Absolute encoder

Abstract

This invention provides an absolute encoder suitable for miniaturization. The absolute encoder includes: a main shaft gear (1A) fixed to a motor shaft (201); a permanent magnet (9) disposed on the main shaft gear (1A); and a first driven gear whose central axis is orthogonal to the central axis of a worm gear portion (181) and meshes with the worm gear portion (181). The absolute encoder also includes: a second drive gear coaxially disposed with the first driven gear and rotating with the rotation of the first driven gear; and a second driven gear whose central axis is orthogonal to the central axis of the first driven gear and meshes with the second drive gear. The main shaft gear (1A) includes: a magnet retainer (170) fitted coaxially with the top end of the motor shaft (201); and a resin gear portion (180) with the worm gear portion (181) disposed radially outward.

Description

Technical Field

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

[0002] In the past, it is known that there are rotary encoders for detecting the position and angle of movable elements in various control mechanical devices. Among such encoders, there are incremental encoders for detecting relative positions or angles, and absolute encoders for detecting absolute positions or angles. For example, Patent Document 1 describes an absolute rotary encoder, which includes a plurality of magnetic encoder parts for detecting the angular positions of a main shaft and a secondary shaft using magnetism, and is used to measure the absolute position of the main shaft through the detection results.

[0003] <Prior Art Literature>

[0004] <Patent Documents>

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-24572 Summary of the invention

[0006] <Problems to be Solved by the Invention>

[0007] In the absolute encoder described in Patent Document 1, a magnetic generating element (magnet) is provided at one end of the secondary shaft, and the magnetism generated by the magnetic generating element is detected by the magnetic detecting element. At this time, if the center of the magnetic generating element, the center of the secondary shaft, and the center of the magnetic detecting element are misaligned, or if there is a synchronization deviation between the rotation of the magnetic generating element and the secondary shaft, there is a concern that the magnetic detecting element may not be able to detect the proper angular position of the main shaft.

[0008] The present invention has been made in view of the above, and an object of the present invention is to provide an absolute encoder capable of holding a magnet more reliably.

[0009] <Methods used to solve the problem>

[0010] The absolute encoder of an embodiment of the present invention includes: a first drive gear, which is fixed to the above-mentioned main shaft in a coaxial manner and rotates with the rotation of the above-mentioned main shaft; a magnet, which is arranged on the above-mentioned first drive gear; a first driven gear, whose center axis is orthogonal to the center axis of the above-mentioned first drive gear and meshes with the above-mentioned first drive gear; a second drive gear, which is arranged coaxially with the above-mentioned first driven gear and rotates with the rotation of the above-mentioned first driven gear; and a second driven gear, whose center axis is orthogonal to the center axis of the above-mentioned first driven gear and meshes with the above-mentioned second drive gear, the above-mentioned first drive gear includes: a cylindrical portion, which is embedded in the top end portion of the above-mentioned main shaft in a coaxial manner with the above-mentioned main shaft; and an annular portion, which has a tooth portion meshing with the first driven gear arranged on the radial outside, and the above-mentioned annular portion is arranged adjacent to the above-mentioned cylindrical portion in a coaxial manner with the above-mentioned main shaft.

[0011] <Effects of the Invention>

[0012] The absolute encoder of the present invention has the effect of being able to hold the magnet more reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a perspective view showing a state where the absolute encoder 100 - 1 according to the first embodiment of the present invention is attached to the motor 200 .

[0014] Figure 2 It is shown from Figure 1 The box body 115 is shown in a three-dimensional view with the cover portion 116 removed.

[0015] Figure 3 It is shown from Figure 2 The illustrated diagram is a perspective view of the absolute encoder 100 - 1 with the base plate 120 and base plate mounting screws 122 removed.

[0016] Figure 4 is a bottom view of the substrate 120 .

[0017] Figure 5 yes Figure 3 A top view of the absolute encoder 100 - 1 is shown.

[0018] 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. However, the second counter gear 138 and the magnetic sensor 90 are shown.

[0019] Figure 7 This is a cross-sectional view of the absolute encoder 100 - 1 cut by a plane that is perpendicular to the center line of the first intermediate gear 102 and passes through the center of the first countershaft gear 105 .

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

[0021] Fig. 9 This 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 This is a perspective view showing a state where an absolute encoder 100 - 2 according to Embodiment 2 of the present invention is attached to a motor 200 .

[0023] Fig.11 It is shown from Fig.10 The illustrated diagram is a three-dimensional view of the absolute encoder 100 - 2 with the box body 15 and the mounting screws 16 removed.

[0024] Fig.12 It is shown from Fig.11 The illustrated diagram is a perspective view of the absolute encoder 100 - 2 in a state where the base plate 20 and the base plate mounting screws 13 are removed.

[0025] Fig.13 It is shown from Fig.12 The absolute encoder 100 - 2 is a perspective view showing a state in which it is mounted on the motor 200 , and the motor 200 and the screw 14 are removed.

[0026] Fig.14 It is a top view Fig.13 The diagram shows the state of the main base 10 and the intermediate gear 2.

[0027] Fig.15 The plane passing through the center of the intermediate gear 2 and parallel to the XY plane is used to Fig.14 The absolute encoder 100 - 2 is shown in a cross-sectional view after being cut.

[0028] Fig.16 It is shown Fig.15 An enlarged partial cross-sectional view showing a state in which the bearing 3 is disengaged from the intermediate gear 2

[0029] Fig.17 It is through Fig.14 The plane at the center of the main shaft gear 1 and perpendicular to the center line of the intermediate gear 2 will be Fig.11 The absolute encoder 100-2 is shown in a cross-sectional view after being cut. However, the substrate 20 and the magnetic sensor 40 are not cut in the cross section.

[0030] Fig.18 It is through Fig.15The plane perpendicular to the center line of the intermediate gear 2 and the center line of the countershaft gear 5 shown in FIG. Fig.11 The absolute encoder 100-2 is shown in a cross-sectional view after being cut. However, the substrate 20 and the magnetic sensor 50 are not cut.

[0031] Fig.19 It is shown Fig.12 A perspective view showing a state in which the intermediate gear 2 is removed from among the multiple components shown.

[0032] Fig. 20 It is shown from Fig.19 The wall portion 70 is shown in a state where the screw 12 is removed, the state of the leaf spring 11 after the screw 12 is removed, and a perspective view of the wall portion 70 having a leaf spring mounting surface 10e facing the leaf spring 11. However, the motor 200 and the main shaft gear 1 are not shown.

[0033] Fig.21 It is through Fig.14 The center of the substrate positioning pin 10g and the center of the substrate positioning pin 10j and the plane parallel to the Z-axis direction will be Fig.11 The absolute encoder 100-2 is shown in a cross-sectional view after being cut. However, the magnetic sensor 40 is not cross-sectionally viewed.

[0034] Fig. 22 Observed from the lower surface 20-1 side Fig.11 FIG. 20 is a diagram of the substrate shown.

[0035] Fig.23 It is Fig.10 The state is shown in the figure with the motor 200 removed and observed from the lower surface 10-2 side of the main base 10.

[0036] Fig.24 yes Fig.10 A three-dimensional view of the box body 15 is shown.

[0037] Fig.25 It is through Fig.12 The center of the substrate positioning pin 10g and the center of the substrate positioning pin 10j are parallel to the Z-axis direction. Fig.10 The absolute encoder 100-2 is shown in a cross-sectional view after cutting. However, the motor 200 and the main shaft gear 1 are not cut.

[0038] Fig.26 yes Fig.18 An exploded perspective view of the permanent magnet 8 , the magnet holder 6 , the countershaft gear 5 and the bearing 7 is shown.

[0039] Fig. 27 yes Fig.17 An exploded perspective view of the permanent magnet 9 , the main shaft gear 1 and the motor shaft 201 is shown.

[0040] Fig.28 The diagram shows the concepts of a waveform (A) for detecting the magnetic flux of a permanent magnet 9 provided on a main shaft gear 101 (main shaft gear 1) by a magnetic sensor 40, a waveform (B) for detecting the magnetic flux of a permanent magnet 8 provided on a first secondary shaft gear 105 (secondary shaft gear 5) by a magnetic sensor 50, and a magnetic interference waveform (C) for 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.

[0041] Fig.29 It is a conceptual diagram showing a waveform (A) in which the magnetic flux of the permanent magnet 8 provided on the first countershaft gear 105 (countershaft gear 5) is detected by the magnetic sensor 50, a waveform (B) in which the magnetic flux of the permanent magnet 9 provided on the main shaft gear 101 (main shaft gear 1) is detected by the magnetic sensor 40, and a magnetic interference waveform (C) in which the magnetic flux of a part of the permanent magnet 9 is detected by the magnetic sensor 50 as leakage flux overlapping with the magnetic flux of the permanent magnet 8.

[0042] Fig.30 This 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.

[0043] Fig.31 1 is a perspective view of a main shaft gear 1A included in an absolute encoder 100 - 2 according to a first modified example of the second embodiment.

[0044] Fig.32 yes Fig.31 A cross-sectional view of mainshaft gear 1A is shown.

[0045] Fig.33 1 is a perspective view of a main shaft gear 1B included in an absolute encoder 100 - 2 according to a second modified example of the second embodiment.

[0046] Fig.34 yes Fig.33 A cross-sectional view of mainshaft gear 1B is shown.

[0047] Fig.35 This is a diagram showing a permanent magnet 9A applicable to the absolute encoders 100 - 1 and 100 - 2 of the first and second embodiments.

[0048] Fig.36 This is a diagram showing a permanent magnet 9B applicable to the absolute encoders 100 - 1 and 100 - 2 of the first and second embodiments. DETAILED DESCRIPTION

[0049] Hereinafter, the configuration of the absolute encoder according to the embodiment of the present invention will be described in detail based on the accompanying drawings. It should be noted that the present invention is not limited to the embodiment.

[0050] <Implementation Method 1>

[0051] Figure 1 1 is a stereoscopic diagram showing a state where the absolute encoder 100-1 according to Embodiment 1 of the present invention is installed on the motor 200. The following description is based on the XYZ orthogonal 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. Sometimes the X-axis direction is expressed as the left direction or the right direction, the Y-axis direction is expressed as the front direction or the back direction, and the Z-axis direction is expressed as the up direction or the down direction. Figure 1 In the figure, the state of observing from above in the Z-axis direction is called the top view, the state of observing from the front in the Y-axis direction is called the front view, and the state of observing from the left and right in the X-axis direction is called the side view. Such a description of the direction 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.

[0052] Figure 2 It is shown from Figure 1 The box body 115 is shown in a three-dimensional view with the cover portion 116 removed. Figure 3 It is shown from Figure 2 The illustrated diagram is a perspective view of the absolute encoder 100 - 1 with the base plate 120 and base plate mounting screws 122 removed. Figure 4 is a bottom view of the substrate 120 . Figure 5 yes Figure 3 A top view of the 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. However, 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 by a plane perpendicular to the center line of the first intermediate gear 102 and passing through the center of the first countershaft gear 105. Figure 7 The description of the box body 115 and the cover 116 is omitted. A cross-sectional view of the state in which the absolute encoder 100-1 is cut by a plane parallel to the Z-axis direction passing through the center of the second countershaft gear 138 and the center of the second intermediate gear 133 as viewed from the substantially right side. Figure 8 In the figure, the description of the box body 115 and the cover 116 is omitted.

[0053] Below, refer to Figures 1 to 8The structure of the absolute encoder 100-1 is described in detail. The absolute encoder 100-1 is an absolute encoder for determining the rotation amount of the main shaft of the motor 200 for multiple rotations and outputting it. The motor 200 is, as an example, a stepping motor, and may also be a DC brushless motor. As an example, the motor 200 may be used as a driving source for driving a robot for industrial use, etc., through a speed reduction mechanism such as a wave gear device. The motor shaft 201 of the motor 200 protrudes on 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.

[0054] The absolute encoder 100-1 is provided 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 when viewed from above, and has a thin horizontally long rectangle in 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) when viewed from the front and side. That is, the absolute encoder 100-1 has a flat rectangular parallelepiped shape in the Z-axis direction.

[0055] The absolute encoder 100-1 includes a hollow square cylindrical box body 115 for accommodating an internal structure. The box body 115 includes a plurality of (e.g., four) outer wall portions 115a, 115b, 115c, and 115d surrounding at least the main shaft and the intermediate rotating body. A cover portion 116 is fixed to the ends of the outer wall portions 115a, 115b, 115c, and 115d of the box body 115. The cover portion 116 has a generally rectangular shape when viewed from above, and is a plate-like component that is relatively thin in the axial direction.

[0056] The outer wall portion 115a, the outer wall portion 115b, the outer wall portion 115c, and the outer wall portion 115d are connected in sequence. 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 on the side ends of the outer wall portion 115a and the outer wall portion 115c, and are 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.

[0057] The absolute encoder 100-1 includes a main base 110, a box body 115, a cover 116, a base plate 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 (e.g., four) pillars 141, an axis 106, an axis 134, and an axis 139.

[0058] The base 110a of the main base 110 is a plate-shaped portion of the absolute encoder 100-1 facing the motor 200, and extends in the X-axis direction and the Y-axis direction. The hollow square cylindrical box body 115 is fixed to the base 110a of the main base 110 by multiple (for example, three) screws 164.

[0059] The support column 141 provided on the main base 110 is a substantially cylindrical portion protruding from the base 110a in the axial 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 using the substrate mounting screw 122. Figure 2 , the substrate 120 is provided so as to cover the inside of the encoder. The substrate 120 has a substantially rectangular shape when viewed from above, and is a plate-shaped printed circuit board that is thinner in the axial direction. The magnetic sensor 50, the magnetic sensor 40, the magnetic sensor 90, and the microcomputer 121 are mainly mounted on the substrate 120.

[0060] In addition, the absolute encoder 100-1 includes a main shaft gear 101, a worm part 101c, a worm wheel part 102a, a first intermediate gear 102, a first worm part 102b, a worm wheel part 105a, a first counter shaft gear 105, a second worm part 102h, and a worm wheel part 133a. In addition, the absolute encoder 100-1 includes a second intermediate shaft gear 133, a fourth drive gear part 133d, a fourth driven gear part 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.

