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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION  
         [0001]    1) Field of the Invention  
           [0002]    The present invention relates to an actuator for a vehicle, and more specifically, to an actuator for a door locking device of a four-wheel automobile.  
           [0003]    2) Description of the Related Art  
           [0004]    It is a common practice to provide a door locking device between an outside handle and a latch mechanism of a door provided in the chassis of the automobile. The latch mechanism normally includes a latch and a ratchet. When the automobile door is shut against the chassis, the latch engages in a striker provided on the chassis and the ratchet maintains this locked state.  
           [0005]    The door locking device is locked and unlocked in a switchable manner by manual operation or electronic control. The manual operation involves using a key on the externally provided key cylinder or from within the chassis by pushing a locking button provided inside. The electronic control is performed,. for example, by a so-called keyless entry with a remote controller.  
           [0006]    The door locking device allows, when being in an unlocked condition, the door to be opened with the outside handle. Concretely, the ratchet releases its hold on the latch and the striker, thus enabling the door to be opened.  
           [0007]    On the other hand, the door locking device does not allow, when being in a locked condition, the door to be opened with the outside handle. In other words, the ratchet maintains its hold on the latch and the striker.  
           [0008]    Such a door locking mechanism includes an actuator disclosed in, for example, Japanese Utility Model Laid-Open Publication No. H5-52150, Japanese Utility Model No. 2513398, and Japanese Utility Model No. 2529569. FIG. 8 is a plan view of a conventional actuator. The actuator  100  includes a driving motor  110 , a worm wheel  120 , and an output lever  130 .  
           [0009]    The driving motor  110  is housed in a casing  1  and can turn both clockwise and counter-clockwise. The driving motor  110  is driven according to the electronic control, and has a driving shaft  1110  and a cylindrical worm  1120  mounted on the driving shaft  1110 . The driving shaft  1110  and the worm  1120  turn in unison.  
           [0010]    The worm wheel  120  is disc-shaped and is housed in the casing  1 . The worm wheel  120  is rotatably supported by a supporting shaft  1210 . The worm wheel  120  is engaged with the worm  1120  at a periphery of the worm wheel  120 . Consequently, the worm wheel  120  is a rotor that turns in a normal direction or the opposite direction through the worm  1120  driven by the driving motor  110 . The worm wheel  120  is illustrated in FIG. 8 as a rotor that turns clockwise or counter-clockwise. The worm wheel  120  is provided with a protrusion  200  that projects from the worm wheel  120 .  
           [0011]    The fan-shaped output lever  130  is swingably supported by an output shaft  1310  disposed on one side of the worm wheel  120 . Precisely, the output lever  130  gradually broadens from a base  1320  of the output lever  130  towards a front end  1330  of the output lever  130 . The base  1320  is shaft-supported and the front end  1330  swings freely. A groove  300  into which the protrusion  200  of the worm wheel  120  engages is provided on the front end  1330  that faces the worm wheel  120 .  
           [0012]    On the output shaft  1310  that shaft-supports the output lever  130 , an output arm  1340  is shaft-supported. The output arm  1340  moves in unison with the output lever  130  through the output shaft  1310 . The output arm  1340  is connected to a locking lever  140  which is a switching member. The locking lever  140  switches the door locking device between locked and unlocked condition by switching between a locked position and an unlocked position.  
           [0013]    The actuator  100  electronically works in the manner described below when the door locking device is in a locked condition (that is, when the locking lever  140  is in the locked position). The driving motor  110  is driven to turn the worm wheel  120  in counter-clockwise direction. By this action the protrusion  200  of the worm wheel  120  engages in a first contact portion  300   a  of the groove  300  of the output lever  130 . Once the worm wheel  120  and the output lever  130  are engaged in this fashion, further counter-clockwise rotation of the worm wheel  120  makes the protrusion  200  push the first contact portion  300   a  and makes the output lever  130  swing counter-clockwise. The output lever  130  switches the locking lever  140  to the unlocked position through the output arm  1340  which turns in unison with the output lever  130 . Thus, the door locking device is in an unlocked condition. When the worm wheel  120  turns a complete 360 degrees and the protrusion  200  is back in its original position, the driving motor  110  ceases its operation.  
