Axis support structure, magnetic detection device, and absolute encoder

Abstract

Provided is a shaft support structure that can improve the mounting accuracy of a press-fit shaft.　The shaft support structure comprises: a main shaft adapter (12); and a main shaft (1a) that serves as a support member and has a press-fitting part (1b) into which the main shaft adapter (12) is press-fit from one end (124) thereof. The main shaft adapter (12) includes a tapered surface portion (126) configured so that the diameter of the end (124) is smaller than the diameter of a peripheral surface (129). The tapered surface portion (126) is machined so that a curved surface is formed at a connection section (126a) between the tapered surface portion (126) and the peripheral surface (129).

Description

Technical Field

[0001] The present invention relates to a shaft support structure, a magnetic detection device, and an absolute encoder.

Background Art

[0002] Conventionally, magnetic detection devices that detect magnetic flux from a magnet using a magnetic sensor have been used in various technologies. In various control machinery devices, there are some rotary encoders that use magnetic detection devices to detect the position and angle of a movable element. Rotary encoders include an incremental type encoder that detects a relative position or angle, and an absolute type absolute encoder that detects an absolute position or angle. Some of these absolute encoders include a magnetic detection device. As an absolute encoder equipped with a magnetic detection device, there is known a magnetic encoder device that attaches a magnetized magnet to a rotating shaft (main shaft) to be measured, and detects the rotation angle of the magnet with a magnetic sensor to detect the rotation amount of the main shaft to be measured. Also, a method is known in which the rotation amount over a plurality of rotations of this main shaft is specified by obtaining the rotation angle of a rotating body that rotates at a reduced speed as the main shaft rotates.

[0003] In such an absolute encoder, in order to widen the range of the detectable rotation amount of the main shaft while maintaining the resolution of the detectable rotation amount of the main shaft, a structure has been proposed in which the rotation amounts of a plurality of magnets are detected by a magnetic sensor as an angle sensor corresponding thereto. For example, a structure has been proposed in which a main shaft and a sub-shaft or subsequent shafts are connected by a reduction mechanism, the rotation amounts of the magnets attached to each shaft are detected by a corresponding magnetic sensor, and the rotation amount of the main shaft is specified (see, for example, Patent Document 1).

[0004] Furthermore, absolute encoders employ a structure in which the shaft is attached to a support member by press-fitting. Examples of press-fitting shaft support structures in absolute encoders include a structure in which a spindle adapter for attaching gears to the spindle is attached to the spindle, or a structure in which the shaft of the sub-spindle gear is press-fitted into a base plate. As a support structure in which the shaft is attached to a support member by press-fitting, for example, a structure is known in which a circumferential groove is provided on the shaft in the press-fit portion (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-15536 [Patent Document 2] Japanese Patent Application Publication No. 6-249218 [Overview of the project] [Problems that the invention aims to solve]

[0006] In an absolute encoder having the shaft support structure described above, a tapered surface is formed at the tip of the shaft that is press-fitted into the hole of the support member.

[0007] However, when only a linear chamfer is applied to the tapered surface of the shaft, there is a problem in that when the tip of the shaft is press-fitted into the hole, the edge of the hole and the tapered surface come into contact, causing shavings to be ejected from both the shaft and the hole. Furthermore, in conventional press-fit shaft support structures, the shaft may be pressed in at an angle due to material being machined. In addition, in conventional press-fit shaft support structures, the press-fit allowance (the dimension required for press-fitting) is sometimes set to be long to account for the tilting of the shaft. For these reasons, there is a need to improve the accuracy of press-fit shaft support structures.

[0008] The present invention has been made in view of the above-mentioned problems, and its object is to provide a shaft support structure, a magnetic detection device, and an absolute encoder that can improve the mounting accuracy of a press-fitted shaft. [Means for solving the problem]

[0009] To achieve the above objective, the shaft support structure according to the present invention comprises a shaft and a support member having a hole into which the shaft is press-fitted from one end, wherein the shaft has a tapered surface portion whose diameter at one end is smaller than the diameter of the circumferential surface, and the tapered surface portion is curved at the connection point with the circumferential surface.

[0010] In a shaft support structure according to one aspect of the present invention, the shaft has a through hole that penetrates from one end to the other end, wherein the diameter of the through hole in a region of a predetermined length in the axial direction from the side of the one end is larger than the diameter of the hole on the other end side.

[0011] To achieve the above objective, the magnetic detection device according to the present invention comprises a magnetized magnet, a magnetic sensor for detecting magnetic flux from the magnet, a magnet holder for holding the magnet, a shaft for rotatably supporting the magnet, and a support member having a hole into which the shaft is press-fitted from one end. The shaft has a press-fit portion that is a region of a predetermined length in the axial direction from one end of the circumferential surface and is press-fitted into the hole, and a tapered surface portion whose diameter at the one end is smaller than the diameter of the circumferential surface, and the tapered surface portion is curved at the connection point with the circumferential surface.

[0012] In a magnetic detection device according to one aspect of the present invention, the shaft has a through hole that penetrates from one end to the other end, and the diameter of the through hole in a region of a predetermined length in the axial direction from the side of the one end is larger than the diameter of the hole on the other end side.

[0013] In a magnetic detection device according to one aspect of the present invention, the case has a boss portion that protrudes upward from the upper surface portion, and the shield member has a boss hole in which the boss portion is housed.

[0014] A magnetic detection device according to one aspect of the present invention comprises a magnet support portion that supports the magnet on the tip side of the shaft, and a magnet holding portion that covers the magnet and the magnet support portion from the tip side of the shaft and holds the magnet on the tip side of the shaft, wherein the magnet holding portion is formed of a material with greater elongation at break characteristics than the magnet support portion, and has a magnet joint portion that contacts the tip side surface and outer circumference of the magnet on the shaft side, and a fitting portion that fits with the outer circumference of the magnet support portion.

[0015] To achieve the above objective, the absolute encoder according to the present invention is characterized by comprising a magnetic detection device according to the present invention. [Effects of the Invention]

[0016] According to the shaft support structure, magnetic detection device, and absolute encoder of the present invention, the mounting accuracy of the press-fitted shaft can be improved. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic perspective view showing the configuration of an absolute encoder according to an embodiment of the present invention. [Figure 2] Figure 1 is a schematic perspective view showing the configuration of the absolute encoder, excluding the case and shield. [Figure 3] Figure 2 is a schematic perspective view showing the configuration of the absolute encoder, excluding the circuit board, connector, and support plate. [Figure 4] Figure 3 is a schematic perspective view showing the configuration of the absolute encoder from a different angle. [Figure 5] Figure 3 is a schematic perspective view showing the configuration of the absolute encoder, excluding the motor. [Figure 6] Figure 5 is a schematic plan view showing the configuration of the absolute encoder. [Figure 7] Figure 1 is a cross-sectional view showing the absolute encoder as it is cut by a plane parallel to the central axis of the main spindle. [Figure 8] In the configuration of the absolute encoder shown in FIG. 1, it is a cross-sectional view schematically showing a state of being cut by a plane passing through the central axis of the main shaft gear and orthogonal to the central axis of the first intermediate gear, with the motor removed. [Figure 9] In the configuration of the absolute encoder shown in FIG. 8, it is an exploded longitudinal cross-sectional view schematically showing the configurations of the magnet, the main shaft gear, the main shaft adapter, and the main shaft of the motor. [Figure 10] It is an enlarged cross-sectional view showing one end of the main shaft adapter shown in FIG. 8. [Figure 11] In the configuration of the absolute encoder shown in FIG. 6, it is a cross-sectional view schematically showing a state of being cut by a plane passing through the central axis of the first intermediate gear and parallel to the XY plane. [Figure 12] It is an enlarged perspective view of the cross-sectional view shown in FIG. 11 as seen from another angle. [Figure 13] In the configuration of the absolute encoder shown in FIG. 6, it is a partial cross-sectional view schematically showing a state of being cut by a plane passing through the central axis of the first intermediate gear and orthogonal to the XY plane. [Figure 14] In the configuration of the absolute encoder shown in FIG. 12, it is an exploded perspective view schematically showing a state in which the base, the first intermediate gear, the first intermediate gear shaft, the leaf spring, and the screw are disassembled. <00001​​​​​​​​​​​​Figure 17 is an enlarged cross-sectional view showing a magnet holder having a second sub-axis gear. [Figure 20] Figure 19 is a schematic exploded perspective view showing the magnet holder in a disassembled state. [Figure 21] Figure 19 is a schematic perspective view showing a cylindrical magnet that can be used as the magnet for the magnet holder shown. [Figure 22] This is an enlarged cross-sectional view showing one end of the lower side of the second sub-shaft gear shaft, as shown in Figure 18. [Figure 23] This is a schematic diagram showing how the second sub-shaft gear shaft is press-fitted into the shaft support portion at the base. [Figure 24] This is a schematic diagram showing how the second sub-shaft gear shaft is press-fitted into the shaft support portion at the base. [Figure 25] This figure schematically illustrates one modified example of a support projection that supports the main shaft side end of the first intermediate gear shaft in an absolute encoder. [Figure 26] This figure schematically illustrates one modified example of a support projection that supports the main shaft side end of the first intermediate gear shaft in an absolute encoder. [Figure 27] This figure schematically illustrates one modified example of a support projection that supports the main shaft side end of the first intermediate gear shaft in an absolute encoder. [Figure 28] Figure 2 shows the substrate as viewed from the bottom. [Figure 29] Figure 1 is a block diagram illustrating the functional configuration of the absolute encoder shown. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described below with reference to the drawings. Note that the dimensions of the components in each drawing have been enlarged or reduced as appropriate for ease of understanding. Also, some components that are not important for explaining the embodiments of the present invention have been omitted in each drawing. Furthermore, the tooth shape of gears has been omitted in the drawings. In addition, terms including ordinal numbers such as "first," "second," etc., are used to describe various components, but these terms are used solely to distinguish one component from others, and do not limit the components. Note that the present invention is not limited by these embodiments.

[0019] The magnetic detection device 60 according to an embodiment of the present invention comprises a magnetized magnet Mr, an angle sensor Sr which is a magnetic sensor that detects the magnetic flux from the magnet Mr, a magnet holder 61 that holds the magnet Mr, and a second sub-axis gear shaft 62 as an axis. The magnet holder 61 is rotatably supported on the second sub-axis gear shaft 62. The second sub-axis gear shaft 62 is formed from a magnetic material, and a magnetic attractive force is generated between the magnet Mr and the second sub-axis gear shaft 62 in the direction of the rotation axis of the magnet holder 61. Furthermore, the absolute encoder 2 according to an embodiment of the present invention includes the magnetic detection device 60 according to the above embodiment of the present invention. The structures of the absolute encoder 2 and the magnetic detection device 60 will be described in detail below.

[0020] Figure 1 is a schematic perspective view showing the configuration of an absolute encoder 2 according to an embodiment of the present invention. Figure 2 is a perspective view showing the configuration of the absolute encoder 2 shown in Figure 1, with the case 4 and shield removed. In Figure 1, the shield, case 4 and substrate 5 of the absolute encoder 2 are shown transparently, while in Figure 2, the substrate 5 of the absolute encoder 2 is shown transparently.

[0021] For convenience, this explanation will describe the absolute encoder 2 based on the XYZ Cartesian coordinate system. The X-axis corresponds to the horizontal left-right direction, the Y-axis corresponds to the horizontal front-back direction, and the Z-axis corresponds to the vertical up-down direction. The Y-axis and Z-axis directions are both perpendicular to the X-axis direction. In this explanation, the X-axis direction will also be referred to as the left side or right side, the Y-axis direction as the front side or rear side, and the Z-axis direction as the top side or bottom side. In the orientation of the absolute encoder 2 shown in Figures 1 and 2 (upright orientation), the left side in the X-axis direction is the left side, and the right side in the X-axis direction is the right side. Also, in the orientation of the absolute encoder 2 shown in Figures 1 and 2, the front side in the Y-axis direction is the front side, and the back side in the Y-axis direction is the rear side. Also, in the orientation of the absolute encoder 2 shown in Figures 1 and 2, the top side in the Z-axis direction is the top side, and the bottom side in the Z-axis direction is the bottom side. A view from above along the Z-axis is called a plan view, a view from the front along the Y-axis is called a front view, and a view along the X-axis is called a side view. These directional notations do not restrict the orientation in which the absolute encoder 2 can be used; the absolute encoder 2 can be used in any orientation.

[0022] As previously described, the absolute encoder 2 is an absolute type encoder that identifies and outputs the amount of rotation over multiple rotations of the main shaft 1a of the motor 1. In the embodiment of the present invention, the absolute encoder 2 is provided at the upper end of the motor 1 in the Z-axis direction. In the embodiment of the present invention, the absolute encoder 2 has a substantially rectangular shape in plan view, and a thin, horizontally elongated rectangular shape in the vertical direction, which is the extending direction of the main shaft 1a, in front view and side view. In other words, the absolute encoder 2 has a flattened rectangular parallelepiped shape that is longer in the horizontal direction than in the vertical direction.

[0023] The absolute encoder 2 comprises a case 4 that houses its internal structure. The case 4 has multiple (e.g., four) outer wall portions 4a that surround at least a portion of the main shaft 1a of the motor 1, the main shaft gear 10, the first intermediate gear 20, the first sub-shaft gear 30, the second intermediate gear 70, and the magnet holder 61. Furthermore, the case 4 has a cover portion 4b that closes the upper openings of the four outer wall portions 4a. The cover portion 4b is covered by a shield.

[0024] Motor 1 may, for example, be a stepping motor or a DC brushless motor. For example, motor 1 may be a motor used as a drive source to drive an industrial robot via a reduction mechanism such as a harmonic drive gear. The main spindle 1a of motor 1 protrudes from the motor case on both the vertical and horizontal sides. The absolute encoder 2 outputs the amount of rotation of the main spindle 1a of motor 1 as a digital signal.

[0025] The shape of motor 1 is approximately rectangular in plan view and also approximately rectangular in the vertical direction. In other words, motor 1 has an approximately cubic shape. In plan view, the length of each of the four outer wall parts that make up the outer shape of motor 1 is, for example, 25 mm, meaning that the outer shape of motor 1 is 25 mm square in plan view. Furthermore, the absolute encoder 2 provided on motor 1 is, for example, 25 mm square in plan view to match the outer shape of motor 1.

[0026] As shown in Figures 1 and 2, the circuit board 5 is provided together with the case 4 to cover the inside of the absolute encoder 2. The circuit board 5 has a roughly rectangular shape in plan view and is a thin, plate-shaped printed circuit board in the vertical direction. A connector 6 is connected to the circuit board 5, and the connector 6 is for connecting the absolute encoder 2 to an external device (not shown).

[0027] Figure 3 is a schematic perspective view showing the configuration of the absolute encoder 2 shown in Figure 2, excluding the circuit board 5 and connector 6. Figure 4 is a schematic perspective view showing the configuration of the absolute encoder 2 shown in Figure 3, viewed from a different angle. Figure 5 is a schematic perspective view showing the configuration of the absolute encoder 2 shown in Figure 3, excluding the motor 1. Figure 6 is a schematic plan view showing the configuration of the absolute encoder 2 shown in Figure 5.

[0028] The absolute encoder 2 includes a main shaft gear 10 having a first worm gear section 11 (first drive gear), a first intermediate gear 20 having a first worm wheel section 21 (first driven gear) and a second worm gear section 22 (second drive gear), a first sub-shaft gear 30 having a second worm wheel section 31 (second driven gear) and a gear section 32 (third drive gear), a second intermediate gear 70, a magnet holder 61 having a second sub-shaft gear 63, a magnet Mp, an angle sensor Sp corresponding to magnet Mp, a magnet Mq, an angle sensor Sq corresponding to magnet Mq, a magnet Mr, an angle sensor Sr corresponding to magnet Mr, and a microcontroller 51.