[0061] The main shaft gear 101 rotates as the motor shaft 201 rotates, and the rotation of the motor shaft 201 is transmitted to the worm part 101c. Figure 6 As shown, the main shaft gear 101 includes a first cylindrical portion 101a fitted on the outer periphery of the motor shaft 201, a disc portion 101b for forming a worm portion 101c, and a magnet holding portion 101d for holding the permanent magnet 9. The magnet holding portion 101d has a cylindrical recessed shape provided at the center 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 a resin material and a metal material. The main shaft gear 101 is formed of, for example, polyoxymethylene resin.

[0062] The worm part 101c is an example of a first drive gear for driving the worm wheel part 102a. In particular, the worm part 101c is a worm having a number of 1 formed on the outer periphery of the disk part 101b. The rotation axis of the worm part 101c extends in the axial direction of the motor shaft 201.

[0063] like Figure 5 As 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 substantially parallel to the base 110a. The first intermediate gear 102 is a substantially cylindrical member extending in the direction of the 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 portion 102b, and a third cylinder portion 102f forming the second worm portion 102h, a through hole is formed inside thereof, and the shaft 104 is inserted into the through hole. The first intermediate gear 102 is axially supported by inserting the shaft 104 into the holes formed in the support portion 110b and the support portion 110c provided in the base 110a of the main base 110. In addition, grooves are provided near both ends of the shaft 104 that protrude outward from the support portion 110b and the support portion 110c, respectively, and a retaining ring 107 and a retaining ring 108 for preventing the shaft 104 from falling off are fitted into the grooves, thereby preventing the shaft 104 from falling off.

[0064] 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 on the side of the first intermediate gear 102 on which the motor shaft 201 is provided in parallel with the outer wall portion 115a. The first intermediate gear 102 can be configured such that its rotation axis La faces an arbitrary direction. The rotation axis La of the first intermediate gear 102 can be provided to be inclined within a range of 5° to 30° 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 in a plan view. 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 case 115 includes the outer wall portion 115a extending in a direction inclined within a range of 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 115a and the rotation axis La of the first intermediate gear 102 is set to 20°.

[0065] In Embodiment 1, the base 102c of the first intermediate gear 102 has a cylindrical shape, and the first cylindrical portion 102d, the second cylindrical portion 102e, and the third cylindrical portion 102f have a cylindrical shape with a larger diameter than the base 102c. In addition, a through hole is formed in the center of the first intermediate gear 102. The base 102c, the first cylindrical portion 102d, the second cylindrical portion 102e, the third cylindrical portion 102f, and the through hole are integrally formed in a manner that the central axes are substantially consistent. The second cylindrical portion 102e, the first cylindrical portion 102d, and the third cylindrical portion 102f are sequentially arranged 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 Embodiment 1, the first intermediate gear 102 is formed of polyoxymethylene resin.

[0066] The support portion 110b and the support portion 110c are 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 110, and are formed with a hole for inserting the shaft 104 of the first intermediate gear 102. In addition, grooves are provided near both ends of the shaft 104 that protrude from the support portion 110b and the support portion 110c, and the retaining ring 107 and the retaining ring 108 for preventing the shaft 104 from falling off are fitted into the grooves, thereby preventing the shaft 104 from falling off. With this configuration, the first intermediate gear 102 is supported so as to be rotatable about the rotation axis La.

[0067] The leaf spring 111 will be described. As the first worm part 102b and the second worm part 102h drive the worm wheels, a reaction force acts on the axial direction Td of the first intermediate gear 102, and the position of the axial direction Td may change. Therefore, in the first embodiment, a leaf spring 111 that applies a force to the first intermediate gear 102 is provided. The leaf spring 111 applies a force in the direction of the rotation axis La of the first intermediate gear 102 to the first intermediate gear 102, thereby suppressing the position change in the axial direction Td. 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 with respect to the mounting portion 111b in the middle. In this way, the leaf spring 111 directly contacts the hemispherical protrusion 102g of the first intermediate gear 102 to press, thereby applying force to the first intermediate gear 102 in the axial direction Td. In addition, the sliding portion 102i of the first intermediate gear 102 contacts the supporting portion 110c of the main base 110 to slide. Thus, the change in the position of the first intermediate gear 102 in the axial direction Td can be suppressed.

[0068] 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 due to the rotation of the first worm portion 102b meshing with the worm wheel portion 105a of the first counter gear 105 is set 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 due to the rotation of the second worm portion 102h meshing with the worm wheel portion 133a of the second intermediate gear 133. In other words, the tooth profiles of the worms are set so that the components of the axial direction Td of the first intermediate gear 102 of the reaction force are opposite to each other. Specifically, the inclination directions of the teeth in the worms are set so that the components of the axial direction Td of the reaction force applied to the first intermediate gear 102 are opposite to each other. In this case, since the combined reaction force of the axial direction Td is smaller than that of the case where the axial direction Td component of the reaction force received by the first intermediate gear 102 from each worm is the same, the force of the leaf spring 111 can be set smaller accordingly. As a result, the rotational resistance of the first intermediate gear 102 can be reduced, so that it can rotate smoothly.

[0069] The above method is effective when the sliding resistance based on the meshing of the worm portion 101c of the main shaft gear 101 and the worm wheel portion 102a of the first intermediate gear 102 is small, and the axial force Td applied to the first intermediate gear 102 due to the rotation of the main shaft gear 101 is small compared to 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 based on the meshing of the worm 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 effective.

[0070] exist Figure 5In the case where the main shaft gear 101 rotates rightward, a force in the right 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 part 101c of the main shaft gear 101 and the worm wheel part 102a of the first intermediate gear 102, and the first intermediate gear 102 intends to move rightward. At this time, when the force in the axial direction Td generated by the worms at both ends of the first intermediate gear 102 is set in the above-mentioned manner to cancel each other out, the force in the right direction acting on the first intermediate gear 102 becomes relatively large due to the sliding resistance caused by the meshing of the worm part 101c of the main shaft gear 101 and the worm wheel part 102a of the first intermediate gear 102. In order to counteract the rightward force acting on the first intermediate gear 102 and prevent the first intermediate gear 102 from moving rightward, the pressing force of the leaf spring 111 must be set to be large. Therefore, the sliding resistance between the sliding portion 111a of the leaf spring 111 and the hemispherical protrusion 102g of the first intermediate gear 102 that is pressed by abutting against the sliding portion 111a, and the sliding resistance between the sliding portion 102i at the opposite end of the first intermediate gear 102 located at the hemispherical protrusion 102g and the supporting portion 110c increase, thereby increasing the rotational resistance of the first intermediate gear 102.

[0071] When the main shaft gear 101 rotates clockwise, the direction of the reaction force received by the first intermediate gear 102 from the worm wheel 105a of the first counter shaft gear 105 due to the rotation of the first worm portion 102b meshing with the worm wheel 105a of the first counter shaft gear 105 and the direction of the reaction force received by the first intermediate gear 102 from the worm wheel 133a of the second intermediate gear 133 due to the rotation of the second worm portion 102h meshing with the worm wheel 133a of the second intermediate gear 133 are both set to a force in a direction to move the first intermediate gear 102 leftward relative to the axial direction Td, thereby reducing the rightward force acting on the first intermediate gear 102 due to the sliding resistance based on the meshing between the worm portion 101c of the main shaft gear 101 and the worm wheel 102a of the first intermediate gear 102. As a result, the force applied to the first intermediate gear 102 by the leaf spring 111 can be set to be small. As a result, the rotational resistance of the first intermediate gear 102 is reduced, so that the first intermediate gear 102 can rotate smoothly.

[0072] 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 part 101c of the main shaft gear 101 and the worm wheel part 102a of the first intermediate gear 102, and the first intermediate gear 102 tries to move leftward. At this time, the reaction forces received by the first worm part 102b and the second worm part 102h at both ends of the first intermediate gear 102 both become forces that 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 be set to be small. Since the 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, the force in the left direction acting on the first intermediate gear 102 due to the meshing of the above three gears becomes small, and the combined force in the left direction applied to the first intermediate gear 102 also becomes small. Thus, the rotation resistance due to the sliding of the sliding portion 102i at the left end in the figure of the first intermediate gear 102 and the supporting portion 110c provided on the base portion 110a of the main base 110 can be set to be small.

[0073] exist Figure 5 1, the worm wheel 102a is an example of a first driven gear meshing with the worm 101c of the main shaft gear 101. The worm wheel 102a is a worm wheel with 20 teeth formed on the outer periphery of the first cylinder 102d. The worm 101c and the worm wheel 102a constitute a first worm gear reduction mechanism. The rotation axis of the worm wheel 102a extends in a direction perpendicular to the axial direction of the motor shaft 201.

[0074] When the number of teeth of the worm 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 1 time (20÷20=1).

[0075] The first worm part 102b is an example of a second drive gear for driving the worm wheel part 105a, and is a gear part of the first intermediate gear 102. In particular, the first worm part 102b is a worm having a number of 5 formed on the outer periphery of the second cylindrical part 102e. The rotation axis of the first worm part 102b extends in a direction perpendicular to the axial direction of the motor shaft 201.

[0076] exist Figure 5 as well as Figure 7In the embodiment, the first countershaft gear 105 is decelerated as the rotation of the motor shaft 201 rotates integrally with the permanent magnet 8. The first countershaft gear 105 is a substantially circular member in a plan view, and includes: a cylindrical bearing portion 105b, which is axially supported by a shaft 106 protruding substantially vertically from a base portion 110a of a main base 110; a disc portion 105c, which forms the worm gear portion 105a; and a retaining portion 105d, which is used to retain the permanent magnet 8.

[0077] exist Figure 7 In the embodiment, the disc portion 105c has a disc shape extending in the radial direction from the outer periphery of the bearing portion 105b. In the first embodiment, the disc portion 105c is provided at a position close to the end of the bearing portion 105b farther from the base portion 110a. The retaining portion 105d has a cylindrical recessed shape provided on the end surface of the disc portion 105c farther from the base portion 110a in the axial direction. The bearing portion 105b, the disc portion 105c, and the retaining portion 105d are integrally formed in a manner such that the central axes thereof are substantially consistent. The first countershaft gear 105 can be formed of various materials such as a resin material and a metal material. In the first embodiment, the first countershaft gear 105 is formed of polyoxymethylene resin.

[0078] The worm wheel portion 105a is an example of a second driven gear meshed with the first worm 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 portion 102b and the worm wheel portion 105a constitute a second worm gear reduction mechanism. The rotation axis of the worm wheel portion 105a extends in a direction parallel to the axial direction of the motor shaft 201.

[0079] When the number of teeth of the first worm portion 102b of the first intermediate gear 102 is 5 and the number of teeth of the worm wheel portion 105a of the first counter gear 105 is 25, the reduction ratio is 5. That is, if the first intermediate gear 102 rotates 5 times, the first counter gear 105 rotates 1 time. Therefore, if the main shaft gear 101 rotates 100 times, the first intermediate gear 102 rotates 5 times (100÷20=5) and the first counter gear 105 rotates 1 time (5÷5=1). Since the first counter gear 105 rotates integrally with the permanent magnet 8, if the main shaft gear 101 rotates 100 times, the permanent magnet 8 rotates 1 time. That is, the magnetic sensor 50 can determine the rotation amount of the main shaft gear 101 for 100 rotations.

[0080] The absolute encoder 100-1 constructed in this way can determine the rotation amount of the main shaft gear 101. As an example, when the main shaft gear 101 rotates 1 turn, the first countershaft gear 105 and the permanent magnet 8 rotate 1 / 100 turn, that is, rotate 3.6°. Therefore, if the rotation angle of the first countershaft gear 105 is less than 3.6°, it can be determined that the main shaft gear 101 rotates within 1 turn.

[0081] exist Figure 5 , the second worm part 102h is an example of a third driving gear for driving the worm wheel part 133a, and is a gear part of the first intermediate gear 102. In particular, the second worm part 102h is a worm with a number of 1 formed on the outer periphery of the third cylinder part 102f. The rotation axis of the second worm part 102h extends in a direction perpendicular to the axial direction of the motor shaft 201.

[0082] exist Figure 5 In the embodiment, the second intermediate gear 133 rotates with the rotation of the motor shaft 201, and is a disc-shaped gear portion that 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 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 includes a worm wheel portion 133a meshed with the second worm portion 102h of the third drive gear, and a fourth drive gear portion 133d for driving the fourth driven gear portion 138a. The second intermediate gear 133 is formed of, for example, polyacetal resin. The second intermediate gear 133 is a substantially circular member in a plan view. The second intermediate gear 133 includes a bearing portion 133b axially supported by the base portion 110a of the main base 110, and an extension portion 133c forming the worm wheel portion 133a.

[0083] exist 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 part 102h. Therefore, the distance between the permanent magnets 9 and 17 can be set to be longer, thereby reducing the influence of the leakage magnetic flux between each other. In addition, by providing the second intermediate gear 133, the range of the reduction ratio that can be set is expanded accordingly, and the degree of freedom of design is improved.

[0084] exist Figure 8 In the embodiment, the extension portion 133c has a disc shape extending in the radial direction from the outer periphery of the bearing portion 133b. In the first embodiment, the extension portion 133c is provided at a position close to the end of the bearing portion 133b which is farther from the base portion 110a of the main base 110. The fourth drive gear portion 133d is formed at the outer periphery of the region closer to the base portion 110a than the extension portion 133c of the bearing portion 133b. The bearing portion 133b and the extension portion 133c are integrally formed in a manner that the central axes thereof are substantially consistent.

[0085] The worm wheel 133a is a gear part of the second intermediate gear 133 meshing with the second worm part 102h. In particular, the worm wheel 133a is a worm wheel with 30 teeth formed on the outer periphery of the extension part 133c. The second worm part 102h and the worm wheel 133a constitute a third worm gear reduction mechanism. The rotation axis of the worm wheel 133a extends in a direction parallel to the axial direction of the motor shaft 201.

[0086] When the number of teeth of the second worm 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 1 time. Therefore, if the main shaft gear 101 rotates 600 times, the first intermediate gear 102 rotates 30 times (600÷20=30) times, and the second intermediate gear 133 rotates 1 time (30÷30=1) time.

[0087] The fourth drive gear portion 133d is a transmission element for driving the fourth driven gear portion 138a. The fourth drive gear portion 133d is provided on the side opposite to the first countershaft gear 105 side of the main shaft gear 101, and rotates with the rotation of the worm gear portion 133a. The fourth drive gear portion 133d is a spur gear with 24 teeth formed on the outer periphery of the bearing portion 133b.

