Parallel link mechanism and link actuator

Abstract

The present invention provides a parallel link mechanism and a link actuation device that can increase rigidity without sacrificing range of motion. [Solution] The parallel link mechanism 9 comprises one bearing, a central housing 25 including the other bearing, and a connecting member 26. The one bearing rotatably supports one end of the rotating shaft 27 at at least one of the connecting portions Rk between the base end link member 15 and the central link member, and the connecting portion Rk between the tip end link member 16 and the central link member 17, and is fitted to either the base end end link member 15, 16 or the central link member 17. The other bearing rotatably supports the other end of the rotating shaft 27 at the target connecting portion Rk. The connecting member 26 connects the member into which the one bearing is fitted to the central housing 25.

Description

Technical Field

[0001] The present invention relates to a parallel link mechanism and a link operating device used for 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.

Background Art

[0002] 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] 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. When the link length increases, there is a problem that the size of the entire mechanism becomes large and the device becomes large. In addition, 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.

[0005] The parallel link mechanism and link actuator configuration shown in Patent Document 2 allows for high-speed, fine changes in attitude, but it has the following problems: Because it is a speed-increasing mechanism in which the attitude of the link hub at the tip moves twice as much as the rotation angle of the attitude control actuator, vibrations during settling become large when a heavy object is mounted. In this case, there is a problem that the mounted weight (load) is limited to small objects in order to perform high-speed operation.

[0006] 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.

[0007] 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.

[0008] 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. [Means for solving the problem]

[0009] 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 and front end link hubs, and a central link member, the other end of which is rotatably connected at both ends via connecting portions, respectively. Of the connection portion between the base end link member and the central link member, and the connection portion between the tip end link member and the central link member, at least one of the connection portions is: One end of the rotating shaft in the target connecting portion is rotatably supported, and one bearing is fitted to either the base end side, the tip end side end link member, or the central link member, A central housing including the other bearing that rotatably supports the other end of the rotating shaft in the aforementioned connecting portion, The system includes a member for fitting one of the bearings and a connecting member for connecting the central housing to each other.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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 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 aforementioned "space" refers to the "gap" between the central link member and the central housing in each link mechanism.

[0016] 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.

[0017] 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 means.

[0018] 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. [Effects of the Invention]

[0019] The parallel link mechanism of the present invention is configured such that a link hub on the distal end side is connected to a link hub on the proximal end side via three or more link mechanisms so as to be able to change its posture. Each of the link mechanisms includes end link members on the proximal end side and the distal end side, one end of each of which is rotatably connected to the link hub on the proximal end side and the link hub on the distal end side, respectively, and a central link member, both ends of which are rotatably connected to the other ends of the end link members on the proximal end side and the distal end side via connecting portions, respectively. The parallel link mechanism is provided with a central housing including one bearing that rotatably supports one end of the rotation axis at at least one of the connecting portions between the end link member on the proximal end side and the central link member and the connecting portion between the end link member on the distal end side and the central link member, the one bearing being fitted to either the end link member on the proximal end side, the end link member on the distal end side, or the central link member, and the other bearing that rotatably supports the other end of the rotation axis at the target connecting portion, a member for fitting the one bearing, and a connecting member for connecting the central housing and the member to each other. Therefore, the rigidity can be increased without sacrificing the movable range.

