Adjustment device for longitudinal adjustment of an adjustable vehicle seat

Abstract

The adjusting device (9) for the longitudinal adjustment of a vehicle seat (2) has a first rail (16), in particular an upper rail, and a second rail (18), in particular a lower rail, and at least one locking element which locks the two rails (16, 18) in the event of a crash. The locking element (10) is movably mounted on the first rail (16) in such a way that, in the event of a crash, the locking element (10) is relatively displaced from a rest position into a locked position due to the force of inertia, and the locking element (10) engages the second rail (18) in a form-fitting manner in the locked position. As a result, an adjusting drive (6) is mechanically relieved in the event of a crash and can be designed cost-effectively, particularly for large seating systems.

Description

The invention relates to an adjusting device for longitudinally adjusting an in particular electrically adjustable vehicle seat having a rail system which has two rails mounted one inside the other in a longitudinally displaceable manner.For the electrical longitudinal adjustment, an adjustment drive designed as a spindle drive is usually used, in which a spindle runs within the rail system, which spindle interacts with a spindle nut in order to effect the longitudinal adjustment. The spindle drive furthermore usually has a gear, via which the rotational movement of a frequently flexurally flexible drive shaft is transmitted. Such adjusting devices must be designed to be crash-proof overall, i.e. they must be able to absorb the forces occurring in the event of an accident. Especially in the case of a frontal crash, high loads can be transmitted in the direction of travel to the adjusting device and in particular to the adjusting drive.This problem increases as the mass of the seat to be adjusted increases. Especially in new seat concepts with larger seat systems, which offer new comfort functions, this problem increases. In such seat systems, because of their weight distribution, structural space requirements and due to their functionalities such as belt integration or the like, especially in the case of a frontal crash, high forces acting on the adjusting drive regularly occur. Crash safety is a problem for conventionally used systems. To ensure crash safety, the entire adjusting device including the adjusting drive would have to be made significantly more robust and under certain circumstances would lead to higher costs and also to higher weight in a disadvantageous manner.DE 102 01 092 A1 discloses a locking mechanism for a vehicle bench seat, in which a locking lever locks into a toothing, wherein an inertia body designed as a pendulum acts on the locking lever for actuation.DE 36 12 474 A1 shows a linearly displaceable blocking element with an acceleration-sensitive locking mechanism, in which a pawl is connected to an inertial mass and the latter actuates the pawl in an inertial manner.Proceeding from this, the invention is based on the object of improving the crash safety in an adjusting device for longitudinally adjusting a vehicle seat, so that in the event of a crash the forces are reliably absorbed, wherein conventional, conventional adjusting drives can still be used, in particular without the entire adjusting device and / or the adjusting drive having to be designed newly and more massive.The object is achieved according to the invention by an adjusting device having the features of claim 1. The adjusting device serves for the longitudinal adjustment of an in particular electrically adjustable vehicle seat and has a rail system which has two rails mounted one inside the other in a longitudinally displaceable manner, namely a first rail, in particular a so-called upper rail, and a second rail, in particular a so-called lower rail. Furthermore, at least one blocking element is arranged, which blocks the two rails in the event of a crash, so that a relative movement between these two rails is blocked.The blocking element is movably mounted on the first rail, namely in such a way that in the event of a crash, i.e. when a predefined acceleration is exceeded in a predefined crash direction, in particular in the direction of travel, the blocking element is displaced from a rest position into a blocking position due to the inertial force and the blocking element engages positively in the second rail in the blocking position.Therefore, an additional locking element is integrated directly in the rail system, which remains in its rest position during normal operation and does not influence the normal adjustment operation of the adjustment device in the latter. In contrast, the blocking element is only activated when a predefined acceleration force, which can occur in the event of a crash, is exceeded. In this case, the blocking element moves and is activated and transferred to a blocking position in which it engages in a form-fitting manner between the two rails, so that they are mechanically blocked in alternation.The blocking element therefore forms a crash lock which is triggered and activated when a predefined acceleration force for which the crash lock is formed is exceeded.In the event of a crash, crash forces are hereby introduced via the locking element directly from one rail into the other rail via the locking element, so that at the same time the remaining adjusting device and in particular an adjusting drive, especially a spindle drive, is mechanically relieved. As a result, the adjustment drive can be