           [0014]    The actuator  100  electronically works in the manner described below when the door locking device is in an unlocked condition (that is, when the locking lever  140  is in the unlocked position). The driving motor  110  is driven to turn the worm wheel  120  in clockwise direction. By this action the protrusion  200  of the worm wheel  120  engages in a second contact portion  300   b  of the groove  300  of the output lever  130 . Once the worm wheel  120  and the output lever  130  are engaged in this fashion, further clockwise rotation of the worm wheel  120  makes the protrusion  200  push the second contact portion  300   a  and makes the output lever  130  swing clockwise. The output lever  130  switches the locking lever  140  to the locked position through the output arm  1340  which turns in unison with the output lever  130 . Thus, the door locking device is in a locked condition. In this case too, when the worm wheel  120  turns a complete 360 degrees and the protrusion  200  is back in its original position, the driving motor ceases to be driven.  
           [0015]    In the case of manual operation such as by insertion of key into the key cylinder or operation of the inside locking button, the locking lever  140  switches between the locked position and the unlocked position by a linking unit such as a link or a wire that links the locking lever  140  and the key cylinder or the inside locking button. The door locking device switches between locked and unlocked state in accordance with the locked or unlocked position of the locking lever  140 . The actuator works in the following manner under such circumstances. The output lever  130  swings in unison with the output arm  1340  in accordance with the locked or unlocked position of the locking lever  140 , while the protrusion  200  of the worm wheel  120  shifts in the groove  300 . As a result, the output lever  130  stops at a predetermined position. Consequently, the switching of position of the locking lever by manual operation does not get transmitted to the worm wheel  120 .  
           [0016]    In the conventional actuator  100 , the protrusion  200  provided on the worm wheel  120  moves in the groove  300  provided in the output lever  130  upon manual operation or electronic control of the door locking device. Consequently, it is necessary to have a fan-shaped output lever  130  which is sufficiently broad. In addition, it is necessary to make the sliding area of the output lever  130  to also cover the area outside of the perimeter of the worm wheel  120 . Hence, the actuator cannot be made compact.  
         SUMMARY OF THE INVENTION  
         [0017]    It is an object of the present invention to at least solve the problems in the conventional technology.  
           [0018]    An actuator for a vehicle according to an aspect of the present invention includes a rotatable rotor; a lever that is disposed so as to be swingable between a first position and a second position; and an engagement mechanism through which the lever is engaged with the rotor, the engagement mechanism including a protrusion that engages with the rotor; and a guide mechanism that makes, along with rotation of the rotor, the lever swing between the first position and the second position, and allows, when the rotor stops rotating, a movement of the lever without turning the rotor.  
           [0019]    The other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a plan view illustrating the main parts of an actuator for a door locking device (an automobile part) according to the present invention;  
         [0021]    [0021]FIG. 2 is a plan view illustrating the mechanism of the actuator;  
         [0022]    [0022]FIG. 3 is a plan view illustrating the mechanism of the actuator;  
         [0023]    [0023]FIG. 4 is a plan view illustrating the mechanism of the actuator;  
         [0024]    [0024]FIG. 5 is a plan view illustrating the mechanism of the actuator;  
         [0025]    [0025]FIG. 6 is a plan view illustrating the mechanism of the actuator;  
         [0026]    [0026]FIG. 7 is a plan view illustrating the mechanism of the actuator; and  
         [0027]    [0027]FIG. 8 is a plan view illustrating a conventional actuator. 
     
    
     DETAILED DESCRIPTION  
       [0028]    Exemplary embodiments of an actuator for a vehicle according to the present invention will be explained below with reference to the accompanying drawings. For the sake of convenience, an actuator for a door locking device will be explained as a specific example of the actuator for an automobile door lock.  
