Magnetization device for magnetic encoder, magnetization method, and magnetic encoder

Abstract

Provided are: a magnetization device for a magnetic encoder with which the structure of a magnetization yoke can be simplified and a magnetic encoder having a double-row magnetic track can be magnetized with high accuracy; a magnetization method; and a magnetic encoder. A magnetization device of a magnetic encoder (1) magnetizes a double row of adjacent non-magnetized magnetic tracks (4) by using a magnetization yoke (11) which opposes the magnetic tracks with a gap δ therebetween. A distal end portion (18) of the magnetization yoke (11) is offset in the Z direction, which is the direction in which the rows of the double-row magnetic tracks (4) are aligned, with respect to a boundary portion (BL) of the adjacent magnetic tracks (4), and the distal end portion (18) of the magnetization yoke (11) is relatively moved in a circumferential direction with respect to the magnetic tracks (4) opposing the magnetization yoke (11), and the magnetic tracks (4) are thus magnetized in each row.

Description

Magnetizing device and method for magnetic encoder, and magnetic encoder Related Applications

[0001] This application claims priority from Japanese Patent Application No. 2024-109820, filed July 8, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a magnetizing device, a magnetizing method, and a magnetic encoder for a magnetic encoder, and relates to a technique applied to a magnetic encoder used for controlling the rotation of various motors, for example.

[0003] Among conventional magnetic encoders (magnetic rings), a multi-track magnetic encoder in which magnetic tracks are arranged adjacent to each other is known, and each track of the magnetic encoder is individually magnetized.

[0004] For example, Patent Document 1 proposes using a magnetic shield to block the flow of leakage magnetic flux to tracks other than those to be magnetized. Patent Document 2 proposes a method of magnetizing in which the tip of a magnetizing yoke, which has a pair of closely opposing tip portions, is brought close to the surface of a magnetic member to be magnetized, and one end face position in the width direction of the tip portion is aligned with the boundary portion of a double row of tracks.

[0005] Japanese Patent No. 5973278 Japanese Patent Application Laid-Open No. 2023-9789

[0006] In Patent Document 1, a magnetic shield member that magnetically shields the tracks that are not to be magnetized is mounted on the magnetizing yoke, which makes the structure of the magnetizing yoke complex. Also, when adjusting the gap between the surface of the track to be magnetized and the tip of the magnetizing yoke, the magnetic shield member gets in the way, making it difficult to see the tip and making the gap adjustment difficult.

[0007] In Patent Document 2, the end faces of the magnetizing yoke are aligned with the boundary between the multiple track rows to magnetize the magnet, which causes leakage flux to leak to the adjacent track. In particular, if the gap between the pair of tip ends of the magnetizing yoke is large, the leakage flux from each tip end increases. If the leakage flux reaches the detection area of ​​the angle sensor, it is expected that the magnetization accuracy will decrease.

[0008] An object of the present invention is to provide a magnetizing device, a magnetizing method, and a magnetic encoder that simplify the structure of the magnetizing yoke and can magnetize a magnetic encoder having multiple magnetic tracks with high precision.

[0009] The magnetizing device for a magnetic encoder of the present invention is a magnetizing device for a magnetic encoder that magnetizes multiple rows of adjacent unmagnetized magnetic tracks using a magnetizing yoke that faces the boundary between the adjacent magnetic tracks, and magnetizes the magnetic tracks row by row by offsetting the tip of the magnetizing yoke in the direction in which the rows of the adjacent unmagnetized magnetic tracks are arranged relative to the boundary between the adjacent magnetic tracks, and moving the tip of the magnetizing yoke circumferentially relative to the magnetic track that faces the magnetizing yoke.

[0010] With this configuration, the tip of the magnetizing yoke is offset in the direction of the rows to magnetize the magnetic tracks for each row. In this case, the tip of the magnetizing yoke can be separated from the other magnetic tracks that are not magnetized. This reduces the extent to which leakage magnetic flux leaking from the tip of the magnetizing yoke crosses the boundary and penetrates into adjacent magnetic tracks. Therefore, even if a simple magnetizing yoke without a magnetic shield or the like is used, a magnetic encoder with multiple magnetic tracks can be magnetized with high precision.

