DEVICE AND METHOD FOR OCCUPANT PROTECTION IN VEHICLES

Abstract: The invention relates to a device for protecting an occupant of a motor vehicle, comprising a steering column (3) which supports a steering shaft (1) and against which a force (F) is applied by said occupant during a collision, whereby the steering column (3) is displaceable with respect to the stress-bearing structure (4) of the vehicle and comprises a first energy-absorbing unit (7, 9) for absorption of energy during said displacement, as well as comprising a sensor for detecting of a condition which indicates that said occupant is restrained by a seatbelt. The invention is characterized in that a second energy-absorbing unit (13, 14, 22) is arranged between the steering column (3) and the stress-bearing structure (4), and in that the sensor is connected to a locking unit (18, 19, 20) which is arranged such that when said condition is detected, it permits displacement of the second energy-absorbing unit (13, 14, 22) with respect to the stress-bearing structure (4), whereby energy is absorbed. By means of the invention, an improved device for protection of occupants of a vehicle is provided where, in particular, an optimal energy-absorption is offered irrespective of whether the driver is wearing his seatbelt.

Description: TITLE: Device and method for occupant protection in vehicles. TECHNICAL FIELD: The present invention relates to a device for protection of occupants in a vehicle according to the preamble of appended claim 1. More particularly, the invention is intended to be used in energy absorbing steering systems for motor vehicles. The invention also relates to a method for occupant protection in vehicles according to the preamble of appended claim 7. BACKGROUND OF THE INVENTION: In motor vehicles, it is a general goal to reduce as far as possible the effects of a collision on the occupants of the vehicle. In today's cars, three-point seatbelts are therefore normally employed to restrain occupants of the vehicle. In a known manner, the seatbelts offer good protection and increased safety for the occupants should a collision take place. Nowadays, there is a desire to provide steering systems in vehicles which are energy-absorbing. The reason for this desire, which is dictated by legislation in certain countries, is that there is a need to offer certain protection to a driver who is not wearing a seatbelt when he is thrown towards the steering wheel in a collision. It is previously known to design the steering system of the vehicle so that it absorbs energy when the driver of the car is thrown forwards and impacts the steering wheel during a collision. This can be achieved, for example, by designing the steering wheel with deformable and flexible spokes. This can also be achieved by arranging the steering shaft of the vehicle in a particularly designed energy- absorbing steering column which is attached to the stress- bearing structure of the vehicle. In the event of a collision, when the steering wheel and thus also the steering column are influenced by a very large force as a result of the occupant being thrown forwards, this force will be transmitted from the steering wheel to the steering column. This implies that the steering column is displaced a certain amount relative to the vehicle structure. During this displacement, energy will be absorbed which, as a consequence, reduces the effects on the driver during the collision sequence. An arrangement is known from US 4 978 138 for energy absorption in a steering system for vehicles. The arrangement is based on the principle that if the driver is not wearing his seatbelt, the steering system will absorb energy when the driver is thrown against the steering wheel during a possible collision. To achieve this, the arrangement includes a particular deformable and energy- absorbing bracket which is connected to the steering column. In order to determine whether the driver is wearing his seatbelt, a sensor is arranged on the seatbelt lock. This known arrangement also includes means for protecting the knees of the driver, which means is activated irrespective of whether the driver is wearing his seatbelt or not. If the driver is wearing his seatbelt, the force from the knees will be absorbed by the knee protector as the steering wheel is displaced, whereby it is possible to prevent the upper body and head of the driver from impacting the steering wheel. The arrangement according to this document suffers from the disadvantage that the circumstances in which the driver can in fact impact the steering wheel during a collision even if he is wearing his seatbelt are not taken into account. This can occur, for example, when the driver has his seat in a well forward position or when the seatbelt is unusually slack. SUMMARY OF THE INVENTION: A primary object of the present invention is thus to solve the above-mentioned problems and to provide an improved device for energy absorption in a steering system for a motor vehicle which primarily provides optimal energy absorption irrespective of whether the seatbelt is being used by the driver. This object is achieved by a device of the above-mentioned type, the characterizing features of which are apparent from claim 1. This object is also attained by means of a method of the above-mentioned type, the characterizing features of which are apparent from claim 7. The invention is intended for use in vehicles having a steering column which supports a steering shaft and in which a force is normally exerted by said occupant against the steering column during a collision, whereby the steering column can thus be displaced with respect to the stress-bearing structure of the vehicle. The invention comprises a first energy-absorbing unit for absorbing energy during said displacement. Furthermore, the invention includes a sensor for detecting a condition which determines that said occupant is wearing his seatbelt. The invention is based on the principle that a second energy absorbing unit is arranged between the steering column and the vehicle's stress-bearing structure and that said sensor is connected to a lock arrangement which, when said condition is detected, permits displacement of the second energy-absorbing unit with respect to the structure. During this displacement, energy is absorbed. In this manner, the energy-absorbing capability of the steering system can be varied depending on whether the driver is wearing his seatbelt or not. This provides increased safety for the driver in the event of a collision. In a preferred embodiment, the second energy absorbing unit comprises a first carriage which is connected to the steering column and a second carriage which is connected to the stress-bearing structure of the vehicle. It further includes an energy-absorbing element for absorbing energy during displacement of the carriages with respect to each other. These two carriages can adopt two different conditions depending on whether the driver is wearing his seatbelt or not. Either the carriages are locked together with respect to each other or they are disconnected so that they can be displaced relative each other. In order to achieve this, the invention comprises the above-mentioned lock arrangement which is controlled with the help of a sensor which detects whether the seatbelt is being used. In this manner, a certain predetermined energy absorption in the steering column is attained when the driver is wearing his seatbelt and another energy absorption when the driver is not wearing his seatbelt. Further, advantageous embodiments of the invention will be apparent from the appended dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS: The invention will be described in the following in greater detail with reference to a preferred embodiment and the attached drawings, in which Fig. 1 is a somewhat simplified elevational view of the invention according to the preferred embodiment, Fig. 2 is a perspective view of a portion of a first energy-absorbing unit according to the embodiment, Fig. 3 is a perspective view of a second energy-absorbing unit according to the invention, Fig. 4 shows schematically a course of events of the invention in a first condition, and Fig. 5 shows schematically a course of events of the invention in a second condition. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS: Fig. 1 shows a somewhat simplified elevational view of a device according to the present invention. The device is primarily intended to be employed in motor vehicles, for example in a car. The vehicle is, in a known manner, provided with a steering shaft 1 which, at its upper end, supports a steering wheel 2. The lower end portion of the steering shaft 1 is connected to a not-shown steering mechanism which, in a known manner, is intended for steering the wheels of the vehicle. The steering shaft 1 is supported in a steering column 3 in a manner which per se is already known and which therefore will not be described in detail here. For example, the steering column 3 can comprise means (not shown) for adjusting the rake and reach of the steering shaft 1. Furthermore, the steering column 3 is substantially box- shaped with a substantially horizontal upper side and a somewhat angled lower side. The steering column 3 is arranged underneath the dashboard 4 of the vehicle, the contours of which are indicated by a chain line 5. In addition, the shape and form of the steering column 3 are adapted to the type of vehicle in which the invention is employed. The steering column 3 is designed so as to be able to absorb energy when influenced by the force which arises should the driver impact the steering wheel 2 during, for example, a collision. To this end, the sides of the steering column 3 are provided with elongate slots 6 which are preferably four in number, whereby two of the slots are arranged on the side of the steering column 3 which is visible in Fig. 1 (and whereby the remaining slots are arranged on the opposite side of the steering column 3 and thus cannot be seen in Fig. 1). Two rods 7 extend through the steering column 3 and the slots 6, which rods extend substantially perpendicular to the extension of the steering shaft 1. The rods 7 are rotatably supported in brackets 8 which are fixedly arranged on the outside of the steering column 3. With reference to Fig. 2, which is a perspective view from the front of the front end region of the steering column 3 and including one of the rods 7, it is apparent that the rod 7 is provided with an energy-absorbing element which is preferably in the form of a wire 9 which can be wound out. The one end of the wire 9 is fixed at an attachment point 10 on the short side 11 of the steering column 3, whilst the rest of the wire 9 is wound about the rod 7 and is preferably also affixed thereto. The wire 9 is preferably a thick steel wire which is rolled out in the event that the steering column 3 attempts to be displaced in relation to the rod 7. During such a displacement of the steering column 3, the wire 9 offers a certain resistance, the amount of which is determined i.a. by the dimensions and material of the wire 9, as well as its winding diameter. In this manner, the steering column 3 can absorb energy should a driver impact the steering wheel during a possible collision. Each bracket 8 is provided with an attachment element in the form of a hook 12. Referring once more to Fig. 1, it is apparent that each hook 12 has a region with a wedge-shaped cross section. Furthermore, each hook 12 is intended to be mounted in a corresponding wedge-shaped groove (not apparent from Fig. 1 ) in a first lower carriage 13 which constitutes a part of a further energy-absorbing arrangement. This carriage 13 is, in turn, displaceably arranged on the lower side of a second upper carriage 14 which is fixedly arranged on the lower side of the dashboard 4. The arrangement with the two carriages 13, 14 will now be described in detail with reference to Fig. 3. The lower carriage 13 is provided with a plurality of, preferably four, grooves or recesses 15 which serve as attachments for the above-mentioned hooks 12 (compare with Fig. 1 and 2) which are arranged on the brackets 8 on the steering column 3. When the complete device is in a mounted condition, the steering column 3 is thus fixedly arranged in relation to the lower carriage 13 via the brackets 8 and the hooks 12. The upper carriage 14 is provided with holes or corresponding attachment means 16 intended for mounting to the dashboard which, in turn, is fixedly attached to the stress-bearing structure of the vehicle. The lower carriage 13 is arranged with respect to the upper carriage 14 in such a manner that it can slide in the direction of its longitudinal extension, which corresponds substantially to the longitudinal direction of the vehicle. For this purpose, the upper carriage 14 is provided with a suspension arrangement which is shown schematically in Fig. 3 in the form of a longitudinally extending guide 17. Of course, more than one such guide 17 can be employed. Alternatively, the carriages can be suspended in a frame or a similar component so that the lower carriage can be displaced in its longitudinal direction. This displacement of the lower carriage 13 with respect to the upper carriage 14 occurs when certain predetermined operational conditions are present in accordance with that which is described in detail below. An electrically-actuated solenoid 8 is arranged on the upper carriage 14. The solenoid 18 is shown schematically in Fig. 3 and, in a known manner, comprises a displaceable piston 19, the position of which is determined by providing a current from a (not shown) source of power. In its non- influenced state, the piston 19 engages a corresponding hole or recess 20 in the lower carriage 13. For this purpose, the piston is influenced in the direction of the hole 20 by a spring 21. With help of the solenoid 18, the movement of the carriages 13, 14 with respect to each other can be controlled. In the condition where no current is connected to the solenoid 18, the piston 19 engages the hole 20 due to the influence of the spring 21. This implies that the carriages 13, 14 are locked with respect to each other. When a current is applied to the solenoid 18, the piston 19 is withdrawn, whereby the force from the spring 21 is overcome. In this manner, the piston 19 is pulled out of engagement of the hole 20, which implies that the lower carriage 13 can be displaced substantially horizontally with respect to the upper carriage 14. In this condition, a second energy- absorbing element is also employed, this being in the form of a tongue or a strip 22 of metal. This strip 22, which is also shown in Fig. 1, is attached at one end to the lower carriage 13 and the other end to the upper carriage 14. The strip 22 is somewhat curved and provides a predefined resistance, i.e. energy absorption, during displacement of the lower carriage 13 with respect to the upper carriage 14. The solenoid 18 is connected to a (not shown) sensor arrangement which is adapted to detect a condition which indicates whether the driver of the vehicle is wearing his seatbelt or not. For this purpose, the locking arrangement of the seatbelt is preferably provided with a switch which is closed when the buckle of the seatbelt is locked. This indicates that the driver is wearing his seatbelt. The switch is also connected to a source of energy which, in turn, is adapted to energize the solenoid 18 in the case that the seatbelt is used. When the solenoid 18 is activated, its piston 8, 19 is retracted from the hole 20, which permits the above-mentioned displacement of the lower carriage 13. The invention will now be described with reference to Figs. 4 and 5 which, in a somewhat simplified manner, show its operation during a collision in which the steering wheel 2 and thus also the steering column 3 are influenced by a force F in a direction to the left in the drawings. Fig. 4 shows the condition which prevails when the seatbelt is not worn by the driver. This implies that the solenoid 18 is in its non-active position, whereby the piston 19 extends down into the hole 20 in the lower carriage 13. Since the lower carriage 13 cannot then be displaced with respect to the upper carriage 14, the steering column 3 will instead be displaced with respect to the lower carriage 13, whereby the steering column 3 is displaced forwardly whilst the rods 7 are guided along the slots 6. During this sequence of events, the energy absorbing wires 9 become rolled out (compare with Fig. 2), which implies that the steering column 3 absorbs energy. This reduces the influences on the driver during an accident. Fig. 5 shows the condition which prevails when the driver is not wearing his seatbelt. In this situation, the solenoid 18 is actuated with the help of the above- mentioned sensor arrangement. This implies that the piston 19 is retracted so that it no longer projects into the hole 20 in the lower carriage 13. In this manner, the lower carriage 13 becomes displaceable with respect to the upper carriage 14. When the driver of the vehicle impacts the steering wheel 2, the force F which thus arises will be transmitted to the lower carriage 13 (via the steering column 3), whereby the lower carriage 13 is displaced to the left in the drawing. During this sequence of events, energy will be absorbed by the energy-absorbing strip 22 which, during displacement of the lower carriage 13, is extended and stretched out. Preferably, the energy absorption capabilities of the wires 9 and the strip 22 are such that the strip 22 is more flexible than the wire 9. In the case when the driver is wearing his seatbelt, this implies that the steering column 3 is not displaced with respect to the lower carriage 13 under the influence of the force F. This also implies that the system offers a lower resistance when a driver who is wearing his seatbelt impacts the steering wheel. This is because an amount of energy absorption during a collision is absorbed by the seatbelt itself. By way of the invention, two different types of energy absorption of the steering system are obtained. This is obtained automatically depending on whether the driver is wearing his seatbelt or not. The invention is not restricted to the above-described embodiments, but can be varied within the scope of the appended claims. For example, the size and choice of material for the steel wire 9 and the strip 22 can be varied depending on the desired energy absorption capability of the steering system. The energy absorption of the wire 9 and strip 22 is thus selected such that suitable energy absorption is obtained for the driver when driving with and without his seatbelt, respectively. The strip 22 can be made more flexible than the wire 9, or vice versa. Furthermore, the wire 9 and the strip 22 can be replaced by other types of energy absorbing elements, for example ribbons, springs, material weakenings, etc. Instead of the steel wire 9 which is rolled about the rod 7, other types of energy-absorbing elements can for example be arranged between the steering column 3 and respective brackets 8 for damping the force during displacement of the steering column 3. The two carriages can be locked with respect to each other either when the driver is wearing his seatbelt or when the driver is not wearing his seatbelt. In accordance with one conceivable variation of the invention, the function of the solenoid can also be controlled so that it is dependent on a weight sensor in the driver's seat which detects whether or not the occupant weighs more than a certain predetermined amount. The two carriages 13, 14 can be designed in different ways, for example in the form of box- or cassette-like elements which can be displaced substantially parallel with respect to each other. Nevertheless, it is a principle underlining the invention that the two can be locked together with respect to each other depending on whether or not the driver is wearing his seatbelt. The attachment of the steering column 3 can be achieved in various ways. For example, screws or similar attachment means can be used instead of the hooks 12. Furthermore, the carriages 13, 14 can be attached to the stress-bearing structure of the vehicle in a manner other than to the underside of the dashboard 4. In addition, the slots 6 which are in the steering column 3 can for example be two in number instead of four as shown in the drawings. The solenoid can be arranged such that its piston projects downwardly (for example Fig. 4), upwardly or to the side. For example, in accordance with a further variation, the solenoid can be arranged in the lower carriage, whereby its piston projects upwardly into a hole in the upper carriage. Furthermore, more than one solenoid can be used as the locking means for the carriages. The two carriages can be arranged as an upper and a lower carriage or, alternatively, as two carriages which are at least partially arranged side by side. According to an alternative embodiment, the lower carriage 13 can be arranged directly against the underside of the dashboard. In such an arrangement, the solenoid and the one end of the strip 22 are also arranged on the underside of the dashboard. Finally, it is to be appreciated that the invention can be employed in different types of vehicle, for example cars, trucks or buses.

