JP7728117B2 - Parallel link mechanism and link actuator - Google Patents

Description

This disclosure relates to a parallel link mechanism and a link actuator.

For example, Patent Document 1 (JP 2014-224564 A) discloses a link actuation device. The link actuation device described in Patent Document 1 includes a base link hub, a tip link hub, multiple link mechanisms, and a wire rod that serves as a rotational power transmission mechanism independent of the link mechanisms.

JP 2014-224564 A

The above-mentioned link actuation device uses flexible wire as the rotational power transmission mechanism, which results in a small transmission torque and limits the types of work it can perform. Furthermore, the above-mentioned link actuation device lacks overall rigidity, which can lead to deformation of the link actuation device due to the workload, potentially reducing positional accuracy and operability.

This disclosure has been made to solve the above-mentioned problems. Specifically, this disclosure provides a parallel link mechanism and link actuator that are highly rigid and capable of transmitting sufficient rotational power to the tip link hub.

The parallel link mechanism according to the present disclosure comprises a base link hub, a tip link hub, a plurality of links, and a beam member. Each of the plurality of links has a first end link member, a second end link member, and an intermediate link member. The first end link member is connected at one end to the base link hub rotatably about a first rotation axis. The second end link member is connected at one end to the tip link hub rotatably about a second rotation axis. The intermediate link member is connected at one end to the other end of the first end link member rotatably about a third rotation axis. The intermediate link member is connected at the other end to the other end of the second end link member rotatably about a fourth rotation axis. The central axis of the base link hub, the first rotation axis, and the third rotation axis intersect at the center point of the first spherical link. The central axis of the tip link hub, the second rotation axis, and the fourth rotation axis intersect at the center point of the second spherical link. The beam member is positioned to pass through the center point of the first spherical link and the center point of the second spherical link. The beam member includes a first connection portion and a second connection portion. The first connection portion is connected to the base link hub so as to be rotatable about the central axis of the base link hub. The second connection portion is connected to the tip link hub so as to be rotatable about the central axis of the tip link hub. The first connection portion and the second connection portion have at least one of a universal joint and a constant velocity joint.

The link actuation device according to the present disclosure comprises the above-described parallel link mechanism and at least two or more drive sources. The positions and orientations of the base end link hub and the tip end link hub are determined by at least two or more drive sources.

As a result of the above, a highly rigid parallel link mechanism and link actuator can be obtained that can transmit sufficient rotational power to the tip link hub.

FIG. 1 is a schematic perspective view of a link actuation device according to a first embodiment. FIG. 2 is a schematic front view of the link actuator shown in FIG. 1 . FIG. 2 is a schematic top view of the link actuator shown in FIG. 1 . FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. FIG. 3 is a schematic cross-sectional view taken along line VV in FIG. 2. 1 is a schematic diagram showing the relationship between the central axis CL1, the central axis CL2, and the first to fourth rotation axes RA1 to RA4. FIG. FIG. 2 is a schematic perspective view for explaining an operating state of the link actuator shown in FIG. 1 . 2 is a partial cross-sectional schematic view for explaining an operating state of the link actuator shown in FIG. 1. FIG. FIG. 10 is a schematic perspective view of a link actuation device according to a second embodiment. FIG. 10 is a schematic front view of the link actuator shown in FIG. 9 . FIG. 10 is a schematic top view of the link actuator shown in FIG. 9 . 12 is a schematic cross-sectional view taken along line XII-XII in FIG. 11. 10 is a schematic cross-sectional view for explaining an operating state of the link actuator shown in FIG. 9 . FIG.

Embodiments of the present disclosure will be described below. Note that identical components will be assigned the same reference numbers and their descriptions will not be repeated.

(Embodiment 1)
The parallel link mechanism 100 and the link actuator 400 according to the first embodiment will be described below.

