Abstract:
A power actuator assembly for a latch includes first and second articulated levers. The first lever includes cam follower surfaces and the second lever includes at least one stop member which pivots between first and second positions as each lever travels between first and second positions. A motor-driven cam having driving members and stop members drives the first lever. More particularly, each driving member has a path of travel that engages one of the cam follower surfaces for a portion of the travel path to drive the first and second levers and is in disengaging alignment with the cam follower for another portion of travel. The cam stop members abut the stop member of the second lever when the cam driving members are in the non-aligned position, whereby the levers may be activated without driving the cam. The assembly can be employed, inter alia, in a lock application or a power release application so as to preclude the necessity of having to backdrive the power actuator.

Description:
FIELD OF THE INVENTION 
   This invention generally relates to a power actuator for a vehicle door latch. 
   BACKGROUND OF THE INVENTION 
   Power lock mechanisms used in vehicles often employ an electric motor or actuator to move one or more lock levers between locked and unlocked positions. Typically, these latches are also equipped with a manual lock, typically an inside lock button and/or outside key cylinder. If the electric motor is constantly coupled with the lock lever(s) it has to be back-driven when the manual lock is operated. This adds to the effort required to actuate the manual lock and increases the noise of the locking/unlocking operation. 
   One solution to avoid back-driving the motor when the lock lever is manually operable is to equip the actuator with a return spring that automatically back-drives the motor to its initial position after each lock or unlock cycle. This allows for enough lost motion in the mechanism so that the next manual cycle can be performed without moving the motor. Alternatively, the lock actuator can include a clutch mechanism for disengaging the motor after each lock or unlock cycle. However, these solutions add parts, complexity, and costs to the lock actuator. For example, approximately 30% of the torque generated by the motor is often used to load the spring. 
   A similar problem arises in a power release application wherein, typically, a lever has to be actuated to move from a first position to a second position. For example, in a trunk release application, a motor is connected to an output arm which drives a release pall from a first position to a second position in order to release a trunk latch. In this case, the output arm is typically biased via a spring to cause the output arm to automatically return to its initial position in order to restart the sequence. Again, it would be desirable to actuate the output arm on the return stroke without having to backdrive the motor. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the invention a power actuator assembly for a latch is provided which includes first and second articulated levers. The first lever includes at least one cam follower and the second lever includes a stop member which pivots between first and second positions as each lever travels between first and second positions. A motor-driven cam having at least one driving member and at least one cam stop member drives the first lock lever. More particularly, the driving member has a path of travel which is in engaging alignment with the cam follower for a portion of travel and is in disengaging alignment with the cam follower for another portion of travel. The cam stop member abuts the stop member of the second lever when the cam driving member is in the non-aligned position, whereby the levers may be activated without driving the cam. 
   Automotive latches generally have two articulated lock levers which are employed as the first and second levers of the actuator assembly when it is employed in a lock/unlock application. Generally speaking, a cam drives one of the lock levers while the other lock lever stops the cam in a position where manual locking/unlocking can be performed without back-driving the motor. 

   
     DESCRIPTION OF THE DRAWINGS 
     In drawings that illustrate the preferred embodiments of the present invention: 
       FIG. 1A  is a perspective view of a power/manual lock actuator assembly of the present invention in a first operative position; 
       FIG. 1B  is a perspective view of the actuator assembly of  FIG. 1A  in a second operative position; 
       FIGS. 2A and 2B  are perspective views of the cam of  FIG. 1 ; 
       FIG. 3  is a perspective view of an inside lock lever of the assembly of  FIG. 1 ; 
       FIG. 4  is a perspective view of an outside lock lever of the assembly of  FIG. 1 ; 
       FIG. 5  is a perspective view of the lock actuator assembly from a reverse perspective from the view in  FIGS. 1A &amp; 1B ; 
       FIG. 6  a plan view illustrating the travel of the cam and outside lock lever of the embodiment of  FIG. 1 ; and 
       FIGS. 7A-E  are schematic plan views illustrating the operation of a second embodiment of the invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Many automotive latches have two articulated lock levers—one lever connected to the outside lock and one for the inside lock. These levers are usually oriented along two orthogonal planes. Examples of such latches can be found in U.S. Pat. Nos. 5,899,508; 5,000,495; and 6,254,148. 
