Patent Description:
To further reduce the weight, and to additionally reduce costs, plastic tailgates were sought after. Initially, plastic tailgates were developed from thermoset SMC-like materials. Sheet molding composite (SMC) is a ready to mold glass-fiber reinforced, thermoset, polyester material. Later on, thermoplastic parts were made of Long fiber reinforced PP (PP-LGF) that partially integrate the aesthetical TPO panels.

When using thermoplastic to make structural parts for vehicle components, creep behavior of the thermoplastic material under constant load must be taken into account. For instance, a gas strut exerts a continuous force acting on a tailgate of a vehicle during the lifetime of the tailgate, even when the tailgate is in a closed position. In a thermoplastic structural part, such a load can cause local creep, which can lead to part failure from stress in the thermoplastic structural part. <CIT> relates to a front end module for a motor vehicle with a front end assembly support. <CIT> relates to a lightweight component of a hybrid design is provided to improve tolerance, stability, and strength, and to reduce the molding temperature required for manufacturing the component. <CIT> relates to a lightweight constructional element (<NUM>) is disclosed. Yet these references fail to address the shortcomings listed above.

It would be desirable to provide a vehicle component with an improved attachment of a strut component to a thermoplastic structural part to decrease stress in the thermoplastic structural part in order to improve time to failure behavior, which can prolong the lifetime of the tailgate, and that mitigates the aforementioned disadvantages.

The invention relates to a vehicle component, comprising a thermoplastic part, a metal insert having an anchoring portion, a peripheral portion, and a first insert surface and an opposite second insert surface, wherein the first surface is overmolded by the thermoplastic part, a thermoplastic rib overmolded on a second surface of the metal insert, the rib extending from the second surface and being at least partly adjacent to the thermoplastic part, and a strut component attached to the metal insert at the anchoring portion on the first surface of the metal insert.

A strut component, for instance a ball strut, a gas strut, or a combination with at least one of those, connected to a vehicle component, for instance a tailgate, exerts a force concentrated at a relatively small surface where the strut component and the vehicle component connect, resulting in a relatively concentrated stress. Strut components exert a continuous force acting on the vehicle component during its full lifetime, in both active and inactive modes, e.g. an open tailgate where the strut component actively supports the tailgate from falling back in the closed position, and when the tailgate is inactive in the closed position and not actively supporting the tailgate. Especially for plastic vehicle components or plastic structural carrier parts, this force causes creep that may lead to part failure if the stress inside the carrier part becomes too high.

By combining the strut component with a metal insert, the stress within the vehicle component exerted by the strut component is distributed over a relatively larger surface, such that creep and time to failure behavior are improved. The life performance of the vehicle component is thus improved. The metal insert may be combined with the strut component directly to eliminate a step in assembly process. For example, the strut component can be attached at the anchoring portion to the metal insert before the overmolding step. This may be done by welding, clinching or riveting. Alternatively, the strut component is integrally formed with the metal insert, wherein the strut component is located at the anchoring portion.

The thermoplastic rib overmolded on the second side of the metal insert is used to fixate the metal insert into the vehicle component, i.e. the metal insert is locked between the thermoplastic part and the thermoplastic rib. The thermoplastic rib is at least partly adjacent the thermoplastic part. The thermoplastic part may have a first part surface and an opposite second part surface. The thermoplastic part may extend from the second insert surface and the second part surface, i.e. the thermoplastic rib overlaps with both the metal insert and the thermoplastic part.

In an embodiment, an exterior edge of the peripheral portion is at least a minimum planar distance from an edge of the anchoring portion closest to said exterior edge of the peripheral portion, wherein the minimum planar distance is <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, preferably at least <NUM>. For a sufficient distribution of the internal stress in the thermoplastic part and thus a reduction in creep and an increase in component life performance, the metal insert may have a minimal dimension, defined as the minimum planar distance from the edge of the anchoring portion closest to the exterior edge of the peripheral portion. The minimum planar distance may be a radius when the metal insert is circular or elliptically shaped. Other metal insert shapes are possible as well, such as triangular, rectangular or any other polygonal shape. The shape may be regular, or irregular. The shape of the metal insert may depend on the shape of the thermoplastic part, and/or the requirements for the vehicle component. The metal insert may be a plate. The metal insert may be provided with an indentation and/or a protrusion. For instance, the anchoring portion may be off set with regard to the peripheral portion. Furthermore, the metal insert may include a cylindrical anchoring portion, such as a threaded cylinder extending from the second insert surface.

In addition to the shape and planar dimensions, the thickness of the metal insert may play a role in the optimization of the stress distribution. The thickness of at least <NUM> and at max <NUM>. or <NUM> to <NUM>, or <NUM> to <NUM>, preferably <NUM> to <NUM>.

The metal insert may comprise stainless steel, titanium, iron, nickel, copper, aluminum, tin, or a combination comprising at least one of the foregoing. The choice of metal for the metal insert may depend on the requirements to the distribution of the internal stress and thus the life performance of the vehicle component, as well as the used plastic material to overmold the metal insert, as not all metals are compatible with every polymer. Cost requirements may play a role as well.

The vehicle component may comprise a plurality of thermoplastic ribs that are overmolded onto the second insert surface. Such a plurality of ribs may improve the fixation of the metal insert to the thermoplastic part. Additionally, or alternatively, the thermoplastic rib overmolded on a second insert surface forms part of a reinforcement rib extending over at least part of the thermoplastic part. The thermoplastic part may be reinforced with a reinforcement structure that comprises a reinforcement rib. The vehicle component may further comprise a network of thermoplastic ribs connected to a lateral side of the thermoplastic rib and extending from the thermoplastic rib over at least part of the thermoplastic part. The network of thermoplastic ribs may form part of the reinforcement structure.

In an embodiment, the thermoplastic rib may be provided with a thermoplastic boss and/or a thermoplastic gusset, and wherein the thermoplastic rib, the thermoplastic boss and/or the thermoplastic gusset is adjacent to the anchoring portion. The thermoplastic rib may be provided with to accommodate any indentations or protrusions on the metal insert, in particular at the anchoring position.

The vehicle component may comprise a polybutylene terephthalate (PBT); acrylonitrile-butadiene-styrene (ABS); polycarbonate (LEXAN™ and LEXAN™ EXL resins, commercially available from SABIC Innovative Plastics); polycarbonate/PET blends; polycarbonate/ ABS blends; acrylic-styrene-acrylonitrile (ASA); phenylene ether resins; blends of polyphenylene ether/polyamide (NORYL GTX™ resins, commercially available from SABIC Innovative Plastics); blends of polycarbonate/polyethylene terephthalate (PET)/ polybutylene terephthalate (PBT) (XENOY™ resins, commercially available from SABIC Innovative Plastics); polyamides; phenylene sulfide resins; polyvinyl chloride PVC; (high impact) polystyrene; polyolefins such as polypropylene (PP), expanded polypropylene (EPP) or polyethylene; polysiloxane; polyurethane and thermoplastic olefins (TPO), as well as combinations comprising at least one of the foregoing. The vehicle component may comprise a fiber filled thermoplastic material, in particular from the list above. For example, a fiber-filled polyolefin can be used. The fiber material may include glass fiber, long or short, carbon fiber, aramid fiber, or any plastic fiber. In particular, long glass fiber filled polypropylene (STAMAX™) may be used.

The thermoplastic part and the thermoplastic rib may comprise or be made of dissimilar but compatible thermoplastic materials. Only when compatible materials are used, the required bonding or joint between the thermoplastic part and the thermoplastic rib may be established.

The vehicle component may be a tailgate, a door, a tail lift or a hood.

The invention also relates to a vehicle comprising the vehicle component as described above, wherein the vehicle is one of a railway vehicle, a marine vehicle, a road vehicle, or an aircraft.

The following figures are exemplary embodiments.

<FIG> shows a schematic representation of a vehicle component <NUM> comprising localized metal inserts <NUM> and a thermoplastic part <NUM> overmolded onto the metal inserts <NUM>. The metal inserts or reinforcements <NUM> are placed at load introduction points of struts and/or hinges to distribute load in thermoplastic part. As the metal inserts <NUM> are limited to the load areas of struts and/or hinges, these inserts do not add increased stiffness to the vehicle component. The vehicle component <NUM> may be stiffened with reinforcement ribs, see <FIG>.

<FIG> shows a detail of an embodiment according to the invention. As shown in <FIG>, a strut component <NUM> (e.g., a ball strut, not shown in <FIG>) is attached to a metal insert <NUM> through an anchoring portion <NUM>. The strut component <NUM> can be attached to the anchoring position at a surface opposite of the shown surface. A thermoplastic structural part <NUM> (e.g., a doorframe or a tailgate) is overmolded on a first surface of the metal insert <NUM> and a thermoplastic rib <NUM> is overmolded on, e.g., onto, a second surface of the metal insert <NUM>. The ball strut <NUM> is positioned opposite of the thermoplastic rib <NUM> (e.g., the metal insert <NUM> is located between the ball strut <NUM> and the thermoplastic rib <NUM>) and is integrally formed with the metal insert <NUM> at the anchoring portion <NUM>. Adjacent to the anchoring portion <NUM> is the peripheral portion <NUM> of the metal insert <NUM>. A gas strut (not shown) can be connected to the ball strut <NUM>. The overmolding of the metal insert <NUM> with the structural part <NUM> and the rib <NUM> may include that at least the peripheral portion <NUM> of the metal insert is embedded within thermoplastic material.

