Information
-
Patent Grant
-
6341809
-
Patent Number
6,341,809
-
Date Filed
Wednesday, December 13, 200024 years ago
-
Date Issued
Tuesday, January 29, 200223 years ago
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Inventors
-
Original Assignees
-
Examiners
- Pape; Joseph D.
- Morrow; Jason
Agents
-
CPC
-
US Classifications
Field of Search
US
- 296 50
- 296 56
- 296 1464
- 296 1468
- 049 110
- 049 340
- 049 351
- 049 352
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International Classifications
-
Abstract
A vehicle liftgate has a counterbalance system comprising a first link pivotally connected to the vehicle body. A second link is pivotally connected to the first link at one end and to the liftgate at the opposite end. The counterbalance system includes a compression spring that is attached to the first link via a pulley. The compression spring stores energy when the liftgate is closed to assist in subsequent opening of the tailgate. The liftgate may be closed manually or with power assistance.
Description
FIELD OF THE INVENTION
This invention relates to vehicles, such as sport utility vehicles, having a liftgate for access to a cargo compartment and more particularly to a counterbalance system for the liftgate.
BACKGROUND OF THE INVENTION
Vehicles that have liftgates usually include a counterbalance system that stores energy when the lift gate is closed with the stored energy then being used to assist in the subsequent lifting of the liftgate to an open position. A common liftgate counterbalance system uses a pair of gas springs that are pivotally attached to opposite sides of the lift gate at one end and to the vehicle body at the opposite end.
A drawback with gas springs is that the gas springs are sensitive to variations in ambient temperature. This results in the use of gas springs that resist closure of the liftgate with considerable force on hot days. For instance, the gas spring or springs must be strong enough to open the liftgate on the coldest day (usually assumed to be −40° C.) Such gas springs increase closing resistance substantially on the hottest day (usually assumed to be 80° C.) Therefore considerable effort must be used to close the liftgate or a very large electric motor used in the case of a power operated system.
Liftgates that have two or more gas springs for a counterbalance system are common. These gas springs generally occupy a position in which their axes is substantially parallel to the liftgate so that the gas springs are hidden when the liftgate is closed. In this closed position the moment arm of the gas springs is quite small. With such systems the liftgate may move about one-third of its total travel range before the ga cylinders exert sufficient force to open the liftgate further without the application of an independent lifting force. There are even some systems in which the gas springs pass over center and bias a liftgate toward a closed position when the liftgate is closed. With these self-closing systems a liftgate may need to be more than one-third open before the gas springs will open the liftgate further. Thus the geometry of the gas spring counterbalance system itself increases the drawback of gas spring counterbalance system.
Decklids have been counterbalanced with steel coil springs for many years. A decklid when open, with spring relaxed has the gravity moment at its minimum. As the decklid is closed the gravity moment and the spring output both increase. With spring and gravity moment tracking together, counterbalancing a decklid is straightforward. The difficulty with counterbalancing a liftgate, in comparison to a decklid is that with the liftgate in the open position, and the counterbalance spring relaxed, the gravity moment is near its maximum. This means that when the spring is at its minimum output the load from the liftgate is maximum. The converse is also true. When the spring is at a maximum output the liftgate has its smallest gravity moment. Thus coil spring counterbalance systems for decklids are not well suited for liftgates.
SUMMARY OF THE INVENTION
The counterbalance system of this invention uses a compression spring or springs as an alternate for gas springs in a liftgate application and thus provides a liftgate counterbalance system that is not sensitive to variations in ambient temperature. The counterbalance system of the invention also has an improved geometry and changing mechanical advantage for applying the compression spring forces of the counterbalance system to assist in opening the liftgate.
BRIEF DESCRIPTION OF THE DRAWINGS
The presently preferred embodiment of the invention is disclosed in the following description and in the accompanying drawings, wherein:
FIG. 1
is a perspective end view of a vehicle equipped with a liftgate and a counterbalance system in accordance with the invention;
FIG. 2
is a side view of the vehicle of
FIG. 1
showing details of the counterbalance system with the liftgate in the open position, and
FIG. 3
is a side view of the vehicle of
FIG. 1
showing details of the counterbalance system with the liftgate in the closed position.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawings, vehicle
10
has a liftgate
12
that is attaches the aft end of the vehicle roof by two hinge assemblies. A portion of a typical right hand hinge assembly
14
is shown in
FIGS. 2 and 3
. Hinge assemblies
14
have hinge portion that are secured to a roof channel of the vehicle
10
and hinge portions that are secured to liftgate
12
. The vehicle hinge portions are attached to the liftgate hinge portions by pivot pins
16
so that liftgate
12
pivots about a substantially horizontal hinge axis
18
at the aligned centerlines of pivot pins
16
from an open position shown in
FIG. 2
to a closed position shown in FIG.