[0011] The magnetic encoder has a detection section facing the sensing surface of an angle sensor that detects the absolute angle, and the distance between the detection section and the boundary is preferably greater than the offset of the magnetizing yoke. In this case, leakage magnetic flux leaking from the tip of the magnetizing yoke can be prevented from crossing the boundary and reaching the detection section of the adjacent magnetic track. This prevents a decrease in magnetization accuracy.

[0012] The magnetic tracks may be magnetized so that the tip of the magnetizing yoke passes over the detection portion, thereby enabling a magnetic encoder having multiple magnetic tracks to be magnetized with higher accuracy.

[0013] The magnetization method of the magnetic encoder of the present invention is a magnetization method of a magnetic encoder that magnetizes multiple rows of adjacent unmagnetized magnetic tracks using a magnetizing yoke that faces the boundary between the adjacent magnetic tracks, and magnetizes the magnetic tracks row by row by offsetting the tip of the magnetizing yoke in the direction in which the rows of the adjacent unmagnetized magnetic tracks are arranged relative to the boundary between the adjacent magnetic tracks, and moving the tip of the magnetizing yoke circumferentially relative to the magnetic track that faces the magnetizing yoke.

[0014] In this case, by offsetting the tip of the magnetizing yoke in the direction of the rows and magnetizing the magnetic tracks for each row, the tip of the magnetizing yoke can be separated from the other magnetic tracks that are not magnetized. This reduces the extent to which leakage magnetic flux from the tip of the magnetizing yoke crosses the boundary and penetrates into adjacent magnetic tracks. This simplifies the structure of the magnetizing yoke and enables highly accurate magnetization of a magnetic encoder with multiple magnetic tracks.

[0015] The magnetic encoder of the present invention is magnetized using the magnetization method for a magnetic encoder described above. In this case, the magnetic encoder can be magnetized with high precision while simplifying the structure of the magnetizing yoke. This reduces the manufacturing cost of the magnetic encoder and also expands the range of motors and other devices to which the magnetic encoder can be applied.

[0016] Any combination of at least two features disclosed in the claims and / or the specification and / or the drawings is included in the present invention. In particular, any combination of two or more of the claims is included in the present invention.

[0017] The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are merely for illustration and explanation, and should not be used to define the scope of the present invention, which is defined by the appended claims. In the accompanying drawings, the same reference numerals in multiple drawings indicate the same or corresponding parts.

[0018] FIG. 1 is a longitudinal sectional view of a magnetic encoder according to a first embodiment of the present invention. FIG. 2 is a diagram showing the configuration of a magnetizing device for the magnetic encoder. FIG. 3 is a plan view of a main part showing the arrangement of a tip of a magnetizing yoke and a magnetic encoder in the magnetizing device. FIG. 4 is a longitudinal sectional view of a main part showing the process of magnetizing a sub-track of the magnetic encoder. FIG. 5 is a longitudinal sectional view of a main part showing the process of magnetizing a main track of the magnetic encoder. FIG. 6 is a schematic view for explaining a magnetizing method for magnetizing the sub-track. FIG. 7 is a schematic view for explaining a magnetizing method for magnetizing the main track. FIG. 8 is a diagram showing the arrangement of a magnetic track that has been magnetized in double rows and an angle sensor capable of detecting an absolute angle. FIG. 9 is a longitudinal sectional view of a main part showing the process of magnetizing a sub-track of a magnetic encoder according to a second embodiment of the present invention. FIG. 10 is a longitudinal sectional view of a main part showing the process of magnetizing a main track of the magnetic encoder.

[0019] [First Embodiment] A magnetizing device according to an embodiment of the present invention will be described with reference to Figures 1 to 5. This magnetizing device is applied to, for example, a magnetic encoder used to detect rotation and rotation angle of various devices. The following description also includes an explanation of the magnetic encoder and a magnetizing method for the magnetic encoder.

[0020] 1, in a magnetic encoder 1, a rubber material kneaded with magnetic powder is placed in a mold together with the core 2, which is made of a cylindrical metal ring, and bonded to the outer circumferential surface of the core 2 by vulcanization, or a mixture of plastic material and magnetic powder is integrally molded with the core 2 to form a radial-type magnetic member 3. Then, a magnetizing device 7 (FIG. 2), which will be described later, is used to manufacture the annular magnetic encoder 1, on the surface of the unmagnetized magnetic member 3, on which multiple magnetic tracks 4 with different numbers of magnetized pole pairs are formed.

