Patent Publication Number: US-2010127512-A1

Title: Vehicle door latch

Description:
BACKGROUND OF THE INVENTION 
     An automotive closure, such as a door for an automobile passenger compartment, is hinged to swing between open and closed positions and conventionally includes a door latch that is housed between inner and outer panels of the door. The door latch functions in a well known manner to latch the door when it is closed and to lock the door in the closed position or to unlock and unlatch the door so that the door can be opened manually. 
     In general terms, the door latch has a forkbolt that engages a striker in the door jamb to latch the door when it is closed and a spring biased detent lever that engages and holds the forkbolt in the latched position. The door latch also typically has a release mechanism for moving the detent to a position releasing the forkbolt so that the door can be unlatched and opened and a lock mechanism for disabling the release mechanism to prevent unauthorized unlatching of the door. U.S. Pat. No. 6,053,543 granted to Frank Joseph Arabia, Jr. et al. Apr. 25, 2000, which is incorporated by reference herein, shows a typical door latch, including a latch and release mechanism, as known in the prior art. 
     Since the point of contact of the spring and the pivot is constant, the torque created by movement of the detent increases linearly as a function of the spring deformation. As a result the force to disengage the forkbolt from the striker is greatest at the end of travel and the lowest at initial engagement. 
     SUMMARY OF THE INVENTION 
     The present invention allows the torque required to disengage the forkbolt to be variable, relative to the travel of the detent. In one embodiment, the invention allows the force vector to change direction by placing a detent spring eccentric to a detent lever travel path. Thus, detent torque varies over the path of detent travel. 
     According to one aspect of the invention, a door latch comprising a forkbolt that has a movement between a latched position and an unlatched position is provided. A detent is included that has movement on a travel path between a first position and a second position, the detent engaging and holding the forkbolt in the latched position when the detent is in the first position. The detent releases the forkbolt for movement to the unlatched position when the detent moves to the second position. A detent spring eccentrically engages the detent relative to the detent travel path and biases the detent toward the first position. A release mechanism is also included for moving the detent against the bias of the detent spring to the second position, thus releasing the forkbolt and producing a non-linear torque on the detent. 
     According to another aspect of the invention, a door latch comprising a forkbolt that has a movement between a latched position and an unlatched position is provided. The latch includes a detent that has movement along a travel path between a first position and a second position, the detent engaging and holding the forkbolt in the latched position when the detent is in the first position, the detent releasing the forkbolt for movement to the unlatched position when the detent is in the second position. A detent spring biases the detent toward the first position. An unlatching lever pivotably engages the detent for moving the detent against the bias of the detent spring to the second position to release the forkbolt, the detent spring eccentrically engaging the detent relative to the travel path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a partial front view of a vehicle door latch, in a latched position, in accordance with the present invention; 
         FIG. 2  is a partial front view of the vehicle door latch of  FIG. 1 , in an unlatched position, in accordance with the present invention; 
         FIG. 3  is a rear pictorial view of the vehicle door latch, in a latched position, in accordance with the present invention; 
         FIG. 4  is a rear pictorial view of the vehicle door latch of  FIG. 3 , in an unlatched position, in accordance with the present invention; and 
         FIG. 5  is a graph showing the torque imparted to the latch in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIGS. 1 and 2 , where the invention will be described with reference to specific embodiments, without limiting same, a vehicle door latch  10  has a multi-piece enclosure that comprises a housing  12 , a metal frame or face plate (not shown) and a back cover (not shown). The housing  12  and the metal face plate are held together by two flanged studs  14  and  15  that are inserted through two holes in the housing  12 , through two aligned holes in the metal face plate and thereafter flanged over the metal face plate to form a forward compartment  17  of door latch  10 . 
     Door latch  10  has a latch mechanism comprising a forkbolt  21  and a cooperating detent  22  that are located in the forward compartment  17  and pivotally mounted on the forward portions of studs  15  and  14 , respectively. Forkbolt  21  is biased clockwise by a compression spring  23  that is disposed in a curved slot (not shown) in housing  12  behind forkbolt  21 . Spring  23  engages a lateral lug  30  of forkbolt  21  at a first end  31  and an end wall (not shown) of the curved slot at a second end  32 . 
