Abstract:
A power actuator is provided for a door latch. A transfer lever within the housing is selectively coupled to a motor-driven worm gear via a lost motion connector. Engaging the motor moves the transfer lever between a locked and an unlocked position, actuating an output lever mounted to a spline on the transfer lever. The worm gear returns to a neutral position when the motor is disengaged, leaving the transfer lever in either the locked or unlocked positions. Manually moving the output lever causes the transfer lever to move between its locked and unlocked positions without back-driving the worm gear. A toggle mechanism prevents the transfer lever from accidentally moving or only moving partially between the locked and unlocked positions.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to locking systems for motor vehicles. More specifically, the present invention relates to power actuator operable to lock or unlock a latch on a sliding side door. 
       BACKGROUND OF THE INVENTION 
       [0002]    Motor vehicles with sliding doors (typically vans), typically use power actuators to electrically lock and unlock the sliding door. The power actuator is typically engaged by interior door lock switches or a remote key fob, and locks or unlocks a side door latch. Normally, the power actuator is connected to a lock lever on the side door latch via a door lock rod. Since the door latch can be locked or unlocked manually as well as electronically, the power actuator must also be able to move between a locked and an unlocked state un-powered, and without undesirable back drive from the power actuator&#39;s motor. Preferably, the power actuator is modular so that it can be easily installed and/or replaced. Additionally, the power actuator should be compact, reliable and inexpensive to manufacture. 
         [0003]    It is therefore desired to provide a power actuator that locks and unlocks a side door latch, and further, will move between a locked and an unlocked state when the door latch is manually locked or unlocked without back-driving the power actuator&#39;s motor. It is further desired to provide a modular power actuator that is compact, reliable and inexpensive to manufacture. 
       SUMMARY OF THE INVENTION 
       [0004]    According to a first aspect of the invention, there is provided a power actuator for a door latch. The power actuator includes a housing; a reversible motor, mounted to the housing; a worm, driven by the motor; and a worm gear, rotatably mounted to the housing and driven by the worm. The worm gear is rotatable between a first and a second angular position upon actuation of the motor. A spring, mounted to the housing, urges the worm gear to a neutral position intermediate the first and second angular positions when the motor is disengaged. The power actuator further includes a transfer lever, pivotally mounted to the housing and movable between a first and second positions. The transfer lever is kinematically coupled to the worm gear via a lost motion connection, thereby enabling the transfer lever to be moved between the first and second position without driving the worm gear when the worm gear is in the neutral position. An output lever is mounted to a spline on the transfer lever. A toggle mechanism prevents the transfer lever from accidentally moving, or only moving partially between the locked and unlocked positions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a plan view of a power actuator in accordance with a first aspect of the invention; 
           [0006]      FIG. 2  is a plan view of an upper housing mounted of the power actuator shown in  FIG. 1 ; 
           [0007]      FIG. 3  is an inner plan view of the power actuator shown in  FIG. 1 ; 
           [0008]      FIG. 4  is a partially exploded view of a drive train mounted in the power actuator of  FIG. 1 ; 
           [0009]      FIGS. 5   a  and  5   b  are fragmentary views of the power actuator shown in  FIGS. 2-3 , showing the motion of a transfer lever; 
           [0010]      FIG. 6  is a fragmentary view of the power actuator shown in  FIGS. 2-3 , showing a locking lever; and 
           [0011]      FIG. 7  is a fragmentary view of the upper housing shown in  FIGS. 1-2 , showing an output lever. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring now to  FIGS. 1-3 , a power actuator according to the preferred embodiment is shown at  10 . Power actuator  10  includes a clam-shell housing  12  formed from a complementary upper housing  14  and a lower housing  16 . Preferably, both upper housing  14  and lower housing  16  are formed from a rigid thermoplastic material. An integrally-formed mounting structure (not shown) is provided on the exterior surface of lower housing  16  to mount power actuator  10  to a vehicle or vehicle module (not shown). Upper housing  14  includes a substrate  20 , and peripheral walls  22  extending out from substrate  20  towards lower housing  16 . Lower housing  16  includes a substrate  24  and peripheral walls  26 . A detent on the top of peripheral walls  22  fits within a groove provided in the top of peripheral walls  26  to provide a weather-tight seal between the two housings. 
