Absolute encoder

Abstract

To provide an absolute encoder capable of achieving reduction in a size in a simple configuration.SOLUTION: An absolute encoder comprises: a main shaft gear that rotates with a main shaft; a first magnet that rotates with the main shaft; a first magnetic sensor that detects a change in a magnetic flux generated from the first magnet; an idle gear that has a smaller number of teeth than the number of teeth of the main shaft gear and that rotates according to the rotation of the main shaft gear; a first secondary shaft disposed parallel to the main shaft; a first driven gear that is attached to the first secondary shaft and that meshes with the idle gear; a second magnet that rotates with the first secondary shaft; a second magnetic sensor that detects a change in a magnetic flux generated from the second magnet; a second secondary shaft disposed parallel to the main shaft; a second driven gear that is attached to the second secondary shaft, that has a different number of teeth from the number of teeth of the first driven gear, and that meshes with the idle gear; a third magnet that rotates with the second secondary shaft; and a third magnetic sensor that detects a change in a magnetic flux generated from the third magnet.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an absolute encoder.

Background Art

[0002] Conventionally, in various control machines, a rotary encoder used to detect the position and angle of a movable element is known. Such an encoder includes an incremental type encoder that detects a relative position or angle, and an absolute type encoder that detects an absolute position or angle. For example, Patent Document 1 describes an absolute type rotary encoder that includes a plurality of magnetic encoders that detect the angular positions of a main shaft and a sub-shaft using magnetism, and measures the absolute position of the main shaft from the detection results.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The absolute encoder described in Patent Document 1 has a problem that it is difficult to reduce the thickness in the axial direction of the main shaft because it includes a worm gear. Further, when a worm gear is provided, there is a risk of angular error due to axis conversion between two orthogonal axes. Further, when a worm gear is provided, in the axial direction of the rotation axis orthogonal to the main shaft, the worm or worm wheel tends to move in the thrust direction during rotation, so the deviation of the clearance during installation affects the angular error. Therefore, it is necessary to provide a leaf spring or the like to always bias in one direction to remove the clearance, which increases the number of parts and complicates the structure.

[0005] The present invention aims to provide an absolute encoder that can be miniaturized while having a simple configuration. [Means for solving the problem]

[0006] An absolute encoder according to an embodiment of the present invention comprises: a spindle gear mounted on the spindle and rotating with the spindle; a first magnet mounted on the spindle and rotating with the spindle; a first magnetic sensor for detecting changes in magnetic flux generated from the first magnet; an idler gear having fewer teeth than the spindle gear and rotating in accordance with the rotation of the spindle gear; a first sub-shaft arranged parallel to the spindle; a first driven gear mounted on the first sub-shaft and meshing with the idler gear; a second magnet mounted on the first sub-shaft and rotating with the first sub-shaft; a second magnetic sensor for detecting changes in magnetic flux generated from the second magnet; a second sub-shaft arranged parallel to the spindle; a second driven gear mounted on the second sub-shaft and having a different number of teeth than the first driven gear and meshing with the idler gear; a third magnet mounted on the second sub-shaft and rotating with the second sub-shaft; and a third magnetic sensor for detecting changes in magnetic flux generated from the third magnet. [Effects of the Invention]

[0007] The absolute encoder according to the present invention can be miniaturized while maintaining a simple configuration. [Brief explanation of the drawing]

[0008] [Figure 1] This is an exploded perspective view showing an absolute encoder according to the first embodiment. [Figure 2] This is a perspective view showing an absolute encoder. [Figure 3] This is a plan view showing an absolute encoder. [Figure 4] This is a cross-sectional view showing a cross-section along the XZ plane of the absolute encoder. [Figure 5] This is a cross-sectional view showing a section of the absolute encoder along the YZ plane. [Figure 6]This is a perspective view showing the main shaft, main shaft gear, idler gear, driven gear, first sub-shaft, and second sub-shaft. [Figure 7] This is a side view showing the main shaft, main shaft gear, idler gear, driven gear, first sub-shaft, and second sub-shaft. [Figure 8] This is a perspective view showing the magnet that will be attached to the main shaft. [Figure 9] This table shows the gear specifications, reduction ratio, and maximum detectable rotational speed. [Figure 10] This is an exploded perspective view showing the bearing, driven gear, first sub-shaft, magnet holder, magnet, and magnetic sensor. [Figure 11] This is an exploded perspective view showing the bearing, driven gear, second sub-shaft, magnet holder, magnet, and magnetic sensor. [Figure 12] This is a perspective view showing the magnets attached to the first and second sub-shafts. [Figure 13] This is a bottom view showing the circuit board, microcontroller, and magnetic sensor. [Figure 14] This is a block diagram showing the functional configuration of the microcontroller implemented in the absolute encoder. [Figure 15] This table shows the tolerances for the rotation angles of the main spindle, the first sub-spindle, and the second sub-spindle. [Figure 16] This is a perspective view showing an absolute encoder according to the second embodiment. [Figure 17] This is a cross-sectional view showing an absolute encoder. [Figure 18] This table shows the gear specifications, reduction ratio, and maximum detectable rotational speed. [Modes for carrying out the invention]

[0009] The configuration of the absolute encoder according to the embodiment of the present invention will be described in detail below based on the drawings. Note that the present invention is not limited by this embodiment. In each drawing, the X-axis direction, the Y-axis direction, and the Z-axis direction may be illustrated by arrows as three mutually orthogonal directions. The X-axis direction is along the direction in which the X-axis extends. The Y-axis direction is along the direction in which the Y-axis extends. The Z-axis direction is along the direction in which the Z-axis extends. Also, when illustrating a gear, the teeth of the gear are not illustrated.

[0010] [First Embodiment] <Schematic of Absolute Encoder> First, referring to FIGS. 1 to 13, the absolute encoder 100 according to the first embodiment will be described. Hereinafter, the "absolute encoder" may be abbreviated as "encoder".

[0011] FIG. 1 is an exploded perspective view showing the absolute encoder according to the first embodiment. FIG. 2 is a perspective view showing the absolute encoder. The encoder 100 is an absolute type encoder that detects the rotation angle of the main shaft 10. The main shaft 10 is, for example, the rotation shaft of the motor 200. The main shaft 10 is along the Z-axis direction. The encoder 100 outputs the rotation angle of the main shaft 10 as a digital signal.

[0012] <Motor> The motor 200 may be, for example, a stepping motor or a DC brushless motor. The motor 200 can be applied as a drive source for driving an industrial robot or the like via a speed reduction mechanism such as a harmonic gear device. The rotation shaft of the motor 200 protrudes on both sides in the Z-axis direction. The encoder 100 is adjacent to the main body of the motor 200 in the Z-axis direction. The main body of the motor 200 includes a magnet and a housing and does not include a rotation shaft.

