Machine element or mechanism – Gearing – Directly cooperating gears
Patent
1992-07-07
1994-02-01
Bonck, Rodney H.
Machine element or mechanism
Gearing
Directly cooperating gears
74467, 74606A, 74479B, F16H 118
Patent
active
052823903
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an industrial robot provided with means for cooling a linear motion mechanism having a linear motion nut and screw shaft, and more particularly, to a linear motion mechanism cooling apparatus for cooling a linear motion nut and screw shaft of a linear motion mechanism also known as a ball-and-screw mechanism accommodated between a robot movable component such as a robot arm and a robot body of an industrial robot and a drive motor for driving the robot movable component for converting a rotative output of the drive motor into a linear motion to be transmitted to the robot movable component, the cooling apparatus being capable of effectively removing frictional heat generated by the rotation of the screw shaft and heat transmitted from the drive motor to the screw shaft, by flowing a cooling medium over the working surface of the screw shaft.
PRIOR ART
A cylindrical coordinate type industrial robot having a telescopically extendable and contractible arm is provided with a linear motion mechanism including a ball-and-screw nut and a screw shaft between a motor used as a rotative drive source and the robot arm for converting a rotary motion into a corresponding linear motion when driving the telescopically movable robot arm for an axial motion or in vertically shifting the robot arm. A multi-articulated industrial robot provided with a linkage-operated swing robot arm turns the swing robot arm on a joint through the operation of the linkage caused by the linear motion of a linear motion nut engaged with a screw shaft.
In the industrial robot employing a linear motion mechanism as a transmission mechanism for converting a rotation into a linear motion, the motion converting accuracy of the linear motion mechanism when converting a rotation into a linear motion by the screw action between the screw shaft connected to the drive motor, and the linear motion nut connected to a movable component, such as the robot arm, directly affects the operating accuracy of the movable component, and accordingly, the working accuracy of the industrial robot, i.e., the operating accuracy of an end effector coupled with a robot wrist attached to an extremity of the robot arm, is directly dependent on the motion converting accuracy, and thus the screw shaft must be finished with a high dimensional accuracy by precision machining. Nevertheless, no effective measure has been taken to deal with the deterioration of the accuracy of robot actions due to the deterioration of the accuracy of displacement of the linear motion nut attributable to the thermal deformation of the screw shaft during operation.
Under such circumstances, a cooling method has been proposed for suppressing the thermal deformation of a screw shaft by cooling the screw shaft. This cooling method passes cooling air through an axial bore of a hollow screw shaft to remove heat generated by screw action between the screw shaft and a screw nut engaged with the ball-and-screw shaft during robot actions, to thereby suppress the thermal deformation of the shaft.
This previously proposed cooling method, however, is applicable only to a hollow screw shaft and is not able to cool the shaft at a sufficiently high cooling efficiency, because the surface area of the bore of the shaft is not always sufficiently large and a flow of cooling air is unable to remove heat at a high efficiency. Furthermore, the cooling method is disadvantageous when applied to a hollow shaft having a small outer diameter. Still further, since a hollow shaft requires an additional machining process for boring, the hollow shaft is a relatively costly component of a robot unit.
DISCLOSURE OF THE INVENTION
Accordingly, an object of the present invention is to solve the foregoing problems encountered by the prior art.
Another object of the present invention is to provide a cooling unit capable of sufficiently and effectively removing heat from a shaft accommodated in a linear motion mechanism incorporated in an industrial robot, by flowing a cooling med
REFERENCES:
patent: 2726278 (1955-12-01), Southern
patent: 3171295 (1965-03-01), Benckert
patent: 3482463 (1969-12-01), Huyots et al.
patent: 4586394 (1986-05-01), Perkins
patent: 4840077 (1989-06-01), Katahira
Sasaki Yasuo
Terada Akihiro
Torii Nobutoshi
Bonck Rodney H.
Fanuc Ltd.
Laub David W.
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