Abstract:
A system and method are disclosed for controlling the opening and closing of a closure panel for a vehicle. The system includes a power actuator having a motor for opening and closing the closure panel. A lift-assist member cooperates with the power actuator and is operated by a controller that controls the operation of the power actuator. A circuit monitors current draw of the motor and signals the controller when the current required for opening the closure panel exceeds a predetermined level to prevent operation of the power actuator. The position of the closure member may be monitored by an encoder, or angle sensor, associated with the motor to detect whether the closure member is falling and actuate a system that prevents rapid movement of the closure member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 61/974,104 filed Apr. 2, 2014, the disclosure of which is hereby incorporated in its entirety by reference herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to a control system for a power actuated vehicle closure member that controls vertical movement of the closure based, in part, upon the level of current required to operate a motor used to operate the vehicle closure member. 
     BACKGROUND 
     Vehicles are provided with closure members that are opened by lifting to provide access to the vehicle interior, such as lift gates, tailgates, deck lids, and the like. Power actuators are used to move such closure members at the push of a button on the dashboard, on a key fob, or by movement in front of a sensor. Power actuators generally include an electric motor and a gearing set that have sufficient torque to raise and lower the closure member. Alternatively, the power actuators may be hydraulic or pneumatic cylinders that have motor driven fluid pumps. 
     Torsion bars, air spring cylinders, tension springs, counterbalance struts, or other lift-assist mechanisms are used to reduce the load on the power actuator that is used to raise and lower the closure member. As power actuators are generally tuned off after opening to conserve battery power, while the lift-assist holds the closure open. Lift-assist mechanisms may be damaged, disconnected, or otherwise become ineffective for a wide variety of reasons. 
     Power actuators may have sufficient power to lift a closure member even if a lift-assist mechanism is disabled or broken. Under some circumstances the power actuator may not be able to hold the closure member in the raised position if the closure member is manually opened, if the lift-assist mechanism breaks, or becomes inoperative. The power actuator normally stops when the closure member is fully opened. The weight of the closure member may cause the closure member to close in an uncontrolled manner under the force of gravity after the motor stops. 
     This disclosure is directed to solving the above problems and other problems as summarized below. 
     SUMMARY 
     Power operated, vertically moved closure members are raised to open and lowered to close and include lift gates, tailgates, deck lids, hoods, or tonneau covers. Power actuator motors may have sufficient torque to raise the closure member even if one or more torsion bars, air spring cylinders, counterbalance struts, or other lift-assist mechanisms are impaired or inoperative. In this situation, it is preferable to prevent the power actuator from either opening the closure member or reversing the power actuator. Alternatively, the control system for the power actuator may allow the closure member to be operated manually with a safety system being enabled to prevent rapid closing of the closure member. A diagnostic code may also be stored to indicate that a system component requires service or replacement. 
     The lifting system may be prevented from opening when the current draw profile indicates that the power actuator system is prevented from opening to avoid the situation in which the closure member unexpectedly closes because the malfunctioning components cannot hold the closure member open. The current draw profile of the malfunctioning system is monitored as a function of the level of current drawn and the position of the closure member. 
     The control system for the power actuator may be provided with a signal relating to the level of current drawn by the power actuator motor. In response to the level of current drawn signal, the control system may be programmed to prevent operation of the power actuator. A broken torsion bar causes an increase in the force required to open the closure member. Alternatively, a problem with the power actuator may also cause an increase in the force required to open the closure member. In either event, the power actuator motor requires additional current to operate. Some power operated closure members may be designed to be raised and lowered manually even if the power actuator is prevented by the controller from operating. Safety systems are disclosed that prevent rapid closing of the closure member that is manually opened. In either case, a “fail safe” condition is provided that eliminates the risk to operators who may otherwise position themselves under a falling closure member. 
     Alternatively, the closure member may be permitted to open fully when a lift-assist component is broken or only partially functional and a brake or catch mechanism may be engaged to prevent rapid closure of the closure member. Lift-assist components may include a counterbalance strut, an air or gas strut, or a torsion bar. The power actuator motor may be provided with an encoder that detects the position and changes in the position of the closure member. If the encoder detects rapid closing of the closure member, a safety system, such as a catch, clutch, or brake mechanism may be actuated or engaged. 
     According to one aspect of this disclosure, a system is disclosed for controlling the operation of a vertically moved closure panel for a vehicle. The system includes a power actuator having a motor for opening and closing the closure panel. A lift-assist member cooperates with the power actuator and is operated by a controller that controls the operation of the power actuator. A controller circuit monitors current draw of the motor providing a signal used to prevent operation of the power actuator when the current required for opening the closure panel exceeds a predetermined level, or profile, to prevent operation of the power actuator. 
