Abstract:
An electromechanical actuator including an output shaft structure coupled to an output gear to allow relative motion therebetween upon application of a predetermined level of force to the output shaft structure. The relative motion opens a normally closed conductive path between a motor for driving the output gear and a power supply input terminal. Integrated position control is provided whereby the conductive path is opened at limits to the range of motion for the output shaft established by location of the ends of stationary contacts. A fuel filler valve system and a method of providing pinch protection are also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application claims the benefit of the filing date of U.S. Provisional Application No. 60/188,742 filed Mar. 13, 2000, the teachings of which are incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to an electromechanical actuator for driving a mechanism between open and closed positions.  
         BACKGROUND OF THE INVENTION  
         [0003]    Automation of fuel filling has been the subject of interest in the automotive industry. In this regard, automatic fuel filler doors, which automatically open and close to allow access to a vehicle fuel filler, are envisioned. In one design, such a door may include a valve, such as a ball valve, which rotates under the control of an actuator to allow access to the fuel filler port. Importantly, the actuator should reliably rotate the valve from the closed position to the open position to permit fueling the vehicle and then drive the mechanism or valve back to the closed position.  
           [0004]    An anti-pinch safety feature may also be required for protecting against a shearing effect created as the valve rotates to close the fuel filler port. For example, absent anti-pinch protection fingers may be injured if inadvertently placed in the port while the door is closing. In addition, system damage may occur, if for example, the door is closed on a gasoline pump nozzle or other robust obstruction.  
           [0005]    Unfortunately, merely by limiting the amount of force applied to the valve by the actuator is not a viable solution to the safety hazard associated with closure of the valve. Despite the need to provide safe conditions during closing, it also necessary to close the valve with sufficient force to work with system features such as seals and gaskets that provide resistance or that need to be compressed by the actuator during some portion of the operation. Also, environmental conditions such as temperature extremes, dust, dirt and ice should not cause the unit to become inoperable due to the actuator not generating sufficient closure force. It may also be desirable for the actuator to firmly hold the ball valve against positive stops. For these and other related reasons, it is not viable to provide for safe operation merely by using a low force actuator.  
           [0006]    Accordingly, there is a need in the art for an actuator that provides an efficient and reliable anti-pinch protection that interrupts normal operation under certain load conditions. There is a further need in the art for an actuator that safely and reliably closes a valve mechanism for an automotive fuel filler port.  
         SUMMARY OF THE INVENTION  
         [0007]    An electromechanical actuator consistent with the invention includes an electric motor and a conductive path normally connecting the motor for receiving a power supply input. An output gear is coupled to an output shaft of the motor, and an output shaft structure is coupled to the output gear to allow relative motion between the output shaft structure and the output gear upon application of a predetermined level of force to the output shaft structure. The relative motion between the output gear and the output shaft structure opens the conductive path. Integrated position control is provided by configuration of stationary contacts whereby the conductive path is opened at limits to the range of motion for the output shaft established by location of the ends of the stationary contacts.  
           [0008]    A fuel filler valve system consistent with the invention includes a valve disposed between a vehicle fuel filler port and a vehicle fuel tank, and an actuator consistent with the invention for moving the valve between the open and closed positions. A method of providing pinch protection in a movable mechanism consistent with the invention includes coupling the mechanism to an actuator consistent with the invention, and energizing the actuator motor to drive the mechanism. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    Advantages of the present invention will be apparent from the following detailed description of exemplary embodiments thereof, which description should be considered in conjunction with the accompanying drawings, in which:  
         [0010]    [0010]FIG. 1 is a perspective cut-away view of an exemplary fuel filler system consistent with the invention;  
         [0011]    [0011]FIG. 2 is a perspective view of an exemplary actuator consistent with the present invention;  
         [0012]    [0012]FIG. 3 is a partially exploded view of an exemplary output gear and output shaft structure portion of an actuator consistent with the invention;  
         [0013]    [0013]FIG. 4 is a perspective view of the wipers and stationary contacts of the actuator assembly shown in FIG. 1;  
         [0014]    [0014]FIG. 5 is a perspective view of another embodiment of an actuator consistent with the invention;  
         [0015]    FIGS.  6 - 8  are plan views of alternative exemplary stationary contact arrangements for an actuator consistent with the invention;  
         [0016]    FIGS.  9  illustrates an exemplary operator control switching scheme for an actuator consistent with the invention;  
         [0017]    [0017]FIG. 10 is a perspective view illustrating an exemplary mounting arrangement for an actuator consistent with the invention relative to a ball valve assembly wherein the actuator is mounted for manual override;  
         [0018]    [0018]FIG. 11 is a perspective view of the exemplary manual override cap illustrated in FIG. 10; and  
         [0019]    [0019]FIG. 12 is a perspective view of the exemplary top housing portion illustrated in FIG. 10. 