[0013] <Absolute Encoder> Figure 3 is a plan view showing an absolute encoder. As shown in Figure 3, the encoder 100 comprises spindle gears 12 and 14, a magnet Mg1, and a magnetic sensor 16. Spindle gear 12 is an example of a first spindle gear, and spindle gear 14 is an example of a second spindle gear. Magnet Mg1 is an example of a first magnet, and magnetic sensor 16 is an example of a first magnetic sensor.

[0014] The encoder 100 includes an idler shaft 20 and idler gears 22 and 24. Idler gears 22 and 24 are examples of first idler gears. The encoder 100 also includes an idler shaft 30 and idler gears 32 and 34. Idler gears 32 and 34 are examples of second idler gears.

[0015] The encoder 100 comprises a first sub-shaft 40, a driven gear 42, a magnet Mg2, and a magnetic sensor 46. The magnetic sensor 46 is shown in Figure 10. The driven gear 42 is an example of a first driven gear. The magnet Mg2 is an example of a second magnet, and the magnetic sensor 46 is an example of a second magnetic sensor.

[0016] The encoder 100 comprises a second sub-shaft 50, a driven gear 52, a magnet Mg3, and a magnetic sensor 56. The magnetic sensor 56 is shown in Figure 11. The driven gear 52 is an example of a second driven gear. The magnet Mg3 is an example of a third magnet, and the magnetic sensor 56 is an example of a third magnetic sensor.

[0017] As shown in Figure 1, the encoder 100 comprises, in order along the Z-axis, a cover plate 62, a housing 110, a substrate 120, a support column 64, a main base 70, and a main spacer 72.

[0018] <Main shaft> The main shaft 10 is cylindrical and has a hollow structure. Wiring that is electrically connected to the motor 200 may be inserted inside the main shaft 10.

[0019] <Main Spacer> The main spacer 72 is positioned adjacent to the body of the motor 200 in the Z-axis direction. The main spacer 72 is plate-shaped. The thickness direction of the main spacer 72 is aligned with the Z-axis direction. The main spacer 72 has an opening for inserting the main shaft 10. teeth It is formed to have a rectangular shape when viewed in the Z-axis direction. The main spacer 72 may be made of, for example, resin.

[0020] <Main Bass> The main base 70 is positioned adjacent to the main spacer 72 in the Z-axis direction. The main base 70 is plate-shaped. The thickness direction of the main base 70 is aligned with the Z-axis direction. The main base 70 has an opening for inserting the main shaft 10. The main base 70 is formed to be rectangular when viewed in the Z-axis direction. The main base 70 is made of a magnetic material and functions as a magnetic shield. For example, stainless steel or cold-rolled steel sheet can be used as the material for the main base 70. Main base 70 teeth It is made of a different material than the main spacer 72.

[0021] <Strut> The support column 64 shown in Figures 1 to 3 is positioned between the main base 70 and the substrate 120 in the Z-axis direction. The support column 64 is provided so as to protrude from the main base 70 in the Z-axis direction on the side opposite to the main spacer 72. The support column 64 is positioned opposite the rectangular corner of the main base 70. The support column 64 has a predetermined length in the Z-axis direction. The support column 64 supports the substrate 120. The support column 64 is formed from, for example, resin. The support column 64 is formed as a separate component from the main base 70. Note that the support column 64 and the main base 70 are not limited to being formed as separate components, but may be formed as a single unit.

[0022] <Circuit board> Figure 4 is a cross-sectional view showing a cross-section along the XZ plane of the absolute encoder. Figure 5 is a cross-sectional view showing a cross-section along the YZ plane of the absolute encoder. The substrate 120 shown in Figures 1, 4, and 5 is a printed circuit board. The substrate 120 is fixed to a plurality of support columns 64. The thickness direction of the substrate 120 is along the Z-axis direction. The substrate 120 is spaced apart from the main base 70 in the Z-axis direction. A predetermined space is formed between the main base 70 and the substrate 120 because the support columns 64 are arranged between the main base 70 and the substrate 120 in the Z-axis direction. The substrate 120 has an opening for inserting the main shaft 10.

[0023] Figure 13 is a bottom view showing the circuit board, microcontroller, and magnetic sensor. As shown in Figure 13, magnetic sensors 46 and 56 are mounted on the circuit board 120. The magnetic sensors 46 and 56 are mounted on the bottom surface of the circuit board 120. The bottom surface of the circuit board 120 is the surface closer to the main base 70 in the Z-axis direction. The microcontroller 121 is mounted on the circuit board 120.

[0024] <Enclosure> The housing 110 shown in Figures 1, 4, and 5 has a top plate 112 and side walls 114 and 116. The top plate 112 is formed to be rectangular when viewed in the Z-axis direction. The thickness direction of the top plate 112 is aligned with the Z-axis direction. The top plate 112 is spaced apart from the substrate 120 in the Z-axis direction. An opening is formed in the top plate 112 for inserting the main shaft 10. The top plate 112 is positioned to cover the substrate 120 from the opposite side of the main base 70 in the Z-axis direction.

[0025] Multiple side walls 114, 116 are formed to form a rectangular tube. The multiple side walls 114 are opposite each other in the X-axis direction, as shown in Figure 4. The thickness direction of the side walls 114 is along the X-axis direction. The multiple side walls 116 are opposite each other in the Y-axis direction, as shown in Figure 5. The thickness direction of the side walls 116 is along the Y-axis direction. The side walls 114, 116 have a predetermined length in the Z-axis direction. The side walls 114, 116 are formed to protrude from the top plate 112 in the Z-axis direction.

[0026] Within the space enclosed by the top plate 112 and the side walls 114 and 116, the circuit board 120, main base 70, main spacer 72, main shaft gears 12 and 14, idler shafts 20 and 30, idler gears 22, 24, 32 and 34, first sub-shaft 40, second sub-shaft 50, driven gears 42 and 52, magnetic sensors 16, 46 and 56, and magnets Mg1, Mg2 and Mg3 are arranged. Note that some of the main spacer 72 and magnets Mg1 may protrude in the Z-axis direction closer to the motor 200 than the side walls 114 and 116.

[0027] <Cover Plate> The cover plate 62 shown in Figures 1, 4, and 5 is formed to have a rectangular shape when viewed in the Z-axis direction. The thickness direction of the cover plate 62 is aligned with the Z-axis direction. The cover plate 62 has an opening through which the main shaft 10 is inserted. The cover plate 62 is positioned to cover the side of the top plate 112 opposite to the motor 200. The cover plate 62 is made of a magnetic material and functions as a magnetic shield.

[0028] <Main shaft gear> Figure 6 is a perspective view showing the main shaft, main shaft gear, idler gear, driven gear, first and second sub-shafts. Figure 7 is a side view showing the main shaft, main shaft gear, idler gear, driven gear, first and second sub-shafts. As shown in Figures 4 to 7, the main shaft gears 12 and 14 are spur gears mounted on the main shaft 10. The gears on the main shaft 10 have a two-stage configuration. The main shaft gears 12 and 14 are positioned on the opposite side of the main base 70 from the motor 200 in the Z-axis direction. The main shaft gears 12 and 14 rotate together with the main shaft 10.