     Detent  22  engages a lateral pin  34  through an opening  25  within the detent  22  that extends between a first side  26  and a second side  27  of the detent. Lateral pin  34  is rotatable within opening  25  and extends through a housing slot  42  that defines a travel path  46  for lateral pin  34  and into a rear compartment  50 . Rear compartment  50 , best seen in  FIGS. 3 and 4 , is formed by housing  12  and the back cover, both of which have been removed from the views shown in  FIGS. 3 and 4  for clarity. Door latch  10  has a release mechanism  51  for releasing or unlatching the latching mechanism that is disposed in the rear compartment  50 . 
     Details of the release mechanism  51  are shown in  FIGS. 3 and 4 . Specifically, an unlatching lever  52  is shown retained on first stud  14  and being adapted to rotate thereabout, as shown by the arrow A in  FIGS. 3 and 4 . Unlatching lever  52  has an intermittent lever slot  53  extending between rear side  54  and front side  55  of the unlatching lever  52 . Retained within intermittent lever slot  53  and pivotably engaging unlatching lever  52  is an intermittent lever  61 . An intermediate portion of intermittent lever  61  includes lateral pin  34 . Extending therefrom is a first arm portion  62  having a first lever pivot  63  that pivotably engages intermittent lever slot  53 . A second arm portion  64  also extends from lateral pin  34 . Extending from second arm portion  64  is a second lever pivot  65  that pivotably engages a slot  67  within a locking lever  71  of a three-piece locking mechanism  72 . Locking lever  71 , being rotatable about second stud  15 , causes door latch  10  to be placed in a locked or unlocked position in a known manner and will not be described in further detail herein. 
     As can be seen from  FIGS. 1 and 3  showing door latch  10  in a latched position and  FIGS. 2 and 4  showing door latch  10  in an unlatched position, detent  22  is rotated clockwise from the latched position shown in  FIGS. 1 and 3  and out of latched engagement with the forkbolt  21  to a release or unlatched position shown in  FIGS. 2 and 4  when the latching mechanism is operated. This releases forkbolt  21  so that it is free to rotate clockwise from the latched position shown in  FIG. 1  to the unlatched position shown in  FIG. 2  under the bias of a detent spring  80  when the vehicle door is opened. The locking mechanism  72  of door latch  10  disables the release mechanism  51  located in rear compartment  50  defined by housing  12  and the back cover, in a conventional manner. 
     Detent  22  is biased counterclockwise into engagement with forkbolt  21  by the detent spring  80 , shown as a torsion spring, that engages an outer circumferential surface  35  of lateral pin  34 . Specifically, in the exemplary embodiment shown, detent spring  80  includes a first finger  81 , a second finger  82  and a central helical portion  83 . Detent spring  80  is held in place at a slot  84  adjacent a lateral edge portion  19  of housing  12 . Second finger  82  rests in slot  84  and bears against lateral edge portion  19  when detent spring  80  is under compression. It will be appreciated that detent spring  80  may alternatively be held in place by any number of known methods, including a pin extending from the back cover of housing  12 , over which central helical portion  83  rests. 
     Detent  22  engages forkbolt  21  at a primary latch shoulder  36  and holds forkbolt  21  in a primary latched position against the bias of detent spring  80 , as shown in  FIG. 1 . Detent  22  engages forkbolt  21  at a foot  40  in its unlatched or release position as shown in  FIGS. 2 and 4 . Detent spring  80  is in contact with lateral pin  34  at all times, and thus, in compression to prevent rattle and wear, including in the primary latched position of  FIGS. 1 and 3 . 
     As described now in detail, and as shown in  FIGS. 1 and 3 , in the latched position, outer circumferential surface  35  of lateral pin  34  is in contact with detent spring  80  at first finger  81  at a first portion  87  adjacent central helical portion  83 . When it is desired to unlatch door latch  10 , unlatching lever  52  is moved in the direction of arrow A, in  FIG. 3 , causing unlatching lever to rotate about first stud  14 . Thereafter, intermittent lever slot  53  captures first lever pivot  63  on first arm portion  62 , causing intermittent lever  61  and lateral pin  34  to push against the bias of first finger  81  of detent spring  80  and lateral pin  34  to move within housing slot  42  along travel path  46 . 
