US Patent No. 9,370,866

WRIST UNIT OF INDUSTRIAL ROBOT


Patent No. 9,370,866
Issue Date June 21, 2016
Title Wrist Unit Of Industrial Robot
Inventorship Akihiro Oikawa, Yamanashi (JP)
Assignee FANUC CORPORATION, Yamanashi (JP)

Claim of US Patent No. 9,370,866

1. A wrist unit of an industrial robot, comprising:
a first wrist element supported rotatably about a first axial line at a first joint of a front end side of a robot arm;
a second wrist element supported rotatably about a second axial line at a second joint of a front end side of the first wrist
element, the second axial line not being on an extension of the first axial line and not being parallel to the first axial
line;

a third wrist element supported rotatably about a third axial line at a third joint of a front end side of the second wrist
element, the third axial line not being on an extension of the second axial line and not being parallel to the second axial
line;

a second wrist drive motor provided at the first wrist element or the robot arm to drive the second wrist element;
a third wrist drive motor provided at the first wrist element or the robot arm to drive the third wrist element; and
an eccentric rocking reduction gear provided at the second joint so that a rotation center axial line matches with the second
axial line to decelerate and transmit a rotation from the second wrist drive motor to the second wrist element,

wherein the eccentric rocking reduction gear comprises:
a carrier forming a hollow part along the rotation center axial line;
a through shaft (i) supported rotatably at the carrier by a pair of first bearings arranged inside the hollow part and (ii)
passing through the hollow part to transmit a rotation from the third wrist drive motor from a side of the first wrist element
to a side of the second wrist element, wherein

at one end of the through shaft, a bevel gear, which is engaged with a bevel gear at the end of the first wrist element, is
attached, and

at the other end of the through shaft, a flat gear, which is engaged with a flat gear at the end of the second wrist element,
is attached;

a plurality of crankshafts arranged around the through shaft, the plurality of crankshafts having flat gears at ends of the
side of the first wrist element; and

a gear member provided rotatably centered about the rotation center axial line, the gear member having
a bevel gear to which a rotational force from the second wrist drive motor is input, and
a flat gear with which the flat gears of the plurality of crankshafts engage;
wherein the gear member is rotatably supported by a pair of second bearings attached to an outer circumferential surface of
the through shaft, the pair of second bearings arranged outside the hollow part in an axial direction along the rotation center
axial line.