Abstract:
A self-locking step-by-step mechanism for an adjustment device of a vehicle seat has a clamping roller lock and a step-by-step device. The clamping roller lock a rotatable release wheel and a toothing. The step-by-step device has a) a pivotably mounted actuating lever, b) a driver pivotably mounted on the actuating lever and which has two driver regions which interact with the toothing of the release wheel, c) a drag lever which has supporting surfaces which enter into contact with the driver, and d) a spring. The spring has at least one projection. The drag lever has at least one indentation which is normally in engagement with the projection. The spring is fixed against rotating.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a National Stage of International Application No. PCT/EP2011/068640 filed on Oct. 25, 2011, which claims the benefit of German Patent Application No. 10 2010 044 081.7 filed on Nov. 17, 2010, the entire disclosures of which are incorporated herein by reference. 
     The invention relates to a self-locking step-by-step switching mechanism for an adjustment device of a vehicle seat comprising a clamping roller lock and a step-by-step switching device, wherein the clamping roller lock comprises an axis and a release wheel that is rotatable about this axis and comprises a gearing, and the step-by-step switching device comprises a) an actuating lever mounted pivotably about the axis, b) a driver which is mounted on the actuating lever so as to be pivotable about a driver axis and which has two driver regions cooperating with the gearing of the release wheel, of which only one, respectively, is in engagement with the gearing in one direction of rotation of the release wheel, respectively, of which both are out of engagement with the gearing in a central position of the actuating lever, and of which one comes into engagement with the gearing and rotates the release wheel when the actuating lever is pivoted out of its central position, whereas the other remains out of engagement with the gearing, c) a drag lever comprising supporting surfaces that enter into contact with the driver, and d) a spring. 
     BACKGROUND 
     Such a self-locking step-by-step switching mechanism is known from DE 195 40 631 C2. The clamping roller lock used in this case is also referred to as a freewheel. Such clamping roller locks are known from DE 10 2010 43 825 and DE 10 2010 031 133. Other step-by-step switching mechanisms are known from DE 44 00 910 A1 and DE 43 44 225 A1. 
     SUMMARY 
     Occasionally, certain problems arise in the step-by-step switching mechanism of the type mentioned in the introduction. An undesired neutral stroke may occur. Another possible occurrence is that the driver does not properly come clear from the gearing of the release wheel after a working stroke. 
     Based on this, the invention has set itself the object of further developing the step-by-step switching mechanism of the type mentioned in the introduction in such a way that it functions more precisely, wherein particularly the lead-in movement of the driver and/or the lead-out movement of the driver is supposed to take place in a precise manner. 
     This object is accomplished by a self-locking step-by-step switching mechanism with the features of claim  1 . 
     In this step-by-step switching mechanism, the drag lever does not move synchronously with the actuating lever. The drag lever is fixated in its normal position by the spring. It is only pivoted out of it when a sufficient torque that is above a threshold acts on the drag lever. 
     Starting from a central position of the actuating lever, the driver, at the beginning of a working stroke, is first pushed against the supporting surface of the drag lever which, in the actuation direction, is located at the front. If the driving movement is continued, the driver region situated, in the direction of rotation, at the front is pivoted into the gearing of the release wheel and comes into engagement with this gearing. Up to this point in time, the drag lever has not yet been moved out of its normal position; the drag lever has not yet moved. 
     If the drive is now continued further, the braking torque that the spring exerts on the drag lever can be overcome and the drag lever is taken along; the actuating lever thus drives the drag lever. This driving process takes place up to a predetermined angular position, for example 24°, which is defined by the designer. 
     At the beginning of an actuation, the driver undergoes a pivoting movement due to the actuating lever, which is made possible by the resting drag lever. The drag lever itself is at first held by the spring in its normal position, which is the central position, until the driver has pivoted completely into the gearing of the release wheel, which results in an increase of the counterforce. Now, the holding force of the spring can be overcome and the drag lever can rotate together with the actuating lever about the axis; the release wheel is driven thereby; a rotary movement on an output shaft of the clamping roller lock is produced. 
     Preferably, the spring has two projections, which are opposite from one another relative to the axis, and two associated indentations are provided on the drag lever, which are normally in engagement with the two projections. A reliable holding force on the drag lever is obtained by means of the two opposite spring loads. The two indentations are preferably situated on a single diameter. This diameter is preferably disposed at an angle of 90° relative to a radial extending through the driver axis. The larger the angle between this radial and the indentations, the larger the angle of the working stroke on the actuating lever can be. 
