Abstract:
A power liftgate drive assembly automatically moves the liftgate of a vehicle between its open and closed positions. The drive assembly is secured to the vehicle at a position near the top of the liftgate. The drive assembly includes a motor that drives a sector gear between two positions. A guide rod is secured to the sector gear to translate the rotational movement of the sector gear into the pivotal movement of the ligtgate. A slot extends through the sector gear that allows the liftgate to be moved manually. A latch locks the guide rod in position with respect to the sector gear for automated movement whereas the latch releases the guide rod to move in the slot for manual operation.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to an assembly for opening and closing a liftgate of a motor vehicle. More specifically, the invention relates to an automated assembly designed to move a liftgate of a motor vehicle between an open position and a closed position.  
         DESCRIPTION OF THE RELATED ART  
         [0002]    Motor vehicles commonly include a liftgate typically connected to the rear of the vehicle. These liftgates are pivotal between an open position and a closed position to selectively provide access to the rear compartment of the vehicle. These liftgates are typically manually operated by pivoting the liftgate about a pair of hinges between the open and closed positions. A pair of hydraulic or pneumatic cylinders are often connected between the liftgate and the vehicle to assist in the opening of the liftgate and in maintaining the liftgate in the open position.  
           [0003]    There is a desire to provide operators of motor vehicles with the ability to open and close liftgates free of manual assistance. This feature of providing power to a liftgate in a manner that moves the liftgate between its two extreme positions could be easily obtained if the task were merely to provide and remove access to a compartment within a motor vehicle. The task is, however, more extensive than that. The ability to open and close the compartment must be provided only when it is coupled with the ability to manually move the liftgate without having to provide an additional force to overcome the automation system. Further, the assembly that creates the force to automatically move the liftgate must be lightweight and minimally impact the capacity of the compartment to which the liftgate provides access.  
           [0004]    Attempts have been made to provide a power liftgate drive mechanism that will automatically raise or lower the liftgate between its open and closed positions. U.S. Pat. No. 5,448,856, issued to Moore et al. on Sep. 12, 1995, discloses a powered liftgate mechanism. This mechanism includes a motor which moves a crank arm using an assembly that includes a worm shaft and gears. While the motor provides a force to move the liftgate between its open and closed positions, it requires the assistance of gas springs or struts to move the liftgate. Little mechanical advantage is provided by the powered liftgate mechanism. Therefore, when using the mechanism disclosed in this patent, modifications to the motor vehicle are required before the liftgate mechanism may operate correctly.  
         SUMMARY OF THE INVENTION  
         [0005]    A power liftgate drive assembly moves a liftgate of a motor vehicle between an open position and a closed position. The power liftgate assembly includes a bracket that is mounted to the motor vehicle adjacent the liftgate. The drive mechanism is fixedly secured to the bracket. The drive mechanism provides a bidirectional rotational force. A gear is pivotally secured to the bracket. The gear is coupled to the drive mechanism to receive the bidirectional rotational force to pivot the gear with respect to the bracket. The gear defines a slot extending between first and second ends. The power liftgate drive assembly also includes a striker bar coupled to the gear. The striker bar slides through the slot. A guide rod connects the striker bar to the liftgate. The power liftgate drive assembly also includes a latch secured to the gear and operable between a latched position and an unlatched position. The latch engages the striker bar when in the latched position. This prevents the striker bar from moving along the slot. The striker bar moves through movement of the gear which is moved to power the liftgate between the open and closed positions. The latch disengages the striker bar when in the unlatched position allowing the striker bar to move along the slot allowing the liftgate to be moved manually between the open and closed positions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    Advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0007]    [0007]FIG. 1 is a rear view, partially cut away, of a motor vehicle incorporating one embodiment of the invention, with the liftgate of the motor vehicle in the open position;  
         [0008]    [0008]FIG. 2 is a prospective view, partially cut away, of one embodiment of the invention;  
         [0009]    [0009]FIG. 3 is a prospective view of one embodiment of the invention;  
         [0010]    [0010]FIG. 4 is a top view of one embodiment of the invention when the striker bar is disengaged;  
         [0011]    [0011]FIG. 5 is a top view of one embodiment of the invention when the striker bar is engaged; and  
         [0012]    [0012]FIG. 6 is a top view of an alternative embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    Referring to the Figures, wherein like reference characters represent like or corresponding elements throughout the several views and, a portion of a motor vehicle is generally shown at  10 . Referring specifically to FIG. 1, the motor vehicle  10  includes a rear portion defining a rear access opening  12 . The rear access opening  12  provides access into the compartment immediately adjacent thereto. A liftgate, or tailgate,  14  is pivotally secured to the rear portion of the motor vehicle  10  by a pair of gooseneck-shaped hinges  16 . The liftgate  14  pivots about the hinges  16  between an open position, shown in FIG. 1, and a closed position covering the rear access opening  12  in a conventional manner.  
