absolute encoder

Abstract

To improve the detection accuracy of the rotation angle of a layshaft. In the absolute encoder (2) of the embodiment of the present application, a second worm wheel portion (41) is a second driven gear whose central axis is orthogonal to the central axis of a first worm wheel portion (21), and the second worm wheel portion (41) is engaged with a second worm portion (22). A support shaft (42) rotatably supports the second worm wheel portion (41). A magnet (Mq) rotates integrally with the support shaft (42). An angle sensor (Sq) is provided in the vicinity of the magnet (Mq) and detects a change in the magnetic flux generated from the magnet (Mq). An outer ring (432) of a first bearing (43) is fixed to the second worm wheel portion (41), and an inner ring (431) thereof is fixed to the support shaft (42). An inner ring (441) of a second bearing (44) is fixed to the support shaft (42).

Description

TECHNICAL FIELD

[0001] The present application relates to an absolute encoder. BACKGROUND

[0002] In the past, as a rotary encoder for detecting a position or an angle of a movable element in various control mechanical devices, an absolute encoder (hereinafter, referred to as "absolute encoder") of an absolute type that detects an absolute position or angle is known.

[0003] Among the absolute encoders, there is an encoder that measures a rotation amount of a main shaft based on a rotation angle of a sub shaft. Such an absolute encoder detects the rotation angle of the sub shaft based on a change in a magnetic field of a magnet that is fitted to the sub shaft or a tip end of a rotating body such as a gear of the sub shaft. The change in the magnetic field is detected by an opposed angle sensor provided to the magnet. The less the vibration of the rotating body, the higher the detection accuracy of the angle sensor.

[0004] However, in the absolute encoder, in a case where a pre-press is not provided to a bearing provided to the sub shaft, vibration due to rotation of the gear sometimes occurs in an outer ring of the bearing. The vibration of the outer ring of the bearing sometimes becomes a cause of error in detection of the rotation angle.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-24572 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] Therefore, in the absolute encoder, it is required to suppress the vibration of the ball bearing by a simple configuration.

[0010] The present application has been achieved in view of the above-described problems, and an object thereof is to provide an absolute encoder that can improve the detection accuracy of the rotation angle of the sub shaft.

[0011] MEANS FOR SOLVING THE PROBLEMS

[0012] To achieve the above object, the absolute encoder according to the present application includes: a first drive gear that rotates with rotation of a main shaft; a first driven gear whose central axis is orthogonal to a central axis of the first drive gear, the first driven gear being engaged with the first drive gear; a second drive gear that is provided coaxially with the first driven gear and rotates with rotation of the first driven gear; a second driven gear whose central axis is orthogonal to the central axis of the first driven gear, the second driven gear being engaged with the second drive gear; a support shaft that supports the second driven gear so as to be rotatable; a magnet that rotates integrally with the support shaft; an angle sensor that is provided in the vicinity of the magnet and detects a change in magnetic flux generated from the magnet; a first bearing whose outer ring is fixed to the second driven gear and whose inner ring is fixed to the support shaft; and a second bearing whose inner ring is fixed to the support shaft.

[0013] Effects of Invention

[0014] According to the absolute encoder of the present application, it is possible to improve the detection accuracy of the rotation angle of the sub shaft. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a perspective view that schematically shows the configuration of the absolute encoder according to the embodiment of the present application.

[0016] Figure 2 is a perspective view that schematically shows the configuration of the absolute encoder shown in Figure 1 FIG. 1, in a state where the shield plate is removed.

[0017] Figure 3 is a perspective view that schematically shows the configuration of the absolute encoder shown in Figure 2 FIG. 1, in a state where the housing is removed.

[0018] Figure 4 is a plan view that schematically shows the configuration of the absolute encoder shown in Figure 3 FIG. 1, in a state where the substrate is removed.

[0019] Figure 5 is a view of the angle sensor support substrate shown in Figure 3 FIG. 1, as viewed from the lower surface side.

[0020] Figure 6 is an A-A sectional view of the absolute encoder shown in Figure 4 FIG. 1.

[0021] Figure 7 is a B-B sectional view of the absolute encoder shown in Figure 4 FIG. 1.

[0022] Figure 8 is a C-C sectional view of the absolute encoder shown in Figure 4A C-C sectional view of the absolute encoder shown.

[0023] Figure 9 is Figure 4 A D-D sectional view of the absolute encoder shown.

[0024] Figure 10 is Figure 9 A sectional view of the first pinion in the absolute encoder shown.

[0025] Figure 11 is a schematic representation Figure 1 A block diagram of the functional configuration of the absolute encoder shown.

[0026] Figure 12 is Figure 9 A sectional view of the first pinion of a modification in the absolute encoder shown. DETAILED DESCRIPTION

[0027] The present inventors have found that, in an absolute encoder, the number of rotations of a main shaft (hereinafter, also referred to as the number of rotations of the main shaft) can be determined by acquiring the rotation angle of a rotating body that rotates at a reduced speed in accordance with the rotation of the main shaft. That is, the number of rotations of the main shaft can be determined by multiplying the rotation angle of the rotating body by the reduction ratio. Here, the range of the number of rotations of the main shaft that can be determined increases in proportion to the reduction ratio. For example, if the reduction ratio is 50, the number of rotations of the main shaft per 50 rotations can be determined.

[0028] On the other hand, the resolution of the rotating body required decreases in proportion to the reduction ratio. For example, if the reduction ratio is 100, the resolution required of the rotating body at the time of one rotation of the main shaft is 360° / 100 = 3.6°, and a detection accuracy of ±1.8° is required. On the other hand, in the case where the reduction ratio is 50, the resolution required of the rotating body at the time of one rotation of the main shaft is 360° / 50 = 7.2°, and a detection accuracy of ±3.6° is required.

[0029] Hereinafter, embodiments of the present application will be described with reference to the drawings. In the embodiments and modifications described below, the same or equivalent constituent elements and members are denoted by the same reference numerals, and repeated description will be appropriately omitted. Furthermore, the sizes of the members in the respective drawings are shown as being appropriately enlarged or reduced for the sake of convenience in understanding. Furthermore, in the respective drawings, a part of the members that is not important in terms of the description of the embodiments is omitted from the representation. Furthermore, in the drawings, gears are represented in a manner in which the tooth shapes are omitted. Furthermore, although terms including first, second, and the like are used for the description of various constituent elements, the terms are used only for the purpose of distinguishing one constituent element from another constituent element, and the constituent elements are not limited by the terms. Note that the present application is not limited by the present embodiments.

[0030] Figure 1 is a perspective view schematically showing the configuration of the absolute encoder 2 of the embodiment of the present application. Figure 2 is a perspective view schematically showing the configuration of the absolute encoder 2 in a state where the shield plate 7 is removed. In Figure 2 , the case 4 and the angle sensor support substrate 5 of the absolute encoder 2 are shown in a manner of being penetrated. Figure 3 is a perspective view schematically showing the configuration of the absolute encoder 2 in a state where the case 4 is removed. In Figure 3 , the angle sensor support substrate 5 of the absolute encoder 2 is shown in a manner of being penetrated. Figure 4 is a plan view schematically showing the configuration of the absolute encoder 2 in a state where the angle sensor support substrate 5 is removed. Figure 5 is a view of the angle sensor support substrate 5 as viewed from the lower side. Figure 6 is an A-A sectional view of the absolute encoder 2. Figure 7 is a B-B sectional view of the absolute encoder 2. Figure 8 is a C-C sectional view of the absolute encoder 2. Figure 9 is a D-D sectional view of the absolute encoder 2.

[0031] As shown in Figures 1 to 9 , the absolute encoder 2 of the embodiment of the present application is provided with a first worm portion 11, a first worm wheel portion 21, a second worm portion 22, a second worm wheel portion 41, a support shaft 42, a magnet Mq, an angle sensor Sq, a first bearing 43, and a second bearing 44. The first worm portion 11 serves as a first driving gear and rotates in accordance with the rotation of the main shaft la. The first worm wheel portion 21 serves as a first driven gear, the center axis of which is orthogonal to the center axis of the first worm portion 11, and the first worm wheel portion 21 is engaged with the first worm portion 11. The second worm portion 22 serves as a second driving gear and is provided coaxially with the first worm wheel portion 21 and rotates in accordance with the rotation of the first worm wheel portion 21. The second worm wheel portion 41 serves as a second driven gear, the center axis of which is orthogonal to the center axis of the first worm wheel portion 21, and the second worm wheel portion 41 is engaged with the second worm portion 22. The support shaft 42 supports the second worm wheel portion 41 so as to be rotatable. The magnet Mq serves as a permanent magnet and is provided in the second worm wheel portion 41 on the axis line A of the support shaft 42. The angle sensor Sq serves as an angle sensor provided in the vicinity of the magnet Mq, for example, on or near the axis line A, which can detect the change in the magnetic flux of the magnet Mq, and detects the rotation angle of the second worm wheel portion 41 corresponding to the change in the magnetic flux generated from the magnet Mq. In the case of the first bearing 43, the outer ring 432 is fixed to the second worm wheel portion 41 by press-fitting, and the inner ring 431 is fixed to the support shaft 42 by press-fitting. In the case of the second bearing 44, the inner ring 441 is fixed to the support shaft 42 by press-fitting. Hereinafter, the structure of the absolute encoder 2 will be described in detail.

[0032] In this embodiment, for ease of explanation, the absolute encoder 2 is described based on an XYZ orthogonal coordinate system. The X-axis corresponds to the horizontal left-right direction, the Y-axis corresponds to the horizontal front-back direction, and the Z-axis corresponds to the vertical up-down direction. The Y-axis and Z-axis are orthogonal to the X-axis. In this description, the X-axis is also referred to as the left or right side, the Y-axis as the front or back side, and the Z-axis as the top or bottom side. Figure 1 , Figure 2 In the pose of the absolute encoder 2 shown, the left side in the X-axis direction is the left side, and the right side in the X-axis direction is the right side. Furthermore, in Figure 1 , Figure 2 In the orientation of the absolute encoder 2 shown, the side in front of the heel in the Y-axis direction is the front side, and the side in the depth direction in the Y-axis direction is the rear side. Furthermore, in Figure 1 , Figure 2 In the orientation of the absolute encoder 2 shown, the upper side in the Z-axis direction is called the top side, and the lower side in the Z-axis direction is called the bottom side. The view from the top in the Z-axis direction is called the top view, the view from the front in the Y-axis direction is called the front view, and the view from the left in the X-axis direction is called the side view. This notation of orientation does not limit the orientation of the absolute encoder 2; the absolute encoder 2 can be used in any orientation.

[0033] like Figure 1 , Figure 2 As shown above, the absolute encoder 2 is an absolute encoder that determines and outputs the amount of rotation of the main shaft 1a of the motor 1 after multiple rotations. In an embodiment of the present invention, the absolute encoder 2 is located at the upper end of the motor 1 in the Z-axis direction. In an embodiment of the present invention, the absolute encoder 2 has a generally rectangular shape when viewed from above, and a horizontally elongated rectangular shape that is thin in the vertical direction, which is the extension direction of the main shaft 1a, when viewed from the front and side. That is, the absolute encoder 2 has a flat cuboid shape that is longer in the horizontal direction than in the vertical direction.

[0034] The absolute encoder 2 has a hollow, cylindrical housing 4 that houses its internal structure. The housing 4 includes multiple (e.g., four) outer wall portions 4a that surround at least a portion of the main shaft 1a of the motor 1, the main shaft gear 10, the first intermediate gear 20, the second intermediate gear 30, the first countershaft gear 40, and the second countershaft gear 50, with an open upper end. Within the housing 4, a shielding plate 7, which is a rectangular plate-like member serving as a magnetic flux shielding member, is fixed to the upper end of the four open outer wall portions 4a. This shielding plate 7 is fixed to the housing 4 and the gear base portion 3 by base plate mounting screws 8a.

[0035] The shield plate 7 is a plate-shaped member provided between the angle sensors Sp, Sq, and Sr and the outside of the absolute encoder 2 in the axial direction (Z-axis direction). The shield plate 7 is formed of a magnetic body in order to prevent the angle sensors Sp, Sq, and Sr provided inside the housing 4 from being subjected to magnetic interference caused by magnetic flux generated outside the absolute encoder 2.

[0036] As one example, the motor 1 can be a stepping motor or a DC brushless motor. As one example, the motor 1 can be a motor applied as a driving source of a robot for industry or the like, which is driven through a reduction mechanism such as a wave gear device. Both sides in the up-down direction of the main shaft la of the motor 1 protrude from the housing of the motor. The absolute encoder 2 outputs the amount of rotation of the main shaft la of the motor 1 as a digital signal.

[0037] The motor 1 has a substantially rectangular shape in plan view, and also has a substantially rectangular shape in the up-down direction. That is, the motor 1 has a substantially cubic shape. The length of each of the four outer wall portions constituting the outer shape of the motor 1 in plan view is, for example, 25 mm, that is, the outer shape of the motor 1 is a 25 mm quadrangle in plan view. Further, the absolute encoder 2 provided to the motor 1 is, for example, a 25 mm quadrangle in cooperation with the outer shape of the motor 1.

[0038] In Figure 1 , Figure 2 , the angle sensor support substrate 5 is provided so as to collectively cover the inside of the absolute encoder 2 with the housing 4 and the shield plate 7.

[0039] As shown in Figure 5 , the angle sensor support substrate 5 has a substantially rectangular shape in plan view, and is a thin plate-shaped printed circuit board in the up-down direction. Further, the connector 6 is connected to the angle sensor support substrate 5, and is a member for connecting the absolute encoder 2 and an external device (not shown).

