Power liftgate drive assembly

Abstract

A powered closure drive mechanism is provided for moving a closure between open and closed positions. An elongated housing extends between first and second ends that are movable in opposite directions toward and away from each other. A rotatable lead screw is disposed longitudinally within the elongated housing. A reversible motor rotates the lead screw in a first direction and a second direction to urge the first and second ends of the housing toward and away from each other. A sensor assembly includes a worm fixed to the lead screw for rotation therewith and a rotatable gear meshingly engaged with the worm. The worm and gear are geared such that the gear rotates less than one revolution in response to the closure moving between the open and closed positions.

1 . A powered closure drive mechanism for moving a closure between an open position and a closed position, said powered closure drive mechanism comprising:
 an elongated housing extending between first and second ends, said first and second ends being movable in opposite directions toward and away from each other;   a rotatable lead screw disposed longitudinally within said elongated housing;   a reversible motor operatively coupled to said lead screw for rotation of said lead screw in a first direction and a second direction thereby urging said first and second ends of said elongated housing toward and away from each other; and   a sensor assembly including a worm fixed to said lead screw for rotation therewith, and a rotatable gear meshingly engaged with said worm, wherein said worm and gear are geared such that said gear rotates not more than one revolution in response to the closure moving between the open and closed positions.   
   
   
       2 . A powered closure drive mechanism as set forth in  claim 1  further including a nut threadingly engaging said lead screw and moving linearly therealong in response to rotation of said lead screw in either said first or second direction thereby urging said first and second ends of said elongated housing toward and away from each other. 
   
   
       3 . A powered closure drive mechanism as set forth in  claim 2  whereby linear movement of said nut in a first linear direction urges said first and second ends of said elongated housing away from each other to move the closure to the open position and whereby linear movement of said nut in a second linear direction allows the weight of the closure to move the closure to the closed position. 
   
   
       4 . A powered closure drive mechanism as set forth in  claim 3  wherein said gear is disposed generally orthogonal to said worm. 
   
   
       5 . A powered closure drive mechanism as set forth in  claim 4  further including a two-pole magnet fixedly secured to said gear for rotation therewith, said magnet generating a magnetic field, and a sensor mounted adjacent said magnet for sensing said magnetic field and resolving a rotational position of said magnet wherein said rotational position of said magnet corresponds to a position of the closure between the open and closed positions. 
   
   
       6 . A powered closure drive mechanism as set forth in  claim 5  further including a controller operatively connected with said motor and said sensor, said controller controlling said motor to move the closure between the open and closed positions based upon said rotational position of said magnet. 
   
   
       7 . A powered closure drive mechanism as set forth in  claim 6  further including a sensor assembly housing, wherein said rotatable gear is rotatably coupled to said sensor assembly housing and meshingly engaged with said worm. 
   
   
       8 . A powered closure drive mechanism as set forth in  claim 7  further including a gearbox operatively coupled to said motor for transmitting an input rotation from said motor to an output shaft. 
   
   
       9 . A powered closure drive mechanism as set forth in  claim 8  further including a clutch assembly operatively coupling said output shaft of said gearbox and said lead screw for transmitting rotation of said output shaft to said lead screw. 
   
   
       10 . A powered closure drive mechanism as set forth in  claim 9  wherein said motor is disposed toward said second end of said elongated housing, said gearbox is disposed adjacent said motor, said clutch assembly is disposed adjacent said gearbox, said sensor assembly is disposed adjacent said clutch assembly, and wherein said lead screw extends through said sensor assembly housing. 
   
   
       11 . A powered closure drive mechanism as set forth in  claim 10  wherein said lead screw extends between a first end operatively coupled to said clutch assembly and a second end disposed toward said first end of said elongated housing. 
   
   
       12 . A powered closure drive mechanism as set forth in  claim 11  wherein said lead screw includes a first unthreaded portion adjacent said first end of said lead screw and a second threaded portion, said worm fixed to said first unthreaded portion and said nut threadingly engaging said second threaded portion. 
   
   
       13 . A powered closure for a motor vehicle having an opening, said powered closure comprising:
 a rear liftgate pivotally coupled to the motor vehicle for movement between an open position pivoted away from the motor vehicle uncovering the opening and a closed position adjacent the motor vehicle covering the opening;   at least one strut assembly extending between a first end operatively coupled to the motor vehicle and a second end operatively coupled to said rear liftgate, wherein said first and second ends are movable in opposite directions toward and away from each other to move said rear liftgate between said open and closed positions; and   an absolute position encoder including a two-pole magnet and a sensor, said magnet having a magnetic field and operatively coupled to said at least one strut assembly to rotate not more than one revolution in response to said rear liftgate moving between said open and closed positions, said sensor mounted to said at least one strut assembly for sensing said magnetic field of said magnet and generating an output signal to determine a rotational position of said magnet which corresponds to the position of said rear liftgate between said open and closed positions.   
   
   
       14 . A powered closure as set forth in  claim 13  wherein said strut assembly includes an elongated housing extending between first and second ends, said first and second ends being movable in opposite directions toward and away from each other, a rotatable lead screw disposed longitudinally within said elongated housing, and a reversible motor operatively coupled to said lead screw for rotation of said lead screw in a first direction and a second direction thereby urging said first and second ends of said elongated housing toward and away from each other. 
   
   
       15 . A powered closure as set forth in  claim 14  further including a worm fixedly secured to said lead screw for rotation therewith, and a rotatable gear meshingly engaged with said worm, wherein said magnet is fixedly secured to said gear, and wherein said worm and gear are geared such that said gear rotates not more than one revolution in response to said rear liftgate moving between said open and closed positions. 
   
   
       16 . A powered closure as set forth in  claim 15  wherein said gear is disposed generally orthogonal to said worm. 
   
   
       17 . An absolute position encoder for determining a position of a rear liftgate on a motor vehicle movable between open and closed positions by a strut assembly, said absolute position encoder comprising:
 a two-pole magnet having a magnetic field, said magnet operatively coupled to the strut assembly and geared to rotate not more than one revolution in response to the rear liftgate moving between the open position and the closed position; and   a sensor adapted to be mounted to the strut assembly, said sensor sensing said magnetic field of said magnet and generating an output signal to determine a rotational position of said magnet which corresponds to the position of the rear liftgate between the open and closed positions.