Abstract:
A door lock system for vehicle doors includes a lock mechanism including a switching lever. The switching lever can be moved freely between a neutral position and a locking position and between the neutral position and an unlocking position. The door can not be opened when the switching lever is moved from the neutral position to the locking position and can be opened when the switching lever is moved from the neutral position to the unlocking position. A link unit that receives a lever operation force from outside of the door and conveys the lever operation force to the switching lever. A holding unit holds the switching lever at the neutral position when the link unit does not receive the lever operation force.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a door lock system applicable to generally vehicles. 
     2. Description of the Related Art 
     As a door lock system to be applied to vehicles such as a four-wheeled vehicle, there is one including a link unit such as a torque cable that links a lock mechanism provided in the door and a key cylinder to each other. The lock mechanism is switched between an unlocked state that allows a door opening movement when an outside handle is operated to open the door, and a locked state that maintains the door being closed, even if the outside handle is operated to open the door, by making ineffective the door opening operation of the outside handle. The key cylinder is for key operations from the outside of the vehicle, and is provided on a door outer panel. In this key cylinder, a cylinder returning spring that keeps a normal position when a key operation is not performed is provided. 
     In this door lock system, when the key cylinder is rotated against an elastic force of the cylinder returning spring in response to a key operation, this rotating force is transmitted to a switching lever of the lock mechanism through the link unit to turn the switching lever from a neutral position to a switching position and switch the lock mechanism to an unlocked state or a locked state. When the key operation force is removed, the key cylinder is returned to the normal position by the cylinder returning spring and the switching lever is returned to the neutral position through the link unit. 
     A conventional door lock system has been disclosed, for example, in Japanese Published Unexamined Patent Application No. 2004-332449. 
     According to the conventional door lock system, the key cylinder can be provided on the door panel without depending on the position of the lock mechanism, thereby increasing degree of freedom of design and layout. However, sometimes, the relative positional relationship between the lock mechanism and the key cylinder influences the power transmission efficiency of the link unit. For example, when a torque cable is used as the link unit, although the key cylinder position with respect to the lock mechanism can be arbitrarily set by greatly bending the torque cable, lowering in power transmission efficiency is unavoidable. 
     In such a state with lowered power transmission efficiency, even when the cylinder returning spring returns the key cylinder to the normal position, the switching lever does not always return to the neutral position from the switching position. As a result, the lock mechanism may not be correctly switched by a successive key operation. This problem may occur not only when the torque cable is used but also when the key cylinder and the lock mechanism are linked via a link unit. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to at least solve the problems in the conventional technology. 
     According to an aspect of the present invention, a door lock system includes a door handle operable from outside of a door for opening/closing the door; a lock mechanism including a switching lever, the switching lever capable of moving freely between a neutral position and a locking position and between the neutral position and an unlocking position, wherein the lock mechanism configured to prevent opening of the door by operation of the door handle when the switching lever is moved from the neutral position to the locking position, and allows opening of the door by operation of the door handle when the switching lever is moved from the neutral position to the unlocking position; a link unit that receives a lever operation force from outside of the door and conveys the lever operation force to the switching lever of the lock mechanism to thereby moving the switching lever between the neutral position and the locking position and between the neutral position and the unlocking position; and a holding unit that holds the switching lever at the neutral position when the link unit does not receive the lever operation force. 
     The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual diagram of a door to which the door lock system of according to an embodiment of the present invention is applied, viewed from the front side of the vehicle; 
         FIG. 2  is a conceptual diagram of a vehicle to which the door lock system; 
         FIG. 3  is a conceptual diagram of the door lock system viewed from the indoor side; 
         FIG. 4  is a sectional view along the line IV-IV shown in  FIG. 3 ; 
         FIG. 5  is a conceptual diagram of a turned state of a switching lever of the door lock system; 
         FIG. 6  is a conceptual diagram of a turned state of the switching lever; 
         FIG. 7  is a conceptual diagram of the door lock system viewed from the outdoor side; 
         FIG. 8  is a sectional side view of a linking state between the door lock system and a link unit; 
         FIG. 9  is a sectional side view of an intermediate dropped state of the link unit from the state of  FIG. 8 ; 
         FIG. 10  is a sectional side view of a completely dropped state of the link unit from the state of  FIG. 9 ; and 
         FIG. 11  is a conceptual diagram of the door lock system viewed from the outdoor side. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present invention are explained below in detail with reference to the accompanying drawings. 
       FIG. 1  is a conceptual diagram of relevant parts of a door lock system according to an embodiment of the invention. The door lock system is applied is applied to a vehicle door.  FIG. 1  depicts a side door (door D on the driver seat side in a vehicle with a right hand steering wheel) with a hinge on its front side, disposed on the right of the front seat of a four-wheeled vehicle. The door D of this vehicle has a latch mechanism in the same manner as in a conventional door although this is not clearly shown in the drawings. The latch mechanism maintains the door D being closed with respect to the vehicle main body B when the latch mechanism engages with a striker (not shown) provided in the vehicle main body B, and allows the door D to be moved to open with respect to the vehicle main body B when the engagement with the striker is released. As shown in  FIG. 1 , this door D has an outside handle (door handle)- 10  and a lock mechanism  20 . 
