absolute encoder

Abstract

This invention improves the detection accuracy of the rotation angle of a rotating shaft caused by the magnetic flux distribution of a magnet. In the absolute encoder (2), one end of the support shaft (42) is fixed to the gear base (3) which serves as a base plate, and the other end has a flange (423). The inner rings of the first bearing (43) and the second bearing (44), which serve as at least one bearing, are fixed to the support shaft (42). The first bearing (43) and the second bearing (44) are disposed between the gear base (3) and the flange (423) in the axial direction. A spacer (45) is disposed between the first bearing (43) and the second bearing (44) and the magnet (Mq) in the axial direction of the support shaft (42). The spacer (45) abuts against the outer rings of the first bearing (43) and the second bearing (44) in the axial direction inside the bearing fixing part (411).

Description

Technical Field

[0001] This invention relates to an absolute encoder. Background Technology

[0002] Previously, as rotary encoders used to detect the position and angle of movable elements in various control mechanisms, there is a known absolute encoder (hereinafter referred to as "absolute encoder") that detects absolute position or angle.

[0003] An absolute encoder is one that measures the rotation of the main shaft based on the rotation angle of the secondary shaft. Such an absolute encoder detects the rotation angle of the secondary shaft based on changes in the magnetic field of a magnet, which is mounted on the top of the secondary shaft or a rotating body such as a gear mounted on the secondary shaft. The change in the magnetic field is detected by an angle sensor positioned opposite the magnet. The smaller the influence of magnetic flux other than that from the magnet of the object being detected, the higher the detection accuracy of the angle sensor.

[0004] It should be noted that a rotation detection device is known, which includes: two magnetic encoders having concentric annular magnetization patterns with magnetic poles arranged on the circumference respectively, and the number of magnetic poles being different; and magnetic sensors for detecting the magnetic fields of the magnetic encoders respectively. In this rotation detection device, a spacer of magnetic material is provided between the magnetization patterns of the two magnetic encoders (for example, see Patent Document 1).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2008-267868 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In the rotating shaft of an absolute encoder, such as in the secondary shaft, a bearing is positioned directly below the magnet used for angle detection. In this type of rotating shaft construction, the bearing, as a magnetic component, acts as a magnetic circuit. Sometimes, disturbances occur in the magnetic flux distribution on the angle detection side (upper side) of the magnet, deteriorating the accuracy of angle error detection.

[0010] The present invention was made in view of the above-mentioned problems, and its object is to provide an absolute encoder that can improve the detection accuracy of the rotation angle of a rotating shaft caused by the magnetic flux distribution of a magnet.

[0011] Solution for solving the problem

[0012] To achieve the above objectives, the absolute encoder of the present invention comprises: a support shaft, one end of which is fixed to a substrate and the other end having a flange; at least one bearing, the inner ring of which is fixed to the support shaft; a magnetized magnet; a spacer disposed between the bearing and the magnet in the axial direction of the support shaft; a magnet retainer for retaining the magnet; and a magnetic sensor for sensing magnetic flux from the magnet, the magnet retainer having: a bearing fixing portion, which is a recess open on one side in the axial direction and fixed to the outer ring of the bearing; and a magnet retaining portion, which is a recess formed on the other end side of the bearing fixing portion, the bearing being disposed between the substrate and the flange in the axial direction, and the spacer abutting against the outer ring of the bearing from the axial direction inside the bearing fixing portion.

[0013] In one embodiment of the absolute encoder of the present invention, the substrate has a hole through which the support shaft is inserted, the support shaft has an external thread at one end, and the external thread is inserted through the hole to fix the support shaft and the bearing together to the substrate.

[0014] In one aspect of the present invention, the absolute encoder includes a washer disposed between the substrate and the bearing in the axial direction.

[0015] In one embodiment of the absolute encoder of the present invention, the spacer abuts against the inner periphery of the bearing fixing portion in the radial direction and against the outer ring of the bearing in the axial direction.

[0016] In one embodiment of the absolute encoder of the present invention, the flange portion has a surface on one end in the axial direction facing the inner ring of the bearing.

[0017] In one embodiment of the absolute encoder of the present invention, the spacer is formed in an annular shape, and the flange is disposed on the inner side of the inner circumferential surface.

[0018] In one embodiment of the absolute encoder of the present invention, the support shaft is formed of a magnetic material.

[0019] Invention Effects

[0020] The absolute encoder of the present invention can improve the detection accuracy of the rotation angle of the rotating shaft caused by the magnetic flux distribution of the magnet. Attached Figure Description

[0021] Figure 1 This is a perspective view that schematically illustrates the configuration of an absolute encoder according to an embodiment of the present invention.

[0022] Figure 2 This is a rough representation with the shielding plate removed. Figure 1The diagram shows a three-dimensional representation of the structure of an absolute encoder.

[0023] Figure 3 This is a rough representation with the casing removed. Figure 2 The diagram shows a three-dimensional representation of the structure of an absolute encoder.

[0024] Figure 4 This is a rough representation with the substrate removed. Figure 3 The diagram shows a top view of the structure of an absolute encoder.

[0025] Figure 5 Viewed from the lower surface side Figure 3 The diagram shows the support substrate for the angle sensor.

[0026] Figure 6 yes Figure 4 The image shows an AA cross-sectional view of the absolute encoder.

[0027] Figure 7 yes Figure 4 The BB cross-sectional view of the absolute encoder is shown.

[0028] Figure 8 yes Figure 4 The CC cross-sectional view of the absolute encoder is shown.

