Parallel link mechanism and link actuator

Abstract

To provide a parallel link mechanism and a link actuation device capable of improving the stiffness of the whole mechanism while making it compact.SOLUTION: A parallel link mechanism 9 couples a link hub 13 on a tip end side to a link hub 12 on a base end side through three sets of link mechanisms 14 so as to change a posture. Each link mechanism 14 has end portion link members 15 and 16 on the base end side and the tip end side rotatably coupled to the link hub 12 on the base end side and the link hub 13 on the tip end side respectively at one end, and a center link member 17 that is rotatably coupled to the other ends of the end portion link members 15 and 16 on the base end side and tip end side respectively at both ends. Concerning the three sets of the link mechanisms 14, both rotary paired parts T3 and T4 including both ends of the end portion link members 15 and 16 on the base end side and tip end side and the center link members 17, are equipped with rotation transmission mechanisms 42 in which the rotations of one rotary paired part reverses the rotations of the other rotary paired part.SELECTED DRAWING: Figure 3

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 or industrial equipment. [Background technology]

[0002] Patent Document 1 proposes a work device that has a base plate and a traveling plate connected by multiple links, and performs a specified task using a parallel link mechanism that moves the traveling plate by operating these links in coordination. In the parallel link mechanism of Patent Document 2, as shown in FIG. 12, a two-degree-of-freedom mechanism is formed by a base-end link hub 12, a tip-end link hub 13, and three or more sets of link mechanisms 14, in which the tip-end link hub 13 can freely rotate around two perpendicular axes relative to the base-end link hub 12. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-94245 A [Patent Document 2] Patent No. 6289973 Summary of the Invention [Problem to be solved by the invention]

[0004] In the parallel link mechanism of Patent Document 1, the operating angle of each link is small, so in order to set a large operating range of the traveling plate, it is necessary to increase the link length. This increases the dimensions of the entire mechanism, which causes the device to become large. In addition, increasing the link length reduces the rigidity of the entire mechanism.

[0005] In the parallel link mechanism of Patent Document 2, theoretically, the two rotation pairs consisting of the central link member 17 and the end link members 15, 16 are subject to a constraint condition (rotation constraint condition of the central link member 17) in which when one rotation pair rotates, the other rotation pair rotates in the opposite direction by the same amount, and the rotation is fixed. In actual parallel link mechanisms, there are cases where there are machining errors in the components and the rigidity of the bearings is low. As a result, the central axes of the rotation pairs do not intersect at a single point at the center of the spherical links on the tip and base ends in Patent Document 2, and the conditions are different from those in a theoretical parallel link mechanism, so the rotation constraint conditions do not necessarily hold. If the rotation constraint condition of the central link member is not satisfied, the rotation angles of the two rotation pairs formed by the central link member and the end link members are not fixed, and the rigidity of the entire mechanism decreases.

[0006] An object of the present invention is to provide a parallel link mechanism and a link actuator that can improve the rigidity of the entire mechanism while being made compact. [Means for solving the problem]

[0007] The parallel link mechanism of the present invention is a parallel link mechanism using a spherical link mechanism in which a tip side link hub is connected to a base side link hub via three or more sets of link mechanisms so that the posture of the tip side link hub can be changed, and each of the link mechanisms has base side and tip side end link members, one end of which is rotatably connected to the base side link hub and the tip side link hub, respectively, and a central link member, both ends of which are rotatably connected to the other ends of the base side and tip side end link members, At least three sets of link mechanisms are provided with a rotation transmission mechanism in both rotation pairs including both ends of the base end and tip end link members and the central link member, such that rotation of one of the rotation pairs causes the other rotation pair to rotate in the opposite direction to the rotation of the one of the rotation pairs.

[0008] According to this configuration, a two-degree-of-freedom mechanism is formed by the base-end link hub, the tip-end link hub, and three or more sets of link mechanisms, in which the tip-end link hub can rotate freely around two orthogonal axes relative to the base-end link hub. In other words, the tip-end link hub can rotate with two degrees of freedom relative to the base-end link hub, allowing for free attitude change. This two-degree-of-freedom mechanism is compact, yet allows for a wide range of movement of the tip-end link hub relative to the base-end link hub.

