Methods for forming and tuning the durability of breakaway sections on a trim panel

Doors for motor vehicles include door trim panel assemblies having multiple door trim panels held together at attachment points. A door trim panel includes a weakened perimeter formed from a series of apertures in the panel, creating a predetermined breakaway point where the assembly will rupture in the event a load is applied. Methods for tuning the durability of a trim panel assembly include a repeatable cycle in which pins are selected and inserted in a mold at varying positions. During injection molding, the pins form apertures to create a predetermined breakaway point. Changing the size, shape, and location of the pins allows tuning of the durability and properties of the breakaway point. Injection molds have variable pin placement capability to facilitate the method.

TECHNICAL FIELD

The present disclosure generally relates to trim for a vehicle interior and, more particularly, to trim designs and methods for making trim that enable predictable break patterns when the trim experiences a load.

BACKGROUND

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it may be described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present technology.

Substantial portions of a vehicle interior are covered with trim panels formed of various plastics and other materials. This trim can be broken during an accident. It is desirable that trim break in a predictable and controlled manner when exposed to a load, such as an impact from an outside object that would be experienced during a collision, or by a secondary force such as when a trim panel assembly strikes an object in a vehicle interior.

SUMMARY

In various aspects, the present teachings provide a door for a motor vehicle. The door includes a door trim panel assembly having a first trim panel, a second trim panel, and at least one attachment point comprising an attachment mechanism for securing the first and second trim panels to one another at the attachment point. The door further includes a plurality of apertures in the first trim panel, forming a weakened perimeter in the first trim panel around the at least one attachment point and configured to create a pre-determined breakaway adjacent to the attachment point if the first trim panel is exposed to a load.

In other aspects, the present teachings provide a method for tuning the durability of a pre-determined breakaway line on a trim panel. The method includes a repeatable cycle, having a step of selecting a plurality of pins for forming apertures in the trim panel. The repeatable cycle also includes a step of choosing a perimeter pattern corresponding to a desired geometric pattern of the weakened perimeter in the trim panel. The repeatable cycle also includes steps of inserting the pins into a mold according to the perimeter pattern; injection molding the trim panel by injecting a molten thermoplastic resin into the mold; and testing the trim panel for a desired break property. The method includes a step of selecting a perimeter pattern corresponding the trim panel found to have the desired break property.

In still other aspects, the present teachings provide an interior trim panel assembly for a motor vehicle. The trim panel assembly includes a first trim panel, a second trim panel, and at least one attachment point comprising an attachment mechanism for securing the first and second trim panels to one another at the attachment point. The door further includes a plurality of apertures in the first trim panel, forming a weakened perimeter in the first trim panel around the at least one attachment point and configured to create a pre-determined breakaway adjacent to the attachment point if the first trim panel is exposed to a load.

Further areas of applicability and various methods of enhancing the disclosed technology will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

It should be noted that the figures set forth herein are intended to exemplify the general characteristics of the methods, algorithms, and devices among those of the present technology, for the purpose of the description of certain aspects. These figures may not precisely reflect the characteristics of any given aspect, and are not necessarily intended to define or limit specific embodiments within the scope of this technology. Further, certain aspects may incorporate features from a combination of figures.

DETAILED DESCRIPTION

Trim assemblies of the present disclosure have pre-set break points facilitating predictable break patterns in the event of receiving a load above a pre-determined threshold, such as during a vehicle collision. Methods of making trim assemblies allow for rapid optimization of such break points.

Trim assemblies of the present disclosure may be formed of multiple panels that are held together at attachment points. Perforated perimeters surrounding these attachment points serve as breakaway lines, otherwise referred to as crack propagation paths, at which the assembly will break in the event of receiving a load that exceeds the failure point of a panel or the assembly. Methods for making and optimizing a trim panel include injection molding to a die having a plurality of pins, each pin corresponding to a perforation in a panel. A given configuration can include parameters of pin shape, pin size, and pin placement. A cycle of manufacture and testing includes making the panel with the above-described method, and testing the panel. The cycle can optionally be repeated using different configurations of parameters such as pin shape, pin size, and pin placement.

FIG. 1shows an exploded perspective view of an exemplary passenger door100for a motor vehicle, whileFIG. 2shows a cross-sectional view of the door ofFIG. 1taken along the line2-2. The door100for can include an outer door110, such as a door panel or skin, and a trim assembly120that can be attached, directly or indirectly, to the outer door110. When incorporated into a vehicle, the outer door110will generally face outside the vehicle and the trim assembly will generally face the vehicle interior. In some implementations, a trim assembly120of the present disclosure stands alone.

