Abstract:
A vehicle subassembly includes a door latch and an emergency release mechanism for use in unlatching the door latch. The mechanism includes a release arranged so as to act on a latch input and to supply an increased unlatching force relative to that normally capable of being supplied to the door latch. An engagement member is actuable by a person to operate the release. In a first non-emergency condition the engagement member is substantially prevented from being actuated, and in a second emergency condition actuation the engagement member is allowed.

Description:
This application claims priority to United Kingdom application number 0127870.4 filed on Nov. 21, 2001. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a vehicle subassembly. More particularly, the present invention relates to a vehicle subassembly comprising a release mechanism to unlatch a vehicle door latch in an emergency situation. 
     Energy is required to unlatch latched vehicle doors. This energy is primarily required to overcome the frictional resistance between a latch bolt and pawl tooth of a latch mechanism when the pawl tooth retains the latch in a latched position. This resistance is largely induced by the force of seals around the door that normally tend to urge the door into an ajar position, but which when the door is latched, act between a striker mounted on the door surround and the latch bolt. This force is commonly known as the “seal force” or “seal load”. Under normal circumstances, the seal load is likely to be less than 1,000 N. 
     When a vehicle suffers an impact, particularly from the side, deformation of the vehicle door may result in an increased unlatching force being required. In light of increasing vehicle safety standards, it is desirable to provide means to permit unlatching at an increased seal load, preferably a seal load of up to 9,000 N, that is due to deformation of the vehicle. 
     SUMMARY OF THE INVENTION 
     Accordingly, one aspect of the present invention provides a vehicle subassembly comprising a door latch and an emergency release mechanism for use in unlatching the latch, the mechanism comprising release means arranged so as to act on a latch input and to supply an increased unlatching force relative to that normally capable of being supplied to the latch and engagement means actuable by a person to operate the release means, wherein a first non-emergency condition of an associated vehicle, the engagement means is substantially prevented from being actuated, and in a second emergency condition of the associated vehicle actuation of the engagement means is allowed. 
     A second aspect of the present invention provides a vehicle subassembly comprising a door latch, and an emergency release mechanism for use in unlatching the latch, the mechanism comprising release means arranged to act on a latch input and to supply an increased unlatching force relative to that normally capable of being supplied to the latch and engagement means actuable by a person to operate the release means, wherein actuation of the engagement means is only possible with an appropriate access authorisation device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic partially cut-away inside view of a vehicle door incorporating a subassembly according to the present invention; 
         FIG. 2  is a schematic view of the subassembly of  FIG. 1  in greater detail; 
         FIG. 3  is a schematic view of the subassembly according to a second embodiment of the present invention 
         FIG. 4  is a schematic view of the subassembly according to a third embodiment of the present invention; 
         FIG. 5  is a schematic view of a subassembly according to a fourth embodiment of the present invention; 
         FIG. 6  is a perspective view of a vehicle illustrating a subassembly according to a fifth embodiment of the present invention; and 
         FIG. 7  is a block diagram of a subassembly according to a sixth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is shown a door  10  hingeably mounted on a vehicle  8  having an inner trim panel  14  in which a recess  16  is provided, typically for the storage of a side airbag  17  (shown uninflated). The door  10  is further provided with a latch  18 . In this embodiment the latch is connected to conventional manual inside and outside release handles (not shown) and a motor (not shown) to lock/unlock the latch in response to signals from a remote keyless entry device. In other embodiments, the latch may be a fully manual or fully electrically driven “power” latch. Indicated generally at  12  is a subassembly incorporating a release mechanism  20 , recess  16 , cover  15  (shown partially cut away) and the latch  18 . 
     Under normal circumstances, the recess  16  is obscured by the cover  15 . When a controller  25  (illustrated schematically in  FIG. 1 ) for the airbag determines that an impact above a predetermined threshold has occurred in response to data it receives from one or more sensors (not shown), the controller signals deployment of the side airbag which is achieved using any suitable known means of inflation (typically involving the use of a squib containing a solid fuel and oxidiser that react to emit a predetermined volume of gas to cause inflation). 
     The pressure induced by inflation of the airbag causes the cover  15  to be displaced. This enables the airbag to inflate within the vehicle passenger compartment and thereby perform its cushioning function on vehicle occupants, as is well known. After the airbag has deployed, it deflates rapidly, thereby revealing recess  16 . 
     Turning now to  FIG. 2  in which the subassembly is shown in greater detail and in a latched state, it can be seen that the release mechanism  20  of the subassembly  12  comprises engagement means in the form of a handle  24  and release means in the form of an arm  22  arranged to act on a pawl lifter  28  of the latch  18 . The handle  24  and arm  22  are in the form of a single bar rotatably mounted to the door about a pivot  26 . 
     It can be seen from  FIG. 2  that rotating handle  24  in anti-clockwise direction A causes the release means to lift pawl lifter  28  thereby unlatching the latch and enabling the door  10  to be opened. The location of the pivot  26  closer to the arm  22  than the handle  24  results in the greater force being imparted on the pawl lifter  28  than is applied to the handle  24  by a vehicle occupant wishing to exit the vehicle after an impact. This means that a greater unlatching force can be imparted to the pawl lifter that a vehicle occupant could apply using a conventional manual latch release handle, or is supplied by a conventional unlatching motor in a power latch. 
