Parallel link mechanism and link operation device

Abstract

To provide a parallel link mechanism and a link operation device capable of moving an end effector in parallel while changing an attitude at a high speed.SOLUTION: A parallel link is a spherical link mechanism, and connects a link hub 3 at a tip side to a link hub 2 at a basic end side in a manner of changing an attitude via two sets or more of link mechanisms 4. The tip-side link hub 3 and the basis end-side link hub 2 are respectively operably connected by a rod member 20 via connecting portions 22, 24 at the tip side and the basic end side. The rod member 20 and the connecting portion 22 at the basic end side are connected rotatably to the link hub 2 at the basic end side, and the rod member 20 and the connecting portion 24 at the tip side are rotatably connected to the link hub 3 at the tip side. A rotation driving source 30 for rotating the rod member 20 is fixed to the link hub 2 at the basic end side, and a conversion mechanism 32 for converting the rotation of the rod member 20 into a linear motion is fixed to the link hub 3 at the tip side.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a parallel link mechanism and a link actuator used in equipment that requires precision and a wide operating range, such as medical equipment and industrial equipment. [Background technology]

[0002] A parallel link mechanism in which a tip-side link hub and a base-side link hub are operably connected by two or more link systems is known (for example, Patent Document 1). A parallel link mechanism like that in Patent Document 1 is compact, yet capable of precisely changing the position of the tip-side link hub with two degrees of freedom of rotation over a wide range relative to the base-side link hub. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-224564 A Summary of the Invention [Problem to be solved by the invention]

[0004] If there is a translational motion mechanism with one degree of freedom at the tip of such a parallel link mechanism, the range of applications will be expanded. For example, such a translational motion mechanism can be used to focus a camera or pull out a screw. One possible solution to this problem is to install a drive source at the tip of the parallel link mechanism.

[0005] However, if a drive source is installed at the tip of a parallel link mechanism, the weight of the tip increases, i.e., the moment of inertia increases. As a result, the movable part at the tip is no longer lightweight and compact, and it is no longer possible to achieve precise and wide-range operation. In addition, since an end effector is attached to the tip of the drive source, the size of the device becomes even larger and the moment of inertia also increases.

[0006] An object of the present invention is to provide a parallel link mechanism and a link actuator that can translate an end effector while quickly changing its posture. [Means for solving the problem]

[0007] The parallel link mechanism of the present invention is a parallel link mechanism including a spherical link mechanism having a base end link member rotatably connected at one end to the base end link hub, a tip end link member rotatably connected at one end to the tip end link hub, and a central link member rotatably connected at both ends to the other ends of the base end and tip end link members. The tip end link hub and the base end link hub are operably connected to each other by a rod-shaped member via a tip end and a base end connecting portion. The rod-shaped member and the base end connecting portion are rotatably connected to the base end link hub, and the rod-shaped member and the tip end connecting portion are rotatably connected to the tip end link hub. A rotary drive source that rotates the rod-shaped member is fixed to the base end link hub, and a conversion mechanism that converts the rotation of the rod-shaped member into linear motion is fixed to the tip end link hub.

[0008] According to this configuration, the parallel link mechanism can operate with two or more degrees of freedom of rotation, and the distance between the centers of the spherical links on the tip and base ends is maintained. This improves the rigidity of the entire link and makes the movement smoother. Furthermore, the rod-shaped members rotate independently regardless of the attitude of the spherical links. In other words, the link mechanism is a parallel link mechanism with three or more degrees of freedom overall. One of the three or more degrees of freedom of rotation at the tip is converted into linear motion by the conversion mechanism. This allows the end effector supported by the link hub on the tip end to move in parallel.

[0009] Furthermore, a rotary drive source is provided on the link hub on the base end side, and a conversion mechanism is provided on the link hub on the tip end side. This suppresses an increase in weight on the tip end side, and prevents the moment of inertia from becoming large. As a result, the configuration on the tip end side is lightweight and compact, and precise and wide-range operation can be achieved.

[0010] In the parallel link mechanism of the present invention, the conversion mechanism may have a friction reducing member that reduces the rotational friction resistance of the rotating sliding parts. The friction reducing member is, for example, a solid or liquid lubricant such as grease oil. With this configuration, the conversion mechanism rotates smoothly, so that wear of the rotating sliding parts is reduced and the life of the conversion mechanism is extended.

[0011] In the parallel link mechanism of the present invention, at least one of the rod-shaped member, the base end side and tip end side connecting portions, and the rotation shaft of the conversion mechanism may be hollow. With this configuration, a cable or the like can be inserted into the hollow portion, resulting in a good appearance.

