Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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POWERED OPENING MECHANISM AND CONTROL SYSTEM
FIELD OF THE INVENTION
[0001] The present invention relates generally to powered systems for
opening and closing closures such as doors and hatches, and more particularly,
to
powered systems for opening and closing motor vehicle closures.
BACKGROUND ART
[0002] Motor vehicle liftgates and deck lids act to close and seal the rear
cargo area of a motor vehicle. Typically, these closures or closure structures
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 motor vehicle is accessible. The liftgate or deck lid itself 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.
[0003] In order to make it easier to open liftgates and deck lids, most
modern motor vehicles use gas or spring-loaded cylindrical struts to assist
the user in
opening and holding open Iiftgates and deck lids. 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 sufficient to overcome the weight of the liftgate,
and to then
hold the Iiftgate in an open position.
[0004] Usually, a motor vehicle liftgate-assist system consists of two struts.
The two struts in a typical liftgate assembly are each pivotally mounted at
opposite
ends thereof, one end pivotally mounted on the liftgate and the other end
pivotally
mounted on the frame or body of the motor vehicle. Each strut's mounting point
is
fixed, and the strut thus possesses a fixed amount of mechanical advantage in
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facilitating the manual opening process. In addition, because the force
provided by
the struts is constant, the user must thrust downward on tlhe Iiftgate and
impart
sufficient momentum to the liftgate to overcome the strut forces in order to
close the
liftgate.
[0005] Automated powered systems to open and close vehicle liftgates are
known in the art. However, these systems typically use a power actuator to
apply a
force directly to the liftgate to enable opening and closing thereof. For
example, U.S.
Patent No. 5,531,498 to Kowall discloses a typical liftgate-opening system in
which
the gas struts are actuated by a pair of cables which are, in turn, wound and
unwound
from a spool by an electric motor. Because this typical type of powered system
acts
as a direct replacement for the user-supplied force, it provides relatively
little
mechanical advantage from its mounted position, typically requires a
significant
amount of power to operate, and is usually large, requiring a significant
amount of
space in the tailgate area of the vehicle, which is undesirable.
[0006] Control systems for the typical powered liftgate systems are also
available. Such control systems usually include at least some form of obstacle
detection, to enable the liftgate to stop opening or closing if an obstacle is
encountered. These obstacle detection systems are usually based on feedback
control
of either the force applied by the liftgate or actuator motor or the speed at
which the
liftgate or motor is moving. One such control system for the type of cable-
driven
liftgate actuator described above is disclosed in U.K. Patent Application No.
GB
2307758A. In general, the control system of this reference is designed to
control the
movement of the liftgate based on the measured liftgate force, using an
adaptive
algorithm to "team" the liftgate system's force requirements. However, the
movement of a liftgate is a complex, non-linear movement and existing control
systems are usually adapted only for conventional "brute force" powered
liftgate
systems.
[0007] Other prior art power liftgate systems are more passive. For
example; DE 198 10 315 A1 discloses an arrangement in which the angular
position
of a strut is changed in order to facilitate opening and closing of a deck
lid. However,
the structural configuration of the disclosed design is such that it permits a
very
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limited range of closure movement and limited mechanical advantage in the
different
positions. In addition, among numerous other disadvantages, the device
disclosed in
DE 198 10 315 A1 does not provide a controlled system that enables dynamic
control
of the closure during movement thereof. This reference also does not
contemplate use
of the closure in manual mode, among other things.
[0008] DE 197 58 130 C2 proposes another system for automated closure
of a deck lid. As with the '315 reference, the '130 reference does not
contemplate or
allow dynamic control over the deck lid, use of the deck lid in manual mode,
and does
not enable a power driven closing force to be applied to the lid. Moreover,
both of the
'130 and '315 references disclose very large structural arrangements, making
packaging in a vehicle very difficult.
[0009] One particular challenge in power liftgate systems, especially those
that are more passive, is dealing with situations in which the vehicle is
parked or
stopped on an incline. If the vehicle is parked or stopped on an incline, it
may negate
some or all of the mechanical advantage of the power Iiftgate system. Another
challenge is designing a powered system such that the liftgate will open at a
particular
speed or within a particular time frame:
SUMMARY OF THE INVENTION
[0010] One aspect of the invention relates to a powered closure drive
mechanism for a vehicle. The drive mechanism comprises a controllable strut, a
motor assembly, a dynamic property detector, and a controller. The
controllable strut
is mountable between a frame of the vehicle and a closure pivotally connected
to the
frame. The strut has opposite ends moveable in opposite directions toward and
away
from one another. The strut also has a lock which, when in a locking
condition,
substantially prevents movement of the opposite ends of the strut relative to
one
another and, when the lock is in a releasing condition, allows movement of the
opposite ends of the strut relative to one another. When the lock of the strut
is in the
releasing condition, the opposite ends of the strut are biased to move away
from one
another. The angular orientation of the strut is adjustable between
orientations in
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which the bias of the strut overcomes a weight of the closure so as to move
the
closure in an opening direction, and orientations in which the weight of the
closure
overcomes the bias of the strut so as to move the closure in a closing
direction. The
motor assembly is operatively coupled with the strut so as to adjust the
angular
orientation of the strut by moving one of the opposite ends of the strut and,
thereby, to
effect opening and closing movement of the closure. The dynamic property
detector
detects one or more dynamic properties of the closure. 'Che controller is
operatively
coupled to the motor, the lock, and the dynamic property detector. The
controller
controls the motor and the lock based, at least in part, upon the one or more
dynamic
properties detected by the dynamic property detector.
[0011] Another aspect of the invention relates to a method of actuating a
pivotally-mounted closure supported by a controllable strut having an integral
lock.
The method comprises moving the controllable strut among angular orientations
of
the strut relative to the closure and the closure frame to move the strut
between
opening angular orientations in which the force bias provided by the
controllable strut
overcomes the weight bias the closure, causing the closure to move toward an
open
position, and closing angular orientations in which the force bias provided by
the
controllable strut is overcome by the weight bias of the closure, causing the
closure to
move toward a closed position. The method also comprises monitoring one or
more
dynamic properties of the closure while the closure moves toward the open and
closed
positions, and, based upon the monitored dynamic properties of the closure,
selectively activating and deactivating the integral lock of the controllable
strut to
maintain the controllable strut at least temporarily at particular lengths.
[OOI2] Yet another aspect of the invention relates to a rear assembly for a
vehicle. The rear assembly comprises a rear assembly frame, a closure, a
motor, a
controllable strut, a connecting member, a dynamic property detector, and a
controller. The rear assembly frame defines an opening. The closuxe is
constructed
and arranged to engage in close of the opening. The closure is mounted on a
generally horizontally-extending hinge for pivotal movement between open and
closed positions. The motor is mounted to the rear assembly frame. The
controllable
strut has opposite ends moveable in opposite directions toward and away from
one
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another, and has a lock that includes a driver within the controllable strut,
a valve
structure within the controllable strut that is driven by the driver to move
between one
or more blocking positions in which a strut working fluid within the
controllable strut
is prevented from moving through a restricted orifice structure within the
strut and
5 one or more non-blocking positions in which the stmt working fluid may flow
through the restricted orifice structure. When the lock is in a locking
condition, it
substantially prevents movement of the opposite ends of the strut relative to
one
another and, when the locking structure is in a releasing condition, it allows
movement of the opposite ends of the strut relative to one another. The
opposite ends
of the strut are biased when the lock is in the releasing condition to move
away from
one another. The connecting member is pivotally connected to the motor and a
first
end of the controllable strut, and is constructed and arranged to move the
first end of
the controllable strut between opening angular orientations in which the bias
of the
controllable strut overcomes a weight of the closure so as to move the closure
.in an
opening direction, and closing orientations in which the weight of the closure
overcomes the bias of the strut so as to move the closure in a closing
direction. The
dynamic property detector detects one or more dynamic properties of the
closure. The
controller is operatively connected to the motor, the lock, and the dynamic
property
detector. The controller controls the motor and the lock based, at least in
part, upon
the one or more dynamic properties detected by the dynamic property detector.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The present invention will be described with reference to the
following drawing Figures, in which like reference numerals represent like
structures
throughout the Figures, and in which:
[0014] FIGURE 1 is a perspective view of the rear assembly of an
automobile according to the present invention;
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[0015] FIGURE 2 is a sectional elevational view taken through line 2-2 of
FIGURE 1, showing the installation of a strut and power operated system in
accordance with the invention in the rear assembly of FIGURE 1;
[OOI6] FIGURE 3 is an exploded perspective view of a portion of the
rearward most pillar of the automobile of FIGURE 1;
[0017] FIGURE 4 is a schematic side elevational view of the automobile of
FIGURE 1, illustrating the liftgate in a closed position;
[0018] FIGURE 5 is a schematic side elevational view similar to that of
FIGURE 4, illustrating initial movement of the door in order to open the
liftgate;
[0019] FIGURE 6 is a sectional side elevational view similar to FIGURE 5,
showing the movement of the strut and the consequent opening of the liftgate;
[0020] FIGURE 7 is a schematic side elevational view similar to FIGURE
6, showing the movement of the strut to move the liftgate into the full open
position;
[0021] FIGURE 8 is a schematic side elevational view of the automobile
similar to FIGURE 7, showing the liftgate in the full open position;
[0022] FIGURE 9 is a schematic side elevational view of the automobile
similar to FIGURE 8, showing the change in angular orientation of the strut
that
begins the closing sequence of the liftgate;
[0023] FIGURE 10 is a schematic side elevational view of the automobile
similar to FIGURE 9, showing the closing sequence of the liftgate;
[0024] FIGURE I1 is a schematic side elevationaI view of the automobile
similar to FIGURE 10, showing the final portion of the closing sequence of the
liftgate;
[0025] FIGURE 12 is a high-level schematic diagram of a control system
for a power-operated system in accordance with the invention;
[0026] FIGURE 13 is a high-level schematic flow diagram of a control
algorithm for opening a liftgate using the control system of FIGURE 12;
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[0027] FIGURE 14 is a high-level schematic; flow diagram of a control
algorithm for closing a liftgate using the control system of FIGURE 12;
[0028] FIGURE 1S is a high-level schematic flow diagram illustrating
portions of the diagram of FIGURE 13 in more detail;
. [0029] FIGURE 16 is a high-level schematic flow diagram illustrating
portions of the diagram of FIGURE 14 in more detail;
[0030] FIGURE 17 is a schematic sectional view of one embodiment of a
controllable strut in accordance with the present invention in an unlocked or
free-flow
condition;
[0031] FIGURE 18 is a schematic sectional view of the strut of FIGURE 17
in a locked or restricted flow condition;
[0032] FIGURE 19 is a sectional schematic view of a strut according to
another embodiment of the invention in an unlocked or free flow condition;
[0033] FIGURE 20 is a sectional schematic view of the strut of FIGURE 19
in the locked or restricted flow condition;
[0034] FIGURE 21 is a high-level schematic diagram of a control system
for a power-operated system in accordance with an embodiment of the invention
that
includes a controllable strut;
[0035] FIGURE 22 is a high-level schematic flow diagram of method for
opening a liftgate using the control system of FIGURE 21; and
[0036] FIGURE 23 high-level schematic flow diagram of method for
closing a liftgate using the control system of FIGURE 2'1.
