JP7681304B2 - Two-way drive - Google Patents

Description

The present invention relates to a two-way drive device.

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

By using such a drive device, it is possible to realize not only two-way drive, but also three rotational degrees of freedom (3-RDoF) by, for example, rotating a spherical gear in two directions (see, for example, Patent Documents 2 and 3 and Non-Patent Document 1), which allows for miniaturization and high functionality of the joints of a robot arm.

JP 2014-237206 A JP 2018-80717 A JP 2019-90495 A

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

However, the bidirectional drive devices described in Patent Documents 1 to 3 use gears when changing the direction of rotation, which causes an output error due to backlash. 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.

The present invention was made with a focus on these issues, and aims to provide a two-way drive device that can reduce backlash and improve output accuracy, and can transmit a relatively large torque even when compact.

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

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 part 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 part also slides relatively along each engagement part. At this time, each engagement part 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.

The two-way 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 of the sides 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, because gears are not used to convert the direction of rotation, there is no need to limit the torque transmitted by the strength of the teeth, and a relatively large torque can be transmitted even when the device is compact.

In the bidirectional drive device according to the present invention, it is preferable that each engagement portion is provided along a trochoid curve drawn by a fixed point inside or outside the circle when the circle is rolled along a straight line extending in the circumferential direction on the inner surface of the outer rotor. In particular, it is preferable that each engagement portion is provided along a trochoid curve that switches left and right every half cycle 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 the 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. In addition, in this case, it is preferable that each trochoid curve 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 correspond the direction of rotation by the outer driving means to the direction of rotation around the second axis of the inner rotor, and to rotate the inner rotor in the desired direction around the second axis. In addition, the amplitude of each engagement portion in the width direction of the inner surface of the outer rotating body may be the same or different.

In the two-way drive device according to the present invention, each of the engagement parts and each of the 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. Also, each of the engagement parts and each of the protrusions may have two or more. For example, each of the protrusions 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 of the engagement parts may have a first slide groove consisting of a groove into which the tip of the first protrusion is inserted and engaged, and a second slide groove consisting 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 consisting of the slide groove, the inner rotor can be smoothly rotated around the second axis.

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, a simpler structure can be achieved. Also, the number of built-in gears can be reduced, further reducing backlash.

In the bidirectional drive device according to the present invention, it is preferable that the inner rotor is arranged so that the first axis passes through the center in the thickness direction. In this case, the inner rotor can be smoothly rotated around the first axis.

The present invention provides a bidirectional drive device that can reduce backlash and increase output accuracy, and can transmit a relatively large torque even when miniaturized.

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. 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. 1 is a vertical cross-sectional view showing a bidirectional drive device according to an embodiment of the present invention; 1A is a perspective view of an outer rotating body of a bidirectional drive device according to an embodiment of the present invention, FIG. 1B is a front view, FIG. 1C is a right side view, FIG. 1D is a cross-sectional view along line A-A, and FIG. 1E is a cross-sectional view along line B-B. 1A is a front view showing an outer rotating body of a bidirectional drive device according to an embodiment of the present invention, FIG. 1B is a developed view of an inner surface, and FIG. 1C is a cross-sectional view taken along line C1-C12 in 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.

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 body 12, an inner rotor 13, an outer rotor 14, an inner drive means 15, and an outer drive means 16.

The support section 11 has a support section main body 21 that is roughly rectangular in shape, and an upper support body 22 that is provided on top of the support section main body 21 and is thinner than the support section main body 21. The support section main body 21 has a cross-sectional shape with an upper portion that rises in an arc shape. The upper support body 22 narrows in width toward the top, and has an upper portion that has an arc-shaped cross-sectional shape.

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 with its rear end embedded in the upper part of the support body 21 with the first shaft 41, which is the central axis, held 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.

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 its central axis, 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.

As shown in FIG. 4, the outer rotor 14 has a cylindrical shape with the center in the width direction bulging outward in an arc shape. The outer rotor 14 has two engagement parts 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. Each trochoid curve 27a, 28a is provided along the circumferential direction of the inner surface of the outer rotor 14 so that one revolution is one cycle, and is provided so that the phases with respect to the circumferential position are different from each other.

