Abstract:
A multi-speed transmission is disclosed having an input and output shafts supported by a housing, two gear sets each having a drive gear and a driven gear, and at least two shift forks coupled with synchronizers. An idler gear is selectively manipulated by a reverse lever to intermesh with a drive gear and a driven gear of one of the gear sets to create a reverse gear ratio. The reverse lever includes a cam portion that is selectively engageable with one of the shift forks. When the reverse lever is manipulated to move the idler gear to intermesh with the reverse gear set, the cam portion of the reverse lever triggers partial engagement of another gear set in order to synchronize the speed between the input and output shaft so that the idler gear is spinning at a similar speed as the driven gear of the reverse gear set.

Description:
FIELD 
     The present disclosure relates generally to transmissions and more specifically to manual transmissions having an idler gear brake employed to reduce gear clash when shifting into a reverse gear ratio. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
     A typical manual transmission includes a plurality of shafts, gears, shift mechanisms, synchronizers or other torque-transmitting mechanisms that cooperate to provide a plurality of forward and reverse gear or speed ratios. The transmission input shaft is selectively connected to an engine output shaft and includes a number of gears that are selectively connectable to the input shaft using, for example, synchronizers. The gears of the input shaft mesh with corresponding gears that are selectively connectable to an output shaft. To achieve a particular forward gear ratio between the transmission input and output shafts, the driver operates a shift mechanism, such as a manual shifter, that controls the engagement of the synchronizers with the desired gears. To achieve a reverse gear ratio, an idler gear is used to slide between an input shaft gear and an output shaft gear to reverse the rotational direction of the output shaft, and thus the drive wheels. 
     The idler gear is free to rotate on an idler gear shaft and the idler gear is not necessarily rotating when the idler gear is engaged to the input shaft reverse gear. However, the input shaft reverse gear is often rotating at a high speed having only recently been disengaged from the engine output shaft. Once the idler gear is meshing with the input shaft reverse gear they will both be rotating at the same high speed. The idler gear must then engage the output shaft gear to complete the torque transfer to the output shaft. However, as often is the case, the output shaft is not rotating and may even be rotating in the opposite direction as the driver may be shifting into reverse before the vehicle has stopped moving forward. The meshing of the fast rotating idler gear with a stationary output gear causes an impact or gear clash that creates noise and grinding that is very objectionable to the driver. Furthermore, gear clash is detrimental to the long term durability of the transmission and is the source of costly customer repair bills. 
     Accordingly, there is room in the art for a transmission that includes a mechanism to reduce or eliminate gear clash and premature component wear by reducing the input shaft and idler gear rotational speed when the driver is shifting into a reverse gear ratio. 
     SUMMARY 
     A multi-speed transmission having a first, a second, and a third shaft supported in parallel by a housing, a first and a second gear set each having a drive gear radially aligned with a driven gear, an idler gear rotatably supported by the third shaft, a first and second shift rails supported by the housing and disposed parallel to the first, second, and third shafts, a first and a second shift fork each having a first and second end portions, a synchronizer rotatably fixed to the first shaft and disposed adjacent the driven gear of the first gear set, a reverse lever having a first end portion, a second end portion, and a cam portion. The drive gears are rotatably fixed to the first shaft, the driven gears are selectively rotatably connectable to the second shaft, and the drive gear of the first gear set meshes with the driven gear of the first gear set. The idler gear is selectively meshed with each of the drive gear and the driven gear of the second gear set. The first end portion of the first shift fork is supported by the first shift rail. The first end portion of the second shift fork is fixed to the second shift rail. The second end portion of the second shift fork is coupled to the idler gear. The synchronizer is coupled to the second portion of the first shift fork and is selectively engageable with the driven gear of the first gear set. The first end portion is fixed to an elongated member having an axis. The reverse lever is rotatable about and movable along the axis of the elongated member. The second end portion is selectively engageable with the second shift rail. The cam portion is selectively engageable with the second portion of the first shift fork. The reverse lever is selectively disposed in one of at least a first, second and third positions. The reverse lever is selectively disposed in one of at least a first, second and third positions. In the first position the reverse lever is fully retracted so that the second end portion is disengaged from the second shift rail. In the second position the reverse lever is axially extended so that the second end portion is fully engaged with the second shift rail. In the third position the reverse lever is fully engaged with the second shift rail and rotated to a first rotational position so that the idler gear is at least partially meshed with the drive gear of the second gear set and the outer surface of the cam portion is in contact with the second portion of the first shift fork which partially engages the synchronizer with the driven gear of the first gear set. 