DETAILED DESCRIPTION
[0037] The present invention will be described below particularly with
respect to its application in the rear liftgates of automobiles, such as mini
vans and
sport-utility vehicles. However, those skilled in the art will 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 an
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application in deck lids for automobiles, panel covers for light trucks, train
doors, bus
doors, and household closures, like windows and doors.
[0038] FIGURE 1 is a perspective view of an automobile, generally
indicated at 10, with a rear assembly, indicated at 12, embodying the
principles of the
present invention. The rear assembly 12 comprises a vehicle body or frame 14
which
defines an opening 16 at the rear of the automobile 10. A rear liftgate or
door 18
(more generally referred to as a "closure") is constructed and arranged to fit
in closed
relation within the opening 16. The weight of the liftgate 18 biases it
towards the
closed position within the opening 16.
[0039] A hinge assembly 10 is connected between an upper portion of the
frame 14 and an upper portion of the liftgate 18, amounting the liftgate 18
for
movement in an upward direction opposed to the weight bias of the liftgate 18.
The
hinge assembly 20 provides a generally horizontally extending hinge axis of
movement for all positions of the liftgate 18.
[0040] The rear assembly 12 also includes a strut assembly 28. The strut
assembly of this embodiment includes two struts 30, one strut mounted on each
side
of the rear assembly 12 between the liftgate 18 and the frame 14. The strut
assembly
28 may include only a single strut connected between the liftgate 18 and the
frame 14.
In other words, while two struts 30 are preferred, the function of the strut
assembly 28
can be performed with a single strut 30.
[0041] Although gas struts 30 are preferred for most automotive
embodiments of the present invention, it should be understood that any
structural
member capable of storing mechanical energy (i.e., a "resilient stored-energy
member") may be used with the present invention. The particular choice of
strut or
other resilient stored-energy member depends on the weight of the liftgate 18,
the
desired movement rate of the liftgate 18 and strut assemlbly 28, and other
conventional
mechanical and structural considerations.
[0042] In particular, the struts 30 of this embodiment are mounted towards
the top of the frame, proximate to the hinge 20. This type of configuration
may be
referred to as an "upper mount configuration." I-Iowever, depending on the
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configuration of the rear assembly twelve, the struts 3U may be mounted on a
lower
portion of the frame 14, for example, below the window line 15 and above the
tail
light 17.
[0043] The mounting of the struts 30 in rear assembly 12 according to the
present invention is significantly different than in prior art rear assemblies
for
automobiles. In the rear assembly 12, one end of the strut 30 is pivotally
mounted to
a fixed pivot 32 on the liftgate 18; the other end of the strut 30 is
pivotally mounted
on a moveable pivot 34 defined at the end of an articulating arm 40. The
articulating
arm 40 is itself pivotally mounted to a power-operatedl system 36 mounted
within a
rearwardly-facing longitudinal channel 38 in the rearward-most pillar 42 of
the
automobile 10. As will be described below in greater detail, movement of the
articulating arm 40 caused by the power-operated system 36 changes the angular
orientation of the struts 30, causing them to move between angular
orientations in
which the force bias provided by the struts 30 is sufficient to overcome the
weight
bias of the liftgate 18 and thereby move the liftgate 18 in to an open
position, and
orientations in which the force bias provided by the struts 30 is insufficient
to
overcome the weight bias of the liftgate 18, causing the liftgate 18 to move
toward the
closed position. When the liftgate 18 is caused to move toward the closed
position,
additional movements of the struts 30 may be used to control the movement of
the
liftgate 18, as will be explained below in greater detail.
[0044] Depending on the particular configuration of the rear assembly 12,
either one or both struts 30 may be connected to a power-operated system 36.
If both
struts are not connected to a power-operated system 36, one strut 30 may be
connected in a normal manner at two fixed pivot points between the frame 14
and the
liftgate 18. If both struts 30 are connected to power-operated systems 36,
they may be
connected to separate, commonly controlled power-operated systems 36, which is
the
configuration shown in FIGURE 1, or they may be connected to a single power-
operated system that transmits power to both struts simultaneously. Commonly
assigned co-pending Application No. 10/131,599, filed on April 25, 2002, which
was
incorporated by reference in its entirety above, discloses an embodiment in
which two
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struts are connected to a single power-operated system that transmits power to
both
struts, and may be referred to for more details on that embodiment.
[0045] FIGURES 2 and 3 show the mounting of the struts 30 and the
power-operated system 36 within the rear assembly 12 in more detail. As was
noted
5 above, the power-operated system 36, which primarily comprises a motor 44
and
gearbox 46, is mounted within the rearward-most pillar 42 of the automobile
10. In
some cases the rearward-most pillar 42 may be the "D" pillar, depending on the
particular automobile 10. An advantage of this type of mounting that the same
automobile 10 can be used for both manual and automatic rear liftgate
platforms.
10 More particularly, because the same structure can be used whether the strut
30 is
mounted to a rotating articulating arm 40 or a fixed point relative to the
rearward-
most pillar 42, the frame structure 14 and interior panels can be the same for
both
manual liftgate and automatic liftgate versions of the vehicle for the
automobile 10,
thus reducing the tooling costs of the automobile frame and panels.
[0046] FIGURE 2 is a sectional view of the rearward-most pillar 42, taken
through Line 2-2 of FIGURE 1, illustrating the arrangement of the power-
operated
system 36 within the rearward-most pillar 42. As shown, the rearward-most
pillar 42
is generally "C-shaped" such that it is provided with a rearwardly facing
longitudinal
channel that receives at least a portion of the strut 30 and at least a
portion of the
articulating arm 40 when the liftgate 18 is in the fully closed position. The
motor 44,
through the gearbox 46, drives a rotatable shaft 48 that extends through a
portion of
the pillar, shown as a hole 50 in FIGURE 2, so as to extend in to the channel
38 and
be connected with the articulating arm 40. Positioning of the struts 30 at
least
partially within the channel 38 formed in the rearward-most pillar 160 when
the
liftgate 18 is closed is advantageous in packaging and positioning the struts
30. A
molded panel 52 covers the rearward-most pillar 42 toward the interior of the
automobile 10.
[0047) FIGURE 3 is an exploded view of a portion of the rearward-most
pillar 42 illustrating the installation of the power-operated system 36 within
the pillar
42. A lateral face 54 of the pillar 42 is removed to allow for the
installation of the
power-operated system 36, providing an access way 56 to tl'e interior of the
pillar 42.
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The power-operated system 36 is installed within the pillar 42 such that the
shaft 48
of the gearbox 46 extends through hole 50. Within the rearwardly-facing
longitudinal
channel 38, the articulating arm 40 provides connecting structure, which in
this case is
hole 58, for connection to the strut 30 and connecting structure, in this case
hole 60
for connection to the shaft 48. The power-operated system 36 is electronically
controlled in a manner that will be described in more detail below.
[0048] An exemplary movement sequence of the liftgate 18 under the
control of the struts 30 and power-operated system 36 will be described with
reference to FIGURES 4-11, which are schematic side elevational views of the
automobile 10 showing one side of the rear assembly 12.
[0049] In FIGURE 4, the liftgate 18 is in a closed position. The latch 24 in
the lower portion of the liftgate is engaged with the latch striker 26 on the
frame 14.
(The latch 24 and latch striker 26 are indicated generally in FIGURE 4 by
reference
numeral 22.) The strut 30 is in a compressed state. The articulating arm 40 is
at an
angle a of about 45 degrees to an imaginary vertical line L, shown in phantom
in
FIGURE 4. In this position of the articulating arm 40, when the system is at
rest, the
strut 30 has minimal or substantially no mechanical advantage for opening
liftgate 18.
Therefore, the leveraged weight of the liftgate 18 is much greater than the
effective
force provided by the struts 30. The struts 30 are compressed by the weight of
the
liftgate 18 while the liftgate 18 remains in a closed position. Because the
weight of
the liftgate 18 is much greater than the effective force provided by the
struts 30 in the
position of FIGURE 4, the liftgate 18 will remain in the closed position for
as long as
the position/orientation of the struts 30 is unchanged, even if the liftgate
18 is
unlatched. That is, while the liftgate 18 may be latched into and unlatched
from the
closed position by the latch 24 and latch striker 26, the liftgate 18 remains
in the
closed position irrespective of whether or not it is latched because of the
angular
orientation of the struts 30. The angular orientation of the struts 30 is
determined by
the position of the articulating arms 40.
[0050] In the "at rest" or "home" position shown in FIGURE 4, the
adjustable pivot axis/point 34 for the strut 30 is located where a strut pivot
axis/point
would be located in a conventional manual strut-mounted rear liftgate, and
provides
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mechanical advantage similar to that of a manual liftgate system. Therefore,
while
the articulating arm 40 is in the "home" position, the liftgate 18 may be
opened
entirely in manual mode, without use of the power operated system 36. The
adjustable pivot axis/point 34 of the strut 30 will be disposed in this same
"home"
position When the liftgate 18 is fully opened (e.g. see FIGURE 8),
irrespective of
whether the liftgate 18 has been moved to the fully open position manually, or
by
operation of the power-operated system. Thus, when the liftgate 18 is fully
opened,
the strut pivot axis/point 34 will be located where a strut pivot axis/point
34 would be
located for a conventional manual strut-mounted rear liftgate. Therefore, the
liftgate
18 may also be closed entirely in manual mode without use of the power-
operated
system 36.
[0051] To open the liftgate 18 using the power-operated system, the liftgate
is unlatched (either automatically or manually) and the articulating arm or
arms 40 are
moved away from the "home" position illustrated in FIGURE 4 to change the
mechanical advantage of the struts 30. That is, to open the liftgate 18 after
it is
unlatched, the articulating arms 40 are moved into a position that
geometrically favors
a liftgate 18 lifting action for the strut 30, by the adjustable pivot
axis/point 34 of each
strut 30 being moved such that the struts 30 each have a greater mechanical
advantage
for liftgate-lifting action and exert a greater effective lifting force or
moment arm on
the liftgate 18. As the effective exerted force or moment arm of the struts 30
on the
liftgate 18 increases, that exerted force/moment arm eventually becomes larger
than
the downward weight bias of the liftgate 18. Consequently, the struts 30 began
to
uncompress, providing the required energy for pushing the liftgate 18 toward
the open
position. For purposes of this description, the orientation or positioning of
the struts
30 When the angular position of the articulating arms 40 (particularly pivot
point 34
on which the strut is mounted) allows the struts 30 enough mechanical
advantage to
push the liftgate 18 open is referred to as the liftgate-raising relation of
the strut or
struts 30. In some cases, the articulating arm 40 may be moved before the
liftgate 18
is unlatched.
[0052] FIGURE 5 illustrates the movement of the articulating arm 40 and
strut 30 into liftgate-raising relation. To establish the liftgate-raising
relation, the
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articulating arm 40 is rotated in a clockwise direction with respect to the
coordinate
system of FIGURE 5, away from the "home" position of FTGURE 4. The precise
amount of rotation that is required to place the strut 30 in liftgate-raising
relation
varies with the type of automobile 10 in which the system is installed, the
precise
position at which the struts 30 are mounted, and the inclination of the
automobile I0,
among other variables. In one eXample, the amount of rotation of the
articulating arm
is approximately 45° from the "home" position.
[0053] As the rotating arm 40 is rotated, the position of the adjustable pivot
axis 34 relative to the pivot axis of hinge assembly 20 provides increasingly
greater
mechanical advantage or moment arm to the strut 30, and the struts 30 thus
provide a
force sufficient to overcome the weight bias of the liftgate 18. As the
mechanical
advantage of the strut 30 is increased, it begins to extend and to push the
liftgate 18
open.
[0054] As was noted briefly above, movement or back and forth cycling of
the articulating arms 40 may commence prior to unlatching the liftgate 18 in
order to
lubricate (or "unstick") the internal works, and also to provide a "boost" to
the initial
opening of the liftgate 18, particularly if the automobile 10 is tilted or
inclined. These
features will be described in more detail below. Depending on the system and
particular operating conditions, the liftgate 18 may also be unlatched prior
to any
movement of arm 40.
[0055] The articulating arm 40 may initially remain in the position
illustrated in FIGURE 5 while the strut 30 extends and moves the liftgate 1$
towaxd
the open position, as illustrated in FIGURE 4. Alternatively, the articulating
arm 40
for one or both struts 30 may actively move and include instantaneous periods
of
stoppage or even instantaneous reverse movement during the initial opening
process,
depending on the particular geometries involved and feedback received by the
control
system. Feedback control of the power operated system 36 would be based on the
door position and/or speed, as may be determined by a door position detector,
such as
an angular position encoder in the hinge assembly 20 or an inclinometer in the
Iiftgate
18. A detailed description of position detection in general and several
suitable types
CA 02485052 2004-10-18
14
of position detectors can be found in commonly-assigned U.S. Patent
Application
10/131,599 and will not be repeated here.
[0056] In the position illustrated in FIGURE 6, the strut 30 has reached the
limit of its extension. To move the liftgate 18 into a fully open position
with respect
to the frame 14, the articulating arm 40 is moved back toward the original
"home"
position shown in FIGURE 4 by a rotation of the arm 40 in a counterclockwise
direction with respect to the figure to push the liftgate 18 through the final
portion of
travel. This movement is illustrated in FIGURE 7. Th.e fully open position of
the
liftgate 18, with the strut 30 fully extended, is illustrated in FIGURE 8.
[0057] In FIGURE 9, the first steps of the liftgate-closing process are
illustrated. The strut 30 is moved into an initial liftgate-closing relation
by clockwise
rotation (e.g., 45°) of the articulating arm 40 with respect to the
figure. In the
illustrated position, the position of pivot axis 34 relative to the hinge
assembly 20 axis
is such that the mechanical advantage or moment arm of the strut 30 is eroded,
and
the force provided by the strut 30 is overcome by the weight bias of the
liftgate 18.
The orientation or positioning of the struts 30 when the angular position of
the
rotating arm 40 reduces the mechanical advantage or moment arm of the struts
30
relative to the liftgate 18 so that the weight of the door moves the liftgate
18 toward
the closed position is referred to as the liftgate-lowering relation of the
strut or struts
30. To establish the liftgate-lowering relatipn, the rotating arm 40 is
rotated so that it
reaches a position that is, for example, 180-degrees displaced from the
neutral or
"home" position.
(0058] Once the rotating arm 40 has reached the position illustrated in
FIGURE 10 (axes 20, 34, and 32 being aligned), the strut 30 has substantially
no
mechanical advantage, and the liftgate 18 moves into a closed or near closed
position,
falling under its own weight. One of skill in the art will appreciate that
when the
weight of the liftgate 18 overcomes the force provided by the struts 30, the
liftgate 18
may fall very quickly into the closed position if the closing action is
uncontrolled.
This type of quick movement is generally undesirable, as it provides little
time to
clear obstacles that may be present in the path of the liftgate 18. Likewise,
if the
ascent of the Iiftgate 18 is too quick, similar problems may arise. Small
movements
CA 02485052 2004-10-18
or oscillations of the arm 4U may be used to control movement of the liftgate
18 to
prevent such rapid door movements.
[0059] The final steps of the closing sequence, which are illustrated in
FIGURES 10 and 11, depend on what type of latch assembly 22 is installed in
the rear
5 assembly 12.
j0060] If a completely mechanical latch assembly 22 containing no
powered actuator is installed, the articulating arm 40 would rotate clockwise,
thus
returning to the neutral or "home" position. The rotation of the articulating
arm 40
clockwise back to the neutral position, together with the weight of the door,
causes an
10 inward force to be applied, forcing the liftgate 18 toward the frame 14 (as
indicated by
arrow. F in FIGURE 11). This inward force will be sufficient to cause an
unpowered
latch 24 and latch striker 26 to engage and releasably lock the liftgate 18 in
a closed
position. In general, when the strut pivot axis 34 of the strut 30 is
positioned
outwardly of a line of action between the hinge 20 and pivot point 32
(illustrated as
15 phantom line D in FIGURE II), the Line of action of the strut 33 causes a
positive,
liftgate closing force to be applied to the liftgate 18.
[0061] The latch assembly 22 that is installed in the rear assembly 12 may
include a powered latch assembly or cinch latch, as discussed above. If such a
powered mechanism is installed, it may only be necessary for the clockwise
rotation
of the articulating arm 40 and weight of the liftgate 18 to move the liftgate
18 close
enough to the fully closed position to enable the powered latch 24 to take
over the
closing action and to cinch the liftgate 18 into sealed, locked relation.
[0062] It is anticipated that the geometry of the system, angular positions
and the length of the articulating arm 40, will be varied depending on the
particular
automobile 10 in which the system is installed. The arm length variation may
be
accomplished by manufacturing articulating arms 40 of different lengths based
upon
the vehicle, or it may be accomplished by a mechanism to adjust the length of
the
rotating arm 40 based upon the automobile 10.
