Abstract:
A motor vehicle seat has a pivoted backrest that can be swung forward in the direction of a seating of the seat, a longitudinal seat adjuster for adjusting the longitudinal position of the seat, a locking device of the longitudinal seat adjuster for locking a longitudinal seat position previously adjusted, and an unlocking mechanism for unlocking the locking device, and a flexible traction device via which the unlocking mechanism is coupled with the backrest so that the locking device is unlocked when the backrest is swung forward. An actuation element acts upon the traction device with a force component at an angle to the direction of extension of the traction device when the backrest is swung forward, thereby tightening the traction device and unlocking the locking device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
   This application is a National Phase Patent Application of International Application Number PCT/DE02/03268, filed on Aug. 30, 2002, which claims priority of German Patent Application Number 101 43 721.8, filed on Aug. 31, 2001. 
   BACKGROUND 
   A vehicle seat comprises a pivotally mounted backrest which can be folded forwards towards the seat surface of the seat, a seat longitudinal adjuster with which the longitudinal position of the seat (position in the vehicle longitudinal direction) can be adjusted, a fixing device for the seat longitudinal adjustment with which a previously set seat longitudinal position can be locked, a release mechanism with which the fixing device can be released in order to be able to set a different seat longitudinal position, as well as a flexible traction means through which the release mechanism is coupled to the backrest so that the fixing device is released when folding the backrest towards the seat surface. 
   With a vehicle seat of this kind, the fixing device can be released by folding the backrest forwards towards the seat surface so that the seat can be moved forwards to facilitate passengers entering the back of the vehicle. An “easy-entry mechanism” of this kind is widely used in the case of two-door vehicles. 
   However a problem exists in that many users find that the amount of force required to fold the backrest forwards is too high. In particular, a considerable force is necessary to release the seat longitudinal adjuster since, as a rule, its locking mechanism is pretensioned for safety reasons towards the locked state by elastic elements. 
   The object of the invention is to improve a vehicle seat of this kind regarding operating comfort. 
   SUMMARY 
   When the backrest is folded forward, an operating element acts on the traction means with a force component transverse to the extension direction of the traction means so that the traction means are tightened and the fixing device is released. The action of the actuating element on the traction means thereby unfolds so that the actuating element is moved with a component perpendicular to the extension direction of the traction means and is thereby in contact with the traction means. In a further embodiment, the actuating element presses against the traction means from above. 
   As opposed to known mechanism for releasing the seat longitudinal adjuster by folding the backrest forwards, here in order to tighten the traction means through which the release is to be actuated, the force is not exerted in the extension direction of the traction means on one end of the traction means, rather it is exerted having a component across the extension direction of the traction means on a section of the traction means. The resulting force need thereby not be aligned exactly perpendicular to the extension direction of the traction means as corresponds to one embodiment. It is sufficient if the force exerted by the actuating element on the traction means has at least a force component transverse to the extension direction of the traction means. 
   With this, when compared with arrangements known from the prior art a reduction of the force necessary to be applied by folding the backrest forwards is achieved by utilizing the advantage present with a block and tackle. 
   Furthermore, with the arrangement according to an embodiment of the invention, the traction means can be completely pre-fitted on the seat lower frame given that no connection is required between the traction means and backrest. In this manner the backrest can act through the actuating element on the traction means fixed on the lower frame. 
   The actuating element preferably acts on a section of the traction means which is spaced from the backrest-end of the traction means. 
   The actuating element is advantageously formed rotationally symmetrical relative to an axis and is mounted rotatable about this axis. In an exemplary embodiment of the present invention, a roller is used as an actuating element. In alternative embodiments, in the case of a vehicle seat, elements which are provided for other purposes, such as e.g. an axle shaft of a seat axle can also be used as actuating elements. In a further embodiment, the actuating element can also be formed through a slider which consisting of plastics. 
   Several actuating elements may also be provided for acting on the traction means for the best possible reduction of the force to be applied. These actuating elements act on the traction means similar to a block and tack having several loose rollers. 
