Electric actuator

Abstract

To provide an electric actuator that can be miniaturized while improving durability. [Solution] The electric actuator 10 includes a motor unit 20 that holds a rotating shaft 22 and a preload member 25, a case 31, a shaft portion 32, a lead screw portion 33, and a thrust bearing 50. The rotating shaft 22 rotates integrally with the rotor 23 housed inside the housing 21. The preload member 25 is interposed between the housing 21 and the rotor 23 in the direction in which the axis L of the rotating shaft 22 extends. The shaft portion 32 is connected to the rotating shaft 22 and has a male screw formed thereon. The lead screw portion 33 is screwed onto the shaft portion 32 and moves in the direction in which the axis L extends as the shaft portion 32 rotates. The thrust bearing 50 rotatably holds the portion of the rotating shaft 22 that protrudes from the housing 21. The thrust bearing 50 is installed in a position with the rotor 23 interposed between the thrust bearing 50 and the preload member 25.

Description

Technical Field

[0004] , , , , , , , , ,

[0006] , , , ,

[0005] , , , , , , ,

[0003] ,

[0001] The present invention relates to an electric actuator.

Background Art

[0002] Conventionally, an electric actuator having a motor unit that holds a rotating shaft and a rotor, a shaft portion, and a feed screw portion is known. The electric actuator rotates the shaft portion by the motor unit, and thereby moves the feed screw portion screwed onto the shaft portion in the direction in which the axis of the rotating shaft extends. Thereby, the electric actuator operates a load connected to the feed screw portion. A preloading member may be provided in the motor unit. The motor unit suppresses relative movement of the rotating shaft and the rotor with respect to the housing of the motor unit by the preloading member.

[0003] For example, Patent Document 1 discloses an electric gripper equipped with a drive mechanism having a rotary drive source as a motor unit and a feed screw portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A load in the direction in which the axis extends may act on the rotating shaft. If the rotating shaft and the rotor move due to the load, there is a risk of a load exceeding the allowable value from the rotor to the preloading member or interference of the rotating shaft with a member provided outside the motor unit. As a result, the durability of the electric actuator may be reduced.

[0006] Furthermore, when the rotating shaft and shaft section are connected by a combination of a bearing unit and coupling capable of withstanding the load acting on the rotating shaft, the electric actuator may become larger. For these reasons, it is desirable for electric actuators to be miniaturized while improving durability. [Means for solving the problem]

[0007] The electric actuator for solving the above problems comprises a motor unit that rotates integrally with a rotor housed inside a housing and has a rotating shaft protruding from the end of the housing, and a preload member interposed between the housing and the rotor in the direction in which the axis of the rotating shaft extends, pressing the rotor against the housing; a case attached to the housing; a shaft portion connected to the rotating shaft and having a male thread formed thereon; and a feed screw portion held by the case and screwed into the shaft portion, and moving in the direction in which the axis extends as the shaft portion rotates, wherein the electric actuator operates a load connected to the feed screw portion by the rotation of the rotating shaft, and has a thrust bearing that rotatably holds the portion of the rotating shaft that protrudes from the housing, the thrust bearing is installed in a position where the rotor is interposed between the thrust bearing and the preload member.

[0008] In an electric actuator, the preload member is preferably interposed between the load and the rotor. The electric actuator further includes an encoder provided on the opposite end of the rotating shaft to which the shaft portion is connected, and configured to detect the rotation of the rotating shaft, and the preload member is preferably interposed between the encoder and the rotor.

[0009] In an electric actuator, it is preferable to have thrust bearings at both ends of the housing in the direction in which the axis extends. In an electric actuator, the thrust bearing preferably includes a fixed portion fixed to the housing, a rotating portion connected to the rotating shaft and rotating integrally with the rotating shaft, and a rolling portion held between the fixed portion and the rotating portion, which rotatably connects the rotating portion to the fixed portion. [Effects of the Invention]

[0010] According to the present invention, it is possible to improve durability while miniaturizing the electric actuator. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a cross-sectional view showing an electric actuator of the first embodiment. [Figure 2] Figure 2 is an enlarged cross-sectional view showing the electric actuator of the first embodiment. [Figure 3] Figure 3 is a cross-sectional view showing an electric actuator of the second embodiment. [Figure 4] Figure 4 is a cross-sectional view showing an electric actuator in a modified example. [Figure 5] Figure 5 is a cross-sectional view showing an electric actuator in a modified example. [Modes for carrying out the invention]

[0012] [First Embodiment] The following describes a first embodiment of the electric actuator. <Overall view of electric actuators> As shown in Figure 1, the electric actuator 10 includes a motor unit 20, a case 31, a shaft portion 32, a lead screw portion 33, an encoder 40, and a thrust bearing 50. In this embodiment, the electric actuator 10 has two thrust bearings 50. The case 31, the shaft portion 32, and the lead screw portion 33 constitute a lead screw mechanism 30. Hereafter, the direction in which the longitudinal side of the electric actuator 10 extends will be referred to as the actuator axis direction A. The electric actuator 10 has the motor unit 20 and the encoder 40 in the portion closer to the first end of the actuator axis direction A, and the lead screw mechanism 30 in the portion closer to the second end.

[0013] <Motor Unit> The motor unit 20 includes a housing 21, a rotating shaft 22, a rotor 23, a stator 24, and a preload member 25.

[0014] The housing 21 has a longitudinal dimension extending in the actuator axial direction A. The housing 21 incorporates a first radial bearing 211 and a second radial bearing 212. The housing 21 has a first housing forming member 21a located near one end in the longitudinal direction and a second housing forming member 21b located near the other end in the longitudinal direction. The housing 21 has a third housing forming member 21c located between the first housing forming member 21a and the second housing forming member 21b in the longitudinal direction.

[0015] The housing 21 has a first radial bearing 211 in a first housing forming member 21a and a second radial bearing 212 in a second housing forming member 21b. The first radial bearing 211 is provided closer to the first end of the electric actuator 10 in the actuator axial direction A. The second radial bearing 212 is provided closer to the second end of the electric actuator 10 in the actuator axial direction A. Hereinafter, among the ends of the housing 21 in the actuator axial direction A, the end closer to the first end of the electric actuator 10 is described as the first end of the housing 21. Also, among the ends of the housing 21 in the actuator axial direction A, the end closer to the second end of the electric actuator 10 is described as the second end of the housing 21.

[0016] Each of the first radial bearing 211 and the second radial bearing 212 is a ball bearing constituted by an outer ring, an inner ring, and rolling elements interposed between the outer ring and the inner ring. The motor unit 20 has an external wiring 213 outside the housing 21. The external wiring 213 is connected to the housing 21 in the first housing forming member 21a. The external wiring 213 is connected to the motor unit 20 at one end and is connected to an external power source (not shown) at the other end.

[0017] The rotating shaft 22 is a columnar body whose axis L extends in the actuator axial direction A. The rotating shaft 22 is held by the housing 21. In other words, the motor unit 20 holds the rotating shaft 22. More specifically, the rotating shaft 22 penetrates the housing 21 in the actuator axial direction A and is rotatably held with respect to the housing 21 by the first radial bearing 211 and the second radial bearing 212. The portion of the rotating shaft 22 closer to the first end is held by the first radial bearing 211, and the portion closer to the second end is held by the second radial bearing 212.

[0018] The rotating shaft 22 protrudes from the end of the housing 21. More specifically, the rotating shaft 22 is held by the housing 21 such that both ends in the direction in which the axis L extends protrude from the housing 21.

[0019] The rotor 23 is a cylindrical body whose central axis extends in the actuator axis direction A. The rotor 23 is housed inside the housing 21. More specifically, the rotor 23 is housed in a portion inside the housing 21 that lies between the first radial bearing 211 and the second radial bearing 212 in the actuator axis direction A.

[0020] The rotating shaft 22 passes through the rotor 23. The rotor 23 is fixed to the rotating shaft 22 so as to be rotatable integrally with the rotating shaft 22. That is, the rotating shaft 22 rotates integrally with the rotor 23. The central axis of the rotor 23 coincides with the axis L.

[0021] Washers 231 are provided at both ends of the rotor 23 in the direction in which the central axis extends. The rotor 23 is connected to each of the first radial bearing 211 and the second radial bearing 212 via the washer 231. The rotor 23 is connected to the housing 21 via the washer 231 that connects to the first radial bearing 211 and the first radial bearing 211.

[0022] The stator 24 has a stator core 241 and a coil 242. The stator core 241 is a cylindrical body whose central axis extends in the actuator axis direction A. The coil 242 is wound around the stator core 241. The coil 242 is electrically connected to the external wiring 213. Thereby, the coil 242 is electrically connected to an external power source (not shown).

[0023] The stator 24 is housed inside the housing 21, electrically connected to the external wiring 213 and the coil 242. The stator 24 is housed in the portion of the housing 21 between the first radial bearing 211 and the second radial bearing 212 in the actuator axial direction A, specifically in the third housing forming member 21c. Inside the housing 21, the stator 24 surrounds the rotor 23. In other words, the stator 24 is interposed between the rotor 23 and the housing 21 in the radial direction of the rotation axis 22.

[0024] The preload member 25 is a thin, plate-shaped annular body. The preload member 25 is, for example, a wave spring. The preload member 25 is deformable in response to an external force applied in the thickness direction and is configured to apply a biasing force in the thickness direction corresponding to the magnitude of the deformation.

[0025] The preload member 25 is held in the housing 21. In other words, the motor unit 20 holds the preload member 25. The preload member 25 is provided in the second housing forming member 21b of the housing 21. The preload member 25 is provided in the second housing forming member 21b such that its thickness direction coincides with the actuator axis direction A. The rotating shaft 22 passes through the preload member 25.

[0026] The preload member 25 is interposed between the housing 21 and the rotor 23 in the direction in which the axis L of the rotating shaft 22 extends. More specifically, the preload member 25 is interposed between the second housing forming member 21b and the second radial bearing 212 in the actuator axial direction A of the housing 21. The preload member 25 is interposed between the second housing forming member 21b and the second radial bearing 212 in the housing 21 such that the thickness direction coincides with the actuator axial direction A. The preload member 25 is held in the housing 21 while deforming slightly in the thickness direction due to the pressure from the second housing forming member 21b and the second radial bearing 212.

