Parallel robots

Abstract

A parallel robot includes a drive rod, two driven rods, two axes, and a support structure. The drive rod is driven to rotate by an actuator. The two driven rods are parallel to each other and rod-shaped, and are respectively connected to the front end of the drive rod. The two axes are fixed to the driven rods with their respective shafts fitted into through holes in the driven rods. The support structure has auxiliary rods that are rotatably assembled relative to the two axes via two bearings fitted into the inner edges of the shafts. The through holes are formed along a first direction orthogonal to a plane containing the long axis of the two driven rods. Each shaft is fitted into the through hole, with a first shaft portion protruding from one end face and a second shaft portion protruding from the other end face. A locking portion applies force within the through hole in a direction that brings the first and second shaft portions closer together.

Description

Technical Field

[0001] This application relates to a parallel robot. Prior Technology

[0002] A conventional DELTA-type parallel robot includes three drive rods, each driven by a separate motor, and two parallel passive rods connected to each drive rod and movable part (see, for example, Patent Document 1). In this parallel robot, an additional actuator is provided between the opposing passive rods, arranged parallel to the passive rods. The additional actuator is rotatably mounted on an auxiliary rod of the passive rod via bearings spanning between the opposing passive rods and is rotatably supported by the bearings. [Previous Technical Documents] [Patent Literature]

[0003] [Patent Document 1] Japanese Invention Patent No. 2020-78839 Publication Specification Summary of the Invention

[0004] (The problem the invention aims to solve)

[0005] In parallel robots, the passive link and auxiliary actuator are subject to significant acceleration and deceleration. Therefore, in the auxiliary link assembly structure used to assemble the auxiliary actuator onto the passive link, it is desirable to effectively reduce the increase in inertia. Furthermore, in order to rotatably assemble the auxiliary link onto the passive link and auxiliary actuator via bearings, the shaft that engages with the inner edge of the bearing needs to be positioned in a direction orthogonal to the long axis of the passive link.

[0006] The passive link system consists of slender components, and the shaft extending orthogonally to its long axis is difficult to machine as a whole to control precision. Therefore, assembling the shaft, a separate component from the passive link, onto the passive link results in fretting wear between the passive link and the shaft due to minute relative movements caused by vibrations during parallel robot operation. Therefore, it is desirable to reduce fretting wear between the passive link and the shaft while considering the lightweight design of the auxiliary link assembly structure, thereby improving its service life. (Solutions)

[0007] In view of this, this application provides a parallel robot according to an embodiment, including a drive rod, two passive rods, two axes, and a support structure. The drive rod is driven to rotate by an actuator. The two passive rods are parallel to each other and are rod-shaped, and are respectively connected to the front end of the drive rod. The two axes are fixed to each passive rod in a state where they are respectively fitted into through holes provided on the path of each passive rod in the long axis direction. The support structure has an auxiliary rod, which is rotatably assembled relative to the two axes through two bearings that fit into the inner edge of each axis. The through holes are formed along a first direction orthogonal to the plane containing the long axis of the two passive rods. Each axis includes a first axis portion, a second axis portion, and a locking portion. The first axis portion is fitted into the through hole from one end face side of the first direction, and the first axis portion protrudes from the end face. The second axis portion is fitted into the through hole from the other end face side of the first direction, and the second axis portion protrudes from the other end face. The locking portion applies force in the through hole in a direction that brings the first axis portion and the second axis portion closer to each other. Simple Explanation of the Diagram

[0008] [Figure 1] is a perspective view of a parallel robot according to an embodiment. [Figure 2] is a schematic diagram showing the relationship between the passive link, the additional actuator and the movable part of the parallel robot in Figure 1. [Figure 3] is a schematic diagram of the operation of the passive rod, additional actuator and movable part in Figure 2. [Figure 4] is a schematic diagram of the structure for transmitting power from the additional actuator of the parallel robot in Figure 1 to the wrist axis. [Figure 5] is a partial perspective view of the support structure of the additional actuator of the parallel robot in Figure 1. [Figure 6] is a cross-sectional view of the support structure in Figure 5. [Figure 7] is a partial sectional view of the axis of the support structure in Figure 6. [Figure 8] is a partial sectional view of the axis of the support structure in Figure 7. [Figure 9] is a partial perspective view of the state in which the shaft of Figure 8 is fixed to the passive rod. [Figure 10] is a partial cross-sectional view of a modified example of the shaft of the support structure in Figure 7. Implementation

