Linking structure and parallel link robot

Abstract

The coupling structure (10) comprises: a pair of attachment members (11a),(11b) that are supported on two links (50a), (50b) that each have a longitudinal axis (C) and move parallel to each other with a gap therebetween so as to be able to rotate about rotation axes (D) that are perpendicular to a plane that includes the longitudinal axes (C) of both the links (50a), (50b); and a coupling mechanism (15) that fixes the distance between the pair of attachment members (11a), (11b) in an adjustable manner.

Description

Technical Field

[0001] The present disclosure relates to a connection structure and a parallel link robot.

Background Art

[0002] A connection structure is known in which two parallel links (connection links) of a parallel link robot are connected with an elastic member interposed therebetween (see, for example, Patent Document 1). This connection structure uses the elastic force of the elastic member to pull both links in a direction approaching each other.

[0003] The two links are each rotatably supported by a ball joint on a driving link (base link). Even if the ball joint wears due to aging, the elastic force of the elastic member is used to pull both links in a direction approaching each other, thereby preventing play from occurring in the ball joint.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] During the operation of a parallel link robot, if an external force exceeding the elastic force of the elastic member acts on the connection structure, it is conceivable that the distance between the two links will widen and the ball joint will come off. To avoid this, if the elastic force of the elastic member is set to be excessively large beyond the appropriate contact pressure of the ball joint, the life of the ball joint will be reduced. Therefore, it is desired to eliminate play caused by aging without attracting two parallel links to each other with excessive force.

Means for Solving the Problems

[0006] One aspect of the present disclosure comprises two links having longitudinal axes and operating parallel to each other and spaced apart, a pair of mounting members each rotatably supported about a rotation axis perpendicular to a plane containing the longitudinal axes of both links, and a connecting mechanism for adjusting the distance between the pair of mounting members, wherein the connecting mechanism comprises a male screw fixed to each of the mounting members and a nut member having two female screws that mesh with the two male screws, the two male screws being arranged on the same axis and having a reverse thread relationship, and each male screw being provided with two fixing nuts to which it is fastened, and in a state where the distance between the mounting members is adjusted by each male screw and each female screw, the two fixing nuts are fastened so as to be in close contact with the nut member, and each fixing nut is on the opposite side from the nut member, the male screw to which the fixing nut is fastened threaded part It is equipped with an outer perimeter wall that surrounds it, and the outer perimeter wall is the Threaded part of The aforementioned This is a connecting structure that extends beyond the base end of the male screw. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic front view showing a parallel link robot according to one embodiment of the present disclosure. [Figure 2] Figure 1 is a schematic front view showing the mounting state of the connecting structure in a pair of passive links of the parallel link robot. [Figure 3] Figure 2 is a partial cross-sectional view showing a schematic of one of the connecting structures. [Figure 4] Figure 2 is a perspective view showing the shape of one of the mounting members in a single connecting structure. [Figure 5] Figure 2 is a partial cross-sectional view showing the disassembled state of one of the connecting structures. [Figure 6] Figure 2 is a partial cross-sectional view illustrating the installation method of one connecting structure. [Figure 7] Figure 2 is a partial cross-sectional view illustrating the installation method of one connecting structure. [Figure 8] Figure 2 is a partial cross-sectional view showing the mounting state of one of the connecting structures. [Figure 9] This is a partial cross-sectional view showing a first modified example of one of the connecting structures shown in Figure 2. [Figure 10] This is a partial cross-sectional view showing a second modified example of one of the connecting structures shown in Figure 2. [Figure 11] This is a partial cross-sectional view showing a third modified example of one of the connecting structures shown in Figure 2. [Figure 12] This is a partial cross-sectional view showing a fourth modified example of one of the connecting structures shown in Figure 2. [Modes for carrying out the invention]

[0008] A linking structure 10 and a parallel link robot 100 according to one embodiment of this disclosure will be described below with reference to the drawings. The parallel link robot 100 according to this embodiment includes, for example, a base 20 that is suspended and fixed from a ceiling or the like, and a movable part 30 that is positioned below the base 20 at intervals, as shown in Figure 1. The parallel link robot 100 also includes three arms 40 that connect the base 20 and the movable part 30.