<Configuration of parallel link mechanism and link actuator>
FIG. 1 is a schematic perspective view of a link actuation device 400 according to the first embodiment. FIG. 2 is a schematic front view of the link actuation device 400 shown in FIG. 1. FIG. 3 is a schematic top view of the link actuation device 400 shown in FIG. 1. FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a schematic cross-sectional view taken along line V-V in FIG. 2. FIG. 6 is a schematic diagram showing the relationship between the central axis CL1, the central axis CL2, and the first to fourth rotation axes RA1 to RA4. FIG. 7 is a schematic perspective view illustrating the operating state of the link actuation device 400 shown in FIG. 1. FIG. 8 is a partial cross-sectional view illustrating the operating state of the link actuation device 400 shown in FIG. 1.

As shown in Figures 1 to 8, the link actuation device 400 mainly comprises a parallel link mechanism 100, three drive sources 500, and a beam member drive source 501.

The parallel link mechanism 100 comprises a base link hub 10, a tip link hub 20, multiple links 30, and a beam member 40.

The base link hub 10 can have any shape, but is, for example, cup-shaped. As shown in FIG. 4, an opening is formed in the bottom surface of the base link hub 10 for inserting part of the beam member 40. A side wall is formed around the outer periphery of the bottom surface of the base link hub 10, extending in a direction intersecting the bottom surface (toward the tip link hub 20). Through holes are formed in the side wall. These through holes are formed in three locations on the side wall. The three through holes are equally spaced on the annular side wall when viewed from a direction perpendicular to the bottom surface. The three through holes do not have to be equally spaced. The central axis of the base link hub 10 may be referred to as the central axis CL1.

The tip link hub 20 can have any shape, but is, for example, cup-shaped. As shown in FIG. 4, an opening is formed in the top surface of the tip link hub 20 for inserting a portion of the beam member 40. A side wall is formed around the outer periphery of the top surface of the tip link hub 20, extending in a direction intersecting the top surface (toward the base link hub 10). Through holes are formed in the side wall. These through holes are formed in three locations on the side wall. The three through holes are equally spaced on the annular side wall when viewed perpendicular to the top surface. The three through holes do not have to be equally spaced. The central axis of the tip link hub 20 may be referred to as the central axis CL2. Although not shown, an end effector is attached to the end of the beam member 40 protruding from the tip link hub 20.

Each of the multiple links 30 has a first end link member 31, a second end link member 32, and an intermediate link member 33. The number of multiple links 30 is, for example, three. However, the number of multiple links 30 may be two or four or more. It is preferable that each of the multiple links 30 have the same shape.

The first end link member 31 is rotatably connected at one end to the base end link hub 10. More specifically, a through hole (not shown) is formed at one end of the first end link member 31. A shaft member 34 passes through both the through hole formed at one end of the first end link member 31 and a through hole formed in the side wall of the base end link hub 10. As a result, the first end link member 31 is rotatably connected at one end to the base end link hub 10 around the central axis of the shaft member 34 (hereinafter sometimes referred to as the first rotation axis RA1). The first end link member 31 has, for example, an L-shape.

The second end link member 32 is rotatably connected at one end to the tip link hub 20. More specifically, a through hole (not shown) is formed at one end of the second end link member 32. A shaft member 35 passes through both the through hole formed at one end of the second end link member 32 and a through hole formed in the side wall of the tip link hub 20. As a result, the second end link member 32 is rotatably connected at one end to the tip link hub 20 around the central axis of the shaft member 35 (hereinafter sometimes referred to as the second rotation axis RA2). The second end link member 32 has, for example, an L-shape.

One end of the intermediate link member 33 is rotatably connected to the other end of the first end link member 31. More specifically, an insertion hole (not shown) is formed in one end of the intermediate link member 33. A through hole (not shown) is formed in the other end of the first end link member 31. A shaft member 36 is passed through both the insertion hole formed in one end of the intermediate link member 33 and the through hole formed in the other end of the first end link member 31.

As a result, the intermediate link member 33 is connected at one end to the other end of the first end link member 31 so as to be rotatable around the central axis of the shaft member 36 (hereinafter sometimes referred to as the third rotation axis RA3).

The other end of the intermediate link member 33 is rotatably connected to the other end of the second end link member 32. More specifically, an insertion hole (not shown) is formed in the other end of the intermediate link member 33. A through hole (not shown) is formed in the other end of the second end link member 32. A shaft member 37 is passed through both the insertion hole formed in the other end of the intermediate link member 33 and the through hole formed in the other end of the second end link member 32.

As a result, the intermediate link member 33 is connected at its other end to the other end of the second end link member 32 so as to be rotatable around the central axis of the shaft member 37 (hereinafter sometimes referred to as the fourth rotation axis RA4).

Figure 6 is a schematic diagram showing the interrelationships between the central axis CL1, central axis CL2, and first rotation axis RA1 to fourth rotation axis RA4. As shown in Figure 6, the central axis CL1, first rotation axis RA1, and third rotation axis RA3 intersect at one point. This point is designated as the spherical link center point P1. The central axis CL2, second rotation axis RA2, and fourth rotation axis RA4 intersect at one point. This point is designated as the spherical link center point P2. The line connecting the spherical link center point P1 and the spherical link center point P2 is designated as line RA5. Line RA5 intersects with the central axis CL1 at the spherical link center point P1. Line RA5 intersects with the central axis CL2 at the spherical link center point P2. This relationship always holds regardless of the posture of the parallel link mechanism 100. Note that Figure 6 shows a unique positional relationship in which the central axes CL1 and CL2 and the line RA5 are aligned on the same straight line. The posture of the parallel link mechanism 100 that results in the positional relationship shown in Figure 6 can be used as the origin posture of the parallel link mechanism 100.

As shown in Figure 8, the beam member 40 is arranged along a straight line RA5 that passes through the first spherical link center point P1 and the second spherical link center point P2. This relationship always holds true regardless of the position and orientation of the base link hub 10 and the tip link hub 20.

As shown in FIG. 4, the beam member 40 includes a linearly extending beam portion 43, connection portions 41 and 42, a base end portion 44, and a tip end portion 45. The connection portion 41, serving as the first connection portion, is connected to the base end link hub 10 so as to be rotatable about the central axis CL1 of the base end link hub 10 (see FIG. 6). The connection portion 42, serving as the second connection portion, is connected to the tip end link hub 20 so as to be rotatable about the central axis CL2 of the tip link hub 20. The connection portions 41 and 42 have universal joints including rotation axes passing through the spherical link center point P1 and the spherical link center point P2, respectively. The base end portion 44 protrudes outward from the opening of the base end link hub. A beam member drive source 501 is connected to the base end portion 44. The tip end portion 45 protrudes outward from the opening of the tip link hub. The beam portion 43 includes a hollow portion 40a. In other words, the beam portion 43 is a hollow cylindrical body.

The beam member 40 can be rotated by the beam member drive source 501 around the line RA5 as the rotation axis. The connection portions 41, 42 of the beam member 40 are connected to the base end link hub 10 or the tip end link hub 20 via a rotational resistance reducing member such as a bearing (not shown). Furthermore, because the connection portions 41, 42 have universal joints, the tip end portion 45 can be easily rotated by rotating the base end portion 44, even when the tip link hub 20 is positioned at various angles relative to the base end link hub 10, as shown in Figures 7 and 8.

The universal joints included in the connecting portions 41 and 42 may be, for example, Cardan joints that include two rotation axes that extend in different directions, intersecting the extension direction of the beam member 40. Any configuration may be used for the joints located in the connecting portions 41 and 42, as long as they are bendable in the extension direction of the beam member 40 and can transmit rotation about the straight line RA5 of the beam member 40.

The position and orientation of the base link hub 10 and the tip link hub 20 may be determined by at least two or more drive sources 500. As shown in Figures 1 to 3, the link actuator 400 is equipped with three drive sources 500. The drive sources 500 are, for example, motors.

Each driving source 500 is connected to the first end link member 31. The driving source 500 rotates the first end link member 31 around the first rotation axis RA1 shown in FIG. 6. The driving source 500 can determine the rotation angle of the first end link member 31 around the first rotation axis RA1. This can change the position and orientation of the distal link hub 20 relative to the proximal link hub 10. Although not shown, each of the multiple driving sources 500 can also rotate the second end link member 32 of each of the multiple links 30 around the second rotation axis RA2. This can change the position and orientation of the proximal link hub 10 relative to the distal link hub 20.

The parallel link mechanism 100 constituting the link actuation device 400 may have three or more links 30. In this case, the number of drive sources 500 may be less than the number of links 30.

<Action and effect>
The parallel link mechanism 100 according to the present disclosure includes a base end link hub 10, a tip end link hub 20, a plurality of links 30, and a beam member 40. Each of the plurality of links 30 includes a first end link member 31, a second end link member 32, and an intermediate link member 33. The first end link member 31 is connected at one end to the base end link hub 10 so as to be rotatable about a first rotation axis RA1. The second end link member 32 is connected at one end to the tip end link hub 20 so as to be rotatable about a second rotation axis RA2. The intermediate link member 33 is connected at one end to the other end of the first end link member 31 so as to be rotatable about a third rotation axis RA3. The intermediate link member 33 is connected at the other end to the other end of the second end link member 32 so as to be rotatable about a fourth rotation axis RA4. The central axis CL1, first rotation axis RA1, and third rotation axis RA3 of the base link hub 10 intersect at the first spherical link center point P1. The central axis CL2, second rotation axis RA2, and fourth rotation axis RA4 of the tip link hub 20 intersect at the second spherical link center point P2. The beam member 40 is disposed so as to pass through the first spherical link center point P1 and the second spherical link center point P2. The beam member 40 includes connection portions 41, 42 rotatably connected to the base link hub 10 and the tip link hub 20, respectively. The connection portions 41, 42 include at least one of a universal joint and a constant velocity joint.

In this way, the beam member 40 is rotatably connected to the base link hub 10 and the tip link hub 20, thereby improving the rigidity of the parallel link mechanism 100. Furthermore, the placement of the beam member 40 improves the positioning accuracy of the links 30 of the parallel link mechanism 100, resulting in smoother operation of the parallel link mechanism 100. Furthermore, because the beam member 40 can rotate independently of the operation of the links 30, the parallel link mechanism 100 as a whole can be realized with three degrees of freedom of rotation.

Furthermore, because the rotational force is transmitted to the tip link hub 20 via the beam member 40, the base link hub 10 can be fixed to the fixed end, unlike when the entire parallel link mechanism 100 is rotated. As a result, the links 30 and other components do not have to bear the rotational force, allowing for the structure of the links 30 and other components to be simplified and made smaller.

In addition, because a beam member 40 is used to transmit rotational force, the transmitted torque can be increased compared to when flexible tubes or the like are used.

In the above-described parallel link mechanism 100, the beam member 40 may include a hollow portion 40a extending from the base link hub 10 side to the tip link hub 20 side. The universal joints included in the connecting portions 41, 42 of the beam member 40 may also include through-hole portions. In this case, when attaching a work machine (end effector) or the like to the tip link hub 20, wiring for the machine or the like can be placed in the hollow portion 40a and through-hole portions. In this way, the wiring can be placed so as not to interfere with the operation of the link 30.

The link actuation device 400 according to the present disclosure comprises the parallel link mechanism 100 described above and at least two or more drive sources 500. The positions and orientations of the base link hub 10 and the tip link hub 20 are determined by the at least two or more drive sources 500. In this case, the relative orientation of the tip link hub 20 with respect to the base link hub 10 can be determined by the drive sources 500. Furthermore, because the parallel link mechanism 100 includes a beam member 40, the rigidity of the parallel link mechanism 100 is high, resulting in high-speed, highly accurate operation of the link actuation device 400.

In the above-described link actuation device 400, each of at least two or more drive sources 500 may rotate the first end link member 31 of each of the multiple links 30 around the first rotation axis RA1. In this case, the drive source 500 is disposed on the base end link hub 10 side, so the moment of inertia of the tip link hub 20 can be made smaller than when the drive source 500 is disposed closer to the tip link hub 20. This allows the link actuation device 400 to operate faster and with greater precision.

The link actuation device 400 may include a beam member drive source 501 that rotates the beam member 40 relative to the base end link hub 10 and the tip end link hub 20. The beam member drive source 501 may be connected to the base end side end 44 of the beam member 40, which is the end of the beam member 40 on the base end link hub 10 side. In this case, the beam member 40 can be rotated by the beam member drive source 501. Furthermore, because the beam member 40 is rotatably connected to the base end link hub 10 and the tip end link hub 20 by the connection portions 41, 42, the beam member 40 can be rotated regardless of the attitude of the parallel link mechanism 100.

(Embodiment 2)
<Configuration of parallel link mechanism and link actuator>
Figure 9 is a schematic perspective view of a link actuation device 400 according to embodiment 2. Figure 10 is a schematic front view of the link actuation device 400 shown in Figure 9. Figure 11 is a schematic top view of the link actuation device 400 shown in Figure 9. Figure 12 is a schematic cross-sectional view taken along line XII-XII in Figure 11. Figure 13 is a schematic cross-sectional view for explaining the operating state of the link actuation device 400 shown in Figure 9.

The link actuator 400 shown in Figures 9 to 13 basically has the same configuration as the link actuator 400 shown in Figures 1 to 8, but the configuration of the beam member 40 differs from that of the link actuator 400 shown in Figures 1 to 8. That is, the link actuator 400 shown in Figures 9 to 13 differs from the link actuator 400 shown in Figures 1 to 8 in that the connecting portions 41, 42 of the beam member 40 are equipped with constant velocity joints, and the beam portion 43 includes a damper portion 48.

The constant velocity joints arranged at the connection portions 41, 42 of the beam member 40 are, for example, Rzeppa-type constant velocity joints. The outer rings of the constant velocity joints arranged at the connection portions 41, 42 are integral with the base end portion 44 or the tip end portion 45. As shown in FIG. 12, the outer rings of the constant velocity joints are rotatably connected to the base end link hub 10 or the tip end link hub 20 via a rotational resistance reduction member 50 such as a bearing. The rotational resistance reduction member 50 can be configured in any manner, such as a bearing with rolling elements arranged between the outer and inner rings, or a sliding bearing.

The centers of the inner rings of the two constant velocity joints overlap with the first spherical link center point P1 or the second spherical link center point P2, respectively, as shown in Figure 13. As a result, the beam member 40 can move smoothly even when the attitude of the tip link hub 20 relative to the base link hub 10 is changed, as shown in Figure 13. As a result, even when the link actuator 400 is in any position, the beam member 40 can reliably transmit rotational force from the base link hub 10 side to the tip link hub 20 side.

Connecting portion 41 and connecting portion 42 are connected via connecting shafts 43a and 43b and damper portion 48. Connecting shaft 43a is connected to one end of damper portion 48. Connecting shaft 43a connects damper portion 48 to connecting portion 41. Connecting shaft 43b is connected to the other end of damper portion 48. Connecting shaft 43b connects damper portion 48 to connecting portion 42. Any configuration can be used for damper portion 48 as long as it can dampen vibrations transmitted from connecting shaft 43a or connecting shaft 43b. For example, damper portion 48 may be a device consisting of a cylinder filled with oil and air and a damper piston with an orifice placed in the cylinder.

