GB2439535A

GB2439535A - Stiffening of automobile panels

Info

Publication number: GB2439535A
Application number: GB0612938A
Authority: GB
Inventors: John Edward Sellors
Original assignee: Lotus Cars Ltd
Current assignee: Lotus Cars Ltd
Priority date: 2006-06-29
Filing date: 2006-06-29
Publication date: 2008-01-02
Anticipated expiration: 2026-06-29
Also published as: WO2008001120A3; GB0822265D0; WO2008001120A2; GB2451612B; GB2439535B; GB2451612A; GB0612938D0

Abstract

A structural panel 20 of an automobile is formed by shaping a metal sheet using a die tool, wherein the structural panel is formed with one or more lines of curvature (100,102, Figure 6) running therealong and the panel is also provided with a plurality of form-holding features 21 at least some of which have a shape and configuration of a bird's beak and which are spaced apart along at least one of the lines of curvature 100 and extend transversely across the line of curvature 100. Also disclosed are the fabrication of body panels (10, figure 2) without undercuts and an arcuate sill (50, figure 7) from three or more straight components.

Description

--2439535

A METHOD OF FABRICATION OF AUTOMOBILE PARTS

The present invention relates to methods of fabrication of automobile parts such as body panels, sills and metal interior folded parts.

In the manufacture of drawn panels for known automobiles there is often a need for extensive cam tooling and secondary operations, because of the need to form complex shapes.

In a first aspect, the present invention provides a method of fabricating a body panel for an automobile, in whicl-the body panel is drawn from a metal sheet and is formed for use without undercuts.

In the manufacture of panels for conventional automobiles, restrike tools are often used to increase panel form definition. Restrike tooling can be very expensive.

In a second aspect the present invention provides a methcd of fabricating a structural panel of an automobile by shaping a metal sheet using a die tool wherein the structural panel is provided with a plurality of holding-form features of shape and configuration whose primary purpose is to increase plastic strain of the metal sheet during shaping to thereby assist the panel in retaining its shape after it is removed from the die tool.

The formation of sills for an automobile often involves investment in stretching and bending tools.

In a third aspect, the present invention provides a method of fabricating an arcuate sill for an automobile which comprises welding at least three components together to form the sill, with the at least three components comprising two end components each welded onto one or more central component(s).

The various aspects of the present invention will now be described with reference to the accompanying drawings, which shows:- Figure 1 shows a plan view of a door ring body panel with the body panel laid flat; Figure 2 is an end-on view of the door ring of Figure 1, with an arrow showing the direction of the press tool draw; Figure 3 is a plan view of an A pillar body panel, laid flat; Figure 4 is a plan view of a hood inner, laid flat, the hood inner having holding form features; Figure 5 is a view of a part of the hood inner of Figure 4, showing the holding form features in greater detail; Figure 6 is a perspective view of a part of the hood of Figure 4 which shows in detail the Figure 5, the Figure 6 perspective view showing more clearly the holding-form features illustrated in Figure 5; Figure 7 is a plan view of a three part welded sill; Figure 8 is a side elevation view of the sill of Figure 7; and Figure 9 is a perspective view of the sill of Figures 7 and 8; Figure 10 is a cross-section through the sill of Figures 7 to 9; and Figure 11 is a simplified version of Figure 7.

Figure 1 shows in plan view a door ring 10 for an automobile, laid flat. The door ring has been designed deliberately to avoid undercuts. Undercuts are typical in the design of drawn panels, but require expensive cam tooling and secondary operations for formation. On the other hand, the door ring 10 of Figure 1 can be manufactured in a single draw tool operation. This can be more clearly seen in Figure 2 where the arrow 11 shows the direction of motion of a press tool used in the panel draw operation. It will be understood that the panel 10 of Figures 1 and 2 is formed from an appropriately shaped substantially flat panel which is then drawn into shape using die tools.

A second component formed without undercuts in the same manner can be seen in Figure 3. Figure 3 shows a plan view of an A-pillar panel 11, laid flat. Again, it can be seen that the formed pillar is devoid of undercuts. Thus it can be formed by a single draw tool operation.

The panels of Figures 1 to 3 are formed in 2 piece die tools. The tooling for formation of a door ring panel is usually a very high investment part and a cost saving is very beneficial in this area. Another panel suitable for forming without undercuts is a roof panel. The use of panels without undercuts requires redesign of mating components to provide suitable abutting surfaces.

Restrike tools are often used in vehicle panel manufacture to increase panel form definition. This can be an expensive process. In order to avoid this the present invention proposes adding form-holding features of shape and configuration to form the panels in order to enhance the plastic strain of the panel and therefore hold panel shape.

This is illustrated with reference to Figures 4 to 6. These show a hood inner panel.