FIGS. 3A and 3Bshow plan views of front and back sides, respectively, of the door trim panel assembly120of the door100ofFIGS. 1 and 2. The trim assembly120as disclosed herein can be formed of multiple trim panels130. In general, a trim assembly120will include at least two trim panels130that, in certain implementations herein, can be referred to as first and second trim panels130. It should be understood that when first and second trim panels130are referenced hereinafter, this does not imply that a trim assembly120necessarily only includes first and second trim panels130, but can include more than two.

FIG. 4shows a magnified view of a portion of the back side of the door trim panel assembly120ofFIG. 3BandFIG. 5is a further magnified view of a portion of the back side of the door trim panel assembly120ofFIG. 3. With continued reference toFIG. 3B, as well as toFIGS. 4 and 5, the trim assembly120also includes at least one attachment point140. An attachment point140defines a discrete point, generally circular or quasi-circular, in the first and second trim panels130, and at which the first and second trim panels130are attached to one another. The attachment point140thus includes an attachment mechanism for maintaining the first and second trim panels130in contact with one another at the attachment point140. Such an attachment mechanism can include, without limitation, a heat stake, a screw, a clip, or any other structural or mechanical fastener or other mechanisms suitable for maintaining the first and second trim panels130in contact with one another at the attachment point140. With particular reference toFIG. 5, the attachment point140will generally be positioned adjacent to at least one panel edge150. In some implementations, the attachment point140will be positioned adjacent to two panel edges150, by being positioned in a corner160of the trim panel130.

The trim assembly120also includes a plurality of apertures170intentionally defined at strategic locations in at least the first trim panel130. The plurality of apertures170define a weakened perimeter180around the attachment point140that is located in the first trim panel130. The weakened perimeter180constitutes a controlled breakaway section in the first trim panel130around the attachment point140, at which the first trim panel130is designed to break and the trim assembly120will separate if a load exceeding a threshold value is applied to the trim assembly120. It will be appreciated that such a threshold value can correspond to a load that would be likely to be exceeded during a vehicle collision, but unlikely to be exceeded by a vehicle occupant during normal use.

Thus, the weakened perimeter180facilitates creation of a pre-determined breakaway adjacent to the attachment point140, facilitating greater predictability and control of the manner in which the trim assembly120will break when strained by a load, such as during an impact or vehicle collision.FIG. 6shows a cross sectional view of the door as shown inFIG. 2, illustrating the application of an external load, V, directed from outside the vehicle. When the external load V is applied to the vehicle door100, such as the fender200of another vehicle colliding with the door100, this can urge the door110, including the trim panel assembly120, toward the vehicle interior. An opposing load, Y, may be applied at or near the weakened perimeter180present in the first panel trim panel130of the trim assembly120when the inward moving trim panel assembly120strikes an object in the vehicle interior. The trim assembly120can then break and separate at the weakened perimeter180, preferentially leading to the result that the upper portion120B ceases moving toward or applying force to the vehicle occupant.

The weakened perimeter180surrounding the attachment point140can, in different implementations, be arcuate, a straight line, or a combination of angled straight lines. In some implementations, the weakened perimeter180can be concentric with the attachment point140. The weakened perimeter180can be characterized by an average distance of separation between each of the apertures in the plurality of apertures170and the attachment point140. In various implementations, the average distance of separation between the plurality of apertures170and the attachment point140can be one centimeter, or two centimeters, or three centimeters, or four centimeters, or five centimeters, or six centimeters, or seven centimeters, or eight centimeters, or nine centimeters, or ten centimeters. In some implementations, all of the apertures in the plurality of apertures170will be equidistant from the attachment point.

The weakened perimeter can further be characterized by the spacing of the apertures170, or the distance of separation between each of the apertures170in the plurality of apertures170. In different implementations, the distance of separation between each of the apertures in the plurality of apertures can be within a range of 1 mm to 1 cm or from 1 mm to several cm. While the apertures170in the plurality of apertures can be evenly spaced relative to one another, they need not necessarily be so. The weakened perimeter can further be characterized by the shape of the apertures170, and the maximum dimension, or the size, of the apertures170. When the apertures170are non-circular, the weakened perimeter can further be characterized by the rotational orientation of the apertures. In many implementations, all apertures170in the plurality of apertures will have the same shape and the same size, or maximum dimension.

