Abstract
A knee airbag for a vehicle occupant restraint device can adopt a deployed position of use between a fixed vehicle component and the legs of a vehicle occupant. The airbag includes an airbag sheath, at least one exhaust orifice formed therein and control features for selectively releasing the exhaust orifice. The control features are disposed inside the knee airbag and arranged so as to release or block the exhaust orifice depending on the expansion of the knee airbag in a particular direction of expansion.
Claims
1. A vehicle occupant restraint device comprising: a knee airbag (10) adapted to adopt a deployed position of use between a fixed vehicle component (12) and legs (14; 16) of a vehicle occupant, the knee airbag, comprising: an airbag sheath (18), at least one exhaust orifice (20) formed therein, and a passive control means for selectively releasing the at least one exhaust orifice (20), wherein the passive control means is disposed inside the knee airbag (10) and is arranged so as to release or block the at least one exhaust orifice (20) in response to an expansion of the knee airbag (10) in a particular direction of expansion; wherein the particular direction of expansion points from the fixed vehicle component (12) to the legs (14, 16) of the vehicle occupant, and wherein a length of a portion of a tether (26) extending between opposed walls of the knee airbag (10) is larger than a minimum distance x of the fixed vehicle component (12) from the legs (14) of a short vehicle occupant seated a first distance from the fixed vehicle component but smaller than a corresponding distance y from the legs (16) of a normal-sized vehicle occupant seated a second distance from the fixed vehicle component, the first distance being less than the second distance.
2. The vehicle occupant restraint device according to claim 1, wherein the at least one exhaust orifice (20) is arranged in an upper area of the knee airbag (10) related to the position of use of the knee airbag (10).
3. The vehicle occupant restraint device according to claim 1, wherein an effective exhaust cross-section of the at least one exhaust orifice (20) depends on the expansion of the knee airbag (10) in the particular direction of expansion.
4. The vehicle occupant restraint device according to claim 1, wherein the at least one exhaust orifice (20) opens into an overflow chamber (44).
5. The vehicle occupant restraint device according to claim 1, wherein the passive control means includes a tether (26) adapted to restrict deployment of the knee airbag (10) in the particular direction of expansion.
6. The vehicle occupant restraint device according to claim 5, wherein the tether (26) is fastened on one hand to a portion of the airbag sheath (18) opposite to the vehicle component (12) and on another hand to a portion of the airbag sheath (18) opposite to the vehicle occupant, related to the position of use of the knee airbag (10).
7. The vehicle occupant restraint device according to claim 5, wherein the passive control means further includes a flap as a closing member for selectively closing the exhaust orifice (20) and a tensile means (24) which is coupled on one hand to the tether (26) and on another hand to the closing member (22).
8. The vehicle occupant restraint device according to claim 7, wherein one end of the tensile means (24) is detachably mounted in or on a fold (28) of the tether (26 by a tear seam (30).
9. The vehicle occupant restraint device according to claim 7, wherein the flap (22) includes an edge portion (32) connected to the airbag sheath (18) and a free portion (36) coupled to the tensile means (24).
10. The vehicle occupant restraint device according to claim 9, wherein the edge portion (32) is fastened to the airbag sheath (18) by means of a seam (34) having a curved path.
11. The vehicle occupant restraint device according to claim 10, wherein the path of the seam (34) substantially corresponds to a circular arc of a circle surrounding the at least one exhaust orifice (20) or to a corresponding arc of an ellipse.
12. The vehicle occupant restraint device according to claim 1, wherein the passive control means further includes a closing member (22) for selectively closing the at least one exhaust orifice (20), wherein a tensile means (24), the tension of which depends on the expansion of the knee airbag (10) in the particular direction of expansion, acts on the closing member (22).
13. The vehicle occupant restraint device according to claim 12, wherein the closing member (22) includes on an outer periphery one or more inwardly protruding recesses (42) and in a peripheral direction only an area outside the one or more recesses and, respectively, the areas between the one or more recesses (42) is/are connected to an edge of the exhaust orifice (20).