     In another example of the present invention, the reverse lever is selectively disposed in a fourth position. In the fourth position the reverse lever is extended in the second direction and fully engaged with the second shift rail and rotated to a second rotational position so that the cam portion of the reverse lever is not in contact with the first shift fork, and the idler gear is fully meshed with each of the drive gear and the driven gear of the second gear set. 
     In yet another example of the present invention, the reverse lever is selectively disposed in a fifth position. In the fifth position the reverse lever is extended in the second direction and fully engaged with the second shift rail and rotated to a third rotational position, and the inner surface of the cam portion is in contact with the first shift fork. 
     In yet another example of the present invention, the second end portion of the first shift fork includes a flange supporting a spring pivot assembly. The flange includes a first portion and a second portion. The first portion of the flange is fixed to the first portion of the first shift fork. The second portion of the flange has a first pivot hole. 
     In yet another example of the present invention, the spring pivot assembly includes a pivot member having a first end portion, a first edge, and a second edge opposite the first edge, a pivot pin disposed in each of the first and second pivot holes, and a spring having a coil portion and two end portions. The pivot member is disposed adjacent to the pivot member of the first shift fork. The second end portion includes a second pivot hole aligned with the first pivot hole of the flange, a pivot dowel fixedly disposed on the second portion of the pivot member so that the axis of the pivot dowel is somewhat perpendicular to the pivot member. The coil portion is disposed on the pivot pin. A first of the two end portion is disposed in contact with the first edge of the pivot member. A second of the two end portions is disposed in contact with the second edge of the pivot member. The spring applies a detent force to the pivot member when the pivot member rotates in either rotational direction about an axis of the pivot pin. 
     In yet another example of the present invention, the reverse lever is in the third position the outer surface of the cam portion is in contact with the pivot dowel of the spring pivot assembly of the first shift fork which partially engages the synchronizer with the driven gear of the first gear set. 
     Further features and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a perspective view of a transmission according to the present disclosure; 
         FIG. 2  is a partial plan view of the transmission according to the present disclosure; 
         FIG. 3  is a perspective view of a reverse gear engagement lever or member according to the present disclosure; 
         FIG. 4A  is an axial view of a synchronizer shift fork member according to the present disclosure; 
         FIG. 4B  is an exploded perspective view of a pre-synchronizer assembly according to the present disclosure; 
         FIG. 4C  is a perspective view of the pre-synchronizer assembly according to the present disclosure; 
         FIG. 4D  is a perspective view of the pre-synchronizer assembly according to the present disclosure; 
         FIG. 5  is a partial plan view of the transmission according to the present disclosure; 
         FIG. 6  is a partial plan view of the transmission according to the present disclosure; 
         FIG. 7  is a partial plan view of the transmission according to the present disclosure; and 
         FIG. 8  is a partial plan view of the transmission according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     Referring to the drawings, wherein like reference numbers refer to like components, in  FIG. 1  a perspective view of a partial transmission  10  of the present invention is illustrated. The transmission  10  includes an input shaft  12 , a main shaft  14 , and an idler shaft  16  with each supported by a housing  18 . The input shaft  12  is connected to, for example, an engine output shaft (not shown) and the main shaft  14  is connected to, for example, a vehicle drive shaft (not shown) that provides torque to a drive wheel of the vehicle. The transmission  10  further includes a plurality of gearsets  20 , a plurality of synchronizers  22 , and a plurality of shift rails  23 . The input and main shafts  12 ,  14  rotatably support the plurality of gear sets  20 . A plurality of synchronizers  22  (one of which is shown) are supported by the main shaft  14  and are selectively manipulated to achieve a desired forward gear ratio between the input shaft  12  and the main shaft  14 . For example, to achieve a forward gear ratio, a synchronizer  22 A is engaged to couple a gear  20 A from one of the plurality of gear sets  20  to the main shaft  14  in order to transfer torque from the input shaft  12  to the main shaft  14 . 
