Absolute encoder

Abstract

An absolute encoder suitable for miniaturization is provided. The absolute encoder comprises a worm gear portion, a permanent magnet (19) arranged on the front end side of the worm gear portion, and a magnetic sensor. When observing from the end face of the permanent magnet (19) in the axial direction, in the permanent magnet (19), a first magnetic pole portion (N) of a first polarity and a second magnetic pole portion (S) of a second polarity different from the first polarity are adjacent to each other. The first magnetic pole portion (N) and the second magnetic pole portion (S) are adjacent to each other in the radial direction with the center of the radial direction of the permanent magnet (19) as the boundary, and the first magnetic pole portion (N) and the second magnetic pole portion (S) are adjacent to each other in the axial direction with the center of the axial direction of the permanent magnet (19) as the boundary.

Description

Technical Field

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

[0002] A rotary encoder used to detect the position or angle of a movable element in various control mechanical devices is well known. Such encoders include incremental encoders for detecting relative positions or angles and absolute encoders for detecting absolute positions or angles. For example, Patent Document 1 discloses an absolute rotary encoder having a plurality of magnetic encoder sections for detecting the angular positions of a main shaft and a secondary shaft using magnetism, and the absolute position of the main shaft can be measured based on the detection results.

[0003] [Reference document]

[0004] [Patent document]

[0005] [Patent Document 1] (Japan) Patent Publication No. 2013-24572 Summary of the invention

[0006] [Technical issues to be solved]

[0007] However, in the magnetic encoder disclosed in Patent Document 1, for example, in the case where a portion of the magnetic flux generated by a plurality of adjacent permanent magnets affects a magnetic detection element, i.e., a magnetic sensor, that does not correspond to the plurality of permanent magnets, the detection accuracy may be degraded due to the influence of noise from external elements other than the magnetic flux from the permanent magnets to be detected.

[0008] The present invention is proposed in view of the above-mentioned problems, and its object is to provide an absolute encoder according to which, for a magnetic sensor that detects magnetic flux from a permanent magnet that should be detected, the adverse effect of leakage magnetic flux from a permanent magnet that should not be detected on the magnetic sensor can be reduced.

[0009] [Technical solution]

[0010] An absolute encoder according to an embodiment of the present invention includes a first drive gear that rotates with the rotation of a main shaft and a first magnet disposed on the front end side of the first drive gear. The absolute encoder includes: a first angle sensor that detects the rotation angle of the first drive gear corresponding to the change in magnetic flux generated from the first magnet; and a first driven gear meshing with the first drive gear, whose center axis is orthogonal to the center axis of the first drive gear. The absolute encoder includes: a second drive gear that is disposed on the same axis as the first driven gear and rotates with the rotation of the first driven gear; and a second driven gear meshing with the second drive gear, whose center axis is orthogonal to the center axis of the first driven gear. The absolute encoder includes: a second magnet disposed on the front end side of the second driven gear; and a second angle sensor that detects the rotation angle of the second driven gear corresponding to the change in magnetic flux generated from the second magnet. In the second magnet, when observed from the end face in the axial direction of the second magnet, the first magnetic pole portion of the first polarity and the second magnetic pole portion of the second polarity different from the first polarity are formed adjacent to each other, the first magnetic pole portion and the second magnetic pole portion are formed adjacent to each other along the radial direction with the center of the radial direction of the second magnet as the boundary, and the first magnetic pole portion and the second magnetic pole portion are formed adjacent to each other along the axial direction with the center of the axial direction as the boundary.

[0011] [Beneficial Effects]

[0012] The absolute encoder of the present invention has the effect of reducing the influence of leakage magnetic flux on the magnetic sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] [ Figure 1 ] is a perspective view showing a state where the absolute encoder 100-1 according to Embodiment 1 of the present invention is mounted on the motor 200.

[0014] [ Figure 2 ] indicates from Figure 1 The illustrated perspective view is of a state in which the cover portion 116 is removed from the housing portion 115 .

[0015] [ Figure 3 ] indicates from Figure 2 The illustrated absolute encoder 100 - 1 is a perspective view showing a state in which a base plate 120 and base plate mounting screws 122 are removed.

[0016] [ Figure 4 ]Bottom surface view of substrate 120.

[0017] [ Figure 5 ] Figure 3 A plan view of an absolute encoder 100 - 1 is shown.

[0018] [ Figure 6] is a cross-sectional view of the absolute encoder 100-1 cut along a plane passing through the center of the motor shaft 201 and parallel to the XZ plane. Here, the second counter gear 138 and the magnetic sensor 90 are shown.

[0019] [ Figure 7 ] A cross-sectional view of the absolute encoder 100-1 cut along a plane perpendicular to the center line of the first intermediate gear 102 and passing through the center of the first countershaft gear 105.

[0020] [ Figure 8 ] A cross-sectional view of the absolute encoder 100-1 when cut along a plane passing through the center of the second countershaft gear 138 and the center of the second intermediate gear 133 and parallel to the Z-axis direction as viewed from approximately the right side.

[0021] [ Fig. 9 ] is a diagram showing the functional configuration of the microcomputer 121 included in the absolute encoder 100-1 according to the first embodiment of the present invention.

[0022] [ Fig.10 ]A schematic diagram of a modified example of the absolute encoder 100-1 according to embodiment 1 of the present invention.

[0023] [ Fig.11 ]A schematic diagram of a cylindrical permanent magnet 18 that can be applied to the absolute encoders 100-1 and 100-2 of embodiments 1 and 2.

[0024] [ Fig.12 ]A schematic diagram of a cylindrical permanent magnet 19 that can be applied to the absolute encoders 100-1 and 100-2 of embodiments 1 and 2.

[0025] [ Fig.13 ] is used for Fig.11 or Fig.12 A diagram illustrating an angular error with respect to a change in a center offset value when a distance (ie, gap) between opposing surfaces (ie, facing surfaces) of a magnet and a magnetic sensor in an axial direction D2 is constant.

[0026] [ Fig.14 ]A conceptual diagram of the magnetic flux density detected by a magnetic flux detection element provided on a magnetic sensor when a surface magnetized magnet is used.

[0027] [ Fig.15 ]A conceptual diagram of the magnetic flux density detected by a magnetic flux detection element provided on a magnetic sensor when a diameter-magnetized magnet is used.

[0028] [ Fig.16 ] Conceptual diagram of the magnetic flux density on the upper surface of a surface magnetized magnet.

[0029] [ Fig.17 ] Conceptual diagram of the magnetic flux density on the upper surface of a diameter magnetized magnet.

[0030] [ Fig.18 ] Fig.10 Schematic diagram of the reduction ratio of the first worm gear portion 102b relative to the main shaft gear 101, the reduction ratio of the driven gear 36 relative to the first worm gear portion 102b, and the allowable error of the rotation angle during one rotation of the main shaft gear 101, etc.

[0031] [ Fig.19 ] is a perspective view showing a state in which an absolute encoder 100-2 according to a second embodiment of the present invention is mounted on a motor 200.

[0032] [ Fig. 20 ] indicates from Fig.19 The illustrated absolute encoder 100 - 2 is a perspective view showing a state in which the housing 15 and the mounting screws 16 are removed.

[0033] [ Fig.21 ] indicates from Fig. 20 The illustrated absolute encoder 100 - 2 is a perspective view showing a state in which the base plate 20 and the base plate mounting screws 13 are removed.

[0034] [ Fig. 22 ] indicates from Fig.21 The perspective view of the absolute encoder 100 - 2 shown in the figure is a perspective view of a state in which the motor 200 and the screw 14 are removed from the absolute encoder 100 - 2 mounted on the motor 200 .

[0035] [ Fig.23 ]right Fig. 22 The main base 10, the intermediate gear 2, etc. shown in the figure are shown in a plan view.

[0036] [ Fig.24 ] Along the plane passing through the center of the intermediate gear 2 and parallel to the X-Y plane Fig.23 The absolute encoder 100 - 2 shown is a cut-away cross-sectional view.

[0037] [ Fig.25 ]right Fig.24 The illustrated partial enlarged cross-sectional view is a state in which the bearing 3 is removed from the intermediate gear 2.

[0038] [ Fig.26 ] Along the way Fig.23 The center of the main shaft gear 1 is shown and the plane perpendicular to the center line of the intermediate gear 2 is Fig. 20 The absolute encoder 100 - 2 shown is a cross-sectional view in which the substrate 20 and the magnetic sensor 40 are not cut.

[0039] [ Fig. 27 ] Along the way Fig.24 The center of the countershaft gear 5 shown is aligned with a plane perpendicular to the center line of the intermediate gear 2. Fig. 20 The absolute encoder 100 - 2 shown is a cross-sectional view in which the substrate 20 and the magnetic sensor 50 are not cut.

[0040] [ Fig.28 ]right Fig.21 This is a perspective view showing a state in which the intermediate gear 2 is removed among the plurality of components shown.

[0041] [ Fig.29 ] Fig.28 The wall portion 70 is shown in a perspective view with the screw 12 removed, the leaf spring 11 removed, and the wall portion 70 having the leaf spring mounting surface 10e facing the leaf spring 11. The motor 200 and the main shaft gear 1 are not shown.

[0042] [ Fig.30 ] Along the way Fig.23 The center of the substrate positioning pin 10g and the center of the substrate positioning pin 10j are aligned with a plane parallel to the Z-axis direction. Fig. 20 The absolute encoder 100 - 2 shown is a cross-sectional view in which a cutout is made. Here, the magnetic sensor 40 does not have a cross section.

[0043] [ Fig.31 ] From the side of the lower surface 20-1 Fig. 20 A diagram showing the substrate 20 as shown.

[0044] [ Fig.32 ]from Fig.19 The motor 200 is removed and the main base 10 is viewed from the lower surface 10 - 2 side.

[0045] [ Fig.33 ] Fig.19 An oblique view of the housing 15 is shown.

[0046] [ Fig.34 ] Along the way Fig.21 The center of the substrate positioning pin 10g and the center of the substrate positioning pin 10j are aligned with a plane parallel to the Z-axis direction. Fig.19 The absolute encoder 100 - 2 is shown in a cutaway cross-sectional view. Here, the motor 200 and the main shaft gear 1 are not shown in cross-section.

[0047] [ Fig.35 ] Fig. 27 An exploded oblique view of the permanent magnet 8, magnet seat 6, countershaft gear 5 and bearing 7 is shown.

[0048] [ Fig.36 ] Fig.26 The permanent magnet 9, the main shaft gear 1 and the motor shaft 201 are shown in an exploded perspective view.

[0049] [ Fig.37 ] Schematic diagram of the concepts of the waveform (A) obtained by detecting the magnetic flux of the permanent magnet 9 provided on the main shaft gear 101 (main shaft gear 1) by the magnetic sensor 40, the waveform (B) obtained by detecting the magnetic flux of the permanent magnet 8 provided on the first secondary shaft gear 105 (secondary shaft gear 5) by the magnetic sensor 50, and the magnetic interference waveform (C) obtained by detecting the state in which a part of the magnetic flux of the permanent magnet 8 is overlapped with the magnetic flux of the permanent magnet 9 as leakage flux by the magnetic sensor 40.

[0050] [ Fig.38 ] Schematic diagram of the concepts of the waveform (A) obtained by detecting the magnetic flux of the permanent magnet 8 provided on the first countershaft gear 105 (countershaft gear 5) by the magnetic sensor 50, the waveform (B) obtained by detecting the magnetic flux of the permanent magnet 9 provided on the main shaft gear 101 (main shaft gear 1) by the magnetic sensor 40, and the magnetic interference waveform (C) obtained by detecting the state in which a part of the magnetic flux of the permanent magnet 9 is overlapped with the magnetic flux of the permanent magnet 8 as leakage flux by the magnetic sensor 50.

[0051] [ Fig.39 ] is a diagram showing the functional configuration of the microcomputer 21 included in the absolute encoder 100-2 according to the second embodiment of the present invention.

[0052] [ Fig.40 ]A schematic diagram of a modified example of the absolute encoder 100-2 according to embodiment 2 of the present invention. DETAILED DESCRIPTION

[0053] Hereinafter, the configuration of the absolute encoder according to the embodiment of the present invention will be described in detail based on the drawings. It should be noted that the present invention is not limited to these embodiments.

[0054] <Implementation method 1>

[0055] Figure 1 This is an oblique view showing a state where the absolute encoder 100-1 according to Embodiment 1 of the present invention is mounted on the motor 200. The following description is based on the XYZ rectangular coordinate system. The X-axis direction corresponds to the horizontal left-right direction, the Y-axis direction corresponds to the horizontal front-back direction, and the Z-axis direction corresponds to the vertical up-down direction. The Y-axis direction and the Z-axis direction are respectively orthogonal to the X-axis direction. The X-axis direction is referred to as the left direction or the right direction, the Y-axis direction is referred to as the front direction or the rear direction, and the Z-axis direction is referred to as the up direction or the down direction. Figure 1In the diagram, the state observed from above along the Z-axis direction is called a plan view, the state observed from the front along the Y-axis direction is called a front view, and the state observed from left and right along the X-axis direction is called a side view. Such a direction representation does not limit the use posture of the absolute encoder 100-1, and the absolute encoder 100-1 can be used in any posture. It should be noted that the tooth shape is omitted in the drawings.

[0056] Figure 2 It means from Figure 1 The illustrated perspective view is of a state in which the cover portion 116 is removed from the housing portion 115 . Figure 3 It means from Figure 2 The illustrated absolute encoder 100 - 1 is a perspective view showing a state in which a base plate 120 and base plate mounting screws 122 are removed. Figure 4 is a bottom view of the substrate 120 . Figure 5 yes Figure 3 A plan view of an absolute encoder 100 - 1 is shown. Figure 6 This is a cross-sectional view of the absolute encoder 100 - 1 cut along a plane that passes through the center of the motor shaft 201 and is parallel to the XZ plane. Here, the second counter gear 138 and the magnetic sensor 90 are shown. Figure 7 This is a cross-sectional view of the absolute encoder 100 - 1 cut along a plane perpendicular to the center line of the first intermediate gear 102 and passing through the center of the first counter gear 105 . Figure 7 In the figure, descriptions of the shell portion 115 and the cover portion 116 are omitted. Figure 8 This is a cross-sectional view of the absolute encoder 100 - 1 when it is cut along a plane passing through the center of the second counter gear 138 and the center of the second intermediate gear 133 and parallel to the Z-axis direction as viewed from the substantially right side. Figure 8 In the figure, description of the shell portion 115 and the cover portion 116 is omitted.

[0057] Below, refer to Figures 1 to 8 The structure of the absolute encoder 100-1 is described in detail. The absolute encoder 100-1 is an absolute encoder that determines and outputs the rotation amount of multiple rotations of the main shaft of the motor 200. As an example, the motor 200 may be a stepping motor or a DC brushless motor. As an example, the motor 200 may also be used as a driving source for driving an industrial robot via a reduction mechanism such as a wave gear device. The motor shaft 201 of the motor 200 protrudes from both sides of the Z-axis direction of the motor 200. The absolute encoder 100-1 outputs the rotation amount of the motor shaft 201 as a digital signal. It should be noted that the motor shaft 201 is an example of a main shaft.

[0058] The absolute encoder 100-1 is disposed at the end of the motor 200 in the Z-axis direction. The shape of the absolute encoder 100-1 is not particularly limited. In the embodiment, the absolute encoder 100-1 has a substantially rectangular shape in a plan view, and has a thin and elongated rectangular shape along the extension direction of the main axis (hereinafter referred to as the axial direction. In the first embodiment, the axial direction is a direction parallel to the Z-axis direction) in the front view and the side view. That is, the absolute encoder 100-1 has a rectangular parallelepiped shape that is flat along the Z-axis direction.

[0059] The absolute encoder 100-1 has a hollow rectangular cylindrical shell 115 that can accommodate its internal structure. The shell 115 includes a plurality of (for example, four) outer wall portions 115a, 115b, 115c, and 115d that surround at least the main shaft and the intermediate rotating body. A cover 116 is fixed to the ends of the outer wall portions 115a, 115b, 115c, and 115d of the shell 115. The cover 116 is a plate-like component that has a generally rectangular shape in a plan view and is thin in the axial direction.

[0060] The outer wall portion 115a, the outer wall portion 115b, the outer wall portion 115c and the outer wall portion 115d are connected in this order. The outer wall portion 115a and the outer wall portion 115c are arranged parallel to each other. The outer wall portion 115b and the outer wall portion 115d are arranged across the side ends of the outer wall portion 115a and the outer wall portion 115c, and are arranged parallel to each other. In this example, the outer wall portion 115a and the outer wall portion 115c extend in the X-axis direction in a plan view, and the outer wall portion 115b and the outer wall portion 115d extend in the Y-axis direction in a plan view.

[0061] The absolute encoder 100-1 includes a main base 110, a shell 115, a cover 116, a substrate 120, a leaf spring 111, and a plurality of screws 164. The main base 110 is a base for axially supporting each rotating body and each gear. The main base 110 includes a base 110a, a plurality of (for example, 4) pillars 141, a shaft 106, a shaft 134, and a shaft 139.

[0062] The base 110a of the main base 110 is a plate-shaped portion of the absolute encoder 100-1 facing the motor 200 and extending in the X-axis direction and the Y-axis direction. The hollow rectangular cylindrical shell 115 is fixed to the base 110a of the main base 110 by a plurality of (for example, three) screws 164.

[0063] The support column 141 provided on the main base 110 is a substantially cylindrical portion protruding from the base 110a in the axial direction and in a direction away from the motor 200, and is used to support the substrate 120. The substrate 120 is fixed to the protruding end of the support column 141 by the substrate mounting screw 122. Figure 21 shows a case where the substrate 120 is arranged in a manner covering the inside of the encoder. The substrate 120 has a generally rectangular shape in a plan view and is a plate-like printed wiring substrate that is relatively thin in the axial direction. The substrate 120 mainly has the magnetic sensor 50, the magnetic sensor 40, the magnetic sensor 90 and the microcomputer 121 mounted thereon.

[0064] In addition, the absolute encoder 100-1 includes a main shaft gear 101, a worm gear portion 101c, a worm wheel portion 102a, a first intermediate gear 102, a first worm gear portion 102b, a worm wheel portion 105a, a first counter shaft gear 105, a second worm gear portion 102h, and a worm wheel portion 133a. In addition, the absolute encoder 100-1 includes a second intermediate shaft gear 133, a fourth drive gear portion 133d, a fourth driven gear portion 138a, a second counter shaft gear 138, a permanent magnet 8, a permanent magnet 9, a permanent magnet 17, a magnetic sensor 50, a magnetic sensor 40, a magnetic sensor 90, and a microcomputer 121.