[0063] The geometries and strut 30 angular orientations described above
may need to be modified according to the ambient temperature in which the
CA 02485052 2004-10-18
16
automobile 10 is operating. In particular, if the strut 30 is a gas strut, the
amount of
force output by the gas strut is temperature dependent, as described by
Charles's Law,
which governs the relationship between the pressure o:F a compressed gas and
the
ambient temperature. Modifications to the movements illustrated in FIGURES 4-
11
to account for temperature and/or automobile 10 inclination will be described
in more
detail below.
Control of the Strut Assembly
[0064] As was described briefly above, the rear assembly 12 is designed to
operate under the control of an electronic control system or controller, shown
schematically in FIGURE 1 at reference numeral 141. In general, the electronic
control system may have up to four functions: (1) moment-to-moment feedback
control over the position of the door, (2) control of the rate of door ascent
and descent,
(3) obstruction detection, and (4) detection of potentially adverse
environmental
conditions. The control system 14.1 may be independent of the power operated
system 36 or integrated with it. The functions of the control system may also
include
compensation for ambient temperature and other environmental considerations.
[0065] FIGURE 12 schematically illustrates the components of control
system 600, which is suitable for use with the two-motor power operated system
36
illustrated in FIGURE 1. As shown, the control system 600 includes a control
module
602, which includes a microprocessor and other appropriate computing devices
as
described above. The control system 600 also includes a vehicle tilt sensor
604 and
powered Latch assembly 22 in communication with the control module 602. The
control module 602 is connected to the main multiplexed communication bus 606
of
the automobile 10. As shown, the vehicle speed sensor 608 (which connects to
the
external body controller 609) is also in communication with the control module
602
through the multiplexed communication bus 606.
[0066] The control system 600 also includes a liftgate position sensor 612
which monitors the position of the Iiftgate 18 as it moves. The liftgate
position sensor
612 may be any one of the types of sensors described above. Depending on the
CA 02485052 2004-10-18
17
design of the rear assembly 12 of the automobile 10, the: liftgate position
sensor 612
may or may not be directly coupled to the liftgate hinge 20, and may be an
absolute or
a relative position sensor. If a gravity-based inclinometer is used as the
liftgate
position sensor 612, vehicle tilt information can be obtained by reading the
value of
the liftgate position sensor 612 prior to actuation of the liftgate 18, which
may make
the vehicle tilt sensor 604 unnecessary. Also, a gravity-based inclinometer
may be
used as a position sensor, as described above.
[0067] The two motors 44 and gearboxes 46 of the powered system (one for
the left-side strut 30 and one for the right-side strut 30) are schematically
illustrated in
FIGURE 12. As shown, each of the gearboxes 4G includes a motor speed sensor
614
and a "home" position sensor 616. The motor speed sensor 614 of this
embodiment is
a Hall Effect sensor or another similar type of sensor. The "home" position
sensor
616 of this embodiment a simple switch that activates when the rotating arm 40
returns to the "home" position, although the "home" position sensor 616 may be
implemented as a Hall Effect or similar sensor in other embodiments. In
general, the
Hall Effect motor speed sensor 614 functions by counting pulses relative to
the
position of the articulating arm 40 in the "home" position. (The articulating
arm 40
would be in the "home" position when the liftgate 18 is either fully opened or
fully
closed.)
[0068] The user inputs to control system 600 are not shown in Figure 18.
The control system 600 may take user input from a control panel mounted in the
dashboard of the vehicle or from a transmitting key fob, 'both of which are
well known
in the art.
[0069] A control algorithm 700 for a door-opening sequence using control
system 600 is shown in the block diagram of FIGURE 13. In FIGURE 13, the
algorithm 700 begins at block 702 with the liftgate 18 in the closed position.
The
algorithm 700 proceeds to block 704. At block 704, the control system 600
determines whether the command to open the Iiftgate I8 has been issued. If the
command to open the liftgate 18 has been issued (block 704:YES), control
passes to
block 706. If the command to open the liftgate 18 has not been issued (block
704:
NO), control returns to block 704.
CA 02485052 2004-10-18
18
[0070] In block 706, pre-opening system checka are performed. These pre-
opening system checks include checking whether the battery voltage is within a
programmed range (e.g., 9-16 VDC), checking whether the vehicle tilt exceeds
the
design limitations, checking whether the automobile 10 transmission is set to
"park,"
checking whether the automobile 10 is moving, and checking for any other
safety
hazards specific to the particular automobile 10. Additionally, if the
articulating arms
40 are not in the "home" position, as indicated by "home" position sensor
616), the
control module 602 may direct the motors 44 to move the articulating arms 40
into the
"home" position so as to ensure a consistent starting position. Each of these
pre-
opening system checks may involve multiple measurements and decision blocks,
although for simplicity, these additional measurement and decision blocks are
not
shown in FIGURE I3. Once block 706 is complete, control passes to block 708, a
decision block. In block 708, if any of the pre-opening checks have failed
(block
706:N0), control returns to block 704 and the Iiftgate 18 remains closed.
Otherwise
(block 708:YES), control passes to block 710.
[0071] In block 710, the control module 602 calculates the, position of the
articulating arms 40 at which the latch assembly 22 will be released. This
release
position is a function of the vehicle tilt, and so input is taken from vehicle
tilt sensor
604, or alternatively, if the liftgate 18 is equipped with an inclinometer
liftgate
position sensor 612, input may be taken from the liftgate position sensor 612
to
determine the vehicle tilt. Once the latch release position has been
calculated, control
passes to block 712.
[0072] In block 712 the motors 44 arc activated to move the articulating
arms 40 to a position at which the struts 30 begin to exert outward and upward
force
on the Iiftgate 18. In this embodiment, the articulating arms 40 are driven
clockwise
during this task. As the articulating arms 40 reach the latch release
position, control
passes to block 714. At block 714, the control module tests whether the
articulating
arms 40 have reached the latch release position. If the articulating arms 40
have
reached the latch release position calculated in block 710 (block 714:YES),
control
passes to block 716. Otherwise (block 714:NO), control returns to block 712
and the
articulating arms 40 continue to move towards the latch release position.
CA 02485052 2004-10-18
19
[0073] In block 716, the latch 24 is released by a command from the control
module 602 and the liftgate 18 begins to open. Control passes to block 718, in
which
the control module 602 tests whether the latch assembly 22 has been released.
If the
latch assembly 22 has been released (block 718:YES), control passes to block
720.
S Otherwise (block 718:N0), control returns to block 716 and the control
module 602
once again attempts to release the latch assembly 22.
[0074] In block 720, the liftgate 18 opens as the motors 44 are activated to
drive the articulating arms 40 as illustrated in FIGURE 6, i.e., in a
clockwise
direction. Control passes to block 722. In block 722, the control module 602
confirms that the liftgate 18 is opening, and if so (block 722:YES), control
passes to
block 724. Otherwise (block 722:N0), control returns to block 720 and the
articulating arms 40 continue to move.
[0075] At block 724; the articulating arms 40 have reached a designated
position. The motors 44 are stopped to allow the struts 30 time to expand
against the
weight bias of the liftgate 18 to push the liftgate 18 toward the open
position. Control
passes to block 726. In block 726, the control module 602 checks whether the
struts
30 have fully extended. If the struts 30 are fully extended (block 726:YES),
control
passes to block 728. Otherwise (block 726:N0) control returns to block 724.
[0076] In block 728, the control module 602 activates the motors 44 to
drive the articulating arms 40 counter-clockwise, back to the "home" position.
Once
the articulating arms 40 are in the "home" position, they liftgate 18 can
remain open
under the bias provided by the struts 30 for an indefinite period of time.
Control
passes to block 730. In block 730, the control module 602 determines whether
the
articulating arms 40 have reached the "home" position. If the articulating
arms 40
have reached the "home" position (block 730:YES), then the liftgate 18 is
fully open,
as indicated at block 732, and control passes to block 734, in which the
algorithm
terminates and returns. Otherwise (block 730:N0), control returns to block
728.
[0077] A control algorithm 750 for a door-closing sequence using control
system 600 is shown in the block diagram of FIGURE 1.4. The algorithm 750
begins
at block 752 with the liftgate 18 open and control passes to block 754. In
block 754,
the control module 602 determines whether the command to open the liftgate 18
has
CA 02485052 2004-10-18
been issued. If the command to open the liftgate 18 has been issued (block
754:YES),
control passes to block 756. If the command to open the liftgate 18 has been
issued
(block 754: YES), control passes to block 756. Othervvise (block 754:N0),
control
returns to block 754.
5 [0078] In block 756, pre=opening system checl~s are performed. These pre-
opening system checks may be the same as those in block 706 of FIGURE 13 and
include checking whether the battery voltage is within a programmed range
(e.g., 9-16
VDC), checking whether the vehicle tilt exceeds the design limitations,
checking
whether the vehicle transmission is set to "park," checking whether the
vehicle is
10 moving, and checking for any other vehicle-specific safety hazards. Each of
these
pre-opening system checks may involve multiple measurements and decision
blocks,
although for simplicity, these additional measurement and decision blocks are
not
shown in FIGURE 14. Once block 756 is complete, control passes to block 758, a
decision block. In block 758, if any of the pre-star checks have failed (block
15 706:N0), control returns to block 754 and the Iiftgate 18 remains open.
Otherwise
(block 708:YES), control passes to block 760.
[0079] In block 760, the control module 602 activates the motors 44,
causing the articulating arms 40 to move clockwise. Once the articulating arms
40 are
moving, control passes to block 762. In block 7fi2, the control module 602
20 determines whether the "collapse point" has been reached, i.e., whether or
not the
struts 30 have begun to collapse under the weight bias of the liftgate 18. If
the
"collapse point" has been reached (block 762:YES), control passes to block
764.
Otherwise (block 762:N0), control returns to block 760 and the articulating
arms 40
continue to move.
[0080] Blocks 760, 762 and 764 include several features that are not shown
in FIGURE 14, including obstacle detection. Block 7fi0 is shown in more detail
in
Figure 22, a detailed schematic diagram. As shown, block 760 begins with
decision
task 760A, in which the control module 602 determines. whether it is the first
second
(or, more generally, the first instant) of door closing. If the present
instant is within
the first second of closing (task 760A:YES), control passes to task 760B,
where the
control module 602 measures and stores in memory the current that the motor
135 is
CA 02485052 2004-10-18
21
drawing. Control then passes from task 760B to task 760C. Otherwise (task
760A:N0), control passes directly to task 760C.
[0081] In task 760C of block 760, the control module 602 determines
whether the present current that the motor 135 is drawing (Imot in Figure 22)
is greater
S than the reference current (Iref iri Figure 22) that was measured and stored
in task
760B. If the motor current is greater than the reference current (task
760C:YES),
control passes to task 760D, at which point an obstruction to door movement is
assumed to exist and the direction of movement of the liftgate 18 is reversed.
Otherwise (task 760C:N0), control passes to block 762 while the articulating
arms 40
conrinue to move.
[0082] Block 760 provides a motor-based type of obstacle detection that is
implemented as the motor begins to activate. The obstruction detection of
block 760
may also be performed continuously or at designated points throughout
algorithms
700 and 750. Additionally, the control module 602 may poll (i.e., interrogate)
any
pinch bars or other obstruction detection systems that are installed to
determine
whether an obstruction exists at any point in algorithms 700 and 750.
[0083] After the "collapse point" detected in block 762, the control system
600 controls the movement of the liftgate 18 somewhat differently. Prior to
the
"collapse point," the struts 30 act as rigid, incompressibYe members, and
movement in
the system is confined to the articulating arms 40. Once the "collapse point"
has been
reached, the struts 30 act as compressible members and collapse while the
articulating
arms 40 are moving. As another feature, the control module 602 may be
programmed
to know or anticipate when the "collapse point" will occur. This type of
anticipation
would be advantageous because the control module 602 would then be able to
accommodate the change and keep the liftgate 18 from moving too quickly. There
are
three ways in which the control module 602 might anticipate the "collapse
point."
First, the current drawn by the motor 135 will spike when gravity begins to
effect the
struts 30, and the control module 602 may be programmed to recognize this
current
spike. Second, the control module 602 may be programmed to detect a sudden
increase in liftgate door velocity from the liftgate position sensor 612 and
to recognize
this event as the "collapse point." Third, the control module 602 may be
programmed
CA 02485052 2004-10-18
22
to conclude, based on the position of the articulating arms 40, that the
"collapse point"
must have been reached for any reasonable inclination of the vehicle 10.
[0084] The "controlled collapse" of block 764 is a segment of the closing
sequence of the door during which the movement rate oaf the liftgate 18 is
maintained
within a desired velocity profile. The "desired velocity profile" is, in one
embodiment, a substantially constant speed, and the movement velocity of the
liftgate
18 is maintained for most of its travel within a certain range (e.g., ~ 25%)
of that
desired constant speed. It should be appreciated that the velocity may jump
out of the
desired range at certain instances during the door movement, such as during
initial
opening, towards the end of opening, during initial closing, towards the end
of
closing, and at the transition when the strut begins to compress (e.g, the
"collapse
point") during closing, and that the system subsequently brings the velocity
back into
the desired velocity range or profile.
[0085] Block 764 is shown in more detail in FIGURE 15, a detailed
schematic diagram. In task 764A, the control module 602 checks the speed of
the
liftgate 18 and compares it with a target speed stored in memory. If the
liftgate door
speed is less than the target speed (task 764A:YES), control passes to task
764B, in
which the control module 602 instructs the motor 135 t:o speed up the movement
of
the articulating arms 40. Control then returns to task 764A. If the speed of
the
liftgate door is not less than the target speed (task 764A:N0), control passes
to task
764C.
[0086] In task 764C, the control module 602 determines whether the liftgate
is moving more than 1.5 times the desired target speed. If the liftgate door
is moving
more than 1.5 times the desired target speed (task 764C:YES), it is assumed
that
slowing the articulating arms 40 is an insufficient speed correction. Control
passes to
task 764D in which the direction of movement of the articulating arms 40 is
reversed.
Otherwise (task 764C:N0), control passes to task 764E.
[0087] In task 764E, the control module 602 determines whether the liftgate
door speed is greater than the target speed. If the liftgate door speed is
greater than
the target speed (task 764E:YES), control passes to task 764F, in which the
control
module 602 directs the motors 44 to slow the articulating arms 40. Control
then
CA 02485052 2004-10-18
23
returns to task 764A. If the liftgate door speed is not greater than the
target speed
(task 764E:N0), control passes directly to block 766.
[0088] In block 766, which is illustrated in FIGURES 15 and 16 for
simplicity and clarity, the control module 602 determiners whether the
liftgate liftgate
18 is close to the closed position. This determination is made based on the
output of
the liftgate position sensor 612. If the liftgate door is close to the closed
position
(block 766:YES), control passes to block 768. Otherwise, control returns to
task
764A and block 764 repeats.
[0089] In block 768, which is shown in FIGURE 14, the control module
602 instructs the motors 44 to drive the articulating arms 40 in a counter-
clockwise
direction at full speed, and the angular orientation of the struts 30 at this
point in the
cycle imparts a force (shown as arrow F in FIGURE 11) to force the liftgate 18
inward, causing the latch 24 to engage the latch striker 26. Control passes to
block
770. In block 770, the control module 602 determines whether the latch
assembly 22
has cinched. If the latch assembly 22 has cinched (block 770:YES), control
passes to
block 772. Otherwise (block 770:N0), control returns to block 768.
[0090] In block 772, the control module 602 instructs the motors 44 to drive
the articulating arms 40 back to the "home" position. Control passes to block
774. In
block 774, the control module 602 checks the "home" position sensors 616 to
determine whether the articulating arms 40 have reached the "home" position.
If the
articulating arms 40 have reached the "home" position (block 774:YES), the
liftgate
18 is assumed to be fully closed, as shown in block 776, and algorithm 750
terminates
and returns at block 778. Otherwise (block 774:N0), control returns to block
772.
[0091] In the description of algorithms 700 and 750 above, the control
module 602 is programmed to repeat the task of a particular block if a later
decision
block demonstrates that the task of that particular block has not been
performed
successfully. In cases where repetitive failure to periForm a task could
indicate a
persistent error condition (for example, in block 708 of algorithm 700 and
block 758
of algorithm 758), the control module 602 may be programmed to abort
operations if
a the tasks of a block are unsuccessful after a specified number of
iterations.
CA 02485052 2004-10-18
24
[0092] As will be appreciated from the description above, the movement of
the liftgate 18 between open and closed positions using the strut 30 and the
power-
operated system 36 represents a delicate balance between the lifting force
provided by
the strut 30 and the weight bias of the liftgate 18. If the liftgate 18 moves
too quickly
and is thus permitted to gain too much momentum, it becomes difficult to
arrest its
movement. Consequently, the movement of the liftgate 18 in the embodiments
described above is typically relatively slow. Slow movements may be
undesirable
because of the time it takes the liftgate 18 to reach the open or closed
positions.
[0093] Accordingly, it may be advantageous in some embodiments of the
invention to use a controllable strut. As used here, the term
'°controllable strut" refers
to any strut that can be stopped and held at a particular extended length to
facilitate
the opening and closing of the liftgate 18. When stopped a particular extended
length,
a controllable strut can be used as a substantially rigid member to push or
pull the
liftgate 18 open or closed, which would allow the opening and closing
sequences to
occur more quickly.
[0094] Several types of controllable struts have previously been used. One
common type of controllable strut is that in which a valve is used to control
the flow
of fluid across the piston of the strut. When the valve is closed, fluid
cannot flow
across the piston, and the strut is thus stopped at a particular extended
length. As
those of skill in the art will realize, when a controllable strut of this type
is stopped, is
that the controllable strut is not entirely rigid. Instead, the gas in each
chamber of the
strut retains its resilience, and the controllable strut essentially becomes a
spring
damper. In engineering terms, the effect of closing the valve of this sort of
controllable strut is to increase the spring constant of the strut, for
example, from
about 1 newton per millimeter to abort 50 newtons per millimeter. Although
controllable struts with external valve structure are suitable for use in
embodiments of
the present invention, the external valve takes up additional space, and may
create
packaging problems, i.e., problems in fitting the struts and power-operated
system 36
within the available space in the rear assembly 12 and the automobile 10.
Additionally, in controllable struts with external valves, the external valve
must work
against both the pressure across the piston itself and the pressure created by
the
CA 02485052 2004-10-18
external hoses that run from the strut to the valve. Thus, external valves may
need to
be large in order to have the required strength to operate. against those
pressures.
[0095) However, in accordance with another embodiment of the invention,
a controllable strut has been developed that include valve structure on its
interior.