     
    
     DETAILED DESCRIPTION  
       [0020]    Referring to FIG. 1, there is illustrated an exemplary automotive fuel filling system  1  including a valve assembly  25  and an actuator  10  consistent with the present invention. Although the present invention will be described in connection with a specific embodiment of a fuel filling system, those skilled in the art will recognize other system configurations where an actuator consistent with the present invention may be utilized. It is to be understood, therefore, that the embodiments described herein are described by way of illustration, not of limitation.  
         [0021]    In general, the valve assembly  25  may be mounted to a vehicle  3  for controlling access to the vehicle fuel tank  5 . In the illustrated embodiment, the actuator  10  reliably and safely drives a ball valve  13  of the valve assembly  25  between open and closed positions. When the valve  13  is in an open position, access to the fuel tank is permitted, allowing a user to fill the tank. When the valve is in a closed position, the valve securely closes the passageway to the fuel tank. Operation of the actuator to achieve an open or closed valve position may be controlled via a switch  15 , e.g. in the vehicle passenger compartment, which controls connection of a power supply  17 , e.g. the vehicle battery, to the actuator.  
         [0022]    Referring to FIGS. 2 through 4, an exemplary embodiment of an actuator  10  consistent with the invention is illustrated. Those skilled in the art will recognize that the actuator  10  may be disposed within a housing  11 , as shown in FIG. 1. In FIGS.  2 - 4 , only a bottom portion  41  of the housing is shown to allow for simplicity and ease of explanation.  
         [0023]    As shown, the actuator  10  may include a motor  12  that drives an output gear  14  through a gear train  16 . Those skilled in the art will recognize that a wide variety of gear trains  16  may be used to drive the output gear  14 . In the illustrated exemplary embodiment, however, the gear train includes a motor worm gear  20 , a spur gear  22  and a worm gear  24  in meshing engagement with the output gear  14 .  
         [0024]    With particular reference to FIG. 3, a pinch protection feature may be accomplished through relative motion between the output gear  14  and an output shaft structure  18  that is coupled to the valve assembly  25  for driving the valve  13  between open and closed positions. Generally, in a pinch protection condition an obstruction to closure of the valve  13  imparts a force to the output shaft structure  18  that causes relative motion between the structure and the gear  14 . This relative motion breaks a normally closed electrical connection between the power supply  17  and the motor  12  to disconnect the motor from the power supply  17  and stop the actuator.  
         [0025]    In the illustrated embodiment, the output gear  14  is coupled via a shaft  21  to the output shaft structure  18  so that the two parts  14  and  18  are coaxial. The gear  14  and shaft structure  18  are biased against each other through use of a torsion spring  26 . The spring  26  may be installed between the output gear  14  and the output shaft structure  18  with a specific preloaded force.  
