GB2426489A - Reinforcement for a bonnet lift actuator assembly - Google Patents

Abstract

A motor vehicle 10 has a bonnet lift actuator assembly 20 used to raise the rear of the bonnet to increase clearance between the bonnet and components located within the engine compartment in the event of a collision between the vehicle and a pedestrian. The actuator assembly 20 includes an extruded aluminium spacer member 22 which supports a bonnet lift actuator 21 and rests upon a substantially horizontal structural member 14 which forms part of the structure of the vehicle. Forces produced by the actuator 21 when it is activated are transferred directly into the structural member 14 through the spacer member 22.

Description

A Bonnet Lift Actuator Assembly for a Motor Vehicle This invention relates to motor vehicles and in particular to a motor vehicle having a pedestrian protection system in which a rear end of a bonnet of the vehicle is raised when an impact with a pedestrian is occurring or is predicted. It has been proposed, for example in patent publications JP-11099906 and EP-A1216171, to provide a system for raising the rear end of a bonnet or hood of a vehicle when impact with a pedestrian is predicted or has actually commenced. A typical system is designed to offer improved pedestrian protection by raising the rear of the bonnet by approximately 100 to 125 mm, thus increasing the clearance between the bonnet and components located within the engine compartment. This reduces the risk of serious injury should a pedestrian fall upon the bonnet of the vehicle due to a collision between the vehicle and the pedestrian. It is preferred to activate the system prior to impact in order to provide sufficient time for the bonnet to be fully raised before the pedestrian makes contact with the bonnet. Hence a typical prior art system comprises an optical or radar sensor in the bumper to detect potential leg impacts so that the bonnet can be raised or lifted prior to the head of the pedestrian striking the bonnet. When a leg impact is detected, the hood is lifted using two actuators positioned in the rear of the engine compartment which apply a large force to each side of the bonnet near to the rear end of the bonnet. Each of the actuators may incorporate a latch to prevent the bonnet from opening fully or other means may be provided to limit the amount by which the bonnet can be lifted.If the bonnet is front hinged then the bonnet latching mechanism is simultaneously released to allow the bonnet to be raised. If the bonnet is rear hinged the hinge mechanisms of the bonnet are reconfigured in some way to allow the normally pivotally located rear end of the bonnet to be freed from this pivotal location. See for example EP-A-1216171 and US-6,543,086. The actuators must generate a very high force in order to accelerate the bonnet to its deployed position within approximately 20ms and so must be securely mounted. However in a typical motor vehicle the major structural components are located low down in the engine compartment and so there is a considerable distance between the inner or lower side of the bonnet and structurally significant members. This is a problem in that a typical actuator has a very limited travel in order to prevent over lifting of the bonnet. Hence it is normal to provide a bonnet actuator support bracket to bridge this gap between the structural member and the bonnet. Typically the support bracket must withstand a reaction force of 5 to 20kN with minimal dynamic deflection and with no permanent set in the support bracket or any of the supporting body structure.Ideally, to meet the performance requirements of the system, the support bracket must transfer the reaction force from the actuator directly into the structural member(s) located below. Although fabricated support brackets can be used, these are time consuming and expensive to produce and, especially when fabricated from aluminium, require large material thicknesses to be used in order to obtain the correct stability and rigidity. It is an object of this invention to provide an improved bonnet lift actuator assembly for a motor vehicle. According to a first aspect of the invention there is provided a bonnet lift actuator assembly for a motor vehicle comprising an actuator having a moveable member for contact with a bonnet so as to apply a force near to a rear end of the bonnet to raise the bonnet from a normally closed position to a raised position and a support bracket to connect the actuator to part of the structure of the motor vehicle wherein the support bracket includes an extruded spacer member which, in use, rests upon a substantially horizontal structural member forming part of the structure of the motor vehicle. The spacer member may be made from aluminium alloy. The support bracket may further comprise a support plate to which the actuator is secured so that the support plate is interposed in use between the actuator and the spacer member. The support plate may have a bent up end used to secure the support plate to a substantially vertical structural component forming part of the structure of the motor vehicle. The spacer member may comprise a tubular outer shell and one or more internal reinforcement members. The reinforcement members may include webs extending across the interior of the tubular outer shell. In one embodiment