U.S. patent number RE36,267 [Application Number 08/927,759] was granted by the patent office on 1999-08-17 for vehicle body with powered lift type tailgate.
This patent grant is currently assigned to Chrysler Corporation. Invention is credited to Delbert D. DeRees, David J. Kowall, Thomas S. Moore.
United States Patent |
RE36,267 |
Moore , et al. |
August 17, 1999 |
Vehicle body with powered lift type tailgate
Abstract
A tailgate is hinged to a passenger van type vehicle body above
a substantially vertical rear access opening for swinging movement
about a horizontal hinge axis. The tailgate is counterbalanced
through its range of movement by spring devices and is opened and
closed by a powered actuator mounted on a rear vehicle body pillar.
The actuator includes a reversible electric motor driving a worm
shaft that drives a worm gear to pivot a crankarm about an axis
parallel to the hinge axis. A roller mounted on the crankarm is
received in a guide channel that is fixed to the tailgate and
extends at right angles to the hinge axis with the pivoting
movement of the crankarm thereby translated into swinging tailgate
opening and closing movement. The motor is connected with torque
sensing circuitry that detects an excessive motor torque demand
when the tailgate encounters an obstacle and stops the motor. A
normally engaged clutch maintains drive connection between the worm
gear and the crankarm to effect normal tailgate opening and closing
by the motor and slips to allow manually applied force on the
tailgate to open and close same when the motor is not
operating.
Inventors: |
Moore; Thomas S. (Northville,
MI), DeRees; Delbert D. (Romeo, MI), Kowall; David J.
(Hartland, MI) |
Assignee: |
Chrysler Corporation (Auburn
Hills, MI)
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Family
ID: |
23125644 |
Appl.
No.: |
08/927,759 |
Filed: |
September 11, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
292662 |
Aug 18, 1994 |
05448856 |
Sep 12, 1995 |
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Current U.S.
Class: |
49/340;
49/28 |
Current CPC
Class: |
E05F
15/611 (20150115); E05Y 2900/546 (20130101); E05Y
2800/11 (20130101); E05F 15/40 (20150115); E05Y
2201/236 (20130101); E05F 15/63 (20150115); E05F
15/41 (20150115); E05F 1/1091 (20130101) |
Current International
Class: |
B60J
5/10 (20060101); E05F 15/12 (20060101); E05F
15/00 (20060101); E05F 011/24 () |
Field of
Search: |
;49/339,340,341,26,28,324,139,140,245,246,247 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3636789 |
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Oct 1986 |
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DE |
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1-314620 |
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Dec 1989 |
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JP |
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1-314520 |
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Dec 1989 |
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JP |
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Primary Examiner: Redman; Jerry
Attorney, Agent or Firm: Stec; Jennifer M.
Claims
What is claimed is:
1. In combination, a vehicle body having a rear opening, a tailgate
adapted to open and close said rear opening, a hinge pivotally
mounting said tailgate on said vehicle body for swinging movement
about a horizontal hinge axis located adjacent an upper edge of
said tailgate so that said tailgate on upward lifting movement is
moveable from a closed position closing said rear opening to an
open position completely opening said rear opening, a pair of
counterbalance devices operatively connected between said vehicle
body and said tailgate substantially counterbalancing the weight of
said tailgate as it swings to open and close said rear opening, a
singular tailgate actuator mechanism mounted on said vehicle body
adjacent said upper edge of said tailgate and operatively connected
to said tailgate, said actuator mechanism comprising a reversible
electric motor, a crankarm pivotal in an arc transverse to said
hinge axis, torque multiplying drive means including a normally
engaged clutch operatively connecting said motor to said crankarm,
a guide channel mounted on and extending along an inner side of
said tailgate transfer to said hinge axis, a roller mounted on said
crankarm and received and retained in said guide channel, said
guide channel having opposing guide rails engaged by said roller at
diametrically opposite locations thereby to effect movement of said
tailgate between said closed and open positions by said roller
rolling in said guide channel on pivotal movement of said crankarm
in opposite directions by said motor, said clutch having a load
capacity sufficient to effect normal tailgate opening and closing
by said motor and to slip to allow an external force on said
tailgate to open and close same independent of motor operation, and
a controller controlling said motor that detects an excessive
amount of motor torque demand when said tailgate encounters an
obstacle during motor powered movement and stops the motor before
slippage in the clutch occurs.
