Patent Publication Number: US-8967682-B2

Title: Vehicle door latch with motion restriction device prohibiting rapid movement of opening lever

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of U.S. patent application Ser. No. 12/190,707 filed Aug. 13, 2008, the contents of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to the use of a motion restriction device for prohibiting the rapid movement of an opening lever in a vehicle door latch, and more particularly for selectively preventing rapid movement of an auxiliary latch pawl in a crash situation but not in a door slam situation. 
     BACKGROUND OF THE INVENTION 
     It is possible in a vehicle crash situation that the impact resulting from the crash could have a deleterious effect on any part of the vehicle door latch system, which is intended to keep the vehicle door latched to the vehicle body. However, in a crash, particularly in a roll-over situation where the door latch may be subjected to inertial forces directed over a wide angular range in three dimensions, the forces acting on the latch system may unintentionally actuate one or more latch system levers (which can be relatively long and have centers of mass located far from the rotation axis) and consecutively act to open the door latch. Needless to say, it is highly undesirable to have the vehicle door fling open in a crash situation, especially in a rollover. 
     It is known to prohibit the unintended movement of one or more release levers in a vehicle door latch due to inertial forces arising from a vehicle crash. See, for example, assignee&#39;s U.S. Publication No. 2006/0131892 by Pereverzev, which describes the use of an inertia lever actuated by a counterweight in a crash situation when the inertial forces exceed a threshold level. However, one of the limitations of that system is that the counterweight is actuated only by inertial forces acting along a relatively narrow angular range. 
     It is desirable to have a vehicular door latch system with a safety device that prohibits movement of a latch opening part when it moves that faster than a threshold speed indicative of a crash situation. In particular, it is desirable to prohibit such movement irrespective of the direction of inertial forces acting upon the latch system. And it is most desirable to have such a door latch safety system that operates in a crash situation, but not in a typical, daily encountered, door slam situation. 
     SUMMARY OF THE INVENTION 
     Generally speaking, the invention employs a motion restriction device coupled to an opening part of a vehicle door latch that prohibits movement of the opening part faster than a threshold speed. The motion restriction devices utilizes a velocity dependent material or shear thickening fluid that stiffens considerably when the material or fluid is subject to high shear rates. 
     In a preferred embodiment, the motion restriction device is coupled to an auxiliary pawl that is connected to the pawl of a ratchet and pawl combination. The auxiliary pawl must be actuated by one or more release levers in order to actuate the pawl and release the ratchet from a striker-containing position and open the latch. By coupling the motion restriction device to a lever located close to the pawl, it is possible to target release motion that originates from a variety of sources within the latch system. In addition, because the only criterion for selectively prohibiting movement of the auxiliary pawl is its speed, it is possible to prevent the latch from unintentionally opening regardless of the direction the inertial forces are applied to door handles, latch or the release levers therein. 
     In the preferred embodiment there is a lost motion or one way connection between the auxiliary pawl and pawl such that when the vehicle door is slammed and the pawl pivots in reaction to the ratchet, the pawl does not engage and actuate the auxiliary pawl. The lost motion or one way connection thus decouples the pawl from the motion restriction device in a door slam situation, but not a door crash situation where release levers are likely to act on the auxiliary pawl. 
     In the preferred embodiment, the auxiliary pawl is coupled to the motion restriction in such a manner that the angular speed of the auxiliary pawl is amplified when applied to the motion restriction device, to increase the speed of a moveable part of the motion restriction device. 
     Thus, one aspect of the invention relates to a vehicle door latch having a housing; a ratchet mounted for pivotal movement in the housing, the ratchet moving between a latched position for retaining a striker and an unlatched position for releasing the striker, the ratchet being biased toward the unlatched position; a pawl mounted for pivotal movement in the housing, the pawl moving between an engaged position maintaining the ratchet in the latched position and a release position enabling the ratchet to move into the unlatched position, the pawl being biased (e.g., with a spring) toward the engaged position; an auxiliary pawl moveably mounted in the housing between an initial position and a release position in which the pawl is actuated into its release position; at least one release lever moveably mounted in the housing for actuating the auxiliary pawl into its release position; and a motion restriction device including a moveable part arranged for movement through a velocity dependent material that substantially inhibits motion of the moveable part when its speed exceeds a threshold speed, wherein the auxiliary pawl is connected to the moveable part of the motion restriction device. 