     The idler shaft  16  is fixed securely with the housing  18  and supports an idler gear  24 . The idler gear  24  is capable of selective movement along the idler shaft  16  to intermesh with both of a reverse gear  26  of the input shaft  12  and a sleeve gear or member  28  on the main shaft  14 . When a reverse gear ratio is desired, the idler gear  24  meshes independently with the reverse gear  26  that is engaged with the input shaft  12  and the sleeve gear  28  that is selectively engaged with the main shaft  14 . When engaged, the idler gear assembly  24  reverses the direction of the sleeve gear  28  of the main shaft  14  and therefore reverses the direction of rotation of the drive shaft (not shown) of the vehicle. For example, the idler gear assembly  24  is coupled to a shift fork linkage  30  that includes a first end  30 A secured to a reverse shift rail or member  32  of the plurality of shift rails  23  and a second end  30 B that engages and moves the idler gear assembly  24  axially along the idler shaft  16  upon axial movement of the reverse shift rail  32 . However, other methods or mechanisms of manipulating the idler gear assembly  24  may be employed without departing from the scope of the present invention. 
     Referring now to  FIG. 2 , a partial plan view of the transmission  10  of the present invention is shown. The transmission  10  further includes a plurality of shift forks  34 , of which one example is shown, and a reverse gear engagement lever  36  configured to interact with the reverse shift rail  32  and the shift fork  34 . The shift fork  34  is coupled for axial movement with the synchronizer  22 . 
     Turning now to  FIG. 3 , the reverse gear engagement lever  36  is illustrated in detail. The reverse gear engagement lever  36  includes a first end portion  36 A, a second end portion  36 B and a cam portion  36 C. The first end portion  36 A is fixed to an elongated member or shaft  39  and is rotatable about an axis i in a first and second rotational directions R 1 , R 2 . The second end portion  36 B is configured for engagement with a reverse notch  32 A of the reverse shift rail  32  as shown in  FIG. 2 . The cam portion  36 C has an outer surface  36 E and an inner surface  36 F. The reverse gear engagement lever  36  is also capable of movement in a first and second axial directions D 1 , D 2 . 
     Turning now to  FIG. 4A , the shift fork  34  is illustrated in detail. The shift fork  34  includes a synchronizer portion  34 A, a shift rail portion  34 B, an actuator portion  34 C, and a pre-synchronizer portion  34 D. The synchronizer portion  34 A maintains a semi-annular shape having an inner diameter configured to engage an outer diameter of the synchronizer  22 A shown in  FIGS. 1 and 2 . The shift rail portion  34 B is rotatably supported on a shift rail  23 , shown in  FIG. 1 , which is disposed parallel to the input and main shafts  12 ,  14 . The actuator portion  34 C includes a notch  34 E that is configured to engage a gear shift linkage (not shown). The shift linkage provides input from the driver through a gear shift mechanism (not shown) via axial movement along the shift rail in directions D 3 , D 4 . The axial movement is transferred to the synchronizer  22 A thus, depending on the axial direction D 3 , D 4 , engages one of two gears  20 A,  20 C with the main shaft  14 . 
     With continuing reference to  FIG. 4A  and additional reference to  FIGS. 4B and 4C , the pre-synchronizer portion  34 D of the shift fork  34  is illustrated in greater detail. The pre-synchronizer portion  34 D of the shift fork  34  includes a flange  38  and a spring pivot assembly  40 . The flange  38  has a first end portion  38 A fixed to the synchronizer portion  34 A of the shift fork  34  and a second end portion  38 B including a pivot hole  38 C. The spring pivot assembly  40  includes a pivot pin  42 , a spring  44 , a pivot member  46 , and a pivot dowel  48 . The pivot pin  42  is rotatably supported in the pivot hole  38 C of the second end portion  38 B of the flange  38 . The pivot member  46  includes a first end portion  46 A and a second end portion  46 B opposite the first end portion  46 A, a hole  46 C disposed in the first end portion  46 A, a first edge  46 D, a second edge  46 E, and an anti-rotation flange  46 F extending perpendicularly from the second edge  46 E of the pivot member  46 . The hole  46 C of the first end portion  46 A is coaxial with the pivot hole  38 C of the flange  38 . The pivot pin  42  passes through both the pivot hole  38 C of the flange  38  and the hole  46 C of the pivot member  46 . Thus the pivot member  46  is rotatably supported by the pivot pin  42  and rotates about the axis of the pivot pin  42  relative to the flange  38 . The pivot member  46  extends adjacent to the flange  38  from the pivot pin  42  toward the synchronizer portion  34 A of the shift fork  34 . The spring  44  is a coil spring disposed on the outer axial surface  42 A of the pivot pin  42  and includes a first end portion  44 A and a second end portion  44 B. However, other types of springs and configurations may be employed without departing from the scope of the invention. The end portions  44 A,  44 B of the spring  44  each form a hook capable of wrapping around opposite edges  38 D,  38 E of the flange  38 . The first end portion  44 B of the spring  44  contacts the first edge  46 D of the pivot member  46  while the second end portion  44 A of the spring  44  wraps around the anti-rotation flange  46 F of the pivot member  46 . The pivot member  46  is aligned with the flange  38  to establish a first or disengaged position P 1 . Rotating the pivot member  46  about the axis j of the pivot pin  42  establishes a second position P 2 . However, as the pivot member  46  rotates in a third rotational direction R 3 , the second end portion  44 B of the spring  44  applies a centering force to the first edge  46 D of the pivot member  46  thus providing a detent feel to the rotation of the pivot member  46 . Alternatively, as the pivot member  46  rotates in a fourth rotational direction R 4  the anti-rotation flange  46 F of the pivot member  46  abuts the edge  38 E of the flange  38 , thus preventing rotation of the pivot member  46  in the fourth rotational direction R 4 . A pivot dowel  48  is fixed to the second end portion  46 B of the pivot member  46 . The axis k of the pivot dowel  48  extends perpendicularly from a top surface  46 G of the pivot member  46 . 