Brief Description of the Drawings

[0020] [Figure 1] It is a perspective view of a link operating device according to a first embodiment of the present invention. [Figure 2] It is a view partially showing a part of the link operating device. [Figure 3] It is a view showing one link mechanism of the link operating device in a straight line. [Figure 4A] It is a view partially showing both end support portions of a central link member in the link mechanism. [Figure 4B] It is a view explaining the arrangement of a position adjustment connecting member and a central housing of both end support portions. [Figure 5] It is a cross-sectional view of both end support portions of the central link member. [Figure 6] It is an exploded perspective view showing an assembling structure of the central link member and the position adjustment connecting member. [Figure 7]This is an exploded perspective view showing the assembly structure of the position-adjusting connecting member and the central housing. [Figure 8] This is a perspective view of a link actuator according to a second embodiment of the present invention. [Figure 9] This is a cross-sectional view of the support portions at both ends of the central link member in the link actuator. [Figure 10] This is a cross-sectional view of the end support portions of the central link member in a link actuation device according to a third embodiment of the present invention. [Figure 11] This is an exploded perspective view showing the assembly structure of the central link member and the position adjustment connecting member in a link actuation device according to a fourth embodiment of the present invention. [Figure 12] This is an exploded perspective view showing the assembly structure of the position-adjusting connecting member and the central housing. [Figure 13] This is a perspective view of a conventional link actuator using a support structure at both ends of the central link member. [Figure 14] This diagram partially shows the central link member and other components of the link actuator. [Figure 15] This is a perspective view showing the posture of the link actuator when the bending angle is large. [Modes for carrying out the invention]

[0021] [First Embodiment] A link actuator according to an embodiment of the present invention will be described with reference to Figures 1 to 7. This link actuator can be used, for example, in medical equipment or industrial equipment.

[0022] <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.

[0023] <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 link mechanisms 14 may be four or more.

[0024] 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.

[0025] 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.

[0026] As shown in Figure 2, the parallel link mechanism 9 is 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.

[0027] 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.

[0028] 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.

[0029] 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 center portion 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 center portion of each central link member 17 is located on a common orbital circle D.

[0030] 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 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.

[0031] 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 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 at right angles, 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° or greater.

[0032] 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.

[0033] 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.

[0034] Condition 1: In each link mechanism 14, the angles of the central axes O1 of the rotational pairs of the base and tip link hubs 12, 13 and the base and tip end link members 15, 16, 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 axis O1 of the rotational pair between the base and tip end link hubs 12, 13 and the base and tip end link members 15, 16 of each link mechanism 14, and the central axis of the rotational pair between the base and tip end link members 15, 16 and the central link member 17, intersect the base and tip end 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 end portion and the tip end 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.

[0035] 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 end link member 15 is connected to the rotating shaft 22.

[0036] The rotating shaft 22 is rotatably supported by a 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 a connecting portion Rk, which is rotatably connected to one end of the central link member 17.

[0037] 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.

[0038] <About the double-ended support structure> In the first embodiment, the following double-ended 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 double-ended 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 double-ended support structure may be provided on only one of the base end or tip end of the central link member 17.

[0039] As shown in Figures 4A and 5, the double-ended support structure comprises a central housing 25 containing one bearing 23 and the other bearing 24, and a connecting member 26 that connects the central link member 17 and the central housing 25 to each other. As shown in Figure 5, one bearing 23 rotatably supports one end of the rotating shaft 27 at the target connecting portion Rk, Rk (see Figure 1) and is fitted into the central link member 17. Specifically, the outer ring surface of one bearing 23 is fitted and fixed to the inner circumferential surfaces of the base end and tip end of the central link member 17. The outer circumferential surface of the rotating shaft at one end (axial base end) of the rotating shaft 27 is fitted and fixed to the inner ring surface of one bearing 23. In this example, the central link member 17 corresponds to the "member into which one bearing is fitted".

[0040] 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 (see Figure 1). Specifically, the outer ring surface of the other bearing 24 is fitted and fixed to the inner circumferential surface of the central housing 25. The outer circumferential surface of the rotating shaft at the other end (axial tip) of the rotating shaft 27 is fitted and fixed to the inner ring surface of the other bearing 24.

[0041] The bearings 23 and 24 on one side are, for example, angular contact ball bearings assembled back-to-back and lubricated with grease. Spacers 28 are provided at both ends of the inner ring of each combined angular contact ball bearing. The bearings 23 and 24 on one side and the other side are aligned by the rotating shaft 27, and a desired fixed position preload is applied by tightening a nut 29 that is screwed onto the tip of the rotating shaft 27. This can increase the rigidity of the bearings 23 and 24.