2. In combination, a vehicle body having a substantially vertical
rear opening, a tailgate adapted to open and close said rear
opening, a hinge pivotally mounting said tailgate on said vehicle
body for swinging movement about a horizontal hinge axis located
adjacent an upper edge of said tailgate so that said tailgate on
upward lifting movement is moveable from a closed substantially
vertical position closing said rear opening to an open upwardly
angled position above horizontal completely opening said rear
opening, a pair of gas springs operatively connected between said
vehicle body and said tailgate substantially counterbalancing the
weight of said tailgate as it swings to open and close said rear
opening, a singular tailgate actuator mechanism mounted on said
vehicle body adjacent said upper edge of said tailgate and
operatively connected to said tailgate, said actuator mechanism
comprising a reversible DC constant speed motor, a crankarm pivotal
in an arc at right angles to said hinge axis, drive means
operatively connecting said crankarm to said motor including a worm
shaft connected to be driven by said motor, a worm gear driven by
said worm shaft, a torque multiplying gear train operatively
connected to pivot said crankarm, a normally engaged clutch
connecting said worm gear to said gear train, a guide channel
mounted on and extending along an inner side of said tailgate at
right angles to said hinge axis, a roller mounted on said crankarm
and received and retained in said guide channel, said guide channel
having opposing guide rails extending longitudinally at right
angles to said hinge axis and extending width wise parallel to said
hinge axis and engaged by said roller at diametrically opposite
locations thereby to effect movement of said tailgate between said
closed and open positions by said roller rolling in said guide
channel on pivotal movement of said crankarm in opposite directions
by said motor, said clutch having a load capacity sufficient to
effect normal tailgate opening and closing by said motor and to
slip against the reaction force of said worm shaft to allow an
external force on said tailgate to open and close same, and a
controller controlling said motor that detects an excessive amount
of motor torque demand when said tailgate encounters an obstacle
during motor powered movement by sensing motor current load and
stops the motor before slippage in the clutch occurs.
3. A combination as set forth in claim 2, and said vehicle body
having a rear pillar adjacent said rear opening, said rear pillar
having an upper end, and said actuator mechanism except for said
guide channel wholly mounted on said rear pillar near said upper
end.
4. A combination as set forth in claim 3, and said tailgate having
a window and said guide channel mounted between a side edge of said
tailgate and said window. .Iadd.
5. A powered lift tailgate mechanism in combination with a vehicle
body and a tailgate comprising:
an electric motor drive coupled to said vehicle body;
a gear train system coupled to said motor drive and to said
tailgate for transferring mechanical forces from said motor drive
to said tailgate to thereby open said tailgate;
a clutch mechanism integrated with said gear train system and
operable to permit manual movement of said tailgate through a
manually applied force and to inhibit the transfer of said manually
applied force to said motor drive;
electronic controller for supplying operating current to said motor
drive, said controller including system for electrically sensing
torque produced by said motor drive and for automatically
inhibiting the supplying of operating current to said motor drive
when said torque produced exceeds a first predetermined torque;
and
said first predetermined torque required to inhibit a supply of
operating current to said motor is slightly greater than an amount
of torque required to cause said clutch mechanism to slip.