[0009] Both rotation pairs, including both ends of the base end and tip end link members and the central link member, are provided with a rotation transmission mechanism in which the rotation of one of the rotation pairs causes the other rotation pair to rotate in the opposite direction to the rotation of the one of the rotation pairs. Therefore, the amount of rotation of the other rotation pair is uniquely determined by the rotation of one of the rotation pairs, and the rotation constraint condition of the parallel link mechanism is satisfied. Therefore, deformation of the parallel link mechanism is suppressed, and the rigidity of the entire mechanism is improved compared to the parallel link mechanism of the prior art in which the rotation constraint condition is not satisfied.

[0010] The rotation transmission mechanism may rotate the other rotation pair in a reverse direction and by the same amount as the one rotation pair. In this case, the design and structure of the rotation transmission mechanism can be simplified, and manufacturing costs can be reduced.

[0011] As the rotation transmission mechanism, a gear that rotates around each rotation axis and meshes with each other may be provided on each of the rotation axes of the rotation pairs between the end link member on the base end side and the central link member and the rotation axis of the rotation pairs between the end link member on the tip end side and the central link member. In this case, the rotation of one rotation pair can be accurately transmitted to the other rotation pair.

[0012] The gears may be bevel gears. When an angle γ between a central axis of a rotation pair between the central link member and a base end link member and a central axis of a rotation pair between the central link member and a tip end link member is set to a predetermined angle, the bevel gears can transmit the rotation of one rotation pair to the other rotation pair with high precision.

[0013] The gears provided on the respective rotary shafts may be gears of the same shape, in which case the gear parts can be used in common, thereby reducing the manufacturing cost of the rotation transmission mechanism.

[0014] As the rotation transmission mechanism, one end of the cable may be wound around a rotating shaft member whose central axis is the rotation axis of the rotation pair between the end link member on the base end side and the central link member, and the other end of the cable may be wound in the opposite direction to the one end around a rotating shaft member whose central axis is the rotation axis of the rotation pair between the end link member on the tip end side and the central link member, and the rotating shaft members may be connected to each other by the cable. Examples of the cord include a wire rope, a belt, and a chain. According to this configuration, for example, by providing a cable body to an existing parallel link mechanism, the rotation of one revolute pair can be accurately transmitted to the other revolute pair.

[0015] The link actuation device of the present invention is provided with a posture control actuator for arbitrarily controlling the posture of the tip-side link hub in two or more of the three or more link mechanisms in the parallel link mechanism of any of the above configurations of the present invention. Therefore, the effects described above for the parallel link mechanism of the present invention can be obtained. By providing the posture control actuator, the posture of the tip-side link hub relative to the base-side link hub can be determined. Effect of the Invention

[0016] According to the parallel link mechanism and link actuator device of the present invention, since a rotation transmission mechanism is provided, the rotation of one of the two rotation pairs including both ends of the end link member and the central link member uniquely determines the rotation of the other one, the angles of the two rotation pairs are fixed, and the rigidity of the entire mechanism is improved. [Brief description of the drawings]

[0017] [Figure 1A]1 is a side view in which a part of a parallel link mechanism according to a first embodiment of the present invention is omitted. [Figure 1B] FIG. 2 is a front view of the parallel link mechanism with a portion thereof omitted. [Diagram 2] FIG. 2 is a diagram showing one link mechanism of the parallel link mechanism as a straight line. [Diagram 3] FIG. 2 is a perspective view of the parallel link mechanism. [Figure 4] FIG. 4 is a perspective view of the parallel link mechanism as viewed from a different angle. [Diagram 5] FIG. 2 is a partially enlarged view showing a main part of the parallel link mechanism. [Figure 6A] FIG. 11 is a partially enlarged view showing a main part of a parallel link mechanism according to a second embodiment of the present invention. [Figure 6B] FIG. 2 is a partially enlarged front view of the parallel link mechanism. [Figure 6C] FIG. 2 is a partially enlarged side view of the parallel link mechanism. [Figure 7A] FIG. 11 is a partially enlarged view showing a main part of a parallel link mechanism according to a third embodiment of the present invention. [Figure 7B] FIG. 2 is a partially enlarged front view of the parallel link mechanism. [Figure 8] FIG. 2 is a diagram showing a state in which both rotation pairs of the parallel link mechanism are connected by a cable. [Figure 9] FIG. 11 is a perspective view of a link actuator including a parallel link mechanism according to a third embodiment of the present invention. [Figure 10] FIG. 4 is a perspective view of the link actuator seen from a different angle. [Figure 11] FIG. 1 is a front view of a simplified model in which two link mechanisms are omitted of a link actuator device equipped with a parallel link mechanism according to a first embodiment of the present invention. [Figure 12] FIG. 1 is a front view of a conventional parallel link mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [First embodiment] A parallel link mechanism using a spherical link mechanism according to a first embodiment of the present invention will be described with reference to Figs. 1 to 5. As shown in Fig. 1A, the parallel link mechanism 9 has a link hub 13 on the tip side connected to a link hub 12 on the base end side so as to be capable of changing its posture via three sets of link mechanisms 14. The number of sets of link mechanisms 14 may be four or more. Note that Figs. 1A and 1B show only one set of link mechanisms 14, and the remaining two link mechanisms are omitted.

[0019] As shown in FIG. 1B, each link mechanism 14 has an end link member 15 on the base end side, an end link member 16 on the tip end side, and a central link member 17, forming a four-bar link mechanism consisting of four revolute pairs.

[0020] As shown in Fig. 1A, the base-side and tip-side end link members 15, 16 are substantially L-shaped. The base-side end link member 15 shown in Fig. 1B has one end connected to the base-side link hub 12 so as to be rotatable about a first rotation shaft 22a. The tip-side end link member 16 has one end connected to the tip-side link hub 13 so as to be rotatable about a second rotation shaft 22b.

[0021] One end of the central link member 17 is connected to the other end of the base end link member 15 so as to be rotatable around the third rotation shaft 22c. At the same time, the other end of the central link member 17 is connected to the other end of the tip end link member 16 so as to be rotatable around the fourth rotation shaft 22d.

[0022] The first rotating shaft 22a shown in FIG. 1A is a rotating shaft that rotates around the central axis O1 of each rotation pair T1 between the base end link hub 12 and the base end end link member 15. The second rotating shaft 22b is a rotating shaft that rotates around the central axis O2 of each rotation pair T2 between the tip end link hub 13 and the tip end end link member 16. The third rotating shaft 22c shown in FIG. 1B is a rotating shaft (rotating shaft member) that rotates around the central axis O3 of each rotation pair T3 between the base end end link member 15 and the central link member 17. The fourth rotating shaft 22d is a rotating shaft (rotating shaft member) that rotates around the central axis O4 of each rotation pair T4 between the tip end end link member 16 and the central link member 17.

[0023] The parallel link mechanism 9 is a combination of two spherical link mechanisms 9a and 9b. In the first spherical link mechanism 9a on the base end side, the central axis QA of the link hub 12 on the base end side intersects with the central axes O1 and O3 of the first and third rotating shafts 22a and 22c at the spherical link center PA on the base end side shown in Fig. 1A. In the second spherical link mechanism 9b on the tip end side, the central axis QB of the link hub 13 on the tip end side intersects with the central axes O2 and O4 of the second and fourth rotating shafts 22b and 22d shown in Fig. 1B at the spherical link center PB on the tip end side shown in Fig. 1A.

