Two-way drive

Abstract

To provide a two-way drive device capable of reducing a backlash to improve output accuracy and capable of transmitting relatively large torque even when reduced in size.SOLUTION: A rotary support 12 is provided rotatably about a first axis. A cylindrical-shaped inner rotor 13 is provided on the rotary support 12 to have a second axis of the central axis orthogonal to the first axis and to be rotatable about the second axis. A cylindrical outer rotor 14 covers both sides of the inner rotor 13 and is provided rotatably about the first axis. The outer rotor 14 has, on an inner surface thereof, a plurality of engagement portions each provided along a trochoidal curve extending in a circumferential direction. The inner rotor 13 has a plurality of protrusion portions that protrude in directions oblique to the second axis and have tips engaged with corresponding engagement portions. When the outer rotor 14 is rotated, each protrusion portion slides relatively along each engagement portion, and the inner rotor 13 rotates about the second axis.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bi-directional drive device. [Background technology]

[0002] Conventionally, as a driving mechanism for the joints of a robot arm, etc., in order to enable driving in multiple directions with a single joint, driving devices have been developed that can convert two rotations around a given axis into rotations around two perpendicular axes using conical gears (tapered gears), bevel gears, worm gears, etc. (see, for example, Patent Documents 1 to 3).

[0003] By using such a drive device, it is possible to realize not only drive in two directions, but also three rotational degrees of freedom (3-RDoF) by driving a spherical gear to rotate in two directions (see, for example, Patent Documents 2 and 3 and Non-Patent Document 1), thereby making it possible to reduce the size and improve the functionality of the joints of a robot arm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-237206 A [Patent Document 2] JP 2018-80717 A [Patent Document 3] JP 2019-90495 A [Non-patent literature]

[0005] [Non-Patent Document 1] Kazuki Abe, Kenjiro Tadakuma, and Riichiro Tadakuma, “ABENICS: Active Ball Joint Mechanism With Three-DoF Based on Spherical Gear Meshings”, IEEE Transactions on Robotics, [online], April 2021, [Retrieved August 7, 2021], Internet〈URL: https: / / www.researchgate.net / publication / 351357682〉, DOI: 10.1109 / TRO.2021.3070124 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the bidirectional drive devices described in Patent Documents 1 to 3 have the problem that backlash causes an error in output because they use gears when changing the direction of rotation. In addition, because the strength of the gear teeth determines the amount of torque that can be transmitted, there is also the problem that it becomes difficult to transmit a large torque when the device is made smaller.

[0007] The present invention has been made in response to these problems, and aims to provide a bidirectional drive device that can reduce backlash and improve output accuracy, and can transmit a relatively large torque even when miniaturized. [Means for solving the problem]

[0008] In order to achieve the above object, the bidirectional drive device according to the present invention comprises a support part, a rotary support supported by the support part and rotatable about a first axis, an inner rotor having a cylindrical shape with a predetermined thickness, a second axis which is the central axis of the inner rotor being perpendicular to the first axis and mounted on the rotary support so as to be rotatable about the second axis, an outer rotor having a cylindrical shape whose central axis coincides with the first axis and on which the inner rotor is disposed so as to cover at least both sides of the inner rotor, the outer rotor being supported by the support part and rotatable about the first axis, inner driving means for rotating the rotary support about the first axis, and a drive means for rotating the outer rotor about the first axis. and an outer driving means for rotating the outer rotor by the outer driving means, the outer rotor having on its inner surface a plurality of engagement portions respectively provided along a plurality of trochoid curves having a predetermined integer period extending in the circumferential direction, the inner rotor having a plurality of protrusions provided corresponding to the respective engagement portions, each protrusion protruding from one of the side surfaces of the inner rotor in a direction oblique to the second axis, with a tip portion engaging with a corresponding engagement portion and provided relatively slidable along the engagement portion, and when the outer rotor is rotated by the outer driving means, the tip portion of each protrusion slides relatively along the corresponding engagement portion, causing the inner rotor to rotate about the second axis.

[0009] In the bidirectional drive device according to the present invention, by rotating the outer rotor around the first axis by the outer drive means, each engagement portion provided on the inner surface of the outer rotor moves along the circumferential direction, and the tip of each protrusion engaged with the corresponding engagement portion also slides relatively along each engagement portion. At this time, each engagement portion is provided along a plurality of trochoid curves having a predetermined integer period, and each protrusion protrudes from one side surface of the inner rotor in a direction oblique to the second axis, so that the tip of each protrusion moves to draw a circle centered on the second axis. This allows the inner rotor to rotate around the second axis. In addition, by rotating the rotating support around the first axis by the inner drive means, the inner rotor provided on the rotating support can be rotated around the first axis. In this way, the bidirectional drive device according to the present invention can convert two rotations around the first axis into rotations of the inner rotor around the first axis and the second axis that are perpendicular to each other.