[0029] Figure 9 yes Figure 4 The DD cross-sectional view of the absolute encoder is shown.

[0030] Figure 10 yes Figure 9 A cross-sectional view of the first auxiliary shaft gear in the absolute encoder shown.

[0031] Figure 11 It is a general representation Figure 1 The diagram shows the functional structure of an absolute encoder. Detailed Implementation

[0032] The inventors have discovered that in an absolute encoder, the amount of rotation of the spindle after multiple rotations (hereinafter also referred to as "the amount of spindle rotation") can be determined by acquiring the rotation angle of a rotating body that decelerates as the spindle rotates. That is, the amount of spindle rotation can be determined by multiplying the rotation angle of the rotating body by the reduction ratio. Here, the range of the spindle rotation amount that can be determined increases proportionally with the reduction ratio. For example, if the reduction ratio is 50, the amount of rotation of the spindle for every 50 rotations can be determined.

[0033] On the other hand, the required resolution of the rotating body decreases proportionally with the reduction ratio. For example, if the reduction ratio is 100, the required resolution of the rotating body is 360° / 100 = 3.6° per spindle revolution, requiring a detection accuracy of ±1.8°. On the other hand, with a reduction ratio of 50, the required resolution of the rotating body is 360° / 50 = 7.2° per spindle revolution, requiring a detection accuracy of ±3.6°.

[0034] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the embodiments and variations described below, the same or equivalent constituent elements and components are labeled with the same reference numerals, and repeated descriptions are omitted where appropriate. Furthermore, the dimensions of the components in each drawing are shown at appropriate enlargements or reductions for ease of understanding. Additionally, in each drawing, portions of components that are not important for the description of the embodiments are omitted. Furthermore, gears are shown in the drawings with the tooth shape omitted. Furthermore, although terms including ordinal numbers such as first and second are used to describe various constituent elements, these terms are used only for the purpose of distinguishing one constituent element from others, and the constituent elements are not limited by these terms. It should be noted that the present invention is not limited to these embodiments.

[0035] Figure 1 This is a perspective view that schematically illustrates the configuration of the absolute encoder 2 according to an embodiment of the present invention. Figure 2 This is a three-dimensional diagram roughly showing the structure of the absolute encoder 2 with the shielding plate 7 removed. Figure 2 In the middle, it is shown through the housing 4 of the absolute encoder 2 and the angle sensor support substrate 5. Figure 3 This is a perspective view roughly showing the structure of the absolute encoder 2 with the housing 4 removed. Figure 3 In the middle, it is shown in the form of an angle sensor support substrate 5 through an absolute encoder 2. Figure 4 This is a top view that roughly shows the configuration of the absolute encoder 2 with the angle sensor support base plate 5 removed. Figure 5 This is a diagram of the angle sensor support substrate 5 viewed from below. Figure 6 This is an AA cross-sectional view of the absolute encoder 2. Figure 7 This is a BB cross-sectional view of the absolute encoder 2. Figure 8 This is a CC cross-sectional view of the absolute encoder 2. Figure 9 This is a DD cross-sectional view of the absolute encoder 2.

[0036] like Figures 1 to 9As shown, the absolute encoder 2 according to an embodiment of the present invention includes: a first countershaft gear 40; a support shaft 42; a magnet Mq; an angle sensor Sq; a bearing fixing portion 411; a magnet holding portion 412; a first bearing 43; a second bearing 44; and a spacer 45. One end of the support shaft 42 is fixed to the gear base 3, which serves as a base plate, and the other end has a flange portion 423. The magnet Mq is magnetized. The first countershaft gear 40 also functions as a magnet holding portion for holding the magnet Mq. The angle sensor Sq functions as a magnetic sensor for sensing the magnetic flux from the magnet Mq. The bearing fixing portion 411 is provided on the first countershaft gear 40. The bearing fixing portion 411 is a recess open on one side in the axial direction and is fixed to the outer ring of the first bearing 43 and the second bearing 44. The magnet holding portion 412 is a recess formed in the first countershaft gear 40 on the other end side of the bearing fixing portion 411. The inner rings of the first bearing 43 and the second bearing 44, which are at least one bearing, are fixed to the support shaft 42. The first bearing 43 and the second bearing 44 are disposed between the gear base 3 and the flange portion 423 in the axial direction. A spacer 45 is disposed between the first bearing 43, the second bearing 44, and the magnet Mq in the axial direction of the support shaft 42. The spacer 45 abuts against the outer rings of the first bearing 43 and the second bearing 44 in the axial direction inside the bearing fixing portion 411. The structure of the absolute encoder 2 will be described in detail below.

[0037] 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.

[0038] like Figure 1 , Figure 2As 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.

[0039] 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.

[0040] The shielding plate 7 is a plate-shaped member disposed in the axial direction (Z-axis direction) between the angle sensors Sp, Sq, Sr and the outside of the absolute encoder 2. The shielding plate 7 is formed of a magnetic material to prevent magnetic interference caused by the magnetic flux generated by the angle sensors Sp, Sq, Sr located inside the housing 4 outside the absolute encoder 2.

[0041] As an example, motor 1 can be a stepper motor or a DC brushless motor. As another example, motor 1 can be a motor used as a drive source for industrial robots, etc., to drive them via a reduction mechanism such as a wave gear mechanism. The vertical sides of the main shaft 1a of motor 1 protrude from the motor housing. The absolute encoder 2 outputs the rotation amount of the main shaft 1a of motor 1 as a digital signal.

