Abstract:
The invention is based on a wiper installation, having at least one wiper bearing ( 10 ), in whose hearing housing ( 12,126 ) a wiper shaft ( 18 ) is supported and axial fixed, and which on its end ( 20 ) protruding from a vehicle body ( 24 ) carries a wiper arm ( 60 ). The wiper shaft ( 18 ) is displaceable into the vehicle body ( 24 ) when an axial force ( 40 ) that exceeds a predetermined magnitude is exerted from outside on the end ( 20 ).

Description:
BACKGROUND OF THE INVENTION 
     Known window wipers have a wiper arm, which is constructed of a fastening part and a joint part, pivotably connected to it, with a wiper rod. They also have a wiper blade, which is constructed of a support bracket system with a predominant center bracket and pivotably connected, subordinate intermediate brackets as well as claw brackets and a wiper strip. The wiper blade is pivotably connected to the wiper arm, in that a free end of the wiper rod holds a bearing part that is disposed between two side cheeks of the center bracket and that includes a hub that is open over a circumferential region and a pivot bolt of the center bracket. The joint thus formed guides the wiper blade over the window during the pivoting motion; the joint and the support bracket system allow the wiper strip to adapt to adapt to any curvature of the window. 
     The fastening part of the wiper arm is seated on the free end of a wiper shaft, which is supported in a wiper bearing and is driven by a wiper motor via a crank and a rod linkage. The wiper motor is held by a mounting bracket, which is fastened to a vehicle body and includes the wiper bearing. Often, the wiper bearings themselves act as fastening points, by protruding through openings in the vehicle body and being screwed to the vehicle body with the interposition of vibration-damping rubber-elastic elements. However, it is also possible for them to be connected to the vehicle body via props on the mounting bracket. 
     The end of the wiper shaft protruding from the vehicle body is a possible cause of injury in the event of accidents involving pedestrians. Proposals for crash regulations by the European Commission (EC III/5021/96 EN), with regard to accidents involving pedestrians, define maximum acceleration values, or so-called head injury criteria, in the region of the vehicle hood at the wiper installation. These criteria can not be met with the conventional wiper installations, even if the vehicle hood covers the wiper shaft, since even in this case, it is still not assured that the spacing between the vehicle hood and the wiper shaft will be large enough, especially when hood gaps are small. 
     SUMMARY OF THE INVENTION 
     According to the invention, the wiper shaft is displaceable into the vehicle body when an axial force that exceeds a predetermined magnitude is exerted from outside on the end. As a result, on the one hand, the prescribed criteria can be met; on the other, the wiper shaft can be prevented from being displaced by lesser axial forces, for instance if the wiper arm becomes blocked by snow or for other reasons. 
     Expediently, a defined displacement distance is specified for the wiper shaft. It must be assured here that the displacement distance can be fully utilized, in that the spacing have the wiper arm from the vehicle body or from the windshield, and the spacing of the inner end of the wiper shaft, or of a part solidly connected to it, from an adjacent vehicle part, corresponds at least to the displacement distance. The fastening part of the wiper arm, in the region of its fastening to the wiper shaft, has a large-area cover cap of solid material, in order to reduce the pressure per unit of surface area in the event of an impact on the protruding end of the wiper shaft, and thus to lessen the risk that the end of the wiper shaft will penetrate a person&#39;s body. It is also advantageous that the impact energy is largely dissipated over the displacement distance, because the motion of the wiper shaft is damped to an increased extent over the displacement distance and in particular toward the end of the displacement distance. 
     For damping the impact, means that deform plastically and/or elastically in the axial direction under the influence of a critical axial force are provided between an inward-acting stop of the wiper shaft and a part solidly connected to the vehicle body, or between such a part in the vehicle body. Such means may be a plastically deformable sheet-metal sheath, which expediently has an axially corrugated region, or they may be thin-walled plate-like elements, which depending on the displacement distance can be disposed multiply, operatively in series. These elements may have so little play from the wiper shaft or other adjacent components that upon their deformation may press against these components and by friction amplify the damping action. Finally, the means can be disposed such that under the influence of the critical axial force, they are upset or pulled apart. 
