Encoders, drive units, and robots

Abstract

We provide an encoder that accurately detects position by incorporating a gear mechanism and an optical unit. [Solution] The encoder 32 comprises a gear mechanism 41, an optical unit 42, a through hole 91 through which a shaft 33 is inserted, and a partition wall 43 separating the gear mechanism 41 and the optical unit 42. The main gear 51 of the gear mechanism 41 is annular in shape surrounding the shaft 33 and has a projection 44 that protrudes toward the optical unit 42 side along the axial direction of the shaft 33. The through hole 91 is spaced apart from the shaft 33. The partition wall 43 has a first recess 92 that opens toward the projection 44 side. The first recess 92 is annular in shape surrounding the shaft 33, and the tip of the projection 44 and the first recess 92 overlap in a plan view from the axial direction of the shaft 33.

Description

Technical Field

[0001] The present invention relates to an encoder, a driving device, and a robot.

Background Art

[0002] For example, Patent Document 1 discloses an encoder including a gear mechanism and an optical encoder device having an optical detector. The encoder has a first housing that isolates between the gear mechanism and the optical encoder device via a seal portion. In the encoder described in Patent Document 1, the seal portion shields the intrusion of grease, wear powder, etc. from the gear mechanism into the optical detector.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the encoder described in Patent Document 1, even if the intrusion of grease, wear powder, etc. from the gear mechanism into the optical encoder device is shielded, wear powder is generated due to the contact between the shaft and the seal portion, and there is a risk that the wear powder may enter the optical encoder device and accurate position detection may not be possible.

Means for Solving the Problems

[0005] An encoder according to an application example of the present invention comprises a gear mechanism having a main gear fixed to a shaft and a sub-gear that meshes with the main gear; an optical unit having an optical scale fixed to the shaft and an optical sensor that receives light from the optical scale; and a partition wall having a through hole through which the shaft is inserted, separating the gear mechanism and the optical unit from each other, wherein the main gear is annular in shape surrounding the shaft and has a projection that protrudes toward the optical unit along the axial direction of the shaft; the through hole is spaced apart from the shaft; the partition wall has a first recess that opens toward the projection; the first recess is annular in shape surrounding the shaft; and the tip of the projection and the first recess overlap in a plan view from the axial direction of the shaft.

[0006] An encoder according to an application example of the present invention comprises a gear mechanism having a main gear fixed to a shaft and a sub-gear that meshes with the main gear; an optical unit having an optical scale fixed to the shaft and an optical sensor that receives light from the optical scale; and a partition wall having a through hole through which the shaft is inserted, separating the gear mechanism and the optical unit from each other. The main gear is annular in shape surrounding the shaft and has a projection that protrudes toward the optical unit along the axial direction of the shaft. The through hole is spaced apart from the shaft. The shaft has a recess that opens toward the projection at a position closer to the optical unit than the projection. The recess is annular in shape surrounding the outer circumference, and the tip of the projection and the recess overlap in a plan view from the axial direction of the shaft.

[0007] An encoder according to an application example of the present invention comprises a gear mechanism having a main gear fixed to a shaft and a sub-gear that meshes with the main gear; an optical unit having an optical scale fixed to the shaft and an optical sensor that receives light from the optical scale; and a partition wall having a through hole through which the shaft is inserted, separating the gear mechanism and the optical unit from each other, wherein the main gear is annular in shape surrounding the shaft and has a projection that protrudes toward the optical unit along the axial direction of the shaft; the through hole is spaced apart from the shaft; the partition wall has a projection that protrudes toward the shaft from the partition wall side forming the through hole; the projection has a projection side that connects to the partition wall side; and a part of the tip of the projection and a part of the projection side overlap in a plan view from the axial direction of the shaft.

[0008] An example of the application of the present invention includes a drive device comprising the encoder and a motor having the shaft.

[0009] A robot according to an application example of the present invention comprises the encoder and a robot arm whose position is detected by the encoder. [Brief explanation of the drawing]

[0010] [Figure 1] This is a side view showing the configuration of the robot system. [Figure 2] This is a schematic cross-sectional view showing the configuration of the drive system of the robot. [Figure 3] This is a cross-sectional view showing the configuration of an encoder according to the first embodiment. [Figure 4] This is a plan view showing the configuration of an optical scale. [Figure 5] This figure shows a magnified view of region A in Figure 3. [Figure 6] This is a cross-sectional view showing a part of the encoder according to the second embodiment. [Figure 7] This is a cross-sectional view showing a part of the encoder according to the third embodiment. [Figure 8] This is a cross-sectional view showing a part of the encoder according to the fourth embodiment. [Modes for carrying out the invention]

[0011] <First Embodiment> The robot system 1 according to the first embodiment will be described with reference to Figure 1. In the following figures, the scale of each layer and component has been altered from the actual scale in order to make each component recognizable.