   The embodiment shown in  FIGS. 1-6  employs a cam to drive one of the lock levers and the other lock lever to stop the cam in a position where manual locking can be performed without back-driving the motor. 
   Referring to  FIGS. 1A and 1B , the actuator assembly  10  of the present invention includes the following major components:
         a motor  12     a gear train assembly  14     a cam  16 , having driving members  18 A,  18 B and cam stop members  20 A,  20 B   a first (inside) lock lever  24 , including a rocker  26  having a stop  28     a second (outside) lock lever  30 , including cam follower surfaces  32 A,  32 B (see  FIGS. 4 and 6 )       

     FIGS. 2A and 2B  are isolated views of the cam  16  from opposing perspectives which show the cam stop members  20 A,  20 B ( FIG. 2A ) and cam driving members  18 A,  18 B in greater detail. 
     FIG. 3  is an isolated view of the inside lock lever  24 . In this embodiment, lock lever  24  is intended for operative connection to an inside lock of the vehicle, i.e., the lock accessible from the interior of the vehicle. 
     FIG. 4  is an isolated view of the outside lock lever  30 , including cam follower surfaces  32 A,  32 B. Lock lever  30  is intended for operative connection to an outside lock of the vehicle, e.g., a key cylinder accessible from the exterior of the vehicle. 
   Motor  12  is mounted on a latch (not illustrated) in a conventional manner. Motor  12  has a shaft having a pinion  13 . 
   Gear train assembly  14  comprises a plurality of gears rotatably mounted relative to the latch in a conventional manner. The number and size of gears that are selected are utilized in a manner well known in the art. 
   Cam  16  is rotatably mounted relative to the latch. Cam  16  preferably rotates about an axis that is orthogonal to an axis of rotation of the motor shaft. Cam  16  is generally disc shaped, having a circular periphery with a series of teeth thereon for driving engagement with the gear train  14 . As is apparent, driving rotation of the motor  12  rotates the cam  16 . 
   Cam  16  has two opposite faces. On one face, cam  16  has a pair of driving members  18 A and  18 B that are diametrically opposed to one another. The opposite face has a pair of cam stop members  20 A and  20 B that are diametrically opposed to one another. 
   Inside lock lever  24  is pivotally mounted relative to the latch. Lock lever  24  pivots about an axis that is orthogonal to both the motor shaft axis and the cam axis. Normally, a mounting plate extends from the latch to facilitate mounting of the lock lever  24 . 
   Inside lock lever  24  is conventionally shaped to provide operative connections to an inside locking mechanism and operatively connect to the latch. Inside lock lever  24  is pivoted with a stop member  28  that is connected thereto by a hollow shaft  26 . Pivotal movement of the inside lock lever  24  responsively pivots the stop member  28  between first and second positions. Inside lock lever  24  also has a pair of feet defining a fork  36 . 
   Outside lock lever  30  is pivotally mounted relative to the latch. Lock lever  30  pivots about an axis parallel to the axis of the cam  16 . Outside lock lever  30  has a tab  31  that operatively connects the lever  30  to the outside locking mechanism, in a manner well known in the art. Outside locking lever  30  has an arm  33  extending from a collar  35 , provided to facilitate the pivotal mounting. Located on the distal end of the arm  33  are opposed cam follower surfaces  32 A and  32 B. Additionally, a ball  34  extends from the arm  33 . 
   Inside lock lever  24  is operatively interconnected with the outside lock lever  30  via ball  34  and fork  36  linkage  38 . In the illustrated embodiment, the levers  24  and  30  are at one extremity of travel in  FIG. 1A  and at an opposite extremity of travel in  FIG. 1B . Arrows  40  show the motions of the levers  24 ,  30  when actuated. Similarly, in  FIG. 1A  the cam  16  is at one extremity of its travel and  FIG. 1B  the cam is at an opposite extremity of its travel. Consequently in  FIG. 1A  the cam  16  rotates in a direction  42  and in  FIG. 1B  the cam  16  rotates in opposing direction  42 ′. 