14. The vehicle occupant restraint device according to claim 12, wherein the closing member (22) is formed by an exhaust portion (48) folded into an interior of the knee airbag (10) in which the at least one exhaust orifice (20) is provided.
15. The vehicle occupant restraint device according to claim 12, wherein the tensile means (24) is arranged between two connecting points so that by an externally caused deformation of the knee airbag (10) a distance between the two connecting points of the tensile means (24) is shortened.
16. The vehicle occupant restraint device according to claim 15, wherein the tensile means (24) is guided through loops (50) which, related to the position of use of the knee airbag (10), are arranged in a transverse direction of the vehicle alternately on an airbag wall facing the fixed vehicle component (12) and on an airbag wall facing the legs (14, 16) of the vehicle occupant.
17. A vehicle occupant restraint device comprising: a knee airbag (10) adapted to adopt a deployed position of use between a fixed vehicle component (12) and legs (14; 16) of a vehicle occupant, the knee airbag comprising: an airbag sheath (18), at least one exhaust orifice (20) formed therein, and a passive control means for selectively releasing the at least one exhaust orifice (20), wherein the passive control means is disposed inside the knee airbag (10) and is arranged so as to release or block the at least one exhaust orifice (20) in response to an expansion of the knee airbag (10) in a particular direction of expansion, the passive control means including a tether (26) adapted to restrict deployment of the knee airbag (10) in the particular direction of expansion, the tether being fixedly fastened on one hand to a portion of the airbag sheath (18) opposite to the vehicle component (12) and on another hand fixedly fastened to a portion of the airbag sheath (18) opposite to the vehicle occupant, related to the position of use of the knee airbag (10), the passive control means further including a tensile means (24) connected to the tether (26) at one end and a closing member for blocking the at least one exhaust orifice (20) at another end, the tensile means (24) extending substantially perpendicular to the particular direction of expansion of the tether (26).
18. The vehicle occupant occupant restraint device according to claim 17, wherein terminal ends of the tether (26) are fixedly fastened to the airbag sheath (18).
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Further features and advantages of the invention are evident from the following description and from the enclosed drawings which are referred to. The drawings schematically show in:
(2) FIG. 1 an interaction of a short vehicle occupant with an inflated knee airbag according to the invention in a vehicle according to a first embodiment;
(3) FIG. 2 an interaction of a normal-size vehicle occupant with an inflated knee airbag according to the invention according to the first embodiment;
(4) FIG. 3 the connection of the tensile means to the tether of the knee airbag according to the invention in accordance with the first embodiment in detail;
(5) FIG. 4 the release of the tensile means when the tether is stressed;
(6) FIG. 5 a top view of a spread knee airbag according to the invention in accordance with the first embodiment with released exhaust orifices;
(7) FIG. 6 a top view of a spread knee airbag according to the invention in accordance with the first embodiment with blocked exhaust orifices;
(8) FIG. 7 a detail view of the flap of a knee airbag according to the invention in accordance with the first embodiment;
(9) FIG. 8 a top view of a closing member of a knee airbag according to the invention in accordance with a second embodiment;
(10) FIG. 9 a detailed sectional view of the knee airbag according to the invention in accordance with the second embodiment with blocked exhaust orifice;
(11) FIG. 10 a detailed sectional view of a knee airbag according to the invention in accordance with the second embodiment with released exhaust orifice;
(12) FIG. 11 a lateral sectional view of the knee airbag according to the invention in accordance with the second embodiment with non-filled overflow chamber;
(13) FIG. 12 a lateral sectional view of the knee airbag according to the invention in accordance with the second embodiment with filled overflow chamber;
(14) FIGS. 13a to 13d top views of part of a spread knee airbag according to the invention in accordance with a third embodiment with an exhaust orifice released to a different extent;
(15) FIGS. 14a to 14d sectional views corresponding to FIGS. 13a to 13d;
(16) FIG. 15 an interaction of a vehicle occupant with an inflated knee airbag according to the invention in accordance with a fourth embodiment;
(17) FIG. 16 an interaction of a vehicle occupant seated further forward with an inflated knee airbag according to the invention in accordance with the fourth embodiment;
(18) FIG. 17 a sectional view along the line A-A from FIG. 15; and
(19) FIG. 18 a sectional view along the line B-B from FIG. 16.
