Abstract:
A latch assembly selectively engages a striker for latching a door to a motor vehicle body. The latch assembly includes a housing. A ratchet is rotatably mounted to the housing for movement between an engaged position engaging the striker and a release position. A ratchet-engaging pawl is rotatably mounted to the housing and engageable with the ratchet to retain the ratchet in the engaged position. An inertia mechanism is operably connected to the ratchet-engaging pawl to prevent the ratchet-engaging pawl from pivoting out of engagement with the ratchet when the ratchet-engaging pawl begins to pivot due to inertial forces acting thereupon.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of and priority to U.S. Provisional Application Ser. No. 60/682,982, entitled “Safety Mechanism for Vehicle Door Latch Systems” and filed May 20, 2005, and U.S. Provisional Application Ser. No. 60/682,981, entitled “Inertia Catch for Door Latches” and filed May 20, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to a latch assembly for selectively locking a motor vehicle door. More particularly, the invention relates to latch assembly including an inertia mechanism for preventing a ratchet from releasing a striker in the event of a motor vehicle impact.  
       DESCRIPTION OF RELATED ART  
       [0003]     Motor vehicles include hinged doors for selectively providing access to motor vehicle passenger or cargo compartments. Typically, a latch mechanism is coupled between one of the doors and a motor vehicle body for releasably locking the door in a closed position. A release mechanism is typically coupled to the latch mechanism for locking and unlocking the latch mechanism. It remains desirable to provide a mechanism for preventing the latch mechanism from unlocking during a side impact of the motor vehicle.  
       SUMMARY OF THE INVENTION  
       [0004]     According to one aspect of the invention, a latch assembly selectively engages a striker for latching a door to a motor vehicle body. The latch assembly includes a housing. A ratchet is rotatably mounted to the housing for movement between an engaged position engaging the striker and a release position. A ratchet-engaging pawl is rotatably mounted to the housing and engageable with the ratchet to retain the ratchet in the engaged position. An inertia mechanism is operably connected to the ratchet-engaging pawl to prevent the ratchet-engaging pawl from pivoting out of engagement with the ratchet when the ratchet-engaging pawl begins to pivot due to inertial forces acting thereupon.  
         [0005]     According to another aspect of the invention, a latch assembly selectively engages a striker for latching a door to a motor vehicle body. The latch assembly includes a housing. A ratchet is rotatably mounted to the housing for movement between an engaged position engaging the striker and a release position. A ratchet-engaging pawl is engageable with the ratchet to retain the ratchet in the engaged position. The latch assembly also includes an auxiliary pawl lever rotatably mounted to the housing and coupled to the ratchet-engaging pawl for moving the ratchet-engaging pawl out of engagement with the ratchet. The auxiliary pawl lever includes a protrusion extending out therefrom. An inertia mechanism is coupled to the housing and includes a plunger movable in response to inertial forces to effect engagement between the plunger and the protrusion and prevent the auxiliary pawl from moving the ratchet-engaging pawl out of engagement with the ratchet.  
         [0006]     According to yet another aspect of the invention, a latch assembly selectively engages a striker for latching a door to a motor vehicle body. The latch assembly includes a housing. A ratchet is rotatably mounted to the housing for movement between an engaged position engaging the striker and a release position. A ratchet-engaging pawl is engageable with the ratchet to retain the ratchet in the engaged position. An auxiliary pawl lever is rotatably mounted to the housing and operably coupled to the ratchet-engaging pawl for moving the ratchet-engaging pawl out of engagement with the ratchet to allow movement of the ratchet to the release position. An inertia mechanism includes a plunger having a first end coupled to the auxiliary pawl lever and an opposing second end. The inertia mechanism includes a bell member having a cavity for receiving the second end during normal latch assembly operation to allow rotation of the auxiliary pawl lever to move the ratchet-engaging pawl out of engagement with the ratchet. The cavity movable out of alignment with the second end of the plunger in response to inertial forces to prevent movement of said plunger into said cavity and rotation of said auxiliary pawl lever. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
         [0008]      FIG. 1  is a fragmentary, perspective view of a motor vehicle including a latch assembly according to one embodiment of the invention fixedly mounted along a door;  
         [0009]      FIG. 2  is a perspective view of the latch assembly including a ratchet in an engaged position and a ratchet-engaging pawl engaging the ratchet;  
         [0010]      FIG. 3  is a perspective view of the latch assembly including the ratchet in a release position;  
