TECHNICAL FIELD

The present invention relates to a technique of an externally-driven joint structure.

BACKGROUND ART

Patent Literature 1 proposes a joint structure of a module-type manipulator. Specifically, the joint structure disclosed in Patent Literature 1 has a built-in motor, and includes attachment faces that can be coupled with another joint structure respectively at two points consisting of a circumferential face and an end face of a rotatable member that rotates in accordance with the rotation of the motor. Accordingly, a plurality of joint structures can be coupled with each other, and thus it is possible to form a manipulator having a multi-joint structure.

Furthermore, Patent Literature 2 proposes a multiaxial joint in which a distal joint part and a proximal joint part are connected such that they can axially pivot and swivel via a rotary pivot joint and a rotary swivel joint that are connected to each other in series. According to this multiaxial joint, it is possible to realize a joint having a high degree of freedom in two directions in a link mechanism of a robot.

CITATION LIST

Patent Literatures

Patent Literature 1: JP S62-282886A

Patent Literature 2: JP 2010-255852A

SUMMARY OF INVENTION

Technical Problem

Joint structures that can be used for link mechanisms of robots such as exoskeletal robots or robot arms include joint structures with a built-in actuator (e.g., Patent Literature 1) that are directly coupled with a drive source or that have a built-in drive source, and externally-driven joint structures (e.g., Patent Literature 2) that are disconnected from a drive source and that are driven by an external force transmitted from an external device such as a link member coupled thereto.

Joint structures with a built-in actuator are internally provided with a housing for accommodating an actuator such as a motor for directly driving the joint structures, and thus the size becomes relatively large. Furthermore, their shape, structure, drive direction, and the like are limited due to the built-in actuator. Thus, use situations of the joint structures with a built-in actuator are limited.

Meanwhile, there is no such a limitation on externally-driven joint structures, and thus they can be relatively freely designed according to a link mechanism that is to be formed. Thus, externally-driven joint structures can be used in various situations, and various link mechanisms can be formed using the externally-driven joint structures.

However, conventionally, externally-driven joint structures are in many cases individually designed so as to be optimal for each use situation, and they are seldom modularized. That is to say, externally-driven joint structures that can be used for general purposes have rarely been developed.

An aspect of the present invention has been made in view of these circumstances, and it is an object thereof to provide a modularized externally-driven joint structure that can be used for general purposes.

Solution to Problem

In order to solve the above-described problems, the present invention employs the following configurations.

That is to say, an aspect of the present invention is directed to an externally-driven joint structure including: a shaft member that extends in an axial direction; and a plurality of rotatable members that are arranged along the axial direction, and are coupled with each other by the shaft member in an axially rotatable manner, wherein each of the rotatable members includes a pair of face portions that face each other in the axial direction, a side wall portion that is arranged along outer circumferential edges of the pair of face portions, and at least one coupling portion that is arranged at the face portions or the side wall portion, and is coupled with a link member constituting a link of a robot.

With this configuration, a plurality of rotatable members are coupled with each other in an axially rotatable manner. Moreover, each of the rotatable members includes at least one coupling portion for coupling a link member constituting a link of a robot.

Thus, it is possible to couple a plurality of link members via the joint structure according to the above-described configuration, by coupling different link members with different rotatable members. Furthermore, when the link members are moved by an external force acting from actuators or the like, the rotatable members coupled with the link members can axially rotate in accordance with the rotation of the link members.