[0065] The main shaft gear 101 rotates with the rotation of the motor shaft 201, and transmits the rotation of the motor shaft 201 to the worm gear portion 101c. Figure 6 As shown, the main shaft gear 101 includes a first cylindrical portion 101a that is engaged with the outer periphery of the motor shaft 201, a disc portion 101b formed with a worm gear portion 101c, and a magnet holding portion 101d that holds the permanent magnet 9. The magnet holding portion 101d has a cylindrical recessed shape provided at the central portion of the disc portion 101b and the upper end surface of the first cylindrical portion 101a. The first cylindrical portion 101a, the disc portion 101b, and the magnet holding portion 101d are integrally formed in a manner such that the central axes thereof are substantially consistent. The main shaft gear 101 can be formed of various materials such as resin materials and metal materials. The main shaft gear 101 can be formed, for example, of polyacetal resin.

[0066] The worm gear 101c is an example of a first drive gear that drives the worm wheel 102a. Specifically, the worm gear 101c is a worm gear having one gear formed on the outer circumference of the disk 101b. The rotation axis of the worm gear 101c extends along the axial direction of the motor shaft 201.

[0067] like Figure 5As shown, the first intermediate gear 102 is a gear portion that transmits the rotation of the main shaft gear 101 to the worm wheel portion 105a and the second intermediate gear 133. The first intermediate gear 102 is axially supported by the shaft 104 around the rotation axis La extending approximately parallel to the base 110a. The first intermediate gear 102 is a substantially cylindrical component extending in the direction of its rotation axis La. The first intermediate gear 102 includes a base 102c, a first cylinder portion 102d forming the worm wheel portion 102a, a second cylinder portion 102e forming the first worm gear portion 102b, and a third cylinder portion 102f forming the second worm gear portion 102h, and a through hole is formed in the interior thereof, and the shaft 104 can be inserted (inserted) into the through hole. The shaft 104 is inserted into the holes formed in the support parts 110b and 110c provided on the base 110a of the main base 110, so that the first intermediate gear 102 can be axially supported. In addition, grooves are provided near both ends of the shaft 104 protruding outward from the support parts 110b and 110c, respectively, and the stop rings 107 and 108 for preventing the shaft 104 from coming out are fitted into the grooves, thereby preventing the shaft 104 from falling off.

[0068] The outer wall portion 115a is provided on the side of the first intermediate gear 102 opposite to the motor shaft 201. The outer wall portion 115c is provided in parallel with the outer wall portion 115a on the side of the first intermediate gear 102 on which the motor shaft 201 is provided. The first intermediate gear 102 can be configured in such a manner that its rotation axis La faces any direction. The rotation axis La of the first intermediate gear 102 can be provided in a range of 5° to 30° in a plan view relative to the extension direction of the outer wall portion 115a provided on the side of the first intermediate gear 102 opposite to the motor shaft 201. Figure 5 In the example, the rotation axis La of the first intermediate gear 102 is inclined by 20° relative to the extension direction of the outer wall portion 115a. In other words, the shell portion 115 includes the outer wall portion 115a extending in a direction inclined by 5° to 30° relative to the rotation axis La of the first intermediate gear 102 in a plan view. Figure 5 In the example, the inclination Ds between the extending direction of the outer wall portion 115 a and the rotation axis La of the first intermediate gear 102 is set to 20°.

[0069] In the first embodiment, the base 102c of the first intermediate gear 102 has a cylindrical shape, and the first cylinder 102d, the second cylinder 102e, and the third cylinder 102f have a cylindrical shape with a diameter larger than that of the base 102c. In addition, a through hole is formed in the center of the first intermediate gear 102. The base 102c, the first cylinder 102d, the second cylinder 102e, the third cylinder 102f and the through hole are integrally formed in a manner that the central axes are roughly consistent. The second cylinder 102e, the first cylinder 102d and the third cylinder 102f are arranged in this order at positions separated from each other. The first intermediate gear 102 can be formed of various materials such as resin materials and metal materials. In the first embodiment, the first intermediate gear 102 can be formed of polyacetal resin.

[0070] The support portion 110b and the support portion 110c are respectively protruding parts protruding from the base portion 110a in the positive direction of the Z axis by cutting and raising a part of the base portion 110a of the main base portion 110, and are formed with a hole for inserting the shaft 104 of the first intermediate gear 102. In addition, grooves are formed near both ends of the shaft 104 extending from the support portion 110b and the support portion 110c, and the stop ring 107 and the stop ring 108 for preventing the shaft 104 from coming out are fitted into the grooves, thereby preventing the shaft 104 from falling off. By configuring in this way, the first intermediate gear 102 can be rotatably supported around the rotation axis La as an axis.

[0071] The leaf spring 111 is described. As for the first intermediate gear 102, each worm gear is driven by the first worm gear portion 102b and the second worm gear portion 102h, and a reaction force acts along the axial direction Td of the first intermediate gear 102, and the position in the axial direction Td can be changed. Therefore, in Embodiment 1, a leaf spring 111 that applies a force to the first intermediate gear 102 is provided. The leaf spring 111 can suppress the position change in the axial direction Td by applying a force in the direction of the rotation axis La of the first intermediate gear 102 to the first intermediate gear 102. The leaf spring 111 includes a mounting portion 111b mounted on the base 110a of the main base 110 and a sliding portion 111a extending from the mounting portion 111b and contacting the hemispherical protrusion 102g. The mounting portion 111b and the sliding portion 111a are formed of a thin plate-shaped spring material, and the root of the sliding portion 111a is bent at a substantially right angle to the mounting portion 111b. In this way, by directly contacting and pressing the hemispherical protrusion 102g of the first intermediate gear 102 with the leaf spring 111, a force can be applied to the first intermediate gear 102 in the axial direction Td. In addition, the sliding portion 102i of the first intermediate gear 102 can contact and slide with the supporting portion 110c of the main base 110. According to this, the change of the position of the first intermediate gear 102 in the axial direction Td can be suppressed.

[0072] In the first embodiment, the direction of the reaction force received by the first intermediate gear 102 from the worm wheel portion 105a of the first counter gear 105 by the rotation of the first worm gear portion 102b meshing with the worm wheel portion 105a of the first counter gear 105 is set to be opposite to the direction of the reaction force received by the first intermediate gear 102 from the worm wheel portion 133a of the second intermediate gear 133 by the rotation of the second worm gear portion 102h meshing with the worm wheel portion 133a of the second intermediate gear 133. That is, the shape of the teeth of each worm gear is set so that the components of the axial direction Td of the first intermediate gear 102 of each reaction force are opposite to each other. Specifically, the inclination direction of the teeth in each worm gear is set to be opposite to the direction of the components of the axial direction Td of the reaction force applied to the first intermediate gear 102. In this case, compared with the case where the components of the axial direction Td of the reaction force received by the first intermediate gear 102 from each worm gear are in the same direction, the combined reaction force in the axial direction Td is smaller, thereby reducing the biasing force of the leaf spring 111. As a result, the rotational resistance of the first intermediate gear 102 is reduced, and the first intermediate gear 102 can rotate smoothly.

[0073] The above method is more effective when the sliding resistance caused by the meshing of the worm gear portion 101c of the main shaft gear 101 and the worm wheel portion 102a of the first intermediate gear 102 is small, and the force in the axial direction Td applied to the first intermediate gear 102 by the rotation of the main shaft gear 101 is smaller than the reaction force received by the first intermediate gear 102 from the worm wheel portion 105a of the first countershaft gear 105 and the worm wheel portion 133a of the second intermediate gear 133; however, when the sliding resistance caused by the meshing of the worm gear portion 101c of the main shaft gear 101 and the worm wheel portion 102a of the first intermediate gear 102 is large, the following method is more effective.

[0074] Figure 5In the case where the main shaft gear 101 rotates rightward, a force in the right direction relative to the axial direction Td is applied to the first intermediate gear 102 by the sliding resistance caused by the meshing of the worm gear portion 101c of the main shaft gear 101 and the worm wheel portion 102a of the first intermediate gear 102, and the first intermediate gear 102 intends to move in the right direction. At this time, when the force in the axial direction Td generated by the worm gears at both ends of the first intermediate gear 102 is set to cancel each other out by the above-mentioned method, the sliding resistance caused by the meshing of the worm gear portion 101c of the main shaft gear 101 and the worm wheel portion 102a of the first intermediate gear 102 as described above causes the force in the right direction acting on the first intermediate gear 102 to become relatively large. In order to resist the rightward force acting on the first intermediate gear 102 and prevent the first intermediate gear 102 from moving in the right direction, it is necessary to increase the pressing force of the leaf spring 111. Accordingly, the sliding resistance between the sliding portion 111a of the leaf spring 111 and the hemispherical protrusion 102g of the first intermediate gear 102 abutting against and pressed by the sliding portion 111a, and the sliding resistance between the sliding portion 102i at the end of the first intermediate gear 102 in the opposite direction of the hemispherical protrusion 102g and the support portion 110c increase, and the rotational resistance of the first intermediate gear 102 becomes larger.

[0075] When the main shaft gear 101 rotates right, the direction of the reaction force received by the first intermediate gear 102 from the worm wheel portion 105a of the first secondary shaft gear 105 due to the rotation of the first worm gear portion 102b meshing with the worm wheel portion 105a of the first secondary shaft gear 105 and the direction of the reaction force received by the first intermediate gear 102 from the worm wheel portion 133a of the second intermediate gear 133 due to the rotation of the second worm gear portion 102h meshing with the worm wheel portion 133a of the second intermediate gear 133 are both set to forces in the direction of moving the first intermediate gear 102 to the left relative to the axial direction Td. As a result, the rightward force acting on the first intermediate gear 102 can be reduced by the sliding resistance caused by the meshing of the worm gear portion 101c of the main shaft gear 101 and the worm wheel portion 102a of the first intermediate gear 102. This can reduce the biasing force applied by the leaf spring 111 to the first intermediate gear 102. Therefore, the rotation resistance of the first intermediate gear 102 is reduced, and the first intermediate gear 102 can rotate smoothly.

[0076] On the other hand, when the main shaft gear 101 rotates counterclockwise, a force in the left direction relative to the axial direction Td acts on the first intermediate gear 102 due to the sliding resistance caused by the meshing of the worm gear portion 101c of the main shaft gear 101 and the worm wheel portion 102a of the first intermediate gear 102, and the first intermediate gear 102 attempts to move leftward. At this time, the reaction forces received by the first worm gear portion 102b and the second worm gear portion 102h located at both ends of the first intermediate gear 102 are both forces that attempt to move the first intermediate gear 102 rightward. Therefore, in this case, the force in the left direction acting on the first intermediate gear 102 can also be reduced. The biasing force applied to the first intermediate gear 102 by the leaf spring 111 is always a force in the left direction relative to the axial direction Td, so the force in the left direction acting on the first intermediate gear 102 due to the meshing of the three gears is reduced, and accordingly, the total force in the left direction applied to the first intermediate gear 102 is also reduced. Therefore, the rotation resistance caused by the sliding between the sliding portion 102i at the left end of the first intermediate gear 102 in the figure and the support portion 110c provided on the base portion 110a of the main base 110 can be reduced.

[0077] Figure 5 1, the worm wheel portion 102a is an example of a first driven gear meshing with the worm gear portion 101c of the main shaft gear 101. The worm wheel portion 102a is a worm wheel having 20 teeth formed on the outer periphery of the first cylinder portion 102d. The worm gear portion 101c and the worm wheel portion 102a constitute a first worm gear transmission mechanism. The rotation axis of the worm wheel portion 102a extends in a direction perpendicular to the axial direction of the motor shaft 201.

[0078] When the number of teeth of the worm gear portion 101c of the main shaft gear 101 is 1 and the number of teeth of the worm wheel portion 102a of the first intermediate gear 102 is 20, the reduction ratio is 20. That is, when the main shaft gear 101 rotates 20 times, the first intermediate gear 102 rotates 20÷20=1 time (one rotation).

[0079] The first worm gear portion 102b is an example of a second drive gear that drives the worm wheel portion 105a, and is a gear portion of the first intermediate gear 102. In particular, the first worm gear portion 102b is a worm gear having a number of 5 formed on the outer periphery of the second cylinder portion 102e. The rotation axis of the first worm gear portion 102b extends in a direction perpendicular to the axial direction of the motor shaft 201.

[0080] Figure 5 and Figure 7, the first countershaft gear 105 is decelerated along with the rotation of the motor shaft 201, and rotates integrally with the permanent magnet 8. The first countershaft gear 105 is a member having a substantially circular shape in a plan view, including a cylindrical bearing portion 105b axially supported by a shaft 106 protruding substantially vertically from a base portion 110a of a main base portion 110, a disc portion 105c formed with a worm gear portion 105a, and a retaining portion 105d for retaining the permanent magnet 8.

[0081] Figure 7 In the embodiment, the disc portion 105c has a disc shape extending from the outer periphery of the bearing portion 105b in the radial direction. In the first embodiment, the disc portion 105c is arranged at a position close to the end of the bearing portion 105b away from the base 110a. The retaining portion 105d has a cylindrical recessed shape arranged on the end surface of the disc portion 105c away from the base 110a in the axial direction. The bearing portion 105b, the disc portion 105c and the retaining portion 105d are integrally formed in a manner in which the central axes are substantially consistent. The first countershaft gear 105 can be formed of various materials such as resin materials and metal materials. In the first embodiment, the first countershaft gear 105 can be formed of polyacetal resin.

[0082] The worm wheel portion 105a is an example of a second driven gear that meshes with the first worm gear portion 102b. In particular, the worm wheel portion 105a is a gear having 25 teeth formed on the outer periphery of the disk portion 105c. The first worm gear portion 102b and the worm wheel portion 105a constitute a second worm gear transmission mechanism. The rotation axis of the worm wheel portion 105a extends in a direction parallel to the axial direction of the motor shaft 201.

[0083] When the number of teeth of the first worm gear portion 102b of the first intermediate gear 102 is 5 and the number of teeth of the worm gear portion 105a of the first countershaft gear 105 is 25, the reduction ratio is 5. That is, if the first intermediate gear 102 rotates 5 times, the first countershaft gear 105 rotates once. Therefore, if the main shaft gear 101 rotates 100 times, the first intermediate gear 102 rotates 100÷20=5 times, and the first countershaft gear 105 rotates 5÷5=1 time. The first countershaft gear 105 rotates integrally with the permanent magnet 8, so if the main shaft gear 101 rotates 100 times, the permanent magnet 8 rotates once. That is, the magnetic sensor 50 can determine the rotation amount of 100 rotations of the main shaft gear 101.

[0084] In the absolute encoder 100-1 thus constructed, the rotation amount of the main shaft gear 101 can be determined. As an example, when the main shaft gear 101 rotates once, the first countershaft gear 105 and the permanent magnet 8 rotate 1 / 100 times, that is, rotate 3.6°. Therefore, if the rotation angle of the first countershaft gear 105 is less than 3.6°, the main shaft gear 101 can be determined to be within 1 rotation.

[0085] Figure 5 , the second worm gear portion 102h is an example of a third drive gear that drives the worm wheel portion 133a, and is a gear portion of the first intermediate gear 102. In particular, the second worm gear portion 102h is a worm gear having a number of = 1 formed on the outer periphery of the third cylinder portion 102f. The rotation axis of the second worm gear portion 102h extends in a direction perpendicular to the axial direction of the motor shaft 201.

[0086] Figure 5 , the second intermediate gear 133 is a disc-shaped gear portion that rotates with the rotation of the motor shaft 201, reduces the rotation of the motor shaft 201, and transmits it to the second countershaft gear 138. The second intermediate gear 133 is provided between the second worm gear portion 102h and the fourth driven gear portion 138a provided on the second countershaft gear 138. The fourth driven gear portion 138a meshes with the fourth drive gear portion 133d. The second intermediate gear 133 has a worm gear portion 133a that meshes with the second worm gear portion 102h of the third drive gear and a fourth drive gear portion 133d that drives the fourth driven gear portion 138a. The second intermediate gear 133 can be formed of, for example, polyacetal resin. The second intermediate gear 133 is a member that is substantially circular in plan view. The second intermediate gear 133 includes a bearing portion 133 b axially supported by the base portion 110 a of the main base 110 , and a projecting portion 133 c on which the worm wheel portion 133 a is formed.

[0087] Figure 5 In the embodiment, by providing the second intermediate gear 133, the second countershaft gear 138 described later can be arranged at a position away from the second worm gear part 102h, that is, the distance away is the second intermediate gear 133, that is, the distance between the second countershaft gear 138 and the second worm gear part 102h is equivalent to the distance between the second intermediate gear 133. For this reason, by lengthening the distance between the permanent magnet 9 and the permanent magnet 17, the influence of the leakage flux between them can be reduced. In addition, by providing the second intermediate gear 133, the range in which the reduction ratio can be set can be expanded by the second intermediate gear 133, thereby improving the degree of freedom in design.

[0088] Figure 8In the embodiment, the extension portion 133c has a disc shape extending from the outer periphery of the bearing portion 133b in the radial direction. In the first embodiment, the extension portion 133c is provided at a position close to the end of the base portion 110a away from the main base portion 110 and close to the bearing portion 133b. The fourth drive gear portion 133d is formed on the outer periphery of the region of the bearing portion 133b that is closer to the base portion 110a side than the extension portion 133c. The bearing portion 133b and the extension portion 133c are integrally formed in a manner that the central axes thereof are substantially consistent.

[0089] The worm wheel portion 133a is a gear portion of the second intermediate gear 133 meshing with the second worm gear portion 102h. In particular, the worm wheel portion 133a is a worm wheel having 30 teeth formed on the outer periphery of the extension portion 133c. The second worm gear portion 102h and the worm wheel portion 133a constitute a third worm gear transmission mechanism. The rotation axis of the worm wheel portion 133a extends in a direction parallel to the axial direction of the motor shaft 201.