         [0011]      FIG. 4  is an exploded, perspective view of the latch assembly including an inertia mechanism and an auxiliary pawl lever operably coupled to the ratchet-engaging pawl;  
         [0012]      FIG. 5  is a fragmentary, perspective view of the latch assembly including the inertia mechanism having a plunger in a retracted position;  
         [0013]      FIG. 6  is a fragmentary, perspective view of the latch assembly including the plunger in an extended position engaging the auxiliary pawl lever;  
         [0014]      FIG. 7  is a cross-sectional view of the latch assembly with the plunger in the retracted position;  
         [0015]      FIG. 8  is a cross-sectional view of the latch assembly with the plunger in the extended position engaging the auxiliary pawl lever;  
         [0016]      FIG. 9  is a perspective view of a latch assembly according to a second embodiment of the invention including an inertia mechanism having a bell member defining a cavity;  
         [0017]      FIG. 10  is a side view of the latch assembly including a plunger in a seated position disposed within the cavity to allow rotation of an auxiliary pawl lever; and  
         [0018]      FIG. 11  is a side view of the latch assembly including the bell member moved off center in response to a motor vehicle impact to prevent the plunger from entering the cavity.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     Referring to  FIG. 1 , a motor vehicle, generally indicated at  10 , includes a body portion  12  and a door  14  pivotally hinged to the body portion  12  for movement between an open position and a closed position. A latch assembly, generally shown at  16 , is fixedly mounted to the door  14  and selectively engages a striker  18  mounted along the body portion  12 . A detailed description of the structure and function of the latch assembly  16  is disclosed in Applicant&#39;s U.S. patent application Ser. No. 11/007,946 filed on Dec. 9, 2004, which is incorporated herein by reference in its entirety.  
         [0020]     The latch assembly  16  includes a housing  20  having a first side  22 , shown in  FIGS. 2 and 3 , and an opposing second side  24 , shown in  FIG. 4 . Referring to  FIGS. 2 and 3 , a plurality of peripheral walls  26  extends along the first side  22  and defines a cavity  28 . A frusto-trapezoidal aperture  30  bisects the first side  22 . The aperture  30  is designed to receive the striker  18 . A seal  32 , preferably formed from a flexible rubber material, is mounted or otherwise integrally formed with the housing  20  at an open end of the aperture  30 . An elastomeric or rubber bumper  34  including a shoulder  36  is fixedly mounted at an opposing end of the aperture  30  for receiving and absorbing the impact of the striker  18 , thereby reducing stresses on the latch assembly  16  and reducing noise. A channel  35  extends from the cavity  28  of the first side  22  to the exterior of the housing  20  to provide a water outlet for the latch assembly  16 .  
         [0021]     A ratchet  38  and a ratchet-engaging pawl  40  are disposed within the cavity  28  formed along the first side  22  of the housing  20 . The ratchet  38  and the ratchet-engaging pawl  40  are preferably constructed from metal and partially covered with a plastic material in order to reduce noise during latch operation. Certain portions that are subject to wear, such as a shoulder  39  of the ratchet  38  and a shoulder  41  of the ratchet-engaging pawl  40 , are not covered by plastic.  
         [0022]     The ratchet  38  is rotatably mounted to the first side  22  of the housing  20  via a pin  42  for movement between an engaged position (shown in  FIG. 2 ), in which a hook portion  44  of the ratchet  38  engages the striker  18 , and a release position (shown in  FIG. 3 ), in which the ratchet  38  releases the striker  18  to allow opening of the door  14 . A spring (not shown) biases the ratchet  38  into the release position. The angular travel of the ratchet  38  about the pin  42  is delimited by the shoulder  36  and a wall  46 .  
         [0023]     The ratchet  38  also includes a lip  48  for selectively engaging a switch  50  disposed within a recess  51 . More specifically, as the ratchet  38  moves from the engaged position to the release position, the lip  48  urges against a leaf spring  52  in order to change the state of the switch  50 . The switch  50  includes a plurality of terminals attached to a wiring harness (not shown) that is disposed in and extends from a tubular construct  53  formed in the housing  20 .  
         [0024]     The ratchet-engaging pawl  40  is rotatably mounted along the first side  22  of the housing  20  via a pin  54 . When the ratchet-engaging pawl  40  is in a pawl engagement position, as shown in  FIG. 2 , the ratchet-engaging pawl  40  retains the ratchet  38  in the engaged position. When the ratchet-engaging pawl  40  is moved out of the pawl engagement position, the ratchet  38  is free to move from the engaged position to the release position. A spring  56  is disposed within a groove  58  for biasing the ratchet-engaging pawl  40  into the pawl engagement position.  