.Iaddend..Iadd.6. A powered life tailgate mechanism as claimed in
claim 5, wherein said clutch mechanism further comprises:
a clutch pad mechanically communicating with said motor drive;
a clutch pressure plate mechanically communicating with said
tailgate, said clutch pressure plate being adjacent to said clutch
pad; and
a clutch spring forcing said clutch pressure plate to engage said
clutch pad, said clutch spring maintaining said clutch pressure
plate and said clutch pad in a locked condition when said motor
drive has a torque output less than a second predetermined amount
of torque, said clutch spring allowing said clutch pad and said
clutch pressure plate to slip when said motor drive has a torque
output greater than said second predetermined amount of torque.
.Iaddend..Iadd.7. A powered lift tailgate mechanism as claimed in
claim 6, wherein said second predetermined amount of torque is a
value greater than an amount of torque required by said motor drive
to
move said tailgate. .Iaddend..Iadd.8. A powered lift tailgate
mechanism as claimed in claim 5, wherein said electronic controller
further comprises:
at least one actuator control circuit, said actuator control
circuit being in electrical communication with said motor drive;
and
a switch electrically connected to said actuator control circuit,
said switch having at least one position, said one position
stopping said motor drive from moving said tailgate at any given
position of said tailgate. .Iaddend..Iadd.9. A powered lift
tailgate mechanism as claimed in claim 5, further comprising at
least one gas spring with a first end and a second end, said first
end of said gas spring being pivotally connected to a vehicle frame
and said second end of said gas spring being pivotally connected to
said tailgate, said gas spring being adjusted to counterbalance the
weight of said tailgate and minimize the amount of torque of said
motor drive required to open and close said tailgate.
.Iaddend..Iadd.10. A powered lift tailgate mechanism as claimed in
claim 5, wherein said tailgate is hingedly attached to said vehicle
body by at least one hinge. .Iaddend..Iadd.11. A powered lift
tailgate mechanism as claimed in claim 5, further comprising a
latch, said latch having a solenoid operated latching mechanism on
a bottom edge of said tailgate and a locking bolt affixed to said
vehicle body. .Iaddend.
Description
TECHNICAL FIELD
This invention relates to vehicle bodies with a tailgate that is
lifted to open and more particularly to powered lift systems for
opening and closing this type tailgate that allow manual tailgate
opening and closing.
BACKGROUND OF THE INVENTION
In vehicle bodies such as the van type having a substantially
vertical rear access opening, there is by choice of vehicle design
provided either a sideways type swinging tailgate that swings about
a generally vertical axis and as a result requires little effort to
open and close or a lift type tailgate that swings upward about a
horizontal axis to open and as a result requires significant
lifting effort. For the convenience of the people using a vehicle
having a lift type tailgate, it is desired that a power lift system
be provided to relieve a person of the required lifting effort and
particularly where the tailgate is a heavy singular gate or door
that closes the entire rear access opening. However, there is very
limited space in the vehicle body for a power lift system with the
capacity to handle the heavy lifting effort required of such a
heavy lift type tailgate. Moreover, it is desirable that the
tailgate be capable of being opened and closed manually independent
of special conditioning of the power lift system and with minimum
effort both as a matter of convenience and in the event the
operation of the power lift system is not available for some reason
such as a malfunction in the actuator mechanism or loss of
power.
Previous power lift tailgate systems that do appear to work
satisfactory in various respects are typically complicated in
structure with many components and require considerable space such
as those employing a sector gear and linkage system with connected
counterbalancing devices to counterbalance the tailgate to reduce
the lift load. Furthermore, they typically require a control system
co-operating with certain of the actuating components to switch
between a power mode and a manual mode that will allow manual
opening and closing free of the power lift mechanism. Moreover,
they are typically insensitive to the tailgate encountering an
obstacle during powered movement.
