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 for detecting the rotation angle of a rotating shaft or the like, and particularly to an angle detection device for detecting an angle in a range of 360° or less with high resolution in order to position a joint of a robot or the like at a target position. 【Background Art】 【0002】 Various magnetic encoder devices for detecting the rotation angle have been proposed. The magnetic encoder device disclosed in Patent Document 1 forms a cylindrical base portion from sintered metal, and performs sizing that presses the outer peripheral surface, inner peripheral surface, and both end surfaces of this base portion. Further, the base portion is inserted into a mold, and a resin material mainly composed of a thermoplastic resin and magnetic powder is injection-molded into the cavity. Thereafter, a plurality of magnetic poles arranged in the circumferential direction are provided in the molded portion, and two magnetic encoder tracks having different numbers of magnetic pole pairs are formed by multi-pole magnetization. 【0003】 The thus-produced magnetic encoder is fixed to a rotating body, and a magnetic sensor is provided in proximity to and facing the magnetic encoder track. The magnetic sensor includes two detection elements and an arithmetic unit that face each of the two magnetic encoder tracks, and calculates the absolute angle of the rotating body with high resolution based on the phase difference of the magnetic signals detected by the two detection elements, and outputs it as a sensor output. 【0004】 The magnetic encoder disclosed in Patent Document 2 includes a magnetic recording rotating body having a tape-shaped magnetic scale member with N poles and S poles alternately magnetized at equal pitches attached to its outer peripheral surface, and magnetic information detection means arranged in proximity to this magnetic recording rotating body. The magnetic information detection means includes two magnetic information detection elements arranged at intervals along the rotation direction of the magnetic recording rotating body. Magnetic information formed on the magnetic scale member is detected by the two magnetic information detection elements, and signals of A phase, B phase, and Z phase are generated from the detection outputs. Thereby, a highly accurate, highly reliable, and highly versatile magnetic encoder can be realized at a relatively low cost. 【Prior Art Documents】 [Patent Documents] 【0005】 [Patent Document 1] Japanese Patent Publication No. 2015-75466 [Patent Document 2] Japanese Patent Publication No. 2012-141259 [Overview of the project] [Problems that the invention aims to solve] 【0006】 In the technology disclosed in Patent Document 1, a plastic magnet is integrally molded onto a press-formed 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 dual-row magnetic encoder while meeting constraints such as available space and cost, it is necessary to use a mass-produced magnetic sensor that integrates all the necessary functions into a single package. 【0007】 Therefore, major specifications such as pole width and number of pole pairs are predetermined, and it is impossible to accommodate individual specifications. For example, once the pole width and number of pole pairs are determined, the diameter of the encoder section is determined by these specifications, making it impossible to manufacture it with an arbitrary diameter, thus limiting the design flexibility. In addition, since each molded part is magnetized individually, it is difficult to improve productivity. Furthermore, it is difficult to integrate the molded part with the rotating body, and it is necessary to attach the magnetized part as a separate component, which leads to an increase in the size and mass of the rotating body, which is also a problem. Furthermore, to manufacture a magnetic encoder device, a mold for the core metal and a plastic magnet are required. One challenge is that injection molding requires the manufacture of molds, which increases production costs. 【0008】 The tape-shaped magnetic scale used in the technology disclosed in Patent Document 2 is lightweight and does not require molding dies, and therefore can address the above-mentioned problems, but it does not demonstrate any improvement in resolution. Furthermore, although both ends of a magnetic scale member attached to a portion of the circumference can be detected by a Z-phase signal, an A-phase or B-phase signal is not output when the ends of the magnetic scale member are detected. For this reason, for example, when using the angle detection signal to control rotating equipment, there is a problem that conventional control methods cannot be used. 【0009】 The objective of the present invention is to solve the above problems and provide a high-resolution angle detection device based on the principle of a double-row magnetic encoder that offers a high degree of design flexibility, can be made smaller and lighter, and can reduce manufacturing costs. [Means for solving the problem] 【0010】 The angle detection devices 4, 4A, 4B of the present invention are angle detection devices comprising encoder units 6, 6A, 6B having magnetic tracks in which N poles and S poles are arranged alternately, and a magnetic sensor unit 7 facing the magnetic tracks with a gap δ between them, The magnetic track is arranged such that, when the reference pole width P and reference pole pair number n are given, a main track 2 with a pole width P and a sub-track 3 with a pole width Pn / (n-1) are provided adjacent to each other and parallel to each other along the longitudinal direction of the sheet-shaped encoder magnetic material 1, and the encoder sections 6, 6A, 6B are formed by winding and fixing the sheet-shaped encoder magnetic material 1 around the outer or inner circumference of the rotating bodies 5, 5A, 5B with a length of reference length L = 2Pn or less. The magnetic sensor unit 7 includes two magnetic detection elements 8 that output magnetic signals facing the main track 2 and the sub-track 3, respectively, and a calculation unit 9 that calculates the absolute angles of the rotating bodies 5, 5A, and 5B based on the magnetic signals from these magnetic detection elements 8. The system includes a correction calculation unit 10 that corrects the absolute angles of the rotating bodies 5, 5A, and 5B by multiplying the calculated absolute angles by a correction coefficient corresponding to the diameters of the encoder units 6, 6A, and 6B. 【0011】 With this configuration, a sheet-shaped encoder magnetic material 1 is wrapped around the outer or inner circumference of the rotating bodies 5, 5A, 5B and fixed, and used as the encoder sections 6, 6A, 6B of the angle detection devices 4, 4A, 4B. Therefore, even if the diameter of the encoder section changes, there is no need to manufacture a mold, and encoder sections 6, 6A, 6B of any diameter can be easily manufactured. The calculation unit 9 can calculate the absolute angle of the rotating bodies 5, 5A, 5B with high resolution based on the magnetic signals of 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 sections 6, 6A, 6B, so that even if the diameter of the encoder section is not L / π, the absolute angle of the rotating bodies 5, 5A, 5B having a circumference length L can be accurately detected with high resolution. Furthermore, if existing rotating parts 11A, 11B, 11C are used as the rotating bodies, there is no need to add a separate encoder component, which simplifies the structure of the angle detection device and makes it smaller and lighter. 【0012】 When the encoder magnetic material 1 of the reference length L is cut to any length, and the diameter of the encoder parts 6, 6A, 6B wound around the outer or inner circumference of the rotating bodies 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 pi, as the correction coefficient. If the diameter S of the encoder units 6, 6A, and 6B is not equal to L / π, the sensor output from the magnetic sensor unit 7 will differ from the actual angle. However, the correct angle can be obtained by multiplying the sensor output by L / (πS) as a correction factor. 【0013】 The encoder magnetic body 1, in which the lengths L1 of the main track 2 and the sub-track 3 are less than or equal to the reference length L, has a circumference longer than the length L1 of the outer circumference of the rotating bodies 5, 5A, and 5B. The encoder parts 6, 6A, and 6B are wound around and fixed to the part or inner circumference, The magnetic track may also include a limit angle storage 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 range of the limit angle and outputs an identification signal indicating whether or not it has deviated from the limit angle. 【0014】 With this configuration, if rotation is stopped when an identification signal indicating a deviation from the limit angle is output, a normal sensor signal indicating the absolute angle will be output, allowing the system to avoid the undetectable region using normal control methods. 【0015】 The rotating bodies 5, 5A, and 5B may also be the rotating parts 11A, 11B, and 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 such cases, if the joint of the encoder magnetic material 1 is placed in a position where angle detection is unnecessary, the influence of the joint can be avoided, and the angle detection device can be established. Furthermore, if the existing robot joint rotating parts 11A, 11B, and 11C are used as rotating bodies, and the encoder magnetic material 1 is wrapped around and fixed directly to the rotating parts 11A, 11B, and 11C, there is no need to attach a separate encoder, making it possible to miniaturize and lighten the robot joint. [Effects of the Invention] 【0016】 The angle detection device of the present invention is 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 with a gap therebetween. When the magnetic track has a reference magnetic pole width P and a reference number of magnetic pole pairs n, along the longitudinal direction of the sheet-shaped magnetic body for the encoder, a main track with a magnetic pole width of P and a sub-track with a magnetic pole width of Pn / (n - 1) are provided adjacent to each other and parallel to each other. The encoder unit has the sheet-shaped magnetic body for the encoder wound around and fixed to the outer peripheral portion or the inner peripheral portion of the rotating body with a length of a reference length L = 2Pn or less. The magnetic sensor unit includes two magnetic detection elements that face the main track and the sub-track respectively and output magnetic signals, and a calculation unit that calculates the absolute angle of the rotating body based on the magnetic signals of these magnetic detection elements. The angle detection device further includes a correction calculation unit that 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. Therefore, a high-resolution angle detection device based on the principle of a multi-row magnetic encoder can be obtained, which has a high degree of design freedom, can be miniaturized and lightened, and can reduce the manufacturing cost. 