[0088] exist Figure 8 In the embodiment, the second counter gear 138 is a gear portion that rotates with the rotation of the motor shaft 201, and reduces the speed of the rotation of the motor shaft 201 and transmits it to the permanent magnet 17. The second counter gear 138 is supported by a shaft around a rotation axis extending substantially vertically from the base 110a of the main base 110. The second counter gear 138 includes a bearing portion 138b supported by the base 110a of the main base 110, a protruding portion 138c forming 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 with a gap therebetween.

[0089] The extension portion 138c has a disc shape extending radially from the outer periphery of the bearing portion 138b. In the first embodiment, the extension portion 138c is provided at a position of the base portion 110a of the main base 110 close to the bearing portion 138b. The magnet holding portion 138d has a cylindrical recessed shape provided on the end surface of the bearing portion 138b which is farther from the base portion 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 such that the central axes thereof are substantially consistent. The second countershaft gear 138 can be formed of various materials such as a resin material and a metal material. In the first embodiment, the second countershaft gear 138 is formed of polyoxymethylene resin.

[0090] 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 with 40 teeth formed on the outer periphery of the extension portion 138c.

[0091] 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 50 (1000÷20=50) times, and the second intermediate gear 133 rotates 5 / 3 (50÷30=5 / 3) times. Therefore, the second counter shaft gear 138 rotates 1 (5 / 3÷5 / 3=1) time. Since the second counter shaft gear 138 rotates integrally with the permanent magnet 17, if the main shaft gear 101 rotates 1000 times, the permanent magnet 17 rotates 1 time. That is, the magnetic sensor 90 can determine the rotation amount of the main shaft gear 101 for 1000 times.

[0092] exist 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. Each of permanent magnet 8, permanent magnet 9 and permanent magnet 17 (hereinafter referred to as each permanent magnet) has a generally 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) or the like. Each permanent magnet is, for example, a rubber magnet including a resin binder, or a bonded magnet. Magnetic poles are provided in each permanent magnet. The magnetization direction of each permanent magnet is not limited, but in embodiment 1, as Fig.35 , Fig.36 As shown, the two-pole magnetic poles are arranged on the end face of each permanent magnet opposite to the magnetic sensor. The magnetic flux density distribution in the rotation direction of each permanent magnet can be in a trapezoidal wave shape, or in a sine wave shape or a rectangular wave shape.

[0093] Part or all of each permanent magnet is accommodated in a recess formed at the end of each rotating body and fixed by, for example, bonding and / or riveting, press-fitting, etc. The permanent magnet 8 is bonded and fixed to the holding portion 105d of the first countershaft gear 105. The permanent magnet 9 is bonded and fixed to the magnet holding portion 101d of the main shaft gear 101. The permanent magnet 17 is bonded and fixed to the magnet holding portion 138d of the second countershaft gear 138.

[0094] If the distance between the permanent magnets is short, the magnetic sensor's detection error will increase due to the influence of the leakage flux of the adjacent magnets. Figure 5In the example of , in a top view, the permanent magnet 9 and the permanent magnet 8 are separately arranged on the line of sight Lm inclined with respect to the outer wall portion 115a of the case 115. The line of sight Lm corresponds to the imaginary line connecting the permanent magnet 8 and the permanent magnet 9. The permanent magnet 9 and the permanent magnet 17 are separately arranged on the line of sight Ln inclined with respect to the outer wall portion 115a of the case 115. The line of sight Ln corresponds to the imaginary line connecting the permanent magnet 17 and the permanent magnet 9. In the first embodiment, since the lines of sight Lm and Ln are inclined with respect to the outer wall portion 115a, the distance between the permanent magnets can be set to be longer than the case where the lines of sight Lm and Ln are parallel to the outer wall portion 115a.

[0095] The magnetic sensor 50, the magnetic sensor 40, and the magnetic sensor 90 (hereinafter referred to as each magnetic sensor) are sensors that detect an absolute rotation angle in the range of 0° to 360° corresponding to one rotation of each rotating body. Each magnetic sensor outputs a signal (e.g., a digital signal) corresponding to the detected rotation angle to the microcomputer 121. Even when the power supply is temporarily stopped and then turned on again, each magnetic sensor outputs the same rotation angle as before the power supply was stopped. Therefore, a configuration without a backup power supply is possible.

[0096] like Figure 4 As shown, each magnetic sensor is fixed on the same plane by welding, bonding, etc. on the surface on the side of the base 110a of the main base 110 of the substrate 120. The magnetic sensor 40 is fixed to the substrate 120 in a position opposite to the end face of the permanent magnet 9 provided on the main shaft gear 101 with a constant gap. The magnetic sensor 40 is a first angle sensor for detecting the rotation angle of the main shaft gear 101 corresponding to the change of the magnetic flux generated from the permanent magnet 9. The magnetic sensor 50 is fixed to the substrate 120 in a position opposite to the end face of the permanent magnet 8 provided on the first countershaft gear 105 with a constant gap. The magnetic sensor 50 is a second angle sensor for detecting the rotation angle of the first countershaft gear 105 corresponding to the change of the magnetic flux generated from the permanent magnet 8. The magnetic sensor 90 is fixed to the substrate 120 in a position opposite to the end face of the permanent magnet 17 provided on the second countershaft gear 138 with a constant gap. The magnetic sensor 90 is a third angle sensor for detecting the rotation angle of the second counter gear 138 corresponding to the change in magnetic flux generated from the permanent magnet 17 .

[0097] A magnetic angle sensor with a relatively high resolution can be used in each magnetic sensor. The magnetic angle sensor is arranged relative to the end surface of each permanent magnet including the magnetic poles in the axial direction of each rotating body with a constant gap, and determines the rotation angle of the relative rotating body based on the rotation of these magnetic poles and outputs a digital signal. As an example, the magnetic angle sensor includes a detection element for detecting the magnetic pole, and an operation circuit that outputs a digital signal based on the output of the detection element. The detection element may include a plurality of (for example, four) magnetic field detection elements such as Hall elements, GMR (Giant Magneto Resistive) elements, etc.

[0098] The operation circuit can be set to use, for example, the difference or ratio of the outputs of multiple detection elements as a key, and determine the rotation angle by table processing using a lookup table. 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 outputs 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. For example, each magnetic sensor outputs the rotation angle of each rotating body as a digital signal of multiple bits (for example, 7 bits).

[0099] Fig. 9 1 is a diagram showing the functional configuration of a microcomputer 121 included in an absolute encoder 100-1 according to Embodiment 1 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, or the like. The microcomputer 121 is composed of a CPU, and obtains digital signals indicating rotation angles outputted from the magnetic sensors 40, 50, and 90, respectively, to calculate the rotation amount of the main shaft gear 101. Fig. 9 Each block of the microcomputer 121 shown represents a function realized by executing a program as the CPU of the microcomputer 121. Although each block of the microcomputer 121 can be realized in hardware by components and mechanical devices headed by the CPU (central processing unit) of the computer, and can be realized in software by computer programs, etc., here, the functional blocks realized by their cooperation are described. Therefore, those skilled in the art who have access to this specification should understand that these functional blocks can be realized in various forms by combining hardware and software.

[0100] 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 the rotation angle Aq, which is the 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 the rotation angle Ap, which is the 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 the rotation angle Ar, which is the angle information indicating the rotation angle of the second counter shaft gear 138 detected by the magnetic sensor 90.

[0101] The table processing unit 121b refers to the first correspondence table storing the rotation angle Ap and the rotation speed of the main shaft gear 101 corresponding to the rotation angle Ap, and determines the rotation speed of the main shaft gear 101 corresponding to the obtained rotation angle Ap. In addition, the table processing unit 121b refers to the second correspondence table storing the rotation angle Ar and the rotation speed of the main shaft gear 101 corresponding to the rotation angle Ar, and determines the rotation speed of the main shaft gear 101 corresponding to the obtained rotation angle Ar.

[0102] The rotation amount determination unit 121c determines the first rotation amount of the multiple rotations of the main shaft gear 101 based on the rotation speed of the main shaft gear 101 determined by the table processing unit 121b and the obtained 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.

[0103] The operation and effects of the absolute encoder 100 - 1 according to the first embodiment configured in this manner will be described.

[0104] 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 portion 101c that rotates with the rotation of the motor shaft 201; a worm wheel portion 102a that meshes with the worm portion 101c; a first worm portion 102b that rotates with the rotation of the worm wheel portion 102a; a worm wheel portion 105a that meshes with the first worm 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 for detecting the rotation angle of the permanent magnet 8. According to 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 absolute encoder 100-1 has a first worm gear reduction mechanism including a worm portion 101c and a worm wheel portion 102a meshing with the worm portion 101c, and a second worm gear reduction mechanism including a first worm portion 102b and a worm wheel portion 105a meshing with the first worm portion 102b, a curved transmission path can be formed, thereby enabling a reduction in thickness.

[0105] The absolute encoder 100-1 of the first embodiment is an absolute encoder for determining the rotation amount of the 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 counter 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 counter gear 105; and a magnetic sensor 50 for detecting the rotation angle of the permanent magnet 8, wherein the rotation axis of the motor shaft 201 is located in a twisted position relative to the rotation axis of the first intermediate gear 102, and is set to be parallel to the rotation axis of the first counter gear 105. According to this configuration, the rotation amount of the 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 in a twisted position relative to the rotation axis of the motor shaft 201 and the first counter gear 105 and is orthogonal in front view, the absolute encoder 100-1 forms a curved transmission path, thereby being able to be thinned.

[0106] The absolute encoder 100-1 of the first embodiment is an absolute encoder for determining the rotation amount of the multiple rotations of the motor shaft 201, and includes: a reduction mechanism including a first worm gear reduction mechanism, and rotating the permanent magnet 8 as the motor shaft 201 rotates; and a magnetic sensor 50, which detects the rotation angle of the permanent magnet 8 based on the magnetic poles of the permanent magnet, and the rotation axis of the motor shaft 201 is set to be parallel to the rotation axis of the permanent magnet 8. According to this configuration, the rotation amount of the multiple rotations of the motor shaft 201 can be determined based on the detection result of the magnetic sensor 50. Since the first worm gear reduction 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 forms a curved transmission path, so that it can be thinned.

[0107] The absolute encoder 100-1 of the first embodiment includes a magnetic sensor 40 for detecting the rotation angle of the motor shaft 201. According to 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 included, the resolution of the rotation angle of the motor shaft 201 that can be determined by the absolute encoder 100-1 can be improved.

[0108] The absolute encoder 100-1 of the first embodiment includes a second worm portion 102h that rotates with the rotation of the worm wheel portion 102a, a worm wheel portion 133a that meshes with the second worm portion 102h, a second counter gear 138 that rotates with the rotation of the worm wheel portion 133a, a permanent magnet 17 that rotates integrally with the second counter gear 138, and a magnetic sensor 90 for detecting the rotation angle of the permanent magnet 17. According to this configuration, the rotation amount of the motor shaft 201 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 range of the rotation amount of the motor shaft 201 that can be determined by the absolute encoder 100-1 can be set to be larger.

[0109] In the absolute encoder 100-1 of the first embodiment, the first intermediate gear 102 is provided with the first worm part 102b and the second worm part 102h, and the direction of the reaction force received by the first intermediate gear 102 due to the rotation of the first worm part 102b and the direction of the reaction force received by the first intermediate gear 102 due to the rotation of the second worm part 102h are set to be opposite. According to this structure, compared with the case where the directions of the reaction forces are the same, the combined reaction force of the two reaction forces can be set to be smaller.

[0110] In the absolute encoder 100-1 of the first embodiment, the outer diameter of the worm wheel 102a is set smaller than the outer diameter of the worm 101c. According to this configuration, it is easier to reduce the thickness than when the outer diameter of the worm wheel 102a is larger.

[0111] Here, for example, when the main shaft gear 101 and the first counter shaft gear 105 are arranged adjacent to each other, a part of the magnetic flux generated in each of the permanent magnets 8 and 9 affects the magnetic sensors that do not correspond to each other, that is, magnetic interference is explained.

[0112] Fig.28 The figure shows the concept of the waveform (A) of the magnetic flux of the permanent magnet 9 provided on the main shaft gear 101 (main shaft gear 1) detected by the magnetic sensor 40, the waveform (B) of the magnetic flux of the permanent magnet 8 provided on the first counter shaft gear 105 (counter shaft gear 5) detected by the magnetic sensor 50, and the magnetic interference waveform (C) of the state in which the magnetic flux of a part of the permanent magnet 8 overlaps with the magnetic flux of the permanent magnet 9 as leakage magnetic flux detected 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. In this way, although the magnetic sensor 40 is expected to detect the waveform (A), when magnetic interference occurs, it becomes the waveform shown in (C), and the correct waveform cannot be detected.

[0113] same, Fig.29 This is a diagram showing the concepts of a waveform (A) for detecting the magnetic flux of the permanent magnet 8 provided on the first countershaft gear 105 (countershaft gear 5) by the magnetic sensor 50, a waveform (B) for 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 a magnetic interference waveform (C) for detecting the state where the magnetic flux of a part 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 first countershaft gear 105. In this way, in the magnetic sensor 50, although it is expected to detect the waveform (A), when magnetic interference occurs, it becomes the waveform shown in (C), and the correct waveform cannot be detected. In addition, there is also a problem related to the main shaft gear 101 and the second countershaft gear 138. Fig.29 (C) There is also a concern about magnetic interference.

[0114] The absolute encoder 100-1 of the first embodiment includes a case 115 including an outer wall portion 115a disposed on the opposite side of the first intermediate gear 102 from the motor shaft 201, and the rotation axis La of the first intermediate gear 102 is inclined at 20° relative to the extension direction of the outer wall portion 115a in a plan view. According to this configuration, the inclination of the arrangement straight line of each permanent magnet relative to the outer wall portion 115a can be set larger than when the rotation axis La of the first intermediate gear 102 is not inclined. Therefore, the distance between each permanent magnet can be set larger. In this way, by setting the distance between each permanent magnet to be larger, the generation of magnetic interference that affects the magnetic sensor that does not correspond to each permanent magnet 8, permanent magnet 9, and permanent magnet 17 due to a part of the magnetic flux generated in each of the permanent magnets 8, permanent magnet 9, and permanent magnet 17 can be reduced. For example, it is possible to reduce the interference of a part of the magnetic flux generated by the permanent magnet 9 provided on the main shaft gear 101 as leakage magnetic flux with 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. In addition, it is possible to reduce the interference of a part of the magnetic flux generated by the permanent magnet 8 provided on the first counter shaft gear 105 as leakage magnetic flux with the magnetic sensor 40 provided for the purpose of detecting the change of the magnetic flux generated by the permanent magnet 9. Therefore, the influence of the leakage magnetic flux of the adjacent magnets can be reduced.

[0115] In addition, in the absolute encoder 100-1 of the first embodiment, a base 110a of the main base 110, which is a plate-shaped member made of a magnetic body such as iron, is 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 functions as a magnetic shield for the magnetic flux leaking from the motor 200. Therefore, the magnetic flux leaking from the motor 200 is unlikely to reach the magnetic sensor 40 or the like. As a result, the decrease in the detection accuracy of the rotation angle or rotation amount of the gear by the magnetic sensor can be reduced compared to the case where the base 110a is made of a non-magnetic body such as aluminum having a low magnetic permeability.

[0116] <Implementation Method 2>

[0117] Fig.10 1 is a stereoscopic diagram showing a state where an absolute encoder 100-2 according to Embodiment 2 of the present invention is installed on a motor 200. The following description is based on an XYZ orthogonal coordinate system, as in Embodiment 1. 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. Sometimes the X-axis direction is expressed as the left direction or the right direction, the Y-axis direction is expressed as the front direction or the back direction, and the Z-axis direction is expressed as the up direction or the down direction. Fig.10In the diagram, the state of observing from above in the Z-axis direction is called the top view, the state of observing from the front in the Y-axis direction is called the front view, and the state of observing from the left and right in the X-axis direction is called the side view. Such a direction description 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.10 In the figure, the components provided inside the box body 15 of the absolute encoder 100-2 are shown in a transparent manner. It should be noted that the tooth shape is omitted in the figure.

[0118] Fig.11 It is shown from Fig.10 The absolute encoder 100-2 is shown in a three-dimensional view with the box body 15 and the mounting screws 16 removed. Fig.11 In the figure, a plurality of components provided on the lower surface 20-1 of the substrate 20 are shown through. Fig.12 It is shown from Fig.11 The illustrated diagram is a perspective view of the absolute encoder 100 - 2 in a state where the base plate 20 and the base plate mounting screws 13 are removed. Fig.13 It is shown from Fig.12 The absolute encoder 100 - 2 is a perspective view showing a state in which it is mounted on the motor 200 , and the motor 200 and the screw 14 are removed. Fig.14 It is a top view Fig.13 The main base 10, the intermediate gear 2, etc. are shown in the figure. Fig.14 , the configuration of main components among the multiple components included in the absolute encoder 100-2 is shown. Fig.15 The plane passing through the center of the intermediate gear 2 and parallel to the XY plane is used to Fig.14 The absolute encoder 100 - 2 is shown in a cross-sectional view after being cut.

[0119] Fig.16 It is shown Fig.15 The enlarged partial cross-sectional view shows the state where the bearing 3 is disengaged from the intermediate gear 2. Fig.16 In order to facilitate understanding of the arrangement relationship between the bearing 3 and the press-fit portion 2d formed on the intermediate gear 2, the bearing 3 is disengaged from the press-fit portion 2d of the intermediate gear 2. Fig.16 In order to facilitate understanding of the configuration relationship between the bearing 3 and the wall portion 80 provided on the base 60 of the main base 10, the bearing 3 is separated from the wall portion 80.

[0120] Fig.17 It is through Fig.14 The plane at the center of the main shaft gear 1 and perpendicular to the center line of the intermediate gear 2 will be Fig.11 The cross-sectional view of the absolute encoder 100-2 is shown. However, the substrate 20 and the magnetic sensor 40 are not shown in cross-section. Fig.17, the permanent magnet 9 is shown mounted on the main shaft gear 1, and the main shaft gear 1 is shown mounted on the motor shaft 201. Fig.17 , the meshing state of the worm portion 1d of the main shaft gear 1 and the worm wheel portion 2a of the intermediate gear 2 is shown. Fig.17 It can be seen that the upper surface 9a of the permanent magnet 9 provided on the main shaft gear 1 exists at a position which is a constant distance away from the magnetic sensor 40 in the Z-axis direction.

[0121] Fig.18 It is through Fig.15 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.11 The absolute encoder 100-2 is shown in a cross-sectional view after cutting. However, the substrate 20 and the magnetic sensor 50 are not shown in cross-section. Fig.18 In FIG. 5 , the meshing state of the worm wheel portion 5a and the worm portion 2b is shown. Fig.18 , 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 are shown. Fig.18 , the state where the radially outer surface of the head 6c of the magnet holder 6 is separated from the tooth top circle of the worm part 2b is shown. Fig.18 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 constant distance in the Z-axis direction. Fig.18 , a cross-sectional shape of the bearing seat portion 10d of the main base 10 is shown.

[0122] Fig.19 It is shown that the removal Fig.12 A perspective view showing the state of the intermediate gear 2 among the multiple components shown. Fig. 20 It is shown from Fig.19 The wall portion 70 is shown in a state where the screw 12 is removed, the state of the leaf spring 11 after the screw 12 is removed, and a perspective view of the wall portion 70 having a leaf spring mounting surface 10e facing the leaf spring 11. However, the motor 200 and the main shaft gear 1 are not shown.

[0123] Fig.21 It is through Fig.14 The center of the substrate positioning pin 10g and the center of the substrate positioning pin 10j and the plane parallel to the Z-axis direction will be Fig.11 The absolute encoder 100-2 is shown in a cross-sectional view after being cut. However, the magnetic sensor 40 is not shown in cross-section.

[0124] Fig. 22 Observed from the lower surface 20-1 side Fig.11 FIG. 20 is a diagram of the substrate shown. Fig.23 It is Fig.10The state is removed from the motor 200 and viewed from the lower surface 10-2 side of the main base 10. The lower surface 10-2 of the main base 10 is Fig. 20 The lower surface 10 - 2 of the main base 10 is also a surface facing the motor 200 . Fig.24 yes Fig.10 A three-dimensional view of the box body 15 is shown.

[0125] Fig.25 It is through Fig.12 The center of the substrate positioning pin 10g and the center of the substrate positioning pin 10j are parallel to the Z-axis direction. Fig.10 The absolute encoder 100-2 is shown in a cross-sectional view after cutting. However, the motor 200, the main shaft gear 1 and the magnetic sensor 40 are not cut. Fig.25 , a state in which the claw portion 15a provided on the case 15 is engaged with the recessed portion 10aa provided on the main base 10, and a state in which the claw portion 15b provided on the case 15 is engaged with the recessed portion 10ab provided on the main base 10 are shown. Fig.26 yes Fig.18 An exploded perspective view of the permanent magnet 8 , the magnet holder 6 , the countershaft gear 5 and the bearing 7 is shown. Fig. 27 yes Fig.17 An exploded perspective view of the permanent magnet 9 , the main shaft gear 1 and the motor shaft 201 is shown.

[0126] Below, refer to Figures 10 to 27 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 box body 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.

[0127] The motor 200 is, for example, a stepping motor, a DC brushless motor, etc. The motor 200 is used as a driving source for driving a robot for industrial use, etc., through a speed reduction mechanism such as a wave gear device. The motor 200 includes a motor shaft 201. Fig.17 As shown in FIG. 1 , one end of the motor shaft 201 protrudes from the housing 202 of the motor 200 in the positive direction of the Z axis. Fig.10 As 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. In addition, the motor shaft 201 is an example of a main shaft.

[0128] The outer shape of the motor 200 when viewed from above is, for example, a square. The length of each of the four sides constituting the outer shape of the motor 200 is, for example, 25 mm. Of the four sides constituting the outer shape of the motor 200, a first side and a second side parallel to the first side are parallel to the Y axis. In addition, of the four sides, a third side adjacent to the first side and a fourth side parallel to the third side are parallel to the X axis. In addition, the absolute encoder 100-2 provided in the motor 200 is a 25 mm square quadrilateral corresponding to the outer shape of the motor 200, which is a 25 mm square quadrilateral when viewed from above.

[0129] Next, the multiple components included in the absolute encoder 100-2 are described separately.

[0130] like Fig.17 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 first cylindrical portion 1a and a second cylindrical portion 1b coaxially arranged with the first cylindrical portion 1a 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 provided on the radial inner side of the second cylindrical portion 1b to connect the first cylindrical portion 1a and the second cylindrical portion 1b, and a worm portion 1d provided on the radial outer side of the second cylindrical portion 1b. By forming the connecting portion 1c in this way, the connecting portion 1c functions as an air outlet when the main shaft gear 1 is pressed into 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 surrounded by the end surface of the connecting portion 1c in the negative direction of the Z axis, that is, 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 on the negative side of the Z axis toward the positive side of the Z axis. The motor shaft 201 is press-fitted into the press-fit portion 1f, so that the shaft gear 1 rotates integrally with the motor shaft 201. The worm portion 1d is a gear portion of the main shaft gear 1.

[0131] The space surrounded by the end surface of the connecting portion 1c in the positive direction of the Z axis, i.e., the bottom surface 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 pressed into the magnet holding portion 1h. The outer peripheral surface of the permanent magnet 9 pressed into the magnet holding portion 1h is in contact with the inner peripheral surface of the second cylindrical portion 1b, and the lower surface 9b is in contact with the bottom surface 1g. In this way, the permanent magnet 9 is positioned in the axial direction, and is positioned in a direction orthogonal to the axial direction. The axial direction of the permanent magnet 9 is equivalent to the central axial direction of the motor shaft 201.

[0132] like Figures 13 to 15 ,as well as Fig.17As shown in FIG. 1 , the worm part 1d is composed of a tooth part formed in a spiral shape, and meshes with the worm wheel part 2a of the intermediate gear 2. The worm wheel part 2a is the gear part of the intermediate gear 2. Fig.17 The shape of the tooth portion is omitted in the figure. The worm portion 1d is formed of, for example, polyacetal resin. The worm portion 1d is an example of a first drive gear.

[0133] like Figures 13 to 16 As shown in the figure, the intermediate gear 2 is supported by the shaft 4 on the upper surface of the main base 10. The central axis of the intermediate gear 2 is parallel to the XY plane. In addition, the central axis of the intermediate gear 2 is not parallel to the X-axis and the Y-axis when viewed from above. That is, the central axis of the intermediate gear 2 is inclined relative to the direction in which the X-axis and the Y-axis extend respectively. The inclination of the central axis of the intermediate gear 2 relative to the direction in which the X-axis and the Y-axis extend respectively means that the central axis of the intermediate gear 2 extends obliquely relative to the four sides of the main base 10. As shown in the figure, the central axis of the intermediate gear 2 is inclined relative to the four sides of the main base 10. Fig.13 as well as Fig.14 As shown, the four sides of the main base 10 are composed of a first side 301 parallel to the YZ plane, a second side 302 parallel to the first side 301, a third side 303 parallel to the XZ 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.

[0134] As an example, the size of the absolute encoder 100-2 in a top view corresponds to the size of the motor 200 of 25 mm square. Therefore, by setting the intermediate gear 2 arranged parallel to the XY plane in a manner extending 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 set small. The horizontal direction is equivalent to the direction orthogonal to the central axis of the motor shaft 201, or the direction parallel to the XY plane.

[0135] like Figures 12 to 16 As shown in the figures, the intermediate gear 2 has a worm wheel portion 2a, a worm 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 passes through 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., and is formed of polyacetal resin as an example.

[0136] The worm wheel portion 2a is a gear meshed with the worm 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 in a portion close to the center of the intermediate gear 2 in the axial direction of the intermediate gear 2. 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.

[0137] The outer diameter of the worm wheel 2a is smaller than that of the worm 1d. Since the central axis of the worm wheel 2a is parallel to the upper surface of the main base 10, the outer diameter of the worm wheel 2a is reduced, thereby miniaturizing the absolute encoder 100-2 in the Z-axis direction (height direction).

[0138] The worm portion 2b is composed of a tooth portion formed in a spiral shape, and is disposed adjacent to the worm wheel portion 2a on the same axis. In addition, the worm portion 2b is disposed on the outer peripheral portion of the cylindrical portion of the intermediate gear 2. The worm portion 2b meshes with the worm wheel portion 5a disposed on the countershaft gear 5, so that the rotational force of the intermediate gear 2 is transmitted to the countershaft gear 5. The worm 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. When viewed from a direction perpendicular to the center line of the worm wheel portion 5a and perpendicular to the center line of the worm portion 2b, the center line of the worm wheel portion 5a and the center line of the worm portion 2b are orthogonal to each other.

[0139] In order to enable miniaturization of the absolute encoder 100 - 2 in the Z-axis direction (height direction), the outer diameter of the worm portion 2 b is set to a smaller value within a possible range.

[0140] like Fig.15 As shown, the bearing portion 2c is provided on the radially inner inner peripheral surface of the intermediate gear 2 on the side opposite to the press-fit portion 2d of the intermediate gear 2, that is, on the sliding portion 2e 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.

[0141] 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 portion 2b, and is connected to the through hole 2g. The press-fit portion 2d can also be interpreted as a portion where the opening diameter of the end of the through hole 2g is enlarged. The outer ring 3a of the bearing 3 is pressed into and fixed in the press-fit portion 2d.

[0142] like Figures 13 to 15 , Fig.19 , Fig. 20As 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 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 separated from the base 11d of the leaf spring 11 in a bifurcated shape. 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.

[0143] A gap larger than the diameter of the shaft 4 is formed between the branches constituting the sliding portion 11a of the leaf spring 11. Therefore, 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 the screw 12 in a manner that the two branches span the shaft 4 without contacting the shaft 4.

[0144] The sliding portion 11a of the leaf spring 11 is provided at a position opposite to the sliding portion 2e of the intermediate gear 2 after the intermediate gear 2 is installed. The sliding portion 2e of the intermediate gear 2 is pressed by contacting with the sliding portion 11a of the leaf spring 11, so that a force is applied in a direction from the one end 4a side of the shaft 4 toward the other end 4b side of the shaft 4 along the central axis of the shaft 4. When the intermediate gear 2 rotates in this state, the sliding portion 2e of the intermediate gear 2 slides while contacting with the sliding portion 11a of the leaf spring 11.