[0012] The link actuation device of the present invention includes the parallel link mechanism of the present invention and an attitude control drive source that controls the attitude of the tip-side link hub. By controlling two or more link mechanisms, it is possible to change the attitude of the tip-side link hub relative to the base-side link hub. This makes it possible to realize precise, wide-range, high-speed operation while being lightweight and compact. Effect of the Invention

[0013] According to the parallel link mechanism and link actuation device of the present invention, the rotational drive source is fixed to the base end link hub and the conversion mechanism is fixed to the tip end link hub, so that the end effector can be translated while changing its posture at high speed. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a front view showing a link actuator according to a first embodiment of the present invention. [Diagram 2]FIG. 2 is a vertical sectional view of the link actuator of FIG. 1. [Diagram 3] FIG. 4 is a front view showing the link actuator when the bending angle is 50°. [Figure 4] FIG. 4 is a vertical sectional view of the link actuator of FIG. 3. [Diagram 5] FIG. 4 is a diagram showing one link mechanism of the link actuator device in the form of a straight line. [Figure 6] FIG. 4 is a horizontal cross-sectional view showing the configuration of each revolute pair of the link actuator device. [Figure 7] FIG. 4 is a front view of the conversion mechanism of the link actuator. [Figure 8] FIG. [Figure 9] FIG. 11 is a front view showing a link actuator according to a second embodiment of the present invention. [Figure 10] FIG. 4 is a perspective view showing the link actuating device with a slide holding member omitted. [Figure 11] FIG. 4 is a plan view showing a conversion mechanism of the link actuator. [Figure 12] FIG. 2 is a horizontal sectional view showing the conversion mechanism. [Figure 13] FIG. 11 is a front view showing a link actuator according to a third embodiment of the present invention. [Figure 14] FIG. 2 is a perspective view showing the link actuator. [Figure 15] FIG. 11 is a front view showing a link actuator according to a fourth embodiment of the present invention. [Figure 16] FIG. 2 is a perspective view showing the link actuator. [Figure 17] FIG. 4 is a perspective view showing a conversion mechanism of the link actuator. [Figure 18] FIG. 2 is a horizontal sectional view showing the conversion mechanism. [Figure 19] FIG. 2 is a vertical cross-sectional view showing the conversion mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. [First embodiment] Figures 1 and 3 are front views showing a link actuator according to a first embodiment of the present invention, and Figures 2 and 4 are longitudinal cross-sectional views of the same link actuator. Figures 1 and 2 show a state in which the bend angle is 0°, and Figures 3 and 4 show a state in which the bend angle is 50°. The link actuator 1 shown in Figure 1 connects a tip-side link hub 3 to a base-side link hub 2 via two or more sets of link mechanisms 4 so that the position can be changed. In this embodiment, the number of link mechanisms 4 is three.

[0016] <Link mechanism> Each link mechanism 4 is a three-section link mechanism consisting of four revolute pairs, including a base end link member 5, a tip end link member 6, and a central link member 7. Specifically, the base end link hub 2 and the base end link member 5 shown in Fig. 5 are connected by the first revolute pair K1, the base end link member 5 and the central link member 7 are connected by the second revolute pair K2, the central link member 7 and the tip end link member 6 are connected by the third revolute pair K3, and the tip end link member 6 is connected to the tip end link hub 3 by the fourth revolute pair K4.

[0017] In this embodiment, the base end side and tip end side end link members 5, 6 shown in FIG. 1 are L-shaped. One end of the base end side end link member 5 of each link mechanism 4 is rotatably connected to the base end side link hub 2. Each base end side end link member 5 is arranged at equal intervals in the circumferential direction on the outer circumferential surface of the base end side link hub 2. Similarly, one end of the tip end side end link member 6 of each link mechanism 4 is rotatably connected to the tip end side link hub 3. Each tip end side end link member 6 is arranged at equal intervals in the circumferential direction on the outer circumferential surface of the tip end side link hub 3. However, the base end side and tip end side end link members 5, 6 do not have to be arranged at equal intervals in the circumferential direction. The other ends of the base end side and tip end side end link members 5, 6 are rotatably connected to both ends of the central link member 7.

[0018] The base-side and tip-side end link members 5, 6 in the three link mechanisms 4 have a spherical link structure. In detail, as shown in Fig. 6, the central axis AX1 of the first revolute pair K1 of the base-side link hub 2 and the base-side end link 5 intersects at the base-side spherical link center P1. Similarly, the central axis AX4 of the fourth revolute pair K4 of the tip-side link hub and the tip-side end link 6 intersects at the tip-side spherical link center P2.

[0019] In this embodiment, the three link mechanisms 4 have the same distance L1 from the base-side spherical link center P1 to the base-side end link 5 shown in Fig. 5. Similarly, the same distance L2 from the tip-side spherical link center P2 to the tip-side end link 6. However, the distances L1 and L2 may be different.

[0020] The central axis AX2 of the second rotation pair K2 between the base end link member 5 and the central link member 7 shown in Figure 1 and the central axis AX3 of the third rotation pair K3 between the tip end link member 6 and the central link member 7 may have a certain intersecting angle or may be parallel.

[0021] The three link mechanisms 4 each have a geometrically identical shape. The geometrically identical shape means that, as shown in Fig. 5, a geometric model in which each link member 5, 6, 7 is represented by a straight line, i.e., a model represented by each revolute pair K1-K4 and the straight lines connecting these revolute pairs K1-K4, has a shape in which a base end portion PP and a tip end portion DP are symmetrical with respect to a midpoint 7a of the central link member 7. However, while they are mechanically symmetrical, the dimensions of the individual parts of the base end portion PP and the tip end portion DP may be different.

[0022] In detail, the base end portion PP consists of the base end link hub 2, the base end end link member 5, and a portion 7b of the central link member 7 that is on the base end side of the midpoint 7a. The tip end portion DP consists of the tip end link hub 3, the tip end link member 6, and a portion 7c of the central link member 7 that is on the tip side of the midpoint 7a. The base end portion PP and the tip end portion DP are symmetrical with respect to a symmetry plane A of the central link member 7. The symmetry plane A is a plane that passes through the midpoints 7a of each central link member 7 and the parallel link center point O.

[0023] The link mechanism 4 of the present embodiment is of a mirror symmetric type, and the positional relationship between the base end part PP and the tip end part DP is mirror symmetric with respect to the symmetry plane A of the central link member 7. Fig. 5 shows a state in which the central axis C of the tip end link hub 3 forms a predetermined bending angle with respect to the central axis B of the base end link hub 2.

[0024] The base-side link hub central axis B is a straight line that passes through the base-side spherical link center P1 of the base-side link hub 2 and extends toward the parallel link center point O. Similarly, the tip-side link hub central axis C is a straight line that passes through the tip-side spherical link center P2 of the tip-side link hub 3 and extends toward the parallel link center point O. The state in which the base-side link hub central axis B and the tip-side link hub central axis C shown in Figure 1 are aligned is defined as the reference posture.

[0025] The parallel link center point O is the intersection O of the base-end and tip-end link hub central axes B, C, and is the midpoint O of the spherical link centers P1, P2 when the base-end and tip-end link hub central axes B, C are aligned on the same line. Even if the posture of each link mechanism 4 changes, the distance L between the base-end and tip-end spherical link centers P1, P2 is always constant.

[0026] A two-degree-of-freedom mechanism is configured in which the tip-side link hub 3 can move freely with two rotational degrees of freedom relative to the base-side link hub 2, using the base-side link hub 2, tip-side link hub 3, and three sets of link mechanisms 4. This two-degree-of-freedom mechanism is compact, yet allows a wide range of movement of the tip-side link hub 3 relative to the base-side link hub 2.

[0027] For example, the maximum bend angle (2×θ) between the base end link hub central axis B and the tip end link hub central axis C can be set to approximately ±90°. Also, the pivot angle φ of the tip end link hub 3 relative to the base end link hub 2 can be set in the range of 0° to 360°. The bend angle (2×θ) is the vertical angle at which the central axis C of the tip end link hub 3 is inclined relative to the central axis B of the base end link hub 2. The pivot angle φ is the horizontal angle at which the tip end link hub central axis C is inclined relative to the base end link hub central axis B.

[0028] In this link actuator 1, if the angular positional relationship between the base end portion PP and the tip end portion DP with respect to the symmetry plane A of the central link member 7 is made the same on the base end and tip end sides, then due to geometric symmetry, the base end link hub 2 and base end end link member 5, and the tip end link hub 3 and tip end link member 6 will move in the same way.

[0029] In this case, for example, if a rotating shaft is provided in the base end link hub 2 coaxially with the base end link hub central axis B, and a rotating shaft is provided in the tip end link hub 2 coaxially with the tip end link hub central axis C, and rotation is transmitted from the base end to the tip side, the base end and tip sides have the same rotational angle and rotate at a constant speed, resulting in a constant velocity universal joint.

[0030] 1, a posture control drive source 10 that controls the posture of the tip side link hub 3 is provided on the base end side end link member 5. In this embodiment, a posture control drive source 10 is provided on each link mechanism 4, but if there are three or more sets of link mechanisms 4, it is sufficient to provide a posture control drive source 10 on two or more sets of link mechanisms 4. By controlling each posture control drive source 10 to rotate the base end side end link member 5, the posture of the tip side link hub 3 relative to the base end side link hub 2 can be changed to any posture.

[0031] <Rod-shaped member and connecting portion> The distal link hub 3 and the proximal link hub 2 are operably connected by a rod-shaped member 20. In detail, as shown in FIG. 4, the rod-shaped member 20 is rotatably connected to the proximal link hub 2 via a proximal connecting portion 22, and is rotatably connected to the distal link hub 3 via a distal connecting portion 24. In other words, the rod-shaped member 20 and the proximal connecting portion 22 are rotatably connected to the proximal link hub 2, and the rod-shaped member 20 and the distal connecting portion 24 are rotatably connected to the distal link hub 3. The rod-shaped member 20 in this embodiment is a rigid body, but the rod-shaped member 20 may be elastic.

[0032] In this embodiment, the rod-shaped member 20 passes through two spherical link centers P1, P2. In detail, as shown in Fig. 6, a through hole 12 is provided in the base-end link hub 2, and an annular base-end connecting part 22 is attached to the through hole 12, and the rod-shaped member 20 is connected to the base-end connecting part 22. The base-end connecting part 22 is cylindrical and has a hollow hole 22a. In the reference position shown in Fig. 1, the central axis of the rod-shaped member 20 coincides with the central axis B of the base-end link hub.

[0033] FIG. 6 shows the base end link hub 2, its through hole 12, and the base end connecting portion 22, but the tip end link hub 3, its through hole 14, and the tip end connecting portion 24 also have the same configuration.