[0040] As shown in Figure 2 , Figure 3 , Figure 4 , the absolute encoder 2 includes a main shaft gear 10 having a first worm portion 11 (first drive gear), and a first intermediate gear 20 having a first worm wheel portion 21 (first driven gear), a second worm portion 22 (second drive gear), and a third worm portion 28 (third drive gear). Further, the absolute encoder 2 includes a second intermediate gear 30 having a third worm wheel portion 31 (third driven gear) and a first spur gear portion 32 (fourth drive gear), a first counter shaft gear 40 having a second worm wheel portion 41 (second driven gear) and a support shaft 42 (see FIG. 2), and a second counter shaft gear 50 having a first spur gear portion 51 (fifth drive gear) and a support shaft 52 (see FIG. 2). Figure 9The absolute encoder 2 includes a magnet Mp, an angle sensor Sp corresponding to magnet Mp, a magnet Mq, an angle sensor Sq corresponding to magnet Mq, a magnet Mr, an angle sensor Sr corresponding to magnet Mr, and a microcomputer 121.

[0041] like Figure 4 , Figure 6 As shown, the main shaft 1a of the motor 1 is the output shaft of the motor 1 and the input shaft that transmits rotational force to the absolute encoder 2. The main shaft gear 10 is fixed to the main shaft 1a of the motor 1 and is rotatably supported integrally with the main shaft 1a by the bearing members of the motor 1. A first worm gear portion 11 is provided on the outer periphery of the main shaft gear 10 such that it rotates with the rotation of the main shaft 1a of the motor 1. In the main shaft gear 10, the first worm gear portion 11 is configured such that its central axis coincides with or is substantially coincident with the central axis of the main shaft 1a. The main shaft gear 10 can be formed of various materials such as resin or metal. For example, the main shaft gear 10 is formed of polyacetal resin.

[0042] like Figure 3 , Figure 4 As shown, the first intermediate gear 20 is the gear portion that transmits the rotation of the main shaft gear 10 to the first countershaft gear 40 and the second intermediate gear 30. The first intermediate gear 20 is pivotally supported by a shaft 23 around a rotation axis extending substantially parallel to the base 3b. The first intermediate gear 20 is a generally cylindrical component extending along its rotation axis. The first intermediate gear 20 includes a first worm gear portion 21, a second worm portion 22, and a third worm portion 28, with a through hole formed inside through which the shaft 23 is inserted. The first intermediate gear 20 is pivotally supported by inserting the shaft 23 into the first intermediate gear pivot support portion 3g provided in the base 3b of the gear base portion 3. The first worm gear portion 21, the second worm portion 22, and the third worm portion 28 are arranged in such a sequence that they are far apart from each other. The first intermediate gear 20 can be formed of various materials such as resin or metal. The first intermediate gear 20 is formed of polyacetal resin.

[0043] like Figure 4 , Figure 7 As shown, the first worm gear portion 21 is disposed on the outer periphery of the first intermediate gear 20. The first worm gear portion 21 is configured to mesh with the first worm portion 11 and rotate as the first worm portion 11 rotates. The axial angle between the first worm gear portion 21 and the first worm portion 11 is set to 90° or approximately 90°.

[0044] There is no particular limitation on the outer diameter of the first worm gear portion 21, but in the illustrated example, the outer diameter of the first worm gear portion 21 is set to be smaller than the outer diameter of the first worm portion 11, and the outer diameter of the first worm gear portion 21 is smaller. Thus, in the absolute encoder 2, miniaturization of the vertical dimension is achieved.

[0045] The second worm gear portion 22 is disposed on the outer periphery of the first intermediate gear 20. The second worm gear portion 22 rotates as the first worm wheel portion 21 rotates. The second worm gear portion 22 meshes with the second worm wheel portion 41 of the first countershaft gear 40 to rotate the first countershaft gear 40. In the first intermediate gear 20, the second worm gear portion 22 is configured such that its central axis coincides with or is substantially coincident with the central axis of the first worm wheel portion 21.

[0046] like Figure 4 , Figure 8 As shown, the third worm portion 28 is disposed on the outer periphery of the first intermediate gear 20. The third worm portion 28 rotates as the first worm wheel portion 21 rotates. The third worm portion 28 meshes with the third worm wheel portion 31 of the second intermediate gear 30 to rotate the second intermediate gear 30. In the first intermediate gear 20, the third worm portion 28 is configured such that its central axis coincides with or is substantially coincident with the central axis of the first worm wheel portion 21.

[0047] like Figure 4 , Figure 9 As shown, the first counterspindle gear 40 is decelerated as the main shaft 1a rotates, and rotates integrally with the magnet Mq. The first counterspindle gear 40 includes a second worm gear portion 41, a support shaft 42, a first bearing 43, a second bearing 44, and a first spacer 45. In the first counterspindle gear 40, the second worm gear portion 41 is pivotally supported by the support shaft 42.

[0048] Figure 10 This is a cross-sectional view of the first auxiliary shaft gear 40 in the absolute encoder 2.

[0049] like Figure 10 As shown, the second worm gear portion 41 is a generally circular component when viewed from above. The second worm gear portion 41 can be formed of various materials such as resin or metal. For example, the second worm gear portion 41 is formed of polyacetal resin. The second worm gear portion 41 includes a bearing housing portion 411, a magnet holding portion 412, and a stepped portion 413.

[0050] The second worm gear portion 41 is disposed on the outer periphery of the first countershaft gear 40 and is configured to mesh with the second worm portion 22, rotating as the second worm portion 22 rotates. The axial angle between the second worm gear portion 41 and the second worm portion 22 is set to 90° or approximately 90°. The axis of rotation of the second worm gear portion 41 is configured to be parallel or approximately parallel to the axis of rotation of the first worm portion 11.

[0051] The bearing accommodation portion 411 is a cylindrical hollow portion provided at a position centered on the axis A of the second worm portion 41. In the bearing accommodation portion 411, the side in the axis A direction, specifically the lower side in the Z-axis direction in Figure 9 , Figure 10 , is open. The dimension in the radial direction (direction perpendicular to the axis A, X-axis direction, Y-axis direction) of the inner peripheral portion 4111 of the bearing accommodation portion 411 is such that the outer rings 432, 442 of the first bearing 43 and the second bearing 44 can be press-fitted. The dimension in the axis A direction (Z-axis direction) of the bearing accommodation portion 411 is such that the outer rings 432, 442 of the first bearing 43 and the second bearing 44 can be accommodated in the axis A direction. Further, in the bearing accommodation portion 411, a stepped portion 413 is provided on the upper side in the Z-axis direction on the other side in the axis A direction, Figure 9 , Figure 10 . The stepped portion 413 is a ring-shaped surface parallel to the X-axis and the Y-axis, centered on the axis A. Note that the second worm portion 41 of the first counter shaft gear 40 can not be provided with the stepped portion 413, for example, in a case where the diameter of the magnet Mq is the same as the diameters of the first bearing 43 and the second bearing 44.

[0052] The magnet holding portion 412 is a ring-shaped hollow portion provided at a position centered on the axis A of the second worm portion 41, similarly to the bearing accommodation portion 411. The magnet holding portion 412 is formed so as to accommodate the magnet Mq. The magnet holding portion 412 is provided on the upper side in the Z-axis direction on the other side in the axis A direction than the stepped portion 413, in Figure 9 , Figure 10 . The magnet holding portion 412 holds the magnet Mq in the above-mentioned hollow portion.