[0029] The number of teeth on the main shaft gears 12 and 14 are different. The number of teeth on the main shaft gear 14 is greater than the number of teeth on the main shaft gear 12. The number of teeth on the main shaft gear 12 may be, for example, 50. The number of teeth on the main shaft gear 14 may be, for example, 51. In the Z-axis direction, the main shaft gear 14 is positioned closer to the body of the motor 200 relative to the main shaft gear 12.

[0030] <Sleeve> The encoder 100 has a sleeve 18 that is mounted on the spindle 10. The spindle 10 is inserted into the opening of the sleeve 18. The spindle 10 is, for example, press-fitted into the sleeve 18. The spindle gears 12, 14 and the sleeve 18 are formed as a single unit. In the Z-axis direction, the sleeve 18 protrudes from the spindle gears 14 towards the body of the motor 200. The spindle gears 12, 14 and the sleeve 18 rotate together with the spindle 10.

[0031] <Magnet Mg1> As shown in Figures 4, 5, and 7, the magnet Mg1 is attached to the spindle 10, for example, via a sleeve 18. The magnet Mg1 is ring-shaped and fixed to the spindle 10. The magnet Mg1 is positioned to contact the outer circumferential surface of the sleeve 18. The magnet Mg1 may be fixed to the spindle 10 via the sleeve 18, or it may be directly fixed to the outer circumferential surface of the spindle 10. In the Z-axis direction, the magnet Mg1 is positioned closer to the motor 200 relative to the main base 70. The magnet Mg1 is positioned within the opening of the main spacer 72. In the Z-axis direction, the magnet Mg1 may protrude closer to the motor 200 than the main spacer 72. As shown in Figure 8, the magnetization direction of the magnet Mg1 is along the radial direction of the spindle 10.

[0032] <Idol Axis 20> As shown in Figures 2, 3, 6, and 7, the idler shaft 20 extends in the Z-axis direction. The idler shaft 20 is fixed to the main base 70, for example, by press-fitting. The idler shaft 20 protrudes from the main base 70 on the side opposite to the body of the motor 200. When viewed in the Z-axis direction, the idler shaft 20 is located outside the main spindle gears 12 and 14 in the radial direction of the spindle 10. The idler shaft 20 is positioned to overlap with the main spindle gears 12 and 14 in the Z-axis direction.

[0033] <First Idol Gear> The first idler gear has a two-stage configuration and includes idler gears 22 and 24. Idler gear 22 is a spur gear rotatably supported with respect to the idler shaft 20. Idler gear 22 is positioned in the Z-axis direction on the opposite side of the main base 70 from the motor 200. Idler gear 22 meshes with the spindle gear 12. The rotation of the spindle 10 is transmitted to idler gear 22 via the spindle gear 12. Idler gear 22 rotates in the opposite direction to the rotation of the spindle 10 around the idler shaft 20.

[0034] Figure 9 is a table showing the gear specifications, reduction ratio, and maximum detectable rotational speed. As shown in Figure 9, the idler gear 22 has, for example, 30 teeth. The speed ratio of the idler gear 22 to the spindle 10 is less than 1. The speed ratio of the idler gear 22 to the spindle 10 is, for example, 0.60. The number of teeth of the idler gear 22 is less than the number of teeth of the spindle gear 12. The number of teeth of the idler gear 22 may be "n-20" when the number of teeth of the spindle gear 12 is "n". Note that "n" and "n-20" are natural numbers.

[0035] As shown in Figures 3, 6, and 7, the idler gear 24 is a spur gear rotatably supported with respect to the idler shaft 20. In the Z-axis direction, the idler gear 24 is positioned on the opposite side of the motor 200 body from the main base 70. In the Z-axis direction, the idler gear 24 is adjacent to the idler gear 22. In the Z-axis direction, the idler gear 24 is positioned closer to the motor 200 body than the idler gear 22. The outer diameter of the idler gear 24 is smaller than the outer diameter of the idler gear 22. The idler gear 24 rotates together with the idler gear 22. The idler gear 24 is integrally molded with the idler gear 22.

[0036] As shown in Figure 9, the number of teeth on idler gear 24 is less than the number of teeth on idler gear 22. For example, idler gear 24 has 21 teeth. The number of teeth on idler gear 24 may also be "n-9" if the number of teeth on idler gear 22 is "n". Note that "n" and "n-9" are natural numbers.

[0037] <First Sub-axis> Figure 10 is an exploded perspective view showing the bearing, driven gear, first sub-shaft, magnet holder, magnet, and magnetic sensor. The bearing 48, driven gear 42, first sub-shaft 40, magnet holder 44, and magnet Mg2 shown in Figure 10 are assembled as a single unit. The magnetic sensor 46 is positioned at a distance from the magnet Mg2.

[0038] The first sub-shaft 40 extends in the Z-axis direction. The first sub-shaft 40 is positioned parallel to the main shaft 10. The first sub-shaft 40 is rotatably supported by a bearing 48. The bearing 48 is fixed, for example, to the main base 70. The first sub-shaft 40 protrudes from the main base 70 on the side opposite to the motor 200.

[0039] <First driven gear> The driven gear 42 is a spur gear mounted on the first sub-shaft 40. The first sub-shaft 40 may be press-fitted into the opening of the driven gear 42. The driven gear 42 is positioned in the Z-axis direction on the opposite side of the main base 70 from the motor 200. The driven gear 42 meshes with the idler gear 24. The rotation of the main shaft 10 is transmitted to the driven gear 42 via the main shaft gear 12 and the idler gears 22 and 24. The first sub-shaft 40 rotates together with the driven gear 42. The driven gear 42 and the first sub-shaft 40 rotate in the same direction as the rotation of the main shaft 10.

[0040] As shown in Figure 9, the number of teeth on the driven gear 42 is, for example, 33. The number of teeth on the driven gear 42 is greater than the number of teeth on the idler gear 24. The number of teeth on the driven gear 42 may also be "n+12" if the number of teeth on the idler gear 24 is "n".

[0041] The speed ratio of the driven gear 42 to the main spindle 10 is close to 1. The speed ratio of the driven gear 42 to the main spindle 10 may be, for example, 0.942857. The speed ratio of the driven gear 42 to the idler gear 24 is greater than 1. The speed ratio of the driven gear 42 to the idler gear 24 may be, for example, 1.571.

[0042] <Magnet Mg2> As shown in Figures 2, 3, and 10, the magnet Mg2 is attached to the tip of the first sub-shaft 40. The magnet Mg2 is, for example, disc-shaped. The tip of the first sub-shaft 40 is the end furthest from the main body of the motor 200 in the Z-axis direction. The thickness direction of the magnet Mg2 is along the Z-axis direction. As shown in Figure 12, the magnetization direction of the magnet Mg2 is along the Z-axis direction.