[0042] The motor 1 has a roughly rectangular shape when viewed from above, and also a roughly rectangular shape in the vertical direction. That is, the motor 1 has a roughly cubic shape. The length of each of the four outer walls constituting the shape of the motor 1 when viewed from above is, for example, 25 mm, meaning the overall shape of the motor 1 is 25 mm square when viewed from above. Furthermore, the absolute encoder 2, which is provided on the motor 1, is, for example, 25 mm square, in accordance with the shape of the motor 1.

[0043] exist Figure 1 , Figure 2 In this configuration, the angle sensor support base plate 5 is arranged to cover the interior of the absolute encoder 2 together with the housing 4 and the shielding plate 7.

[0044] like Figure 5As shown, the angle sensor support substrate 5 has a generally rectangular shape when viewed from above, and is a thin, plate-shaped printed circuit board in the vertical direction. Furthermore, the connector 6 is connected to the angle sensor support substrate 5 and is a component used to connect the absolute encoder 2 to an external device (not shown).

[0045] like Figure 2 , Figure 3 , Figure 4 As shown, 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). Furthermore, 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); and a first countershaft gear 40 having a second worm wheel portion 41 (second driven gear) and a support shaft 42 (see reference). Figure 9 The 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.

[0046] 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, serving as a first drive gear, is disposed 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 substantially coincides with the central axis of the main shaft 1a. The main shaft gear 10 can be formed from various materials such as resin or metal. For example, the main shaft gear 10 is formed from polyacetal resin.

[0047] like Figure 3 , Figure 4As 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 axially 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 axially supported by inserting the shaft 23 into the first intermediate gear shaft 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.

[0048] 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 as the first driven gear. 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°. That is, the central axis of the first worm gear portion 21 is orthogonal to the central axis of the first worm portion 11.

[0049] 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.

[0050] The second worm gear portion 22 is disposed on the outer periphery of the first intermediate gear 20 as a second drive gear. The second worm gear portion 22 is configured to rotate 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.

[0051] 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 is configured to rotate with the rotation of the first worm wheel portion 21. The third worm portion 28 meshes with the third worm wheel portion 31 of the second intermediate gear 30, causing the second intermediate gear 30 to rotate. 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.

[0052] 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 spacer 45. In the first counterspindle gear 40, the second worm gear portion 41 is axially supported by the support shaft 42 via the first bearing 43 and the second bearing 44.

[0053] Figure 10 This is a DD cross-sectional view of the first auxiliary shaft gear 40 in the absolute encoder 2.

[0054] 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 fixing portion 411, a magnet holding portion 412, and a step portion 413.

[0055] The second worm gear 41, serving as the second driven gear, is disposed on the outer periphery of the first counterspindle gear 40, and is configured to mesh with the second worm 22, rotating as the second worm 22 rotates. The axial angle between the second worm gear 41 and the second worm 22 is set to 90° or approximately 90°. That is, the central axis of the second worm gear 41 is orthogonal to the central axis of the first worm gear 21. The axis of rotation (axis A) of the second worm gear 41 is set to be parallel or approximately parallel to the axis of rotation of the first worm 11.

[0056] The bearing fixing part 411 is a cylindrical cavity portion located centered on the axis A of the second worm gear part 41. Specifically, on one side of the bearing fixing part 411 along the axis A direction... Figure 9 , Figure 10 The bearing fixing part 411 is open to the lower side along the Z-axis. The radial dimension (direction perpendicular to axis A, X-axis direction, Y-axis direction) of the inner peripheral portion 4111 of the bearing fixing part 411 is such that it can fix the outer ring of the bearing of the first secondary shaft gear 40 and the second worm gear part 41. Specifically, the radial dimension of the inner peripheral portion 4111 of the bearing fixing part 411 is such that the outer rings 432 and 442 of the first bearing 43 and the second bearing 44 can be pressed and fitted. The dimension of the bearing fixing part 411 in the axis A direction (Z-axis direction) is such that it can accommodate the outer ring 432 of the first bearing 43 and the outer ring 442 of the second bearing 44 in the axis A direction. In addition, a stepped portion 413 is provided in the bearing fixing part 411. The stepped portion 413 is on the other side of the axis A direction, Figure 9 , Figure 10The annular surface centered on axis A, which is parallel to the X and Y axes, is located on the upper side of the Z-axis. It should be noted that the second worm gear portion 41 of the first secondary shaft gear 40 may not have the stepped portion 413, for example, if the diameter of the magnet Mq is the same as the diameter of the first bearing 43 and the second bearing 44.

[0057] The magnet holding portion 412 is an annular cavity portion located at a position centered on the axis A of the second worm gear portion 41, similar to the bearing fixing portion 411. The magnet holding portion 412 is configured to accommodate the magnet Mq. The magnet holding portion 412 is located on the opposite side of the stepped portion 413 in the direction of axis A. Figure 9 , Figure 10 The magnet is positioned upward along the Z-axis. The magnet holding part 412 holds the magnet Mq in the aforementioned cavity portion.

