Patent Application
20070151825
The present invention relates generally to vehicle clutches, and more particularly relates to clutch actuating lever arrangements for friction clutches.
Clutches for vehicles are used to couple and decouple an engine to a drive shaft. Examples of prior art friction clutches are disclosed in U.S. Pat. Nos. 4,989,711 and 5,785,163, which are incorporated herein by reference. In such designs, clutch actuating levers are pivotally mounted on a pressure ring by devises and pins that allow each lever to centrifugally apply pressure to the pressure ring through its respective clutch clevis. A clutch clevis is a part of a friction clutch unit that provides support for the clutch lever and bolts to the clutch pressure ring. The pressure ring applies pressure to friction discs and steel plates. These components are attached to a clutch cover, which in turn is attached to a flywheel. The flywheel and clutch cover may be provided as a unit that is bolted directly to the back of a vehicle crankshaft. The clutch unit allows the vehicle to gradually move from a standing start by allowing the clutch to slip, thereby preventing the engine of the vehicle from stalling or straining, or preventing the drive tires from losing traction by applying too much power to the driveline.
Currently, actuating levers used in friction clutch units extend radially inward from the pressure ring toward the axial center of the clutch unit. Although effective, such radially aligned lever designs have shortcomings including limited gain in lever ratio, which prevents the clutch units from performing to their potential. Furthermore, the current radial lever design severely limits the diameter of clutch units that can be built. Because it is important that the lever and clevis apply an even plate load to the pressure ring, current designs prevent the manufacture of smaller, lighter and more efficient clutch designs.
Also, on smaller diameter clutch designs, the current radial levers cause uneven pressure applied from the lever through the clevis to the pressure ring because pressure is applied on the outer diameter of the pressure ring. This off-center pressure may cause permanent damage to the flatness of the pressure ring, which degrades operation of the clutch assembly. Because it is important for the pressure ring to remain flat throughout its life for maximum performance, a deformed or bent pressure ring causes a decrease in performance.
From the foregoing, it can be appreciated that there exists a need for a friction clutch actuating lever design that allows a gain in lever ratio while still providing the desired direct pressure from the lever to the clevis to the pressure ring without damage to the flat surface of the pressure ring, which in turn allows the design of smaller, lighter and more efficient clutch units.
The present invention provides an angled clutch actuating lever arrangement which allows friction clutches to gain greater amounts of lever ratio to the clutch pressure ring. The angled levers and their respective devises apply direct pressure at optimal locations on the pressure ring to achieve direct and even plate load through the levers to the pressure ring. Benefits of the present invention include increased lever ratios, the application of even plate loads to the clutch pressure ring, the reduction or elimination of flexing and permanent damage to the flatness of the pressure ring, the ability to produce smaller and lighter clutch units, and reduced effort in lifting of the pressure ring for disengagement of the clutch.
The present invention provides an efficient and effective friction clutch design. In one embodiment of the invention, each lever is pivotally attached to the clutch cover and to the pressure ring, and extends inwardly at an angle offset from the radial direction of the clutch unit, e.g., at an angle greater than 0° and less than 90° with respect to the radial direction. Because the levers are attached at such angles, additional lever ratio is obtained, and smaller, lighter and more efficient clutch units can be designed without compromising cross-directional load and proper direct pressure to the pressure ring. The present design reduces or eliminates the flexing that distorts or bends the pressure ring, while reducing the clutch peddle pressure required for clutch disengagement.
An aspect of the present invention is to provide a clutch cover and pressure ring assembly comprising a generally annular clutch cover having a central axis, a generally annular pressure ring having a central axis substantially aligned with the central axis of the clutch cover, wherein the clutch cover and pressure ring are rotatable with each other around their central axes and axially movable with respect to each other, and at least one actuating lever pivotally mounted on the clutch cover and/or pressure ring and extending radially inward at an angle offset from a radial direction of the clutch cover and pressure ring.
Another aspect of the present invention is to provide an annular clutch cover having a central axis and comprising a plurality of slots structured and arranged for receiving actuating levers, wherein each slot extends radially inward at an angle offset from a radial direction of the clutch cover.
A further aspect of the present invention is to provide an annular clutch pressure ring having a central axis and comprising a plurality of recesses structured and arranged to receive actuating levers, wherein each recess is oriented at an angle offset from a radial direction of the pressure ring.
These and other aspects of the present invention will be more apparent from the following description.
Details of the clutch cover 20 are most clearly shown in
As shown most clearly in
As shown in the bottom view of the clutch cover 20 in
Details of the clutch pressure ring 30 are provided in
As shown most clearly in
As most clearly shown in
The actuating levers 40 include an arm 41 extending radially inward toward a release tip 42. A hole 43 extends through an upper portion of each actuating lever 40 in order to allow the optional installation of bolts (not shown) or other centrifugal weights which may be used to adjust the amount of centrifugal force applied through the levers 40 during rotation of the clutch assembly. Each actuating lever 40 includes an elongated hole 44 which receives the pin 39 of a respective clevis 36 mounted on the pressure ring 30. Each actuating lever 40 also includes a pin 45 extending from opposite faces of the lever 40 which is received in a respective recess 28 of the clutch cover 20. The pin 45 may be fixedly mounted or rotatably mounted on the lever 40. Each lever 40 is thus pivotally mounted with respect to the pressure ring 30 by means of the hole 44 and clevis pin 39, and is also pivotally mounted with respect to the clutch cover 20 by means of the pins 45 received within the recesses 28. When the lever release tips 42 are forced downward (e.g., by a conventional throw out bearing - not shown), the pressure ring 30 is forced upward toward the clutch cover 20 against the bias of springs 33 to disengage the clutch. When the lever release tips 42 move upward due to centrifugal force generated by the rotating clutch unit, the pressure ring 30 is forced downward away from the clutch cover 20 to increase the clutch engagement force.
As an alternative embodiment, the lever 40 may be pivotally mounted on the clutch cover as shown in the figures, but the pivotal pressure ring mounting 44, 39 may be replaced with direct contact between the lever 40 and the upper surface of the pressure ring, in which case the bottom edge of the lever 40 may act as a cam surface against the pressure ring 30.
In accordance with the present invention, the actuating levers 40 are oriented at offset angles A from the radial direction of the assembly 10. The offset angle A enables the length of the lever arms 41 to be extended beyond the length possible with conventional radial lever designs. As shown in
The lever offset angle A may range from greater than 0° to less than 90°, for example, from about 5° to about 80°. Typically, the lever offset angle may range from about 10° to about 60°, for example, from about 20° to about 40°. For larger diameter clutches, smaller offset angles may be desirable.
The angled lever arrangement of the present invention also provides increased distance between the clevis pin hole 44 and the pin 45 of each actuating lever 40. This increased distance provides an increased lever ratio and an increased axial throw distance between the clutch cover 20 and pressure ring 30. In addition, the angled levers 40 and their respective clevises 36 apply pressure at optimal radial locations around the circumference of the pressure ring in order to achieve an evenly distributed plate load. This is accomplished by allowing the devises 36 to be centrally located C between the inner ID and outer OD diameters of the pressure ring 30, as shown in
Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. ______ entitled “Method of Clutch Lever Design for Friction Clutch Units” naming Robin Christopher Boninfante and Nicholas John Boninfante, Sr. as inventors, which was mailed by First Class mail to the U.S. Patent and Trademark Office on Jan. 4, 2005 and has a filing date of January ______ , 2005, and which is incorporated herein by reference.
