Abstract:
An actuator containing a drive mechanism that moves a locking pin forward and backward. Said drive mechanism is provided with the following: a holder that holds the locking pin; a cam member that has a cam gear; and a power-transmitting member in which a lower gear to which power from a motor is transmitted and an upper gear coupled to the cam gear are formed. The cam is offset from the center of rotation of the cam gear. The holder is pushed in a forward/backward direction by reciprocal motion of the cam within a range that constitutes less than a full revolution about the center of rotation of the cam gear. A region into which part of the lower gear fits and a region through which the cam moves are provided in a space above one surface of the cam gear.

Description:
TECHNICAL FIELD 
     The present invention relates to an actuator. 
     BACKGROUND ART 
     The charging of a storage battery installed in a vehicle such as an electric vehicle or a hybrid vehicle is achieved by: coupling a charging connector of a charging cable to a power receiving connector provided to the vehicle body; and supplying electric power to the storage battery via the charging cable. 
     Among locking mechanisms each configured to prevent the charging connector from coming off the power receiving connector, there is a locking mechanism including: a hook inclinably provided to the charging connector; an engagement protrusion provided to the power receiving connector; and an actuator provided near the power receiving connector (see, for example, Patent Literature 1). 
     The actuator includes a resin-made housing in which to house a drive mechanism. A locking pin projecting from the housing is capable of extending from and retracting into the housing. 
     The housing is attached to an inner surface of a wall portion of a charging port of the vehicle body. In addition, the locking pin projects to the outside through an insertion hole in the wall portion of the charging port. 
     The above-described locking mechanism is designed such that when the charging connector is coupled to the power receiving connector, the hook on the charging connector is brought into engagement with the engagement protrusion on the power receiving connector. In addition, the locking pin of the actuator extends to a position at which the locking pin restricts inclining movement of the hook. Thereby, the hook is fixed in a state of being in engagement with the engagement protrusion. For this reason, it is possible to prevent the charging connector from coming off the power receiving connector. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent Application Publication No. 2012-181985 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the above-described conventional actuator, multiple drive members configured to move the locking pin in the forward-backward direction are housed in the housing. The above-described conventional actuator involves a problem that the housing is large, because the drive members are largely spaced out from one another. 
     The present invention attempts to provide an actuator capable of: solving the foregoing problem; reducing the size of the space in the housing where the drive members are placed; and reducing the size of the housing. 
     Solution to Problem 
     To solve the above problems, the present invention is an actuator which includes: a hollow housing; and a pin projecting from an outer surface of the housing, a drive mechanism housed in the housing, and the drive mechanism configured to extend and retract the pin. The drive mechanism includes: a holder configured to hold the pin; a cam member including a cam gear provided with a cam; a motor; and a drive transmission member in which a first gear and a second gear are formed coaxial with each other, driving force being transmitted from the motor to the first gear, and the second gear being connected to the cam gear. The cam is projectingly provided to one surface of the cam gear, and is eccentric from a center of turn of the cam gear. The cam reciprocatingly turns around the center of turn of the cam member within a range less than one rotation, and thereby pushes out the holder in a direction of extension and retraction of the pin. A space on a side of the one surface of the cam gear includes an area which a part of the first gear enters, and a movement area of the cam. 
     This configuration does not allow the cam to make one rotation around the center of turn of the cam member. For this reason, the movement area of the cam formed in the space on the side of the one surface of the cam gear becomes smaller. Thereby, in the space on the side of the one surface of the cam gear, the first gear can be placed closer to the center of turn of the cam member. Thus, the space where the cam member and the drive transmission member are placed can be made smaller as shown in  FIG. 4 . Accordingly, the size of the housing can be reduced. 
     Moreover, since the first gear is placed closer to the center of turn of the cam gear, the second gear is also placed closer to the center of turn of the cam gear. For this reason, an outer diameter of the cam gear can be made smaller. Thus, the present invention can reduce the size of the housing, can make the outer diameter of the cam gear smaller, and accordingly can cut back material costs. 
     In the foregoing actuator, a cam housing frame in which to house the cam is formed in the holder; and the cam pushes an inner surface of the cam housing frame, and thereby pushes out the holder in the direction of extension and retraction of the pin. In addition, a recessed portion set back to an inside of the cam housing frame is formed in the holder. The recessed portion is disposed in the space on the side of the one surface of the cam gear, and between the first gear and the cam. 
     This configuration places the first gear closer to the recessed portion, and thereby can place the first gear closer to the center of turn of the cam gear without allowing the first gear to interfere with the cam housing frame. Furthermore, because the cam housing frame can be formed in an endless shape, the strength of the cam housing frame can be secured sufficiently. 
     In the foregoing actuator, it is desirable that the first gear interfere with an imaginary movement area of the cam which would make one rotation around the center of turn of the cam gear. This configuration disposes a part of the first gear in an area into which the cam does not move, which is in the imaginary movement area of the cam. Thereby, the first gear can be placed closer to the center of turn of the cam gear. 
     It should be noted that the state where the first gear interferes with the imaginary movement area of the cam includes a state where an outer peripheral edge portion of the first gear is in touch with an outer peripheral edge portion of the imaginary movement area of the cam. 
     Advantageous Effects of Invention 
     In the actuator of the present invention, the space where the cam member and the drive transmission member are placed can be made smaller. For this reason, the size of the housing can be reduced. Furthermore, since the size of the housing can be reduced, and since the outer diameter of the cam gear can be made smaller, material costs can be cut back. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view showing how an actuator of an embodiment is used. 
         FIG. 2  is a perspective view showing the actuator of the embodiment. 
         FIG. 3  is an exploded perspective view showing the actuator of the embodiment. 
         FIG. 4  is a plan view showing the inside of a housing chamber of the actuator of the embodiment with a locking pin retracted into the housing. 
         FIG. 5  is a plan view showing the inside of the housing chamber of the actuator of the embodiment with the locking pin extended from the housing. 
         FIG. 6  is a diagram showing a position of a cam gear, a position of a drive transmission mechanism, and a movement area of a cam. 
         FIG. 7  is a diagram showing rotated state of the cam which turns inside the actuator of the embodiment, wherein the rotated state of the cam is shown in each certain angle of turn of the cam. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings as needed. 
     As shown in  FIG. 1 , an actuator  10  of an embodiment is a part of a locking mechanism  5  installed in a charging port  2   a  of a vehicle  1  such as an electric vehicle or a hybrid vehicle. The locking mechanism  5  prevents a charging connector  4  from coming off a power receiving connector  3  while a storage battery (not illustrated) installed in the vehicle  1  is being charged. 
     It should be noted that the directional references “up,” “down,” “forward,” “backward,” “right” and “left” in relation to the actuator  10  in the following descriptions are given just for the sake of convenience in order to describe the structure of the actuator  10 , and are not intended to limit the orientation and the like of the actuator  10 .  FIG. 1  shows how the actuator  10  of the embodiment is installed in the vehicle. As shown in  FIG. 1 , the actuator  10  of the embodiment is attached to the vehicle in a way that the rear of the actuator  10  is inclined downward at approximately 30 degrees to a horizontal plane. 
     The charging port  2   a  in the vehicle body  2  is a space in which a tip end portion of a power receiving connector  3  is housed. The power receiving connector  3  is inserted through an opening in a wall portion  2   b  of the charging port  2   a , and the tip end portion of the power receiving connector  3  projects into the charging port  2   a . The power receiving connector  3  is electrically connected to the storage battery (not illustrated) via a cable (not illustrated). It should be noted that the axis of the power receiving connector  3  is inclined at approximately 30 degrees to the horizontal plane in a way that the power receiving connector  3  becomes lower toward the inside of vehicle from a tip end of the power receiving connector  3 . 
     A charging cable  4   a  is provided to a charging apparatus (not illustrated) such a charging station. A tip end portion of the charging cable  4   a  is provided with the charging connector  4 . The coupling of the charging connector  4  to the power receiving connector  3  enables the storage battery (not illustrated) to be supplied with electric power from the charging apparatus via the charging cable  4   a.    
     The locking mechanism  5  is formed from: a hook  4   b  provided to a tip end portion of the charging connector  4 ; an engagement protrusion  3   b  formed on the tip end portion of the power receiving connector  3 ; and the actuator  10  provided above the power receiving connector  3 . The hook  4   b  is inclinable in the vertical direction. 
     As the charging connector  4  is put deeper into the power receiving connector  3 , the hook  4   b  having been in contact with the engagement protrusion  3   b  moves inclined upward. Thereafter, once the hook  4   b  climbs over the engagement protrusion  3   b , the hook  4   b  moves inclined downward, and eventually gets into engagement with the engagement protrusion  3   b . Once the hook  4   b  hooks around the engagement protrusion  3   b  in this manner, a condition is established in which the charging connector  4  cannot be unplugged from the power receiving connector  3 . 
     The actuator  10  restricts the inclining movement of the hook  4   b  while the hook  4   b  is in a state of being in engagement with the engagement protrusion  3   b . The actuator  10  includes: a housing  20  in which a drive mechanism  100  (see  FIG. 3 ) is housed; and a locking pin  50  projecting from a front surface of the housing  20 . 
     The housing  20  is disposed on the vehicle inner side of the wall portion  2   b  of the charging port  2   a . The locking pin  50  is extendable from and retractable into the housing  20  in the forward-backward direction, and projects into the charging port  2   a  through an insertion hole formed in the wall portion  2   b.    
     As shown in  FIG. 2 , the housing  20  is a resin-made box body. The locking pin  50  projects from a hole portion  36   c  formed in a front surface  34   a . As shown in  FIG. 3 , the housing  20  includes: a housing lower  30  whose inner space forms a housing space  31 ; and a housing upper  40  configured to close an opening  32  of the housing lower  30 . The assembling of the housing lower  30  and the housing upper  40  makes the housing space  31  inside the housing  20 . 
     The housing lower  30  is a box-shaped member including the opening  32  which is formed in the upper surface of the housing lower  30 . The housing lower  30  includes: a bottom portion  33  shaped like a flat plate; and a peripheral wall portion  34  uprightly provided on an outer peripheral edge portion of the bottom portion  33 . The peripheral wall portion  34  is a frame surrounding the housing space  31 , and is shaped almost like a square in a plan view. 
     The bottom portion  33  is shaped almost like a square in the plan view (see  FIG. 4 ). A male connector  35  projects downward from a right rear portion of the bottom portion  33 . A female connector (not illustrated) configured to supply the electric power to the drive mechanism is coupled to the male connector  35 . The female connector is electrically connected to a controller (not illustrated) installed in the vehicle  1  (see  FIG. 1 ). 
     An attachment portion  36   a  configured to be attached to the inner surface of the wall portion  2   b  of the charging port  2   a  (see  FIG. 1 ) is projectingly provided to the front surface  34   a  of the peripheral wall portion  34  of the housing lower  30 . The hole portion  36   c  through which to insert the locking pin  50  penetrates through a middle portion of the attachment portion  36   a  in the right-left direction. 
     A couple of left and right housing supporting portions  36   b  configured to be attached to the power receiving connector  3  (see  FIG. 1 ) is formed in the lower surface of the housing lower  30 . 
     An opening edge portion  37  of the housing lower  30  (an upper end edge portion of the peripheral wall portion  34 ) projects outward from an outer surface of the peripheral wall portion  34  in a way that the opening edge portion  37  is shaped like a flange. A seal groove  37   a  into which to fit an endless seal member (not illustrated) is formed along the full circumference of the upper surface of the opening edge portion  37  (see  FIG. 4 ). 
     The housing upper  40  is a flat plate-shaped lid member configured to close the opening  32  of the housing lower  30 . An outer periphery of the housing upper  40  is formed in the same shape as is that of the opening edge portion  37  of the housing lower  30 . 
     An outer peripheral edge portion of the housing upper  40  is brought into engagement with the opening edge portion  37  of the housing lower  30 , and is bonded to the opening edge portion  37  with an adhesive such as a hot-melt adhesive. 
     In addition, the seal member (not illustrated) provided to the opening edge portion  37  of the housing lower  30  fluid-tightly seals the gap between the housing lower  30  and the housing upper  40 . 
     The locking pin  50  is a shaft member whose cross section is shaped like a circle. The axial direction of the locking pin  50  is oriented in the forward-backward direction. The front end portion of the locking pin  50  is shaped like a hemispherical surface. 
     As shown in  FIG. 4 , a rear portion of the locking pin  50  is housed in the housing space  31  of the housing lower  30 , while a front portion of the locking pin  50  projects to the outside of the housing lower  30  through the hole portion  36   c  formed in the front surface  34   a  of the peripheral wall portion  34 . 
     As shown in  FIG. 3 , the drive mechanism  100  configured to extend and retract the locking pin  50  in the forward-backward direction is housed in the housing space  31  of the housing lower  30 . 
     The drive mechanism  100  includes: a holder  60  configured to hold the locking pin  50 ; a cam member  70  including a cam gear  72  projectingly provided with a cam  73 ; an electric motor  80 ; and a drive transmission member  90  provided between an output shaft  81  of the electric motor  80  and the cam gear  72 . The drive mechanism  100  further includes: switches  210  configured to detect the position of the locking pin  50 ; and a board  200  to which the electric motor  80  and the switches  210  are electrically connected. 
     The cam member  70  is a member configured to move the holder in the forward-backward direction. The cam member  70  includes: a rotary shaft  71  whose axial direction is oriented in the vertical direction; the cam gear  72  which is a spur gear, and which is coaxial with the rotary shaft  71 ; and the cam  73  projectingly provided to a lower surface of the cam gear  72 . The cam  73  is eccentric from a center of turn of the cam gear  72 . 
     As shown in  FIG. 4 , the cam member  70  is disposed in a central portion of the housing space  31 . A lower portion of the rotary shaft  71  is inserted through a cam housing frame  62 , which will be described later. A lower end portion of the rotary shaft  71  is rotatably supported by a bottom surface  33   a  of the housing lower  30 . An upper end portion of the rotary shaft  71  projects to the outside of the housing upper  40  (see  FIG. 3 ) through a through-hole in the housing upper  40 . 
     A teeth surface is formed on almost a left haft of an outer peripheral surface of the cam gear  72  in  FIG. 4 . In addition, a rod  74  projecting outward in the radial direction is formed on the cam gear  72  (see  FIG. 3 ). The rod  74  is a part configured to push in a detector of the switch  210  (see  FIG. 3 ) for detecting the extension, which will be described later. 
     The cam  73  is a part configured to push out the holder  60 , which will be described later, in the forward-backward direction (see  FIG. 5 ), and is projectingly provided to the lower surface of the cam gear  72  (see  FIG. 3 ). 
     An outer periphery of the cam  73  is shaped almost like a triangle in the plan view. As shown in  FIG. 6 , a vicinity of one of the three corner portions of the cam  73  is disposed on the center of turn  72   a  of the cam gear  72 . In other words, the center of turn  72   a  of the cam gear  72  is disposed eccentrically from a central position  73   a  of the cam  73  toward the vicinity of the one corner portion of the cam  73 . Thus, the central position  73   a  of the cam  73  is eccentric from the center of turn  72   a  to the right. 
     In the cam member  70 , an angle of turn of the cam gear  72  is set in a way that the cam  73  reciprocatingly turns around the center of turn  72   a  of the cam gear  72  within a range less than one rotation. Incidentally, in the embodiment, the cam  73  reciprocatingly turns around the center of turn  72   a  of the cam gear  72  within a range of approximately a third of one rotation (approximately 128 degrees). 
     Regardless of where the cam gear  72  is located during its turn, the central position  73   a  of the cam  73  is always disposed in an area to the right of the center of turn  72   a  of the cam gear  72  (an area to the right of the axis of the locking pin  50 ). For this reason, a movement area S 2  of the cam  73  is shaped almost like a semicircle in a way that an amount of rightward protrusion of the movement area S 2  of the cam  73  from the center of turn  72   a  of the cam gear  72  is larger than an amount of leftward protrusion of the movement area S 2  of the cam  73  from the center of turn  72   a  of the cam gear  72 . 