[0058] The support shaft 42 has a shaft body 420, an outer peripheral portion 421, an external thread portion 422, and a flange portion 423. The shaft body 420 of the support shaft 42 is a shaft-shaped member extending along its longitudinal dimension in the direction of axis A. In the support shaft 42, the outer peripheral portion 421 is a circumferential surface centered on axis A, for example, in a cylindrical or substantially cylindrical shape. The external thread portion 422 is provided at one end of the shaft body 420... Figure 9 , Figure 10 The outer periphery 421 extends from the lower end 424 on the lower side in the Z-axis direction within a defined range. A flange 423 is provided on the other end side of the shaft body 420. Figure 9 , Figure 10 The upper end portion 425 on the upper side of the Z-axis direction. The flange portion 423 extends radially outward from the surface of the outer periphery 421 of the shaft body 420 at the upper end portion 425. Figure 10 The flange portion 423 protrudes in the direction of the Y-axis. The upper surface (upper surface portion 426) and the lower surface (lower surface portion 427) of the flange portion 423 are in a direction perpendicular to the axis A, i.e., radially (in the direction of the Y-axis). Figure 10 The middle part is a flat surface along the Y-axis.

[0059] The support shaft 42 is mounted in a manner that protrudes substantially vertically from the base 3b of the gear base 3. The base 3b of the gear base 3 has a first auxiliary gear shaft support 3h as a hole through which the external thread 422 of the support shaft 42 can be inserted. The support shaft 42 is fixed to the base 3b of the gear base 3 together with the first bearing 43 and the second bearing 44 as described below. With the first bearing 43 and the second bearing 44 pressed in, the external thread 422 of the support shaft 42 is inserted from the upper side to the lower side in the Z-axis direction into the first auxiliary gear shaft support 3h. A nut 60 is tightened at the external thread 422 protruding downward toward the base 3b. In this way, the support shaft 42 fixed to the base 3b supports the second worm gear 41 for rotatability via the first bearing 43 and the second bearing 44.

[0060] The first bearing 43 has an inner ring 431, an outer ring 432, and rolling elements 433. The inner ring 431 is an annular member having an inner peripheral portion 4311 that can be fitted onto the outer peripheral portion 421 of the support shaft 42. The outer ring 432 is located on the outer peripheral side of the inner ring 431. The outer ring 432 is an annular member that is coaxial with the inner ring 431 and has a larger diameter than the inner ring 431. The rolling elements 433 are a plurality of spherical members disposed between the inner ring 431 and the outer ring 432. In the first bearing 43, the inner ring 431 is pressed into 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 pressed into the inner peripheral portion 4111 of the bearing fixing portion 411 of the second worm gear portion 41. In the first bearing 43, the disc portion 4321 on the upper side of the outer ring 432 in the axial direction A (Z-axis direction) abuts against the spacer 45. Furthermore, in the first bearing 43, the disk portion 4323 on the upper side of the inner ring 431 in the axial direction A (Z-axis direction) is in contact with the lower surface portion 427 of the flange portion 423. In this way, the first bearing 43 is fixed to the second worm gear portion 41 and the support shaft 42 with high precision in the axial direction A and radial direction.

[0061] The second bearing 44 has an inner ring 441, an outer ring 442, and rolling elements 443. The inner ring 441 is an annular member having an inner peripheral portion 4411 that can be fitted onto the outer peripheral portion 421 of the support shaft 42. The outer ring 442 is located on the outer peripheral side of the inner ring 441. The outer ring 442 is an annular member that is coaxial with the inner ring 441 and has a larger diameter than the inner ring 441. The rolling elements 443 are a plurality of spherical members disposed between the inner ring 441 and the outer ring 442. In the second bearing 44, the inner ring 441 is pressed into the outer peripheral portion 421 of the support shaft 42. In the second bearing 44, the disk portion 4421 on the upper side of the outer ring 442 in the axial direction A (Z-axis direction) abuts against the disk portion 4321 on the lower side of the outer ring 432 of the first bearing 43. Furthermore, in the second bearing 44, the cylindrical portion 4422 of the outer ring 442 is pressed into the inner circumference portion 4111 of the bearing fixing portion 411 of the second worm gear portion 41.

[0062] The spacer 45 is an annular or substantially annular member having an annular disk portion 451 centered on axis A, a cylindrical outer peripheral portion 452, and an inner peripheral portion 453. The spacer 45 is radially disposed on the inner peripheral portion 4111 of the bearing fixing portion 411. The spacer 45 abuts against the disk portion 4321 of the outer ring 432 of the first bearing 43 on one side (lower side in the Z-axis direction) in the direction of axis A. Furthermore, the spacer 45 contacts the disk surface Mq1 of the magnet Mq on the lower side in the Z-axis direction on the other side (upper side in the Z-axis direction) in the direction of axis A. The disk surface Mq2 of the magnet Mq on the upper side in the Z-axis direction is in contact with the upper side of the magnet holding portion 412 on the Z-axis direction. Therefore, the spacer 45 abuts against the magnet holding portion 412 of the second worm gear portion 41 via the magnet Mq. A flange portion 423 of the support shaft 42 is disposed radially inside the inner peripheral portion 453 of the spacer 45.

[0063] Washer 46 is disposed between base 3b and second bearing 44 in the direction of axis A. The diameter of washer 46 is smaller than the diameter of outer ring 442 of second bearing 44. By disposing washer 46, whose diameter is smaller than that of outer ring 442 of second bearing 44, between base 3b and second bearing 44, outer ring 432 of first bearing 43 and outer ring 442 of second bearing 44 can rotate relative to support shaft 42. That is, in first countershaft gear 40, second worm gear portion 41 can rotate relative to support shaft 42. Washer 46 can contact the disk portion 4412 of inner ring 441 of second bearing 44 in the Z-axis direction on the other side (upper side in the Z-axis direction) of axis A.

