Abstract:
A shifter rod assembly used in automotive vehicles extends between a manual shifter assembly having a manual shift lever and a transmission spaced from the manual shift lever. Large tolerance universal joints with play between the components thereof connect the shifter rod assembly to the manual shifter assembly and to the transmission. In order to eliminate rattle noise in the universal joints, the universal joints are each encased in a layer of elastomer. A preferred elastomer is silicone elastomer can be applied in liquid form, cures at room temperature and maintains integrity at temperatures in a range of about 200° F. to 240° F.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to shifter rod assemblies for automotive transmissions. More particularly, this invention relates to shifter rod assemblies which extend from gear shift levers to transmissions for manually changing output speeds and rotational directions of transmissions.  
       BACKGROUND OF THE INVENTION  
       [0002]     Typically, automotive vehicles include a powertrain comprising an engine which is coupled by a clutch to a transmission that is in turn connected to road wheels. To select gear ratios, the gears of manual transmissions are axially shifted and rotated by a lever in the passenger compartment. When the transmission is not positioned adjacent to the person driving the vehicle, it is necessary to connect the shift lever to the transmission with a linkage. In some automotive vehicles, the transmission is positioned proximate the rear road wheels, while the engine is disposed adjacent to the front road wheels. Since in this arrangement the transmission is behind the driver, there is a need for a shifter rod assembly which transmits shift lever positions back to the transmission. This involves axial pushing, pulling, and rotation of the shifter rod assembly. Moreover, an actuator shaft extending transversely from the shift lever is not aligned with the far end of shifter rod assembly. Consequently, the shifter rod assembly has parts which move relative to one another during shifting to accommodate axial misalignment. In accordance with one arrangement, this misalignment is accommodated by universal joints positioned at opposite ends of the shifter rod assembly.  
         [0003]     When an automotive component such as a universal joint is assembled with parts which move relative to one another, the cost of the assembly becomes a consideration because there is a tendency to decrease tolerances in order to minimize vibration. Decreasing tolerances requires increasing machining expenses. Consequently, there is a need to minimize vibration of shifter rod assemblies having universal joints without substantially increasing cost.  
       SUMMARY OF THE INVENTION  
       [0004]     In view of the aforementioned considerations, a shifter rod assembly is provided having a first end for connection to a manual gear shift and a second end for connection to a transmission for transmitting both axial and rotational motion from the manual gear shift to the transmission. The first end of the shifter rod is connected to the gear shift assembly through a first universal joint and the second end of the shifter rod is connected to the transmission through a second universal joint. Elastomer encases the first universal and second universal joints.  
         [0005]     In a further aspect of the shifter rod assembly, first and second boots are disposed over the elastomer.  
         [0006]     In still a further aspect of the shifter rod assembly, the first and second universal joints are low precision, large tolerance universal joints having components with play therein permitting noise to emanate from the universal joints in the absence of elastomer encasing the universal joints.  
         [0007]     In still a further aspect of the shifter rod assembly, the elastomer is comprised of a silicone elastomer compound that cures at room temperature. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     Various other features and attendant advantages of the shifter rod assembly will be more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:  
         [0009]      FIG. 1  is a schematic side view of an automotive vehicle employing the shifter rod assembly of the present invention;  
         [0010]      FIG. 2  is an elevation taken along lines  2 - 2  of  FIG. 1 ;  
         [0011]      FIG. 3  is a perspective view of a shifter rod assembly extending between a manual gear shift assembly and a transmission;  
         [0012]      FIG. 4  is a perspective view of the shifter rod assembly of  FIG. 3  shown in isolation;  
         [0013]      FIG. 5  is a side perspective view of the shifter rod assembly of  FIG. 4  with uncovered universal joints;  
         [0014]      FIG. 6  is a side perspective view of a shifter rod assembly similar to  FIG. 5  but showing universal joints encased in elastomer, and  
         [0015]      FIG. 7  is a view similar to  FIGS. 5 and 6  showing rubber boots positioned over the elastomer of  FIG. 6 .  
     
    
     DETAILED DESCRIPTION  
       [0016]     Referring now to  FIGS. 1-2  there is shown an automotive vehicle  10  having a passenger compartment  11  behind which is positioned a rear transaxle  12  for driving rear road wheels of the vehicle. The transaxle  12  has a bell housing  13  connected by a torque tube  14  to an engine  15 . A propeller shaft  16  that rotates within the torque tube  14  drives a manual transmission  18  which is part of the transaxle  12 .  