[0034] In this embodiment, constant velocity joints (for example, Rzeppa constant velocity joints) are used as the base end side and tip end side connecting parts 22, 24. As shown in FIG. 4, the base end side and tip end side connecting parts 22, 24 have outer members 22b, 24b and inner members 22c, 24c. Each of the outer members 22b, 24b rotates around the central axes B, C of the base end side and tip end side link hubs relative to the base end side and tip end side link hubs 2, 3. The inner members 22c, 24c are connected to the outer members 22b, 24b so as to be able to change their posture with two degrees of freedom of rotation around the respective spherical link centers P1, P2, and transmit the rotation of the outer members 22b, 24b around the central axes B, C of the base end side and tip end side link hubs to the rod-shaped member 20.

[0035] However, the connecting parts 22, 24 are not limited to constant velocity joints, and may be universal joints such as Cardan joints. In this embodiment, both ends of the rod-shaped member 20, the base end and the tip end, are operably connected by the connecting parts 22, 24, but only one end may be operably connected by the connecting part 22, 24.

[0036] As shown in Fig. 1, a rotational drive source 30 is fixed to the base-end link hub 2. The rotational drive source 30 rotates the rod-shaped member 20. In this embodiment, the rotational drive source 30 rotates the rod-shaped member 20 together with the connecting portions 22, 24. In this manner, the rotational drive source 30 rotates the rod-shaped member 20 together with the connecting portions 22, 24, thereby transmitting rotational motion to the tip-end link hub 3. The rotational motion of the rod-shaped member 20 is independent of the attitude control of the parallel link mechanism 4, and the parallel link mechanism 4 can rotate independently in any attitude.

[0037] <Conversion mechanism> On the other hand, a conversion mechanism 32 is fixed to the link hub 3 on the tip side. The conversion mechanism 32 converts the rotation of the rod-shaped member 20 into linear motion. In detail, the conversion mechanism 32 converts the rotational motion about the link hub central axis C of the tip side transmitted to the link hub 3 on the tip side into linear motion along the link hub central axis C of the tip side. The linear motion of the conversion mechanism 32 is controlled by the rotational motion of the rod-shaped member 20. Since the conversion mechanism 32 converts the rotational motion of the rod-shaped member 20 into linear motion in this manner, the linear motion of the conversion mechanism 32 is also independent of the attitude control of the parallel link mechanism 4.

[0038] The conversion mechanism 32 of this embodiment will be described below. Fig. 7 is a front view of the conversion mechanism 32, and Fig. 8 is a longitudinal sectional view of the conversion mechanism 32. The conversion mechanism 32 has a screw member 34 and a slide member 40. The screw member 34 is connected to the tip-side connecting portion 24 and converts the rotational motion of the tip-side connecting portion 24 into linear motion. In detail, the rotational motion of the tip-side connecting portion 24 around the tip-side link hub central axis C is converted into linear motion along the tip-side link hub central axis C.

[0039] In this embodiment, the screw member 34 of the conversion mechanism 32 is configured with a trapezoidal screw 35. However, the screw member 34 is not limited to a trapezoidal screw, and may be, for example, a ball screw, a sliding screw, or the like. In detail, the screw member 34 has a base portion 36 to which the trapezoidal screw 35 is fixed, and a column portion 38 that fixes the base portion 36 to the outer member 24b of the connecting portion 24 on the tip side. In this embodiment, the screw member 34 has three column portions 38 spaced apart in the circumferential direction. However, the number of column portions 38 is not limited to this. As a result, when the outer member 24b of the connecting portion 24 on the tip side rotates, the screw member 34 also rotates.

[0040] <Slide component> The slide member 40 is connected to the tip side link hub 3 so as to be movable relative to the tip side link hub 3. In detail, the slide member 40 is movable relative to the tip side link hub 3 in the direction of the tip side link hub central axis C. The end effector 25 is disposed on the slide member 40. The end effector 25 may be detachably attached to the slide member 40, or the slide member 40 itself may have the function of an end effector.

[0041] The slide member 40 has an annular nut portion 42 and a pillar portion 44. The nut portion 42 has a female thread 42a in its hollow hole and is screwed into the trapezoidal thread 35 of the screw member 34. The nut portion 42 is supported by the tip-side link hub 3 via the pillar portion 44 so as to be relatively movable. In this embodiment, three pillar portions 44 are arranged side by side in the circumferential direction and are inserted into the tip-side link hub 3 so as to be freely movable in the direction of the tip-side link hub central axis C. This allows the slide member 40 to move linearly in the direction of the link hub central axis C relative to the tip-side link hub 3, but not to rotate.

[0042] The slide member 40 only needs to be supported so that it can move linearly in the direction of the link hub central axis C relative to the link hub 3 at the tip side and cannot move rotationally, and the support structure of the slide member 40 relative to the link hub 3 at the tip side is not limited to the structure of this embodiment.

[0043] In this manner, the screw member 34, which is the rotational motion part of the conversion mechanism 32, is connected to the connecting portion 24 on the tip side, and the slide member 40, which is the linear motion part, is connected to the link hub 3 on the tip side. In other words, the trapezoidal screw 35 of the screw member 34 connected to the connecting portion 24 on the tip side rotates, and the nut portion 42 of the slide member 40 connected to the link hub 3 on the tip side moves parallel to the link hub central axis C on the tip side. In this manner, in this embodiment, the trapezoidal screw 35 of the screw member 34 forms the rotation axis of the conversion mechanism 32.