[0064] By configuring it as described above, in the absolute encoder 2, the multiple bearings (first bearing 43 and second bearing 44) of the first secondary shaft gear 40 are pressed into the bearing fixing part 411 for fixing, thereby fixing the first secondary shaft gear 40 to the support shaft 42 with high precision in the axial direction A and radial direction.

[0065] Magnet Mq is a permanent magnet located on the axis A of the support shaft 42, at the top end side (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 fixing portion 411. Magnet Mq contacts the spacer 45, thereby fixing it to the upper side in the axis A direction of the bearing fixing portion 411. Angle sensor Sq is similarly located on axis A as magnet Mq. Angle sensor Sq is located near magnet Mq, within the range that can detect changes in the magnetic flux of magnet Mq, for example, on or near axis A. Angle sensor Sq detects changes in the magnetic flux generated by magnet Mq.

[0066] exist Figure 4 , Figure 8In 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 countershaft 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 countershaft gear 50. The second spur gear portion 51 meshes with the first spur gear portion 32. The second intermediate gear 30 has: 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, for example, formed of polyacetal resin. The second intermediate gear 30 is a generally circular component when viewed from above. The second intermediate gear 30 is axially supported on the base 3b of the gear base portion 3.

[0067] By incorporating the second intermediate gear 30, the second counterspindle gear 50 (described later) can be positioned away from the third worm gear 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 widened, increasing the design freedom.

[0068] 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 or substantially parallel to the rotation axis of the first worm portion 11.

[0069] 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 supported by a shaft 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.

[0070] The second spur gear portion 51 is disposed on the outer periphery of the second counterspindle gear 50. The second spur gear portion 51 is configured to mesh with the first spur gear portion 32 and rotate as the third worm gear portion 31 rotates. The axis of rotation of the second spur gear portion 51 is configured to be parallel or substantially parallel to the axis of rotation of the first spur gear portion 32. The second counterspindle gear 50 can be formed of various materials such as resin or metal. The second counterspindle gear 50 is formed of polyacetal resin.

[0071] Here, the direction in which the first worm gear 21 faces the first worm shaft 11 for meshing with the first worm portion 11 is defined as the first meshing direction P1. Figure 4 (The direction of arrow P1). Similarly, for the second worm portion 22 to mesh with the second worm wheel portion 41, the direction of the second worm portion 22 toward the second worm wheel portion 41 is defined as the second meshing direction P2 ( ). Figure 4 (The direction of arrow P2). Furthermore, for the third worm portion 28 to mesh with the third worm wheel portion 31, the direction of the third worm portion 28 toward the third worm wheel portion 31 is designated as the third meshing direction P3 (…). Figure 4 (The direction of arrow P3). In this embodiment, the first meshing direction P1, the second meshing direction P2, and the third meshing direction P3 are all along the horizontal plane (XY plane).

[0072] Magnet Mp is fixed to the upper surface of the main shaft gear 10 in a manner that the central axes of both magnets coincide or are substantially coincident. Magnet Mp is supported by a magnet support portion 17 located on the central axis of the main shaft gear 10 via a retainer portion 16. The retainer portion 16 is formed of a non-magnetic material such as aluminum alloy. The inner circumferential surface of the retainer portion 16 is formed, for example, an annular shape corresponding to the outer diameter and outer circumferential surface of magnet Mp, so that the inner circumferential surface of the retainer portion 16 contacts the radially outer circumferential surface of magnet Mp to retain the outer circumferential surface. Similarly, the inner circumferential surface of the magnet support portion 17 is formed, for example, an annular shape corresponding to the outer diameter and outer circumferential surface of retainer portion 16, so that the inner circumferential surface of the magnet support portion 17 contacts the outer circumferential surface of retainer portion 16. Magnet Mp has two magnetic poles arranged in a direction perpendicular to the rotation axis of the main shaft gear 10. In order to sense the rotation angle of the spindle gear 10, the angle sensor Sp is disposed on the lower surface 5a of the angle sensor support substrate 5 with its lower surface facing the upper surface of the magnet Mp in the vertical direction through a gap.

[0073] As an example, the angle sensor Sp is fixed to the angle sensor support base 5, which is supported by the base plate support 110 of the gear base portion 3 (described later) disposed on the absolute encoder 2. The angle sensor Sp senses the magnetic poles 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 input sensing information related to the magnetic poles, thereby determining the rotation angle of the main shaft gear 10, i.e., the rotation angle of the main shaft 1a. The resolution of the rotation angle of the main shaft 1a corresponds to the resolution of the angle sensor Sp. As described later, the microcomputer 121 determines the rotation amount of the main shaft 1a based on the determined rotation angle of the first secondary shaft gear 40 and the determined rotation angle of the main shaft 1a and outputs it. As an example, the microcomputer 121 may also output the rotation amount of the main shaft 1a of the motor 1 as a digital signal.

[0074] An angle sensor Sq senses the rotation angle of the second worm gear 41, which is also the rotation angle of the first counterspindle gear 40. A magnet Mq is fixed to the upper surface of the first counterspindle gear 40 in a manner that aligns or substantially aligns with the central axes of both gears. The magnet Mq has two magnetic poles arranged in a direction perpendicular to the rotation axis of the first counterspindle gear 40. For example... Figure 3 As shown, the angle sensor Sq is configured to have its lower surface facing the upper surface of the magnet Mq in the vertical direction with a gap between it and the rotation angle of the first countershaft gear 40.