3
. Liftgate
12
is generally permitted to pivot about 90° about the substantially horizontal axis
18
defined by pivot pins
16
. However, the range of movement can be varied substantially from one model of vehicle to another.
Liftgate
12
is opened and closed manually or by a suitable power operating system and includes two identical counterbalance units
22
that are installed in the aft end of the vehicle body. Counterbalance units
22
are laterally spaced from each other and near the respective vertical body pillars
23
at the aft end of vehicle
10
, commonly referred to as the D pillars, that define the width of the rear opening that is closed by liftgate
12
. The typical counterbalance unit
22
is shown in greater detail in
FIGS. 2 and 3
.
Each counterbalance unit
22
comprises a first link
24
that is pivotally connected to a body portion of the vehicle by a first hinge pin
25
at or near the D pillar
23
. A second link
26
is pivotally connected to the first link
24
adjacent one end by a second hinge pin
27
and pivotally connected to the vehicle liftgate
12
adjacent an opposite end by a third hinge pin
29
. The first and second links
24
and
26
form an obtuse angle when liftgate
12
is open as shown in FIG.
2
and an acute angle when liftgate
12
is closed as shown in FIG.
3
.
Each counterbalance unit
22
includes a coil shaped compression spring
28
that is disposed in a tubular housing
30
that is fixed the vehicle body, preferably at or near the D pillar
23
. The upper end of the compression spring
28
abuts an upper annular flange
32
of the housing
30
. Each counterbalance unit
22
includes a pulley having a flexible tension member
34
that is connected to the lower end of the coil shaped compression spring
28
. Tension member
34
extends through the open center of the coil shaped compression spring
28
axially and out a concentric hole in an upper annular wall
32
of housing
30
. Tension member
34
then continues upward and wraps around a roller
36
that is part of the pulley. Roller
36
revolves around an axis
37
that is substantially parallel to and spaced below the hinge axis
18
of the liftgate
12
defined by pivot pins
16
. Tension member
34
is then attached to link
24
near the hinge pin
27
connecting links
24
and
26
. The tension member
34
may be made of any flexible material and preferably is a steel cable.
The operation of the counterbalance system is as follows. When liftgate
12
is in the open position as shown in
FIGS. 1 and 2
, the coil shaped compression spring
28
is in an expanded state as shown in FIG.
2
. Spring
28
is preferably slightly compressed when liftgate
12
is open to take up any lash in hinge assemblies
14
or the counterbalance units
22
due to manufacturing tolerances. The liftgate
12
is moved manually with the assistance of gravity to the closed position shown in FIG.
3
. During closure the assistance of gravity initially increases and then decreases substantially as liftgate
12
approaches the closed position shown n
FIG. 2
due to the changing moment arm. As liftgate
12
is moved manually to the closed position, tension member
34
pulls the lower end of compression spring
28
up compressing spring
28
and storing energy in the compressed spring
28
as shown in FIG.
3
. This stored energy reaches a maximum when liftgate
12
is closed and assists in a subsequent opening the liftgate
12
. When the closed liftgate
12
shown in
FIG. 3
is opened, the compressed spring
28
expands and rotates link
24
counterclockwise about hinge pin
25
as viewed in
FIG. 3
from the closed position shown in
FIG. 3
to the open position shown in FIG.
2
. Link
24
simultaneously rotates link
26
clockwise about the hinge pin
29
connecting link
26
to liftgate
12
. This increases the angle between links
24
and
26
and the distance between the hinge pins
25
and
29
causing liftgate
12
to pivot counterclockwise about the hinge axis
18
from the closed position shown in
FIG. 3
to the open position shown in FIG.
2
.
The counterbalance system
22
may also be power operated by providing a drive roller
38
between the upper end of housing
30
and roller
36
that is driven by a suitable motor, such as an electric motor (not shown). In the case of power operation, the liftgate
12
is moved from open position of
FIGS. 1 and 2
to the closed position of
FIG. 3
by controlling the motor to rotate drive roller
38
counterclockwise as shown in
FIG. 2
to drive tension member
34
up which compresses spring
28
and allows liftgate
12
to close under the influence of gravity. The liftgate
12
is then capable of being opened as described above or with the assistance of the motor driven roller
38
being driven clockwise.