         [0025]     Referring to  FIG. 4 , the second side  24  of the housing  20  includes upper  60  and lower  61  cavities. A tubular post  62  is disposed within the upper cavity  60  and encompasses the pin  54  extending through the opposing first side  22  of the housing  20 . An auxiliary pawl lever  64  is pivotally mounted about the tubular post  62  along the second side  24  of the housing  20 . The auxiliary pawl lever  64  defines an aperture  65  for receiving the tubular post  62  therethrough and includes a protrusion  66 . The auxiliary pawl lever  64  also includes a slot  68  that receives a projection  70 , shown in  FIGS. 5 through 8 , of the ratchet-engaging pawl  40  extending through an opening  69  in the housing  20 . Thus, the auxiliary pawl lever  64  is operably coupled to the ratchet-engaging pawl  40 .  
         [0026]     Referring again to  FIG. 4 , an outside release lever  74  is also pivotally mounted about the tubular post  62 . The outside release lever  74  includes a slot  76  and is coupled to the auxiliary pawl lever  64  by a slidable link  78 . The slidable link  78  includes a tab  80  that slides in and out of the slot  76 . A toggle spring  82  biases the link  78  either into or out of the slot  76 . When the tab  80  is adjacent an open end of the slot  76 , the link  78  is in an unlocked position. When the link  78  is in the unlocked position, rotation of the outside release lever  74  causes the tab  80  to engage the auxiliary pawl lever  64 , which causes the auxiliary pawl lever  64 , and the ratchet-engaging pawl  40  coupled thereto, to rotate. As a result of this rotation, the ratchet-engaging pawl  40  moves out of the engagement position, which allows the ratchet  38  to move to the release position and release the striker  18 . On the other hand, when the tab  80  is adjacent a closed end of the slot  76 , the link  78  is in the locked position. When the link  78  is in the locked position, the outside release lever  74  will rotate relative to the auxiliary pawl lever  64  and the ratchet  38  remains in the engaged position.  
         [0027]     The link  78  is actuated by a lock link lever  84 , which in turn is actuated by a key cylinder lever  86  connected to a key cylinder (not shown). The lock link lever  84  includes a shelf  88  with side ridges. The key cylinder lever  86  is seated in the shelf  88  and has an angular freedom of motion of about 20 degrees (“lost motion”) before the key cylinder lever  86  engages one of the side ridges and imparts rotational motion to the lock link lever  84 . The lock link lever  84  also includes an aperture  90 , which receives a coupling projection  92  depending from the link  78 . As a result, the link  78  is kinematically coupled to the lock link lever  84  and the key cylinder lever  86 . Consequently, only a full rotation of the key cylinder lever  86  causes the link  78  to move between the locked and unlocked positions. A switch  94  is capable of indicating any of three positions of the key cylinder: neutral, unlock and lock.  
         [0028]     An inside lock lever  96  and an inside release lever  98  are coupled to the key cylinder lever  86  and the auxiliary pawl lever  64 , respectively. More specifically, the inside release lever  98  includes a foot  100  that abuts an appendage  102  of the auxiliary pawl lever  64 . The inside release lever  98  also includes a toe  104  for engaging a pedal  106  of the inside lock lever  96  for unlocking the inside lock lever  96  when the inside release lever  98  is actuated.  
         [0029]     Referring to  FIGS. 5 through 8 , the latch assembly  16  further includes an inertia mechanism, generally shown at  108 , for preventing the ratchet  38  from releasing the striker  18  in the event of a motor vehicle impact or similar acceleration above a predetermined threshold. The inertia mechanism  108  includes a cover  110  that is fixedly secured to the housing  20  by a plurality of fasteners  112 .  
         [0030]     The inertia mechanism  108  also includes a body portion  114  surrounded by the cover  110  and disposed along a portion of the housing  20 . An inner conical surface, generally indicated at  116 , is formed at one end  117  of the body portion  114 . The inner conical surface  116  includes a bottom  118  and an upper rim  120 . The body portion  114  defines a groove  121  at an opposite end  119  of the inner conical surface  116 .  
         [0031]     The inertia mechanism  108  further includes a plunger  122  extending out from the end  119  of the body portion  114 . The plunger  122  is movable between a retracted position, shown in  FIGS. 5 and 7 , and an extended position, shown in  FIGS. 6 and 8 . When the plunger  122  is in the retracted position, the auxiliary pawl lever  64  is able to rotate unimpeded about the tubular post  62  in order to move the ratchet-engaging pawl  40  out of the pawl engagement position, which allows movement of the ratchet  38  from the engaged position to the release position. In the extended position, the plunger  122  engages the protrusion  66  of the auxiliary pawl lever  64  to prevent rotation thereof such that the ratchet-engaging pawl  40  is not able to move out of the pawl engagement position. A spring  124  is disposed within the groove  121  and biases the plunger  122  into the retracted position.  
         [0032]     The inertia mechanism  108  includes a ball  126  disposed along the inner conical surface  116  of the body portion  114 . The cover  110  maintains the ball  126  in contact with the inner conical surface  116 . The motion of the ball  126  along the inner conical surface  116  causes the plunger  122  to move between the retracted and extended positions.  