【Brief Description of the Drawings】 【0017】 [Figure 1] It is a diagram showing a configuration example of an angle detection device according to the first embodiment of the present invention. [Figure 2] It is a perspective view showing the structure of the magnetic body for the encoder of the angle detection device. [Figure 3] It is a side view of the angle detection device. [Figure 4A] It is a block diagram of the control system of the angle detection device. [Figure 4B] It is a block diagram in which a part of the control system in FIG. 4A is partially modified. [Figure 5] It is a diagram showing the phase of the detection signal of the magnetic sensor unit of the angle detection device and the phase difference between the two detection signals. [Figure 6] It is a diagram showing a configuration example of an angle detection device when the diameter of the encoder unit is different from L / π. [Figure 7] It is a block diagram of the correction calculation unit of the angle detection device. [Figure 8] This figure shows an example configuration of an angle detection device in which there is a gap at the joint of the encoder section. [Figure 9] This is a block diagram of the control system for the same angle detection device. [Figure 10] This figure shows an example of applying one of the angle detection devices to a robot joint. [Modes for carrying out the invention] 【0018】 [First Embodiment] An angle detection device according to an embodiment of the present invention will be described with reference to Figures 1 to 5. As shown in Figures 1 and 3, the angle detection device 4 comprises 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 Figure 2, the encoder unit 6 has a magnetic track in which north poles and south poles are arranged alternately. The magnetic track consists of a main track 2 with a magnetic pole width (circumferential width) of P and a sub-track 3 with a magnetic pole width of Pn / (n-1), arranged adjacent to each other and parallel to each other along the longitudinal direction of the sheet-shaped encoder magnetic material 1, where the reference magnetic pole width is P and the reference magnetic pole pair is n. As shown in Figure 1, the encoder unit 6 is fixed by winding the sheet-shaped encoder magnetic material 1 around the cylindrical outer circumference 5a of the rotating body 5 to a length of L or less. 【0019】 The encoder magnetic material 1 shown in Figure 2 is manufactured, for example, by vulcanizing a rubber material mixed with magnetic powder into a sheet, cutting it to the required length, and then alternately magnetizing the north and south poles in the longitudinal direction with a predetermined magnetic pole width determined by the reference magnetic pole width P and the reference magnetic pole logarithm n, thereby forming 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 production equipment or material availability may be cut to the required length according to the application. The reference length is L = 2Pn. 【0020】 For example, when the reference pole width P is 2 mm and the reference number of pole pairs n is 32 pole pairs, the magnetization width (magnetization pitch) p2 (=P) of the main track 2 is 2 mm, and the magnetization 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 pole pairs (number of pole pairs) n2 (=n) of the main track 2 is set to 32 pole pairs (64 poles in total, including N and S poles), and the number of pole pairs (=n-1) of the sub-track 3 is set to 31 pole pairs (62 poles in total, including N and S poles). The length of the magnetic track in this case is the reference length L, and L = 2Pn = 128 mm. 【0021】 Here, the main track 2 of the encoder magnetic material 1 is set to have a magnetization width of 2 mm and 32 pole pairs, and the sub-track 3 is set to have a magnetization width of 2.0645 mm and 31 pole pairs. However, the specifications of the magnetic poles of the encoder magnetic material can be appropriately selected depending on the magnetic sensor used. 【0022】 The angle detection device 4 shown in Figure 1 comprises an encoder unit 6, in which an encoder magnetic material 1 is fixed to the outer circumference 5a of a rotating body 5 by adhesive or double-sided tape, 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. By "integrated," it means that the rotating shaft and the rotating body 5 are not formed by combining multiple elements, but rather are formed from a single material, for example, by forging, machining, etc., as part of or as a whole of a single object. 【0023】 As shown in Figure 4(A), the magnetic sensor unit 7 includes two magnetic detection elements 8 that output magnetic signals facing the main track 2 and sub-track 3 from the radially outer side of the rotating body 5, respectively, and a calculation unit 9 that calculates the absolute angle of the rotating body 5 with high resolution based on the phase difference of the magnetic signals detected by these magnetic detection elements 8 and outputs it as a sensor output. 【0024】 As shown in Figure 2, when an encoder magnetic body 1 of length L, which has a magnetic track of reference length L along its entire length, is wound once around the outer circumference 5a of the rotating body 5 as shown in Figure 1 to produce an encoder section 6 with a diameter of L / π, the calculation unit 9 can detect the absolute angle with standard accuracy by utilizing 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)) equals one pole pair per rotation, as shown in Figures 4(A) and 5. 【0025】 Furthermore, if the encoder magnetic material 1, which has a magnetic track of standard length L as shown in Figure 2, is cut so that the length of the magnetic track is shorter than the standard length L, and wound around the rotating body 5 shown in Figure 1, In addition, even if there is a gap (circumferential gap) at the joint T between one end and the other end of the encoder section 6 in the longitudinal direction, if the diameter of the encoder section 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 material 1 is fixed. 