Abstract:
A vibration isolation system reduces rattling in a reverse lockout mechanism for a manual shifter. A shaft retained in a shifter housing has an upper end for a shift knob and an enlarged barrel section proximate the housing. A lockout skirt slides on the shaft between upper and lower positions. The lockout skirt has a shoulder extending radially outward, and the housing includes a stop block such that the shaft is prevented from pivoting to a reverse gear position when the lockout skirt is in the lower position and is free to move to the reverse gear position when the lockout skirt is in the upper position. A spring retained on the shaft biases the lockout skirt toward the lower position. A plurality of lubricated O-rings are disposed on the shaft to define sliding interfaces between the lockout skirt and the shaft and between the lockout skirt and the barrel.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. provisional application Ser. No. 62/236,181, filed Oct. 2, 2015, which is hereby incorporated by reference in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates in general to a gear shift selector for manual transmissions, and, more specifically, to a reverse lockout mechanism for a shifter. 
         [0004]    A typical manual transmission shift lever consists of a metal shift rod with a plastic reverse lock out mechanism. The lock out prevents the shift lever from gating into reverse without first manually lifting a lock out ring. The lock out mechanism typically is comprised of three components, namely two plastic cylinders and a metal return spring. All three components slide (up and down) relative to a stationary metal shift rod. The shifter assembly is exposed to high levels of vibration because the shifter is bolted directly to the tail of the transmission. As a result, objectionable rattles and buzzes can propagate due to contact between the metal shift rod and the three components of the shifter lock out mechanism. 
       SUMMARY OF THE INVENTION 
       [0005]    To remedy this problem, an isolation system disclosed herein prevents hard contact between the lock out mechanism components and the shift rod. The isolation mechanism allows for smooth sliding motion between the lock out mechanism and shift rod, while providing sufficient isolation to prevent rattle and buzz. 
         [0006]    An isolation mechanism of the invention may include 1) a lubricated rubber O-ring between the top of the shift rod and the upper sliding section (i.e., lift ring), 2) a lubricated rubber O-ring between the middle of the shift rod and upper neck of the lower sliding section (i.e., lock out skirt), 3) a lubricated rubber O-ring between the bottom of the shift rod and the bottom of the lower lock out skirt, 4) at least one non-lubricated elastomeric bumper between the middle of the lock out skirt and a flattened portion of the shift rod, 5) a return spring with an elastomeric or damping material coating the spring, and 6) a tapered bumper mounted on the shaft as a bottom support or rest for the lift ring at its bottom position. 
         [0007]    In one preferred embodiment, the invention provides a vibration isolation system for a reverse lockout mechanism in a manual shifter comprising a shaft. A lockout skirt and a plurality of lubricated O-rings are provided on the shaft. There is a gap between the inside diameter of the skirt and the outside diameter of the O-rings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic diagram showing elements of a shifter. 
           [0009]      FIG. 2  is a perspective view of a shifter and portion of a transmission housing. 
           [0010]      FIG. 3  is a perspective view of the shifter without a boot or lift ring. 
           [0011]      FIG. 4  is a perspective view of the shifter with a lockout skirt removed. 
           [0012]      FIG. 5  is a perspective view of a lockout skirt. 
           [0013]      FIG. 6  is an exploded, perspective view showing the mounting of a shifter to a floor panel. 
           [0014]      FIG. 7  is a side view of a shifter shaft and lockout skirt. 
           [0015]      FIGS. 8-10  are a perspective view, cross-sectional view, and bottom view of a lift ring with a boot, respectively. 
           [0016]      FIG. 11  is a cross section of a shifter including a lower lockout skirt. 
           [0017]      FIG. 12  is a cross section of a shifter including an upper lift ring. 
           [0018]      FIG. 13  is a perspective view showing the upper lift ring and lower lockout skirt mounted on the shaft. 
           [0019]      FIGS. 14 and 15  are perspective views of a keyed barrel for receiving the lower lockout skirt, with and without a rubber O-ring. 
           [0020]      FIG. 16  is a horizontal cross section of a keyed barrel and lockout skirt. 
           [0021]      FIG. 17  is a top, plan view of an O-ring for the keyed barrel of  FIGS. 14-16 . 
           [0022]      FIG. 18  is a cross section of an alternative embodiment of a keyed barrel and lockout skirt with sliding bumpers. 
           [0023]      FIG. 19  is a perspective view of the bumper of  FIG. 18 . 
           [0024]      FIG. 20  is a perspective view of another embodiment of the lockout skirt. 
           [0025]      FIG. 21  is a side view of an alternative embodiment of a keyed barrel. 
           [0026]      FIG. 22  is a cross section of an alternative embodiment of a sliding bumper and keyed barrel. 
           [0027]      FIG. 23  is a perspective view of the shifter identifying the sliding interfaces. 