         [0029]    [0029]FIG. 1 is a plan view illustrating the main parts of the actuator for a door locking device (automobile part) according to the present invention. FIG. 2 through FIG. 7 are plan views illustrating the mechanism of the actuator shown in FIG. 1. In FIG. 1 through FIG. 7, the actuator  10  includes a driving motor  11 , a worm wheel  12 , and an output lever  13 .  
         [0030]    The driving motor  11  is housed in a not shown casing and can turn both clockwise and counter-clockwise. The driving motor  111  is driven electronically, and has a driving shaft  111  and a cylindrical worm  112  mounted on the driving shaft  111 . The driving shaft  111  and the worm  112  turn in unison.  
         [0031]    The worm wheel  12  is disc-shaped and is housed in a casing. The worm wheel  12  is rotatably supported by a supporting shaft  121 . One portion of the worm wheel  12  is engaged with the worm  112 . Consequently, the worm wheel  12  is a rotor that turns in a normal direction or the opposite direction through the worm  112  driven by the driving motor  11 . The worm wheel  12  is illustrated in FIG. 1 as a rotor that turns clockwise or counter-clockwise. A groove (an engaging guiding member)  30 , which is a part of an engaging unit, is formed on worm wheel  12 .  
         [0032]    The output lever  13  is shaft-supported by an output shaft  131  disposed on a predetermined position on one side of the worm wheel  12 , and is swingable. Precisely, a base  132  of the output lever  13  is shaft-supported by the output shaft  131  disposed away from the driving motor  11  and the worm wheel  12 . A front end  133  of the output lever  13  swings freely. In other words, the output lever  13  slides between a first position in FIG. 1 and a second position in FIG. 7. The output lever  13  shown in the drawings broadens gradually from the base  132  to the front end  133 . The base  132  is connected to a locking lever  140  which is a switching member. The locking lever  14  switches the door locking device between a locked position and an unlocked position. To be more specific, when the output lever  13  is at the first position (see FIG. 1), the locking lever  14 , which is connected to the output lever  13 , is in the unlocked position, and when the output lever  13  is at the second position (see FIG. 7), the locking lever  14  is in the locked position.  
         [0033]    A protrusion  20  projects toward the worm wheel  12  from the portion of the front end  133  of the output lever  13  that faces the end facet of the worm wheel  12 . The protrusion  20  along with the groove  30  forms the engaging unit.  
         [0034]    In the actuator  10  according to the present invention, the protrusion  20  on the output lever  13  moves within the groove  30  provided in the worm wheel  12 . The output lever  13  engages with the worm wheel  12  when the protrusion  20  engages into the groove  30 . The groove  30  includes a first sliding member  31 , a second sliding member  32 , a contact member  33 , a guiding member  34 , and an allowing member  35 . The first sliding member  31  has a first sliding surface  310  along the outer periphery of the worm wheel  12 , and the second sliding member  32  has a second sliding surface  320  along the outer periphery of the worm wheel  12 . The first sliding surface  310  and the second sliding surface  320  face each other with a supporting shaft  121  between them. When the worm wheel  12  turns, the first sliding member  31  and the second sliding member  32  slide and come in contact with the protrusion  20  of the output lever  13  and guide the protrusion  20  to the guiding member  34  and the allowing member  35 , respectively.  
         [0035]    The contact member  33  is pinned on the worm wheel  12  by the supporting shaft  121 . The contact member  33  includes a first contact member  331  and a second contact member  332  which extend in different directions with respect to the supporting shaft  121 .  
         [0036]    When the worm wheel  12  turns clockwise, the first contact member  331  attaches with the protrusion  20  of the output lever  13  and swings the output lever  13  counter-clockwise. The first contact member  331  is disposed in such a way that it does not attach with the protrusion  20  when due to the turning of the worm wheel  12  the protrusion  20  is moving along the second sliding surface  320 .  
         [0037]    When the worm wheel  12  turns counter-clockwise, the second contact member  332  attaches with the protrusion  20  of the output lever  13  and swings the output lever  13  clockwise. The second contact member  332  is disposed in such a way that it does not attach with the protrusion  20  when due to the turning of the worm wheel  12  the protrusion  20  is moving along the first sliding surface  310 .  
