Actuator and mechanical device

Abstract

To reduce the size of an actuator including a screw shaft and a nut relatively rotatably fitted to the screw shaft.SOLUTION: Each of the actuators 50 includes a screw shaft 53, a nut 54 that has a main body portion 54a through which the screw shaft 53 penetrates and is fitted to the screw shaft 53 so as to be relatively rotatable, a plurality of balls B that circulate between the nut 54 and the screw shaft 53 in the nut 54, and a guide shaft member 55 that penetrates the main body portion 54a and guides the nut 54.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to actuators and mechanical devices. [Background technology]

[0002] Patent Document 1 discloses a linear motion device as an example of an actuator. The linear motion device includes a screw shaft, a moving body (nut) fitted onto the screw shaft so as to be rotatable relative to the screw shaft, a drive motor that rotates the screw shaft, a table fixed to the nut, a moving block fixed to the table, and a guide rail that guides the table and the nut via the moving block. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 240743 Summary of the Invention [Problem to be solved by the invention]

[0004] When the actuator of Patent Document 1 is applied to a mechanism for operating fingers in a robot hand with multiple fingers, for example, the direction in which the fingers extend is the same as the direction in which the screw shaft extends, and a guide rail is placed between two adjacent fingers. In this case, the fingers become relatively thick, leading to an increase in the size of the robot hand. When the robot hand becomes large, it becomes difficult to grasp relatively small objects. It also becomes difficult to place the robot hand in a relatively small space. In order to reduce the size of the robot hand, it is necessary to reduce the size of the actuator.

[0005] An object of the present disclosure is to achieve miniaturization of an actuator including a screw shaft and a nut fitted onto the screw shaft so as to be rotatable relative to the screw shaft. [Means for solving the problem]

[0006] An actuator according to one aspect of the present disclosure includes a screw shaft, a nut having a main body through which the screw shaft passes and fitted onto the screw shaft so as to be rotatable relative to the screw shaft, a plurality of balls circulating within the nut between the nut and the screw shaft, and a guide shaft member that passes through the main body and guides the nut.

[0007] According to this, the guide shaft member that guides the nut passes through the main body of the nut, thereby enabling the actuator to be made smaller.

[0008] In the actuator according to an aspect of the present disclosure, the lead angle of the screw of the screw shaft is 45°±15°.

[0009] This allows the actuator to operate appropriately in both cases where the screw shaft is rotated to move the nut, and where the screw shaft is rotated to move the nut.

[0010] In the actuator according to the aspect of the present disclosure, the lead angle of the screw of the screw shaft is equal to or greater than 45° and equal to or less than 60°.

[0011] This allows the actuator to operate appropriately both when the nut is moved by rotating the screw shaft and when the nut is moved to rotate the screw shaft. Furthermore, when the nut is moved to rotate the screw shaft, the force required to move the nut can be made smaller than when the lead angle of the screw of the screw shaft is greater than 45°. This makes it easier to manually move the nut.

[0012] Moreover, an actuator according to one aspect of the present disclosure includes a plurality of the guide shaft members.

[0013] This reduces the force acting on one guide shaft member when the actuator operates, allowing the diameter of the guide shaft member to be reduced, thereby enabling further miniaturization of the actuator.

[0014] In the actuator according to one aspect of the present disclosure, the thread of the screw shaft is a multiple-start thread.

[0015] This allows the lead to be larger than when the screw shaft has a single thread, and therefore, even when the lead angle of the screw shaft thread is greater than 45°, a sufficient amount of movement of the nut can be ensured.

[0016] Furthermore, a mechanical device according to one aspect of the present disclosure includes two of the above-described actuators, and the two actuators are arranged in parallel.

[0017] This allows the actuator to be made smaller, thereby enabling the mechanical device to be made smaller. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing the configuration of a mechanical device. [Figure 2] FIG. 2 is a perspective view of the finger portion. [Figure 3] FIG. 3 is a perspective view of the screw shaft, nut, and guide shaft member of the actuator. [Figure 4] FIG. 4 is a diagram showing the cross-sectional shapes of the screw shaft and the nut taken along the central axis of the screw shaft. [Figure 5] FIG. 5 is a diagram showing the cross-sectional shapes of the screw shaft and the nut when cut along a plane perpendicular to the central axis of the screw shaft. [Figure 6] FIG. 6 is a side view of the screw shaft. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited thereto. The components of each embodiment and each modified example described below can be combined as appropriate. In addition, some components may not be used.

