WO2011075011A1

WO2011075011A1 - Reinforcement for vehicle door with door extension

Info

Publication number: WO2011075011A1
Application number: PCT/SE2009/000524
Authority: WO
Inventors: Jonas Svedberg; Andreas Wikman; Svante Borged
Original assignee: Volvo Lastavagnar Ab
Priority date: 2009-12-17
Filing date: 2009-12-17
Publication date: 2011-06-23

Abstract

The present invention generally relates to a reinforcing structure (10) for a motor vehicle door (13), in particular for a side door in a commercial vehicle provided with a cab. The invention relates to an structure for reinforcing a vehicle door (13) comprising a door frame (23) with a door extension (14) extending downwards from a lower portion of the vehicle door (13).

Description

Reinforcement for Vehicle Door with Door Extension

TECHNICAL FIELD

The present invention generally relates to reinforcing structures for a motor vehicle door, in particular for a side door in a commercial vehicle provided with a cab. The invention relates to an structure for reinforcing a vehicle door provided with a door extension extending downwards from a lower portion of the door.

BACKGROUND ART Certain types of vehicles may be provided with a door extension, sometimes referred to as an apron or a fairing, extending downwards from a lower portion of a vehicle door.

A door extension of this type is commonly used for improving the aerodynamic properties of the vehicle and/or for covering one or more steps in the lower side surface of the vehicle when the door is closed. The said steps are used for entering or exiting the vehicle when the door is opened.

Known vehicle doors provided with a with door extension are described in DE 10 2006 005 713, which shows a door extension that can be adjusted relative to the door in both the longitudinal and transverse directions thereof, and EP 2 017 128, which shows a door extension covering a number of side steps.

A problem with door extensions of this type is that vibrations and/or rattling of the extensions may occur when the vehicle travels at speed or over an uneven road surface. Over certain speeds, the turbulent airflow past the door extension may cause it to vibrate, which may cause a vibrating noise that can be annoying to the driver. When travelling over uneven tarmac or on pitted gravel roads, the movement of the vehicle may cause sudden displacements of the door extension and create a rattling noise that can also be annoying to the driver. Such noise is sometimes referred to as Buzz, Squeak & Rattle (BSR) or Squeak and Rattle (S&R) and may cause customer dissatisfaction, in particular if the source of the noise can not be identified.

In addition, for a commercial vehicle of the cab-over type, bending of the door extension may occur when the cab is tilted during servicing of the engine, etc. Inadvertent excessive bending forces applied to the door extension during this procedure may cause damage to the attachment points where the door extension is attached along the lower side edge of the door.

It is an object of the invention to provide an improved vehicle door with a door extension that overcomes the above problems.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a vehicle door with a reinforcing structure which functions to increase the stiffness of the door and to reduce vibrations caused by movement of a door extension. This object is achieved by means of a vehicle door with a reinforcing structure according to the appended claims.

The present invention aims to provide a vehicle door assembly located in a side surface of a vehicle frame with a reinforcing structure. The reinforcing structure aims to strengthen a portion of the door in a region comprising a lower door hinge and attachment means for a door extension. The invention further aims to reduce vibrations in the door extension and to reduce the transmission of such vibrations to the vehicle frame. In the text, the terms "vehicle door" or "vehicle door assembly" relates to a complete door comprising an inner skin panel, an outer skin panel and a door frame, onto which the inner and outer skin panels and a number of accessories are attached. Accessories may comprise component parts such as a hinge assembly, a latching means, a window operating mechanism, etc. The door frame is preferably a pressed sheet metal component that may include a frame surrounding a window opening. The vehicle frame comprises all chassis components surrounding the vehicle door assembly, including the A-pillar extending along the front portion of the door frame and the B-pillar extending along the rear portion of the door frame. References to a relative position, such as "front", "rear", "inner", "outer", "longitudinal" or "transverse" are taken relative to a central longitudinal axis through the vehicle in its main direction of travel. With respect to the vehicle door, the said positions are to be taken with the door in its closed position in the vehicle frame.