[0024] Also, the distance between the center of the rotational joint T1 between the base end link hub 12 and the base end end link member 15 and the base end spherical link center PA is the same. The distance between the center of the rotational joint T3 between the base end end link member 15 and the central link member 17 shown in FIG. 1B and the base end spherical link center PA is the same. Similarly, the distance between the center of the rotational joint T2 between the tip end link hub 13 and the tip end link member 16 shown in FIG. 1A and the tip end spherical link center PB is the same. The distance between the center of the rotational joint T4 between the tip end link member 16 and the central link member 17 shown in FIG. 1B and the tip end spherical link center PB is the same. In this example, the third and fourth rotation axes 22c and 22d of the rotational joints T3 and T4 between the base end and tip end end link members 15 and 16 and the central link member 17 have a certain cross angle (also called "axis angle") γ, but may be parallel. The arm angle, which is the angle between the first rotation shaft 22a and the third rotation shaft 22c, is set to a fixed angle.

[0025] The three link mechanisms 14 are geometrically identical in shape. The geometrically identical shape means that, as shown in FIG. 2, a geometric model in which each link member 15, 16, 17 is represented by a straight line, i.e., a model represented by each rotation pair T1, T3, T4, T2 and a straight line connecting these rotation pairs T1, T3, T4, T2, has a shape in which the base end side portion and the tip end side portion with respect to the center of the central link member 17 are symmetrical in shape no matter what posture the model takes. Note that each rotation pair T1, T3, T4, T2 may be referred to as "each rotation pair T1, etc." in the following description. FIG. 2 is a diagram in which one link mechanism 14 is represented by a straight line. The parallel link mechanism 9 of this embodiment is a rotationally symmetric type, and the positional relationship between the base end link hub 12 and the base end end link member 15 and the tip end link hub 13 and the tip end end link member 16 is rotationally symmetrical with respect to the center line C of the central link member 17.

[0026] The base end link hub 12, the tip end link hub 13, and the three link mechanisms 14 constitute a two-degree-of-freedom mechanism in which the tip end link hub 13 can rotate freely around two perpendicular axes relative to the base end link hub 12. In other words, the tip end link hub 13 can rotate with two degrees of freedom relative to the base end link hub 12, allowing for free posture change. This two-degree-of-freedom mechanism is compact, yet allows for a wide range of movement of the tip end link hub 13 relative to the base end link hub 12.

[0027] The vertical angle at which the central axis QB of the link hub 13 on the tip side is inclined relative to the central axis QA of the link hub 12 on the base side is called the bend angle θ. The maximum value of this bend angle θ is called the maximum bend angle θ max The rotation angle φ of the tip side link hub 13 relative to the base side link hub 12 can be set in the range of 0° to 360°. The rotation angle φ is the horizontal angle at which the central axis QB of the tip side link hub 13 is inclined relative to the central axis QA of the base side link hub 12.

[0028] The attitude of the tip side link hub 13 relative to the base side link hub 12 is changed around the intersection O of the central axis QA of the base side link hub 12 and the central axis QB of the tip side link hub 13, which serves as the center of rotation. Fig. 1B shows a state in which the central axis QA of the base side link hub 12 and the central axis QB of the tip side link hub 13 are on the same line, and Fig. 2 shows a state in which the central axis QB forms a certain operating angle (bend angle) with respect to the central axis QA. Even if the attitude of the tip side link hub 13 relative to the base side link hub 12 changes, the distance L between the base side and tip side spherical link centers PA, PB does not change.

[0029] The three link mechanisms 14 shown in Fig. 3 are arranged at equal intervals of 120 degrees in the circumferential direction, but do not necessarily have to be arranged at equal intervals. The link hub 12 on the base end side has a flat base end member 6 and three rotating shaft connecting members 21 provided integrally with the base end member 6. As shown in Fig. 4, the base end member 6 has a circular through hole 6a in the center, and the three rotating shaft connecting members 21 are arranged at equal intervals in the circumferential direction around the through hole 6a.

[0030] Each of the rotation pairs T1 and the like is provided with a rolling bearing (not shown) as a rotation resistance means for the rotation pairs. At the rotation pair T1 between the base-end link hub 12 and the base-end end link member 15, a first rotating shaft 22a is rotatably connected to each rotating shaft connecting member 21 via the rolling bearing. One end of the base-end end link member 15 is connected to the first rotating shaft 22a, and the first rotating shaft 22a and the base-end end link member 15 rotate together.

