Abstract:
A synchronizer actuating system for use in an automated manual transmission or a dual clutch transmission includes an apply finger and a fork mounted on a shifting rail. The fork grips and actuates a synchronizer sleeve. A piston is operable to engage and actuate the apply finger. The piston has an opening with a dual frusto-conical inner surface. The opening receives an extension of the apply finger therein. The dual frusto-conical inner surface allows the apply finger to be engaged by the piston at the center of the piston even if the apply finger or shifting rail is bent relative to the piston.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/909,293, filed on Mar. 30, 2007. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to actuating systems, and more particularly to a synchronizer actuating system for a transmission. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0004]    A typical manual transmission automated (MTA) or a dual clutch transmission (DCT) includes a plurality of gear sets that are selectively engaged by a plurality of torque transmitting devices, such as, for example, dog clutches or synchronizers. The synchronizers are preferably hydraulically or pneumatically actuated by an actuator. The actuator generally includes a fork connected to the synchronizer, a shifting rail connected to the fork, and a piston or other actuator that contacts and actuates a member extending from the shifting rail. While useful for its intended purpose, there is room in the art for an improved synchronizer actuating system that reduces mechanical wear and minimizes the effects of the piston tilting relative to the member and that includes features that allow for efficient assembly of the system. 
       SUMMARY 
       [0005]    The present invention provides a synchronizer actuating system for use in a manual transmission automated or a dual clutch transmission. 
         [0006]    In one aspect of the present invention the synchronizer actuating system includes an apply finger and a fork mounted on a shifting rail. The fork grips and actuates a synchronizer sleeve. A piston is operable to contact and actuate the apply finger. The piston has an opening with a dual frusto-conical inner surface. The opening receives an extension of the apply finger therein. The dual frusto-conical inner surface allows the apply finger to be engaged by the piston at the center of the piston even if the apply finger or shifting rail is out of alignment with the piston. 
         [0007]    In another aspect of the present invention, the apply finger is secured from moving relative to the shifting element by a plurality of snap rings. 
         [0008]    In another aspect of the present invention, the apply finger is secured from moving relative to the shifting element by a tapered snap ring on one side of the apply finger and by a regular snap ring on an opposite side of the apply finger. 
         [0009]    In another aspect of the present invention, the apply finger is secured from moving relative to the shifting element by a clip. 
         [0010]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0011]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0012]      FIG. 1  is an isometric view of an exemplary synchronizer actuating system according to the principles of the present invention; 
           [0013]      FIG. 2  is a side view of the synchronizer actuating system of the present invention; 
           [0014]      FIG. 3  is an enlarged, isometric view of a portion of the synchronizer actuating system; 
           [0015]      FIG. 4  is an enlarged cross-sectional view of a first embodiment of a pre-load feature of the present invention taken in the direction of arrows  4 - 4  in  FIG. 3 ; 
           [0016]      FIG. 5  is an enlarged cross-sectional view of a second embodiment of the pre-load feature of the synchronizer actuating system; 
           [0017]      FIG. 6  is an enlarged cross-sectional view of a third embodiment of the pre-load feature of the synchronizer actuating system. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0019]    With combined reference to  FIGS. 1 and 2 , a synchronizer actuating system is shown and generally indicated by reference number  10 . The synchronizer actuating system  10  is configured to actuate a plurality of synchronizers (not shown) in an automated manual transmission or a dual clutch transmission. Actuation of the synchronizers by the synchronizer actuating system  10  allows the plurality of gears within the transmission to produce a plurality of forward and reverse gear ratios. The synchronizer actuating system  10  generally includes a plurality of synchronizer actuating elements  12 . In the particular example provided, four synchronizer actuating elements  12  are illustrated, though it should be appreciated that any number of synchronizer actuating elements  12  may be employed without departing from the scope of the present invention. Each synchronizer actuating element  12  is substantially similar to another, accordingly, only one synchronizer actuating element  12  will be described in detail. 
         [0020]    Each synchronizer actuating element  12  generally includes a cylindrical shifting rail  14 . The shifting rail  14  is has a first end  16  opposite a second end  18 . A fork  20  is mounted on the shifting rail  14  near the first end  16 . The fork  20  includes a pair of extending fork arms  22 . The fork arms  22  grip a synchronizer sleeve  24  (shown in  FIG. 2 ). The synchronizer sleeve  24  is sized to receive a synchronizer (not shown) therein. 
         [0021]    The synchronizer actuating element  12  further includes an apply finger  26  mounted on the shifting rail  14  near the second end  18 . The apply finger  26  includes a base portion  28  that defines a mounting hole or bore  30 . The mounting hole  30  is sized to receive the shifting rail  14  therein. Furthermore, a cylindrical extension  32  extends out from the base portion  28  of the apply finger  26 . 