The vehicle door comprises a door frame and a hinge assembly and a latching means. The hinge assembly comprises at least an upper and a lower hinge which pivotally interconnects the door and its door extension with the vehicle frame. The latching means may retain the vehicle door in a closed position in the vehicle frame. The reinforced door assembly further comprises a reinforcement member connected to a lower hinge in the hinge assembly.

The motor vehicle may preferably, but not necessarily, be a commercial vehicle, which comprises a cab. The invention is particularly suitable for commercial vehicles of the cab-over type.

According to one embodiment, the invention relates to a vehicle door comprising a door extension attached to and extending downwards from a lower portion of a door frame of the vehicle door, and at least an upper and a lower hinge attached to the vehicle door. The hinges are arranged to connect the vehicle door to an adjacent A-pillar in the vehicle frame. The hinges pivotally interconnect the vehicle door and its door extension with a vehicle frame. The vehicle door is provided with a reinforcing structure comprising at least

- a first reinforcing member comprising;

- a first portion attached to the door frame adjacent the lower hinge, - a second portion attached to the door extension, and

- a third portion connecting the first and second portions;

- at least one second reinforcing member comprising;

- first portion is connected to the door and to the first portion of the first reinforcing member

- a second portion attached to the door frame and to the second portion of the first reinforcing member,

- a third portion connecting the first and second portions, which third portion is attached to the lower hinge,

wherein the first and at least one second reinforcing members form a closed section connected to the door frame of the vehicle door, the door extension and the lower hinge.

The reinforcing structure is preferably, but not necessarily, shaped to conform to the corresponding contact surface on the vehicle door. Hence the said first and second portions may extend in respective first and second planes, which planes are substantially parallel and extend in the vertical and the longitudinal directions, with local deviations in order to conform with the shape of the sheet metal portions making up the inner structure of the vehicle door. In addition, the reinforcing structure is preferably, but not necessarily, arranged so that its lower portion does not extend past the lower portion of the vehicle door.

The reinforcing structure is connected to the vehicle door, the door extension and the lower hinge. According to one example, the reinforcing structure may be connected to the vehicle door by suitable means, such as a continuous welding, spot welding, riveting, or by using screws, bolts or a suitable adhesive. The hinge and the door extension may be removably attached to the vehicle door during a subsequent assembly operation. Preferably, a hinge bracket for the lower hinge is attached to the door and the said at least one second reinforcing member. In order to optimize the stiffness of the vehicle door adjacent the lower hinge, the at least one second reinforcing member may be arranged to overlap all attachment points between the vehicle door and the lower hinge. The hinge or hinge bracket may preferably be attached by means of a screw and nut connection.

The vehicle door outlined above may further be provided with a reinforcing structure comprising at least

- a first reinforcing member comprising;

- a first portion located in a first plane having a predetermined extension in the longitudinal and the vertical direction of the vehicle door, which first portion is attached to the door adjacent the lower hinge,

- a second portion located in a second plane having a predetermined extension in at least the longitudinal and the vertical direction of the vehicle door, which second portion is spaced from the first portion in the longitudinal and the transverse direction and is attached to the door extension, and

- a third portion connecting the first and second portions of the first reinforcing member and having a predetermined extension in the transverse and the longitudinal direction of the vehicle door; and

- at least one second reinforcing member comprising;

- a first portion located in the said first plane, which first portion is connected to the door and to the first portion of the first reinforcing member,

- a second portion located in and/or adjacent the said second plane, which second portion is spaced from the first portion in the longitudinal and the transverse direction and is attached to the door and to the second portion of the first reinforcing member, and - a third portion connecting the first and second portions of the at least one second reinforcing member, which third portion has a predetermined extension in the transverse direction of the vehicle door and is attached to the lower hinge.

As stated above, the first and at least one second reinforcing members form a closed section extending in the vertical direction of the door between the lower hinge and the door extension, in particular an attachment point of the door extension.