         [0026]    In one embodiment output shaft electrical contacts or wipers  30 ,  32 ,  34  may be attached to a radial extension  23  of the output shaft structure  18 , and a corresponding set of output gear contacts or wipers  42 ,  44 ,  46 , may be attached to a radial extension  27  the output gear. The wipers  30 ,  32 ,  34  move in tandem with the output shaft structure  18  at all times. The output shaft wipers  30 ,  32 ,  34  and the output gear wipers  42 ,  44 ,  46  interact with each other as well as with stationary contacts, e.g. contacts  36 ,  38 ,  40  in FIG. 4 that are fixed to the bottom  41  of the housing  11 . The wipers may be spring temper stampings. In the embodiment illustrated in FIGS.  2 - 4 , the wipers  30 ,  32 ,  34  and  42 ,  44 ,  46  are normally in contact, as shown in FIG. 4, but separate upon relative motion between the output gear  14  and the output shaft structure  18  to open an electrical path between the power supply and the motor, as will be described in more detail below.  
         [0027]    In another embodiment  10   a  illustrated in FIG. 5, opening and closing of the motor/power supply connection is achieved by relative motion of the output gear  14   a  and the output shaft structure  18   a , except the wipers  42 ,  44 ,  46  are not provided on the output gear  14   a . Instead, cam contacts or wipers  48 ,  50  may be provided on the extension  23   a  of output shaft structure  18   a . In the embodiment illustrated in FIG. 5, the wipers  48 ,  50  and  30 ,  32 ,  34  are moved into and out of contact with each other by engagement and disengagement of the wipers  48 , 50  with cam lobes  52 ,  54  on the output gear  14   a.    
         [0028]    More particularly, when the actuator is driving a mechanism, e.g. the valve  13 , from an open to a closed position, the gear train  16  drives the output gear  14   a , which transmits torque to the output shaft structure  18   a  through the torsion spring  26 . Under normal operating conditions, the output shaft structure  18   a  is free to turn with less torque than that required to overcome the preloaded force of the torsion spring  26 . The output gear  14   a  and output shaft structure  18   a  thus behave as one piece, and the cam lobes  52 ,  54  force the wipers  48 ,  52  into contact with the wipers  30 ,  32 ,  34  on extension  23   a . It is intended that the normal operating torque for the valve  13  be below the torque provided by the preloaded spring  26  so that the system will behave as described under ordinary circumstances.  
         [0029]    If the valve encounters an obstruction when being closed (such as a finger or fuel filler nozzle), then the output shaft structure  18   a  may stop rotating. Since the motor  12  may still be providing power through the gear train  16 , the output gear  14   a  may continue to move. This may result in relative motion between the output gear  14   a  and the output shaft structure  18   a  and corresponding deflection of the torsion spring  26 . Calibration of this pinch protection trip point may be achieved by varying the designed force characteristics of the spring.  
         [0030]    As the output gear  14   a  rotates relative to the output shaft structure  18   a , it also rotates relative to the wipers  48 ,  50  disposed on the output shaft structure  18   a . As the output gear  14   a  progresses through this relative rotation, the cam lobes  52 ,  54  on the face of the output gear move relative to the wipers  48 , 50 . These cam lobes  52 ,  54  are shaped and positioned in such a manner as to predictably release the wipers allowing them to spring apart from the wipers  30 ,  32 ,  34  on extension  23   a  that they were being held in contact with. The motor connection circuit is arranged in such way that if the system is in a “Pinch Protection Zone” this separation of the wipers interrupts the supply of electrical power to the motor  12  and the output gear  14   a  will cease to rotate. As long as the obstruction remains, this relationship may be maintained because the output gear  14   a  may be driven by a worm drive that has a small lead angle so that it is resistant to being back-driven by the spring.  
         [0031]    When the obstruction is removed, the spring  26  may release stored energy and drive the output shaft structure  18   a  relative to the output gear  14   a . The output shaft structure  18   a  may align with the output gear  14   a , and the ordinary and usual relationship between the parts may then be restored. When this occurs, the cam lobes  52 ,  54  on the output gear may have moved back into proximity with the wipers  48 ,  50  respectively, and the wipers  48 ,  50  and  30 ,  32 ,  34  may once again be held in contact with each other. This action restores the supply of electrical power to the motor and the actuator may resume closing the mechanism.  