[0043] <Magnet holder> The magnet holder 44 shown in Figure 10 is formed integrally with, for example, the first sub-shaft 40. The magnet holder 44 is provided at the tip of the first sub-shaft 40. The magnet holder 44 has a recess into which the magnet Mg2 fits. The magnet Mg2 is fitted into the recess of the magnet holder 44. The magnet Mg2 is held by the magnet holder 44 and rotates together with the first sub-shaft 40.

[0044] <Idol axis 30> As shown in Figures 2, 3, 6, and 7, the idler shaft 30 extends in the Z-axis direction. The idler shaft 30 is fixed to the main base 70. The idler shaft 30 protrudes from the main base 70 on the side opposite to the body of the motor 200. When viewed in the Z-axis direction, the idler shaft 30 is positioned outside the main shaft gears 12 and 14 in the radial direction of the main shaft 10. The idler shaft 30 is positioned to overlap with the main shaft gears 12 and 14 in the Z-axis direction.

[0045] <Second Idol Gear> The second idler gear has a two-stage configuration and includes idler gears 32 and 34. Idler gear 32 is a spur gear rotatably supported with respect to the idler shaft 30. Idler gear 32 is positioned in the Z-axis direction on the opposite side of the main base 70 from the motor 200. Idler gear 32 meshes with the spindle gear 14. The rotation of the spindle 10 is transmitted to idler gear 32 via the spindle gear 14. Idler gear 32 rotates in the opposite direction to the rotation of the spindle 10 around the idler shaft 30.

[0046] As shown in Figure 9, the idler gear 32 has, for example, 30 teeth. The speed ratio of the idler gear 32 to the spindle 10 is less than 1. The speed ratio of the idler gear 22 to the spindle 10 is, for example, 0.58. The speed ratio of the idler gear 32 to the spindle 10 is smaller than the speed ratio of the idler gear 22 to the spindle 10. The number of teeth on the idler gear 32 is less than the number of teeth on the spindle gear 14. The number of teeth on the idler gear 32 may also be "n-21" when the number of teeth on the spindle gear 14 is "n". Note that "n" and "n-21" are natural numbers.

[0047] As shown in Figures 2, 3, and 7, the idler gear 34 is a spur gear rotatably supported with respect to the idler shaft 30. In the Z-axis direction, the idler gear 34 is positioned on the opposite side of the motor 200 body from the main base 70. In the Z-axis direction, the idler gear 34 is adjacent to the idler gear 32. In the Z-axis direction, the idler gear 34 is positioned further from the motor 200 body than the idler gear 32. The outer diameter of the idler gear 34 is smaller than the outer diameter of the idler gear 32. The idler gear 34 rotates together with the idler gear 32. The idler gear 34 is integrally molded with the idler gear 32.

[0048] As shown in Figure 9, the number of teeth on idler gear 34 is less than the number of teeth on idler gear 32. For example, idler gear 34 has 20 teeth. The number of teeth on idler gear 34 is less than the number of teeth on idler gear 32. The number of teeth on idler gear 34 may also be "n-10" if the number of teeth on idler gear 32 is "n". Note that "n" and "n-10" are natural numbers.

[0049] <Second Sub-axis> Figure 11 is an exploded perspective view showing the bearing, driven gear, second sub-shaft, magnet holder, magnet, and magnetic sensor. The bearing 58, driven gear 52, second sub-shaft 50, magnet holder 54, and magnet Mg3 shown in Figure 11 are assembled as a single unit. The magnetic sensor 56 is positioned spaced apart from the magnet Mg3.

[0050] The second sub-shaft 50 extends in the Z-axis direction. The second sub-shaft 50 is positioned parallel to the main shaft 10. The second sub-shaft 50 is rotatably supported by a bearing 58. The bearing 58 is fixed, for example, to the main base 70. The second sub-shaft 50 protrudes from the main base 70 on the side opposite to the body of the motor 200.

[0051] <Second driven gear> The driven gear 52 is a spur gear mounted on the second sub-shaft 50. The second sub-shaft 50 may be press-fitted into the opening of the driven gear 52. The driven gear 52 is positioned in the Z-axis direction on the opposite side of the main base 70 from the motor 200. The driven gear 52 meshes with the idler gear 22. The rotation of the main shaft 10 is transmitted to the driven gear 52 via the main shaft gear 12 and idler gears 32, 34. The second sub-shaft 50 rotates together with the driven gear 52. The driven gear 52 and the second sub-shaft 50 rotate in the same direction as the rotation of the main shaft 10.

[0052] As shown in Figure 9, the number of teeth on the driven gear 52 is, for example, 33. The number of teeth on the driven gear 52 is greater than the number of teeth on the idler gear 34. The number of teeth on the driven gear 52 may also be "n+13" if the number of teeth on the idler gear 34 is "n". The number of teeth on the driven gear 52 may also be the same as the number of teeth on the driven gear 42.

[0053] The speed ratio of the driven gear 52 to the main spindle 10 is close to 1. The speed ratio of the driven gear 52 to the main spindle 10 may be, for example, 0.970588. The speed ratio of the driven gear 52 to the idler gear 34 is greater than 1. The speed ratio of the driven gear 52 to the idler gear 34 may be, for example, 1.65. The speed ratio of the driven gear 52 to the idler gear 34 is greater than the speed ratio of the driven gear 42 to the idler gear 24.

[0054] <Magnet Mg3> As shown in Figures 2, 3, and 11, the magnet Mg3 is attached to the tip of the second sub-shaft 50. The magnet Mg3 is, for example, disc-shaped. The tip of the second sub-shaft 50 is the end furthest from the main body of the motor 200 in the Z-axis direction. The thickness direction of the magnet Mg3 is aligned with the Z-axis direction. As shown in Figure 12, the magnetization direction of the magnet Mg3 is aligned with the Z-axis direction.

[0055] <Magnet holder> The magnet holder 54 shown in Figure 11 is formed integrally with, for example, the second sub-shaft 50. The magnet holder 54 is provided at the tip of the second sub-shaft 50. The magnet holder 54 has a recess into which the magnet Mg3 fits. The magnet Mg3 is fitted into the recess of the magnet holder 54. The magnet Mg3 is held by the magnet holder 54 and rotates together with the second sub-shaft 50.

[0056] <Direction of magnetization of magnet Mg1> Next, the magnetization direction DM1 of the magnet Mg1 will be explained with reference to Figure 8. Figure 8 is a perspective view showing the magnet attached to the main shaft. The magnet Mg1 is magnetized in the radial direction D1 of the main shaft 10. The radial direction D1 of the main shaft 10 is the radial direction of the ring-shaped magnet Mg1 and intersects with the Z-axis direction. The radial direction D1 may also be along the X-axis direction, the Y-axis direction, or any other direction. Note that when magnetization is performed in the radial direction, it may be described as "radial magnetization".