           [0028]      FIGS. 24 and 25  depict O-rings at sliding interfaces with a preferred clearance, with and without lubricant, respectively. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]      FIG. 1  generally depicts the functional elements of a manual transmission shifter. A shifter housing  10  has an internal opening receiving a pivot ball  11  of a shaft  12 . Shaft  12  has a shift knob  13  on one end and attaches to a shift linkage  14  at the other end. For example, linkage  14  attaches to a transmission selector rod on a transmission (not shown). Linkage  14  rotates and moves longitudinally in response to movement of shaft  12  around a pivot point (i.e., ball  11 ) in housing  10 . Housing  10  has a rear bushing for attaching to a vehicle body (not shown). A reaction arm  17  extends from the front of housing  10  to attach via a front bushing  16  to a transmission housing (not shown). 
         [0030]      FIGS. 2 and 3  show a transmission  18  connected with linkage  14  and reaction arm  17  of the manual shifter. Housing  10  receives shaft  12  which supports knob  13 . To provide a reverse lockout feature, shifter housing  10  includes a stop block  19  that interfaces with a lower lockout skirt  20  having a shoulder  21  projecting towards stop block  19 . Lockout skirt  20  is axially movable along shaft  12  in order to lift shoulder  21  over stop block  19  to allow shaft  12  to be moved into a gate for the reverse gear when the driver pulls upward on a lift ring (i.e., upper lockout skirt)  22  which is rigidly attached with lower lockout skirt  20 . A return spring  24  normally urges lockout skirt  20  toward a downward position where movement into reverse is blocked. The shifter further includes a boot  9  which attaches to upper lift ring/lockout skirt  22 . Lift ring  22  is slidable into a recess beneath knob  13  so that a driver can pull lift ring  22  upward when shifting into reverse. 
         [0031]      FIG. 4  shows shaft  12  and housing  10  with lower lockout skirt  20  removed to reveal a barrel  23  mounted on shaft  12 . As shown in  FIG. 5 , lower lockout skirt  20  may be generally cylindrical (e.g., has a generally cylindrical internal cavity) in order to encircle barrel  23 . Shoulder  21  extends radially outward and has a slanted edge  25  for interfacing over a matching surface on stop block  19  to help guide the shifter into the reverse gate. At the upper end of lockout skirt  20 , an outer ring  26  includes clips  27  for snapping together with corresponding features on the upper lockout skirt. An inner flange  28  has a central hole to receive shaft  12  and provides a small clearance (i.e., gap) with respect to shaft  12 . One end of return spring  24  bears against flange  28 . 
         [0032]    Movable components which may tend to create rattle in the reverse lockout mechanism include the upper and lower lockout skirts and the return spring. By isolating these components with respect to shaft  12  and barrel  23 , undesirable rattle and buzz can be reduced or avoided. The isolation system may include lubricated O-ring interfaces strategically placed as shown in  FIG. 4 . Thus, an upper groove  30  in shaft  12  is shown for receiving an O-ring at an axial position that interfaces with an inside diameter of the upper lockout skirt. An O-ring  31  is placed in another groove on shaft  12  corresponding to an inside diameter at the upper end of the lower lockout skirt. An O-ring  32  is mounted in another corresponding groove at the lower end of barrel  23  for interfacing with the lower end of lower lockout skirt  20 . A disk-shaped bumper  33  may be mounted to the upper end of barrel  23  to avoid the thumping of a hard impact which could otherwise occur when a driver releases their grip on the upper lockout skirt and then the mechanism drops down into its rest position as a result of spring action. 
         [0033]      FIG. 6  illustrates the act of installing a shifter into a vehicle via an opening  71  in a upper front floor panel  70  next to a driver&#39;s seating position. After the portion of the shifter mechanism shown in  FIG. 6  is installed up through floor panel  70  and attached by fasteners (e.g., fastener  73 ) and the housing is attached via the front and rear bushings, then a boot portion of the shifter as shown in  FIG. 8  is installed from above. 
         [0034]      FIG. 7  shows additional details for the shifter mechanism assembly prior to attachment of the boot portion and upper lockout skirt. An O-ring  34  is installed in slot  30  and an additional O-ring/bumper  35  may be mounted on shaft  12  to provide a bottom stop for engaging a bottom edge of the upper lockout skirt/lift ring. Bumper  35  may be retained by a pin  36  (see  FIG. 11 ) passing through a corresponding aperture  37  in shaft  12  (see  FIG. 4 ). Bumper  35  or pin  36  may also provide an end stop and/or attachment for the upper end of return spring  24 . 
         [0035]      FIGS. 8-10  show boot portion  40  carrying upper lockout skirt  22  arranged so that shaft  12  extends through the top of skirt  22  for attachment with knob  13  (which screws onto the end of shaft  12 ). Skirt  22  includes ledge  42  for receiving clips  27  of the lower skirt. 
