Abstract:
A pull-type friction clutch having an annular part that is axially clamped to a disk spring and is axially fixedly connectable to an actuation sleeve of an actuation system. The annular part has axially raised lugs on its face bearing against the disk spring, and the lugs engage in slots that are provided between the disk spring tongues where the tongues are appropriately widened, to provide a form locking connection in the peripheral direction. As a result of the peripherally fixed attachment of the annular part to the disk spring, wear caused by a relative twist between the annular part and the disk spring is prevented.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a pull-type friction clutch having a compression plate and an axially displaceable pressure plate that is acted upon by a disk spring. An annular part that extends behind the disk spring is axially clamped to the spring and is axially fixedly connectable to an actuation sleeve of a clutch actuation system. 
         [0003]    2. Description of the Related Art 
         [0004]    Friction clutches are known from the prior art. To enable pull, for example a pull or push of the friction clutch to the engaged position or to the disengaged position, there is provided on the side of the disk spring facing the pressure plate an annular part that reaches radially over the disk spring. A sleeve part of the friction clutch, which is axially fixedly connected to the annular part, acts axially thereon in the direction of the transmission and is actuated by the actuation system. The actuation system, which is arranged to be rotatably fixed, is uncoupled from rotation by the actuation sleeve. As a result, the pressure plate, which is axially displaceable in the housing of the friction clutch, is acted upon by the disk spring and is clamped against the compression plate, the friction linings of the clutch disk being arranged between the compression plate and the pressure plate. The actuation sleeve is displaced by means of a hydrostatic entraining cylinder that is arranged around the transmission input shaft, or mechanically by means of an externally actuated lever. 
         [0005]    Varying the load on the friction clutch has the effect of transmitting a load moment from the fixed actuation system through the roller bearing and the actuation sleeve to the annular part, and that load moment can result in wear on the disk spring and/or the annular part. 
         [0006]    An object of the present invention is thus a friction clutch that is resistant to wear of that kind. 
       SUMMARY OF THE INVENTION 
       [0007]    The object is achieved by a friction clutch having a compression plate, a housing, and a pressure plate. The pressure plate is rotatably fixed and is axially displaceable in relation to the compression plate and the housing by a disk spring that is supported against the housing. An actuation device is fixedly arranged relative to the housing and is uncoupled from rotation to exert a pulling movement on disk spring tongues that are arranged radially inwardly on the disk spring. An annular part is provided with a flange on the side of the disk spring tongues and axially facing the pressure plate, wherein the flange extends radially over the disk spring tongues and is axially biased by the disk spring tongues and form-lockingly connectable to an actuation sleeve of the actuation device. The flange has an effective form-locking circumferential connection with the disk spring tongues. As a result of that form-locking connection, secure entraining of the annular part by the disk spring is achieved, with the result that axial clamping of the annular part on the disk spring has to be exerted less forcefully, since there is no need for an alternative friction fit between the annular part and the disk spring. The component that clamps the annular part to the disk spring can be made lighter and simpler, with the result that in the simplest case only one means of preventing detachment need be retained. 
         [0008]    An advantageous exemplary embodiment is provided by an annular part having a flange that has axially projecting lugs that are circumferentially distributed on its side facing the disk spring tongues, and that engage in slots provided between the disk spring tongues. The slots are advantageously formed by respective pairs of mutually adjacent disk spring tongues. To make allowance for changes in the slots during axial action on the disk spring, a profile can be provided at the tips of the disk spring tongues that widens the slots. For example, the disk spring tongues can be stamped or finished by the removal of material from the tips thereof at faces pointing in the peripheral direction. Thereby the ends of the disk spring tongues pointing in the radial direction can be rounded. The lugs can have a similarly rounded profile in their cross section, with the result that rolling is made possible in the slots and the annular part can be positioned better on the disk spring. 
         [0009]    To enable the annular part coupled to the actuation system to be centered in relation to its axis of rotation, the radial extent of the widened slots can be greater than the radial extent of the lugs. 
         [0010]    The annular part can be clamped by means of a spring part that is supported axially on the opposite side of the disk spring tongues to that with the contact pressure plate, that extends axially through the annular part and that clamps the annular part axially against the disk spring tongues by radially angled tongues. The tongues can thereby be angled radially inward and/or radially outward in the radial direction. 
