IMPACT RESISTANT CHASSIS

Abstract: A motor vehicle (V) having a body structure arranged to carry an engine (1), the structure having a forward impact absorbing device (16) which connects to a pair of forked members (10), each having a pair of fork arms (F1/F2) which connect in turn to a transverse part (13) and a longitudinal sill (12); one fork arm (F2) is preferably weaker than the other, so as to cause asymmetric collapse on asymmetric frontal collision to cause vehicle rotation and absorb energy; on symmetrical frontal collision the engine acts forwardly on the absorbing device through the structure.

Description: IMPACT RESISTANT CHASSIS The invention relates to a vehicle, more particularly a land vehicle. It is well known that vehicles are prone to impacts and crashes. It is known to provide crush tubes alongside and projecting forward from the engine in the engine front compartment of a vehicle so that in the event of a front crash the tubes will collapse to protect the driver and passengers in the passenger compartment. It is an object of this invention to provide a vehicle having an improved impact absorbing device. According to one aspect of the invention, a motor vehicle has an engine and a body structure arranged to carry the engine, the structure having a forward impact absorbing device projecting forward of the engine, the device being arranged to collapse rearwardly so as to absorb forces due to a collision at the forward end, the structure having a pair of forked members each comprising a forward portion extending to the impact absorbing device and fork arms extending rearwardly, a first of the fork arms being connected to a transverse part of the body structure and a second of the fork arms being connected to a longitudinal sill part of the body structure, the engine being mounted to the body structure so that on collision at the forward end, the forward kinetic energy of the engine acts on the impact absorbing device. According to another aspect of the invention, a motor vehicle has an engine and a body structure arranged to carry the engine, the structure having a forward impact absorbing device projecting forward of the engine, the device being arranged to collapse rearwardly so as to absorb forces due to a collision at the forward end, the structure having a pair of forked members each comprising a forward portion extending to the impact absorbing device and fork arms extending rearwardly to other parts of the structure, a first of the fork arms being structurally weaker than a second of the fork arms so that in the case of the forward collision acting asymmetrically with respect to the longitudinal axis of the vehicle, the weaker fork arm collapses before the stronger fork arm to cause rotation of the forward end of the vehicle. The weaker fork arm may take a variety of forms; preferably it comprises a tubular element of relatively reduced cross- sectional area compared to the stronger fork arm. The weaker arm may be as little as 10% weaker than the stronger fork arm but is preferably about 20% weaker. Preferably the impact absorbing device comprises an elongate tubular element rigidly mounted to the forked members. It is much preferred that two impact absorbing devices are present, one on each side. In such a case it is much preferred that a cross member bridges the two elongate tubular elements at a location in front of the engine such that the engine acts on the cross member to transmit forces to the elongate tubular elements as the engine moves forward on impact of the vehicle with a front obstacle. The tubular elements may be formed of steel or aluminium. Preferably the tubular elements and the sills are formed as extrusions, and have a box section but they may have a circular or oval cross section. Certain components of the device are collapsible by which is meant that they will collapse under the impact of a collision. The degree of collapsibility is selected according to the requirement for safety in the event of a collision. The components may be friable in the sense that they will be crushed to small particles, if that is appropriate. The invention is especially effective in the case of a full frontal impact. When such impact occurs the mass of the engine in a front engined vehicle will trigger the crush sequence by engagement of the engine mass and the first cross member, thereby ensuring that the rearward end of the device collapses sequentially after collapse of the frangible forward structure. In addition however, this invention is particularly beneficial in the case of an offset crash situation which is generally regarded as the most representative crash test sequence and it is one that vehicles are least capable of resisting since the impacted obstacle is presented non-symmetrically to the friable structure at the front of the vehicle. This usually results in the structure deforming away from the impacted obstacle creating, in effect, a linkage which under the decelerative forces generated by the impact forces carries the impacting vehicle towards the impacted obstacle. According to the invention the geometry and balance of stiffness of either device will collapse sequentially so as to rotate the structure towards the impacted obstacle, thereby creating a linkage which will force the impacting vehicle away from the impacted obstacle. This is because in the case of an offset impact the weaker fork arm will collapse before, or at the same time as, the forward part of the structure thereby rotating the structure towards the impacted obstacle. Advantageously the decelerative forces resulting from the impact are directed into the outer structure of the passenger cell, thus greatly reducing the deformation of the passenger cell and thereby reducing the probability of injury to the vehicle occupants. In order that the invention may be well understood it will now be described by way of example with reference to the accompanying diagrammatic drawings, in which Figure 1 shows schematically a layout of a representative vehicle incorporating two impact absorbing devices of the invention; Figure 2 shows the vehicle of Figure 1 at different stages after a front collision; and Figure 3 shows the vehicle of Figure 1 at different stages after a sideways collision. The vehicle V of Figure 1 has an engine 1 mounted in a forward engine compartment 2 to the rear of which is a passenger compartment or cell 3. The vehicle includes a pair of impact absorbing devices 16 IAD, one on each side of the vehicle and thus generally parallel to the longitudinal axis A of the vehicle. Each device comprises an elongate tubular element, 10, each made of metal such as aluminium or steel. The device may be a box section extrusion. The elements 10 project forward of the engine and have frangible end portion made up of sections 11 in the manner of known crush tubes. At their rearward end the elements 10 are connected to sills 12 by a fork arm FI, of substantially the same cross-sectional area. The bend may be made by the method of my British patent application GB9622234.4. A second fork arm F2 , of relatively smaller cross section metal tube, extends from the rearward end of the tubular element 10, and is connected to the front wall 13 of the passenger compartment. The impact absorbing device is thus of generally Y shape as seen in plan, one arm of the Y being thinner than the other and so more collapsible. A first cross member 14 bridges the elements 10 slightly in front of the engine 1; a second cross member 15 is present just below the engine 1 and rearward of the first 14. In the event of an impact occurring symmetrically about the vehicle centre-line, events occur in the sequence, as shown in Figure 2 from A to B. Upon impact with tubes 11 engine 1 continues to move forwards as the vehicle decelerates until it engages with the first cross member 14. The decelerative forces required to slow the engine are then transferred into the element 10, thereby triggering collapse of the tubes 11. The forces imposed upon the supporting structure members, fork arms FI and F2 are balanced and the structure remains stable, the forces required to decelerate the remaining mass of the vehicle being transmitted equally down the sills 12, which are an extension of the forks FI. When the collapsible tubes 11 have completely collapsed, the forces in the supporting structure rise and the forks F2 collapse absorbing the remaining decelerative energy. Once the fork arms F2 have collapsed any remaining impact forces are passed to the forks Fl and into the sills 12. In the event of an offset impact, as shown in Figure 3, only the collapsible tube 11 on one side engages with the impacted object, hence the decelerative forces are approximately half that which would be experienced in a symmetrical impact; as a result, the engine 1 does not engage with the cross member 14 before the supporting structure members Fl and F2 on one side undergo the full decelerative forces. Under these circumstances the forces are not balanced across the supporting structure. Fork arm F2 then collapses, thereby causing the frangible structure to rotate towards the impacted object and in so doing, maximises the energy absorbing capabilities of the structure and generates a lateral force driving the vehicle away from the impacted object. As shown in the last view of Figure 3 the far arm fork F2 may separate from the element 10. The invention is applicable to any automobile not only having a front mounted engine, such as a saloon or a sports car but also where the engine is centrally or rearwardly mounted, the action of the engine's movement during collision being transferred to the impact absorbing devices by suitable additional longitudinal structure.

Claims: CLAIMS 1. A motor vehicle having an engine and a body structure arranged to carry the engine, the structure having a forward impact absorbing device projecting forward of the engine, the device being arranged to collapse rearwardly so as to absorb forces due to a collision at the forward end, the structure having a pair of forked members each comprising a forward portion extending to the impact absorbing device and fork arms extending rearwardly, a first of the fork arms being connected to a transverse part of the body structure and a second of the fork arms being connected to a longitudinal sill part of the body structure the engine being mounted to the body structure so that on collision at the forward end, the forward kinetic energy of the engine acts on the impact absorbing device. 2. A motor vehicle having an engine and a body structure arranged to carry the engine, the structure having a forward impact absorbing device projecting forward of the engine, the device being arranged to collapse rearwardly so as to absorb forces due to a collision at the forward end, the structure having a pair of forked members each comprising a forward portion extending to the impact absorbing device and fork arms extending rearwardly to other parts of the structure, a first of the fork arms being structurally weaker than a second of the fork arms so that in the case of the forward collision acting asymmetrically with respect to the longitudinal axis of the vehicle, the weaker fork arm collapses before the stronger fork arm to cause rotation of the forward end of the vehicle. 3. A vehicle according to claim 1 or 2 wherein the engine is forwardly mounted in the body structure. 4. A vehicle as claimed in any one of the preceding claims wherein a pair of impact absorbing devices is provided, one on each side of the forward part of the body structure. 5. A vehicle as claimed in claim 4 wherein a cross member is provided transversely of the body structure to connect the impact absorbing devices such that on collision at the forward end, the engine acts on the cross member which transmits forces to both impact absorbing devices. 6. A vehicle according to claim 5 including a second cross member provided transversely across the body structure to the rear of the first cross member so as to connect the forked members. 7. A vehicle according to claim 1 or 2 wherein the engine is centrally or rearwardly mounted and wherein means are provided to transmit any forward forces from the engine on collision to the impact absorbing device or devices.

Inventors: RANDLE JAMES NEVILLE, RANDLE, JAMES, NEVILLE
Applicants: RANDLE JAMES NEVILLE, RANDLE, JAMES, NEVILLE
Application year: 1998
Main classification: B62D21
IPC codes: B62D21