[0044] The conversion mechanism 32 of this embodiment has a friction reduction member 50 that reduces the rotational friction resistance of the rotation sliding part 45. The friction reduction member 50 is, for example, a solid or liquid lubricant such as grease oil that is provided on the rotation sliding part 45. The friction reduction member 50 reduces wear on the rotation sliding part 45, extending its lifespan, and reduces backlash in the rotation sliding part 45, improving positional accuracy. However, the friction reduction member 50 is not essential.

[0045] In this embodiment, the rod-shaped member 20, the base-side connecting portion 22, the tip-side connecting portion 24, and the rotation shaft (trapezoidal screw 35) of the conversion mechanism 32 are hollow. That is, as shown in FIG. 1, the rod-shaped member 20, the base-side connecting portion 22, the tip-side connecting portion 24, and the trapezoidal screw 35 have hollow holes 20a, 22a, 24a, and 35a. A cable (not shown) of the end effector 25 can be wired through these hollow holes 20a, 22a, 24a, and 35a. It is not necessary for all of the rod-shaped member 20, the base-side connecting portion 22, the tip-side connecting portion 24, and the rotation shaft (trapezoidal screw 35) of the conversion mechanism 32 to be hollow, and at least one of them may be hollow, and all of them may not be hollow.

[0046] <Link actuator operation> Next, the operation of the link actuation device 1 of this embodiment will be described. By controlling the link mechanism 4 with the attitude control drive source 10, the attitude of the tip-side link hub 3 relative to the base-side link hub 2 changes with two rotational degrees of freedom. Furthermore, regardless of the attitude of the link mechanism 4, the rod-shaped member 20 rotates independently via the base-side and tip-side connecting portions 22, 24. Therefore, the link actuation device 1 operates with three rotational degrees of freedom: the two rotational degrees of freedom of the link mechanism 4 and the one rotational degree of freedom of the rod-shaped member 20.

[0047] The rod-shaped member 20 rotates together with the connecting portions 22, 24 on the base end and tip end sides due to the rotational drive source 30. Since a conversion mechanism 32 is attached to the link hub 3 on the tip side, the rotational motion by the rotational drive source 30 is converted into linear motion, and the end effector 25 can move in the direction of the central axis C of the link hub on the tip side. In this way, the link actuating device 1 can be used for a wide range of applications due to the operation with three rotational degrees of freedom and one linear degree of freedom. For example, the link actuating device 1 can be used for applications such as focusing a camera or pulling out a screw.

[0048] According to the above configuration, the link mechanism 4 can operate with two or more degrees of freedom of rotation, and the distance between the center points of the distal end and proximal end spherical links 2, 3 is maintained. This improves the rigidity of the entire link and makes the movement smoother. Furthermore, the rod-shaped member 20 rotates independently regardless of the attitude of the spherical link 4. In other words, the link mechanism 4 constitutes a parallel link mechanism with three or more degrees of freedom as a whole. One degree of freedom of rotation of the distal end, among the three or more degrees of freedom of rotation, is converted into linear motion by the conversion mechanism 32. This allows the end effector 25 supported by the distal end link hub 3 to move in parallel (linear motion).

[0049] Furthermore, a rotary drive source 30 is provided on the link hub 2 on the base end side, and a conversion mechanism 32 is provided on the link hub 3 on the tip end side. This suppresses an increase in weight on the tip end side, and prevents the moment of inertia from becoming large. As a result, the configuration on the tip end side becomes lightweight and compact, and precise and wide-range operation can be achieved.

[0050] 8, the conversion mechanism 32 has a friction reducing member 50 that reduces the rotational friction resistance of the rotational sliding part 45. This allows the conversion mechanism 32 to rotate smoothly, reducing wear on the rotational sliding part 45 and extending the life of the conversion mechanism 32.

[0051] 2, the rod-shaped member 20, the base-side connecting part 22, the tip-side connecting part 24, and the trapezoidal screw 35 have hollow holes 20a, 22a, 24a, and 35a. For example, the cable of the end effector 25 can be inserted through these hollow holes 20a, 22a, 24a, and 35a, which makes the wiring compact, makes it difficult for the mechanism to pinch the cable, and improves the appearance.

[0052] A link actuator according to another embodiment of the present invention will be described below. In the description of the other embodiment, the same reference numerals as in the first embodiment are used for the configurations common to the first embodiment, and detailed description thereof will be omitted.

[0053] [Second embodiment] 9 to 12 show a link actuating device 1A according to a second embodiment of the present invention. The link actuating device 1 of the first embodiment has a conversion mechanism 32 which is a feed screw mechanism, whereas the link actuating device 1A of the second embodiment has a conversion mechanism 32A which is a rack and pinion mechanism, which is a difference between the two. The conversion mechanism 32A of the second embodiment will be described in detail below.

[0054] <Conversion mechanism> In Fig. 9, the conversion mechanism 32A of the second embodiment converts rotational motion about the tip-side link hub center C into linear motion in a direction perpendicular to the tip-side link hub center C. In detail, the conversion mechanism 32A shown in Fig. 10 has a drive gear 52 connected to the tip-side connecting portion 24, a pinion gear 54 meshing with the drive gear 52, and a rack gear 56 meshing with the pinion gear 54. In this embodiment, the drive gear 52 and the pinion gear 54 are spur gears.

