GB2488560A

GB2488560A - Vehicle trim components

Info

Publication number: GB2488560A
Application number: GB1103486.5A
Authority: GB
Inventors: Brian Bugeja
Original assignee: Bentley Motors Ltd
Current assignee: Bentley Motors Ltd
Priority date: 2011-03-01
Filing date: 2011-03-01
Publication date: 2012-09-05
Also published as: GB201103486D0

Abstract

A vehicle trim component has a surface portion forming a tactile interface, the component comprising a thermally conductive polymer composition (1, figure 2) that forms, or is in thermal contact with a material forming, the surface portion. The surface portion may be at least partially coated with a metallic finish or with metal, which may be deposited by vapour deposition, such as sputter coating, or by electroplating. The surface portion is preferably at least partially coated by two or more layers of metal, which may be successive layers of copper (2), semi-bright nickel, bright nickel (3) and chromium (4). The polymer composition may comprise acrylonitrile butadiene styrene (ABS), polycarbonate (PC), epoxy resin, polyetherimide (PEI), polyphenylene sulphide (PPS) or nylon, and is preferably a blend of two or more polymers. The polymer may contain carbon graphite particles, carbon fibres, or carbon nano-fibres, nano-rods, nano-particles or nano-tubes, metal particles or metal nano particles. The component may be a handle, switch (5, figure 3), button (6), dial (7) or air vent (8). Also disclosed is a method of producing a vehicle trim component having the steps of injection moulding a thermally conductive polymer composition and depositing a metal coating.

Description

A VEHICLE TRIM COMPONENT AN]) PROIWCTION METHOD THEREFOR Technical of the InventiQn The present invention relates to vehicle trim. More particularly, the invention relates to a tactile interface for vehicle trim components.

Background.tgjhe Invention

In many fields, manufacturers have incentives to reduce the weight of their products. For example, in automotive and aerospace applications, weight reduction may allow greater fuel efficiencies and/or may compensate for the increased weight of new safety features. Such pressures to reduce weight have sometimes resulted in the replacement of metal components by plastics or composites. These may have the advantage of being lighter, and are often cheaper to manufacture to high tolerances.

However, this may be undesirable in some instances where the component is intended to provide a tactile interface to a user. For example, in situations where a plastic or composite component such as a switch, button, dial, lever, handle, or other manual 1 5 interface, is intended to be comfortably or firmly handed, the user's perception that the part is made of plastic may influence his or her usage of the component, for example out of fear that the part is of inferior quality and therefore too weak to safely grip or use. It may therefore be advantageous to create the impression that the part is made of metal in order to instil confidence in the user. A metallic look and/or feel to a plastic but structurally sound part may help to create the impression of high quality materials and manufacture, and may thereby reassure the user of the part's quality and structural integrity.

To create the impress ion that a plastic or composite part is made of metal, it may be painted with a shiny or reflective finish to resemble metal, or coated with a thin layer of metal. However, it is often apparent to the user upon skin contact with its surface that the part is plastic, due to the generally much lower thermal conductivity of the underlying plastic or composite* when compared with metals, which results in the plastic or composite surface having little immediate thermal effect on the skin, while a metal surface would feel cold to the touch.

Alternatively, during prolonged use, the surface of a plastic or composite handle, a switch or switch housing, or a fascia for an electronic display or control device, may become warm when it stays in contact with the user's hand. This excess warmth may result in an increased level of perspiration from the user's hand, resulting in the surface becoming undesirably slippery and difficult or unsafe to use.

An object of the present invention is therefore to provide an improved vehicle trim component having a tactile interface that may approximate the cold feel of a metal.

1 5 Another object ofthe invention is to provide a method for fabricating such a vehicle trim component.

jimanof the jjyjjtion According to a first aspect of the invention, there is provided a vehicle trim component having a surface portion forming a tactile interface, the trim component comprising a thermally conductive polymer composition forming, or in thermal contact with a material forming the surface portion.

Such a vehicle trim component may have a reduced weight when compared with a similar component fabricated from metal, but may provide a user with the tactile reassurance of a cold metal feel.

Advantageously, the surface portion is at least partial]y coated with a metallic finish. Preferably, the surface portion is at least partially coated with metal.

Conveniently, the surface portion is at least partially coated by vapour deposition of a metal. Alternatively, the surface portion is at least partially coated by electroplating with a metal. Preferably, the surface portion is at least partially coated by two or more layers of metal. The surface portion may be at least partially coated with successive layers of nickel and chromium The surface portion may be at least partially coated with successive layers of copper, bright nickel, and chromium. The surface portion may be at least partially coated with successive layers of copper, semi-bright nickel, bright nickel, and chromium, The copper layer may have a minimum thickness of substantially 20 to 25 microns. The semi-bright nickel layer may have a minimum thickness of substantially 7.5 1 5 microns. The bright nickel layer may have a minimum thickness of substantially 7.5 to 10 microns. The chromium layer may have a minimum thickness of substantially 0.3 to 1.0 microns. The chromium layer may have a minimum thickness of substantially 0.8 microns. Alternatively, the surface portion is at least partially coated with metal-rich paint. Preferably, the surface portion is at least partially coated with a layer having a thermal conductivity greater than 20 W/m-K. More preferably, the surface portion is at least partially coated with a layer having a thermal conductivity greater than 60 W/m-K.

