Planetary gear transmission systems or components – Nonplanetary variable speed or direction transmission... – Nonplanetary transmission is friction gearing
Reexamination Certificate
2002-01-11
2003-05-06
Estremsky, Sherry (Department: 3681)
Planetary gear transmission systems or components
Nonplanetary variable speed or direction transmission...
Nonplanetary transmission is friction gearing
C475S185000, C476S048000, C476S045000
Reexamination Certificate
active
06558286
ABSTRACT:
FIELD OF INVENTION
The present invention relates to the field of machine-building and, in particular, to a continuously variable transmission and may be used in various fields of technology in cases where it is necessary to ensure continuously variable torque transmission while adjusting the transmission ratio depending on a load at the transmission output. It may be used, in particular, for means of transportation and variable-speed drive units.
PRIOR ART
At present, continuously variable transmissions made on the basis of a friction variable-speed drive are of wide use.
Known in the art is a planetary friction variable-speed drive comprising the outer central friction discs and the intermediate conical friction discs as well as the pressure members that apply an axial action to the central friction discs and the intermediate conical discs arranged therebetween, a radial movement of the intermediate discs and associated change in the transmission ratio of the variable-speed drive taking place due to applying an axial action to the said discs. Thus, the pressure members are at the same time mechanisms changing the transmission ratio. GB Patent 1384679, IPC
6
F16H 15/50, 1975.
The closest to the claimed solution under the first variant as to the technical substance and achieved result is a continuously variable transmission comprising a planetary friction variable-speed drive consisting of the inner and outer central friction discs laterally embracing the intermediate friction discs, a mechanism for combined modification of the transmission ratio and of the pressure made in the form of rotating levers carrying the intermediate friction discs and arranged on the planetary variable-speed drive carrier with the possibility of changing the position of the rotating levers. Patent RF 2091638 IPC
6
F16H 15/52, 1997 (the prototype). In the known solution the mechanisms for combined modification of the transmission ratio and of the pressure press the central friction discs to the intermediate discs with forces proportional to transmitted torques, subject to pre-pressing by springs.
The prototype transmission has several inherent deficiencies, namely:
the pressure members of the mechanism for combined modification of the transmission ratio and pressure are complex, and, what is most important, they do not solve the task of optimal pressing the discs to each other due to the fact that the friction coefficient at the points of the friction oil contact is varied greatly; according to the results of the study performed by the author the value of this coefficient for the central inner friction discs is varied in the range from 0.015 to 0.03 and for outer ones
from 0.02 to 0.08; therefore the pressure, which is proportional to the torque only, does not achieve the required result in the planetary systems;
the systems of pressure members of the said mechanisms, including automatic adjustment with pre-pressing by a spring with a force that is usually corresponds to 25-35% of the maximum force, also do not achieve the required result; there the initial working adjustment for an outer central friction disc should be app. 5-7% of the maximum force, and even that, the most complex, combined system creates the pressure 5 times greater than the necessary one and leads to a sharp reduction in the efficiency, but for a car transmission this working mode is most widely used, especially when moving along a road (at the highest transmission);
the friction coefficient depends heavily on the rotation speed of the variable-speed drive shafts, and the above pressure members system do not enable to correct it.
The closest to the claimed solution under the second variant as to the technical substance and achieved result is a continuously variable transmission comprising a planetary friction variable-speed drive consisting of the inner and outer central friction discs laterally embracing the intermediate friction discs, a mechanism for combined modification of the transmission ratio and of the pressure made in the form of rotating levers carrying the intermediate friction discs and arranged on the planetary variable-speed drive carrier with the possibility of changing the position of the rotating levers by pushers moved along guides. Patent RF 2091637 IPC
6
F16H 15/52, 1997 (the prototype).
A specific feature of the invention according to the prototype is that the pushers are spring-loaded to the guides by centrifugal forces created due to the unbalanced state of the rotating levers relative to their rotation. Such implementation creates very inconvenient conditions of loading the pushers, resulting in inaccuracy and low reliability of regulation. For example, given the rotation speed of a low-speed shaft is changed tenfold (this is the real range of a variable-speed drive transmission-ratio variation), the centrifugal force varies hundredfold, the torque “exerting a counter-action” to that force in the regulation system varies approximately tenfold, and the maximum torque, which on a low-speed shaft corresponds to the minimum rotation speed, will just correspond to the minimum centrifugal force. Practical studies have showed that such a system does not ensure the necessary accuracy of the transmission-ratio regulation.
DESCRIPTION OF THE INVENTION
The objective of this invention is to create a continuously variable transmission on the basis of a variable-speed friction disc drive having a higher efficiency, durability, reliability and convenient in operation due to simplifying the design of the mechanism for combined modification of the transmission ratio and pressure, ensuring compliance of the friction discs pressure force in different operation modes with the transmission ratio value as well as due to dependence of the variable-speed drive transmission ratio on the output shaft load.
According to the first variant, in order to achieve the said technical result in a known continuously variable transmission comprising a planetary friction variable-speed drive consisting of the inner and outer central friction discs laterally embracing the intermediate friction discs, a mechanism for combined modification of the transmission ratio and of the pressure made in the form of rotating levers carrying the intermediate friction discs and arranged on the planetary variable-speed drive carrier with the possibility of changing their position, the mechanism for combined modification of the transmission ratio and of the pressure is provided with power members applying an axial action, which are arranged on the end sides of the inner and outer central friction discs so as to ensure their contact in the annular areas opposite to the annular areas of contact between the inner and outer central friction discs and the intermediate friction discs, an average axial rigidity of the power members applying an axial action, which are brought into contact with the outer central friction discs, is made so as to be higher, in terms of absolute value, than an average axial rigidity of the power members applying an axial action, which are brought into contact with the inner central friction discs.
Some other embodiments of the first variant of this invention are possible, according to which it is advisable that:
a mechanism for combined modification of the transmission ratio and the pressure would be provided with support members arranged on the central shaft and on the epicycle on the rear side of the power members applying an axial action and made with the stops contacting the power members applying an axial action with the possibility of varying their axial rigidity both in magnitude and in negative/positive value;
each power member applying an axial action, as included in the mechanism for combined modification of the transmission ratio and the pressure, would be made in the form of a chamber communicating with the pressurized working medium and arranged on an epicycle with the possibility of pressing of, at least, one outer central friction disc to the respective intermediate friction discs depending on the working medium pressure
Dellett and Walters
Estremsky Sherry
Ferenc Martin
Lewis Tisha D.
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