Abstract:
A shift rod assembly for a transmission of a vehicle having a pair of shift rod members, a gear set assembly, and a pair of link members. The shift rod members each have a splined portion formed in the outer surface that mesh with a gear of the gear set assembly to translate rotational movement from one shift rod member to the other. The link members connect the shift rods to translate axial movement from one shift rod member to the other.

Description:
FIELD 
     The present disclosure relates to a mechanical shift linkage assembly for a transmission, and more particularly to a mechanical shift rod assembly linkage between a stick shift gear selector and a manual transmission. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
     Some vehicle powertrains are designed to include a front mounted engine with a transmission located near the rear axle. For manual transmission applications, this design requires a linkage or connection between the driver controlled gear stick shift and the transmission. Additionally, the connection point of the stick shift and the transmission were offline or simply not a straight connection. In the past, a non-straight linkage or shift rod was utilized to transfer rotational and translational movement from the stick shift to the transmission. The shift rod was designed to compensate for the non-aligning connection with a twisted design requiring u-joints. While this worked well for its intended purpose, there are several shortcomings associated with the shift rod design. For example, the shift rod tended to twist upon itself instead of translating the rotational motion to the transmission. The torsional flexibility in the shift rod leads to increased shift effort for the driver and longer shift time. Therefore, there is room in the art for improved gear set shifter connection that reduce shift time, driver shift effort, and improved shift quality that translates into a better driving experience. 
     SUMMARY 
     The present invention provides a shift linkage assembly for a transmission of a vehicle. The shift linkage assembly includes a first and a second shift linkage member, a gear set assembly, and a first and a second axial movement link member. Each shift linkage member has a first end and a second end opposite the first end, and a first radial channel formed proximate the second end. The first end of the first shift linkage member is fixed to a gear selection lever for common rotational and axial movement and the first end of the second shift linkage member is fixed to a transmission gear selection mechanism for common rotational and axial movement. The gear set assembly has a first, a second, and a third gear, and a housing. The housing rotatably supports the shift linkage members proximate the second end. The third gear is rotatably supported by the housing and is disposed in a meshing relationship with the first and second gears. The first gear is engaged for common rotation with the first shift linkage member and the second gear is engaged for common rotation with the second shift linkage member. Each of the first and second axial movement link members have at least a first bore. The first link member is disposed in the first radial channel of the first shift linkage member. The first link member is configured to engage the second end of the second shift linkage member the second link member is disposed in the first radial channel of the second shift linkage member. The second link member is configured to engage the second end of the first link member. The shift linkage members are rotatable relative to the link members. 
     In another example of the present invention, each of the shift linkage members have a second radial channel formed at the second end of the shift linkage members on an opposite side of the splined portion from the first radial channel. 
     In yet another example of the present invention, each of the link members have an elongated flat shape, the first bore is disposed proximate a first end of the link members, a second bore is disposed proximate a second end of the link member, the first link member is further disposed such that the second bore of the first link member is in the second radial channel of the second shift linkage member, and the second link member is further disposed such that the second bore of the second link member is in the second radial channel of the first shift linkage member. 
     In yet another example of the present invention, each of the shift linkage members have an axial bore disposed in the second end. 
     In yet another example of the present invention, each of the link members have an elongated flat shape, the first bore is disposed proximate a first end of the link members, a boss is disposed proximate a second end of the link member, the first link member is further disposed such that the boss of the first link member is disposed in the bore of the second shift linkage member, and the second link member is further disposed such that the boss of the second link member is disposed in the bore of the first shift linkage member. 
     In yet another example of the present invention, the housing of the gear set assembly is grounded to the vehicle. 
     In yet another example of the present invention, the housing of the gear set assembly is fixed to a torque tube of the vehicle. 
     In yet another example of the present invention, the shift linkage members are axially straight. 
     In yet another example of the present invention, a rotation of the first shift linkage results in a single rotation of the second shift linkage. 
     In yet another example of the present invention, a rotation of the first shift linkage results in less than one rotation of the second shift linkage. 
     In yet another example of the present invention, a single rotation of the first shift linkage results in more than one rotation of the second shift linkage. 
     In yet another example of the present invention, the first and second linkage members include a splined portion formed in an outer surface of the shift rod members between the first radial channel and the second end. 
     In yet another example of the present invention, each of the first and second gears include a splined inner surface that is meshed with the splined portions of each of the first and second linkage members. 
     Further features and advantages of the present disclosure 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 an illustration of a manual transmission gear shift and shift linkage assembly according to the present disclosure; 
         FIG. 2  is an illustration of a shift linkage assembly according to the present disclosure; 
         FIG. 3A  is an illustration of a shift linkage assembly installed on a powertrain torque tube according the present disclosure; 
         FIG. 3B  is an illustration of a gear set portion of a shift linkage assembly according the present disclosure; and 
         FIG. 4  is an illustration of a gear set portion of a shift linkage assembly according 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. 
