GB2492157A

GB2492157A - Heel plate comprising a structural foam

Info

Publication number: GB2492157A
Application number: GB1110707.5A
Authority: GB
Inventors: Gregor Schmich; Karsten Scholz
Original assignee: Zephyros Inc
Current assignee: Zephyros Inc
Priority date: 2011-06-24
Filing date: 2011-06-24
Publication date: 2012-12-26
Also published as: GB201110707D0

Abstract

Vehicle heel plates are provided comprising a structural foam preferably provided on a carrier 4. Preferably the structural foam provides a bond between the centre tunnel and the rear floor of the vehicle. The structural foam may be derived from a heat foamable material and preferably foams at temperatures experienced in the automobile assembly process. The carrier may be made from metal or strong plastic. The structural foam may be an epoxy-based material. The invention provides strength and reinforcement to the heel plate whilst at the same time reducing the weight of metal previously required to impart these properties to that location in the vehicle.

Description

t V.' INTELLECTUAL ..* PROPERTY OFFICE Application No. GB 1110707.5 RIM Date:11 October 2011 The following terms are registered trademarks and should be read as such wherever they occur in this document: L & L Products Intellectual Properly Office is an operating name of the Patent Office www.ipo.gov.uk

IMPROVEMENTS IN OR RELATING TO VEHICLE HEEL PLATES

The present invention is concerned with the heel plates of vehicles and in particular to the reduction in the weight of heel plates whilst retaining and/or enhancing their strength and S ease of manufacture.

The heel plate of a vehicle forms the rear boundary of the legroom in the passenger compartment connecting the left and right sill and the tunnel formed in the centre of the floor to the rear floor of the vehicle. The heel plate is a heavy metal component bridging the transverse rear seat support and the longitudinal tunnel of the body of the vehicle. The heel plate is designed to strengthen the vehicle in a crash and also to reduce the noise, vibration and harshness (NVH) in the vehicle. Heel plates traditionally have been steel components weighing several kilograms which are welded to the rear seat support and the metal components forming the longitudinal tunnel. Attempts have been made to reduce the weight of the heel plate by reducing metal thickness but this has reduced the crash resistance and NVH performance at that location to unacceptably low levels.

We have found that the weight of the heel plate may be reduced without a significant change in the performance in relation to impact resistance and the reduction in NVH if at least part of the metal component is replaced by a structural foam. In a preferred embodiment the structural foam is provided upon a carrier.

The invention provides a heel plate comprising a structural foam which provides reinforcement which will improve the bond between the tunnel/centre floor and the rear floor and therefore will improve the global bending stiffness of the entire body. The reinforcement forms a composite by gluing the rear floor and the heel plate together by means of a structural foam.

The structural foam may be provided across all or part of the width of the vehicle depending upon the design and structure of the vehicle and the strength required. In a preferred embodiment the structural foam is provided across the width of the heel plate. The shape of the component providing the structural foam will be chosen according to the design of the vehicle however it should be shaped to provide strength to the joint between the rear floor and the heel plate in both the vertical and horizontal directions. Reinforcement in the vertical direction provides support to the components that are placed upon the rear floor panel and reinforcement in the horizontal direction provides resistance to side crash impact. The part will also impart a general reduction in NVH at that location in the vehicle.

A preferred design for providing the structural foam comprises a carrier provided with a section that carries a material that can be foamed to provide a structural foam which upon foaming bonds to the metal components of the heel plate and the rear floor of the vehicle.

S The foamable material may be provided over all or part of the surface of the carrier.

In an additional embodiment the invention provides a method for providing a lateral reinforcement in the area of the rear seat of a vehicle comprising providing a carrier which carries a material that can be foamed to produce a structural adhesive foam within a cavity formed between the rear floor and the heel plate and causing the foamable adhesive to foam and develop adhesive properties and thereby bond to the rear floor and the heel plate.

This method has been found to result in the desirable crash impact properties and NVH characteristics that have previously been obtained with metal components weighing several kilograms but which could not be realised by reducing the weight of metal (i.e. the thickness of the metal components). The invention enables a 25 % or greater weight reduction in the overall heel plate whilst retaining the desired crash impact resistance and NVH performance.