[0012] For the sake of explanation, each diagram shows three mutually orthogonal axes: the X-axis, Y-axis, and Z-axis. The direction along the X-axis is called the "X-axis direction," the direction along the Y-axis is called the "Y-axis direction," and the direction along the Z-axis is called the "Z-axis direction." The side of each axis indicated by the arrow is called the "positive side," and the side opposite the arrow is called the "negative side." The plane parallel to the plane containing the X-axis and Y-axis is called the "XY plane." The Z-axis direction is vertical, the +Z direction is vertically upward, and the -Z direction is vertically downward.

[0013] Figure 1 is a side view showing the configuration of robot system 1. Robot system 1 is used, for example, to perform tasks such as feeding, removing, transporting, and assembling precision equipment and its constituent parts. Robot system 1 includes a robot 2 that performs predetermined tasks and a control device 3 that controls the driving of robot 2.

[0014] Robot 2 has a base 10 fixed to the floor and a robot arm 20 connected to the base 10. Robot 2 is a horizontal articulated robot. The robot arm 20 has a first arm 11 and a second arm 12. The first arm 11 is connected to the base 10 at one end and rotates around a first axis J1 when driven. The second arm 12 is connected to the other end of the first arm 11 at one end and rotates around a second axis J2 when driven. The first axis J1 and the second axis J2 are parallel to each other. Also, the first axis J1 and the second axis J2 are parallel to the Z axis. The first arm 11 and the second arm 12 extend in directions perpendicular to the first axis J1 and the second axis J2.

[0015] The second arm 12 has a shaft 13 at its other end. The shaft 13 extends along a third axis J3. The third axis J3 is parallel to the first axis J1 and the second axis J2. When a driving force is applied, the shaft 13 moves relative to the second arm 12 in the direction of the third axis J3. The shaft 13 is also capable of rotating around the third axis J3 when a driving force is applied.

[0016] An end effector 14 is provided at the tip of the shaft 13. The end effector 14 is, for example, a hand, a suction nozzle, or a screwdriver. The end effector 14 is sometimes referred to as a tool. In this embodiment, the tip of the shaft 13 on which the end effector 14 is provided is the -Z end. However, the tip of the shaft 13 on which the end effector 14 is provided is not particularly limited and may also be the +Z end. The shaft 13 is sometimes referred to as the third arm.

[0017] Robot 2 has multiple drive devices 21 to 24 that generate driving force. Drive device 21 rotates the first arm 11 relative to the base 10. Drive device 22 rotates the second arm 12 relative to the first arm 11. Drive device 23 moves the shaft 13 relative to the second arm 12 in the direction of the third axis J3. Drive device 24 rotates the shaft 13 relative to the second arm 12 around the third axis J3.

[0018] The control device 3 independently controls the drive devices 21 to 24 to cause the robot 2 to perform a predetermined operation. The control device 3 is composed of, for example, a computer and has a processor that processes information, a memory communicably connected to the processor, and an external interface. Further, various programs executable by the processor are stored in the memory, and the processor can read and execute various programs and the like stored in the memory.

[0019] Next, the configuration of the drive devices 21 to 24 will be described with reference to FIG. 2. Since the drive devices 21 to 24 have the same configuration, the drive device 22 will be described as a representative, and the descriptions of the other drive devices 21, 23, and 24 will be omitted.

[0020] FIG. 2 is a schematic cross-sectional view showing the configuration of the drive device 22. The drive device 22 has a motor 31 and an encoder 32. The encoder 32 detects the rotational state of the shaft 33 of the motor 31. In FIG. 2, only the shaft 33 is shown among the components of the motor 31 and the encoder 32, and the display of the other components is omitted.

[0021] The motor 31 and the encoder 32 are connected to each other in the Z-axis direction. The encoder 32 is arranged on the +Z side with respect to the motor 31.

[0022] The motor 31 is, for example, various motors such as a two-phase AC brushless motor, a three-phase AC brushless motor, and a three-phase synchronous motor. The motor 31 has a shaft 33 arranged along an axis parallel to the Z-axis, a rotor fixed to the shaft 33, and a stator arranged around the rotor. The shaft 33 extends in a direction parallel to the Z-axis and rotates around the axis Jx of the shaft 33. The axis Jx is parallel to the Z-axis.