         [0038]    The guiding member  34  is disposed between and in continuation with the first sliding member  31  and the second sliding member  32 . When the worm wheel  12  turns clockwise, the guiding member  34  guides the protrusion  20  that slides from the first sliding member  31  so that the protrusion  20  comes in contact with the first contact member  331 , and when the worm wheel  12  turns counter-clockwise, the guiding member  34  guides the protrusion  20  that slides from the second sliding member  32  such that the protrusion  20  comes in contact with the second contact member  332 .  
         [0039]    The allowing member  35  is disposed in continuation with the first sliding member  31  and the second sliding member  32  and facing the guiding member  34 , with the supporting axis  121  (the contact member  33 ) disposed in between. An apparent arc track R is disposed on the allowing member  35  with the output lever  131  as its center. The allowing member  35  allows the movement of the protrusion  20  of the output lever  13  when the output lever  13  slides between the first position and the second position at the time when the worm wheel  12  is not turning.  
         [0040]    The actuator  10  that has the structure described above works in the manner described below when operated electronically and manually. An electronic control of the actuator  10  will be explained followed by explanation of manual operation. The electronic control refers to the so-called keyless entry involving usage of a remote controller for locking and unlocking the door locking device in a switchable manner.  
         [0041]    As illustrated in FIG. 1, the output lever  13  and the worm wheel  12  are engaged when the protrusion  20  at a position (hereinafter also “first halting position”) near the first sliding position  31  in the allowing member  35  of the groove  30 . When the output lever  13  and the worm wheel  12  are engaged, the output lever  13  is in the first position and the locking lever  14  which is connected to the output lever  13  is in the unlocked position. Consequently, the door locking mechanism is in the unlocked condition.  
         [0042]    When the driving motor  11  is driven electronically, the worm wheel  12  turns clockwise through the driving shaft  11  and the worm  112 . When the worm wheel  12  turns a complete 360 degrees, the driving motor  11  ceases to be driven.  
         [0043]    When the worm wheel  12  turns clockwise, as shown in FIG. 2, the protrusion  20  of the output lever  13  moves along the first sliding surface  310  of the groove  30  of the worm wheel  12 . When the worm wheel  12  turns further clockwise, as shown in FIG. 3, the protrusion  20  moves from the first sliding surface  310  to the guiding member  34 .  
         [0044]    Upon further turning of the worm wheel  12 , as shown in FIG. 4, the protrusion  20  that has moved to the guiding member  34  is further guided by the guiding member  34  to the first contact member  331 . The protrusion thus guided to the first contact member  331  comes in contact with the first contact member  331  by further turning of the worm wheel  12 , as shown in FIG. 5. This action swings the output lever  13  counter-clockwise.  
         [0045]    Upon further turning of the worm wheel  12 , the protrusion which is in contact with the first contact member  331  moves along the second sliding surface  320 , as shown in FIG. 6, and comes in contact with the allowing member  35 , as shown in FIG. 7. At this point, the worm wheel  12  completes a full 360 degrees, and stops turning. As a result, the driving motor  11  ceases to be driven. Consequently, the output lever  13  and the worm wheel  12  are engaged with the protrusion  20  of the output lever  13  at a position (hereinafter also “second halting position”) near the second sliding member  32  on the allowing member  34  of the groove  30 . The output lever  13  is thus in the second position. Therefore, the locking lever  14 , which is connected to the output lever  13 , switches to the locked position, thus leaving the door locking device in the locked state.  
         [0046]    Explained below is the working of the actuator  10  when the door locking device changes from the locked to the unlocked condition electronically.  