of the invention, the webs are arranged as a cruciform and intersect at a point which, when the spacer member is in use, is positioned directly below the actuator. In an alternative embodiment, the spacer member further comprises a tubular inner shell and the webs connect the tubular outer shell to the tubular inner shell. The tubular inner shell may be a cylindrical inner shell. Advantageously, when the spacer member is in use, the tubular inner shell is positioned directly below the actuator. Alternatively, the reinforcement members comprise ribs extending inwardly from the tubular outer shell.Advantageously, when the spacer member is in use, at least some of the ribs are positioned directly below the actuator. The support plate may be welded to an end of the tubular outer shell. One or more integrally formed flanges may extend outwardly from the tubular outer shell for use in securing the spacer member to a substantially vertical structural component forming part of the structure of the vehicle. An L-shaped bracket may be welded to the tubular outer shell for use in securing the tubular outer shell in use to the substantially horizontal structural member. The invention also provides, according to a second aspect thereof, a motor vehicle having an engine compartment covered by a bonnet and two bonnet lift actuator assemblies according to said second aspect located and secured within the engine compartment, each spacer member resting upon a respective horizontal structural member so that, upon activation of each actuator, the load from the actuator is transferred through the spacer member into the respective horizontal structural member. There are several advantages to using an extruded aluminium spacer member. Firstly, the length of an extrusion is not in practical terms limited. Secondly, virtually any shape can be used and this can incorporate additional features such as attachment flanges. Thirdly, an extruded support spacer is very strong in direct tension and compression allowing relatively thin material sections to be used and fourthly, the manufacturing costs are relatively low as very little fabrication work is required. In addition, if the vehicle has a body structure constructed from aluminium, then the probability or severity of corrosion between the actuator assembly and the body structure is reduced because similar materials can be used. The invention will now be described by way of example with reference to the accompanying drawings, of which:- Fig.1 is a perspective view of part of an engine compartment of a motor vehicle showing a bonnet lift actuator assembly according to the invention; Fig.2 is a perspective view of on a slightly enlarged scale of the bonnet lift assembly shown in Fig.1 viewed from a slightly different angle; Fig.3 is a perspective view of the bonnet lift assembly shown in Figs. 1 and 2 in a partially assembled condition: Fig.4 is a top view of a spacer member forming part of the bonnet lift assembly shown in Figs. 1 to 3; Fig.5 is a top view of a second example of a spacer member for use in a bonnet lift assembly as shown in Figs. 1 to 3;Fig.6 is a top view of a third example of a spacer member for use in a bonnet lift assembly as shown in Figs. 1 to 3; and Fig.7 is a top view of a fourth example of a spacer member for use in a bonnet lift assembly as shown in Figs. 1 to 3. With particular reference to Figs. 1 to 4 there is shown a motor vehicle having an engine compartment covered by a bonnet or hood (not shown) and two bonnet lift actuator assemblies of which only the right hand rear portion of the engine compartment and the right hand side bonnet lift actuator assembly 20 are shown on Fig.1. The vehicle 10 has an aluminium body structure including a right hand front suspension turret 11, a substantially vertical structural member in the form of an inner wing or shotgun panel 12, a rear firewall 13 which separates the engine compartment from a passenger compartment (not shown) and a lower substantially horizontal structural member 14. The lower structural member 14 has a substantially horizontal upper surface upon which is supported the bonnet lift actuator assembly 20. The lower structural member 14 is used to transfer load from structural members such as side rails located within the engine compartment to the main body structure of the vehicle 10 and is very strong and rigid. The actuator assembly 20 comprises an actuator 21 having a member which can be urged upwardly when the actuator 21 is activated to raise the rear end of the bonnet, i.e., the actuator 21 can apply a force near to a rear end of the bonnet to raise the bonnet from a normally closed position to a raised position. The actuator 21 can be of any suitable type but will normally include a pyrotechnic device and/or one or more springs. Examples of such actuators are shown in, for example, DE-A-10247800 and DE-A-10247801. It will however be appreciated that the invention is not limited to use with these actuators and can be more generally applied. The actuator 21 has four outwardly extending lugs 25 used to secure it to a support plate 23 positioned on top of an extruded aluminium spacer member 22. It will be appreciated that the term "aluminium" as meant herein includes alloys of aluminium. The support plate 23 has a bent up end in which are formed two apertures 26 through which in use fixings