<FIG> is an illustration of an embodiment of a vehicle component <NUM> having a metal insert <NUM> for anchoring a strut component <NUM> (e.g., a ball strut). The second insert surface is shown to be overmolded with multiple ribs <NUM>. These multiple ribs form a network <NUM> of ribs that also extend over the thermoplastic part <NUM>. In this way, the ribs <NUM> may act as reinforcement ribs of the thermoplastic part <NUM>. <FIG> is a cross-sectional of the vehicle component of <FIG> along line A-A' shown in <FIG>. The vehicle component includes a metal insert <NUM> having an anchoring portion <NUM> (see <FIG>) and a peripheral portion <NUM>. The thermoplastic structural part <NUM> (e.g., a doorframe) is overmolded onto a first surface of the metal insert <NUM>. The thermoplastic rib <NUM> and a thermoplastic boss <NUM> (see <FIG>) are overmolded onto a second surface of the metal insert <NUM>. The thermoplastic rib <NUM> is part of a network of ribs <NUM>. A ball strut <NUM> is integral with the metal insert <NUM> at the anchoring portion <NUM>. A gas strut (not shown) can be connected to ball strut <NUM>. With reference to <FIG> and <FIG>, the ball strut <NUM> being combined with the metal insert <NUM> can eliminate a step in assembly of the vehicle component <NUM>.

Metal inserts for anchoring strut components were modeled as illustrated in <FIG> and simulation tested in Examples <NUM>-<NUM>, respectively. Each metal insert <NUM>, <NUM>, <NUM>, <NUM> included two circular anchoring portions <NUM>, <NUM>, <NUM>, <NUM> and a peripheral portion <NUM>, <NUM>, <NUM>, <NUM>. On each of the metal inserts <NUM>, <NUM>, <NUM>, <NUM> was an integral ball strut (not shown) for connection to a gas strut (not shown) at one anchoring portion <NUM>, <NUM>, <NUM>, <NUM> and a bump strut (not shown) attached at the other anchoring portion <NUM>, <NUM>, <NUM>, <NUM>.

<FIG> shows a large metal insert used in Example <NUM>. The two anchoring portions <NUM> each had a radius of <NUM>. An exterior edge <NUM> of peripheral portion <NUM> of metal insert <NUM> was a minimum radial distance <NUM> of <NUM> from an edge <NUM> of anchoring portion <NUM> of metal insert <NUM>. The anchoring portion is assumed to be rigid in the model, such that for the simulation, the geometry of the anchoring portion <NUM> does not need to be included, only the location of the anchoring portion, the force applied on the anchoring portion, and where the anchoring portion attached to the metal insert <NUM> need to be specified.

<FIG> shows the medium sized metal insert <NUM> used in Example <NUM>. The two anchoring portions <NUM> each had a radius of <NUM>. An exterior edge <NUM> of peripheral portion <NUM> of metal insert <NUM> was a minimum radial distance <NUM> of <NUM> from an edge <NUM> of anchoring portion <NUM> of metal insert <NUM>.

<FIG> shows the small metal insert <NUM> used in Example <NUM>. The two anchoring portions <NUM> each had a radius of <NUM>. An exterior edge <NUM> of peripheral portion <NUM> of metal insert <NUM> was a minimum radial distance <NUM> of <NUM> from an edge <NUM> of anchoring portion <NUM> of metal insert <NUM>.

<FIG> shows the very small metal insert <NUM> used in Example <NUM>. The two anchoring portions <NUM> each had a radius of <NUM>. An exterior edge <NUM> of peripheral portion <NUM> of metal insert <NUM> was a minimum radial distance <NUM> of <NUM> from an edge <NUM> of anchoring portion <NUM> of metal insert <NUM>. While <FIG> illustrate two anchoring portions <NUM>, an embodiment can include one anchoring portion and optionally a hole for a stop (e.g., not a ball strut).

Comparative Example <NUM> comprises a vehicle component as shown in FIG. 1A in which no metal insert was used. Rather, a strut component was attached to bolt, which is screwed onto a threaded metal cylinder and overmolded with a thermoplastic boss.

Each metal insert <NUM>, <NUM>, <NUM>, <NUM> was simulation tested in the system illustrated in <FIG> (e.g., the metal insert illustrated in <FIG> was substituted with each metal insert <NUM>, <NUM>, <NUM>, <NUM>). The stress levels were measured using a static elastic finite element simulation applying <NUM> N of force on the ball strut perpendicular to the axis connecting the ball strut and the metal insert, resulting in a (bending) moment on the metal insert plane. Each metal insert was steel with a thickness of <NUM> millimeters (mm). As illustrated in <FIG>, thermoplastic ribs were modeled to form a network including triangular spaces between the thermoplastic ribs. Each of the thermoplastic ribs was modeled as long glass fiber reinforced polypropylene (comprising <NUM> volume percent (vol. %) glass fiber) with a height of ranging from <NUM>-<NUM> millimeters (mm), a thickness of <NUM> average (not taking into account the draft angle), and a length of <NUM> to <NUM>. The results are illustrated in <FIG>, in which X denotes the critical stress level, which is determined assuming <NUM>-year lifetime of the article at <NUM> under given load without failure. The graph in <FIG> shows the stress levels (y-axis) for each example (example numbers on x-axis), decreasing in size with increasing stress levels.

As shown in <FIG>, stress increases as the minimum radial distances decreased and the critical stress level was reached in Comparative Example <NUM>. Thus, all the metal inserts simulation tested in Examples <NUM>-<NUM> were capable of anchoring a ball strut while providing improved, e.g., decreased, stress level under the critical stress level compared to Comparative Example <NUM>.

In <FIG> the metal inserts modeled in Examples <NUM> and <NUM>, respectively, were each taken with varying metal insert thicknesses of <NUM>, <NUM>, <NUM>, and <NUM>. The metal inserts were simulation tested for force levels in the manner described for Examples <NUM>-<NUM>. As shown in <FIG>, the thickness of the metal insert could be decreased to <NUM> without reaching the critical stress level X.

<FIG> shows a graphical illustration of the local stress levels in the vehicle component at the location of the metal inserts of <FIG>, Examples <NUM> and <NUM>, respectively, for various thicknesses. The metal inserts of Examples <NUM> and <NUM>, respectively, were each modeled with varying metal insert thicknesses of <NUM>, <NUM>, <NUM>, and <NUM>. The metal inserts were simulation tested in the vehicle component illustrated in <FIG> but without thermoplastic ribs overmolded on the metal insert. The systems were simulation tested for force levels in the manner described for Examples <NUM>-<NUM>. As shown in <FIG>, all the components simulation tested exceeded the critical stress level. As shown, the increase in thickness for Example <NUM> does not show a significant lowering of the stress level in the vehicle component, irrespective of the non-use of the thermoplastic ribs. For Example <NUM>, the increase in thickness does lower the stress levels significantly, but not below the initial maximum stress level of <NUM> MPa at X. As shown earlier in <FIG>, the metal insert of Example <NUM> combined with thermoplastic ribs allows for a much lower stress level, well below the maximum stress level at X.

<FIG> is a graphical representation of stress versus time to failure for a thermoplastic vehicle component at <NUM> degrees Celsius, made of a thermoplastic material typically used for such a thermoplastic vehicle component at <NUM> degrees Celsius. As the temperature is a constant, and the stress is varied, it is clearly shown that the higher the stress applied to a thermoplastic component, the shorter the time to failure is. Failure may be defined as the moment of fracture of the component, up to breaking point.

<FIG> is a graphical illustration of part weight versus maximum measured peak stress for three situations. Situation A shows the maximum peak stress versus weight of the vehicle component for the Comparative Example <NUM>. Situation B shows the maximum peak stress versus weight of the vehicle component for a relatively small, overmolded metal insert, such as shown in <FIG>. Situation C shows the maximum peak stress versus weight of the vehicle component for a relatively large overmolded metal insert, such as shown in <FIG>.

The results indicate that an improvement in creep life time of thermoplastic structural parts loaded by continuous forces can be realized by a metal insert having a radial distance from an exterior edge of a peripheral portion of the metal insert to an edge of a ball strut location of, for example, <NUM> and a thickness of the metal insert of, for example, <NUM>, combined with overmolded ribbing.

Claim 1:
A vehicle component (<NUM>), comprising:
- a thermoplastic part (<NUM>);
- a metal insert (<NUM>, <NUM>, <NUM>, <NUM>) having an anchoring portion (<NUM>), a peripheral portion (<NUM>), and a first insert surface and an opposite second insert surface, wherein the first surface is overmolded by the thermoplastic part (<NUM>),
- a thermoplastic rib (<NUM>) overmolded on a second surface of the metal insert (<NUM>, <NUM>, <NUM>, <NUM>) the rib (<NUM>) extending from the second surface and being at least partly adjacent to the thermoplastic part (<NUM>); and
- a strut component (<NUM>) attached to the metal insert (<NUM>, <NUM>, <NUM>, <NUM>) at the anchoring portion (<NUM>) on the first surface of the metal insert (<NUM>, <NUM>, <NUM>, <NUM>), characterized in that, an exterior edge (<NUM>) of the peripheral portion (<NUM>) is at least a minimum planar distance
from an edge (<NUM>) of the anchoring portion (<NUM>) closest to said exterior edge (<NUM>) of the peripheral portion (<NUM>), wherein the minimum planar distance is <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, preferably at least <NUM>.