[0027] The preload member 25 presses the rotor 23 against the housing 21. The preload member 25 deforms slightly due to the housing 21 and the second radial bearing 212, and in proportion to the magnitude of this deformation, it applies a biasing force to the rotor 23 via the second radial bearing 212 and the washer 231. This biasing force biases the rotor 23 in the actuator axial direction A and presses it against the first housing forming member 21a in the housing 21 via the washer 231 and the first radial bearing 211.

[0028] <Lead screw mechanism> The lead screw mechanism 30 is provided at the second end of the housing 21. More specifically, the lead screw mechanism 30 is provided on the second housing forming member 21b.

[0029] Case 31 is a columnar body whose longitudinal length extends in the actuator axis direction A. Case 31 is attached to the housing 21. Case 31 is connected to the second end of the housing 21 at one end. Hereafter, the end of Case 31 in the longitudinal direction that is connected to the second end of the housing 21 will be referred to as the first end of Case 31. The end of Case 31 opposite the first end in the longitudinal direction will be referred to as the second end of Case 31.

[0030] Case 31 consists of a first case forming section 311 and a second case forming section 312. Case 31 is formed by connecting the first case forming section 311 and the second case forming section 312 in the longitudinal direction of case 31. The first case forming section 311 is connected to the second housing forming member 21b and constitutes the portion of case 31 closer to the first end. The second case forming section 312 constitutes the portion of case 31 closer to the second end than the first case forming section 311.

[0031] The case 31 has a case hole 31a. The case hole 31a penetrates the case 31 in the longitudinal direction and opens at the first end and the second end of the case 31. The case hole 31a consists of a portion defined by the first case forming portion 311 and a portion defined by the second case forming portion 312. Of the case hole 31a, the diameter of the hole defined by the first case forming portion 311 is smaller than the diameter of the hole defined by the second case forming portion 312.

[0032] Case 31 has a sliding portion 313. The sliding portion 313 is provided in the second case forming portion 312 near the second end of case 31. The sliding portion 313 is housed in a case hole 31a in the second case forming portion 312. The sliding portion 313 is fixed to case 31. The case hole 31a connects to the outside of case 31 at the second end of case 31 via the inside of the sliding portion 313. A through hole is formed in the sliding portion 313. The through hole of the sliding portion 313 is oval-shaped when viewed from the opening direction of the through hole.

[0033] The shaft portion 32 is cylindrical. The shaft portion 32 is held in the case hole 31a. The shaft portion 32 is held in the case 31 such that its central axis coincides with the axis L. The shaft portion 32 is connected to the rotating shaft 22. The shaft portion 32 is connected to the rotating shaft 22 at its first end. The shaft portion 32 and the rotating shaft 22 are connected by a rigid coupling 34. The rotating shaft 22 and the shaft portion 32 are inserted into the rigid coupling 34, respectively. The rigid coupling 34 connects the first end of the shaft portion 32 to the second end of the rotating shaft 22 and also fixes the shaft portion 32 to the rotating shaft 22. The rigid coupling 34 allows the shaft portion 32 to rotate integrally with the rotating shaft 22.

[0034] A male thread is formed on the shaft portion 32. The male thread is formed on the circumferential surface of the shaft portion 32. More specifically, the male thread is formed on the portion of the shaft portion 32 that is not inserted into the rigid coupling 34.

[0035] The feed screw portion 33 has a threaded portion 331, a rod member 332, and a movement restricting portion 333. The feed screw portion 33 has its longitudinal side extending in the actuator axial direction A. The threaded portion 331 is cylindrical. The threaded portion 331 has an internal thread on its inner circumferential surface. The rod member 332 is cylindrical. The rod member 332 has its longitudinal side extending in the actuator axial direction A. The rod member 332 is inserted through the through hole of the sliding portion 313. The rod member 332 is oval-shaped when viewed from the actuator axial direction A. The outer circumferential surface of the rod member 332 engages with the inner circumferential surface that defines the through hole of the sliding portion 313. The movement restricting portion 333 is disc-shaped.

[0036] The feed screw portion 33 is formed integrally with the threaded portion 331, the rod member 332, and the movement restricting portion 333. The threaded portion 331 is housed in the rod member 332. The threaded portion 331 is fixed to the inner circumferential surface of the rod member 332. The threaded portion 331 is provided near one end of the rod member 332. The movement restricting portion 333 is fixed to that end of the rod member 332. A portion of the rod member 332 in the longitudinal direction is housed in the case hole 31a. In other words, a portion of the feed screw portion 33 in the longitudinal direction is housed in the case hole 31a.

[0037] The case 31 houses the feed screw portion 33 in a way that prevents it from rotating within the case hole 31a. In other words, the feed screw portion 33 is immobile within the case 31 about an axis extending in the longitudinal direction of the feed screw portion 33. More specifically, the feed screw portion 33 is immobile relative to the case 31 due to the engagement between the rod member 332 and the sliding portion 313.