     In kinematic reversal, the spring can also have a indentation and the projection can be provided on the drag lever. The indentation can be made very small; it can also be omitted entirely. 
     In a preferred development, a tongue is provided which is located between the driver regions of the driver and the release wheel when the actuating lever is in its central position. In a preferred development, the tongue is a section of the spring. At the end of an actuation stroke and when returning the actuating lever, this tongue prevents the driver from being overridden. For it prevents the driver from pivoting in the opposite direction into the gearing of the release wheel. It thus prevents the other, so far passive, driver region from entering an active position. In that case, the actuating lever would get caught and would partially or completely return the stroke that was carried out just before. The tongue is located between the driver region and the gearing when the return of the actuating lever begins. Thus, the driver region cannot come into contact with the gearing. The tongue ends shortly before reaching the central position. The tongue frees the path of the driver without a pivoting into the gearing taking place. Preferably, the tongue is in approximately the same angular position as the driver axis, i.e. at 12 o&#39;clock. The two indentations are preferably situated at 3 and 9 o&#39;clock. 
     In another improvement, it is proposed that a braking tab is provided which rests in a dragging manner against the drag lever. Preferably, this tab is a section of the spring. This tab produces a frictional moment. It brakes the rotary movement of the drag lever. It thus prevents free rotatability of the drag lever. Due to the tab, the drag lever has to be transported until the central position is reached. Now, no noise is produced when the spring latches into the indentations. The elastic regions of the spring are deposited in the indentations in a positively guided manner. The indentations can have any shape; they can be configured as cut-outs. Preferably, the tab is situated diametrically opposite from the tongue and/or the driver axis. Preferably, the tab is situated at 6 o&#39;clock. 
     Preferably, the drag lever has a recess in which the driver is located. Thus, the driver is arranged in a protected manner. In this case, the drag lever preferably has a wall which seals this recess on the side facing away from the actuating lever. Thus, the driver can be inserted into the recess only in an axial direction. Preferably, the recess is accessible only in one direction. 
     Preferably, the spring is connected to a base plate of the self-locking step-by-step switching mechanism and/or a housing of the clamping roller lock. In this way, the spring is non-rotatable. It does not move if the actuating lever is actuated. Preferably, the spring comprises a holding arm engaging an opening of the base plate. A positive-fit rotary connection is thus accomplished. 
     Independently of the characterizing feature of the claim  1 , a special feature of the present invention lies in the fact that, based on the features of the preamble of the claim  1 , no physically formed pivoting axis is provided between the drag lever and the driver. In the step-by-step switching mechanism according to DE 195 40 631 C2, such a real axis is provided. The consequence of this is that the drag lever always pivots synchronously with the actuating lever. If no physically formed pivoting axis is provided, the actuating lever, with the driver that is pivotably mounted thereon, can be pivoted over a small angular range without the drag lever also being pivoted. There is no pivot connection by a real pivoting axis between the actuating lever and the pivot lever. Thus, the lead-in movement of the driver can be separated from a rotation of the drag lever. 
     The applicant reserves the right to combine any features and sub-features from the claims and/or from sentences from the description with one another, even if such a combination is not expressly indicated. Any combination of different features and individual features, if mentioned in the application, are part of the content of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Other advantages and features of the invention become apparent from the other claims as well as from the following description of an exemplary embodiment of the invention, which shall be understood not to be limiting and which will be explained below with reference to the drawing. In the drawing: 
         FIG. 1 : shows a perspective assembly illustration of the self-locking step-by-step switching mechanism, 
         FIG. 2 : shows a detail from  FIG. 1 , i.e. the right-hand assembly, with the spring and the zero-position spring removed, 
         FIG. 3 : shows a perspective front view of the components as they are shown in  FIG. 1 , but without the actuating lever, in the assembled state, in the initial position, 
         FIG. 4 : shows the arrangement according to  FIG. 3 , in the engaged state of the driver, 
         FIG. 5 : shows the arrangement as in  FIG. 3 , but at the start of the release wheel being driven, 
         FIG. 6 : shows the illustration as in  FIG. 3 , but at the end of the actuating stroke, and 
         FIG. 7 : shows the illustration as in  FIG. 3 , but during a return stroke. 
