Abstract:
A synchronizer for first and second drives is provided which includes a first drive having a first fluid passage, a hub affixed with the first drive having a second fluid passage connected with the first fluid passage, a piston mounted on the hub forming a control volume between the piston and the hub, the control volume intersecting the second passage, the piston being responsive to fluid pressure within the control volume, a friction member rotated with the hub being moved by the piston and a friction surface rotating with the second drive member for engagement with the friction member to synchronize the first and second drives together, first teeth rotating with the hub being moved by the piston, and second teeth rotating with said second drive member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/765,402 filed Feb. 3, 2006. 

   TECHNICAL FIELD 
   The present invention relates to synchronizers, especially synchronizers used in dual clutch automatic transmissions (DCT) such as shown in U.S. Pat. No. 6,012,561, Reed Jr. et al., the disclosure of which is incorporated by reference herein. 
   BACKGROUND OF THE INVENTION 
   The conventional gear selection system used for most if not all of DCTs in production today is synchronizers. The synchronizers are engaged and disengaged through a hydraulic actuation valve via a standard manual shift fork and rail system. One of the disadvantages to this system is the differential speed between the shift fork and the sleeve of the synchronizer. The above noted interface requires sufficient lubrication to prevent wear. Another issue with DCT is that high clutch drag can sometime cause block out of the engagement of the synchronizer or prevent a blocker ring from indexing. 
   SUMMARY OF THE INVENTION 
   The present invention provides a hydraulic actuated synchronizer that eliminates the shift fork in a manner that is an alternative to those revealed prior. 
   Other features of the invention will become more apparent to those skilled in the art as the invention is further revealed in the accompanying drawings and Detailed Description of the Invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded view of a synchronizer of the present invention. 
       FIG. 2  is a partial sectional view of the synchronizer shown in  FIG. 1 . 
       FIG. 3  is an operational view of the synchronizer shown in  FIGS. 1 and 2 . 
       FIG. 4  is a view similar to  FIG. 2  of the alternate preferred embodiment synchronizer to that shown in shown in  FIGS. 1 and 2 . 
       FIG. 5  is an exploded view of another alternative embodiment synchronizer of the present invention. 
       FIG. 6  is a partial sectional view of the synchronizer shown in  FIG. 5 . 
       FIG. 7  is an operational view of the synchronizer shown in  FIGS. 5 and 6 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1-3 , a synchronizer  7  of the present invention is provided. The synchronizer  7  has a hub  10 . The hub  10  is affixed on a first drive provided by a rotating shaft  12  by a series of spline teeth  14 . The spline teeth  14  engage spline teeth  16  of the shaft  12 . Accordingly, the shaft  12  and hub  10  rotate about a common axis  17 . The shaft  12  has a shoulder  18  that can be used to axially captures the hub  10  against a stop  20  to secure against axial movement of the hub  10  relative to the shaft  12 . Extending at least partially through the shaft  12  is a first fluid passage  22 . The hub  12  has a second fluid passage  24  that is fluidly connected to the first fluid passage  22 . 
   Press fitted on the hub  10  is a cylinder  28 . Press fitted on the hub  10  against hub shoulders  30  are two end plates  32 . A radial extreme end of the end plates  32  mount a ring sealing member  34 . Slideably sealably mounted on an outer diameter of the hub  10  is a dual piston  36 . The piston  36  has a divider plate  38  that mounts on its extreme end a ring sealing member  40  forming connected pistons with a common body. The piston  36  forms variable control volumes  42  and  120  with the hub  10 . The control volume  42  intersects the second passage  24 . The piston  36  has axial movement along an axis  17  in response to the fluid pressure within the control volume  42 . 
   The synchronizer  7  has two brackets  46 . The bracket  46  has spline teeth  48  that engage hub spline teeth  56  causing the bracket  46  to rotate with the hub  10 . The bracket  46  has a shoulder  52  that abuts an axial end  54  of the piston  36  to allow the bracket  46  to be moved along the axis  17  by the piston  36 . The bracket  46  has gear teeth  50 . 
   The synchronizer  7  has a friction member provided by a synchronizer cone  58 . The cone  58  has a friction surface  60  that is angled with respect to the axis  17 . As shown in  FIGS. 1-3 , a paper fiber base friction material provides the surface  60 . The cone  58  has a flange  62 . The cone  58  has a tab  64  that extends into a notch  66  or  67  of the hub  10  allowing the cone  58  to rotate with the hub  10 . 
   The bracket  48  has a series of pin holes  70 . Extending through each pinhole  70  is a spring pin  72 . The pin  72  has shoulders  74  that abut against an inboard surface  76  of the brackets  46  to limit the position of the brackets  46  relative to the pin  72 . The pin  72  at its opposite end has a connected nail head  78 . The nail head  78  captures between itself and the bracket  46  a coil return coiled spring  80  to bias the bracket  46  and the piston  36  to a neutral non-engaged position. 
   A second drive is provided by a gear  82  rotatably connected on the shaft  12  by a needle bearing  84 . In a similar manner, a third drive is provided by a gear  86  mounted on a needle bearing  88 . The gears  82 ,  86 , and the hub  10  are axially fixed on the shaft  12 . The gear  82  has a side face  90  and a gear tooth face  92 . A second drive lubrication passage  94  connects the side face  90  with the gear face  92 . Interference or press fitted on the gear  82  is a dog leg  96 . The dog leg  96  has a friction surface  98  and gear teeth  100 . 
   In a manner similar to that described for a the gear  82 , gear  86  has a side face  102 , a third drive lubricating passage  104 , gear face  106  and a dog leg  108  a with friction surface  110  and gear teeth  112 . 
