Abstract:
The invention relates to a drive for adjustment devices in motor vehicles, more particularly for vehicle seats, having a stepped switch mechanism acting on both sides for manually producing a rotary movement. The object of the present invention is to provide a simplified and cost-effective device for adjusting the vehicle seat components in two directions. This is achieved by connecting the output side of the stepped switch mechanism to a self-blocking gear.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of German Application No. 198 55 004.9 filed Nov. 20, 1998, the disclosure of which is incorporated fully herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a drive for adjustment devices in motor vehicles. In particular, the invention serves to facilitate the adjustment of component parts of a vehicle seat or of the entire vehicle seat. 
     BACKGROUND OF THE INVENTION 
     DE 196 53 722 A1 discloses a manual drive acting on both sides to produce a rotary movement. The device has a stepped switch mechanism that contains a fixing device that locks torque occurring on the output side. The stepped switch mechanism is arranged between a drive and an output element. The fixing device is formed as a loop spring brake and prevents the undesired displacement of the adjustment device, for example a seat back. 
     In order to achieve this fixing position a relatively complicated mechanism is required having a number of component parts that have to be fitted together in an expensive assembly process. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide a simple, cost-effective drive that can be adapted with low expense to different components of a vehicle adjustment device. The drive is to be particularly suitable for adjusting seat components. 
     By arranging a self-locking gearbox between a stepped switch mechanism and the device that is to be adjusted it is possible, in a simple and cost-effective manner, to prevent torque applied on the output side from causing undesired displacement of the device that is to be adjusted, such as the seat back or seat cushion of a vehicle seat. 
     Furthermore, through a suitable transmission ratio of a gearbox, it is possible to adapt to the requirements of the device or components that are to be adjusted. For example, for a seat height adjustment as compared to a seat length adjustment, a substantially smaller step width is used per displacement stroke with a simultaneously higher force expense. 
     In order to adapt the displacement path per stroke of the stepped switch mechanism to the relevant area of use, a reduction or translation step is arranged between the self-locking gearbox and the stepped switch mechanism. When adjusting the seat length, as a rule, greater displacement paths per stroke are desired than when adjusting the seat height. Consequently, for adjusting the seat length a gear step will be provided with a translation step, while for adjusting the seat height a reduction will be applied. When adjusting the seat height, a reduction does indeed have an advantage, in addition to the finer adjustability, that the relatively high operating forces based on the weight of the seat user are reduced. 
     In addition to the gear step, or as an alternative thereto, it is possible to mount a transmission member between the self-locking gear and the stepped switch mechanism whereby a spatial uncoupling of the two structural groups becomes possible. The stepped switch mechanism can thus be mounted at a place where it can be easily operated by the user, irrespective of where the displacement is actually to take place. The gear is preferably mounted near the device that is to be displaced but can however equally be connected to the device to be displaced through a transmission member. Transmission members can be for example shafts and traction drives, but are not restricted to these. 
     The type of self-locking gear is thereby freely selected in principle, however planetary, tumbler, or eccentric gears are preferred wherein an inclined spur wheel, an inclined ball wheel, or cyclo gears, as well as worm or spindle gears, can all be used depending on conditions. 
     While the gear is driven by a stepped switch mechanism it is connected on the output side to a seat height, seat incline, seat length, seat cushion depth, or head rest adjustment device. 
     In another embodiment of the present invention, the gear is connected on the output side directly to a seat backrest to produce a direct adjustment. 
     As an alternative to a direct action on the device to be displaced, the gear may have an output shaft with an output element mounted thereon for moving the device to be adjusted. This output element is preferably formed as a pinion however, other designs such as a worm, spur wheel, or friction clutch element are also possible. 
     In order to allow the simplest possible interface between the stepped switch mechanism and the gear, the stepped switch mechanism has at its output a drive element, coupled to the gear. The drive element operates as a coupling member between the structural groups of the stepped switch mechanism and gear and can be a common constituent part of both structural groups. 
     In an embodiment of the present invention, the drive element is formed as a pinion and can in the case of a tumbler or eccentric gear be both the eccentrically rotating gearwheel and the stepping element of the stepped switch mechanism. 
     In an alternative embodiment of the present invention, the drive element can be formed as only a constituent part of the gear that is driven by the stepped switch mechanism through for example, an eccentric bearing, the formation of a planetary gear part, or the like. 
     Furthermore, it is possible to arrange at least one gear step between the drive element and the gearbox to produce a suitable input transmission. 