     
    
    
     DETAILED DESCRIPTION 
     The self-locking step-by-step switching mechanism is intended for an adjustment device of a vehicle seat. Such an adjustment device is, for example, the adjusting means for a backrest relative to a seat frame, the height adjusting means for a front edge of a seat relative to the seat frame or the adjusting means for a rear rocker of a base frame of a motor vehicle seat. Such adjustment devices are known to the person skilled in the art from the prior art. 
     The step-by-step switching mechanism comprises a clamping roller lock. This will not be discussed in detail below. A clamping roller lock is used as it is known from the two patent applications mentioned in the introduction. This clamping roller lock comprises an axis  20 , which at the same time is the axis of the step-by-step switching mechanism. Furthermore, it comprises a release wheel  22 . This is configured as a normal, externally toothed gear. It is rotatable about the axis  20 . 
     The step-by-step switching mechanism moreover comprises a step-by-step switching device. The step-by-step switching device comprises an actuating lever  24 , which is mounted so as to be pivotable about the axis  20 . It comprises connecting means in order to connect it to a hand lever. A user grips such a hand lever, which is not shown, and initiates an actuating movement. 
     Furthermore, the step-by-step switching device comprises a driver  26 . This comprises two driver regions  28 , which are configured as gearings; they are directed towards the release wheel  22 . The driver  26  comprises a bore through which an axis pin  30  reaches that is disposed on the actuating lever  24 . It forms a driver axis  32  about which the driver  26  can pivot relative to the actuating lever  24 . 
     In the known manner, in particular just like in the step-by-step switching device of the type mentioned in the introduction, only one of the two driver regions  28 , respectively, is in engagement with the gearing of the release wheel  22  in one direction of rotation of the release wheel, i.e. in the case of a driving process. In the central position of the actuating lever  24 , none of the two driver regions  28  is in engagement with the gearing. If the actuating lever  24  is pivoted starting from the central position, one of the two driver regions  28  comes into engagement with the gearing, the other remains out of engagement. Once the engagement has taken place, the release wheel  22  can be driven and rotated. 
     The step-by-step switching device moreover comprises a drag lever  34 . It is preferably configured as a plastic part, whereas the other parts are formed as metal parts. The drag lever  34  is substantially annular. In the assembled state of the step-by-step switching device, it grasps around the release wheel  22  and is supported by it. The drag lever  34  has a recess  36  which accommodates the driver  26 . In the assembled state, this recess  36  is covered by partial sections of the actuating lever  24 . Thus, the driver  26  is fixed in the axial direction. It can be pulled free in a radially inward direction. 
     The step-by-step switching device moreover comprises a spring  38 . In this specific exemplary embodiment, this spring  38  has a variety of tasks; it is a bent spring punched out from flat stock. The spring  38  has two projections  40 . They are disposed a three o&#39;clock and nine o&#39;clock and are situated diametrically opposite from one another. They are formed by flat sheet metal strips which are connected to the main body of the spring  38  via an upper and a lower bridge. The sheet metal strips stand in a plane transverse to the main body; it is defined by the axes  20  and  32 . The driver axis  32  is situated in the central position of the actuating lever in the 12 o&#39;clock direction. In their central region, the sheet metal strips are bent out towards the release wheel  22 ; these bent-out portions form the projections  40 . The projections  40  cooperate with indentations  42  that are provided in the same position on the outer shell of the drag lever  34 . 
     The spring  38  comprises a holding arm  44  disposed in the 12 o&#39;clock position. This holding arm  44  serves for the rotational fixation of the spring  38 . The holding arm  44  comprises a lug that points downwards, towards the axis  20 . It reaches into an opening of a base plate  46 . This base plate  46  comprises an arm  48  located beneath the holding arm  44 . The latter&#39;s function will be discussed below. 
     The spring  38  forms a tongue  50  located in the 12 o&#39;clock position. The tongue  50  is substantially rectangular; it reaches freely over the gearing of the release wheel  22  over a small angle range, for example 1 to 8°. In the assembled state of the step-by-step switching device, it is located, viewed radially, between the gearing of the release wheel  22  and the driver  26 . The tongue  50  protrudes transversely from the main body of the spring  38 . 
     The spring  38  has a braking tab  52 , which, similar to the tongue  50 , axially protrudes transversely from the main body of the spring  38 . The tab  52  is disposed in the 6 o&#39;clock position. It rests in a dragging manner on the outer shell of the drag lever  34  and causes a braking torque. 