         [0014]    Referring to FIG. 2, a bracket  18  is mounted to a portion of the ceiling  19  of the motor vehicle  10  adjacent the rear access opening  12 . In the embodiment shown in FIG. 2, a headliner  20  covers the bracket  18  and the rest of the invention  22 , discussed in greater detail subsequently. A portion of the headliner  20  is shown cut away to view the invention  22 . While the invention  22  is shown secured to the ceiling  19  under the headliner  20 , it should be appreciated by those skilled in the art that the invention  22  may be mounted to a pillar or another structural element of the motor vehicle  10  other than the ceiling  19  thereof.  
         [0015]    The invention  22  is a sector gear power liftgate assembly. The sector gear power liftgate assembly  22  includes a gear, generally shown at  24 . While any gear may be used, including a linear rack, the gear shown in the embodiments is a sector gear  24 . A pivot axle  26  is used to mount the sector gear  24  to the mounting bracket  18  to allow the sector gear  24  to pivot thereabout. As is shown in the Figures, the sector gear  24  is positioned in a plane generally parallel to the mounting bracket  18 .  
         [0016]    The sector gear  24  includes a rack of gear teeth  28  on an arcuate edge thereof opposite the pivot axle  26 . The sector gear  24  defines a slot  30 . The slot  30  extends along a line in the embodiment shown in FIGS. 1 through 5. The slot  30  is arcuate in the embodiment shown in FIG. 6. This embodiment will be discussed in greater detail subsequently.  
         [0017]    The slot  30  extends between a first end  32  and a second end  34  in a chord-like manner. The slot  30  is between the pivot axle  26  and the rack of gear teeth  28 .  
         [0018]    A drive mechanism, generally shown at  36 , is fixedly secured to the bracket  18 . The drive mechanism  36  provides a bidirectional rotational force to drive the sector gear  24  between its two extreme positions. The drive mechanism  36  includes a motor  38  that is powered through the electrical power system of the motor vehicle (not shown). The motor  38  drives an output shaft  39  to rotate in either a clockwise or counter clockwise direction, depending on whether the liftgate  14  is to be opened or closed.  
         [0019]    The output shaft  39  drives a toothed drive gear  40 . The toothed drive gear  40 , in turn, meshes with the rack of gear teeth  28  and drives the sector gear  24  between its two extreme positions. The toothed drive gear  40  acts as a pinion as it moves the rack of gear teeth  28 .  
         [0020]    The sector gear power liftgate assembly  22  also includes a striker bar  42 . The striker bar  42  is slideably retained within the slot  30  between the first  32  and second  34  ends.  
         [0021]    An elongated guide rod  44  is connected to the striker bar  42 . The guide rod  44  extends between a first end  44 , connected to the striker bar  42 , and a second end  48 . The second end  48  is connected to the hinge  16  and, hence, the liftgate  14 . Therefore, the guide rod  44  moves the liftgate  14  when the striker bar  42  is moved by the desires of the operator of the liftgate  14 . More specifically, the hinge  16  includes a distal end  50  connected to the liftgate  14  and a proximal end  52 . The hinge  16  has a first pivot  54  pivotally connected to the mounting bracket  18  adjacent the rear access opening  12 . The hinge  16  also includes a second pivot  56  disposed adjacent to and offset from the first pivot  54 . Both the first  54  and second  56  pivots are disposed adjacent the proximal end  52 .  
         [0022]    An arcuate hinge plate  58  interconnects the second end  48  of the guide rod  44  and the second pivot  56  of the hinge  16 . The hinge plate  58  provides the relationship between the hinge  16  and the guide rod  44  so that the hinge  16  pivots about the first pivot  54 . The hinge plate  58  and second end  48  of the guide rod  44  are connected by a shaft  60 .  
         [0023]    The power liftgate assembly  22  further includes a latch mechanism, generally shown at  62 . The latch  62  is secured to the sector gear  24 . The latch  62  operates between a latched position and an unlatched position. When in the latched position, the latch  62  engages the striker bar  42  to prevent it from moving relative to the sector gear  24 . More specifically, the latch  62  engages the striker bar  24  to prevent the striker bar  42  from moving along the slot  30 . By doing so, the movement of the sector gear  24  will translate into movement of the striker bar  42 . This will result in the movement of the guide rod  44 , hinge  16  and the liftgate  14 . By unlatching the latch  62 , the striker bar  42  is free to move through the slot  30  in the sector gear  24  providing the freedom to manually open and close the liftgate  14 .  
         [0024]    The latch  62  includes a latch bracket  64  that is fixedly secured to the sector gear  24 . The latch  62  also includes a generally U-shaped latch plate  66  that is pivotally connected to the latch bracket  64 . The striker bar  42  is received within the latch plate  66  when the latch plate is in the latched position. A latch pawl  68  is pivotally coupled to the bracket  64  for engaging and pivoting the latch plate  66  between the latched position and the unlatched position. A coil spring  70  is connected to the latch pawl  68  to bias the latch plate  68  in the unlatched position.  
         [0025]    An actuator  72  is also fixedly secured to the sector gear  24 . The actuator  72  is powered to move the latch plate  68  between the latched and unlatched positions. In the embodiments shown in the Figures, the actuator is solenoid driven.  
         [0026]    Referring to FIG. 6, wherein like primed numerals represent similar elements to that shown in FIGS. 1 through 5, the power liftgate drive assembly  22 ′ is configured to have an arcuate slot  30 ′. The arcuate slot  30 ′ extends through the same arc that the rack of gear teeth  28 ′ extend.  
         [0027]    Another feature that differs between this embodiment and the first embodiment shown is the location of the solenoid actuator  72 ′. In this embodiment, the solenoid actuator  72 ′ and the solenoid  74  are removed from the sector gear  24 ′. By being off to the side, the cover, headliner or otherwise, does not have to extend out as far because the solenoid actuator  72 ′ and solenoid  74  do not travel through an arcuate path with the sector gear  24 ′. This reduces the amount of space consumed in the compartment by the power liftgate drive assembly  22 ′.  
         [0028]    In operation, the powered liftgate drive assembly  22  enables both powered and manual opening and closing of the liftgate  14  of the motor vehicle  10  to provide selective access to the rear compartment of the motor vehicle  10 . First, the power liftgate drive assembly  22  allows the liftgate  14  to be manually pivoted between the open and closed positions. The power liftgate drive assembly  22  shown in FIG. 4 with the liftgate  14  in the closed position. The striker bar  42  is positioned along the slot  30  toward the first and  32  by the force of the guide rod  44  connected to the hinge  16 . To manually open the liftgate  14 , the operator pivots the liftgate  14  about its hinges  16 . The hinges  16  pivot about the first pivot  54  and, thus, rotate the second offset pivot  56 . The guide rod  44 , which is connected between the hinge  16  of the striker bar  42  forces the striker bar  42  to slide along the slot  30  from the second end  34 , as shown in FIG. 5, to the first end  32 , as shown in FIG. 4. The latch plate  66  remains in the unlatched position disengaged from the striker bar  42  and the sector gear  24  remain stationary about the pivot axle  26 . The reverse movement occurs when the liftgate is manually pivoted about its hinges  16  back to the closed position. More specifically, the guide rod  44  is pulled by the hinges  16  to slide the striker bar  42  along the slot  30  from the first end  32  to the second end  34 .  
         [0029]    Additionally, the liftgate  14  may be automatically pivoted between the open and closed positions by the power liftgate drive assembly  22 . Referring to FIG. 5, with the liftgate  14  in the open position, the operator activates a switch within the motor vehicle  10 , a key fob, or controller (none shown) to actuate the latch mechanism  62  and drive mechanism  36 . The solenoid actuator  72  engages the latch pawl  68  to pivot the latch plate  66  from the unlatched position to the latched position to engage the striker bar  42 .  
         [0030]    The motor  38  is then powered, or energized, to drive the drive gear  40 . The drive gear  40 , which is matched with the rack of gear teeth  28 , drives or pivots the sector gear  24  about the pivot axle  26  in the counterclockwise direction. With the striker bar  42  locked in the slot  30  by the latch plate  66 , as the sector gear  24  rotates, the striker bar  42  pulls on the guide rod  44 . The guide rod  44  pulls on the second offset pivot  56  to pivot the hinge  16  about the pivot  54  to close liftgate  14 . In order to power open the liftgate  14  from the closed position, the motor  38  is reversed so that the drive gear  40  pivots the sector gear  24  in a clockwise direction about the pivot axle  26 . Again, with the striker bar  42  locked in the slot  30  by engagement with the latch plate  66 , the guide rod  44  forces the hinge  16  to pivot about the first pivot  54  and open liftgate  14 .  
         [0031]    Still further, the actuator  72  of the latch mechanism  62  may be controlled such that the latch plate  66  is returned to the unlatched position, or parked position, when the liftgate  14  is in either the open or closed positions to enable manual operation of the liftgate  14 . In order to transition from the manual operation and power operation of the drive mechanism  22 , the motor  38  includes a hall effect sensor which acts as a position sensor to identify the position of the sector gear  24  for alignment and engagement between the striker bar  42  and the latch plate  66 . Therefore, whether the liftgate  14  is in the open or closed position, the sector gear  24  may be pivoted about the axle  26  to position the latch mechanism  62  with the striker bar  42  for actuation of the latch plate  66  from the unlatched position to the latched position engaged with the striker bar  42  for power operation of the liftgate  14 .  
         [0032]    During normal operation, a capacitor is charged to the voltage of the vehicle battery (not shown) and is electrically isolated from a coil (not shown) of the solenoid actuator  72 . For solenoid engagement, the voltage is applied to the coil in a specific polarity. This causes the solenoid piston to be drawn in towards the coil. Once the piston is completely retracted into the coil, a permanent magnet maintains the piston in position.  
         [0033]    For solenoid disengagement, the capacitor is discharged through the solenoid in the reverse polarity to that used for engagement. The capacitor need only charge the solenoid enough to counterbalance the magnetic field generated by the permanent magnet, since a mechanical spring is used to assist the disengage process. The capacitor is electrically on such that, in the event of a mid-cycle power failure, the capacitor will discharge through the solenoid and disengage the solenoid. Once disengaged, the power liftgate assembly  22  is returned to the manual operation condition.  
         [0034]    The preferred embodiment has been described as the assembly  22  being mounted on the roof panel. However, it is now apparent to those skilled in the art that assembly  22  may also be mounted in the quarter panel of the vehicle  10 .  
         [0035]    The invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.