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CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a United States National Phase Application of International Application PCT/EP2013/060235 filed May 17, 2013 and claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2012 015 854.8 filed Jun. 1, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a locking unit for a vehicle seat with a pivotably mounted rotary latch for locking with a bolt and with a latching pawl which, in the event of a crash, secures a locked state of the locking unit by the rotary latch being supported on a first contact point on the latching pawl. The invention also relates to a vehicle seat with the at least one locking unit. 
     BACKGROUND OF THE INVENTION 
     DE 10 2008 051 832 A1 discloses a locking unit of the type in question for a vehicle seat. A locking unit of this type comprises a pivotably mounted rotary latch for locking with a bolt. A latching pawl which is mounted pivotably about another pivot axis secures the rotary latch in the locked state. A tensioning element which is referred to as a tolerance-compensating pawl exerts a closing moment on the rotary latch and thereby eliminates play present between the rotary latch and the bolt. 
     The latching pawl and the tensioning element are arranged axially offset next to each other on a bearing bolt so as to be pivotable about the same axis and interact with the rotary latch. In the event of a crash, first of all only the latching pawl secures the rotary latch by the rotary latch being supported on a contact point on the latching pawl. The crash load which is transmitted by the bolt to the rotary latch in the event of a crash is absorbed here by the contact point of the rotary latch with the latching pawl. 
     In the event of a high crash load, the rotary latch is displaced until it comes to bear against the housing of the locking unit. This gives rise to a second contact point which can additionally absorb the crash load. A deformation of the rotary latch by the bolt can also occur. 
     SUMMARY OF THE INVENTION 
     The invention is based on an object of improving a locking unit of the type mentioned at the beginning, in particular of specifying an alternative possibility for increasing the load-absorption capacity in the event of a crash, in order to increase the crash safety of a vehicle seat. 
     A locking unit of the type in question for a vehicle seat comprises a pivotably mounted rotary latch for locking with a bolt, and a latching pawl which, in the event of a crash, secures a locked state of the locking unit by the rotary latch being supported on a first contact point on the latching pawl. 
     According to the invention, it is provided that, during a deformation in the event of a crash, the rotary latch is additionally supported on a second contact point, the second contact point being provided on the latching pawl. 
     Owing to the fact that, in the event of a crash, when the rotary latch is deformed, there is in addition to the first contact point with the latching pawl also a second contact point with the latching pawl, the crash load transmitted by the bolt to the rotary latch can be absorbed by two contact points. The load-absorbing capability of the locking unit is therefore increased. 
     The rotary latch is advantageously mounted pivotably here about a first bearing bolt, and the latching pawl is mounted pivotably about a second bearing bolt, the bearing bolts running offset in parallel. 
     Owing to the geometrical arrangement of the rotary latch and of the latching pawl on two bearing bolts which are offset in parallel and each define a pivot axis, it is relatively simple to ensure that, during the locking and unlocking of the locking device, the second contact point does not exist and therefore does not obstruct locking or unlocking. 
     The second contact point is realizable in a relatively simple manner in that the latching pawl has a latching pawl cutout which is bounded by a latching pawl step which forms the second contact point during the deformation in the event of a crash. 
     For the interaction with the second contact point, the rotary latch advantageously has a lug which, in the locked state, projects into the latching pawl cutout. 
     During the deformation in the event of a crash, the rotary latch is advantageously in self-locking contact with the latching pawl at the second contact point. Opening of the locking device is thereby prevented. 
     According to an advantageous refinement of the invention, during the deformation in the event of a crash, the rotary latch bears in a form-fitting manner against the second contact point. 
     It is particularly advantageous in this case if the second contact point has a toothing with which a rotary latch toothing of the rotary latch enters into toothed engagement during the deformation in the event of a crash. 
     If, in the locked state, a tensioning element exerts a closing moment on the rotary latch, a play present between the rotary latch and the bolt can thereby be eliminated. 
     According to an advantageous refinement of the invention, the rotary latch and the latching pawl are arranged within an at least partially closed housing. 