         [0047]    When the output lever  13  and the worm wheel  13  are engaged with the protrusion of the output lever  13  at the second halting position, or in other words, when the output lever  13  is in the second position, the driving motor  11  is electronically driven to turn the worm wheel  12  counter-clockwise. Due to the turning of the worm wheel  12 , the protrusion  20  of the output lever  13  moves along the second sliding surface  320  and reaches the guiding member  34 . Further turning of the worm wheel  12 , the protrusion  20  is guided by the guiding member  34  into the second contact member  332 . When the protrusion  20  comes in contact with the second contact member  332 , the output lever  13  swings clockwise. When the worm wheel  12  turns further, the protrusion  20  moves along the first sliding surface  310  and comes in contact with the allowing member  35 . With this, the worm wheel completes a full 360 degrees turn and stops turning. As a result, the driving motor  11  ceases to be driven. Consequently, the output lever  13  and the worm wheel  12  are now engaged with the protrusion  20  of the output lever  13  at the first halting position. The output lever  13  is thus in the first position. Therefore, the locking lever  14 , which is connected to the output lever  13 , switches to the unlocked position, thus leaving the door locking device in the unlocked state.  
         [0048]    The working of the actuator  10  when operated manually will be described next. Manual operation refers to using a key on the externally provided key cylinder or from within the chassis by pushing a locking button provided inside in order to lock and unlock the door locking device in a switchable manner. Precisely, the door locking device is rendered in a locked or unlocked state in a switchable manner by switching the position of the locking lever  14  between the locked and unlocked position.  
         [0049]    In the case of manual operation, the driving motor  11  of the actuator  10  is not driven and hence the worm wheel also does not turn. Therefore, while the locking lever  14  is switched between the unlocked and the locked position by manual operation, the output lever  13  which is connected to the locking lever  14  slides between the first position and the second position.  
         [0050]    When the locking lever  14  is in the unlocked position (that is, when the door locking device is in the unlocked state), the output lever  13  of the actuator  10  is in the first position as shown in FIG. 1, and the protrusion  20  is in the first halting position.  
         [0051]    When the locking lever  14  is switched from the unlocked position to the locked position by manual operation, the output lever  13  swings counter-clockwise. In other words, the output lever  13  slides from the first position to the second position. When the output lever  13  slides, the protrusion  20  of the output lever  13  slides along the arc track R from the first halting position to the second halting position and stops there.  
         [0052]    When the locking lever  14  is switched from the locked position to the unlocked position by manual operation, the protrusion  20  of the output lever  13  slides along the arc track R from the second halting position to the first halting position and stops there. This sliding of the protrusion  20  is not transmitted to the worm wheel  12 . Consequently, the manual switching of the locking lever between the locked and unlocked position can be carried out smoothly.  
         [0053]    To sum up, in the actuator  10  according to the present invention, by providing a mechanism in which the protrusion  20  provided in the front end  133  of the output lever  13  engages into and slides in the groove  30  provided on the end facet of the worm wheel  12  and thereby engaging the output lever  13  and the worm wheel  12 , a compact output lever  13  can be realized since the width of the output lever  13  need not exceed the size of the protrusion  20 .  
         [0054]    In the actuator  10  according to the present invention, by providing a mechanism in which the protrusion  20  provided in the front end  133  of the output lever  13  engages into and slides in the groove  30  provided on the end facet of the worm wheel  12  and thereby engaging the output lever  13  and the worm wheel  12 , the sliding area of the output lever  13  can be restricted within the perimeter of the worm wheel  12 . Consequently, the actuator  10  can be made compact.  
         [0055]    In the actuator  10  according to the present invention, the locking lever  14  can be switched between the locked and unlocked state by the turning of the worm wheel  12  to a full 360 degrees and by the sliding of the output lever  13  that engages with the worm wheel  12 . Consequently, the need for an elastic body such as a spring, and the like, for returning the worm wheel  12  to a neutral position is obviated.  
         [0056]    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 which fairly fall within the basic teaching herein set forth.

Summary:
An actuator for a vehicle, in particular for an automobile door lock includes a rotatable rotor; a lever that is disposed so as to be swingable between a first position and a second position; and an engagement mechanism through which the lever is engaged with the rotor. The engagement mechanism also includes a protrusion that engages with the rotor; and a guide mechanism that makes, along with rotation of the rotor, the lever swing between the first position and the second position, and allows, when the rotor stops rotating, a movement of the lever without turning the rotor.