In Figure 5 there can be seen the addition of form-holding features 21 to a panel 20 (see Figure 4) which allow the panel 20 to hold its form and negate the need for the use of restrike tools. The added features are "bird beaks" in shape and are formed during the initial forming of the panel 20 from a flat metal sheet. The material of the panel plastically deforms in the region of the added form-holding features 21 shown in Figure 5. Form-holding features 21 are added solely for the purpose of creating extra plastic deformation in order that the formed panel 22 retains its shape after forming. The features 21 are form- holding features in that they hold the rest of the panel in shape.

The features can be seen in more detail in Figure 6 where they can be seen to take the shape of "bird beaks" in nature.

The form-holding features are formed simultaneously with the other features of shape and configuration of the panel as it is formed by drawing in a die. The form-holding features are chosen to span areas of curvature e.g. 100, 102 in Figure 6 in the formed panel to hold the shape of such areas of curvature in the panels.

Instead of the use of a "bird's beak" shape, other shapes could be used, e.g. a sausage shape. A smoothly curving form-holding feature is desired because some materials, e.g. aluminium, can split if the shape of the form-holding feature is not "soft" in nature.

A number of discrete and separate form-holding features will be provided in a panel to hold the shape of the panel, e.g. in Figure 6 the area of curvature l00.forms a line along the panel and the form-holding features 100 will be spaced along the line crossing transversely across the line; this can also be seen with the line formed by the area of panel curvature 102.

Figure 7, 8, 9, 10 and 11 show an arcuate sill 50 for an automobile. it is common for such arcuate sills to be manufactured by stretching and bending tools. However, this involves significant investment. Instead, the arcuate sill is made of three components 51,52, 53 which are welded together in the form that can be best seen in the isometric view of Figure 9. The end components 52 and 54 are not parallel to the central component 50 and instead incline away from the curved component 50 at an angle. They both extend away from the component 50 in the same direction away from the component 50 when the component 50 is viewed in plan view and the inclination is considered in a lateral sense perpendicular to a side face of component 50. The component 52 is formed with a end face surface which abuts an end face surface of the component 51 and is welded along the abutment. The end face surfaces of the components 51 and 52 are both sloped in comparison to the side faces of the components 50 and 52, as can be seen in Figure 11. The abutting surfaces must both be cut at the same or a similar angle so that the abutting surfaces are of the same length.

The three components si, 52, 53 will be set in a welding fixture (akin to a "jig") and then welded to ensure good alignment. In a similar fashion the component 53 has an end face which abuts an end face of the component 5]. and defines a junction which is welded. Again, both of the abutting end faces of the component 51 and the component 53 are inclined with respect to the side faces of the components. In this way a sill formed for the vehicle which is arcuate when viewed in plan view as in figure 10, in that the component arcs from ends which are more inboard of the vehicle than the central portion 5]..

Each of the arrangements 51, 52, 53 is typically an extrusion, typically in an alloy of aluminium Each could be section cut from a common extrusion and Figure 10 shows a cross-section transversely taken through each component 51, 52, 53, in such a case. The cross-section shows that each component 51, 52, 53 is hollow, but has internal webs 200, 201 extending across. Three voids 202, 203, 204 are shown.

The section of sill forming the void 204 tapers from a greater width at the web 201 to a lesser width at an end surface 205 of the sill. The thickness of metal in the webs is less than the thickness of the metal in the remainder of the component.

Whilst each of the components 51, 52, 53 could be of a common cross-section, gauge and material, in some circumstances it may be preferable to use components of differing properties, e.g. a high strength thicker gauge section could be used for the front of the three sill components, to help with crash performance of the sill, whilst the other two sections could be formed of a thinner gauge material for lightness. The type of alloy used in each component could be different, e.g. different extrusion grades could be used for each section, high strength in the front, lower strength at the rear.

In the Figure 9 there can be seen holes 60 in a laterally-facing side surface of the sill. These holes enable the joining of body panels to the sill.

Whilst above the sill has been described as a sill fabricated out of extruded aluminium and the method of the invention is ideal for such a purpose, the invention could also be applied to steel tubing, hollow section steel arrangements (e.g. rectangular or square for section components) and also rolled steel components.

Whilst above the sill has been described as a sill fabricated out of three components, a sill can alternatively be made of more than three components. In particular, the sill can be formed from five components. A five component sill may be formed by adding an additional component to the front and rear of a three component sill.

Claims

CLAIMS

].. A method of fabricating a body panel for an automobile, in which the body panel is drawn from a metal sheet and is formed for use without undercuts.

2. A method as claimed in claim 1 wherein the body panel formed is a door ring panel.

3. A method as claimed in claim 1 wherein the body panel formed is an A-pillar body panel.

4. A method as claimed in claim 1 wherein the body panel formed is a roof panel.

5. A method of manufacture of an automobile which includes assembling a body of the automobile from a plurality of body panels including door ring panels, wherein each door ring panel is fabricated by the method of claim
2.

6. A method of manufacture of an automobile which includes assembling a body of the automobile from a plurality of body panels including A-pillar panels, wherein each A-pillar panel is fabricated by the method of claim
3.