     Turning generally now to FIGS.  2  and  5 - 9 , a schematic of the partial transmission  10  is illustrated in five positions including the first or disengaged position ( FIG. 2 ), a second or reverse lever engagement position ( FIG. 5 ), a third or partial engagement position ( FIG. 6 ), a fourth or full engagement position ( FIG. 7 ), and a fifth or released position ( FIG. 8 ). In the first position, as shown in  FIG. 2 , the idler gear  24  does not contact or mesh with either of the reverse gear  26  of the input shaft  12  or the sleeve gear  28  of the main shaft  14 . Additionally, the reverse gear engagement lever  36  is disengaged from the reverse notch  32 A of the reverse shift rail  32 . 
     In the second position, as shown in  FIG. 5 , the reverse gear engagement lever  36  is moved along the axis i in the D 1  direction as shown in  FIG. 3 . The second end  36 B of the reverse gear engagement lever  36  engages the reverse notch  32 A of the reverse shift rail  32 . However, the idler gear  24  still does not contact or mesh with either of the reverse gear  26  of the input shaft  12  or the sleeve gear  28  of the main shaft  14 . 
     In the third position, the reverse gear engagement lever  36  rotates about the axis i in the first rotational direction R 1  to a first rotational position, thus translating the reverse shift rail  32  and therefore the idler gear  24  axially along the idler shaft  16  to contact and mesh with the reverse gear  26  of the input shaft  12  but does not yet contact or mesh with the sleeve gear  28  of the main shaft  14 . The outer surface  36 E of the cam portion  36 D of the reverse gear engagement lever  36  contacts and applies a force to the pivot dowel  48  which in turn applies a force to the spring  44  which has capacitive effect in applying a force to the shift fork  34  and the synchronizer  22 A which triggers partial engagement of the corresponding gear  20 A to the main shaft. Since the gear  20 A meshes with a corresponding gear  20 B rotatably fixed to the input shaft  12 , the rotational speed of the input shaft  12  is reduced to the same rotational speed of the main shaft  14 . 
     In the fourth position, as shown in  FIG. 7 , the reverse gear engagement lever  36  rotates further about the axis i in the first direction R 1  to a second rotational position to achieve engagement of the reverse idler gear  24  and the sleeve gear  22  of the main shaft  14 . While in the forth position, the synchronizer  22 B adjacent the sleeve gear  28  engages the main shaft  14  and the sleeve gear  28  for common rotation. Also, the cam portion  36 D of the reverse gear engagement lever  36  is no longer in contact with the pivot dowel  48  of the shift fork  34  thus releasing the synchronizer  22 A which returns to a neutral position and disengages the gear  20 A from the main shaft  14 . 
     In the fifth position, as shown in  FIG. 8 , the reverse gear engagement lever  36  rotates in the opposite rotational direction R 2  about the axis i to a third rotational position, moving the idler gear  24  axially so that it no longer meshes with the reverse gear  26  of the input shaft  12  and the sleeve gear  28  of the main shaft  14 . The pivot dowel  48  is in contact with the inner surface  36 F of the cam portion  36 D of the reverse gear engagement lever  36 . The spring  44  provides a compliant link between the reverse gear engagement lever  36  and the shift fork  34  thus preventing the shift fork  34  from engaging the synchronizer with either gear  20 A,  20 C of the main shaft  14 . As the reverse gear engagement lever  36  returns to the first position, the pivot dowel  48  is released into the neutral position as shown in  FIG. 2 . 
     The description of the disclosure is merely exemplary in nature and variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.