         [0032]    The arrangement of the stationary electrical contacts on the housing may vary. Exemplary arrangements are illustrated in FIGS.  6 - 8 . The range of motion defining the operational zones, e.g. the “Pinch Protection Zone”, for the actuator may vary depending on the specific configuration of the stationary contacts. It may be desirable, however, to have the pinch protection scheme employed in the range of motion where an object could become trapped between an edge of the opening in the stationary valve housing and an opposing edge in the moving portion of the valve mechanism.  
         [0033]    With reference to the exemplary embodiment illustrated in FIG. 6, for example, the wipers  30 ,  32 ,  34  may travel relative to the stationary contacts  36 ,  38 ,  40  between an open position indicated by line  150  and a closed position indicated by line  152 . When traveling from a closed to an open position as indicated by arrow  154 , the stationary contacts  36 ,  38 ,  40  are maintained in contact with the wipers  30 ,  32 ,  34  to ensure full torque from the motor.  
         [0034]    However, when traveling from an open position to a closed position as indicated by arrows  156  and  158  pinch protection may be enabled in a first zone referred to as zone A. In this zone relative motion between the output gear  14 ,  14   a  and the output shaft structure,  18 ,  18   a , disconnects the motor from the power supply to provide pinch protection. Once the closing valve has gone beyond the region where it presents an opening where an object could become trapped, it may no longer be desirable to have active pinch protection. In fact, it may be desirable to have the full power of the system available to provide power for compression of seals, driving the system firmly against fixed stops or for other system needs. The invention may accommodate this need by providing a second zone, i.e. zone B, where the pinch protection feature is disabled.  
         [0035]    When the wipers  30 ,  32 ,  34  are positioned on the stationary contacts in zone B. if the output shaft encounters high resistance torque (torque greater than that available form the preloaded torsion spring), e.g. from seals, hard stops, etc., the output gear  14   a  may begin to rotate relative to the output shaft structure  18   a , just as in the preceding description of the pinch protection feature. However, within zone B, the arrangement of the stationary contacts  36 ,  38 ,  40  differs so that even though the wipers  48 , 50  spring apart and loose contact with each other, electrical power to the motor is not interrupted. This results in the motor continuing to drive the system.  
         [0036]    The output gear  14   a  may continue to rotate relative to the output shaft structure  18   a  and deflect the torsion spring  26  until it reaches a rigid interface point with the output shaft, e.g. until a rigid stop  62  on the output shaft structure  18   a  contacts a rigid stop  60  or  64  on the output gear  14   a . At this point, the output gear  14   a  may no longer be transmitting torque to the output shaft structure  18  through the spring  26 , but may be transmitting torque to the structure  18  through the rigid interface. The result is that the full power of the motor (less gear train inefficiency, of course) is delivered to the output shaft structure  18   a  and subsequently, the mechanism or valve.  
         [0037]    The output may resume rotating as long as the obstruction is unable to resist the torque that is now being delivered directly to the output shaft structure  18   a  (not through the spring). When the output shaft  14   a  reaches the desired closed position, electrical power to the motor  12  will be interrupted by a gap, e.g. gap  70 , or other transition in the stationary contacts. When the wiper enters this gap or transition area, electrical power to the motor is interrupted and the rotation of the system stops.  
         [0038]    When the actuator is driving the mechanism from the closed to the open position, the motor  12  and gear train  16  may drive the output gear  14   a . The output gear  14   a  transmits torque to the output shaft structure  18   a  through the preloaded torsion spring  26 . The pre-load torque of the spring  26  will cause the output gear  14   a  and the output shaft structure  18   a  to behave in tandem or as if they were one piece. This remains true so long as the torque required to rotate the output shaft structure (and the mechanism that it is attached to) remains below the preloaded torque of the spring.  
         [0039]    If the mechanism encounters rotational resistance higher than the preloaded torque of the spring, then relative motion will occur between the output gear and shaft, just as with operation in the closing direction. Also, as is the case with the operation in the closing direction, the relative motion is limited to a defined distance by contact of the output gear with a rigid interface  62  on the output shaft structure. This defeats the spring and causes the gear to act directly upon the shaft. For the opening direction, the cam lobes  52 , 54  are shaped so that the wipers  48 , 50  and wipers  30 , 32 , 34  remain held in contact with each other so that electrical power to the motor is not interrupted and the actuator will continue to drive the mechanism.  
