U.S. patent application number 12/143279 was filed with the patent office on 2008-10-16 for power liftgate drive assembly.
Invention is credited to Timothy DeZorzi, Karsten Hennze, Peter Lance Oxley.
Application Number | 20080250720 12/143279 |
Document ID | / |
Family ID | 39735388 |
Filed Date | 2008-10-16 |
United States Patent
Application |
20080250720 |
Kind Code |
A1 |
Oxley; Peter Lance ; et
al. |
October 16, 2008 |
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.
Inventors: |
Oxley; Peter Lance; (Mount
Albert, CA) ; Hennze; Karsten; (Gormley, CA) ;
DeZorzi; Timothy; (South Lyon, MI) |
Correspondence
Address: |
MAGNA INTERNATIONAL, INC.
337 MAGNA DRIVE
AURORA
ON
L4G-7K1
CA
|
Family ID: |
39735388 |
Appl. No.: |
12/143279 |
Filed: |
June 20, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11680285 |
Feb 28, 2007 |
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12143279 |
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PCT/CA06/00254 |
Feb 20, 2006 |
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11680285 |
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Current U.S.
Class: |
49/358 ;
324/207.2 |
Current CPC
Class: |
E05Y 2900/546 20130101;
E05Y 2800/232 20130101; E05Y 2201/654 20130101; E05F 15/646
20150115; E05Y 2201/11 20130101; E05Y 2900/531 20130101; E05Y
2800/238 20130101; E05Y 2600/40 20130101; E05F 15/622 20150115;
E05Y 2201/664 20130101; E05Y 2400/326 20130101 |
Class at
Publication: |
49/358 ;
324/207.2 |
International
Class: |
E05F 15/00 20060101
E05F015/00 |
Claims
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.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 11/680,285, filed Feb. 28, 2007, which is a
continuation-in-part of International Application No.
PCT/CA2006/000254, with an international filing date of Feb. 20,
2006.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to power liftgates for motor vehicles,
and more particularly, to a power liftgate drive assembly having an
absolute position encoder.
[0004] 2. Description of Related Art
[0005] Motor vehicle liftgates or closure panels act to close and
seal a rear cargo area of a van, minivan, or sport utility type of
motor vehicle. Typically, these closure panels are mounted in a
frame located at the rear of the vehicle, usually on a horizontally
extending axis provided by a hinge. The liftgate is thus positioned
to rotate between a closed position adjacent to the frame and an
open position, in which the cargo area of the vehicle is
accessible. The liftgate is often very heavy, and because of its
mounting, it must be moved against gravity in order to reach the
open position. Because of the liftgate's weight, it would be a
great burden if a user was required to lift the liftgate into the
open position and then manually hold it in place in order to access
the vehicle's cargo area.
[0006] In order to make it easier to open liftgates, most modern
motor vehicles use gas or spring-loaded cylindrical struts to
assist the user in opening and holding open liftgates. The struts
typically provide enough force to take over the opening of the
liftgate after the liftgate has been manually opened to a partially
opened position at which the spring force and moment arm provided
by the struts are sufficiently to overcome the weight of the
liftgate, and to then hold the liftgate in an open position.
[0007] Automated power systems to open and close vehicle liftgates
are well known in the art. These systems typically use a power
actuator to apply a force directly to the liftgate to enable
opening and closing thereof. Such automated powered systems act as
a direct replacement for the user-supplied force.
[0008] With automated power systems to open and close vehicle
liftgates it is desirable to provide a position sensor to monitor
the position of the liftgate. Most position sensors, however, are
limited by the fact that if power is temporarily lost or
disconnected, and the liftgate is manually moved, the position
sensor cannot detect the position of the liftgate until the
position sensor is recalibrated or reset. Therefore, it is
desirable to provide a power liftgate drive assembly having a
position sensor capable of monitoring the position of the liftgate
even after power is temporarily lost or disconnected and the
liftgate is manually moved to another position.
SUMMARY OF THE INVENTION
[0009] According to one aspect of the invention, a powered closure
drive mechanism is provided for moving a closure between an open
position and a closed position. The drive mechanism includes an
elongated strut assembly extending between first and second ends. A
rotatable lead screw is disposed within the strut assembly and a
reversible motor turns the lead screw in first and second
directions to move the first and second ends toward and away from
each other to move the closure between the open and closed
positions. A sensor assembly includes a worm fixed to the lead
screw for rotation therewith and a gear meshingly engaged with the
worm. The worm and gear are geared so that the gear rotates not
more than one revolution in response to the closure moving between
the open and closed positions.
[0010] According to another aspect of the invention, a powered
closure drive mechanism is provided for moving a rear liftgate on a
motor vehicle between an open position pivoted away from the
vehicle and a closed position adjacent the vehicle. The drive
mechanism or electro-mechanical strut assembly includes an
elongated strut housing extending between the liftgate and the
vehicle. A rotatable lead screw is disposed longitudinally within
the strut housing and a reversible motor turns the lead screw in a
first direction and a second direction to move first and second
ends of the strut housing toward and away from each other to move
the liftgate between the open and closed positions. A sensor
assembly is provided to determine a position of the liftgate
between the open and closed positions. The sensor assembly includes
a worm fixed to the lead screw for rotation therewith, a gear
meshingly engaged with the worm, a two-pole magnet, and a sensor.