         [0017]     The torque tube  14  is isolated from the passenger compartment  11  of the vehicle  10  by a tunnel  19  in which a manual shifter assembly  20  having a housing  22  is disposed. The housing  22  is bolted by bolts  24  to the exterior of the torque tube  14 . Projecting from the housing  22  and upward out of the tunnel  19  is a manual shift lever  26  that is operated by a driver in the passenger compartment  11  of the vehicle  10 .  
         [0018]     Referring now mainly to  FIG. 3 , within the housing  20  the manual shift lever  26  is connected by an actuator shaft  28  to a shifter rod assembly  30  that extends to the transmission  18  within the transaxle  12 . In accordance with one example in which the transaxle is behind the driver, the shifter rod assembly  30  has a length of about 0.6 meters.  
         [0019]     Referring now to  FIG. 4  in combination with  FIG. 3 , the shifter rod assembly  30  has a first end  32  that is connected by a clamp  34  onto the actuator shaft  28 , which is shifted both axially with respect to a first axis  36  and rotated with respect to the first axis by the manually operated lever  26  of  FIGS. 1-3 . In order to fix the shifter rod assembly  30  to the actuator shaft  28 , the clamp  34  is retained by a bolt  38  that is received through aligned slots disposed proximate the first end  32  of the shifter rod assembly  30  and the free end of the actuator shaft  28 .  
         [0020]     A second end  42  of the shifter rod assembly  30  includes an end sleeve  43  that is connected to a gear operating shaft  44  extending into the transmission  18  in order to select gear ratios in the transmission with which to drive the road wheels of the vehicle  10 . The gear operating shaft  44  is retained on the end sleeve  43  of the shifter rod assembly  30  by a roll pin  46  which passes through aligned holes  47  and  48  in the end sleeve and operating shaft, respectively, so that the operating shaft is fixed axially and rotationally to the second end  42  of the shifter rod assembly.  
         [0021]     The shifter rod assembly  30  includes a tubular shifter rod  50  made of steel and having three portions. The tubular shifter rod  50  has a first portion  52  that extends parallel to the torque tube  14  along an upper side surface thereof; a second portion  54  rigidly connected to the first portion  52  by a bend  56 , and a third portion  58  rigidly joined by a bend  60  to the second portion  54 . The second portion  54  extends obliquely up and over the top of the torque tube  14  ( FIG. 3 ) while the third portion  58  extends along the top of the torque tube in a direction parallel to the axis of the torque tube. The second end  42  of the shifter rod assembly  30  is mounted to the third section  58  of the shifter rod  50  through a crank  64  disposed at the end of the third section. The crank  64  offsets the third section  58  of the shifter rod  50  with respect to a second axis  68  that is the axis of the second end  42  of the shifter rod assembly  30 .  
         [0022]     Referring now to  FIG. 5  there is shown a first universal joint  70  and a second universal joint  72 , both preferably machined of steel at relatively large tolerances. The first universal joint  70  is disposed between the first section  52  of the tubular shifter rod  50  and a sleeve  74  which receives therein the actuator shaft  28  (see  FIGS. 1 and 2 ) from the manual shift assembly  20 . The sleeve  74  has a slot  76  formed therein which is complemented by a similar slot in the actuator shaft  28  so that the bolt  38  which passes through the clamp  34  of  FIGS. 1 and 2  fixes the collar  74  with respect to the actuator shaft, wherein the collar  74  rotates with and axially shifts with the actuator shaft.  
         [0023]     The sleeve  74  is either unitary or fixed integrally with respect to a first yoke portion  80  of the first universal joint  70 . The first universal joint  70  has a first pin  84  which extends through the legs of the first yoke portion  80  and through an internal block  86 . The internal block  86  is connected by a second pin  88  to a second yoke  90  that has a pair of legs disposed in the gap between the legs of the first yoke  80 , which are in turn retained in a gap between the legs of the first yoke by the second pin  88 . The second yoke  90  is welded or otherwise fixed to the first portion  52  of the tubular shifter rod  50 .  