designed to be simpler and less robust than in comparison to a situation in which the adjustment drive would have to absorb the entire crash forces. The locking element therefore makes it possible to use conventional adjusting devices even in the case of relatively large seat installations, which keeps costs low and also leads to a low weight.In a preferred embodiment, the second rail has at least one latching recess and preferably a plurality of latching recesses arranged one behind the other in the longitudinal direction. In the blocking position, the blocking element engages in at least one of these latching recesses, which are typically designed as windows, and thus establishes the form-fitting connection with the second rail. For this purpose, the locking element has, in particular, a locking nose, that is to say a formation with which it engages in the latching recess.In an expedient development, a holding element is formed which holds the blocking element in its rest position. In particular, it is a mechanical holding element which engages in a positive-locking manner in the blocking element.In a preferred embodiment, the blocking element has a bulge in which the holding element engages. The holding element in turn has or is formed by an extension or holding lug protruding in the direction of the blocking element. The retaining element ensures that, during normal operation, the blocking element remains in the rest position.In an expedient embodiment, the blocking element is held in its rest position by spring force. In particular, the spring force presses the blocking element with its bulge against the holding element. The spring force is preferably dimensioned such that it is overcome when the predetermined acceleration force is exceeded and thus also taking into account the mass of the locking element, so that the locking element is transferred from the rest position into the locking position. The inertial force occurring when the predetermined acceleration force is exceeded is therefore greater than the spring force.According to the invention, an abutment for the blocking element is formed, against which the blocking element is pressed due to inertia in the event of a crash and in the crash direction. The blocking element is therefore displaced in the direction of the abutment in the event of a crash. A (counter) force is exerted on the blocking element by the abutment, wherein the abutment and a corresponding abutment section on the blocking element are formed and / or positioned in such a way that the force generated in this case transfers the blocking element into its blocking position. In this preferred embodiment variant, therefore, the inertial force is suitably deflected by means of the abutment in order to cause a change in direction of the movement of the locking element, so that the latter is transferred into the locking position.In a preferred alternative embodiment variant, a guide is formed, for example, in the manner of a link for the blocking element, so that the latter is guided along a predefined path by the inertial force in the event of a crash and is transferred in particular along an arcuate path into the blocking position. In particular, in such a way that the locking element is displaced in the direction of the second rail, specifically in order to engage in the previously described latching recess.According to a further alternative embodiment variant, the blocking element or at least a part thereof is prestressed by means of spring force in the direction of the blocking position. In addition, a locking mechanism for a spring or for the prestressed part of the blocking element is active in the rest position, wherein this locking mechanism is canceled due to inertia in the event of a crash.In the preferred embodiment variant with the abutment, which is formed opposite the blocking element in the crash direction and thus in particular in the direction of travel, the abutment and the blocking element are positioned and / or formed in combination in such a way that a torque is exerted on the blocking element, so that in the event of a crash this exerts a rotational movement for transferring into the blocking position.In a preferred embodiment, the abutment and the corresponding abutment section are arranged eccentrically with respect to a center of mass of the blocking element, so that the desired torque is generated by the eccentric, one-sided support and the inertial force.Specifically, a tilting movement of the entire locking element about a tilting axis is provided here. In particular, the tilting movement pivots a rear end of the blocking element downward in the direction of the lower rail.With regard to the highest possible rigidity, the first rail (upper rail) is regularly designed in the manner of a profile rail which can also have a plurality of rail profiles connected to one another, wherein for stability reasons a circumferentially closed or at least largely closed profile is frequently designed. In an expedient embodiment, the first rail has an opening oriented in the direction of the lower rail, which is formed in particular as a recess in a base of the upper rail. In the region of the opening, the blocking element is arranged through which the blocking element, at least the blocking nose, which engages in the second rail in a positive-locking manner, passes during the transition from the rest position into the blocking position.In the event of a crash, the adjusting device is generally typically subjected to such high forces that a deformation