     The outside handle  10  is an operating member that operates the door D to open when the door D is moved to open from the vehicle main body B, and is provided on the door outer panel OP positioned on the outdoor side. A key cylinder  11  is attached to this outside handle  10 . The key cylinder  11  becomes rotatable when a key that fits the key cylinder is inserted from the outside of the vehicle main body B, and is provided on the door outer panel OP while a key hole is exposed to the outside. The rotational motion of the key cylinder is indicated by rotation lines as shown in  FIGS. 1 and 2 . In this key cylinder  11 , a cylinder returning spring  12  that keeps the key cylinder at a normal position when no key operation is performed is provided. The cylinder returning spring  12  applied in this embodiment has a spring constant set smaller than that of a normal key cylinder  11 . 
     To the key cylinder  11 , a torque cable (link unit)  15  is connected. The torque cable  15  is formed by housing an inner cable  17  inside an outer tube  16  so as to rotate, and when the key cylinder  11  rotates, the inner cable  17  rotates in the same direction with respect to the outer tube  16 . At an extending end of this torque cable  15 , an engaging portion  16   a  is formed in the outer tube  16 , and an engaging piece  17   a  is provided on the inner cable  17 . The engaging portion  16   a  is an annular concavity formed in the outer circumference of the outer tube  16 . The engaging piece  17   a  is a plate-shaped portion, and is continued from the inner cable  17  so as to interlock with the rotation of the inner cable  17 . 
     The lock mechanism  20  is interposed between the outside handle  10  and the latch mechanism, and is disposed inside the door D, that is, between the door outer panel OP and the door inner panel IP positioned on the indoor side while being housed in the housing  21 . In the lock mechanism  20 , at a portion to be exposed to the outside of the housing  21 , an open lever  22  is provided. The open lever  22  serves as an input unit that inputs a door opening operation of the outside handle  10 , and is disposed so as to turn around the center of axle extending horizontally along the front and rear direction of the vehicle main body B. The open lever  22  is linked to the outside handle  10  by a link mechanism  23  so as to turn downward when the outside handle  10  is operated to open the door. 
     In the lock mechanism  20 , as shown in  FIG. 3  through  FIG. 6 , a switching lever  24  is disposed inside the housing  21 . The switching lever  24  extends outward radially from the circumferential surface of a columnar lever shaft  25 , and is supported on the housing  21  via both ends of the lever shaft  25  so as to turn around the center of axle of the lever shaft  25 . This switching lever  24  switches the lock mechanism  20  into an unlocked state when turning from the neutral position shown in  FIG. 3  to the unlocking position shown in  FIG. 5 , and switches the lock mechanism  20  into a locked state when turning from the neutral position shown in  FIG. 3  to the locking position shown in  FIG. 6 . 
     In an unlocked state of the lock mechanism  20 , when the open lever  22  turns downward according to a door opening operation of the outside handle  10 , this turning of the open lever  22  is transmitted to the latch mechanism and releases the latch mechanism. Therefore, even when the latch mechanism engages with the striker, the door opening operation of the outside handle  10  releases this engagement and can move the door D to open. 
     On the other hand, in a locked state of the lock mechanism  20 , even when the open lever  22  turns downward according to a door opening operation of the outside handle  10 , this turning of the open lever  22  is made ineffective and is not transmitted to the latch mechanism, and the latch mechanism is not released. Therefore, in the state in that the latch mechanism engages with the striker, this engagement is not released by the door opening operation of the outside handle  10 , and the door D is maintained as being closed. 
     As seen in  FIG. 4 , this switching lever  24  has an engaging groove  26 , a lever returning spring  27 , and a spring working piece  28 . The engaging groove  26  is a slit-shaped notch formed from the end face of the lever shaft  25  extending to the outdoor side. In this engaging groove  26 , the engaging piece  17   a  of the torque cable  15  fits through a cylindrical hole  30  formed in the housing  21 . The cylindrical hole  30  of the housing  21  has a cylindrical shape with an inner diameter that is capable of housing the outer tube  16  of the torque cable  15 . On the inner circumferential surface of this cylindrical hole  30 , a claw piece  31  that engages with the engaging portion  16   a  of the outer tube  16  and prevents the outer tube  16  from slipping off the cylindrical hole  30  when the engaging piece  17   a  of the inner cable  17  fits the engaging groove  26  of the switching lever  24  is provided. 
     The lever returning spring  27  is a coil spring formed by spirally winding a middle portion of an elastic wire member and projecting both ends outward radially, and is disposed between the switching lever  24  and the housing  21  while the middle portion is disposed around the lever shaft  25  and both ends are press-engaged with a spring engaging piece  40  of the housing  21 . The spring engaging piece  40  of the housing  21  is an arc-shaped protrusion formed at a position to be covered by the switching lever  24  when the switching lever  24  is at the neutral position. This lever returning spring  27  has a spring constant set smaller than that of the cylinder returning spring  12  of the key cylinder  11 . 