The first portion of the first reinforcing member, located in the said first plane, may extend forwards of an attachment point of the lower hinge. The first portion of the first reinforcing member is preferably attached to the vehicle door at this point, via a corresponding section of the first portion of the second reinforcing member. The attachment is preferably made by welding, such as spot welding, along the vertical extension of the respective first portions. The lower hinge may have three or more attachment points located in a transverse plane at or substantially at right angles to the said first plane.

In addition, the second portion of the first reinforcing member can overlap and be connected to at least one attachment point of the door extension.

Also, the second portion of the first reinforcing member may be attached to the door and the at least one second reinforcing member remote from the at least one attachment point of the door extension.

In this way the first reinforcing member may be attached to and extend from a first plane at a front portion of the vehicle door, past the location of the lower hinge, at an angle directly or indirectly towards a second plane parallel to and to the rear of the said first plane, where after it is attached to the vehicle door and to an upper, front portion of the door extension.

The door extension may have a number of attachment points along its upper periphery, where it is attached to the vehicle door. In addition, one or more attachment points, preferably at least two attachment points, are arranged at the front portion of the door extension adjacent the reinforcing structure.

According to one example, at least two such attachment points may be separated in the vertical direction of the plane of the vehicle door. Alternatively, the said at least two attachment points may be separated both in the vertical and the longitudinal direction.

The vehicle door may also be provided with a door stop, which prevents the door from being opened past a predetermined angle. One reason for this is to prevent damage to the hinge, should the door be opened past an allowable opening angle. The door stop should therefore preferably be attached to a reinforced portion of the vehicle door, in order to allow forces transmitted through the door stop to be absorbed. The door stop may preferably attached to the second portion of the at least one second reinforcing member. In this way, the same reinforcing structure may be utilised for both the hinge and the door stop.

In the above examples, the second reinforcing member has been described as comprising a single member or a single bracket. Alternatively, the second reinforcing member may be and assembled reinforcing member comprising a first bracket and a second bracket. The first and second brackets may be arranged to overlap at least within the closed section formed by the first reinforcing member and the assembled second reinforcing member.

The first bracket may comprise the first portion and a part of the second and the third portions of the second reinforcing member, which portions have been defined above in relation to the single bracket.

The first portion of the first bracket extends forwards of an attachment point of the lower hinge. This means that the first portion will extend forwards in a plane substantially parallel to the vehicle door, past the transverse plane in which the attachment points of the hinge are located. As described above, the transverse plane can be arranged at or substantially at right angles to the said first plane. The first portion of the first bracket is preferably attached to the vehicle door at this point, together with an overlapping corresponding section of the first portion of the first reinforcing member. The attachment is preferably made by welding, such as spot welding, along the vertical extension of the respective first portions.

The second portion of the first bracket may be arranged to overlap the second portion of the second bracket and is preferably, but not necessarily, terminated within the closed section. As in the above example, the third portion is arranged to connect the first and second portions.

The second bracket may comprise a part of the second and the third portions of the second reinforcing member, which portions have been defined above in relation to the single bracket. The second portion of the second bracket may be arranged to extend past the second portion of the first bracket and is attached to the vehicle door between the door and the second portion of the first reinforcing member. The attachment is preferably made by welding, such as spot welding, along the vertical extension of the respective second portions. The second portion of the first bracket is preferably terminated within the closed section, before this attachment point. Similarly, the second portion of the second bracket is terminated before the attachment point between the first reinforcing member and the door extension.

The third portion of the second bracket overlaps the third portion of the first bracket and is terminated within the closed section. The respective third portions have a predetermined extension in the transverse direction of the vehicle door and are both attached to the lower hinge. As will be described in further detail below, a door stop is attached to the second portions of the first and second brackets within the closed section. Similarly, the lower hinge is attached to the third portions of the first and second brackets within the closed section formed by the first and second reinforcing members.

The first and second brackets are arranged in contact with each other, at least within the closed section. One of the first or the second bracket may be placed in direct contact with the vehicle door, while the other bracket is mounted subsequently, so that one bracket is placed on top of the other. The brackets are attached to the vehicle door and are used to reinforce the attachment points for the lower hinge and the door stop, respectively. Although other means of attachment are possible within the scope of the invention, the reinforcing structure is preferably welded to the vehicle door.