     The auxiliary pawl preferably has a one way connection with the pawl such that movement of the pawl out of its engaged position and in the direction of its release position as a result of a reaction with the ratchet does not move the auxiliary pawl. The auxiliary pawl and pawl preferably have a common axis of rotation. And the one way connection may be provided by a coupling pin disposed on one of the pawl and the auxiliary pawl and slot disposed in the other of the pawl and the auxiliary pawl, the coupling pin riding in the slot. Alternatively, the one way connection can be provided by the auxiliary pawl pushing a tab on the pawl, or with a tab on the auxiliary pawl pushing the pawl. 
     The auxiliary pawl is preferably pivotally mounted for rotation in the housing. The motion restriction device preferably includes a stator and the moveable part of the motion restriction device is preferably a rotor having a shaft mounted for rotation within the stator, the stator containing the velocity dependent material which substantially inhibits rotation of the rotor when its angular speed exceeds a threshold speed. An input arm is connected to the rotor shaft; and the auxiliary pawl is connected to the input arm. 
     The input arm and the auxiliary pawl preferably have different centers of rotation and are slidingly connected at a substantially common point. The sliding connection may be provided by a coupling pin disposed on one of the input arm and the auxiliary pawl and a slot disposed in the other of the input arm and the auxiliary pawl, the coupling pin riding in the slot. Alternatively, the connection can also be provided by a gear pair (e.g., a sector arm profile on the auxiliary pawl and a pinion mounted on the rotor shaft of the device). The radial distance between the common point to the rotation axis for the auxiliary pawl is preferably greater than the radial distance between the common point to the rotation axis for the input arm whereby the angular speed of the input arm is greater than the angular speed of the auxiliary pawl. 
     Preferably, the rotor and stator have inter-fitting annular disks or coaxial cylinders, and the velocity dependent material is present in the interstitial area. 
     The latch may also include an inside release lever and an outside release lever located in planes perpendicular to one another. The latch system may also include an outside handle and an inside handle. 
     According to another broad aspect of the invention a method is provided for preventing the opening of a vehicle door latch having at least one pivotal lever for opening the latch. The method includes: (i) providing a motion restriction device having an input shaft, wherein the motion restriction device prohibits movement of its input shaft when the angular speed thereof exceeds a threshold speed; (ii) monitoring the speed of the opening lever by coupling it to the input shaft; (iii) amplifying rotational movement of the opening lever and applying the amplified rotational movement to the input shaft whereby the angular speed of the input shaft exceeds the angular speed of the opening lever; and resisting the motion of the opening lever when its angular speed exceeds a predetermined angular speed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of 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: 
         FIG. 1  is a perspective view of a door latch assembly including a pawl maintaining a ratchet in a latched position; 
         FIG. 2  is a fragmentary perspective view of the door latch assembly shown in  FIG. 1 , taken from a somewhat different viewpoint; 
         FIG. 3  is another fragmentary perspective view of the door latch assembly shown in  FIG. 1 , taken from a different viewpoint; 
         FIG. 3A  is a fragmentary perspective view of a variant of the door latch assembly shown in  FIG. 1 ; 
         FIG. 3B  is a fragmentary perspective view of another variant of the door latch assembly shown in  FIG. 1 ; 
         FIG. 4  is an exploded view of a first embodiment of a motion restriction device employed in the latch assembly for preventing unintended unlatching of the ratchet; 
         FIG. 5  is a cross-sectional view of the motion restriction device shown in  FIG. 4 ; 
         FIG. 6  is an perspective view of a second embodiment of a motion restriction device employable in the latch assembly for preventing unintended unlatching of the ratchet; and 
         FIG. 7  is a cross-sectional view of the motion restriction device shown in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 through 3 , a door latch assembly, generally shown at  110 , includes a housing  112  (shown in phantom as the details thereof are not important to understanding the invention) adapted to be attached to a motor vehicle door. The motor vehicle door may be, but is not limited to, a side door, a liftgate, a hood, a decklid, a sliding door, or a cargo door. 
     A first member or ratchet  114  and a second member or pawl  116  each are rotatably mounted to the housing  112 . The ratchet  114  includes a shoulder  118  and defines an opening  120 . The ratchet  114  is movable between a latched position, shown in  FIG. 1 , in which a striker (not shown) positioned along a motor vehicle body is retained within the opening  120  to lock the motor vehicle door and an unlatched position in which the striker is released from the ratchet  114  to allow opening of the motor vehicle door. The ratchet pivots about pin  115  and a spring  122  biases the ratchet  114  towards the unlatched position. 