[0090] When the number of teeth of the second worm gear portion 102h of the first intermediate gear 102 is 1 and the number of teeth of the worm wheel portion 133a of the second intermediate gear 133 is 30, the reduction ratio is 30. That is, if the first intermediate gear 102 rotates 30 times, the second intermediate gear 133 rotates once. Therefore, if the main shaft gear 101 rotates 600 times, the first intermediate gear 102 rotates 600÷20=30 times, and the second intermediate gear 133 rotates 30÷30=1 time.

[0091] The fourth drive gear portion 133d is a transmission element that drives the fourth driven gear portion 138a. The fourth drive gear portion 133d is provided on the side of the main shaft gear 101 opposite to the first countershaft gear 105 side, and rotates with the rotation of the worm gear portion 133a. The fourth drive gear portion 133d is a spur gear having 24 teeth formed on the outer periphery of the bearing portion 133b.

[0092] Figure 8 , the second countershaft gear 138 is a gear portion having a circular shape in a plan view, which rotates with the rotation of the motor shaft 201, reduces the speed of the rotation of the motor shaft 201, and transmits it to the permanent magnet 17. The second countershaft gear 138 is axially supported around a rotation axis extending substantially vertically from the base 110a of the main base 110. The second countershaft gear 138 includes a bearing portion 138b axially supported by the base 110a of the main base 110, an extension portion 138c formed with the fourth driven gear portion 138a, and a magnet holding portion 138d for holding the permanent magnet 17. The bearing portion 138b has a cylindrical shape that surrounds the shaft 139 protruding from the base 110a of the main base 110 via a gap.

[0093] The extension portion 138c has a disc shape extending from the outer periphery of the bearing portion 138b in the radial direction. In Embodiment 1, the extension portion 138 is arranged at a position of the base 110a of the main base 110 close to the bearing portion 138b. The magnet holding portion 138d has a cylindrical recessed shape arranged on the end surface of the bearing portion 138b away from the base 110a in the axial direction. The bearing portion 138b, the extension portion 138c and the magnet holding portion 138d are integrally formed in a manner in which the central axes are roughly consistent. The second countershaft gear 138 can be formed of various materials such as resin materials and metal materials. In Embodiment 1, the second countershaft gear 138 can be formed of polyacetal resin.

[0094] The fourth driven gear portion 138a is a transmission element driven by the fourth driving gear portion 133d. The fourth driven gear portion 138a and the fourth driving gear portion 133d constitute a speed reduction mechanism. In particular, the fourth driven gear portion 138a is a spur gear having 40 teeth formed on the outer periphery of the extension portion 138c.

[0095] When the number of teeth of the fourth driving gear portion 133d is 24 and the number of teeth of the fourth driven gear portion 138a is 40, the reduction ratio is 40 / 24=5 / 3. If the main shaft gear 101 rotates 1000 times, the first intermediate gear 102 rotates 1000÷20=50 times, and the second intermediate gear 133 rotates 50÷30=5 / 3 times. Therefore, the second countershaft gear 138 rotates 5 / 3÷5 / 3=1 time. The second countershaft gear 138 rotates integrally with the permanent magnet 17, so if the main shaft gear 101 rotates 1000 times, the permanent magnet 17 rotates once. That is, the magnetic sensor 90 can determine the rotation amount of 1000 rotations of the main shaft gear 101.

[0096] Figures 5 to 8 , permanent magnet 9 is the first permanent magnet, permanent magnet 8 is the second permanent magnet, and permanent magnet 17 is the third permanent magnet. Permanent magnet 8, permanent magnet 9 and permanent magnet 17 (hereinafter referred to as each permanent magnet) each have a roughly cylindrical shape that is flat in the axial direction. Each permanent magnet is formed of, for example, a magnetic material such as ferrite, Nd (neodymium) -Fe (iron) -B (boron) and the like. Each permanent magnet may be, for example, a rubber magnet or a bonded magnet containing a resin binder. A magnetic pole is provided on each permanent magnet. There is no particular limitation on the magnetization direction of each permanent magnet. In embodiment 1, as Fig.11 and Fig.12 As shown, the two-pole magnetic pole is provided on the end face of each permanent magnet facing the magnetic sensor. The magnetic flux density distribution in the rotation direction of each permanent magnet can be a trapezoidal waveform, or a sine wave or a rectangular wave.

[0097] Part or all of each permanent magnet is stored in a recess formed at the end of each rotating body, and can be fixed by, for example, bonding, forging, press-fitting, etc. The permanent magnet 8 is bonded and fixed to the retaining portion 105d of the first countershaft gear 105. The permanent magnet 9 is bonded and fixed to the magnet retaining portion 101d of the main shaft gear 101. The permanent magnet 17 is bonded and fixed to the magnet retaining portion 138d of the second countershaft gear 138.

[0098] If the distance between the permanent magnets is short, the leakage flux of the adjacent magnets will cause the detection error of the magnetic sensor to increase. Figure 5 In the example, the permanent magnet 9 and the permanent magnet 8 are arranged in a mutually isolated manner on the line of sight Lm inclined relative to the outer wall portion 115a of the shell 115 in a plan view. The line of sight Lm is a virtual line connecting the permanent magnet 8 and the permanent magnet 9. The permanent magnet 9 and the permanent magnet 17 are arranged in a mutually separated manner on the line of sight Ln inclined relative to the outer wall portion 115a of the shell 115. The line of sight Ln is equal to the virtual line connecting the permanent magnet 17 and the permanent magnet 9. In Example 1, the lines of sight Lm and Ln are arranged in a tilted manner relative to the outer wall portion 115a, so that the distance between the permanent magnets can be made longer compared to the case where the lines of sight Lm and Ln are parallel to the outer wall portion 115a.

[0099] The magnetic sensor 50, the magnetic sensor 40, and the magnetic sensor 90 (hereinafter referred to as each magnetic sensor) are sensors for detecting the absolute rotation angle of each rotating body in the range of 0° to 360° corresponding to one rotation. Each magnetic sensor outputs a signal (e.g., a digital signal) based on the detected rotation angle to the microcomputer 121. Each magnetic sensor can output the same rotation angle as before the power supply was stopped even when the power supply is temporarily stopped and then turned on again. For this reason, a configuration without a backup power supply is also possible.

[0100] For each magnetic sensor, Figure 4As shown in FIG. 1 , the substrate 120 is fixed on the same plane by welding, bonding, or the like on the surface of the base 110a side of the main base 110. The magnetic sensor 40 is fixed on the substrate 120 so as to be located at a position facing the end face of the permanent magnet 9 provided on the main shaft gear 101 with a certain gap. The magnetic sensor 40 is a first angle sensor that detects the rotation angle of the main shaft gear 101 corresponding to the change of the magnetic flux generated by the permanent magnet 9. The magnetic sensor 50 is fixed on the substrate 120 so as to be located at a position facing the end face of the permanent magnet 8 provided on the first countershaft gear 105 with a certain gap. The magnetic sensor 50 is a second angle sensor that detects the rotation angle of the first countershaft gear 105 corresponding to the change of the magnetic flux generated by the permanent magnet 8. The magnetic sensor 90 is fixed on the substrate 120 so as to be located at a position facing the end face of the permanent magnet 17 provided on the second countershaft gear 138 with a certain gap. The magnetic sensor 90 is a third angle sensor that detects the rotation angle of the second counter gear 138 corresponding to the change in magnetic flux generated from the permanent magnet 17 .

[0101] Each magnetic sensor may use a magnetic angle sensor with a relatively high resolution. The magnetic angle sensor is arranged relative to the end face of each permanent magnet containing the magnetic poles in the axial direction of each rotating body with a certain gap therebetween. According to the rotation of these magnetic poles, the rotation angle of the relative rotating body can be determined and a digital signal can be output. As an example, the magnetic angle sensor includes a detection element for detecting the magnetic pole and an operation circuit for outputting a digital signal based on the output of the detection element. The detection element may include, for example, a plurality of (for example, 4) Hall elements, GMR (Giant Magneto Resistive) elements and other magnetic field sensing elements.

[0102] The operation circuit can be configured, for example, to use the difference or ratio of the outputs of multiple detection elements as a key and use a lookup table, thereby determining the rotation angle by table processing. The detection element and the operation circuit can be integrated on an IC chip. The IC chip can be embedded in a resin having a thin rectangular shape. Each magnetic sensor can output a digital signal corresponding to the rotation angle of each rotating body detected, that is, an angle signal, to the microcomputer 121 via a wiring component not shown in the figure. For example, each magnetic sensor can output the rotation angle of each rotating body as a digital signal of multiple bits (for example, 7 bits).

[0103] Fig. 91 is a diagram showing the functional configuration of the microcomputer 121 included in the absolute encoder 100-1 according to the first embodiment of the present invention. The microcomputer 121 is fixed to the surface of the base 110a side of the main base 110 of the substrate 120 by welding, bonding, etc. The microcomputer 121 is composed of a CPU, and can obtain digital signals indicating the rotation angles outputted from the magnetic sensors 40, 50, and 90, respectively, and calculate the rotation amount of the main shaft gear 101. Fig. 9 Each block of the microcomputer 121 shown represents a function (Function) realized by executing a program (Program) as the CPU of the microcomputer 121. As for each block of the microcomputer 121, from the perspective of hardware, it can be realized by components or mechanical devices headed by the CPU (central processing unit) of the computer, and from the perspective of software, it can be realized by a computer program, etc. Here, the functional blocks realized by the cooperation of hardware and software are drawn. Therefore, those skilled in the art who have read this specification can understand that these functional blocks can be realized in various ways by combining hardware and software.

[0104] 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 121q acquires a rotation angle Aq as angle information indicating the rotation angle of the main shaft gear 101 based on the signal output from the magnetic sensor 40. The rotation angle acquisition unit 121p acquires a rotation angle Ap as angle information indicating the rotation angle of the first counter shaft gear 105 based on the signal output from the magnetic sensor 50. The rotation angle acquisition unit 121r acquires a rotation angle Ar as angle information indicating the rotation angle of the second counter shaft gear 138 detected by the magnetic sensor 90.

[0105] The table processing unit 121b can determine the rotation number of the main shaft gear 101 corresponding to the acquired rotation angle Ap by referring to the first correspondence table storing the rotation angle Ap and the rotation number of the main shaft gear 101 corresponding to the rotation angle Ap. In addition, the table processing unit 121b can determine the rotation number of the main shaft gear 101 corresponding to the acquired rotation angle Ar by referring to the second correspondence table storing the rotation angle Ar and the rotation number of the main shaft gear 101 corresponding to the rotation angle Ar.

[0106] The rotation amount determination unit 121c can determine the first rotation amount of the multiple rotations of the main shaft gear 101 based on the number of rotations of the main shaft gear 101 determined by the table processing unit 121b and the acquired rotation angle Aq. The output unit 121e converts the rotation amount of the multiple rotations of the main shaft gear 101 determined by the rotation amount determination unit 121c into information indicating the rotation amount, and outputs it.

[0107] The operation and effects of the absolute encoder 100 - 1 according to the first embodiment configured in this manner will be described below.

[0108] The absolute encoder 100-1 of the first embodiment is an absolute encoder for determining the rotation amount of the motor shaft 201 for multiple rotations, and includes a worm gear portion 101c that rotates with the rotation of the motor shaft 201, a worm wheel portion 102a that meshes with the worm gear portion 101c, a first worm gear portion 102b that rotates with the rotation of the worm wheel portion 102a, a worm wheel portion 105a that meshes with the first worm gear portion 102b, a first countershaft gear 105 that rotates with the rotation of the worm wheel portion 105a, a permanent magnet 8 that rotates integrally with the first countershaft gear 105, and a magnetic sensor 50 that detects the rotation angle of the permanent magnet 8. With this configuration, the rotation amount of the motor shaft 201 for multiple rotations can be determined based on the detection result of the magnetic sensor 50. Furthermore, since the absolute encoder 100-1 is provided with a first worm gear change mechanism including a worm gear portion 101c and a worm wheel portion 102a meshing with the worm gear portion 101c, and a second worm gear change mechanism including a first worm gear portion 102b and a worm wheel portion 105a meshing with the first worm gear portion 102b, a curved transmission path can be formed to reduce the thickness of the absolute encoder 100-1.

[0109] The absolute encoder 100-1 of the first embodiment is an absolute encoder for determining the rotation amount of multiple rotations of the motor shaft 201, and includes a first intermediate gear 102 that rotates at a first reduction ratio as the motor shaft 201 rotates, a first countershaft gear 105 that rotates at a second reduction ratio as the first intermediate gear 102 rotates, a permanent magnet 8 that rotates integrally with the first countershaft gear 105, and a magnetic sensor 50 that detects the rotation angle of the permanent magnet 8. The rotation axis of the motor shaft 201 is located at a position skewed relative to the rotation axis of the first intermediate gear 102, and is set to be parallel to the rotation axis of the first countershaft gear 105. With this configuration, the rotation amount of multiple rotations of the motor shaft 201 can be determined based on the detection result of the magnetic sensor 50. Since the rotation axis of the first intermediate gear 102 is located at a position oblique to the rotation axes of the motor shaft 201 and the first counter gear 105 and is orthogonal in a front view, the absolute encoder 100 - 1 can be made thinner by forming a curved transmission path.

[0110] The absolute encoder 100-1 of the first embodiment is an absolute encoder for determining the rotation amount of the motor shaft 201 for multiple rotations, and includes a reduction mechanism including a first worm gear transmission mechanism and rotating the permanent magnet 8 with the rotation of the motor shaft 201, and a magnetic sensor 50 for detecting the rotation angle of the permanent magnet 8 based on the magnetic poles of the permanent magnet 8, and the rotation axis of the motor shaft 201 is set to be parallel to the rotation axis of the permanent magnet 8. With this configuration, the rotation amount of the motor shaft 201 for multiple rotations can be determined based on the detection result of the magnetic sensor 50. Since the first worm gear transmission mechanism is included and the rotation axis of the motor shaft 201 and the rotation axis of the permanent magnet 8 are set to be parallel, the absolute encoder 100-1 can be made thinner by forming a curved transmission path.

[0111] The absolute encoder 100-1 of the first embodiment includes a magnetic sensor 40 for detecting the rotation angle of the motor shaft 201. With this configuration, the rotation angle of the motor shaft 201 can be determined based on the detection result of the magnetic sensor 40. Compared with the case where the magnetic sensor 40 is not provided, the absolute encoder 100-1 can improve the resolution of the rotation angle of the motor shaft 201 that can be determined.

[0112] The absolute encoder 100-1 of the first embodiment includes a second worm gear portion 102h that rotates with the rotation of the worm wheel portion 102a, a worm wheel portion 133a that meshes with the second worm gear portion 102h, a second countershaft gear 138 that rotates with the rotation of the worm wheel portion 133a, a permanent magnet 17 that rotates integrally with the second countershaft gear 138, and a magnetic sensor 90 that detects the rotation angle of the permanent magnet 17. With this configuration, the rotation amount of the motor shaft 201 for multiple rotations can be determined based on the detection result of the magnetic sensor 90. Compared with the case where the magnetic sensor 90 is not provided, the absolute encoder 100-1 can increase the range of the rotation amount of the motor shaft 201 that can be determined.

[0113] In the absolute encoder 100-1 of the first embodiment, the first intermediate gear 102 is provided with a first worm gear portion 102b and a second worm gear portion 102h, and the direction of the reaction force received by the first intermediate gear 102 due to the rotation of the first worm gear portion 102b is set to be opposite to the direction of the reaction force received by the first intermediate gear 102 due to the rotation of the second worm gear portion 102h. With this configuration, the combined reaction force of the two reaction forces can be reduced compared to the case where the directions of the reaction forces are the same.

[0114] In the absolute encoder 100 - 1 of Embodiment 1, the outer diameter of the worm wheel 102 a is set smaller than the outer diameter of the worm gear 101 c . This configuration makes it easier to reduce the thickness of the worm wheel 102 a than when the outer diameter of the worm wheel 102 a is larger.

[0115] Here, for example, when the main shaft gear 101 and the first secondary shaft gear 105 are arranged adjacent to each other, a portion of the magnetic flux generated by the permanent magnet 8 and the permanent magnet 9 will affect the magnetic sensor that does not correspond to the permanent magnet 8 and the permanent magnet 9, that is, the so-called magnetic interference, which is explained below.

[0116] Fig.37 This is a diagram showing the concept of a waveform (A) obtained by detecting the magnetic flux of the permanent magnet 9 provided on the main shaft gear 101 (main shaft gear 1) by the magnetic sensor 40, a waveform (B) obtained by detecting the magnetic flux of the permanent magnet 8 provided on the first counter shaft gear 105 (counter shaft gear 5) by the magnetic sensor 50, and a magnetic interference waveform obtained by detecting a state in which a part of the magnetic flux of the permanent magnet 8 overlaps with the magnetic flux of the permanent magnet 9 as leakage flux by the magnetic sensor 40. The vertical axis represents the magnetic flux, and the horizontal axis represents the rotation angle of the main shaft gear 101. Thus, in the magnetic sensor 40, it is expected to detect the waveform (A), but when magnetic interference occurs, it becomes a waveform as shown in (C), so the correct waveform cannot be detected.

[0117] same, Fig.38 This is a conceptual diagram showing the waveform (A) obtained by detecting the magnetic flux of the permanent magnet 8 provided on the first countershaft gear 105 (countershaft gear 5) by the magnetic sensor 50, the waveform (B) obtained by detecting the magnetic flux of the permanent magnet 9 provided on the main shaft gear 101 (main shaft gear 1) by the magnetic sensor 40, and the magnetic interference waveform (C) obtained by detecting the state in which a part of the magnetic flux of the permanent magnet 9 overlaps with the magnetic flux of the permanent magnet 8 as leakage flux by the magnetic sensor 50. The vertical axis represents the magnetic flux, and the horizontal axis represents the rotation angle of the first countershaft gear 105. In this way, the waveform (A) is expected to be detected in the magnetic sensor 50, but when magnetic interference occurs, it becomes the waveform shown in (C), so the correct waveform cannot be detected. In addition, the main shaft gear 101 and the second countershaft gear 138 are also connected. Fig.38 (C) There is also the possibility of magnetic interference occurring.

[0118] The absolute encoder 100-1 of the first embodiment includes a housing 115 including an outer wall portion 115a disposed on the side of the first intermediate gear 102 opposite to the motor shaft 201, and the rotation axis La of the first intermediate gear 102 is inclined by 20 degrees relative to the extending direction of the outer wall portion 115a in a plan view. With this configuration, the inclination of the arrangement straight line of each permanent magnet relative to the outer wall portion 115a can be increased compared to the case where the rotation axis La of the first intermediate gear 102 is not inclined. For this reason, the distance between each permanent magnet can be increased. In this way, by increasing the distance between each permanent magnet, the occurrence of magnetic interference that affects the magnetic sensor that does not correspond to the permanent magnet 8, the permanent magnet 9, and the permanent magnet 17 can be reduced. For example, the interference caused by a part of the magnetic flux generated by the permanent magnet 9 provided on the main shaft gear 101 as leakage magnetic flux to the magnetic sensor 50 provided for the purpose of detecting the change of the magnetic flux generated by the permanent magnet 8 provided on the first counter shaft gear 105 can be reduced. Furthermore, it is possible to reduce interference caused by a part of the magnetic flux generated by the permanent magnet 8 provided on the first countershaft gear 105 as leakage flux on the magnetic sensor 40 provided for the purpose of detecting changes in the magnetic flux generated by the permanent magnet 9. Therefore, the influence of the leakage flux of the adjacent magnet can be reduced.

[0119] It should be noted that, in the absolute encoder 100-1 of the first embodiment, the smaller the size of the absolute encoder 100-1 in the direction orthogonal to the Z-axis direction, the more the distance between the magnetic sensor 40 and the magnetic sensor 50 and the distance between the magnetic sensor 40 and the magnetic sensor 90 tend to be relatively shorter. Therefore, the distance between adjacent permanent magnets is also relatively shorter. In this way, if the distance between adjacent permanent magnets is shortened, the above-mentioned magnetic interference is likely to occur. In view of this, the absolute encoder 100-1 of the first embodiment preferably has the following structure. The structure of the absolute encoder 100-1 of the modified example of the first embodiment is described below.

[0120] Fig.10 It is a schematic diagram of a modified example of the absolute encoder 100 - 1 according to the first embodiment of the present invention. Fig.11 This is a schematic diagram of a cylindrical permanent magnet 18 that can be applied to the absolute encoder 100 - 1 according to the first embodiment. Fig.12 This is a cylindrical permanent magnet 19 applicable to the absolute encoders 100 - 1 and 100 - 2 of the first and second embodiments.

[0121] Fig.10 In the absolute encoder 100-1 shown in FIG. Figure 3 The permanent magnets 8 and 17 shown in FIG. Fig.12 The permanent magnet 19 shown. In addition, Fig.10 In the absolute encoder 100-1 shown in FIG. Figure 3 The permanent magnet 9 shown in the figure uses Fig.11 The permanent magnet 18 is shown.

[0122] Fig.11 The permanent magnet 18 of the first configuration example is shown. In the permanent magnet 18 , a first magnetic pole portion N of a first polarity and a second magnetic pole portion S of a second polarity different from the first polarity are arranged in the radial direction D1 of the permanent magnet 18 . Fig.12 The permanent magnet 19 of the second configuration example is shown. In the permanent magnet 19, the first magnetic pole portion N and the second magnetic pole portion S are arranged along the axial direction D2 of the permanent magnet 19 in the left half of the figure, with the center of the permanent magnet 19 as the boundary. On the other hand, in the right half of the figure, the first magnetic pole portion N and the second magnetic pole portion S are arranged in the axial direction D2 of the permanent magnet 9 in the figure in a direction upside down from the left half. That is, in the permanent magnet 19, the first magnetic pole portion N and the second magnetic pole portion S are arranged adjacent to each other in the radial direction D1 with the center of the radial direction D1 of the permanent magnet 19 as the boundary, and the first magnetic pole portion N and the second magnetic pole portion S are arranged adjacent to each other in the axial direction D2 with the center of the axial direction D2 as the boundary. Fig.11 and Fig.12 The arrow "DM" shown indicates the magnetization direction. Hereinafter, a magnet that is magnetized in a manner such that the first magnetic pole portion N and the second magnetic pole portion S are arranged in the radial direction, such as the permanent magnet 18, is sometimes referred to as a diameter magnetized magnet. In addition, a magnet that is constructed in a manner such that the first magnetic pole portion N and the second magnetic pole portion S are reversed up and down, such as the permanent magnet 19, is sometimes referred to as a surface magnetized magnet.

[0123] Both the permanent magnet 18 and the permanent magnet 19 can be used as the permanent magnet 9 of the absolute encoder 100-1 and 100-2 of embodiments 1 and 2. However, in the permanent magnet 19, the magnetic field formed by a plurality of magnetic lines of force is distributed more widely (wide) along the axial direction D2 than the magnetic field generated in the permanent magnet 18. On the other hand, in the permanent magnet 18, the magnetic field formed by a plurality of magnetic lines of force is distributed more widely along the radial direction D1 than the magnetic field generated in the permanent magnet 19. For this reason, when the permanent magnet 18 is used in the absolute encoder 100-1 and 100-2 of embodiments 1 and 2, the magnetic field generated by the permanent magnet 18 in a manner extending outward in the radial direction is likely to generate magnetic interference that affects other magnetic sensors as described above.

[0124] In the absolute encoders 100-1 and 100-2 of the respective modified examples of the first and second embodiments, when the permanent magnet 19 is used as the permanent magnet 9 (the first magnet), the leakage magnetic flux generated from the permanent magnet 9 flows into the magnetic sensor 50 less than when the permanent magnet 18 is used as the permanent magnet 9. When the permanent magnet 19 is used as the permanent magnet 9 (the first magnet), the first magnetic pole portion and the second magnetic pole portion of the permanent magnet 19 are adjacently formed in the radial direction with the center of the radial direction of the permanent magnet 19 as the boundary, and the first magnetic pole portion and the second magnetic pole portion of the permanent magnet 19 are adjacently formed in the axial direction with the center of the axial direction of the permanent magnet 19 as the boundary. In addition, when the permanent magnet 19 is used as the permanent magnet 8 (the second magnet), the leakage magnetic flux generated from the permanent magnet 8 flows into the magnetic sensor 40 less than when the permanent magnet 18 is used as the permanent magnet 8. When the permanent magnet 19 is used as the permanent magnet 8 (the second magnet), the first magnetic pole portion and the second magnetic pole portion of the permanent magnet 19 are adjacent to each other in the radial direction with the center of the radial direction of the permanent magnet 19 as the boundary, and the first magnetic pole portion and the second magnetic pole portion of the permanent magnet 19 are adjacent to each other in the axial direction with the center of the axial direction of the permanent magnet 19 as the boundary. As a result, the reduction in the detection accuracy of the rotation angle or the rotation amount of the first countershaft gear 105 or the main shaft gear 101 can be reduced. In addition, by reducing the reduction in the detection accuracy of the rotation angle or the rotation amount, the absolute encoder 100-1, 100-2 can be further miniaturized. It should be noted that the permanent magnet 19 can also be used as the permanent magnet 17 (the third magnet) provided on the second countershaft gear 138. In the case of such a configuration, the same effect as when the permanent magnet 19 is used as the permanent magnet 8 (the second magnet) can be obtained.

[0125] Next, the reason why a diametrically magnetized magnet (permanent magnet 18 ) is used as a permanent magnet corresponding to the magnetic sensor 40 will be described.

[0126] The radial magnetized magnet has the following property: when the position of the magnet deviates from the magnetic sensor, the change in the magnetic flux density of the radial magnetized magnet relative to the radial direction is smaller than the change in the magnetic flux density of the surface magnetized magnet relative to the radial direction. Thus, when the change in the magnetic flux density relative to the radial direction is small, the larger the center offset value (the difference between the position of the magnetic sensor center and the magnet center relative to the radial direction of the magnet) is, the larger the angular error when the surface magnetized magnet is used is than the angular error when the radial magnetized magnet is used. The center offset value is equal to the deviation width from the center of the magnetic flux detection area of ​​the magnetic sensor 50 or the magnetic sensor 40 to the radial center of the radial magnetized magnet when the radial magnetized magnet is viewed in the axial direction. The angular error is equal to the angular difference between the actual rotation angle of the rotation angle of the main shaft gear 101, the first worm gear part 102b, the first countershaft gear 105, etc. and the rotation angle detected by the magnetic sensor 50, the magnetic sensor 40, the magnetic sensor 90, etc.

[0127] Fig.13 It is used for Fig.11 or Fig.12 FIG. 1 is a diagram for explaining the angular error with respect to the change of the center offset value when the distance (gap) between the facing surfaces of the magnet and the magnetic sensor in the axial direction D2 is constant. Fig.13 The horizontal axis represents the center offset value. Fig.13 The vertical axis represents the angle error. The curve represented by the dotted line represents the change in the angle error when the center offset value of the surface magnetized magnet with a diameter of about 4 mm is increased. The curve represented by the dashed line represents the change in the angle error when the center offset value of the surface magnetized magnet with a diameter of 5 mm is increased. The curve represented by the bold line represents the change in the angle error when the center offset value of the diameter magnetized magnet with a diameter of about 4 mm is increased. The curve represented by the general line represents the change in the angle error when the center offset value of the diameter magnetized magnet with a diameter of 5 mm is increased.

[0128] from Fig.13 It can be seen that when a surface magnetized magnet with a diameter of about 4 mm is used, the angle error (curve represented by the dotted line) is the largest, and when a diameter magnetized magnet with a diameter of 5 mm is used, the angle error (continuous general line) is the smallest. It should be noted that when comparing magnets of the same type but different diameters, the angle error when using a magnet with a smaller diameter tends to be larger than the angle error when using a magnet with a larger diameter. The reason is that, when the center offset value is the same, the smaller the diameter of the magnet, the larger the ratio of the center offset value to the radial dimension of the magnet.

[0129] Fig.14This is a conceptual diagram of the magnetic flux density detected by the magnetic flux detection element provided on the magnetic sensor when a surface magnetized magnet is used. Fig.15 This is a conceptual diagram of the magnetic flux density detected by the magnetic flux detection element provided on the magnetic sensor when a diameter magnetized magnet is used. Fig.14 and Fig.15 The scale of the vertical axis is the same. Fig.14 or Fig.15 It is shown in the figure that a Hall sensor for magnetic flux detection is set at a position which is deviated by 0.5 mm from the radial center of the surface magnetized magnet or the diameter magnetized magnet toward the radial outer side, and the magnetic flux density is measured by the analyzer every time the Hall sensor is away from the surface magnetized magnet or the diameter magnetized magnet in the range of 1.0 mm to 1.3 mm in the axial direction by 0.05 mm. Fig.14 or Fig.15 The vertical axis conceptually represents the value of the magnetic flux density. Fig.14 or Fig.15 The horizontal axis is the rotation angle of the main shaft gear 101, the first worm gear portion 102b, the first counter shaft gear 105, etc. Fig.14 or Fig.15 In the example, the magnetic flux density changes in accordance with the rotation angle in a sinusoidal shape. Fig.14 or Fig.15 , which respectively represent the magnetic flux density detected when the Hall sensor is moved away from the axial direction by 0.05 mm in the range of 1.0 mm to 1.3 mm. For example, the sine wave with the largest absolute value of magnetic flux density represents the magnetic flux density when the gap with the Hall sensor is 1.0 mm. The sine wave with the smallest absolute value of magnetic flux density represents the magnetic flux density when the gap with the Hall sensor is 1.3 mm.

[0130] Depend on Fig.14 or Fig.15 The measurement results show that, based on the magnetic flux density when the gap between the Hall sensor is 1.0 mm, the absolute value of the magnetic flux density decreases as the gap increases by 0.05 mm.

[0131] It can also be seen that the flux change from the magnetic flux density of the surface magnetized magnet when the gap between the Hall sensor is 1.0 mm to the magnetic flux density of the diameter magnetized magnet when the gap is 1.3 mm is smaller than the flux change from the magnetic flux density of the diameter magnetized magnet when the gap is 1.0 mm to the magnetic flux density of the surface magnetized magnet when the gap is 1.3 mm.

[0132] Thus, since the change in magnetic flux density measured when using a diameter magnetized magnet is smaller than that measured when using a surface magnetized magnet, it can be said that the axis deviation tolerance of the diameter magnetized magnet is higher than that of the surface magnetized magnet. It can also be said that the gap tolerance of the diameter magnetized magnet is higher than that of the surface magnetized magnet. Axis deviation refers to, for example, when the diameter magnetized magnet is viewed in a plane, the gap tolerance of the diameter magnetized magnet is higher than that of the surface magnetized magnet. Fig.11 or Fig.12 When observing the permanent magnet 18 or the permanent magnet 19 shown in the figure, the central axis AX of the permanent magnet 18 or the permanent magnet 19 is deviated from the central axis of the detection element in the magnetic sensor corresponding to these permanent magnets. Axis deviation tolerance means that even if the amount of axis deviation increases, the change in the magnetic flux density of the magnet is small. Gap means, for example, from Fig.11 or Fig.12 The gap between the surface of the permanent magnet 18 or the permanent magnet 19 shown and the opposing surface of the magnetic sensor corresponding to the permanent magnet. Gap tolerance means that even when the gap increases, the change in the magnetic flux density of the magnet is small.

[0133] Fig.16 This is a conceptual diagram of the magnetic flux density on the upper surface of a surface magnetized magnet. Fig.17 This is a conceptual diagram of the magnetic flux density on the upper surface of the diameter magnetized magnet. The upper surface is the surface facing the magnetic sensor among the surfaces of the surface magnetized magnet and the diameter magnetized magnet. Fig.16 or Fig.17 The vertical axis conceptually shows the value of the magnetic flux density measured by the analyzer at a position 1.0 mm away from the upper surface of each of the surface magnetized magnet and the diameter magnetized magnet. The magnetic flux of the surface magnetized magnet has a steep shape, but the magnetic flux of the diameter magnetized magnet has a lower peak in the direction extending from the central axis AX than the magnetic flux of the surface magnetized magnet, and the width in the direction orthogonal to the direction extending from the central axis AX is also wider, and has a softer shape. Fig.16 or Fig.17 The measurement results of the magnetic flux shown also indicate that the axis misalignment resistance of the diameter-magnetized magnet is superior to the axis misalignment resistance of the surface-magnetized magnet.

[0134] Fig.18 Yes means Fig.10Graph showing the reduction ratio of the first worm gear portion 102b to the main shaft gear 101, the reduction ratio of the first countershaft gear 105 to the first worm gear portion 102b, and the permissible error of the rotation angle during one rotation of the main shaft gear 101, etc. In the graph, "main shaft" corresponds to the main shaft gear 101, "countershaft 1" corresponds to the first worm gear portion 102b, and "countershaft 2" corresponds to the first countershaft gear 105. The permissible error of the rotation angle during one rotation of the main shaft gear 101 is 1.8° (±0.9°). The reduction ratio of the first worm gear portion 102b to the main shaft gear 101 is, for example, 50. The permissible error of the rotation angle during one rotation of the first worm gear portion 102b is 7.2° (±3.6°). The reduction ratio of the first countershaft gear 105 to the first worm gear portion 102b is, for example, 20. The permissible error of the rotation angle during one rotation of the first counter gear 105 is 18° (±9°).

[0135] Since the permissible error of the rotation angle of the main shaft gear 101 is smaller than the permissible error of the rotation angle of each of the first worm gear portion 102b and the first counter gear 105, it is preferable to use the permanent magnet 18 of the diameter magnetized magnet so as not to exceed the permissible error of the main shaft gear 101 for the magnet corresponding to the magnetic sensor 40 for detecting the rotation angle of the main shaft gear 101. On the other hand, the permissible error of the rotation angle of each of the first worm gear portion 102b and the first counter gear 105 is larger than the permissible error of the rotation angle of the main shaft gear 101. Therefore, it is preferable to use the permanent magnet 19 of the surface magnetized magnet so as to preferentially suppress the occurrence of the above-mentioned magnetic interference for the magnet corresponding to the magnetic sensor 50 for detecting the rotation angle of the first worm gear portion 102b. It is also preferable to use the permanent magnet 19 of the surface magnetized magnet for the magnet corresponding to the magnetic sensor 90 for detecting the rotation angle of the first counter gear 105 for the same reason.

[0136] As mentioned above, Fig.10In the absolute encoder 100-1 shown, a diameter magnetized magnet is used as a magnet for detecting the rotation angle of the main shaft gear 101, and a surface magnetized magnet is used as a magnet for detecting the rotation angle of each of the magnet holder 6 and the driven gear 36. For this reason, magnetic interference with the permanent magnet 18 is less likely to occur than in the case where the diameter magnetized magnets of the permanent magnet 8 and the permanent magnet 17 are used respectively. Therefore, by allowing the leakage magnetic flux generated from the two permanent magnets 19 to flow into the magnetic sensor 40, the reduction in the detection accuracy of the rotation angle or the rotation amount of the main shaft gear 101 caused by the magnetic sensor 40 can be suppressed. In addition, by using the diameter magnetized magnet, the rotation angle of the main shaft gear 101 detected by the magnetic sensor 40 for detecting the rotation angle of the main shaft gear 101 can be suppressed from exceeding the allowable error of the main shaft gear 101. As a result, the reduction in the detection accuracy of the rotation angle or the rotation amount of the main shaft gear 101 caused by the magnetic sensor 40 can be suppressed. In addition, by selecting the appropriate magnetization direction of the permanent magnet, the distance between the plurality of permanent magnets in the XY plane can be shortened, thereby miniaturizing the absolute encoder 100-1. Alternatively, the detection accuracy of the absolute encoder 100-1 can be ensured without using a high-performance and expensive magnetic sensor.

[0137] In addition, in the absolute encoder 100-1 of the first embodiment, a plate-shaped member made of a magnetic body such as iron, that is, a base 110a of the main base 110 is further provided between the second angle sensor and the motor 200 or between the third angle sensor and the motor 200. That is, the base 110a can function as a magnetic shielding part for the magnetic flux leaking from the motor 200. Therefore, it is difficult for the magnetic flux leaking from the motor 200 to reach the magnetic sensor 40, etc. As a result, compared with the case where the base 110a is made of a non-magnetic body such as aluminum with a low magnetic permeability, the reduction in the detection accuracy of the rotation angle or rotation amount of the gear caused by the magnetic sensor can be reduced.