As indicated in the examples given above, the door stop is mounted through the respective overlapping second portions of the first and second brackets. Similarly, the lower hinge is mounted through the respective overlapping third portions of the first and second brackets. The lower hinge and the door stop are preferably, but not necessarily, mounted by means of bolt and nut connectors to facilitate assembly and replacement thereof. According to one example, the door stop may be attached level with the lower hinge in the horizontal plane.

A hinge bracket for the lower hinge is attached to the side of the vehicle door facing the vehicle frame. As a consequence, the lower hinge is mounted on the outer side of the metal sheet making up the door and the at least one second reinforcing member is attached to the opposite, inner side thereof. The door stop is mounted in the same way on the side of the vehicle door facing the vehicle frame. The door extension may comprise a double wall structure at least adjacent the lower portion of the door and the reinforcing structure. The double wall structure may comprise an inner and an outer panel of a suitable material, such as aluminium, plastic or steel sheets, joined together along the outer periphery of the door extension. Attachment points for the door extension are preferably located along an upper section, adjacent the lower section of the vehicle door, and at the upper front section, adjacent the vertical extension of the reinforcing structure.

The door extension is preferably attached by mechanical means, such as bolt and nut connectors or rivets, to facilitate replacement of the extension. If incompatible materials are used in the door and the door extension, such as steel and aluminium, steps should be taken to prevent direct contact between these materials. According to one example, coated nuts or screws may be used for preventing galvanic corrosion between steel and aluminium. One or both of the door and the door extension may be sprayed or coated with an oxidation preventing layer of a suitable material.

BRIEF DESCRIPTION OF DRAWINGS

In the following text, the invention will be described in detail with reference to the attached drawings. These drawings are used for illustration only and do not in any way limit the scope of the invention. In the drawings:

Figure 1 shows a schematic perspective view of a vehicle provided with a reinforcing structure according to the invention;

Figure 2 shows a schematic side view of an outer panel of a vehicle door according to the invention;

Figure 3 shows a schematic side view of an inner portion of the vehicle door in Figure 2;

Figure 4 shows a perspective view of the reinforcing structure indicated in Figure 3;

Figure 5 shows a an enlarged view of the reinforcing structure in Fig. 4; Figure 6A-B shows cross-sections through the reinforcing structure in the planes X-X and Y-Y of Figure 5; and

Figure 7A-B shows cross-sections through an alternative embodiment of the reinforcing structure in the planes X-X and Y-Y of Figure 5. EMBODIMENTS OF THE INVENTION

Figure 1 shows a schematic perspective view of a motor vehicle provided with a reinforcing structure 10 according to a first embodiment of the invention. The motor vehicle 11 is a commercial vehicle of the cab-over type comprising a vehicle frame 12 having at least one door 13 in a longitudinal side surface thereof. In the case of a commercial vehicle of this type, the door 13 can be provided with a door extension 14 for improving the aerodynamic properties of the vehicle and/or for covering one or more steps in the lower side surface of the vehicle when the door 13 is closed.

The door 13 is attached by means of lower and upper hinges 15, 16 and a door latching means 16 is arranged to retain the door in its closed position. The lower and upper hinges 15, 16 and the door latching means 17 are schematically indicated in Figure 1 , as they are not normally visible from the outside of the cab. The reinforcing structure 10 and the upper edge of the door extension 14 is schematically indicated with dash-dotted lines inside the door 13 of the cab. In this figure, the door 13 is shown with an outer skin panel covering the reinforcing structure.

Figure 2 shows a schematic side view of the vehicle door 13, indicating the location of the reinforcing structure 10. The reinforcing structure is visible in the view shown in Figure 2, as the outer skin panel has been removed for clarity. With the outer skin panel removed, an internal door frame 23 forming the internal supporting structure of the door 13 is exposed. As can be seen from the figure, the door 13 has a lower edge 21 extending below the reinforcing structure 10. The reinforcing structure 10 is attached to a front portion of the door frame 23 between the outer panel and the door extension 14, as will be described below.

