Patent Publication Number: US-9410345-B2

Title: Vehicle door lock device

Description:
CROSS-REFERENCE 
     This application is the US national stage of International Patent Application No. PCT/JP2011/056188 filed on Mar. 16, 2011. 
     TECHNICAL FIELD 
     The present invention relates to a vehicle door lock device. 
     BACKGROUND ART 
     A prior-art vehicle door lock device is disclosed in Patent Document 1. The vehicle door lock device includes amounting member, a fork, a pawl, and a switching mechanism. 
     The mounting member is provided on a door that opens and closes an opening of a vehicle body. A striker is fixed to the vehicle body, and an entry opening that the striker enters is formed in the mounting member. The fork is pivotably provided on the mounting member. The fork is switched between a latched state, in which the striker is locked in the entry opening, and an unlatched state, in which the locking of the striker in the entry opening is released. The pawl is pivotably provided on the mounting member. The pawl is capable of fixing or allowing pivotal movement of the fork. 
     The switching mechanism acts on the pawl to switch the fork from the latched state to the unlatched state. More specifically, the switching mechanism includes an outside lever, which is pivotably supported by the mounting member, and an intermediate lever, which is pivotably supported at one end of the outside lever. The other end of the outside lever is coupled to an outside handle for a door-opening operation via a cable. When the other end of the outside lever is pulled upward by the door-opening operation, the one end of the outside lever and the intermediate lever are moved downward. 
     An engaging projection that projects downward and an engaging hole, which surrounds the engaging projection from below in a U-shape, are formed at a center of the intermediate lever. Two coil springs that face each other are provided between the intermediate lever and the mounting member. The intermediate lever is held at an initial position by the respective coil springs, and assumes a substantially vertically upright posture. 
     The pawl includes a ratchet abutting the fork, a rotation shaft having one of its ends integrally coupled to the ratchet, and an opening lever formed with an engaging claw portion that is integrally coupled to the other end of the rotation shaft. The engaging claw portion of the open lever is inserted into the engaging hole of the intermediate lever, and is positioned below the engaging projection. 
     In the prior-art vehicle door lock device having the above-described structure, when the intermediate lever is moved downward by the door-opening operation in a normal state, the engaging projection of the intermediate lever at the initial position presses the engaging claw portion of the opening lever. Therefore, the pawl pivots about the rotating shaft, the ratchet moves away from the fork, and the fork is switched from the latched state to the unlatched state. 
     Furthermore, in this vehicle door lock device, if the door or the vehicle body experiences an impact from the outside of the vehicle due to a collision or the like towards the vehicle, an inertia force will act on the intermediate lever in the direction of impact. Therefore, because the intermediate lever pivots from the initial position in the direction opposite to the direction of impact, the engaging projection is not positioned above the engaging claw portion. In addition, in this state, an opening operation of the door occurs due to the impact, and what results is a “swing-and-miss state”, in which even if the intermediate lever moves downward, the engaging claw portion is not pressed by the engaging projection, i.e. the fork is not switched from the latched state to the unlatched state. In this manner, the prior-art vehicle door lock device prevents an unintended opening of the door at the time of impact, to ensure the safety of the passenger(s). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Document 1: JP-A-2005-120764 
       
    
     SUMMARY OF THE INVENTION 
     However, in the above-described prior-art vehicle door lock device, an improvement of the design flexibility relating to a relative positional relationship between the switching mechanism and the pawl is difficult, as will be described below as detailed examples; accordingly, a reduction in size and an improvement of the mountability with respect to the vehicle are difficult. 
     For example, in order to cope with a variety of relative positional relationships such as the door, the opening, the striker, and the outside handle, a situation is considered that changes the positions of the opening lever and the engaging claw portion, which constitute the pawl, from the one end side to the other end side of the outside lever. In this situation, in order to cause the intermediate lever supported by the one end of the outside lever to press the engaging claw portion that has changed in position, it is necessary to elongate the intermediate lever until it reaches the engaging claw portion. Accordingly, the weight of the intermediate lever is excessively increased and it becomes difficult to set the inertia force for causing the intermediate lever to pivot from the initial position in accordance with an impact having a desired magnitude. Furthermore, in the above-described situation, if it is attempted to bring the intermediate lever closer to the engaging claw portion that is changed in position from the one end side to the other end side of the outside lever, the components will be concentrated at the other end side of the outside lever and hence an installation space of the intermediate lever will be difficult to ensure. 
     It is therefore an object of the present teachings to disclose a device that is capable of preventing a vehicle door from being unintentionally opened at the time of an impact in a manner that preferably realizes an improvement in design flexibility with regard to the relative positional relationship of a switching mechanism and a pawl. 
     In one aspect of the present teachings, a vehicle door lock device preferably includes: 
     a mounting member provided on a door that opens and closes an opening of a vehicle body and is formed with an entry opening, into which a striker fixed to the vehicle body is inserted; 
     a fork pivotably provided on the mounting member and that switches between a latched state, in which the striker is locked within the entry opening, and an unlatched state, in which the locking of the striker within the entry opening is released; 
     a pawl pivotably provided on the mounting member and capable of fixing or allowing pivotal movement of the fork; and 
     a switching mechanism provided on the mounting member and that acts on the pawl to switch the fork from the latched state to the unlatched state, wherein 
     the switching mechanism includes: 
     a first lever coupled to an outer door handle or an inner door handle and that is pivotable about a first axial center of pivotal movement by an opening operation of the outer door handle or the inner door handle; 
     a second lever that acts on the pawl by pivoting about a second axial center of pivotal movement; 
     an inertial lever provided on one of the first lever and the second lever, being pivotable about an axis extending in a direction orthogonal to the direction of advance and retraction with respect to the opening, and that pivots from an initial position about the axis by application of an inertia force exceeding a preset value; and 
     a transmitting portion provided on the other one of the first lever and the second lever, that transmits the pivotal movement of the first lever to the second lever by abutting against the inertia lever when the inertial lever is at the initial position and, in contrast, that does not transmit the pivotal movement of the first lever to the second lever by not abutting against the inertial lever when the inertial lever has pivoted from the initial position, and 
     the first axial center of pivotal movement and the second axial center of pivotal movement are coaxial axial centers of pivotal movement. 
     In the vehicle door lock device of this aspect of the present teachings, the switching mechanism includes the first lever, the second lever, the inertial lever, and the transmitting portion. In a normal state, the inertial lever is disposed in its initial position. Therefore, in the normal state, when the first lever pivots about the first axial center of pivotal movement in response to the opening operation of the outer door handle or the inner door handle, the inertial lever provided on one of the first lever and the second lever and the transmitting portion provided on the other one of the first lever and the second lever abut against each other. The pivotal movement of the first lever is transmitted to the second lever. Therefore, since the second lever acts on the pawl by pivoting about the second axial center of pivotal movement, the fork is switched from the latched state to the unlatched state. 
     In the vehicle door lock device, the inertial lever pivots from the initial position about the axis by application of the inertia force exceeding the preset value. In other words, when the door or the vehicle body receives the impact in the direction of advance and retraction with respect to the opening of the vehicle due to a collision or the like towards the vehicle, the inertia force acts on the inertial lever in the direction opposite to the direction of impact. Therefore, the inertial lever pivots from the initial position in the direction opposite to the direction of impact about the axis extending in the direction orthogonal to the direction of advance and retraction with respect to the opening. Therefore, even when the first lever is unintentionally displaced, what results is a “swing-and-miss state” in which the inertial lever and the transmitting portion do not abut against each other. Therefore, since the pivotal movement of the first lever is not transmitted to the second lever, the second lever avoids acting on the pawl, whereby the fork is not switched from the latched state to the unlatched state. Consequently, an unintentional opening of the door at the time of impact does not occur, and hence the safety of the passenger(s) can be ensured. 
     In addition, in this vehicle door lock device, the inertial lever and the transmitting portion transmit or block forces between the first lever and the second lever, which constitute the switching mechanism. In addition, the first axial center of pivotal movement of the first lever and the second axial center of pivotal movement of the second lever correspond to the coaxial axial centers of pivotal movement. Therefore, the positions and the lengths of the inertial lever and the transmitting portion are not changed irrespective of the direction of the position of the pawl with respect to the axial center of pivotal movement, and the second lever is allowed to act on the pawl by setting the direction of projection of a portion, which acts on the pawl of the second lever, arbitrarily within a range from 0° to 360° about the axial center of pivotal movement. Also, since the length of the inertial lever need not to be increased, the inertial lever is unlikely to become excessively heavy; consequently, setting of the inertia force for causing the inertial lever to pivot from the initial position in accordance with an impact having a desired magnitude is facilitated. 
     Therefore, such a vehicle door lock device is capable of preventing an unintentional opening of the door at the time of impact and, simultaneously, is capable of improving or increasing the design flexibility with respect to the relative positional relationship between the switching mechanism and the pawl. Accordingly, a reduction in size of the vehicle door lock device and an improvement of the mountability with respect to the vehicle may be realized. 
     The inertia force for causing the inertial lever to pivot from the initial position may be set by adjusting a balance between a mass member of the inertial lever and an urging force of a spring provided between one of the first lever and the second lever and the inertial lever. The corresponding inertia force may be set by adjusting the balance between the mass member of the inertial lever and a frictional force acting on the inertial lever about the axis. 
     Preferably, the first lever includes a first input portion coupled to the outer door handle or the inner door handle and a first output portion integrated with the first input portion with the axial center of pivotal movement interposed therebetween. Preferably, the second lever includes a second input portion and a second output portion integrated with the second input portion with the axial center of pivotal movement interposed therebetween, the second output portion acting on the pawl. In addition, the inertial lever is preferably provided on one of the first output portion and the second input portion. In addition, the transmitting portion is preferably provided on the other one of the first output portion and the second input portion. In this configuration, both of the first lever and the second lever are disposed with the axial center of pivotal movement interposed therebetween in a balanced manner. Therefore, even when an inertia force caused at the time of impact acts on the first lever and the second lever, it is possible to prevent a conversion of a portion of the inertia force into a rotational force which causes the first lever and the second lever to pivot about the axial center of pivotal movement; consequently, the opening of the door at the time of a collision may be reliably prevented. 
     Preferably, a movable mechanism is provided on the second output portion or on the pawl, the movable mechanism disabling the pawl by a locking operation which prevents the fork in the latched state from being switched to the unlatched state and, in contrast, enabling the pawl by an unlocking operation which allows the fork in the latched state to be switched to the unlatched state. In this configuration, a locking and unlocking mechanism can easily be provided at the periphery of the axial center of pivotal movement, so that a further reduction in size may be realized. 
     Preferably, the first lever and the second lever are urged towards their respective original positions by a single torsion coil spring provided coaxially with the axial center of pivotal movement. In this configuration, in comparison with an embodiment in which urging members are provided separately on the first lever and the second lever, the number of components may be reduced. Moreover, by arranging the torsion coil spring coaxially with the axial center of pivotal movement, the space occupied by the torsion coil spring may be reduced. 
     Preferably, the axial center of pivotal movement is also the axial center of a pivot shaft body that supports the first lever and the second lever and a projecting portion that projects from the pivot shaft body towards the outside of the vehicle opening. In this configuration, even when an outer panel of the door has been smashed, sufficient spaces can be preserved between the first lever, the second lever, the inertial lever, and the transmitting portion, and the smashed outer panel due to the projecting portion. Therefore, it is possible to reduce the probability of the occurrence of the problem in which pivotal movement of the inertial lever caused by the inertia force will be impaired or blocked by the smashed outer panel, whereby it is possible to reliably prevent the opening of the door at the time of a collision. 
     Preferably, by bending the first lever and the second lever into a crank shape toward an interior of the vehicle opening, the inertial lever and the transmitting portion are inclined toward the interior of the vehicle opening. In this configuration, even when the outer panel of the door has been smashed, sufficient space may be reliably preserved between the inertial lever and the transmitting portion, which are inclined toward the vehicle opening, and the smashed outer panel. Therefore, it is possible to further reduce the probability of the occurrence of the problem in which pivotal movement of the inertial lever caused by the inertia force will be impaired or blocked by the smashed outer panel, whereby it is possible to further reliably prevent the opening of the door at the time of a collision. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a vehicle door lock device of an example. 
         FIG. 2  is a perspective view of the vehicle door lock device of the example. 
         FIG. 3  is an exploded perspective view of the vehicle door lock device of the example. 
         FIG. 4  relates to the vehicle door lock device of the example, and is a schematic drawing illustrating a fork and a pawl viewed in the direction of arrow IV in  FIG. 1  (illustrating the fork in a latched state). 
         FIG. 5  relates to the vehicle door lock device of the example, and is a schematic drawing illustrating the fork and the pawl viewed in the direction of arrow IV in  FIG. 1  (illustrating the fork in an unlatched state). 
         FIG. 6  relates to the vehicle door lock device of the example, and is a rear view illustrating a first lever, a second lever, an inertial lever, and a transmitting portion viewed in the direction of arrow VI in  FIG. 1 . 
         FIG. 7  relates to the vehicle door lock device of the example, and is a side view illustrating the first lever, the second lever, the inertial lever, and the transmitting portion viewed in the direction of arrow VII in  FIG. 6 . 
         FIG. 8  relates to the vehicle door lock device of the example, and is a top view illustrating the first lever, the second lever, the inertial lever, and the transmitting portion viewed in the direction of arrow VIII in  FIG. 6 . 
         FIG. 9  relates to the vehicle door lock device of the example, and is a rear view illustrating the first lever, the second lever, the inertial lever, and the transmitting portion pivoted about an axial center of the pivotal movement from the state illustrated in  FIG. 6 . 
         FIG. 10  relates to the vehicle door lock device of the example, in which (a) and (b) are side views for explaining a relative relationship between the inertia lever and the transmitting portion in a case in which an inertia force exceeding a preset value has acted on the inertial lever. 
         FIG. 11  relates to the vehicle door lock device of the example, in which (a) and (b) are rear views for explaining the operations of a movable mechanism and a locking and unlocking mechanism. 
         FIG. 12  shows a vehicle door lock device of a modified example of the present teachings in the same view shown in  FIG. 7 , wherein the inertial lever is pivotably attached to the second lever and the transmitting portion is provided on the first lever. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     Referring now to the drawings, representative examples of the present teachings will be described below. 
     First Embodiment 
     As illustrated in  FIG. 1 , a vehicle door lock device  1  (hereinafter, simply referred to as “door lock device  1 ”) of a first representative example may be utilized in a vehicle such as an automotive vehicle, a bus, or an industrial vehicle. The door lock device  1  is disposed on the lower end edge side of a tail gate  2  that opens and closes an opening  9 A of a vehicle body  9 . The tail gate  2  is an example of a door according to the present teachings. In the alternative, the door lock device  1  may be provided on a side door that opens and closes in a left and right direction with respect to the vehicle body  9 . 
     In  FIG. 1 , only a lower end edge of the vehicle opening  9 A is illustrated. The opening  9 A widely opens in a substantially rectangular shape at a rear portion of the vehicle body  9  and enables an interior of the vehicle body  9  to communicate with the exterior in the fore-and-aft direction. In  FIG. 1 , the side of the paper plane corresponds to the front side of the vehicle, and the right left side of the paper plane corresponds to the rear side of the vehicle. In  FIG. 1 , the near side of the paper plane corresponds to the right side of the vehicle and the inner (opposite) side of the paper plane corresponds to the left side of the vehicle. In addition, the fore-and-aft direction, the vertical direction, and the left-and-right direction of the respective drawings from  FIG. 2  onward are all indicated in the same manner that corresponds to  FIG. 1 . 
     Although an illustration is omitted, an upper end edge of the tail gate  2  is pivotably supported on the vehicle body  9  via a hinge. As illustrated in  FIG. 1 , in a state in which a lower end edge of the tail gate  2  hangs downward, the tail gate  2  closes the opening  9 A. In addition, although an illustration is omitted, by pivoting the lower end edge of the tail gate  2  rearward and obliquely upward, the tail gate  2  opens the opening  9 A. A substantially “U” shaped striker  99  is formed at the lower end edge of the opening  9 A so as to project toward the lower end edge of the tail gate  2 . 
     As illustrated in  FIG. 1  to  FIG. 3 , the door lock device  1  includes a mounting member  90 , a fork  11 , a pawl  12 , a switching mechanism  100 , a locking and unlocking mechanism  180 , and an electric actuator  190 . 
     As illustrated in  FIG. 3 , the mounting member  90  includes a mounting member body  91  and a back plate  92 , which are bent steel plates respectively formed by press working. 
     The mounting member body  91  includes a concave portion  91 A that concaves downwardly and a pair of mounting portions  91 B that extend substantially horizontally from both the left and right sides of the concave portion  91 A. The concave portion  91 A is formed with an entry opening  98  formed by being notched in a deep groove shape from the front of the vehicle towards the rear. When the door lock device  1  moves in association with the opening and closing of the tail gate  2 , the striker  99  is adapted to relatively enter into the entry opening  98  as illustrated in  FIG. 1  and  FIG. 4 . As illustrated in  FIG. 3  and  FIG. 4 , the fork  11  and the pawl  12  are disposed on the left and right of the entry opening  98  in the concave portion  91 A. In  FIG. 4 , the entry opening  98  is positioned on the near side in the paper plane with respect to the fork  11  and the pawl  12 , and hence is illustrated by a double-dashed chain line. The same applies to  FIG. 5 . 
