Planetary gear transmission systems or components – Electric or magnetic drive or control
Patent
1996-03-08
1998-01-27
Wright, Dirk
Planetary gear transmission systems or components
Electric or magnetic drive or control
H02K 7116
Patent
active
057117365
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a motor apparatus with a reduction gear in which a motor portion is disposed around the center shaft and a reduction gear portion is disposed at the outer circumferential side of the motor portion to thereby reduce the number of rotations of the motor portion to provide an output of the reduced number of rotations.
BACKGROUND ART
Hitherto, in assembling; various equipment such as electric equipment, and so forth, automatic assembling robots are used. As an automatic assembling robot of this kind, there are, e.g., robots adapted for grasping or holding parts or components delivered through a parts delivery unit by an arm provided with grasping (holding) mechanism to rotationally operate the arm which has grasped or held the parts to mount them at predetermined mount positions of equipment to be assembled.
In the case of carrying out assembling of equipment by using such a robot, it is necessary to securely grasp or hold the delivered parts to precisely carry or convey them to predetermined mount positions of the equipment. In order to realize secure holding of parts and precise carrying thereof, it is necessary to precisely control the operation of the arm for holding and carrying the parts. In addition, in order to precisely control the operation of the arm, it is necessary to drive the arm by low speed and high torque.
In order to realize such a requirement to drive the arm of the robot by low speed and high torque, a motor having a reduction gear connected to the output shaft thereof is used.
As a reduction gear for reducing the number of rotations of the motor, a gear box comprised of a plurality of gears connected to each other is used. In order to obtain higher reduction gear ratio by using such gear box, it is necessary to connect a large number of gears in a multi-stage form. However, the gear box in which a large number of gears are connected in a multi-stage form would become large-sized. Further, it has been also put into practical use that a plurality of gear boxes are used. However, when such a large sized gear box or plural gear boxes is or are arranged at the output shaft side of the motor, the drive portion including the motor becomes large sized. As a result, it becomes difficult to attain miniaturization of the robot. Moreover, when a large number of gears are connected, or a plurality of gear boxes are connected, noise resulting from meshing between gears becomes large at the time of driving, thus making it difficult to constitute a silent robot. In addition, back-lash produced between respective gears becomes large, thus making it difficult to carry out precise drive control of the arm.
In order to solve such problems that the gear box has, a small reduction gear called a harmonic reduction gear which can obtain a reduction gear ratio of about 1/several tens to 1/hundred by one stage is used as a reduction gear of the motor which drives the arm of the robot. Similarly to the gear box, the harmonic reduction gear is used in the state attached to the front surface side from which the output shaft of the motor is projected so that the input/output shafts become coaxial with the output shaft of the motor.
Since the harmonic a reduction gear can obtain reduction ratio of about 1/several tens to 1/hundred by one stage, it has been caused to sufficiently become compact as compared to the gear box by which the same reduction ratio can be obtained. However, since the harmonic reduction gear is used in such a manner that it is disposed at the front surface of the motor in the state where the input/output shafts are caused to be concentric with respect to the output shaft of the motor, it cannot be avoided that the length in the output shaft direction of the drive system including the reduction gear and the motor is elongated.
In addition, since the harmonic reduction gear requires parts such as flex-in-belt and/or elliptical bearing, and so forth for which special precision processing is required, not only manufacturing is difficult, but also the cost
REFERENCES:
patent: 4994004 (1991-02-01), Meijer et al.
Kananen Ronald P.
Sony Corporation
Wright Dirk
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