[0145] 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 race 3a of the bearing 3. The outer race 3a is pressed into the press-fit portion 2d until the side surface 3c of the outer race 3a contacts the bottom surface 2f.

[0146] The through hole 2g of the intermediate gear 2 penetrates from the bearing portion 2c toward the press-fit portion 2d along the central axis of the intermediate gear 2 and is arranged coaxially with the shaft 4. Since the inner diameter of the through hole 2g is larger than the outer diameter of the shaft 4, a space is ensured between the through hole 2g and the outer peripheral surface of the shaft 4.

[0147] like Fig.15 as well as Fig.16 As shown, the bearing 3 has an outer ring 3a, an inner ring 3b, a side 3c, and a side 3d. The side 3c of the bearing 3 is Fig.15 The side surface 3d of the bearing 3 is the side surface of the inner wheel 3b in the axial direction Td of the shaft 4 as shown by the middle arrow. 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 recorded as Td.

[0148] The outer ring 3a of the bearing 3 is pressed into the press-fit portion 2d, and the side surface 3c is fixed by contacting the bottom surface 2f. The shaft 4 is inserted into the inner side of the inner ring 3b. Fig.15As shown, the side surface 3d of the inner race 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, since 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 action of the leaf spring 11, the side surface 3c of the outer race 3a of the bearing 3 in contact with the bottom surface 2f of the intermediate gear 2 is also urged in the same direction. As a result, the inner race 3b of the bearing 3 is also urged in the same direction, and the side surface 3d of the inner race 3b of the bearing 3 abuts against the abutment surface 10c of the wall portion 80. As a result, the acting force is transmitted to the abutment surface 10c of the wall portion 80, so that the intermediate gear 2 is stably supported in the axial direction Td of the shaft 4. The acting force will be described later in detail.

[0149] The outer wheel 3a of the bearing 3 is set to be able to rotate freely relative to the inner wheel 3b. Fig.15 The bearing portion 2c and the bearing 3 of the intermediate gear 2 are rotatably supported by the shaft 4. The shaft 4 is made of, for example, stainless steel.

[0150] like Fig.15 As shown, the wall portion 70 and the wall portion 80 are an example of a holding portion for holding 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 paired manner 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 provided in a position close to the second side 302 in the region and close to the center in the Y-axis direction. The wall portion 70, the wall portion 80 and the shaft 4 function as a holding portion for holding 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 pressed into the hole 10b formed in the wall portion 80 of the main base 10 and fixed. On the other hand, the one end 4a of the shaft 4 can be inserted into the hole 10a formed in the wall portion 70 to be positioned, and the one end 4a of the shaft 4 does not need to be pressed into the hole 10a. In this way, the one end 4a of the shaft 4 is inserted into the hole 10a instead of being pressed into the hole 10a, so that the assembly of the shaft 4 becomes easier than the case where the one end 4a of the shaft 4 is pressed into the hole 10a.

[0151] like Fig.14 As shown in the examples, 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 surrounded by the four sides of the main base 10, close to the corner of the main base 10. The corner is, for example, Fig.14The portion where the second side 302 and the third side 303 intersect is shown. In this way, the counter gear 5 and the main gear 1 are arranged with the intermediate gear 2 interposed therebetween using the limited area on the main base 10. As a result, compared with the case where the counter gear 5 and the main gear 1 are arranged adjacent to each other without the intermediate gear 2 interposed therebetween, the distance from the counter gear 5 to the main gear 1 can be increased.

[0152] The magnetic sensor 40 can detect the rotation angle of the corresponding main shaft gear 1 by detecting the change in 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 in 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.

[0153] Here, for example, when the main shaft gear 1 and the counter shaft gear 5 are arranged adjacent to each other, a part of the magnetic flux generated by each permanent magnet 8 and permanent magnet 9 affects the magnetic sensor that does not correspond to each permanent magnet 8 and permanent magnet 9, which is called magnetic interference.

[0154] Fig.28 The figure shows the concept of the waveform (A) of the magnetic flux of the permanent magnet 9 provided on the main shaft gear 1 detected by the magnetic sensor 40, the waveform (B) of the magnetic flux of the permanent magnet 8 provided on the counter shaft gear 5 detected by the magnetic sensor 50, and the magnetic interference waveform (C) of the magnetic sensor 40 detecting the state where the magnetic flux of a part of the permanent magnet 8 overlaps with the magnetic flux of the permanent magnet 9 as leakage magnetic flux. The vertical axis represents the magnetic flux, and the horizontal axis represents the rotation angle of the main shaft gear 1. In this way, although the magnetic sensor 40 is expected to detect the waveform (A), when magnetic interference occurs, it becomes the waveform shown in (C), and the correct waveform cannot be detected.

[0155] same, Fig.29 The figure shows the concept of the waveform (A) of the magnetic flux of the permanent magnet 8 provided on the counter gear 5 detected by the magnetic sensor 50 when the main shaft gear 1 rotates, the waveform (B) of the magnetic flux of the permanent magnet 9 provided on the main shaft gear 1 detected by the magnetic sensor 40, and the magnetic interference waveform (C) of the magnetic sensor 50 detecting the state where the magnetic flux of a part of the permanent magnet 9 overlaps with the magnetic flux of the permanent magnet 8 as leakage flux. The vertical axis represents the magnetic flux, and the horizontal axis represents the rotation angle of the counter gear 5. In this way, although the magnetic sensor 50 is expected to detect the waveform (A), when magnetic interference occurs, it becomes the waveform shown in (C), and the correct waveform cannot be detected.

[0156] Therefore, according to the absolute encoder 100-2 of the second embodiment, since the main shaft gear 1 and the permanent magnet 9 are arranged at a distance from the counter shaft gear 5 and the permanent magnet 8 via the intermediate gear 2, it is possible to reduce the generation of magnetic interference that affects the magnetic sensors that do not correspond to the permanent magnets 8 and 9 due to a part of the magnetic flux generated in each permanent magnet 8 and the permanent magnet 9. For example, it is possible to reduce the interference of a part of the magnetic flux generated in the permanent magnet 9 provided in the main shaft gear 1 as leakage magnetic flux with the magnetic sensor 50 provided for the purpose of detecting the change of the magnetic flux generated by the permanent magnet 8 provided in the counter shaft gear 5. In addition, it is possible to reduce the interference of a part of the magnetic flux generated in the permanent magnet 8 provided in the counter shaft gear 5 as leakage magnetic flux with the magnetic sensor 40 provided for the purpose of detecting the change of the magnetic flux generated in the permanent magnet 9.

[0157] Thus, according to the absolute encoder 100-2 of the second embodiment, the size of the absolute encoder 100-2 when viewed from above can be set relatively small, while preventing the detection accuracy of the rotation angle or rotation amount of the counter shaft gear 5 by the magnetic sensor 50 from being reduced. In addition, according to the absolute encoder 100-2, the size of the absolute encoder 100-2 when viewed from above can be set relatively small, while preventing the detection accuracy of the rotation angle or rotation amount of the main shaft gear 1 by the magnetic sensor 40 from being reduced.

[0158] like Fig.18 As shown, the counter gear 5 is a cylindrical component that is pressed into and fixed to the shaft portion 6b of the magnet holder 6. The counter gear 5 has a worm gear portion 5a and a through hole 5b. The counter gear 5 is a component integrally formed of metal or resin, and is formed of polyacetal resin as an example.

[0159] The worm wheel 5a is a gear meshing with the worm wheel 2b. The worm wheel 5a is an example of a second driven gear. The worm wheel 5a is composed of a plurality of teeth provided on the outer circumference of the cylindrical portion of the counter gear 5. Fig.13 In the embodiment, the intermediate gear 2 rotates, and the rotational force of the intermediate gear 2 is transmitted to the counter gear 5 via the worm portion 2b and the worm wheel portion 5a.

[0160] The through hole 5b is a hole that penetrates along the central axis of the cylindrical counter gear 5. The shaft portion 6b of the magnet holder 6 is press-fitted into the through hole 5b, and the counter gear 5 and the magnet holder 6 rotate integrally.

[0161] like Fig.18 as well as Fig.26 As shown, the magnet holder 6 has a magnet holding portion 6a, a shaft portion 6b, and a head portion 6c. The magnet holder 6 is a component integrally formed of metal or resin, and is formed of non-magnetic stainless steel as an example.

[0162] The outer races 7a of two bearings 7 are press-fitted into 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 the outer race 7a and the inner race 7b, respectively.

[0163] The shaft portion 6b of the magnet holder 6 is a cylindrical member, which is pressed into the through hole 5b of the counter gear 5, and the lower portion of the shaft portion 6b is inserted into the inner rings 7b of the two bearings 7. Therefore, the magnet holder 6 is axially supported relative to the main base 10 through the two bearings 7, so as to rotate integrally with the counter gear 5.

[0164] In addition, a head 6c is provided at the upper end of the magnet holder 6. The head 6c is a cylindrical component with a bottom. A magnet holding portion 6a is formed in 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 disposed in the magnet holding portion 6a is in contact with the inner peripheral surface of the head 6c. Thus, the permanent magnet 8 is fixed to the magnet holding portion 6a of the head 6c.

[0165] The shaft portion 6b of the magnet holder 6 is supported by two bearings 7 disposed in the bearing seat portion 10d formed in the main base 10, thereby preventing the magnet holder 6 from tilting. Therefore, if the two bearings 7 are disposed as far apart as possible in the axial direction of the shaft portion 6b, the effect of preventing the magnet holder 6 from tilting can be expected.

[0166] like Fig.18 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 in 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 in the entire bearing seat portion 10d. A bearing 7 is provided inside the lower portion 10da of the bearing seat portion 10d.

[0167] like Fig.18As shown, a portion of the housing 202 of the motor 200 is provided with a notch 202a. The notch 202a is a recessed portion that is recessed toward the negative direction of the Z axis. In the main base 10, since the lower portion 10da of the bearing seat portion 10d is protrudingly provided, by providing the notch 202a in the housing 202 of the motor 200, interference with each other is prevented. 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 in the entire bearing seat portion 10d. A bearing 7 is provided inside the lower portion 10da of the bearing seat portion 10d. In this way, by providing the notch 202a in the housing 202 of the motor 200, the two bearings 7 can be provided at a distance in the Z axis direction compared to the case where the notch 202a is not provided. In addition, 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 in the entire bearing seat portion 10d.

[0168] In the axial direction of the shaft portion 6b of the magnet holder 6, if the bearing 7 is provided at a position closer to the magnet holder 6a and the permanent magnet 8, the shaft vibration of the magnet holder 6 and the permanent magnet 8 during rotation can be reduced. On the other hand, since the outer diameter of the upper portion 10db of the bearing seat portion 10d is close to the intermediate gear 2, by forming an inclined surface on the upper portion 10db of the bearing seat portion 10d, interference with the tooth top circle of the intermediate gear 2 can be avoided, and the bearing 7 can be provided at a position closer to the magnet holder 6a and the permanent magnet 8.

[0169] The magnetic sensor 40 can detect the rotation angle of the corresponding main shaft gear 1 by detecting the change in 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 in 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.

[0170] like Fig.18 , Fig.26 As shown, the permanent magnet 8 has a surface 8a. The permanent magnet 8 is substantially 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) coincides with the central axis HC1 of the magnet holder 6, the central axis GC1 of the counter gear 5, and the central axis BC of the bearing 7. The surface 8a of the permanent magnet 8 is opposed to the surface 50a of the magnetic sensor 50 at a constant distance. In this way, by aligning the central axes, it is possible to detect the rotation angle or the rotation amount with further high accuracy.

[0171] It should be noted that, in this embodiment, Fig.26As shown, the two magnetic poles (N / S) of the permanent magnet 8 are formed adjacent to each other in a plane (XY plane) perpendicular to the central axis MC1 of the permanent magnet 8. That is, in the central axis MC1, it is desired that the rotation center of the permanent magnet 8 coincides with the center of the boundary of the magnetic poles. As a result, the detection accuracy of the rotation angle or the rotation amount is further improved.

[0172] like Fig.17 , Fig. 27 As shown, the permanent magnet 9 is a substantially cylindrical permanent magnet pressed into 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 opposed to the surface 40a of the magnetic sensor 40 at a constant distance therefrom. The lower surface 9b is in contact with the bottom surface 1g of the magnet holding portion 1h of the main shaft gear 1, thereby defining 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 indicating the center of the permanent magnet 9, or the axis passing through the center of the boundary of the magnetic pole) coincides with the center axis GC2 of the main shaft gear 1 and the center axis RC of the motor shaft 201. By aligning the center axes in this way, it is possible to detect the rotation angle or the rotation amount with further high accuracy.

[0173] It should be noted that, in this embodiment, Fig. 27 As shown, it is desirable that the two magnetic poles (N / S) of the permanent magnet 9 are formed adjacent to each other in a plane (XY plane) perpendicular to the central axis MC2 of the permanent magnet 9. Thus, the detection accuracy of the rotation angle or the rotation amount is further improved.

[0174] It should be noted that the permanent magnets 8 and 9 are respectively formed of magnetic materials such as ferrite, Nd (neodymium)-Fe (iron)-B (boron), etc. The permanent magnets 8 and 9 can be respectively made of rubber magnets including resin binders, bonded magnets, etc.

[0175] exist Fig. 22 , a plurality of through holes formed in the substrate 20, namely, the positioning hole 20a, the positioning hole 20b, the hole 20c, the hole 20d, and the hole 20e are shown. The shape of the wall surface forming the positioning hole 20a is, for example, a circle. The shape of the wall surface forming the positioning hole 20b is, for example, an ellipse. Each hole 20c, the hole 20d, and the hole 20e are used to pass Fig.11 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 each hole 20c, hole 20d and hole 20e is, for example, a circle. The diameter of the wall surface forming each hole 20c, hole 20d and hole 20e is larger than the diameter of the external thread portion of the substrate mounting screw 13 and smaller than the diameter of the head of the substrate mounting screw 13.