[0020] <Mechanical equipment 1> FIG. 1 is a diagram showing the configuration of a mechanical device 1. The X, Y, and Z directions shown in FIG. 1 are perpendicular to one another and indicate the directions of the mechanical device 1. The mechanical device 1 is a robot hand that grasps an object. The mechanical device 1 is controlled by a control device.

[0021] The mechanical device 1 includes a base 10, two first connecting portions 20, two second connecting portions 30, and four finger portions 40. The base 10 is attached to, for example, a robot arm or the like.

[0022] The first connecting portion 20 connects the base portion 10 and one finger portion 40 so as to be relatively rotatable about a first axis A1 parallel to the Z direction. The two first connecting portions 20 are arranged adjacent to each other with their first axes A1 parallel to each other.

[0023] The first connecting part 20 includes a first fixed part 21 fixed to the base part 10, and a first rotating part 22. The first rotating part 22 has a U-shape. Both ends of the first rotating part 22 are attached to the first fixed part 21 so as to be rotatable around a first axis A1. The first connecting part 20 also includes a first motor housed in the first fixed part 21 and rotating the first rotating part 22.

[0024] The second connecting portion 30 connects the base portion 10 and one finger portion 40 to be rotatable relative to each other about a second axis A2 parallel to the Y direction. The two first connecting portions 20 are arranged adjacent to each other with their second axes A2 aligned on the same straight line. The second axis A2 is perpendicular to the first axis A1.

[0025] The second connecting unit 30 includes a second fixed unit 31 fixed to the base unit 10, and a second rotating unit 32. The second rotating unit 32 has a U-shape. Both ends of the second rotating unit 32 are attached to the second fixed unit 31 so as to be rotatable about a second axis A2. The second connecting unit 30 also includes a second motor housed in the second fixed unit 31 and rotating the second rotating unit 32. The first motor and the second motor are controlled by a control device.

[0026] 2 is a perspective view of the finger unit 40. The finger unit 40 includes a first link 41, a second link 42, a tip portion 43, a third link 44, and an actuator 50.

[0027] The first link 41 is L-shaped. The first end and second end of the first link 41 are each U-shaped. An actuator 50 is attached to the inside of the first end of the first link 41 (details will be described later). The first end of the second link 42 is attached to the inside of the second end of the first link 41 so as to be rotatable around the third axis A3.

[0028] One of the first rotating part 22 and the second rotating part 32 is fixed to a portion of the first link 41 between the first end and the second end (see FIG. 1).

[0029] The second link 42 is L-shaped. A tip portion 43 is attached to a second end portion of the second link 42 so as to be relatively rotatable about a fourth axis A4 parallel to the third axis A3.

[0030] The tip 43 comes into contact with the object when the mechanical device 1 grips the object.

[0031] The third link 44 is formed by a pair of plate members 44a facing each other in the direction in which the third axis A3 extends. The pair of plate members 44a have the same L-shape. The first link 41, the second link 42, and the tip end portion 43 are disposed between the pair of plate members 44a.

[0032] A first end of the third link 44 is attached to the tip end portion 43 so as to be rotatable relative to the tip end portion 43 about a fifth axis A5 parallel to the third axis A3. The fifth axis A5 is located closer to the base end of the tip end portion 43 than the fourth axis A4. A portion of the third link 44 between the first end and the second end is attached to the first link 41 so as to be rotatable relative to the tip end portion 43 about a sixth axis A6 parallel to the third axis A3.

[0033] The actuator 50 includes a mounting portion 51, a drive portion 52, a screw shaft 53, a nut 54, and a guide shaft member 55. The mounting portion 51 is attached to the inside of the first end portion of the first link 41 so as to be relatively rotatable about a seventh axis A7 parallel to the third axis A3.