     According to another aspect of this disclosure, a method is disclosed for controlling the operation of a vertically moved closure panel for a vehicle. The method comprises actuating a motor of a power actuator that moves the closure panel while measuring a level of current drawn by the motor. The level of current is compared to a predetermined level or a current profile based upon the position of the closure member as indicated by the encoder. The power actuator may be disabled if the level exceeds the predetermined level or deviates from the current profile, thereby providing an unopened closure that has failed in a safe manner for the benefit of the closure operator. 
     The method may further comprise a lift-assist mechanism that counterbalances the weight of the closure panel, and wherein the level of current drawn by the motor increases when the function of the lift-assist mechanism is impaired. According to the method, the level of current drawn by the motor increases when the function of the power actuator is impaired. For instance, when a gear box is jammed, requiring high torque to turn. 
     The above aspects of this disclosure and other aspects will be described in greater detail below with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary perspective view of the rear portion of a vehicle provided with a power lift gate having a gas or mechanical spring strut raised, or in the open, position; 
         FIG. 2  is a fragmentary perspective view of the vehicle showing an alternative power actuator holding a lift gate having a set of torsion bars in a raised position; 
         FIG. 3  is a fragmentary perspective view of a power operated deck lid with a power actuator attached between the vehicle and deck lid hinge having a gas or mechanical spring strut in the raised, or open, position; 
         FIG. 4  is a fragmentary perspective view of a controller for a power actuator; 
         FIG. 5  is a flowchart illustrating the steps followed by the controller of the power actuator system illustrating one way of practicing the concept disclosed in this application; and 
         FIG. 6  is a flowchart illustrating an alternative embodiment of the system that permits manual operation of the closure member with a catch or brake that prevents rapid closing of the closure member. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrated embodiments are disclosed with reference to the drawings. However, it is to be understood that the disclosed embodiments are intended to be merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but as a representative basis for teaching one skilled in the art how to practice the disclosed concepts. 
     Referring to  FIG. 1 , a vehicle  10  including a lift gate  12  that engages a door frame  14  in a closed position and is raised to an open position (as shown in  FIG. 1 ) to provide access to the interior of the vehicle  10 . Power actuator  16  includes a motor  17  that is actuated to move the lift gate  12 , or closure member, between the open position and the closed position. The power actuator  16  is shown in  FIG. 1  holding the lift gate  12  in the open position in conjunction with a gas cylinder  18 . The gas cylinder  18  may be generally referred to as a “lift-assist mechanism.” Other lift assist mechanisms may include a counterbalance strut, a tension spring, a combination gas/mechanical spring strut, or a torsion bar. 
     Referring to  FIG. 2 , a torsion bar  20  is shown that is interconnected between the lift gate  12  and the door frame  14  to exert a lifting force that partially counterbalances the weight of the lift gate  12 . The torsion bar is connected by torsion bar brackets  22  to the lift gate  12  and the door frame  14 . 
     In  FIG. 2 , the power actuator  16  and motor  17  are shown separated from the door frame  14  and the lift gate  12  for better visibility. The power actuator  16  and torsion bars  20  are shown with the lift gate  12  open. The torsion bars  20  apply a lifting force to the lift gate  12  to facilitate raising the closure member into its open position in conjunction with the power strut actuator  16 . A wiring connector  26  is connected by wires  28  to the power actuator  16 . Control signals for the motor  17  and system monitoring encoder signals are provided through the wiring  28  to a controller, as will be described more fully below. 
     A pivot end  30  of the power actuator  16  is connected to a pin  32  or other type of pivot connector on the door frame  14 . A rod end  36 , or extensible end, of the power actuator  16  is connected by a pivot bracket  38 , or pin, to the lift gate  12 . 
     Referring to  FIG. 3 , a deck lid  40  is shown in its open position on a vehicle  10 . The deck lid  40  is moved by a gooseneck hinge  42  between its open and closed positions. A power strut  44  is operated by an actuator motor  46  that is external to the power strut  44  in  FIG. 3 . The power strut  44  is connected at a vehicle attachment end  48  to the vehicle  10  by a pivot pin  50 , or pivot bracket. A deck lid end  52  of the power strut  44  is connected by a hinge connector pin  54  to the hinge  42  of the deck lid  40 . A tension spring  59  is one example of a list assist mechanism that may be used in cooperation with the power actuator. Other lift assist mechanisms used to cooperate with the power actuator may include a counter balance strut, a combination gas/mechanical spring strut, or torsion bars. The actuator motor  46  is connected by an electrical connector  56  through wiring  58  to the controller, as will be described below. 
     Referring to  FIG. 4 , a controller  60  that may be used with any of the embodiments of  FIGS. 1-3  is attached to the vehicle at an internal location. The controller  60  may only control the closure member or may be integrated as part of another vehicle control system. The controller  60  is attached by connectors  62  and wiring  64  to either motor  17  of the power actuator  16  (as shown in  FIG. 2 ) or the motor  46  of the power strut  44  (as shown in  FIG. 3 ). Operation of the controller  60  as it relates to controlling the power actuator  16  and motor  17 , or the power strut  44  and actuator motor  46  is described below with reference to  FIGS. 5 and 6 . 