[0176] like Figures 12 to 15 , Figures 19 to 21 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 top portion 10h, a top 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 10i is formed between the top 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 tip 10h of the substrate positioning pin 10g is inserted into the positioning hole 20a formed in the substrate 20, a gap is formed between the lower surface 20-1 of the substrate 20 and the step 10i. Similarly, a step 101 is formed between the tip 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 tip 10k of the substrate positioning pin 10j is inserted into the positioning hole 20b formed in the substrate 20, a gap is formed between the lower surface 20-1 of the substrate 20 and the step 101. 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 is limited. However, since a gap is formed between each step 10i and the step 101 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.

[0177] The base 60 of the main base 10 is, for example, an integrally formed aluminum die-cast component, and is a substantially square plate-shaped component 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 .

[0178] Fig.12 The opening 10-1 shown passes through the base 60 in the thickness direction (Z-axis direction). The main shaft gear 1 is inserted into the opening 10-1. The opening 10-1 is an example of a first through hole.

[0179] like Fig.13 , Fig.14 , Fig.19 , Fig. 20As 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 with the upper surface of the base 60, and extends from the base 60 in the positive direction of the Z axis. When viewed from above, 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 has 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 the figure, Fig.10 , Fig.23 ,as well as Fig.24 As shown, the mounting screw 16 is inserted into the hole 15d of the box body 15 and is threadedly fastened to the screw hole 10ae, so that the inner surface of the box body 15 is abutted and fixed to the mounting surface 10ad of the wall portion 71.

[0180] like Fig.14 As shown, the wall portion 72 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 third side 303 than the center in the Y-axis direction when viewed from above. The wall portion 72 is connected to the wall portion 71 and extends from the wall portion 71 toward the vicinity of 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 oblique directions with respect to the X-axis and the Y-axis, respectively, when viewed from above.

[0181] like Fig. 20 As shown, the screw 12 is inserted into the hole 11c formed in the mounting portion 11b of the leaf spring 11, and is screwed into the screw hole 10f formed in the wall portion 72 of the main base 10. As a result, the mounting portion 11b of the leaf spring 11 abuts against the leaf spring mounting surface 10e formed in the wall portion 72, and the leaf spring 11 is fixed to the wall portion 72. The wall portion 72 functions as a fixing portion for fixing the leaf spring 11. At this time, as shown in FIG. Fig.14 as well as Fig.15 As shown, the sliding portion 11a of the leaf spring 11 abuts against the sliding portion 2e of the intermediate gear 2 into which the shaft 4 is inserted.

[0182] right Fig.15The installation angle θ shown in the figure is explained. Since the worm portion 1d of the main shaft gear 1 meshes with the worm wheel portion 2a, the first thrust is generated in the intermediate gear 2 in the direction from the other end 4b of the shaft 4 to the one end 4a of the shaft 4 or from the one end 4a of the shaft 4 to the other end 4b of the shaft 4 as the worm portion 1d of the main shaft gear 1 rotates. In addition, due to the meshing of the worm portion 2b and the worm wheel portion 5a of the counter shaft gear 5, the second thrust is also generated in the intermediate gear 2 in the direction from the other end 4b of the shaft 4 to the one end 4a of the shaft 4 or from the one end 4a of the shaft 4 to the other end 4b of the shaft 4. In this way, in order to accurately transmit the rotation amount of the worm portion 1d of the main shaft gear 1 to the worm wheel portion 5a of the counter shaft gear 5 even when the first thrust and the second thrust are generated, it is necessary to suppress the movement of the intermediate gear 2 in the axial direction Td of the shaft 4. The leaf spring 11 applies a force to the intermediate gear 2 in the direction from the one end 4a of the shaft 4 to the other end 4b of the shaft 4. The biasing force generated by the leaf spring 11 is set to a value greater 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 .

[0183] exist Fig.15 In the embodiment, the mounting angle θ is equal to the angle formed by the base 11d of the leaf spring 11 fixed to the wall portion 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 portion 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 in this embodiment is orthogonal to the shaft 4, but it is not limited to this. The mounting angle θ is set to an angle at which 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 bends by a predetermined amount, thereby appropriately applying a force in the axial direction Td of the shaft 4 to the intermediate gear 2. As a result, the leaf spring 11 applies a force to the intermediate gear 2 in the direction from the one end 4a side of the shaft 4 to the other end 4b side of the shaft 4, thereby suppressing 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 to the one end 4a of the shaft 4. As a result, it is possible to prevent the rotation accuracy of the countershaft gear 5 from being reduced. It should be noted that the greater the force, Fig.15 The sliding resistance when the intermediate gear 2 rotates increases. Therefore, it is desirable to set the mounting angle θ to an appropriate value so that sufficient force can be generated to minimize the sliding resistance when the intermediate gear 2 rotates and to suppress the movement of the intermediate gear 2 caused by the thrust. 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 where the leaf spring 11 is mounted and reduce the error of the mounting angle of the wall portion 70 to the base portion 60.

[0184] In the absolute encoder 100-2 of the second embodiment, since the main base 10 is formed by aluminum die casting, the error of the mounting angle of the base 60 to the wall 70 can be set smaller than when the base 60 and the wall 70 are separately manufactured by metal plate processing, and the surface accuracy of the leaf spring mounting surface 10e can be improved. As a result, the error of the mounting angle θ to the wall 72 of the leaf spring 11 becomes smaller, and the management of the acting force becomes easier.

[0185] like Fig.19 As shown, the main base 10 is fixed by inserting three screws 14 into three holes formed in the main base 10 and screwing them into screw holes formed in the motor 200. Screw holes 10v, 10u, and 10w are formed on the top ends of the columns 10q, 10m, and 10s extending in the positive direction of the Z axis from the main base 10, respectively. Fig.11 As shown, the substrate mounting screws 13 are inserted into the holes 20c, 20e and 20d formed in the substrate 20. As a result, the upper end faces 10r, 10p and 10t of the columns 10q, 10m and 10s are respectively connected to the substrate 20. Fig.21 The lower surface 20-1 of the substrate 20 shown is in contact. The lower surface 20-1 of the substrate 20 is the surface opposite to the main base 10 of 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 is defined.

[0186] like Fig.10 , Figure 23 to Figure 25 As shown in the figure, the box body 15 includes an upper surface portion 15-1, a first side portion 15A, a second side portion 15B, a third side portion 15C, and a fourth side portion 15D, and is a box-shaped component with one side open. The box body 15 is made of resin, for example, and is an integrally formed component. The upper surface portion 15-1 is equivalent to the bottom of the box-shaped component. The upper surface portion 15-1 is Fig.11The surface opposite to 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 opposite side to the lower surface 20-1 of the substrate 20. The first side surface portion 15A is a plate-like component extending in the negative direction of the Z axis from the edge of the upper surface portion 15-1 on the positive direction of the X axis. The second side surface portion 15B is a plate-like component extending in the negative direction of the Z axis from the edge of the upper surface portion 15-1 on the negative direction of the X axis. The third side surface portion 15C is a plate-like component extending in the negative direction of the Z axis from the edge of the upper surface portion 15-1 on the negative direction of the Y axis. The fourth side surface portion 15D is a plate-like component extending in the negative direction of the Z axis from the edge of the upper surface portion 15-1 on the positive direction of the Y axis. The shape of the box body 15 when viewed from above is a rectangle corresponding to the shape of the motor 200 when viewed from above. The space inside the box body 15 accommodates a plurality of components of the absolute encoder 100-2.

[0187] like Fig.24 As shown, the box body 15 has a claw 15a, a claw 15b, a claw 15c, a hole 15d, a recess 15e, a recess 15f, a recess 15g, a connector box body 15h, and an opening 15i. The claw 15a is provided at 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 opposite to the third side surface 15C. The claw 15a and the Fig.23 The claw portion 15b is provided at 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 in a manner opposite to the fourth side portion 15D. Fig.23 The claw portion 15c is provided at 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 in a manner opposite to the first side portion 15A. Fig.23 The recess 10ac provided on the main base 10 is shown to be engaged.

[0188] To avoid Fig.24 Recesses 15e, 15f and 15g are shown in Fig.11 In order to prevent interference between the heads of the three substrate mounting screws 13, a portion of the upper surface 5-1 of the box body 15 is formed as a recessed portion in a manner recessed toward the positive direction of the Z axis.

[0189] The connector box body portion 15h is a portion of the upper surface 5-1 of the box body 15 to cover the Fig.11The connector 24 is formed by being recessed in the positive direction of the Z axis. The bottom surface of the connector box body 15h is rectangular when viewed from above. The connector box body 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 near the center in the Y-axis direction. In addition, the connector box body 15h is provided in a portion of the area that is close to the first side surface 15A.

[0190] The opening portion 15i is formed between the bottom surface of the connector case portion 15h and the first side surface portion 15A. Fig.11 The connector 24 is arranged to face the bottom surface of the connector box body 15h. The connector 24 is, for example, a female connector, and a male connector provided at one end of the external wiring is inserted into the connector 24. The male connector is inserted into the connector 24 by Fig.24 The connector 24 disposed in the connector box body 15h is inserted into the opening 15i shown. As a result, the conductive terminal provided in the connector 24 is electrically connected to the conductive terminal of the male connector provided at one end of the external wiring. As a result, the external device connected to the other end of the external wiring is electrically connected to the connector 24, so that the signal transmission between the absolute encoder 100-2 and the external device becomes possible.

[0191] In addition, since the connector box body 15h is disposed near the first side surface 15A, Fig.11 As shown, the position of the connector 24 when viewed from above is the same as the position of the connector 400 when viewed from above the motor 200. By configuring the absolute encoder 100-2 in this way, the position where the external wiring electrically connected to the conductive pin provided on the connector 24 is led out can be close to the position where the external wiring electrically connected to the conductive pin provided on the connector 400 is led out. Therefore, these external wirings can be bundled together near the absolute encoder 100-2 and the motor 200, and the bundled wiring group can be easily led to the external device.

[0192] like Fig. 22 As shown in FIG. 1 , a magnetic sensor 40, a magnetic sensor 50, a microcomputer 21, a bidirectional driver 22, and a line driver 23 are provided on the lower surface 20-1 of the substrate 20. The lower surface 20-1 of the substrate 20 is a mounting surface for the magnetic sensor 40 and the magnetic sensor 50. As described 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 in contact with the lower surface 20-1 of the substrate 20. Fig.13As shown, the column 10q, the column 10m, and the column 10s are provided on the main base 10 in such a manner that the difference in the distance between each other when the main base 10 is viewed from above becomes small. For example, the column 10q is provided near the center of the main base 10 in the Y-axis direction and close to the second side 302. The column 10q is integrated with the wall portion 80. The column 10m is provided near the corner where the first side 301 and the fourth side 304 intersect. The column 10s is provided near the center of the main base 10 in the X-axis direction and close to the third side 303. The column 10s is integrated with the wall portion 70 and the substrate positioning pin 10g. In this way, by providing the column 10q, the column 10m, and the column 10s, the position of each of the magnetic sensor 40 and the magnetic sensor 50 provided on the substrate 20 in the Z-axis direction can be accurately defined. It should be noted that if the pillars 10q, 10m, and 10s are formed at positions as far apart as possible in the XY plane direction in the main base 10, the position of the substrate 20 can be further stably maintained.

[0193] In the absolute encoder 100-2 of the second embodiment, the main base 10 is formed by die casting. Therefore, compared with the case where the base 60 of the main base 10 is manufactured by metal plate processing, and the columns 10q, 10m, 10s, substrate positioning pins 10g, substrate positioning pins 10j, wall portions 70, wall portions 80, etc. are manufactured separately and assembled, the positional accuracy between the components is improved. In addition, by reducing the number of components during manufacturing, the structure of the absolute encoder 100-2 can be simplified, and assembly becomes easy, which can shorten the manufacturing time and improve the reliability of the absolute encoder 100-2.

[0194] 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 detects the change in 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, thereby detecting and determining the corresponding rotation angle of the main shaft gear 1, and outputs angle information indicating the determined rotation angle as a digital signal.

[0195] The magnetic sensor 50 is an example of an angle sensor. The counter gear 5 is a rotating body that rotates as the second driven gear, i.e., the worm gear portion 5a, rotates. The magnetic sensor 50 is arranged at a predetermined interval just above the permanent magnet 8. The magnetic sensor 50 detects the change in magnetic flux generated from the permanent magnet 8 due to the rotation of the permanent magnet 8 that rotates together with the counter gear 5, thereby detecting and determining the rotation angle of the corresponding counter gear 5, and outputs angle information indicating the determined rotation angle as a digital signal.

[0196] The magnetic sensor 40 and the magnetic sensor 50 each include, 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 based on the output of the detection element. The detection element may be a combination of a plurality of magnetic field detection elements such as a Hall element, a GMR (Giant Magneto Resistive) element, etc. The number of magnetic field detection elements is, for example, four.

[0197] When the number of teeth of the worm 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 1 time. On the other hand, when the number of teeth of the worm 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 1 time. Therefore, if the main shaft gear 1 rotates 90 times, the intermediate gear 2 rotates 18 times (90÷5=18) times, and the counter shaft gear 5 rotates 1 time (18÷18=1) time.

[0198] The main shaft gear 1 and the counter shaft gear 5 are provided with permanent magnets 9 and 8 that rotate integrally. Therefore, the corresponding magnetic sensors 40 and 50 can determine the rotation amount of the motor shaft 201 by detecting the rotation angles of the main shaft gear 1 and the counter shaft gear 5. If the main shaft gear 1 rotates 1 turn, the counter shaft gear 5 rotates 1 / 90 turn, that is, 4°. 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 turn, 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 turn and less than 2 turns. In this way, in the absolute encoder 100-2, the rotation speed of the main shaft gear 1 can be determined according to the rotation angle of the counter shaft gear 5. In particular, the absolute encoder 100-2 can determine the rotation speed of the main shaft gear 1 even if the rotation speed of the main shaft gear 1 is multiple turns by utilizing the reduction ratio between the worm part 1d and the worm wheel part 2a, and the reduction ratio between the worm part 2b and the worm wheel part 5a.

[0199] 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 are electrically connected via a wiring pattern on the substrate 20.

[0200] The microcomputer 21 is composed of a CPU (Central Processing Unit), and obtains digital signals indicating the rotation angles outputted from the magnetic sensor 40 and the magnetic sensor 50 , and calculates the rotation amount of the main shaft gear 1 .