[0029] The main shaft 1a of motor 1 is the output shaft of motor 1 and the input shaft that transmits rotational force to the absolute encoder 2. The main shaft gear 10 is fixed to the main shaft 1a of motor 1 and is rotatably supported integrally with the main shaft 1a by the bearing member of motor 1. The first worm gear section 11 is provided on the outer circumference of the main shaft gear 10 so as to rotate in accordance with the rotation of the main shaft 1a of motor 1. In the main shaft gear 10, the first worm gear section 11 is provided so as to coincide with or substantially coincide with the central axis of the main shaft 1a. The first worm wheel section 21 is provided on the outer circumference of the first intermediate gear 20 and is provided so as to mesh with the first worm gear section 11 and rotate in accordance with the rotation of the first worm gear section 11. The axial angle between the first worm wheel section 21 and the first worm gear section 11 is set to 90° or substantially 90°.

[0030] There are no special restrictions on the outer diameter of the first worm wheel section 21, but in the illustrated example, the outer diameter of the first worm wheel section 21 is set to be smaller than the outer diameter of the first worm gear section 11 (see Figure 8), resulting in a smaller outer diameter for the first worm wheel section 21. This allows for a reduction in the vertical dimensions of the absolute encoder 2.

[0031] The second worm gear section 22 is located on the outer circumference of the first intermediate gear 20 and rotates in conjunction with the rotation of the first worm wheel section 21. In the first intermediate gear 20, the second worm gear section 22 is located such that its central axis coincides with or substantially coincides with the central axis of the first worm wheel section 21. The second worm wheel section 31 is located on the outer circumference of the first sub-shaft gear 30 and meshes with the second worm gear section 22, rotating in accordance with the rotation of the second worm gear section 22. The axial angle between the second worm wheel section 31 and the second worm gear section 22 is set to 90° or substantially 90°. The rotation axis of the second worm wheel section 31 is located parallel to or substantially parallel to the rotation axis of the first worm gear section 11. The gear section 32 is located on the outer circumference of the first sub-shaft gear 30 and rotates in conjunction with the rotation of the second worm wheel section 31. In the first sub-shaft gear 30, the gear portion 32 is provided such that its central axis coincides with or substantially coincides with the central axis of the second worm wheel portion 31.

[0032] Here, in order for the first worm wheel portion 21 to mesh with the first worm gear portion 11, the direction in which the first worm wheel portion 21 moves toward the first worm gear portion 11 is defined as the first meshing direction (direction of arrow P1 in Figure 12). Similarly, in order for the second worm gear portion 22 to mesh with the second worm wheel portion 31, the direction in which the second worm gear portion 22 moves toward the second worm wheel portion 31 is defined as the second meshing direction (direction of arrow P2 in Figure 12). In this embodiment, both the first meshing direction P1 and the second meshing direction P2 are directions along the horizontal plane (XY plane).

[0033] The second intermediate gear 70 has a gear section 71 (third driven gear) and a gear section 72 (fourth driving gear). The gear section 71 is provided on the outer circumference of the second intermediate gear 70 and meshes with the gear section 32 of the first sub-shaft gear 30, and rotates in accordance with the rotation of the gear section 32. The gear section 72 is provided on the outer circumference of the second intermediate gear 70 and rotates in accordance with the rotation of the gear section 71. In the second intermediate gear 70, the gear section 72 is provided so that its central axis coincides with or substantially coincides with the central axis of the gear section 71. The rotation axes of the gear sections 71 and 72 are provided parallel to or substantially parallel to the rotation axis of the gear section 32 of the first sub-shaft gear 30.

[0034] The magnet holder 61 has a second sub-shaft gear 63, and as will be described later, it has a gear portion 64 (fourth driven gear) provided on the second sub-shaft gear 63. The gear portion 64 is provided on the outer circumference of the second sub-shaft gear 63 and meshes with the gear portion 72 of the second intermediate gear 70, and rotates in accordance with the rotation of the gear portion 72. The rotation axis of the gear portion 64 is provided parallel or substantially parallel to the rotation axis of the gear portion 72 of the second intermediate gear 70.

[0035] The angle sensor Sq detects the rotation angle of the second worm wheel section 31, that is, the rotation angle of the first sub-shaft gear 30. The magnet MQ is fixed to the upper surface of the first sub-shaft gear 30 such that their central axes coincide or substantially coincide. The magnet MQ has two magnetic poles aligned perpendicular or substantially perpendicular to the rotation axis of the first sub-shaft gear 30. The angle sensor Sq is positioned so that its lower surface faces the upper surface of the magnet MQ in the vertical direction, with a gap in between, in order to detect the rotation angle of the first sub-shaft gear 30.

[0036] For example, the angle sensor Sq is fixed to a circuit board 5, which is supported by a circuit board support column 110 located on the base 3 of the absolute encoder 2 (described later). The angle sensor Sq detects the magnetic flux of the magnet MQ and outputs the detection information to the microcontroller 51. Based on the detected information regarding the input magnetic flux, the microcontroller 51 determines the rotation angle of the magnet MQ, that is, the rotation angle of the first sub-shaft gear 30.

[0037] The angle sensor Sr detects the rotation angle of the magnet holder 61, i.e., the rotation angle of the second sub-shaft gear 63. The magnet Mr is fixed to the upper surface of the second sub-shaft gear 63 such that their central axes coincide or substantially coincide. The magnet Mr has two magnetic poles aligned perpendicular to the rotation axis of the second sub-shaft gear 63. The angle sensor Sr is positioned so that its lower surface faces the upper surface of the magnet Mrr in the vertical direction, with a gap in between, in order to detect the rotation angle of the second sub-shaft gear 63.

[0038] For example, the angle sensor Sr is fixed to the substrate 5 on which the angle sensor Sq is fixed, on the same plane as the surface on which the angle sensor Sq is fixed. The angle sensor Sr detects the magnetic flux of the magnet Mr and outputs the detection information to the microcontroller 51. Based on the detected information regarding the input magnetic flux, the microcontroller 51 determines the rotation angle of the magnet Mr, that is, the rotation angle of the second sub-shaft gear 63.

[0039] The magnet Mp is fixed to the upper surface of the spindle gear 10 such that its central axes coincide or nearly coincide. The magnet Mp has two magnetic poles aligned perpendicular to the rotation axis of the spindle gear 10. The angle sensor Sp is provided to detect the rotation angle of the spindle gear 10 such that its lower surface faces the upper surface of the magnet Mp in the vertical direction, with a gap between them.

[0040] For example, the angle sensor Sp is fixed to the substrate 5 on which the angle sensor Sq is fixed, on the same plane as the surface on which the angle sensor Sq is fixed. The angle sensor Sp detects the magnetic flux of the magnet Mp and outputs the detection information to the microcontroller 51. The microcontroller 51 determines the rotation angle of the main spindle gear 10, that is, the rotation angle of the main spindle 1a, by determining the rotation angle of the magnet Mp based on the detection information regarding the input magnetic flux. The resolution of the rotation angle of the main spindle 1a corresponds to the resolution of the angle sensor Sp. As will be described later, the microcontroller 51 determines the amount of rotation of the main spindle 1a based on the determined rotation angle of the first sub-spindle gear 30, the rotation angle of the second sub-spindle gear 63, and the determined rotation angle of the main spindle 1a, and outputs this. For example, the microcontroller 51 may output the amount of rotation of the main spindle 1a of the motor 1 as a digital signal.

[0041] The absolute encoder 2 configured in this way can determine the rotation speed of the main spindle 1a based on the rotation angle of the first sub-shaft gear 30 determined based on the detection information of the angle sensor Sq, and the rotation angle of the second sub-shaft gear 63 determined based on the detection information of the angle sensor Sr, and can also determine the rotation angle of the main spindle 1a based on the detection information of the angle sensor Sp. The microcontroller 51 then determines the amount of rotation of the main spindle 1a over multiple rotations based on the determined rotation speed and rotation angle of the main spindle 1a.

[0042] The spindle gear 10 mounted on the spindle 1a has, for example, 5 threads in the first worm gear section 11 and, for example, 20 teeth in the first worm wheel section 21. In other words, the first worm gear section 11 and the first worm wheel section 21 constitute a first speed change mechanism R1 with a reduction ratio of 20 / 5 = 4 (see Figure 6). When the first worm gear section 11 rotates 4 times, the first worm wheel section 21 rotates 1 time. The first worm wheel section 21 and the second worm gear section 22 are mounted coaxially and constitute a first intermediate gear 20, and since they rotate together, when the first worm gear section 11 rotates 4 times, that is, when the spindle 1a and spindle gear 10 rotate 4 times, the first intermediate gear 20 rotates 1 time and the second worm gear section 22 rotates 1 time.

[0043] The second worm gear section 22 has, for example, 2 teeth, and the second worm wheel section 31 of the first sub-shaft gear 30 has, for example, 25 teeth. In other words, the second worm gear section 22 and the second worm wheel section 31 constitute a second transmission mechanism R2 with a reduction ratio of 25 / 2 = 12.5 (see Figure 6). When the second worm gear section 22 rotates 12.5 times, the second worm wheel section 31 rotates once. The first sub-shaft gear 30 on which the second worm wheel section 31 is formed rotates together with the magnet holder 35 and the magnet MQ, as will be described later. Therefore, when the second worm gear section 22 constituting the first intermediate gear 20 rotates 12.5 times, the magnet MQ rotates once.

[0044] The gear portion 32 of the first sub-shaft gear 30 has, for example, 18 teeth, and the gear portion 71 of the second intermediate gear 70 has, for example, 36 teeth. In other words, the gear portion 32 and the gear portion 71 constitute a third transmission mechanism R3 with a reduction ratio of 40 / 20=2 (see Figure 5). When the gear portion 32 of the first sub-shaft gear 30 rotates twice, the gear portion 71 of the second intermediate gear 70 rotates once. Also, the gear portion 72 of the second intermediate gear 70 has, for example, 19 teeth, and the gear portion 64 of the second sub-shaft gear 63 has, for example, 38 teeth. In other words, the gear portion 64 and the gear portion 72 constitute a fourth transmission mechanism R4 with a reduction ratio of 38 / 19=2 (see Figure 5). When the gear portion 72 of the second intermediate gear 70 rotates twice, the gear portion 64 of the second sub-shaft gear 63 rotates once.

[0045] Gear sections 71 and 72 are mounted coaxially to form the second intermediate gear 70, and since they rotate together, when gear section 71 rotates once, gear section 72 rotates once. Therefore, the reduction ratio of the second intermediate gear 70 as a whole is 4. In other words, when the gear section 32 of the first sub-shaft gear 30 rotates 4 times, the second intermediate gear 70 rotates 2 times, and the gear section 64 of the second sub-shaft gear 63 rotates once. The second sub-shaft gear 63, on which the gear section 64 is formed, forms a magnet holder 61 as will be described later, and rotates together with the magnet Mr. Therefore, when the gear section 32 of the first sub-shaft gear 30 rotates 4 times, the magnet Mr rotates once.

[0046] From the above, when the main spindle 1a rotates 200 times, the first intermediate gear 20 rotates 50 times, the first sub-spindle gear 30 and magnet MQ rotate 4 times, the second intermediate gear 70 rotates 2 times, and the second sub-spindle gear 63 and magnet Mr rotate 1 time. In other words, the number of rotations of the main spindle 1a equivalent to 50 rotations can be determined by the detection information of the rotation angle of the first sub-spindle gear 30 from the angle sensor Sq, and the number of rotations of the main spindle 1a equivalent to 200 rotations can be determined by the detection information of the rotation angle of the second sub-spindle gear 63 from the angle sensor Sr. Furthermore, the reduction ratio of the first sub-spindle gear 30 to the main spindle gear 10 is smaller than that of the second sub-spindle gear 63, and the resolution of the amount of rotation of the main spindle 1a based on the detection information of the magnetic sensor Sq corresponding to magnet MQ which rotates with the first sub-spindle gear 30 is higher than the resolution of the amount of rotation of the main spindle 1a based on the detection information of the magnetic sensor Sr corresponding to magnet Mr which rotates with the second sub-spindle gear 63. Therefore, in the absolute encoder 2, the range of identifiable spindle rotation amounts can be expanded without reducing the resolution of the identifiable spindle rotation amount 1a.

[0047] The configuration of absolute encoder 2 will be explained in more detail below.

[0048] As described above (see Figures 1-6), the absolute encoder 2 includes a base 3, a case 4, a circuit board 5, and a connector 6. The absolute encoder 2 also includes a magnet holder 61 having a main shaft gear 10, a first intermediate gear 20, a first sub-shaft gear 30, a second intermediate gear 70, and a second sub-shaft gear 63, and a biasing mechanism 40. The absolute encoder 2 also includes magnets Mp, MQ, Mr and angle sensor It includes Sp, Sq, and Sr, and also includes a microcontroller 51 for controlling the drive unit, detection unit, etc. of the absolute encoder 2.

[0049] Base 3 is a base that rotatably holds each rotating body such as the main shaft gear 10, the first intermediate gear 20, the first sub-shaft gear 30, the second intermediate gear 70, and the magnet holder 61 (second sub-shaft gear 63), and also fixes each component such as the substrate 5 and the biasing mechanism 40. As shown in Figures 3 to 6 and Figures 11 to 14, Base 3 has a base portion 101 and various support portions, which will be described later, for supporting each component of the absolute encoder 2 provided on the base portion 101. As shown in Figure 7, the case 4 is fixed to Base 3 via a support plate 3a. The support plate 3a is sandwiched between Base 3 and the motor 1, and the case 4 is fixed to the support plate 3a by a screw 8c at, for example, one location. The substrate 5 is also fixed to Base 3 by screws 8a at, for example, three locations. The base portion 101 is a plate-shaped part of the absolute encoder 2 that has a pair of surfaces facing the vertical direction and extends horizontally (in the X-axis and Y-axis directions).

[0050] The upper surface 104, which is the upper surface of the base portion 101, is provided with substrate support columns 110 and substrate positioning pins 120, which are parts for supporting the substrate 5. The base 3 has, for example, three substrate support columns 110 and two substrate positioning pins 120.

[0051] As shown in Figure 5, etc., the substrate support column 110 is a portion that protrudes upward from the upper surface 104 of the base 101, and is, for example, a cylindrical or substantially cylindrical portion. A screw hole 112 extending downward is formed in the upper end face (upper end face 111) of the substrate support column 110. The upper end face 111 of each substrate support column 110 is formed to extend on the same horizontal plane or to extend along the same horizontal plane. In the absolute encoder 2, the substrate 5 has its lower surface 5a in contact with the upper end face 111 of the substrate support column 110 and is fixed to the substrate support column 110 by a screw 8a screwed into the screw hole 112. As will be described later, one of the substrate support columns 110 is integrated with one substrate positioning pin 120 and a support projection 45 that constitutes the biasing mechanism 40 described later. The substrate support column 110 may also have ribs for reinforcement.

[0052] As shown in Figure 5, the substrate positioning pin 120 is a portion that protrudes upward from the upper surface 104 of the base 101, and is, for example, cylindrical or substantially cylindrical. The upper end (tip portion 121) of the substrate positioning pin 120 is thinner than the lower portion (base 122), and a stepped surface 123 is formed between the tip portion 121 and the base 122. The tip portion 121 of the substrate positioning pin 120 is insertable into a positioning hole 5b formed in the substrate 5, as shown in Figure 28, which will be described later. By inserting the tip portion 121 of the substrate positioning pin 120 into the positioning hole 5b of the substrate 5, the substrate 5 is positioned relative to the base 3.

[0053] Furthermore, as shown in Figure 5, etc., the base 3 has support protrusions 131, 132, and 141 that are provided on the upper surface 104 of the base portion 101 and protrude upward (see Figures 3 to 6, etc.). Support protrusion 132 is a part that supports a leaf spring 9 that pushes the first intermediate gear 20 in the direction of the central axis of the first intermediate gear 20, as will be described later. Support protrusions 131 and 141 are parts that rotatably support the first intermediate gear 20, as will be described later. The base 3 also has a bearing holder portion 134 that supports a bearing 135 that rotatably holds the first sub-shaft gear 30 (see Figure 15). The base 3 also has a shaft support portion that supports the second sub-shaft gear shaft 62 that rotatably supports the magnet holder 61 on which the second sub-shaft gear 63 is formed, as will be described later. 137 , and a shaft support part that supports the shaft 75 which rotatably supports the second intermediate gear 70 136 It has the above characteristics (see Figures 17-19). In addition, a support projection 45 is provided on the upper surface 104 of the base portion 101 of the base 3. As will be described later, the support projection 45 is a part that constitutes a biasing mechanism 40 that biases the second worm gear portion 22 toward the second worm wheel portion 31, and is a part that supports the biasing spring 41.

[0054] Next, we will specifically describe each component supported by the base 3 of the absolute encoder 2.

[0055] (Main shaft gear) Figure 8 is a schematic cross-sectional view of the absolute encoder 2 shown in Figure 1, with the motor 1 removed, cut across a plane passing through the central axis of the spindle gear 10 and perpendicular to the central axis of the first intermediate gear 20. Figure 9 is an exploded longitudinal cross-sectional view of the absolute encoder 2 shown in Figure 8, showing the configuration of the magnet Mp, spindle gear 10, spindle adapter 12, and the spindle 1a of the motor 1.

[0056] As shown in Figures 8 and 9, the spindle gear 10 is a cylindrical member provided coaxially or substantially coaxially with the spindle 1a and spindle adapter 12 of the motor 1. The spindle gear 10 comprises a cylindrical portion 13 and a first worm gear portion 11 provided radially outward of the cylindrical portion 13. The first worm gear portion 11 is the gear portion of the spindle gear 10. As shown in Figure 9, a cylindrical press-fit portion 1b is formed at the upper end of the spindle 1a of the motor 1, forming a space on the inner circumference side, and the spindle adapter 12 is pressed into and fixed in the press-fit portion 1b. In addition, a cylindrical press-fit portion 14 is formed in the cylindrical portion 13 of the spindle gear 10, forming a space on the inside, and the spindle adapter 12 is pressed into and fixed in the press-fit portion 14.

[0057] Furthermore, as shown in Figures 8 and 9, a magnet holding portion 15 for holding the magnet Mp is formed in the cylindrical portion 13 of the main shaft gear 10. The magnet holding portion 15 is a part that forms a recess corresponding to the shape of the magnet Mp that is recessed downward from the upper end surface 13a of the cylindrical portion 13, and is capable of accommodating the magnet Mp. The magnet holding portion 15 is in communication with the press-fit portion 14 and has a cylindrical inner circumferential surface 15a having a larger diameter than the press-fit portion 14, and an annular bottom surface 15b connecting the inner circumferential surface 15a and the press-fit portion 14.

[0058] The inner circumferential surface 15a of the magnet holder 15 is formed to contact the outer circumferential surface Mpd of the magnet Mp housed in the magnet holder 15. In the absolute encoder 2, the upper end surface 12a of the spindle adapter 12 is located above the bottom surface 15b of the magnet holder 15. In the absolute encoder 2, the lower surface Mpb of the magnet Mp is in contact with the upper end surface 12a of the spindle adapter 12, but not with the bottom surface 15b of the magnet holder 15 of the spindle gear 10. Thus, the vertical positioning of the magnet Mp is performed by the upper end surface 12a of the spindle adapter 12, and the horizontal positioning is performed by the inner circumferential surface 15a of the magnet holder 15. The lower surface Mpb of the magnet Mp, thus positioned, is bonded and fixed to the upper end surface 12a of the spindle adapter 12.

[0059] As described above, the magnet Mp is fixed to the spindle adapter 12, and the magnet Mp, spindle gear 10, and spindle adapter 12 rotate together with the spindle 1a of the motor 1. The magnet Mp, spindle gear 10, and spindle adapter 12 rotate around the same axis as the spindle 1a of the motor 1.

[0060] The first worm gear portion 11 is composed of helically formed teeth and is designed to mesh with the first worm wheel portion 21 of the first intermediate gear 20. The first worm gear portion 11 is made of, for example, polyacetal resin. The first worm gear portion 11 is an example of a first drive gear.

[0061] As shown in Figure 9, the magnet Mp is a disc-shaped or substantially disc-shaped permanent magnet inserted inside the magnet holder 15 of the spindle gear 10, and has an upper surface Mpa and a lower surface Mpb facing away from each other. In the absolute encoder 2, the position of the magnet Mp in the direction of the central axis GC1 of the spindle gear 10 (position in the vertical direction) is defined by the upper end surface 12a of the spindle adapter 12 as described above, such that the upper surface Mpa of the magnet Mp faces the surface of the angle sensor Sp at a fixed distance in the vertical direction.

[0062] The central axis MpC of the magnet Mp (the axis representing the center of the magnet Mp or the axis passing through the center of the boundary of the magnetic poles) coincides with or approximately coincides with the central axis GC1 of the spindle gear 10, the central axis SaC of the spindle adapter 12, and the central axis MoC of the spindle 1a of the motor 1. By making each central axis coincide or approximately coincide in this way, the angle sensor Sp can detect the rotation angle or amount of rotation of the magnet Mp with higher accuracy.

[0063] In the embodiments of the present invention, it is desirable that the two magnetic poles (N / S) of the magnet Mp be formed adjacent to each other in a horizontal plane (XY plane) perpendicular to the central axis MpC of the magnet Mp. This can further improve the detection accuracy of the rotation angle or amount of rotation of the angle sensor Sp. The magnet Mp is formed from a magnetic material such as a ferrite-based or Nd (neodymium)-Fe (iron)-B (boron)-based material. The magnet Mp may also be a rubber magnet containing a resin binder, a bonded magnet, or the like.

[0064] (Spindle adapter) Figure 10 is an enlarged cross-sectional view showing one end 124 of the spindle adapter 12.

[0065] The spindle adapter 12 according to an embodiment of the shaft support structure of the present invention is a shaft that is press-fitted into press-fit portions 1b and 14, with the spindle 1a of the motor 1 and the cylindrical portion 13 of the spindle gear 10 serving as support members. As shown in Figures 8, 9, and 10, the spindle adapter 12 has tapered surface portions 126, 127 and a through hole 128.

[0066] The through-hole 128 penetrates one end 124 and the other end 125 of the spindle adapter 12. The through-hole 128 has a first hole portion 128a that occupies a predetermined length in the axial direction from the side of the one end 124, and a second hole portion 128c that communicates with the first hole portion 128a and occupies a region up to the other end 125. In the through-hole 128, the diameter of the hole in the first hole portion 128a in the predetermined length in the axial direction from the side of the one end 124 is larger than the diameter of the hole in the second hole portion 128c provided on the side of the other end 125. The end portion 128b between the first hole portion 128a and the second hole portion 128c is a portion that is created when machining the first hole portion 128a with a drill that has an angled tip, and when machining with an end mill, the end portion 128b does not exist.

[0067] The absolute encoder 2 has a structure in which the spindle gear 10 is attached to the spindle 1a of the motor 1. In order to accommodate spindles 1a of various diameters, the spindle gear 10 is not directly attached to the spindle 1a, but is fixed via a spindle adapter 12. Here, the spindle 1a is the rotation axis of the motor and requires rigidity. Also, as mentioned above, the spindle adapter 12 needs to have the magnet Mg fixed with adhesive, so it is desirable to use metal for both the spindle 1a and the spindle adapter 12. Therefore, a high pressing force is required when pressing the spindle adapter 12 into the press-fit portion 1b of the spindle 1a. In this case, the pressing force may cause buckling deformation of the spindle 1a or wear on the press-fit fitting portion (inner diameter portion, outer diameter portion) of the spindle 1a and the spindle adapter 12, which may cause damage.

[0068] In the absolute encoder 2, the diameter of the first hole 128a of the through hole 128 of the spindle adapter 12 is made larger than the diameter of the second hole 128c, and the wall thickness is made thinner, which makes the spindle adapter 12 more flexible, reduces the pressing force on the spindle 1a, and reduces the load on the spindle 1a. On the other hand, the upper part (tip side) of the spindle adapter 12 requires a contact area with the magnet Mp (wall thickness between the outer diameter and inner diameter of the spindle adapter 12) in order to fix the magnet Mp with adhesive. Therefore, the spindle adapter 12 has different diameters for the through hole 128 at predetermined positions in the axial direction, for example, a region corresponding to the press-fit allowance (dimensions required for press-fitting) on ​​the end 124 side.

[0069] In other words, the spindle adapter 12 has a first hole 128a on the side of one end 124 (the lower side in Figure 9) that is larger than the second hole 128c, which facilitates deformation of the circumferential surface 129 of the spindle adapter 12 and makes it easier to press-fit into the press-fit portion 1b. Also, the diameter of the second hole 128c on the side of the other end 125 (the upper side in Figure 9) that is smaller than the first hole 128a is made smaller than the first hole 128a, which ensures a sufficient bonding area with the magnet Mp and reduces the pressing force without compromising the adhesive holding force.

[0070] The tapered surfaces 126 and 127 are inclined outer surfaces such that the diameters of one end 124 and the other end 125 are smaller than the diameter of the circumferential surface 129. In the tapered surface 126, the connection portion 126a of the outer surface between the tapered surface 126 of the spindle adapter 12 and the circumferential surface 129 is connected by a curved surface. Similarly, in the tapered surface 127 on the other end 125 side, the connection portion 127a of the outer surface between it and the circumferential surface 129 is connected by a curved surface. In other words, the connection portions 126a and 127a of the outer surface between the tapered surfaces 126 and 127 and the circumferential surface 129 are machined to have curved surfaces.

[0071] As shown in Figure 9, the spindle adapter 12 is press-fitted into a press-fit portion 1b formed on the upper end of the spindle 1a of the motor 1, for a predetermined length in the axial direction from one end 124. The other end 125 of the spindle adapter 12 is press-fitted into a press-fit portion 14 formed on the cylindrical portion 13 of the spindle gear 10, for a predetermined length in the axial direction.

[0072] Here, if only a linear chamfer is applied to the tapered surface portion 126, when one end 124 of the spindle adapter 12 is press-fitted into the press-fit portion 1b, if the edge of the hole in the press-fit portion 1b comes into contact with the tapered surface portion 126, shavings will be ejected from both the spindle adapter 12 and the press-fit portion 1b. Similarly, if only a linear chamfer is applied to the tapered surface portion 127, when the other end 125 of the spindle adapter 12 is press-fitted into the press-fit portion 14, if the edge of the hole in the press-fit portion 14 comes into contact with the tapered surface portion 127, shavings will be ejected from both the spindle adapter 12 and the press-fit portion 14.

[0073] On the other hand, when the spindle adapter 12 and the press-fit portion 1b and press-fit portion 14 are press-fitted, after the tapered surface portions 126 and 127 are inserted into the press-fit portions 1b and 14, the connecting portions 126a and 127a on the outer circumferential surface between the tapered surface portions 126 and 127 and the circumferential surface 129 come into contact with the press-fit portions 1b and 14. Because the spindle adapter 12 has curved surface machining on the connecting portions 126a and 127a on the outer circumferential surface between the tapered surface portions 126 and 127 and the circumferential surface 129, the spindle adapter 12 is smoothly press-fitted into the press-fit portions 1b and 14, thus preventing both the spindle adapter 12 and the press-fit portions 1b and 14 from being worn down. Therefore, the spindle adapter 12 can suppress the scattering of shavings and the like. In addition, the spindle adapter 12 can suppress the spindle adapter 12 from being pressed in at an angle (tilted) due to wear on the material. Furthermore, the spindle adapter 12 reduces the tilt of the spindle adapter 12, thereby reducing the press-fit allowance (the dimension required for press-fitting).

[0074] The curved surface machining of the connecting portions 126a and 127a should preferably be set to a radius of approximately R = 1 [mm]. Furthermore, by making the surface roughness of the tapered surface portions 126 and 127, including the circumferential surface 129 and the connecting portions 126a and 127a of the spindle adapter 12 smoother, it is possible to prevent material from being worn down on the surfaces of both the spindle adapter 12 and the press-fit portion 14. The surface roughness Rmax (maximum roughness) of the spindle adapter 12 should preferably be 1.6 [μm] or less. Note that the curved surface machining of the connecting portions 126a and 127a may be performed on either one end 124 or the other end 125.

[0075] (First intermediate gear) Figure 11 is a schematic cross-sectional view showing the absolute encoder 2 configuration shown in Figure 6, cut by a plane passing through the central axis of the first intermediate gear 20 and parallel to the horizontal plane (XY plane). Figure 12 is an enlarged perspective view of the absolute encoder 2, cross-sectioned as shown in Figure 11, viewed from above the sub-shaft end 23b of the first intermediate gear shaft 23. Figure 13 is a schematic partial cross-sectional view showing the absolute encoder 2 configuration shown in Figure 6, cut by a plane passing through the central axis of the first intermediate gear 20 and perpendicular to the horizontal plane (XY plane).

[0076] As shown in Figures 4 to 6 and Figures 11 to 13, the first intermediate gear 20 is rotatably supported by the first intermediate gear shaft 23 on the upper side of the base portion 101 of the base 3. The first intermediate gear shaft 23 extends parallel to the horizontal plane. Furthermore, the first intermediate gear shaft 23 is not parallel to the left-right direction (X-axis direction) and the front-back direction (Y-axis direction) in a plan view. That is, the first intermediate gear shaft 23 is oblique to the left-right direction and the front-back direction. The fact that the first intermediate gear shaft 23 is oblique to the left-right direction and the front-back direction means that the first intermediate gear shaft 23 extends obliquely to the outer circumferential surfaces 105-108 of the base portion 101 of the base 3 (see Figure 11). In the absolute encoder 2, the first intermediate gear shaft 23 is supported on the base 101 of the base 3 by a support projection 131 located on the main shaft gear 10 side and a support projection 141 located on the first sub-shaft gear 30 side.

[0077] As shown in Figure 11, the outer circumferential surface of the base 3 is composed of a right outer circumferential surface 105 and a left outer circumferential surface 107 parallel to the YZ plane, and a rear outer circumferential surface 106 and a front outer circumferential surface 108 that are parallel to the XZ plane and extend between the right outer circumferential surface 105 and the left outer circumferential surface 107. The right outer circumferential surface 105 is a side surface provided on the right side (right side in the X-axis direction) of the base 3. The left outer circumferential surface 107 is a side surface provided on the left side (left side in the X-axis direction) of the base 3. The rear outer circumferential surface 106 is a side surface provided on the rear side (rear side in the Y-axis direction) of the base 3. The front outer circumferential surface 108 is a side surface provided on the front side (front side in the Y-axis direction) of the base 3.

[0078] As shown in Figures 3 to 6, the dimensions of the absolute encoder 2 in plan view are matched to the dimensions of a 25 mm square motor 1, for example. Therefore, by positioning the first intermediate gear 20, which is parallel to the upper surface 104 of the base 3, so as to extend diagonally with respect to the outer circumferential surfaces 105-108 of the base 3, the dimensions of the absolute encoder 2 in the horizontal direction can be reduced. Note that the horizontal direction is equal to the direction perpendicular to the central axis of the main shaft 1a of the motor 1, and also equal to the direction parallel to the XY plane.

