Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Load responsive
Reexamination Certificate
2001-05-07
2003-01-14
Estremsky, Sherry (Department: 3681)
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Load responsive
C474S028000
Reexamination Certificate
active
06506136
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to change speed transmissions in general, and more particularly to improvements in transmissions of the type known as continuously variable transmissions (CVT) which can be utilized with advantage in the power trains of motor vehicles, e.g., to transmit torque from the output element of a prime mover (such as the camshaft or the crankshaft of an internal combustion engine) to the front and/or rear wheels of a motor vehicle.
A continuously variable transmission normally comprises a first shaft which can receive torque from a prime mover, a second shaft which is or can be parallel with the first shaft, an adjustable pulley or sheave on each of the two shafts, and an endless flexible element (such as a chain or a belt and hereinafter referred to as chain) trained over the two pulleys to transmit torque from the first shaft to the second shaft when the first shaft is driven by the prime mover. The two pulleys are adjustable and, to this end, each pulley comprises a first conical flange which is affixed to the respective shaft, and a second conical flange which is rotatable with the first flange and is movable axially relative to the respective shaft toward and away from the respective first flange. Such adjustability of the pulleys enables the chain to move one of its looped portions radially inwardly toward one of the shafts while its other looped portion moves radially outwardly and away from the other shaft, or vice versa.
It is already known to make at least one flange of each adjustable pulley of one or more parts at least one of which consists of a metallic sheet material. This contributes to lower cost and to a reduction of the overall weight of the transmission. The axially movable flanges normally cooperate with cylinder and piston units which define with the movable flanges one or more plenum chambers for the reception of a hydraulic fluid which compels the respective mobile flange to move axially toward the associated axially fixed flange. Such movability of the axialy movable flanges is utilized to establish a desired amount of friction between the chain and the adjacent conical surfaces of the flanges (this ensures that the chain shares the angular movements of the flanges or that the chain is entrained with a desired degree of slip) Axial movability of one flange of each pulley is further utilized to select a desired transmission ratio by moving one looped portion of the chain away from the periphery of the respective shaft while the other looped portion of the chain is compelled to move toward the periphery of the associated shaft.
Continuously variable transmissions are often preferred over automatic transmissions which employ a hydrokinetic torque converter in combination with a so-called bypass or lockup clutch. The reason is that a power train employing a continuously variable transmission affords a greater comfort to the occupant or occupants of the motor vehicle because the shifts into different gear ratios invariably take place gradually without any or without appreciable shocks. Moreover, the utilization of a continuously variable transmission in the power train entails substantial savings in fuel requirements of the motor vehicle.
Published German patent application Serial No. 43 42 736 A1 discloses a continuously variable transmission wherein the axially shiftable flange of each adjustable pulley is located between the corresponding axially fixed flange and a support which is affixed to the respective shaft. The support and the adjacent axially movable flange define a plenum chamber which can receive pressurized hydraulic fluid to move the axially movable flange toward the respective fixedly mounted flange. The flanges are or can be made of a metallic sheet material, and this can entail considerable savings in the initial cost of the adjustable pulleys. However, the axially movable flanges and the adjacent fixedly mounted supports are designed to define a single plenum chamber for each of the two pulleys. This is unsatisfactory in those types of continuously variable transmissions wherein each axially shiftable flange must be adjusted by a first unit to select the frictional engagement with the adjacent portion of the chain as well as by a second unit which enables the transmission to select the desired speed ratio, i.e., any one of an infinite number of different speed ratios.
OBJECTS OF THE INVENTION
An object of the invention is to provide a novel and improved continuously variable transmission, particularly for use in the power trains of motor vehicles.
Another object of the invention is to provide novel and improved adjusting means for the adjustable flanges of pulleys which can be utilized in continuously variable transmissions.
A further object of the invention is to provide novel and improved fluid-operated adjusting systems for the adjustable flanges of pulleys in continuously variable transmissions.
An additional object of the invention is to provide novel and improved adjustable pulleys for use in continuously variable transmissions.
Still another object of the invention is to provide a power train which is designed for use in motor vehicles and embodies a continuously variable transmission of the above outlined character.
A further object of the invention is to provide a transmission which constitutes an improvement over and a further development of continuously variable transmissions of the type disclosed in published German patent application Serial No. 43 42 736 A1.
Another object of the invention is to provide a simple, compact and inexpensive continuously variable transmission which can be utilized as a superior substitute for heretofore known transmissions of such character in the power trains of motor vehicles.
An additional object of the invention is to provide novel and improved combinations of axially movable conical flanges and moving means therefor for use in power trains employing continuously variable transmissions.
SUMMARY OF THE INVENTION
One feature of the present invention resides in the provision of a transmission, such as a continuously variable transmission, which comprises a shaft rotatable about a predetermined axis, and a pulley having a first flange affixed to the shaft and a second flange rotatable with and movable axially of the shaft toward and away from the first flange. The flanges have confronting conical surfaces which surround an annular space having a width, as seen in the axial direction of the shaft, which varies in response to movement of the second flange relative to the first flange. At least one of the flanges comprises a plurality of interconnected components consisting at least in part of a metallic sheet material. The transmission further comprises an endless flexible element which is trained over the pulley and includes a looped portion received in the aforementioned annular space, and means for moving the second flange. The moving means includes a support which is affixed to the second flange and the latter is disposed between the support and the first flange. The support and the second flange define a plurality of annular plenum chambers, and the moving means further comprises means for sealing the chambers; such sealing means extends in at least one of a plurality of directions including radially and axially of the shaft.
The at least one flange is or can constitute the axially movable second flange; such second flange has a side which confronts the support and is or can be defined by at least one of the components which consist of or contain sheet metal. The at least one component can comprise a conical disc and the support can comprise a supporting part non-rotatably mounted on the shaft, a frustoconical part connected with a median portion of the at least one component and extending from the at least one component axially end radially of the shaft toward the periphery of the shaft, and a second component remote from the axis of the shaft and defining with the frustoconical part one of the plenum chambers.
In accordance with a presently preferred
Eidloth Rainer
Hölz Roland
Schmid Jochen
Walter Bernhard
Weinhold Carsten
Estremsky Sherry
Lewis Tisha D.
LuK Geriebe-Systeme GmbH
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