     As illustrated in  FIG. 3 , the back plate  92  includes a lid portion  92 A having a substantially flat-plate shape, a pair of the left and right mounting portions  92 B extending substantially horizontally from both the left and right sides of the lid portion  92 A, and an upright wall portion  92 C standing up substantially vertically from a rear end edge of the lid portion  92 A. By assembling the back plate  92  onto the mounting member body  91  from above, the lid portion  92 A covers the concave portion  91 A, and the mounting portions  92 B overlap the mounting portions  91 B. The switching mechanism  100  and the locking and unlocking mechanism  180  are assembled onto the rear surface side of the upright wall portion  92 C. The electric actuator  190  is assembled onto the front side of the upright wall portion  92 C. In addition, as illustrated in  FIG. 1 , by fastening both of the mounting portions  91 B,  92 B onto an inner frame of the tail gate  2 , the door lock device  1  is fixed to the lower end edge of the tail gate  2 . 
     As illustrated in  FIG. 4 , the fork  11  is pivotably supported by the fork pivot shaft  11 S disposed on the left side of the entry opening  98 . In addition, the fork  11  is urged by a not-illustrated coil spring to pivot in the direction D 1  about the fork pivot shaft  11 S. 
     The fork  11  is formed with a rear side projection  11 A and a front side projection  11 B. In addition, the striker  99  inserted in the entry opening  98  is configured to be accommodated in a concave portion  11 C formed between the rear side projection  11 A and the front side projection  11 B. In the state illustrated in  FIG. 4 , the fork  11  holds the striker  99  at a bottom portion of the entry opening  98 . A latch surface  11 D that is capable of abutting against a stopper surface  12 A, which will be described later, is formed on the front end side of the rear side projection  11 A, which front end side faces the pawl  12 . 
     The pawl  12  is pivotably supported by a pawl pivot shaft  12 S disposed on the right side of the entry opening  98 . In addition, the pawl  12  is urged by a not-illustrated coil spring to pivot in the direction D 2  about the pawl pivot shaft  12 S. Normally, the posture illustrated in  FIG. 4  is maintained. 
     The pawl  12  is formed with the stopper surface  12 A. The stopper surface  12 A is a curved surface curving in an arcuate shape about the pawl pivot shaft  12 S, and is formed so as to face the latch surface  11 D described above. An arc which constitutes the stopper surface  12 A is discontinued on the side of the fork  11 , and from that point, a sliding surface  12 C extending on the pawl pivot shaft  12 S side is formed. 
     The pawl  12  is formed with an abutting portion  12 P adjacent to the stopper surface  12 A. The abutting portion  12 P projects so as to extend away from the pawl pivot shaft  12 S towards the rear. 
     As illustrated in  FIG. 4 , in a state in which the fork  11  holds the striker  99  at the bottom portion of the entry opening  98 , the stopper surface  12 A of the pawl  12  abuts against the latch surface  11 D of the rear side projection  11 A. In this manner, the pawl  12  fixes the fork  11  so as to not allow the fork  11  to pivot in the direction D 1 . Accordingly, the fork  11  is brought into the latched state in which the tail gate  2  is locked. 
     Then, when an operating portion  151  of a movable mechanism  150 , which will be described later with reference to  FIG. 11 , is displaced rightward from the state illustrated in  FIG. 4  and presses the abutting portion  12 P as illustrated in  FIG. 5 , the pawl  12  pivots about the pawl pivot shaft  12 S in the direction opposite to the direction D 2  while opposing the urging force of the not-illustrated coil spring. In this case, since the stopper surface  12 A moves away from the latch surface  11 D, the pawl  12  releases the fork  11 . Therefore, the fork  11  pivots about the fork pivotal shaft  11 S in the direction D 1  due to the urging force of the not-illustrated coil spring, and displaces the striker  99  in the direction away from the entry opening  98 . As a result, the fork  11  is switched to the unlatched state in which the striker  99  is not locked in the entry opening  98 . At this time, the tail gate  2  displaces from a completely closed state to a slightly opened state. 
     In contrast, when the striker  99  enters the entry opening  98 , the fork  11  and the pawl  12  act in the order opposite to that described above. In other words, when the striker  99  in the state illustrated in  FIG. 5  enters into the bottom portion of the entry opening  98  as illustrated in  FIG. 4 , the striker  99  presses the rear side projection  11 A to pivot the fork  11  toward the original state. Accordingly, the stopper surface  12 A pivots in the direction D 2  due to the urging of the not-illustrated coil spring, and abuts against the latch surface  11 D. Consequently, the fork  11  is returned to the latched state. 
     As illustrated in  FIG. 1  and  FIG. 2 , the switching mechanism  100  includes a pivot shaft  160 , a first lever  110 , a second lever  120 , an inertial lever  130 , a transmitting portion  140 , and the movable mechanism  150 . These components are extracted and illustrated in  FIG. 6  to  FIG. 11 . 
     As illustrated in  FIG. 3 ,  FIG. 7 , and  FIG. 8 , the pivot shaft  160  is a metallic shaft body composed of a pivot shaft body  161  formed into a column shape extending in the fore-and-aft direction, a projecting portion  162  that continues to a rear end of the pivot shaft body  161 , and a flange portion  163  that continues to a rear end of the projecting portion  162  and has a thin disc shape with an outer diameter larger than that of the projecting portion  162 . 
     As illustrated in  FIG. 3 , and  FIGS. 6 to 8 , the first lever  110  is an injection molded product formed of a thermoplastic resin, and is formed into a substantially plate shape extending longitudinally in the left and right direction. A shaft hole  110 H is formed so as to penetrate through a center of the first lever  110  in the fore-and-aft direction. The second lever  120  is a metallic steel-plate member formed by sheet-metal pressing, and the second lever  120  is formed into an inverted “J” shape when viewed from the rear. A shaft hole  120 H is formed so as to penetrate at a center of the second lever  120  in the fore-and-aft direction. 
     As illustrated in  FIG. 1  to  FIG. 3 , a torsion coil spring  169  is mounted on the projecting portion  162 . As illustrated in  FIG. 3  and  FIG. 7 , the shaft hole  110 H of the first lever  110  and the shaft hole  120 H of the second lever  120  allow the pivot shaft body  161  to be inserted therethrough. At this time, the shaft hole  110 H is positioned on the front side relative to the shaft hole  120 H. Furthermore, as illustrated in  FIG. 3 , the front end of the pivot shaft body  161  is fitted into a shaft hole  92 H formed so as to penetrate through the upright wall portion  92 C. Accordingly, the pivot shaft  160  is fixed to the upright wall portion  92 C. The first lever  110  and the second lever  120  are pivotably supported by the pivot shaft body  161 . As illustrated in  FIG. 1 , when the door lock device  1  is fixed to the lower end edge of the tail gate  2 , the projecting portion  162  is brought into a state of projecting from the pivot shaft body  161  outward (that is, rearward) of the opening  9 A. 
     The center axis of the pivotal shaft  160  constitutes an axial center of pivotal movement X 1 . In other words, a first axial center of pivotal movement of the first lever  110  according to the present invention and a second axial center of pivotal movement of the second lever  120  according to the present invention correspond to the coaxial axial centers of pivotal movement X 1 . 
     As illustrated in  FIG. 3 , a rearward-projecting locking strip  92 D is formed on an upper portion of the upright wall portion  92 C. As illustrated in  FIG. 2 , one end  169 A of the torsion coil spring  169  is hooked by the locking strip  92 D. As illustrated in  FIG. 3 , a rearward-projecting prismatic column portion  110 D is formed above the shaft hole  110 H of the first lever  110 . In addition, as illustrated in  FIG. 2 , the other end  169 B of the torsion coil spring  169  is hooked on a lower surface of the prismatic column portion  110 D. 
     The first lever  110  is urged by the above-described torsion coil spring  169  in the direction D 3  about the axial center of pivotal movement X 1  as illustrated in  FIG. 3  and  FIG. 6 . In addition, by abutting a right side surface of the prismatic column portion  110 D against a left end edge of the second lever  120 , the second lever  120  is also urged in the direction D 3  about the axial center of pivotal movement X 1 . Furthermore, by abutting and stopping a right end edge of the second lever  120  against the locking strip  92 D, the postures of the first lever  110  and the second lever  120  are determined when not in operation. 
     The first lever  110  and the second lever  120  when not in operation are extracted and illustrated in  FIG. 6 .  FIG. 7  illustrates a side view as viewed from the direction indicated by arrow VII in  FIG. 6 , and  FIG. 8  illustrates a top view as viewed from the direction indicated by arrow VIII in  FIG. 6 . 
     As illustrated in  FIG. 6  to  FIG. 8 , the first lever  110  includes a first input portion  111  and a first output portion  112  which are formed integrally with the axial center of pivotal movement X 1  interposed therebetween. 
     As illustrated in  FIG. 6 , the first input portion  111  extends leftward from the axial center of pivotal movement X 1 . As illustrated in  FIG. 2 , a lower end  7 B of a rod  7  extending in the vertical direction in a rod shape is coupled to a left end of the first input portion  111 . 
     As illustrated in  FIG. 1  and in  FIG. 6 , an upper end  7 A of the rod  7  is coupled to an outer door handle  8 . As illustrated in  FIG. 6 , a second rod (unnumbered) couples the first input portion  11  to an inner door handle  8 A via a cable, rod or wire  7 C. When either the outer door handle  8  or the inner door handle  8 A is operated by a passenger, the corresponding rod is displaced downward, and this downward displacement is transmitted to the left end of the first input portion  111 . As a result, as illustrated in  FIG. 9 , the first lever  110  pivots about the axial center of pivotal movement X 1  in the direction opposite to the direction D 3  while opposing the urging force of the torsion coil spring  169 . In addition, when neither the outer door handle  8  nor the inner door handle  8 A is being operated (pulled) and hence the rods  7 ,  7 C are displaced upward, the first lever  110  is restored to the original position by the urging force of the torsion coil spring  169 . 
     As illustrated in  FIG. 6 , the first output portion  112  extends rightward from the axial center of pivotal movement X 1 . In the plan view as illustrated in  FIG. 8 , the first lever  110  is bent into a crank shape so that the first output portion  112  is positioned forward of the shaft hole  110 H. By projecting the projecting portion  162  rearward, the first lever  110  is positioned forward of the flange portion  163 . 
     As illustrated in  FIG. 3  and  FIG. 6  to  FIG. 8 , a supporting wall portion  112 A projecting rightward in a substantially flat plate shape is formed on the first output portion  112 . Also, as illustrated in  FIG. 3  and  FIG. 6 , a boss portion  112 B projecting rightward in a cylindrical shape is formed on the first output portion  112 . The boss portion  112 B is positioned below and rearward of the supporting wall portion  112 A. 
     A torsion coil spring  139  is mounted on the outer peripheral side of the boss portion  112 B. In contrast, an inertial lever pivot shaft  112 S formed into a multi-step column shape is inserted into the boss portion  112 B on the inner peripheral side. In addition, a right end portion of the inertial lever pivot shaft  112 S projects rightward from the boss portion  112 B. 
     As illustrated in  FIG. 3 , the inertial lever  130  includes a mass member  131 , which is a die-cast product formed of a zinc alloy and having a substantially parallelepiped shape, and a supported portion  132  projecting downward from the mass member  131 . The supported portion  132  is formed with a shaft hole  130 H that penetrates therethrough in the left-and-right direction. By inserting the right end portion of the inertial lever pivot shaft  112 S into the shaft hole  130 H, the inertial lever  130  is pivotably supported about an axis X 3 , which is an axial center of the inertial lever pivot shaft  112 S. The axis X 3  extends in the direction orthogonal to the direction of advance and retraction (that is, the fore-and-aft direction) in the opening  9 A (that is, the left and right direction). 
     As illustrated in  FIG. 2  and  FIG. 6 , the torsion coil spring  139  extends coaxially with the axis X 3 . One end  139 A of the torsion coil spring  139  is hooked on the inertial lever  130 . Although an illustration is omitted, the other end of the torsion coil spring  139  is hooked on the first output portion  112 . Accordingly, as illustrated in  FIG. 2  and  FIG. 7 , the torsion coil spring  139  urges the inertial lever  130  in the direction D 4  about the axis X 3 . In this manner, as illustrated in  FIG. 1 ,  FIG. 2 , and  FIG. 6  to  FIG. 9 , the inertial lever  130  takes a posture positioned right above the supported portion  132  in a normal state with the mass member  131  abutting against and stopping on the supporting wall portion  112 A. This position of the inertial lever  130  is an initial position of the present invention. 
     As illustrated in  FIG. 1  and  FIG. 10( a ) , the urging force of the torsion coil spring  139  and the mass of the mass member  131  are set so that, when an inertia force F 1  exceeding a preset value is applied to the inertial lever  130 , the inertial lever  130  pivots relative to the first lever  110  about the axis X 3  from the initial position in the direction opposite to the direction D 4 , i.e. the inertial lever  130  pivots towards the rear of the vehicle body  9 . Here, the preset value is determined as needed in accordance with an impact F 0  that the tail gate  2  or the vehicle body  9  receives from the outside of the vehicle due to a collision towards the vehicle. The impact F 0  acts in the direction from the rear towards the front. 
     As illustrated in  FIG. 6  to  FIG. 8 , the second lever  120  includes a second input portion  121  and a second output portion  122  which are formed integrally with the axial center of pivotal movement X 1  interposed therebetween. 
     As illustrated in  FIG. 6 , the second input portion  121  extends upward from the axial center of pivotal movement X 1 , then bends and extends rightward, and further bends and extends downward. In contrast, the second output portion  122  extends downward from the axial center of pivotal movement X 1 . As illustrated in  FIG. 3  and  FIG. 6 , an elongated hole  122 A elongated in the vertical direction is formed in the second output portion  122 . The second output portion  122  is formed on a left end edge thereof with a guide portion  122 B extending in the vertical direction and formed by bending a projecting strip. In the plan view as illustrated in  FIG. 8 , the second lever  120  is bent into a crank shape so that the second input portion  121  is positioned forward of the shaft hole  120 H. By projecting the projecting portion  162  rearward, the second lever  120  is positioned forward of the flange portion  163 . 
     The transmitting portion  140  is a distal end that extends downward from the second input portion  121 . As illustrated in  FIG. 1 ,  FIG. 2 , and  FIG. 6  to  FIG. 8 , in the first lever  110  and the second lever  120  when not in operation, the transmitting portion  140  faces an upper surface of the inertial lever  130  at an initial position. In this state, a moderate amount of play is secured between the two. 
     In the normal state, i.e. in case the inertial lever  130  is at the initial position, when the first lever  110  pivots about the axial center of pivotal movement X 1  in the direction opposite to the direction D 3  as illustrated in  FIG. 9 , the mass member  131  of the inertial lever  130  is displaced upward to press the transmitting portion  140  upward. Accordingly, the transmitting portion  140  transmits the pivotal movement of the first lever  110  to the second lever  120 , and the second lever  120  pivots in the direction opposite to the direction D 3  about the axial center of pivotal movement X 1  while opposing the urging force of the torsion coil spring  169 . In addition, when the first lever  110  is restored to its original position, the second lever  120  is restored to its original position together with the first lever  110  by the torsion coil spring  169  and the prismatic column portion  110 D. 
     As illustrated in  FIG. 2 ,  FIG. 3 ,  FIG. 6 , and  FIG. 7 , the movable mechanism  150  is an injection molded product formed of a thermoplastic resin, and is provided on the lower end side of the second output portion  122 . The movable mechanism  150  includes the operating portion  151  formed into a substantially thick flat panel shape attached to a front surface of the second output portion  122  on the lower end side thereof, a first column portion  152  projecting rearward from the operating portion  151  in a column shape and inserted into the elongated hole  122 A of the second output portion  122 , a guided surface  153  formed in a left side surface of the operating portion  151  and coming into sliding contact with the guide portion  122 B of the second output portion  122  as illustrated in  FIG. 3  and  FIG. 6 , and a second column portion  154  projecting forward from the operating portion  151  in a column shape as illustrated in  FIG. 7  and  FIG. 11 . 
     As illustrated in  FIG. 9 , by pivoting the second lever  120  about the axial center of pivotal movement X 1  in the direction opposite to the direction D 3 , the operating portion  151  is displaced rightward so as to be capable of pressing the abutting portion  12 P of the pawl  12 . 
     Furthermore, by guiding the first column portion  152  and the guided surface  153  on the elongated hole  122 A and the guide portion  122 B respectively, the operating portion  151  is capable of displacing from the position illustrated in  FIG. 6  and  FIG. 11( a )  to the position illustrated in  FIG. 11( b ) . 
     As illustrated in  FIG. 3 , the locking and unlocking mechanism  180  includes a third lever  181  and a fourth lever  185 . As illustrated in  FIG. 2 , the third lever  181  and the fourth lever  185  are positioned between the upright wall portion  92 C and the first lever  110  and the second lever  120 . 
     As illustrated in  FIG. 3 , the third lever  181  is formed into a substantially “L” shape when viewed from the rear. The fourth lever  185  is formed into a substantially fan shape when viewed from the rear. 
     In  FIG. 11 , the third lever  181  and the movable mechanism  150  are shown in an extracted manner. In  FIG. 11 , the operating portion  151  is positioned on the near side of the paper plane with respect to the third lever  181 . However, in order to make the third lever  181  easily viewable, the operating portion  151  is illustrated with a double-dashed chain line instead of a solid line in the region that overlaps with the third lever  181 . The third lever  181  is pivotably supported about a third lever pivot shaft  181 S whose bent portion projects rearward from the upright wall portion  92 C. The third lever  181  is formed to penetrate therethrough with a passive portion  181 A positioned rightward of the third lever pivot shaft  181 S and projecting forward in a column shape as illustrated in  FIG. 3  and  FIG. 11 , and an elongated hole  181 B extending in an arcuate shape in the left-right direction. As illustrated in  FIG. 11 , the second column portion  154  of the movable mechanism  150  extends forward from the operating portion  151  on the near side of the paper plane and is inserted into the elongated hole  181 B. In order to make the relative relationship between the second column portion  154  and the elongated hole  181 B easily viewable, the second column portion  154  is illustrated in a hatched cross section in  FIG. 11 . 