[0038] The feed screw portion 33 is held in the case 31 and screwed onto the shaft portion 32. More specifically, the feed screw portion 33 is screwed into the male thread of the shaft portion 32 by the female thread of the threaded portion 331 in the case hole 31a. The shaft portion 32 passes through the movement restricting portion 333. The shaft portion 32 is connected to the rod member 332 via the threaded portion 331. The feed screw portion 33 houses a portion of the shaft portion 32 within the rod member 332.

[0039] <Encoder> The encoder 40 is provided on the first housing forming member 21a, which is the first end of the housing 21. The encoder 40 is provided on the opposite end of the rotating shaft 22 from the end to which the shaft portion 32 is connected. The encoder 40 is provided on the portion of the rotating shaft 22 that protrudes from the first end of the housing 21. The encoder 40 includes an encoder cover 41, a magnet 42, and a magnetic sensor 43.

[0040] The magnet 42 is fixed to the end of the rotating shaft 22. More specifically, the magnet 42 is attached to the rotating shaft 22 by a magnet retaining cap 44 attached to the end of the rotating shaft 22. The magnet retaining cap 44 is fixed to the rotating shaft 22. In other words, the magnet 42 rotates in conjunction with the rotation of the rotating shaft 22.

[0041] The magnet retaining cap 44 covers the end of the rotating shaft 22 while being spaced apart from the first housing forming member 21a in the direction in which the axis L extends. The magnetic sensor 43 is attached to the encoder cover 41. The magnetic sensor 43 is located on the part of the encoder cover 41 that faces the magnet 42. In other words, the magnetic sensor 43 faces the magnet 42. The magnetic sensor 43 is positioned so as to be spaced apart from the magnet 42 in the direction in which the axis L extends.

[0042] The encoder 40 is configured to detect the rotation of the rotating shaft 22. When the rotating shaft 22 rotates, the magnet 42 also rotates in conjunction with it. As the magnet 42 rotates, the magnetic field generated by the magnet 42 changes. The encoder 40 detects the rotation of the rotating shaft 22 by detecting the change in the magnetic field using the magnetic sensor 43. The encoder 40 transmits the detected change in the magnetic field to a control device (not shown).

[0043] <Thrust bearing> The two thrust bearings 50 are provided at the first and second ends of the housing 21, respectively. In other words, the electric actuator 10 has thrust bearings 50 at both ends of the housing 21 in the direction in which the axis L extends. First, the thrust bearing 50 provided at the first end of the housing 21 will be described. Hereafter, the thrust bearing 50 provided at the first end of the housing 21 will be simply referred to as the first thrust bearing 501, and the thrust bearing 50 provided at the second end of the housing 21 will be referred to as the second thrust bearing 502. The first thrust bearing 501 is provided in the first housing forming member 21a. The second thrust bearing 502 is provided in the second housing forming member 21b.

[0044] <First thrust bearing> The first thrust bearing 501 is located inside the encoder cover 41. More specifically, the first thrust bearing 501 is located between the housing 21 and the magnet retaining cap 44 in the actuator axial direction A. In the actuator axial direction A, the preload member 25, the second radial bearing 212, the washer 231, the rotor 23, the washer 231, the first radial bearing 211, the first thrust bearing 501, and the magnet retaining cap 44 are arranged in this order. In other words, the first thrust bearing 501 is installed with the rotor 23 interposed between the thrust bearing 50 and the preload member 25.

[0045] The first thrust bearing 501 has a fixed portion 51, a rotating portion 52, and a rolling portion 53. The first thrust bearing 501 is a ball bearing. The fixed portion 51 is disc-shaped. The center of the fixed portion 51 penetrates in the thickness direction. The rotating portion 52 is disc-shaped. The center of the rotating portion 52 penetrates in the thickness direction. In the first thrust bearing 501, the thickness direction of the fixed portion 51 and the thickness direction of the rotating portion 52 coincide. In the thrust bearing 50, the fixed portion 51 and the rotating portion 52 are arranged such that their centers are aligned in a straight line.

[0046] The rolling portion 53 consists of a plurality of spheres. The rolling portion 53 is interposed between the stationary portion 51 and the rotating portion 52. The rolling portion 53 is held between the stationary portion 51 and the rotating portion 52. The rolling portion 53 rotatably connects the rotating portion 52 to the stationary portion 51. More specifically, the first thrust bearing 501 connects the stationary portion 51 and the rotating portion 52 by the rolling portion 53 so that the rotating portion 52 is rotatable relative to the stationary portion 51. Therefore, the stationary portion 51 and the rotating portion 52 are immovable relative to each other in the actuator axial direction A.

[0047] The fixed part 51 is fixed to the housing 21. The fixed part 51 is fixed to the first housing forming member 21a, which is the first end of the housing 21. The rotating part 52 is fixed to the magnet retaining cap 44. In other words, the rotating part 52 is connected to the rotating shaft 22 via the magnet retaining cap 44. The rotating part 52 moves in conjunction with the rotating shaft 22 via the magnet retaining cap 44. That is, the rotating part 52 is connected to the rotating shaft 22 and rotates integrally with the rotating shaft 22. The portion of the rotating shaft 22 that protrudes from the first end of the housing 21 passes through the first thrust bearing 501.

[0048] As the rotating shaft 22 rotates, the fixed part 51, which is fixed to the housing 21, remains stationary, while the rotating part 52, which is linked to the magnet holding cap 44, rotates together with the rotating shaft 22. In other words, the first thrust bearing 501 rotatably holds the portion of the rotating shaft 22 that protrudes from the housing 21.

[0049] <Second thrust bearing> Next, the second thrust bearing 502 will be described. The configuration of the second thrust bearing 502 is the same as that of the first thrust bearing 501. Therefore, the configuration of the second thrust bearing 502 will not be described. The configuration of the second thrust bearing 502 will use the same component names as the configuration of the first thrust bearing 501, but with different reference numerals. The second thrust bearing 502 consists of a fixed part 54, a rotating part 55, and a rolling part 56. The second thrust bearing 502 is a ball bearing.

[0050] As shown in Figures 1 and 2, the second thrust bearing 502 is located inside the case 31. More specifically, the second thrust bearing 502 is located in the case hole 31a, near the first end of the case 31. The second thrust bearing 502 is located between the rigid coupling 34 and the housing 21 in the actuator axial direction A.

[0051] In the second thrust bearing 502, the fixed portion 54 is fixed to the housing 21. The fixed portion 54 is fixed to the second housing forming member 21b, which is the second end of the housing 21. The rotating portion 55 is fixed to the rigid coupling 34. In other words, the rotating portion 55 is connected to the rotating shaft 22 via the rigid coupling 34. The rotating portion 55 is linked to the rotating shaft 22 via the rigid coupling 34 and the shaft portion 32. That is, the rotating portion 55 is connected to the rotating shaft 22 and rotates integrally with the rotating shaft 22. The portion of the rotating shaft 22 that protrudes from the second end of the housing 21 passes through the second thrust bearing 502.

[0052] As the rotating shaft 22 rotates, the fixed part 54, which is fixed to the housing 21, remains stationary, while the rotating part 55, which is linked to the rigid coupling 34, rotates together with the rotating shaft 22. In other words, the second thrust bearing 502 rotatably holds the portion of the rotating shaft 22 that protrudes from the housing 21.

[0053] <Operation of electric actuator> The operation of the electric actuator 10 will be described. The operation of the electric actuator 10 when moving a workpiece W, which is a load installed on the part opposite to the second end will be described. The workpiece W, the feed screw part 33, the housing 21, and the encoder 40 are arranged in this order in the actuator axis direction A. In other words, the preload member 25 is interposed between the workpiece W and the rotor 23.

[0054] When the electric actuator 10 is operating, the housing 21 is fixed in a location that does not move during the operation of the electric actuator 10. The housing 21 is installed, for example, on a workbench (not shown) on which the electric actuator 10 is mounted.

[0055] When the workpiece W is facing the second end of the electric actuator 10, an external power supply (not shown) supplies power to the coil 242 via external wiring 213. The energization of the coil 242 causes the motor unit 20 to rotate the rotating shaft 22. By rotating the rotating shaft 22, the motor unit 20 rotates the shaft portion 32 integrally with the rotating shaft 22 via the rigid coupling 34.

[0056] The rotating shaft 22 and shaft portion 32 rotate relative to the housing 21 fixed to the workbench. Therefore, the rotating shaft 22 and shaft portion 32 rotate relative to the case 31 fixed to the housing 21. In other words, the rotating shaft 22 and shaft portion 32 rotate relative to the feed screw portion 33, whose rotation relative to the case 31 is restricted by the sliding portion 313.

[0057] The lead screw portion 33 moves in the direction that extends the shaft portion 32 due to the rotation of the shaft portion 32. The lead screw portion 33, which is screwed with the shaft portion 32 at the threaded portion 331, moves in the actuator axis direction A relative to the case 31 due to the rotation of the shaft portion 32. In the actuator axis direction A, the direction in which the lead screw portion 33 moves is determined by the direction of rotation of the rotating shaft 22. The electric actuator 10 pushes the workpiece W with the rod member 332 of the lead screw portion 33 by rotating the rotating shaft 22 so that the lead screw portion 33 moves away from the housing 21. In this way, the electric actuator 10 operates the workpiece W connected to the lead screw portion 33 by the rotation of the rotating shaft 22. The electric actuator 10 may also have a tool (not shown) attached to the second end of the rod member 332 and operate the workpiece W with the tool.

[0058] The feed screw section 33 operates within the range in which the movement restricting section 333 can move. More specifically, the feed screw section 33 can move in the direction of pushing the workpiece W until the movement restricting section 333 reaches the sliding section 313.

[0059] [Effects of this embodiment] The effects of this embodiment will now be explained. (1-1) The preloading member 25 applies a biasing force to the rotor 23 in a direction that presses the rotor 23 against the housing 21, thereby suppressing movement of the rotating shaft 22 and the rotor 23 inside the housing 21.

