Planetary gear transmission systems or components – Planet periphery surrounds axis of interacting gear – Circumferentially spaced connector pins
Reexamination Certificate
1998-12-09
2001-05-15
Estremsky, Sherry (Department: 3681)
Planetary gear transmission systems or components
Planet periphery surrounds axis of interacting gear
Circumferentially spaced connector pins
C475S162000, C475S179000, C475S180000
Reexamination Certificate
active
06231469
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an internally meshing planetary gear device wherein a circular arc tooth form is used for an internal gear and an epitrochoid tooth form is used for an outer gear of a planetary gear. More specifically, the present invention relates to useful art for simultaneously achieving high efficiency, low abrasion, low backlash, high loading ability, high rigidity, high precision and excellent control ability in a planetary gear device of such a type.
The present invention is aimed to enhance efficiency of a motion control device for an indexing device of a machine tool, an industrial robot or the like, or a servo actuator.
2. Description of Related Art
In conventional indexing devices used for machining center (MC), a combination of an AC servo motor and a worm gear reduction device is mainly used. However, a worm gear reduction device has extremely low efficiency and causes a problem when it is sped up due to a large slip between meshing surfaces and a high pressure at contact surfaces. Further, it also suffers from backlash due to the slip at the gear surfaces, and its efficiency further decreases. In order to avoid backlash, an adjusting mechanism is necessary, and maintenance of such an adjusting mechanism is troublesome.
Contrary to this, in addition to the worm gear reduction device, there are internally meshing planetary gear devices, wherein a circular arc tooth form is used for an internal gear, and wave gear devices, both of which are widely used at articulations of industrial robots, by which high reduction ratio can be obtained easily.
For example, Japanese Utility Model Publication No. Sho 61-16439 discloses an internally meshing planetary reduction device wherein an internal gear has a circular arc tooth comprising pins and rollers and an outer gear has a trochoid tooth form, characterized in that outer rollers which is longitudinally divided into two are rotatably supported on outer pins which are disposed on the internal surface of an annular frame which forms a housing of internal gear, and an intermediate supporting portion for supporting the outer pin is formed between the outer rollers which are longitudinally spaced from each other by a small distance.
Further, Japanese Utility Model laid-open No. Sho 58-102855 discloses an eccentric swing type reduction device comprising a case having internal teeth in a pin shape, a support block which is rotatable relative to the case, a pinion which has outer teeth meshing with the internal teeth and which performs eccentric revolution, and an eccentric crank mechanism which is disposed on the support block and which activates the pinion, characterized in that both ends of the pins are rotatably supported on the case by means of rolling bearings.
PROBLEMS TO BE SOLVED BY THE INVENTION
As described above, a combination of an AC servo motor and a worm gear reduction device, which combination is used in a conventional indexing device for MC, has a problem when the operating speed is enhanced since the efficiency of the worm gear reduction device is extremely low. Further, backlash increases due to slip between tooth surfaces, and accordingly, the efficiency decreases. An adjusting mechanism is required in order to reduce backlash, and maintenance of such an adjusting mechanism is troublesome.
In the above-described Japanese Utility Model Publication No. Sho 61-16439, the rolling bearings (rollers), which are supported on the pins, mesh with the trochoid tooth formed on the outer gear, and in this device, slip is inevitable at either position between the rollers and the outer gear or that between the rollers and the pins.
In the above-described Japanese Utility Model Laid-open No. Sho 58-102855, both the ends of the pin are supported by the rolling bearings, and the pin meshes with the outer gear. Since two outer gears, the phases of which are different from each other, mesh with one single pin at the same time, slip causes necessarily in at least one contacting portion. There is not disclosed any means for adjusting backlash in this prior art.
Further, Japanese Utility Model Laid-open No. Sho 58-149438 discloses a pin supporting a rolling bearing, one end of which pin is supported in a cantilever fashion. The device does not have sufficient rigidity, and contact condition is not uniform, and the mechanism for adjusting backlash is complicated.
However, in these reduction devices, slip between the meshing tooth surfaces inevitably occurs, and there is a problem of increase of backlash due to abrasion of the tooth surfaces. There is no mechanism for adjusting backlash during operation of these devices, and accordingly, these conventional reduction devices cannot be used actually as a high precision motion control device for an indexing device of an MC.
BRIEF SUMMARY OF THE INVENTION
OBJECTS OF THE INVENTION
It is an object of the present invention to speed up a motion control device, to reduce maintenance operation of the motion control device, and to enhance the efficiency of the motion control device. More specifically, it is an object of the present invention to provide a speed increasing or reducing device suitable for precious motion control by which decrease or change of the efficiency is small as it is operated, which has s mall backlash, small hysteresis and high linearity so that the output highly corresponds to the input, by which the efficiency is high and the change in efficiency is small so that the loading torque or inertia at the output can be estimated from the input value, and which has high rigidity.
MEANS TO SOLVE THE PROBLEMS
According to the present invention, the above-described object is achieved by an internally meshing planetary gear device which comprises an internal gear having a circular arc tooth form and an outer gear of a planetary gear having an epitrochoid tooth form, the internal gear comprises pins, both ends of which are supported, and rolling bearings inserted onto the pins, and the rolling bearings have outer races meshing with the outer gear.
Further, the present invention achieves the object by a method for fabricating an internally meshing planetary gear device wherein a circular arc tooth form is used for an internal gear and an epitrochoid tooth form is used for an outer gear of a planetary gear, characterized in that rolling bearings are used as the internal gear which meshes with the outer gear, that the rolling bearings are supported by pins which are supported at both ends thereof, fitting clearance of the pins being so selected that the pins can be inserted freely into the rolling bearings and the epitrochoid gear form of the outer gear being modified so as to avoid interference between tooth tip and tooth base, that the pins are freely inserted into the rolling bearings without pressurizing tooth surfaces locating at a predetermined meshing position and that the tooth surfaces are pressurized at meshing positions other than the predetermined meshing position due to displacement of the planetary gear from the meshing position.
The present invention provides the internally meshing planetary gear device, wherein the circular arc tooth form is used for the internal gear and the epitrochoid tooth form is used for the outer gear of the planetary gear, and the means meshing with the outer gear is the outer races of the rolling bearings which are inserted onto the pins, the both ends of which are supported. The fitting clearance between the pins supporting the rolling bearings and the rolling bearings includes such a clearance that the pins can be freely inserted into the rolling bearings. Further, in order to easily reduce backlash, adequate pins are so selected taking into consideration the diameter of the outer gear and the diameter of the internal gear that the tooth surfaces are pressurized. The fitting between the pins and the rolling bearings is clearance fit, and it is preferred that the tooth form of the outer gear is modified so as to avoid interference between the tooth tip and the tooth base. T
Hirose Jun
Juman Shinji
Wang Hong You
Yoshikawa Toshio
Estremsky Sherry
Rothwell Figg Ernst & Manbeck
Teijin Seiki Co. Ltd.
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