Planetary gear transmission systems or components – Condition responsive control – Eccentrically weighted planet
Patent
1996-11-01
1999-10-19
Ta, Khoi Q.
Planetary gear transmission systems or components
Condition responsive control
Eccentrically weighted planet
475170, F16H 3318
Patent
active
059679336
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an automatic continuously variable positive mechanical transmission, comprising an input shaft, an output shaft, a point of support connected to a transmission case, a positive kinematic link provided with a planetary gear train unit and linking the input shaft, the point of support and the output shaft, and torque compensation means comprising eccentric weights subject to centrifugal forces which produce torques on two sets of planet wheels of the planetary unit. The invention also relates to a method for actuating such a transmission.
By the term positive kinematic link, we wish to designate here any link between moving or fixed parts by means of a positive engagement with cooperating shapes, preferably gears, but also other means with similar effects such as chains and toothed belts.
BACKGROUND OF THE INVENTION
Such a transmission is in particular usable in motor, rail or other vehicles, but also to drive any kind of variable speed machines, for example winches, ventilating fans, compressors, farmiing or public works machines, crushers, weaving machines, as well as to drive constant speed machines such as generators using wind power engines or variable speed turbines.
To drive motor vehicles, a standard type automatic transmission comprises a switchable gearbox, preceded by a fluffy torque converter. The latter presents losses of energy. At the present time, we are seeking to reduce these losses by adding a high gear clutch, as well as a power by-pass via a positive transmission channel arranged parallel to the converter. To make such a transmission work automatically and perfectly, an electronic control device is necessary. All these means further increase the complexity, the weight and the construction and maintenance costs.
This is why we are seeking to replace these transmissions by mechanisms of other types, which are continuously variable over the whole range of speeds of the output shaft, to avoid using a switchable gearbox. One known solution uses a variable speed belt and pulley drive with a variable diameter. These variable speed drives can have an automatic setting system based on the centrifugal force. However, the belt transmits the loads by friction and that always implies losses of energy and overheating problems which limit the application of these transmissions to the field of lower power outputs. Furthermore, there is always a risk of the belt slipping.
Moreover, we know of mechanical couplings allowing a difference in speed between the input shaft and the output shaft, due to a centrifugal torque compensation device which acts on a differential gear linking the input shaft to the output shaft. The patent GB-A-995305 describes a coupling of this type, where the planet wheels of the planetary differential gear each carry a secondary planetary gear train formed by a secondary planet wheel carrier integral with the main planet wheel four secondary planet wheels each provided with an eccentric weight, and a secondary planet pinion designed to hold each weight in a constant position in relation to the direction of the centrifugal force it is subject to, so that this force creates a centrifugal torque which is as even as possible while the unit rotates. A manual control device can act on the position of each secondary planet wheel to select one of four positions of the weights, i.e. in the respective positions of forward drive, neutral, reverse drive and lock against overdrive. In an alternative, the secondary planet wheels are replaced by a set of articulated levers carrying mobile weights which create a centrifugal torque on the main planet wheel. This is a complicated and delicate construction which is not suitable for transmitting high torques at high speeds. Above all, the major drawback inherent in such couplings is that they can not operate as torque converters, because there is no point of support or reaction point on a fixed part, for example a case. This is why they can not apply a torque greater than the input torque to the output shaft, whateve
REFERENCES:
patent: 1701823 (1929-02-01), Rhodes
patent: 1741862 (1929-12-01), Lyman
patent: 2564211 (1951-08-01), O'Hara
patent: 3363483 (1968-01-01), Osman
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