[0031] 1A, the first rotating shaft 22a is rotatably supported at its axially intermediate portion by the rotating shaft connecting member 21 via the rolling bearing. The rolling bearing is set and fixed in a state in which the outer peripheral surface of the outer ring is fitted into an inner diameter groove provided in the rotating shaft connecting member 21. The rolling bearings provided in the other rotation pairs T2, T3, and T4 (FIG. 1B) are installed in substantially the same manner.

[0032] As shown in FIG. 1B, the tip-side link hub 13 has a flat tip member 40 and three rotating shaft connecting members 41 arranged at equal intervals in the circumferential direction on the bottom surface of the tip member 40. The center of the circumference on which each rotating shaft connecting member 41 is arranged is located on the central axis QB of the tip-side link hub 13. A second rotating shaft 22b whose axis intersects with the central axis QB of the tip-side link hub 13 is rotatably connected to each rotating shaft connecting member 41. One end of the tip-side end link member 16 is connected to the second rotating shaft 22b. The other end of the tip-side end link member 16 is connected to a fourth rotating shaft 22d rotatably connected to the other end of the central link member 17.

[0033] <About the rotation transmission mechanism> 3, a rotation transmission mechanism 42 is provided at both rotation pairs T3, T4 including both ends of the base-end and tip-end end link members 15, 16 and the central link member 17. When one of the rotation pairs T3 (T4) rotates, the other rotation pair T4 (T3) rotates in the opposite direction to the one of the rotation pairs T3 (T4), i.e., in the opposite direction and by the same amount of rotation.

[0034] As shown in FIG. 5, the rotation transmission mechanism 42 includes gears that rotate around the third and fourth rotating shafts 22c and 22d and mesh with each other. The gears are bevel gears 43. The pair of meshing bevel gears 43 rotate according to the operating angles of the base end and tip end link members 15 and 16. One bevel gear 43 is fixed to the other end of the base end end link member 15 together with the third rotating shaft 22c. The other bevel gear 43 is connected to one end of the central link member 17 so as to be rotatable around the third rotating shaft 22c.

[0035] The other bevel gear 43 is fixed to the other end of the tip-side end link member 16 together with the fourth rotation shaft 22d. The other bevel gear 43 is connected to the other end of the central link member 17 so as to be rotatable around the fourth rotation shaft 22d. In this embodiment, the one bevel gear 43 and the other bevel gear 43 are gears of the same shape. This pair of bevel gears 43, 43 are disposed close to the intersection Px of the third rotation shaft 22c and the fourth rotation shaft 22d.

[0036] <Action and effect> 3 described above, a two-degree-of-freedom mechanism is configured in which the tip-side link hub 13 can rotate freely around two perpendicular axes relative to the base-side link hub 12, with the base-side link hub 12, the tip-side link hub 13, and three or more sets of link mechanisms 14. In other words, the tip-side link hub 13 can rotate with two degrees of freedom relative to the base-side link hub 12, and can freely change its attitude. This two-degree-of-freedom mechanism is compact, yet allows a wide range of movement of the tip-side link hub 13 relative to the base-side link hub 12.

[0037] Since both rotation pairs T3, T4 are provided with a rotation transmission mechanism 42 that rotates one rotation pair T4 (T3) in the opposite direction by the rotation of the other rotation pair T3 (T4), the amount of rotation of the other rotation pair T4 (T3) is uniquely determined by the rotation of one rotation pair T3 (T4), satisfying the rotation constraint condition of the parallel link mechanism 9. Therefore, deformation such as twisting of the parallel link mechanism 9 is suppressed, and the rigidity of the entire mechanism is improved compared to the parallel link mechanism of the prior art in which the rotation constraint condition is not satisfied.