in particular also of the first rail occurs. This is now utilized in the present case in such a way that the locking element and in particular the previously described locking nose is preferably irreversibly clamped between the two rails and is also clamped accordingly in the event of a crash.For this purpose, in particular the locking nose is clamped between an opening edge of the first rail and an opening edge of the second rail. The locking nose therefore abuts with a front locking flank on one opening edge and with a rear locking flank on the other opening edge. The opening edges are in particular an opening edge of the latching recess in the second rail and an opening edge of the opening of the first rail.By the supplementary utilization of the deformation occurring in the event of a crash for clamping the locking nose, it is reliably ensured that the locking element remains in the locking position. Since the deformation is a plastic deformation, this clamping of the locking nose between the two rails is irreversible and permanent.According to a preferred embodiment, an adjusting element and in particular a spindle for the longitudinal adjustment is arranged within the rail system. Specifically, the adjusting element runs in a cavity of the rail system in the longitudinal direction. In a preferred embodiment, the blocking element is now arranged laterally next to this adjusting element. This thus makes use of the installation space which is present in any case and no additional installation space is required.In a preferred development, the blocking element is arranged in a guide housing and forms with the latter an in particular prefabricated structural unit which is inserted into the rail system and in particular into the upper rail. This structural unit therefore forms the crash lock.This offers the advantage that minor changes need to be made at most to a conventional, conventional rail system in order to realize the crash safety described here. The structural unit and thus the guide housing is placed at a suitable location in the rail system, specifically on the upper rail, and is fastened there in a suitable manner, for example by welding, adhesive bonding or else by means of a latching or screw connection. Since the crash lock is inoperative in normal operation, it is not loaded in normal operation. And also in the event of a crash, the fastening of the crash lock in the rail system plays no role, since its effect is based on the locking element being transferred into the locking position and the locking nose in particular being irreversibly clamped there, as described above. The guide housing does not have to be able to absorb and transmit forces.All of the features described above, such as, for example, the abutment, the holding element or else a spring element which generates the spring force, are preferably integral functional components of the structural unit and / or of the guide housing.In a preferred embodiment, a chamber is formed in the guide housing, in which a spring element is located, via which a spring force is generally exerted on the blocking element, specifically in order to hold it in its rest position, as has been explained above. The spring element is arranged in particular opposite the above-described holding element.The guide housing preferably has a side wall which runs in the longitudinal direction and in particular parallel to a lateral rail wall. In the transverse direction to this, further transformations are formed which are configured for guiding the blocking element in particular. The guide housing is preferably open to one side in the transverse direction, so that the blocking element can be inserted into the guide housing.In a preferred embodiment, the blocking element has an upper and a lower edge side, via which the blocking element is mounted so as to be longitudinally displaceable, so that in the event of a crash it is guided over these edge sides. These cooperate with corresponding guide surfaces, which are formed in particular on the guide housing. For this purpose, the guide housing has in particular an upper and a lower guide web along which the edge sides of the locking element slide.In a preferred embodiment, a plurality of locking elements are furthermore arranged, which are arranged one behind the other in particular in the longitudinal direction of the rail system. This measure increases the blocking force and thus the crash safety. This is the case in particular in seat systems in which very long rails are used and in which, for example, a plurality of adjustable seats are also mounted on the rail system.In a preferred embodiment, the blocking element is formed as a flat sheet metal component, in particular made of steel, which extends in the longitudinal direction and which forms the blocking nose on its lower edge side. Overall, therefore, this is a simple, flat component which is produced cost-effectively, for example, by punching from a flat sheet metal.An exemplary embodiment of the invention is explained in more detail below with reference to the figures. These show: FIG. 1 is a perspective side view of a seat system for a motor vehicle, FIG. 2 shows a detail longitudinal section through a rail system with a blocking element as a crash barrier, FIG. 3 shows an exploded view of a structural unit which forms the crash lock with a guide housing and a locking element, FIG. 4 shows a perspective view of a detail and a partial section of the rail system in the region of the blocking element, and FIG. 5 shows a cross-sectional illustration through the rail system in the region of the blocking element.FIG. 1 shows a seat system having two vehicle seats 2, which are mounted jointly on a rail system 4 and can be adjusted electrically in or counter to a longitudinal direction L. In the present case, the longitudinal direction L corresponds, in the mounted state and during operation, to a (forward) direction of travel of the vehicle. For the electrical adjustment, an electrical adjustment drive 6 is arranged, which is designed in particular as a spindle drive. In the region marked with a dashed circle, a crash barrier 8 is attached, as is explained in detail below in connection with the further figures. The rail system 4 together with the adjustment drive 6 and the crash lock 8 form an adjustment device 9.In the exemplary embodiment, the crash lock 8 is designed as a pre-assembled structural unit (see in particular also FIG. 3 ), which has as essential components a locking element 10 and a guide housing 12, in which the locking element 10 is located and in which it is guided. Furthermore, in the exemplary embodiment, the crash lock 8 also has a spring element 14. Further elements preferably do not have the crash lock 8.The rail system 4 has two rail strands arranged parallel to one another, each of which has a first rail, referred to below as upper rail 16, and a second rail, referred to below as lower rail 18. The two rails 16, 18 are mounted on one another in a longitudinally displaceable manner. The lower rail 18 is fixedly connected in the assembled state to a supporting body component of the vehicle, in particular by screws.The crash lock 8 is arranged in a free inner hollow space, in particular of the upper rail 16. For this purpose, the guide housing 12 is suitably fastened to the upper rail 16, especially to a side wall of the upper rail 16.The upper rail 16 can consist of several rail profiles connected to one another. It has an opening 20 on its underside oriented in the direction of the lower rail 18. This is formed, for example, as a recess in an otherwise closed base of the upper rail 16. Alternatively, the upper rail 16 is open downward toward the lower rail 18.The bottom side of the lower rail 18 has a plurality of latching recesses 24, which follow one another in the longitudinal direction L, in particular at the same distance from one another.The opening 20 in the upper rail 16 is formed below the crash lock 8 and in particular below the locking element 10. At the same time, the guide housing 12 also has a passage region 22 in the direction of the opening 20 of the upper rail 16 and thus in the direction of the lower rail 18 or is open in the direction of the lower rail 18.The exact structure and the function of the crash lock 8 will be explained in more detail in connection with FIGS. 2 and 3 :In normal operation, the blocking element 10 is in a rest position, as is illustrated in FIG. 2 by a solid line of the blocking element 10. In the event of a crash, especially in the event of a frontal crash and the high forces accompanying it in the longitudinal direction L (direction of travel), the locking element 10 is displaced in the crash direction due to inertia and is transferred into a locking position. In the event of a frontal crash, the crash direction corresponds to the direction of travel and thus to the longitudinal direction L. This movement process is illustrated in FIG. 2 by a dashed illustration of the locking element 10 in two different positions.The blocking element 10 is preferably a flat sheet metal component, in particular made of steel, with a high rigidity. It extends in the longitudinal direction L from a rear end to a front end. It has an upper edge side 25 and a lower edge side 26, which each extend in the longitudinal direction L. On the lower edge side 26, a locking nose 28 is formed, which is oriented downwards in the direction of the lower rail 18. In the longitudinal direction L directly adjacent to the locking nose 28, the locking element 10 has an indentation 30.The front edge side of the locking nose 28 in the longitudinal direction forms a front locking flank 32, and a rear locking flank 34 is formed opposite, namely in particular by a section of a front edge of the rear end. On this end edge, the blocking element 10 furthermore has a depression or indentation, which forms a holding element 36. Assigned to this, a retaining lug 38 is formed on the guide housing 12 at its rear end, which retaining lug engages in the retaining element 36 formed by the indentation in the rest position of the blocking element 10 and thus fixes the blocking element 10, specifically in particular in a defined height position.In the exemplary embodiment, a downwardly projecting nub 40 is formed on the lower edge side 26 in a front sub-region. The blocking element 10 is therefore curved at this location.At the front end, the blocking element 10 has a guide nose protruding forward, which serves to hold the spring element 14.The guide housing 12 also extends, corresponding to the locking element 10, from a rear end to a front end in the longitudinal direction L. The spring element 14 is arranged at the front end. For this purpose, the guide housing 12 forms a chamber 42 in which the spring element 14 is located and transmits a spring force counter to the longitudinal direction L to the blocking element 10. The spring force therefore presses the blocking element 10 with its rear end against a rear wall of the guide housing 12 and specifically against the retaining lug 38, so that the blocking element 10 is fixed in its rest position.As can be seen in particular from FIG. 3, the guide housing 12 has a flat, lateral base plate which forms a side wall 44. By means of further wall regions, the previously described chamber 42 as well as the previously described retaining noses 38 are formed. On the upper side, the guide housing has an upper guide web 46. In the rest position, the locking element 10 rests with its upper edge side 25 on this upper guide web 46 and is guided by it.On the opposite underside, the guide housing 12 has a lower guide web 48 which adjoins the passage region 22 to the front. The locking element 10 is supported on this lower guide web 48 with its lower edge side 26 and in particular with the nub 40.As can be seen specifically from FIG. 3, in the exemplary embodiment, the guide housing 12 has, on its side opposite the side wall 44, an open region on which preferably extends virtually (for example greater than 90%) over the entire length of the blocking element 10 and preferably additionally preferably also virtually or over the entire width of the blocking element 10, such that said blocking element can be inserted laterally into the guide housing 12 from the one side. The guide housing 12 is therefore formed as an open housing toward one side.At its front end, the guide housing 12 also has an abutment 50, on which the blocking element 10 is supported by an abutment portion 52 in the event of a crash. In the exemplary embodiment, this is formed in the manner of a nub protruding forward. It should be emphasized that the abutment section 52 is arranged eccentrically. This is understood to mean that the abutment section 52 is arranged laterally next to and in particular above a center of mass M of the blocking element 10 and in particular above a center of mass line running parallel to the longitudinal direction, with respect to the longitudinal direction L. The line of gravity passes through the center of gravity M.The blocking element 10 is freely supported within the guide housing 12 and is preferably held in its rest position exclusively by the spring force of the spring element 14 in cooperation with the holding element 36 and the holding lug 38.As can also be seen in particular from FIG. 2, the opening 20 has an opening edge 20A which is formed by an end face of a section of the upper rail 16. This section and thus the opening edge 20A are preferably positioned such that in the rest position the locking element 10 is arranged with a rear support section 54 formed subsequently to the locking nose 28 above this section of the upper rail 16 and is supported in particular in a complementary manner on the upper rail 16 in the rest position.In the event of a crash, an inertial force acting in the longitudinal direction L is applied to the locking element 10, so that the latter is displaced forward in the longitudinal direction L. As a result, the holder in the region of the holding element 36 is initially released. Preferably, the locking element 10 is offset in the longitudinal direction to such an extent that the rear end and thus the support section 54 is located in front of the opening edge 20 in the longitudinal direction and thus above the opening 20.During this longitudinal displacement, the blocking element 10 is pressed with its abutment section 52 against the abutment 50 on the guide housing 10. Due to the off-center placement-i.e. due to the arrangement of the abutment 50 and the abutment section 52 laterally next to and in particular above the center of mass M-a torque is generated so that the locking element 10 is rotated in the direction of the lower rail 18 due to the inertial force. Preferably, the blocking element 10 is supported, in particular with its nub 40, on the lower guide web 48, so that a pivot bearing is formed in the region of this nub 40.The locking nose 28 thereby engages in the locking recess 24 and the front locking flank 32 comes to rest against an opening edge 24A of the locking recess 24, which already achieves a positive locking and thus a blocking between the two rails 16, 18.In addition, it is also utilized in the present case that the upper rail 16 is deformed by the crash forces that occur, so that it is compressed more or less in the longitudinal direction L, as a result of which the opening edge 20A of the opening 20 is likewise offset in the longitudinal direction L and is pressed against the rear locking flank 34 of the locking nose 28. As a result, the locking nose 28, in particular the two locking flanks 32, 34, is clamped between the two opening edges 20A, 24A. This results in a permanent, massive blocking of the relative displacement between the two rails 16, 18.With reference to FIGS. 4 and 5, the positioning of the crash barrier 8 within the rail system 4 can be clearly seen. Specifically, the entire structural unit which forms the crash lock 8 is arranged within a cavity of the rail system 4 and specifically within the upper rail 16. Within this cavity, an adjusting element, in particular a spindle 56 of the adjusting drive 6 designed as a spindle drive, preferably also runs.As can be seen specifically from FIG. 4, the crash lock 8 is arranged laterally next to the spindle 56. Therefore, no additional installation space is required.The two rails 16, 18 are, as usual, mutually interlaced and guided displaceably on one another. In the exemplary embodiment, the upper rail 16 consists of a plurality of rail elements which are firmly connected to one another. The upper rail 16 is surrounded on the edge side by