The present invention therefore provides a vehicle heel plate comprising a structural foam located upon a carrier wherein the heel plate is bonded to the rear floor structure by means of the structural foam. In a preferred embodiment the structural foam is supported on a carrier.

The reinforcement of certain areas of vehicle bodies with structural foam optionally provided on a carrier is known. For example WO 9939882 shows the reinforcement of roof and tailgate supports.

European Patent Publication 1354789 Al and United States Patent 6495126 discloses the use of structural foam to reinforce bolted sections. However, it has not been recognised that the weight of a heei plate may be reduced whilst retaining crash resistance strength and desirable NVH properties by means of a structural foam particularly a structural foam supported on a carrier.

In one embodiment the structural foam is derived from a heat foamable material that develops strength and adhesive properties as it foams. It is further preferred that the material foams at temperatures experienced in the automobile assembly process such as in the paint or anti-corrosion (e-coat) coating bake operations. This enables the subframe, main frame and reinforcing materials to be assembled on an assembly line and passed into an oven where the foamable material foams, develops strength and adhesive properties to bond to the metal component of the heel plate and to the rear floor so as to provide strong reinforcement to the heel plate region of the vehicle.

The bond between the heel plate and the rear floor structure may be provided exclusively by the structural foam optionally together with the carrier, alternatively welding may be employed. However, the invention provides the additional benefit that the need for welding of components in the heel plate region may be reduced or eliminated.

Where the structural foam is located upon a carrier the carrier may be of metal or strong plastic material such as fibre reinforced polyamide or polypropylene. Where the carrier is of metal it may be a stamping from steel or aluminium. Where the carrier is of plastic it may be produced by injection moulding or extrusion. The foamable material which forms the structural foam may be applied to the carrier by extrusion or injection moulding of the material onto the carrier at temperatures below that at which foaming and/or curing to develop strength occur.

Structural foam is a well-known term in the automobile art and it relates to a foamed material that provides a structural reinforcement to a component of the vehicle. Typical structural foams have a lap shear of 5 MPa or greater and a modulus of I GPa or greater with a degree of expansion of up to 500%, typically from 50% to 200% to give a density between I and 2.5 Kg/dm3. The reinforcement member may include a polymeric carrier, which may be amenable to injection moulding or other such mouldable material such as polymeric, metallic or ceramic, and a load distributing foamable medium disposed on the carrier. The load distributing foamable medium disposed on the carrier is such that on foaming it produces a structural foam and is preferably a curable (by cross linking) epoxy-based foamable material.

The preferred load distributing medium is an epoxy based structural foam such as the products foam derived from the L0506, L0507, L5001, L5204, L5206, L5207, L5214, L5234, L5235, [52365 L5244, L8050 and L8051 structural foam, which is commercially available from L&L Products of Romeo, Michigan and L&L Products Europe of Strasbourg, France.

During an automobile assembly process the reinforcement member with the foamable material in an unfoamed un-cured state is positioned close to the heel plate and rear floor panel so that the uncured structural foamable material can be heated to cause foaming and curing to provide the structural foam. Once the foam is cured, the reinforcement member adheres to the heel plate and the rear floor panel and distributes any loads that impact the area in the vehicle and reduces NVH. The reinforcement member may be provided with means of attachment to aid in mounting the member in the desired position close to the heel plate and the rear floor.

S The carrier can be formed of a polymeric material, a preferred polymeric material being nylon, but may also consist of a metallic or ceramic material. More preferably the nylon material is glass filled nylon. However, it will be appreciated that other materials having similar properties may be used.

The carrier may have any suitable geometric configurations. For example, the carrier may be rectangular or a variety of complex geometrical configurations. The particular configuration chosen for the carrier will vary depending on the configuration of the area that is to be reinforced.

When a carrier is used reinforcement is provided by both the structural strength and stiffness of the carrier together with the strength of the structural foam and it may be provided by load distributing structural foam on the selected surfaces of the carrier member. The structural foam increases the strength and structural stiffness of the carrier without adding significantly to the overall weight. Typically, the structural foam is provided on to the carrier in the areas corresponding to heel plate areas where reinforcement is desired such as a continuous load transfer medium or bonding surface application.

The structural foam is preferably heat-activated and foams upon heating, typically by a foaming reaction such as the release of gas by a blowing agent. The foamable material is generally applied to the carrier in an unfoamed solid or semi-solid state. The structural foam may be applied to the outer perimeter of the carrier in a fluid state using commonly known injection techniques, wherein the material is heated to a temperature that permits it to flow slightly. Upon cooling the unfoamed material hardens and adheres to the outer surface of the carrier, or via adhesive characteristics in the material formulation itself. Alternatively, the material may be applied to the carrier as precast pellets, which are heated slightly to permit the pellets to bond to the outer surface of the carrier. At this stage, the material is heated just enough to cause it to flow slightly, but not enough to cause it to expand or cure. Note that other expandable materials can be used, such as, without limitation, an encapsulated mixture of materials that, when activated by temperature, pressure, chemically, or other by other ambient conditions, will expand.

The structural foam is preferably an epoxy-based material, but may include other polymers such as ethylene copolymers or terpolymers. A copolymer or terpolymer, is composed of two or three different monomers.

S In applications where a heat activated, thermally expanding material is employed, an important consideration involved with the selection and formulation of the material which provides the structural foam is the temperature at which a material reaction or foaming, and possibly curing, will take place. For instance, in most applications, it is undesirable for the material to be reactive at room temperature or otherwise at the ambient temperature in a production line environment. More typically, the material becomes active at higher processing temperatures, such as those encountered in an automobile assembly plant, when the material is processed along with the automobile components to foam and cure at elevated temperatures or at higher applied energy levels. While temperatures encountered in an automobile assembly operation may be in the range of 130°C to 210°C, body and paint shop applications are commonly about 90°C or slightly higher. Generally, the foams have a range of expansion ranging from approximately 0 to over 1000 percent. The level of expansion of the structural foam may be increased to as high as 1500 percent or more.

However, expansion levels of 50 to 200 percent are preferred because higher expansion levels can result in mechanical property reduction.

The invention therefore provides strength and reinforcement to vehicle heel plates and results in comparable strength and NVH performance with reduced weight with the attendant fuel economy benefits.

The invention is illustrated by reference to the accompanying drawings in which Figure 1 illustrates the location of a heel plat2 in a vehicle Figure 2 illustrates a conventional all metal heel plate weighing about 2200 grams Figure 3 illustrates a system similar to Figure 2 in which the weight of the metal heel plate has been reduced to about 1280 grams Figure 1 shows a heel plate (1) circled welded to the rear floor section (2). Figure 2 is an expanded end version of Figure 1 showing that heel plate (1) of steel of thickness 1.5 mm bonded to the rear floor material comprising a steel sheet of thickness 0.8mm. The system of Figure 1 satisfies the crash and noise, vibration and hardness requirements of the vehicle.

In Figure 2 the heel plate (1) of Figure 1 has been replaced by a metal heel plate (3) of thickness 1.0mm. The system of Figure 2 does not satisfy the crash and noise, vibration and harness requirements of the vehicle. Figure 3 shows the system of Figure 2 in which

S

the heel plate (3) has been removed to show where the structural foam on the carrier (4) can be positioned to provide sufficient strength at a lower weight than the system of Figure 1 and yet satisfy the crash and noise, vibration and hardness requirements of the vehicle.

S Figure 3 therefore illustrates a heel plate according to the invention in which the thickness of the metal is reduced and a component comprising a structural foam and a carrier is provided so that the overall weight is about 1500 grams. This system provides similar crash resistance and NVH properties as those provided by the heel plat of Figure 1 at a 28 % weight reduction.

Claims

CLAIMS1. A heel plate comprising a structural foam.
2. A heel plate according to Claim 1 in which the structural foam provides a bond between the centre tunnel and the rear floor of the vehicle.
3. A heel plate according to Claim 1 or Claim 2 in which the structural foam is provided on a carrier.
4. A heel plate according to any of the preceding claims in which the structural foam is derived from a heat foamable material that develops strength and adhesive properties as it foams.
5. A heel plate according to Claim 4 in which the material foams at temperatures experienced in the automobile assembly process such as in the paint or anti-corrosion (e-coat) coating bake operations.
6. A heel plate according to any of Claims 3 to 5 in which the carrier is of metal or strong plastic material such as fibre reinforced polyamide or polypropylene.
7. A heel plate according to any of the preceding claims in which the structural foam is an epoxy-based material.