Figure 3 shows a schematic side view of an inner portion of the vehicle door 13, indicating the relative location of the reinforcing structure 10 and the door extension 14. The reinforcing structure 10 is indicated in dashed lines as it is located on the outer side of the door frame 23, while the door extension 14 is located on the inner side thereof. As can be seen from the figure, the door frame 23 has a lower edge 21 (dashed lines) extending below the reinforcing structure 10, while the door extension has an upper edge 31 extending at least up to the same horizontal level as the reinforcing structure 10 in the vertical plane of the door 13. The door extension 14 is provided with a number of attachment points 32 along its upper edge, where it is attached to corresponding attachment points along the lower portion of the door frame 23. A front portion of the door extension 14 is arranged to partially overlap a rear portion of the reinforcing structure 10. In this overlapping area, the door extension 14 is provided with at least two additional attachment points 33, 34 where the door extension 14 is attached to the both the door frame 23 and the reinforcing structure 10. As shown in the figure, the additional upper and lower attachment points 33, 34 are arranged both vertically and horizontally separated.

Figure 4 shows a perspective view of the reinforcing structure 10 indicated in Figure 3. The figure shows a lower, front portion on the outer side of the door frame 23 and its door extension 14, wherein the reinforcing structure 10 forms a strengthening means connecting the door frame 23, the door extension 14 and the lower hinge 5. The reinforcing structure 10 comprises a first reinforcing member 41 and a second reinforcing member 42, partially hidden by said first reinforcing member 41. The first reinforcing member 41 comprises a first portion 41a attached to the door frame 23 adjacent the lower hinge 15, in a first plane parallel to the door frame, a second portion 41b attached to the door frame 23 and the door extension 14 at the upper and lower attachment points 33, 34, in a second plane parallel to the door frame and remote from the first plane, and an intermediate third portion 41c connecting the first and second portions 41 a, 41 b. Figure 5 shows an enlarged view of the reinforcing structure in Figure 4, with the first reinforcing member 41 removed to show the location of the second reinforcing member 42. In this example, the second reinforcing member 42 is an assembled reinforcing member comprising a first bracket 51 and a second bracket 52. The first and second brackets 51 , 52 are arranged to overlap at least within the closed section formed by the first reinforcing member 41 and the assembled second reinforcing member 42.

The first bracket 51 comprises a first portion 51a, located in the said first plane, a second portion 51b, located in the said second plane, and a third portion 51c connecting the said first and second portions 51a, 51b, located in a third plane substantially transverse to the first and second planes. The first portion 51a of the first bracket 51 extends forwards of an attachment point of the lower hinge 15. This means that the first portion 51a will extend forwards in the said first plane, past the transverse plane of the third portion 51c in which two attachment points 53, 54 of the lower hinge 15 are located. The said transverse plane can be arranged at or substantially at right angles to the said first plane. The first portion 51a of the first bracket 51 is preferably attached to the door frame 23 at this point, together with an overlapping corresponding section of the first portion 41a of the first reinforcing member 41. The attachment is preferably made by welding, such as spot welding, along the vertical extension of the respective first portions 41a, 51a. The second portion 51b of the first bracket 51 is arranged to overlap the second portion 52b of the second bracket 52 and is terminated within the closed section formed by the first and the second reinforcing members 41 ,42. As in the above example, the third portion 51c is arranged to connect the first and second portions 51a, 51b.

The second bracket 52 comprises a second portion 52b, located in the said second plane, and third portion 52c, located in the said third plane. The second portion 52b of the second bracket 52 is arranged to extend rearwards past the second portion 51b of the first bracket 51 and is attached to the vehicle frame 23 between the door frame 23 and the second portion 41b of the first reinforcing member 41. The attachment is preferably made by welding, such as spot welding, along the vertical extension of the respective second portions 41b, 51b. The second portion 51b of the first bracket 51 is preferably terminated within the closed section, before this attachment point. Similarly, the second portion 52b of the second bracket 52 is terminated before the attachment point 33 between the first reinforcing member 41 and the door extension 14.