[0057] When the magnetization direction DM1 is radial D1, the magnetic field generated by the magnet Mg1 tends to spread more easily in the radial direction D1 compared to when the magnetization direction DM2 is in the Z-axis direction.

[0058] <First Magnetic Sensor> The magnetic sensor 16 shown in Figures 1 and 8 detects the rotation angle of the main shaft 10. The magnetic sensor 16 is positioned, for example, in the Z-axis direction, overlapping with the magnet Mg1, and is located outside the magnet Mg1 in the radial direction of the magnet Mg1. The magnetic sensor 16 faces the outer circumferential surface of the magnet Mg1 in the radial direction of the magnet Mg1. The magnetic sensor 16 detects changes in the magnetic flux of the magnet Mg1. The magnetic sensor 16 detects the rotation angle of the main shaft 10 from the changes in the magnetic flux of the magnet Mg1.

[0059] <Direction of magnetization of Mg2 magnet> Next, the magnetization direction DM2 of the magnet Mg2 will be explained with reference to Figure 12. Figure 12 is a perspective view showing the magnets attached to the first and second sub-shafts. The magnet Mg2 is magnetized in the axial direction of the first sub-shaft 40. The axial direction of the first sub-shaft 40 is along the Z-axis direction. In the magnet Mg2, the north pole is formed on one side and the south pole is formed on the other, with the center of the radial direction D2 of the magnet Mg2 as the boundary. Also, in the magnet Mg2, the north and south poles are reversed with respect to the center of the Z-axis direction. As shown in Figure 12, the north pole is located on the left side of the upper row, and the south pole is located on the right side of the upper row. The south pole is located on the left side of the lower row, and the north pole is located on the right side of the lower row. The magnetization direction DM2 of the magnet Mg2 is along the Z-axis direction. Note that magnetization in the axial direction may be described as "plane magnetization".

[0060] When the magnetization direction DM2 is in the Z-axis direction, the magnetic field due to the magnet Mg2 is distributed in a way that spreads out in the Z-axis direction, and the peak is higher, compared to when the magnetization direction is in the radial direction D2.

[0061] <Second Magnetic Sensor> The magnetic sensor 46 shown in Figures 10, 12, and 13 detects the rotation angle of the first sub-shaft 40. The magnetic sensor 46 is positioned so as to overlap with the first sub-shaft 40 when viewed in the Z-axis direction. The magnetic sensor 46 is spaced apart from the magnet Mg2 in the Z-axis direction. The magnetic sensor 56 is mounted on the substrate 120. The magnetic sensor 46 is mounted on the bottom surface of the substrate 120. The magnetic sensor 46 detects changes in the magnetic flux of the magnet Mg2. The magnetic sensor 46 detects the rotation angle of the first sub-shaft 40 from the changes in the magnetic flux of the magnet Mg2.

[0062] <Direction of magnetization of Mg3 magnet> The magnetization direction of magnet Mg3 is the same as the magnetization direction DM2 of magnet Mg2, so the explanation is omitted here.

[0063] <Third Magnetic Sensor> The magnetic sensor 56 shown in Figures 11, 12, and 13 detects the rotation angle of the second sub-shaft 50. The magnetic sensor 56 is positioned so as to overlap with the second sub-shaft 50 when viewed in the Z-axis direction. The magnetic sensor 56 is spaced apart from the magnet Mg3 in the Z-axis direction. The magnetic sensor 56 is mounted on the substrate 120. The magnetic sensor 56 is mounted on the bottom surface of the substrate 120. The magnetic sensor 56 detects changes in the magnetic flux of the magnet Mg3. The magnetic sensor 56 detects the rotation angle of the second sub-shaft 50 from the changes in the magnetic flux of the magnet Mg3.

[0064] <Microcontroller> As shown in Figure 13, a microcontroller 121 is mounted on the circuit board 120. The microcontroller 121 is mounted on the bottom surface of the circuit board 120. Figure 14 is a block diagram showing the functional configuration of the microcontroller. The microcontroller 121 consists of a CPU and acquires digital signals representing the rotation angle output from the magnetic sensor 16, magnetic sensor 46, and magnetic sensor 56, respectively. Based on the signals acquired from the magnetic sensor 16, magnetic sensor 46, and magnetic sensor 56, the microcontroller 121 calculates the rotation angle of the main shaft 10.

[0065] Figure 14 is a block diagram showing the functional configuration of a microcontroller implemented in an absolute encoder. Each block of the microcontroller 121 shown in Figure 14 represents a function realized by the execution of a program by the CPU of the microcontroller 121. Each block of the microcontroller 121 can be realized in hardware terms by elements and mechanical devices such as the CPU (central processing unit) of a computer, and in software terms by computer programs, etc., but here we are depicting the functional blocks realized by the cooperation of these. Therefore, these functional blocks can be realized in various forms by combinations of hardware and software.

[0066] The microcontroller 121 includes a rotation angle acquisition unit 121p, a rotation angle acquisition unit 121q, a rotation angle acquisition unit 121r, a table processing unit 121b, a rotation amount determination unit 121c, and an output unit 121e. The rotation angle acquisition unit 121q acquires rotation angle Aq, which is angle information indicating the rotation angle of the main shaft 10, based on the signal output from the magnetic sensor 16. The rotation angle acquisition unit 121p acquires rotation angle Ap, which is angle information indicating the rotation angle of the first sub-shaft 40, based on the signal output from the magnetic sensor 36. The rotation angle acquisition unit 121r acquires rotation angle Ar, which is angle information indicating the rotation angle of the second sub-shaft 50 detected by the magnetic sensor 46.

[0067] The table processing unit 121b refers to a first correspondence table that stores the rotation angle Ap of the first sub-spindle 40 and the rotation speed of the spindle 10 corresponding to the rotation angle Ap, and identifies the rotation speed of the spindle 10 corresponding to the acquired rotation angle Ap. The table processing unit 121b also refers to a second correspondence table that stores the rotation angle Ar of the second sub-spindle 50 and the rotation speed of the spindle 10 corresponding to the rotation angle Ar, and identifies the rotation speed of the spindle 10 corresponding to the acquired rotation angle Ar.

[0068] The rotation amount determination unit 121c determines the amount of rotation over multiple rotations of the spindle 10, according to the rotation speed of the spindle 10 determined by the table processing unit 121b and the acquired rotation angle Aq. The output unit 121e converts the amount of rotation over multiple rotations of the spindle 10 determined by the rotation amount determination unit 121c into information indicating that amount of rotation and outputs it.

[0069] <Tolerance for rotation angle> Figure 15 is a table showing the tolerances for the rotation angles of the main spindle, the first sub-spindle, and the second sub-spindle. The tolerance for the rotation angle of the main spindle 10 during one revolution is 1.8° ± 0.9°. The tolerance for the rotation angle of the first sub-spindle 40 during one revolution is 10.29° ± 5.15°. The tolerance for the rotation angle of the second sub-spindle 50 during one revolution is 10.59° ± 5.19°.

