Patent Publication Number: US-6991272-B2

Title: Vehicle latch assembly

Description:
REFERENCE TO RELATED APPLICATIONS 
   The present invention claims priority from United Kingdom (GB) patent application number 0213908.7, filed Jun. 18, 2002. 
   TECHNICAL FIELD 
   The present invention relates to latch assemblies, in particular to latch assemblies for releasing, locking and unlocking vehicle closures. 
   BACKGROUND OF THE INVENTION 
   In currently known vehicle latch assemblies, a door handle (e.g., an inside door handle) can have a locked, an unlocked and a release position. The locked and unlocked positions are stable positions; that is, when the handle is placed in the locked position or the unlocked position, it stays in that position. However, moving the inside handle to the release position requires the inside handle to oppose a spring biasing force in the latch assembly. The inside handle is therefore unstable in the release position and will return toward the unlocked position when released due to the spring biasing force. 
   Pulling the handle from the locked position to the unlocked position unlocks the door. Further movement of the handle to the released position then unlatches the door. If the handle is pulled to unlatch the door and then released quickly, there is the possibility that excess spring biasing forces on the handle will cause the handle to move past the unlocked position back to the locked position. This phenomenon is called “snap back” locking and potentially causes customer dissatisfaction. 
   Although it may be possible to reduce the spring force to prevent the release handle from snapping back past the unlocked position to the locked position, adjusting the spring force is not always possible since the spring forces must still be kept high enough to both resist the inertia of system components during crash deceleration and return all moving elements to their rest positions to ensure full engagement of the latch pawl and claw in the latch assembly. It may also be possible to increase the locking mechanism spring force to counter the spring force in the system, but this would undesirably increase the effort needed to operate a key in the latch assembly. 
   One suggested solution is described commonly-assigned, co-pending patent application EP1182310, where the “snap back” phenomenon is overcome by using the inertial and/or centripetal forces associated with the handle movement to move an element that is pivotally mounted on the handle. The element prevents the handle from moving to the locked position from the released position. 
   An object of the present invention is to provide an alternative method of overcoming the “snap back” phenomenon. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a vehicle latch assembly including a release lever and a pawl, the release lever having a locked, an unlocked and a release position where the unlocked position is in the path of movement of the release lever from the release position to the locked position. The release lever is biased by a biasing means toward the unlocked position when it is in the release position. The latch assembly is arranged so that the release lever moves toward the locked position due to the biasing force of the biasing means when the release lever is released. The kinetic energy of the release lever is transferred to the pawl in the latch assembly, and the pawl uses the transferred kinetic energy to prevent the release lever from reaching the locked position. When the release lever is stationary in the unlocked position, the pawl still allows movement of the release lever from the unlocked to the locked position. 
   In one embodiment, the kinetic energy in the release lever is transferred to the pawl by engagement between a first engagement region of the release lever and a first engagement region of the pawl. Preferably, the first engagement region of the pawl lies in the path of the first engagement region of the release lever as the release lever moves from the released position to the unlocked position. Thus, the first engagement regions will always engage when the release lever is released from the release position. 
   In one embodiment, the pawl has a second engagement region, and the release lever has a second engagement region, and the transfer of kinetic energy from the release lever to the pawl moves the pawl to a position where the second engagement region of the pawl and the second engagement region of the release lever engage to prevent the release lever from reaching the locked position. 
   Because the inventive structure ensures that the first engagement regions of the pawl and the release lever always engage, at a given level of kinetic energy in the release lever, the pawl will move to a position where the second engagement regions engage, and therefore the release lever is prevented from snapping back into the locked position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
       FIG. 1  is a view of an assembly with the release lever in the release position according to one embodiment of the present invention; 
       FIG. 1A  is a schematic view of a latch arrangement including the assembly of  FIG. 1 ; 
       FIG. 2  is a view of the assembly of  FIG. 1  just after release of the release lever from the position shown in  FIG. 1 ; 
       FIG. 3  is a view of the assembly of  FIG. 1  just after engagement between the first engagement regions of the release lever and the pawl has occurred; 
       FIG. 4  is a view of the assembly of  FIG. 1  with the release lever in the unlocked position; and 
       FIG. 5  is a view of the assembly of  FIG. 1  with the release lever in the locked position. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
     FIGS. 1 and 1A  show a latch arrangement  60  having a latch assembly  10  according to one embodiment of the invention. The latch arrangement  60  includes a latch assembly  10  and a latch housing  90 . 
