Parallel link mechanism and link operation device

Abstract

Provided are a parallel link mechanism and a link operation device that can be increased in rigidity without sacrificing a movable range. A parallel link mechanism (9) is provided with one bearing, a central housing (25) including the other bearing, and a connecting member (26). The one bearing rotatably supports one end of a rotary shaft (27) in a target connection part (Rk) for at least one connection part (Rk) among a connection part (Rk) between an end link member (15) on a proximal side and a center link member and a connection part (Rk) between an end link member (16) on a distal side and a center link member (17), and is fitted to the end link member (15, 16) on either the proximal side or the distal side or the center link member (17). The other bearing rotatably supports the other end of the rotary shaft (27) in the target connection part (Rk). A connecting member (26) connects a member to which the one bearing is fitted and a central housing (25) to each other.

Description

Parallel Link Mechanism and Link Actuator Related Application

[0001] This application claims the priority of Japanese Patent Application No. 2024-165008 filed on September 24, 2024, and the entire disclosure of which is incorporated herein by reference and made a part of this application.

[0002] The present invention relates to a parallel link mechanism and a link actuator used in equipment that requires high speed, high precision, a wide working range, and fine-grained operation, such as industrial equipment like medical devices or appearance inspection devices.

[0003] Conventionally, a parallel link mechanism has been proposed (Patent Document 1). The parallel link mechanism is a mechanism that connects a base-end hub and a tip-end hub by a plurality of link systems, and the link systems are often arranged radially from the center.

[0004] Japanese Patent Application Laid-Open No. 2000-94245, U.S. Patent No. 5,893,296, Japanese Patent Application Laid-Open No. 2005-144627

[0005] In the parallel link mechanism of Patent Document 1, since the operating angle of each link is small, in order to set a large operating range for the traveling plate, it is necessary to increase the link length. As the link length increases, there is a problem that the size of the entire mechanism becomes large and the device becomes large. Further, increasing the link length not only causes a decrease in the rigidity of the entire mechanism, but also when a tool or the like is mounted on the traveling plate, the moment of inertia of the mounted object becomes large, and there is also a problem that the weight of the tool mounted on the traveling plate, that is, the portable weight of the traveling plate is limited to a small value.

[0006] In the configuration of the parallel link mechanism and the link actuator shown in Patent Document 2, fine attitude changes can be performed at high speed, but there are the following problems. Due to the speed-up mechanism in which the attitude of the tip-side link hub moves twice with respect to the rotation angle of the attitude control actuator, when a heavy object is mounted, the vibration during settling becomes large. In this case, there is a problem that the mounting weight (load) is limited to a small value in order to perform high-speed operation.

[0007] The link actuation device shown in Patent Document 3 addresses the above-mentioned problems by supporting each rotating pair of the link mechanism at both ends to increase the rigidity of the link actuation device. However, when the bending angle becomes large, the central link member interferes with the base end and tip end link members, resulting in a problem where a sufficient range of motion cannot be obtained.

[0008] Figure 13 shows a conventional link actuation device in which plate members 71, 71 are sandwiched at both ends of the central link member 70. Figure 14 is a partial excerpt showing the area around the central link member in Figure 13. In the link actuation devices shown in Figures 13 and 14, a bearing (not shown) is fitted into the central link member 70, and the axial ends of the bearing are sandwiched between plate members 71, 71, resulting in a configuration with support at both ends. In this configuration, if the angle of bending of the central axis of the tip-side link hub 73 with respect to the central axis of the base-side link hub 72 is increased, the following problems arise. As shown in Figure 15, there is a risk of collision between the central link member 70 and the base-side link member 74 or the tip-side link member 75 or the plate member 71. Therefore, the angle of bending is limited. In other words, the range of motion of the link actuation device is limited.

[0009] The object of the present invention is to provide a parallel link mechanism and a link actuation device that can increase rigidity without sacrificing the range of motion.

[0010] The parallel link mechanism of the present invention is a parallel link mechanism in which a front link hub is connected to a base link hub via three or more link mechanisms so as to be able to change its orientation, and each link mechanism comprises a base and front end link member, one end of which is rotatably connected to the base link hub and the front link hub, and a central link member, the other end of which is rotatably connected to the other end of the base and front end link member via connecting portions, and the central link mechanism comprises, for at least one of the connecting portions of the base end link member and the central link member, one bearing that rotatably supports one end of the rotation axis at the target connecting portion and is fitted to either the base end or the front end link member or the central link member, and the other bearing that rotatably supports the other end of the rotation axis at the target connecting portion, and a connecting member that connects the one bearing to the central housing to each other.

[0011] In this configuration, the target connecting section has a double-ended support structure in which one end of the rotating shaft at the connecting section is rotatably supported by one bearing, and the other end of the rotating shaft is rotatably supported by the other bearing. This double-ended support structure increases the axial rigidity of the rotating shaft compared to conventional structures. As a result, the overall rigidity of the parallel link mechanism can be increased compared to conventional structures. Therefore, vibrations during operation and settling of the parallel link mechanism can be reduced. Increasing the overall rigidity of the parallel link mechanism also contributes to increasing the payload capacity.

[0012] One bearing is fitted to one of the link members, while the other bearing is provided in a central housing, which is connected to one of the link members via a connecting member. This allows the central housing and connecting member to be positioned in limited locations within the entire parallel link mechanism. Consequently, the central housing and connecting member can be avoided by not placing them within the range of motion of the end link members at the base and tip ends. Therefore, it is possible to create a parallel link mechanism that increases rigidity without sacrificing the range of motion compared to conventional structures.

[0013] To increase the rigidity of a parallel link mechanism, for example, if bearings are placed at both ends of the central link member, the following problems arise when the housing that fits these bearings is constructed as a single unit: Due to the machining precision of the housing, it is difficult to ensure coaxiality between both bearings, and there is a possibility of overloading the bearings.

[0014] The connecting member may be a position-adjustable connecting member that connects the member into which one bearing is fitted and the central housing so as to be able to adjust their positions relative to each other. In this case, by connecting the member into which one bearing is fitted and the central housing including the other bearing with a position-adjustable connecting member, the positions of both members can be easily adjusted. Therefore, the coaxiality of one bearing and the other bearing can be kept below a desired value, preventing overload from acting on the bearings, and improving the durability of the bearings compared to the configuration using the integrated housing.

[0015] The position-adjusting connecting member may be adjustable in the axial direction of the rotating shaft and in a direction perpendicular to this axial direction. In this case, it is not necessary to specify the coaxiality between the member into which one bearing is fitted and the central housing, and processing costs can be reduced compared to the configuration using the integrated housing. Because the position can be adjusted by the position-adjusting connecting member, the assembly of the parallel link mechanism can be improved compared to the conventional structure.

[0016] A parallel link mechanism in which, in the origin position of the parallel link mechanism, the connecting member and the central housing are installed such that, in the end link member to which the central housing is connected together with the central link member, there is a space in the direction in which the central link member and the end link member face each other, and in the direction in which the central housing and the end link member face each other. The "space" refers to the "gap" between the central link member and the central housing in each link mechanism.

[0017] In this configuration, the central link member and the central housing are connected and movable, but they are not positioned within the range of motion of the base-side and tip-side end link members. Therefore, the parallel link mechanism operates without interference between the base-side and tip-side end link members and the central link member and the central housing. Here, "end link member" in "the end link member to which the central housing is connected together with the central link member" refers to at least one of the base-side end link member and the tip-side end link member.

[0018] Either one or both of the base and tip end link members may be bent into a substantially L-shape. In this case, the link mechanism can be manufactured at a lower cost than if the base and tip end link members were machined by cutting or other methods.

[0019] The link actuator of the present invention is equipped with attitude control actuators that arbitrarily control the attitude of the tip-side link hub in two or more of the three or more link mechanisms in any of the parallel link mechanisms of the present invention. Therefore, the above-mentioned effects can be obtained with respect to the parallel link mechanism of the present invention. Because the attitude control actuators are provided, the attitude of the tip-side link hub relative to the base-side link hub can be determined. By combining the attitude control actuators with a parallel link mechanism equipped with a central housing and connecting members, precise and wide-range high-speed operation becomes possible, resulting in a lightweight and compact link actuator.

[0020] Any combination of at least two configurations disclosed in the claims and / or the specification and / or drawings is included in the present invention. In particular, any combination of two or more of each claim is included in the present invention.

[0021] The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustrative and explanatory purposes only and should not be used to define the scope of the invention. The scope of the invention is defined by the accompanying claims. In the accompanying drawings, the same reference numerals in multiple drawings indicate the same or corresponding parts.

[0022] This is a perspective view of a link actuator according to the first embodiment of the present invention. This is a diagram partially showing a part of the link actuator. This is a diagram showing one link mechanism of the link actuator represented by straight lines. This is a diagram partially showing the end support portions of the central link member in the link mechanism. This is a diagram illustrating the arrangement of the position adjustment connecting member and the central housing of the end support portions. This is a cross-sectional view of the end support portions of the central link member. This is an exploded perspective view showing the assembly structure of the central link member and the position adjustment connecting member. This is an exploded perspective view showing the assembly structure of the position adjustment connecting member and the central housing. This is a perspective view of a link actuator according to the second embodiment of the present invention. This is a cross-sectional view of the end support portions of the central link member in the link actuator. This is a cross-sectional view of the end support portions of the central link member in the link actuator according to the third embodiment of the present invention. This is an exploded perspective view showing the assembly structure of the central link member and the position adjustment connecting member in the link actuator according to the fourth embodiment of the present invention. This is an exploded perspective view showing the assembly structure of the position adjustment connecting member and the central housing. This is a perspective view of a conventional example of a link actuator using an end support structure for the central link member. This is a diagram partially showing the central link member and the like of the link actuator. This is a perspective view showing the posture of the link actuator when the bending angle is large.

[0023] [First Embodiment] A link actuation device according to an embodiment of the present invention will be described with reference to Figures 1 to 7. This link actuation device is used, for example, in medical equipment or industrial equipment.

[0024] <Link Actuator> As shown in Figure 1, the link actuator 7 comprises a parallel link mechanism 9, an attitude control actuator 10 that drives the parallel link mechanism 9, and a control device Cu that controls the attitude control actuator 10.

[0025] <Parallel Link Mechanism> The parallel link mechanism 9 connects the link hub 13 at the tip end to the link hub 12 at the base end via three sets of link mechanisms 14, allowing for orientation changes. The number of sets of link mechanisms 14 may be four or more.

[0026] As shown in Figure 2, each link mechanism 14 has a base end link member 15, a tip end link member 16, and a central link member 17, forming a four-bar link mechanism consisting of four rotational pairs. As shown in Figure 1, the base end and tip end link members 15 and 16 are bent into a roughly L-shape, with one end rotatably connected to the base end link hub 12 and the tip end link hub 13, respectively.

[0027] The central link member 17 is rotatably connected at both ends to the other ends of the base-side and tip-side end link members 15 and 16, respectively, via connecting portions Rk. In the following description, the base-side end link member 15 may be referred to as the base-side link member 15 or link member 15. The tip-side end link member 16 may be referred to as the tip-side link member 16 or link member 16.

[0028] As shown in Figure 2, the parallel link mechanism 9 has a structure that combines two spherical link mechanisms. The central axes of the rotational pairs of the base-side link hub 12 and the base-side end link member 15, and the central axes of the rotational pairs of the base-side end link member 15 and the central link member 17, intersect at the base-side spherical link center PA. Similarly, the central axes of the rotational pairs of the tip-side link hub 13 and the tip-side end link member 16, and the central axes of the rotational pairs of the tip-side end link member 16 and the central link member 17, intersect at the tip-side spherical link center PB.

[0029] Furthermore, the distance from the center of each rotational pair between the base-side link hub 12 and each end-side link member 15 to the base-side spherical link center PA is the same. The distance from the center of each rotational pair between each end-side link member 15 and each central link member 17 to the base-side spherical link center PA is the same. Similarly, the distance from the center of each rotational pair between the tip-side link hub 13 and each end-side link member 16 to the tip-side spherical link center PB is the same. The distance from the center of each rotational pair between each end-side link member 16 and each central link member 17 to the tip-side spherical link center PB is the same. The central axes of each rotational pair between the base-side and tip-side end-link members 15, 16 and the central link member 17 may have a certain intersection angle γ or may be parallel.

[0030] As shown in Figure 1, the angle between the central axis O1 of each rotational pair between the base end link hub 12 and the base end link member 15, and the central axis of each rotational pair between the base end link member 15 and the central link member 17, is 90°. However, the angle may be other than 90°. The shape and positional relationship of the tip end link hub 13 and the tip end link member 16 are the same as the shape and positional relationship of the base end link hub 12 and the base end link member 15.

[0031] The three sets of link mechanisms 14 have the same geometric shape. Geometrically identical shape means that, as shown in Figure 3, the geometric model in which each link member 15, 16, and 17 are represented by straight lines, that is, the model represented by each rotational pair and the straight lines connecting these rotational pairs, has a shape in which the base end portion and the tip end portion are symmetrical with respect to the central part of the central link member 17, regardless of the orientation. Figure 3 is a diagram in which one set of link mechanisms 14 is represented by straight lines. The parallel link mechanism 9 of this embodiment is of the rotationally symmetric type, and the positional relationship between the base end link hub 12 and the base end link member 15 and the tip end link hub 13 and the tip end link member 16 is configured to be rotationally symmetric with respect to the center line C of the central link member 17. The central part of each central link member 17 is located on a common orbital circle D.

[0032] The base link hub 12, the tip link hub 13, and three sets of link mechanisms 14 constitute a two-degree-of-freedom mechanism in which the tip link hub 13 can rotate freely around two orthogonal axes relative to the base link hub 12. In other words, the tip link hub 13 is configured as a mechanism that allows for two degrees of freedom of rotation and change of orientation relative to the base link hub 12. This two-degree-of-freedom mechanism is compact while allowing for a wide range of motion of the tip link hub 13 relative to the base link hub 12.

[0033] For example, if the central axes QA and QB of the base and tip link hubs 12 and 13 are defined as straight lines passing through the base and tip spherical link centers PA and PB and intersecting at right angles with the central axes O1 (Figure 1) of the respective rotational pairs of the base and tip link hubs 12 and 13 and the base and tip end link members 15 and 16, then the maximum bending angle θ is the maximum value of the bending angle θ between the central axis QA of the base link hub 12 and the central axis QB of the tip link hub 13. ｍａｘ The angle can be set to approximately ±90°. Furthermore, the rotation angle φ of the tip-side link hub 13 relative to the base-side link hub 12 can be set within the range of 0° to 360°. The bending angle θ is the vertical 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. On the other hand, 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. The maximum bending angle θ is also shown. ｍａｘ It is acceptable for the angle to be 90 degrees or greater.

[0034] The orientation of the tip-side link hub 13 relative to the base-side link hub 12 is changed using the intersection point 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 as the center of rotation. Even if the orientation of the tip-side link hub 13 relative to the base-side link hub 12 changes, the distance L between the spherical link centers PA and PB of the base-side and tip-side links does not change.

[0035] As shown in Figures 1 and 3, in this parallel link mechanism 9, when all of the following conditions are met, the base-side link hub 12 and base-side end link member 15, and the tip-side link hub 13 and tip-side end link member 16 move in the same way due to geometric symmetry. Therefore, when the parallel link mechanism 9 transmits rotation from the base end to the tip end, the base end and tip end rotate at the same angle and at a constant speed, functioning as a constant-velocity universal joint.

[0036] Condition 1: The angles of the central axes O1 of the rotational pairs of the base and tip end link hubs 12, 13 and the base and tip end link members 15, 16 in each link mechanism 14, as well as the lengths from the base and tip spherical link centers PA, PB to the centers of each rotational pair, are equal. Condition 2: The central axes O1 of the rotational pairs of the base and tip end link hubs 12, 13 and the base and tip end link members 15, 16 in each link mechanism 14, and the central axes of the rotational pairs of the base and tip end link members 15, 16 and the central link member 17 intersect the base and tip spherical link centers PA, PB at the base and tip ends. Condition 3: The geometric shapes of the base end link member 15 and the tip end link member 16 are equal. Condition 4: The geometric shapes of the base portion and the tip portion of the central link member 17 are equal. Condition 5: With respect to the plane of symmetry of the central link member 17, the angular positional relationship between the central link member 17 and the end link members 15 and 16 on the base and tip sides is the same on the base and tip sides.

[0037] As shown in Figure 1, the base end link hub 12 has a flat base member 6 and three rotating shaft connecting members 21 integrally provided with the base member 6. The base member 6 has a circular through hole 6a in its center, and the three rotating shaft connecting members 21 are arranged around this through hole 6a at equal intervals in the circumferential direction. The center of the through hole 6a is located on the central axis QA (Figure 3) of the base end link hub 12. A rotating shaft 22 whose axis intersects the central axis QA (Figure 3) of the base end link hub 12 is rotatably connected to each rotating shaft connecting member 21. One end of the base end link member 15 is connected to the rotating shaft 22.