[0070] Since the tolerance for the rotation angle of the main spindle 10 is smaller than the tolerance for the rotation angles of the first sub-spindle 40 and the second sub-spindle 50, it is desirable to use a radially magnetized magnet for the magnet Mg1 corresponding to the magnetic sensor 16 used to detect the rotation angle of the main spindle 10, so as not to exceed the tolerance of the main spindle 10.

[0071] On the other hand, the tolerances for the rotation angles of the first sub-shaft 40 and the second sub-shaft 50 are larger than the tolerances for the rotation angle of the main shaft 10. Therefore, it is desirable to use an axially magnetized magnet for the magnet Mg2 corresponding to the magnetic sensor 46 used to detect the rotation angle of the first sub-shaft 40, in order to prioritize suppressing the occurrence of magnetic interference. For similar reasons, it is desirable to use an axially magnetized magnet for the magnet Mg3 corresponding to the magnetic sensor 56 used to detect the rotation angle of the second sub-shaft 50.

[0072] <Maximum detection rotation speed> When the main spindle 10 rotates 35 times, the first sub-spindle 40 completes one cycle (360 ÷ 35 = 10.285). When the main spindle 10 rotates 34 times, the second sub-spindle 50 completes one cycle (360 ÷ 34 = 10.588). In this case, the maximum detectable rotation speed is 1190 (34 × 35 = 1190).

[0073] <Operation of an absolute encoder> When the motor 200 is driven, the main shaft 10, which is the rotation axis of the motor 200, rotates. In the encoder 100, when the main shaft 10 rotates, the main shaft gears 12, 14 and the magnet Mg1 rotate together with the main shaft 10.

[0074] The idler gear 22 meshes with the main shaft gear 12 and rotates in accordance with the rotation of the main shaft gear 12. The idler gear 24 rotates together with the idler gear 22. The driven gear 42 meshes with the idler gear 24 and rotates in accordance with the rotation of the idler gear 24. The first sub-shaft 40 and the magnet Mg2 rotate together with the driven gear 42.

[0075] The idler gear 32 meshes with the main shaft gear 14 and rotates in accordance with the rotation of the main shaft gear 14. The idler gear 34 rotates together with the idler gear 32. The driven gear 52 meshes with the idler gear 34 and rotates in accordance with the rotation of the idler gear 34. The second sub-shaft 50 and the magnet Mg3 rotate together with the driven gear 52.

[0076] <Effects of absolute encoders> In conventional configurations using worm gears, a spring and a mechanism to support the spring were necessary to suppress the influence of angle errors due to axis conversion and displacement in the axial direction. In the encoder 100 according to this embodiment, a worm gear is not included, so a simpler configuration can be achieved and the number of parts can be reduced. As a result, the assembly of the encoder 100 becomes easier.

[0077] The encoder 100 is equipped with main shaft gears 12, 14, idler gears 22, 24, 32, 34, and driven gears 42, 52. Since all of these gears are spur gears, the thickness in the Z-axis direction can be reduced. Compared to conventional configurations with worm gears, the encoder 100 is thinner in the Z-axis direction.

[0078] The encoder 100 detects the rotation angle of the main shaft 10, the rotation angle of the first sub-shaft 40, and the rotation angle of the second sub-shaft 50, and from these angles, it can detect the rotation speed and rotation angle of the main shaft 10. The encoder 100 is equipped with main shaft gears 12 and 14 with different numbers of teeth, and the idler gear includes idler gears 22 and 24 that rotate in accordance with the rotation of the main shaft gear 12, and idler gears 32 and 34 that rotate in accordance with the rotation of the main shaft gear 14, the driven gear 42 meshes with idler gear 24, and the driven gear 52 meshes with idler gear 34. With this configuration, the encoder 100 has a simple structure, is thin, and has a maximum detection rate Turn The number can be increased. The encoder 100 can prevent the main spindle 10, the first sub-spindle 40, and the second sub-spindle 50 from having the same rotation angle combination until the main spindle 10 rotates 1190 times. The encoder 100 can achieve a maximum rotation speed of 1190.

[0079] In the encoder 100, a main base 70 is positioned between magnet Mg1 and magnets Mg2 and Mg3 in the axial direction of the main shaft 10 to suppress the transmission of magnetic flux. Magnet Mg1 is positioned closer to the body of the motor 200 than the main base 70, while magnets Mg2 and Mg3 are positioned further away from the body of the motor 200 than the main base 70. Similarly, the magnetic sensor 16 corresponding to magnet Mg1 is positioned closer to the body of the motor 200 than the main base 70, while the magnetic sensor 46 corresponding to magnet Mg2 and the magnetic sensor 56 corresponding to magnet Mg3 are positioned further away from the body of the motor 200 than the main base 70.

[0080] In an encoder 100 with this configuration, the main base 70 suppresses the transmission of magnetic flux, thereby suppressing the detection of magnetic flux generated from magnet Mg1 by magnetic sensors 46 and 56, and suppressing the detection of magnetic flux generated from magnets Mg2 and Mg3 by magnetic sensor 16. Furthermore, the main base 70 of the encoder 100 suppresses the transmission of magnetic flux generated from the magnets of the motor 200. In the encoder 100, the main base 70 suppresses the transmission of magnetic flux, thus suppressing magnetic flux leakage to the outside of the encoder 100.

[0081] In the encoder 100, the magnet Mg1 with the stronger magnetic flux is positioned closer to the motor 200 body in the axial direction of the main shaft 10, while the magnets Mg2 and Mg3 with weaker magnetic flux are positioned further away from the motor 200 body. In an encoder 100 with this configuration, the magnetic flux generated from the magnet Mg1 closer to the motor 200 body is strong, which suppresses the influence of the magnetic flux of the motor 200's magnets, while the magnetic sensor 16 can detect changes in the magnetic flux of magnet Mg1.

[0082] In encoder 100, magnet Mg1 is magnetized radially on the main shaft 10, and magnets Mg2 and Mg3 are magnetized axially on the first sub-shaft 40 and the second sub-shaft 50. In encoder 100 with this configuration, since magnet Mg1 is radially magnetized, the magnetic field from magnet Mg1 tends to spread more easily in the radial direction D1 compared to the case of planar magnetization. In encoder 100, since magnets Mg2 and Mg3 are planar magnetized, the magnetic fields from magnets Mg2 and Mg3 are distributed to spread in the Z-axis direction and have a higher peak compared to the case of radial magnetization. As a result, each magnetic sensor 16, 46, and 56 can reliably detect changes in magnetic flux generated from the corresponding magnets Mg1, Mg2, and Mg3.