More preferably, the surface portion is at least partially coated with a layer having a thermal conductivity greater than 90 W/m-K.

A metallic finish may enhance the visual likeness of the component to a metal alloy component, visually enhancing the tactile reassurance of the cold metal feel. Metal or metal-rich coatings may provide high thermal conductivity on the surface of the component that further enhances the cold metal feel.

The thermally conductive polymer may comprise acrylonitrile butadiene styrene (ADS) or may comprise polycarbonate (PC) or may comprise epoxy resin or may comprise polyetherimide (PEI) or may comprise polyphenylene sulfide (PPS) or may comprise nylon. The thermally conductive polymer may comprise a blend of two or more polymers. The thermally conductive polymer may comprise a blend of ABS and another polymer. The thermally conductive polymer may comprise a blend of ABS and PC.

Advantageously, the thermally conductive polymer may contain carbon graphite particles or may contain carbon fibres or may contain carbon nano-fibres or may contain carbon nano-rods or may contain carbon nano-particles or may contain carbon nano-tubes. The thermally conductive polymer may contain metal particles or may contain metal nano-particles.

Conveniently, the thermal conductivity of the polymer composition is at least I W/m-K. Preferably, the thermal conductivity of the polymer composition is at least 4 W/m-K. More preferably, the thermal conductivity of the polymer composition is at least W/m-K. Most preferably, the thermal conductivity of the polymer composition is at least 20 W/m-K.

Conveniently, the vehicle trim component may be an interior trim component.

The vehicle trim component may be a handle, Alternatively, the vehicle trim component is a manual control element. For example, the vehicle trim component may be a switch, button or dial; alternatively, the vehicle trim component may be part of an air vent.

Conversely, the vehicle trim component may form part of a decorative fascia for a control or display element. For example, the vehicle trim component may be part of a housing for a switch, button or dial; alternatively, the vehicle trim element may be part of a housing for a display screen or display dial.

According to a second aspect of the invention, there is provided a vehicle having a vehicle trim component as described above. The vehicle may be a motor vehicle.

Alternatively, the vehicle may be an aircraft.

According to a third aspect of the present invention, there is provided a method of producing a vehicle trim component having the steps of injection moulding a thermally * conductive polymer composition to form a component and depositing a metal coating onto a portion of the surface of the component.

Depositing the metal coating may comprise vapour deposition. Alternatively, depositing the metal coating may comprise electroplating. Advantageously, depositing 1 5 the metal coating may comprise depositing successive layers of two or more metals.

More specifically, depositing the metal coating may comprise depositing successive layers of nickel and chromium. Preferably, depositing the metal coating comprises depositing successive layers of copper, bright nickel, and chromium. Depositing the metal coating may comprise depositing successive layers of copper, semi-bright nickel, bright nickel, and chromium. The chromium may be deposited from hexavalent chromium electrolytes.

The thermally conductive polymer may comprise acrylonitrile butadiene sty rene (ABS) or may comprise polycarbonate (PC) or may comprise epoxy resin or may comprise polyetherimide (PH) or may comprise polyphenylene sulfide (PPS) or may comprise nylon. The thermally conductive polymer may comprise a blend of two or more polymers. The thermally conductive polymer may comprise a blend of ABS and another polymer. The thermally conductive polymer may comprise a blend of ABS and PC.

io D tailel Deçription c, shejnvenUon In order that the invention may be more clearly understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a schematic showing a method according to the present invention for producing a vehicle trim component; Figure 2 is a section through a surface region of a vehicle trim component according to the present invention; and Figure 3 is a view of the interior of a car according to an embodiment of the present invention showing handles, air vents, switches, dials, switch housings and display housings, each according to further respective embodiments of the present invention.

The invention concerns the use of a thermally conductive polymer composition to create the cold feel of metal in lightweight vehicle trim components. This is most effective if the polymer composition has a thermal conductivity similar to common metal alloys, which may typically be in the range 10-50 W/m-K for stainless steels, 105-W/m-k for zinc alloys, and 100-250 W/m-K for aluminium alloys. By contrast, common polymers typically have a thermal conductivity of 0.1-0.3 W/m-K, although this is typically higher in reinforced polymer composites, at around 0,3-I.0 W/m-K. Some polymer compositions known as thermally conductive have values in the range 1.5-W/m-K, which is comparable to that of stainless steels, for example. Such polymer compositions are generally composites having dispersed fibres, particles, nano-fibres, nano-particles, or nano-tubes of a more conductive substance, such as carbon or metal.

These conductive elements may also have a reinforcing effect, beneficially influencing the stiffness and/or strength of the composition. For example ThermaTechTM branded compounds SF-4500 thermally conductive polyphenylene suiphide (TC PPS) and PT- 5000 thermally conductive polyetherimide (TC PEI), made by PolyOne Corporation, Ohio, USA, both have a thermal conductivity of 11 W/m-K and an elastic modulus of 31 OPa, and densities of 1670 and 1630 kg/m3 respectively. This means that they may 1 5 feel cold and hard enough to the touch to create the feel of a metal surface, while being significantly lighter (about 40 % lighter) than an equivalent volume of aluminium alloy.