         [0033]     In normal conditions, the ball  126  is located at the bottom  118  of the inner conical surface  116 . When the ball  126  is at the bottom  118  of the inner conical surface  116 , the spring  124  is extended and the body portion  114  is raised so that the plunger  122  is in the retracted position. Therefore, the auxiliary pawl lever  64  is able to rotate unimpeded about the tubular post  62  in order to move the ratchet-engaging pawl  40  out of the pawl engagement position, which in turn allows the ratchet  38  to move from the engaged position to the release position.  
         [0034]     In the event of a motor vehicle impact, however, the ball  126  is urged towards the upper rim  120  of the inner conical surface  116 . The spring  124  compresses and the body portion  114  lowers, thereby moving the plunger  122  from the retracted position to the extended position, as shown in  FIGS. 6 and 8 , for engaging the protrusion  66  of the auxiliary pawl lever  64 . As a result, the auxiliary pawl lever  64  is prevented from rotating about the tubular post  62 , which in turn prevents the ratchet-engaging pawl  40  from moving out of the pawl engagement position. The ratchet  38  thus remains in the engaged position. Therefore, the striker  18  is not released and the door  14  does not inadvertently open from the motor vehicle impact.  
         [0035]     Referring to  FIGS. 9 through 11 , wherein like primed reference numerals represent similar elements as those set forth above, the inertia mechanism  108 ′ according to a second embodiment of the invention includes a bell member  128  disposed within a bell housing  130  having a peripheral wall  132 . The bell housing  130  is fixedly secured to the housing  20 ′ adjacent the auxiliary pawl lever  64 ′. It is appreciated that a portion of the bell housing  130  has been cut away in  FIGS. 9 through 11  for clarity.  
         [0036]     The bell member  128  includes a top portion  134  terminating at a distal sphere  136 . A centering spring  138  is disposed around the top portion  134  below the distal sphere  136  for biasing the bell member  128  into the center of the bell housing  130 . The bell member  128  also includes a bottom surface  139  defining a cavity  140 . One end of the centering spring  138  abuts the distal sphere  136  and an opposite end of the centering spring  138  abuts an intermediate surface  143  of the bell member  128 .  
         [0037]     The plunger  122 ′ includes a first end  142 , an opposing second end  144 , and a middle segment  146  disposed between the first  142  and second  144  ends. The first end  142  abuts a ramp  148  positioned along the auxiliary pawl lever  64 ′. The rotation of the auxiliary pawl lever  64 ′ about the tubular post  62 ′ moves the plunger  122 ′ from a neutral position, shown in  FIG. 9 , to a seated position, shown in  FIG. 10 , in which the second end  144  of the plunger  122 ′ is received within the cavity  140  of the bell member  128 . A compression spring  150  is wrapped around the middle segment  146  of the plunger  122 ′ for biasing the plunger  122 ′ into the neutral position.  
         [0038]     During normal operation, the auxiliary pawl lever  64 ′ is rotated as one of the outside  74 ′ and inside  98 ′ levers is actuated. The rotation of the auxiliary pawl lever  64 ′ urges the first end  142  of the plunger  122 ′ up the ramp  148 , which in turn pushes the second end  144  of the plunger  122 ′ into the cavity  140  so that the plunger  122 ′ moves from the neutral position to the seated position. Thus, the auxiliary pawl lever  64 ′ is free to rotate, which urges the ratchet-engaging pawl  40 ′ out of the pawl engagement position. As a result, the ratchet  38 ′ is free to move from the engaged position to the release position and release the striker  18 ′.  
         [0039]     In the event of a motor vehicle impact, a portion of the bell member  128  is forced towards the peripheral wall  132  so that the cavity  140  is no longer aligned with the second end  144  of the plunger  122 ′, as shown in  FIG. 11 . Thus, as the auxiliary pawl lever  64 ′ begins to rotate as a result of the force of the motor vehicle impact, the second end  144  of the plunger  122 ′ will not enter the cavity  140 . Instead, the second end  144  of the plunger  122 ′ will abut the bottom surface  139  of the bell member  128 . As a result, the plunger  122 ′ is not able to move to the seated position. The plunger  122 ′ therefore engages the auxiliary pawl lever  64 ′ and prevents rotation thereof. As a result, the ratchet-engaging pawl  40 ′ is not allowed to move out of the pawl engagement position and the ratchet  38 ′ is not able to move to the release position. Once the impact forces have subsided, the centering spring  138  re-centers the bell member  128  to allow release of the ratchet  38 ′ during normal operation as described above.  
         [0040]     The invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.