[0060] In the electric actuator 10, a load may be applied to the rotating shaft 22 and the shaft portion 32 in a direction from the first end to the second end, for example, due to the installation environment or the reaction force applied to the shaft portion 32 when the lead screw portion 33 moves. Even in this case, the electric actuator 10 can suppress the movement of the rotating shaft 22 due to the load by having a first thrust bearing 501 with a rotor 23 interposed between the first thrust bearing 501 and the preload member 25. This allows the electric actuator 10 to suppress deformation of the preload member 25. In other words, the electric actuator 10 can suppress the movement of the rotating shaft 22 due to a load in the direction in which the axis L extends by interposing the rotor 23 between the thrust bearing 50 and the preload member 25. The electric actuator 10 can suppress the movement of the rotor 23 in the motor unit 20 by the preload member 25, while the first thrust bearing 501 can suppress the movement of the rotating shaft 22 due to an externally applied load. This improves the durability of the electric actuator 10. Furthermore, the electric actuator 10 can suppress the decrease in detection accuracy at the encoder 40 caused by the change in distance between the rotating shaft 22 and the magnetic sensor 43 due to the load.

[0061] For example, consider the case where the rotating shaft 22 and the shaft portion 32 are connected by a combination of an Oldham-type coupling and a bearing unit capable of receiving the load acting on the rotating shaft 22. Compared to this case, the electric actuator 10 can be made smaller in the direction in which the axis L extends, while still being able to receive the load with the thrust bearing 50. As a result, the electric actuator 10 can be made smaller while improving durability.

[0062] (1-2) The electric actuator 10 has an encoder 40. The electric actuator 10 has a second thrust bearing 502, so that even if a load exceeding the allowable amount for the first radial bearing 211 acts on the rotating shaft 22, for example, the load can be borne by the second thrust bearing 502. This prevents the electric actuator 10 from damaging the first radial bearing 211.

[0063] (1-3) The electric actuator 10 has a first thrust bearing 501 and a second thrust bearing 502 at both ends of the housing 21. For example, consider the case where a load acts on the rotating shaft 22 in the direction from the second end to the first end of the electric actuator 10 due to a reaction force from the workpiece W. In this case, even if the load acting on the rotating shaft 22 exceeds the magnitude that can be tolerated by the first radial bearing 211, the electric actuator 10 can receive the load with the second thrust bearing 502. In other words, by having thrust bearings 50 at both ends of the housing 21, the electric actuator 10 can improve durability compared to, for example, the case where only the first thrust bearing 501 is present.

[0064] Furthermore, in order to suppress the load acting on the rotating shaft 22 in the direction in which the axis L extends, the rotating shaft 22 or the shaft portion 32 may be held by two angular contact ball bearings. Compared to this case, the electric actuator 10 can suppress the acting of such load on the rotating shaft 22 while keeping costs down by using two thrust bearings 50.

[0065] (1-4) The thrust bearing 50 is a ball bearing. For example, the electric actuator 10 can reduce the influence of the torque caused by the thrust bearing 50 on the rotating shaft 22 compared to the case where the thrust bearing 50 has a resin spacer. As a result, the electric actuator 10 can control the rotation of the rotating shaft 22 with high precision. In other words, by having a ball bearing as the thrust bearing 50, the electric actuator 10 can move the workpiece W with greater precision compared to, for example, the case where the thrust bearing 50 has a resin spacer.

[0066] [Second Embodiment] The following describes a second embodiment of the electric actuator. As shown in Figure 3, in the second embodiment, the electric actuator 10 operates a gripping member 64 connected to a lead screw mechanism 30 by the rotation of a rotating shaft 22 by a motor unit 20. In other words, the electric actuator 10 in the second embodiment is an electric gripper. The main difference from the first embodiment is that the load operated by the lead screw mechanism 30 of the electric actuator 10 is the lever 62 of the electric gripper. For this reason, a detailed explanation of the same configuration as the first embodiment will be omitted.

[0067] <Overall view of the electric gripper> The electric actuator 10 has a gripping mechanism 60 at its second end in the actuator axial direction A. The electric actuator 10 operates the gripping mechanism 60 by rotating the rotating shaft 22 in the motor unit 20.

[0068] In the electric actuator 10, the rotating shaft 22 and the shaft portion 32 are directly connected. More specifically, the end of the rotating shaft 22 is inserted into the shaft portion 32. The rotating shaft 22 is fixed to the shaft portion 32 by a fixing pin P.

[0069] <Gripping mechanism> The gripping mechanism 60 includes a gripper housing 61, a pair of levers 62 which are loads, a guide member 63, and a pair of gripping members 64.

[0070] The gripper housing 61 is attached to the second end of the housing 21. More specifically, the gripper housing 61 is attached to the second housing forming member 21b via a connecting plate 611. Hereafter, the end of the gripper housing 61 to which the connecting plate 611 is provided will be referred to as the first end of the gripper housing 61, and the end opposite the first end in the actuator axial direction A will be referred to as the second end. The gripper housing 61 penetrates in the actuator axial direction A.

[0071] The portion of the rotating shaft 22 that protrudes from the second end of the housing 21 is inserted into the gripper housing 61. The gripper housing 61 has a pair of levers 62 near the second end. The pair of levers 62 are plate-shaped. Each lever 62 is an L-shaped body bent in a plane perpendicular to the thickness direction. The pair of levers 62 overlap in the thickness direction at one end of each. Hereafter, the overlapping end of the levers 62 will be referred to as the first end, and the end opposite the first end will be referred to as the second end of the levers 62.

[0072] Each of the pair of levers 62 has a support portion 62a in the area between the first end and the second end, along the shape of the lever 62. Each support portion 62a pivotably supports the lever 62 relative to the gripper housing 61.

[0073] The guide member 63 is attached to the second end of the gripper housing 61. A pair of levers 62 are inserted through the guide member 63. Each of the pair of gripping members 64 has a base portion 641 and a gripping portion 642. Each gripping member 64 is formed by erecting the gripping portion 642 on the base portion 641. Each gripping member 64 has its base portion 641 fitted into the guide member 63, and the gripping portion 642 is located on the side of the base portion 641 that does not face the guide member 63. The pair of gripping members 64 are each connected to a pair of levers 62.

[0074] <Lead screw mechanism> The feed screw mechanism 30 of the second embodiment is built into the gripper housing 61. The feed screw mechanism 30 of the second embodiment has a shaft portion 32 and a feed screw portion 33.

[0075] The shaft portion 32 is housed in the part of the gripper housing 61 closer to the first end. The shaft portion 32 is a columnar body having a coupling hole 32a that opens at one end. The shaft portion 32 has male threads formed on its outer surface.

[0076] An installation plate 612 is provided at the end of the shaft portion 32 where the coupling hole 32a is open. The portion of the rotating shaft 22 that is inserted into the gripper housing 61 is inserted into the coupling hole 32a of the shaft portion 32. Within the coupling hole 32a, the rotating shaft 22 is restricted from relative movement to the shaft portion 32 by a fixing pin P. In other words, the rotating shaft 22 is fixed to the shaft portion 32. As a result, the shaft portion 32 rotates integrally with the rotating shaft 22.

[0077] The lead screw portion 33 is housed inside the gripper housing 61. The lead screw portion 33 extends in the direction of the axis L. An internal thread is formed on the inner circumferential surface of the lead screw portion 33.

[0078] The female thread of the feed screw portion 33 is screwed into the male thread of the shaft portion 32. A pair of levers 62 are pivotably held on the end of the feed screw portion 33 opposite to the end into which the shaft portion 32 is inserted. In the thickness direction of each lever 62, one lever 62, the feed screw portion 33, and the other lever 62 are arranged in this order.

[0079] <Thrust bearing> The electric actuator 10 has two thrust bearings 50. In the second embodiment, the two thrust bearings 50 are a first thrust bearing 501 which is a sliding bearing and a second thrust bearing 502 which is a ball bearing.

[0080] The first thrust bearing 501 is a resin spacer. In other words, the first thrust bearing 501 is an annular body made of resin material. Examples of materials for the first thrust bearing 501 include polyacetal, polyphenylene sulfide, polyethylene, and fluororesin. The first thrust bearing 501 is interposed between the magnet holding cap 44 and the first housing forming member 21a, which is the first end of the housing 21. The portion of the rotating shaft 22 that protrudes from the first end of the housing 21 is inserted through the first thrust bearing 501.

[0081] The second thrust bearing 502 is located inside the gripper housing 61, near the first end. The second thrust bearing 502 is interposed between the shaft portion 32 and the connecting plate 611 in the actuator axial direction A. It can also be said that the second thrust bearing 502 is interposed between the shaft portion 32 and the housing 21 in the direction in which the axis L extends.

[0082] The second thrust bearing 502 has a fixed portion 54 fixed to the connecting plate 611 and a rotating portion 55 fixed to the shaft portion 32. More specifically, the second thrust bearing 502 has its rotating portion 55 fixed to the shaft portion 32 via the mounting plate 612.

[0083] <Operation of the electric actuator in the second embodiment> In the second embodiment, the electric actuator 10 operates a pair of levers 62 while moving the lead screw portion 33 in the actuator axis direction A by rotating the rotation shaft 22 with the motor unit 20. As the lead screw portion 33 moves in the actuator axis direction A, each of the pair of levers 62 swings about the support portion 62a. The swinging of the pair of levers 62 causes the pair of gripping members 64 to move along the guide member 63.

[0084] For example, when the lead screw portion 33 moves from the first end to the second end of the electric actuator 10, the pair of levers 62 swing in a direction that separates their second ends. As a result, the pair of gripping members 64 move along the guide member 63 in a direction that separates them. In other words, in this case, the electric actuator 10 operates the pair of gripping members 64 in an opening direction. The electric actuator 10 operates the pair of gripping members 64 in a closing direction by moving the lead screw portion 33 from the second end to the first end of the electric actuator 10.

[0085] [Effects of this embodiment] The effects of this embodiment will be explained along with their operation. (2-1) The electric actuator 10 converts the rotation of the rotating shaft 22 by the motor unit 20 into linear motion in the lead screw mechanism 30, and then into oscillating motion in the pair of levers 62. In the electric actuator 10 having a gripping mechanism 60, a load is generated from the shaft portion 32 to the rotating shaft 22 when the rotation is converted to linear motion, and a load is generated from the pair of levers 62 to the rotating shaft 22 via the shaft portion 32 when the linear motion is converted to oscillating motion. The electric actuator 10 has a second thrust bearing 502, which helps to suppress the acting of each of the above loads on the rotating shaft 22.

[0086] (2-2) The electric actuator 10 has a first thrust bearing 501 which is a sliding bearing. This makes the electric actuator 10 smaller and reduces costs compared to the case where the first thrust bearing 501 has a ball bearing.