[0021] The magnetic track 4 of the magnetic encoder 1 includes two rows of tracks: a main track 5 and a sub-track 6. A boundary BL between the main track 5 and the sub-track 6 is set based on the dimensions of the magnetic encoder 1. For example, in the example of FIG. 1 , the boundary BL is set at approximately the center of the width of the magnetic member 3.

[0022] The number of magnetized pole pairs differs by one between the main track 5 and the sub-track 6. For example, the number of magnetized pole pairs in the main track 5 and the sub-track 6 is 32 and 31, respectively. The main track 5 of the magnetic encoder 1 serves as the reference for angle calculation. The sub-track 6 is used to calculate the phase difference with the main track 5. The magnetic encoder 1 can detect the absolute angle by utilizing the fact that a difference of one pole pair occurs per rotation.

[0023] In order to detect the absolute angle with high accuracy by combining the magnetic encoder 1 and the angle sensor, it is necessary to improve the magnetization accuracy of the magnetic track 4 including the main track 5 and the sub-track 6. In particular, to improve the accuracy of magnetization of the main track 5, it is preferable to magnetize the sub-track 6 first and then magnetize the main track 5 last.

[0024] 2 , the magnetizing device 7 of the magnetic encoder 1 is an index magnetizing device that magnetizes N poles and S poles alternately one by one. The magnetizing device 7 magnetizes adjacent unmagnetized magnetic tracks in multiple rows using magnetizing yokes 11 that face each other with a gap δ ( FIG. 3B ) between them. The magnetizing device 7 includes a spindle 9, a motor 10, the magnetizing yoke 11, first and second positioning means 12 and 17, a magnetic sensor 16, a magnetizing power supply 13, and a control means 14.

[0025] The spindle 9 rotates a chuck 8 that holds the unmagnetized magnetic encoder 1 to be magnetized. The spindle 9 is supported so that its rotation axis is concentric with the rotation axis C1 of the magnetic encoder 1. The motor 10 is a rotation drive source that rotates the spindle 9. The motor 10 has a high-precision encoder device 15, which is a detection device that detects the rotation angle.

[0026] The first positioning means 12 positions the magnetizing yoke 11 in three axial directions. The three axial directions are the X, Y, and Z directions, which are orthogonal to one another. Specifically, the direction parallel to the rotation axis C1 is the Z direction, the X direction is orthogonal to the Z direction and is the direction in which the tip 18 of the magnetizing yoke 11 protrudes, and the Y direction is orthogonal to both the X and Z directions.

[0027] The magnetic sensor 16 is a magnetic sensor for measuring the magnetization accuracy when magnetization of the magnetic encoder 1 held by the chuck 8 is completed. The second positioning means 17 supports the magnetic sensor 16 so that it can be positioned in three axial directions, that is, the X, Y, and Z directions. In other words, the magnetic sensor 16 is fixed to the second positioning means 17, which can be positioned in three axial directions. The motor 10, the spindle 9, and the first positioning means 12 constitute a positioning device 22. The positioning device 22 positions the tip end 18 of the magnetizing yoke 11 relative to the unmagnetized magnetic encoder 1.

[0028] The magnetizing power supply 13 supplies a magnetizing current to the excitation coil 21 of the magnetizing yoke 11. The control means 14 is composed of a computer or the like, and controls the first positioning means 12, motor 10, and magnetizing power supply 13 shown in Fig. 2 so that the unmagnetized magnetic encoder 1 is magnetized sequentially for each of the magnetic tracks 4 (main track 5, sub-track 6) shown in Fig. 1. As for the order of magnetization, for example, the main track 5 (Fig. 1) is magnetized after the sub-track 6 (Fig. 1). The control means 14 also controls the first positioning means 12, motor 10, and magnetizing power supply 13 of the positioning device 22 by numerical control or the like so that the N and S magnetic poles are arranged alternately.