   The latch assembly  10  includes a latch  36  and a release handle  34  that is operable to release, lock, and unlock the latch. Although the examples described below focus on an inside release handle and its associated operating parts, the invention is not limited in this manner and can be incorporated with any handle in any latch mechanism. 
   The latch  36  is housed within the latch housing  90 . Typically, the latch housing  90  is fixed to part of a vehicle door, such as a door inner skin (not shown). In other embodiments, the latch housing may be fixed to another part of the vehicle door, for example, a door module (not shown). 
   The assembly  10  includes a release lever  12  and a pawl  14 , both of which are pivotally attached to the latch housing  90 . 
   In other embodiments the release lever  12  and pawl  14  may be attached to a point remote from the latch housing, for example on an inside handle housing, with the inside handle housing being fixed to part of a vehicle door. 
   The release lever  12  is pivotally attached to the latch housing  90  at a release lever pivot  28  using a pin  35 . The pawl  14  is pivotally attached to the latch housing  90  at a pawl pivot  24  using a pin  25 . The pawl  14  and the release lever  12  rotate about separate pivot points  24 ,  28  on the latch housing  90 , and the pawl  14  rotates independently from the release lever  12 . 
   The release lever  12  of the latch assembly  10  is connected to the latch  36  by a latch rod  32  and to the inside handle  34  by an inside handle rod  30 . The latch rod  32 , the inside handle rod  30 , and the latch assembly  10  together form a transmission path  70  between the latch  36  and the inside handle  34 , operably connecting the inside handle  34  to the latch  36 . 
   The release lever  12  is movable between a release position as shown in  FIG. 1 , an unlocked position as shown in  FIG. 4 , and a locked position as shown in  FIG. 5 , which respectively correspond to equivalent released, unlocked and locked conditions of the latch. The release, unlocked and locked positions all correspond to equivalent positions of the inside handle  34 ; that is, moving the inside handle  34  to the release, unlocked or locked position will also move the release lever  12  to the release, unlocked or locked position, respectively. 
   The assembly includes a biasing means, such as a release lever spring  50  (shown schematically), that biases the release lever  12  towards the unlocked position from the release position. As can be seen by comparing  FIGS. 1 ,  4 , and  5 , the unlocked position lies between the released and the locked position. 
   The release lever  12  includes a first lever engagement region in the form of an engagement pin  16  and a second lever engagement region  18 . The engagement pin  16  moves on a radius R 1  as the release lever  12  moves about its pivot  28 . 
   In the illustrated embodiment, the pawl  14  is U-shaped with a first arm  40  and a second arm  42 . The first and second arms  40 ,  42  meet at a curved portion  44 . The second arm  42  has an inside arm surface  46  and the curved portion has an inside curved surface  48 . The inside arm surface  46  is in the form of an arc having a radius R 2 . 
   The first arm  40  has a first pawl engagement region  20  and the second arm  42  has a second pawl engagement region  22 . The first pawl engagement region  20  has a rounded edge profile  39  where it meets the inside arm surface  46 . The pawl  14  is pivotally mounted part way along second arm  42  on the pin  25  of the housing  90 . 
   A helical pawl spring  26  is located on the pin  25 , with a first end  29  abutting against a pawl spring stop  31  located on the first arm  40  and a second end  27  abutting against a latch housing spring stop  33  located on the latch housing  90 . The pawl spring  26  and the two stops  31 ,  33  are arranged such that the pawl  14  is biased counterclockwise against a further stop (not shown) to a first pawl position as shown in FIG.  1 . 
   Starting at the unlocked position shown in  FIG. 2 , opening the vehicle door from inside the vehicle is conducted by pulling the inside handle  34  to release the latch  36 . Pulling the inside handle  34  moves the release lever  12  in the direction of arrow A and moves rod  32  to unlatch the latch  36 . The movement of the release lever  12  to the release position ( FIG. 1 ) moves against the direction of the biasing force in the release lever spring  50 , thereby storing energy in the release lever spring  50 . 