     The pawl  116  is rotatable about a pin  124 . The pawl  116  includes a retention portion  126 . When the pawl  116  is in a pawl engagement position, shown in  FIG. 1 , the retention portion  126  engages the shoulder  118  to maintain the ratchet  114  in the latched position. When the pawl  116  is moved out of the pawl engagement position, the ratchet  114  is free to move from the latched position to the unlatched position. A spring  130  biases the pawl  116  towards the pawl engagement position. 
     The door latch assembly  110  includes a motion restriction device, generally indicated at  132 , positioned along the housing  112 . The motion restriction device  132  selectively prevents or blocks movement of the pawl  116  out of the pawl engagement position, depending on the angular or rotational speed of the pawl  116 . (As discussed in greater detail below, the speed of an auxiliary pawl is directly monitored rather than the speed of the pawl, but the speed of the pawl is related to the speed of the auxiliary pawl.) In the embodiment described herein, the motion restriction device  132  does not operate to block the pawl  116  if its high speed motion is caused as a reaction to fast movement of the ratchet  114  from the unlatched to latched position due to the motor vehicle door being slammed shut. However, the motion restriction device  132  will function to substantially resist movement of the pawl  116  out of the pawl engagement position in a crash situation that causes the pawl to pivot at an angular or rotational speed above a threshold value. 
     More particularly, the pawl  116  is actuated or moved out of the pawl engagement position into its release position by an auxiliary pawl  150  that is connected to the motion restriction device as discussed in greater detail below. The auxiliary pawl  150  is mounted for pivotal or rotational movement about pin  124 , thus having the same center of rotation as the pawl  116 . The auxiliary pawl  150  is moveable between a rest position coincident with the engaged position of the pawl  116  as shown in the drawings and a release position coincident with the pawl release position. In the illustrated embodiment the pawl spring  130  also biases the auxiliary pawl  150 , but if desired separate biasing springs may be provided for these components. 
     As seen best in  FIG. 3  the pawl  116  and auxiliary pawl  150  are coupled via a one way or lost motion connection comprising a coupling pin  128  fixedly secured or integrated with the pawl  116  that travels in a slot  152  of the auxiliary pawl  150 . When the motor vehicle door is slammed, the ratchet  114  moves from its unlatched to its latched position and pivots about pin  115  in a counterclockwise direction (with reference to  FIG. 3 , which shows the ratchet in the latched position). In the process, a leading shoulder  114   a  of the ratchet  114  interacts with portion  126  of the pawl  116 , pushing it so as to pivot in the counterclockwise direction as indicated by arrow  154 . The one way or lost motion connection, including the size and relative locations of the pin  128  and slot  152 , is configured to ensure that the rotation of the pawl  116  as a result of a slam will not engage and actuate the auxiliary pawl  115  which, in  FIG. 3 , would otherwise cause the auxiliary pawl  150  to rotate counterclockwise and possibly be affected by the motion restriction device  132 . In particular, the slot  152  is long enough to accommodate the maximum allowable rotational travel of the pawl  116 , which is limited by biasing spring  130  and a hard stop (not shown) on the housing interacting with protrusion  155  of the pawl. 
     However, the independent pivotal movement of the auxiliary pawl  150  in the counterclockwise direction into its release position does affect and move the pawl  116  counterclockwise to its release position because, in the biased position of the pawl  116  as shown in  FIG. 3 , the pawl coupling pin  128  abuts an edge  152   a  of the auxiliary pawl slot  152  and thus pin  128  will be dragged along when the auxiliary pawl  150  pivots counterclockwise. 
     The auxiliary pawl  150  may be actuated into its release position by one or more other levers, depending on the design of the latch in question. 
     In the illustrated embodiment, the latch is based on the latch described in Assignee&#39;s U.S. Pat. No. 7,264,283, the contents of which are incorporated herein by reference in their entirety. In this latch, an inside release lever  160  (FIGS.  2  and  3 —hidden from view in  FIG. 1 ) features a leg  162  for engaging a raised tab  156  of the auxiliary pawl  150  in order to actuate it into its release position. Also, an outside release lever  164  (shown only in  FIGS. 1 and 2 ) may be utilized to actuate the auxiliary pawl  150  into its release position. In the illustrated embodiment, as explained more fully in U.S. Pat. No. 7,264,283, the outside release lever  164  is selectively connected to the auxiliary pawl  150  by means of a slidable link  166  (shown only partially in  FIGS. 1 and 2 ) that has a depending tab  168  ( FIG. 2 ) that slides in and along a slot  170  disposed in the outside release lever  164 . The tab  168  slides between a first position, near the open end of the slot  170 , and a second position, near the closed end of the slot  170 . When the tab  168  is located in the first position adjacent the open end of the slot  170 , rotation of the outside release lever  164  causes the tab  168  to engage an abutment  186  of the auxiliary pawl  150  (as seen in  FIG. 2 ) and thus cause it, and correspondingly pawl  116 , to rotate. However, when the tab  168  is located in the second position adjacent the closed end of the slot  170 , the tab  168  is positioned in a void  188  (seen best in  FIGS. 1 and 3 ) of auxiliary pawl  150  whereby rotation of the outside release lever  164  is not coupled to the auxiliary pawl  150 . The slidable link  166  is controlled ultimately by an outside key cylinder (not shown) or an inside lock rod (not shown). 
     Note that in the illustrated latch the outside release lever  164  and inside release lever  160  are located in planes perpendicular to one another, and the inertial forces in a crash may affect any one of these release levers  160 ,  164 . 
     The auxiliary pawl  150  is also coupled to the motion restriction device  132 . More particularly, the auxiliary pawl  150  includes a leg  158  with a small slot  159  therein. As seen in  FIGS. 1 and 2 , the motion restriction device  132  has a rotatable input arm  134  with a coupling pin  136  that engages and rides in the auxiliary pawl slot  159 . The arrangement and sizing of the pin  136  and slot  159  are such that pivotal movement of the auxiliary pawl  150  results in the pivotal movement of the input arm  134 . The angular speed of the input arm  134  will be approximately twice the angular speed of the auxiliary pawl because the radial distance D 1  between the coupler pin  136  and the auxiliary pawl center of rotation (at pin  124 ) is approximately twice the radial distance D 2  between the coupler pin  136  and the center of rotation of the input arm  134 , as indicated by axis C in  FIG. 1 . It should be noted, however, that this ratio could be adjusted to suit the needs of any particular latch system. The pin  136  and slot  159  thus provide a sliding connection between the auxiliary pawl  150  and input arm  134  in order to accommodate for the different centers of rotation of these components. 
     The motion restriction device is preferably filled with a velocity-dependent material that can be a fluid, gel, foam, or like material. The velocity-dependent material also includes solid particles. An exemplary fluid that can be used for this purpose is described in U.S. Pat. No. 7,342,049. The velocity-dependent material transitions between a fluid-like state having a low viscosity and providing only negligible or limited resistance to deformation, and a solid-like state having a high viscosity and providing considerable resistance to deformation. Whether the velocity-dependent material acts as a fluid or a solid depends upon the velocity of the member acting upon the motion restriction device. If the velocity of the member is below a predetermined threshold, such as would occur at rest or during normal operation of the latch system, the velocity-dependent material will be in a fluid-like state. On the other hand, if the velocity of the member is above a predetermined threshold, the solid particles aggregate and the velocity-dependent material will be in a solid-like state. Once the velocity of the member drops below the predetermined threshold, the velocity-dependent material transitions back to the fluid-like state. Thus, a single motion restriction device  132  with the velocity-dependent material may be utilized to permit movement of a member or component in certain situations and substantially resist the same movement in other situations. 
     One embodiment of the motion restriction device  132  designated by reference numeral  200  is shown in  FIGS. 4 and 5 . The motion restriction device  200  includes a stator or housing  210 , a rotor  220 , a foam washer  230  and a cover  240 . The housing  210  has a base  212  and features a plurality concentric circular walls  214   a ,  214   b    214   c , and  214   d  depending from and arranged transverse to the major plane of the base  212 . Walls  214   a ,  214   b  and  214   c  form longitudinally orientated concentric outer toroidal cavities  216  about the center axis C of the device  200 . Walls  214   c  and  214   d  form an inner toroidal cavity  218 . 
     The rotor  220  includes a shaft  222  defining the central axis C of the device. The shaft  222  features a keyed end  224  for securely connecting the input arm  134  to the shaft. The opposing end of the shaft  222  is connected to or formed with a web such as a circular plate  226  from which concentric circular walls or cylindrical sleeves  228  depend transverse to the web in a longitudinal orientation relative to the central axis C of the device  300 . 
     In assembly, the rotor cylindrical sleeves  228  are disposed in the respective toroidal cavities  216  of the housing. The rotor cylindrical sleeves  228  preferably occupy most of the volume in the housing toroidal cavities  216  resulting in a relatively thin layer of the velocity dependent material between the rotor cylindrical sleeves  228  and the housing circular walls  214   a ,  214   b ,  214   c , resulting in a relatively high shear on the velocity dependent material. The design also maximizes the surface area available for subjecting the velocity dependent material to shear forces in a relatively small package space. 