[0029] <Magnetic Yoke> The magnetic yoke 11 has a pair of tip portions 18, 19 that magnetically face each other across a magnetic gap, and magnetizes the magnetic track 4 ( FIG. 1 ) of the unmagnetized magnetic encoder 1 that is disposed at a predetermined position and posture relative to these tip portions 18, 19. Specifically, the magnetic yoke 11 has a U-shaped magnetic yoke body 20, an exciting coil 21, and first and second tip portions 18, 19 provided at one end and the other end of the magnetic yoke body 20, respectively. The exciting coil 21 is wound around the outer periphery of the magnetic yoke body 20 and is electrically connected to the magnetizing power supply 13.

[0030] The magnetizing yoke 11 allows the magnetic flux for magnetization to pass through the magnetic encoder 1, and as shown in Fig. 3A, the first tip portion 18 of the magnetizing yoke 11 has a pointed structure. That is, in a plan view of the magnetizing yoke 11, the first tip portion 18 is formed in a tapered shape that narrows toward the tip. As shown in Fig. 3B, one end 18a of the first tip portion 18 in the Z direction is formed parallel to the XY plane, and the other end 18b in the Z direction is also formed parallel to the XY plane.

[0031] During magnetization, the first tip 18 is opposed to the surface of the magnetic encoder 1. As shown in Fig. 2, the second tip 19 is opposed to the outer peripheral surface of the chuck 8 with a gap therebetween. Therefore, during magnetization, a magnetic loop is formed that extends from the first tip 18 through the magnetic encoder 1 and chuck 8 to the second tip 19. The second tip 19 may be omitted. Note that, since residual magnetism remaining in the magnetic member 3 (Fig. 1) of the magnetic encoder 1 affects the magnetization accuracy, it is preferable to demagnetize the magnetic encoder 1 before the magnetization process.

[0032] <Method of Magnetizing a Magnetic Encoder> Figures 3A to 3C show the arrangement of the tip 18 of the magnetizing yoke 11, which is a main part of the magnetizing device, and the magnetic encoder 1. Figure 3A shows a state in which the tip 18 of the magnetizing yoke 11 faces the magnetic track 4 of the magnetic encoder 1 with a gap δ therebetween. In this state, while the magnetic encoder 1 is rotated around the rotation axis C1, either the main track 5 or the sub-track 6 is magnetized pole by pole, as shown in Figures 3B and 3C. In order to improve the magnetization accuracy of the main track 5, it is preferable to magnetize the sub-track 6 first and then the main track 5 last.

[0033] 3B shows the process of magnetizing the sub-track 6, with the tip 18 of the magnetizing yoke 11 facing the sub-track 6 in the X direction with a certain gap δ between them. The gap δ is, for example, about 0.1 mm to 0.3 mm, with 0.1 mm being more preferable. This is because the smaller the gap δ, the less leakage magnetic flux there is and the greater the magnetization strength. Note that if the deflection of the magnetic encoder 1 is small, the gap δ may be 0 (the tip 18 and the sub-track 6 are in contact).

[0034] In particular, in this magnetizing device and magnetizing method, the tip 18 of the magnetizing yoke 11 is offset in the arrangement direction of the rows of the multiple rows of magnetic tracks 4 (in this example, the Z direction) with respect to the boundary BL between adjacent magnetic tracks 4. In addition, the tip 18 of the magnetizing yoke 11 is moved circumferentially relative to the magnetic track 4 facing the magnetizing yoke 11, thereby magnetizing the magnetic track 4 row by row.

[0035] Specifically, one end 18a of the tip 18 of the magnetizing yoke 11 in the Z direction is offset from the boundary BL toward the sub-track 6 by an offset amount αn. The other end 18b of the tip 18 in the Z direction is positioned to protrude beyond the width of the sub-track 6. In this state, the sub-track 6 is magnetized one pole at a time while the magnetic encoder 1 is rotated about its rotation axis C1. After the sub-track 6 is magnetized, the magnetizing yoke 11 is positioned as shown in FIG. 3C by the first positioning means 12 shown in FIG. 2.

[0036] 3C shows the process of magnetizing the main track 5, in which the tip 18 of the magnetizing yoke 11 faces the main track 5 in the X direction with a certain gap δ therebetween. The gap δ is the same as the gap δ with respect to the sub-track 6 shown in FIG. 3B.

