Quaternion Joints

Abstract

To decrease weight of components and downsize a mechanism.SOLUTION: A quaternion joint with a first component and a second component rotatably connected with the first component through a plurality of links where orbit of intersections of the links respectively form hemispherical shapes on end faces of the first component and the second component so that the hemispherical shapes contact with each other at the intersections and the links are arranged to move the second component rotationally comprises: a plurality of first pullies which are swingably arranged on the end face of the first component; a plurality of second pullies which are swingably arranged on an end face of the second component facing the end face of the first component corresponding to the first pullies; and a plurality of wires which are installed between the first pully and the second pully corresponding to the first pully. A rotation axis of the first pully is offset in a turning state around the wire extending direction relative to a rotation axis of the second pully corresponding to the first pully.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to quaternion joints. [Background technology]

[0002] A quaternion joint is known which includes a plurality of first pulleys swingably mounted on an end face of a first member, a plurality of second pulleys swingably mounted on an end face of a second member opposing the end faces of the first member so as to correspond to the first pulleys, and a wire hung between the first pulleys and the second pulleys corresponding to the first pulleys (see, for example, Patent Document 1).

[0003] In the above quaternion joint, the rotation axis of the first pulley and the rotation axis of the second pulley corresponding to the first pulley are arranged in parallel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2021 / 0197407 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the above-mentioned quaternion joint has a movable pulley structure with multiple pulleys stacked on top of each other (Fig. 2), which means that there is a wire that is hung diagonally (Fig. 3). Since the wire that is hung diagonally is likely to come off the pulley, a part to guide the wire is required. This guide part may lead to an increase in the weight of the part. In addition, the structure has two degrees of freedom of the pulleys arranged coaxially, which may lead to an increase in the size of the mechanism.

[0006] The present disclosure has been made to solve such problems, and has as its main object to provide a quaternion joint that can reduce the weight of components and the size of the mechanism. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the present disclosure is to A first member; a second member rotatably connected to the first member via a plurality of links; a quaternion joint in which a hemispherical shape is formed on an end surface of the first member and a hemispherical shape is a trajectory of an intersection of the link, and the link is disposed so that the second member rotates while the hemispherical shapes are in contact with each other at the intersection, A plurality of first pulleys pivotably provided on an end surface of the first member; a plurality of second pulleys provided on an end surface of the second member opposed to an end surface of the first member so as to be swingable in correspondence with the first pulleys; A plurality of wires are hung between the first pulley and the second pulley corresponding to the first pulley; Equipped with The rotation axis of the first pulley is offset from the rotation axis of the second pulley corresponding to the first pulley in a state of rotation about the direction in which the wire extends. Quaternion Joints It is. In this embodiment, the rotation axis of the first pulley may be offset from the rotation axis of the second pulley corresponding to the first pulley by rotating 90° around the direction in which the wire extends. In this embodiment, the center-to-center distance between the first pulley and the corresponding second pulley is L, the distance between the rotation axis of the second pulley and the oscillation axis is a, and the distance between the rotation axis of the first pulley and the oscillation axis is b, and the parameters L, a, and b may be set so as to satisfy the following constraint condition equation.

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[0008] According to the present disclosure, it is possible to provide a quaternion joint that can reduce the weight of components and the size of the mechanism. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a perspective view of a quaternion joint according to the present embodiment. [Diagram 2] FIG. 13 is a diagram showing a configuration in which two degrees of freedom of a pulley are arranged coaxially. [Diagram 3] FIG. 13 is a diagram showing a configuration in which a diagonal wire is present. [Figure 4] FIG. 1 is a diagram of a conventional configuration in which the two degrees of freedom of a pulley are arranged coaxially. [Diagram 5] FIG. 2 is a diagram showing the arrangement of first and second pulleys according to the embodiment. [Figure 6] FIG. 13 is a diagram showing parameters of constraint conditions. [Figure 7] FIG. 13 is a diagram showing changes in the central link length and the wire length when each parameter is set in accordance with the constraint conditions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A quaternion joint according to the present embodiment is mounted on a joint portion such as a wrist joint of a robot, for example.

[0011] 1 is a perspective view of a quaternion joint according to this embodiment. The quaternion joint 1 includes a first member 2 and a second member 4 rotatably connected to the first member 2 via a plurality of links 3 that intersect in a side view.

[0012] Both ends of each link 3 are connected to end faces 21, 41 of the first and second members 2, 4, respectively, via a swing mechanism 5. The swing mechanism 5 can swing the link 3 in any direction by rotating the link 3 around first and second rotation shafts 51, 52 that are arranged perpendicular to each other and stacked on top of each other. During this swing, each link 3 is bent to avoid interference between the links 3.

[0013] In the quaternion joint 1, virtual hemispherical shapes that are the orbits of the intersections of the links 3 are formed on the end faces 21, 41 of the first and second members 2, 4, respectively, and each link 3 is arranged so that the second member 4 rotates while the hemispherical shapes come into contact with each other at the intersections.