     If the gear is formed as a tumbler or eccentric gear there is the advantage of providing an output element with an inner gearing in which an eccentrically mounted spur wheel rotates with a smaller number of teeth compared to the inner gearing, the spur wheel being coupled in force locking or positive locking engagement with the drive element. 
     As an alternative to a force locking or positive locking connection between the spur wheel and drive element, the drive element can be formed as the spur wheel of the tumbler or eccentric gear and mounted eccentric relative to the inner teeth of the output element. 
     In an additional embodiment of the present invention, an eccentric is formed on the drive element, and a spur wheel is mounted on the eccentric and is driven by the eccentric to engage in a tumbler or eccentric gear. 
     In an additional embodiment of the present invention, the tumbler or eccentric gear has a housing in which are mounted an eccentric, driven by the drive pinion and connected to a planetary wheel, and also an output hollow wheel connected to an output shaft and engaging with the planetary wheel. The planetary wheel has a drive wheel engaging with the output hollow wheel, and an axially adjoining support wheel that engages with a support hollow wheel fixed on the housing. 
     In order to ensure a simple force-saving operation of the adjustment device, the stepped switch mechanism has a drive lever that is hand operated and with which the stepped switch mechanism, and thus the drive element, is moved or turned in one direction or another selectively, starting from a neutral position. The drive element is thereby only turned when the drive lever is moved from the neutral position while it is not turned when the drive lever is moved in the direction of the neutral position. 
     In a preferred embodiment of the drive, the drive lever can swivel about a drive axis and is in active connection with the drive element through at least one rocker element which rocks to and fro between two end positions depending on the drive direction. In each end position of the rocker movement, toothed areas of the rocker element engage teeth of the drive element and thus produce a force locking connection between the drive lever and the drive element. In this way the drive element is turned stepwise about a certain angle. 
     In order to take up the smallest possible structural space, the drive element is provided with inner teeth in which the rocker element engages during each relevant rocker movement. The rocker element is mounted for example to swivel on a holding plate that in turn is mounted on the drive axis of the stepped switch mechanism. The rocker element and the holding plate can thereby be made of plastics or metal and are preferably connected together prior to assembly through a film hinge or an ideal break point. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The idea on which the invention is based will now be explained in further detail with reference to the embodiments shown in the drawings in which: 
     FIG. 1 is an exploded view of a device for adjusting a vehicle seat. 
     FIG. 2 is an exploded view of a stepped switch mechanism adjustable through a lever. 
     FIG. 3 is a section through a stepped switch mechanism with an intermediate gear. 
     FIG. 4 is a section through a stepped switch mechanism with a coupled eccentric gear. 
     FIG. 5 is a section through a stepped switch mechanism with a pinion formed thereon. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows an exploded view of a device for adjusting a vehicle seat having a drive for the adjustment device formed as a stepped switch mechanism  1 , and a self-locking gear  10  that transfers a torque on the drive side for the adjustment device or vehicle seat components, but blocks a torque on the output side. The stepped switch mechanism  1  consists of a drive lever  100  that can swivel a restricted amount about a drive axle  6  in the direction of the double arrow. Furthermore, a holding plate  3  with a rocker element  2  mounted thereon outside of the drive axle  6 , as well as a drive element  4  are mounted on the drive axle  6 . From the point of view of the stepped switch mechanism  1  the drive element  4  provides the output, but the drive element acts as the drive for the gear  10  so that here the term drive element has been selected. 
     As a result of its bearing outside of the drive axle  6 , when the drive lever  100  is swivelled out of a rest position, the rocker element  2  is brought into engagement by its detent elements  20  with the corresponding detent elements  401  of the drive element  4 . In the selected embodiment the detent elements are formed as teeth. Through the engagement of the detent elements  20 ,  401  a torque produced through the drive lever  100  is transferred to the drive element  4  and converted into a rotation of the drive element  4 . 
     A pinion  9  is formed or fixed on the drive element  4  and transfers the rotation through a gear step  8  to the self-locking gear  10 . The gear  10  is formed as a tumbler or eccentric gear and has an eccentric wheel  61  on which an eccentric  60  is formed. The rotation transferred to the eccentric  60  creates, through the bearing point of the eccentric  60 , a tumbling movement of the planetary wheel  30  which is mounted on the eccentric  60 . With this tumbling movement the drive wheel  32  of the planetary wheel  30  rolls on the inner teeth  14  of the output hollow wheel  40 . 