Claims: CLAIMS : 1. Device for protecting an occupant of a motor vehicle, comprising a steering column (3) which supports a steering shaft (1) and on which a force (F) is exerted by said occupant during a collision, whereby the steering column (3) is displaceable with respect to the stress-bearing structure (4) of the vehicle and comprises a first energy- absorbing unit (7, 9) for absorption of energy during said displacement, and comprising a sensor for detecting a condition which indicates that said occupant is restrained by a seatbelt, c h a r a c t e r i z e d i n that a second energy-absorbing unit (13, 14, 22) is arranged between the steering column (3) and the stress-bearing structure (4), and in that the sensor is connected to a locking unit (18, 19, 20) which is arranged such that, when said condition is detected, it permits displacement of the second energy-absorbing unit (13, 14, 22) with respect to the stress-bearing structure (4), whereby energy is absorbed. 2. Device according to claim 1, c h a r a c t e r i z e d i n that the locking unit (18, 19, 20) is arranged such that, when said condition is not present, it locks said second energy-absorbing unit (13, 14, 22) against displacement with respect to the stress- bearing structure (4). 3. Device according to claim 1 or 2, c h a r a c t e r i z e d i n that the second energy- absorbing unit (13, 14, 22) is designed with an energy absorption capability which is lower than the energy- absorbing capability of the first energy-absorbing unit (13, 1,4 22) . 4. Device according to any one of the preceding claims, c h a r a c t e r i z e d i n that said second energy- absorbing unit (13, 14, 22) comprises a further carriage (13) which is fixedly secured to said steering column (3), a second carriage (14) fixedly attached to said stress- bearing structure (4) and an energy-absorbing element (22) for absorption of energy during displacement of the carriages (13, 14) with respect to each other. 5. Device according to claim 4, c h a r a c t e r i z e d i n that said locking unit (18, 19, 20) is in the form of an electrically operating solenoid which is arranged in the one carriage (14) and includes a piston (19) which, when locking, cooperates with a recess (22) in the second carriage (13). 6. Device according to claim 4 or 5, c h a r a c t e r i z e d i n that said energy-absorbing element (22) is in the form of a strip whose one end is affixed to the one carriage (13) and whose other end is affixed to the second carriage (14). 7. Method for protecting an occupant of a vehicle, comprising a steering column (3) which supports a steering shaft (1), comprising absorbing energy during displacement of the steering column (3) with respect to the stress-bearing structure (4) of the vehicle under the influence of a force (F) of an occupant, and detecting a condition which corresponds to said occupant being restrained by a seatbelt, c h a r a c t e r i z e d by the method further comprising: actuating a locking unit (18, 19, 20) when detecting said condition, releasing a second energy-absorbing unit (13, 14, 22) when actuating said locking unit (18, 19, 20) whereby displacement of the second energy-absorbing unit (13, 14, 22) with respect to the stress-bearing structure (4) is permitted during energy-absorption under the influence of said force (F) . 8. Method according to claim 7, c h a r a c t e r i z e d i n that said locking unit (17) locks said second energy-absorbing unit (13, 14, 22) against displacement with respect to the stress-bearing structure (4) when detecting that said condition is not present. 9. Method according to claim 7 or 8, c h a r a c t e r i z e d i n that the energy-absorption capability when the second energy-absorbing unit (13, 14, 22) is released, is lower than the energy-absorbing capability of the first energy-absorbing unit (13, 14, 22). 10. Method according to any one of the claims 7-9, c h a r a c t e r i z e d i n that said actuation of the locking unit (18, 19, 20) comprises feeding a current to an electrically operated solenoid. 11. Method according to any one of the claims 7-10, c h a r a c t e r i z e d i n that said release of the second energy-absorbing unit (13, 14, 22) comprises releasing a first carriage (13) arranged on the steering column (3) with respect to a second carriage (14) arranged on the stress-bearing structure (4).

Inventors: FOSSE TORE, FOSSE, TORE
Applicants: FOSSE TORE, VOLVO AB, AB VOLVO, FOSSE, TORE
Application year: 1997
Main classification: B62D1
IPC codes: B62D1