[0014] In this embodiment, the number of links 3 is three, but is not limited to this, and any number may be used, for example, two or four or more, as long as the above operating conditions are satisfied.

[0015] Four first pulleys 6 are attached to the end surface 21 of the first member 2 via a swing mechanism 7. The first pulleys 6 are provided, for example, circumferentially at equal intervals of 90 degrees on the end surface 21 of the first member 2. The swing mechanism 7 has a pulley holding portion 71 that holds the first pulleys 6, and a swing shaft 72 that passes through the pulley holding portion 71.

[0016] The first pulley 6 oscillates in the circumferential direction around the oscillation shaft 72. The first pulley 6 has a structure in which multiple pulleys are stacked horizontally, and the rotation shaft 61 passes through the center of each pulley. The first pulley 6 rotates around the rotation shaft 61. The rotation shaft 61 of the first pulley 6 is disposed perpendicular to the oscillation shaft 72.

[0017] That is, the rotation shaft 61 of the first pulley 6 is offset from the oscillation shaft 72 by rotating 90° around the extending direction of the wire 11. The rotation shaft 61 of the first pulley 6 and the oscillation shaft 72 are arranged side by side so as to be stacked in the extending direction of the wire 11.

[0018] Four second pulleys 8 are attached via a swing mechanism 9 to an end face 41 of the second member 4 opposing the end face 21 of the first member 2 so as to correspond to the first pulleys 6. The second pulleys 8 are provided, for example, circumferentially at equal intervals of 90 degrees on the end face 41 of the second member 4. The swing mechanism 9 has a pulley holding portion 91 that holds the second pulleys 8, and a swing shaft 92 that passes through the pulley holding portion 91.

[0019] The second pulley 8 oscillates in the radial direction around the oscillation shaft 92. The second pulley 8 has a structure in which multiple pulleys are stacked horizontally, and the rotation shaft 81 passes through the center of each pulley. The second pulley 8 rotates around the rotation shaft 81. The rotation shaft 81 of the second pulley 8 is disposed perpendicular to the oscillation shaft 92.

[0020] That is, the rotation shaft 81 of the second pulley 8 is offset from the oscillation shaft 92 by rotating 90° around the extending direction of the wire 11. Moreover, the rotation shaft 81 and the oscillation shaft 92 of the second pulley 8 are arranged side by side so as to be stacked in the extending direction of the wire 11.

[0021] A wire 11 is hung between the first pulley 6 and a second pulley 8 corresponding to the first pulley 6. By pulling the wire 11, the second member 4 can be rotated in a roll direction, a pitch direction, etc. relative to the first member 2 via the multiple links 3.

[0022] Although four first and second pulleys 6, 8 are provided on the end faces 21, 41 of the first and second members 2, 4, respectively, this is not limited to this. The number of first and second pulleys 6, 8 provided on the end faces 21, 41 of the first and second members 2, 4 may be arbitrary.

[0023] Incidentally, with regard to the two-degree-of-freedom operation of a quaternion joint, when one degree of freedom is moved, it is required that the wire length L (the distance between the pulleys) in the other degree of freedom does not change, as shown in Fig. 2. For this reason, a configuration in which the two degrees of freedom of the pulley 100 are arranged coaxially has been adopted.

[0024] In addition, since the pulley structure has multiple overlapping pulleys 100, there is a conventional wire that is hung diagonally, as shown in Fig. 3. When tension is applied to the wire, it tends to approach a vertical state, which is the minimum distance. Therefore, the diagonal wire is likely to come off the pulley 100, and a part that guides the wire is required. This may lead to an increase in the weight of the parts.

[0025] Furthermore, in the conventional configuration in which the two degrees of freedom of the pulley 100 are arranged on the same axis, wire interference may occur as shown in Fig. 4(a). In order to avoid this interference, for example, a configuration in which the pulley 100 is supported by a cantilever structure as shown in Fig. 4(b) is assumed. Furthermore, in order to suppress an increase in the moment on the support member, a configuration in which the pulley is supported by a double-support structure as shown in Fig. 4(c) is assumed. This may lead to an increase in the size of the mechanism.

[0026] In contrast, in the quaternion joint 1 according to this embodiment, as shown in FIG. 1, the rotation axis 61 of the first pulley 6 is offset relative to the rotation axis 81 of the second pulley 8 corresponding to the first pulley 6, in a state rotated about the extension direction of the wire 11.

[0027] This allows for an arrangement in which, as shown in FIG. 5, for the two-degree-of-freedom operation of the quaternion joint 1, when one degree of freedom is moved, the wire length L (the distance between the pulleys) in the other degree of freedom does not change.

[0028] In addition, with this arrangement, interference with the wire 11 as described above can be avoided, and therefore the above-mentioned cantilever or double-supported pulley structure is unnecessary, allowing the mechanism to be made more compact.

