DE20023228U1 - Front hood assembly for motor vehicle has multijoint hinge with connecting rod which pivot front hood to chassis, such that connecting rod varies in length under collision impact - Google Patents

Abstract

A front hood (1) is pivoted to the chassis by a multijoint hinge (4) including a connecting rod (6) that varies in length under collision impact. A hood lock fixes the front hood.

Description

(Ed 105 99 G)

Front hood arrangement

The invention relates to a front hood arrangement according to the preamble of claim 1.

In practice, numerous safety devices such as airbags and the like for the occupants of passenger cars are now known. In contrast, protective measures for pedestrians who are hit by the front of a passenger car have hardly been proposed or implemented in practice. Accidents involving pedestrians at speeds of up to 60 km/h are particularly problematic, as the pedestrian, if hit head-on, often hits his head on the bonnet of the car and dies from this injury. The severity of the injury arises from the fact that the front or bonnet, which is usually made of thin sheet metal, would tend to bend, but the impact occurs on parts located under the bonnet that are practically impossible or difficult to deform, such as the engine block, the spring strut, the air filter, the valve cover or the longitudinal and cross members of the vehicle. It would be desirable if the consequences of the impact, particularly to the head of a pedestrian, could be mitigated. At speeds above 60 km/h, however, the pedestrian is thrown over the vehicle after being hit.

DE 29 22 893 Cl proposes to provide the bonnet and the fender in the area of the joint formed between these two parts with energy-absorbing U-profiles running along the two parts.

-2- Body parts
which convert the impact into deformation energy in the event of a collision. The disadvantage of this arrangement is that considerable forces have to be exerted on the profiles in order to bend them. In addition, these otherwise useless U-profiles are expensive to purchase and difficult to install.

DE 27 37 876 A1 describes an impact protection device which uses a pre-tensioned pivoting flap to move a net-like catch element from a rest position, in which the net essentially rests against the front hood, into a catch position which essentially runs in front of the windshield of the motor vehicle. This device serves more to protect the windshield than to protect the pedestrian from an impact on the front hood which is too hard. In addition, any contact with the sensor which triggers the pivoting movement and is integrated in the front bumper can cause the net to be triggered, which leads to a variety of situations in which the net blocks the driver's entire view.

DE 28 41 315 A1 describes a safety device in which, in response to a signal from a sensor arranged in the front area of a vehicle to detect a collision with a pedestrian, the front hood is moved from a rest position to a raised impact position by a piston-cylinder unit, the movement being carried out by an energy storage device. When raised, the front hood is pivoted about a horizontal axis of rotation arranged on the front of the vehicle.

DE 197 10 417 Al describes an arrangement for lifting the front hood, in which a pivoting about a horizontal axis of rotation arranged on the front of the vehicle is carried out by the same gas spring

-3- triggered
which also supports the lifting of the front hood hinged at the other end.

DE 197 21 565 A1 describes a safety device on motor vehicles for raising the front hood, in which the raising of the front hood is speed-dependent by a mechanism integrated with the hood lock. For this purpose, either the unlocking of the lock, which is actuated by a compression spring and is usually triggered from the driver's cab for safety reasons, is triggered by a sensor that is triggered by an impact, or alternatively, particularly at higher speeds, a piston-cylinder unit integrated into the locking bolt of the hood lock is expanded by a propellant charge. The disadvantage of this arrangement is first of all that the force required to close the front hood must not exceed a certain threshold value in order to allow the driver to close the front hood comfortably. Since the impact forces are significant in the event of a personal accident, the front hood is quickly pushed down and the well-known personal injuries occur, particularly in the head area. The provision of a propellant charge to expand the piston-cylinder unit is also problematic, since its durability, particularly in a poorly protected arrangement, is limited and replacement is problematic. There is also a risk that the compression spring and the piston-cylinder unit will be triggered at the same time, which would cause the opening in the front hood to become so large that the wind would force the hood against the windshield and block the driver's view.

DE 27 11 338 A1 describes a device for cushioning the impact of a pedestrian, in which an airbag is arranged in the area of the cowl, the filling of which is triggered by a sensor signal.

-4- This
the airbag can be arranged in such a way that it simultaneously lifts part of the front hood, overcoming a spring force that pre-tensions two links connected to one another via a pivot point, one of which is rotatably mounted on the front hood and the other rotatably mounted on a fixed part of the motor vehicle, into an angled position. It is also proposed to arrange flexible profiled bodies in strip form in the manner of a seal between the hood and the side parts in order to provide further protection in the event of an impact.

DE 27 11 339 A1 describes a front hood hinged at the front, in which the hinge is designed to be flexible enough to allow the front hood to be moved horizontally when a pedestrian hits it, with the rear-displaced front hood being connected at the rear to one end of a rigid locking element, the other end of which is displaced upwards and backwards in a guide curve when the front hood is moved backwards so that the front hood moves upwards. This lifting only works if the front hood actually moves horizontally, which is not always guaranteed when children hit it, for example.

EP 0 509 690 A1 describes a front hood which is hinged to the vehicle structure at its front in such a way that the front hood is displaced backwards in the event of an impact, whereby the locking or pivoting means arranged on the rear side trigger a pivoting movement of the front hood upwards in the event of a rearward movement of the front hood, so that the deformation path of the hood is increased in the event of an impact by a pedestrian. The pivoting movement is guided, for example, by a four-joint hinge which is otherwise used to pivot the front hood when access to the

engine and other parts. Here too, the bonnet is only lifted when the bonnet is moved very forcefully, while a weak impact does not move the bonnet backwards and therefore also not upwards.

DE 197 12 961 A1 describes the arrangement of a front hood on a vehicle in which a hinge is arranged on a hinge support, which hinge support is pivoted upwards in the event of a pedestrian impact in order to raise the front hood. The problem with this arrangement is that the hood lock for the front hood defines a pivot axis that does not allow the hinge support to be moved freely, which is why the hinge support described blocks, for example.

JP 04 212 677 A describes a hinge designed to absorb a pedestrian impact on the front hood. In this case, predetermined bending points are provided in the area of the body-side stop part so that this can fall through elongation into an area kept free for this purpose below the stop part, while the front hood is bent in its rear area.

US 3 643 755 A describes a front hood arrangement in which the front hood is pivotably connected to the body of a vehicle via a hinge with a swivel joint, wherein a stop part of the hinge associated with the front hood forms a gooseneck. A stop part associated with the body has a third, pivotably mounted, link-shaped part, wherein this third part is mounted on the body-side stop part via a further joint arranged outside the overlap area of the front hood. A pin which can be sheared off by plastic deformation and which is also located outside the

-6- Coverage area
the front hood, the third part is fastened to the stop part on the body side, whereby in the event of overloading due to a collision the pin is sheared off and the corresponding plastic deformation causes the third part to be released from the stop part on the body side, whereby the swivel joint and the front hood can be lowered by the further joint below an edge of the engine compartment to such an extent that the front hood does not crash into the windshield. The disadvantage here is that the joints are arranged in such a way that a significant lowering of the front hood is only conceivable if the front hood is simultaneously displaced backwards, i.e. in the event of a frontal crash, whereas the arrangement of the joints outside the area covered by the front hood is kinematically unfavorable in the event of a pedestrian impact. The resulting hinge is very large and accordingly requires a lot of material.

DE 30 47 969 C2 describes a front hood arrangement in which deformation members are formed between the front hood and the body outside the hinges, which resiliently dampen the impact when a pedestrian hits the front hood.

Overall, no solution has yet been proposed that proposes a cost-effective arrangement that can be easily restored after use and that is structurally sophisticated enough to be used in series vehicles.
25

It is the object of the invention to propose a front hood arrangement according to the preamble of claim 1, which provides pedestrian protection that is cost-effective and technically feasible.

♦ t · &psgr; 9

-7- This
This object is achieved in the front hood arrangement mentioned at the outset with the characterizing features of claim 1.

The front hood arrangement according to the invention makes it possible to arrange the front hood, which is arranged above the dangerous parts such as the engine block and the like, relatively close to these parts in the event of a pedestrian impact, so that the styling of the vehicle does not suffer from the higher hood. Similar to predetermined breaking points, soft elements are used in the hinges which allow a targeted deformation in position and orientation as a result of a body impacting the front hood, which simultaneously ensures that on the one hand the relative movement around the hood lock defining a pivot axis of the front hood is possible and on the other hand the impact energy is converted into defined deformation energy during the plastic deformation of the hinge elements.

According to a preferred development of the invention, it is provided that a force acting essentially normal to the front hood triggers the deformation of the hinge by overcoming small counterforces, while in the event of axial pressure being applied to the vehicle, as is to be expected in a frontal collision with another vehicle as the main direction of stress, the hinge elements supporting the front hood remain essentially unchanged or hardly plastically changed, so that the crash behavior of the vehicle as a whole is not reduced by the measure for protecting impacting pedestrians.

The front hood is expediently not only secured at its rear by the hinge units designed according to the invention

Not only is the hood lock raised relative to an end position following an impact by a pedestrian, but the hood lock is also arranged in a raised position which allows it to yield in response to the impact of a human body, whereby the displacement path of the hood lock is taken into account in the design of the predetermined bending points of the hinge elements.

By designing the hinge elements as plastically changeable connections between the front hood and, for example, the longitudinal member

The use of the motor vehicle ensures that after impact with the human body, no rebound is hurled back onto the road by the pre-tension of the bent hinge elements. Rather, the vast majority of the impact energy is converted into deformation energy and thus dissipated for the pedestrian. This strong energy transformation softens the impact, particularly on the head of a pedestrian, in a way that can save lives, and this measure requires only a small investment.

It is possible to couple the plastically deformable hinge elements to the longitudinal beam of the motor vehicle via extendable lifting elements or the like, which enable the front hood to be extended upwards when an impact is detected, for example by a sensor arranged in the front strip of the vehicle or by other suitable means, the front hood then being deformed essentially back to its original position by means of plastic deformation of the raised hinge elements, the deformation path depending in detail on the vehicle speed and the severity and location of the impact. It should be noted that when using such lifting elements, the time required until the

·

-9- Lifting links
elapses should be less than 1/10 of a second, so that the maximum distance has already been covered when the pedestrian or his head hits the ground. The extension of the lifting links can be triggered by pneumatic and hydraulic piston-cylinder units to the units or pyrotechnically or mechanically.

The deformation path provided by raising the front hood above the load-bearing and solid parts of the engine compartment should be 120 mm if possible and at least 70 mm in order to ensure a sufficiently long path for the transformation of the impact energy. It must be taken into account that the front hood, which is usually made of sheet metal, can itself undergo severe deformation in the event of a central impact and that in the event of an eccentric impact the load on one of the two front hood hinges can be greater than that on the other. However, it is possible to improve the deformation of the front hood itself by providing more rigid front hoods, for example made of glass fiber reinforced plastics or with a reinforcing matrix made of glass fibers, which reduces the change in shape of the front hood itself, which initially increases the risk of impact, by transferring the impact energy to the hinges according to the invention, so that a significantly higher amount of energy can be dissipated in the hinges and thus lower installation heights are possible. This is particularly important in the case of impacts involving children, which occur in the front area of the bonnet and where the lever arm for transmitting the forces is different from that of an adult.

A significant advantage of designing the hinges as plastically deformable parts is that these parts can be replaced with little effort, for example if they are accidentally triggered or after a pedestrian has hit them. Unlike

pyrotechnic charges and the like, a plastic change in the hinge parts is possible even after a long period of use of the vehicle. Finally, it should be noted that with the arrangement according to the invention, the front hood can generally be opened even after the deformation as a result of an impact has been completed, after the hood lock has been unlocked, so that a rapid inspection of the condition of the engine compartment is possible following an impact.

Further advantages and features of the invention will become apparent from the following description and from the subclaims.

The invention is explained in more detail below using embodiments with reference to the accompanying drawings.

Fig. 1 shows a side view of the front section of a motor vehicle with a front hood arrangement according to the invention.

Fig. 2 shows the hinge of the front hood assembly from Fig. 1.

Fig. 3 shows an alternative hinge with reduced section modulus for a front hood arrangement according to the invention.

Fig. 4 shows an alternative hinge with reduced section modulus for a front hood arrangement according to the invention.

Fig. 5 shows another alternative hinge for a front hood assembly according to the invention.