     With reference to  FIG. 1 , an exemplary transmission gear shift selector assembly is generally indicated by reference number  10 . The gear shift selector assembly  10  establishes a mechanical connection between a driver of the vehicle and a transmission gear selector (not shown). The gear shift selector assembly includes a gear selector lever or stick  12  and a shift linkage assembly  14 . More specifically, the shift linkage assembly  14  mechanically connects the gear selector lever  12  to the transmission gear selector and transfers rotational and translational motion from the gear selector lever or suck  12  to the transmission gear selector. The shift linkage assembly  14  includes a first and a second linkage member or rod  16 ,  18 , a first and a second axial movement members or links  38 ,  40 , and a gear set assembly  20 . The first linkage member  16  has a first end  22  and a second end  24  opposite the first end  22 . The first end  22  is connected for common rotational movement and common axial translational movement with the gear selector lever  12 . The second end  24  is engaged with the gear set assembly  20 . The second linkage member  18  includes a first end  26  and a second end  28  opposite the first end  26 . The first end  26  is connected for common rotational movement and common axial translational movement with the transmission gear selector. The second end  28  is engaged with the gear set assembly  20 . 
     Referring now to  FIG. 2 , another example of the gear set assembly  20  and linkage members  16 ,  18  is illustrated and will now be described. Each of the linkage members  16 ,  18  further include a first radial groove or channel  50 ,  52  proximate the second end  24 ,  26  of the linkage members  16 ,  18 , a splined portion  28 ,  29  formed into the outer surface of the linkage members adjacent to the first radial groove or channel  50 ,  52 , and a second radial groove or channel  54 ,  56  disposed on the opposite side of the splined portion  28 ,  29  from the first groove or channel  50 ,  52 . The gear set assembly  20  includes a first gear  30 , a second gear  32 , a third gear  34 , and a housing or mount  36  (shown in  FIG. 1 ). The third gear  34  is rotationally supported by the housing  36  and rotates about an axis k that is parallel to axis i, j of the first and second linkage members  16 ,  18 . The first gear  30  includes an inner splined surface  30 A that is disposed on the splined portion  28  of the first linkage member  16  so that inner splined surface  30 A of the gear  30  meshes for common rotation with the splined portion  28  of the first linkage member  16 . The second gear  32  includes an inner splined surface  32 A that is disposed on the splined portion  29  of the second linkage member  18  so that inner splined surface  32 A of the gear  32  meshes for common rotation with the splined portion  29  of the second linkage member  18 . The gear  34  meshes with each of the first gear  30  and the second gear  32 . The linkage members  16 ,  18  are capable of axial translation or movement with respect to the first and second gears  30 ,  32  while still keeping in common rotational movement of the gears  30 ,  32 . In this example, the gears  30 ,  32 ,  34  are spur gears, however, other types of gears can be used without departing from the scope of the invention. 
     The first and second axial movement links  38 ,  40  are elongated flat members each having a first and a second bore  42 ,  44 ,  46 ,  48  disposed symmetrically in the links  38 ,  40 . The links  38 ,  40  are disposed on the linkage members  16 ,  18 . The linkage members  16 ,  18  pass through the bores  42 ,  44 ,  46 ,  48  of the links  38 ,  40  such that the links  38 ,  40  are captured by or disposed in the radial channels  50 ,  52 ,  54 ,  56  so that the linkage members  16 ,  18  rotate freely with respect to the links  38 ,  40  and translate axial movement from the first linkage member  16  to the second linkage member  18 . 
     Referring now to  FIGS. 3A and 3B , another example of the shift linkage assembly  14  is illustrated and will now be described. In the assembled state,  FIG. 3A  shows the linkage members  16 ,  18  rotationally supported by the housing  36 . Furthermore, the housing is grounded or fixed to a torque tube  58  that provides a housing through which passes the drive shaft from the engine (not shown) to the transmission (not shown).  FIG. 3A  also displays the shift linkage assembly  14  in an axially neutral position. Referring to  FIG. 3B , the shift linkage assembly  14  is shown in an axially shifted or non-neutral position. 
     Referring now to  FIG. 4 , another example of the shift linkage assembly  10  is illustrated and will now be described with reference numbers from  FIGS. 1-3B  carried-over for similar elements. In particular, the shift linkage assembly  14  includes a first and second axial movement links  58 ,  60  are elongated flat members each having a bore  62 ,  64  and a cylindrical extension portion  66 ,  68 . The links  58 ,  60  are disposed on the linkage members  16 ,  18 . For example, each linkage member includes a bore  70 ,  72  disposed in the second end  24 ,  26  of the linkage members  16 ,  18 , and a radial groove or channel  54 ,  56  disposed on the opposite side of the splined portion  30 ,  32  formed on the outer surface of the linkage members  16 ,  18 . The linkage members  16 ,  18  pass through the bores  62 ,  64  of the links  38 ,  40  such that the links  58 ,  60  are captured by or disposed in the radial channels  54 ,  56 . The extension portion  66 ,  68  of the links  38 ,  40  are disposed in the bores  70 ,  72  of the linkage members  16 ,  18  so that the linkage member  16 ,  18  rotate freely with respect to the links  58 ,  60  and translate axial movement from the first linkage member  16  to the second linkage member  18 . 
     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.