7. A method of manufacture of an automobile which includes assembling a body of the automobile from a plurality of body panels including door ring panels and A-pillar panels, wherein each of the door ring panels is fabricated by the method of claim 2 and each of the A-pillar panels is fabricated by the method of claim 3.

8. A method of manufacture of an automobile as claimed in any one of claims 5 to 6 wherein the body of the automobile is additionally assembled from a roof panel fabricated by the method of claim
4.

9. A method of fabricating a structural panel of an automobile by shaping a metal sheet using a die tool wherein the structural panel is provided with a plurality of form-holding features of shape and configuration whose primary purpose is to increase plastic strain of the metal sheet during shaping to thereby assist the panel in retaining its shape after it is removed from the die tool.

10. A method as claimed in claim 9 wherein each form-holding feature is a domed protrusion from the metal sheet.

11. A method as claimed in claim 10 wherein each form-holding feature is shaped as a bird's beak.

12. A method as claimed in claim 9 wherein each form-holding feature is sausage-shaped.

13. A method as claimed in any of the claims 10 to 12 where each form-holding feature is a smooth curving feature in the panel.

14. A method as claimed in any one of claims 9 to 12 wherein the form-holding features are provided spanning areas of curvature of the structural panel.

15. A method as claimed in claim 14, wherein the panel is formed with one or more lines of curvature running -10 -therealong and the form-holding features are provided at spaced apart intervals along at least one of the lines of curvature extending transversely across the line of curvature.

16. A method of fabricating an arcuate sill for an automobile which comprises welding at least three components together to form the sill, with the at least three components comprising two end components each welded onto one or more central component(s).

17. A method as claimed in claim 16 wherein the end components and the central component(s) are all elongate components and each end component has an end surface which abuts a respective end surface of the central component(s) and the abutting surfaces are all inclined relative to a longitudinal axis of the relevant component.

18. A method as claimed in claim 16 or claim 17 wherein at least one of the components is formed from an extrusion.

19. A method as claimed in claim 18 where each of the components is formed from an extrusion.

20. A method as claimed in any of claims 16 and 19 wherein each of the components is hollow.

2].. A method as claimed in any one of claims 16 to 20 wherein a gauge of metal in one of the components is different to a gauge of metal in at least one of the other components.

-11 - 22. A method as claimed in any one of claims 16 to 20 wherein material properties of metal in one of the components differ from material properties of metal in at least one of the other components.

22. A method of fabricating automobile parts substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

Amendments to the claims have been filed as follows:

CLAI MS

1. A method of fabricating a structural panel of an automobile by shaping a metal sheet using a die tool wherein the structural panel is formed with one or more lines of curvature and is also provided with a Plurality of form-holding features at least some of which have a shape and configuraj of a bird's beak and which are spaced apart along at least one of the lines of curvature and extend transversely across the line of curvature 2. A method of manufacture of an automobile comprising fabricating for the automobile a structural panel using the method of claim i and fabricating an arcuate sill for the automobile by welding at least three sill components together to form the sill, with the at least three sill components comprising two end sill components each welded onto one or more central sill component (s).

3. A method as claimed in claim 2 wherein the end sill components and the central sill component(s) are all elongate components and each end sill component has an end surface which abuts a respective end surface of the central sill Component(s) and the abutting surfaces are all inclined *. 25 relative to a longitujn axis of the relevant sill Component. * .0* * *

4. A method as claimed in claim 2 or claim 3 wherein at least one of the sill components is formed from an extrusion.

5. A method as claimed in claim 4 where each of the sill components is formed from an extrusion.

6. A method as Claimed in claim 2 or claim 5 wherein each of the sill components is hollow.

7. A method as Claimed in any one of claims 2 to 6 wherein a gauge of metal in one of the sill components is different to a gauge of metal in at least one of the other sill components.

8. A method as claimed in any one of claims 2 to 7 wherein material propertj of metal in one of the sill components differ from material properties of metal in at least One of the other components 9. A method of manufacture of an automobile, comprising fabricating a structural panel using the method of claim 1 and fabricating a body panel for the automobile by drawing from a metal sheet and forming the body panel for use without undercuts * 0 S *** * 0.* 10. A method as claimed in claim 9 wherein the body panel 00.I formed without undercuts is a door ring panel.

*:. 25 *S.

11. A method as claimed in claim 9 wherein the body panel formed without undercuts is an A-pillar body panel. *

12. A method as claimed in claim 9 wherein the body panel formed without undercuts is a roof panel.

13. A method of manufacture as claimed in claim io wherein each door ring panel of the automobile is fabricated without undercuts 14. A method of manufacture as claimed in claim 11 wherein each A-pillar panel of the automobile is fabricated without undercuts 15. A method of fabricating automobile parts substantially as hereinbefore described with reference to and as Shown in the accompanying drawings.

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