[0138] <Implementation method 2>

[0139] Fig.19 This is an oblique view showing a state where the absolute encoder 100-2 according to the second embodiment of the present invention is mounted on the motor 200. The following description is based on the XYZ rectangular coordinate system in the same manner as the first embodiment. The X-axis direction corresponds to the horizontal left-right direction, the Y-axis direction corresponds to the horizontal front-back direction, and the Z-axis direction corresponds to the vertical up-down direction. The Y-axis direction and the Z-axis direction are respectively orthogonal to the X-axis direction. There are also cases where the X-axis direction is called the left direction or the right direction, the Y-axis direction is called the front direction or the rear direction, and the Z-axis direction is called the up direction or the down direction. Fig.19In the diagram, the state when viewed from above along the Z-axis direction is called a plan view, the state when viewed from the front along the Y-axis direction is called a front view, and the state when viewed from the left and right along the X-axis direction is called a side view. Such directional representation does not limit the use posture of the absolute encoder 100-2, and the absolute encoder 100-2 can be used in any posture. Fig.19 , the components provided inside the housing 15 of the absolute encoder 100 - 2 are shown in a perspective manner. It should be noted that the shape of the teeth is omitted in the drawings.

[0140] Fig. 20 It means from Fig.19 The illustrated absolute encoder 100 - 2 is a perspective view showing a state in which the housing 15 and the mounting screws 16 are removed. Fig. 20 In FIG. 2 , a plurality of components provided on the lower surface 20 - 1 of the substrate 20 are perspectively shown. Fig.21 It means from Fig. 20 The illustrated absolute encoder 100 - 2 is a perspective view showing a state in which the base plate 20 and the base plate mounting screws 13 are removed. Fig. 22 It is from Fig.21 The perspective view showing the absolute encoder 100 - 2 being mounted on the motor 200 is a perspective view showing a state where the motor 200 and the screw 14 are removed. Fig.23 Yes means Fig. 22 The diagram shows the main base 10, the intermediate gear 2, etc. in a plan view. Fig.23 2 shows the arrangement of main components among the plurality of components included in the absolute encoder 100 - 2 . Fig.24 Yes Fig.23 The absolute encoder 100 - 2 shown is a cross-sectional view cut along a plane passing through the center of the intermediate gear 2 and parallel to the XY plane.

[0141] Fig.25 yes Fig.24 The illustrated partial enlarged cross-sectional view shows a state where the bearing 3 is removed from the intermediate gear 2 . Fig.25 In order to easily understand the configuration relationship between the bearing 3 and the press-fit portion 2d formed on the intermediate gear 2, the bearing 3 and the press-fit portion 2d of the intermediate gear 2 are separated. Fig.25 In order to facilitate understanding of the arrangement relationship between the bearing 3 and the wall portion 80 provided on the base 60 of the main base 10 , the bearing 3 and the wall portion 80 are also separated.

[0142] Fig.26 It passes through Fig.23 The plane perpendicular to the center line of the intermediate gear 2 and the center line of the main shaft gear 1 is shown. Fig. 20The absolute encoder 100 - 2 shown is a cross-sectional view in which the substrate 20 and the magnetic sensor 40 are not cut. Fig.26 , the permanent magnet 9 is mounted on the main shaft gear 1 and the main shaft gear 1 is mounted on the motor shaft 201. Fig.26 The figure also shows the state in which the worm gear portion 1d of the main shaft gear 1 and the worm wheel portion 2a of the intermediate gear 2 are meshed. Fig.26 It can be seen that the upper surface 9 a of the permanent magnet 9 provided on the main shaft gear 1 exists at a position separated from the magnetic sensor 40 by a certain distance in the Z-axis direction.

[0143] Fig. 27 It passes through Fig.24 The plane perpendicular to the center line of the intermediate gear 2 and the center line of the countershaft gear 5 shown in FIG. Fig. 20 The absolute encoder 100 - 2 shown is a cross-sectional view in which the substrate 20 and the magnetic sensor 50 are not cut. Fig. 27 The worm wheel portion 5a and the worm gear portion 2b are shown in the state of meshing. Fig. 27 The figure also shows the state where the shaft portion 6b of the magnet holder 6 is held by two bearings 7 and the state where the permanent magnet 8 is held by the magnet holder 6. Fig. 27 The figure also shows a state where the radially outer surface of the head 6c provided on the magnet seat 6 is separated from the tooth top circle of the worm gear part 2b. Fig. 27 It can be seen that the surface 8a of the permanent magnet 8 provided on the magnet holder 6 exists at a position away from the magnetic sensor 50 by a certain distance in the Z-axis direction. Fig. 27 The cross-sectional shape of the bearing seat portion 10 d of the main base 10 is also shown.

[0144] Fig.28 Yes means Fig.21 This is a perspective view of a state where the intermediate gear 2 is removed from among the multiple components shown. Fig.29 It is from Fig.28 The wall portion 70 shown is a perspective view showing a state where the screw 12 is removed, a state where the leaf spring 11 is removed, and a leaf spring mounting surface 10e facing the leaf spring 11. The motor 200 and the main shaft gear 1 are not shown here.

[0145] Fig.30 It passes through Fig.23 The center of the substrate positioning pin 10g and the center of the substrate positioning pin 10j are aligned with a plane parallel to the Z-axis direction. Fig. 20 The absolute encoder 100 - 2 shown is a cross-sectional view in which the magnetic sensor 40 is not cut.

[0146] Fig.31 Yes Fig. 20 The substrate 20 shown is a diagram when viewed from the lower surface 20 - 1 side. Fig.32 is from Fig.19 The motor 200 is removed from the main base 10 and viewed from the lower surface 10-2 side. The lower surface 10-2 of the main base 10 is Fig.29 The lower surface 10 - 2 of the main base 10 is also a surface facing the motor 200 . Fig.33 yes Fig.19 An oblique view of the housing 15 is shown.

[0147] Fig.34 It passes through Fig.21 The center of the substrate positioning pin 10g and the center of the substrate positioning pin 10j are aligned with a plane parallel to the Z-axis direction. Fig.19 The absolute encoder 100 - 2 shown is a cross-sectional view in which the motor 200 , the main shaft gear 1 , and the magnetic sensor 40 are not shown in cross section. Fig.34 1 and 2 show a state where the claw portion 15 a provided on the shell portion 15 is interlocked (engaged) with the recessed portion 10 aa provided on the main base 10 , and a state where the claw portion 15 b provided on the shell portion 15 is interlocked with the recessed portion 10 ab provided on the main base 10 . Fig.35 yes Fig. 27 An exploded oblique view of the permanent magnet 8, magnet seat 6, countershaft gear 5 and bearing 7 is shown. Fig.36 yes Fig.26 The permanent magnet 9, the main shaft gear 1 and the motor shaft 201 are shown in an exploded perspective view.

[0148] Below, refer to Figures 19 to 36 The structure of the absolute encoder 100-2 is described in detail. The absolute encoder 100-2 includes a main shaft gear 1, an intermediate gear 2, a bearing 3, a shaft 4, a counter shaft gear 5, a magnet holder 6, a bearing 7, a permanent magnet 8, a permanent magnet 9, a main base 10, a leaf spring 11, a screw 12, a substrate mounting screw 13, a screw 14, a housing 15, a mounting screw 16, a substrate 20, a microcomputer 21, a bidirectional driver 22, a line driver 23, a connector 24, a magnetic sensor 40, and a magnetic sensor 50.

[0149] The motor 200 is, for example, a stepping motor, a DC brushless motor, etc. The motor 200 can be used as a driving source for driving an industrial robot via a speed reduction mechanism such as a wave gear device. The motor 200 includes a motor shaft 201. Fig.26 As shown in FIG. 1 , one end of the motor shaft 201 protrudes from the frame 202 of the motor 200 in the positive direction of the Z axis. Fig.19As shown, the other end of the motor shaft 201 protrudes from the housing 202 of the motor 200 in the negative direction of the Z axis. The motor shaft 201 is an example of a main shaft.

[0150] The outer shape of the motor 200 in the plan view is, for example, square. The lengths of the four sides constituting the outer shape of the motor 200 are, for example, 25 mm each. The first side of the four sides constituting the outer shape of the motor 200 and the second side parallel to the first side are parallel to the Y axis. In addition, the third side adjacent to the first side and the fourth side parallel to the third side are parallel to the X axis. In addition, as for the absolute encoder 100-2 provided on the motor 200, in the plan view, the length is also 25 mm in accordance with the outer shape of the motor 200 with a side length of 25 mm.

[0151] Next, a plurality of components included in the absolute encoder 100 - 2 will be described respectively.

[0152] like Fig.26 As shown, the main shaft gear 1 is a cylindrical member coaxially arranged with the motor shaft 201. The main shaft gear 1 includes a cylindrical first cylindrical portion 1a, and a cylindrical second cylindrical portion 1b coaxially arranged on the positive direction side of the first cylindrical portion 1a in the Z axis. In addition, the main shaft gear 1 includes a connecting portion 1c that connects the first cylindrical portion 1a and the second cylindrical portion 1b arranged on the radial inner side of the second cylindrical portion 1b, and a worm gear portion 1d arranged on the radial outer side of the second cylindrical portion 1b. By forming the connecting portion 1c in this way, the connecting portion 1c can function as an escape path for air when the main shaft gear 1 is press-fitted to the motor shaft 201. The inner diameter of the connecting portion 1c is smaller than the inner diameter of the first cylindrical portion 1a and the inner diameter of the second cylindrical portion 1b. The space enclosed by the end surface of the connecting portion 1c in the negative direction of the Z axis, i.e., the bottom surface 1e, and the inner peripheral surface of the first cylindrical portion 1a is a press-fit portion 1f for fixing the main shaft gear 1 to the end of the motor shaft 201. The press-fit portion 1f is a recessed portion that is recessed from the end of the first cylindrical portion 1a in the negative direction of the Z axis toward the positive direction of the Z axis. After the motor shaft 201 is press-fitted into the press-fit portion 1f, the main shaft gear 1 can rotate integrally with the motor shaft 201. The worm gear portion 1d is the gear portion of the main shaft gear 1.

[0153] The space enclosed by the end face of the connecting portion 1c in the positive direction of the Z axis, i.e., the bottom face 1g, and the inner peripheral surface of the second cylindrical portion 1b is a magnet holding portion 1h for fixing the permanent magnet 9. The magnet holding portion 1h is a recessed portion that is recessed from the end of the second cylindrical portion 1b in the positive direction of the Z axis toward the negative direction of the Z axis. The permanent magnet 9 is press-fitted into the magnet holding portion 1h. As for the permanent magnet 9 that is press-fitted into the magnet holding portion 1h, its outer peripheral surface is in contact with the inner peripheral surface of the second cylindrical portion 1b, and its lower surface 9b is in contact with the bottom face 1g. Based on this, the permanent magnet 9 can be positioned in the axial direction, and positioning in a direction orthogonal to the axial direction can also be performed. The axial direction of the permanent magnet 9 is the same as the central axis direction of the motor shaft 201.

[0154] like Figure 22 to Figure 24 and Fig.26 As shown, the worm gear portion 1d is composed of a tooth portion formed in a spiral shape, and meshes with the worm wheel portion 2a of the intermediate gear 2. The worm wheel portion 2a is a gear portion of the intermediate gear 2. Fig.26 In the figure, the shape of the tooth portion is omitted. The worm gear portion 1d can be formed of, for example, polyacetal resin. The worm gear portion 1d is an example of a first drive gear.

[0155] like Figure 22 to Figure 25 As shown in the figures, the intermediate gear 2 is axially supported by the shaft 4 on the upper surface of the main base 10. The center axis of the intermediate gear 2 is parallel to the X-Y plane. In addition, the center axis of the intermediate gear 2 is not parallel to the X-axis and the Y-axis in the plan view. That is, the center axis direction of the intermediate gear 2 is inclined to the extension direction of the X-axis and the Y-axis. The center axis direction of the intermediate gear 2 is inclined to the extension direction of the X-axis and the Y-axis means that the center axis of the intermediate gear 2 extends obliquely relative to the four sides of the main base 10. As shown in the figures, the center axis of the intermediate gear 2 is parallel to the X-Y plane. Fig. 22 and Fig.23 As shown, the four sides of the main base 10 are composed of a first side 301 parallel to the Y-Z plane, a second side 302 parallel to the first side 301, a third side 303 parallel to the X-Z plane and adjacent to the first side 301, and a fourth side 304 parallel to the third side 303. The first side 301 is a side provided on the positive side of the X-axis of the main base 10. The second side 302 is a side provided on the negative side of the X-axis of the main base 10. The third side 303 is a side provided on the positive side of the Y-axis of the main base 10. The fourth side 304 is a side provided on the negative side of the Y-axis of the main base 10.

[0156] As for the size of the absolute encoder 100-2 in the plan view, as an example, it matches the size of the motor 200 with a side length of 25 mm. For this reason, by setting the intermediate gear 2 arranged in parallel in the X-Y plane so as to extend obliquely relative to the four sides of the main base 10, the size of the absolute encoder 100-2 in the horizontal direction can be reduced. The horizontal direction is equal to the direction orthogonal to the central axis of the motor shaft 201 and also equal to the direction parallel to the X-Y plane.

[0157] like Figure 21 to Figure 25 As shown in the figures, the intermediate gear 2 has a worm wheel portion 2a, a worm gear portion 2b, a bearing portion 2c, a press-fit portion 2d, a sliding portion 2e, a bottom surface 2f, and a through hole 2g. The intermediate gear 2 is a cylindrical component in which the shaft 4 is inserted into the through hole 2g that penetrates along the center axis. The through hole 2g is a space surrounded by the inner circumferential surface of the intermediate gear 2. The intermediate gear 2 is a component integrally formed of metal, resin, etc. Here, as an example, it can be formed of polyacetal resin.

[0158] The worm wheel portion 2a is a gear meshing with the worm gear portion 1d of the main shaft gear 1. The worm wheel portion 2a is an example of a first driven gear and is a gear portion of the intermediate gear 2. The worm wheel portion 2a is provided at a position close to the center of the intermediate gear 2 in the axial direction of the intermediate gear 2. In addition, the worm wheel portion 2a is composed of a plurality of teeth provided on the outer peripheral portion of the cylindrical portion of the intermediate gear 2.

[0159] The outer diameter of the worm wheel 2a is smaller than that of the worm gear 1d. The central axis of the worm wheel 2a is parallel to the upper surface of the main base 10, so by reducing the outer diameter of the worm wheel 2a, the absolute encoder 100-2 can be miniaturized in the Z-axis direction (height direction).

[0160] The worm gear portion 2b is composed of a tooth portion formed in a spiral shape, and is arranged coaxially and adjacent to the worm wheel portion 2a. In addition, the worm gear portion 2b is arranged on the outer peripheral portion of the cylindrical portion of the intermediate gear 2. By meshing the worm gear portion 2b with the worm wheel portion 5a provided on the countershaft gear 5, the rotational force of the intermediate gear 2 can be transmitted to the countershaft gear 5. The worm gear portion 2b is an example of a second drive gear and is a gear portion of the intermediate gear 2. The worm wheel portion 5a is a gear portion of the countershaft gear 5. As for the center line of the worm wheel portion 5a and the center line of the worm gear portion 2b, they are perpendicular to the center line of the worm wheel portion 5a, and are orthogonal to each other when viewed in a direction perpendicular to the center line of the worm gear portion 2b.

[0161] In order to reduce the size of the absolute encoder 100 - 2 in the Z-axis direction (height direction), the outer diameter of the worm gear portion 2 b is set to a value as small as possible.

[0162] like Fig.24As shown, the bearing portion 2c is provided on the inner peripheral surface of the intermediate gear 2 on the side opposite to the press-fit portion 2d side, that is, on the sliding portion 2e side of the intermediate gear 2. The shaft 4 is slidably inserted into the bearing portion 2c, and the intermediate gear 2 is rotatably supported by the shaft 4.

[0163] The press-fit portion 2d is a recessed portion that is recessed from the end surface of the intermediate gear 2 toward the center of the axial direction Td of the intermediate gear 2 on the inner side of the worm gear portion 2b, and is connected to the through hole 2g. The press-fit portion 2d can also be considered as a portion that enlarges the opening diameter of the end of the through hole 2g. The outer ring 3a of the bearing 3 is press-fitted to the press-fit portion 2d and fixed.

[0164] like Figure 22 to Figure 24 , Fig.28 , Fig.29 As shown in the figures, the sliding portion 2e of the intermediate gear 2 is provided on one end side of the intermediate gear 2, that is, on the side opposite to the worm gear portion 2b side in the axial direction Td of the intermediate gear 2. The sliding portion 2e of the intermediate gear 2 abuts against the sliding portion 11a of the leaf spring 11. The leaf spring 11 is an example of an elastic member, and is made of metal, for example. The sliding portion 11a of the leaf spring 11 is composed of two branches branched from the base 11d of the leaf spring 11. The base 11d of the leaf spring 11 is a plate-shaped member provided between the mounting portion 11b and the sliding portion 11a in the entirety of the leaf spring 11.

[0165] A gap larger than the diameter of the shaft 4 is formed between the two branches constituting the sliding portion 11a of the leaf spring 11. For this reason, the mounting portion 11b of the leaf spring 11 is fixed to the leaf spring mounting surface 10e provided on the wall portion 72 of the main base 10 by screws 12 in a manner that the two branches straddle the shaft 4 without contacting the shaft 4.

[0166] The sliding portion 11a of the leaf spring 11 is provided at a position facing the sliding portion 2e of the intermediate gear 2 after the intermediate gear 2 is mounted. The sliding portion 2e of the intermediate gear 2 is urged along the central axis of the shaft 4 and in a direction from the one end 4a side of the shaft 4 toward the other end 4b side of the shaft 4 by abutting against and being pressed by the sliding portion 11a of the leaf spring 11. When the intermediate gear 2 rotates in this state, the sliding portion 2e of the intermediate gear 2 slides while abutting against the sliding portion 11a of the leaf spring 11.

[0167] The bottom surface 2f of the intermediate gear 2 is located next to the press-fit portion 2d and contacts the side surface 3c of the outer ring 3a of the bearing 3. The outer ring 3a is press-fitted into the press-fit portion 2d until the side surface 3c of the outer ring 3a contacts the bottom surface 2f.

[0168] The through hole 2g of the intermediate gear 2 penetrates from the bearing portion 2c toward the press-fit portion 2d along the center axis of the intermediate gear 2 and is arranged coaxially with the shaft 4. The inner diameter of the through hole 2g is larger than the outer diameter of the shaft 4, so that a space can be ensured between the through hole 2g and the outer peripheral surface of the shaft 4.