     As shown in  FIG. 4 , the electric motor  80  includes a motor housing  82  which is disposed in a left front portion of the housing space  31 . In addition, the output shaft  81  projects backward from the motor housing  82 . A screw gear  81   a  shaped like a cylinder is fitted on to the output shaft  81 . 
     The drive transmission member  90  transmits drive force of the electric motor  80  to the cam gear  72 . As shown in  FIG. 3 , the drive transmission member  90  includes: a rotary shaft  91  whose axial direction is oriented in the vertical direction; a lower gear  92  which is a helical gear, and which is coaxial with the rotary shaft  91 ; and an upper gear  93  which is a spur gear, and which is coaxial with the rotary shaft  91 . The upper gear  93  is smaller in diameter than the lower gear  92 . The lower gear  92  is referred to as a “first gear” in the claims, while the upper gear  93  is referred to as a “second gear” in the claims. 
     In the housing space  31 , as shown in  FIG. 4 , the drive transmission member  90  is disposed backward of the motor housing  82 , and between the screw gear  81   a  and the holder  60 . 
     A lower end portion of the rotary shaft  91  is rotatably supported by the bottom surface  33   a  of the housing lower  30 . An upper end portion of the rotary shaft  91  is rotatably supported by the housing upper  40  (see  FIG. 3 ). 
     A teeth surface of the lower gear  92  is connected to a teeth surface of the screw gear  81   a  of the electric motor  80  from above. A teeth surface of the upper gear  93  is connected to the teeth surface of the cam gear  72 . 
     A right front portion of the lower gear  92  enters a space S 1  under the lower surface of the cam gear  72 . As shown in  FIG. 6 , the space S 1  under the lower surface of the cam gear  72  includes: an area S 3  which a part of the lower gear  92  enters; and the movement area S 2  of the cam  73 . 
     Since the amount of leftward projection of the movement area S 2  of the cam  73  from the center of turn  72   a  of the cam gear  72  (from the axis of the locking pin  50 ) is smaller, the lower gear  92  can be placed closer to the center of turn  72   a  of the cam gear  72 . Incidentally, an imaginary movement area S 2 ′, in which the cam  73  would move if the cam  73  would make one rotation around the center of turn  72   a  of the cam gear  72 , would interfere with the lower gear  92 . In the embodiment, an outer peripheral edge portion of an imaginary movement area S 2 ′ comes into contact with an outer peripheral edge portion of the lower gear  92 . 
     As shown in  FIGS. 4 and 5 , once the screw gear  81   a  of the electric motor  80  is rotated, its drive force is transmitted to the lower gear  92 , and the drive transmission member  90  thus rotates about its axis. Thereby, the drive force is transmitted from the upper gear  93  to the cam gear  72 , and the cam gear  72  thus turns about its axis. Hence, the cam  73  turns about the axis of the rotary shaft  71 . 
     As shown in  FIG. 4 , the holder  60  is disposed in the intermediate portion of the housing space  31  in the right-left direction. Front, rear, left and right side surfaces, as well as upper and lower surfaces are formed on the holder  60 . A vertically-opened opening  60   a  and the cam housing frame  62  are formed in a rear portion of the holder  60 . In addition, a recessed portion  63  is formed in a left rear portion of the holder  60 . 
     A rod  64  projecting rightward is formed on a front portion of the right side surface of the holder  60 . The rod  64  is a part configured to push in a detector of the switch  210  (see  FIG. 3 ) for detecting the retraction, which will be described later. 
     A pair of left and right guide rails  33   b  extended in the forward-backward direction are provided to the bottom surface  33   a  of the housing lower  30 . The holder  60  is mounted on the two guide rails  33   b , and is movable along the two guide rails in the forward-backward direction. 