[0038] Since the rotation transmission mechanism 42 rotates one rotation pair T4 (T3) in the opposite direction and by the same amount as one rotation pair T3 (T4), the design and structure of the rotation transmission mechanism 42 can be simplified, and further, the manufacturing cost of the entire parallel link mechanism can be reduced. For example, even if the machining accuracy of the components of the parallel link mechanism 9 is low or the rigidity of the rolling bearings provided in each rotation pair T1, etc. is low, the rotation constraint condition of the parallel link mechanism 9 is satisfied by the rotation transmission mechanism 42, and therefore the manufacturing cost can be reduced.

[0039] As the rotation transmission mechanism 42, a bevel gear 43 is provided on each of the third rotation shaft 22c of the rotation pair T3 between the end link member 15 on the base end side and the central link member 17, and the fourth rotation shaft 22d of the rotation pair T4 between the end link member 16 on the tip end side and the central link member 17. The bevel gear 43 is a gear that rotates around each rotation shaft 22c, 22d and meshes with each other. Therefore, the rotation of one rotation pair T3 (T4) can be accurately transmitted to the other rotation pair T4 (T3). Since the bevel gears 43 provided on each rotation shaft 22c, 22d have the same shape, it is possible to use the same parts and reduce the manufacturing cost of the rotation transmission mechanism 42. Since the pair of bevel gears 43, 43 are arranged close to the intersection Px (FIG. 5) between the third rotation shaft 22c and the fourth rotation shaft 22d, the bevel gears 43, 43 themselves can be made small, which can contribute to making the parallel link mechanism 9 more compact.

[0040] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description is omitted. When only a part of the configuration is described, the other parts of the configuration are the same as the previously described embodiment unless otherwise specified. The same configuration has the same action and effect. It is possible to combine not only the parts specifically described in each embodiment, but also partially combine embodiments together, provided that there is no particular problem with the combination.

[0041] [Second embodiment: Figs. 6A to 6C] As shown in Fig. 6A, the rotation transmission mechanism 42 may be configured such that bevel gear portions 43A, 43A are integrated with the base end side and tip end side end link members 15, 16. That is, one bevel gear portion 43A serving as a sector gear is integrally provided with the other end of the base end side end link member 15, and the other bevel gear portion 43A serving as a sector gear is integrally provided with the other end of the tip end side end link member 16, and these pair of bevel gear portions 43A, 43A mesh with each other as shown in Fig. 6B.

[0042] As shown in Fig. 6C, the pair of bevel gear portions 43A, 43A are formed at least over the angle of the operating range of the end link members 15, 16 on the base end side and the tip end side, and mesh with each other. The bevel gear portions 43A, 43A are provided rotatably around the third and fourth rotation shafts 22c, 22c. As shown in Fig. 6B, the pair of bevel gear portions 43A, 43A are provided on the inner space side of the parallel link mechanism 9. The rest of the configuration is the same as that of the above-mentioned embodiment.

[0043] According to this configuration, the bevel gear parts 43A, 43A are integrated with the end link members 15, 16 on the base end side and the tip end side, so that the number of parts of the entire parallel link mechanism can be reduced compared to the above-mentioned embodiment. This simplifies the structure of the parallel link mechanism 9 and reduces costs. Since the bevel gear parts 43A, 43A are integrated with each end link member 15, 16, this can contribute to improving the rigidity of the entire mechanism. Since the pair of bevel gear parts 43A, 43A are provided on the inner space side of the parallel link mechanism 9, it can be made more compact than the above-mentioned embodiment. The bevel gear parts 43A, 43A may be fixed to the end link members 15, 16 on the base end side and the tip end side by welding or bolts, etc.

[0044] [Third embodiment: Figs. 7A to 8] As shown in Fig. 7A, one end of a wire rope 44, which is a cable, may be wound around the third rotating shaft (rotating shaft member) 22c, and the other end of the wire rope 44 may be wound around the fourth rotating shaft (rotating shaft member) 22d, and as shown in Fig. 7B, the third and fourth rotating shafts 22c and 22d may be connected to each other by the wire rope 44. Specifically, one end of the wire rope 44 is fixed to the third rotating shaft 22c by welding or the like, and the central link member 17 is mounted with one end of the wire rope 44 wound around the circumference of the third rotating shaft 22c over at least the operating range of the rotation pair T4 of the central link member 17 or more.

[0045] The other end of the wire rope 44 is fixed to the fourth rotating shaft 22d by welding or the like, and is mounted in a state in which the other end of the wire rope 44 is wound around the circumference of the fourth rotating shaft 22d over at least the operating range of the rotation pair T3 of the central link member 17. The operating range of the central link member 17 is determined by the design of the spherical link mechanism. In Fig. 8, the wire rope 44 is wound around each of the rotating shafts 22c, 22d by an operating angle δ of both rotation pairs T3, T4 of the central link member. Regarding the direction in which the wire rope 44 is wound, the winding direction R2 of the fourth rotating shaft 22d is opposite to the winding direction R1 of the third rotating shaft 22c. Also, in order to make the winding amount and the withdrawal amount of the wire rope 44 the same, the shaft portions around which the wire rope 44 is wound are made to have the same diameter for each of the rotating shafts 22c and 22d. According to this configuration, the rotation of one of the rotating pairs T3 (T4) rotates one of the rotating shafts 22c (22d), and the wire rope 44 is wound or drawn out by the operating angle along the circumference of the one of the rotating shafts 22c (22d). Since the wire rope 44 is wound around the third and fourth rotating shafts 22c, 22d in the opposite directions, when a part of the wire rope 44 is wound around the circumference of one of the rotating shafts 22c (22d) as described above, the tension of the wire rope 44 applies a rotational force to the other rotating shaft 22d (22c) in the opposite direction to that of the one of the rotating shafts 22c (22d). Therefore, for example, by providing the wire rope 44, which is a cable body, to an existing parallel link mechanism, the rotation of one of the rotating pairs can be accurately transmitted to the other rotating pair.

[0046] 7A, the rotation transmission mechanism 42 may have a guide 45 for winding the wire rope 44 perpendicularly to the rotation axis of each of the rotation shafts 22c, 22d. This guide 45 is provided on the central link member 17. This guide 45 is formed in a concave shape, for example, by guide fixing parts 45a, 45a fixed to both side parts of the central link member 17 and a guide main body part 45b installed across the tip parts of these guide fixing parts 45a, 45a.

[0047] The wire rope 44 is guided as shown in FIG. 7B while being in contact with the longitudinal intermediate portion of the guide body portion 45b facing the central link member 17, so that the wire rope 44 is wound vertically as described above. The guide 45 may be provided with a rotation structure (not shown) for reducing frictional resistance at the contact portion with the wire rope 44. When the guide 45 is provided with this rotation structure, the durability of the rotation transmission mechanism 42 can be increased and the maintenance period can be extended. The guide 45 may be provided with a tension adjustment mechanism (not shown) for adjusting the tension of the wire rope 44. When the guide 45 is provided with this tension adjustment mechanism, the rotation of one rotation pair T3 (T4) can be accurately transmitted to the other rotation pair T4 (T3) over a long period of time.

[0048] <Other embodiments> When the number of link mechanisms 14 is four or more, at least three link mechanisms need to be provided with rotation transmission mechanisms at both rotation pairs including both ends of the base end and tip end link members and the central link member. The pair of gears that mesh with each other in the rotation transmission mechanism 42 may have different shapes. The rotation transmission mechanism 42 may be gears having two parallel shafts that mesh with each other. The cord may be a belt, a chain, or the like.

[0049] <Link actuator: Fig. 9~Fig. 10> 9, a link actuating device 7 according to an embodiment of the present invention includes the parallel link mechanism 9 according to the third embodiment described above, and a posture control actuator 10 that arbitrarily controls the posture of the link hub 13 at the tip end side of the parallel link mechanism 9. The link actuating device 7 may employ the parallel link mechanism 9 according to the first embodiment shown in FIG. 11 or the parallel link mechanism 9 according to the second embodiment (FIG. 6B) instead of the parallel link mechanism 9 described above.