[0038] The rotating shaft 22 is rotatably supported by the rotating shaft connecting member 21 via a bearing (not shown). The rotating shaft 22 is arranged concentrically with the output shaft of the reduction mechanism 52, which will be described later. One end of the base end link member 15 is connected to the rotating shaft 22 so as to rotate integrally with the rotating shaft 22. The other end of the base end link member 15 is connected to the rotating shaft of the connecting portion Rk, which is rotatably connected to one end of the central link member 17.

[0039] The tip-side link hub 13 has a flat tip member 40 and three rotating shaft connecting members 41 provided on the bottom surface of the tip member 40 at equal circumferential intervals. The center of the circumference on which each rotating shaft connecting member 41 is located is on the central axis QB (Figure 3) of the tip-side link hub 13. A rotating shaft whose axis intersects the central axis QB (Figure 3) 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 this rotating shaft. The other end of the tip-side end link member 16 is connected to the rotating shaft of a connecting portion Rk that is rotatably connected to the other end of the central link member 17.

[0040] <Regarding the end-end support structure> In the first embodiment, the following end-end support structure is provided for the connection portion Rk between the base end link member 15 and the central link member 17, and for the connection portion Rk between the tip end link member 16 and the central link member 17. In other words, the end-end support structure is provided on both the base end and the tip end of the central link member 17. As will be described later, the end-end support structure may be provided on only one of the base end or tip end of the central link member 17.

[0041] As shown in FIGS. 4A and 5, the both-end support structure includes one bearing 23, a central housing 25 including the other bearing 24, and a connecting member 26 that connects these central link members 17 and the central housing 25 to each other. As shown in FIG. 5, one bearing 23 rotatably supports one end of a rotating shaft 27 in the target connecting portions Rk, Rk (see FIG. 1) and is fitted to the central link member 17. Specifically, the outer-ring outer peripheral surface of one bearing 23 is fitted and fixed to the inner peripheral surfaces of both the base end side and the tip end side of the central link member 17. The outer peripheral surface of the rotating shaft at one end (axial base end portion) of the rotating shaft 27 is fitted and fixed to the inner peripheral surface of the inner ring of one bearing 23. In this example, the central link member 17 corresponds to the "member for fitting one bearing".

[0042] The other bearing 24 is fitted to the central housing 25, and the other bearing 24 rotatably supports the other end of the rotating shaft 27 in the target connecting portions Rk, Rk (see FIG. 1). Specifically, the outer-ring outer peripheral surface of the other bearing 24 is fitted and fixed to the inner peripheral surface of the central housing 25. The outer peripheral surface of the rotating shaft at the other end (axial tip end portion) of the rotating shaft 27 is fitted and fixed to the inner peripheral surface of the inner ring of the other bearing 24.

[0043] For example, angular ball bearings combined back-to-back are respectively applied to one and the other bearings 23 and 24, and grease lubrication is used. Spacers 28 are provided at both end portions of the inner ring of each combined angular ball bearing. One and the other bearings 23 and 24 are ensured coaxiality by the rotating shaft 27, and a desired fixed-position preload is applied by tightening a nut 29 screwed onto the tip end portion of the rotating shaft 27. Thereby, the rigidity of the bearings 23 and 24 can be increased.

[0044] The bearings 23 and 24 are not limited to the above-described configuration. For example, angular ball bearings combined face-to-face may be applied as one and the other bearings 23 and 24. As one and the other bearings 23 and 24, for example, a configuration in which two deep groove ball bearings are arranged axially or a configuration consisting of one deep groove ball bearing may be used. In addition, a fixed-pressure preload may be applied to one and the other bearings 23 and 24 instead of the fixed-position preload.

[0045] As shown in FIGS. 6 and 7, the connecting member 26 is a position adjustment connecting member 26A that connects the central link member 17 and the central housing 25 to be position-adjustable relative to each other. As shown in FIG. 6, the position adjustment connecting member 26A is position-adjustable in the axial direction C1 of the rotation axis 27 in the connecting portion Rk to be targeted. A plurality (two in this example) of tapping holes Th for bolt fastening are provided in the mating surface of the central link member 17 that faces the position adjustment connecting member 26A.

[0046] A countersunk hole Zh facing outward is formed in the position adjustment connecting member 26A. In the countersunk hole Zh of the position adjustment connecting member 26A, drill holes Kh, Kh corresponding to the positions of the plurality of tapping holes Th, Th are formed. Each drill hole Kh is formed to have a larger diameter by a predetermined gap than the diameter dimension of the bolt 30 to be inserted. Due to this gap, the position adjustment connecting member 26A can be position-adjusted in the axial direction C1 of the rotation axis 27. The predetermined gap is a gap arbitrarily determined by design or the like, and is determined, for example, by obtaining an appropriate gap through either or both of tests and simulations. The same applies to the predetermined gap of each drill hole 32 described later.