     It is preferable that the release means acts directly on the pawl lifter  28  since this means that it is irrelevant whether the vehicle is locked, and emergency unlatching can be effected even if the latch is locked or super locked. This is particularly advantageous on vehicles fitted with power latches since power may cease to be supplied to the latch motors after an impact, and unlocking would otherwise be prevented. 
     Referring now to  FIG. 3 , a vehicle subassembly according to a second embodiment of the present invention is illustrated in a latched state. Like numerals have been used, where possible, for like parts with the addition of the prefix “1”. 
     In this embodiment, the emergency release mechanism comprises a handle  124  located in recess  116 . A Bowden cable having a fixed outer sheath  130  and a relatively slidable inner cable  132  is connected at one end to handle  124  and at its other end to release means. In this embodiment, the release means is in the form of a compressed gas canister and piston arrangement  122 . It will be noted that some slack is provided in the cable to prevent the mechanism being triggered due to deformation of the door in an impact that may otherwise cause the cable to be placed under tension. 
     In order to release the latch, a vehicle occupant pulls on handle  124  in direction B, which in turn causes the inner cable  132  to cause compressed gas to be released from the canister using any suitable valve mechanism (not shown). In turn, this causes the piston arrangement to extend under the influence of the compressed gas and actuate pawl lifter  128 , thus effecting unlatching. In other classes of embodiment, the gas canister and piston arrangement  122  may be dispensed with and addition force may be applied to the pawl lifter by extending the length of the pawl lifter in a direction out of the paper as shown in FIG.  3  and connecting the inner cable  132  to the free end of the lifter. 
     A third embodiment of the vehicle subassembly according to the present invention is illustrated in FIG.  4 . Again, like numerals are used where possible for like parts, with the addition of the prefix “2”. 
     In this embodiment, the engagement means comprises a handle  224  located in recess  216 . The handle is secured to an axially slidable and vertically restrained rod  234 . In the non-deployed state showing in  FIG. 4 , the end  236  of the rod  234  remote from handle  224  retains a release means in the form of a compression spring  222  in a pre-loaded condition. To release the compression spring  222 , a vehicle occupant pulls handle  224  in direction C, thereby enabling the spring  222  to extend to its rest position and lift the pawl lifter  228 . 
     A fourth embodiment of a vehicle subassembly according to the present invention is shown in  FIG. 5  in which like parts have where possible been designated by like numerals with the addition of the prefix “3”. 
     The release mechanism  320  of this embodiment is similar to that of the third embodiment of  FIG. 4  except that the compression spring is replaced by a pre-loaded helical torsion spring  322 . Again, pulling handle  324  in direction D releases the torsion spring to act on pawl lifter  328  and release the latch  318 . In this embodiment, rod  334  has been extended so as to substantially reduce the risk that door deformation will cause accidental release of the release mechanism  320 . In other classes of embodiment, a Bowden cable in which slack is provided may interconnect the handle  324  and a section of rod adjacent pawl lifter  328  to reduce the risk of accidental release caused by door deformation. 
     By placing the engagement means of the release mechanism in an airbag recess, unauthorised personnel, such as potential thieves are substantially prevented from overriding the locked state of a vehicle by breaking a vehicle window and pulling the release means to gain access to the vehicle. It will nevertheless be appreciated that engagement means may be placed in other locations, such as in an airbag recess providing on the steering wheel of a vehicle or in a recess provided for a passenger airbag within the vehicle fascia in front of the passenger. A suitable linkage may be provided to the release means, such as a Bowden cable. Alternatively, a covered recess may be provided in the vehicle door trim or elsewhere in the vehicle specifically for the engagement means, the cover being displaced in response to the sensing of an impact by a controller associated with the cover. 
     Referring to  FIG. 6 , as an alternative to, or in addition to the release mechanism as described above, engagement means may be provided on the exterior of a vehicle  408  to enable emergency personnel to release the doors  410  of the vehicle from the vehicle exterior, even if the vehicle occupant(s) are unable to do so themselves due to injuries they may have sustained, for example. To prevent such external engagement means from being actuated by unauthorised personnel, it is preferable that firstly the engagement means  424  be placed in an obscured position on the vehicle  408 , such as on the underside of a door sill  450 , behind the fuel filler cover  452 , or behind a vehicle number plate  454 , and secondly that the engagement means  424  may only be actuated with the use of a key  456 , coded access means, or a similar access authorisation device to be carried by emergency personnel. 
     Referring to  FIG. 7 , it will be understood that numerous other suitable release means may be employed such as solid fuel squibs  522  as described above in relation to airbag inflators, but from which the gas produced is used to cause a piston or ram  523  to extend and actuate the pawl lifter  528  in response to a handle  524  being pulled. Other means of mechanically increasing the force to the pawl lifter may be employed, such as the use of gears, for example.