[0009] Regarding a parallel robot 1 according to an embodiment of this application, please refer to the drawings and the following description. As shown in FIG1, the parallel robot 1 of this embodiment includes a base part 2 fixed to an external structure such as a ceiling or frame, a movable part 3 disposed below the base part 2, and three arms 4, 5, and 6 arranged side by side and connected to the base part 2 and the movable part 3.

[0010] The base portion 2 includes three actuators (e.g., servo motors and reducers) 7, 8, and 9 for driving three arms 4, 5, and 6 respectively. Each arm 4, 5, and 6 includes drive rods 10, 11, and 12 connected to and rotatable by the respective actuators 7, 8, and 9, and a pair of parallel rod-shaped passive rods 13, 14, and 15 connected to the drive rods 10, 11, and 12 and the movable portion 3. The passive rods 13, 14, and 15 are rotatably connected to the drive rods 10, 11, and 12 and the movable portion 3 respectively via spherical bearings 16. As shown in Figures 2 and 3, four spherical bearings 16 are provided at both ends of the two passive rods 13, 14, and 15 of each arm 4, 5, and 6, forming quadrilaterals with the center of the spherical bearings 16 as vertices, and are positioned to constitute a parallelogram.

[0011] The movable part 3, as shown in FIG4, includes, for example, a circular plate-shaped sleeve 17 arranged with the central axis A facing vertically, a wrist shaft member 18 rotatably supported relative to the sleeve 17 about the central axis A, and a drive force transmission mechanism 19. The lower end of the wrist shaft member 18 includes an assembly surface 18a for assembling tools such as handles. The drive force transmission mechanism 19 includes a first gear 20 rotatably supported on the sleeve 17 and a second gear 21 fixed to the wrist shaft member 18 and meshing with the first gear 20.

[0012] As shown in Figure 1, the three arms 4, 5, and 6 are arranged at equal intervals around the central axis of the base 2. Through the synchronous control of the three actuators 7, 8, and 9, while the central axis A of the movable part 3 is kept in the vertical direction, the movable part 3 can be translated and positioned to a specified position in the three-dimensional direction of two horizontal directions and one vertical direction.

[0013] As shown in Figures 1 and 5, the parallel robot 1 has an additional actuator 22 between the passive shafts 13 of one arm 4. The additional actuator 22 is an actuator (e.g., a servo motor and a reducer) used to drive the wrist shaft member 18 of the movable part 3 to rotate. The output shaft (not shown) of the additional actuator 22 is connected to the first gear 20 of the drive force transmission mechanism 19 via a drive shaft 23, which is used to transmit the driving force generated by the additional actuator 22 to the first gear 20.

[0014] The drive shaft 23 extends parallel to the center of the two driven rods 13 in the direction of their interval and is connected to the first gear 20 of the drive force transmission mechanism 19 via a universal joint 24. The center point of the universal joint 24 is located on the straight line formed by connecting the center points of the two spherical bearings 16 that connect the two driven rods 13 and the movable part 3.

[0015] The additional actuator 22 is supported by the support structure 25 on the two driven rods 13. The support structure 25 includes two parallel shafts 26, as shown in FIG6. Along the path of the long axis of the two driven rods 13, the two shafts 26 are fixed to each driven rod 13 with through holes 28 formed in a direction orthogonal to the plane containing the long axis of the two driven rods 13. Hereinafter, this direction is referred to as the first direction. Furthermore, the support structure 25 also includes a shaft 30, one end of which has a flat assembly portion 27. The shaft 30 is fixed to the assembly portion 27 with through holes (another through hole) 29 in a direction parallel to the first direction.