[0079] As shown in Figures 5, 6 and 11-14, the first intermediate gear 20 is a cylindrical member formed to be rotatable around the first intermediate gear shaft 23, and has a first worm wheel portion 21, a second worm gear portion 22, a cylindrical portion 24, a main shaft side sliding portion 25, and a sub-shaft side sliding portion 26. The cylindrical portion 24 is a cylindrical member and has an inner circumferential surface 24b that forms a through hole 24a through which the first intermediate gear shaft 23 can be inserted. The through hole 24a is a space surrounded by the inner circumferential surface 24b of the cylindrical portion 24. The inner circumferential surface 24b is slidably formed on the outer circumferential surface of the first intermediate gear shaft 23 inserted through the through hole 24a, and the first intermediate gear 20 is supported on the first intermediate gear shaft 23 so as to be rotatable around the first intermediate gear shaft 23. The first intermediate gear 20 is a component integrally molded from metal, resin, etc., and in this example, it is formed from polyacetal resin.

[0080] As shown in Figures 5 to 8, the first worm wheel portion 21 is a gear that meshes with the first worm gear portion 11 of the spindle gear 10. The first worm wheel portion 21 is an example of a first driven gear. The first worm wheel portion 21 is provided on one end side of the cylindrical portion 24 of the first intermediate gear 20, and is composed of multiple teeth provided on a cylindrical surface formed on one end side of the cylindrical portion 24 of the first intermediate gear 20. In the absolute encoder 2, the first intermediate gear 20 is provided such that the first worm wheel portion 21 is located near the center of the base portion 101 of the base 3. Therefore, the one end of the cylindrical portion 24 to which the first worm wheel portion 21 is provided is the end of the first intermediate gear 20 that faces the spindle gear 10.

[0081] As shown in Figure 8, the outer diameter of the first worm wheel portion 21 is smaller than the outer diameter of the first worm gear portion 11. The central axis of the first worm wheel portion 21 is coaxial with or approximately coaxial with the central axis of the inner circumferential surface 24b of the cylindrical portion 24. In the absolute encoder 2, since the central axis of the first worm wheel portion 21 is parallel with or approximately parallel to the upper surface 104 of the base portion 101 of the base 3, the outer diameter of the first worm wheel portion 21 is reduced, which makes it possible to miniaturize the absolute encoder 2 in the vertical direction (height direction).

[0082] As shown in Figures 5, 6, 11 to 15, the second worm gear portion 22 is composed of helically formed teeth and is arranged coaxially or substantially coaxially with the first worm wheel portion 21. The second worm gear portion 22 is an example of a second drive gear. Specifically, the second worm gear portion 22 is provided on the other end side of the cylindrical portion 24 and is composed of helically formed teeth provided on a cylindrical surface formed on the other end side of the cylindrical portion 24. The other end side of the cylindrical portion 24 is the end side of the first intermediate gear 20 that faces the first sub-shaft gear 30. Furthermore, the central axis of the second worm gear portion 22 is coaxial or substantially coaxial with the central axis of the inner circumferential surface 24b of the cylindrical portion 24. The rotational force of the first intermediate gear 20 is transmitted to the first sub-shaft gear 30 when the second worm gear section 22 meshes with the second worm wheel section 31 provided on the first sub-shaft gear 30.

[0083] As described above, the axial angle between the first worm gear section 11 and the first worm wheel section 21 is 90° or approximately 90°, and the central axis of the first worm gear section 11 and the central axis of the first worm wheel section 21 are orthogonal or approximately orthogonal to each other when viewed from a direction perpendicular to the central axis of the first worm gear section 11 and perpendicular to the central axis of the first worm wheel section 21. Furthermore, the axial angle between the second worm gear section 22 and the second worm wheel section 31 is 90° or approximately 90°, and the central axis of the second worm gear section 22 and the central axis of the second worm wheel section 31 are orthogonal or approximately orthogonal to each other when viewed from a direction perpendicular to the central axis of the second worm gear section 22 and perpendicular to the central axis of the second worm wheel section 31.

[0084] As shown in Figure 15, the outer diameter of the second worm gear section 22 is set to the smallest possible value in order to enable miniaturization of the absolute encoder 2 in the vertical direction (height direction).

[0085] As shown in Figures 6 and 11-13, the spindle-side sliding portion 25 of the first intermediate gear 20 is provided at one end of the first intermediate gear 20, that is, the end of the first intermediate gear 20 that faces the spindle gear 10. Specifically, the spindle-side sliding portion 25 is the end face of one end of the cylindrical portion 24, and is an annular surface formed on one end of the cylindrical portion 24 that faces the direction of the central axis of the first intermediate gear 20. In the absolute encoder 2, the spindle-side sliding portion 25 of the first intermediate gear 20 contacts one end 9a of the leaf spring 9, which will be described later.

[0086] The leaf spring 9 is an example of an elastic member, and is made of metal, for example. In the absolute encoder 2, the leaf spring 9 is a member that pushes the first intermediate gear 20 in the direction of the central axis of the first intermediate gear shaft 23. As shown in Figures 4 to 6 and Figure 13, the other end 9b of the leaf spring 9 is supported by a projection 132a of a support projection 132 of the base 3, and is also fixed to a support projection 45 of the base 3 by a screw 8b, and is supported by the base 3. One end 9a of the leaf spring 9 is formed to contact the main shaft side sliding portion 25 of the first intermediate gear 20, and specifically, as shown in Figures 4 and 13, one end 9a of the leaf spring 9 is composed of two bifurcated branches. A gap larger than the diameter of the first intermediate gear shaft 23 is formed between the two branches that make up one end 9a of the leaf spring 9. As a result, in the absolute encoder 2, the two branched parts of one end 9a of the leaf spring 9 pass through the first intermediate gear shaft 23 and contact the main shaft side sliding portion 25 of the first intermediate gear 20.

[0087] As shown in Figures 4, 6, 11, and 13, in the absolute encoder 2, the leaf spring 9 is supported at its other end 9b by a support projection 132 of the base 3 and fixed to a support projection 45 of the base 3, such that when the leaf spring 9 is bent, one end 9a contacts the main shaft side sliding portion 25 of the first intermediate gear 20. As a result, an elastic force is generated in the leaf spring 9, and the main shaft side sliding portion 25 of the first intermediate gear 20 is pressed by one end 9a of the leaf spring 9. Due to this pressing force of the leaf spring 9, the first intermediate gear 20 is biased along the first intermediate gear shaft 23 in the direction from the support projection 131 on the main shaft gear 10 side toward the support projection 141 on the first sub-shaft gear 30 side. When the first intermediate gear 20 rotates in this state, the main shaft side sliding portion 25 of the first intermediate gear 20 rotates while in contact with one end 9a of the leaf spring 9.

[0088] As shown in Figures 4, 6 and 11 to 14, the sub-shaft side sliding portion 26 of the first intermediate gear 20 is provided at the other end of the first intermediate gear 20, that is, the end of the first intermediate gear 20 that faces the first sub-shaft gear 30. Specifically, the sub-shaft side sliding portion 26 is the end face of the other end of the cylindrical portion 24, an annular surface formed at the other end of the cylindrical portion 24 that faces the direction of the central axis of the first intermediate gear 20, and is facing away from the main shaft side sliding portion 25 in the direction of the central axis of the first intermediate gear 20.

[0089] In the absolute encoder 2, the sub-shaft side sliding portion 26 of the first intermediate gear 20 is in contact with the support projection 141, and the support projection 141 defines the position of the first intermediate gear 20 in the central axis direction of the first intermediate gear shaft 23. As described above, the first intermediate gear 20 is pressed by the leaf spring 9 in the direction from the support projection 131 on the main shaft gear 10 side toward the support projection 141 on the first sub-shaft gear 30 side, so the sub-shaft side sliding portion 26 of the first intermediate gear 20 is also pressed in the same direction and comes into contact with the support projection 141. In this way, the pressing force of the leaf spring 9 is transmitted from the first sub-shaft gear 30 to the support projection 141, and the first intermediate gear 20 is stably supported in the direction from the support projection 131 toward the support projection 141. When the first intermediate gear 20 rotates, the sub-shaft side sliding portion 26 of the first intermediate gear 20 rotates while in contact with the support projection 141.

[0090] As described above, the support projections 131 and 141 are examples of a first shaft support and a second shaft support, respectively, that rotatably hold the first intermediate gear 20 via the first intermediate gear shaft 23. As shown in Figures 5, 6 and 11 to 13, the support projections 131 and 141 are paired and, for example, are roughly rectangular parallelepiped parts or parts having roughly rectangular parallelepiped parts that protrude upward from the base 101 of the base 3. The support projection 131 is provided near the main shaft gear 10 and, in a plan view (see Figures 6 and 11), is located on the left side of the base 3 and near the center in the front-rear direction. The support projection 141 is provided near the first sub-shaft gear 30 and, in a plan view, is located on the right side and front of the base 3.

[0091] As shown in Figures 6 and 11 to 13, the support projections 131 and 141 function as support members that support the first intermediate gear shaft 23 so that it can swing along the horizontal plane, that is, they function as support members that support the first intermediate gear 20 so that it can swing along the horizontal plane. The first intermediate gear shaft 23 is a cylindrical rod-shaped member and has a main shaft side end 23a as one end and a sub-shaft side end 23b as the other end. The main shaft side end 23a is the end of the first intermediate gear shaft 23 located on the main shaft gear 10 side in the absolute encoder 2, and the sub-shaft side end 23b is the end of the first intermediate gear shaft 23 located on the first sub-shaft gear 30 side in the absolute encoder 2.

[0092] The first worm wheel portion 21, provided on the main shaft end 23a side of the first intermediate gear shaft 23, is movable in the first meshing direction (direction of arrow P1 in Figure 12) by a biasing mechanism 40, which will be described later, but is immovable in the direction in which the first intermediate gear shaft 23 extends (direction of the central axis of the first intermediate gear shaft 23) and in the direction perpendicular to the first meshing direction P1 (up and down direction). The first meshing direction is, as described above, the direction in which the first worm wheel portion 21 moves toward the first worm gear portion 11 in order for the first worm wheel portion 21 to mesh with the first worm gear portion 11.

[0093] As shown in Figures 11 to 14, the support projection 131 has a through hole 143 into which the main shaft end 23a of the first intermediate gear shaft 23 is inserted. The shape of the through hole 143 in a cross section perpendicular to the direction of extension is a circular hole. A circular hole is a shape having a perfect circle or a nearly perfect circle outline.

[0094] Furthermore, the absolute encoder 2 may have a retaining ring (not shown) as a fixing part formed to engage with the main shaft side end 23a of the first intermediate gear shaft 23. The retaining ring is a member that forms on the main shaft side end 23a of the first intermediate gear shaft 23 a portion that cannot pass through the through hole 143 of the support projection 131, and is a member that partially increases the outer diameter of the main shaft side end 23a of the first intermediate gear shaft 23. The retaining ring is, for example, an annular member such as an e-ring that engages with a groove (not shown) formed in the first intermediate gear shaft 23. In addition, the retaining ring is provided on the main shaft side end 23a of the first intermediate gear shaft 23 such that in the absolute encoder 2 the retaining ring is located on the opposite side of the support projection 131 from the sub-shaft side end 23b side. In other words, the retaining ring is provided so as to contact the outer surface 131a of the support projection 131. The outer surface 131a is the surface of the support projection 131 that faces the opposite side from the support projection 141 side. As a result, the movement of the first intermediate gear shaft 23 in the direction from the main shaft end 23a to the sub-shaft end 23b is restricted by contact with the outer surface 131a of the retaining ring support projection 131.

[0095] The second worm gear portion 22, provided on the sub-shaft end 23b side of the first intermediate gear shaft 23, is movable in the second meshing direction (direction of arrow P2 in Figure 12) by a biasing mechanism 40, which will be described later. However, the first intermediate gear shaft 23 is immobile in the direction in which the first intermediate gear shaft 23 extends (the direction of the central axis of the first intermediate gear shaft 23) and in the direction perpendicular to the second meshing direction P2 (the Z-axis direction). The second meshing direction is, as described above, the direction in which the second worm gear portion 22 moves toward the second worm wheel portion 31 in order for the second worm gear portion 22 to mesh with the second worm wheel portion 31.

[0096] The support projection 141 has a through hole 145 into which the sub-shaft end 23b of the first intermediate gear shaft 23 is inserted. The shape of the through hole 145 in a cross section perpendicular to the direction of extension is an elongated hole shape. This elongated hole shape of the through hole 145 has a major axis and a minor axis perpendicular to the major axis. The width on the major axis side is greater than the width on the minor axis side. The width on the major axis side of the elongated hole shape of the through hole 145 of the support projection 141 on the first sub-shaft gear 30 side is greater than the diameter of the outer circumferential surface of the first intermediate gear shaft 23. Also, the width on the minor axis side of the through hole 145 is the same as or approximately the same as the diameter of the outer circumferential surface of the first intermediate gear shaft 23. In the absolute encoder 2, the direction of the major axis of the through hole 145 of the support projection 141 is parallel to or approximately parallel to the horizontal plane. As will be described later, a biasing spring 41 engages with the first intermediate gear shaft 23, in which the sub-shaft side end 23b of the first intermediate gear shaft 23 is inserted into the through hole 145 of the support projection 141, and the biasing spring 41 biases the sub-shaft side end 23b of the first intermediate gear shaft 23 in the second meshing direction P2.

[0097] In this way, the first intermediate gear shaft 23 is configured such that the main shaft end 23a acts as a pivot point (= pivot center), and the sub-shaft end 23b moves parallel or approximately parallel to the horizontal direction, with the biasing mechanism 40, support projections 131 and 141 described later. Furthermore, the second worm gear portion 22 on the sub-shaft end 23b side can move with a larger width parallel or approximately parallel to the horizontal direction than the first worm wheel portion 21 on the main shaft end 23a side. As a result, the first intermediate gear shaft 23, i.e., the first intermediate gear 20, which is biased by the biasing mechanism 40 and supported by the support projections 131 and 141, can swing along the horizontal plane (XY plane).

[0098] In this configuration, the amount of movement (oscillation) of the first intermediate gear shaft 23 is determined by the depth of the through hole 143 formed in the support projection 131, that is, the thickness of the support projection 131 in the direction of the central axis of the first intermediate gear shaft 23, the clearance between the through hole 143 and the first intermediate gear shaft 23, and the width of the through hole 145 on the long axis side. However, if the clearance between the through hole 143 and the first intermediate gear shaft 23 is large, the play of the first intermediate gear shaft 23 will increase and misalignment will occur, so it is desirable to avoid making this clearance large. For this reason, by forming the support projection 131 from a thin plate or the like and reducing the thickness of the support projection 131, that is, by making the through hole 143 shallower, it is possible to reduce the clearance between the through hole 143 and the first intermediate gear shaft 23 while securing the amount of movement of the first intermediate gear shaft 23. Furthermore, by designing the first intermediate gear shaft 23 to move more due to the thickness of the support projection 131 than due to the width of the through hole 145 on the long axis side, the amount of movement of the first intermediate gear shaft 23 can be defined by the width of the through hole 145 on the long axis side.

[0099] (First sub-shaft gear) Figure 15 is a schematic partial cross-sectional view showing the configuration of the absolute encoder 2 shown in Figure 2, cut by a plane passing through the central axis of the first sub-shaft gear 30 and perpendicular to the central axis of the first intermediate gear 20. Figure 16 is a schematic exploded perspective view showing the configuration of the absolute encoder 2 shown in Figure 15, with the magnet MQ, magnet holder 35, first sub-shaft gear 30, and bearing 135 disassembled.

[0100] As shown in Figures 15 and 16, the first sub-shaft gear 30 is a cylindrical member into which the shaft portion 35b of the magnet holder 35 is press-fitted and fixed to the magnet holder 35. The first sub-shaft gear 30 comprises a second worm wheel portion 31, a gear portion 32, and a through hole 33. The first sub-shaft gear 30 is a member integrally molded from metal or resin, and in this example, it is formed from polyacetal resin.

[0101] The second worm wheel portion 31 is a gear that meshes with the second worm gear portion 22 of the first intermediate gear 20. The second worm wheel portion 31 is an example of a second driven gear. The second worm wheel portion 31 is composed of multiple teeth provided on the outer circumference of the upper cylindrical portion of the first sub-shaft gear 30, for example. As the first intermediate gear 20 rotates, the rotational force of the first intermediate gear 20 is transmitted to the first sub-shaft gear 30 via the second worm gear portion 22 and the second worm wheel portion 31 of the first intermediate gear 20.