   In operation, the gears  82  and  86  mesh with other gears on a different shaft (not shown) of a transmission. Typically, the gears  82  and  86  provide the transmission with two gear ratios that are two gear shift ratios apart. For example, gear  86  can be the second gear and gear  82  can be the fourth gear. If the transmission is in fifth gear, the synchronizer  7  is in the neutral position as shown at the top of  FIG. 3 . In the neutral position, both gears  82  and  86  are free to turn on the shaft  12 . Another gear (not shown) is torsionally connected with the shaft  12  to cause the transmission to be in the fifth gear. If the transmission controller desires to down shift to the fourth gear, a hydraulic valve (not shown) is signaled to pressurize the first fluid passage  22 . Fluid (transmission fluid) then flows into the control volume  42  via the second passage  24 . Pressure within the control volume  42  causes the piston  36  to be pushed rightward thereby moving the bracket  46  to the right. The rightward movement of the bracket  46  compress the springs  80  against the nail heads  78 . The rightward movement of the nail head  78  pushes the cone flange  62  rightward causing the friction surface  60  to engage with the dog leg friction surface  98 . As the friction surfaces  60  and  98  slip with respect to one another, the gear  82  is brought up to a rotational speed of the shaft  12 . As a piston  36  is further moved to the right the synchronization between the shaft  12  and the gear  82  rotational speeds is achieved. Further rightward movement of the piston  36  causes the bracket gear teeth  52  to engage with the gear teeth  100  of the dog leg  96 . At this point, the gear  82  is fully torsionally connected with the shaft  12  and the transmission is in the fourth gear. 
   The shaft  12  also has a shaft lubrication supply passage  114  that intersects with the first fluid passage  22 . The shaft lubrication supply passage  114  is fluidly connected with a hub lubrication passage  116 . Pressurize oil (transmission fluid) flowing through the hub lubrication passage  116  lubricates the interface between the friction surfaces  60  and  98  as well as the interface between the gear teeth  50  and  100 . The oil from the hub lubrication passage  116  will eventually pass through the second drive lubrication passage  94  before lubricating the gear tooth face  92 . 
   If the transmission down shifts to third gear, fluid pressure within the first fluid passage  22  will be released causing a depressurization of the first control volume  42 . Return springs  80  will pushed the bracket  46  leftward causing the teeth  50  and  100  to disengage. Further leftward movement of the bracket  46  causes the friction surfaces  60  and  98  to disengage. 
   When the control volume  42  is pressurized and the bracket  46  is moved rightward, return springs  80  on both sides of the hub  10  both are compressed. The return springs  80  on the right hand side of the hub will be compressed a greatest amount. The return springs  80  on both sides of the hub  10  will contribute to the return of the pin  72  to the neutral position increasing the reaction time of the synchronizer  7  to the released or neutral position. The spring constant of the return springs  80  can vary due to manufacturing tolerances. If the springs  80  are not equally matched in their spring constant across the hub  10 , the springs  80  can cause the synchronizer  7  to have a tendency to self-engage. To prevent the above noted tendency pin shoulders  74  are provided which limit the axial position of the brackets  46  on the pins  72 . 
   In an alternate preferred embodiment synchronizer  127  shown in  FIG. 4 , the pin  72  function is performed by two pins  72 A. In this design, returned springs  80  on one side of the hub  10  are used to return the piston  36  to the neutral position. Reaction time to the neutral position can be improved by momentarily pressurizing the control volume  120 . The embodiment of  FIG. 4  saves the machining costs of a through bore in the hub  10  for a pin  72 . 
   To place the transmission into the second gear, the control volume  120  is pressurized via a separate fluid passage  122  (hereinafter referred to as the third fluid passage) and a fourth fluid passage  124 . The operation for engagement of the second gear  86  to the shaft  12  is substantially identical to that described for engagement of the gear  82 . 
   Referring to  FIGS. 5-7 , an alternate preferred embodiment synchronizer  137  is provided with like items performing similar functions to that shown for synchronizer being given identical reference numerals. Dog leg  140  of the gear  86  has its gear teeth  142  at a common diameter with the gear teeth face  106 . The synchronizer  137  has a hub  143  with an annular groove  144 . Slideably mounted in the groove  144  is a piston  146 . The pistons  146  have radial tabs  148  captured in a radial slot  150  of an apply cylinder  152 . The apply cylinder  152  has an inboard inner diameter with spline teeth  154  allowing the apply cylinder  152  to rotate with the spline teeth  156  of the hub outer diameter. The cylinder  152  along an outboard inner diameter has gear teeth  158  for engaging with gear teeth  100  or  142  one of the dog legs  140  or  162 . Teeth  154  and  158  can be a common structure. The pin  164  has enlarged center portion  165 . The enlarged center portion  165  at its ends has shoulders  166  to axially limit the position of the piston  146  to prevent self-activation due to uneven strength in the return springs  80  as previously described. Additionally the center portion  165  is closely fitted with a pinhole  168  of the hub to prevent bleed through to the opposite groove  144  when the piston  146  is actuated. 
   In operation, a second passage  170  is pressurized to pressurize the control volume provided by the groove  144 . The piston  146  is pushed rightward causing the nail head  78  to go against the cone flange  62 . The friction surfaces  60 ,  98  engage as previously described. When the speed the gear  82  has been synchronized the gear teeth  158  mesh with the gear teeth  100 . To activate the gear  86 , the opposite piston  146  is activated in a similar manner. 
   While preferred embodiments of the present invention have been disclosed, it is to be understood it has been described by way of example only, and various modifications can be made without departing from the spirit and scope of the invention as it is encompassed in the following claims.