Abstract:
A damper assembly including a cover having at least one aperture therein, a flange operatively connected to the cover, and a spring having at least one leg engaged with a radially outer surface of the flange, the spring having at least one post engaged in the aperture of the cover, wherein engaging the post in the aperture preloads the spring against the radially outer surface of the flange for exerting a force on the damper.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/373,510 filed Aug. 13, 2010 which application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention broadly relates to torque converter damper assemblies, more specifically to damper assemblies which use centrifugal forces to modify or vary hysteresis during operation of a torque converter. 
       BACKGROUND OF THE INVENTION 
       [0003]    Torque converters are well known in the art. Commonly, torque converters include a damper assembly for improving noise or resonance of the torque converter or components of the torque converter during operation. 
         [0004]    An example of a typical constant friction torque converter damper is shown in  FIG. 1 . As shown, damper  10  includes covers  12  and  14  on either side of flange  16 . Torque from piston plate  18  is transmitted to cover plates  12  and  14 , typically via a riveted connection. Cover plates  12  and  14  impart torque to compression springs  20  by contact with an edge of a spring window. Energy absorption is often accomplished through friction, sometimes called hysteresis, which includes friction from windup and unwinding of the damper plates. The hysteresis package generally consists of diaphragm (or Belleville) spring  22  which is placed between flange  16  and cover plate  14  to urge flange  16  into contact with cover plate  12 . By controlling the amount of force exerted by diaphragm spring  22 , the amount of friction torque can also be controlled. However, the amount of friction in this arrangement is constant regardless of the rotational speed of the assembly, whereas it has been found that high friction is desired for reducing resonance in low speed operations, while low friction is desired for reducing resonance in high speed operations. Additionally, in order for spring  22  to operate, it must be included about the entire circumference of the damper flange, and results in a significant quantity of scrap material when stamped during manufacture. 
         [0005]    Such a damper arrangement is also described in several patent references, including U.S. Patent Publication No. 2009/0032364 (MacDonald et al.), which publication is hereby incorporated by reference in its entirety. 
         [0006]    Accordingly, there have been attempts to modify or vary the friction in a damper during operation of the torque converter, such as to improve resonance more effectively at high and low rates of rotational speed, instead of constant friction at all rates of speed. Examples include: U.S. Pat. No. 4,640,402 (Hartig et al.), which shows a damper with a manually adjustable hysteresis for reduced tolerance variation; U.S. Pat. No. 4,465,172 (Gatewood), which shows a damper with friction that varies with the windup angle; U.S. Pat. No. 6,681,911 (Kroll et al.), which shows a damper with hysteresis that is adjustable by fluid pressure; and U.S. Pat. No. 4,376,477 (Loizeau), which shows a damper that uses a centrifugally acting element to engage and disengage spring sets. U.S. Pat. Nos. 4,640,402 (Hartig et al.), 4,465,172 (Gatewood), 6,681,911 (Kroll et al.), and 4,376,477 (Loizeau) are hereby incorporated by reference in their respective entireties. 
         [0007]    The use of centrifugal clutches in torque converters is also generally known, however these clutches are known to increase friction with increased rotational speed, although the exact opposite is desired for damper&#39;s hysteresis package. Examples can be found in U.S. Pat. Nos. 4,657,122 (Sakakibara et al.) and 4,383,596 (Jaeckel). All of these various patents teach complicated assemblies consisting of numerous parts that require significant circumferential or angular space for installation. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The present invention broadly comprises a damper assembly including a cover having at least one aperture therein, a flange operatively connected to the cover, and a spring having at least one leg engaged with a radially outer surface of the flange, the spring having at least one post engaged in the aperture of the cover, wherein engaging the post in the aperture preloads the spring against the radially outer surface of the flange for exerting a force on the damper. In one embodiment, the leg is operatively arranged to bend radially away from the flange due to centrifugal forces resulting from rotational movement of the damper, the centrifugal forces opposing and reducing the force exerted by the spring on the flange. In one embodiment, the leg includes a weight for facilitating tuning of a rate at which a change in speed of the rotational movement changes the force exerted by the spring. In one embodiment, the weight is a rivet received in a hole in the leg. In one embodiment, the flange is secured between the cover and a second cover. In one embodiment, the aperture is operatively arranged to receive a rivet for connecting the cover to the second cover, and wherein upsetting the rivet locks the post in the aperture for preloading the spring. In one embodiment, the second cover includes at least one second aperture, the spring element includes at least one second post, and the at least one second post is engaged in the at least one second aperture. 