     The wiper shaft can be axially secured to the bearing housing of the wiper bearing via positive engagement elements with a rated breaking point, which in response to a critical axial force either break or bend over into a free space. Such rated breaking points can be produced by means of notches, bores, or shearing pins. 
     In a further feature, the wiper shaft is supported axially inward via an element nonpositively connected to the bearing housing, with the nonpositive engagement dimensioned such that it yields under the influence of a critical axial force. The nonpositive engagement element can be a bushing which is inserted into the bearing housing with a press fit. A bearing bush can expediently be used for the purpose. 
     A further advantage is that the means are mounted at different points, acting in series. Thus first means can be provided between the wiper shaft and an element, such as a bearing bush, guided in the bearing housing; second means can be provided between that element and the bearing housing; third means can be provided between the bearing housing and the vehicle body or the mounting bracket; and fourth means can be provided between the mounting bracket and the vehicle body. 
     As a result, on the one hand a long displacement distance with high energy consumption can be attained; on the other, the means can be adapted to one another in such a way that with an increasing critical axial force, they become operative in succession, so that depending on the severity of the accident, only some of the means have to be replaced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages will become apparent from the ensuing description of the drawings. In the drawings, a wiper installation and exemplary embodiments of the invention are shown, to the extent necessary for comprehension of the invention. The drawing, specification and claims include numerous characteristics in combination. One skilled in the art will expediently consider the characteristics as well and combine them into suitable further combinations. 
     Shown are: 
     FIG. 1, a schematic section through a wiper bearing, whose end is covered by a vehicle hood; 
     FIG. 2, a variant of FIG. 1 with a free-standing wiper bearing; 
     FIG. 3, a detail marked III in FIG. 3, with the right half of FIG. 3 showing the arrangement after a crash; 
     FIG. 4, a variant of FIG. 3; 
     FIG. 5, a detail corresponding to FIG. 3 with a nonpositive engagement element; 
     FIG. 6, a variant of FIG. 5; 
     FIG. 7, a detail of FIG. 3 with a positive engagement element with a rated breaking point; 
     FIGS. 8 through 10, a variant of FIG. 7; 
     FIG. 11, a variant of FIG. 7 with bending elements; 
     FIG. 12, a variant if FIG. 3 with first, second and third plastically and/or elastically deformable means, in the outset state; 
     FIG. 13, the embodiment of FIG. 12 in the state after a severe crash; 
     FIG. 14, an arrangement with a deformation element in the outset state, which pulls apart in the crash; 
     FIG. 15, an arrangement of FIG. 14 after a crash; 
     FIG. 16, a section through a deformation element with a welded nut; 
     FIG. 17, a section through a deformation element with an integrally molded lead through for a self-tapping screw; and 
     FIG. 18, a perspective view of a mounting bracket with wiper bearings. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A wiper bearing  10 , whose bearing housing  12 ,  126  is a component of a mounting bracket  130  (FIG. 18) for fastening the wiper installation to a vehicle body  24 , includes a wiper shaft  18 , which is supported in the bearing housing  12  via two bearing bushes  14 ,  16  (FIG.  1 ). The bearing housing  12  is inserted by one end through an opening in the vehicle body  24  and, with the interposition of rubber-elastic vibration-damping elements  36  and  38 , is screwed by a flange  34  and a shim  42  to the vehicle body  24  by means of a nut  44 . The space between the vehicle body  24  and a vehicle hood  32 , which can extend across the wiper bearing  10 , is bounded by a cover  26 , which presses with a disk seal  28  against a windshield  30 . The wiper shaft  18  is driven via a rod linkage, not shown, by a wiper motor, also not shown, via a crank  72  with a joint head  74 . A stop disk  48 , which represents an axial fixation of the wiper shaft  18  on its inner end  22 , is located between the crank  72  and the inner face end of the bearing housing  12 . On its outer end  20 , the wiper shaft  18  is supported axially, via a stop disk  50 , a sheet-metal sheath  56 , a shim  54 , and a securing ring  58 , on the bearing housing  12  that is solidly joined to the vehicle body  24 . On the face end, the bearing housing  12  protrudes past the bearing bush  16  and together with the wiper shaft  18  and the stop disk  50  forms an annular chamber in which a sealing ring  52  is placed. Secured to the outer end  20  of the wiper shaft  18  is a fastening part  60  of a wiper arm; via a clamping cone  62 , a nut  64  presses the fastening part  60  against a support ring  68 , which is supported on a shoulder  70  of the wiper shaft  18 . Toward the outside, the nut  64  carries a large-area cover cap  66 , for reducing the pressure per unit of surface area in the event of a collision. 