[0075] As an example, angle sensor Sq is fixed to angle sensor support substrate 5 on the same surface as fixed angle sensor Sp, which in turn is fixed to angle sensor support substrate 5. Angle sensor Sq senses the magnetic poles of magnet Mq and outputs the sensing information to microcomputer 121. Microcomputer 121 determines the rotation angle of magnet Mq, i.e., the rotation angle of first counterspindle gear 40, based on the input sensing information related to the magnetic poles.

[0076] An angle sensor Sr senses the rotation angle of the second spur gear 51, which is also the rotation angle of the second counterspindle gear 50. A magnet Mr is fixed to the upper surface of the second counterspindle gear 50 in a manner that aligns or substantially aligns with the central axes of both gears. The magnet Mr has two magnetic poles arranged in a direction perpendicular to the rotation axis of the second counterspindle gear 50. Figure 3 As shown, the angle sensor Sr is configured to have its lower surface facing the upper surface of the magnet Mr in the vertical direction, with a gap between them, in order to sense the rotation angle of the second countershaft gear 50.

[0077] As an example, the angle sensor Sr is fixed to the angle sensor support base 5, which is supported by the base plate support 110 of the gear base portion 3 (described later) disposed in the absolute encoder 2. The angle sensor Sr senses the magnetic poles of the magnet Mr and outputs sensing information to the microcomputer 121. The microcomputer 121 determines the rotation angle of the magnet Mr, i.e., the rotation angle of the second counterspindle gear 50, based on the input sensing information related to the magnetic poles.

[0078] High-resolution magnetic angle sensors can also be used in each magnetic sensor. The magnetic angle sensor is positioned axially opposite the end faces of the magnetic poles, including the permanent magnets, with a certain gap. It determines the rotation angle of the opposite rotating body based on the rotation of these magnetic poles and outputs a digital signal. As an example, the magnetic angle sensor includes a sensing element that senses the magnetic poles and a processing circuit that outputs a digital signal based on the output of the sensing element. The sensing element may include, for example, multiple (e.g., four) Hall elements, GMR (Giant Magneto Resistive) elements, or other magnetic field sensing elements.

[0079] Alternatively, the arithmetic circuit can use the difference or ratio of the outputs of multiple sensing elements as keys, and determine the rotation angle through table processing using a lookup table. The sensing elements and the arithmetic circuit can be integrated onto a single IC chip. This IC chip can be embedded in a thin, rectangular resin substrate. Each magnetic sensor outputs an angle signal as a digital signal corresponding to the sensed rotation angle of each rotating body to the microcomputer 121 via wiring components not shown. For example, each magnetic sensor outputs the rotation angle of each rotating body as a digital signal of multiple bits (e.g., 7 bits).

[0080] Figure 11 This is a block diagram that roughly represents the functional structure of an absolute encoder. For example... Figure 11 As shown, the microcomputer 121 is fixed to the base 3b side of the gear base portion 3 of the angle sensor support substrate 5 by methods such as welding and bonding. The microcomputer 121 is composed of a CPU, which acquires digital signals representing 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 11 The modules of the microcomputer 121 shown represent the functions implemented by the CPU of the microcomputer 121 executing programs. Regarding each module of the microcomputer 121, in hardware, they can be implemented using components and mechanical devices, such as the computer's CPU (Central Processing Unit) and RAM (Random Access Memory); in software, they can be implemented using computer programs, etc. However, this description focuses on functional modules implemented through their cooperation. Therefore, those skilled in the art who have access to this specification will understand that these functional modules can be implemented in various forms through a combination of hardware and software.

[0081] The microcomputer 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 121p acquires a rotation angle Ap, representing the 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 unit 121q acquires a rotation angle Aq, representing the rotation angle of the first counterspindle gear 40, based on a signal output from the angle sensor Sq. The rotation angle acquisition unit 121r acquires a rotation angle Ar, representing the rotation angle of the second counterspindle gear 50, sensed by the angle sensor Sr.

[0082] The table processing unit 121b refers to a first correspondence table storing rotation angle Ap and the number of revolutions of the spindle gear 10 corresponding to the rotation angle Ap, and determines the number of revolutions of the spindle gear 10 corresponding to the acquired rotation angle Ap. Furthermore, the table processing unit 121b refers to a second correspondence table storing rotation angle Ar and the rotational speed of the spindle gear 10 corresponding to the acquired rotation angle Ar, and determines the rotational speed of the spindle gear 10 corresponding to the acquired rotation angle Ar.

[0083] The rotation amount determination unit 121c determines the first rotation amount of the spindle gear 10 after multiple rotations based on the number of revolutions of the spindle gear 10 determined by the table processing unit 121b and the obtained rotation angle Aq. The output unit 121e converts the rotation amount of the spindle gear 10 after multiple rotations determined by the rotation amount determination unit 121c into information representing that rotation amount and outputs it.

[0084] It should be noted that the meter processing unit 121b, the rotation amount determination unit 121c, and the output unit 121e also function as angle position information output units, which output the angle position information of the first worm gear 11 to an external control device (controller). Furthermore, the meter processing unit 121b, the rotation amount determination unit 121c, and the output unit 121e also output angle error information, which is used to correct the angle position information of the first worm gear 11, to the external control device.

[0085] The absolute encoder 2 configured in this way can determine the rotational speed of the main shaft 1a based on the rotational angles of the first and second counterspindle gears 40 and 50, which are determined based on the sensing information of angle sensors Sq and Sr, and determine the rotational angle of the main shaft 1a based on the sensing information of angle sensor Sp. Furthermore, the microcomputer 121 determines the amount of rotation of the main shaft 1a after multiple rotations based on the determined rotational speed and rotational angle of the main shaft 1a.