The third portion 52c of the second bracket 52 overlaps the third portion 51c of the first bracket 51 and is terminated within the closed section. The respective third portions 51c, 52c have a predetermined extension in the transverse direction of the door and are both attached to the lower hinge 15. As will be described in further detail below, a door stop (not shown) is attached to the second portions 51b, 52b of the first and second brackets 51 , 52 within the closed section. The door stop is attached on the inner side of the door frame 23 by means of bolt and nut connectors 55, 56, 57. Similarly, the lower hinge 15 is attached to the third portions 51c, 52c of the first and second brackets 51 , 52 within the closed section formed by the first and second reinforcing members 41 , 42. The first and second brackets 51 , 52 are arranged in contact with each other, at least within the closed section. In this example, the second bracket 52 is placed in direct contact with the door frame 23, while the first bracket 51 is mounted subsequently, so that the first bracket 51 is placed on top of the second bracket 52. The brackets are welded to the door frame 23 and are used to reinforce the attachment points 53, 54 for the lower hinge 15 and the attachment points 55, 56, 57 for the door stop, respectively.

As indicated in the examples given above, the door stop is mounted through the respective overlapping second portions 51 b, 52b of the first and second brackets 51 , 52. Similarly, the lower hinge 15 is mounted through the respective overlapping third portions 51c, 52c of the first and second brackets 51 , 52. The lower hinge 15 and the door stop are preferably mounted by means of bolt and nut connectors to facilitate assembly and replacement thereof. According to this particular example, the door stop is attached substantially level with the lower hinge in the horizontal plane of the door frame 23.

Figure 6A shows a cross-section through the reinforcing structure in the plane X-X of Figure 5. This figure shows how the first and second reinforcing members 41 , 42 are assembled to form a closed section 61. As described above, the first reinforcing member 41 comprises the first portion 41a, located in a first plane Pi, the second portion 41b, located in a second plane P2, and the third portion 51c connecting the said first and second portions 41a, 41b, and extending at an angle between the first and second planes. The first portion 51a of the first bracket 51 extends forwards of an attachment point of the lower hinge 15. Similarly, the second reinforcing member 42 comprises a first bracket 51 comprising the first portion 51a, located in a first plane Pi, the second portion 51b, located in a second plane P₂, and the third portion 51c connecting the said first and second portions 51a, 51b, located in a plane P3 substantially transverse to the first and second planes. The first portion 51a of the first bracket 51 extends forwards of an attachment point of the lower hinge 15. The second bracket 52 comprises a second portion 52b, located in the said second plane P₂, and third portion 52c, located in the said third plane P₃.

In the cross-section X-X, both the respective second portions 51b, 52b of the second reinforcing member 42 are terminated within the closed section 61 , before reaching the attachment point 33 of the door extension 14. Also, the third portion 52c of the second bracket 52 is terminated within the closed section 61 , before reaching the first plane

Figure 6A also shows how the reinforcing structure comprising the said first and second reinforcing members 41 , 42 is attached to the door frame 23 in order to connect the lower hinge 15, with its attachment points 53, 54, and the door stop 62, with its attachment points 55, 56, 57, to the door extension 14, with its attachment points 33, 34 (only one shown).

Figure 6B shows a cross-section through the reinforcing structure in the plane Y-Y of Figure 5, below the cross-section X-X. This figure shows how the first and second reinforcing members 41 , 42 are assembled to form a closed section 61. As can be seen from this figure, the second portion 52b of the second bracket 52 forms a local extension extending a predetermined distance out of the closed section 61. This allows the first reinforcing member 41 and the end of the second bracket 52 to be welded to the door frame 23. In addition, the first reinforcing member 41 is welded to the door frame 23 along its outer periphery above and below this extension of the second bracket 52.

