Patent Description:
One of the current trends in the automobile industry is to lower vehicle weight to help achieve better fuel economy, thus helping to meet fuel economy standards and to offset the higher fuel prices. Another trend is that there is a broader range of vehicle models, which in turn reduces the volume of vehicles produced on a per model basis. sport utility and crossover vehicles remain popular and typically include fairly heavy rear liftgates making this part of the vehicle a target area for weight reduction. Liftgates are traditionally made from stamped steel panels that are heavy and have a high tooling cost. Traditional steel liftgates are expensive investments, heavy, take up a lot of OEM floor space in areas from stamping plant, body shop, paint shop, and trim line. Further, steel liftgates have limited styling flexibility, take a lot of time to tool, and have corrosion concerns. Sheet Molding Compound (SMC) is an alternative to steel for the inner and outer panels of the liftgate. Using SMC has several manufacturing concerns related to the material and process. Steel and SMC liftgates have a mass penalty over thermoplastics. There are also styling restrictions with traditional sheet metal components. Thermoplastic composite type materials used for liftgate applications also have difficulty meeting customer performance specifications.

Another concern with the manufacture of liftgates is that typical liftgates are manufactured as a relatively flat or smoothly contoured panel, with structural reinforcements such as ribs added onto the panel. This will also add weight and increase manufacturing complexity as well and when thermoplastics are used there are read through areas where the ribs are placed which must be dealt with by design modifications or expensive processes such as gas assist injection molding. Ribs are also weaker and do not carry the load through the liftgate panel. Recently magnesium inner reinforcement panels have been used with an outer polymer skin in order to reduce weight. While such panels are an improvement in weight, this is an expensive solution. Another concern with typical liftgates is that the structural reinforcements are steel or larger steel structures adding weight and increased manufacturing complexity. Another concern is typically reinforcement material is used for reinforcement in the structural areas and attachment structures are fixed using bolts. However, the use of bolts does not provide a continuous attachment structure and improved strength since there is distance between the bolts. Yet another concern with the manufacture of liftgates is that typical liftgates are manufactured as relatively solid with no access features such as access doors added into the panel to allow for easy access for general maintenance and repair of built in components.

A known <NUM> Nissan Murano composite liftgate system helped to satisfy the weight savings and the tooling cost concerns, but utilized a typical bolt in small steel reinforcement at the latch which secures one end of the liftgate to the vehicle. This does not meet the higher load requirements desired in some applications, such as the latch pull test. A known Nissan Rogue composite liftgate system utilizes a steel one-peice outer panel and steel brackets. This does not improve density, painting efficiency, hold tighter tolerances, is more expensive and complex to manufacture, and adds weight to the liftgate/vehicle.

Accordingly, there exists a need for a composite liftgate which is both lightweight, as well as structurally sound enough to meet various load requirements, while being more mass and cost effective.

<CIT> relates to a vehicle door with an inner section made of plastic, where the inner section is braced by a reinforcement, wherein an exterior paneling section is provided for covering the vehicle door partially from the outer side.

<CIT> discloses a thermoplastic composite liftgate system with reinforcements in key areas. The thermoplastic composite liftgate system includes an inner panel and at least one bracket or reinforcement member connected to the inner panel such that when a force is applied to the bracket, the force is distributed to the inner panel.

In accordance with the present invention, there is provided a composite liftgate system with the features of claim <NUM>.

Referring to the figures generally, there is provided a composite liftgate assembly with bonded composite preform reinforcements. Structural channels molded into an inner panel of the liftgate add structure where needed and manage the main loading paths as the liftgate is utilized in the various load cases. Also composite preforms structurally bonded in place (or Insert molded) to add structure where needed are used, allowing for the need for no steel reinforcements and/or minimization of the size of steel tapping plates. Bonding through the use of adhesive provides a more continuous attachment structure and improved strength over bolting alone. A two-piece outer panel allows for styling, molding, painting, tolerance, weight, and assembly advantages. The features and process of the present invention help to achieve desired weight targets, while keeping costs at target levels. In addition, the composite liftgate has several business case advantages for supplying a module, and reducing assembly plant complexity and improving throughput. Additionally, the present invention improves styling options and flexability when compared to sheet metal and one-piece panels. Corrosion and durability are also improved.

An embodiment of a composite liftgate system is shown in the Figures generally at <NUM>. The liftgate <NUM> includes an outer panel <NUM> formed of an upper outer panel, shown generally at <NUM>, and a lower outer panel, shown generally at <NUM>. A spoiler <NUM> is incorporated into the upper outer panel <NUM>. A glass window <NUM> or rear window liftgate of the tailgate <NUM> is adhered to the upper and lower outer panels <NUM>,<NUM> and to an inner panel. The upper outer panel <NUM> and separate lower panel <NUM> thereby form a two-piece outer panel. This has significant benefits and superior results over having a one-piece panel (especially over one that is also steel or not bonded in place), including, but not limited to, improved density, more efficient painting, tighter tolerances, less manufacturing issues, and more cost effectiveness. Alternatively, the outer panel <NUM> may be formed as a single piece.

The spoiler <NUM> incorporated with the upper outer panel <NUM> has significant benefits and superior results over having a separate spoiler, including, but not limited to, optimized structure and strength and efficient processing.

The inner panel <NUM> is formed with a channel pattern arrangement including a plurality of structural channels molded into the inner panel <NUM> to manage the loading paths as the liftgate is utilized in various load cases. The channel pattern of the present invention provides more structural shape where needed and allows for carrying the full thickness and load through the part, whereas ribbing is weaker and will not carry the load. The channels have significant benefits and superior results over ribbing. The channels will now be explained in greater detail.

Molded into the inner panel <NUM> are at least one first pair of channels <NUM> that run horizontally, substantially parallel to and below a horizontal plane of the viewing opening <NUM> formed in the inner panel <NUM>. The channels of the first pair <NUM> are substantially centrally located in the portion of the inner panel <NUM> below the opening <NUM> and an upper first pair channel <NUM> is longer than a lower first pair channel <NUM>. The first pair of channels <NUM> are raised, as in substantially extending outward generally toward the rear of the vehicle (See <FIG> and <FIG>).

The first pair of channels <NUM> terminate at a second pair of channels <NUM> that run in a diagonal pattern at a predetermined angle, substantially in diagonal directions away from each other with the largest distance apart being toward the opening <NUM>. The second pair of channels <NUM> are depressed, as in substantially extending inward generally toward the interior of the vehicle (See <FIG> and <FIG>).

A third pair of channels <NUM> extend substantially along each side of the second pair of channels <NUM> on the side away from the center of the inner panel <NUM>. The third pair of channels <NUM> are raised, as in substantially extending outward generally toward the rear of the vehicle (See <FIG> and <FIG>). Preferably, the second pair of channels <NUM> and fourth pair of channels <NUM> have one side wall longer than the other side wall, sharing the common of the longer wall.

Each of the channels in the second pair of channels <NUM> is substantially a mirror image of the other channel of the pair <NUM>. Each of the channels in the third pair of channels <NUM> is substantially a mirror image of the other channel of the pair <NUM>.

A fourth pair of channels <NUM> run substantially vertically from the lower first pair channel <NUM> to the upper first pair channel <NUM> of the first pair of channels <NUM>. The fourth pair of channels <NUM> are depressed, as in substantially extending inward generally toward the interior of the vehicle (See <FIG> and <FIG>).

Each of the pairs of channels <NUM> and <NUM>-<NUM> have predetermined lengths, widths, depths, and material thickness suitable to provide structural support and strength for the inner panel <NUM>, including under predetermined load conditions. Optionally, additional channels can be formed as part of the inner panel <NUM>.

Formed as part of the inner panel <NUM> is an upper trim ring portion, generally shown at <NUM>, incorporated into a D-pillar area ('D' <FIG>) rather than providing the upper trim ring as a separate panel. The upper trim ring <NUM> incorporated into the inner panel <NUM> in the D-pillar area has significant benefits and superior results over having a separate panel, including, but not limited to, optimized structure and strength. The upper trim ring portion <NUM> has a predetermined size that is small suitable for access, e.g., for a lower trim panel installation and retention.

The liftgate <NUM> is additionally reinforced in areas where extra structure is needed. There is provided a plurality of composite preforms or composite reinforcements to add structure where needed to reinforce areas such as the D-pillar, top corners of the inner panel <NUM> at the hinge nuts, side nuts, backlight, and/or latch areas, as will be described further below. Composite preforms have significant benefits and superior results over steel reinforcements, which steel, among other things, adds weight.

All of the composite reinforcements are bonded directly to the inner panel <NUM> such that the composite reinforcements are structurally bonded in place (or, alternatively, insert molded to connect the reinforcements to the inner panel <NUM>) to add structure where needed. This allows for the elimination of steel reinforcements and to minimize the size of a plurality of tapping plates made of metal. The bonding of the present invention uses predetermined adhesive(s) applied to select the areas of the inner panel <NUM>. Most preferably, the adhesive is a structural two-part urethane adhesive. The bonding with the use of adhesives has significant benefits and superior results over steel reinforcements connected to the inner panel by bolts. Tapping plates that are formed of steel are minimized in size and are not only bolted in place - but additionally bonded with adhesive for added strength and structure, as will be described further below. This has significant benefits and superior results over the conventional need for larger steel tapping plates that are merely bolted.