         [0036]      FIG. 11  is a cross-section showing lower skirt  20  mounted on shaft  12  with spring  24  held in place between bumper  35 /pin  36  and an upper end of the inner collar of skirt  20 . From top to bottom, O-rings  34 ,  31 , and  32  provide vibration isolation.  FIG. 12  is a cross-section showing upper lockout skirt  22  snapped together with lower lockout skirt  20 . The O-ring vibration isolators interface with the corresponding cylindrical surfaces, each of which has an axial length sufficient to provide a sliding distance necessary to lift up over the reverse lockout features.  FIG. 13  is a perspective view showing skirts  20  and  22  snapped together over shaft  12 . 
         [0037]    In a preferred embodiment, the outer diameters of O-rings  34  and  31  and the corresponding inner diameters of skirts  41  and  17  are chosen such that an open clearance (i.e., gap) is maintained. Preferably, a lubricant such as grease is applied to the O-rings to obtain a freely slidable interface. O-ring  32  at the lower end of lockout skirt  17  may also be provided “in clearance,” with or without a corresponding lubricant. Alternatively, any of the interfaces could be “in interference” (i.e., under slight compression) or flush if desired. The gap between O-ring  34  and skirt  22  is preferably about 0.26 mm (+/−0.225 mm), and the gap between O-ring  31  and the upper neck of skirt  20  is preferably about 0.27 mm (+/−0.225 mm). A similar gap is preferably used between O-ring  32  and the lower end of skirt  20 . 
         [0038]    As shown in  FIGS. 14-16 , barrel  23  may include flats  44  and  45  on opposite longitudinal sides. A lower skirt  46  has a matching profile in order to reduce or eliminate the ability of skirt  46  from rotating about the axis of the shaft as would be possible with a circular shape. A circumferential groove  47  is provided at the lower end of barrel  23  for receiving O-ring  48  which may have a specially molded shape (e.g., molded rubber) as shown in  FIG. 17  to match the shape of groove  47 . Alternatively, a circular O-ring can be used by stretching it over groove  47 . While the non-circular profile of barrel  23  and skirt  46  prevent rotation of the reverse lockout mechanism, the possibility of rattle at the corners  49  along the lateral side edges of flats  44  and  45  is introduced. To further reduce the occurrence of rattling and/or rotation, the interface between O-ring  48  installed in groove  47  and the inside surface of a skirt  46  could preferably include an interference fit (e.g., without any lubrication). 
         [0039]    In an alternative embodiment shown in  FIG. 18 , instead of an O-ring to reduce rattling of specially-shaped lockout skirt  46  on barrel  23 , resilient bumpers  50  and  51  may be mounted to an interior surface of skirt  46  to interface (either “in interference” or “in clearance”) with flats  44  and  45 , respectively. Bumpers  50  and  51  may be comprised of rubber, for example. In one embodiment of an interference fit, an overlap in the nominal dimensions of the barrel and bumpers may be about 0.2 mm (+0.1/−0.2 mm). As shown in  FIG. 19 , bumper  50  may have a tab  52  for extending through a mounting hole in the side of the lower lockout skirt. As shown in  FIG. 20 , a bumper strip  53  can be mounted along an inside surface of a lockout skirt  54  by a pair of tabs  55  and  56  captured in respective mounting holes in the lockout skirt. 
         [0040]    As shown in  FIG. 21 , barrel  23  may include a side flat  57  with a longitudinal notch  58  machined into the top edge of flat  57 . As shown in cross-section in  FIG. 22 , a matching lower lockout skirt  60  may have a mounting hole for a bumper  59  arranged to ride within notch  58  in a manner that prevents rotation of lockout skirt  60  (thereby keeping it centered on barrel  23 ). 
         [0041]      FIG. 23  indicates sliding interfaces A-D that can be employed in the isolation system of the invention. Interface A is between the upper lockout skirt/lift ring and the shaft. The upper lockout skirt is partially removed in order to shown Interface B which is between an upper end of the lower lockout skirt and the shaft. 
         [0042]    Interface C is between the lower end of the lower lockout skirt and the shaft. Interface D is between the lower lockout skirt and a flat or groove on the barrel for preventing rotation of the lower lockout skirt. 
         [0043]      FIG. 24  shows an interface “in clearance” with a gap  62  between a lockout skirt  63  and an O-ring  64  in a groove  65  on the shifter shaft or barrel.  FIG. 25  shows a lubricant  66  applied to O-ring  64  and packing the gap  62 . In order to achieve an acceptable balance between stability of the lockout skirts and ease of up/down motion, the gap size is a critical parameter. For at least interfaces A and B, a gap in the range of about 0.1 to 0.4 mm is selected, with the gap most preferably being about 0.26 mm (+/−0.225 mm). Interface C may also be in clearance, using the same range. Interface D (corresponding to the bumpers of  FIGS. 18-20 ) may use an “in interference” interface with an interference overlap in the range of about 0.0 to about 0.3 mm, with a most preferred overlap of 0.2 mm. 
         [0044]    To address rattle related to the return spring, a metal coiled spring is utilized with a damping material coating the return spring (or the underlying shaft). The damping material can be a resilient material such as rubber or foam. A clearance between the inside diameter of the return spring and the shaft may be about 0.47 mm (+/−0.3 mm), for example.