[0016] The central axes B and C of the three shafts 26 and 30 are located in the same plane parallel to the straight line formed by connecting the center points of the two spherical bearings 16 that connect the two driven rods 13 on the drive rod 10. Furthermore, the support structure 25 includes six rolling bearings (one bearing and another bearing) 31 and a pair of auxiliary rods 32. The six rolling bearings (one bearing and another bearing) 31 fit the two ends of the three shafts 26 and 30 into their respective inner edges. The pair of auxiliary rods 32 respectively fix the outer edges of the three rolling bearings 31.

[0017] Each auxiliary rod 32 is provided with three recesses 33 for respectively fitting into the outer edges of the three rolling bearings 31. The inner circumferential surfaces of the recesses 33 and the outer circumferential surfaces of the outer edges of the rolling bearings 31 are fixed to each other, for example, by pressing or adhesive. Thus, along the first direction, separated by two passive rods 13, the two auxiliary rods 32 are rotatably connected on the two passive rods 13 about the central axis B of the shaft 26. In addition, the two auxiliary rods 32 are separated by two assemblies 27 of the auxiliary actuator 22 in the first direction, allowing the auxiliary actuator 22 to be rotatably supported about the central axis (axis line) C of the shaft 30.

[0018] In Figure 6, reference numeral 34 is a spacer for applying preload to the rolling bearing 31 to adjust it to the appropriate length, and reference numeral 35 is a bolt for assembling the spacer 34 between the two auxiliary rods 32.

[0019] In this embodiment, the two shafts 26 fixed to the passive rod 13, as shown in Figures 7 to 9, include a first shaft portion 36 and a second shaft portion 37. The first shaft portion 36 includes a first fitting portion 38 located at one end in the axial direction, which can be fitted into the through hole 28; a second fitting portion 39 located at the other end in the axial direction, which can be fitted into the inner edge of the rolling bearing 31; and a flange portion 40 located at the middle position in the axial direction, which protrudes radially outward from the first fitting portion 38.

[0020] One end of the flange 40, which has a first fitting portion 38, has a central hole centered on the central shaft B, and the inner circumferential surface of the central hole has an internal thread 41. In addition, the outer circumferential surface of the flange portion 40, on both sides of the central shaft B, has one or more parallel flat portions 40a that allow tools such as wrenches to engage.

[0021] The second shaft portion 37, arranged sequentially from one end in the axial direction, includes an external thread 42 that locks with the internal thread of the first shaft portion 36, a first fitting portion 43 that can be fitted into the through hole 28, a flange portion 44 that protrudes radially outward from the first fitting portion 43, and a second fitting portion 45 that can be fitted into the inner edge of the rolling bearing 31. The locking portion 46 is formed by the internal thread 41 of the first shaft portion 36 and the external thread 42 of the second shaft portion 37. The flange portion 44 of the second shaft portion 37 also has a flat portion 44a for tooling.

[0022] As shown in Figure 8, two shafts 26 are fixed to the driven rods 13 by screwing the external thread 42 of the second shaft portion 37, which is fitted with the first fitting portion 43 at one end face, to the internal thread 41 of the first shaft portion 36, which is fitted with the first fitting portion 38 at one end side. By locking the external thread 42 of the second shaft portion 37 to the internal thread 41 of the first shaft portion 36 located in the through hole 28, the flange portions 40 and 44 abut against one end face and the other end face. In this state, by further locking the external thread 42 and the internal thread 41, as shown in Figure 9, the driven rods 13 are clamped between the flange portion 40 of the first shaft portion 36 and the flange portion 44 of the second shaft portion 37 along the first direction, and pressure can be applied to each driven rod 13.

[0023] The shaft 30, which is fixed to the assembly part 27 of the additional actuator 22, includes a first shaft part (another first shaft part) 36 and a second shaft part (another second shaft part) 37, which have the same shape as the two shafts 26 fixed to the driven rod 13. That is, the first shaft part 36, arranged sequentially from one end in the axial direction, includes a first fitting part 38, a flange part 40, and a second fitting part 39. The end in the axial direction where the first fitting part 38 is provided has an internal thread 41 formed on the inner circumferential surface of the central hole centered on the central axis C.

[0024] Furthermore, the second shaft portion 37, arranged sequentially from one end in the axial direction, includes an external thread 42, a first fitting portion 43, a flange portion 44, and a second fitting portion 45. The locking portion 46 is formed by the internal thread 41 of the first shaft portion 36 and the external thread 42 of the second shaft portion 37.