[0047] As shown in FIG. 7, the position adjustment connecting member 26A is position-adjustable in the direction orthogonal to the axial direction C1 of the rotation axis 27. A plurality (two in this example) of tapping holes 31 for bolt fastening are provided in the mating surface 26Aa of the position adjustment connecting member 26A that faces the central housing 25. A countersunk hole 25a facing outward is formed in the central housing 25. In the countersunk hole 25a of the central housing 25, drill holes 32, 32 corresponding to the positions of the plurality of tapping holes 31, 31 are formed. Each drill hole 32 is formed to have a larger diameter by a predetermined gap than the diameter dimension of the bolt 33 to be inserted. Due to this gap, the position adjustment connecting member 26A can be position-adjusted in the direction orthogonal to the axial direction C1 of the rotation axis 27.

[0048] In the origin position of the parallel link mechanism 9 shown in Figure 1, as shown in Figure 4B, the position adjustment connecting member 26A and the central housing 25 are installed so that a space S1 is created in the direction A1 where the central link member 25 faces the base end link members 15 and 16, and in the direction A1 where the central housing 25 faces the base end end link members 15 and 16, to which the central housing 25 is connected together with the central link member 17. This prevents the position adjustment connecting member 26A and the central housing 25 from being positioned within the range of motion of the base end link members 15 and 16. The origin position is defined as the position in which the central axis QA of the base end link hub 12 (Figure 3) and the central axis QB of the tip end link hub 13 (Figure 3) are aligned in a straight line. In the origin position of the parallel link mechanism 9, the bending angle θ (Figure 3) is 0 degrees and the swivel angle φ (Figure 3) is 0 degrees. Based on the aforementioned origin position, the orientation of the tip-side link hub 13 is changed relative to the base-side link hub 12.

[0049] <Attitude Control Actuator> The attitude control actuator 10 is a rotary actuator consisting of a servo motor equipped with a reduction mechanism 52. The attitude control actuator 10 is mounted coaxially with the rotation axis 22 on the surface of the base member 6 of the base end link hub 12. The attitude control actuator 10 and the reduction mechanism 52 are provided integrally, and the reduction mechanism 52 is fixed to the base member 6 by a motor fixing member 53. The attitude control actuator 10 may also be equipped with a brake.

[0050] In this example, attitude control actuators 10 are provided on all three sets of link mechanisms 14. However, if attitude control actuators 10 are provided on at least two of the three sets of link mechanisms 14, the attitude of the tip-side link hub 13 relative to the base-side link hub 12 can be determined.

[0051] The link actuator 7 rotates each attitude control actuator 10, thereby operating the parallel link mechanism 9. More specifically, when the attitude control actuator 10 is rotated, its rotation is reduced via the reduction mechanism 52 and transmitted to the rotating shaft 22. As a result, the angle of the base end link member 15 relative to the base end link hub 12 changes, and the attitude of the tip end link hub 13 relative to the base end link hub 12 can be arbitrarily changed.

[0052] <End Effector> An end effector (not shown) is attached to the tip member 40 of the tip-side link hub 13. Examples of end effectors include a hand including a grip, a cleaning nozzle, a dispenser, a welding torch, and image processing equipment including a camera.

[0053] <Control device> The control device Cu controls each attitude control actuator 10 to change the attitude of the tip-side link hub 13 relative to the base-side link hub 12 from its current attitude to a target attitude provided by an external command means to the control device Cu. The control device Cu is, for example, a computer-controlled numerical control type.

[0054] <Effects> As described above, the link actuation device 7 is equipped with double-ended support structures at both the base and tip ends of the central link member 17. This double-ended support structure increases the axial rigidity of the rotation axis compared to conventional structures. As a result, the overall rigidity of the parallel link mechanism can be increased compared to conventional structures. By increasing the rigidity of the parallel link mechanism 9, the following effects are achieved.

[0055] - Vibration of the link hub 13 at the tip end can be further suppressed during operation or when the parallel link mechanism 9 is stopped, without reducing speed or acceleration. - When the same load weight (load) as before, the speed or acceleration can be increased and the cycle time can be shortened compared to the conventional example. - When the load weight (load) on the tip member 40 is increased, the settling time can be shortened compared to the conventional example without reducing speed or acceleration.