[0055] The drive gear 52 rotates integrally with the connecting portion 24 on the tip side, and the pinion gear 54 rotates in conjunction with the drive gear 52. Furthermore, the rotational force of the pinion gear 54 causes the rack gear 54 to move linearly (horizontally).

[0056] The conversion mechanism 32A of this embodiment has a pair of rack gears, i.e., two rack gears 56, 56, which move linearly in parallel and opposite directions. Each rack gear 56 has an engagement protrusion 56a. The engagement protrusion 56a protrudes in a direction perpendicular to the moving direction, upward in FIG. 10. In this embodiment, the rack gear 56 is integrated with a slide member 58, and is held by the link hub 3 on the tip side via a slide holding member 60 so as to be capable of linear motion. The slide holding member 60 is omitted in FIG. 10.

[0057] As shown in FIG. 12, the slide holding member 60 has a first shaft insertion hole 60a and a second shaft insertion hole 60b. The gear shaft body 52a of the drive gear 52 is rotatably supported in the first shaft insertion hole 60a. The gear shaft body 52a is fixed to the outer member 24b of the connecting portion 24 on the tip side via the pillar portion 52b shown in FIG. 9. In this embodiment, three pillar portions 52b are provided spaced apart in the circumferential direction. However, the number of pillar portions 52b is not limited to this. As a result, when the outer member 24b of the connecting portion 24 on the tip side rotates, the drive gear 52 also rotates.

[0058] The gear shaft body 54a of the pinion gear 54 is rotatably supported in the second shaft insertion hole 60b shown in Fig. 12. The gear shaft body 54a is rotatably supported by the link hub 3 on the tip side shown in Fig. 9. As a result, when the drive gear 52 rotates, the pinion gear 54 also rotates.

[0059] In this way, by disposing the drive gear 52 between the connecting portion 24 on the tip side and the pinion gear 54, it is possible to change the gear ratio between the drive gear 52 and the pinion gear 54. In addition, by disposing the drive gear 52, either the clockwise or counterclockwise direction can be used as the rotational motion to be converted into linear motion.

[0060] In this embodiment, a mechanism for equally opening and closing is obtained by extracting linear motion in opposite directions across the shaft body 54a from one pinion gear 54. Alternatively, linear motion in the same direction but at different speeds can be obtained by providing two pinion gears 54 or extracting linear motion directly from the drive gear.

[0061] Furthermore, by disposing the drive gear 52 between the tip-side connecting portion 24 and the pinion gear 54, the shaft body 54a of the pinion gear 54 can be disposed at a position away from the tip-side link central axis C. In this embodiment, the drive gear 52 made of a spur gear disposes the shaft body 54a of the pinion gear 54 at a position away from the tip-side link central axis C, but instead of the spur gear, for example, a belt and pulley, or a chain and sprocket may be used.

[0062] As shown in Fig. 12, the slide holding member 60 has two slide grooves 60c, 60c. The slide grooves 60c are arranged on a plane perpendicular to the link central axis C on the tip side, and the two slide grooves 60c, 60c extend in parallel. The engaging protrusions 56a of the rack gear 56 engage with each slide groove 60c. In other words, the engaging protrusions 56a are guided by the slide grooves 60c, and the rack gear 56 moves along the slide grooves 60c of the slide holding member 60. In this way, the slide holding member 60 limits the range in which the rack gear 56 can move linearly.

[0063] As described above, in this embodiment, the end effector 25A is configured by the tip-side link hub 3, the conversion mechanism 32A, the slide member 58, and the slide holding member 60. In detail, the end effector 25A in this embodiment has a function of equally opening and closing by sliding two slide members 58 in opposite directions by one pinion gear 54 (spur gear), thereby gripping a workpiece.

[0064] As in the first embodiment, the conversion mechanism 32A of the second embodiment may also have a friction reducing member 50 that reduces the rotational friction resistance of the rotational sliding part 45. As in the first embodiment, at least one of the rod-shaped member 20, the base end side connecting part 22, the tip end side connecting part 24, and the gear shaft body 52a of the drive gear 52 may have a hollow hole.

[0065] In the second embodiment, the same effect as in the first embodiment can be obtained, that is, the end effector 25A can be translated while changing its posture at high speed.

[0066] [Third embodiment] 13 and 14 show a link actuation device 1B according to a third embodiment of the present invention. The link actuation device 1B of the third embodiment also differs from the first and second embodiments in the configuration of a conversion mechanism 32B. The conversion mechanism 32B of the link actuation device 1B of the third embodiment is composed of bevel gears 62, 64, and 66, pulleys 68 and 70, and belts 72 and 74. The conversion mechanism 32B will be described in detail below.

[0067] <Conversion mechanism> In the conversion mechanism 32B of the third embodiment, the rotational motion of the tip-side connecting portion 24 about the tip-side link hub central axis C is converted in rotation direction by the bevel gears 62, 64, 66, and linear motion is extracted from the belts 72, 74.

[0068] In this embodiment, three bevel gears are provided: one input bevel gear 62 and two output bevel gears 64, 66 meshing therewith. The number of output bevel gears may be one or three or more. These bevel gears 62, 64, 66 are supported on the link hub 3 at the tip side via a stage 69. The stage 69 has a main body 69a made of a flat plate, and the main body 69a is fixed to the link hub 3 at the tip side by a plurality of pillars 69b. In this embodiment, three pillars 69b spaced apart in the circumferential direction are provided. However, the structure of the pillars 69b is not limited to that of this embodiment.