[0025] The shaft 30 is fixed to the auxiliary actuator 22 by screwing the external thread 42 of the second shaft portion 37, which is fitted to the other end face, into the internal thread 41 of the first shaft portion 36, which is fitted to one end side, through the through hole 29 of the assembly portion 27 of the auxiliary actuator 22. By locking the external thread 42 of the second shaft portion 37 into the internal thread 41 of the first shaft portion 36 located in the through hole 29, the flange portions 40 and 44 abut against one end face and the other end face. In this state, by further locking the external thread 42 and the internal thread 41, as shown in FIG9, the assembly portion 27 is clamped between the flange portion 40 of the first shaft portion 36 and the flange portion 44 of the second shaft portion 37 along the first direction, and the shaft 30 can be stably fixed to the auxiliary actuator 22.

[0026] Regarding the effectiveness of the parallel robot 1 according to an embodiment of this application, please refer to the following description. The parallel robot 1 of this embodiment is driven by three actuators 7, 8, and 9 on the base 2, causing three drive rods 10, 11, and 12 to rotate respectively. The front ends of each drive rod 10, 11, and 12 are connected to two passive rods 13, 14, and 15 via spherical bearings 16, maintaining a pair of parallel rods while passively moving between the drive rods 10, 11, and 12 and the movable part 3. Thus, with the central axis A of the wrist shaft member 18 remaining vertical, the movable part 3 translates with three degrees of freedom in two horizontal directions and one vertical direction, and is positioned at a designated location.

[0027] Furthermore, by driving the auxiliary actuator 22, the driving force of the auxiliary actuator 22 is transmitted to the wrist shaft member 18 via the drive shaft 23, the first gear 20, and the second gear 21. The wrist shaft member 18 rotates about the central axis A relative to the sleeve 17. In this way, the posture of tools such as handles assembled on the mounting surface 18a at the lower end of the wrist shaft member 18 can be changed by rotating about the central axis A of the wrist shaft member 18.

[0028] When the three arms 4, 5, and 6 are actuated and the movable part 3 is moved at high speed relative to the base part 2, the passive rods 13, 14, and 15 and the additional actuator 22 are subjected to significant acceleration and deceleration. In addition, the support structure 25 on which the additional actuator 22 is assembled to the passive rods 13, 14, and 15 is also subjected to significant acceleration and deceleration.

[0029] In this configuration, the auxiliary rod 32 is rotatably assembled to the driven rod 13, and the shafts 26 and 30 are fixed by fitting into the through holes 28 and 29 of the driven rod 13. This allows the driven rod 13 to have a thinner structure compared to the case where the shafts 26 and 30 are rotatably assembled into the through holes 28 and 29. Furthermore, because the internal thread 41 of the first shaft portion 36 and the external thread 42 of the second shaft portion 37 are locked within the through holes 28 and 29, the driven rod 13 located around the through holes 28 and 29 can have a thinner structure compared to the case where it is locked to the radially outer side of the through holes 28 and 29. This reduces the inertia increased by rotation of the driven rod 13 and the shafts 26 and 30.

[0030] Furthermore, compared to rotatably assembling shafts 26 and 30 into the through holes 28 and 29 of the driven rod 13, the rolling bearing 31 can be positioned away from the shafts 26 and 30 in the axial direction, thus reducing the load on the rolling bearing 31 relative to the torque applied to the driven rod 13. Additionally, by treating the driven rod 13 and shafts 26 and 30 as separate components, the driven rod 13 can be more easily machined, reducing costs.

[0031] Furthermore, shafts 26 and 30 are constructed with a first shaft portion 36, a second shaft portion 37, and a locking portion 46. The locking portion 46, which clamps the driven rod 13 in a first direction through the first shaft portion 36 and the second shaft portion 37 fitted into the through holes 28 and 29, stably fixes shafts 26 and 30 to the driven rod 13. Thus, the friction between shafts 26 and 30 is increased by the greater pressure exerted between their flange portions 40 and 44 and the driven rod 13. As a result, the high-speed acceleration and deceleration of the movable part 3 during translation prevents relative movement between the driven rod 13 and shafts 26 and 30, even if vibration occurs in the driven rod 13, effectively preventing fretting wear.