These or equivalent materials may therefore be used to create or cover surfaces that. ate designed to be both lightweight and to function as a tactile interface with a cold, metallic feel. Furthermore, they may bring advantages in terms of tooling and production costs, since polymer injection moulding techniques may be used. Further reinforcing elements, such as carbon or glass fibres, may be added to such thermally conductive composites to further improve stiffness and strength properties.

In several embodiments of the present invention, the surface of a component fabricated from such a polymer composition may be left untreated or may be given a coloured and/or textured finish. This may be a dark or non-reflective finish, for example, to create the visual appearance of high tempered steel, unpolished or oxidised metal, or painted metal. Alternatively, the finish may be a metallic paint that creates a reflective and/or glossy coating which visually resembles polished metal.

In several preferred embodiments, the surface of such a component is coated with a layer of highly thermally conductive material. This further enhances the surface conductivity of the tactile interface, enhancing the cold metallic feel of the component.

This may, for example, be a pure metal or metal alloy, or a metal-rich compound. In a preferred embodiment, this coating is sufficiently thick, continuous, and metallic in appearance as to provide a metallic visual appearance to the component. For example, in several embodiments, chromium or aluminium, or another metal or alloy, may be applied by vapour deposition, such as sputter coating, to the surface of the component to form a very thin metal coating that nevertheless creates the visual impression of a solid metal component. Alternatively, since some thermally conductive polymers are also electrically conductive, electrodeposition of the metal coating is possible. For example, in several embodiments, chromium or aluminium, or another metal or alloy, may be applied by electroplating to a component manufactured from an electrically and thermally conductive polymer composition. Examples of suitable polymers for electroplating include ThermaTechTM branded polymers LC-6000 thermally conductive liquid crystal polymer (TC LCP) and SF-6000 polyphenylene sulfide (IC PPS) made by PolyOne Corporation, Ohio, USA. These have thermal conductivities of 19 and 10-I I W/m-K, respectively, both have relatively low electrical resistivity of 0.01-0.1 Ohm-m, and have elastic moduli of 20.7 and 26.2 OPa, respectively. In a preferred embodiment, such an electrically and thermally conductive polymer is electroplated with layers of nickel and chromium to create a bright, reflective finish, using electrolyte solutions and currents selected, as would be appreciated by the skilled practitioner, as suitable for chrome-plating the polymer composition. Figure 1 shows a process for achieving such a coating, in which an iniection-moulded plastic component is chemically etched to promote adhesion of the metal coating and acid cleaned to remove surface dirt and grease.

Successive layers of metal are then applied by electrolytic deposition. An optimum surface finish such as that shown in Figure 2 may be achieved, for example, by electrolytic deposition onto the polymer composition (1) of consecutive layers of copper (2), bright nickel (3), and chromium (4); or by electrolytic deposition onto the polymer composition (1) of consecutive layers of copper (2) semi-bright nickel (not shown), bright nickel (3), and chromium (4). Suitable nominal minimum thicknesses according to DfN EN ISO 2177 for these coatings include 20 to 25 microns for the copper layer, 7.5 microns for the semi-bright nickel layer (if present), 7.5 to 10 microns for the bright nickel layer, and 0.3 to 1.0 microns (and in particular 0.8 microns) for the chromium 1 5 layer. The plastic part may typically have a thickness greater than I mm, preferably around 1-2 mm, and possibly much greater than this value.

In several preferred embodiments, the vehicle trim component is, or forms a part of, a switch (5), button (6) or control dial (7), as indicated in Figure 3. The control dial (7) has a trim component of a metal-coated, thermally conductive polymer composite forming a band around its circumference, as this corresponds to the part where the user would most often touch it during use. This may be a separate band added to the main body of the dial, or it may be a region of metal coating selectively applied to the circumferential region of a dial wholly composed of the thermally conductive polymer composition. In another embodiment, a manually-adjustable air vent (8) has similar metal-coated thermally conductive polymer construction, to create a cold feel to the user In yet another embodiment, the gear stick (9) similarly has a thermally conductive composite structure with a metal coating, to create a hançlle that looks and feels like solid metal alloy but is substantially lighter. In further embodiments, parts of the housings for * 5 control or display elements have a similar construction from thermally conductive polymer composition with metal coating. These include faceplates (10) for switches, buttons and control dials; and fascias, frames and bezels (11) for display screens, touch screens, clocks, and display dials.

In a preferred embodiment, vehicle trim components such as those in the above 1 0 described embodiments form part of the interior trim of a motor vehicle. In another embodiment, they form part of the interior trim of an aircraft. In another embodiment, similar metal-effect components form part of the external trim or body hardware for a motor vehicle.

As is apparent from the embodiments herein described, the term trim component' is used throughout to denote a superficial or exposed and at least partially visible and/or tangible component of a vehicle, and is not in any way limited to purely decorative fascias.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims