IMPACT-ABSORBING DEVICE FOR PROTECTION OF PASSENGERS IN A VEHICLE

Abstract: An arrangement for driver protection in a motor vehicle, comprising a steering bracket (6) which supports a steering main shaft (2) and comprises an upper part (7) and a lower part (8) which are displaceably interconnected, the upper part (7) being fixed to the body of the motor vehicle and the lower part (8) being fixed to the steering main shaft (2). The arrangement has means for force transmission between the lower part (8) and the upper part (7), the arrangement comprising an energy-absorbing mechanism (18) which has two or more longitudinal grooves and also a cutting member (26) which is adapted to run along one of said grooves when there is relative displacement between the upper part (7) and the lower part (8). The arrangement also comprises means for setting the cutting member (26) to a predetermined groove (30), at least two of the grooves (30) having different deformation resistance in relation to one another, by virtue of which the deformation resistance in the energy-absorbing mechanism (18) can be adjusted by setting the cutting member (26) to a predetermined groove (30).

Description: TITLE IMPACT-ABSORBING DEVICE FOR PROTECTION OF PASSENGERS IN A VEHICLE TECHNICAL FIELD The invention relates to an arrangement for passenger protection in a motor vehicle, comprising a steering bracket which supports a steering main shaft and comprises an upper part and a lower part which are displaceably interconnected, the upper part being fixed to the body of the motor vehicle and the lower part being fixed to the steering main shaft, the arrangement also having means for force transmission between the lower part and the upper part, the arrangement comprising an energy- absorbing mechanism which has two or more longitudinal grooves and also a cutting member which is adapted to run along one of said grooves when there is relative displacement between the upper part and the lower part. BACKGROUND In connection with motor vehicles, it is generally desirable to reduce force stresses and associated injuries to the occupants of the vehicle to the greatest possible extent in the event of a collision. For example, use is in general made of safety belts of the three-point type to secure the occupants of the vehicle. Such safety belts provide, in a known manner, a good protective effect and increased safety for the occupants in the event of a collision. There are always drivers, however, who for various reasons choose not to use a safety belt. In order to afford these drivers also a certain protection in a collision, it has become desirable for the steering system of the vehicle to be adapted so that it is energy- absorbing. Furthermore, the legislation in certain countries requires the steering system in a vehicle to be designed to protect drivers who are thrown against the steering wheel of the vehicle in the event of a collision. It is previously known that the steering system in a vehicle can be designed so that it absorbs energy when the driver of the vehicle is thrown forward and strikes the steering wheel in connection with a collision. Such energy absorption can be brought about, for example, by the steering wheel being designed with deformable and flexible spokes. Furthermore, the steering main shaft of the vehicle can be arranged in a specially designed energy-absorbing steering column which is in turn mounted in the body of the vehicle. In the event of a collision, when the steering wheel and consequently the steering column also are acted on by a very great force as a result of the driver being thrown forward, this force is transmitted from the steering wheel to the steering column. This results in the steering column being moved a certain distance in relation to the vehicle body. During this movement, energy is absorbed, which in turn reduces the stresses on the driver during the course of the crash. In American patent specification US 4 978 138, an arrangement for energy absorption in a steering system for vehicles is described. The arrangement functions according to the principle that if the driver is not secured by the seat belt, the steering system will absorb energy when the driver is thrown against the steering wheel in the event of a collision. For this purpose, the arrangement comprises a special deformable, energy- absorbing plate which is connected to the steering column. In order to determine whether the driver has the seat belt on, a sensor is arranged in association with the fastening of the seat belt. This known arrangement also comprises a device for the protection of the knees of the driver, which device is activated depending on whether or not the driver is secured by the seat belt. If the driver is secured, the force from the knees of the driver will be absorbed by the knee protection while the steering wheel is moved, by virtue of which the upper body and the head of the driver are prevented from striking the steering wheel. The arrangement according to US 4 978 138 does have a disadvantage, however, in that it does not make allowance for the risk that even a driver who is secured with a safety belt can, under certain circumstances, actually strike the steering wheel in connection with a collision. This can happen, for example, if the driver has the vehicle seat positioned a long way forward or if the seat belt has an abnormally large amount of slack. DESCRIPTION OF THE INVENTION One aim of the invention is to produce an improved and simplified energy-absorbing protection arrangement for steering systems in motor vehicles. In particular, the invention aims to make available such a protection arrangement which comes into operation in the event of a collision irrespective of whether or not the driver of the motor vehicle is using a safety belt. The aim of the invention is achieved by an arrangement which is mainly characterized in that the arrangement comprises means for setting the cutting member to a predetermined groove and in that at least two of the grooves have different deformation resistance in relation to one another, by virtue of which the deformation resistance in the energy-absorbing mechanism can be adjusted by setting the cutting member to a predetermined groove. According to one embodiment of the invention, the energy-absorbing mechanism comprises a tube, the grooves being arranged in the longitudinal direction of the tube, from a first end of the tube, the tube being connected to one of the two displaceable parts of the steering bracket and the cutting member being connected to the other part. Alternatively, the grooves can be arranged in a plate, a half-tube, a U beam or the like. The grooves in the energy-absorbing mechanism can have different deformation resistance by virtue of the grooves having a smaller material thickness than the surrounding parts of the material in the energy- absorbing mechanism, at least two grooves having different material thickness in relation to one another. Another manner of bringing about different deformation resistance is by virtue of at least two grooves being of different width in relation to one another. In this respect, the width of the knife must be taken into account so that the width of the grooves lies within the range in which the knife, when introduced into the groove, will widen this. A further manner of bringing about different deformation resistance in different grooves is by virtue of the material in the grooves having a different physical nature to the surrounding material in the energy- absorbing mechanism. This can be achieved by, for example, the material in the grooves being treated so that it becomes softer or more porous than the surrounding material. It is of course possible to envisage designing an energy-absorbing mechanism in which the grooves consist of a different material to the surrounding parts of the energy-absorbing mechanism. The grooves in the energy-absorbing mechanism perform two main functions. In the event of a collision, the intention is that the cutting member, which consists of a knife for example, will be brought to cut open the material in the energy-absorbing mechanism along a predetermined groove by the action of the force to which the steering column is subjected when the driver is thrown against the steering wheel of the vehicle. In a preferred embodiment of the invention, the material thickness in the groove influences the deformation resistance in the energy- absorbing mechanism. By selecting the groove depth, it is possible to determine in advance the extent to which the groove will resist deformation by the cutting member under the action of a certain force. The other main function of the groove is to guide the cutting member along the groove so that cutting deformation in the course of the collision takes place in a predetermined and controlled manner. Grooves of the type concerned here can be produced, for example, by milling out material from the energy-absorbing mechanism, by etching, or by the energy- absorbing mechanism comprising a component which is from the outset cast or moulded into the desired shape. It is of course possible to use grooves with a groove depth which varies along the length of the groove. Given that the energy-absorbing mechanism comprises a tube, it is advantageous if the tube has two or more longitudinal grooves. In this respect, it is particularly advantageous if at least two and preferably more grooves have different material thickness in relation to one another. This is because such an embodiment makes it possible to select the deformation resistance for the energy-absorbing mechanism by setting the cutting member to a suitable groove. To make setting of the deformation resistance possible, either the cutting member or the tube is mounted rotatably on the respective steering bracket part. Accordingly, the cutting member can be mounted on a guide piston which is mounted rotatably on one steering bracket part and is introduced at the first end of the tube, while the tube is fixed. Alternatively, a possibility for rotation of the tube and the cutting member in relation to one another is obtained by virtue of the cutting member being fixed on one steering bracket part, while the tube is mounted rotatably on the other steering bracket part. An arrangement according to the invention can in this respect comprise a special means for setting the cutting member to a predetermined groove. An example of such a means is an electric actuating device which can advantageously be arranged to control the setting of the deformation resistance in the energy-absorbing mechanism by being coupled to a servomotor which drives a gearing. The gearing is in turn coupled to either the tube or the guide piston, depending on which of these is rotatable. The means for setting the cutting member can in turn be coupled to a weight transducer which is arranged for registering the weight of the driver so that the setting of the cutting member can be adapted according to whether the driver weighs a lot or little. In a corresponding manner, the setting of the cutting member can be adjusted by virtue of the means for setting the cutting member being coupled to an arrangement which is adapted to detect a state which indicates whether or not the driver has the seat belt on. In this respect, it is suitable to register in the fastening arrangement of the safety belt whether or not the locking tongue of the safety belt is introduced into the fastening arrangement. It is of course possible to envisage embodiments in which two or more cutting members are arranged for interaction with grooves arranged in the energy-absorbing mechanism. It is also conceivable to use more than one energy-absorbing mechanism for the steering system in one and the same vehicle. For example, two or more tubes can be arranged on that surface of the upper part which faces the lower part, while the cutting members are on the one hand fixed to a guide piston introduced into the tube and on the other hand fixed to the lower part. In such an embodiment, the lower part is consequently mounted on the cutting members. Alternatively, the energy-absorbing mechanism can be arranged the other way round, that is to say with the cutting members fixed on the upper part and the tubes fixed on the lower part. According to a preferred embodiment, the tube forming part of the energy-absorbing mechanism is fixed to the upper part of the steering bracket. The force- transmitting member between the upper part and the lower part consists of a cable which is fixed at a first end in a guide piston at the first end of the tube and runs through the tube and out through a second end of the tube via a guide member, such as a pulley, arranged outside the tube and is fixed to a second end in the lower part. In order to ensure that the cutting member is directed towards a groove in the tube, it is suitable that the tube has at the first end at least one notch or recess in the end edge of the tube at the beginning of a groove in the tube, the notch or the recess constituting a guide member for guiding the cutting member towards the groove. When the tube is provided with a number of grooves arranged around its periphery, the end edge of the tube can be saw-toothed, each notch between two sawteeth being arranged at the beginning of a groove in the tube. The invention is intended for motor vehicles which comprise a steering column supporting a steering main shaft. The steering column is mounted in the motor vehicle in a manner which allows movement in relation to the vehicle body in the event that the steering column is subjected to the action of force in a collision by the driver of the vehicle being thrown against the steering wheel. BRIEF DESCRIPTION OF THE FIGURES The invention will be described in greater detail below with reference to the exemplary embodiment which is shown in the appended drawings, in which: Figure 1 shows a diagrammatic side view of the driver's seat in a motor vehicle with a steering arrangement provided with an energy-absorption arrangement according to the invention, Figure 2 shows a perspective view of the energy-absorption arrangement shown in Figure 1, Figure 3 shows a side view of the energy- absorbing mechanism in the energy- absorption arrangement in Figure 2 , Figure 4 shows a detail of the mechanism in Figure 3, Figure 5a shows a diagrammatic side view of the energy-absorption arrangement as it appears after a collision and Figure 5b shows an enlargement of part of Figure 5a. DESCRIPTION OF AN EXEMPLARY EMBODIMENT Figure 1 shows a simplified side view of the driver's seat in a motor vehicle with an energy- absorbing arrangement 1 according to the invention. The arrangement 1 is primarily intended to be used in connection with motor vehicles, for example private cars. The vehicle is, in a known manner, provided with a steering main shaft 2 which supports a steering wheel 4 at an upper end part 3. At a lower end part 5 , the steering main shaft 2 is connected to a steering apparatus (not shown) which, in a known manner, is intended for steering the wheels of the vehicle. The steering main shaft 2 is mounted in a steering bracket 6 in a manner which is known per se and is therefore not described in detail in this context. The connection between the steering bracket and the steering main shaft 2 can comprise, for example, means (not shown) for adjusting the steering main shaft 2 in the upward and the downward direction. Furthermore, the steering bracket 6 is in the main box-shaped and comprises, as can be seen from Figure 2 , an upper part 7 and a lower part 8 which are slidably interconnected. Accordingly, the lower part 8 is inserted into the upper part 7 and has two pins 9, 10 which project from a side surface 11 on the lower part 8 and which are arranged to interact with two parallel slots 12, 13 arranged in a corresponding side surface 14 on the upper part 7. The upper part 7 of the steering bracket 6 is fixed to the underside of the instrument panel 16 of the vehicle and the steering main shaft 2 is fixed to the lower part of the steering bracket 6. The fact that the upper part 7 of the steering bracket is slidably connected to the lower part 8 means that the steering main shaft 2 can be moved in relation to the instrument panel 16 by displacement of the lower part 8 of the steering bracket 6 in relation to the upper part 7. The steering bracket 6 also has an energy-absorbing mechanism 18 which, together with an electric actuating device 20, is centrally mounted on that surface 22 of the upper part 7 facing the instrument panel 16. As can be seen most clearly in Figure 3, the energy- absorbing mechanism 18 comprises a guide piston 24, on which a knife 26 is mounted. The guide piston 24 is introduced at one end of a tube 28 which is provided with a number of grooves 30, or recesses with reduced material thickness. As can be seen most clearly in Figure 4, the end edge 32 of the tube 28 is designed with a saw-toothed profile, each of the grooves 30 in the tube 28 beginning in a notch 33 between two saw-teeth 34 at the end edge 32 and running parallel in the longitudinal direction of the tube 28. The saw-toothed end edge 32 on the tube 28 ensures that the knife follows a certain given groove 30 from the outset by always guiding the knife into the notch 33 between two saw-teeth 34. Even if by mistake the knife arrives directly in front of a saw-tooth 34, it will still be guided into the notch 33 and in towards one of the grooves 30 closest to the saw-tooth 34. In order to make it possible to set the energy-absorbing mechanism 18 so that the deformation resistance in the mechanism can be changed, the grooves 30 have different depths in the radial direction of the tube 28. This means that the material thickness in the tube 28 varies among the different grooves. By virtue of this, it is possible to adapt the deformation resistance according to whether or not the driver of the vehicle is equipped with a safety belt. It is also possible to select different deformation resistance depending on the weight of the driver. A further manner of adjusting the deformation resistance is by angling the cutting surface of the knife in relation to the tube. In this respect, the knife can have a certain predetermined angle, which can be different for different deformation mechanisms but is constant for each individual mechanism. Alternatively, the knife can be coupled to a control and adjustment arrangement (not shown) which makes it possible to set the knife at different angles for one and the same deformation mechanism. The latter variant increases the possibility of selecting an optimum deformation resistance for each car driver. In order to make possible setting of the deformation resistance, the vehicle is suitably provided with an arrangement (not shown) which is adapted to detect a state which indicates whether or not the driver of the vehicle has the seat belt on. Such an arrangement is preferably connected to the fastening arrangement of the seat belt and detects whether the locking tongue of the seat belt is securely locked. This indicates that the driver is using the seat belt. The information from the fastening arrangement of the seat belt is transmitted to the electric actuating device 20 which is mounted on the upper part 9 of the steering bracket 6. The actuating device 20 controls the setting of the deformation resistance in the energy-absorbing mechanism 18 by, via a servomotor 36 which drives a gearing 38, rotating the piston 24 so that the knife 26 fixed on the piston is guided towards a groove 30 suitable for the circumstances concerned. In a corresponding manner, the vehicle can be provided with an arrangement which is adapted to detect the weight of the driver. In this respect, such an arrangement is suitably placed in or associated with the driver's seat 31 of the vehicle. The information regarding the weight of the driver is also transmitted to the actuating device 20 and is used in order to select that groove 30 in the energy-absorbing mechanism 18 which offers optimum deformation resistance with regard to the weight of the driver and whether or not the driver is equipped with a safety belt. The piston 24 which is introduced into the tube 28 on the energy-absorbing mechanism 18 is connected to the lower part 8 of the steering bracket 6 via a cable 40 which runs around a pulley 42. In this respect, the cable is fastened by, for example, being welded, riveted or screwed firmly to the lower part. In the event of a collision, when the driver of the vehicle is thrown against the steering wheel 4 , the lower part 8 connected to the steering column 2 is displaced in relation to the upper part 7. The appearance of the energy-absorbing mechanism 18 after a collision is shown in Figure 5a. The direction of displacement is indicated by an arrow A in Figure 5b. The displacement of the lower part 8 of the steering bracket 6 leads to a tensile force arising in the cable 40, by virtue of which the piston 24 is drawn through the tube 28 in a drawing direction indicated by an arrow B. In this respect, movement of the piston takes place in the opposite direction to the direction of displacement of the lower part 8. When the piston 24 moves in the direction indicated in Figure 5b, this leads to the knife 26 at the same time working its way through the material in the tube 28. The resistance encountered by the knife 26 in this respect depends on the material thickness in the particular groove 30 to which the knife 26 is set. The grooves 30 in the tube 28 thus perform two main functions, namely on the one hand to influence the energy absorption in the event of a collision and on the other hand to guide the knife 26 during the course of deformation. The reason why a cable 40 has been selected as the force-transmitting member between the energy-absorbing mechanism 18 and the lower part 8 of the steering bracket 6 is that a very functionally reliable mechanism is thus obtained. If tracks or the like are used for transmitting forces, the risk of leaving the tracks is great if the steering bracket 6 is deformed in the event of unforeseen complications. Another reason is that the piston 24 can be rotated very easily inside the tube 28 when the knife 26 is to be set in a suitable notch 33 on the toothed tube edge 32. The invention is not to be considered as being limited to the exemplary embodiment described here but a number of further variants and modifications are conceivable within the scope of the patent claims below.

Claims: PATENT CLAIMS 1. Arrangement for driver protection in a motor vehicle, comprising a steering bracket (6) which supports a steering main shaft (2) and comprises an upper part (7) and a lower part (8) which are displaceably interconnected, the upper part (7) being fixed to the body of the motor vehicle and the lower part (8) being fixed to the steering main shaft (2), the arrangement also having means for force transmission between the lower part (8) and the upper part (7), the arrangement also comprising an energy-absorbing mechanism (18) which has two or more longitudinal grooves and also a cutting member (26) which is adapted to run along one of said grooves when there is relative displacement between the upper part (7) and the lower part (8), characterized in that the arrangement also comprises means for setting the cutting member (26) to a predetermined groove (30) and in that at least two of the grooves (30) have different deformation resistance in relation to one another, by virtue of which the deformation resistance in the energy-absorbing mechanism (18) can be adjusted by setting the cutting member (26) to a predetermined groove (30). 2. Arrangement according to Claim 1, characterized in that the energy-absorbing mechanism (18) comprises a tube (28) and in that the grooves (30) are arranged in the longitudinal direction of the tube (28), from a first end of the tube (28), the tube (28) being connected to one of the two displaceable parts (7, 8) of the steering bracket (6) and the cutting member (26) being connected to the other part (7, 8). 3. Arrangement according to Claim 1 or 2 , characterized in that the grooves (30) have a smaller material thickness than the surrounding parts of the tube (28) and in that at least two grooves (30) have different material thickness in relation to one another. 4. Arrangement according to Claim 1 , 2 or 3, characterized in that at least two grooves (30) are of different width in relation to one another. 5. Arrangement according to Claim 1 or 2, characterized in that the grooves (30) have lower deformation resistance than surrounding parts of the energy-absorbing mechanism (18) by virtue of the material in the grooves having a different physical nature to the surrounding material in the energy-absorbing mechanism (18). 6. Arrangement according to any one of the preceding claims, characterized in that the means for setting the cutting member (26) to a predetermined groove is coupled to a weight transducer which is arranged for registering the weight of the driver. 7. Arrangement according to any one of Claims 2-6, characterized in that the cutting member (26) is firmly mounted on a rotatable guide piston (24) which is indirectly connected to one of the two displaceable parts (7, 8) of the steering bracket (6), the guide piston (24) being introduced at the first end of the tube (28). 8. Arrangement according to any one of Claims 2-6, characterized in that the cutting member (26) is fixed on one of the two displaceable parts (7, 8) of the steering bracket (6) and in that the tube (28) is mounted rotatably on the other displaceable part (7, 8). 9. Arrangement according to any one of the preceding claims, characterized in that the means for setting the cutting member (26) consists of an electric actuating device (20). 10. Arrangement according to Claims 7 and 9, characterized in that the electric actuating device (20) is arranged to control the setting of the deformation resistance in the energy-absorbing mechanism (18) by virtue of the actuating device (29) being coupled to a servomotor (36) which drives a gearing (38) connected to the guide piston (24). 11. Arrangement according to Claims 8 and 9, characterized in that the electric actuating device is arranged to control the setting of the deformation resistance in the energy-absorbing mechanism (18) by virtue of the actuating device being coupled to a servomotor which drives a gearing connected to the tube (28). 12. Arrangement according to any one of the preceding claims, characterized in that the means for setting the cutting member (26) is coupled to an arrangement which is adapted to detect a state which indicates whether or not the driver has the seat belt on. 13. Arrangement according to any one of Claims 2-12, characterized in that two or more cutting members are arranged to interact with grooves (30) arranged in the tube (28) . 14. Arrangement according to any one of Claims 2-13, characterized in that the tube (28) forming part of the energy-absorbing mechanism (18) is fixed to the upper part (7) of the steering bracket (6) and in that the force-transmitting member between the upper part (7) and the lower part (8) consists of a cable (40) which is fixed at a first end in the guide piston (24) at the first end of the tube (28) and runs through the tube (28) and out through a second end of the tube (28) via a guide member, such as a pulley (42), arranged outside the tube, and is fixed at a second end in the lower part ( 8 ) . 15. Arrangement according to any one of Claims 2-14, characterized in that the tube (28) has at the first end at least one notch (33) arranged in the end edge (32) of the tube at the beginning of a groove (30) in the tube (28), the notch (33) constituting a guide member for guiding the cutting member (26) towards the groove (30). 16. Arrangement according to Claim 15, characterized in that the end edge (32) of the tube is saw- toothed, each notch (33) between two saw-teeth (34) being arranged at the beginning of a groove (30) in the tube (28).

Inventors: ANDERSSON BJOERN, ASPLUND NIKLAS, DE VERDIER JOACHIM, FURTENBACH LARS, ANDERSSON, BJOERN, ASPLUND, NIKLAS, DE VERDIER, JOACHIM, FURTENBACH, LARS
Applicants: ANDERSSON BJOERN, ASPLUND NIKLAS, FURTENBACH LARS, VERDIER JOACHIM DE, VOLVO AB, AB VOLVO, ANDERSSON, BJOERN, ASPLUND, NIKLAS, DE VERDIER, JOACHIM, FURTENBACH, LARS
Application year: 1998
Main classification: B62D1
IPC codes: B60R21, B62D1, F16F7