Articular structure for robot and robot with incorporated articular structure

1. An articular structure for a robot, with a second member rotating relative to a first member about two axes perpendicular to each other, the articular structure comprising:

a first intermediate link supported on the first member to be rotatable about a first axis;

a first arm having one end connected to the second member with a ball joint interposed therebetween and the other end connected to the first intermediate link with a ball joint interposed therebetween;

a first actuator for rotating the first intermediate link about the first axis;

a second intermediate link supported on the first member to be rotatable about a second axis;

a second arm having one end connected to the second member with a ball joint interposed therebetween and the other end connected to the second intermediate link with a ball joint interposed therebetween; and

a second actuator for rotating the second intermediate link about the second axis, wherein

the first axis of the first intermediate link and the second axis of the second intermediate link are positioned on the same straight line.

each of the first and second actuators includes a main body portion, a shaft portion with a helical thread groove formed on an outer peripheral face thereof and a ball screw nut housed in the main body portion and engaged with the thread groove of the shaft portion, the first and second actuators being linear actuators each including the shaft portion for moving linearly relative to the main body portion when the ball screw nut is rotated,

the main body portion of each of the first and second actuators is rotatably supported on the first member, and

a tip end of the shaft portion of each of the first and second actuators is fixed to a connecting shaft rotatably supported on a bracket portion of each of the first and second intermediate links.

2. The articular structure for the robot according to claim 1 ,

wherein, when the first and second actuators rotate the first and second intermediate links in the same direction, the second member rotates relative to the first member about one of the two axes perpendicular to each other and,

when the first and second actuators rotate the first and second intermediate links in opposite directions, the second member rotates relative to the first member about the other of the two axes perpendicular to each other.

3. The articular structure for the robot, with a second member rotating relative to a first member about two axes perpendicular to each other, the articular structure comprising:

a first intermediate link supported on the first member to be rotatable about a first axis;

a first arm having one end connected to the second member with a ball joint interposed therebetween and the other end connected to the first intermediate link with a ball joint interposed therebetween;

a first actuator for rotating the first intermediate link about the first axis;

a second intermediate link supported on the first member to be rotatable about a second axis;

a second arm having one end connected to the second member with a ball joint interposed therebetween and the other end connected to the second intermediate link with a ball joint interposed therebetween; and

a second actuator for rotating the second intermediate link about the second axis, wherein

the first axis of the first intermediate link and the second axis of the second intermediate link are positioned on the same straight line,

when the first and second actuators rotate the first and second intermediate links in the same direction, the second member rotates relative to the first member about one of the two axes perpendicular to each other and,

when the first and second actuators rotate the first and second intermediate links in opposite directions, the second member rotates relative to the first member about the other of the two axes perpendicular to each other, and

the first intermediate link and the second intermediate link come in contact with each other in order to prevent an angle formed between the first intermediate link and the second intermediate link from becoming smaller than a predetermined angle when the angle formed between the first intermediate link and the second intermediate link is the predetermined angle.

4. The articular structure for the robot according to claim 1 , wherein a spring for biasing at least one of the first and second intermediate links for rotation in one direction is disposed between at least of the first and second intermediate links and the first member.

5. The articular structure for the robot according to claim 1 ,

wherein the first member and the second member are connected by a joint having two axes orthogonal to each other in a plane, and

the first member is rotatably connected to one of the two axes orthogonal to each other and the second member is rotatably connected to the other of the two axes orthogonal to each other.

6. The articular structure for the robot according to claim 1 , wherein the first member is provided with a driver for controlling the first and second actuators.

7. A robot into which the articular structure for the robot according to claim 1 is incorporated.