5 One embodiment of the controllable strut, generally indicated at 300, is
shown in the
schematic sectional view of FIGURES 17 and 18. FIGURE 17 is a view of the
strut
300 in its unlocked or free-flow condition. As shown in FIGURE 17, the strut
300
generally comprises a hollow housing 302 a piston 304, a. baffle 306, a valve
308, and
a driver 3I0.
10 [0096) The hollow housing 302 is hermetically sealed and has an opening
303 at one end. The piston 304 passes through the opening, and the sealed
condition
of the housing 302 is maintained by a sealing structure 305 proximate to the
opening
303 that forms a seal between the piston 304 and the opening 303. As installed
within
the housing 302, the piston 304 is capable of reciprocating between an
extended
15 position and a retracted position. The piston 304 includes a baffle 306
mounted on
the end of the piston rod within the housing 302. The baffle 306 seafingly and
slidingly engages the interior walls of the housing 302. The baffle 306 has a
number
of orifices 312 that, in an open condition, allow fluid to pass from one side
of the
piston 304 to the other. The size and number of the orifices 312 determine the
20 amount of damping that the strut 300 provides.
[0097) The valve 308 is shaped as a plunger having a steam portion 316 and
a flange portion 314 that extends radially outward. The steam 316 of the valve
308 is
slidingly mounted within a channel 309 in the piston 304, such that the valve
308 may
reciprocate between open and closed positions. A coil spring 311 within the
channel
25 309 biases the valve 308 toward the open position shown in FIGURE 17. In
the
closed position in FIGURE 18, the flange portion 314 of the valve 308 is in
contact
with the baffle 306, blocking the orifices 3I2 and preventing fluid from
flowing
across the baffle 306. Preferably, the working fluid within the strut 300 is a
gas, such
as air. However, other fluids may also be used in struts 300 according to the
present
invention.
CA 02485052 2004-10-18
26
[0098] The valve 308 is driven between the open and closed positions by
the driver 310, which is operatively associated with the valve 308. The
driver.310 is
fixedly mounted to the piston 304 on the inside of the housing 302. As shown
in
FIGURES 17 and 18, the position of the driver 310 on the piston 304
corresponds to
the location of the channel 309 in the piston 304.
[0099] In this embodiment, the driver 310 is an electromagnetic coil.
Activation of the electromagnetic coil driver 310 pulls the valve against the
baffle
306, such that the valve is in the closed position illustrated in FIGURE 18.
The
electrical leads for the driver 310 are routed through the interior of the
piston 304 and
extend to the exterior of the housing 302 for electrical. connection to the
electrical
system of the automobile 10 and the controller for the power-operated system
36.
The controller provides electrical signals to energize the driver 310.
[00100] Because the driver 310 is located within the housing 302, the
engagement force is required to drive the valve 308 into the closed position
adjacent
the baffle 306 are significantly lower than prior art desilms. In the strut
300, the only
forces that the valve 308 must resist are the forces caused by the pressure
differenrial
across the piston, which is typically not large.
[00101] Another embodiment of a controllable strut 350 is shown in the
schematic sectional views of FIGURES 19 and 20. FIGURE 19 illustrates the
strut
350 in the open or free flow condition; FIGURE 20 illustrates the strut 350 in
the
locked or restricted flow condition. In the strut 350, a solenoid 320 is
mounted on a
hollow cylinder 322 within the housing 302. The hollow cylinder 322 has a
number
of passageways 324 circumferentially spaced about the mounting end thereof,
which
is proximate to the baffle 306. The cylinder 322 is mounted to the baffle 306.
The
valve of this embodiment, indicated at reference numeral 323, is a block of
sealing
material proximate to the baffle 306. Springs 326 and 328 extend between the
valve
323 and solenoid 320 and are arranged to bias the valve 323 into the open
position
shown in FIGURE 19. When the solenoid 320 is energized, the valve 323 moves to
the position shown in FIGURE 20, in which it blocks the orifices 312 in the
baffle
306. As with the previous embodiment, the electrical connections for the
solenoid
CA 02485052 2004-10-18
27
320 run through the interior of the piston 304 for external connection to the
controller
for the power-operated system 36.
[00102] In addition to the above, controllable struts 300, 350 have several
other advantages. For example, if the driver 310 is an electromagnetic coil,
in
addition to its function as a driver 310 to control the strut, it may be used
to detect the
temperature inside the strut 300, 350; as well as to heat the interior of the
strut 300,
350.
[00103] The resistance of an electromagnetic coil used as a driver 310 is
typically specified very precisely by its manufacturer. Because the resistance
of a coil
is a function of the ambient temperature, the temperature inside the strut
300, 350 can
be monitored by monitoring the resistance of the electromagnetic coil and
comparing
it to known values specified by the manufacturer. In order to heat the
interior of the
strut 300, 350, current can be supplied to the driver 3I0, turning it into a
resistive
heating element. This feature can be used to increase the temperature within
the strut
on very cold days, during which the gas pressure within the strut might
otherwise not
be sufficient to open the liftgate.
[00104] In addition to temperature measurement, technology for remotely
measuring and sensing pressure is well known and may also be used in a
controllable
strut 300, 350 according to the invention. For example, such technology is
used
widely in the tire industry, as disclosed in U.S. Patent No. 6,612,165. If a
pressure
measurement sensor is used in a controllable strut accarding to the invention,
it may
transmit its data wirelessly, or it may transmit its data through wires routed
through
the piston.
[00105] Embodiments of the invention using controllable struts 300, 350
may use one controllable strut 300, 350 or two. In embodiments with one
controllable
strut 300, 350 is used, the other strut may be a conventional strut 30 of the
type
described above. Alternatively, an embodiment of the invention may use ane
controllable strut 300, 350 and no conventional strut 30, in which case the
controllable strut 300, 350 would have enough force generating capability to
raise the
liftgate 18 without a second strut 30. In addition to the embodiments of
controllable
struts 300, 350 described here, several embodiments of controllable struts are
CA 02485052 2004-10-18
28
described in U.S. Provisional Application No. 60/419,286, as well as in the
corresponding commonly assigned non-provisional application, titled "LOCKING
STRUT," which was filed on October 17, 2003, and is also incorporated by
reference
in its entirety.
[00106] In embodiments using a controllable strut 300, 350; the opening
sequence of the liftgate 18 is similar to the opening sequence of a liftgate
18 moving
under the force bias of two standard struts 30. Specifically, the rotating arm
40 is
moved to give the struts 30, 300, 350 mechanical advantage, and the two struts
30,
300, 350 are allowed to expand under their own force bias. In environmental
conditions that disfavor opening, such as low temperature or large
inclination, the
controllable strut 300, 350 may be locked at a particular length and used to
help
maintain a desired opening speed as the conventional strut 30 expands. To some
extent, the controllable stmt 300, 350 may be used in the locked state as a
partially
rigid link to push the liftgate open; however, this is limited by the power of
the motor
44 and by the resiliency of the controllable strut 300, 350 in the locked
state.
[00107] However, the closing sequence of such embodiments does differ
somewhat from that of the embodiments presented above. Such a closing sequence
may be conceptually divided into four phases for purposes of explanation. In
the first
phase of the closing sequence, the rotating arms 40 move to an appropriate
closing
position. In the second phase of the closing sequence, midway through its
retraction/travel, the controllable strut 300, 350 is locked, and its
continued, partially-
extended motion is used to force the conventional strut 30 to retract. During
this
second phase, the rotating arms 40 connected to the two struts 30, 300, 350
may move
at different rates and in different directions so as to rr~inimize the time
necessary to
cause both struts to retract. In the third phase of the closing sequence, the
controllable
strut 300, 350 is alternately locked and unlocked according to a specified
duty cycle
in order to control the rate of closure of the liftgate 18. The fourth and
final phase of
the closing sequence takes place as the liftgate 18 has closed and the
rotating arms 40
return to their "home" position. Each of these sequences will be described in
more
detail below.
CA 02485052 2004-10-18
29
[00108] FIGURE 21 schematically illustrates the components of a control
system 800, which is suitable for use with a two-motor power operated system
driving
one controllable strut 300, 350 and one conventional strut 30. Control system
800 is
substantially similar to control system 600 shown in FIGURE 12; for that
reason,
components common to the two systems 600, 800 will not be discussed further
here.
However, control system 800 and its algorithms are simpler than those of
control
system 600 in some respects.
[00109] For example, because of the ability to control the rate of ascent and
descent of the liftgate 18 conferred by the controllable strut 300, 350, it is
not
absolutely necessary to have an independent measure of the vehicle tilt, or to
calculate
the "collapse point" of the struts per se. For this reason, the vehicle tilt
sensor 604 is
an optional component of the control system 800 and may be omitted, or,
alternatively, used to determine only if the automobile 10 is too inclined to
safely
open the liftgate 18.
[00110] In control system 800, the liftgate position sensor 812 is preferably
an accelerometer mounted on the liftgate 18. For example, the accelerometer
812
may be mounted on the window of the liftgate 18, a highly damped area that may
prevent the accelerometer 812 from reading excessive. amounts of noise:
Suitable
accelerometers that may be used as the liftgate position sensor 812 include
the BHZ
02 and BSZ 02 accelerometers manufactured by Temic Telefunken Microelectronic
GmbH (Kirchheim, Germany). As those of ordinary skill in the art will realize,
the
output from an accelerometer may be integrated witlh respect to time to
provide
velocity or position measurements. Of course, other types of sensors may be
used,
including position sensors placed directly at the hinge 20 of the liftgate 18.
[00111] In embodiments of the invention using control system 800 and one
or more controllable struts 300, 350, as well as in the other embodiments of
the
invention, obstacle detection may be accomplished in several ways using
several
different types of sensors. One preferred way to detect obstacles is to
monitor the
electric current drawn by each motor 44. A spike in the amount of current
drawn by
the motors 44 indicates that an obstruction is present.
CA 02485052 2004-10-18
[00112] The ability to detect obstacles well by measuring motor current draw
is one advantage of embodiments of the present invention. Because the motors
44
draw relatively little current, the control system 800 is able to resolve very
small
changes in the amount of current drawn by each motor 44. That is not the case
when
5 using a conventional large motor to open a liftgate using; a "brute force"
approach; the
large amount of current drawn by a typical motor makes it difficult to resolve
the
small changes in motor current that indicate the presence of obstructions.
[00113] In addition to motor current, obstacle detection may be
accomplished by monitoring the output of the accelerometer or other liftgate
position
10 sensor 812. Unexpected velocity and acceleration changes can be taken to
mean than
an obstruction has been encountered.
[00114] Finally, obstruction detection may be accomplished by conventional
"pinch bars" placed around the opening 16 and connected to the control system
800.
However, such "pinch bars" may be unnecessary, and may be added to the
automobile
15 10 only to satisfy particular manufacturer requirements. Embodiments of the
invention typically cause the liftgate 18 to impart very low "pinch forces"
because the
liftgate 18 is not connected to the motors by a rigid link; instead, the
resiliency of the
struts 30, 300, 350 reduces the pinch forces.
[00115] FIGURE 22 is a high-level schematic flow diagram of a method 900
20 for opening a liftgate 18 according to the present invention. In the
following
description, the terms "left" and '°right" are used for convenience to
describe the
respective articulating arms 40. Method 900 anticipates the use of one
controllable
strut 300, 350 and one ordinary strut 30. In the following description, it is
assumed
that the controllable strut 300, 350 is attached to the left articulating arm
40.
25 However, the controllable strut 300, 350 may be attached to either of the
articulating
arms 40 without affecting the method 900.
[00116] Method 900 begins at block 902, and control passes to block 904.
As method 900 begins, it is assumed that the liftgate 18 is in the closed
position and
that the latch assembly 22 is engaged. At block '904, the control system 800
30 determines whether the command to open the liftgate 18 has been issued.
(The
command to open the liftgate 18 may be issued from a control panel within the
CA 02485052 2004-10-18
31
vehicle or from a key fob attached to a user's key chain, for example.) If the
command to open the liftgate 18 has been issued (block 904:xES), control
passes to
block 906. If the command to open the liftgate has not been issued (block
904:N0),
control returns to block 904.
[00117] In block 906, pre-opening system checks are performed. The pre-
opening system checks performed in block 906 may be identical to those
described
above with respect to method 700 of the previous embodiment. However, in some
variations on method 900 that will be described below, it may not be necessary
to
move the articulating arms 40 to "home°' position. Once the pre-opening
system
checks have been performed, control passes to block 908, a decision block.
[00118] In block 908, if any of the pre-opening system checks have failed
(block 908:N0), control returns to block 904 and . the liftgate 18 remains
closed.
Otherwise (block 908:YES), control passes to block 91C~.
[00119] In block 910, the control module 802 mends the latch assembly 22
to release. Control passes to block 912, a decision block. In block 912, the
controller
802 communicates with the latch status switches embedded in the latch assembly
22
through the vehicle communication bus 602. If the latch assembly 22 has not
released
(block 912:N0), control remains in block 912 and tlhe controller 802 repeats
the
query. Otherwise (block 912:YES), control passes to block 914.
[00120] In block 914, the motion of the articulating arms 40 begins. In
contrast with method 700, method 900 makes use of variable actuation speeds of
the
articulating arms 40 as well as coordinated but opposite direction movement of
the
two articulating arms 40. The use of variable speeds and movements of the
articulating arms 40 in opposite directions during part of the actuation cycle
maximizes the advantages of the controllable strut 300, 350. In block 914,
movement
of the articulating arms 40 begins when the controller 802 causes both motors
44 to
move the articulating arms 40 clockwise at 50°70 of maxiimum speed.
Once movement
of the articulating arms 40 has begun, control passes to block 916, a decision
block.
[00121] In block 916, the control module 802. takes input from the liftgate
position sensor 812 to determine whether the liftgate 18 is opening. If the
liftgate 18
CA 02485052 2004-10-18
32
is opening (block 916:YES), control of method 900 passes to block 926. If the
liftgate 18 is not opening (block 916:N0), control passes to block 918.
[00122] When control of method 900 reaches block 918, it is assumed that
there is some problem in opening the liftgate 18. The control module 802
considers
the input from the motor Hall Effect sensors 614 to determine whether the
articulating
arms 40 have reached a position in which they exert maximum force. If the
articulating arms have not reached a position of maximum force (block 918:N0),
control of method 900 returns to block 916. If the control module determines
in block
918 that the articulating arms 40 have reached a position of maximum force
(block
918:YES), control of method 900 passes to block 92Ci. (The position of maximum
force is geometry dependent and can be calculated by one of skill in the art
based on
the geometry of the particular vehicle 10.)
[00123] In block 920, the control module 802 atops the right articulating arm
40 and increases the clockwise speed of the left articulating arm 40
(connected to the
controllable strut 300, 350) to 100°10. Control of method 900 passes to
block 922, a
decision block
[00124] In block 922, the control module 802 again decides whether or not
the liftgate 18 is opening. If the liftgate 18 is opening (block 922:YES)
control of
method 900 passes to block 926. Otherwise (block 922:N0), control passes to
block
924.
[00125] In block 924, the control module 8I~2 takes input from the Hall
Effect sensors 614 in the motors 44 to determine by the position of the
articulating
arms 40 whether the controllable strut 300, 350 has reached a position in
which it
should be fully extended. If the articulating arms 40 have reached a position
in which
the controllable strut 300, 350 should be fully extended (block 924:YES),
control of
method 900 passes to block 946. Otherwise (block 924:N0), control of method
900
returns to block 922.
[00126] In block 946, the controllable strut 300, 350 is locked, e.g., by
closing the valve 308, 323 within the controllable strut 300, 350. Control of
method
900 then passes to block 948.
CA 02485052 2004-10-18
33
[00127] In block 948, the fully extended and locked controllable strut 300,
350 is used to assist the extension of the other strut 30. To do this, the
left articulating
arm 40 attached to the controllable strut 300, 350 is driven counter clockwise
at 100%
of its speed while the articulating arm 40 connected to the regular strut 30
is driven at
50% of its maximum speed. Control passes to block 950, a decision block.
[00128] In block 950, the control module 802 takes input from the liftgate
position sensor 812 to determine whether the liftgate 18. is half open. If the
liftgate 18
is half open (block 950:YES), control of method 900 passes to block 952. If
the
liftgate 18 is not half open (block 950:NO), control of method 900 remains at
block
950 and the control module 802 repeats the query.
[00129] In block 952, the controllable strut 300, 350 is unlocked, e.g., by
opening the valve 308, 323. The articulating arms 40 continue to rotate.
Control of
method 900 passes to block 954.
[00130] In block 954, the control module takes input from the home position
sensor 616 to determine whether the articulating arms 40 have reached the home
position. If the articulating arms 40 have reached the home position (block
954:YES),
both articulating arms 40 are stopped as indicated in block 942. Otherwise
(block
954:N0), control of method 900 remains at block 954 and the control module 802
repeats the query. Once the articulating arms 40 are stopped at block 942,
control of
method 900 passes to block 944, where method 900 terminates and returns.
[00131] Blocks 946-954 illustrate the tasks performed by the control module
802 if movement of the liftgate 18 is not detected after movement of the
articulating
arms 40 has been initiated. However, as was described earlier, if movement of
the
liftgate 18 is detected either at block 916 or at block 922, control of method
900
passes directly to block 926.
[00132] Before block 926 receives control oiF method 900, the articulating
arns 40 have been moving clockwise (i.e., with respect to the coordinate
system of
FIGURE 4). The clockwise movement of the articulating arms 40 covers only a
small
sector of the total 360° possible travel of the articulating arms 40,
and is enough to
place the controllable strut 300, 350 and the regullar strut 30 in a position
of
CA 02485052 2004-10-18
34
mechanical advantage sufftcient to begin opening the liftgate 18. In block
926, the
clockwise movement of the articulating arms 40 is stopped and reversed, such
that the
articulating arms 40 begin moving counter clockwise with respect to the
coordinate
system of FIGURE 4. Initially, both articulating arms are moved counter
clockwise at
30% of maximum speed. Control of method 900 passes to block 928, a decision
block.
[00133] In block 928, the control module 802 takes input from the liftgate
position sensor 812 to determine whether the liftgate 18 is opening at a speed
greater
than a desired target speed. If the liftgate is opening at a greater speed
than desired
(block 928:YES), control passes to block 930, in which. the speed of the
articulating
arms 40 is decreased by same fraction, e.g., 5%. If the speed of the liftgate
18 is not
above the desired target speed (block 928:N0), control of method 900 passes to
block
932, a decision block. In block 932, the control module 802 takes input from
the
liftgate position sensor 812 to determine whether the liftgate speed is below
a desired
target speed. If the speed of the liftgate 18 is below a desired target speed
(block
932:YES), control of method 900 passes to. block 934, in which the control
module
802 increases the speed of the articulating arms 40. Otherwise (block 932:N0),
control passes to block 936, another decision block.