[0023] The motor 31 is fixed to the +Z side of the second arm 12. The first arm 11 is connected to the end of the shaft 33 opposite to the encoder 32. As a result, the output of the motor 31 is transmitted from the second arm 12 to the first arm 11, causing the second arm 12 to rotate relative to the first arm 11. In other words, axis Jx coincides with the second axis J2.

[0024] Next, the configuration of the encoder 32 will be described with reference to Figures 3 to 5. Figure 3 is a cross-sectional view showing the configuration of the encoder 32. Figure 4 is a plan view showing the configuration of the optical scale 71. Figure 5 is an enlarged view of area A in Figure 3. The encoder 32 comprises a gear mechanism 41, an optical unit 42, and a partition wall 43.

[0025] The encoder 32 has a housing 45. The housing 45, together with a partition wall 43, divides a first space S1 and a second space S2. The gear mechanism 41 is housed in the first space S1, and the optical unit 42 is housed in the second space S2.

[0026] The gear mechanism 41 and the optical unit 42 are separated by a partition wall 43. The gear mechanism 41, the partition wall 43, and the optical unit 42 are arranged side by side in the Z-axis direction. The gear mechanism 41 is positioned on the +Z side relative to the optical unit 42. That is, the partition wall 43 is positioned between the gear mechanism 41 and the optical unit 42 in the Z-axis direction.

[0027] The gear mechanism 41 includes a main gear 51 fixed to the shaft 33 and a secondary gear 52 that meshes with the main gear 51. The secondary gear 52 includes a first secondary gear 53 that meshes with the main gear 51 and a second secondary gear 54 that meshes with the main gear 51. The main gear 51 and the secondary gear 52 are spur gears. The first secondary gear 53 is supported by a first bearing 55. The second secondary gear 54 is supported by a second bearing 56. The rotation axis Js1 of the first secondary gear 53 and the rotation axis Js2 of the second secondary gear 54 are parallel to axis Jx.

[0028] The gear mechanism 41 has magnets 60 fixed to the auxiliary gear 52. The magnets 60 are located on the -Z side of the auxiliary gear 52 and rotate together with the auxiliary gear 52. The magnet 60 fixed to the first auxiliary gear 53 is the first magnet 61, and the magnet 60 fixed to the second auxiliary gear 54 is the second magnet 62.

[0029] The encoder 32 has a sensor substrate 57. The sensor substrate 57 is provided in the second space S2 between the partition wall 43 and the optical unit 42. A magnetic sensor 63 is provided on the sensor substrate 57. The magnetic sensor 63 overlaps the magnet 60 in a plan view from the Z-axis direction. The magnetic sensor 63 includes a first magnetic sensor 64 on which the magnetic field of the first magnet 61 acts, and a second magnetic sensor 65 on which the magnetic field of the second magnet 62 acts. The magnetic sensor 63 detects the rotation angles of the first sub-gear 53 and the second sub-gear 54 by detecting the magnetic fields of the first magnet 61 and the second magnet 62.

[0030] The number of teeth on the main gear 51, the first auxiliary gear 53, and the second auxiliary gear 54 are set to be relatively prime. For example, the main gear 51 has 25 teeth, the first auxiliary gear 53 has 24 teeth, and the second auxiliary gear 54 has 23 teeth. When the rotational speed of the shaft 33 is initially n=0, as the shaft 33 begins to rotate, the rotational angles of the first auxiliary gear 53 and the second auxiliary gear 54 gradually diverge from the main gear 51. Then, when the rotational speed n=552, the rotational angles of the main gear 51, the first auxiliary gear 53, and the second auxiliary gear 54 coincide again. The rotational speed n at which they coincide is based on 24 × 23 = 552. Therefore, between rotational speeds of 0 and 552 of the shaft 33, once the combination of the rotational angles of the first auxiliary gear 53 and the second auxiliary gear 54 is determined, the rotational speed of the shaft 33 corresponding to that combination can be detected.

[0031] The encoder 32 has a circuit (not shown) that receives a signal from the magnetic sensor 63 and detects the rotation state. The circuit that receives the signal from the magnetic sensor 63 is located on the sensor board 57.

[0032] The optical unit 42 includes an optical scale 71 fixed to the shaft 33, a light-emitting element 72 that emits light L toward the optical scale 71, and an optical sensor 73 that receives the light L from the optical scale 71.

