Machine element or mechanism – Gearing
Reexamination Certificate
1999-08-11
2001-08-07
Marmor, Charles A (Department: 3681)
Machine element or mechanism
Gearing
C384S512000
Reexamination Certificate
active
06269711
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a transmission device using a flexible gear (hereafter referred to as a flexible type transmission device, when applicable) which provides a speed-reduced output using a large number of external teeth on a flexible member capable of flexing substantially in an elliptical manner and a large number of internal teeth capable of meshing partially with the external teeth. The flexible type transmission device can be used not only as a speed-reducing device, but also as a speed-increasing device and a differential device.
A flexible type transmission device generally comprises: a fixed case (serving as a circular spline) including a large number of internal teeth formed on the inner periphery thereof; a flexible member (serving as a flexible spline) inserted into the fixed case and including a large number of external teeth formed on the outer periphery thereof with the number of the external teeth slightly smaller than the number of the internal teeth of the fixed case, the external teeth being capable of partially meshing with the internal teeth of the fixed case when the flexible member is flexed substantially in an elliptical manner; a wave generator accommodated within the flexible member and rotatable with respect to the flexible member for applying a substantially elliptical flexural deflection to the flexible member; and, an output member connected to the flexible member. To rotatably support the output member on the fixed case, interposed between the fixed case and output member is a cross roller bearing composed of a large number of cylindrical-shaped rollers arranged in the peripheral direction thereof with the inclining directions thereof alternately reversed. Alternatively, there is interposed a taper roller bearing composed of two roller races, each roller race including a large number of cylindrical-shaped rollers disposed in the peripheral direction and spaced from one another, the rollers of the respective roller races being inclined in the opposite directions with respect to the axial direction.
However, the above-noted support structure for the flexible type transmission device suffers from a problem in that since the outer surfaces of the rollers of the cross roller bearing or taper roller bearing are slidingly contacted with the output member and the race surfaces of the fixed case during the rotation of the output shaft, the rollers, output member and fixed case are worn out early and thus the service lift of them is shortened. Further, the cross roller bearing and taper roller bearing are both expensive generally.
SUMMARY OF THE INVENTION
The invention aims at eliminating the drawbacks found in the above-structured transmission device. Accordingly, it is an object of the invention to provide a flexible type transmission device which can be manufactured at a low cost as well as can extend its life.
In attaining the above object, according to a first aspect of the invention, there is provided a flexible type transmission device, comprising: a case including a large number of internal teeth formed on the inner periphery thereof; a flexible member which is inserted into the case and includes a large number of external teeth formed on the outer periphery thereof in such a manner that, when the flexible member is flexed and deformed in a substantially elliptical manner, the external teeth partially mesh with the internal teeth of the case; a wave generator accommodated within the flexible member and rotatable with respect to the flexible member for applying substantially elliptical flexure and deformation to the flexible member; and, a support member connected to the flexible member, wherein an angular ball bearing is interposed between the case and support member, whereby the support member and case are supported by the angular ball bearing in such a manner that they can be rotated with respect to each other.
According to a second aspect of the invention, there is provided a flexible type transmission device, comprising: a case including a large number of internal teeth formed on the inner periphery thereof; a flexible member which is inserted into the case and includes a large number of external teeth formed on the outer periphery thereof, the external teeth being partially in mesh with the internal teeth of the case; a wave generator accommodated within the flexible member and rotatable with respect to the flexible member for applying substantially elliptical flexural deformation to the flexible member; and, a support member including on the inner periphery thereof a large number of inner teeth, the number of the inner teeth of the support member differing from the number of the internal teeth of the case, the internal teeth being partially in mesh with the external teeth of the flexible member, wherein an angular ball bearing is interposed between the case and support member, whereby the support member and case are supported by the angular ball bearing in such a manner that they can be rotated with respect to each other.
In the transmission device structured according to the first aspect of the invention, since there is interposed the angular ball bearing between the case and support member, even if a thrust load and a radial load are acting thereon, the support member can be rotated smoothly. Because the angular ball bearing supports the loads with its rolling contact, there is hardly produced friction, which makes it possible to extend the life of the transmission device. Also, since the angular ball bearing is more inexpensive than the cross roller bearing and taper roller bearing, the production cost of the transmission device can be lowered. The transmission device structured according to the second aspect of the invention can obtain similar operation and effects as those described above.
If the transmission device is structured in such a manner the flexible member and the support member are formed as a single unitary member, the flexible member and support member can be worked at the same time, resulting in the enhanced concentricity thereof. And, there is eliminated the need for use of members which have been conventionally used to fasten together the flexible member and support member, such as bolts, positioning pins, O rings and the like. This not only can simplify the structure of the transmission device, but also eliminates the need for execution of operations for fastening together the flexible member and support member, such as an operation to work holes for the bolts, an operation to work holes for the positioning pins, an operation to work grooves for the O rings, an operation to screw the bolts, and the like, thereby being able to simplify the manufacturing process of the transmission device. Further, it is possible to omit the boss portions that have been conventionally used to fasten together the flexible member and support member. Moreover, it is possible to form a thickness reduced portion (a hollow portion) in the central portion of the support member without degrading the sealing property thereof. Consequently, the weight of the transmission device can be reduced.
Assuming that the race surface of the angular ball bearing is formed directly on the outer surface of the support member, it is inevitable to employ an expensive thermal treatment (for example, high-frequency quenching) in order to increase the surface hardness of the race surface only. This can be overcome with the use of the structure in which a discrete inner race member is fixed to the support member. To harden the race surface of the angular ball bearing requiring high hardness, the inner race member is subjected to an inexpensive thermal treatment (for example, simple quenching, i.e. simply dipping the heated inner race member into a fluid) prior to fixing the inner race member onto the support member. Therefore, the hardening operation can be made inexpensive and easy.
It is preferable to form portions, each V-shaped in section, on the inner race member and the case as inner and outer race surfaces and hold a lar
Akin Gump Strauss Hauer & Feld L.L.P.
Ho Ha
Marmor Charles A
Teijin Seiki Company Limited
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