[0102] The gear portion 32 is a gear that meshes with the gear portion 71 of the second intermediate gear 70. The gear portion 32 is an example of a third drive gear. The gear portion 32 is composed of multiple teeth provided on the outer circumference of the lower cylindrical portion of the first sub-shaft gear 30, for example. Also, as shown in Figure 15, the gear portion 32 is formed on the lower side of the second worm wheel portion 31, and its tip circle diameter is smaller than the tip circle diameter of the second worm wheel portion 31. When the first sub-shaft gear 30 rotates, the rotational force of the first sub-shaft gear 30 is transmitted to the second intermediate gear 70 via the gear portion 32 of the first sub-shaft gear 30 and the gear portion 71 of the second intermediate gear 70.

[0103] As shown in Figures 15 and 16, the through-hole 33 is a hole that penetrates the cylindrical first sub-shaft gear 30 along its central axis. The shaft portion 35b of the magnet holder 35 is press-fitted into the through-hole 33, so that the first sub-shaft gear 30 rotates together with the magnet holder 35.

[0104] The magnet holder 35 has a magnet holding portion 35a and a shaft portion 35b. The magnet holder 35 is a component integrally molded from metal or resin, and here, as an example, it is made of non-magnetic stainless steel. The outer rings of two bearings 135 are press-fitted into the inner circumferential surface of a cylindrical bearing holder portion 134 formed on the base 3. The shaft portion 35b of the magnet holder 35 is a cylindrical component. The shaft portion 35b is press-fitted into a through hole 33 of the first sub-shaft gear 30, and the lower part of the shaft portion 35b is inserted into and fixed to the inner rings of the two bearings 135. Thus, the magnet holder 35 is supported by the two bearings 135 on the base 3 and rotates together with the first sub-shaft gear 30. The magnet holder 35 is held in the bearing holder portion 134 via the bearings 135 so as to be rotatable around a rotation axis parallel or substantially parallel to the Z-axis. A bearing stopper 35c is press-fitted onto the shaft portion 35b of the magnet holder 35. In assembling the first sub-shaft gear 30, first, the outer ring of the bearing 135, which is installed on the upper surface 104 side of the base 3, is press-fitted into the bearing holder portion 134, and then the shaft portion 35b of the magnet holder 35 is inserted into the inner ring of the bearing 135. Next, the bearing stopper 35c is press-fitted onto the shaft portion 35b of the magnet holder 35 until it contacts the lower side of the inner ring of the bearing 135. After that, the shaft portion 35b of the magnet holder 35 is inserted into the inner ring of the bearing 135, which is installed on the lower surface 102 side of the base 3, and the outer ring is press-fitted into the bearing holder portion 134 to fix it in place. Therefore, the bearing stopper 35c prevents the magnet holder 35, which is inserted into the bearing 135, from coming out of the bearing 135, and secures the bearing 135 and the magnet holder 35 without any gaps, thereby minimizing vertical rattle of the magnet Mg. The positions in which the two bearings 135 are pressed in are determined by contacting the bearing positioning member 35d provided on the base 3, but the bearing positioning member 35d may be omitted, and the bearings 135 may be positioned so that the surfaces of the upper surface 104 and lower surface 102 of the base 3 and the surfaces of the bearings 135 are at the same height.

[0105] Furthermore, the magnet holding portion 35a is provided at the upper end of the magnet holder 35. The magnet holding portion 35a is a bottomed cylindrical member. The magnet holding portion 35a has a recess that extends downward from the upper end surface of the magnet holder 35. The inner circumferential surface of this recess of the magnet holding portion 35a is formed to be in contact with the outer circumferential surface MQd of the magnet MQ. As a result, in the absolute encoder 2, the magnet MQ is fixed to the magnet holding portion 35a by being housed in the recess of the magnet holding portion 35a.

[0106] The shaft portion 35b of the magnet holder 35 is supported by two bearings 135 arranged in the bearing holder portion 134 formed on the base 3, thereby preventing the magnet holder 35 from tilting. Furthermore, the effect of preventing the magnet holder 35 from tilting is greatly enhanced when the two bearings 135 are arranged as far apart as possible in the vertical direction of the shaft portion 35b.

[0107] As shown in Figure 16, the magnet MQ is a disc-shaped or substantially disc-shaped permanent magnet that is press-fitted into the magnet holding portion 35a of the magnet holder 35, and has an upper surface MQa and a lower surface MQb. In the absolute encoder 2, the upper surface MQa of the magnet MQ faces the lower surface of the angle sensor Sp at a fixed distance. The central axis MQC of the magnet MQ (the axis representing the center of the magnet MQ or the axis passing through the center of the boundary of the magnetic poles) coincides with the central axis SC of the magnet holder 35, the central axis GC2 of the first sub-axis gear 30, and the central axis BC of the bearing 135. By aligning each central axis in this way, it is possible to detect the rotation angle or amount of rotation with higher precision.

[0108] In the embodiments of the present invention, it is desirable that the two magnetic poles (N / S) of the magnet MQ are formed adjacent to each other in a horizontal plane (XY plane) perpendicular to the central axis MQC of the magnet MQ. This further improves the detection accuracy of the rotation angle or amount of rotation of the angle sensor Sq. The magnet MQ is formed from a magnetic material such as a ferrite-based or Nd (neodymium)-Fe (iron)-B (boron)-based material. The magnet MQ may also be a rubber magnet containing a resin binder, a bonded magnet, or the like.

[0109] (Second intermediate gear) Figure 17 is a schematic partial cross-sectional view showing the configuration of the absolute encoder 2 shown in Figure 2, cut across a plane passing through the central axis of the second intermediate gear 70 and the second sub-shaft gear 63. Figure 18 is an enlarged cross-sectional view showing the second intermediate gear 70 shown in Figure 17.

[0110] As shown in Figures 17 and 18, the second intermediate gear 70 is a member rotatably supported on a shaft 75 fixed to a shaft support portion 136 of the base 3, and comprises a gear portion 71, a gear portion 72, and a main body portion 73. The second intermediate gear 70 is a member integrally molded from, for example, a resin material with low sliding resistance, and an example of the resin material for the second intermediate gear 70 is polyacetal resin. The shaft 75 is fixed to the shaft support portion 136 of the base 3 such that the central axis GC3 of the second intermediate gear 70 is parallel or substantially parallel to the central axis GC2 of the first sub-shaft gear 30, for example, the lower end (lower end face 75a) portion of the shaft 75 is press-fitted into the through hole 136a of the shaft support portion 136 of the base 3 and fixed.

[0111] The main body portion 73 is a cylindrical or substantially cylindrical portion and has a through hole 74 inside. The through hole 74 is formed so that the shaft 75 can be slidably inserted into it. The gear portion 71 is a gear that meshes with the gear portion 32 of the first sub-shaft gear 30. The gear portion 71 is an example of a third driven gear. The gear portion 71 is composed of multiple teeth provided on the lower outer circumference of the main body portion 73, for example. As the first sub-shaft gear 30 rotates, the rotational force of the first sub-shaft gear 30 is transmitted to the gear portion 71 of the second intermediate gear 70 via the gear portion 32 of the first sub-shaft gear 30. This causes the second intermediate gear 70 to rotate.

[0112] The gear portion 72 is a gear that meshes with the gear portion 64 of the second sub-shaft gear 63. The gear portion 72 is an example of a fourth drive gear. The gear portion 72 is composed of multiple teeth provided on the upper outer circumference of the main body portion 73, and is located above the gear portion 71. As the second intermediate gear 70 rotates, the rotational force of the second intermediate gear 70 is transmitted to the gear portion 64 of the second sub-shaft gear 63 via the gear portion 72. This causes the second sub-shaft gear 63 to rotate.

[0113] As shown in Figures 17 and 18, in the second intermediate gear 70, the through hole 74 is a hole that extends through the main body 73 such that the central axis of the through hole 74 coincides with or substantially coincides with the central axes of the gear portion 71 and the gear portion 72, respectively. Furthermore, the through hole 74 is formed such that the central axis GC3 of the second intermediate gear 70 coincides with or substantially coincides with the central axis of the shaft 75.

[0114] The lower end face (lower end face 73a) of the main body portion 73 is formed to contact the upper surface 104 of the base 3 and to be slidable relative to the upper surface 104. The lower end face 73a of the main body portion 73 is, for example, a plane or substantially plane perpendicular or nearly perpendicular to the central axis GC3 of the second intermediate gear 70. The upper end face (upper end face 73b) of the main body portion 73 is formed to contact the member that the upper end face 73b faces and to be slidable relative to this member. The upper end face 73b of the main body portion 73 is, for example, a plane or substantially plane perpendicular or nearly perpendicular to the central axis GC3 of the second intermediate gear 70.

[0115] An annular groove 75c is formed around the axis of the shaft 75 on the upper end (upper end face 75b) side of the shaft 75, and a retaining ring 76 is formed in the groove 75c so as to be engageable with it. The retaining ring 76 is a member that maintains the second intermediate gear 70 in a rotatable supported state on the shaft 75, and is a member that partially increases the outer diameter of the part of the shaft 75 on the upper end face 75b side. As shown in Figure 18, the retaining ring 76 is an annular member such as a c-ring or e-ring. In the absolute encoder 2, the groove 75c is provided on the shaft 75 such that the retaining ring 76 faces the upper end face 73b of the main body 73 of the second intermediate gear 70. In the absolute encoder 2, the retaining ring 76 attached to the groove 75c may be in contact with the upper end face 73b of the second intermediate gear 70, or it may be facing the upper end face 73b of the second intermediate gear 70 with a gap between them. The retaining ring 76 restricts the axial movement of the shaft 75 of the second intermediate gear 70.

[0116] As described above, the second intermediate gear 70 is configured such that in the absolute encoder 2, the shaft 75 is inserted into the through hole 74 of the second intermediate gear 70, and a retaining ring 76 is attached to the groove 75c of the shaft 75, thereby mounting the second intermediate gear 70 in the absolute encoder 2. In the absolute encoder 2, the second intermediate gear 70 is rotatable around a rotation axis parallel or approximately parallel to the central axis GC2 of the first sub-shaft gear 30, with the shaft 75 as the axis of rotation. Furthermore, the second intermediate gear 70 is slidable between the upper surface 104 of the base 3 and the retaining ring 76 attached to the shaft 75, thereby restricting the axial movement of the shaft 75.

[0117] (Second sub-shaft gear) Figure 19 is an enlarged cross-sectional view showing the magnet holder 61 having the second sub-shaft gear 63 shown in Figure 17, and Figure 20 is an exploded perspective view schematically showing the magnet holder 61 shown in Figure 19 in a disassembled state.

[0118] As shown in Figures 17, 19, and 20, the magnet holder 61 is a member rotatably supported on a second sub-shaft gear shaft 62 fixed to a shaft support portion 137 of the base 3, and comprises a second sub-shaft gear 63, a magnet holder portion 65, and a magnet Mr. The magnet holder portion 65 is a member for fixing the magnet Mr in the magnet holder 61 by sandwiching the magnet Mr between itself and the second sub-shaft gear 63. The second sub-shaft gear shaft 62 is fixed to the shaft support portion 137 of the base 3 such that its axis (central axis GC4) is parallel or substantially parallel to the central axis GC3 of the second intermediate gear 70. For example, the lower end (lower end face 62a) portion of the second sub-shaft gear shaft 62 is press-fitted into and fixed to a through hole 137a of the shaft support portion 137 of the base 3. Furthermore, the second sub-axis gear shaft 62 is fixed to the base 3 in the absolute encoder 2 such that the magnet Mr of the magnet holder 61 faces the angle sensor Sr attached to the substrate 5 in the direction of the central axis GC3.

[0119] The second sub-shaft gear 63 comprises a gear portion 64, a body portion 66, and a magnet support portion 67. The second sub-shaft gear 63 is a component integrally molded from, for example, a resin material with low sliding resistance. That is, the gear portion 64, the body portion 66, and the magnet support portion 67 are integrally formed from the same material and each forms a part of the second sub-shaft gear 63. An example of the resin material for the second sub-shaft gear 63 is polyacetal resin. The body portion 66 is a cylindrical or substantially cylindrical portion and has a through hole 66a inside. The through hole 66a is formed so that the second sub-shaft gear shaft 62 can be slidably inserted into the second sub-shaft gear shaft 62. The gear portion 64 is a gear that meshes with the gear portion 72 of the second intermediate gear 70. The gear portion 64 is an example of a fourth driven gear. The gear portion 64 is composed of a plurality of teeth provided on the outer circumference of the body portion 66, for example. In the illustrated example, the gear portion 64 forms a disc-shaped portion that protrudes outward from the outer circumferential surface of the main body portion 66, and multiple teeth are provided on the outer circumferential surface of this disc-shaped portion. When the second intermediate gear 70 rotates, the rotational force of the second intermediate gear 70 is transmitted to the gear portion 64 of the second sub-shaft gear 63 via the gear portion 72 of the second intermediate gear 70. This causes the second sub-shaft gear 63 to rotate.

[0120] As shown in Figures 17 and 19, in the second sub-shaft gear 63, the through-hole 66a is a hole that extends through the main body 66 such that the central axis of the through-hole 66a coincides with or substantially coincides with the central axes of the gear portions 64. Furthermore, the through-hole 66a is formed such that the central axis GC4 of the second sub-shaft gear 63 coincides with or substantially coincides with the central axis of the second sub-shaft gear shaft 62.

[0121] The lower end face (lower end face 66b) of the main body portion 66 is formed to contact the upper surface 104 of the base 3 and to be slidable relative to the upper surface 104. The lower end face 66b of the main body portion 66 is, for example, a plane or substantially plane perpendicular or nearly perpendicular to the central axis GC4 of the second sub-shaft gear 63. The upper end face (upper end face 66c) of the main body portion 66 is formed to contact the member that the upper end face 66c faces and to be slidable relative to this member. The upper end face 66c of the main body portion 66 is, for example, a plane or substantially plane perpendicular or nearly perpendicular to the central axis GC4 of the second sub-shaft gear 63.

[0122] The magnet support portion 67 is a portion of the main body portion 66 that extends upward from the portion above the gear portion 64, and is a cylindrical portion that extends along the central axis GC4 of the second sub-shaft gear 63. The magnet support portion 67 extends upward beyond the upper end surface 66c of the main body portion 66, and the upper end surface 66c of the main body portion 66 and the surface facing the inner circumference of the magnet support portion 67 (inner circumferential surface 67a) form a cylindrical space inside the magnet support portion 67. The outer circumferential surface 67b of the magnet support portion 67 is located on the inner circumference side of the tip of the gear portion 64. The magnet support portion 67 is, for example, a cylindrical or substantially cylindrical member with the central axis GC4 of the second sub-shaft gear 63 as its center or substantially center. As shown in Figure 19, the upper end surface 66c of the main body 66 is connected to the inner circumferential surface 67a of the magnet support portion 67. The main body 66 may be larger on the outer circumference side than the portion below the gear portion 64 at the point where it connects to the magnet support portion 67, or it may not be larger on the outer circumference side than the portion below the gear portion 64 at the point where it connects to the magnet support portion 67. The shape of the magnet support portion 67 is not limited to cylindrical or substantially cylindrical, but may be other shapes. For example, the shape of the magnet support portion 67 may be a rectangular tube or the like.