[0029] The rotation axis 61 of the first pulley 6 is offset from the rotation axis 81 of the second pulley 8 corresponding to the first pulley 6 by, for example, rotating 90° around the direction in which the wire 11 extends.

[0030] Furthermore, as described above, the rotation axis 61 of the first pulley 6 is offset from the rotation axis 81 of the corresponding second pulley 8 by rotating 90° around the direction in which the wire 11 extends, and the first pulley 6 and the corresponding second pulley 8 are arranged alternately. Note that this 90° range includes a range around 90° due to design errors, etc.

[0031] This prevents the wire 11 from being hung diagonally as described above, making the wire guide for preventing the wire from coming off as described above unnecessary. This allows the weight of the parts to be reduced. In other words, the mechanism can be made smaller while still reducing the weight of the parts.

[0032] In this embodiment, the rotation axis 61 of the first pulley 6 is offset in a rotated state relative to the rotation axis 81 of the second pulley 8 corresponding to the first pulley 6, but this is not limited to this, and taking into consideration the shapes of the first and second pulleys 6, 8 and twisting of the wire 11, the angle may be in the range of, for example, 85° to 95°, and any angle may be used as long as the above-mentioned arrangement is possible and the wire 11 is not hung diagonally.

[0033] Next, a description will be given of constraint conditions for making the wire length follow the link length in the above-mentioned quaternion joint 1. Fig. 6 is a diagram showing parameters of the constraint conditions.

[0034] 6, the inclination angle of the central link 3 is θ, the center distance between the rotation shaft 61 of the first pulley 6 and the corresponding rotation shaft 81 of the second pulley 8 is L, the distance between the rotation shaft 81 of the second pulley 8 and the oscillation shaft 92 is a, and the distance between the rotation shaft 61 of the first pulley 6 and the oscillation shaft 72 is b. Using the above parameters L, a, and b, the following equation for the constraint condition can be derived from the geometric relationship shown in FIG.

[0035]

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[0036] By setting the parameters L, a, and b so as to satisfy the above constraint condition equation, it is possible to make the wire length follow the central link length in the above-mentioned quaternion joint 1.

[0037] Fig. 7 shows the change in the central link length and wire length when the parameters L, a, and b are set according to the above constraints. In Fig. 7, the horizontal axis indicates the link motion angle ψ [deg], the left vertical axis indicates the wire length [mm], and the right vertical axis indicates the central link length [mm].

[0038] As shown in Figure 7, the wire length changes in accordance with the change in the center link length, so that the extension and contraction of the wire caused by the movement of link 3 can be suppressed.

[0039] Although some embodiments of the present disclosure have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0040] 1 quaternion joint, 2 first member, 3 link, 4 second member, 5 oscillating mechanism, 6 first pulley, 7 oscillating mechanism, 8 second pulley, 9 oscillating mechanism, 11 wire, 21 end face, 41 end face, 51 rotation axis, 61 rotation axis, 71 pulley holder, 72 oscillating axis, 81 rotation axis, 91 pulley holder, 92 oscillating axis

Claims

1. A first member; a second member rotatably connected to the first member via a plurality of links, a quaternion joint in which a hemispherical shape is formed on an end surface of the first member and a hemispherical shape is a trajectory of an intersection of the link, and the link is disposed so that the second member rotates while the hemispherical shapes are in contact with each other at the intersection, A plurality of first pulleys pivotably provided on an end surface of the first member; a plurality of second pulleys provided on an end surface of the second member opposed to an end surface of the first member so as to be swingable in correspondence with the first pulleys; a plurality of wires hung between the first pulley and the second pulley corresponding to the first pulley; Equipped with The rotation axis of the first pulley is offset from the rotation axis of the second pulley corresponding to the first pulley in a state of rotation about the direction in which the wire extends. Quaternion joint.

2. 2. The quaternion joint of claim 1, The rotation axis of the first pulley is offset from the rotation axis of the second pulley corresponding to the first pulley by rotating 90° around the direction in which the wire extends. Quaternion joint.

3. 3. The quaternion joint according to claim 1 or 2, The center distance between the first pulley and the corresponding second pulley is L, the distance between the rotation axis and the oscillation axis of the second pulley is a, and the distance between the rotation axis and the oscillation axis of the first pulley is b, The parameters L, a, and b are set so as to satisfy the following constraints: [0030] Quaternion joint.

4. 3. The quaternion joint according to claim 1 or 2, The rotation axis of the first pulley is offset from the oscillation axis of the first pulley by rotating 90° around the direction in which the wire extends, and the rotation axis of the second pulley is offset from the oscillation axis of the second pulley by rotating 90° around the direction in which the wire extends. Quaternion joint.

5. 3. The quaternion joint according to claim 1 or 2, The rotation shaft of the first pulley and the oscillation shaft of the first pulley are arranged side by side in the direction in which the wire extends, and the rotation shaft of the second pulley and the oscillation shaft of the second pulley are arranged side by side in the direction in which the wire extends. Quaternion joint.

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