[0010] The bidirectional drive device of the present invention uses a cam mechanism that utilizes each engagement portion provided on the inner surface of the outer rotor and each protrusion provided on one side of the inner rotor, rather than gears, when converting the rotation about a first axis by the outer drive means into rotation about a second axis that is perpendicular to the first axis. This makes it possible to reduce the number of built-in gears compared to conventional devices that use gears to convert the direction of rotation, thereby reducing backlash and improving output accuracy. In addition, since gears are not used to convert the direction of rotation, there is no need to limit the torque to be transmitted by the strength of the teeth, and a relatively large torque can be transmitted even when the device is compact.

[0011] In the bidirectional drive device according to the present invention, it is preferable that each of the engagement parts is provided along a trochoid curve drawn by a fixed point inside or outside the circle when a circle is rolled on the inner surface of the outer rotor along a straight line extending in the circumferential direction. In particular, it is preferable that each of the engagement parts is provided along a trochoid curve that switches left and right every half period with respect to a line where a plane perpendicular to the first axis and including the second axis intersects with the inner surface of the outer rotor. These trochoid curves can be drawn by rolling a circle so that the center of the circle moves on a line where a plane perpendicular to the first axis and including the second axis intersects with the inner surface of the outer rotor. In this case, the inner rotor can be smoothly rotated around the second axis. Also, in this case, it is preferable that each of the trochoid curves has a different phase with respect to the position in the circumferential direction of the inner surface of the outer rotor. This makes it possible to make the direction of rotation by the outer driving means correspond to the direction of rotation around the second axis of the inner rotor, and to rotate the inner rotor in a desired direction around the second axis. The amplitudes of the engagement portions in the width direction of the inner surface of the outer rotating body may be the same or different.

[0012] In the bidirectional drive device according to the present invention, the engagement parts and protrusions may have any configuration as long as the tip of each protrusion is engaged with the corresponding engagement part and can slide relatively along the engagement part. The number of each engagement part and each protrusion may be two or more. For example, each protrusion may have a first protrusion having a cylindrical tip and protruding from one side surface of the inner rotor, and a second protrusion having a cylindrical tip and protruding from the other side surface of the inner rotor, with a larger tip diameter than the first protrusion and a smaller protrusion amount from the inner rotor, and each engagement part may have a first slide groove formed of a groove into which the tip of the first protrusion is inserted and engaged, and a second slide groove formed of a groove into which the tip of the second protrusion is inserted and engaged, and is wider and shallower than the first slide groove. In this way, by changing the size and protrusion amount of each protrusion and the width and depth of each engagement part formed of the slide groove, the inner rotor can be smoothly rotated around the second axis.

[0013] In the bidirectional drive device according to the present invention, the inner drive means may be configured to rotate the rotary support by a motor having a rotation axis parallel to the first axis or a rotation axis coaxial with the first axis, and the outer drive means may be configured to rotate the outer rotor by a motor having a rotation axis parallel to the first axis or a rotation axis coaxial with the first axis. In this case, the structure can be made simpler. Also, the number of built-in gears can be reduced, and backlash can be further reduced.

[0014] In the bidirectional drive device according to the present invention, the inner rotor is preferably disposed so that the first shaft passes through the center in the thickness direction. In this case, the inner rotor can be smoothly rotated about the first shaft. Effect of the Invention

[0015] According to the present invention, it is possible to provide a bidirectional drive device that can reduce backlash and increase output accuracy, and that can transmit a relatively large torque even when made compact. [Brief description of the drawings]

[0016] [Figure 1] 1A is a perspective view showing a bidirectional drive device according to an embodiment of the present invention, and FIG. 1B is a partially cutaway perspective view showing a support portion and an outer rotor. [Diagram 2] 1A and 1B are a right side view and a front view, respectively, showing a bidirectional drive device according to an embodiment of the present invention. [Diagram 3] 1 is a vertical cross-sectional view showing a bidirectional drive device according to an embodiment of the present invention. [Figure 4] 2A is a perspective view, FIG. 2B is a front view, FIG. 2C is a right side view, FIG. 2D is a cross-sectional view taken along line AA, and FIG. 2E is a cross-sectional view taken along line BB, showing an outer rotating body of a bidirectional drive device according to an embodiment of the present invention. [Diagram 5] 1A is a front view of an outer rotor of a bidirectional drive device according to an embodiment of the present invention, FIG. 1B is a developed view of the inner surface, and FIG. 1C is a cross-sectional view taken along the lines C1 to C12 in FIG. [Figure 6] FIG. 1A is a perspective view showing a state in which the bidirectional drive device according to an embodiment of the present invention is used as a joint of a robot arm, and FIG. 1B is a perspective view showing a state in which the inner rotor is a saddle gear. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 5 show a bidirectional drive device according to an embodiment of the present invention. As shown in FIGS. 1 to 3, the bidirectional drive device 10 includes a support portion 11, a rotary support 12, an inner rotor 13, an outer rotor 14, an inner drive means 15, and an outer drive means 16.

[0018] The support 11 has a support body 21 having a generally rectangular parallelepiped shape, and an upper support 22 provided on the upper part of the support body 21 and thinner than the support body 21. The support body 21 has a cross-sectional shape with an upper part rising in an arc shape. The upper support 22 narrows in width toward the top, and has an upper part in an arc shape in cross-section.

[0019] The rotary support 12 has a roll rotor 23 having a generally cylindrical shape and a pair of annular mounting parts 24 arranged in an annular shape. The roll rotor 23 is attached to the support body 21 such that the rear end is embedded in the upper part of the support body 21 with the first shaft 41, which is the central axis, horizontal. The roll rotor 23 is attached to the support body 21 via a bearing 31 so as to be rotatable around the first shaft 41. Each annular mounting part 24 protrudes from the end of the tip surface of the roll rotor 23 toward the tip side and is arranged to face each other across the central axis of the roll rotor 23. Each annular mounting part 24 has the same inner diameter.

[0020] The inner rotor 13 has a cylindrical shape with a thickness smaller than its diameter. The inner rotor 13 is sandwiched between the annular mounting parts 24 so that the second axis 42, which is the central axis of the inner rotor 13, is perpendicular to the first axis 41 and the first axis 41 passes through the center in the thickness direction. The inner rotor 13 is attached to each annular mounting part 24 via a bearing 32 so as to be rotatable around the second axis 42. The inner rotor 13 has a first protrusion 25 and a second protrusion 26 that are provided so as to protrude from each side surface in a direction oblique to the second axis 42 through the inside of each annular mounting part 24. The first protrusion 25 and the second protrusion 26 have a cylindrical tip, and a bearing 33 is attached along the periphery of the tip. The second protrusion 26 has a larger diameter at the tip than the first protrusion 25, and is formed so as to protrude less from the inner rotor 13.

[0021] As shown in FIG. 4, the outer rotor 14 has a cylindrical shape with a central portion in the width direction bulging outward in an arc shape. The outer rotor 14 has two engagement portions, consisting of a first slide groove 27 and a second slide groove 28, provided along the circumferential direction on the inner surface. As shown in FIG. 5, the first slide groove 27 and the second slide groove 28 are provided along two trochoid curves 27a, 28a that switch sides every half cycle with respect to the center line 14a in the width direction of the inner surface of the outer rotor 14. The first slide groove 27 has a predetermined depth and width, and is formed so that the trochoid curve 27a is at the center of its width. The second slide groove 28 has a width that is shallower and wider than the first slide groove 27, and is formed so that the trochoid curve 28a is at the center of its width. The trochoid curves 27a, 28a are provided along the circumferential direction of the inner surface of the outer rotor 14 so that one revolution is one cycle, and are provided so that their phases with respect to the circumferential position are different from each other.

[0022] The outer rotor 14 is arranged so that its central axis coincides with the first shaft 41 and covers both sides of the inner rotor 13 with the inner rotor 13 inserted inside. The outer rotor 14 has a cylindrical flange portion 29 that protrudes toward the rear end side along the rear end surface. The flange portion 29 has teeth formed on the outer surface and forms a spur gear. As shown in Figures 1 to 3, the flange portion 29 of the outer rotor 14 is attached to the side surface of the tip of the roll rotor 23 via a bearing 34 so as to be rotatable around the first shaft 41. In this way, the outer rotor 14 is supported by the support portion 11.