In different variations, and with continued reference toFIG. 5, the shapes of the apertures170can be tuned to create a desired strength or weakness of the weakened perimeter180. For example, triangles, squares, rectangles, diamond (e.g. rhombus or parallelogram)170A teardrop shapes, or any other shape having at least one angled edge, can be used to create very sharp stress concentrations to direct the crack propagation. In general, it will be desirable to orient such apertures so that the angle defining the angled edge has a bisector pointing in the desired direction of crack propagation. For a stronger panel130, circles170B, ellipses170C, or other shapes lacking an angled edge can be used. A weakened perimeter will generally have two terminal apertures170D,170E170F,170G,170H. A terminal aperture is an aperture170at an end of a weakened perimeter that is nearest to an edge150of the trim panel130. In some instances, such as terminal aperture170D, a terminal aperture will intersect a panel edge150, causing an indentation in the panel edge150, the indentation corresponding to a partial aperture shape. In other instances, such as terminal aperture170F, a terminal aperture will not contact the edge150. Such variations in the terminal apertures can also be used to tune the weakness or durability of the weakened perimeter180.

With reference toFIG. 7, a method300for tuning the durability of a pre-determined breakaway line on a trim panel130for a vehicle is also disclosed. The method300includes a repeatable cycle305that can be repeated any desired number of times, including zero. Thus in some implementations, the repeatable cycle305be unrepeated, or performed only a single time. The repeatable cycle includes a step of selecting310a plurality of pins410for forming apertures170in the trim panel130. The pins410can be selected310on the basis of size, shape, or both. With reference toFIGS. 8A and 8B, a pin410will generally have a maximum longitudinal dimension, x, and a maximum lateral dimension, y. The maximum lateral dimension, y, will typically be within a range of from about 100 μm to about 10 mm, inclusive. In some implementations, the maximum lateral dimension, y, will be within a range of from about 1 mm to about 5 mm, inclusive.

A pin410will generally have a cross sectional shape, the cross sectional shape corresponding to an internal, lateral cross section, C, that is perpendicular to the maximum longitudinal dimension, x, and parallel to the maximum lateral dimension, y. In many implementations, a pin410will have identical cross sectional shape across most or all of the maximum longitudinal dimension, x. In some implementations, a pin can be tapered such that the size of the cross sectional shape decreases along the maximum longitudinal dimension, x. In general, the pins410will be selected310on the basis of the geometry of the cross sectional shape. In some, but not necessarily all, implementations, all pins410selected310in the plurality will be substantially similar to, if not identical to, one another.

The repeatable cycle305can include a step of choosing320a perimeter pattern corresponding to a desired geometric pattern of the weakened perimeter180in the trim panel130. The chosen perimeter pattern can therefore have the same geometric features as those of the weakened perimeter180, as described above, including that the perimeter pattern can be arcuate, a straight line, or a combination of angled straight lines.

FIG. 9Ais a perspective view of an injection mold400that can be used in the method ofFIG. 6;FIG. 9Bis a cross-sectional view of the mold400ofFIG. 9A, taken along the line9B-9B; andFIG. 9Cis a plan view of a top plate402of the mold400ofFIG. 9A. The exemplary mold400if formed of two mold plates402,404and includes inlet/outlet ports406for injection of molten material. When the two mold plates402,404are coupled, interior surfaces403,405define the internal cavity407which defines the shape of the panel120to be formed.

With continued reference toFIG. 7, and toFIGS. 9A-9C, the repeatable cycle305further includes a step of inserting330the pins410into the mold400according to the perimeter pattern450. In some implementations, this will require that the mold400have an adjustable pin placement region420, as shown inFIGS. 9A and 9C. The adjustable pin placement region420is a region integrated into either or both of the first and second plates402that is able to receive and hold one or more pins410at a variety of locations during the inserting320step. The location for inserting each pin can be selected multiple possible locations. Stated alternatively, two molds400that are identical to one another prior to the inserting320step, and that have an adjustable pin placement region420, would be able to accommodate different perimeter patterns.

In some implementations, an adjustable pin placement region420can include a two-dimensional array of holes, each defining a potential pin placement. Generally, during a single performance of the repeatable cycle305, some but not all of the potential pin placements will be used. In such implementations, a pin placement that is not to be used can be filled with a blank that plugs the hole but does not extend through the internal cavity407, while a pin placement that is to be used can be filled with a pin410, thereby forming an aperture170in the panel130at that position.

In some implementations, the adjustable pin placement region420can include a removable insert. Pin placements can be drilled or otherwise formed at desired locations in the removable insert to form the perimeter pattern. If a subsequent performance of the repeatable cycle305is desired, the used removable insert can be replaced with an unused removable insert, into which holes can be drilled or otherwise formed at different positions and/or with different shapes or orientations, to define a new perimeter pattern.

In many implementations, the mold400can include an attachment point forming portion430, such as a pocket configured to form a stake, or a protrusion configured to form a stake hole, during injection molding. In some such cases, the perimeter pattern can be concentric with the attachment point forming portion430. The perimeter pattern can be characterized by an average distance of separation between each of the pins410and the attachment point forming portion430. In various implementations, the average distance of separation between each of the pins410and the attachment point forming portion430can be one centimeter, or two centimeters, or three centimeters, or four centimeters, or five centimeters, or six centimeters, or seven centimeters, or eight centimeters, or nine centimeters, or ten centimeters. In some implementations, all of the pins410will be equidistant from the attachment point forming portion430. The perimeter pattern can further be characterized by the spacing of the pins410, the distance of separation between each of the pins410, or the rotational orientation of the pins when a lateral cross-section of the pins is non-circular.

The repeatable cycle305includes a step of injection molding340the trim panel130by injecting a molten thermoplastic resin into the mold400, after completion of the inserting320step. The injection molding340step produces a trim panel130having apertures170forming a weakened perimeter180corresponding to the perimeter pattern as discussed above.

The repeatable cycle305includes a step of testing350the trim panel130for a desired break property. For example, the trim panel130can be incorporated into a vehicle door100as part of a trim assembly120, and the door100can be tested in a vehicle side impact test. The trim assembly120can be monitored to determine whether it breaks or releases at a desired position, such as along the perimeter180of the trim panel130. The repeatable cycle305then includes a step of determining360whether to repeat the cycle305. In certain implementations, the determining360step can be performed by comparing the testing350results to a predetermined threshold criterion. For example, if the testing350shows that the current panel130iteration is within a threshold distance of a desired location and/or within a threshold value of a desired applied force, than it can be determined360that the repeatable cycle305is not to be repeated. As described above, the desired force can be such that it is likely to be exceed during a vehicle collision but unlikely to be exceeded by a vehicle occupant during normal use. Thus it will be appreciated that the disclosed method300for tuning the durability of a pre-determined breakaway line on a trim panel is advantageously suited to designing a trim panel that is robust for normal use and weakened to a desired degree and location for potential high duress events such as side impact testing or other collisions.

If the current panel130iteration does not meet the threshold criteria, then it can be determined360that the repeatable cycle305is to be repeated. The repeatable cycle305can be repeated any number of times, varying the geometry of the pins410and/or the perimeter pattern450until the testing340step reveals a design of the trim panel130that produces the desired results. The method300includes a step of selecting370the trim panel130design that produces the desired results. As shown inFIG. 7, a trim panel130design will be selected370when it is determined360that the repeatable cycle305should not be repeated.

The headings (such as “Background” and “Summary”) and sub-headings used herein are intended only for general organization of topics within the present disclosure, and are not intended to limit the disclosure of the technology or any aspect thereof. The recitation of multiple embodiments having stated features is not intended to exclude other embodiments having additional features, or other embodiments incorporating different combinations of the stated features.

As used herein, the terms “comprise” and “include” and their variants are intended to be non-limiting, such that recitation of items in succession or a list is not to the exclusion of other like items that may also be useful in the devices and methods of this technology. Similarly, the terms “can” and “may” and their variants are intended to be non-limiting, such that recitation that an embodiment can or may comprise certain elements or features does not exclude other embodiments of the present technology that do not contain those elements or features.

The broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the specification and the following claims. Reference herein to one aspect, or various aspects means that a particular feature, structure, or characteristic described in connection with an embodiment or particular system is included in at least one embodiment or aspect. The appearances of the phrase “in one aspect” (or variations thereof) are not necessarily referring to the same aspect or embodiment. It should be also understood that the various method steps discussed herein do not have to be carried out in the same order as depicted, and not each method step is required in each aspect or embodiment.