[0033] The light-emitting element 72 and the optical sensor 73 are mounted on the sensor substrate 57 and are arranged side by side. That is, the light-emitting element 72 and the optical sensor 73 are positioned on the same side as the gear mechanism 41 in the Z-axis direction relative to the optical scale 71. The light-emitting element 72 and the optical sensor 73 face the -Z direction and are opposite to the optical scale 71. With this structure, the direction in which the light-emitting element 72 and the optical sensor 73 face is opposite to the gear mechanism 41 relative to the light-emitting element 72 and the optical sensor 73. This prevents wear particles or grease from adhering to the light-emitting element 72 and the optical sensor 73 even if wear particles or grease enter from the gear mechanism 41.

[0034] The optical scale 71 is disc-shaped and fixed to the shaft 33, and has two faces 74 and 75 that are in a front-back relationship. The optical scale 71 rotates with the shaft 33. The optical scale 71 is spaced apart from the partition wall 43, the light-emitting element 72, and the optical sensor 73. The optical scale 71 has a pattern 76 on the +Z side face 74. The pattern 76 consists of two alternating regions with different light reflectivity and is arranged along the circumferential direction of the shaft 33. The two regions with different reflectivity are the reflective portion 77 and the non-reflective portion 78.

[0035] The optical sensor 73 receives the light L emitted from the light-emitting element 72 and reflected by the pattern 76. This allows the optical unit 42 to detect the rotation angle within a 360° range of the optical scale 71. In other words, the optical unit 42 detects the rotation angle of the shaft 33 within a 360° range.

[0036] The encoder 32 has a circuit (not shown) that receives a signal from the optical sensor 73 and detects the rotation angle. The circuit that receives the signal from the optical sensor 73 is located on the sensor substrate 57. By arranging the magnetic sensor 63, the circuit that receives the signal from the magnetic sensor 63, the light-emitting element 72, the optical sensor 73, and the circuit that receives the signal from the optical sensor 73 on the sensor substrate 57, the encoder 32 can be made smaller in the Z-axis direction.

[0037] In this way, the encoder 32 can detect the rotational speed of the shaft 33 by the gear mechanism 41 and the rotation angle of the shaft 33 within a 360° range by the optical unit 42. Then, the encoder 32 can detect the amount of rotation of the shaft 33 from the rotational speed and rotation angle.

[0038] The main gear 51 has a projection 44. The projection 44 is an annular shape surrounding the shaft 33 and protrudes toward the -Z side along the Z-axis direction. The projection 44 has a tip 81, a first side surface 82 facing away from the shaft 33, a second side surface 83 facing towards the shaft 33, and a bottom surface 84 provided between the second side surface 83 and the shaft 33 and facing toward the -Z side. The first side surface 82 and the second side surface 83 are each connected to the tip 81. The bottom surface 84 is recessed toward the +Z side relative to the tip 81. The second side surface 83 is inclined with respect to the axis Jx. The second side surface 83 forms part of a cone that surrounds the shaft 33 and has its apex toward the +Z side.

[0039] In a plan view from the Z-axis direction, the position of the tip 81 is on the shaft 33 side of the meshing position P between the main gear 51 and the auxiliary gear 52. Also, the position of the tip 81 in the Z-axis direction is on the -Z side with respect to the meshing position P.

[0040] The protruding portion 44 is integrally formed with the main gear 51. The protruding portion 44 rotates together with the shaft 33.

[0041] The partition wall 43 has a through-hole 91 through which the shaft 33 is inserted, and is provided between the gear mechanism 41 and the optical unit 42, separating them from each other. The first space S1 and the second space S2 are connected only at the through-hole 91.

[0042] The inner diameter of the through-hole 91 is larger than the diameter of the shaft 33 so as not to come into contact with the shaft 33. The through-hole 91 is spaced apart from the shaft 33. That is, the side surface forming the through-hole is spaced apart from the shaft. This prevents contact between the shaft 33 and the partition wall 43, thus preventing the generation of wear particles and other debris.

[0043] The partition wall 43 has a first recess 92 that opens towards the protruding portion 44. The first recess 92 is an annular shape surrounding the shaft 33 and is located in a position surrounding the through hole 91. The first recess 92 has a third side surface 93 facing the shaft 33 and a fourth side surface 94 facing in the opposite direction from the shaft 33.

[0044] As shown in Figure 5, the tip portion 81 and the first recess 92 are aligned in the Z-axis direction. That is, in a plan view from the Z-axis direction, the tip portion 81 and the first recess 92 overlap. With this structure, wear particles and grease generated in the gear mechanism 41 can be guided to the first recess 92 by the first side surface 82 or the third side surface 93. The wear particles and grease guided to the first recess 92 are blocked by the first recess 92 and have difficulty reaching the through hole 91. Therefore, it is possible to prevent wear particles and grease from entering the optical unit 42 side from the through hole 91.