     The base plate  46  is connected to a housing  54  of the clamping roller lock. This housing  54  is located between the base plate  46  and the spring  38 . The spring  38  is located between the housing  54  and the release wheel  22 ; only parts of it are located in the plane of the release wheel. 
     The step-by-step switching device moreover comprises a zero-position spring  56 . It is configured as a leg spring. It has two windings and two legs  58 . The legs  58  substantially protrude radially outwards. One leg  58  is located in a position between twelve and one o&#39;clock, the other leg  58  is located in a position between eleven and twelve o&#39;clock. In the assembled state, these legs  58  rests resiliently against holding indentations  60  formed by the actuating lever  24 . Specifically, they are formed in a transverse part of the actuating lever  24  which, in the assembled state, reaches over the holding arm  44  of the spring  38 . The arm  48  is located between the two legs  58 . 
     The driver  26  is displaceable within the recess  36  of the drag lever  34 . No physical axis is provided about which the driver  26  is pivotable relative to the drag lever  34 . Thus, this is a difference to the prior art of the kind mentioned in the introduction. 
     Opposing supporting surfaces  62  are provided the recess  36 ; the driver  26  can come into contact with them. The contact takes place on corresponding counter surfaces of the driver  26 . In the central position of the actuating lever  24 , a small amount of play may be present between the supporting surface  62  and the associated counter surface of the driver  26  on both sides. However, this play can also be very small, it has to be just sufficient for assembly. As can be seen from  FIG. 3 , in particular, the counter surfaces are configured in a partially cylindrical or ball-like shape. The recess  36  is generally configured in a step-shape; the supporting surfaces  62  are located on opposite steps. 
     The zero-position spring  56  is manufactured from spring wire. It has an annular portion formed by two windings. This annular portion grasps around the housing  54  of the clamping roller lock. The zero-position spring  56  is fixated by its legs  58  resting, as described, in the holding indentations  60  and the grasp around the housing  54 . When the actuating lever  24  is deflected from the central position shown in  FIG. 3 , the leg  58  present in the direction of rotation is also moved. The zero-position spring  56  is tightened. In the process, the other leg  58  braces itself on the arm  48 . 
       FIG. 3  shows the initial position. The assembly shown, apart from the three coupling sections for the release wheel  22 , is axially symmetrical to a plane defined by the axis  20  and the driver axis  32 . The two driver regions  28  are not in engagement with the gearing of the release wheel  22 . The tongue  50 , viewed radially, is located between the driver  26  and the gearing of the release wheel  22 . Seen in the circumferential direction, the tongue  50  is located between the two driver regions  28 . 
     The illustration according to  FIG. 4  shows the state of the left-hand driver region  28  latching into the gearing of the release wheel  22 . Starting from the initial position according to  FIG. 3 , which shows the central position, a force F, which is introduced via the actuating lever  24 , acts on the driver  26 . It causes the driver  26  to pivot towards the left. Thus, its left counter surface comes into contact with the corresponding supporting surface  62 ; a reaction force R is produced there. Both forces F and R cause the driver  26  to tilt in a generally counter-clockwise direction and thus cause the left driver region  28  to come into engagement with the gearing; this engagement is shown in  FIG. 4 . It is apparent in  FIG. 4  that the projections  40  are in engagement with the respective indentation  42 . 
       FIG. 5  shows an intermediate position during the actual drive of the release wheel  22 . Now, the drag lever  34  is also rotated about the axis  20  in the counter-clockwise direction. The two indentations  42  are now free from the projections  40 . 
       FIG. 6  shows the end state of the actuation stroke. This is limited by a stop for the actuating lever  24  which is not shown here. The state is as in  FIG. 5 , but the indentation  42  has distanced itself even more from the projection  40  on each side. 
       FIG. 7  shows the beginning return stroke, starting from the position according to  FIG. 6 . As the pivoting movement of the actuating lever in the opposite direction, i.e. now in the clockwise direction, is initiated, the other supporting surface  62  of the recess  36  comes into contact with its associated counter surface on the driver  26 , so that the latter is pivoted in the opposite direction and its previously driving driver region  28  gets out of engagement with the gearing. In order for the other driver region  28  not to be led into the engagement, the tongue  50  is provided, which is now located beneath the other engagement region. It forms a kind of protection and prevents the engagement of the other engagement region. This impediment lasts for so long until the initial position according to  FIG. 3  has been reached again.