192 clutches and power-stop control – Elements – Clutch element resiliently carried on hub
Reexamination Certificate
1999-09-09
2001-06-12
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Elements
Clutch element resiliently carried on hub
C192S10700R, C192S10700R, C219S091200
Reexamination Certificate
active
06244414
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to friction clutches and in particular to the structure of clutch driven discs.
BACKGROUND OF THE INVENTION
Clutches are well known devices used to selectively connect a source of rotational power, such as the crankshaft of an internal combustion engine and its flywheel, to a driven mechanism, such as a transmission. Typically, clutches have a driven disc rotatably fixed to the transmission input shaft and axially disposed between a flywheel and a pressure plate. Both the flywheel and the pressure plate are rotatably fixed to the output shaft of the engine. The pressure plate is axially biased toward the flywheel by an axial spring load. When the clutch is in an engaged condition, the pressure plate clamps the driven disc against the flywheel. Friction material is disposed on both sides of the driven disc to resist slipping between the driven disc and both the pressure plate and the flywheel. When the clutch is in a released condition, the axial spring load is overcome by a release mechanism, unclamping the driven disc. With the driven disc unclamped, relative rotation between the transmission input shaft and the engine output shaft becomes possible. When the clutch is reengaged, the pressure plate is pressed against the friction material, halting relative rotation between the engine output shaft and the transmission input shaft.
When the clutch is reengaged, and to a lesser degree when the clutch is released, the friction material wears due to the contact at relative speed with the pressure plate and flywheel.
Commonly, the friction material on the driven disc is provided in the form of a plurality of discrete elements or cookies. The cookies are adhesively bonded or brazed to metal plates to form friction material buttons. The buttons are in turn fixed to radially extending paddles of the driven disc assembly by rivets which pass through laterally extending flanges of the backing plates overlying the paddles. The thickness of the rivet heads limits the amount of the friction material available for wear which can be usefully employed to provide engagement between the engine and the transmission. To compensate for the rivet head thickness, the friction material is made thicker than would otherwise be necessary. Also, the backer plate and the disc paddles are both larger than the cookies to enable the buttons to be riveted to the paddles at their outer edges.
Disadvantages of riveting the buttons to the paddles include: the need to provide the necessary extra thickness of friction material for clearing the rivet heads and the associated increased rotational inertia contributed by the friction material; the extra rotational inertia attributable to the extra backer plate material and extra disc material used at the rivet locations; and a susceptibility to warpage of the cookie, characterized by the center or edges of the friction material lifting off of the backer plate with usage of the clutch and wear of the friction material.
It is desired to provide a driven disc with a reduced height attachment for friction material buttons which alternatively enables the use of thinner friction material cookies or extended wear of the friction material. It is also desired to provide a driven disc assembly having lower inertia. It is also desired to provide a driven disc having the buttons mounted thereto in such a manner that the tendency of the cookies to distort relative to the driven disc is reduced.
It is also desired to provide a method of making a driven disc having a reduced height attachment for friction material buttons which enables the use of thinner friction material cookies, or, alternatively, enables the extended wear of the friction material. It is also desired to provide a method of making a driven disc having lower inertia. It is also desired to provide a driven disc having buttons mounted thereto in such a manner that any tendency of the cookies to distort relative to the driven disc is reduced.
SUMMARY OF THE INVENTION
A clutch driven disc assembly includes a hub and an annular spring plate fixed to the hub. A friction disc assembly is mounted concentric with an axis of rotation of the hub and is rotatably relative to the spring plate. A plurality of drive springs are operably disposed between the spring plate and the friction disc assembly. The friction disc assembly further includes a reinforcing plate and a substantially annular disc fixed to the reinforcing plate. A friction material button is fixed to the annular disc. Friction material button has a metallic friction material cookie with at least three apertures. A backer plate is fixed to the friction material. At least three spot welds are within three corresponding apertures in the cookie. At least one of the welds are offset from a line joining two others of the welds. The welds join the substantially annular disc and the backer plate, in turn fixing the friction material button to the substantially annular disc.
A method for fabricating a clutch driven disc including the steps of forming a hub, and rotatably fixing an annular spring plate to the hub concentric thereto. A friction disc assembly is mounted concentric with the hub for rotation relative to the spring plate. A plurality of drive springs are installed between the spring plate and the disc assembly. The friction disc assembly is formed by forming both a reinforcing plate having spring pocket configured to receive the drive springs, by forming a substantially annular disc extending radially beyond the reinforcing plate, and fixing the substantially annular disc to the reinforcing plate. A cookie is formed out of metallic friction material so as to have at least three apertures therethrough. The apertures in the cookie are oriented so that at least one of the apertures is offset from a line joining two others of the apertures. A backer plate of is formed of steel. The friction cookie is brazed to the backer plate to form a friction material button. The friction material button is welded to the annular disc by forming spot welds aligned with the apertures in the cookies.
A method of fixing a friction material cookie to a driven disc paddle including the steps of forming a disc having a radially extending paddle and forming a friction material cookie of sintered metal having at least three apertures therethrough. The apertures are oriented in the cookie so that at least one of the apertures is offset from a line joining two others of the apertures. A backer plate is formed of steel. The friction cookie is brazed to the backer plate to form a friction material button. The friction material button is spot welded to the annular disc by forming spot welds aligned with the apertures in the cookies.
The invention provides a clutch driven disc with a reduced height attachment for friction material buttons which alternatively enables the use of thinner friction material cookies or extended wear of the friction material. The invention also provides a driven disc assembly having lower inertia than a clutch driven disc employing rivets to join friction material buttons to the driven disc. The invention also provides a driven disc having the buttons mounted thereto in such a manner that the tendency of the cookies to distort relative to the driven disc is reduced.
The invention additionally provides a method of making a driven disc having a reduced height attachment for friction material buttons enabling the use of thinner friction material cookies, or, alternatively, enabling the extended wear of the friction material. The invention provides a method of making a driven disc having lower inertia. The invention also provides a driven disc having buttons mounted thereto in such a manner that any tendency of the cookies to distort relative to the driven disc is reduced relative to distortion which would be anticipated for cookies fixed to a clutch driven disc by rivets passing through latterly extending flanges of the backer plates.
REFERENCES:
patent: 1085769 (1914-02-01), Thomson
patent: 3037860 (1962-06-01),
Dykema Gossett PLLC
Eaton Corporation
Lorence Richard M.
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