   The motor  12  is actuated in one sense to drive the cam  16  in one direction and in the other sense to drive the cam  16  in the other direction, as explained in greater detail below. 
   In  FIG. 6 , the position of the cam  16  corresponds to that shown in  FIG. 1A . In order to reach this position, the cam  16  and lock levers  24 ,  30  were initially in the position shown in  FIG. 1B . The motor  12  is interconnected to the cam  16  via the gear train  14 , so the motor is actuated to cause the cam  16  to rotate in direction  42 ′ ( FIG. 1B ). As the cam  16  rotates, the cam driving member  18 B engages the cam follower surface  32 B of the outside lock lever  30  (as seen best in  FIG. 6 ). The cam driving member  18 B follows an arcuate path  42 ′ defined by cam  16  and the cam follower surface  32 B follows a different arcuate path  46  (See  FIG. 6 ). Consequently, the cam driving member  18 B eventually disengages from the cam follower surface  32 B, as shown best in  FIG. 6 . As seen best in  FIGS. 1A and 6 , the cam  16  is prevented from further revolution by the cam stop member  20 B which abuts the stop member  28  of shaft  26 . 
   At this point, with the cam driving member  18 B being in disengaged alignment with the outside lock lever  30 , either lock lever  24 ,  30  (the two being articulated, as described above) is free to travel reversely (to the left in  FIG. 6 ) without driving the cam  16 . The housing, not shown, prevents the lock levers  24 ,  30  from continuing to travel along the arcuate path  46  (clockwise in  FIG. 6 ). Consequently, the vehicle may be manually locked, or unlocked, as the case may be, without back driving the motor  12 . 
   In one embodiment a sensor (not shown) may be employed to determine the position of the outside lock lever  30  relative to the cam  16 . This enables control logic to determine the rotational sense required of the motor. Thus, for instance, if the levers  24 ,  30  are manually reversed in  FIG. 6 , the cam follower face  32 A will be positioned adjacent to the cam driving member  18 A. At the same time, due to the rigid connection between the rocker  26  and the inside lock lever  24 , the rocker  26  pivots such that cam stop member  20 A abuts stop member  28 : On the next power cycle, the control logic actuates the motor  12  to drive the cam  16  clockwise in  FIG. 6  such that cam driving member  18 A engages cam follower surface  32 B of the outside lock lever  30 . 
   Alternatively, if the lock levers  24 ,  30  are not manually activated or are manually returned to the position shown in  FIG. 6 , on the next power cycle the control logic actuates the motor  12  to drive the cam  16  counterclockwise in  FIG. 6 . In this case, the cam driving member  18 B engages cam follower surface  32 A to reverse the lock levers  24 ,  30 . Simultaneously, the rocker  26  pivots such that the cam stop member  20 B abuts stop  28  as shown in  FIG. 1B  to prevent continued travel of the cam. The operation of the actuator  10  henceforth is similar to that already described with respect to the other operating position shown in  FIGS. 1A and 6 . 
   In an alternative embodiment the sensor can be omitted. If the device  10  is in the locked position and the motor is drive in the locking sense, the motor will stall since cam stop member  20 A or  20 B abuts the stop member  28  of rocker  26 . Similarly, if the device  10  is in the unlocked position and the motor is driven in the unlocking sense, the motor will stall since earn stop member  20 A or  20 B abuts the stop member  28  of rocker  26 . 
   The outside lock lever  30  includes a passage  50  sized to accept a shaft  48  of cam  16  without interference from the travel of the lock lever  30 . 
   While the illustrated embodiment has shown the cam  16  driving the outside lock lever  30  and the rocker  26  connected to the inside lock lever  24 , it will be appreciated that in the alternative the cam  16  can drive the inside lock lever  24  with the rocker  26  being connected to the outside lock lever  30 . 