such as bolts or rivets pass so as to secure the support plate 23 to the shotgun panel 12. The support plate 23 is pressed from aluminium and is secured to an upper end of the spacer member 22 by welding it to a tubular outer shell 30 forming part of the spacer member 22. The spacer member 22 also includes internal reinforcement members in the form of four webs 32 extending across the interior of the tubular outer shell 30 which connect the tubular outer shell 30 to a tubular inner shell 31. It will be appreciated that a different number of webs could be used if required. The tubular inner shell 31 is cylindrical and is positioned within the spacer member 22 such that, in use, it is positioned directly below the actuator 21. This is so that any forces applied to the support plate 23 from the actuator 21 are transferred directly into the spacer member 22 and from there into the horizontal structural member 14 without producing significant deformation of the support plate 23. In this way a very stable and rigid support for the actuator 21 is produced. An L-shaped aluminium bracket 24 is welded to the lower end of the spacer member 22 to secure it to the horizontal structural member 14. The L-shaped bracket 24 is only used to maintain the spacer member 22 in position and does not transfer any significant forces from the actuator 21 as these are transferred directly from the support member 22 to the horizontal structural member 14. It will be appreciated that the tubular outer and inner shells 30 and 31 and the webs 32 are all formed as a single extrusion. This has the advantage that no additional fabrication is required and so there is no risk of any distortion occurring to the thin walls of the outer and inner shells 30 and 31 which could occur if these components are secured together by welding. In addition, the use of an extrusion process provides a structure with uniform material properties which allows a smaller safety factor to be used in the design process. This will normally result in a structure that is lighter and more compact than a design using a fabrication process because thinner material cross-sections can be used. With reference to Fig.5 there is shown a second example of spacer member which in most respects is identical to that shown in Fig. 4 and which is intended to replace that component in the bonnet lift assemblies shown in Figs. 1 and 2. The only significant difference between this spacer member and the spacer member described above is that two outwardly extending flanges 33, 34 are also formed as part of the extrusion. The flanges 33, 34 extend outwardly from the tubular outer shell 30 and can be used to secure the spacer member 22 directly to the shotgun panel 12 without the need for a support plate 23 or in addition to the support plate 23. Thus with such a construction it would be possible to dispense with the support plate 23 and mount the actuator 21 directly to the top of the spacer member 22 provided suitable fixings are provided in the spacer member 22. With reference to Fig.6 there is shown a third example of spacer member 122 which in some respects is the same as those previously described, in that it has a tubular outer shell 130 which is internally reinforced by webs 132 extending across the interior of the tubular outer shell 130 and is intended to be a direct replacement for the spacer member shown in Fig.4. However in this case there is no tubular inner shell and the webs 132 are arranged in a cruciform so they intersect at a point which, when the spacer member 122 is in use, is positioned directly below the actuator. As before, this ensures that the support plate 23 which is welded to the top of the spacer member 122 is well supported and will not significantly deform when the actuator is activated. In effect the forces from the actuator are transferred directly into the webs 132 of the spacer member 122. With reference to Fig. 7 there is shown a fourth example of a spacer member 222 which is intended to be a direct replacement for the spacer member shown in Fig. 4. As before, a support plate (not shown) is welded to the top of the spacer member 222 for use in attaching the actuator to the spacer member 222. The spacer member 222 has a tubular outer shell 230 but in this case is strengthened by a number of inwardly extending ribs 234. The ribs 234 have two primary functions, firstly they permit the use of a relatively thin wall section for the tubular outer shell 230 by increasing the resistance to buckling of the support member 222 and secondly, because at least some of the ribs 234 are located such that, in use, they are positioned directly under the actuator, forces from the actuator are transferred into the spacer member 222 without any significant deformation of the support plate from occurring. It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention. For example, although the invention has been described with reference to several preferred embodiments all having a tubular outer shell, it will be appreciated that it is not limited to these examples and that various alternative extruded shapes could be used for the spacer member, it not being a requirement for the spacer member to have a tubular outer shell. For example, a spacer member could have a cross-section similar to the internal structures shown in Figs. 4 to 6 without the tubular outer shell.