     The foam washer  230  is installed in housing cavity  218  and functions as compressible resilient member to account for volumetric changes in the velocity dependent material due to temperature changes. An O-ring  229  seated in a circumferential groove  219  of the housing  210  and mounted about the shaft  224  seals the device  200  against leakage of the velocity dependent material. 
     Another embodiment of the motion restriction device  132  designated by reference numeral  300  is shown in  FIGS. 6 and 7 . The motion restriction device  300  includes a stator or housing  310 , a rotor  320 , and a cover  340 . The housing  310  has a base  312  with a transverse sidewall  314  from which depend a plurality of circular walls  316  concentric about the center axis C of the device  300 . In the illustrated embodiment, the circular walls  316  are provided in part by a plurality of stacked disks  317  interconnected by a fastener  319 . The circular walls  316  form latitudinal orientated concentric shallow cylindrical cavities  318 . The cavities  318 , which are in fluid communication with one another, are filled with the velocity dependent material. 
     The rotor  320  includes a partially hollow shaft  322  defining the central axis C of the device  300 . The shaft  322  features a keyed end  324  for securely connecting the input arm  134  to the shaft. The opposing end of the shaft  322  is journaled about a spindle  326  installed in the housing. A plurality of latitudinal orientated disks  328  depend from the shaft  322 , each disk  328  respectively disposed in one of the shallow cylindrical cavities  318 . The rotor disks  328  preferably occupy most of the volume in the shallow cylindrical cavities  318  resulting in a relatively thin layer of the velocity dependent material between the rotor disks  328  and the housing circular walls  316 , resulting in a relatively high shear on the velocity dependent material. The design also maximizes the surface area available for subjecting the velocity dependent material to shear forces in a relatively small package space. 
     A seal  330  with a compliant or foam lower portion is installed between the rotor shaft and cover  340  to prevent leakage of the velocity dependent material and functions as compressible resilient member to account for volumetric changes in the velocity dependent material due to temperature fluctuations. 
     It will thus be seen that the two illustrated embodiments  200 ,  300  of the motion restriction device are quite similar with the orientation of the rotor cylinders and disks and corresponding stator cavities being arranged either generally parallel to the rotor shaft or generally transverse to the rotor shaft. As such, the motion restriction device can be considered to have a rotor and stator with inter-fitting coaxial cylinders or annular disks. 
     The one way connection between the pawl and auxiliary pawl has been shown as being provided by a pin on the pawl and a slot in the auxiliary pawl. However, the reverse orientation, where the pin is disposed on the auxiliary pawl and the slot is disposed on the pawl, is also possible. Alternatively, the one way connection can be provided by the auxiliary pawl pushing a tab on the pawl, or with a tab on the auxiliary pawl pushing or pulling the pawl. In push tab embodiments, there is no slot—and no danger of contact during door slam. For instance,  FIG. 3A  shows a variant of the latch shown in  FIG. 1  where the pawl  116  includes a tab  117  that interacts with the auxiliary pawl  150  via slidable link  166 . As the movement of the pawl  116  to the release position from the engaged position (as shown) is in the clockwise direction with reference to  FIG. 3A  (which is in reverse orientation relative to  FIG. 3 ), the overslam condition will also result in the pawl  116  pivoting clockwise without causing corresponding movement of the auxiliary pawl  150 . However, when the auxiliary pawl  150  pivots clockwise into its release position, it also moves the pawl  116  into its release position. 
     The connection between the auxiliary pawl and the motion restriction device has been shown as a pin and slot sliding connection between these components. An alternative arrangement for coupling the auxiliary pawl to the motion restriction device could include a pair of gears as shown in  FIG. 3B , preferably one formed as a sector gear on auxiliary pawl  150  and the second gear  133  mounted to the rotor shaft of the motion restriction device  132 . 
     In alternative embodiments of the invention, one or more other operating parts of the latch can be operatively connected to the motion restriction device  132 . For example, any of the inside or outside release levers may be connected to the motion restriction device via a suitably shaped input arm and suitably positioned motion restriction device. Alternatively, the motion restriction device may be placed at the outside or inside handles. Also, if door slams situations are not a concern, or if the threshold speed is set very high above what would typically be encountered in a door slam situation, the lost motion or one way connection between the pawl and auxiliary pawl may be omitted, or the pawl may itself be directly coupled to the motion restriction device. 
     While the above describes a particular embodiment(s) of the invention, it will be appreciated that modifications and variations may be made to the detailed embodiment(s) described herein without departing from the spirit of the invention.