[0083] Furthermore, in the encoder 100, the magnet Mg1 is ring-shaped, the main shaft 10 is inserted through the opening of the magnet Mg1, the magnetic sensor 16 is positioned outside the magnet Mg1 in the radial direction of the main shaft 10, the magnet Mg2 is positioned at the axial end of the first sub-shaft 40, the magnetic sensor 46 is positioned opposite the magnet Mg2 in the axial direction of the first sub-shaft 40, the magnet Mg3 is positioned at the axial end of the second sub-shaft 50, and the magnetic sensor 56 is positioned opposite the magnet Mg3 in the axial direction of the second sub-shaft 50.

[0084] With this encoder 100 configuration, the magnetic sensor 16 is positioned radially outside the magnet Mg1, allowing for a thinner design in the Z-axis direction compared to the case where the magnetic sensor 16 is positioned overlapping with the magnet Mg1 in the Z-axis direction. Furthermore, the magnetic sensor 46 is positioned opposite the magnet Mg2 located at the end of the first sub-shaft 40 in the Z-axis direction, allowing it to be positioned at a distance from the magnet Mg1 in the Z-axis direction. This reduces the influence of the magnetic flux generated by the magnet Mg1 on the magnetic sensor 46. Similarly, the magnetic sensor 56 is positioned opposite the magnet Mg2 located at the end of the second sub-shaft 50 in the Z-axis direction, allowing it to be positioned at a distance from the magnet Mg1 in the Z-axis direction. This reduces the influence of the magnetic flux generated by the magnet Mg1 on the magnetic sensor 56.

[0085] Furthermore, in the encoder 100, idler gears 22, 24, 32, and 34 are positioned between the magnet Mg2 and magnetic sensor 46 and the magnet Mg3 and magnetic sensor 56 when viewed in the Z-axis direction.

[0086] With this encoder 100 configuration, by positioning the magnetic sensor 46 at a distance from the magnet Mg3, the influence of the magnetic flux generated by the magnet Mg3 on the magnetic sensor 46 can be reduced. Similarly, by positioning the magnetic sensor 56 at a distance from the magnet Mg2, the influence of the magnetic flux generated by the magnet Mg2 on the magnetic sensor 56 can be reduced.

[0087] Furthermore, the encoder 100 is positioned to cover the top plate 112 of the housing 110 and includes a cover plate 62 that suppresses the transmission of magnetic flux. With this configuration of the encoder 100, the cover plate 62 suppresses the transmission of magnetic flux to the motor 200. magnetBy suppressing the transmission of magnetic flux generated from Mg1, Mg2, and Mg3, magnetic flux leakage to the outside of the encoder 100 can be suppressed. The encoder 100 is equipped with a cover plate 62 in addition to the main base 70, so that the transmission of magnetic flux generated from the motor 200's magnet and magnet Mg1 is suppressed by the main base 70, and further suppressed by the cover plate 62. As a result, magnetic flux leakage to the outside of the encoder 100 is further suppressed. The risk of magnetic interference to external equipment of the encoder 100 is reduced.

[0088] [Second Embodiment] Next, the encoder 100B according to the second embodiment will be described with reference to Figures 16 to 18. Figure 16 is a perspective view showing the encoder according to the second embodiment. Figure 17 is a cross-sectional view showing the encoder. Figure 18 is a table showing the gear specifications, reduction ratio, and maximum detectable rotational speed. The difference between the encoder 100B according to the second embodiment shown in Figures 16 and 17 and the encoder 100 according to the first embodiment described above is the difference in the gear configuration. Specifically, the encoder 100B has a single-stage main shaft gear 12B instead of the two-stage main shaft gears 12 and 14, idler gears 32B and 34B instead of idler gears 22, 24, 32, and 34, and driven gears 42B and 52B that mesh with the same idler gear 34B instead of driven gears 42 and 52 that mesh with different idler gears 24 and 34. Note that in the description of the encoder 100B, explanations similar to those for the encoder 100 may be omitted.

[0089] As shown in Figure 16, encoder 100B includes a main shaft gear 12B, a magnet Mg1, and a magnetic sensor 16. Encoder 100B includes an idler shaft 30B and idler gears 32B, 34B. Encoder 100B includes a first sub-shaft 40B, a driven gear 42B, a magnet Mg2, and a magnetic sensor 46. Encoder 100B includes a second sub-shaft 50B, a driven gear 52B, a magnet Mg3, and a magnetic sensor 56.

[0090] The main shaft gear 12B and magnet Mg1 rotate together with the main shaft 10. The idler gears 32B and 34B are integrally constructed, similar to the idler gears 32 and 34. Idler gear 32B meshes with the main shaft gear 12B and rotates in accordance with the rotation of the main shaft gear 12B. Idler gear 34B rotates together with idler gear 32B. Idler gears 32B and 34B rotate around the idler shaft 30B.

[0091] The first sub-shaft 40B, driven gear 42B, magnet Mg2, and magnetic sensor 46 have the same configuration as the first sub-shaft 40, driven gear 42, magnet Mg2, and magnetic sensor 46 of the first embodiment shown in Figure 10. The driven gear 42B meshes with the idler gear 34B and rotates in accordance with the rotation of the idler gear 34B. The driven gear 42B, the first sub-shaft 40B, and magnet Mg2 rotate as a single unit.

[0092] The second sub-shaft 50B, driven gear 52B, magnet Mg3, and magnetic sensor 56 have the same configuration as the second sub-shaft 50, driven gear 52, magnet Mg3, and magnetic sensor 56 of the first embodiment shown in Figure 11. The driven gear 52B meshes with the idler gear 34B and rotates in accordance with the rotation of the idler gear 34B. The driven gear 52B, the second sub-shaft 50B, and magnet Mg3 rotate as a single unit.

[0093] As shown in Figure 18, the number of teeth of the spindle gear 12B is, for example, 50. The number of teeth of the idler gear 32B is, for example, 29. The speed ratio of the idler gear 32B to the spindle 10 is less than 1. The speed ratio of the idler gear 32B to the spindle 10 is, for example, 0.58. The number of teeth of the idler gear 32B is less than the number of teeth of the spindle gear 12B. The number of teeth of the idler gear 32B may be "n-21" when the number of teeth of the spindle gear 12 is "n". Note that "n" and "n-21" are natural numbers.

[0094] The number of teeth on idler gear 34B is less than the number of teeth on idler gear 32B. For example, idler gear 34B has 20 teeth. The number of teeth on idler gear 34B can also be "n-9" if the number of teeth on idler gear 32B is "n". Note that "n" and "n-9" are natural numbers.

[0095] The driven gear 42B has, for example, 33 teeth. The number of teeth on the driven gear 42B is greater than the number of teeth on the idler gear 34B. The number of teeth on the driven gear 42B may also be "n+13" if the number of teeth on the idler gear 34B is "n".

[0096] The speed ratio of the driven gear 42B to the main spindle 10 is close to 1. The speed ratio of the driven gear 42B to the main spindle 10 may be, for example, 0.957. The speed ratio of the driven gear 42B to the idler gear 34B is greater than 1. The speed ratio of the driven gear 42B to the idler gear 34B may be, for example, 1.65.