         [0040]    The spring feature is utilized in the opening direction primarily as a shock absorber to cushion the gear train  16  from loads that would occur by any abrupt obstruction of the output shaft or from reaching an end-of-travel stop. When the ball reaches the end-of-travel stop (the fully open position) the output shaft structure  18   a  will not be able to continue rotating. The motor will have shut down because, just as in the other direction, there will be a gap, e.g. gap  72 , or other transition in the stationary contacts that the wiper will ride into, breaking electrical continuity to the motor. The spring  26  will absorb any remaining energy (“coast”) due to inertia of the moving system.  
         [0041]    Control of the actuator in its operational zones is thus accomplished through internal switching. The control switches allow the actuator to complete its last command. For example, if the pinch protection feature is activated, the obstruction that caused it can remain in place indefinitely without causing damage to the motor since the pinch protection mechanism breaks the electrical circuit. Due to the spring  26 , the mechanism will reset automatically when the obstruction is removed and the actuator will complete its instruction to close the valve. This instruction may be provided by selectively supplying electrical power, e.g. through switch  15 , to the stationary contacts through an electrical connector that is part of the actuator.  
         [0042]    Turning now to FIG. 9, an operator control switching scheme is illustrated. In the illustrated embodiment, the actuator may be energized to open or close using a double-pole/double through (DPDT) relay  200 . The relay facilitates connection of the power supply  17 , e.g. 12 VDC, through a fuse  202  to contact points  160 ,  162 , and  164  depending on the position of the control switch  15 . The connections established by the relay  200  as a function of the switch position may be as set forth in Table 1 below:  
                                             TABLE 1                                   Open   Close           Door   Door                                        Control Switch 15   Closed   Open           Contact 160   12 VDC   Open           Contact 162   Open   Ground           Contact 164   Ground   12 VDC                      
 
         [0043]    The contact points  160 , and  162  are electrically connected to stationary contacts  40 ,  38 , as shown in FIG. 6, and contact  164  is electrically connected to a first motor input terminal with the other motor terminal connected to stationary contact  36 . In normal mode, the output shaft and output gear structure rotate together, and the power supply is connected across the motor  12  through wipers  30 ,  32 ,  34  and wipers  48 ,  50 , which connect either stationary contact  40  (and contact  160 ) to stationary contact  36  in the opening direct ion, or stationary contact  38  (and contact  16   2 ) to stationary contact  36  in the closing direction.  
         [0044]    In the closing direction, when an obstruction prevents the mechanism from closing, the output shaft structure  18   a  stops rotating, the drive gear continues to move, and the cams  52 ,  54  release the wipers  48 ,  50  from the wipers  30 ,  32 ,  34 . This may cause one of two events. In the pinch protection zone, continuity between contact  38  (and  162 ) and  36  is interrupted. The motor stops until the obstruction is removed. When the obstruction is removed, alignment between the output gear  14   a  and the output shaft structure  18   a  is restored by the spring  26 , and normal function returns. Beyond the pinch protection zone continuity is maintained between contacts  38  and  36  and the actuator drives to the closed position.  
         [0045]    Similar operation may be achieved using the alternative stationary contact configurations illustrated in FIGS. 7 and 8. In those configurations, the wipers  30 ,  32 ,  34  engage/disengage associated stationary contacts to achieve the above-stated functions. Those skilled in the art will recognize that a variety of stationary contact and wiper configurations may be utilized in an actuator consistent with the invention. It is to be understood, therefore, that the exemplary configurations provided herein are provided by way of illustration, but not of limitation.  
         [0046]    Consistent with the invention, therefore, the stationary contacts define the limits of the open and closed positions, and the actuator stops when these positions are reached. This is significant because it prevents motor degradation that would occur more quickly if the actuator were driven to stall every time. In the absence of this feature, control would have to be more sophisticated with a timed source of current. Also, driving the system to a hard internal stop every time would increase fatigue on the gear train. Current draw would be higher when the motor stalled.  