     Because the support wheel  31  of the planetary wheel  30  is supported on the inner teeth  14  of the hollow support wheel  50  the tumbling movement of the planetary wheel  30  leads to a rotation of the hollow output wheel  40  that is reduced in speed. 
     As a result of the connection of the hollow output wheel  40  with the output shaft  11  the rotary movement is transferred to the output element  12  which is here formed as a pinion. Displacement of, for example, a backrest incline, seat incline, or seat height can be carried out with this output pinion  12 . 
     The entire arrangement of stepped switch mechanism  1  and gear  10  is thereby mounted in a housing  15  having a gear cover  16  and a lower housing part  15 ′. 
     In FIG. 2 a stepped switch mechanism  1  serving as a drive for a seat adjustment device is shown isolated in an exploded view illustrating the functioning principle of the stepped switch mechanism  1 . The drive lever  100 , the rocker element  2 , the holding plate  3  as well as the drive element  4  with inner teeth  401  are mounted on a distance sleeve  5  which is mounted along a drive axle  6 . 
     The rocker element  2  has two symmetrically arranged toothed areas  201 ,  202  lying on a circular circumference wherein one of the toothed areas  201 ,  202  can be brought into engagement with the detent elements  401  of the drive element  4  depending on the drive direction. Two bearing points radially spaced relative to the drive axle  6  are arranged on the axis of symmetry of the rocker elements  2  and through these bearing points the rocker element  2  is connected on the one hand to the drive lever  100  and on the other to the holding plate  3 . The bearing point between the rocker  2  and drive lever  100  is thereby formed by a pin or pivot  204  that engages in a corresponding recess in the drive lever  100 . The bearing point between the holding plate  3  and rocker element  2  is formed in a corresponding way by a pin or stud of the holding plate  3  which engages in a hole  203  of the rocker element  2 . 
     During swivel movement of the drive lever  100  from the neutral position the pin  204  of the rocker element  2  mounted in the hole of the drive lever  100  is likewise swivelled about the drive axle  6 . As a result of friction forces between the holding plate  3  and the distance sleeve  5  as well as where applicable the drive element  4  or by using a torsional spring the holding plate  3  first opposes co-rotation with the drive lever  100 . The pin of the holding plate  3  thereby forms a counter bearing so that a torque engages on the rocker element  2  whereby the rocker element  2  tilts and depending on the drive direction one of the toothed areas  201 ,  202  of the rocker  2  engages in the detent elements  401  of the drive element  4 . 
     When the drive lever  100  swivels upwards out of the neutral position the rocker element  2  is tilted for example, to the left so that the toothed area  201  comes into engagement with the teeth  401  of the drive element  4 . In this way a rotary movement of the drive lever  100  is transferred to the drive element  4 . 
     When the drive lever  100  swivels back into the neutral position the torque applied to the rocker element  2  is lifted and the toothed areas  201 ,  202  come out of engagement. When the drive lever  100  returns it does not result in a resetting movement of the drive element  4 . 
     When the drive lever  100  is operated in the opposite direction a stepped rotation of the drive element  4  is effected accordingly. 
     FIG. 3 shows a section through a stepped switch mechanism  1  having a drive lever  100  that can swivel about the drive axle  6  and a holding plate  3  on which a rocker element  2  is mounted. The rocker element  2  is likewise connected to the drive lever  100  and during rotation engages into the drive element  4  which is connected in force locking and positive locking engagement with the shaft  7  thereby transferring the rotary movement to the shaft. A pinion  9  is fixed on the shaft  7  for example by press-fitting or multi-toothed connection and is secured axially by means of a deformation element or a rivet connection. The pinion  9  meshes with a gear step  8  which transfers the rotary movement or torque to the self-locking gear  10  (not shown). 
     FIG. 4 shows an additional type of coupling between a stepped switch mechanism  1  and a gear  10 . The construction of the stepped switch mechanism  1  is identical with that described in FIG.  3 . The shaft  7  is however mounted eccentric relative to the drive axle  6  and supports a spur wheel  13  that engages in inner teeth  14  of a hollow output wheel  40 . The hollow output wheel  40  in turn rotates the output shaft  11  which is connected to the seat components that are to be displaced but are not shown, as displacement device. 
     FIG. 5 shows an embodiment of a coupling between a stepped switch mechanism  1  and an eccentric gear  10  wherein a spur wheel  13  that is mounted eccentric relative to the drive axis  6  is formed directly on the drive element  4  and meshes with inner teeth  14  thereby forming together with the hollow output wheel  40  an eccentric gear  10 .