[0053] The support shaft 42 supports the second worm portion 41 so as to be rotatable, via the first bearing 43 and the second bearing 44. The support shaft 42 protrudes substantially perpendicularly from the base portion 3b of the gear base portion 3.

[0054] The first bearing 43 has an inner ring 431, an outer ring 432, and rolling elements 433. The inner ring 431 is a ring-shaped member having an inner peripheral portion 4311 that can be fitted to the outer peripheral portion 421 of the support shaft 42. The outer ring 432 is provided on the outer peripheral side of the inner ring 431. The outer ring 432 is a ring-shaped member that is coaxial with the inner ring 431 and has a larger diameter than the inner ring 431. The rolling elements 433 are members that are configured with a plurality of spherical members between the inner ring 431 and the outer ring 432. In the first bearing 43, the inner ring 431 is press-fitted to the outer peripheral portion 421 of the support shaft 42. In the first bearing 43, the cylindrical portion 4322 of the outer ring 432 is press-fitted to the inner peripheral portion 4111 of the bearing accommodating portion 411 of the second worm wheel portion 41. In the first bearing 43, the disc portion 4321 on the axis A direction (Z-axis direction) upper side of the outer ring 432 abuts against the first spacer 45. In this way, the first bearing 43 is fixed to the second worm wheel portion 41 and the support shaft 42 with high accuracy in the axis A direction and the radial direction.

[0055] The second bearing 44 has an inner ring 441, an outer ring 442, and rolling elements 443. The inner ring 441 is a ring-shaped member having an inner peripheral portion 4411 that can be fitted to the outer peripheral portion 421 of the support shaft 42. The outer ring 442 is provided on the outer peripheral side of the inner ring 441. The outer ring 442 is a ring-shaped member that is coaxial with the inner ring 441 and has a larger diameter than the inner ring 441. The rolling elements 443 are members that are configured with a plurality of spherical members between the inner ring 441 and the outer ring 442. In the second bearing 44, the inner ring 441 is press-fitted to the outer peripheral portion 421 of the support shaft 42. In the second bearing 44, the disc portion 4421 on the axis A direction (Z-axis direction) upper side of the outer ring 442 abuts against the disc portion 4321 on the lower side of the outer ring 432 of the first bearing 43. Further, in the second bearing 44, the cylindrical portion 4422 of the outer ring 442 is press-fitted to the inner peripheral portion 4111 of the bearing accommodating portion 411 of the second worm wheel portion 41.

[0056] The first spacer 45 is a disc-shaped member having a ring-shaped disc portion 451 and a cylindrical cylindrical portion 452 centered on the axis A. The first spacer 45 is fitted to the inner peripheral portion 4111 of the bearing accommodating portion 411 in the radial direction. In the first spacer 45, the disc portion 4321 of the outer ring 432 on one side in the axis A direction (lower side in the Z-axis direction) abuts against. Further, in the first spacer 45, the magnet holding portion 412 of the second worm wheel portion 41 on the other side in the axis A direction (upper side in the Z-axis direction) abuts against by the magnet Mq.

[0057] By being configured in the above-described manner, in the absolute encoder 2, the plurality of bearings (the first bearing 43 and the second bearing 44) of the first countershaft gear 40 are press-fitted to the bearing accommodating portion 411 to be fixed, whereby the first countershaft gear 40 is fixed to the support shaft 42 with high accuracy in the axis A direction and the radial direction.

[0058] Magnet Mq is a permanent magnet located on the axis A of the support shaft 42, at the top end (upper side in the Z-axis direction) of the second worm gear portion 41. Magnet Mq is radially fitted into the inner circumference 4111 of the bearing housing portion 411. Magnet Mq is fixed to the upper side in the axis A direction of the bearing housing portion 411 by contacting the first spacer 45. An angle sensor Sq is similarly located on axis A, as with magnet Mq. Angle sensor Sq detects changes in magnetic flux generated by magnet Mq.

[0059] exist Figure 4 , Figure 8 In this configuration, the second intermediate gear 30 is a disc-shaped gear portion that rotates with the main shaft 1a and transmits the rotation of the main shaft 1a to the second counterspindle gear 50 in a decelerating manner. The second intermediate gear 30 is disposed between the second worm portion 22 and the second spur gear portion 51 disposed on the second counterspindle gear 50. The second spur gear portion 51 meshes with the first spur gear portion 32. The second intermediate gear 30 includes: a third worm gear portion 31 that meshes with the third worm portion 28 of the first intermediate gear 20; and a first spur gear portion 32 that drives the second spur gear portion 51. The second intermediate gear 30 is formed, for example, from polyacetal resin. The second intermediate gear 30 is a generally circular component when viewed from above. The second intermediate gear 30 is pivotally supported on the base 3b of the gear base portion 3.

[0060] By incorporating the second intermediate gear 30, the second countershaft gear 50 (described later) can be positioned away from the third worm gear portion 28. Therefore, the distance between magnets Mp and Mq can be increased, thereby reducing the influence of mutual leakage flux. Furthermore, by incorporating the second intermediate gear 30, the range of the reduction ratio can be expanded, increasing the design freedom.

[0061] The third worm gear portion 31 is disposed on the outer periphery of the second intermediate gear 30 and is configured to mesh with the third worm portion 28, rotating as the third worm portion 28 rotates. The first spur gear portion 32 is disposed on the outer periphery of the second intermediate gear 30 and is configured such that its central axis coincides with or is substantially coincident with the central axis of the third worm gear portion 31. The first spur gear portion 32 is configured to mesh with the second spur gear portion 51 and rotate as the third worm gear portion 31 rotates. The rotation axes of the third worm gear portion 31 and the first spur gear portion 32 are configured to be parallel to or substantially parallel to the rotation axis of the first worm portion 11.

[0062] exist Figure 8 In this configuration, the second counterspindle gear 50 is a circular gear portion that rotates with the main shaft 1a and transmits the rotation of the main shaft 1a to the magnet Mr in a decelerating manner. The second counterspindle gear 50 is pivotally supported around a rotation axis that extends substantially vertically from the base 3b of the gear base portion 3. The second counterspindle gear 50 includes a second spur gear portion 51 and a magnet holding portion that holds the magnet Mr.

[0063] The second spur gear portion 51 is provided on the outer periphery of the second lay shaft gear 50, and is provided so that the center axis thereof coincides or substantially coincides with the center axis of the first spur gear portion 32. The second spur gear portion 51 is provided so as to mesh with the first spur gear portion 32, and rotates along with the third worm gear portion 31. The rotational axis of the second spur gear portion 51 is provided so as to be parallel or substantially parallel to the rotational axis of the first spur gear portion 32. The second lay shaft gear 50 can be formed of various materials such as a resin material, a metal material, or the like. The second lay shaft gear 50 is formed of a polyacetal resin.