     If a collision occurs, an axial force  40  acts on the wiper shaft  18 . If this forces exceeds a predetermined critical amount, the sheet-metal sheath  56  is compressed, and the wiper shaft  18  displaces inward by a displacement distance  76  (FIG.  3 ). Because of the deformability of the sheet-metal sheath  56 , the motion of the wiper shaft  18  is damped, and the impact energy is dissipated. The deformation work to be performed can be modified by varying the design of a corrugated region  90  of the sheet-metal sheath  56 . The play between the sheet-metal sheath  56  and the wiper shaft  18  can also be dimensioned such that upon deformation, the sheet-metal sheath  56  presses against the wiper shaft  18 , so that by friction, the damping rises with an increasing displacement distance. If the displacement distance  76  is to be fully utilized, the spacing between the fastening part  60  of the wiper arm and the vehicle body  24 , or the cover  26  or the windshield  30  and the spacing  80  between the joint head  74  and an adjacent vehicle part  86  must correspond at least to the displacement distance  76 . 
     FIG. 2 shows a version with a wiper bearing  10  that is not covered on the outside by the vehicle hood  32 . An intermediate ring  84  is also provided on the outer end  20  of the wiper shaft  18 , and the sheet-metal sheath  56  on one side and the fastening part  60  on the other are supported on this ring. This economizes on axial structural length, so that with otherwise identical given conditions, a longer displacement distance  76  is possible. 
     In the version of FIG. 4, instead of the sheet-metal sheath  56 , thin-walled plate-like elements  88  are provided, which are operatively disposed in series and are pressed flat (shown on the right in FIG. 4) under the influence of a critical axial force  40 . 
     In the version of FIG. 5, the wiper shaft  18  is supported on its face end, via the shim  54 , on a nonpositive engagement element  92 , which at the same time serves as a bearing bush and is inserted with a press fit  98  into the bearing housing  12 . On the interface end of the nonpositive engagement element  92 , a free space  94  is provided, which permits a displacement travel  76  if the critical axial force  40  overcomes the press fit  98 . The version of FIG. 6 differs from the version of FIG. 5 in that the nonpositive engagement element  92  is embodied with thinner walls and on its outer end has a collar  96 , which is adjoined toward the inside by a free space  102 . The nonpositive engagement element  92  is retained in the bearing housing  12  via a press fit  100  and optionally a further press fit  98 ; the free spaces  94  and  102  permit a displacement travel  76  when the critical axial force  40  overcomes the press fits  98  and  100  (right-hand half of FIG.  5 ). 
     In the version of FIG. 7, a bush  108 , which at the same time can be a bearing bush for the wiper shaft  18 , is provided on the outer end  20 . This bush is supported in the bush  108  on the bearing housing  12  via the shim  54  and an edge  104 . Between the edge  104  and the inner part of the bush  108 , a rated breaking point in the form of a notch  106  is provided, so that upon a critical axial force  40 , the edge  104  breaks off, and the bush  108 , by utilizing the free spaces  94  and  102 , can be displaced inward (right half of FIG. 7) by the displacement distance  76 , along with the wiper shaft  18 . 