SUMMARY OF THE INVENTION
The present invention offers a very simple, cost effective, space
saving, easy to install, powered actuator system for a lift type
tailgate having a singular electric motor powered actuator that
operates to lift the tailgate with minimized effort, automatically
shuts off operation when the tailgate encounters an obstacle, and
releases the tailgate for manual operation without having to be
automatically or manually switched from its power mode to a manual
mode. In the tailgate powered lift system of the present invention,
separate spring devices are connected directly between the vehicle
body and opposite sides of the tailgate and provide upwardly acting
balancing forces thereon that substantially counterbalance its
weight through its range of movement from a substantially vertical
closed position to an upwardly angled, above horizontal wide open
position. This permits the use of a singular, electric motor
powered tailgate actuator that is mounted on a rear pillar of the
vehicle body adjacent the upper edge of the tailgate at one side of
the rear access opening.
The actuator includes a DC motor, a crankarm pivotal in a plane at
right angles to the hinge axis, and a gear train drivingly
connecting the crankarm to the motor. The gear train includes a
worm shaft driven by the motor and a worm gear that is driven by
the worm shaft and is driving connected through additional
reduction gearing to pivot the crankarm. A guide channel is mounted
on and extends longitudinally along an inner side of the tailgate
at right angles to the hinge axis and a roller is mounted on the
crankarm and received and retained in the guide channel. The roller
has an axis parallel to the hinge axis and the guide channel has
parallel guide rails that are parallel and at right angles to the
hinge axis and are engaged by the roller at diametrically opposite
locations. There is thus effected smooth and efficient opening and
closing of the tailgate by the roller rolling in the guide channel
on pivotal movement of the crankarm in opposite directions by
operation of the motor and with the counterbalancing of the
tailgate minimizing the effort required of the motor to effect the
tailgate movement.
The actuator motor is controlled by a microprocessor controller
having a torque sensing circuit that senses motor current load and
is set to open the motor circuit to stop the motor and thereby
tailgate movement at a certain excessive motor torque demand when
the tailgate encounters an obstacle. In addition, a normally
engaged clutch is strategically located between the worm gear and
crankarm and operates to normally maintain a drive connection
therebetween to effect normal tailgate opening and closing by the
motor and is preset to slip against the reaction force of the DC
motor connected worm shaft to allow manually applied force on the
tailgate to open and close same when the motor is not operating. On
the other hand, the clutch is not required to continuously slip
when the tailgate encounters an obstacle during powered movement
because the motor is then automatically stopped until the excessive
motor load is relieved and this can then be accomplished by manual
movement of the tailgate, if required, to clear the obstacle from
the tailgate.
Among the several features of the invention in addition to those
mentioned above is that the structure of the powered tailgate
actuator is not encumbered by that of the tailgate counterbalancing
devices. This allows flexibility in choosing the best suited
location for the mounting of both the actuator and the
counterbalancing devices in a particular vehicle body design. For
example, the counterbalancing devices can be remotely located
relative to the powered tailgate actuator to suit the most
accommodating mounting or attachment location for these devices on
both the tailgate and vehicle body without requiring special
accommodating modifications of the latter structures. On the other
hand, the compactness of the power actuator similarly permits it to
be mounted directly on a rear pillar in a normally open space in
the vehicle body rather than requiring special accommodating space
between one or both sides of the tailgate and the rear pillar
structure. Another feature is that the clutch for manual tailgate
operation in its preferred form is a simple, low cost, spring
biased friction clutch that releases at a preset torque setting
that can be factory adjusted to suit a particular tailgate
installation. This is in contrast to an electrically operated
on-off type clutch that would require an additional control
function to switch from a power lift mode to a manual mode and then
have to be switched back to the power mode for power operation.
It is therefore an object of the present invention to provide a new
and improved powered tailgate actuator system for a lift type
tailgate on a vehicle body.
Another object is to provide a powered actuator system for a lift
type tailgate on a vehicle body wherein the tailgate is
counterbalanced through its range of movement by spring devices and
the tailgate is positioned by a motor powered actuator mounted on
the vehicle body having a crankarm with a roller operating in a
guide channel on the tailgate.
Another object is to provide on a vehicle body a hinged lift type
tailgate operated by a powered actuator with the assist of a
tailgate counterbalance arrangement wherein the tailgate can be
operated manually without power lift mode shifting.