One of the composite preforms connected to the inner panel <NUM> is a pair of strut reinforcements <NUM> or strut preforms. The pair of strut reinforcements <NUM> are bonded to the inner panel <NUM> using adhesive. These are located generally in the area adjacent to the lower corner of the opening <NUM>.

A pair of strut reinforcement brackets <NUM> or tapping plates, preferably formed of steel, are bonded to the pair of strut reinforcements <NUM> using adhesive. A first plurality of fasteners <NUM>, e.g., push nuts, are added to further hold the strut reinforcements <NUM> and strut reinforcement brackets <NUM> in position.

Another one of the composite preforms connected to the inner panel <NUM> is a pair of hinge reinforcements <NUM> or hinge preforms. These are located generally in the area adjacent to the upper corner of the opening <NUM>. The pair of hinge reinforcements <NUM> are bonded to the inner panel <NUM> using adhesive. A second plurality of fasteners <NUM>, e.g., push nuts, are added to further hold the hinge reinforcements <NUM> in position. The lower end portion <NUM> of each hinge reinforcement <NUM> overlaps an upper end portion <NUM> (<FIG>) of each strut reinforcement <NUM>. Preferably, this upper end portion <NUM> has a lower profile for connecting to the inner panel <NUM> below the lower end portion <NUM> of hinge reinforcement <NUM> and provide a butting engagement with the hinge reinforcement <NUM>. Most preferably, the lower end portion <NUM> is bonded to the upper end portion <NUM> with adhesive.

A pair of hinge reinforcement brackets <NUM> or tapping plates, preferably formed of steel, are bonded to the pair of hinge reinforcements <NUM> using adhesive. A third plurality of fasteners <NUM>, e.g., screws, are added to further hold the hinge reinforcements <NUM> and hinge reinforcement brackets <NUM> in position.

Each hinge reinforcement bracket <NUM> also has a hinge assembly <NUM> coupled thereto. Each hinge reinforcement <NUM> and strut reinforcement <NUM> also has at least one compression limiter <NUM> coupled thereto. At least one compression limiter <NUM> is coupled near the bottom rear edge of the inner panel <NUM>.

A latch reinforcement bracket <NUM> or tapping plate, preferably formed of steel, is bonded to the inner panel <NUM> using adhesive in the area where a latch handle <NUM> is connected to the lower outer panel <NUM>. Optionally, a fourth plurality of fasteners, e.g., screws, are added to further hold the latch reinforcement bracket <NUM> in position. The latch handle <NUM> actuates a latch manual and/or power liftgate device <NUM> coupled to the inner panel <NUM> generally adjacent to the latch reinforcement bracket <NUM> when engaged by an operator of the liftgate <NUM>.

Formed as part of the inner panel <NUM> are additional structural reinforcements such as ribs and fins. A set of sloped fin-like shaped <NUM> ridges are each connected to a top surface of both channels of the fourth pair of channels <NUM> and within the upper first pair channel <NUM> (<FIG>). At least one pair of first ribs <NUM> are connected to a bottom surface of the fourth pair of channels <NUM>. A plurality of second ribs <NUM>, e.g., at least three ribs, are connected within each of the second pair of channels <NUM>. A plurality of third ribs <NUM>, e.g., two pairs of two ribs, are connected to a top surface of the upper first pair channel <NUM> and run generally vertically to a predetermined distance below the opening <NUM>. A plurality of fourth rips <NUM>, e.g., at least three ribs, run substantially diagonal across the lower inside corner areas of the inner panel <NUM>. Each fin or rib in the respective sets and pairs are substantially parallel with one another.

Each fin or rib in the respective sets and pairs have predetermined lengths, widths, depths, and material thickness suitable to provide structural support and strength for the inner panel <NUM> and improve the rigidity of the liftgate <NUM> system, including under predetermined load conditions. Optionally, additional fins and/or ribs can be formed as part of the inner panel <NUM>.

There is provided a main wiring harness <NUM> and a washer device <NUM> with a motor and wider coupled to the inner panel <NUM>. The outer panel <NUM> is bonded to the inner panel <NUM> by using adhesive <NUM> ("<NUM>" indicates adhesive for various components, e.g., <FIG> and <FIG>) applied in a predetermined pattern and locations on the inner panel <NUM>. Also provided is a center high-mount stop light (CHMSL) device <NUM> connected to the upper outer panel <NUM>. A tail light assembly <NUM> is operably connected to the lower outer panel <NUM>. Preferably, the tail light assembly <NUM> is bonded to the lower outer panel <NUM> with adhesive and additionally a plurality of fasteners.

As further illustrated in <FIG>, the inner panel <NUM> is bonded to the glass panel <NUM> and reinforcement brackets, e.g., each strut reinforcement bracket <NUM>, through the use of adhesive <NUM> such that packaging for wiring, e.g., the main wiring harness <NUM>, and an adjacent gas strut is provided. The reinforcement has a predetermined thickness and is bonded, rather than merely bolting in a few locations, with structural adhesive to bond in place with continuous attachment of the structure. The inner panel connected to the brackets and outer panel forms predetermined operable cross sections.

Also connected to the inner panel <NUM> is a lower trim panel, shown generally at <NUM>, substantially facing toward the vehicle interior and running generally from the D-pillar to near the bottom edge of the inner panel <NUM>. The lower trim panel has class A surfaces and at least one access panel <NUM> or door. A pair of handle pockets <NUM> is also provided in the lower trim panel <NUM> for an operator to selectively grasp when operating the liftgate <NUM>, in particular to cycle to the liftgate <NUM> from an open to a closed position.

The access door <NUM> is removable and/or rotatable for gaining access to at least the latch mechanism assembly <NUM> for maintenance and/or repair. The access panel <NUM> is a significant benefit over conventional liftgates requiring disassembly and maintenance/repair complexity. Preferably, there are at least five access panels <NUM> suitably situated where maintenance and repair of various components not otherwise easily accessible is desired. Most preferably, at least one access panel <NUM> is located in each of the following areas: the latch mechanism assembly <NUM>, tail light assembly <NUM> (e.g., for changing both burnt out tail lights), CHMSL <NUM>, and wiper device <NUM> (e.g., to access a wiper motor) areas.

A pair of gas struts <NUM> is operably connected to the inner panel <NUM> and/or a hinge system. The gas strut and hinge system are connected to the vehicle.

By non-limiting example, the inner panel <NUM> is bonded to the outer panel <NUM> to using urethane bonding. The inner panel <NUM> provides structural support for the composite liftgate of the present invention not only through the shape of the inner panel as described above, but the material used to make the inner panel provides structural support as well. The inner panel <NUM> is made of a structural thermoplastic, such as a polypropylene, a thermoset or thermoplastic such as a reinforced polypropylene (RPP), and is preferably a <NUM>% glass-filled polypropylene. The inner panel <NUM> is preferably thermoplastic <NUM> inch long glass filament filled polypropylene. By way of non-limiting example, the outer panel <NUM> is made of a suitable thermoplastic used as a show surface, such as a thermoplastic polyolefin (TPO). The structural composite reinforcements preferably comprise woven glass reinforcement.

Claim 1:
A composite liftgate system (<NUM>) for a vehicle, comprising:
an inner panel (<NUM>) that is a glass-filled polypropylene;
an outer panel (<NUM>) having an upper outer panel (<NUM>) and a lower outer panel (<NUM>) connected to the inner panel (<NUM>);
a lower trim panel connected to the inner panel (<NUM>);
a strengthening channel pattern arrangement including a plurality of structural channels (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) formed in the inner panel (<NUM>) to manage loading paths applied to the inner panel (<NUM>);
a plurality of additional structural reinforcements (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) located in at least a portion of the plurality of structural channels (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
wherein the outer panel (<NUM>) is connected to the inner panel (<NUM>) through use of at least structural adhesive;
characterized in that the composite liftgate further comprises:
a plurality of composite preforms (<NUM>, <NUM>) connected to the inner panel (<NUM>) to add structure in at least a strut and upper corner area of the inner panel (<NUM>), where at least a portion of the plurality of composite preforms (<NUM>, <NUM>) are additionally connected to one another in an overlapping manner;
a plurality of fasteners (<NUM>) further holding the upper corner area composite preform (<NUM>) in position;
a plurality of reinforcement brackets (<NUM>, <NUM>) connected to the plurality of composite preforms(<NUM>, <NUM>); and
wherein at least a portion of the plurality of composite preforms (<NUM>, <NUM>) and/or plurality of reinforcement brackets (<NUM>, <NUM>) are connected to the inner panel (<NUM>) through the use of at least structural adhesive.