the lower rail 18.The crash lock 8 described here mechanically relieves the adjustment drive 6 in the event of a crash. The forces to be absorbed are therefore absorbed in particular partially by the crash lock 8 and partially by the adjusting drive 6. Preferably, a plurality of such crash locks 8 are arranged one behind the other offset in the longitudinal direction L.List of reference characters2 Vehicle seat 4 rail system 6 adjusting drive 8 crash lock 9 adjusting device 10 locking element 12 guide housing 14 spring element 16 upper rail 18 lower rail 20 opening 20A opening edge of the opening 22 passage region 24 latching recess 24A opening edge of the latching recess 25 upper edge side 26 lower edge side 28 locking nose 30 indentation 32 front locking flank 34 rear locking flank 36 holding element 38 holding nose 40 nub 42 chamber 44 side wall 46 upper guide web 48 lower guide web 50 abutment 52 abutment portion 54 support portion 56 spindle L longitudinal direction M center of mass

Claims

Adjusting device (9) for longitudinally adjusting an adjustable vehicle seat (2) having a rail system (4) extending in a longitudinal direction (L) and having two rails mounted one inside the other in a longitudinally displaceable manner, namely a first rail (16), in particular an upper rail and a second rail (18), in particular a lower rail, having at least one blocking element which blocks the two rails (16, 18) in the event of a crash, wherein the blocking element (10) is mounted movably on the first rail (16), characterized in that the blocking element (10) is mounted in such a way that, in the event of a crash, the blocking element (10) is displaced relatively from a rest position into a blocking position due to the force of inertia and the blocking element (10) engages positively in the second rail (18) in the blocking position, wherein an abutment (50) for the blocking element (10) is formed and, in the event of a crash, the blocking element (10) is displaced in a crash direction, In particular, in the longitudinal direction (L) the force is pressed against the abutment (50) due to inertia and a force is exerted on the blocking element (10) by the abutment (50), so that the blocking element (10) is transferred into its blocking position.Adjusting device (9) according to the preceding claim, wherein the second rail (18) has at least one latching recess (24) and in particular a plurality of latching recesses (24) in the longitudinal direction (L), and the locking element (10) has a locking nose which engages in the at least one latching recess (24) in the locking position.Adjusting device (9) according to one of the preceding claims, wherein a holding element (36) is formed and the blocking element (10) is held in its rest position by the holding element (36).Adjusting device (9) according to one of the preceding claims, wherein the blocking element (10) is held in its rest position by spring force.Adjusting device (9) according to one of the preceding claims, wherein the abutment and the blocking element (10) are designed in such a way that a torque is exerted on the blocking element (10) and this exerts a rotational movement and in particular a tilting movement in the event of a crash, wherein the blocking element (10) is supported eccentrically on the abutment (50), so that the torque is generated.Adjusting device (9) according to one of the preceding claims, wherein the first rail (16) has an opening (20) oriented in the direction of the second rail (18), through which the blocking element (10) passes during the transition from the rest position into the blocking position.Adjusting device (9) according to one of the preceding claims, wherein the first rail (16) is subject to deformation in the event of a crash such that the blocking element (10) is in particular irreversibly clamped between the two rails (16, 18).Adjusting device (9) according to the preceding claim, wherein a locking nose (28) of the locking element (10) is clamped between an opening edge (20A) of the first rail (16) and an opening edge (24A) of the second rail (18).Adjusting device (9) according to one of the preceding claims, wherein an adjusting element (56), in particular a spindle (56) for the longitudinal adjustment, is arranged within the rail system (4) and the blocking element (10) is arranged laterally next to the adjusting element (56).Adjusting device (9) according to one of the preceding claims, wherein the blocking element (10) is arranged in a guide housing (12), with which it forms a structural unit which is inserted into the rail system (4).Adjusting device (9) according to the preceding claim, wherein the guide housing (12) has a chamber (42), in which a spring element (14) is located, via which a spring force is exerted on the blocking element (10).Adjusting device (9) according to one of the preceding claims, wherein the blocking element (10) has an upper and a lower edge side (25, 26), via which it is mounted in a longitudinally displaceable manner.Adjusting device (9) according to one of the preceding claims, wherein the blocking element (10) is formed as a flat sheet metal component which extends in the longitudinal direction (L) and which has a blocking nose (28) on a lower edge side (26), with which the blocking element (10) engages positively in the second rail (18) in the blocking position.Adjusting device (9) according to one of the preceding claims, in which a plurality of locking elements (10) are arranged in the rail system (4).

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