Another object is to provide on a vehicle body a hinged lift type
tailgate operated by a powered actuator with the assist of a
tailgate counterbalance arrangement wherein the tailgate can be
operated manually without power lift mode control and the power
lift stopped automatically when the tailgate encounters an
obstacle.
Another object is to provide a hinged lift type tailgate on a
vehicle body with a counterbalancing system of direct acting spring
devices and a powered actuator whose tailgate lifting requirement
is reduced thereby and allows manual tailgate operation through
slipping clutch action without having to be switched from a power
mode to a manual mode.
Another object is to provide a hinged lift type tailgate on a
vehicle body with a counterbalancing system of direct acting spring
devices and a powered tailgate actuator whose tailgate lifting
requirement is reduced thereby and wherein the actuator allows
manual tailgate operation through slipping clutch action without
having to be switched from a power mode to a manual mode and
wherein the powered movement of the tailgate is ceased
automatically on the tailgate encountering an obstacle.
These and other objects, advantages and features of the present
invention will become more apparent from the following description
and accompanying drawings wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary perspective view of the rear portion of a
passenger van type vehicle body having a lift type tailgate
operated by an actuator system according to the present invention,
the vehicle body being illustrated in phantom lines and the
tailgate being shown in its closed position;
FIG. 2 is an enlarged view of the tailgate actuator installation
taken along the line 2--2 in FIG. 1 when looking in the direction
of the arrows;
FIG. 3 is an enlarged view taken along the line 3--3 in FIG. 1 when
looking in the direction of the arrows and illustrates the tailgate
in its closed and wide open positions;
FIG. 4 is a diagram of the electrical control system that controls
the actuator system in FIG. 1;
FIG. 5 is an enlarged view taken along the line 5--5 in FIG. 2 when
looking in the direction of the arrows;
FIG. 6 is an enlarged view taken along the line 6--6 in FIG. 2 when
looking in the direction of the arrows;
FIG. 7 is an enlarged view of the operating end of the actuator
crankarm taken along the line 2--2 in FIG. 1 when looking in the
direction of the arrows; and
FIG. 8 is a slightly enlarged view taken along the line 8--8 in
FIG. 7.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring to FIGS. 1 and 3, there is illustrated in phantom lines
the rear portion of a passenger van type vehicle body designated
generally as 10 including a roof structure 12, a pair of left and
right quarter panel structures 14 and 16 and a pair of left and
right body pillars 18 and 20 interconnecting the roof structure and
the respective quarter panel structures. The above structures
cooperate with a laterally extending rear bumper structure 22 in
defining a generally vertical rear opening 24 that provides access
to the interior of the vehicle body and is closed and opened by a
lift type tailgate or rear door 26 having a window 28. The tailgate
26 is mounted at its upper lateral edge with hinges 30 on the roof
structure for swinging movement about a horizontal axis 31
extending transverse of the vehicle body. The tailgate 26 is
swingable about this axis between the closed position shown in FIG.
1 where it closes the opening 24 and a wide open position where it
completely uncovers the opening for free access to the vehicle body
interior and assumes a slightly upwardly angled uplifted position
above horizontal as shown in phantom line in FIG. 3. The tailgate
26 is secured in its closed position by a suitable conventional
latch 32 including a solenoid operated latching mechanism 34 on the
bottom edge 35 of the tailgate that engages a locking bolt 36 on
the tailgate sill 37 of the vehicle body. The tailgate 26 is opened
and closed by a powered actuator system generally designated as 38
with the assist of a pair of tailgate counterbalancing gas springs
40 and wherein the powered actuator system also allows manual
opening and closing of the tailgate.