     FIGS. 1  to  4  illustrate the sequence of events that occurs when the inside handle is released quickly. When the release lever  12  is released quickly from the release position, it rotates counterclockwise relatively quickly about pivot  28  toward the unlocked position due to the biasing force of the release lever spring  50 . 
   Just before the release lever  12  reaches the unlocked position, the engagement pin  16  in the release lever  12  engages with the first pawl engagement region  20 . As shown in  FIGS. 1 and 2 , when the pawl  14  is in the first pawl position (FIG.  1 ), the first pawl engagement region  20  lies in the path of movement of the pin  16  of the release lever  12  as the release lever  12  moves from the release to the unlocked position. 
   The movement of the release lever  12  from the release position under the action of the release lever spring  50  generates kinetic energy in the release lever  12 . The kinetic energy in the release lever  12  is transferred to the pawl  14  after engagement between the engagement pin  16  in the release lever  12  and the first pawl engagement region  20 . The transfer of kinetic energy is sufficient to overcome the pawl spring force and move the pawl  14  counterclockwise (in the direction of arrow B) momentarily to a second pawl position as shown in FIG.  3 . 
   It can be seen in  FIG. 3  that when the pawl  14  is in the second pawl position, the second engagement region  22  of the pawl momentarily engages with the second engagement region  18  of the release lever, and thus the release lever  12  is prevented from further clockwise movement towards the locked position. Thus, the clockwise movement of the pawl has caused the second engagement region  22  to momentarily lie in the path of movement of the second engagement region  18 . 
   Thus it is the kinetic energy generated in the release lever due to the release lever spring which has resulted in a transfer of kinetic energy to the pawl which is sufficient to move the pawl to prevent further movement of the release lever towards the locked position. 
   After engagement between the second engagement regions  18  and  23 , the pawl  14  and the release lever  12  will both become momentarily stationary, i.e. the release lever  12  will cease to move towards the locked position, and the pawl  14  will cease to move in the direction of arrow B, and a reaction force between the pawl and release lever second engagement regions will cause disengagement. This disengagement allows the pawl  14  to move back towards the second pawl position under the action of the pawl spring  26  as shown in FIG.  4 . 
   After the pawl  14  has returned to the first pawl position, the release lever  12  remains in the unlocked position as shown in FIG.  4 . It will be appreciated that as the pawl  14  and the release lever  12  disengage, the release lever  12  may move slightly, with the engagement pin  16  coming into contact with the rounded edge profile  39 . 
   The sequence of events shown in  FIGS. 1  to  4  can be contrasted with the operation of the assembly when the inside handle is only released relatively slowly, i.e., when the inside handle is allowed to move from the release position to the unlocked position only relatively slowly. Under these circumstances, the speed of movement of the components is lower and hence the levels of kinetic energy are lower. Thus under these circumstances the components move relatively slowly from the position shown in  FIG. 1  to the position shown in  FIG. 4 , and at no time will second engagement region  22  lie in the path of second engagement region  18 . However, under these circumstances, because the components are moving slower, ‘snap back’ locking will not occur, and thus active prevention of ‘snap back’ locking is not required. 
   Thus it can be seen that ‘snap back’ locking is actively prevented when it would otherwise occur (i.e. when the components are allowed to move relatively quickly) and ‘snap back’ locking is not actively prevented when it would not otherwise occur. 
   When the components stationary in the unlocked position shown in  FIG. 4 , it can be seen that the second engagement region  22  of the pawl no longer lies in the path of the second engagement region of the release lever  12 . Hence, the release lever is not restricted from moving to the locked position in FIG.  5 . 
   Thus, pushing the inside handle  34  and thus release lever  12  counterclockwise in the direction of arrow C toward the locked position will cause engagement pin  16  on the release lever  12  to move past the rounded edge profile  39  of the pawl  14  and then along the inside surface  46  of the pawl  14  to the position shown in FIG.  5 . 
   Note that the pawl  14  may be moved slightly clockwise beyond the first pawl position due to contact between the engagement pin  16  and the inside arm surface  46  as the release lever  12  is moved to the locked position. 
   From the locked position of  FIG. 5 , the release lever  12  can either be moved just to the unlocked position or straight to the release position by appropriate operation of the inside door handle. In particular, the speed of unlocking for release is not affected by the pawl  14 . 
   It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby.