Transmission

Details Transmission Transmission

1999-11-03

2002-01-08

Bucci, David A. (Department: 3611)

Endless belt power transmission systems or components

Pulley with belt-receiving groove formed by drive faces on...

Fluid pressure actuator for adjustment of member

C474S018000, C474S070000

Reexamination Certificate

active

06336879

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to improvements in transmissions, and more particularly to improvements in transmissions which constitute or resemble so-called continuously variable transmissions (CVT). Still more particularly, the invention relates to improvements in apparatus which can be utilized to transmit variable torque in transmissions of the above outlined character and embody so-called torque sensors.
It is known to provide a continuously variable transmission with a mechanical or other suitable torque sensor which is (or can be) integrated into a pulley of the transmission. As a rule, the transmission comprises at least two pulleys which are mounted on discrete parallel shafts, and an endless flexible element (such as a belt or a chain) which is trained over the pulleys. Each pulley comprises a first conical flange which is rigidly affixed to (e.g., of one piece with) the respective shaft, and a second conical flange which is rotatable with the respective shaft and is movable axially of the shaft toward and away from the respective first flange. If the transmission comprises a torque sensor, such device serves to vary the pressure of a hydraulic fluid in at least one plenum chamber (which is adjacent the axially adjustable flange of one of the pulleys) as a function of variable torque being transmitted by the transmission.
The torque sensor can comprise rolling elements abutting cam faces provided on two components which are movable relative to each other; the rolling elements transmit torque which is being applied to the flanges of the corresponding pulley. The two components of the torque sensor move relative to each other (to thus influence fluid pressure in the at least one plenum chamber) in response to changes of the magnitude of torque being transmitted by the transmission and the resulting movements of the rolling elements along the cam faces.
A continuously variable transmission of the above outlined character is disclosed, for example, in published German patent application Serial No. 42 34 294 A1. This transmission comprises a torque sensor wherein one of the cam faces for the rolling elements (each of which is a sphere) is provided on a seal carrier; the latter is adjacent that side of an axially movable flange which faces away from the associated axially fixed flange of one of two pulleys forming part of the transmission. The seal carrier is adjacent and bounds a portion of a radially outer plenum chamber, namely the plenum chamber which confines the rolling elements of the torque sensor and contains a supply of fluid having a pressure corresponding to the torque being then transmitted by the transmission. The seal carrier further bounds a portion of a radially inner second plenum chamber. The pressure of fluid in the second plenum chamber is variable to thus select the ratio of the continuously variable transmission.
The other cam face for the rolling element or elements of the torque sensor disclosed in the aforementioned published German patent application is provided on a piston which is movable axially of the respective shaft and is outwardly adjacent the seal carrier (the latter is disposed between the piston and the axially movable flange of the respective pulley). The piston receives torque from a gear which mates with teeth provided on the piston. Axial movements of the piston result in controlled changes of the rate of fluid flow from a plenum chamber associated with that one of the aforementioned chambers which serves to determine the extent of frictional engagement between the flanges of the pulley and the adjacent surfaces of the endless flexible device (e.g., a chain).
In order to regulate the torque in dependency upon the selected transmission ratio, the rolling elements of the torque sensor are acted upon by an annular biasing member which urges them radially outwardly against the conical guide surface of a member which is rigidly secured to the axially movable flange of the respective pulley. The rolling elements are compelled to move radially inwardly and to roll along different portions of the properly configurated (three-dimensional) cam faces when the distance between the cam faces decreases.
A drawback of the aforedescribed continuously variable transmission is that the torque sensor and the mode of installing it in the transmission are quite complex and expensive. Thus, the number of discrete component parts is very high. Furthermore, the transmission is bulky, i.e., it occupies much room (as seen in the axial direction of its shafts) and a large number of its parts must be installed outside of the plenum chambers.
Another continuously variable transmission which embodies a torque sensor having spherical rolling elements between two cam faces in the form of ramps is disclosed in U.S. Pat. No. 5,295,915 granted Mar. 22, 1994 to Oswald Friedmann for “CONTINUOUSLY VARIABLE SPEED TRANSMISSION”. U.S. Pat. No. 5,667,448 granted Sep. 16, 1997 to Oswald Friedmann for “POWER TRAIN” discloses a further continuously variable transmission, and a continuously variable transmission with a hydromechanical torque sensor is disclosed in U.S. Pat. No. 5,711,730 granted Jan. 27, 1998 to Oswald Friedmann et al. for “TORQUE MONITORING APPARATUS”. The disclosures of the German priority application Serial No. 198 50 527.2 filed Nov. 3, 1998, of the aforementioned published German patent application Serial No. 42 34 294 A1, and of all other US and foreign patents and patent applications identified in the present application are incorporated herein by reference.
OBJECTS OF THE INVENTION
An object of the invention is to provide a continuously variable transmission which employs an integrated torque sensor and is more compact and comprises fewer parts (i.e., it is less expensive) than heretofore known transmissions.
Another object of the invention is to provide an apparatus which embodies a novel and improved torque sensor and can be installed in a continuously variable transmission to achieve savings in space, a reduction of the overall number of parts and other important savings and improvements.
A further object of the invention is to provide a continously variable transmission with a novel and improved combination of parts which render it possible to take advantage of space that remains unoccupied in heretofore known continuously variable transmissions.
Still another object of the invention is to provide a novel and improved torque sensor which can be utilized in the power trains of motor vehicles or in other power trains which employ continuously variable transmissions.
A further object of the invention is to provide novel and improved pulleys for use in a transmission of the above outlined character.
Another object of the invention is to provide a motor vehicle wherein the power train embodies a continuously variable transmission of the above outlined character.
An additional object of the invention is to provide a continuously variable transmission wherein certain parts are capable of additional use in a motor vehicle or elsewhere.
SUMMARY OF THE INVENTION
One feature of the present invention resides in the provision of an apparatus which is constructed and assembled to transmit variable torque and comprises a shaft which is rotatable about a predetermined axis, a pulley including a first flange affixed to the shaft for axial and angular movements with the shaft and a second flange which is rotatable with the shaft but is movable relative to the shaft in the direction of the predetermined axis toward and away from the first flange, an endless flexible torque transmitting device (such as a chain or a belt) which is trained over the pulley, a fluid-containing plenum chamber at the second flange, and a torque sensor which is arranged to vary the pressure of fluid (such as oil) in the chamber in dependency upon the magnitude of the torque being transmitted by the improved apparatus. The torque sensor comprises first and second components having confronting cam faces (or analogous surfaces) and rolling elements disposed between the cam

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