[0123] The upper end face (upper end face 67c) of the magnet support portion 67 is a plane or substantially plane perpendicular or nearly perpendicular to the central axis GC4 of the second sub-shaft gear 63. In the absolute encoder 2, the inner circumferential surface 67a of the magnet support portion 67 is positioned on the inner side of the surface facing the outer circumferential side of the magnet Mr (outer circumferential surface Mrd) so that the magnet Mr can contact the entire circumference of the upper end face 67c. Furthermore, in the absolute encoder 2, the magnet support portion 67 is formed such that the upper end face 67c is positioned above the upper end face (upper end face 62b) of the second sub-shaft gear shaft 62. The upper end face 67c of the magnet support portion 67 is parallel or substantially parallel to the upper surface 104 of the base 3 so that when the second sub-shaft gear 63 rotates, the upper end face 67c rotates without surface runout relative to the upper surface 104 of the base 3.

[0124] The magnet holder portion 65 is a component formed from a bottomed cylindrical resin material. The resin material of the magnet holder portion 65 is, for example, a resin material to which adhesive can be attached. Specifically, the magnet holder portion 65 has a cylindrical portion 68 that extends in a cylindrical shape and a bottom portion 69 that extends inward from one end of the cylindrical portion 68. The cylindrical portion 68 houses the magnet support portion 67 of the second sub-shaft gear 63 and forms a fitting portion 65a that allows the magnet holder portion 65 to be fitted onto the magnet support portion 67, and the cylindrical portion 68 and the bottom portion 69 form a magnet housing portion 65b that houses and holds the magnet Mr inside.

[0125] The cylindrical portion 68 of the magnet holder portion 65 has a cylindrical or substantially cylindrical inner circumferential surface 68a that extends along the central axis that coincides with or substantially coincides with the central axis MC4 of the second sub-shaft gear 63 in the absolute encoder 2. The inner circumferential surface 68a is a surface facing the inner circumference and extends from the end opposite to the bottom portion 69 side of the cylindrical portion 68 (open end 68c) toward the bottom portion 69, forming an opening at the open end 68c of the cylindrical portion 68. The space formed inside by the inner circumferential surface 68a becomes the fitting portion 65a. The inner circumferential surface 68a is formed to contact the outer circumferential surface 67b of the magnet support portion 67 so that when the magnet support portion 67 of the second sub-shaft gear 63 is housed in the fitting portion 65a, the magnet support portion 67 becomes tightly fitted to the magnet holder portion 65. Note that the shape of the inner circumferential surface 68a of the cylindrical portion 68 is not limited to cylindrical or substantially cylindrical, but may be other shapes. The shape of the inner circumferential surface 68a of the cylindrical portion 68 corresponds to the shape of the magnet support portion 67 that houses it.

[0126] Furthermore, the cylindrical portion 68 of the magnet holder portion 65 has a cylindrical or substantially cylindrical inner circumferential surface 68b that extends along the central axis that coincides with or substantially coincides with the central axis MC4 of the second sub-shaft gear 63 in the absolute encoder 2, and also along the central axis that coincides with or substantially coincides with the central axis MrC of the magnet Mr. The inner circumferential surface 68b is a surface that faces the inner circumference and extends between the inner circumferential surface 68a and the bottom surface 69a of the bottom portion 69. The space formed internally by the inner circumferential surface 68b and the bottom surface 69a of the bottom portion 69 becomes the magnet housing portion 65b. The inner circumferential surface 68b is formed so as to face radially the outer circumferential surface Mrd of the magnet Mr when the magnet Mr is housed in the magnet housing portion 65b. The inner circumferential surface 68b is located on the inner circumference side of the inner circumferential surface 68a, and a step is formed between the inner circumferential surface 68a and the inner circumferential surface 68b. Furthermore, the inner circumferential surface 68b has a width in the central axis direction that is smaller than the width in the direction of the central axis MrC of the magnet Mr. The inner circumferential surface 68b may be formed to face the outer circumferential surface Mrd of the magnet Mr with a space in the radial direction when the magnet Mr is housed in the magnet housing portion 65b, or it may be formed to face the outer circumferential surface Mrd of the magnet Mr without a space in the radial direction.

[0127] The bottom portion 69 of the magnet holder portion 65 is a disc-shaped portion that extends inward from the end opposite to the open end 68c of the cylindrical portion 68 (closed end 68d), and has the bottom surface 69a described above. The bottom surface 69a is the surface facing the magnet housing portion 65b and is a plane or surface along a plane that is perpendicular or approximately perpendicular to the central axis of the cylindrical portion 68. The bottom portion 69 also has an opening 69b which is a through hole that penetrates the bottom portion 69 in the direction of the central axis of the cylindrical portion 68. The bottom surface 69a of the bottom portion 69 is formed so that when the magnet Mr is housed in the magnet housing portion 65b, the central axis MrC of the magnet Mr is parallel or approximately parallel to the central axis of the cylindrical portion 68, and the bottom surface 69a of the bottom portion 69 is in contact with the upper surface Mra of the magnet Mr. The opening 69b of the bottom portion 69 is formed so that when the magnet Mr is housed in the magnet housing portion 65b, the magnetic flux of the magnet Mr passes through the opening 69b.

[0128] As described above, the second sub-shaft gear shaft 62 is made of a magnetic material, and a magnetic attraction force is generated between the magnet Mr and the second sub-shaft gear shaft 62 in the direction of the rotation axis of the magnet holder 61. Specifically, the second sub-shaft gear shaft 62 generates a magnetic force that biases the magnet Mr in the direction of the second sub-shaft gear shaft 62.

[0129] Furthermore, an annular groove 62c is formed around the axis of the second sub-shaft gear shaft 62 on the upper end (upper end face 62b) side of the second sub-shaft gear shaft 62, and a retaining ring 62d is formed to engage with the groove 62c. The retaining ring 62d is a member for restricting the axial movement of the second sub-shaft gear shaft 62 of the magnet holder 61, and is a member that partially increases the outer diameter of the portion of the second sub-shaft gear shaft 62 on the upper end face 62b side. As shown in Figure 19, the retaining ring 62d is an annular member such as a c-ring or e-ring. In the absolute encoder 2, the groove 62c is provided on the second sub-shaft gear shaft 62 such that the retaining ring 62d faces the upper end face 66c of the main body portion 66 of the second sub-shaft gear 63 with a space between them.

[0130] As shown in Figures 19 and 20, the magnet Mr is a disc-shaped or substantially disc-shaped permanent magnet housed in the magnet housing portion 65b of the magnet holder portion 65, and has an upper surface Mra, a lower surface Mrb, and an outer peripheral surface Mrd. In the embodiment of the present invention, it is desirable that the two magnetic poles (N / S) of the magnet Mr are formed adjacent to each other in a horizontal plane (XY plane) perpendicular to the central axis MrC of the magnet Mr. This further improves the detection accuracy of the rotation angle or amount of rotation of the angle sensor Sr. The magnet Mr is formed from a magnetic material such as a ferrite-based or Nd (neodymium)-Fe (iron)-B (boron)-based material. The magnet Mr may also be a rubber magnet containing a resin binder, a bonded magnet, etc. Figure 21 is a schematic perspective view showing a cylindrical magnet Mr applicable to the embodiment of the present invention. In the illustrated example of magnet Mr, the first magnetic pole portion N and the second magnetic pole portion S are arranged adjacent to each other in the radial direction D1, with the center or approximate center of the magnet Mr in the radial direction D1 as the boundary. Also, in the illustrated example of magnet Mr, the first magnetic pole portion N and the second magnetic pole portion S are arranged adjacent to each other in the axial direction D2, with the center or approximate center of the axial direction D2 (central axis MrC) as the boundary. Note that the arrow DM shown in Figure 21 represents the magnetization direction. This type of magnetization direction is generally called planar magnetization, and magnets with planar magnetization are used in magnet Mr.

[0131] As described above, the magnet holder 61 is configured such that in the absolute encoder 2, the second sub-shaft gear shaft 62 is inserted into the through hole 66a of the main body portion 66 of the second sub-shaft gear 63, and the retaining ring 62d is attached to the groove 62c of the second sub-shaft gear shaft 62, thereby mounting the second sub-shaft gear 63 in the absolute encoder 2. In the absolute encoder 2, the magnet holder 61 is rotatable around the axis of rotation. The axis of rotation of the magnet holder 61 coincides with or approximately coincides with the central axis GC4 of the second sub-shaft gear shaft 62. The retaining ring 62d and the portion on the upper end face 62b side of the second sub-shaft gear shaft 62 are housed in the space formed on the inner circumference side by the magnet support portion 67 of the second sub-shaft gear 63.

[0132] Furthermore, in the absolute encoder 2, the magnet Mr is housed in the magnet housing portion 65b of the magnet holder portion 65, and the magnet Mr is fixed to the magnet holder portion 65. The magnet Mr is fixed to the magnet holder portion 65 by adhesive bonding. For example, the inner circumferential surface 68b that forms the magnet housing portion 65b of the magnet holder portion 65 and the outer circumferential surface Mrd of the magnet Mr are bonded together with adhesive. By fixing the magnet Mr to the magnet holder portion 65 with the lower surface Mrb of the magnet Mr in contact with the bottom surface 69a that forms the magnet housing portion 65b of the magnet holder portion 65, the central axis MrC of the magnet Mr can be aligned with the central axis of the second sub-shaft gear shaft 62, and the central axis MrC of the magnet Mr can be aligned with the rotation axis of the second sub-shaft gear shaft 62, thereby enabling more accurate detection of the amount of rotation or rotation angle of the magnet Mr by the angle sensor Sr. Furthermore, the fixing of magnet Mr to the magnet housing 65b is not limited to adhesive, but may also be done by other fixing methods, such as press-fitting magnet Mr into the magnet housing 65b, such as the first sub-shaft gear 30.

[0133] Furthermore, in the absolute encoder 2, as described above, the magnet holder portion 65 to which the magnet Mr is fixed is fitted onto the magnet support portion 67 of the second sub-shaft gear 63, thereby fixing the magnet holder portion 65 to the second sub-shaft gear 63 and assembling the magnet holder 61. Specifically, the magnet support portion 67 is press-fitted into the fitting portion 65a of the magnet holder portion 65, the inner circumferential surface 68a forming the fitting portion 65a of the magnet holder portion 65 presses the outer circumferential surface 67b of the magnet support portion 67 inward, and the outer circumferential surface 67b of the magnet support portion 67 presses the inner circumferential surface 68a of the magnet holder portion 65 outward, thereby fixing the magnet holder portion 65 to the second sub-shaft gear 63. Note that the fixing of the magnet holder portion 65 to the second sub-shaft gear 63 is not limited to fitting, but may be done by other fixing methods.

[0134] In a magnet holder 61 assembled by fixing the magnet holder portion 65 to the second sub-shaft gear 63, the magnet Mr is sandwiched and fixed between the second sub-shaft gear 63 and the magnet holder portion 65. Specifically, the upper end surface 67c of the magnet support portion 67 contacts the lower surface Mrb of the magnet Mr, and the magnet Mr is sandwiched between the upper end surface 67c of the magnet support portion 67 and the bottom surface 69a of the bottom portion 69 of the magnet holder portion 65, thereby fixing the magnet Mr in the direction of its central axis MrC. On the other hand, fixing the magnet Mr in the radial direction perpendicular to its central axis MrC is achieved by adhesion between the outer circumferential surface Mrd of the magnet Mr and the inner circumferential surface 68b of the magnet holder portion 65.

[0135] Furthermore, in the absolute encoder 2, the upper surface Mra of the magnet Mr faces the angle sensor Sr in the direction of the central axis MrC of the magnet Mr, through an opening 69b formed in the bottom portion 69 of the magnet holder portion 65. This allows the angle sensor Sr to detect the magnetic flux from the magnet Mr.

[0136] As described above, the magnet holder 61 attached to the absolute encoder 2 is rotatable around a rotation axis parallel or approximately parallel to the central axis GC3 of the second intermediate gear 70, with the second sub-axis gear shaft 62 as the axis of rotation.

[0137] Furthermore, the second sub-shaft gear shaft 62 is made of a magnetic material and generates a magnetic force that biases the magnet Mr in the direction of the second sub-shaft gear shaft 62. Therefore, in the absolute encoder 2, a magnetic force from the second sub-shaft gear shaft 62 acts on the magnet Mr, and this magnetic force from the second sub-shaft gear shaft 62 attracts the magnet Mr toward the second sub-shaft gear shaft 62. When the absolute encoder 2 is in the illustrated position (upright), the lower end surface 66b of the main body portion 66 of the second sub-shaft gear 63 is in slidable contact with the upper surface 104 of the base 3, and the magnet holder 61 is biased by the axial force from the second sub-shaft gear shaft 62 so that the lower end surface 66b of the second sub-shaft gear 63 contacts the upper surface 104 of the base 3. Here, a magnet magnetized in the planar direction has the characteristic that the magnetic flux density is concentrated in the center of the magnet compared to a magnet magnetized in the radial direction. As described above, the magnet Mr is a magnetized magnet in the planar direction, and the second sub-shaft gear shaft 62 is made of a magnetic material. Therefore, the magnetic flux density of the magnet Mr is concentrated more towards the center of the magnet Mr by the magnetic material of the second sub-shaft gear shaft 62, which enables the angle sensor Sr to detect the magnetic flux accurately in the absolute encoder 2.

[0138] On the other hand, when the absolute encoder 2 is inverted from the upright position shown in the figure and its vertical direction is reversed (inverted state), the gap between the retaining ring 62d and the upper end surface 66c of the main body portion 66 of the second sub-shaft gear 63 allows the magnet holder 61 to move relative to the second sub-shaft gear shaft 62 in the direction of the central axis MC4 of the second sub-shaft gear 63. In other words, the magnet Mr moves towards the angle sensor Sr, and the angle between the magnet Mr and the angle sensorThe distance between Sr and the magnet Mr can change. However, in the absolute encoder 2, the second sub-axis gear shaft 62 is made of a magnetic material, and the second sub-axis gear shaft 62 attracts the magnet Mr toward the second sub-axis gear shaft 62 by its magnetic force. Therefore, even if the absolute encoder 2 is inverted, the magnet holder 61 is held in a state where the lower end surface 66b of the second sub-axis gear 63 is in contact with the upper surface 104 of the base 3, the magnet holder 61 maintains its position in the direction of the central axis MC4 as in the upright state, and the magnet Mr is prevented from moving toward the angle sensor Sr. Therefore, even in the inverted state, the distance between the magnet Mr and the angle sensor sensor The distance between Sr and the other element is maintained at the same distance as in the upright position.

[0139] Thus, in the absolute encoder 2, the angle between the magnet Mr and the absolute encoder 2 depends on the orientation in which the absolute encoder 2 is used. sensor Since the distance between Sr and the encoder remains constant, the influence of the operating orientation of the absolute encoder 2 on detection accuracy can be reduced.

[0140] Furthermore, the movement of the second sub-shaft gear 63 in the axial direction of the second sub-shaft gear shaft 62 is restricted by a retaining ring 62d attached to the second sub-shaft gear shaft 62. In other words, the movement of the magnet holder 61 in the axial direction of the second sub-shaft gear shaft 62 is restricted. Therefore, even if a large impact is applied to the absolute encoder 2, and a force is applied that moves the magnet holder 61 upward in the axial direction of the second sub-shaft gear shaft 62 against the magnetic force of the second sub-shaft gear shaft 62, the movement of the magnet holder 61 is restricted by the retaining ring 62d. This prevents malfunctions such as the magnet holder 61 becoming detached from the second sub-shaft gear shaft 62.

[0141] As described above, the magnet support portion 67 of the second sub-shaft gear 63 also functions as a magnet support portion, with its upper end face 67c supporting the magnet Mr on the upper side of the second sub-shaft gear 63. The magnet holder portion 65 covers the magnet Mr and the second sub-shaft gear 63 from above and functions as a magnet holder portion that holds the magnet Mr on the upper end face 67c of the magnet support portion 67.

[0142] Furthermore, the magnet holder portion 65 is made of a resin material with greater elongation characteristics at break than the second sub-shaft gear 63. The magnet holder portion 65 has a bottom surface 69a of the bottom portion 69 which functions as a magnet joint portion, and an inner circumferential surface 68a which functions as a fitting portion 65a.