[0050] <Attitude control actuator> In the example of Fig. 10, all three link mechanisms 14 are provided with a posture control actuator 10. Each posture control actuator 10 is a rotary actuator equipped with a speed reducing mechanism (not shown), and is installed coaxially with the first rotation shaft 22a on the surface of the base end member 6 of the base end link hub 12. If posture control actuators 10 are provided in at least two of the three link mechanisms 14 shown in Fig. 10, the posture of the tip end link hub 13 relative to the base end link hub 12 can be determined.

[0051] The link actuation device 7 rotates and drives each of the attitude control actuators 10, thereby actuating the parallel link mechanism 9. More specifically, when the attitude control actuators 10 are rotated, the rotation is decelerated via the reduction mechanism and transmitted to the first rotation shaft 22a. This allows the attitude of the tip-side link hub 13 relative to the base-side link hub 12 to be changed as desired. An end effector (not shown) is attached to the tip member 40 of the tip-side link hub 13. Examples of the end effector include a hand including a gripper, a cleaning nozzle, a dispenser, a welding torch, and an image processing device.

[0052] Although the embodiment of the present invention has been described above, the disclosed embodiment is illustrative in all respects and is not restrictive. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0053] 7...link actuator, 9...parallel link mechanism, 9a, 9b...spherical link mechanism, 10...attitude control actuator, 12...base end link hub, 13...tip end link hub, 14...link mechanism, 15...base end end link member, 16...tip end end link member, 17...central link member, 22c...third rotating shaft, 22d...fourth rotating shaft, 42...rotation transmission mechanism, 43...bevel gear (gear), 43A...bevel gear portion (gear), 44...wire rope (cord)

Claims

1. A parallel link mechanism using a spherical link mechanism in which a tip-side link hub is connected to a base-side link hub via three or more sets of link mechanisms so that its posture can be changed, and each of the link mechanisms has base-side and tip-side end link members, one end of which is rotatably connected to the base-side link hub and the tip-side link hub, respectively, and a central link member, both ends of which are rotatably connected to the other ends of the base-side and tip-side end link members, A parallel link mechanism in which at least three sets of link mechanisms are provided with a rotation transmission mechanism at both rotation pairs including both ends of the base end and tip end link members and the central link member, such that rotation of one of the rotation pairs causes the other rotation pair to rotate in the opposite direction to the rotation of the one of the rotation pairs, and components of the rotation transmission mechanism are integrated into the base end and tip end link members.

2. 2. The parallel link mechanism according to claim 1, wherein the rotation transmission mechanism rotates the one rotation pair in a direction opposite to and by the same amount as the other rotation pair relative to the one rotation pair.

3. 3. The parallel link mechanism according to claim 1 or 2, wherein, as the rotation transmission mechanism, gears that rotate about the respective rotation axes and mesh with each other are provided on a rotation axis of a rotation pair portion between the end link member on the base end side and the central link member, and on a rotation axis of a rotation pair portion between the end link member on the tip end side and the central link member.

4. 4. The parallel link mechanism according to claim 3, wherein the gears are bevel gears.

5. 5. The parallel link mechanism according to claim 3, wherein the gears provided on the respective rotation shafts have the same shape.

6. 3. The parallel link mechanism according to claim 1 or 2, wherein the rotation transmission mechanism is such that one end of a cable is wound around a rotating shaft member having a central axis which is the rotation axis of the rotation pair between the end link member on the base end side and the central link member, and the other end of the cable is wound in the opposite direction to the one end around a rotating shaft member having a central axis which is the rotation axis of the rotation pair between the end link member on the tip end side and the central link member, so that the rotating shaft members are connected to each other by the cable.

7. 7. A link actuation device comprising: a posture control actuator for arbitrarily controlling a posture of the tip-side link hub in two or more of the three or more link mechanisms in the parallel link mechanism according to claim 1.

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