[0023] As shown in FIG. 1(b) and FIG. 3, the first slide groove 27 is provided so that the tip of the first protrusion 25 can be inserted and engaged therein, and the second slide groove 28 is provided so that the tip of the second protrusion 26 can be inserted and engaged therein. The first protrusion 25 is provided so that it can slide relatively along the first slide groove 27 when its tip is engaged with the first slide groove 27. The second protrusion 26 is also provided so that it can slide relatively along the second slide groove 28 when its tip is engaged with the second slide groove 28. The first slide groove 27 and the second slide groove 28 are provided along trochoid curves 27a, 28a that switch sides every half cycle with respect to a line (center line 14a) where a plane that is perpendicular to the first axis 41 and includes the second axis 42 intersects with the inner surface of the outer rotor 14.

[0024] The inner driving means 15 is made up of a motor, and is attached to the support body 21 from the rear end side so that its rotating shaft 15a is coaxial with the first shaft 41. The inner driving means 15 penetrates the support body 21, and the tip of its rotating shaft 15a is connected to the rear end surface of the roll rotating body 23, and is provided so as to be able to rotate the rotary support 12 around the first shaft 41.

[0025] The outer driving means 16 is composed of a motor, and a transmission gear 30 consisting of a spur gear is attached to the tip of the rotating shaft 16a. The transmission gear 30 is provided so as to mesh with the spur gear of the flange portion 29. The outer driving means 16 is attached so that its rotating shaft 16a is parallel to the first shaft 41 and penetrates the upper support 22 from the rear end side so that the transmission gear 30 meshes with the spur gear of the flange portion 29. The outer driving means 16 is provided so as to be able to rotate the outer rotor 14 around the first shaft 41 via the transmission gear 30.

[0026] When the outer rotating body 14 is rotated about the first axis 41 by the outer driving means 16 in the two-direction driving device 10, the first slide groove 27 and the second slide groove 28 move along the circumferential direction of the outer rotating body 14, and the tip portions of the first protrusion 25 and the second protrusion 26 are configured to relatively slide along the first slide groove 27 and the second slide groove 28, respectively. Further, thereby, the tip portions of the first protrusion 25 and the second protrusion 26 move so as to draw a circle about the second axis 42, and the inner rotating body 13 is configured to rotate about the second axis 42.

[0027] Next, the operation will be described. In the two-direction driving device 10, the inner rotating body 13 can be rotated about the second axis 42 by rotating the outer rotating body 14 about the first axis 41 by the outer driving means 16. Further, the inner rotating body 13 provided on the rotation support 12 can be rotated about the first axis 41 by rotating the rotation support 12 about the first axis 41 by the inner driving means 15. Thus, the two-direction driving device 10 can convert two rotations around the first axis 41 into the rotation of the inner rotating body 13 around the first axis 41 and the second axis 42 which are orthogonal to each other.

[0028] The two-way drive device 10 uses a cam mechanism that utilizes the first slide groove 27 and the second slide groove 28 provided on the inner surface of the outer rotor 14 and the first protrusion 25 and the second protrusion 26 provided on each side of the inner rotor 13, instead of gears, when converting the rotation about the first axis 41 by the outer drive means 16 into rotation about the orthogonal second axis 42. This allows the number of built-in gears to be reduced compared to conventional devices that use gears to convert the direction of rotation, reducing backlash and improving output accuracy. In addition, compared to conventional devices that use worm gears, there is no sliding friction caused by the worm gear, so transmission efficiency can be improved. In addition, since gears are not used to convert the direction of rotation, there is no need to limit the torque to be transmitted by the strength of the teeth, and a relatively large torque can be transmitted even when the device is made small. In addition, the number of components can be reduced, allowing for a relatively simple structure.

[0029] In the bidirectional drive device 10, the trochoid curves 27a, 28a of the first slide groove 27 and the second slide groove 28 are provided so that their phases with respect to the circumferential position on the inner surface of the outer rotor 14 are different from each other, so that the rotation direction by the outer drive means 16 can correspond to the rotation direction about the second shaft 42 of the inner rotor 13, and the inner rotor 13 can be rotated in a desired direction about the second shaft 42. Note that the trochoid curves 27a, 28a of the first slide groove 27 and the second slide groove 28 may have the same amplitude in the width direction of the inner surface of the outer rotor 14 or different amplitudes.

[0030] In the bi-directional drive device 10, the first protrusion 25 and the second protrusion 26 have different sizes and protrusion amounts, and the first slide groove 27 and the second slide groove 28 have different widths and depths, so that the inner rotor 13 can be smoothly rotated about the second shaft 42. Also, in the bi-directional drive device 10, the first shaft 41 is provided to pass through the center of the inner rotor 13 in the thickness direction, so that the inner rotor 13 can be smoothly rotated about the first shaft 41.