         [0047]    A manual override may also be provided to account for actuator failure or electrical power loss. This feature may allow the actuator to be manually driven to open the valve allowing for fuel delivery. The manual override may also facilitate manual closure of the valve, but the preferred action upon actuator failure with the valve in the open position may be replacement of the system. Advantageously, the manual override may be designed so that the actuator can “self heal” when re-powered by back-driving (rotating in reverse) itself and dropping into mounting detents at the completion of cycle.  
         [0048]    An exemplary manual override arrangement is illustrated in FIGS.  10 - 12 . As shown in FIG. 10, the actuator housing  11  may include a top housing portion  115  and a bottom manual override cap  102  secured to the valve assembly  25 . The cap  102  is illustrated more particularly in FIG. 11. In the illustrated embodiment, the cap generally includes the circular bottom panel portion  41  and an axially extending perimeter sidewall  122 . The bottom portion includes portions  128  defining an aperture through which an input shaft of the ball valve assembly  25  may extend for coupling to the actuator output shaft structure  18 ,  18   a . The sidewall includes key slots for receiving associated locking tabs  108  on the top portion  115 .  
         [0049]    As shown in FIG. 12, the top housing portion  115  may include a first large diameter cylindrical portion  132  with a concentric small diameter cylindrical portion  134  disposed thereon. The large diameter cylindrical portion  132  may include a sidewall  120  with the locking tabs  108  extending radially from an exterior surface  124  thereof. The tabs  108  may be generally rectangular in shape with a chamfered forward edge  132 . The top portion  115  may be concentrically and rotatably arranged relative to the cap  102 , with the interior surface  120  of the cap side-wall  122  disposed adjacent to the exterior surface  124  of the top portion side wall  126  as shown in FIG. 10.  
         [0050]    In normal operating mode, a locking tab  108  on the actuator housing engages a corresponding retention ramp  110  on the cap to prevent rotation of the top portion  115  relative to the cap  102 . In manual override mode, however, the top portion  115  may be manually rotated, e.g. by operation of an override cable accessible through the vehicle trunk or passenger compartment and connected to an override arm extending from the top portion  115  of the housing. Rotation of the top portion causes sufficient rotation of the output shaft to open the valve. Rotation of the top portion during manual override is arrested by engagement of the locking tab  108  with a manual override position stop  112 . Advantageously, due to the bias force established by the spring  26  the mechanical override self-heals by returning to the normal position upon energization of the actuator following a mechanical override.  
         [0051]    In an actuator consistent with the invention, therefore, pinch protection is enabled in a simple and efficient manner. Other methods that are sometimes employed are more elaborate solutions using, for example, electronic sensors that can detect the presence of objects. The present invention, however, employs a method that is simple and cost effective and accomplished through electromechanical means rather than with electronics. This translates lower cost through less expensive components and simplified assembly and test.  
         [0052]    Also, since the actuator moves to an open or closed position and then turns itself off, automatic control is facilitated in an efficient manner. This means that the actuator could, for example, be electrically connected to a vehicle park interlock so that the fuel door will automatically close upon placing the vehicle in gear. The actuator could also be configured so that the ignition had to be off to permit opening. Essentially, the automated control allows the control of the actuator based on a variety of conditions and inputs.  
         [0053]    The invention has applicability beyond the scope of fuel filler access. This system may find utility in the operation of any valve. In fact, the actuator would find utility in any device requiring movement of a mechanism while providing an anti-pinch feature that is active throughout the full range of motion of the actuator or within a specific range of the motion. Further, by converting the rotating members of the design to a “sled” assembly, a linear version could be made that employs these same unique features.  
         [0054]    The embodiments that have been described herein, however, are but some of the several which utilize this invention and are set forth here by way of illustration but not of limitation. It is obvious that many other embodiments, which will be readily apparent to those skilled in the art, may be made without departing materially from the spirit and scope of the invention as defined in the appended claims.