The gas springs 40 are mounted parallel to each other at opposite
sides of the rear access opening 24 with the anchor end of their
cylinder 42 connected by a pivot mounting 44 to the respective
opening defining rear pillars 18 and 20 at a point above the
vehicle body belt line. The gas springs are connected at the end of
their projecting piston rod 46 by a pivot mounting 48 to the
respective longitudinal edge 50 of the tailgate at a point about
midway of the height of the tailgate and slightly below the level
of the lower edge of the window 28. The gas springs 40 which are
also commonly referred to as gas struts are of a conventional
suitable type such as those currently used with the rear deck
closures on hatch back type vehicle bodies. The gas springs are
adjusted to provided substantially equal upwardly directed forces
on the tailgate that substantially counterbalance the weight of the
tailgate through its swinging range of movement between its
substantially vertical closed position in FIG. 1 and its uplifted
upwardly angled wide open position in FIG. 3.
The powered tailgate actuator mechanism 38 is separate from the gas
springs 40 so as to not influence their operation and is mounted
high on either of the rear body pillars. In the embodiment
illustrated, the actuator mechanism is mounted on the right rear
body pillar 20 and hidden behind a rear quarter trim panel (not
shown). Referring to FIGS. 2, 5 and 6, the actuator mechanism
comprises a two-piece housing 54 that is secured with three bolts
56 to a bracket 58 that is welded to an upper portion of the pillar
20 close to the vehicle body ceiling and at a location that
positions the actuator mechanism clear of the tailgate in its
closed position. A reversible DC motor 60 is mounted on the housing
54 in a generally upright position that is angled backward from the
tailgate toward the interior of the vehicle body so as to have a
relatively low profile and allow close positioning of the output
point of the mechanism to the tailgate.
As shown in FIG. 5, the motor 60 powers a worm shaft 62 that is
mounted in the housing 54 and meshes with a worm gear 64 that is
rotatably supported on a gear shaft 66 and is normally clutched
thereto by a spring biased clutch generally designated as 67. The
gear shaft 66 is mounted at right angles to the worm shaft and a
clutch pressure plate 68 that is a part of the clutch assembly is
received on the gear shaft and fixed thereto by a woodruff key 70.
A pinion gear 72 is also similarly fixed to the gear shaft 66 and
bears against an interior side of the housing 54. A snap ring 74
mounted in a groove on the gear shaft 66 between the outboard side
of the worm gear 64 and an interior side of the housing restrains
the worm gear from outward movement on this shaft relative to the
pinion gear 72 that is fixed to this shaft.
The clutch assembly further includes an annular clutch pad 76 that
is riveted to the side of worm gear opposite the snap ring 74 and a
clutch spring 78 in the form of a wave washer that is received on
the gear shaft 66 between the pinion gear 72 and the pressure plate
68. The clutch spring 78 is loaded in its assembly and forces the
pressure plate 68 to engage the clutch pad 76 to normally clutch
the worm gear 64 to the gear shaft 66 and release when manual force
is applied to the tailgate as described in more detail later.
The pinion gear 72 meshes with a spur gear 80 of larger pitch
diameter that is fixed with a woodruff key (not shown) to a second
gear shaft 82 that is rotatably mounted in the housing 54 parallel
with the gear shaft 66. A second pinion gear 84 is fixed with a
woodruff key (not shown) to gear shaft 82 adjacent the spur gear 80
and meshes as shown in FIG. 6 with a second spur gear 86 of larger
pitch diameter that is fixed with a woodruff key to a third gear
shaft 90 that is rotatably mounted in the housing 54 parallel with
the other gear shafts. The pinion gears have the same pitch
diameter as do the larger spur gears and together with the worm
shaft and worm gear provide a very high speed reduction/torque
multiplying ratio between the worm shaft 62 and the third gear
shaft 90.
The third gear shaft 90 extends at one end outside the housing and
receives one end of a crankarm 92. The crankarm 92 is fixed to this
shaft by a head 94 formed on this end of the shaft that is staked
with stake formations 96 to the outboard side of the crankarm as
shown in FIG. 6. The opposite end of the third gear shaft 90 also
extends outward of the housing 54 and has a groove that receives a
snap ring 98 to hold this shaft and connected crankarm in the
assembly while also maintaining a close sliding clearance between
the crankarm and the housing to maintain their staked connection.
The crankarm 92 is thus normally clutched and connected by the
torque multiplying gear train to the motor 60 to be pivoted or
swung thereby about the axis of the gear shaft 90.
The crankarm 92 is operatively connected to the tailgate 26 to
swing same between its closed and wide open positions by a
cylindrical roller 100 that is mounted on the distal end of the
crankarm 92 opposite its mounting end on the actuator mechanism.
Referring to FIGS. 6, 7 and 8, the roller 100 is rotatably mounted
on a pin 102 that is fixed to the distal end of the crankarm. The
pin may by fixed to the crankarm by any suitable means such as
riveting or staking and the roller is retained on the pin by a snap
ring 104. Operating efficiency for this drive connection with the
tailgate is maximized by mounting the actuator mechanism on the
rear pillar 20 so that the axis about which the roller 100 turns is
parallel to the hinge axis 31 of the tailgate.
The connection between the crankarm 92 and the tailgate 26 is
provided by a straight guide channel 112 having a uniform,
generally C-shape, cross-section that receives and retains the
roller 100 and is connected to an upper portion 114 of the tailgate
structure adjacent the right edge of the window 28 and the right
edge of the tailgate and near the pillar 20. The channel 112 is
rigidly connected to the upper portion 114 of the tailgate by two
similar brackets 116 that are welded to the channel and the
tailgate portion 114. The guide channel 112 is formed with two
inner, opposing, parallel, guide rails or tracks 118 that are
engaged by the roller 100 and extend longitudinally the length the
guide channel at right angles to the tailgate hinge axis 31 and
laterally the width of the rails parallel to the tailgate hinge
axis to thus complement the rolling motion of the roller 100. The
guide rails 118 are engaged by the roller 100 at diametrically
opposite locations thereby to effect smooth movement of the
tailgate between its closed and wide open positions by the roller
rolling on these guide rails in the guide channel on pivotal
movement of the crankarm in opposite directions by operation of the
motor.
Referring to FIG. 4, the tailgate actuator mechanism 38 is
controlled by an electronic control system including a
microprocessor controller 120 having an actuator control circuit
122 and a motor control circuit 124. The actuator control circuit
includes two tailgate actuating switches 126 (the details of only
one being shown). One of the switches 126 is mounted on the driver
side door or instrument panel (not shown) and the other is
preferably mounted on a hand carried key fob (not shown) and
adapted to transmit electronic signals to the controller to operate
the tailgate actuator motor from a remote location outside the
vehicle. The switches 126 are of the three-position type having a
single actuator 132 that is moveable laterally as viewed in FIG. 4.
When the switch actuator 132 is in a center position as shown the
switch is open or off. On lateral movement of the switch actuator
in one direction from this off position to a second or tailgate
opening position, the actuator closes one set of switch contacts to
apply a ground signal to the controller 120 to power the motor 60
at constant speed in a tailgate opening turning direction. On
movement of the switch actuator in the opposite direction from the
off position to a third or tailgate closing position, the actuator
closes another set of contacts that are connected to apply a ground
signal to the controller to power the motor in a tailgate closing
direction. The microprocessor controller 120 includes torque
sensing circuitry of a suitable conventional type that detects the
motor current load and is set according to the present invention to
open the motor control circuit 124 to stop the motor and thereby
tailgate movement when this load exceeds a certain level as
described later.
Describing now the operation of the tailgate operating system and
the setting of the clutch 67 and the motor control circuit 124 and
starting with the tailgate closed and tailgate latch 34 released,
either one of the tailgate actuating switches 126 may be switched
to its tailgate opening position to power the actuator motor 60 at
constant speed in a direction that effects counterclockwise
movement of the crankarm 92 as viewed in FIGS. 1-3. In the closed
position, the crankarm is angled downward and the roller 100 is
located in the guide channel 112 at its remotest point from the
tailgate hinge axis 31 as shown in solid lines in FIGS. 1, 2 and 3.