[0086] The number of teeth in the first worm gear 11 of the main shaft gear 10 on the main shaft 1a is, for example, 1, and the number of teeth in the first worm wheel 21 is, for example, 20. That is, the first worm gear 11 and the first worm wheel 21 constitute a first transmission mechanism with a reduction ratio of 20 / 1 = 20 (see reference). Figure 4 When the first worm gear 11 rotates 20 times, the first worm wheel 21 rotates 1 time. The first worm wheel 21 and the second worm gear 22 are coaxial, forming the first intermediate gear 20, and rotate as a whole. Therefore, when the first worm gear 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 gear 22 rotates 1 time.

[0087] The second worm gear section 22 has, for example, 5 teeth, and the second worm wheel section 41 has, for example, 25 teeth. That is, the second worm gear section 22 and the second worm wheel section 41 constitute a second transmission mechanism with a reduction ratio of 25 / 5 = 5 (see reference). Figure 4 When the second worm gear 22 rotates 5 times, the second worm wheel 41 rotates 1 time. The first counterspindle gear 40, on which the second worm wheel 41 is formed, rotates integrally with the magnet Mq. Therefore, when the second worm gear 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 counterspindle gear 40 and the magnet Mq rotate 1 time. That is to say, the rotational speed of the main shaft 1a rotating 50 times can be determined based on the sensing information from the angle sensor Sq related to the rotational angle of the first counterspindle gear 40.

[0088] 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.

[0089] The second spur gear section 51 has, for example, 40 teeth, and the first spur gear section 32 has, for example, 24 teeth. That is, the first spur gear section 32 and the second spur gear section 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 rotational speed of the main shaft 1a rotating 1000 revolutions can be determined based on the sensing information of the angle sensor Sr related to the rotation angle of the second counterspindle gear 50.

[0090] [The role of an absolute encoder]

[0091] The function of the absolute encoder 2 will be explained below.

[0092] As described above (refer to) Figures 1 to 11 The first counterspindle 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 spacer 45. The external thread portion 422 of the support shaft 42 is fixed to the first counterspindle gear shaft support portion 3h of the gear base 3 by a nut 60. The support shaft 42 has a flange portion 423 at its upper end 425. The first bearing 43 and the second bearing 44 are disposed between the gear base 3 and the flange portion 423 in the axial direction. The outer ring 432 of the first bearing 43 and the outer ring 442 of the second bearing 44 are fixed to the bearing fixing portion 411 of the first counterspindle gear 40. The magnet Mq is held by the magnet holding portion 412 of the first counterspindle gear 40. In the axial direction A, a spacer 45 is disposed between the magnet Mq and the first bearing 43 and the second bearing 44. The flange portion 423 of the support shaft 42 is disposed radially inside the inner circumference portion 453 of the spacer 45. The upright position of the support shaft 42 of the first counterspindle gear 40 is achieved as follows: Specifically, on the lower side of the first counterspindle gear 40 along the axis A, the disc portion 4423 on the lower side of the inner ring 441 of the second bearing 44 along the axis A is connected to the base 3b of the gear base 3 via a washer 46. Furthermore, on the upper side of the first counterspindle gear 40 along the axis A, the disc portion 4323 on the upper side of the inner ring 431 of the first bearing 43, which is pressed into the support shaft 42, is connected to the lower surface portion 427 of the flange portion 423. Moreover, the support shaft 42 is inserted into the first counterspindle gear shaft support portion 3h and fixed to the base 3b by screwing a fastening nut 60 into the external thread portion 422. In this state, the force acting on the support shaft 42 by tightening the nut 60 acts on the disc portion 4323 on the upper side of the inner ring 431 of the first bearing 43. Thus, for the first secondary shaft gear 40, the support shaft 42 is upright by positioning the flange portion 423 provided at the upper end 425 of the support shaft 42 and the first bearing 43 and the second bearing 44 pressed into the support shaft 42.

[0093] By constructing it as described above, the absolute encoder 2 achieves the upright position of the support shaft 42 as described above, thus eliminating the need for a support structure with an upright flange (not shown) on the lower side of the support shaft 42 in the axial direction A. Therefore, according to the absolute encoder 2, the increase in the height (axial direction A) of the first countershaft gear 40 as a whole can be suppressed, and the thickness of the spacer 45 in the vertical direction can be sufficiently ensured. Furthermore, according to the absolute encoder 2, the thickness of the spacer 45 in the vertical direction can be sufficiently ensured, thereby increasing the distance between the magnet Mq and the first bearing 43 and the second bearing 44, which are magnetic bodies, in the axial direction A. Therefore, according to the absolute encoder 2, the influence of the first bearing 43 and the second bearing 44 forming a magnetic circuit can be reduced. Specifically, in the absolute encoder 2, by stabilizing the distribution of the surface magnetic flux density on the angle detection surface side of the magnet Mq, the detection accuracy of the angle information of the first countershaft gear 40 used in determining multiple rotation amounts of the main shaft 1a can be improved. As a result, according to the absolute encoder 2, the improvement effect of poor determination of multiple rotation amounts can be obtained. Therefore, based on the absolute encoder 2, the error in detecting the rotation angle can be suppressed.

[0094] The embodiments of the present invention have been described above, but the present invention is not limited to the absolute encoder 2 of the embodiments described above, but includes all solutions included in the concept and claims of the present invention. Furthermore, in order to achieve at least some of the above-described problems and effects, the various components can be selectively combined appropriately, or combined with known technologies. For example, the shape, material, configuration, size, etc., of the various components in the above embodiments can be appropriately modified according to the specific use of the present invention.

[0095] For example, in the absolute encoder 2, the configuration of the first countershaft gear 40 described above can be combined with the second countershaft gear 50 to suppress the vibration of the second countershaft gear 50 and improve the detection accuracy of the rotation angle of the countershaft.

[0096] For example, in the absolute encoder 2, the bearings included in the first secondary shaft gear 40 described above are not limited to the first bearing 43 and the second bearing 44; there can be three or more bearings. In this case, for bearings whose outer rings are pressed in, it is sufficient that the outer rings of at least one bearing are pressed into the first secondary shaft gear 40.

[0097] For example, in the absolute encoder 2, the shape of the spacer 45 provided in the first counterspindle gear 40 is only required to abut against the outer ring 432 of the first bearing 43. In other words, the shape of the spacer 45 is only required to ensure that the inner ring 431 and the support shaft 42 do not contact the magnet Mq or the spacer 45. Therefore, the shape of the spacer 45 is not limited to the above-mentioned annular shape; for example, it may be formed as a disc and have a recess in a portion.

[0098] For example, in the support shaft 42 of the absolute encoder 2, the support shaft 42 can be made of a magnetic material. By making the support shaft 42 a magnetic material, the flange portion 423 extending radially outward (perpendicular to the direction of axis A) from the shaft body 420 can form a magnetic circuit for the magnetic flux from the magnet Mq. That is, for the support shaft 42 made of a magnetic material, by making the flange portion 423 function as a magnetic shield for the magnetic flux from the magnet Mq toward the first bearing 43 and the second bearing 44, the first bearing 43 and the second bearing 44 can be prevented from functioning as a magnetic circuit. Therefore, by making the support shaft 42 a magnetic material, disturbances in the magnetic flux distribution on the angle detection surface (upper side) of the magnet Mq can be suppressed, improving the detection accuracy of angle errors.

[0099] Explanation of reference numerals in the attached figures

[0100] 1: Motor, 1a: Main shaft, 1b: Press-in part, 2: Absolute encoder, 3: Gear base, 3b: Base, 3g: First intermediate gear shaft support, 3h: First secondary gear shaft support, 4: Housing, 4a: Outer wall, 5: Angle sensor support base plate, 5a: Lower surface, 6: Connector, 7: Shielding plate, 8a: Base plate mounting screw, 10: Main shaft gear, 11: First worm gear, 16: Holding part, 17: Magnet support, 20: First intermediate gear, 2 1: First worm gear section, 22: Second worm section, 23: Shaft, 28: Third worm section, 30: Second intermediate gear, 31: Third worm gear section, 32: First spur gear section, 40: First counterspindle gear, 41: Second worm gear section, 42: Support shaft, 43: First bearing, 44: Second bearing, 45: Spacer, 46: Washer, 50: Second counterspindle gear, 51: Second spur gear section, 60: Nut, 110: Base plate support, 121: Microcomputer, 121b: Surface treatment section, 121c: Rotation amount determination section, 121e: Output section, 121p: Rotation angle acquisition section, 121q: Rotation angle acquisition section, 121r: Rotation angle acquisition section, 411: Bearing fixing section, 412: Magnet holding section, 413: Stepped section, 420: Shaft body, 421: Outer peripheral section, 422: External thread section, 423: Flange section, 424: Lower end section, 425: Upper end section, 426: Upper surface section, 427: Lower surface section, 431: Inner ring, 4 32: Outer ring, 433: Rolling element, 441: Inner ring, 442: Outer ring, 443: Rolling element, 451: Disc portion, 452: Outer peripheral portion, 453: Inner peripheral portion, 4111: Inner peripheral portion, 4311: Inner peripheral portion, 4321, 4323: Disc portion, 4322: Cylindrical portion, 4411: Inner peripheral portion, 4412, 4421, 4423: Disc portion, 4422: Cylindrical portion, Sp: Angle sensor, Sq: Angle sensor, Sr: Angle sensor.

Claims

1. An absolute encoder, the absolute encoder comprising: The support shaft is fixed to the base plate at one end and has a flange at the other end. At least one bearing, the inner ring of which is fixed to the support shaft; A magnetized magnet; A spacer is disposed between the bearing and the magnet in the axial direction of the support shaft; A magnet holder holds the magnet in place. A magnetic sensor that senses magnetic flux from the magnet; and A washer, disposed between the base plate and the bearing in the axial direction. The magnet retainer has: A bearing retaining portion, which is a recessed portion open on one side in the axial direction, is fixed to the outer ring of the bearing; and The magnet retaining portion is a recess formed on the other end side of the bearing fixing portion. The bearing is disposed between the base plate and the flange portion in the axial direction. The spacer abuts against the outer ring of the bearing from the axial direction inside the bearing fixing part. The substrate has a hole through which the support shaft can be inserted. The support shaft has an external thread at one end. The external thread is inserted into the hole to fix the support shaft and the bearing together to the base plate. The support shaft is formed of a magnetic material.

2. The absolute encoder according to claim 1, wherein, The spacer abuts against the inner circumference of the bearing fixing part in the radial direction and against the outer ring of the bearing in the axial direction.

3. The absolute encoder according to claim 1, wherein, In the flange portion, the surface on one end in the axial direction faces the disk portion of the inner ring of the bearing.

4. The absolute encoder according to claim 1, wherein, The spacer is formed in a ring shape, and the flange portion is disposed on the inner side of the inner circumferential surface.

Images