     As shown in  FIG. 4 , an elastic member  51  is provided between a front end surface of the holder  60  and an inner surface of the peripheral wall portion  34 . The elastic member  51  is a coil spring, and the locking pin  50  is inserted through the elastic member  51 . It should be noted that: the elastic member  51  is not limited to the coil spring; and various elastic members such as rubber and a disk spring may be used as the elastic member  51 . 
     The cam housing frame  62  is an endless frame forming a peripheral wall of the opening  60   a  formed in the rear portion of the holder  60 . 
     The lower portion of the rotary shaft  71  of the cam member  70  is inserted through the cam housing frame  62 , and the cam  73  projectingly provided to the lower surface of the cam gear  72  is inserted into the cam housing frame  62  from above. Front and rear inner surfaces of the cam housing frame  62  form cam receiving surfaces in which a cam surface of the cam  73  comes into contact. 
       FIG. 7  shows rotated state of the cam  73  which turns inside the cam housing frame  62  in each quarter of the overall angle of turn of the cam  73 . As shown in  FIG. 7 , all the rotated state of the turning cam  73  falls inside the cam housing frame  62 . 
     In the embodiment, since as shown in  FIG. 6 , the amount of rightward protrusion of the movement area S 2  of the cam  73  from the center of turn  72   a  of the cam gear  72  is larger, the cam housing frame  62  is disposed eccentrically from the center of turn  72   a  of the cam gear  72  (the axis of the locking pin  50 ) to the right. 
     As shown in  FIG. 4 , the recessed portion  63  set back toward the inside of the cam housing frame  62  (the opening  60   a ) is formed in the left rear portion of the holder  60 . 
     As shown in  FIG. 7 , the recessed portion  63  is formed in an area outside an area where the cam  73  turns in the cam housing frame  62 . Furthermore, as shown in  FIG. 6 , the recessed portion  63  is disposed in the space S 1  under the lower surface of the cam gear  72 , and between the lower gear  92  and the cam  73 . 
     Reference sign L 1  in  FIG. 6  denotes an imaginary outline of the left half which would be made symmetrical with the right half of the cam housing frame  62  with respect to the axis of the locking pin  50  when the holder  60  is moved furthest backward. If in this manner, the left and right halves of the cam housing frame  62  would have axial symmetry with respect to the axis of the locking pin  50 , the cam housing frame  62  would interfere with the lower gear  92 . In contrast, in the embodiment, the recessed portion  63  is formed in the left rear portion of the holder  60 . Thereby, the holder  60  is designed such that the rear portion of the holder  60  does not come into touch with the lower gear  92 . 
     Furthermore, the recessed portion  63  is designed such that when the holder  60  is moved furthest backward, the right front portion of the lower gear  92  enters the recessed portion  63 . To this end, the width of the recessed portion  63  in the right-left direction becomes larger toward the rear end in a way that the recessed portion  63  evades the lower gear  92 . Thereby, an inclination portion  62   a  which inclines further rightward toward the rear end is formed in the left half of the cam housing frame  62 . 
     As shown in  FIG. 3 , a holding hole  61  is opened in a central portion of the front end surface of the holder  60 . The locking pin  50  can be held by the holder  60  by: inserting the rear portion of the locking pin  50  through the holding hole  61 ; and bringing a claw portion (not illustrated) in the holder  60  into engagement with an engagement groove  50   a  formed in the rear portion of the locking pin  50 . 
     In the embodiment, the attachment of the locking pin  50  to the holder  60  can be achieved by: housing only the holder  60  in the housing lower  30 ; and thereafter inserting the locking pin  50  through the hole portion  36   c  from outside the peripheral wall portion  34 . Since in this manner, only the holder  60  is housed in the housing lower  30  when the locking pin  50  and the holder  60  are attached to the housing lower  30 , the size of the housing lower  30  can be made smaller. 
     As shown in  FIG. 3 , the board  200  is formed wider in the right-left direction, and is disposed in a front portion of the opening  32  of the housing lower  30 . The board  200  is configured to control the drive of the electric motor  80 . The switches  210 , the electric motor  80  and the male connector  35  are electrically connected to the board  200 . 