[0143] Press-fit assembly is a relatively simple method that does not require special equipment and ensures concentricity between the assembled components. In press-fit structures of resin components such as the magnet holder 65 and the second sub-shaft gear 63, it is necessary to consider the holding and centering of the assembled components, as well as the holding strength of the press-fit components, by using a part of the shape of the components, specifically the outer surface 67b of the magnet support 67, as a guide. For this reason, it is necessary to select a resin material for the magnet holder 65 and the second sub-shaft gear 63 that is reinforced with fillers and has a tendency toward a low coefficient of thermal expansion and a high modulus of elasticity. However, such resin materials with a low coefficient of thermal expansion and a high modulus of elasticity are prone to cracking during press-fitting in terms of strength, and it has been difficult to obtain durability to maintain the press-fitted state.

[0144] The magnet holder portion 65, which has a fitting portion 65a, has room for deformation in the outer circumferential direction after press-fitting and is therefore susceptible to tensile stress. On the other hand, the second sub-shaft gear 63 on the shaft side that is press-fitted has no room for deformation after the magnet holder portion 65 is press-fitted, and therefore has a lower risk of failure due to stress compared to the magnet holder portion 65. Therefore, in the absolute encoder 2, by focusing on the elongation at break characteristics of the material, the magnet holder portion 65 is made of a material with a greater elongation at break than the second sub-shaft gear 63 without changing the reinforcing filler content, thereby preventing failure during press-fitting. Here, elongation at break characteristic (elongation at break) is the elongation of a test piece at the time of fracture in a tensile test, or the elongation just before fracture between a specified gauge marks.

[0145] (Second sub-shaft gear shaft) The specific shape of the second sub-shaft gear shaft 62 described above will be explained below. Figure 22 is an enlarged cross-sectional view showing one end portion 62f on the lower end surface 62a side of the second sub-shaft gear shaft 62.

[0146] As described above, the second sub-shaft gear shaft 62 of the second sub-shaft gear 63 is a shaft that is press-fitted and fixed into the through hole 137a of the shaft support portion 137 of the base portion 101 of the base 3. As shown in Figure 22, the second sub-shaft gear shaft 62 has a tapered surface portion 62e. The tapered surface portion 62e is an inclined outer surface such that the diameter of one end portion 62f is smaller than the diameter of the circumferential surface 62g. The connection portion 62h of the outer surface between the tapered surface portion 62e and the circumferential surface 62g of the second sub-shaft gear shaft 62 is connected by a curved surface. In other words, the connection portion 62h of the outer surface between the tapered surface portion 62e and the circumferential surface 62g is curved.

[0147] Figures 23 and 24 are schematic diagrams showing how the second sub-shaft gear shaft 62 is press-fitted into the through hole 137a of the base portion 101 of the base 3.

[0148] As shown in Figures 23 and 24, in another embodiment of the shaft support structure of the present invention, when the second sub-spindle gear shaft 62 is press-fitted into the through-hole 137a of the base 3, the tapered surface portion 62e is inserted into the through-hole 137a, and then the connecting portion 62h of the outer circumferential surface between the tapered surface portion 62e and the circumferential surface 62g comes into contact with the through-hole 137a. Similar to the connecting portions 126a and 127a of the tapered surface portions 126 and 127 of the spindle adapter 12, the connecting portion 62h is also curved, which allows the second sub-spindle gear shaft 62 to be smoothly press-fitted into the through-hole 137a, thus preventing both the second sub-spindle gear shaft 62 and the through-hole 137a from being worn down. Furthermore, the surface roughness Rmax (maximum roughness) of the surface of the spindle adapter 12 should be, for example, 1.6 [μm] or less. Therefore, the second sub-shaft gear shaft 62, like the main spindle adapter 12, can suppress the scattering of shavings and other debris. Furthermore, the second sub-shaft gear shaft 62 can prevent it from tilting (tilting) during press-fitting, which can occur due to material being machined. In addition, by suppressing the tilt of the second sub-shaft gear shaft 62, the press-fitting allowance (the dimension required for press-fitting) can be reduced.

[0149] Furthermore, in the support structure for the shaft of the absolute encoder 2, the example of a curved surface being applied to the connection portion of the outer circumferential surface between the tapered surface and the circumferential surface of the shaft that is press-fitted into the support member is not limited to the main shaft adapter 12 or the second sub-shaft gear shaft 62 described above. In the absolute encoder 2, for example, a curved surface may be applied to the connection portion of the outer circumferential surface between the tapered surface and the circumferential surface of the support shaft of the first sub-shaft gear 30.

[0150] In the absolute encoder 2, the main shaft gear 10, the first intermediate gear 20, the first sub-shaft gear 30, the second intermediate gear 70, and the second sub-shaft gear 63 are provided as described above. The rotation axes of the main shaft gear 10 and the first sub-shaft gear 30 are parallel to each other, and the rotation axis of the first intermediate gear 20 is in a twisted position relative to the rotation axes of the main shaft gear 10 and the first sub-shaft gear 30, respectively. The rotation axes of the first sub-shaft gear 30, the second intermediate gear 70, and the second sub-shaft gear 63 are also parallel to each other. This arrangement of gears makes it possible to determine the amount of rotation of the main shaft gear 10 over multiple rotations according to the detection results of the angle sensors Sq and Sr. Because the rotation axis of the first intermediate gear 20 is in a twisted position relative to the rotation axes of the main shaft gear 10 and the first sub-shaft gear 30 and is perpendicular to them in a front view, the absolute encoder 2 can be made thinner by configuring a curved transmission path.

[0151] (Backlash reduction mechanism) As described above, the absolute encoder 2 has a biasing mechanism 40 that biases the second worm gear section 22 toward the second worm wheel section 31, and the biasing mechanism 40 is a backlash reduction mechanism that reduces the backlash between the second worm gear section 22 and the second worm wheel section 31. As shown in Figures 5, 6, 11, 14, etc., the biasing mechanism 40 has a biasing spring 41, a support projection 45, and a screw 8b for fixing the biasing spring 41 to the support projection 45. In addition, the through hole 143 of the support projection 131 and the through hole 145 of the support projection 141 of the base 3 described above also constitute the biasing mechanism 40.

[0152] The biasing spring 41 is an elastic member that generates a pressing force to press the second worm gear portion 22 toward the second worm wheel portion 31. The biasing spring 41 is, for example, a leaf spring and is formed from a metal plate. As shown in Figures 12 and 14, the biasing spring 41 specifically has a spring portion 42 which is elastically deformed to generate a pressing force, and an engaging portion 43 and a fixing portion 44 which are opposing portions sandwiching the spring portion 42. The engaging portion 43 and the fixing portion 44 are portions that form a pair of ends in the biasing spring 41.

[0153] The fixing portion 44 is formed so as to be fixable by a screw 8b to a support projection 45 that protrudes from the upper surface 104 of the base portion 101 of the base 3. The screw 8b is an example of a fixing member, and the fixing portion 44 has a hole 44a through which the screw 8b is inserted. The fixing portion 44 extends in a planar shape and is fixed to the support projection 45 by the screw 8b while in contact with the planar support surface 45a of the support projection 45.

[0154] The engaging portion 43 has a shape that allows it to engage with the sub-shaft end 23b of the first intermediate gear shaft 23. The engaging portion 43 has an engaging groove 43a that forms a gap along the direction of extension from the spring portion 42 of the engaging portion 43, as shown in Figures 13 and 14, for example. The engaging groove 43a is a groove that opens towards the tip edge 43b, which is the end edge opposite to the connection portion 43c with the spring portion 42 of the engaging portion 43, and forms a bifurcated branch like one end 9a of the leaf spring 9 described above. The engaging portion 43 also extends in a planar shape. An annular groove called a receiving groove 23d is formed at the sub-shaft end 23b of the first intermediate gear shaft 23, extending in a direction perpendicular or approximately perpendicular to the central axis of the first intermediate gear shaft 23, and the engaging groove 43a of the engaging portion 43 is capable of engaging with this receiving groove 23d. One side of the engagement groove 43a, parallel to the vertical direction, presses against the first intermediate gear shaft 23 in the engaged groove 23d, thereby biasing the first intermediate gear 20 so that the second worm gear portion 22 moves toward the second worm wheel portion 31. In addition, two sides of the engagement groove 43a, parallel to the left and right directions, contact the first intermediate gear shaft 23 in the engaged groove 23d, and the vertical movement of the biasing spring 41 is restricted by the first intermediate gear shaft 23.

[0155] The spring portion 42 has a shape that is easily elastically deformed in the direction of engagement of the engaging portion 43 with the first intermediate gear shaft 23. Specifically, as shown in Figure 14, it has a shape that is easily deflected in the direction of extension of the engaging groove 43a. For example, the spring portion 42 is curved to protrude in the direction opposite to the direction that biases the first intermediate gear 20.

[0156] The biasing spring 41 is fixed to the support projection 45 at the fixing part 44 by a screw 8b, with the spring portion 42 rising from the fixing part 44 on the opposite side from the support projection 45. In this fixed state, the dimensions of the spring portion 42 and the engaging portion 43, the angle of the engaging portion 43 relative to the extending direction of the spring portion 42, etc., are set so that the engaging groove 43a of the engaging portion 43 engages with the engaged groove 23d of the first intermediate gear shaft 23, and in this engaged state, the spring portion 42 generates a pressing force that presses the engaging portion 43 against the first intermediate gear shaft 23. When the aforementioned retaining ring (not shown) is attached to the first intermediate gear shaft 23, the retaining ring 144 is in contact with the outer surface of the support projection 141 in this fixed and engaged state of the biasing spring 41. Backlash reduction will be described later. mechanism Therefore, it is preferable that the engagement groove 43a of the engagement portion 43 extends in a direction perpendicular or substantially perpendicular to the central axis of the first intermediate gear shaft 23 when the biasing spring 41 is fixed. Furthermore, since this biasing spring 41 can also restrict the movement of the first intermediate gear shaft 23 in the direction of the central axis, the retaining ring may be omitted as described above.

[0157] As shown in Figures 5, 6, 11, and 14, the leaf spring 9 and the biasing spring 41 are formed as a single unit. Specifically, the other end 9b of the leaf spring 9 and the fixing portion 44 of the biasing spring 41 are formed as a single unit and are made of the same material. In other words, the leaf spring 9 and the biasing spring 41 are formed from a continuous elastic member, and the leaf spring 9 and the biasing spring 41 are each part of this continuous elastic member, with the other end 9b of the leaf spring 9 and the fixing portion 44 of the biasing spring 41 being formed on the same part of this continuous elastic member.

[0158] Next, the operation of the biasing mechanism 40 of the absolute encoder 2 will be explained.

[0159] In the absolute encoder 2, the first intermediate gear shaft 23 is supported by the base 3, with its main shaft end 23a inserted through a through hole 143 formed in a support projection 131 of the base 3, and its sub-shaft end 23b inserted through a through hole 145 formed in a support projection 141 of the base 3. In this way, the first intermediate gear shaft 23 is supported by the support projections 131 and 141.

[0160] The first intermediate gear 20 is rotatably supported on the first intermediate gear shaft 23 in this manner. Furthermore, due to the action of the leaf spring 9, the first intermediate gear 20 is biased toward the support projection 141, and the sub-shaft side sliding portion 26 of the first intermediate gear 20 is in contact with the inner surface 141a of the support projection 141 (see Figure 13).

[0161] As described above, the elongated through-hole 145 supporting the sub-shaft end 23b of the first intermediate gear shaft 23 has a longer major axis than a minor axis, and the sub-shaft end 23b is supported so as to be movable along the major axis of the through-hole 145, that is, along the horizontal plane, within the width of the major axis of the through-hole 145. On the other hand, the through-hole 143 supporting the main shaft end 23a of the first intermediate gear shaft 23 is a round hole. Therefore, in the absolute encoder 2, the first intermediate gear shaft 23 is able to swing along the horizontal plane with the support portion of the main shaft end 23a as the center or approximately the center, by means of the through-holes 143 and 145 of the support projections 131 and 141 and the biasing mechanism 40.

[0162] Furthermore, the engaging portion 43 of a biasing spring 41 is engaged with the engaging groove 23d of the sub-shaft end 23b of the first intermediate gear shaft 23, which is supported in this manner. The biasing spring 41 applies a biasing force to the sub-shaft end 23b of the first intermediate gear shaft 23 so that the second worm gear portion 22 of the first intermediate gear 20 is pressed toward the second worm wheel portion 31 of the first sub-shaft gear 30 (second meshing direction P2). As a result, the second worm gear portion 22 of the first intermediate gear 20 is pressed toward the second worm wheel portion 31 of the first sub-shaft gear 30, causing the second worm gear portion 22 and the second worm wheel portion 31 to bottom out, resulting in zero backlash between the gears.

[0163] Furthermore, since the sub-shaft end 23b on the moving side of the pivotably supported first intermediate gear shaft 23 is biased by a biasing spring 41, the first intermediate gear shaft 23 is constantly biased in the direction that the second worm gear section 22 moves toward the second worm wheel section 31 during oscillation. As a result, the oscillation of the first intermediate gear shaft 23 does not cause any problems in the rotation between the gears, and the backlash between the second worm gear section 22 and the second worm wheel section 31 can always be kept at zero.

[0164] For example, if the ambient temperature around the absolute encoder 2 becomes high, the first sub-shaft gear 30 expands according to the coefficient of linear expansion of its material, and the pitch circle of the gear of the second worm wheel portion 31 expands. At this time, if the through hole 145 formed in the support projection 141 of the base 3 is a round hole rather than an elongated hole as in this embodiment, the sub-shaft side end 23b of the first intermediate gear shaft 23 will be fixed by the through hole 145, and the first intermediate gear shaft 23 will not be able to swing as in this embodiment. As a result, the second worm wheel portion 31 of the first sub-shaft gear 30, whose pitch circle has expanded due to the temperature rise, may come into contact with the second worm gear portion 22 of the first intermediate gear 20 with a strong force, and the gear may stop rotating.

[0165] Conversely, if the ambient temperature of the absolute encoder 2 becomes low, the first sub-shaft gear 30 will contract according to the coefficient of linear expansion of its material, and the pitch circle of the gear of the second worm wheel portion 31 will shrink. At this time, if the through hole 145 formed in the support projection 141 of the base 3 is a round hole rather than an elongated hole as in this embodiment, the sub-shaft side end 23b of the first intermediate gear shaft 23 will be fixed by the through hole 145, and the first intermediate gear shaft 23 will not be able to swing as in this embodiment. In this case, the first intermediate gear 20 The backlash between the second worm gear section 22 and the second worm wheel section 31 of the first sub-shaft gear 30 becomes large, and the rotation of the first intermediate gear 22 is no longer transmitted accurately to the first sub-shaft gear 30.

[0166] In contrast, in the absolute encoder 2 according to this embodiment, as described above, the first intermediate gear shaft 23 is supported so as to be able to swing along the horizontal plane with the support portion of the main shaft side end 23a as the center or approximately the center, and the first intermediate gear 20 is always biased from the second worm gear portion 22 side to the second worm wheel portion 31 side by the biasing mechanism 40. Furthermore, the first intermediate gear 20 supported on the first intermediate gear shaft 23 is biased toward the support projection 141 by the leaf spring 9. Therefore, even if a change in ambient temperature occurs as described above and the pitch circle of the gear of the second worm wheel portion 31 of the first sub-shaft gear 30 changes, the tooth surfaces of the second worm gear portion 22 and the second worm wheel portion 31 are always in contact with an appropriate pressing force, resulting in zero backlash. Therefore, it is possible to avoid the gears stopping rotating due to temperature changes or the accuracy of the rotation transmitted from the first intermediate gear 20 to the first sub-shaft gear 30 deteriorating.