         [0024]     The crank arm  64  on the third portion  58  of the shifter rod  50  has the end sleeve  43  of the shifter rod assembly  30  attached thereto by the second universal joint  72 . The second universal joint  72  has a first yoke portion  102  which is unitary or fixed integrally with the end sleeve  43  that receives the gear operating shaft  44  connected to the transmission  18 . The first yoke  102  is connected to an internal block  104  by a pin  106 . A pin  108  also extends through the block  104  and connects the legs of a second yoke portion  110  to the internal block  104 . The yoke portion  110  is welded to the crank arm  64  that is fixed in the end of the third portion  58  of shifter rod  50 .  
         [0025]     The shifter rod assembly  30 , which is comprised of all the components between the first and second ends  32  and  42  thereof, is preferably provided with universal joints  70  and  72  that are low-precision universal joints having relatively large tolerances in order to minimize the expense of fabricating the shifter rod assembly. Since the transmission  18  is only intermittently operated, and since there is relatively small rotational and axial motion transmitted by the shifter rod assembly  30  from the manual shift lever  26  to the transmission  18 , there is no mechanical need to precision machine the components of the universal joints  70  and  72 . Precision machining the universal joints  70  and  72  adds considerable expense to the shifter rod assembly  30  without increasing reliability or smooth operational feel. Since the universal joints  70  and  72  are subject to engine, drive train and road vibration, low precision universal joints  70  and  72 , configured as in  FIG. 3  with large tolerances, tend to rattle.  
         [0026]     As is seen in  FIG. 6 , in order to preclude rattling, the large tolerance universal joints  70  and  72  are encased in elastomer layers  120  and  122 , respectively. In a preferred embodiment, the material of the elastomer layers  120  and  122  cures at room temperature. Materials such as, but not limited to, silicone elastomers (for example, room temperature vinyl silicone elastomer) provide suitable materials for encasing the universal joints  70  and  72 . Preferably, the elastomer layers  120  and  122  fill voids in the universal joints  70  and  72 , such as the voids between the block  86  and the yokes  80  and  90  of the universal joint  70  and the voids between the block  104  and the yokes  110  and  102  of the universal joint  72 . As is seen in  FIG. 6 , the elastomer layers  120  and  122  also extend over the outer surfaces of the yokes  80  and  90  and  102  and  110  and over the exposed ends of the pins  84  and  88  and the pins  104 , 106 , as well as any other exposed surfaces of the universal joints. While it is preferable that complete filling of voids and coating of surfaces occur, it is sufficient that encasement of the universal joints  70  and  72  is complete enough to substantially minimize rattle or the risk of rattle in the universal joints. Silicone elastomer is a preferable material because it will retain its integrity at sustained temperatures of about 200° F. with periodic increases to about 240° F.  
         [0027]     Referring now to  FIG. 7 , optional first and second rubber boots  130  and  132  are positioned over the elastomer layers  120  and  122 , respectively. However, if the elastomeric layers  120  and  122  completely encase the universal joints  70  and  72  and themselves keep out dust, then in accordance with one embodiment of the invention, the boots may be dispensed with.  
         [0028]     According to another embodiment of the invention, after the boots  130  and  132  have been slipped over the universal joints  70  and  72 , a technique for reducing rattle in the universal joints  70  and  72  is to inject liquid elastomer between the universal joints and the boots. If the liquid elastomer is a silicone elastomer, it coats the universal joints  70  and  72  and cures at room temperature.  
         [0029]     Instead of utilizing the first and second boots  130  and  132  as molds to retain and form injected liquid elastomer, other processes may be employed such as dipping the universal joints  70  and  72  in liquid elastomer and then allowing the silicone to cure. In another process the universal joints  70  and  72  are surrounded by molds (not shown) into which elastomer is injected in liquid form. The molds are removed after the elastomer has solidified and has cured or is curing.  
         [0030]     Other approaches comprise applying sleeves of heat shrinkable polymers over the universal joints  70  and  72  and then applying heat to constrict the sleeves against surfaces of the universal joints.  
         [0031]     Other materials suggested for the elastomer layers  120  and  122  are TEFLON®, neoprene, butyl rubber, styrene-butadine rubber, acrylonitrite-styrene based rubber and polyvinyl chloride; however, silicone elastomer is preferable because of its liquid application, room temperature cure and high temperature resistance.  
         [0032]     From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing form the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.