Then on the above crankarm pivoting movement, the roller 100 is
forced with this crankarm movement to roll in the guide channel 112
on the rails 118 toward the tailgate hinge axis thereby lifting the
tailgate toward its wide open position shown in phantom line in
FIG. 3. The gas springs 40 are adjusted to substantially
counterbalance the weight of the tailgate during this lifting
movement and thus minimize the amount of motor torque required in
this lifting action. The actuator motor can be stopped at any time
with the actuating switch being utilized to hold the tailgate in a
partially open position or the motor operation can be continued as
desired until the tailgate is positioned in its wide open position
where the roller 100 is then at it closest point in the guide
channel 112 to the tailgate hinge axis 31 as shown in phantom line
in FIG. 3.
To close the tailgate, either one of the actuating switches 126 is
then switched to its tailgate closing position to reverse the
direction of the actuating motor causing the crankarm to pivot
clockwise as viewed in FIGS. 1, 2 and 3 and pull the tailgate
closed with the forced action of the roller 100 in the guide
channel 112 wherein the roller then rolls in the guide channel away
from the tailgate hinge axis. During the closing movement, the gas
springs again counterbalance the tailgate but now to minimize the
pulling torque required of the actuator motor and the tailgate can
be stopped at any mid-open position by the actuating switch being
utilized.
During the above opening and closing operation of the tailgate, the
drive from the worm gear 64 to the crankarm 92 is maintained by the
clutch 67 by setting its torque capacity with the clutch spring 78
at a certain limited value or load capacity that will effect normal
tailgate opening and closure without clutch slippage. The clutch
load capacity is limited to the extent that when the tailgate is
stopped with the actuator motor 60 and held in any of its positions
with the actuator mechanism, a person can then apply a relatively
low manual force to the tailgate that is effective to slip the
clutch 67 against the reaction force of the motor connected worm
shaft and either close or fully open the tailgate or adjust it to
any mid-position as desired and thus without requiring the use of
the actuator. This manual operation offers convenience to the
vehicle user in then not having to operate one of the actuating
switches and also allows tailgate opening and closing by the
vehicle user in the event the actuator operation is not available
for some reason such as a malfunction in the actuator mechanism or
loss of power. The clutch setting is limited so that the manually
applied torque on the tailgate required to slip the clutch 67 is
greater than that required of the motor powered crankarm 92 in its
action only by an amount that establishes a suitable or
non-excessive manual effort for a typical vehicle user.
On the other hand, if during powered tailgate movement the tailgate
encounters an obstacle such as a package, grocery cart, lane pylon,
etc. in its path of movement in either direction, the motor control
circuit 124 detects the resulting excessive or unusual torque
demand by sensing the motor current load and is set to open the
motor circuit at a relatively high current load above which damage
at the tailgate could occur should it continue to be powered. The
opening of the motor circuit stops the motor to prevent further
forced movement of the tailgate by the actuator mechanism until
this overload torque on the motor is relieved. This threshold
overload level is set at a level slightly above that of the
manually applied torque described above to slip the clutch 67 for
manual positioning of the tailgate. The motor circuit remains open
until the obstacle is removed and with the motor stopped there can
be no possible clutch slippage occasioned by the motor that would
wear same while the obstacle remains in the tailgate path. In
addition, the actuator switch being utilized may then be opened to
prevent resumption of the actuator motor should the obstacle
require considerable time to be completely removed from the path of
the tailgate or the tailgate may then be manually positioned as
described above to clear the obstacle.
The invention has been described in an illustrative manner with
respect to presently preferred embodiments, and it is to be
understood that the terminology that has been used is intended to
be in the nature of words of description rather than words of
limitation. Obviously, many modifications and variations of the
present invention in light of the above teachings may by made. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically shown and described.
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