The worm and gear are geared so that the gear rotates not more than
one revolution in response to the liftgate moving between the open
and closed positions. The magnet has a magnetic field and is
mounted to the gear for rotation therewith. The sensor senses the
magnetic field and generates an output signal to determine a
rotational position of the magnet which corresponds to the position
of the liftgate.
[0011] According to yet another aspect of the invention, an
absolute position encoder is provided for determining a position of
a rear liftgate on a motor vehicle that is movable between an open
position and a closed position by a strut assembly. The encoder
includes a two-pole magnet and a sensor. The magnet has a magnetic
field and is operatively coupled to the strut assembly to rotate
not more than one revolution in response to the liftgate moving
between the open position and the closed position. The sensor is
adapted to be mounted to the strut assembly and senses the magnetic
field of the magnet. The sensor outputs a signal in response to
sensing the magnetic field to determine a rotational position of
the magnet which corresponds to the position of the liftgate
between the open and closed positions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] 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:
[0013] FIG. 1 is a perspective view of a motor vehicle with a rear
liftgate in an open position;
[0014] FIG. 2 is a side view of the motor vehicle with the rear
liftgate in a closed position;
[0015] FIG. 3 is a cross-sectional view of a liftgate strut
assembly according to the invention;
[0016] FIG. 4 is a fragmentary, enlarged cross-sectional view of
the liftgate strut assembly;
[0017] FIG. 5 is a partially cut-away perspective view of a sensor
assembly; and
[0018] FIG. 6 is a cross-sectional end view of the sensor
assembly.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0019] The present invention will be described below particularly
with respect to its application in rear liftgates of motor
vehicles. Those skilled in the art will, however, realize that the
present invention may be applied to other types of vehicle closures
and also to closures that are not mounted on vehicles. For example,
the present invention may find application in trunk lids for motor
vehicles, panels covers for light trucks, train doors, bus doors,
and household closures such as windows and doors. In addition, it
is contemplated that the present invention has utility for other
automotive applications such as steering wheel position sensing,
gas pedal position sensing, transmission gearbox encoder, headlight
position control, and power seat position sensing.
[0020] Referring now more particularly to the drawings, there is
shown in FIG. 1 a motor vehicle, generally shown at 10, with a
vehicle body or frame 12 which defines an opening 14 at a rear end
thereof. A liftgate or door 16 (or more generally referred to as a
"closure") is adapted to fit within the opening 14. The weight of
the closure 16 biases it towards a closed position within the
opening 14, as shown in FIG. 1.
[0021] A hinge assembly 18 is connected between an upper portion 20
of the vehicle body 12 and an upper portion 22 of the closure 16,
pivotally mounting the closure 16 to the vehicle body 12. The hinge
assembly 18 provides a generally horizontally extending axis 24 for
pivotal movement of the closure 16 between the closed position,
adjacent the vehicle body 12, as shown in FIG. 2, and an open
position, pivoted away from the vehicle body 12 such that the cargo
area of the vehicle 10 is accessible, as shown in FIG. 1.
[0022] A latch assembly 26 having cooperating parts mounted on the
closure 16 and the vehicle body 12 is also shown in FIG. 1. The
latch assembly 26 is provided for releasably locking the closure 16
in the closed position. The latch assembly 26 includes a latch 28
disposed within a lower portion 30 of the closure 16 and a
complimentary latch striker 32 disposed within a lower portion 34
of the vehicle body 12.
[0023] A powered closure drive mechanism, generally shown at 36, is
provided for opening and closing the closure 16. More particularly,
the powered closure drive mechanism 36 is disclosed as a pair of
electro-mechanical strut assemblies 38. Each strut assembly 38
extends between a first end 40 and a second end 42, the first 40
and second 42 ends being movable in opposite directions toward and
away from each other. In the illustrated embodiment, one strut
assembly 38 is mounted on each side of the vehicle 10, extending
between the closure 16 and the vehicle body 12. It is appreciated
by one of skill in the art that a single strut assembly 38
connected between the closure 16 and the vehicle body 12 will
provide the necessary function of opening and closing the closure
16. The first end 40 of the strut assembly 38 is operatively
coupled to the vehicle body 12, adjacent the upper portion 20
thereof. The second end 42 of the strut assembly 38 is pivotally
coupled to an edge 44 of the closure 16, between the upper 22 and
lower 30 portions thereof.
[0024] One strut assembly 38 is shown in detail in FIG. 3. The
strut assembly 38 includes a housing 46 enclosing the various
components of the strut assembly 38. Internally, a motor 48 is
disposed toward the second end 42 of the strut assembly 38. The
motor 48 is electrically connected to an electric energy source
(not shown). It is contemplated that the motor 48 operates using
electric energy that is standard in a motor vehicle protocol. The
motor 48 is bi-directional allowing for rotation of a drive shaft
50 in two directions. The drive shaft 50 extends axially within the
strut assembly 38 and is operatively coupled to a gearbox 52. The
gearbox 52 is disposed adjacent the motor 48.