[0032] Furthermore, the structure in which the driven rod 13 is clamped in the first direction through the flange portions 40 and 44 of the first shaft portion 36 and the second shaft portion 37, and pressure is applied to the driven rod 13 to fix the shafts 26 and 30, can reduce stress concentration in the first fitting portions 38 and 43 that fit into the through holes 28 and 29. In this way, the shafts 26 and 30 can be kept in a durable and sound working condition.

[0033] Furthermore, by directly fitting the first shaft portion 36 and the second shaft portion 37 into the through holes 28 and 29, the possibility of fretting wear in areas where it may occur can be minimized. Moreover, compared to fixing the shafts 26 and 30 to the through holes 28 and 29 with adhesive as a simple fixing method, the locking portion 46, secured by the external thread 42 and the internal thread 41, is easier to assemble and also provides stable fixing strength.

[0034] In other words, when fixing with adhesive, besides the inconvenience of uniformly applying the adhesive, variations in the amount of adhesive applied, the cleanliness of the bonding surface, and temperature differences during drying all affect the adhesive strength. In contrast, when fixing with the locking part 46, the fixing strength can be kept stable by controlling the locking torque. Furthermore, unlike adhesive fixing, the fixing force does not decrease due to adhesive peeling, thus maintaining stable fixing strength.

[0035] Furthermore, in this embodiment, the structure in which the auxiliary actuator 22 is rotatably assembled on the auxiliary rod 32 has the same construction as the structure in which the auxiliary rod 32 is rotatably assembled on the passive rod 13. Thus, in addition to allowing for a reduction in the size of the assembly portion 27 of the auxiliary actuator 22 around the shaft 30, it also suppresses fretting wear and stress concentration, keeping the shaft 30 in a durable and healthy working condition.

[0036] Furthermore, by having the same structure for rotatably assembling the auxiliary rod 32 onto the auxiliary rod 32 and rotatably assembling the auxiliary rod 32 onto the passive rod 13, the number of components can be reduced and costs can be reduced.

[0037] Furthermore, in this embodiment, although the structure in which the auxiliary actuator 22 is rotatably assembled on the auxiliary rod 32 has the same construction as the structure in which the auxiliary rod 32 is rotatably assembled on the passive rod 13, it can also be a different construction. That is, since the size of the assembly part 27 of the auxiliary actuator 22 is smaller than that of the passive rod 13, the shaft 30 can be rotatably assembled to the assembly part 27 through the bearing 31. In addition, in this embodiment, as the locking part 46, an internal thread 41 is provided on the first shaft part 36 and an external thread 42 is provided on the second shaft part 37, but it is not limited to this, and the external thread 42 can also be provided on the first shaft part 36 and the internal thread 41 can be provided on the second shaft part 37.

[0038] Furthermore, the locking part 46 for securing the first shaft portion 36 and the second shaft portion 37 is composed of an internal thread 41 provided on the first shaft portion 36 and an external thread 42 provided on the second shaft portion 37. Alternatively, as shown in FIG10, the first shaft portion 36 is provided with a threaded hole (internal thread) 47 along the central axis B, and the second shaft portion 37 is provided with a guide hole (screw through hole) 48 and a countersunk hole 49 along the central axis B. The locking part 46 is composed of a bolt 50 passing through the guide hole 48 and the threaded hole 47 of the first shaft portion 36. Alternatively, the threaded hole 47 can be provided on the second shaft portion 37, and the guide hole 48 and the countersunk hole 49 can be provided on the first shaft portion 36.

[0039] Furthermore, in this embodiment, the auxiliary rod 32 is provided on both sides separated by two passive rods 13. Alternatively, the auxiliary rod 32 may be provided on only one side. In addition, although in this embodiment, the support structure 25 is provided on the arm 4 with the additional actuator 22 between the passive rods 13, it is not limited to this. The support structure 25 may also be provided on the arms 5 and 6 without the additional actuator 22.

[0040] In this configuration, the support structure 25 of arms 5 and 6 includes two parallel shafts 26, four rolling bearings 31, and a pair of auxiliary rods 32. The shafts 26 are fixed to each of the passive rods 14 and 15. The four rolling bearings 31 engage the two ends of the two shafts 26 with their respective inner edges. The pair of auxiliary rods 32 fix the outer edges of the two rolling bearings 31. Thus, in arms 5 and 6 without additional actuators 22, rotation of the passive rods 14 and 15 around their long axes can be suppressed. Furthermore, as a parallel robot 1, the support structure 25 can be provided in at least one of the three arms 4, 5, and 6.

[0041] 1: Parallel Robot 2: Base section 3: Movable parts 4, 5, 6: Arm 7, 8, 9: Actuators 10, 11, 12: Drive lever 13, 14, 15: Passive lever 16: Spherical bearing 17: Sleeve 18: Wrist shaft component 18a: Assembly surface 19: Drive force transmission mechanism 20: First Gear 21: Second Gear 22: Additional actuator 23: Drive shaft 24: Universal Joint 25: Supporting Structure 26: Axis 27: Assembly Department 28: Through hole 30: Axis 31: Rolling bearing 32: Auxiliary rod 33: concave part 34: Spacer 35: Bolt 36: First shaft section 37: Second shaft section 38:First chimeric part 39:Second chimeric part 40: Flange section 40a: Planar part 41: Internal thread 42: External thread 43:First chimeric part 44: Flange section 45:Second chimeric part 46: Locking part 47: Screw hole 48: Guide hole 49: Countersunk hole 50: Bolt A: Central axis B: Central axis C: Central axis

Claims

1. A parallel robot, comprising: A drive rod is driven to rotate by an actuator; two driven rods are parallel to each other and rod-shaped, and the two driven rods are respectively connected to the front end of the drive rod; two shafts are fixed to each of the driven rods in a state where they are respectively fitted into a through hole provided on the path of each driven rod along a major axis; and a support structure having an auxiliary rod, which is rotatably assembled relative to the two shafts through two rolling bearings located at a position away from the axis of the driven rods and fitting into the inner edge of each shaft; wherein the through hole is formed along a first direction orthogonal to the plane containing the major axis of the two driven rods; wherein each shaft includes: a first shaft portion fitted into the through hole from one end face side of the first direction, and the first shaft portion protruding from the end face; A second shaft portion is fitted into the through hole from the other end face side of the first direction, and the second shaft portion protrudes from the other end face; and a locking portion applies force in the through hole in a direction that brings the first shaft portion and the second shaft portion closer to each other.

2. The parallel robot as described in claim 1, wherein, An additional actuator is provided between the two passive rods, and is supported on the two passive rods via the support mechanism. The additional actuator is rotatably supported relative to the auxiliary rod about an axis parallel to the first direction.

3. The parallel robot as described in claim 2, wherein, The auxiliary rod and the two rolling bearings are respectively disposed on both sides of the passive rod along the first direction, and the additional actuator is supported by the auxiliary rods on both sides.

4. A parallel robot as described in claim 2 or 3, wherein, The locking portion includes an internal thread formed in one of the first shaft portion or the second shaft portion, and an external thread formed in the other shaft portion to lock with the internal thread.

5. A parallel robot as described in claim 2 or 3, wherein, The locking part includes an internal thread formed in one of the first shaft portion or the second shaft portion, a threaded hole formed in the other, and a bolt passing through the threaded hole and locked to the internal thread.

6. A parallel robot as described in claim 2 or 3, wherein, A structure in which the additional actuator is rotatably supported on the auxiliary rod about the axis includes: a second shaft fixed to the additional actuator in a state of being fitted into a second through hole formed on the additional actuator along the direction of the axis; and a second bearing disposed on the auxiliary rod such that the second shaft is fitted into the inner edge of the second bearing; wherein the second shaft includes: a second first shaft portion fitted into the second through hole from one end face side in the direction of the axis, and the second first shaft portion protruding from the one end face; a second second shaft portion fitted into the second through hole from another end face side in the direction of the axis, and the second second shaft portion protruding from the other end face; and a second locking portion that applies force in the second through hole in a direction that brings the second first shaft portion and the second second shaft portion closer to each other.

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