Claims (18)

1. A bonnet lift actuator assembly for a motor vehicle comprising an actuator having a moveable member for contact with a bonnet so as to apply a force near to a rear end of the bonnet to raise the bonnet from a normally closed position to a raised position and a support bracket to connect the actuator to part of the structure of the motor vehicle wherein the support bracket includes an extruded spacer member which, in use, rests upon a substantially horizontal structural member forming part of the structure of the motor vehicle.

2. An assembly as claimed in claim 1 wherein the spacer member is made from aluminium alloy.

3. An assembly as claimed in claim 1 or in claim 2 wherein the support bracket further comprises a support plate to which the actuator is secured so that the support plate is interposed in use between the actuator and the spacer member.

4. An assembly as claimed in claim 3 wherein the support plate has a bent up end used to secure the support plate in use to a substantially vertical structural component forming part of the structure of the motor vehicle.

5. An assembly as claimed in any of claims 1 to 4 wherein the spacer member comprises a tubular outer shell and one or more internal reinforcement members.

6. An assembly as claimed in claim 5 wherein the reinforcement members include webs extending across the interior of the tubular outer shell.

7. An assembly as claimed in claim 6 wherein the webs are arranged as a cruciform and intersect at a point which, when the spacer member is in use, is positioned directly below the actuator.

8. An assembly as claimed in claim 6 wherein the spacer member further comprising a tubular inner shell and the webs connect the tubular outer shell to the tubular inner shell.

9. An assembly as claimed in claim 8 wherein the tubular inner shell is a cylindrical inner shell.

10. An assembly as claimed in claim 8 or in claim 9 wherein, when the spacer member is in use, the tubular inner shell is positioned directly below the actuator.

11. An assembly as claimed in claim 5 wherein the reinforcement members comprises ribs extending inwardly from the tubular outer shell.

12. An assembly as claimed in claim 11 wherein, when the spacer member is in use, at least some of the ribs are positioned directly below the actuator.

13. An assembly as claimed in any of claims 5 to 12 wherein the support plate is welded to an end of the tubular outer shell.

14. An assembly as claimed in any of claims 5 to 13 wherein one or more integrally formed flanges extend outwardly from the tubular outer shell for use in securing the spacer member in a substantially vertical structural component forming part of the structure of the motor vehicle.

15. An assembly as claimed in any of claims 5 to 14 wherein an L-shaped bracket is welded to the tubular outer shell for use in securing the tubular outer shell to the substantially horizontal structural member.

16. A motor vehicle having an engine compartment covered by a bonnet and two bonnet lift actuator assemblies as claimed in any of claims 1 to 15 located and secured within the engine compartment, each spacer member resting upon a respective horizontal structural member so that, upon activation of each actuator, the load from the actuator is transferred through the spacer member into the respective horizontal structural member.

17. A bonnet lift actuator assembly for a motor vehicle substantially as described herein with reference to Figs. 1 to 4 or with further reference to Fig.5, Fig.6 or Fig.7 of the accompanying drawings.

18. A motor vehicle substantially as described herein with reference to Figs. 1 to 4 or with further reference to Fig.5, Fig.6 or Fig.7 of the accompanying drawings.