         [0013]    A motor  28  is mounted within a motor housing  30  formed in substrate  24  on lower housing  16 . Motor  28  is a bi-directional DC motor and is operable to drive a worm  32 . The shat of worm  32  is journalled within a centering hole  34  on a support wall  36  integrally formed from substrate  24 . 
         [0014]    As can be more clearly seen in  FIG. 4 , worm  32  drives a worm gear  38  that is rotably mounted to a post  40  integrally formed from substrate  24 . The angular travel of worm gear  38  is delimited by a stop tab  42  abutting a first shoulder  44 , or a second shoulder  46 . Thus, worm gear  38  is rotatable between a first or “locking” position, where stop tab  42  abuts the first shoulder  44 , and a second or “unlocking” position, where stop tab  42  abuts the second shoulder  46 . A centering spring  48  with a pair of toggle arms  50  is located around post  40  between worm gear  38  and substrate  24 . As worm gear  38  rotates to either of the locking or unlocking positions, a depending tab  52  engages and pushes the leading toggle arm  50 . A retaining tab  54  extending out from substrate  24  impedes the rotational motion of the trailing toggle arm  50 , causing the centering spring  48  to twist and thereby load the spring. When motor  28  disengages, the tension on centering spring  48  is released, so that centering spring  48  reverses the direction of worn gear  38 , backdriving motor  28 . Worm gear  38  returns to a “neutral” position midway between the locking and the unlocking positions, where depending tab  52  and retaining tab  54  are aligned. 
         [0015]    A transfer lever  55  is pivotally mounted to power actuator  10 . An axial post  56  locates transfer lever  55  in a hole  58  in upper housing  14  ( FIG. 2 ) and lower housing  16  (not shown). The angular motion of transfer lever  55  is delimited by a wall  60  and a wall  62 , both integrally formed in upper housing  14 . When transfer lever  55  abuts wall  60 , it is in its “locked” position, and when transfer lever  55  abuts wall  62 , it is in its “unlocked” position. Rotating worm gear  38  to the locking position actuates transfer lever  55  to its locked position, and conversely, rotating worm gear  38  to the unlocking position actuates transfer lever  55  to the unlocked position. In the illustrated embodiment, worm gear  38  includes a pair of curved transfer lobes  64   a  and  64   b  extending outward from the surface of the gear towards upper housing  14 . While at rest, a depending tab  66  on the end of transfer lever  55  abuts one of the transfer lobes  64 . As worm gear  38  rotates clockwise or counterclockwise towards either the locking or unlocking positions, the abutting transfer lobe  64  engages depending tab  66  to actuate transfer lever  55 . When transfer lever  55  is in its locked position, depending tab  66  abuts transfer lobe  64   a  ( FIG. 5   a ), and when transfer lever  55  is in its unlocked position, depending tab  66  abuts transfer lobe  64   b  ( FIG. 5   b ). The arc of travel of transfer lobes  64  is substantially similar to the arc of travel of transfer lever  55 . In addition, depending tab  66  includes a pair of symmetrically curved engagement surfaces  68 , so that an even transfer of torque from worm gear  38  to transfer lever  55  is maintained for both the clockwise and counterclockwise rotation of worm gear  38 . As is described above, once motor  28  disengages, the recoiling of centering spring  48  returns worm gear  38  to its neutral position. Thus, depending tab  66  now abuts the other transfer lobe  64 , so it can quickly be actuated to the other position. 