[0056] As shown in Figure 5, one bearing 23 is fitted into the central link member 17, while the other bearing 24 is provided in the central housing 25, which is connected to the central link member 17 via a connecting member 26. Therefore, the central housing 25 and the connecting member 26 can be positioned in limited locations within the entire parallel link mechanism. Thus, the central housing 25 and the connecting member 26 can be avoided from being located within the movable range of the base and tip end link members 15 and 16. Consequently, it is possible to create a parallel link mechanism that can increase rigidity without sacrificing the range of motion compared to conventional structures.

[0057] By connecting the central link member 17, into which one bearing 23 is fitted, and the central housing 25, which includes the other bearing 24, with a position adjustment connecting member 26A, the positions of both members 17 and 26A can be easily adjusted. Therefore, the coaxiality of one bearing 23 and the other bearing 24 can be kept below a desired value, preventing overload from acting on the bearings 23 and 24, and improving the durability of the bearings 23 and 24 compared to the configuration using an integrated housing shown in Figure 1 of Patent Document 3.

[0058] As shown in Figures 6 and 7, the position-adjusting connecting member 26A can be adjusted in the axial direction C1 of the rotating shaft 27 and in a direction perpendicular to this axial direction C1. Therefore, it is not necessary to specify the coaxiality between the central link member 17 into which one bearing is fitted and the central housing 25, and processing costs can be reduced compared to the configuration using the integrated housing. Because the position can be adjusted by the position-adjusting connecting member 26A, the ease of assembly of the parallel link mechanism can be improved compared to the conventional structure.

[0059] As shown in Figure 1, in the origin position of the parallel link mechanism 9, as shown in Figure 4B, the central housing 25 and the position adjustment connecting member 26A are installed so that a space S1 is created in the direction A1 in which the central link member 25 faces the base end link members 15 and 16, and in the direction A1 in which the central housing 25 faces the base end end link members 15 and 16, which are connected to the central housing 25 together with the central link member 17. The central link member 17 and the central housing 25, which are fitted with one bearing, are connected and movable, but are not positioned in the movable range of the base end end link members 15 and 16. Therefore, the parallel link mechanism 9 operates without interference between the base end end link members 15 and 16, the central link member 17, and the central housing 25. Consequently, it is possible to widen the movable range of the parallel link mechanism 9 (Figure 1) compared to the conventional double-ended support structure shown in Figure 15.

[0060] As shown in Figure 1, both the base and tip end link members 15 and 16 are bent into a roughly L-shape. In this case, the link mechanism 14 can be manufactured at a lower cost than if the base and tip end link members were machined by cutting or other means. This reduces the overall manufacturing cost of the parallel link mechanism compared to conventional structures with link members made of machined parts.

[0061] Since the link actuator 7 is equipped with the attitude control actuator 10, the attitude of the tip-side link hub 13 relative to the base-side link hub 12 can be determined. By combining the attitude control actuator 10 with the parallel link mechanism 9, which is equipped with a central housing 25 and a position adjustment connecting member 26A, precise and wide-range high-speed operation is possible, resulting in a lightweight and compact link actuator 7.

[0062] <Regarding Other Embodiments> In the following description, parts corresponding to matters previously described in each embodiment will be denoted by the same reference numerals, and redundant explanations will be omitted. When only a part of the configuration is described, the other parts of the configuration will be the same as those in the previously described embodiment unless otherwise specified. The same configuration will produce the same effects. Not only are combinations of the parts specifically described in each embodiment possible, but it is also possible to partially combine embodiments, provided that there are no particular problems with the combination.

[0063] [Second Embodiment: Double-Ended Support Structure with Bearings Arranged on Base and Tip Link Members] As shown in Figures 8 and 9, one bearing 23 may be fitted to the other end of each of the base and tip end link members 15 and 16. In this example, the base and tip end link members 15 and 16 correspond to the "members into which one bearing is fitted". The other ends of the base and tip link members 15 and 16 and the central housing 25 are connected to each other by a position adjustment connecting member 26A so as to be position-adjustable. The other bearing 24 is fitted into the central housing 25, and the other bearing 24 rotatably supports the other end of the rotating shaft 27 at the target connecting portion Rk, Rk. The second embodiment also provides the same effects as the first embodiment.