[0037] 3C , in the process of magnetizing the main track 5, the other end 18b in the Z direction of the tip 18 of the magnetizing yoke 11 is offset from the boundary BL toward the main track 5 by an offset amount αm. One end 18a of the tip 18 in the Z direction is positioned to protrude beyond the width of the main track 5. In this state, the main track 5 is magnetized one pole at a time while the magnetic encoder 1 is rotated around its rotation axis C1.

[0038] One end 18a in the Z direction (or the other end 18b in the Z direction) of the tip portion 18 is offset in the Z direction from the boundary portion BL to be magnetized, thereby reducing the range of leakage magnetic flux leaking from the tip portion 18 beyond the boundary portion BL and penetrating into adjacent magnetic tracks.

[0039] The offset amounts αm and αn shown in Figures 3B and 3C are set by testing and / or simulation so as not to affect the detection units Sm and Sn (Figure 5) that face the sensing surface of the angle sensor, which will be described later. For example, as shown in Figure 5, if the distance βm (βn) in the Z direction from the boundary portion BL to the detection unit Sm (Sn) is 1.8 mm, the offset amount αm (αn) is set to approximately 0.3 mm to 1.5 mm. The offset amounts αm and αn are set to be approximately the same. Details of this will be explained using Figures 4A to 5.

[0040] 4A and 4B are plan views showing the arrangement of the tip portion 18 of the magnetizing yoke and the magnetic encoder 1 shown in FIGS. 3B and 3C . In the magnetizing process, the sub-track 6 is magnetized first, as shown in FIG. 4A , and then the main track 5 is magnetized last. FIG. 4A shows the process of magnetizing the sub-track 6 and corresponds to FIG. 3B . As shown in FIG. 4A , one end 18a of the tip portion 18 of the magnetizing yoke 11 on the Z direction is offset so as to coincide with an offset portion Ln set on the Z direction sub-track 6 side from the boundary portion BL. This offset amount is αn.

[0041] As shown in Fig. 5, a detection portion Sn is set on the magnetized sub-track 6 so as to face the sensing surface (i.e., the magnetic sensing surface 23n) of the angle sensor 23 that detects the absolute angle. As shown in Fig. 4A, the distance βn in the Z direction between the detection portion Sn and the boundary portion BL is greater than the offset amount αn of the magnetizing yoke 11 (αn < βn). For example, the offset amount αn is set to 0.3 mm to 1.5 mm, and the distance βn is set to 1.8 mm.

[0042] The tip 18 of the magnetizing yoke 11 magnetizes the sub-track 6 of the magnetic track 4 so as to pass over the detection portion Sn. Specifically, the tip 18 of the magnetizing yoke 11 intersects (overlaps) with the detection portion Sn and passes over the detection portion Sn during magnetization. The other end 18b of the tip 18 in the Z direction is positioned to protrude beyond the width of the sub-track 6. The width of the tip 18 (the distance in the Z direction from one end 18a to the other end 18b) is greater than the width of the sub-track 6.

[0043] In this state, the magnetic encoder 1 is rotated in the direction of arrow R, and magnetization is performed one pole at a time to magnetize the sub-track 6. Leakage magnetic flux 24 is generated from one end 18a of the tip portion 18 in the Z direction, leaking toward the adjacent main track 5. Here, the area of ​​the leakage magnetic flux 24 is simply shown as a square, and this area is indicated by hatching.

[0044] At this stage, the main track 5 is not yet magnetized, but if residual magnetism remains in the main track 5 due to leakage magnetic flux 24 generated during the magnetization process of the sub-track 6, it is expected that this will affect the magnetization accuracy of the main track 5. For this reason, it is preferable to prevent residual magnetism from remaining in the vicinity of the detection portion Sm. It is preferable to prevent the leakage magnetic flux 24 from reaching the detection portion Sm of the adjacent main track 5, and more preferably to prevent it from exceeding the offset portion Lm of the main track 5.

