CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Application No. 2019-098409, the content of which is incorporated herein by reference.

FIELD

The present disclosure relates to a parallel link robot.

BACKGROUND

To date, there is a known parallel link robot including a base portion on which three motors are disposed, a movable portion disposed below the base portion, and three arms connected to the base portion and the movable portion in parallel with each other and respectively driven by the motors (for example, refer to The Publication of Japanese Patent No. 4653848). Each arm includes a drive link connected to the motor and two parallel passive links that connect the drive link and the movable portion to each other.

The movable portion is provided with an orientation changing mechanism that changes the orientation of an element attached to the movable portion. In addition, between the two passive links of one arm, an additional actuator disposed parallel to each passive link, and a power transmission shaft portion having a key shaft or a spline shaft that transmits a rotational driving force of the additional actuator to the orientation changing mechanism are attached. The additional actuator is supported by auxiliary links bridging the two passive links. In the power transmission shaft portion, a distal end of the key shaft or spline shaft is connected to an input shaft of the orientation changing mechanism via a universal joint.

The parallel link robot described in The Publication of Japanese Patent No. 4653848 is configured such that two quadrilaterals, which respectively have vertices at a bearing that connects the additional actuator to the auxiliary links, at bearings that connect the auxiliary links to the respective passive links, at bearings that connect the respective passive links to the movable portion, and at the universal joint, each form a parallelogram. In addition, the universal joint is disposed on a straight line that links the intersections of the two passive links and the movable portion to each other.

SUMMARY

One aspect of the present disclosure is directed to a parallel link robot including a base portion, a movable portion movable with respect to the base portion, a plurality of arms that connect the base portion and the movable portion in parallel, a plurality of base actuators that are disposed on the base portion and that drive the respective arms, an additional actuator that drives an additional mechanism portion attached to the movable portion, an auxiliary link that pivotally connects the additional actuator to at least one of the arms, and a power transmission shaft portion that transmits a rotational driving force of the additional actuator to the additional mechanism portion, in which each of the arms includes a drive link that is connected to a corresponding one of the base actuators and that has one degree of freedom with respect to the base portion, and two passive links that connect the drive link and the movable portion to each other and that are disposed parallel to each other, the auxiliary link bridges the two passive links and is pivotally connected to each of the two passive links, and the power transmission shaft portion includes a ball spline in which a spline shaft and a nut are meshed with each other, the spline shaft being fixed to one of a universal joint attached to an input shaft of the additional mechanism portion and an output shaft of the additional actuator, the nut being fixed to another one of the universal joint and the output shaft.