   The traction means itself is fixed by its backrest end at a suitable fixing point on the seat frame, e.g. on a seat side part. The fixing point is selected so that when the backrest is folded forwards the fixing point is not moved; more particularly it is not pivoted together with the backrest. 
   In a further embodiment of the invention, a guide element is provided to guide the traction means so that a section of the traction means runs at a suitable angle, more particularly perpendicular to the active direction of the actuating element. This guide element is preferably formed by a roller (which may be a fixed roller) which interacts with the actuating element provided for acting on the traction means for obtaining the block and tackle effect. 
   The actuating element can be readily arranged so that when the backrest is folded forwards by pivoting, it can be brought into engagement with the traction means. For this the actuating element is mounted on a body which is movable, more particularly pivotal, when the backrest is folded forwards. 
   In a further embodiment, the backrest acts with a follower on a stop associated with the actuating element when folding forwards in order to bring the actuating element into engagement with the traction means. The follower and stop are thereby positioned so that the release process only starts after folding the backrest forwards about a certain minimum amount. 
   Further features and advantages of the invention will be apparent from the following description of an embodiment with reference to the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an arrangement in which a backrest raised up substantially vertical, when folded forwards to release the fixing device of a seat longitudinal adjuster, acts on a traction means; 
       FIG. 2  shows the arrangement of  FIG. 1  in which the backrest is folded forwards towards the seat surface; 
       FIG. 3  shows a diagrammatic view of a motor vehicle seat. 
   

   DETAILED DESCRIPTION 
     FIG. 3  shows diagrammatically a frame G of a motor vehicle seat having a seat side part T which is connected through a lever pair H 1  and H 2  vertically adjustable to the top rail O of a rail longitudinal guide. The rail longitudinal guide consists of two rails O, U displaceable relative to each other in the longitudinal direction L and serve to hold a seat trough having a seat cushion. The rail longitudinal guide is lockable by means of a fixing device F so that the seat longitudinal position actually set is fixed. For safety reasons, the fixing device F is normally pretensioned towards its locked state by means of elastic elements so that the seat longitudinal position is constantly fixed unless the locking of the fixing device F is actively released against the action of the elastic element. 
   A backrest frame R of a seat back is pivotably attached to the seat side part T, and can pivot in a useful region in order to set the backrest incline corresponding to the requirements of the relevant seat user. The backrest frame R can be folded forwards towards the seat surface (or seat cushion) in order to release the fixing device F and slide the seat, with the backrest folded forwards (this is known as an easy-entry function). For this, the backrest frame R is coupled to the fixing device F, which will be described with reference to  FIGS. 1 and 2 , through a coupling mechanism K (diagrammatically shown in  FIG. 3 ). 
   An easy-entry mechanism of the type described with reference to  FIG. 3  is known from, for example, WO 00/55002 (apart from the novel action according to the invention of the backrest with R on the coupling mechanism K which will be described with reference to  FIGS. 1 and 2 ). As such, details regarding the design of this mechanism will not be described. Instead, in this respect reference is made to the WO 00/55002A1. 
     FIG. 1  shows a part of the backrest R of the vehicle seat according to  FIG. 3  which is pivotably attached to a projection FT of a seat side part T of the vehicle seat. The backrest R can be set in different useful positions by pivoting about its swivel axis to support the back of the occupant. The backrest can also be folded forwards towards the seat surface in order to release the easy-entry mechanism explained with reference to  FIG. 3 . 
   In  FIG. 1 , the backrest R is located in a useful position in which it is set substantially perpendicular. 
   On the protection FT of the seat side part T on which the backrest R is mounted for swivel movement, body a  1  comprising a cam is mounted to pivot what the backrest R about an axis  10 . The pivotal body  1  has a stop  15  associated with a follower  16  which is pivoted clockwise together with the backrest when the backrest R is folded forwards towards the seat surface. In this manner the follower  16  moves into engagement with the stop  15  so that on folding the backrest R further forward, the pivotal body  1  is entrained by the follower  16  through the stop  15 , and is pivoted about its axis  10 . 