[0025] The gearbox 52 includes an output shaft 54 that is driven by
the drive shaft 50 of the motor 48 and extends coaxially therewith.
The output shaft 54 of the gearbox 52 is operatively coupled to a
lead screw 56 by a clutch assembly 58, disposed adjacent the
gearbox 52. The clutch assembly 58 rotates the lead screw 56 in
response to a rotational input from the output shaft 54 of the
gearbox 52. The clutch assembly 58 is an overload-type clutch in
that it slips at a predetermined torque, but not below the
predetermined torque. The clutch assembly 58 allows selective
manual movement of the closure 16 between the open and closed
positions.
[0026] The lead screw 56 extends coaxially with the output shaft 54
of the gearbox 52 between a first end 60 disposed within the clutch
assembly 58 and a second end 62 disposed at the first end 40 of the
strut assembly 38. A first portion 66 of the lead screw 56 adjacent
the first end 60 is unthreaded while a remaining second portion 68
is threaded. A support nut 70 threadingly engages the threaded
second portion 68 of the lead screw 56. As the lead screw 56
rotates, the support nut 70 is driven linearly along the lead screw
56 in either a first direction or a second direction depending on
the direction of rotation of the lead screw 56. Linear travel of
the support nut 70 along the lead screw 56 causes the first end 40
of the strut assembly 38 to move towards and away from the second
end 42, thereby causing the closure 16 to pivot between the open
and closed positions. In one embodiment of the invention, the lead
screw 56 is rotated approximately ten (10) revolutions to drive the
support nut 70 between a first location, which corresponds to the
closure 16 being in the closed position, and a second location,
which corresponds to the closure 16 being in the open position.
[0027] It is necessary to monitor exactly where the closure 16 is
within its range of travel between the open and closed positions.
To accomplish this, the strut assembly 38 also includes a sensor
assembly 72 disposed between the clutch assembly 58 and the support
nut 70. The lead screw 56 extends through the sensor assembly 72.
The sensor assembly 72 includes a sensor housing 74 that defines an
internal compartment 76. A worm 78 and gear 80 are disposed within
the internal compartment 76 and oriented generally orthogonal to
each other. The unthreaded first portion 66 of the lead screw 56
extends axially through the worm 78 and the worm 78 is keyed or
fixed to the lead screw 56 such that it rotates therewith. The gear
80 is mounted in meshing engagement with the worm 78 such that
rotation of the worm 78 causes the gear 80 to rotate. The gear
ratio between the worm 78 and the gear 80 is approximately 10:1
such that the gear 80 rotates not more than one (1) revolution for
every ten (10) revolutions of the worm 78, which corresponds to
full travel of the closure 16 between the open and closed positions
or alternatively between the closed and open positions.
[0028] A diametrically charged or two-pole magnet 82 is generally
disc-shaped and is fixedly secured to a distal end of the gear 80
and rotates therewith. Therefore, the magnet 82 rotates not more
than one (1) revolution for full travel of the closure 16. The
magnet 82 has a north pole and a south pole which create a magnetic
field. A board 84 with a chip 86 mounted thereon is fixedly secured
to the sensor housing 74 adjacent the magnet 82. The chip 86
includes at least one sensor mounted therein for sensing the
magnetic field of the magnet 82 in order to resolve its rotational
position. The chip 86 then outputs the rotational position of the
magnet 82 to a controller 88 located within the vehicle. The
controller 88 is electrically connected to the chip 86 and to the
motor 48. The chip 86 may output the rotational position of the
magnet 82 in any number of suitable ways. For example, the chip 86
may output a linear analog signal that is proportional to position
wherein approximately zero volts corresponds to the closed position
of the closure 16 and approximately five volts corresponds to the
open position of the closure 16. One benefit of this powered
closure drive mechanism 36 is that the chip 86 can always determine
the absolute rotational position of the magnet 82 based on its
magnetic field, even after a power disconnect during which the
closure 16 is manually moved to a new position. The chip 86 is any
suitable chip for sensing the magnetic field of the magnet 82 and
outputting the rotational position of the magnet 82, for example,
the AS5040-10 bit Programmable Rotary Encoder manufactured by
Austria Micro Systems AC.
[0029] To initially calibrate the chip 86, the magnet 82 needs to
be set to a predetermined position relative to the lead screw 56,
so that approximately zero volts will correspond to the closed
position of the closure 16 and approximately five volts will
correspond to the open position of the closure 16. Alternatively,
the system can be assembled without paying attention to the
alignment of the magnet 82 relative to the lead screw 56. In this
situation, with the closure 16 in the closed position the zero
position is programmed into the chip 86.
[0030] It is appreciated that the lead screw threads can be
selected such that any number of revolutions of the lead screw 56
is required to drive the support nut 70 between the first and
second locations without varying from the scope of the invention.
However, in order to accommodate a different number of revolutions
of the lead screw 56, the worm 78 and gear 80 must be selected such
that the magnet 82 rotates not more than one (1) revolution for
full travel of the closure 16.
[0031] 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.
* * * * *