That is to say, the joint structure according to the above-described configuration can be driven by an external force transmitted from the link members, and thus it is possible to change a positional relationship between the link members coupled with different rotatable members. Accordingly, with this configuration, it is possible to provide a modularized externally-driven joint structure that can be used for general purposes.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that at least one rotatable member of the plurality of rotatable members includes a plurality of the coupling portions arranged at the side wall portion. With this configuration, a plurality of link members can be coupled with a side wall portion of at least one rotatable member, and thus it is possible to realize a complex link mechanism such as a parallel-linked Scott Russell mechanism, which will be described later.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that at least one rotatable member of the plurality of rotatable members includes at least one coupling portion arranged at either one of the pair of face portions, and other rotatable members of the plurality of rotatable members include at least one coupling portion arranged at the side wall portion. With this configuration, the link connecting direction can be changed between a link member coupled with a face portion of at least one rotatable member and a link member coupled with a side wall portion of another rotatable member. Accordingly, the link connecting direction can be changed without a special structure, and thus the link mechanism that is to be constructed can be made compact on the whole.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that the face portions of the rotatable members are provided with a recess portion with a shape that allows a bearing in the shape of a ring that receives a force that acts in the axial direction to be accommodated between rotatable members that are adjacent to each other in the axial direction. With this configuration, it is possible to provide a modularized joint structure that can be reinforced in the axial direction by a bearing.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that an encoder for detecting a relative rotational angle between the rotatable members that are adjacent to each other in the axial direction is further accommodated between the recess portions of the adjacent rotatable members. With this configuration, an encoder for detecting a rotational angle is built in the joint structure. Thus, it is possible to provide a compact and modularized joint structure that can detect an angle.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that the recess portions are formed in the shape of a circular ring, bases of inner circumferential faces of the recess portions are provided with a step portion in the shape of a circular ring extending inward in a radial direction from the inner circumferential faces, a face portion of a rotatable member that faces the recess portions, the rotatable member being adjacent to the rotatable members, is provided with a projecting portion in the shape of a circular ring with a diameter smaller than that of the recess portions, a base of an outer circumferential face of the projecting portion is provided with a step portion in the shape of a circular ring extending outward in the radial direction from the outer circumferential face of the projecting portion, and a cross roller bearing as the bearing in the shape of a ring is arranged so as to be supported by the inner circumferential face of the recess portion, a face along the axial direction of the step portion of the recess portion, the outer circumferential face of the projecting portion, and a face along the axial direction of the step portion of the projecting portion. With this configuration, since a cross roller bearing is used, it is possible to increase the outer diameter of the shaft member compared with the case in which a thrust bearing is used. Accordingly, the rigidity of the shaft member can be improved.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that the joint structure includes two rotatable members, the coupling portions of the rotatable members are arranged symmetric about the axial direction such that, even when the joint structure is reversed about an axis that is perpendicular to the axial direction, the joint structure can be used while a positional relationship between the link members is maintained, one of the two rotatable members is formed in one piece with the shaft member, the other rotatable member of the two rotatable members has a through hole into which the shaft member is allowed to be inserted, and a radial bearing is arranged so as to be interference-fitted to the shaft member and clearance-fitted to an inner circumferential wall of the through hole, or so as to be clearance-fitted to the shaft member and interference-fitted to the inner circumferential wall of the through hole. With this configuration, it is possible to provide a joint structure that can be applied to situations with different load conditions such as unbalanced loads and stationary loads, because the structure is symmetric about the axial direction. In this case, the coupling portions can be coupled with the same type of link members. Furthermore, following link mechanisms can be constructed using the joint structure according to this embodiment. That is to say, an aspect of the present invention is directed to a link mechanism including: two or more joint structures according to this embodiment; and a link member that is coupled with the coupling portions of the joint structures, wherein two joint structures that are adjacent to each other via the link member are arranged such that one of the joint structures is used in a state of being reversed about an axis that is perpendicular to the axial direction with respect to the other joint structure so that the rotatable members face each other in the direction that is perpendicular to the axial direction. With this configuration, it is possible to construct a link mechanism that is compact in the width direction.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that the joint structure includes two rotatable members, the coupling portions of the rotatable members are arranged symmetric about the axial direction such that, even when the joint structure is reversed about an axis that is perpendicular to the axial direction, the joint structure can be used while a positional relationship between the link members is maintained, the shaft member is formed separately from the two rotatable members, the rotatable members each have a through hole into which the shaft member is allowed to be inserted, and a radial bearing is arranged between the shaft member and the rotatable members so as to be interference-fitted to the shaft member and clearance-fitted to an inner circumferential wall of the through hole, or so as to be clearance-fitted to the shaft member and interference-fitted to the inner circumferential wall of the through hole. With this configuration, it is possible to provide a joint structure that is symmetric about the axial direction.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that the joint structure includes three or more rotatable members, and the coupling portions of at least two rotatable members of the three or more rotatable members are coupled with a same link member. With this configuration, one link member is supported by a plurality of rotatable members, and thus an external force that acts from the link member can be dispersed between the rotatable members. Accordingly, with this configuration, even when a relatively large force acts from a link member, deformation of the shaft member of the joint structure can be suppressed.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that coupling between the coupling portions and the link member is constituted by a magnet. With this configuration, it is easy to couple the rotatable members and the link member with each other, and thus it is easy to produce a link mechanism.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that the rotatable members have at least one coupling portion arranged at the side wall portions, the side wall portions of the rotatable members are formed in the shape of a cylinder, and the coupling portions arranged at the side wall portions have a shape obtained by cutting, in a tangential direction, arc portions of the side wall portions. With this configuration, it is possible to provide a joint structure that can be more easily produced through lathe machining or the like. Note that a side wall portion being in the shape of a cylinder refers to a state in which the outer shape of the side wall portion is cylindrical, except for the portion obtained by cutting for forming the coupling portion.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that the side wall portions of the rotatable members have a height that matches a thickness of the link member. With this configuration, it is possible to provide a joint structure that can form a compact link mechanism.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that the coupling portions arranged at the side wall portions have a projecting portion projecting outward in the radial direction at a center in the tangential direction, in conformity with a recess portion provided at a center of an end face of the link member. With this configuration, the portion obtained by cutting as a coupling portion in each rotatable member can be arranged on the outer side in the radial direction, and thus it is possible to provide a joint structure in which a bearing with a relatively large diameter can be arranged.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that a reinforcing plate for supporting a coupling region of the coupling portion arranged at the side wall portion of the rotatable member and the link member is provided on at least one of both sides in the axial direction of the coupling region. With this configuration, it is possible to provide a joint structure that is unlikely to be broken by twisting.

Furthermore, as another mode of the externally-driven joint structure according to the above-described aspect, it is possible that each of the rotatable members has a plurality of the coupling portions at the side wall portion, and the plurality of coupling portions are arranged symmetric about an axis in each of the rotatable members. With this configuration, it is possible to provide a joint structure that can be used while a positional relationship between the link members is maintained even when the joint structure is axially rotated.

Furthermore, an aspect of the present invention is directed to a link mechanism including: the joint structure according to any one of above-described aspects; and a link member that is coupled with the coupling portion arranged at the side wall portions of the rotatable members of the joint structure, wherein the side wall portions of the rotatable members of the joint structure include a wire-driving groove portion, a fixture is attached to the link member, and a wire that is driven by an external drive source is arranged along the wire-driving groove portion, and the end portion of the wire is fixed to the fixture.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a modularized externally-driven joint structure that can be used for general purposes.