         [0022]    The synchronizer actuating system  10  further includes a plurality of pistons  34  that engage the synchronizer actuating elements  12 . Accordingly, the number of pistons  34  is equal to the number of synchronizer actuating elements  12 . As each piston  34  is substantially similar to another, only one piston  34  will be described in detail. The piston  34  is preferably hydraulically or pneumatically activated. With reference to  FIG. 3 , the piston  34  defines a hole or bore  36 . The hole  36  includes a dual frusto-conical inner surface  37  that defines a first conical portion  38  and a second conical portion  40 . The conical portions  38  and  40  are aligned with one another such that the narrow ends of the conical portions  38  and  40  meet and define a neck or reduced diameter portion  42 . Accordingly, the hole  36  has diameters on either side of the neck  42  that are larger than the diameter of the hole  36  at the neck  42 . The neck  42  is located on longitudinal axis of the piston  34 , indicated by reference number  44  in  FIG. 3 , at the center of the piston  34  within the hole  36 . 
         [0023]    The extension  32  of the apply finger  26  fits within the hole  36  of the piston  34 . In order to change the gear ratio of the transmission that the synchronizer actuating system  10  is coupled to, the piston  34  is first actuated by a force, indicated by arrow “F” in  FIG. 3 . The force “F” is aligned with the axis  44  of the piston  34 . As the piston  34  is moved, the piston  34  engages the extension  32  of the apply finger  26  and moves the apply finger  26  in a direction parallel to the axis  44 . Axial movement of the apply finger  26  in turn moves the shifting rail  14 , the fork  20 , the synchronizer sleeve  24 , and finally the synchronizer (not shown). Movement of the synchronizer allows for various gear combinations within the transmission. 
         [0024]    The geometry of the hole  36  is such that when the force “F” is applied to the piston  34 , the neck  42  first contacts the extension  32 . However, in the event that the shifting rail  14  or the apply finger  26  is out of alignment with the piston  34 , the geometry of the hole  36  is such that the neck  22  remains the first contact point between the piston  34  and the extension  32  of the apply finger  26 . Accordingly, the neck  42  remains the first contact point without regard to the distance between the centerline of the shifting rail  14  and the centerline of the piston  34 . By keeping the contact point located along the axis  44  of the piston  34 , mechanical wear and piston tilting on the piston  34  is minimized. 
         [0025]    The synchronizer actuating element  12  includes a plurality of linear bearings or bushings  48  mounted on the shifting rail  14 . The linear bearings  48  support the synchronizer actuating element  12  within the transmission. 
         [0026]    Turning now to  FIG. 4 , the synchronizer actuating element  12  further includes a pre-loading feature generally indicated by reference number  50 . The pre-loading feature  50  includes a first snap ring  52  disposed within a first groove  54  located in the shifting rail  14  and a second snap ring  56  disposed within a second groove  58  located in the shifting rail  14 . The snap rings  52 ,  56  are sized such that there is some clearance between the snap rings  52 ,  56  and the grooves  54 ,  58 , as shown throughout the several views. The apply finger  26  is located between the first snap ring  52  and the second snap ring  56 . The snap rings  52  and  56  cooperate to restrict the axial movement of the apply finger  26  along the shifting rail  14 . A biasing member  60  engages the apply finger  26  and urges the apply finger  26  against the first snap ring  52 . In the particular example provided, the biasing member  60  is a spring that extends between the apply finger  26  and the bushing  48 . The pre-loading feature  50  prevents the apply finger  26  from rotating about the shift rail  14  during assembly of the synchronizer actuating system  10 . 
         [0027]    With reference to  FIG. 5 , a second embodiment of the pre-loading feature is indicated by reference number  150 . The pre-loading feature  150  includes a first snap ring  152  disposed within a first groove  154  located in the shift rail  14 . A first tapered snap ring  156  is disposed within a second groove  158  located in the shift rail  14 . The apply finger  26  is located between the first snap ring  152  and the tapered snap ring  156 . The first snap ring  152  and the tapered snap ring  156  cooperate to restrict the axial movement of the apply finger  26  along the shifting rail  14 . The tapered snap ring  156  has a generally trapezoidal cross-section and is positioned such that it engages the apply finger  26  to urge the apply finger  26  against the first snap ring  152 . More specifically, in the present embodiment the tapered snap ring  156  has two parallel sides, one side perpendicular to both parallel sides, and an angled side. However, the tapered snap ring  156  may have other shapes without departing from the scope of the present invention. The pre-loading feature  150  prevents the apply finger  26  from rotating about the shifting rail  14  during assembly of the synchronizer actuating system  10 . 
         [0028]    With reference to  FIG. 6 , a third embodiment of the pre-loading feature is indicated by reference number  250 . The pre-loading feature  250  includes a first snap ring  252  disposed within a first groove  254  located in the shifting rail  14 . A second snap ring  256  is disposed within a second groove  258  located in the shifting rail  14 . The apply finger  26  is located between the first snap ring  252  and the second snap ring  256 . The snap rings  252  and  256  cooperate to restrict the axial movement of the apply finger  26  along the shifting rail  14 . A clip or spring  260  is disposed within a third groove  262  located in the shifting rail  14 . The third groove  262  may be located on either side of the apply finger  26 . The clip  260  contacts the first snap ring  252  and urges the first snap ring  252  against the apply finger  26 . The pre-loading feature  250  prevents the apply finger  26  from rotating about the shifting rail  14  during assembly of the synchronizer actuating system  10 . 
         [0029]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.