     The spring working piece  28  is a projection provided from the end face on the indoor side of the switching lever  24  toward the housing  21 . This spring working piece  28  is disposed so as to project between two ends of the lever returning spring  27  on the side closer to the lever shaft  25  than the spring engaging piece  40  of the housing  21  when the switching lever  24  is at the neutral position. 
     When the lever returning spring  27  is at the neutral position, as shown in  FIG. 3 , the spring working piece  28  is at a position apart from the two ends of the lever returning spring  27 . When the switching lever  24  is made to turn to the locking position or the unlocking position from this state by applying an external force, as shown in  FIG. 5  and  FIG. 6 , the spring working piece  28  engages with the end of the lever returning spring  27  and moves against the elastic force of the lever returning spring  27 . Therefore, by removing the external force on the lever returning spring  27 , the switching lever  24  returns to the neutral position due to the elastic returning force of the lever returning spring  27 . 
     Furthermore, the door lock system includes a shutter spring  50  around the cylindrical hole  30  of the housing  21 . The shutter spring  50  is constructed by appropriately molding an elastic wire member as shown in  FIG. 7 , and has a winding portion  51 , a supporting portion  52 , a latching portion  53 , and an arresting portion  54 . The winding portion  51  is formed by winding the elastic wire member by a plurality of turns. The supporting portion  52  is inserted in the slit  21   a  of the housing  21  after extending outward radially from the winding portion  51 . The latching portion  53  is bent to separate from the supporting portion  52  after extending outward radially from the winding portion  51 . The arresting portion  54  is curved at the extending end of the latching portion  53 . This shutter spring  50  is attached between the circumferential wall of the housing  21  and a stopper projection  32  provided around the cylindrical hole  30  while the latching portion  53  is made proximal to the supporting portion  52  in an elastic manner. In this state, as shown in  FIG. 8 , the arresting portion  54  of the shutter spring  50  projects inward from the notch  30   a  of the cylindrical hole  30  at the same height as the claw piece  31  of the cylindrical hole  30  and engages with the engaging portion  16   a  of the outer tube  16 . 
     In the door lock system constructed as described above, when the key cylinder  11  is rotated by a key operation, this rotating force is transmitted to the switching lever  24  of the lock mechanism  20  through the torque cable  15  and turns the switching lever  24  from the neutral position to the unlocking position or the locking position, whereby the lock mechanism  20  is switched to an unlocked state or a locked state. 
     On the other hand, when the key operation force is removed, the key cylinder  11  is returned to the normal position by the cylinder returning spring  12 . Furthermore, not only is the returning movement of the key cylinder  11  transmitted to the switching lever  24  through the torque cable  15 , but also the switching lever  24  is returned to the neutral position by the lever returning spring  27 . 
     As a result, even when the torque cable  15  is curved to increase the degree of freedom of design and layout and the power transmission efficiency is much lower than 100%, the switching lever  24  always reliably returns to the neutral position, so that the lock mechanism  20  can be correctly switched by a successive key operation. 
     In the door lock system including the lock mechanism  20  housed inside the housing  21  as described above, when the torque cable  15  is pulled out of the housing  21 , the switching lever  24  is exposed to the outside through the cylindrical hole  30 , and if this switching lever  24  is directly operated, the lock mechanism  20  may become capable of switching to an unlocked state. 
     However, according to the door lock system described above, when the torque cable  15  is pulled out, the arresting portion  54  of the shutter spring  50  projects to the inside of the cylindrical hole  30  and effectively prevents the switching lever  24  from being directly operated. Namely, when the torque cable  15  is pulled out from the state of  FIG. 8 , as shown in  FIG. 9 , the arresting portion  54  fitting the engaging portion  16   a  of the outer tube  16  moves together with the torque cable  15 , and the engagement between the latching portion  53  and the stopper projection  32  is released soon. Thereafter, when the torque cable  15  is completely pulled out, as shown in  FIG. 10  and  FIG. 11 , the arresting portion  54  projects to the inside through the notch  30   a  of the cylindrical hole  30  due to the elastic force of the shutter spring  50 , and maintains this state. Therefore, even if a malicious person tries to directly operate the switching lever  24  through the cylindrical hole  30 , this can be prevented, and the theftproof performance of the vehicle main body B to which the invention is applied can be improved. 
     In addition, when the door lock system is assembled, by inserting the outer tube  16  into the cylindrical hole  30  from the state of  FIG. 7  and  FIG. 8 , the arresting portion  54  of the shutter spring  50  temporarily elastically withdraws from the cylindrical hole  30  and then automatically fits the engaging portion  16   a , and this does not deteriorate the assembling workability at all. 
     According to the invention, a normal state holding unit reliably returns the switching lever to the neutral position when a key operation force is removed. Therefore, the lock mechanism can be correctly switched by a successive key operation. 
     Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth. 
     This application claims priority from Japanese Patent Application 2005-053358, filed Feb. 28, 2005, which is incorporated herein by reference in its entirety.