【0026】 Figure 5(A) shows the waveform of the detection signal corresponding to the main track 2, and Figure 5(B) shows the waveform of the detection signal corresponding to the sub-track 3. Figure 5(C) shows the waveform of the output signal of the phase difference calculated by the calculation unit 9 (Figure 4A) based on the detection signals in Figures 5(A) and (B). The calculation unit 9 (Figure 4A) performs a process to convert the calculated phase difference into an absolute angle according to preset calculation parameters. These calculation parameters are stored, for example, in a storage means Mr such as a non-volatile memory provided in the magnetic sensor unit 7 shown in Figure 4(A). In addition to the calculation parameters, this storage means Mr also stores rewritable information necessary for the operation of the device, such as the reference magnetic pole width P of the magnetic track, the reference number of magnetic pole pairs n, the number of magnetized pole pairs of each track 2 and 3, and the signal output method. 【0027】 This angle detection device 4 includes a correction calculation unit 10 after the calculation unit 9. The correction calculation unit 10 corrects the absolute angle of the rotating body 5 by multiplying the absolute angle output from the calculation unit 9 by a correction coefficient corresponding to the diameter of the encoder unit 6. When a magnetic material 1 for an encoder with a standard length L is cut to an arbitrary length, and the diameter of the encoder part 6 wound around the outer circumference 5a (Figure 1) of the rotating body 5 is S, the correction calculation unit 10 uses the value L / (πS), obtained by dividing the standard length L by the value obtained by multiplying the diameter S by pi, 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, but the correct angle can be obtained by multiplying the sensor output by a correction coefficient. As described above, if the diameter of the encoder unit 6 is S, then the absolute angle output from the calculation unit 9 should 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 a correction calculation according to the calculation function using the stored correction coefficient. In this example, the correction calculation unit 10 is provided after the calculation unit 9 within the magnetic sensor unit 7, but the correction calculation unit 10 may also be provided within the calculation unit 9. Furthermore, as shown in Figure 4(B), the correction calculation unit 10 may be provided as a dedicated circuit near the magnetic sensor unit 7, and although not shown, the correction calculation unit may also be included in a higher-level control unit. 【0029】 <Effects and Effects> As described above, the angle detection device 4 uses a sheet-shaped encoder magnetic material 1 shown in Figure 1, which is wrapped around the outer circumference 5a of the rotating body 5 and fixed to serve as the encoder part 6 of the angle detection device 4. Therefore, even if the diameter of the encoder part 6 changes, there is no need to manufacture a mold, and an encoder part 6 of any diameter can be easily manufactured. The calculation unit 9 can calculate the absolute angle of the rotating body 5 with high resolution based on the magnetic signals of 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 part 6, so that the absolute angle of the rotating body 5 can be accurately detected with high resolution even if the diameter of the encoder part 6 is not L / π. Furthermore, if an existing rotating part is used as the rotating body 5, there is no need to add an encoder made of a separate component, which simplifies the structure of the angle detection device 4 and makes it smaller and lighter. 【0030】 <Regarding other embodiments> In the following description, parts corresponding to matters previously described in each embodiment will be denoted by the same reference numerals, and redundant explanations will be omitted. When only a part of the configuration is described, the other parts of the configuration will be the same as those described previously unless otherwise specified. The same configuration will produce the same effects. Not only are combinations of the parts specifically described in each embodiment possible, but it is also possible to partially combine embodiments, provided that there are no particular problems with the combination. 【0031】 [Second Embodiment] Figure 6 shows an example configuration of the angle detection device 4A when the diameter of the encoder section is different from L / π. Figure 7 is a block diagram of the correction calculation unit 10 of the same angle detection device. If the diameter of the encoder section, which is formed by winding a magnetic material of standard length L around a rotating body, differs from L / π, the sensor output from the magnetic sensor section will differ from the actual angle. In this case, by providing a correction calculation unit 10 in the angle detection device 4A and multiplying the sensor output by a correction coefficient, an accurate absolute angle can be obtained. 【0032】 Figure 6 shows an angle detection device 4A in which an encoder magnetic material 1 of length L, which has a magnetic track of standard length L along its entire length, is cut to a length L / 2 and wound around the outer circumference 5Aa of a rotating body 5A once in the circumferential direction, forming an encoder section 6A capable of detecting an absolute angle of 360° with a diameter of L / (2π). Since the outer circumference of the encoder unit 6A is half the reference length L, the absolute angle detection output from the magnetic sensor unit 7 is half the actual angle. Therefore, by providing the correction calculation unit 10 shown in Figure 7 and multiplying the sensor output by a correction coefficient of "2", the actual absolute angle can be obtained. 【0033】 [Third Embodiment] Figure 8 shows an angle detection device 4B in which the encoder magnetic material 1 is wound around a portion of the outer circumference 5Ba of the rotating body 5B, and a large gap exists between one end and the other end in the longitudinal direction of the encoder section 6B. Even when the diameter S of the encoder section 6B is not L / π (S ≠ L / π), the actual absolute angle can be detected by performing a correction calculation of the sensor output using the correction calculation unit 10 shown in Figure 7. 【0034】 For example, when detecting the absolute angle of a robot joint, the required angle detection range is often less than one rotation (360°), and seams or gaps may occur in the magnetic material used for the encoder. In such cases, by placing the seams or gaps in the magnetic material in a location where angle detection is not required, it is possible to detect the absolute angle while avoiding the influence of the seams or gaps. The robot joint shown in Figure 10 is required to be small and lightweight. However, by cutting the encoder magnetic material 1 (Figure 2) to the required length, and using rotating parts 11A, 11B, and 11C, similar to the annular parts of existing robot joints, as the rotating body, and directly wrapping the encoder magnetic material 1 around the outer circumference of each rotating part 11A, 11B, and 11C to form an angle detection device 4B, it becomes unnecessary to attach a separate encoder, thus enabling miniaturization and weight reduction of the robot joint. 【0035】 As shown in the example in Figure 8, if the magnetic track is shorter than the outer circumference 5Ba of the rotating body 5B, there is no magnetic track at a position opposite the magnetic sensor unit 7. 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. The angle detection device 4B of this embodiment can detect the absolute angle simply by turning on the power, so as shown in Figure 9, it is equipped with a limit angle storage unit 12 that stores the angle (limit angle) output from the magnetic sensor unit at both ends of the magnetic track. Furthermore, a detection range determination unit 13 is provided that compares the contents of the limit angle storage unit 12 with the sensor output to determine whether the magnetic sensor unit is within the limit angle range and outputs an identification signal. 【0036】 In other words, the angle detection device 4B in Figure 8 includes an encoder unit 6B in which an encoder magnetic body 1, whose main track and sub-track lengths L1 are less than or equal to the reference length L, is wound and fixed around the outer circumference 5Ba of a rotating body 5B with a circumference longer than length L1. In this case, the angle detection device 4B includes a limit angle storage unit 12 in Figure 9 that stores the 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 or not it has deviated from the limit angle. 【0037】 With this configuration, if rotation is stopped when an identification signal indicating a deviation from the limit angle is output, the normal sensor signal indicating the absolute angle is output, allowing the system to avoid the undetectable region using normal control methods. Furthermore, by setting the limit angle in the limit angle storage unit 12 with a margin of 1 to several magnetic pole pairs from both ends of the magnetic track, the reliability of the operation can be increased. 【0038】 A sheet-shaped magnetic material for the encoder may be wrapped around the inner circumference of a cylindrical rotating body and fixed in place. Each angle detection device can be used not only in robot joints, but also in applications such as wheel bearings, steering systems, precision positioning devices, machine tools, and industrial machinery. While embodiments for carrying out the present invention have been described above, the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols] 【0039】 1…Magnetic material 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 unit, 10…Correction calculation unit, 11A,11B,11C…Rotating parts, 12…Limit angle storage unit, 13…Detection range determination unit

Claims

[Claim 1] An angle detection device comprising an encoder unit having a magnetic track in which north poles and south poles are arranged alternately, and a magnetic sensor unit facing the magnetic track with a gap in between, The magnetic track is provided parallel to each other and adjacent to a main track, whose magnetic pole width is the reference magnetic pole width, and a sub-track, whose magnetic pole width is different from that of the main track, along the longitudinal direction of the sheet-shaped encoder magnetic material. The magnetic sensor unit comprises two magnetic detection elements that output magnetic signals facing the main track and the sub-track, respectively, and a calculation unit that calculates the absolute angle of the rotating body based on the magnetic signals from these magnetic detection elements. An angle detection device comprising a correction calculation unit that corrects the absolute angle of a rotating body by multiplying the calculated absolute angle by a correction coefficient corresponding to the diameter of the encoder part, which is fixed to the outer or inner circumference of the rotating body by winding the sheet-like encoder magnetic material around it.