[0042] The bearings 23 and 24 are not limited to the configuration described above. For example, angular contact ball bearings arranged face-to-face may be used as one and the other bearings 23 and 24. The bearings 23 and 24 may each consist of, for example, two deep groove ball bearings arranged axially, or one deep groove ball bearing each. In addition, constant pressure preload may be applied to one and the other bearings 23 and 24 instead of the fixed position preload.

[0043] As shown in Figures 6 and 7, the connecting member 26 is a position-adjustable connecting member 26A that connects the central link member 17 and the central housing 25 in a position-adjustable manner. As shown in Figure 6, the position-adjustable connecting member 26A is adjustable in the axial direction C1 of the rotation axis 27 at the target connecting portion Rk. Multiple tapped holes Th for bolt fastening are provided (two in this example) on the mating surface of the central link member 17 that faces the position-adjustable connecting member 26A.

[0044] The position-adjustable connecting member 26A has a counterbore hole Zh facing outward. Within the counterbore hole Zh of the position-adjustable connecting member 26A, there are drill holes Kh, Kh corresponding to the positions of multiple tapped holes Th, Th. Each drill hole Kh is formed to be larger in diameter by a predetermined gap than the diameter of the bolt 30 through which it is inserted. This gap allows the position-adjustable connecting member 26A to be adjusted in the axial direction C1 of the rotation shaft 27. The predetermined gap is a gap that can be arbitrarily determined by design, etc., and is determined by finding an appropriate gap, for example, by testing and / or simulation. The same applies to the predetermined gaps of each drill hole 32 described later.

[0045] As shown in Figure 7, the position adjustment connecting member 26A is adjustable in a direction perpendicular to the axial direction C1 of the rotation axis 27. Multiple tapped holes 31 for bolt fastening are provided (two in this example) on the mating surface 26Aa of the position adjustment connecting member 26A that faces the central housing 25. The central housing 25 has a counterbore hole 25a facing outwards. Within the counterbore hole 25a of the central housing 25, multiple drilled holes 32, 32 corresponding to the positions of the tapped holes 31, 31 are formed. Each drilled hole 32 is formed with a diameter larger by a predetermined gap than the diameter of the bolt 33 through which it is inserted. This gap allows the position adjustment connecting member 26A to be adjusted in a direction perpendicular to the axial direction C1 of the rotation axis 27.

[0046] In the origin position of the parallel link mechanism 9 shown in Figure 1, as shown in Figure 4B, The central housing 25 is positioned and connected to the central housing 25 in the base and tip end link members 15 and 16, to which the central housing 25 is connected together with the central link member 17. The position adjustment connecting member 26A and the central housing 25 are installed so that a space S1 is created in the direction A1 in which the central link member 25 and the base and tip end link members 15 and 16 face each other, and in the direction A1 in which the central housing 25 faces each other. This prevents the position adjustment connecting member 26A and the central housing 25 from being positioned within the range of motion of the base and tip end link members 15 and 16. The origin position is defined as the orientation in which the central axis QA of the base link hub 12 (Figure 3) and the central axis QB of the tip 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 rotation angle φ (Figure 3) is 0 degrees. The orientation of the tip link hub 13 is changed relative to the base link hub 12 using the origin position as a reference.

[0047] <Actuator for attitude control> 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 integrally mounted, 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.

[0048] In this example, attitude control actuators 10 are provided on all three sets of link mechanisms 14, but the attitude of the tip-side link hub 13 relative to the base-side link hub 12 can be determined by providing attitude control actuators 10 on at least two of the three sets of link mechanisms 14.

[0049] The link actuator 7 operates the parallel link mechanism 9 by rotationally driving each attitude control actuator 10. Specifically, when the attitude control actuator 10 is rotationally driven, 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.

[0050] <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 with a grip, a cleaning nozzle, a dispenser, a welding torch, and image processing equipment including a camera.

[0051] <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.

[0052] <Effects and Effects> As described above, the link actuator 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 rotating shaft compared to conventional structures. As a result, the overall rigidity of the parallel link mechanism can be increased compared to conventional structures. Increasing the rigidity of the parallel link mechanism 9 produces the following effects.