[0045] The first recess 92 is integrally formed as part of the partition wall 43. The partition wall 43 is made of polyphenylene sulfide (PPS). Polyphenylene sulfide has excellent moldability and a high degree of freedom in the shape of the molded product. Therefore, it is a suitable material for the partition wall 43 having the first recess 92.

[0046] The fourth side surface 94 surrounds the through hole 91 and forms a part of a cone with its apex on the +Z side. The fourth side surface 94 is inclined in the direction in which the opening 95 of the first recess 92 widens. That is, the fourth side surface 94 approaches the shaft 33 as it moves from the bottom 96 of the first recess 92 towards the opening 95. The angle θ1 at which the fourth side surface 94 is inclined with respect to the axis Jx is preferably 10 to 80°. When the angle θ1 is 10 to 40°, the depth of the first recess 92 can be increased, so that the amount of wear particles and grease that can be retained can be increased. When the angle θ1 is 20 to 80°, the molded partition wall 43 can be easily removed from the mold during the molding process of the partition wall 43. Therefore, a more preferable angle θ1 is 20 to 40°. In this way, the amount of wear particles and grease that can be retained can be increased. In addition, the moldability of the partition wall 43 is good.

[0047] Furthermore, the partition wall 43 has a surface 97 connecting the fourth side surface 94 and the through hole 91. The first side surface 82 faces the third side surface 93, and the bottom surface 84 faces the surface 97. With this structure, a labyrinth path can be formed by the protrusion 44 and the first recess 92. This enhances the effect of preventing wear particles and grease generated in the gear mechanism 41 from reaching the through hole 91 of the partition wall 43.

[0048] As shown in Figure 3, the optical unit 42 has a second recess 101 that opens towards the gear mechanism 41. The second recess 101 is an annular shape surrounding the shaft 33 and is provided on the +Z side surface 74 of the optical scale 71. When viewed from the Z-axis direction, the second recess 101 is provided between the pattern 76 and the shaft 33. With this structure, even if wear particles or grease enter the optical unit 42 from the gear mechanism 41 side through the through hole 91, the second recess 101 can block the wear particles or grease. Therefore, it is possible to prevent wear particles or grease from adhering to the pattern 76.

[0049] Furthermore, as shown in Figures 3 and 5, the partition wall 43 has a third recess 111 that opens towards the gear mechanism 41. The third recess 111 is an annular shape that surrounds the shaft 33. The third recess 111 is integrally formed with the partition wall 43. In the Z-axis direction, the position where the third recess 111 is provided is closer to the gear mechanism 41 than the bottom 96 of the first recess 92. In a plan view from the Z-axis direction, the position where the third recess 111 is provided is between the first bearing 55 and the first recess 92, and between the second bearing 56 and the first recess 92.

[0050] The third recess 111 has a side surface 112 on the shaft 33 side. The partition wall 43 also has a surface 113 connecting the side surface 112 and the third side surface 93. Surface 113 faces the main gear 51.

[0051] The partition wall 43 has a protrusion 114. The protrusion 114 is formed by a surface 113, a side surface 112, and a third side surface 93. The protrusion 114 is an annular shape surrounding the shaft 33 and protrudes toward the gear mechanism 41. In the Z-axis direction, the position where the protrusion 114 is provided is closer to the gear mechanism 41 than the bottom portion 96. In a plan view from the Z-axis direction, the position where the protrusion 114 is provided is between the meshing position P and the first recess 92.

[0052] This structure allows the protrusions 114 to also block wear particles and grease. Therefore, the effect of preventing wear particles and grease from entering the optical unit 42 side through the through hole 91 can be further enhanced.

[0053] Furthermore, since wear particles and grease can be retained in the third recess 111, it is possible to further prevent them from entering the optical unit 42.

[0054] In this embodiment, the shaft Jx is described as coinciding with the second shaft J2, but this is not a limiting factor. For example, the shaft 33 may be positioned offset from the second shaft J2, and the driving force may be transmitted from the shaft 33 to the second shaft J2 using, for example, a belt and pulley.

[0055] Furthermore, although the first recess 92 and the third recess 111 have been described as being integrally formed with the partition wall 43, the design is not particularly limited to this. For example, the portion including the first recess 92 and the portion including the third recess 111 may be constructed separately from the partition wall 43 and attached to the partition wall 43 by adhesive or the like.

[0056] As described above, the drive device 22 according to this embodiment includes an encoder 32 and a motor 31 having a shaft 33. With this configuration, it is possible to provide a drive device 22 that has high position detection accuracy and high reliability.

[0057] Although the description assumes that the shaft 33 of the encoder 32 is integrated with the shaft 33 of the motor 31, this is not a limiting factor, and they may be constructed as separate components. If they are constructed as separate components, the encoder 32 may have another shaft instead of the shaft 33, and the shaft of the encoder 32 and the shaft 33 of the motor 31 may be connected by a joint or the like. Furthermore, the main gear 51 and the shaft 33 may be integrated or separate components.

[0058] As described above, the robot 2 according to this embodiment includes an encoder 32 and a robot arm 20 whose position is detected by the encoder 32. With this configuration, it is possible to provide a robot 2 that has high positioning accuracy and high reliability for the robot arm 20.

[0059] Although robot 2 has been described as a horizontal articulated robot, it is not particularly limited to this, and for example, it could be a vertical articulated robot. In the case of a vertical articulated robot, the encoder 32 should be provided on the robot's base, and the gear mechanism 41 should be positioned vertically above the optical unit 42.

[0060] <Second Embodiment> The encoder 32a according to the second embodiment will be described with reference to Figure 6. Figure 6 is a cross-sectional view showing a part of the encoder 32a according to the second embodiment, and corresponds to area A in Figure 3.

[0061] The encoder 32a according to the second embodiment comprises a gear mechanism 41, an optical unit 42, and a partition wall 43 having a first recess 92. The gear mechanism 41 has a main gear 51 and a sub-gear 52. The main gear 51 has a protrusion 44. The encoder 32a is the same as the encoder 32 of the first embodiment except that the position of the first recess 92 relative to the protrusion 44 is different. The optical unit 42 is not shown in Figure 6, but it is positioned on the -Z side relative to the partition wall 43.

[0062] As shown in Figure 6, in a plan view from a direction perpendicular to the Z-axis, the tip 81 of the protrusion 44 is located inside the first recess 92. The second side surface 83 of the protrusion 44 and the fourth side surface 94 of the first recess 92 are facing each other. In other words, the protrusion 44 and the first recess 92 constitute a labyrinth path.

[0063] For wear particles and grease generated in the gear mechanism 41 to move from the meshing position P between the main gear 51 and the auxiliary gear 52 to the through hole 91, they must first move in the -Z direction through the gap between the third side surface 93 of the first recess 92 and the first side surface 82 of the projection 44. Furthermore, the wear particles and grease then need to move in a direction that includes a component in the +Z direction through the gap between the fourth side surface 94 and the second side surface 83. The +Z direction is vertically upward, and the labyrinth path includes a path that goes in a direction that includes a vertically upward component. This further enhances the effect of preventing wear particles and grease generated in the gear mechanism 41 from reaching the through hole 91 of the partition wall 43.

[0064] <Third Embodiment> The encoder 32b according to the third embodiment will be described with reference to Figure 7. Figure 7 is a cross-sectional view showing a part of the encoder 32b according to the third embodiment, and corresponds to area A in Figure 3.

[0065] The encoder 32b according to the third embodiment comprises a gear mechanism 41, an optical unit 42, a partition wall 43b, and a recess 121. The encoder 32b is the same as the encoder 32 of the first embodiment except that the recess 121 is provided on the shaft 33. The optical unit 42 is not shown in Figure 7, but is positioned on the -Z side relative to the partition wall 43b.

[0066] The shaft 33 has a recess 121 located on the -Z side of the protrusion 44, which opens towards the protrusion 44. The recess 121 is an annular shape provided around the shaft 33. The recess 121 is located on the -Z side of the through hole 91 and the protrusion 44. In a plan view from the Z-axis direction, the recess 121 overlaps with the side surface 98 of the through hole 91 and the tip 81 of the protrusion 44. With this configuration, even if wear particles or grease pass through the through hole 91, the recess 121 can block them. Therefore, it is possible to prevent wear particles or grease from entering the optical unit 42. Furthermore, since there is no need to provide the recess 121 in the partition wall 43b, the manufacturing of the partition wall 43b becomes easier, and a low-cost encoder 32b can be provided.

[0067] In a plan view from a direction perpendicular to the Z-axis, the tip 81 of the protrusion 44 is located inside the recess 121. This ensures that wear particles and grease guided by the protrusion 44 are reliably directed into the recess 121. Therefore, wear particles and grease cannot enter the optical unit 42.