     In the actuator  10 , as shown in  FIG. 4 , once the screw gear  81   a  of the electric motor  80  is rotated, its drive force is transmitted to the cam gear  72  via the drive transmission member  90 . 
     As shown in  FIG. 5 , once the cam gear  72  is rotated in the right direction (in the clockwise direction), the cam  73  rotationally moves forward while in a state of being in contact with a front-side inner peripheral surface of the cam housing frame  62 . Thus, the cam  73  pushes out the inner peripheral surface of the cam housing frame  62  forward. 
     Thereby, the holder  60  moves forward, and the locking pin  50  extends forward. Accordingly, an amount of protrusion of the locking pin  50  from the housing  20  increases. During this time, the elastic member  51  contracts between the holder  60  and the peripheral wall portion  34 . 
     Once the rod  74  of the cam gear  72  pushes in the detector of the switch  210  (see  FIG. 3 ) for detecting the extension while the holder  60  is moving forward, the switch  210  (see  FIG. 3 ) for detecting the extension outputs a detection signal to the controller (not illustrated), and the rotation of the output shaft  81  thereby stops. 
     It should be noted that when the holder  60  is moving forward, elastic force of the elastic member  51  acts on the holder  60 , and the front-side inner peripheral surface of the cam housing frame  62  is held in a state of being in touch with the cam  73 . Thereby, the holder  60  and the locking pin  50  become stable. For this reason, the locking pin  50  can be made to stay at a predetermined extension position accurately. 
     Once as shown in  FIG. 4 , the cam gear  72  is rotated in the left direction (in the counterclockwise direction) starting from the state where the locking pin  50  extends, the cam  73  rotationally moves backward, and thus pushes out the inner surface of the cam housing frame  62  backward. Thereby, the locking pin  50  retracts backward. Accordingly, the amount of protrusion of the locking pin  50  from the housing  20  can be decreased. 
     Once the rod  64  of the holder  60  pushes in the detector of the switch  210  (see  FIG. 3 ) for detecting the retraction while the holder  60  is moving backward, the switch  210  for detecting the retraction outputs a detection signal to the controller, and the rotation of the output shaft  81  thereby stops. 
     In the embodiment, while the cam  73  is turning backward, the elastic force of the elastic member  51  acts on the holder  60 . Thereby, in response to the turn of the cam  73 , the holder  60  moves backward while the front-side inner peripheral surface of the cam housing frame  62  is in the state of being in contact with the cam  73 . Since in this manner, the front-side inner peripheral surface of the cam housing frame  62  is held in the state of being in touch with the cam  73  while the locking pin  50  is retracting, the holder  60  and the locking pin  50  become stable. For this reason, the locking pin  50  can be made to stay at a predetermined retraction position accurately. 
     Once the controller (not illustrated) detects that as shown in  FIG. 1 , the charging connector  4  is coupled to the power receiving connector  3 , the locking pin  50  extends from the housing  20 , and the front portion of the locking pin  50  is deployed above the hook  4   b  of the charging connector  4 . 
     Thereby, the locking pin  50  restricts the inclining movement of the hook  4   b , and the hook  4   b  is fixed in the state of being in engagement with the engagement protrusion  3   b  of the power receiving connector  3 . For this reason, it is possible to prevent the charging connector  4  from coming off the power receiving connector  3 . 
     Thereafter, once the extension of the locking pin  50  stops, the charging apparatus (not illustrated) starts to charge the storage battery (not illustrated). 
     In addition, once an unlock signal is inputted into the controller (not illustrated) after the charging, the locking pin  50  retracts into the housing  20 , and the front portion of the locking pin  50  withdraws from above the hook  4   b  of the charging connector  4 . 
     This makes the hook  4   b  become able to make inclining movement. Thereby, the hook  4   b  can be detached from the engagement protrusion  3   b  of the power receiving connector  3 , and the charging connector  4  accordingly can be unplugged from the power receiving connector  3 . 