[0087] (2-3) In the electric actuator 10, the first thrust bearing 501 is a resin spacer. By having a resin spacer as the first thrust bearing 501, the electric actuator 10 can be made smaller, lighter, and less expensive compared to, for example, a case where the first thrust bearing 501 is a ball bearing.

[0088] [Example of changes] Furthermore, each of the above embodiments can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0089] ○ The thrust bearing 50 does not have to be a ball bearing. More specifically, the first thrust bearing 501 may be a ball bearing or a sliding bearing. Also, the second thrust bearing 502 may be a ball bearing or a sliding bearing.

[0090] ○ The electric actuator 10 does not necessarily have thrust bearings 50 at both ends of the housing 21 in the direction in which the axis L extends. In other words, the thrust bearing 50 may be provided at only one end of the housing 21. When the thrust bearing 50 is provided at one end of the housing 21, the thrust bearing 50 is installed such that the rotor 23 is positioned between the thrust bearing 50 and the preload member 25.

[0091] ○ As shown in Figure 5, the preload member 25 may be provided in the part of the housing 21 closer to the first end. In other words, the preload member 25 is provided in the part of the housing 21 closer to the encoder 40. The preload member 25 is interposed between the encoder 40 and the rotor 23. The second thrust bearing 502, rotor 23, preload member 25, first thrust bearing 501, and encoder 40 are arranged in this order. In other words, the second thrust bearing 502 is installed in a position with the rotor 23 interposed between the second thrust bearing 502 and the preload member 25.

[0092] The second thrust bearing 502 prevents the transmission of a load from the shaft portion 32 to the rotating shaft 22 in the direction from the second end to the first end of the electric actuator 10. This load is generated, for example, by a reaction force acting on the shaft portion 32 from the load. The direction of movement of the rotating shaft 22 due to this load is in the direction in which the end of the rotating shaft 22 approaches the magnetic sensor 43. In other words, by having the second thrust bearing 502, the electric actuator 10 can suppress a decrease in detection accuracy in the encoder 40 due to the movement of the rotating shaft 22 and avoid collision of the rotating shaft 22 with the magnetic sensor 43.

[0093] ○ As shown in Figure 4, the electric actuator 10 does not necessarily have to be equipped with an encoder 40. In this case, the electric actuator 10 may have a manual part M instead of a magnet retaining cap 44. The electric actuator 10 may apply torque to the rotating shaft 22 by having an operator manually rotate the manual part M instead of applying torque to the rotating shaft 22 by supplying power from an external power source.

[0094] ○ In the second embodiment, the first thrust bearing 501 does not have to be made of resin. The first thrust bearing 501 may be made of, for example, metal or carbon.

[0095] ○ In the electric actuator 10 of the first embodiment, the configuration of the case 31 and the lead screw mechanism 30 is not limited to this. For example, the case 31 may have guides (not shown) arranged in a direction perpendicular to the actuator axis A, and the rod member 332 of the lead screw mechanism 30 may operate while being guided by these guides. [Explanation of Symbols]

[0096] 10...Electric actuator, 20...Motor unit, 21...Housing, 22...Rotating shaft, 23...Rotor, 25...Preload member, 31...Case, 32...Shaft section, 33...Lead screw section, 40...Encoder, 50...Thrust bearing, 51, 54...Fixed section, 52, 55...Rotating section, 53, 56...Rolling section, 62...Pair of levers as load, 501...First thrust bearing, 502...Second thrust bearing, L...Axis, W...Workpiece as load.

Claims

1. A motor unit that holds a rotating shaft that rotates integrally with a rotor housed inside a housing and protrudes from the end of the housing, and a preload member that is interposed between the housing and the rotor in the direction in which the axis of the rotating shaft extends, and presses the rotor against the housing, The case attached to the aforementioned housing, A shaft portion connected to the aforementioned rotating shaft and having a male thread formed thereon, It has a feed screw portion that is held in the case and screwed onto the shaft portion, and moves in the direction in which the axis extends as the shaft portion rotates, An electric actuator that operates a load connected to the feed screw portion by the rotation of the aforementioned rotating shaft, An electric actuator having a thrust bearing that rotatably holds a portion of the rotating shaft that protrudes from the housing, wherein the thrust bearing is installed in a position with the rotor interposed between the thrust bearing and the preload member.

2. The electric actuator according to claim 1, wherein the preloading member is interposed between the load and the rotor.

3. The rotating shaft further includes an encoder provided on the opposite end of the shaft portion to which the shaft portion is connected, and configured to detect the rotation of the rotating shaft. The electric actuator according to claim 1, wherein the preloading member is interposed between the encoder and the rotor.

4. The electric actuator according to claim 1, wherein the thrust bearings are provided at both ends of the housing in the direction in which the axis extends.

5. The thrust bearing is, A fixing part fixed to the housing, A rotating part that is connected to the aforementioned rotating shaft and rotates integrally with the aforementioned rotating shaft, An electric actuator according to any one of claims 1 to 4, comprising a rolling portion that is held between the fixed portion and the rotating portion and rotatably connects the rotating portion to the fixed portion.

Images