[0034] The drive unit 52 is attached to the mounting portion 51 and rotates the screw shaft 53. The drive unit 52 is, for example, a motor. The drive unit 52 is controlled by a control device. The screw shaft 53 is disposed so as to extend in a direction perpendicular to the third axis A3.

[0035] The nut 54 is disposed between the pair of plate members 44a at the second end of the third link 44 so as to be rotatable relative to the screw shaft 53 about an eighth axis A8 parallel to the third axis A3. The nut 54 is fitted onto the screw shaft 53 so as to be rotatable relative to the screw shaft 53. The guide shaft member 55 guides the movement of the nut 54. The guide shaft member 55 is aligned with the extension direction of the screw shaft 53. The configuration of the actuator 50 will be described in detail later. Note that the actuator 50 is not shown in FIG. 1.

[0036] 1, a first link 41 of a finger 40 is fixed to the first rotating part 22 with the first axis A1 and the third axis A3 perpendicular to each other. The position of the first rotating part 22 with respect to the first fixed part 21 shown in FIG. 1 is such that the third axis A3 of the finger 40 fixed to the first rotating part 22 is along the Y direction. The finger 40 is fixed to the second rotating part 32 with the second axis A2 and the third axis A3 parallel to each other.

[0037] Hereinafter, the finger 40 fixed to the first rotating part 22 will be referred to as the "first finger 40a," and the finger 40 fixed to the second rotating part 32 will be referred to as the "second finger 40b." Furthermore, when the first finger 40a and the second finger 40b are described without distinction, they will simply be referred to as the "finger 40."

[0038] In the state shown in FIG. 1, the two first fingers 40a are arranged adjacent to each other in the Y direction and in parallel. As a result, the actuators 50 of the two first fingers 40a are arranged in parallel. Arranging the two actuators 50 in parallel means that the screw shafts 53 of the two actuators 50 are arranged in parallel. Furthermore, the two second fingers 40b are arranged in parallel in the Y direction. As a result, the actuators 50 of the two second fingers 40b are arranged in parallel. Furthermore, in the state shown in FIG. 1, the tip 43 of the first finger 40a and the tip 43 of the second finger 40b face each other.

[0039] Next, the operation of the mechanical device 1 will be described.

[0040] When the screw shaft 53 is rotated by the drive unit 52, the nut 54 moves along the guide shaft member 55. As a result, the first link 41 and the third link 44 rotate relatively about the sixth axis A6, the first link 41 and the second link 42 rotate relatively about the third axis A3, the second link 42 and the tip end portion 43 rotate relatively about the fourth axis A4, and the tip end portion 43 and the third link 44 rotate relatively about the fifth axis A5. At this time, the first link 41 and the mounting portion 51 rotate relatively about the seventh axis A7, and the nut 54 and the third link 44 rotate relatively about the eighth axis A8.

[0041] When the nut 54 moves in a direction away from the mounting portion 51, the fingers 40 bend, and the tips 43 of the four fingers 40 move closer to each other, thereby enabling the mechanical device 1 to grip an object.

[0042] On the other hand, when the nut 54 moves in a direction approaching the mounting portion 51, the fingers 40 operate to extend, and the tips 43 of the four fingers 40 move away from each other. This allows the mechanical device 1 to release the gripped object.

[0043] <Actuator 50> Next, the configuration of the actuator 50 will be described in detail.

[0044] Fig. 3 is a perspective view of the screw shaft 53, nut 54, and guide shaft member 55 of the actuator 50. Fig. 4 is a diagram showing the cross-sectional shapes of the screw shaft 53 and the nut 54 along the central axis Ac of the screw shaft 53. Fig. 5 is a diagram showing the cross-sectional shapes of the screw shaft 53 and the nut 54 when cut along a plane perpendicular to the central axis Ac of the screw shaft 53. Fig. 6 is a side view of the screw shaft 53.