[0031] Note that in the two-way drive device 10, the engaging portions of the outer rotating body 14 and the protruding portions of the inner rotating body 13 are not limited to two, and may be three or more. Further, each engaging portion and each protruding portion may have any configuration as long as the tip of each protruding portion can slide relative to the corresponding engaging portion along the engaging portion in a state where the tip is engaged with the corresponding engaging portion, and is not limited to a configuration in which each engaging portion is formed by a groove.

[0032] The two-way drive device 10 can extract the movement of the inner rotating body 13 as an output from the opening on the tip side of the outer rotating body 14. Since the two-way drive device 10 can rotate the inner rotating body 13 in two directions, for example, as shown in FIG. 6(a), by connecting an arm 51 to the inner rotating body 13, it can be used to drive joints of a robot arm that can be driven in multiple directions. Further, for example, as shown in FIG. 6(b), teeth are formed on the outer surface of the inner rotating body 13 to form a saddle-shaped gear described in Patent Documents 2, 3, or Non-Patent Document 1, and two of these two-way drive devices 10 are used to rotationally drive the spherical gears described in Patent Documents 2, 3, or Non-Patent Document 1 from different directions, thereby realizing three rotational degrees of freedom (3-RDoF). Also, the inner rotating body 13 itself, the spherical gear driven by the inner rotating body 13, etc. can be used as omnidirectional moving wheels.

Explanation of Reference Numerals

[0033] 10 Two-way drive device 11 Support portion 21 Support portion main body 22 Upper support body 12 Rotation support body 23 Roll rotating body 24 Annular mounting portion 13 Inner rotating body 25 First protruding portion 26 Second protruding portion 14 Outer rotating body 14a Center line 27 First slide groove 27a Trochoid curve 28 Second slide groove 28a Trochoid curve 29 Flange 15 Inner drive means 16 Outer drive means 30 Transmission Gear 31, 32, 33, 34 Bearings 51 Arm

Claims

1. A support portion; a rotation support supported by the support portion and rotatably provided around a first axis; an inner rotor having a cylindrical shape with a predetermined thickness, a second axis serving as a central axis of the inner rotor being perpendicular to the first axis and being provided on a rotary support so as to be rotatable about the second axis; an outer rotor having a cylindrical shape, a central axis of which coincides with the first axis, the inner rotor being disposed inside the outer rotor so as to cover at least both sides of the inner rotor, the outer rotor being supported by the support portion, and being rotatable about the first axis; an inner drive means for rotating the rotary support about the first axis; an outer driving means for rotating the outer rotor about the first axis; the outer rotating body has, on an inner surface thereof, a plurality of engagement portions provided along a plurality of trochoid curves having a predetermined integer period extending in a circumferential direction, the inner rotating body has a plurality of protrusions provided corresponding to the respective engagement portions, each protrusion protruding from one side surface of the inner rotating body in a direction oblique to the second axis, a tip portion of the protrusion engaging with a corresponding engagement portion and being provided relatively slidably along the engagement portion, When the outer rotating body is rotated by the outer driving means, the tip ends of the protrusions slide relatively along the respective engagement portions, thereby causing the inner rotating body to rotate about the second shaft. A two-way drive device.

2. 2. The bidirectional drive device according to claim 1, wherein each engagement portion is provided along a trochoid curve that alternates left and right every half period with respect to a line that is perpendicular to the first axis and includes the second axis and intersects with the inner surface of the outer rotating body.

3. 3. The bidirectional driving device according to claim 2, wherein the trochoid curves have mutually different phases with respect to positions in the circumferential direction of the inner surface of the outer rotor.

4. each protruding portion has a first protruding portion having a cylindrical tip portion protruding from one side surface of the inner rotating body, and a second protruding portion has a cylindrical tip portion protruding from the other side surface of the inner rotating body, the tip portion having a larger diameter than the first protruding portion, and a smaller amount of protrusion from the inner rotating body, Each of the engagement portions has a first slide groove, which is a groove into which the tip of the first protrusion is inserted and can be engaged, and a second slide groove, which is a groove into which the tip of the second protrusion is inserted and can be engaged, and which is wider and shallower than the first slide groove.

4. A bidirectional drive device according to claim 1 , wherein the drive mechanism is a drive shaft.

5. 5. The bidirectional drive device according to claim 1, wherein the inner rotor is disposed so that the first axis passes through a center in a thickness direction.

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