[0201] The bidirectional driver 22 performs bidirectional communication with an external device connected to the connector 24. The bidirectional driver 22 converts data such as an operation signal into a differential signal and communicates with the external device. The line driver 23 converts data indicating the amount of rotation into a differential signal and outputs the differential signal in real time to the external device connected to the connector 24. The connector of the external device is connected to the connector 24.

[0202] Fig.30 This 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. Fig.30 Each block of the microcomputer 21 shown represents a function realized by the CPU serving as the microcomputer 21 executing a program.

[0203] 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 refers to a correspondence table storing the rotation angle Ap and the rotation speed of the main shaft gear 1 corresponding to the rotation angle Ap, thereby determining the rotation speed of the main shaft gear 1 corresponding to the acquired rotation angle Ap. The rotation amount determination unit 21c determines the rotation amount of the main shaft gear 1 for multiple rotations based on the rotation speed of the main shaft gear 1 determined by the table processing unit 21b and the acquired rotation angle Aq. The output unit 21 e converts the rotation amount of the specified plurality of rotations of the main shaft gear 1 into information indicating the rotation amount and outputs the information.

[0204] As described above, in the absolute encoder 100-2 of the second embodiment, Fig.14 As shown in FIG. 1 , since the counter gear 5 is disposed on the side opposite to the main gear 1 side of the intermediate gear 2, the generation 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, the absolute encoder 100-2 can be set to a relatively small size when viewed from above by adopting a structure that can reduce the generation of magnetic interference. Therefore, the absolute encoder 100-2 can be miniaturized, and the detection accuracy based on the magnetic flux of each of the magnetic sensors 40 and 50 can be prevented from being reduced.

[0205] In addition, 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. Therefore, the main shaft gear 1, the intermediate gear 2, and the counter shaft gear 5 can be arranged in a narrow area of ​​a part of the entire area of ​​the upper surface of the main base 10, so that the size of the absolute encoder 100-2 relative to the horizontal direction can be set to be small.

[0206] In the absolute encoder 100-2 of the second embodiment, the outer diameters of the worm wheel 2a and the worm shaft 2b are set to smaller values ​​within a possible range. Thus, the dimension of the absolute encoder 100-2 in the Z-axis direction (height direction) can be set smaller.

[0207] Thus, according to the absolute encoder 100-2 of the second embodiment, it is possible to prevent the detection accuracy of the rotation amount of the main shaft gear 1 from being reduced, and to set the dimension in the Z-axis direction and the dimension in the direction orthogonal to the Z-axis direction to be smaller.

[0208] In addition, in the absolute encoder 100-2 of embodiment 2, although the intermediate gear 2 is axially supported, that is, supported to be rotatable, relative to the shaft 4 fixed or inserted into each wall portion 80 and the wall portion 72, the supporting method of the intermediate gear 2 is not limited to this as long as the intermediate gear 2 can be axially supported.

[0209] For example, the absolute encoder 100-2 is 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. Furthermore, the absolute encoder 100-2 may be configured such that the outer race 3a of the bearing 3 is press-fitted and fixed in the press-fit portion 2d formed in the intermediate gear 2, and the shaft 4 is press-fitted and fixed in the inner race 3b of the bearing 3. Thus, the movement of the intermediate gear 2 fixed to the shaft 4 in the axial direction Td is restricted. When the absolute encoder 100-2 is configured in this way, the intermediate gear 2 is also axially supported by the shaft 4. Furthermore, the movement of the shaft 4 in the axial direction Td is restricted by the wall portion 72 and the wall portion 80, and the movement of the intermediate gear 2 in the axial direction is also restricted by the inner race 3b of the bearing 3 fixed to the shaft 4. Therefore, the leaf spring 11 is not required.

[0210] In addition, for example, the absolute encoder 100-2 can be used without Fig.15 The bearing 3 is not shown in the figure, but is configured so that 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 when the intermediate gear 2 is fixed to the shaft 4.

[0211] When the outer ring of the bearing (not shown) 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 supported by the bearing (not shown), so the shaft 4 and the intermediate gear 2 can rotate together. In this case, since the shaft 4 is not fixed to the inner ring of the bearing but is only inserted into the inner ring, the shaft 4 can move in the axial direction Td together with the intermediate gear 2. Therefore, a leaf spring 11 is required to apply force to the intermediate gear 2 in the axial direction Td to limit the position.

[0212] Alternatively, the outer ring of the bearing (not shown) may be fixed to the wall portion 72 or the wall portion 80, and one end 4a or the other end 4b of the shaft 4 may be pressed into the inner ring (not shown). In this case, the movement of the intermediate gear 2 fixed to the shaft 4 in the axial direction Td is restricted. Therefore, the intermediate gear 2 fixed to the shaft 4 is not only supported in a rotatable manner by the bearing (not shown), but also the movement of the shaft 4 in the axial direction Td is restricted, so the movement of the intermediate gear 2 in the axial direction Td is also restricted. Therefore, the leaf spring 11 is not required.

[0213] like Fig.17 As shown, originally, the magnetic sensor 40 detects the change of the magnetic flux from the permanent magnet 9 rotating together with the main shaft gear 1, thereby detecting and determining the rotation angle of the main shaft gear 1. Fig.18 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 generation of magnetic interference. In addition, the influence of the magnetic flux from the permanent magnet 9 on the magnetic sensor 50 can be reduced. In other words, it is possible to prevent the reduction 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.

[0214] exist Fig.10 , the absolute encoder 100-2 is shown as being mounted on the motor 200, but the motor 200 has a permanent magnet and a driving coil built therein. Therefore, the motor 200 generates magnetic flux even when the motor shaft 201 is not rotating. In addition, when a drive signal is given to the motor 200 from the outside to rotate the motor shaft 201, the generated magnetic flux further increases. Due to the magnetic flux generated from the motor 200, there is a case where the magnetic sensor 40 and the magnetic sensor 50 provided inside the absolute encoder 100-2 are adversely affected, thereby causing a decrease in detection accuracy. In the case where there is such an influence of unnecessary magnetic flux from the motor 200, if the main base 10 is made of a ferromagnetic body such as iron, the influence of the magnetic flux from the motor 200 can be reduced.

[0215] here, Fig.17 The main shaft gear 1 shown is a cylindrical component formed integrally with a first cylindrical portion 1a into which the motor shaft 201 is pressed and fitted, and a second cylindrical portion 1b into which the permanent magnet 9 is pressed and fitted, but it may also be configured as follows. Axis deviation refers to a state in which the radial center portion of the permanent magnet 9 is separated from a predetermined position of the magnetic sensor 40 corresponding to the permanent magnet 9 (for example, the center portion of the magnetic flux detection area) in a direction orthogonal to the Z-axis direction when the permanent magnet 9 is viewed from above.

[0216] Fig.31 1 is a perspective view of a main shaft gear 1A included in an absolute encoder 100 - 2 according to a first modified example of the second embodiment. Fig.32 yes Fig.31 1A is a cross-sectional view of a main shaft gear 1A. The main shaft gear 1A is a gear that is coaxially arranged with the motor shaft 201 and fixed to the motor shaft 201. The main shaft gear 1A includes a magnet holder 170 and a resin gear portion 180.

[0217] The magnet holder 170 is a cylindrical component made of a non-magnetic metal material such as copper, aluminum, or brass. The magnet holder 170 is a cylindrical portion that is coaxially arranged with the motor shaft 201 and is press-fitted into the top end of the motor shaft 201. The magnet holder 170 includes a first inner peripheral surface 171 of a first inner diameter that is opposite to the outer peripheral surface of the permanent magnet 9, a second inner peripheral surface 172 of a second inner diameter that is smaller than the first inner diameter, and a first step portion 173.

[0218] The first inner diameter of the first inner circumferential surface 171 is slightly larger than the outer diameter of the permanent magnet 9. The term "slightly" means that when the permanent magnet 9 is installed in the space surrounded by the first inner circumferential surface 171, it is not necessary to press the permanent magnet 9 in and the angle error of the magnetic sensor 40 with respect to the change in the axial offset is a value below a predetermined value. The angle error is equivalent to the angle difference between the actual rotation angle of the main shaft gear 1A and the rotation angle detected by the magnetic sensor 40. Since the permanent magnet 9 does not need to be pressed in, the operation of installing the permanent magnet 9 on the main shaft gear 1A becomes easy, and the cracking of the permanent magnet 9 caused by pressing into the main shaft gear 1A can be suppressed.

[0219] In such a configuration, since the adhesive is easily attached to the metal magnet holder 170, the adhesive is provided between the permanent magnet 9 and the first inner peripheral surface 171 of the magnet holder 170, so that the bonding strength of the permanent magnet 9 to the magnet holder 170 can be ensured. Therefore, since the adhesive acts as a member to prevent the permanent magnet 9 from coming off, it is possible to suppress the permanent magnet 9 from coming off from the main shaft gear 1A during the operation of the absolute encoder 100-2.

[0220] The second inner peripheral surface 172 forms an opening formed between the permanent magnet 9 and the motor shaft 201. The axial end surface of the permanent magnet 9 is in contact with the first step portion 173 provided at the boundary between the second inner peripheral surface 172 and the first inner peripheral surface 171. Fig.32 The direction indicated by the middle arrow D2 is equivalent to the axial direction of the motor shaft 201.

[0221] In addition, the magnet holder 170 includes a third inner peripheral surface 174 having a third inner diameter larger than the second inner diameter and facing the outer peripheral surface of the motor shaft 201, and a second step portion 175 provided at a boundary portion between the second inner peripheral surface 172 and the third inner peripheral surface 174. In order to press the motor shaft 201 into the space surrounded by the third inner peripheral surface 174, the third inner diameter of the third inner peripheral surface 174 is smaller than the outer diameter of the motor shaft 201.

[0222] The resin gear part 180 is a member formed of, for example, polyoxymethylene resin in an annular shape. The resin gear part 180 is disposed adjacent to the magnet holder 170 in a coaxial manner with the motor 200. The resin gear part 180 is an annular part whose inner peripheral surface is opposite to the outer peripheral surface 176 of the magnet holder 170 and in which the worm part 181 is disposed radially outward. The resin gear part 180 includes an inner peripheral surface 182 opposite to the outer peripheral surface 176 of the magnet holder 170 and a worm part 181 disposed radially outward of the resin gear part 180. The worm part 181 corresponds to Fig.17 The inner diameter of the inner circumferential surface 182 of the resin gear portion 180 is slightly smaller than the outer diameter of the outer circumferential surface 176 of the magnet holder 170. The “slightly” here means that the magnet holder 170 can be pressed into the space surrounded by the inner circumferential surface 182 of the resin gear portion 180.

[0223] When the main shaft gear 1A is mounted on the motor shaft 201, the motor shaft 201 is first press-fitted into the space surrounded by the third inner peripheral surface 174 of the magnet holder 170. Thus, the magnet holder 170 is fixed to the motor shaft 201 without a gap between the magnet holder 170 and the motor shaft 201.

[0224] Next, the resin gear part 180 is pressed into the outer peripheral surface 176 of the magnet holder 170. At this time, if the resin gear part 180 is pressed in the axial direction until the entire inner peripheral surface 182 of the resin gear part 180 is in contact with the outer peripheral surface 176 of the magnet holder 170, the resin gear part 180 is firmly fixed to the magnet holder 170.

[0225] In the main shaft gear 1A thus constructed, the resin gear portion 180 manufactured separately from the magnet holder 170 is press-fitted into the outer peripheral surface 176 of the magnet holder 170. Fig.32If the contact part of the magnet holder 170 with the motor shaft 201, the resin gear part 180, and the worm part 181 are overlapped and arranged in the radial direction of the main shaft gear 1A, the main shaft gear 1A is further firmly fixed. Fig.32 The direction is indicated by the arrow D1.

[0226] Therefore, the permanent magnet 9 and the main shaft gear 1A can be reliably fixed to the motor shaft 201, the uneven rotation angle from the main shaft gear 1A to the intermediate gear 2 is reduced, and further, the gear teeth jam between the main shaft gear 1A and the intermediate gear 2 is suppressed. In addition, by forming the magnet holder 170 from a non-magnetic metal material, the holding portion of the permanent magnet 9 can be formed with higher accuracy than a resin molded product, thereby ensuring the position accuracy of the motor shaft 201, the worm portion 181, and the center axis of the permanent magnet 9.

[0227] Fig.33 1 is a perspective view of a main shaft gear 1B included in an absolute encoder 100 - 2 according to a second modified example of the second embodiment. Fig.34 yes Fig.33 1B is a cross-sectional view of the main shaft gear 1B. The main shaft gear 1B is a first driving gear coaxially arranged with the motor shaft 201 and fixed to the motor shaft 201. The main shaft gear 1B includes a magnet holder 170 and a resin gear portion 190. Fig.32 The main shaft gear 1A shown is different from the main shaft gear 1B in that the axial dimension of the magnet holder 170 is shorter, and the motor shaft 201 is press-fitted not only to the magnet holder 170 but also to the resin gear portion 190 .

[0228] The resin gear portion 190 is disposed adjacent to the magnet holder 170 in a coaxial manner with the motor shaft 201. The resin gear portion 190 is an annular portion whose inner peripheral surface faces the outer peripheral surface 176 of the magnet holder 170 and in which the worm portion 191 is disposed radially outward. The resin gear portion 190 includes a first inner peripheral surface 192 of a first inner diameter in contact with the outer peripheral surface of the motor shaft 201, and a second inner peripheral surface 193 of a second inner diameter that faces the outer peripheral surface 176 of the magnet holder 170 and is larger than the first inner diameter.

[0229] In addition, the resin gear portion 190 includes a third inner peripheral surface 194 having a third inner diameter that is opposite to the outer peripheral surface 176 of the magnet holder 170 and is larger than the second inner diameter, and a worm portion 191 provided on the radially outer side of the resin gear portion 190. The worm portion 191 corresponds to Fig.17 The worm portion 1d is shown in FIG.

[0230] The first inner circumferential surface 192 , the second inner circumferential surface 193 , and the third inner circumferential surface 194 are arranged in this order in the direction from the motor shaft 201 toward the permanent magnet 9 .