[0169] like Fig.24 and Fig.25 As shown, the bearing 3 has an outer ring 3a, an inner ring 3b, a side surface 3c and a side surface 3d. The side surface 3c of the bearing 3 is Fig.24 The side surface of the outer ring 3a in the axial direction Td of the shaft 4 indicated by the middle arrow is the side surface of the inner ring 3b in the same direction. It should be noted that in the embodiment of the present invention, the (center) axial direction of the intermediate gear 2 or the shaft 4 is denoted as Td.

[0170] The outer ring 3a of the bearing 3 is press-fitted to the press-fit portion 2d and fixed, and the side surface 3c is in contact with the bottom surface 2f and fixed. The shaft 4 is inserted into the inner side of the inner ring 3b. Fig.24 As shown, the side surface 3d of the inner ring 3b abuts against the abutment surface 10c of the wall portion 80 of the main base 10. The abutment surface 10c defines the position of the intermediate gear 2 in the axial direction Td. As described above, the intermediate gear 2 is urged in the axial direction Td from the one end 4a of the shaft 4 toward the other end 4b of the shaft 4 by the leaf spring 11, so the side surface 3c of the outer ring 3a of the bearing 3 in contact with the bottom surface 2f of the intermediate gear 2 is also urged in the same direction. Accordingly, the inner ring 3b of the bearing 3 is also urged in the same direction, so that the side surface 3d of the inner ring 3b of the bearing 3 can abut against the abutment surface 10c of the wall portion 80. As a result, the applied force can be transmitted to the abutment surface 10c of the wall portion 80, and the intermediate gear 2 can be stably supported in the axial direction Td of the shaft 4. The details of the applied force will be described later.

[0171] The outer ring 3a of the bearing 3 is arranged to be freely rotatable relative to the inner ring 3b. Fig.24 The intermediate gear 2 shown in the figure can be rotatably supported at two locations, namely the bearing portion 2c and the bearing 3, by the shaft 4. It should be noted that the shaft 4 can be formed of, for example, stainless steel.

[0172] like Fig.24As shown, the wall portion 70 and the wall portion 80 are an example of a holding portion that can hold the intermediate gear 2 rotatably via the shaft 4. The wall portion 80 is integrally provided on the upper surface of the base 60 in a pair with the wall portion 70, and extends from the upper surface of the base 60 in the positive direction of the Z axis. The wall portion 80 is provided in a region of the entire upper surface of the base 60 that is closer to the second side 302 than the center in the X-axis direction and closer to the third side 303 than the center in the Y-axis direction. In addition, the wall portion 80 is also provided in a position close to the second side 302 and close to the center in the Y-axis direction in this region. The wall portion 70, the wall portion 80 and the shaft 4 can function as a holding portion that can hold the intermediate gear 2 rotatably. The shaft 4 is a cylindrical member having one end 4a and the other end 4b. The other end 4b of the shaft 4 is press-fitted into a hole 10b formed in the wall portion 80 of the main base 10, and is fixed on this basis. On the other hand, the one end 4a of the shaft 4 only needs to be inserted into the hole 10a formed in the wall portion 70 to be positioned, and there is no need to press-fit the one end 4a of the shaft 4 into the hole 10a. In this way, the shaft 4 can be easily mounted compared to the case where the one end 4a of the shaft 4 is press-fitted into the hole 10a.

[0173] like Fig.23 As shown in FIG. 1 and FIG. 2 , in the absolute encoder 100-2, the counter gear 5 is provided on the side of the intermediate gear 2 opposite to the main gear 1. For example, the counter gear 5 is arranged in an area close to a corner of the main base 10 in an area surrounded by four sides of the main base 10. The corner is, for example, Fig.23 The portion where the second side 302 and the third side 303 are intersecting is shown. In this way, the counter gear 5 and the main shaft gear 1 can be arranged to sandwich the intermediate gear 2 by utilizing the limited area on the main base 10. Accordingly, compared with the case where the counter gear 5 and the main shaft gear 1 are arranged adjacent to each other without sandwiching the intermediate gear 2, the distance from the counter gear 5 to the main shaft gear 1 can be increased.

[0174] The magnetic sensor 40 can detect the rotation angle of the corresponding main shaft gear 1 by detecting the change of the magnetic flux generated by the permanent magnet 9 due to the rotation of the permanent magnet 9 rotating together with the main shaft gear 1. On the other hand, the magnetic sensor 50 can detect the rotation angle of the corresponding counter shaft gear 5 by detecting the change of the magnetic flux generated by the permanent magnet 8 due to the rotation of the permanent magnet 8 rotating together with the counter shaft gear 5.

[0175] Here, for example, when the main shaft gear 1 and the counter shaft gear 5 are arranged adjacent to each other, a portion of the magnetic flux generated by the permanent magnet 8 and the permanent magnet 9 will affect the magnetic sensor that does not correspond to the permanent magnet 8 and the permanent magnet 9, which is the so-called magnetic interference, which is explained below.

[0176] Fig.37 This is a conceptual diagram of the waveform (A) obtained by detecting the magnetic flux of the permanent magnet 9 provided on the main shaft gear 1 by the magnetic sensor 40 when the main shaft gear 1 rotates, the waveform (B) obtained by detecting the magnetic flux of the permanent magnet 8 provided on the counter shaft gear 5 by the magnetic sensor 50, and the magnetic interference waveform (C) obtained by detecting the state in which a part of the magnetic flux of the permanent magnet 8 overlaps with the magnetic flux of the permanent magnet 9 as leakage magnetic flux by the magnetic sensor 40. The vertical axis represents the magnetic flux, and the horizontal axis represents the rotation angle of the main shaft gear 1. In this way, the magnetic sensor 40 is expected to detect the waveform (A), but when magnetic interference occurs, it becomes the waveform shown in (C), so the correct waveform cannot be detected.

[0177] same, Fig.38 The waveform (A) obtained by detecting the magnetic flux of the permanent magnet 8 provided on the counter gear 5 by the magnetic sensor 50 when the main shaft gear 1 rotates, the waveform (B) obtained by detecting the magnetic flux of the permanent magnet 9 provided on the main shaft gear 1 by the magnetic sensor 40, and the magnetic interference waveform (C) obtained by detecting the state where a part of the magnetic flux of the permanent magnet 9 overlaps with the magnetic flux of the permanent magnet 8 as leakage magnetic flux by the magnetic sensor 50. The vertical axis represents the magnetic flux, and the horizontal axis represents the rotation angle of the counter gear 5. In this way, the waveform (A) is expected to be detected in the magnetic sensor 50, but when magnetic interference occurs, it becomes the waveform shown in (C), so the correct waveform cannot be detected.

[0178] Therefore, according to the absolute encoder 100-2 of the second embodiment, since the main shaft gear 1 and the permanent magnet 9 and the counter shaft gear 5 and the permanent magnet 8 are arranged to sandwich the intermediate gear 2 with a distance between them, the occurrence of magnetic interference that affects the magnetic sensors that do not correspond to the permanent magnets 8 and 9 can be reduced. For example, the interference caused by a part of the magnetic flux from the permanent magnet 9 provided on the main shaft gear 1 as leakage magnetic flux to the magnetic sensor 50 provided for the original purpose of detecting the change of the magnetic flux from the permanent magnet 8 provided on the counter shaft gear 5 can be reduced. In addition, the interference caused by a part of the magnetic flux from the permanent magnet 8 provided on the counter shaft gear 5 as leakage magnetic flux to the magnetic sensor 40 provided for the original purpose of detecting the change of the magnetic flux from the permanent magnet 9 can also be reduced.

[0179] Thus, according to the absolute encoder 100-2 of the second embodiment, it is known that not only the size of the absolute encoder 100-2 in a plan view can be relatively reduced, but also the detection accuracy of the rotation angle or the rotation amount of the counter shaft gear 5 caused by the magnetic sensor 50 can be prevented from being reduced. In addition, according to the absolute encoder 100-2, it is known that not only the size of the absolute encoder 100-2 in a plan view can be relatively reduced, but also the detection accuracy of the rotation angle or the rotation amount of the main shaft gear 1 caused by the magnetic sensor 40 can be prevented from being reduced.

[0180] like Fig. 27 As shown, the countershaft gear 5 is a cylindrical member fixed by being press-fitted to the shaft portion 6b of the magnet holder 6. The countershaft gear 5 has a worm gear portion 5a and a through hole 5b. The countershaft gear 5 is a member integrally molded from metal or resin, and here, as an example, can be formed from polyacetal resin.

[0181] The worm wheel 5 a is a gear that meshes with the worm gear 2 b. The worm wheel 5 a is an example of a second driven gear. The worm wheel 5 a is composed of a plurality of teeth provided on the outer circumference of the cylindrical portion of the counter gear 5 . Fig. 22 In the embodiment, by the rotation of the intermediate gear 2, the rotational force of the intermediate gear 2 can be transmitted to the counter gear 5 via the worm gear portion 2b and the worm wheel portion 5a.

[0182] The through hole 5b is a hole that penetrates along the central axis of the cylindrical counter gear 5. When the shaft portion 6b of the magnet holder 6 is press-fitted into the through hole 5b, the counter gear 5 and the magnet holder 6 can rotate integrally.

[0183] like Fig. 27 and Fig.35 As shown, the magnet holder 6 includes a magnet holding portion 6a, a shaft portion 6b, and a head portion 6c. The magnet holder 6 is a member integrally formed of metal or resin, and can be formed of non-magnetic stainless steel as an example.

[0184] The outer rings 7a of the two bearings 7 are press-fitted onto the inner peripheral surface 10dc of the bearing seat portion 10d formed on the main base 10. It should be noted that the two bearings 7 have an outer ring 7a and an inner ring 7b, respectively.

[0185] The shaft portion 6b of the magnet seat 6 is a cylindrical member that can be press-fitted into the through hole 5b of the countershaft gear 5, and the lower portion of the shaft portion 6b can be inserted into the inner rings 7b of the two bearings 7. Therefore, the magnet seat 6 can be axially supported by the two bearings 7 relative to the main base 10, thereby being integrally rotated with the countershaft gear 5.

[0186] In addition, a head 6c may be provided at the upper end of the magnet seat 6. The head 6c is a cylindrical component with a bottom. A magnet holding portion 6a may be formed on the head 6c. The magnet holding portion 6a is a recessed portion that is recessed from the upper end surface of the head 6c toward the lower side. The outer peripheral surface of the permanent magnet 8 arranged on the magnet holding portion 6a is in contact with the inner peripheral surface of the head 6c. Accordingly, the permanent magnet 8 can be fixed on the magnet holding portion 6a of the head 6c.

[0187] The magnet seat 6 can be prevented from tilting by axially supporting the shaft portion 6b of the magnet seat 6 with two bearings 7 disposed on the bearing seat portion 10d formed on the main base 10. Therefore, if the two bearings 7 are disposed as far away from each other as possible in the axial direction of the shaft portion 6b, the magnet seat 6 can be expected to be further prevented from tilting.

[0188] like Fig. 27 As shown, the upper portion 10db of the bearing seat portion 10d is the upper side region of the bearing seat portion 10d in the Z-axis direction of the entire bearing seat portion 10d. A bearing 7 is provided inside the upper portion 10db of the bearing seat portion 10d. In addition, the lower portion 10da of the bearing seat portion 10d is the lower side region of the bearing seat portion 10d in the Z-axis direction of the entire bearing seat portion 10d. A bearing 7 is provided inside the lower portion 10da of the bearing seat portion 10d.

[0189] like Fig. 27 As shown, a cutout portion 202a is provided on a part of the frame 202 of the motor 200. The cutout portion 202a is a recessed portion that is recessed toward the negative direction of the Z axis. On the main base 10, the lower portion 10da of the bearing seat portion 10d is protruded, so by providing the cutout portion 202a on the frame 202 of the motor 200, mutual interference can be prevented. The lower portion 10da of the bearing seat portion 10d is the lower side area of ​​the bearing seat portion 10d in the Z axis direction of the entire bearing seat portion 10d. A bearing 7 is provided on the inner side of the lower portion 10da of the bearing seat portion 10d. In this way, by providing the cutout portion 202a on the frame 202 of the motor 200, the distance between the two bearings 7 in the Z axis direction can be separated compared to the case where the cutout portion 202a is not provided. Furthermore, the upper portion 10db of the bearing seat portion 10d is an upper region of the bearing seat portion 10d in the Z-axis direction in the entire bearing seat portion 10d.

[0190] If the bearing 7 is arranged at a position closer to the magnet holding portion 6a and the permanent magnet 8 in the axial direction of the shaft portion 6b of the magnet seat 6, the axial vibration of the magnet seat 6 and the permanent magnet 8 during rotation can be reduced. On the other hand, the outer diameter of the upper portion 10db of the bearing seat portion 10d is close to the intermediate gear 2, so by forming an inclined surface on the upper portion 10db of the bearing seat portion 10d, not only can the interference with the tooth top circle of the intermediate gear 2 be avoided, but the bearing 7 can also be arranged at a position closer to the magnet holding portion 6a and the permanent magnet 8.

[0191] The magnetic sensor 40 can detect the rotation angle of the corresponding main shaft gear 1 by detecting the change of the magnetic flux generated by the permanent magnet 9 due to the rotation of the permanent magnet 9 rotating together with the main shaft gear 1. On the other hand, the magnetic sensor 50 can detect the rotation angle of the corresponding counter shaft gear 5 by detecting the change of the magnetic flux generated by the permanent magnet 8 due to the rotation of the permanent magnet 8 rotating together with the counter shaft gear 5.

[0192] like Fig. 27 and Fig.35 As shown, the permanent magnet 8 has a surface 8a. The permanent magnet 8 is roughly cylindrical, and the central axis MC1 of the permanent magnet 8 (the axis representing the center of the permanent magnet 8 or the axis passing through the center of the boundary of the magnetic pole) is consistent with the central axis HC1 of the magnet holder 6, the central axis GC1 of the countershaft gear 5, and the central axis BC of the bearing 7. The surface 8a of the permanent magnet 8 is spaced a certain distance from and faces the surface 50a of the magnetic sensor 50. In this way, by making each central axis consistent, the rotation angle or rotation amount can be detected with higher accuracy.

[0193] It should be noted that in this embodiment, Fig.35 As shown, the two magnetic poles (N / S) of the permanent magnet 8 are formed adjacent to each other in a plane (X-Y plane) perpendicular to the central axis MC1 of the permanent magnet 8. That is, it is preferable that the rotation center of the permanent magnet 8 and the center of the boundary of the magnetic poles on the central axis MC1 are aligned. Accordingly, the detection accuracy of the rotation angle or the rotation amount can be further improved.

[0194] like Fig.26 and Fig.36 As shown, the permanent magnet 9 is a substantially cylindrical permanent magnet that is press-fitted into the interior of the magnet holding portion 1h of the main shaft gear 1, and has an upper surface 9a and a lower surface 9b. The upper surface 9a is spaced a certain distance from and faces the surface 40a of the magnetic sensor 40. The lower surface 9b is in contact with the bottom surface 1g of the magnet holding portion 1h of the main shaft gear 1, and can define the position in the direction of the center axis GC2 of the main shaft gear 1 (the position in the Z-axis direction). The center axis MC2 of the permanent magnet 9 (the axis representing the center of the permanent magnet 9 or the axis passing through the center of the boundary of the magnetic pole) is consistent with the center axis GC2 of the main shaft gear 1 and the center axis RC of the motor shaft 201. In this way, by making each center axis consistent, the rotation angle or rotation amount can be detected with higher accuracy.

[0195] It should be noted that in this embodiment, Fig.36 As shown, the two magnetic poles (N / S) of the permanent magnet 9 are preferably formed adjacent to each other in a plane (XY plane) perpendicular to the central axis MC2 of the permanent magnet 9. This can further improve the detection accuracy of the rotation angle or the rotation amount.

[0196] It should be noted that permanent magnets 8 and 9 can be formed of, for example, ferrite-based magnetic materials, Nd (neodymium)-Fe (iron)-B (boron)-based magnetic materials, etc. Permanent magnets 8 and 9 can also be, for example, rubber magnets containing resin binders, bonded magnets, etc.

[0197] Fig.31 The figure shows a plurality of through holes formed on the substrate 20, namely, the positioning hole 20a, the positioning hole 20b, the hole 20c, the hole 20d, and the hole 20e. The shape of the wall surface forming the positioning hole 20a is, for example, circular. The shape of the wall surface forming the positioning hole 20b is, for example, elliptical. The holes 20c, 20d, and 20e are respectively used to Fig.14 The substrate mounting screw 13 shown fixes the substrate 20 to the through hole of the main base 10. The shape of the wall surface forming the hole 20c, the hole 20d and the hole 20e is, for example, circular. The diameter of the wall surface forming the hole 20c, the hole 20d and the hole 20e is larger than the diameter of the male screw part of the substrate mounting screw 13 and smaller than the diameter of the head of the substrate mounting screw 13.

[0198] like Figure 21 to Figure 24 , Figures 28 to 30 As shown in the figures, the main base 10 has a hole 10a, a hole 10b, a contact surface 10c, a bearing seat portion 10d, a leaf spring mounting surface 10e, a base 60, a wall portion 70, a wall portion 80, an opening 10-1, and a screw hole 10f. The main base 10 has a substrate positioning pin 10g, a substrate positioning pin 10j, a front end portion 10h, a front end portion 10k, a column 10m, a column 10q, a column 10s, a screw hole 10u, a screw hole 10v, and a screw hole 10w. The substrate positioning pin 10g, the substrate positioning pin 10j, the column 10m, the column 10q, and the column 10s are examples of columnar components. A step portion (step portion) 10i is formed between the front end portion 10h of the substrate positioning pin 10g extending from the main base 10 in the Z-axis direction and the base 10g1 of the substrate positioning pin 10g. When the front end 10h of the substrate positioning pin 10g is inserted into the positioning hole 20a formed on the substrate 20, a gap can be formed between the lower surface 20-1 of the substrate 20 and the step portion 10i. Similarly, a step portion 10l is formed between the front end 10k of the substrate positioning pin 10j extending from the main base 10 in the Z-axis direction and the base 10j1 of the substrate positioning pin 10j. When the front end 10k of the substrate positioning pin 10j is inserted into the positioning hole 20b formed on the substrate 20, a gap can be formed between the lower surface 20-1 of the substrate 20 and the step portion 10l. In this way, when two substrate positioning pins 10g and 10j are used, the position of the substrate 20 in the direction orthogonal to the Z-axis direction can be limited. However, since gaps are formed between the step portion 10i and the step portion 10l and the substrate 20, the position of the substrate 20 in the Z-axis direction is not limited by the two substrate positioning pins 10g and 10j.

[0199] The base 60 of the main base 10 is, for example, an integrally formed aluminum die-cast member, and is a substantially square plate-shaped member in a plan view. The base 60 is an example of a plate portion. The base 60 is attached to the upper surface of the motor 200 .

[0200] Fig.21 The opening 10 - 1 shown penetrates the base 60 in the thickness direction (Z-axis direction). The main shaft gear 1 is inserted through the opening 10 - 1. The opening 10 - 1 is an example of a first through hole.

[0201] like Fig. 22 , Fig.23 , Fig.28 , Fig.29 As shown in the figures, the wall portion 70 includes a wall portion 71 and a wall portion 72. The wall portion 70 has the function of supporting the shaft 4 and fixing the leaf spring 11. The wall portion 71 is integrally provided on the upper surface of the base 60 and extends from the base 60 in the positive direction of the Z axis. The wall portion 70 is provided in a region of the entire upper surface of the base 60 that is closer to the first side 301 than the center in the X-axis direction and closer to the fourth side 304 than the center in the Y-axis direction. The wall portion 71 includes a mounting surface 10ad located on the positive direction side of the X-axis and a screw hole 10ae that penetrates in the X-axis direction. As shown in FIG. Fig.19 , Fig.32 and Fig.33 As shown, by inserting the mounting screw 16 through the hole 15d of the case 15 and tightening it in the screw hole 10ae, the inner surface of the case 15 can abut against the mounting surface 10ad of the wall 71, thereby being fixed.

[0202] like Fig.23 As shown, the wall portion 72 is provided in a region of the entire upper surface of the base 60 that is further toward the first side 301 than the center in the X-axis direction and further toward the third side 303 than the center in the Y-axis direction in a plan view. The wall portion 72 is connected to the wall portion 71 and extends from the wall portion 71 toward the center of the third side 303. The end of the wall portion 72 on the third side 303 is connected to the column 10s. The column 10s connected to the wall portion 72 is provided at a position close to the center of the main base 10 in the X-axis direction and at a position close to the third side 303 of the main base 10. In this way, the wall portion 72 extends from the wall portion 71 toward the column 10s. That is, the wall portion 72 extends in directions oblique to the X-axis and the Y-axis in a plan view.

[0203] like Fig.29As shown, the screw 12 is inserted through the hole 11c formed on the mounting portion 11b of the leaf spring 11 and is tightened to the screw hole 10f formed on the wall portion 72 of the main base 10. As a result, the mounting portion 11b of the leaf spring 11 can abut against the leaf spring mounting surface 10e formed on the wall portion 72, thereby fixing the leaf spring 11 to the wall portion 72. The wall portion 72 can function as a fixing portion for fixing the leaf spring 11. At this time, as shown in FIG. Fig.23 and Fig.24 As shown, the sliding portion 11 a of the leaf spring 11 abuts against the sliding portion 2 e of the intermediate gear 2 into which the shaft 4 is inserted.

[0204] right Fig.24 The following description will be made with reference to the mounting angle θ shown in FIG. 1 . The worm gear portion 1d of the main shaft gear 1 meshes with the worm wheel portion 2a. Therefore, as the worm gear portion 1d of the main shaft gear 1 rotates, a first thrust is generated on the intermediate gear 2 in a direction from the other end 4b of the shaft 4 toward the one end 4a of the shaft 4 or from the one end 4a of the shaft 4 toward the other end 4b of the shaft 4. In addition, due to the meshing of the worm gear portion 2b with the worm wheel portion 5a of the counter shaft gear 5, a second thrust is generated on the intermediate gear 2 in a direction from the other end 4b of the shaft 4 toward the one end 4a of the shaft 4 or from the one end 4a of the shaft 4 toward the other end 4b of the shaft 4. Thus, even when the first thrust and the second thrust are generated, in order to accurately transmit the rotation amount of the worm gear portion 1d of the main shaft gear 1 to the worm wheel portion 5a of the counter shaft gear 5, it is necessary to suppress the movement of the intermediate gear 2 in the axial direction Td toward the shaft 4. The leaf spring 11 urges the intermediate gear 2 in a direction from the one end 4a of the shaft 4 toward the other end 4b of the shaft 4. The value of the biasing force generated by the leaf spring 11 is set to be higher than the combined force of the first thrust and the second thrust in the direction from the other end 4 b of the shaft 4 toward the one end 4 a of the shaft 4 .

[0205] Fig.24In the embodiment, the installation angle θ is equal to the angle formed by the base 11d of the leaf spring 11 fixed to the wall 72 of the main base 10 and the side surface 73 on the side of the intermediate gear 2, which is the surface of the hole 10a of the wall 72 into which the one end 4a of the shaft 4 is inserted, when the intermediate gear 2 is not inserted into the shaft 4. It should be noted that the side surface 73 and the shaft 4 are orthogonal in the present embodiment, but the present invention is not limited thereto. With respect to the installation angle θ, when the intermediate gear 2 is installed on the shaft 4, the sliding portion 11a of the leaf spring 11 abuts against the sliding portion 2e of the intermediate gear 2, and the leaf spring 11 is bent by a predetermined amount, thereby being set to an angle that can appropriately apply a force in the axial direction Td of the shaft 4 to the intermediate gear 2. Therefore, by causing the leaf spring 11 to apply force to the intermediate gear 2 in the direction from the one end 4a side of the shaft 4 toward the other end 4b side of the shaft 4, the movement of the intermediate gear 2 caused by the combined force of the first thrust and the second thrust in the direction from the other end 4b of the shaft 4 toward the one end 4a of the shaft 4 can be suppressed. As a result, the reduction in the rotation accuracy of the countershaft gear 5 can be prevented. It should be noted that the larger the value of the applied force, Fig.24 The larger the sliding resistance when the intermediate gear 2 shown rotates. For this reason, it is preferable to set the mounting angle θ to an appropriate value in a manner that can minimize the sliding resistance when the intermediate gear 2 rotates and generate a sufficiently large force that can suppress the movement of the intermediate gear 2 caused by the thrust. In this way, in order to set the mounting angle θ to an appropriate value, it is necessary to improve the surface accuracy of the leaf spring mounting surface 10e for mounting the leaf spring 11, and it is also necessary to reduce the error of the mounting angle of the wall portion 70 to the base 60.

[0206] In the absolute encoder 100-2 of the second embodiment, the main base 10 is formed by aluminum die casting, so that, for example, compared with the case where the base 60 and the wall 70 are separately made by sheet metal and combined with each other, the error of the mounting angle of the wall 70 to the base 60 can be reduced, and the surface accuracy of the leaf spring mounting surface 10e can be improved. As a result, the error of the mounting angle θ of the leaf spring 11 to the wall 72 is reduced, and the management of the applied force can be easily performed.

[0207] like Fig.28 As shown, the main base 10 can be fixed by inserting three screws 14 through the holes formed at three positions on the main base 10 and tightening them into the screw holes formed on the motor 200. The columns 10q, 10m and 10s extending from the main base 10 in the positive direction of the Z axis are respectively formed with screw holes 10v, 10u and 10w at the front ends in the positive direction of the Z axis. Fig. 20The substrate mounting screws 13 of the holes 20c, 20e and 20d formed on the substrate 20 are respectively tightened in the screw holes 10v, 10u and 10w. Fig.30 The lower surface 20 - 1 of the substrate 20 shown is in contact with each other. The lower surface 20 - 1 of the substrate 20 is the surface facing the main base 10 among the two substrate surfaces in the Z-axis direction of the substrate 20. As a result, the position of the substrate 20 in the Z-axis direction can be defined.

[0208] like Fig.19 , Figure 32 to Figure 34 As shown in the figures, the shell 15 includes an upper surface 15-1, a first side surface 15A, a second side surface 15B, a third side surface 15C, and a fourth side surface 15D, and is a box-shaped component with one side opened. The shell 15 is made of resin, for example, and is an integrally molded component. The upper surface 15-1 corresponds to the bottom of the box-shaped component. The upper surface 15-1 is facing the Fig.14 The surface of the upper surface 20-2 of the substrate 20 shown. The upper surface 20-2 of the substrate 20 is the substrate surface on the side opposite to the lower surface 20-1 of the substrate 20. The first side surface 15A is a plate-shaped member extending from the side of the upper surface 15-1 on the positive direction of the X axis in the negative direction of the Z axis. The second side surface 15B is a plate-shaped member extending from the side of the upper surface 15-1 on the negative direction of the X axis in the negative direction of the Z axis. The third side surface 15C is a plate-shaped member extending from the side of the upper surface 15-1 on the negative direction of the Y axis in the negative direction of the Z axis. The fourth side surface 15D is a plate-shaped member extending from the side of the upper surface 15-1 on the positive direction of the Y axis in the negative direction of the Z axis. The shape of the shell 15 in a plan view is a rectangular shape corresponding to the shape of the motor 200 in a plan view. The space inside the shell 15 can accommodate a plurality of components provided in the absolute encoder 100-2.

[0209] like Fig.33 As shown in FIG. 1 , the shell 15 includes a claw 15a, a claw 15b, a claw 15c, a hole 15d, a recess 15e, a recess 15f, a recess 15g, a connector shell 15h, and an opening 15i. The claw 15a is provided near the end of the fourth side surface 15D in the negative direction of the Z axis. The claw 15a extends from the fourth side surface 15D in the negative direction of the Y axis in a manner facing the third side surface 15C. Fig.32 The claw portion 15b is provided near the end of the third side portion 15C in the negative direction of the Z axis. The claw portion 15b extends from the third side portion 15C in the positive direction of the Y axis so as to face the fourth side portion 15D. Fig.32The claw portion 15c is provided near the end of the second side portion 15B in the negative direction of the Z axis. The claw portion 15c extends from the second side portion 15B in the negative direction of the X axis so as to face the first side portion 15A. Fig.32 The recesses 10ac provided on the main base 10 are shown to interlock.

[0210] Fig.33 The recesses 15e, 15f and 15g shown are for avoiding Fig. 20 The heads of the three substrate mounting screws 13 shown interfere with each other, and a part of the upper surface 5 - 1 of the shell 15 is recessed in the positive direction of the Z axis to form a recessed portion.

[0211] The connector shell 15h is for Fig. 20 The connector 24 shown in the figure is covered by a recessed portion formed in a manner that a portion of the upper surface 5-1 of the shell 15 is recessed in the positive direction of the Z axis. The shape of the bottom surface of the connector shell 15h in a plan view is a rectangle. The connector shell 15h is provided in an area of ​​the upper surface 5-1 that is closer to the first side surface 15A than the center in the X-axis direction and is located near the center in the Y-axis direction. In addition, the connector shell 15h is provided in a portion of the area close to the first side surface 15A.

[0212] The opening 15i is formed between the bottom surface of the connector shell 15h and the first side surface 15A. Fig. 20 The connector 24 shown is configured. The connector 24 is, for example, a female connector, into which a male connector provided on one end of an external wiring can be inserted. The male connector can be connected via Fig.33 The opening 15i shown is inserted into the connector 24 arranged on the connector shell 15h. According to this, the conductive terminal provided on the connector 24 can be electrically connected to the conductive terminal of the male connector provided on one end of the external wiring. As a result, the external device connected to the other end of the external wiring and the connector 24 can be electrically connected, thereby transmitting signals between the absolute encoder 100-2 and the external device.

[0213] In addition, by arranging the connector shell 15h at a position close to the first side surface 15A, Fig. 20As shown, the position of the connector 24 in a plan view is equal to the position of the connector 400 in a plan view of the motor 200. By configuring the absolute encoder 100-2 in this way, the pull-out position of the external wiring electrically connected to the conductive pin provided on the connector 24 can be close to the pull-out position of the external wiring electrically connected to the conductive pin provided on the connector 400. Therefore, these external wirings can be bundled together near the absolute encoder 100-2 and the motor 200, thereby making it easy to pull the bundled wiring group to the external device.

[0214] like Fig.31 As shown, the magnetic sensor 40, the magnetic sensor 50, the microcomputer 21, the bidirectional driver 22, and the line driver 23 can be arranged on the lower surface 20-1 of the substrate 20. The lower surface 20-1 of the substrate 20 is the mounting surface of the magnetic sensor 40 and the magnetic sensor 50. As mentioned above, the upper end surface 10r of the column 10q, the upper end surface 10p of the column 10m, and the upper end surface 10t of the column 10s are connected to the lower surface 20-1 of the substrate 20. In addition, as Fig. 22 As shown, the column 10q, the column 10m and the column 10s are arranged on the main base 10 in a manner that the difference in the intervals between the main base 10 in the plane view is small. For example, the column 10q is arranged at a position close to the center of the Y-axis direction of the main base 10 and close to the second side 302. The column 10q is integrated with the wall portion 80. The column 10m is arranged near the corner where the first side 301 and the fourth side 304 intersect. The column 10s is arranged at a position close to the center of the X-axis direction of the main base 10 and close to the third side 303. The column 10s is integrated with the wall portion 70 and the substrate positioning pin 10g. By arranging the columns 10q, the columns 10m and the columns 10s in this way, the positions of the magnetic sensors 40 and the magnetic sensors 50 arranged on the substrate 20 in the Z-axis direction can be correctly defined. It should be noted that if the pillars 10 q , 10 m , and 10 s are formed at positions on the main base 10 that are as far apart as possible in the XY plane direction, the position of the substrate 20 can be maintained more stably.

[0215] In the absolute encoder 100-2 of the second embodiment, the main base 10 can be formed by die casting. For this reason, compared with, for example, the case where the base 60 of the main base 10 is made by sheet metal and assembled with the columns 10q, 10m, 10s, substrate positioning pins 10g, substrate positioning pins 10j, wall portions 70, wall portions 80, etc. that are made separately, the positional accuracy between the components can be improved. In addition, by reducing the number of components during manufacturing, the structure of the absolute encoder 100-2 can be simplified, thereby making it easy to assemble and thus shortening the manufacturing time, and also improving the reliability of the absolute encoder 100-2.

[0216] The magnetic sensor 40 is an example of a main shaft angle sensor. The magnetic sensor 40 is arranged at a predetermined interval just above the permanent magnet 9. The magnetic sensor 40 can detect and determine the rotation angle of the corresponding main shaft gear 1 by detecting the change in magnetic flux from the permanent magnet 9 caused by the rotation of the permanent magnet 9 rotating together with the main shaft gear 1, and can output angle information indicating the determined rotation angle as a digital signal.

[0217] The magnetic sensor 50 is an example of an angle sensor. In addition, the countershaft gear 5 is a rotating body that rotates with the rotation of the second driven gear, that is, the worm gear portion 5a. The magnetic sensor 50 is arranged just above the permanent magnet 8 at a predetermined interval. The magnetic sensor 50 can detect and determine the rotation angle of the corresponding countershaft gear 5 by detecting the change in the magnetic flux from the permanent magnet 8 caused by the rotation of the permanent magnet 8 rotating with the countershaft gear 5, and can output the angle information representing the determined rotation angle as a digital signal.

[0218] The magnetic sensor 40 and the magnetic sensor 50 are respectively provided with, for example, a detection element for detecting a change in magnetic flux and an operation circuit for outputting a digital signal representing a rotation angle according to the output of the detection element. The detection element may be, for example, a combination of multiple magnetic field sensing elements such as a Hall element and a GMR (Giant Magneto Resistive) element. The number of magnetic field sensing elements is, for example, four.

[0219] When the number of teeth of the worm gear portion 1d of the main shaft gear 1 is 4 and the number of teeth of the worm wheel portion 2a of the intermediate gear 2 is 20, the reduction ratio is 5. That is, if the main shaft gear 1 rotates 5 times, the intermediate gear 2 rotates once. In addition, when the number of teeth of the worm gear portion 2b of the intermediate gear 2 is 1 and the number of teeth of the worm wheel portion 5a of the counter shaft gear 5 is 18, the reduction ratio is 18. That is, if the intermediate gear 2 rotates 18 times, the counter shaft gear 5 rotates once. Therefore, if the main shaft gear 1 rotates 90 times, the intermediate gear 2 rotates 90÷5=18 times, and the counter shaft gear 5 rotates 18÷18=1 time.

[0220] The main shaft gear 1 and the counter shaft gear 5 are provided with permanent magnets 9 and 8 that rotate as one body. Therefore, the rotation angles of the main shaft gear 1 and the counter shaft gear 5 are detected by the magnetic sensors 40 and 50 corresponding thereto, and the rotation amount of the motor shaft 201 can be determined. If the main shaft gear 1 rotates once, the counter shaft gear 5 rotates 1 / 90 times, that is, it rotates 4 degrees. Therefore, when the rotation angle of the counter shaft gear 5 is less than 4 degrees, the rotation amount of the main shaft gear 1 is less than 1 rotation, and when the rotation angle of the counter shaft gear 5 is greater than 4 degrees and less than 8 degrees, the rotation amount of the main shaft gear 1 is greater than 1 rotation and less than 2 rotations. In this way, in the absolute encoder 100-2, the number of rotations of the main shaft gear 1 can be determined according to the rotation angle of the counter shaft gear 5. In particular, in the absolute encoder 100 - 2 , by utilizing the reduction ratios between the worm gear 1 d and the worm wheel 2 a and between the worm gear 2 b and the worm wheel 5 a , the number of rotations of the main shaft gear 1 can be determined even if the main shaft gear 1 rotates multiple times.

[0221] The microcomputer 21, the bidirectional driver 22, the line driver 23, and the connector 24 are mounted on the substrate 20. The microcomputer 21, the bidirectional driver 22, the line driver 23, and the connector 24 can be electrically connected via pattern wiring on the substrate 20.

[0222] The microcomputer 21 is composed of a CPU (Central Processing Unit), and can obtain digital signals indicating the rotation angles outputted from the magnetic sensor 40 and the magnetic sensor 50 , respectively, and calculate the rotation amount of the main shaft gear 1 .

[0223] The bidirectional driver 22 can communicate bidirectionally with an external device connected to the connector 24. The bidirectional driver 22 can convert data (Data) such as an operation signal into a differential signal and communicate with the external device. The line driver 23 can convert data representing the rotation amount into a differential signal and output the differential signal to the external device connected to the connector 24 in real time. The connector 24 is connected to a connector of an external device.

[0224] Fig.39 This is a diagram showing a functional configuration of a microcomputer 21 included in an absolute encoder 100 - 2 according to Embodiment 2 of the present invention. Fig.39 Each block of the microcomputer 21 shown represents a function that is realized by the CPU of the microcomputer 21 executing a program.

[0225] The microcomputer 21 includes a rotation angle acquisition unit 21p, a rotation angle acquisition unit 21q, a table processing unit 21b, a rotation amount determination unit 21c, and an output unit 21e. The rotation angle acquisition unit 21q acquires the rotation angle Aq of the main shaft gear 1 based on the signal output from the magnetic sensor 40. The rotation angle Aq is angle information indicating the rotation angle of the main shaft gear 1. The rotation angle acquisition unit 21p acquires the rotation angle Ap of the counter shaft gear 5 based on the signal output from the magnetic sensor 50. The rotation angle Ap is angle information indicating the rotation angle of the counter shaft gear 5. The table processing unit 21b can determine the rotation number of the main shaft gear 1 corresponding to the acquired rotation angle Ap by referring to a correspondence table storing the rotation angle Ap and the rotation number of the main shaft gear 1 corresponding to the rotation angle Ap. The rotation amount determination unit 21c can determine the rotation amount of the main shaft gear 1 for multiple rotations based on the rotation number of the main shaft gear 1 determined by the table processing unit 21b and the acquired rotation angle Aq. The output unit 21e can convert the rotation amount of the determined plurality of rotations of the main shaft gear 1 into information indicating the rotation amount and output the information.

[0226] As described above, in the absolute encoder 100-2 according to the second embodiment, Fig.23 As shown in the figure, the countershaft gear 5 is arranged on the side of the intermediate gear 2 opposite to the mainshaft gear 1, so that the occurrence of magnetic interference that affects the magnetic sensors that do not correspond to the permanent magnets 8 and 9 can be reduced. In this way, with respect to the absolute encoder 100-2, by adopting a structure that can reduce the occurrence of magnetic interference, the size of the absolute encoder 100-2 in a plan view can be made relatively small. Therefore, not only can the absolute encoder 100-2 be miniaturized, but also the decrease in detection accuracy caused by the magnetic flux of each of the magnetic sensors 40 and 50 can be prevented.

[0227] Furthermore, in the absolute encoder 100-2 of the second embodiment, the intermediate gear 2 arranged in parallel with the upper surface of the main base 10 extends obliquely relative to the four sides of the main base 10, and the main shaft gear 1 and the counter shaft gear 5 are arranged on the opposite sides of the intermediate gear 2 relative to the intermediate gear 2. For this reason, the main shaft gear 1, the intermediate gear 2, and the counter shaft gear 5 can be arranged in a narrow area that is part of the entire area of ​​the upper surface of the main base 10, thereby reducing the size of the absolute encoder 100-2 relative to the horizontal direction.

[0228] In the absolute encoder 100 - 2 of Embodiment 2, the outer diameters of the worm wheel 2 a and the worm gear 2 b are set to be as small as possible. This can reduce the dimension of the absolute encoder 100 - 2 in the Z-axis direction (height direction).

[0229] As described above, the absolute encoder 100 - 2 according to the second embodiment has the effect of preventing the detection accuracy of the rotation amount of the main shaft gear 1 from being reduced and reducing the dimension in the Z-axis direction and the dimension in the direction perpendicular to the Z-axis direction.

[0230] In addition, in the absolute encoder 100-2 of embodiment 2, the intermediate gear 2 is axially supported relative to the shaft 4 respectively fixed to or inserted in the wall portion 80 and the wall portion 72, that is, it is rotatably supported, but the supporting method of the intermediate gear 2 is not limited to this as long as the intermediate gear 2 can be axially supported.

[0231] For example, the absolute encoder 100-2 may be configured such that one end 4a of the shaft 4 is inserted into the hole 10a formed in the wall portion 72, and the other end 4b of the shaft 4 is press-fitted and fixed in the hole 10b formed in the wall portion 80. In addition, the absolute encoder 100-2 may be configured such that the outer ring 3a of the bearing 3 is press-fitted and fixed to the press-fit portion 2d formed on the intermediate gear 2, and the shaft 4 is press-fitted and fixed to the inner ring 3b of the bearing 3. According to this, the movement of the intermediate gear 2 fixed to the shaft 4 in the axial direction Td can be restricted. When the absolute encoder 100-2 is configured in this way, the intermediate gear 2 can be axially supported by the shaft 4. In addition, the movement in the axial direction Td of the shaft 4 is restricted by the wall portion 72 and the wall portion 80, and the movement in the axial direction of the intermediate gear 2 is also restricted by the inner ring 3b of the bearing 3 fixed to the shaft 4. Therefore, it is not necessary to provide the leaf spring 11.

[0232] In addition, the absolute encoder 100-2 may be configured, for example, not to use Fig.24 Instead of the bearing 3 shown in the figure, the shaft 4 is axially supported by a bearing (not shown) provided on at least one of the wall portion 72 and the wall portion 80 in a state where the intermediate gear 2 is fixed to the shaft 4.

[0233] When the outer ring of the bearing not shown in the figure is fixed to the wall portion 72 or the wall portion 80, and one end 4a or the other end 4b of the shaft 4 is inserted into the inner ring, the intermediate gear 2 is fixed to the shaft 4, and the shaft 4 is axially supported by the bearing not shown in the figure, so the shaft 4 and the intermediate gear 2 can rotate integrally. In this case, the shaft 4 is not fixed to the inner ring of the bearing, but is only inserted into the inner ring, so the shaft 4 can move in the axial direction Td together with the intermediate gear 2. For this purpose, it is necessary to provide a leaf spring 11 for applying force to the intermediate gear 2 in the axial direction Td to limit the position.

[0234] Alternatively, the outer ring of the bearing not shown in the figure can be fixed to the wall portion 72 or the wall portion 80, and the inner ring not shown in the figure can be press-fitted into one end 4a or the other end 4b of the shaft 4. In this case, the movement of the intermediate gear 2 fixed on the shaft 4 in the axial direction Td can be restricted. For this reason, the bearing not shown in the figure can not only rotatably support the intermediate gear 2 fixed on the shaft 4, but also restrict the movement of the shaft 4 in the axial direction Td, so the movement of the intermediate gear 2 in the axial direction Td can also be restricted. Therefore, it is not necessary to provide the leaf spring 11.

[0235] like Fig.26 As shown, the magnetic sensor 40 originally detects and determines the rotation angle of the main shaft gear 1 by detecting the change of the magnetic flux from the permanent magnet 9 rotating together with the main shaft gear 1. Fig. 27 As shown, the magnetic sensor 50 detects the change in the magnetic flux of the permanent magnet 8 rotating together with the counter gear 5, thereby detecting and determining the rotation angle of the counter gear 5. As described above, the absolute encoder 100-2 of the second embodiment can reduce the influence of the magnetic flux from the permanent magnet 8 on the magnetic sensor 40 by adopting a structure that can reduce the occurrence of magnetic interference. In addition, the influence of the magnetic flux from the permanent magnet 9 on the magnetic sensor 50 can also be reduced. That is, the decrease in the detection accuracy of the rotation caused by the mutual magnetic interference between the main shaft gear 1 and the counter shaft gear 5 can be prevented.

[0236] Fig.19 The absolute encoder 100-2 is shown in a state where it is mounted on the motor 200. A permanent magnet and a driving coil are built into the motor 200. Therefore, the motor 200 generates magnetic flux even when the motor shaft 201 does not rotate. In addition, when a driving signal is given to the motor 200 from the outside to rotate the motor shaft 201, the generated magnetic flux will further increase. For this reason, there is a situation where the magnetic flux generated by the motor 200 has a bad influence on the magnetic sensor 40 and the magnetic sensor 50 provided inside the absolute encoder 100-2, thereby resulting in a decrease in detection accuracy. In the case where there is such an influence of unnecessary magnetic flux from the motor 200, if a strong magnetic body such as iron is used to form the main base 10, the influence of the magnetic flux from the motor 200 can be reduced.

[0237] Fig.40 It is a schematic diagram of a modified example of the absolute encoder 100 - 2 according to the second embodiment of the present invention. Fig.40In the absolute encoder 100-2 shown, two surface magnetized permanent magnets 19 are used instead of the permanent magnets 8 and 9. By using the permanent magnets 19, magnetic interference caused by the arrangement direction of the first magnetic pole portion N and the second magnetic pole portion S is less likely to occur. For this reason, compared with the case where diameter magnetized magnets are used as the permanent magnets 8 and 9, the reduction in the detection accuracy of the rotation angle or rotation amount of the main shaft gear 1 caused by the magnetic sensor 40 can be further suppressed, and the reduction in the detection accuracy of the rotation angle or rotation amount of the counter shaft gear 5 caused by the magnetic sensor 50 can also be further suppressed.

[0238] It should be noted that the absolute encoder 100-1 of embodiment 1 and the absolute encoder 100-2 of embodiment 2 can both be constructed using permanent magnets 8 and 9 having a diameter of approximately 4 mm. In addition, the absolute encoder 100-2 of embodiment 2 can also be constructed using a permanent magnet 17 having a diameter of approximately 4 mm. With this structure, the magnetic flux generated by a permanent magnet having a diameter of approximately 4 mm can be less than the magnetic flux generated by a permanent magnet having a diameter greater than approximately 4 mm, and the above-mentioned magnetic interference is less likely to occur. Therefore, for the absolute encoders 100-1 and 100-2 using permanent magnets having a diameter of approximately 4 mm, the detection accuracy of the rotation angle or rotation amount of each gear can be improved compared to the case of using permanent magnets having a diameter greater than approximately 4 mm. It should be noted that approximately 4 mm means, for example, 3.7 mm to 4.3 mm, taking into account the manufacturing tolerance of the permanent magnet.

[0239] It should be noted that the absolute encoder 100-1 of the first embodiment is configured such that the central axes of the permanent magnet 8 and the magnet holder 6 are aligned with each other. Fig.35 The permanent magnet 8 and the magnet holder 6 shown in the figure are also aligned with each other. In addition, the absolute encoder 100-1 of the first embodiment is configured so that the central axes of the permanent magnet 17 and the second counter gear 138 are aligned with each other. Fig.35 The permanent magnet 8 and the magnet holder 6 shown in the figure are also aligned with each other. In addition, the absolute encoder 100-1 of the first embodiment is configured so that the central axes of the permanent magnet 9 and the main shaft gear 1 are aligned with each other. Fig.36 The permanent magnet 9 and the main shaft gear 1 shown are also aligned with each other. With this configuration, the absolute encoder 100 - 1 according to the first embodiment can detect the rotation angle or the rotation amount with higher accuracy.

[0240] It should be noted that the configuration shown in the above embodiment is only an example of the content of the present invention and can be combined with other well-known technologies. In addition, part of the above configuration can be omitted or changed without departing from the scope of the present invention.

[0241] It should be noted that the present application claims priority based on Japanese Patent Application No. 2019-066047 filed on March 29, 2019, and the contents of the Japanese Patent Application are incorporated herein in their entirety.

[0242] [Explanation of Reference Numerals]

[0243] 1 Main shaft gear, 1a 1st cylindrical portion, 1b 2nd cylindrical portion, 1c communicating portion, 1d worm gear portion, 1e bottom surface, 1f press-fit portion, 1g bottom surface, 1h magnet holding portion, 2 intermediate gear, 2a worm wheel portion, 2b worm gear portion, 2c bearing portion, 2d press-fit portion, 2e sliding portion, 2f bottom surface, 2g through hole, 3 bearing, 3a outer ring, 3b inner ring, 3c side surface, 3d side surface, 4 shaft, 4a one end, 4b the other end, 5 counter shaft gear, 5-1 upper surface, 5a worm wheel portion, 5b through hole, 6 magnet seat, 6a magnet holding portion, 6b shaft portion, 6c head portion, 7 bearing, 7a outer ring, 7b inner ring, 8 permanent magnet, 8a surface, 9 permanent magnet, 9a upper surface, 9b lower surface, 10 main base portion, 10-1 opening portion , 10-2 lower surface, 10a hole, 10aa recess, 10ab recess, 10ac recess, 10ad mounting surface, 10ae screw hole, 10b hole, 10c abutment surface, 10d bearing seat, 10da lower part, 10db upper part, 10dc inner peripheral surface, 10e leaf spring mounting surface, 10f screw hole, 10g substrate positioning pin, 10g1 base, 10h front end, 10i step difference, 10j substrate positioning pin, 10j1 base, 10k front end, 10l step difference, 10m column, 10p upper end surface, 10q column, 10r upper end surface, 10s column, 10t upper end surface, 10u screw hole, 10v screw hole, 10w screw hole, 11 leaf spring, 11a sliding portion, 11b mounting portion, 11 c hole, 11d base, 12 screw, 13 substrate mounting screw, 14 screw, 15 shell, 15-1 upper surface, 15A 1st side surface, 15B 2nd side surface, 15C 3rd side surface, 15D 4th side surface, 15a claw, 15b claw, 15c claw, 15d hole, 15e recess, 15f recess, 15g recess, 15h connector shell, 15i opening, 16 mounting screw, 17 permanent magnet, 18 permanent magnet, 19 permanent magnet, 20 substrate, 20-1 lower surface, 20-2 upper surface, 20a positioning hole, 20b positioning hole, 20c hole, 20d hole, 20e hole, 21 microcomputer, 21b table processing unit, 21c rotation amount determination unit, 21e output unit, 21p rotation angle acquisition unit part, 21q rotation angle acquisition part, 22 bidirectional driver, 23 line driver, 24 connector, 36 driven gear, 40 magnetic sensor, 40a surface, 50 magnetic sensor, 50a surface, 60 base, 70 wall, 71 wall, 72 wall, 73 side, 80 wall, 90 magnetic sensor, 100-1 absolute encoder, 100-2 absolute encoder, 101 main shaft gear, 101a first cylindrical part, 101b disk part, 101c worm gear part, 101d magnet holding part, 102 first intermediate gear, 102a worm wheel part, 102b first worm gear part, 102c base, 102d first cylindrical part, 102e second cylindrical part, 102f third cylindrical part, 102g hemispherical protrusion,102h second worm gear portion, 102i sliding portion, 104 shaft, 105 first countershaft gear, 105a worm gear portion, 105b bearing portion, 105c disk portion, 105d holding portion, 106 shaft, 107 blocking ring, 108 blocking ring, 110 main base portion, 110a base portion, 110b supporting portion, 110c supporting portion, 111 leaf spring, 111a sliding portion, 111b mounting portion, 115 shell portion, 115a outer wall portion, 115b outer wall portion, 115c outer wall portion, 115d outer wall portion, 116 cover portion, 120 substrate, 121 microcomputer, 121b table processing portion, 121c rotation amount determining portion, 121e Output part, 121p rotation angle acquisition part, 121q rotation angle acquisition part, 121r rotation angle acquisition part, 122 substrate mounting screw, 133 second intermediate gear, 133a worm gear part, 133b bearing part, 133c extension part, 133d fourth drive gear part, 138 second countershaft gear, 138a fourth driven gear part, 138b bearing part, 138c extension part, 138d magnet holding part, 139 shaft, 141 support, 164 screw, 200 motor, 201 motor shaft, 202 frame, 202a cutout part, 301 first side, 302 second side, 303 third side, 304 fourth side, 400 connector. ,

Claims

1. An absolute encoder having: The first driving gear rotates with the rotation of the main shaft; a first magnet disposed on the front end side of the first driving gear; a first angle sensor for detecting a rotation angle of the first drive gear corresponding to a change in magnetic flux generated from the first magnet; a first driven gear, the center axis of which is orthogonal to the center axis of the first driving gear and meshes with the first driving gear; a second driving gear, which is disposed on the same shaft as the first driven gear and rotates with the rotation of the first driven gear; a second driven gear, the center axis of which is orthogonal to the center axis of the first driven gear and meshes with the second driving gear; a second magnet disposed on the front end side of the second driven gear; and a second angle sensor for detecting a rotation angle of the second driven gear corresponding to a change in magnetic flux generated from the second magnet; in, When viewed from an end face of the first magnet in the axial direction, in the first magnet, a first magnetic pole portion having a first polarity and a second magnetic pole portion having a second polarity different from the first polarity are formed adjacent to each other. The first magnetic pole portion and the second magnetic pole portion of the first magnet are adjacently formed along the radial direction with the center of the radial direction of the first magnet as the boundary. When the second magnet is viewed from an end face in the axial direction, a first magnetic pole portion having a first polarity and a second magnetic pole portion having a second polarity different from the first polarity are adjacent to each other in the second magnet. The first magnetic pole portion and the second magnetic pole portion of the second magnet are adjacently formed in the radial direction with the center of the radial direction of the second magnet as the boundary, The first magnetic pole portion and the second magnetic pole portion of the second magnet are adjacently formed along the axial direction with the center of the axial direction of the second magnet as a boundary. The permissible error of the rotation angle detected by the first angle sensor is set to be smaller than the permissible error of the rotation angle detected by the second angle sensor.

2. The absolute encoder according to claim 1, further comprising: a third driving gear disposed on the opposite side of the first driving gear to the second driven gear side and rotating along with the rotation of the first driven gear; a third driven gear meshing with the third driving gear; a third magnet disposed on the front end side of the third driven gear; and a third angle sensor for detecting a rotation angle of the third driven gear corresponding to a change in magnetic flux generated from the third magnet, in, When the third magnet is viewed from an end face in the axial direction, a first magnetic pole portion having a first polarity and a second magnetic pole portion having a second polarity different from the first polarity are adjacent to each other in the third magnet. The first magnetic pole portion and the second magnetic pole portion of the third magnet are adjacently formed along the radial direction with the center of the radial direction of the third magnet as the boundary. The first magnetic pole portion and the second magnetic pole portion of the third magnet are formed adjacent to each other in the axial direction with the center of the axial direction of the third magnet as a boundary.

3. The absolute encoder according to claim 1 or 2, wherein: A diameter of at least one of the first magnet and the second magnet is approximately 4 mm.

4. The absolute encoder according to claim 2, wherein: The diameter of the third magnet is about 4 mm.

Images