[0064] [Third Embodiment: Double-Ended Support Structure with Bearings on the Tip-Side Link Member] As shown in Figure 10, the double-ended support structure may be provided only at the connection Rk between the tip-side end link member 16 and the central link member 17. Conversely to this embodiment, the double-ended support structure may be provided only at the connection between the base-side link member 15 and the central link member 17.

[0065] As described above, at least one of the connecting portions Rk between the base end link member 15 and the central link member 17, and the connecting portion Rk between the tip end link member 16 and the central link member 17, may be provided with a double-ended support structure. Although these double-ended support structures reduce rigidity compared to the first and second embodiments, they increase rigidity without sacrificing the range of motion compared to the conventional structure.

[0066] [Fourth Embodiment, Double-Ended Support Structure with Positioning Pins] As shown in Figures 11 and 12, multiple positioning pins Pn may be driven into the mating surface between the central link member 17 and the connecting member 26, and the mating surface between the connecting member 26 and the central housing 25. In this case, the position adjustment of the connecting member 26 can be omitted. The bearings 23 and 24 on one and the other (see Figure 5) can be reliably kept below a specified value in terms of coaxiality by each pin Pn without adjusting the position of the connecting member 26. Therefore, according to the fourth embodiment, the number of assembly steps can be reduced compared to the embodiments described above, and the rigidity of the parallel link mechanism can be increased. Other effects and advantages similar to those of the embodiments are also achieved.

[0067] Multiple positioning pins may be driven into the mating surfaces of the tip-side link member 16 and the connecting member 26, and the mating surface of the connecting member 26 and the central housing 25, as shown in Figure 9. Multiple positioning pins may also be driven into the mating surfaces of the base-side link member 15 and the connecting member 26, and the mating surface of the connecting member 26 and the central housing 25, as shown in Figure 8. In these cases as well, the same effects and advantages as the double-ended support structure with positioning pins described above are achieved.

[0068] Either the base end link member 15 or the tip end link member 16 may be bent into a substantially L-shape, while the other end may be a machined part obtained by cutting or other machining.

[0069] As described above with reference to the drawings, preferred embodiments have been explained, but various additions, modifications, and deletions are possible without departing from the spirit of the present invention. Therefore, such additions and deletions are also included within the scope of the present invention.

[0070] 7...Link actuation device 9...Parallel link mechanism 10...Actuator for attitude control 12...Link hub at the base end 13...Link hub at the tip end 14...Link mechanism 15...End link member at the base end 16...End link member at the tip end 17...Central link member 23...One bearing 24...The other bearing 25...Central housing 26...Connecting member 26A...Position adjustment connecting member 27...Rotation shaft Rk...Connecting part

Claims

1. A parallel link mechanism in which a front link hub is connected to a base link hub via three or more link mechanisms so as to be able to change its orientation, and each link mechanism comprises a base and front end link member, one end of which is rotatably connected to the base link hub and the front link hub, and a central link member, the other end of which is rotatably connected to the other end of the base and front end link member via connecting portions, wherein at least one of the connecting portions between the base end link member and the central link member, and the connecting portion between the front end link member and the central link member, comprises a central housing including a bearing that rotatably supports one end of the rotation axis at the target connecting portion and is fitted to either the base end or the front end link member or the central link member, and a member that rotatably supports the other end of the rotation axis at the target connecting portion, and a connecting member that connects the one bearing to the central housing.

2. A parallel link mechanism according to claim 1, wherein the connecting member is a position-adjustable connecting member that connects the member into which one bearing is fitted and the central housing so as to be position-adjustable relative to each other.

3. The parallel link mechanism according to claim 2, wherein the position-adjusting connecting member is adjustable in the axial direction of the rotation axis and in a direction perpendicular to this axial direction.

4. A parallel link mechanism according to at least one of claims 1 to 3, wherein, in the origin position of the parallel link mechanism, the connecting member and the central housing are installed such that, in the end link member to which the central housing is connected together with the central link member, there is a space in the direction in which the central link member and the end link member face each other, and in the direction in which the central housing and the end link member face each other.

5. A parallel link mechanism according to at least one of claims 1 to 3, wherein either one or both of the base end and tip end link members are members bent into a substantially L-shape.

6. A link actuation device comprising attitude control actuators for arbitrarily controlling the attitude of the tip-side link hub in two or more of the three or more link mechanisms in the parallel link mechanism according to at least one of claims 1 to 3.

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