DESCRIPTION OF EMBODIMENTS
(20) In each of the FIGS. 1 and 2 a knee airbag 10 of a vehicle occupant restraint device in a vehicle is illustrated which has deployed out of an acceptance between the lower part of the instrument panel 12 of the vehicle and the legs 14 and, resp., 16 of a vehicle occupant. The position of the knee airbag 10 illustrated in FIGS. 1 and 2 after complete inflation by an inflator will hereinafter be referred to as position of use of the knee airbag 10 to which the indications of upper, lower etc. refer.
(21) The knee airbag 10 is substantially formed of an airbag sheath 18 in which at least one exhaust orifice 20 is formed through which gas may escape from the knee airbag 10 under certain circumstances which will be discussed in detail below. The exhaust orifice 20 is arranged in the upper area of the knee airbag 10, more exactly speaking in the upper third related to the position of use of the knee airbag 10.
(22) The exhaust orifice 20 can be covered by a closing member, here in the form of a flap 22, disposed inside the knee airbag 10. A flexible tensile means 24, e.g. in the form of a ribbon or a string, inter alia serves for controlling the flap 22. A first end of the tensile means 24 is connected to the flap 22 and the second end is connected to a tether 26 equally disposed inside the knee airbag 10 and provided for restricting the deployment of the knee airbag 10 in the direction of the vehicle occupant. For this purpose, the tether 26 is fastened on the one hand to a portion of the airbag sheath 18 opposed to the instrument panel 12 and on the other hand to a portion opposed to the vehicle occupant.
(23) The connection of the tensile means 24 to the tether 26 is shown in detail in FIG. 3. The second end of the tensile means 24 is stitched into or onto a fold 28 of the tether 26. The seam 30 used for this is a tear seam that does not withstand a predetermined stress and tears open. Especially when a particular force acts on the tether 26 in the longitudinal direction thereof and the fold 28 is accordingly strongly pulled apart, the seam 30 tears and releases the second end of the tensile means 24 as FIG. 4 illustrates.
(24) The flap 22 for covering the one or more exhaust orifices 20 is shown in FIGS. 5 and 6 in different positions and in FIG. 7 in detail. The flap 22 includes an edge portion 32 connected to the airbag sheath 18. In the shown embodiments the flap 22 substantially takes the shape of a rectangle stitched to the airbag sheath 18 on one side. The seam 34 used for this purpose is not straight but curved in a special way. More exactly speaking, the path of the seam 34 substantially corresponds to a circular arc of a circle surrounding the exhaust orifice 20 or to a corresponding arc of an ellipse. Also an appropriate angular path is possible and is equally supposed to be covered by the term curved. The free portion 36 of the flap 22 not fastened to the airbag sheath 18 is connected to the tensile means 24.
(25) FIG. 5 illustrates the flap 22 in an initial state. The tensile means 24 put under tension which is fastened to the tether 26 keeps the flap 22 away from the exhaust orifices 20. This position of the flap 22 therefore can also be referred to as release position.
(26) FIG. 6 illustrates the flap 22 in a state in which it is not retained by the tensile means 24. The tensile forces acting in the airbag sheath 18 when the knee airbag 10 deploys and, resp., is held under tension ensure that the flap 22 is folded onto the exhaust orifices 20. The special curved path of the seam 34 is responsible for the flap 22 being swiveled to the right direction. This position of the flap 22 in which it covers the exhaust orifices thus can be referred to as blocking position.
(27) Referring to FIGS. 1 and 2, the different operating mode of the knee airbag 10 for a short and a normal-sized vehicle occupant is described.
(28) FIG. 1 shows a situation with a short vehicle occupant (corresponding to a 5 percent dummy). The legs 14 and especially the knee 38 of the short vehicle occupant have a particular minimum distance x from the Instrument panel 12 in the seating position and posture usually provided for crash tests. The length of the portion of the tether 26 extending between the opposite walls of the knee airbag 10 including the fold 28 to which the tensile means 24 is fastened is larger than the distance x so that the deployment of the knee airbag 10 in the direction of the vehicle occupant is not restricted by the tether 26 but by the vehicle occupant him-/herself, more exactly speaking by his/her legs 14. The tether 26 is not put under tension or is put under so little tension that the seam 30 does not tear.
(29) This state corresponds to the initial state in which the flap 22 is in the release position (cf. FIGS. 3 and 5). That is to say that the tensile means 24 fastened to the tether 26 and to the free portion 36 of the flap 22 is tensioned and keeps the flap 22 away from the exhaust orifice(s) 20 so that gas may escape from the knee airbag 10. Thus the internal pressure of the knee airbag 10 is reduced so that the Impact of the knees 38 of the short vehicle occupant on the fully inflated knee airbag 10 is dampened.
(30) In FIG. 2 the same situation as in FIG. 1 is shown, however with a normal-sized vehicle occupant (corresponding to a 50 percent dummy). The minimum distance y of the legs 16 and, resp., the knees 40 from the instrument panel 12 related to the usual crash test conditions is larger than the distance x in this case. The length of the portion of the tether 26 including the fold 28 is dimensioned so that on these conditions the portion is tensioned so strongly upon deployment of the knee airbag 10 in the direction of the vehicle occupant that the seam 30 tears and releases the tensile means 24.
(31) Since the tensile means 24 is no longer tensioned, the tensile forces in the airbag sheath 18 and the path of the seam 34 ensure that the flap 22 folds onto the exhaust orifice(s) 20 and closes the same. Thus the internal airbag pressure is kept largely constant so as to ensure a protective effect sufficient for the normal-sized vehicle occupant.
(32) As already mentioned, the design and the arrangement of the knee airbag 10 are geared to the leg and knee positions of the respective crash test dummies (5 percent dummy or 50 percent dummy), as they are predetermined by the seating posture and position of the dummies common in the impact tests (no so called OOP positions).
(33) The FIGS. 8 to 12 relate to a special embodiment different from the afore-described embodiment by the configuration of the closing member (flap 22) and the attachment thereof to the airbag sheath 18.
(34) As is evident from FIG. 8, the flat closing member 22 is substantially circular, wherein at the outer periphery equally spaced semicircular recesses 42 are provided. Viewed in the peripheral direction, only the areas between the recesses 42 are provided with seams 34. The individual seams 34 in total result in a curved path. More exactly speaking, the path of the seams 34 substantially corresponds to an (interrupted) circular arc of a circle surrounding the exhaust orifice 20 or a corresponding arc of an ellipse. Also an appropriate angular path is possible and is supposed to be equally covered by the term curved.
(35) FIG. 9 illustrates the mounting of the closing member 22 on the airbag sheath 18 by the seams 34. The closing member 22 is arranged so that it completely covers the exhaust orifice 20 and no gas or only very little gas can escape from the knee airbag 10 through the exhaust orifice 20. Opposite to the exhaust orifice 20, approximately in the center of the closing member 22, the tensile means 24 acts on the closing member 22 on the side facing away from the exhaust orifice 20.
(36) In contrast to the blocking position of FIG. 9, FIG. 10 shows a situation in which the tensile means 24 is put under tension and partly removes the closing member 22 from the exhaust orifice 20 via a deflection arranged for example on the opposite side. This position of the closing member 22 in which, thanks to the recesses 42, gas may exhaust from the knee airbag 10 through the exhaust orifice 20 corresponds to the release position.
(37) The operating mode of the knee airbag 10 including the control means according to FIGS. 8 to 10 is similar to the afore-described embodiment. When, comparable to the situation shown in FIG. 1, the legs 14 or the knees 38 of a short vehicle occupant (corresponding to a 5 percent dummy) have a particular minimum distance x from the instrument panel 12, the deployment of the knee airbag 10 in the direction of the vehicle occupant is not restricted by the tether 26 but by the vehicle occupant him-/herself. In this event the length of the portion of the tether 26 extending between the opposite walls of the knee airbag 10 including the fold 28 to which the tensile means 24 is fastened by the seam 30 is so much larger than the distance x that the seam 30 is not significantly stressed and does not tear (cf. FIG. 3). Hence the tensile means 24 fastened to the tether 26 and the closing member 22 is put under tension and removes the closing member 22 from the exhaust orifice 20as illustrated in FIG. 10so that gas may escape from the knee airbag 10. Thus the internal pressure of the knee airbag 10 is reduced so that the load on the knees 38 of the short vehicle occupant is dampened.
(38) When, on the other hand, comparable to the situation shown in FIG. 2, in the case of a normal-sized vehicle occupant (corresponding to a 50 percent dummy) the minimum distance y of the legs 16 and/or the knees 40 from the instrument panel 12 is larger than the distance x, the portion of the tether 26 including the fold 28 is tensioned so strongly in the direction of the vehicle occupant upon deployment of the knee airbag 10 that the seam 30 tears and the tensile means 24 is released (cf. FIG. 4). Under these circumstances, the tensile forces in the airbag sheath 18 and the internal airbag pressure ensure that the closing member 22 is pressed onto the exhaust orifice 20 and closes the same, as illustrated in FIG. 9. The internal airbag pressure is thus kept largely constant so as to guarantee a protective effect sufficient for the normal-sized vehicle occupant.
(39) In order to meet the described function the closing member 22 need not necessarily be of circular shape. The shape of the recesses 42, too, may deviate from a semi-circle. Basically already one single recess 42 is sufficient as long as the closing member 22 can completely cover the exhaust orifice 20.
(40) In both embodiments the gas escaping through the exhaust orifice(s) 20 can exhaust either directly to the ambience or into an overflow chamber of the knee airbag, as described hereinafter by way of FIGS. 11 and 12.
(41) Related to the flow direction upon filling the knee airbag 10, an overflow chamber 44 of the knee airbag 10 is provided behind the exhaust orifice 20. The overflow chamber 44 is formed by an additional layer 46 that may be attached to the outside of the airbag sheath 18 by a tear seam. The overflow chamber 44 is provided in the lower third of the knee airbag 10.
(42) FIG. 11 shows the knee airbag 10 in the Inflated state with the exhaust orifice 20 being closed. The overflow chamber 44 is not filled with gas in this case, as no gas can flow past the closing member 22.
(43) When the closing member 22 is opened or removed from the exhaust orifice 20, however, i.e. adopts its release position, gas may flow into the overflow chamber 44, as shown in FIG. 12.
(44) Compared to FIGS. 1 and 2, FIGS. 11 and 12 illustrate a variant of the knee airbag 10 in which the overflow orifice 20 is not arranged in the upper third but in the lower third of the knee airbag 10. Moreover, the tensile means 24 is not fastened to a tether but to the instrument panel 12 in this case. The tensile means 24 can act either passively on the closing member 22 or can be actively controlled. In any case the exhaust orifice 20 is released or blocked depending on the expansion of the knee airbag 10 in a particular direction of expansion (especially from the Instrument panel 12 to the legs 14, 16 of the vehicle occupant), just as in all embodiments described hereinafter.
(45) In FIGS. 13 and 14 a special embodiment of the knee airbag 10 is shown in which the effective exhaust cross-section of the exhaust orifice(s) 20 is variable. The closing member 22 in this case is formed as a portion 48 of the knee airbag 10 itself which is folded into the inside of the knee airbag 10, as is evident most clearly from FIG. 14a. In the portion 48 one or more exhaust orifice(s) is/are formed; therefore this portion will be referred to as exhaust portion 48 in the following.
(46) Depending on how far the exhaust portion 48 protrudes from the interior of the airbag to the outside, a differently large effective exhaust cross-section is released. The effective exhaust cross-section is adjusted in turn with the aid of the tensile means 24 whose one end is attached to the exhaust portion 48. The other end of the tensile means 24 can be attached, as in the afore-described embodiments, to a tether 26 or to the instrument panel 12 of the vehicle.
(47) FIGS. 13a and 14a illustrate a situation in which, when the knee airbag 10 is inflated, the tensile means 24 is put under very strong tension and retains the exhaust portion 48 completely inside the airbag. Accordingly, the effective exhaust cross-section is equal to zero and no gas escapes. In the situation shown in FIGS. 13d and 14d the tensile means 24 is not tensioned at all, on the other hand, so that the exhaust portion 48 completely protrudes to the outside. The exhaust cross-section has its maximum size here. FIGS. 13b and 13c and, resp., 14b and 14c show situations between the two extremes in which the tensile means 24 is strongly (FIGS. 13b, 14b) and, resp., weakly tensioned (FIGS. 13c, 14c) and the exhaust cross-section adjusts appropriately.
(48) The exhaust cross-section 48 may also be a separate element connected to the airbag sheath 18.
(49) Another embodiment of the knee airbag 10 is represented in FIGS. 15 through 18. The closing member 22 for blocking and releasing the exhaust orifice(s) 20 in this case is formed similarly to the afore-described embodiment as exhaust portion 48, either as a portion of the knee airbag 10 itself folded into the interior of the knee airbag 10 or as a separate exhaust element connected to the airbag sheath 18.
(50) In this embodiment the tensile means 24 extends in the transverse direction, related to the position of use of the knee airbag 10 in the vehicle, preferably inside a central vertical portion of the knee airbag 10. The tensile means 24 is fastened by one end on the inside of the airbag sheath 18 and by the other end on the exhaust portion 48.
(51) There between the tensile means 24 shows a zigzag path, i.e. the distance of the tensile means 24 from the airbag wall facing the instrument panel 12 and, resp., to the airbag wall facing the legs 14, 16 of the vehicle occupant varies strongly, as is evident most dearly from FIG. 17. This is achieved in the shown embodiment by plural loops 50 arranged in the transverse direction alternately on said airbag walls. The tensile means 24 is guided through the loops 50 like a shoestring so that the zigzag path is resulting.
(52) FIGS. 15 and 17 illustrate a situation in which the legs 16 and, resp., the knees 40 of a vehicle occupant have a distance from the instrument panel 12 which is so large that the knee airbag 10 can fully deploy. This is usually the case with a normal-sized vehicle occupant adopting a normal seating position. The length of the tensile means 24 is dimensioned so that in the case of the fully deployed knee airbag 10 it is tensioned so strongly that the exhaust portion 48 is retained inside the knee airbag 10. Thus no gas is allowed to exhaust from the knee airbag 10 to the ambience or into a possible overflow chamber.
(53) FIGS. 16 and 18 illustrate a situation in which the legs 14 and, resp., the knees 38 of a vehicle occupant have a comparatively small distance from the instrument panel 12. More exactly speaking, the distance is so small that the knee airbag 10 cannot freely deploy, as the legs 14 and, resp., knees 38 penetrate the airbag wall facing them. This can be the case especially with short vehicle occupants who are seated further forward than otherwise usual. Due to the curvatures of the airbag wall facing the legs, the position of at least some loops 50 varies so that the distance of opposite loops is reduced. Thus the tensile means 24 is relaxed as the deflection of the tensile means 24 in total is reduced. As a result the exhaust portion 48 can fold to the outside so that the exhaust orifice(s) 20 is/are released.
(54) The knee airbag 10 can be configured so that also intermediate positions having partly released exhaust orifice(s) are possible corresponding to the afore-described embodiment.
(55) Within the scope of the invention it is possible, as a matter of course, to combine particular aspects of the various embodiments with each other.
LIST OF REFERENCE NUMERALS
(56) 10 Knee airbag 12 fixed vehicle component (instrument panel) 14 legs of a short vehicle occupant 16 legs of a normal-sized vehicle occupant 18 airbag sheath 20 exhaust orifice 22 closing member 24 tensile means 26 tether 28 fold 30 tear seam 32 edge portion 34 seam 36 free portion 38 knee of a short vehicle occupant 40 knee of a normal-sized vehicle occupant 42 recesses 44 overflow chamber 46 additional airbag layer 48 exhaust portion 50 loops