[0064] Here, a direction in which the first worm gear portion 21 is meshed with the first worm portion 11, and the first worm gear portion 21 is directed toward the first worm portion 11, is set as a first meshing direction P1 (arrow P1 direction of Figure 4 ). Similarly, a direction in which the second worm portion 22 is meshed with the second worm gear portion 41, and the second worm portion 22 is directed toward the second worm gear portion 41, is set as a second meshing direction P2 (arrow P2 direction of Figure 4 ). Furthermore, a direction in which the third worm portion 28 is meshed with the third worm gear portion 31, and the third worm portion 28 is directed toward the third worm gear portion 31, is set as a third meshing direction P3 (arrow P3 direction of Figure 4 ). In the present embodiment, the first meshing direction P1, the second meshing direction P2, and the third meshing direction P3 are all directions along the horizontal plane (XY plane).

[0065] The magnet Mp is fixed so that both center axes thereof coincide or substantially coincide with each other on the upper surface of the main shaft gear 10. The magnet Mp is supported by a retainer portion 16 to a magnet support portion 17 provided on the center axis of the main shaft gear 10. The retainer portion 16 is formed of a non-magnetic body such as an aluminum alloy. The inner peripheral surface of the retainer portion 16 is formed, for example, in a ring shape in correspondence with the shape of the outer diameter and the outer peripheral surface of the magnet Mp, so as to hold the outer peripheral surface of the magnet Mp with the inner peripheral surface of the retainer portion 16 abutting on the outer peripheral surface of the magnet Mp in the radial direction. Further, the inner peripheral surface of the magnet support portion 17 is formed, for example, in a ring shape in correspondence with the shape of the outer diameter and the outer peripheral surface of the retainer portion 16, so as to abut on the outer peripheral surface of the retainer portion 16. The magnet Mp has two magnetic poles arranged in a direction perpendicular to the rotational axis of the main shaft gear 10. The angle sensor Sp is provided on the lower surface 5a of the angle sensor support substrate 5 so as to oppose the upper surface of the magnet Mp in the vertical direction with a gap therebetween, in order to sense the rotational angle of the main shaft gear 10.

[0066] As one example, the angle sensor Sp is fixed to an angle sensor support substrate 5 that is supported by a substrate support 110 of a gear base portion 3 of the absolute encoder 2 described later. The angle sensor Sp senses the magnetic pole of the magnet Mp and outputs the sensing information to the microcomputer 121. The microcomputer 121 determines the rotation angle of the magnet Mp based on the sensing information relating to the magnetic pole that is input, and thereby determines the rotation angle of the main shaft gear 10, that is, the rotation angle of the main shaft la. The resolution of the rotation angle of the main shaft la corresponds to the resolution of the angle sensor Sp. As described later, the microcomputer 121 determines and outputs the rotation amount of the main shaft la based on the determined rotation angle of the first counter gear 40 and the determined rotation angle of the main shaft la. As one example, the microcomputer 121 can be configured to output the rotation amount of the main shaft la of the motor 1 as a digital signal.

[0067] The angle sensor Sq senses the rotation angle of the second worm gear portion 41, that is, the rotation angle of the first counter gear 40. The magnet Mq is fixed to both of the center axes of the first counter gear 40 so as to coincide or substantially coincide with each other on the upper surface of the first counter gear 40. The magnet Mq has two magnetic poles arranged in a direction perpendicular to the rotation axis of the first counter gear 40. As shown in FIG. 6, the angle sensor Sq is disposed so that the lower surface thereof opposes the upper surface of the magnet Mq in the vertical direction with a gap therebetween, in order to sense the rotation angle of the first counter gear 40. Figure 3

[0068] As one example, the angle sensor Sq is fixed to the angle sensor support substrate 5 on which the angle sensor Sp is fixed, on the same plane as the plane on which the angle sensor Sp is fixed. The angle sensor Sq senses the magnetic pole of the magnet Mq and outputs the sensing information to the microcomputer 121. The microcomputer 121 determines the rotation angle of the magnet Mq based on the sensing information relating to the magnetic pole that is input, that is, the rotation angle of the first counter gear 40.

[0069] The angle sensor Sr senses the rotation angle of the second spur gear portion 51, that is, the rotation angle of the second counter gear 50. The magnet Mr is fixed to both of the center axes of the second counter gear 50 so as to coincide or substantially coincide with each other on the upper surface of the second counter gear 50. The magnet Mr has two magnetic poles arranged in a direction perpendicular to the rotation axis of the second counter gear 50. As shown in FIG. 8, the angle sensor Sr is disposed so that the lower surface thereof opposes the upper surface of the magnet Mr in the vertical direction with a gap therebetween, in order to sense the rotation angle of the second counter gear 50. Figure 3

[0070] ​​As an example, the angle sensor Sr is fixed to an angle sensor support substrate 5 supported by a substrate support pillar 110 of a gear base portion 3 of the absolute encoder 2 described later. The angle sensor Sr senses the magnetic pole of the magnet Mr and outputs the sensing information to the microcomputer 121. The microcomputer 121 determines the rotation angle of the magnet Mr, that is, the rotation angle of the second lay shaft gear 50, based on the sensing information on the magnetic pole input.

[0071] A magnetic angle sensor having a higher resolution can also be used in each magnetic sensor. The magnetic angle sensor is disposed in opposition to the end surface of the magnetic pole including each permanent magnet with a certain gap in the axial direction of each rotating body, and determines the rotation angle of the opposing rotating body based on the rotation of the magnetic pole and outputs a digital signal. As an example, the magnetic angle sensor includes a sensing element that senses the magnetic pole and an arithmetic circuit that outputs a digital signal based on the output of the sensing element. The sensing element can include, for example, a plurality of (for example, four) Hall elements, GMR (Giant Magneto Resistive) elements, or the like.

[0072] The arithmetic circuit can determine the rotation angle by table processing using a look-up table, for example, using the difference or ratio of the outputs of a plurality of sensing elements as a key. The sensing element and the arithmetic circuit can be integrated on one IC chip. The IC chip can be embedded in resin having a rectangular parallelepiped shape. Each magnetic sensor outputs an angle signal corresponding to the sensed rotation angle of each rotating body as a digital signal to the microcomputer 121 through a wiring member not shown. For example, each magnetic sensor outputs the rotation angle of each rotating body as a digital signal of a plurality of bits (for example, 7 bits).

[0073] Figure 11 is a block diagram schematically showing the functional configuration of the absolute encoder. As shown in Figure 11 The microcomputer 121 is fixed to the face of the gear base portion 3 on the base 3b side of the angle sensor support substrate 5 by welding, adhesion, or the like. The microcomputer 121 is configured of a CPU, acquires digital signals indicating the rotation angles output from the angle sensors Sp, Sq, and Sr, respectively, and calculates the rotation amount of the main shaft gear 10. Figure 11The modules of the microcomputer 121 shown are configured to express functions (functions) realized by execution of programs by the CPU of the microcomputer 121. In terms of the modules of the microcomputer 121, on the hardware side, they can be realized by elements represented by a CPU (Central Processing Unit) and a RAM (Random Access Memory) of a computer, mechanical devices, and the like, and on the software side, they can be realized by computer programs and the like, but the functional modules realized by cooperation of these are described here. Therefore, it should be understood by those skilled in the art who come across this specification that these functional modules can be realized in various forms by a combination of hardware and software.