     FIGS. 8,  9  and  10  show possible designs of the rated breaking point. In the version of FIG. 8, the edge  104  (FIG. 7) is relieved and is formed by individual radially oriented tongues  110  distributed over the circumference. In the version of FIG. 8 the edge  104  includes numerous bores  112 , which determine the rated breaking load. Finally, in the version of FIG. 10, the bush  108  is joined to the bearing housing  12  via shearing pins  118 , which are sheared off if there is an overload. 
     The version of FIG. 11 differs from the versions of FIGS. 7 through 10 in that the edge  104  is formed by tabs  114 , which under a critical axial force  40  bend at a bending point  116  and are pressed into the free space  94 . Here, the ball friction and damping over the displacement distance  76  are increased. 
     The version of FIGS. 12 and 13 shows a wiper shaft  18 , which is supported on a bearing element  124  via a first means  120 , in the form of a corrugated sheet-metal sheath, that is plastically deformable and to a slight extent elastically deformable. This sheath is supported in turn relative to a bearing housing  126  via second, plastically deformable means  122 . The bearing housing  126  has a bearing eyelet  136 , in which a rubber damper  134  is inserted in order to prevent noise from being transmitted to the vehicle body. The rubber damper  134  is secured, by means of a screw  138  and a shim  146 , to a third plastically deformable means  128 , in the form of a corrugated sheet-metal sheath, by way of which the bearing housing  126  is supported relative to the vehicle housing  24 . 
     If in a crash the critical axial force  40  exceeds a specified amount, the first means  120 , second means  122  and third means  128  are deformed, producing a maximum displacement distance for the wiper shaft  18 . In principle, it is also possible for the bearing housing  126  to be supported via the third means  128  relative to a mounting bracket  130  (FIG.  18 ), which in turn is supported relative to the vehicle body  24  via fourth plastically deformable means  132 . As needed, the means  120 ,  122 ,  128  and  132  can be used individually or several can be used together, and as a result the displacement distance and the amount of deformation energy can be adapted to the particular application. It may be expedient for the means  120 ,  122 ,  128 ,  132  to be adapted to one another in such a way that with an increasing axial force  40 , they come into action successively, so that in the event of minor accidents, only the means that become active first have to be replaced. The deformation work can be reinforced by friction work, in that the means  120 ,  122 , during the deformation, press against the wiper shaft  18 , or the bearing element  124 , or a wall  148  of the bearing housing  126 . 
     Instead of or in combination with the corrugated sheet-metal sheaths, the above-described provisions for damping the axial motion of the wiper shaft  18  can also be provided. FIG. 13 shows the version of FIG. 12, in which all the means  120 ,  122  and  128  are maximally stressed, and thus a maximum displacement distance of the wiper shaft  18  is attained. The means  120 ,  122 ,  128  are upset under the influence of the axial force  40 . By comparison, the version of FIG. 14 shows a deformation element  162 , which is stretched (FIG. 15) under the influence of the axial force  40 . In FIG. 16, a deformation element  158  is shown, which is secured by one end to the vehicle body  24  via welded spots  144  and on its other end has a bottom  142  with a welded nut  140  that can be engaged by the screw  138 . If a self-tapping screw is used as the screw  138 , then it is expedient for a leadthrough  152  for the screw  138  to be integrally formed onto the bottom  142  of a deformation element  160  (FIG.  17 ). 
     FIG. 8 shows a version in which the bearing housing  126  is secured to the vehicle body  24  via a mounting bracket  130  with a motor mounting bracket  166 , via a bracket  150  and props  164 . The third means  128  are disposed between the bearing eyelets  136  and the props  164 , while fourth means  132  are provided between the bracket  150  and the motor mounting bracket  166 . The axes  156  of the means  128 ,  132  are expediently oriented essentially parallel to the axes  154  of the wiper shafts  18 , so that the critical axial force  40  will be introduced optimally into the means  128 ,  132 .