[0069] The main body 69a has a through hole 69c in its center, and the input bevel gear 62 is rotatably supported in this through hole 69c. The input bevel gear 62 is fixed to the outer member 24b of the connecting portion 24 on the tip side via the pillar portions 62a. In this embodiment, three pillar portions 62a are provided spaced apart in the circumferential direction. However, the number of pillar portions 62a is not limited to this. As a result, when the outer member 24b of the connecting portion 24 on the tip side rotates, the input bevel gear 62 also rotates.

[0070] The stage 69 has mounting portions 69d, 69d connected to the main body portion 69a. The mounting portions 69d, 69d are formed by bending a metal plate, and extend from the main body portion 69a in a direction along the tip-side link hub central axis C to the opposite side to the tip-side link hub 3.

[0071] Each mounting portion 69d has an insertion hole 69e, and the output bevel gears 64, 66 are rotatably supported in the insertion hole 69e. The rotation axes AX5, AX6 of the output bevel gears 64, 66 extend in a direction perpendicular to the link hub central axis C on the tip side. In this embodiment, the two output bevel gears 64, 66 are arranged so that their rotation axes AX5, AX6 coincide with each other. However, the arrangement of the two output bevel gears 64, 66 is not limited to this. As a result, when the input bevel gear 62 rotates around the link hub central axis C on the tip side, the two output bevel gears 64, 66 rotate around the rotation axes AX5, AX6.

[0072] The output bevel gears 64, 66 are connected to gear shaft bodies 64a, 66a, and pulleys 68, 70 are connected to the gear shaft bodies 64a, 66a. The pulleys 68, 70 are provided as a pair spaced apart in the direction of the link hub central axis C on the tip side. A belt 72 is stretched between the pair of pulleys 68, 68, and a belt 74 is stretched between the pair of pulleys 70, 70. The belts 72, 74 may be timing belts or chains. Using a timing belt reduces slippage loss with the pulleys.

[0073] An end effector 25B is attached to each of the belts 72, 74. The end effector 25B may be attached directly to the belts 72, 74, or may be attached to the belts 72, 74 via an intermediate member such as a stay. As a result, when the output bevel gears 64, 66 rotate in conjunction with the input bevel gear 62, the rotation is transmitted from the drive pulleys 68a, 70a connected to the bevel gears 64, 66 to the driven pulleys 68b, 70b via the belts 72, 74, and the end effector 25B attached to the belts 72, 74 moves linearly.

[0074] According to the third embodiment, the end effector 25B is attached to the belts 72, 74 which rotate infinitely, so that both linear motion and rotational motion can be used. In addition, the arrangement of the driven pulleys 68b, 70b allows a high degree of freedom in the direction of rotational motion and linear motion. Specifically, the direction of linear motion using the belts 72, 74 can be arranged radially from the input bevel gear 62. Furthermore, guides, rails, etc. that assist the linear motion of the belts 72, 74 or the end effector 25B may be provided.

[0075] As in the first embodiment, the conversion mechanism 32B of the third embodiment may also have a friction reducing member 50 that reduces the rotational friction resistance of the rotational sliding part 45. As in the first embodiment, at least one of the rod-shaped member 20, the base end side connecting part 22, the tip end side connecting part 24, and the gear shaft body 62a of the input bevel gear 62 may have a hollow hole.

[0076] In the third embodiment, too, it is possible to obtain the same effect as in the first and second embodiments, that is, the effect that the end effector 25B can be translated while changing the posture at high speed.

[0077] [Fourth embodiment] 15 to 19 show a link actuation device 1C according to a fourth embodiment of the present invention. FIG. 15 and FIG. 16 are a front view and a perspective view of the link actuation device 1C according to the fourth embodiment, respectively. FIG. 17 is a perspective view of a conversion mechanism 32C according to the fourth embodiment, FIG. 18 is a horizontal cross-sectional view of the conversion mechanism 32C, and FIG. 19 is a vertical cross-sectional view of the conversion mechanism 32C. The link actuation device 1C according to the fourth embodiment also differs from the first to third embodiments in the configuration of the conversion mechanism 32C. The conversion mechanism 32C of the link actuation device 1C according to the fourth embodiment is composed of a sun gear 76, a planetary gear 78, and a worm gear 80. The conversion mechanism 32C will be described in detail below.

[0078] <Conversion mechanism> In the conversion mechanism 32C of the fourth embodiment, rotational motion about the link hub central axis C on the tip side of the connecting portion 24 on the tip side is converted into linear motion by three planetary gears 78 on the outer periphery of a sun gear 76 and a worm gear 80 connected thereto. In this embodiment, the sun gear 76 and the planetary gears 78 are spur gears. The worm gear 80 has a screw gear 82 and a female screw 84 that meshes with the screw gear 82.

[0079] The sun gear 76 is fixed to the outer member 24b of the connecting portion 24 on the tip side via the pillar portions 76a. In this embodiment, three pillar portions 76a are provided spaced apart in the circumferential direction. However, the structure of the pillar portions 76a is not limited to the structure of this embodiment. As a result, when the outer member 24b of the connecting portion 24 on the tip side rotates, the sun gear 76 also rotates.