[0068] The partition wall 43b has an annular recess 122 that opens to the -Z side around the through hole 91. The portion between this recess 122 and the through hole 91 is a protrusion 123 that projects to the -Z side. The portion of the protrusion 123 includes the -Z side end of the through hole 91. In a plan view from a direction perpendicular to the Z axis, the -Z side end of the through hole 91 is located inside the recess 121. Furthermore, the first side surface 82 of the protrusion 44 faces the side surface 98 of the through hole 91. In this way, wear particles and grease can be reliably guided into the recess 121. Therefore, wear particles and grease can be prevented from entering the optical unit 42.

[0069] <Fourth Embodiment> The encoder 32c according to the fourth embodiment will be described with reference to Figure 8. Figure 8 is a cross-sectional view showing a part of the encoder 32c according to the fourth embodiment, and corresponds to area A in Figure 3.

[0070] The encoder 32c according to the fourth embodiment comprises a gear mechanism 41, an optical unit 42, and a partition wall 43c. The encoder 32c is similar to the encoder 32 of the first embodiment except that the partition wall 43c has a projection 131 instead of a first recess 92. The optical unit 42 is not shown in Figure 8, but is positioned on the -Z side with respect to the partition wall 43c.

[0071] The bulkhead 43c has a projection 131 that protrudes toward the shaft 33 from the bulkhead side 132 that forms the through hole 91. The projection 131 comprises a projection side 133 and a projection side 135. The projection side 133 is connected to the bulkhead side 132. The projection side 133 connects the bulkhead side 132 to the side 98 of the through hole 91. The projection 131 protrudes toward the +X side. The bulkhead side 132 is an annular shape facing toward the shaft 33 side. The projection side 133 is an annular shape facing toward the +Z side. The angle θ2 between the bulkhead side 132 and the projection side 133 is 90°. The inner diameter of the bulkhead side 132 is larger than the inner diameter of the through hole 91.

[0072] The tip 81 of the protrusion 44 faces the projection side surface 133. A portion of the tip 81 and a portion of the projection side surface 133 overlap in a plan view from the Z-axis direction. The first side surface 82 of the protrusion 44 faces the partition wall side surface 132. In other words, the protrusion 44, the partition wall side surface 132, and the projection side surface 133 form a crank-shaped path. This reduces the intrusion of wear particles and grease generated in the gear mechanism 41 into the optical unit 42.

[0073] In this embodiment, the protruding portion 44 does not have a second side surface 83 and a bottom surface 84, but it is not limited to this.

[0074] Furthermore, the angle θ2 formed by the partition wall side surface 132 and the projection side surface 133 is not particularly limited to 90°. For example, the angle θ2 may be acute. In this way, wear particles and grease can be retained on the projection side surface 133.

[0075] Furthermore, the shape of the through hole 91 in the Z-axis direction, on the side opposite to the projection 131, is not particularly limited.

[0076] The encoders 32, 32a, 32b, 32c, drive unit 22, and robot 2 of the present invention have been described above based on the illustrated embodiments. However, the present invention is not limited thereto, and the configuration of each part can be replaced with any configuration having a similar function. Furthermore, the encoders 32, 32a, 32b, 32c, drive unit 22, and robot 2 of the present invention may have other arbitrary components added to them.

[0077] Furthermore, although the explanation assumed that the Z-axis direction is vertical, the +Z direction is vertically upward, and the -Z direction is vertically downward, it is not particularly limited to this. Even if the Z-axis direction is inclined with respect to the vertical, it is preferable that the angle of inclination is within 30°.

[0078] Furthermore, although the explanation assumed that the axis Jx of shaft 33 is parallel to the Z-axis, it is not particularly limited to this. Even if the axis Jx is inclined with respect to the Z-axis, it is preferable that the angle of inclination is within 30°. [Explanation of symbols]