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 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 of the tip of the roll rotor 23 via a bearing 34 so that it can rotate around the first shaft 41. In this way, the outer rotor 14 is supported by the support portion 11.

1(b) and 3, the first slide groove 27 is provided so that the tip of the first protrusion 25 can be inserted and engaged, and the second slide groove 28 is provided so that the tip of the second protrusion 26 can be inserted and engaged. 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 left and right 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.

The inner drive means 15 is made 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 drive 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 the rotating support 12 is provided so that it can rotate around the first shaft 41.

The outer driving means 16 is made of a motor, and a transmission gear 30 consisting of a spur gear is attached to the tip of its rotating shaft 16a. The transmission gear 30 is arranged 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 arranged so that the outer rotating body 14 can rotate around the first shaft 41 via the transmission gear 30.

The bidirectional drive device 10 is configured such that, when the outer rotor 14 is rotated around the first shaft 41 by the outer drive means 16, the first slide groove 27 and the second slide groove 28 move along the circumferential direction of the outer rotor 14, and the tips of the first protrusion 25 and the second protrusion 26 slide relatively along the first slide groove 27 and the second slide groove 28, respectively. As a result, the tips of the first protrusion 25 and the second protrusion 26 move in a circle centered on the second shaft 42, and the inner rotor 13 rotates around the second shaft 42.

Next, the operation will be described.
The bidirectional drive device 10 can rotate the inner rotor 13 about the second shaft 42 by rotating the outer rotor 14 about the first shaft 41 by the outer drive means 16. Also, the inner drive means 15 can rotate the inner rotor 13 provided on the rotary support 12 about the first shaft 41 by rotating the rotary support 12 about the first shaft 41. In this way, the bidirectional drive device 10 can convert two rotations about the first shaft 41 into rotations of the inner rotor 13 about the first shaft 41 and the second shaft 42 that are perpendicular to each other.

When converting the rotation around the first axis 41 by the outer driving means 16 into the rotation around the second axis 42, which is perpendicular to the first axis 41, 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. 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, the transmission efficiency can be improved because no sliding friction occurs due to the worm gear. In addition, since no gears are used to convert the direction of rotation, there is no need to limit the torque to be transmitted due to 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.

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

The bidirectional drive device 10 allows the inner rotor 13 to rotate smoothly around the second shaft 42 because 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. In addition, the bidirectional drive device 10 allows the inner rotor 13 to rotate smoothly around the first shaft 41 because the first shaft 41 is arranged to pass through the center of the thickness of the inner rotor 13.

In the bidirectional drive device 10, the number of engaging portions of the outer rotor 14 and the number of protruding portions of the inner rotor 13 are not limited to two, and may be three or more. Furthermore, as long as the tip of each engaging portion and each protruding portion is engaged with the corresponding engaging portion and can slide relatively along the engaging portion, each engaging portion is not limited to being configured as a groove, and may have any configuration.

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

REFERENCE SIGNS LIST 10 Bidirectional drive device 11 Support portion 21 Support portion main body 22 Upper support 12 Rotation support 23 Roll rotor 24 Annular mounting portion 13 Inner rotor 25 First protrusion 26 Second protrusion 14 Outer rotor 14a Center line 27 First slide groove 27a Trochoid curve 28 Second slide groove 28a Trochoid curve 29 Flange portion 15 Inner drive means 16 Outer drive means 30 Transmission gear 31, 32, 33, 34 Bearings

51 Arm

Claims (5)

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,
a bidirectional drive device configured such that, when the outer rotating body is rotated by the outer driving means, the tip ends of each protrusion move relatively slidingly along each engagement portion, thereby causing the inner rotating body to rotate about the second axis. The bidirectional drive device according to claim 1, characterized in that each engagement portion is provided along a trochoid curve that alternates left and right every half cycle 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 rotor. The bidirectional drive device according to claim 2, characterized in that the phases of the trochoid curves with respect to the circumferential position of the inner surface of the outer rotor are different from each other. 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,
The bidirectional drive device according to any one of claims 1 to 3, characterized in that each engagement portion has a first slide groove consisting of a groove into which a tip portion of the first protrusion can be inserted and engaged, and a second slide groove consisting of a groove into which a tip portion of the second protrusion can be inserted and engaged, the second slide groove being wider and shallower than the first slide groove. 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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