     As illustrated in  FIG. 3 , the passive portion  181 A passes through an elongated hole  92 E formed in the upright wall portion  92 C so as to penetrate therethrough and through an opening  190 A of the electric actuator  190 , and projects into the electric actuator  190 . 
     As illustrated in  FIG. 2  and  FIG. 3 , the fourth lever  185  is pivotably supported at an intermediate portion thereof by a shaft hole  92 F formed so as to penetrate through the upper portion of the upright wall portion  92 C. A lower end of the fourth lever  185  is coupled to the upper end side of the third lever  181 . As illustrated in  FIG. 2 , an upper portion of the fourth lever  185  is coupled to a rod  6 . The rod  6  is coupled to a not-illustrated locking and unlocking operation lever provided on an inner surface of the tail gate  2 . When the passenger operates the locking and unlocking operation lever, the action is transmitted to the third lever  181  via the rod  6  and the fourth lever  185 . Accordingly, the third lever  181  is displaced from the position illustrated in  FIG. 11( a )  to the position illustrated in  FIG. 11( b ) , or is displaced vice versa. 
     The electric actuator  190  includes a not-illustrated electric motor and a gear mechanism in the interior thereof. When the passenger performs the locking and unlocking operation using a remote control key or the like, the electric motor and the gear mechanism act on a distal end of the passive portion  181 A projecting into the electric actuator  190 , and the passive portion  181 A is displaced in the vertical direction. Accordingly, the third lever  181  is displaced from the position illustrated in  FIG. 11( a )  to the position illustrated in  FIG. 11( b ) , or is displaced vice versa. 
     When the rod  6  or the electric actuator  190  is activated by the locking operation by the passenger and the third lever  181  is displaced from the position illustrated in  FIG. 11( a )  to the position illustrated in  FIG. 11( b ) , the elongated hole  181 B and the second column portion  154  inserted into the elongated hole  181 B get closer to the axial center of pivotal movement X 1 ; accordingly, the operating portion  151  gets closer to the axial center of pivotal movement X 1  as well. In this case, when the second lever  120  pivots about the axial center of pivotal movement X 1  in the direction opposite to the direction D 3 , the second column portion  154  slides in the elongated hole  181 B, and the operating portion  151  is displaced rightward in a state of being close to the axial center of pivotal movement X 1  and passes above the abutting portion  12 P of the pawl  12 . In other words, the movable mechanism  150  disables the pawl  12  and disables switching of the fork  11  in the latched state to the unlatched state by the locking operation. 
     In contrast, when the rod  6  or the electric actuator  190  is activated reversely by the unlocking operation by the passenger and the third lever  181  is displaced from the position illustrated in  FIG. 11( b )  to the position illustrated in  FIG. 11( a ) , the elongated hole  181 B and the second column portion  154  inserted into the elongated hole  181 B move away from the axial center of pivotal movement X 1 ; accordingly, the operating portion  151  moves away from the axial center of pivotal movement X 1  as well. In this case, when the second lever  120  pivots about the axial center of pivotal movement X 1  in the direction opposite to the direction D 3 , the second column portion  154  slides in the elongated hole  181 B, and the operating portion  151  is displaced rightward in a state of being away from the axial center of pivotal movement X 1 , and presses the abutting portion  12 P of the pawl  12 . In other words, the movable mechanism  150  enables the operation of the pawl  12  and enables switching of the fork  11  in the latched state to the unlatched state by the unlocking operation. 
     &lt;Operational Effects&gt; 
     In the door lock device  1  of the example configured as described above, the inertial lever  130  is at the initial position illustrated in  FIG. 1 ,  FIG. 2 , and  FIGS. 6 to 8  in the normal state. Therefore, when the first lever  110  pivots about the axial center of pivotal movement X 1  in the direction opposite to the direction D 3  by the opening operation of the outer door handle  8  in the normal state as illustrated in  FIG. 9 , the inertial lever  130  provided in the first output portion  112  of the first lever  110  and the transmitting portion  140  provided on the second input portion  121  of the second lever  120  abut against each other, and the pivotal movement of the first lever  110  is transmitted to the second lever  120 . Therefore, the second lever  120  also pivots about the axial center of pivotal movement X 1  in the direction opposite to the direction D 3 . In addition, since the operating portion  151  of the movable mechanism  150  provided on the second output portion  122  of the second lever  120  presses the abutting portion  12 P of the pawl  12 , the fork  11  is switched from the latched state to the unlatched state. 
     In this door lock device  1  as illustrated in  FIG. 10( a ) , by applying an inertia force F 1  that exceeds the preset value, the inertial lever  130  pivots about the axis X 3  from the initial position in the direction opposite to the direction D 4 . In other words, when the tail gate  2  and the vehicle body  9  receive an impact F 0  in the direction from the rear towards the front due to a collision or the like towards the vehicle, the inertia force F 1  acts on the inertial lever  130  in the direction opposite to the direction of impact. Therefore, the inertial lever  130  pivots about the axis X 3  from the initial position in the direction opposite to the direction of impact (the direction from the front towards the rear). Therefore, as illustrated in  FIG. 10( b ) , due to the displacement of the outer door handle  8 , the deformation of the rod  7 , etc. caused by the impact F 0 , the first lever  110  unintentionally pivots about the axial center of pivotal movement X 1  in the direction opposite to the direction D 3 , and even though the first output portion  112  is displaced upward, what results is a “swing-and-miss state” in which the transmitting portion  140  and the inertial lever  130 , which has pivoted from the initial position due to the inertia force F 1 , do not abut against each other. Therefore, since the pivotal movement of the first lever  110  is not transmitted to the second lever  120 , the second output portion  122  of the second lever  120  and the movable mechanism  150  avoid operating on the pawl  12 , whereby the fork  11  is not switched from the latched state to the unlatched state. Consequently, an unintentional opening of the tail gate  2  at the time of impact does not occur, and hence the safety of the passenger(s) may be ensured. 
     In addition, in this door lock device  1 , the inertial lever  130  and the transmitting portion  140  transmit or block forces between the first lever  110  and the second lever  120  which constitute the switching mechanism  100 . In addition, the first axial center of pivotal movement of the first lever  110  and the second axial center of pivotal movement of the second lever  120  correspond to the coaxial axial centers of pivotal movement X 1 . Therefore, the positions and the lengths of the inertial lever  130  and the transmitting portion  140  are not changed irrespective of the direction of the position of the pawl  12  with respect to the axial center of pivotal movement X 1 , and the second lever  120  is allowed to act on the pawl  12  by setting the direction of projection of the second output portion  122  of the second lever  120  within a range from 0° to 360° about the axial center of pivotal movement X 1 . For example, when the abutting portion  12 P of the pawl  12  is positioned within regions E 1 , E 2  in  FIG. 6 , what is required is to change the direction of projection of the second output portion  122  so as to be directed toward the regions E 1 , E 2 . In this case, since the length of the inertial lever  130  need not be increased, the inertial lever  130  is unlikely to become excessively heavy. Consequently, setting of the inertia force F 1  to cause the inertial lever  130  to pivot from the initial position in accordance with an impact having a desired magnitude is facilitated. 
     Therefore, the door lock device  1  of the example is capable of preventing the unintentional opening of the tail gate  2  at the time of impact and, simultaneously, is capable of improving the design flexibility relating to a relative positional relationship between the switching mechanism  100  and the pawl  12 . Consequently, a variety of relative positional relationships among the tail gate  2 , the opening  9 A, the striker  99 , and the outer door handle  8  can be easily accommodated, and hence a reduction in size of the door lock device  1  and an improvement of the mountability thereof with respect to the vehicle may be realized. 
     Also, in this door lock device  1 , both of the first lever  110  and the second lever  120  are disposed with the axial center of pivotal movement X 1  interposed therebetween in a balanced manner. Therefore, even when an inertia force caused by the impact F 0  acts on the first lever  110  and the second lever  120 , conversion of a portion of the inertia force into a rotational force that causes the first lever  110  and the second lever  120  to pivot about the axial center of pivotal movement X 1  may be restrained. Consequently, realization of prevention of the opening of the tail gate  2  at the time of collision may be ensured. 
     Furthermore, in this door lock device  1 , since the movable mechanism  150  is provided on the second output portion  122 , the movable mechanism  150  can easily be brought closer to the axial center of pivotal movement X 1 , whereby a further reduction in size may be realized. 
     Also, in this door lock device  1 , the first lever  110  and the second lever  120  are urged so as to be restored to their original positions by a single torsion coil spring  169  provided coaxially with the axial center of pivotal movement X 1 . In this configuration, in comparison with a case where urging members are provided separately on the first lever  110  and the second lever  120 , the number of components may be reduced. Also, by arranging the torsion coil spring  169  coaxially with the axial center of pivotal movement X 1 , the space occupied by the torsion coil spring  169  may be reduced. 
     Furthermore, in this door lock device  1 , even if an outer panel of the tail gate  2  as illustrated in  FIG. 1  is smashed, the smashed outer panel  2 A abuts against and is stopped by the projecting portion  162  projecting rearward from the pivotal shaft body  161 , and hence spaces may be preserved between the first lever  110 , the second lever  120 , the inertial lever  130 , and the transmitting portion  140 , and the smashed outer panel  2 A. Also, by bending the first lever  110  and the second lever  120  into a crank shape toward the interior of the opening  9 A (that is, toward the front), the inertial lever  130  and the transmitting portion  140  are inclined toward the interior of the opening  9 A. In this configuration, even when the outer panel of the tail gate  2  is smashed, a space is reliably preserved between the smashed outer panel  2 A and the inertial lever  130  inclined toward the interior of the opening  9 A and transmitting portion  140 . Therefore, according to this door lock device  1 , the probability of the occurrence of the problem that the pivotal movement of the inertial lever  130  caused by the inertia force F 1  is impaired by the smashed outer panel  2 A is further reduced, and hence the prevention of the opening of the tail gate  2  at the time of a collision may further be ensured. 
     Although the present invention has been described with reference to the example in the description described thus far, the invention is not limited to the example described above, and may be utilized by changing as needed within a range not departing the scope thereof. 
     For example,  FIG. 12  shows a vehicle door lock device of a modified example of the present teachings in the same view shown in  FIG. 7 , wherein the inertial lever  130  is pivotably attached to the second lever  120  and the transmitting portion  140  is provided on the first lever  110 . 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable to vehicles such as automotive vehicles, buses, and industrial vehicles. 
     EXPLANATION OF THE REFERENCE NUMBERS 
     
         
         
           
               9  . . . vehicle body 
               9 A . . . opening 
               2  . . . door (tail gate) 
               99  . . . striker 
               98  . . . entry opening 
               90  . . . mounting member 
               11  . . . fork 
               12  . . . pawl 
               100  . . . switching mechanism 
               1  . . . vehicle door lock device 
               8  . . . outer door handle 
             X 1  . . . axial center of pivotal movement (first axial center of pivotal movement, second axial center of pivotal movement) 
               110  . . . first lever 
               120  . . . second lever 
             X 3  . . . axis 
             F 1  . . . inertia force 
               130  . . . inertial lever 
               140  . . . transmitting portion 
               111  . . . first input portion 
               112  . . . first output portion 
               121  . . . second input portion 
               122  . . . second output portion 
               150  . . . movable mechanism 
               169  . . . torsion coil spring 
               161  . . . pivot shaft body 
               162  . . . projecting portion