Figure 7A shows a cross-section through an alternative embodiment of the reinforcing structure, taken in the same plane X-X of Figure 5. As shown in this figure, the second reinforcing member comprises a single bracket 71 , replacing the first and second brackets 51 , 52 shown in Figure 6A. In this alternative embodiment, the second reinforcing member comprises a first bracket 71 comprising the first portion 71a, located in a first plane Pi, the second portion 51b, located in a second plane P₂, and the third portion 71c connecting the said first and second portions 71a, 71 b, located in a plane P₃ substantially transverse to the first and second planes. The first portion 71a of the first bracket 71 extends forwards of an attachment point of the lower hinge 15. The second portion 71b of the first bracket 71 is terminated within the closed section 61 in the cross-section X-X.

Figure 7B shows a cross-section through an alternative embodiment of the reinforcing structure, taken in the same plane Y-Y of Figure 5. As can be seen from this figure, the second portion 71b of the first bracket 71 forms a local extension extending a predetermined distance out of the closed section 61. This allows the first reinforcing member 41 and the end of the first bracket 71 to be welded to the door frame 23.

A hinge bracket for the lower hinge 15 is attached to the side of the vehicle door 13 facing the vehicle frame 12. As a consequence, the lower hinge 15 is mounted on the outer, forward facing side of the metal sheet making up the door frame 23 and the at least one second reinforcing member 42 is attached to the opposite, inner side thereof. The door stop 62 is mounted in the same way on the inner side of the door frame 23, facing the vehicle frame 12.

As indicated in Figures 6a and 7A, the door extension 14 may comprise a double wall structure at least adjacent the lower portion of the door frame 23 and the reinforcing structure. The double wall structure may comprise an inner and an outer panel 64a, 64b of a suitable material, such as aluminium, plastic or steel sheets, joined together along the outer periphery of the door extension. Attachment points for the door extension 14 are preferably located along an upper section thereof, adjacent the lower section of the door frame 23, and at the upper front section, adjacent the vertical extension of the reinforcing structure 10, as indicated in Figure 3.

The door extension is preferably attached by mechanical means 33, 34, such as bolt and nut connectors or rivets, to facilitate replacement of the extension. If incompatible materials are used in the door and the door extension, such as steel and aluminium, steps should be taken to prevent direct contact between these materials. According to one example, coated nuts or screws may be used for preventing galvanic corrosion between steel and aluminium. One or both of the door and the door extension may be sprayed or coated with an oxidation preventing layer of a suitable material.

Claims

1. Vehicle door comprising a door extension (14) attached to and extending downwards from a lower portion of a door frame (23) of the vehicle door (13), and at least an upper and a lower hinge (15, 16) attached to a front portion of the vehicle door, which hinges pivotally interconnect the vehicle door (13) and its door extension (14) with a vehicle frame, c h a r a c t e r i z e d i n that the vehicle door is provided with a reinforcing structure comprising at least:

- a first reinforcing member (41) comprising;

- a first portion (41a) attached to the door frame (23) adjacent the lower hinge (15),

- a second portion (41b) attached to the door extension (14), and

- a third portion (41c) connecting the first and second portions (41a, 41b);

- at least one second reinforcing member (42) comprising;

- first portion (42a) is connected to the door frame (23) and to the first portion (41a) of the first reinforcing member (41),

- a second portion (42b) attached to the door frame (23) and to the second portion (41b) of the first reinforcing member (41),

- a third portion (42c) connecting the first and second portions (42a, 42b), which third portion (42c) is attached to the lower hinge (15),

wherein the first and at least one second reinforcing members (41 , 42) form a closed section (61) connected to the door frame (23), the door extension (14) and the lower hinge (15).

2. Vehicle door according to claim 1 , c h a r a c t e r i z e d i n that the reinforcing structure further comprises:

- a first reinforcing member (41) comprising;

- a first portion (41a) located in a first plane having a predetermined extension in the longitudinal and the vertical direction of the vehicle door, which first portion is attached to the door frame (23) adjacent the lower hinge (15),

- a second portion (41b) located in a second plane having a predetermined extension in at least the longitudinal and the vertical direction of the vehicle door, which second portion (41b) is spaced from the first portion (41a) in the longitudinal and the transverse direction and is attached to the door extension (14), and