[0079] 1...Robot system, 2...Robot, 3...Control device, 10...Base, 11...First arm, 12...Second arm, 13...Shaft, 14...End effector, 20...Robot arm, 21~24...Drive unit, 31...Motor, 32,32a,32b,32c...Encoder, 33...Shaft, 41...Gear mechanism, 42...Optical unit, 43,43b,43c...Bulkhead, 44...Protrusion, 45...Housing, 51...Main gear, 52...Sub-gear, 53...First sub-gear, 54...Second sub-gear, 55...First bearing, 56...Second bearing, 57...Sensor board, 60...Magnet, 61...First magnet, 62...Second magnet, 63...Magnetic sensor, 64...First magnetic sensor, 65...Second magnetic sensor 71…Optical scale, 72…Light-emitting element, 73…Optical sensor, 74,75…Surface, 76…Pattern, 77…Reflective part, 78…Non-reflective part, 81…Tip, 82…First side, 83…Second side, 84…Bottom, 91…Through hole, 92…First recess, 93…Third side, 94…Fourth side, 95…Opening, 96…Bottom, 97…Surface, 98…Surface, 101…Second recess, 111…Third recess, 112…Surface, 113…Surface, 114…Convex part, 121…Concave, 122…Concave, 123…Convex part, 131…Projection, 132…Partition side, 133…Projection side, Jx…Axis, J1…First axis, J2…Second axis, J3…Third axis, S1…First space, S2…Second space, θ1,θ2…Angle

Claims

1. A gear mechanism having a main gear fixed to a shaft and a secondary gear that meshes with the main gear, An optical unit having an optical scale fixed to the shaft and an optical sensor that receives light from the optical scale, The gear mechanism and the optical unit have a through hole through which the shaft is inserted, and a partition wall that separates them from each other. The main gear is an annular shape surrounding the shaft and has a projection that protrudes toward the optical unit side along the axial direction of the shaft. The through hole is spaced apart from the shaft. The partition wall has a first recess that opens towards the protruding portion, The first recess is an annular shape surrounding the shaft, An encoder characterized in that the tip of the protruding portion and the first recess overlap in a plan view from the axial direction of the shaft.

2. The partition wall has a protrusion that projects toward the gear mechanism side, The aforementioned protrusion is, It is an annular ring surrounding the aforementioned shaft, The encoder according to claim 1, wherein in the axial direction of the shaft, it is located on the gear mechanism side of the bottom of the first recess, and in a plan view from the axial direction of the shaft, it is positioned between the meshing position of the main gear and the sub-gear and the first recess.

3. The encoder according to claim 1 or 2, wherein the optical sensor is positioned on the same side as the gear mechanism in the axial direction of the shaft with respect to the optical scale.

4. The optical scale has a second recess that opens towards the gear mechanism side, The second recess is, It is an annular ring surrounding the aforementioned shaft, The encoder according to claim 3, which is positioned between the pattern of the optical scale and the shaft in a plan view from the axial direction of the shaft.

5. The protruding portion has a first side facing the opposite direction from the shaft, a second side facing the shaft, and a bottom surface provided between the second side and the shaft and facing the optical unit. The first recess has a third side facing the shaft and a fourth side facing in the opposite direction from the shaft. The first side faces the third side, The encoder according to claim 1 or 2, wherein the surface connecting the fourth side surface and the through hole faces the bottom surface.

6. The encoder according to claim 1 or 2, wherein, in a plan view from a direction perpendicular to the axis of the shaft, the tip of the protrusion is located inside the first recess.

7. A gear mechanism having a main gear fixed to a shaft and a secondary gear that meshes with the main gear, An optical unit having an optical scale fixed to the shaft and an optical sensor that receives light from the optical scale, The gear mechanism and the optical unit have a through hole through which the shaft is inserted, and a partition wall that separates them from each other. The main gear is an annular shape surrounding the shaft and has a projection that protrudes toward the optical unit side along the axial direction of the shaft. The through hole is spaced apart from the shaft. The shaft has a recess that opens toward the protrusion, located closer to the optical unit than the protrusion. The aforementioned recess is an annular shape surrounding the shaft, An encoder characterized in that the tip of the protruding portion and the recessed portion overlap when viewed in a plan view from the axial direction of the shaft.

8. A gear mechanism having a main gear fixed to a shaft and a secondary gear that meshes with the main gear, An optical unit having an optical scale fixed to the shaft and an optical sensor that receives light from the optical scale, The gear mechanism and the optical unit have a through hole through which the shaft is inserted, and a partition wall that separates them from each other. The main gear is an annular shape surrounding the shaft and has a projection that protrudes toward the optical unit side along the axial direction of the shaft. The through hole is spaced apart from the shaft. The partition wall has a projection that protrudes toward the shaft from the side surface of the partition wall that forms the through hole, The projection comprises a projection side that connects to the partition wall side, An encoder characterized in that a portion of the tip of the protruding part and a portion of the side surface of the protrusion overlap when viewed in a plan view from the axial direction of the shaft.

9. The encoder described in claim 1, A drive device comprising a motor having the aforementioned shaft.

10. The encoder described in claim 1, A robot comprising a robot arm whose position is detected by the encoder.

Images