     Furthermore, as shown in  FIG. 3 , an unlock lever  42  attached to the upper end portion of the rotary shaft  71  of the cam member  70  is provided to an upper surface of the housing upper  40  (see  FIG. 2 ). The turning of the unlock lever  42  makes it possible to forcibly turn the cam member  70  by hand, and thereby to makes the locking pin  50  retract. 
     In the above-described actuator  10 , since as shown in  FIG. 6 , the cam  73  does not make one rotation around the center of turn of the cam gear  72 , the movement area S 2  of the cam  73  which is formed in the space S 1  under the lower surface of the cam gear  72  becomes smaller. In addition, the part of the lower gear  92  is disposed in the area into which the cam  73  does not move, which is in the imaginary movement area S 2 ′ in which the cam  73  would move if the cam  73  would make one rotation around the center of turn  72   a  of the cam gear  72 . Thereby, in the space S 1  under the lower surface of the cam gear  72 , the lower gear  92  can be placed closer to the center of turn  72   a  of the cam gear  72 . 
     Accordingly, in the actuator  10  of the embodiment, the space where the cam member  70  and the drive transmission member  90  are placed can be made smaller as shown in  FIG. 4 . For this reason, the size of the housing  20  (see  FIG. 2 ) can be reduced. 
     Moreover, since the lower gear  92  is placed closer to the center of turn of the cam gear  72 , the upper gear  93  is also placed closer to the center of turn of the cam gear  72 . For this reason, an outer diameter of the cam gear  72  can be made smaller. 
     Accordingly, in the actuator  10  of the embodiment, since the size of the housing  20  (see  FIG. 2 ) can be reduced, and since the outer diameter of the cam gear  72  can be made smaller, material costs can be cut back. 
     Besides, the recessed portion  63  is formed in the cam housing frame  62  in the holder  60  of the actuator  10 . In addition, the lower gear  92  is placed closer to the recessed portion  63 . For these reason, the lower gear  92  can be placed closer to the center of turn  72   a  of the cam gear  72  (see FIG.  6 ) without allowing the lower gear  92  to interfere with the cam housing frame  62 . Furthermore, since the cam housing frame  62  can be formed in the endless shape, the strength of the cam housing frame  62  can be secured sufficiently. 
     Although the foregoing descriptions have been provided for the embodiment of the present invention, the present invention is not limited to the embodiment, and modifications may be made to the present invention as needed, within a scope not departing from the gist of the present invention. 
     Although in the embodiment, as shown in  FIG. 4 , the cam housing frame  62  of the holder  60  is formed in the endless shape, the cam housing frame  62  does not have to be formed in the endless shape as long as at least front and rear inner surfaces with which the cam  73  comes into contact are formed. 
     For example, if the cam housing frame  62  is opened by cutting away a portion of the cam housing frame  62  between a part corresponding to the lower gear  92  and a part corresponding to the cam  73  (the portion of the cam housing frame  62  where the recessed portion  63  is formed), the lower gear  92  can be placed much closer to the center of turn  72   a  of the cam gear  72 . 
     Moreover, although in the embodiment, as shown in  FIG. 1 , the actuator of the present invention is applied to the locking mechanism  5  configured to prevent the charging connector  4  from coming off the power receiving connector  3 , the actuator of the present invention is applicable to various actuators. 
     REFERENCE SIGNS LIST 
     
         
           1  vehicle 
           2   a  charging port 
           3  power receiving connector 
           3   b  engagement protrusion 
           4  charging connector 
           4   b  hook 
           5  locking mechanism 
           10  actuator 
           20  housing 
           30  housing lower 
           31  housing space 
           34  peripheral wall portion 
           40  housing upper 
           50  locking pin 
           60  holder 
           60   a  opening 
           61  holding hole 
           62  cam housing frame 
           63  recessed portion 
           70  cam member 
           72  cam gear 
           73  cam 
           80  electric motor 
           90  drive transmission member 
           92  lower gear  92  (first gear) 
           93  upper gear (second gear) 
           100  drive mechanism 
         S 1  space under lower surface of cam gear 
         S 2  movement area of cam 
         S 3  area which part of lower gear enters