     Referring to  FIG. 5 , a control algorithm  70  is illustrated as a flowchart to the extent that it relates to operation of the motor  17  and power actuator  16  or actuator motor  46  and power strut  44 . The controller  60  is also expected to provide other functions, such as obstruction detection, proximity sensors and other functions such as lighting control and may be otherwise integrated with the vehicle operating system. 
     With continued reference to  FIGS. 1-4  and particular reference to  FIG. 5 , the control algorithm  70  illustrated by the flowchart starts at  72 . A command to the power strut system to open or close the enclosure member is provided at  74 . The command may be from an internal switch from the dashboard of the vehicle, a key fob, a proximity sensor, or other device that may be used to control a closure function. Upon receiving the command to open or close the closure member at  74 , the controller monitors the power strut motor current draw levels at  76 . The controller  60  may also receive data from an encoder, or angle sensor (not shown), that is integral with the motor  17 ,  46 . The encoder is used to provide a reliable indication of the position of the closure member  12 . 
     In one example, the power strut motor may normally draw an expected level of current of, for example, between 6 and 10 amps. The current draw level is compared at  78  to a predetermined level of current. The predetermined level is less than the level of current drawn by the motor than if the closure member contacts an obstruction that would prevent the closure member from opening. The predetermined level of current in one example is 14 amps, but may be set a different level depending upon the calibration of the system and components. The predetermined level of 14 amps is appropriate for a power strut motor that requires a current draw level of between 6 and 10 amps. The level of current drawn by the motor may be normalized to a battery source to maintain separation of a failure mode population from a nominal population of the level of the current drawn. Alternatively, the current draw level may be compared to the data from the encoder to permit correlation of the current draw level and the encoder data. 
     The current draw level increases if the torsion bar  20  is broken or if the counterbalance cylinder  18  is broken or damaged. The current draw level may also be increased if the power strut or motor  17 ,  46  malfunctions or is damaged. By monitoring the power strut motor current draw level at  76 , it is possible to detect a malfunction of any part of the actuators  16 ,  44  or lift-assist mechanisms that causes the level of current drawn to increase, for example, to between 18 and 27 amps. 
     Depending upon the other components of the system, the extent that the current draw level increases may differ from the range in the above example. If the current draw level is not greater than the predetermined level, the controller provides a command on line  80  to the power strut motor to open or close the closure panel at  82 . 
     If the current draw level is greater than the predetermined level at  78 , the controller provides a signal on line  84  to either deactivate or reverse the power strut system at  86 . By deactivating or reversing the power strut system at  86 , the closure member  12  is prevented from being opened by the power strut system and may be limited to manual operation. In manual operation, it is important that the closure member is capable of being opened by the user so that access is still provided in a manual mode so that access is provided to the vehicle interior. 
     Once the power strut system is deactivated at  86 , a signal is sent to the controller to set a diagnostic flag at  88 . The diagnostic flag set at  88  remains effective to prevent activation of the power strut system until the system is serviced by a service technician who then can reset the diagnostic flag and enable operation of the power strut system. The number of times that the closure member may be opened after the diagnostic flag is set may be limited to a fixed number of openings, for example a manual opening may be limited to  10  times with the system locking the closure member on the eleventh attempt to be sure that the vehicle is properly serviced. 
     Referring to  FIGS. 1-4 and 6 , an alternative embodiment of a control algorithm  90  is illustrated by a flowchart. The control algorithm  90  is applicable to systems that permit manual operation of a closure member  12 . The closure member is closed at  92  until the opening cycle is initiated at  94 . The current draw of the motor is monitored at  96  and if the current drawn by the motor exceeds a threshold current level at  98 , the opening cycle of the system is stopped or reversed at  100 . If the system is stopped or reversed a diagnostic trouble code may be set at  101 . The closure member may be manually opened at  102 . 
     If the closure member is manually operated, a system for preventing rapid closing of the closure member is actuated or engaged at  104 . The encoder associated with the motors  17 ,  46  (or other closure member position sensor) may be used to monitor the position of the closure member when open so that if the closure member begins to fall, the system for preventing rapid closure may be engaged. The system for preventing rapid closing of the closure member may be a catch mechanism, a clutch, or a brake that is internal to the motor  17 ,  46 . Alternatively, the motor may be actuated to stop the motion of the lift gate or may function to close the lift gate under control by the motor  17 ,  46 . 
     If the motor current draw is not greater than the threshold at  98 , the opening cycle continues at  106  until the closure member is fully open at  108 . The encoder may be monitored at  110  to detect a rapid closing event and engage the safety system at  104 . 
     The embodiments described above are specific examples that do not describe all possible forms of the disclosure. The features of the illustrated embodiments may be combined to form further embodiments of the disclosed concepts. The words used in the specification are words of description rather than limitation. The scope of the following claims is broader than the specifically disclosed embodiments and also includes modifications of the illustrated embodiments.