[0045] The thread of the screw shaft 53 is a multiple-start thread. Specifically, the thread of the screw shaft 53 is a four-start thread. That is, in this embodiment, the screw shaft 53 has four thread grooves Gs. Specifically, as shown in FIG. 6, the screw shaft 53 has a first thread groove Gs1, a second thread groove Gs2, a third thread groove Gs3, and a fourth thread groove Gs4. It goes without saying that the thread of the screw shaft 53 is not limited to a four-start thread.

[0046] 6 has a lead angle θ of 45°±15°. This allows the nut 54 to move appropriately and the screw shaft 53 to rotate appropriately when an external force F acting along the central axis Ac of the screw shaft 53 acts on the nut 54, and also allows the nut 54 to move appropriately when the screw shaft 53 is rotated by the drive unit 52.

[0047] For example, when an external force F acting along the central axis Ac of the screw shaft 53 acts on the nut 54 to move it, if the lead angle θ is smaller than 30°, the component of the external force F acting along the thread groove Gs of the screw shaft 53 is smaller than when the lead angle θ is 45°±15°. This may cause friction between the screw shaft 53 and the nut 54 to hinder the movement of the nut 54 and the rotation of the screw shaft 53. Furthermore, the thread lead of the screw shaft 53 becomes smaller, and the amount of movement of the nut 54 becomes smaller.

[0048] On the other hand, when the screw shaft 53 rotates and the nut 54 moves as a result of the driving of the drive unit 52, if the lead angle θ is greater than 60°, the component of the rotational torque T in the direction along the thread groove Gs becomes smaller than when the lead angle θ is 45°±15°. This may cause friction between the screw shaft 53 and the nut 54, which may hinder the movement of the nut 54 and the rotation of the screw shaft 53.

[0049] By setting the lead angle θ to 45°±15° in this manner, the nut 54 can be appropriately moved relative to the threaded shaft 53 by the external force F acting on the nut 54, thereby allowing the threaded shaft 53 to be appropriately rotated, and the nut 54 can be appropriately moved by the rotation of the threaded shaft 53 driven by the drive unit 52. For example, the movement of the finger 40 from a bent state to an extended state can be performed manually. Specifically, when the finger 40 is in a bent state, the operator grasps the tip 43 and moves the tip 43 in the direction in which the finger 40 extends. This moves the nut 54 in a direction approaching the mounting unit 51, rotates the threaded shaft 53, and extends the finger 40. Similarly, the movement of the finger 40 from an extended state to a bent state can be performed manually.

[0050] The lead angle θ is preferably 45°±5°. This facilitates movement of the nut 54 and rotation of the screw shaft 53 when an external force F acting on the nut 54 along the central axis Ac of the screw shaft 53, and also facilitates movement of the nut 54 due to the rotation of the screw shaft 53. Needless to say, the lead angle θ is not limited to the above angle.

[0051] As shown in Figure 3, the actuator 50 includes at least one, and preferably multiple, guide shaft members 55. The number of guide shaft members 55 is four, but needless to say, this is not limited to four. The multiple guide shaft members 55 are parallel to one another. The direction in which the guide shaft members 55 extend is parallel to the central axis Ac of the screw shaft 53. The multiple guide shaft members 55 are arranged at equal intervals in the circumferential direction of the screw shaft 53.

[0052] The nut 54 shown in FIGS. 3, 4 and 5 includes a main body portion 54a through which the screw shaft 53 passes, and a plurality of lid members 54b that cover the outside of the main body portion 54a.

[0053] The main body 54a has a rectangular parallelepiped shape and has a screw hole H1 through which the screw shaft 53 passes so as to be relatively rotatable, and a plurality of first through holes H2 through which the guide shaft members 55 pass.

[0054] The actuator 50 further includes a plurality of balls B. The actuator 50 also has a plurality of circulation paths R through which the balls B circulate when the screw shaft 53 and the nut 54 rotate relative to each other. The number of circulation paths R is equal to the number of threads on the screw shaft 53. That is, in this embodiment, the actuator 50 has four circulation paths R. FIG. 4 mainly shows the first circulation path R1 corresponding to the first screw groove Gs1 and the second circulation path R2 corresponding to the second screw groove Gs2. FIG. 5 shows portions of the first circulation path R1, the second circulation path R2, the third circulation path R3 corresponding to the third screw groove Gs3, and the fourth circulation path R4 corresponding to the fourth screw groove Gs4.