[0009] Each arm 40 is equipped with three drive links (arms) 45 that are rotatably supported around three horizontal axes A relative to the base 20. Each arm 40 is also equipped with a pair of parallel passive links 50a, 50b that connect each drive link 45 to the movable part 30. Furthermore, the parallel link robot 100 includes a connecting structure 10 according to one embodiment of the present disclosure, which is stretched between the upper and lower ends of each pair of passive links 50a, 50b.

[0010] The base portion 20 includes three servo motors 60 for driving the three drive links 45 respectively. The servo motors 60 are arranged at equal intervals in the circumferential direction around an axis B that extends vertically through the center of the base portion 20, and each has a rotary drive shaft (not shown) that is rotated around a horizontal axis A. Further, each servo motor 60 includes a speed reducer 61 that reduces the rotation of the rotary drive shaft.

[0011] The base end of each drive link 45 is connected to the rotary drive shaft of the corresponding servo motor 60 and is rotatable relative to the base portion 20 around the axis A. Also, as shown in FIGS. 1 and 2, the tip ends of each drive link 45 and the passive links 50a, 50b are connected by ball joints 70a, 70b respectively. Each ball joint 70a, 70b includes ball studs 71a, 71b attached to the tip ends of the respective drive links 45 and sockets 51a, 51b connected to the ball studs 71a, 71b.

[0012] The ball studs 71a, 71b each include balls 72a, 72b and columnar studs 73a, 73b that extend radially outward from the outer spherical surfaces of the balls 72a, 72b. The end faces of the studs 73a, 73b are fixed by bolts 74 on both sides in the direction of the axis A (see FIG. 1) sandwiching the tip ends of the drive links 45.

[0013] As shown in FIG. 2, the sockets 51a, 51b each constitute one end portion of the passive links 50a, 50b in the longitudinal axis C direction. The sockets 51a, 51b each include inner spherical surfaces 52a, 52b that cover approximately half of the range of the outer spherical surfaces of the balls 72a, 72b. Also, a thin resin layer (not shown) made of a resin material such as silicon is disposed inside the inner spherical surfaces 52a, 52b, and the balls 72a, 72b are fitted inside thereof and are supported rotatably around the center points respectively.

[0014] Next, the connection structure 10 according to the present embodiment will be described. The connection structure 10 according to this embodiment includes a pair of attachment members 11a and 11b respectively attached to pins 53p provided on sockets 51a and 51b, and a connection mechanism 15 that connects the attachment members 11a and 11b to each other.

[0015] In this embodiment, the three pairs of passive links 50a and 50b and the connection structure 10 that connects the upper and lower ends of each pair of passive links 50a and 50b have the same configuration. Therefore, in the following, the configuration of the connection structure 10 that connects one end of a pair of passive links 50a and 50b will be described by way of example.

[0016] As shown in FIG. 3, the pins 53p are attached to the sockets 51a and 51b so as to project along an axis (rotation axis) D orthogonal to a plane including two longitudinal axes C on both sides of the plane. In the figure, the pin 53p has a flange in the shape of a collar, is fitted into a hole penetrating the sockets 51a and 51b in the radial direction from one direction, and is positioned by abutting the flange against the outer surface of the sockets 51a and 51b.

[0017] Moreover, bushes 53a and 53b are respectively attached to the portions of the pins 53p protruding from the sockets 51a and 51b. The bushes 53a and 53b each have a cylindrical shape in which a hollow hole 53h is formed. In addition, a groove 53d that is recessed radially inward over the entire circumference is formed at the axial center of the outer peripheral surface of the bushes 53a and 53b.

[0018] The bushes 53a and 53b are respectively supported by the pins 53p so as to be rotatable about the axis D by fitting the pins 53p into the hollow holes 53h. In the figure, the same-shaped bushes 53a and 53b are used. The bushes 53a and 53b are provided with notches to avoid interference with the flanges of the pins 53p. The flange is accommodated in the notch of one of the bushes 53a and 53b, and the notch of the other bush 53a and 53b is hollow. Furthermore, if the pin 53p is integrally fixed to the sockets 51a and 51b by welding or the like, the flange of the pin 53p and the notches in the bushes 53a and 53b do not need to be provided.

