder unit 6B. Even if the diameter S of the encoder unit 6B is not L / π (S ≠ L / π), the actual absolute angle can be detected by performing a correction calculation for the sensor output using the correction calculation unit 10 shown in FIG.

[0034] For example, when detecting the absolute angle of a robot joint or the like, the required angle detection range is often less than one rotation (360°), which can result in a joint or gap in the magnetic material for the encoder. In such cases, if the joint or gap in the magnetic material for the encoder is positioned where angle detection is not required, the absolute angle can be detected while avoiding the influence of the joint or gap. The robot joint shown in FIG. 10 is required to be small and lightweight. After cutting the magnetic material for encoder 1 (FIG. 2) to the required length, rotating parts 11A, 11B, and 11C, such as the annular parts of existing robot joints, are used as rotating bodies, and the magnetic material for encoder 1 is wound directly around the outer periphery of each of rotating parts 11A, 11B, and 11C to form angle detection device 4B. This eliminates the need to attach a separate encoder, and enables the robot joint to be made small and lightweight.

[0035] As in the example of Figure 8, when the magnetic track is shorter than the outer periphery 5Ba of the rotating body 5B, there is no magnetic track facing the magnetic sensor unit 7, and to avoid a situation where the current position of the rotating body 5B cannot be detected, it is necessary to detect both ends of the magnetic track. Since the angle detection device 4B of this embodiment can detect the absolute angle simply by turning on the power, it is equipped with a limit angle memory unit 12 that stores the angle (limit angle) output from the magnetic sensor unit at both ends of the magnetic track, as shown in Figure 9. Furthermore, it is equipped with a detection range determination unit 13 that compares the contents of the limit angle memory unit 12 with the sensor output, determines whether the magnetic sensor unit is within the limit angle range, and outputs an identification signal.

[0036] 8 includes an encoder unit 6B in which an encoder magnetic body 1, whose main track and sub-track length L1 is equal to or less than the reference length L, is wound around and fixed to an outer circumferential portion 5Ba of a rotor 5B whose circumferential length is longer than length L1. In this case, the angle detection device 4B includes a limit angle memory unit 12 shown in FIG. 9 that stores limit angles corresponding to the output of the magnetic sensor unit 7 at both ends of the magnetic track, and a detection range determination unit 13 that determines whether the absolute angle output from the magnetic sensor unit 7 is within the limit angle range and outputs an identification signal indicating whether the angle has deviated from the limit angle.

[0037] With this configuration, if rotation is stopped when an identification signal indicating deviation from the limit angle is output, a normal sensor signal indicating the absolute angle is output, and operation to avoid the undetectable area can be performed using a normal control method. Also, if the limit angle storage unit 12 sets the limit angle with a margin of one to several magnetic pole pairs from both ends of the magnetic track, the reliability of operation can be increased.

[0038] A sheet-shaped magnetic material for an encoder may be wound around the inner periphery of a cylindrical rotating body and fixed thereto. In addition to robot joints, each angle detection device can be used in, for example, wheel bearings, steering devices, precision positioning devices, machine tools, industrial machinery, etc. Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0039] 1...Magnetic body for encoder, 2...Main track, 3...Sub-track, 4, 4A, 4B...Angle detection device, 5, 5A, 5B...Rotating body, 6, 6A, 6B...Encoder section, 7...Magnetic sensor section, 8...Magnetic detection element, 9...Calculation section, 10...Correction calculation section, 11A, 11B, 11C...Rotating part, 12...Limit angle storage section, 13...Detection range determination section

Claims

1. An angle detection device including an encoder unit having a magnetic track in which N poles and S poles are alternately arranged, and a magnetic sensor unit facing the magnetic track via a gap, The magnetic tracks are provided in such a manner that a main track having a magnetic pole width of P and a sub-track having a magnetic pole width of Pn / (n-1) are adjacent to each other and parallel to each other along the longitudinal direction of the sheet-like encoder magnetic material, where P is a reference magnetic pole width and n is the number of reference magnetic pole pairs; the encoder unit is formed by wrapping the sheet-like encoder magnetic material around the outer circumferential part or inner circumferential part of a rotating body at a length equal to or less than a reference length L=2Pn and fixing it thereto; the magnetic sensor unit includes two magnetic detection elements facing the main track and the sub-track, respectively, and outputting magnetic signals; and a calculation unit that calculates the absolute angle of the rotating body based on the magnetic signals of the magnetic detection elements, an angle detection device comprising a correction calculation unit that corrects the absolute angle of the rotating body by multiplying the calculated absolute angle by a correction coefficient according to the diameter of the encoder unit;

2. 2. The angle detection device according to claim 1, wherein when the encoder magnetic material having the reference length L is cut to an arbitrary length and the diameter of the encoder portion wound around the outer periphery or inner periphery of the rotating body is S, the correction calculation unit sets the value L / (πS), obtained by dividing the reference length L by the value obtained by multiplying the diameter S by the constant π, as the correction coefficient.

3. 3. The angle detection device according to claim 1, wherein the length L1 of the main track and the sub-track is equal to or less than the reference length L, and the encoder magnetic body is wound around and fixed to an outer circumferential portion or an inner circumferential portion of the rotating body having a circumferential length longer than the length L1, An angle detection device comprising: a limit angle memory unit that stores limit angles corresponding to the output of the magnetic sensor unit at both ends of the magnetic track; and a detection range determination unit that determines whether the absolute angle output from the magnetic sensor unit is within the limit angle range and outputs an identification signal indicating whether the limit angle has deviated.

4. 4. The angle detection device according to claim 1, wherein the rotating body is a rotating part of a robot joint.

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