[0055] The first circulation path R1 is constituted by the first screw groove Gs1, the first main body portion inner groove Gi1, the first main body portion outer groove Go1, the pair of second through holes H3, and the first cover member groove Gc1.

[0056] The first body inner groove Gi1 is disposed in the threaded hole H1 and has a helical shape facing the first screw groove Gs1. The first body outer groove Go1 is located on the outer surface of the body 54a and extends along the central axis of the threaded hole H1. A pair of second through holes H3 connect the ends of the first body inner groove Gi1 and the first body outer groove Go1, respectively. The first cover member groove Gc1 is disposed in the cover member 54b and faces the first body outer groove Go1.

[0057] The second circulation path R2 is constituted by the second screw groove Gs2, the second main body inner groove Gi2, the second main body outer groove Go2, the pair of third through holes H4, and the second cover member groove Gc2.

[0058] The second body inner groove Gi2 is disposed in the threaded hole H1 and has a helical shape facing the second screw groove Gs2. The second body outer groove Go2 is located on the outer surface of the body 54a and extends along the central axis of the threaded hole H1. A pair of third through holes H4 connect the ends of the second body inner groove Gi2 and the second body outer groove Go2, respectively. The second cover member groove Gc2 is disposed in the cover member 54b and faces the second body outer groove Go2.

[0059] 4 and 5 also show a part of the third circulation path R3 and a part of the fourth circulation path R4.

[0060] The third circulation path R3 includes a third screw groove Gs3 and a third body portion inner groove Gi3. The third body portion inner groove Gi3 is disposed in the threaded hole H1 and has a helical shape facing the third screw groove Gs3. The third circulation path R3 also includes a first body portion outer groove Go1, a pair of second through holes H3, a third body portion outer groove Go3 corresponding to the first cover member groove Gc1, a pair of fourth through holes H5, and a third cover member groove Gc3.

[0061] The fourth circulation path R4 includes a fourth screw groove Gs4 and a fourth body portion inner groove Gi4. The fourth body portion inner groove Gi4 is disposed in the threaded hole H1 and has a helical shape facing the fourth screw groove Gs4. The fourth circulation path R4 also includes a first body portion outer groove Go1, a pair of second through holes H3, a fourth body portion outer groove Go4 corresponding to the first cover member groove Gc1, a pair of fifth through holes H6, and a fourth cover member groove Gc4. The first body portion outer groove Go1, the second body portion outer groove Go2, the third body portion outer groove Go3, and the fourth body portion outer groove Go4 are located at different positions in the circumferential direction of the threaded hole H1. The pair of second through holes H3, the pair of third through holes H4, the pair of fourth through holes H5, and the pair of fifth through holes H6 are located at different positions in the circumferential direction of the threaded hole H1. The first cover member groove Gc1, the second cover member groove Gc2, the third cover member groove Gc3 and the fourth cover member groove Gc4 are located at different positions in the circumferential direction of the screw hole H1.

[0062] The plurality of balls B circulate through each of the four circulation paths R, thereby circulating between the nut 54 and the screw shaft 53 within the nut 54. In other words, the screw shaft 53, the nut 54, and the balls B constitute a so-called ball screw. Therefore, in this case, compared to a case in which the screw shaft 53 and the nut 54 do not constitute a ball screw, it is possible to reduce friction between the screw shaft 53 and the nut 54, thereby enabling smoother movement of the nut 54 and rotation of the screw shaft 53.

[0063] As described above, according to this embodiment, the actuator 50 comprises a screw shaft 53, a nut 54 having a main body portion 54a through which the screw shaft 53 passes and fitted onto the screw shaft 53 so as to be rotatable relative to the screw shaft 53, a plurality of balls B circulating within the nut 54 between the nut 54 and the screw shaft 53, and a guide shaft member 55 passing through the main body portion 54a and guiding the nut 54.