[00134] In block 936, the control module 802 takes input from the liftgate
position sensor 812 to determine whether the liftgate 18 is 50% open. If the
liftgate
18 is 50% open (block 936:YES), control of method !I00 passes to block 938, in
which the control module 802 continues to drive both ;articulating arms 40
counter
clockwise toward the home position at 100% speed. if the gate is not 50% open
(block 936:N0), control of method 900 returns to block 928, the two
articulating arms
40 continue to move counter clockwise at 30% speed, and the speed control
decision
blocks 928 and 932 are repeated.
[00135] In block 940, the control module 802 takes input from the home
position sensor 616 to determine whether the articulating arms 40 have reached
the
home position. If the articulating arms 40 have reached the home position
(block
940:YES), control of method 900 passes to block 942, in which the articulating
arms
are stopped, before passing to block 944, in which method 900 terminates and
CA 02485052 2004-10-18
returns. If the articulating arms 40 have not reached the home position (block
940:N0), the articulating arms 40 continue to rotate counter clockwise toward
the
home position at 100% speed.
[00136] Although not explicitly shown in FIGURE 22 so as not to
5 complicate the description of method 900, the valves 308, 323 within the
controllable
strut 300, 350 may be used in either continuous or cycling operation to
maintain the
desired movement speed of the liftgate 18, in addition to controlling the
speed of the
articulating arms 40. Blocking the controllable strut 300, 350 can be
particularly
useful if the liftgate 18 is moving too fast and it becomes necessary to slow
its ascent.
10 [00137] FIGURE 23 is a high-level schematic flow diagram of a method 960
for closing the liftgate 18 using an embodiment with one controllable strut
300, 350
and one regular strut 30. In the following descriptiion of method 960, the
same
coordinate system is used as in the description of method 900, i.e., the
coordinate
system as shown in FIGURE 4. Method 960 begins at block 962, and control
passes
15 to block 964, a decision block.
[00138] In block 964, the control module 802 determines whether the
command to close the liftgate 18 has been received. If the command to close
the
liftgate has been received (block 964:YES), control of method 960 passes to
block
966. Otherwise (block 964:N0), control of method 900 remains at block 964 and
the
20 control module 802 repeats the query.
[00139] In block 966, the control module performs a number of pre-closing
checks. The type of pre-closing checks performed in block 966 may be the same
as
the pre-closing checks that were described above with respect to method 750.
Once
the pre-closing checks have been completed in block 966, control of method 960
25 passes to block 968, a decision block.
[00140] In block 968, the control module 802, determines whether the pre-
closing checks were passed. If the pre-closing checks were passed (block
968:YES),
control of method 960 passes to block 970. If the pre-cllosing checks were not
passed
(block 968:N0), control of method 960 returns to block '964
CA 02485052 2004-10-18
36
[00141] In block 970, the movement of the articulating arms 40 begins as the
right articulating arm 40, the articulating arm 40 connected to the regular
strut 30, is
driven clockwise at 100% of its maximum speed. During this movement, the left
articulating arm 40, the articulating arm connected to the controllable strut
300, 350,
remains still. Control of method 960 passes to block 972, a decision block.
(00142] In block 972, the control module 802 takes input from the liftgate
position sensor 812 and the motor Hall Effect sensors 614 to determine whether
the
liftgate 18 is 30% closed. If the liftgate 18 is 30% closed (block 972:YES),
control of
method 960 passes to block 974. If the Iiftgate 972 is not yet 30% closed
(block
972:N0), control of method 960 returns to block 970 and the movement of the
right
articulating arm 40 continues.
[00143] By the time block 974 has been reached, the right articulating arm
40, connected to the regular strut 30, has been moving clockwise for some time
while
the left articulating arm 40, connected to the controllable strut 300, 350,
has been
stopped. In block 974, the valve 308, 323 in the controllable strut 300, 350
is
engaged, thereby locking the controllable strut 300, 35~J. This allows the
controllable
strut 300, 350 to be used to force the regular strut 30 to retract. Once the
controllable
strut 300, 350 is locked, the left articulating arm 40, connected to the
controllable
strut 300, 350, is driven clockwise at 100% of its maximum speed. At the same
time,
the right articulating arm 40, connected to the regular strut 30, slows down
and begins
moving at 20% of its maximum speed. Control of method 960 passes to block 976,
a
decision block.
[00144] In block 976, the control module 802 takes input from the motor
Hall Effect sensors 614 and the liftgate position sensor 812 to determine
whether the
Iiftgate is 60% closed. If the Iiftgate 18 is 60% closed (block 976:YES),
control of
method 960 passes to block 978. If the liftgate 18 is not 60% closed (block
976:N0),
control of the method 960 remains at block 974 and the movement of the two
articulating arms 40 continues.
(00145] In block 978, the control module 8U2 reduces the speed of the Ieft
articulating arm 40, connected to the controllable strut 300, 350, to 30% of
its
maximum speed. Control passes to block 980, in which the control module 802
sends
CA 02485052 2004-10-18
37
pulses to the driver 310 within the controllable strut 300, 350, causing the
valves 308,
323 within the controllable strut 300, 350 to cyclically open and close at a
predefined
standard duty cycle. Control of method 960 then passes to block 982, a
decision
block.
[00146] In block 982, the control module 802 takes input from the liftgate
position sensor 812 to determine whether the speed of the liftgate 18 is above
the
desired target speed. If the speed of the liftgate 18 is above the desired
target speed
(block 982:YES), control of method 960 passes to block 984, in which the duty
cycle
of the controllable strut 300, 350 is increased, such that the controllable
strut 300, 350
is in the locked condition a greater percentage of the tune. If the speed of
the liftgate
18 is not above the desired target speed (block 982:N0), control of method 960
passes
to block 986, another decision block.
(00147] In block 986, the control module 802 takes input from the liftgate
position sensor 8I2 to determine whether the speed of the liftgate 18 is below
the
desired target speed. If the speed of the liftgate 18 is below the desired
target speed,
control of method 960 passes to block 988, in which the duty cycle of the
controllable
strut 300, 350 is decreased, such that the controllable strut 300, 350 is in
the locked
state a lesser percentage of the time. After blocks 984 a,nd 988, and if the
speed of the
liftgate 18 is not below the desired target speed (block 986:N0), control of
method
960 passes to block 990, another decision block.
[00148] At block 990, the control module 802 takes input from the sensors
within the latch assembly 22 to determine whether the latch assembly 22 has
engaged.
The latch assembly 22 has engaged (block 990:YES), control of method 960
passes to
block 992. If the latch assembly 22 has not engaged (block 990:N0), control of
method 960 returns to block 982, and the speed control algorithm is repeated.
(00149] In block 992, once the latch assembly 22 has engaged, the
controllable strut 300, 350 is unlocked. Once the controllable strut 300, 350
is
unlocked, both struts are driven clockwise at 100% of their anaximum speed
toward
the home position. Control of method 960 passes to block 994, a decision
block.
CA 02485052 2004-10-18
38
[00150] In block 994, the control module 802 takes input from the home
position sensors 616 to determine whether the articulating arms 40 have
reached the
home position. If the articulating arms 40 have reached the home position
(block
994:YES), control of method 960 passes to block 996, in which the motors 44
are shut
off, before method 960 terminates and returns at block 998. If the rotating
arms 40
have not reached the home position (block 994:N0), control of method 960
remains at
block 994, and the control module 802 repeats the query.
[00151] In the methods 900, 960 described above, the relative speeds set
forth depend on a number of factors, including the desired speed at which the
liftgate
18 is to open. The speeds will depend on a number of factors, including the
geometry
of the vehicle 10, the weight of the liftgate 18, and the power of the motors
44.
[00152] The last tasks of methods 900 and 960 are to move the articulating
arms 40 back into the home position. However, moving the articulating arms 40
back
into the home position after each and every movement of the liftgate 18 is
time
IS consuming and increases the amount of time a user must wait, for example,
after
closing the liftgate 18 before it can be opened again. (Also known as the
"cycle
time.") That delay can be undesirable.
(00153] Typically, when the gate is initially fully closed, the articulating
arms 40 are about 180° away from the home position. In certain
embodiments, the
articulating arms 40 may simply be left in that position when the gate is
closed,
thereby eliminating the cycle time delay created by moving the articulating
arms back
to the home position.
[00154] In that 180°-from-home position, the struts 30, 300, 350 may
not be
in a position such that the user will be able to open the Iiftgate 18
manually. (As was
described above, in the normal operation of the liftgate 18, the home position
is the
position in which traditional struts 30 would be mounted if they were not
attached to
articulating arms 40 and motors 44. This allows completely manual opening of
the
liftgate 18.) Despite the fact that completely manual opening of the liftgate
18 may
not be possible if the articulating arms 40 are left 180° from the home
position,
control system 800 could be provided with a program whereby an attempt by the
user
to open the Iiftgate I8 manually would be detected, and the articulating arms
40
CA 02485052 2004-10-18
39
would be caused to move in whatever direction was necessary to assist the user
in the
manual movement of the door.
[00155] Although the invention has been described with respect to several
embodiments, the embodiments described are meant to be exemplary and not
limiting.
Modifications and variation to the invention will occur to those of ordinary
skill in the
art, and may be made within the scope of the appended claims.