[0167] Therefore, in the absolute encoder 2, the impact of the backlash of the reduction mechanism on detection accuracy can be reduced. This makes it possible to widen the range of rotation amounts of the spindle 1a that can be identified while maintaining the resolution of the rotation amount of the spindle 1a that can be identified.

[0168] Furthermore, it is preferable to set the biasing mechanism 40 such that a constant or approximately constant pressing force is generated from the biasing spring 41 regardless of the position of the sub-shaft end 23b of the first intermediate gear shaft 23 due to the oscillation.

[0169] As described above, the through hole 143 of the support projection 131 that supports the main shaft side end 23a of the first intermediate gear shaft 23 is a round hole, and the through hole 145 of the support projection 141 that supports the sub-shaft side end 23b is an elongated hole with a width on the long axis side greater than the width on the short axis side, so that the first intermediate gear shaft 23 can swing horizontally parallel or approximately parallel with the through hole 143 of the support projection 131 as a pivot point. For this reason, when the first intermediate gear shaft 23 swings, the amount of movement of the second worm gear portion 22 relative to the second worm wheel portion 31 is greater than the amount of movement of the first worm wheel portion 21 relative to the first worm gear portion 11, so that even if the second worm gear portion 22 and the second worm wheel portion 31 bottom out, the first worm gear portion 11 and the first worm wheel portion 21 do not bottom out.

[0170] As shown in Figures 10-13, the through-hole 145 supporting the first intermediate gear shaft 23 at the sub-shaft end 23b forms a cylindrical or substantially cylindrical surface, but the through-hole 145 is not limited to having such a shape. For example, as shown in Figure 25, the through-hole 145 may have a rectangular or substantially rectangular cross-sectional shape instead of an elongated hole. In other words, the through-hole 145 may be a rectangular prism-shaped through-hole forming a pair of opposing surfaces 145a and a pair of opposing surfaces 145b. The pair of surfaces 145a and 145b forming the through-hole 145 may be flat or curved. In the absolute encoder 2, the pair of surfaces 145a extends horizontally, and the pair of surfaces 145b extends vertically. The horizontal width of surface 145a is longer than the vertical width of surface 145b. In the through-hole 145 shown in Figure 25, the first intermediate gear shaft 23 can be made swingable in the same way as the through-hole 145 described above.

[0171] Similarly, the through-hole 143 is not limited to having the shape described above. For example, the through-hole 143 may have a so-called knife-edge structure. Specifically, the through-hole 143 may contact the first intermediate gear shaft 23 by line contact or point contact. For example, as shown in Figures 26(a) and (b), the through-hole 143 may be formed by a pair of conical or substantially conical inclined surfaces 143c that decrease in diameter towards the interior in the extending direction of the through-hole 143. In this case, the through-hole 143 contacts and supports the first intermediate gear shaft 23 at an annular line (connecting line 143d) that draws a round hole at the point where the pair of inclined surfaces 143c connect. The round hole shape of the connecting line 143d has a similar shape in plan view to the round hole shape of the through-hole 143 described above. Since the through-hole 143 supports the first intermediate gear shaft 23 by line contact or point contact, the first intermediate gear shaft 23 can still swing even if the diameter of the round hole in the through-hole 143 is made closer to the diameter of the first intermediate gear shaft 23. For this reason, the cross-sectional shape of the through-hole 143 can be made closer to a shape that does not have a gap between the through-hole 143 and the first intermediate gear shaft 23. This makes it possible to suppress the movement of the part of the first intermediate gear shaft 23 that contacts the through-hole 143 when the first intermediate gear shaft 23 swings, and to suppress fluctuations in the distance between the first worm gear part 11 and the first worm wheel part 21 due to the swing of the first intermediate gear shaft 23. The through-hole 145 of the support projection 141 may also have a so-called knife-edge structure like the through-hole 143 of the support projection 131 described above, or it may be formed by a pair of conical or substantially conical inclined surfaces that form an annular line drawing an elongated hole.

[0172] Furthermore, as shown in Figures 27(a) and (b), the through hole 145 may be formed by a pair of square pyramidal or substantially square pyramidal inclined surfaces 145e that become narrower toward the interior in the direction of extension of the through hole 145. In this case, the through hole 145 contacts and supports the first intermediate gear shaft 23 at the annular line (connecting line 145f) that forms a square or substantially square shape at the point where the pair of inclined surfaces 145e connect. The connecting line 145f has a pair of opposing parts, namely line sections 145g and a pair of opposing parts, namely line sections 145h. The pair of line sections 145g and the pair of line sections 145h may be straight or curved. In the absolute encoder 2, the pair of line sections 145g extends horizontally, and the pair of line sections 145h extends vertically. The length of the line section 145g is longer than the vertical length of the line section 145h. Furthermore, the through-hole 143 of the support projection 131 may also be formed by a pair of square pyramidal or roughly square pyramidal inclined surfaces that form an annular line drawing a square or roughly square, similar to the through-hole 145 of the support projection 142 described above. In this case, the annular line will be a square or roughly square. In this case as well, as in the case of Figure 26 described above, the through-hole 143 supports the first intermediate gear shaft 23 by line contact or point contact, so even if the length of the vertically extending line portion (corresponding to the line portion 145h in Figure 27) and the length of the horizontally extending line portion (corresponding to the line portion 145g in Figure 27) are made closer to the diameter of the first intermediate gear shaft 23, the first intermediate gear shaft 23 can still be made to swing. For this reason, the shape of the through-hole 143 can be made closer to a shape that does not have vertical or horizontal gaps between the through-hole 143 and the first intermediate gear shaft 23. This makes it possible to suppress the movement of the portion of the first intermediate gear shaft 23 that contacts the through hole 143 when the first intermediate gear shaft 23 swings, and to suppress fluctuations in the distance between the first worm gear portion 11 and the first worm wheel portion 21 due to the swing of the first intermediate gear shaft 23.

[0173] (Control Unit) Next, the control unit of the absolute encoder 2 will be described. Figure 28 is a view of the circuit board 5 shown in Figure 2, seen from the bottom 5a side. The microcontroller 51, line driver 52, bidirectional driver 53, and connector 6 are mounted on the circuit board 5. The microcontroller 51, line driver 52, bidirectional driver 53, and connector 6 are electrically connected by pattern wiring on the circuit board 5.

[0174] The bidirectional driver 53 performs bidirectional communication with an external device connected to the connector 6. The bidirectional driver 53 converts data such as operation signals into differential signals and communicates with the external device. The line driver 52 converts data representing the amount of rotation into differential signals and outputs the differential signals to the external device connected to the connector 6 in real time. The connector of the external device is connected to the connector 6.

[0175] Figure 29 is a block diagram schematically showing the functional configuration of the absolute encoder 2 shown in Figure 1. Each block of the microcontroller 51 shown in Figure 29 represents a function that is realized by the CPU (Central Processing Unit) of the microcontroller 51 executing a program.

[0176] The microcontroller 51 includes a rotation angle acquisition unit 51p, a rotation angle acquisition unit 51q, a rotation angle acquisition unit 51r, a table processing unit 51b, a rotation amount determination unit 51c, and an output unit 51e. The rotation angle acquisition unit 51p acquires the rotation angle Ap of the main spindle gear 10 based on the signal output from the angle sensor Sp. The rotation angle Ap is angle information indicating the rotation angle of the main spindle gear 10. The rotation angle acquisition unit 51q acquires the rotation angle Aq of the first sub-spindle gear 30 based on the signal output from the magnetic sensor Sq. The rotation angle Aq is angle information indicating the rotation angle of the first sub-spindle gear 30. The rotation angle acquisition unit 51r acquires the rotation angle Ar of the magnet holder 61, i.e., the second sub-spindle gear 63, based on the signal output from the magnetic sensor Sr. The rotation angle Ar is angle information indicating the rotation angle of the second sub-spindle gear 63.

[0177] The table processing unit 51b refers to a first correspondence table that stores the rotational speeds of the spindle gear 10 corresponding to the rotational angle Aq of the first sub-spindle gear 30 and the rotational angle Ar of the second sub-spindle gear 63, and identifies the rotational speeds of the spindle gear 10 corresponding to the acquired rotational angles Aq and Ar. The rotational amount identification unit 51c identifies the rotational amount of the spindle gear 10 over multiple rotations according to the rotational speed of the spindle gear 10 (spindle 1a) identified by the table processing unit 51b and the acquired rotational angle Ap. The output unit 51e converts the rotational amount of the spindle gear 10 over multiple rotations identified by the rotational amount identification unit 51c into information indicating this rotational amount and outputs it.

[0178] Although embodiments of the present invention have been described above, the present invention is not limited to the absolute encoder 2 according to the above embodiments of the present invention, but includes all embodiments included in the concept and claims of the present invention. Furthermore, each component may be selectively combined as appropriate, or combined with known technologies, in order to achieve at least some of the above-described problems and effects. For example, the shape, material, arrangement, size, etc. of each component in the above embodiments may be appropriately changed depending on the specific use of the present invention. [Explanation of symbols]

[0179] 1…Motor, 1a…Spindle, 1b…Press-fit section, 2…Absolute encoder, 3…Base, 3a…Support plate, 4…Case, 4a…Outer wall section, 4b…Lid section, 4c…Claw section, 5…Circuit board, 5a…Bottom surface, 5b…Positioning hole, 6…Connector, 8a…Screw, 8b…Screw, 8c…Screw, 9…Leaf spring, 9a…One end, 9b…Other end, 10…Spindle gear, 11…First worm gear section, 12…Spindle adapter, 12a…Upper end surface, 13…Cylindrical section, 13a…Upper end surface, 14…Press-fit section, 15…Magnet holder section, 15a…Inner circumferential surface, 15b…Bottom surface, 20…First intermediate gear, 21…First worm wheel 22... Second worm gear section, 23... First intermediate gear shaft, 23a... Main shaft side end, 23b... Sub-shaft side end, 23c... Groove, 23d... Engaged groove, 24... Cylindrical section, 24a... Through hole, 24b... Inner circumferential surface, 25... Main shaft side sliding section, 26... Sub-shaft side sliding section, 30... First sub-shaft gear, 31... Second worm wheel section, 32... Gear section, 33... Through hole, 35... Magnet holder, 35a... Magnet holding section, 35b... Shaft section, 35c... Bearing stopper, 35d... Bearing positioning member, 40... Biasing mechanism, 41... Biasing spring, 42... Spring section, 43... Engaged section, 43a... Engaged groove, 43b... Tip edge, 43c...connection part, 44...fixing part, 44a...hole, 45...support projection, 45a...support surface, 51...microcontroller, 51b...table processing unit, 51c...rotation amount determination unit, 51e...output unit, 51p...rotation angle acquisition unit, 51q...rotation angle acquisition unit, 51r...rotation angle acquisition unit, 52...line driver, 53...bidirectional driver, 60...magnetic detection device, 61...magnet holder, 62...second sub-shaft gear shaft, 62a...lower end surface, 62b...upper end surface, 62c...groove, 62d...retaining ring, 62e...tapered surface part, 62f...one end, 62g...circumferential surface, 62h...connection part, 63...second sub-shaft gear, 64...gear part, 65...Magnet holder part, 65a...Fitting part, 65b...Magnet housing part, 66...Main body part, 66a...Through hole, 66b...Lower end surface, 66c...Upper end surface, 67...Magnet support part, 67a...Inner circumferential surface, 67b...Outer circumferential surface, 67c...Upper end surface, 68...Cylinder part, 68a...Inner circumferential surface, 68b...Inner circumferential surface, 68c...Open end, 68d...Closed end, 68e...Outer circumferential surface, 69...Bottom part, 69a...Bottom surface, 69b...Opening, 70...Second intermediate gear, 71...Gear part, 72...Gear part, 73...Main body part, 73a...Lower end surface, 73b...Upper end surface, 74...Through hole, 75...Shaft, 75a...Lower end surface, 75b...Upper end surface, 75c...Groove76…Retaining ring, 78…Screw, 100…Shielding member, 101…Base, 102…Bottom surface, 103…Recess, 104…Top surface, 105…Outer peripheral surface, Right outer peripheral surface, 106…Rear outer peripheral surface, 106…Outer peripheral surface, 107…Left outer peripheral surface, 107…Outer peripheral surface, 108…Outer peripheral surface, 108…Front outer peripheral surface, 110…Substrate support, 111…Upper end surface, 112…Screw hole, 120…Substrate positioning pin, 121…Tip, 122…Base, 123…Stepped surface, 124…One end, 125…Other end, 126…Tapered surface, 126a…Connecting part, 127…Tapered surface, 127a…Connecting part, 128…Through hole, 128a…First hole, 128b…End Part, 128c...Second hole part, 129...Circumferential surface, 131...Support projection, 131a...Outer surface, 132...Support projection, 132a...Protrusion, 134...Bearing holder part, 135...Bearing, 136...Shaft support part, 136a...Through hole, 137...Shaft support part, 137a...Through hole, 141...Support projection, 141a...Inner surface, 142...Support projection, 143...Through hole, 143c...Inclined surface, 143d...Connecting wire, 144...Retaining ring, 145...Through hole, 145a...Surface, 145b...Surface, 145e...Inclined surface, 145f...Connecting wire, 145g...Line part, 145h...Line part, Ap...Angle information, Aq...Angle information, BC...Center of the bearing shaft GC1...Central axis of the main spindle gear, GC2...The 1 GC3...Center axis of sub-shaft gear, GC4...Center axis, MoC...Center axis of motor main spindle, Mp...Magnet, Mpa...Top surface, Mpb...Bottom surface, MpC...Center axis of magnet, Mpd...Outer surface, MQ...Magnet, MQa...Top surface, MQb...Bottom surface, MQC...Center axis of magnet, MQd...Outer surface, Mr...Magnet, Mra...Top surface, Mrb...Bottom surface, MrC...Center axis of magnet, Mrd...Outer surface, P...Biasing direction, P1...First meshing direction, P2...Second meshing direction, R1...First speed change mechanism, R2...Second speed change mechanism, SaC...Center axis of main spindle adapter, SC...Center axis of magnet holder, Sp...Angle sensor, Sq...Angle sensor, Sr...Angle sensor, XYZ...Orthogonal coordinate system

Claims

1. The axis and A support member having a hole into which the shaft is press-fitted from one end, It is a shaft support structure equipped with, The aforementioned shaft is The aforementioned end has a tapered surface portion whose diameter is smaller than the diameter of the circumferential surface, The tapered surface portion has a curved surface at the connection point with the circumferential surface. The shaft has a through hole that penetrates from one end to the other end. The through hole is such that the diameter of the hole in a region of a predetermined length in the axial direction from one end is larger than the diameter of the hole on the other end. Axle support structure.

2. A magnetized magnet and A magnetic sensor that detects the magnetic flux from the magnet, A magnet holder for holding the aforementioned magnet, A shaft that rotatably supports the aforementioned magnet, A support member having a hole into which the shaft is press-fitted from one end, Equipped with, The aforementioned shaft is A region of a predetermined length extending axially from one end of the circumferential surface, comprising a press-fit portion that is press-fitted into the hole, The aforementioned end has a tapered surface portion whose diameter is smaller than the diameter of the circumferential surface, The tapered surface portion has a curved surface at the connection point with the circumferential surface. The shaft has a through hole that penetrates from one end to the other end. The through hole is such that the diameter of the hole in a region of a predetermined length in the axial direction from one end is larger than the diameter of the hole on the other end. Magnetic detection device.

3. A magnet support portion that supports the magnet on the tip side of the shaft, A magnet holding part that covers the magnet and the magnet support part from the tip side of the shaft and holds the magnet towards the tip side of the shaft, Equipped with, The magnet holding portion is formed of a material with greater elongation at break characteristics than the magnet support portion. A magnetic joint portion that contacts the tip side surface and outer circumference of the shaft of the magnet, A fitting portion that fits with the outer circumference of the magnet support portion, Having, The magnetic detection device according to claim 2.

4. An absolute encoder comprising the magnetic detection device according to claim 2 or 3.

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