         [0009]    A damper assembly including a first cover having at least one aperture therein, the aperture aligned in a substantially axial direction with respect to the damper assembly, the aperture operatively arranged for receiving a securing means, a flange housed between the first cover and a second cover, a spring element, the spring element having a body portion with at least one post extending in a substantially axial direction with respect to the damper assembly, the at least one post engaged in the aperture in the first cover, wherein at least one leg is generally extending circumferentially from the body for engagement with a radially outer surface of the flange, wherein engaging the securing means in the aperture in the first cover locks the post and the spring element in position and preloads the at least one leg of the spring element against the radially outer surface of the flange for exerting a force on the flange, wherein the at least one leg includes a free end, wherein the free end enables the leg to bend radially away from the flange due to centrifugal forces resulting from rotational movement of the damper in order to reduce the force exerted by the spring element on the flange. In one embodiment, the leg includes a weight for facilitating tuning of a rate at which the rotational movement reduces the force exerted by the spring. In one embodiment, the weight is a rivet received in a hole in the leg. 
         [0010]    The current invention also broadly comprises a hysteresis package for providing friction in a torsional damper including a spring element having a body having at least one post protruding therefrom operatively arranged for engagement in a hole in the damper, and at least one leg extending from the body for engagement with a radially outer surface of the damper. In one embodiment, the at least one post is extending in a substantially axial direction with respect to the damper. In one embodiment, the at least one leg comprises two legs extending in generally opposite circumferential directions from the body of the spring element. In one embodiment, the at least one leg includes a weighted free end. In one embodiment, the package further comprises a securing means for securing a first cover plate of the damper to a second cover plate of the damper while also locking the spring in a preloaded state in which the at least one leg of the spring is pressed against the radially outer surface. 
         [0011]    It is a general object of the present invention to provide a hysteresis package for a damper assembly of a torque converter which results in increased friction in the damper assembly during low speed operation and decreased friction in the damper assembly during high speed operation. 
         [0012]    It is another general object of the present invention to provide a hysteresis package which is compact and does not result in much waste or scrap material during manufacture. 
         [0013]    These and other objects and advantages of the present invention will be readily appreciable from the following description of preferred embodiments of the invention and from the accompanying drawings and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
           [0015]      FIG. 1  is a cross-sectional view of a prior art damper assembly and piston plate; 
           [0016]      FIG. 2  is a front view of a damper assembly according to the current invention; 
           [0017]      FIG. 3  is a cross-sectional view of a damper assembly according to the current invention; 
           [0018]      FIG. 4  is a top view of a spring of the damper assembly shown in  FIG. 2 ; 
           [0019]      FIG. 5  is a top view of a spring of the damper assembly, wherein the spring includes weighted ends; and, 
           [0020]      FIG. 6  is a damper assembly including the spring of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred aspects, it is to be understood that the invention as claimed is not limited to the disclosed aspects. 
         [0022]    Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims. 
         [0023]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described. 
         [0024]    Referring now to the figures,  FIGS. 2 and 3  show a portion of damper assembly  100  according to the current invention. Damper assembly  100  includes cover plates  102  and  104  which are included on opposite sides of flange  106 . The second cover plate is removed in  FIG. 2  so that the flange is shown. It should be appreciated that cover plates  102  and  104  and flange  106  substantially resemble prior art plates  12  and  14  and flange  16 , respectively, although any known cover plates and flange arrangements could be used for cover plates  102  and  104  and flange  106 , and that these components are shown as one example only. Also like damper  10 , damper  100  includes compression springs  108  in order to damper torque received from a piston plate. The piston plate and means for securing damper assembly  100  to the piston plate are not shown in the Figures, but could be any piston and corresponding means of securing known in the art, such as taught with respect to damper assembly  10  of  FIG. 1 . Damper  100  is shown with a greater number of springs than damper  10 , but it should be appreciated that the exact number or configuration of the compression springs is not germane to the invention. Accordingly, only one such compression spring is labeled in  FIG. 2  for clarity of discussion, any damper arrangement known in the art could be utilize the teachings of the current invention. 
         [0025]    Unlike damper  10 , damper  100  does not include a diaphragm spring or Belleville washer to create friction axially against damper flange. Instead, damper assembly  100  includes spring  110  which acts on radially outer surface or circumference  111  of flange  106 , as shown. Specifically, as can be seen in  FIGS. 2 and 4 , spring  110  resembles a stamped leaf spring. Body  116  of spring  110  includes two legs  118  that extend from opposite sides of the body, with legs  118  terminating in feet  120 . As shown, the legs extend from the body both circumferentially and radially towards flange  106  until the legs engage against the flange, while the feet extend slightly radially and circumferentially away from flange  106 . 
         [0026]    As shown in  FIG. 3 , spring  110  includes posts  114  extending from opposite sides of body  116  in a generally axial direction with respect to the damper. From  FIGS. 2-4 , it can be seen that posts  114  are arranged for engagement in rivet holes  112  of cover  102 . In the shown embodiment, rivets  126  are so-called sheet metal rivets generally resembling a thin H-shaped metal body similar in shape to body portion  116  of spring  110 . As shown in the embodiment of  FIG. 3 , rivet  126  is laid over body  116  of spring  110  such that posts  128  of the rivet, corresponding to posts  114  of the spring, are aligned in each hole  112  and deformed or upset so as to form ends  130 . The upsetting of the rivet locks posts  114  and therefore body  116  of spring  110  in place such that legs  118  of the spring are preloaded against flange  106  of the damper, which preloading provides the friction in the damper during the windup and unwinding of the flange. It should be appreciated that any other securing means could be used in order to preload the spring against the damper flange. For example, rivet  126  could be replaced by a bolt, pin, screw, plate, etc. for locking the spring in a preloaded state with respect to the damper flange. Moreover, the rivet or its equivalent could be used to secure the first cover to a piston, such as piston  18 , or some other component of the torque converter, instead of a second cover. 
         [0027]    Since feet  120  are free ends which are not secured to any other component, centrifugal forces resulting from rotational speed cause legs  118  and feet  120  to pull radially outward, away from surface  111  of the flange, reducing the preload against the flange and thereby also reducing hysteresis. That is, the centrifugal forces caused by rotational movement are generally opposite to the preloaded force of the spring on the damper flange (radially outward as opposed to radially inward). Thus, when subjected to centrifugal forces during rotation of the damper, the centrifugal forces cause the feet and legs to bend radially outwards away from the damper flange, lessening the force exerted by the spring, and thereby the amount of friction in the damper. It follows that since the feet and legs bend farther away from the damper flange as rotational speed increases (and therefore the centrifugal forces increase), faster rotational speeds will result in less friction and lower speeds will result in more friction. Advantageously, this behavior reflects the desired operation of a hysteresis package for a torque converter damper assembly; more friction at low speeds and less friction at higher speeds. Thus, the current invention arrangement dynamically reacts to the speed of rotation of the damper to more effectively reduce the resonance in the torque converter. Tuning of spring  110  of damper  100  to match the desired resonances of the system at various rotational speeds can be accomplished, for example, by selecting a proper stiffness of spring  110  and setting a predetermined preload force in order to establish a desired rate at which changing rotational speed changes the force exerted by the spring. 
         [0028]    In the embodiment shown in  FIG. 5 , each foot  120  of spring  110  includes aperture  122 . As shown in  FIG. 6 , apertures  122  are arranged to receive weights  124 . Weights  124  could be, for example, rivets installed through apertures  122 , or any other weighted components. The use of weights  124  may result in an easier or more accurate tuning of spring  110 , since the mass of weights  124  can easily be adjusted to tune the friction under various speeds for specific noise, vibration, and hysteresis requirements for different damper assembly or torque converter applications. 
         [0029]    Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention.