Machine element or mechanism – Gearing
Patent
1996-10-03
1998-02-10
Ta, Khoi Q.
Machine element or mechanism
Gearing
475180, F16H 132
Patent
active
057157324
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a silk-hat flexible meshing gear device including a flexible external gear shaped like a silk hat. More particularly, this invention relates to a silk-hat flexible meshing gear device including a flexible external gear shaped like a silk hat wherein stress concentration in the flexible external gear can be relieved and the flexible external gear can be reduced in outer diameter and axial length.
BACKGROUND ART
A type of flexible meshing gear device with a flexible external gear shaped like a silk hat is known to the art. In this specification, this type of flexible meshing gear device will be referred to as a "silk-hat flexible meshing gear device."
FIG. 6 is a vertical sectional view of the silk-hat-shaped flexible external gear of a silk-hat flexible meshing gear device taken along a plane including the device axis. As shown in this figure, the flexible external gear 1 comprises a cylindrical body 2, an annular diaphragm 3 whose inner edge is continuous with the open proximal end of the body 2, and a thick annular boss 5 continuous with the outer edge of the diaphragm 3. External teeth 4 are formed integrally with the outer surface at the open distal end of the body 4 to run in the circumferential direction.
This type of device is suitable for use in cases where a rotating member or the like is passed through the device along the device axis 1a. This is because the provision of the diaphragm 3 of the flexible external gear so as to extend radially outward from the end of the body 2 facilitates accommodation of the rotating member in the internal space of the body 3.
Recent years have seen increased demand for more compact speed reducing mechanisms for use in small robots and the like. One way of responding to this demand is to shorten the axial length of the silk-hat flexible meshing gear device. For this it is necessary to shorten the axial length of the silk-hat-shaped flexible external gear. In the external gears in general use, the ratio of the axial length of the flexible external gear to the pitch circle diameter of its external teeth is around 1:1. Making the axial length shorter than this increases the coning angle of the external gear.
In other words, the coning angle .theta. of the flexible external gear 1 increases as shown in FIG. 5. As a result, excessive stress concentration may occur at such points as the inner edge 3a and the outer edge 3b of the diaphragm 3 shown in FIG. 6. It may also become impossible to maintain proper meshing of the external and internal gears. Because of this, a conventional flexible external gear merely shortened in axial length is not useful in practical applications.
In the silk-hat flexible meshing gear device, since, as explained in the foregoing, the diaphragm 3 of the flexible external gear extends radially outward from the end of the body 2, a rotating member or the like can be passed through and accommodated in the internal space of the body 3. However, this radially outward extension of the diaphragm 3 gives the device a larger outer diameter than that of a cup-shaped flexible meshing gear device equipped with a cup-shaped flexible external gear. The outer diameter of the device can be reduced by reducing the outer diameter of the diaphragm 3.
As shown by the arrows in FIG. 6, however, a large bending stress repeatedly acts on the diaphragm 3 owing to deformation of the body 2 flexed in the radial direction by a wave generator (not shown). If the diameter of the diaphragm 3 is reduced, therefore, the stress arising at the inner edge 3a and outer edge 3b of the diaphragm 3 increases in inverse proportion. This leads to undesirable concentration of stress at these inner and outer edge portions.
The applicant therefore earlier proposed a structure for relieving the concentration of stress at the inner edge and outer edge of the diaphragm. This structure, which is disclosed in JU-B 3-118346, is obtained by thinning the diaphragm at its middle portion and thickening it at both edge portions. However, this publicatio
REFERENCES:
patent: 4817457 (1989-04-01), Carlson
patent: 5269202 (1993-12-01), Kiyosawa et al.
patent: 5282398 (1994-02-01), Ishikawa
patent: 5388483 (1995-02-01), Ishida et al.
patent: 5429556 (1995-07-01), Ishida et al.
patent: 5485766 (1996-01-01), Ishikawa
patent: 5662008 (1997-09-01), Aubin et al.
Shirasawa Naomi
Takizawa Noboru
Harmonic Drive Systems Inc.
Kwon Peter T.
Ta Khoi Q.
LandOfFree
Harmonic flexible meshing gear device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Harmonic flexible meshing gear device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Harmonic flexible meshing gear device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2069458