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CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Korean Patent Application Number 10-2008-0062587, filed on Jun. 30, 2008, the entire contents of which application is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a door latch apparatus for vehicles which is constructed such that a door is prevented from opening when a vehicle is involved in a collision. 
     2. Description of Related Art 
     Generally, outside door handles are provided on outer surfaces of door panels and are used to open or close the doors. As shown in  FIG. 1 , a handle base plate  21  is installed in a door panel  10 , and a lever  30 , which is operated in conjunction with the rotation of an outside door handle  20 , is coupled to the handle base plate  21  by a pin shaft  31 . 
     The lower end of the lever  30  is connected to a door latch by a rod or cable  40 . A balance weight  50  is integrally provided on the upper end of the lever  30 . Furthermore, a return spring is fitted over the pin shaft  31 . A first end of the return spring is fastened to the inner surface of the outside door handle  20 , and a second end of the return spring is fastened to the inner surface of the balance weight  50 . 
     The construction is such that when the outside door handle  20  is pulled, the lower end of the lever  30  is rotated in the direction corresponding to the direction in which the outside door handle  20  is pulled. Thus, the rod or cable  40 , which is connected to the lower end of the lever  30 , is pushed. Thereby, the door latch is unlocked, so that the door is opened. 
     Here, the balance weight applies an inertia load to the lever  30  in the direction opposite the direction in which the outside door handle is operated, in other words, in the direction in which the operation of the outside door handle is restricted and the latched door is prevented from being unlatched. 
     However, in the conventional technique in which the balance weight is provided on the outside door handle, when the outer panel of the door is deformed by an impact force F generated by a vehicle collision, the balance weight may be pushed inwards. At this time, the lower end of the lever, which is pushed inwards along with the balance weight, is rotated in the same direction as the direction in which the outside door handle is pulled during manual unlatching. Thereby, the door latch may be undesirably unlatched. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Various aspects of the present invention are directed to provide a door latch apparatus for vehicles which is constructed such that even if an outside door handle is operated by inertia force or deformation of a door panel when a vehicle is involved in a side collision, the door is prevented from opening. 
     In an aspect of the present invention, a door latch apparatus for vehicles may include a latch bracket, an outside handle lever pivotally coupled to the latch bracket, wherein one end of the outside handle lever is coupled to an outside handle, a pawl lift, one end of which is pivotally hinged to the other end of the outside handle lever and the other end of which includes a locking portion, a pawl including a pawl pin, wherein the pawl pin is pivotally movable on the latch bracket, and the pawl pin and the other end of the pawl lift are coupled in a normal state, a latch fork connected to the pawl to lock or unlock a door depending on rotation of the pawl, and/or a balance weight mounted to the other end of the pawl lift to apply an inertia load to the other end of the pawl lift toward outside the door such that the locking portion of the pawl lift is released from the pawl pin when a vehicle collision occurs. 
     The locking portion of the pawl lift may be configured to be recessed from a surface of the other end of the pawl lift so as to receive the pawl pin therein. 
     The pawl pin may be elastically supported by an elastic member toward the locking portion of the paw lift. 
     The door latch apparatus may further include a locking lever pivotally coupled to the latch bracket, wherein the locking lever is rotated by an external signal to activate the other end of the pawl lift so as to couple or decouple the pawl pin and the other end of the pawl lift when the external signal is transmitted to the locking lever. 
     The locking lever may include a contact protrusion to push the other end of the pawl lift when the locking lever is rotated by the external signal, such that the locking portion of the pawl lift is released from the pawl pin. 
     The other end of the pawl lift may include a locking protrusion configured to correspond to the contact protrusion of the locking lever. 
     The one end of the pawl lift may be elastically coupled to the other end of the outside handle lever by an elastic member so as to bias the pawl lift toward the pawl pin. 
     The outside handle lever may be elastically supported by an elastic member coupled to the latch bracket so as to return its original position after an external force applied to the one end of the outside handle lever is removed. 
     A position adjustment slot may be formed in the other end of the outside handle lever so as to adjust a position coupling the one end of the pawl lift and the other end of the outdoor handle lever. 
     A hinge shaft formed at the one end of the pawl lift may be coupled to the position adjustment slot so as to be adjustable in position therein. 
     In another aspect of the present invention, a door latch apparatus for vehicles may include a latch bracket, an outside handle lever pivotally coupled to the latch bracket, wherein one end of the outside handle lever is coupled to an outside handle, a pawl lift, one end of which is pivotally hinged to the other end of the outside handle lever and the other end of which includes a locking portion, a pawl including a pawl pin, wherein the pawl pin is pivotally movable on the latch bracket, and the pawl pin and the other end of the pawl lift being coupled in a normal state, a latch fork connected to the pawl to lock or unlock a door depending on rotation of the pawl, a balance weight mounted to the other end of the pawl lift to apply an inertia load to the other end of the pawl lift toward outside the door such that the locking portion of the pawl lift is released from the pawl pin when a vehicle collision occurs, and/or a locking lever pivotally coupled to the latch bracket, wherein the locking lever is rotated by an external signal to activate the other end of the pawl lift so as to couple or decouple the pawl pin and the other end of the pawl lift when the external signal is transmitted to the locking lever. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing the construction of an outside handle of a door for vehicles, according to a conventional technique. 
         FIG. 2  is a perspective view of an exemplary door latch apparatus for vehicles according to the present invention. 
         FIG. 3  is an enlarged perspective view of a circled portion “A” of  FIG. 2 . 
         FIG. 4  is a perspective view of an enlargement of an exemplary outside handle lever of the door latch apparatus according to the present invention. 
         FIGS. 5A and 5B  are views illustrating the operation of the door latch apparatus when it is in an unlocked state according to the present invention. 
         FIGS. 6A and 6B  are views are views illustrating the operation of the door latch apparats when it is in a locked state according to the present invention. 
         FIGS. 7A through 7C  are views illustrating the operation of the door latch apparatus when the vehicle is involved in a side collision according to the present invention. 
         FIGS. 8A and 8B  are views illustrating the operation of the door latch apparatus when it is in the unlocked state after the vehicle has been involved in the side collision according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
       FIG. 2  is a perspective view of a door latch apparatus for vehicles, according to various embodiments of the present invention.  FIG. 3  is an enlarged perspective view of a circled portion “A” of  FIG. 2 .  FIG. 4  is a perspective view of an enlargement of an outside handle lever of the door latch apparatus according to various embodiments of the present invention. 
     As shown in  FIGS. 2 through 4 , the door latch apparatus for vehicles according to various embodiments is characterized in that it includes a balance weight for providing an inertia load so that when the vehicle is involved in a collision, the door is prevented from undesirably opening, and after the collision, the door latch can be normally operated. 
     To achieve the above purpose, the door latch apparatus, as does various embodiments of the present invention, includes an outside handle lever  100  that is rotatably mounted to a latch bracket  700 , a pawl lift  200 , which is hinged to the outside handle lever  100  and is selectively locked to a pawl pin  310  of a pawl  300 , and a balance weight  500 , which is mounted to the pawl lift  200 . 
     The outside handle lever  100  is connected at a first end thereof to an outside handle through an actuation cable. A second end of the outside handle lever  100  is rotatably coupled to the pawl lift  200  using a hinge shaft  240 . An elastic spring  110  is provided between the outside handle lever  100  and the latch bracket  700  to elastically support the outside handle lever  100 . 
     When the outside handle is pulled, the actuating force thereof is transmitted to the outside handle lever  100  through the actuation cable. Then, the outside handle lever  100  rotates around the hinge shaft  115  and thus pulls the pawl lift  200 . When the outside handle is released, the outside handle lever  100  is rotated to its original position by the elastic restoring force of the elastic spring  110  and the pawl lift  200  is thus returned to its original position. 
     Preferably, a position adjustment slot  120 , into which the hinge shaft  240  of the pawl lift  200  is inserted, may be formed in the outside handle lever  100 . The position adjustment slot  120  enables the hinge shaft  240  of the pawl lift  200  to be adjusted in position during an assembly process, thus reducing an assembly tolerance. 
     The pawl lift  200  is hinged to the outside handle lever  100  and has a recessed locking portion  210 , which is selectively locked to the pawl pin  310  of the pawl  300 . 
     In various embodiments, an elastic spring  230  is provided between the pawl lift  200  and the outside handle lever  100  to elastically support a first end of the pawl lift  200 . In an unlocked state of the door, when the pawl lift  200  is rotated by the outside handle lever  100 , the recessed locking portion  210  of the pawl lift  200  is locked to the pawl pin  310  of the pawl  300 . The pawl pin  310 , which is in the locked state, is rotated by the pawl lift  200 , thus enabling a latch operation of a latch fork  400 . 
     A locking protrusion  220  is provided on a second end of the pawl lift  200  such that the pawl lift  200  is operated in conjunction with a locking lever  600 . The locking lever  600  has a contact protrusion  610 , which rotates the second end of the pawl lift  200  when a locking signal of the door is transmitted. The locking lever  600  is rotatably mounted to a support bracket  710  of the latch bracket  700 . 
     Therefore, when the locking lever  600  is rotated in the locked state of the door, the contact protrusion  610  of the locking lever  600  pushes the locking protrusion  220  of the pawl lift  200 , thus rotating the pawl lift  200 . Thereby, the recessed locking portion  210  of the pawl lift  200  which has held the pawl pin  310  is removed from the pawl pin  310 . As a result even though the pawl lift  200  is rotated by the outside handle lever  100 , the door is prevented from being opened because the pawl pin  310  does not rotate to operate the latch fork  400 . 
     In various embodiments of the present invention, the pawl lift  200  is provided with the balance weight  500 . The balance weight  500  functions to apply an inertia load to the second end of the pawl lift  200  when the vehicle is involved in a collision, and release the recessed locking portion  210  of the pawl lift  200  from the pawl pin  310 , thus preventing the door from being opened. In other words, when a load is applied to the door by a vehicle collision, the balance weight  500  rotates the pawl lift  200  in the direction, in which the recessed locking portion  210  of the pawl lift  200  is removed from the pawl pin  310  by the inertial load. Therefore, even if the outside handle lever  100  is rotated by undesirable rotation of the outside handle as a result of vehicle collision, because the recessed locking portion  210  of the pawl lift  200  cannot rotate the pawl pin  310  of the pawl  300 , the door is prevented from opening. 
     After the vehicle collision has occurred, the pawl lift  200 , which has been rotated in the direction in which the recessed locking portion  210  becomes removed from the pawl pin  310 , is returned to its original position by the elastic restoring force of the elastic spring  230 . Thus, the recessed locking portion  210  of the pawl lift  200  is locked to the pawl pin  310  again. Hence, even after the vehicle collision has occurred, the door latch can be normally operated. 
     The operation and effect of various embodiments of the present invention, having the above-mentioned construction will be explained herein below. 
       FIGS. 5A and 5B  are views illustrating the operation of the door latch apparatus when it is in an unlocked state according to various embodiments of the present invention. 
     As shown in  FIGS. 5A and 5B , when the outside handle is pulled in the unlocked state of the door, the actuation force is transmitted to the outside handle lever  100  through the actuation cable and the outside handle lever  100  is thus rotated in a counterclockwise direction. Then, the pawl lift  200  is rotated in a counterclockwise direction by the rotation of the outside handle lever  100 , so that the recessed locking portion  210  of the pawl lift  200  is locked to the pawl pin  310  of the pawl  300 . 
     Thereafter, the pawl lift  200  rotates the pawl  300 , which is locked to the recessed locking portion  210 . The latch fork  400  is also rotated by the rotation of the pawl  300 . As a result, the door is opened by the operation of the latch fork  400 . 
     The pawl pin  310  is elastically supported by an elastic spring  320  so that the pawl pin  310  return its original position by the elastic spring  320  as the outdoor handle lever  100  rotates in the clockwise direction. 
       FIGS. 6A and 6B  are views are views illustrating the operation of the door latch apparatus when it is in a locked state according to various embodiments of the present invention. 
     As shown in  FIG. 6A , when the locking lever  600  is rotated in a counterclockwise direction in the locked state of the door, the contact protrusion  610  of the locking lever  600  pushes the locking protrusion  220  and thus rotates the pawl lift  200  in the clockwise direction. Thus, the recessed locking portion  210  of the pawl lift  200  which has been held by the pawl pin  310  is removed from the pawl pin  310 . The pawl pin  310  is elastically supported by an elastic spring  320  and maintains its original position by the elastic spring  320  so that the door is locked. 
     In other words, as shown in  FIG. 6B , even though the pawl lift  200  is rotated in a counterclockwise direction by the outside handle lever  100 , the latch operation of the door using the pawl pin  310  cannot be conducted. Therefore, the locked state of the door is maintained. 
       FIGS. 7A through 7C  are views illustrating the operation of the door latch apparatus when the vehicle is involved in a side collision according to various embodiments of the present invention. 
     As shown in  FIGS. 7A through 7C , when the vehicle is involved in a side collision, the balance weight  500  applies an inertia load to the second end of the pawl lift  200 , thus rotating the pawl lift  200  in a clockwise direction. Thereby, the recessed locking portion  210  of the pawl lift  200  is removed from the pawl pin  310 . 
     Therefore, as shown in  FIG. 7C , even if the outside handle is rotated by the vehicle collision and the outside handle lever  100  is thus rotated, the door is prevented from being opened. 
       FIGS. 8A and 8B  are views illustrating the operation of the door latch apparatus when it is in the unlocked state after the vehicle has been involved in the side collision according to various embodiments of the present invention. 
     As shown in  FIGS. 8A and 8B , after the vehicle collision has occurred, the pawl lift  200 , which has been rotated by the balance weight  500  in a counterclockwise direction, is returned to its original position by the elastic restoring force of the elastic spring  230 . Thus, the recessed locking portion  210  of the pawl lift  200  is locked to the pawl pin  310  again. 
     In this state, when the outside handle is pulled, the pawl lift  200  pulls and rotates the pawl  300 , which is locked to the recessed locking portion  210 . Then, the latch fork  400  is also rotated by the rotation of the pawl  300 . Therefore, the door can be opened by the operation of the latch fork  400 . As such, even after the vehicle collision has occurred can the door latch be normally operated. 
     As described above, in a door latch apparatus according to various aspects of the present invention, even if an outside handle of a door is undesirably operated by inertia force or deformation of the door when a side collision occurs, the door can be prevented from being opened. Furthermore, even after the vehicle collision is over can the door latch be normally operated. 
     In particular, a balance weight, which provides an inertia load when a vehicle collision occurs, is provided in the door latch apparatus. Therefore, the balance weight is prevented from being undesirably moved by deformation of the outer panel of the door when the collision occurs. Thus, the present invention can reliably prevent the door latch from being undesirably released when the vehicle is involved in a collision. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper” and “lower” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.

Summary:
A door latch apparatus for vehicles includes a latch bracket, an outside handle lever pivotally coupled to the latch bracket, wherein one end of the outside handle lever is coupled to an outside handle, a pawl lift pivotally hinged to the other end of the outside handle lever and including a locking portion, a pawl including a pawl pin, wherein the pawl pin is pivotally movable on the latch bracket, the pawl pin and the pawl lift being coupled in a normal state, a latch fork connected to the pawl to lock or unlock a door depending on rotation of the pawl, and a balance weight mounted to the other end of the pawl lift to apply an inertia load to the pawl lift such that the locking portion of the pawl lift is released from the pawl pin when a vehicle collision occurs.