         [0011]    An axial extension, with which the sleeve part axially overlaps, can be provided on the annular part for receiving the actuation sleeve, wherein the axial extension and the actuation sleeve are axially fixedly secured to one another. That axial securement can be in the form of a shaped wire spring or a securing ring against which a radially widened extension that is provided in the actuation sleeve is supported. Advantageously, the annular part can have openings in which a shaped wire spring that acts over a peripheral region engages with appropriately shaped lugs that can be displaced to a limited extent when the actuation sleeve is pushed into the profile of the openings, wherein the shaped wire spring, which is open on one side, is widened by a phase made on the radial protrusion and, when the actuation sleeve is pushed in further, snap-fits over the extension and fixes the actuation sleeve on the annular part. The two parts are separated by widening the ends of the shaped wire spring, and for that purpose the ends can have corresponding wings. The actuation sleeve and/or the annular part are advantageously produced by a descending tool, for example from sheet metal by a deep drawing method or other sheet metal forming methods. 
         [0012]    The proposed pull-type friction clutch can be a tensioned-open or tensioned-closed friction clutch. In the case of a tensioned-open friction clutch, the disk spring is clamped to the housing such that in the absence of a tensile force acting on the actuation sleeve the friction linings of the clutch disk are clamped between the compression plate and the pressure plate with the maximum force, and the maximum moment that the friction clutch can transmit is transmitted. The disk spring is thereby advantageously supported radially outwardly against the housing and forms a single-armed lever with the annular part at the disk spring tongues. The pressure plate provides an annular contact surface, radially between the outside force-exerting rim and the disk spring tips, to support the spring force. When a pulling force acts on the actuation sleeve, as a function of the distance by which the disk spring is raised away from the contact surface, with the support of the plate spring between the housing or pressure plate on the one hand and the contact pressure plate on the other, clamping of the disk spring against the contact pressure plate is released and so the transmissible moment of the friction clutch through a slipping friction clutch is successively reduced until the friction clutch is fully disengaged. 
         [0013]    In the case of the push-type friction clutch, the disk spring serves as a two-armed lever, and when no pulling force acts on the actuation sleeve one end of the two-armed lever abuts radially outward against the pressure plate, which is at the maximum spacing from the compression plate, such that the friction clutch remains disengaged. Between the contact surface of the pressure plate and that of the disk spring tongue tips, the disk spring is supported against the housing such that when a pulling force is applied to the actuation sleeve the contact pressure plate increasingly clamps the friction linings to the compression plate. It will be appreciated that in the case of a tensioned-closed friction clutch a relatively rigid lever system can be used instead of the disk spring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The structure, operation, and advantages of the present invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings in which: 
           [0015]      FIG. 1  is a longitudinal cross section of an exemplary embodiment of a pull-type friction clutch; 
           [0016]      FIG. 2  is a longitudinal cross section of a tensioning device of the friction clutch shown in  FIG. 1 ; 
           [0017]      FIG. 3  is a perspective view of an annular component of the tensioning device shown in  FIG. 2 ; 
           [0018]      FIG. 4  is an enlarged, fragmentary cross-sectional view of a portion of the annular part component of  FIG. 3 ; and 
           [0019]      FIG. 5  is a front view of the disk spring of the clutch shown in  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]      FIG. 1  shows an exemplary embodiment of a pull-type friction clutch  1  in the engaged condition, but only indicating a compression plate  2 , a housing  3  that is secured to the compression plate, and a pressure plate  5  that is non-rotatably and axially displaceably arranged on the housing  3  or on the pressure plate  2  by means of plate springs  4 . A force-exerting rim of a disk spring  7  contacts an annular face of the housing  3 , or contact lobes  6  that are circumferentially distributed, and biases the pressure plate  5  against the compression plate  2 . Friction linings of a clutch disk (not shown) are clamped between the friction faces  8 ,  9  of the compression plate  2  and the pressure plate  5 . 
         [0021]    To disengage the friction clutch  1 , the tongues  10  of the disk spring  7  are urged axially in the pulling direction  12  by the pulling device  11 , wherein the pulling device  11  is axially actuated by an actuation device (not shown) and is uncoupled from rotation relative to the pulling device. For that purpose, an actuation sleeve (not shown) having a return element is pushed axially into the central opening in the annular part  13  and is axially fixed by means of the shaped wire spring  14 . The actuation sleeve is connected to the actuation device by means of a roller bearing, which can be a central disengaging means that is actuated hydrostatically, pneumatically, or mechanically, for example, by means of an external lever. The annular part  13  is secured to the disk spring tongues  10  by means of a spring part  20 . 
         [0022]      FIG. 2  shows a detail of the pulling device  11 . The annular part  13  has a radially widened flange  16  that radially overlaps the disk spring tongues  10 , so that if the annular part  13  is acted upon by the actuation device the disk spring tongues  10  are carried along. The flange  16  includes a bend relative to its radial extent, with the result that during the engaging and disengaging movements the disk spring tongues  10  can roll on the annular crowned bearing surface  17  that is formed as a result of the bend, despite having a substantially radial path. 
         [0023]    In the region of the radial flange  16 , several outwardly extending circumferentially distributed lugs  18  are provided, such as by means of a forming method, and axially engage slots  19  that are formed between two disk spring tongues  10 . As a result of the axial engagement of the lugs  18  in the slots  19 , the annular part  13  is received on the disk spring  7  such that it cannot twist ( FIG. 1 ). Thereby wear caused by twisting of the annular part  13  relative to the disk spring tongues is avoided or at least limited. 
         [0024]    The annular part  13  is arranged such that detachment is prevented by means of a spring part  20  that is arranged on the other side of the disk spring tongues  10 . For that purpose, the spring part  20  is supported axially on the disk spring tongues  10  and extends through the annular part  13 , in which corresponding openings  21  are provided (see  FIG. 3 ). The annular part  13  is axially clamped to the disk spring tongues  10  by means of the tongues  22 , which extend around the annular bead  23  of the annular part  13 . 
         [0025]    The shaped wire spring  14  is introduced into the inner periphery of the annular part  13  and is supported axially against a radially inwardly directed locating surface  24 . To connect the actuation device to the pulling device, the actuation sleeve (not shown) is pushed axially into the annular part  13 , and thereby the shaped wire spring  14  is widened by that installation step. To prevent the simultaneous occurrence of an axial displacement of the shaped wire spring  14 , the spring is radially deformed to form radial lugs  25  that extend into openings  26  in the annular part  13 . The openings  26  are in this case in the form of an elongated hole in the axial direction, whereby the diameter of the axial extension  27  of the annular part simultaneously increases in the axial direction, so that by axial displacement the diameter of the shaped wire spring  14  can widen more easily. During the return stage of the actuation sleeve, the shaped spring  14  snap-fits into the return element and axially secures the actuation sleeve relative to the annular part  13 . That snap-fit closure is released—for example during repair—by pressing the two radially outwardly guided ends  28  of the shaped wire spring  14  apart that leads to the shaped wire spring  14  being widened so that the actuation sleeve can be withdrawn from the extension  27 . 
         [0026]      FIG. 3  shows the annular part  13  in a view of the flange  16  and the axial extension  27 . The annular part is made from sheet metal by means of a multiple-step forming and stamping method, wherein the openings  21 ,  26  can readily be punched out of the circular blank in a die. As a result of appropriate plastic forming steps, the extension  27  and the various indentations are given their final shape only once those steps have been performed. The annular part  13  can be made by a descending tool in a punching and forming method. The openings  16  are made in the axial extension  27  for the shaped wire spring to engage. The ends of the shaped wire spring are guided out of the opening  26 . The flange  16  includes the openings  21  through which tongues  22  of the spring part  20  ( FIG. 2 ) extend. 
         [0027]    The lugs  18  for preventing the annular part  13  from twisting relative to the disk spring  7  are preferably formed by an extrusion process. In that regard,  FIG. 4  shows a detail of the annular part  13  in cross section. During the manufacturing, process a punch is pressed into the flange  16  on the opposite side of the flange  16  to that having the lugs  18 , and that punch leaves an indentation  29 . The displaced material is pressed into a recess in the manufacturing tool and forms the lug  18 . The height of the lug  18  varies in the radial direction to form a curved upper surface, with the result that when the disk spring tongues are displaced during an actuation procedure, at least part of the lug  18  extends into the slot between the disk spring tongues. 
         [0028]      FIG. 5  shows a detail of a disk spring  7  in a front view. At the disk spring tongue tips  31 , on the inner periphery of the disk spring  7 , the disk spring tongues  10  have a profile  32  of reduced width, with the result that wider slots  19  are produced in which the lugs  18  engage ( FIG. 4 ). As a result of the slots  19  being widened, the lugs  18  can be made wider and hence are easier to produce in a forming process. The profiles  32  can have a rounded shape at the inner periphery of the disk spring  7 , and can be produced during the process of punching the disk spring. The disk spring tongue tips  31  can be partially hardened, in addition to the hardening process of the disk spring  7 , such as by induction hardening. 
         [0029]    Although particular embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit of the present invention. It is therefore intended to encompass within the appended claims all such changes and modifications that fall within the scope of the present invention.