     The object is also achieved by a vehicle seat with at least one locking unit according to the invention. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is an exploded illustration of a locking unit; 
         FIG. 2  is a top view of parts of the locking unit according to a first exemplary embodiment in the event of a crash; 
         FIG. 3  is a top view of the parts of the locking unit according to  FIG. 2  in the event of a crash after deformation of the rotary latch; 
         FIG. 4  is a detailed illustration of parts of the locking unit according to a second exemplary embodiment in the event of a crash; and 
         FIG. 5  is a schematized illustration of a vehicle seat. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in particular, in a motor vehicle, a locking unit  10  for connecting a backrest  3  of a vehicle seat  1 , in particular a rear seat, to a vehicle structure is provided. The backrest  3  here is attached to a seat part  5  so as to be pivotable from a use position into a not-in-use position. 
     However, the locking unit  10  can also be used at different locations, for example for fastening the seat part  5  of the vehicle seat  1  to the floor structure of the motor vehicle, or in a door lock. 
     The arrangement of the vehicle seat  1  within the vehicle and the customary direction of travel thereof define the directional details used below. A direction oriented perpendicularly to the ground is referred to below as the vertical direction and a direction perpendicular to the vertical direction and perpendicular to the direction of travel is referred to below as the transverse direction. 
     The locking unit  10  has a lock housing which comprises a first side plate  16  and a second side plate  18 . In the present case, the basic surfaces of the side plates  16 ,  18  are of flat configuration and are arranged in a plane defined by the direction of travel and the vertical direction, i.e. perpendicularly to the transverse direction. Each of the side plates  16 ,  18  comprises two bearing bores  13  which, in the present case, are of circular design. 
     The first side plate  16  and the second side plate  18  form a receptacle which opens in the direction of a bolt  12  in order to receive the latter for locking purposes. The locking unit  10  in the present case is fastened to the backrest  3  and the bolt  12  is fastened to the vehicle structure. It is also conceivable for the locking unit  10  to be fastened to the vehicle structure and for the bolt  12  to be fastened to the backrest  3 . That portion of the bolt  12  which is to be received by the receptacle generally runs horizontally in the transverse direction. 
     A rotary latch  20  is mounted pivotably on a first bearing bolt  51  which, in turn, is fastened to the first side plate  16  and to the second side plate  18 . For this purpose, the rotary latch  20  has a rotary latch hole  24  which is penetrated by the first bearing bolt  51 . The rotary latch  20  furthermore has a hook mouth  21  for interaction with the bolt  12 . The rotary latch  20  is pretensioned in the opening direction by means of a first spring  71 . 
     The rotary latch  20  has a functional surface  22  which partially laterally bounds the hook mouth  21 . In the locked state, the functional surface  22  approximately faces in the direction of a second bearing bolt  52  which is arranged parallel to the first bearing bolt  51  and therefore likewise runs in the transverse direction. In the present case, the functional surface  22  is of planar design, but can also be, for example, curved in the shape of an arc of a circle and of concave design. 
     On that side of the hook mouth  21  which faces away from the rotary latch hole  24  and is opposite the functional surface  22 , the hook mouth  21  is bounded laterally by a lug  28  of the rotary latch  20 . 
     The rotary latch  20  has a basic body which is bounded in the axial direction by a flat basic surface in each case. The width of the functional surface  22  corresponds to the thickness of the basic body of the rotary latch  20 , i.e. to the extent of the basic body in the axial direction. 
     The first bearing bolt  51  is inserted into respective bearing bores  13  in the side plates  16 ,  18  and protrudes perpendicularly from the basic surfaces of the side plates  16 ,  18 . The first bearing bolt  51  therefore runs horizontally in the transverse direction. In the present case, the preferably metallic first bearing bolt  51  is riveted or calked to the side plates  16 ,  18 . The first bearing bolt  51  is preferably designed in the form of a hollow cylinder in order to receive a fastening means, for example a screw, by means of which the locking unit  10  is fastened to the backrest  3  during the installation. 
     The second bearing bolt  52  is also inserted into respective bearing bores  13  in the side plates  16 ,  18  and protrudes perpendicularly from the basic surfaces of the side plates  16 ,  18 . The second bearing bolt  52  therefore likewise runs horizontally in the transverse direction. In the present case, the preferably metallic second bearing bolt  52  is riveted or calked to the side plates  16 ,  18 . In the same manner as the first bearing bolt  51 , the second bearing bolt  52  is preferably designed in the form of a hollow cylinder in order to receive a fastening means, for example a screw, by means of which the locking unit  10  is fastened to the backrest  3  during the installation. 
     A tensioning element  40  is mounted pivotably on the second bearing bolt  52 . For this purpose, the tensioning element  40  has a tensioning element hole  44  which, in the present case, is circular and is penetrated by the second bearing bolt  52 . The tensioning element  40  is pretensioned toward the rotary latch  20  by means of a third spring  73 . 
     In the locked state, when the hook mouth  21  of the rotary latch  20  receives the bolt  12 , the tensioning element  40  exerts a closing moment on the rotary latch  20  owing to the pretensioning by the third spring  73  as a securing element. For this purpose, the tensioning element  40  has a tensioning surface  41  which is curved eccentrically with respect to the second bearing bolt  52  and is in non-self-locking contact with the functional surface  22  of the rotary latch  20 . In the present case, the tensioning surface  41  is curved in the shape of an arc of a circle and is of convex design. 
     A latching pawl  30  is arranged on the second bearing bolt  52  axially next to the tensioning element  40  and is likewise mounted pivotably on the second bearing bolt  52 , i.e. in alignment with the tensioning element  40 . For this purpose, the latching pawl  30  has a latching pawl hole  34  which, in the present case, is circular and is penetrated by the second bearing bolt  52 . The latching pawl  30  is pretensioned toward the rotary latch  20  by means of a second spring  72 . 
     In the present case, the latching pawl  30  is arranged adjacent to the first side plate  16  and, in the present case, the tensioning element  40  is arranged adjacent to the second side plate  18 . The latching pawl  30  and the tensioning element  40  are coupled by empty travel for carrying-along purposes, for example by means of a slot and pin guide or by means of an axially protruding driver. 
     The latching pawl  30  has a latching surface  31  which is in the vicinity of the tensioning surface  41  of the tensioning element  40 . In the locked state, the latching surface  31  is positioned spaced apart from the functional surface  22  of the rotary latch  20 . In the present case, the latching surface  31  is curved in the shape of an arc of a circle and is of convex design, but may also be planar. 
     The width of the functional surface  22 , which corresponds to the thickness of the basic body of the rotary latch  20 , also approximately corresponds to the total of the thickness of the latching pawl  30  and the thickness of the tensioning element  40 . The rotary latch  20  therefore has approximately the same material thickness as the latching pawl  30  and the tensioning element  40  together. 
     The latching pawl  30  furthermore has a latching pawl cutout  36  which is bounded radially inward, i.e. in the direction of the latching pawl hole  34 , by a latching pawl step  38 . 
       FIG. 2  illustrates the positions of the rotary latch  20  and the latching pawl  30  of the locking unit  10  according to a first exemplary embodiment in the event of a crash. 
     The bolt  12  bears against the lug  28  of the rotary latch  20  in the hook mouth  21 . In the event of a crash, the rotary latch  20  experiences an opening moment by means of the bolt  12  and pushes the tensioning element  40  (not illustrated here) away. As a result, the latching surface  31  of the latching pawl  30  enters into contact with the functional surface  22  of the rotary latch  20 . 
     The latching pawl  30  thus serves to support the rotary latch  20  and, as a securing element, prevents a further rotation of the rotary latch  20  in the opening direction. The latching pawl  30  therefore prevents the rotary latch  20  from opening. 
     The lug  28  of the rotary latch  20  projects in this position into the latching pawl cutout  36  of the latching pawl  30 , but without touching the latching pawl  30 . 