[0045] Therefore, one end 18a in the Z direction of the tip 18 of the magnetizing yoke 11 is offset to match the offset portion Ln set on the side away from the boundary portion BL in the Z direction. Because the end 18a is positioned away from the main track 5 that is not magnetized, leakage magnetic flux 24 leaking from the end 18a can be prevented from reaching the detection portion Sm of the main track 5. This prevents a decrease in the magnetization accuracy of the main track 5 that will be magnetized in a subsequent process.

[0046] 4B shows the process of magnetizing the main track 5 on the magnetic track 4 after the magnetization of the sub-track 6 has been completed, and corresponds to FIG. 3C. As shown in FIG. 4B, the other end 18b of the tip portion 18 in the Z direction is offset in the Z direction so as to coincide with an offset portion Lm set on the main track 5 side in the Z direction from the boundary portion BL. The offset amount is αm.

[0047] As shown in Fig. 5, a detection portion Sm is set on the main track 5 during magnetization, facing the sensing surface of the angle sensor 23 (i.e., the magnetic sensing surface 23m). As shown in Fig. 4B, the distance βm in the Z direction between the detection portion Sm and the boundary portion BL is greater than the offset amount αm of the magnetization yoke 11 (αm < βm). For example, when the distance βm is 1.8 mm, the offset amount αm is set to 0.3 mm to 1.5 mm.

[0048] The tip 18 of the magnetizing yoke 11 magnetizes the main track 5 of the magnetic track 4 so as to pass over the detection portion Sm. Specifically, the tip 18 of the magnetizing yoke 11 intersects (overlaps) with the detection portion Sm and passes over the detection portion Sm during magnetization. One end 18a of the tip 18 in the Z direction is positioned to protrude beyond the width of the main track 5. The width of the tip 18 (the distance in the Z direction from one end 18a to the other end 18b) is greater than the width of the main track 5.

[0049] In this state, the magnetic encoder 1 is rotated in the direction of arrow R, and magnetization is performed one pole at a time to magnetize the main track 5. Leakage magnetic flux 25 is generated from the other end 18b of the tip portion 18 in the Z direction, leaking toward the adjacent sub-track 6. Here, the area of ​​the leakage magnetic flux 25 is simply shown as a square, and this area is displayed by hatching.

[0050] The sub-track 6 has already been magnetized, but the other end 18b of the tip 18 in the Z direction is positioned at an offset portion Lm away from the boundary portion BL in the Z direction to magnetize the main track 5. Therefore, the leakage magnetic flux 25 does not reach the detection portion Sn of the sub-track 6, preventing a decrease in the magnetization accuracy of the sub-track 6. It is more preferable that the leakage magnetic flux 25 does not exceed the offset portion Ln of the sub-track 6.

[0051] 5, the angle sensor 23 is disposed opposite the magnetic tracks 4 (main track 5 and sub-track 6) of the magnetic encoder 1 with a certain gap (e.g., 0.4 mm) between them. The angle sensor 23 has two magnetically sensitive surfaces 23m and 23n, which face the detection units Sm and Sn, respectively.

[0052] The detection portions Sm, Sn are disposed further outward in the Z direction than the offset portions Lm, Ln. Furthermore, as shown in Figures 4A and 4B, the detection portions Sm, Sn are located in a region that overlaps with the tip portion 18 of the magnetizing yoke 11 and is magnetized, and are not affected by leakage magnetic fluxes 24, 25 that are generated when the adjacent magnetic track 4 (main track 5 or sub-track 6) is magnetized, so that high magnetization accuracy is maintained. High magnetization accuracy here means that the error between the magnetized magnetic poles (pitch) and the ideal magnetization width can be reduced.

[0053] In addition, in the region sandwiched between the offset portions Lm and Ln with the boundary portion BL as the center, the magnetization accuracy is reduced due to the influence of the leakage magnetic fluxes 24 and 25. However, since this is an unused region that does not face the magnetic sensitive surfaces 23m and 23n of the angle sensor 23 shown in FIG. 5, the reduction in magnetization accuracy does not pose a problem.

[0054] The sensing surfaces 23m, 23n of the angle sensor 23 are arranged opposite the detection units Sm, Sn, which have high magnetization accuracy, so that the absolute angle can be detected with high accuracy. The magnetization accuracy refers to pitch accuracy, cumulative pitch accuracy, etc. The magnetic encoder 1 is magnetized using the above-described magnetic encoder magnetization method.

[0055] 2 described above, the tip 18 of the magnetizing yoke 11 is offset in the direction of the rows to magnetize the magnetic tracks 4 ( FIG. 1 ) for each row. In this case, the tip 18 of the magnetizing yoke 11 can be separated from the other magnetic tracks that are not magnetized. This reduces the extent to which leakage magnetic flux leaking from the tip 18 of the magnetizing yoke 11 crosses the boundary BL ( FIG. 3B ) and invades adjacent magnetic tracks. Therefore, even if a simple magnetizing yoke 11 without a magnetic shield or the like is used, the magnetic encoder 1 having multiple magnetic tracks can be magnetized with high precision.

[0056] <Regarding Other Embodiments> In the following description, parts corresponding to matters previously described in each embodiment are assigned the same reference numerals, and duplicated description will be omitted. When only part of the configuration is described, the other parts of the configuration are the same as those in the previously described embodiment unless otherwise specified. The same configuration produces the same effects. It is possible to combine not only the parts specifically described in each embodiment, but also parts of the embodiments together, provided that there is no particular problem with the combination.

[0057] 6A and 6B, an axial type magnetic encoder 1A may be provided in which multiple rows of magnetic tracks 4A with different numbers of magnetized pole pairs are formed on one side surface of a disk-shaped core 2. This axial type magnetic encoder 1A can also be fabricated using substantially the same magnetizing device 7 (FIG. 2) and magnetizing method as described above.

[0058] In the magnetic encoder 1A, for example, the main track 5 is magnetized on the outer diameter side of one side of the core 2, and the sub-track 6 is magnetized on the inner diameter side. In particular, to magnetize the main track 5 with greater precision, it is preferable to first magnetize the sub-track 6 as shown in Figure 6A, and then magnetize the main track 5 last as shown in Figure 6B. In this case, the same effects as those of the above-mentioned embodiment can be achieved.

[0059] Although not shown, in a radial or axial type magnetic encoder, the number of double magnetic tracks is not limited to two, but may be three or more.

[0060] As described above, the preferred embodiment has been described with reference to the drawings, but various additions, modifications, and deletions can be made without departing from the spirit of the present invention. Therefore, such additions, modifications, and deletions are also included in the scope of the present invention.

[0061] 1, 1A...magnetic encoder, 4, 4A...magnetic track, 7...magnetizing device, 11...magnetizing yoke, 18...tip portion, 23...angle sensor, 23m, 23n...magnetic sensing surface (sensing surface), BL...boundary portion, Sm, Sn...detecting portion, αm, αn...offset amount, δ...gap

Claims

1. A magnetization device for a magnetic encoder that magnetizes adjacent double-row unmagnetized magnetic tracks using a magnetizing yoke that faces the boundary between the adjacent magnetic tracks, offsetting the tip of the magnetizing yoke in the direction in which the rows of adjacent double-row unmagnetized magnetic tracks are arranged relative to the boundary between the adjacent magnetic tracks, and moving the tip of the magnetizing yoke relatively in the circumferential direction relative to the magnetic track that faces the magnetizing yoke, thereby magnetizing the magnetic tracks row by row.

2. A magnetizing device for a magnetic encoder according to claim 1, wherein the magnetic encoder has a detection section that faces the sensing surface of an angle sensor that detects the absolute angle, and the distance between the detection section and the boundary section is greater than the offset amount of the magnetizing yoke.

3. A magnetizing device for a magnetic encoder according to claim 2, wherein the tip of the magnetizing yoke magnetizes the magnetic track so that it passes over the detecting section.

4. A method for magnetizing a magnetic encoder that uses a magnetizing yoke that faces adjacent unmagnetized magnetic tracks in multiple rows, wherein the tip of the magnetizing yoke is offset from the boundary between the adjacent magnetic tracks in the direction in which the rows of the adjacent unmagnetized magnetic tracks in the multiple rows are arranged, and the tip of the magnetizing yoke is moved circumferentially relative to the magnetic track that faces the magnetizing yoke, thereby magnetizing the magnetic tracks row by row.

5. A magnetic encoder magnetized using the method for magnetizing a magnetic encoder according to claim 4.

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