[0074] The microcomputer 121 has a rotation angle acquisition section 121p, a rotation angle acquisition section 121q, a rotation angle acquisition section 121r, a table processing section 121b, a rotation amount determination section 121c, and an output section 121e. The rotation angle acquisition section 121p acquires a rotation angle Ap that is angle information indicating a rotation angle of the main shaft gear 10, i.e., the main shaft 1a, based on a signal output from the angle sensor Sp. The rotation angle acquisition section 121q acquires a rotation angle Aq that is angle information indicating a rotation angle of the first countershaft gear 40 based on a signal output from the angle sensor Sq. The rotation angle acquisition section 121r acquires a rotation angle Ar that is angle information indicating a rotation angle of the second countershaft gear 50 sensed by the angle sensor Sr.

[0075] The table processing section 121b refers to a first correspondence table in which the rotation angle Ap and the number of revolutions of the main shaft gear 10 corresponding to the rotation angle Ap are stored, and determines the number of revolutions of the main shaft gear 10 corresponding to the acquired rotation angle Ap. In addition, the table processing section 121b refers to a second correspondence table in which the rotation angle Ar and the number of revolutions of the main shaft gear 10 corresponding to the rotation angle Ar are stored, and determines the number of revolutions of the main shaft gear 10 corresponding to the acquired rotation angle Ar.

[0076] The rotation amount determination section 121c determines a first rotation amount in which the main shaft gear 10 is rotated a plurality of times, based on the number of revolutions of the main shaft gear 10 determined by the table processing section 121b and the acquired rotation angle Aq. The output section 121e converts the rotation amount in which the main shaft gear 10 is rotated a plurality of times, determined by the rotation amount determination section 121c, into information indicating the rotation amount and outputs it.

[0077] Note that the table processing section 121b, the rotation amount determining section 121c, and the output section 121e also function as an angle position information output section that outputs angle position information of the first worm section 11 to an external control device (controller) as described later. Further, the table processing section 121b, the rotation amount determining section 121c, and the output section 121e also output angle error information for correcting the angle position information of the first worm section 11 to the external control device as also described later.

[0078] The absolute encoder 2 thus configured is able to determine the number of rotations of the main shaft 1a from the rotation angles of the first countershaft gear 40 and the second countershaft gear 50 determined based on the sensing information of the angle sensors Sq, Sr, and determine the rotation angle of the main shaft 1a based on the sensing information of the angle sensor Sp. Further, the microcomputer 121 determines the rotation amount of the main shaft 1a for a plurality of rotations based on the determined number of rotations of the main shaft 1a and the rotation angle of the main shaft 1a.

[0079] The number of the first worm section 11 provided to the main shaft gear 10 of the main shaft 1a is, for example, 1, and the number of teeth of the first worm wheel section 21 is, for example, 20. That is, the first worm section 11 and the first worm wheel section 21 constitute a first speed change mechanism (refer to FIG. 2) having a speed reduction ratio of 20 / 1 = 20. Figure 4 When the first worm section 11 rotates 20 times, the first worm wheel section 21 rotates 1 time. The first worm wheel section 21 and the second worm section 22 are provided coaxially to constitute the first intermediate gear 20, and rotate integrally, and thus, when the first worm section 11 rotates 20 times, that is, when the main shaft 1a and the main shaft gear 10 rotate 20 times, the first intermediate gear 20 rotates 1 time, and the second worm section 22 rotates 1 time.

[0080] The number of the second worm section 22 is, for example, 5, and the number of teeth of the second worm wheel section 41 is, for example, 25. That is, the second worm section 22 and the second worm wheel section 41 constitute a second speed change mechanism (refer to FIG. 2) having a speed reduction ratio of 25 / 5 = 5. Figure 4 When the second worm section 22 rotates 5 times, the second worm wheel section 41 rotates 1 time. The first countershaft gear 40 in which the second worm wheel section 41 is formed rotates integrally with the magnet holder 35 and the magnet Mq as described later, and thus, when the second worm section 22 constituting the first intermediate gear 20 rotates 5 times, the magnet Mq rotates 1 time. In summary, when the main shaft 1a rotates 100 times, the first intermediate gear 20 rotates 5 times, and the first countershaft gear 40 and the magnet Mq rotate 1 time. That is, the number of rotations of the amount of 50 rotations of the main shaft 1a can be determined from the sensing information of the angle sensor Sq related to the rotation angle of the first countershaft gear 40.

[0081] The third worm gear section 28 has, for example, 1 tooth, and the third worm wheel section 31 has, for example, 30 teeth. That is, the third worm gear section 28 and the third worm wheel section 31 constitute a third transmission mechanism with a reduction ratio of 30 / 1 = 30 (see reference). Figure 4 When the third worm gear 28 rotates 30 times, the third worm wheel 31 rotates 1 time. A first spur gear 32 is provided in the second intermediate gear 30, where the third worm wheel 31 is formed. This first spur gear 32 has a central axis that is aligned with or substantially aligned with the central axis of the third worm wheel 31. Therefore, when the third worm wheel 31 rotates, the first spur gear 32 also rotates. The first spur gear 32 meshes with the second spur gear 51 provided in the second counterspindle gear 50; therefore, when the second intermediate gear 30 rotates, the second counterspindle gear 50 also rotates.

[0082] The second spur gear 51 has, for example, 40 teeth, and the first spur gear 32 has, for example, 24 teeth. That is, the first spur gear 32 and the second spur gear 51 constitute a fourth transmission mechanism with a reduction ratio of 40 / 24 = 5 / 3 (see reference). Figure 4 When the first spur gear 32 rotates 5 revolutions, the second spur gear 51 rotates 3 revolutions. The second counterspindle gear 50, to which the second spur gear 51 is formed, rotates integrally with the magnet Mr as described later. Therefore, when the third worm gear 28, which constitutes the first intermediate gear 20, rotates 5 revolutions, the magnet Mr rotates 1 revolution. In summary, when the main shaft 1a rotates 1000 revolutions, the first intermediate gear 20 rotates 50 revolutions, the second intermediate gear 30 rotates 5 / 3 revolutions, and the second counterspindle gear 50 and the magnet Mr rotate 1 revolution. That is, the number of revolutions required for the main shaft 1a to rotate 1000 revolutions can be determined based on sensing information from the angle sensor Sr related to the rotation angle of the second counterspindle gear 50.

[0083] [The role of an absolute encoder]

[0084] The function of the absolute encoder 2 will be explained below.