   The illustrated embodiment offers following advantages:
         a) No additional parts are required—the inside lock lever  24 , outside lock lever  30  and a power actuator such as the motor  12  and gear train  14  or a solenoid or pneumatic arrangement are part of the lock mechanism. The illustrated embodiment includes a novel arrangement forcing the levers  24  and  30  to stop at a desired position. No clutch part(s) has to be added.   b) Since a return spring is not used, full motor torque can be utilized for locking/unlocking instead of winding the spring.   c) The mechanical advantage changes with travel. At the beginning of travel where more force is needed the advantage is larger and at the end of the travel where a toggle spring (not shown) helps move the levers the ratio decreases. The toggle spring is positioned between one of the lock levers and the housing. The spring biases the lock levers to one of its two positions/extremities of travel, depending on position/extremity is closer. In conventional gear mechanisms the mechanical advantage ratio is constant throughout full travel.       

     FIGS. 7A-7D  illustrate an alternative embodiment of the invention wherein the levers of the actuator assembly lie in the same plane. More specifically, these drawings show an actuator assembly  100  comprising a cam  102  having a plurality of pin-shaped cam driving members  104 A . . .  104 D (which, in the drawings, extend upward from the cam body) and a plurality wedge-shaped cam stop members  106 A . . .  106 D (which, in the drawings, extend downward from the cam body). A power actuator, not shown, engages the cam  102  to rotate it either clockwise or counterclockwise about axis  107 . 
   The assembly  100  includes a first lever  108  that rotatably pivots about axle  110  and a second lever  112  that rotatably pivots about an axle  114 . The first and second levers are articulated via a pin  116  extending from the first lever  108  that engages a slot  118  present in the second lever  112 . The first lever  108  includes an arcuate-ridge cam follower  120 , and the second lever  112  includes tabs  122 A,  122 B that function as lever stop members. 
   In this embodiment the first lever  108  functions as an output lever and the second lever  112  functions to limit the travel of the first lever  108 . More particularly,  FIG. 7A  shows the actuator assembly  100  in a first operative position wherein tab  122 B abuts wedge-shaped cam stop member  106   d . As a result of the articulated linkage between the first and second levers  108  &amp;  112 , the first lever  108  cannot be rotated counterclockwise in the drawing. However, as the pin-shaped cam driving member  104 B is not in engaging alignment with the arcuate-ridge cam follower  120 , the first and second levers  108  &amp;  112  are free to be manually driven to a position shown in  FIG. 7E , without having to actuate the cam  102  and thus without having to energize or backdrive the power actuator or motor. 
   Referring back to  FIG. 7A , the cam  102  may be actuated to rotate clockwise in the drawings. As seen in  FIG. 7B ,  7 C &amp;  7 D, as the cam  102  is rotated, the pin-shaped cam driving member  104 B has a path of travel which is in engaging alignment with the arcuate-ridge cam follower  120  for a portion of the travel path. More specifically,  FIG. 7B and 7C  show the pin-shaped cam driving member  104 B engaging the arcuate-ridge cam follower  120 , causing the first and second levers  108  &amp;  112  to rotate clockwise toward a second position shown in  FIG. 7D . In  FIG. 7D , the pin-shaped cam driving member  104 B is in a disengaged alignment with the arcuate-ridge cam follower  120 . Contemporaneously, tab  122 A abuts the wedge-shaped cam stop member  106 D, preventing the first lever  108  from rotating clockwise any further yet enabling the first and second levers  108  &amp;  112  to be manually driven in a counterclockwise direction without the necessity of actuating the cam  102 . 
   The operation of the actuator assembly  100  is similar as the cam  102  is driven in the counterclockwise direction from the second position shown in  FIG. 7D  to the first position shown in  FIG. 7A . 
   The actuator assembly  100  can be employed in a latch power lock/unlock application wherein the first, output, lever  108  is a lock lever (inside or outside). Alternatively, the actuator assembly  100  can be employed in a power release application wherein the first, output, lever  108  can be used to engage a pawl release lever. In this case, once the power actuator moves the first lever  108  to the second position, the first lever may be urged backed to the first position by a loaded spring  130 , shown in phantom in  FIG. 7E . In this application, because the cam  102  is always driven in one rotational direction, the cam driving members  104 A . . . D serially drive the first lever  108  on subsequent cycles of operation. 
   Those skilled in the art will appreciate that a variety of modifications may be made to the embodiments described herein without departing from the spirit of the invention.