   A roller  2  is mounted rotatable about an axis  20  on a lug  11  of the pivotal body  1 . Underneath the roller  2 , a section  50  of a traction means  5  (which in the exemplary embodiment shown comprise a cable) is guided. The traction means  5  serves to couple the backrest R to the fixing device of a seat longitudinal adjuster. By tightening the traction means  5 , the fixing device can be released. The traction means  5  is connected by one end to the fixing device. The other end  51  (backrest side end) of the traction means  5  comprises a nipple, and is suspended through a stop  52  from the seat side part T. The traction means  5  extends by its section  50  beneath the pivotal body  1  to a roller  3  (fixed roller) rotatably mounted on the seat side part about an axis  30 . The roller  3  serves as a guide element. Using the roller  3 , the traction means is guided towards the fixing device to be actuated. The traction means is guided in a Bowden sleeve  6  along the connecting path from the roller  3  to the fixing device to be actuated. The Bowden sleeve is supported on a support element  60  provided on the seat side part T. 
   The arrangement illustrated in  FIG. 2  shows the backrest R of  FIG. 1  folded forwards from its substantially perpendicular position towards the sitting surface of the seat. 
   On folding the backrest R forwards the follower  16 , which is connected in suitable manner to the backrest R and at first is spaced from the stop  15  of the pivotal body  1 , is moved (clockwise) and thereby strikes the stop  15  after a certain pivotal angle. Only at this point does a swivel movement of the body  1  start which is entrained by the follower  16  and the associated stop  15  and is thus pivoted together with the backrest R. The pivotal body  1  can be pretensioned by means of an elastic element (not shown) in the direction of its position illustrated in  FIG. 1  (in which it does not act on the traction means  5 ). In this manner, the pivotal body  1  would be entrained by the follower  16  against this pretensioning force if the backrest is folded forwards and thereby act on a section  50  of the traction means  5 . 
   When swiveling the body  1  clockwise (corresponding to folding the backrest R forwards) its nose  11  is moved with the roller  2  mounted rotatable thereon towards the section  50  of the flexible traction means extending underneath the body  1 . The roller  2  thereby acts with a force component running perpendicular to the extension direction of the said section  50  of the traction means  5  onto the section  50  of the traction means  5 . The traction means  5  is thereby guided in suitable guide channels of the rollers  2  and  3 . In addition, further guide means may also be provided on the seat side part in order to guide the section  50  of the traction means  5  running underneath the rotary mounted roller  2  along a defined path so that the roller may act thereon. 
   In this manner, the said section  50  of the traction means  5  is curved and the traction means tightened overall. A force thus acts on the part of the traction means  5  guided in the Bowden sleeve  6  along a traction direction Z towards the cable roller  3  serving to deflect the traction means  5  (and thus away from the fixing device of the seat longitudinal adjuster). As known in the prior art, the fixing device of the seat longitudinal adjuster may thus be released by the locking elements of the fixing device being lifted from their locking position against the action of elastic elements. 
   As opposed to the arrangements known from the prior art, to tighten the traction means  5  in an exemplary embodiment of the present invention, no force is exerted on the backrest side end  51  of the traction means  5  in the extension direction of the corresponding section  50  of the traction means  5 . The backrest side end  51  of the traction means  5  is rather fixed spatially and is not moved when folding the backrest forwards. Instead of this, an action of an actuating element on a section  50  of the traction means takes place perpendicular to its extension direction through which this section is curved. This has the result of tightening the traction means  5  (corresponding to a shortening of the effective length of the traction means) through which the fixing device of the seat longitudinal adjuster can be released. In order to slide the traction means  5  with its section guided in the Bowden sleeve  6  about a certain amount in the traction direction Z sufficient to release the fixing device, there is need for a larger adjusting path of the roller  2  acting on the traction means  5  compared with an actuating element which acts with a tractive force directly on the backrest side end  51  of the traction means  5 . Since the work to be applied to overcome the pretensioning force of the elastic elements of the fixing device is the same in both cases, this has the result that it is not necessary to apply as large a force with the embodiments of the present invention shown as compared to the prior art.