[0085] As described above (refer to) Figures 1 to 11 The first secondary shaft gear 40 of the absolute encoder 2 includes a second worm gear portion 41 serving as a second driven gear, a support shaft 42, a first bearing 43, a second bearing 44, and a first spacer 45. Regarding the first bearing 43 and the second bearing 44, outer rings 432 and 442 are pressed into a bearing receiving portion 411, which is a cylindrical cavity formed at a position centered on the axis A of the second worm gear portion 41. Furthermore, regarding the first bearing 43 and the second bearing 44, inner rings 431 and 441 are pressed into the support shaft 42.

[0086] By being configured in the above-described manner, in the absolute encoder 2, the plurality of bearings, i.e., the outer ring 432 of the first bearing 43 and the outer ring 442 of the second bearing 44, of the first countershaft gear 40 that are fixed to the support shaft 42 are fixed to the inner circumferential portion 4111 of the bearing housing portion 411. Therefore, according to the absolute encoder 2, the inclination of the outer ring 432 of the first bearing 43 and the outer ring 442 of the second bearing 44 with respect to the support shaft 42 can be suppressed. That is, according to the absolute encoder 2, the movement of the first bearing 43 and the second bearing 44 inside the bearing housing portion 411 can be suppressed, and the vibration of the outer rings 432, 442 of the first bearing 43 and the second bearing 44 that occurs due to the rotation of the second worm portion 41 can be suppressed. Therefore, according to the absolute encoder 2, the error in the detection of the rotational angle can be suppressed.

[0087] Further, in the absolute encoder 2, the first spacer 45 is housed in the bearing housing portion 411. In the first spacer 45, the disc portion 451 on the axis A direction side abuts against the magnet Mq held in the magnet holding portion 412. Further, the first spacer 45 abuts against the disc portion 4321 of the outer ring 432 of the first bearing 43 from the axis A direction. Due to the provision of the first spacer 45, in the absolute encoder 2, the outer ring 432 of the first bearing 43 abuts against (comes into contact with) the first spacer 45 on the axis A direction side, and thus the inclination of the outer ring 432 with respect to the support shaft 42 (axis A) can be suppressed. Further, in the absolute encoder 2, the disc portion 4421 of the outer ring 442 of the second bearing 44 abuts against the disc portion 4321 of the outer ring 432 of the first bearing 43 that abuts against the first spacer 45 on the axis A direction, and thus the inclination of the outer ring 442 with respect to the support shaft 42 (axis A) can be suppressed.

[0088] That is, in the absolute encoder 2, the plurality of bearings (first bearing 43 and second bearing 44) are fitted and fixed in a manner of being pressed into the bearing housing portion 411, and thus the first countershaft gear 40 is supported with high precision in the axis A direction and the radial direction with respect to the support shaft 42.

[0089] Therefore, according to the absolute encoder 2, the movement of the first bearing 43 and the second bearing 44 inside the bearing housing portion 411 can be suppressed, and the vibration of the outer rings 432, 442 of the first bearing 43 and the second bearing 44 that occurs due to the rotation of the second worm portion 41 can be suppressed. Therefore, according to the absolute encoder 2, the error in the detection of the rotational angle can be suppressed.

[0090] According to the above-described absolute encoder 2, the detection precision of the rotational angle of the countershaft can be improved.

[0091] [Modified Example of First Countershaft Gear]

[0092] Next, a modified example of the first countershaft gear 40 in the above-described absolute encoder 2 will be described.

[0093] Figure 12 is an enlarged sectional view of the first counter shaft gear 40B which is a modification of the absolute encoder 2.

[0094] As Figure 12 shown, in the first counter shaft gear 40B of the modification, the shape of the bearing accommodating portion 411B which is a cylindrical cavity portion provided at a position centered on the axis A of the second worm gear portion 41 is different from the bearing accommodating portion 411 described above. Further, in the first counter shaft gear 40B, the point at which the second spacer 46 is provided between the first bearing 43 and the second bearing 44 is different from the first counter shaft gear 40 described above. Hereinafter, the configuration of the first counter shaft gear 40B of the modification in the absolute encoder 2 will be described in detail.

[0095] In the bearing accommodating portion 411B, the dimension in the radial direction (X-axis direction, Y-axis direction) is set to be larger than the inner peripheral portion 4111B, that is, the enlarged diameter portion 4112 in which the outer rings 432, 442 of the first bearing 43 and the second bearing 44 are enlarged in diameter, in the vicinity of the open end on the lower side in the Z-axis direction. Due to the provision of the enlarged diameter portion 4112, the cylindrical portion 4422 of the outer ring 442 of the second bearing 44 is not pressed into the bearing accommodating portion 411B of the second worm gear portion 41B.

[0096] The second spacer 46 is provided between the first bearing 43 and the second bearing 44 in the axis A direction as described above. The second spacer 46 abuts against the disc portion 4321 on the lower side of the outer ring 432 of the first bearing 43 and the disc portion 4421 on the upper side of the outer ring 442 of the second bearing 44 from the axis A direction. Desirably, the second spacer 46 is a ring-shaped member formed of an elastomer like a rubber sheet or an O-ring.

[0097] By being configured in the above-described manner, in the absolute encoder 2 provided with the first counter shaft gear 40B, the outer ring 432 of the first bearing 43 is fixed to the inner peripheral portion 4111B of the bearing accommodating portion 411B. Therefore, according to the absolute encoder 2, the inclination of the outer ring 432 of the first bearing 43 can be suppressed similarly to the absolute encoder 2 provided with the first counter shaft gear 40 described above.

[0098] Further, in the absolute encoder 2 provided with the first counter shaft gear 40B, in the bearing accommodating portion 411B, the second spacer 46 is accommodated between the first bearing 43 and the second bearing 44. The second spacer 46 abuts against the disc portion 4321 on the lower side of the outer ring 432 of the first bearing 43 and the disc portion 4421 on the upper side of the outer ring 442 of the second bearing 44 from the axis A direction, and exerts an elastic force against the disc portions 4321, 4421. Due to the provision of the second spacer 46, in the absolute encoder 2, the outer ring 442 of the second bearing 44 can be pre-pressed from the upper side in the axis A direction, and thus the inclination of the outer ring 442 can be suppressed.

[0099] That is, according to the absolute encoder 2 provided with the first layshaft gear 40B, the movement of the first bearing 43 and the second bearing 44 inside the bearing housing portion 411 is suppressed, and the vibration of the outer rings 432, 442 of the first bearing 43 and the second bearing 44 generated according to the rotation of the second worm portion 41 is suppressed. Thus, according to the absolute encoder 2, the error of the detection of the rotation angle is suppressed.

[0100] According to the absolute encoder 2 provided with the first layshaft gear 40B of the modification described above, the detection accuracy of the rotation angle of the layshaft can be improved similarly to the absolute encoder 2 provided with the first layshaft gear 40 described above.

[0101] The embodiments of the present application have been described above, but the present application includes all aspects included in the concept of the present application and the claims, and is not limited to the absolute encoder 2 of the above-described embodiments of the present application. Furthermore, in order to achieve at least a part of the above-described problems and effects, each of the configurations can be appropriately combined, or can be combined with publicly known technologies. For example, the shape, material, arrangement, size, and the like of each of the configuration elements in the above-described embodiments can be appropriately changed according to the specific use aspect of the present application.

[0102] For example, it can also be that, in the absolute encoder 2, the configuration of the above-described first layshaft gear 40, 40B is combined with the second layshaft gear 50, and the vibration of the second layshaft gear 50 is suppressed to improve the detection accuracy of the rotation angle of the layshaft.

[0103] For example, in the absolute encoder 2, the bearings provided in the above-described first layshaft gear 40, 40B are not limited to the two of the first bearing 43 and the second bearing 44, and can be three or more. In this case, as for the bearings into which the outer rings are pressed, it is sufficient that the outer ring of at least one bearing is pressed into the first layshaft gear 40, 40B.

[0104] For example, in the absolute encoder 2, as for the shape of the first spacer 45 provided in the first layshaft gear 40, 40B, it is sufficient that the first spacer 45 abuts against the outer ring 432 of the first bearing 43. In other words, the shape of the first spacer 45 is only required to be a configuration in which the inner ring 431 and the support shaft 42 do not come into contact with the magnet Mq and the first spacer 45. Thus, the shape of the first spacer 45 is not limited to the above-described ring shape, and for example, can be a disc shape with a recess in a part thereof.

[0105] Explanation of Reference Signs

[0106] 1: motor;

[0107] 1a: main shaft;

[0108] 1b: press-in portion;

[0109] 2: absolute encoder;

[0110] 3: gear base portion;

[0111] 4: housing;

[0112] 4a: outer wall portion;

[0113] 5: angle sensor support substrate;

[0114] 5a: lower surface;

[0115] 6: connector;

[0116] 7: shield plate;

[0117] 8a: substrate mounting screw;

[0118] 10: main shaft gear;

[0119] 11: first worm portion;

[0120] 16: retainer portion;

[0121] 17: magnet support portion;

[0122] 20: first intermediate gear;

[0123] 21: first worm wheel portion;

[0124] 22: second worm portion;

[0125] 23: shaft;

[0126] 28: third worm portion;

[0127] 30: second intermediate gear;

[0128] 31: third worm wheel portion;

[0129] 32: first spur gear portion;

[0130] 35: magnet retainer;

[0131] 40, 40B: first counter shaft gear;

[0132] 41, 41B: second worm wheel portion;

[0133] 42: support shaft;

[0134] 43: first bearing;

[0135] 44: second bearing;

[0136] 45: first spacer;

[0137] 46: second spacer;

[0138] 50: second lay shaft gear;

[0139] 51: second spur gear portion;

[0140] 121: microcomputer;

[0141] 121b: table processing portion;

[0142] 121c: rotation amount determination portion;

[0143] 121e: output portion;

[0144] 121p: rotation angle acquisition portion;

[0145] 121q: rotation angle acquisition portion;

[0146] 121r: rotation angle acquisition portion;

[0147] 411, 411B: bearing housing portion;

[0148] 412: magnet holding portion;

[0149] 413: step portion;

[0150] 421: outer peripheral portion;

[0151] 431: inner ring;

[0152] 432: outer ring;

[0153] 433: rolling element;

[0154] 441: inner ring;

[0155] 442: outer ring;

[0156] 443: rolling element;

[0157] 451: disc portion;

[0158] 452: cylindrical portion;

[0159] 4111, 4311, 4411, 4111B: inner peripheral portion;

[0160] 4112: diameter expansion portion;

[0161] 4321, 4421: disc portion;

[0162] 4322, 4422: cylindrical portion

[0163] Mp, Mq, Mr: magnet;

[0164] Sp, Sq, Sr: angle sensor.

Claims

1. An absolute encoder comprising: a first drive gear that rotates with rotation of a spindle; a first driven gear whose central axis is orthogonal to a central axis of the first drive gear, the first driven gear being engaged with the first drive gear; a second drive gear that is provided coaxially with the first driven gear and rotates with rotation of the first driven gear; a second driven gear whose central axis is orthogonal to the central axis of the first driven gear, the second driven gear being engaged with the second drive gear; a support shaft that supports the second driven gear so as to be rotatable; a magnet that rotates integrally with the second driven gear; an angle sensor that is provided in the vicinity of the magnet and detects a change in magnetic flux generated from the magnet; a first bearing whose outer ring is fixed to the second driven gear and whose inner ring is fixed to the support shaft; and a second bearing whose inner ring is fixed to the support shaft, the second driven gear having a cylindrical bearing accommodating portion as a hollow portion at a position centered on an axis, the outer ring of the first bearing being fixed to the bearing accommodating portion by press-fitting, the outer ring of the second bearing being fixed to the bearing accommodating portion by press-fitting, the radial dimension and the axial dimension of the bearing accommodating portion being dimensions in which the outer rings of the first and second bearings can be press-fitted, and the absolute encoder having a first spacer that is accommodated in the bearing accommodating portion and abuts against the outer ring of the first bearing in the axial direction.

2. An absolute encoder comprising: a first drive gear that rotates with rotation of a spindle; a first driven gear whose central axis is orthogonal to a central axis of the first drive gear, the first driven gear being engaged with the first drive gear; a second drive gear that is provided coaxially with the first driven gear and rotates with rotation of the first driven gear; a second driven gear whose central axis is orthogonal to the central axis of the first driven gear, the second driven gear being engaged with the second drive gear; a support shaft that supports the second driven gear so as to be rotatable; a magnet that rotates integrally with the second driven gear; an angle sensor that is provided in the vicinity of the magnet and detects a change in magnetic flux generated from the magnet; a first bearing whose outer ring is fixed to the second driven gear and whose inner ring is fixed to the support shaft; and a second bearing whose inner ring is fixed to the support shaft, the second driven gear having a cylindrical bearing accommodating portion as a hollow portion at a position centered on an axis, the bearing accommodating portion having a diameter-expanded portion that expands the diameter of the outer ring of the second bearing, the outer ring of the first bearing being fixed to the bearing accommodating portion, the absolute encoder further comprising: a second spacer composed of an elastic body, which is provided between the first bearing and the second bearing and abuts against the outer rings of the first and second bearings in the axial direction, the radial dimension and the axial dimension of the bearing accommodating portion being dimensions in which the outer rings of the first and second bearings can be press-fitted. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The second bearing is not pressed into the bearing accommodation portion, and an outer ring of the second bearing is pre-pressed from an axial direction by the second spacer.

3. The absolute encoder according to claim 1 or 2, comprising: a first spacer that is accommodated in the bearing accommodation portion in a radial direction by fitting with an inner peripheral portion of the bearing accommodation portion, and that abuts against an outer ring of the first bearing in an axial direction.

4. The absolute encoder according to claim 3, wherein: one side in the axial direction of the bearing accommodation portion is open, the first spacer abuts against the inner peripheral portion of the bearing accommodation portion in the radial direction, and abuts against the outer ring of the first bearing in the axial direction.

5. The absolute encoder according to claim 1 or 2, wherein: the outer ring of the second bearing abuts against the outer ring of the first bearing in the axial direction.

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