     As lateral pin  34  moves in the arc of housing slot  42  that is travel path  46 , the outer circumferential surface  35  of pin  34  slides along the first finger  81  from first portion  87  to a second portion  88 , adjacent an end  89  of first finger  81  and opposite central helical portion  83 . As lateral pin  34  is engaged through opening  25  of the detent  22 , detent  22  rotates about first stud  14  causing a catch  94  of detent  22  to move out of the engagement with primary latch shoulder  36  of forkbolt  21 . Thereafter, as seen in  FIGS. 1 and 2 , compression spring  23  causes forkbolt  21  to rotate clockwise to an unlatched position shown in  FIG. 2 . During this movement, striker pin  90  moves out of a rear portion  92  of throat  91 , thus releasing striker pin  90 . 
     In a like manner, when the door latch  10  is in an unlatched and unlocked condition, forkbolt  21  is poised to receive a striker pin  90  as shown in  FIG. 2 . When a door having latch  10  is shut, the striker pin  90  enters the throat  91  of forkbolt  21 , engages the rear portion  92  of throat  91  and rotates forkbolt  21  counterclockwise against the bias of compression spring  23  until forkbolt  21  is rotated to the primary latched position shown in  FIG. 1  and  FIG. 3  where forkbolt  21  captures striker pin  90  in throat  91 . Forkbolt  21  is held in the latched position by catch  94  of detent  22  engaging primary latch shoulder  36  of forkbolt  21 . 
     As forkbolt  21  rotates counterclockwise from the unlatched position of  FIGS. 2 and 4  to the primary latch position of  FIGS. 1 and 3 , catch  94  rides along the periphery of the forkbolt  21  under the full bias of detent spring  80 . During this travel, catch  94  of detent  22  rides on the foot  40  to the edge  41  of foot  40  and then snaps into engagement with an intermediate secondary latch shoulder  38 . If the door is shut solidly, catch  94  continues—riding up a ramp  43  to an edge  45  and then snaps into engagement with the primary latch shoulder  36 . 
     During the latching movement described above, movement of detent  22  is causing the lateral pin  34  to ride within housing slot  42  along the travel path  46 . The outer circumferential surface  35  of pin  34  slides along the first finger  81  from second portion  88 , adjacent the end  89  of first finger  81  toward first portion  87  adjacent central helical portion  83 . 
     Referring now to the chart of  FIG. 5 , which shows a typical application of the invention, the detent torque applied to the detent  22  by detent spring  80  varies relative to the position of detent  22  along travel path  46 . Specifically, a standard detent spring curve is shown. As can be seen, the torque required to unlatch the forkbolt  21 , as applied at the unlatching lever  52 , generally increase as a function of spring deformation. After a certain initial torque, spring torque increases linearly. 
     However, when using the detent spring of the present invention, as shown and described herein, the torque required to unlatch the forkbolt  21 , as applied at the unlatching lever  23 , is non-linear. The ability of lateral pin  34  to ride along first finger  81  of detent spring  80  causes the unlatching force vector at detent spring  80  to change direction as detent lever  22  moves along travel path  46 . This change in direction allows the torque shown in  FIG. 5  to non-linearly vary as a function of detent travel. The torque slope function shown flattens as detent travel increases during unlatching. Thus, after an initial torque is placed by an operator to unlatch door lock  10 , the force required need not increase, as it would in a standard latch. Instead, the force required to operate door latch  10  is significantly less. As shown in  FIG. 5 , the torque required is one-third less than a standard door latch at the unlatch point, i.e. 300 Newton millimeters required by a standard door latch and 200 Newton millimeters required when using the present invention. 
     It will be appreciated that variations of the disclosed embodiment are contemplated. For instance a non-linear torque may be applied to detent lever  22  in ways different than shown. For instance, different detent springs  80  may be used other than the torsion spring shown. In addition, a non-linear torque may be applied to a standard compression spring by modifying detent lever  22  to rotate as a cam. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.