[0019] Furthermore, as shown in Figure 2, the other ends of the passive links 50a and 50b in the longitudinal axis C direction have the same configuration as one end. That is, sockets 51a and 51b are also attached to the other ends of the passive links 50a and 50b. The sockets 51a and 51b are connected to the ball studs 71a and 71b attached to the outer circumferential surface of the movable part 30 by sandwiching them from both outer sides in the direction of axis A.

[0020] As shown in Figures 3 and 4, the mounting member 11a comprises a hook portion 12a and a male screw 16a fixed to the hook portion 12a. The hook portion 12a is formed by curving a long, narrow strip of metal plate, having a thickness equal to the groove width of the groove 53d of the bush 53a, into a roughly U-shape. The two metal plates extending roughly parallel to each other in the roughly U-shaped hook portion 12a are spaced at an interval equal to the distance W between the grooves 53d of a pair of bushes 53a mounted on both sides of the socket 51a in the axial direction D.

[0021] Furthermore, the two metal plates extending substantially parallel to the hook portion 12a are each provided with two hooks 13a that can be hooked into grooves 53d of a pair of bushes 53a attached to the socket 51a. The two hooks 13a are formed by cutting notches in the thickness direction of two substantially parallel metal plates of the hook portion 12a.

[0022] Specifically, each hook 13a is provided with an elongated hole 13h that extends in the longitudinal direction of the hook portion 12a. At one end of the elongated hole 13h in the longitudinal direction, an inner circumferential surface 13i is formed, having the same inner diameter as the outer diameter of the groove bottom of the groove 53d of the bush 53a. At the other end of the elongated hole 13h in the longitudinal direction, an opening 13o is provided that causes the elongated hole 13h to open to one side in the width direction of the hook portion 12a. The opening 13o is formed to be larger than the outer diameter of the groove bottom of the groove 53d of the bush 53a. The male screw 16a is formed as a right-hand thread and extends parallel to the hook 13a in the opposite direction from the hook 13a at a position between the hooks 13a on both sides of the hook portion 12a.

[0023] On the other hand, the mounting member 11b is equipped with a hook portion 12b that has the same shape as the hook portion 12a of the mounting member 11a. Furthermore, a male screw 16b is fixed between the hooks 13b provided on both sides of the hook portion 12b, having the same outer diameter (nominal diameter) and pitch as the male screw 16a, but differing only in the circumferential direction of the threaded portion. In other words, the male screws 16a and 16b have a reverse thread relationship with each other.

[0024] As shown in Figures 3 and 5, the connecting mechanism 15 includes male screws 16a and 16b provided on mounting members 11a and 11b, and nut members 17 that are fastened to the male screws 16a and 16b. The nut member 17 is a cylindrical member having a through hole 17h along its central axis. On the inner surface of the through hole 17h of the nut member 17, a female thread 17a that engages with the male thread 16a and a female thread 17b that engages with the male thread 16b are formed side by side in the direction of the central axis.

[0025] The right-hand thread female thread 17a is formed on one end of the nut member 17 from the center in the direction of the central axis, and the left-hand thread female thread 17b is formed on the other end of the nut member 17 from the center in the direction of the central axis. In other words, the female threads 17a and 17b are arranged side by side on the same axis and are reverse threads that open in opposite directions to each other. Furthermore, the outer surface of the nut member 17 is provided with a pair of parallel flat surfaces on both sides of the central axis, for engaging a tool such as a wrench.

[0026] Furthermore, fixing nuts 18a and 18b engage with the male threads 16a and 16b, respectively. The fixing nuts 18a and 18b are identical in shape except that they have reverse threads, and can be general commercially available nuts.

[0027] The operation of the connecting structure 10 and the parallel link robot 100 configured in this way will be explained below. However, as described above, the explanation will also use as an example a connecting structure 10 that is stretched across one end of a pair of links 50a and 50b.

[0028] For the assembly of the parallel link robot 100, it is assumed that a unit comprising a base 20, three servo motors 60, three reduction gears 61, and three drive links 45 is pre-assembled. First, as shown in Figures 1 and 2, a pair of ball studs 71a and 71b are fixed to the tip of the drive link 45 and the outer surface of the movable part 30, respectively, with bolts 74.

[0029] Next, as shown in Figure 2, the sockets 51a and 51b at one end of the pair of passive links 50a and 50b are brought close to the ball studs 71a and 71b at the tip of the drive link 45 from the outside in the direction of axis A. Then, the inner spherical surfaces 52a and 52b of the sockets 51a and 51b are fitted onto the balls 72a and 72b of the ball studs 71a and 71b, respectively. Similarly, the inner spherical surfaces 52a and 52b of the sockets 51a and 51b at the other ends of the pair of passive links 50a and 50b are fitted onto the balls 72a and 72b of the ball studs 71a and 71b attached to the movable part 30.

[0030] Next, as shown in Figure 5, the fixing nuts 18a and 18b are engaged with the male screws 16a and 16b fixed to the mounting members 11a and 11b, respectively. Next, as shown in Figure 6, the male threads 16a and 16b are engaged with the female threads 17a and 17b of the nut member 17, respectively, to connect the two mounting members 11a and 11b using the nut member 17. In this case, the length at which the male threads 16a and 16b and the female threads 17a and 17b engage is adjusted so that the distance between the openings 13o of the mounting members 11a and 11b is approximately the same as the distance between the two axes D.

[0031] In this state, as shown in Figure 6, the mounting members 11a and 11b connected by the nut member 17 are positioned so that each pair of hooks 13a and 13b sandwiches the sockets 51a and 51b in the direction of axis D. Then, as shown in Figure 7, the bushes 53a and 53b are passed through the respective openings 13o of the mounting members 11a and 11b, and the bushes 53a and 53b are placed in the respective elongated holes 13h.

[0032] Next, the flat surface of the outer circumferential surface of the nut member 17 is gripped with a tool or the like, and the nut member 17 is rotated in one direction around its central axis. This simultaneously increases the length over which the male threads 16a, 16b and the female threads 17a, 17b engage. As a result, the distance between the mounting members 11a and 11b is shortened, and as shown in Figure 8, the inner circumferential surfaces 13i of the mounting members 11a and 11b come into close contact with the grooves 53d of the bushes 53a and 53b, respectively. This pulls the pair of passive links 50a and 50b closer to each other, and applies pressure to the ball joints 70a and 70b between the passive links 50a and 50b and the drive link 45.

[0033] Then, for example, by measuring the torque applied to the tool when rotating the nut member 17, the rotation of the nut member 17 is stopped once it is confirmed that the appropriate pressure has been applied to the ball joints 70a and 70b. After stopping the rotation of the nut member 17, the fixing nuts 18a and 18b are fastened so that they are tightly attached to the nut member 17, as shown in Figure 8. In other words, the position of the nut member 17 relative to the male threads 16a and 16b is fixed by the double-nut effect of the fixing nuts 18a and 18b. This completes the assembly work.

[0034] Thus, according to the connecting structure 10 of this embodiment, the two passive links 50a and 50b can be connected while adjusting the distance between them to an appropriate distance. This prevents the gap between the passive links 50a and 50b from widening even when a large external force is applied during the operation of the parallel link robot 100. Furthermore, it avoids applying excessive pressure to the ball joints 70a and 70b between the passive links 50a and 50b and the drive link 45. Therefore, wear of the resin layer between the sockets 51a, 51b and the balls 72a, 72b is suppressed, and the lifespan of the ball joints 70a, 70b can be improved.

[0035] Furthermore, over time, the resin layer of ball joints 70a and 70b may wear down and become thinner. In this case, the fixing nuts 18a and 18b are loosened, and the nut member 17 is rotated around its central axis to increase the length of engagement between the male threads 16a and 16b and the female threads 17a and 17b. This allows the mounting members 11a and 11b to be brought closer together by the amount of wear on the resin layer. Therefore, even if the distance between the two passive links 50a and 50b changes, the distance connecting the two passive links 50a and 50b can be readjusted in accordance with that change, preventing play from occurring in the ball joints 70a and 70b.

[0036] In other words, unlike conventional designs, it is possible to suppress the occurrence of play in the ball joints 70a and 70b without interposing a coil spring between the pair of passive links 50a and 50b. Furthermore, since a coil spring is not used, the workability when cleaning or subsequently drying the parallel link robot 100 can be improved.

[0037] Furthermore, in this embodiment, the engagement length between the male threads 16a, 16b and the female threads 17a, 17b can be adjusted simultaneously simply by rotating the nut member 17 in one direction around its central axis. In other words, there is also the advantage that the distance between the passive links 50a, 50b can be easily adjusted with a single operation of the nut member 17.

[0038] In this embodiment, the fixing nuts 18a and 18b were of a general shape as shown in Figure 2. Alternatively, as shown in Figure 9, the fixing nuts 18a and 18b may have an outer peripheral wall 18c that protrudes axially along the entire circumference of the outer peripheral edge.

[0039] In this case, when the fixing nuts 18a and 18b are in close contact with both ends of the nut member 17, the portions of the male threads 16a and 16b that are positioned axially outward from the nut member 17 are surrounded by the outer peripheral walls 18c. This prevents the male threads 16a and 16b from being exposed to the outside, and prevents external dust and moisture from adhering to the male threads 16a and 16b.

[0040] In addition, grooves (not shown) may be provided around the entire circumference of the outer surface of the base portion of the male threads 16a and 16b at intermediate positions in the axial direction, and an O-ring 18o may be fitted into these grooves. In this case, the outer diameter of the O-ring 18o is set to be slightly larger than the inner diameter of the outer peripheral wall 18c. As a result, the O-ring 18o is slightly compressed all around and adheres tightly to the inner peripheral surface of the outer peripheral wall 18c that covers the base portions of the male threads 16a and 16b. Consequently, the gap between the outer peripheral surface of the base portions of the male threads 16a and 16b and the inner peripheral surface of the outer peripheral wall 18c that covers them is sealed. This has the advantage of providing more reliable protection for the male threads 16a and 16b from external dust or moisture.

[0041] In this embodiment, the mounting members 11a and 11b were attached to the sockets 51a and 51b by a pair of bushings 53a and 53b, respectively. Alternatively, as shown in Figure 10, the mounting members 11a and 11b may be attached to the sockets 51a and 51b by bearings 11c fixed to the mounting members 11a and 11b.

[0042] In the example shown in Figure 10, the mounting members 11a and 11b each have a pair of parallel plate-shaped first portions 11d, each having a thickness sufficient to accommodate a bearing 11c. The mounting members 11a and 11b also have a second portion 11e that connects one end of each pair of first portions 11d. Pins 53p protruding from the outer surfaces of sockets 51a and 51b in the direction of axis D are fitted onto the bearings 11c fitted to the other ends of each first portion 11d of the mounting members 11a and 11b. With this configuration, the mounting members 11a and 11b that connect the passive links 50a and 50b can be attached to the sockets 51a and 51b so as to be rotatable around axis D.

[0043] Furthermore, in this embodiment, the connecting mechanism 15 included male threads 16a and 16b fixed to the mounting members 11a and 11b, and a nut member 17 having corresponding female threads 17a and 17b formed thereon. Alternatively, female threads 17a and 17b may be formed on the mounting members 11a and 11b, respectively.

[0044] For example, as shown in Figure 10, the second portion 11e of the mounting members 11a and 11b, which are rotatably connected to the sockets 51a and 51b around axis D, may each have a shaft portion 11f that protrudes toward the mating side. Furthermore, a right-hand threaded female screw 17a may be formed on the shaft portion 11f of the mounting member 11a, and a left-hand threaded female screw 17b may be formed on the shaft portion 11f of the mounting member 11b.

[0045] In this case, the connecting mechanism 15 may be replaced with a screw member 19 having a right-hand threaded male screw 16a and a left-hand threaded male screw 16b arranged side by side on the same axis. The screw member 19 may, for example, have a hexagonal prism-shaped main body 19c, with the male screws 16a and 16b extending outward from both ends along the central axis of the main body 19c. This allows the mounting members 11a and 11b to be connected in a way that allows the distance between them to be adjusted, by engaging the male threads 16a and 16b of the screw member 19 with the female threads 17a and 17b of the mounting members 11a and 11b, respectively.

[0046] In this embodiment, one mounting member 11a and 11b were attached to each side of the sockets 51a and 51b in the direction of axis D. Alternatively, two mounting members 11a and 11b may be attached to each side of the sockets 51a and 51b in the direction of axis D.

[0047] For example, as shown in Figure 11, flat mounting members 11a and 11b may be connected to both sides of the sockets 51a and 51b in the direction of axis D, respectively, so as to be rotatable around axis D. Furthermore, a right-hand threaded female screw 17a is formed at the tip of each mounting member 11a, and a left-hand threaded female screw 17b is formed at the tip of each mounting member 11b. Then, each pair of mounting members 11a and 11b are connected by a screw member 19 similar to that in the embodiment shown in Figure 10. In this case, the mounting members 11a that sandwich the sockets 51a and 51b in the axial direction D, and the mounting members 11b that sandwich each other, may be integrally connected by a connecting member 11j.

[0048] Furthermore, in this embodiment, the mounting members 11a and 11b were connected via a nut member 17, but instead, the nut member 17 may be omitted and the mounting members 11a and 11b may be connected directly. For example, as shown in Figure 12, the mounting member 11a may have a male screw 16c extending toward the mounting member 11b, and the mounting member 11b may have a through hole 17c through which the male screw 16c passes.

[0049] In other words, the connecting mechanism 15 in this case consists of a male screw 16c on the mounting member 11a, a through hole 17c formed in the mounting member 11b, and two connecting nuts (nut members) 18 that engage with the male screw 16c. With the male screw 16c passing through the through hole 17c, the two connecting nuts 18 are tightened from both sides in the axial direction of the through hole 17c. As a result, the two connecting nuts 18 sandwich the peripheral edges on both sides in the axial direction of the through hole 17c, connecting the mounting members 11a and 11b. Furthermore, by adjusting the fastening position of the two connecting nuts 18 with respect to the male thread 16c, the length of the male thread 16c inserted into the through hole 17c can be changed. In this way, the passive links 50a and 50b can be connected while adjusting the distance between them, as described above.

[0050] Although embodiments of this disclosure have been described in detail above, this disclosure is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of the invention or from the spirit and intent of the invention derived from the claims and their equivalents. For example, the order of operations and processes in the embodiments described above are shown as examples only and are not limited thereto. [Explanation of symbols]

[0051] 10 Connection structure 11a, 11b Mounting components 15 Connection mechanism 16a, 16b, 16c Male thread 17 Nut component 17a, 17b Female thread 17c through hole 18. Connecting nuts (nut components) 18a, 18b Fixing nuts 18c outer wall 19 Screw member 20 Foundation 30 Moving parts 45 Drive link (arm) 50a, 50b Passive link (link) 100 Parallel Link Robots C Long axis D-axis (rotation axis)

Claims

1. Two links, each having a longitudinal axis and operating parallel to each other and spaced apart, are supported by a pair of mounting members that are rotatably supported around a rotation axis perpendicular to the plane containing the longitudinal axes of both links. It comprises a connecting mechanism that allows the distance between a pair of mounting members to be adjusted and fixed, The connecting mechanism comprises a male screw fixed to each of the mounting members, and a nut member having two female screws that engage with the two male screws, respectively. The two male screws are arranged on the same axis and have a reverse thread relationship. Each of the aforementioned male threads is provided with two fixing nuts to which it is fastened. With the distance between the mounting members adjusted by each of the male and female threads, the two fixing nuts are fastened so as to be in close contact with the nut member. Each of the aforementioned fixing nuts has an outer peripheral wall on the side opposite to the nut member that surrounds the threaded portion of the male screw to which the fixing nut is fastened. A connecting structure in which the outer peripheral wall extends beyond the threaded portion toward the base end of the male thread.

2. The foundation and, A movable part is positioned at a distance from the base, Multiple arms are pivotably connected to the base, A pair of links having parallel longitudinal axes connecting the arm and the movable part, A parallel link robot comprising a connecting structure according to claim 1 provided between a pair of links.

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