With a counterbalance system, it is also preferably to locate drive roller
38
between roller
36
and compression spring
28
and to locate roller
36
so that the flexible tension member or cable
34
is forced against drive roller
38
for good driving engagement.
While the tension member
34
is illustrated as being attached to the first link
24
near the hinge pin
27
, the tension member
34
may be connected to either link
24
or
26
, the precise location of the attachment being determined by the physical characteristics of the vehicle and the lifting assistance that is desired.
In other words, while the present invention has been described as carried out in a specific embodiment thereof, it is not intended to be limited thereby but is intended to cover the invention broadly within the scope and spirit of the appended claims.
Claims
- 1. A counterbalance system for a vehicle liftgate that is pivotally attached to an aft end of a vehicle roof for pivotal movement about a hinge axis between a generally horizontal open posit ion and a closed generally vertical position, the counterbalance system storing energy during closure of the vehicle liftgate for assisting subsequent opening of the liftgate, the counterbalance system comprising:a first link pivotally connected to a body portion of the vehicle by a pivot member, a second link pivotally connected to the first link adjacent one end and pivotally connected to the vehicle liftgate adjacent an opposite end, a compression spring abutting a body portion of the vehicle at one end, and a tension member connected to an opposite end of the spring at one end and to one of the first links and the second links at the opposite end whereby the spring stores energy when the liftgate is closed and releases the stored energy upon subsequent opening of the liftgate to assist in the subsequent opening of the liftgate, and a drive roller that engages the tension member to drive the tension member downwardly to store energy to assist in opening the liftgate.
- 2. A counterbalance system for a vehicle liftgate that is pivotally attached to an aft end of a vehicle roof for pivotal movement about a hinge axis between a generally horizontal open position and a closed generally vertical position, the counterbalance system storing energy during closure of the vehicle liftgate for assisting subsequent opening of the liftgate, the counterbalance system comprising:a first link pivotally connected to a body portion of the vehicle by a pivot member, a second link pivotally connected to the first link adjacent one end and pivotally connected to the vehicle liftgate adjacent an opposite end, a compression spring abutting a body portion of the vehicle at one end, and a tension member connected to an opposite end of the spring at one end and to one of the first links and the second links at the opposite end whereby the spring stores energy when the liftgate is closed and releases the stored energy upon subsequent opening of the liftgate to assist in the subsequent opening of the liftgate wherein the tension member is flexible and wraps around a roller that is located between the hinge axis and the pivot member.
- 3. The vehicle as defined in claim 2 wherein the counterbalance system includes a pulley and the tension member is a cable that is part of the pulley.
- 4. The vehicle as defined in claim 3 wherein the pulley includes the roller that is located between the hinge axis and the pivot member.
- 5. The vehicle as defined in claim 4 whereina drive roller engages the tension member to drive the tension member downwardly to store energy to assist in opening the liftgate, and the drive roller is below the roller of the pulley.
- 6. A vehicle having a counterbalance system for opening and closing a vehicle liftgate that is pivotally attached to an aft end of a vehicle roof for pivotal movement between an open position and a closed position about a hinge axis, the counterbalance system having at least one drive unit, comprising:a first link pivotally connected to a body portion of the vehicle at one end, a second link pivotally connected to an opposite end of the first link at one end and pivotally connected to the vehicle liftgate at an opposite end of the second link, a roller located between the hinge axis and the first end of the first link, a compression spring disposed in a housing attached to the body portion of the vehicle, the compression spring having an end proximate the roller abutting an end wall of the housing, and a cable having a first end connected to an opposite remote end of the spring, the cable having a second end connected to one of the first links and the second links at the opposite end after the cable wraps around the roller whereby the spring stores energy when the liftgate is closed and releases the stored energy upon subsequent opening of the liftgate to assist in the subsequent opening of the liftgate.
- 7. The vehicle as defined in claim 6 wherein the cable is connected to the first link.
- 8. The vehicle as defined in claim 6 further including a drive roller that engages the cable to drive the cable downwardly to assist in opening the liftgate.
- 9. The vehicle as defined in claim 6 further including a drive roller that is located between the roller and the compression spring and that engages the cable to drive the cable downwardly to assist in opening the liftgate.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4601446 |
Opsahl |
Jul 1986 |
A |
4765026 |
Dochnahl |
Aug 1988 |
A |
6120080 |
Hori et al. |
Sep 2000 |
A |