       FIG. 3  illustrates the positions of the rotary latch  20  and of the latching pawl  30  of the locking unit  10  according to the first exemplary embodiment in the event of a crash after deformation of the rotary latch  20 . 
     After a relatively severe crash, the rotary latch  20  experiences a further opening moment by means of the bolt  12  bearing against the lug  28  in the hook mouth  21 . However, because of the contact of the latching surface  31  against the functional surface  22 , the latching pawl  30  prevents further rotation of the rotary latch  20 . 
     As a result, the rotary latch  20  experiences deformation in the direction of movement of the bolt  12 . The tip of the lug  28 , which projects into the latching pawl cutout  36  of the latching pawl  30 , moves toward the latching pawl step  38  of the latching pawl  30  and comes to bear there. Further deformation of the lug  28  of the rotary latch  20  in the direction of movement of the bolt  12  is therefore prevented. 
     In this position, the rotary latch  20  has two contact points with the latching pawl  30 . Firstly, the functional surface  22  of the rotary latch  20  bears against the latching surface  31  of the latching pawl  30 , and, secondly, the tip of the lug  28  of the rotary latch  20  bears against the latching pawl step  38  of the latching pawl  30 . 
     If the bolt  12  then exerts a further opening moment on the rotary latch  20 , said moment is supported on the two contact points mentioned between the rotary latch  20  and the latching pawl  30 . 
       FIG. 4  illustrates, in a detailed view, the positions of the rotary latch  20  and of the latching pawl  30  of the locking unit  10  according to a second exemplary embodiment in the event of a crash. 
     On the side facing away from the hook mouth  21 , i.e. facing radially outward, the lug  28  of the rotary latch  20  has a rotary latch toothing  29 . The latching pawl  30  has a latching pawl toothing  39  for interaction with the rotary latch toothing  29  of the rotary latch  20  in the event of a crash. The latching pawl toothing  39  is attached here on the latching pawl step  38  within the latching pawl cutout  36 . 
     In the event of a crash, the rotary latch  20  experiences an opening moment by means of the bolt  12  bearing against the lug  28  of the rotary latch  20  in the hook mouth  21  and pushes the tensioning element  40  (not illustrated here) away. As a result, the latching surface  31  of the latching pawl  30  enters into contact with the functional surface  22  of the rotary latch  20 . 
     In this position, the lug  28  of the rotary latch  20  projects into the latching pawl cutout  36  of the latching pawl  30 , but without touching the latching pawl  30 . The latching pawl toothing  39  and the rotary latch toothing  29  are therefore remote from each other. 
     After a relatively severe crash, the rotary latch  20  undergoes a further opening moment by means of the bolt  12  bearing against the lug  28  in the hook mouth  21 . As a result, the lug  28  of the rotary latch  20  undergoes deformation in the direction of movement of the bolt  12 , and the tip of the lug  28 , which projects into the latching pawl cutout  36  of the latching pawl  30 , moves in the process toward the latching pawl step  38  of the latching pawl  30 . 
     In this position (not illustrated here), the latching pawl toothing  39  of the latching pawl  30  comes to bear against the rotary latch toothing  29  of the rotary latch  20  and enters into toothed engagement therewith. Further deformation of the lug  28  of the rotary latch  20  in the direction of movement of the bolt  12  is therefore prevented. 
     Furthermore, the toothed engagement of the latching pawl toothing  39  with the rotary latch toothing  29  prevents the lug  28  of the rotary latch  20  from being pulled out of the latching pawl cutout  36  of the latching pawl  30 . The toothed engagement of the latching pawl toothing  39  with the rotary latch toothing  29  acts as an additional form-fitting connection between the rotary latch  20  and the latching pawl  30 . 
     In this position (not illustrated here), the rotary latch  20  has two contact points with the latching pawl  30 . Firstly, the functional surface  22  of the rotary latch  20  bears against the latching surface  31  of the latching pawl  30 , and, secondly, the rotary latch toothing  29  of the rotary latch  20  enters into toothed engagement with the latching pawl toothing  39  of the latching pawl  30 . 
     If the bolt  12  then exerts a further opening moment on the rotary latch  20 , said moment is supported on the two contact points mentioned between the rotary latch  20  and the latching pawl  30 . 
     It is also conceivable to configure the latching pawl  30  in such a manner that the latter undergoes deformation because of the force transmitted by the rotary latch  20 . Owing to said targeted deformation, the latching pawl cutout  36  is compressed and reduced in the radial direction until the lug  28  of the rotary latch  20  is clamped from two sides between the latching pawl step  38  and the opposite wall of the latching pawl cutout  36 . 
     In all of the exemplary embodiments described here, the first bearing bolt  51 , as illustrated in  FIG. 1 , is encased by a first slide bush  61 . The first slide bush  61  is also designed in the form of a hollow cylinder. The first slide bush  61  is therefore located in the radial direction between the first bearing bolt  51  and the rotary latch  20 . 
     As illustrated in  FIG. 1 , the second bearing bolt  52  is encased by a second slide bush  62 . The second slide bush  62  is also designed in the form of a hollow cylinder. The second slide bush  62  is therefore located in the radial direction between the first bearing bolt  51  and the latching pawl  30  and also the tensioning element  40 . 
     The first sliding bush  61  and the second sliding bush  62  can also be omitted or formed integrally with the first bearing bolt  51  and the second bearing bolt  52 . 
     In the locked state of the locking unit  10 , the bolt  12  is located in the receptacle formed by the side plates  16 ,  18  and in the hook mouth  21  of the closed rotary latch  20 . The tensioning element  40  secures the rotary latch  20  by interaction of the tensioning surface  41  with the functional surface  22 . The latching surface  31  of the latching pawl  30  is slightly spaced apart from the functional surface  22  of the rotary latch  20 . 
     In order to open the locking unit  10 , the latching pawl  30  is pivoted away from the rotary latch  20 , as a result of which the latching surface  31  of the latching pawl  30  is further away from the functional surface  22  of the rotary latch  20 . The latching pawl  30  carries along the tensioning element  40  owing to the carrying-along coupling, and therefore the rotary latch  20  is no longer secured. 
     By means of the pretensioning on account of the first spring  71 , the rotary latch  20  opens, i.e. pivots in the opening direction. Alternatively, or in addition to, the pretensioning by the first spring  71 , the rotary latch  20  can also be carried along for opening purposes by the latching pawl  30  or by the tensioning element  40 . 
     Owing to the pivoting movement of the rotary latch  20 , the hook mouth  21  draws back from the receptacle formed by the side plates  16 ,  18  and releases the bolt  12  which moves away from the locking unit  10  counter to the pivoting-in direction. If the bolt  12  has left the hook mouth  21 , the locking unit  10  is in the unlocked state. 
     If, in said unlocked state, the bolt  12  passes again into the receptacle formed by the side plates  16 ,  18  and enters into contact with the border of the hook mouth  21 , the bolt  12  pushes the rotary latch  20  into the closed position thereof. The tensioning element  40 , owing to the pretensioning thereof by the third spring  73 , moves along the functional surface  22 . Carried along by the tensioning element  40  or owing to the pretensioning by the second spring  72 , the latching pawl  30  pivots toward the rotary latch  20 , with the latching surface  31  approaching the functional surface  22  of the rotary latch  20 . The locking unit  10  is then in the locked state again. 
     The features disclosed in the above description, the claims and the drawings can be of importance both individually and in combination for realizing the invention in the various configurations thereof. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

Summary:
A locking unit ( 10 ) for a vehicle seat ( 1 ) includes a pivotally mounted rotary latch ( 20 ) for locking to a bolt ( 12 ), and a detent ( 30 ) which secures the locking unit ( 10 ) in the locked state in the event of a crash, in which the rotary latch ( 20 ) supports itself on a first contact point against the detent ( 30 ). The rotary latch ( 20 ) also supports itself on a second contact point in the event of a deformation of the latch ( 20 ) in the event of a crash. The second contact point is provided on the detent ( 30 ).