Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Load responsive
Reexamination Certificate
2000-02-23
2001-08-21
Wright, Dirk (Department: 3681)
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Load responsive
Reexamination Certificate
active
06277043
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This Application claims foreign priority benefits under 35 U.S.C. § 119(a)-(d) to German patent application 199 07 816.5, filed Feb. 24, 1999 by inventor, Oswald Friedmann, for an invention entitled, “Getriebe” (Transmission).
BACKGROUND OF THE INVENTION
Field of Invention
This invention relates to improvements in power trains of the type wherein the means for transmitting torque from the rotary output element of a primary power source (such as an internal combustion engine) to a rotary driven element (such as the output shaft of an infinitely variable speed transmission) comprises a torque monitoring sensor integrated with such transmission, in which an endless flexible element (such as a belt or chain) is trained over a pair of adjustable pulleys or sheaves. Each pair of sheaves is adjustable by the torque sensor in response to abrupt changes in the transmitted torque to vary the transmission ratio. More particularly, the present invention relates to the integration of wear reduction elements into such a torque monitoring sensor, which function to minimize the hysteresis associated with physical strains introduced into the torque transmitting apparatus in response to abrupt changes in the load or in the torque being transmitted.
DESCRIPTION OF RELATED PRIOR ART
An infinitely variable ratio transmission, which can be utilized in conjunction with the improved torque sensor of the present invention is disclosed in U.S. Pat. No. 5,169,365 to Friedmann and is incorporated herein by reference. The disclosure in U.S. Pat. No. 5,879,253 entitled: “Torque Monitoring Apparatus”, filed Nov. 26, 1997 by inventors, Oswald Friedmann and Armin Veil, is hereby incorporated herein by this reference; and the disclosure in U.S. Pat. No. 5,725,447 entitled: “Power Train with Infinitely Variable Ratio Transmission”, filed Dec. 14, 1995, by inventors, Oswald Friedmann, Urban Panther, and Ivo Agner, is also hereby incorporated herein by this reference. The torque sensors, which are disclosed in these prior patents, are designed to establish a clamping engagement between component parts of a torque transmitting apparatus depending upon the load or depending upon the transmitted torque. As a rule such torque sensors are designed to ensure a frictional engagement between component parts, which are urged against or toward each other by a force depending upon the transmitted loads or upon the transmitted torque, in such a way that the force acting to urge the component parts into frictional engagement with one another at least approximates the force, which is necessary for the transmission of torque. The application of an excessive force for urging the component parts against each other results in excessive wear whereas the application of an insufficient force entails a slip and hence again excessive wear between the parts which are maintained in frictional engagement with one another.
A conventional torque monitoring sensor includes a valve whose operation depends upon the magnitude of transmitted torque. Those portions of the torque sensor which are located downstream of a plenum chamber are constructed and assembled to comprise the aforementioned valve and the plenum chamber receives pressurized hydraulic fluid from a suitable pump. The valve acts as a flow restrictor or throttle, which seals the path for the flow of fluid from the plenum chamber so that the pressure of fluid in the plenum chamber increases in response to abrupt increases or peaks of transmitted torque. This results in a corresponding rise of fluid pressure in the plenum chamber as well as in the cylinder chamber or chambers of one or more piston and cylinder units. The piston and cylinder units are provided to adjust the infinitely variable transmission including a pair of adjustable tapered discs or sheaves and an endless flexible element, which is trained over and serves to transmit torque between the adjustable sheaves. The flexible element may constitute either a belt or a chain.
An increase in pressure in the cylinder chamber or chambers brings about a corresponding increase of the clamping force between the endless flexible element and the sheave or sheaves of the transmission. In other words, the frictional engagement between the sheave or sheaves on the one hand and the flexible element on the other hand increases in response to an increase of the transmitted torque and/or in response to the development of an abrupt increase of transmitted torque.
In order to adjust the above-described valve, the torque monitoring sensor includes so-called cam discs that are provided with confronting cam faces or ramps bearing upon spherical rolling elements, which are retained between them with a force generated by the source of pressurized hydraulic fluid. If the transmitted torque develops abrupt increases or peaks, especially peaks in the torque being transmitted from the primary power source, the cam discs are caused to move axially and away from each other such that an axially movable portion reduces the effective cross-sectional area of the outlet for the flow of hydraulic fluid from the plenum chamber at a rate proportional to the magnitude of the peaks of transmitted torque.
In addition, the cam discs serve as a means for mechanically transmitting at least a portion of the driving torque to adjust the effective cross-sectional area of the outlet from the plenum chamber as a function of the magnitude of transmitted torque. Thus, the proper frictional clamping force between the adjustable sheaves and the endless flexible element of the infinitely variable transmission is maintained.
This so-called pumping action in the torque sensor introduces severe physical strains and high axial thrust forces and on the rotating and axially displaceable components in the torque sensor, which can cause premature wear of such components and mechanical failure of the torque transmitting apparatus. Thus, the present invention provides wear reduction elements which are integrated into these components of the torque sensor to minimize the hysteresis produced by the pumping action of the torque monitoring sensor in normal operation.
SUMMARY OF THE INVENTION
Accordingly, the present invention is an improved torque sensor for an infinitely variable ratio transmission, which includes wear reduction elements integrated into components of the torque sensor or, in the alternative, wear reduction elements mechanically adaptable to such components. The present wear reduction elements are designed to elastically compensate for the physical strains, axial thrust forces and mechanical friction, which are introduced to the rotating and axially displaceable components of the torque sensor during the so-called pumping action of the torque sensor in response to abrupt changes in the load or torque being transmitted in normal operation.
In one embodiment the present wear reduction elements include the formation of a symmetrical pattern of circumferentially arranged slots in the cylindrical sheet metal housing of an axially displaceable cam disc component to provide a degree of structural flexibility to the housing. So modified, the cam disc housing undergoes slight flexion in response to micro-movements produced by physical strain and/or axial thrust in the supporting bearings to prevent translation of such micro-movements into premature frictional wear of axially displaceable splines and other components in the torque transmitting apparatus.
In an alternative embodiment such physical strains and/or axial micro-movements between torque sensor components are compensated for by the installation of spring elements, which are disposed between the axially displaceable cam disc and the mating components thereof to resiliently absorb such movements in the torque monitoring sensor.
In view of the above it is an object of the present invention to provide an improved torque monitoring sensor for an infinitely variable transmission incorporating wear reduction elements for minimizing the hysteresis associated with physical strains and/or axi
LuK Lamellen und Kupplungsbau GmbH
Mangels Alfred J.
Wright Dirk
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