[0053] - Vibration of the tip-side link hub 13 during operation or when the parallel link mechanism 9 is stopped can be further suppressed without reducing speed or acceleration. • With the same load capacity as before, it is possible to increase speed or acceleration and shorten cycle time compared to conventional examples. When the weight (load) mounted on the tip member 40 increases, the settling time can be shortened without reducing the speed or acceleration compared to conventional examples.

[0054] 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.

[0055] 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 ensured to be 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.

[0056] 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 assembly of the parallel link mechanism can be improved compared to the conventional structure.

[0057] As shown in Figure 1, in the origin position of the parallel link mechanism 9, 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 in which the central link member 25 and the base end link members 15 and 16 face each other, and in the direction A1 in which the central housing 25 faces each other. The central link member 17 and central housing 25, which are fitted with one of the bearings, are connected and movable, but are not positioned within the range of motion of the base and tip end link members 15 and 16. Therefore, the parallel link mechanism 9 operates without interference between the base and tip end link members 15 and 16, the central link member 17, and the central housing 25. Consequently, it is possible to widen the range of motion of the parallel link mechanism 9 (Figure 1) compared to the conventional double-ended support structure shown in Figure 15.

[0058] 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.

[0059] 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.

[0060] <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. Identical configurations will produce the same effects. Not only are combinations of the parts specifically described in each embodiment possible, but partial combinations of embodiments are also possible, provided that there are no particular problems with the combination.

[0061] [Second embodiment: Double-ended support structure with bearings placed on the base end / tip end 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.

[0062] [Third embodiment: Double-ended support structure with bearings placed on the tip-side link member] As shown in Figure 10, the end-end 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 end-end support structure may be provided only at the connection between the base-side link member 15 and the central link member 17.

[0063] 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.

[0064] [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 surfaces of the central link member 17 and the connecting member 26, and the mating surfaces of the connecting member 26 and the central housing 25, respectively. 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 assembly man-hours 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.

[0065] 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. As shown in Figure 8, multiple positioning pins may be driven into the mating surface between the base end link member 15 and the connecting member 26, and the mating surface between the connecting member 26 and the central housing 25. In these cases as well, the same effects and advantages as the aforementioned double-ended support structure with positioning pins are achieved.

[0066] Either the base end link member 15 or 16 at the tip end may be bent into a roughly L-shape, while the other end may be a machined part obtained by cutting or other machining.

[0067] While embodiments for carrying out the present invention have been described above based on the embodiments, the embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0068] 7...Link actuation device, 9...Parallel link mechanism, 10...Attitude control actuator, 12...Base end link hub, 13...Tip end link hub, 14...Link mechanism, 15...Base end link member, 16...Tip end link member, 17...Central link member, 23...One bearing, 24...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 has a base and front end link member, one end of which is rotatably connected to the base and front end link hubs, and a central link member, both ends of which are rotatably connected to the other ends of these base and front end link members via connecting parts, Of the connection portion between the base end link member and the central link member, and the connection portion between the tip end link member and the central link member, at least one of the connection portions is: One end of the rotating shaft in the target connecting portion is rotatably supported, and one bearing is fitted to either the base end side, the tip end side end link member, or the central link member, A central housing including the other bearing that rotatably supports the other end of the rotating shaft in the aforementioned connecting portion, A parallel link mechanism comprising a member for fitting one of the bearings and a connecting member for connecting the central housing to each other.

2. A parallel link mechanism according to claim 1, wherein the connecting member is a position-adjustable connecting member that connects a 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 a parallel link mechanism whose position can be adjusted in the axial direction of the rotation axis and in a direction perpendicular to this axial direction.

4. A parallel link mechanism according to any one of claims 1 to 3, wherein the connecting member and the central housing are installed such that, in the origin position of the parallel link mechanism, there is 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 any one of claims 1 to 3, wherein either or both of the base end and tip end link members are members bent into a substantially L-shape.

6. A link actuation device in a parallel link mechanism according to any one of claims 1 to 3, wherein two or more of the three or more link mechanisms are equipped with attitude control actuators for arbitrarily controlling the attitude of the tip-side link hub.

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