         [0016]    A locking lever  70  acts as a toggle mechanism and reduces the possibility of transfer lever  55  pivoting accidentally. or pivoting only partially between the locked and unlocked position. Referring now to  FIG. 6 , locking lever  70  is slidably retained within a slot  72  ( FIG. 2 ) in substrate  20  via a post  74 . Locking lever  70  is further pivotable between a “locked” and an “unlocked” position. As will be described in greater detail below, locking lever  70  is in its locked position when transfer lever  55  is in its locked position, and conversely, locking lever  70  is in its unlocked position when transfer lever  55  is in its unlocked position. A key post  76  extending from locking lever  70 , and offset from post  74  is located in a keyhole  78  on a locking arm  80  of transfer lever  55 , so that rotating transfer lever  55  rotates locking lever  70  in the opposite direction. A toggle spring  82  is hooked around post  74  on locking lever  70  and a depending post  84  on locking arm  80  near axial post  56 . As transfer lever  55  begins to pivots from either the locked or unlocked position to the other position, the counter-rotation of keypost  76  within keyhole  78  on locking arm  80  displaces locking lever  70  away from transfer lever  55  within slot  72 . The distance between post  74  and depending post  84  increases, stretching locking toggle spring  82 . Thus, toggle spring  82  provides a resisting force against the rotation of transfer lever  55 . When both transfer lever  55  and locking lever  70  are midway between positions, toggle spring  82  is under maximal tension. When the two levers move past the midway point, the distance between post  74  and depending post  84  diminishes. Now, toggle spring  82  contracts, providing an assisting force urging the two levers into their destined position. As will be apparent to those of skill in the art, the strength of toggle spring  82  can be changed in order to increase or decrease the effort required to pivot transfer lever  55 . 
         [0017]    An output lever  86  ( FIG. 1 ) is mounted to transfer lever  55  on the exterior of upper housing  14 . Referring now to  FIG. 7 , a star-shaped mounting hole  92  on output lever  86  locates the output lever on a complementary star-shaped spline  94  extending out from axial post  56  on transfer lever  55 . In the current embodiment, spline  94  includes seven radial teeth  96 . The drafted slopes on both mounting hole  92  and teeth  96  provide for the optimum distribution of torque between transfer lever  56  and output lever  86 . The complementary angles of mounting hole  92  and teeth  96  increases the contact surface area of the two levers, improving the mating component to withstand more stress. A fastener  98 , such as a screw or rivet, is mounted through coaxial holes on output lever  86  and spline  94 , and assists in coupling output lever  86  and transfer lever  55  together. An O-ring seal  100  prevents moisture from entering power actuator  10  through hole  58 . 
         [0018]    As can be clearly seen in  FIG. 1 , output lever  86  includes a lock arm  102  and a latch arm  104 , the two arranged in a V-shaped configuration around mounting hole  92 . Lock arm  102  includes a lock loop  106  operable to retain a manual release door lock rod (not shown). Latch arm  102  includes a mounting hole  108  operable to retain a clip for a cable connected to a side door latch (not shown). Manually actuating the door lock rod causes output lever  86  to pivot around mounting hole  92 , causing the cable to actuate the side door latch. Pivoting output lever  86  between first and second positions causes transfer lever  55  and locking lever  70  to pivot as well. Locking lever  70  moves between its locked and unlocked positions, thereby ensuring that output lever  86  is moved completely into its new position. Depending tab  66  on transfer lever  55  moves from abutting one transfer lobe  64  to abutting the other transfer lobes  64 . Center toggle spring  58  provides a degree of lost motion in worm gear  38  so that it does not rotate. Thus, there is no backdriving of motor  28 . 
         [0019]    Referring back to  FIG. 2 , an electronic or mechanical switch  110  having a “locked” and an “unlocked” state is mounted in upper housing  16 . When transfer lever  55  is in its locked position, it triggers switch  110  into the locked state, and when transfer lever  55  is in its second position, it releases switch  110  into the unlocked state. State information from switch  110  is transmitted to a vehicle controller (not shown) via blades  112  (also not shown). Electrical power for motor  26  is also provided via blades  112 .