[0231] The first inner circumferential surface 192 of the first inner diameter of the resin gear portion 190 is pressed into the motor shaft 201 and is therefore smaller than the outer diameter of the outer circumferential surface of the motor shaft 201. In addition, since the second inner circumferential surface 193 of the second inner diameter of the resin gear portion 190 would be difficult to assemble if it were to contact the outer diameter of the outer circumferential surface 176 of the magnet holder 170, it is smaller than the outer diameter of the outer circumferential surface 176 in a non-contact manner.

[0232] When the main shaft gear 1B is mounted on the motor shaft 201, first, the motor shaft 201 is press-fitted into the space surrounded by the first inner peripheral surface 192 of the resin gear part 190. At this time, the motor shaft 201 is pressed in such a way that its top end 201a is arranged above the step 195 provided at the boundary between the first inner peripheral surface 192 and the second inner peripheral surface 193. Thus, the resin gear part 190 is firmly fixed to the motor shaft 201. In addition, the magnet holder 170 can be mounted on the outer peripheral surface of the motor shaft 201 near the top end 201a.

[0233] Next, the magnet holder 170 is press-fitted into the outer peripheral surface near the tip portion 201a of the motor shaft 201. Thus, the resin gear portion 190 is firmly fixed to the motor shaft 201.

[0234] So, in Fig.34 In the main shaft gear 1B shown, the magnet holder 170 and the resin gear part 190, which are manufactured separately, are each press-fitted into the outer peripheral surface of the motor shaft 201. Therefore, the position accuracy of the main shaft gear 1B is not affected by the dimensional accuracy of the magnet holder 170, and there is no need to worry about the influence of the dimensional accuracy of the main shaft gear 1B overlapping on this basis. Therefore, the axial deviation of the magnet holder 170 does not overlap with the axial deviation of the worm part 191, and the accumulation of the axial deviation, that is, the occurrence of uneven rotation angle caused by the accumulation of the axial deviation, that is, the accumulation error, is suppressed. In addition, the occurrence of gear tooth jamming between the main shaft gear 1B and the intermediate gear 2 caused by the accumulation error is suppressed.

[0235] In addition, Fig.34 In the main shaft gear 1B shown, since the metal magnet holder 170 is used similarly to the main shaft gear 1A, the adhesive is easily attached to the magnet holder 170. Since the adhesive acts as a member to prevent the permanent magnet 9 from coming off, it is possible to prevent the permanent magnet 9 from coming off from the main shaft gear 1B during the operation of the absolute encoder 100-2.

[0236] It should be noted that, when the magnet holder 170 is a resin molded product, the surface accuracy of the first inner peripheral surface 171 tends to be lower than when the magnet holder 170 is made of metal. Since the metal magnet holder 170 is used in the main shaft gear 1A of the first modification and the main shaft gear 1B of the second modification, the reduction in the surface accuracy of the respective first inner peripheral surfaces 171 is suppressed, thereby suppressing the increase in the axial deviation amount of the central axis of the permanent magnet 9 mounted on the first inner peripheral surface 171 relative to the central axis of the motor shaft 201.

[0237] Therefore, the amplitude ratio of the worm part 191 relative to the central axis is Fig.17 The amplitude of the worm part 1d relative to the center axis is small. As a result, the uneven rotation angle from the main shaft gear 1B to the intermediate gear 2 is reduced, and the gear teeth jam between the main shaft gear 1B and the intermediate gear 2 is suppressed. In addition, by forming the magnet holder 170 from a non-magnetic metal material, the holding part of the permanent magnet 9 can be formed with higher accuracy than a resin molded product, thereby ensuring the position accuracy of the motor shaft 201, the worm part 191, and the center axis of the permanent magnet 9.

[0238] It should be noted that although Fig.34 In the main shaft gear 1B shown in FIG. 1 , the contact portion of the magnet holder 170 with the motor shaft 201, the resin gear portion 190, and the worm portion 191 are as shown in FIG. Fig.34 The main shaft gear 1B is arranged in a radially overlapping manner as shown by the part marked "PP" in the figure, but the main shaft gear 1B can be a disc-shaped component. Specifically, the disc-shaped component does not include Fig.34 The second inner circumferential surface 193 and the third inner circumferential surface 194 are shown, and the first inner circumferential surface 192 and the worm part 191 are arranged in a manner contained on a plane parallel to the radial direction of the main shaft gear 1B. In addition, the disc-shaped component is provided below the axial end of the magnet holder 170. In other words, the magnet holder 170 is not as Fig.34 In this way, even if the resin gear part 190 and the magnet holder 170 are arranged in the axial direction, the magnet holder 170 and the resin gear part 190, which are manufactured separately, are each press-fitted into the outer peripheral surface of the motor shaft 201, so the above-mentioned cumulative error does not occur. Therefore, the occurrence of uneven rotation angle caused by the cumulative error is suppressed, and the occurrence of gear tooth jam between the main shaft gear 1B and the intermediate gear 2 caused by the cumulative error is suppressed. In addition, by using the main shaft gear 1B configured in this way, the structure of the resin gear part 190 is simplified, and the manufacturing time of the resin gear part 190 can be shortened.

[0239] It should be noted that the main shaft gear 1 of the absolute encoder 100-1 of the first embodiment can be configured in the same manner as the main shaft gear 1A of the first modified example or the main shaft gear 1B of the second modified example of the second embodiment. By configuring the absolute encoder 100-1 in this manner, the same effects as those of the first modified example or the second modified example can be obtained.

[0240] Fig.35 This is a diagram showing a permanent magnet 9A applicable to the absolute encoders 100 - 1 and 100 - 2 of the first and second embodiments. Fig.36 FIG. 1 is a diagram showing a permanent magnet 9B applicable to the absolute encoders 100 - 1 and 100 - 2 of the first and second embodiments. Fig.35 , a permanent magnet 9A of a first configuration example is shown. In the permanent magnet 9A, 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 a radial direction D1 of the permanent magnet 9A. Fig.36 , a permanent magnet 9B of a second configuration example is shown. In the permanent magnet 9B, with the center of the permanent magnet 9B as the boundary, in the left 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 9B in the figure, and 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, which is opposite to the left half. Fig.35 as well as Fig.36 The arrow "DM" shown indicates the direction of magnetization.

[0241] Both the permanent magnet 9A and the permanent magnet 9B can be used as the permanent magnet 9 of the absolute encoders 100-1 and 100-2 of the first and second embodiments. However, in the permanent magnet 9B, the magnetic field formed by a plurality of magnetic force lines is distributed more widely in the axial direction D2 than the magnetic field generated by the permanent magnet 9A. On the other hand, in the permanent magnet 9A, the magnetic field formed by a plurality of magnetic force lines is distributed more widely in the radial direction D1 than the magnetic field generated by the permanent magnet 9B. Therefore, when the permanent magnet 9A is used in the absolute encoders 100-1 and 100-2 of the first and second embodiments, the magnetic field generated by the permanent magnet 9A extending radially outward is likely to cause magnetic interference that affects the above-mentioned other magnetic sensors.

[0242] When the absolute encoders 100-1 and 100-2 of the modified examples of the first and second embodiments use the permanent magnet 9B as the permanent magnet 9, the leakage flux generated from the permanent magnet 9 flows into the magnetic sensor 50 less than when the permanent magnet 9A is used. Also, when the permanent magnet 9B is used as the permanent magnet 8, the leakage flux generated from the permanent magnet 8 flows into the magnetic sensor 40 less than when the permanent magnet 9A is used. As a result, the reduction in the detection accuracy of the rotation angle or the rotation amount of the counter gear 5 or the main shaft gear 1 can be reduced. In addition, the reduction in the detection accuracy of the rotation angle or the rotation amount can be reduced, and accordingly, the absolute encoders 100-1 and 100-2 can be further miniaturized.

[0243] It should be noted that in the absolute encoder 100-1 of the first embodiment, the central axis of each of the permanent magnet 8 and the magnet holder 6 is aligned with Fig.26 The permanent magnet 8 and the magnet holder 6 are similarly configured to be consistent with each other. In the absolute encoder 100-1 of the first embodiment, the central axis of each of the permanent magnet 17 and the second countershaft gear 138 is aligned with the center axis of the second countershaft gear 138. Fig.26 The permanent magnet 8 and the magnet holder 6 are similarly configured to be aligned with each other. In the absolute encoder 100-1 of the first embodiment, the central axis of the permanent magnet 9 and the main shaft gear 1 are aligned with each other. Fig. 27 The permanent magnet 9 and the main shaft gear 1 are configured to be identically aligned with each other. According to this configuration, the absolute encoder 100-1 of the first embodiment can detect the rotation angle or the rotation amount with higher accuracy.

[0244] It should be noted that the structure shown in the above embodiment shows an example of the content of the present invention, which can be combined with other existing technologies, and part of the structure can be omitted or changed without exceeding the scope of the main purpose of the present invention.

[0245] In addition, this application claims the priority based on Japanese Patent Application No. 2019-064970 filed on March 28, 2019, and all the contents of this Japanese Patent Application are cited as reference in this application.

[0246] Description of Reference Numerals

[0247] 1 Main shaft gear, 1A Main shaft gear, 1B Main shaft gear, 1a First cylindrical portion, 1b Second cylindrical portion, 1c Communication portion, 1d Worm portion, 1e Bottom surface, 1f Press-fit portion, 1g Bottom surface, 1h Magnet holding portion, 2 Intermediate gear, 2a Worm wheel portion, 2b Worm wheel portion, 2c Bearing portion, 2d Press-fit portion, 2e Sliding portion, 2f Bottom surface, 2g Through hole, 3 Bearing, 3a Outer race, 3b Inner race, 3c Side surface, 3d Side surface, 4 Shaft, 4a One end, 4b Other end, 5 Countershaft gear, 5-1 Upper surface, 5a Worm wheel portion, 5b Through hole, 6 Magnet holding member, 6a Magnet holding portion, 6b Shaft portion, 6c Head portion, 7 Bearing, 7a Outer race, 7b Inner race, 8 Permanent magnet, 8a Surface, 9 permanent magnet, 9A permanent magnet, 9B permanent magnet, 9a upper surface, 9b lower surface, 10 main base, 10-1 opening, 10-2 lower surface, 10a hole, 10aa recess, 10ab recess, 10ac recess, 10ad mounting surface, 10ae screw hole, 10b hole, 10c contact 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 top end, 10i step portion, 10j substrate positioning pin, 10j1 base, 10k top end, 10l step portion, 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, 11c hole, 11d base, 12 screw, 13 substrate mounting screw, 14 screw, 15 box body, 15-1 upper surface portion, 15A first side portion, 15B second side portion, 15C third side portion, 15D fourth side portion, 15a claw portion, 15b claw portion, 15c claw portion, 15d hole, 15e recessed portion, 15f recessed portion, 15g recessed portion, 15h connector box body portion, 15i opening portion, 16 mounting screw, 17 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, 21q rotation angle acquisition unit, 22 bidirectional driver, 23 line driver, 24 connector, 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, 100-2Absolute encoder, 101 main shaft gear, 101a first cylindrical portion, 101b disk portion, 101c worm portion, 101d magnet holding portion, 102 first intermediate gear, 102a worm wheel portion, 102b first worm portion, 102c base portion, 102d first cylindrical portion, 102e second cylindrical portion, 102f third cylindrical portion, 102g hemispherical protrusion, 102h second worm portion, 102i sliding portion, 104 shaft, 105 first counter shaft gear, 105a worm wheel portion, 105b bearing portion, 105c disk portion, 105d holding portion, 106 shaft, 107 retaining ring, 108 retaining ring, 110 main base, 110a base portion, 110b support portion, 110c support portion, 111 leaf spring, 111a Sliding portion, 111b mounting portion, 115 case, 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 determination portion, 121e output portion, 121p rotation angle acquisition portion, 121q rotation angle acquisition portion, 121r rotation angle acquisition portion, 122 substrate mounting screw, 133 second intermediate gear, 133a worm gear portion, 133b bearing portion, 133c extension portion, 133d fourth drive gear portion, 134 shaft, 138 second countershaft gear, 138a fourth driven gear portion, 138b bearing portion, 138c extension portion, 138d magnet holding portion, 139 shaft, 141 support column, 164 screw, 170 magnet holder, 171 first inner peripheral surface, 172 second inner peripheral surface, 173 first step portion, 174 third inner peripheral surface, 175 second step portion, 176 outer peripheral surface, 180 resin gear portion, 181 worm portion, 182 inner peripheral surface, 190 resin gear portion, 191 worm portion, 192 first inner peripheral surface, 193 second inner peripheral surface, 194 third inner peripheral surface, 195 step portion, 200 motor, 201 motor shaft, 201a top end portion, 202 housing, 202a notch portion, 301 first side, 302 second side, 303 third side, 304 fourth side, 400 connector.

Claims

1. An absolute encoder, comprising: A first driving gear is fixed to the main shaft in a coaxial manner and rotates with the rotation of the main shaft; A magnet, which is disposed on the first driving gear; A first driven gear, the central axis of which is orthogonal to the central axis of the first driving gear and meshes with the first driving gear; A second driving gear, which is coaxially arranged with the first driven gear and rotates along with the rotation of the first driven gear; as well as The second driven gear has a central axis that is orthogonal to the central axis of the first driven gear and is meshed with the second driving gear. The first driving gear comprises: a cylindrical portion, which is coaxially engaged with the top end of the main shaft; and The annular portion has a toothed portion on the radially outer side that meshes with the first driven gear. The annular portion is disposed adjacent to the cylindrical portion in a manner coaxial with the main axis. The cylindrical portion and the annular portion are separate structures. The inner peripheral surface of the annular portion is fitted to the outer peripheral surface of the cylindrical portion and to the outer peripheral surface of the main shaft.

2. The absolute encoder according to claim 1, wherein: A portion of the inner peripheral surface of the annular portion faces the outer peripheral surface of the cylindrical portion in a spaced-apart manner.

3. The absolute encoder according to claim 1, wherein: An outer diameter of the first driven gear is smaller than an outer diameter of the first drive gear.

4. The absolute encoder according to claim 1, wherein: A contact portion of the cylindrical portion with the main shaft, the annular portion, and the first drive gear are arranged so as to overlap in a radial direction of the first drive gear.

5. The absolute encoder according to claim 1, wherein: The magnet is fixed to the cylindrical portion made of a non-magnetic metal material by an adhesive.

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