The front section of a motor vehicle shown in Fig. 1 comprises a front hood 1, which is provided at its front end 2 with a hood lock 3

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-11- lockable
and which is connected at its rear end to a longitudinal member of the motor vehicle via one of two hinges 4 on the outside. The hinge 4 has a first leg 5 which is rigidly connected to the front hood 1 by screwing or riveting and whose joint 6, in the operating state, forms the pivot point of the hood 1 when the hood lock 3 is unlocked. The joint 6 is fastened in a holder 7 fastened to the bodywork, with a curved guide 8 being formed in the holder 7, the catches 9 of which can brake or clamp the pin defining the joint 6. The holder 7 fastened to the bodywork comprises an essentially horizontal leg 10 and a leg 11 which is essentially at a 45° angle and is plate-shaped and in which the guide 8 is recessed approximately in the shape of a quarter circle. At the point where the two legs 10 and 11 meet, the holder 7 has a notch or weakening 12 which runs essentially horizontally and perpendicular to the direction of travel of the motor vehicle and which allows the rear leg 11 to be bent away from the front leg 10, which is firmly screwed or riveted to the longitudinal member, in such a way that the leg 11 can be bent into a position in which both 10, 11 lie horizontally. In order to prevent the leg 11 from bending too far and thus breaking off, appropriate stop means are provided.

The holding force of the catches 9 is sufficient to take the weight of the front hood 1 when it is opened without causing the body-side bracket 7 to bend. In such a case, the forces acting on the joint 6 are in the order of magnitude of approx. 400 N, corresponding to a weight of up to 40 kg, which are again distributed over both hinges 4 and thus halved. When a body impacts, a weight of 2,000 N to 5,000 N acts on the front hood 1, which is distributed evenly or unevenly across the two hinges depending on the location of the impact.

-12- Hinges
4. This force, indicated by the arrow F, which presses the joint 6 and thus the leg 11 downwards, is sufficient to spread the predetermined bending point 12 and to execute a pivoting movement of the second leg 11. The pivoting movement of the leg 11 indicated by the other arrow G results from this, whereby the joint 6 is displaced downwards in the notch-shaped guide 8 in accordance with the pivoting radius around the hood lock 3. A large part of the impact energy is converted into deformation work at the joint 12 of the legs 10 and 11, whereby it can also be provided that

&iacgr;&ogr; that the catches progressively clamp the joint 6 and thus also convert impact energy.

As can easily be seen, the stress lever around the notch 12, with which the force F acts on the leg 11, decreases with increasing deformation path and thus requires progressively increasing forces for further plastic deformations due to bending of the leg 11. It is therefore guaranteed that in an initial phase of the impact, a strong deformation gradually decreases over time. At the same time, the plastic deformation ensures that there is no rebound and thus no throwing of the impacting pedestrian from the front hood 1. The minimum force F at which a first deformation of the hinge 4 is triggered can be determined in such a way that the impact of a child's head in the front area of the front hood 1 already triggers a considerable deformation of the hinge 4, while, for example, the impact of an adult's head in the rear area of the front hood, which has a significantly higher energy, essentially results in the complete deformation (path S) of the two hinge elements.

-13- Referring
Fig. 3 shows a simpler variant of the front hood hinge, in which a guide track for the joint 6 is not provided. The same reference numerals as in Figs. 1 and 2 essentially designate the same parts. This embodiment is particularly suitable for arrangements of the front hood 1 on flexible hood locks 3, which in particular allow the front hood 1 to be moved backwards to a certain extent and thereby absorb energy, whereby the swivel radius also shifts.

Fig. 4 shows a further embodiment of a front cover hinge in which the otherwise flat leg 11 has been rotated once by 180°, whereby its section modulus under bending stress is reduced. The advantage of this arrangement is essentially the completely retained strength with respect to tensile stress, which is significant for passenger safety in the event of a frontal collision of the motor vehicle, for example.

Fig. 5 shows a further alternative of a front hood hinge, in which the joint 6 is firmly connected to the part 7 of the hinge 4 arranged on the longitudinal member, but this plate-shaped part 7 itself has a guide 8 which, in the manner of a curved slot, takes into account the pivot radius around the hood lock 3. A screw connection 14 provided on the longitudinal member defines a firm frictional connection with the part 7, with the shaft of the screw connection 14 passing through the guide 8. The guide 8 can be designed to gradually narrow so that when the hinge part 7 is displaced downwards in response to the impact of a human body, the deformation energy to be applied gradually increases with the displacement path. The body of the plate part 7 can also be slightly wedge-shaped.

so that increasing energy is required to complete the deformation.

The invention has been explained in more detail above using several exemplary embodiments, the general functional principle of an at least local permanent change in shape in the area of the hinge to which the front hood 1 is hinged being common. It is understood that the individual measures of the exemplary embodiments can also be combined with one another to achieve a better result.

Claims (14)

1. Front hood arrangement, in which a front hood ( 1 ) of a vehicle is articulated to the frame of the vehicle via a hinge ( 4 ) with a joint ( 6 ) defining the pivot axis of the front hood ( 1 ), the hinge ( 4 ) undergoing a plastic deformation when a pedestrian impacts it, the front hood ( 1 ) being lockable via at least one hood lock ( 3 ), the joint ( 6 ) defining the pivot axis of the front hood ( 1 ) being displaced within a predetermined radius, characterized in that the radius is defined by the distance of the joint ( 6 ) from the hood lock ( 3 ). 2. Front hood arrangement according to claim 1, characterized in that a part ( 11 ) of the hinge ( 4 ) is spread relative to another part ( 10 ) of the same hinge ( 4 ) by plastic change along a predetermined bending line ( 12 ). 3. Front hood arrangement according to claim 2, characterized in that the joint ( 6 ) is guided in a guide track ( 8 ) provided in the part ( 11 ) in accordance with the displacement of the first part ( 11 ). 4. Front hood arrangement according to claim 3, characterized in that locking means ( 9 ) are arranged in the guide track ( 8 ) which brake the joint ( 6 ) during displacement in the guide track ( 8 ). 5. Front hood arrangement according to one of claims 2 to 4, characterized in that the first part ( 11 ) is spread apart from the second part ( 10 ) by up to 45°. 6. Front hood arrangement according to one of claims 1 to 5, characterized in that a part of the hinge ( 4 ) is designed in the manner of a flat iron which is rotated by 180°. 7. Front hood arrangement according to claim 1, characterized in that the part ( 7 ) of the hinge ( 4 ) fastened to the frame is arranged on the frame so as to be pivotable about a horizontal axis, and that in the event of an impact on the front hood ( 1 ) the part ( 7 ) is pivoted about this horizontal axis. 8. Front hood arrangement according to claim 7, characterized in that the part ( 7 ) is fixed to the frame of the vehicle via a connecting means ( 14 ) which can be overcome in the event of an impact by a pedestrian and is arranged outside the pivot axis and outside the joint ( 6 ), and that the plastic deformation takes place in the region of the connecting means ( 14 ) and the part ( 7 ). 9. Front hood arrangement according to claim 7 or 8, characterized in that a guide track ( 8 ) is formed in the part ( 7 ), through which a screw connection ( 14 ) passes, whereby a relative movement between the screw connection ( 14 ) and the part ( 7 ) causes an expansion of the guide track ( 8 ) or a surface pressure of the part ( 7 ). 10. Front hood arrangement according to one of claims 7 to 9, characterized in that the horizontal axis has a fixed distance from the joint ( 6 ). 11. Front hood arrangement according to one of claims 7 to 10, characterized in that the horizontal axis and the axis of the joint ( 6 ) are parallel to each other. 12. Front hood arrangement according to one of claims 7 to 11, characterized in that the horizontal axis is arranged further forward in the direction of travel of the vehicle than the joint ( 6 ). 13. Front hood arrangement according to one of claims 7 to 12, characterized in that the screw connection ( 14 ), the joint ( 6 ) and the further joint form a triangle, and that the screw connection ( 14 ) and the further joint are arranged at approximately the same height on the frame. 14. Front hood arrangement according to one of claims 1 to 13, characterized in that the front hood ( 1 ) is arranged in a raised position in the region of the joint ( 6 ) in the ready-to-drive state, and that the hinge ( 4 ) is arranged in a rear region of the front hood ( 1 ) in the direction of travel.