- a third portion (41c) connecting the first and second portions (41a, 41b) of the first reinforcing member (41) and having a predetermined extension in the transverse and the longitudinal direction of the vehicle door; and

- at least one second reinforcing member (42) comprising;

- a first portion (42a) located in the said first plane, which first portion is connected to the door frame (23) and to the first portion (41a) of the first reinforcing member (41),

- a second portion (42b) located in and/or adjacent the said second plane, which second portion (42b) is spaced from the first portion (42a) in the longitudinal and the transverse direction and is attached to the door and to the second portion (41b) of the first reinforcing member (41), and

- a third portion (42c) connecting the first and second portions (42a, 42b) of the at least one second reinforcing member (42), which third portion (42c) has a predetermined extension in the transverse direction of the vehicle door and is attached to the lower hinge (15).

3. Vehicle door according to claims 1 or 2, c h a r a c t e r i z e d i n that the first portion (41a) of the first reinforcing member (41) extends forwards of an attachment point (53, 54) of the lower hinge (15).

4. Vehicle door according to any one of claims 1-3, c h a r a c t e r i z e d i n that the second portion (41b) of the first reinforcing member (41) overlaps and is connected to at least one attachment point (33, 34) of the door extension (14).

5. Vehicle door according to any one of claims 1-3, characterized in that the second portion (41b) of the first reinforcing member (41) is attached to the door frame (23) and the at least one second reinforcing member (42) remote from the at least one attachment point (33, 34) of the door extension (14).

6. Vehicle door according to claim 4 or 5, characterized in that at least two attachment points (33, 34) of the door extension (14) are separated vertically.

7. Vehicle door according to claim 4 or 5, characterized in that at least two attachment points (33, 34) of the door extension (14) are separated vertically and horizontally.

8. Vehicle door according to any one of claims 1-7, characterized in that a door stop is attached to the second portion (42b) of the at least one second reinforcing member (42).

9. Vehicle door according to any one of claims 1-7, characterized in that the second reinforcing member (42) comprises a first bracket (51) and a second bracket (52).

10. Vehicle door according to claim 9, characterized in that the first and second brackets (51, 52) are arranged to overlap within the closed section (61).

11. Vehicle door according to claim 9 or 10, characterized in that the first bracket (51) comprises the first portion (51a) and a part of the second and the third portions (51b, 51c) of the second reinforcing member (42).

12. Vehicle door according claim 11, characterized in that the first portion (51a) of the first bracket (51) extends forwards of an attachment point of the lower hinge (15).

13. Vehicle door according claim 11 or 12, characterized in that the second portion (51b) of the first bracket (51) overlaps the second portion

(52b) of the second bracket (52) and is terminated within the closed section (61).

15. Vehicle door according to any one of claims 9-13, characterized in that the second bracket (52) comprises a part of the second and the third portions (52b, 52c) of the second reinforcing member (42).

15. Vehicle door according claim 14, characterized in that the second portion (52b) of the second bracket (52) extends past the second portion (51b) of the first bracket (51) and is attached to the door frame (23) and to the second portion (41b) of the first reinforcing member (41).

16. Vehicle door according claim 14 or 15, characterized in that the third portion (52c) of the second bracket (52) overlaps the third portion (51c) of the first bracket (51) and is terminated within the closed section (61).

17. Vehicle door according to any one of claims 14-16, characterized in that the lower hinge (15) is attached to the third portions(51c, 52c) of the first and second brackets (51 , 52) within the closed section (61).

18. Vehicle door according to any one of claims 14-17, characterized in that a door stop (62) is attached to the second portions (51b, 52b) of the first and second brackets (51, 52) within the closed section (61).

19. Vehicle door according to claim 18, characterized in that the door stop (62) is attached level with the lower hinge (15) in the horizontal plane.

20. Vehicle door according to any one of claims 1-19, characterized in that the door extension (14) comprises a double wall structure (64a, 64b) at least adjacent the lower portion of the door frame (23) and the reinforcing structure.

21. Vehicle door according to any one of claims 1-20, characterized in that the reinforcing structure is welded to the door frame (23) of the vehicle door.