<Action and effect>
In the above-described link actuation device 400 or parallel link mechanism 100, the connecting portions 41, 42 have constant velocity joints, so that the same effects as those of the link actuation device 400 or parallel link mechanism 100 shown in FIGS. 1 to 8 can be obtained. Furthermore, by using constant velocity joints in the connecting portions 41, 42, constant velocity is achieved, with no speed change during rotation. This constant velocity improves quietness. Furthermore, the load on the connecting portions 41, 42 is borne by multiple rolling elements, such as steel balls, arranged between the inner and outer rings of the constant velocity joints, so the durability and reliability of the link actuation device 400 and the parallel link mechanism 100 are improved.

The above-described link actuation device 400 or parallel link mechanism 100 may further include a rotational resistance reduction member 50 that rotatably connects the base end link hub 10 or the tip end link hub 20 to the beam member 40. In this case, the beam member 40 can be reliably rotated while being supported by the base end link hub 10 and the tip end link hub 20.

In the parallel link mechanism 100, the beam member may include a damper portion 48. In this case, the transmission of vibration between the base end link hub 10 side and the tip end link hub 20 side can be suppressed.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Unless inconsistent, at least two of the embodiments disclosed herein may be combined. The basic scope of the present disclosure is indicated by the claims, not the above description, and all modifications within the meaning and scope of the claims are intended to be included.

10 Base end link hub, 20 Tip end link hub, 30 Link, 31 First end link member, 32 Second end link member, 33 Intermediate link member, 34, 35, 36, 37 Shaft member, 40 Beam member, 40a Hollow portion, 41, 42 Connection portion, 43 Beam portion, 43a, 43b Connection shaft portion, 44 Base end portion, 45 Tip end portion, 48 Damper portion, 50 Rotational resistance reduction member, 100 Parallel link mechanism, 400 Link actuator, 500 Drive source, 501 Beam member drive source, CL1, CL2 Central axis, P1 First spherical link center point, P2 Second spherical link center point, RA1 First rotation axis, RA2 Second rotation axis, RA3 Third rotation axis, RA4 Fourth rotation axis, RA5 Straight line.

Claims (7)

a proximal link hub;
A tip link hub;
Multiple links and
a beam member;
Each of the plurality of links includes a first end link member, a second end link member, and an intermediate link member;
the first end link member is connected at one end to the base end link hub so as to be rotatable about a first rotation axis;
The second end link member is connected at one end to the tip link hub so as to be rotatable about a second rotation axis,
the intermediate link member is connected at one end to the other end of the first end link member so as to be rotatable about a third rotation axis, and is connected at the other end to the other end of the second end link member so as to be rotatable about a fourth rotation axis,
the central axis of the base end link hub, the first rotation axis, and the third rotation axis intersect at a first spherical link center point,
the central axis of the tip link hub, the second rotation axis, and the fourth rotation axis intersect at a center point of a second spherical link,
the beam member is disposed so as to pass through the first spherical link center point and the second spherical link center point,
the beam member includes a first connection portion connected to the base end link hub so as to be rotatable about the central axis of the base end link hub, and a second connection portion connected to the tip end link hub so as to be rotatable about the central axis of the tip end link hub,
the first connecting portion and the second connecting portion include at least one of a universal joint and a constant velocity joint;
An end effector can be attached to the end of the beam member on the tip link hub side . The parallel link mechanism according to claim 1, further comprising a rotational resistance reduction member that rotatably connects the base end link hub or the tip end link hub to the beam member. A parallel link mechanism according to claim 1 or claim 2, wherein the beam member includes a damper portion. A parallel link mechanism according to claim 1 or claim 2, wherein the beam member includes a hollow portion extending from the base end link hub side to the tip end link hub side. The parallel link mechanism according to any one of claims 1 to 4;
At least two drive sources;
A link actuator, wherein the positions and orientations of the base end link hub and the tip end link hub are determined by the at least two drive sources. The link actuation device described in claim 5, wherein each of the at least two drive sources rotates the first end link member of each of the plurality of links around the first rotation axis. The link actuator according to claim 5 or 6, further comprising a beam member drive source that rotates the beam member relative to the base end link hub and the tip end link hub.