[0064] According to this, the guide shaft member 55 that guides the nut 54 passes through the main body 54a of the nut 54. Therefore, the actuator 50 can be made smaller in size.

[0065] The lead angle θ of the screw shaft 53 is 45°±15°.

[0066] This allows the actuator 50 to operate appropriately both when the screw shaft 53 is rotated to move the nut 54 and when the nut 54 is moved to rotate the screw shaft 53.

[0067] The actuator 50 also includes a plurality of guide shaft members 55.

[0068] This reduces the force acting on one guide shaft member 55 when the actuator 50 operates. This allows the diameter of the guide shaft member 55 to be reduced, enabling the actuator 50 to be made even more compact.

[0069] In the actuator 50, the thread of the screw shaft 53 is a multiple start thread.

[0070] This allows the lead to be larger than when the screw shaft 53 has a single thread. Therefore, even when the lead angle θ of the thread of the screw shaft 53 is larger than 45°, the amount of movement of the nut 54 can be sufficiently ensured.

[0071] The mechanical device 1 also includes two actuators 50. The two actuators 50 are arranged in parallel.

[0072] According to this, the actuator 50 can be made smaller, and the mechanical device 1 can be made smaller.

[0073] Next, a mechanical device 1 according to a modified embodiment of the present disclosure will be described, focusing mainly on the differences from the mechanical device 1 of the above embodiment.

[0074] For example, the mechanical device 1 may include three or more first connecting portions 20 and first finger portions 40a. The mechanical device 1 may also include three or more second connecting portions 30 and second finger portions 40b. In this case, three or more actuators 50 may be arranged in parallel.

[0075] Furthermore, the finger 40 does not necessarily have to include the third link 44. In this case, the finger 40 includes a wire that connects the tip 43 and the nut 54. In this case, when the nut 54 moves relative to the screw shaft 53, the tip 43 is displaced via the wire, and the finger 40 operates.

[0076] The screw shaft 53 may have a single thread. The number of guide shaft members 55 provided in the actuator 50 may be one.

[0077] Furthermore, the actuator 50 does not necessarily have to include the ball B. In this case, the screw shaft 53 and the nut 54 form a so-called sliding screw.

[0078] Furthermore, the lead angle θ may be 45° or greater and 60° or less. In this case, compared to when the lead angle θ is smaller than 45°, when an external force F acting along the central axis Ac of the screw shaft 53 acts on the nut 54 and causes the nut 54 to move, the component of the external force F acting in the direction along the thread groove Gs of the screw shaft 53 can be made larger. This further reduces the interference with the movement of the nut 54 and the rotation of the screw shaft 53 due to friction between the screw shaft 53 and the nut 54.

[0079] According to this modification, the lead angle θ of the screw of the screw shaft 53 is equal to or greater than 45° and equal to or less than 60°.

[0080] This allows the actuator 50 to operate appropriately both when the nut 54 is moved by rotating the screw shaft 53 and when the nut 54 is moved to rotate the screw shaft 53. Furthermore, when the nut 54 is moved to rotate the screw shaft 53, the force required to move the nut 54 can be made smaller than when the lead angle θ of the screw of the screw shaft 53 is smaller than 45°. This makes it easier to manually move the nut 54. [Explanation of symbols]

[0081] 1 Mechanical equipment 50 Actuator 53 Screw shaft 54 Nut 54a Main body 55 Guide shaft member B-ball θ lead angle

Claims

1. A screw shaft, A nut having a main body through which the screw shaft passes and fitted to the screw shaft so as to be rotatable relative to the screw shaft; a plurality of balls circulating within the nut between the nut and the screw shaft; a guide shaft member that penetrates the main body and guides the nut, Actuator.

2. The lead angle of the screw shaft is 45°±15°. The actuator of claim 1 .

3. The lead angle of the screw shaft is 45° or more and 60° or less. The actuator of claim 1 .

4. A plurality of the guide shaft members are provided. The actuator of claim 1 .

5. The screw of the screw shaft is a multiple thread. The actuator of claim 1 .

6. Two actuators according to claim 1 are provided, The two actuators are arranged in parallel. Mechanical equipment.

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