[0097] The driven gear 52B has, for example, 34 teeth. The number of teeth on the driven gear 52B is greater than the number of teeth on the idler gear 34B. The number of teeth on the driven gear 52B may also be "n+14" if the number of teeth on the idler gear 34B is "n".

[0098] The speed ratio of the driven gear 52B to the main spindle 10 is close to 1. The speed ratio of the driven gear 52B to the main spindle 10 may be, for example, 0.986. The speed ratio of the driven gear 52B to the idler gear 34B is greater than 1. The speed ratio of the driven gear 52B to the idler gear 34B may be, for example, 1.7. The speed ratio of the driven gear 52B to the idler gear 34B is greater than the speed ratio of the driven gear 42B to the idler gear 34B.

[0099] <Maximum detection rotation speed> In the case of the gear conditions shown in Figure 18, the maximum detectable rotational speed is 999. Here, the initial state of the three detected values ​​for the main spindle 10, the first sub-spindle 40B, and the second sub-spindle 50B is set to 0 (zero). Then, the rotational speed of the main spindle 10 just before the detected values ​​for the main spindle 10, the first sub-spindle 40B, and the second sub-spindle 50B simultaneously become 0 is the maximum detectable rotational speed.

[0100] <Effects of absolute encoders> The encoder 100B according to the second embodiment also provides the same effects as the encoder 100 according to the first embodiment. Compared to the encoder 100, the encoder 100B has fewer idler shafts and idler gears, thus reducing the number of parts and allowing for a simpler configuration.

[0101] The configurations shown in the above embodiments are merely examples of the content of the present invention, and can be combined with other known technologies. Furthermore, it is possible to omit or modify parts of the configuration without departing from the spirit of the present invention.

[0102] The above embodiment describes a case where the encoder 100 includes a main base 70 made of a magnetic material, but the encoder 100 is not limited to this. The encoder 100 may include a main base 70 made of, for example, a non-magnetic material. Alternatively, the encoder 100 may be configured to include a magnetic shield attached to the main base 70 made of a non-magnetic material.

[0103] In the above embodiment, the spindle 10 is described as a cylindrical spindle having a hollow structure, but the spindle 10 is not limited to being cylindrical. The encoder 100 may, for example, have a cylindrical spindle. [Explanation of Symbols]

[0104] 100, 100B Encoder (Absolute Encoder), 10 Main shaft, 12 Main shaft gear (1st main shaft gear), 12B Main shaft gear, 14 Main shaft gear (2nd main shaft gear), 16 Magnetic sensor (1st magnetic sensor), 22, 24 Idler gear (1st idler gear), 32, 34 Idler gear (2nd idler gear), 40, 40B 1st sub-shaft, 42 Driven gear (1st driven gear), 46 Magnetic sensor (2nd magnetic sensor), 50, 50B 2nd sub-shaft, 52 Driven gear (2nd driven gear), 56 Magnetic sensor (3rd magnetic sensor), 70 Main base (Magnetic shield), Mg1 Magnet (1st magnet), Mg2 Magnet (2nd magnet), Mg3 Magnet (3rd magnet), XX axis direction, YY axis direction, ZZ axis direction (axis direction of the main shaft).

Claims

1. A spindle gear attached to the spindle and rotating together with the spindle, A first magnet attached to the main shaft and rotating together with the main shaft, A first magnetic sensor for detecting changes in magnetic flux generated from the first magnet, An idler gear having fewer teeth than the main shaft gear and rotating in accordance with the rotation of the main shaft gear, A first sub-shaft arranged parallel to the main shaft, A first driven gear attached to the first sub-shaft and meshing with the idler gear, A second magnet is attached to the first sub-shaft and rotates together with the first sub-shaft, A second magnetic sensor for detecting changes in magnetic flux generated from the second magnet, A second sub-shaft is arranged parallel to the main shaft, A second driven gear is attached to the second sub-shaft, has a different number of teeth than the first driven gear, and meshes with the idler gear. A third magnet attached to the second sub-shaft and rotating together with the second sub-shaft, A third magnetic sensor that detects changes in magnetic flux generated from the third magnet, In the axial direction of the main shaft, the first magnet and the second and third magnets are positioned to provide a magnetic shield that suppresses the transmission of magnetic flux, The aforementioned main shaft is the rotation axis of the motor, The first magnet is positioned closer to the motor body than the second and third magnets in the axial direction of the main shaft. Absolute encoder.

2. A spindle gear attached to the spindle and rotating together with the spindle, A first magnet attached to the main shaft and rotating together with the main shaft, A first magnetic sensor for detecting changes in magnetic flux generated from the first magnet, An idler gear having fewer teeth than the main shaft gear and rotating in accordance with the rotation of the main shaft gear, A first sub-shaft arranged parallel to the main shaft, A first driven gear attached to the first sub-shaft and meshing with the idler gear, A second magnet is attached to the first sub-shaft and rotates together with the first sub-shaft, A second magnetic sensor for detecting changes in magnetic flux generated from the second magnet, A second sub-shaft is arranged parallel to the main shaft, A second driven gear is attached to the second sub-shaft, has a different number of teeth than the first driven gear, and meshes with the idler gear. A third magnet attached to the second sub-shaft and rotating together with the second sub-shaft, The system includes a third magnetic sensor that detects changes in the magnetic flux generated from the third magnet, The first magnet is magnetized in the radial direction of the main shaft, The second magnet and the third magnet are magnetized in the axial direction of the first sub-shaft and the second sub-shaft. Absolute encoder.

3. The aforementioned spindle gear includes a first spindle gear and a second spindle gear having different numbers of teeth. The idler gear includes a first idler gear that rotates in accordance with the rotation of the first spindle gear, and a second idler gear that rotates in accordance with the rotation of the second spindle gear. The first driven gear meshes with the first idler gear, The absolute encoder according to claim 1 or 2, wherein the second driven gear meshes with the second idler gear.

4. The first magnet is ring-shaped, and the main shaft is inserted through the opening of the first magnet. The first magnetic sensor is positioned outside the first magnet in the radial direction of the main shaft, The second magnet is positioned at the end of the first sub-shaft in the axial direction, The second magnetic sensor is positioned so as to face the second magnet in the axial direction of the first sub-axis, The third magnet is positioned at the end of the second sub-shaft in the axial direction, The absolute encoder according to claim 2, wherein the third magnetic sensor is arranged to face the third magnet in the axial direction of the second sub-shaft.

5. The absolute encoder according to claim 1 or 2, wherein the number of teeth of the idler gear is less than the number of teeth of the first driven gear and the number of teeth of the second driven gear.

6. The number of teeth of the first idler gear is less than the number of teeth of the first spindle gear and the number of teeth of the first driven gear. The absolute encoder according to claim 3, wherein the number of teeth of the second idler gear is less than the number of teeth of the second spindle gear and the number of teeth of the second driven gear.

Images