[0080] The three planetary gears 78, 78, 78 are arranged at equal intervals in the circumferential direction on the outer periphery of the sun gear 76 and mesh with the sun gear 76. A gear shaft body 78a of each planetary gear 78 is rotatably supported by the link hub 3 on the tip side. As a result, when the sun gear 76 rotates around the central axis C of the link hub on the tip side, the three planetary gears 78, 78, 78 rotate in unison.

[0081] A screw gear 82 of a worm gear 80 is connected to a gear shaft body 78a of each planetary gear 78. The screw gear 82 is made of a ball screw and extends in the direction of the link hub central axis C on the tip side. A female screw 84 meshes with each screw gear 82.

[0082] In this embodiment, three through holes having female threads 84 on the inside are formed in a single slide member 86. In detail, the slide member 86 has a triangular shape when viewed from the direction of the link hub central axis C on the tip side, with through holes formed at three corners of the triangle and a female thread 84 formed in each through hole. A screw gear 82 meshes with the three female threads 84. As a result, when the three planetary gears 78 rotate in conjunction with the sun gear 76, the screw gear 82 connected to the planetary gear 78 rotates, and the slide member 86 moves linearly.

[0083] The end effector 25C is attached to the slide member 86. In this embodiment, the slide member 86 has a through hole 86a in the center thereof, and a tip rotating member 88 is rotatably supported in the through hole 86a. The end effector 25C is detachably attached to this tip rotating member 88. The end effector 25C may be attached directly to the slide member 86.

[0084] As shown in Fig. 15, in this embodiment, the rotation axis AX7 of the tip rotating member 88 coincides with the central axis C of the tip link. As shown in Fig. 19, the rotating shaft 88a of the tip rotating member 88 is connected to the rotating shaft 76b of the sun gear 76. This allows the end effector 25C to move linearly in the direction of the central axis C of the tip link and to rotate around the central axis C of the tip link.

[0085] According to the fourth embodiment, the slide member 86 is supported at three points by the three worm gears 80, so that the slide member 86 and the end effector 25C attached thereto are stably supported. In addition, by providing the slide member 86 capable of linear motion in the direction of the link hub central axis C on the tip side and the tip rotating member 88 rotatable relative to this slide member 86, the end effector 25C can simultaneously achieve rotational motion and linear motion.

[0086] As in the first embodiment, the conversion mechanism 32C of the fourth embodiment may also have a friction reducing member 50 that reduces the rotational friction resistance of the rotational sliding part 45. As in the first embodiment, at least one of the rod-shaped member 20, the base end side connecting part 22, the tip end side connecting part 24, and the gear shaft body 76a of the sun gear 76 may have a hollow hole.

[0087] In the fourth embodiment, too, it is possible to obtain the same effect as in the first to third embodiments, that is, the effect that the end effector 25C can be translated while changing its posture at high speed.

[0088] The present invention is not limited to the above-described embodiment, and various additions, modifications, and deletions are possible without departing from the scope of the present invention. For example, in the link actuation device 1 of the above-described embodiment, each link mechanism 4 is of a mirror-symmetric type, but each link mechanism 4 may be of a point-symmetric type. Therefore, such a structure is also included in the scope of the present invention. [Explanation of symbols]

[0089] 1,1A,1B,1C Link actuator 2 Base end link hub 3 Tip link hub 4 Link mechanism (parallel link mechanism, spherical link mechanism) 5 End link member on the base end side 6 End link member on tip side 7 Central link member 10 Attitude control drive source 20 Rod-shaped member 22 Base end connection part 24 Tip connection 30 Rotational drive source 32, 32A, 32B, 32C conversion mechanism 45 Rotating and sliding part 50 Friction reducing materials

Claims

1. A link hub on a tip side is connected to a link hub on a base end side via two or more link mechanisms so that the position can be changed; Each of the link mechanisms is a parallel link mechanism including a spherical link mechanism having a base end link member having one end rotatably connected to the base end link hub, a tip end link member having one end rotatably connected to the tip end link hub, and a central link member having both ends rotatably connected to the other ends of the base end and tip end link members, the distal link hub and the proximal link hub are operably connected to each other by a rod-shaped member via distal and proximal connecting portions, the rod-shaped member and the base-side connecting portion are rotatably connected to the base-side link hub, and the rod-shaped member and the tip-side connecting portion are rotatably connected to the tip-side link hub, a rotary drive source that rotates the rod-shaped member is fixed to the link hub on the base end side; A parallel link mechanism in which a conversion mechanism that converts the rotation of the rod-shaped member into linear motion is fixed to the link hub on the tip side.

2. 2. The parallel link mechanism according to claim 1, wherein the conversion mechanism has a friction reducing member that reduces the rotational friction resistance of the rotational sliding portion.

3. 3. The parallel link mechanism according to claim 1, wherein at least one of the rod-shaped member, the base end side and tip end side connecting portions, and the rotation shaft of the conversion mechanism is hollow.

4. The parallel link mechanism according to any one of claims 1 to 3, and a posture control drive source for controlling the posture of the tip-side link hub.

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